CA1256227A - Scavengers for one-component alkoxy-functional rtv compositions and processes - Google Patents

Abstract

SCAVENGERS FOR ONE-COMPONENT
ALKOXY-FUNCTIONAL RTV COMPOSITIONS AND PROCESSES

ABSTRACT OF THE DISCLOSURE
The present invention relates to an alkoxy-functional one-component RTV silicone rubbers composition which is shelf-stable and fast-curing. The composition is formed by reacting an alkoxy-terminated polysiloxane polymer with an alkoxy-functional cross-linking agent in the presence of a condensation catalyst. The present invention lies in the use of silicon-nitrogen compounds and silicon-nitrogen polymers as scavengers for unendcapped hydroxy groups in the above polyalkoxy-functional RTV systems. A preferred silicon-nitrogen compound is hexamethyldisilazane. The compositions are useful as binders and sealants.

Description

; 60Si-579 ~5~ 7 SCAVENGERS FOR ONE-COMPONENT
ALKOXY-FUNCTIONAL TV COMPOSITIONS AND PROCESSES
Background of the Invention The present invention relates to one-component alkoxy-functional RTV compositions, and more particular ly, the present invention relates to scavenaers for al-koxy-'unctional, one-component RTV compositions. The scavengers in such compositions resul~ in the compositi~n heing shel r stable.
Early types of one-component RTV silicone rubber compositions are, for instance, disclosed in Cey7eriat, U.S. Patent 3,133,891, and Bruner, U~S. Patent 3~035,016.
;: Such patents disclose the use of acyloxy-functional ~
silanes as cross linking a~ents for such RTV compositions .
(RTY in this application refers to room temperature vul~
caniza~le.) Th~ compositions of Ceyzeriat were packaaed ~::
lS in a su~stantially anhydrous state and when exposed to atmospheric moisture cured to a silicone elastomer. It was highly desirable to make such compositions as non-corrosive as possible, to be self-bcsndina, to be shelf stable and to have a fast cure rate. l~.'hile the Ceyzeriat ~:
and ~run~r compositions werè shelf stable and fast-curing,~
; nevertheless they had the disadvantage tnat they were somewhat corrosive and emit a somewhat punaent odor while ~.-curing.
3~''.' ' `""

-: . . .. - .
: . . - - . - . -.- . -60Si~579 ~5~i~2~

It was highly desirable to make such compositions self-bonding, so that they would bond to.most substrates without the use of a primer. This resulted in a ~.
saving on labor costs. Examples of disclosures which -relate to increasing the adhesiveness o_ self-bonding properties of the Ceyzeriat composition ar~ for instance, ~.
disclosed in Kulpa, U.S~ Patent 2,961,161, Goossens, U.S. Patent 3,296,195, and Beers, ~.S. Patent 3,42~,g~0.
A further example of acyloxy-functional RTV compositions can be, for instance, found in Beers, U.S. Patent 4,257,932 and other related patents. However, even the composition of Beers, U.S. Patent 4,257,932 which dis-closed the use of a high carbon atom acyloxy-functional RTV, there resulted some discoloration of the metal on whi.ch the RTV was applied as a result of the fact that the composition released a high molecular weight acid when it cured (2-ethylhexanoic acid).
Accordingly, it was highly desirable to make a one-componentj non-corrosive RTV composition, comparable in shelf stability and curing properties to t~e Bruner and Ceyzeriat corrosive acyloxy-functional, one-component RTV systems. It was early known that two-component RTV
compositian~ were noncor-osive since they relied on a cross-linking agent which released an alcohol upon cuxing.
~n axampl~! of a two-component P.TV composition is, for , ..... .

.

60Si-579 ~25~2~7 instance, to be found in Nitzsche et al., U.S. Patent 3,127,363. The only trouble with the Nitzsche et al.
composition was that it was t:wo-component and required the additional labor step of takin~ the packages and mix-ing them together in the appropriate ratios and then quicXly applying the composition to whatever form was desired in which it was to be cured. The composition had to be applied in a rapid manner since it had a very poor shelf life once it was ~.ixed. Accordingly, such compositions were not altogether desirable.
It was desired to make such compositions one-component because of the noncorrosive characteristics.
Accordingly, an early disclosure of a one-component alXoxy-functional R'FV system is to be found in Nitzsche et al., U.S. Patent 3,065,194. The difficulty with the Nitzsche et al , U.S. Patent 3,065,194 composition was that the composition had to be viaorously dried during preparation and had a very short shelf life. Early one-component alkoxy-curing systems are to be found in Brown et al., U.S. Patent 3,122,522, Brown et al., U.S. Patent 3,161,614 or U.S. Patent RE-29760, which disclosed poly-al~oxy-terminated polymers. The di_ficulty with these polymers was that they did not cure at a sufficient rate, that is they were not ast-curin~, and furthermore if they cured at all, had a very poor shelf life.

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60Si-579 .56;2~7 It should be noted that the term "shelf life" in this application means that the com2osition, after it has been stored for periods of one month to one year after manufacture, will cure at about the same rate and to about the same degree of final cure as the composi~ion that is cured immediately or a few days after manufacture.
~ ccordingly, it was highly desirable to make such comDositions shelf stable and be fast-curing. Examples of noncorrosive, one-component alkoxy-functional RTV
systems which, in some cases,were commercialized are dis-closed by Weyenberg, U.S. Patent ~,334,067, Cooper et al., U.S. Patent 3,542,901 and by Smith et al., U.S. Patent 3,689,454 and 3,779,986. ~hese applications relied on the particular use of specific titanium chelate catalysts in plac~ of a tin soap condensation catalyst to accelerate the cure of the composition. ~s stated ~reviously, al-though some of the compositions disclosed in the above ~atents were commercialized, nevertheless, the compositions still did not have a sufficiently fast cure rate even with the specialized chelate catalysts and even then did not have a sufficient shelf life. ~ soecific type of alkoxy-functional, one-component RTV system which has ~een com-mercialized and has a number of advantages in terms of noncorrosiveness and low modulus properties is to ~e ............. __.__ _~.. __ .___.~._ ___._._ ~_ _.___~._...... ~ ~.. _.. ...... .. .=............ .

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~2~6~7 60SI-579 found, for instance, the disclosure of Beers, U.S.
Patent 4,100,129. The composition of this patent is noncorrosive, is low modulus and has self-bonding properties in view of the self-bonding additives incor-porated into the composition. Howe~er, even thecomposi-tion of this patent was not sufficiently fast-curing and did not have a sufficient shelf life, that is, after a period of six months, one year of more, the shelf li~e of the composition was poor. Examples of adhesion promoters that could be utilized with such a composition are, for instance, to be found disclosed in Mitchell et al., U.S. Patent 4,273,698. However good the self-bonding properties of the Beers composition are, it neverthelessstill suffered from not having as good a shelf life as would be desired and not being as fa~t curing as would be desired. Accordingly, it was highly desirable to find a noncorrosive self-bonding RTV COTnpOSitiOn which was low modulus and was shelf stable and fast-curing.
The above RTV systems that have been disclosed - are alkoxy-functional and acyloxy-functional. Theré
are also other types of functional one-component RTV
systems. An examples of an amine-functional RTV system is, for instance, to be found is disclosures of the following U.S. Patents: Nitzsche et al., U.S. Patent 3,032,528; Hittmair et al., U.S. Patent 3,408,325;
- Nitzsche et al., U.S. Patent 3,923,736; Hittmair et al., . . .
U.S. Patent 3,464,951.
There are also disclosed in various patents one-component amide-functional RTV systems, aminoxy-functional RTV systems, ketoxime-functional RTV systems, etc.
Recently, there has been developed a one-component alkoxy-functio~al RT~ system which is shelf stable and fast curing as disclosed in White et al., Canadian Application 5erial Number 404,949, filed June 11, 1982. A companion disclosure to that case is Halgren, Canadian Application _5_ :. ' . - . . - - .
' ' :
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.
~ ' '' ' ' '' ' . ' :

~ 7 60SI-579 Serial Number 399,994 filed March 31, 1982.
Basically, the White et al application discloses the production of a shelf-stable, fast-curing, one-component alkoxy-functional RTV system which is cured with a tin compound by having a scavenger in this system.
The scavenger, which can be either a separate compound or part of the alkoxy-functional cross-linking a~ent, operates by absorbing all unbonded or free hydroxy groups in the RT~ mixture so as to prevent the hydroxy groups from degrading and cross-linkinc3 the polymer mixture, thus deleteriously affecting its shelf life and curing properties. It is disclosed in this application that the scavenger may be amine-functional, that is, either the separate scavenger compound may be amine-functional or the combined cross-linking agent scavenger may be amine-functional. There is further disclosed that amine-functional accelerators may be utilized in the composition especially when the scavenger is enoxy-functional. Although certain simple types of amines are disclosed in this application, there is nowhere disclosed the utilization of silazanes and silyl-nitrogen polyme~s. Thè difficulty with the amine sca~enger as disclosed in the White et al application ls that while they are known, nevertheless they have to be specifically prepared for the composition of White. On the other hand, silazanes like hexamethyl-disilazane are readily available in any silicone manufacturing plant. More importantly, however ! the amines of White et al, serial no. 404,g49, give a noticeable odor to the composition while on the other hand, hexamethyl-disilazane impart to the RTV co~position a slight odor of ammonia.
Be that as it may, there are other silyl-nitrogen compounds that can be utilized as scavengers for the compositions of Serial No. 404,949, other than the ones 3S disclosed in White et al, which is the object of the present invention.

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60Si-579 ~ ccordin~ly, it is one object of the present ïnvention to provide for a noncorrosive, alkoxy-functional, one-component RTV system that is shelf stable and fast-curing~
It is an additional object of the present invention to provide for silyl-nitrogen scavengers for alkoxy-func-tional, one-component RTV s~stems so as to make them shelf stable and fast curing.
It is yet an additional object of the present inven-tion to provide silyl-nitrogen scavengers for alkoxy-functional, one-component RTV systems such that the ~ompo-sitions do not have an objectionable odor.
It is still an additional object of the present in-vention to provide for a noncorrosive, alkoxy-functional, one-component RTV system that is relatively inexpensi~e lS to produce.
It is a further object of the ~resent invention to pro~ide a process for producing a relatively inexDensive noncorrosive, one-component RTV composition which is shel stable and fast curing and which does not have an objec-tionable odor.
This and other objects of the present invention are accom?lished by means of the disclosures set for~h herein ~nd below~ ;

. . .
, , 60Si-579 ~L2~2~7 Summary of the Invention In accordance with the above objects, there is pro-vided by the present invention a stable, one-package, substantially anhydrous and substantially acid-free, room temperature vulcanizable organopolysiloxane composition stable under ambient conditions in the substantial abseoce of moistur~ over an extended period of time and con-vertible to a tack-free elastomer comprising: (1) an organopolysiloxane wherein the silic~n atom at each poly~er ~.
chain end is terminated with at least 2 alkoxy radicals;

(2) an effective amount of a condensation catalyst; (3) a stabilizing amount of -ilane scavenser for hydroxy~
functional groups which is selected from a silicon-nitrogen ~.
compound selected îrom the class consisting of .
(~) a silicone-nitrogen compound havlng the ~.
formula ~"
(Y) (R"')25i N Si (R )2 Y

. where Y is selected from R7" and R2N - and (B) a silicon-nitrogen polymer comprising (1) :~ .
from 3 to 100 mole percent chemically combined structured ; :
~nits selected from the class consisting of units having -8- ;

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- : - ~ , . . .
, 60si-s7s ~;25~;~7 R"' R"' ~R" R"
(R ) 2~ liO--t ~R" ) 2NSiN-- , (R"' ) 3SiN--I~ "'R "' R "' ~R" R "' ~R" R "
----SiN--, --SiN~ SiN--R 'l' and ~2) from O to 97 mole ~ercent chemically combined structural units represented by the formula (R"' )c Sig-c and mixtures thereof where the silicon atoms of said silicon-nitrogen polymer are joined to each other by a .:
member selected from an SiOSi linkage and a siNR"Sl ~:
linkage, the free valences of said silicon atoms other than ::
1~ those joined to oxygen to ~orm a siloxy unit and nitrogen to form a silazy unit are joined to a member selected : from an R" radical and ~R"~2N radical, and where the ratio - of the sum of said R"' radicals and said (R")2N radicals .~ to the silicon atoms of said silicon-nitrogen polvmer has a value of 1.~ to 3, inclusive R" is a mem~er selected ' .
_ g : -:

:

~.... ____. .. . .__.. _. ~__ _........ ~_.,.. ... . .............. ___. __.. ___ ~

60Si-579 ~5~27 from the class consisting of hydrt~gen and C~ 12) mono-valent hydrocarbon radicals, and fluoroalkyl ~adicals, R"' is a member selected from hydrogen, monovalent hydro-carbon radicals and fluoroalkyl radicals, and c is a whole number equal to 0 to 3, inclusive, and optionally (4) an ef~ective amount of a curing accelerator selected from the group consisting of substituted guanidines, amines ;
and mixtures thereof.
The most ~referred compound within the scope of the formula of the silicon-nitrogen compound is a silazane and more particularly hexamethyldisilazane. Other compounds within the scope of the formula may be utilized as scavengers in the instant case such as hydrogen-containing amines, as will be explained below.
1~ There is envisioned within the present invention that such sca~engers are not mixed cross-linking a~ents scaven-ger compounds, but rather there is utilized a seF~ra~ cros5-; linker and the silyl-nitrogen ma~erial is a separate com-pound which is added t~ that composition. Su_h scavengexs may be utili2ed to prepare the composition in a number of ways as disclosed in Can. App. Ser. No. 404,949that is~
all the ingredients may be mixed together at the same time with the scavenger mixed in ~long with the other ingredients or the polyalkoxy-termina ed polymer may be -10- ;, .............. _.. -- , _.. ._.. _.. , _._._____...... ._.. _. ._.. __........ .. _ = _.
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~0Si-579 ~2~6~
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prepared first and then the scavenger and other ingredients added. The latter method is the preferred method of the instant case since it has been found that it yields the composition that is more shelf stable and has better curing properties~ Thus in the preferred embodiment of the instant case, there is ~irst added the cross-linking agent to the silanol-terminated diorganopolysiloxane poly-mer in the presence of a condensation catalyst. The pre-ferred condensation catalyst for this purpose ils di-n-hexylamine. Other preferred condensation catalysts areas follows: diethylamine; dipropylamine, dibutylamine, cyclohexylamine, dioctylamine, guanidine, alkylguanidine diisopropylamine, diisobutylamine.
Once the polyalkoxy-terminated polymer is formed, then the scavenger is added, that is, one of the silicon-nitrogen compounds disclosed abo~e to absorb all unend~
capped hydroxyl groups. Then all the other in~redients may be added into the composition whereupon the scavenger will absorb ~he free hydroxy groups from such materials also. As a result OI the preparation ol the composition .

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60Si-579 ~6~7 in this manner there will be prepared a composition which is substantially free of fr~e hydroxy groups and as a result is shelf-stable and fast-curing; by shelf stable it is meant that it will have a rate of c~re and degree of cure which is about the same six months or one year after it has been manufactured as it was after its manufacture and preparation.
The silane-nitrogen scavengers for accomplishing this will be more fully explained below.

1~ DescriDtion of the Preferred Embodiment :
In the above formulas of the ~ilicon-nitrogen com-oound and silicone-nitrogen polymer, the R" and ~" radi-cals may be selected from hydogen and anv monovalent hydrocarbon ra~icals including fluoroalkyl radicals.

Examples of the radicals from which the R" and R"' c~n be selected are, for instance, alkyl radicals such as methyl, ethyl, propyl, etc.; cycloalkyl radicals such as cyclohexyl, cycloheptyl, etc.; monon~clear aryl radicals such as phenyl, methylphenyl, ethylphenyl, etc.; alkenyl radicals such ~s vinyl, aIlyl, etc.;
fluoroalkyl radicals such as 3,3,3,trifluoropropyl.
&enerally, the R" and R"' radicals may have from 1 to 12 car~on atoms an~ more preferably the ra~icals nay ha-Je from 1 to 8 carbon atoms.

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.

In addition to the above described silicon-nitrogen materials, there are also included in the present inven-tion, silicon-nitrogen materialshavino divalent hydrocar-bon radicals attached to silicon atoms through silicon-carbon linka~es. For example, also included among the silicon-nitrogen materials that can be employed in the practice of the invention, are arylensilazanes, such as phenylene silazanes, and alkylenesilazanes such as methylenesilazanes. In addition, various other silicon-nitrogPn materials, containing divalent hydrocarbon radicals are also contemplated including copolymers and terpolymers such as silicon-nitroyen materials containing intercondensed siloxane units and silarylenesilazane units, intercondensed silazane units, silarylenesiloxane units, and siloxane units, etc. The silicon-nitroqen -polymers that can be employed in the practice of the present invention include silicon-nitrogen polymers in the form of silazane/siloxane copolymers having at least 3 mole percent o~ chemically combined silazy units and u~
to 97 mole percent of combined si loxy units .
~ ccordingly, the silazane polymers can incluàe cyclics consisting of chemically-combined R"' fR
- SiN -R"' - : . ,. ., ,. .. ~
. . . .
: : . . ,: .- . ' ' : . ~
.: :. , -. : . , : :- ' ' . 60Si-579 3L;~S~:2~

units where R" and R"' are as previously defined to provide for a ratio of 1.5 to 3.0 of the sum of the R"' arld R2 radicals for silicon atoms in the silazane polymer.
The definition of a silazane polymer includes linear polymers having at least one unit of the class consisting of R"
(R2N)lR"')~ Si b_ ~ ..

units and R" .
(R"')2 li N

lQ or R" and R"' are as previously defined to provide for a ratio of 1.5 to 3 of the sum of the R"' and R2N radicals per silicon atoms in the silazane polymer.
Further silazane polymers which are included within the definition of the above polymers comprise linear polymers consisting essentially of R"' R~
-5iN -R"' units where R" and R"' are defined to provide for a ratio of 1.5 to 3.0 of the sum of ~he R"' and R2N radicals per silicon ato:m in the silazane ?olymer.

.. ~ .. . .. _.. __. _. .. ... __ ., _._ _ .. _..... ~._.. __.. _..... _ ... . - ~:- ' - ' :` ~ -', :' :: - , , . . , - , . . ~. : `

60~i-579 ~;S~27 In a~dition, the silazane polymers include polymers having at least one unit selected from the class consisting of R"' R"
(R") --SiN -units and R
(R"')3 SiN -where R" and R"' are as previously defined to provide aratio of 1.5 to 3 of the sum of the R"' and R2~ radicals per silicon atom in the silazane polymer.
In addition the silazane polymers can comprise also polymers having a sufficient amount of units selected rrom :
R"' R" R"' R" R
- 7iN - _ SiN - ~ - SiN - ~:

where R" and ~"' are as previously defined to provide for a ra,io of 1.5 to 3 of the sum of the R"'.and R'2~ radicals per silicon atom in the silazane polymer.
The sila~ane~siloxane copolymers can also be in .he . .
form of cyclics and consist of chemically combined R2"SiO

- : . .: - . .

~OSi-579 units and R"' ~ R"
- SiN -~,.t units where R" and R"' are as previously defined.
Linear silazane-siloxane copolymers are also included where the mole percent of (R'''~csiO4-c units can be as high as 97 mole percent with the balance of the units ~eing selected from R" :
~R"') SiN4 c c - :

R"' R" P~" :
I
(R")2N SiO-- (R")2N Sli ~ ~:
R"' R"' where R" and R"' are as previously defined to provide for a ratio of the sum of R"' + R2N radicals per silicon or the sila~ane-siloxane copol~mer from 1;5 to 3.

~, .. . - -. : . ' ': . .
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.. . . . .

. 60Si-579 ~L%~6~7 Other linear silazanes that are included within the scope of the above formulas are ones having the formula ~ Rn- R"' Rn ~

(R'")3 SiN - d - Sl-- N- ~ Si IR~ 3 d where R" and R"' are as previously defined, n is a positive whole number and is preferably from 0 to 20 inclusive, and d is a whole number equal to 0 to 1 inclusive and where d is equal to 0 and n is preferably equal to 3 to 7, inclusive.
Illustrating the silazanes that can be em-ployed in the practice of the present invention within the scope of the above formulas are hexamethylcyclotri-silaz2ne, octamethylcyclotetrasiloxane, trimethyltri-phenylcyclotrisilazane, trivinyltrimethylcyclotrisilazane, etc. Other silazanes within the scope of the above formulas are as follows:
' ...... _ ............. _.. ~._.. _ ....... __ ____ ..... _..... ~ ..... ... _ =___ , . . . . .

60Si-579 CH CH CH
¦ 3 H ¦ 3 H 1 3

3 1 i N I i N - 7i_ CH3 There can be phenyl~ vinyl, CH3 CH3 CH3 3,3,3-trifluoropropyl and various al~cyl ~rouDs C~
fH3 CH3fH3 fH3fH3 middle Si atoms ~ethyl, CH3- Si - N - Si - N - Si - CH3 propyl, butyl).

\3 fH3 fH3 fH3 ~CH3 N - Si - N- Si - N

CH3 - Si - O - Si CH3 CH3 Si - O - Si CH3 Si - N
NH
-- li - M
l l _ CY.3 ~ _ X

-18~

..... . .... , .. ~ .. . .. .... ............................ . ......... , .... _.. ____~ _ .

. - , .

60Si-579 ~5~227 In additi~n to the silazanes of the above formulas, there is also included polysiloxanes havin~ terminal silylamine units or sila~ane units as shown by the for.~ula R~ ~ R"' R"
ZN - - SiO SiN - Z
I I I
R"' jn R"' where R" and R"' are as defined ~reviously,Z is a member sel~cted from R" and SiR3", where R" and R"' and n are as defined previously. The polysiloxane compounds of the above formula may be prepared by taking ammonia or an amine and reacting it at a temperature within the ranse of between a~out ~ to 60C. with a halogenated ~olysiloxane having the formula - ¦ R"' ¦ R"' X~--SiO SiX
R"' I n R"' where R"' and n are as defined above and X is a haloaen radical such as chloro or bromo. If a termin21 sil~zane 15 radical is desired, for exam~le, a molar amount of (~"')3Si X can be reacted along with the halogenated poly- -~
siloxane, at least equivalent to the moles of halogen radicals contained therein. It ~ill, or course, be a~
preciated that amines of ~he ~or~ula - -19~ '.' "

... . . .
.: ,, . -:: , , , . : . , : , - : . . :. ~, -. :: -.; . . . . ~ .. : .. , ~ , 60Si-~7g are utilized for forming the silazy chain-stopped poly-siloxanes of the invention where R" is as defined above, while in the case when materials are desired having terminal silyl amine radicals, amines, including amines of the above formula can be employed having at least one hydrogen available for reaction to produce the desired polysiloxane.
The halogen chain-stopped polydiorganosiloxanes of the above formula can he made by conventional procedures such as by the controlled hydrolysis of a diorganodihalo-silane, for example, dimethyldichlorosilane as taught in Patnode ~atent 2,381,366 ~nd Hyde Patents 2,629,726 an~
2,902,507. ~nother procedur~ that can be employed in-volves equilibrating a mixture of a diorganodichlorosilane and a cyclic polydiorganosiloxane in the presence of a metal catalyst such as fe~ric chloride as shown in Sauer Patent 2,421,653. ~lthoush the various procedures utilized in forming the above polysiloxanes are not critical, generally it has been found desirable to main-tain the halo~en content of the resulting chain-stopped ?olysiloxane in the range of about 0.4 to about 3; per-cent, by weight, and preferably from about S to about 20 percent by weight. ~he halogen chain-stopped polysiloxane is preferably in the form of a chlorinated chain-stopped polvdimethylsiloxane ....... _._ .. ___.. .__ .. _ . _ .. _ __ __ . _ _.. _ .. _. _ , . .. _ , . . ...... ...... .. . ....

.

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6~Si-579 -~562; :7 Included among the amines which can be employëd with the halogenated polysiloxanes are ammonia, m~hyl amine, aniline, dimethyl amine, ethylphenyl amine, methyl-ethyl amine, etc.
The ~rocess for producin~ the rest of the silazane compounds and silazane polymers is ~ell known to a worker skilled in the art.
The silicon nitrogen materials that can be employed as process aids in the practice of the present invention 1~ can be volatile liquids or gum~y, resinous or crystalling solids, depending upon such factors as the molecular weight and the nature and average functionality of their respec-tive chemically combined units. ~hese silicon-nitro~en materials include for exam~le, silyl amines, silazanes and fluid polymers conslsting essentially of intercon-densed siloxane units and silazane units terminated by triorganosiloxane units, polymers consistin~ essentially of intercondensed siloxane units wi.h or without silazane units terminated by silyl amine units, etc. Typic21 of the methods that can be employed ~o make the materials that can be used in the present invention include the method shown by R. O. Sauer, er al., J.~.C.S., Vol. 68, 1946, p 241-44, anc~ in ~aten~ 2,462,635 - Haber, 2,885,37~-Groszo- et a:L., 2,579,416, 2,57g,~17, and 2,579,418-. . ~. .

60Si-579 ~l2~27 Cheronis. ~xamples of the polymers containing intercon-densed siloxane and silazane units, and pol~siloxanes ter-minated by silyl amine units that are operable in the present invention are shown in ~atent 2,503,919- Patnode, and 2,865,918 - Hurwitz et al. Some of the silyl amines that can be employed in the practice of the invention are shown in Patents 2,429,~83 - Johannson, 2,807,635-Breedervelt et al., and 2,758,127 - Goldschmidt et al., etc.

~ccordingly, the ~rocess for producing such polymers and compounds is well known.
~s an example, there is given here a process for pre-paring hexamethylcyclotrisilazane. This is pre~ared by - taking dimethyldichlorosilane, adding it to a saturated `;

solution of ammonia in benzene while a~itatin~ the mix ture. During the subsequent addition of the di~ethyldi-chlorosilane ammonia can be bubbled through the mixture while the temperature is maintained below 50DC. P.ddition-al ammonia was bubbled through the mixture until no further ammonium chloride is precipitated. The product can be recovered by stripping off the benzene under vacuum. Utilizing such a method, there can be ob~ai~ed he~amethylchlotrisilazane as well as trisilazane. Similar methods can be em~loyed to produce any of the a`bove com-pounds for which formulas were given above.

.. ,.. : =-: . . . - , .

1~7 60SI-579 The existence of such silyl-nitrogen compounds and silyl-nitrogen polymers as well as their methods of preparation is disclosed in U.S. Patent 3,243,404 to which a worker skilled in the art can refer to for more information.
In addition to the foregoing silyl-nitrogen compounds and silyl-nitrogen polymers disclosed above, there can also be utilized in the instant invention scavengers which are silyl amines of the formula I

Hg Si [N(R )2]4-g-h where R20 is a radical selected from the class consisting of C(l 8) monovalent hydrocarbon radicals and C(l 8) al- ~:
koxy radicals and fluoroalkyl radicals, and R" is selected from hydrogen and a C(l 8) monovalent hydrocarbon radical, ]5 and g is a whole number that varies from 1 to 3, h is ~
a whole number that varies from 0 to 2 and the sum of h -~ -g does not exceed 3. Compounds coming within the scope of the above formula are, for instance, methyl di(methylamino)- ~ :
silane, tris(methylamino)silane, methyl bis(diethylamino) ~
.

.

. .
,~

60Si-579 ~256~

silane as well as the following:

tris(diethylamino~silane methylbis(dimethylamino)silane tri(ethylamino)silane ethyl di tmethylamino)silane ethyl di (ethylamino)silane ethyl bis(dimethylamino)silane Such amines are disclosed in V.S. Patent 3,243,404 and can be produced by the methods disclosed in ,hat ~atent. The silyl-nitrogen compounds and polymers are the mos~ preferred in the instant compositions as scaven-gers, then ~he above amines can also be utilized as scavengers in the RTV composition of the instant case.
The only dificulty with the hydride amines is that they do tend ~o liberate hydrogen upon standing and also they tend to impar~ the undesirable odor of amines to the RTV
composition. However, if this is not a problem, then they can be tolerated in the instant composition. Preferably, the si~l-nitrogen compounds such as hexametnyldisilazane . ..................... _ .. __.__~____~.. ____._._.. __.. _. _.. _.. _._.. _.. _.. _.. _.. .......... _._ .. .
- . ': , ' ; - ' ` ' `
. ~ . ' '.:.'' . . : . .
~ ~ . . ~ , . , -.. . .
- : , : ~ .
, - - .. . .

605i-57~
2~

and the rest, are utilized in a concentration of 0.5 to 10 parts by weight per 100 parts of the base ~rgano-polysiloxane polymer.
Examples of fluorosilicone silazan~ compounds within the scope of the above formulas are, for instance, com-pounds such as on~s having the formulas [CF3 C~2 CH2 (CH3)2 Si]2NH

[CF3 CH2 CH2 (CH3) Si NH]3 :

Cl 3 (CH3)3Si-H~ H Si(CH3)3 ~:
f 2 ~:
fH2 ~CF3 CH2 CH2(CH3)2si]2 3 ~F3 CH2 CH2 (CH3) Si 7 1 L 3~ 3 _ _ 3 2 2 ( 3~ 1 _ C~3 4 . ,.. __.. _.. _._... _ __~ _._____.. . ._ _ .. , . ... ,_ _.. , .. . .... ...... . .. . _ _ ... ~ : . ..

. ~ - . . .
' . . .:

-60Si-579 ii6~27 ~ccordingly, the preferred silyl-nitro~en compounds and ~olymers within the scope of the above for~ulas may be utilized in the instant invention. ~s stated pre-viously, ~enerally, ~referably from 0.5 to 10 parts of the scavenger is used per 100 ~arts by wei~ht of either the silanol base ~olymer or the oolyalkoxy base p~lymer.
Whether the base polymer is silanol-stopped or polyal-koxy-stopped as will be explaine~ below, makes little difference in the concentration of the scavenger since the molecular weight of both com?ounds is approximately the same. More generally, the scavenqer may be utili~ in a concentration of 1 part to any concentration that is desired. It is not desirable to add too much of the scaven~er since a~ove 10 parts may detract from the cured ~hysical ~roperties of the composit-on. ~s will be ex-plained below, it is generally desired ~o hav~ at least 3% excess of the scaven~er in the composition, that is, ~% excess over the amount necessary to absorb o~ endcap all the ~ree hydroxy groups in the composition. The com~ositions with which the scavenger in the instant case may be utilized are varied but are specifically disclosed below~ ;
;
~ .

.

....................... _.. ,.. _ _.. _.. _._.. _.. _.. _.______.__ _._ . _............. __.. ._.. _.. _.__.. _ , 60si-s7s ~:56~:27 :. .

~ s utilized hereinafter, the term "stable" as applied to the one-packa~e ~olyalkoxy-terminated organopolysiloxane RTV's of the present invention means a moisture curable mixture çapable of remaining substantially unchanged while excluded from atmosphexic moisture and which cures to a tack-free elastomer after an extended shelf period. -~
In addition, a stable RTV also means that the tack-free time exhibited by freshly mixed RTV ingredients under atmospheric conditions will be substantially the same as that exhibited by the same mixture ingredients exposed to atmospheric moisture after having been held in a ~ois-~ure-resistant and moisture-free container for an ex-tended shelf period at ambient conditions, or an equivalent period based on accelerated aging at an elevated tempera- -ture.
~ s noted previously, the present RTV composition is substantially acid-free. The expression "substantially acid-free" with respect to definin~ the elastomer made from the RTV composition of the present invention upon ~o exposure to atmospheric moisture means yielding by-products havin~ a pKa of 5.5 or greater with 6 or greater ~referred and 10 or greater being ~articularly preferred.
The s~lanol-terminated ?olydiorganosiloxane has the formula ..i, . . ~:. , ' . ..
- , : - .. ~. . , ' .

60Si-579 tR t 1 1 ) where R is a C(l 13) monovalent substituted or unsubstituted hydrocarbon radicalj which i5 preferably methyl, or a mixture of a major amo~nt of methyl and a minor amount of phenyl, cyanoethyl, trifluoropropyl, vinyl, ~nd mix-~ures thereof and n is an integer having a value of from about 50 to about 2500 with a cross-linking silane having hydrolyzable radicals attached to silicon. Preferably n var~es so that the viscosity of the polymer varies from 60,000 to 200,000 centipoise at 25 C.
~lthough the compositions may be expressed i~ terms of a silanol polymer, that is a silanol polymer with a cross-linking agent as will be explained below, and a sca~enger of the formulas indicated above and as has been done in the su~mary of the invention, it can be expressed in other terms. ~.
The present invention is based on the discovery that stable, substantially acid-free, one-~ackage, moisture curable polyalkoxy-terminated orsanopolysiloxane RTV
compositions can be made by using a cilanol terminated polydiorganosiloxane consisting essentially of chemically --28~

-:, , . . : , ~ -, - . - . . :
-60Si-579 ~5~2~

combined diorganosiloxy units of the formula R
- SiO - (2) R
such as a silanol-terminated polydiorganosiloxane of For-mula (1), where R is as previously defined, with an ef-fective amount of certain silane scavengers for chemically combined hydroxy ra~icals. In the silanol-termin2ted poly-diorganosiloxane consisting essentially of chemically com-bined Formula (2~ units, the presence of silicon bonded C(l 8) alkoxy radicals such as methoxy radical is not pre-cluded. The hydroxy radicals which can be removed by thesilane scavenger can be found in materials normally present in the RTV composition of the present invention, for ex-ample, trace amounts of water, methanol, silanol radicals on the silica filler (if used), the silanol polymer of Formula (1), or a silanol-terminated polymer having Por-mula (2) units. The silane scaven~er is a separate com-pound of the formulas indicated above.
~ mong the ingredients of the Rl~r com~ositions which a-e formed as a result of the use of the hydroxy scavenger is silanol-free polydior~anosiloxane, chain-terminated with tWQ or ,~hree -ORl radicals. The silanol-free ?ol~-diorganosiloxane optionally can be comb~ned ~ith an ef-`~; ., . , - . . . . . , :.... .
.
- .
': ~ ` ~: ; . ' `
.. :............ .. ~ ' ' . .
.
. , 605i-579 ~5~2~

fective amount of a cross-linking silane, as defined hereinafter, under substantially anhydrous conditions.
The cross-linking polyalkoxysilane which can be utilized in combination with the scavenging silane has the formula ( R ~2 (R )4-b i where Rl, R2 and b are as previously defined. ~he ore-ferred condensation catalysts which can be used in the practice of the invention include metal compounds selscted 19 from tin com~ounds, zirconium compounds, and titanium com- -pounds or mixtures thereof. ~dditional condensation catalys~s which can be used are de,ined more particularly hereinafter.
It is believed the reason the present scavenger func-lS tions to make the composition shelf stable is that theyabsorb free and end-capped hydroxy groups so that they can-not hydrolyze to crossolink and degrade the basic poly-al~oxydiorganopolysiloxane polymer. If such cross-linking and hydrolysis does not occur, then the composition is 2~ shelf stable. If it does occur, and depending to the ex-tent that it does occur, then the polymer will not only have poor shelf stability, it will not be very fast curing ,, ,,,, ,, . ....... __._.. _ ....... .... ..... _................. . .

60Si-579 1~5~2;~7 .

when it does eventually cure after it has been stored for some time such as a month or more.
- The use of the silane scaven~er substantially eliminates und~sirable water in the filler and silicone polymer, as well as residual moisture i~ the RTV composi-tion durinq the shelf period. In determining what level of silane scavenger to use in the practice of the inven-tion, the total hydroxy functionality of the RTV composi-tion can be estimated. The total hydroxy functionality of the polymer can be ~etermined by infrared analysis.
Tn order to insure that an effective or stabilizing amount of scavenger is used to ~aintain the stability of the composition over an extended shelf perlod of six months or mor~ at ambient temperature while in a sealed con-tainer, there can be used an additional amount ofscavenger over that ~mount req-~ired to endstop the poly-mer. This excess of scavenger can be up to about 3% by weight~ based on the weight of the polymer. The afore-mentioned 3% of scavenger by weight exceeds that amount required to substantially eliminate availa~le hydroxy functionality in the polymer as a result Oc reaction be-twe~n OH functionality and X radicals. In composi.ions which also contain filler and other additives, the additional amount of scavenge- of Formulas (3) or (5) ~; which is re~uired is estimated by running a 48-hour .

.... . .. .. _.. _........ _ .. =.,.................... ... ~.. _ _.. ~ . :.:_.. _ ....

.- : : : .

~ - , .

605i-579 ~L2~6~

stability check at 100 C. to determine whether the tack-free time remains substantially unchan~ed as compared to the tack-free time of the composition before aging measured under substantially the same conditions.
The polyalkoxy-terminated organo~olysiloxane of the present invention has the formula (R )3 (b+e)slo + SiO ~ Si~R )3-(b+e) (4) where R, Rl, R2, are as defined above and below, and b is equal to 0 to 1. The polyalkoxy-terminated organo-polysiloxane of Formula (4), can be made by various pro-cedures. One procedure is taught by Cooper et al., U.S.
Patent 3,542,901 invol~ing the use of a ~olyalkoxysilane with a silanol-terminated polydior~anosiloxane in the presence of an amine catalyst.
In Formulas ~1-4), R is pre~erably selected from C(l 13) monovalent hydroca-bon radlcals, halogenated hydro-carbon radicals and cyano alkyl radicals, R i5 preferably a ~(1 8) alXyl radical or a C~? 13) aralkyl radical, R
is preferably methyl, phenvl, or vinyl.
~s disclosed in Se~al No. 404,949 additional amounts of amines and guanidines can be ?resent as cure ac-celerators. Such amines and cure accelerators ~ay be ..

- . . . : -. . . . . .

60Si-579 ~2,~3~227 - :

utilized with advantage to increase the cure rate with the compositions of the present invention, especially with the hydride amines of the present case. However, while such is desirable it is not strictly necessary and the scavengers of the present invention will substantially maintain the shelf-stability of the com~osition and main-tain the cure rate of the composition if they are utilized in the quantities indicated above.
It has been further found that improved cure r~tes ;
can be achieved it minor amounts of amines, substituted guanidines, or mixtures thereof, are utilized as curing accelerators in the poiyalkoxy compositions of the present invention. There can be used from 0.1 to 5 parts, and prefera~ly from about .3 to 1 part of curing accel-eratos, per 100 parts of the silanol-terminated polymer of Formula (1), or which consists of chemically combi~ed units of Formula f2), or 100 parts of the polyalXoxy- `
terminated polymer of Formula (4) to substantially reduce the tack-free time (TFT) of the RTV composition of the present invention. This enhanced oure rate is maintained after it has been aged for an extended shelf period, for example, 6 months or more at ambient tem?e atures, or a . . .. ~ :

' ~ , : . ' :
, ' - . ~ ` - `

605i-57g ~5~2;~7 comparable period under accelerated aqing conditions. Its cure properties after the extende~ shelf period will he substantially similar to its initial cure properties, for example, tack-free time (TFT), shown by the RTV
composition upon being freshly mixed and immediately exposed to atmospheric moisture.
It appears that the curing accelerators described herein, in addition to decreasing the tack-free times of the RTV compositions of this invention, also provide 1~ a surprising stabilizing effect for particular RTV com-positions catalyzed with certain condensation catalysts which exhibit a marked lengthening of tack-free time after accelerated agins. For this class of condensation catalysts, addition of amines, substituted guanicines and mixtures thereof described herein provide stable RTV compositions which exhibit a fast cure rate initially, that is less than about 30 minutes which remains substan-tially unchanged after accelerated a~ing.
The ~TV compositions of the ~resent invention can cure to a depth of lJ8" thickness within 24 hours. Durom-eter ~ardness (Shore ~) can then be determined and used to evaluate the cure of the compositions as shown in the examples.

.

- - ~ - . .. . . .

, .

60si-57g In a further aspect of the present invention, there is orovided a stable room tem~erature vulcanizable poly-alkoxy-terminated organopolysiloxane composition curable under ambient conditions to a tack-free, substantially acid-free elastomer comprisi~
t~) lO0 parts of a polyalkoxy-terminated organopolysiloxane of Formula (4);
(B) 0 to 10 ~arts of a cross-linking silane of Formula (3);
(C) an effective amount of condensation cat~lyst, and (D) a stabilizing a~ount of any of the scavenging silane of the above formulas. ::
~nother method of the present invention is making ~:
a room temperature vulcanizable organopolysiloxane com-position under substantially anhy2rous conditions utilizing an effective amount of a condensation catalvst with an orsanopolysiloxan.e whe~ein the silicon atom at each polymer chain end is terminated with at le~st two al~oxy~ radicals, which involves the improve- :
ment which com~rises adding to said polyalkoxy-~erminated organopolysiloxane (1) a stabilizing .-mount of one or the silane scavengers for hydroxy functional groups OI ~he above formul.as. :
:' :: , .: , : . . . . . , .. .... , . :

': - , .
~ i . . . . . .

60Si-57g ~S~27 In an additional aspect of the present invention, there is provided a method of makinn a stabl2, one-package room temperature vulcanizable polyalkoxy-terminated organo-polysiloxane composition which comprises aaitat~n~, under :
substantially anhydrous condi.tions, a room temperature vulcanizable material selected from (i) a mixture comprising on a weight basis (a3 100 parts of a silanol-terminated polydiorganosiloxane consisting essentially ~0 of chemically combined units of Formula (2), Ib) 1 to 10 parts of the cross-linkin~
silane of Formula ~3), (c) 0 to 5 parts of curina acceler2tor selected from substituted guanidines, amines and mixtures thereof wherein, the condensation catalyst is added after the silanol~terminated polydiorcanos~loxane and cross-linking silane are mixed, (d) an amount of silvl-nitro~en materials of the above formulas sufficient to scavenge a~ailable -OH in tne RTV composition :~ `
and provide u~ to 3~ by weiaht excess, based on the weight of ~TV composition, Ie) an e~~ective amount or a condensation catalyst; and :~

. ~ I' .

.. , . . , .. . . . - .. ... .

60Si-5~9 ~ 5 ~

~ii) a mixture comprising, (a) 100 parts of the polyal~oxy-terminated organopolysiloxane of Formula (4), (~ 0 to 10 ~arts of the cross-linking silane of Formula ~3~, (c) an effective amount of a condensation catalyst, (d) a stabilizing amount of silane scavenger of the above formulas, and (e~ 0 to 5 parts of curing accelerator seiected from substituted guanidines, amines and mixtures thereof.
Radicals included within R of Formulas (1), (2) and 16) are, for example, aryl radicals and halogenated aryl radicals, such as phenyl, tolyl, chlorophenyl, naphthyl;
aliphatic and cycloaliphatic radicals, for example, cyclohexyl, cyclobutyl; alkyl and alkenyl radicals, such as methyl, eth~1, propyl, chloropropyl, vinyl, allyl, trifluoropropyl; and cyanoalkyl radicals, for ; ~o example, cyanoethyl, cyanopropvl, cyanobutyl. Radicals .preferabl~ included within ~1 are, for example, C(l 8) alkyl radicals, for example, methyl, ethyl, propyl, butvl, Qentyl; C~7 13) aralkyl radicals, for e~ample, benzyl;

., ~: . ` - .: ~
~' ~' ,, . . ,:
: ... . : .

. 60Si-579 .

~25~2~

ohenethyl; alkylether radicals such as 2-methoxyethyl;
alkylester radicals, for exam~le 2-acetoxyethyl; alkyl-ketone radicals, for example l-butan-3-onyl; alkylcyano radicals, for example 2-cyanoethyl. Padicals included within R~ are the same or different radicals incluaed within R radicals. In Formulas (1-4), where R, Rl, and R2, can be more than 1 r~dical, these radicals can be the same or different.
Some of the cross-linking ~olyalXoxysilanes in~luded within Formula (4) are, for example, methyltrimethoxysilane;
methyltriethoxysilane; ethyltrimethoxysilane~ tctra-ethoxysilane; vinyltrimethoxysilane; etc.
~ong the curing accelerators which can be used in the practice of the invention are silyl substituted guani-dines having the formula (Z) Si(oR )4 ~ (5) where R is as previously defined, Z is a guanidine radical of the formula, tR )2N 3 ~ C=N-R -tR ) N

R is divalent C(2 8) alkylene radical, R and R5 re selected from hydrogen and C(l 8) ~lkyl radicals and g is an integer e~ual to.l to 3 inclusive. In addition, alkyl subs.itutecl guanidines having the ~ormula ,:
....... _.. ... _._.. _ ...... _ . . =_ ..... _.. _.... . __ ._ . .~ . ..... _ ................... ~.. __ :,' : '~ ' . . , , , ' . ' .
. ..
.

60Si-579 ~25~7 (R ) N
2 ~C=N-R6 (R5)2N

where R4 and R5 are as previously defined and R6 is a C~1_8) alkyl radical, also can be employed. Some of the silyl su~stituted guanidines included within Formula ~5) aré shown by Takago, U.S. Patents 4,180,642 and 4,248,993.
In addition to the above su~stituted ~uanidines, there can be used various amines, for example, di-n-hexyl-amine, dicylohexylamine, di-n-octylamine, hexamethoxy-methylmelamine, and silylated amines, for exam~le, y-aminopropyltrimethoxysilane and methy1dimethoxy-di-n-hexylaminosilane. .~ethyldimethoxy-di-n-hexylaminosilane acts as ~oth a scavenger and curing accelerator. The ;~
- primary amines, secondary amines, silylated secondary amines are preferred, and secondary~a~ines, and silylated ~ -secondary amines are particularly preferred. Sllylated secondary amines such as alkyldialkoxy-n-dialkylaminosi-lanes and suanidines such as alkyldialkoxyalkyl~uanidyl-silanes which are use~ul as cure accelerators herein also act as scavensers and, in certain instances, as stabiliz-ers in the compositions of th s invention.

.~ -, . ,~ .. , .. , .. . .. ..... . .. . .. _ .. , ._ . _. _ _., .. .. . . . . _ _ ............. ... _ .. . ............. _.. ............ .

c 60Si-579 The silanol-terminated diorganopolysiloxane of Formula (1) are well known to a worker skilled in the ar~
and can be produced by various methods as disclosed in Lampe et al., U.S. Patent 3,888,815.
Effective amounts of the condensation catalysts which can be used in the practice of the present invention to facilitate the cure of the RTV compositions are, for examole, 0.001 to 1 part based on the weight of 100 parts of the silanol-terminated polydiorganosiloxane of Formula (1). There are included tin compounds, for exam~le dihutyltindilaurate; dibutyltindiacetate; dibutyl-tindimethoxide; carbomethoxy?henyl tin tris-uberate; tin octoate; isobutyl tin triceroate; dimethyl tin dibu-tyrate; dimethyl di-neodeconoate; triethyl tin tartrate;
dlbutyl tin dibenzoate; tin oleate, tin naphthenate;
butyltintri-2-ethylhexoate; tinbutyrate. The preferred condensation catalysts are tin compounds and dibutyltin-diacetate is particularly preferred.
Titanium comoounds which can be used are, for example, 1,3-propanedioxytitanium bis(ethylacetoacetate); 1,3-pro-panedioxytitanium bis(acetylacetonate); diisopro~oxy.i-tanium bis(acetylacetonate); titanium naDhthenate;
tetrabutyltitanate; tetra-~-ethylhexyltitanate; ~etra-phenyltitanate; tetraoc-adecyltitanate; ethyltrlethano-. ~ . - . '. '-- - . . ' ~' , . .
:`. ' . . ' ~ . - . ~ ' : ' ' . ~ . . . ~ . . . :

60Si-57g 1~56;~27 }aminetitanate. In addition heta-dicarbonyltitanium com-pounds as ~hown by Weyenberg U.S. Patent 3,334,067 can ~e used as condensation catalysts in the present in~ention.
Zirconium compounds, for example, zirconium octoate, also can be used.
Further examples of metal condensation catalysts are, for exam~le, lead 2-eth~lhexoate; iron 2-ethylhexoate;
co~alt 2-ethylhexoate; manganese 2-ethylhexoate; zinc 2-ethylhexoate; antimony octoate; bismuth naphthenate;

zinc na~hthenate; zinc stearate.
Examples of nonmetal condensation catalysts are hexylammonium acetate and benzyltrimethylammonium acetate.
Various fillers and pigments can be incorporated in the silanol or alkoxy-terminated organo~olysiloxane, suc~
- 15 as for example, titanium dioxide, zirconium 5i licate, silica aerogel, iron oxide, diatomaceous earth, f~med silica, carbon black, precipitate~ silica, glass fibers, - polyv-nyl chloride, ground quartz, calcium carbonate, e~
The amounts of filler used can obviously be varied within wide limi~s in accordance with the intended use. ~or example, in some sealant apDlications, the curable com-positions of the present invention can be used free of fil~er. In other applications, such as employment of the curable compositions for making binding mat~rial on a - . , : ~

6nsi-57~ ~

.
':

weigh~ basis, as much as 700 parts or more of filler, per 100 parts of organopolysiloxane can be employed. In such applications, the filler can consist of a major amount of extending materials, such as ground quartz, polyvinyl-chloride, or mixtures thereof, preferably having an averageparticle size in the range of from about 1 to 10 microns.
The compositions of the present invention also can be employed as csns~ruction sealants and caulking com-pounds. The exact amount of filler, therefore, will de-~end upon such factors as the application for which theorganopolysiloxane composition is intended, the type of filler utilized (that is, the density of the filler and its particle size). Preferably, a ?roportion of rrom 10 to 300 parts of filler, which can include up to about 35 parts of a reinforcing filler, such as fumed silica filler, per 100 parts of sil nol-terminated organopolysiloxane is utilized.
In the practice of the invention, the room temperature vulcanizable compositions can be made by agitating, for example stirring, a mixture of materials which can consist of the silanol termi~ated polydiorganosiloxane, which hereinafter will include ~o.mula !l) or polymer con- :
sisting essentially of ~ormula ~2) uni~s along with the c-oss-linkin5 si~anc of the above Formula (3), -~

- . .

. _ 60Si-;79 ~56~2~7 where the blending is performed in the substantial a~-sence of atmospheric moisture. Thereafte. the condensa-tion catalyst and scavengin~ silane of the above f~rmula is added also in the substantial absence of atmospheric moisture.
As used hereinafter, the expressions ~moisture-free conditions~ and "substantially anhydrous conditions,"
with reference to making the RTV compositi~ns of the pre-sent invention, mean mixing in a dry box, or in a close~
container which has been subjected to vacuum to remove air, which thereafter is replaced with a dry inert gas, such as nitrogen. Experience has shown that sufficlcnt scavenging ~ilane of the above formulas should be utilized as previously defined. Temperatures can vary from about 0C. to about 180C. depending upon the degree of blend-ing, the type and amount of filler.
A preferred procedure for making the RTV compo-sition of the Dresent invention is to a~itate under su~-stantially anhydrous conditions, a mixture of the silanol terminated polydiorganosiloxane filler and an effecti~e amount of the cross-linking silane sufSicie~t to effect the substantial elimination of hvdroxy Cunctional radicals and to endcap the polymer. This "endcapping" procedure can reguire several minutes, hours, or even days, de?endins upon such factors as the nature .................... _... _ ... __.. ____.. _. ... _. __ __.. __._. .____..... . _.. __.________... _ .__._. .__.. _._ '' ,~ . :' . .

. . . - . . ~ . .. .

.
. - '' . ' ,"' . . .

60Si-579 ~

- .
of the X le~ving gxoup, the nL~ er of -ORl radicals on the cross-linking silane, etc. There can be added to the substantially silanol-free mixture, the condensa-tion catalyst, the scavenging silane, or mixture S thereof, along with other ingredients, for example, the curing accelerator and pigments. A stabilizino excess of the scavenging silane is used in the final stages of the mixing procedure in amounts previously defined.
Irrespective of the above methods for making the instant RT~ compositions, the preferred method ~or making the instant RTV compositions is to react the base silanol polymer of Formula (l) with the cross-linking agent of Formula (3~ in the presence of an amine condensation catalyst as disclosed in the foreqoing Cooper et al., U.S. Patent 3,542,901. The preferred amine catalyst which can be utilized for this purpose is, for instance, -di-n-hexylamine. Once the polyalkoxy-terminated diorgano-polysiloxane polymer is formed, then there can be added the scavenger in the foreaoing quantitites indicated above and the other additives that are added to the ccm-position such as fillers, self-bonding additives, etc.

.

................. _.. _ .. .__._.. __.~__._.. __.~ _ _._. ..... . __... _ _ ...... _.. _.. .. _ _. ......... ..... _ .............
.
.

,, ~ .. .
.

. ~ . , . - . . .

6~Si-579 _ ~2 ~2 ~ ~

.... .

The scavenger will react with free hydroxy groups to substanti~lly remove and endcap them so that they cannot degrade the polyalkoxy base E~olymer. Accordingly, the -cure rate and the shelf stability of the composition will be maintained. The silazanes of the instant case are preferred over other sca~enging compounds disclosed in the above formulas, since all of them are known com-pounds and the simplest ones are readily available to silicone manufacturers. Further, they do not impart objectionable odor to the composition and they are of relatively low cost to make. They also are very efficient water and methanol absorbers and will make the composition ~
shelf stable and fast-curin~ even after it has been ~-stored for a substantial period of time such as six months, one year, or more.

-- .

- ~ ... . _.. ,_.. _.. _.. ..... _.. _._._.. _.. _._.. _.. _.. _.. __.. _. . .. .. =
,: , :
', ''' ' '' ~''' - ': ' ' ' , ~ , '' . :
.' ~
.~

~5~27 60SI-579 The instant scavengers may be utilized with any of the basic compositions disclosed in White et al, Canadian Application Serial No. 404,949. The only compositions that are disclosed in the White et al application that cannot be utilized in the instant case are compositions in which the scavenger and cross-linking agent is the same compound; that is, when a cross-linking agent has functionality in addition to alkoxy-functionality. In accordance with the instant invention, the scavenger of the instant case are additional compounds in addition to the cross-linking agents. It would be very difficult if not impossible to include the silicon-nitrogen functionality disclosed by the above formulas in the same compound.
Accordingly, in the present case the scaveng~r compound is one of the compounds in the formulas shown above and is preferably a silazane compound which is a different compound from the cross-linking agent and which is preferably added after the polyalkoxy-terminated diorganopolysiloxane base polymer is formed.
The examples below are given for purposes of illustrating the present invention. They are not given for any purpose of setting limits and boundaries to the instant invention. A11 parts are by weight.

c 60Si-57g :; :
3L~5~

Example 1 ~
To 100 parts of methyldimethoxy endca~ped dimethyl- -polysiioxane polymer of 2500 c~.~ntipoise viscosity at 25C.
containing .6% ~y weight of di--n-hexylamine was added 15 parts of cyclo-octamethyltetrasiloxane treated fumed silica to ~ive a base composition.
To this base composition there was added various .:~-catalyst compositions. The compositions o such catalysts ~:
(A) (B) and (C) are as follows:
Catalyst A contained 0.5 or 1.0 parts of bis~dimethyl-amino)methylvinylsilane (A) along with 0.23 parts of di~utyl tin diacetate per 100 parts of base compound and 4.37 parts ofalO0 centipoise,at 25C, trimethyl~
silyl stopped polydimethylsiloxane fluid per 100 parts of base compound.
Catalyst B contained 1.0 or 1~5 parts of methyl tris(dimethylamino)silane (B) per 100 parts of base com-pound along with 0.23 parts of dibutyl tin diacetate ?er 100 parts of base compound and4~37 parts o ~ 100 ..
centipoise,at 25C, trimethylsiloxy endstopped fluid per 100 parts of base compound.

: -47-, . . . ...... __ ____ ..... .. _._ _ ., .. _, __.. . .,_ _. .. _.. _ .... _ .. ~.. . _.. _.~.

. 60Si-579 Catalyst C contained l.0 or l.5 parts ~f dimethyl-aminotrimethylsilane (C) per :L00 parts of base compound ~long wi~h 0.23 parts of dibu1:yltin diacetate per 100 parts of base compound and 4.:37 parts of a lO0 centipoise, at 25~C.,trimethylsiloxy endstopped fluid per 100 parts of base compound.
Following the mixing, the material was placed in sealed metal tubes and stored at 100C. Periodically the tubes were removed and checXed ~or tac~-free ~--time (TFT) at 77~ + 5F and 50 ~ 5% relative humidity.
Table I lists the results.
~.

'' ~
/
.

.... , .. . ,,, . , _ .. ~ , ._ . ... _ .. ~.. .. .... _.. _.. . ... ........ __ .~.. ......... .. ..... .........

~- ~ ...... .. :

6~si-s7s . ..

, j, ~

TAB~E I
TFrr) Min . ) ~4 hrs. 48 hrs.
Formulation Initial100C._ 100C.
Parts A]100 pts. base 0.5 25 gelled -----1.5 30 30 30 Parts B/100 pts. base 1.0 2!; 20 gelled 19 1.5 2~ 15 20 Parts C/100 pts. base 1.0 25 No Cure -----1.5 ~5 25 20 As ~he re~ults of Table I indicate, the amino silanes impart good shelf stability to the al~oxy-functional one-com~onent RTV system.

ExamDle 2 Hexamethyldisllazane offers the advantage of being readily available and since it is difunctional with ~0 respect to nitrogen can react with two equivalen~s of chemically combined hydroxy groups to ~enerateone equilvalent of by-product. Thus less amine by-product is generated per given amau~ of methanol, water, or silanol scavenged. In addition, such silazane is desirable 2s a scavenger since the odor it im~arts to the RTV composi-tion is a slight odor of am~onia.

.

............... ... ._.. ... _.. _ ..... _. _._.. _................. .......................................................

, . . . . . .

.. : , : - :: . .: . , . : ~: - - ::
.

' , . ~ , ' . ~.' ' .: ' . ~ ' -, , , ~OSi-575 , .. . .
~25~ 7 ... .
.. ..

To 100 parts of methyldimethoxy stopped polydimethyl-siloxane polymer of 150,000 centipoise at 25'~C. contain- .
ing .6~ by weiaht of di-n-hexylamine as a result by which it was made, there was added 16 parts of an octamethylcyclotetrasiloxane (D4) treated fumed silica filler along with 10 parts of a trifunctional fluid, con-taining 20 mole percent of monomethylsiloxy units, 76 mole percent of dimethylsiloxy units and 4 mole percent -:
of trimethylsiloxy units. In the base composition there :.
was also added 20 parts of a trimethylsiloxy endstop di-methylpolysiloxane polymer having a 100 centipoise vis- :
cosity at 25C. - -To 100 parts of this base composition there was added various amounts of hexamethyldisilazane shown in Table II below along with .76 parts o~ a trimethyl- :
siloxy endstop dimethylpolysiloxane polymer fluid having a 100 centipoise viscosity at 25~C. This mixture W25 stirred for fifteen minutes at which time 4.6 parts of a 5% solution of dibutyltindiacetate in a trimethylsiloxy endstop ~imethylpolysiloxane fluid havina 100 centipoise viscosity at 25C.w~s adde~ t~ pr~uce.~e~ stem. ~1 ~e ~rimethylsiloxy endstop dimethylpolysiloxane fluids dis-closed above'navea silanol content of anywhere from S00 to 1500 parts per million as a result OI the manner in.
2S which they were made. ~urther, in these e~amples, 'he - : . :, . . : ~ . .

. . . - ~- . , : ~ ~ . -- : , .

605i-579 ~ 25~i2;~7 tack-_ree time of the samples was tested initially and after accelerated aging. The tack-free time is a measure of the shelf stability and the curing ability of the polymer initially and after it has been aged. The tack-free time test is c~rriecl out as follows.
A sample of the R~V is olaced on a clean dry sur-face to a depth of ~" and exposed to an atmosphere of 77 ~ ~~. and 50 ~ ~% relative humidity. The tack-free time is the time required for the surface to become 1~ tack-free to a light touch of the finqer.
The results are set forth in Table II below.

TABLE II
Hexamethvldisilazane tHMDZ) as Scavenaer TPT IMin.) lS 24 hrs. 72 hrs. UseCul FormulationInitial 100C. lOO~C. Ran~e _ _ _ Parts HMDZ/
pts. base 0 3 4~ 55 gelled 0.5-5.0 0.67 45 55 25 ~ s the results of Tabie II indicate, hexamethyldi-silazane even in iow concentrations produces a shelf-stable composition, that is while at .33 p2rts per 100 - . : ~ ' ' . : . .
.

~ ~jy_~
60Si-579 ~

, . .

parts of base it is ineffective, at .67 parts it produced a substantially shelf-stabl,e composition~ Such materials may be utilized at a concentration as stated previously of anywhere from 0.5 to 10 parts and more preferably from .5 to 5 parts per 100 parts of diorganopolysiloxane base polymer, and those amounts impart to the RTV composition and particularly, to the polydiorganopolysiloxane polymer shelf stability and good curing pro~erties.

Example 3 To 100 parts of a methyldimethoxy stopped polydi- ;
methylsiloxane pol mer of 150,000 centipoise at 25C. `~
containing 0.6~ by weight or di-n-hexylamine was added 15 parts of a cyclotetrasiloxane treated silica filler to make an ~TV base.
To 100 parts of this base was added 7.8 parts of a solution containing 1.2 parts o~ hexamethyldisilizane, 2 parts of methyltrimethoxy silane and 4.6 parts of a 5%
solution of dibutyltindiacetate in a 100 centipoise trimethylsiloxy endstopped fluid. ;~
~ ollowing the mixing, .he material was placed in sealed metal tubes and stored at 100C. Periodically the tubes were removed,cooled and checked for tack-free time at 77 + 5F. and 50 ~ ;~ relative humidity. Ta~le IIT _ists th~e results.

;. , .

. ~ . ...... .. __.. .. ,.. ,. ... _. ............................. ....... _ ........................... _.. .

c ' 60Si-579 ~L2562Z~7 .... ~.:

TABLE III
~ -- .
Tack-free Time vs. Time at 100C.

Time at lOO~C.(hrs.) TFT (Min. ) ::
-- ._ Example 4 .
A base was prepared as in Example 2. To 100 parts of the base was added 3 parts of a solution containina 1 part of methyltrimethoxysilane and 2 parts of hexamethyl disilazane. Immediately after mixing, 2 parts of a second solution was added containing 1 part of amino-ethylaminopropyltrimethoxy silane and 1 part of a 23 per-cent solution of dibutyl tin diac tate in a S0 centipoise,~t 25 C , trimethylsiloxy endstopped dimethyl~olysiloxane flu' d.
Again, this material was aged at 100C. in sealed metal tubes and periodically removed, cooled and tested Ior tack free time at 77 + 5~F. and 50 1 5% relative humiditv. Ta~le IV llsts the results.

`' ' :.

. . ~', . . . ' ` : .
:.. , : ' . . ' ' - ' 60Si-579 .~
~5~2;~ _ T~BLE IV
TacX-~ree Time vs. Time at 100C.
Time at 100C.(hrs.) TFT (min.) o . 10 .~ ., rxample 5 To 100 parts of a methyldimethoxy stopped ~olydi-methylsiloxane polymer of 150,000 centipoise at 25C. con-taining 0.6 percent by wei~ht di-n-hexylamine was added: -160 parts of a stearic acid treated calci D carbonate fi}ler, 3 parts of a cyclo.etrasiloxane treated fumed silica filler; 35 parts of a 100 centipoise trimethy}-siloxy dimethylpolysiloxane endstopped f~luid containing S00-1500 ppm silanol; 10 ~arts of a tri~unctional Cluid containing 20 mole percent o monometXylsiloxy units, 76 mole percent dimethylsiloxy units,~ar.d 4 mole percent tri-methylsiloxy units: and 0.2 parts of a trimethylolpro-~ane ~ropylene glycol ether to form a base compound.
~0 ~o 100 parts of this base compound W2S added 4.075 parts of a catalyst solution containing 2.5 ~arts of a ~ .
hexa~ethyldisilazane, O.S ~arts OI met-hyltrimethoxy silane, 1 paxt of a~inoethylaminopropyltrimethoxy silane . .
ând 0. 075 parts of dibutyltindiacetate. The results are in Table V-below.
-5~-'~ ' .

60Si-579 ~ 7 ._ . ~j".: .

TABLE V
Tack-free Time vs. Time at 100 DC. -Time at 100C.(hrs.l TFT ~Min.l 2~ 45 Exam~le 6 There was prepared a Base Composition X comprising 100 parts of a mixture A having in it 100 parts of a silanol-terminated dimethylpolysiloxane polymer having a viscosi.. y of 150,000 centipoise at 25C.; 160 parts of ste~ric acid treated calcium carbonate sold under the -name ~ydrocarb 95T which is the trade name of OMYA, Inc.
of Proctor, Vermont; 10 parts of a highly trifunctional polysiloxane fluid containing 20 mole percent of mono-lS methylsiloxy units, 76 mole percent of dimethylsiloxar.e - units and 4 mole percent of trimethylsiloxy units, and having a silanol content of .; weight percent silanol;
35 pa~ts of a trimethylsiloxy terminated dimethylpoly-siloxane linear fluid hav~ng a viscosity of 100 centi-~oise at 25C. and 3 par_s of octacyclotetrasiloxane treated fumed silica having a surface area of 200 ~eters square per gram. To 100 parts o~ this mixture A the.e was added .2 parts or acetic acid, .~ ?arts of di-~-he~yl-. . .

.. .. .. ._ 1____._ ... _._.. .............. _. . .. .................. ................. .

- -: . ..
- . .:: ' . ' - , .. .. - - . . . , . :
' : ' ' ` ~ . .: , ' .. ' ''.
. ` ' . .' .:

~~ 60Si-579 ~-~7~5~27 ~, amine and 2~7 parts of methyltrimethoxysilane.
The mixing was carried out under sub~tantially an-hydrous conditions. The resulting Composition X, once formed, was heated at 110C. for ~ifteen minutes under substantially anhydrous conditions to form the polyalkoxy-terminat~d dimethylpolysiloxane linear polymer having a viscosity of about 150,000 centipoise at 25C. To this :-base Composition X there was added under substantially ~ .
anhydrous conditions 1.0 parts of aminoethylaminopropyl-trimethoxysilane as the adhesion pramoter, .3 parts of dibutyl tin diacetate and 2.7 parts o~ a silazane dariva tive identified in Table VI below. Table VI below in-dicates the tack-free time of the composition after the composition was cured for 24 hours at room temperature ~-~
and arter it had been accelerated heat-aged at iO0C. ::
for 72 hours. There is also indicated the Short A, :
Durometer, the percent Elongation and the Tensile Strength of the sampies in Table VI. As the results in Table VI indicate,~the cyclic trisilazane was considerably :
superior in shelf stability to the hexamethylsilazane.
'.

-S6- ;.
,:' ~ ' :
, .: ~ . -: - - .~ .- . .. : ... . .:

oSi-57 9 ~o~27 ,~. -E ~

Q)s . ' .
_ ~ _, o ' ' ~ ~
. ~u~ ~' .~ o ~ .
s ,. ,, u~
~D
t:r ~ r~
~ o .~
P; E~ , .~ . . ..

~ o o s ~ ~
H U~

E~ ~ .
Ul .~ O
O ~ ~; ` .
O ~

.
o ~n " r~
\ /
. -- ~
O / \._~/ Z
.,1 ~--Z U~ --U~ ,_ ~1 Z _ O U~
O

..................... .... _.. _ .. __~ ~~_ ~__._ _.. = . = = . ...... . ......

, .. :- , : ~ ........... .. , .:

. - .. . . . ., . :

60Si-579 .;:
~2562~7 ~

Example 7 There was prepared a base Composition Z comprising 100 parts by weight of a dimethoxymethylsilyl-terminated polydimethylsiloxane polymer having a viscosity of 150,000 centipoise at 25C~ which had in it .S parts of di-n-hexylamine as a condensation catalyst. To this mixture, there was added 220 parts of the stearic acid treated calcium carbonate of Example 6; 2.5 parts of carbon black; 35 parts of a trimethylsiloxy-~erminated dimethyl-polysiloxane polymer having a viscosity of 100 centipoiseat 2~C., 10 parts by weight of a highly trifunctional fluid containing 3 mole percent of trimethylsiloxy mono-functional units, 20 mole percent of methylsiloxy tri-functional units, and 77 mole percent of dimethyl di~unc-tional siloxy units having a silanol content of .5 weight percent and a viscosity of 50 centipoise at 25C. To this . -there was added .2 parts of a thixotrope which lS a poly-ether sold under the trade name UCON-1145 by Union Carbide Corporation, Connecticut. The above base Composition Z
was mixed under su~stantially anhydrous conditions. To 100 parts of this base Composition Z there was added t~e various ingredients in the amounts indicated in Table VII
. below under substantially anhydrous conditions. The cyclo-.

~osi-s7s ~25~27 .. ~, ;:~ t !
trisilazane had the same formula as the silazane cyclotri-silazane in Example 6 above.
i TABLE VII

Sample A SamDle B

Base Composition Z 100 100 Methyltrimethoxysilane 0.5 0.5 AminDethylaminopropyltri- 1.0 1.0 methoxysilane Dibutyltindiacetate 0.07 0.07 Hexamethyldisilazane 2.5 Silazane Trimer --- 2.5 ' The physical properties of the A co~umn mixture of Table VII and the B CQlUmIl mixture of Table VII are indicated in Table VIII-below. There is qiven below in Table VIII
both the physical properties and the tack-free time after the sample had been cured for 24 hours at room temperature and after accelerated aging for 48 hours at lOO~C. The results are set forth in Table VIII below.
~' '-~, ~ ':

. . .
_59_ .
. ' i ~' .

....... ............. .. __.. ~.. _.. _.. .... .. __ . ........... _ _ _ ... ... _ .. _. .................. _ _.. . . ., .. ... ~ .. ... ........
.......... ...

.. . . . . ..

.

60Si-579 ~

~5~2Z7 u-.. ~ .

TABLE VIII
~ Sample B
Tack-free time, minutes 12 17 Shore A, hardness 30 30 Tensile Strength, psi 179 175 Elongation, ~ 380 275 50% modulus, psi 63 68 75% modulus, psi 76 79 100% modulus, psi 89 92 10 Accelerated Aging 48 hrs./10~C.
Shore A, hardness 36 38 Tensile Strength, psi 264 233 Elongation, % 330 310 50% modulus 70 74 - 15 75~ modulus 91 93 - 100~ modulus 113 111 . In Table VIII the 50%, 75~ and 100% Modul~s is the Modulus of the sample at those present Plongations of the samples.

-60- .

.- , - . , ~ , . ... . .

:

, - , - : . ~ :

6CSi-579 ~L~56~2~

~ .

As the data in Table VIII indicates, samples A and B had comparable physical p-operties. However, the cyclic silazanes generally is hypothesized and more specifically it is ~nown that the cyclic tri.silazane has two main ad-vantages o~er the linear hexamethyldisilazane. Thus, thehexamE~hy~a~sllazana appears t:o inhibit the cure of the compositicn when the total RTV composition is applied to a hiqh moisture-containing surface such as moist concrete, cement, or other masonry surfaces. This inhibition may also be experienced under high-temperature, high-humidi~y atmospheric conditions. Accordingly, under those conditions when the RTV composition is to be used, it is desirable that the scavenger in the system be a cyclic silazane, specifical-ly a cyclic trisilazane or cyclictetrasilazane or that there be a~ least some cyclicsilazane in the com?osition.
The other advantage of the cyclic silazanes over the linear silazanes that has been noticed at leas~
with the cyclictrisilazane/that th~ modulus of the cured composition does not vary with the thickness of the layer of the cured RTV composition. On the other hand, with linear silazanes and specificallv with hexamethyldisil~7.ane it has been noted the t~.icker the section of the RTV compo~ :~
sition, the lower the modulus and the thinner the layer of ~TV composition that is applied, the.highe~ the modulus ~5 of the cured c:omposition. :

61- ~ :
~'.

.',' . : - . . : ': ::. :, . -'', '- - . : . . . ' ~ , . . . .

60Si-579 5~227 , . ~ r-Accordingly, if this variation is a factor, then the cyclictrisilazanes should be present at least in some quantities as a scavenger in the RTV compositions of the present case.
In all other cases, it appears the linear silazanes and the cyclicsilazanes behave in similar manners to give the composition the properties that have been specified ~ -abo~e.

: ::

.

` -62- :
' . ~ . - - . . -. . - .. .. . ... ~ .-., ~ .. : ~-'., : - - . . ' -.. .. . . . .

Claims (90)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A stable, one-package, substantially anhydrous and substantially acid-free, room temperature vulcanizable organopolysiloxane composition stable under ambient conditions in the substantial absence of moisture over an extended period of time and convertible to a tack-free elastomer comprising: (1) an organopolysiloxane wherein the silicon atom at each polymer chain end is terminated with at least 2 alkoxy radicals; (2) an effective amount of a condensation catalyst; and (3) a stabilizing amount of silicon scavenger compound for hydroxy functional groups which is a silicon-nitrogen compound selected from the group consisting of (A) a silicon-nitrogen compound having the formula where Y is selected from R"' and R"2N- and (B) a silicon-nitrogen polymer comprising (1) from 3 to 100 mole percent chemically combined structural units selected from the group consisting of units having the formula and (2) from 0 to 97 mole percent chemically combined structural units represented by the formula where the silicon atoms of said silicon-nitrogen polymer are joined to each other by a member selected from a SiOSi linkage and a SiNR"Si linkage, the free valences of said silicon atoms other than those joined to oxygen to form a siloxy unit and nitrogen to form a silazy unit are joined to a member selected from an R"' radical and an (R")2N radical, and where the ratio of the sum of said R"' radicals and said (R")2N radicals to the silicon atoms of said silicon-nitrogen polymer has a value of 1.5 to 3, inclusive, and R" is a member selected from the group consisting of hydrogen, C(1-12) monovalent hydrocarbon radicals, and fluoroalkyl radicals, R"' is a member selected from the group consisting of hydrogen, monovalent hydro-carbon radicals and fluoroalkyl radicals, and c is a whole number equal to 0 to 3, inclusive.

2. The composition of claim 1 wherein there is present from 0.5 to 10 parts by weight of the silicon scavenger per 100 parts by weight of the organopolysiloxane.

3. The composition of claim 2 wherein the silicon scavenger is a cyclic silazane polymer of chemically combined units where R", R"' are as defined in claim 1 to provide for a ratio of 1.5 to 3.0 of the sum of the R"' and (R")2N radicals per silicon atom in said silazane polymer.

4. The composition of claim 2 wherein the silicon scavenger is a silazane polymer having at least one unit selected from the group consisting of units, and units where R", R"' are as defined in claim 1 to provide for a ratio of 1.5 to 3 of the sum of the R"' and (R")2N
radicals per silicon atom in said silazane polymer.

5. The composition of claim 2 wherein the silicon scavenger is a silazane polymer which is a linear polymer consisting essentially of units where R" and R"' are as defined in claim 1 to provide for a ratio of 1.5 to 3.0 of the sum of the R"' and (R")2N radicals per silicon atom in said silazane polymer.

6. The composition of claim 2 wherein the silicon scavenger comprises a silazane polymer having at least one unit selected from the group. consisting of units and units where R" and R"' are as defined in claim 1 to provide for a ratio of 1.5 to 3 of the sum of the R"' and (R")2N
radicals per silicon atom in said silazane polymer.

7. The composition of claim 2 wherein the silicon scavenger comprises a polymer having units selected from the group consisting of where R" and R'" are as defined in claim 1 to provide for a ratio of 1.5 to 3 of the sum of the R"' and (R")2N radicals per silicon atom in said polymer.

8. The composition of claim 2 wherein the silicon scavenger compound is a copolymer with up to 97 mole percent of units wherein the silicon-nitrogen units are selected from the group consisting of, where R" and R"', and c are as defined in claim 1 to provide for a ratio of the sum of R"' and (R")2N radicals per silicon atom of said copolymer of from 1.5 to 3.

9. The composition of claim 2 wherein the silicon scavenger compound is a cyclic polymer consisting of chemically combined (R"')2SiO units and units where R" and R"' are as defined in claim 1.

10. The composition of claim 2 wherein the silicon scavenger compound is selected from the group consisting of linear silazanes and cyclic silazanes having the formula where R" and R"' are as defined in claim 1, where n is 0 or an integer and is 0 to 20, inclusive, and d is a whole number equal to 0 to 1, inclusive, and where d is equal to 0, n is equal to 3 to 7, inclusive.

11. The composition of claim 2 wherein the silicon scavenger compound is a polysiloxane having the formula where R", R"' and n are as defined in claims 1 and 10 and Z is a member selected from the group consisting of R" and -Si(R"')3.

12. The composition of claim 2 wherein the silicon scavenger compound is hexamethyldisilazane.

13. The composition of claim 2 wherein the silicon scavenger compound is hexamethylcyclotrisilazane.

14. The composition of claim 2 wherein the silicon scavenger compound is octamethylcyclotetrasilazane.

15. The composition of claim 2 wherein the silicon scavenger compound has the formula [CF3CH2CH2(CH3)2Si]2NH.

16. The composition of claim 2 wherein the silicon scavenger compound has the formula [CF3CH2CH2(CH3)SiNH]3 .

17. The composition of claim 2 wherein the silicon scavenger compound is [CF3CH2CH2(CH3)2Si]2NCH3.
18. A stable, one-package, substantially anhydrous and substantially acid-free, room temperature vulcanizable organopolysiloxane composition stable under ambient conditions in the substantial absence of moisture over an extended period of time convertible to a tack-free elastomer comprising (1) an organopolysiloxane wherein the silicon atom at each polymer chain end is terminated with at least 2 alkoxy radicals; (2) an effective amount of a condensation catalyst; (3) a stabilizing amount of silicon scavenger compound for hydroxy functional groups, selected from the group consisting of A() a silicon-nitrogen compound having the formula

Claim 18 continued:
where Y is selec-ted from R"' and (R")2N- and (B) a silicon nitrogen polymer comprising (i) from 3 to 100 mole percent chemically combined structured units selected from the group consisting of units having the formula and (ii) from 0 to 97 mole percent chemically combined structural units represented by the formula where the silicon atoms of said silicon nitrogen polymer are joined to each other by a member selected from an SiOSi linkage and a SiNR"Si linkage, the free valences of said silicon atoms other than those joined to oxygen to form a siloxy unit and nitrogen to form a silazy unit are joined to a member selected from an R"' radical and (R")2N radical, and where the ratio of the sum of said R"' radicals and said (R")2N radicals to the silicon atoms of said silicon nitrogen polymer has a value of 1.5 to 3, inclusive, and R" is a member selected from the group consisting of hydrogen, C(1-12) monovalent hydrocarbon radicals, and fluoroalkyl radicals, R"' is a member selected from the group consisting of hydrogen, monovalent hydro-carbon radicals and fluoroalkyl radicals, and c is a whole number equal to 0 to 3, inclusive, and (4) an effective amount of a curing accelerator selected from the group consisting of substituted guanidines, amines and mixtures thereof.

19. The composition of claim 18 wherein there is present from 0.1 to 10 parts by weight of the silicon scavenger per 100 parts by weight of the organopolysiloxane.

20. The composition of claim 19 wherein the silicon scavenger is a cyclic silazane polymer is chemically combined units where R", R"' are as defined in claim 18 to provide for a ratio of 1.5 to 3.0 of the sum of the R"' and (R")2N radicals per silicon atom in said silazane polymer.

21. The composition of claim 19 wherein the silicon scavenger is a silazane polymer having at least one unit selected from the group consisting of units, and units where R", R"' are as defined in claim 18 to provide for a ratio of 1.5 to 3.0 of the sum of the R"' and (R")2N radicals per silicon atom in said silazane polymer.

22. The composition of claim 19 wherein the silicon scavenger is a silazane polymer which is a linear polymer consisting essentially of units where R" and R"' are as defined in claim 18 to provide for a ratio of 1.5 to 3.0 of the sum of the R"' and (R")2N radicals per silicon atom in said silazane polymer.

23. The composition of claim 19 wherein the silicon scavenger comprises a silazane polymer having at least one unit selected from the group consisting of units and units where R" and R"' are as defined in claim 18 to provide for a ratio of 1.5 to 3 of the sum of the R"' and (R")2N radicals per silicon atom in said silazane polymer.

24. The composition of claim 19 wherein the silicon scavenger comprises a polymer having units selected from the group consisting of units where R" and R"' are as defined in claim 18 to provide for a ratio of 1.5 to 3 of the sum of the R"' and (R")2N radicals per silicon atom in said polymer.

25. The composition of claim 19 wherein the silicon scavenger compound is a copolymer with up to 97 mole percent of units wherein the silicon-nitrogen units are selected from the group consisting of units where R" and R"' and c are as defined in claim 18 to provide for a ratio of the sum of R"' and (R")2N
radicals per silicon atom of said copolymer of from 1.5 to 3.

26. The composition of claim 19 wherein the silicon scavenger compound is a cyclic polymer consisting of chemically combined (R"')2SiO units and units where R" and R"' are as defined in claim 18.

27. The composition of claim 19 wherein the silicon scavenger compound is selected from the group consisting of linear silazanes and cyclic silazanes having the formula where R" and R"' are as defined in claim 18, where n is 0 or an integer and is 0 to 20, inclusive, and d is a whole number equal to 0 to 1, inclusive, and where d is equal to 9, n is equal to 3 to 7, inclusive.

28. The composition of claim 19 wherein the silicon scavenger compound is a polysiloxane having the formula where R", R"' and n are as defined in claim 18 and Z is a member selected from the group consisting of R" and -Si(R"')3.

29. A one-package, room temperature vulcanizable polyalkoxy-terminated organopolysiloxane composition in accordance with claim 1, where the polyalkoxy-terminated organopolysiloxane has the formula where R is a C(1-13) monovalent substituted or unsubstituted hydrocarbon radical, R1 is a C(1-8) aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano radicals, or a C(7-13) aralkyl radical, R2 is a C(1-3) monovalent substituted or unsubstituted hydrocarbon radical, b is a whole number equal to 0 or 1, and n is an integer having a value of from about 50 to about 2500 inclusive.

30. A room temperature vulcanizable composition in accordance with claim 1 having an effective amount of a cross-linking silane of the formula where R1 is a C(1-8) aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkyl-ester, alkylketone and alkylcyano radicals, or a C(7-13) aralkyl radical, R2 is a C(1-13) monovalent substituted or unsubstituted hydrocarbon radical, and b is a whole number equal to 0 or 1.

31. A room temperature vulcanizable composition in accordance with claim 1, where the silane scavenger is hexamethyldisilazane.

32. A room temperature vulcanizable composition in accordance with claim 1, which contains a tin compound as the condensation catalyst.

33. A stable, one-package, substantially anhydrous and substantially acid-free, room temperature vulcanizable composition of claim 1 comprising a poly-methoxy-terminated polydimethylsiloxane, an effective amount of a tin containing condensation catalyst, an effective amount of trimethoxysilylpropyltetramethyl-guanidine curing accelerator and a stabilizing amount of a hexamethyl disilazane.

34. A room temperature vulcanizable composition in accordance with claim 32 in which the tin compound is dibutyltindiacetate.

35. A room temperature vulcanizable composition in accordance with claim 32 containing a polymethoxysilane cross-linking agent.
36. A stable and substantially acid-free one-package room temperature vulcanizable polyalkoxy-terminated organopolysiloxane composition curable under ambient conditions to a tack-free elastomer over an extended period of time comprising on a weight basis (i) 100 parts of a substantially silanol-free polyalkoxysiloxydiorganopolysiloxane of the formula (ii) 0 to 10 parts of a cross-linking poly-alkoxysilane of the formula (iii) an effective of a condensation catalyst, (iv) a stabilizing amount of a silicon scavenger compound for hydroxy functional groups which is a silicon-nitrogen compound selected from the group consisting of (A) a silicon-nitrogen compound having the formula where Y is selected from R"' and R"2N- and (B) a silicon-nitrogen polymer comprising (1) from 3 to 100 mole percent chemically combined structural units selected from the group consisting of units having the formula Claim 36 continued:

and (2) from 0 to 97 mole percent chemically combined structural units represented by the formula where the silicon atoms of the silicon-nitrogen polymer are joined to each other by a member selected from an SiOSi linkage and a SiNR"Si linkage, the free valences of said silicon atoms other than those joined to oxygen to form a siloxy unit and nitrogen to form a silazy unit are joined to a member selected from an R"' radical and (R")2N radical, and where the ratio of the sum of said R"' radicals and said (R")2N
radicals to the silicon atoms of said silicon-nitrogen polymer has a value of 1.5 to 3, inclusive, where R" is a member selected from the group consisting of hydrogen, C(1-12) monovalent hydro-carbon radicals, and fluoroalkyl radicals, R"' is a member selected from the group consisting of hydrogen, monovalent hydrocarbon radicals and fluoroalkyl radicals, and c is a whole number equal to 0 to 3, inclusive, where R is a C(1-13) monovalent substituted or unsubstituted hydro-carbon radical, R1 is a C(1-8) aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano radicals, or a C(7-13) aralkyl radical,

Claim 36 continued:
R2 is a C(1-13) monovalent substituted or unsubstituted hydrocarbon radical, and b is a whole number equal to 0 or 1, and n is an integer having a value of from about 50 to about 2500 inclusive; and (v) 0 to 5 parts of a curing accelerator selected from the group consisting of substituted guanidines, amines and mixtures thereof.

37. A one-package room temperatuxe vulcanizable composition in accordance with claim 36, where R, R1 and R2 are methyl.

38. A one-package room temperature vulcanizable composition in accordance with claim 36, where the condensation catalyst is a tin compound.

39. A stable and substantially acid-free, one-package, room temperature vulcanizable composition of claim 36 comprising a polymethoxy-terminated polydimethylsiloxane, a polymethoxysilane, 0 to 5 parts of curing accelerator selected from the group consisting of substituted guanidines, amines and mixtures thereof, an effective amount of a tin compound condensation catalyst, and a stabilizing amount of a silane scavenger which is hexamethyl disilazane.

40. A one-package room temperature vulcanizable composition in accordance with claim 36 where the cross-linking polyalkoxysilane is methyltrimethoxysilane.

41. A room temperature vulcanizable polyalkoxy-terminated organopolysiloxane composition in accordance with claim 36 containing 0 to 5 parts of butyltetramethyl-guanidine.

42. A substantially acid-free room temperature vulcanizable composition of claim 36 comprising methyl-dimethoxysiloxy-terminated polymethylsiloxane, a reinforcing amount of octamethylcyclotetrasiloxane treated silica filler, an effective amount of dibutyltindiacetate condensation catalyst, 0 to 5 parts of trimethoxysilylpropyltetramethylguanidine and an excess of up to 3% by weight, based on the weight of the polydimethylsiloxane of hexamethyldisilazane.

43. A one-package, stable room temperature vulcanizable composition in accordance with claim 40, having as the scavenging silicon compound an excess of up to 3% by weight, based on the weight of the polydimethyl-siloxane of hexamethylcyclotrisilazane.

44. The composition of claim 36 wherein there is present from 0.5 to 10 parts by weight of the silicon scavenger per 100 parts by weight of the organopolysiloxane.
45. A method of making a one-package and substantially acid-free room temperature vulcanizable composition curable to the solid elastomeric state, which method comprises agitating under substantially anhydrous conditions at a temperature in the range of from 0°C to 180°C, a room temperature vulcanizable material selected from (i) a mixture comprising (A) 100 parts of a silanol-terminated poly-diorganosiloxane consisting essentially of chemically combined units of the formula (B) from 1 to 10 parts of an alkoxy-functional cross-linking silane of the formula (C) 0 to 5 parts of a curing accelerator selected from the group consisting of substituted guanidines, amines and mixtures thereof, (D) a stabilizing amount of silicon scavenger compound for hydroxy functional groups, selected from a silicon-nitrogen compound having the formula Claim 45 continued:
where Y is selected from R"' and (R")2N- and a silicon-nitrogen polymer comprising (1) from 3 to 100 mole percent chemically combined structural units selected from the group consisting of units having the formula and (2) from 0 to 97 mole percent chemically combined structural units represented by the formula where the silicon atoms of said silicon-nitrogen polymer are joined to each other by a member selected from an SiOSi linkage and a SiNR"Si linkage, the free valence of said silicon atoms other than those joined to oxygen to form a siloxy unit and nitrogen to form a silazy unit are joined to a member selected from an R"' radical and (R")2N radical, and where the ratio of the sum of said R"' radicals and said (R")2N radicals to the silicon atoms of said silicon-nitrogen polymer has a value of 1.5 to 3, inclusive, and R" is a member selected from the group consisting of hydrogen, C(1-12) monovalent hydrocarbon radicals, and fluoroalkyl radicals, R"' is a member selected from the group consisting of hydrogen, monovalent hydrocarbon radicals

Claim 45 continued:
and fluoroalkyl radicals, and c is a whole number equal to 0 to 3, inclusive; and (E) an effective amount of a condensation catalyst, and (ii) a mixture comprising (A) 100 parts of a polyalkoxy-terminated polydiorganosiloxane of the formula (B) 0 to 10 parts of a cross-linking silane of the formula (C) an effective amount of a condensation catalyst, (D) a stabilizing amount of the silicon scavenger for hydroxy functional groups of (i)(D), and (E) 0 to 5 parts of a curing accelerator selected from the group consisting of substituted guanidines, amines and mixtures thereof, where b is 0 or 1, inclusive, R is selected from C(1-13) monovalent substituted or unsubstituted hydrocarbon radicals, R1 is a C(1-8) aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkyl ester, alkylketone and alkylcyano radicals, or a C(7-13) alkaryl radical, R2 is a C(1-13) monovalent substituted or unsubstituted hydro-carbon radical.

46. The method of claim 45 wherein there is present from 0.5 to 10 by weight of the silicon scavenger compound per 100 parts by weight of the organopolysiloxane.

47. A method in accordance with claim 45 where the silicon scavenger is hexamethyldisilazane.

48. A method in accordance with claim 45 where the cross-linking silane is methyltrimethoxysilane.

49. A method in accordance with claim 45 where the condensation catalyst is a tin compound.

50. A mixture comprising (A) 100 parts of a silanol-terminated polydiorgano-siloxane consisting essentially of chemically combined units of the formula (B) 1 to 10 parts of a cross-linking silane of the formula (C) 0 to 5 parts of a curing accelerator selected from the group consisting of substituted guanidines, amines and mixtures thereof, (D) a stabilizing amount of a silicon scavenger compound of hydroxy functional groups selected from a silicon-nitrogen compound having the formula where Y is selected from R"' and (R")2N- and a silicon-nitrogen polymer comprising (1) from 3 to 100 mole percent chemically combined structural units selected from the group consisting of units having the formula and (2) from 0 to 97 mole percent chemically combined structural units represented by the formula where the silicon atoms of said silicon-nitrogen polymer are joined to each other by a member selected from an SiOSi linkage and a SiNR"Si linkage, the free valences of said silicon atoms other than those joined to oxygen to form a siloxy unit and nitrogen to form a silazy unit are joined to a member selected from an R"' radical and (R")2N radical, and where the ratio of the sum of said R"' radicals and said (R")2N radicals to the silicon atoms of said silicon-nitrogen polymer has a value of 1.5 to 3, inclusive, where R" is a member selected from the group consisting of hydrogen, C(1-12) monovalent hydrocarbon adicals, and fluoroalkyl radicals, R"' is a member selected from the group consisting of hydrogen, monovalent hydro-carbon radicals and fluoroalkyl radicals, and c is a whole number equal to 0 to 3, inclusive, and (E) an effective amount of a condensation catalyst, where R is selected from C(1-13) monovalent substituted or unsubstituted hydrocarbon radicals, R1 is a C(1-8) aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano radicals, or a C(7-13) aralkyl radical, R2 is a C(1-13) monovalent substituted or unsubstituted hydrocarbon radical, b is a whole number equal to 0 or 1.

51. The composition of claim 50 wherein there is present from 0.5 to 10 parts by weight of the silicon scavenger per 100 parts by weight of the organopolysiloxane.
52. In the method of making a substantially acid-free room temperature vulcanizable organopolysiloxane composition under substantially anhydrous conditions utilizing an effective amount of a condensation catalyst with a silanol-terminated organopolysiloxane and poly-Claim 52 continued:
alkoxysilane cross-linking agent, characterized in the improvement which comprises adding to the organopoly-siloxane mixture a stabilizing amount of a silicon scavenger compound which is a scavenger for hydroxy functional groups selected from (A) a silicon-nitrogen compound having the formula, where Y is selected from R"' and (R")2N- and (B) a silicon-nitrogen polymer comprising (1) from 3 to 100 mole percent chemically combined structural units selected from the group consisting of units having the formula and (2) from 0 to 97 mole percent chemically combined structural units represented by the formula where the silicon atoms of said silicon-nitrogen polymer are joined to each other by a member selected from an SiOSi linkage and a SiNR"Si linkage, the free valences of said silicon atoms other than those joined to oxygen to form a siloxy unit and nitrogen to form a silazy unit are joined to a member selected from an R"' radical and (R")2N radical, and where the ratio of the sum of said R"' radicals and said (R")2N radicals to the silicon atoms of said silicon-nitrogen polymer has a value of 1.5 to 3, inclusive, where R" is a member selected from the group con-sisting of hydrogen, C(1-12) monovalent hydrocarbon radicals,

Claim 52 continued:
and fluoroalkyl radicals, R"' is a member selected from the group consisting of hydrogen, monovalent hydrocarbon radicals and fluoroalkyl radicals, and c is a whole number equal to 0 to 3, inclusive and thereafter adding an effective amount of a condensation catalyst.

53. A method in accordance with claim 52 where the silane scavenger is hexamethyldisilazane.

54. A method in accordance with claim 52 using an effective amount of dibutyltindiacetate as the condensation catalyst.

55. In the method of making a substantially acid-free room temperature vulcanizable organopolysiloxane composition under substantially anhydrous conditions utilizing an effective amount of a condensation catalyst with an organopolysiloxane wherein the silicon atom at each polymer chain end is terminated with at least two alkoxy radicals, characterized in the improvement which comprises adding to said polyalkoxy-terminated organopoly-siloxane a stabilizing amount of a silicon scavenger compound for hydroxy functional groups, selected from (A) a silicon-nitrogen compound having the formula where Y is selected from R"' and (R")2N- and (B) a silicon-nitrogen polymer comprising from 3 to 100 mole percent chemically combined structural units selected from the group consisting of units having the formula and from 0 to 97 mole percent chemically combined structural units represented by the formula where the silicon atoms of said silicon-nitrogen polymer are joined to each other by a member selected from an SiOSi linkage and a SiNR"Si linkage, the free valences of said silicon atoms other than those joined to oxygen to form a siloxy unit and nitrogen to form a silazy unit are joined to a member selected from an R"' radical and (R")2N radical, and where the ratio of the sum of said R"' radicals and said (R")2N radicals to the silicon atoms of said silicon-nitrogen polymer has a value of 1.5 to 3, inclusive, where R" is a member selected from the group consisting of hydrogen, C(1-12) monovalent hydro-carbon radicals, and fluoroalkyl radicals, R"' is a member selected from the group consisting of hydrogen, monovalent hydrocarbon radicals and fluoroalkyl radicals, and c is a whole number equal to 0 to 3, inclusive, an effective amount of a condensation catalyst, whereby improved stability is achieved in the resulting room temperature vulcanizable organopolysiloxane composition.

56. The method of claim 55 where there is present from 0.5 to 10 parts by weight of the silicon scavenger per 100 parts by weight of the organopolysiloxane.

57. The method of claim 55 wherein the silicon scavenger is a cyclic silazane polymer of chemically comb units where R", R"' are as defined in claim 55 to provide for a ratio of 1.5 to 3.0 of the sum of the R"' and (R")2N radicals per silicon atom in said silazane polymer.

58. The method of claim 55 wherein the silicon scavenger is a linear silazane polymer having at least one unit selected from the group consisting of units and units where R", R"' are as defined in claim 55 to provide for a ratio of 1.5 to 3 of the sum of the R"' and (R")2N
radicals per silicon atom in said polymer.

59. The method of claim 55 wherein the silicon scavenger comprises a linear polymer consisting essentially of units where R" and R"' are as defined in claim 55 to provide for a ratio of 1.5 to 3.0 of the sum of the R"' and (R")2N radicals per silicon atom in said polymer.

60. The method of claim 55 wherein the silicon scavenger compound comprises a silazane polymer having at least one unit selected from the group consisting of units and units where R" and R"' are as defined in claim 55 to provide for a ratio of 1. 5 to 3 of the sum of the R"' and (R")2N radicals per silicon atom in said polymer. ~;/,

61. The method of claim 55 wherein the silicon scavenger compound comprises a polymer having units selected from the group consisting of units where R" and R"' are as defined in claim 55 to provide for a ratio of 1.5 to 3 of the sum of the R"' and (R")2N radicals per silicon atom in said polymer.

62. The method of claim 55 wherein the silicon scavenger compound is a copolymer with up to 97 mole percent of units wherein the silicon-nitrogen units are selected from the group consisting of where R" and R"' and c are as defined in claim 55 to provide for a ratio of the sum of R"' and (R")2N radicals per silicon atom of said copolymer of from 1.5 to 3Ø

63. The method of claim 55 wherein the silicon scavenger compound is a cyclic polymer consisting of chemically combined (R"')2SiO units and units where R" and R"' are as defined in claim 55.

64. The method of claim 55 wherein the silicon scavenger compound is selected from the group consisting of linear silazanes and cyclic silazanes having the formula where R" and R"' are as defined in claim 55 where n is 0 or an integer and is preferably 0 to 20, inclusive, and d is a whole number equal to 0 to 1, inclusive, and where d is equal to 0, n is preferably equal to 3 to 7, inclusive.

65. The method of claim 55 wherein the silicon scavenger compound is a polysiloxane having the formula where R", R"' and n are as defined in claim 55 and 64 and Z is a member selected from the group consisting of R" and -Si(R"')3.

66. The method of claim 55 wherein the silicon scavenger compound is hexamethyldisilazane.

67. A stable, one-package, substantially anhydrous and substantially acid-free, room temperature vulcanizable organopolysiloxane composition stable under ambient conditions in the substantial absence of moisture over an extended period of time and convertible to a tack-free elastomer comprising (1) an organopolysiloxane wherein the silicon atom at each polymer chain end is terminated with at least 2 alkoxy radicals; (2) an effective amount of a condensation catalyst; (3) a stabilizing amount of silane scavenger for hydroxy functional groups which is silyl amine of the formula where R" is a radical selected from the group consisting of hydrogen, and C(1-8) monovalent hydrocarbon radicals, R20 is selected from a C(1-8) monovalent hydrocarbon radicals, C(1-8) alkoxy radicals and fluoroalkyl radicals, and g is a whole number that varies from 1 to 3, h is a whole number that varies 0 to 2 and the sum of h + g does not exceed 3.

68. The composition of claim 67 wherein the silicon scavenger is methyl di(methylamino)silane.

69. The composition of claim 67 wherein the silane scavenger is tris(methylamino)silane.

70. The composition of claim 67 wherein the silane scavenger is methyl bis(diethylamino)silane.

71. A stable, one-package, substantially anhydrous and substantially acid-free, room temperature vulcanizable organopolysiloxane composition stable under ambient conditions in the substantial absence of moisture over an extended period of time and convertible to a tack-free elastomer comprising: (1) an organopolysiloxane wherein the silicon atom at each polymer chain end is terminated with at least 2 alkoxy radicals; (2) an effective amount of a condensation catalyst; (3) a stabilizing amount of silane scavenger for hydroxy functional groups which is a silyl amine of the formula where R" is a radical selected from the group consisting of hydrogen, and C(1-8) monovalent hydrocarbon radicals R20 is selected from C(1-8) monovalent hydrocarbon radicals, C(1-8) alkoxy radicals and fluoroalkyl radicals, and g is a whole number that varies from 1 to 3, h is a whole number that varies from 0 to 2 and the sum of g + h does not exceed 3; and (4) an effective amount of a curing accelerator selected from the group consisting of substituted guanidines, amines and mixtures thereof.

72. A room temperature vulcanizable composition in accordance with claim 67 having an effective amount of a cross-linking silane of the formula where R1 is a C(1-8) aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano radicals, or a C(7-13) aralkyl radical, R2 is a C(1-13) monovalent substituted or unsubstituted hydrocarbon radical, and b is a whole number equal to 0 or 1.

73. A room temperature vulcanizable composition in accordance with claim 72 which contains a tin compound as the condensation catalyst.

74. A stable and substantially acid-free, one-package room temperature vulcanizable polyalkoxy-terminated organopolysiloxane composition curable under ambient conditions to a tack-free elastomer over an extended period of time comprising on a weight basis, (i) 100 parts of a substantially silanol-free polyalkoxysiloxydiorganopolysiloxane of the formula (ii) 0 to 10 parts of a cross-linking polyalkoxy-silane of the formula (iii) an effective amount of a condensation catalyst, and (iv) a stabilizing amount of a silane scavenger for hydroxy functional groups which is a silyl amine of the formula where R" is a radical selected from the group consisting of hydrogen, and C(1-8) monovalent hydrocarbon radicals, R20 is selected from C(1-8) monovalent hydrocarbon radicals C(1-8) alkoxy radicals and fluoroalkyl radicals and g is a whole number that varies from 1 to 3, h is a whole number that varies from 0 to 2 and the sum of h + g does not exceed 3, where R is a C(1-13) monovalent substituted or unsubstituted hydrocarbon radical, R is a C(1-8) aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano radicals, or a C(7-13) aralkyl radical, R2 is C(1-13) monovalent substituted or unsubstituted hydrocarbon radical and b is a whole number equal to 0 or 1, and n is an integer having a value of from about 50 to about 2500 inclusive;
(v) 0 to 5 parts of a curing accelerator selected from the group consisting of substituted guanidines, amines and mixtures thereof.

75. A substantially acid-free room temperature vulcanizable composition of claim 74 comprising methyl-dimethoxysiloxy terminated polydimethylsiloxane, a reinforc-ing amount of octamethylcyclotetrasiloxane treated silica filler, an effective amount of dibutyltindiacetate condensation catalyst, a cure accelerating amount of trimethoxysilylpropyltetramethylguanidine and an excess of up to 3% by weight, based on the weight of the polydimethylsiloxane of methyl di(methylamino)silane.

76. A room temperature vulcanizable composition in accordance with claim 75 having up to 10 parts of methyltrimethoxysilane per 100 parts of the polydimethylsi-loxane.
77. A method of making a one-package and substan-tially acid-free room temperature vulcanizable composition curable to the solid elastomeric state, which method comprises agitating under substantially anhydrous conditions at a temperature in the range of from 0°C to 180°C a room temperature vulcanizable material selected from (i) a mixture comprising (A) 100 parts of a silanol-terminated polydiorganosiloxane consisting essentially of chemically combined units of the formula

Claim 77 continued:

(B) 1 to 10 parts of cross-linking silane of the formula (C) 0 to 5 parts of a curing accelerator selected from the group consisting of substituted guanidines, amines and mixtures thereof;
(D) a stabilizing amount of a silane scavenger for hydroxy functional groups which is a silyl amine of the formula where R" is a radical selected from the group consisting of hydrogen and C(1-8) monovalent hydrocarbon radicals, R20 is selected from the group consisting of C(1-8) monovalent hydrocarbon radicals, C(1-8) alkoxy radicals and fluoroalkyl radicals and g is a whole number that varies from 1 to 3, h is a whole number that varies from 0 to 2 and the sum of g + h does not exceed 3;
and (E) an effective amount of a condensation catalyst, and (ii) a mixture comprising (A) 100 parts of a polyalkoxy-terminated polydiorganosiloxane of the formula (B) 0 to 10 parts of a cross-linking silane of the formula (C) an effective amount of a condensation catalyst, (D) a stabilizing amount of the silicon scavenger for hydroxy functional groups of (i)(D), and (E) 0 to 5 parts of a curing accelerator selected from the group consisting of substituted guanidines, amines and mixtures thereof, where R is selected from C(1-13) monovalent substituted or unsubstituted hydrocarbon radicals, R1 is a C(1-8) aliphatic organic radical selected from the group consisting of alkyl, alkylether, alkylester, alkylketone and alkylcyano radicals, or a C(7-13) alkaryl radical, R2 is a C(1-13) monovalent substituted or unsubstituted hydrocarbon radical, b is a whole number equal to 0 or 1, n is an integer having a value of from about 50 to about 2500 inclusive.

78. A mixture comprising (i) 100 parts of a silanol-terminated polydiorgano-siloxane consisting essentially of chemically combined units of the formula (ii) 1 to 10 parts of a cross-linking silane of the formula (iii) 0 to 5 parts of a curing accelerator selected from the group consisting of substituted guanidines, amines and mixtures thereof, (iv) a stabilizing amount of a silane scavenger for hydroxy functiona] groups which is a silyl amine of the formula where R" is a radical selected from the group consisting of hydrogen, and C(1-8) monovalent hydrocarbon radicals, R20 is selected from C(1-8) monovalent hydrocarbon radicals,C(1-8) alkoxy radicals and fluoroalkyl radicals, and g is a whole number that varies from 1 to 3, h is a whole number that varies from 0 to 2 and the sum of g + h does not exceed 3, (v) an effective amount of a condensation catalyst, and where R is selected from C(1-13) monovalent substituted or unsubstituted hydrocarbon radicals, R1 is a C(1-8) aliphatic organic radical selected from the group consisting of alkyl,alkylether, alkylester, alkylketone, and alkylcyano radicals, or a C(1-13) aralkyl radical, R2 is a C(1-13) monovalent substituted or unsubstituted hydrocarbon radical, b is a whole number equal to 0 or 1.

79. In the method of making a substantially acid-free room temperature vulcanizable organopolysiloxane composition under substantially anhydrous conditions utilizing an effective amount of a condensation catalyst with a silanol-terminated organopolysiloxane and a poly-alkoxysilane cross-linking agent, the improvement which comprises added to the organopolysiloxane mixture and a stabilizing amount of a silyl amine of the formula where R" is a radical selected from the group consisting of hydrogen, and C(1-8) monovalent hydrocarbon radicals, R2 is selected from a C(1-8) monovalent hydrocarbon radical,C(1-8) alkoxy radicals and fluoroalkyl radicals, and g is a whole number that varies from 1 to 3, h is a whole number that varies from 0 to 2 and the sum of g + h does not exceed 3, and thereafter adding an effective amount of condensation catalyst, whereby improved stability is achieved in the resulting room temperature vulcanizable organopolysiloxane composition.

80. In the method of making a substantially acid-free room temperature vulcanizable organopolysiloxane composition under substantially anhydrous conditions utilizing an effective amount of a condensation catalyst with an organopolysiloxane wherein the silicon atom at each polymer chain end is terminated with at least two alkoxy radicals, the improvement which comprises adding to said polyalkoxy-terminated organopolysiloxane (1) a stabilizing amount of a silane scavenger for hydroxy functional groups which is a silyl amine of the formula where R" is a radical selected from the group consisting of hydrogen, and C(1-8) monovalent hydrocarbon radicals, R20 is selected from C(1-8) monovalent hydrocarbon radicals, C(1-8) alkoxy radicals and fluoroalkyl radicals, g is a whole number that varies from 1 to 3, h is a whole number that varies from 0 to 2 and the sum of g + h does not exceed 3, and (2) an effective amount of a condensation catalyst, whereby improved stability is achieved in the resulting room temperature vulcanizable organopolysiloxane composition, and (3) optionally adding before or with the scavenger an effective amount of a curing accelerator selected from the group consisting of substituted guanidines, amines and mixtures thereof.

81. A room-temperature vulcanizable composition in accordance with claim 30, where the cross-linking silane is methyltrimethoxysilane, the condensation catalyst is dibutyltindiacetate or dibutyltindilaurate, and the curing accelerator is di-n-hexylamine or di-n-butylamine.

82. A one-package room-temperature vulcanizable composition in accordance with claim 38, where the tin compound is dibutyltindiacetate or dibutyltindilaurate, the cross-linking silane is methyltrimethoxysilane and the curing accelerator is di-n-hexylamine or di-n-butylamine.

83. A one-package room-temperature vulcanizable composition in accordance with claim 40, where the tin compound is dibutyltindiacetate or dibutyltindilaurate, and the curing accelerator is di-n-hexylamine or di-n-butylamine.

84. A method in accordance with claim 36, using an effective amount of metnyltrimethoxysilane, and an effective amount of di-n-hexylamine or di-n-butylamine as the curing accelerator.

85. A method in accordance with claim 55 using an effective amount of dibutyltindilaurate as the conden-sation catalyst.

86. A method in accordance with claim 85, using an effective amount of methyltrimethoxysilane and an effective amount of di-n-hexylamine or di-n-butylamine as the curing accelerator.

87. A room temperature vulcanizable composition in accordance with claim 72, where the cross-linking silane is methyltrimethoxysilane, the condensation catalyst is dibutyltindiacetate or dibutyltindilaurate, and the curing accelerator is di-n-hexylamine or di-n-butylamine.

88. A one-package room temperature vulcanizable composition in accordance with claim 74 where the tin compound is dibutyltindiacetate or dibutyltindilaurate, the cross-linking silane is methyltrimethoxysilane and the curing accelerator is di-n-hexylamine or di-n-butylamine.

89. A method in accordance with Glaim 80, using an effective amount of methyltrimethoxysilane, and an effective amount of di-n-hexylamine or di-n-butylamine as the curing accelerator.

90. A method in accordance with claim 80, using an effective amount of dibutyltindilaurate as the condensation catalyst.