CA2165580A1 - Allyl- and xylyl-amine containing elastomers and products having reduced hysteresis - Google Patents

Abstract

An anionic polymerization initiator includes the C-lithio reaction product of an organolithium compound and a tertiary-amino allyllithium or a tertiary-amino xylyllithium. When used in an anionic polymerization, a functional group from the initiator is incorporated onto the head of the growing polymer and a lithium atom is incorporated at the "living" end of the polymer chain prior toquenching. The initiator may be used to polymerize a monomer(s) including diolefin monomers, monovinyl aromatic monomers and trienes, and the living ends of the polymers are effectively maintained even at temperatures of up to 300°F
and higher. Such polymers exhibit an increased efficiency in coupling termination reactions, and products prepared from such polymers exhibit improved hysteresis characteristics. Products such as tires and the like can be prepared from such polymers and from vulcanizable elastomer compositions employing the polymers.

Description

~165S80 -ALLYL- AND XYLYL-AMINE CONTAINING
EIASTOMERS AND PRODUCTS HAVING
REDUCED HYSTERESIS

TECHNICAL FIELD
The subject invention relates to the anionic polymerization of diene polymer and copolymer elastomers. More particularly, the present invention relates to anionic polymerization employing an' amine-containing initiator compound. The amine initiator is a tertiary-amino allyllithium or a tertiary-amino 1 0 xylyllithium.
Diene polymers and copolymers prepared according to the present invention, have reduced hysteresis characteristics. Articles such as tires, power belts and the like prepared from these polymers exhibit increased rebound, decreased rolling resistance and less heat build-up during mechanical stress operations. Further, the present initiators allow poly"lcr;~ations to be run at high - temperatures which is useful, for example, in promoting subsequent termination reactions such as coupling, or additions of hysteresis-reducing terminal groups.
BACKGROUND OF THE INVENTION
In the art it is desirable to produce elastomeric compounds exhibiting reduced hysteresis. Such elastomers, when compounded to form articles such as tires, power belts and the like, will show an increase in rebound, a decreased rolling resistance and less heat build-up when mechanical stresses are applied.
Previous attempts at preparing reduced hysteresis compounds have included high temperature mixing of the filler-rubber mixtures in the presence of selectively-reactive promoters to promote compounding material reinforcement;
surface oxidation of the compounding materials; chemical modifications to the terminal end of polymers using tetramethyldiaminobenzophenone (Michler's ketone), tin coupling agents and the like and, surface grafting thereon. All of these approaches have focused upon increased interaction between the elastomer and the compounding materials.
It has also been recognized that carbon black, employed as a reinforcing filler in rubber compounds, should be well dispersed throughout the 9312059 FIR.P.US0098 - 216~580 rubber in order to improve various physical properties. One example of the recognition is provided in published European Pat. Appln. EP 0 316 255 A2 which discloses a process for end capping polydienes by reacting a metal terminated polydiene with a capping agent such as a halogenated nitrile, a heterocyclic 5 aromatic nitrogen-containing compound or an alkyl benzoate. Additionally, the application discloses that both ends of th,e polydiene chains can be capped withpolar groups by utilizing functionalized initiators, such as lithium amides.
The present invention provides novel initiators for anionic poly.~llel;~ation, to form elastomers with functional groups derived from said 1 Q initiators. The functional groups are incorporated into the polymer chain providing improved dispersability of carbon black throughout the elastomeric composition during compounding. As wiil be described hereinbelow, these initiators are compounds containing a moiety derived from a tertiary-amino allyllithium or a tertiary-amino xylyllithium.
Organolithium polymerization initiators are also known in the art. For example, U.S. Pat. No. 3,326,881 discloses phenyllithium initiator and U.S. Pat.No. 3,439,049 discloses an organolithium initiator prepared from a halophenol ina hydrocarbon medium. Phenyllithium initiators have proven to be unstable.
U.S. Pat. No. 4,015,061 is directed toward amino-functional initiators which polymerize diene monomers to form mono- or di-primary aryl amine-terminated diene polymers upon acid hydrolysis.
U.S. Pat. No. 4,914,147 discloses terminal modifying agents including dialkylamino-substituted aromatic vinyl compounds such as N,N'-dimethylamino benzophenone and p-dimethylamino styrene, in rubber compositions having reduced hysteresis characteristics. In U.S. Pat. No. 4,894,409, an am;no group-containing monomer, such as 2-N,N-dimethylaminostyrene is polymerized to form an amino group~ontaining diene based polymer.
It is also known in the art to conduct polymerizations employing hydrocarbon lithium initiators at high temperatures. However, elevated temperatures make it more difficult to maintain the "living" ends or the polymer-lithium bonds needed for efficient polymerization and termination reactions. With 9312059 FIR.P.US0098 known initiators it has been found that the lithium constituent will often combine with an available alpha-hydrogen atom, resulting in lithium hydride, especially at elevated temperatures, thereby destroying the initiator and causing additional harmful side reactions. Hence, high temperature polymerizations have proven to 5 be difficult to maintain and difficult to terminate efficiently.
A need exists therefore, for ~ polymerization initiator which when employed in an anionic pol~---eri~ation, will result in a polymer chain having afunctional group derived from the initiator. A need also exists for such an initiator which will perform effectively at high temperatures resulting in narrow molecular 10 weight distribution polymers and retention of "living" ends.

SUMMARY OF INVENTION
It is therefore an object of the present invention to provide anionic poly...~r;~alion initiators which promote the incorporation of functional, active 15 groups in the polymer chain.
It is another object of the present invention to provide a method of preparing an anionic poly...e.;~dtion initiator.
It is another object of the present invention to provide a functionalized polymer.
It is still another object of the prese.. t invention to provide a method for the preparation of a functionalized polymer and for the polymerization of the polymer at high temperatures.
At least one or more of the foregoing objects together with the advantages thereof over the existing art, which shall become apparent from the 25 specification which follows, are accomplished by the invention as hereinafter described and claimed.
In ~eneral an anionic polyme~ization initiator of the present invention comprises the metalation product of an organo lithium compound and a tertiary-amino compound having a general formula selected from 9312059 FIR.P.US0098 R

.
and - (~)x ~

i.
where R1 and R2 are the same or different and are selected from alkyls, cycloalkyls and aralkyls having from about 1 to about 12 carbon atoms; R3 is a group selected from allyl, 2-methallyl and xylyl; R4 is a carbocyclic group of from 20 about 3 to about 20 ,~elhylene groups; each Rs is an alkyl having from about 1 to about 20 carbon atoms; and x is an integer of from about 0 to about 10.
There is also provided a method of preparing an anionic poly.ner;~ation initiator, which comprises reacting an organo lithium compound with a tertiary-amino compound having a general formula selected from Rl\
, ~N--R3 9312059 FIR.P.US0098 ~ 2165~8~

and (Rs)x >~

S ~

where R1~ R2~ R3~ R4, Rs and x are as des~ibel hereinabove.
A polymer according to the invention com~,r;ses a polymer chain having the general formula R6-polymer-L; prior to quenching; wherein R6 ;s a functionalgroup derived from a ,~cly~..eli~ation initiator having a general formula selected 15 from Rl~
~N--R'3--Li and ~RS~

R4 N--R'3--Li 931211S9 FIR.P.US0098 - 21~80 where R1, R2, R4, Rs and x are as des~,;l,ed here;nabove and R'3 is formed by removing a hydrogen atom from the aforedescr;bed R3 group.
A method according to the invention for preparing a polymer comprises initiating polymerization of at least one n~ono,.,er selected from diolefin monomers S having from about 4 to about 12 carbon atoms, monovinyl aromatic monomers having from about 8 to about 20 carbon a~oms, and trienes, in the presence of a polymerization initiator having a general formula selected from 1 0 P`l\
N--R'3--Li 1 5 and ~s)~
f R4 N--R'3--Li ~0 ~

wherein R1, R2, R'3, R4, Rs and x are as described hereinabove.
PREFERRED MODE FOR CARRYING OUT THE INVENTION
As will become apparent from the description which follows, the present invention provides a novel lithio amine initiator for anionic polymerization of diene homopolymer and copolymer elastomers. Polymer molecules prepared 30 with these initiators contain a functional group, and it has been discovered herein that vulcanizable elastomeric compounds and articles thereof made from such q~1 70cn FIR.P.US0098 functionalized polymer molecules exhibit useful properties, particularly, reduced hysteresis. When compounded to make products such as tires, power belts and the like, these polymeric products of this invention exhibit increased rebound, decreased rolling resistance and less heat build-up during periods of applied 5 mechanical stress.
It has been further unexpectedly found that polymerizations employing initiators according to the invention can be conducted at elevated temperatures as high as the peak temperatures resulting from the exothermic polymerization reactions, such as from about 120F to ablo`ut 300F (about 49C to about 149C), 10 or even higher temperatures. It is theorized that because the invention initiators either have no alpha-hydrogens proximate the lithium atom, or because the alpha-hydrogens are bonded to a carbon atom having a double bond, such~ as when the alpha hydrogen is bonded to a vinyl carbon, there is a reduced tendency for the lithium constituent of the initiator to be eliminated as lithium hydride.
15 Furthermore, the lithium amide functionality, which is a likely promoter of side reactions, is absent in the present initiators. Hence, the living ends of the - polymers are effectively maintained even at high temperatures. It is to be appreciated that polymerizations conducted at such elevated temperatures result in more efficient polymerizations and improved termination reactions, including 20 improved monomer randomization and improved coupling ability of the polymers.The initiators according to the present invention are amine-containing compounds. More particularly, the initiators according to the present invention are C-lithio allyl- or xylyl-amines having one or the other of the following general formulas:

Rl~
~N--R'3--Li 9~12059 FIR.P.US0098 -- 216~5~0 and (Rs)~
R4 N--R'3--Li where R1 and R2 are the same or different and cari be, for example, alkyls having from 1 to about 12 carbon atoms, cycloalkyls having from 3 to about 14 carbon atoms, and aralkyls having from 6 to about 20 carbon atoms. R'3 is derived by removal of a hydrogen atom from an allyl, Z-methallyl, or a xylyl group, and R4 contains from about 3 to about 20 methylene groups to form a cyclic amine group.The cyclic amines are preferred, and further, of the xylyl amines, ortho-xylyls are 15 preferred. Such ortho-xylyl amines can be depicted as:

RIR2NCH2~3 LiC~

and (Rs)~
~ J--CH~

The methylene groups in R4 can be substituted with preferably an alkyl Rs, having 30 from about 1 to about 20 carbon atoms. Either none, a part or all of the methylenes in R4 may be substituted, and hence, "x" is an integer of from 0 to q~12~ IR.P.US0098 2165~80 about 20. When x is 0, all the methylenes are -CH2- groups; when x is 1, one of the methylenes is a -CHR4 or the like. Examples of initiators with substituted R4 methylenes include >~CH3 ~ J~CH, 1 0 ll (where R4 is a pentamethylene and x is 3) ~CH3 R'3 li (where R4 is pentamethylene and x is 1) and the like.
The initiators according to the present invention are preferably the metalation reaction product of an organolithium compound and an allyl- or xylyl-amine compound. One preferred class of organolithium compounds has the general formula RLi, where R is selected from the group consisting of alkyls andcycloalkyls having from about 1 to about 20 carbon atoms. Typical alkyls include30 n-butyl, s-butyl, methyl, ethyl, isopropyl and the like. The cycloalkyls include cyclohexyl, menthyl and the like. It has been found, that at least certain of the 9~12059 FIR.P.US0098 _ 216S580 ~o metalated iniliators according to the invention, are more stable than lithium amide in;tiators as will be demonstrated l,erei.-below.
As stated above, the organolithium compound is reacted with a an allyl, 2-methallyl or xylyl-amine compound, such as one of those having the following S general structure:
r' Rl~
~R ~N--R3 or 1 5 (RS)~C
>~

where R1, R2, R3, R4, Rs and x are as defined hereinabove. The metalation reaction forming the initiators of this invention can, thus, be depicted as:

Rl\ Rl\
RLi + ~N--R3 ~ N--R'3--Li ~ RH

9312059 FIR.P.US0098 CH
wherein R3 is an allyl (-CH2CH = CH2), methallyl(~H2-CCH3) or xylyl (-CH2PhCH3) group, or the like; R, R1, R2, R3 and R'3 are as described hereinabove; and Ph is a phenyl group.
Examples of useful initiators include hexamethyleneimino-o-xylyllithium (HMl-XyLi),pyrrolidino-o-xylyllithium(Py-XyLi)~piperidino-o-xylyllithium(pip-xyLi)~
hexamethyleneimino-methallyllithium (HMI-MAl;i), hexamethyleneimino-allyllithium (HMI-AlLi) and N,N-dioctylamino-allyllithium (DOA-MAlLi).
The initiator according to the present invention can be prepared by 10 forming a solution of the allyl- or xylyl-amine compound in an anhydrous, aprotic solvent, such as cyclohexane or hexane. To this solution is then added the organolithium compound (RLi) in the same or a similar solvent. Both are allowed to react for approximately one to 24 hours at ambient temperature (25C to 30C). The metalation process is facilitated by additions of small amounts of an15 aprotic polar solvent such as an ether such as tetrahydrofuran (THF) in an amount of about 1 to about 40 mM THF per mM Li, with about 2-10 mM of THF being prefel . ed. Amounts of the two reactants range from about 1.0 moles of the amine compound to about 1.0 to about 1.4 moles of organolithium compound, with a slight excess (5-10 molar percent) of organolithium being preferred. It is to be20 appreciated by one skilled in the art that various reaction temperatures and times may be useful and are within the scope of the present invention. Furthermore, other polar aprotic solvents such as tertiary amines and various other ethers may be added to give a soluble catalyst and enhanced metalation.
The initiator thus prepared, is employed to polymerize any anionically-25 polymerizable monomer to yield a polymer elastomer. Typically the initiator isused to polymerize unsaturated hydrocarbon monomers such as butadiene, isoprene and the like, and copolymers thereof with monovinyl aromatics such as styrene, alpha methyl styrene and the like, or trienes such as myrcene. Thus, the elastomers include diene homopolymers from monomer A and copolymers thereof 30 with monovinyl aromatic monomers B. Exemplary diene homopolymers are those prepared from diolefin monomers having from 4 to about 12 carbon atoms.

9312059 FIR.P.US0098 ~ 2165580 Exemplary vinyl aromatic copolymers are those prepared from monomers having from 8 to about 20 carbon atoms. Preferred elastomers include diene homopolymers such as polybutadiene and polyisoprene and copolymers such as styrene butadiene rubber (S8R). Copolymers can comprise from about 99 to 20-5 percent by weight of diene units and from about 1 to about 80 percent by weightof monovinyl aromatic or triene units, totalling 100 percent. The polymers and copolymers of the present invention may have 1,2-microstructure contents rangingfrom about 10 to about 80 percent, with the preferred polymers or copolymers having 1,2-microstructure contents of from about 25 to 65 percent, based upon~
10 the diene content.
The copolymers are preferably random copolymers which result from simultaneous copolymerization of the monomers A and B as is known in the art.
The block copolymers, poly (~-B-_-A-b-B), result from the separate polymerization of the monomers forming the A and B polymers as is known in the art. Often, 15 such block copolymers which include poly(~-styrene-b-butadiene-b-styrene) are thermoplastic elastomers, sometimes referred to as S-B-S polymers.
The initiators of the present invention form "living polymers" from the foregoing monomers, the general formula of which prior to quenching is R6 - polymer - Li where the polymer is any of the foregoing diene homopolymers, monovinyl aromatic homopolymers, diene/monovinyl aromatic random copolymers and block copolymers and R6 is a functional group derived from the initiator. Thus, the 25 polymers of this invention, R6-polymer Li, can also be represented by the following formulas:

Rl~ ICI H2 ~N--CH2-C--CH2--polyme~Li 9312059 FIR.P.US0098 - 216~0 (R5)x cl H2 R4 N--CH2-C~H2--polyme~Li .
s r ~ . _ Rl~
~N-CHcCH~CH2-polymer Li R,~
N-CH PlYme~Li ICl H

(Rs)x >~
R4 N--CH=CH--CH2--polyme~Li 9312059 FIR.P.US0098 21~5580 .
_, ~s)~c R4 N--CH--Polyme~Li \ ~/ CH - -"

, . .. ... ~ ~ = . . .

Rl~
N--CH2.
~1 Li--PlYme~CH2 or (Rs)~c [~

CH2--PolYme~Li 9312059 FIR.P.US0098 where polymer, R1, R2, R4, Rs and x are as defined hereinabove and Li is a lithium atom bonded to a carbon atom. The lithium proceeds to move down the growing chain polymer, as poly...er;~ation continues, until the reaction is quenched.
Polymerization is usually conducted in a conventional solvent for anionic polymerizations such as hexane, cyclohexane, benzene and the like. Othertechniques for pol~llle. ;~alion, such as semi-batch and continuous polymerization may be employed. In order to promote randomization in copolymerization and to incf~a~e v;nyl content, a polar coordinator may optionally be added to the polymerization ingredients. Amo~nts range between 0 to 90 or more equivalents per equivalent of lithium. The amount depends upon the type of polar coordinatorthat is employed, the amount of Yinyl desired, the level of styrene employed andthe temperature of the pol~..,er;~dlions, as well as the selected initiator.
Compounds useful as polar coordinators are organic and include tetrahydrofuran, linear and cyclic oli~me,;c oxolanyl alkanes such as 2-2'-di(tetrahydrofuryl) propane,2,2-bis (tetrahydrofuryl) propane, di-piperidyl ethane, ht:~a"~etl~rlphosphoramide~ N-N'~Ji.-,.ll"rlpip~ ;,.e, diazabicyclooctane, dimethyl ether, diethyl ether,- tributylamine and the like. The linear and cyclic oligomeric oxolanyl alkane polar coordinators are described in U.S. Pat. No. 4,429,091 the subject matter of which regarding polar co-ordinators is incorporated herein by reference. Other compounds useful as polar coordinators include those having an oxygen or nitrogen hetero-atom and a non-bo.,d~d pair of electrons. Examples include dialkyl ethers of mono and oligo alkylene glycols; "crown" ethers; tertiary amines such as tetramethylethylene diamine (TMEDA).
Polymerization is begun by charging a blend of the monomer(s) and solvent to a suitable reaction vessel, followed by the addition of the polar coordinator and the initiator solution previously described. The procedure is carried out under anhydrous, anaerobic conditions. Often, it-is conducted under a dry, inert gas atmosphere. The polymerization can be carried out at any convenient temperature such as 32F (0C) to 300F (149C). For semi-batch polymerizations, temperatures of at least about 180F (82C) are preferred. For 9312059 FlR.P.US009o - 216~80 batch polymerizations, it is preferred to maintain the peak temperature at from about 120F to about 300F (about 49C to about 149C), and more preferably from about 180F to about 250F (about 82C to about 121C). Polymerization is allowed to continue under agitation for about 0.15 to 24 hours. After 5 polymerization is complete, the product is terminated in one or more ways.
For example, a protic quenching agent may be employed to give a monofunctional polymer chain. Quenching may be conducted in water, steam or an alcohol such as isopropanol, or any other suitable method. Quenching may also ~e conduct~d with a functional terminating agent, resulting in a difunctional 10 polymer. Compounds providing terminal functionality (e.g., "endcappingn) can be used such as tin tetrachloride, (R7)3SnCI, (R7)2Sncl2, R7SnCI3, carbodiimides, N-cyclic amides, N,N' disubstituted cyclic ureas, cyclic amides, cyclic ureas, isocyanates, Schiff bases, 4,4'-bis(diethylamino) benzophenone, and the like. Tin tetrachloride is preferred. The organic moiety R7 is selected from the group 15 consisting of alkyls having from about 1 to about 20 carbon atoms, cycloalkyls having froni about 3 to about 20 carbon atoms, aryls having from about 6 to about 20 carbon atoms and aralkyls having from about 7 to about 20 carbon atoms.
Typical alkyls include n-butyl, s-butyl, methyl, ethyl, isopropyl and the like. The cycloalkyls include cyclohexyl, menthyl and the like. The aryl and aralkyl groups 20 include phenyl, benzyl and the like. Prefel,ed endcapping agents are selectedfrom the group consisting of tin tetrachloride, tributyl tin chloride, dibutyl tin dichloride and 1,3-dimethyl-2-imidazolidinone.
While terminating to provide a functional group on the terminal end of the polymer is preferred, it is further preferred to terminate by a coupling 25 reaction, with for example, tin tetrachloride or other coupling agent such assilicon tetrachloride (SiC4), esters and the like. As stated above, it has been found that the invention initiators provide for polymers having living ends maintainedthereon. This allows effective and efficient tin coupling using tin tetrachloride, which results in a polymer having improved processability and resistance to hot 30 and cold flow. It is preferred that the polymers according to the present invention have at least about 40 percent tin coupling. That is, about 40 percent of the 9312059 FIR.P.US0098 polymer mass after coupling is of higher molecular weight than the polymer before coupling as measured, for example, by gel pel"-~tion chromotography. DOA-MAlLi (N,N-dioctylaminomethallyllithium), while effective for initiating polymerizations resulting in an elastomers exhibiting reduced hysteresis, also results in terminated polymers having only about 30 percent-tin coupling, and hence, is not as preferred as the others initiators, as will be shown hereinbelow.
The terminating agent is added to the reac~ion vessel, and the vessel is agitated for about 1 to about 1000 minutes. Further examples of terminating agents include fhe terminators described in U.S. Pat. No. 5,066,729, the subjectmatter of which regarding terminating agents is incorporated by reference herein.
It is to be understood that practice of the present invention is not limited solely to these terminators inasmuch as other compounds that are reactive with the polymer bound carbon-lithium moiety can be selected to provide a desired functional group.
Quenching is usually conducted by stirring the polymer and quenching agent for about 0.05 to about 2 hours at temper~tures of from about 30C to 1 20C to ensure complete reaction. Pol~...el ~ terminated with a functional group as discussed hereinabove, are s~-~sequently quenched with alcohol or other quenching agent as also described hereinabove.
Lastly, the solvent is removed from the polymer by conventional techniques such as drum drying, extruder drying, vacuum drying or the like, which may be combined with co~gl-lation with water, alcohol or steam. If coagulation with water or steam is used, oven drying may be desirable.
The polymers of the present invention contain a functional group at the head of the polymer chain (derived from the initiator) in addition to an optional functionality at the terminal end of the chain (derived from the terminating agent).
- These functional groups have an affinity for compounding materials such as silica or carbon black. Such compounding results in products exhibiting reduced hysteresis, which means a product having increased rebound, decreased rolling resistance and lessened heat build-up when subjected to mechanical stress.
- Products including tires, power belts and the like are contemplated. Decreased 9312059 Fl R.P. US0098 - 216S~80 rolling resistance is, of course, a useful property for pneumatic tires, both radial as well as bias ply types and thus, the vulcanizable elastomeric composit;ons of the present invention can be utilized to form treadstocks for such tires. The composition can also be used to form other elastomeric tire components such as 5 subtreads, black sidewalls, body ply skims, bead fillers and the like.
Polymers prepared according to the present invention and terminated or coupled with tin tetrachloride, show reduced hyste'resis and increased coupling as compared to polymers initiated with conventional initiators such as n-butyllithium, as will be more fully explored hereinbelow.
The polymers of the present invention can be utilized as 100 parts of the rubber in the treadstock compound or, they can be blended with any conventionally employed treadstock rubber which includes natural rubber, synthetic rubber and blends thereof. When the polymers of the present invention are blended with conventional rubbers, the amounts can vary widely with a lower limit comprising about 10 to 20 percent by weight of the total rubber. It is to be appreciated that the minimum amount will depend primarily upon the degree of hysteresis reduction desired. Thus, the compounds can contain 10-100% by weight of the inventive polymer, with the balance, if any, being a conventional rubber.
The polymers can be compounded with all forms of carbon black ;n amounts ranging from about 5 to 80 parts by weight, per 100 parts of rubber (phr), with about 35 to 60 phr being preferred. The carbon blacks may include any of the commonly available, commercially-produced carbon blacks but those having a surface area (EMSA) of at least 20 m2/gram and more preferably at least35 m2/gram up to 200 m2/gram or higher are preferred. Surface area values used in this application are those determined by ASTM test D-1765 using the cetyltrimethyl-ammonium bromide (CTAB) technique. Among the useful carbon blacks are furnace black, channel blacks and lamp blacks. More specifically, examples of the carbon blacks include super abrasion furnace (SAF) blacks, high abrasion furnace (HAF) blacks, fast extrusion furnace (FEF) blacks, fine furnace (FF) blacks, intermediate super abrasion furnace (ISAF) blacks, semi-reinforcing furnace 9312059 FIR.P.US0098 (SRF) blacks, medium processing channel blacks, hard processing channel blacks and conducting channel blacks. Other carbon blacks which may be utilized include acetylene blacks. Mixtures of two or more of the above blacks can be used in preparing the carbon black-containing compositions of the invention.
5 Typical values for surface areas of usable carbon blacks are summarized in theTABLE I hereinbelow.
"

TABLE I
CJ~RI~ON BLAacs ASTM Surface Area Designation (m2/g) (D-1765-82a) (D-3765) The carbon blacks utilized in the preparation of the rubber compounds of the invention may be in pelletized form or an unpelletized flocculent mass.
Preferably, for more uniform mixing, unpelletized carbon black is preferred.
The reinforced rubber compounds can be cured in a conventional manner with known vulcanizing agents at about 0.1 to 10 phr. For a general disclosure of suitable vulcanizing agents one can refer to Kirk-Othmer, - Encyclopedia of Chemical Technology,3rd ed., Wiley Interscience, N.Y.1982, Vol.
20, pp. 365-468, particularly "Vulcanization Agents and Auxiliary Materials" pp.390-402. Vulcanizing agents can be used alone or in combination.

9312059 FIR.P.US0098 _ 2165580 Vulcanizab!e elastomeric compositions of the invention can be prepared by compounding or mixing the functionalized polymers herein with carbon black and other conventional rubber additives including for example, fillers, such as silica, plasticizers, antioxidants, curing agents and the like using standard rubber 5 mixing equipment and procedures. Such elastomeric compositions when vulcanized using conventional rubber v~ulcanization conditions have reduced hysteresis properties and are particularly adapted for use as tread rubbers for tires having reduced rolling resistance.

GENERAL EXPERIMENTAL
In order to demonstrate the preparation and properties of elastomers prepared according to the present invention, a number of initiators were prepared.
The initiators were then used to polymerize a solution of butadiene/styrene monomers. For comparison, polymerizations employing butyllithium and lithium 15 amide initiators were also carried out.
TABLE ll prov;des a listing of abbreviations, compound names and structures as used in the following examples and tables.

9312059 FIR.P.USOO98 216~S80 TABLE ll Abbreviations/CompoundstStructures AssREvlAnoN CoMrouND STRUCTURE

BuLi n-butyllithium r CH3CH2CH2CH2CH2Li HMI-Li Iithium ~--\N--Li hexamethyleneimide ~J

PyLi lithium pyrrolidinide CN Li HMI-XyLi hexamethyleneimino-o- ,/~CH2--N J
xylyllithium lQJ`cH2Li Py-XyLi pyrrolidino~xylyllithium ~CH2--N3 CH2Li 9312059 FIR.P.US0098 A~BREVIATION ~ COMPOUND STRUC~URE

Pip-XyLi piperidino-o-xylyllithium ~CH2--N~>
CH2Li-HMI-MAI Li hexamethyleneimino- ~ CH2 methallyllithium l ~N--CH2--C--CHzLi HMI-AI Li hexamethyleneimino- ,/~
allyllithium l ~N--CH=CH--CH2U

DOA-MAlLi N,N-dioctylamino- (c~Hlr~N-cH2--RC--CH21i methallyllithium cH2 1. HMI-XyLi Initiator In order to prepare HMI-XyLi, 60.8 grams of N-ortho-xylylhexamethyleneimine, 60 milliliters (ml) of dry tetrahydrofuran (THF) and 240 ml of dry hexane were added to a 28 ounce beverage bottle with a magnetic stirrer. The bottle was capped with a rubber liner and a crown two-hole cap. Thebottle was then purged with nitrogen and placed on a magnetic stirrer plate. One20 hundred and ninety-six ml of a 1.68 molar solution of n-butyllithium (n-BuLi) in hexane, was added dropwise via a syringe to the stirred solution of N-ortho-xylylhexamethyleneimine at room temperature, and stirring continued overnight.
9312059 FIR.P.USOO98 In order to determine the amount of conversion, a small sample of the reaction mixture was reacted with ClSiMe3 (where Me is methyl) in THF. The reaction product was analyzed by gas chromatography, which showed an absence of BuSiMe3. This indicated that all of the n-BuLi has reacted. Gilman titrationsS of additional samples of the reaction mixture showed that 89.6 percent of the lithium present was in the form of C-Li bonds.

2. Polymer Preparation Using HMI-XyLi A 28 ounce beverage bottle was washed and then dried ;n an oven at 10 145C, capped with a rubber liner/2 hole crown cap, and purged with nitrogen until room temperature was reached. To the bottle was added 236.8 grams of a blend of 75 percent by weight of 1,3-butadiene and 25 percent by weight of styrene in hexane. The two monomers ,co ,rr;sed 20 percent by weight of the blend with hexane. To promote randomization, 0.26 millimoles (mM) of 2,2-bis 15 (tetrahydrofuryl) propane in hexane (0.5 molar) was added. To this was then added 0.474 mM of HMI-XyLi prepared as hereinabove.
The beverage bottle was tumbled in-an 80C water bath for 45 minutes, following which 0.38 ml of a 0.25 molar solution of tin tetrachloride in hexane was added. The bottle was then tumbled in a 50C water bath for 1 hour, after 20 which the bottle was cooled to room ten~pe.dl-lre. There was then added to the viscous ceme.ll in the bottle, 1 cubic centimeter (cc) of isopropanol and 4 cc of a di-t-butyl-p-cresol (DBPC) solution (11.0 grams of DBPC in 700 cc hexane). TheDBPC solution served as an antioxidant to prevent degradation of the polymer.
The polymer was isolated by coagulation in 1100 cc of isopropanol followed by 25 vacuum oven drying at 50-55C.
The polymer showed a glass transition temperature (Tg) at -34C and an Mn of 164,390, and a percent coupling of 61 percent (by gel permeation chromatography, G.P.C., analysis).

9~12ns9 FIR.P.US0098 216~80 3. Lar~e Scale POIYmN rreParat;On A. Batch Polyme. ;~dti ~ ~
Larger quantities of polymer were prepared under N2 pressure in a 2 gallon, closed, stainless steel reactor vessel. The reactor allowed for temperature control and monitoring.
An "initial charge" preparation of a styrene!butadiene rubber (SBR) was made with the reactor temperature set at 122F (50C). A 75 weight percent butadiene and 25 weight percent styrene blénd in hexane (19 percent by weight of monomers) was added to the reactor, followed by HMI-XyLi at 0.9 millimoles per 100 grams of monomer. The batch temperature peaked at 197F. Five minutes after this temperature was reached, tin tetrachloride was added and the mixture was stirred for 30 minutes while the temperature was allowed to fall. The polymer was placed into isopropanol containing an antioxidant.

B. Semi-Batch Polymerization In a semi~atch poly..~ lion, the butadieneJstyrene monomers were metered into the reactor at 200F (93.3C). This allowed for random distributionof the styrene monomer. It was found that with N-Li initiators such as hexamethyleneimine^lithium (HMI-Li), poor conversions to polymer and very littletin tetrachloride coupling would result. In contrast, with the HMI-XyLi initiator of this invention, high converaions to polymer (greater than 95 percent) and acceptable coupling (51-55 percent) were realized.

4. Polymer Evaluations TABLE lll below shows percent couplings of SBR polymers made with the recited initiators and terminated with tin tetrachloride. The table also shows the hysteresis loss, tan delta, of the polymers compounded in the standard test formula as provided in TABLE IV. All of the polymers in TABLE lll were prepared at 80C in a manner similar to the methods described hereinabove. The desired target properties of the polymers prepared included an improvement, i.e., a reduction in the tan delta values over the control n-BuLi initiated polymers while a~1~n~q FIR.P.USOO98 _ 216S~80 still maintaining high levels, preferably greater than 40 percent, of coupling. In TABLE lll, zero percent coupling indicates a polymer which was not reacted with tin tetrachloride, but rather was terminated with isopropanol. Also, where ranges are given the results are from more than one sample.

TABLE lll Tan Delta and % SnC14 Coupl;ng For SBR's (20-25% styrene) Prepared at 80C

Initiator Percent Coupling Tan. Delta (50C:) BuLia - 56-64 0.116-0.124 BuLia 0 0.183 v, pyLia 17-20 0.094-0.102 HMI-Lia 22-34 0.102 HMI-Lia 0 0.103 HMI-XyLi 47-63 0.096-0.108 HMI-XyLi 0 0.117-0.138 Py-XyLi 55 0-103 Py-XyLi 0 0.147 Pip-XyLi 47 0.109 Pip-XyLi 0 0.150 HMI-MAlLi 48-57 0.105-0.106 HMI-MAI Li 0 0.147 HMI-AI Li 35-52 0.109-0.123 HMI-AI Li 0 0.104-0.118 DOA-MAlLi 30 0.138 DOA-MAlLi 0 0.157 aComparative, i.e., non-invention examples 9312059 FIR.P.US0098 216~580 . - TABLE IV
Compounding Test Formulation COMPONENT PARTS BY WEIGHT
Polymer 100 Black (N-35 1 ) 55 Naphthenic Oil r 10 Zinc Oxide 3 Antioxidant Wax 2 Stearic Acid 2 Sulfur 1.5 Accelerator High levels of coupling are desirable in order to maintain good processdbility in the s~ se~uent manufacturing of rubber products. Further, it is known that when polymers are compounded as for example, in the formulation shown in TABLE IV, compound viscosilies are increased significantly. To attain 20 manageable compound viscosilies, lower molecular weight polymers must be used.
However, these lower molecular weights result in both cold and hot flow problems during manufacturing processes and polymer storage. A known remedy for these problems is to tin couple the living anionic polymers using for example, tin tetrachloride. It has been found according to the present invention, that high 25 couplings of 40 percent or higher are achieved.
From the data reported in TABLE lll, it is shown that the N-Li or lithium amide type initiators (HMI-Li and PyLi) give polymers having reduced tan delta as compared to n-BuLi initiated polymers. However, these same polymers give unacceptably low levels of tin tetrachloride coupling. The ;nitiators according to 30 the present invention, including HMI-XyLi, PyXyLi, Pip-XyLi, HMI-MAlLi and HMI-AlLi, gave both low tan deltas and high levels-of tin tetrachloride coupling.
TABLE V shows stress/strain data for vulcanizates made from the test formulation of TABLE IV. Samples were cured for 20 minutes at 165C. All of 9312059 FlR.P.USOO98 - 2165~80 the SBR polymers were random copolymers, i.e., styrene distribution was random or non-block, with 20-25 percent by weight of styrene. Regardless of styrene content, the polymers were all targeted for glass transition temperatures of -40C, within 5 degrees. Thus the lower styrene polymers generally contained higher 5 levels of 1,2 microstructure in the butadiene portion of the polymers. Examples of microstructure variations versus Tg are given in TABLE Vl. The microstructures were determined by NMR analysis which also confirmed the random styrene distribution.

TABLE V
Stress/Strain for SBR's Made at 80C with Various Initiators/SnC14 - Coupling Initiator300% M, psi Tensile Slr~ , psi Elong. ~ Break P~rce.,ta~e Py Lia 2189 2210 353 py Lja 2315 2728 388 HMI-Lia 2792 3144 377 HMI-Lia 2452 3023 405 HMI-XyLi 2520 3279 416 HMI-XyLi 2365 3107 369 Py-XyLi 2471 2471 345 Pip-XyLi 2338 2796 401 HMI-MAlLi 2691 3073 371 HMI-AlLi 2357 2846 400 DOA-MalLi 2111 2679 415 aComparative, i.e., non-invention examples 9312059 FIR.P.US0098 - 2165~80 TABLE Vl Microstructure - Tg Relationship Pcrccnta6~ Pc~c.. t.. 6. 1,2 Bd Initiator Tg, C Styrene (Bd=100) HMI-Lia 45 26.3 43.0 HMI-Lia -38 r20.4 53.1 HMI-Lia 39.5 26.4 47.4 HMI-XyLi -32 26.4 54.4 aComparative, i.e., non-invention examples Ranges of molecular weights and molecular weight,distributions (Mw/Mn) together with respective Tg data, are shown in TABLE Vll. Molecular weights of 110,000 for the non~oupled polymers were expected from the amounts of monomers and initiators charged.

9312059 FIR.P.US0098 ~ 2165580 - TABLE Vll Molecular Weight Data for Polymers Made at 80C

Perc... ...... .............. ......... .................. ... ~ldgc Cgupling I,.ilidlcr Mn Mw/Mn (SnC14) Tg, C
PyLia 138~046 1.80 20 -37 HMI-Lia 133~862 1.60 r 26 -41 HMI-Lia 105~364 1.26 0 -37 HMI-XyLi 206/545 2.02 54 -38 HMI-XyLi 119~120 1.16 0 -40 HMI-XyLi 164~386 1.86 61 -34 HMI-MAlLi196~217 2.38 48 -33 Py-XyLi 175~465 1.78 55 ~ -33 Py-XyLi 106,711 1.20 0 -36 Pip-XyLi 228~512 1.91 47 -35 Pip-XyLi 147~814 1.20 0 -42 HMI-AlLi 127~464 1.89 35 -38 HMI-AlLi 110,280 1.22 0 -37 aComparative, i.e., non-invention examples b~o" coupling indicates terminations with isopropanol instead of SnC14 In batch polymerizations, the polymerizations were allowed to exotherm, resulting in a peak temperature of about 180F to.about 300F (about 82C to about 149C). As the concentration of monomers was increased, the peak temperatures also increased. Normally, if undesirable results at high temperatures are encountered, the monomer concentration must be decreased, resulting in reduced productivity. The effects of peak temperature increases on tin tetrachloride coupling with N-Li initiators are shown in TABLE Vlll.

9312059 FIR.P.US0098 216~580 TABLE Vlll Temperature Effects on % Coupling Via Sna4 In Initial Charge Reactor Polymerizations Percentage InitiatorPeak Ternp., F Coupling Polymer HMI-Lia 140 74 SBR
HMI-Lia 194 58 SBR
HMI-Lia 202 59 SBR
HMI-XyLi 197 93 SBR
HMI Lja 228 26BR (low 1,2 content) HMI-XyLi 228 67BR (low 1,2 content) aComparative, i.e., non-invention examples The percent coupling is significantly reduced as peak temperature is increased in pol~-,.er;~a(ions with HMI-Li initiators. In the polybutadiene (BR)example, a fairly high peak temperature was ol,sel~rcd because of the higher starting temperature necessary in polymerizations with no or very little vinyl 20 modifier (e.g., ethers or trialkyl amines). With the HMI-XyLi invention initiator, improved level of coupling at high temperatures is observed.
In the semi-batch SBR pol~ er;~dlions/ the monomers are charged at high temperatures, preferably about 200F to about 250F (about 93C to about 121 C), which forces random distribution of styrene in the copolymer. With N-Li25 type initiators such as HMI-Li, there is low conversion to polymer and poor tin tetrachloride coupling. TABLE IX shows results obtained from semi-batch preparation of SBR using HMI-XyLi at 202F to 205F (94.4C to 96.1 C), with tin tetrachloride coupling.

9312059 FIR.P.US0098 216~80 - TABLE IX
Selni-Batch Preparation of SBR Us;ng HMI-XyLi Batch T,F P~rc~.,l Percent Percent 50C Tan C~ ,-rer D . Coupling Styrene Tg, C Delta 205 98.5 55 34.2 ~2 0.103 202 97.5 51 r 38.5 -35 0.111 The data shows high conversion to SBR with desirable tan deltas and 10 sufficiently high percent coupling to prevent subsequent flow problems. The polymers had a molecular weight before coupling of from 115,800 to 121,700.
As stated above, other terminators can also be employed in the practice of the present invention. For example, 1,3~imethyl-2-imidazolidinone and 1-methyl-2-pyrrolidinone were employed and resulted in SBR polymers with Mn of 74,127 and 91,129 respectively, and when compounded, tan deltas of 0.102 and 0.107 respectively.
In conclusion, it is clear from the foregoing examples and specification disclosure that the initiators of the present invention are useful for the anionic polymerization of diene monomel s at elevated temperatures, to form 20 homopolymers as well as copolymers with monovinyl aromatic polymers or trienes. The resulting elastomeric polymers have a functional group at the site of initiation and a lithium atom at the terminal, "living" end. After quenching, the polymers still retain the functional group at the site of initiation, which promotes uniform and homogeneous mixing with carbon black. As a result vulcanizable 25 elastomeric compounds containing these polymers exhibit improved hysteresis which provides lower rolling resistance in tires and improved fuel economy.
Additionally, the lithium terminated polymers can be quenched with compounds to provide terminal functional groups and hence, difunctional polymer chains. The polymers also exhibit improved tin tetrachloride coupling.
It is to be understood that the invention is not limited to the specific reactants, initiators, and organolithium compounds disclosed nor to any particular modifier or solvent. Similarly, the examples have been provided merely to 9~12n.59FIR.P.US0098 demonstrate practice of the subject invention and do not constitute limitations of the invention. Those skilled in the art may readily select other monomers and process conditions, according to the disclosure made hereinabove.
Thus, it is believed that any of the variables disclosed herein can readily 5 be determined and controlled without departing from the scope of the inventionherein disclosed and desc. ;bed. Moreover~the scope of the invention shall include all modifications and variations that fall within the scope of the attached claims.

9312059 FIR.P.US0098

Claims (19)

1. An anionic polymerization initiator comprising:
the reaction product of an organo lithium compound and a tertiary-amino compound having a general formula selected from and where R1 and R2 are the same or different and are selected from alkyls having from 1 to about 12 carbon atoms, cycloalkyls having from 3 to about 14 carbon atoms, and aralkyls having from 6 to about 20 carbon atoms; R3 is a group selected from allyl, 2-methallyl or xylyl; R4- is a carbocyclic groupof from about 3 to about 20 methylene groups; each R5 is an alkyl substituent on a methylene group having from about 1 to about 20 carbon atoms; and, x is an integer of from 0 to about 10.

2. An initiator, as set forth in claim 1, wherein said organolithium compound has the general formula RLi, where R is selected from the group consisting of alkyls and cycloalkyls having from about 1 to about 20 carbon atoms.

3. An initiator, as set forth in claim 1, wherein said reaction product is selected from hexamethyleneimino-o-xylyllithium, pyrrolidino-o-xylyllithium, piperidino-o-xylyllithium, hexamethyleneimino-methallyllithium, hexamethyleneimino-allyllithium, and N,N-dioctylamino-allyllithium.

4. A method of preparing an anionic polymerization initiator, comprising:
reacting an organo lithium compound with a tertiary-amino compound having a general formula selected from and where R1 and R2 are the same or different and are selected from alkyls having from 1 to about 12 carbon atoms, cycloalkyls having from 3 to about 14 carbon atoms, and aralkyls having from 6 to about 20 carbon atoms; R3 is a group selected from allyl, 2-methallyl or xylyl; R4 is a carbocyclic group of from about 3 to about 20 methylene groups; each R5 is an alkyl substituent on a methylene group having from about 1 to about 20 carbon atoms; and, x is an integer of from 0 to about 10.

5. A method, as set forth in claim 4, wherein each said organolithium compound and said tertiary amine are dissolved in an anhydrous aprotic solvent containing from about 1 to about 40 mM of tetrahydrofuran per mM
of Li.

6. A method, as set forth in claim 5, wherein said step of reacting includes reacting about 1.0 mole of said tertiary amine compound with about 1.0 to about 1.4 moles of said organolithium compound.

7. A polymer comprising:
a polymer chain having the general formula R6-polymer-Li prior to quenching; wherein R6 is a functional group derived from a polymerization initiator having a general formula selected from and where R1 and R2 are the same or different and are selected from alkyls, cycloalkyls and aralkyls having from about 1 to about 12 carbon atoms; R'3 is a group selected from allyl, 2-methallyl or xylyl, having one hydrogen atom removed; R4 is a carbocyclic group of from about 3 to about 20 methylene groups; each R5 is an alkyl substituent on a methylene group having from about 1 to about 20 carbon atoms; and, x is an integer of from 0 to about 10.

8. A polymer, as set forth in claim 7, wherein the polymer component of said polymer chain is selected from diolefin monomers having from about 4 to about 12 carbon atoms, and copolymers of said diolefin monomers together with monovinyl aromatic monomers having from about 8 to about 20 carbon atoms, or trienes.

9. A polymer, as set forth in claim 7, wherein said polymer chain has a general formula selected from and

10. A vulcanizable elastomer composition formed from the polymer of claim 7 and from about 5 to about 80 parts by weight of carbon black, per 100 parts by weight of the polymer.

11. A tire having at least one component formed from the vulcanizable elastomer composition of claim 10.

12. A method of preparing a polymer comprising: polymerizing at least one monomer selected from diolefin monomers having from about 4 to about 12 carbon atoms, monovinyl aromatic monomers having from about 8 to about 20 carbon atoms, and trienes, in the presence of a polymerization initiator having a general formula selected from and wherein R1 and R2 are the same or different and are selected from alkyls, cycloalkyls and aralkyls having from about 1 to about 12 carbon atoms; R'3 is a group selected from allyl, 2-methallyl or xylyl, with one hydrogen atom removed; R4 is a carbocyclic group of from about 3 to about 20 methylene groups; each R5 is an alkyl substituent on a methylene group having from about 1 to about 20 carbon atoms; and, x is an integer of from 0 to about 10.

13. A high temperature polymerization method, as set forth in claim 12, wherein the polymerizing includes polymerzing at a temperature of from about 49°Cto about 149°C.

14. A polymer prepared according to the method of claim 12.

15. A vulcanizable elastomer composition comprising the polymer of claim 14 and from about 5 to 80 parts by weight of carbon black, per 100 parts of the polymer.

16. A tire having at least one component formed from the vulcanizable elastomer composition of claim 15.

17. A method, as set forth in claim 12, comprising the further step of terminating said polymerization with a terminating or coupling agent.

18. A method, as set forth in claim 17, wherein said terminating agent is selected from SnCI4,R7(3)SnCI,R7(2)SnCI2,R7SnCI3, carbodiimides, N-cyclic amides, N,N' disubstituted cyclic ureas, cyclic amides, cyclic ureas, isocyanates, Schiff bases, and 4,4'-bis(diethylamino) benzophenone, where R7 is selected from alkyls having from about 1 to about 20 carbon atoms, cycloalkyls having from about 3 to about 20 carbon atoms, aryls having from about 6 to about 20 carbon atoms and aralkyls having from about 7 to about 20 carbon atoms.

19. A functionalized polymer formed by the polymerization of at least one anionically polymerizable monomer, and improved with respect to its hysteresis properties, monomer randomization and coupling ability, the improvement comprising:
initiating polymerization of at least one monomer selected from diolefin monomers having from about 4 to about 12 carbon atoms, monovinyl aromatic monomers having from about 8 to about 20 carbon atoms, and trienes, at a temperature of from about 82°C to about 149°C, in the presence of a polymerization initiator having a general formula selected from and wherein R1 and R2 are the same or different and are selected from alkyls, cycloalkyls and aralkyls having from about 1 to about 12 carbon atoms; R'3 is a group selected from allyl, 2-methallyl or xylyl, with one hydrogen atom removed;R4 is a carbocyclic group of from about 3 to about 20 methylene groups; each R5 is an alkyl substituent on a methylene group having from about 1 to about 20 carbon atoms; and, x is an integer of from 0 to about 10.