CA2181428A1 - Silica reinforced rubber composition and tire with tread - Google Patents
Silica reinforced rubber composition and tire with treadInfo
- Publication number
- CA2181428A1 CA2181428A1 CA002181428A CA2181428A CA2181428A1 CA 2181428 A1 CA2181428 A1 CA 2181428A1 CA 002181428 A CA002181428 A CA 002181428A CA 2181428 A CA2181428 A CA 2181428A CA 2181428 A1 CA2181428 A1 CA 2181428A1
- Authority
- CA
- Canada
- Prior art keywords
- rubber composition
- silica
- rubber
- tire
- tread
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C1/00—Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
- B60C1/0016—Compositions of the tread
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/02—Elements
- C08K3/04—Carbon
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/34—Silicon-containing compounds
- C08K3/36—Silica
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/54—Silicon-containing compounds
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/54—Silicon-containing compounds
- C08K5/5406—Silicon-containing compounds containing elements other than oxygen or nitrogen
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/54—Silicon-containing compounds
- C08K5/544—Silicon-containing compounds containing nitrogen
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/54—Silicon-containing compounds
- C08K5/544—Silicon-containing compounds containing nitrogen
- C08K5/5455—Silicon-containing compounds containing nitrogen containing at least one group
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/54—Silicon-containing compounds
- C08K5/548—Silicon-containing compounds containing sulfur
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
- C08L9/06—Copolymers with styrene
Abstract
The present invention relates to a silica reinforced rubber composition and to pneumatic tires having treads comprised of the silica reinforced rubber compositions.
The silica reinforced rubber composition comprises at least one elastomer, silica, a silica coupler, a silylating agent and, optionally, carbon black,
The silica reinforced rubber composition comprises at least one elastomer, silica, a silica coupler, a silylating agent and, optionally, carbon black,
Description
2181q28 SI~ICA REII~FORCED RIJBBER COMPOSITION
AND TIRE WITH TREAD
Field This invention relates to rubber compositions which are quantitatively reinforced with silica. In one aspect, the rubber composition i9 comprised of rubber, particularl~r sulfur curable, or cured, rubber, reinforced with a, ;n~t10n of silica, silica coupling agent, sil~lating agent and, optionally, carbon black.
Background For various applications utilizing rubber which require high strength and abrasion resistance, particularly applications such as tires and various industrial products, sulfur cured rubber is utilized which contains substantial amounts of reinforcing fillers. Carbon black is commonly used for such purpose and normall~ provides or enhances good physical properties for the sulfur cured rubber.
Particulate silica is also often used for such purpose, particular~y when the ~ilica i5 used in conjunction with a coupling agent. In some cases, a combination of silica and carbon black is utilized for reinforcing fillers for various rubber products, including treads f or tires . The use of such reinforcing fillerg ~or elastomers, including sulfur curable elastomers, is well known to those having skill in such art.
It is important to appreciate that, conventionally, carbon black is a considerably more effective reinforcing filler for rubber products, and particularly for rubber tire treads than silica if the silica is used without a coupling agent, or silica coupler as it may be sometimes referred to herein.
Often coupling agents are composed of a silane which has at least one f irst constituent component, or moiety, (such as a ~3ilane portion) capable of reacting with the silica suri ace and, also, an additional 5 moiety capable of irlteracting with the rubber, particularly a suli ur vulcanizable rubber which ~-,,n~ ~ nq carbon- to - carbon double bonds, or unsaturation. Usua~ly the additional moiety is sulfur in a form of a poly~3ulfide and particularly a 10 polysulfide bridge between said i irst moieties . In this manner, then t~le coupler acts as a connecting bridge between the silica and the rubber and thereby f~nh;~nrf~c the rubber reinforcement aspect of the silica .
The rubber-reactive group component, namely the said additional moiety, of such coupler may be, for example, one or more of groups such as mercapto, amino, vinyl, epoxy, and sulfur groups, preferably a sulfur or mercapto moiety and more preferably sulfur in a i orm of a poly~3ulfide as a polysulfide bridge between at least two of said first moieties.
Numerous of such coupling agents are taught for use in ct~mh;n~ng silica and rubber, such as, for example, silane coupling agents ~-nn~;n;n~ a polysulfide component, or structure such as, for example, trialkoxyo~.ganosilane polysulfides, such as for example bis- (3-trialkoxysilylorgano) polysulfides, c~m~n~ng from about 2 to about 8 sulfur atoms in a polysulfide bridge such as, for example, bis- (3-triethoxysilylpropy~) tetrasulfide and/or trisulfide.
Various U.S. patents relating to silicas and silica reinforced tire treads include, for example, U.S. Patents Nos. 3l451,458; 3,664,403; 3,768,537;
3,884,285; 3,g38,574; 4,482,663; 4,590,052 and 5, 089, 554 .
218~428 . ~
In one aspect, and in contrast to the aforesaid rubber reactive silica coupling agents, other silica-reactive materials might be utilized to interact with the silica which have only one constituent component, 5 or moiety, and which is capable of reacting with the silica surface. Such materials are not readily reactive with the rubber 80 that they do not readily promote interaction between the silica and the rubber.
Therefore, by itself, such material is not r~n~;~Pred 10 herein to enable the silica to sat~ c~artrrily reinf orce the rubbe]- .
The term "phr" if used herein, and according to conventional practice, ref ers to "parts of a respective material per 100 parts by weight of rubber, 15 or elastomer".
In the description of this invention, the terms "rubber" and "elastomer" if used herein, may be used interchangeably, un:Less otherwise prescribed. The terms "rubber compo~3ition", "compounded rubber" and 20 "rubber compound", :if used herein, are used interchangeably to refer to "rubber which has been blended or mixed wi~ h various ingredients and materials " and such terms are well known to those having skill in the rubber mixing or rubber 2 5 compounding art .
Summary and Prac~ice of the Inventiorl In accordance ~ith this invention, a rubber composition is provided which comprises (A) 100 parts 30 by weight of at least one diene-based elastomer, (~3) about 50 to about lO0, optionally about 60 to about 90, phr particulate reinforcing filler composed of precipitated silica and carbon black, compri8ed of about 60 to about 100, alternatively about 60 to about 35 90, phr of precipitated silica which r~n~A;nA silanol groups thereon and correspondingly zero to about 10, 2~8~428 ~ ~S
alternatively zero to about 7 or about 3 to about 7, phr of carbon black, wherein the weight ratio of silica to carbon black is at least about 6/1 and alternatively, at least about 10/1, (C) at least one 5 silica coupler having a moiety reactive with said silica and another moiety interactive with said elastomer(s), (D) about 0.5 to about 10, alternatively about 2 to about 6 phr of a silanol-reactive, trialkylsilyl functional group-cnnt~;n;nrJ silylating 10 agent having the formula:
RlR2R3Si -X
where X is a radical ,selected from the group consisting of:
~1 ) halogen radical selected f rom one of chlorine, b~-omine and iodine (2) -NH-C=OR1, (3 ) -NR4 -A, (4) -NH-C=ONH-A, and (5) -N(R4)2 20 where R1, R2, R3 and R~l are individually selected from the group consisting of primary, secondary and tertiary alkyl radicals and alkaryl radicals having from 1 to 30, alternatively about 1 to about 3, carbon atoms, wherein R4 is alternatively 11YdLUY~ and A is 2 5 - S iRlR2R3 -It is an important feature of this invention thata relatively highly silica loaded elastomer composition is provided which cnnt~;nq the silica-reactive, silylating agent together with the silica 30 coupler rather than the silylating agent or silica coupler individually.
The term ~silylating agent" Conv~nt;nn~lly relates to materials which are capable of reacti~g with an active hydrogen-rr,nt~;n;ng substrate, for 35 example, a silanol group (SiOH) on a silica surface for this invention, to introduce a silyl functional , . ~
2~81428 ~' group to the substrate material, or silica surface for this invention.
The term "silylating agent" is used herein to mean the said trialkylsilyl functioIlal group-5 cr-n~;n;ng material which can react, for example, with a silanol group (SioH) on a silica surface to introduce the trialkylsilyl group onto the silica surf ace .
E3y the term "silica-reactive silylating agent", 10 it is meant herein that the trialkylsilyl groups of the agent react with silanol groups at the silica surface and, thus, chemically combine with the silica.
A trialkylsilyl group from the silylating agent is, thus, placed on the silica sur~ace in place of the 15 hydrogen atom of the silanol group.
It is important that the alkoxysilane component of a silica coupler ~qhich rrnt~1nc alkoxysilane units also reacts with the silanol groups at the surface of the silica and thereby also chemically combines with 20 the silica.
While it is recognized that both the silica coupler (the silane moiety of the coupler) and the silylating agent compete for the silanol groups on the silica surface, only the additional moiety of the 25 silica coupler such as, for example, a polysulfide bridge, has reactivity with the diene-based elastomer.
Because both the alkoxysilane moiety of a silane-crn~;n;ng silica coupler and the trialkylsilyl moiety of the silylating agent are reactive with and, thus, 30 compete for the silanol groups on the surface of the silica, it is important that the silylating agent be added to the silica concurrent with or subseo~uent to the silica coupler. As a result, while the precise mechanism, or result, may not be completely known, it 35 is considered herein that the silylating agent exerts a synergistic benefit to the ~ilica coupler, but does 218l428 ' ' ~' not replace its use. Such a synergistic benefit might be ob8erved, for example, as improved performance as might be exemplified by higher 300 percent modulus values, reduced hysteres~s a8 evidenced by hot rebound 5 value8 and/or improved abrasion resistance as may be evidenced by DIN abrasion te8t, when using a combination of both of the silylating agent and the silica coupler in the silica reinforced elastomer compo8ition, relative to the performance obtainable by 10 using eit~er the silylating agent or the silica coupler individually.
For the said silanol-reactive silylating agent, and for said Rl, R2, R~ and R~L, repre8entative examples of primary alkyl radicals are those 8elected from at 15 least one of methyl, ethyl, propyl, octyl, n-octadecyl, and n-hexadecyl radicals; representative examples of secondary alkyl radicals are those selected ~rom at lea~t one of isopropyl and sec-butyl radicals and representative examples of tertiary alkyl 20 radicals are those selected from at least one of tert-butyl, and dimethylbutyl radicals_ It i8 the trial~cylsilyl moiety of the silylating agent that is reacti~e with the surface of the precipitated silica ~hich is usually the silanol 25 groups on the surface of the 8ilica.
Representative, although not intended to be limitative, of various silylating agents are, for example, trimethylsilyl diethyl amine, N,N'-bis (trimethylsilyl) ~Irea, trimethyl chlorosilane, 30 hexamethyl disilazane and monotrimethylsilyl acetamide .
In the practice of this invention, it has been observed that the adclition of the aforesaid silica silylating agent to the rubber silica composition, 35 which C~n~ n~ the silica coupler, results in not only improved processing characteristics for the silica reinforced elastomer composition, such as reduced viscosity, but also in improved cured elastomer composition performance properties such as, for example, abrasion resistance, tear strength and rebound.
Cured physical properties such as abrasion resistance, tear stl~ength and rebound values may be simultaneously improved. This is r(~n~ red herein to be benef icial because tire treads having such properties are anticipated herein to provide one or more of improved treadwear, rolling resistance and durability .
It is re- o~n; 7F.~ that various silylating agents have hereinbefore been used for various purposes in various elastomeric composition8 such as, for example, silica and carbon black reinforced rubber compositions with 5-50 phr of si] ica and 10- 60 phr of carbon black.
For example, see (Japanese patent publication abstract No. 5051484) .
It is considered herein that this invention is a departure f rom such prior practice because the silica silylating agent cr1nt~;n;ng a trialkylsi~yl moiety is used in combination with a silica coupler, which ~ nt;l;nq a silane moiety, in a subst~nt;~lly silica reinforced ~eg. at least 60 phr of silica and less than 10 phr of carbon black) rubber composition.
In one aspect, a synergistic performance has been observed when using both the said silylating agent and silica coupler which was not observed when using either of the silylating agent or silica coupler alone for a silica reinforced elastomer composition.
Moreover, the synergistic effect seemed to be dependant upon using only a limited amount, or level, of the silylating agent.
While, in the practice of this invention various silica couplers can be used, one preferred coupler is 2181~28 ' ~' a bis- (trialkoxysilylalkyl) polysulfide c~nt~;n;ng from about 2 to about 8 sulfur atoms in the polysul~ide bridge an hereinbefore described. For example, the silica coupler can be bis- (3-5 triethoxysilylpropyl) tetrasulfide having an averageof about 4 sulfur atoms in its polysulfide bridge or, in an alternative, a polysulfide having about 2 sulfur atoms in its polysulfide bridge.
Conventionally a weight ratio of silica coupler 10 to silica is in a range of about 0 . 01/1 to about 0 . 25/1 .
In practice, a molar ratio based on trialkylsilyl functionality of the silica silylating agent to silane functionality of the silica coupler in a range of about 0.1/1 to about 4/1 alternatively, a molar ratio of about 0.5/1 to about 3/1, i9 preferred.
In one aspect of the invention, the rubber composition ~ nt;~; nc: a high level, or amount, of silica, namely at least about 50 phr ag a tlt-m;n;;nt elastomer reinforci~g pigment with less than 10 phr of carbon black as a secondary elastomer reinforcing material .
The rubber composition itself can also be provided as being a sulfur cured composition through vulcanization o~ the uncured elastomer composition.
The sulfur curing i8 accomplished in a conventional manner, namely by curing under conditions of elevated temperature and pre~sure for a suitable period of time .
Further, and in accordance with this invention, a tire is provided having a tread of the rubber composition of this invention.
The said curatives f or the process are curatives conventionally used for sulfur curable elastomers which typically include sulfur and one or more appropriate cure accelerator~ and somet~nes also a 2181~28 g retarder. Such curatives and use thereof for sulfur curable elastomer compositions are well known to those skilled in the art.
Further, sec~uential mixing processes for 5 preparing sulfur curable rubber compositions in which elastomers and associated ingredients exclusive of curatives are f irst mixed in one or more secruential steps followed by a final mixing step for adding curatives are also ~rell known to those skilled in the 10 art.
In the practice of this invention, as hereinbefore pointed out, the rubber composition is comprised of at least one diene-based elastomer, or rubber. Such elastc)mers are typically selected from 15 homopolymers and copolymers of conjugated dienes and copolymers of con; ugated diene ( g ) and vinyl aromatic compound. Such dienes may, for example, be selected from isoprene and 1,3-butadiene and suoh vinyl aromatic compounds may be selected f rom styrene and 20 alphamethylstyrene. Such elastomer, or rubber, may be selected, for examp~e, from at least one of cis 1,4-polyir~oprene rubber (natural and/or synthetic, and preferably natural rubber), 3,4-polyisoprene rubber, styrene/butadiene copolymer rubbers, 25 isoprene/butadiene copolymer rubbers, styrene/isoprene copolymer rubbers, styrene/isoprene/butadiene terpolymer rubbers, cis 1, 4 -polybutadiene rubber, trans 1,4-polybutadiene rubber (70-95 percent trans), low vinyl polybutadiene rubber (10-30 percent vinyl), 30 medium vinyl polybutadiene rubber (30-50 percent vinyl) and high vin~l polybutadiene rubber (50-90 percent vinyl ) .
In one aspect, particularly for a tire tread, the rubber is preferabl~ of at least two of diene based 35 rubbers . For examp] e, a combination of two or more rubbers is preferred such as cis 1,4-polyisoprene 2181~28 . ~
rubber (natural or synthetic, although natural is preferred), 3,4-pol~risoprene rubber, styrene/isoprene/bu~ ; PnP rubber, emulsion and/or solution polymerization derived styrene/butadiene 5 rubbers, cis 1,4-poly~tAr~ n-~ rubbers and emulsion polymerization prepared butadiene/acrylonitrile copolymers .
In one aspect of this invention, an emulsion polymerization derived styrene/butadiene (E-SBR) might 10 be used having a relatively conventional styrene content of about 20 to about 28 percent bound styrene or, for some applications, an E-SBR having a medium to relatively high bound styrene content, namely a bound styrene content of about 30 to about 45 percent.
The relatively high styrene content of about 30 to about 45 for the E-SBR can be considered beneficial for a purpose of ,on~An~ ;ny traction, or skid resistance, of the tire tread. The presence of the E-SBR itself is considered beneficial for a purpose of 20 enhancing processability of the uncured elastomer composition mixture, especially in comparison to a utilization of a solution polymerization prepared SBR
(S - SBR) .
By emulsion polymerization prepared E-SBR, it is 25 meant that styrene and 1,3-blltA~l;onP are copolymerized as an aqueous emulsion. Such are well known to those skilled in such art The bound styrene content can vary, for example, from about 5 to 50~6. In one aspect, the E-SBR m~y also contain acrylonitrile to 30 form a terpolymer rubber, as E-SBAR, in amounts, for example, of about 2 to about 3 0 weight percent bound acrylonitrile in the terpolymer.
Emulsion polymerization prepared styrene/butadiene/acrylonitrile terpolymer rubbers 35 contA;n1n~ about 2 to about 40 weight percent bound acrylonitrile in the copolymer are also Cont ~1 ~ted as diene based rubbers for use in this invention, particularly if used in ~:l ;n~;on with other diene-based elastomers.
The solution polymerization prepared SsR (S-SBR) 5 typically has a bound styrene content in a range of about 5 to about 50, preferably about 9 to about 36, percent. The S-SBR can be conveniently prepared, for example, by organo lithium catalyzation in the pre~ence of an organic hydrocarbon solvent.
A purpose of using S-SBR may be to promote a reduction in tire rolling resistance as a result of lower hysteresis when it is used in a tire tread composition .
The 3,4-polyisoprene rubber (3,4-PI) is 15 considered beneficial for a purpose of promoting the tire' s traction when it is used in a tire tread composition .
The 3,4-PI and use thereof is more fully described in U.S. Patent No. 5,087,668 which is 20 incorporated herein by reference. The Tg refers to the glass transition temperature which can conveniently be det~;n~r7 by a differential scanning calorimeter at a heating rate of 10~C per minute.
The cis 1,4-polybutadiene rubber (BR) is 25 considered to be beneficial for a purpose of promoting the tire tread' 8 wear, or treadwear.
Such BR can be prepared, for example, by organic solution polymerization of 1, 3-butadiene.
The BR may be conveniently characterized, for 30 ex~nple, by having at least a 90% cis 1,4-content.
The cis 1,4-polyisoprene and cis 1,4-polyisoprene natural rubber are well known to those having skill in the rubber art.
The vulcanized rubber composition should contain 35 a sufficient amount of precipitated silica reinforcing filler namely, greater than about 50 phr, to -218~428 ' . ~
contribute a reasonably high modulus, high abrasion resistance and resistance to tear ~or the cured rubber composition. The amount of the silica, as hereinbefore referenced, may be a3 low as about 50 5 parts per 100 part3 rubber, but is preferably ~rom about 60 to about 90 or even up to about 100 parts by weight .
Carbon black may be present in levels below about 10 phr or not at all. Carbon black is not intended to 10 serve as a principal reinforcing filler in the elastomer compositions of this invention Herein, the carbon black if used, is used primarily as a colorant where a black colored elastomer composition is desired and/or as a carrier for liquid additives for elastomer 15 composition such as, for example, the silica coupler if it would otherwise be added to the elastomer composition in a li~lid form.
The commonly employed siliceous pigments used in rubber compounding applications can be used as the 20 silica in this invention, including pyrogenic and precipitated siliceou8 pigments (silica), although precipitated silicas are preferred.
The siliceous pigments preferably employed in this invention are p~~ecipitated silicas such as, for 25 example, those obtained by the acidification of a soluble silicate, e.g., sodium silicate, generally exclusive of silica gels.
Such silicas might be characterized, for example, by having a BET surface area, as mea3ured using 30 nitrogen gas, preferc1bly in the range of about 40 to about 600, and more usually in a range of about 50 to about 300 square meters per gram. The B~T method of measuring suri~ace area is described in the ~Jol~rn~l Of the ~mprican ~h.-m~ Society, Volume 60, page 304 (1930).
~
The silica may also be typically characterized by having a dibutylphth.alate (DBP) absorption value in a range of about 100 to about 400, and more usually about 150 to about 300.
The 8ilica might be expected to have an average ultimate particle size, for example, in the range of O . 01 to 0 . 05 micron as detPrm; nPtl by the electron microscope, although. the silica particles may be even smaller, or possibly larger, in size Various commercially available silicas may be considered for use in this invention such as, only for example herein, and without limitation, silicas commercially available from PPG Industries under the Hi-Sil trademark with designations 210, 243, etc;
silicas available from Rhone-Poulenc, with, for example, designations of Zeosil 1165MP and silicas available from Degussa A(~ with, for example, designations VN2 and VN3, etc.
It is readily understood by those having skill in the art that the rubber composition would be compounded by methods generally known in the rubber compounding art, such as mixing the various sulfur-wlcanizable constituent rubbers with various commonly used additive materials such as, for example, curing aids, such as sulfur, activators, retarders and accelerators, processing additives, such as oils, resins including tackifying resins, silicas, and plasticizers, fillers, pigments, fatty acid, zinc oxide, waxes, antin~;~ntq and antiozonants, peptizing agents and reinforcing materials such as, for example, carbon black. As known to those skilled in the art, ~lPrPnr~1ng on the ;ntpnflp~l use of the sulfur wlcanizable and sulfur wlcanized material (rubbers), the additives mentioned above are selected and commonly used in conventional amounts.
~ ow amounts of reinforcing type carbon blacks (8), for this invention, if used, are hereinbefore set f orth .
It is to be appreciated that the silica coupler 5 and/or the silica silylating agent, if in a liquid form, may be used in con~unction with a carbon black carrier, namely, pre-mixed with a carbon black prior to the addition to the rubber composition, and such carbon black is to be included in the aforesaid amount 10 of carbon black accounted for in the rubber composition formlllAtion.
Typical amounts of tackif ier resins, if used, comprise about O . 5 to about 10 phr, usually about 1 to about 5 phr. Typical amounts of processing aids 15 comprise about 1 to about 50 phr. Such processing aids can include, for example, aromatic, napthenic, and/or paraffinic processing oils. Typical amounts of anti~ ;flAnt~ comprise about 1 to about 5 phr.
Representative antioxidants may be, for example, 20 diphenyl-p-phenyl~n~rl;Am;nl~ and others, such as, for example, those disclosed in the Vanderbilt R~lhher E~andbook (1978), pages 344-346. Typical amounts of antiozonants comprise about 1 to 5 phr.
Typical amounts of fatty acids, if used, which 25 can include stearic acid, palmitic acid, linoleic acid or mixtures of one or more fatty acids, can comprise about O . 5 to about 3 phr .
Often stearic acid is used in a relatively impure state and is commonly referred to in the rubber 30 compounding practice as "stearic acid" and is 80 referred to in the description and practice of this invention .
Typical amounts of zinc oxide comprise about 2 to about 5 phr. Typical amounts of waxes comprise about 35 1 to about 5 phr. Often microcrystalline waxes are used. Typical amounts of peptizers, if used, comprise 218~428 about 0.1 to about 1 phr. Typical peptizers may be, for example, pentachlorothiophenol and dib~n7~m;~nrl;phenyl disulfide.
The vulr~n;7~t;on i8 conducted in the presence of 5 a sulfur vulcanizlng agent. Examples of suitable sul f ur vul cani z ing agents include el emental sul f ur (free sulfur) or sulfur donating wlcanizing agents, for example, an amine disulfide, polymeric polysulfide or sulfur olefin adducts. Preferably, the sulfur 10 vulr~n;7~ng agent is Pl~m~nti~l sulfur. As known to those skilled in the art, sulfur wlr~n~7~ng agents are used in an amount ranging from about 0 . 5 to about 4 phr, or even, in some circumstances, up to about 8 phr, with a range of from about 1 to about 2.5, 15 sometimes from about 1 to about 2, being preferred.
Accelerators are used to control the time and/or temperature required for vulr~n;7~t~on and to improve the properties of the vulr~n; 7~tf'. In one embodiment, a single accelerator system may be used, i . e ., primary 20 accelerator. Conventionally and preferably, a primary accelerator(s) is used in total amounts ranging from about 0 . 5 to about 4, pref erably about 0 . 8 to about 2, phr. In another f~mh~9; t, combinations of a primary and a secondary accelerator might be used with the 25 secondary accelerator being used in amounts of about 0 . 05 to about 3 phr in order to activate and to improve the properties of the vulcanizate.
Combinations of these accelerators might be expected to produce a synergistic effect on the final 30 properties and are somewhat better than those produced by use of either accelerator alone. In addition, delayed action accelerators may be used which are not affected by normal processing temperatures but produce a satisfactory cure at ordinary vulri~n;7~t;on 35 temperatures. Vulr~n;7~t;on retarders might also be used. Suitable types of accelerators that may be used 2~81428 in the present invention are amines, disulfides, guanidines, thioureas, thiazoles, thiurams, sulf~n~m;~ , dithiocarbamates and ~n~h~
Preferably, the primary accelerator i9 a sulfenamide.
5 If a second accelerator is used, the secondary accelerator is preferably a gll~n;~q;no, dithiocarbamate or thiuram compound. The presence and relative amounts of sulfur vulr~n;7:;ng agent and accelerator(s) are not considered to be an aspect of this invention 10 which is more primarily directed to the use of the pre3cribed silylating agent in combination with a silica coupler in a silica reinforced rubber composition .
The presence and relative amounts of the other 15 additives, as hereinbef ore described, are not considered to be an aspect of the present invention which is more primarily directed to the utilization of the prescribed silylating agent (s), required to be used in combination with a silica coupler, in a silica 20 reinforced rubber composltion.
The mixing of the rubber composition can be ac~ mrl ;~h,~(l by methods known to those having skill in the rubber mixing art. For example, the ingredients are typically mixed in at least two stages, namely, at 25 least one non-productive stage followed by a productive mix stage. The final curatives are typically mixed in the f inal stage which is conventionally called the "productive" mix stage in which the mixing typically occurs at a tf~mr~or~tllrel or 30 ultimate temperature, lower than the mix temperature (s) than the preceding non-productive mix ~tage (s) . The rubber, silica, silica coupler, silica silylating agent, and carbon black if used, are mixed in one or more non-productive mix stages. The terms 35 "non-productive" and "productive" mix stages are well known to those having skill in the rubber mixing art.
2181~28 ' ~
The rubber composition o~ this invention can be used for various purposes. For example, it can be used for various tire compounds. Such tires can be built, shaped, molded and cured by various methods 5 which are known and will be readily apparent to those having skill in such art.
The invention may be better understood by reference to the following examples in which the parts and percentages are by weight unless otherwise 10 indicated EXI~MP~E I
In this Example, the trialkylgilyl-cnnt~;n~ng 15 silylating agent was evaluated as a component of compounding ingredients for a quantitatively silica reinforced elastomer composition Rubber compositions cnnt~n~ng the materials set out in Table l were prepared in a ~obe~ internal mixer 20 using two separate stages of addition (mixing), one non-productive mix stage and a productive mix stage to temperatures of 160~C and 100~C and times of 6 minutes and 2 minutes, respectively. The amount of silylating agent is listed as being "variable" in Table l and is 25 more specifically set forth in Table 2.
In comparison with Sample 1, Samples 2 and 3, which were prepared with addition of 3 and 6 phr silylating agent, respectively, clearly show the processing advantages of lower compound viscosity, 3 0 plus the cured property advantages in modulus, rebound and abrasion resistance. In particular, the tire tread performance indicator properties of Samples 2 and 3, which contain 3 and 6 phr of the silylating agent, are better than those of Sample 1, namely, the 35 300 percent modulus is higher and the abrasion weight 1088 is less, indicative of better treadwear 2 ~
potential, and the rebound is higher indicative o~
better (reduced) rolling resistance.
Table 1 Non-Productive M; Staqe IsR2 45 Cis 1,4-Polybutadiene3 20 10 Processing Oils, Waxes 24 . 9 Zinc Oxide 2 . 5 ~atty Acid 3 Antioxidantss 3 Silica6 80 15 Bis- (3-triethoxylsilylpropyl) 12 .8 tetrasulf ide7 N.N-bis (trimethylsilyl) urea8 variable Productive M; ~ taqe Sulfur 1. 4 20 Accelerators, sulfenamide and 3.7 guanidine types 1) Emulsion polymerization prepared styrene/butadiene copolymer rubber having a styrene content of about 40 percent and obtained from T:he Goodyear Tire & Rubber Company;
2 ) isoprene/butadiene copolymer rubber c-~ntA;n;ng about 50 percent isoprene and having a Tg of about -43~C obtained from The Goodyear Tire & Rubber Company;
2~81~28 3) cis 1,4-polybutadiene rubber obtained as Budene 1254 from The Goodyear Tire ~ Rubber Company;
AND TIRE WITH TREAD
Field This invention relates to rubber compositions which are quantitatively reinforced with silica. In one aspect, the rubber composition i9 comprised of rubber, particularl~r sulfur curable, or cured, rubber, reinforced with a, ;n~t10n of silica, silica coupling agent, sil~lating agent and, optionally, carbon black.
Background For various applications utilizing rubber which require high strength and abrasion resistance, particularly applications such as tires and various industrial products, sulfur cured rubber is utilized which contains substantial amounts of reinforcing fillers. Carbon black is commonly used for such purpose and normall~ provides or enhances good physical properties for the sulfur cured rubber.
Particulate silica is also often used for such purpose, particular~y when the ~ilica i5 used in conjunction with a coupling agent. In some cases, a combination of silica and carbon black is utilized for reinforcing fillers for various rubber products, including treads f or tires . The use of such reinforcing fillerg ~or elastomers, including sulfur curable elastomers, is well known to those having skill in such art.
It is important to appreciate that, conventionally, carbon black is a considerably more effective reinforcing filler for rubber products, and particularly for rubber tire treads than silica if the silica is used without a coupling agent, or silica coupler as it may be sometimes referred to herein.
Often coupling agents are composed of a silane which has at least one f irst constituent component, or moiety, (such as a ~3ilane portion) capable of reacting with the silica suri ace and, also, an additional 5 moiety capable of irlteracting with the rubber, particularly a suli ur vulcanizable rubber which ~-,,n~ ~ nq carbon- to - carbon double bonds, or unsaturation. Usua~ly the additional moiety is sulfur in a form of a poly~3ulfide and particularly a 10 polysulfide bridge between said i irst moieties . In this manner, then t~le coupler acts as a connecting bridge between the silica and the rubber and thereby f~nh;~nrf~c the rubber reinforcement aspect of the silica .
The rubber-reactive group component, namely the said additional moiety, of such coupler may be, for example, one or more of groups such as mercapto, amino, vinyl, epoxy, and sulfur groups, preferably a sulfur or mercapto moiety and more preferably sulfur in a i orm of a poly~3ulfide as a polysulfide bridge between at least two of said first moieties.
Numerous of such coupling agents are taught for use in ct~mh;n~ng silica and rubber, such as, for example, silane coupling agents ~-nn~;n;n~ a polysulfide component, or structure such as, for example, trialkoxyo~.ganosilane polysulfides, such as for example bis- (3-trialkoxysilylorgano) polysulfides, c~m~n~ng from about 2 to about 8 sulfur atoms in a polysulfide bridge such as, for example, bis- (3-triethoxysilylpropy~) tetrasulfide and/or trisulfide.
Various U.S. patents relating to silicas and silica reinforced tire treads include, for example, U.S. Patents Nos. 3l451,458; 3,664,403; 3,768,537;
3,884,285; 3,g38,574; 4,482,663; 4,590,052 and 5, 089, 554 .
218~428 . ~
In one aspect, and in contrast to the aforesaid rubber reactive silica coupling agents, other silica-reactive materials might be utilized to interact with the silica which have only one constituent component, 5 or moiety, and which is capable of reacting with the silica surface. Such materials are not readily reactive with the rubber 80 that they do not readily promote interaction between the silica and the rubber.
Therefore, by itself, such material is not r~n~;~Pred 10 herein to enable the silica to sat~ c~artrrily reinf orce the rubbe]- .
The term "phr" if used herein, and according to conventional practice, ref ers to "parts of a respective material per 100 parts by weight of rubber, 15 or elastomer".
In the description of this invention, the terms "rubber" and "elastomer" if used herein, may be used interchangeably, un:Less otherwise prescribed. The terms "rubber compo~3ition", "compounded rubber" and 20 "rubber compound", :if used herein, are used interchangeably to refer to "rubber which has been blended or mixed wi~ h various ingredients and materials " and such terms are well known to those having skill in the rubber mixing or rubber 2 5 compounding art .
Summary and Prac~ice of the Inventiorl In accordance ~ith this invention, a rubber composition is provided which comprises (A) 100 parts 30 by weight of at least one diene-based elastomer, (~3) about 50 to about lO0, optionally about 60 to about 90, phr particulate reinforcing filler composed of precipitated silica and carbon black, compri8ed of about 60 to about 100, alternatively about 60 to about 35 90, phr of precipitated silica which r~n~A;nA silanol groups thereon and correspondingly zero to about 10, 2~8~428 ~ ~S
alternatively zero to about 7 or about 3 to about 7, phr of carbon black, wherein the weight ratio of silica to carbon black is at least about 6/1 and alternatively, at least about 10/1, (C) at least one 5 silica coupler having a moiety reactive with said silica and another moiety interactive with said elastomer(s), (D) about 0.5 to about 10, alternatively about 2 to about 6 phr of a silanol-reactive, trialkylsilyl functional group-cnnt~;n;nrJ silylating 10 agent having the formula:
RlR2R3Si -X
where X is a radical ,selected from the group consisting of:
~1 ) halogen radical selected f rom one of chlorine, b~-omine and iodine (2) -NH-C=OR1, (3 ) -NR4 -A, (4) -NH-C=ONH-A, and (5) -N(R4)2 20 where R1, R2, R3 and R~l are individually selected from the group consisting of primary, secondary and tertiary alkyl radicals and alkaryl radicals having from 1 to 30, alternatively about 1 to about 3, carbon atoms, wherein R4 is alternatively 11YdLUY~ and A is 2 5 - S iRlR2R3 -It is an important feature of this invention thata relatively highly silica loaded elastomer composition is provided which cnnt~;nq the silica-reactive, silylating agent together with the silica 30 coupler rather than the silylating agent or silica coupler individually.
The term ~silylating agent" Conv~nt;nn~lly relates to materials which are capable of reacti~g with an active hydrogen-rr,nt~;n;ng substrate, for 35 example, a silanol group (SiOH) on a silica surface for this invention, to introduce a silyl functional , . ~
2~81428 ~' group to the substrate material, or silica surface for this invention.
The term "silylating agent" is used herein to mean the said trialkylsilyl functioIlal group-5 cr-n~;n;ng material which can react, for example, with a silanol group (SioH) on a silica surface to introduce the trialkylsilyl group onto the silica surf ace .
E3y the term "silica-reactive silylating agent", 10 it is meant herein that the trialkylsilyl groups of the agent react with silanol groups at the silica surface and, thus, chemically combine with the silica.
A trialkylsilyl group from the silylating agent is, thus, placed on the silica sur~ace in place of the 15 hydrogen atom of the silanol group.
It is important that the alkoxysilane component of a silica coupler ~qhich rrnt~1nc alkoxysilane units also reacts with the silanol groups at the surface of the silica and thereby also chemically combines with 20 the silica.
While it is recognized that both the silica coupler (the silane moiety of the coupler) and the silylating agent compete for the silanol groups on the silica surface, only the additional moiety of the 25 silica coupler such as, for example, a polysulfide bridge, has reactivity with the diene-based elastomer.
Because both the alkoxysilane moiety of a silane-crn~;n;ng silica coupler and the trialkylsilyl moiety of the silylating agent are reactive with and, thus, 30 compete for the silanol groups on the surface of the silica, it is important that the silylating agent be added to the silica concurrent with or subseo~uent to the silica coupler. As a result, while the precise mechanism, or result, may not be completely known, it 35 is considered herein that the silylating agent exerts a synergistic benefit to the ~ilica coupler, but does 218l428 ' ' ~' not replace its use. Such a synergistic benefit might be ob8erved, for example, as improved performance as might be exemplified by higher 300 percent modulus values, reduced hysteres~s a8 evidenced by hot rebound 5 value8 and/or improved abrasion resistance as may be evidenced by DIN abrasion te8t, when using a combination of both of the silylating agent and the silica coupler in the silica reinforced elastomer compo8ition, relative to the performance obtainable by 10 using eit~er the silylating agent or the silica coupler individually.
For the said silanol-reactive silylating agent, and for said Rl, R2, R~ and R~L, repre8entative examples of primary alkyl radicals are those 8elected from at 15 least one of methyl, ethyl, propyl, octyl, n-octadecyl, and n-hexadecyl radicals; representative examples of secondary alkyl radicals are those selected ~rom at lea~t one of isopropyl and sec-butyl radicals and representative examples of tertiary alkyl 20 radicals are those selected from at least one of tert-butyl, and dimethylbutyl radicals_ It i8 the trial~cylsilyl moiety of the silylating agent that is reacti~e with the surface of the precipitated silica ~hich is usually the silanol 25 groups on the surface of the 8ilica.
Representative, although not intended to be limitative, of various silylating agents are, for example, trimethylsilyl diethyl amine, N,N'-bis (trimethylsilyl) ~Irea, trimethyl chlorosilane, 30 hexamethyl disilazane and monotrimethylsilyl acetamide .
In the practice of this invention, it has been observed that the adclition of the aforesaid silica silylating agent to the rubber silica composition, 35 which C~n~ n~ the silica coupler, results in not only improved processing characteristics for the silica reinforced elastomer composition, such as reduced viscosity, but also in improved cured elastomer composition performance properties such as, for example, abrasion resistance, tear strength and rebound.
Cured physical properties such as abrasion resistance, tear stl~ength and rebound values may be simultaneously improved. This is r(~n~ red herein to be benef icial because tire treads having such properties are anticipated herein to provide one or more of improved treadwear, rolling resistance and durability .
It is re- o~n; 7F.~ that various silylating agents have hereinbefore been used for various purposes in various elastomeric composition8 such as, for example, silica and carbon black reinforced rubber compositions with 5-50 phr of si] ica and 10- 60 phr of carbon black.
For example, see (Japanese patent publication abstract No. 5051484) .
It is considered herein that this invention is a departure f rom such prior practice because the silica silylating agent cr1nt~;n;ng a trialkylsi~yl moiety is used in combination with a silica coupler, which ~ nt;l;nq a silane moiety, in a subst~nt;~lly silica reinforced ~eg. at least 60 phr of silica and less than 10 phr of carbon black) rubber composition.
In one aspect, a synergistic performance has been observed when using both the said silylating agent and silica coupler which was not observed when using either of the silylating agent or silica coupler alone for a silica reinforced elastomer composition.
Moreover, the synergistic effect seemed to be dependant upon using only a limited amount, or level, of the silylating agent.
While, in the practice of this invention various silica couplers can be used, one preferred coupler is 2181~28 ' ~' a bis- (trialkoxysilylalkyl) polysulfide c~nt~;n;ng from about 2 to about 8 sulfur atoms in the polysul~ide bridge an hereinbefore described. For example, the silica coupler can be bis- (3-5 triethoxysilylpropyl) tetrasulfide having an averageof about 4 sulfur atoms in its polysulfide bridge or, in an alternative, a polysulfide having about 2 sulfur atoms in its polysulfide bridge.
Conventionally a weight ratio of silica coupler 10 to silica is in a range of about 0 . 01/1 to about 0 . 25/1 .
In practice, a molar ratio based on trialkylsilyl functionality of the silica silylating agent to silane functionality of the silica coupler in a range of about 0.1/1 to about 4/1 alternatively, a molar ratio of about 0.5/1 to about 3/1, i9 preferred.
In one aspect of the invention, the rubber composition ~ nt;~; nc: a high level, or amount, of silica, namely at least about 50 phr ag a tlt-m;n;;nt elastomer reinforci~g pigment with less than 10 phr of carbon black as a secondary elastomer reinforcing material .
The rubber composition itself can also be provided as being a sulfur cured composition through vulcanization o~ the uncured elastomer composition.
The sulfur curing i8 accomplished in a conventional manner, namely by curing under conditions of elevated temperature and pre~sure for a suitable period of time .
Further, and in accordance with this invention, a tire is provided having a tread of the rubber composition of this invention.
The said curatives f or the process are curatives conventionally used for sulfur curable elastomers which typically include sulfur and one or more appropriate cure accelerator~ and somet~nes also a 2181~28 g retarder. Such curatives and use thereof for sulfur curable elastomer compositions are well known to those skilled in the art.
Further, sec~uential mixing processes for 5 preparing sulfur curable rubber compositions in which elastomers and associated ingredients exclusive of curatives are f irst mixed in one or more secruential steps followed by a final mixing step for adding curatives are also ~rell known to those skilled in the 10 art.
In the practice of this invention, as hereinbefore pointed out, the rubber composition is comprised of at least one diene-based elastomer, or rubber. Such elastc)mers are typically selected from 15 homopolymers and copolymers of conjugated dienes and copolymers of con; ugated diene ( g ) and vinyl aromatic compound. Such dienes may, for example, be selected from isoprene and 1,3-butadiene and suoh vinyl aromatic compounds may be selected f rom styrene and 20 alphamethylstyrene. Such elastomer, or rubber, may be selected, for examp~e, from at least one of cis 1,4-polyir~oprene rubber (natural and/or synthetic, and preferably natural rubber), 3,4-polyisoprene rubber, styrene/butadiene copolymer rubbers, 25 isoprene/butadiene copolymer rubbers, styrene/isoprene copolymer rubbers, styrene/isoprene/butadiene terpolymer rubbers, cis 1, 4 -polybutadiene rubber, trans 1,4-polybutadiene rubber (70-95 percent trans), low vinyl polybutadiene rubber (10-30 percent vinyl), 30 medium vinyl polybutadiene rubber (30-50 percent vinyl) and high vin~l polybutadiene rubber (50-90 percent vinyl ) .
In one aspect, particularly for a tire tread, the rubber is preferabl~ of at least two of diene based 35 rubbers . For examp] e, a combination of two or more rubbers is preferred such as cis 1,4-polyisoprene 2181~28 . ~
rubber (natural or synthetic, although natural is preferred), 3,4-pol~risoprene rubber, styrene/isoprene/bu~ ; PnP rubber, emulsion and/or solution polymerization derived styrene/butadiene 5 rubbers, cis 1,4-poly~tAr~ n-~ rubbers and emulsion polymerization prepared butadiene/acrylonitrile copolymers .
In one aspect of this invention, an emulsion polymerization derived styrene/butadiene (E-SBR) might 10 be used having a relatively conventional styrene content of about 20 to about 28 percent bound styrene or, for some applications, an E-SBR having a medium to relatively high bound styrene content, namely a bound styrene content of about 30 to about 45 percent.
The relatively high styrene content of about 30 to about 45 for the E-SBR can be considered beneficial for a purpose of ,on~An~ ;ny traction, or skid resistance, of the tire tread. The presence of the E-SBR itself is considered beneficial for a purpose of 20 enhancing processability of the uncured elastomer composition mixture, especially in comparison to a utilization of a solution polymerization prepared SBR
(S - SBR) .
By emulsion polymerization prepared E-SBR, it is 25 meant that styrene and 1,3-blltA~l;onP are copolymerized as an aqueous emulsion. Such are well known to those skilled in such art The bound styrene content can vary, for example, from about 5 to 50~6. In one aspect, the E-SBR m~y also contain acrylonitrile to 30 form a terpolymer rubber, as E-SBAR, in amounts, for example, of about 2 to about 3 0 weight percent bound acrylonitrile in the terpolymer.
Emulsion polymerization prepared styrene/butadiene/acrylonitrile terpolymer rubbers 35 contA;n1n~ about 2 to about 40 weight percent bound acrylonitrile in the copolymer are also Cont ~1 ~ted as diene based rubbers for use in this invention, particularly if used in ~:l ;n~;on with other diene-based elastomers.
The solution polymerization prepared SsR (S-SBR) 5 typically has a bound styrene content in a range of about 5 to about 50, preferably about 9 to about 36, percent. The S-SBR can be conveniently prepared, for example, by organo lithium catalyzation in the pre~ence of an organic hydrocarbon solvent.
A purpose of using S-SBR may be to promote a reduction in tire rolling resistance as a result of lower hysteresis when it is used in a tire tread composition .
The 3,4-polyisoprene rubber (3,4-PI) is 15 considered beneficial for a purpose of promoting the tire' s traction when it is used in a tire tread composition .
The 3,4-PI and use thereof is more fully described in U.S. Patent No. 5,087,668 which is 20 incorporated herein by reference. The Tg refers to the glass transition temperature which can conveniently be det~;n~r7 by a differential scanning calorimeter at a heating rate of 10~C per minute.
The cis 1,4-polybutadiene rubber (BR) is 25 considered to be beneficial for a purpose of promoting the tire tread' 8 wear, or treadwear.
Such BR can be prepared, for example, by organic solution polymerization of 1, 3-butadiene.
The BR may be conveniently characterized, for 30 ex~nple, by having at least a 90% cis 1,4-content.
The cis 1,4-polyisoprene and cis 1,4-polyisoprene natural rubber are well known to those having skill in the rubber art.
The vulcanized rubber composition should contain 35 a sufficient amount of precipitated silica reinforcing filler namely, greater than about 50 phr, to -218~428 ' . ~
contribute a reasonably high modulus, high abrasion resistance and resistance to tear ~or the cured rubber composition. The amount of the silica, as hereinbefore referenced, may be a3 low as about 50 5 parts per 100 part3 rubber, but is preferably ~rom about 60 to about 90 or even up to about 100 parts by weight .
Carbon black may be present in levels below about 10 phr or not at all. Carbon black is not intended to 10 serve as a principal reinforcing filler in the elastomer compositions of this invention Herein, the carbon black if used, is used primarily as a colorant where a black colored elastomer composition is desired and/or as a carrier for liquid additives for elastomer 15 composition such as, for example, the silica coupler if it would otherwise be added to the elastomer composition in a li~lid form.
The commonly employed siliceous pigments used in rubber compounding applications can be used as the 20 silica in this invention, including pyrogenic and precipitated siliceou8 pigments (silica), although precipitated silicas are preferred.
The siliceous pigments preferably employed in this invention are p~~ecipitated silicas such as, for 25 example, those obtained by the acidification of a soluble silicate, e.g., sodium silicate, generally exclusive of silica gels.
Such silicas might be characterized, for example, by having a BET surface area, as mea3ured using 30 nitrogen gas, preferc1bly in the range of about 40 to about 600, and more usually in a range of about 50 to about 300 square meters per gram. The B~T method of measuring suri~ace area is described in the ~Jol~rn~l Of the ~mprican ~h.-m~ Society, Volume 60, page 304 (1930).
~
The silica may also be typically characterized by having a dibutylphth.alate (DBP) absorption value in a range of about 100 to about 400, and more usually about 150 to about 300.
The 8ilica might be expected to have an average ultimate particle size, for example, in the range of O . 01 to 0 . 05 micron as detPrm; nPtl by the electron microscope, although. the silica particles may be even smaller, or possibly larger, in size Various commercially available silicas may be considered for use in this invention such as, only for example herein, and without limitation, silicas commercially available from PPG Industries under the Hi-Sil trademark with designations 210, 243, etc;
silicas available from Rhone-Poulenc, with, for example, designations of Zeosil 1165MP and silicas available from Degussa A(~ with, for example, designations VN2 and VN3, etc.
It is readily understood by those having skill in the art that the rubber composition would be compounded by methods generally known in the rubber compounding art, such as mixing the various sulfur-wlcanizable constituent rubbers with various commonly used additive materials such as, for example, curing aids, such as sulfur, activators, retarders and accelerators, processing additives, such as oils, resins including tackifying resins, silicas, and plasticizers, fillers, pigments, fatty acid, zinc oxide, waxes, antin~;~ntq and antiozonants, peptizing agents and reinforcing materials such as, for example, carbon black. As known to those skilled in the art, ~lPrPnr~1ng on the ;ntpnflp~l use of the sulfur wlcanizable and sulfur wlcanized material (rubbers), the additives mentioned above are selected and commonly used in conventional amounts.
~ ow amounts of reinforcing type carbon blacks (8), for this invention, if used, are hereinbefore set f orth .
It is to be appreciated that the silica coupler 5 and/or the silica silylating agent, if in a liquid form, may be used in con~unction with a carbon black carrier, namely, pre-mixed with a carbon black prior to the addition to the rubber composition, and such carbon black is to be included in the aforesaid amount 10 of carbon black accounted for in the rubber composition formlllAtion.
Typical amounts of tackif ier resins, if used, comprise about O . 5 to about 10 phr, usually about 1 to about 5 phr. Typical amounts of processing aids 15 comprise about 1 to about 50 phr. Such processing aids can include, for example, aromatic, napthenic, and/or paraffinic processing oils. Typical amounts of anti~ ;flAnt~ comprise about 1 to about 5 phr.
Representative antioxidants may be, for example, 20 diphenyl-p-phenyl~n~rl;Am;nl~ and others, such as, for example, those disclosed in the Vanderbilt R~lhher E~andbook (1978), pages 344-346. Typical amounts of antiozonants comprise about 1 to 5 phr.
Typical amounts of fatty acids, if used, which 25 can include stearic acid, palmitic acid, linoleic acid or mixtures of one or more fatty acids, can comprise about O . 5 to about 3 phr .
Often stearic acid is used in a relatively impure state and is commonly referred to in the rubber 30 compounding practice as "stearic acid" and is 80 referred to in the description and practice of this invention .
Typical amounts of zinc oxide comprise about 2 to about 5 phr. Typical amounts of waxes comprise about 35 1 to about 5 phr. Often microcrystalline waxes are used. Typical amounts of peptizers, if used, comprise 218~428 about 0.1 to about 1 phr. Typical peptizers may be, for example, pentachlorothiophenol and dib~n7~m;~nrl;phenyl disulfide.
The vulr~n;7~t;on i8 conducted in the presence of 5 a sulfur vulcanizlng agent. Examples of suitable sul f ur vul cani z ing agents include el emental sul f ur (free sulfur) or sulfur donating wlcanizing agents, for example, an amine disulfide, polymeric polysulfide or sulfur olefin adducts. Preferably, the sulfur 10 vulr~n;7~ng agent is Pl~m~nti~l sulfur. As known to those skilled in the art, sulfur wlr~n~7~ng agents are used in an amount ranging from about 0 . 5 to about 4 phr, or even, in some circumstances, up to about 8 phr, with a range of from about 1 to about 2.5, 15 sometimes from about 1 to about 2, being preferred.
Accelerators are used to control the time and/or temperature required for vulr~n;7~t~on and to improve the properties of the vulr~n; 7~tf'. In one embodiment, a single accelerator system may be used, i . e ., primary 20 accelerator. Conventionally and preferably, a primary accelerator(s) is used in total amounts ranging from about 0 . 5 to about 4, pref erably about 0 . 8 to about 2, phr. In another f~mh~9; t, combinations of a primary and a secondary accelerator might be used with the 25 secondary accelerator being used in amounts of about 0 . 05 to about 3 phr in order to activate and to improve the properties of the vulcanizate.
Combinations of these accelerators might be expected to produce a synergistic effect on the final 30 properties and are somewhat better than those produced by use of either accelerator alone. In addition, delayed action accelerators may be used which are not affected by normal processing temperatures but produce a satisfactory cure at ordinary vulri~n;7~t;on 35 temperatures. Vulr~n;7~t;on retarders might also be used. Suitable types of accelerators that may be used 2~81428 in the present invention are amines, disulfides, guanidines, thioureas, thiazoles, thiurams, sulf~n~m;~ , dithiocarbamates and ~n~h~
Preferably, the primary accelerator i9 a sulfenamide.
5 If a second accelerator is used, the secondary accelerator is preferably a gll~n;~q;no, dithiocarbamate or thiuram compound. The presence and relative amounts of sulfur vulr~n;7:;ng agent and accelerator(s) are not considered to be an aspect of this invention 10 which is more primarily directed to the use of the pre3cribed silylating agent in combination with a silica coupler in a silica reinforced rubber composition .
The presence and relative amounts of the other 15 additives, as hereinbef ore described, are not considered to be an aspect of the present invention which is more primarily directed to the utilization of the prescribed silylating agent (s), required to be used in combination with a silica coupler, in a silica 20 reinforced rubber composltion.
The mixing of the rubber composition can be ac~ mrl ;~h,~(l by methods known to those having skill in the rubber mixing art. For example, the ingredients are typically mixed in at least two stages, namely, at 25 least one non-productive stage followed by a productive mix stage. The final curatives are typically mixed in the f inal stage which is conventionally called the "productive" mix stage in which the mixing typically occurs at a tf~mr~or~tllrel or 30 ultimate temperature, lower than the mix temperature (s) than the preceding non-productive mix ~tage (s) . The rubber, silica, silica coupler, silica silylating agent, and carbon black if used, are mixed in one or more non-productive mix stages. The terms 35 "non-productive" and "productive" mix stages are well known to those having skill in the rubber mixing art.
2181~28 ' ~
The rubber composition o~ this invention can be used for various purposes. For example, it can be used for various tire compounds. Such tires can be built, shaped, molded and cured by various methods 5 which are known and will be readily apparent to those having skill in such art.
The invention may be better understood by reference to the following examples in which the parts and percentages are by weight unless otherwise 10 indicated EXI~MP~E I
In this Example, the trialkylgilyl-cnnt~;n~ng 15 silylating agent was evaluated as a component of compounding ingredients for a quantitatively silica reinforced elastomer composition Rubber compositions cnnt~n~ng the materials set out in Table l were prepared in a ~obe~ internal mixer 20 using two separate stages of addition (mixing), one non-productive mix stage and a productive mix stage to temperatures of 160~C and 100~C and times of 6 minutes and 2 minutes, respectively. The amount of silylating agent is listed as being "variable" in Table l and is 25 more specifically set forth in Table 2.
In comparison with Sample 1, Samples 2 and 3, which were prepared with addition of 3 and 6 phr silylating agent, respectively, clearly show the processing advantages of lower compound viscosity, 3 0 plus the cured property advantages in modulus, rebound and abrasion resistance. In particular, the tire tread performance indicator properties of Samples 2 and 3, which contain 3 and 6 phr of the silylating agent, are better than those of Sample 1, namely, the 35 300 percent modulus is higher and the abrasion weight 1088 is less, indicative of better treadwear 2 ~
potential, and the rebound is higher indicative o~
better (reduced) rolling resistance.
Table 1 Non-Productive M; Staqe IsR2 45 Cis 1,4-Polybutadiene3 20 10 Processing Oils, Waxes 24 . 9 Zinc Oxide 2 . 5 ~atty Acid 3 Antioxidantss 3 Silica6 80 15 Bis- (3-triethoxylsilylpropyl) 12 .8 tetrasulf ide7 N.N-bis (trimethylsilyl) urea8 variable Productive M; ~ taqe Sulfur 1. 4 20 Accelerators, sulfenamide and 3.7 guanidine types 1) Emulsion polymerization prepared styrene/butadiene copolymer rubber having a styrene content of about 40 percent and obtained from T:he Goodyear Tire & Rubber Company;
2 ) isoprene/butadiene copolymer rubber c-~ntA;n;ng about 50 percent isoprene and having a Tg of about -43~C obtained from The Goodyear Tire & Rubber Company;
2~81~28 3) cis 1,4-polybutadiene rubber obtained as Budene 1254 from The Goodyear Tire ~ Rubber Company;
4) natural Ci8 1,4-polyisoprene rubber;
5 ) of the phenylene diamine types;
6) Z1165MP from Rhone Poulenc;
7) a 50/50 blend or composite of bis- (3-triethoxysilylpropyl ) tetrasul f ide, said composite co~ercially available from Degussa GmbH as X50S. Technically, the tetrasulfide is understood to be an organosilane polysulfide as a composite, or mixture, in which the average polysulfide bridge t~f~nt~l~nq about 3.5 to about 4 connectiny sulfur atoms, although the mixture may contain such polysulfides with about 2 to about 8 connecting sulfur atoms;
8) silylating agent obtainable from Eluls America, Inc .
~81428 ~ 20 ~
Tabl e 2 Sam~le # 1 2 -i N,N'-bis (trimethylsilyl) 0 3 6 urea, phr Cured Physical Pro~erties 30096 Modulus, MPa 10.1 11 7 11 8 Rebound (100~C) 60 62 62 DIN Abrasion Resistance, 108 104 102 rel wt. loss 10 Visc08itY - Uncured (M~oney MS 1+1~5r lC0~C) Non-productive mixed 98 78 72 elastomer composition Productive mixed 55 52 50 elastomer composition In particular, ~this Example shows that the silylating agent, N,]~' -bis (trimethylsilyl) urea, as utilized in Samples 2 and 3 ~ in conjunction with the silica coupler, can provide significant impL~v.
For example, the processing of the elastomer composition of Samples 2 and 3 ~ as compared to Control Sample 1, was ; ~ ~,vl :d as evidenced by the reduced uncured viscosities Eor both the non-productive mixed elastomer compositions and the productive mixed elastomer compositiol1s.
Further, the 3 0 0 percent modulus, hot rebound and DIN abrasion resistance values were improved for Samples 2 and 3 as compared to Control Sample No. 1 which rnnt;3;n~1 only the silica coupler without the silylating agent.
EXAMP~E II
Rubber compositions ~nnt~;n;ng the materials set out in Table 3 and as described in ~xample I were prepared in a Robe~ internal mixer using one non-~ 2181428 productive mix stage and a productive mix stage, to temperatures of 160~C and 100~C and times of 8 minutes and 2 minutes, respectively. The amounts of both silica coupler and silylating agent are listed as 5 variable in Table 3 and are more 8pecif ically set forth in Table 4.
Sample No. 7 which c~rt~ only the silylating agent at 6 phr and no silica coupler, when compared to Sample No. 4 which contains only silica coupler at 6.4 10 phr and no silylating agent, clearly shows much inferior cured physical properties, including 300 percent modulus, DIN abrasion resistance and room temperature rebound.
Sample No. 5, w]lich contains the silylating agent 15 at 6 phr in addition to silica coupler, exhibits superior cured physical properties such as DIN
abrasion resistance, tear strength and room temperature rebound ~vhich are indicative of improved tire performance such as durability, treadwear and 20 rolling resistance.
Sample No. 6, in contrast, and which contains the silylating agent at 12 phr in addition to the silica coupler, has cured physical properties similar to those of Sample No. 4, and inferior to those of Sample 25 No. 5. In particular, the abrasion resistance, room temperature rebound and tear strength of Sample No. 6 are inf erior to those properties of Sample No . 5 .
This indicates that an upper limit exists for the beneficial synergistic activity of the silylating 30 agent in conjunction with the silica coupler in a highly silica reinforced rubber composition.
Thus, the use of silylating agent without silica coupler is observed to be inferior in the physical property reinforcing characteristics which corre8ponds 35 to the tire tread treadwear and rolling resistance performance indicators. The use of the silylating 2181~28 .
agent at 6 phr in rl ' ;nAt;on with silica coupler provided what is rnn~ Pred herein to be synergistic improvements in the cured physical properties such as abrasion resistance, modulus ratio, rebound and tear 5 resistance. ~he use of the silylating agent at 12 phr in cnmh;n~t;nn with the silica coupler was observed to be no longer optimum and did not show the synergistic ~ Jv. -ntc geen for the lower level of silylating agent .
Table 3 Non- Productive Mi Staqe 15 Cis 1,4-Polybllt~fl;~nf~ 20 Processing Oils, Waxes 24 . 9 Zinc Oxide 2 . 5 Fatty Acid 3 2 0 Anti n~ n t c 3 Silica 30 Bis- (3-triethoxylsilylpropyl) variable tetrasulf ide N.N-bis (trimethylsilyl) urea variable Productive Mix taqe Sulfur 1. 4 Accelerators, sulfenamide and 3.7 guanidine types 2~8~428 Table 4 Sam~le # 4 5 6 7 N,N'-bis 0 6 12 6 ( trimethylsilyl ) 5urea, phr Bis- (3- 6.4 6.4 6.4 0 trieth~,~y~ yl) tetrasulf ide, phr Cured Phy~ical Pro~e~ties 10 300~ Modulus, MPa 13.4 11.7 13.6 2.9 Rebound (23 ~C) 40 42 40 34 DIN Abrasion 103 92 97 125 Resistance. rel.
wt. 1098 15 Strebler Tear 54 79 52 141 Resistance, N
While certain r~presentative embodiments and 20 details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in thi~ art that various changes and modif ications may be made therein without departing from the spirit or scope of the invention.
~81428 ~ 20 ~
Tabl e 2 Sam~le # 1 2 -i N,N'-bis (trimethylsilyl) 0 3 6 urea, phr Cured Physical Pro~erties 30096 Modulus, MPa 10.1 11 7 11 8 Rebound (100~C) 60 62 62 DIN Abrasion Resistance, 108 104 102 rel wt. loss 10 Visc08itY - Uncured (M~oney MS 1+1~5r lC0~C) Non-productive mixed 98 78 72 elastomer composition Productive mixed 55 52 50 elastomer composition In particular, ~this Example shows that the silylating agent, N,]~' -bis (trimethylsilyl) urea, as utilized in Samples 2 and 3 ~ in conjunction with the silica coupler, can provide significant impL~v.
For example, the processing of the elastomer composition of Samples 2 and 3 ~ as compared to Control Sample 1, was ; ~ ~,vl :d as evidenced by the reduced uncured viscosities Eor both the non-productive mixed elastomer compositions and the productive mixed elastomer compositiol1s.
Further, the 3 0 0 percent modulus, hot rebound and DIN abrasion resistance values were improved for Samples 2 and 3 as compared to Control Sample No. 1 which rnnt;3;n~1 only the silica coupler without the silylating agent.
EXAMP~E II
Rubber compositions ~nnt~;n;ng the materials set out in Table 3 and as described in ~xample I were prepared in a Robe~ internal mixer using one non-~ 2181428 productive mix stage and a productive mix stage, to temperatures of 160~C and 100~C and times of 8 minutes and 2 minutes, respectively. The amounts of both silica coupler and silylating agent are listed as 5 variable in Table 3 and are more 8pecif ically set forth in Table 4.
Sample No. 7 which c~rt~ only the silylating agent at 6 phr and no silica coupler, when compared to Sample No. 4 which contains only silica coupler at 6.4 10 phr and no silylating agent, clearly shows much inferior cured physical properties, including 300 percent modulus, DIN abrasion resistance and room temperature rebound.
Sample No. 5, w]lich contains the silylating agent 15 at 6 phr in addition to silica coupler, exhibits superior cured physical properties such as DIN
abrasion resistance, tear strength and room temperature rebound ~vhich are indicative of improved tire performance such as durability, treadwear and 20 rolling resistance.
Sample No. 6, in contrast, and which contains the silylating agent at 12 phr in addition to the silica coupler, has cured physical properties similar to those of Sample No. 4, and inferior to those of Sample 25 No. 5. In particular, the abrasion resistance, room temperature rebound and tear strength of Sample No. 6 are inf erior to those properties of Sample No . 5 .
This indicates that an upper limit exists for the beneficial synergistic activity of the silylating 30 agent in conjunction with the silica coupler in a highly silica reinforced rubber composition.
Thus, the use of silylating agent without silica coupler is observed to be inferior in the physical property reinforcing characteristics which corre8ponds 35 to the tire tread treadwear and rolling resistance performance indicators. The use of the silylating 2181~28 .
agent at 6 phr in rl ' ;nAt;on with silica coupler provided what is rnn~ Pred herein to be synergistic improvements in the cured physical properties such as abrasion resistance, modulus ratio, rebound and tear 5 resistance. ~he use of the silylating agent at 12 phr in cnmh;n~t;nn with the silica coupler was observed to be no longer optimum and did not show the synergistic ~ Jv. -ntc geen for the lower level of silylating agent .
Table 3 Non- Productive Mi Staqe 15 Cis 1,4-Polybllt~fl;~nf~ 20 Processing Oils, Waxes 24 . 9 Zinc Oxide 2 . 5 Fatty Acid 3 2 0 Anti n~ n t c 3 Silica 30 Bis- (3-triethoxylsilylpropyl) variable tetrasulf ide N.N-bis (trimethylsilyl) urea variable Productive Mix taqe Sulfur 1. 4 Accelerators, sulfenamide and 3.7 guanidine types 2~8~428 Table 4 Sam~le # 4 5 6 7 N,N'-bis 0 6 12 6 ( trimethylsilyl ) 5urea, phr Bis- (3- 6.4 6.4 6.4 0 trieth~,~y~ yl) tetrasulf ide, phr Cured Phy~ical Pro~e~ties 10 300~ Modulus, MPa 13.4 11.7 13.6 2.9 Rebound (23 ~C) 40 42 40 34 DIN Abrasion 103 92 97 125 Resistance. rel.
wt. 1098 15 Strebler Tear 54 79 52 141 Resistance, N
While certain r~presentative embodiments and 20 details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in thi~ art that various changes and modif ications may be made therein without departing from the spirit or scope of the invention.
Claims (44)
1. A rubber composition comprised of (A) 100 parts by weight of at least one diene-based elastomer, (B) about 50 to about 100 phr of particulate reinforcing filler composed of silica and optionally carbon black, composed of about 60 to about 100 phr of precipitated silica and correspondingly zero to about 10 phr of carbon black, wherein the weight ratio of silica to carbon black, if carbon black is used, is at least about 6/1, (C) at least one silica coupler having a moiety reactive with said silica and another moiety interactive with said elastomer(s), (D) about 0.5 to about 10 phr of silica-reactive, trialkylsilyl functional group-containing silylating agent wherein the molar ratio based on silane functionality of the silylating agent to silica coupler is in a range of about 0.1/1 to 4/1; wherein said silylating agent has the formula:
R1R2R3Si-X
where X is a radical selected from the group consisting of:
(1) halogen radical selected from one of chlorine, bromine and iodine, (2) -NH-C=OR1, (3) -NR4-A, (4) -NH-C=ONH-A, and (5) -N(R4)2 R1, R2, R3 and R4 are individually selected from the group consisting of primary, secondary and tertiary alkyl radicals and alkaryl radicals having from 1 to 30 carbon atoms and A is -SiR1R2R3.
R1R2R3Si-X
where X is a radical selected from the group consisting of:
(1) halogen radical selected from one of chlorine, bromine and iodine, (2) -NH-C=OR1, (3) -NR4-A, (4) -NH-C=ONH-A, and (5) -N(R4)2 R1, R2, R3 and R4 are individually selected from the group consisting of primary, secondary and tertiary alkyl radicals and alkaryl radicals having from 1 to 30 carbon atoms and A is -SiR1R2R3.
2. The rubber composition of claim 1 wherein for said R1, R2, R3 and R4 of said silylating agent, representative examples of primary alkyl radicals are those selected from at least one of methyl, ethyl, propyl, octyl, n-octadecyl, and n-hexadecyl radicals;
representative examples of secondary alkyl radicals are those selected from at least one of isopropyl and sec-butyl radicals and representative examples of tertiary alkyl radicals are those selected from at least one of tert-butyl and dimethylbutyl radicals.
representative examples of secondary alkyl radicals are those selected from at least one of isopropyl and sec-butyl radicals and representative examples of tertiary alkyl radicals are those selected from at least one of tert-butyl and dimethylbutyl radicals.
3. The rubber composition of claim 1 wherein said silylating agent is selected from at least one of trimethylsilyl diethyl amine, N,N'-bis(trimethylsilyl) urea, trimethyl chlorosilane, hexamethyl disilazane and monotrimethylsilyl acetamide.
4. The rubber composition of claim 1 wherein the silica coupler is a bis-(trialkoxysilylorgano) polysulfide containing from about 2 to about 8 sulfur atoms in the polysulfide bridge.
5. The rubber composition of claim 1 wherein the silica coupler is a bis-(trialkoxysilylalkyl) polysulfide.
6. The rubber composition of claim 4 wherein the silica coupler is a bis-(3-triethoxysilylpropyl) tetrasulfide.
7. The rubber composition of claim 1 wherein the diene based elastomer is selected from at least one of cis 1,4-polyisoprene rubber, 3,4-polyisoprene rubber, styrene/butadiene copolymer rubbers, isoprene/butadiene copolymer rubbers, styrene/isoprene copolymer rubbers, styrene/isoprene/butadiene terpolymer rubbers, cis 1,4-polybutadiene rubber, trans 1,4-polybutadiene rubber (70-95 percent trans), low vinyl polybutadiene rubber (10-30 percent vinyl), medium vinyl polybutadiene rubber (30-50 percent vinyl), high vinyl polybutadiene rubber (50-90 percent vinyl) and emulsion polymerization prepared styrene/butadiene/acrylonitrile terpolymer rubber and butadiene/acrylonitrile copolymer rubber.
8. The rubber composition of claim 1 wherein the silica is a precipitated silica characterized by having a BET surface area in a range of about 50 to about 300 square meters per gram and a dibutylphthalate (DBP) absorption value in a range of about 150 to about 300 cc/100 gm.
9. A rubber composition comprised of (A) 100 parts by weight of at least one diene based one diene-based elastomer, (B) about 60 to about 90, phr particulate reinforcing filler composed of silica and optionally carbon black, composed of about 60 to about 90 phr of precipitated silica and about 3 to about 7 phr of carbon black, wherein the weight ratio of silica to carbon black is at least about 6/1, (C) at least one silica coupler having a moiety reactive with said silica and another moiety interactive with said elastomer(s), (D) about 0.5 to about 10 phr of silica-reactive, trialkylsilyl functional group-containing silylating agent wherein the molar ratio based on silane functionality of the silylating agent to silica coupler is in a range of about 0.1/1 to 4/1; wherein said silylating agent has the formula:
R1R2R3Si-X
where X is a radical selected from the group consisting of:
(1) halogen radical selected from one of chlorine, bromine and iodine, (2) -NH-C=OR1, (3) -NR4-A, (4) -NH-C=ONH-A, and (5) -N(R4)2 R1, R2, R3 and R4 are individually selected from the group consisting of primary, secondary and tertiary alkyl radicals and alkaryl radicals having from 1 to about 3 carbon atoms, and A is -SiR1R2R3.
R1R2R3Si-X
where X is a radical selected from the group consisting of:
(1) halogen radical selected from one of chlorine, bromine and iodine, (2) -NH-C=OR1, (3) -NR4-A, (4) -NH-C=ONH-A, and (5) -N(R4)2 R1, R2, R3 and R4 are individually selected from the group consisting of primary, secondary and tertiary alkyl radicals and alkaryl radicals having from 1 to about 3 carbon atoms, and A is -SiR1R2R3.
10. The rubber composition of claim 9 wherein for said R1, R2, R3 and R4 of said silylating agent, representative examples of primary alkyl radicals are those selected from at least one of methyl, ethyl, propyl, octyl, n-octadecyl, and n-hexadecyl radicals;
representative examples of secondary alkyl radicals are those selected from at least one of isopropyl and sec-butyl radicals and representative examples of tertiary alkyl radicals are those selected from at least one of tert-butyl and dimethylbutyl radicals.
representative examples of secondary alkyl radicals are those selected from at least one of isopropyl and sec-butyl radicals and representative examples of tertiary alkyl radicals are those selected from at least one of tert-butyl and dimethylbutyl radicals.
11. The rubber composition of claim 9 wherein said silylating agent is selected from at least one of trimethylsilyl diethyl amine, N,N'-bis(trimethylsilyl) urea, trimethyl chlorosilane, hexamethyl disilazane and monotrimethylsilyl acetamide.
12. The rubber composition of claim 9 wherein the silica coupler is a bis-(trialkoxysilylorgano) polysulfide containing from about 2 to about 8 sulfur atoms in the polysulfide bridge.
13. The rubber composition of claim 10 wherein the silica coupler is a bis-(trialkoxysilylalkyl) polysulfide.
14. The rubber composition of claim 11 wherein the silica coupler is a bis-(3-triethoxysilylpropyl) tetrasulfide.
15. The rubber composition of claim 9 wherein the diene based elastomer is selected from at least one of cis 1,4-polyisoprene rubber, 3,4-polyisoprene rubber, styrene/butadiene copolymer rubbers, isoprene/butadiene copolymer rubbers, styrene/isoprene copolymer rubbers, styrene/isoprene/butadiene terpolymer rubbers, cis 1,4-polybutadiene rubber, trans 1,4-polybutadiene rubber (70-95 percent trans), low vinyl polybutadiene rubber (10-30 percent vinyl), medium vinyl polybutadiene rubber (30-50 percent vinyl), high vinyl polybutadiene rubber (50-90 percent vinyl) and emulsion polymerization prepared styrene/butadiene/acrylonitrile terpolymer rubber and butadiene/acrylonitrile copolymer rubber.
16. The rubber composition of claim 9 wherein the silica is a precipitated silica characterized by having a BET surface area in a range of about 50 to about 300 square meters per gram and a dibutylphthalate (DBP) absorption value in a range of about 150 to about 300 cc/100 gm.
17. A rubber composition comprised of (A) 100 parts by weight of at least one diene based one diene-based elastomer, (B) about 60 to about 90, phr particulate reinforcing filler composed of silica and optionally carbon black, composed of about 60 to about 90 phr of precipitated silica and about 3 to about 7 phr of carbon black, wherein the weight ratio of silica to carbon black is at least about 6/1, (C) at least one silica coupler having a moiety reactive with said silica and another moiety interactive with said elastomer(s), (D) about 0.5 to about 10 phr of silica-reactive, trialkylsilyl functional group-containing silylating agent wherein the molar ratio based on silane functionality of the silylating agent to silica coupler is in a range of about 0.1/1 to 4/1; wherein said silylating agent has the formula:
R1R2R3Si-X
where X is a radical selected from the group consisting of:
(1) halogen radical selected from one of chlorine, bromine and iodine, (2) -NH-C=OR1, (3) -NR4-A, (4) -NH-C=ONH-A, and (5) -N(R4)2 R1, R2 and R3 are individually selected from the group consisting of primary, secondary and tertiary alkyl radicals and alkaryl radicals having from 1 to about 3 carbon atoms, where R4 is hydrogen, and A is -SiR1R2R3.
R1R2R3Si-X
where X is a radical selected from the group consisting of:
(1) halogen radical selected from one of chlorine, bromine and iodine, (2) -NH-C=OR1, (3) -NR4-A, (4) -NH-C=ONH-A, and (5) -N(R4)2 R1, R2 and R3 are individually selected from the group consisting of primary, secondary and tertiary alkyl radicals and alkaryl radicals having from 1 to about 3 carbon atoms, where R4 is hydrogen, and A is -SiR1R2R3.
18. The rubber composition of claim 17 wherein for said R1, R2 and R3 of said silyIating agent, representative examples of primary alkyl radicals are those selected from at least one of methyl, ethyl, propyl, octyl, n-octadecyl, and n-hexadecyl radicals;
representative examples of secondary alkyl radicals are those selected from at least one of isopropyl and sec-butyl radicals and representative examples of tertiary alkyl radicals are those selected from at least one of tert-butyl and dimethylbutyl radicals.
representative examples of secondary alkyl radicals are those selected from at least one of isopropyl and sec-butyl radicals and representative examples of tertiary alkyl radicals are those selected from at least one of tert-butyl and dimethylbutyl radicals.
19. The rubber composition of claim 17 wherein said silylating agent is selected from at least one of trimethylsilyl diethyl amine, N,N' -bis (trimethylsilyl) urea, trimethyl chlorosilane, hexamethyl disilazane and monotrimethylsilyl acetamide.
20. The rubber composition of claim 17 wherein the silica coupler is a bis-(trialkoxysilylorgano) polysulfide containing from about 2 to about 8 sulfur atoms in the polysulfide bridge.
21. The rubber composition of claim 18 wherein the silica coupler is a bis-(trialkoxysilylalkyl) polysulfide.
22. The rubber composition of claim 19 whereln the silica coupler is a bis-(3-triethoxysilylpropyl) tetrasulfide.
23. A tire having a tread of the rubber composition of claim 1.
24. A tire having a tread of the rubber composition of claim 2.
25. A tire having a tread of the rubber composition of claim 3.
26. A tire having a tread of the rubber composition of claim 4.
27. A tire having a tread of the rubber composition of claim 5.
28. A tire having a tread of the rubber composition of claim 6.
29. A tire having a tread of the rubber composition of claim 7.
30. A tire having a tread of the rubber composition of claim 8.
31. A tire having a tread of the rubber composition of claim 9.
32. A tire having a tread of the rubber composition of claim 10.
33. A tire having a tread of the rubber composition of claim 11.
34. A tire having a tread of the rubber composition of claim 12.
35. A tire having a tread of the rubber composition of claim 13.
36. A tire having a tread of the rubber composition of claim 14.
37. A tire having a tread of the rubber composition of claim 15.
38. A tire having a tread of the rubber composition of claim 16.
39. A tire having a tread of the rubber composition of claim 17.
40. A tire having a tread of the rubber composition of claim 13.
41. A tire having a tread of the rubber composition of claim 19.
42. A tire having a tread of the rubber composition of claim 20.
43. A tire having a tread of the rubber composition of claim 21.
44. A tire having a tread of the rubber composition of claim 22.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/617,245 US5719207A (en) | 1996-03-18 | 1996-03-18 | Silica reinforced rubber composition and tire with tread |
| US08/617,245 | 1996-03-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2181428A1 true CA2181428A1 (en) | 1997-09-19 |
Family
ID=24472847
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002181428A Abandoned CA2181428A1 (en) | 1996-03-18 | 1996-07-17 | Silica reinforced rubber composition and tire with tread |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US5719207A (en) |
| EP (1) | EP0796891A1 (en) |
| JP (1) | JPH1025368A (en) |
| BR (1) | BR9701321A (en) |
| CA (1) | CA2181428A1 (en) |
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| US9663640B2 (en) | 2013-12-19 | 2017-05-30 | Soucy Techno Inc. | Rubber compositions and uses thereof |
| US9840611B2 (en) | 2013-10-18 | 2017-12-12 | Soucy Techno Inc. | Rubber compositions and uses thereof |
| US9879131B2 (en) | 2012-08-31 | 2018-01-30 | Soucy Techno Inc. | Rubber compositions and uses thereof |
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| DE2933345C2 (en) * | 1979-08-17 | 1983-01-20 | Degussa Ag, 6000 Frankfurt | Vulcanizable rubber mixture based on halogen-free rubbers and process for vulcanizing these rubber mixtures |
| US4436847A (en) * | 1982-05-27 | 1984-03-13 | Ppg Industries, Inc. | Rubber compositions |
| DE3424732C1 (en) * | 1984-07-05 | 1985-11-21 | Hüls AG, 4370 Marl | Heat-vulcanizable treads for the production of treads for automotive pneumatic tires |
| US4714734A (en) * | 1985-02-26 | 1987-12-22 | Bridgestone Corp. | Rubber compounds |
| JP2939278B2 (en) * | 1989-11-28 | 1999-08-25 | 出光興産株式会社 | Stampable sheet |
| ES2085959T5 (en) * | 1990-03-02 | 2001-02-01 | Bridgestone Corp | TIRES |
| JP2851715B2 (en) * | 1991-04-09 | 1999-01-27 | 出光興産株式会社 | Thermoplastic resin composition |
| JP3103153B2 (en) * | 1991-08-26 | 2000-10-23 | 株式会社ブリヂストン | Rubber composition |
| CA2105334C (en) * | 1993-04-02 | 2004-03-30 | Jean Bergh | Tire with silica reinforced tread |
| DE69610228T2 (en) * | 1995-01-13 | 2001-02-22 | Bridgestone Corp | Process for the production of pneumatic tires |
-
1996
- 1996-03-18 US US08/617,245 patent/US5719207A/en not_active Expired - Fee Related
- 1996-07-17 CA CA002181428A patent/CA2181428A1/en not_active Abandoned
-
1997
- 1997-03-11 EP EP97104026A patent/EP0796891A1/en not_active Withdrawn
- 1997-03-17 BR BR9701321A patent/BR9701321A/en active Search and Examination
- 1997-03-18 JP JP9064890A patent/JPH1025368A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9879131B2 (en) | 2012-08-31 | 2018-01-30 | Soucy Techno Inc. | Rubber compositions and uses thereof |
| US9840611B2 (en) | 2013-10-18 | 2017-12-12 | Soucy Techno Inc. | Rubber compositions and uses thereof |
| US9663640B2 (en) | 2013-12-19 | 2017-05-30 | Soucy Techno Inc. | Rubber compositions and uses thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| US5719207A (en) | 1998-02-17 |
| BR9701321A (en) | 1998-11-10 |
| MX9701752A (en) | 1997-09-30 |
| JPH1025368A (en) | 1998-01-27 |
| EP0796891A1 (en) | 1997-09-24 |
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