GB2503189A

GB2503189A - Hydrolysable silanes and polymeric materials modified by silanes

Info

Publication number: GB2503189A
Application number: GB1121129.9A
Authority: GB
Inventors: Michael Backer; Thomas Chaussee; Fabien Rialland
Original assignee: Dow Corning Corp
Current assignee: Dow Silicones Corp
Priority date: 2011-12-08
Filing date: 2011-12-08
Publication date: 2013-12-25
Also published as: GB201121129D0

Abstract

A process for modifying a polymeric material having a carbon backbone containing carbon-to-carbon unsaturation by reaction with a hydrolysable silane, characterised in that the hydrolysable silane has the formula wherein each R represents a hydrolysableÂ group; each R" represents a hydrocarbyl group having 1 to 8 carbon atoms; n = 1 to 3; Y represents a divalent organic spacer linkage having 1 to 20 carbon atoms; z = 1 to 8; y = 0 or 1; x = 0 or 1; x+y= 0 or 1; R1 represents hydrogen or a hydrocarbyl or substituted hydrocarbyl group having 1 to 8 carbon atoms; and R2 represents a hydrocabyl or substituted hydrocabyl group having 1 to 20 carbon atoms. In another aspect, a diene elastomer composition comprising a diene elastomer, a curing agent and the above hydrolysable silane. The hydrolysable silanes are useful in the modification of elastomers, and as coupling agents for diene elastomer compositions containing a filler. In particular, hydrolysable silanes containing a keto group and the preparation of such hydrolysable silanes, to a process for modifying a polymeric material by reaction with a hydrolysable silane, to diene elastomer compositions containing a hydrolysable silane and to the use of the hydrolysable silanes as coupling agents for diene elastomer compositions containing a filler.

Description

HYDROLYSABLE SILANES AND POLYMERIC MATERIALS MODIFIED BY SILANES

[0001] This invention relates to hydrolysable silanes useful in the modification of elastomers, and as coupling agents for diene elastomer compositions containing a filler. In particular the invention relates to novel hydrolysable silanes containing a keto group and to the preparation of such hydrolysable silanes, to a process for modifying a polymeric material by reaction with a hydrolysable silane, to diene elastomer compositions containing a hydrolysable silane and to the use of the hydrolysable silanes as coupling agents for diene elastomer compositions containing a filler.

[0002] Examples of hydrolysable silanes which have been proposed as coupling agents between an inorganic filler and an elastomer include unsaturated silanes containing an ester group, such as an acryloxypropyltrialkoxysilane, described in WO-A-2010/125i24. WO-A- 2010/1 39473 also describes various hydrolysable silanes useful as coupling agents.

[0003] US-A-2008/0249271 describes an adhesive containing a ladder-type polysilsesquioxane. The polysilsesquioxane can be prepared by condensing an alkoxysilane compound containing an epoxy, acryloxy, vinyl, alkyl, cyano, mercapto, amino, acetoacetoxy or acetoxy group.

[0004] In a process according to the invention for modifying a polymeric material having a carbon backbone containing carbon-to-carbon unsaturation by reaction with a hydrolysable silane, the hydrolysable silane has the formula 0 0 II i II wherein each R represents a hydrolysable group; each R" represents a hydrocarbyl group having 1 to 8 carbon atoms; n = 1 to 3; Y represents a divalent organic spacer linkage having ito 20 carbon atoms; z= 1 to8; y0 on; x=0 on; x+y= 0 on; R1 represents hydrogen or a hydrocarbyl or substituted hydrocarbyl group having 1 to 8 carbon atoms; and R2 represents a hydrocarbyl or substituted hydrocarbyl group having 1 to 20 carbon atoms.

[0005] A diene elastomer composition according to the invention comprises a diene elastomer, a hydrolysable silane and a curing agent for the diene elastomer, characterised in that the hydrolysable silane has the formula o 0 II i II wherein R, R", n, Y, z, y, x, R1 and R2 are defined as above.

[0006] The invention also comprises the use of a hydrolysable silane having the formula o 0 II i II wherein R, R", n, Y, z, y, x, R1 and R2 are defined as above as a coupling agent for a diene elastomer composition containing a filler.

[0007] The invention includes a hydrolysable silane of the formula 0 Q o

II I II I II

RflR"3flSi-Y-(OC(CH2)Z)y-(NCH2CH2)X-C-(CH2CH2N)X-CH2)ZCO) y-Y'-SiRflR"3fl wherein each R represents a hydrolysable group; each R" represents a hydrocarbyl group having 1 to 8 carbon atoms; n = 1 to 3; Y and Y each represent a divalent organic spacer linkage having ito 20 carbon atoms; z= 1 to8; y=Oorl; x=0 on; x+yOoni; x' =0 or 1; y' = 0 or 1; x'+y' = 0 on; z' = 1 to 8; and R1 and R3 each represent hydrogen ora hydrocarbyl or substituted hydrocarbyl group having ito 8 carbon atoms.

[0008] The invention also includes a hydrolysable silane of the formula r RnR"3nSiY(NCH2CH2)xCR2 wherein each R represents a hydrolysable group; each ft represents a hydrocarbyl group having 1 to 8 carbon atoms; n = 1 to 3; Y represents a divalent organic spacer linkage having 1 to 20 carbon atoms; Ri represents a hydrocarbyl or substituted hydrocarbyl group having 1 to 8 carbon atoms; and R2 represents a hydrocarbyl or substituted hydrocarbyl group having 1 to 20 carbon atoms.

[0009] The hydrolysable silanes of the formula 9 1 are capable of bonding strongly to diene elastomers under the processing conditions used for producing elastomer products such as tyres. We believe that upon heating to the temperatures used in elastomer processing, the ketone function of the hydrolysable silane reacts with the C=C bonds present in diene elastomers through [2+2] cycloaddition. The hydrolysable silanes of the invention are also capable of bonding strongly to fillers having surface hydroxyl groups through hydrolysis of the silane group, thus forming very effective coupling agents.

[0010] Hydrolysable silanes in which n = 3 may be preferred as having the maximum number of hydrolysable groups. Examples of groups of the formula RR"3Si-Y in which n = 3 include trialkoxysilylalkyl groups such as triethoxysilylalkyl or trimethoxysilylalkyl groups, or triacetoxysilylalkyl groups. However hydrolysable silanes in which n = 2 or n = 1 are also useful coupling agents. In such hydrolysable silanes the group R" is a hydrocarbyl group having ito 8 carbon atoms. Preferred groups R" include alkyl groups having ito 4 carbon atoms such as methyl or ethyl, but R" can be an alkyl group having more carbon atoms such as hexyl or 2-ethylhexyl or can be an aryl group such as phenyl. Examples of groups of the formula RR"3Si-Y in which a = 2 include diethoxymethylsilylalkyl, diethoxyethylsilylalkyl, dimethoxymethylsilylalkyl or diacetoxymethylsilylalkyl groups.

[0011] Hydrolysable silanes in which the group R is an ethoxy group are often preferred.

The alcohol or acid RH may be released when the silane is hydrolysed, and ethanol is the most environmentally friendly compound among the alcohols and acids.

[0012] In the group of the formula -Y-SiRR"3, Y represents a divalent organic spacer linkage having ito 20 carbon atoms. Preferably Y has 2 to 20 carbon atoms. Y can conveniently be an alkylene group, particularly an alkylene group having 2 to 6 carbon atoms.

Preferred examples of linkage Y are -(CH2)3-, -(CH2)4-, and -CH2CH(CH3)CH2-groups.

The group of the formula RR'3Si-Y can for example be a 3-(triethoxysilyl)propyl, 4- (triethoxysilyl)butyl, 2-methyl-3-(triethoxysilyl)propyl, 3-(trimethoxysilyl)propyl, 3- triacetoxysilylpropyl, 3-(diethoxymethylsilyl)propyl, 3-(diethoxyethylsilyl)propyl or 3- (diacetoxymethylsilyl)propyl group.

[0013] The hydrolysable silanes of the formula 1? wherein y = 0 and x = 1, and in particular the hydrolysable silanes of the formula

I II

RR"3Si-Y-(NCH2CH2)X-C-R2 wheiein each S represents a hydiolysable group; each R" lepiesents a hydiocarbyl group having 1 to 8 carbon atoms; n = 1 to 3; Y represents a divalent organic spacei linkage having 1 to 20 carbon atoms; R1 represents a hydrocarbyl or substituted hydrocarbyl group having 1 to 8 carbon atoms; and R2 represents a hydrocarbyl or substituted hydrocarbyl group having 1 to 20 carbon atoms; can be prepared by reacting an aminoalkylsilane of the foimula (S)R"3Si-Y-NHR1 wherein each R represents a hydrolysable gioup; each R" represents a hydrocarbyl group having 1 to 8 carbon atoms; n = 1 to 3; Y represents a divalent organic spacer linkage having 1 to 20 carbon atoms; and R1 represents hydrogen or a hydrocarbyl or substituted hydrocarbyl group having ito 8 carbon atoms; with a vinyl ketone of the formula CH2=CH-C(O)-R2 where R2 represents a hydrocarbyl or substituted hydrocarbyl group having ito 20 carbon atoms.

[0014] The aminoalkylsilane of the formula (R)S"3Si-Y-NHR1 and the vinyl ketone are preferably ieacted in substantially equimolar amounts, for example in a molar ratio of 1.5:1 to 1:1.5.

[0015] Examples of preferred groups R1 include hydrocarbyl groups having ito 8 carbon atoms, for example alkyl groups, particularly alkyl groups having 1 to 4 carbon atoms such as methyl, ethyl or butyl, but R1 can be an alkyl group having more carbon atoms such as hexyl or 2-ethylhexyl or can be an aryl group such as phenyl or an aralkyl group such as benzyl. Thus examples of the aminoalkylsilane of the formula (R)R"3Si-Y-NHR1 include N-methyl-3-aminopropyltiiethoxysilane, N-ethyl-3-aminopropyltriethoxysilane and N-methyl- 4-aminobutyltriethoxysilane.

[0016] Alternative prefeired examples of the group 51 include substituted hydrocarbyl groups of the formula RR'3Si-Y"-in which each R represents a hydrolysable group; each R" represents a hydrocarbyl group having 1 to 8 carbon atoms; n = 1 to 3; and Y represents a divalent organic spacer linkage having 1 to 20 carbon atoms. The aminoalkylsilane which is ieacted with the vinyl ketone can for example be of the formula ((R)R"3Si-Y-N)2H, where ft R", n and Y are defined as above, for example N,N-bis(3-aminopropyltriethoxysilane) or N,N-bis(4-aminobutyltriethoxysilane).

[0017] Examples of preferred groups R2 include hydrocarbyl groups having ito 8 carbon atoms, for example alkyl groups, particularly alkyl groups having 1 to 4 carbon atoms such as methyl, ethyl or butyl, but S2 can be an alkyl group having more carbon atoms such as hexyl or 2-ethylhexyl or can be an aryl group such as phenyl. The vinyl ketone can for example be methyl vinyl ketone or ethyl vinyl ketone. Thus one example of a preferred hydrolysable ketone according to the invention is N, N-bis(triethoxysilylpropyl)-2-aminoethyl methyl ketone of the formula (EtO)3S (EtO)3Si wherein Et represents an ethyl group.

[0018] Alternatively the vinyl ketone can be divinyl ketone. In this case the divinyl ketone is preferably reacted with the aminoalkylsilane of the formula (R)R"3Si-Y-NHR1 in a molar ratio of substantially 2:1, for example in a molar ratio of 1.5:1 to 2.5:1. Thus another example of a preferred hydrolysable ketone according to the invention is di(N,N-bis(triethoxysilylpropyl)-2-aminoethyl) ketone of the formula (EtO)Si Si(OEt)3 wherein Et represents an ethyl group.

[0019] The hydrolysable silane of the formula o o II i II can be partially hydrolysed and condensed into oligomers containing siloxane linkages. It is preferred that such oligomers still contain at least one hydrolysable group bonded to Si per silicon atom to enhance coupling of the unsaturated silane with fillers having surface hydroxyl groups.

[0020] The polymeric material having a carbon backbone containing carbon-to-carbon unsaturation and the hydrolysable silane of the formula 0 0 II i II are preferably heated together at a temperature of at least 80°C, more preferably to a temperature between 90°C and 200°C, most preferably between 120°C and 180°C. The polymeric material and the hydrolysable silane can be mixed followed by a separate heating step, or mixing and heating can be carried out together.

[0021] The preferred polymeric material is a hydrocarbon polymer containing ethylenic unsaturation such as a diene elastomer, but the hydrolysable silanes defined above can also be used to modify other polymeric material having a carbon backbone containing carbon-to-carbon unsaturation such as carbon fibre or carbon black. When the polymeric material is an elastomer, mixing and heating are preferably carried out together so that the elastomer is subjected to mechanical working while it is heated.

[0022] In the diene elastomer compositions of the invention, the diene elastomer can be natural rubber. We have found that the hydrolysable silanes of the formula 9 1 is as defined above react readily with natural rubber under the processing conditions used for producing rubber products such as tyres and also act as an effective coupling agent in a curable filled natural rubber composition.

[0023] The diene elastomer can alternatively be a synthetic polymer which is a homopolymer or copolymer of a diene monomer (a monomer bearing two double carbon-carbon bonds, whether conjugated or not). Preferably the elastomer is an "essentially unsaturated" diene elastomer, that is a diene elastomer resulting at least in part from conjugated diene monomers, having a content of members or units of diene origin (conjugated dienes) which is greater than 15 mol %. More preferably it is a "highly unsaturated" diene elastomer having a content of units of diene origin (conjugated dienes) which is greater than 50 mol %. Diene elastomers such as butyl rubbers, copolymers of dienes and elastomers of alpha-olefins of the ethylene-propylene diene monomer (EPDM) type, which may be described as "essentially saturated" diene elastomers having a low (less than 15 mol %) content of units of diene origin are less preferred.

[0024] The diene elastomer can for example be: (a) any homopolymer obtained by polymerization of a conjugated diene monomer having 4 to 12 carbon atoms; (b) any copolymer obtained by copolymerization of one or more dienes conjugated together or with one or more vinyl aromatic compounds having 8 to 20 carbon atoms; (c) a ternary copolymer obtained by copolymerization of ethylene, of an o-olefin having 3 to 6 carbon atoms with a non-conjugated diene monomer having 6 to 12 carbon atoms, such as, for example, the elastomers obtained from ethylene, from propylene with a non-conjugated diene monomer of the aforementioned type, such as in particular 1,4-hexadiene, ethylidene norbornene or dicyclopentadiene; (d) a copolymer of isobutene and isoprene (butyl rubber), and also the halogenated, in particular chlorinated or brominated, versions of this type of copolymer.

[0025] Suitable conjugated dienes include 1 3-butadiene, 2-methyl-i 3-butadiene, 2,3- di(Ci-C5 alkyl)-1,3-butadienes such as, for instance, 2,3-dimethyl-1 3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene, 2-methyl-3-isopropyl-1,3-butadiene, an aryl-i,3-butadiene, 1,3-pentadiene and 2,4-hexadiene.

[0026] Suitable vinyl aromatic compounds are, for example, styrene, ortho-, meta-and para-methylstyrene, the commercial mixture "vinyltoluene", para-tert.-butylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene and vinylnaphthalene.

The copolymers may contain between 99% and 20% by weight of diene units and between 1 % and 80% by weight of vinyl aromatic units. The elastomers may have any microstructure, which is a function of the polymerization conditions used, in particular of the presence or absence of a modifying and/or randomizing agent and the quantities of modifying and/or randomizing agent used. The elastomers may for example be block, statistical, sequential or microsequential elastomers, and may be prepared in dispersion or in solution; they may be coupled and/or starred or alternatively functionalized with a coupling and/or starring or functionalizing agent. Examples of preferred block copolymers are styrene-butadiene-styrene (SBS) block copolymers and styrene-ethylene/butadiene-styrene (SEBS) block copolymers.

[0027] The elastomer can be an alkoxysilane-terminated diene polymer or a copolymer of the diene and an alkoxy-containing molecule prepared via a tin coupled solution polymerization.

[0028] When preparing a filled elastomer composition, the elastomer and the hydrolysable silane can be reacted and then mixed with the filler, but the tiller is preferably present during the reaction between the elastomer and the unsaturated silane. The elastomer, the silane, the filler and the radical initiator can all be loaded to the same mixer and mixed while being heated, for example by thermo-mechanical kneading. Alternatively the filler can be pre-treated with the hydrolysable silane and then mixed with the elastomer and the radical initiator, preferably under heating. When the hydrolysable silane and radical generator are present during thermo-mechanical kneading of the diene elastomer and the filler, the silane reacts with the elastomer to form a modified diene elastomer and also acts as a coupling agent bonding the filler to the elastomer.

[0029] The filler is preferably a reinforcing filler. Examples of reinforcing fillers are silica, silicic acid, carbon black, or a mineral oxide of aluminous type such as alumina trihydrate or an aluminium oxide-hydroxide, or a silicate such as an aluminosilicate, or a mixture of these different fillers.

[0030] Use of a hydrolysable silane of the formula 0 0 II i II as defined above is particularly advantageous in a curable elastomer composition comprising a filler containing hydroxyl groups, particularly in reducing the mixing energy required for processing the rubber composition and improving the performance properties of products formed by curing the rubber composition. The hydroxyl-containing filler can for example be a mineral filler, particularly a reinforcing filler such as a silica or silicic acid filler, as used in white tire compositions, or a metal oxide such as a mineral oxide of aluminous type such as alumina trihydrate or an aluminium oxide-hydroxide, or carbon black pre-treated with a alkoxysilane such as tetraethyl orthosilicate, or a silicate such as an aluminosilicate or clay, or cellulose or starch, or a mixture of these different fillers.

[0031] The reinforcing filler can for example be any commonly employed siliceous filler used in rubber compounding applications, including pyrogenic or piecipitated siliceous pigments or aluminosilicates. Precipitated silicas are preferred, for example those obtained by the acidification of a soluble silicate, e.g., sodium silicate. The precipitated silica preferably has a BET surface area, as measured using nitrogen gas, in the range of about to 600m2/g, and more usually in a range of about 40 or 50 to about 300m2/g. The BET method of measuring surface area is described in the Journal of the American Chemical Society, Volume 60, Page 304 (1930). The silica may also be typically characterized by having a dibutylphthalate (DBP) value in a range of about 100 to about 350cm3/1 Dog, and more usually about 150 to about 300cm3/lOOg, measured as described in ASTM D2414. The silica, and the alumina or aluminosilicate if used, preferably have a CTAB surface area in a range of about 100 to about 220m21g (ASTM D3849). The CTAB surface area is the external surface area as evaluated by cetyl trimethylanimonium bromide with a pH of 9. The method is described in ASTM D 3849.

[0032] Various commercially available silicas may be considered for use in elastomer compositions according to this invention such as silicas commercially available from Rhodia with, for example, designations of Zeosil® 1 165MP, 11 15MP, or HRS 1200MP; 200MP premium, 8OGR or equivalent silicas available from PPG Industries with designations Hi-Sil® EZ15OG, 210, 243, etc; silicas available from Degussa AG with, for example, designations VN3, Ultrasil® 7000 and Ultrasil 7005, and silicas commercially available from Huber having, for example, a designation of Hubersil® 8745 and Hubersil 8715. Treated precipitated silicas can be used, for example the aluminium-doped silicas described in EP-A-735088.

[0033] If alumina is used in the elastomer compositions of the invention, it can for example be natural aluminium oxide or synthetic aluminium oxide (A1203) prepared by controlled precipitation of aluminium hydroxide. The reinforcing alumina preferably has a BET surface area from 30 to 400m2/g, more preferably between 60 and 250m2/g, and an average particle size at most equal to 500 nm, more preferably at most equal to 200 nm. Examples of such reinforcing aluminas are the aluminas A125. CR125, D65CR from Baiotakowski.

[0034] Examples of aluminosilicates which can be used in the elastomer compositions of the invention are Sepiolite, a natural aluminosilicate which might be obtained as PANSIL® from Tolsa S.A., Toledo, Spain, and SILTEG®, a synthetic aluminosilicate from Degussa GmbH.

[0035] The hydroxyl-containing filler can alternatively be talc, magnesium dihydroxide or calcium carbonate, or a natural organic filler such as cellulose fibre or starch. Mixtures of mineral and organic fillers can be used, as can mixtures of reinforcing and non-reinforcing fillers.

[0036] The filler can additionally or alternatively comprise a filler which does not have hydroxyl groups at its surface, for example a reinforcing tiller such as carbon black and/or a non-reinforcing filler such as calcium carbonate. The filler can also be carbon-fibre, (expandable) graphene, carbon black, carbon (nano)tubes or fullerene.

[0037] The hydrolysable silane is preferably present in the diene elastomer composition at least 0.2% by weight based on the diene elastomer and can be up to 20% or more.

Preferably the hydrolysable silane is present at 0.5 to 15.0% by weight based on the diene elastomer during thermal processing of the elastomer composition, most preferably 0.5 to 10.0%.

[0038] Curing of the diene elastomer composition of the invention can be carried out as a batch process or as a continuous process using any suitable apparatus.

[0039] Continuous processing can be effected in an extruder such as a single screw or twin screw extruder. The extruder is preferably adapted to mechanically work, that is to knead or compound, the materials passing through it, for example a twin screw extruder.

One example of a suitable extruder is that sold under the trade mark ZSK from Coperion Werner Pfleiderer. The extruder preferably includes a vacuum port shortly before the extrusion die to remove any unreacted silane. The residence time of the diene elastomer, the unsaturated silane and the free radical initiator at above 100°C in the extruder or other continuous reactor is generally at least 0.5 minutes and preferably at least 1 minute and can be up to 15 minutes. More preferably the residence time is 1 to 5 minutes.

[0040] A batch process can for example be carried out in an internal mixer such as a Banbury mixer or a Brabender Flastograph (Trade Mark) 350S mixer equipped with roller blades. An external mixer such as a roll mill can be used for either batch or continuous processing. In a batch process, the elastomer, the hydrolysable silane and the free radical initiator are generally mixed together at a temperature above 100°C for at least 1 minute and can be mixed for up to 20 minutes, although the time of mixing at high temperature is generally 2 to 10 minutes.

[0041] The elastomer compositions are preferably produced using the conventional two successive preparation phases of mechanical or thermo-mechanical mixing or kneading ("non-productive" phase) at high temperature, followed by a second phase of mechanical mixing ("productive" phase) at lower temperature, typically less than 110°C, for example between 40°C and 100°C, during which the cross-linking and vulcanization systems are incorporated.

[0042] During the non-productive phase, the hydrolysable silane, the diene elastomer, the filler and the radical generator are mixed together. Mechanical or thermo-mechanical kneading occurs, in one or more steps, until a maximum temperature 01110°C to 190°C is reached, preferably between 130°C and 180°C. When the apparent density of the reinforcing inorganic filler is low (generally the case for silica), it may be advantageous to divide the introduction thereof into two or more parts in order to improve further the dispersion of the filler in the rubber. The total duration of the mixing in this non-productive phase is preferably between 2 and 10 minutes.

[0043] After cooling of the mixture thus obtained, the curing system is then incorporated at low temperature, typically on an external mixer such as an open mill, or alternatively on an internal mixer (Banbury type). The entire mixture is then mixed (productive phase) for several minutes, for example between 2 and 10 minutes.

[0044] The curing agent for the elastomer composition can for example be a conventional sulfur vulcanizing agent. Examples of suitable sulfur vulcanizing agents include, for example, elemental sulfur (free sulfur) or sulfur donating vulcanizing agents, for example, an amine disulfide, polymeric polysulfide or sulfur olefin adducts which are conventionally added in the final, productive, rubber composition mixing step. Preferably, in most cases, the sulfur vulcanizing agent is elemental sulfur. Sulfur vulcanizing agents are used in an amount ranging from about 0.4 to about 8% by weight based on elastomer, preferably 1.5 to about 3%, particularly 2 to 2.5%.

[0045] Accelerators are generally used to control the time and/or temperature required for vulcanization and to improve the properties of the vulcanized elastomer composition. In one embodiment, a single accelerator system may be used, i.e., primary accelerator.

Conventionally and preferably, a primary accelerator(s) is used in total amounts ranging from about 0.5 to about 4% by weight based on elastomer, preferably about 0.8 to about 1.5%. In another embodiment, combinations of a primary and a secondary accelerator might be used with the secondary accelerator being used in smaller amounts of about 0.05 to about 3% in order to activate and to improve the properties of the vulcanisate. Delayed action accelerators may be used which are not affected by normal processing temperatures but produce a satisfactory cure at ordinary vulcanization temperatures. Suitable types of accelerators that may be used in the present invention are amines, disulfides, guanidines, thioureas, thiazoles, for example mercaptobenzothiazole, thiurams, sulfenamides, dithiocarbamates, thiocarbonates, and xanthates. Preferably, the primary accelerator is a sulfenamide. If a second accelerator is used, the secondary accelerator is preferably a guanidine, dithiocarbamate or thiuram compound. Vulcanization retarders can also be used, for example phthalic anhydride, benzoic acid or cyclohexylthiophthalimide.

[0046] The curable diene elastomer composition can contain another coupling agent in addition to the hydrolysable silane of the formula o o II i II RnR"3nSi-Y-(OC(CH2)Z)Y-(NCH2CH2)X-C-R2 as defined above, for example a trialkoxy, dialkoxy or monoalkoxy silane coupling agent, particularly a sulfidosilane or mercaptosilane or an azosilane, acrylamidosilane, blocked mercaptosilane, aminosilane alkylsilane or alkenylsilane having 1 to 20 carbon atoms in the alkyl group and ito 6 carbon atoms in the alkoxy group. Examples of preferred coupling agents include a bis(trialkoxysilylpropyl)disulfane or tetrasulfane as described in US-A- 5684171, or a bis(dialkoxymethylsilylpropyl)disulfane ortetrasulfane such as bis(methyldiethoxysilylpropytetrasulfane or disulfane, or a bis(dimethylethoxysilylpropyoligosulfane, or a dimethylhydroxysilylpropyl dimethylalkoxysilylpropyl oligosulfane as described in WO-A-2007/061 550, or a mercaptosilane such as triethoxysilylpropylmercaptosilane. Such a coupling agent promotes bonding of the filler to the organic elastomer, thus enhancing the physical properties of the filled elastomer. The filler can be pre-treated with the coupling agent or the coupling agent can be added to the mixer with the elastomer and filler and the unsaturated silane according to the invention. We have found that use of a hydrolysable silane according to this invention in conjunction with such a coupling agent can reduce the mixing energy required for processing the elastomer composition and improve the performance properties of products formed by curing the elastomer composition compared to compositions containing the coupling agent without the hydrolysable silane of the formula 0 0 II i II as defined above.

[0047] The elastomer composition can be compounded with various commonly-used additive materials such as processing additives, for example oils, resins including tackifying resins, silicas, and plasticizers, fillers, pigments, fatty acid, zinc oxide, waxes, antioxidants and antiozonants, heat stabilizers, UV stabilizers, dyes, pigments, extenders and peptizing agents.

[0048] Typical amounts of tackifier resins, if used, comprise about 0.5 to about 10% by weight based on elastomer, preferably 1 to 5%. Typical amounts of processing aids comprise about 1 to about 50% by weight based on elastomer. Such processing aids can include, for example, aromatic, naphthenic, and/or paraffinic processing oils.

[0049] Typical amounts of antioxidants comprise about 1 to about 5% by weight based on elastomer. Representative antioxidants may be, for example, N-i 3-dimethylbutyl-N-phenyl- para-phenylenediamine, sold as "Santoflex 6-PPD"® from Flexsys, diphenyl-p-phenylenediamine and others, for example those disclosed in The Vanderbilt Rubber Handbook (1978), Pages 344 through 346. Typical amounts of antiozonants also comprise about ito 5% by weight based on elastomer.

[0050] Typical amounts of fatty acids, if used, which can include stearic acid or zinc stearate, comprise about 0.1 to about 3% by weight based on elastomer. Typical amounts of zinc oxide comprise about 0 to about 5% by weight based on elastomer alternatively 0.1 to 5%.

[0051] Typical amounts of waxes comprise about 1 to about 5% by weight based on elastomer. Microcrystalline and/or crystalline waxes can be used.

[0052] Typical amounts of peptizers comprise about 0.1 to about 1% by weight based on elastomer. Typical peptizers may for example be pentachlorothiophenol or dibenzamidodiphenyl disulfide.

[0053] The diene elastomer composition of the invention containing a curing agent can be shaped and cured into an article. The elastomer composition can be used to produce tyres, including any part thereof such as the bead, apex, sidewall, inner liner, tread or carcass. The elastomer composition can alternatively be used to produce any other engineered rubber goods, for example bridge suspension elements, hoses, belts, shoe soles, anti seismic vibrators, and dampening elements. The elastomer composition can be cured in contact with reinforcing elements such as cords, for example organic polymer cords such as polyester, nylon, rayon, or cellulose cords, or steel cords, or fabric layers or metallic or organic sheets.

[0054] When a sulphur curing system is used the vulcanization, or curing, of a rubber product such as a tire or tire tread is carried out in known manner at temperatures preferably between 13000 and 200°C, under pressure, for a sufficiently long period of time. The required time for vulcanization may vary for example between 5 and 90 minutes.

[0055] The elastomer composition of the invention is particularly advantageous for use in producing a tyre for a heavy vehicle such as a truck. Preferred elastomers for this use are isoprene elastomers; that is an isoprene homopolymer or copolymer, in other words a diene elastomer selected from the group consisting of natural rubber (NR), synthetic polyisoprenes (IR), the various isoprene copolymers or a mixture of these elastomers. Isoprene copolymers include isobutene-isoprene copolymers (butyl rubber-IIR), isoprene-styrene copolymers (SIR), isoprene-butadiene copolymers (BIR) and isoprene-butadiene-styrene copolymers (SBIR). The isoprene elastomer is most preferably natural rubber or a synthetic cis-1,4 polyisoprene; of these synthetic polyisoprenes, preferably polyisoprenes having a content (mole %) of cis-1,4 bonds greater than 90%, more preferably still greater than 98%, are used. For such a tyre for a heavy vehicle, the elastomer may also be constituted, in its entirety or in part, of another highly unsaturated elastomer such as, for example, an SBR or a BR elastomer. The hydrolysable silane of the invention disperses silica into Natural Rubber to form an elastonier composition for truck tyres whereby tyres made from the composition have reduced rolling resistance with maintained wear compared to known tyres containing carbon black as reinforcing filler.

[0056] The elastomer composition of the invention can alternatively be used for a passenger car tire, in which case the preferred starting diene elastomer is for example a styrene butadiene rubber (SBR), for example an SBR prepared in emulsion ("ESBR") or an SBR prepared in solution ("SSBR"), or an SBRIBR, SBRINR (or SBR/IR), alternatively BRINR (or BR/IR), or SIBR (isoprene-butadiene-styrene copolymers), IBR (isoprene-butadiene copolymers), or blends (mixtures) thereof. The hydrolysable silane of the formula 1? RR"3Si-Y-(OC(CH2)j-(NCH2CH2)-C-R2 shows advantages of reduced rolling resistance with maintained wear when used to partially replace sulfido-silane in elastomer compositions for the passenger car tyre market.

[0057] When the elastomer composition is for use as a tile sidewall, the elastomer may comprise at least one essentially saturated diene elastomer, in particular at least one EPDM copolymer, which may for example be used alone or in a mixture with one or more of the highly unsaturated diene elastomers.

[0058] The modified elastomer composition containing a vulcanizing system can for example be calendered, for example in the form of thin slabs (thickness of 2 to 3 mm) or thin sheets of rubber in order to measure its physical or mechanical properties, in particular for laboratory characterization, or alternatively can be extruded to form rubber profiled elements used directly, after cutting or assembling to the desired dimensions, as a semi-finished product for tires, in particular as treads, plies of carcass reinforcements, sidewalls, plies of radial carcass reinforcements, beads or chaffers, inner tubes or air light internal rubbers for tubeless tires.

Claims

CLAIMSA process for modifying a polymeric material having a carbon backbone containing carbon-to-carbon unsaturation by reaction with a hydrolysable silane, characterised in that the hydrolysable silane has the formula 1? wherein each R represents a hydrolysable group; each S' represents a hydrocarbyl group having 1 to 8 carbon atoms; n = 1 to 3; Y represents a divalent organic spacer linkage having ito 20 carbon atoms; z = ito 8; y = 0 or 1; x = 0 or 1; x÷y = 0 or 1 51 represents hydrogen or a hydrocarbyl or substituted hydrocarbyl group having 1 to 8 carbon atoms; and 2 represents a hydrocarbyl or substituted hydrocarbyl group having 1 to 20 carbon atoms.
2. A process according to Claim 1, characterised in that the polymeric material is a diene elastomer.
3. A diene elastomer composition comprising a diene elastomer, a hydrolysable silane and a curing agent for the diene elastomer, characterised in that the hydrolysable silane has the formula 0 0 II i II wherein each S represents a hydrolysable group; each 5" represents a hydrocarbyl group having 1 to 8 carbon atoms; n = 1 to 3; Y represents a divalent organic spacer linkage having ito 20 carbon atoms; z = ito 8; y = 0 or 1; x = 0 or 1; x÷y = 0 or 1 1 represents hydrogen or a hydrocarbyl or substituted hydrocarbyl group having 1 to 8 carbon atoms; and 2 represents a hydrocarbyl or substituted hydrocarbyl group having 1 to 20 carbon atoms.
4. A composition according to Claim 3 wherein 52 represents a hydrocarbyl group having 1 to 8 carbon atoms.
5. A composition according to Claim 3 or Claim 4 wherein y = 1.
6. A composition according to Claim 3 or Claim 4 wherein x = 0 and y = 0.
7. A composition according to any of Claims 3 to 6, characterised in that each group R is an alkoxy group having 1 to 4 carbon atoms.
8. A composition according to Claim 7, characterised in that each group R is an ethoxy group.
9. A composition according to any of Claims 3 to 8, characterised in that a = 3.
10. A composition according to any of Claims 3 to 9, characterised in that the silane is partially hydrolysed and condensed into oligomers containing siloxane linkages.
11. A composition according to any of Claims 3 to 10 characterised in that the hydrolysable silane is present at 0.5 to 15.0% by weight based on the diene elastomer.
12. A composition according to any of Claims 3 to 11, characterised in that a tiller is present in the composition, whereby the hydrolysable silane acts as a coupling agent between the filler and the diene elastomer.
13. A composition according to Claim 12 characterised in that the filler is silica.
14. A composition according to any of Claims 3 to 13 characterised in that the curing agent for the diene elastomer is sulfur or a sulfur compound.
15. A process for the production of a rubber article characterized in that an elastomer composition according to any of Claims 3 to 14 is shaped and cured.
16. A process according to Claim 15 characterised in that the elastomer composition is cured at a temperature in the range 130°C to 180°C.
17. Use of a hydrolysable silane having the formula 1? wherein each S represents a hydrolysable group; each S' represents a hydrocarbyl group having 1 to 8 carbon atoms; n = 1 to 3; Y represents a divalent organic spacer linkage having ito 20 carbon atoms; z = ito 8; y = 0 or 1; x = 0 or 1; x+y = 0 or 1; 1 represents hydrogen or a hydrocarbyl or substituted hydrocarbyl group having 1 to 8 carbon atoms; and R2 represents a hydrocarbyl or substituted hydrocarbyl group having 1 to 20 carbon atoms, as a coupling agent for a diene elastomer composition containing a tiller.
18. A process according to Claim 1 characterised in that the polymeric material is carbon fibre or carbon black.
19. A hydrolysable silane of the formula 0 0 53II I IIwherein each S represents a hydrolysable group; each S' represents a hydrocarbyl group having 1 to 8 carbon atoms; n = 1 to 3; Y and Y' each represent a divalent organic spacer linkage having 1 to 20 carbon atoms; z = 1 to 8; y = 0 or 1; x = 0 or 1; x+y=Oorl;x' =Oorl; y' =Oorl;x'+y' =Oorl;z' = 1 to8; and 1 and 3 each represent a hydrocarbyl or substituted hydrocarbyl group having 1 to 8 carbon atoms.
20. A hydrolysable silane according to Claim 19 wherein x = 1; x' = 1; and Ri and R3 each represent a hydrocarbyl group having 1 to 8 carbon atoms.
21. A hydrolysable silane according to Claim 19 wherein x = 1; x' = 1; and 51 and 53 each represent a substituted hydrocarbyl group of the formula (R0)nR"3-nSi-Y"-in which each S represents a hydrolysable group; each 5" represents a hydrocarbyl group having 1 to 8 carbon atoms; n = 1 to 3; and each Y" represents a divalent organic spacer linkage having 1 to 20 carbon atoms.
22. A hydrolysable silane according to Claim 19 wherein y = 1 andy' = 1.
23. A hydrolysable silane according to Claim 19 wherein x =0; y =0; x' = 0; and y' = 0.
24. A hydrolysable silane of the formulaI IIRR"3Si-Y-(NCH2CH2)X-C-R2 wherein each R represents a hydrolysable group; each S' represents a hydrocarbyl group having ito 8 carbon atoms; n = 1 to 3; Y represents a divalent organic spacer linkage having 1 to 20 carbon atoms; 51 represents a hydrocarbyl or substituted hydrocarbyl group having 1 to 8 carbon atoms; and 2 represents a hydrocarbyl or substituted hydrocarbyl group having 1 to 20 carbon atoms.
25. A hydrolysable silane according to Claim 24 wherein 52 represents a hydrocarbyl group having 1 to 8 carbon atoms.
26. A hydrolysable silane according to Claim 24 or Claim 25 wherein Si represents a hydrocarbyl group having 1 to 8 carbon atoms.
27. A hydrolysable silane according to Claim 24 or Claim 25 wherein Si represents a substituted hydrocarbyl group of the formula RnR"3-nsi-Y"-in which each S represents a hydrolysable group; each 5" represents a hydrocarbyl group having 1 to 8 carbon atoms; n = 1 to 3; and Y" represents a divalent organic spacer linkage having 1 to 20 carbon atoms.
28. A hydrolysable silane according to any of Claims 19 to 27, characterised in that each group S is an alkoxy group having 1 to 4 carbon atoms.
29. A hydrolysable silane according to any of Claims 19 to 28, characterised in that a = 3.
30. A hydrolysable silane according to any of Claims 19 to 29, characterised in that Y represents an alkylene group having 2 to 6 carbon atoms.
31. N,N-bis(triethoxysilylpropyl)-2-aminoethyl methyl ketone of the formula (EtO)33 N (EtO)3Si wherein Ft represents an ethyl group.
32. Di(N N-bis(triethoxysilylpropyl)-2-aminoethyl) ketone of the formula (EtO)3SiSi(OEt)3 (EtO)3Si Si(OEt)3 wherein Et represents an ethyl group.
33. Bis(triethoxysilylpropyl) ketone of the formula (H5C20)3Si-(CH2)3-C-(CH2)3-Si(0C2H5)3
34. A hydrolysable silane according to any of Claims 19 to 33, characterised in that the silane is partially hydrolysed and condensed into oligomers containing siloxane linkages.
35. A process for the preparation of a hydrolysable silane according to Claim 24, characterised in that an aminoalkylsilane of the formula (R)nR"3-nSi-Y-NHR1 wherein each S represents a hydrolysable group; each S' represents a hydrocarbyl group having 1 to 8 carbon atoms; n = 1 to 3; Y represents a divalent organic spacer linkage having 1 to 20 carbon atoms; and Ri represents hydrogen or a hydrocarbyl or substituted hydrocarbyl group having 1 to 8 carbon atoms is reacted with a vinyl ketone of the formula CH2=CH-C(O)-R2, where R2 represents a hydrocarbyl or substituted hydrocarbyl group having 1 to 20 carbon atoms.
36. A process according to Claim 35 for the preparation of a hydrolysable silane according to Claim 19 wherein x = 1 and x' = 1, characterised in that the aminoalkylsilane of the formula (R)nR"3-nsi-Y-NHR1 is reacted with divinyl ketone.