WO2011083048A1 - Diene elastomers modified by silicones - Google Patents

Abstract

The invention provides a modified diene elastomer composition comprising a thermoplastic diene elastomer and a polysiloxane, characterized in that the polysiloxane is a branched silicone resin containing at least one group of the formula -X-CH=CH-R" (I) or -X-C≡C-R" (II), in which X represents a divalent organic linkage having an electron withdrawing effect with respect to the -CH=CH- or -C≡C- bond and/or containing an aromatic ring or a further olefinic double bond or acetylenic unsaturation, the aromatic ring or the further olefinic double bond or acetylenic unsaturation being conjugated with the olefinic unsaturation of -X-CH=CH-R" or with the acetylenic unsaturation of -X-C≡C-R", and X being bonded to the branched silicone resin by a C-Si bond, and R" represents hydrogen or a group having an electron withdrawing effect or any other activation effect with respect to the -CH=CH- or - C≡C- bond.

Description

DIENE ELASTOMERS MODIFIED BY SILICONES

[0001] This invention relates to the modification of diene elastomers by reaction with a polysiloxane (branched silicone resin), to the modified elastomers produced and to articles produced by shaping and curing modified elastomer compositions.

[0002] By a diene elastomer we mean a polymer having elastic properties at room temperature, mixing temperature or at the usage temperature, which can be polymerized from a diene monomer. Typically, a diene elastomer is a polymer containing at least one ene (carbon-carbon double bond, C=C) having a hydrogen atom on the alpha carbon next to the C=C bond. The diene elastomer can be a natural polymer such as natural rubber or can be a synthetic polymer derived at least in part from a diene.

[0003] A modified elastomer composition according to the present invention comprises a diene elastomer and a polysiloxane, characterized in that the polysiloxane is a branched silicone resin containing at least one group of the formula -X-CH=CH-R" (I) or -X-C≡C-R" (II), in which X represents a divalent organic linkage having an electron withdrawing effect with respect to the -CH=CH- or -C≡C- bond and/or containing an aromatic ring or a further olefinic double bond or acetylenic unsaturation, the aromatic ring or the further olefinic double bond or acetylenic unsaturation being conjugated with the olefinic unsaturation of -X-CH=CH-R" or with the acetylenic unsaturation of -X-C≡C-R" and X being bonded to the branched silicone resin by a C-Si bond, and R" represents hydrogen or a group having an electron withdrawing effect or any other activation effect with respect to the -CH=CH- or -C≡C- bond.

[0004] A process according to the invention for grafting silicone onto a diene elastomer comprises reacting the diene elastomer with a silicon compound containing an unsaturated group, characterized in that the silicon compound is a branched silicone resin containing at least one group of the formula -X-CH=CH-R" (I) or -X-C≡C-R" (II), in which X represents a divalent organic linkage having an electron withdrawing effect with respect to the -CH=CH- or -C≡C- bond and/or containing an aromatic ring or a further olefinic double bond or acetylenic unsaturation, the aromatic ring or the further olefinic double bond or acetylenic unsaturation being conjugated with the olefinic unsaturation of -X-CH=CH-R" or with the acetylenic unsaturation of -X-C≡C-R", and X being bonded to the branched silicone resin by a C-Si bond, and R" represents hydrogen or a group having an electron withdrawing effect or any other activation effect with respect to the -CH=CH- or -C≡C- bond.

[0005] The invention includes the use of a branched silicone resin containing at least one group of the formula -X-CH=CH-R" (I) or -X-C≡C-R" (II), in which X represents a divalent organic linkage having an electron withdrawing effect with respect to the -CH=CH- or -C≡C- bond, and X being bonded to the branched silicone resin by a C-Si bond, and R" represents hydrogen or a group having an electron withdrawing effect or any other activation effect with respect to the -CH=CH- or -C≡C- bond, in grafting silicone moieties to a diene elastomer. The use of a branched silicone resin containing at least one group of the formula

-X-CH=CH-R" (I) or -X-C≡C-R" (II) in which X represents a divalent organic linkage having an electron withdrawing effect with respect to the -CH=CH- or -C≡C- bond gives enhanced grafting compared to an unsaturated silicone not containing a -X-CH=CH-R" or -X-C≡C-R" group.

[0006] The invention also includes the use of a branched silicone resin containing at least one group of the formula -X-CH=CH-R" (I) or -X-C≡C-R" (II), in which X represents a divalent organic linkage containing an aromatic ring or a further olefinic double bond or acetylenic unsaturation, the aromatic ring or the further olefinic double bond or acetylenic unsaturation being conjugated with the olefinic unsaturation of -X-CH=CH-R" or with the acetylenic unsaturation of -X-C≡C-R" and bonded to the branched silicone resin by a C-Si bond and R" represents hydrogen or a group having an electron withdrawing effect or any other activation effect with respect to the -CH=CH- or -C≡C- bond, in grafting silicone moieties to a diene elastomer. The use of a branched silicone resin containing at least one group of the formula -X-CH=CH-R" (I) or -X-C≡C-R" (II), in which X represents a divalent organic linkage containing an aromatic ring or a further olefinic double bond or acetylenic unsaturation conjugated with the olefinic unsaturation of -X-CH=CH-R" or with the acetylenic unsaturation of -X-C≡C-R" achieves grafting with less degradation of the polymer compared to grafting with an unsaturated silicon compound not containing an aromatic ring

[0007] It will be appreciated that the high shear rate generated by a melt extrusion process can generate free radical sites in the diene elastomer. However, it has been identified that whilst it is possible to use an "external" means capable of generating free radicals when grafting the silicone onto a diene elastomer none are required. By "external means for generating free radical sites in the diene elastomer", we mean additional to normal processing steps such as shear rate due to mixing. Hence, the introduction of a compound capable of generating free radicals and thus capable of generating free radical sites in the diene elastomer e.g. organic peroxides or azo compounds may be used but is not necessary for the invention to function. Preferably, if present, the radical formed by the decomposition of the free-radical initiator is an oxygen-based free radical. Other possible means include applying heat from an external heat source or irradiation such as electron beam radiation. Preferably the process as described herein is undertaken in the absence of an "external" means for generating free radical sites in the diene elastomer. [0008] We have found that a silicone resin containing at least one group of the formula -X-CH=CH-R" (I) or -X-C≡C-R" (II), in which X represents a divalent organic linkage having an electron withdrawing effect with respect to the -CH=CH- or -C≡C- bond, has particularly high grafting efficiency to the diene elastomer, readily linking modified polymer or reactive polymer to a substrate in which the diene elastomer and the silicone resin are well bonded. The enhanced grafting efficiency can lead to a silane grafted polymer with enhanced physical properties, such as, e.g., coupling and adhesion properties, heat resistance and/or impact resistance.

[0009] The obtained grafted diene elastomer can also be used to improve filler dispersion. Preferably the polymer treatment and filler dispersion can be achieved in a single mixing phase. Additionally the functional silicone resin can be used in combination with a coupling or covering agent in the case of filler dispersion.

[0010] An electron-withdrawing moiety is a chemical group which draws electrons away from a reaction centre. The electron-withdrawing linkage X can in general be any of the groups listed as dienophiles in Michael B. Smith and Jerry March; March's Advanced Organic Chemistry, 5^th edition, John Wiley & Sons, New York 2001 , at Chapter 15-58 (page 1062). The linkage X can be especially a C(=0)R^*, C(=0)OR^*, OC(=0)R^*, C(=0)Ar linkage in which Ar represents arylene and R^* represents a divalent hydrocarbon moiety. X can also be a C(=0)-NH-R^* linkage. The electron withdrawing carboxyl, carbonyl, or amide linkage represented by C(=0)R^*, C(=0)OR^*, OC(=0)R^*, C(=0)Ar or C(=0)-NH-R^* can be bonded to the branched silicone resin structure by a divalent organic spacer linkage comprising at least one carbon atom separating the C(=0)R^*, C(=0)OR^*, OC(=0)R^*, C(=0)Ar or C(=0)-NH-R^* linkage X from the Si atom. [0011] Electron-donating groups, for example alcohol group or amino group may decrease the electron withdrawing effect. In one embodiment, the branched silicone resin is free of such group. Steric effects for example steric hindrance of a terminal alkyl group such as methyl, may affect the reactivity of the olefinic or acetylenic bond. In one embodiment, the branched silicone resin is free of such sterically hindering group. Groups enhancing the stability of the radical formed during the grafting reaction, for example double bond or aromatic group conjugated with the unsaturation of the group -X-CH=CH-R" (I) or

-X-C≡C-R" (II), are preferably present in (I) or (II). The latter groups have an activation effect with respect to the -CH=CH- or -C≡C- bond.

[0012] In a preferred embodiment, the composition contains not only (A) or (Α') monomer together with compound (B) but also an olefinically unsaturated silane having at least one hydrolysable group bonded to silicon, characterized in that the silane has the formula: · R"-CH=CH-C(0)A-B-SiR_aR'₍3-a) (I) or

R"-C≡C-C(0)A-B-SiR_aR'₍3-a) (II) in which R represents a hydrolysable group; R' represents a hydrocarbyl group having 1 to 6 carbon atoms; a has a value in the range 1 to 3 inclusive; B represents a divalent organic spacer linkage comprising at least one carbon atom separating the linkage -C(0)X- from the Si atom, and R" represents hydrogen or a group having an electron withdrawing effect with respect to the -CH=CH- or -C≡C- bond; A is selected from S and O. Such olefinically unsaturated silane is described in WO2010/125123 and WO2010/125124. [0013] Sulfido-functional silanes, silicone resin or sulfido-functional resins may be used in rubber for improving silica dispersion and reducing the amount of volatile organic compounds (VOCs) released into the atmosphere during processing). However, in the case of natural rubbers these sulfido-functional silanes and resins are not sufficiently efficient to modify the rubber to obtain good silica dispersion. We have found that a silicone resin containing at least one group of the formula:

-X-CH=CH-R" (I) or

-X-C≡C-R" (II); in which X represents a divalent organic linkage containing an aromatic ring or a further olefinic double bond or acetylenic unsaturation, the aromatic ring or the further olefinic double bond or acetylenic unsaturation being conjugated with the olefinic unsaturation of -X-CH=CH-R" or with the acetylenic unsaturation of -X-C≡C-R", grafts efficiently to natural rubber, and to other diene elastomers as defined herein in order to improve rubber properties of adhesion and dispersion.

[0014] A silicone resin containing at least one group of the formula -X-CH=CH-R" (I) or -X-C≡C-R" (II), in which X represents a divalent organic linkage having an electron withdrawing effect with respect to the -CH=CH- or -C≡C- bond, but not containing an aromatic ring or a further olefinic double bond or acetylenic unsaturation, the aromatic ring or the further olefinic double bond or acetylenic unsaturation being conjugated with the olefinic unsaturation of -X-CH=CH-R" or with the acetylenic unsaturation of -X-C≡C-R", can be grafted efficiently to natural rubber and to other diene elastomers.

[0015] Polyorganosiloxanes, also known as silicones, generally comprise siloxane units selected from R₃SiOi_/2 (M units), R₂Si0₂/2 (D units), RSi0₃/2 (T units) and Si0₄/2 (Q units), in which each R represents an organic group or hydrogen or a hydroxyl group. Branched silicone resins contain T and/or Q units, optionally in combination with M and/or D units. In the branched silicone resins used in the present invention, no more than 50 mole % of the siloxane units in the resin are D units.

[0016] Branched silicone resins can for example be prepared by the hydrolysis and condensation of hydrolysable silanes such as alkoxysilanes. Trialkoxysilanes such as alkyltrialkoxysilanes generally lead to T units in the silicone resin and tetraalkoxysilanes generally lead to Q units. Branched silicone resins containing at least one group of the formula -X-CH=CH-R" (I) or -X-C≡C-R" (II) can for example be formed by condensing trialkoxysilanes of the formula (RO)₃Si-X-CH=CH-R" or (R'0)₃Si -X-C≡C-R", in which X and R" have the meanings above and R' represents an alkyl group, preferably methyl or ethyl, alone or with other alkoxysilanes. Alternatively a branched silicone resin can be produced from monoalkoxysilanes or dialkoxysilanes containing a group of the formula -X-CH=CH-R" or -X-C≡C-R" by co-condensation with a trialkoxysilane or tetraalkoxysilane not containing a group of the formula -X-CH=CH-R" or -X-C≡C-R". Condensation is catalysed by acids or bases. A strong acid catalyst such as trifluromethanesulfonic acid or hydrochloric acid is preferred. [0017] The branched silicone resins containing at least one group of the formula

-X-CH=CH-R" (I) or -X-C≡C-R" (II) can alternatively be prepared from an existing branched silicone resin containing Si-OH and/or Si-bonded alkoxy groups by an end-capping reaction with an alkoxysilane containing a group of the formula -X-CH=CH-R" or -X-C≡C-R". The end-capping reaction is a condensation reaction between the Si-OH or Si-alkoxy group of the branched silicone resin and a Si-alkoxy group of the silane. The existing branched silicone resin can for example be a T resin or MQ resin containing Si-OH and/or Si-bonded alkoxy groups. The alkoxysilane can be a monoalkoxysilane, dialkoxysilane or

trialkoxysilane and may preferably be a trialkoxysilane of the formula (R'0)₃Si-X-CH=CH-R" or (R'0)₃Si -X-C≡C-R", in which X and R" have the meanings above and R' represents an alkyl group, preferably methyl or ethyl. The end-capping condensation reaction is catalysed by acids or bases as discussed above. [0018] Examples of groups of the formula -X-CH=CH-R" (I) in which X represents a divalent organic linkage having an electron withdrawing effect with respect to the -CH=CH- bond include acryloxy groups e.g. acryloxyalkyl groups such as 3-acryloxypropyl or acryloxymethyl. Such groups can be introduced into a branched silicone resin by reaction of 3-acryloxypropyltrimethoxysilane, acryloxymethyltrimethoxysilane, 3- acryloxypropyltriethoxysilane, acryloxymethyltriethoxysilane, 3-acryloxypropyltrichlorosilane or acryloxymethyltrichlorosilane.

[0019] 3-acryloxypropyltrimethoxysilane can be prepared from allyl acrylate and

trimethoxysilane by the process described in US-A-3179612.

Acryloxymethyltrimethoxysilane can be prepared from acrylic acid and

chloromethyltrimethoxysilane by the process described in US-A-3179612. Branched silicone resins containing acryloxy groups, and their preparation, are described for example in WO- A-2006/019468 and in EP-A-776945. We have found that silicone resins containing acryloxyalkyl groups graft to diene elastomers more readily than silicone compounds containing methacryloxyalkyl groups.

[0020] By an aromatic ring we mean any cyclic moiety which is unsaturated and which shows some aromatic character or ττ-bonding. The aromatic ring can be a carbocyclic ring such as a benzene or cyclopentadiene ring or a heterocyclic ring such as a furan, thiophene, pyrrole or pyridine ring, and can be a single ring or a fused ring system such as a

naphthalene, quinoline or indole moiety.

[0021] Examples of groups of the formula -X-CH=CH-R" (I) or -X-C≡C-R" in which X represents a divalent organic linkage containing an aromatic ring or a further olefinic double bond or acetylenic unsaturation, the aromatic ring or the further olefinic double bond or acetylenic unsaturation being conjugated with the olefinic unsaturation of -X-CH=CH-R" or with the acetylenic unsaturation of -X-C≡C-R" include those of the formula CH2=CH-C₆H4-A- or CH≡C-C₆H₄-A-, wherein A represents a direct bond or a spacer group. The group -X-CH=CH-R" (I) can for example be styryl (-C6H5CH=CH2 or C6H5CH=CH-), styrylmethyl, 2-styrylethyl or 3-styry I propyl. Such groups can be introduced into a branched silicone resin by reaction of for example 4-(trimethoxysilyl)styrene or styrylethyl trimethoxysilane. 4- (trimethoxysilyl)styrene can be prepared via the Grignard reaction of 4-bromo- and/or 4- chlorostyrene with tetramethoxysilane in the presence of magnesium as described in EP-B- 1318153. Styrylethyltrimethoxysilane is e.g. commercially available from Gelest, Inc as a mixture of meta and para, as well as alpha, and beta isomers. The spacer group A can optionally comprise a heteroatom linking group particularly an oxygen, sulfur or nitrogen heteroatom, for example the group -X-CH=CH-R" (I) can be vinylphenylmethylthiopropyl. [[0022] Examples of groups of the formula -X-CH=CH-R" (I) in which X represents a divalent organic linkage having an electron withdrawing effect with respect to the -CH=CH- bond and also containing an aromatic ring or a further olefinic double bond or acetylenic unsaturation, the aromatic ring or the further olefinic double bond or acetylenic unsaturation being conjugated with the olefinic unsaturation of -X-CH=CH-R" or with the acetylenic unsaturation of -X-C≡C-R" include sorbyloxyalkyl groups such as sorbyloxypropyl

CH3-CH=CH-CH=CH-C(=0)0-(CH₂)3- derived from condensation of a trialkoxysilane such as

cinnamyloxyalkyl groups such as cinnamyloxypropyl derived from condensation of a trialkoxysilane such as

whose preparation is described in US-A-3179612, or 3-(2-furyl)acryloxyalkyl groups such as 3-(2-furyl)acryloxypropyl derived from condensation of a trialkoxysilane such as

[0023] The branched silicone resin can for example be a T resin in which at least 50 mole %, and preferably at least 75% or even 90%, of the siloxane units present in the branched silicone resin are T units. Such a resin can be formed by condensation of one or more trialkoxysilane, optionally with minor amounts of tetraalkoxysilane, dialkoxysilane and/or monoalkoxysilane. In general, 0.1 to 100 mole % of the siloxane T units present in such a branched silicone resin are of the formula R"-CH=CH-X-Si0₃/2. [0024] Other organic groups present in the branched silicone resin can in general be alkyl, substituted alkyl, alkenyl, substituted alkenyl, aryl, substituted aryl or aralkyl groups or heterocyclic groups bonded to the branched silicone resin by a C-Si bond, but are most usually alkyl, particularly Ci_-4 alkyl such as methyl, ethyl or propyl, or vinyl or phenyl. [0025] The T-resin can have a cage-like structure. Such structures containing 100% T units are known as polyhedral oligomeric silsesquioxanes (POSS). They can be prepared by condensing trialkoxysilanes of the formula (RO)₃Si-X-CH=CH-R" or (R'0)₃Si -X-C≡C-R" alone or in combination with other trialkoxysilanes having aryl and alkyl, particularly methyl, ethyl, propyl, or phenyl substituents. Closed cages can be formed bearing -X-CH=CH-R" or -X-C≡C-R" in possible combination with the mentioned alkyl and aryl substituents in the corners of the cages, while open cages might still have unreacted alkoxy groups remaining or can carry silanol groups from hydrolysis reaction thereof.

[0026] The branched silicone resin can alternatively be a MQ resin in which at least 50 mole %, and preferably at least 70% or 85%, of the siloxane units present in the branched silicone resin are selected from Q units and M units as herein defined. The molar ratio of M units to Q units is preferably in the range 0.4:1 to 1 .5:1. Such resins can be produced by the condensation of a monoalkoxysilane such as trimethylmethoxysilane with a

tetraalkoxysilane such as tetraethoxysilane. The groups of the formula -X-CH=CH-R" (I) or -X-C≡C-R" (II) can be introduced by incorporating them in a monoalkoxysilane or by reacting a trialkoxysilane as described above with the monoalkoxysilane and tetraalkoxysilane to introduce some T units of the formula R"-CH=CH-X-Si0₃/2 into the MQ resin.

[0027] For many uses it is preferred that the branched silicone resin contains Si-bonded hydroxyl or hydrolysable groups, so that the grafted product can be further crosslinked in the presence of water by hydrolysis of the hydrolysable groups if required and siloxane condensation. Preferred hydrolysable groups are Si-bonded alkoxy groups, particularly Si-OR groups in which R represents an alkyl group having 1 to 4 carbon atoms. Such Si-OH or Si-OR groups can be present in the branched silicone resin at 1 to 100 Si-OH or hydrolysable groups per 100 siloxane units, preferably 5 to 50 Si-OR groups per 100 siloxane units.

[0028] The branched silicone resin is preferably present in the composition at 1 to 30% by weight based on the diene elastomer during the grafting reaction. [0029] If the branched silicone resin contains hydrolysable groups, for example silyl-alkoxy groups, these can react in the presence of moisture with hydroxyl groups present on the surface of many fillers and substrates, for example of minerals and natural products. The moisture can be ambient moisture or a hydrated salt can be added. Grafting of the diene elastomer with a branched silicone resin according to the invention can be used to improve compatibility of the diene elastomer with fillers. The diene elastomer grafted with

hydrolysable groups can be used as a coupling agent improving filler/polymer adhesion; for example diene elastomer grafted according to the invention can be used as a coupling agent for unmodified diene elastomer in filled compositions. The diene elastomer grafted with hydrolysable groups can be used as an adhesion promoter or adhesion interlayer improving the adhesion of a low polarity polymer such as diene elastomer to surfaces. The

hydrolysable groups can also react with each other in the presence of moisture to form Si-O- Si linkages between polymer chains.

[0030] The hydrolysable groups, for example silyl-alkoxy groups, react with each other in the presence of moisture to form Si-O-Si linkages between polymer chains even at ambient temperature, without catalyst, but the reaction proceeds much more rapidly in the presence of a siloxane condensation catalyst. Thus the grafted polymer can be crosslinked by exposure to moisture in the presence of a silanol condensation catalyst. The grafted polymer can be foamed by adding a blowing agent, moisture and condensation catalyst. Any suitable condensation catalyst may be utilised. These include protic acids, Lewis acids, organic and inorganic bases, transition metal compounds, metal salts and organometallic complexes.

[0031] Preferred catalysts include organic tin compounds, particularly organotin salts and especially diorganotin dicarboxylate compounds such as dibutyltin dilaurate, dioctyltin dilaurate, dimethyltin dibutyrate, dibutyltin dimethoxide, dibutyltin diacetate, dimethyltin bisneodecanoate, dibutyltin dibenzoate, dimethyltin dineodeconoate or dibutyltin dioctoate.

Alternative organic tin catalysts include triethyltin tartrate, stannous octoate, tin oleate, tin naphthate, butyltintri-2-ethylhexoate, tin butyrate, carbomethoxyphenyl tin trisuberate and isobutyltin triceroate. Organic compounds, particularly carboxylates, of other metals such as lead, antimony, iron, cadmium, barium, manganese, zinc, chromium, cobalt, nickel, aluminium, gallium or germanium can alternatively be used.

[0032] The condensation catalyst can alternatively be a compound of a transition metal selected from titanium, zirconium and hafnium, for example titanium alkoxides, otherwise known as titanate esters of the general formula Ti[OR⁵]₄ and/or zirconate esters Zr[OR⁵]₄ where each R⁵ may be the same or different and represents a monovalent, primary, secondary or tertiary aliphatic hydrocarbon group which may be linear or branched containing from 1 to 10 carbon atoms. Preferred examples of R⁵ include isopropyl, tertiary butyl and a branched secondary alkyl group such as 2,4-dimethyl-3-pentyl. Alternatively, the titanate may be chelated with any suitable chelating agent such as acetylacetone or methyl or ethyl acetoacetate, for example diisopropyl bis(acetylacetonyl)titanate or diisopropyl bis(ethylacetoacetyl)titanate. [0033] The condensation catalyst can alternatively be a protonic acid catalyst or a Lewis acid catalyst. Examples of suitable protonic acid catalysts include carboxylic acids such as acetic acid and sulphonic acids, particularly aryl sulphonic acids such as

dodecylbenzenesulphonic acid. A "Lewis acid" is any substance that will take up an electron pair to form a covalent bond, for example, boron trifluoride, boron trifluoride monoethylamine complex, boron trifluoride methanol complex, FeCI₃, AICI₃, ZnCI₂, ZnBr₂ or catalysts of formula MR⁴ _fX_g where M is B, Al, Ga, In or Tl, each R⁴ is independently the same or different and represents a monovalent aromatic hydrocarbon radical having from 6 to 14 carbon atoms, such monovalent aromatic hydrocarbon radicals preferably having at least one electron-withdrawing element or group such as -CF₃, -N0₂ or -CN, or substituted with at least two halogen atoms; X is a halogen atom; f is 1 , 2, or 3; and g is 0, 1 or 2; with the proviso that f+g =3. One example of such a catalyst is B(C₆F₅)₃.

[0034] An example of a base catalyst is an amine or a quaternary ammonium compound such as tetramethylammonium hydroxide, or an aminosilane. Amine catalysts such as laurylamine can be used alone or can be used in conjunction with another catalyst such as a tin carboxylate or organotin carboxylate.

[0035] The siloxane condensation catalyst is typically used at 0.005 to 1.0 by weight of the total composition. For example a diorganotin dicarboxylate is preferably used at 0.01 to 0.1 % by weight of the total composition.

[0036] For specific rubber uses (e.g. filled elastomers) it is preferred that the branched silicone resin contains hydroxy, so that the grafted product can be further crosslinked in the presence of water by condensation of the OH groups. Such Si-OH groups can be present in the branched silicone resin at 1 to 100 hydrolysable groups per 100 siloxane units, preferably 5 to 50 Si-OH groups per 100 siloxane units.

[0037] The diene elastomer can be natural rubber. We have found that the unsaturated functional resins described herein graft readily to natural rubber.

[0038] 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, i.e. 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, can alternatively be used but are less preferred.

The diene elastomer can for example be: any homopolymer obtained by polymerization of a conjugated diene monomer having 4 to 12 carbon atoms;

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;

a ternary copolymer obtained by copolymerization of ethylene, of an [alphaj-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;

a copolymer of isobutene and isoprene (butyl rubber), and also the halogenated, in particular chlorinated or brominated, versions of this type of copolymer.

[0040] Suitable conjugated dienes are, in particular, 1 ,3-butadiene, 2-methyl-1 ,3-butadiene, 2,3-di(CrC₅ 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-1 ,3-butadiene, 1 ,3-pentadiene and 2,4-hexadiene. 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.

[0041] 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.

The elastomer can be epoxidised rubber, for example Epoxidised Natural Rubber (ENR). Epoxidised rubber is obtained by modifying rubber, for example natural rubber, in which some insaturation are replaced by epoxy groups through a chemical modification. Useful epoxidized rubber will have an extent of epoxidation of about 5 to about 95 mole %, preferably from about 15 to about 80 mole %, and more preferably from about 20 to about 50 mole %, where the extent of epoxidation is defined as the mole percentage of olefinically unsaturated sites originally present in the rubber that have been converted to oxirane, hydroxyl, or ester groups.

Epoxidation reactions can be effected by reacting an unsaturated rubber with an epoxidizing agent. Useful epoxidizing agents include peracids such as m-chloroperbenzoic acid and peracetic acid. Other examples include carboxylic acids, such as acetic and formic acid, or carboxylic anhydrides such as acetic anhydride, together with hydrogen peroxide. A catalyst, such as sulfuric acid, p-tolulene sulfonic acid, or a cationic exchange resin such as sulfonated polystyrene may optionally be employed.

Epoxidation is preferably conducted at a temperature from about 0° to about 150° C. and preferably from about 25° to about 80° C. The time required to effect the epoxidation reaction is typically from about 0.25 to about 10 hours, and preferably from about 0.5 to about 3 hours.

The epoxidation reaction is preferably conducted in a solvent that is capable of substantially dissolving the rubber both in its original condition and after epoxidation. Suitable solvents include aromatic solvents such as benzene, tolulene, xylene, and chlorobenzene, as well as cycloaliphatic solvents such as cyclohexane, cycloheptane, and mixtures thereof.

After epoxidation, the epoxidized rubber is preferably removed or isolated from the acidic environment, which may include the epoxidizing agents as well as the acidic catalyst. This isolation can be accomplished via filtration, or by adding a dilute aqueous base to neutralize the acid and then subsequently coagulate the polymer. The polymer can be coagulated by using an alcohol such as methanol, ethanol, or propanol. An antioxidant is typically added after the isolation procedure, and the final product may be dried using techniques such as 13a

vacuum distillation. Alternatively, other known methods for removing polymers from hydrocarbon solvents and the like may be employed including steam stripping and drum drying.

Other diene elastomer can also be used in epoxydised form such as, but not limited to, those rubbers that derive from the polymerization of conjugated dienes alone or in combination with vinyl aromatic monomers.

[0042] Preferred are polybutadienes, and in particular those having a content of 1 ,2-units between 4% and 80%, or those having a content of cis-1 ,4 of more than 80%, polyisoprenes, butadiene-styrene copolymers, and in particular those having a styrene content of between 5% and 50% by weight and, more particularly, between 20% and 40%, a content of 1 ,2- bonds of the butadiene fraction of between 4% and 65%, and a content of trans-1 ,4 bonds of between 20% and 80%, butadiene-isoprene copolymers and in particular those having an isoprene content of between 5% and 90% by weight. In the case of butadiene-styrene- isoprene copolymers, those which are suitable are in particular those having a styrene content of between 5% and 50% by weight and, more particularly, between 10% and 40%, an isoprene content of between 15% and 60% by weight, and more particularly between 20% and 50%, a butadiene content of between 5% and 50% by weight, and more

particularly between 20% and 40%, a content of 1 ,2-units of the butadiene fraction of between 4% and 85%, a content of trans-1 ,4 units of the butadiene fraction of between 6% and 80%, a content of 1 ,2- plus 3,4-units of the isoprene fraction of between 5% and 70%, and a content of trans-1 ,4 units of the isoprene fraction of between 10% and 50%.

[0043] 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.

[0044] The elastomer and the unsaturated functional resin can be reacted by various procedures. Although some reaction occurs at ambient temperature, the elastomer and the unsaturated-functional silicone resin are preferably heated together at a temperature of at least 80°C, more preferably to a temperature between 90°-200°C, most preferably between 120°C and 180°C. The diene elastomer and the unsaturated-functional silicone resin can be mixed by pure mechanical mixing, followed if desired by a separate heating step, but mixing 13b

and heating are preferably carried out together so that the elastomer is subjected to mechanical working while it is heated.

[0045] The elastomer and the unsaturated-functional silicone resin can be reacted in the presence of a catalyst which accelerates the ene-addition reaction between the activated unsaturated-functional silicone resin and the diene containing rubber polymer, for example a

14

Lewis Acid such as boron triacetate. Use of such a catalyst can reduce the temperature of the thermo-mechanical processing required to effect reaction between the elastomer and the unsaturated-functional silicone resin. This catalyst can also help to disperse further the filler. The catalyst can control the number of links created during the mixing phase to optimize the torque, the grafting and, when hydroxyl containing filler is present, its dispersion. However the diene elastomer and the unsaturated-functional silicone resin according to the invention react readily at the temperatures conventionally used for thermomechanical kneading of rubber, and it may be desirable to avoid catalyst residues in the grafted elastomer. [0046] The catalyst such as a Lewis acid can also be added during the productive phase in order to accelerate the cure behaviour under heating of the semi-finished article.

[0047] Diene elastomer compositions according to the invention which are to be cured to a shaped rubber article generally contain a filler, particularly a reinforcing filler such as silica or carbon black. The filler is usually mixed with the elastomer in a non-productive thermo- mechanical mixing or kneading phase. In the present case when preparing a filled rubber composition, the elastomer and the unsaturated-functional silicone resin can be reacted and then mixed with the filler, but the filler is preferably present during the reaction between the elastomer and the unsaturated-functional silicone resin. The elastomer, the silane and the filler 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 unsaturated- functional silicone resin and then mixed with the elastomer, preferably with heating. When the unsaturated-functional silicone resin is present during thermo-mechanical kneading of the diene elastomer and the filler, it reacts with the elastomer to form a modified diene elastomer and also acts as a coupling agent bonding the filler to the elastomer.

[0048] 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.

[0049] Use of an unsaturated-functional silicone resin according to the invention 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 15

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.

[0050] The reinforcing filler can for example be any commonly employed siliceous filler used in rubber compounding applications, including pyrogenic or precipitated 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 20 to about 600 m²/g, and more usually in a range of about 40 or 50 to about 300 m²/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 350 cm³/100 g, and more usually about 150 to about 300 cm³/100 g, 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 220 m²/g (ASTM D3849). The CTAB surface area is the external surface area as evaluated by cetyl trimethylammonium bromide with a pH of 9. The method is described in ASTM D 3849.

[0051] 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, 1 1 15MP, or HRS 1200MP; 200MP premium, 80GR or equivalent silicas available from PPG Industries under the Hi-Sil trademark with designations Hi-Sil^® EZ150G, 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 aluminum-doped silicas described in EP-A-735088.

[0052] If alumina is used in the elastomer compositions of the invention, it can for example be natural aluminum oxide or synthetic aluminum oxide (Al₂0₃) prepared by controlled precipitation of aluminum hydroxide. The reinforcing alumina preferably has a BET surface 16

area from 30 to 400 m²/g, more preferably between 60 and 250 m²/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 Baikowski or the neutral, acidic, or basic Al₂0₃ that can be obtained from the Aldrich Chemical Company. Neutral alumina is preferred.

[0053] 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.

[0054] 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.

[0055] The filler can additionally or alternatively comprise a filler which does not have hydroxyl groups at its surface, for example a reinforcing filler such as carbon black and/or a non-reinforcing filler such as calcium carbonate.

[0056] The reaction between the diene elastomer and the unsaturated-functional silicone resin (I) or (II) can be carried out as a batch process or as a continuous process using any suitable apparatus. [0057] 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 Pfeidener. The extruder preferably includes a vacuum port shortly before the extrusion die to remove any unreacted silane. The residence time of the diene elastomer and the unsaturated-functional silicone resin 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. 17

[0058] A batch process can for example be carried out in an internal mixer such as a Banbury mixer or a Brabender Plastograph (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 and the unsaturated-functional silicone resin 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.

[0059] 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 1 10°C, for example between 40°C - 100°C, during which the cross-linking and vulcanization systems are incorporated.

[0060] During the non productive phase, the unsaturated-functional silicone resin, the diene elastomer and the filler are mixed together. Mechanical or thermo-mechanical kneading occurs, in one or more steps, until a maximum temperature of 1 10°-190°C is reached, preferably between 130°-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. [0061] Compositions comprising the modified elastomer produced by reaction with the unsaturated-functional silicone resin according to the invention can be cured by various mechanisms. The curing agent for the modified elastomer can be a conventional rubber curing agent such as a sulfur vulcanizing agent. Alternatively the modified elastomer can be cured by a radical initiator such as a peroxide. Alternatively the modified elastomer can be cured by exposure to moisture in the presence of a silanol condensation catalyst. The hydrolysable silane groups grafted onto the elastomer can react with each other to crosslink the elastomer and/or can be further reacted with a polar surface, filler or polar polymer.

[0062] For many uses curing by a conventional sulfur vulcanizing agent is preferred. Examples of suitable sulfur vulcanizing agents include, for example, elemental sulfur (free 18

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%.

[0063] 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. Vulcanization retarders can also be used, e.g. phthalic anhydride, benzoic acid or cyclohexylthiophthalimide.

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.

[0064] In case the curing system is composed of sulphur, 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 130°-200°C, under pressure, for a sufficiently long period of time. The required time for vulcanization may vary for example between 2 and 30 minutes.

[0065] In one preferred procedure the diene elastomer and the unsaturated-functional silicone resin and possibly the filler are mixed together above 100°C in an internal mixer or extruder.

[0066] By way of example, the first (non-productive) phase is effected in a single thermomechanical step during which in a first phase the reinforcing filler, the unsaturated- functional silicone resin and the elastomer are mixed in a suitable mixer, such as a 19

conventional internal mixer or extruder, then in a second phase, for example after one to two minutes' kneading, any complementary covering agents or processing agents and other various additives, with the exception of the vulcanization system, are introduced into the mixer. A second step of thermomechanical working may be added in this internal mixer, after the mixture has dropped and after intermediate cooling to a temperature preferably less than 100°C, with the aim of making the compositions undergo complementary

thermomechanical treatment, in particular in order to improve further the dispersion, in the elastomeric matrix, of the reinforcing inorganic filler. The total duration of the kneading, in this non-productive phase, is preferably between 2 and 10 minutes.

[0067] After cooling of the mixture thus obtained, the vulcanization 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.

[0068] Any other additives such as a grafting catalyst can be incorporated either in the "non productive" phase or in the productive phase.

[0069] The curable rubber composition can contain a coupling agent other than the unsaturated-functional silicone resin, 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 1 to 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 , such as bis(triethoxysilylpropyl)tetrasulfane or bis(triethoxysilylpropyl)disulfane, or a bis(dialkoxymethylsilylpropyl)disulfane or tetrasulfane such as bis(methyldiethoxysilylpropyl)tetrasulfane or bis(methyldiethoxysilylpropyl)disulfane, or a bis(dimethylethoxysilylpropyl)oligosulfane such as

bis(dimethylethoxysilylpropyl)tetrasulfane or bis(dimethylethoxysilylpropyl)disulfane, or a bis(dimethylhydroxysilylpropyl)polysulfane as described in US-B1 -6774255, or a

dimethylhydroxysilylpropyl dimethylalkoxysilylpropyl oligosulfane as described in WO-A- 2007/061550, 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 20

unsaturated-functional silicone resin according to the invention. We have found that use of an unsaturated-functional silicone resin (I) or (II) according to the 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 with no such unsaturated-functional silicone resin. Alternatively for natural rubber system the coupling agent can be acryloxypropytriethoxysilane or acryloxymethyltriethoxysilane.

[0070] The curable rubber composition can contain a covering agent other than the unsaturated-functional silicone resin , for example a trialkoxy, dialkoxy or monoalkoxy silane covering agent, particularly n-octyltriethoxysilane or 1 -hexadecyltriethoxysilane, or hexamethyldisilazane or a polysiloxane covering agent such as a hydroxyl-terminated polydimethylsiloxane, hydroxyl-terminated polymethylphenylsiloxane, or a linear

polyfunctionalsiloxane, or a silicone resin. The covering agent can alternatively be an aryl- alkoxysilane or aryl-hydroxysilane, a tetraalkoxysilane such as tetraethoxysilane, or a polyetherpolyol such as polyethylene glycol, an amine such as a trialkanolamine. The filler can be pre-treated with the covering agent or the coupling agent can be added to the mixer with the elastomer and filler and the unsaturated-functional silicone resin according to the invention. We have found that use of an unsaturated-functional silicone resin (I) or (II) according to the invention in conjunction with such a covering 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 covering agent with no such unsaturated-functional silicone resin.

[0071] 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.

[0072] 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. 21

[0073] Typical amounts of antioxidants comprise about 1 to about 5% by weight based on elastomer. Representative antioxidants may be, for example, N-1 ,3- dimethylbutyl-N-phenyl- para-phenylenediamine, sold as "Santoflex 6-PPD" (trade mark) 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 1 to 5% by weight based on elastomer.

[0074] 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%.

[0075] Typical amounts of waxes comprise about 1 to about 5% by weight based on elastomer. Microcrystalline and/or crystalline waxes can be used.

[0076] 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.

[0077] The modified elastomer composition containing a curing agent such as a

vulcanizing system is 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.

[0078] In the case of a passenger car tire, 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 SBR/BR, SBR/NR (or SBR/IR), alternatively BR/NR (or BR/IR), or SIBR (isoprene-butadiene-styrene copolymers), IBR (isoprene-butadiene copolymers), or blends (mixtures) thereof. In the case of an SBR 22

elastomer, in particular an SBR having a styrene content of between 20% and 30% by weight, a content of vinyl bonds of the butadiene fraction of between 15% and 65%, and a content of trans-1 ,4 bonds of between 15% and 75% is preferred. Such an SBR copolymer, preferably an SSBR, is possibly used in a mixture with a polybutadiene (BR) having preferably more than 90% cis-1 ,4 bonds.

[0079] In the case of a tyre for a heavy vehicle, the elastomer is in particular an isoprene elastomer; 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. Of the isoprene copolymers, mention will be made in particular of isobutene-isoprene copolymers (butyl rubber-IIR), isoprene-styrene copolymers (SIR), isoprene-butadiene copolymers (BIR) or isoprene- butadiene-styrene copolymers (SBIR). This isoprene elastomer is 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 tire 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, a SBR or a BR elastomer. [0080] When the elastomer composition is for use as a tire 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. [0081] 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.

[0082] As an alternative to curing by a sulfur vulcanizing system, the modified elastomer composition can be cured by a peroxide. Examples are di(tert-butyl)peroxide; t-butylcumyl 23

peroxide; dicumyl peroxide; benzoyl peroxide; 1 ,1 '-di(t-butylperoxy)-3,3,5- trimethylcyclohexane; 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne; 2,5-dimethyl-2,5-di(t- butylperoxy)hexane; a,a'-di(t-butylperoxy)-m/p-diisopropylbenzene; and n-buty I-4 ,4'-d i (tert- butylperoxy)valerate.

[0083] This invention relates to the use of activated unsaturated functional silane to graft to diene polymer without any radical initiator to help the grafing. However, vulcanization can still be done using peroxides. Heat or UV radiation can be used to vulcanise the rubber in order to activate the peroxide. Heat activation of the peroxide is the preferred way, for example with temperature from 100 to 200°C for a time comprised between 1 to 90 minutes, preferably 5 to 20 minutes.

[0084] A further alternative to sulfur and peroxide cure is the use of the alkoxysilane groups of the obtained grafted polymer. If the grafted elastomer is crosslinked by exposure to moisture in the presence of a silanol condensation catalyst, any suitable condensation catalyst may be used. These include protic acids, Lewis acids, organic and inorganic bases, transition metal compounds, metal salts and organometallic complexes. Preferred condensation catalysts include those as hereinbefore described. [0085] The siloxane condensation catalyst is typically used at 0.005 to 1 .0% by weight based on the modified diene elastomer. For example a diorganotin dicarboxylate is preferably used at 0.01 to 0.1 % by weight based on the elastomer.

[0086] When curing a modified diene elastomer by exposure to moisture, the modified elastomer is preferably shaped into an article and subsequently crosslinked by moisture. In one preferred procedure, the silanol condensation catalyst can be dissolved in the water used to crosslink the grafted polymer. For example an article shaped from grafted polyolefin can be cured by water containing a carboxylic acid catalyst such as acetic acid, or containing a diorganotin carboxylate.

[0087] Alternatively or additionally, the silanol condensation catalyst can be incorporated into the modified elastomer before the modified elastomer is shaped into an article. The shaped article can subsequently be crosslinked by moisture. The catalyst can be mixed with the diene elastomer before, during or after the grafting reaction. 24

[0088] A silanol condensation catalyst can be used in addition to other curing means such as vulcanization by sulphur. In this case, the silanol condensation catalyst can be incorporated either in the "non productive" phase or in the productive phase of the preferred vulcanization process described above.

[0089] When curing is done using alkoxysilane groups of the grafted elastomer, care should be taken when forming a cured elastomer article to avoid exposure of the silane and catalyst together to moisture, or of the composition of silane-modified elastomer and catalyst to moisture before its final shaping into the desired article.

[0090] The modified diene elastomer according to the invention has improved adhesion both to fillers mixed with the elastomer and silane during the grafting reaction and to substrates to which the modified diene elastomer is subsequently applied. Improved adhesion to fillers results in better dispersion of the fillers during compounding. Substrates to which the modified diene elastomer is applied include metal cords and fabrics and organic polymer cords and fabrics which are incorporated into the structure of a finished article, for example a tyre, made from the modified diene elastomer. Improved adhesion to such substrates leads to a finished article having improved mechanical and wear properties. [0091] The ability of the unsaturated-functional silicone resin of the invention to react with a diene elastomer in the absence of any free radical initiator allows formation of a modified elastomer, especially modified natural rubber, without polymer degradation, leading to improved rubber performance, for example improved mechanical properties and/or resistance to thermal degradation, compared to a diene elastomer grafted in the presence of a free radical initiator such as peroxide. When the modified elastomer is used to

manufacture tire treads, improved mechanical properties can give improved tyre properties such as decreased rolling resistance, better tread wear and improved wet skid performance.

[0092] Crosslinked diene elastomer articles produced according to the invention have improved mechanical strength, melt strength, heat resistance, chemical and oil resistance, creep resistance and/or environmental stress cracking resistance compared to articles formed from the same diene elastomer without grafting or crosslinking.

[0093] The invention provides a modified diene elastomer composition comprising a thermoplastic diene elastomer and a polysiloxane, characterized in that the polysiloxane is a 25

branched silicone resin containing at least one group of the formula -X-CH=CH-R" (I) or -X- C≡C-R" (II), in which X represents a divalent organic linkage having an electron withdrawing effect with respect to the -CH=CH- or -C≡C- bond and/or containing an aromatic ring or a further olefinic double bond or acetylenic unsaturation, the aromatic ring or the further olefinic double bond or acetylenic unsaturation being conjugated with the olefinic unsaturation of -X-CH=CH-R" or with the acetylenic unsaturation of -X-C≡C-R", and X being bonded to the branched silicone resin by a C-Si bond, and R" represents hydrogen or a group having an electron withdrawing effect or any other activation effect with respect to the -CH=CH- or -C≡C- bond.

• Preferably, at least 50 mole % of the siloxane units present in the branched silicone resin are T units as herein defined.

• Preferably, 0.1 to 100 mole % of the siloxane T units present in the branched

silicone resin are of the formula R"-CH=CH-X-Si0₃/2.

• Preferably, at least 50 mole % of the siloxane units present in the branched silicone resin are selected from Q units and M units as herein defined. · Preferably, the unsaturated groups of the formula -X-CH=CH-R" are present as T units of the formula R"-CH=CH-X-Si0₃/₂-

• Preferably, the branched silicone resin contains hydrolysable Si-OR groups, in which R represents an alkyl group having 1 to 4 carbon atoms.

• Preferably, the branched silicone resin containing at least one group of the formula -X-CH=CH-R" (I) or -X-C≡C-R"(II) is present at 1 to 30% by weight of the total composition. · Preferably, X represents a divalent organic linkage having an electron withdrawing effect with respect to the -CH=CH- or -C≡C- bond.

• Preferably, the group of the formula -X-CH=CH-R" (I) is an acryloxyalkyl group or an acrylthioalkyl group. 26

• Preferably, the group of the formula -X-CH=CH-R" (I) or -X-C≡C-R" (II) contains an aromatic ring or a further olefinic double bond or acetylenic unsaturation, the aromatic ring or the further olefinic double bond or acetylenic unsaturation being conjugated with the olefinic -C=C- or acetylenic -C≡C- unsaturation of the group - X-CH=CH-R" (I) or -X-C≡C-R" (II).

Preferably, the group -X-CH=CH-R" (I) or -X-C≡C-R" (II) has the formula CH₂=CH- C₆H₄-A- (III) or CH≡C-C₆H₄-A- (IV), wherein A represents a direct bond or a divalent organic group having 1 to 12 carbon atoms optionally containing a divalent heteroatom linking group chosen from -0-, -S- and -NH-.

Preferably, the group -X-CH=CH-R" (I) has the formula R²-CH=CH-CH=CH-X-, where R² represents hydrogen or a hydrocarbyl group having 1 to 12 carbon atoms. · Preferably, the group -X-CH=CH-R" (I) is a sorbyloxyalkyl group.

• Preferably, the modified diene elastomer composition contains an organic peroxide compound capable of generating free radical sites in the diene elastomer, the organic peroxide being present at 0.01 to 2% by weight of the total composition.

• Preferably, the composition contains a suitable curing system selected from sulphur, an organic peroxide or a sulphur compound.

• Preferably, when the composition is curable by moisture, said composition

additionally comprises a hydrolysis/condensation catalyst.

• Preferably, the composition additionally contains one or more filler(s) more

preferably silica. [0094] The invention provides a process for grafting silicone onto a diene elastomer, comprising reacting the diene elastomer with a silicon compound containing an unsaturated group in the presence of means capable of generating free radical sites in the diene elastomer, characterized in that the silicon compound is a branched silicone resin containing at least one group of the formula -X-CH=CH-R" (I) or -X-C≡C-R" (II), in which X represents a divalent organic linkage having an electron withdrawing effect with respect to the -CH=CH- 27

or -C≡C- bond and/or containing an aromatic ring or a further olefinic double bond or acetylenic unsaturation, the aromatic ring or the further olefinic double bond or acetylenic unsaturation being conjugated with the olefinic unsaturation of -X-CH=CH-R" or with the acetylenic unsaturation of -X-C≡C-R" and X being bonded to the branched silicone resin by a C-Si bond and R" represents hydrogen or a group having an electron withdrawing effect or any other activation effect with respect to the -CH=CH- or -C≡C- bond.

Preferably, the group of the formula -X-CH=CH-R" (I) is an acryloxyalkyl group or an acrylthioalkyl group.

Preferably, the diene elastomer is natural rubber or alternatively a homopolymer or copolymer of a diene monomer.

• Preferably, the silicone resin and the diene elastomer are reacted together at a temperature in the range of 90°C to 200°C.

[0095] The invention provides a process for the production of a rubber article from the composition characterised in that the elastomer composition is shaped and cured. [0096] The invention provides the use of a branched silicone resin containing at least one group of the formula -X-CH=CH-R" (I) or -X-C≡C-R" (II), in which X represents a divalent organic linkage having an electron withdrawing effect with respect to the -CH=CH- or -C≡C- bond, and bonded to the branched silicone resin by a C-Si bond, and R" represents hydrogen or a group having an electron withdrawing effect or any other activation effect with respect to the -CH=CH- or -C≡C- bond, in grafting silicone moieties to a diene elastomer, to give enhanced grafting compared to an unsaturated silicone not containing a -X-CH=CH-R" or -X-C≡C-R" group.

[0097] The invention provides the use of a branched silicone resin containing at least one group of the formula -X-CH=CH-R" (I) or -X-C≡C-R" (II), in which X represents a divalent organic linkage containing an aromatic ring or a further olefinic double bond or acetylenic unsaturation, the aromatic ring or the further olefinic double bond or acetylenic unsaturation being conjugated with the olefinic unsaturation of -X-CH=CH-R" or with the acetylenic unsaturation of -X-C≡C-R" and X being bonded to the branched silicone resin by a C-Si bond, and R" represents hydrogen or a group having an electron withdrawing effect or any 28

other activation effect with respect to the -CH=CH- or -C≡C- bond, in grafting silicone moieties to a diene elastomer with less degradation of the polymer compared to grafting with an unsaturated silicon compound not containing an aromatic ring. [0098] The curable rubber composition produced by the process according to the invention may be used in the production of tyres or any parts thereof or engineered rubber goods, belts, or hoses.

[0099] The invention is illustrated by the following Examples.

T(Acryloxypropyltrimethoxysilane)T(Ph) resin [0100] T₃(Ph)o.₅293 T₃(Ph, C₈H₁₄0₄Si) 04707

In a 250 ml three neck flask, 28.34 g of a phenyl hydroxysilyl resin are dissolved in 48.95 g of toluene. Then 23.46 g of acryloxypropyltrimethoxysilane and 1 .41 g of tetrabutyl orthotitanate are added. The reaction mixture is kept at room temperature under vigorous stirring for around 18 hours. After removal of the solvent and formed methanol at reduced pressure at the rotary evaporator, 44.43 g of a whitish-ivory, viscous liquid have been isolated (91.45 wt% of theory).

2⁹Si NMR recorded 1 .2% of remaining non reacted acryloxypropyltrimethoxysilane.

Example 1

[0101] Rubber goods were prepared according to the procedure described below for example 1 and comparative examples C1 and C2, using the ingredients described below.

The amounts expressed in parts per hundred parts of rubber (phr) are described in table 1.

• NR SMR 10, CV60 - Natural rubber Standard Malaysian Rubber, purity grade 10, Constant viscosity (CV) 60 m.u. (Mooney unit)

• Silica - Zeosil^® 1 165MP from Rhodia

• Resin 1 - T(Ph) resin known as 217 Flake resin by Dow Corning

• Resin 2 - T(Acryloxypropyltrimethoxysilane)T(Ph) resin

• Silane - acryloxypropyltriethoxysilane

· ACST - Stearic Acid 29

• ZnO - Zinc Oxide

• 6PPD - N-1 ,3- dimethylbutyl-N-phenyl-para-phenylenediamine ("Santoflex^® 6-PPD")

• S - Elemental sulfur

• CBS - N-cyclohexyl-2-benzothiazyl sulfenamide ("Santocure^® CBS" from Flexsys)

• DPG - Diphenylgunaidine from Flexsys

• N234 - Conventional carbon black according to ASTM D1765

[0102] The comparative example C1 is a standard natural rubber formulation for tyre treads using carbon black filler.

Table 1

[0103] During a first non-productive phase, the reaction of the natural rubber, the silica and silane in presence of peroxides was carried out using thermomechanical kneading in a Banbury mixer. The procedure was as shown in Table 2, which indicates the time of addition of various ingredients. The temperature at the end of mixing was measured inside the rubber after dumping it from the mixer. 30

Table 2

[0104] The maximum temperature reached in the mixer 165°C for all rubber compound. Rubber was then passed through the mil until a smooth sheet was obtained.

[0105] During a second non-productive phase stearic acid, Zinc Oxide and 6PPD were added as shown in table 3: Table 3

[0106] The natural rubber composition thus produced was milled on a two-roll mill at a temperature of about 70°C during which milling the curing agents were added (productive phase). The mixing procedure for the productive phase is shown in Table 4.

31

Table 4

[0107] The modified rubber sheet produced was tested as follows. The results of the tests are shown in Table 5 below.

[0108] The rheometry measurements were performed at 160° C using an oscillating chamber rheometer (i.e., Advanced Plastic Analyzer) in accordance with Standard ISO 3417:1991 (F). The change in rheometric torque over time describes the course of stiffening of the composition as a result of the vulcanization reaction. The measurements are processed in accordance with Standard ISO 3417:1991 (F). Minimum and maximum torque values, measured in deciNewtonmeter (dNm) are respectively denoted ML and MH time at a% cure (for example 5%) is the time necessary to achieve conversion of a% (for example 5%) of the difference between the minimum and maximum torque values. The difference, denoted MH-ML, between minimum and maximum torque values is also measured. In the same conditions the scorching time for the rubber compositions at 160°C is determined as being the time in minutes necessary to obtain an increase in the torque of 2 units, above the minimum value of the torque (Time@2dNm scorch S'). 32

[0109] The tensile tests were performed in accordance with ISO Standard IS037: 1994(F) using tensile specimen ISO 37 - type 2. The nominal stress (or apparent stresses, in MPa) at 10% elongation (M10), 100% elongation (M 100) and elongation (M250 or M300) are measured at 10%, 100% and 250% or 300% of elongation. Breaking stresses (in MPa) are also measured. Elongation at break (in %) was measured according to Standard ISO 37. High values of Elongation at break are preferred. Preferably the Elongation at break is at least 300%. All these tensile measurements are performed under normal conditions of temperature and relative humidity in accordance with ISO Standard ISO 471 . The ratio of M300 to M100 correlates with tread wear resistance of a tyre made from the rubber composition, with an increase in M300/M100 ratio indicating potential better tread wear resistance.

[0110] The dynamic properties were measured on a viscoanalyser (Metravib VA4000), in accordance with ASTM Standard D5992-96.

Strain sweep: The response of a sample of vulcanized composition (thickness of 2.5 mm and a cross-section of 40 mm²), subjected to an alternating single sinusoidal shearing stress, at a frequency of 10 Hz, under a controlled temperature of 55° C is recorded. Scanning is performed at amplitude of deformation of 0.1 to 50% the maximum observed value of the loss factor tan d is recorded, the value being denoted tan δ 6%. The tan δ 6% value is well correlated to the rolling resistance of the tire, the lower the tan δ 6% the lower the rolling resistance is, the better the tire performance will be. GO is the elastic modulus measured at very low strain, when the behaviour is linear with the stress. G'_max is the elastic modulus at 50% strain. Dynamical properties have been recorded after a first strain sweep (GO) from 0.1 to 50%, then the second strain sweep from 50% to 0.1 % has been also recorded. The difference between the modulus at first strain sweep and the modulus after the return to low strain (GO return) is denoted AGO which is well correlated to the handling stability of the tire under stress. The difference between GO return and G'_max after the second strain sweep is denoted AG' return. The tan δ 6%, second strain sweep value corresponds to the maximum of the loss factor tan (δ) during the second strain sweep. A reduction in both tan δ 6% and tan δ 6%, second strain sweep is well correlated to a decrease in the rolling resistance of a tire manufactured from the rubber composition. 33

Temperature sweep: The response of a sample of vulcanized composition

(thickness of 2.5 mm, height of 14 mm and length of 4.0 mm), subjected to an alternating single sinusoidal shearing stress, at a frequency of 10 Hz, under a controlled displacement of 1 .25 micron. The sample is placed at room temperature and cooled down to -100°C with a rate of 5°C/min. The temperature is then stabilised at -100°C for 20 minutes to allow the sample to be at an equilibrium temperature state. The temperature is then increased up to 100°C at a rate of 5°C/min. The loss factor and the stiffness, giving the modulus and the tan (δ). The tan δ max and/or the value at 0°C (tan δ ₀°c) is related to the wet skid performances. An increase in the tan δ _max and in the tan (δ) value at 0°C (tan δ ₀°c) is indicative of improved wet skid performance. The Shore A hardness was measured according to ASTM D2240-02b.

34

Table 5

Run C1 1 C2

Mooney Viscosity @100°C

Mmax (m.u.) 66 63 65

ML1 +4 (m.u.) 48 43 44

Rheometer @160°C

ML (dNm) 1 ,7 1 ,2 1 ,2

MH (dNm) 15,4 14,4 14,7

Time@5% cure S' (min) 2,9 4,5 4,4

Time@95% cure S' (min) 6,4 7,4 7,4

Time@2 dNm scorch S' (min) 3,6 5,3 5,2

MH-ML (dNm) 13,7 13,2 13,5

Dynamic properties, strain sweep @55°C, simple shear

G' o (Pa) 4,53 2,52 3,41

G'o return (Pa) 3,69 2,05 2,71

AGO (Pa) 0,836 0,474 0,698

G'_max (Pa) 1 ,183 1 ,209 1 ,336

AG' (Pa) 3,345 0,839 2,075

Tan δ6% 0,161 0,081 0,087

Tan δ 6%, second strain sweep 0,164 0,075 0,088

Dynamic properties, T°C sweep

Tan δ max 0,927 1 ,184 1 ,032

Physical properties

M10 (MPa) 0,6 0,6 0,6

M100 (MPa) 3,4 3,7 3,6

M250 (Mpa) 13,6 15,8 15,2

M300 (MPa) 17,7 20,4 19,6

M250/M100 4,0 4,3 4,2

M300/M100 5,2 5,5 5,4

Tensile break (MPa) 30,9 29,9 29,6

Elong max (%) 473 413 427

Shore A 59 58 58

Tear Strength (N/mm) 144,6 91 105,6 35

[0112] Shore A and ML1 +4 value for example 1 were in a good range as required by the application. [0113] The strain sweep results for example 1 showed a reduction in Tan δ 6%, second strain sweep compared to the conventional carbon black formulation in comparative examples C1 and C2. This is associated with a decrease of the rolling resistance of a tyre made from the corresponding rubber composition. [0114] Example 1 showed increase modulus M300 and reinforcing index M300/M100 than comparative example C1 linked to a possible better tread wear performance

[0115] The results of tan 8_max value during the temperature sweep for example 1 was increased compared to comparative example C1 and C2 indicating improved wet skid performance of tyres made from the rubber compositions of example 1.

Claims

36 CLAIMS

1 . A modified diene elastomer composition comprising a thermoplastic diene

elastomer and a polysiloxane, characterized in that the polysiloxane is a branched silicone resin containing at least one group of the formula -X-CH=CH-R" (I) or -X- C≡C-R" (II), in which X represents a divalent organic linkage having an electron withdrawing effect with respect to the -CH=CH- or -C≡C- bond and/or containing an aromatic ring or a further olefinic double bond or acetylenic unsaturation, the aromatic ring or the further olefinic double bond or acetylenic unsaturation being conjugated with the olefinic unsaturation of -X-CH=CH-R" or with the acetylenic unsaturation of -X-C≡C-R", and X being bonded to the branched silicone resin by a C-Si bond, and R" represents hydrogen or a group having an electron withdrawing effect or any other activation effect with respect to the -CH=CH- or -C≡C- bond.

2. A modified diene elastomer composition according to Claim 1 , characterized in that at least 50 mole % of the siloxane units present in the branched silicone resin are T units as herein defined.

3. A modified diene elastomer composition according to Claim 1 or Claim 2,

characterized in that 0.1 to 100 mole % of the siloxane T units present in the branched silicone resin are of the formula R"-CH=CH-X-Si03/2.

4. A modified diene elastomer composition according to Claim 1 , characterized in that at least 50 mole % of the siloxane units present in the branched silicone resin are selected from Q units and M units as herein defined.

5. A modified diene elastomer composition according to Claim 4, characterized in that the unsaturated groups of the formula -X-CH=CH-R" are present as T units of the formula R"-CH=CH-X-Si03/2.

6. A modified diene elastomer composition according to any of Claims 1 to 5,

characterized in that the branched silicone resin contains hydrolysable Si-OR groups, in which R represents an alkyl group having 1 to 4 carbon atoms. 37

7. A modified diene elastomer composition according to any of Claims 1 to 6

characterised in that the branched silicone resin containing at least one group of the formula -X-CH=CH-R" (I) or -X-C≡C-R"(II) is present at 1 to 30% by weight of the total composition.

8. A modified diene elastomer composition according to any of Claims 1 to 7

characterised in that X represents a divalent organic linkage having an electron withdrawing effect with respect to the -CH=CH- or -C≡C- bond.

9. A modified diene elastomer composition according to Claim 8 characterised in that the group of the formula -X-CH=CH-R" (I) is an acryloxyalkyl group or an acrylthioalkyl group.

10. A modified diene elastomer composition according to any of Claims 1 to 7

characterised in that the group of the formula -X-CH=CH-R" (I) or -X-C≡C-R" (II) contains an aromatic ring or a further olefinic double bond or acetylenic

unsaturation, the aromatic ring or the further olefinic double bond or acetylenic unsaturation being conjugated with the olefinic -C=C- or acetylenic -C≡C- unsaturation of the group -X-CH=CH-R" (I) or -X-C≡C-R" (II).

1 1 . A modified diene elastomer composition according to any preceding Claim

characterised in that the group -X-CH=CH-R" (I) or -X-C≡C-R" (II) has the formula CH2=CH-C6H4-A- (III) or CH≡C-C6H4-A- (IV), wherein A represents a direct bond or a divalent organic group having 1 to 12 carbon atoms optionally containing a divalent heteroatom linking group chosen from -0-, -S- and -NH-.

12. A modified diene elastomer composition according to any one of claims 1 to 10 characterised in that the group -X-CH=CH-R" (I) has the formula R2-CH=CH- CH=CH-X-, where R2 represents hydrogen or a hydrocarbyl group having 1 to 12 carbon atoms.

13. A modified diene elastomer composition according to Claim 12 characterised in that the group -X-CH=CH-R" (I) is a sorbyloxyalkyl group. 38

14. A modified diene elastomer composition according to any of Claims 1 to 13

containing an organic peroxide compound capable of generating free radical sites in the diene elastomer, the organic peroxide being present at 0.01 to 2% by weight of the total composition.

15. A modified diene elastomer composition in accordance with any preceding claim characterised in that the composition contains a suitable curing system selected from sulphur, an organic peroxide or a sulphur compound.

16. A modified diene elastomer composition in accordance with any one of claims 1 to 14 characterised in that when the composition is curable by moisture, said composition additionally comprises a hydrolysis/condensation catalyst.

17. A modified diene elastomer composition in accordance with any preceding claim characterised in that the composition additionally contains one or more filler(s).

18. A process in accordance with claim 17 characterised in that the filler is silica.

19. A process for grafting silicone onto a diene elastomer, comprising reacting the

diene elastomer with a silicon compound containing an unsaturated group in the presence of means capable of generating free radical sites in the diene elastomer, characterized in that the silicon compound is a branched silicone resin containing at least one group of the formula -X-CH=CH-R" (I) or -X-C≡C-R" (II), in which X represents a divalent organic linkage having an electron withdrawing effect with respect to the -CH=CH- or -C≡C- bond and/or containing an aromatic ring or a further olefinic double bond or acetylenic unsaturation, the aromatic ring or the further olefinic double bond or acetylenic unsaturation being conjugated with the olefinic unsaturation of -X-CH=CH-R" or with the acetylenic unsaturation of

-X-C≡C-R" and X being bonded to the branched silicone resin by a C-Si bond and R" represents hydrogen or a group having an electron withdrawing effect or any other activation effect with respect to the -CH=CH- or -C≡C- bond.

20. A process in accordance with claim 19 characterised in that the group of the

formula -X-CH=CH-R" (I) is an acryloxyalkyl group or an acrylthioalkyl group. 39

21 . A process according to claim 19 or 20 characterised in that the diene elastomer is natural rubber or alternatively a homopolymer or copolymer of a diene monomer.

22. A process according to any one of claims 19 to 21 characterised in that the silicone resin and the diene elastomer are reacted together at a temperature in the range of 90°C to 200°C.

23. A process for the production of a rubber article from the composition of any one of claims 1 to 19 characterised in that the elastomer composition is shaped and cured.

24. Use of a branched silicone resin containing at least one group of the formula

-X-CH=CH-R" (I) or -X-C≡C-R" (II), in which X represents a divalent organic linkage having an electron withdrawing effect with respect to the -CH=CH- or -C≡C- bond, and bonded to the branched silicone resin by a C-Si bond, and R" represents hydrogen or a group having an electron withdrawing effect or any other activation effect with respect to the -CH=CH- or -C≡C- bond, in grafting silicone moieties to a diene elastomer, to give enhanced grafting compared to an unsaturated silicone not containing a -X-CH=CH-R" or -X-C≡C-R" group.

25. Use of a branched silicone resin containing at least one group of the formula

-X-CH=CH-R" (I) or -X-C≡C-R" (II), in which X represents a divalent organic linkage containing an aromatic ring or a further olefinic double bond or acetylenic unsaturation, the aromatic ring or the further olefinic double bond or acetylenic unsaturation being conjugated with the olefinic unsaturation of -X-CH=CH-R" or with the acetylenic unsaturation of -X-C≡C-R" and X being bonded to the branched silicone resin by a C-Si bond, and R" represents hydrogen or a group having an electron withdrawing effect or any other activation effect with respect to the

-CH=CH- or -C≡C- bond, in grafting silicone moieties to a diene elastomer with less degradation of the polymer compared to grafting with an unsaturated silicon compound not containing an aromatic ring.

26. Use of the curable rubber composition produced by the process of any of Claims 19 to 23 in the production of tyres or any parts thereof or engineered rubber goods, belts, or hoses.