WO2008045395A2

WO2008045395A2 - Process for making organopolysiloxane compositions

Info

Publication number: WO2008045395A2
Application number: PCT/US2007/021507
Authority: WO
Inventors: Tommy Detemmerman; Robert Andrew Drake; Jary David Jensen; Jean Willieme
Original assignee: Dow Corning Corporation
Priority date: 2006-10-10
Filing date: 2007-10-09
Publication date: 2008-04-17
Also published as: WO2008045395A3

Abstract

A method for the production of an extended and/or plasticised organopolysiloxane composition comprising the steps:- Mixing a polysiloxane containing polymer and/or precursors thereof during or subsequent to polymerisation of the polysiloxane containing polymer with an extender and/or plasticiser during or subsequent to polymerisation of the polysiloxane containing polymer and/or Filler and introducing residual extender and/or plasticiser and/or filler together with a first cure package for curing the polymer subsequent to polymerisation characterised in that the extender and/or plasticiser is chemically functionalised so as to substantially not participate in any chemical reaction(s) with the polymer and/or its precursors but is independently chemically curable, optionally in combination with a second cure system, prior to, simultaneously with or subsequent to cure of the polymer.

Description

PROCESS FOR MAKING ORGANOPOLYSILOXANE COMPOSITIONS

JOOOl] This invention is concerned with the use of plasticisers and extenders in silicone rubber based compositions.

[0002] Organosiloxane compositions which cure to elastomeric solids are well known and such compositions can be produced to cure at either room temperature in the presence of moisture or with application of heat. Typically those compositions which cure at room temperature in the presence of moisture are obtained by mixing a polydiorganosiloxane based polymer having condensable terminal groups, with a suitable silane (or siloxane) based cross-linking agent in the presence of one or more fillers and a curing catalyst. These compositions are typically either prepared in the form of one-part compositions curable upon exposure to atmospheric moisture at room temperature or two part compositions curable upon mixing at room temperature and pressure.

[0003] Such condensation cured compositions are commonly used as sealants in the construction and DIY markets. In use as a sealant, it is important that the composition has a blend of properties which render it capable of being applied as a paste to a joint between substrate surfaces where it can be worked, prior to curing, to provide a smooth surfaced mass which will remain in its allotted position until it has cured into an elastomeric body adherent to the adjacent substrate surfaces. Typically sealant compositions are designed to cure quickly enough to provide a sound seal within several hours but at a speed enabling the applied material to be tooled into a desired configuration shortly after application. The resulting cured sealant is generally formulated to have a strength and elasticity appropriate for the particular joint concerned.

[0004] In view of the nature and use of many sealants as merely a means of filling gaps between e.g. a wall and a bath or sink or the like, the shrinkage of such sealant compositions during the curing process is typically not viewed as detrimental to the function of the resulting cured product and thus the introduction of additives which are unreactive with the silicone composition and which at least to an extent may evaporate during the curing of the sealant has become common practice in the sealants industry.

[0005] These additives are said to "extend" and/or "plasticise" the silicone sealant composition by blending the or each extending compound (henceforth referred to as an "extender") and/or plasticising compound (henceforth referred to as a "plasticiser") with a pre-prepared polymer and other ingredients of the composition.

[0006] An extender (sometimes also referred to as a process aid or secondary plasticiser) is used to dilute the sealant composition and basically make the sealant more economically competitive without substantially negatively affecting the properties of the sealant formulation. The introduction of one or more extenders into a silicone sealant composition not only reduces the overall cost of the product but can also affect the properties of resulting uncured and/or cured silicone sealants. The addition of extenders can, to a degree, positively effect the rheology, adhesion tooling properties and clarity of a silicone sealant and can cause an increase in elongation at break and a reduction in hardness of the cured product both of which can significantly enhance the lifetime of the cured sealant provided the extender is not lost from the cured sealant by, for example, evaporation or exudation.

[0007] A plasticiser (otherwise referred to as a primary plasticiser) is added to a sealant composition to provide properties within the final polymer based product to increase the flexibility and toughness of the final sealant composition. This is generally achieved by reduction of the glass transition temperature (T_g) of the cured polymer composition thereby generally, in the case of sealants for example, enhancing the elasticity of the sealant which in turn enables movement capabilities in a joint formed by a silicone sealant with a significant decrease in the likelihood of fracture of the bond formed between sealant and substrate when a sealant is applied thereto and cured. Plasticisers are typically used to also reduce the modulus of the sealant formulation. Plasticisers may reduce the overall unit cost of a sealant but that is not their main intended use and indeed some plasticisers are expensive and could increase the unit cost of a sealant formulation in which they are used. Plasticisers tend to be generally less volatile than extenders and are typically introduced into the polymer composition in the form of liquids or low melting point solids (which become miscible liquids during processing.

[0008] Typically, for silicone based condensation cure, compositions, which are generally used in sealant compositions, plasticisers are organopolysiloxanes which are unreactive with the siloxane polymer of the composition, such as polydimethylsiloxane having terminal triorganosiloxy groups wherein the organic substituents are, for example, methyl, vinyl or phenyl or combinations of these groups. Such polydimethylsiloxanes normally have a viscosity of from about 5 to about 100,000 mPa.s at 25⁰C. Compatible organic plasticisers may additionally be used, examples include dialkyl phthalates wherein the alkyl group may be linear and/or branched and contains from six to 20 carbon atoms such as dioctyl, dihexyl, dinonyl, didecyl, diallanyl and other phthalates; adipate, azelate, oleate and sebacate esters, polyols such as ethylene glycol and its derivatives, organic phosphates such as tricresyl phosphate and/or triphenyl phosphates.

[0009) A wide variety of organic compounds and compositions have been proposed for use as extenders for reducing the cost of the silicone sealant compositions. Whilst polyalkylbenzenes such as heavy alkylates (alkylated aromatic materials remaining after distillation of oil in a refinery) have been proposed as extender materials for silicone sealant compositions in recent years the industry has increasingly used mineral oil based (typically petroleum based) paraffinic hydrocarbons as extenders as described in GB 2424898 which was published after the priority date of this application and the following publications: EP0885921 describes the use of mineral oil based hydrocarbon mixtures containing 60 to 80% paraffinic and 20 to 40% naphthenic and a maximum of 1% aromatic carbon atoms. EP 0807667 appears to describe a similar extender comprising wholly or partially of a paraffin oil comprising 36-40 % cyclic paraffin oils and 58 to 64% non-cyclic paraffin oils. WO99/65979 describes an oil resistant sealant composition comprising a plasticiser which may include paraffinic or naphthenic oils and mixtures thereof amongst other plasticisers. EP1481038 describes the use of a hydrocarbon fluid containing more than 60 wt.% naphthenics, at least 20 wt.% polycyclic naphthenics and an ASTM D-86 boiling point of from 235⁰C to 400⁰C. EP 1252252 describes the use of an extender comprising a hydrocarbon fluid having greater than 40 parts by weight cyclic paraffinic hydrocarbons and less than 60 parts by weight monocyclic paraffinic hydrocarbons based on 100 parts by weight of hydrocarbons. EPl 368426 describes a sealant composition for use with alkyd paints containing a liquid paraffinic hydrocarbon "extender" which preferably contains greater than 40% by weight of cyclic paraffins.

[0010] It will be appreciated by the reader that there is a degree of overlap between plasticisers and extenders used for silicone polymer based compositions. This is at least partially due to the relative decrease in compatibility of the organic compounds concerned with the silicone compositions.

[0011] Silicone rubber compositions which can but generally do not involve curing via a condensation reaction pathway are used for a wide variety of applications including automotive, aviation and aerospace products, babycare products such as teats for bottles, insulators for power and utilities applications, extruded profiles, gaskets and seals for e.g. air water, fuel and oil applications e.g. hoses, keypads, in medical and office equipment such as protective equipment and masks, rollers for e.g. photocopiers, sponges, and wire and cable coating applications. For such applications it is imperative that the shrinkage during curing of the composition is kept to a minimum to avoid problems with their end use i.e. in the case of cable coating one can't afford for the loss of the electrical integrity of the casing around the wire. Hence, for such applications industry practise teaches that extenders and/or plasticisers, particularly organic extenders and/or organic plasticisers are unusable because of the certainty that any significant shrinkage is detrimental to the applications typically used for the resulting cured products. One result of the above is that the cost of silicone rubber is significantly greater than organic rubber and/or natural rubber products. This cost differential results in the fact that whilst silicone rubbers provide the user with significant technical benefits, the cost of such products is considered prohibitive and as such industry prefers to utilise cheaper options because the lower price for organic and natural rubbers outweigh the technical benefits.

[0012 J One of the biggest problem relating to the use of organic plasticisers and or extenders in silicone compositions is compatibility. Whilst the volatile nature of many of the unreactive plasticisers and extenders used results in shrinkage during the curing process, the actual chemical nature of the sealant composition and organic plasticiser and/or organic extender can result in significant compatibility problems both during pre-cure storage and post-cure because the plasticisers and extenders are not part of the cure reaction mechanism . Typically plasticisers are more compatible with polymer compositions than extenders and tend to be significantly less volatile and as such are significantly more likely to remain at high levels within the polymer matrix after curing.

[0013] Extenders need to be both sufficiently compatible with the remainder of the composition and as non-volatile as possible at the temperature at which the resulting cured elastomeric solid is to be maintained (e.g. room temperature).

[0014] Compatibility of organic extenders and/or plasticisers with the other ingredients in an organopolysiloxane based polymer composition, is a significantly greater problem than with respect to organic based polymers, silicone polymers into which the extenders and/or plasticisers are introduced tend to be highly viscous polymers, and the chemical nature of the polymer being organopolysiloxane based as opposed to organic based can have significant effects on compatibility. The level of compatibility effectively determines the amount of extender and/or plasticiser which can be introduced into a polymer composition. Typically this results in the introduction of significantly lower amounts of, in particular, extenders into the composition than may be desired because the extender will not physically mix into the polymer composition sufficiently well, particularly with the pre-formed polymer which is usually the largest component, other than the filler, in the composition. [0015] EPl 127920 describes a curable silicone composition comprising a blend of the following pre-prepared polymers:- a mixture of an organopolysiloxane having at least 2 alkoxy groups per molecule but no alkenyl groups with an organopolysiloxane having at least 2 alkenyl groups per molecule but no alkoxy groups or Ab an organopolysiloxane having at least 2 alkoxy groups per molecule and at least 2 alkenyl groups per molecule with B an organopolysiloxane which has at least two Si-H bonds per molecule, a condensation catalyst, a platinum type catalyst and an air oxidation-curable unsaturated compound.

[0016] US2004/0209972 describes a dual-cure silicone compositions which exhibits both UV- and moisture-initiated curing mechanisms having a first polysiloxane with terminal mercapto and alkoxy end-groups and a second polysiloxane with terminal alkenyl and alkoxy end-groups. These blends are cured with the addition of a photoinitiator and a condensation catalyst. Other additives which may be added include plasticisers such as alkylbenzene derivatives or trimethylsilyl terminated polyorganosiloxanes. WO 02/058641 describes a two part organopolysiloxane composition comprising a pre-prepared organopolysiloxane having at least 2 alkenyl group per molecule an organohydrogensiloxane and a hydrosilylation catalyst which additionally comprises a pre-prepared polymer comprising Si-OR groups and a condensation catalyst.

[0017] The applicants have now identified a means of avoiding many of the post- cure compatibility and shrinkage problems currently connected with the use of extended and/or plasticised organopolysiloxane compositions thereby enabling the use of such extenders and plasticisers not only in silicone sealant formulations but also in silicone rubber formulations.

[0018] A method for the production of an extended and/or plasticised organopolysiloxane composition comprising the steps:-

Mixing a polysiloxane containing polymer and/or precursors thereof with an extender and/or plasticiser prior to and/or during polymerisation of the polysiloxane containing polymer and optionally

Filler prior to and/or during polymerisation of the polysiloxane containing polymer and introducing residual extender and/or plasticiser and/or filler together with a first cure package for curing the polymer subsequent to polymerisation characterised in that the extender and/or plasticiser is chemically functionalised so as to substantially not participate in any chemical reaction(s) with the polymer and/or its precursors but is independently chemically curable, optionally in combination with a second cure system, prior to, simultaneously with or subsequent to cure of the polymer.

[0019) Hence as a consequence of the above the filler and/or extender/plasticiser may be mixed with the polymer and/or its precursors during the polymer polymerisation process, by making a pre-blend of polymer and extender/plasticiser before introducing the other ingredients of the composition or merely as a ingredient in the composition. Preferably the plasticiser/extender is always introduced into the mixture before or simultaneously with the filler, more preferably before the filler. Most preferably the plasticiser/extender is introduced during the polymerisation of the polymer.

[0020] A method for the production of a cured organopolysiloxane based elastomer comprising the steps of

(i) Preparing an extended and/or plasticised polysiloxane containing polymer by intermixing the polymer and/or precursors thereof with an extender and/or plasticiser and optionally filler, prior to and/or during polymerisation of the polysiloxane containing polymer

(ii) Mixing the resulting extended and/or plasticised polysiloxane containing polymer product with: optionally residual filler and (extender and/or plasticiser) a suitable cure system to form a curable composition; and optionally filler; and

(iii) curing the resulting polymer composition to form a cured elastomer having a cross-linked matrix; characterised in that the extender and/or plasticiser is chemically functionalised so as to substantially not participate in any chemical reaction(s) with the polymer and/or its precursors during steps (i) (ii) or (iii) but is independently chemically cured during step (iii), optionally in combination with a second cure system, prior to, simultaneously with or subsequent to polymer composition cure.

[0021] A method for the production of an extended and/or plasticised organopolysiloxane composition comprising the steps:-

(ii) Mixing the resulting polysiloxane containing polymer product with:

Optional residual filler and (extender and/or plasticiser), a suitable first cure system and optionally filler to form a curable composition; characterised in that the extender and/or plasticiser is chemically functionalised so as to substantially not participate in any chemical reaction(s) with the polymer and/or its precursors during step (i) or step (ii) but is independently chemically curable, optionally in combination with a second cure system, prior to, simultaneously with or subsequent to cure of the curable composition. [0022] The concept of "comprising" where used herein is used in its widest sense to mean and to encompass the notions of "include" and "consist of. All viscosity measurements referred to herein were measured at 25⁰C unless otherwise indicated.

[0023] Preferably each extender and or plasticiser is miscible or at least substantially miscible with the monomeric/oligomeric starting materials with which they are initially mixed, and more particularly with both intermediate polymerisation reaction products and the final polymerisation product. Extenders and/or plasticisers which are "substantially miscible" are intended to include extenders and/or plasticisers which are completely or largely miscible with the monomer(s) and/or the reaction mixture during polymerisation and hence may include low melting point solids which become miscible liquids in a reaction mixture during the polymerisation process.

[0024] Preferably, the extended and/or plasticised polysiloxane containing polymer is prepared by polymerising siloxane containing monomers and/or oligomers in the presence of the extender and/or plasticiser, a suitable polymerisation catalyst and optionally an end-blocking agent and/or filler; and

Where required quenching the polymerisation process;

[0025] For the sake of clarification, the term "oligomer" and derivatives thereof are used herein to mean monomer(s) or oligomer(s) or polymer(s) utilised as a starting material involved in a polymerisation process.

[0026] Any appropriate polymerisation process may be utilised to generate the polymer in (i) in the presence of the extender and/or plasticiser provided that the polymer, polymer intermediates and monomers and/or oligomers substantially do not chemically react and preferably do not react with the extender(s) and/or plasticiser(s), whilst the extender(s) and/or plasticiser(s) are independently curable as hereinbefore described. [0027) Preferred polymerisation processes where the polymer is prepared in the presence of the extender and/or plasticiser, which may be utilised in accordance with this invention include, for example, polycondensation and polyaddition polymerisation routes:-

POLYCONDENSATION ROUTE

[0028] One preferred polymerisation process is polycondensation using extenders and/or plasticisers which do not become chemically involved in the polymerisation reaction.

[0029) Polycondensation (otherwise known as condensation polymerisation) is the polymerisation of monomers and/or oligomers with the elimination of low molecular weight by-product(s) such as water, ammonia or methanol etc.). In this embodiment preferably each monomer/oligomer comprise at least two condensable groups preferably terminal groups, that will, in appropriate conditions, undergo a condensation reaction. Preferably the condensable groups in the present invention are hydroxyl containing terminal groups or hydrolysable end groups (e.g. alkoxy groups).

[0030] An organosiloxane containing polymer is intended to mean a polymer comprising multiple organopolysiloxane groups per molecule and is intended to include a polymer substantially containing only organopolysiloxane groups in the polymer chain or polymers where the backbone contains both organopolysiloxane groups and e.g. organic polymeric groups in chain.

[0031] Polycondensation type polymerisation reactions are most generally linked to the interaction of compounds having hydroxyl and/or hydrolysable end groups such as alkoxy groups, which can interact with the release of e.g. water or methanol or the like. [0032] A selection of condensation reactions which may be alternatively utilised for the polymerisation process in accordance with this embodiment of the invention between monomers and/or oligomers in accordance with the present invention include:-

1) the condensation of organohalosilyl groups with an organoalkoxysilyl groups

2) the condensation of organohalosilyl groups with organoacyloxysilyl groups

3) the condensation of organohalosilyl groups with organosilanols

4) the condensation of organohalosilyl groups with silanolates

5) the condensation of organo-hydrosilyl groups with organosilanol groups 6) the condensation of organoalkoxysilyl groups with organoacyloxysilyl groups

7) the condensation of organoalkoxysilyl groups with organosilanol groups

8) the condensation of organoaminosilyl groups with organosilanols

9) the condensation of organoacyloxysilyl groups silanolate groups 10) the condensation of organoacyloxysilyl groups with organosilanols

1 1) the condensation of organooximosilyl groups with organosilanol groups

12) the condensation of organoenoxysilyl groups with organosilanols

13) The condensation of a siloxane compound comprising one or more hydrosilane functional groups with a siloxane compounds containing at least one alkoxysilane functional group, generating hydrocarbon by-products.

[0033] Any of the above condensation type reactions may be used for the block co- polymerisation of monomer(s)/oligomer(s) and as such may be the basis for the polymerisation process in accordance with the present invention.

[0034] Preferably the condensable end groups are hydroxyl end groups or hydrolysable end groups, most preferably alkoxy groups.

[0035] Hence, one preferred method for the polymerisation process is the polymerisation of straight chain and/or branched organopolysiloxanes with condensable end groups comprising units of formula (Ia)

wherein each R' may be the same or different and denotes a hydrocarbon group having from 1 to 18 carbon atoms, a substituted hydrocarbon group having from 1 to 18 carbon atoms or a hydrocarbonoxy group having up to 18 carbon atoms and a has, on average, a value of from 1 to 3, preferably 1.8 to 2.2.

[0036] For the purpose of this application in the case of a hydrocarbon group "Substituted" means one or more hydrogen atoms in a hydrocarbon group has been replaced with another substituent. Examples of such substituents include, but are not limited to, halogen atoms such as chlorine, fluorine, bromine, and iodine; halogen atom containing groups such as chloromethyl, perfluorobutyl, trifluoroethyl, and nonafluorohexyl; oxygen atoms; oxygen atom containing groups such as (meth)acrylic and carboxyl; nitrogen atoms; nitrogen atom containing groups such as amines, amino-functional groups, amido-functional groups, and cyano-functional groups; sulphur atoms; and sulphur atom containing groups such as mercapto groups.

[0037] The hydrocarbon groups of R' may be of any suitable type but are preferably alkyl groups and optionally to an extent unsaturated groups such as alkenyl groups and alkynyl groups. The presence of unsaturated groups in the side chains means that the condensable groups used in the polymerisation process do not require end-capping before they are mixed into the composition to be cured because the unsaturated groups situated along the polymer chain may be utilised in a hydrosilylation cure or peroxide cure process for curing the polymer composition subsequently prepared. Particularly preferred examples of groups R' include methyl, ethyl, propyl, butyl, vinyl, hexenyl, cyclohexyl, phenyl, tolyl group, a propyl group substituted with chlorine or fluorine such as 3,3,3-trifluoropropyl, chlorophenyl, beta- (perfluorobutyl)ethyl or chlorocyclohexyl group. Preferably, at least some and more preferably substantially all of the groups R are methyl. When no unsaturated groups, particularly alkenyl and/or alkynyl groups are present per molecule of polymer, some R' groups may be hydrogen groups. [0038] Preferably the polydiorganosiloxane monomer/oligomer starting materials are polydialkylsiloxanes, most preferably polydimethylsiloxanes. They are preferably substantially linear materials, which have siloxane end groups of the formula R"₃SiO|/₂, wherein each R" is the same or different and is R' or a condensable group. Any suitable combination of condensable end groups may be used for the polymerisation process of the present invention (i.e. the condensable groups chosen must be able to undergo a condensation reaction together in order to polymerise). Preferably at least one R" group per molecule is a hydroxyl or hydrolysable group. Typically the condensable groups used as monomer/oligomer end-groups are preferably silicon-bonded hydroxyl groups or hydrolysable groups such as alkoxy groups, which may form silanol groups in situ.or the like but may be any groups which will participate in a polycondensation of the monomer/oligomer in the presence of the diluent in accordance with the present invention. In a small amount (<20%) of the R"₃ SiCv₂ groups, each R" group may be an alkyl group.

[0039] Preferably the starting materials have a viscosity of between lOmPa.s and 50000mPa.s at 25⁰C. Some of the starting materials may comprise non-hydrolysable end-groups but this is not desired. It will also be appreciated that where required organic monomers and/or oligomers having appropriate condensable end groups so as to be polymerisable with said organopolysiloxane monomers and/or oligomers may be introduced in order to form ABA or AB_n type block copolymers.

[0040] In the case of polydiorganosiloxane co-polymers the polymeric chain may comprise blocks made from chains of units depicted in figure (Ia) where a is 2 and the two R' groups are:- both alkyl groups (preferably both methyl or ethyl), or alkyl and phenyl groups, or alkyl and fluoropropyl, or alkyl and vinyl or alkyl and hydrogen groups.

Typically at least one block will comprise siloxane units in which both R' groups are alkyl groups. [0041) In accordance with the present invention organic monomers and/or oligomers may be utilised with the intention of providing block copolymers with the siloxane containing monomers and/or oligomers. Preferably the organic monomers and/or oligomers comprise two or more condensable groups which are condensable with the condensable groups of the siloxane monomers and/or oligomers. Examples of organic monomers which may be used, providing the have a suitable number of condensable groups attached thereto, in accordance with the present invention include, for example polystyrene and/or substituted polystyrenes such as poly(α-methylstyrene), poly(vinylmethylstyrene), poly(p-trimethylsilylstyrene) and poly(p-trimethylsilyl-α- methylstyrene). Other organic components may include acetylene terminated oligophenylenes, vinylbenzyl terminated aromatic polysulphones oligomers, aromatic polyesters and aromatic polyester based monomers.

[00421 However perhaps the most preferred organic based oligomers are polyoxyalkylene based oligomers having two or more condensable groups per molecule. Such polyoxyalkylene compounds preferably comprise a linear predominantly oxyalkylene polymer comprised of recurring oxyalkylene units illustrated by the average formula (-C_bH_2b-O-)_c wherein b is an integer from 2 to 4 inclusive and c is an integer of at least four. The average molecular weight of each polyoxyalkylene polymer block may range from about 50 to about 10,000. Moreover, the oxyalkylene units are not necessarily identical throughout the polyoxyalkylene monomer, but can differ from unit to unit. A polyoxyalkylene block, for example, can be comprised of oxyethylene units, (-C₂H₄-O-); oxypropylene units (-C₃H₆-O-); or oxybutylene units (-C₄H₈-O-); or mixtures thereof.

[0043] Other polyoxyalkylene monomers and/or oligomers having two or more condensable groups per molecule may include for example units of the structure-

-[-R'-O-(-R²-O-)_d-Pn-C(R³) ₂-Pn-O-(-R²-O-)e-R¹]- in which Pn is a 1 ,4-phenylene group, each R¹ is the same or different and is a divalent hydrocarbon group having 2 to 8 carbon atoms, each R² is the same or different and, is, an ethylene group, propylene or isoprpylene group, each R³ is the same or different and is a hydrogen atom or methyl group and each of the subscripts d and e is a positive integer in the range from 3 to 30.

[0044] The polycondensation process as hereinbefore described requires a suitable condensation catalyst for reactions to proceed. Any suitable polycondensation catalyst may be utilised. These include protic acids, Lewis acids, organic and inorganic bases, metal salts and organometallic complexes. Lewis acid catalysts, (a "Lewis acid" is any substance that will take up an electron pair to form a covalent bond). suitable for the polymerisation in the present invention include, for example, boron trifluoride FeCl₃, AlCl₃, ZnCl₂, ZnBr₂ , catalysts of formula M¹R⁴ _fX'_g where M¹ is B, Al, Ga, In or Tl each R⁴ is independently the same (identical) 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, -NO₂ or -CN, or substituted with at least two halogen atoms; X¹ 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 being B(C₆Fs)₃.

[0045] Catalysts which will promote condensation reactions but also act as equilibration catalysts such as sulphuric acid, hydrochloric acid, Lewis acids, sodium hydroxide, tetramethylammonium hydroxide, tetrabutyl phosphonium silanolate and amines may be used but are not preferred provided the presence of low molecular weight species in the polymer is not to be avoided, or provided the catalyst is inactivated prior to the rearrangement of polymers.

[0046] Further suitable condensation catalysts which may be used as the catalyst for the polymerisation reaction in the present invention include condensation catalysts incorporating tin, lead, antimony, iron, cadmium, barium, manganese, zinc, chromium, cobalt, nickel, aluminium, gallium or germanium and zirconium. Examples include metal triflates, organic tin metal catalysts such as triethyltin tartrate, tin octoate, tin oleate, tin naphthate, butyltintri-2-ethylhexoate, tinbutyrate, carbomethoxyphenyl tin trisuberate, isobutyltintriceroate, and diorganotin salts especially diorganotin dicarboxylate compounds such as dibutyltin dilaurate, dimethyltin dibutyrate, dibutyltin dimethoxide, diburyltin diacetate, dimethyltin bisneodecanoate Dibutyltin dibenzoate, , stannous octoate, dimethyltin dineodeconoate, dibutyltin dioctoate of which dibutyltin dilaurate, dibutyltin diacetate are particularly preferred.

[0047) Titanate and/or zirconate based catalysts may comprise a compound according to the general formula Ti[OR⁵J₄ and Zr[OR⁵J₄ respectively 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. Optionally the titanate may contain partially unsaturated groups. However, preferred examples of R⁵ include but are not restricted to methyl, ethyl, propyl, isopropyl, butyl, tertiary butyl and a branched secondary alkyl group such as 2,4-dimethyl-3-pentyl. Preferably, when each R⁵ is the same, R⁵ is an isopropyl, branched secondary alkyl group or a tertiary alkyl group, in particular, tertiary butyl.

[0048] Alternatively, the titanate may be chelated. The chelation may be with any suitable chelating agent such as an alkyl acetylacetonate such as methyl or ethylacetylacetonate. Any suitable chelated titanates or zirconates may be utilised. Preferably the chelate group used is a monoketoester such as acetylacetonate and alkylacetoacetonate giving chelated titanates such as, for example diisopropyl bis(acetylacetonyl)titanate, diisopropyl bis(ethylacetoacetonyl)titanate, diisopropoxytitanium Bis(Ethylacetoacetate) and the like. Examples of suitable catalysts are additionally described in EP 1254192 and WO200149774 which are incorporated herein by reference.

[0049] More preferred are condensation specific catalysts. These include acidic condensation catalysts of the formula R⁶SO₃H in which R⁶ represents an alkyl group preferably having from 6 to 18 carbon atoms such as for example a hexyl or dodecyl group, an aryl group such as a phenyl group or an alkaryl group such as dinonyl- or didoecyl-naphthyl. Water may optionally be added. Preferably R⁶ is an alkaryl group having an alkyl group having from 6 to 18 carbon atoms such as dodecylbenzenesulphonic acid (DBSA). Other condensation specific catalysts include n- hexylamine, tetramethylguanidine, carboxylates of rubidium or caesium, hydroxides of magnesium, calcium or strontium and other catalysts as are mentioned in the art, e.g. in GB895091, GB918823 and EP 0382365. Also preferred are catalysts based on phosphonitrile chloride, for example those prepared according to US 3839388, US4564693 or EP215470 and phosphonitrile halide ion based catalysts, as described in GB2252975, having the general formula [X²(PX² ₂=N)/_IPX² ₃]⁺[M²X² _(/ _ _{k +}

wherein X² denotes a halogen atom, M² is an element having an electronegativity of from 1.0 to 2.0 according to Pauling's scale, R¹" is an alkyl group having up to 12 carbon atoms, h has a value of from 1 to 6, j is the valence or oxidation state of M² and k has a value of from 0 to v- 1.

[0050] Alternatively, the catalyst may comprise an oxygen-containing chlorophosphazene containing organosilicon radicals having the following general formula:-

z'-PCl₂=N(-PCl₂=N)_m-PCl₂-O

in which

Z¹ represents an organosilicon radical bonded to phosphorus via oxygen, a chlorine atom or the hydroxyl group and m represents 0 or an integer from 1 to 8. The catalyst may also comprise condensation products of the above and/or tautomers thereof (the catalyst exists in a tautomeric form when Z¹ is a hydroxyl group). All or some of the chlorine atoms can be replaced by radicals Q, in which Q represents the hydroxyl group, monovalent organic radicals, such as alkoxy radicals or aryloxy radicals, halogen atoms other than chlorine, organosilicon radicals and phosphorus-containing radicals. The oxygen-containing chlorophosphazenes are preferably those in which no chlorine atom is replaced by a radical Q. [0051] A further alternative catalyst which might be used as the catalyst in the present invention is any suitable compound providing a source of anions comprising at least one quadri-substituted boron atom and protons capable of interaction with at least one silanol group as defined in WO 01/79330. For this type of catalyst, it is important that the boron containing anion does not itself form a covalent bond directly to a silicon atom and that it does not decompose or rearrange to produce an anion which forms a covalent bond directly to a silicon atom. Suitable materials include those incorporating one or more boron atoms disposed within a grouping and several, for example ten or more, halogen atoms connected with each boron atom. The halogen atoms in such compound may be connected to boron atoms by linkages incorporating at least one carbon atom and are selected from fluorine, chlorine and bromine, the most preferred being fluorine.

[0052] Preferred anions incorporate one or more atoms of boron having four organic substituents thereon the most preferred being quadri-substituted borates. The organic substituents are suitably halogenated hydrocarbon groups. Such as pentafluorinated phenyl groups and bis (trifluoromethyl) phenyl groups and preferred materials have four such groups bonded to each boron atom. Examples include tetrakis (pentafluoro phenyl) borate anion (perfluorinated aryl borate ion) and the material is preferably employed as the acid of this anion namely H⁺ ((C₆Fs)₄B }^'. Other operative materials include anions having two quadri-substituted boron atoms, for example diperfluoroinatedaryl borate ions, e.g. .H⁺(B(C₆Fs)₃CNB (C₆Fs)₃ }^"■ Other suitable boron-containing anions for use in the process of the present invention include carboranes, for example of the formula {CB9 Hιo}\ (CBgX²S H₅}\ (CB11H12}^" and {CB| |X² ₆H₆}^' wherein each X² is the same or different and is as hereinbefore described. Carboranes may contain boron atoms which are more highly substituted than quadri-substituted, e. g. pentasubstituted and hexa-substituted, and for the sake of clarity "quadri-substituted" where used herein is intended to include those anions containing quadri-substituted and higher substituted boron atoms.

[0053] A further group of catalysts which may be utilised are materials providing in the polymerisation reaction mixture a source of (a) protons capable of interaction with at least one of said silicon bonded hydroxy or alkoxy groups and (b) weakly coordinating anions (i.e. an anion which has a negative charge distributed through a comparatively large radical in such a way that the anion is comparatively weakly attractive to proton in the organosilicon reaction mixture i.e. e. is not a strong nucleophile). These include materials having one or more suitable atoms M², of an element selected from the group consisting of boron, niobium, and aluminium, disposed within the grouping and several, for example ten or more, halogen atoms connected with each atom M². The halogen atoms in such compound may be connected to atoms M² by linkages incorporating at least one carbon atom. The halogen atoms are preferably selected from fluorine, chlorine and bromine, the most preferred being fluorine. The preferred weakly coordinating anions may incorporate one or more atoms M of any suitable element capable of supporting an anion substituted to the extent of one more substituent on the atom M² than its neutral valence, for example four substituents on aluminium or boron or six substituents on niobium. Preferred anions incorporate one or more atoms of boron having four organic substituents thereon the most preferred being quadri-substituted borates. The organic substituents are suitably hydrocarbon groups. Three and preferably four of these hydrocarbon groups are preferably aromatic groups, and are preferably highly halogenated. Preferred halogenated hydrocarbons are pentafluorinated phenyl groups and bis (trifluoromethyl) phenyl groups and preferred materials have four such groups bonded to each boron atom. One operative weakly co-ordinating anion is the tetrakis (pentafluoro phenyl) borate anion (otherwise herein referred to as the perfluorinated aryl borate ion) and the material providing the source of protons (a) and weakly coordinating anions (b) is the acid of this anion namely H⁺ ((C₆Fs)₄B }^'.

[0054] The temperatures and pressures used in the process can be the same as those in the processes known to date for the polycondensation of organosilicon compounds.

[0055] The polymerization reaction with the present invention may be carried out at any appropriate temperature and pressure in either batch or continuous mode. The reaction conditions need to be set depending on the specific catalyst used and the chemical equilibrium of the polymerization reaction. In the case of the phosphazene catalysed methods the polymerisation may occur at temperatures of from room temperature to 200⁰C preferably between 5O⁰C to 200⁰C, more preferably 8O⁰C to 16O⁰C.

[0056] The activity of the catalyst is preferably quenched by using a neutralizing agent which reacts with the catalyst to render it non-active. Typically in the case of the acid type condensation catalysts the neutralising agent is a suitable base, for example, an amine such as a mono/di and trialkanolamine, specific examples include but are not limited to monoethanolamine (MEA) and triethanolamine (TEA), magnesium oxide and/or calcium carbonate. In the case of systems using a DBSA catalyst alternative quenching means include aluminasilicate zeolite materials that were found to absorb DBSA and leave a stable polymer. In most cases catalyst residues remain in the polymer product or where appropriate may be removed by filtration or alternative methods. In the case of phosphazene based catalysts once the desired polymer viscosity has been reached, the viscosity of the organosilicon compound obtained in the process can be kept substantially constant by a procedure in which the catalyst used, or a reaction product which has been formed incorporating catalyst residues which likewise promotes the polymerisation process, is inhibited or deactivated by addition of inhibitors or deactivators. Any suitable inhibitors and/or inactivators may be used. Specific examples include but are not restricted to triisononylamine, n-butyllithium, lithium siloxanolate, hexamethylcyclotrisilazane and hexamethyldisilazane.

[0057] Any suitable method for making the polymer in accordance with the method of the present invention may be used.

[0058] The polycondensation reactions may be carried out at any suitable pressure although in order to facilitate removal of by-products formed during the condensation, for example, water, HCl or alcohol, the polymerisation process may take place at a pressure below 80 kPa. Condensation type reactions involving equilibration, may be carried out at pressures above atmospheric if so desired. [0059) The polymerisation process in accordance with the invention may be carried out either batchwise or continuously using any suitable mixers. Where the polycondensation by-product is water, the water can either be removed by chemical drying using e.g. hydrolysable silanes like methyltrimethoxysilane or by physical separation using evaporation, coalescing or centrifuging techniques.

[0060] Hence, in this embodiment of the invention preferably the resulting polymer used in the present invention is a polysiloxane containing polymer containing at least two OH or otherwise condensable terminal groups Hence, the polymer has the general formula

X-A-X³ (1)

X and X³ are independently selected from siloxane groups which terminate in hydroxyl or hydrolysable groups and A is a siloxane containing polymeric chain.

[0061] It will be appreciated that A will be dependent on the structure of the monomers and oligomers used as starting materials (as described above) and the reaction pathway of polymerisation. Any combination of the monomer/oligomers described above may be utilised as the basis of A in the prepared polymer. Hence, examples of typical siloxane groups A in formula (I) are those which comprise a polydiorganosiloxane chain. Thus group A preferably includes siloxane units of formula (2)

in which each R⁷ is independently an organic group such as a hydrocarbon group having from 1 to 18 carbon atoms, a substituted hydrocarbon group having from 1 to 18 carbon atoms or a hydrocarbonoxy group having up to 18 carbon atoms and p has, on average, a value of from 1 to 3, preferably 1.8 to 2.2. Preferably R⁷ is a hydrocarbyl group having from 1 to 10 carbon atoms optionally substituted with one or more halogen group such as chlorine or fluorine and p is 0, 1 or 2. Particular examples of groups R⁷ include methyl, ethyl, propyl, butyl, vinyl, hexenyl, cyclohexyl, phenyl, tolyl group, a propyl group substituted with chlorine or fluorine such as 3,3,3-trifluoropropyl, chlorophenyl, beta-(perfluorobutyl)ethyl or chlorocyclohexyl group. Suitably, at least some and preferably substantially all of the groups R⁷ are methyl.

[0062] Group A in the compound of formula (1) may include any suitable siloxane or siloxane/organic molecular chain providing the resulting polymer a viscosity (in the absence of diluents in accordance with the present invention of up to 20 000 000 mPa.s, at 25⁰C (i.e. up to or even more than 200 000 units of formula (2)). In one preferred embodiment A is a linear organopolysiloxane molecular chain (i.e. p = 2) for all chain units. Preferred materials have polydiorganosiloxane chains of units according to the general formula (3)

-(R⁷ ₂Si0)_q- (3) in which each R⁷ is as defined above and is preferably a methyl group and q has a value of up to at least (or even more than) 200 000. Suitable polymers have viscosities of up to 20 000 OOOmPa.s at 25⁰C.

[0063] As previously indicated if organic monomers/oligomers are utilised as starting materials in the polymerisation process of the present invention A may be a block copolymeric backbone comprising at least one block of siloxane groups of the type depicted in formula (2) above and an organic component comprising any suitable organic based polymer backbone for example the organic polymer backbone prepared by the introduction of aforementioned organic monomers/oligomers into the polymer backbone.

[0064] X and X³ are independently selected from siloxane groups which terminate in hydroxyl or hydrolysable groups. Examples of hydroxyl-terminating or hydrolysable groups which terminate X or X³ include -Si(OH)₃, (R^a)Si(OH)₂, -(R^a)₂SiOH, - R^aSi(OR^b)₂, -Si(OR^b)₃, -R^a ₂SiOR^b or -R^a ₂ Si -R^c- SiR^d _n(OR^b)₃._n where each R^a independently represents a monovalent hydrocarbyl group, for example, an alkyl group, in particular having from 1 to 8 carbon atoms, (and is preferably methyl); each R^b and R^d group is independently an alkyl or alkoxy group in which the alkyl groups suitably have up to 6 carbon atoms; R^c is a divalent hydrocarbon group which may be interrupted by one or more siloxane spacers having up to six silicon atoms; and n has the value 0, 1 or 2. Preferably X and/or X³ contain hydroxyl groups or groups which are otherwise hydrolysable in the presence of moisture.

(00651 Whilst in most instances the condensation polymerisation process relies on the presence of -OH terminal and/or alkoxy terminal groups more complex terminal groups such as some described in the preceding paragraph may be introduced through the use of an end-blocking agent. An end-blocking agent may be additionally introduced into the polymerisation process to regulate the molecular weight of the polymer and/or add functionality. End-blocking agents are a means of controlling the reactivity /polymer chain length of the polymer by introducing compounds which will react with only one hydrolysable end group. In the present situation it is imperative to ensure that any end- blocked polymer produced in accordance with the process herein described is independently curable from the extender and/or plasticiser which is cured via an alternative cure route. Hence typically polymers produced via the condensation polymerisation process described above are typically only end-blocked with alternative condensable groups such as those in the preceding paragraph. Alternative end-groups may be introduced to terminate the polymer but these must cure via a different reaction pathway than the plasticiser and/or extender but groups. Hence, in this embodiment preferably each end-blocking compound comprises a condensable group which will react with the -OH and/or alkoxy groups or the like on the polymer and introduce the end groups described above.

POLYADDITION POLYMERISATION PROCESS

[0066] In an alternative embodiment of the present invention the polymer may be prepared using a polyaddition copolymerisation route by reacting a siloxane containing material with:- i) one organopolysiloxane polymer(s) and/or ii) one or more organic oligomer(s) via an addition reaction pathway in the presence of an extender and/or plasticiser, a suitable catalyst and optionally an end-blocking agent; and where required quenching the polymerisation process;

[0067] An "addition polymerisation" process is a polymerisation process whereby unlike in a condensation reaction no by-products such as water or alcohols are generated from the monomer co-reactants during polymerisation. A preferred addition polymerisation route is a hydrosilylation reaction between an unsaturated organic group e.g. an alkenyl or alkynyl group and an Si-H group in the presence of a suitable catalyst.

[0068] The siloxane containing material is preferably an organopolysiloxane monomer or oligomer which contains groups capable of undergoing addition type reactions with polymer (i) and/or oligomer (ii). The preferred addition reaction involved in the addition copolymerisation in accordance with the present invention is a hydrosilylation reaction between an unsaturated group and an Si-H group but any other suitable addition type reaction may be involved.

[0069] The link between the siloxane containing material and organopolysiloxane polymer (a) or organic oligomer(b) may comprise, for the sake of example any one of the following divalent organic groups:-

~R⁸ - ~R⁸--CO" -R⁸--NHCO~

-R⁸--NHCONH— R⁹--NHCO" -R⁸-OOCNH— R⁹-NHCO-

and the like, wherein R⁸ is a divalent alkylene radical such as ethylene, propylene, butylene and the like; and R⁹ represents a divalent alkylene group, e.g. R⁸, or a divalent arylene group, such as a phenylene radical, i.e. -C₆H₄-. Illustrative of the other preferred examples of said divalent organic groups are; -(CH₂)₂ CO-; -(CH₂)3 NHCO-; "(CH₂)₃ NHCONH-C₆H₄-NHCO--; -(CH₂)₃OOCNH-C₆H₄-NHCO-; and the like. Most preferably as the addition copolymerisation reaction preferred is a hydrosilylation reaction the link is in the form of a divalent alkylene group.

[0070) The nature of the reactive groups involved in the copolymerisation reaction determines the structure of the divalent organic group linking the constituents of the polymerisation reaction. Typically the reactions involved in the polymerisation of copolymers in accordance with the present invention may be as follows:-

a. w CH₂ =CHCH₂O(C_n H_2n O)_x CH2 CH=CH₂ + WHSiMe₂- 0(SiMe₂ O)₃-

SiMe₂H.→

-[(CH₂)₃ 0(C₁₁-H_2nOV (CH₂)₃ SiMe₂- 0(SiMe₂ O)₈ SiMe₂-Jw

b. w CH₂ -CHO(C_n H_2n O)_x- CH-CH₂ + WHSiMe₂- 0(SiMe₂ O)₈- SiMe₂H → -- [(CH₂)₂ 0(C_n H_2n OV (CH₂)₂ SiMe₂- O(SiMe₂ O)₈- SiMeHw

c. w HO(C_n H_2n-O)_x' H + wOCN(CH₂)₃ SiMe₂- 0(SiMe₂ O)₈- SiMe₂ (CH₂)₃ NCO →.

-- [(C_n-H_2nOV OCNH(CH₂)₃ SiMe₂- 0(SiMe₂ O)₃ SiMe₂ (CH₂)₃ NHC00]w

d. w OCNC₆H₄ NHCOO(C_n-H_2n-OV CONHC₆ H₄ NCO + w H₂N(CH₂)₃ SiMe₂- 0(SiMe₂ O)₃ SiMe₂ (CH₂)₃ NH2 →.-[OCN HC₆H₄ NHCOO(C_n H_2n O)_x- CONH C₆H₄ NHCONH(CH₂)₃ SiMe₂- 0(SiMe₂ O)₃- SiMe₂ (CH₂)₃ NH]w

e. w OCN C₆H₄ NHCOO(C_n-H_2n-O)_x- CONH C₆H₄ NCO + w HO(CH₂)₃ SiMe₂- 0(SiMe₂ O)₈- SiMe₂ (CH₂)₃ OH →.-[0CNH C₆H₄ NHCOO(C_n-H_2n-O)_x- CONH C₆H₄ NHCOO(CH₂)₃ SiMe₂- 0(SiMe₂ O)₃- SiMe₂ (CH₂)₃ 0]w

f. WCH₂=CHSiPh₂-O(SiPh₂VSiPh₂CH=CH₂ + WHSiMe₂-O(SiMe₂O)₃-SiMe₂H → -[- C₂H₄SiPh₂O(SiPh₂O)_x-SiPh₂C₂H₄SiMe₂-O(SiMe₂O)₃-SiMe₂-K g. WCH₂=CHCH₂CH₂CH-CH₂ + WHSiMe₂-O(SiMe₂O)₃SiMe₂H → -[-

(CH₂)₆SiMe₂0(SiMe₂0)_aSiMe₂-]_w-

wherein Me represents a methyl radical; n' is an integer of from 2 to 4 inclusive; a' is an integer of at least 5; y' is an integer of at least 4 and w is an integer of at least 4.

[0071] Whilst the siloxane containing material may comprise any of the groups in reactions (a) to (g) above, it is preferably an organopolysiloxane monomer, more preferably in the form of a straight chain and/or branched organopolysiloxane comprising units of formula (Ia)

wherein each R¹⁰ may be the same or different and is R' is as hereinbefore described or hydrogen and a is as hereinbefore described. When the siloxane containing material is an Organopolysiloxane monomer, said organopolysiloxane monomer must have at least one group which is readable with at least two groups, typically the terminal groups, of polymer (i) and/or oligomer (ii) via an addition reaction process. Preferably when the siloxane containing material is an organopolysiloxane monomer said organopolysiloxane monomer comprises at least one Si-H per molecule, preferably at least two Si-H groups per molecule. Preferably when the siloxane containing material is an organopolysiloxane said organopolysiloxane is end-blocked with a silyl group of the formula H(alkyl)₂Si-, and each alkyl group may be the same or different and is preferably methyl or ethyl. Preferably when the siloxane containing material is an organopolysiloxane said organopolysiloxane has a viscosity of between lOmPa.s and 5000mPa.s at 25⁰C

|0072] In cases where the siloxane containing material comprises only one addition readable group and polymer (i) and/or oligomer (ii) comprises two addition readable groups which will react with the siloxane containing material , the resulting product will be an "ABA" type polymeric product. Whereas when both the siloxane containing material comprises two addition readable groups and polymer (a) and/or oligomer (b) comprises two addition reactable groups which will react with the siloxane containing material interaction between the two components would lead to (AB)n block copolymers in which the length of the polymer is largely determined by the relative amounts of the two constituents.

(0073) Organopolysiloxane polymer (i) may comprise any suitable organopoly siloxane polymeric backbone but is preferably linear or branched, and comprises at least one, preferably at least two substituent groups which will react with the aforementioned groups in the siloxane containing material via an addition reaction pathway., Preferably the or each substituent group of polymer (i) is a terminal group. When the siloxane containing material comprises at least one Si-H group, the preferred substituent groups on organopolysiloxane polymer (i), which are designed to interact with the Si-H groups, are preferably unsaturated groups (e.g. alkenyl terminated e.g. ethenyl terminated, propenyl terminated, allyl terminated (CH₂=CHCH₂-)) or terminated with acrylic or alkylacrylic such as CH₂=C(CH₃)-CH₂- groups Representative, non- limiting examples of the alkenyl groups are shown by the following structures; H₂C=CH-, H₂C=CHCH₂-, H₂C=C(CH₃)CH₂- , H₂C=CHCH₂CH₂-, H₂C=CHCH₂CH₂CH₂-, and H₂C=CHCH₂CH₂CH₂CH₂-. Representative, non- limiting examples of alkynyl groups are shown by the following structures; HC≡C-, HC≡CCH₂-, HC≡CC(CH₃) - , HC≡CC(CH₃)₂ - , HC≡CC(CH₃)₂CH₂- Alternatively, the unsaturated organic group can be an organofunctional hydrocarbon such as an acrylate, methacrylate and the like such as alkenyl an/or alkynyl groups. Alkenyl groups are particularly preferred.

[0074] Organopolysiloxane polymer (i) is preferably a straight chain and/or branched organopolysiloxane comprising units of formula (Ic)

wherein each R'" may be the same or different and is R' as hereinbefore described and a is as hereinbefore described. No R'" groups may be hydrogen groups. Preferably each R'" is the same or different and are exemplified by, but not limited to alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, undecyl, and octadecyl; cycloalkyl such as cyclohexyl; aryl such as phenyl, tolyl, xylyl, benzyl, and 2-phenylethyl; and halogenated hydrocarbon groups such as 3,3,3-trifluoropropyl, 3-chloropropyl, and dichlorophenyl.

(00751 The organic oligomer (ii) as hereinbefore described may comprise any suitable organic based monomer, oligomer and/or polymer suitable as a constituent of the addition polymerisation polymer backbone. For example the organic oligomer (ii) may comprise any of organic compounds depicted as extenders and/or plasticisers above for the polycondensation polymerisation route as discussed below. In each case the oligomers used for organic oligomer (ii) comprise at least two substituent groups which will react with the reactive group(s) of the siloxane containing material. Typically the organic oligomer (ii) comprises at least two unsaturated terminal groups, preferably alkenyl terminal groups available for interaction with e.g. Si-H groups of the siloxane containing material. Additional organic based oligomers (ii) which may be utilised include acetylene terminated oligophenylenes, vinylbenzyl terminated aromatic polysulphones oligomers. Further organic polymeric backbones suitable as oligomer (b) include aromatic polyester based monomers and aromatic polyester based monomers, both preferably comprising alkenyl terminal groups.

[0076) Perhaps the most preferred oligomer (ii) are polyoxyalkylene based polymers as described above with respect to the polycondensation route but in this instance the polyoxyalkylene based polymers have unsaturated (e.g. alkenyl) terminal groups instead of condensable end groups. Such polyoxyalkylene polymers again preferably comprise a linear predominantly oxyalkylene polymer comprised of recurring oxyalkylene units, (-C_bH_2b-O-) illustrated by the average formula (-CbH₂b-O-)_c wherein b and c are as hereinbefore described. The average molecular weight of each polyoxyalkylene polymer (b) may range from about 300 to about 10,000. Moreover, the oxyalkylene units are not necessarily identical throughout the polyoxyalkylene monomer, but can differ from unit to unit. A polyoxyalkylene block, for example, can be comprised of oxyethylene units, (-C₂H₄-O-); oxypropylene units (-C₃H₆-O-); or oxybutylene units, (-C₄H₈-O-); or mixtures thereof. [0077] Other polyoxyalkylene monomers having unsaturated (e.g. alkenyl) terminal groups suitable for use as oligomer (b) may include for example:-

-[-R'-O-(-R²-O-)_d-Pn-C(R³) ₂-Pn-O-(-R²-O-)_e-R¹]-

in which Pn, R¹, R², R³, d and e are as hereinbefore described.

[0078] Linear copolymers formed by the polymerisation of siloxane containing material in combination with oligomer (b) when oligomer (b) is a polyoxyalkylene is of a size wherein the average molecular weight of each siloxane block being is from about 100 to about 10,000; the average molecular weight of each polyoxyalkylene block being from about 50 to about 10,000; said siloxane blocks constituting from about 20 to about 50 weight per cent of the copolymer; the polyoxyalkylene blocks constituting about 80 to about 50 weight per cent of the copolymer; and the block copolymer having an average molecular weight of at least about 5,000, preferably above 15000.

[0079] The linkage between the two different copolymeric blocks resulting from the addition copolymerisation reaction in accordance with the present invention are generally non-hydrolysable, comprising a divalent organic group attached to the adjacent silicon atom by a carbon to silicon bond and when (b) is a polyoxyalkylene, to the polyoxyalkylene block by an oxygen atom. Such linkages are readily apparent and determined by the reaction employed to produce the e.g. siloxane- polyoxyalkylene block copolymer. Moreover, these linear (AB)n block copolymers are also end-blocked, generally with the residual reactive groups of the reactants used to produce the linear block (AB)n copolymers unless end-blocking compounds are introduced into the reaction mixture

[0080] Hence linear non-hydrolyzable (AB)n block copolymers in accordance with the present invention of this invention can be prepared by platinum catalyzed hydrosilation of alkenyl terminated polyethers with SiH-terminated dialkylsiloxane fluids. The resulting copolymer being a combination of polyoxyalkylene blocks linked through silicon to carbon to oxygen linkages (i.e. a propyleneoxy group) and the end-blocking groups being selected from the group consisting of allyl, propenyl and/or hydrogen (dialkyl) siloxy groups (dependent on the relative amounts of the constituents which are present).

[0081] This preferred method for preparing non-hydrolyzable linear (AB)n silicone- polyoxyalkylene block copolymers having average molecular weights ranging from at least about 30,000 involves the platinum catalyzed hydrosilylation of allyl terminated polyethers with SiH-terminated dihydrocarbyl siloxane fluids. Of course it is understood that the reactants are preferably in as pure as form as possible and that the general process requires equimolar quantities or as near to this as possible, since deviations from the 1 : 1 stoichiometry will not yield as high a molecular weight block copolymer as desired. However, when allyl terminated polyalkylene compounds are used an excess of said allyl compound may be desirable to allow for isomerisation of the allyl group to propenyl.

[0082] The linear siloxane-polyoxyalkylene block copolymers can have an average molecular weight of about 30,000 on up to about 250,000 or higher. The upper limit is not critical, its value merely being dependent upon the practicalities of process limitations in preparing such high molecular weight (AB)n type polymers. The siloxane blocks of said block copolymers can constitute about 20 to about 50 weight per cent of the block copolymer, while the polyoxyalkylene blocks can constitute about 80 to about 50 weight per cent of the block copolymer. Preferably the non- hydrolyzable type (AB)n polymers in accordance with the present invention have a number average molecular weight of at least about 30,000.

[0083] Preferably the polymer produced in accordance with the polyaddition process has an average number molecular weight (Mn) greater than 132,000 and a degree of polymerisation of greater than 1800 as determined by ASTM D5296-05 with the weight values being determined in terms of polystyrene molecular weight equivalents. [0084] It is to be understood that while said (AB)n block copolymers of this invention can be discrete chemical compounds they are usually mixtures of various discrete block copolymers species due at least in part to the fact that the siloxane and polyoxyalkylene reactants used to produce said (AB)n block copolymers are themselves usually mixtures.

[0085] In carrying out the process it is generally preferred to mix all of the ingredients including the extender and/or plasticiser together at about room temperature (25⁰C) and allow the reaction to proceed at elevated temperatures, preferably about 6O⁰C to about 15O⁰C. Lower or higher temperatures up to 200⁰C may be employed depending on the extender and/or plasticiser being used, but there normally is no advantage. Likewise the reaction is generally conducted at atmospheric pressures, although other pressures could be used if desired. The removal or neutralization of the platinum catalyst, e.g. chloroplatinic acid is desirable and can be accomplished in any conventional manner.

[0086] Of course as is readily apparent to those skilled in the art the choice of the particular hydrogen terminated siloxane polymer and allyl terminated polyoxyalkylene diol reactant merely depends on the particular block copolymer desired. Moreover the final molecular weight of the block copolymer product is also a function of reaction time and temperature. Thus those skilled in the art will readily recognize that it is obvious that an extremely large number and variety of block copolymers can be predetermined and selectively prepared by routine experimentation, which permits tailoring the compositions and products made therefrom to individual specifications and needs rather than vice versa.

[0087] The silicone block copolymer in accordance with the present invention may alternatively having at least one repeating polyether-amide unit represented by the formula

wherein

T is a linear or branched C1-C30 alkylene chain;

J is a divalent organic group containing at least one polyoxyalkylene group having the formula -(C_vH_2vO)_x - or one polyalkylene group having the formula -

where v is 2 to 4 inclusive, x is 1 to 700, D to D _are independently a monovalent organic group; Each DP is independently an integer having a value of 1-500;

[0088] The viscosity of the organopolysiloxanes which may be produced by the process using a catalyst according to the present invention may be in the range of from 1000 to many millions mPa.s at 25⁰C, depending on the reaction conditions and raw materials used in the method of the invention.

[0089] The process according to the invention can be used to make a whole range of organopolysiloxane containing polymers, including liquid siloxane polymers and gums of high molecular weight and viscosities of from for example from IxIO⁴ to 100x10⁹ mPa.s at 25⁰C. The molecular weight of silicone polymers is effected by the concentration of end groups, stoichiometry of the reagents. The catalyst used in the present invention has sufficient activity to enable the formation of polymers in a reasonable time at a low catalyst concentration.

[0090] When the addition reaction chosen is a hydrosilylation reaction, any suitable hydrosilylation catalyst may be utilised. Such hydrosilylation catalysts are illustrated by any metal-containing catalyst which facilitates the reaction of silicon-bonded hydrogen atoms of the SiH terminated organopolysiloxane with the unsaturated hydrocarbon group on the polyoxyethylene. The metals are illustrated by ruthenium, rhodium, palladium, osmium, iridium, or platinum.

[0091] Hydrosilylation catalysts are illustrated by the following; chloroplatinic acid, alcohol modified chloroplatinic acids, olefin complexes of chloroplatinic acid, complexes of chloroplatinic acid and divinyltetramethyldisiloxane, fine platinum particles adsorbed on carbon carriers, platinum supported on metal oxide carriers such as Pt(Al2θ3), platinum black, platinum acetylacetonate, platinum(divinyltetramethyldisiloxane), platinous halides exemplified by PtCl2, PtClφ Pt(CN)2, complexes of platinous halides with unsaturated compounds exemplified by ethylene, propylene, and organovinylsiloxanes, styrene hexamethyldiplatinum, Such noble metal catalysts are described in US Patent 3,923,705, incorporated herein by reference to show platinum catalysts. One preferred platinum catalyst is Karstedt's catalyst, which is described in Karstedt's US Patents 3,715,334 and 3,814,730, incorporated herein by reference. Karstedt's catalyst is a platinum divinyl tetramethyl disiloxane complex typically containing one weight percent of platinum in a solvent such as toluene. Another preferred platinum catalyst is a reaction product of chloroplatinic acid and an organosilicon compound containing terminal aliphatic unsaturation. It is described in US Patent 3,419,593, incorporated herein by reference. Most preferred as the catalyst is a neutralized complex of platinous chloride and divinyl tetramethyl disiloxane, for example as described in US Patent 5,175,325.

[0092] Ruthenium catalysts such as RhCl3(Bu2S)3 and ruthenium carbonyl compounds such as ruthenium 1,1,1-trifluoroacetylacetonate, ruthenium acetylacetonate and triruthinium dodecacarbonyl or a ruthenium 1,3-ketoenolate may alternatively be used.

[0093] Other hydrosilylation catalysts suitable for use in the present invention include for example rhodium catalysts such as [Rh(O₂CCH3)2]2, Rh(O₂CCHs)₃, Rh₂(C₈H, ₅O₂)₄, Rh(C₅H₇O₂)₃, Rh(C₅H₇O₂)(CO)₂, Rh(CO)[Ph₃P](C₅H₇O₂), RhX⁴ ₃[(R¹³)₂S]₃, (R¹⁴ ₃P)₂Rh(CO)X⁴, (R¹⁴ ₃P)₂Rh(CO)H, Rh₂X⁴ ₂Y⁴ ₄,

H_a"Rh_b"Olefin_C"Cld", Rh (O(CO)R^{l 3})₃._n >(OH)_n" where X⁴ is hydrogen, chlorine, bromine or iodine, Y⁴ is an alkyl group, such as methyl or ethyl, CO, C₈H_H or 0.5 C₈Hi₂, R¹³ is an alkyl radical, cycloalkyl radical or aryl radical and R¹⁴ is an alkyl radical an aryl radical or an oxygen substituted radical, a" is 0 or 1, b" is 1 or 2, c" is a whole number from 1 to 4 inclusive and d" is 2, 3 or 4, n" is 0 or 1. Any suitable iridium catalysts such as Ir(OOCCH₃)₃, Ir(C₅H₇O₂)₃, [Ir(Z³)(En)₂]₂, or (Ir(Z³)(Dien)]₂, where Z³ is chlorine, bromine, iodine, or alkoxy, En is an olefin and Dien is cyclooctadiene may also be used.

[0094] Additional components can be added to the hydrosilylation reaction which are known to enhance such reactions. These components include salts such as sodium acetate which have a buffering effect in combination with platinum catalysts.

[0095] The amount of hydrosilylation catalyst that is used is not narrowly limited as long as there is a sufficient amount to accelerate a reaction between the polyoxyethylene having an unsaturated hydrocarbon group at each molecular terminal and the SiH terminated organopolysiloxane at room temperature or at temperatures above room temperature. The exact necessary amount of this catalyst will depend on the particular catalyst utilized and is not easily predictable. However, for platinum- containing catalysts the amount can be as low as one weight part of platinum for every one million weight parts of components the polyoxyethylene having an unsaturated hydrocarbon group at each molecular terminal and the SiH terminated organopolysiloxane. The catalyst can be added at an amount 10 to 120 weight parts per one million parts of components the polyoxyethylene having an unsaturated organic group at each molecular terminal and the SiH terminated organopolysiloxane, but is typically added in an amount from 10 to 60 weight parts per one million parts of the polyoxyethylene having an unsaturated organic group at each molecular terminal and the SiH terminated organopolysiloxane.

[0096] When the siloxane containing material is an organopolysiloxane having at least two Si-H groups, typically, the process is carried out using approximately a 1 : 1 molar ratio of ≡Si-H containing polysiloxane and the material containing unsaturation. It is expected that useful materials may also be prepared by carrying out the process with an excess of either the ≡Si-H containing polysiloxane or the material containing unsaturation, but this would be considered a less efficient use of the materials. Typically, the material containing the unsaturation is used in slight excess to ensure all the SiH is consumed in the reaction.

(0097) A small degree of chemical reaction may occur between the OH groups in any such extender and/or plasticiser and Si-H bonds in the compounds involved in the polyaddition process used to prepare the polymer. However, because of the preferential reaction kinetics of the hydrosilylation reaction between alkenyl groups and Si-H groups such interactions will kept to a minimum.

[0098] In the case of the present embodiment of the invention end-blocking agents may be introduced into the system to e.g. introduce alternative unsaturated groups on to the polymer backbone. However, typically end-blockers will not be used.

EXTENDERS AND/OR PLASTICISERS

[0099] Any suitable extender and/or plasticiser may be utilised provided its chemical reactivity meets the criteria for the present invention.

[0100] Polymers having -OH or otherwise condensable groups - polymers of this nature typically will have any reactive extender which is unreactive with the -OH or otherwise condensable groups of the polymer. Typically such extenders/plasticisers are envisaged as comprising a siloxane or organic backbone, no -OH or otherwise condensable groups and two or more unsaturated groups, preferably alkenyl or alkynyl groups, most preferably alkenyl groups. Such extenders /plasticisers will not react with the polymer during preparation of the uncured composition and/or during the polymerisation process but can be independently cured as will be discussed further below. [0101] Preferred extenders/plasticisers utilised for condensation polymerisation processes have two or more sterically unhindered unsaturated groups include organic compounds such as , for example, polystyrene and/or substituted polystyrenes such as poly(α-methylstyrene), poly(vinylmethylstyrene), poly(p-trimethylsilylstyrene), polybutadiene, isoprene, linear and or branched α Ω dienes (which may be optionally substituted, examples include 1,5-hexadiene and 1 ,7-octadiene and poly(p-trimethylsilyl- α-methylstyrene) or organopolysiloxanes with at least two alkenyl or alkynyl groups, natural oils which comprise suitable reactive groups such as linseed oil, safflower oil, tung oil, soya oil, sunflower oil, rape oil and/or castor oil. Such a sterically unhindered aspect is not required where the plasticiser/extender is to be cured by a peroxide cure system.

[0102] Preferably therefore in a process in accordance with the present invention the polymer is prepared in the presence of such an extender/plasticiser having two or more sterically unhindered unsaturated groups via a polycondensation process. The resulting polymer is optionally end-capped to introduce a preferred condensable end group onto the polymer.

[0103] Compositions comprising polymers having at least two unsaturated groups typically will be have any reactive extender which is substantially unreactive with the unsaturated groups. Polymers prepared by a polyaddition process require extenders/plasticisers which will substantially not react with the monomers and oligomers involved in the polymerisation process. Typically such a polyaddition process is preferably via a hydrosilylation route as discussed above, in which case the extender/plasticiser has to be substantially unreactive with both unsaturated groups and groups containing Si-H bonds. Preferably extenders/plasticisers used for this purpose are envisaged as comprising a siloxane or organic backbone, at least two -OH or otherwise condensable groups and no unsaturated groups. Such extenders /plasticisers will not react with the unsaturated groups during the polymerisation process. It should be noted however that a small degree of chemical reaction may occur between the OH groups in any such extender and/or plasticiser and Si-H bonds in the compounds involved in the polyaddition process used to prepare the polymer. However, because of the preferential reaction kinetics of the hydrosilylation reaction between alkenyl groups and Si-H groups such interactions will kept to a minimum.

[0104] The extenders and/or plasticisers utilised in the polyaddition polymerisation in accordance with this invention preferably do not contain any unsaturated groups or groups containing Si-H bonds. Preferably they comprise organic diols or organic compounds containing at least two hydrolysable groups preferably alkoxy groups.

Examples include polypropylene glycols, polyethylene glycols, poly(l,4- butanediols), organic diols such as 1,16-hexadecanediol, 1 , 12-dodecanediol hydroxy end-blocked siloxanes (containing no unsaturated groups) natural oils containing no unsaturation but at least two -OH groups such as castor oil. Other possible extenders include saturated polyoxyalkylene based diols which preferably comprise recurring oxyalkylene units illustrated by the average formula (-C_bH_2b-O-)_c wherein b is an integer from 2 to 4 inclusive and c is an integer of at least four. The average molecular weight of each polyoxyalkylene polymer block may range from about 300 to about 10,000. Moreover, the oxyalkylene units are not necessarily identical throughout the polyoxyalkylene monomer, but can differ from unit to unit. A polyoxyalkylene block, for example, can be comprised of oxyethylene units, (-C₂H₄- O-); oxypropylene units (-C₃H₆-O-); or oxybutylene units,(-C₄H₈-O-); or mixtures thereof. Further additional plasticiser/extenders are silanol end blocked saturated organic polymers. Mixtures of any of the above may be included.

[0105] The extenders/plasticisers as hereinbefore described effectively act as unreactive extenders and/or plasticisers until at least the introduction of any cure package for curing the extender/plasticiser into the composition. Such extenders/plasticisers are substantially unable to chemically react into the polymer, intermediates or monomers/oligomers involved in the polymerisation process. If the polymer produced has unsaturated end groups then typically said polymer is cured via the normal hydrosilylation process and the extender and or plasticiser is cured via a condensation cure package as described herein. Conversely for condensation polymerisation polymers said polymers will be cured by way of a condensation process and typically the extender and/or plasticiser is cured via a hydrosilylation cure process as described herein. [0106] The amount of extender and/or plasticiser which may be included in the composition will depend upon factors such as the purpose to which the composition is to be put, the molecular weight of the extender(s) and/or plasticiser(s)concerned etc. In general however, the higher the molecular weight of the extender(s) and/or plasticisers, the less will be tolerated in the composition but such high molecular weight extenders have the added advantage of lower volatility thus enabling the sealant composition to meet ISO 10563 requirements. Typical compositions will contain up to 70%w/w extender(s) and/or plasticisers. More suitable polymer products comprise from 5-60%w/w of linear extender(s) and/or plasticiser(s).

[0107] Preferably each extender and or plasticiser is miscible or at least substantially miscible with the monomeric starting materials with which they are initially mixed, and more particularly with both intermediate polymerisation reaction products and the final polymerisation product. Extenders and/or plasticisers which are "substantially miscible" are intended to include extenders and/or plasticisers are intended to include extenders and/or plasticisers which are completely or largely miscible with the monomer(s) and/or the reaction mixture during polymerisation and hence may include low melting point solids which become miscible liquids in a reaction mixture during the polymerisation process.

[0108] As hereinbefore described the composition prepared in accordance with the present invention into which such a diluted polymer is introduced contains the said diluted polymer, filler and a suitable cure system to form a curable composition.

[0109] The compositions prepared using the above polymers and extenders/plasticisers also contain fillers and a polymer cure system.

[0110] Any suitable filler or combination of fillers may be utilised. The compositions may contain one or more finely divided, reinforcing fillers (e) such as high surface area fumed and precipitated silicas and to a degree calcium carbonate or additional non-reinforcing fillers such as crushed quartz, diatomaceous earths, barium sulphate, iron oxide, titanium dioxide and carbon black, talc, wollastonite. Other fillers which might be used alone or in addition to the above include aluminite, calcium sulphate (anhydrite), gypsum, calcium sulphate, magnesium carbonate, clays such as kaolin, aluminium trihydroxide, magnesium hydroxide (brucite), graphite, copper carbonate, e.g. malachite, nickel carbonate, e.g. zarachite, barium carbonate, e.g. witherite and/or strontium carbonate e.g. strontianite

[0111] Aluminium oxide, silicates from the group consisting of olivine group; garnet group; aluminosilicates; ring silicates; chain silicates; and sheet silicates. The olivine group comprises silicate minerals, such as but not limited to, forsterite and

Mg₂SiO₄. The garnet group comprises ground silicate minerals, such as but not limited to, pyrope; Mg₃Al₂Si₃Oi₂; grossular; and Ca₂Al₂Si₃Oi₂. Aluninosilicates comprise ground silicate minerals, such as but not limited to, sillimanite; Al₂SiO₅ ; mullite; 3Al₂O₃.2SiO₂; kyanite; and Al₂SiO₅. The ring silicates group comprises silicate minerals, such as but not limited to, cordierite and Al₃(Mg₁Fe)₂[Si₄AlOi₈].

The chain silicates group comprises ground silicate minerals, such as but not limited to, wollastonite and Ca[SiO₃].

[0112] The sheet silicates group comprises silicate minerals, such as but not limited to, mica; K₂AIi₄[Si₆Al₂O₂₀](OH)₄; pyrophyllite; Al₄[Si₈O₂₀](OH)₄; talc; Mg₆[Si₈O_2O](OH)₄; serpentine for example, asbestos; Kaolinite; Al₄[Si₄O ιo](OH)₈; and vermiculite.

[0113] In addition, a surface treatment of the filler(s) may be performed, for example with a fatty acid or a fatty acid ester such as a stearate, or with organosilanes, organosiloxanes, or organosilazanes hexaalkyl disilazane or short chain siloxane diols to render the filler(s) hydrophobic and therefore easier to handle and obtain a homogeneous mixture with the other sealant components The surface treatment of the fillers makes the ground silicate minerals easily wetted by the silicone polymer. These surface modified fillers do not clump, and can be homogeneously incorporated into the silicone polymer. This results in improved room temperature mechanical properties of the uncured compositions. Furthermore, the surface treated fillers give a lower conductivity than untreated or raw material.

[0114] The proportion of such fillers when employed will depend on the properties desired in the elastomer-forming composition and the cured elastomer. Usually the filler content of the composition will reside within the range from about 5 to about 500 parts by weight per 100 parts by weight of the polymer excluding the extender portion.

[0115] In the case where the polymer comprise OH groups or other hydrolysable groups (and the latter at least contains no unsaturated groups) then the cure package for curing the polymer is a suitable condensation cure package comprising a cross- linker and appropriate condensation catalyst.

[0116] Any suitable cross-linker for condensation (i.e. moisture) cure may be used. The cross-linker used in the moisture curable composition as hereinbefore described is preferably a silane compound containing hydrolysable groups. These include one or more silanes or siloxanes which contain silicon bonded hydrolysable groups such as acyloxy groups (for example, acetoxy, octanoyloxy, and benzoyloxy groups); ketoximino groups (for example dimethyl ketoximo, and isobutylketoximino); alkoxy groups (for example methoxy, ethoxy, an propoxy) and alkenyloxy groups (for example isopropenyloxy and l-ethyl-2-methylvinyloxy).

[0117] In the case of siloxane based cross-linkers the molecular structure can be straight chained, branched, or cyclic.

[0118] The moisture cure cross-linker may have two but preferably has three or four silicon-bonded condensable (preferably hydrolysable) groups per molecule. When the cross-linker is a silane and when the silane has three silicon-bonded hydrolysable groups per molecule, the fourth group is suitably a non-hydrolysable silicon-bonded organic group. These silicon-bonded organic groups are suitably hydrocarbyl groups which are optionally substituted by halogen such as fluorine and chlorine. Examples of such fourth groups include alkyl groups (for example methyl, ethyl, propyl, and butyl); cycloalkyl groups (for example cyclopentyl and cyclohexyl); alkenyl groups (for example vinyl and allyl); aryl groups (for example phenyl, and tolyl); aralkyl groups (for example 2-phenylethyl) and groups obtained by replacing all or part of the hydrogen in the preceding organic groups with halogen. Preferably however, the fourth silicon-bonded organic groups is methyl.

[0119] Silanes and siloxanes which can be used as cross-linkers include alkyltrialkoxysilanes such as methyltrimethoxysilane (MTM) and methyltriethoxysilane, alkenyltrialkoxy silanes such as vinyltrimethoxysilane and vinyltriethoxysilane, isobutyltrimethoxysilane (iBTM). Other suitable silanes include ethyltrimethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane, alkoxytrioximosilane, alkenyltrioximosilane, , 3,3,3-trifluoropropyltrimethoxysilane, methyltriacetoxysilane, vinyltriacetoxysilane, ethyl triacetoxysilane, di-butoxy diacetoxysilane, phenyl-tripropionoxysilane, methyltris(methylethylketoximo)silane, vinyl-tris-methylethylketoximo)silane, methyltris(methylethylketoximino)silane, methyltris(isopropenoxy)silane, vinyltris(isopropenoxy)silane, ethylpolysilicate, n- propylorthosilicate, ethylorthosilicate, dimethyltetraacetoxydisiloxane. The cross-linker used may also comprise any combination of two or more of the above.

[0120] The amount of cross-linker present in the composition will depend upon the particular nature of the cross-linker and in particular, the molecular weight of the molecule selected. The compositions suitably contain cross-linker in at least a stoichiometric amount as compared to the polymeric material described above. Compositions may contain, for example, from 2-30% w/w of cross-linker, but generally from 2 to 10% w/w. Acetoxy cross-linkers may typically be present in amounts of from 3 to 8 %w/w preferably 4 to 6 %w/w whilst oximino cross-linkers, which have generally higher molecular weights will typically comprise from 3-8% w/w.

[0121] The composition further comprises a condensation catalyst. This increases the speed at which the composition cures. The catalyst chosen for inclusion in a particular silicone sealant composition depends upon the speed of cure required. Any suitable condensation catalyst may be utilised to cure the composition. Particularly preferred catalysts for curing the moisture curable composition are the tin, lead, antimony, iron, cadmium, barium, manganese, zinc, chromium, cobalt, nickel, titanium, aluminium, gallium or germanium and zirconium based catalysts such as organic tin metal catalysts and 2-ethylhexoates of iron, cobalt, manganese, lead and zinc may alternatively be used. Organotin, titanate and/or zirconate based catalysts as hereinbefore described.

[0122] The present compositions containing polymers having two or more unsaturated groups is preferably cured and/or cross-linked by a hydrosilylation reaction catalyst in combination with an organohydrogensiloxane as the curing agent. In the case of hydrosilylation cure systems substantially all the polymer must, comprise a majority of polymer molecules which contain at least two unsaturated groups suitable for cross-linking with the organohydrogensiloxane. The unsaturated groups are typically alkenyl groups, most preferably vinyl groups. Any hydrosilylation reaction catalyst as hereinbefore described may be utilised for this purpose.

[0123] In this case curing such compositions the hydrosilylation catalyst may be added to the present composition in an amount equivalent to as little as 0.001 part by weight of elemental platinum group metal, per one million parts (ppm) of the composition. Preferably, the concentration of the hydrosilylation catalyst in the composition is that capable of providing the equivalent of at least 1 part per million of elemental platinum group metal. A catalyst concentration providing the equivalent of about 3-50 parts per million of elemental platinum group metal is generally the amount preferred.

[0124] To effect curing of the present composition, the organohydrogensiloxane cross-linker must contain more than two silicon bonded hydrogen atoms per molecule. The organohydrogensiloxane can contain, for example, from about 4-20 silicon atoms per molecule, and but could have a viscosity of up to about 10 Pa. s at 25⁰C. The silicon-bonded organic groups present in the organohydrogensiloxane can include substituted and unsubstituted alkyl groups of 1-4 carbon atoms that are otherwise free of ethylenic or acetylenic unsaturation. The organohydrogensiloxane which functions as a cross-linker contains an average of at least two silicon-bonded hydrogen atoms per molecule, and no more than one silicon- bonded hydrogen atom per silicon atom, the remaining valences of the silicon atoms being satisfied by divalent oxygen atoms or by monovalent hydrocarbon radicals comprising one to seven carbon atoms. The monovalent hydrocarbon radicals can be, for examples, alkyls such as methyl, ethyl, propyl, tertiary butyl, and hexyl; cylcoalkyls such as cyclohexyl; and aryls such as phenyl and tolyl. Such materials are well known in the art. The molecular structure of the organohydrogensiloxane may be linear, linear including branching, cyclic, or network-form or mixture thereof. There are no particular restrictions on the molecular weight of the organohydrogensiloxane, however it is preferable that the viscosity at 25⁰C be 3 to 10,000 mPa-s. Furthermore, the amount of cross-linker that is added to the composition is an amount such that the ratio of the number of moles of hydrogen atoms bonded to silicon atoms to the number of moles of alkenyl groups in the polymer and extender/plasticiser is in the range of 0.5: 1 to 20: 1, and preferably in the range of 1 :1 to 5:1. If this molar ratio is less than 0.5, curing of the present composition becomes insufficient, while if this molar ratio exceeds 20 hydrogen gas is evolved so that foaming occurs.

[0125] Optionally when the cure catalyst is a hydrosilylation catalyst particularly a platinum based catalyst a suitable hydrosilylation catalyst inhibitor may be required. Any suitable platinum group type inhibitor may be used. One useful type of platinum catalyst inhibitor is described in U.S. Pat. No. 3,445,420, which is hereby incorporated by reference to show certain acetylenic inhibitors and their use. A preferred class of acetylenic inhibitors are the acetylenic alcohols, especially 2- methyl-3-butyn-2-ol and/or l-ethynyl-2-cyclohexanol which suppress the activity of a platinum-based catalyst at 25⁰C. A second type of platinum catalyst inhibitor is described in U.S. Pat. No. 3,989,667, which is hereby incorporated by reference to show certain olefinic siloxanes, their preparation and their use as platinum catalyst inhibitors. A third type of platinum catalyst inhibitor includes polymethylvinylcyclosiloxanes having three to six methylvinylsiloxane units per molecule.

[0126] The optional cure package for the extenders/plasticisers are typically the same as used for the polymer above. Extender/plasticiser provided with at least two sterically unhindered condensable groups may be cured using any suitable condensation catalyst as hereinbefore described optionally in the presence of a condensable cross- linker also as hereinbefore described. Preferably in such a case the polymer is cured using a hydrosilylation process involving the incorporation of a suitable hydrosilylation catalyst as hereinbefore described together with a siloxane containing at least two Si-H bonds as hereinbefore described which acts as a cross-linker. The polymer may be cured prior to, simultaneously with or after the extender/plasticiser cure process. For example the composition might be heated in the absence of moisture to affect the hydrosilylation cure of the polymer and then moisture may be introduced to assist in the condensation cure of the extender/plasticiser or vice versa. Alternatively the hydrosilylation cure may take place in the presence of moisture thereby enabling simultaneous cure of both polymer and extender/plasticiser.

[0127] Analogously, Extender/plasticiser provided with at least two sterically unhindered unsaturated groups may be cured using any suitable hydrosilylation catalyst together with a siloxane containing at least two Si-H bonds as hereinbefore described which acts as a cross-linker. The polymer may be cured prior to, simultaneously with or after the extender/plasticiser cure process. For example the composition might be heated in the absence of moisture to affect the hydrosilylation cure of the extender/plasticiser and then moisture may be introduced to assist in the condensation cure of the polymer or vice versa. Alternatively the hydrosilylation cure may take place in the presence of moisture thereby enabling simultaneous cure of both polymer and extender/plasticiser.

[0128] Preferably in both alternatives provided above it is suggested that the hydrosilylation cure process is undertaken prior to or simultaneously with, but most preferably prior to, the condensation cure process, [0129] Other ingredients which may be included in the compositions include but are not restricted to co-catalysts for accelerating the cure of the composition such as metal salts of carboxylic acids and amines; rheological modifiers; Adhesion promoters, pigments, Heat stabilizers, Flame retardants, UV stabilizers, cure modifiers, electrically and/or heat conductive fillers, Fungicides and/or biocides and the like (which may suitably by present in an amount of from 0 to 0.3% by weight), water scavengers, (typically the same compounds as those used as cross-linkers or silazanes). It will be appreciated that some of the additives are included in more than one list of additives. Such additives would then have the ability to function in all the different ways referred to.

[0130] The rheological additives include silicone organic co-polymers such as those described in EP 0802233 based on polyols of polyethers or polyesters; non-ionic surfactants selected from the group consisting of polyethylene glycol, polypropylene glycol, ethoxylated castor oil, oleic acid ethoxylate, alkylphenol ethoxylates, copolymers or ethylene oxide (EO) and propylene oxide (PO), and silicone polyether copolymers; as well as silicone glycols. For some systems rheological additives, particularly copolymers of ethylene oxide (EO) and propylene oxide (PO), and silicone polyether copolymers may enhance the adhesion of the sealant to substrates, particularly plastic substrates.

[0131] Any suitable adhesion promoter(s) may be incorporated in a sealant composition in accordance with the present invention. These may include for example alkoxy silanes such as aminoalkylalkoxy silanes, epoxyalkylalkoxy silanes, for example, 3-glycidoxypropyltrimethoxysilane and, mercapto-alkylalkoxy silanes and γ-aminopropyl triethoxysilane, reaction products of ethylenediamine with silylacrylates. Isocyanurates containing silicon groups such as 1,3,5- tris(trialkoxysilylalkyl) isocyanurates may additionally be used. Further suitable adhesion promoters are reaction products of epoxyalkylalkoxy silanes such as 3- glycidoxypropyltrimethoxysilane with amino-substituted alkoxysilanes such as 3- aminopropyltrimethoxysilane and optionally alkylalkoxy silanes such as methyl- trimethoxysilane. epoxyalkylalkoxy silane, mercaptoalkylalkoxy silane, and derivatives thereof.

[0132] Heat stabilizers may include Iron oxides and carbon blacks, Iron carboxylate salts, cerium hydrate, barium zirconate, cerium and zirconium octoates, and porphyrins.

[0133] Flame retardants may include for example, carbon black, hydrated aluminium hydroxide, and silicates such as wollastonite, platinum and platinum compounds.

[0134] Electrically conductive fillers may include carbon black, metal particles such as silver particles any suitable, electrically conductive metal oxide fillers such as titanium oxide powder whose surface has been treated with tin and/or antimony, potassium titanate powder whose surface has been treated with tin and/or antimony, tin oxide whose surface has been treated with antimony, and zinc oxide whose surface has been treated with aluminium.

[0135] Thermally conductive fillers may include metal particles such as powders, flakes and colloidal silver, copper, nickel, platinum, gold aluminium and titanium, metal oxides, particularly aluminium oxide (Al₂O₃) and beryllium oxide (BeO);magnesium oxide, zinc oxide, zirconium oxide; Ceramic fillers such as tungsten monocarbide, silicon carbide and aluminium nitride, boron nitride and diamond.

[0136] Any suitable Fungicides and biocides may be utilised, these include N- substituted benzimidazole carbamate, benzimidazolylcarbamate such as methyl 2- benzimidazolylcarbamate, ethyl 2-benzimidazolylcarbamate, isopropyl 2- benzimidazolylcarbamate, methyl N-{2-[l-(N,N- dimethylcarbamoyl)benzimidazolyl]} carbamate, methyl N-{2-[l-(N,N- dimethylcarbamoyl)-6-methylbenzimidazolyl] } carbamate, methyl N- {2-[ 1 -(N,N- dimethylcarbamoyl)-5-methylbenzimidazolyl] } carbamate, methyl N- {2-[ 1 -(N- methylcarbamoyl)benzimidazolyl] }carbamate, methyl N-{2-[l-(N- methylcarbamoyl)-6-methy lbenzimidazolyl] } carbamate, methyl N- { 2-[ 1 -(N- methylcarbamoyl)-5-methylbenzimidazolyl]} carbamate, ethyl N-{2-[l-(N,N- dimethylcarbamoyl)benzimidazolyl]} carbamate, ethyl N- { 2-[2-(N- methylcarbamoyl)benzimidazolyl]} carbamate, ethyl N-{2-[l-(N,N- dimethylcarbamoyl)-6-methylbenzimidazolyl] } carbamate, ethyl N- {2-[ 1 -(N- methylcarbamoyl)-6-methylbenzimidazolyl] } carbamate, isopropyl N- {2-[ 1 -(N,N- dimethylcarbamoyl)benzimidazolyl] } carbamate, isopropyl N- {2-[ 1 -(N- methylcarbamoyl)benzimidazolyl]} carbamate, methyl N-{2-[l-(N- propylcarbamoyl)benzimidazolyl]} carbamate, methyl N-{2-[l-(N- butylcarbamoyl)benzimidazolyl] } carbamate, methoxyethyl N- {2-[ 1 -(N- propylcarbamoyl)benzimidazolyl] } carbamate, methoxyethyl N- {2-[ 1 -(N- butylcarbamoyl)benzimidazolyl]} carbamate, ethoxyethyl N-{2-[l-(N- propylcarbamoyl)benzimidazolyl] } carbmate, ethoxyethyl N- {2-[ 1 -(N- butylcarbamoyl)benzimidazolyl]} carbamate, methyl N-( I-(N ,N- dimethylcarbamoyloxy)benzimidazoly 1] } carbamate, methyl N- { 2-[N- methylcarbamoyloxy)benzimidazolyl]} carbamate, methyl N- (2-[1-(N- butylcarbamoyloxy)benzoimidazolyl] } carbamate, ethoxyethyl N- {2-[ 1 -(N- propylcarbamoyl)benzimidazolyl] } carbamate, ethoxyethyl N- { 2-[ 1 -(N- butylcarbamoyloxy)benzoimidazolyl]} carbamate, methyl N-{2 -[1-(N₅N- dimethylcarbamoyl)-6-chlorobenzimidazolyl]} carbamate, and methyl N-{2-[l-(N,N- dimethylcarbamoyl)-6-nitrobenzimidazolyl] } carbamate. 10, 10'-oxybisphenoxarsine (trade name: Vinyzene, OBPA), di-iodomethyl-para-tolylsulfone, benzothiophene-2- cyclohexylcarboxamide-S,S-dioxide, N-(fluordichloridemethylthio)phthalimide (trade names: Fluor-Folper, Preventol A3). Methyl-benzimideazol-2-ylcarbamate (trade names: Carbendazim, Preventol BCM), Zinc-bis(2-pyridylthio-l -oxide) (zinc pyrithion) 2-(4-thiazolyl)-benzimidazol, N-phenyl-iodpropargylcarbamate, N-octyl-4- isothiazolin-3-on, 4,5-dichloride-2-n-octyl-4-isothiazolin-3-on, N-butyl- 1 ,2- benzisothiazolin-3-on and/or Triazolyl-compounds, such as tebuconazol in combination with zeolites containing silver. [0137] Other optional ingredients which may be incorporated in the composition of a high consistency silicone rubber include handling agents, acid acceptors, and UV stabilisers.

[0138] Handling agents are used to modify the uncured properties of the silicone rubber such as green strength or processability sold under a variety of trade names such as SILASTIC^® HA-I, HA-2 and HA-3 sold by Dow Corning corporation)

[0139) The acid acceptors may include Magnesium oxide, calcium carbonate, Zinc oxide and the like.

[0140] The ceramifying agents can also be called ash stabilisers and include silicates such as wollastonite.

[0141] The silicone rubber composition in accordance with this embodiment may be made by any suitable route, for example one preferred route is to first make a silicone rubber base by heating a mixture of fumed silica, a treating agent for the silica, and the diluted organopolysiloxane containing polymer of the present invention. The silicone rubber base is removed from the first mixer and transferred to a second mixer where generally about 150 parts by weight of a non-reinforcing or extending filler such as ground quartz is added per 100 parts by weight of the silicone rubber base. Other additives are typically fed to the second mixer such as curing agents, pigments and colouring agents, heat stabilizers, anti-adhesive agents, plasticizers, and adhesion promoters. In a second preferred route the diluted organopolysiloxane containing polymer of the present invention and any desired filler plus any desired treating agent are fed into a reactor and mixed, further additives as described above including cure agents are then fed into the same reactor and further mixed.

[0142] Hence in a further embodiment of the present invention there is provided an extended and/or plasticised organopolysiloxane composition capable of cure to an elastomeric body, the composition comprising A polysiloxane containing polymer at least one independently curable extender and/or plasticiser Filler and a suitable first cure system adapted to cure the polymer and optionally a second cure system adapted to independently cure the extender and/or plasticiser within the elastomeric body.

(0143] In a still further embodiment of the present invention there is provided an extended and/or plasticised organopolysiloxane composition capable of cure to an elastomeric body obtainable in accordance with the following steps:-

(i) Preparing an extended and/or plasticised polysiloxane containing polymer by intermixing the polymer and/or precursors thereof with an extender and/or plasticiser during or subsequent to polymerisation of the polysiloxane containing polymer

(ii) Mixing the resulting polysiloxane containing polymer product with: Filler and a suitable first cure system to form a curable composition; characterised in that the extender and/or plasticiser is chemically functionalised so as to substantially not participate in any chemical reaction(s) with the polymer and/or its precursors during step (i) or step (ii) but is independently chemically curable, optionally in combination with a second cure system, prior to, simultaneously with or subsequent to cure of the curable composition.

[0144] The compositions provided in accordance with the present invention are made in accordance with any method as hereinbefore described and may comprise any combination of components hereinbefore described as well as any additive or combination of additives as hereinbefore described.

[0145] Elastomers prepared from silicone rubber compositions in accordance with the present invention may be used in a wide variety of applications including in the manufacture of for example:- automotive, aviation and aerospace products, babycare products such as teats for bottles, insulators for power and utilities applications, extruded profiles, gaskets and seals for e.g. air water, fuel and oil applications e.g. hoses, keypads, in medical and office equipment such as protective equipment and masks, rollers for e.g. photocopiers, sponges, and wire and cable coating applications.

(0146) The invention will now be described by way of Example.

EXAMPLES

[0147] In the following examples all viscosity measurements relating to organopolysiloxane polymers were taken at 25⁰C unless otherwise indicated. All reference to parts are in terms of parts by weight unless otherwise indicated.

EXAMPLE 1: BASE PREPARATION

[0148] A mixture of 80 parts by weight of a silanol end-blocked poly- dimethylsiloxane, (Mn = 2400, average degree of polymerisation (DP) = 30, Viscosity of 70mPa.s) with 20 parts by weight of a vinyldimethylsiloxy end-blocked polydimethylsiloxane diluent, (Viscosity 9,500 mPa.s) was prepared and charged to a Brabender plasticorder mixer. Dodecylbenzene sulphonic Acid (DBSA), (5 parts by weight vs. total siloxane), was then added and well mixed. Polymerisation was allowed to proceed at room temperature. After 90 minutes the reaction mixture was neutralised with Magnesium Oxide.

[0149] To the resulting product was added 100 parts by weight of a methyltrimethoxysilane treated calcined Kaolin prepared according to methods described in WO 2005/054352. The mix was mixed in a Brabender plasticorder mixer at 20 rpm for 90 minutes to give a siloxane rubber base 1.

EXAMPLE 2: COMPARATIVE

THERMAL CURE ONLY OF SILOXANE RUBBER BASE 1

[0150] The siloxane rubber base 1 was mixed with 0.5 parts of a Vinyl siloxane - Platinum complex (0.12% Pt by weight); 0.4 parts of a Dimethyl-methylhydrogen siloxane copolymer (15 mPa.s, 0.85% SiH as H) and 0.1 parts of 1-Ethynyl-l- Cyclohexanol on a two roll mill. This mix was stored for 2 weeks and then cured for 10 minutes at 150 °C under 2MPa pressure in a suitable mould to give a test sheet, this sheet was very soft and tore easily, table 1. [0151] Samples of this mix were tested on a moving die rheometer (Alpha Technologies RPA 2000, 0.5 degree strain, 100 cpm, temperature ramp from 50 to 170 ⁰C over 15 minutes) and the results are provided in Table 2 below.

EXAMPLE 3: COMPARATIVE

MOISTURE CURE ONLY OF SILOXANE RUBBER BASE 1

[0152] The siloxane rubber base 1 was mixed with 0.5 parts of a solution of Bis(2- ethylhexyloxy) titanium bis(2,4-pentanedionate) 66 wt% 2-Ethylhexanol and 2 parts of Methyltrimethoxysilane on a two roll mill. This mix was stored for 2 weeks under ambient conditions and did not fully cure during this time. Attempts to thermally cure this material for 10 minutes at 150 ⁰C under 2MPa pressure in a suitable mould gave a very soft foam product that could not be further tested.

EXAMPLE 4

MOISTURE AND THERMAL CURE OF SILOXANE RUBBER BASE 1

[0153] The siloxane rubber base 1 was mixed with 0.5 parts by weight of a Vinyl siloxane - Platinum complex (0.12% Pt by weight); 0.4 parts by weight of a Dimethyl-methylhydrogen siloxane copolymer (15 mPa.s, 0.85% SiH as H); 0.1 parts by weight of 1-Ethynyl-l-Cyclohexanol; 0.1 parts by weight of a solution of Bis(2- ethylhexyloxy) titanium bis(2,4-pentanedionate) 66 wt% 2-Ethylhexanol and 1 part of Methyltrimethoxysilane on a two roll mill.

[0154) This mix was stored for 2 weeks under ambient conditions and did not cure during this time. This mix was stored for 2 weeks and then cured for 10 minutes at 150 ⁰C under 2MPa pressure in a suitable mould to give a test sheet. No evidence of foaming during thermal cure was observed, table 1. [0155) Samples of this mix were tested on a moving die rheometer (Alpha Technologies RPA 2000, 0.5 degree strain, 100 cpm, temperature ramp from 50 to 170 ⁰C over 15 minutes), table 2.

EXAMPLE 5

MOISTURE AND THERMAL CURE OF SILOXANE RUBBER BASE 1, AS EXAMPLE 4 BUT HIGHER MOISTURE CURE LOADINGS

[0156] The siloxane rubber base 1 was mixed with 0.5 parts of a Vinyl siloxane - Platinum complex (0.12% Pt by weight); 0.4 parts of a Dimethyl-methylhydrogen siloxane copolymer (15 mPa.s, 0.85% SiH as H); 0.1 parts of 1-Ethynyl-l- Cyclohexanol; 0.5 parts of a solution of Bis(2-ethylhexyloxy) titanium bis(2,4- pentanedionate) 66 wt% 2-Ethylhexanol and 2 parts of Methyltrimethoxysilane on a two roll mill.

[0157] This mix was stored for 2 weeks under ambient conditions and did not cure during this time. This mix was stored for 2 weeks and then cured for 10 minutes at 150 ⁰C under 2MPa pressure in a suitable mould to give a test sheet. No evidence of foaming during thermal cure was observed, table 1.

[0158] Samples of this mix were tested on a moving die rheometer (Alpha Technologies RPA 2000, 0.5 degree strain, 100 cpm, temperature ramp from 50 to 170 °C over 15 minutes), table 2.

TABLE 1

TABLE 2

[0159] The increase in minimum S' values after 2 weeks for examples 3, 4 and 5 shows evidence of moisture cure on storage. Only when both cure systems are combined, examples 4 and 5, can a good test sheet be obtained and in these cases maximum S' values, tensile strengths and hardness all increase whilst elongation at break decreases. This shows evidence of increased cross-link density compared to a single cure, example 2.

Claims

1. A method for the production of an extended and/or plasticised organopolysiloxane composition comprising the steps:-

2. A method for the production of a cured organopolysiloxane based elastomer comprising the steps of

(i) Preparing an extended and/or plasticised polysiloxane containing polymer by intermixing the polymer and/or precursors thereof with an extender and/or plasticiser and optionally filler prior to and/or during polymerisati of the polysiloxane containing polymer

(ii) Mixing the resulting extended and/or plasticised polysiloxane contain: polymer product with:

Filler and optionally residual extender or plasticiser; and a suitable cure system to form a curable composition; and (iii) curing the resulting polymer composition to form a cured elastomer hav a cross-linked matrix; characterised in that the extender and/or plasticiser is chemically functionalised so as to substantially not participate in any chemical reaction(s) with the polymer and/or its precursors during steps (i) (ii) or (iii) but is independently chemically cured during step (iii), optionally in combination with a second cure system, prior to, simultaneously with or subsequent to polymer composition cure.

3. A method for the production of an extended and/or plasticised organopolysiloxane composition comprising the steps:-

(ii) Mixing the resulting polysiloxane containing polymer product with: Filler and optionally residual extender and/or plasticiser; and a suitable first cure system to form a curable composition; characterised in that the extender and/or plasticiser is chemically functionalised so as to substantially not participate in any chemical reaction(s) with the polymer and/or its precursors during step (i) or step (ii) but is independently chemically curable, optionally in combination with a second cure system, prior to, simultaneously with or subsequent to cure of the curable composition.

4. A method in accordance with claim 1, 2 or 3 characterised in that the extend and/or plasticised polysiloxane containing polymer is prepared by blending extender and/or plasticiser with a pre-formed polymer.

5. A method in accordance with claim 1 2 or 3 characterised in that extended and plasticised polysiloxane containing polymer is prepared by means of polymerisation process wherein siloxane containing monomers and/or oligomers ; polymerised in the presence of the extender and/or plasticiser, a suitable catalyst and optionally an end-blocking agent and/or fillers; and Where required quenching the polymerisation process.

6. A method in accordance with claim 5 characterised in that the polymerisation process is a polycondensation process and the catalyst is a condensation catalyst.

7. A method in accordance with claim 5 or 6 characterised in that each siloxane containing polymer, monomer and/or oligomer comprise at least two condensable groups selected from -OH groups and alkoxy groups having from 1 to 10 carbon atoms.

8. A method in accordance with claim 7 characterised in that in that the extender and/or plasticiser contains at least two organic unsaturated groups having from 2 to 10 carbon atoms and no condensable groups.

9. A method in accordance with claim 8 characterised in that the unsaturated groups are alkenyl groups or alkynyl groups.

10. A method in accordance with any preceding claim characterised in that the polymer is cured via a condensation process and the extender and/or plasticiser is cured via a hydrosilylation process.

1 1. A method in accordance with claim 5 characterised in that the polymerisati process is a polyaddition process.

12. A method in accordance with claim 1 1 in that the polyaddition process is hydrosilylation polymerisation process.

13. A method in accordance with claim 12 characterised in that at least 50% of I siloxane containing monomers and/or oligomers comprise at least two unsatural organic groups having from 2 to 10 carbon atoms per molecule and the remaining siloxane containing monomers and/or oligomers comprise at least two Si-H bonds per molecule.

14. A method in accordance with any one of claims 12 or 13 characterised in that the extender and/or plasticiser contains at least two groups selected from hydroxyl groups and/or alkoxy groups having from 1 to 10 carbon atoms and no unsaturated groups or groups comprising Si-H bonds.

15. A method in accordance with any one of claims 12 to 14 characterised in that the polymer is cured via a hydrosilylation process and the extender and/or plasticiser is cured via a condensation reaction.

16. A method in accordance with any preceding claim characterised in that the polymer composition additionally comprises one or more additives selected from rheological modifiers; adhesion promoters, pigments, Heat stabilizers, Flame retardants, UV stabilizers, Chain extenders, electrically and/or heat conductive fillers, Fungicides and/or biocides

17. A silicone rubber made in accordance with the method of any preceding claim.

18. An extended and/or plasticised organopolysiloxane composition capable of cure to an elastomeric body, the composition comprising

A polysiloxane containing polymer prepared in accordance with claim 1, 2 or 3 at least one independently curable extender and/or plasticiser

Filler and a suitable first cure system adapted to cure the polymer and optionally a second cure system adapted to independently cure the extender and/or plastici; within the elastomeric body.

9. An extended and/or plasticised organopolysiloxane composition capable of cure to an elastomeric body obtainable in accordance with the following steps:-

(i) Preparing an extended and/or plasticised polysiloxane containing polymer by intermixing the polymer and/or precursors thereof with an extender and/or plasticiser and optionally filler prior to and/or during polymerisation of the polysiloxane containing polymer

(ii) Mixing the resulting polysiloxane containing polymer product with: Any residual filler and residual extender and/or plasticiser a suitable first cure system to form a curable composition; characterised in that the extender and/or plasticiser is chemically functionalised so as to substantially not participate in any chemical reaction(s) with the polymer and/or its precursors during step (i) or step (ii) but is independently chemically curable, optionally in combination with a second cure system, prior to, simultaneously with or subsequent to cure of the curable composition.