WO1993011167A1

WO1993011167A1 - Polymerisation process

Info

Publication number: WO1993011167A1
Application number: PCT/GB1992/002204
Authority: WO
Inventors: Rowena Jane Sellens; Anthony Pickering; Peter James Inglis Runciman
Original assignee: Imperial Chemical Industries Plc
Priority date: 1991-12-05
Filing date: 1992-11-27
Publication date: 1993-06-10
Also published as: GB9125928D0; TW219941B; GB9224742D0; AU2952992A

Abstract

A polymerisation process for preparing a polymerisable composition comprising a polymer, e.g. (poly)methyl acrylate, and a monomeric component, e.g. methyl methacrylate, which process employs selective catalytic polymerisation of the methyl acrylate monomer, e.g. using an organosilicon catalyst, in the presence of the methyl methacrylate monomer to produce a solution or dispersion without the need for initially preparing the polymer in isolation.

Description

POLYMERISATION PROCESS

The present invention relates to a process for preparing polymer in monomer compositions, which process comprises contacting a monomer composition comprising a mixture of ethylenically unsaturated, addition poiymerisable monomers with a polymerisation catalyst which selectively effects the polymerisation of a particular ethylenically unsaturated, addition poiymerisable monomer contained in the said monomer composition. In this specification, the term polymer includes oligomer.

Poiymerisable compositions comprising a polymer dissolved or dispersed in an ethylenically unsaturated, addition poiymerisable monomer are conventionally prepared by blending a preformed polymer in the monomer. The preparation of polymer in monomer compositions using this technique therefore involves two distinct steps, in the first of which the polymer is prepared and in the second of which the thus formed polymer is dissolved or dispersed in the monomer. Such a technique is far from ideal, particularly as the process of dispersing or dissolving the polymer in the monomer may require long periods of vigorous mixing. The present applicants have found a new and useful technique for preparing, in what is effectively a single step process, a poiymerisable composition comprising a polymer and an ethylenically unsaturated, addition poiymerisable monomer. The polymer may be either in solution in the monomer or in a state of dispersion therein.

According to the present invention there is provided a process for preparing a poiymerisable composition comprising: (i) an addition polymerised polymer species, and (ii) at least one ethylenically unsaturated, addition poiymerisable monomer, said process comprising contacting a poiymerisable composition comprising a first ethylenically unsaturated, addition poiymerisable monomer or monomer mixture and a second ethylenically unsaturated, addition poiymerisable monomer or monomer mixture with a catalyst system which selectively polymerises the first monomer or monomer mixture.

In talking about the selective polymerisation of the first monomer or monomer mixture, we do not, of course, exclude the possibility that a small proportion of the second monomer or monomer mixture may also polymerise in the process, say up to δ % by weight thereof. Furthermore, we do not exclude the possibility that a minor proportion of the first monomer or monomer mixture, say up to 30 % by weight thereof, may not react in the process of the invention. However, in the preparation of polymer in monomer compositions by the process of the present invention, it is an essential requirement of the process that the first monomer or monomer mixture, or a substantial proportion thereof, is polymerised exclusively or substantially exclusively in the presence of the second monomer or monomer mixture. Preferably, of course, the polymerisation of the first monomer or monomer mixture is complete, or essentially complete, and is exclusive of any polymerisation of the second monomer or monomer mixture.

The process of the present invention may, of course, be carried out in the presence of an inert solvent vehicle (described hereinafter).

The selective polymerisation which characterises the process of the present invention can be obtained by employing a catalyst system which is effective for polymerising the first monomer or monomer mixture, but ineffective for polymerising the second monomer or monomer mixture. Alternatively, the selective polymerisation may be achieved by employing a catalyst system which is able to differentiate between the polymerisation reactivities of the various ethylenically unsaturated monomers contained in a poiymerisable composition and effect selective polymerisation of the higher reactivity monomer(s) therein. With such a catalyst system the monomer or monomers forming the first monomer or monomer mixture should be appreciably more reactive than the monomer or monomers forming the second monomer or monomer mixture.

With the process of the present invention, poiymerisable compositions comprising a polymer and an addition poiymerisable, ethylenically unsaturated monomer(s) can be readily prepared. In effect, the second monomer or monomer mixture, optionally together with an inert solvent vehicle, functions as a reaction medium in which the first monomer or monomer mixture is polymerised. After the polymerisation process of the invention is complete, the second monomer or monomer mixture, optionally together with an inert solvent, constitutes a liquid vehicle in which the polymer derived from the first monomer or monomer mixture is dispersed or dissolved. The second monomer or monomer mixture can then be polymerised, either before or after removal of the inert solvent where it is used, to yield the desired polymeric product. Such a polymeric product may comprise discrete polymers respectively formed from the first and second monomers or monomer mixtures. For example, the polymer derived from the second monomer or monomer mixture may form a continuous phase in which the polymer derived from the first monomer or monomer mixture is present as a discontinuous phase.

In one particular embodiment of the present invention, the catalyst system which is used yields a living polymer which contains terminal and/or pendent initiating sites and is capable of further polymerisation. By using such a catalyst system, the living polymer produced on polymerising an initial charge of a first monomer or monomer mixture in the presence of the second monomer or monomer mixture may participate in a further polymerisation reaction with a subsequent charge of a different first monomer or monomer mixture to yield a diblock copolymer. The diblock copolymer which is formed is also living, and can therefore participate in yet another polymerisation reaction involving yet another charge of a first monomer or monomer mixture to produce a triblock copolymer. Thus, poiymerisable compositions comprising a block copolymer having any number of blocks, and an ethylenically unsaturated monomer (i.e. the second monomer or monomer mixture) may be prepared by successively polymerising an initial charge and one or more subsequent charges of a first monomer or monomer mixture in the presence of the second monomer or monomer mixture. The block copolymers will comprise two or more polymer blocks respectively derived from the initial charge and subsequent charge(s) of the first monomer or monomer mixture.

In the process of the invention, the first monomer or monomer mixture may comprise or consist of a monomer containing a first ethylenically unsaturated, addition poiymerisable group(s) which polymerises on contact with the catalyst system, and a second ethylenically unsaturated, addition poiymerisable group which is either unreactive in the presence of the catalyst system, or which exhibits an appreciably lower reactivity than the first ethylenically unsaturated group, so that the said first group can be caused to polymerise selectively. In this way, the polymerisation of the first monomer or monomer mixture results in the formation of a polymer containing reactive ethylenic unsaturation which can copolymerise with the second monomer or monomer mixture in which it is dissolved or dispersed to form a cross-linked polymer. The copolymerisa ion of the ethylenically unsaturated polymer derived from the first monomer or monomer mixture with the second monomer or monomer mixture may be achieved using free radical, cationic, anionic or group transfer polymerisation techniques.

The preferred catalyst systems for use in the process of the present invention are two component catalyst systems comprising:

(a) at least one tetracoordinate organosilicon, organotin or organogermanium initiator having at least one initiating site in which a silicon, tin or germanium atom is bound by a nitrogen, phosphorous or arsenic atom to a nitrogen, phosphorous or arsenic containing organic group which is devoid of reactive hydrogen atoms ; and

(b) at least one nucleophilic co-catalyst. The above catalyst systems are able to distinguish between the reactivities of the monomers contained in a poiymerisable composition, and are capable of selectively polymerising a higher reactivity ethylenically unsaturated monomer(s) contained in a poiymerisable composition comprising said higher reactivity monomer(s) and a lower reactivity ethylenically unsaturated monomer(s) .

Moreover, the above catalyst systems result in the formation of living polymers, so that an initial and one or more subsequent charges of higher reactivity monomers can be successively polymerised in the presence of a lower reactivity monomer or monomer mixture so as to produce a block copolymer having any number of blocks.

For example, acrylic acid ester monomers (acrylates) are appreciably more reactive than methacrylic acid ester monomers (methacrylates). Accordingly, the above catalyst systems can be used to selectively polymerise an acrylate monomer(s) in the presence of a methacrylate monomer(s) to generate a poiymerisable resin comprising an acrylate homopolymer or copolymer (random or block) dispersed or dissolved in a methacrylate monomer(s). The methacrylate monomer portion of the poiymerisable composition may be subsequently polymerised by a different (second) catalyst system, e.g. a free radical, cationic or anionic catalyst system, to form a polymeric composition which comprises polymerised residues derived from the acrylate and methacrylate monomers. The catalyst for the polymerisation of the methacrylate monomer may be added after the reaction to form the acrylate polymer is complete. Alternatively, such catalyst may be added before the acrylate monomer(s) is polymerised, provided that it does not interfere with the polymerisation reaction to form the acrylate polymer, and provided that the conditions under which the acrylate monomer(s) is polymerised do not activate such catalyst. In practice, for heat activated free radical catalysts, this means keeping the temperature of the acrylate polymerisation reaction below that at which the catalyst is activated.

The acrylate monomer may carry one or more other ethylenically unsaturated groups which are either unreactive in the presence of the two component catalyst systems described above or are of lower reactivity than the acrylate double bond, so that the acrylate double bonds can be selectively polymerised in the polymerisation process leaving the lower reactivity unsaturated groups essentially unreacted. In this way, the poiymerisable process of the invention can be used to generate a cross-linkable poiymerisable composition in which the acrylate polymer bears pendent ethylenically unsaturated groups for reaction which the methacrylate monomer(s) in which it is dissolved or dispersed. Such compositions may be subsequently polymerised using the techniques described above. Suitable ethylenically unsaturated groups which are either unreactive in the presence of such two component catalysts or which are of lower reactivity than acrylate groups are methacrylate, allyl and vinyl groups.

The above described two component catalyst system can also be ' used to selectively polymerise an acrylate or methacrylate monomer(s) in a monomer composition comprising said acrylate or methacrylate monomer(s) and at least one other ethylenically unsaturated monomer which does not react or react to any appreciable extent in the presence of the polymerising acrylate or methacrylate monomer(s) and which does not disrupt or interfere with the operation of the catalyst system with respect to the polymerisation of the acrylate or methacrylate monomer(s). In this embodiment of the present invention, suitable second monomers may be selected from the vinyl aromatic monomers or the conjugated dienes.

When the two component catalyst systems described above are used to effect the polymerisation process of the present invention, suitable acrylate monomers for the first monomer or monomer mixture are the acrylate monomers which do not contain any functional groups possessing acidic hydrogen atoms. Such monomers are known to those skilled in the art and include, in particular, monomers having the formula CH_=CHC0.0R where R is an alkyl, aryl, aralkyl, alkaryl or cycloalkyl group. The preferred acrylate monomers are the alkyl acrylates having the formula CH =CHCO.OR^a where R is a C, .. alkyl group. Preferred monomers therefore include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate and hexyl acrylate. Other suitable acrylate monomers include glycidyl acrylate and the trialkoxysilylalkyl acrylate monomers such as 3-{trimethoxysilyl) ropyl acrylate.

When the two component catalyst systems described above are used to effect the polymerisation process of the present invention, suitable acrylate monomers containing at least one other ethylenically unsaturated group include allyl acrylate and 2-(methacryloyloxy)ethyl acrylate.

When the two component catalyst systems described above are used to effect the polymerisation process of the present invention, suitable methacrylate monomers for the first or second monomer or monomer mixture are the methacrylate monomers which do not contain any functional groups possessing acidic hydrogen atoms. Such monomers are known to those skilled in the art, and include, in particular, monomers having the formula CH₂=C(CH,)C0.0R where R is an alkyl, aryl, aralkyl, alkaryl or cycloalkyl group. The preferred methacrylate monomers are the o fl. alkyl methacrylates having the formula CH„=C(CH„)C0.0R where R is a C_._₁₀ alkyl group. Preferred monomers therefore include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate and hexyl methacrylate. Methyl methacrylate is an especially preferred methacrylate monomer.

When the two component catalyst systems described above are used to effect the polymerisation process of the present invention, suitable aromatic vinyl monomers for the second monomer or monomer mixture are the aromatic vinyl monomers which do not contain any functional groups possessing acidic hydrogen atoms. Such monomers are known to those skilled in the art, and include, in particular, styrene and substituted derivatives of styrene such as the halogenated derivatives thereof and vinyl toluene.

When the two component catalyst systems described above are used to effect the polymerisation process of the present invention, a suitable conjugated diene monomer for the second monomer or monomer mixture is butadiene.

Under the polymerisation process conditions the co-catalyst component (b) must be available to effect polymerisation of the first monomer or monomer mixture, and this often means it must be at least partially soluble in at least one liquid monomer species or in an inert liquid solvent which is compatible with the monomers. Thus, if the co-catalyst is not soluble in a monomer, an inert solvent may be used in the polymerisation process in sufficient quantities to effect dissolution of the co-catalyst.

By an inert solvent, we mean a solvent which does not react in, or in any way interfere with the polymerisation process.

Therefore, suitable solvents are in general compounds which do not contain labile hydrogen or halogen atoms or activated alkenyl groups. Examples of suitable inert solvents or vehicles include ether solvents such as diethyl ether, dimethoxyethane, diethoxyethane, diethylene glycol dimethyl ether or tetrahydrofuran; and hydrocarbon solvents such as benzene, toluene or xylene.

Suitable nucleophilic co-catalysts are salts which comprise a nucleophilic anion and a cation which is inert under the polymerisation conditions of the process, yet renders the co-catalyst available in the polymerising medium to effect polymerisation.

Where the co-catalyst component is a salt, suitable anions are selected from azide, cyanide, cyanate, fluoride, bifluoride, nitrate, nitrite and organic mono- and poly- phosphonates, phosphinates, sulphonates, sulphinates, carboxylates, siloxides and oxides. The organic anions include the aromatic, alicyclic and aliphatic anions and the organic groups may be substituted, e.g. by electron withdrawing groups such as cyano, halo including chloro and fluoro, and nitro in aromatic groups. The preferred anions in the co-catalyst component are fluoride, bifluoride and the aliphatic or aromatic mono-sulphonates, in particular fluoride, bifluoride and methanesulphonate ions. Preferred cations in the co-catalyst salt are the organo-substituted -onium cations, in particular quaternary ammonium, quaternary phosphonium, and tris(dialkylamino)-sulphonium cations, often substituted by C„_„ alkyl groups such as butyl. More preferably, the cation is a tetraalkylammonium or tris(dialkylamino)-sulphonium cation in which the alkyl groups contain from 1 to 20, preferably from 1 to

8 carbon atoms. Tetraalkylammonium cations are especially preferred.

Alkali and alkaline earth metal cations are less preferred, but co-catalyst salts comprising such cations may possibly be used, particularly if a solubilisation aid, such as a crown ether, is used in the polymerisation process to complex the cations.

Lewis acids and non-ionic Lewis bases may also be useful as a co-catalyst component.

The initiator may be soluble in at least one liquid monomer species or in an inert liquid solvent which is compatible with the monomers. Alternatively, the initiator may be in insoluble form or comprised in an insoluble composition together with an insoluble catalyst support.

A suitable initiator component (a) for use in the process of the present invention is one having the formula:

MX Y Z I m n p wherein

M is a tetravalent Si, Ge or Sn atom; X, Y and Z are bonded to H; m is an integer and denotes the number of X groups bonded to

M; n is an integer and denotes the number of Y groups bonded to

M; p is 0 or an integer and denotes the number of Z groups bonded to M; m + n + p = 4; each X is independently a group R²

I I

- - C( ²) - Q¹ - R³

R¹ where and are independently N, P or As; ² is 0, S, NR' or PR' where R' is C alkyl;

1 R is H or an optionally substituted hydrocarbyl group; and

2 3 R and R are each independently optionally substituted hydrocarbyl groups, or R and R together are an optionally substituted hydrocarbadiyl group;

1 2 3 all such R , R and R groups being inert in the conditions of the polymerisation process of the present invention; each Y is independently an optionally substituted hydrocarbyl or hydrocarbyloxy group which is inert in the conditions of the polymerisation process of the present invention, or trialkylsilylalkyl; and each Z (where present) is independently any group as defined for Y or an organic oligomer or polymer radical comprising further

MX Y moieties, m n

In the initiator component of Formula I: M is preferably Si.

The term optionally substituted in relation to groups Y and Z

1 2 3 and the R , R and R groups within X includes substitution by pendent monovalent or divalent atoms or groups and substitution by

1 ^~ 3 in-chain hetero-atoms. In relation to groups R , R" and R , the in-chain heteroatom may be directly bonded to or as appropriate. It will be appreciated that although bonds between M and at least one of X, Y or Z break in the catalytic process of the present invention, the groups themselves should be inert in the process conditions. For this reason such groups, even when described as optionally substituted, are often unsubstituted by pendent monovalent substituents.

Unsubstituted hydrocarbyl and hydrocarbadiyl groups tend to be inert in the conditions of the process of the present invention.

Hydrocarbyl and hydrocarbadiyl groups which are substituted and also inert in the conditions of the process of the present invention may include such groups substituted by electron donor groups, e.g. amino substituted by organic groups such as alkyl, cycloalkyl and alkoxy.

Within X as hereinbefore defined each of Q and are preferably N and ? is preferably 0, so that X is a ureido functional group having the formula:

0 R²

I I

- N - C - N - R³ la

I I

R¹ When R 1, R2 and R3 in Formulae I and la above are optionally substituted hydrocarbyl groups, they may be independently optionally substituted aliphatic, alicyclic, aromatic or mixed aliphatic-aromatic hydrocarbyl groups. Suitable optionally substituted hydrocarbyl groups for R 1, R2

' 3 and R may be selected from the optionally substituted alkyl and cycloalkyl groups (including polycycloalkyl groups). Optionally

1 ^~ 3 substituted alkyl groups are preferred for each of E , E" and R respectively. Suitable optionally substituted hydrocarbyl groups for R 1, R2

3 and R may also be selected from the optionally substituted aryl, aralkyl and aralkenyl groups.

Further suitable optionally substituted hydrocarbyl groups

1 1 2⁹ 33 for R I ,, RR~" aanndd RR mmaayy bbee sseelleecctteed from the optionally substituted alkenyl and cycloalkenyl groups.

1 2 3 Suitable alkyl groups for R , R and R alkyl and suitable

1 9 3 alkyl groups in R , R" and R substituted alkyl may be selected from the C, _in alkyl groups, in particular the C, ~ straight chain

1 2 3 alkyl groups. Preferred alkyl groups for R , R and R optionally substituted alkyl are independently selected from methyl, ethyl, n-propyl, n-butyl, n-pentyl and n-hexyl, especially methyl.

Suitable substituted alkyl groups may be selected from the oxa-substituted alkyl groups, in particular C. _, straight-chain

1—to alkoxy groups, or the sila-substituted alkyl groups, in particular trialkylsilyl groups where each alkyl bonded to the silicon atom is independently a C. , straight-chain alkyl group.

1 2 3 Suitable cycloalkyl groups for R , R and R optionally substituted cycloalkyl may be selected from the C₅__g cycloalkyl groups, for example cyclohexyl.

1 2 3 Suitable optionally substituted aryl groups for R , R and R may be selected from phenyl optionally substituted by substituents which are inert in the desired polymerisation conditions such as alkyl and aryl.

1 2 Suitable optionally substituted aralkyl groups for R , R and

3

R may include the above suitable alkyl groups substituted by the above suitable aryl groups, and thus include benzyl optionally substituted in the phenyl ring.

Suitable optionally substituted alkenyl groups for R , R and 3 R may be selected from the optionally substituted C__. alkenyl groups, e.g. methylprop-1-enyl (methallyl).

Suitable optionally substituted cycloalkenyl groups for R ,

2 3 R and R may be selected from the optionally substituted C_ _Q

0—o cycloalkenyl groups, e.g. cyclohex-I-enyl. Suitable optionally substituted aralkenyl groups for R 1, R" ">

3 and R may include the above suitable alkenyl groups substituted by the above suitable aryl groups, and thus include 2-methyl-l-phenylprop-l-enyl (phenylmethallyl) optionally substituted in the phenyl ring.

In another type of initiator which may be used in the process of the invention, R 2 and R3 together are an optionally substituted hydrocarbadiyl group. The hydrocarbadiyl group (R 2 + R3) may be substituted by in-chain hetero-atoms and/or by pendent monovalent or divalent substituents. Suitable (R 2 + R3) optionally substituted hydrocarbadiyl groups include optionally substituted aliphatic and alicyclic hydrocarbadiyl groups, such as the optionally substituted alkanediyl, cycloalkanediyl (including polycycloalkanediyl) , alkenediyl and cycloalkenediyl groups, and the diradical combinations of such groups. Suitable (R 2 + R3) optionally substituted alkanediyl include α, - C„__β alkanediyl optionally substituted by at least one in-chain hetero atom. Suitable substituent hetero atoms include 0,

S or N. Where N is the substituent hetero atom it will be bonded to a pendent group which is any group as defined for R hereinbefore, or an MY Z group as defined.

~ ⁿ 3 Examples of (R" + R ) groups thus include 4 to 7-member heterocyclyl groups, such as pyrrolidino, piperidino and morpholino.

A particularly preferred group X has the formula:

0 R⁶

I I - N - C - N - R⁷ lb

I I

R⁵ where

R is C.1-₁lU_ft alkyl, in particular Cl.-D„ straight-chain alkyl; and

R and R are independently C. _n alkyl, in particular C. ,,

1—1U 1—D straight-chain alkyl, or sila-substituted alkyl, in particular trialkylsilyl in which each alkyl bonded to the silicon is independently C, „ straight-chain alkyl.

1-b

Suitable optionally substituted hydrocarbyl groups for Y and

Z and within Y and Z optionally substituted hydrocarbyloxy include

1 2 3 those recited for R , R and R hereinbefore.

Thus, suitable hydrocarbyl groups for Y and Z include the optionally substituted alkyl, cycloalkyl (including polycycloalkyl), alkenyl, cycloalkenyl, aryl, aralkyl and aralkenyl groups.

Suitable alkyl groups for Y and Z may be selected from the

^Cl-20 ^alk^y groups, in particular the C, „ alkyl groups. Preferred

C, _ alkyl groups are the straight-chain C, . alkyl groups, in particular methyl and ethyl and especially methyl. Suitable alkyl groups may also be selected from the branched C.__fi alkyl groups. The alkyl groups may be substituted, but are often unsubstituted.

Suitable cycloalkyl groups for Y and Z may be selected from the C.__ cycloalkyl groups, e.g. cyclohexyl, and polycycloalkyl groups, e.g. adamantyl. The cycloalkyl groups may be substituted, but are often unsubstituted.

Suitable aryl and aralkyl groups for Y and Z may be selected from phenyl, 1-naphthyl and benzyl. The aryl/aralkyl groups may be substituted, e.g. they may carry substituents in the aromatic ring(s), but are often unsubstituted.

Suitable optionally substituted hydrocarbyloxy groups for Y and Z include the optionally substituted alkoxy, cycloalkoxy (including polycycloalkoxy), alkenoxy, cycloalkenoxy, aryloxy, aralkoxy and aralkenoxy groups.

Suitable alkoxy groups for Y and Z may be selected from the C, ₄ alkoxy groups such as methoxy and ethoxy. The alkoxy groups may be substituted, but are often unsubstituted.

Suitable cycloalkoxy groups for Y and Z may be selected from the C, , cycloalkoxy groups such as cyclohexyloxy. The cycloalkoxy

4-/ groups may be substituted, but are often unsubstituted.

Suitable aryloxy and aralkoxy groups for Y and Z may be selected from phenoxy and benzyloxy. The aryloxy/aralkoxy groups may be substituted, e.g. they may carry substituents in the aromatic ring(s), but are often unsubstituted.

Where the above mentioned hydrocarbyl and hydrocarbyloxy groups for Y and Z are substituted, suitable substituents include pendent mono- or di-valent atoms/groups which are inert in the polymerisation process of the present invention.

Where Z is a monovalent organic polymer radical, the polymer is conveniently a particulate one insoluble in any desired polymerisation system (for example a highly cross-linked polymer) with the MX Y moieties on its surface. The polymer may be a solid m n granulate of relatively high surface area, for example in the range 200 to 600 m²/g, and may carry a concentration of MX Y n moieties of 1 every 3 to 30 square Angstroms. M in each MX Y moiety may be linked to the polymer via a carbon atom, e.g. a carbon atom of a pendent alkyl chain of the type described for Y and Z straight-chain alkyl above. Generally, the MX Y groups on m n the polymer will all be identical.

Depending on the polymerisation medium in which the present catalyst system is used, where the initiator is to be in an insoluble form, highly cross-linked alkylene, arylene, acrylic or styrene homo- or co- polymers may be appropriate for the polymer containing group Z.

A further suitable initiator for use in the process of the present invention is one having the formula:

MX ¹ YY ZZ m n p II wherein

M is a tetravalent Si, Ge or Sn atom;

X , Y and Z are bonded to M; m is an integer and denotes the number of X groups bonded to M; n is an integer and denotes the number of Y_, groups bonded to M; p is 0 or an integer and denotes the number of Z groups bonded to M;

5 m + n + p = 4; each Xi is independently a group of formula - iR8R9 where

Q¹ is N, P, As or G.P(=T).D where T is 0 or S and G and D are each independently a bond, 0 or S; and

8 9 0 R and R are each independently optionally substituted hydrocarbyl groups, or R 8 and R9 together are an optionally substituted hydrocarbadiyl group, all such groups being inert in the conditions of the polymerisation process of the present invention, or when i is G.P(=T).D, R8 and R9 are each

^ independently MY Z moieties; and n p each Y and each Z (where present) are as defined hereinbefore in relation to initiator components of Formula I.

In relation to initiator components of Formula II, the term optionally substituted in relation to groups Y and Z and 20 the R and R groups within X includes substitution by pendent mono- or di-valent atoms or groups and substitution by in-chain hetero-atoms.

Within group X¹, ¹ is preferably N, P, P=0 or -0-P(=0)-0-, in particular N or P and especially N.

*-^~\ 8

^D Suitable optionally substituted hydrocarbyl groups for R and

R 9 include those recited above in relation to groups R1, R2 and

3

R . Thus, suitable optionally substituted hydrocarbyl groups for R 8 and R9 include the optionally substituted alkyl, cycloalkyl

(including polycycloalkyl), alkenyl, cycloalkenyl, aryl, aralkyl 0 and aralkenyl groups.

When in group X is N or P, as is preferred, suitable groups for R 8 and R9 also include oxo-substituted hydrocarbyl groups, i.e. acyl groups, having the formula R'CO.- where R' is hydrocarbyl. Suitable acyl groups include alkanoyl groups such as acetyl. The acyl groups may be further substituted, e.g. by halo substituents. An example of a halo substituted acyl group is trifluoroacetyl.

8 9 Where R and R are optionally substituted hydrocarbyl groups, suitable groups for X include N^"-methylacetamido,

N-methyltrifluoroacetamido, N-cyclohex-1-enyl-N-methylamino, diphenylamino, diphenylphosphino, dibenzylamino, dibenzylphosphino, N-acetyl-N-phenylamino, N-trifluoroacetyl-N-phenyl- amino, benzoyl(phenyl)phosphino, 0 diethylphosphino, phenyl(2-methyl-l-phenylpropenyl)phosphino and benzyl(benzoyl)phosphino. i 8 9

Preferably, is N or P, especially N, and R and R together form an optionally substituted hydrocarbadiyl group. The

8 9 hydrocarbadiyl group (R + R ) may optionally be substituted by 5 in-chain hetero atoms and/or by pendent monovalent or divalent

8 9 atoms or groups. Where R and R together form a hydrocarbadiyl

8 9 i i 8 9 group (R + R ), the resulting X group - (R + R ) is a nitrogen or phosphorous containing heterocyclyl group which is bonded to the M nucleus via the Q nitrogen or phosphorous atom. The said 0 nitrogen or phosphorous containing heterocyclyl groups may contain

. further heteroatom substitution which may be the same as or different from the heteroatom . Furthermore, the heterocyclyl groups may be substituted by pendent monovalent or divalent groups such as oxo substituents. By heterocyclyl groups we are intending

- to include, inter alia, the fused hetero substituted polycyclyl groups such as the benzo-fused heterocyclyl groups. i 8 9 Accordingly, representative groups for - (R + R ) include pyrrolidino, piperidino, morpholino and N'-C. . alkylpiperazino, and the phospha-analogues thereof; 4 to 7 member lactamido or 0 cycloimido groups such as N-piperidonyl and succinimido, and oxazolid-2-on-3yl; 5 to 7 member unsaturated heterocyclyl groups such as 1-pyrrolyl, 1-pyrrolinyl, 1-imidazolyl and 1-imidazolinyl;

9-carbazolyl and its phospha analogue; benzo-fused 5 to 7 member saturated heterocyclyl groups such as 1-indolinyl; and the benzo-fused 5 to 7 member unsaturated heterocyclyl groups such as

1-indolyl, 1-indazolyl and their phospha analogues. Other heterocyclyl groups that are known to those skilled in the art may all be suitable as a group X .

5 A further suitable initiator for use in the process of the present invention is one having the formula:

wherein

M is a tetravalent Si, Ge or Sn atom; 1° X¹¹, Y and Z¹ are bonded to M; q is 1 or 2 and denotes the number of X groups bonded to M; - r is 0 or 1 and denotes the number of Y groups bonded to M; q + r = 2; each X is a group X or a group X as hereinbefore defined 1 in relation to initiator components of Formula I and Formula II;

Y (where present) is as defined hereinbefore in relation to initiator components of Formula I; and

Z is a divalent group which is doubly bonded to atom M and has the formula:

2 ^~-0^~ _/(i-_x) -_ΛO_ιS_e,i._DR10_τR,ll_ΛOS_i.R_n12_oR130_.- wh,ere _DR10, _DRll, _DR12 and, R_13 are each independently selected from H or optionally substituted hydrocarbyl, or

(ii) -J- or -EJE- where E is oxygen and J is an oligomer or a polymer carrying further -MX qYr- or -EMX qYrE- moieties, or 5 (iii) -ELE- where E is oxygen and L is an inorganic solid on whose surface the two -0- groups are located, said L carrying further -EMX¹¹ Y E- moieties. When Zi is^q a^r divalent group having the formula

-OSiR¹⁰R¹¹0SiR¹²R¹³O-, R¹⁰, R¹¹, R¹² and R¹³ are conveniently the 0 same and may be, for example, optionally substituted benzyl, ^ . alkyl or phenyl.

Where Z is a divalent group -J- or -0J0- where J is a poljπner, the polymer is conveniently a particulate one insoluble in any desired polymerisation system (for example a highly cross-linked polymer) with the MX Y moieties on its surface. q r

The polymer may be a solid granulate of relatively high surface area, for example in the range 200 to 600 m²/g, and may carry a concentration of MX Y moieties of 1 every 3 to 30 square Angstroms. M in each MX Y moiety may be linked to the polymer via a carbon atom, e.g. a carbon atom of a pendent alkyl chain of the type described for Y and Z straight-chain alkyl above.

Generally, the MX Y groups on the polymer will all be q r identical. 0 Depending on the polymerisation medium in which the present catalyst system is used, where the initiator is to be insoluble, highly cross-linked alkylene, arylene, acrylic or styrene homo- or co- polymers may be appropriate for a polymer containing group Z .

Further suitable divalent Z groups include those having the ~ formula -OLO- where L is an inorganic solid with a plurality of surface hydroxyl functions, such as silica or a metal hydroxide or hydrated oxide, e.g. alumina.

L may be inter alia a flat body of low specific surface area or a particulate with a relatively high specific surface area, for 0 example in the range 200 to 600 mVg.

The -OMX Y 0- moieties may be present on the surface of the inorganic solid at a concentration of 1 every 3 to 30 square Angstroms.

Such concentrations may be achieved by involving at least 5

20%, preferably at least 60%, of the available surface hydroxyl functions in -OLO- bonding to MX Y moieties. q r

Still further suitable initiators for use in the process of the present invention are disclosed in the present applicant's published European patent application EP-405787 A2, the disclosure 0 in which is incorporated herein by way of reference.

The preferred initiators for use in the process of the present invention are those of Formula I or Formula II described above. Particularly preferred initiators are those having the formula:

wherein

M is Si, Ge or Sn, preferably Si; s and t are each an integer such that s + t = 4; each X is group X or a group X as defined above in relation to initiators of Formula I and Formula II respectively; and each group Y is independently a group Y as defined in Formula I above. Suitable and preferred groups for X are as so described for X and X hereinbefore.

Preferably, s is 1 or 2, especially 1, so that the preferred initiators of Formula IV have one or two X groups bonded to the central M atom. In the preferred initiators of Formula IV, each group Y is independently an alkyl, aryl, aralkyl, alkoxy, aryloxy, or aralkoxy group. Preferred optionally substituted hydrocarbyl and hydrocarbyloxy groups for Y therefore include methyl, ethyl, propyl, butyl, pentyl, phenyl, benzyl, methoxy, ethoxy, benzoxy and benzyloxy. Preferably each group Y is independently alkyl, in particular C, _fl alkyl and especially C, . straight-chain alkyl. In particularly preferred embodiments, each Y group is the same, and in especially preferred embodiments is methyl.

The amount of initiator which is used is generally such that the molar ratio of initiator to first monomer or monomer mixture is in the range of from 1:10 to 1:1000 and preferably in the range of from 1:10 to 1:500, except where the initiator comprises an insoluble polymeric or inorganic solid grouping (i.e. in initiators of Formulae I and II above Z is an organic polymer radical or in initiators of Formula III above Z is a group -J-,

-EJE- or -ELE-), when the initiator is generally used in an amount such that the molar ratio of initiator to first monomer or monomer mixture is in the range of from 1:5 to 1:100. The amount of co-catalyst which is used is generally such that the molar ratio of initiator to co-catalyst is in the range of from 1000:1 to 3:1, preferably in the range of from 1000:1 to 10:1.

All the initiator components may be used as such, or they may be formulated into compositions with other materials. For example, they may be formulated into insoluble or non-dispersible compositions, e.g. with such conventional materials as catalyst supports. Such compositions may be of use in the process of the present invention.

Where such a composition is insoluble it may be seen as an alternative to insoluble forms of the initiator component itself, i.e. when Z is a monovalent polymer radical or Z is a divalent group -J-, -0J0- or -OLO- as described hereinbefore. The initiator component in such a composition may be adhered to or embedded in the surface of the support rather than chemically bonded to it. The support may comprise a polymer, e.g. a highly cross-linked acrylic or styrene homo- or co-polymer, e.g. a particulate one insoluble in any desired poiymerisable composition, or a similarly insoluble (particulate) inorganic solid. Any co-catalyst component (b) which in use of the catalyst is available in the polymerisation as described hereinbefore may be suitable for use with initiator compositions in the process of the present invention.

The co-catalyst components (b) are known materials. The initiator components (a) of Formula I and Formula II may be prepared analogously to, or are routinely derivable, from known materials. For example many of the groups X, X , Y and Z may be introduced to form the compounds of Formula (I) and Formula (II) by conventional nucleophilic displacement at the M nucleus with suitable corresponding moieties.

Where the M nucleus is linked by two -0- groups to an inorganic solid or polymer as hereinbefore defined, the links may be formed by conventional silylation of adjacent hydroxyl groups. The preparation of initiator components (a) of Formula I and Formula II is more particularly described in the present applicant's published European patent applications EP-323082 A2 and EP-405785 A2, the disclosures in which are incorporated herein by way of reference.

When the preferred two component catalyst systems described supra are employed in process of the present invention, the polymerisation process may be conducted at temperatures in the range of from -100°C to +150°C, with temperatures in the range of from -20 to +60°C being preferred. The process may be conducted under 0.1 to 50 atmospheres pressure but normally atmospheric pressure is suitable.

It is desirable to conduct the process of the invention under anhydrous conditions. Accordingly, in preferred embodiments the water content of the monomers, the polymerisation initiator and co-catalyst and any solvent should be minimised, and the process conducted in atmospheres that have been dried in order to prevent the penetration of any water. Such atmospheres include dry air, or atmospheres of dried inert gases such as nitrogen or argon; dried inert gas atmospheres are preferable.

No particular restrictions are placed on the order in which the polymerisation initiator (a) or a composition comprising it, co-catalyst (b) and monomers are added to the reaction system in the process of the invention, and polymerisation will proceed whatever sequence is used. For example, the catalyst components may be mixed and added to the monomers. However, in terms of being able to control the polymerisation reaction easily it is desirable to add the initiator (a) or a composition comprising it and co-catalyst (b) separately to the monomers, or to add one catalyst component to the monomer or vice versa and add the product mixture to the other catalyst component, or vice versa.

Initiator (a) and/or co-catalyst (b) may be added to the monomers either neat, or in the form of a solution in an inert solvent. Often the initiator is added first to the monomers. The monomers themselves may also be dissolved in an inert solvent. Where the initiator (a) or its composition is insoluble it is often desired to add the co-catalyst (b) to the monomers and to contact the product mixture with the initiator (a) or its composition. The present invention is now illustrated, but not limited, by reference to the following Examples. Examples In the Examples:

The initiator used was either 3-trimethylsilyl- oxazolid-2-one (hereinafter OTMS) or 9-trimethylsilylcarbazole (hereinafter CTMS). The initiators were dried before use.

The co-catalyst used was tetrabutylammonium fluoride trihydrate (hereinafter TBAF). The TBAF was pre-dried under high vacuum over

and was then dissolved in dry methyl methacrylate to give a 0.1 M solution. Examples 1 to 3

These Examples illustrate the polymerisation of n-butyl acrylate in methyl methacrylate.

Dry methyl methacrylate (10 mis; 0.0936 moles) and dry n-butyl acrylate (5mls; 0.0349 moles) were mixed together in a dry schlenk tube under a nitrogen atmosphere. The resulting mixture was stirred at room temperature and OTMS initiator (0.1 ml; 6.5 x

-4 10 moles) was then added followed by the TBAF co-catalyst (lOμl

— ~ of the 0.1 M solution; 1 x 10 moles). After the addition of the TBAF co-catalyst, an induction period of between 20 and 25 seconds was observed before the exothermic polymerisation reaction was detectable by a thermocouple. The peak exotherm temperature was reached after a period of 3 to 5 minutes from the addition of the co-catalyst, and the increase in temperature was about 20 °C.

The final products were slightly viscous solutions containing poly(n-butyl acrylate) polymer, residual unreacted n-butyl acrylate, and methyl methacrylate. The polymer in monomer solutions were analysed by gel permeation chromatography. In Example 1, 87 % of the n-butyl acrylate monomer had polymerised to form the polymer. The polymer in monomer solution therefore comprised 28.10 % by weight of poly(n-butyl acrylate) and 71.90 % by weight of unreacted monomer. Of the unreacted monomer 5.84 % by weight was unreacted n-butyl acrylate. If all the n-butyl acrylate had polymerised to the exclusion of the methyl methacrylate, the final product would have comprised 32.3 % by weight of poly{n-butyl acrylate) and 67.7 % by weight of methyl methacrylate. The poly(n-butyl acrylate) polymer had a number average molecular weight (M ) of 16,218, a weight average molecular weight (M ) of 31,623 and a polydispersity (M /M ) of 1.95.

In Example 2, 94 % of the n-butyl acrylate monomer had polymerised to form the polymer. The polymer in monomer solution therefore comprised 30.36 % by weight of poly(n-butyl acrylate) and 69.64 % by weight of unreacted monomer. Of the unreacted monomer 2.78 % by weight was unreacted n-butyl acrylate. If all the n-butyl acrylate had polymerised to the exclusion of the methyl methacrylate, the final product would have comprised 32.3 % by weight of poly(n-butyl acrylate) and 67.7 % by weight of methyl methacrylate. The poly(n-butyl acrylate) polymer had a number average molecular weight (M ) of 15,136, a weight average n molecular weight (M ) of 30,903 and a polydispersity (M /M ) of w w n

2.04. In Example 3, 84 % of the n-butyl acrylate monomer had polymerised to form the polymer. The polymer in monomer solution therefore comprised 27.14 % by weight of poly(n-butyl acrylate) and 72.86 % by weight of unreacted monomer. Of the unreacted monomer 7.09 % by weight was unreacted n-butyl acrylate. The poly(n-butyl acrylate) polymer had a number average molecular weight (M ) of 15,488, a weight average molecular weight (M ) of n w

30,200 and a polydispersity (M /M ) of 1.95.

Example 4

The same procedure as described in Examples 1 to 3 was used except that 0.2 ml (1.3 x 10 moles) of the OTMS initiator and 20 μl of

— ~ the 0.1 M TBAF solution (2 x 10 moles) were used.

The induction period was less than 10 seconds, and the peak exotherm temperature (30 'C above the ambient temperature at which the polymerisation reaction was initiated) was reached after 2 minutes.

The final product, a slightly viscous solution containing poly(n-butyl acrylate) polymer and unreacted methyl methacrylate monomer, was analysed by gel permeation chromatography. All the n-butyl acrylate monomer had polymerised to form the polymer. The polymer in monomer solution therefore comprised 32.3 % by weight of poly(n-butyl acrylate) and 67.7 % by weight of methyl methacrylate monomer. The polymer had a number average molecular weight (M ) of 10,715, a weight average molecular weight (M ) of 22,387 and a polydispersity (Mw/Mπ) of 2.09.

Example 5

The same basic procedure as described in Examples 1 to 3 was used to polymerise methyl acrylate in the presence of methyl methacrylate using CTMS as the initiator in place of OTMS. Dry methyl methacrylate (10 mis; 0.0936 moles) and dry methyl acrylate (5mls; 0.0556 moles) were mixed together in a dry schlenk tube under a nitrogen atmosphere. The resulting mixture was stirred at room temperature and CTMS initiator (7.4 x 10 -4 moles) was then added followed by the TBAF co-catalyst (lOμl of the 0.1 M solution; 1 x 10 moles).

After the addition of the TBAF co-catalyst, an induction period was observed before the exothermic polymerisation reaction was detectable by a thermocouple.

The final product, a slightly viscous solution containing poly(methyl acrylate) polymer, residual unreacted methyl acrylate, and methyl methacrylate, was analysed by gel permeation chromatography.

84 % of the methyl acrylate monomer had polymerised. The polymer in monomer solution therefore comprised 28.40 % by weight of poly(methyl acrylate) and 71.60 % by weight of unreacted monomer. Of the unreacted monomer 7.56 % by weight was unreacted methyl acrylate. If all the methyl acrylate had polymerised to the exclusion of the methyl methacrylate, the final product would have comprised 33.81 % by weight of poly(methyl acrylate) and 66.19 % by weight of methyl methacrylate. The poly(methyl acrylate) polymer had a number average molecular weight (M ) of 5,484, a weight average molecular weight (M ) of 10,317 and a w polydispersity (M /M ) of 1.88. Example 6

This Example illustrates the polymerisation of methyl acrylate in methyl methacrylate with subsequent free radical polymerisation of the methyl methacrylate using azoisobutyronitrile (hereinafter

AIBN) as the initiator. Dry methyl methacrylate (10 mis; 0.0936 moles) and dry methyl acrylate (5mls; 0.0556 moles) were mixed together in a dry schlenk tube under a nitrogen atmosphere and the resulting mixture cooled to 0"C using an ice/water bath. AIBN (2 % by weight on the weight of the methyl methacrylate monomer) was added to the cooled monomer mixture with stirring, followed by the addition of CTMS

-4 initiator (7.1 x 10 moles) and then TBAF co-catalyst (lOμl of the 0.1 M solution; 1 x 10 moles).

After the addition of the TBAF co-catalyst, an induction period was observed before the exothermic polymerisation reaction was detectable by a thermocouple. Cooling the reaction medium with the ice/water bath ensured that the temperature of that medium remained below the activation temperature of the AIBN initiator. Accordingly, only the CTMS/TBAF catalyst system was operative causing the methyl acrylate monomer to polymerise selectively. The final product was a slightly viscous solution containing poly(methyl acrylate) polymer, residual unreacted methyl acrylate, and methyl methacrylate monomer. This product was then heated to 60 ^*C for 16 hours in order to activate the AIBN initiator and effect the polymerisation of the methyl methacrylate free radically. The final polymer product was analysed by gel permeation chromatography and was shown to be bimodal, comprising a low molecular weight poly(methyl acrylate) polymer (M 10,000;

M /M 1.6) which was formed in the initial polymerisation reaction w n and a high molecular weight poly(methvl methacrylate) polymer (M n

303,000; M /M 4.8) which was formed in the subsequent w n free-radical polymerisation reaction.

It will be appreciated, of course, that cooling of the reaction medium is only necessary when initiators such as AIBN having low activation temperatures are used and are present at the beginning of the two-step polymerisation process. Therefore, cooling can be avoided by using a free-radical initiator which is activated at higher temperatures, or by adding an initiator having a low activation temperature after the first step polymerisation of the methyl acrylate monomer is complete. Example 7

This Example illustrates the polymerisation of a methyl acrylate/allyl acrylate monomer mixture in methyl methacrylate, with subsequent free radical polymerisation of the unsaturated copolymer. produced with the methyl methacrylate using AIBN as the initiator.

Dry methyl methacrylate (10 mis; 0.0936 moles), dry methyl acrylate (0.0445 moles) and dry allyl acrylate (0.0084 moles) were mixed together in a dry schlenk tube under a nitrogen atmosphere.

The resulting mixture was stirred at room temperature and CTMS

-4 initiator (7.5 x 10 moles) was then added followed by the TBAF

— ~ co-catalyst (lOμl of the 0.1 M solution; 1 x 10 moles).

The product, a slightly viscous, soluble resin, was analysed by NMR and was found to contain an unsaturated poly(methyl acrylate/allyl acrylate) random copolymer, residual unreacted methyl acrylate and allyl acrylate monomers, and methyl methacrylate monomer. Analysis by gel permeation chromatography revealed that the random copolymer produced had a number average molecular weight (M ) of 4,649, a weight average molecular weight

(M ) of 9,000 and a polydispersity (M /M ) of 1.94. w w n This resin was then cured free radically. AIBN (0.1 % by weight on the weight of the methyl methacrylate monomer) was added to the resin and the resulting mixture was heated at 60 ^*C for 20 hours to effect the curing reaction. The final product was a homogeneous, water white, insoluble and cross-linked polymer. A small sample of the polymer product was extracted with chloroform to determine whether the product contained any residual (unreacted) monomer. Analysis of the chloroform extract showed that the polymer product contained a small amount of residual monomer. Drying the product under vacuum removed all this monomer yielding a product which could be granulated and then compression moulded to give a polymer article. Example 8

This Example illustrates the preparation of a methyl acrylate/allyl acrylate unsaturated diblock copolymer in methyl methacrylate as the solvent, with subsequent free radical polymerisation of the unsaturated di-block copolymer produced with the methyl methacrylate using AIBN as the initiator.

Dry methyl methacrylate (10 mis; 0.0936 moles) and dry methyl acrylate (0.0445 moles) were mixed together in a dry schlenk tube under a nitrogen atmosphere. The resulting mixture was stirred at

-4 room temperature and CTMS initiator (7.9 x 10 moles) was then added followed by the TBAF co-catalyst (lOμl of the 0.1 M

—fi solution; 1 x 10 moles).

After the reaction exotherm had subsided, dry allyl acrylate monomer (0.0084 moles) was added resulting in a second polymerisation exotherm. The product, a slightly viscous resin, was analysed by NMR and was found to contain- an unsaturated poly(methyl acrylate/allyl acrylate) diblock copolymer, residual unreacted methyl acrylate and allyl acrylate monomers, and methyl methacrylate monomer. Analysis by gel permeation chromatography revealed that the diblock copolymer produced had a number average molecular weight

(Mn) of 4,415, a weight average molecular weight (Mw) of 8,940 and a polydispersity (Mw/Mn) of 2.02.

This resin was then cured free radically. AIBN (0.1 % by weight on the weight of the methyl methacrylate monomer) was added to the resin and the resulting mixture was heated at 60 ^*C for 20 hours to effect the curing reaction. The final product was a homogeneous, water white, insoluble and cross-linked polymer. A small sample of the polymer product was extracted with chloroform to determine whether the product contained any residual

(unreacted) monomer. Analysis of the chloroform extract showed that the polymer product contained a small amount of residual monomer. Drying the product under vacuum removed all this monomer yielding a product which could be granulated and then compression moulded to give a polymer article.

Claims

1. A process for preparing a poiymerisable composition, which process comprises contacting under a first set of polymerising conditions a poiymerisable precursor comprising at least one first ethylenically unsaturated addition poiymerisable monomer, containing at least one first and optionally at least one second ethylenically unsaturated addition poiymerisable group, and at least one second ethylenically unsaturated addition poiymerisable monomer with a catalyst system which is capable of selectively polymerising the at least one first monomer, in the presence of the at least one second monomer, to form an addition polymerised polymer species under the first set of polymerisation conditions and wherein the poiymerisable composition contains the addition polymerised polymer species and the at least one second ethylenically unsaturated addition poiymerisable monomer.

2. A process as claimed in claim 1 wherein the catalyst system is a two component catalyst system comprising:

(a) at least one tetracoordinate organosilicon, organotin or or anogermanium initiator having at least one initiating site in which a silicon, tin or germanium atom is bound by a nitrogen, phosphorous or arsenic atom to a nitrogen, phosphorous or arsenic containing organic group which is devoid of reactive hydrogen atoms; and

(b) at least one nucleophilic co-catalyst.

3. A process as claimed in 2 wherein the initiator component (a) has the formula:

MX Y Z I m n p wherein

M is a tetravalent Si, Ge or Sn atom;

X, Y and Z are bonded to M; m is an integer and denotes the number of X groups bonded to

M; n is an integer and denotes the number of Y groups bonded to

M; p is 0 or an integer and denotes the number of Z groups bonded to M; m + n + p = 4; each X is independently a group 2

„1 where and are independently N, P or As;

2 is 0, S, NR' or PR' where R' is C-_. alkyl;

R is H or an optionally substituted hydrocarbyl group; and

2 3 R and R are each independently optionally substituted

2 3 hydrocarbyl groups, or R and R together are an optionally substituted hydrocarbadiyl group;

1 2 3 all such R , R and R groups being inert in the conditions of the polymerisation process of the present invention; each Y is independently an optionally substituted hydrocarbyl or hydrocarbyloxy group which is inert in the conditions of the polymerisation process of the present invention, or trialkylsilylalkyl; and each Z (where present) is independently any group as defined for Y or an organic oligomer or polymer radical comprising further MX Y moieties, m n

4. A process as claimed in 2 wherein the initiator component (a) has the formula:

MX¹ Y Z II m n p wherein

M is a tetravalent Si, Ge or Sn atom;

X , Y and Z are bonded to M; m is an integer and denotes the number of X groups bonded to

M; n is an integer and denotes the number of Y groups bonded to M; p is 0 or an integer and denotes the number of Z groups bonded to M; m + n + p = 4; i i 8 9 each X is independently a group of formula - R R where

8 9 R and R are each independently optionally substituted

8 9 hydrocarbyl groups, or R and R together are an optionally substituted hydrocarbadiyl group, all such groups being inert in the conditions of the polymerisation process of the i 8 9 present invention, or when is G.P(=T).D, R and R are each independently MY Z moieties; and each Y is independently an optionally substituted hydrocarbyl or hydrocarbyloxy group which is inert in the conditions of the polymerisation process of the present invention, or trialkylsilylalkyl; and each Z (where present) is independently any group as defined for Y or an organic oligomer or polymer radical comprising further MX Y moieties, n

5. A process as claimed in 2 wherein the initiator component (a) has the formula:

MX¹¹ Y Z¹ III q r wherein

M is a tetravalent Si, Ge or Sn atom;

X , Y and Z are bonded to M; q is 1 or 2 and denotes the number of X groups bonded to M; r is 0 or 1 and denotes the number of Y groups bonded to M; q + r = 2; each X is independently a group X of the form R~

2 1

- - C( ^~T ) - - R

I

.1 where

Q and are independently N, P or As; ² is 0, S, NR' or PR' where R' is C alkyl; R 1 is H or an optionally substituted hydrocarbyl group; and

2 3 R and R are each independently optionally substituted hydrocarbyl groups, or R 2 and R3 together are an optionally substituted hydrocarbadiyl group;

1 ^~ 3 all such R , R" and R groups being inert in the conditions of the polymerisation process of the present invention, or a group Xi of the formula - iR8R9 where is N, P, As or G.P(=T).D where T is 0 or S and G arid D are each independently a bond, 0 or S; and

8 9 R and R are each independently optionally substituted hydrocarbyl groups, or R 8 and R9 together are an optionally substituted hydrocarbadiyl group, all such groups being inert in the conditions of the polymerisation process of the i 8 9 present invention, or when Q is G.P(=T).D, R and R are each independently MYnZ p moieties; each Y is independently an optionally substituted hydrocarbyl or hydrocarbyloxy group which is inert in the conditions of the polymerisation process of the present invention, or trialkylsilylalkyl; and

Z is a divalent group which is doubly bonded to atom M and has the formula:

(i) -OSiR¹⁰R^UOSiR¹²R¹³O- where R¹⁰, R¹¹, R¹² and R¹³ are each independently selected from H or optionally substituted hydrocarbyl, or

(ii) -J- or -EJE- where E is oxygen and J is an oligomer or a polymer carrying further -MX. Y - or ii -EMX Y E- moieties, or q r

(iii)-ELE- where E is oxygen and L is an inorganic solid on whose surface the two -0- groups are located, said L carrying further -EMX Y E- moieties. q r

6. A process as claimed in 2 wherein the initiator component (a) has the formula:

wherein

M is Si, Ge or Sn, preferably Si; s and t are each an integer such that s + t = 4; each X is independent ^■lljy a group X of the form 2

- Q - C(<_T) - Q^A - H^*

I

„1 where and Q are independently N, P or As;

Q² is 0, S, NR' or PR' where R' is C alkyl;

1 R is H or an optionally substituted hydrocarbyl group; and

2 3 R and R are each independently optionally substituted

1 2 3 all such R , R and R groups being inert in the conditions of the polymerisation process of the present invention, i i 8 9 or a group X of the formula - B E where ¹ is N, P, As or G.P(=T).D where T is 0 or S and G and D are each independently a bond, 0 or S; and

8 9 R and R are each independently optionally substituted

8 9 hydrocarbyl groups, or R and R together are an optionally substituted hydrocarbadiyl group, all such groups being inert in the conditions of the polymerisation process of the i 8 9 present invention, or when Q is G.P(=T).D, R and R are each independently MY Z moieties; and _i n p each group Y is independently an optionally substituted hydrocarbyl or hydrocarbyloxy group which is inert in the conditions of the polymerisation process of the present invention, or trialkylsilylalkyl.

7. A process as claimed in any one of claims 1 to 6 wherein the at least one second monomer is subsequently polymerised by a second catalyst system.

8. A process as claimed in claim 7 wherein the second catalyst system is inert under the first polymerisation conditions and is added to the poiymerisable precursor before the at least first monomer is polymerised.

9. A process as claimed in claim 8 wherein the second catalyst system comprises a heat activated free radical catalyst and the first polymerisation conditions are at a temperature below that at which the free radical catalyst is activated.

10. A process as claimed in any one of claims 1 to 9 wherein the at least one first monomer is an acrylate monomer or a methacrylate monomer which does not contain any functional groups possessing acidic hydrogen atoms.

11. A process as claimed in claim 10 wherein the at least one first monomer is at least one of

(a) an acrylate monomer of the formula CH„=CHC0.0R where R is an alkyl, aryl, aralkyl, alkaryl or cycloalkyl group;

(b) an acrylate monomer which contains at least one second ethylenically unsaturated group selected from allyl acrylate, 2-(methacryloyloxy)ethyl acrylate, an acrylate substituted vinyl aromatic monomer and an acrylate substituted conjugated diene.

12. A process as claimed 10 wherein the at least one first monomer is at least one of

(a) a methacrylate monomer of the formula CH_?=C(CH„)C0.0R where R is an alkyl, aryl, aralkyl, alkaryl or cycloalkyl group; (b) a methacrylate monomer which contains at least one second ethylenically unsaturated group selected a methacrylate substituted vinyl aromatic monomer and a methacrylate substituted conjugated diene.

13. A process as claimed in either claim 10 or claim 11 wherein the at least one first monomer is an acrylate monomer, the at least one second monomer is a methacrylate monomer and the poiymerisable composition is a poiymerisable resin comprising an acrylate homopolymer or copolymer in the methacrylate monomer.

14. A process as claimed in any one of claims 1 to 12 wherein the at least one second monomer is selected from at least one vinyl aromatic monomer or conjugated diene.

15. A process as claimed in claim 14 wherein the at least one second monomer is a vinyl monomer which does not contain any functional groups possessing acidic hydrogen atoms.

16. A process as claimed in claim 15 wherein the at least one second monomer is selected from styrene, substituted derivatives of styrene and vinyl toluene.

17. A process as claimed in claim 14 wherein the at least one second monomer is butadiene.