Particulate polymer composition, a method of making particulate polymer compositions, and light-scattering thermoplastic polymer compositions containing the particulate polymers

Claim 2

A particulate polymer composition suitable for incorporating into a thermoplastic polymer matrix to form a light-diffusing polymer composition, comprises particles of core/shell polymer having an average diameter of from 2 to 15 µm, a particle size distribution such that at least 90% by weight of the particles fall within ±20% of the average particle diameter, a core of rubbery alkyl acrylate polymer, the alkyl group having from 2 to 8 carbon atoms, copolymerised with 0 or upto 5% crosslinker and 0 or upto 5% graftlinker (based on the total weight of the core) and having a refractive index (n ) within 0.2 units of, but preferably no closer than ±0.003 to, the refractive index of the matrix polymer, and one or more polymer shells, the outer most of which is compatible with the matrix polymer, which shells comprise from 5 to 40% of the weight of the particles.

Claim 3

The particulate polymer composition as claimed in Claim 1, wherein the rubbery alkyl acrylate polymer is a copolymer of alkyl acrylate and upto 50% of one or more copolymerizable vinyl monomers, preferably being a monovinyl monomer.

Claim 4

The particulate polymer composition as claimed in Claim 2, wherein the alkyl acrylate monomer is copolymerised with one or more alkyl methacrylate and/or vinyl arene, preferably one or more monovinyl arene.

Claim 5

The particulate polymer composition as claimed in Claim 2 or Claim 3, wherein the, or one of the, copolymerizable monovinyl monomer(s) is styrene.

Claim 6

The particulate polymer composition as claimed in any one of the preceding claims, wherein the alkyl acrylate monomer is butyl acrylate.

Claim 7

The particulate polymer composition as claimed in any one of the preceding claims, wherein the outer most shell is a polymer of an alkyl methacrylate, vinyl arene, vinyl carboxylate and/or alkyl acrylate.

Claim 8

A process for preparing a particulate polymer composition, suitable for incorporating into a thermoplastic matrix polymer to form light-diffusing polymer compositions, comprising particles of core/shell polymer having an average diameter of from 2 to 15µm, a particle size distribution such that at least 90% by weight of the particles fall within ±20% of the average particle diameter, a core of rubbery alkyl acrylate polymer, the alkyl group having from 2 to 8 carbon atoms, copolymerised with 0 or upto 5% crosslinker and 0 or upto 5% graftlinker (based on the total weight of the core) and having a refractive index (n ) within 0.2 units of, but preferably no closer than ±0.003 to, the refractive index of the matrix polymer, and one or more polymer shells, the outer most of which is compatible with the matrix polymer, which shells comprise from 5 to 40% of the weight of the particles; wherein the process comprises A) polymerizing a first aqueous emulsion of one or more monomers which, when polymerized, produce a particulate composition comprising particles of a rubbery alkyl acrylate polymer, the alkyl group having from 2 to 8 carbon atoms, B) 1. swelling the particles of the particulate composition produced in A), or if appropriate the particles of B2), with one or more monomers, and 2. polymerizing the swelling monomer within the particles until all of the monomers have been polymerized, steps B1 and B2 being repeated, if necessary, until at least 90% by weight of the particles of the particulate composition fall within ±20% of a desired size, in which case such particles are to be referred to as core polymer particles, and C) 1. suspending the core polymer particles of B2, or if appropriate the particles of C2, in a second aqueous monomer emulsion, and 2. polymerizing onto the core polymer particles a polymer shell from the monomer in the second emulsion, steps C1) and C2) being repeated as necessary with the same or a different aqueous monomer emulsion to form the required core/shell polymer particles.

Claim 9

A process for preparing a particulate polymer composition, suitable for incorporating into a thermoplastic matrix polymer to form light-diffusing polymer compositions, comprising particles of core/shell polymer having an average diameter of from 2 to 15µm, a particle size distribution such that at least 90% by weight of the particles fall within ±20% of the average particle diameter, a core of rubbery alkyl acrylate polymer, the alkyl group having from 2 to 8 carbon atoms, copolymerised with 0 or upto 5% crosslinker and 0 or upto 5% graftlinker (based on the total weight of the core) and having a refractive index (n ) within 0.2 units of, but preferably no closer than ±0.003 to, the refractive index of the matrix polymer, and one or more polymer shells, the outer most of which is compatible with the matrix polymer, which shells comprise from 5 to 40% of the weight of the particles; wherein the process comprises A) polymerizing a first aqueous emulsion of one or more monomers which, when polymerized, produce a particulate composition comprising particles of a rubbery alkyl acrylate polymer, the alkyl group having from 2 to 8 carbon atoms, B) 1. swelling the particles of the particulate composition produced in A), or if appropriate the particles of B2), with one or more monomers, and 2. polymerizing the swelling monomer within the particles until all of the monomers have been polymerized, steps B1 and B2 being repeated, if necessary, until at least 90% by weight of the particles of the particulate composition fall within ±20% of a desired size, in which case such particles are to be referred to as core polymer particles, and C) 1. suspending the core polymer particles of B2, or if appropriate the particles of C2, in a second aqueous monomer emulsion, and 2. polymerizing onto the core polymer particles a polymer shell from the monomer in the second emulsion, steps C1) and C2) being repeated as necessary with the same or a different aqueous monomer emulsion to form the required core/shell polymer particles.

Claim 10

The process of Claim 7, wherein the polymerization of step A) is conducted under conditions that form the emulsion polymer as an easily swellable oligomer, preferably conditions including the presence of a chain-transfer moderator, for example or mercaptan.

Claim 11

The process of Claim 7 or 8, wherein one or more polymerizations of step B-2) are conducted under conditions that form a readily swellable oligomer from the swelling monomer, preferably conditions including the presence of a chain-transfer moderator, for example a mercaptan.

Claim 12

10 The process of any of Claims 7 to 9, wherein the first and second monomer emulsions are such that the core/shell polymer particles formed are as claimed in any one of Claims 2 to 6.

Claim 13

A light-diffusing thermoplastic polymer composition which comprises a thermoplastic matrix polymer and, distributed throughout the matrix polymer, from about 0.1% to about 10% of the total composition weight of particles of polymer as claimed in any one of Claims 1 to 6 or particles made in accordance with the process claimed in any one of Claim 7 to 10.

Claim 14

The light-diffusing composition of Claim 11 wherein the matrix polymer is clear and preferably has a glass-transition temperature no less than 50°C.

Claim 15

The light-diffusing composition of Claim 11 or Claim 12, wherein the matrix polymer is a homopolymer of poly(methylmethacrylate), poly(styrene), poly(vinyl chloride), poly(cellulose acetate butylate), poly(ethylene terephthalate) or poly(glutarimides).

Claim 16

The light-diffusing composition of Claim 11 or Claim 12, wherein the matrix polymer is a copolymer of poly(methyl methacrylate-co-alkyl acrylate) wherein the alkyl group contains 1 to 8 carbon atoms, poly(styrene-co-acrylonitrile) wherein acrylonitrile polymer comprises up to 40% of the copolymer, poly(styrene-co-methyl methacrylate), poly( alpha -methylstyrene-co-methyl methacrylate), poly( alpha -methylstyrene-co-alkyl acrylate) wherein the alkyl group contains 1 to 8 carbon atoms, poly(vinyl chloride-co-vinyl acetate) and poly(vinyl chloride-co-propylene).