Polymer, process and composition
There is described a low number average molecular weight (M N <10 kD) and high glass transition temperature (>75° C.) copolymer (optionally a solid grade oligomer (SGO)) that comprises (a) at least 20 wt-% of itaconate functional monomer(s), (b) not more than 40% of a hydrophilic monomer, preferably an acid functional monomer(s) in an amount sufficient to achieve an acid value from 65 to 325 mg KOH per g of solid polymer; (c) optionally not more than 70% of other monomers not being either (a) or (b), having a max content of vinyl aromatic monomer(s) of 40 wt-% and/or max content of methacrylate(s) of 40 wt-%; where the weight percentages of monomers (a), (b) and (c) are calculated as a proportion of the total amount of monomers in the copolymer being 100%.
1. A process for preparing a copolymer having a low molecular weight and high glass transition temperature, wherein the process comprises conducting a solution polymerisation process of a monomer composition comprising:
(a) from 20 to 80 wt-% of at least one itaconate functional monomer not containing acidic groups or precursor acid groups,
(b) not more than 40 wt-% of an acid functional monomer in an amount sufficient to achieve an acid value from 160 to 325 mg KOH per g of solid copolymer, and
(c) optionally not more than 72 wt. % of monomers other than monomers (a) or (b); wherein
the weight percentages of monomers (a), (b) and (c) total 100% and are calculated as a proportion of the total amount of monomers in the copolymer being 100%; and with the provisos:
(I) the copolymer has a number average molecular weight (Mn) of no more than 15 kilograms per mole; and
(II) the copolymer has a glass transition temperature of at least 75° C., and
(III) the copolymer contains less than 40 wt-% vinyl aromatic monomer; and optionally
(IV) the copolymer contains less than 40 wt-% methacrylate monomer.
2. The process as claimed in claim 1 , wherein monomer (a) comprises a compound of Formula 1:
where Ra and Rb independently represent any optionally substituted hydrocarbo moiety; and
X and Y independently represent —O— and/or —NRc-, where Rc independently in each case represents H and/or any optionally substituted hydrocarbo moiety;
with the proviso that Formula 1 does not contain:
any acidic group, or
any precursor acid group which readily generates an acid group under polymerisation process conditions.
3. The process as claimed in claim 1 , wherein monomer (b) is an acid functional monomer or precursor thereof selected form at least one ethylenically unsaturated carboxylic acid and/or derivatives thereof.
4. The process as claimed in claim 3 , wherein the monomer composition is substantially free of arylalkylene and/or vinyl aromatic monomers.
5. The process as claimed in claim 1 , wherein the copolymer is a solid grade oligomer (SGO).
6. The process as claimed in claim 1 , wherein the solution polymerization process comprises the steps of:
(i) polymerising monomers (a), (b) and (c) under solution polymerisation process conditions in the presence of solvent, and
(ii) removing substantially all the solvent from step (i) to thereby obtain a copolymer comprising at least 95% solids.