Patent ID: 8907049

Claim:
A block copolymer (M) suitable for toughening a thermoset resin (R), said block copolymer (M) having one or more segments of a thermoplastic aromatic polymer (A) chemically linked to one or more segments of a low Tg polymer (B) wherein: (i) the low T g polymer (B) exhibits a Tg in the range of from about −130° C. to about +40° C.; (ii) the one or more segments of aromatic polymer (A) is soluble in uncured thermoset resin precursor(s) (P) of said thermoset resin (R), (iii) the one or more segments of low Tg polymer (B) is insoluble in the uncured thermoset resin precursor(s) (P), (iv) the aromatic polymer (A) is a polyarylsulphone comprising ether-linked repeating units, the units being selected from: —[ArSO 2 Ar] n — and optionally from: —[Ar] a — wherein: Ar is phenylene; n=1 to 2 and can be fractional; a=1 to 3 and can be fractional and when a exceeds 1, said phenylene groups are linked linearly through a single chemical bond or a divalent group other than —SO 2 —, or are fused together, provided that the repeating unit —[ArSO 2 Ar] n — is always present in the polyarylsulphone in such a proportion that on average at least two of said —[ArSO 2 Ar] n — units are in sequence in each polymer chain present, and wherein the polyarylsulphone has one or more reactive pendant or end group(s), (v) the low Tg polymer (B) is selected from saturated aliphatic polyesters derived from at least divalent linear, branched or cyclic aliphatic alcohols having from 2 to 60 carbon atoms, and at least divalent linear, branched or cyclic aliphatic carboxylic acids having from 3 to 60 carbon atoms, with the proviso that at least one of the alcohol or the acid components has at least 4 carbon atoms.