An impact modified acrylic polymer composition comprising a. a base polymer of an acrylic polymeric composition comprising a melt blend of a thermoplastic high molecular weight acrylic material (HMWA) and a thermoplastic low molecular weight acrylic material (LMWA), at least 70% w/w, based on the total weight of the HMWA, of the said HMWA comprising an alkyl (alk)acrylate (co)polymer, the said (co)polymer comprising at least 80% w/w of a first polymer derived from C 1 -C 12 alkyl (C 1 -C 8 alk) acrylate monomer units and optionally, up to 20% w/w, based on the said alkyl (alk)acrylate (co)polymer of a first copolymer derived from C 1 -C 12 alkyl (C 0 -C 8 alk) acrylate and/or (C 0 -C 8 alk)acrylic acid monomer units, the said HMWA having a weight average molecular weight of between 40k Daltons and 1000k Daltons, at least 70% w/w, based on the total weight of the LMWA, of the said LMWA comprising an alkyl(alk)acrylate (co)polymer, the said (co)polymer comprising at least 80% w/w of a second polymer derived from C 1 -C 12 alkyl (C 1 -C 8 alk)acrylate monomer units and optionally, up to 20% w/w, based on the said alkyl (alk) acrylate (co)polymer of a second copolymer derived from C 1 -C 12 alkyl (C 0 -C 8 alk) acrylate and/or (C 0 -C 8 alk)acrylic acid monomer units, the said LMWA having a weight average molecular weight of between the entanglement molecular weight (M e) (expressed in k Daltons) and 250k Daltons, with the proviso that the HMWA has a higher Mw than the LMWA, wherein the first polymer of the HMWA and the second polymer of the LMWA are the same, and wherein the weight ratio of HMWA:LMWA in the composition is greater than 1:1; and b. a core-shell impact modifier, wherein the level of component (b) in the impact modified acrylic polymer composition is in the range 30-50% w/w. a. a base polymer of an acrylic polymeric composition comprising a melt blend of a thermoplastic high molecular weight acrylic material (HMWA) and a thermoplastic low molecular weight acrylic material (LMWA), at least 70% w/w, based on the total weight of the HMWA, of the said HMWA comprising an alkyl (alk)acrylate (co)polymer, the said (co)polymer comprising at least 80% w/w of a first polymer derived from C 1 -C 12 alkyl (C 1 -C 8 alk) acrylate monomer units and optionally, up to 20% w/w, based on the said alkyl (alk)acrylate (co)polymer of a first copolymer derived from C 1 -C 12 alkyl (C 0 -C 8 alk) acrylate and/or (C 0 -C 8 alk)acrylic acid monomer units, the said HMWA having a weight average molecular weight of between 40k Daltons and 1000k Daltons, at least 70% w/w, based on the total weight of the LMWA, of the said LMWA comprising an alkyl(alk)acrylate (co)polymer, the said (co)polymer comprising at least 80% w/w of a second polymer derived from C 1 -C 12 alkyl (C 1 -C 8 alk)acrylate monomer units and optionally, up to 20% w/w, based on the said alkyl (alk) acrylate (co)polymer of a second copolymer derived from C 1 -C 12 alkyl (C 0 -C 8 alk) acrylate and/or (C 0 -C 8 alk)acrylic acid monomer units, the said LMWA having a weight average molecular weight of between the entanglement molecular weight (M e) (expressed in k Daltons) and 250k Daltons, with the proviso that the HMWA has a higher Mw than the LMWA, wherein the first polymer of the HMWA and the second polymer of the LMWA are the same, and wherein the weight ratio of HMWA:LMWA in the composition is greater than 1:1; and b. a core-shell impact modifier, wherein the level of component (b) in the impact modified acrylic polymer composition is in the range 30-50% w/w.