Multilayer structures containing biopolymers

A multilayer structure, having at least three layers, said multilayer sheet comprising, in order:

• a) at least one outer layer, covering the inner layer, comprising a thermoplastic polar polymer matrix, being on the outer side of the structure exposed to the environment, wherein said thermoplastic polar polymer matrix is selected from the group consisting of acrylic-based polymers, styrenic-based polymers, polycarbonate, polyvinylidene fluoride, polystyrene, high-impact polystyrene (HIPS), acrylonitrile-butadiene-styrene (ABS) copolymers, acrylonitrile-styrene-acrylate (ASA) copolymers, styrene acrylonitrile (SAN) copolymers, methacrylate-butadiene-styrene (MBS) copolymers, styrene-butadiene copolymers, styrene-butadiene-styrene block (SBS) copolymers and their partially or fully hydrogenenated derivatives, styrene-isoprene copolymers, styrene-isoprene-styrene (SIS) block copolymers and their partially or fully hydrogenenated derivatives, styrene-(meth)acrylate copolymers, styrene-methyl methacrylate copolymers (S/MMA) and compatible mixtures thereof,
• b) at least one inner layer comprising a biopolymer/acrylic polymer alloy, wherein said alloy is a single intimate mixture, and wherein said acrylic polymer is an acrylic copolymer having from 70-99.5 weight percent of methyl methacrylate units, and 0.5 to 30 weight percent of one or more C1-8 straight or branched alkyl acrylate units,
• c) a substrate layer, said biopolymer/acrylic layer, b), being between the substrate layer and the polar polymer layer, with layers a) and b) forming a capstock, said capstock making up from 5 to 25 percent for the thickness of the multi-layer structure.