Multilayer acrylic film with improved optical and mechanical properties

Multilayer acrylic film having a thickness between 40 and 300 μm, comprising in this order:

• a layer A made from a thermoplastic acrylic composition (A) comprising from 75 to 95% of a methacrylic (co)polymer containing mostly methyl methacrylate units and fi-on 5 to 25% of an impact modifier:
• a layer B2 made from a composition (B2) that can be obtained by the method comprising:
• 1) preparation by sequential polymerization in aqueous emulsion:
• a) of a first copolymer, by reaction of a system of monomers comprising:
• from 75 to 99.8% of at least one acrylate of an alkyl radical comprising from 1 to 8 carbon atoms, and
• from 0.1 to 5% of a crosslinking agent selected from the polyacrylic and polymethacrylic esters of polyols, the di- or trivinyl benzenes or the vinyl esters, and
• from 0.1 to 20% of at least one grafting agent selected from the allylic, methallylic or crotonic esters of an α,β-unsaturated monocarboxylic or dicarboxylic acid;
• then
• b) of a second copolymer, in the presence of the aqueous system resulting from stage a), by reaction of a system of monomers comprising:
• from 10 to 90% of at least one first acrylate of an alkyl radical containing from 1 to 8 carbon atoms, and
• from 9 to 89.9% of at least one second acrylate of an alkyl radical containing from 1 to 8 carbon atoms, different from the first one, and
• 0.1 to 1% of at least one crafting agent selected from the allylic, methallylic or crotonic esters of an α,β-unsaturated monocarboxylic or dicarboxylic acid;
• then
• c) of a third copolymer, in the presence of the aqueous system resulting from stage b), by reaction of a system of monomers comprising:
• from 5 to 40% of at least one acrylate of an alkyl radical containing from 1 to 8 carbon atoms, and
• from 60 to 95% of at least one second acrylate of an alkyl radical containing from 1 to 8 carbon atoms, different from the first one;
• then
• d) of a fourth polymer, in the presence of the aqueous system resulting from stage c), by reaction of a system of monomers comprising:
• from 80 to 100% of at least one acrylate of an alkyl radical containing from 1 to 8 carbon atoms, and
• from 0 to 20% of at least one second acrylate of an alkyl radical containing from 1 to 8 carbon atoms, different from the first one;
• it being stipulated that:
• the weight of the copolymer obtained in stage a) represents from 10 to 75%, and
• the total weight of the copolymers introduced in stages b), c) and d) represents from 25 to 90%, relative to the total weight of the composition comprising the 4 copolymers obtained after stage d);
• then
• 2) drying of the aqueous emulsion thus obtained;
• then
• 3) optionally, granulation of the product thus dried;
• optionally a layer C made from a thermoplastic acrylic composition (C) comprising from 75 to 95% of a methacrylic (co)polymer containing mostly methyl methacrylate units and from 5 to 25% of an impact modifier;
• the layers A, B2 and optionally C being joined together in their respective contact zones.

Multilayer acrylic film having a thickness between 40 and 300 μm, comprising in this order:

• a layer A made from a thermoplastic acrylic composition (A) comprising from 75 to 95% of a methiacrylic (co)polymer containing mostly methyl methacrylate units and from 5 to 25% of an impact modifier:
• a layer B3 made from a composition (B3) comprising from 0 to 5 wt % of at least one polymer A and from 95 to 100 wt % of at least one block copolymer of formula B(-A)n composed of a block B and n blocks A obtained by radical polymerization controlled by means of an alkoxyamine of formula I(-T)n in which I denotes a multivalent group, T denotes a nitroxide and n denotes an integer greater than or equal to 2;
• optionally a layer C made from a thermoplastic acrylic composition (A) comprising from 75 to 95% of a methacrylic (co)polyiner containing mostly methyl methacrylate units and from 5 to 25% of an impact modifier;
• layers A, B3 and optionally C being joined together in their respective contact zones.