PMMA provided with impact resistance and having improved optical properties

A moulding composition comprising respectively, based on its total weight:

• I. from 10.0 to 50.0% by weight of a core-shell-shell particle having a core, a first shell, and a second shell, produced by the process comprising
• a) employing water and an emulsifier as an initial charge,
• b) adding to the initial charge from 20.0 to 45.0 parts by weight of a first composition comprising:
• A) from 50.0 to 99.9 parts by weight of alkyl methacrylates having from 1 to 20 carbon atoms in the alkyl moiety,
• B) from 0.0 to 40.0 parts by weight of alkyl acrylates having from 1 to 20 carbon atoms in the alkyl moiety,
• C) from 0.1 to 10.0 parts by weight of crosslinking monomers, and
• D) from 0.0 to 8.0 parts by weight of styrenic monomers of formula (I)
• wherein moieties R1 to R5 are each independently hydrogen, a halogen, a C1-6-alkyl group, or a C2-6-alkenyl group, and moiety R6 is hydrogen or an alkyl group having from 1 to 6 carbon atoms, to obtain a first mixture, and polymerizing the first mixture until conversion is at least 85.0% by weight, based on the total weight of components A), B), C), and D),
• c) adding to the first mixture from 35.0 to 55.0 parts by weight of a second composition comprising:
• E) from 80.0 to 100.0 parts by weight of (meth)acrylates,
• F) from 0.05 to 5.0 parts by weight of crosslinking monomers, and
• G) from 0.0 to 25.0 parts by weight of styrenic monomers of formula (I) to obtain a second mixture, and polymerizing the second mixture until conversion is at least 85.0% by weight, based on the total weight of components E), F) and G),
• d) adding to the second mixture from 10.0 to 30.0 parts by weight of a third composition comprising:
• H) from 50.0 to 100.0 parts by weight of alkyl methacrylates having from 1 to 20 carbon atoms in the alkyl moiety,
• I) from 0.0 to 40.0 parts by weight of alkyl acrylates having from 1 to 20 carbon atoms in the alkyl moiety, and
• J) from 0.0 to 10.0 parts by weight of styrenic monomers of formula (I) to obtain a third mixture, and polymerizing the third mixture until conversion is at least 85.0% by weight, based on the total weights of components H), I), and J),
• and wherein the stated parts by weight of the compositions b), c), and d) represent a total of 100.0 parts by weight, wherein the relative proportions of all the substances A) to J) provide, after polymerizing the third mixture, the core-shell-shell particles with a total radius, measured by the Coulter method, in the range of 70.0 to 125.0 nm, wherein the core, the first shell, and the second shell comprise compositions b), c), and d), respectively;
• II. from 1.0 to 90.0% by weight of at least one (meth)acrylic polymer,
• III. from 0.0 to 45% by weight of styrene-acrylonitrile copolymers, and
• IV. from 0.0 to 10.0% by weight of additives,
• wherein II. or mixture of II., III., and/or IV. provide a measurement in accordance with ASTM D542 a refractive index that differs from the refractive index of I. by no more than 0.01 unit.