Thermoplastic molding compositions with improved optical properties

1. A thermoplastic molding composition comprising a mixture of

(a) from 10 to 50% by weight, based on the entirety of components (A), (B), and (C), of a methyl methacrylate polymer as component (A), obtainable via polymerization of a mixture composed of

(a1) from 90 to 100% by weight, based on (A), methyl methacrylate as component (A1), and

(a2) from 0 to 10% by weight, based on (A), of a C 1 -C 8 -alkyl ester of acrylic acid as component (A2), and

(b) from 20 to 60% by weight, based on the entirety of components (A), (B), and (C), of a copolymer as component (B), obtainable via polymerization of a mixture composed of

(b1) from 70 to 90% by weight, based on (B), of a vinylaromatic monomer as component (B1), and

(b2) from 10 to 30% by weight, based on (B) of a vinyl cyanide as component (B2), and

(c) from 20 to 70% by weight, based on the entirety of components (A), (B), and (C), of a graft copolymer as component (C), obtainable from

(c1) from 50 to 70% by weight, based on (C), of a core as component (C1), obtainable via polymerization of a monomer mixture composed of

(c11) from 65 to 89.9% by weight, based on (C1) of a 1,3-diene as component (C11), and

(c12) from 10 to 34.9% by weight, based on (C1), of a vinylaromatic monomer as component (C12), and

(c13) from 0.1 to 5% by weight, based on (C1), of an agglomeration polymer as component (C13), and

(c2) from 15 to 25% by weight, based on (C), of a first graft shell as component (C2), obtainable via polymerization of a monomer mixture composed of

(c21) from 30 to 49.9% by weight, based on (C2), of a vinylaromatic monomer as component (C21), and

(c22) from 50 to 69.9% by weight, based on (C 2 ), of a C 1 -C 8 -alkyl ester of methacrylic acid and/or of a C 1 -C 8 -alkyl ester of acrylic acid as component (C22), and

(c23) from 0.1 to 3% by weight, based on (C2), of a crosslinking monomer as component (C23), and

(c3) from 15 to 25% by weight, based on (C), of a second graft shell as component (C3), obtainable via polymerization of a monomer mixture composed of

(c31) from 20 to 80% by weight, based on (C3), of a C 1 -C 8 -alkyl ester of methacrylic acid as component (C31) and

(c32) from 20 to 80% by weight, based on (C3), of a further monomer as component (C32), and

(d) optionally, amounts of up to 20% by weight, based on the entirety of components (A), (B), and (C), of additives as component (D),

wherein

component (C32) is a vinylaromatic monomer and

the graft copolymer (C) is produced via emulsion polymerization and is isolated from the reaction mixture by precipitation resulting from shear.

2. The thermoplastic molding composition according to claim 1 , wherein the graft copolymer (C) has a particle size distribution that is bimodal, and the first maximum of the particle size distribution lies within the range from 80 to 200 nm, and the second maximum of the particle size distribution lies within the range from 250 to 500 nm.

3. The thermoplastic molding composition according to claim 1 , wherein a mixture of from 2 to 20% by weight of n-butyl acrylate and from 80 to 98% by weight of methyl methacrylate, based in each case on the total weight of component (C22), is used as component (C22).

4. The thermoplastic molding composition according to claim 1 , wherein allyl methacrylate is used as component (C23).

5. The thermoplastic molding composition according to claim 1 , where styrene, α-methylstyrene, or a mixture of said monomers is used as components (B1), (C12), (C21), and/or (C32).

6. The thermoplastic molding composition according to claim 1 , wherein copolymers of from 80 to 99.9% by weight of ethyl acrylate and from 0.1 to 20% by weight of methacrylamide, based in each case on the total weight of component (C13), are used as agglomeration polymer (C13).

7. A thermoplastic molding composition comprising a mixture of copolymer (AB) and (C), wherein the thermoplastic molding composition comprises

(ab) from 30 to 80% by weight, based on the entirety of component (AB) and (C), of a copolymer as component (AB), obtainable via polymerization of a mixture composed of

(ab1) from 30 to 50% by weight, based on (AB), of methyl methacrylate as component (A1), and

(ab2) from 0 to 10% by weight, based on (AB), of a C 1 -C 8 -alkyl ester of acrylic acid as component (A2), and

(ab3) from 40 to 65% by weight, based on (AB), of a vinylaromatic monomer as component (B1), and

(ab4) from 5 to 20% by weight, based on (AB), of a vinyl cyanide as component (B2), and

(c) from 20 to 70% by weight of a graft copolymer as component (C), based on the entirety of components (AB) and (C), wherein the graft copolymer as component (C) is obtainable from

(c1) from 50 to 70% by weight, based on (C), of a core as component (C1), obtainable via polymerization of a monomer mixture composed of

(c11)from 65 to 89.9% by weight, based on (C1) of a 1,3-diene as component (C11), and

(c12) from 10 to 34.9% by weight, based on (C1), of a vinylaromatic monomer as component (C12), and

(c13) from 0.1 to 5% by weight, based on (C1), of an agglomeration polymer as component (C13), and

(c2) from 15 to 25% by weight, based on (C), of a first graft shell as component (C2), obtainable via polymerization of a monomer mixture composed of

(c21) from 30 to 49.9% by weight, based on (C2), of a vinylaromatic monomer as component (C21), and

(c22) from 50 to 69.9% by weight, based on (C2), of a C 1 -C 8 -alkyl ester of methacrylic acid and/or of a C 1 -C 8 -alkyl ester of acrylic acid as component (C22), and

(c23) from 0.1 to 3% by weight, based on (C2), of a crosslinking monomer as component (C23), and

(c3) from 15 to 25% by weight, based on (C), of a second graft shell as component (C3), obtainable via polymerization of a monomer mixture composed of

(c31) from 20 to 80% by weight, based on (C3), of a C 1 -C 8 -alkyl ester of methacrylic acid as component (C31) and

(c32) from 20 to 80% by weight, based on (C3), of a further monomer as component (C32), and

(d) optionally, amounts of up to 20% by weight, based on the entirety of components (AB) and (C), of component (D).

8. A process for producing a thermoplastic molding composition which comprises mixing the following in the melt:

either

(a) from 10 to 50% by weight, based on the entirety of components (A), (B), and (C), of a methyl methacrylate polymer as component (A), obtainable via polymerization of a mixture composed of

(a1) from 90 to 100% by weight, based on (A), methyl methacrylate as component (A1), and

(a2) from 0 to 10% by weight, based on (A), of a C 1 -C 8 -alkyl ester of acrylic acid as component (A2), and

(b) from 20 to 60% by weight, based on the entirety of components (A), (B), and (C), of a copolymer as component (B), obtainable via polymerization of a mixture composed of

(b1) from 70 to 90% by weight, based on (B), of a vinylaromatic monomer as component (B1), and

(b2) from 10 to 30% by weight, based on (B) of a vinyl cyanide as component (B 2 ), or

(ab) from 30 to 80% by weight, based on the entirety of component (AB) and (C), of a copolymer as component (AB), obtainable via polymerization of a mixture composed of

(ab1) from 30 to 50% by weight, based on (AB), of component (A1), and

(ab2) from 0 to 10% by weight, based on (AB), of component (A2), and

(ab3) from 40 to 65% by weight, based on (AB), of component (B1), and

(ab4) from 5 to 20% by weight, based on (AB), of component (B2), and with

(c) from 20 to 70% by weight, based on the entirety of component (A), (B), and (C) or, respectively, (AB) and (C), of a graft copolymer as component (C), obtainable from

(c1) from 50 to 70% by weight, based on (C), of a core as component (C1), obtainable via polymerization of a monomer mixture composed of

(c11) from 65 to 89.9% by weight, based on (C1) of a 1,3-diene as component (C11), and

(c12) from 10 to 34.9% by weight, based on (C1), of a vinylaromatic monomer as component (C12), and

(c13) from 0.1 to 5% by weight, based on (C1), of an agglomeration polymeras component (C13), and

(c2) from 15 to 25% by weight, based on (C), of a first graft shell as component (C2), obtainable via polymerization of a monomer mixture composed of

(c21) from 30 to 49.9% by weight, based on (C2), of a vinylaromatic monomer as component (C21), and

(c22) from 50 to 69.9% by weight, based on (C2), of a C 1 -C 8 -alkyl ester of methacrylic acid and/or of a C 1 -C 8 -alkyl ester of acrylic acid as component (C22), and

(c23) from 0.1 to 3% by weight, based on (C2), of a crosslinking monomer as component (C23), and

(c3) from 15 to 25% by weight, based on (C), of a second graft shell as component (C3), obtainable via polymerization of a monomer mixture composed of

(c31) from 20 to 80% by weight, based on (C3), of a C 1 -C 8 -alkyl ester of methacrylic acid as component (C31) and

(c32) from 20 to 80% by weight, based on (C3), of a further monomer as component (C32), and

(d) optionally, amounts of up to 20% by weight, based on the entirety of components (A), (B), and (C), or, respectively, (AB) and (C), of conventional additives as component (D),

which comprises

using a vinylaromatic monomer as component (C32) and

producing the graft copolymer (C) via emulsion polymerization and isolating it from the reaction mixture by precipitation resulting from shear.

9. A process for producing a molding which comprises injection molding or blow molding the thermoplastic molding compositions according to claim 1 to form the molding.

10. A molding comprising the thermoplastic molding composition according to claim 1 .