Polyacrylate graft rubber copolymer and impact modified thermoplastic molding composition

1. A graft copolymer B composed of:

B1: 50 to 70 wt.-%, based on B, of at least one graft base B1 obtained by emulsion polymerization of the following monomers:

i. b11: 70 to 99.9 wt.-%, based on B1, of at least one acrylate;

ii. b12: 0 to 29.9 wt.-%, based on B1, of at least one further comonomer selected from: styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, methylmethacrylate, and N-phenylmaleimide (N-PMI); and

iii. b13:0.1 to 10 wt.-%, based on B1, of one or more bi- or polyfunctional, crosslinking monomers;

where the sum of b11, b12 and b13 adds up to 100 wt.-%; and

B2: 30 to 50 wt.-%, based on B, of a graft shell B2, which is obtained via emulsion polymerization in the presence of at least one graft base B1, which graft shell B2 comprises a first layer B21 made of at least one vinylaromatic monomer, and a second layer B22 made of a mixture comprising at least one vinylaromatic monomer B21-1 and at least one nitrile monomer B22-2;

where the sum of B1 and B2 adds up to 100 wt.-%;

wherein:

i. the weight average particle diameter d w of the graft base B1 is in the range of from 255 to 290 nm;

ii. the fraction of B21, based on the total amount of B2, is 10 to 26 wt.-%; and

iii. the amount of B22-2, based on the total amount of B22, is 20 to 30 wt.-%.

2. The graft copolymer B of claim 1 , wherein the weight average particle diameter d w of the graft base B1 is in the range of from 260 to 285 nm.

3. The graft copolymer B of claim 1 , wherein the fraction of B21, based on the total amount of B2, is 12 to 22 wt.-%.

4. The graft copolymer B of claim 1 , wherein graft base B1 is made of monomers b11, b12, and b13 in the following amounts:

b11: 75 to 99.5 wt.-%;

b12: 0 to 20 wt.-%; and

b13: 0.5 to 5 wt.-%.

5. The graft copolymer B of claim 1 , wherein graft base B1 is obtained by emulsion polymerization of:

b11: at least one C2-C8-alkyl acrylate; and

b13: at least one bifunctional comonomer having two olefinic double bonds.

6. The graft copolymer B of claim 1 , wherein graft shell B2 comprises a first layer B21 made of styrene, and a second layer B22 made of a mixture consisting of styrene B21-1 and acrylonitrile B22-2.

7. A process for the preparation of the graft copolymer B of claim 1 ,

comprising the following steps:

(i) first, production of a graft base B1 in the presence of a seed polymer latex (S-B1), wherein S-B1 has a weight average particle diameter dw of below that of the particles of the final graft base B1, by emulsion polymerization of the monomer b11, optionally the comonomer b12, and the crosslinking monomer b13 in an aqueous emulsion with a free-radical initiator at temperatures of from 30° to 120° C.; and

(ii) second, on the obtained graft base B1, in aqueous emulsion, in a first graft reaction (ii1) a first layer B21 of graft shell B2 is prepared by addition and polymerization of a vinyl aromatic monomer, and then, in a second graft reaction (ii2) a second layer B22 of graft shell B2 is prepared by addition and polymerization of monomers B22-1 and B22-2.

8. The process for the preparation of the graft copolymer B of claim 7 , wherein the seed polymer latex (S-B1) is used in amounts of from 0.01 to 3 wt.-%, based on the total amount of monomer used for the preparation of graft base B1, and wherein the weight average particle diameter d w of S-B1 is less than 120 nm.

9. A thermoplastic molding composition comprising a polymer mixture PM comprising components A and B:

(A) 30 to 85 wt.-% of at least one thermoplastic copolymer A comprising at least one vinylaromatic monomer A1, and at least one nitrile monomer A2;

(B) 15 to 70 wt.-% of at least one graft copolymer B of claim 1 ;

where the sum of A and B adds up to 100 wt.-%.

10. The thermoplastic molding composition of claim 9 , comprising further components C, D, and/or E:

40 to 100 wt.-% of a polymer mixture PM composed of components A and B;

0 to 30 wt.-% of at least one further graft copolymer C, different from graft copolymer B, composed of an elastomeric, crosslinked acrylate polymer C1 as graft base C1 and at least one graft shell C2, wherein the graft copolymer C is obtained via emulsion polymerization in the presence of at least one graft base C1, wherein graft shell C2 is made of a mixture comprising at least one vinylaromatic monomer C2-1 and at least one nitrile monomer C2-2;

0 to 20 wt.-% of additives and/or auxiliaries D; and

0 to 50 wt.-% of at least one further thermoplastic polymer E selected from aromatic polycarbonates and polyamides;

based in each case on the overall molding composition, and where the sum of PM, and components C, D, and/or E adds up to 100 wt.-%.

11. The thermoplastic molding composition of claim 9 , wherein the proportion of the nitrile monomer A2, based on A, of thermoplastic copolymer A is from 20 to 35% by weight.

12. The thermoplastic molding composition of claim 10 , wherein graft copolymer C has one graft shell C2 consisting of only one layer made of a mixture comprising at least one vinylaromatic monomer C2-1, and at least one nitrile monomer C2-2, where the amount of C2-2, based on the total amount of C2, is 20 to 35 wt.-%.

13. The thermoplastic molding composition of claim 10 , wherein the graft shell C2 of graft copolymer C consists of a first layer C21 made from at least one vinylaromatic monomer, and a second layer C22 made of a mixture comprising at least one vinylaromatic monomer C22-1 and at least one nitrile monomer C22-2; where the amount of C22-2, based on the total amount of C22, is 20 to 35 wt.-%, and wherein the weight average particle diameter dw of the graft base C1 of graft copolymer C is in the range of from 300 to 700 nm.

14. The thermoplastic molding composition of claim 13 , wherein the fraction of the first layer C21 of graft shell C2, based on the total amount of C21 and C22, is more than 30 wt.-%.

15. A process for the preparation of the thermoplastic molding composition of claim 10 by melt-mixing graft copolymer B with copolymer A and, where present, with the further components C, D, and/or E in a mixing apparatus.

16. A shaped article produced from the thermoplastic molding composition of claim 9 .

17. An article comprising the graft copolymers of claim 1 for automotive industry, building and construction, toy, and/or leisure applications.

18. An article comprising the graft copolymers of the molding composition of claim 9 for automotive industry, building and construction, toy, and/or leisure applications.