Emulsion copolymerisates, process for producing them and their use as impact modifier

Emulsion copolymers (I) (obtained by emulsion polymerization of monomer mixture (A) with the monomer mixture (B, C and D), subsequent graft polymerization of monomer mixture (B) with monomer mixtures (A, C and D), further subsequent graft polymerization of monomer mixture (C) with monomer mixtures (A, B and D) and further subsequent graft polymerization of monomer mixture (D) with monomer mixtures (A, B and C)) is new. Emulsion copolymers (I), obtained by (A) emulsion polymerization of monomer mixture (A) (10-50 wt.%) with the monomer mixture (B, C and D) (altogether to make 100 wt.%) of (a1) 50-99.99 wt.% of styrene or its core substituted derivatives (monomer I), (a2) 0-5 wt.% of aliphatic conjugated diene with up to 6C (monomer II), (a3) 0-49.99 wt.% of 1-12C alkyl ester of the acrylic acid or methacrylic acid (monomer III), (a4) 0.01-10 wt.% of bi- or polyfunctional non conjugated monomer (monomer IV), (a5) 0-5 wt.% of further radical polymer monomer (monomer V), where the wt.% of (a1-a5) related to the total quantity of the monomer (A) and added altogether to make 100 wt.%; (B) the subsequent graft polymerization of monomer mixture (B) (20-80 wt.%) with the monomer mixtures (A, C and D) (altogether to make 100 wt.%) of (b1) 80-99.99 wt.% of 1-12C acrylic acid ester (monomer IIIa), (b2) 0-5 wt.% of monomer (II), (b3) 0.01-10 wt.% of monomer (IV), where the wt.% of (b1-b3) are related to the total quantity of monomer (B) and added altogether to make 100 wt.%; (C) further subsequent graft polymerization of 5-50 wt.% of monomer mixture (C) with monomer mixture (A, B and D) (altogether to make 100 wt.%) of (c1) 51-98.99 wt.% of monomer (I), (c2) 0.01-10 wt.% of monomer (IV), (c3) 1-48.99 wt.% of monomer (III), 0-5 wt.% of further radical polymer monomer that are different of monomer (I, III and IV), where the wt.% of (c1-c4) are related to the total quantity of monomer (C) and added altogether to make 100 wt.%; and (D) further subsequent graft polymerization of 5-30 wt.% of monomer mixture (D) with the monomer mixture of (A, B and C) (added altogether to make 100 wt.%) of (d1) 80-100 wt.% of at least a monomer (III), (d2) 0-20 wt.% of at least another monoethylenic unsaturated monomer, (d3) 0-10 wt.% of monomer (I), (d4) 0-5 wt.% of monomer (IV), where the wt.% of (d1-d4) are related to the total quantity of monomer (D) and added altogether to make 100 wt.%. In the method, the emulsion polymerization is carried out in the presence of neutralizing agent (mo