Process for the production of copolymers

A process for the production of copolymers comprising:

• (i) forming a reaction mixture comprising an elastomer and a vinyl aromatic compound;
• (ii) introducing the reaction mixture to a reaction vessel;
• and
• (iii) performing a polymerization reaction;
• wherein steps (i) (iii) are performed in that order;
• thereby obtaining a copolymer comprising:
• (a) a phase comprising a reaction product of the elastomer with the vinyl aromatic compound;
• and
• (b) a phase comprising a reaction product of the vinyl aromatic compound;
• wherein a sample from the reaction vessel is obtained during step (iii) to determine of the formed copolymer:
• the content of phase (b);
• and/or
• the molecular weight of phase (b);
• wherein the determination of the content of phase (b) in the formed copolymer and the molecular weight of phase (b) is performed by a method comprising isolation of phase (b) from the sample of the formed copolymer by (1) preparing a solution of the formed copolymer in a solvent;
• and (2) removing an insoluble fraction from the solution obtained in step (1) by filtration to obtain phase (b) as a filtered sample and subjecting the obtained phase (b) to molecular analysis, wherein
• the filtration is in a filter system comprising at least the following filtration layers through which the solution is transported in this order;
• a layer 1 comprising glass fibres such that particles of ≥1.00 μm do not pass these layers;
• a layer 2 comprising a membrane filter such that particles of ≥0.45 μm do not pass this layer;
• and
• the molecular analysis is performed by gel permeation chromatography in accordance with ASTM D5296-11.