Process for the production of a vinyl chloride-(meth)acrylate copolymer and composition comprising such a copolymer

A process for the production of a vinyl chloride-(meth)acrylate copolymer, C, by reacting a vinyl chloride monomer, A, and an alkyl (meth)acrylate monomer, B, said process comprising:

• A) In a first step:
• i) Providing a first mixture comprising vinyl chloride monomer, A, and alkyl (meth)acrylate monomer, B, in an aqueous medium in a reactor, wherein:
• a. the amount of B is between 20 and 100% of the total amount of B,
• b. the amount of A is between 15 and 80% of the total amount of A, and
• c. the weight ratio of A:B is 25:75 to 75:25;
• ii) Polymerising said first mixture, said polymerisation taking place by:
• a. heating the reactor to a temperature, T1, wherein the temperature, T1, is at least 55 °C,
• b. adding an initiator to start polymerisation,
• And wherein:
• c. where the amount of B at the start of the polymerisation is less than 100% of the total amount of B, the rest of B is added to the reactor in this first step after initiation of the polymerisation,
• d. where the amount of A at the start of the polymerisation is less than 80% of the total amount of A, optionally further monomer A is added to the reactor in this first step after initiation of the polymerisation, but with the proviso that the amount of monomer A added in this first step remains less than 80% of the total amount of A, and
• e. polymerisation is continued until at least 50% of the total amount of monomer B has reacted;
• B) In a second step:
• i) Adding the rest of monomer A to form a second mixture, and polymerising the second mixture
• wherein prior to the addition of the rest of monomer A in this second step, the temperature of the reactor is reduced to a temperature, T2, which is at least 10 °C below the temperature, T1,
• and further wherein the vinyl chloride-(meth) acrylate copolymer produced comprises 30-50wt % alkyl (meth) acrylate and 50-70wt % vinyl chloride.