Enhanced polymerization process

A process to prepare ABS graft polymers having an improved impact strength, said method comprising:

• preparing a diene rubber latex via a semi-batch process wherein a chain transfer agent is added to said process on a continuous basis for said diene substrate to have an appropriate crosslink density % A to achieve a desired impact strength;
• charging a reaction system with said diene rubber latex;
• adding to the reaction system, over a predetermined time, acrylonitrile and styrene monomers and optionally, an initiator;
• and
• polymerizing said reaction mixture of polybutadiene, styrene and acrylonitrile.

A process to prepare ABS graft polymers having a low end content of unreacted residual monomers, said process comprising:

• charging a reaction system with a diene emulsion;
• adding to the reaction system, over a predetermined time, acrylonitrile and styrene monomers and optionally, an initiator;
• polymerizing the reaction mixture of polybutadiene, styrene and acrylonitrile;
• and
• adding up to 5% of the total polymer and monomer content of a third monomer, that is highly reactive with both acrylonitrile and styrene monomers, to the reaction mixture after greater than 98% of said styrene and acrylonitrile monomers have reacted.

An emulsion polymerization process for the preparation of diene grafted with styrene and acrylonitrile monomers in a reaction system to form grafted ABS polymers having a low end content of unreacted residual monomers and an improved impact strength, said process comprising:

• charging the reaction system with an emulsion comprising a diene substrate having a crosslink density % A which has been selected based on a desired impact strength of an ABS graft polymer product;
• adding a first portion of at least one of styrene monomer and acrylonitrile monomer to the diene emulsion;
• polymerizing said reaction mixture of diene, styrene and acrylonitrile;
• and
• adding a third monomer to the reaction mixture after at least 95% of said styrene and acrylonitrile monomers have reacted.