Process of manufacturing graft polymer compositions

An emulsion polymerization process of manufacturing a graft polymer composition with a reduced residual monomer content, the process comprising:

• feeding a vinyl aromatic monomer, an unsaturated nitrile, and a first portion of an initiator to a reactor having a temperature of 55 to 60° C., during a first charging period, the reactor containing an initial reaction system comprising water and a diene emulsion;
• after 100 to 20% of the first portion of the initiator has been added to the reactor, increasing the reactor temperature to a second temperature of 70 to 80° C. during the first charging period;
• allowing a polymerization reaction in the reactor to proceed for a first non-charging reaction time of 0 to 30 minutes at the second temperature after the first charging period ends and before a second charging period starts;
• feeding a second portion of the initiator and a third monomer to the reactor having the second temperature during the second charging period, wherein the third monomer is at least one of a methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, benzyl acrylate, isopropyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isopropyl methacrylate, isodecyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, acrylamide, methacrylamide, vinylidine chloride, vinylidine bromide, vinyl ester, dialkyl maleate, or dialkyl fumarate;
• and
• allowing the polymerization reaction to proceed for a second non-charging reaction time to produce a graft polymer composition having a residual vinyl aromatic monomer content of less than 350 ppm, and a residual unsaturated nitrile content of less than 50 ppm,
• wherein the vinyl aromatic monomer and the unsaturated nitrile are fed to the reactor over a period of 30 to 35 minutes.