| abstract |
The present invention relates to a method for preparing a copolymer, comprising the steps of: 1) injecting, together, an aromatic vinyl-based monomer and a cyanovinyl monomer into a reactor and initiating polymerization; and 2) after initiating polymerization, continuously injecting the aromatic vinyl-based monomer into the reactor at a predetermined rate and polymerizing same, wherein the continuous injection of the aromatic vinyl-based monomer is initiated when a polymerization conversion rate is 10% or less, the continuous injection of the aromatic vinyl-based monomer is terminated when a polymerization conversion rate is 80-90%, step 2) comprises a first temperature section and a second temperature section where predetermined temperatures are respectively maintained, and the temperature of the second temperature section is higher than the temperature of the first temperature section. Additionally, provided is a copolymer having a low standard deviation of the composition of a cyanovinyl unit and having excellent transparency. |