Copolymer composition, method for producing same, and molded article obtained using copolymer composition

A copolymer composition comprising a copolymer (A) having a constitutional unit (a1) derived from 1,1-dicyanoethylene and a constitutional unit (a2) derived from a compound represented by general formula (I) below,

• wherein a weight reduction rate is 5.0% by mass or less when held for 30 minutes at a temperature (T) at which a complex viscosity measured under conditions of a frequency of 1 Hz and a distortion of 1% becomes 10,000 Pa·s:
• wherein, R1 represents one or more selected from a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, and a halogen atom, and
• R2 represents one or more selected from a hydrogen atom, an alkyl group, an alkoxy group, a carboxy group, an ester group represented by —COOR3, in which R3 represents an alkyl group having 1 to 12 carbon atoms, an acid anhydride group, an acyl group represented by —COR4, in which R4 represents an alkyl group having 1 to 12 carbon atoms, and an acyloxy group represented by —OCOR5, in which R5 represents an alkyl group having 1 to 12 carbon atoms.