Copolymer and use thereof for improving the cold flow properties of middle distillate fuels

A copolymer formed from

• (i) 10 to 90 mol % of repeat units of the structure W1
• in which the variables R1 and R2 are each hydrogen, C1- to C4-alkyl or carboxyl ester moieties of the formula —COOR9 where R9 is a C6- to C30-hydrocarbyl radical and where one of the variables R1 and R2 is hydrogen or C1- to C4-alkyl and the other is a carboxyl ester moiety of the formula —COOR9, and
• in which variables R3 and R4 are each hydrogen, C1- to C4-alkyl, carboxyl ester moieties of the formula —COOR9 where R9 is a C6- to C30-hydrocarbyl radical, or carboxyl groups which may also be present in the form of the alkali metal, alkaline earth metal or ammonium salts thereof, where one of the variables R3 and R4 is hydrogen or C1- to C4-alkyl and the other is a carboxyl ester moiety of the formula —COOR9 and/or a carboxyl group which may also be present in the form of the alkali metal, alkaline earth metal or ammonium salt thereof, and
• (ii) 90 to 10 mol % of repeat units of the structure W2
• in which the variable R5 is the radical of a carboxylic ester of the formula
• -A-CO—O—R10
• where the variable A is a C1- to C20-alkylene group and the variable R10 is a C1- to C30-hydrocarbyl radical, and
• in which the variables R6, R7 and R8 are each independently hydrogen or C1- to C4-alkyl,
• where the sum of the repeat units W1 and W2 adds up to 100 mol %.