Linear polydimethylsiloxane-polyoxyalkylene block copolymers linked with carboxylic ester groups via SIC groups, a process for preparing them and their use

Linear silicon carbide groups and carboxylic acid ester group containing polydimethylsiloxane-polyoxyalkylene-block copolymer (I) having repeating units (A), are new. Linear silicon carbide groups and carboxylic acid ester group containing polydimethylsiloxane-polyoxyalkylene-block copolymer (I) having repeating units of formula (A 1>B 1>A 2>B 1>) (A), are new. A 1>, A 2>polydimethylsiloxane unit of formula (-Si(CH 3) 2-[O-Si(CH 3) 2] n-P-Si(CH 3) 2-), where the number of Si is equal to (n+2), which is 15-30 and the number of Si in A 1>is different from the number of Si in A 2>; B 1>ester group of formula (-CH 2-CH 2-(CH 2) a-CO[O-CH 2-CH(R)] c-O-[D-O] e-[-CH 2-CH(R)-O] d-OC-(CH 2) b-CH 2-CH 2-) (b), where the total molecular weight of (b) is 600-10000 g/mole; R : H, CH 3or C 2H 5; a, b : 0-20; c, d : >= 1; e : 0 or 1; and D : 2-10C hydrocarbon. Where: the average molecular weight of polydimethylsiloxane (A 1>+A 2>) is 1.665-1.998 g/mole; and in (b), when R is H in [O-CH 2-CH(R)], then the total molecular wei