BLOCK COPOLYMER AND ITS USE

PROBLEM TO BE SOLVED: To obtain a block copolymer useful as an additive in the production of surfactants and polyurethane foams by selecting a block copolymer in which siloxane blocks are bonded through one rigid spacer in the molecule. SOLUTION: This polymer is represented by formula I (wherein A is group R , group B, group E or formula II; B is formula II or formula III; D is formula IV, R is a 1-30C alkyl, an aryl or an alkaryl, provided that at least 80% of R s are methyl groups; a is 3-200; b is 0.50; c is 0-10; d is 0-5; E is formula V (wherein R is a divalent alkyl; f is 0 or 1; m is 2-4; n is 0-100; R is H, a 1-6C alkyl, an acyl or an -O-CO-NH-R group; and R is an alkylor an aryl); an epoxy-functionalized alkyl substituent; mono-(di- or tri-)hydroxyalkyl substituent; a halogen-substituted alkyl; a halogen-substituted aryl; or a halogen- substituted aralkyl).