Method of preparing polyurethane foam utilizing block copolymers having linked siloxane blocks

A method of optimizing the properties of polyurethane foam utilizing block copolymers of the general average formula:

• ##STR12## as an additive, where the groups and indices can have the following meanings:
• A=R.sup.1 group, an E group or a radical of the following formula IIa ##STR13## or a radical of the following formula IIb ##STR14## B=a group of formula IIa or IIb, Y=Y.sup.1 = ##STR15## or Y.sup.2 = ##STR16## D=a group of the formula ##STR17## R.sup.1 =an unsubstituted or substituted alkyl group having from 1 to 30 carbon atoms, an unsubstituted or substituted aryl group or an unsubstituted or substituted alkaryl group, but with at least 80% of the R.sup.1 groups being methyl groups,
• a is from 3 to 200,
• b is from 0 to 50,
• c is from 0 to 10,
• d is from 0 to 5 and
• e is from 0 to 4,
• where the values of a, b, c, d and e in the individual segments A, B, D and Z can be different and at least one of b or c is not equal to 0,
• E=a group of the general formula;
• --R.sub.f.sup.2 --O--(C.sub.m H.sub.2m O--).sub.n R.sup.3
• where
• R.sup.2 is a divalent alkyl group which may also be branched
• f is 0 or 1;
• m has an average value of from 2 to 4;
• n is from 0 to 100;
• R.sup.3 is hydrogen, an unsubstituted or substituted alkyl group having from 1 to 6 carbon atoms, an acyl group or a --O--CO--NH--R.sup.4 group in which R.sup.4 is an unsubstituted or substituted alkyl or aryl group;
• and
• X=a polyvalent organic group.