Siloxane copolymers containing alkenyloxy groups, a process for preparing the same and their use

A siloxane copolymer which contains alkenyloxy groups and contains

• (a) siloxane units of the formula ##STR17## in which R is selected from the group consisting of hydrocarbon radicals having from 1 to 18 carbon atom(s) per radical and halogenated hydrocarbon radicals having from 1 to 18 carbon atom(s) per radical, R.sup.1 is an alkyl radical having from 1 to 4 carbon atom(s) per radical which can be substituted by an ether oxygen atom, a is 0, 1, 2 or 3, b is 0, 1, 2 or 3 and the sum of a+b is not greater than 3,
• (b) at least one siloxane unit per molecule of the formula ##STR18## in which R is the same as above, c is 0, 1 or 2 and Q represents a radical of the formula
• --CH.sub.2 CHR.sup.2 CHR.sup.2 OY(OCR.sup.2 .dbd.CR.sup.2 CH.sub.3).sub.x-1
• in which R.sup.2 is a radical selected from the group consisting of a hydrogen atom or a methyl radical, Y is a trivalent, tetravalent, pentavalent or hexavalent hydrocarbon radical having from 2 to 20 carbon atoms per radical which can be substituted with a group from the formula
• --OH,
• --OR.sup.3,
• --OSiR.sup.4.sub.3, ##STR19##
• --X,
• or can be interrupted by at least one oxygen atom or sulfur atom or one carbonyl group, or Y represents a trivalent radical of the formula
• .tbd.P, .tbd.P.dbd.O or .tbd.SiR.sup.5
• in which R.sup.3 is an alkyl radical having from 1 to 6 carbon atom(s) per radical, R.sup.4 is a radical selected from the group consisting of a methyl, ethyl, isopropyl, tert-butyl and phenyl radical, X is a halogen atom, and R.sup.5 is a monovalent hydrocarbon radical having from 1 to 8 carbon atom(s) per radical, or Y represents a tetravalent element selected from the group consisting of ##STR20## and x is 3, 4, 5 or 6 and optionally (c) at least one unit per molecule selected from the group consisting of units of the formula ##STR21## in which R and c are the same as above, Q.sup.1 represents a radical of the formula ##STR22## Q.sup.2 represents a radical of the formula ##STR23## Q.sup.3 represents a radical of the formula ##STR24## in which R.sup.2, Y and x are the same as above