Primer compositions

Improved primer compositions comprise (A) at least one member of a specified group of ethylenically unsaturated organosilicon compounds containing silicon-bonded alkoxy groups, (B) silicone/organic copolymers prepared from esters of ethylenically unsaturated organic acids and organosilicon compounds derived from these acids, (C) organohydrogensiloxane curing agents and (D) a solvent. The improvement resides in the presence in the solvent of an ethylenically unsaturated alcohol containing from 4 to 6 carbon atoms. The alcohol constitutes at least 50 percent by weight of the solvent.

That which is claimed is:

1. In a primer composition comprising

A. an organosilicon compound of the formula (R.sup.1 O).sub.n (R.sup.2 O).sub.(3-n) SIR.sup.3 Si(OR.sup.1).sub.r (OR.sup.2).sub.(3-r), where R.sup.1 represents CH.sub.2 .dbd.CHR.sup.4 OR.sup.5 --; R.sup.2 represents an alkyl radical containing from 1 to 4 carbon atoms; R.sup.3 represents an alkylene radical containing at least 2 carbon atoms; R.sup.4 represents an alkylene radical; R.sup.5 represents an alkylene or substituted alkylene radical, where R.sup.5 contains at least two carbon atoms and the substituent is a hydroxy, alkoxy or CH.sub.2 .dbd.CHR.sup.4 O-- group, n is 1 or 2, and n is 0 or 1;

B. a copolymer derived from (1) at least one ester of an ethylenically unsaturated aliphatic carboxylic acid and (2) at least one silane of the formula R.sup.7 COOR.sup.6 SiX.sub.3 where R.sup.6 represents an alkylene radical, R.sup.7 represents a terminally unsaturated alkenyl radical and X represents a hydrolyzable group;

C. an organohydrogensiloxane containing an average of at least two silicon-bonded hydrogen atoms per molecule; and

D. an amount of solvent sufficient to dissolve said composition;

the improvement comprising the presence in said solvent of at least 50 weight percent, based on the weight of said solvent, of an ethylenically unsaturated alcohol containing 4, 5 or 6 carbon atoms or a mixture of said alcohols.

2. A composition according to claim 1 where, in ingredients A, R.sup.2 is methylene, R.sup.3 is ethylene, R.sup.4 is methylene, R.sup.5 is ethylene, propylene 1,4-butylene or ##STR1## in ingredient B, R.sup.6 is propylene, R.sup.7 is CH.sub.2 .dbd.CH or CH.sub.2 .dbd.C(CH.sub.3)--, X is methoxy or ethoxy, and said ester of an ethylenically unsaturated carboxylic acid is methyl methacrylate and, the organohydrogensiloxane (ingredient C) is a polymethylhydrogensiloxane.

3. A composition according to claim 2 where, in ingredient D, the alcohol is crotyl alcohol, 2-methyl-2-buten-2-ol or 3-methyl-1- penten-3-ol.

4. A composition according to claim 2 where, in ingredient D, the ethylenically unsaturated alcohol contains 4 or 5 carbon atoms.

5. A composition according to claim 1 where said solvent (ingredient D) consists essentially of said alcohol and up to 50 percent, based on the weight of said solvent, of a monoether or diether of ethylene or propylene glycol.