Protective coating for wood

A method of protecting a surface of wood against damage by light by treatment with a coating composition comprising a benzophenone of the formula I ##STR18## in which i is a number from one to four;

• L if i is one is H, C.sub.1 -C.sub.20 alkyl, c.sub.2 -c.sub.20 alkyl which is substituted by one or two --OH, by carboxyl, by C.sub.1 -C.sub.12 alkoxy, by phenoxy, by C.sub.2 -C.sub.20 alkylcarbonyl, by C.sub.3 -C.sub.20 alkenylcarbonyl, by C.sub.2 -C.sub.20 alkanoyloxy, by C.sub.3 -C.sub.20 alkenoyloxy or by phenyl, glycidyl, C.sub.4 -C.sub.20 alkyl which is interrupted by one to six O atoms or by one or two carbonyloxy or oxycarbonyl groups, C.sub.2 -C.sub.18 alkenyl, C.sub.2 -C.sub.18 alkanoyl, C.sub.3 -C.sub.18 alkenoyl, benzoyl, benzoyl which is substituted by one or two C.sub.1 -C.sub.4 alkyl groups, substituted or unsubstituted phenyl or naphthyl, or a group of the formula II, III, IV, V or VI:
• --(CH.sub.2).sub.j --CH(OH)--(CH.sub.2).sub.k --O--R.sub.9 (II) where j,k=0-4;
• --(CH.sub.2).sub.m --COOR.sub.9 (III) where m=1-4;
• in which R.sub.9 is C.sub.1 -C.sub.18 alkyl or phenyl;
• ##STR19## in which a=0-50, b=0-50 and c=0-50;
• A is R.sub.7 or --O--Si(R.sub.7).sub.3 ;
• E.sub.1 is OH, C.sub.1 -C.sub.12 alkyl, C.sub.1 -C.sub.4 alkoxy, cyclohexyl, phenyl or --O--Si(R.sub.7).sub.3 ;
• E.sub.2 is H, C.sub.1 -C.sub.12 alkyl, cyclohexyl, phenyl, --Si(R.sub.7).sub.3 or --Si(R.sub.6)(R.sub.7).sub.2 ;
• in which E.sub.1 and E.sub.2 together may also be a direct bond;
• L.sub.1 is a direct bond or a divalent group of the formula --C.sub.n H.sub.2n --, --(CH.sub.2).sub.n --O--,
• --CH.sub.2 CH(OH)CH.sub.2 --O-- --CH.sub.2 CH(OH)CH.sub.2 --O--(CH.sub.2).sub.3 --, where n=1-4;
• R.sub.6 is a radical of the formula ##STR20## R.sub.7 is C.sub.1 -C.sub.12 alkyl, C.sub.1 -C.sub.4 alkoxy, cyclohexyl or phenyl;
• and
• R.sub.8 is C.sub.1 -C.sub.18 alkyl, C.sub.1 -C.sub.4 alkoxy, C.sub.5 -C.sub.7 cycloalkyl or phenyl;
• ##STR21## in which x is 0, 1 or 2;
• R.sub.1 is C.sub.1 -C.sub.12 alkyl or C.sub.5 -C.sub.8 cycloalkyl;
• and
• R.sub.1 ' is secondary or tertiary C.sub.3 -C.sub.12 alkyl or C.sub.5 -C.sub.8 cycloalkyl;
• ##STR22## in which L.sub.2 is as defined for L if i is two;
• and R.sub.3 ' is H or C.sub.1 -C.sub.18 alkyl;
• L if i is two is C.sub.1 -C.sub.12 alkylene, C.sub.3 -C.sub.12 alkylene which is substituted by --OH, by C.sub.1 -C.sub.8 alkoxy, by C.sub.2 -C.sub.20 alkoxycarbonyl, by C.sub.2 -C.sub.20 alkanoyloxy, by C.sub.3 -C.sub.20 alkenoyloxy or by a silyl group of the formula (IV), C.sub.4 -C.sub.20 alkylene which is interrupted by one to six O atoms or by one or two carbonyloxy or oxycarbonyl groups, o-xylylene, m-xylylene, p-xylylene, isophthaloyl, phthaloyl, terephthaloyl or .alpha., .omega.-C.sub.4 -C.sub.12 alkanedioyl;
• L if i is three is C.sub.3 -C.sub.12 alkanetriyl, C.sub.3 -C.sub.12 alkanetrioyl, trimellitoyl or C.sub.6 -.sub.20 alkanetriyl which is interrupted by three carbonyloxy or oxycarbonyl groups;
• L if i is four is C.sub.4 -C.sub.16 alkanetetrayl, C.sub.4 -C.sub.16 alkanetetroyl, pyromellitoyl or C.sub.8 -C.sub.24 alkanetetrayl which is interrupted by four carbonyloxy or oxycarbonyl groups;
• R.sub.2 is H, C.sub.1 -C.sub.18 alkyl or Cl;
• R.sub.3 is H, Cl, --SR.sub.10, --SOR.sub.10 or --SO.sub.2 R.sub.10 ;
• R.sub.4 is H, --OH, C.sub.1 -C.sub.18 alkyl or C.sub.2 -C.sub.18 alkenyl;
• R.sub.5 is H, --OL, where L is as defined for if i is one, or C.sub.1 ;
• and
• R.sub.10 is C.sub.1 -C.sub.20 alkyl, C.sub.2 -C.sub.20 alkyl which is substituted by --OH, by C.sub.1 -C.sub.12 alkoxy, by a silyl group of the formula (IV), by C.sub.2 -C.sub.12 alkanoyloxy, by C.sub.3 -C.sub.12 alkenoyloxy or by halogen, C.sub.3 -C.sub.18 alkenyl, C.sub.5 -C.sub.12 cycloalkyl, C.sub.7 -C.sub.15 phenylalkyl, C.sub.6 -C.sub.10 aryl, C.sub.6 -C.sub.10 aryl which is substituted by one or two C.sub.1 -C.sub.4 alkyl groups, or 1,1,2,2-tetrahydroperfluoro-C.sub.6 -C.sub.16 alkyl;
• under the condition that, if i is one, at least one of the radicals R.sub.2, R.sub.3 and R.sub.5 is other than H.