Process for stabilizing ethylenically unsaturated compounds and stabilized monomer compositions

A process for preventing the premature polymerization of (a) an ethylenically unsaturated monomer or mixture of monomers, polymerizable by free radical initiation, which comprises

• adding to said monomer (a) an effective amount, sufficient to inhibit the premature polymerization of monomer (a), of (b) a compound or mixture of compounds selected from the group consisting of the compounds of formulas I, II, V, VI, VIII and X, and N-(1-hydroxy-2,2,6,6-tetramethylpiperidin-4-yl)caprolactam and salts thereof, ##STR8## wherein G.sub.1 and G.sub.2 are independently alkyl of 1 to 4 carbon atoms, or G.sub.1 and G.sub.2 together are pentamethylene;
• n is 1 or 2,
• when n is 1,
• R is C.sub.1 -C.sub.18 -alkyl optionally interrupted by one or more oxygen atoms, cyanoethyl, benzyl, glycidyl, a monovalent acyl radical of an aliphatic, cycloaliphatic, araliphatic or aromatic acid, or of carbamic acid or of a phosphorus-containing acid, or a monovalent silyl radical;
• or
• when n is 2,
• R is C.sub.1 -C.sub.12 -alkylene, C.sub.4 -C.sub.12 -alkenylene, xylylene, a divalent acyl radical of an aliphatic, cycloaliphatic, araliphatic or aromatic dicarboxylic acid, or of a dicarbamic acid or of a phosphorus-containing acid, or a bivalent silyl radical;
• p is 1, 2 or 3,
• R.sub.1 is hydrogen, C.sub.1 -C.sub.12 -alkyl, C.sub.5 -C.sub.7 -cycloalkyl, C.sub.7 -C.sub.8 -aralkyl, C.sub.2 -C.sub.18 -alkanoyl, C.sub.3 -C.sub.5 -alkenoyl or benzoyl;
• when p is 1,
• R.sub.2 is hydrogen, C.sub.1 -C.sub.18 -alkyl, C.sub.5 -C.sub.7 -cycloalkyl, C.sub.2 -C.sub.8 -alkenyl unsubstituted or substituted by a cyano, carbonyl or carbamide group, or is glycidyl, a group of the formula --CH.sub.2 CH(OH)--Z or of the formula --CONH--Z wherein Z is hydrogen, methyl or phenyl;
• or
• when p is 2,
• R.sub.2 is C.sub.2 -C.sub.12 -alkylene, C.sub.6 -C.sub.12 -arylene, xylylene, a --CH.sub.2 CH(OH)CH.sub.2 --O--X--O--CH.sub.2 CH(OH)CH.sub.2 -- wherein X is C.sub.2 -C.sub.10 -alkylene, C.sub.6 -C.sub.15 -arylene or C.sub.6 -C.sub.12 -cycloalkylene;
• or, provided that R.sub.1 is not alkanoyl, alkenoyl or benzoyl, R.sub.2 can also be a divalent acyl radical of an aliphatic, cycloaliphatic or aromatic dicarboxylic acid or dicarbamic acid, or can be the group --CO--;
• or R.sub.1 and R.sub.2 together when p is 1 can be the cyclic acyl radical of an aliphatic or aromatic 1,2- or 1,3-dicarboxylic acid;
• or
• R.sub.2 is ##STR9## where T.sub.7 and T.sub.8 are independently hydrogen, alkyl of 1 to 18 carbon atoms, or T.sub.7 and T.sub.8 together are alkylene of 4 to 6 carbon atoms or 3-oxapentamethylene, preferably T.sub.7 and T.sub.8 are 3-oxapentamethylene;
• when p is 3,
• R.sub.2 is 2,4,6-triazinyl;
• Q.sub.1 is --N(R.sub.7)-- or --O--;
• E is C.sub.1 -C.sub.3 -alkylene, the group --CH.sub.2 CH(R.sub.8)--O-- wherein R.sub.8 is hydrogen, methyl or phenyl, the group --(CH.sub.2).sub.3 --NH-- or a direct bond;
• R.sub.7 is hydrogen, C.sub.1 -C.sub.18 -alkyl, C.sub.5 -C.sub.7 -cycloalkyl, C.sub.7 -C.sub.12 -aralkyl, cyanoethyl, C.sub.6 -C.sub.10 -aryl, the group --CH.sub.2 CH(R.sub.8)--OH;
• or a group of the formula ##STR10## or a group of the formula ##STR11## wherein G is C.sub.2 -C.sub.6 -alkylene or C.sub.6 -C.sub.12 -arylene;
• or R.sub.7 is a group --E--CO--NH--CH.sub.2 --OR.sub.6 ;
• R.sub.6 is hydrogen or C.sub.1 -C.sub.18 -alkyl;
• formula VI denotes a recurring structural unit of a polymer where T is ethylene or 1,2-propylene, or is a repeating structural unit derived from an .alpha.-olefin copolymer with an alkyl acrylate or methacrylate;
• k is 2 to 100;
• when n is 1,
• T.sub.2 is hydrogen, C.sub.1 -C.sub.12 -alkyl, C.sub.3 -C.sub.5 -alkenyl, C.sub.7 -C.sub.9 -aralkyl, C.sub.5 -C.sub.7 -cycloalkyl, C.sub.2 -C.sub.4 -hydroxyalkyl, C.sub.2 -C.sub.6 -alkoxyalkyl, C.sub.6 -C.sub.10 -aryl, glycidyl, a group of formula --(CH.sub.2).sub.m --COO--Q or of the formula --(CH.sub.2).sub.m --O--CO--Q wherein m is 1 or 2 and Q is C.sub.1 -C.sub.4 -alkyl or phenyl;
• or
• when n is 2,
• T.sub.2 is C.sub.2 -C.sub.12 -alkylene, C.sub.6 -C.sub.12 -arylene, a group --CH.sub.2 CH(OH)CH.sub.2 --O--X--O--CH.sub.2 CH(OH)CH.sub.2 -- wherein X is C.sub.2 -C.sub.10 -alkylene, C.sub.6 -C.sub.15 -arylene or C.sub.6 -C.sub.12 -cycloalkylene, or a group --CH.sub.2 CH(OZ.sub.1)CH.sub.2 --(OCH.sub.2 CH(OZ.sub.1)CH.sub.2).sub.2 -- wherein Z.sub.1 is hydrogen, C.sub.1 -C.sub.18 -alkyl, allyl, benzyl, C.sub.2 -C.sub.12 -alkanoyl or benzoyl;
• T.sub.3 and T.sub.4 are independently alkylene of 2 to 12 carbon atoms, of T.sub.4 is ##STR12##