Hydroxyl-functional copolymer and coating compositions formed therewith

摘要

Coating compositions which provide scratch resistant and acid resistant coating films, having a Tg in the range of from 1 to 70 DEG C and which comprise a hydroxyl containing copolymer and a cross-linking agent, wherein the hydroxyl containing copolymer has a weight average molecular weight in the range of from 9000 to 30,0000, has an OH concentration of 3.5 to 5 wt% relative to the total weight of all comonomers, and has a Tg of from 0 to 35 DEG C and is obtainable by free radical copolymerization of (a) a glycidyl ester of an alpha -branched alkane carboxylic acid (a'), the acid moiety of which contains 9 to 13 carbon atoms, in an amount of from 0 to 40 wt% and preferably from 10 to 25 wt%, relative to the total mass of all comonomers and/or a vinyl ester of an alpha -branched alkane carboxylic acid (a''), the acid moiety of which contains 9 to 13 carbon atoms, in an amount of from 0 to 40 wt%, relative to the total mass of all components, wherein the total amount of (a') and (a'') is between 5 and 55wt% relative to the total mass of all components, and (b) acrylic acid, which optionally is alpha -substituted by an alkyl group of from 1 to 3 carbon atoms, in an amount of from 0.7 to 12 wt%. relative to the total mass of all comonomers, and (c) alkyl acrylate and optionally an alkyl methacrylate, the alkyl of which contains from 1 to 6 carbon atoms, and preferably from 1 to 4 carbon atoms, in a total amount of from 4 to 65 wt% (this, if c covers the amount of BA and MMA) relative to the total mass of all comonomers, and (d) styrene, divinylbenzene, alpha -methylstyrene, vinylnaphtalene or alkyl substituted styrene, the alkyl of which contains from 1 or 2 carbon atoms, in an amount of from 15 to 30 wt%, relative to the total mass of all comonomers, and (e) optionally a hydroxyalkyl acrylate and/or hydroxyalkyl methacrylate, wherein the alkyl residue contains from 1 to 4 carbon atoms, and preferably 2 carbon atoms, in an amount of from 5 to 38 wt% relative to the total mass of all comonomers, and wherein the sum of the weight percentages of the amounts of components (a) - (e) is always 100%, and wherein the hydroxyl group concentration in the copolymer component is in the range of from 115.5 to 165 mg KOH/g copolymer, and wherein the weight ratio between said hydroxyl containing copolymer and the cross-linking agent is in the range of from 90/10 to 60/40; and cured coating films derived from said coating compositions.