Blocked isocyanates

In a storage-stable coating composition curable by heat unblocking at 100.degree. C. to 120.degree. C., said composition comprising an active hydrogen-containing compound and a blocked polyisocyanate of the formula:

• R--Y.sub.m
• wherein m is an integer greater than 1, Y is a blocking group and R is an m-valent aromatic residue of an isocyanate compound selected from the group consisting of .omega., .omega.'-diisocyanato-1,3-dimethyl benzene, .omega., .omega.'-diisocyanato-1,4-dimethyl benzene, .omega., .omega.'-diisocyanato-diethyl benzene, .omega., .omega.'-diisocyanato-dimethyl toluene, .omega., .omega.'-diisocyanato-diethyl toluene, 1,3-bis-(2-isocyanato-prop-2-yl) benzene, and 1,4-bis-(2-isocyanato-prop-2-yl) benzene or R is an m-valent residue of a polyisocyanate reaction product of an isocyanate and an active hydrogen-containing compound selected from the group consisting of water, a lower molecular weight polyol having a molecular weight less than or equal to 300 and a medium molecular weight polyol having a molecular weight greater than 300 and less than 8000 or R is an m-valent residue of an isocyanurate, the improvement whereby said composition is curable by heat unblocking at 100.degree. C. to 120.degree. C., and each Y, which may be the same or different, is ##STR8## wherein R.sub.1 is, or, where n is more than 1, each R.sub.1, which may be the same or different, is a C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkenyl, phenyl C.sub.1 -C.sub.4 alkenyl, phenyl, NO.sub.2, halogen or a ##STR9## group where R.sub.2 is a C.sub.1 -C.sub.4 alkyl group;
• and n is 0, 1, 2 or 3, provided that, when R is an aromatic residue the groups Y are not directly attached to an aromatic nucleus.