NEW MATERIAL:Polymerizable compounds of formula I [R1 is H or methyl; A is formula II, III or IV; X is 2-4C alkylene, formula V, VI, etc.; R2 is H or 1-10C alkyl; R3 is -R6-(OR7)m-, etc.; R4 is 1-4C lower alkyl; R5 is -R6-(OR7)m-, etc.; R6 is 1-4C alkylene; R7 is 2-4C alkylene, etc.; m is 0, 1-4; n is 1-50].

USE: Amorphous, low viscosity, excellent in crosslinking properties and useful as a component of a curable resin composition capable of a high solid formation and capable of producing a cured material (e.g. high elastic film or rubber material) excellent in hydrolysis resistance, alkalline resistance, weather resistance, etc.

PREPARATION: A ring-opening addition (polymerization) of β-methyl-δ- valerolactone to a compound of formula VII having a polymerizable double bond and a hydroxyl group is carried out and the terminal hydroxyl group of the resultant addition (polymer) is acetoacetylated, thus giving the objective compound of formula I.