PURPOSE: A reactive cyclized resin, obtained by cyclizing a specific random copolymer of cetylene with a conjugated diene compound, having a reactivity, and suitable for many industrial purposes, and having diallyl active methylene groups.

CONSTITUTION: A reactive cyclized resin obtained by cyclizing a random copolymer of acetylene with a conjugated diene compound having rich 1,4-bonds and 200W10,000, preferably 500W5,000, molecular weight in an organic solvent, e.g. benzene, in the presence of an acidic catalyst, e.g. chlorosulfonic acid, in an atmosphere of an inert gas, etc. at 50W250°C under stirring for a given time, and removing the catalyst and solvent. The starting raw material is obtained by random copolymerizing acetylene with a conjugated diene compound, e.g. butadiene.

USE: Printing, coating materials, adhesive, coating and electrical insulating materials.