PURPOSE: To crosslink polyvinyl chloride (PVC) at a low temperature region near room temperature, by incorporating a photosensitizer and a silicone containing an olefinically unsaturated bond in PVC, irradiating the resultant mixture with ultraviolet light, and bringing the irradiated mixture into contact with water in the presence of a silanol condensing catalyst.

CONSTITUTION: A mixture obtained by incorporating polyvinyl chloride (PVC) with (A) a photosensitizer, e.g. benzophenone, (B) an organosilicon compound having one or more olefinically unsaturated bonds in the molecule, e.g. vinyltrimethoxysilane, and if necessary (C) an organic peroxide, e.g. dicumyl peroxide, is molded into a film, and irradiated with ultraviolet light at a wavelength of 200W 400nm, and the irradiated film is then brought into contact with water in the presence of a silanol condensing catalyst, e.g. dibutyltin dilaurate, to crosslink the PVC at a low temperature. Preferably, the components are used in amounts based on 100pts.wt. PVC base material as follows: 0.05W10pts.wt. component (A), 0.05W6pts.wt. component (B) and 0.01W4pts.wt. component (C).