Process for producing a graft copolymer of polyethylene-chloro-trifluoroethylene by utilizing beams of radiation

The graft polymerization of chloro-trifluoroethylene (CTEF) on polyethylene is effected by a pre-irradiation process to provide inexpensive polyethylene with the chemical corrosion resistance and thermal stability of CTEF. The process comprises either irradiating polyethylene at a low temperature or lowering the temperature of irradiated polyethylene immediately after irradiation, and then introducing chloro-trifluoroethylene into the irradiated polyethylene. The polymerization is effected mainly in a liquid phase. The specific surface area of polyethylene may preferably be 0.01 - 200 m2/g, particularly 100 m2/g. The irradiation temperature is below 200C. When irradiated between -780C and 200C, the material is cooled down to -780C to trap the active radicals. The temperature of monomer introduction is below -280C. In one of the examples, a powder of polyethylene having a number average molecular weight of 2.4 x 104 and a specific surface area of 100 m2/g was irradiated with gamma-rays from a Co-60 source, and then washed with benzene. The washed polyethylene is irradiated in a breakable ampoule under 10-4 to 10-5 mmHg with gamma-rays from a Co-60 source at a dose rate of 3.0x105r/hr. After the irradiation, the polyethylene was kept at -780C. CTEF was introduced into the ampoule at -350C. The reaction product was washed with benzene to remove the residual monomer. The graft efficiency was 21% with a dose of 30x10+6 r for 42 hrs. (Iwakiri, K.)