STUDIES ON GRAFTING OF MALEIC-ANHYDRIDE ONTO POLYPROPYLENE IN MOLTEN STATE BY USE OF SCREW EXTRUDER .2. REMOVAL OF UNREACTED MALEIC-ANHYDRIDE BY HEAT-TREATMENT IN GRAFTING OF MALEIC-ANHYDRIDE ONTO POLYPROPYLENE IN MOLTEN STATE BY USE OF SCREW EXTRUDER

There exists much unreacted maleic anhydride (MAH) in modified polypropylenes (PP) which have been made by melt-mixing mixtures of PP, MAH, and peroxide (PO) with a screw extruder. This unreacted material hampers the adhesion of the modified PP to polar materials. In the method of removal of unreacted MAH by heat treatment, the effects of kind of base PP, content of ethylene-butene-1 random copolymer (EBR), and concentrations of MAH and PO on the adhesion to saponified ethylene-vinyl acetate copolymer were studied. (1) With increasing EBR content, the graft efficiency increases and the adhesion improves. (2) The adhesion is poor if the ratio of MAH concentration to PO concentration is too low or too high; an optimum ratio exists. (3) The adhesion is improved by the removal of unreacted MAH by heat treatment. The heat treatment has another good effect on adhesion beside removal of unreacted MAH