Patent ID: 8129438
Filing Date: 2012-03-06
Classification: B29C,C08J,Y10T

Abstract:
1. A method for producing foamed polyolefin resin beads having antistatic properties, the method comprising: dispersing polyolefin resin beads into an aqueous medium in an autoclave; injecting a blowing agent, pressurizing the autoclave, and impregnating the polyolefin resin beads with the blowing agent; stirring under heating; and releasing the aqueous medium and contents of the autoclave into a low-pressure area with an internal constant pressure sufficient to allow the polyolefin resin beads to foam and expand, wherein the polyolefin resin beads are composite resin beads comprising a core layer of a core layer polyolefin resin and a covering layer of a covering layer polyolefin resin, obtained by cutting a strand comprising the core layer and the covering layer laminated on a surface of the core layer by co-extruding the polyolefin resin for forming the core layer and the polyolefin resin for forming the covering layer, (a) the core layer polyolefin resin is a crystalline polyolefin resin having a melting point (A), (b) the covering layer polyolefin resin is a crystalline polyolefin resin which has a lower melting point (B) than the melting point (A) of the core layer polyolefin resin, and a temperature difference [(A)−(B)] between the melting point (B) and the melting point (A) is within the range of 0° C.<[(A)−(B)]≦80° C., or the covering layer polyolefin resin is a noncrystalline polyolefin resin which has a softening point (C) lower than the melting point (A) of the core layer polyolefin resin, and a temperature difference [(A)−(C)] between the softening point (C) and the melting point (A) is within the range of 0° C.<[(A)−(C)]≦100° C., and (c) the covering layer comprises a polymer antistatic agent in an amount (D) within the range of 10%≦D<50% by total weight of the covering layer.