CPC C08J 9/232 (2013.01) [C08J 9/18 (2013.01); C08J 9/228 (2013.01); C08L 53/00 (2013.01); A43B 13/04 (2013.01); C08J 2201/026 (2013.01); C08J 2203/22 (2013.01); C08J 2353/00 (2013.01)] | 5 Claims |
1. A method of producing expanded beads provided with through-holes, wherein the expanded beads consist of a multi-block copolymer of a polyethylene block and an ethylene/octene copolymer block, an inside diameter of the expanded beads is 1 to 5 mm, a ratio of the inside diameter of the expanded beads to an outside diameter of the expanded beads is 0.29 to 0.8, the expanded beads having a voidage of 5 to 30%, the method comprising:
Step (a): dispersing polymer particles provided with through-holes and composed of the multi-block copolymer of the polyethylene block and the ethylene/octene copolymer block in a dispersing medium within a closed vessel,
wherein the multi-block copolymer has a flexural modulus of 10 to 50 MPa,
a type A durometer hardness of the multi-block copolymer is 75 to 88, and
the polymer particles have an inside diameter of 0.2 to 3 mm, an outside diameter of the polymer particles is 0.5 to 3 mm, and a ratio of the inside diameter to the outside diameter of the polymer particles of 0.2 to 0.7, wherein the polymer particles are extruded from a cylindrical die having a circular slit and are cut;
Step (b): impregnating the polymer particles with an organic peroxide satisfying a relation of the following formula (1) at a temperature lower than decomposition temperature of the organic peroxide, and crosslinking the polymer particles at a temperature equal to or higher than a melting point of the multi-block copolymer of the polyethylene block and the ethylene/octene copolymer block, which constitutes the polymer particles, and not higher than a temperature of (the melting point+80° C.):
5≤(Tm−Th)≤45 (1)
wherein Tm represents a melting point (C) of the multi-block copolymer of the polyethylene block and the ethylene/octene copolymer block, which constitutes the polymer particles; and Th represents a 10-hour half-life temperature (° C.) of the organic peroxide, wherein the 10-hour half-life temperature Th of the organic peroxide is from 87 to 100° C.;
Step (c): impregnating the resulting polymer particles with a blowing agent; and
Step (d): expanding the resulting expandable polymer particles containing the blowing agent.
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