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AssigneeMitsui Chemicals, Inc.
InventorsShigeo Nishikawa, Masashi Arimoto, Michio Eriguchi
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The expanded product of the present invention is an expanded product having a density of from 0.02 to 0.7 g/cm3, which is obtained by expanding ultra-high-molecular-weight polyethylene having a viscosity average molecular weight of from 300,000 to 10,000,000. This expanded product can be prepared by adding carbon dioxide to ultra-high-molecular-weight polyethylene in the molten state in an extruder, and expanding the resin by extrusion such that each of the surface temperature and the central part temperature of the resin immediately after discharge from the die may be a predetermined temperature, while at the same time setting the residence time and pressure of the resin at the die section to specific values. Based on these, the invention provides an expanded product with good external appearance, having a skin layer to which the functions such as light weight, insulating property, sound absorption, low dielectric constant, impact absorption, flexibility and the like can be imparted without significantly deteriorating the excellent features of abrasion resistance, self-lubrication, impact strength, cryogenic properties and chemical resistance that are inherent to ultra-high-molecular-weight polyethylene; and a process for preparation of the expanded product stably.
An expanded ultra-high-molecular-weight polyethylene product, which is obtained by expanding ultra-high-molecular-weight polyethylene having a viscosity average molecular weight of from 300,000 to 10,000,000, wherein the density of the expanded product is from 0.02 to 0.7 g/cm3, and the value of the tensile-impact strength X (kJ/m2) at the temperature of −40° C. is represented by the following Equation (1):
A process for preparation of an expanded ultra-high-molecular-weight polyethylene product having a density of from 0.02 to 0.7 g/cm3, which is obtained by expanding ultra-high-molecular-weight polyethylene having a viscosity average molecular weight of from 300,000 to 10,000,000, wherein the resin pressure at the front of a screw is from 10 to 100 MPa, and the residence time taken by the ultra-high-molecular-weight polyethylene having a blowing agent dissolved therein to pass from the front end of screw to the die outlet of an extruder is represented by the following Equation (3):
Dependencies are inferred from the claim text.