PURPOSE: To raise the moldability and dimensional stability of foam moldings by a method in which pre-expanded granules of polyethylene resin are shrunk by heating, packed into molds capable of closely confining the granules but incapable of being enclosed hermetically, and expanded by heating.
CONSTITUTION: Polyethylene resin granules and a volatile blowing agent are dispersed in a dispersion medium in an enclosed container and heated at a given temperature. One end of the container is then opened in such a way as to cause the resin granules and the dispersion medium to discharge concurrently from the inside of the container to a low-pressure atmosphere in order to obtain pre-expanded granules of polyethylene resin. The pre-expanded resin granules are thrunk by heating to temperature higher than the thermal deformation temperature of the resin granules and then packed into molds with small holes enough to permit the passage of heating medium, e.g., steam, etc., on their faces, which are capable of closely confining the resin granules but incapable of being enclosed hermetically. The molds are heated using a steam of 1W5kg/cm2G for expanding the resin granules to obtain expanded moldings matching the shape of the molds.
KUWABARA HIDEKI
YAMAGUCHI TOORU
SUDOU YOSHIMI
| JP56175988A |