Patent ID: 6083434
Filing Date: 2000-07-04
Classification: B29C,B29K,C08J

Abstract:
A process for rotationally molding articles having a foamed interior and a non-foamed exterior skin which comprises introducing a rotomolding composition comprising polymers to a mold and heating the mold and its contents to a temperature above the melt temperature of the polymers and above decomposition temperatures of a chemical foaming agent and an organic peroxide while biaxially rotating, said rotomolding composition comprising:(a) 25 to 75 wt. %, based on the weight of the total composition, ethylene polymer pellets ranging in size from about 1/16 inch to about 3/16 inch in diameter and containing 0.25 to 7.5 wt. % chemical foaming agent, based on the weight of the ethylene polymer and 0.1 to 2.0 wt. % organic peroxide, based on the weight of the ethylene polymer, said ethylene polymer having a melt index from 0.25 g/10 mins to 25 g/10 mins; and(b) 75 to 25 wt. %, based on the weight of the total composition, ethylene polymer powder containing:(i) a major proportion of fractional melt index ethylene polymer powder wherein 80 percent or more of the powder particles are greater than 250 microns in size and(ii) a minor proportion of ethylene polymer powder wherein 80 percent or more of the powder particles are less than 250 microns in size and the ethylene polymer has a melt index greater than 1 g/10 mins., and with the proviso that the mean particle size of (b)(i) and (b)(ii) differ by at least 100 microns.