| 摘要 |
PURPOSE:To produce nonflammable foamed particles having low toxicity, high quality and high expansion ratio by impregnating monochlorodifluoromethane in polyolefin resin particles, expanding the particles and subjecting to secondary expansion and tertiary expansion under specific conditions. CONSTITUTION:The objective foamed particles are produced by (1) impregnating 2-8wt.% (based on the resin) of a foaming agent composed mainly of monochlorodifluoromethane into polyolefin resin particles and expanding the particles at a ratio of 2-5.5, (2) applying a pressure to said primarily expanded particles with a gas and expanding the particles at a ratio of 6-20 with hot steam (the expansion ratio between the primary expansion and the secondary expansion is <=8) to obtain secondarily expanded particles and (3) applying a pressure to the secondarily expanded particles with a gas and subjecting the particles to tertiary expansion with hot steam at an expansion ratio of 21-40 (the expansion ratio between the secondary expansion and the tertiary expansion is <=4). |
