| 摘要 |
PROBLEM TO BE SOLVED: To obtain a sheet having beautiful appearance, a high closed-cell rate, and excellent thermoformability by adding a blowing agent to a modified polypropylene resin obtained by melt-kneading a polypropylene resin, an isoprene monomer and a radical polymerization initiator and extrusion-foaming the mixture in a molten state. SOLUTION: One hundred pts.wt. polypropylene resin, 0.1-20 pts.wt. isoprene monomer, and 0.1-10 pts.wt. radical polymerization initiator are kneaded for 30 sec to 60 min at a temperature (13-400 deg.C) at which the resin can melt to obtain a modified polypropylene resin. The modified polypropylene resin is molten, and 0.5-10 pts.wt. per 100 pts.wt. resin, blowing agent such as an aliphatic hydrocarbon, an alicyclic hydrocarbon, a halohydrocarbon, an inorganic gas, or water is injected into the molten resin, and the resulting mixture is adjusted to the optimal foaming temperature in an extruder and extruded through a ring die or a slit die to obtain a foamed sheet having a density of 0.04-0.5 g/cm<3> , a closed-cell rate of 70% or above, and a thickness of 0.1-10 mm. |
