PURPOSE: To obtain foam having uniform fine foam cells by melting and kneading a resin compsn. consisting of a thermoplastic resin, a crosslinking agent and a thermal decomosable foaming agent at specific temp. to supply the same to a die and supplying a lubricant with specific melt viscosity to heat the same to specific temp. and emitting the resin compsn. from a die to heat the same to the decomposition temp. of the foaming agent or higher.
CONSTITUTION: A resin compsn. is melted and kneaded within the temp. range from the softening point of a thermoplastic resin to the decomposition temp. of a crosslinking agent and a lubricant wherein the melt viscosity at the time of the decomposition temp. of the crosslinking agent and shearing speed of 10/s is 300 poise or more and the ratio of this melt viscosity and the zero shearing viscosity of the thermoplastic resin is 5×10-2 or less is supplied. The resin compsn. is heated to temp. from the decomposition temp. of the crosslinking agent to the decomposition temp. of a foaming agent and extruded from a die to be heated to the decomposition temp. of the foaming agent or higher. That is, the lubricant supply slit 3 communicating with a synthetic resin passage 21 is provided between the first and latter half parts 22, 23 of the die and the lubricant is supplied from a lubricant supply device 4 through a lubricant supply pipe 6. A cooling die 5 is connected to the outlet of the die 2.
TSUJIMOTO NORITAKA
NAKAGAWA HIROAKI
