To obtain a sealant film which bas the possibility of exhibiting a sufficient warming effect even under low-temperature conditions, has excellent heat sealability and seal strength, and is alleviated in adverse effects on the environment by dispersing bamboo char microparticles having a specified particle diameter.
A felled thick-stemmed bamboo (Phyllostachys pubeseens) is charred by heating to 1,000-1,600°C and finely ground to obtain bamboo char microparticles having a specific surface area of 1,000 m2/cm3 and a mean particle diameter of 0.01-30 μm. The microparticles in an amount of 0.5-20 wt.%, desirably, 0.5-10 wt.% are added to at least one resin selected from among a polyethylene, a polypropylene, a polystyrene, an ethylene/(meth)acrylic acid copolymer, etc., and uniformly dispersed therein. The obtained mixture is extruded through an extruder having a screw diameter of 25-200 mm and a screw L/D ratio of 15-35 under conditions including an extrusion temperature of 120-125°C, a die lip gap of 0.5-5.0 mm, and a blow-up ratio of 1.0-4.0 to obtain a far-infrared-emitting sealant film having a thickness of 20-250 μm.
SHINKAWA YASUKO
MORITA SATOSHI
