| 摘要 |
PURPOSE:To obtain the title sheet having excellent heat-shrinkability and heat resistance and suitable for use as a covering material for pins, etc., by mixing a styrene/methacrylic acid copolymer with a low-boiling org. compd., melting the mixture by heating, extruding it under specified conditions and taking up the extrudate around a cooling drum. CONSTITUTION:100g of a styrene/methacrylic acid copolymer (A) composed of 5-50wt% methacrylic acid and 95-50wt% styrene is mixed with 0.01-0.07mol of a (halogenated) hydrocarbon compd. (B) (e.g., butane or Freon 12). The mixture is molten by heating it at a resin temp. higher by 20-80 deg.C than the heat distortion temp. thereof in an extruder and discharged into the air from a ring slit die provided at the tip of the extruder. The extrudate is taken up at a take-up rate of not lower than 1.1 along a cooling drum, thus obtaining the title sheet having an apparent density of 0.10-0.35g/cc and a shrinkage factor of 20% or above in one direction and lower than 10% in a direction perpendicular to said one direction when heated to 140 deg.C. |
