PURPOSE: To reduce only the diameter of a pore while keeping the porosity of a membrane by treating a melt-spun crystalline org. high molecular hollow yarn with corona discharge and then stretching the yarn by ≥1.5 times at a temp. higher than the glass transition temp. and lower than the m.p.
CONSTITUTION: A melt-formable crystalline org. polymer is melt-spun by using a spinneret for producing hollow yarn to obtain unstretched hollow yarn having substantially no through-pores leading from the outer wall to the inner wall. The hollow yarn is treated with corona discharge at 1W50W/m2. The yarn is then stretched by 1.5W4 times at temps. ranging from the glass transition temp. of the org. polymer to the m.p. at ≥2/sec deformation speed with use of ≥2 rolls.
YOSHIDA HARUHIKO
HASEGAWA AKIRA
TAKAHASHI HIROSHI
