| 摘要 |
PURPOSE:Fine hollow balls with a larger diamether than the thickness of the resin membrane are dispersed in the membrane of a thermoplastic resin and they are pressed to crush the balls, thus forming fine through-holes in the membrane without punching. CONSTITUTION:Fine hollow balls made of alumina or phenelic resin, preferably of 10-800 micron particle sizes, 1-5 times the thickness of the resin membrane cited later, are added to a thermoplastic resin such as polyethylene, preferably in an amount of 0.1-10wt% and the composition is made into a film, e.g., by inflation, so that the both top and bottom ends of each particle are exposed to both surface of the film. Then, the resin film is pressed with a milling roll to crush the balls into many fine pieces, thus forming fine through-holes in the resin film. EFFECT:The resultant film has high air permeation but supresses the permeation of water, thus it is suitably used as a package for desiccants, food wrapping or in agricultural application. |
