Abstract: The present invention is related to a composite microporous polyolefin membrane having a high separation, a high flux and a high strength, comprising a microporous layer, b-layer, providing a reinforcing function, the b-layer being stacked on at least one surface of a microporous layer, a-layer, providing a separate function, wherein micropores in a-layer and b-layer are mutually interconnected inside of the layer and also between layers, thereby forming micropores connected from one surface of the membrane to the other surface thereof, and the ratio of the mean distance Da between microfibril bundles of micropores existing in a-layer to the mean distance Db between microfibril bundles of micropores existing in b-layer is in the range of 1.3.ltoreq.Db/Da.ltoreq.15, and furthermore all of the inner and the outer surfaces of the composite membrane and the surface inside of micropores are coated by a thin film of a hydrophilic copolymer.

Abstract: Disclosed is a porous membrane comprising (1) a hydrophilic copolymer X composed principally of (poly)alkylene glycol mono(meth)acrylate units A and ethylene units B and (2) a polyolefin Y, the (poly)alkylene glycol mono(meth)acrylate units A being of the formula ##STR1## where R.sup.1 and R.sup.2 independently represent hydrogen or methyl, and n has a value in the range of 1 to 9. This porous membrane has permanent hydrophilicy suitable for the treatment of water-based liquids and can be produced by an industrially advantageous process. This process comprises melt-forming a blend of (1) a hydrophilic copolymer X composed principally of (poly)alkylene glycol mono(meth)acrylate units A and ethylene units B and (2) a polyolefin Y; heat-treating the melt-formed product in a vacuum or an inert gas medium at a temperature not higher than the melting point of polyolefin Y for a period of an hour or more; and stretching the heat-treated, melt-formed product to make it porous.

Abstract: Disclosed are porous polyethylene fibers without a central cavity extending along the longitudinal axis thereof, and having (a) a porous structure containing pores defined by lamellar crystal portions and a large number of fibrils interconnecting the lamellar crystal portions, the pores communicating with each other anywhere from the surface to the center of the fiber, (b) a porosity of 50 to 80%, (c) a tensile strength of 1 to 8 g/d, and (d) an elongation of 1 to 300%.These porous polyethylene fibers do not exhibit the waxy feeling characteristic of polyethylene, have very light weight and a soft feeling, and are useful as a high-strength fiber material for the manufacture of clothing.