Hydrophilic polymer alloy, fiber and porous membrane comprising this polymer alloy, and methods for preparing them

• US 5,677,360 A
• Filed: 06/02/1995
• Issued: 10/14/1997
• Est. Priority Date: 02/13/1991
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Rayon Company Limited (Mitsubishi Chemical Holdings Corporation)
• Original Assignee: Mitsubishi Rayon Company Limited (Mitsubishi Chemical Holdings Corporation)
• Inventors: Uchida, Makoto, Koshoji, Toshinobu, Niikawa, Kenji, Yamamori, Hisayoshi
• Primary Examiner(s): Warzel, Mark L.
• Application Number:
  US08/459,633
• Time in Patent Office: 865 Days
• Field of Search: 521/134, 521/61, 521/75, 521/79, 521/141, 525/56, 525/57, 525/58, 264/185, 264/203, 264/211.13, 264/211.19, 210/500.21, 210/500.36
• US Class Current: 521/134
• CPC Class Codes: B01D 2325/36 Hydrophilic membranes
• CPC Class Codes: B01D 67/0027 by stretching
• CPC Class Codes: B01D 71/261 Polyethylene
• CPC Class Codes: B01D 71/262 Polypropylene
• CPC Class Codes: B01D 71/381 Polyvinylalcohol
• CPC Class Codes: B01D 71/383 Polyvinylacetates
• CPC Class Codes: B01D 71/76 Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74 rubbers in general B01D71/24
• CPC Class Codes: C08J 2323/02 not modified by chemical after treatment
• CPC Class Codes: C08J 5/18 Manufacture of films or sheets
• CPC Class Codes: C08L 2203/12 used for fibers
• CPC Class Codes: C08L 23/06 Polyethene
• CPC Class Codes: C08L 23/0861 Saponified vinylacetate
• CPC Class Codes: C08L 2666/06 Homopolymers or copolymers of unsaturated hydrocarbons; Derivatives thereof
• CPC Class Codes: D01F 6/46 of polyolefins

Abstract

A hydrophilic polymer alloy which has a permanent hydrophilic nature, a sufficient mechanical strength and a high safety and which is suitable for the formation of hydrophilic porous membranes manufacturable by an industrially advantageous process can be prepared by blending an amorphous hydrophilic copolymer (X) containing 10 mole % or more of an ethylene unit, 10 to 60 mole % of a vinyl alcohol unit and 1 mole % or more of a vinyl acetate unit with a polyolefin (Y). Furthermore, this polymer alloy is also suitable for the formation of hydrophilic (porous) fibers having a sufficient mechanical strength and antistatic function.

Claims

1. A method for preparing a hydrophilic porous membrane which comprises the steps of melting-shaping a polymer alloy obtained by blending a polyolefin (Y) with an amorphous hydrophilic copolymer (X) containing 10 mole % or more of ethylene units, 20 to 80 mole % of vinyl alcohol units and 1 mole % or more of vinyl acetate units, the melt-shaping being performed at a temperature in the range of from a temperature 10°

C. higher to a temperature 100°

C. higher than the melting point of the polyolefin (Y), subjecting the melt-shaped article to a heat treatment at a temperature more than the crystal dispersion temperature and less than the melting point of the polyolefin (Y), and then stretching the material to make it porous.

2. A method for preparing a porous membrane which comprises the step of immersing the porous membrane obtained by a method according to claim 1 in water in a temperature range of not less than the glass transition temperature of the hydrophilic polymer alloy constituting the porous membrane.

3. A method for preparing a porous membrane which comprises the step of immersing the porous membrane obtained by a method according to claim 1 in an alcohol/water mixing solution in which the content of an alcohol represented by the formula C_m H_n OH (wherein each of m and n is an integer and m ≦

5 and n =2m +1) is from 2 to 95% by volume.