Method of producing a hydrophilic resin

Details Method of producing a hydrophilic resin Method of producing a hydrophilic resin

1997-09-29

2000-11-21

Lipman, Bernard

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

5253303, 525383, 525384, 525386, C08F 800

Patent

active

061504696

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a denaturing method of a hydrophilic polymer and a producing method of a hydrophilic resin, and more particularly, to a producing method of a hydrophilic resin having excellent physical properties, such as an absorbing property, by uniformly denaturing a hydrophilic polymer, for example, by applying a crosslinking treatment to an absorbent resin.


TECHNICAL BACKGROUND

Recently, an absorbent resin is used extensively in sanitary goods, such as paper diapers, sanitary napkins, and incontinence pads, to absorb body fluids. Besides the sanitary goods, the absorbent resin is also used extensively in water-retaining materials for soil to keep water in soil or drip absorbing materials to absorb drip from foods or the like.
Examples of such absorbent resins include: a partially neutralized crosslinked polymer of polyacrylic acid, a hydrolyzed graft polymer of starch-acrylonitrile, a neutralized graft polymer of starch-acrylic acid, a saponified copolymer of vinyl acetate-acrylic ester, a hydrolyzed copolymer of acrylonitrile or acrylamide, or a crosslinked product thereof, and a crosslinked polymer of a cationic monomer.
Notable properties of the absorbent resin include absorbency and absorbing rate when brought into contact with an aqueous liquid like a body fluid, liquid permeability, gel strength of swelled gel, and absorbing power of absorbing water from a base material containing an aqueous liquid, etc. However, each property is not necessarily correlated positively to one another. For example, the higher the absorbency, the lower the absorbing rate, liquid permeability, and gel strength. To solve the above problem, a crosslinking treatment (secondary crosslinking treatment) using a crosslinking agent (denaturant) is conventionally applied to the absorbent resin to well balance (improve) these properties and enhance the absorbing property.
A secondary crosslinking structure is introduced into the absorbent resin in the following manner: a swelling liquid in which the absorbent resin is swelled with a solvent, or a dispersing liquid in which the absorbent resin is dispersed in a dispersing medium is prepared, and a crosslinking agent or a solution thereof is added to the above prepared liquid and mixed with each other, so that the reaction of the absorbent resin and crosslinking agent takes place in a so-called solid-liquid system. The solvent or dispersing medium referred to herein is, for example, a hydrophilic compound, such as water and alcohol.
Examples of the above method of introducing the secondary crosslinking structure into the absorbent resin using a crosslinking agent include: a method of using polyhydric alcohol (Japanese Laid-open Patent Application No. 180233/1983 (Tokukaisho No. 58-180233) and Japanese Laid-open Patent Application No. 16903/1986 (Tokukaisho No. 61-16903)), a method of using a polyglycidyl compound, a polyaziridine compound, a polyamine, or polyisocyanate (Japanese Laid-open Patent Application No. 189103/1984 (Tokukaisho No. 59-189103)), a method of using glyoxal (Japanese Laid-open Patent Application No. 117393/1977 (Tokukaisho No. 52-117393)), a method of using polyvalent metal compound (Japanese Laid-open Patent Application No. 136588/1976 (Tokukaisho No. 51-136588), Japanese Laid-open Patent Application No. 257235/1986 (Tokukaisho No. 61-257235), and Japanese Laid-open Patent Application No. 7745/1987 (Tokukaisho No. 62-7745)), a method of using a silane coupling agent (Japanese Laid-open Patent Application No. 211305/1986 (Tokukaisho No. 61-211305), Japanese Laid-open Patent Application No. 252212/1986 (Tokukaisho No. 61-252212), and Japanese Laid-open Patent Application No. 264006/1986 (Tokukaisho No. 61-264006)), a method of using an epoxy compound and a hydroxy compound (Japanese Laid-open Patent Application No. 132103/1990 (Tokukaihei No. 2-132103)), a method of using alkylene carbonate (German Patent No. 4,020,780), etc.
Also, a variety of methods are proposed to distribute the crosslinking agent over the surface of t

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