Catalyst – solid sorbent – or support therefor: product or process – Solid sorbent – Organic
Patent
1997-07-23
2000-10-17
Wu, David W.
Catalyst, solid sorbent, or support therefor: product or process
Solid sorbent
Organic
526240, 5263171, 5263181, 528274, 528486, 428402, B01J 2026
Patent
active
061331937
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a novel absorbent resin composition and a method for the production thereof. More particularly, it relates to an absorbent resin composition which features high speed of absorption, excels in fluid permeability, and high absorption capacity under load and a method for economically advantageous production of the absorbent resin composition.
BACKGROUND ART
In recent years, absorbent resins which are capable of absorbing some tens to some hundreds times their own weights of water have been developed. Various absorbent resins of this class have been finding utility in applications requiring absorption and retention of water such as in the field of hygienic materials including sanitary goods and disposable diapers, the field of agriculture and horticulture, the field of foodstuffs requiring retention of freshness, and the field of industrial products requiring protection against dew formation and retention of refrigeration.
The absorbent resins of this class known to the art include the hydrolyzate of a starch-acrylonitrile graft polymer (JP-B-49-43,395), the neutralized starch-acrylic acid graft polymer (JP-A-51-125,468), the saponified vinyl acetate-acrylic ester copolymer (JP-A-52-14,689), the hydrolyzate of an acrylonitrile copolymer or acrylamide copolymer (JP-B-53-15,959), the cross-linked derivatives thereof, the self-crosslinking sodium polyacrylate obtained by reversed-phase suspension polymerization (JP-A-53-46,389), and the partially neutralized cross-linked polyacrylic acid (JP-A-55-84,304), for example.
The behaviors that the absorbent resins are required to possess vary depending on the kinds of use to be found for the absorbent resins. As the properties required of the absorbent resins which are intended for hygienic materials, high absorption capacity under load, high speed of absorption, and excels in fluid permeability to be manifested on contact with an aqueous liquid may be cited. These properties do not necessarily show positive correlations. It has been difficult to have these properties simultaneously adapted for one another.
In an effort to heighten the speed of absorption of an absorbent resin, attempts are being made to enlarge the surface area of the resin by such means as, for example, decreasing the particle size of the resin, granulating the resin, or molding the resin in the form of scales. Generally, when an absorbent resin is molded in the form of particles of a small size, the absorbent resin particles on contact with an aqueous liquid form the so-called "wet clusters" and incur a decrease in the speed of absorption. When an absorbent resin is granulated, the granules on contact with an aqueous liquid individually succumb to the phenomenon of being converted into "wet clusters" and rather suffer a decrease in the speed of absorption. When an absorbent resin is molded in the form of thin flakes, though the thin flakes are improved in terms of the absorption speed, the improvement is not fully satisfactory because the thin flakes induce the phenomenon of gel blocking. Further, the formation of thin flakes of the absorbent resin is uneconomical because the produced thin flakes inevitably assume a large volume and incur a large cost for transportation and storage.
Techniques for exalting the absorption speed of an absorbent resin by cross-linking molecular chains in the surface region of the absorbent resin and heightening the cross-link density in the surface layer and thereby precluding the formation of wet clusters have been proposed. These techniques are disclosed in JP-A-57-44,627, JP-A- 58-42,602, JP-B-60-18,690, JP-A-58-180,233, JP-A-59-62,665, and JP-A-61-16,903, for example. The improvement of absorbent resins in absorption speed has been attained to a certain extent by these techniques. The particles of these absorbent resins in their existent state contain particles of smaller size than the optimum size in a fairly high extent. When such a technique for improvement is used on an absorbent resin of such particle size distribut
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Hatsuda Takumi
Kajikawa Katsuhiro
Nakamura Masatoshi
Harlan R.
Nippon Shokubai Co. , Ltd.
Wu David W.
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