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Water-absorbing resin and process for producing same

a technology of water-absorbing resin and process, which is applied in the direction of chemistry apparatus and processes, bandages, wood layered products, etc., can solve the problems of unpleasant slimy feeling, lack of water-soluble content in the aspect, and inability to achieve satisfactory absorbing properties, small amount of water-soluble content, and high safety

Inactive Publication Date: 2001-01-16
NIPPON SHOKUBAI CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

Another object of the present invention is to provide a process for producing a water-absorbing resin having a markedly small amount of water-soluble content and high safety.
Further object of the present invention is to provide an expedient and highly productive process for producing a water-absorbing resin having satisfactory absorbing properties and a small amount of water-soluble content.
Still further object of the present invention is to provide a water-absorbing resin having a small amount of water-soluble content, high salt resistance, and excellent absorbing properties under pressure.
Still further object of the present invention is to provide a water-absorbing article containing a water-absorbing resin having a small amount of water-soluble content, high salt resistance, and excellent absorbing properties under pressure.
Still further object of the present invention is to provide a water-absorbing article having a reduced change in absorbing properties after absorption, which has been a problem in water-absorbing articles containing conventional water-absorbing resins.

Problems solved by technology

The presence of the water-soluble content sometimes is not desirable in the aspect of both the performance and the safety of the water-absorbing resin.
When a large amount of the water-soluble content is in contact with a human body, etc., such a water-soluble content sometimes is not desirable from the viewpoint of safety as it gives unpleasant slimy feeling, etc.
In the step for neutralization of the water-absorbing resin after polymerization, and the step for mixing additives with the water-absorbing resin after polymerization, a uniform neutralization or mixing is difficult and may cause a decrease in the productivity.
However, as a result of the use of an increased amount of a crosslinking agent, the absorbing properties of the water-absorbing resin decreases.
Further, it is probable that methanol remains in the resulting resin and, hence, the process is not desirable from the standpoint of safety.
The water-absorbing resin containing an electrolytic structure such as the partially neutralized acrylic acid described above generally has poor salt resistance.
If such a water-absorbing resin is used as a diaper, the absorbing properties are changed due to the change in concentration of salts from electrolytes in urine and the lapse of time, resulting in fluctuation of product quality.
However, these water-absorbing resins have low gel strength, resulting in deteriorated absorbing properties under pressure.
However, these water-absorbing resins having high absorbing properties under pressure do not have high salt resistance.

Method used

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  • Water-absorbing resin and process for producing same

Examples

Experimental program
Comparison scheme
Effect test

example 1

A jacketed 13-liter-content stainless steel double-arm kneader equipped with two sigma-type blades having a rotating diameter of 120 mm was charged with 6,538 g of an aqueous solution (D) containing 2,168 g of a monomer component (A) composed of 35 mol% of acrylic acid and 65 mol% of sodium acrylate; 24.5 g of polyethylene glycol diacrylate (an average molecular weight: 478) as a compound (B); 13.1 g of ethylene glycol diglycidyl ether as a compound (C) and 4,332.4 g of deionized water. The resulting aqueous solution (D) was degassed and the reaction system was replaced with a nitrogen gas.

Water at 20.degree. C. was passed through the jacket to control the temperature of the vessel. 12.56 g of a 10 wt% aqueous solution of 2,2-azobis-2-amidinopropane dihydrochloride, 0.88 g of a 1 wt% aqueous solution of L-ascorbic acid, 12.56 g of a 10 wt% aqueous solution of sodium persulfate, and 5.6 g of a 0.35 wt% aqueous solution of hydrogen peroxide as initiators were added to the reaction sys...

example 2

A water-absorbing resin was obtained in the same manner as in Example 1 except for changing the amount of ethylene glycol diglycidyl ether in Example 1 to 21.8 g. The properties of the resulting water-absorbing resin are shown in Table 1.

example 3

A water-absorbing resin was obtained in the same manner as in Example 1 except for changing the amount of ethylene glycol diglycidyl ether in Example 1 to 4.4 g. The properties of the resulting water-absorbing resin are shown in Table 1.

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Abstract

A process for producing a water-absorbing resin, which comprises polymerizing (D) an aqueous solution comprising (A) at least one monomer component selected from the group consisting of an unsaturated carboxylic acid and salts thereof; (B) a compound having two or more unsaturated groups in a molecule; and (C) a compound having two or more functional groups which are capable of reacting with carboxyl groups in a molecule, the polymerization being conducted in such a manner that the following conditions (a) to (c) are simultaneously satisfied: (a) the molar ratio (B) / (C) being in the range of from 2x10-3 to 300, (b) the polymerization being initiated by a redox polymerization initiator, and (c) the maximum reaction temperature being in the range of from 60° to 100° C., and a water-absorbing resin having a degree of reduction in absorption magnification of from 1 to 16, and n absorption magnification under pressure of from 20 to 40.

Description

FIELD OF THE INVENTIONThe present invention relates to a process for producing a water-absorbing resin, and more specifically, relates to a process for producing a water-absorbing resin that is excellent in absorbing properties and has a reduced amount of water-soluble content. The present invention also relates to a water-absorbing resin, and more specifically it relates to a water-absorbing resin that has a reduced amount of water-soluble content, a high salt resistance, and excellent absorbing properties under pressure. The present invention also relates to a water-absorbing article, and more specifically it relates to a water-absorbing article containing a water-absorbing resin that has a reduced amount of water-soluble content, a high salt resistance, and excellent absorbing properties under pressure.BACKGROUND OF THE INVENTIONWater-absorbing resins have been used in various absorbing articles. Such article include diapers, sanitary goods, soil water-retaining agent, freshness-...

Claims

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Application Information

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IPC IPC(8): A61L15/24A61L15/16C08F220/04
CPCA61L15/24C08F220/04A61L15/60C08L33/02
Inventor AIDA, KENJI
Owner NIPPON SHOKUBAI CO LTD
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