Nippon Shokubai Co., Ltd.

Toru Yanase

Takumi Hatsuda

Kazuki Kimura

Kinya Nagasuna

Koji Miyake

Yasuhiro Fujita

Kunihiko Ishizaki

Nobuyuki Harada

Yorimichi Dairoku

Hirotama Fujimaru

Yoshifumi Adachi

Yoshihiko Masuda

Shin-Ichi Fujino

Akito Yano

Kazutaka Yano

A manufacturing method of absorbent resin of the present invention includes, in addition to a drying step of drying hydrogel of a crosslinked polymer to obtain a dried product and a pulverizing step of pulverizing the dried product, a separating step of separating a incompletely dried product contained in the dried product therefrom. Since particles of the incompletely dried product are larger than those of the dried product, the former can be readily separated from the latter in the separating step by classifying the dried product to particles of a particle size within a predetermined range. Consequently, the incompletely dried product is never delivered to the pulverizing step, and therefore, it has become possible to prevent inconveniences, such as causing a trouble in pulverizing the dried product, and the incompletely dried product being mixed into the absorbent resin. Hence, in drying and subsequently pulverizing the hydrogel of a crosslinked polymer, that is, in manufacturing the absorbent resin, it has become possible to provide a method capable of manufacturing absorbent resin efficiently while avoiding troubles caused by the production of the incompletely dried product during the drying step.

Manufacturing method of absorbent resin

A method for producing a cross-linked polymer manifesting a high absorption capacity and having a small content of soluble component by a convenient and expeditious process with high productivity is provided. An absorbent resin such that disposable diapers and other products incorporating the absorbent resin manifest outstanding qualities and a method for the production of the absorbent resin are proposed. The cross-linked polymer according to this invention is produced by a method of polymerizing an aqueous polymerizable monomer solution containing a water-soluble ethylenically unsaturated monomer and a first cross-linking agent capable of forming a hydrogel polymer by polymerization, which method comprises the steps of performing the polymerization in a substantially static state from the time at which the polymerization is initiated till the time at which the whole polymerization system is gelated, subsequently giving the polymerization system a thorough shearing force thereby granulating the hydrogel polymer before the polymerization system has the temperature thereof elevated by the heat of polymerization to the highest level, and further continuing the polymerization.

Method for production of cross-linked polymer

The present invention provides a production process, in which hydrophilic crosslinked polymers can be dried uniformly with good efficiency, and the deterioration during the drying is little. The production process of a hydrophilic crosslinked polymer comprises the steps of polymerizing an aqueous solution including a hydrophilic monomer and a crosslinking agent to obtain a hydrogel crosslinked polymer, and drying the hydrogel crosslinked polymer, thus obtaining the hydrophilic crosslinked polymer, and is characterized in that: the hydrogel crosslinked polymer is dried in a static state until it becomes possible to disintegrate an aggregate of the hydrogel crosslinked polymer; the dried hydrogel crosslinked polymer is disintegrated into a particle size of 20 mm or less; and the disintegrated hydrogel crosslinked polymer is dried in a stirred state and/or a fluidized state.

Production process of hydrophilic crosslinked polymer

A hydrogel polymer obtained by polymerizing a monomer component including acrylic acid (salt) is post-neutralized so that each of polymer particles derived from a polymer produced by neutralizing the hydrogel polymer has an allowable neutralization ratio. The polymer as obtained by neutralizing the hydrogel polymer is reacted with a crosslinking agent reactive to a functional group of the polymer. The allowable neutralization ratio, for example, is a neutralization ratio which is not lower, by not less than 20 mole percent, or more than, at least 55 mole percent, than an average neutralization ratio of a mass of the polymer particles, and the post-neutralization is carried out so that a number of polymer particles having a non-allowable neutralization ratio outside the allowable neutralization range is not more than 10 in 200 polymer particles, thus obtaining a water-absorbent agent having high absorbency under no applied pressure and high pressure wherein the amount of water soluble component is lower compared with the conventional water-absorbent agent and a change in pH of a swollen gel is small.

Water-absorbent agent and method for manufacturing the same

A method for the production of an absorbent resin retaining at a high level an absorption capacity without load, one of the basic physical properties of absorbent resin, and excelling in an absorption capacity under load is provided. The production is attained by mixing an absorbent resin as a base polymer possessing a carboxyl group with a first cross-linking agent possessing a solubility parameter (SP value) of not less than 12.5 (cal/cm.sup.3).sup.1/2 and exhibiting reactivity with the carboxyl group and a second cross-linking agent possessing a solubility parameter (SP value) of less than 12.5 (cal/cm.sup.3).sup.1/2 and exhibiting reactivity with the carboxyl group and then subjecting the resultant mixture to a heat treatment at a temperature not less than 160.degree. C.

Method for production of absorbent resin

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Hyogo, Japan

Toru Yanase