Poly (METH) acrylic acid (SALT) granular water absorbent and method for producing same

Abstract

To provide a disposable diaper in which, regardless of the concentration of water absorbent in the absorbent article and the configuration thereof, the liquid return quantity is reduced, and liquid can be captured at an excellent speed. While adjusting the absorption factor and surface tension of the water absorbent to within specific ranges, the water-containing gel-form cross-linked polymer obtained in the polymerization step is crushed to a specific weight-average particle diameter, and after drying has a liquid permeability improver added during or after surface crosslinking, thereby obtaining a water absorbent with excellent GCA (Gel Capillary Absorption) and FGBP (Free Gel Bed Permeability).

Description

technical field [0001] The present invention relates to a particulate water-absorbing agent mainly composed of poly(meth)acrylic acid (salt)-based water-absorbing resin particles. In more detail, it is related with the particulate water absorbing agent which can improve the performance of absorbent articles, such as a paper diaper. Background technique [0002] The water-absorbent resin (SAP / Super Absorbent Polymer) is a water-swellable and water-insoluble polymer gelling agent, and exhibits characteristics of excellent absorption of body fluids. Therefore, water-absorbing agents mainly composed of water-absorbing resins are widely used in absorbent articles such as disposable diapers and sanitary napkins, water-retaining agents for agriculture and gardening, and water-blocking materials for industrial use. Many monomers and hydrophilic polymers have been proposed as raw materials for water-absorbent resins constituting such water-absorbing agents, but (meth)acrylic acid an...

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Problems solved by technology

[0010] For the foaming technology described in the above-mentioned Patent Document 7, etc., it is difficult to stabilize the dispersion of the bubbles in the monomer solution, and it is difficult to stably produce

In addition, when the air bubbles are stabilized by using a large amount of surfactant, etc., there may be problems such as a decrease in surface tension.

[0011] The technology of introducing foaming described in the above-mentioned Patent Document 7 etc. has the following problems: the amount of fine powder that cannot be made into a product increases during pulverization, and the production efficiency is greatly reduced; the dried water-absorbent resin becomes brittle, and the transportation process It is easy to be damaged, so the physical properties such as absorption rate under pressure are greatly reduced.

In addition, in the granulation technology described in the above-mentioned Patent Document 7 and the like, water or hot water is added to the dried product of the water-absorbent resin in the form of particles, granulated, and dried, so there is room for improvement in the production efficiency, and there is a problem due to multiple steps. Deterioration of the water-absorbent resin due to the drying process, resulting in a decrease in performance

In addition, techniques related to gel pulverizers and pulverization conditions (Patent Documents 8 to 14), techniques to add additives such as polyethylene glycol and hydrophobic substances during polymerization or pulverization of polymer gels (Patent Documents 15 to 12) Among them, there is a problem that the pulverization conditions are not enough to increase the GCA, or the surface tension is greatly reduced

The technology of producing granulated particles by the reverse phase suspension polymerization method has also been proposed (Patent Documents 21 and 22), but there are problems of complicated procedures, problems caused by the residue of organic solvents, and the reflux rate is reduced due to the decrease of surface tension. increase, etc., the performance improvement effect of disposable diapers is insufficient

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