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Water-absorbing agent, manufacture method thereof, and absorbent and absorbent article made therefromRelated Patent Categories: Synthetic Resins Or Natural Rubbers -- Part Of The Class 520 Series, Natural Rubber Compositions Having Nonreactive Materials (dnrm) Other Than: Carbon, Silicon Dioxide, Glass Titanium Dioxide, Water, Hydrocarbon, Halohydrocarbon, Ethylenically Unsaturated Reactant Admixed With A Preformed Reaction Product Derived From: (a) At Least One Polycarboxylic Acid, Ester, Or Anhydride; (b) At Least One Polyhydroxy Compound; And (c) At Least One Fatty Acid Glycerol Ester, Or A Fatty Acid Or Salt Derived From A Naturally Occurring Glyceride, Tall Oil, Or A Tall Oil Fatty Acid, At Least One Solid Polymer Derived From Ethylenic Reactants Only, Chemically After Treated Solid Polymers Derived From Ethylenically Unsaturated Monomers Only, Polymer Derived From Acrylic Or Methacrylic Esters, Or Vinyl Acetate MonomerWater-absorbing agent, manufacture method thereof, and absorbent and absorbent article made therefrom description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070173610, Water-absorbing agent, manufacture method thereof, and absorbent and absorbent article made therefrom. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] The present invention relates to water-absorbing agents primarily composed of water-absorbing resin suitably used in, for example, paper diapers (disposable diapers), sanitary napkins, so-called incontinence pads, and other hygiene materials. More specifically, the invention relates to water-absorbing agents (resins), as well as their manufacturing methods and uses, of which crosslinked: have a heat retention indicator 1 of 3.0 or less, a centrifuge retention capacity (CRC) of 34 g/g or less in a 0.90 wt. % aqueous solution of sodium chloride, and an absorbency of 30 g/g or less in a 0.90 wt. % aqueous solution of sodium chloride against a pressure of 2.0 kPa; contain 60 wt. % or more particles measuring 600 .mu.m to 300 .mu.m in diameter and 3 wt. % or less particles measuring less than 150 .mu.m in diameter; and have a mass-average (weight-average) particle diameter of 400 .mu.m to 600 .mu.m, a standard deviation of logarithm (.sigma..zeta.) of particle size distribution of 0.250 to 0.400, and a saline flow conductivity (SFC) of less than 20.times.10.sup.-7 cm.sup.3sec/g for a 0.69 wt. % aqueous solution of sodium chloride. BACKGROUND ART [0002] Water-absorbing resins are popularly used as water-absorbing agent absorbing body fluids (urine, blood, etc.) and the like, providing major components for paper diapers, sanitary napkins, incontinence pads, and other hygiene materials. [0003] Recent years have seen development of deodorizing or otherwise value-added water-absorbing resins in response to increasing demands for adult disposable diapers from aging populations. Also under development are diapers which feel comfortable when worn. These diapers well fit body shape and allow no leak. These enhancements are mostly due to structural improvements of the absorbent, but partly attributable to improved performance of the water-absorbing resin. [0004] The performance includes, for example, seepage and diffusing absorbency. Related improvements have been made in terms of centrifuge retention capacity (CRC), absorbency against pressure (AAP), gel strength, and absorption rate. [0005] Document 1, or U.S. Pat. No. 5,147,343, discloses a porous fiber matrix and an absorbent composition made from a superabsorbent polymer dispersed in the pores in the fiber matrix. The superabsorbent polymer can absorb at least 27 ml of a 0.9 wt. % solution of sodium chloride against a pressure of 21000 dyne/cm.sup.2. The absorbent composition advantageously contains a 10 wt. % to 60 wt. % superabsorbent polymer. [0006] Document 2, or U.S. Pat. No. 5,149,335, describes an absorbent structure of a 60 wt. % to 100 wt. % superabsorbent polymer. The superabsorbent polymer is characterized by a free-swell rate of less than 60 seconds and at least a 5-minutes AUL (absorption under load) of 15 g/g. [0007] Document 3, or European patent 0532002, discloses a porous fiber matrix and an absorbent composition containing an at least 30 wt. % superabsorbent polymer. The superabsorbent polymer has a deformation under load of less than 0.60 mm and a wicking index of 10 cm or more. [0008] Document 4, or European patent 0615736, relates to an absorbent composition containing a 30 wt. % to 100 wt. % superabsorbent polymer which has a pressure absorbency index of at least 100 and an extractable content of less than 13 wt. % (during a 16-hour extraction in a 0.9 wt. % aqueous solution of sodium chloride). [0009] Document 5, or European patent 0761191, describes a fiber matrix and an absorbent composition containing an at least 30 wt. % superabsorbent polymer which has a suction parameter of 700 or more. [0010] Document 6, or U.S. Pat. No. 6,297,335, discloses an absorbent composition with a pressure absorbency index of less than 100 and a vertical absorption of at least 12 g/g against a pressure of 1922.8 Pa. [0011] Document 7, or U.S. Pat. No. 5,599,335, discloses an absorbent composition with a saline flow conductivity (SFC) of at least about 30.times.10.sup.-7 cm.sup.3sec/g for a 0.69 wt. % aqueous solution of sodium chloride and a performance of at least 23 g/g under a load of 0.7 psi (performance under load, or PUP). [0012] One of obvious conditions of comfort in wearing a diaper or similar absorbent is quick absorption of urine or other body fluids after excretion. The foregoing, conventional methods focus on the water-absorption performance of the water-absorbing resin or absorbent such as the diaper. This approach alone however will fall short of providing sufficient comfort when the diaper or like absorbent is worn. Examining causes of discomfort, we have found that a "drop in temperature" of the absorbent after the diaper or like absorbent absorbs excreted urine or other body fluids, that is, the "cool feel" of the wearer, is the factor that seriously affects comfort. No conventional absorbents can prevent a drop in their temperature. Heat retention has not been considered. None of them have achieved a satisfactory level of heat retention in actual use. [0013] Sacrificing absorption performance to give high heat retention would result in the water-absorbing resin failing to accomplish its basic goals of absorbing body fluids (urine, blood, etc.). Therefore, it is both important to give high heat retention and attain a required level of absorption performance. [0014] As in the foregoing, a lot of improvements have been made on the absorption performance of the water-absorbing resin. [0015] One of obvious conditions for a diaper or similar absorbent that is comfortable to wear is quick absorption of urine or other body fluids after excretion. However, many absorbents after being wet cool down (toward room temperature) with time after the absorption of a body fluid (generally at about body temperature). The cool feel is never comfortable. To put it differently, the wearer's problem, that is, discomfort, will be eased if the absorbent remains near the body temperature level for an extended period after the absorption of a body fluid. DISCLOSURE OF INVENTION [0016] The present invention has an objective to provide a water-absorbing agent, absorbent, and absorbent article with excellent heat retention and absorption performance, as well as a method of manufacturing the water-absorbing resin. [0017] To achieve excellent heat retention and absorption performance with a diaper or like absorbent, the inventors have focused on the water-absorbing resin that greatly affects the performance of the absorbent. [0018] During the course of the research, the inventors have found that the heat retention of a diaper can be enhanced by improving a particular capability of the water-absorbing resin, which has led to the completion of the invention. [0019] Some causes of discomfort in actual use of a diaper and like absorbent are stickiness due to seeping liquid and the feel of cold gel which has absorbed liquid. Attempts have been conventionally made to reduce stickiness. In the present invention, however, the feel of cold gel, as well as stickiness, is reduced. [0020] The aforementioned particular capability is measured by a "heat retention indicator 1" of the water-absorbing resin in the present invention. This is an absolutely novel parameter for the water-absorbing resin. The calculation of the heat retention indicator 1 will be discussed later in detail by way of examples along with related experiments. In short, the heat retention indicator 1 is a representation of a temperature change on the surface of the water-absorbing resin over a unit time after a liquid is poured into the water-absorbing resin. The unit time here is 5 to 10 minutes. The lower the heat retention indicator 1, the smaller the temperature change on the water-absorbing resin surface, and the better the heat retention. [0021] The inventors have also found that a water-absorbing resin with a satisfactory heat retention indicator 1 value in accordance with the present invention can be prepared by controlling the centrifuge retention capacity, absorbency against pressure, and particle diameter of the water-absorbing resin in particular ranges during manufacture. Continue reading about Water-absorbing agent, manufacture method thereof, and absorbent and absorbent article made therefrom... Full patent description for Water-absorbing agent, manufacture method thereof, and absorbent and absorbent article made therefrom Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Water-absorbing agent, manufacture method thereof, and absorbent and absorbent article made therefrom patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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