JP2005194524A - Water-absorbing agent, manufacture method thereof, and absorbent and absorbent article made therefrom - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-absorbing resin having excellent heat retention together with absorbing property, an absorbent and an absorbent article and method for producing the absorbing resin. <P>SOLUTION: The invention relates to the water-absorbing agent comprising a water-absorbing resin having a crosslinked structure obtained by polymerizing an unsaturated monomer component, wherein the water-absorbing agent is surface-treated, and the water-absorbing agent meets all of properties (1) through (4), (1) heat retention indicator 1 (maximum temperature decrease per minute 5 to 10 minutes after 10 times swelling at 50°C) is from 0 to 3.0 °C/min ; (2) an absorption rate under pressure free condition in a 0.90 wt. % aqueous solution of sodium chloride (30 minute value) is 34 g/g or less; (3) an absorbency in a 0.90 wt.% aqueous solution of sodium chloride against a pressure of 2.0 kPa (60 minute value) is less than 30 g/g; and (4) a saline flow conductivity (SFC) for a 0.69 wt.% aqueous solution of sodium chloride is less than 20x10<SP>-7</SP>cm<SP>3</SP>sec/g. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a water-absorbing agent mainly composed of a water-absorbing resin that is suitably used for sanitary materials such as paper diapers (disposable diapers), sanitary napkins, so-called incontinence pads, and more specifically, crosslinked. A water-absorbing agent comprising a water-absorbing resin as a main component and having a heat retention index 1 of 3.0 ° C./min or less and an absorption capacity under no pressure with respect to a 0.90% by weight sodium chloride aqueous solution (Centrifuge retention capacity / abbreviated as CRC) Is 34 g / g or less, 0.90 wt% sodium chloride aqueous solution with an absorption capacity under pressure of 2.0 kPa (absorbency again pressure / abbreviated as AAP) is less than 30 g / g, and particles having a particle size of 600 to 300 μm are 60 wt%. As mentioned above, the particle | grains below 150 micrometers are 3 weight% or less, and a mass mean particle diameter is 4. 0~600μm and logarithmic standard deviation of particle size distribution ([sigma] [zeta]) is 0.250 to 0.400, further, 0.69 flow wt% aqueous sodium chloride solution under ^{20 × 10 -7 cm 3 sec /} g, The present invention relates to a water absorbing agent having an inductive (Saline Flow Conductivity: SFC) value, a method for producing the same, and use thereof.

  The water-absorbent resin is widely used as a main constituent material of sanitary materials such as paper diapers, sanitary napkins, incontinence pads, etc., as a water-absorbing agent that absorbs body fluids (such as urine and blood).

  In recent years, water-absorbing resins having added value such as a deodorizing function have been developed due to an increase in demand for paper diapers for adults accompanying aging. In addition, diapers that are comfortable to wear are being developed, improving fit to the body and preventing leakage. Most of these are not only due to improvements in the structure of the absorber, but also due to improvements in the performance of the water absorbent resin.

  For example, the improvement of the return amount and the diffusion absorption amount is applicable. Improvements in this respect include an increase in absorption capacity without pressure, an increase in absorption capacity under pressure, an increase in gel strength, an increase in absorption speed, and the like.

Patent Document 1 discloses an absorbent composition comprising a porous fiber matrix and the amount of superabsorbent polymer dispersed in the pores of the fiber matrix. The superabsorbent polymer can absorb at least 27 ml of 0.9% strength by weight sodium chloride solution under a pressure of 21000 dynes / cm ² . The amount of superabsorbent polymer in the absorbent composition is preferably from 10 to 60% by weight.

  Patent Document 2 describes an absorptive structure composed of 60 to 100% by weight of a superabsorbent polymer. Superabsorbent polymers are characterized by a free swell rate (Free-Swell Rate) of less than 60 seconds and an AUL (absorption under load) of at least 15 g / g for 5 minutes.

  U.S. Patent No. 6,057,031 discloses an absorbent composition comprising a porous fiber matrix and at least 30 wt.% Superabsorbent polymer, the superabsorbent polymer having an on-load deformation of less than 0.60 mm and a wicking of 10 cm or more. It has an index (Wicking Index).

  U.S. Patent No. 6,057,059 has a pressure absorbency index (Pressure Absorbency Index) of at least 100 and an extractable content of less than 13 wt% (16 hours extraction in 0.9 wt% aqueous sodium chloride solution), 30 It relates to an absorbent composition consisting of ˜100% by weight of superabsorbent polymer.

  U.S. Patent No. 6,057,056 describes an absorbent composition consisting of at least 30 wt% superabsorbent polymer having a fiber matrix and a wicking parameter of 700 or more.

  U.S. Patent No. 6,057,059 is characterized by having a pressurized absorption index of less than 100 and a vertical absorption of at least 12 g / g under a pressure of 1922.8 Pa, respectively.

Patent Document 7 states that a flow inductive (SFC) value of a 0.69 wt% sodium chloride aqueous solution is at least about 30 × 10 ⁻⁷ cm ³ sec / g, and a pressure performance (PUP) capacity value of 0.7 psi is at least 23 g. / G.

  Needless to say, as a condition of comfort when an absorbent body such as a diaper is worn, body fluid due to urination or the like is quickly absorbed. In the conventional methods reported above, the water absorption performance of an absorbent body such as a water absorbent resin or a diaper is regarded as important. However, that alone does not provide sufficient comfort when an absorbent body such as a diaper is attached. As a result of searching for the cause, the `` diaper temperature drop '' that occurs after the absorbent body such as diapers absorbs bodily fluids such as urination etc., that is, the person who wears it `` feels cold '' significantly reduces comfort. Turned out to be. Conventional absorbers do not take into consideration the temperature decrease of the absorber, that is, do not take into account the heat retention, and have not reached a satisfactory level as the heat retention exhibited in actual use.

Moreover, if the absorption performance is sacrificed in order to exhibit high heat retention, the original purpose of the water-absorbent resin for absorbing body fluid (such as urine and blood) cannot be achieved. Therefore, it is important to achieve a level at which the high heat retention is exhibited and the absorption performance is sufficiently satisfactory.
US Patent Application Publication No. 5147343 US Patent Application No. 5149335 European Patent Application No. 053002 European Patent Application No. 0615736 European Patent Application No. 0761191 US Pat. No. 6,297,335 US Pat. No. 5,599,335

  As described above, many improvements in the absorption performance of the water absorbent resin have been made.

  Needless to say, it is a comfortable condition for the absorbent body to quickly absorb bodily fluids such as urination when an absorbent body such as a diaper is attached. However, in the case of many absorbent bodies, after absorbing body fluid (usually about body temperature), the temperature of the absorbent body after being wet decreases (approaches to room temperature) over time, so that the cool feeling is not comfortable. . That is, it is considered that, even after the absorber absorbs the body fluid, by maintaining the temperature close to the body temperature for a longer time, the burden on the person wearing the absorber, that is, the discomfort is eased.

  Therefore, the problem to be solved by the present invention is to provide a water-absorbing agent, an absorbent body, an absorbent article, and a method for producing a water-absorbing resin, which have excellent heat retaining properties and excellent absorption performance.

  The present inventors paid attention to a water-absorbent resin that has a great influence on the performance of the absorbent body in developing an absorbent body such as a diaper which is excellent in heat retention and is excellent in absorption performance.

  As the study progressed, it was found that improving the specific performance of the water-absorbent resin in order to increase the heat retaining property of the diaper, and the present invention has been achieved.

  As an unpleasant sensation element of an absorbent body such as a diaper in actual use, a sticky feeling due to liquid return and a cold gel feeling after liquid absorption can be mentioned. Conventionally, the sticky feeling has been reduced, but according to the present invention, not only the sticky feeling but also the cold gel feeling can be reduced.

  The specific performance is called a heat retention index 1 of the water absorbent resin in the present invention, and is a completely new parameter of the water absorbent resin. The details of the calculation method of the heat retention index 1 and the experimental method are described in the Examples, but the heat retention index 1 changes per unit time from 5 minutes to 10 minutes after the liquid is poured into the water absorbent resin. This represents the amount of temperature change on the surface of the water absorbent resin. That is, the lower the value of the heat retention index 1, the smaller the amount of temperature change on the surface of the water absorbent resin, and the higher the heat retention property.

  Further, in order to obtain a water-absorbent resin satisfying the heat retention index 1 of the present invention, the absorption coefficient under pressure, the absorption capacity under pressure, and the particle diameter of the water-absorbent resin are controlled to be within a specific range. It was found for the first time that the thermal insulation index 1 of the invention is satisfied.

Specifically, the absorption capacity of the water-absorbing resin with respect to a 0.90% by weight sodium chloride aqueous solution under pressure is 34 g / g or less, and the absorption capacity under pressure at 2.0 kPa with respect to a 0.90% by weight sodium chloride aqueous solution is 30 g / g. less than g, particles having a particle size of 600 to 300 μm are 60% by weight or more, particles having a particle size of less than 150 μm are 3% by weight or less, and the mass average particle size is 400 to 600 μm, logarithmic standard deviation of particle size distribution (σζ) Satisfying 0.250 to 0.400, and further, the flow inductive (SFC) value of the 0.69 wt% sodium chloride aqueous solution is less than 20 × 10 ⁻⁷ cm ³ sec / g, Thermal insulation index 1 (maximum temperature decrease per minute after 5 to 10 minutes after swelling 10 times at 50 ° C.) can be 3.0 or less, and has high absorption performance while having excellent absorption performance. It has been clarified that the cooling sensation of the absorbent body such as a diaper after absorbing a body fluid (ie, urine or blood) is relieved.

That is, the water-absorbing agent according to the present invention is mainly composed of a water-absorbing resin having a cross-linked structure obtained by polymerizing an unsaturated monomer component, the water-absorbing resin is subjected to a surface treatment, and the water-absorbing agent. If necessary, water-insoluble inorganic fine particles can be added to the water-absorbent resin, the heat retention index 1 is 3.0 or less, and the absorption capacity under no pressure with respect to a 0.90% by weight sodium chloride aqueous solution is 34 g / g. Hereinafter, the absorption capacity under pressure at 2.0 kPa against a 0.90% by weight sodium chloride aqueous solution is less than 30 g / g, particles having a particle size of 600 to 300 μm are 60% by weight or more, and particles having a particle size of less than 150 μm are 3% by weight or less, The mass average particle diameter is 400 to 600 μm, the logarithmic standard deviation (σζ) of the particle size distribution is 0.250 to 0.400, and the flow conductivity (SFC) of 0.69 wt% sodium chloride aqueous solution. The value is less than 20 × 10 ⁻⁷ cm ³ sec / g.

  The water-absorbing agent according to the present invention preferably has a heat retention index 2 (gel surface temperature after 10-fold swelling at 50 ° C. and 10 minutes later) of 20 ° C. or higher.

  In the water-absorbing agent according to the present invention, the heat retention index 3 (the time for the gel surface temperature to reach 37 ° C. after 10-fold swelling at 50 ° C.) is preferably 120 seconds or more.

  Moreover, the water absorbing agent according to the present invention may further contain a polyol in addition to the water absorbing resin.

  Moreover, as for the water absorbing agent which concerns on this invention, it is preferable that an unsaturated monomer is acrylic acid (salt), and another monomer is 0-30 mol% with respect to acrylic acid (salt).

  The absorbent body according to the present invention includes the water-absorbing agent of the present invention and hydrophilic fibers.

  Moreover, it is preferable that content of the said water absorbing agent with respect to the total weight of the said water absorbing agent and hydrophilic fiber is 20 weight% further as for the absorber concerning this invention.

  The absorbent article concerning this invention is equipped with the back sheet | seat which has the absorber of this invention, the surface sheet which has liquid permeability, and liquid impermeability.

The method for producing a water-absorbing agent according to the present invention is a method for producing a water-absorbing agent mainly comprising a water-absorbing resin having a crosslinked structure obtained by polymerizing an unsaturated monomer component, and comprising an acid group-containing unsaturated monomer. A polymerization step for polymerizing monomer components mainly composed of monomers to obtain a water-absorbing resin, a surface treatment step for surface-treating (crosslinking) the water-absorbing resin obtained by the polymerization step, and if necessary inorganic A step of adding fine particles, the heat retention index 1 of the water-absorbing agent obtained through the above-mentioned steps is 3.0 or less, and the absorption capacity under no pressure with respect to a 0.90% by weight sodium chloride aqueous solution is 34 g / g or less, Absorption capacity under pressure with respect to 0.90% by weight sodium chloride aqueous solution at 2.0 kPa is less than 30 g / g, particles having a particle size of 600 to 300 μm are 60% by weight or more, and particles having a particle size of less than 150 μm are 3% by weight or less, mass average particle The diameter is 400 to 600 μm, the logarithmic standard deviation (σζ) of the particle size distribution is 0.250 to 0.400, and the flow conductivity (SFC) value of a 0.69 wt% sodium chloride aqueous solution is 20 × 10 ⁻⁷ cm. It is characterized by being less than ³ sec / g.

  According to the present invention, the water-absorbing agent constituting the absorbent body such as a diaper absorbs a body fluid such as urine and swells, thereby improving the heat retention than the conventional absorbent body, reducing the cooling sensation after urination, and absorbing A water-absorbing agent, an absorbent body, an absorbent article, and a method for producing a water-absorbing agent that are also excellent in performance can be provided.

  The inventors of the present invention are not only good in water absorption but also as a characteristic required for an absorbent body (absorbent article) such as a diaper, and are mounted by lowering the gel temperature after liquid absorption. The aim was to develop an absorber that aims to reduce the discomfort of “coldness” felt by the person. Therefore, attention has been paid to a water-absorbing agent that greatly affects the performance of the absorber. The present inventors have found that the heat retaining property of the absorbent body is enhanced by the specific performance of the water-absorbing agent, and have reached the present invention. That is, the present inventors have found that the heat retention (comfort) during actual use in the absorbent body (diaper) correlates very well with the specific parameter of the water-absorbing agent.

  This specific performance is called the water retention index 1 of the water-absorbing agent in the present invention, and is a parameter of a completely new water-absorbing agent (or water-absorbing resin) which has not been conventionally used. The details of the calculation method of the heat retention index 1 and the experimental method are described in the examples. The heat retention index 1 is a unit from 5 minutes to 10 minutes after the liquid is poured into the water absorbing agent (or water absorbent resin). It represents the amount of temperature change on the surface of the water-absorbing agent (or water-absorbent resin) that changes per hour. That is, the lower the value of the heat retention index 1, the smaller the surface temperature change amount, and the higher the heat retention property.

  The present inventors satisfy the heat retention index 1 of the present invention by controlling the absorption capacity of the water-absorbing agent (or water-absorbent resin) under non-pressure, the absorption capacity under pressure, and the particle diameter within a specific range. For the first time.

  Hereinafter, the water-absorbing agent (or water-absorbing resin) according to the present invention will be described in detail. However, the scope of the present invention is not limited to these explanations, and other than the following exemplifications, the scope of the present invention can be appropriately implemented without departing from the spirit of the present invention.

  First, the water-absorbent resin, water-absorbing agent, absorber and absorbent article of the present invention will be briefly described (defined) below.

(Water absorbent resin)
The water-absorbent resin of the present invention is a conventionally known water-absorbent resin, for example, absorbs a large amount of water of 50 to 1000 times in ion-exchanged water, and is anionic, nonionic, or cationic. It is a conventionally known crosslinked polymer that forms a water-insoluble hydrogel.

  The water-absorbing resin must be water-swellable and water-insoluble, and an uncrosslinked water-soluble component (water-soluble polymer) in the water-absorbing resin is preferably 0 to 30% by weight or less. More preferably, 0 to 25% by weight or less, further preferably 0 to 20% by weight or less, particularly preferably 0 to 15% by weight or less is used. The specific configuration of the water absorbent resin will be described later.

[Water absorbing agent]
The water-absorbing agent of the present invention is a water-absorbing agent comprising the above-mentioned water-absorbing resin as a main component, preferably containing 80% by weight or more, particularly preferably 90% by weight or more of the water-absorbing resin. It is surface-crosslinked (secondary crosslinked). Its shape is usually a powder. The specific configuration of the water absorbing agent will be described later.

  In addition, it cannot be overemphasized that this invention can fulfill | perform the function as a water absorbing agent only with water absorbing resin. Therefore, in the following description, the term “water-absorbing agent” may be used even when the water-absorbing resin is used alone.

〔Absorber〕
The absorbent body of the present invention is a molded product (for example, a sheet) containing the above-described water-absorbing agent (or water-absorbing resin) and hydrophilic fibers as a water-absorbing auxiliary material.

[Absorbent article]
The absorbent article of the present invention is, for example, a diaper or a sanitary napkin provided with the above-described absorber, a liquid-permeable top sheet, and a liquid-impermeable back sheet.

  Next, the manufacturing method of a water absorbing resin is demonstrated.

[Production method of water-absorbent resin (polymerization step)]
The water-absorbing resin according to the present invention is generally obtained by polymerizing in the state of a monomer solution, drying the polymer as necessary, and pulverizing as necessary before and / or after drying. . Such water-absorbing resins include polyacrylic acid partially neutralized polymer, hydrolyzate of starch acrylonitrile graft polymer, starch acrylic acid graft polymer, saponified vinyl acetate-acrylic ester copolymer, acrylonitrile. A hydrolyzate of a copolymer or an acrylamide copolymer, or one or more of these cross-linked products, a carboxyl group-containing cross-linked polyvinyl alcohol modified product, a cross-linked isobutylene-maleic anhydride copolymer can be used. .

  These water-absorbing resins may be used alone or as a mixture. Among them, an acid group-containing water-absorbing resin, more preferably a carboxyl group-containing water-absorbing resin or a mixture thereof, typically acrylic acid. The main component is a polymer obtained by polymerizing and crosslinking a monomer mainly composed of a salt (neutralized product) thereof. Here, in order to distinguish “crosslinking” in the process of “polymerizing / crosslinking monomers” from the crosslinking in the process of producing a water-absorbing agent described later (surface crosslinking, also known as secondary crosslinking), This is referred to as “primary crosslinking”.

  Examples of the acrylate include alkali metal salts such as sodium, potassium and lithium of acrylic acid, ammonium salts and amine salts. The water-absorbent resin preferably has a constitutional unit in the range of 0 to 50 mol% acrylic acid and 100 to 50 mol% acrylate (however, the total amount of both is 100 mol%). What is in the range of 10-40 mol% and acrylate 90-60 mol% (however, the total amount of both shall be 100 mol%) is more preferable. Neutralization of the water-absorbing resin for forming the salt may be performed in a monomer state before polymerization, or may be performed in the state of a polymer during or after polymerization, or a combination thereof. May be.

  In general, when neutralization is performed in the state of a polymer obtained by polymerizing unneutralized or low-neutralized monomers (acid type polymerization method), a water-absorbing resin having a high absorption ratio and a low soluble content tends to be obtained. However, the uniform neutralization of the individual particles of the water-absorbent resin requires considerable labor, equipment and time (Japanese Patent Laid-Open No. 10-10173: European Patent No. 882502). Is preferred.

  The monomer for obtaining the water absorbent resin used in the present invention may contain a monomer other than the acrylic acid (salt) as required. Although it does not specifically limit as monomers other than acrylic acid (salt), Specifically, for example, methacrylic acid, maleic acid, vinyl sulfonic acid, styrene sulfonic acid, 2- (meth) acrylamide- Anionic unsaturated monomers such as 2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid and salts thereof; acrylamide, methacrylamide, N-ethyl (meth) Acrylamide, Nn-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene Glycol (meth) acrylate, poly Nonionic hydrophilic group-containing unsaturated monomers such as tylene glycol mono (meth) acrylate, vinylpyridine, N-vinylpyrrolidone, N-acryloylpiperidine, N-acryloylpyrrolidine, N-vinylacetamide; N, N-dimethylamino Cations such as ethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, and quaternary salts thereof Unsaturated unsaturated monomers. These monomers may be used alone or in combination of two or more as appropriate.

  In the present invention, when a monomer other than acrylic acid (salt) is used, the monomer other than acrylic acid (salt) is based on the total amount of acrylic acid and its salt used as a main component. Preferably it is 0-30 mol% or less, More preferably, it is a ratio of 0-10 mol% or less. By using a monomer other than the acrylic acid (salt) in the above proportion, the absorption characteristics of the finally obtained water-absorbing resin (or water-absorbing agent) are further improved, and the water-absorbing resin (or water-absorbing agent) is further improved. ) Can be obtained even more inexpensively.

  When polymerizing the above-mentioned monomer to obtain the water-absorbent resin used in the present invention, bulk polymerization or precipitation polymerization can be performed. However, performance and ease of control of polymerization, and swelling gel From the viewpoint of the absorption characteristics, it is preferable to perform aqueous solution polymerization or reverse phase suspension polymerization by using the monomer as an aqueous solution.

  When the monomer is an aqueous solution, the concentration of the monomer in the aqueous solution (hereinafter referred to as the monomer aqueous solution) is determined by the temperature of the aqueous solution and the monomer and is not particularly limited. Is preferably in the range of 10 to 70% by weight, and more preferably in the range of 20 to 60% by weight. Moreover, when performing the said aqueous solution polymerization, you may use together solvents other than water as needed, and the kind of solvent used together is not specifically limited.

  Reverse phase suspension polymerization is a polymerization method in which an aqueous monomer solution is suspended in a hydrophobic organic solvent. For example, U.S. Pat. Nos. 4,093,764, 4,367,323, 4,446,261, 4,683,274, and 5,244,735, etc. In U.S. Patents. Aqueous solution polymerization is a method of polymerizing an aqueous monomer solution without using a dispersion solvent. For example, U.S. Pat. Nos. 4,462,001, 4,873,299, 4,286,082, 4,973,632, 4,985,518, 5,124,416, No. 5,250,640, US Pat. No. 5,264,495, US Pat. No. 5,145,906, US Pat. No. 5,380,808, and European patents such as European Patent Nos. 081636, 09555086, and 0922717. Monomer components and initiators exemplified in these polymerization methods can also be applied to the present invention.

  As a method of aqueous solution polymerization, a monomer aqueous solution is polymerized in a double-arm kneader while crushing the resulting hydrogel, or a monomer aqueous solution is supplied in a predetermined container or on a driving belt for polymerization. And a method of pulverizing the obtained gel with a meat chopper or the like.

  When starting the polymerization, for example, potassium persulfate, ammonium persulfate, sodium persulfate, t-butyl hydroperoxide, hydrogen peroxide, 2,2′-azobis (2-amidinopropane) dihydrochloride, etc. A radical polymerization initiator or a photopolymerization initiator such as 2-hydroxy-2-methyl-1-phenyl-propan-1-one can be used.

  Further, a reducing agent that promotes the decomposition of the polymerization initiator can be used in combination, and a redox initiator can be obtained by combining the two. Examples of the reducing agent include (bi) sulfurous acid (salt) such as sodium sulfite and sodium bisulfite, L-ascorbic acid (salt), reducing metal (salt) such as ferrous salt, amines, and the like. Although it is mentioned, it is not particularly limited.

  The amount of these polymerization initiators used is usually 0.001 to 2 mol%, preferably 0.01 to 0.1 mol%. When the amount of these polymerization initiators used is less than 0.001 mol%, the amount of unreacted monomers increases, and therefore the amount of residual monomers in the resulting water-absorbing resin and water-absorbing agent increases. It is not preferable. On the other hand, when the usage-amount of these polymerization initiators exceeds 2 mol%, since the amount of water-soluble components in the obtained water-absorbing resin or water-absorbing agent increases, it may not be preferable.

  Further, the polymerization reaction may be initiated by irradiating the reaction system with active energy rays such as radiation, electron beam, and ultraviolet rays, and the polymerization initiator may be used in combination. In addition, although the reaction temperature in the said polymerization reaction is not specifically limited, The range of 15-130 degreeC is preferable and the inside of the range of 20-120 degreeC is more preferable. Further, the reaction time and the polymerization pressure are not particularly limited, and may be appropriately set according to the type of monomer or polymerization initiator, the reaction temperature, and the like.

  The water-absorbent resin may be a self-crosslinking type that does not use a crosslinking agent, but is a cross-link having two or more polymerizable unsaturated groups or two or more reactive groups in one molecule. It is more preferable to copolymerize or react an agent (inner cross-linking agent for water absorbent resin).

  Specific examples of these internal crosslinking agents include, for example, N, N′-methylenebis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, trimethylolpropane tri ( (Meth) acrylate, glycerin tri (meth) acrylate, glycerin acrylate methacrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, pentaerythritol hexa (meth) acrylate, triallyl cyanurate, triallyl isocyanurate, triallyl phosphate, tri Allylamine, poly (meth) allyloxyalkane, (poly) ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ethylene glycol, polyethylene Glycol, propylene glycol, glycerol, pentaerythritol, ethylenediamine, ethylene carbonate, propylene carbonate, polyethylenimine, and glycidyl (meth) acrylate.

  These internal cross-linking agents may be used alone or in combination of two or more. These internal cross-linking agents may be added to the reaction system all at once or in divided portions. In the case of using at least one kind or two or more kinds of internal cross-linking agents, a compound having two or more polymerizable unsaturated groups in consideration of the absorption characteristics of the finally obtained water-absorbing resin or water-absorbing agent Is preferably used during polymerization.

  The amount of these internal crosslinking agents used is preferably in the range of 0.001 to 2 mol%, more preferably in the range of 0.005 to 0.5 mol%, relative to the monomer. Preferably, it is more preferable to set it within the range of 0.01 to 0.2 mol%. When the amount of the internal cross-linking agent used is less than 0.001 mol% and more than 2 mol%, sufficient absorption characteristics may not be obtained.

  When a cross-linked structure is introduced into the polymer using the internal cross-linking agent, the internal cross-linking agent is added to the reaction system before or during the polymerization of the monomer, after the polymerization, or after the neutralization. What should I do?

  In the polymerization, the reaction system includes starch / cellulose, starch / cellulose derivatives, polyvinyl alcohol, polyacrylic acid (salt), polyacrylic acid (salt) cross-linked hydrophilic polymer 0 to 50% by weight. Further, 0 to 10% by weight (with respect to the monomer), other 0 to 10% by weight, and further 0 to 1% by weight of carbonic acid (hydrogen) salt, carbon dioxide, azo compound, inert organic solvent, etc. Various foaming agents; various surfactants; chelating agents; chain transfer agents such as hypophosphorous acid (salt) may be added.

  When the cross-linked polymer is obtained by aqueous solution polymerization and is in a gel form, that is, a hydrogel cross-linked polymer, the cross-linked polymer is dried as necessary, and before and / or after drying. Is usually pulverized to make a water-absorbent resin. Moreover, drying is normally performed in a temperature range of 80 ° C to 250 ° C, preferably 100 ° C to 220 ° C, more preferably 120 ° C to 200 ° C. The drying time depends on the surface area of the polymer, the moisture content, and the type of dryer, and is selected to achieve the desired moisture content.

  Neutralization rate of the water-absorbent resin that can be used in the present invention [mol% of neutralized acid groups (salts) in the total acid groups: neutralization rate = (neutralized acid groups (salts)) / (not yet) Sum acid group + neutralized acid group (salt))] is not particularly limited, but is preferably 30 to 90 mol%, more preferably 50 to 80 mol%, in order to fully exhibit the effects of the present invention. More preferably, it is 60 to 75 mol%.

  The water content of the water-absorbent resin that can be used in the present invention (specified by the amount of water contained in the water-absorbent resin / measured by loss on drying at 180 ° C. for 3 hours) is not particularly limited, but the physical properties of the resulting water-absorbing agent From the above, preferably the moisture content is 0.1 to 50% by weight, more preferably 0.2 to 30% by weight, still more preferably 0.3 to 15% by weight, and particularly preferably 0.5 to 10% by weight. The mass average particle diameter is preferably about 100 to 1000 μm.

  Since it is difficult to make the water content of the water absorbent resin zero, a small amount of water (for example, 0.3 to 15% by weight, and further 0.5 to 10% by weight) is contained in the water absorbent resin to form a powder. This water-absorbing resin containing a small amount of water is also referred to as a water-absorbing resin (powder) in this specification.

  In the case of a commercially available water-absorbing resin (or water-absorbing agent) or a water-absorbing resin (or water-absorbing agent) in diapers, the water content is adjusted to 10% by weight or less, preferably 5 ± 2% by weight, for example, by drying. Then, the physical properties defined in this specification may be measured. The drying conditions for adjusting the moisture content are not particularly limited as long as the water-absorbing resin (or water-absorbing agent) is not decomposed or modified, but is preferably dried under reduced pressure.

  Moreover, as a water absorbing resin which can be used for the manufacturing method of this invention, a particulate thing can be mentioned. The water-absorbent resin particles obtained by the polymerization reaction may have a gel-like mass-average particle diameter before drying and grinding exceeding 1000 μm, but usually, depending on the purpose by drying, grinding and classification. Adjusted to powder particle size.

  The particle shape of the water-absorbent resin thus obtained is not particularly limited as a particle shape (also known as powder), such as a spherical shape, a crushed shape, and an indefinite shape. A regular pulverized one can be preferably used.

  Further, the bulk specific gravity (specified in JIS K-3362) is preferably within a range of 0.40 to 0.80 g / ml, more preferably 0.50 to fully exhibit the effects of the present invention. It is in the range of 0.75 g / ml, more preferably in the range of 0.60 to 0.73 g / ml.

  The water-absorbent resin obtained by the above method usually has a saturated absorption ratio of about 10 to 100 g / g with respect to physiological saline under no pressure, and the physical properties such as the absorption ratio are appropriately adjusted according to the purpose. Is done.

  Next, although the manufacturing method of a water absorbing agent is demonstrated, as above-mentioned, the function as a water absorbing agent can be achieved only by water absorbing resin. Therefore, when the water absorbing agent is constituted only by the water absorbing resin, the water absorbing agent is manufactured by the above manufacturing method.

[Surface treatment of water-absorbent resin (surface crosslinking step)]
The water-absorbing agent that can be used in the present invention is obtained by further surface cross-linking (secondary cross-linking) of the water-absorbing resin. The surface treatment in the present invention is secondary crosslinking of the surface of the water-absorbent resin, and the surface treatment and the surface crosslinking treatment mean the same thing.

  There are various types of cross-linking agents (surface cross-linking agents) for performing surface cross-linking, and are not particularly limited, but from the viewpoint of improving the physical properties of the resulting water-absorbing agent, polyhydric alcohol compounds, epoxy compounds, polyhydric amines. A compound or a condensate thereof with a haloepoxy compound, an oxazoline compound, a mono-, di- or polyoxazolidinone compound, a polyvalent metal salt, an alkylene carbonate compound and the like are preferable.

  Although it does not specifically limit as a surface crosslinking agent which can be used by this invention, For example, the surface crosslinking agent illustrated by US Patent 6228930, 6071976, 6254990 etc. can be used. For example, mono, di, tri, tetra or polyethylene glycol, monopropylene glycol, 1,3-propanediol, dipropylene glycol, 2,3,4-trimethyl-1,3-pentanediol, polypropylene glycol, glycerin, polyglycerin , 2-butene-1,4-diol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, etc. Alcohol compounds; epoxy compounds such as ethylene glycol diglycidyl ether and glycidol; ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, polyamide polyamine, etc. Haloepoxy compounds such as epichlorohydrin, epibromohydrin, α-methylepichlorohydrin; condensates of the polyvalent amine compounds and the haloepoxy compounds; oxazolidinone compounds such as 2-oxazolidinone; ethylene urea And cyclic carbonates such as ethylene carbonate, and the like. These may be used alone or in combination of two or more. In order to sufficiently exhibit the effects of the present invention, it is preferable to use a polyhydric alcohol among these surface crosslinking agents. As a polyhydric alcohol, a C2-C10 thing is preferable and a C3-C8 thing is more preferable.

  The amount of the surface cross-linking agent used depends on the compounds used and combinations thereof, but is preferably in the range of 0.001 to 10% by weight, and in the range of 0.01 to 5% by weight with respect to the water absorbent resin. Is more preferable.

  When performing surface cross-linking in the present invention, it is preferable to use water. At this time, the amount of water used depends on the water content of the water-absorbing resin to be used, but is preferably in the range of 0.5 to 20% by weight, more preferably 0.5 to It is within the range of 10% by weight. In addition to water, a hydrophilic organic solvent may be used.

  Specific examples of the hydrophilic solvent include lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, and t-butyl alcohol; Ketones; ethers such as dioxane, tetrahydrofuran and alkoxy polyethylene glycol; amides such as N, N-dimethylformamide; sulfoxides such as dimethyl sulfoxide and the like. When a hydrophilic organic solvent is used, the amount used is preferably in the range of 0 to 10% by weight, more preferably in the range of 0 to 5% by weight, and still more preferably 0 to 3% by weight with respect to the water absorbent resin. Is within the range.

  In the case of carrying out surface crosslinking in the present invention, a method in which water and / or a hydrophilic organic solvent and a surface crosslinking agent are mixed in advance and then the aqueous solution is sprayed or mixed dropwise onto the water-absorbent resin is preferably sprayed. The method is more preferred. The size of the droplets to be sprayed is preferably in the range of 0.1 to 300 μm, more preferably in the range of 0.1 to 200 μm, in terms of average particle diameter. When mixing water and / or a hydrophilic organic solvent and a surface cross-linking agent, a water-insoluble fine particle powder or a surfactant may be allowed to coexist within a range not impeding the effects of the present invention.

  It is preferable that the water-absorbent resin after mixing the surface cross-linking agent is heat-treated. The heating temperature (heating medium temperature or material temperature) is preferably in the range of 100 to 250 ° C, more preferably in the range of 150 to 250 ° C, and the heating time is preferably in the range of 1 minute to 2 hours. Preferable examples of the combination of the heating temperature and the heating time are 0.1 to 1.5 hours at 180 ° C. and 0.1 to 1 hour at 200 ° C.

  As described above, the water-absorbing agent obtained by performing the surface cross-linking treatment is preferably adjusted to a specific particle size in order to sufficiently exhibit the effects of the present invention.

  The particle size may be adjusted before the surface treatment or after the surface treatment. It has been found that the effect of the present invention in actual use (for example, urine gelling agents such as paper diapers) is excellent by making the water-absorbing agent used in the present invention have a specific particle size.

  Although it is not clear about the mechanism of manifestation of the above-mentioned effect by performing surface treatment and adjusting to a specific particle size, the gel particle diameter after the water absorbent (or water absorbent resin) swells and the surface of the gel particle The condition is considered to be affecting. The difference in gel particle size is thought to affect the contact area between the gel particles. When the gel particle size is small, the contact area between the gel particles increases, so that the heat retention decreases, and the gel particle size decreases. When is large, the contact area of a gel particle is small and heat retention is improved. In addition, the surface state of the gel particles subjected to the surface treatment has a stronger hydrophobic interaction on the surface of the gel particles than the untreated gel particles, and the heat retention can be improved by reducing the contact area between the gel particles. Conceivable. Further surprisingly, in the present invention, when the surface treatment is performed and the particle size is adjusted to a specific particle size, the effect obtained by simply adjusting the particle size or simply by performing the surface treatment is obtained by these synergistic effects. It was possible to obtain a much higher heat retention effect. It should be noted that the above description is presumed and the correctness is not related to the right of the present invention.

  Such a water-absorbent resin (or water-absorbing agent) is in the form of particles (powder), and the particle size of the water-absorbent resin (or water-absorbing agent) is 850 to 600 μm in particle size of 10% by weight or more, less than 40% by weight, 600 to 600%. 300 μm is preferably 60% by weight or more, and less than 150 μm is preferably 3% by weight or less. When the particle size is 850 to 600 μm less than 10% by weight, 600 to 300 μm less than 60% by weight, and less than 150 μm particle size of 3% by weight or more, the heat retention index 1 is high, and therefore, it is not suitable for the present invention. Moreover, when 850-600 micrometers is 40 weight% or more, there exists a possibility that the absorption rate of a bodily fluid (urine, blood, etc.) may fall remarkably, and it is not suitable.

  On the other hand, when the mass average particle diameter is less than 400 μm, the heat retention index 1 becomes high, and thus is not suitable for the present invention. Similarly, when the mass average particle diameter exceeds 600 μm, the absorption rate of body fluids (urine, blood, etc.) may be remarkably lowered, which is not appropriate.

  The logarithmic standard deviation (σζ) of the particle size distribution is preferably in the range of 0.250 to 0.400, more preferably in the range of 0.270 to 0.380. The logarithmic standard deviation (σζ) of the particle size distribution may be adjusted by granulation, if necessary. When the logarithmic standard deviation (σζ) of the particle size distribution is smaller than 0.250, the heat retaining property is increased (the heat retaining index 1 is lowered), but the manufacturing cost is remarkably increased, which is not appropriate. Further, when the logarithmic standard deviation (σζ) of the particle size distribution exceeds 0.400, the heat retention index 1 is remarkably increased, which is not suitable for the present invention.

The water-absorbing agent of the present invention taking the above production method as an example is a novel water-absorbing agent, that is, the water-absorbing agent according to the present invention is mainly composed of a water-absorbing resin having a crosslinked structure obtained by polymerizing unsaturated monomer components. The water-absorbing resin is subjected to a surface treatment, and the water-absorbing agent can add water-insoluble inorganic fine particles to the water-absorbing resin as necessary, and the heat retention index 1 is 3.0 ° C./min or less. Absorption capacity under no pressure with respect to 0.90 wt% sodium chloride aqueous solution is 34 g / g or less, Absorption capacity under pressure at 2.0 kPa with respect to 0.90 wt% sodium chloride aqueous solution is less than 30 g / g, 600-300 μm is 60% by weight or more, less than 150 μm is 3% by weight or less, mass average particle diameter is 400-600 μm, logarithmic standard deviation (σζ) of particle size distribution is 0.250-0.400, and It is a water-absorbing agent having a flow conductivity (SFC) value of a 69 wt% sodium chloride aqueous solution of less than 20 × 10 ⁻⁷ cm ³ sec / g.

  Hereinafter, although the water absorbing agent of this invention is demonstrated, the manufacturing method is not limited above.

  The water-absorbing agent that can be used in the present invention preferably has an absorbency against pressure of 0.90% by weight sodium chloride aqueous solution of 20 g / g or more and 34 g / g or less, more preferably 20 g / g or more and 32 g. / G or less, more preferably 20 g / g or more and 30 g / g or less. When the absorbency against pressure of 0.90% by weight sodium chloride is less than 20 g / g, it is necessary to have many crosslinking agents when producing a water-absorbing agent, which not only increases the production cost but also the water-absorbing agent. Insufficient absorption of water causes a feeling of stickiness such as an increase in the amount of liquid returned in an absorbent body such as a diaper. Further, if the absorption capacity without load with respect to a 0.90% by weight sodium chloride aqueous solution is larger than 34 g / g, the gel strength of the gel particles swollen by the water absorption agent decreases, so The gel particles are deformed and the gel layer volume of the water-absorbing agent is reduced. As a result, not only the heat retaining property of the absorbent body, which is the effect of the present invention, can be exhibited sufficiently, but also leakage from the absorbent body may occur.

  The water-absorbing agent that can be used in the present invention preferably has an absorption capacity under pressure of 2.0 kPa with respect to a 0.90% by weight sodium chloride aqueous solution of 20 g / g or more and less than 30 g / g, more preferably 20 g / g. g or more and less than 27 g / g. The use environment of an absorbent body such as a diaper is such that body pressure is always applied, and when the absorption capacity under pressure at 2.0 kPa against a 0.90% by weight sodium chloride aqueous solution is smaller than 20 g / g, a water absorbent resin The amount of absorption under pressure is insufficient, which may cause leakage of body fluid (such as urine and blood) and / or a sticky feeling from the absorber. Moreover, in order to increase the absorption capacity under pressure at 2.0 kPa with respect to a 0.90% by weight sodium chloride aqueous solution to 30 g / g or more, it is necessary to improve the water-absorbing agent, leading to an increase in production cost. Since an effect commensurate with it cannot be obtained, it is not necessary that the absorption capacity under pressure at 2.0 kPa with respect to a 0.90% by weight sodium chloride aqueous solution is 30 g / g or more.

The water-absorbing agent that can be used in the present invention has a flow inductive (SFC) value of 0.69 wt% sodium chloride aqueous solution of 0 × 10 ⁻⁷ cm ³ sec / g or more, 20 × 10 ⁻⁷ cm ³ sec / g. Is preferably 0 × 10 ⁻⁷ cm ³ sec / g or more and less than 10 × 10 ⁻⁷ cm ³ sec / g. The fluid permeability of body fluids (such as urine and blood) in the gel layer is one of the factors that efficiently exerts the performance of the water-absorbing agent contained in the absorber. There are many cases where sexual fibers are present. The performance of the water-absorbing resin (or water-absorbing agent) is sufficiently exhibited by the diffusibility of the liquid possessed by the hydrophilic fiber. In addition, when the flow inductive (SFC) value of the 0.69 wt% sodium chloride aqueous solution is as high as 20 × 10 ⁻⁷ cm ³ sec / g or more, the fluidity of the body fluid (such as urine and blood) is high, so the body fluid Tends to spread throughout the absorbent body before it is absorbed by the water-absorbing agent. This may cause unpleasant feelings such as anxiety and leakage for the person wearing the absorber, such as whether body fluid may leak from the absorber, and is not suitable for the present invention.

  The water-absorbing agent that can be used in the present invention has a heat retention index 1 (maximum temperature decrease per minute in 5 to 10 minutes after swelling 10 times at 50 ° C.) of 0 to 3.0 ° C./min. More preferably, it is 0-2.7 degreeC / min, More preferably, it is 0-2.5 degreeC / min, Most preferably, it is 0-2.2 degreeC / min. When the heat retention index 1 is greater than 3.0 ° C./min, sufficient heat retention cannot be obtained, and the burden on the wearing person, which is the object of the present invention, is reduced, and the absorbent body has excellent absorption performance. Not suitable for the offer.

  The water-absorbing agent that can be used in the present invention preferably further has a heat retention index 2 of 20 ° C. or higher (gel surface temperature after 10-fold swelling at 50 ° C., 10 minutes later), more preferably 21 ° C or higher, more preferably 22 ° C or higher, more preferably 23 ° C or higher, and most preferably 24 ° C or higher. When the heat retention index 2 is lower than 20 ° C., sufficient heat retention cannot be obtained, and it is possible to reduce the burden on the wearing person who is the object of the present invention and to provide an absorbent body excellent in absorption performance. Not right. In general, the upper limit is preferably about 50 ° C.

  The water-absorbing agent that can be used in the present invention preferably further has a heat retention index 3 of 120 seconds or longer (the time for the gel surface temperature to reach 37 ° C. after 10-fold swelling at 50 ° C.), and more preferably Is 130 seconds or longer, more preferably 140 seconds or longer, more preferably 150 seconds or longer, and most preferably 160 seconds or longer. When the heat retention index 3 is earlier than 120 seconds, sufficient heat retention cannot be obtained, reducing the burden on the person wearing the object, which is the object of the present invention, and providing an absorbent body excellent in absorption performance Not right. In addition, there is no upper limit in particular, and although it is preferable that it is long, 600 seconds is generally sufficient.

In order to maximize the effects of the present invention, the absorbency against pressure of 0.90 wt% sodium chloride aqueous solution is 34 g / g or less, and the pressure is 2.0 kPa against 0.90 wt% sodium chloride aqueous solution. Absorption rate is less than 30 g / g, 0.69 wt% sodium chloride aqueous solution flow inductivity (SFC) value is less than 20 × 10 ⁻⁷ cm ³ sec / g, and heat retention index 1 is 3.0 ° C./min or less. It is particularly preferable to use a water-absorbing agent having a specific performance. In addition, water-insoluble inorganic fine particles, other chelating agents, deodorizing agents, cationic polymers, and the like can be added to the water-absorbing agent as necessary so as not to depart from the physical property range. The addition amount is 0.0001 to 10% by weight, more preferably 0.0001 to 5% by weight (vs. a water absorbing agent). When the amount is less than 0.0001% by weight, the added effect does not appear. On the other hand, when the amount is more than 10% by weight, not only the production cost is increased, but also the performance of the water-absorbing agent is lowered, which is not suitable.

  In addition, the water-absorbing agent according to the present invention only needs to satisfy any one of the above-described heat retention indexes 1 to 3, and preferably satisfies two of the heat retention indexes 1 to 3. Preferably, the heat retention indices 1 and 2 are satisfied, and it is most preferable that all of the heat retention indices 1 to 3 are satisfied.

[Manufacturing method of absorber]
The absorber according to the present invention can be obtained by molding a powdery water-absorbing agent containing a water-absorbing resin as a main component together with any other absorbent material. The shape of the absorber is not particularly limited, but is preferably processed into a sheet shape, a cylindrical shape, a film shape, and a fiber shape, and particularly preferably processed into a sheet shape (also called a web shape) to obtain an absorber. Moreover, when a water absorbing resin (or water absorbing agent) is obtained in a sheet form, it may be used as an absorbent as it is.

  The absorber according to the present invention is mainly composed of a water-absorbing resin (or water-absorbing agent) having a crosslinked structure obtained by polymerizing an unsaturated monomer component in order to exert the effects of the present invention, and is hydrophilic. An absorber comprising fibers.

  The hydrophilic fiber that can be used in the present invention is not particularly limited, and examples thereof include pulverized wood pulp, other examples such as cotton linter and crosslinked cellulose fiber, rayon, cotton, wool, acetate, vinylon, etc. They are airlaid.

  This absorber is an absorber manufactured using the water-absorbing agent and hydrophilic fiber according to the present invention described above.

  In the absorbent body according to the present invention, the content (core concentration) of the water-absorbing agent with respect to the total weight of the water-absorbing agent and the hydrophilic fiber is preferably in the range of 20 to 100% by weight, more preferably 25 to 90% by weight. %, More preferably in the range of 30-80% by weight, even more preferably in the range of 40-80% by weight, particularly preferably in the range of 50-80% by weight, more preferably in the range of 60-80% by weight, 70 It is in the range of ˜80 wt%. When the core concentration is less than 20% by weight, the amount of the water-absorbent resin used is small, and for example, heat retention may not be sufficiently imparted to the entire diaper, which is not preferable.

When the absorbent body according to the present invention is produced from the water-absorbing agent and the hydrophilic fiber, the production method is not particularly limited. For example, the water-absorbent resin and the hydrophilic fiber are mixed at a ratio of the above-mentioned core concentration. After dry-mixing using the mixer, the resulting mixture is formed into a web shape by, for example, air-making, and then compression-molded as necessary, or the mixture obtained by dry-mixing, water, Examples thereof include a method of spraying or dropping and mixing an aqueous liquid or various organic solvents. Such an absorber is preferably compression-molded in a range of density 0.001 to 0.50 g / cc and basis weight 0.01 to 0.20 g / cm ² .

[Method of manufacturing absorbent article]
As described above, the absorbent article according to the present invention includes the absorber according to the present invention, a top sheet having liquid permeability, and a back sheet having liquid impermeability.

  Although the manufacturing method of the absorbent article concerning this invention is not specifically limited, For example, an absorber is comprised by the base material (surface sheet) which has liquid permeability, and the base material (back sheet) which has liquid impermeability. It is sufficient to make an absorbent article, for example, an adult paper diaper or a sanitary napkin, by sandwiching, and if necessary, equipped with an elastic member, a diffusion layer, an adhesive tape, and the like.

  The water-absorbing agent or absorbent according to the present invention can impart heat retention to an absorbent article and exhibits excellent heat retention and absorption characteristics over a long period of time. Specific examples of such absorbent articles include adult paper diapers that have grown significantly in recent years, hygiene materials such as diapers for children, sanitary napkins, so-called incontinence pads, and the like, and are particularly limited thereto. Although it is not a thing, the water-absorbing agent and the absorbent body present in the absorbent article have a very good heat retention, a small amount of return, and a dry feeling that is remarkable. The burden can be greatly reduced.

〔Example〕
EXAMPLES Examples and comparative examples of the present invention will be specifically described below, but the present invention is not limited to the following examples.

  Various performances of the water-absorbing agent (or water-absorbing resin) and the absorbent article were measured by the following methods. Further, the water-absorbing agent (or water-absorbing resin) and the absorbent article were used under conditions of 25 ° C. ± 2 ° C. and RH 50% unless otherwise specified.

<Moisture content>
In the water absorbent resin (or water absorbent), it represents the ratio of moisture. The relationship with the solid content is as follows.

Moisture content (% by weight) = 100-solid content (% by weight)
The method for measuring the moisture content was as follows.

Weigh out about 1 g of water-absorbent resin powder or its water content (weight W ₁ ) in an aluminum cup (weight W ₀ ) having a bottom diameter of about 5 cm, and leave it in a windless dryer at 180 ° C. for 3 hours. dry. The weight (W ₂ ) of the dried aluminum cup + water-absorbent resin was measured, and the water content was determined from the following formula.

Water content (% by weight) = (1− (W ₂ −W ₀ ) / W ₁ ) × 100
<Amount of soluble component (water-soluble component)>
Weigh out 184.3 g of 0.90 wt% aqueous sodium chloride solution (saline) in a 250 ml plastic container with a lid, add 1.00 g of water-absorbing resin (or water-absorbing agent) to the aqueous solution, and stir for 16 hours. As a result, the soluble component in the resin was extracted. 50.0 g of the filtrate obtained by filtering this extract using a filter paper (No. 2 manufactured by Toyo Filter Paper Co., Ltd.) was measured and used as a measurement solution.

  First, physiological saline alone is titrated to pH 10 with a 0.1N aqueous sodium hydroxide solution, then titrated to pH 2.7 with 0.1N hydrochloric acid, and an empty titration (blank) ([bNaOH] ml [BHCl] ml).

  The titration ([NaOH] ml, [HCl] ml) was determined by performing the same titration operation on the measurement solution.

For example, in the case of a water-absorbing resin comprising a known amount of acrylic acid and its sodium salt, based on the average molecular weight of the monomer and the titration amount obtained by the above operation, the soluble content in the water-absorbing resin is calculated as follows: Soluble content (% by weight) = 0.1 * (average molecular weight) * 184.3 * 100 * ([HCl]-[bHCl]) / 1000 / 1.00 / 50.0
Can be calculated. In the case of an unknown amount, the average molecular weight of the monomer is calculated using the neutralization rate obtained by titration.

<Absorption capacity under non-pressure (CRC) with respect to 0.90 wt% sodium chloride aqueous solution (saline)>
Put 0.20 g of water-absorbing resin (or water-absorbing agent) uniformly in a non-woven bag (60 mm x 85 mm) and immerse it in a 0.90 wt% aqueous sodium chloride solution (saline) adjusted to 25 ± 2 ° C. did. After 30 minutes, the bag was pulled up, drained at 250 G for 3 minutes using a centrifuge, and the weight W ₁ (g) of the bag was measured. The same operation was performed without using a water absorbent resin (or water absorbent), and the weight W ₀ (g) at that time was measured. From W ₁ and W ₀ , absorption capacity without load (g / g) = {(weight W ₁ (g) −weight W ₀ (g)) with respect to the following formula 0.90 wt% sodium chloride aqueous solution (saline) / Weight of water absorbent resin (or water absorbent) (g)}-1
Thus, the absorption capacity without load (g / g) was calculated.

<Absorption capacity under pressure at 2.0 kPa against 0.90 wt% sodium chloride aqueous solution (saline) (AAP 0.3 psi)>
0.90 g of a water-absorbing agent (or a water-absorbing resin) is uniformly sprayed on a metal mesh at the bottom of a plastic support cylinder having an inner diameter of 60 mm in which a stainless steel mesh having a mesh opening of 38 μm is welded to one side (bottom) of the cylindrical cross section. A piston (cover plate) that has an outer diameter slightly smaller than 60 mm, does not create a gap in the wall surface with the support cylinder, and does not hinder vertical movement is placed on the support cylinder and the water absorbing agent ( Or the water absorption resin) and the weight W ₃ (g) of the piston were measured. A load adjusted so that a load of 2.0 kPa (about 0.3 psi) including the piston can be uniformly applied to the water absorbent (or water absorbent resin) on this piston is measured. Completed the device. Place a glass filter with a diameter of 90 mm and a thickness of 5 mm inside a Petri dish with a diameter of 150 mm, and 0.90 wt% sodium chloride aqueous solution (saline) adjusted to 25 ± 2 ° C at the same level as the upper surface of the glass filter It was added to become. On top of that, a sheet of 90 mm diameter filter paper (No. 2 manufactured by Toyo Filter Paper Co., Ltd.) was placed so that the entire surface was wetted, and excess liquid was removed.

The set of measuring devices was placed on the wet filter paper, and the liquid was absorbed under load. When the liquid level dropped from the top of the glass filter, the liquid was added to keep the liquid level constant. After 60 minutes, the set of measuring devices was lifted, and the weight W ₄ (g) (weight of the support cylinder, swollen water absorbent (or water absorbent resin) and piston) after removing the load was measured again. And from these weights W ₃ and W ₄ , the absorption capacity under pressure (g / g) at 2.0 kPa with respect to the following formula 0.90 wt% sodium chloride aqueous solution (saline) = (weight W ₄ (g) − Weight W ₃ (g)) / weight of water absorbent (or water absorbent resin) (g)
Thus, the absorption capacity (g / g) under pressure at 2.0 kPa with respect to a 0.90% by weight sodium chloride aqueous solution (saline) was calculated.

<Mass average particle diameter (D50) and logarithmic standard deviation (σζ)>
The water-absorbing agent (or water-absorbing resin) is sieved with JIS standard sieves such as 850 μm, 710 μm, 600 μm, 500 μm, 425 μm, 300 μm, 212 μm, 150 μm, 106 μm, 75 μm, 45 μm, and the residual percentage (R) is logarithmic probability paper. Plot to Thereby, the mass average particle diameter (D50) was read. The logarithmic standard deviation (σζ) is expressed by the following equation: σζ = 0.5 × ln (X ₂ / X ₁ )
(X ₁ is R = 84.1%, X ₂ is each particle size when R = 15.9%)
The smaller the value of σζ, the narrower the particle size distribution.

  For screening, JIS standard sieves (The IIDA TESTING SIEVE) having an opening of 850 μm, 710 μm, 600 μm, 500 μm, 425 μm, 300 μm, 212 μm, 150 μm, 106 μm, 75 μm, 45 μm, etc. are used. : 80 mm in inner diameter), and classified for 5 minutes by a low tap type sieve shaker (manufactured by Iida Seisakusho, ES-65 type sieve shaker). The mass average particle size (D50) is a particle size corresponding to 50% by weight of the whole particles sieved with a standard sieve having a constant mesh as described in US Pat. No. 5,051,259.

<Flow Inducibility (SFC) of 0.69 wt% Sodium Chloride Aqueous Solution>
It was measured according to the method described in JP-T 9-510889 (p.82 “F. Test Method 1. Salt Flow Inductivity (SFC) Test”) (US Pat. No. 5,599,335).

<Heat retention index of water absorbent resin>
<Insulation index 1>
FIG. 1 is a schematic diagram showing a configuration of a measuring device 10 used for a heat retention index, which is one of the performances of the water-absorbing agent according to the present invention. As shown in FIG. 1, the measuring apparatus 10 includes an aluminum cup 2, a thermography 3, and an ice water bath 5 (2400 ml).

  Indoors at room temperature 24 ± 1 ° C, RH 50%, no wind (no air flow), bottom diameter is about 5cm, height is about 2cm, bottom thickness is 0.05mm, side thickness is 0.16-0 Weigh out 2.0 g of water-absorbing agent (or water-absorbing resin) into an aluminum cup (Foil Container Part No. 107) manufactured by Toyo Echo Co. 20 ml of 0.90% by weight sodium chloride aqueous solution (physiological saline) is poured quickly and swollen for 2 minutes so that the gel layer becomes uniform. At this time, the height of the gel layer 1 is about 1 cm.

  After swelling, the sample was quickly transferred into an ice water bath (2400 ml) 5 of 3 ° C. prepared in advance with ice 8 and water 9, preferably within 3 seconds, and simultaneously swelled with thermography 3 (Avio Neo Thermo) 3. Recording of the surface temperature of the central portion of the upper surface of the gel layer 1 was started. This recording was continuously performed for 20 minutes after the start of cooling. During the temperature recording, the ice water bath 5 is maintained at 3 ° C. by stirring with a stirrer 7 controlled by the stirring device 4, and the aluminum cup 2 is at least separated from the bottom of the aluminum cup 2 with the gel layer 1. It must be immersed in the ice water bath 5 to the height of the aluminum cup 2 at the same height (about 1 cm) or more. Such adjustment of the height of the aluminum cup 2 can be performed using, for example, the adjustment table 6. In consideration of the temperature of the aluminum cup 2, the adjusting table 6 preferably has a lattice-like (mesh-like) structure.

  After observing the gel layer surface temperature for 20 minutes after the start of cooling, the gel layer surface temperature recorded up to 20 minutes after the end of recording, with the cooling start time being 0 minutes, is a graph with the X axis as time and the Y axis as temperature. Plot in minutes. The amount of change in temperature of the gel surface temperature per minute between 5 minutes and 10 minutes after the start of cooling (5 minutes-6 minutes, 6 minutes-7 minutes, 7 minutes-8 minutes, 8 minutes-9 minutes, 9 minutes- (Each temperature change amount in 10 minutes) is calculated, and the highest absolute value is defined as a heat retention index 1.

<Insulation index 2>
In the measurement of the heat retention index 1, the temperature of the gel surface after 10 minutes from the start of cooling the swollen gel is defined as the heat retention index 2.

<Insulation index 3>
In the measurement of the heat retention index 1, the time (seconds) from the start of cooling of the swollen gel until the gel surface temperature reaches 37 ° C. is defined as the heat retention index 3.

<Monitor test>
Ten healthy adults were put on a diaper (water absorbent article) having a core concentration of 70% by weight so that there was no gap between the body and heated to 37 ° C. 0.90% by weight sodium chloride aqueous solution (saline solution) ) 150 ml was injected with a syringe in about 1 minute, and the cooling sensation at the point of 15 minutes and 30 minutes after the injection was evaluated in five stages, and the average value was evaluated.
1: Uncomfortable 2: Slightly uncomfortable 3: Feeling nothing 4: Slightly comfortable 5: Comfortable <Reference Example 1: Production / neutralization polymerization of water absorbent resin (a)>
6600 g of an aqueous solution of sodium acrylate having a neutralization rate of 68 mol% (single quantity) in a reactor formed by attaching a lid to a stainless steel double-armed kneader with a volume of 10 liters and having two sigma type blades Polyethylene glycol diacrylate (n = 9) 5.98 g was dissolved in a body concentration of 37.7% by weight to prepare a reaction solution. Next, the reaction solution was purged with nitrogen for 20 minutes in a nitrogen gas atmosphere. Subsequently, 35.8 g of a 10% by weight aqueous sodium persulfate solution and 1.49 g of a 1% by weight aqueous L-ascorbic acid solution were added to the reaction solution with stirring. Polymerization started after about 20 seconds. Then, polymerization was performed at 20 to 95 ° C. while pulverizing the generated gel, and a hydrogel crosslinked polymer was taken out 42 minutes after the polymerization started. The obtained hydrogel crosslinked polymer was subdivided to have a diameter of about 5 mm or less. This finely divided hydrogel crosslinked polymer was spread on a 20-mesh (mesh 850 μm) wire mesh and dried with hot air at 180 ° C. for 40 minutes. Subsequently, the mixture is pulverized using a roll mill, and further classified and prepared with a JIS standard sieve having an opening of 850 μm and 150 μm, whereby the ratio of the resin having a mass average particle diameter of 450 μm and a particle diameter of 850 to 600 μm is 28% by weight, An irregularly crushed water-absorbing resin (a) having a ratio of the resin having a particle diameter of less than 150 μm of 2% by weight, a logarithmic standard deviation (σζ) of 0.364, and a water content of 6% by weight was obtained.

  When the physical properties of the obtained water-absorbent resin (a) were measured, CRC = 42.6 (g / g) and the soluble content was 12.5% by weight.

<Reference Example 2: Production of water-absorbent resin (b) / neutralization polymerization>
The mass average particle diameter was the same as in Reference Example 1 except that the monomer concentration of Reference Example 1 was 40 wt%, the neutralization rate was 75 mol%, and the cross-linking agent was 3.97 g of trimethylolpropane triacrylate. The ratio of the resin having a particle diameter of 450 μm and 850 to 600 μm is 28% by weight, the ratio of the resin having a particle diameter of less than 150 μm is 2% by weight, the logarithmic standard deviation (σζ) is 0.364, and the water content is 6% by weight. %, An irregularly crushed water-absorbing resin (b) was obtained.

  When the physical properties of the water-absorbent resin (b) obtained were measured, CRC = 37.6 (g / g) and the soluble content was 12.3% by weight.

[Example 1: Water absorbing agent]
500 g of the water-absorbent resin (a) obtained in Reference Example 1 was placed in a 5 L Ladige mixer (manufactured by M5R type Ladige), and while rotating the main shaft (squilled blade) of the Ladige mixer at 330 rpm, 22.5 g of a glycerin / water / isopropyl alcohol = 0.75 / 3 / 0.75% by weight mixed solution was added while spraying and mixed for 1 minute.

  Stirring was then stopped and the resulting mixture was quickly removed.

  Next, the obtained mixture was put into a 5 L mortar mixer (manufactured by West Japan Testing Machine Co., Ltd.) whose container was heated to 210 ° C. by an oil bath, and stirred and mixed so that heat was uniformly applied to the mixture. After about 20 minutes, the mixture was taken out from the mortar mixer, and the whole amount was passed through a 850 μm JIS standard sieve to perform surface crosslinking.

  480 g of the surface-crosslinked one is put again into a 5 L Ladige mixer (manufactured by M5R type Ladige), and 9.6 g of water is added while rotating the main shaft of the Laedige mixer at a speed of 330 rpm. A water-containing product was obtained by charging while spraying and mixing for 1 minute.

  The obtained hydrated product was transferred to a sealed container, and heated and cured (absorbed moisture added to the hydrated product) for 1 hour in a 60 ° C. windless dryer. After 1 hour, the water-containing product was taken out from the dryer, and the whole amount was passed through a 850 μm JIS standard sieve to obtain a water-absorbing agent (1).

  CRC of the obtained water-absorbing agent (1), AAP 0.3 psi, mass average particle diameter (D-50), logarithmic standard deviation of particle size distribution, SFC value, heat retention index 1, heat retention index 2, and heat retention index 3, The results are shown in Table 1 below.

[Example 2: Water absorbing agent]
The water-absorbing agent (2) was obtained by adding 0.30% by weight of Aerosil 200 (manufactured by Aerosil) to the water-absorbing agent (1) obtained in Example 1. The obtained water-absorbing agent (2) was evaluated in the same manner as in Example 1, and the results are summarized in Table 1 below.

[Example 3: Water absorbing agent]
500 g of the water-absorbent resin (b) obtained in Reference Example 2 was placed in a 5 L Ladige mixer (manufactured by M5R type Ladige), and while rotating the main shaft (squilled blade) of the Ladige mixer at 330 rpm, 11.25 g of a glycerin / water = 0.75 / 1.5 wt% mixed solution was added while spraying and mixed for 1 minute. Stirring was then stopped and the resulting mixture was quickly removed.

  Next, the obtained mixture was put into a 5 L mortar mixer (manufactured by West Japan Testing Machine Co., Ltd.) whose container was heated to 205 ° C. by an oil bath, and stirred and mixed so that heat was uniformly applied to the mixture. After about 40 minutes, the mixture was taken out from the mortar mixer, and the whole amount was passed through a 850 μm JIS standard sieve to perform surface crosslinking.

  480 g of the surface-cross-linked one is again put into a 5 L Ladige mixer (manufactured by M5R type Ladige), and 9.6 g of water is added while rotating the main shaft (squilled blade) of the Ladige mixer at 330 rpm. A water-containing product was obtained by charging while spraying and mixing for 1 minute.

  The obtained hydrated product was transferred to a sealed container, and heated and cured (absorbed moisture added to the hydrated product inside) in a 60 ° C. windless dryer for 1 hour. After 1 hour, the water-containing material was taken out from the dryer, and the whole amount was passed through a 850 μm JIS standard sieve to obtain water-containing powder.

  A water-absorbing agent (3) was obtained by adding 0.30% by weight of Aerosil 200 (manufactured by Aerosil) to the obtained water-containing powder.

  The obtained water-absorbing agent (3) was evaluated in the same manner as in Example 1, and the results are summarized in Table 1 below.

[Comparative Example 1: Water absorbing agent]
The water absorbent resin (a) obtained in Reference Example 1 was used as a comparative water absorbing agent (4) and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 2: Water absorbing agent]
The water-absorbing agent (1) obtained in Example 1 was further classified into 300 to 150 μm using a JIS standard sieve to obtain a comparative water-absorbing agent (5), which was evaluated in the same manner as in Example 1. The results are shown in Table 1. Indicated.

[Comparative Example 3: Water absorbing agent]
500 g of the water-absorbent resin (a) obtained in Reference Example 1 was placed in a 5 L Ladige mixer (manufactured by M5R type Ladige), and while rotating the main shaft (squilled blade) of the Ladige mixer at 330 rpm, 1,4-butanediol / propylene glycol / water = 28.0 g of a 0.3 / 0.5 / 3.0 wt% mixed solution was added while spraying and mixed for 1 minute.

  Stirring was then stopped and the resulting mixture was quickly removed.

  Next, the obtained mixture was put into a 5 L mortar mixer (manufactured by West Japan Testing Machine Co., Ltd.) whose container was heated to 200 ° C. by an oil bath, and stirred and mixed so that heat was uniformly applied to the mixture. After about 40 minutes, the mixture was taken out from the mortar mixer, and the whole amount was passed through a 850 μm JIS standard sieve to perform surface crosslinking.

  480 g of the surface-crosslinked product is again put into a 5 L Ladige mixer (manufactured by M5R type Ladige), and 9.6 g of water is rotated while rotating the main shaft (saddle blade) of the Ladige mixer at 330 rpm. Was added while spraying and mixed for 1 minute to obtain a hydrated product.

  The obtained hydrated product was transferred to a sealed container, and heated and cured (absorbed moisture added to the inside of the water-absorbent resin) in a 60 ° C. windless dryer for 1 hour. After 1 hour, the water-containing product was taken out from the dryer, and the whole amount was passed through a 850 μm JIS standard sieve to obtain a comparative water-absorbing agent (6).

  The obtained comparative water-absorbing agent (6) was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Comparative Example 4: Water absorbing agent]
In a reactor formed by attaching a jacket to a stainless steel double-armed kneader with a volume of 10 liters and having two sigma blades, 1.18 g of trimethylolpropane triacrylate (0.04 mol%) and 720 g of acrylic acid ) Was dissolved to prepare a reaction solution. Next, the reaction solution was purged with nitrogen for 20 minutes in a nitrogen gas atmosphere. Subsequently, 10% by weight 2,2′-azobis (2-amidinopropane) dihydrochloride aqueous solution 21.6 g, 1% by weight L-ascorbic acid aqueous solution 18.0 g, and 3.5% by weight hydrogen peroxide were added to the reaction solution. Polymerization was initiated by adding 20.6 g of aqueous solution with stirring. Stirring was stopped simultaneously with the start of polymerization, and after the temperature of the reaction solution reached the maximum temperature, the reaction solution was aged for 3 hours while maintaining the temperature of the reaction solution at 55 ° C or higher. After completion of the reaction, the generated gel was pulverized by rotating the blade to obtain a hydrogel crosslinked polymer.

  Next, the blade was rotated to keep the hydrated gel-like crosslinked polymer at about 50 ° C. while further crushing, and 700 g of a 40 wt% sodium hydroxide aqueous solution as a neutralizing agent was dropped and mixed over 40 minutes. . Thereafter, the blade was stopped and held at 50 ° C. for 80 minutes, and then 400 g of deionized water was added to the polymer, mixed, and kept at room temperature for 24 hours to complete neutralization (neutralization rate 70 mol%). ).

  Subsequently, the neutralized hydrogel crosslinked polymer was spread on a 20 mesh (mesh 850 μm) wire mesh and dried with hot air at 160 ° C. for 40 minutes. Next, the mixture is pulverized using a roll mill and further classified with a JIS standard sieve having an opening of 850 μm, so that the proportion of the resin having a mass average particle size of 405 μm and a particle size of 850 to 600 μm is 20% by weight and less than 150 μm An irregularly crushed water-absorbing resin (c) having a ratio of the resin having a diameter of 12% by weight, a logarithmic standard deviation (σζ) of 0.520, and a moisture content of 6% by weight was obtained.

  When the physical properties of the obtained water-absorbent resin (c) were measured, CRC = 38.1 (g / g) and the soluble content was 9.8% by weight.

  Subsequently, 500 g of the obtained water-absorbing resin (c) was placed in a 5 L Ladige mixer (manufactured by M5R type Ladige), and while rotating the main shaft (saddle-shaped blade) of the Ladige mixer at 330 rpm, 16.0 g of 1,3-dioxolan-2-one / water / ethanol = 0.2 / 1.0 / 2.0 wt% mixed solution was added while spraying and mixed for 1 minute.

  Stirring was then stopped and the resulting mixture was quickly removed.

  Next, the obtained mixture was put into a 5 L mortar mixer (manufactured by West Japan Testing Machine Co., Ltd.) whose container was heated to 180 ° C. by an oil bath, and stirred and mixed so that heat was uniformly applied to the mixture. After about 60 minutes, the mixture was taken out from the mortar mixer, and the whole amount was passed through a 850 μm JIS standard sieve to obtain a comparative water-absorbing agent (7).

  The obtained comparative water-absorbing agent (7) was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.

[Comparative Example 5: water absorbing agent]
In the same manner as in Reference Example 1, except that the monomer concentration of Reference Example 1 is 40% by weight, the neutralization rate is 75% by mole, and the crosslinking agent is polyethylene glycol diacrylate (n = 9) 4.54 g, the mass average An irregularly shaped water-absorbing resin (d) having a particle size of 395 μm and a resin having a particle size of less than 150 μm of 5% by weight, logarithmic standard deviation (σζ) of 0.363, and water content of 6% by weight Obtained.

  When the physical properties of the water-absorbent resin (d) were measured, CRC = 47.0 (g / g) and the soluble content was 20.0% by weight.

  500 g of the obtained water-absorbing resin (d) was put into a 5 L Ladige mixer (M5R type Ladige), and while rotating the main shaft (saddle-shaped blade) of the Ladige mixer at 330 rpm, diethylene glycol diglycidyl ether / 25.2 g of a mixed solution of propylene glycol / water / isopropyl alcohol = 0.03 / 1/3/1% by weight was added while spraying and mixed for 1 minute.

  Stirring was then stopped and the resulting mixture was quickly removed.

  Next, the obtained mixture was put into a 5 L mortar mixer (manufactured by West Japan Testing Machine Co., Ltd.) whose container was heated to 210 ° C. by an oil bath, and stirred and mixed so that heat was uniformly applied to the mixture. After about 40 minutes, the mixture was taken out from the mortar mixer, and the whole amount was passed through a 850 μm JIS standard sieve to perform surface crosslinking.

  480 g of the surface-crosslinked one is put again into a 5 L Ladige mixer (manufactured by M5R type Ladige), and 9.6 g of water is added while rotating the main shaft of the Laedige mixer at a speed of 330 rpm. A water-containing product was obtained by charging while spraying and mixing for 1 minute.

  The obtained hydrated product was transferred to a sealed container, and heated and cured (absorbed moisture added to the hydrated product) for 1 hour in a 60 ° C. airless dryer. After 1 hour, the water-containing product was taken out from the dryer, and the whole amount was passed through a 850 μm JIS standard sieve to obtain a comparative water-absorbing agent (8).

  Using the obtained comparative water-absorbing agent (8), evaluation was made in the same manner as in Example 1, and the results are shown in Table 1.

[Comparative Example 6: Water absorbing agent]
Evaluation was performed in the same manner as in Example 1 using the water-absorbing agent obtained in Example 10 described in JP-A No. 2001-98170 (US Pat. No. 6,586,549), and the results are shown in Table 1. This water absorbing agent is referred to as a comparative water absorbing agent (9).

[Comparative Example 7: water absorbing agent]
Evaluation was conducted in the same manner as in Example 1 using the water-absorbing agent obtained in Example 1 described in JP-A-2002-45395 (US Pat. No. 6,617,489), and the results are shown in Table 1. This water absorbing agent is referred to as a comparative water absorbing agent (10).

[Comparative Example 8: water absorbing agent]
Evaluation was conducted in the same manner as in Example 1 using the water-absorbing agent obtained in Example 3 described in JP-A-2002-45395 (US Pat. No. 6,617,489), and the results are shown in Table 1. This water absorbing agent is referred to as a comparative water absorbing agent (11).

[Comparative Example 9: water absorbing agent]
Evaluation was performed in the same manner as in Example 1 using the water-absorbing agent obtained in Comparative Example 2 described in JP-A-2002-45395 (US Pat. No. 6,617,489), and the results are shown in Table 1. This water absorbing agent is referred to as a comparative water absorbing agent (12).

[Example 4: Absorbent article]
70 parts by weight of the water-absorbing agent (1) obtained in Example 1 and 30 parts by weight of wood pulverized pulp were dry-mixed using a mixer. Next, the obtained mixture was formed into a web having a size of 130 mm × 400 mm by air-making on a wire screen formed to 400 mesh (mesh size: 38 μm) using a batch type air-making machine. . Further, this web was pressed at a pressure of 196.14 kPa for 5 seconds to obtain an absorbent having a basis weight of about 0.05 g / cm ² .

  Subsequently, a so-called back sheet (liquid-impermeable sheet) made of liquid-impermeable polypropylene, the absorbent body, and a non-woven fabric surface sheet (liquid-permeable sheet) made of liquid-permeable polypropylene, double-sided tape By adhering to each other in this order, an absorbent article (that is, a pad type of an adult paper diaper) (1) was obtained. The weight of this absorbent article (1) was 50 g.

  The obtained absorbent article (1) was subjected to a monitor test, and the results are summarized in Table 2.

[Example 5: Absorbent article]
An absorbent article (2) was obtained by changing the water absorbent resin (1) used in Example 4 to the water absorbent resin (2) obtained in Example 2.

  A monitor test was performed on the resulting absorbent article (2), and the results are summarized in Table 2.

[Example 6: Absorbent article]
An absorbent article (3) was obtained by changing the water absorbent resin (1) used in Example 4 to the water absorbent resin (3) obtained in Example 3.

A monitor test was performed on the resulting absorbent article (3), and the results are summarized in Table 2.
[Comparative Examples 10 to 18: Absorbent articles]
By changing the water-absorbent resin (1) used in Example 4 to the comparative water-absorbing agents (4) to (12) obtained in Comparative Examples 1 to 9, comparative absorbent articles (1) to (9) )

  The obtained comparative absorbent articles (1) to (9) were subjected to a monitor test, and the results are summarized in Table 2.

  It should be noted that the specific embodiments or examples made in the best mode for carrying out the invention are merely to clarify the technical contents of the present invention, and are limited to such specific examples. The present invention should not be construed as narrowly defined but can be implemented with various modifications within the spirit of the present invention and the scope of the following claims.

  The water-absorbing agent obtained by the present invention, when used in a water-absorbing body such as a diaper, exhibits excellent heat retention and also has excellent absorption performance. There is an effect that can be provided. Furthermore, since the absorbent article using the water-absorbing agent obtained according to the present invention has excellent heat retention and absorption performance, there is an effect that it is possible to reduce discomfort to the absorbent article by consumers.

  Therefore, the water-absorbing agent of the present invention is widely used as a hygroscopic agent, a dehumidifying agent, a building material, etc., and particularly suitable as a sanitary material for absorbing feces, urine or blood, represented by paper diapers, sanitary napkins and the like. Used.

It is the schematic which shows the structure of the measuring apparatus used for the heat retention parameter | index which is one of the performances which the water absorbing agent concerning this invention shows.

Explanation of symbols

1 Gel layer (water absorbing agent)
2 Aluminum cup 3 Thermography 4 Stirrer 5 Ice water bath 6 Control stand 7 Stirrer 8 Ice 9 Water 10 Measuring device

Claims (13)

A water-absorbing agent mainly composed of a water-absorbing resin having a crosslinked structure obtained by polymerizing an unsaturated monomer component,
The water-absorbing agent is subjected to a surface treatment,
And the water absorbing agent is
(1) Thermal insulation index 1 (maximum temperature decrease per minute in 5 to 10 minutes after 10-fold swelling with 0.90 wt% sodium chloride aqueous solution at 50 ° C.) is 0 to 3.0 ° C./minute,
(2) Absorption capacity without load (value for 30 minutes) with respect to a 0.90% by weight sodium chloride aqueous solution is 34 g / g or less,
(3) Absorption capacity under pressure at 2.0 kPa against a 0.90 wt% aqueous sodium chloride solution (60 minutes value) is less than 30 g / g,
(4) The flow inductive (SFC) value of the 0.69 wt% sodium chloride aqueous solution is less than 20 × 10 ⁻⁷ cm ³ sec / g,
A water-absorbing agent characterized by satisfying all the requirements (1) to (4).   The water-absorbing agent is composed of particles, particles having a particle size of 600 to 300 μm as defined by sieving classification are composed of 60% by weight or more, and particles having a particle size of less than 150 μm are composed of 3% by weight or less (lower limit 0% by weight). The water-absorbing agent according to claim 1, wherein a logarithmic standard deviation (σζ) of 0.250 to 0.400 is satisfied.   The water-absorbing agent according to claim 1 or 2, further comprising water-insoluble inorganic fine particles in addition to the water-absorbing resin.   The heat retention index 2 (gel surface temperature after 10-fold swelling with a 0.90% by weight sodium chloride aqueous solution at 50 ° C, 10 minutes later) is 20 ° C or higher. Water-absorbing agent.   5. The heat retention index 3 (the time for the gel surface temperature to reach 37 ° C. after 10-fold swelling with a 0.90 wt% sodium chloride aqueous solution at 50 ° C.) is 120 seconds or more. The water-absorbing agent described in 1.   The water-absorbing agent according to any one of claims 1 to 5, wherein a mass average particle diameter (specified by sieve classification) is 400 to 600 µm.   The water-absorbing agent according to claim 1, further comprising a polyol in addition to the water-absorbing resin.   The unsaturated monomer is acrylic acid (salt), and the other monomer is 0 to 30 mol% based on acrylic acid (salt). Water-absorbing agent.   A molded absorbent comprising the water-absorbent resin according to any one of claims 1 to 8 and a hydrophilic fiber.   It is an absorber of Claim 9, Comprising: Content of the said water absorbing agent with respect to the total weight of the water absorbing agent in any one of Claims 1-8 and a hydrophilic fiber is 20 weight% or more. Characteristic absorber.   An absorbent article comprising the absorbent body according to claim 9 or 10, a top sheet having liquid permeability, and a back sheet having liquid impermeability. A method for producing a water-absorbing agent mainly comprising a water-absorbing resin having a crosslinked structure obtained by polymerizing an unsaturated monomer component,
A polymerization step for obtaining a water-absorbent resin by polymerizing a monomer component mainly composed of an acid group-containing unsaturated monomer;
A surface cross-linking process (surface treatment process) for performing a surface cross-linking process (surface treatment) on the water absorbent resin obtained by the polymerization process,
In the polymerization step,
The water-absorbent resin is a particle, and the water-absorbent resin has an absorption capacity without load (30 minutes value) with respect to 0.90% by weight sodium chloride of 35 g / g or more,
(1) The particles are 60% by weight or more of particles having a particle diameter of 600 to 300 μm defined by sieve classification, and 3% by weight or less of particles having a particle size of less than 150 μm,
(2) Logarithmic standard deviation (σζ) of particle size distribution is 0.250-0.400,
Polymerized to meet each specific particle size of
In the surface crosslinking step,
A method for producing a water-absorbing agent, wherein the water-absorbent resin satisfying each specific particle size in the polymerization step is subjected to surface cross-linking treatment to perform surface cross-linking. In the surface crosslinking step,
The water absorbent resin satisfying each specific particle size in the polymerization step,
Absorption capacity without load (value for 30 minutes) with respect to 0.90% by weight sodium chloride aqueous solution is 34 g / g or less, and
Absorption capacity under load at 2.0 kPa against a 0.90% by weight sodium chloride aqueous solution (60 minutes value) is less than 30 g / g,
The method for producing a water-absorbing agent according to claim 12, wherein surface crosslinking treatment is performed until

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