JP3434028B2 - Method for modifying water absorbent resin, water absorbent and water absorbent resin composition - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for modifying a water absorbent resin, a water absorbent and a water absorbent resin composition. More specifically, (1) it is excellent in safety, (2) it shows a great effect of improving the water absorption capacity under pressure while keeping the water absorption capacity at normal pressure high, and (3) it causes the aggregation of powder even under high humidity. A method for modifying a water absorbent resin, a water absorbent and a water absorbent resin composition.

[0002]

2. Description of the Related Art In recent years, a water-absorbent resin that absorbs a large amount of water and gelates has been developed and is widely used in the field of sanitary materials such as paper diapers and sanitary napkins, as well as in the fields of agriculture and forestry, the field of civil engineering, etc. There is.

Therefore, many water-absorbent resins have been developed up to now, for example, a hydrolyzate of a starch-acrylonitrile graft polymer (US Pat. No. 3,661,815).
No.), a starch-acrylic acid graft polymer (US Pat.
76663), polyacrylic acid partially neutralized crosslinked products (US Pat. Nos. 4,654,039 and 4,280,082), saponified products of vinyl acetate-acrylic acid ester copolymers (US Pat. No. 4,124,748), isobutylene-maleic anhydride copolymers. Combined (US Pat. No. 4,389,513), hydrolyzate of acrylonitrile copolymer (US Pat. No. 3935099)
No.), a hydrolyzate of an acrylamide polymer or a copolymer (US Pat. No. 3,959,569), a cross-linked copolymer of 2-acrylamido-2-methylpropanesulfonic acid and acrylic acid (European patent No. 068189), a cationic monomer. Crosslinked (co) polymers of US Pat. No. 4,906,717.
No. 5075399, European Patent No. 0304143
No.), cross-linked 2-sulfomethyl methacrylate, and other various polymerization-type water-absorbing resins, and cross-linked carboxymethyl cellulose salts (US Pat. Nos. 4,650,716 and 4,689).
408, European Patent 0538904), crosslinked carboxyalkyl starch (US Pat. No. 5,079,354),
Crosslinked starch (British Patent 1550614, US Patent 44
Various types of post-crosslinking water-absorbent resins of natural products such as No. 83950) are known, but polymerized water-absorbent resins are the mainstream because of their excellent physical properties.

These water-absorbent resins are water-insoluble and water-swellable hydrophilic resins having a uniform crosslinked structure inside the polymer, but today, in order to improve various physical properties, they are usually further crosslinked and then polymerized. The surface of the particles has been modified.

The surface modification of such a water-absorbent resin is to improve the water-absorption rate of the water-absorbent resin, prevent the formation of mamako, improve the gel strength, improve the water absorption ratio under pressure, prevent gel blocking, liquid permeability and liquid diffusibility. Many methods have been proposed so far because they have a great influence on basic physical properties such as. Then, roughly dividing these many methods, the surface of the water-absorbent resin particles is coated with (a) an inert additive,
And (b) the method of further surface-crosslinking with a crosslinking agent is roughly classified into two.

That is, various coating additives have been proposed as a method for coating the surface of particles with (a) an inert additive. For example, inorganic powder (US Pat. No. 4,179,936) is proposed.
No. 7, 4,500,670), water-soluble polymers and water-soluble surfactants (JP-A-56-54851), aliphatic hydrocarbons and their derivatives (European patent 0009977), polyethers (US Pat. No. 4,190,563). , Water-soluble powder (US Reissue Patent No. 33839) and the like are known.

However, the coating of the water-absorbent resin with these simple additives is insufficient in improving the water-absorbing speed and preventing the mamako. In particular, the water-absorption capacity under pressure (US Pat. No. 5,147,343), which is important in the field of hygiene, etc. the improvement of No., etc.), was circumstances that most of no effect. Further, the addition of the finely divided inorganic powder having a particle size of several μm to several nm may cause a safety problem due to dust generation during use or during addition.

Therefore, in recent years, for the purpose of improving the absorbency against pressure of the water-absorbent resin, many methods have been proposed for surface-crosslinking the water-absorbent resin particles (b). For details of the surface cross-linking method for these water-absorbent resins and similar techniques,
U.S. Pat. Nos. 4043952, 4051086, and 4
No. 340706, No. 4497930, No. 450743
No. 8, No. 4541871, No. 4558091, No. 4
No. 587308, No. 4666983, No. 472709.
No. 7, No. 4735987, No. 4734478, No. 4
755560, 4771105, and 478351.
No. 0, No. 4798861, No. 4806578, No. 4
No. 973632, No. 5026800, No. 511501
No. 1, No. 5140076, No. 5164459, No. 5
US patents such as 244735 and European patent 031
No. 7106, No. 0514724, No. 0536128
No. 0555692, and Japanese Patent Publication No. Sho 6
It is described in many documents such as 0-147475 and JP-A-2-153903.

Therefore, many surface cross-linking agents used for these surface cross-links have been proposed so far, for example, polyvalent glycidyl compounds, haloepoxy compounds, polyvalent isocyanate compounds, polyvalent aziridine compounds (JP-A-59-59).
189103), polyhydric oxazoline compounds, polyhydric amine compounds, polyhydric alcohols (JP-A-58-180233).
No. 61, JP-A 61-16903), alkylene carbonate (DE-4020780C), glyoxal (US Pat. No. 4,510,865, JP-A 52-117393).
No.), polyvalent metal salts (JP-A-51-136588, JP-A-61-257235, JP-A-62-7745),
Reaction product of epihalohydrin with ammonia or amines (JP-A-2-248404), silane coupling agent (JP-A-61-211305, JP-A-61-252).
212, JP-A-61-264006), peroxide radical initiator (JP-A-63-99211), and other special glycidyl compounds having a specific structure (JP-A-62-5).
0305, JP-A-61-213206, JP-A-63
-199205, JP-A-63-118308, JP-A-4-87638, JP-A-1-201312, and JP-A-61-293228).

The surface cross-linking agents are roughly classified as follows.
(1) Ring-opening reactive crosslinking agent such as glycidyl compound,
(2) Condensation-reactive crosslinking agents such as isocyanate compounds, (3) Ion-bonding crosslinking agents such as polyvalent metals, and (4) Dehydration-reactive agents such as polyhydric alcohols.

Among the above-mentioned four kinds of surface cross-linking agents, the ion-bonding cross-linking agent (3) has a weak binding force with the water-absorbent resin functional group, and therefore the effect of improving the water absorption capacity under pressure is extremely low. Further, the crosslinking agents (1) to (3) are highly reactive and react at the same time as they are mixed with the water-absorbent resin, resulting in changes in various physical properties of the water-absorbent resin. It is difficult to evenly distribute the crosslinking agent near the surface of the water absorbent resin. Therefore, it is difficult to achieve good physical properties by uniform cross-linking with the cross-linking agents (1) to (3), although many methods of adding the above-mentioned surface cross-linking agents have been proposed. Further, a special crosslinking agent such as a glycidyl compound is generally expensive, and a water-absorbent resin whose main field is disposable has a large cost problem.

Moreover, in general, even if any surface cross-linking agent is used, at least a part thereof may remain unreacted and remain on the surface. Therefore, a surface cross-linking agent having high reactivity such as a glycidyl compound is water-absorbing. Remaining on the surface of the resin is naturally unfavorable for safety. Therefore, a method of reducing the remaining surface crosslinking agent (Japanese Patent Laid-Open No. 19570/1993)
No. 5) has been proposed, but it requires complicated steps and the actual reduction is extremely difficult.

On the other hand, (4) the polyhydric alcohol, which is a dehydration-reactive crosslinking agent, is excellent in physical properties and safety, and specifically, it has high safety such that it is used as a food additive. Since there is no inconvenience that it reacts simultaneously with mixing like other cross-linking agents, even after mixing or during heat treatment, a uniform surface treatment is performed by gradually and uniformly distributing it on the surface of the water-absorbent resin. It is easy to do. However, in general, a cross-linking agent such as a polyhydric alcohol has extremely high hydrophilicity and hygroscopicity, so that it may penetrate into the inside of the water-absorbent resin depending on its mixing condition and reaction condition and may reduce its effect. .

In addition to physical properties and safety, water-absorbent resin is a major problem of water-absorbent resin, which has been attracting attention in recent years. When the water-absorbent resin is actually used in a factory at a particularly humid time such as rainy season, the water-absorbent resin is blocked. Then, a phenomenon of agglomeration, that is, a decrease in hygroscopic fluidity sometimes occurred. Therefore,
The present inventor, who has earnestly pursued such a cause, has found that the hygroscopic fluidity is lowered due to the surface crosslinking agent remaining on the surface of the water absorbent resin.

Incidentally, in order to prevent blocking of the water-absorbent resin and improve the hygroscopic fluidity, a method of adding an inorganic fine powder of about several μm to several nm to the water-absorbent resin (JP-A-59-8).
0459, Japanese Patent Laid-Open No. 2-238035 and US Pat.
87656) has been proposed. However, since such an inorganic fine powder does not participate in water absorption, no improvement in water absorption capacity under pressure is observed. To obtain expensive and sufficient hygroscopic fluidity, at least 0.1 wt% or more, usually 0.5 wt% The above is necessary and is disadvantageous in terms of cost and physical properties. Also, in terms of safety, the addition of such fine particles has poor workability and is not preferable as dust during mixing.

Further, the above-mentioned surface cross-linking is often carried out in order to improve the water absorption capacity under pressure, but strong crosslinking is usually required for sufficiently improving the water absorption capacity under pressure (US Pat. No. 5,164,164).
No. 459), no matter which surface cross-linking agent known so far was used, the water absorption capacity at atmospheric pressure was inevitably accompanied by a large decrease. Therefore, in such surface cross-linking,
It was difficult to exhibit a large effect of improving the water absorption capacity under pressure while keeping the water absorption capacity at normal pressure high.

[0017]

The present invention has been made in view of the above situation. Therefore, an object of the present invention is to provide (1) excellent safety in a method of coating the surface of a water-absorbent resin with an inert additive or a method of further surface-crosslinking with a crosslinking agent, and (2) to obtain a water absorption capacity at normal pressure. (3) A method for modifying a water-absorbent resin that does not cause agglomeration of powder even under high humidity, a water-absorbent agent, and a water-absorbent resin composition, while maintaining a high value and showing a large effect of improving the water absorption capacity under pressure. is there.

[0018]

Means and Actions for Solving the Problems The present inventors have
As a result of intensive studies to solve the above problems, the present inventor found that
All of the above problems are solved by adding at least one polyhydric alcohol derivative selected from a ketalized product, an acetalized product, and an inactive etherified product of a polyhydric alcohol to a specific water-absorbing resin, and performing heat treatment. They have found what they can do and have completed the present invention.

That is, the present invention provides "an acid group-containing unsaturated monomer having a neutralization ratio of 20 to 98 mol% and a polymerizable cross-linking agent of 0.03".
Particle size 1 obtained by polymerization of an aqueous monomer solution containing ˜1 mol% (relative to total monomers) at a monomer concentration of 30-45 wt%.
100 to 100 parts by weight of a water-absorbent resin in which particles of 50 to 1000 μm are 90% by weight or more, at least one selected from the group consisting of ketalized polyhydric alcohols, acetalized polyhydric alcohols and alkyl ethers of polyhydric alcohols A method for modifying a water absorbent resin, which comprises mixing 0.01 to 9 parts by weight of a polyhydric alcohol derivative and then heat-treating the mixture in a temperature range of 160 to 300 ° C. ",
"Acid group-containing unsaturated monomer having a neutralization rate of 20 to 98 mol% and a polymerizable cross-linking agent of 0.03 to 1 mol% (vs. all monomers), having a particle size of 150 to 1000 µm. A water-absorbing agent obtained by modifying a water-absorbent resin having particles of 90% by weight or more, having a particle size in the range of 10 to 1000 μm,
Water absorption capacity under pressure at 20 g / cm ² is 27 (ml / g)
Above, and the evaluation of the hygroscopic fluidity measured by the following method
A water absorbing agent characterized by being ○ . Moisture absorption and fluidity JIS-Z8801 standard sieve 1000 μm water absorbent
2.0g powder of powder on one side of aluminum cup of diameter 52mm
By applying evenly, 94 mg / cm ² was applied.
After that, in a thermo-hygrostat at a temperature of 25 ° C and a humidity of 50% for 30 minutes
Absorb moisture. Then, place the aluminum cup after absorbing moisture at an angle of 45.
Place it on a ° table to absorb the fluidity of the water absorbent on the aluminum cup.
Check in comparison with the previous powder. Moisture absorption, which is a comparison standard
The previous powder flowed in powder form on the aluminum cup surface at an angle of 45 °.
Fall down. The results are evaluated in the following three stages. ◯: The fluidity is as good as before moisture absorption, and the powder flows. Δ: Part of the powder is blocked or adheres to the aluminum cup. ×: The powder is blocked or formed into a film and is almost fluid.
None "and" a water-absorbent resin composition comprising a water-absorbent resin and at least one polyhydric alcohol derivative selected from ketalized and acetalized polyhydric alcohols. "

The present invention will be described in more detail below.

In the present invention, the water-absorbent resin to be surface-treated means a large amount of water in water, preferably 10 to 1000 times its own weight, more preferably 20 to 500 times as much water as it absorbs water and swells to form an insoluble hydrogel. Which is a water-absorbent resin, for example, polyacrylic acid salt cross-linked product, hydrolyzate of starch-acrylonitrile graft polymer, starch-acrylic acid (salt) graft polymer, vinyl acetate-acrylic acid ester copolymer Saponification product, 2-acrylamide-2
-Methylpropanesulfonic acid (salt) polymer, hydrolyzate of polyacrylamide cross-linked product, neutralized product of isobutylene maleic anhydride copolymer, and the like can be mentioned. Therefore, the highly crosslinked water-absorbent resin obtained by using the acid group-containing monomer and the polymerizable crosslinking agent is essential.

First, the water absorbent resin to be modified according to the present invention will be described.

That is, in order to achieve the object of the present invention, the water-absorbent resin of the present invention is essentially obtained by using an acid group-containing unsaturated monomer as a monomer. 50 in
To 100 mol%, preferably 70 to 100 mol%, more preferably 90 to 100 mol%.

[0024] As the acid group-containing unsaturated monomer used in essential in the present invention, if example embodiment, the acrylic acid (salt), methacrylic acid (salt), maleic acid (salt), maleic anhydride (salt), beta -Acryloyloxypropionic acid (salt),
Fumaric acid (salt), crotonic acid (salt), itaconic acid (salt), vinylsulfonic acid (salt), styrenesulfonic acid (salt), 2- (meth) acrylamido-2-methylpropanesulfonic acid (salt), 2 - (meth) acryloyl ethanesulfonic acid (salt), 2- (meth) acryloyl propane sulfonic acid (salt), sulfoethoxy polyethylene glycol mono (meth) are shown acrylate such Dogarei,
Among these as the main component, acrylic acid (salt), methacrylic acid (salt), β-acryloyloxypropionic acid (salt), 2- (meth) acryloylethanesulfonic acid (salt), 2- (meth) acrylamide- One or more selected from the group consisting of 2-methylpropanesulfonic acid (salt) is preferable, and acrylic acid (salt) is more preferable.

The above-mentioned acid group-containing unsaturated monomer of the present invention is usually and preferably partially neutralized from the viewpoint of modifying effect.
Preferably 20 to 98 mol% neutralization, more preferably 30
.About.95 mol% neutralization, more preferably 50 to 90 mol% neutralization. In the present invention, the water-absorbent resin having a neutralization ratio out of this range, even if surface-modified with the specific polyhydric alcohol derivative of the present invention, generally tends to have a low surface-modifying effect. Magnification and speed under pressure are low. This difference is particularly remarkable when an alkyl ether of a polyhydric alcohol is used, and thus, particularly when an alkyl ether of a polyhydric alcohol is used in the present invention, an acid group-containing monomer that is essentially partially neutralized, most preferably A water-absorbent resin obtained from a 50 to 90 mol% neutralized acid group-containing monomer is used. The basic substance used for neutralizing these acid group-containing monomers includes carbonic acid (hydrogen) salts, alkali metal hydroxides, ammonia, organic amines and the like.

In addition to the acid group-containing monomer, it may be used in combination with a nonionic unsaturated monomer, a cationic unsaturated monomer, or a hydrophobic unsaturated monomer. Is usually 0 to 50 mol%, preferably 0 based on all monomers.
-30 mol%, more preferably 0-10 mol%.

Examples of the nonionic unsaturated monomer used in the present invention include 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,
Examples thereof include polyethylene glycol mono (meth) acrylate, vinylpyridine, N-vinylpyrrolidone, N-acryloylpiperidine, N-acryloylpyrrolidine and the like. Examples of the cationic unsaturated monomer used in combination include N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth).
Examples thereof include acrylate, N, N-dimethylaminopropyl (meth) acrylamide and quaternary salts thereof. Further, as the hydrophobic unsaturated monomer that can be used in combination, for example, styrene, vinyl chloride, butadiene, isobutene,
Examples thereof include ethylene, propylene, stearyl (meth) acrylate, and lauryl (meth) acrylate.
In addition, you may use the monomer which forms a hydrophilic resin by hydrolysis of the functional group after a polymer like methyl (meth) acrylate, ethyl (meth) acrylate, vinyl acetate. And among these monomers that can be used in combination,
One or more hydrophilic monomers composed of methoxy polyethylene glycol (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate and a quaternary salt thereof, and acrylamide are preferable.

In order to obtain the water absorbent resin, the above unsaturated monomer is copolymerized with a polymerizable crosslinking agent to introduce a crosslinked structure into the polymer. The amount of the polymerizable cross-linking agent used is essentially in the range of 0.02 to 5 mol% based on all the monomers. Free-radical self-crosslinking, radiation cross-linking, cross-linking methods that do not copolymerize polymerizable cross-linking agents such as cross-linking agents with reactive cross-linking agents, and low cross-linking in which the amount of polymerizable cross-linking agents used is less than 0.02 mol% Although the water absorption capacity may be high, the effect of the surface modification of the present invention is generally low, and particularly in the case of a modification method using a polyhydric alcohol alkyl ether, the object of the present invention is to improve the water absorption capacity under pressure. Not achieved. When the amount of the polymerizable cross-linking agent used exceeds 5 mol%, the water absorption capacity at normal pressure is excessively reduced, which is not preferable. In order to achieve the object of the present invention, the more preferable amount of the polymerizable cross-linking agent used is in the range of 0.03 to 1 mol%, and further 0.04 to 0.5 mol%.

The polymerizable cross-linking agent used in the present invention is, for example, N, N'-methylenebisacrylamide,
(Poly) ethylene glycol di (meth) acrylate,
(Poly) propylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane di (meth) acrylate,
One or more of trimethylolpropane tri (β-acryloyloxypropionate), polyethylene glycol di (β-acryloyloxypropionate), (meth) allyloxyalkane, glycerin acrylate methacrylate, etc. are exemplified. , And more preferably a polyfunctional acrylate.

In addition to the above-mentioned polymerizable cross-linking agent, (poly) ethylene glycol diglycidyl ether, (poly) ethylene glycol, glycerin, pentaerythritol may be added to the monomer before or during the polymerization, if necessary. , Ethylenediamine, polyethyleneimine, alkylene carbonate (US Pat. No. 4,813,945), aluminum chloride and the like may be used in combination with about 0.001 to 5 mol% of a reactive crosslinking agent.

The polymerization of the above-mentioned monomer in the present invention can be carried out by bulk polymerization or precipitation polymerization, but it is usually preferable to use the solution of water or an aqueous liquid as the monomer. The concentration of the monomer is not particularly limited to exceed the saturation concentration, but it is usually 20
% -Saturated concentration range, preferably 30-45% by weight
Is the range.

During the polymerization, various hydrophilic polymers, surfactants, chain transfer agents, etc. may be added to the monomers before or during the polymerization. These additives are described in US Pat.
76663, 42882, 432040
No. 4833222, No. 5149750, No. 52
64495 and European Patents 03729831, 04.
No. 96594 and the like.

In the present invention, as a method for polymerizing the above-mentioned monomer, for example, polymerization by a radical polymerization initiator,
Known polymerization methods such as radiation polymerization, electron beam polymerization, and ultraviolet polymerization with a photosensitizer are used without particular limitation, but polymerization with a radical polymerization initiator is preferable in order to obtain a water-absorbent resin having excellent performance. As such a radical polymerization method,
Well-known polymerization methods such as various aqueous solution polymerization, reverse phase suspension polymerization and reverse phase emulsion polymerization are widely used, but reverse phase suspension polymerization or aqueous solution polymerization is particularly preferable. During the polymerization, continuous polymerization,
The distinction between the semi-batch polymerization and the batch polymerization and the distinction between depressurization, pressurization and normal pressure are not particularly limited, and a fiber, a fibrous base material and the like may coexist during the polymerization.

The method of polymerizing the water-absorbent resin is described in US Pat. Nos. 4,625,001, 4,769,427 and 48.
73299, 4093776, and 4376323.
Nos. 4,446,261, 4,552,938, 46
83274, 4690996, and 4721647.
Nos. 4,387,867, 4748076, 48
80886, 4957984, 4985514
No. 4,985,518, 5026800, 50
98775, 5124416, 5247225.
No., etc.

As the radical polymerization initiator used in the polymerization in the present invention, sodium persulfate, t-butyl hydroperoxide, hydrogen peroxide, 2,2'-azobis (2
-Amidino propane) dihydrochloride and the like known polymerization initiators are widely used. Further, these polymerization initiators are used in combination with a reducing agent such as a sulfite (hydrogen) salt or L-ascorbic acid, ultraviolet rays or radiation during polymerization. There is no limit to the combined use such as. These radical polymerization initiators may be added to the polymerization system all at once or may be added one after another, but the amount thereof is usually 0.001 to 2 mol% with respect to all the monomers, preferably 0.01
Is in the range of to 1 mol%.

In the method for producing a water absorbent resin of the present invention, the gel polymer obtained by polymerization is preferably dried by heating in order to further enhance the surface modification effect. The heating and drying method used in the present invention includes hot air drying, drying with specific steam (US Pat. No. 4,920,202), infrared drying,
Known drying methods used for producing a water-absorbent resin such as microwave drying (US Pat. No. 5,075,344), reduced pressure drying, drum dryer drying, azeotropic dehydration in a hydrophobic organic solvent and the like can be applied without limitation. In addition, prior to drying,
The polymer gel may be pre-milled by a method such as European Patent 497623, or the supply to the dryer may be controlled by a method such as US Pat. No. 5,229,487.

In the present invention, the gel-like polymer after the polymerization is solidified by 80% or more, further 90% by the drying method.
It is preferable to heat and dry up to the above. The drying temperature in the present invention is preferably 130 to 250 ° C, more preferably 150 to 220 ° C. If the drying temperature or the solid content is removed, the surface modification of the present invention is performed,
In some cases, a sufficient effect cannot be obtained, and in some cases, the amount of residual monomer increases.

The water-absorbent resin obtained as described above is preferably in the form of powder, and its shape is not particularly limited, such as amorphous, spherical, rod-like, but preferably spherical or amorphous, more preferably other base materials. It is an amorphous type that can be easily compounded and molded with. Further, the particle size of the water absorbent resin may be adjusted by further pulverizing, granulating, classifying or the like. In order to further achieve the object of the present invention, the particle size of the water absorbent resin before surface modification is such that 90% by weight or more of the particles have a particle size of 100 to 2000 μm, more preferably 125 to 140.
The thickness is adjusted to 0 μm, most preferably 150 to 1000 μm.

[0039] for a particular water-absorbing resin obtained in the above manner, in the present invention, ketals products of polyhydric alcohols, polyhydric alcohols A acetal compound, a polyhydric alcohol
At least one polyhydric alcohol derivative is heated with the addition of surface modification selected from A Ruki ethers of is made.

A ketalized product of a polyhydric alcohol (hereinafter simply referred to as a polyhydric alcohol ketal) and an acetalized product of a polyhydric alcohol (hereinafter simply referred to as a polyhydric alcohol acetal), which are indispensable for the surface modification of the present invention. ), And polyhydric alcohol derivatives selected from alkyl ethers of polyhydric alcohols are exemplified below.

The structure of the polyhydric alcohol derivative used in the surface treatment of the present invention is not particularly limited, but it is preferable that the polyhydric alcohol derivative does not have a plurality of hydroxyl groups, especially in the case of a polyhydric alcohol alkyl ether. And the number of hydroxyl groups in one molecule is zero or one. Further, this polyhydric alcohol derivative can have a free carboxyl group, phosphoric acid group, sulfonic acid group, or a functional group in the form of an inorganic salt thereof.

These polyhydric alcohol derivatives are usually obtained by reacting polyhydric alcohols and their precursors such as cyclic ethers such as ethylene oxide and unsaturated alcohols such as methallyl alcohol with alcohols, ketones, aldehydes and the like. To be

Specific examples of the polyhydric alcohol derivative of the present invention include diol derivatives (eg, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,2-propylene glycol, 1,3-). Propylene glycol, 2,2-dimethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,3-butanediol, 1,4-butanediol, 2-butene-1 , 4-diol, 2-butyne-
1,4-diol, 1,5-pentanediol, 1,6
-Hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2-
Cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,7-heptanediol, 1,8-octanediol, 2-ethyl-1,3-hexanediol, 1,9-nonanediol, 1 , 10-decanediol, 1,12-dodecanediol, N-methyldiethanolamine, N-ethyldiethanolamine, N-butyldiethanolamine, derivatives of glycerophosphoric acid, etc., derivatives of triol (eg, glycerol, 2-ethyl-2-hydroxy) Methyl-1,3-propanediol, derivatives such as trimethylolpropane), tetrol derivatives (eg, pentaerythritol, etc.), hexanol derivatives (eg, dipentaerythritol, sorbitol, etc.), octa Lumpur derivatives (e.g., derivatives such as tripentaerythritol), other, etc. derivatives of polyglycerol are exemplified.

Among these polyhydric alcohol derivatives, ethylene glycol, diethylene glycol,
Polyethylene glycol, polyethylene glycol, diethanolamine, triethanolamine, glycerin, trimethylolpropane, 1,3-propanediol, 2,3-propanediol, pentaerythritol, sorbitol, polyglycerin, glycerophosphoric acid derivatives A polyhydric alcohol derivative is more preferable.

Among the polyhydric alcohol derivatives used in the present invention, polyhydric alcohol ketals and polyhydric alcohol acetals include polyhydric alcohols described above and aliphatic or aromatic ketones or aldehydes and polyhydric alcohols. Usually obtained by etherification, the structure is not particularly limited,
A polyhydric alcohol ketal or a polyhydric alcohol acetal obtained from a compound selected from (para) formaldehyde, acetaldehyde and benzaldehyde is preferable, and a ketal having an isopropylidene structure obtained from acetone is more preferable. From the viewpoint of the effect, the boiling point of the ketal or acetal used in the present invention is preferably 70 ° C. or higher, and more preferably 1 at normal pressure.
One having a temperature of 00 ° C. or higher, more preferably 120 ° C. or higher is used.

Therefore, more specific examples of the polyhydric alcohol ketal or polyhydric alcohol acetal used in the present invention include acetone ethylene ketal, cyclohexanone ethylene ketal, benzophenone ethylene ketal, 2-benzyl-1,3-dioxolane and the like. A glycol derivative of 1,2-methyleneglycerin,
Trihydric alcohols such as 1,3-methyleneglycerin, 1,2-ethylideneglycerin, 1,3-ethylideneglycerin, 1,2-isopropylideneglycerin, 1,3-isopropylideneglycerin, benzylideneglycerin and other glycerine ketals and acetals. Ketal, acetal, diisopropylidene pentaerythritol,
Ketals and acetals of tetrahydric alcohols such as dibenzylidene pentaerythritol, ketals and acetals of pentahydric alcohols such as 1,4-3,5-dibenzylidene xylit and 2,4-3,5-isopropylidene xylit Is exemplified. Among these various polyhydric alcohol ketals and acetals, in the surface modification method of the present invention, preferably ketals and acetals of glycerin or ethylene glycol, more preferably ketals or acetals of glycerin, and even more preferably 2,2-dimethyl-
1,3-dioxolane-4-methanol is used.

Of the polyhydric alcohol derivatives used in the present invention, the polyhydric alcohol alkyl ether is usually
Obtained by etherification of the above-mentioned polyhydric alcohol and aliphatic alcohol, and specifically, methanol, ethanol, n-propanol, iso-propanol, n-
Butanol, iso-butanol, t-butanol, n
Examples of the polyhydric alcohol ether include various aliphatic alcohols such as -pentanol, iso-pentanol, neo-pentanol, n-hexanol, and cyclohexanol and various aromatic alcohols such as phenol, but more preferably carbon. It is a polyhydric alcohol alkyl ether obtained from an aliphatic monoalcohol having a number of 4 or less, and its boiling point is 100 ° C. or higher at atmospheric pressure, preferably 1
It is a polyhydric alcohol alkyl ether having a temperature of 20 ° C. or higher.

Therefore, when the polyhydric alcohol alkyl ether used in the present invention is specifically exemplified,
Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monon
-Propyl ether, ethylene glycol monoiso-
Various ethylene glycol monoalkyl ethers such as propyl ether, ethylene glycol mono n-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono n-propyl ether, diethylene glycol mono iso-propyl ether, diethylene glycol mono n-butyl ether, etc. Various triethylene glycol monoalkyl such as monoalkyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol mono n-propyl ether, triethylene glycol mono iso-propyl ether, triethylene glycol mono n-butyl ether Ether, propi Glycol monomethyl ether,
Various propylene glycol monoalkyl ethers such as propylene glycol monoethyl ether, propylene glycol mono n-propyl ether, propylene glycol mono iso-propyl ether, propylene glycol mono n-butyl ether, dipropylene glycol mono n-propyl ether, dipropylene glycol In addition to polyhydric alcohol ethers having one hydroxyl group in the molecule, such as various isopropyglycol monoalkyl ethers such as mono-iso-propyl ether and dipropylene glycol mono-n-butyl ether, ethylene glycol di-n-butyl ether and diethylene glycol are further added. Diethyl ether, triethylene glycol dimethyl ether, tetraethylene dimethyl ether, tetraethylene glycol Such as methyl ethyl ether, polyhydric alcohol ethers having no hydroxyl group in the molecule are exemplified. In the present invention, among these polyhydric alcohol ethers,
Preferably, (poly) ethylene glycol monoalkyl ether is used, and the n number thereof is 1 to 10, more preferably 1 to 4, and further preferably 1.

A ketalized product of the above polyhydric alcohol ,
Polyhydric alcohols A acetal compound, the amount used in the present invention of at least one polyhydric alcohol derivative selected from A <br/> Ruki ethers of polyhydric alcohols are widely used, but more achieve the object of the present invention In order to do so, preferably 0.001 to 100 parts by weight of the solid content of the water absorbent resin.
30 parts by weight, more preferably 0.005 to 10 parts by weight,
The proportion is more preferably 0.01 to 9 parts by weight, and most preferably 0.5 to 8 parts by weight. Particularly, in the case of alkyl ether, if it is 10 parts by weight or more, it tends to be excessive, and therefore 9 parts by weight or less Is.

A method for adding at least one polyhydric alcohol derivative selected from the ketalized product of the polyhydric alcohol, the acetalized product of the polyhydric alcohol, and the alkyl ether of the polyhydric alcohol to the water-absorbent resin is known. The method described above is used, and examples thereof include a method of directly adding a polyhydric alcohol derivative or a solution / dispersion thereof to a water absorbent resin, and a method of adding a polyhydric alcohol derivative to a water absorbent resin dispersed in a solvent. In the case of using the former method, a very small amount of an inorganic compound such as silicon oxide fine powder or a surfactant may be used in order to more uniformly add the polyhydric alcohol derivative.

When the polyhydric alcohol derivative is added to the water absorbent resin, it may be added as a solution or an emulsion dispersion. As the solvent used, hydrophilic organic solvents having a boiling point of less than 100 ° C. such as methyl alcohol, ethyl alcohol, n-propyl alcohol, iso-propyl alcohol, acetone and tetrahydrofuran, and water are preferable.
The amount used is usually 20 parts by weight or less, and more preferably 8 parts by weight or less, based on 100 parts by weight of the solid content of the water absorbent resin.

In the present invention, when heat treatment is performed after mixing the water-absorbent resin and the polyhydric alcohol derivative, it is preferable that water be present in view of the effect of surface treatment. Therefore, when using the dried water-absorbent resin, it is preferable to add water at the same time as or separately from the polyhydric alcohol derivative, and the amount thereof is 2 per 100 parts by weight of the solid content of the water-absorbent resin.
The amount is 0 parts by weight or less, preferably 0.5 to 10 parts by weight.

After the water-absorbent resin and the polyhydric alcohol derivative are mixed according to the above-mentioned method, the heat treatment is essential in the present invention. If heat treatment is not performed after mixing, no improvement in water absorption capacity under pressure is observed.

The heat treatment temperature is essentially 160 to 300 ° C.,
Preferably 170 to 250 ° C, more preferably 190 to 250 ° C.
It is in the range of 240 ° C. If the temperature is lower than 160 ° C, not only the heat treatment will take a long time to cause a decrease in productivity, but also a uniform and strong surface treatment is difficult to be achieved, and if the temperature exceeds 300 ° C, the water absorbent resin may be thermally deteriorated. Caution must be taken. Further, in order to accelerate the heat treatment, various organic acids such as lactic acid, citric acid, tartaric acid, succinic acid, phosphoric acid and inorganic acids may be coexistent in an amount of 0 to 10 parts by weight.

The heating time is appropriately determined depending on the desired surface treatment effect, heating temperature, etc., but is usually in the range of 1 minute to 10 hours, preferably 5 minutes to 3 hours. In the above temperature range, suitable physical properties can be obtained, but the water absorption capacity of the water absorbent resin described below is 25 (ml / g).
It is more preferable to perform heat treatment within the above temperature range, preferably up to 27 (ml / g) or more.

As a method for carrying out the heat treatment, known means are used. (1) a method of directly adding a polyhydric alcohol derivative to a water-absorbent resin and then heat-treating as it is, or (2) a water-absorbing agent dispersed in a solvent. Examples thereof include a method in which a polyhydric alcohol derivative is added to a resin and then heat-treated while being dispersed, and (3) a method in which heat treatment is performed by filtering from a dispersion medium.
Among these methods, the method (1) or (3) which does not use a large amount of solvent, and the method (1) is particularly preferable. In addition,
There is no particular limitation on the heat treatment device, a hot air dryer,
Known devices such as a fluidized bed dryer and a Nauta type dryer are used.

Conventionally, improvement of the water absorption capacity under pressure by surface cross-linking using a crosslinking agent has been accompanied by a large decrease in the water absorption capacity under normal pressure. However, in place of the conventional cross-linking agent, a ketalized product of a polyhydric alcohol, an acetalized product of a polyhydric alcohol, a polyhydric alcohol alkyl ether, at least one selected from compounds is used in the surface modification method of the present invention. It exhibits an excellent effect of improving the water absorption capacity under pressure while maintaining a high water absorption capacity under pressure. The polyhydric alcohol derivative used in the invention is usually an inactive compound,
Since there is no inconvenience that the physical properties of the polyhydric glycidyl compound, which have been frequently used, are changed at the same time as mixing, it is easy to uniformly mix it with the water-absorbent resin. It is presumed that it is more hydrophobic and does not easily penetrate into the water-absorbent resin, but it is easy to mix and the treatment agent easily penetrates. Can be easily performed and is preferable. Further, the polyhydric alcohol derivative of the present invention has no problem of hygroscopic fluidity and safety even if it remains.

The water-absorbent resin of the present invention obtained as described above is preferably used in the form of powder, but it may be further granulated, and if necessary, it may be used in combination with another substrate to form a sheet. ，
It may be formed into a fiber, gel, film, block, or pellet. The method for granulating the water absorbent resin is described in US Pat. Nos. 4,732,968 and 4,734,478.
Issue No. 5002986, No. 5112902, No. 52
48709 and European Patents 450922 and 4800.
No. 31, etc. are illustrated.

Further, for the water absorbent resin before surface modification and the water absorbent resin after modification, a reducing agent, an inert inorganic substance, an oxidizing agent,
Various physical properties may be improved by adding various additives such as an antioxidant, a surfactant and a deodorant. Additives to the water-absorbent resin are disclosed in U.S. Pat. Nos. 4,179,367, 4,190,563, 4,500,670, and 4,6937.
No. 13, No. 4812486, No. 4929717, No. 49959060, No. 4972019, No. 50789.
No. 92, No. 5087656, No. 5229488,
It is exemplified in European Patent No. 0009977.

Further, the surface modification method of the present invention is a novel water absorbing agent, that is , an acid group-containing unsaturated monovalent compound having a neutralization ratio of 20 to 98 mol%.
Polymer and polymerizable cross-linking agent 0.03 to 1 mol% (vs. total unit weight)
Particle size 150-1000μ obtained by the polymerization of
by modifying the water absorbent resin in which the particles of m are 90% by weight or more
A resultant water-absorbing agent, the particle size is 10 to 1000 [mu] m,
Preferably in the range of 45 to 1000 μm, 20 g / cm ²
Pressure under absorption water ratio in the 27 (ml / g) or more and 9
There is also provided a surface-modified water-absorbing agent characterized in that it retains fluidity at a tilt angle of 45 ° for at least 30 minutes at a temperature of 25 ° C and a humidity of 50% in a sprayed state of 4 mg / cm ² .

Heretofore, a water-absorbent resin whose water absorption capacity under pressure has been improved by surface cross-linking with a polyhydric alcohol or a polyhydric glycidyl has been known, but by the present inventor,
It has been found that such surface cross-linking causes a decrease in hygroscopic fluidity. Further, conventionally, in order to improve the hygroscopic fluidity, a method of adding an inorganic fine powder of about several μm to several nm to a water-absorbent resin has been proposed, but in this case, not only the water absorption capacity under pressure does not improve, On the contrary, it also had a problem of decreasing. Furthermore, in the water absorbing agent of the present invention,
It was also found that the irregular shape of the particles facilitates the compounding with other materials such as pulp while maintaining the above effect.

Therefore, the water-absorbing agent of the present invention not only has a high water-absorption capacity under pressure, but also has a novel characteristic that it maintains fluidity at an inclination angle of 45 ° at a temperature of 25 ° C. and a humidity of 50% for at least 30 minutes. Since it has enough resistance to use in normal diaper factories even during the rainy season, and virtually no particles smaller than 10 μm are included, dust is virtually observed even in actual use in factories. It is a new water-absorbing agent that is not used.

The present invention also provides at least one ketalized or acetalized polyhydric alcohol.
There is also provided a novel water-absorbent resin composition comprising a polyhydric alcohol derivative and a water-absorbent resin. The novel water-absorbent resin composition of the present invention is heated to significantly improve the water absorption capacity under pressure, and at a temperature of 25 ° C. and a humidity of 50%, at least 30%.
The component is a novel water-absorbent resin composition that not only maintains fluidity at an inclination angle of 45 °, but that the composition itself has unexpectedly excellent urine resistance in addition to plasticity and moldability.

The urine resistance of the water-absorbent resin means to prevent the phenomenon that the water-absorbent resin swollen with urine deteriorates and collapses with time, and a specific additive is added to the water-absorbent resin. Method for imparting urinary resistance by the method (US Pat. No. 4,971,201)
9, US Pat. No. 4,863,989, European Patent 03729
81, JP-A-63-127754, JP-A-63-1.
18375, JP 63-153060, JP 6
No. 3-272349, JP-A-64-33158) and the like have been proposed, but, by chance, at least one polyhydric alcohol derivative selected from ketalized and acetalized polyhydric alcohols and water absorption. It was found that the water absorbent resin composition made of a water-soluble resin has high urine resistance.

[0065] Thus, water absorbent and water-absorbent resin sets composition as the present invention is not only highly safe and absorbency against pressure, moreover, is excellent in moisture absorption fluidity and urine resistance, disposable diapers, sanitary napkins, Various sanitary materials such as tampons, medical fields such as bandages, poultices, and medical waste liquid treatment agents, food fields such as freshness retention sheets, dew condensation prevention sheets, industrial fields such as water-in-oil removers, and other water retention for agriculture and horticulture. Can be widely used as an agent.

[0066]

As described above, in comparison with the conventional method of coating the surface of the water absorbent resin with an inert additive and the conventional method of further surface crosslinking with a crosslinking agent, the surface modification method of the present invention has the following (1)
It has excellent characteristics such as (3).

(1) Compared with the conventional method of using a crosslinking agent such as polyvalent glycidyl and the conventional method of adding an inorganic fine powder, there is no problem of residual crosslinking agent or fine dust powder, and safety is excellent. .

(2) Compared with the case of using a conventional crosslinking agent,
It shows a great effect of improving the water absorption capacity under pressure while keeping the water absorption capacity at normal pressure high.

[0069] (3) It does not cause agglomeration of the powder even under high humidity, is also shown improvement in urine resistance in composition and be Rukoto of polyhydric alcohols ketal compound or an acetal compound.

[0070]

EXAMPLES The present invention will be described below with reference to examples.
The scope of the invention is not limited to only these examples. The physical properties described in the examples are values measured by the following test methods.

(1) Water absorption ratio The water absorption ratio at constant pressure was determined by the tea bag test method.
That is, 0.2 g of the water absorbing agent was uniformly put in a non-woven tea bag type bag (40 * 150 mm) and immersed in a 0.9 wt% sodium chloride aqueous solution. After one hour, the tea bag-type bag was pulled up and drained for a certain period of time, then the weight of the tea-bag-type bag was measured, and the water absorption capacity was calculated by the following formula.

[0072]

[Equation 1]

(2) Absorption capacity under load The water absorption capacity under load was determined by the apparatus for measuring the absorption capacity under load of the water-absorbing agent shown in the explanatory sectional view (FIG. 1).

That is, artificial urine (1.9 wt% urea in the solution, 0.8 wt% NaCl, 0.1 wt% CaCl ₂ ,
The top 2 of the burette 1 filled with 0.1% by weight of MgSO _{4 (} deionized water) was capped with the stopper 3, and the measuring table 4 and the air port 5 were set at the same height, and then the diameter in the measuring table 4 was set. 70
The filter paper 7 is placed on the glass filter (NO. 1) 6 mm. Separately, the non-woven fabric 8 is fixed to the lower end of the support cylinder 10 having a diameter of 55 mm, and 0.2 g of the water absorbing agent is placed on the non-woven fabric 8.
Is evenly distributed, and a load of 20 g / cm ² is further applied.
Then, this non-woven fabric-water absorbing agent-supporting cylinder provided with a load was placed on the filter paper 7 on the glass filter 6 and left for 30 minutes, and then the amount (Aml) of artificial urine absorbed by the water absorbing agent through the filter paper 7 was buretted. Then, the absorption capacity under pressure (ml / g) was determined by the following formula.

[0075]

[Equation 2]

(3) Moisture absorption and flowability JIS-Z8801 standard sieve 1000 μm After passing 2.0 g of a powder of a water absorbent as a permeation product on one surface of an aluminum cup having a diameter of 52 mm, a dispersion state of 94 mg / cm ² was obtained. was moisture 30 minutes at humidity of 50% constant temperature constant humidity vessel at a temperature 25 ° C.. Then, place the aluminum cup after absorbing moisture at an angle of 45.
The fluidity of the water absorbing agent on the aluminum cup was examined by placing it on a table at a temperature of 50 ° C and comparing it with the powder before moisture absorption. It should be noted that the powder before moisture absorption, which is a comparison reference, flows down in powder form on the aluminum cup surface at an angle of 45 °.

The results are as follows: ○ (flowability is good as before moisture absorption, powder flows), △ (part of powder is blocked or adheres to aluminum cup), × (powder is blocked or filmed) No liquidity) evaluated in 3 stages, ○
In the present invention, the state of is defined as maintaining fluidity.

(4) Urine resistance Using human urine evenly sampled from 10 healthy adult males, 2 g of water-absorbent resin in a 100 ml glass bottle with a lid.
Was swelled 25 times and left in an atmosphere of a temperature of 37 ° C. and a relative humidity of 90% for a predetermined time. The appearance of the swollen gel after 16 hours was visually observed, and at the same time, the water-soluble content of the swollen gel was measured for 1 hour. Turned into

The water-soluble component was measured by swelling and dispersing 0.5 g of the water-absorbent resin in 1 L of ion-exchanged water as a solid component, stirring the swelled gel for 1 hour, and then filtering the swollen gel with a filter paper. It was determined by measuring the solid content.

(Production Example 1) Neutralization rate of 75 mol% and concentration of 37
% Partially Neutralized Acrylic Acid Alkali Metal Salt Aqueous Solution 550
Trimethylolpropane triacrylate (0.05 mol% of all monomers) as a polymerizable internal cross-linking agent was dissolved in 0 g, and the inner volume was 10 L and the jacketed stainless steel double-armed type having two sigma type blades Nitrogen was purged in a reactor equipped with a lid on a kneader. Next, while the blade of the kneader was being stirred, 0.2 mol% of sodium persulfate and 0.01 mol% of L-ascorbic acid were added as polymerization initiators to the monomer. Polymerization started after 1 minute, and after 16 minutes, the hydrogel polymer was subdivided into particles having a diameter of about 5 mm. 60 minutes after initiation of the polymerization, the hydrogel polymer was taken out and dried with hot air at 150 ° C. for 60 minutes. . The dried product is crushed using a vibration mill, and JIS-Z8801 standard sieve 8
By classifying 50 to 45 μm, a water-absorbent resin (1) having a solid content of 96% in an amorphous form containing 4% by weight of particles less than 150 μm was obtained.

(Production Example 2) Polymerization and drying were conducted in the same manner as in Production Example 1 except that the amount of the polymerizable cross-linking agent used was 0.1 mol% (relative to all monomers). Done, 15
96% solid content in an amorphous form containing 4% by weight of particles less than 0 μm
Water absorbent resin (2) was obtained.

(Production Example 3) Polymerization and drying were conducted in the same manner as in Production Example 1 except that the amount of the polymerizable cross-linking agent used was 0.01 mol% (relative to all monomers). Done 1
96% by weight of amorphous particles containing 4% by weight of particles less than 50 μm
% Water absorbent resin (3) was obtained.

(Production Example 4) In Production Example 1, as the monomer, an unneutralized 37% aqueous solution of acrylic acid 5500 was used.
Polymerization was carried out in the same manner as in Example 1 except that trimethylolpropane triacrylate (0.05 mol% of all monomers) as a polymerizable internal crosslinking agent was dissolved in g. Polymerization started 1 minute after the addition of the polymerization initiator, and 16 minutes later, the hydrogel polymer was finely divided into particles having a diameter of about 5 mm. 60 minutes after the initiation of polymerization, the hydrogel polymer was taken out, and 48% by weight
With 1765 g of a caustic soda aqueous solution, using phenolphthalein as an indicator, 75 mol% of acid groups in the hydrogel polymer
Neutralized. Thereafter, after being dried in the same manner as in Example 1, the same pulverization and classification are carried out to obtain 4% by weight of particles of less than 150 μm.
A water-absorbent resin (3) having an amorphous shape and a solid content of 96% was obtained.

Example 1 100 parts of the water-absorbent resin (1) obtained in Production Example 1 was mixed with 6 parts of ethylene glycol monoethyl ether (boiling point 135 ° C.) and 6 parts of water, and then the resulting mixture was obtained. Was heated at 195 ° C. for 2 hours to obtain a water absorbing agent (a).

The analysis results of Examples and Comparative Examples are all shown in Table 1 below, but the particle sizes of all the water absorbing agents obtained were substantially in the range of 850 to 45 μm.

Example 2 A water absorbing agent (b) was obtained in the same manner as in Example 1 except that the heat treatment of the mixture was changed to 210 ° C. for 30 minutes. (Example 3) A water absorbing agent (c) was obtained in the same manner as in Example 1 except that the heat treatment of the mixture was changed to 180 ° C for 2 hours.

Example 4 100 parts of the water absorbent resin (1) was mixed with ethylene glycol monomethyl ether (boiling point 12
(5 ° C) 2 parts and 6 parts of water were mixed, and the resulting mixture was mixed with 1 part.
A water absorbing agent (d) was obtained by heat treatment at 95 ° C for 90 minutes.

Example 5 100 parts of the water absorbent resin (1) was mixed with ethylene glycol monobutyl ether (boiling point: 17).
After mixing 3 parts of water (1 ° C.), 3 parts of water, and 6 parts of isopropanol, the resulting mixture was heated at 195 ° C. for 90 minutes to obtain a water absorbing agent (e).

Example 6 To 100 parts of the water absorbent resin (1) was added diethylene glycol monoethyl ether (boiling point 2
(18 ° C.) and 3 parts of water were mixed, and the resulting mixture was heat-treated at 195 ° C. for 2 hours to obtain a water absorbing agent (f).

Example 7 100 parts of the water absorbent resin (1) was mixed with diethylene glycol diethyl ether (boiling point 18).
(8 ° C.) 3 parts of water and 3 parts of water were mixed, and the resulting mixture was mixed with 1 part.
A water absorbing agent (g) was obtained by heat treatment at 95 ° C. for 2.5 hours.

Example 8 100 parts of the water absorbent resin (1) was mixed with 3 parts of ethylene glycol dibutyl ether, and the resulting mixture was heated at 195 ° C. for 1 hour to give the water absorbing agent (h). Obtained.

Example 9 0.7 part of 2,2-dimethyl-1,3-dioxolane-2-methanol (also known as 1,2-diisopropylideneglycerin) was added to 100 parts of the water absorbent resin (1). After mixing 3 parts of water and 8 parts of isopropanol, the resulting mixture was heat-treated at 195 ° C. for 75 minutes to obtain a water absorbent resin composition (i).

Example 10 To 100 parts of the water absorbent resin (2) obtained in Production Example 2 were mixed 2 parts of 2-benzyl-1,3-dioxolane, 3 parts of water and 8 parts of ethanol.
The water-absorbent resin composition (j) was obtained by heat-treating the obtained mixture at 195 ° C. for 75 minutes.

(Examples 11 and 12) 100 parts by weight of the water absorbent resin (1) obtained in Example 1 was mixed with 10 parts and 5 parts of 1,2-diisopropylideneglycerin to prepare polyhydric alcohols. Water absorbent resin compositions (k) and (l) containing 10 parts and 5 parts of the ketal compound were obtained. When the urine resistance of the water-absorbent resin compositions (k) and (j) and the water-absorbent resin (1) was measured, the water-absorbent resin (1) was visually deteriorated in gel and its soluble content was 25 Although it was a large amount of weight%,
The gels of the water-absorbent resin compositions (k) and (j) were firm, and the soluble contents thereof were significantly reduced to 17% and 19% by weight, showing urine resistance.

Comparative Example 1 A comparative water absorbing agent (a) was obtained in the same manner as in Example 1 except that the heating temperature of the mixture was changed to 150 ° C. (Comparative Example 2) Example 2 is repeated except that in place of the water absorbent resin (1) in Example 1, the water absorbent resin bulk powder (3) obtained from 0.01 mol% of the polymerizable crosslinking agent in Production Example 3 is used. Similar to Example 1, a comparative water absorbing agent (b) was obtained by mixing ethylene glycol monoethyl ether and the like and heating.

(Comparative Example 3) Example 1 except that the water absorbent resin (1) in Example 1 was replaced with the water absorbent resin (4) obtained from unneutralized acrylic acid in Production Example 4. Similarly to the above, a comparative water absorbing agent (c) was obtained by mixing ethylene glycol monoethyl ether and the like and performing heat treatment.

(Comparative Example 4) Comparative Example 4 was carried out in the same manner as in Example 6 except that 3 parts of ethylene glycol was used instead of diethylene glycol monoethyl ether in the same manner as in Example 6. The agent (d) was obtained.

(Comparative Example 5) The procedure of Example 6 was repeated, except that 3 parts of ethylene glycol diglycidyl ether was used instead of diethylene glycol monoethyl ether, and the same mixing and heat treatments were performed. A comparative water absorbing agent (d) was obtained.

(Comparative Examples 6 to 9) The water absorbent resins (1) to (4) obtained in Production Examples 1 to 4 were used as they are as comparative water absorbing agents (f) to (i).

Comparative Example 10 100 parts of the comparative water-absorbing agent (a) obtained in Comparative Example 1 was mixed with 0.02 of Aerosil 200 (trademark, manufactured by Nippon Aerosil Co., Ltd., silica fine particles having an average particle diameter of 0.012 μm). Comparative water-absorbent resin (j) was obtained by adding a part. The hygroscopic fluidity of this comparative water absorbent resin (j) was evaluated, but it was insufficient (Δ), and a slight amount of dust was observed during mixing.

As is apparent from Table 1, the present invention (1) has excellent safety, and (2) shows a great effect of improving the water absorption capacity under pressure while keeping the water absorption capacity at normal pressure high.
(3) A method for modifying a water-absorbent resin, a water-absorbing agent and a water-absorbent resin composition which do not cause aggregation of powder even under high humidity are provided. Unexpectedly, the water-absorbent resin composition of the present invention containing a ketalized product or acetalized product of a polyhydric alcohol also exhibited urine resistance as in Examples 11 and 12, and exhibited more suitable properties.

[0102]

[Table 1]

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a water absorption magnification measuring device under pressure used in the present invention.

[Explanation of symbols]

1 ... Burette 2 ... Top of burette 3 ... stopper 4 ... Measuring stand 5: Air intake 6 ... Glass filter 7: Filter paper 8: Non-woven fabric 9 ... load 10 ... Supporting cylinder 11 ... Water absorbing agent

Continuation of front page (56) Reference JP-A-2-153903 (JP, A) JP-A-4-214735 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08J 3 / 00-3/28 C08L 33/00

Claims (6)

(57) [Claims] 1. An acid group-containing unsaturated monomer having a neutralization ratio of 20 to 98 mol% and a polymerizable cross-linking agent of 0.03 to 1 mol% (relative to all monomers) in a monomer concentration of 30 to 45% by weight. %, Obtained by polymerizing an aqueous monomer solution containing 100% by weight of 150 to 1000 μm
100 parts by weight of a water-absorbent resin having 90% by weight or more of particles, at least one polyhydric alcohol selected from the group consisting of polyhydric alcohol ketals, polyhydric alcohol acetals, and polyhydric alcohol alkyl ethers. After mixing 0.01 to 9 parts by weight of the derivative, 1 part of the mixture is added.
A method for modifying a water-absorbent resin, which comprises performing heat treatment in a temperature range of 60 to 300 ° C. 2. A particle size of 150 obtained by polymerization of an acid group-containing unsaturated monomer having a neutralization rate of 20 to 98 mol% and a polymerizable cross-linking agent of 0.03 to 1 mol% (relative to all monomers). ~ 1000
A water absorbing agent obtained by modifying a water-absorbent resin having 90% by weight or more of particles having a particle size of 10 to 1000 μm.
Range, the water absorption capacity under pressure at 20 g / cm ² is 27 (m
l / g) and above, and hygroscopic fluidity measured by the following method
The water-absorbing agent is characterized by a rating of . Moisture absorption and fluidity JIS-Z8801 standard sieve 1000 μm water absorbent
2.0g powder of powder on one side of aluminum cup of diameter 52mm
By applying evenly, 94 mg / cm ² was applied.
After that, in a thermo-hygrostat at a temperature of 25 ° C and a humidity of 50% for 30 minutes
Absorb moisture. Then, place the aluminum cup after absorbing moisture at an angle of 45.
Place it on a ° table to absorb the fluidity of the water absorbent on the aluminum cup.
Check in comparison with the previous powder. Moisture absorption, which is a comparison standard
The previous powder flowed in powder form on the aluminum cup surface at an angle of 45 °.
Fall down. The results are evaluated in the following three stages. ◯: The fluidity is as good as before moisture absorption, and the powder flows. Δ: Part of the powder is blocked or adheres to the aluminum cup .
None Wherein the water absorbent resin, grinding after the polymerization
The water-absorbing agent according to claim 2, which has an irregular shape . 4. A water absorbent resin composition comprising a water absorbent resin and at least one polyhydric alcohol derivative selected from a ketalized product and an acetalized product of a polyhydric alcohol. 5. A sanitary material using the water absorbing agent according to claim 2 or 3. 6. A sanitary material using the water absorbent resin composition according to claim 4.