JP2003313446A - Water absorbent having main component of highly water absorptive resin with crosslinking structure, method for manufacturing it, and medical supply using this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing at a low temperature and for a short time a water absorbent which is excellent in absorptive characteristics such as the balance of a water absorption under no pressure and a water absorption under pressure and which is excellent in safety. <P>SOLUTION: The water absorbents are each such one that a highly water absorptive resin (a) is blended with an oxetane compound (b) and a water-soluble additive (c) indicating acidity in water; such another one that a highly water absorptive resin (a) is blended with an oxetane compound (b) and the second crosslinker (d) having a structure different from that of the above oxetane compound; and such still another one that a highly water absorptive resin (a) is blended with an oxetane compound (b) and a compound (e) which is different from the above oxetane compound and has at least one hydroxy group. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a water absorbing agent and a water absorbing agent.

[0002]

2. Description of the Related Art In recent years, super absorbent polymers (water absorbents) have been widely used as constituent materials for water absorbent articles such as disposable diapers, sanitary napkins, so-called incontinence pads, etc. for the purpose of absorbing body fluids. ing.

Such highly water-absorbent resin is described in, for example, Japanese Industrial Standard (JIS) K7223-1996 and is already known.

Examples of the above superabsorbent resin include crosslinked polyacrylic acid partially neutralized products, hydrolyzates of starch-acrylic acid graft polymers, saponified vinyl acetate-acrylic acid ester copolymers, and acrylonitrile copolymers. Hydrolyzates of polymers or acrylamide copolymers or crosslinked products thereof, and crosslinked products of cationic monomers are known.

The properties which the above-mentioned superabsorbent resin should have are as follows: An excellent water absorption amount and water absorption rate when contacted with an aqueous liquid such as a body fluid, gel strength, and suction by which water is absorbed from a substrate containing an aqueous liquid. Power, etc. are chanted. Further, conventionally, various superabsorbent resins (water-absorbing agents) have been proposed, which have a plurality of these characteristics in combination and exhibit excellent performance (absorption characteristics) when used in water-absorbent articles such as paper diapers and sanitary napkins. ing.

[0006] For example, a technique for cross-linking the vicinity of the surface of the super absorbent polymer has been known as a method for improving the absorption characteristics of the super absorbent polymer such as water absorption capacity without load and water absorption capacity under load with good balance. Various methods are disclosed in. As an example thereof, a method using a polyhydric alcohol (JP-A-58-180233, JP-A-61-16903).
(JP-A No. 52-117393), a method using a polyvalent glycidyl compound, a polyvalent aziridine compound, a polyamine compound, and a polyisocyanate compound (JP-A-59-189103) and a method using glyoxysal (JP-A-52-117393). Japanese Patent Application Laid-Open No. 51-1365.
88, JP-A-61-257235, JP-A-62-7745), and the method using a silane coupling agent (JP-A-61-211305, JP-A-61-21305).
-252212, JP-A-61-264006), a method using alkylene carbonate (German Patent No. 4020780), a method using oxazolidinone (WO99 / 42494), and a method using polyvalent oxazolidinone (WO99). / 43720),
Method using oxazine (WO00 / 31153), method using oxazoline compound (JP 2000
-197818) and the like are known. However, in the surface cross-linking of such a water absorbent resin, there are problems of safety and reactivity of the cross-linking agent used. That is, in general, when the cross-linking agent is a compound having a highly reactive functional group such as epoxy, the cross-linking agent itself has skin irritation although the reaction can be performed at a low temperature, and it is possible to control the residual amount and the like. There is a problem in that it needs to be performed strictly, and that complicated work is required in the process to reduce the remaining amount. On the other hand, a highly safe crosslinking agent such as a polyhydric alcohol has a low reactivity of the crosslinking agent, and thus requires a high temperature or a long time for the crosslinking reaction, and in some cases, the super absorbent resin may be colored by heating. , There was a possibility of deterioration. further,
In manufacturing highly water-absorbent resins (water-absorbing agents), efficient production with less energy is required from the viewpoint of protecting the global environment, and also improves productivity and absorbs water during the manufacturing process. It is also preferable in order to prevent thermal deterioration of the resin. Therefore, improvement of a crosslinking agent having low reactivity is required.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above conventional problems. That is, the present invention is to provide a method for producing a water-absorbing agent having excellent absorption characteristics such as a balance between a water absorption capacity without load and a water absorption capacity under load and having excellent safety at low temperature in a short time.

[0008]

Means for Solving the Problems The present inventor produced a water-absorbing agent at low temperature in a short time, and as a result of diligent study of a water-absorbing agent having excellent absorption characteristics, as a result, a specific compound and an additive were cross-linked with a water-absorbing resin. The inventors have found that the above problems can be solved by using it as an agent, and have completed the present invention.

That is, the method for producing the water absorbing agent of the present invention is
A method for producing a water-absorbing agent containing a superabsorbent resin having a crosslinked structure as a main component, comprising: an oxetane compound (b) and a water-soluble additive that is acidic in water with respect to the superabsorbent resin (a). (C) and are mixed.

The method for producing a water-absorbing agent of the present invention is a method for producing a water-absorbing agent containing a superabsorbent resin having a crosslinked structure as a main component, wherein the oxetane compound is added to the superabsorbent resin (a). (B) and the second oxetane compound and a second crosslinking agent (d) having a different structure are mixed.

The method for producing a water-absorbing agent of the present invention is a method for producing a water-absorbing agent containing a superabsorbent resin having a crosslinked structure as a main component, wherein the oxetane compound is added to the superabsorbent resin (a). (B) and the compound (e) having at least one hydroxyl group different from the oxetane compound are mixed.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. (1) Superabsorbent Resin Having Crosslinked Structure The superabsorbent resin referred to in the present invention is a water-swellable and water-insoluble crosslinked polymer, and is essentially 3 times or more, more preferably 10 times or more, of its own weight, preferably Is a cross-linked polymer which absorbs a large amount of water or physiological saline of 50 to 1000 times and forms anionic, nonionic or cationic hydrogel. The term "water-insoluble" as used in the present invention means that a water-soluble component is essentially 50% by weight or less, preferably 25% by weight or less, more preferably 20% by weight or less, further preferably 15% by weight.
The following is used, particularly preferably 10% by weight or less. These measuring methods are specified in the examples. Further, the water absorbing agent in the present invention is mainly composed of a super absorbent resin, preferably 7
The modified superabsorbent resin is contained in an amount of 0% by weight or more, and further 85% by weight to 100% by weight, and is preferably a superabsorbent resin in which the vicinity of the surface is crosslinked. In the present invention, the highly water-absorbent resin includes a crosslinked polyacrylic acid partially neutralized product grafted as necessary, a hydrolyzate of a starch-acrylonitrile graft polymer, a hydrolyzate of a starch-acrylic acid graft polymer, and vinyl acetate. -Saponified product of acrylic acid ester copolymer, hydrolyzate of acrylonitrile copolymer or acrylamide copolymer or crosslinked products thereof, carboxyl group-containing crosslinked polyvinyl alcohol modified product, crosslinked isobutylene-maleic anhydride copolymer, etc. 1 type or 2 types or more are mentioned, Preferably,
A cross-linked polymer of a water-soluble unsaturated monomer is used. These super absorbent polymers may be used alone or in a mixture,
Among them, one having a carboxyl group or a mixture thereof is preferable, and most preferably, a monomer having a graft backbone and containing acrylic acid and / or its salt (neutralized product) as a main component is polymerized and crosslinked. This is a crosslinked polyacrylic acid partially neutralized product, which is obtained by grafting as necessary. Examples of the acrylate include alkali metal salts such as sodium, potassium and lithium acrylate, ammonium salts and amine salts. The superabsorbent resin has a constitutional unit in the range of 0 mol% to 50 mol% of acrylic acid and 100 mol% to 50 mol% of acrylate (however, the total amount of both is 100 mol% or less). Is preferred, acrylic acid 1
0 mol% to 40 mol% and acrylate 90 mol%
More preferably, it is in the range of 60 mol% (however, the total amount of both is 100 mol% or less). Neutralization of the superabsorbent resin for forming the salt may be carried out in a monomer state before the polymerization, or may be carried out in the polymer state during or after the polymerization, and they are used in combination. You may.
The monomer for obtaining the highly water-absorbent resin used in the present invention may contain a monomer other than the acrylic acid (salt) if necessary. In the present invention, when a monomer other than acrylic acid (salt) is used, from the viewpoint of physical properties, the monomer other than acrylic acid (salt) is based on the total amount of acrylic acid and its salt used as the main components. Therefore, the ratio is preferably 30 mol% or less, more preferably 10 mol% or less.

When the above-mentioned monomers are polymerized in order to obtain the superabsorbent resin used in the present invention, bulk polymerization or precipitation polymerization can be carried out. Turbid polymerization is preferred. When the above monomer is used as an aqueous solution, the concentration of the monomer in the aqueous solution (hereinafter referred to as an aqueous monomer solution) is preferably 10 to 70% by weight,
It is more preferably 20 to 60% by weight, and a solvent other than water may be used in combination as necessary.

When initiating the above-mentioned polymerization, for example, potassium persulfate, ammonium persulfate, sodium persulfate, t-butyl hydroperoxide, hydrogen peroxide,
It is possible to use a radical polymerization initiator such as 2,2′-azobis (2-amidinopropane) dihydrochloride or a photopolymerization initiator such as 2-hydroxy-2-methyl-1-phenyl-propan-1-one. it can. Furthermore, a redox initiator can be used in combination with a reducing agent. As a reducing agent,
Examples thereof include (bis) sulfite (salt) such as sodium sulfite and sodium bisulfite, L-ascorbic acid (salt), reducing metal (salt) such as ferrous salt, amines, etc., but are not particularly limited. Not something. The amount of the polymerization initiator or reducing agent used is usually 0.001 to 2 mol%, preferably 0.01 to 0.1 mol%.

The polymerization reaction may be initiated by irradiating the reaction system with active energy rays such as radiation, electron beams and ultraviolet rays, and the above polymerization initiator may be used in combination. The reaction temperature in the above polymerization reaction is not particularly limited, but is preferably in the range of 15 to 130 ° C, more preferably in the range of 20 to 110 ° C. Also,
The reaction time and pressure are not particularly limited, and may be appropriately set depending on the types of the monomer and the polymerization initiator, the reaction temperature, and the like.

The highly water-absorbent resin may be a self-crosslinking type resin which does not use a crosslinking agent, but it may have two or more polymerizable unsaturated groups or two or more reactive groups in one molecule. Those obtained by copolymerizing or reacting an internal crosslinking agent having a group are more preferable.

Specific examples of these internal crosslinking agents include, for example, N, N'-methylenebis (meth) acrylamide,
(Poly) ethylene glycol di (meth) acrylate,
Trimethylolpropane tri (meth) acrylate,
Ethylene oxide modified trimethylolpropane tri (meth) acrylate, pentaerythritol hexa (meth) acrylate, triallyl cyanurate, triallylamine, poly (meth) allyloxyalkane, (poly) ethylene glycol diglycidyl ether, propylene glycol, glycerin, Examples thereof include polyethyleneimine. Moreover, you may use the oxetane compound mentioned later which is a crosslinking agent of this invention. These internal cross-linking agents may be used alone, or may be used by appropriately mixing two or more kinds. Further, these internal cross-linking agents may be added to the reaction system all at once or may be added in portions. An internal cross-linking agent having a plurality of polymerizable double bonds is preferably used, and the amount of these internal cross-linking agents used is preferably 0.005 to 2 mol%, more preferably 0. 02
To 0.5 mol%, particularly preferably 0.04 to 0.2 mol%, which is appropriately determined.

In the above polymerization, various foaming agents such as carbonic acid (hydrogen) salt, carbon dioxide, azo compounds, inert organic solvents, etc. are added to the reaction system; starch / cellulose, starch / cellulose derivatives, polyvinyl alcohol, poly Hydrophilic polymers such as acrylic acid (salt) and polyacrylic acid (salt) cross-linked products; various surfactants; chelating agents; chain transfer agents such as hypophosphorous acid (salt) may be added. In the case of graft polymerization, the hydrophilic polymer is used in an amount of 30% by weight or less, preferably 10% by weight or less based on the monomers. In addition, a known method is widely used as a method for producing a superabsorbent resin, such as a monomer other than acrylic acid, a crosslinking agent used, and an additive at the time of polymerization, and the patents shown below are also applicable to the present application. . In addition, the reverse phase suspension polymerization is a polymerization method in which an aqueous monomer solution is suspended in a hydrophobic organic solvent, for example, US Pat.
No. 76, No. 4376323, No. 4446261, No. 4683274, No. 5244735 and the like. Aqueous solution polymerization is a method of polymerizing an aqueous monomer solution without using a dispersion solvent.
No. 625001, No. 4873299, No. 428608
No. 2, No. 4973632, No. 4985518, No. 5
No. 124416, No. 5250640, No. 5264449
5, US Pat. No. 5,145,906, US Pat. No. 5,380,808, and European patents 0811636 and 09550.
European patents such as 86 and 09222717, WO20
It is described in international patents such as 01/38402.
If the cross-linked polymer is obtained by aqueous solution polymerization and is gel-like, that is, if it is a hydrogel cross-linked polymer,
The crosslinked polymer is dried if necessary, and usually pulverized before and / or after drying to obtain a highly water-absorbent resin. The drying is usually 60 ° C to 250 ° C, preferably 100 ° C.
To 220 ° C, more preferably 120 ° C to 200 ° C, and the drying time is 10 minutes to 12 hours, preferably 20.
Minutes to 6 hours, more preferably 30 minutes to 3 hours.

The water content of the superabsorbent resin which can be used in the present invention is not particularly limited, but the water content is preferably 0.
The content is preferably not less than 400% by weight and more preferably not less than 40% by weight and more preferably not less than 0.2% by weight and not more than 10% by weight. Further, the super absorbent polymer that can be used in the production method of the present invention may be in the form of particles. The particle size of the superabsorbent resin is 10 times the average particle size of the gel obtained by the polymerization reaction before dry pulverization.
Although those having a particle diameter of more than 00 μm can be used, the weight average particle diameter is usually 10 μm to 1000 μm, preferably 50
7 μm to 800 μm, more preferably more than 75 μm
60 μm or less, particularly preferably more than 150 μm
It is 0 μm or less. More preferably, the amount of fine powder (for example, 100 μm or less) particles in the water absorbent resin is preferably small, specifically 10% by weight or less, more preferably 5% by weight or less, and particularly preferably 1% by weight or less. The particle shape of the water-absorbent resin having a crosslinked structure thus obtained is not particularly limited, such as spherical, crushed, and irregular shapes, but the irregular crushed shape obtained through the crushing step is It can be preferably used.

(2) Oxetane Compound The oxetane compound described in the present invention is a compound having at least one oxetane structure in one molecule. Preferably, the one represented by the following structural formula (1) can be used.

[0021]

[Chemical 2]

(Wherein R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R
⁶ independently represents a hydrogen atom, a hydroxyl group, an alkyl group, an alkenyl group, an aromatic group, a halogen group, a substituted alkyl group, a substituted alkenyl group or a substituted aromatic group. ) R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are each independently a hydrogen atom, an alkyl group, an alkenyl group, an aromatic group, a halogen group, a substituted alkyl group, a substituted alkenyl group or a substituted aromatic group. Preferably, R ¹ is a hydrogen atom, a hydroxyl group, an alkyl group, a substituted alkyl group, R ² is a hydrogen atom, a hydroxyl group,
The alkyl group, the substituted alkyl group, and R ^{3 to} R ⁶ are independently a hydrogen atom, a hydroxyl group, or an alkyl group, and more preferably R
¹ is a hydrogen atom, a hydroxyl group, an alkyl group of Cl to 6, Cl to 6 substituted alkyl group having a hydroxyl group, ^{R 2} is a hydrogen atom,
Hydroxyl group, C1-6 alkyl group, C1 having hydroxyl group
The substituted alkyl group of 6 and R ^{3 to} R ⁶ are hydrogen atoms. Further, the oxetane compound may be insoluble in water, but is preferably water-soluble, and 100 g of water at 25 ° C.
On the other hand, it dissolves 0.5 g or more, more preferably 1 g or more, and further preferably 5 g or more.

Specifically, oxetane and 3-methyl-3
-Oxetane methanol, 3-ethyl-3-oxetane methanol, 3-butyl-3-oxetane methanol,
3-Methyl-3-oxetane ethanol, 3-ethyl-
Compounds having an oxetane ring and a hydroxyl group such as 3-oxetane ethanol and 3-butyl-3-oxetane ethanol, 3-methyl-3-aminomethyloxetane, 3-
A compound having an oxetane ring and an amino group such as ethyl-3-aminomethyloxetane, 3-chloromethyl-3
-A compound having a halogen such as methyl oxetane or 3-chloromethyl-3-ethyl oxetane, 3-methyl-
3-allyloxymethyl oxetane, 3-ethyl-3-
Allyloxymethyl oxetane, 3-methyl-3- (meth) acryloxymethyl oxetane, 3-ethyl-3
-(Meth) acryloxymethyl oxetane, 3-methyl-3- (2-propenyloxy) methyl oxetane,
3-ethyl-3- (2-propenyloxy) methyl oxetane, 3-methyl-3- (2-methyl-2-propenyloxy) methyl oxetane, 3-ethyl-3- (2-
Compounds having an aliphatic unsaturated group such as methyl-2-propenyloxy) methyloxetane, 3-methyl-3-phenyloxymethyloxetane, 3-ethyl-3-phenyloxymethyloxetane, 3-methyl-3-benzyloxymethyl Examples thereof include compounds having an aromatic unsaturated group such as oxetane and 3-ethyl-3-benzyloxymethyloxetane. Further, the hydroxyl group, amino group, oxetane compound having a halogen may be esterified, amidated, etherified, for example, glycolic acid, lactic acid, acetic acid, propionic acid, glutaric acid, succinic acid, tartaric acid, malonic acid, apple Acid, citric acid, esterification product of polyacrylic acid and oxetane compound having hydroxyl group (for example, diesterification product of tartaric acid and 3-methyl-3-oxetanemethanol), amidation product of oxetane compound having amino group, methyl alcohol , Ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, t-
Butyl alcohol, ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, polypropylene glycol , Glycerin, polyglycerin, 2-butene-1,4-diol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanediene Methanol, 1,2-cyclohexanol, trimethylolpropane, pentaerythritol,
Sorbitol, dibromomethane, dichloromethane, diiodomethane, 1,1-dibromoethane, 1,2-dibromoethane, 1,2-dichloroethane, 1,2-diiodoethane, 1,2-dibromopropane, 1,2-dichloropropane, 1 , 3-dibromopropane, 1,3-dichloropropane, 1,3-diiodopropane, 1,2,3-
Tribromopropane, 1,2,3-trichloropropane, 2,2-dibromopropane, 1,3-dibromobutane, 1,4-dibromobutane, 1,4-dichlorobutane, 2,3-dichlorobutane, benzyl bromide Etc. and an etherified product of an oxetane compound.

The oxetane compound of the present invention is not limited to one oxetane skeleton, and may be a compound having a plurality of oxetane skeletons. The oxetane skeleton is a cyclic structure having a 4-membered ring ether structure having an oxygen atom, and specifically, at least one structure represented by the following general formula (2) or the following general formula (3) is used. Examples thereof include di-, tri-, tetra-, and polyoxetane compounds (high molecular weight compounds) having three or more.

[0025]

[Chemical 3]

(Wherein R ⁷ represents an oxygen atom, an alkyl group, an aromatic group, a substituted alkyl group or a substituted aromatic group, and R ⁸
R ⁹ , R ¹⁰ , R ¹¹ and R ¹² each independently represent a hydrogen atom, a hydroxyl group, an alkyl group, an alkenyl group, an aromatic group, a halogen group, a substituted alkyl group, a substituted alkenyl group or a substituted aromatic group, and n is 1 It is an integer above the above. )

[0027]

[Chemical 4]

(In the formula, R ¹³ represents an oxygen atom, an alkyl group, an aromatic group, a substituted alkyl group, a substituted alkenyl group or a substituted aromatic group, and R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ^17
18 independently represents a hydrogen atom, a hydroxyl group, an alkyl group, an alkenyl group, an aromatic group, a halogen group, a substituted alkyl group, a substituted alkenyl group or a substituted aromatic group. ) Examples of the polyvalent oxetane compound having a plurality of oxetane skeletons include those represented by the following general formula (4).

[0029]

[Chemical 5]

(Wherein R ¹⁹ is an oxygen atom, an alkyl group, an alkenyl group, an aromatic group, a halogen group, a substituted alkyl group,
A substituted alkenyl group or a substituted aromatic group, R ²⁰ and R ²¹ are independently a hydrogen atom, a hydroxyl group, an alkyl group, an alkenyl group,
It represents an aromatic group, a halogen group, a substituted alkyl group, a substituted alkenyl group or a substituted aromatic group. ) The amount of the oxetane compound used in the present invention is preferably 0.02 per 100 parts by weight of the solid content of the super absorbent polymer.
-10 parts by weight, more preferably 0.05-5 parts by weight,
More preferably 0.1 to 4 parts by weight, particularly preferably 0.1.
It is in the range of 2 to 3 parts by weight. By using the oxetane compound within the above range, the absorption characteristics for body fluid (aqueous liquid) such as urine, sweat and menstrual blood can be further improved. If the amount of the oxetane compound used is less than 0.02 part by weight, the crosslink density in the vicinity of the surface of the superabsorbent polymer cannot be increased, and the absorption characteristics may not be improved. Further, when the amount of the oxetane compound used is more than 10 parts by weight, the amount of the oxetane compound becomes excessive, which is uneconomical, and it is difficult to control the crosslinking density to an appropriate value, so that the water absorption capacity may not be improved. is there.

(3-1) Compound to be added together with oxetane-water-soluble additive showing acidity in water (c) The present invention relates to a superabsorbent resin (a), an oxetane compound (b), and A water-soluble additive (c) showing acidity in water and a second structure having a structure different from that of the oxetane compound
Of the crosslinking agent (d) and at least one additive selected from the compound (e) having at least one hydroxyl group different from the oxetane compound. The water-soluble additive (c) which shows acidity in water different from the oxetane compound will be described. The additive used in the present invention is a water-soluble additive (c) that exhibits acidity in water. By using the water-soluble additive (c) that exhibits acidity in water, the crosslinking reaction can be further accelerated and the physical properties of the water absorbing agent can be further improved. As the water-soluble additive (c) of the present invention, water-soluble means that the solubility in 100 g of water (water temperature 25 ° C.) is preferably 0.5 g or more, more preferably 5 g or more, and further preferably 10 g or more. In addition, acidic means the aqueous solution (water 1
Solution in which 0.025 mol of water-soluble additive is dissolved in kg) 2
The pH at 5 ± 1 ° C. is preferably 5.5 or less, more preferably 4.5 or less, still more preferably 3.0 or less.
Preferably, the water-soluble additive (c) that exhibits acidity in water is selected from an inorganic acid, an organic acid, and an acid salt of a polyvalent acid. As these inorganic acids, organic acids, and acid salts of polyvalent acids, specifically, sulfuric acid, phosphoric acid, hydrochloric acid, citric acid, glyoxylic acid, glycolic acid, glutaric acid, cinnamic acid, succinic acid,
Acetic acid, tartaric acid, lactic acid, boric acid, pyruvic acid, fumaric acid, propionic acid, 3-hydroxypropionic acid, malonic acid,
Butyric acid, isobutyric acid, imidinoacetic acid, malic acid, isethionic acid, citraconic acid, adipic acid, itaconic acid, crotonic acid, oxalic acid, salicylic acid, gallic acid, sorbic acid, gluconic acid, p-toluenesulfonic acid, dihydrogen phosphate Sodium, acidic sodium pyrophosphate, acidic sodium metaphosphate, sodium hydrogensulfate, aluminum sulfate 14-1
Octahydrate, aluminum chloride hexahydrate, polyaluminum chloride, potassium aluminum sulfate 24 hydrate, ammonium aluminum sulfate dodecahydrate, zirconium nitrate, zirconium acetate, zirconium sulfate, zirconium phosphate, zirconium hydroxychloride Is preferred,
Sulfuric acid, phosphoric acid, succinic acid, lactic acid, citric acid, aluminum sulfate, aluminum chloride and zirconium sulfate are more preferable, and aluminum sulfate is particularly preferable.
The amount of the compound (c) having an acid group to be used is appropriately determined depending on its type, reaction conditions and the like, but as in the cases of (d) and (e) described later, usually, the solid content of the super absorbent polymer is 100 parts by weight. On the other hand, 0.001 to 10 parts by weight, preferably 0.01 to 5
It is used in parts by weight, more preferably 0.5 to 4 parts by weight.

(3-2) Compound added together with oxetane-Second cross-linking agent having a structure different from that of the oxetane compound (d) In the present invention, the super absorbent polymer (a) is different from the oxetane compound. There is also provided a method for producing a water-absorbing agent, which comprises mixing a second cross-linking agent (d) having a structure, and then a second structure having a structure different from that of the oxetane compound.
The cross-linking agent (d) will be described. The second crosslinking agent (d) having a structure different from that of the oxetane compound used in the present invention is not particularly limited as long as it is a compound capable of reacting with the functional group of the polymer. By using the second crosslinking agent (d), the crosslinking reaction can be further accelerated and the physical properties of the water absorbing agent can be further improved.

The second crosslinking agent (d) used is
Specifically, for example, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, 2,3,4-trimethyl-1. , 3-pentanediol, polypropylene glycol, glycerin,
Polyglycerin, 2-butene-1,4-diol, 1,
3-butanediol, 1,4-butanediol, 1,5
-Pentanediol, 1,6-hexanediol, 1,
2-Cyclohexanedimethanol, 1,2-cyclohexanediol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-oxypropylene block copolymer, pentaerythritol, sorbitol, and other polyhydric alcohol compounds; ethylene glycol Diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether,
Epoxy compounds such as glycidol; ethylenediamine,
Multivalent amine compounds such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, polyamidepolyamine; epichlorohydrin, epibromhydrin,
Haloepoxy compounds such as α-methylepichlorohydrin; Condensates of the above polyvalent amine compounds and the above haloepoxy compounds; Polyisocyanate compounds such as 2,4-tolylene diisocyanate and hexamethylene diisocyanate; 1,2-Ethylenebis Polyvalent oxazoline compounds such as oxazoline; silane coupling agents such as γ-glycidoxypropyltrimethoxysilane and γ-aminopropyltrimethoxysilane; 1,3-dioxolan-2-one, 4-methyl-1,3- Dioxolan-2-one,
4,5-dimethyl-1,3-dioxolan-2-one,
4,4-dimethyl-1,3-dioxolan-2-one,
4-ethyl-1,3-dioxolan-2-one, 4-hydroxymethyl-1,3-dioxolan-2-one,
1,3-dioxan-2-one, 4-methyl-1,3-
Examples thereof include alkylene carbonate compounds such as dioxan-2-one, 4,6-dimethyl-1,3-dioxan-2-one, and 1,3-dioxoban-2-one; but are not particularly limited. . The second cross-linking agent (d) used is described in JP-A-58-180233, JP-A-61-16903, and JP-A-59-18.
9103, JP-A-52-117393, JP-A-51-136588, JP-A-61-2572.
35, JP 62-7745, JP 61
-211305, JP-A-61-252212, JP-A-61-264006, German Patent No. 40
20780, WO99 / 42494, WO
Examples thereof include 99/43720, WO00 / 31153, and JP-A-2000-197818, and known crosslinking agents including these are used.

The amount of the second cross-linking agent (d) used is appropriately determined depending on its type and reaction conditions, but like the above-mentioned (c) and (e), it is usually a solid of a high water-absorbing resin. Minute 100
It is used in an amount of 0.001 to 10 parts by weight, preferably 0.01 to 5 parts by weight, and more preferably 0.1 to 4 parts by weight with respect to parts by weight. The second cross-linking agent (d) is preferably water-soluble like the water-soluble additive (c), and the water-solubility means a solubility in 100 g of water (water temperature 25 ° C.). The amount is 0.5 g or more, more preferably 5 g or more, and further preferably 10 g or more.
Further, among the above-mentioned cross-linking agents, a polyhydric alcohol compound and / or a polyvalent metal salt is preferably used as the second cross-linking agent (d), and more preferably a polyvalent metal salt is used. Specifically, aluminum sulfate, aluminum sulfate 14-18 hydrate, aluminum chloride, zirconium compound, zinc compound, iron compound, magnesium compound are preferable. Further, the second cross-linking agent (d) may be the water-soluble additive (c) showing acidity in the above, or (e), but preferably the water-soluble additive (c). ) Is the second crosslinking agent (d)
Is to combine with.

(3-3) Compound added with oxetane-Compound having at least one hydroxyl group different from the above oxetane compound (e) In the present invention, the super absorbent polymer (a) is different from the above oxetane compound. Also provided is a method for producing a water-absorbing agent, which comprises mixing a compound (e) having at least one hydroxyl group, and then, a compound (e) having at least one hydroxyl group different from the oxetane compound will be described below. To do. The compound (e) having at least one hydroxyl group different from the oxetane compound used in the present invention is not particularly limited as long as it is a compound having at least one hydroxyl group. By using the compound (e) having at least one hydroxyl group, the crosslinking reaction can be further accelerated and the physical properties of the water absorbing agent can be further improved. The compound (e) having at least one hydroxyl group is preferably the above water-soluble additive (c).
It is preferably water-soluble as well as water-soluble.
The solubility with respect to 00 g (water temperature 25 ° C.) is preferably 0.5 g or more, more preferably 5 g or more, and further preferably 10 g or more. More specifically the at least 1
As the compound (e) having two hydroxyl groups, alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, t-butyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene Glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, polypropylene glycol, glycerin, polyglycerin, 2-butene-1,4 -Diol, 1,3-butanediol, 1,4
-Butanediol, 1,5-pentanediol, 1,6
-Hexanediol, 1,2-cyclohexanedimethanol, 1,2-cyclohexanol, trimethylolpropane, diethanolamine, triethanolamine,
Polyhydric alcohols such as polyoxypropylene, oxyethylene-oxypropylene block copolymer, pentaerythritol, sorbitol and the like can be mentioned. Further, the compound (e) having at least one hydroxyl group may be the water-soluble additive (c) showing acidity in the above, or the second crosslinking agent (d), but is preferably That is, the compound (e) having at least one hydroxyl group also serves as the second crosslinking agent (d). The amount of the compound (e) having at least one hydroxyl group used is appropriately determined depending on the type and reaction conditions thereof, but as in the cases (c) and (d), the solid content of the superabsorbent polymer is usually 100% by weight. 0.001 to 10 parts by weight, preferably 0.01 to 5 parts by weight
It is used in parts by weight, more preferably 0.1 to 4 parts by weight.

(4) The above (b) to the superabsorbent resin (a)
Mixing of (e) The present invention relates to a super absorbent polymer (a), an oxetane compound (b), a water-soluble additive (c) showing acidity in water, and a oxetane compound having a structure different from that of the oxetane compound. 2 is a cross-linking agent (d), a method for producing a water-absorbing agent, which comprises mixing at least one additive selected from the compound (e) having at least one hydroxyl group different from the oxetane compound. A method for mixing them will be described. Mixing of the oxetane compound (b) and at least one additive selected from the above (c) to (e) with respect to the super absorbent resin (a) is carried out by mixing the above oxetane compound (b)
After mixing the above, the above (c) to (e) may be mixed,
On the contrary, the oxetane compound (b) may be added after mixing the above (c) to (e), but it is preferable that the oxetane compound (b) and the above (c) to (e) are mixed in advance. The mixture is mixed with the super absorbent polymer (a). Oxetane compound (b) and the above (c) to (e)
The mixture of at least one additive selected from the above may be carried out in a state in which the superabsorbent polymer (a) is dispersed in an organic solvent such as cyclohexane or pentane, but preferably, for example, water is added if necessary. And / or the above mixture containing a hydrophilic organic solvent is directly sprayed or dropped onto the superabsorbent resin (a) to be mixed. The size of the sprayed droplets is preferably 300 μm or less, and further 200
μm or less. In the present invention, the super absorbent resin (a)
With respect to the oxetane compound (b) and the above (c) ~
When mixing (e), it is preferable to further add water (f). Water may be added before mixing, during mixing, or after mixing, but water is added to the above (c) because of the simplicity of the process.
(E) is preferably mixed at the same time, more preferably a method of adding and mixing in the form of an aqueous dispersion or an aqueous solution. At this time, the amount of water used is in the range of 0.5 to 10 parts by weight, preferably 0.5 to 3 parts by weight, based on 100 parts by weight of the super absorbent polymer (a). Water usage is 1
If it exceeds 0 parts by weight, the water absorption capacity may decrease. If it is less than 0.5 part by weight, the water absorption capacity under pressure may not be improved. Further, in the present invention, when the oxetane compound (b) and the above (c) to (e) are mixed with the super absorbent polymer (a), the above (c) to (e) other than the above water (f) are mixed. Other hydrophilic organic solvent (g) may be used in combination.

As the hydrophilic organic solvent (g) used, ketones such as acetone and methyl ethyl ketone; ethers such as dioxane, alkoxy (poly) ethylene glycol and tetrahydrofuran; ε-caprolactam,
Examples include amides such as N, N-dimethylformamide; sulfoxides such as dimethyl sulfoxide. The amount of the hydrophilic organic solvent used varies depending on the type and particle size of the water absorbent resin, but is usually 0 to 10 parts by weight, preferably 0 to 5 parts by weight, relative to 100 parts by weight of the water absorbent resin.
The range is more preferably 0.1 to 5 parts by weight. Further, in the present invention, an additive such as a surfactant or an inert inorganic fine particle powder may be used for improving the mixing property and the physical properties. Surfactants and inert inorganic fine particle powders used include US Pat. No. 5,164,459, European Patent No. 827753, European Patent No. 349240, and European Patent No. 76.
No. 1241 publication and the like. A suitable mixing device used for said mixing is required to be able to generate a large mixing force in order to ensure uniform mixing. Examples of the mixing device that can be used in the present invention include a cylindrical mixer, a double-walled cone mixer, a high-speed stirring mixer, a V-shaped mixer, a ribbon mixer, a screw mixer, and a fluidizer. Type furnace rotary disk type mixer, air flow type mixer, double arm type kneader, internal mixer, crushing type kneader, rotary type mixer,
A screw type extruder or the like is suitable.

(5) Heat treatment In the method for producing a water-absorbing agent of the present invention, in the present invention, the oxetane compound (b) and the above-mentioned (c) to (e) are mixed with or after being mixed with the superabsorbent resin (a). At the same time, preferably, heat treatment or light irradiation treatment is performed. When the heat treatment is performed in the present invention, the heating temperature and time are appropriately determined, but the treatment time is preferably 1 to 180 minutes, more preferably 3 to 120 minutes, further preferably 5 to 10 minutes.
0 minutes, the treatment temperature is preferably 60 to 250 ° C., more preferably 100 to 220 ° C., further preferably 12
It is 0 to 200 ° C. When the heating temperature is lower than 60 ° C, not only the heat treatment takes a long time to cause a decrease in productivity, but also uniform crosslinking cannot be achieved, and an excellent water absorbing agent may not be obtained. On the other hand, if the treatment temperature exceeds 250 ° C., the water absorbent resin obtained may be damaged, and it may be difficult to obtain a water absorbent resin having an excellent water absorption capacity. The heat treatment can be carried out by using an ordinary dryer or a heating furnace, and a groove type mixing dryer, a rotary dryer, a disk dryer, a fluidized bed dryer, an airflow type dryer, a hot air circulation type dryer and an infrared dryer. A machine is illustrated. In addition, when performing light irradiation processing in this invention instead of heat processing, it is preferable to irradiate with ultraviolet rays and a photopolymerization initiator can be used.

(6) Water-Absorbing Agent The water-absorbing agent of the present invention exhibits a high absorptivity even under a high load, and specifically, a water absorption capacity under pressure (0.93% by weight physiological saline) (4.83 kPa) is preferable. Is 15 (g / g) or more, more preferably 20 (g / g) or more, still more preferably 23 (g / g) or more, even more preferably 25.
A water absorbing agent of (g / g) or more can be obtained. Also, the water absorption capacity without load is preferably 24 (g / g) or more, more preferably 27 (g / g) or more, and further preferably 30.
A water absorbing agent of (g / g) or more can be obtained. In addition, the saline flow conductivity of the water absorbing agent (Saline Flow Conducti
vity / abbreviation SFC) is also 10 (10 ⁻⁷ × cm ³ × s × g)
⁻¹ ) or more, further 20 to 200 (10 ⁻⁷ × cm ^3).
Xs * g <^-1> . In the method for producing a water absorbent according to the present invention, further, if necessary, a deodorant,
Antibacterial agents, fragrances, inorganic powders such as silicon dioxide and titanium oxide,
Foaming agent, pigment, dye, hydrophilic short fiber, plasticizer, adhesive,
Surfactants, fertilizers, oxidizers, reducing agents, water, salts, chelating agents, bactericides, hydrophilic polymers such as polyethylene glycol and polyethyleneimine, hydrophobic polymers such as paraffin, thermoplastic resins such as polyethylene and polypropylene. It may also include a step of imparting various functions to the water absorbent resin, such as addition of a thermosetting resin or the like such as polyester resin or urea resin. The water content of the water-absorbing agent of the present invention, the average particle size and the amount of fine powder are preferably in the range of the above-mentioned high water-absorbing resin, and the water-absorbing agent of the present invention may be in the form of a sheet, but preferably it is in the form of dried particles. It is used as a water absorbent. Further, the amount of soluble components in the water absorbing agent is preferably in the range of the above-mentioned super absorbent polymer.

Further, according to the present invention, a water absorbing agent obtained by treating a super absorbent polymer with an oxetane compound, wherein the unreacted oxetane compound remaining in the water absorbing agent is 100 pp.
m or less and / or the reaction rate of the oxetane compound is 80% or more,
Will also be provided. That is, in the present invention, the amount of the remaining oxetane compound is 100 ppm or less, and further 50 ppm.
Or less, particularly preferably 10 ppm or less, and / or the reaction rate of the oxetane compound is 80% or more,
Further, it is preferably 90% or more, and particularly preferably 95% or more. Further, the particle size of the water absorbing agent is preferably 90% or more based on the weight of the entire water absorbing agent in the range of 850 μm to 150 μm. Further, the water absorbing agent is preferably 0.02 to 10 parts by weight, more preferably 0.05 to 5 parts by weight, and more preferably 0.1 to 10 parts by weight of the oxetane compound with respect to 100 parts by weight of the solid content of the super absorbent polymer. -4 parts by weight, particularly preferably 0.2-3 parts by weight. Further, the absorbency of the water-absorbing agent (water absorption capacity without load, water absorption capacity under load with respect to 0.9 wt% physiological saline (4.83 kPa), SFC) is preferably in the above range. The water absorbing agent is more preferable because it has high physical properties and has very little residual crosslinking agent.

(7) Hygiene material for absorbing feces, urine or blood containing the water absorbing agent of the present invention The hygiene material for absorbing feces, urine or blood of the present invention contains the water absorbing agent of the present invention. It is characterized by The sanitary material product of the present invention has an absorbent layer made of an absorbent body that absorbs body fluids and the like. Examples of the sanitary material of the present invention include disposable diapers and pads for infants, adults, and incontinence, and menstrual blood absorption napkins for women. The structure of the disposable diaper and the menstrual blood absorption napkin can adopt various structures similarly to the conventionally well-known structure, and the materials for the top sheet and the back sheet, etc. are particularly limited. Can be used without any. Since the sanitary material according to the present invention is composed of the absorber produced using the water absorbent of the present invention, it is possible to exhibit the effects of the water absorbent of the present invention, such as high absorbency, and the hygroscopic property at the time of manufacturing the sanitary material. It is possible to achieve an effect with less problems caused by using a water absorbent having a high water content. The structure of the absorber is not particularly limited as long as it is a structure used for a general water-absorbent article, for example, a water absorbent is disposed between hydrophilic fiber materials formed into a sheet shape, a so-called sandwich structure absorber, An absorbent body having a so-called blend structure, which is formed by molding a mixture of a hydrophilic fiber material and a water absorbing agent, may be mentioned. The weight ratio of the water absorbing agent to the hydrophilic fiber material in the absorber is, for example, water absorbing agent: hydrophilic fiber material = 20: 80.
˜100: 0, preferably 30:70
˜100: 0. These ratios can be appropriately selected depending on the purpose of use.

[0042]

The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The physical properties of the water absorbent and the water absorbent resin were measured by the following methods. (1) Absorption capacity under no load Highly water-absorbent resin or water-absorbing agent 0.2 g
0mm x 60mm) and put at room temperature 0.9% by weight
It was immersed in physiological saline. After 30 minutes, pull up the bag and centrifuge to 250 G (250 x 9.81 m / se).
After draining with c ² ) for 3 minutes, the bag weight W1 (g)
Was measured. Further, the same operation was performed without using the super absorbent polymer or the water absorbent, and the weight W0 (g) at that time was measured. Then, the water absorption capacity without load (g / g) was calculated from these W1 and W0 according to the following formula. Water absorption capacity without load (g / g) = (W1 (g) -W0
(G)) / 0.2 (g) When measuring the water absorption capacity with ion-exchanged water, it is measured with a highly water-absorbent resin or a water-absorbing agent of 0.02 g.

(2) Water absorption capacity under pressure A stainless steel 400-mesh wire mesh (mesh size 38 μm) is fused to the bottom of a plastic support cylinder having an inner diameter of 60 mm, and a highly water-absorbent resin or water-absorbing agent is applied on the mesh. 0.90
0 g was evenly sprayed, and the outer diameter was slightly smaller than 60 mm and was adjusted so that a load of 4.83 kPa could be uniformly applied to the super absorbent resin or water absorbing agent. A piston and a load that did not cause a gap and prevented from moving up and down were placed in this order, and the weight Wa (g) of this set of measuring devices was measured.

Inside the Petri dish with a diameter of 150 mm, the diameter 9
Place a 0 mm glass filter and add 0.9 wt% saline to the same level as the glass filter. A filter paper having a diameter of 90 mm is placed on it so that the entire surface is wet, and excess liquid is removed.

The above set of measuring devices is placed on the wet filter paper to absorb the liquid under load. After one hour, the set of measuring device is lifted and its weight Wb (g) is measured. And
Water absorption capacity under pressure (g /
g) was calculated. Water absorption capacity under pressure (g / g) = (Wb (g) -Wa
(G)) / weight of water absorbing agent ((0.9) g)

(3) Weight-average particle size Super-water-absorbing resin or water-absorbing agent after pulverization is opened to 850 μm.
m, 600 μm, 500 μm, 425 μm, 300 μ
m, 212 μm, 150 μm, 106 μm, 75 μm, and other JIS standard sieves, and the residual percentage R was plotted on a log probability paper. Thereby, the weight average particle diameter (D50) was read.

(4) Soluble content 0.5 g of highly water-absorbent resin or water-absorbent agent was dispersed in 1000 ml of ion-exchanged water, stirred for 16 hours, and then the swollen gel was filtered with a filter paper. Then, the water-soluble polymer in the obtained filtrate, that is, the amount of soluble components eluted from the superabsorbent resin or water-absorbing agent (% by weight, based on the superabsorbent resin or water-absorbing agent)
Was measured by colloid titration.

(5) Saline flow conductivity (SFC) test (see Table 9-509591) Saline flow conductivity (SF) according to Table 9-509591
C) It carried out according to the test. The superabsorbent resin or water absorbent (0.900 g) uniformly put in the container was swollen in artificial urine (1) under a pressure of 0.3 psi (2.07 kPa) for 60 minutes to form a gel layer of the swollen gel. The height is recorded and then a 0.69 wt% aqueous sodium chloride solution is passed under constant hydrostatic pressure through the swollen gel layer under a pressure of 0.3 psi (2.07 kPa). This SFC test was performed at room temperature (20 to 25 ° C.). Using a computer and a balance, record the amount of liquid passing through the gel layer at intervals of 20 seconds for 10 minutes as a function of time. The flow rate F _s (t) through the swollen gel (mainly between particles) is determined in units of g / s by dividing the weight gain (g) by the weight increase time (s).
t _s the only data obtained in the course of 10 minutes using a flow rate calculation, by using the flow rate obtained in the course of t _s and 10 minutes F _{s (t}
= 0), ie the initial flow rate through the gel layer. F _s (t = 0) is calculated by extrapolating the result of the least squares method of F _s (t) vs. time to t = 0. Artificial urine (1) contains 0.25 g of calcium chloride dihydrate, 2.0 g of potassium chloride, and 0.5 of magnesium chloride hexahydrate.
0 g, sodium sulfate 2.0 g, ammonium dihydrogen phosphate 0.85 g, diammonium hydrogen phosphate 0.15
g and pure water 994.25 g were used.

Saline flow conductivity = (F _s (t = 0) × L ₀ ) / (ρ × A × ΔP) = (F _s (t = 0) × L ₀ ) / 139506 where F _s (T = 0): Flow rate in g / s L ₀ : Height of gel layer in cm: ρ: Density of NaCl solution (1.003 g / cm ³ ) A: Area of gel layer upper side in the cell ( 28.27 cm ² ) ΔP: Hydrostatic pressure applied to the gel layer (4920 dyne / cm)
² ) Moreover, the unit of the SFC value is (10 ⁻⁷ × cm ³ × s × g).
^-1 ). Measurement of the amount of unreacted (remaining) oxetane compound 1.0 g of the super absorbent polymer or water absorbent was dispersed in 100 g of 0.9 wt% physiological saline and stirred for 1 hour, and then the swollen gel was filtered with a filter paper. Then, the amount of unreacted (residual) oxetane compound in the obtained filtrate, that is, the amount of oxetane compound eluted from the superabsorbent resin or water-absorbing agent (p
pm, with respect to superabsorbent resin or water absorbent) was measured by liquid chromatography. The reaction rate of the oxetane compound was calculated from the measured values of the amount of the treated oxetane compound and the amount of the remaining oxetane compound.

(Reference Example 1) Production of Superabsorbent Resin (a) In a reactor formed by attaching a stainless steel double-arm kneader with a jacket having two sigma type blades and an internal volume of 10 liters to a lid, 5500 g of an aqueous solution of sodium acrylate having a neutralization ratio of 75 mol% (monomer concentration: 39% by weight) was added to polyethylene glycol diacrylate (n =
9) 7.70 g was dissolved to obtain a reaction solution. Next, this reaction liquid was degassed for 30 minutes under a nitrogen gas atmosphere. Subsequently, 2.9 g of ammonium persulfate and 4.3 g of a 1 wt% L-ascorbic acid aqueous solution were added to the reaction solution with stirring, and polymerization started after about 1 minute. Then, polymerization was carried out at 20 to 90 ° C. while pulverizing the produced gel, and 35 minutes after the polymerization was started, the hydrogel crosslinked polymer (1) was taken out. The obtained hydrogel crosslinked polymer (1) was subdivided into particles having a diameter of about 10 mm or less. The hydrated gel-like crosslinked polymer (1) that had been subdivided was spread on a wire net having an opening of 300 μm, and dried with hot air at 175 ° C. for 60 minutes. Then, it was pulverized using a roll mill and further classified by a JIS vibrating screen having openings of 850 μm and 106 μm to obtain a highly water-absorbent resin (A). The soluble content of the obtained super absorbent polymer (A) was 10% by weight, the water content was 5% by weight, and the weight average particle diameter (D50) was 470 μm.
Met. (Examples 1 and 2) ... Use of compound (c) showing acidity in water / second cross-linking agent (d) To 500 g of superabsorbent resin (A) obtained in Reference Example 1, 3-ethyl was used. -3-Oxetane methanol 2.0 g,
Ion-exchanged water 30.0g, aluminum sulfate 14-1
Water is absorbed by spray-mixing a surface treatment agent consisting of a mixture of 2.5 g of octahydrate with a rotary mixer and then heating it for 25 minutes using a reaction vessel with a stirrer whose jacket temperature is set to 212 ° C. The agent (1) was obtained. Similarly, 35
A water absorbing agent (2) was obtained by heating for a minute. The physical properties of the resulting water absorbing agents (1) and (2) are shown in Table 1.

(Examples 3 and 4) Use of compound (c) showing acidity in water Example 1 except that 2.5 g of aluminum sulfate · 14-18 hydrate was changed to 2.5 g of 50% by weight sulfuric acid aqueous solution. A water absorbing agent (3) was obtained by heating for 25 minutes in the same manner as in 2. In addition, a water absorbing agent (4) was obtained by heating in the same manner for 35 minutes. Table 1 shows the physical properties of the obtained water absorbing agents (3) and (4).

(Examples 5 and 6) ... Use of compound (c) showing acidity in water / compound (e) having hydroxyl group except that 2.5 g of aluminum sulfate · 14-18 hydrate was changed to 2.5 g of lactic acid In the same manner as in Examples 1 and 2, the water absorbent (5) was obtained by heating for 25 minutes. In addition, a water absorbing agent (6) was obtained by similarly heating for 35 minutes. Table 1 shows the physical properties of the obtained water absorbing agents (5) and (6).

(Examples 7 and 8) Second cross-linking agent (d) /
Use of Compound (e) Having Hydroxyl Group To 500 g of the super absorbent polymer (A) obtained in Reference Example 1, 1.5 g of 3-ethyl-3-oxetane methanol,
Ion-exchanged water 16.5 g, 1,4-butanejil 1.9
After spray-mixing a surface treatment agent consisting of a mixed solution of 3.0 g of 1,2 propanediol with a rotary mixer, heating for 25 minutes using a reaction vessel with a stirrer whose jacket temperature is set to 212 ° C. By doing so, a water absorbing agent (7) was obtained. Similarly, by heating for 35 minutes in the same manner, the water absorbing agent (8)
Got The physical properties of the resulting water absorbing agents (7) and (8) are shown in Table 1. The amount of unreacted residual oxetane compound (reaction rate of oxetane compound) in the obtained water-absorbing agents (7) and (8) was 80 ppm (97%) and 40 ppm (9%), respectively.
9%).

(Comparative Example 1) Physical Properties of Super Water Absorbent Resin (A) The physical properties of the super water absorbent resin (A) obtained in Reference Example 1 are shown in Table 1 as a comparative water absorbent (1).

(Comparative Examples 2 and 3) ... (c) to (d) None In Examples 1 and 2, aluminum sulfate.14 to 18
Processed without hydrate. That is, to 500 g of the super absorbent polymer (A) obtained in Reference Example 1, 2.0 g of 3-ethyl-3-oxetane methanol and 30.0 g of deionized water.
The comparative water absorbing agent (2) was obtained by spray-mixing the surface-treating agent consisting of the mixed solution of 1. using a rotary mixer and then heating it for 25 minutes using a reaction vessel with a stirrer whose jacket temperature was set to 212 ° C. It was Further, a comparative water absorbing agent (3) was obtained by heating for 35 minutes in the same manner. The physical properties of the obtained comparative water absorbing agents (2) and (3) are shown in Table 1.

[0056]

[Table 1]

Water absorbing agents (1) to (4) described in Examples 1 to 4
Is larger in water absorption capacity under pressure than the comparative water absorption agent (1) described in Comparative Example 1 which is a water-absorbent resin which is not treated with a surface cross-linking agent, and has a good balance between a water absorption capacity under no pressure and a water absorption capacity under pressure. Are better.

Further, the water-absorbing agents (1), (3), (5) and (7) described in Examples 1, 3, 5, and 7 were compared with the comparative water-absorbing agent (2) described in Comparative Example 2. Despite the same heating time, it has an excellent balance of water absorption capacity without load, water absorption capacity under load, and saline flow conductivity. Further, the water absorbing agents (2), (4), (6) described in Examples 2, 4, 6, and 8,
(8) is compared with the comparative water-absorbing agent (3) described in Comparative Example 3,
Even though the heating time is the same, as in the above, it is excellent in the balance of the water absorption capacity without load, the water absorption capacity under load, and the physiological saline flow conductivity. As described above, the water-absorbing agent of the present invention has an excellent balance of water absorption capacity without load, water absorption capacity under load, and saline flow conductivity, and further has good performance with excellent energy efficiency such as heating time. It is a water absorbing agent.

[0059]

EFFECTS OF THE INVENTION By using a specific compound and an additive as a cross-linking agent for a water-absorbent resin, a water-absorbing agent having excellent absorption characteristics such as a balance between water absorption capacity without load and water absorption capacity under load and having excellent safety can be used at low temperature. I was able to find a way to manufacture in a short time.

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Claims (11)

[Claims] 1. A method for producing a water-absorbing agent containing a superabsorbent resin having a crosslinked structure as a main component, which comprises a superabsorbent resin (a).
On the other hand, a method for producing a water-absorbing agent, which comprises mixing an oxetane compound (b) and a water-soluble additive (c) showing acidity in water. 2. A method for producing a water absorbing agent containing a superabsorbent resin having a crosslinked structure as a main component, the superabsorbent resin (a).
On the other hand, a method for producing a water-absorbing agent, which comprises mixing the oxetane compound (b) and the second cross-linking agent (d) having a different structure from the oxetane compound. 3. A method for producing a water-absorbing agent containing a superabsorbent resin having a crosslinked structure as a main component, which comprises the superabsorbent resin (a).
On the other hand, a method for producing a water absorbing agent, which comprises mixing an oxetane compound (b) and a compound (e) having at least one hydroxyl group different from the oxetane compound. 4. The water-soluble additive (c) has a solubility of water 10
The production method according to claim 1, which is 0.1 g or more relative to 0 g and has a pH in water of 5 or less. 5. The water absorbing agent according to claim 1, wherein the water-soluble additive (c) is at least one selected from an inorganic acid, an organic acid, and an acid salt of a polyvalent acid. Production method. 6. The method according to claim 2, wherein the second crosslinking agent (d) is a polyvalent metal salt and / or a polyhydric alcohol. 7. The method for producing a water absorbing agent according to claim 1, wherein the oxetane compound (b) is an oxetane compound represented by the following structural formula (1). [Chemical 1] (In the formula, R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are independently a hydrogen atom, a hydroxyl group, an alkyl group, an alkenyl group, an aromatic group, a halogen group, a substituted alkyl group, a substituted alkenyl group or a substituted group. Represents an aromatic group.) 8. A compound having an oxetane compound (b), the water-soluble additive (c), the second crosslinking agent (d) and the at least one hydroxyl group with respect to the super absorbent resin (a). The method for producing a water absorbent according to any one of claims 1 to 3, wherein after mixing one or more compounds selected from (e), heat treatment is further performed at 100 to 230 ° C. 9. A water absorbing agent, which is produced by the method according to any one of claims 1 to 8. 10. A non-reacted oxetane compound which is obtained by treating a superabsorbent resin with an oxetane compound, and which comprises a superabsorbent resin having a crosslinked structure as a main component and which remains in the adsorbent. Is 100 ppm or less and / or the reaction rate of the oxetane compound is 80% or more. 11. A sanitary material for absorbing feces, urine or blood, which comprises the water absorbing agent according to claim 9 or 10.