JP2000026738A - Highly water-absorbing resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition causing no degradation of the highly water-absorbing resin even in e.g. an aqueous solution containing radical- generating matter such as L-ascorbic acid and transition metal ion(s) such as iron ion despite being high in water absorption by including a highly water- absorbing resin, a specific metal compound such as of titanium, and a chelate compound. SOLUTION: This composition is obtained by including (A) a highly water- absorbing resin, (B) a metal compound containing Ti and/or Zr, pref. a polyvalent metal salt composed of a hydroxy acid (salt) and Ti and/or Zr (mixed with alkoxide(s) of Ti and/or Zr), and (C) a chelate compound (pref. a water-soluble inorganic phosphorus-based compound, aminocarboxylic acid-based compound, organophosphorus-based compound, surfactant-based compound, or the like); alternatively, by including the component A and (D) a compound with the component C coordinated on the above metal(s).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a superabsorbent resin composition.

[0002]

2. Description of the Related Art In the field of hygiene products, superabsorbent resins are used in absorbent articles such as disposable diapers (disposable diapers) for infants, adults or incontinent persons or sanitary napkins for women. It is used as a water-absorbing substance in articles. The water-soluble polymer (crosslinked product) constituting the superabsorbent resin has a molecular weight that decreases with time and deteriorates in the presence of radicals such as hydrogen peroxide and L-ascorbic acid or a salt thereof. It is known that there is a problem. In particular, when the superabsorbent resin is used in absorbent articles such as disposable diapers and sanitary napkins, urine, menstrual blood, sweat, and other body fluids also contain L-ascorbic acid or salts thereof. The superabsorbent resin in the disposable diaper or sanitary napkin that has absorbed the water decomposes and degrades over time due to radical species generated from L-ascorbic acid or a salt thereof. Is a particularly serious problem.

[0003] The decomposition reaction of a water-soluble polymer by the above-mentioned radical-generating species is in a state of absorbing an aqueous liquid or a bodily fluid such as urine, blood or sweat (hereinafter referred to as a "water-containing state").
Under the air atmosphere, especially in the presence of iron or copper.
This is remarkable under a water-containing state in which a transition metal ion capable of taking an oxidation number of more than one species coexists.

[0004] Techniques for suppressing the decomposition and deterioration of the superabsorbent resin include: 1) sealing the superabsorbent resin under reduced pressure or under a nitrogen atmosphere to prevent contact with air (particularly oxygen); Avoid, 2) Use highly purified water and raw materials to prevent metal ions from being mixed into the superabsorbent resin. 3) Add antioxidant or reducing agent to the superabsorbent resin. 4) adding a protein or enzyme to the superabsorbent resin; 5) adding citric acid, (poly) phosphoric acid or a salt thereof, ethylenediaminetetraacetic acid (EDTA) or a salt thereof to the superabsorbent resin, A method of adding a metal chelating agent is known. However, the above methods 1) and 2) are often impossible in practice depending on the purpose of use of the superabsorbent resin. In addition, the method of adding an existing additive as described in 3), 4) and 5) suppresses the decomposition and deterioration of the superabsorbent resin, but the effect is not always sufficient. In order to achieve the effect, it is often necessary to add the above-mentioned additive in a large amount, or to use an additive having a very strong effect. Under such circumstances, there is a problem that the original physical properties and functions of the superabsorbent resin are significantly impaired. According to the study of the present inventors, E
When DTA or sodium tripolyphosphate is used, it is highly effective in stabilizing the superabsorbent resin in the presence of water or an aqueous solution containing hydrogen peroxide, a radical generating species such as L-ascorbic acid or a salt thereof, or water. It became clear that there was none.

[0005] In addition to the above-mentioned stability over time in a water-containing state (stability over time of the gel), the performance of the superabsorbent resin is not limited to water absorption capacity (water absorption), water absorption rate, and gel strength after swelling. Physical properties such as liquid permeability are important. However, these physical properties are often performances that conflict with each other,
It is very difficult to balance them, and this is one of the issues in developing a superabsorbent resin. For example, generally, there is a problem that, when an attempt is made to increase the water absorption capacity, the gel strength after swelling, the liquid permeability, etc., decrease.

In order to improve these problems, for example,
JP-A-62-36411 discloses a method of grafting a superabsorbent resin containing a carboxyl group and / or a carboxylate group with a silane coupling agent, and JP-A-6-306118. A method of treating with alkoxytitanium has been proposed. However, even these methods were insufficient to achieve both high water absorption performance such as water absorption capacity and stability over time of the gel after swelling.

As one method for simultaneously improving the gel strength after water absorption, the gel stability, and the tackiness of the gel surface, Japanese Patent Application Laid-Open No. Hei 7-145326 discloses a method in which titanium, zirconium and vanadium are used as superabsorbent polymers. A method of adding a polyvalent metal sulfate of a selected metal is disclosed. However, even with this method, the present inventors consider that, especially in a polymer having a high water absorption, not only the stability with time of the gel is insufficient, but also the addition of a polyvalent metal sulfate, In some cases, the initial water absorption rate of the superabsorbent polymer may decrease, or the polymer particles before water absorption may easily aggregate due to the hygroscopicity of the polyvalent metal sulfate.

Accordingly, an object of the present invention is to provide a high water absorption,
In addition, even in the presence of an aqueous solution or water in which a radical-generating species such as L-ascorbic acid or a salt thereof and a transition metal ion such as iron or copper are present, a highly water-absorbent resin is stably present without decomposition and deterioration. It is to provide a water-absorbing resin composition.

[0009]

The present invention provides a superabsorbent resin composition containing the following components (A), (B) and (C) or the following components (A) and (D). (A); superabsorbent resin. (B): a metal compound containing one or two metals (a) selected from the group consisting of titanium and zirconium. (C); a chelate compound. (D): a compound in which the component (C) is coordinated with the metal (a).

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the superabsorbent resin composition of the present invention will be described in detail. The superabsorbent resin which is the component (A) used in the present invention is not particularly limited, and examples thereof include a crosslinked polyacrylate and a poly (vinyl alcohol / acrylate) copolymer (crosslinked). ), Starch-acrylate graft copolymer (cross-linked)
And partially cross-linked polymers such as polyvinyl alcohol-polymaleic anhydride graft copolymers (cross-linked products) having a carboxyl group or a salt thereof, and partially cross-linked polysaccharides such as carboxymethyl cellulose salts. No. Among them, from the viewpoint of water absorption performance, it is preferable to use a crosslinked polyacrylate or a starch-acrylate graft copolymer (crosslinked product), and it is most preferable to use a crosslinked polyacrylate. The above superabsorbent resins may be used alone or in combination of two or more.

The “salt” constituting the various superabsorbent resins exemplified as the above superabsorbent resin includes, for example,
Alkali metal salts (sodium salt, potassium salt, lithium salt, etc.), alkaline earth metal salts (calcium salt, magnesium salt, barium salt, etc.), ammonium salts (quaternary ammonium salt, quaternary alkyl ammonium salt, etc.), etc. Is mentioned. Here, the degree of neutralization of the superabsorbent resin is preferably 0.01 to 100%, more preferably 1 to 99%, and particularly preferably 40 to 100, based on the number of moles of acid groups in the superabsorbent resin. ~ 95%. In the present invention,
The term “degree of neutralization” refers to the ratio (based on moles) of the acid groups in the superabsorbent resin that constitute the salt, that is, (moles of the acid groups constituting the salt) / ( The total number of moles of free acid groups that can form a salt and acid groups that form a salt) × 10
It means 0 (%).

The metal compound as the component (B) used in the present invention contains one or two metals (a) selected from the group consisting of titanium and zirconium.

Preferred examples of the metal compound as the component (B) include the following compounds (B-1) to (B-6). (B-1) a hydroxyacid or a salt thereof, and a polyvalent metal salt composed of one or two metals (a) selected from the group consisting of titanium and zirconium, or an alkoxide of the metal (a) Compound obtained by mixing. (B-2) In the presence of a hydroxy acid or a salt thereof, a polyvalent metal salt composed of one or two metals (a) selected from the group consisting of titanium and zirconium, or a polyvalent metal salt of the metal (a) A compound obtained by hydrolyzing an alkoxide. (B-3) Titanium dioxide. (B-4) One or two metals selected from the group consisting of titanium and zirconium (A) and one or two or more metals selected from the group consisting of zinc, aluminum, calcium, magnesium and silicon Metal hydrate containing metal (b). (B-5) Alkoxy titanium. (B-6) Sulfur oxides of one or two metals (a) selected from the group consisting of titanium and zirconium.

The compounds (B-1) to (B-
6) will be described sequentially in detail. The compound (B-
1) is, as described above, a polyvalent metal salt composed of a hydroxy acid or a salt thereof and one or two kinds of metals (a) selected from the group consisting of titanium and zirconium, or a polyvalent metal salt of the metal (a). It is obtained by mixing with an alkoxide.

Here, the above-mentioned hydroxy acid is a compound having both a hydroxyl group and a carboxyl group in the molecule, and there is no particular limitation on its type, but a preferred example is an α-hydroxy acid. Further, as described later, the compound (B-1) is hydrolyzed to give the compound (B-1).
When it is desired to obtain -2), it is desired that the product after the hydrolysis is water-soluble. Therefore, the above-mentioned hydroxy acid is preferably a water-soluble hydroxy acid, and more preferably a water-soluble α. -Hydroxy acids are preferred. Examples of the α-hydroxy acid include gluconic acid, citric acid, isocitric acid, alloisocitric acid, lactic acid, hydroxyacetic acid, malic acid, tartaric acid and the like, among which gluconic acid and citric acid are preferably used. Examples of the salts of the hydroxy acids include alkali metal salts of hydroxy acids (such as sodium, potassium, and lithium salts), alkaline earth metal salts (such as calcium, magnesium, and barium).
And ammonium salts (quaternary ammonium salts, quaternary alkyl ammonium salts, etc.). These hydroxy acids or salts thereof are used alone or in combination of two or more.

As described above, the metal (a) is one or two selected from the group consisting of titanium and zirconium. That is, titanium and zirconium may be used alone, respectively, or these two types may be used simultaneously. Particularly, titanium is preferable as the metal (a) from the viewpoint of further improving the effect and economical aspect.

Examples of the polyvalent metal salt composed of the above-mentioned metal (a) are not particularly limited, and include, for example, sulfate, oxysulfate, chloride, oxychloride, nitrate, and the like of the metal (a).
Examples thereof include oxynitrate and carboxylate, and among them, sulfate, oxysulfate, chloride, and oxychloride, particularly, sulfate and chloride are preferably used. Examples of the metal (a) alkoxide include metal (a) tetraisopropoxide and tetrabutoxide.

When mixing the above-mentioned hydroxy acid or its salt with the above-mentioned polyvalent metal salt or alkoxide, it is preferable to carry out as an aqueous solution or an alcohol solution. In particular, when the polyvalent metal salt is used, it is more preferable to mix as an aqueous solution, and when the alkoxide is used, it is more preferable to mix as an alcohol solution. As described above, by mixing as an aqueous solution or an alcohol solution, a compound having more excellent effects can be obtained.

The amount of the hydroxy acid or a salt thereof used is as follows:
The molar amount is preferably at least twice the amount of the metal (a) in the polyvalent metal salt or alkoxide. The amount used is 2
If the molar ratio is less than twice, the system (mixed solution) may be non-uniform, which is not preferable in terms of effects and handling.

As described above, not only is the above-mentioned hydroxy acid or its salt and the above-mentioned polyvalent metal salt or alkoxide mixed, but also in the presence of the above-mentioned hydroxy acid or its salt,
Hydrolysis of the above polyvalent metal salt or alkoxide is preferable because a metal compound having more excellent effects can be obtained.

The compound (B-2) is a polyvalent metal salt composed of one or two metals (a) selected from the group consisting of titanium and zirconium in the presence of a hydroxy acid or a salt thereof. Or a compound obtained by hydrolyzing the alkoxide of the metal (a). That is,
The compound (B-2) can be obtained by hydrolyzing the compound (B-1). Therefore, what is not particularly described below [the compound used to obtain the compound (B-2) and the amount thereof used] is the same as that described in the section of the compound (B-1).

The hydrolysis method is not particularly limited, and includes various methods. For example, there is a method in which a base such as sodium hydroxide, potassium hydroxide, ammonia, or an amine is added, and heating is performed as necessary. Here, an example of the conditions of this hydrolysis is shown below. That is, the amount of the base to be added is preferably 2 to 4 times the molar amount of the metal (a), and the heating temperature when heating is preferably 6 times.
0-100 ° C., the reaction time of the hydrolysis is preferably 20-60 minutes, and the amount of water (preferably ion-exchanged water) used is preferably 100 parts by weight of the polyvalent metal salt or alkoxide. 100 to 1000 parts by weight.

The product after hydrolysis (containing the compound (B-2)) is preferably water-soluble. If the water solubility of the product is low and the insoluble content is high, the effect and handling properties are deteriorated, which is not preferable.

The obtained compound (B-1) or compound (B-2) is not particularly limited in its use form, but preferably, in the case of compound (B-1), an aqueous solution or In the case of the compound (B-2), a solution of the product obtained by the above-mentioned hydrolysis remains as a solution of the metal compound as a metal compound solution. Used in the preparation of the superabsorbent resin composition. The content of the metal (a) in the metal compound solution is preferably 0.05 to 5% by weight,
More preferably, it is 2% by weight.

The titanium dioxide as the compound (B-3) is not particularly limited, but has an average particle size of 0.1 μm.
m, preferably 0.05 μm or less, more preferably 0.03 μm or less, and a specific surface area (hereinafter, referred to as “BET specific surface area”) measured by the Brunauer-Emmett-Taylor method of 50 m ² / g or more, preferably 100 m ² or more.
² / g or more, still more preferably used titanium dioxide is 200 meters ² / g or more. Further, the crystal form of the titanium dioxide is not particularly limited, but an anatase type is more preferable than a rutile type because the effect of the present invention can be more exhibited.

As described above, the compound (B-4) is a compound selected from the group consisting of titanium and zirconium.
It is a metal hydrate oxide containing one or two kinds of metals (a) and one or more kinds of metals (b) selected from the group consisting of zinc, aluminum, calcium, magnesium and silicon. The form of the metal hydrate is not particularly limited, but is preferably in the form of a fine powder composed of an aggregate of the metal hydrate. In the present specification, the “hydrated oxide” is also called a hydrated oxide, and refers to a hydrate of a metal oxide containing a so-called hydroxide.

The metal hydrate as the compound (B-4) has a bond of -M ¹ -OM ² -when the metal (a) is M ¹ and the metal (b) is M ^2. , At least in part, the hydrated oxide of M ¹ and M ²
With a hydrated oxide alone.

The metal (a) and the metal (b) exert the effects of the present invention when used in any combination. However, from the viewpoint of further improving the effects and economical aspects, the metal (a) is used.
It is preferable to use titanium, and to use zinc or aluminum, particularly zinc, as the metal (b). That is, a combination of titanium and zinc or titanium and aluminum is preferable.

The molar ratio between the content of the metal (a) and the content of the metal (b) in the metal hydrate is preferably 30/70 to 99/1, more preferably 40/70 to 99/1. 60 to 90/10. If the molar ratio is outside the above range, the effect of using the metal (a) in combination with the metal (b) may be reduced.

The crystal structure of the metal hydrated oxide (crystal structure determined by X-ray diffraction or the like) suppresses the decomposition and deterioration of the superabsorbent resin even when the superabsorbent resin is in a hydrated state absorbing body fluid. It is preferable that the resin is amorphous in view of the fact that the superabsorbent resin can be stable with time.

The above-mentioned metal hydrate can be obtained by various methods such as a liquid phase method, a gas phase method and a solid phase method. However, from the viewpoint of equipment and production cost, it is preferable to obtain the metal hydrate by a liquid phase method. Preferably, it is obtained by a coprecipitation method.
Generally, the above-mentioned "coprecipitation method" refers to a method of simultaneously precipitating two or more ions. In the present invention, by changing the concentration, pH, temperature, solvent, etc. of the mixed solution containing two or more ions by the above-mentioned coprecipitation method, specifically, two or more kinds of ions are mixed. This is a method in which ions are simultaneously coprecipitated to obtain a coprecipitate having a predetermined composition, and the coprecipitate is obtained by separating and drying. Therefore, for each metal,
This is different from a method in which precipitates are individually formed, the precipitates are separated, and then the powders obtained by drying are simply mixed.

When the above-mentioned metal hydrate is obtained by the above-mentioned coprecipitation method, the method of causing coprecipitation is as follows.
Various methods are not particularly limited, and examples thereof include a method of adding animonia water or urea to a mixed solution containing the salt of the metal (a) and the salt of the metal (b), and heating as necessary. Is mentioned.

Here, examples of the salt of the metal (a) and the salt of the metal (b) are not particularly limited, and for example, sulfates and oxysulfates of the metals (a) and (b), respectively. Salt, chloride, oxychloride, nitrate, oxynitrate,
Carboxylates and the like can be mentioned, and among them, sulfates, oxysulfates, chlorides and oxychlorides are preferably used.

As a method of causing the above-mentioned co-precipitation, in addition to the above-mentioned method using a salt as a raw material, the above-mentioned metal (a)
A method in which a co-precipitation is caused by simultaneous hydrolysis from a mixed solution containing the alkoxide of the above (a) and the alkoxide of the above metal (b) is also suitably used. Here, examples of the salt of the metal (a) and the alkoxide of the metal (b) are not particularly limited. For example, methoxide, ethoxide, propoxide, butoxide of each of the metals (a) and (b) And the like.

The precipitation conditions for the coprecipitation are important because they affect the precipitation rate, the shape of the coprecipitate, etc., but the starting materials, the composition and concentration of the mixed solution, and The precipitation conditions vary depending on the type, the method of causing precipitation, and the like.

The coprecipitate formed by the above coprecipitation is filtered, washed, and dried. At this time, the drying temperature is preferably relatively low, for example, 100 ° C to 200 ° C. When the drying temperature exceeds 600 ° C.,
The stability over time of the superabsorbent resin decreases.

It is desirable that the above-mentioned metal hydrate has a large specific surface area, and the BET specific surface area is 100 m ² / g or more, particularly 200 m ² / g, from the viewpoint of the stability over time of the superabsorbent resin. It is preferable that it is above.

The alkoxytitanium compound (B-5) may be any organic titanium compound containing a reactive alkoxy group. Examples thereof include tetramethoxytitanium, tetraethoxytitanium and tetraisopropoxy. Titanium, tetrabutoxytitanium, tetrastearyloxytitanium, tetrakis (2-ethylhexyloxy) titanium, tetraisopropoxytitanium polymer, tetrabutoxytitanium polymer, diisopropoxybis (acetylacetonato) titanium, dibutoxybis (triethanolaminato) titanium , Tributoxytitanium stearate, diisopropoxytitanium distearate and the like.

Examples of the sulfates of one or two metals (a) selected from the group consisting of titanium and zirconium, which are the compounds (B-6), include, for example, titanium sulfate, titanyl sulfate, sulfate Zirconium and the like can be mentioned.

The content of the metal (a) in the metal compound as the component (B) is preferably 0.001 to 1 part by weight based on 100 parts by weight of the superabsorbent resin as the component (A). , More preferably 0.005 to 0.5 part by weight, and even more preferably 0.01 to 0.1 part by weight. When the content is less than 0.001 part by weight, the stability of the gel is insufficient, and when the content exceeds 1 part by weight, the effect is not much improved. Therefore, the content is preferably within the above range. In the present invention, the “highly water-absorbent resin” used as a standard for the content refers to a dry state in which all water is not absorbed.

As the chelate compound which is the component (C) used in the present invention, a compound having a metal chelating ability and having a bidentate or higher ligand capable of binding to a metal ion to form a metal chelate is exemplified. Can be However, as the metal compound [component (B)], the compound (B-1) or (B
When -2) is used, the hydroxy acid or a salt thereof does not belong to the chelate compound [component (C)].

Specific examples of the chelate compound as the component (C) include, for example, tripolyphosphoric acid, tetrapolyphosphoric acid, pentapolyphosphoric acid, pyrophosphoric acid, metaphosphoric acid, polyphosphoric acid, and salts thereof (Na and K salts). Water-soluble inorganic phosphoric acid compound, ethylenediaminetetraacetic acid, 1,3-
Propanediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, L-glutamic acid diacetate, N, N-bis (carboxymethyl) -L-glutamic acid, hydroxyethylethylenediaminetriacetic acid or salts thereof (Na, K, ammonium) Salts), polycarboxylic compounds such as glycol and glycerin, ethylenediamine, 1,10-
Amine compounds such as phenanthroline, 2,2'-bipyridine and terpyridine, oxalic acid or salts thereof (N
a, K, ammonium salts) and the like.
Aminotri (methylenephosphonic acid), 1-hydroxyethylidene-1,1-diphosphonic acid, ethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid), 2-phosphonobutane-
1,2,4-tricarboxylic acid or a salt thereof (Na,
Organic phosphorus compounds such as K, ammonium salts), tropolone derivative compounds such as tropolone, β-thiaprisin, γ-thiaprisin or salts thereof (Na, K, ammonium salts), monoalkylamide citrate and monoalkenyl citrate And the following general formula (I)
A compound represented by the following general formula (II), such as a compound represented by the formula, monoalkyl citrate and monoalkenyl citrate, and a compound represented by the following formula 3, such as alkylmalonic acid and alkenylmalonic acid Of the general formula (III)
A compound represented by the following general formula (IV) such as N-alkyl-N'-carboxymethylaspartic acid and N-alkenyl-N'-carboxymethylaspartic acid; The following [Chemical Formula 5] such as phosphate ester and monoalkenyl phosphate ester
A compound represented by the following general formula (VI), such as a compound represented by the following general formula (V), N-acylated glutamic acid; and a compound represented by the following [formula 7], such as an N-acylated aspartic acid: A surfactant-based compound such as a compound represented by the general formula (VII),
Examples include, but are not limited to, β-diketone-based compounds such as acetylacetone, 4-hydroxy-benzoylacetone, and 4-hydroxy-benzoylmethane-tert-butylketone. Among the above examples, a water-soluble inorganic phosphate compound, an aminocarboxylic acid compound, an organic phosphorus compound, and a surfactant compound can be preferably used. Among them, tripolyphosphoric acid, polyphosphoric acid, ethylenediaminetetraacetic acid, 1-hydroxyethylidene-1,
1-diphosphonic acid, monoalkyl phosphate, 2-
Phosphonobtan-1,2,4-tricarboxylic acid, L-glutamic acid diacetate, N, N-bis (carboxymethyl)
-L-glutamic acid, hydroxyethylethylenediaminetriacetic acid or salts thereof (Na, K, ammonium salts) can be particularly preferably used. Further, as the metal compound [component (B)], the compound (B-
When a metal compound selected from 3), (B-4), (B-5) and (B-6) is used, tartaric acid, gluconic acid, citric acid and the like may be used as the chelate compound [component (C)]. An oxycarboxylic acid compound such as an acid, salicylic acid, or a salt thereof (Na, K, ammonium salt) can be used.

[0043]

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[0044]

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[0045]

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[0046]

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[0047]

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[0048]

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[0049]

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The content of the chelate compound as the component (C) is preferably 0.01 to 5 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the superabsorbent resin as the component (A). It is 0.5 to 2 parts by weight. The above content is 0.0
When the amount is less than 1 part by weight, the stability of the gel is insufficient, and when the amount exceeds 5 parts by weight, the effect is little improved. Here, [Component (C)] / [Metal (A)] is preferably a molar ratio from the viewpoint of stability over time in the presence of water in which radical-generating species such as L-ascorbic acid (salt) dissolve. 0.8 to 10, more preferably 1.5 to 5.

In the present invention, the component (C) may be in a form coordinated to the metal (a). Here, the compound (metal chelate compound) in which the component (C) is coordinated with the metal (a) is referred to as the component (D). The content of the component (D) [relative to the component (A)] is preferably the total of the preferred contents of the metal (a) and the component (C) described above.

The superabsorbent resin composition of the present invention comprises the above superabsorbent resin [component (A)], the above metal compound [component (B)] and the above chelate compound [component (C)], or the above superabsorbent resin. Water may be contained in addition to the water-soluble resin [component (A)] and the metal chelate compound [component (D)]. In this case, the superabsorbent resin may be a water-containing polymer in a state containing water, or the composition of the present invention may be in a state of a water-containing gel. Here, when the superabsorbent resin composition of the present invention contains water, its water content may be any ratio within the range of the saturated water absorption.

Further, the superabsorbent resin composition of the present invention includes:
If necessary, various additives such as a water-soluble organic solvent, a surfactant, salts, inorganic fine particles, a stabilizer, an antioxidant, a reducing agent, and / or a preservative can be added. Is 50% by weight or less based on the superabsorbent resin composition of the present invention.

As a method for producing the superabsorbent resin composition of the present invention, there is a method of mixing the above components (A), (B) and (C). For example, the following methods 1 to 3 and the like can be mentioned. 1. A method in which the metal compound and the chelate compound are added in advance during the production of the superabsorbent resin. For example, when a water-soluble vinyl monomer is used as a monomer of the superabsorbent resin, in the method for producing a superabsorbent resin performed by polymerization of the water-soluble vinyl monomer, the metal compound and the chelate compound are mixed with the water-soluble vinyl monomer. To carry out polymerization. 2. A method in which an aqueous solution of the metal compound and the chelate compound is sprayed on the dried or water-absorbing superabsorbent resin, and dried if necessary. 3. A method in which a dried product of the superabsorbent resin, the metal compound and the chelate compound is mixed in a dry state.

The metal compound and the chelate compound may be mixed before addition to the superabsorbent resin, or may be added separately without mixing. Further, the metal compound and the chelate compound are the same as those in the above-mentioned 1
Or 3 may be added by the same method, or may be added by a different method.

The superabsorbent resin composition of the present invention has a water absorption of 35 g / g or more, particularly no less than 35 g / g, which is measured by the following [method of measuring retention by centrifugal dehydration]. It is preferably at least 38 g / g.

In general, the superabsorbent resin composition contributes to a reduction in the thickness and cost of a disposable diaper because the higher the water absorption, the smaller the amount of resin per disposable diaper when used in a disposable diaper. it can. However, when the water absorption increases, the stability of the gel over time, gel strength,
A resin having a high water absorption is difficult to use for a disposable diaper because the performance such as liquid permeability is reduced. On the other hand, the super-water-absorbent resin composition of the present invention has a relatively high water absorption, in which the holding amount is 35 g / g or more. is there.

As described above, the superabsorbent resin composition of the present invention is particularly useful as a water-absorbing substance in sanitary articles such as absorbent articles such as disposable diapers and sanitary napkins. Such an absorbent article comprises a water-permeable top sheet, a water-impermeable back sheet, and an absorber interposed between the top sheet and the back sheet. As such an absorbent, fluff pulp obtained by pulverizing wood pulp can be used. The superabsorbent resin composition of the present invention is used in combination with the flap pulp, and in this case, it may be used in combination with the fluff pulp, or may be present in a layer only in a specific portion of the fluff pulp. You may. As the above-mentioned absorber, as another embodiment, a heat-treated mixture of a thermoplastic resin, fluff pulp and the superabsorbent resin composition of the present invention can be used.

Further, as described above, L-
Since ascorbic acid or a salt thereof is contained, the superabsorbent resin in the conventionally known superabsorbent resin composition deteriorates due to such a substance in the absorbent article that has absorbed body fluid. On the other hand, when the superabsorbent resin composition of the present invention used as a water absorbent substance in an absorbent article is used, deterioration of the superabsorbent resin is suppressed. In addition, since the superabsorbent resin composition of the present invention has high gel strength and liquid permeability after swelling, it can be preferably used for absorbent articles such as disposable diapers and sanitary napkins.

[0060]

EXAMPLES Unless otherwise specified, "%" in the following Examples and Comparative Examples represents "% by weight".

First, test methods performed in Examples and Comparative Examples are shown below. [Measurement of Retention Amount by Centrifugal Dehydration Method] After swelling 1 g of the superabsorbent resin composition with 150 ml of physiological saline (0.9% NaCl solution, manufactured by Otsuka Pharmaceutical Co., Ltd.) for 30 minutes, put in a nonwoven bag and centrifuged The mixture was dehydrated at 143 G for 10 minutes using a machine, and the total weight (total weight) after dehydration was measured. Then, the retention amount after centrifugal dehydration was measured according to the formula (1) shown in the following [Equation 1].

[0062]

(Equation 1)

[Evaluation Method of Stability of Gel After Swelling with Time] 1 g of the superabsorbent resin composition was swollen with 45 g of physiological saline containing 0.05% of L-ascorbic acid, and sealed in a screw tube. And left at 40 ° C. for 3 hours. The temporal stability of the gel after swelling was evaluated by visually observing the state of the gel after swelling. In addition, the evaluation of the stability over time of the gel after swelling was carried out in four steps based on the criteria shown in the following [Table 1] for the fluidity, spinnability and shape retention of the gel. The fluidity of the gel was observed by tilting the screw tube, the spinnability was observed by stirring the gel with a spatula, and the gel retention was visually observed by taking the gel out of the screw tube. If it has fluidity and spinnability, it means that the superabsorbent resin is decomposed, and if the shape retention property is reduced, it means that the superabsorbent resin is decomposed. In this evaluation, when the evaluation is ◎ or ○, it indicates that it is suitable as a water-absorbing substance used for sanitary napkins, disposable diapers, adult sheets, tampons, sanitary cotton and the like.

[0064]

[Table 1]

Next, examples of synthesizing the superabsorbent resin, metal compound and metal chelate compound used in Examples and Comparative Examples will be described. The metal compound and the metal chelate compound were all prepared as solutions thereof.

Synthesis Example 1 [Synthesis of superabsorbent resin] Cyclohexane was placed in a 1000 mL (“L” represents a unit liter) four-necked flask equipped with a stirrer, a reflux condenser, a dropping funnel and a nitrogen gas inlet tube. 400 mL and 0.625 g (0.5%) of ethyl cellulose as a dispersant (manufactured by Hercules, trade name ethyl cellulose N-100)
The polymer was added to the reaction mixture, nitrogen gas was blown in to expel dissolved oxygen, and the temperature was raised to 75 ° C. In another flask, 102.0 g of acrylic acid was diluted with 25.5 g of ion-exchanged water and cooled from the outside,
Neutralized with 140 g of a 30% aqueous sodium hydroxide solution. Next, 0.204 g of potassium persulfate (0.2% with respect to acrylic acid) dissolved in 7.5 g of water was added and dissolved, and nitrogen gas was blown thereinto to remove oxygen remaining in the aqueous solution. The contents of the flask were added dropwise to the four-necked flask over 1 hour to polymerize. After completion of the polymerization, azeotropic dehydration was performed using a dehydration tube, and the water content of the superabsorbent resin was adjusted to 30 parts by weight based on 100 parts by weight of the superabsorbent resin. Then, as a crosslinking agent, polyglycerol polyglycidyl ether (trade name Denacol EX manufactured by Nagase Kasei Kogyo Co., Ltd.)
-512) A solution prepared by dissolving 0.04 g (0.04% of acrylic acid) in 4 g of water was added and reacted at 75 to 80 ° C for 1 hour. After cooling, cyclohexane was removed by decantation to obtain a highly water-absorbent resin (hydrated product). This is referred to as a superabsorbent resin. In addition, a highly water-absorbing resin,
It was dried at 100 ° C. under a reduced pressure of 50 Torr. This is referred to as a superabsorbent resin.

Synthesis Example 2 [Synthesis of superabsorbent resin] 1.5 g of a 25% aqueous solution of sodium salt of polyoxyethylene lauryl ether sulfate (average ethylene oxide addition mole = 2) was used as a dispersant instead of ethyl cellulose. 0.04 g to 0.06 g of polyglycerol polyglycidyl ether (trade name: Denacol EX-512, manufactured by Nagase Kasei Kogyo Co., Ltd.) as a crosslinking agent
Except that the amount was increased, a superabsorbent resin (hydrate) was obtained in the same manner as in Synthesis Example 1. This is referred to as a superabsorbent resin. Further, the superabsorbent resin is further subjected to 50 To at 80 to 100 ° C.
It was dried under reduced pressure with heating at rr. This is referred to as a superabsorbent resin.

Synthesis Example 3 [Synthesis of Metal Compound] Ice-cooled 43.6 g of sodium gluconate and 150 g
20 g of titanium tetrachloride was added dropwise to a solution consisting of After confirming that the solution became transparent, about 48 g of a 30% aqueous sodium hydroxide solution was added dropwise to adjust the pH of the solution to 7. The resulting solution was slightly yellow and transparent. The titanium content in this solution was 1.9% (calculated value).

Synthesis Example 4 [Synthesis of Metal Compound] 50 g of titanyl sulfate solution having a titanium content of 4.9% [trade name "Titanyl sulfate solution" manufactured by Rare Metals, Ltd.]
2.2 g of citric acid-hydrate and 25 g of ion-exchanged water were added and mixed. After confirming that the citric acid was completely dissolved, about 104 g of a 30% aqueous sodium hydroxide solution was added dropwise while cooling from the outside, and the pH of the solution was adjusted to 7. The resulting solution was a slightly turbid yellow solution. The titanium content in this solution was 1.2% (calculated value).

Synthesis Example 5 [Synthesis of Metal Compound] A solution of 23.3 g of titanium tetrachloride (TiCl ₄ ) in 51 mL of water, and 20 g of zinc chloride (ZnCl ₂ )
Was mixed with 100 mL of water and diluted with water to a total volume of 5 L. To this was added 71.5 g of urea and the solution was stirred. The pH of the solution at this time was 2. When this solution was heated at 95 ° C. for 20 minutes, a white coprecipitate gradually formed. The solution was further heated until the pH was 7. The coprecipitate was filtered and dried at 120 ° C. for 3 hours to obtain a fine powder composed of an aggregate of metal hydrates, which was used as a metal compound. BET of the obtained metal compound
The specific surface area is 250 m ² / g, and the molar ratio between the content of Ti and the content of Zn in the metal compound (Ti: Z
n) was 46:54.

Synthesis Example 6 [Synthesis of metal compound] 34.0 g of zirconium chloride octahydrate and 150 g
43.6 g of sodium gluconate was added to and dissolved in a solution consisting of About 22 g of a 30% aqueous solution of caustic soda was added dropwise thereto, and the pH of the solution was adjusted to 7. The resulting solution was slightly yellow and transparent. The zirconium content in this solution was 3.86% (calculated value).

Synthesis Example 7 [Synthesis of Metal Chelate Compound] 29.3 g of titanyl sulfate solution having a titanium content of 4.9%
And 50% citric acid aqueous solution (made by Fuso Chemical Industry Co., Ltd.)
23.0 g was added and mixed. Furthermore, a 60% 1-hydroxyethylidene-1,1-diphosphonic acid aqueous solution (trade name "Diequest 2010C" manufactured by Monsanto Japan Limited)
S ") 20.6 g was added, mixed and, while cooling from the outside, 27 g of a 30% aqueous sodium hydroxide solution was added dropwise to adjust the pH of the solution to 7. The resulting solution is a pale yellow solution,
It was slightly cloudy. The titanium content in this solution is 1.5
%, 1-hydroxyethylidene-1,1-diphosphonic acid content was 13.4%. 1.6 g of heavy water was added to 2.4 g of this solution, and ¹³ C-NMR was measured (measuring device;
Varian UNITY INOVA 300WB). As a result, the peak at 1-position carbon atom of 1-hydroxyethylidene-1,1-diphosphonic acid at 72 ppm was split into 68 to 72 ppm, and the peak at 20 ppm of methyl group carbon atom was 18 ppm.
And it was confirmed that the phosphonic acid coordinated to titanium.

[Examples 1 to 10] The superabsorbent resin (A) shown in the following [Table 2] was put into a double-armed kneader, and the kind and the content of the metal (a) shown in the following [Table 2] were added. A certain amount of the metal compound (B) and a chelate compound (C) of the kind and addition amount (100 parts by weight with respect to the resin) shown in the following [Table 2] were added, and the mixture was sufficiently stirred and mixed. Powder was added as it was, or an aqueous solution was added by spraying (see Table 2 below). Here, when a superabsorbent resin or is used, after addition and mixing, at 80 ° C to 100 ° C,
Drying was performed under heating and reduced pressure of 50 Torr to obtain a superabsorbent resin composition. The obtained superabsorbent resin composition was evaluated (the retention amount after centrifugal dehydration and the stability of the swollen gel) according to the above test method. The evaluation results are shown in the following [Table 2]. In the evaluation, particles having a size of 850 μm or more were removed from the composition using a sieve. In the following Example 11 and Comparative Examples 1 to 5, evaluation was performed in the same manner.

Example 11 A super-absorbent resin was placed in a double-armed kneader, and the metal chelate compound (14.9% aqueous solution) obtained in Synthesis Example 7 was added as a component (D) by spraying. In this case, the amount of addition was such that the Ti content was 0.03 parts by weight based on 100 parts by weight of the resin. Thereafter, a superabsorbent resin composition was obtained by the same procedure as in Example 1, and the same evaluation was performed. As a result of the evaluation, the retention amount after centrifugal dehydration was 43 g / g, and the stability of the swollen gel was ◎.

[Comparative Examples 1 and 2] Using the superabsorbent resin (A) shown in [Table 3] below, without adding the metal compound (B) and the chelate compound (C), the superabsorbent resin was used as it was. The resin composition was evaluated (retained amount after centrifugal dehydration and stability of the swollen gel) according to the test method described above. The evaluation results are shown in the following [Table 3].

Comparative Examples 3 to 5 Using the superabsorbent resin (A) shown in Table 3 below, only one of the metal compound (B) and the chelate compound (C) was used in the same manner as in the above example. After adding and mixing in the superabsorbent resin used here,
In the same manner as in the example, at 80 ° C. to 100 ° C., 50 Torr
The resulting superabsorbent resin composition was dried under heating and reduced pressure of r, and the obtained superabsorbent resin composition was evaluated (retained amount after centrifugal dehydration and stability of the swollen gel) according to the test method described above. The evaluation results are shown in the following [Table 3].

* 1 in the following [Table 2] and [Table 3]
* 3 is as follows. * 1: Metal per 100 parts by weight of superabsorbent resin (a)
Content of (Ti or Zr) * 2: Titanium dioxide having an anatase crystal form and a mean particle size of 7 nm and a BET specific surface area of 320 m ² / g, manufactured by Ishihara Sangyo * 3; Diameter 40
nm, titanium dioxide with a BET specific surface area of 40 m ² / g

[0078]

[Table 2]

[0079]

[Table 3]

As apparent from the above results, the superabsorbent resin composition of the present invention containing the above-mentioned components (A), (B) and (C) or the above-mentioned components (A) and (D) It can be seen that Examples 1 to 11) are superior to the composition of Comparative Example in both the amount retained after centrifugal dehydration and the stability of the swollen gel.

[0081]

The superabsorbent resin composition of the present invention has an aqueous solution containing a radical-generating species such as L-ascorbic acid or a salt thereof and a transition metal ion such as iron or copper, despite the high water absorption. Alternatively, even in the presence of moisture, the superabsorbent resin is excellent in stability without decomposing or deteriorating.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 33/02 C08L 33/02 (72) Inventor Isao Tsuru 1334 Minato, Wakayama-shi, Wakayama Pref. (72) Inventor Yoko Hanada 1334 Minato, Wakayama-shi, Wakayama Pref. EP017 EU047 EW127 EZ006 EZ008 GB01 GC00 GD03

Claims (8)

[Claims] 1. A super water-absorbent resin composition containing the following components (A), (B) and (C) or the following components (A) and (D). (A); superabsorbent resin. (B): a metal compound containing one or two metals (a) selected from the group consisting of titanium and zirconium. (C); a chelate compound. (D): a compound in which the component (C) is coordinated with the metal (a). 2. A polyvalent metal in which the metal compound as the component (B) is composed of a hydroxy acid or a salt thereof and one or two metals (a) selected from the group consisting of titanium and zirconium. The superabsorbent resin composition according to claim 1, which is a metal compound obtained by mixing a salt or an alkoxide of the metal (a). 3. The metal compound as the component (B) is composed of one or two metals (a) selected from the group consisting of titanium and zirconium in the presence of a hydroxy acid or a salt thereof. The superabsorbent resin composition according to claim 1, which is a metal compound obtained by hydrolyzing a polyvalent metal salt or an alkoxide of the metal (a). 4. The metal compound as the component (B), wherein the metal compound is one or two metals selected from the group consisting of titanium and zirconium and a group consisting of zinc, aluminum, calcium, magnesium and silicon. 1 selected from
The superabsorbent resin composition according to claim 1, which is a metal hydrated oxide containing one or more kinds of metals (b). 5. The chelating compound as the component (C) is a water-soluble inorganic phosphorus compound, an aminocarboxylic acid compound, an organic phosphorus compound or a surfactant compound. The superabsorbent resin composition according to the above. 6. The chelating compound as the component (C) is tripolyphosphoric acid, polyphosphoric acid, ethylenediaminetetraacetic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, monoalkyl phosphoric acid ester, 2-phosphonobutane-1, It is 2,4-tricarboxylic acid, L-glutamic acid diacetate, N, N-bis (carboxymethyl) -L-glutamic acid, hydroxyethylethylenediamine triacetic acid or a salt thereof. Water-absorbing resin composition. 7. The retention amount after swelling with physiological saline for 30 minutes and centrifugal dehydration is 35 g / g or more.
7. The superabsorbent resin composition according to any one of items 1 to 6. 8. A method for producing a superabsorbent resin composition according to claim 1, wherein the following components (A), (B) and (C) are mixed. (A); superabsorbent resin. (B): a metal compound containing one or two metals (a) selected from the group consisting of titanium and zirconium. (C); a chelate compound.