JP2002241627A - Discoloration-with-time inhibitor for highly water- absorbing resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discoloration-with-time inhibitor for highly water- absorbing resin composition having further high discoloration inhibitory effect, and to provide a method for inhibiting discoloration with time. SOLUTION: This discoloration-with-time inhibitor for highly water-absorbing resin composition consists of a metal compound which is obtained by mixing an organic acid or a salt thereof with polyvalent metal salt (s) or alkoxide (s) of the metal (s); wherein the metal(s) is titanium and/or zirconium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coloring agent for a superabsorbent polymer with time and a method for preventing coloration with time.

[0002]

2. Description of the Related Art In the field of hygiene products, superabsorbent resins are used in absorbent products 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, and in the agricultural and horticultural fields, it is used as a water retention agent, and in the civil engineering business field, it is widely used as a coagulant for sludge, an anti-condensation agent, or a water stopping agent. Have been. It is known that such superabsorbent resins not only decompose and deteriorate over time, but also have a problem of browning or yellowing when stored for a long time under high temperature and high humidity. In particular, when the superabsorbent resin is used in sanitary articles such as disposable diapers and sanitary napkins, there is a problem that its commercial value is significantly reduced. In Japanese Patent No. 3107873, coloring is prevented by adding an organic phosphoric acid compound or a salt thereof.

Accordingly, an object of the present invention is to provide an anti-aging coloring agent and an anti-aging coloring method for a highly water-absorbent resin composition having a higher anti-coloring effect.

[0004]

According to the present invention, there is provided a polyvalent metal salt comprising an organic acid or a salt thereof, and one or two kinds of metals (a) selected from the group consisting of titanium and zirconium. The above object has been achieved by providing an anti-aging coloring agent and an anti-aging coloring method for a superabsorbent resin composition comprising a metal compound obtained by mixing an alkoxide of metal (a).

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The superabsorbent resin composition used in the present invention will be described in detail below. The superabsorbent resin used in the present invention is not particularly limited, and examples thereof include a crosslinked polyacrylate, a poly (vinyl alcohol / acrylate) copolymer (crosslinked product), and a starch-
Partially crosslinked products of polymer compounds having a carboxyl group or a salt thereof, such as acrylate graft copolymers (crosslinked products) and polyvinyl alcohol-polymaleic anhydride graft copolymers (crosslinked products), and carboxymethyl cellulose salt crosslinked products And partially cross-linked polysaccharides such as a carbohydrate. 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 particularly preferable to use a crosslinked polyacrylate. The superabsorbent resins may be used alone or in combination of two or more.

[0006] Examples of the “salt” constituting the various superabsorbent resins exemplified as the above superabsorbent resins include, 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%, 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 anti-aging coloring agent of the present invention is a polyvalent metal salt composed of an organic acid or a salt thereof, and one or two metals (a) selected from the group consisting of titanium and zirconium, or the metal. It is a metal compound obtained by mixing the alkoxide of (a). In this case, the organic acid is preferably a hydroxy acid.

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, in the case of hydrolysis, since it is desired that the product after the hydrolysis becomes water-soluble, the hydroxy acid is preferably a water-soluble hydroxy acid. 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. In particular, titanium is preferable as the metal (a) from the viewpoint of further improving the effect and cost.

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 the metal (a) tetraisopropoxide and tetrabutoxide.

When mixing the above-mentioned organic 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 above polyvalent metal salt is used, it is more preferable to mix as an aqueous solution, and when the above alkoxide is used, it is more preferable to mix as an alcohol solution. Thus, by mixing as an aqueous solution or an alcohol solution, a metal compound having more excellent effects can be obtained.

The amount of the organic acid or salt thereof used is preferably at least twice the molar amount of the metal (a) in the polyvalent metal salt or alkoxide. If the amount is less than 2 times, the system (mixed solution) may be non-uniform,
It is not preferable in terms of effect and handling.

As described above, not only the above-mentioned organic acid or its salt and the above-mentioned polyvalent metal salt or alkoxide are mixed, but also in the presence of the above-mentioned organic acid or its salt, the above-mentioned polyvalent metal salt or alkoxide. Is preferable because a metal compound having a further excellent effect can be obtained.

When performing the above-mentioned hydrolysis, the method of the hydrolysis is not particularly limited, and various methods can be mentioned. 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 added is preferably 2 to 4 times the molar amount of the metal (a), the heating temperature when heating is preferably 60 to 100 ° C, and the hydrolysis reaction time is preferably 20 to 60 minutes, and the amount of water (preferably ion-exchanged water) used is preferably 100 parts by weight based on 100 parts by weight of the polyvalent metal salt or alkoxide.
１０００1000 parts by weight.

In performing the above-mentioned hydrolysis, it is desirable that the metal compound as a product after the hydrolysis is 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.

Although the obtained metal compound is not particularly limited in its use form, it is preferably in the form of a solution obtained when mixed as an aqueous solution or an alcohol solution (when performing the above-mentioned hydrolysis, The product obtained by the hydrolysis is used as a solution), and used as a metal compound solution in the preparation of the superabsorbent resin composition described later. The content of the metal (a) in the metal compound solution is preferably 0.05 to 5% by weight, and more preferably 0.2 to 2% by weight.

The content of the metal (a) in the metal compound is preferably 0.00
It is 1 to 1 part by weight, more preferably 0.005 to 0.5 part by weight, and most 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 little improved, so that 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.

The superabsorbent resin composition according to the present invention may contain water in addition to the superabsorbent resin and the metal compound. In this case, the superabsorbent resin may be a water-containing polymer containing water, or may be a water-containing gel.

The superabsorbent resin composition according to the present invention may contain, if necessary, a water-soluble organic solvent, a surfactant, salts, inorganic fine particles, a stabilizer, a chelating agent, an antioxidant, a reducing agent, And / or various additives such as preservatives can be added, but the amount of water and these additives is 50% by weight or less in the superabsorbent resin composition.

The superabsorbent resin composition of the present invention can prevent coloration with time by adding one or two metals selected from the group consisting of an organic acid or a salt thereof, and titanium and zirconium to the superabsorbent resin composition. The method is carried out by adding a metal compound obtained by mixing the polyvalent metal salt constituted by (a) or the alkoxide of the metal (a). Specifically, for example, the following methods 1 to 3 and the like can be mentioned.

1. A method in which a coloring inhibitor comprising the metal compound is 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 super-water-absorbent resin, in the method for producing a super-water-absorbent resin performed by polymerization of the water-soluble vinyl monomer, the metal compound is present in the water-soluble vinyl monomer to perform polymerization. Method. 2. A method of spraying an aqueous solution of a coloring inhibitor comprising the metal compound onto the dried or water-containing superabsorbent resin and, if necessary, drying. 3. A method in which a dried product of the coloring agent comprising the superabsorbent resin and the metal compound is mixed in a dry state.

The superabsorbent resin composition according to the present invention has a water absorption of 35 g / g, which is measured by a centrifugal dehydration method described below, although the water absorption is not particularly limited.
Above, it is particularly preferable that it is 38 g / g or more.

There is no particular limitation on the method in which the coloring inhibitor made of the metal compound is added in advance during the production of the superabsorbent resin, and the metal compound is added during the polymerization of the water-soluble vinyl monomer. I just need.
In addition, the metal compound can be added as a metal compound solution, if necessary, by dissolving it in a suitable solvent or in the form of a solution at the time of mixing. Specifically, for example, the following production method (I), (ii) or (iii).

(I) A method for producing a super water-absorbent resin composition comprising the following steps: Step: A hydroxy acid or a salt thereof and a polyvalent metal salt composed of one or two kinds of metals (a) selected from the group consisting of titanium and zirconium or an alkoxide of the metal (a) in a liquid medium Mixing to obtain the mixture. Step: a step of mixing the water-soluble vinyl monomer with the mixture obtained in the above step. Step: a step of polymerizing a water-soluble vinyl monomer to obtain a polymer thereof, followed by drying to obtain a superabsorbent resin composition.

(Ii) A method for producing a super water-absorbent resin composition comprising the following steps: Step: A hydroxy acid or a salt thereof and a polyvalent metal salt composed of one or two kinds of metals (a) selected from the group consisting of titanium and zirconium or an alkoxide of the metal (a) in a liquid medium Mixing to obtain the mixture. Step: While mixing the reaction solution during the polymerization of the water-soluble vinyl monomer with the mixture obtained in the above step, the polymerization of the water-soluble vinyl monomer is continued to obtain a polymer, and then the polymer is dried and superabsorbed. A step of obtaining a resin composition;

(Iii) A method for producing a superabsorbent resin composition comprising the following steps: Step: A hydroxy acid or a salt thereof and a polyvalent metal salt composed of one or two kinds of metals (a) selected from the group consisting of titanium and zirconium or an alkoxide of the metal (a) in a liquid medium Mixing to obtain the mixture. Step: a step of mixing a polymer of a water-soluble vinyl monomer and the mixture obtained in the above step, and drying as necessary to obtain a super water-absorbent resin composition.

As a method for polymerizing the water-soluble vinyl monomer, any method may be adopted, but a method of polymerizing an aqueous solution (preferably, a concentration of 1 to 70% by weight) of the water-soluble vinyl monomer is preferable. Various methods such as a polymerization method, a reversed-phase suspension polymerization method, and a pearl polymerization method can be employed. Above all, from the viewpoint of workability during polymerization and the water absorption performance of the resulting superabsorbent resin, an aqueous solution polymerization method or a reversed phase suspension polymerization method is preferable, and particularly, from the viewpoint of water absorption performance, a reversed phase suspension polymerization method is preferred. preferable.

Examples of the water-soluble vinyl monomer include:
There is no particular limitation, and examples thereof include those which can polymerize those exemplified as the superabsorbent resin in the composition of the present invention described above. Above all, it contains at least 50% by weight of one or more selected from the group consisting of acrylic acid, alkali metal acrylate and ammonium acrylate from the viewpoint of cost and performance of the resulting superabsorbent resin. Are preferred. The water-soluble vinyl monomer is preferably homopolymerized using only one kind thereof, or is preferably copolymerized using two or more kinds thereof, but is preferably a water-insoluble vinyl monomer copolymerizable with the water-soluble vinyl monomer. 50 of all monomers
Copolymerization can also be carried out in an amount of not more than% by weight.

In the polymerization of the water-soluble vinyl monomer, a known polymerization initiator is used. If necessary, a known crosslinking agent is added before, during, after or during the polymerization. And a modifier can also be used. The amounts of these are not particularly limited as long as the effects of the present invention are not impaired. The polymerization temperature of the water-soluble vinyl monomer is preferably 20 to 120 ° C, and the polymerization time is preferably 20 to 180 minutes.

The content of the metal compound in the metal compound is preferably from 0.001 to 1 part by weight, more preferably from 0.005 to 1 part by weight, based on 100 parts by weight of the water-soluble vinyl monomer. It is preferable to carry out the polymerization of the water-soluble vinyl monomer in an amount of 0.5 to 0.5 part by weight, most preferably 0.01 to 0.1 part by weight.

When a metal compound obtained by using an α-hydroxy acid as the organic acid and titanium as the metal (a) is used, a highly effective superabsorbent resin composition is obtained. It is preferable because it can be manufactured.

[0033]

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. 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 Method of Retained 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 fabric bag, and centrifuge 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].

[0035]

(Equation 1)

[Evaluation Method of Coloring with Time] The superabsorbent polymer composition was sealed in a polyethylene bag having a thickness of 50 μm, stored in an atmosphere of 70 ° C. and 65% RH for 1 week and 2 weeks, and then colored. The degree (YI value) is measured. For the measurement of the degree of coloring, "SM Color Computer" (model SM-6-1S-2B) manufactured by Suga Test Instruments Co., Ltd. is used.

Next, synthesis examples (synthesis examples 1 to 9) of metal compounds used in Examples and Comparative Examples are shown. The metal compounds in each of the synthesis examples were all prepared as solutions of the metal compounds.

[Synthesis Example 1] (Synthesis of Metal Compound (I)) 20 g of titanium tetrachloride was added dropwise to an ice-cooled solution composed of 43.6 g of sodium gluconate and 150 g of ion-exchanged water. After confirming that the solution became clear, about 48 g of 30%
An aqueous solution of caustic soda 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 2] (Synthesis of Metal Compound (II)) 43.6 g of sodium gluconate was added to a solution composed of 34.0 g of zirconium chloride octahydrate and 150 g of ion-exchanged water and dissolved. I let it. 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 is
It was slightly yellow and transparent. The zirconium content in this solution was 3.86% (calculated value).

[Synthesis Example 3] (Synthesis of Metal Compound (III)) A titanyl sulfate solution with a titanium content of 4.9% [trade name "Titanyl sulfate solution" manufactured by Rare Metals Co., Ltd.] 2 g of citric acid monohydrate 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 is 1.2
% (Calculated value).

[Synthesis Example 4] (Synthesis of Metal Compound (IV)) 5.36 g of DL-malic acid was dissolved in 100 ml of 2-propyl alcohol, and 5.68 g of tetraisopropyltitanium was added thereto. Stirred for hours. Thereafter, 20 g of ion-exchanged water was added, and the mixture was further stirred under reflux for 5 hours. The resulting solution is
It was cloudy. The titanium content in this solution was 0.73
% (Calculated value).

Synthesis Example 5 (Synthesis of Metal Compound (V)) 80.3 g of a solution composed of 14.7 g of zinc sulfate heptahydrate and 50 g of ion-exchanged water was added.
Was added and mixed. About 23 g of 30% caustic soda was added dropwise to adjust the pH of the solution to 7. The resulting solution was yellow and clear. Solution zinc content 2.0% (calculated).

Synthesis Example 6 (Synthesis of Metal Compound (VI)) Titanyl sulfate solution with a titanium content of 4.9% [trade name "Titanyl sulfate solution" manufactured by Rare Metals Co., Ltd.] 2 g of citric acid monohydrate and 25 g of ion-exchanged water were added and mixed. The resulting solution was yellow and transparent. The titanium content in this solution was 2.3% (calculated value). Synthesis Examples 1 to 6 above
The metal compound solutions obtained in the above are summarized in the following [Table 1].

[0044]

[Table 1]

Example 1 A 1000 ml four-necked flask equipped with a stirrer, a reflux condenser, a dropping funnel and a nitrogen gas inlet tube was charged with 40 ml of cyclohexane and ethyl cellulose as a dispersant (trade name "Ethyl Cellulose N" manufactured by Hercules). -100 ") was charged with 0.625 g, and nitrogen gas was blown into the flask to expel dissolved oxygen. After the inside of the flask was set to a nitrogen atmosphere, the four-necked flask was immersed in a 75 ° C water bath.

In a separate flask, acrylic acid 1
02.0 g was diluted with 25.5 g of ion-exchanged water, and 140 g of a 30% aqueous sodium hydroxide solution was cooled from the outside.
To prepare a monomer aqueous solution.

Next, 0.204 g of potassium persulfate dissolved in 7.5 g of ion-exchanged water as a polymerization initiator,
As a crosslinking agent, polyglycerol polyglycidyl ether [trade name "Denacol EX-" manufactured by Nagase Kasei Kogyo Co., Ltd.]
512 "] A solution of 0.04 g in 5 g of ion-exchanged water and 2.5 g of the above metal compound (I) solution were added and dissolved in the above monomer aqueous solution to prepare a monomer / initiator aqueous solution. Thereafter, nitrogen gas was blown in to remove oxygen dissolved in the monomer / initiator aqueous solution.

This monomer / initiator aqueous solution was added dropwise to the four-necked flask over 1 hour, and after completion of the addition, the mixture was stirred for 15 minutes while maintaining the temperature of the water bath at 75 ° C. Thereafter, azeotropic dehydration is performed using a dehydration tube, and the water content of the superabsorbent resin is determined based on 100 parts by weight of the resulting superabsorbent resin (shown in a dry state. The same applies to the following water content). To 30 parts by weight. This is 100
By drying under reduced pressure at a temperature of 103 ° C., 103 g of a superabsorbent resin composition was obtained.

As a result of elemental analysis of the obtained superabsorbent resin composition, the content of titanium with respect to 100 parts by weight of the superabsorbent resin was 0.047%. In addition, the retained amount after centrifugal dehydration and coloring with time of the obtained superabsorbent resin composition were measured. The results are shown in the following [Table 2] together with the content of titanium. In performing the evaluation, particles having a size of 850 μm or more were removed from the composition using a sieve.

Example 2 Metal Compound (I) Solution 2.5
Polymerization was carried out under the same conditions and in the same manner as in Example 1 except that 2.0 g of the metal compound (II) solution was used instead of g, to obtain a superabsorbent resin composition. The same evaluation as in Example 1 was performed for the obtained superabsorbent resin composition. The results are shown in Table 2 below.

Example 3 Instead of 0.625 g of ethyl cellulose as a dispersant, 1.5 g of a 25% solution of sodium salt of polyoxyethylene lauryl ether sulfate (average number of moles of ethylene oxide added = 2) was used.
As a crosslinking agent, polyglycerol polyglycidyl ether [trade name "Denacol EX-" manufactured by Nagase Kasei Kogyo Co., Ltd.]
512 "] from 0.04 g to 0.06 g, and replacing the metal compound (VI) with 2.5 g of the metal compound (I) solution.
The same conditions as in Example 1 except that 2.4 g of the solution were used,
Polymerization was carried out by the method to obtain a superabsorbent resin composition. The same evaluation as in Example 1 was performed for the obtained superabsorbent resin composition. The results are shown in Table 2 below.

Example 4 Metal Compound (I) Solution 2.5
Polymerization was carried out under the same conditions and in the same manner as in Example 1 except that 3.2 g of the metal compound (IV) solution was used instead of g, to obtain a superabsorbent resin composition. The same evaluation as in Example 1 was performed for the obtained superabsorbent resin composition. The results are shown in Table 2 below.

Example 5 Polymerization was carried out without adding the metal compound (I) solution to the aqueous monomer solution, and instead, 1.5 g of the metal compound (I) solution was placed in four ports before azeotropic dehydration. Polymerization was carried out under the same conditions and in the same manner as in Example 1 except that the mixture was dropped into the flask over 5 minutes, to obtain a superabsorbent resin composition. About the obtained superabsorbent resin composition, Example 1
The same evaluation was performed. The results are shown in Table 2 below.

[Example 6] Polymerization was carried out without adding the metal compound (VI) solution to the aqueous monomer solution. Instead, 2.7 g of the metal compound (VI) solution was added in four ports before azeotropic dehydration. Polymerization was carried out under the same conditions and in the same manner as in Example 3 except that the mixture was dropped into the flask over 5 minutes, to obtain a superabsorbent resin composition. The same evaluation as in Example 1 was performed for the obtained superabsorbent resin composition. The results are shown in Table 2 below.

Example 7 Polymerization was carried out under the same conditions and in the same manner as in Example 3 except that the metal compound (VI) solution was not added to the aqueous monomer solution to obtain a superabsorbent resin. The superabsorbent resin was placed in a double-arm kneader, and while mixing, 5.0 g of the metal compound (III) solution was sprayed evenly on the superabsorbent resin. Then, 50T at 80-100 ° C
By drying under heating and reduced pressure at orr, a superabsorbent resin composition was obtained. The same evaluation as in Example 1 was performed for the obtained superabsorbent resin composition. The results are shown in Table 2 below.

Example 8 Polymerization was carried out under the same conditions and in the same manner as in Example 3 except that the metal compound (VI) solution was not added to the aqueous monomer solution to obtain a superabsorbent resin. Separately, 7.0 g of the metal compound (III) solution was sufficiently dried at 80 ° C. under reduced pressure, and then pulverized with a mill to obtain a white powder.
The superabsorbent resin and the white powder obtained from the metal compound (III) solution were placed in a double-arm kneader and mixed well to obtain a superabsorbent resin composition. The same evaluation as in Example 1 was performed for the obtained superabsorbent resin composition. The results are shown in Table 2 below.

Comparative Example 1 Polymerization was carried out under the same conditions and in the same manner as in Example 1 except that the metal compound (I) solution was not added to the aqueous monomer solution, to obtain a superabsorbent resin. About the obtained superabsorbent resin, the same evaluation as Example 1 was performed. The results are shown in Table 2 below.

Comparative Example 2 Polymerization was carried out under the same conditions and in the same manner as in Example 3 except that the metal compound (VI) solution was not added to the aqueous monomer solution to obtain a superabsorbent resin. About the obtained superabsorbent resin, the same evaluation as Example 1 was performed. The results are shown in Table 2 below.

Comparative Example 3 Metal Compound (I) Solution 2.5
Instead of g, titanyl sulfate solution having a titanium content of 4.9% [trade name "Titanyl sulfate solution" manufactured by Rare Production Metals Co., Ltd.]
Polymerization was carried out under the same conditions and method as in Example 1, except that a solution consisting of 0.8 g and 2.2 g of ion-exchanged water was used.
A superabsorbent resin composition was obtained. The same evaluation as in Example 1 was performed for the obtained superabsorbent resin composition. The results are shown in Table 2 below.

Comparative Example 4 Metal Compound (I) Solution 2.5
Polymerization was carried out under the same conditions and in the same manner as in Example 1 except that 4.0 g of the metal compound (VII) solution was used instead of g, to obtain a superabsorbent resin composition. The same evaluation as in Example 1 was performed for the obtained superabsorbent resin composition. The results are shown in Table 2 below.

[0061]

[Table 2]

[0062]

According to the present invention, the coloring with time of the superabsorbent resin composition can be prevented by adding the colorant with time of the superabsorbent resin composition of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09K 15/02 A61F 13/18 307B 15/06

Claims (5)

[Claims] 1. An organic acid 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). A time-dependent coloring inhibitor for a superabsorbent resin composition comprising a metal compound obtained by mixing. 2. The anti-coloring agent according to claim 1, wherein the organic acid is an α-hydroxy acid. 3. The method according to claim 1, wherein the α-hydroxy acid is gluconic acid,
3. The anti-coloring agent for a superabsorbent resin composition according to claim 2, wherein the agent is one or more selected from the group consisting of citric acid, isocitric acid, alloisocitric acid, lactic acid, hydroxyacetic acid, malic acid and tartaric acid. . 4. The content of the metal (a) in the metal compound is 0.001 to 100 parts by weight of the superabsorbent resin.
The time-dependent coloring inhibitor for the superabsorbent resin composition according to any one of claims 1 to 3, which is 1 part by weight. 5. A polyvalent metal salt comprising an organic acid or a salt thereof and one or two metals (a) selected from the group consisting of titanium and zirconium, or a polyvalent metal salt or a salt thereof. A method for preventing coloring with time of a highly water-absorbent resin composition, comprising adding a metal compound obtained by mixing an alkoxide of a metal (a).