JPH0753884A - Highlywater absobing polymer composition - Google Patents

Abstract

PURPOSE:To simultaneously improve the strength and stability of a gel and 'stickiness' on the surface of the gel after absorbing water in a highly water absorbing polymer (especially when a humor such as human urine having a great personal difference is absorbed). CONSTITUTION:This highly water absorbing polymer composition comprises (A) 100 pts.wt. highly water absorbing polymer, having a cross-liked structure and containing carboxyl group and/or carboxylate group as a constituent component of the polymer, (B) 0.05-10 pts.wt. crystalline or amorphous high-purity fine particulate titania, having <=1mum average particle diameter and >=10m<2>/g specific surface area measured by the Brunaurer-Emmett-Teller method and a crystal structure compound of a mixed type of the rutile with the anatase types and (C) 0.01-2 pts.wt. sulfites.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to superabsorbent polymer compositions. More specifically, the present invention provides a highly water-absorbent polymer composition containing titania powder and sulfites, in which the strength of the gel after absorbing water, the stability of the gel over time, and the "stickiness" of the gel surface are simultaneously improved. Regarding

[0002]

2. Description of the Related Art Super absorbent polymers have been widely used in recent years in the field of sanitary products such as sanitary products and disposable paper diapers, as well as water-stopping materials, anti-condensation materials, freshness-retaining materials, solvent dehydrating materials, etc. Is a synthetic polymer that is being put to practical use in various industrial products, as well as in the fields of greening and agriculture and horticulture, and is expected to expand its application range in the future. Recently, sanitary ware, sanitary ware such as disposable paper diapers and incontinence pads have improved wearing sensation due to improvements in materials used, three-dimensional cutting, and various gathers, and the wearing time has been lengthening. In addition, industrial products and agricultural and horticultural products are also being used under extremely severe conditions.

On the other hand, a super absorbent polymer swells due to water absorption and becomes a gel. Especially, when a body fluid such as urine is absorbed, the gel loses its strength with the passage of time, and at the same time, the surface becomes "sticky". Tends to become. This has become a particularly serious problem for hygiene products, which have been wearing for a long time. It is considered that such gel deterioration over time occurs because various redox compounds, enzyme active substances, and the like contained in body fluids such as urine break the chemical bonds of the superabsorbent polymer. Moreover, it is considered that the decomposition of the gel does not proceed by a single mechanism but by a plurality of mechanisms. Therefore, it is the actual situation that the degree of decomposition of the highly water-absorbent polymer varies greatly depending on the state of liquid absorption and individual differences in body fluids. Therefore, a super absorbent polymer having excellent gel strength and gel stability against body fluids such as urine is desired.

As a method for improving the gel strength and the gel stability, for example, a method of increasing the crosslink density of the superabsorbent polymer can be considered, but in this case, there is a problem that the water absorption ability decreases as the crosslink density increases. . In addition, by adding oxygen-containing inorganic salts, radical scavengers, antioxidants, oxidizing agents, sulfur-containing reducing agents, metal chelating agents, radical chain inhibitors, phosphinic acid-containing amines, etc. to superabsorbent polymers, gel stability is improved. There are various proposals to improve the sex, but the use of these drugs is not always effective for body fluids with large individual differences, and there are safety problems depending on the amount added. There is also.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned state of the art, the present invention is to absorb water (particularly human urine and other body fluids having large individual differences) without impairing the original water-absorbing performance of the superabsorbent polymer. It is an object of the present invention to provide a super absorbent polymer composition in which the strength of the gel (when applied), the stability of the gel over a long period of time, and the “stickiness” of the gel surface are simultaneously improved.

[0006]

[Means for Solving the Problems]

[Summary of the Invention] The present inventors have blended a superabsorbent polymer with a certain amount of high-purity fine particulate titania having a sulfite and an amorphous or a specific crystal structure and having a specific large specific surface area. It has been found that the above object can be achieved by the above superabsorbent polymer composition. That is, the superabsorbent polymer composition according to the present invention is (A) a superabsorbent polymer 1 having a crosslinked structure and containing a carboxyl group and / or a carboxylate group as a constituent component of the polymer.
00 parts by weight, (B) an average particle size of 1 μm or less, a specific surface area of 10 m ² / g or more measured by the Brunauer-Emmett-Taylor method, and a crystal structure of a mixed rutile type and anatase type crystal. It is characterized by comprising 0.05 to 10 parts by weight of high-quality or amorphous high-purity fine particulate titania and 0.01 to 2 parts by weight of (C) sulfite.

[Detailed Description of the Invention] <Superabsorbent Polymer> The superabsorbent polymer used in the present invention has a crosslinked structure and has a carboxyl group and / or a carboxylate group as a constituent component of the polymer. Specifically, polyacrylic acid crosslinked product, starch-acrylic acid salt graft copolymer crosslinked product, starch-acrylonitrile graft copolymer crosslinked hydrolyzate, acrylic ester-acetic acid Examples thereof include a hydrolyzate of a crosslinked vinyl copolymer, a crosslinked product of an acrylate-acrylamide copolymer, and a hydrolyzed product of a polyacrylonitrile crosslinked product. These may be used alone or in combination of two or more. The super absorbent polymer powder has an average particle size of 10 to 2,000 μm, particularly 50 to 1,
000 μm is preferable. These superabsorbent polymers can be produced by a known method, or commercially available products can be used.

The super absorbent polymer used in the present invention may have a surface cross-linked. As the cross-linking agent used for surface cross-linking, any cross-linking agent having two or more functional groups capable of reacting with a carboxyl group and / or a carboxylate group can be used.
For example, polydiglycidyl ether compounds, haloepoxy compounds, aldehyde compounds, isocyanate compounds and the like can be used, but polydiglycidyl ether compounds are common. The amount of these cross-linking agents used is not particularly limited, but usually 0.005 to 5.0 wt% relative to the polymer.
Used in the range of.

Further, the superabsorbent polymer used in the present invention may have a polymer surface modified.
Examples of the compound used as the surface modifier include a polyvalent metal compound such as aluminum hydroxide and a silane compound represented by the following general formula. X (R) _m Si (Y) _3-m (wherein, X is a functional group capable of reacting with a carboxyl group and / or a carboxylate group in the superabsorbent polymer, R is a hydrocarbon group, and Y is a hydrolyzed group. Represents a decomposable group, m is 0, 1 or 2.) Specific examples of the silane compound represented by the above formula include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ -(2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl)
Aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, Examples include γ-chloropropylmethyldimethoxysilane and octadecyldimethyl [3- (trimethoxysilyl) propyl] ammonium chloride. The amount of the surface modifier used is not particularly limited, but is usually 0.001 to 10.0% by weight based on the polymer.

<High-purity fine-particle titania> The high-purity fine-particle titania used in the present invention has a specific large specific surface area and is limited to an amorphous or specific crystal structure. Specifically, the fine particles have an average particle diameter of 1 μm or less, preferably 0.01 to 0.1 μm, and a specific surface area measured by the Brunauer-Emmett-Taylor method of 10 m ² / g or more, preferably 30 m. ² / g
The above is the crystalline structure of a mixed structure of rutile type and anatase type or amorphous. When a crystalline product is used, the composition ratio of rutile type and anatase type is rutile type / anatase type (weight ratio) = 90/1.
It is preferably 0 to 10/90, and particularly preferably 80/20 to 20/80. In the present invention, “high purity” for titania means that the pure titania content is 99% or more. The amount of the high-purity fine particulate titania used is 0.05 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the super absorbent polymer.

<Sulfites> Examples of sulfites used in the present invention include sulfites such as sodium sulfite, potassium sulfite, calcium sulfite, zinc sulfite, ammonium sulfite, and sodium hydrogen sulfite, potassium hydrogen sulfite, calcium hydrogen sulfite, Examples thereof include bisulfite salts such as ammonium bisulfite. Among these, sodium sulfite and sodium hydrogen sulfite are preferable. The amount of sulfite used is 100
0.01 to 2 parts by weight, preferably 0.0
5 to 1 part by weight. If the amount used is less than 0.01 parts by weight, the effect is small, and if it exceeds 2 parts by weight, water absorption capacity may decrease and safety problems may occur.

<Superabsorbent Polymer Composition> The superabsorbent polymer composition of the present invention comprises the above superabsorbent polymer to which a predetermined amount of the above-mentioned high-purity fine particulate titania and sulfites is added and uniformly mixed. , Can be obtained by dispersing. The mixing can be performed by any conventionally known method or means, and can be easily performed using a mixer generally used for powder mixing. Further, in some cases, it may be added or dispersed during the steps of polymerization, aging, dehydration, surface modification, granulation and the like of the superabsorbent polymer.

[0013]

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. The characteristic values described below of the superabsorbent polymer compositions obtained in the examples are those measured by the following methods.

<Water absorption capacity> 250 g of highly water-absorbent polymer
Nylon bag of mesh (size of 10 cm x 20 cm)
And soak in 1 liter of artificial urine for 30 minutes. After 30 minutes, the nylon bag was pulled up, drained for 15 minutes, weighed, blank-corrected, and the weight of the artificial urine absorbed by 1 g of the superabsorbent polymer was defined as the water absorption capacity. The composition of artificial urine is shown below. Artificial urine composition Urine 1.94% Sodium chloride 0.80% Calcium chloride 0.06% Magnesium sulfate 0.11% Pure water 97.09%

<Gel Strength> 25 g of adult human urine (mixed with urine of 5 adults) was absorbed in 1 g of superabsorbent polymer to give 25
The gel after being left at 30 ° C. for 30 minutes was subjected to a rheometer (NRM-2002J type manufactured by Fudo Kogyo Co., Ltd.), and the force when the cell entered the gel was taken as the gel strength.

<Stability of gel> A sample similar to the case of gel strength after water absorption as described above was prepared and set at a set temperature of 40 ° C.
It was left for 16 hours in a constant temperature bath. The gel strength after standing was measured by the above method, and the stability of the gel after water absorption was evaluated. still,
This test was performed 5 times by changing the measurement date in consideration of individual differences in human urine.

<Gel surface "stickiness"> The "stickiness" of the swollen gel after measuring the stability of the gel after water absorption was evaluated by touch according to the following evaluation criteria. ◯: The swollen gel is quite “crispy” and has a dry feeling. Δ: Swelling gel is partly sticky x: Swelling gel is sticky and hands are greasy.

<Super absorbent polymer> In the examples and comparative examples described below, the following super absorbent polymers were used. Superabsorbent polymer (A) Stirrer, reflux condenser, thermometer, into a four-necked round-bottomed flask with a capacity of 5,000 ml equipped with a nitrogen gas inlet tube, 1210 g of cyclohexane was added, and 9 g of sorbitan monostearate was added. After dissolving it, blow nitrogen gas,
Dissolved dissolved oxygen. Separately, while 350 g of acrylic acid was ice-cooled from the outside in a beaker having a capacity of 2,000 ml, 143.1 g of 95% pure sodium hydroxide dissolved in 727.7 g of water was added thereto to add 7% of the carboxyl group.
0% was neutralized. The monomer concentration in the aqueous solution in this case corresponds to 35% by weight as the monomer concentration after neutralization. Next, 0.37 g of N, N'-methylenebisacrylamide and 0.94 g of potassium persulfate were added to and dissolved therein, and then nitrogen gas was blown thereinto to expel residual oxygen.
The contents of the four-necked round-bottomed flask described above should have this volume of 2,000.
When 0 ml of the contents of a beaker was added, the mixture was stirred and dispersed, and the temperature inside the flask was raised by a water bath while bubbling nitrogen gas, the temperature inside reached about 60 ° C. After several tens of minutes, the temperature reached 75 ° C. Then, the internal temperature was maintained at 60 to 65 ° C., and the reaction was carried out for 3 hours while stirring. The stirring was performed at 145 rpm. When the stirring was stopped after the reaction for 3 hours, the wet polymer particles settled to the bottom of the round bottom flask, so that the cyclohexane phase could be easily separated by decantation. The separated wet polymer was transferred to a vacuum dryer and heated to 90 ° C. to remove the attached cyclochihesan and water, and 400 g of a free-flowing superabsorbent polymer was obtained. 500 ml of 100 g of the dry polymer thus obtained
In an eggplant-shaped flask, and then cyclohexane 12
2.5 g was added to make a slurry. While stirring this slurry, a liquid prepared by dispersing 0.44 g of γ-glycidoxypropyltrimethoxysilane in 22.5 g of water was added, and the mixture was stirred at room temperature for 30 minutes. Then 30 in a 105 ° C oil bath
After soaking for a minute, the pressure was reduced while keeping the same oil bath temperature to evaporate to dryness to obtain 95 g of a dry polymer.

Superabsorbent Polymer (B) In the above synthesis of the superabsorbent polymer (A), 0.8 g of ethylene glycol diglycidyl ether was used instead of γ-glycidoxypropyltrimethoxysilane. By the same operation, 95 g of a dry polymer was obtained.

Superabsorbent polymer (C) Starch-acrylic acid salt graft polymer crosslinked product (trade name: Sunwet IM-1000, manufactured by Sanyo Kasei) was used.

Super absorbent polymer (D) polyacrylate cross-linked product (trade name: Aquaric CAW
-4, manufactured by Nippon Shokubai) was used.

Examples 1 to 30 To the superabsorbent polymer (A), (B), (C) or (D), high-purity fine particulate titania and sulfites were added, and these were uniformly mixed for 30 minutes using a V blender. The above powders were mixed to obtain a super absorbent polymer composition. Table 1 shows the types and amounts of the superabsorbent polymer, the high-purity fine particulate titania and the sulfite. The above measurement was performed on the obtained superabsorbent polymer composition. The results are shown in Table 3.

Comparative Examples 1 to 33 The above-mentioned measurement was carried out for superabsorbent polymers in which high-purity fine particulate titania and sulfites were not mixed. Further, the above-mentioned superabsorbent polymer composition obtained by adding various kinds of high-purity fine particulate titania and sulfites to the superabsorbent polymer alone or in combination and uniformly mixing for 30 minutes using a V blender Was measured. Table 2 shows the types and amounts of the superabsorbent polymer used, the high-purity fine-particle titania and the sulfites, and the measurement results are shown in Table 3.

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[Table 5]

[Table 6]

[Table 7]

[Table 8]

[Table 9]

[Table 10]

[Table 11]

[0024]

EFFECTS OF THE INVENTION The superabsorbent polymer composition of the present invention can be used after absorbing water (particularly when absorbing body fluid such as human urine having a large individual difference) without impairing the original water absorbing performance of the superabsorbent polymer. The strength of the gel, the stability of the gel over a long period of time, and the "stickiness" of the gel surface are simultaneously improved regardless of individual differences in body fluid. Therefore, it can be advantageously used particularly in the field of hygiene products such as disposable diapers.

Claims (7)

[Claims] 1. (A) 100 parts by weight of a super absorbent polymer having a crosslinked structure and containing a carboxyl group and / or a carboxylate group as a constituent component of a polymer, (B) having an average particle diameter of 1 μm or less. And Brunauer Emmet
0.05 to 10 parts by weight of crystalline or amorphous high-purity fine particulate titania having a specific surface area of 10 m ² / g or more measured by the Taylor method and a mixed crystal structure of rutile type and anatase type Parts and (C) sulfites.
A superabsorbent polymer composition, characterized in that it comprises from 1 to 2 parts by weight. 2. A superabsorbent polymer (A) is a polyacrylate crosslinked product, a starch-acrylic acid salt graft copolymer crosslinked product, a starch-acrylonitrile graft copolymer crosslinked hydrolyzate, an acrylic acid ester- One or more selected from the group consisting of a hydrolyzate of a vinyl acetate copolymer crosslinked product, an acrylic acid salt-acrylamide copolymer crosslinked product and a hydrolyzate of a polyacrylonitrile crosslinked product,
The superabsorbent polymer composition according to claim 1. 3. The superabsorbent polymer (A) is surface-crosslinked with a crosslinking agent having two or more functional groups capable of reacting with a carboxyl group and / or a carboxylate group, according to claim 1 or 2. The superabsorbent polymer composition described. 4. The superabsorbent polymer composition according to claim 3, wherein the crosslinking agent is a polydiglycidyl ether compound. 5. The superabsorbent polymer composition according to claim 1, wherein the superabsorbent polymer (A) is surface-modified with a silane compound represented by the following general formula. X (R) _m Si (Y) _3-m (wherein, X is a functional group capable of reacting with a carboxyl group and / or a carboxylate group in the superabsorbent polymer, R is a hydrocarbon group, and Y is a hydrolyzed group. Represents a decomposable group, and m is 0, 1 or 2.) 6. The silane compound is γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ- (2- Aminoethyl) aminopropyltrimethoxysilane, γ- (2
-Aminoethyl) aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-chloropropyl The superabsorbent polymer composition according to claim 5, which is one or more selected from trimethoxysilane, γ-chloropropylmethyldimethoxysilane and octadecyldimethyl [3- (trimethoxysilyl) propyl] ammonium chloride. object. 7. The super absorbent polymer composition according to claim 1, wherein the sulfite (C) is a sulfite or a hydrogen sulfite.