JPH07145326A - Highly water-absorbing polymer composition improved in gel stability after absorption of body fluid - Google Patents

Abstract

PURPOSE:To obtain a highly water-absorbing polymer composition which upon absorption of a body fluid, e.g. human urine, forms a gel improved in all of strength, long-term stability, and nontackiness regardless of body-fluid differences among individuals and which has intact water-absorbing capacity by incorporating a specific sulfate of a polyvalent metal into a specific highly water-absorbing polymer. CONSTITUTION:This polymer composition is formed by adding 0.05-10 pts.wt. sulfate of a polyvalent metal selected from titanium, zirconium, and vanadium to 100 pts.wt. highly water-absorbing crosslinked polymer containing structural units having a carboxyl group and/or a carboxylate group and then evenly dispersing the sulfate into the polymer. The polymer may be the one whose surface has been crosslinked with a crosslinking agent or modified with a silane compound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superabsorbent polymer composition having improved gel stability after absorbing body fluids. More specifically, the present invention provides a highly water-absorbing material containing a specific polyvalent metal sulfate, in which the strength of the gel after absorbing body fluid, the stability of the gel over time, and the "stickiness" of the gel surface are simultaneously improved. It relates to a polymer composition.

[0002]

2. Description of the Related Art In recent years, superabsorbent polymers have been used not only in the field of sanitary products such as sanitary products and disposable paper diapers, but also in various industrial products such as water-stopping agents, dew-preventing agents, freshness-retaining agents and solvent dehydrating agents. It has also been put to practical use in the fields of greening and agriculture and horticulture, and its application range is expanding further. Among these applied fields, sanitary items, hygiene items such as disposable paper diapers and incontinence pads have recently been improved in materials used, three-dimensional cutting,
The wearing feeling is improved by various gathers and the like, and the wearing time is becoming longer. Further, it is often used under extremely harsh conditions in the fields of industrial products and agricultural and horticultural fields. On the other hand, superabsorbent polymer becomes gel when it absorbs body fluids such as urine, menstrual blood, sweat, etc., but the gel deteriorates and decomposes over time and loses its strength, and at the same time, the gel surface and the inside become sticky. Will end up. That is, the liquid retention of the gel decreases with time. Due to this, problems such as liquid leakage during use of sanitary goods and deterioration of wearing feeling have become serious with the recent extension of wearing time. Although the cause of degradation and decomposition of the gel is not clear, it is presumed that trace active impurities contained in body fluids such as urine promote the decomposition of the super absorbent polymer gel according to a single or multiple expression mechanism. Therefore, the degree of decomposition and the behavior thereof differ depending on the state when absorbing the liquid and the individual difference of the body fluid, and in reality, there is a large variation. Against this background,
In the industry, gel properties with excellent strength and stability over time are used to prevent such variations during absorption, excretion of body fluids, and variations due to individual differences, and to maintain stability against body fluids such as urine. The advent of superabsorbent polymers having

As a method for improving the strength and stability of the gel, for example, a method of increasing the crosslink density of the superabsorbent polymer can be considered. Also, JP-A-63-118375
JP-A-63-153 discloses a method of incorporating an oxygen-containing reducing inorganic salt and / or an organic antioxidant in a polymer.
No. 060, a method of incorporating an oxidant, JP-A-63-63
No. 127,754, a method of adding an antioxidant, JP-A-63-272349, a method of adding a sulfur-containing reducing agent, and JP-A-63-146964, a method of adding a metal chelating agent. JP-A-63-1
5266 discloses a method of incorporating a radical chain inhibitor, JP-A-1-275661 discloses a method of incorporating an amine compound containing a phosphinic acid group or a phosphonic acid group, or a salt thereof, and JP-A 64-29257. Is a method of incorporating a polyvalent metal oxide, JP-A-2-255804.
Japanese Patent Application Laid-Open No. 3-179008 proposes a method of allowing a water-soluble chain transfer agent to coexist during polymerization, and the like. However, all of these methods have problems that the prevention of gel deterioration is insufficient and that the deterioration prevention effect varies greatly depending on the individual body fluid.
Furthermore, in the case of these methods, the effect of improving the gel strength related to the stickiness of the gel is hardly recognized.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned state of the art, the present invention provides a gel after absorbing a body fluid such as human urine having a large individual difference, without impairing the original water absorption performance of the superabsorbent polymer. It is an object of the present invention to provide a highly water-absorbent polymer composition in which the strength, the stability of the gel over time, and the tackiness of the gel are simultaneously improved regardless of individual differences in body fluids.

[0005]

[Means for Solving the Problems]

[Summary of the Invention] The present inventors have completed the present invention by discovering that the above object can be achieved by incorporating a specific polyvalent metal sulfate in a superabsorbent polymer. That is, the superabsorbent polymer composition according to the present invention has (A) 100 parts by weight of a superabsorbent polymer having a crosslinked structure and containing a carboxyl group and / or a carboxylate group as a constituent component of the polymer, and (B ) 0.05 to 10 parts by weight of a polyvalent metal sulfate of a metal selected from titanium, zirconium and vanadium.

[Detailed Description of the Invention] <Superabsorbent Polymer> The superabsorbent polymer used in the present invention has a crosslinked structure and has a carboxyl group or / and a carboxylate group as a constituent component of the polymer. Any superabsorbent polymer having can be used, and the type and polymerization method of the polymer are not limited. Among them, polyacrylate crosslinked product, starch-acrylic acid salt graft copolymer crosslinked product, starch-acrylonitrile graft copolymer crosslinked product saponified product, acrylic ester-vinyl acetate copolymer crosslinked product saponified product, acrylic Saponified products of acid salt-acrylamide copolymer cross-linked products and polyacrylonitrile cross-linked products are preferred examples. In addition to the above, polyethylene oxide crosslinked with acrylic acid,
Crosslinked sodium carboxymethyl cellulose, maleic anhydride-isobutylene copolymer crosslinked product, maleic acid salt, itaconic acid salt, 2-acrylamido-2-methyl sulfonic acid salt, 2-acryloyl ethane sulfonic acid, and 2 Examples thereof include those obtained by copolymerizing a comonomer such as -hydroxyethyl acrylate. Examples of the salt type of the carboxylate group in the superabsorbent polymer include an alkali metal salt, an alkaline earth metal salt, an ammonium salt and the like. Among them, the alkali metal salt is preferable.

The above superabsorbent polymer is generally prepared by adding a polymerizable monomer having a carboxyl group and / or a carboxylate group such as acrylic acid (salt) or maleic anhydride (salt) to water, a radical polymerization initiator, It can be obtained by polymerization by a known aqueous solution polymerization method, solution polymerization method, reverse phase suspension polymerization method or the like in the presence or absence of a crosslinking agent. For example, Japanese Patent Publication Sho-60-25
045, Japanese Patent Application No. 59-210198, and Japanese Patent Application Laid-Open No. 57-
158210, JP-A-57-21405, JP-B-5
3-46199, JP-A-58-71907, JP-A-55-84304, JP-A-56-91837, JP-A-2-49002, JP-A-61-157513 and JP-A-62-62807. It can be produced by the method described in each publication. The cross-linking carried out here indicates internal cross-linking of the higher water-based polymer matrix, and is different in operation and content from the cross-linking shown in the surface treatment described later. That is, this cross-linking is one in which the cross-linking agent is uniformly dispersed in the polymer before or after the polymerization to uniformly cross-link the inside of the polymer. On the other hand, this internal cross-linking occurs even when no cross-linking agent is used, for example, so-called self-cross-linking derived from the polymerizable monomer itself due to heat during polymerization. As the cross-linking agent, one having two or more double bonds in the molecule and exhibiting copolymerizability with the polymerizable monomer, or a functional group in the polymerizable monomer in the molecule, for example, a carboxyl group and / or Alternatively, those having two or more functional groups capable of reacting with the carboxylate group during the treatment such as drying during or after the polymerization are exemplified. As the former cross-linking agent, N, N-methylenebis (meth) acrylamide, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth)
Examples thereof include acrylate, propylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, diallyl phthalate, diallyl maleate, diallyl terephthalate, triallyl cyanurate, triallyl isocyanurate and triallyl phosphate. Examples of the latter crosslinking agent include ethylene glycol diglycidyl ether, polyethylene glycol glycidyl ether, and di- or polyglycidyl ether of aliphatic polyhydric alcohol. Further, those having both the former and latter functions include, for example, N-methylolacrylamide, glycidyl (meth) acrylate and the like.

The above superabsorbent polymer is generally obtained as a hydrogel containing water after polymerization, and this hydrogel is usually dried as it is or by azeotroping with an inert solvent and finally dried. The product is then crushed / classified as required. Further, the superabsorbent polymer used in the present invention may be a polymer which has been subjected to a treatment such as surface cross-linking or surface modification in the course of the above manufacturing process or on the product. As the cross-linking agent used for the surface cross-linking of the super absorbent polymer, 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 is usually 0.005 to 5.0 with respect to the polymer.
Used in the weight% range.

Further, examples of the compound used for the surface modification of the superabsorbent polymer include silane compounds represented by the following general formula. X (R) _m Si (Y) _3-m (In the formula, X is a functional group capable of reacting with the carboxyl group and / or the 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, γ-chloropropylmethyldimethoxysilane, octadecyldimethyl [3- (trimethoxysilyl) propyl] ammonium chloride and the like can be mentioned. The amount of the silane compound used is not particularly limited, but is usually 0.001 to 10.0% by weight based on the polymer. The average particle size of the superabsorbent polymer used in the present invention is generally 10 to 2000 μm, preferably 50 to 10 μm.
It is 00 μm.

<Polyvalent Metal Sulfate> The polyvalent metal sulfate used in the present invention is a sulfate of a metal selected from titanium, zirconium and vanadium, and specifically, titanium sulfate, titanyl sulfate, zirconium sulfate. , Vanadyl sulfate and the like. Polyvalent metals other than the above, for example, sulfates of divalent metals such as magnesium, calcium, barium, and subsalts, and sulfates of trivalent metals such as aluminum and iron have extremely small effects, and achieve the object of the present invention. I can't. The amount of the polyvalent metal sulfate used varies depending on the type, properties, and average particle size of the superabsorbent polymer used, but is generally 0.05 to 10 parts by weight, preferably 100 parts by weight, based on 100 parts by weight of the superabsorbent polymer. Is 0.1 to 5 parts by weight. If the amount used is 0.05 parts by weight or less, the effect is insufficient, and if it is 10 parts by weight or more, the effect is saturated. When the polyvalent metal sulphate is used in the form of powder, the average particle size is preferably smaller, and is preferably 10 μm or less, particularly preferably 1 μm or less.

<Production of Superabsorbent Polymer Composition> In the superabsorbent polymer composition of the present invention, a predetermined amount of the above polyvalent metal sulfate is added to the above superabsorbent polymer and uniformly mixed, It can be obtained by dispersing or by dissolving in a solvent such as water and then impregnating. Mixing or impregnation can be carried out by any conventionally known method or means. Generally, a mixer used for powder mixing or solid-liquid mixing, for example, a tank type mixer with stirring blades, a rolling type mixer. , A flow mixer, an airflow mixer, a vibration mixer, and a high-speed rotary paddle machine. Also, in some cases, polymerization of superabsorbent polymer,
It may be added, dispersed or impregnated during the steps such as aging, dehydration, surface modification and granulation. The temperature during mixing or impregnation is generally room temperature to 150 ° C, preferably room temperature to 50 ° C.

[0012]

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 measured by the following methods. <Water absorption capacity> 1 g of a super absorbent polymer is put in a 250-mesh nylon bag (size of 10 cm x 20 cm) and immersed 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 sulphate 0.11% Pure water 97.09% <Gel strength> Adult human urine (adult 5 It absorbs 25g of mixed urine and is left at 25 ° C for 30 minutes, and the gel is put into a rheometer (NRM-2 manufactured by Fudo Kogyo).
002J type), and the force at the time when the cell entered the gel was taken as the gel strength. <Gel Stability> A sample similar to the above gel strength was prepared and left in a constant temperature bath at a set temperature of 40 ° C. for 16 hours. The gel strength after standing was measured by the above method to evaluate the stability of the gel. In addition, 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 gel stability 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: The swollen gel is sticky and the hands are greasy.

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 melting, 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 cyclohexane and water.
400 g of a smooth superabsorbent polymer was obtained.
100 g of the dry polymer thus obtained was added to 500
The mixture was placed in a ml eggplant-shaped flask, and then 122.5 g of cyclohexane was added to form 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, after dipping in a 105 ° C. oil bath for 30 minutes, the temperature was reduced while keeping the oil bath temperature to evaporate to dryness to obtain 95 g of a dried polymer. Super absorbent polymer (B) The same procedure as in the above super absorbent polymer (A) was used except that 0.8 g of ethylene glycol diglycidyl ether was used instead of γ-glycidoxypropyltrimethoxysilane. 95 g of a dry polymer was obtained. A super absorbent polymer (C) starch-acrylic acid graft polymer crosslinked product (trade name: Sunwet IM-1000, manufactured by Sanyo Kasei) was used. Super absorbent polymer (D) crosslinked polyacrylate (trade name: Arialic CAW
-4, manufactured by Nippon Shokubai) was used.

Examples 1 to 12 A polyvalent metal sulfate was added to the superabsorbent polymer (A), (B), (C) or (D), and a V blender (manufactured by Tsutsui Rikagaku Kikai Co., Ltd., S-) was added. Type 5] at room temperature
For minutes, these powders were mixed uniformly to obtain a super absorbent polymer composition. The types and amounts of the superabsorbent polymer and polyvalent metal sulfate used are as shown in Table 1. The above measurement was performed on the obtained superabsorbent polymer composition. The results are shown in Table 2.

Comparative Examples 1 to 7 The superabsorbent polymer (A) (Comparative Example 1), polymer (B) (Comparative Example 2) containing no polyvalent metal sulfate compound,
Polymer (C) (Comparative Example 3), polymer (D) (Comparative Example 4), and superabsorbent polymer (A) (100 g) were each treated as a polyvalent metal sulfate with 1 g of magnesium sulfate (Comparative Example 5) and 1 g of calcium sulfate (Comparative). The above measurement was performed on the composition containing Example 6) and 1 g of aluminum sulfate (Comparative Example 7). The results are shown in Table 2.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3] As is clear from the results shown in Table 2, the superabsorbent polymer composition according to the present invention has a significantly improved water-absorbent gel strength without impairing the original water-absorbing performance of the superabsorbent polymer, and variations in individual differences. The stability of the gel and the "stickiness" of the gel surface are greatly improved for large human urine.

[0019]

EFFECT OF THE INVENTION The superabsorbent polymer composition according to the present invention has a gel strength when absorbing body fluids such as human urine, which greatly differ from individual to individual, without impairing the original water-absorbing performance of the superabsorbent polymer. The stability of the gel over time, and the "stickiness" of the gel surface are greatly improved. Therefore, the superabsorbent polymer composition of the present invention can be particularly preferably used in the field of hygiene products such as paper diapers, sanitary napkins, and various pads.

Front Page Continuation (72) Inventor Miho Tanaka No. 1 Toho-cho, Yokkaichi-shi, Mie Prefecture Yokkaichi Research Institute, Mitsubishi Petrochemical Co., Ltd. (72) Inventor Kiichi Ito No. 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Oil Chemical Company Yokkaichi Research Institute

Claims (6)

[Claims] 1. A superabsorbent polymer having 100% by weight of (A) a crosslinked structure and containing a carboxyl group and / or a carboxylate group as a constituent of the polymer, and (B) titanium, zirconium and vanadium. A superabsorbent polymer composition comprising 0.05 to 10 parts by weight of a polyvalent metal sulfate of a metal. 2. A superabsorbent polymer (A) is a polyacrylate crosslinked product, a starch-acrylic acid salt graft copolymer crosslinked product, a hydrolyzate of a starch-acrylonitrile graft copolymer crosslinked product, and acrylic. The acid ester-vinyl acetate copolymer cross-linked hydrolyzate, an acrylate-acrylamide copolymer cross-linked product and a polyacrylonitrile cross-linked hydrolyzate selected from the group consisting of, 1 Super absorbent polymer composition. 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 (In the formula, X is a functional group capable of reacting with the carboxyl group and / or the 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 selected from the group consisting of trimethoxysilane, γ-chloropropylmethyldimethoxysilane and octadecyldimethyl [3- (trimethoxysilyl) propyl] ammonium chloride.