JPH0762252A - Production of high-water absorb polymer improved in gel strength - Google Patents

Abstract

PURPOSE:To simultaneously improve the gel strength, the gel stability and the surface stickiness of a high water absorb polymer which absorbed water (especially in the case the body fluid such as human urine having remarkable differences between individuals was absorbed). CONSTITUTION:This method for production of a high water absorb polymer improved in gel strength comprises applying an alkoxy-titanium treatment to a high water absorb polymer having a crosslinked structure and containing carboxyl groups and/or carboxylate groups as constituent groups of the polymer.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a super absorbent polymer. More specifically, the present invention relates to a method for producing a superabsorbent polymer 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.

[0002]

2. Description of the Prior 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, and also as water-stopping materials, anti-condensation materials, freshness-retaining materials, solvent dewatering 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, superabsorbent polymers swell due to absorption of water to form a gel. Particularly, when absorbing body fluid such as urine, 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 significant problem for hygiene products where equipment time is increasing. 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 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 method for producing a superabsorbent polymer in which the strength of the gel (when applied), the stability of the gel for a long 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 found that the above object can be achieved by treating a superabsorbent polymer with alkoxytitanium. That is, the method for producing a superabsorbent polymer with improved gel strength according to the present invention is an alkoxylated superabsorbent polymer having a crosslinked structure and containing a carboxyl group and / or a carboxylate group as a constituent of the polymer. It is characterized by being treated with titanium.

[Detailed Description of the Invention] <Superabsorbent Polymer> The superabsorbent polymer used in the method of the present invention has a crosslinked structure and has a carboxyl group and / or a carboxylate group as a polymer. It is contained as a constituent component, and specifically, it is a polyacrylate cross-linked product, a starch-acrylic acid salt graft copolymer cross-linked product, a starch-acrylonitrile graft copolymer cross-linked hydrolyzate, an acrylic acid ester. Examples thereof include a hydrolyzate of a crosslinked vinyl acetate copolymer, a crosslinked product of an acrylic acid salt-acrylamide copolymer, and a hydrolyzed product of a crosslinked polyacrylonitrile. The superabsorbent polymer powder has an average particle size of 10 to 2,000 μm, particularly 50 to 1.0.
00 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, γ-chloropropylmethyldimethoxysilane, octadecyldimethyl [3- (trimethoxysilyl) propyl] ammonium chloride and the like. 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.

<Alkoxytitanium> As the alkoxytitanium used in the present invention, any organic titanium compound having a reactive alkoxy group in the molecule can be used. Specifically, tetramethoxy titanium,
Tetraethoxy titanium, tetraisopropoxy titanium,
Tetrabutoxy titanium, tetrakis (2-ethylhexyloxy) titanium, tetrastearyloxy titanium, tetraisopropoxy titanium polymer, tetrabutoxy titanium polymer, diisopropoxy bis (acetylacetonato) titanium, dibutoxy bis (triethanol aminato) titanium, tri Examples thereof include butoxytitanium stearate, dihydroxybis (lacto) titanium, diisopropoxytitanium distearate and the like, and one or more of these can be used. Among these compounds, tetraisopropoxy titanium and dibutoxy bis (triethanolaminato) titanium are preferable. The amount of the alkoxytitanium used in the present invention varies depending on the type of the polymer used and cannot be specified unconditionally, but is generally 0.001 to 10% by weight, preferably 0.05 to 3% by weight based on the polymer. is there. When the amount used is less than 0.001%, the gel stability of the superabsorbent polymer against body fluid is insufficiently improved, and when it exceeds 10% by weight, the water absorbing ability of the superabsorbent polymer decreases.

<Treatment Method> The treatment of the superabsorbent polymer according to the present invention with alkoxytitanium can be carried out in various modes. For example, a wet method of adding alkoxytitanium in a slurry state in which a superabsorbent polymer is dispersed in a solvent, a dry method of spraying alkoxytitanium with dry air or nitrogen gas while forcibly stirring the superabsorbent polymer can be performed. it can. As the solvent used in the wet method, any inert solvent such as hydrocarbons, alcohols and ethers can be used. The alkoxytitanium treatment according to the invention is usually carried out on the polymer in the hydrated state, but it can also be carried out on the dried polymer.
The treatment temperature is generally 10 to 180 ° C., preferably 80 to 180 ° C.
It is 120 ° 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 polymers obtained in the examples are 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 0.10% Pure water 97.10%

<Gel strength> 25 g of adult human urine (mixed with urine of 5 adults) was absorbed into 1 g of super absorbent polymer, and 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.

<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 is
Taking into consideration individual differences in human urine and the like, the measurement was performed 5 times with different measurement dates.

<Gel surface "stickiness"> The "stickiness" of the swollen gel after the gel stability was measured was evaluated by touch according to the following evaluation criteria. ◯: The swollen gel is quite “crispy” and has a dry feeling. Δ: A part of the swollen gel is 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. In a four-necked round bottom flask with a capacity of 5,000 ml equipped with a superabsorbent polymer (A) stirrer, a reflux condenser, a thermometer, and a nitrogen gas introduction 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 the 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. As a result, 400 g of a free-flowing superabsorbent polymer was obtained. 500 g of 100 g of the dry polymer thus obtained
1 eggplant-shaped flask, then cyclohexane 1
22.5 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,
Stir for 30 minutes at room temperature. Then 3 in a 105 ° C oil bath
After soaking for 0 minute, the temperature of the oil bath was maintained and the pressure was reduced to evaporate to dryness to obtain 95 g of a dry polymer.

Super absorbent polymer (B) Except for using 0.8 g of ethylene glycol diglycidyl ether instead of γ-glycidoxypropyltrimethoxysilane in the synthesis of the super absorbent polymer (A ) described above. Then, 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.

Example 1 100 g of super absorbent polymer (A) and 10 cyclohexane
9 g of water was added to the slurry consisting of 0 g with stirring,
At 50 ° C., 1 g of di-n-butoxybis (triethanolaminato) titanium was added and mixed for 30 minutes. Then, it was dried at a bath temperature of 105 ° C. under reduced pressure for 30 minutes to obtain a super absorbent polymer.

Example 2 100 g of super absorbent polymer (A) and 10 cyclohexane
To the slurry consisting of 0 g, 10 g of water was added with stirring, and 2 g of di-i-propoxybis (acetylacetonato) titanium was added at 10 ° C. and mixed for 30 minutes. Then, it was dried at a bath temperature of 105 ° C. under reduced pressure for 30 minutes to obtain a super absorbent polymer.

Example 3 100 g of superabsorbent polymer (A) and 10 of cyclohexane
6 g of water was added to the slurry consisting of 0 g with stirring,
0.2 g of tetraisopropoxy titanium was added at 10 ° C. and mixed for 30 minutes. Then, it was dried at a bath temperature of 105 ° C. under reduced pressure for 30 minutes to obtain a super absorbent polymer.

Example 4 100 g of super absorbent polymer (A) and 10 cyclohexane
6 g of water was added to the slurry consisting of 0 g with stirring,
0.5 g of tetraisopropoxy titanium was added at 10 ° C. and mixed for 30 minutes. Then, it was dried at a bath temperature of 105 ° C. under reduced pressure for 30 minutes to obtain a super absorbent polymer.

Example 5 100 g of super absorbent polymer (A) and 10 cyclohexane
0.5 g of tetraisopropoxy titanium was added to the slurry of 0 g at 10 ° C. with stirring and mixed for 30 minutes. Then, it was dried at a bath temperature of 105 ° C. under reduced pressure for 30 minutes to obtain a super absorbent polymer.

Example 6 100 g of super absorbent polymer (A) and 10 cyclohexane
6 g of water was added to the slurry consisting of 0 g with stirring,
1.0 g of tetraisopropoxy titanium was added at 10 ° C. and mixed for 30 minutes. Then, it was dried at a bath temperature of 105 ° C. under reduced pressure for 30 minutes to obtain a super absorbent polymer.

Example 7 100 g of super absorbent polymer (A) and 10 cyclohexane
1.0 g of tetraisopropoxy titanium was added to the slurry of 0 g at 10 ° C. with stirring and mixed for 30 minutes. Then, it was dried at a bath temperature of 105 ° C. under reduced pressure for 30 minutes to obtain a super absorbent polymer.

Example 8 100 g of super absorbent polymer (A) and 10 cyclohexane
With stirring, 25 g of water was added to the slurry consisting of 0 g, and 1 g of tetra-n-butoxytitanium polymer (B-4, manufactured by Nippon Soda Co., Ltd.) was added at 50 ° C. and mixed for 30 minutes. Then, it was dried at a bath temperature of 105 ° C. under reduced pressure for 30 minutes to obtain a super absorbent polymer.

Example 9 100 g of super absorbent polymer (A) and 10 of cyclohexane
With stirring, 20 g of water was added to the slurry of 0 g, and 3 g of tetrastearyloxytitanium was added at 50 ° C. and mixed for 30 minutes. Then, it was dried at a bath temperature of 105 ° C. under reduced pressure for 30 minutes to obtain a super absorbent polymer.

Example 10 100 g of super absorbent polymer (B) and cyclohexane 10
9 g of water was added to the slurry consisting of 0 g with stirring,
At 50 ° C., 1 g of di-n-butoxybis (triethanolaminato) titanium was added and mixed for 30 minutes. Then, it was dried at a bath temperature of 105 ° C. under reduced pressure for 30 minutes to obtain a super absorbent polymer.

Example 11 100 g of superabsorbent polymer (B) and 10 of cyclohexane
6 g of water was added to the slurry consisting of 0 g with stirring,
0.5 g of tetraisopropoxy titanium was added at 10 ° C. and mixed for 30 minutes. Then, it was dried at a bath temperature of 105 ° C. under reduced pressure for 30 minutes to obtain a super absorbent polymer.

Example 12 100 g of superabsorbent polymer (B) and 10 of cyclohexane
0.5 g of tetraisopropoxy titanium was added to the slurry of 0 g at 10 ° C. with stirring and mixed for 30 minutes. Then, it was dried at a bath temperature of 105 ° C. under reduced pressure for 30 minutes to obtain a super absorbent polymer.

Example 13 100 g of super absorbent polymer (B) and 10 cyclohexane
With stirring, 20 g of water was added to the slurry of 0 g, and 3 g of tetrastearyloxytitanium was added at 50 ° C. and mixed for 30 minutes. Then, it was dried at a bath temperature of 105 ° C. under reduced pressure for 30 minutes to obtain a super absorbent polymer.

Example 14 100 g of super absorbent polymer (C) and 10 of cyclohexane
9 g of water was added to the slurry consisting of 0 g with stirring,
At 50 ° C., 1 g of di-n-butoxybis (triethanolaminato) titanium was added and mixed for 30 minutes. Then, it was dried at a bath temperature of 105 ° C. under reduced pressure for 30 minutes to obtain a super absorbent polymer.

Example 15 100 g of super absorbent polymer (C) and 10 of cyclohexane
6 g of water was added to the slurry consisting of 0 g with stirring,
0.5 g of tetraisopropoxy titanium was added at 10 ° C. and mixed for 30 minutes. Then, it was dried at a bath temperature of 105 ° C. under reduced pressure for 30 minutes to obtain a super absorbent polymer.

Example 16 100 g of super absorbent polymer (D) and 10 of cyclohexane
6 g of water was added to the slurry consisting of 0 g with stirring,
0.5 g of tetraisopropoxy titanium was added at 10 ° C. and mixed for 30 minutes. Then, it was dried at a bath temperature of 105 ° C. under reduced pressure for 30 minutes to obtain a super absorbent polymer. The above measurements were performed on the superabsorbent polymers obtained in the above examples. The results are shown in Table 1.

Comparative Examples 1 to 4 Superabsorbent Polymer (A) (Comparative Example 1) and Superabsorbent Polymer (B) not treated with alkoxytitanium according to the present invention.
The above measurement was performed for (Comparative Example 2), superabsorbent polymer (C) (Comparative Example 3) and superabsorbent polymer (D) (Comparative Example 4). The results are shown in Table 1.

[Table 1]

[0038]

The superabsorbent polymer produced by the method of the present invention absorbs water (particularly human urine and other body fluids having large individual differences) without impairing the original water-absorbing performance of the superabsorbent polymer. The gel strength (in the case), 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.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shunko Nakamura 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Petrochemical Co., Ltd. Yokkaichi Research Institute

Claims (6)

[Claims] 1. A method for improving gel strength, which comprises treating a superabsorbent polymer having a crosslinked structure and containing a carboxyl group and / or a carboxylate group as a constituent component of a polymer with alkoxy titanium. And a method for producing a superabsorbent polymer. 2. A superabsorbent polymer is a polyacrylate crosslinked product, a starch-acrylic acid salt graft copolymer crosslinked product, a starch-acrylonitrile graft copolymer crosslinked product hydrolyzate, an acrylic ester-vinyl acetate. The method according to claim 1, which is selected from the group consisting of a hydrolyzate of a cross-linked copolymer, a cross-linked acrylate-acrylamide copolymer, and a hydrolyzed polyacrylonitrile cross-linked product. 3. The superabsorbent polymer 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.
Or the method described in 2. 4. The method according to claim 3, wherein the cross-linking agent is a polydiglycidyl ether compound. 5. The method according to claim 1 or 2, wherein the water-absorbing polymer 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-amino Ethyl) aminopropyltrimethoxysilane, γ- (2-
Aminoethyl) aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane The method according to claim 5, which is one or more selected from methoxysilane, γ-chloropropylmethyldimethoxysilane and octadecyldimethyl [3- (trimethoxysilyl) propyl] ammonium chloride.