JPH05222107A - Production of water-absorbing fine polymer particle - Google Patents

Abstract

PURPOSE:To obtain a polymer in the form of homogeneous fine particles with a narrow particle size distribution which polymer has a water-absorbing capacity of at least 5 times its own weight and is extremely useful in the field of cosmetics particularly as a perspiration-absorbing antiperspirant ingredient. CONSTITUTION:A monomer which is an alpha,beta-unsaturated carboxylic acid and/or a salt thereof is finely dispersed into an oil phase using as a dispersion stabilizer one or more compounds having an HLB of 3-9 and selected among sucrose/fatty acid esters, sorbitan esters, and polyoxyalkylene adducts thereof. This W/O dispersion is dropped into a heated organic solvent to polymerize the monomer by reversed-phase suspension polymerization, thereby giving fine particles of a water-absorbing polymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a water-absorbent polymer, and more specifically, to easily and inexpensively industrially produce water-absorbent polymer fine particles having a water-absorbing ability and a particle size suitable as an antiperspirant material. It relates to a method of manufacturing.

[0002]

2. Description of the Related Art In recent years, water-absorbent polymers have been used in a wide range of fields such as sanitary products, sanitary agents for diapers, water retention agents in the agricultural field, soil conditioners, artificial snow on artificial ski slopes, and scrub agents for facial cleansers. It has been used. In addition to these applications, there is also an example in which it is used in the field of cosmetics, in particular, as an antiperspirant that absorbs sweat, European Patent No. 1162 and JP-A No. 50-1268.
No. 20, No. 50-77548, No. 60-81120
And Japanese Patent Application Laid-Open No. 3-109316. In this case, since it is used for the human body, not only the safety but also the feeling during use, especially the feeling during sweating, the persistence of a refreshing feeling, etc. are emphasized.

The water-absorbing polymer used for this type of application includes a cross-linked product of an acrylate polymer, a cross-linked product of an acrylamide-acrylate copolymer, a vinyl alcohol-
Acrylate copolymer cross-linked product, acrylate-methacrylate copolymer cross-linked product, starch-acrylic acid graft copolymer cross-linked product, starch-acrylonitrile graft copolymer hydrolyzed product cross-linked product And carboxymethyl cellulose cross-linked products are known, but they are considered to be the most preferable water-absorbing polymers because the cross-linked products of acrylate polymers are inexpensive and easily have high water absorption ability.

Conventionally, as a method for polymerizing an acrylate,
Reverse phase emulsion polymerization and reverse phase suspension polymerization have been industrially generalized because of the advantage of easy removal of the heat of polymerization. A method for obtaining a powder polymer from an α, β-unsaturated carboxylic acid by using these polymerization methods is described in, for example, JP-B-34-10644 and JP-A-5-10644.
3-45357, 53-46389, 54-3
0710, JP-A-56-26909, JP-B-60-
25045, JP-A-57-167302, 61-
No. 43606 and the like.

[0005]

However, in these conventional polymerization methods, it is difficult to control the temperature of the polymerization reaction tank, reaction runaway, agglomerate formation, etc. occur, and the particle size is small and there is no agglomerate. Alternatively, it has been difficult to obtain few water-absorbent polymer fine particles. Therefore, an object of the present invention is to provide a method for industrially easily producing water-absorbing polymer fine particles having a suitable water-absorbing capacity and a small particle size, which can be used as a cosmetic material such as an antiperspirant material. ..

[0006]

Therefore, as a result of various studies on the conditions of the reverse phase suspension polymerization method and the reverse phase emulsion polymerization method from the above viewpoints, the present inventors have found that a specific HLB is used as a dispersion stabilizer. By using the compound having a monomer to form water-in-oil type micro-dispersed droplets before polymerization, and polymerizing while dropping the droplets, the polymerization reaction can be gradually progressed and aggregation is suppressed. The inventors have found that water-absorbent polymer fine particles having excellent performance can be obtained, and completed the present invention.

That is, according to the present invention, HLB is used as a dispersion stabilizer in a method for producing a water-absorbing polymer in which an α, β-unsaturated carboxylic acid monomer or / and a salt thereof is subjected to water-in-oil type reverse phase suspension polymerization. 3 to 9 sucrose fatty acid ester, sorbitan ester and one or more selected from polyoxyalkylene adducts thereof,
Provided is a method for producing water-absorbing polymer fine particles, characterized in that water-in-oil type fine dispersion droplets of a monomer are formed in advance before polymerization, and the fine dispersion droplets are dropped into an organic solvent to be polymerized for polymerization. It is a thing.

Examples of the α, β-unsaturated carboxylic acid monomer used in the present invention include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid and fumaric acid. The most preferred of these is acrylic acid. Examples of the salt include alkali metal salts such as sodium salt and potassium salt, but sodium salt is the most inexpensive and preferred. These α, β-
Among the unsaturated carboxylic acid monomer salts, sodium acrylate is a sodium polyacrylate that passes the cosmetic material standard, and is particularly preferable from the viewpoint of safety.

In the present invention, the .alpha.,. Beta.-unsaturated carboxylic acid is usually neutralized with an alkali for polymerization, and the degree of neutralization is preferably 50 to 95%, particularly preferably 65 to 75%. If it is too low, the acidity of the polymer increases, and if it is too high, it is difficult to increase the concentration of the aqueous monomer solution, which is not preferable.

The monomer concentration is preferably 40% by weight or more, and if it is less than 40% by weight, it is not economical, and in the case of using a crosslinking agent such as a diepoxy compound which is deactivated by reacting with water,
There is a problem that efficient crosslinking does not proceed.

In the present invention, the crosslinking agent is not always necessary, but the polymerization can be carried out in the presence of the crosslinking agent. Generally, the water absorption amount of a water-absorbent polymer decreases as the degree of cross-linking is increased. However, it is possible to prevent the water-absorbent polymer from swelling more than necessary by being cross-linked to some extent and causing a feeling on the skin, particularly a feeling of foreign matter.

The cross-linking agent used in the present invention includes α,
Any polymer may be used as long as it can crosslink the polymer obtained from the β-unsaturated carboxylic acid monomer or / and its salt, and examples of the polymerizable crosslinking agent include methylenebisacrylamide and methylenebismethacrylamide. Bisamides and di- or tri (meth) acrylates of polyols such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol diacrylate, propylene glycol dimethacrylate, polyoxyethylene glycol diacrylate, and glycerin triacrylate;
Examples of the cross-linking agent utilizing the reactivity with the carboxyl group present in the α, β-unsaturated carboxylic acid monomer and its salt or its polymer include, for example, (poly) ethylene glycol diglycidyl ether and (poly) propylene glycol diglycidyl. Ether, (poly) glycerol diglycidyl ether, (poly) glycerol triglycidyl ether, (poly) glycerol tetraglycidyl ether, sorbitol diglycidyl ether, sorbitol triglycidyl ether, sorbitol tetraglycidyl ether, pentaerythritol diglycidyl ether, pentaerythritol tri Glycidyl ether,
Examples include polyglycidyl compounds such as pentaerythritol tetraglycidyl ether, haloepoxy compounds such as epichlorohydrin, epibromhydrin, α-methylepichlorohydrin, and isocyanate compounds such as 2,4-tolylene diisocyanate and hexamethylene diisocyanate. Be done. Of these, methylenebisacrylamide and ethylene glycol diglycidyl ether are most preferable.

The cross-linking agent is generally 0.00
It is preferably used in a proportion of 1 to 10% by weight, in particular 0.01 to 6% by weight. If it is less than 0.001% by weight, the resulting water-absorbing polymer swells more than necessary and the feel is deteriorated, and if it exceeds 10% by weight, the water-absorbing ability is remarkably lowered and stickiness is felt, which is not preferable.

As the polymerization initiator, a usual water-soluble radical polymerization initiator can be used. Water-soluble azo initiators include 2,2'-azobis (2-amidinopropane)
Hydrochloride, 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide], 2,2'-azobis {2- [1- (2-hydroxyethyl) -2-imidazoline- 2-yl] propane}
Examples thereof include dihydride, and examples of the water-soluble peroxide include potassium persulfate, ammonium persulfate, hydrogen peroxide, etc., and a reducing substance such as sulfite, or an amine and the like. The redox initiator may be used in combination.

The amount of the polymerization initiator used is based on the monomer.
0.01 to 1% by weight is preferable, and if it is too small, smooth polymerization is difficult to start, and if it exceeds 1% by weight, there is a high risk of polymerization being started before dropping the monomer dispersion droplets into the organic solvent, which is not preferable. ..

In the present invention, the organic solvent is used as an oil phase component when the monomer is made into water-in-oil type finely dispersed droplets, and also as a solvent in a reaction vessel for dropping the dispersed droplets. As the organic solvent, petroleum hydrocarbons are preferable, for example, normal hexane, normal heptane, aliphatic hydrocarbons such as ligroin, cyclohexane, alicyclic hydrocarbons such as methylcyclohexane, benzene, toluene, aromatic hydrocarbons such as xylene. However, aliphatic or alicyclic hydrocarbons such as normal hexane and cyclohexane are more preferable than aromatic hydrocarbons that may cause fusion of dry water-absorbing polymer particles. The amount of the organic solvent used can be varied over a wide range with respect to the amount of the aqueous monomer solution, but it is generally advantageous from the economical viewpoint that the amount of the organic solvent is small. However, if the amount is too small, it becomes difficult to remove the heat generation, and it is also necessary to prepare the reaction solution in a reaction tank so that the reaction solution can be stirred. Therefore, it is usually appropriate that the volume ratio of the aqueous monomer solution to the organic solvent be 1: 1 to 1: 6.

In the present invention, the dispersion stabilizer is α, β-
It is used to stabilize an aqueous solution of an unsaturated carboxylic acid monomer or / and a salt thereof in an oil phase (organic solvent), and is an oil-soluble surfactant of HLB3 to
One or more selected from sucrose fatty acid ester, sorbitan ester and polyoxyalkylene adduct thereof of 9 are used. The sucrose fatty acid ester is preferably a sucrose ester in which the fatty acid is a saturated or unsaturated fatty acid such as stearic acid, palmitic acid, lauric acid and oleic acid. The number of esters can be 1 to 6 per unit of sucrose. Specific sucrose fatty acid esters include sucrose monostearate, sucrose distearate, sucrose tristearate, sucrose monopalmitate, sucrose dipalmitate, sucrose tripalmitate, sucrose monolaurate, sucrose. Examples thereof include dilaurate, sucrose trilaurate, sucrose monooleate, sucrose dioleate, sucrose trioleate, sucrose polystearate, sucrose polypalmitate, sucrose polylaurate and sucrose polyoleate. The sorbitan ester is preferably a sorbitan ester in which the fatty acid is a saturated or unsaturated fatty acid such as stearic acid, palmitic acid, lauric acid and oleic acid, and the number of the ester can be 1 to 4 per 1 unit of sorbitan.
Specifically, sorbitan monostearate, sorbitan distearate, sorbitan tristearate, sorbitan monopalmitate, sorbitan dipalmitate, sorbitan tripalmitate, sorbitan monolaurate,
Sorbitan dilaurate, sorbitan trilaurate,
Examples thereof include sorbitan monooleate, sorbitan diolate and sorbitan trioleate. Examples of these polyoxyalkylene adducts include polyoxyethylene adducts and polyoxypropylene adducts, such as polyoxyethylene sorbitan monostearate,
Examples thereof include polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monooleate and polyoxyethylene sorbitan tristearate. These dispersion stabilizers can be used alone or in combination of two or more. HLB is a suitable range of 3-9,
If it is too low, a gelled substance other than the fine particles will be produced, and if it is too high, the solubility in petroleum hydrocarbon solvents will be reduced, and the dispersibility will be reduced, which is uneconomical.

A suitable amount of the dispersion stabilizer added is usually 0.1 to 15% by weight, preferably 1
~ 5% by weight. When the amount is too small, stable dispersed droplets in oil are not formed, and when the amount is too large, it is uneconomical, and a large amount of the dispersion stabilizer is mixed in the produced polymer, so that the water absorption ability is lowered.

The polymerization reaction in the present invention is carried out by preparing finely dispersed droplets of an aqueous monomer solution in advance before the polymerization reaction and dropping them into an organic solvent in a reaction vessel to carry out polymerization. The method for preparing the fine dispersion droplets is not particularly limited as long as it is a dispersion method that can obtain a desired average particle size as polymer fine particles, and for example, an aqueous monomer solution and an organic solvent, a polymerization initiator, a dispersion stabilizer, and if necessary. If necessary, mix with a cross-linking agent and disperse using a homogenizer using a strong water flow, a continuous emulsification disperser using a high shear applied to the rotating blade and the machine wall or the gap between the rotating blades, an ultrasonic disperser, etc. Alternatively, a method of dispersing by using a method of pressurizing an aqueous monomer solution through a ceramic microporous membrane as disclosed in JP-A No. 2-95433 and pressurizing it into a dispersion medium is preferable.

The obtained dispersion droplets are added to an organic solvent and, if necessary, a dispersion stabilizer, and are dropped into a reaction tank whose temperature is raised by nitrogen substitution with stirring. The amount of the dispersion stabilizer at this time is preferably a concentration according to the concentration of the dispersion stabilizer of the added dispersion drops, and if it is too small, the dispersion drops of the monomer dropped in the reaction tank collapse and gel before polymerization, or the inner wall of the reaction tank. If it is too much, it becomes uneconomical.
The reaction temperature is preferably 50 to 85 ° C. In this case, it is preferable that the polymerization occurs at the same time as the dropping. It is uneconomical to raise the temperature more than necessary, and it becomes difficult to stably drop the monomer-dispersed drops during the dropping. It is also possible to appropriately perform cooling or heating depending on the state of heat generation during the process.

After the entire amount of the monomer dispersed droplets has been dropped, aging may be carried out at the reflux temperature in order to complete the polymerization reaction and the crosslinking reaction. After completion of the reaction, the reaction mixture may be cooled and the target polymer fine particles may be directly extracted and dried, or an appropriate amount of dehydration may be performed by azeotropy before cooling, and then cooling and drying may be performed. May be cooled and dried after concentration. It is also possible to adopt a method in which after adequate dehydration, further aging is carried out to further promote the crosslinking reaction with the remaining crosslinking agent. Considering the ease of manufacturing,
It is advantageous to dry the particles as they are without dehydration, but if the polymer particles swollen with water are dried as they are, fusion of the particles is likely to occur. Therefore, it is preferable to perform appropriate dehydration and dry after the completion of the reaction.

The polymer fine particles thus obtained are preferably washed with a mixed solution of water and a hydrophilic solvent for applications where safety is extremely important. The method is described, for example, in Japanese Examined Patent Publication No. 43-1096 and Japanese Patent Laid-Open No. 1-292.
No. 003 and the like.

The water-absorbent polymer fine particles thus obtained usually have an average particle size of 1 to 50 μm, have a narrow particle size distribution, are homogeneous primary particles, or are physically weakly aggregated.
Obtained as secondary particles. Therefore, it can be used as it is as a sweat absorbent material, but it is preferable to use it as a sweat absorbent material after performing simple crushing and classification to remove a very small amount of impurities as necessary.

[0024]

EFFECT OF THE INVENTION The polymer obtained by the method of the present invention is a fine particle, is a homogeneous particle having a narrow particle size distribution, has a water absorption capacity of 5 times or more of its own weight, and is an antiperspirant which absorbs sweat in the field of cosmetics. Not only is it a polymer that is extremely effective as a raw material, but it can also be widely used in the fields of agriculture, such as sanitary products in which large amounts of water-absorbing polymers are usually used, sanitizers such as paper diapers, water retention agents, soil conditioners, and the like.

[0025]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

Example 1 255 g of 80% by weight industrial acrylic acid was placed in a 2 l beaker, and 280 g of a 30% by weight caustic soda aqueous solution was added dropwise under cooling with stirring to neutralize 74%. Solution of 0.8 g of potassium sulfate dissolved in 20 ml of water and ethylene glycol diglycidyl ether as a cross-linking agent (trade name, Denacol EX810, manufactured by Nagase Kasei Co., Ltd.)
10.2 g was added and uniformly dissolved. The resulting solution is 2
In a 1-liter beaker, 1 g of cyclohexane is heated with 5 g of sucrose stearate (trade name, equal weight mixture of Ryoto sugar ester S-570 and S-770, manufactured by Mitsubishi Food Chemical Co., Ltd.) which is a dispersion stabilizer. Add to the solution obtained by dissolving and use a homomixer to rotate at 1000 rpm.
The mixture was vigorously stirred at 0 rpm for 5 minutes to form fine water-in-oil type dispersed droplets. Next, in a 5 liter stainless steel reaction kettle equipped with a reflux condenser, 5 g of the dispersion stabilizer of the same kind as the above dispersion stabilizer and 1 kg of cyclohexane were put and stirred at 400 rpm, and the system was preheated to 80 ° C. and nitrogen was added. Into the replaced solution, the above-mentioned water-in-oil type partially dispersed oil neutralized with acrylic acid was added dropwise to initiate polymerization at the same time. After the entire amount was added dropwise over 1 hour, the mixture was aged at reflux temperature (72 ° C.) for 4 hours. After that, attach a dehydration tube, raise the temperature to dehydrate 270 ml, and further 1500
After evaporating and distilling off ml of cyclohexane, the mixture was allowed to cool to complete the reaction. By evaporating to dryness under reduced pressure, 250 g of fine powdery white dry polymer was obtained. Further, this polymer was washed with 1250 g of 70% by weight ethanol and 95% by weight ethanol, and then evaporated to dryness under reduced pressure again. Crushing was performed with a coffee mill to obtain 200 g of a fine powdery white dry polymer. It was found that the average particle diameter of the obtained dry polymer fine particles was 2.0 μm, and the maximum particle diameter was 10 μm, which were homogeneous fine particles having a narrow particle size distribution. Further, the particles swollen with a large excess of saline have an average particle size of 7.4 μm and a maximum particle size of 30 μm or less, and when used as a material for an antiperspirant, feel a foreign body sensation during sweating. It was proved to be a suitable material because of its size.

Example 2 Ryoto-Sugar Ester S-970 was used as the dispersion stabilizer.
Production was carried out under the same conditions as in Example 1 except that the product was manufactured by Mitsubishi Food Chemical Co., Inc., and 210 g of fine powdery white dry polymer was obtained. The average particle size of this dry polymer is 2.1μ
m, and the particle size of the largest particles was 12 μm. Particles swollen with a large excess of saline solution
The average particle size is 7.8 μm, and the maximum particle size is 28 μm.
It was m.

Example 3 Ryoto Sugar Ester S-570 was used as a dispersion stabilizer.
Production was carried out under the same conditions as in Example 1 except that the product was manufactured by Mitsubishi Food Chemical Co., Inc., and 205 g of fine powdery white dry polymer was obtained. The average particle size of this dry polymer is 1.9μ.
m, and the maximum particle size was 10 μm. Particles swollen with a large excess of saline solution
The average particle size is 7.3 μm, and the maximum particle size is 25 μm.
It was m.

Example 4 Production was carried out under the same conditions as in Example 1 except that the dispersion stabilizer was changed to sorbitan monostearate, the organic solvent was changed to normal hexane, and the temperature elevation temperature at the start of polymerization was 68 ° C. Then, 200 g of fine powdery white dry polymer was obtained. The average particle size of this dry polymer was 2.3 μm, and the maximum particle size was 18 μm. The particles swollen with a large excess of physiological saline have an average particle size of 12.
It was 5 μm, and the maximum particle size was 50 μm.

Example 5 A dispersion stabilizer mixed with sorbitan monostearate, sorbitan distearate, sorbitan tristearate and polyoxyethylene sorbitan monostearate in a mixing ratio of 10: 4: 3: 3 by weight. Was used under the same conditions as in Example 4 except that was used to obtain 195 g of a fine powdery white dry polymer. The average particle size of this dry polymer is 2.0 μm, and the maximum particle size is 20 μm.
The particle size distribution was m. The particles swollen with a large excess of physiological saline had an average particle size of 10.3 μm and a maximum particle size of 42 μm.

Example 6 Production was carried out under the same conditions as in Example 4 except that sorbitan monopalmitate was used as the dispersion stabilizer, and 215 g of fine powdery white dry polymer was obtained. The average particle size of this dry polymer is 2.1 μm and the maximum particle size is 15 μm.
The particle size distribution was m. The particles swollen with a large excess of physiological saline had an average particle size of 7.8 μm and a maximum particle size of 28 μm.

Example 7 Except that the cross-linking agent was changed to methylenebisacrylamide.
The production was performed under the same conditions as in Example 1 to obtain 200 g of a fine powdery white dry polymer. The average particle size of this dry polymer was 2.3 μm, and the maximum particle size was 18 μm. The particles swollen with a large excess of physiological saline had an average particle size of 14.8 μm and a maximum particle size of 72 μm.

Example 8 The disperser for predispersion was changed from a homomixer to a continuous emulsification disperser, which was added dropwise while dispersing at a rotation speed of 15000 rpm.
Production was carried out under the same conditions as in Example 1 except that the dehydration amount was changed to 220 ml, and 210 g of fine powdery white dry polymer was obtained. The average particle size of this dried polymer was 1.5 μm, and the maximum particle size was 8 μm. The particles swollen with a large excess of physiological saline had an average particle size of 6.9 μm and a maximum particle size of 22 μm.

Example 9 Production was carried out under the same conditions as in Example 8 except that the rotation speed of the continuous emulsification disperser was changed to 10000 rpm, and 230 g of fine powdery white dry polymer was obtained. The average particle size of this dry polymer is 5.0 μm, and the maximum particle size is 20 μm.
It was the particle size distribution. The particles swollen with a large excess of physiological saline had an average particle size of 24.0 μm and a maximum particle size of 61 μm.

Example 10 Production was carried out under the same conditions as in Example 3 except that the amount of the crosslinking agent was changed to 0.26 g, and 220 g of fine powdery white dry polymer was obtained. The average particle size of this dry polymer was 2.0 μm, and the maximum particle size was 12 μm. The particles swollen with a large excess of physiological saline had an average particle size of 31.9 μm and a maximum particle size of 125 μm.
It was m. Also, 40 g per 1 g of this dry polymer
When 0 g of ion-exchanged water was added to swell, 250
g of water was absorbed. Therefore, since the obtained polymer absorbs 200 times or more of its own weight of water, it is useful as a sanitary agent and a water retention agent for agriculture.

Example 11 The same procedure as in Example 1 was repeated except that 305 g of 80% by weight methacrylic acid was used instead of methacrylic acid as the monomer acrylic acid, and 230 g of fine powdery white dry polymer was obtained. Obtained. The average particle size of this dry polymer is 2.3μ.
The particle size of the largest particles was 14 μm. Particles swollen with a large excess of saline solution
The average particle size is 6.5 μm, and the maximum particle size is 28 μm.
It was m.

Example 12 Production was carried out under the same conditions as in Example 8 except that the rotation speed of the continuous emulsification disperser was changed to 5000 rpm, to obtain 225 g of a fine powdery white dry polymer. The average particle size of this dry polymer was 14.4 μm, and the maximum particle size was 71.
The particle size distribution was 8 μm. The particles swollen with a large excess of saline have an average particle size of 32.3 μm,
The maximum particle size was 158.6 μm.

Comparative Example 1 Except that an aqueous monomer solution was added dropwise without performing preliminary dispersion.
The total amount charged was the same as in Example 1 and the manufacturing conditions were the same, and 250 g of a white polymer was obtained before the washing step. However, the product contained a considerable amount of gelled substance in addition to the fine particles. The average particle size of the dried polymer is 120 μm,
Aggregates of 1 mm or more were also mixed.

Comparative Example 2 The same production conditions as in Example 1 were used except that all the monomer dispersed droplets were added to the reaction tank before the temperature was raised for the polymerization and then the temperature was raised to start the polymerization. On the way, bumping occurred due to the rapid generation of polymerization heat. The polymer obtained after the reaction was quenched was 160 g of a white powdery polymer.
Met. The average particle size of this dry polymer was 6.8 μm, and the maximum particle size was 58 μm. The particles swollen with a large excess of physiological saline had an average particle size of 18.2 μm, and the maximum particle size was a large particle close to 1 mm.

Comparative Example 3 The dispersion stabilizer was sorbitan tristearate (HLB).
Except having changed to 2.1), it manufactured on the same conditions as Example 4, and obtained 230g of fine powdery white dry polymer. The average particle size of this dry polymer was 14.5 μm, and the maximum particle size was 105 μm. Particles swollen with a large excess of saline have an average particle size of 4
The particle size was 3.5 μm, the maximum particle size was 980 μm, and a gelled product was also included.

Test Example As a physical evaluation of the water-absorbent polymer obtained in the present invention, the average particle size and particle size distribution (Cu value) of dry polymer particles were measured, and the results are shown in Table 1. The smaller the Cu value, the narrower the particle size distribution. The Cu value is a value representing the size of the relative scattering with respect to the average value (average particle diameter), and can be calculated by the following general formula.

[0042]

[Equation 1]

[0043]

[Table 1]

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[Submission date] March 16, 1992

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Test Example As a physical evaluation of the water-absorbent polymer obtained in the present invention, the average particle size and particle size distribution ( Cv value) of dry polymer particles were measured, and the results are shown in Table 1. The smaller the Cv value, the narrower the particle size distribution. The Cv value is a value representing the size of the relative scattering with respect to the average value (average particle diameter), and can be calculated by the following general formula.

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[Equation 1]

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[0043]

[Table 1]

Claims (2)

[Claims] 1. A method for producing a water-absorbing polymer in which an α, β-unsaturated carboxylic acid monomer or / and a salt thereof is subjected to water-in-oil type reverse phase suspension polymerization, and HL is used as a dispersion stabilizer.
By using one or more selected from sucrose fatty acid ester having B of 3 to 9, sorbitan ester and polyoxyalkylene adducts thereof, the water-in-oil type micro-dispersed droplets of the monomer are formed in advance before the polymerization. A method for producing fine particles of a water-absorbing polymer, characterized in that the finely dispersed droplets are dropped into an organic solvent having a raised temperature and polymerized. 2. The production method according to claim 1, wherein the average particle diameter of the water-absorbent polymer fine particles after drying is 1 to 50 μm.