KR910003869B1 - Preparation of alkaly metal arcrylate resin having good absorption - Google Patents

Abstract

The acrylic acid alkali metal salt polymer is prepd. by dispersion suspending a high concn. monomer soln. of at least 40 wt.% acrylic acid and acrylic acid alkali metal salt in the alicyclic hydrocarbon solvent contg. surfactants of 3-6 HLB and 8- 15 HLB, polymerizing and crossliking the suspension in the water-soluble radical polymn. initiator by the reverse suspension polymn., and adding silica or cellulose fiber to the crosslinked polymer. The polymer is granul type having regular particle size, and has a good absorption- and water holding- capacity.

Description

Method for producing acrylic acid alkali metal salt polymer having excellent water absorption

The present invention relates to a method for producing an alkali metal acrylate metal salt having excellent water absorption and water retention ability. More specifically, the preparation of a super absorbent polymer material having the property of absorbing aqueous materials such as water, body fluids (pee, blood), salt solution, etc., and the absorbed aqueous materials are hardly released even under some pressure. It is about a method.

Since superabsorbent polymer materials are more absorbent and water-repellent than conventional materials, recently absorbent materials for hygiene products such as diapers, women's menstrual products, medical bandages, agricultural and horticultural soil repair agents, wastewater treatment coagulants, civil construction It is used as an antistatic agent or an agent for controlling release of various chemicals.

Such superabsorbent polymers include semisynthetic polymers using natural products such as crosslinked products of carboxymethylcellulose, hydrolyzates of starch-acrylic acid graft polymers and starch-acrylonitrile graft polymers, crosslinked products of alkali metal salts of polyacrylic acid and polyvinyl. Synthetic polymers such as alcohols, polyethylene oxides and the like are known.

In particular, the crosslinked product of the alkali metal salt of polyacrylic acid, which is an object of the present invention, is the most widely used as an absorbent material for hygiene products, which is the main use of the superabsorbent polymer, because it has the best absorption capacity and excellent water retention ability among synthetic polymers. .

Conventionally, as a polymerization method of acrylic acid and an alkali metal alkali metal salt, methods, such as block polymerization, aqueous solution polymerization, reverse phase emulsion polymerization, or reverse phase suspension polymerization, are known.

In general, polymerization of acrylic acid and alkali metal alkali metal salt has a very high polymerization reaction rate unlike other acrylic monomers, and in particular, since a large amount of heat of polymerization is released, it is very important to control the polymerization rate and to release uniform polymerization heat.

Reversed phase suspension and reversed phase emulsion polymerization have the advantage of easily removing the heat of polymerization generated during the polymerization reaction by dispersing or emulsifying the hydrophilic monomer in a lipophilic organic solvent, and obtaining a powdery polymer after polymerization.

The surfactant used to disperse the monomer in the organic solvent is particularly important than any other polymerization reaction factors in order to obtain a polymer of the powdered acrylic acid alkali salt having excellent water absorption and water retention ability by the aforementioned reverse phase suspension polymerization method. This is because the stability of the emulsion formed is greatly changed depending on the range of HLB, which is a value indicating the properties of the surfactant.

According to Japanese Patent Publication No. 54-30710 and Japanese Patent Laid-Open Publication No. 56-72005, sorbitan monostearate, sorbitan monostearate, which is a kind of sorbitan fatty acid ester in the production of alkali metal salt of polyacrylic acid When (sorbitan monooleate) or sorbitol mono stearate is used as a surfactant, the formed W / O emulsion is stable, and the polymer particles obtained after polymerization are not cohesive with each other, so that the average particle diameter when drying It is said that fine powder of 50 micrometers or less is obtained. However, since the HLB 3-6 surfactant used in the known manufacturing technique has a higher hydrophobicity than hydrophilicity, the surface-coated surfactant has affinity with water and the absorption rate is slow when the polymer is absorbed. This is actually pointed out as a big disadvantage when using a super absorbent polymer as an absorbent material for hygiene products. In addition, since the dried powdery polymer particles are fine in size and have severe scattering during the drying process, they have a high loss and are difficult to mix with fibers or pulp when used for end use. Therefore, in order to avoid these disadvantages, they must be made into granular products after drying by a separate granulation process or aftertreatment process.

On the other hand, in the case of using a surfactant having a HLB value of 8-12, i.e., sorbitan monolaurate, that the emulsion produced during the W / O type reverse phase suspension polymerization is unstable, It is possible to obtain a polymer having a much higher absorbing capacity than a polymer obtained by using the surfactant of HLB 3-6, and to obtain a granular polymer having no scattering phenomenon caused by the aforementioned fine polymer particles (US patent). 4,340,706). However, the resulting emulsion is unstable, and a large amount of polymer sticks out in the polymerization reactor during the polymerization reaction, and it is difficult to obtain a uniform granular powder polymer due to excessive aggregation phenomenon between the polymers.

In particular, recently, when using a saccharose-fatty acid ester having an HLB value of 2-16 as a surfactant, it is possible to prepare a superabsorbent polymer having large particles (100-400 μm) having no scattering properties upon drying. It is published in Publication 86-3280.

The present inventors conducted a careful study of the known manufacturing techniques mentioned above, and found that all the physical properties of the polymer are closely related to the stability of the emulsion formed in the W / O type reverse phase suspension. At the same time, it has developed a method to safely and inexpensively prepare a superabsorbent polymer of granular acrylate alkali metal salt in a unified process that is excellent in absorbency and water-retaining ability and does not require a separate granulation process or post-treatment process after drying.

The present invention disperses a high concentration aqueous solution of at least 40% by weight of acrylic acid and alkali metal alkali metal salt in an aliphatic or alicyclic hydrocarbon solvent containing a mixture of two or more selected from surfactants having a HLB value of 3-6 and surfactants of 8-15. It is characterized by producing a granular acrylic acid alkali metal salt polymer having excellent water absorption and water-retaining ability by suspending, polymerizing and crosslinking by reverse phase suspension polymerization in the presence of a water-soluble radical polymerization initiator, and then adding an inorganic additive such as cellulose fiber or silica. The features of the present invention will be discussed further below.

Acrylic acid monomers used in the present invention should be partially neutralized with alkalis such as sodium hydroxide, potassium hydroxide, ammonium hydroxide and the like. Neutralization is suitably 50-95 mol%. In particular, the range of the degree of neutralization varies depending on the final physical properties, but if it is 95 mol% or more, the majority of the obtained polymer is dissolved in water, and at 50 mol% or less, the absorbent capacity of the obtained polymer is not only greatly reduced but also difficult to handle, such as elastic rubber. Indicates.

The concentration of the neutralized aqueous monomer solution is at least 40% by weight or more. The reason is that in the reverse phase suspension polymerization, a gel effect phenomenon occurs in the polymerization reaction of a high concentration aqueous solution, assuming that each droplet of W / O type monomer solution dispersed and suspended in an organic solvent is assumed to be a reaction system of a high concentration aqueous solution. This is to take advantage of the phenomenon that when the viscosity of the polymerization reaction system is high, the growth rate of the polymer is much faster than the stop rate and the overall polymerization rate is rapidly accelerated. At this time, since the conversion rate of the monomer into the polymer is almost consistent with the theoretical value, it is not necessary to remove the unreacted monomer after the polymerization. In order to apply the gel effect phenomenon to the reverse phase suspension polymerization reaction, it is necessary to sufficiently remove the heat of polymerization emitted from the polymerization reaction system. In addition, the stability of the emulsion already formed must be maintained adequately while the heat of polymerization is released, which can be satisfied from the composition of the surfactants used in the present invention.

Organic solvents may be aliphatic hydrocarbons such as n-hexane, n-heptane, petroleum ether, ligroin or cycloaliphatic hydrocarbons such as cyclohexane, cyclopentane, methylcyclohexane, etc., but inexpensive and non-toxic for industrial use. Cyclohexane or n-hexane are preferred. However, cyclohexane has a higher boiling point than n-hexane, so it is easy to control the heat of polymerization generated during the polymerization reaction. In particular, cyclohexane is selected from surfactants having a HLB value of 3-6 and HLB 8-15, respectively Since the effect on the stability of the emulsion resulting from the composition of two or more mixtures is great, it is better as a solvent.

The amount of solvent used was 1-5 times (weight ratio) of the amount of acrylic acid as a monomer, and the amount of solvent was determined according to the polymerization heat control ability.

In addition, aromatic hydrocarbons such as benzene, toluene, and xylene may be used as the organic solvent, but the resulting polymer is obtained as a completely entangled mass. This is because the solvent of the aromatic hydrocarbon does not stabilize the suspension system more sufficiently than the alicyclic hydrocarbon or the aliphatic hydrocarbon, and because the compatibility with the produced polymer is greater, the produced polymer is partially dissolved to cause welding of the polymer.

As a polymerization initiator, water-soluble peroxides, such as potassium persulfate or ammonium persulfate which are water-soluble radical polymerization initiators normally used in emulsion polymerization, are preferable. The concentration of the initiator is suitably 0.001-1.0 mol% based on the total monomer concentration.

The surfactant used in the reverse phase suspension polymerization of the present invention includes HLB values such as sorbitan fatty acid esters (monostearates, monooleates), sorbitan fatty acid ester ethers, glyceryl oleate, glycerol monostearate, ethylene glycol monostearate, and the like. 3-6 and sorbitan monolaurate, polyoxyethylene sorbitan fatty acid esters (monolaurate, monostearate, monooleate), polyoxyethylene fatty acid esters (monolaurate, monostearate, monooleate It is suitable to use two or more mixtures having an HLB value of 8-15 such as). The surfactants used are mainly used as food additives and are therefore harmless to the human body.

It is preferable that the composition of surfactant is adjusted to 3-50 weight% of HLB value 3-6, and 97-50 weight% of HLB value 8-15.

The use of some of the above-mentioned surfactants in the manufacturing process of the superabsorbent polymers of the alkali metal salt of polyacrylic acid is already known from the aforementioned Japanese Patent Publications and Patent Publications and US Patents. However, the surfactants used in these known production techniques are those which use only those having an HLB value of 3-6 or those having an HLB value of 8-12 alone to cause a reverse phase suspension polymerization reaction.

Therefore, it should be noted that there is a significant difference between using two or more mixtures as surfactants in the present invention when considering the effect of the heat of polymerization on the stability of the emulsion in the polymerization step. In other words, when sorbitan monostearate having a low HLB value of 3-6 as a surfactant is used, the formed W / O emulsion is so stable that the resulting polymer particles are fine. On the contrary, when sorbitan monolaurate having an HLB value of 8-12 is used, it is difficult to control the granule size and the heat of polymerization of the polymer because the resulting polymer particles are excessively granulated or aggregated due to the unstable emulsion.

On the other hand, according to the present invention, when using surfactants mixed with the above-mentioned surfactant composition, the formed W / O emulsion has a metastable state in which the HLB values used are complemented by different surfactants. There is an advantage to obtain a granular polymer having a uniform particle size in the polymerization reaction step. The production of uniform granular superabsorbent polymers is very important in terms of preventing the loss of work performed by the scattering of the fine powder in the drying step, simplifying the process, and improving workability, and are a feature of the present invention.

The total amount of surfactant used is preferably in the range of 1-10% by weight of the monomer. The size of the granulated polymer particles depends on the composition and amount of the surfactant.

The range of polymerization temperatures used is 40-75 ° C. and the polymerization reaction is almost complete within 4 hours.

The use of a crosslinking agent in the preparation of the superabsorbent polymer is essential for improving the absorption rate of the resulting superabsorbent polymer into the aqueous material and for stability in the swollen state (gel strength).

Generally, crosslinking agents which react with the carboxyl groups of α, β-unsaturated carboxylic acids and their alkali metal salts or polymers thereof are mainly water-soluble diglycidyl ether compounds, haloepoxy compounds, di- or polyisocyanate compounds and dialdehydes. Although the same crosslinking agents have been known, water-soluble diglycidyl ether compounds are preferred to improve the rate of absorption and gel strength without substantially reducing the absorption capacity characteristic of superabsorbent polymers (US Pat. No. 4,340,706). For example, polyethyleneglycol diglycidyl ether, polypropylene glycol diglycidyl ether, polyglycerol diglycidyl ether, or the like having different molecular weights may be used.

Therefore, also in the present invention, when ethylene glycol diglycidyl ether or polyethylene glycol diglycidyl ether is used as a crosslinking agent, an acrylic acid alkali metal salt polymer having a desired absorption capacity and gel strength can be obtained. The amount of crosslinking agent used is 0.001-2.0% by weight of monomer. If it is 0.001% or less, the gel strength after absorption is low and the absorption rate is slow. If it is 2% or more, the absorbency is too small. It was found that the absorbency and absorption rate of the obtained superabsorbent polymer depend not only on the concentration of the crosslinking agent used but also on the chain length of the crosslinking agent.

Existing superabsorbent polymers prepared by the known manufacturing techniques already mentioned are somewhat different depending on the manufacturing method, but the absorption rate as well as the absorption capacity is considerably high. Polymer particles are aggregated with each other. Therefore, its use in powder form is difficult and difficult to handle. In order to remove these disadvantages, to improve the stability of the powder product and to improve the dispersibility of the superabsorbent polymer in water, the hydrous silica (SiO ₂ , nH ₂ 0) stable at room temperature without affecting the original polymer properties, Inorganic additives such as hydrous aluminum oxide (Al ₂ O ₃ , nH ₂ O), hydrous titanium oxide (TiO ₂ , nH ₂ O) (JP-A-59-80459; U.S. 4535098) or cellulose Fiber (Japanese Patent Laid-Open No. 59-86657) has been used in a mixture of dried powdery superabsorbent polymers. However, in order to prepare these known polymer mixtures, there is a complexity in the manufacturing process that a separate mixer having excellent mixing ability after drying must be used separately. This actually causes the manufacturing atoms of the superabsorbent polymer to increase.

According to the present invention, it was found that the same effect can be obtained without dispersing an inorganic additive or a fiber such as cellulose in an organic solvent and then adding the mixture directly to the polymerization mixture after the polymerization. This is a phenomenon in which the additive used is effectively dissolved without dissolving in the organic solvent, which is fundamentally different from the known manufacturing techniques in that the process of preparing the super absorbent polymer for the end use is simplified into a single continuous process. Another feature of the present invention. In addition, the introduction of an additive prevents agglomeration between particles due to the hygroscopicity of the superabsorbent polymer in the drying step, so that drying is easy.

As the additive used in the present invention, inorganic additives such as silica and aluminum oxide or fibers such as cellulose, cellulose acetate, ethyl cellulose and the like are suitable. Among these, silica, cellulose and ethyl cellulose fibers are more preferable.

The amount of additive used is suitably 0.01-10% of the monomer weight, but the amount used depends on the hydrophobicity of the silica, the length of the fiber, or the degree of substitution of the ethyl group.

The crosslinked polymer of acrylic acid alkali salt prepared by the production method of the present invention has a high water absorption capacity of at least 600 times and 60 times the weight of the distilled water and 0.9% brine solution, respectively. This super absorbent polymer is excellent in absorbency and water retention ability, so it can be used as the absorbent of hygiene products, agricultural horticultural soil repair agent, wastewater coagulant, petroleum moisture remover and civil engineering, building index agent.

The absorbency of the superabsorbent polymer prepared in the present invention was measured by the following method. That is, 1 g of the dried polymer was poured into 2 L of distilled water (or 150 g of 0.9% brine solution), swelled for 30 minutes with stirring, and then filtered through a 100 mesh metal network for 3 hours to obtain a weight of filtered water (or 0.9% brine solution). Was subtracted from the weight of the originally used water (or 0.9% brine solution) as the absorbency value.

Hereinafter, the present invention will be described with reference to Examples. However, these examples are not given to limit the present invention.

Example 1

Into a 500 ml flask, 72.4 g of acrylic acid having a purity of 99.5% was added thereto, followed by neutralization by adding 138 g of a 21.7% sodium hydroxide solution. After cooling at room temperature, 0.14 g of potassium persulfate was added to dissolve to prepare a monomer solution. In a 1 liter three-necked flask equipped with a reflux condenser and agitator, 360 g of cyclohexane and 1.30 g of sorbitan monostearate (SPAN-60, HLB-4.7) as a surfactant, sorbitan monolaurate (SPAN-20, HLB-8.6) 2.8g, 0.22g polyoxyethylene sorbitan monostearate (TWEEN-60, HLB-14.9) was added to dissolve, and then a pre-prepared partially neutralized aqueous monomer solution was added dropwise for a predetermined time to disperse. I was. After the polymerization reactor was sufficiently filled with nitrogen gas, the temperature was raised to polymerize for 4 hours. At this time, the polymerization temperature was maintained at 55-75 ℃. After the polymerization was completed, 0.009 g of ethylene glycol diglycidyl ether was added as a crosslinking agent, and then crosslinked at 60 ° C. for 3 hours. The polymerization mixture was dried under reduced pressure to obtain 88 g of granulated polymer powder (400-800 µm) with uniform particles.

The absorbency of the obtained granular polymer (400-800 µm) in distilled water and 0.9% brine solution was 900 and 80 times the weight of the polymer itself, respectively. At this time, the time taken to absorb by the above-mentioned absorption capacity was within 5 minutes, and the absorption rate was very fast. In addition, the absorbent swollen polymer gel was stable enough that the absorption capacity did not change for a long time.

Example 2

Except that 0.7 g of SPAN-60 and 1.0 g of TWEEN-60 were used as the surfactant, 87 g of a granular polymer (500-1000 µm) powder was obtained by drying in the same manner as described in Example 1.

The polymers absorbed in distilled water and 0.9% brine solution were 650 and 65 times, respectively. Absorption rate was as fast as Example 1.

Example 3

The same method as described in Example 1, except that 1.0 g of sorbitan monooleate (SPAN-80, HLB-4.3), 3.1 g of SP AN-20, and 0.22 g of TWEEN-60 were added as the surfactant. 86 g of a granular polymer (300-600 μm) powder was obtained by drying under reduced pressure.

The polymers absorbed in distilled water and 0.9% brine solution were 800 and 80 times, respectively. The rate of absorption is very fast and the absorbed and swollen polymer gel did not change its absorption capacity for a long time.

Example 4

As described in Example 1, except that 1.5 g of SPAN-60, 2.5 g of SPAN-20 and 0.3 g of polyoxyethylene sorbitan monolaurate (TWEEN-21, HLB-13.3) were added as the surfactant. 87 g of granular polymer powder (200-500 µm) was obtained by drying under reduced pressure after preparing in the same manner. The polymers absorbed in distilled water and 0.9% brine solution were 800 and 75 times, respectively. Absorption rate was very fast.

Example 5

Except that 2.5g of SPAN-60 and 1.5g of TWEEN-60 were added as a surfactant, the same procedure as described in Example 1 was carried out, followed by drying under reduced pressure, drying under reduced pressure to obtain granular polymer powder (250-600 Μm) 86 g was obtained.

The polymers absorbed in distilled water and 0.9% brine solution were 850 and 80 times, respectively.

Example 6

Except that 1.3 g of SPAN-80 and 2.9 g of SPAN-20 were added as surfactants, 88 g of granular polymer powder (100-300 µm) was prepared by drying under reduced pressure. Got it.

The polymers absorbed in distilled water and 0.9% brine solution were 850 and 80 times, respectively.

Example 7

Except that the neutralization degree of acrylic acid was set to 50 mol% using 92 g of sodium hydroxide solution, 88 g of granular polymer powder (300-800 µm) was prepared by drying in the same manner as described in Example 1, followed by drying under reduced pressure. Got it.

The polymers absorbed in distilled water and 0.9% brine solution were 600 and 60 times, respectively. Absorption rate was very fast.

Example 8

Except that 0.1 g of ammonium persulfate was used as an initiator, 88 g of granular polymer powder (400-800 µm) was obtained by drying under reduced pressure after preparing the same method as described in Example 1. The polymers absorbed in distilled water and 0.9% brine solution were 850 and 80 times, respectively.

Example 9

Except that 0.01 g of ethylene glycol diglycidyl ether was used as the crosslinking agent, 86 g of a granular polymer powder (400-800 µm) was obtained by drying in the same manner as described in Example 1.

The polymers absorbed in distilled water and 0.9% brine were 1200 and 100 times, respectively, but the strength of the swollen gel was weak and some of them were lost through the mesh network.

Example 10

Except that 0.09 g of ethylene glycol diglycidyl ether was used as a crosslinking agent, it manufactured and dried in the same manner as described in Example 1, and obtained 88 g of granular polymer powder (400-800 micrometers).

The polymers absorbed in distilled water and 0.9% brine were 600 and 60 times, respectively. The rate of absorption was the fastest and the absorbed and swollen polymer gel had a high gel strength.

Example 11

A polyethylene glycol (600) diglycidyl ether as a crosslinking agent was prepared in the same manner as described in Example 1 except that it was used in the same manner as described in Example 1, followed by drying under reduced pressure to obtain 88 g of a granular polymer powder (350-800 µm). Got it.

The polymers absorbed in distilled water and 0.9% brine solution were 700 and 70 times, respectively.

Example 12

After crosslinking, 0.9 g of hydrous silica (trade name: AEROSIL, manufactured by Degussa) was dispersed in 50 g of cyclohexane as a solvent, and then prepared in the same manner as in Example 1, followed by drying under reduced pressure to obtain a uniform granular polymer. 88 g of a powder (400-800 μm) was obtained.

The absorption capacity of the polymer into distilled water and 0.9% brine solution is 900 times and 80 times, respectively, which is the same as the polymer obtained in Example 1. However, the dispersibility in water was much better when absorbed.

Example 13

After the crosslinking, 0.1 g of hydrous silica was dispersed and introduced into 50 g of cyclohexane as a solvent, and then prepared and dried in the same manner as described in Example 1 to obtain 88 g of a granular polymer powder (400-800 µm).

The polymers absorbed in distilled water and 0.9% brine solution were 900 and 80 times, respectively, and had excellent dispersibility.

Example 14

After the crosslinking, 0.15 g of cellulose fiber (trade name: KC-FLOCK, manufactured by Sanyo Kogyo Co., Ltd.) was dispersed in 50 g of cyclohexane as a solvent, and then prepared in the same manner as described in Example 1, followed by drying under reduced pressure and uniformity. 88 g of one granular polymer powder (400-800 µm) was obtained.

The polymer's ability to absorb distilled water and 0.9% brine in solution was 930 and 85 times, respectively. The dispersion rate at the time of absorption was excellent.

Example 15

After the crosslinking, 1.35 g of cellulose was dispersed in 50 g of cyclohexane as a solvent, and then prepared in the same manner as described in Example 1, followed by drying under reduced pressure to obtain 88 g of uniform granular polymer powder (400-800 µm). Got it.

The polymer's ability to absorb distilled water and 0.9% brine in solution was 950 and 85 times, respectively.

Comparative Example 1

Except that 4.3g of SPAN-60 was used as surfactant, it manufactured and dried in the same manner as described in Example 1, and obtained 86g of fine powdery polymers (10-50 micrometers).

The polymers had absorption capacity of distilled water and 0.9% brine solution 600 and 60 times, respectively, and the absorption rate was very slow.

Comparative Example 2

Except having used 4.3 g of SPAN-20 as surfactant, it manufactured and dried in the same way as Example 1, and obtained 80 g of lump-shaped hard polymers (1500 micrometers) of uniform particle size.

Comparative Example 3

Except that 180g of sodium hydroxide solution was used and the neutralization degree of acrylic acid was 98 mol%, it manufactured by the same method as described in Example 1, and dried under reduced pressure, and obtained granular polymer powder.

Absorption capacity of the polymer in distilled water and 0.9% brine solution was 150 and 20 times, respectively, but the strength of the swollen gel was weak, and some of the polymer was lost through the mesh network.

[Comparative Example 4]

Except that toluene was used as an organic solvent, it manufactured by the same method as described in Example 1, and dried under reduced pressure, and obtained 80 g of lump-like polymers with nonuniform particle distribution.

Claims (18)

Aqueous solutions of high concentration monomers containing at least 40% by weight of acrylic acid and alkali metal alkali metal salts are dispersed and suspended in an alicyclic hydrocarbon solvent containing a surfactant having a HLB value of 3-6 and a surfactant of 8-15, and suspended in the presence of a water-soluble radical polymerization initiator. A method for producing a granular acrylic acid alkali metal salt polymer having excellent water absorption and uniform particle size in a single step, characterized in that it is polymerized and crosslinked by a polymerization method and then silica or cellulose fibers are added as an additive. A sorbitan fatty acid ester according to claim 1, a sorbitan fatty acid ester having a HLB value of 3-6, glyceryl oleate, glycerol monostearate, or ethylene glycol monostearate and a sorbitan monolaurate having a HLB value of 8-15, Using two or more mixtures each selected from polyoxyethylene sorbitan fatty acid esters, or polyoxyethylene fatty acid esters. The method according to claim 2, wherein the fatty acid component of the sorbitan fatty acid ester having an HLB value of 3-6 is monostearic acid or monooleic acid. The method according to claim 2, wherein the fatty acid component of the polyoxyethylene sorbitan fatty acid ester or polyoxyethylene fatty acid ester having an HLB value of 8-15 is monolauric acid, monostearic acid, or monooleic acid. The method of claim 2 wherein the composition of the surfactant, HLB 3-6, and the surfactant, HLB 8-15, are 3-50% and 97-50% by weight, respectively. The method of claim 2 wherein the amount of surfactant is 1-10% of the monomer weight. The process according to claim 1, wherein cyclohexane is used as the alicyclic hydrocarbon solvent. The method according to claim 1, wherein sodium acrylate salt is used as alkali metal acrylate salt. The method of claim 1 wherein the degree of neutralization of acrylic acid is 50-95 mol%. The method according to claim 1, wherein potassium peroxide or ammonium persulfate is used as the water-soluble radical polymerization initiator. The method of claim 10 wherein the amount of water soluble radical polymerization initiator is 0.001-1.0 mol% of monomer concentration. The process of claim 1 wherein the polymerization temperature is 40-75 ° C. The method according to claim 1, wherein ethylene glycol diglycidyl ether or polyethylene glycol diglycidyl ether is used as a crosslinking agent. The method of claim 13, wherein the amount of the diglycidyl ether compound that is a crosslinking agent is 0.001-2% of the weight of the monomer. The method of claim 1 wherein hydrous silica is used as an additive. The method of claim 15, wherein the amount of silica is 0.01-10% of the monomer weight. The method of claim 1 wherein cellulose or ethylcellulose fibers are used as additives. 18. The method of claim 17, wherein the amount of cellulose or ethylcellulose is 0.01-10% of the monomer weight.