JPH0696606B2 - Dispersant for reverse phase suspension polymerization and method for reverse phase suspension polymerization - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a dispersant for reversed-phase suspension polymerization used when polymerization is carried out while suspending a water-soluble monomer in a hydrophobic solvent, and the dispersion. More specifically, it relates to a reverse phase suspension polymerization method using a dispersant, and a dispersant for reverse phase suspension polymerization and a reverse phase suspension polymerization capable of stably maintaining a suspended state of a polymerization system and reliably obtaining a granular polymer. Regarding the method.

[Prior Art] Conventionally, as a method of polymerizing a water-soluble monomer, a so-called reverse polymerization is carried out by suspending and dispersing an aqueous solution of a water-soluble monomer in a polymerization-inert and hydrophobic solvent. Phase suspension polymerization methods are well known.

In carrying out this method, it is important to appropriately select the dispersant in order to stably disperse the polymerizable monomer, and therefore various dispersants have been conventionally proposed.

For example, it has been proposed to use a nonionic surfactant such as sucrose fatty acid ester, sorbitan fatty acid ester, ethoxylated fatty acid amide, or glycerin fatty acid ester as a dispersant (Japanese Patent Publication No. 54-30710). .

In addition, a carboxyl group-containing polymer having an organic solvent affinity such as a methacrylic acid-methyl methacrylate--2-ethylhexyl acrylate copolymer (JP-A-57-98512),
Polymers such as a dispersant for reversed-phase suspension polymerization in which a cation portion is selected as a hydrophilic portion and a styrene derivative is selected as a lipophilic portion (JP-A-63-8402), a maleic anhydride-treated product of a resin having an allyl group, and the like. A water-soluble ethylenically unsaturated compound consisting of a compound or a monoalkyl phosphoric acid having a linear alkyl group (JP-A-61-209201) and a specific phosphoric acid monoester compound having an ethylenically unsaturated bond in the molecule A method using a monomer as a reactive dispersant (Japanese Patent Laid-Open No. 61-231003) has been proposed.

[Problems to be Solved by the Invention]

However, when a nonionic surfactant is used as a dispersant, the produced polymer becomes fine particles, and problems such as generation of powder gin in the separation and drying steps occur, and the handling thereof is difficult.

On the other hand, when a polymer compound or the like is used as the dispersant,
The produced polymer becomes small particles and although the above drawbacks can be improved to some extent, on the other hand, during the polymerization operation, a considerable amount of adhesion occurs between the polymer particles and the tank wall of the polymerization tank or the stirrer, and the reaction is performed. It is unavoidable that a part of the polymer will be lost as unusable polymerization vessel deposits. A great deal of labor is generally required to remove such water-soluble monomer deposits in the polymerization tank, which hinders efficient production of the granular polymer.

The present invention has been made in view of the above circumstances, and it is possible to stably disperse a water-soluble monomer in a hydrophobic solvent to obtain a granular polymer that is easy to handle, and to polymerize it in a polymerization device, a stirrer, or the like. An object of the present invention is to provide a dispersant for reverse phase suspension polymerization capable of suppressing adhesion of substances as much as possible and improving workability and productivity, and a reverse phase suspension polymerization method using the dispersant. And

[Means and Actions for Solving the Problems]

The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object. As a result, when reverse-phase suspension polymerization of a water-soluble monomer in a hydrophobic solvent, the lipophilic inorganic fine powder is used as a dispersant. It was found that it is effective to use as.

That is, when a lipophilic treatment-treated inorganic fine powder, for example, a hydrophilic inorganic fine powder is surface-treated and the solvent-affined inorganic fine powder is used as a dispersant in the reverse phase suspension polymerization method, it is unexpectedly water-soluble. Particles that can be stably dispersed in a hydrophobic solvent with little formation of polymer aggregates, stable production is possible, and easy-to-handle particles containing almost no fine-particle polymer It is possible to obtain a polymer (mainly having an average primary particle diameter of 230 to 730 μm), and to suppress the adhesion of the polymer to a polymerization device, a stirrer, etc. as much as possible, and thereby the whole process of polymer production. The inventors have found that the workability and the productivity can be remarkably improved, and have completed the present invention.

In the suspension polymerization method in which the continuous phase is a hydrophilic solvent (usually water) and the dispersed phase is a hydrophobic monomer such as a styrene monomer, conventionally, in addition to a dispersant such as polyvinyl alcohol or hydroxyethyl cellulose, An example is known in which an inorganic compound is used as a protective colloid agent or a dispersion stabilizer.

For example, in the presence of a nonionic surfactant and an anionic surfactant, a method of emulsion polymerizing a silicic acid colloid as a thickening agent (JP-A-49-113839), an inorganic filler such as calcium carbonate as a protective colloid and vinyl acetate monohydrate. Methods such as emulsion polymerization of monomers and the like (JP-A-57-67609), suspension polymerization using a poorly water-soluble inorganic compound such as calcium phosphate as a dispersion stabilizer (JP-A-1-100562), and the like. Proposed. Further, a method of crosslinking in the presence of an inorganic substance such as talc or montmorillonite (Japanese Patent Laid-Open No. 62-2548).
41, 62-254842), a method of adding an inorganic substance to a slurry obtained by reverse phase suspension polymerization (JP-A-59-59).
No. 8711), a method of mixing an inorganic substance for polymer modification and surface treatment (JP-A-56-133028, 59-80).
No. 459 and No. 60-84360) are proposed.

However, when the above-mentioned method is applied to the reverse phase suspension polymerization method and a polymerization-inert inorganic substance is added, the suspension system generally becomes unstable and easily agglomerates, as shown in Comparative Examples to be described later, and it becomes granular. In addition to not being able to obtain the above polymer, there is a problem that the stirrer is overloaded and it is impossible to take it out of the polymerization tank.

Hereinafter, the present invention will be described in more detail.

The dispersant for reverse phase suspension polymerization according to the present invention is composed of an inorganic fine powder that has been subjected to a lipophilic treatment.

Here, the degree of lipophilicity of the dispersant according to the present invention is determined by, for example, taking an equal volume of the monomer aqueous solution and the hydrophobic solvent in a test tube, adding a small amount of inorganic fine powder thereto, and thoroughly shaking and then statically stirring. The inorganic fine powder can be identified by observing which liquid the inorganic fine powder migrates to, and as the inorganic fine powder having preferable lipophilicity, one that migrates into a hydrophobic solvent, or an interface between both liquids The ones that float are.

In the reverse phase suspension polymerization method of the present invention, the inorganic fine powder used as a dispersant is a lipophilic treatment, and if it is hydrophilic, it may be used by hydrophobizing it to impart lipophilicity. However, silica-based, aluminum oxide-based, and titanium oxide-based fine powders are preferably used. In addition,
When the hydrophobic treatment is carried out, the degree of hydrophobicity is preferably 35 or more, and the particle size and specific surface area of the inorganic fine powder are not particularly limited, but usually the average primary particle size is 10 μm or less,
From the viewpoint of dispersibility, it is preferable that the specific surface area (BET method) is about 1 m ² / g or more.

Here, as the hydrophobic treatment method for imparting lipophilicity to the hydrophilic inorganic fine powder, for example, hydrous silicic acid, silicic acid anhydride, a salt thereof, or a silica diameter inorganic fine powder such as silicon dioxide is present on the surface. The method of chemically changing the silanol group to make it lipophilic and increasing the affinity to the hydrophobic solvent is suitably adopted. Furthermore, in this method, a silane coupling agent that can chemically react with a silanol group or an OH group on the surface of a metal oxide, a tinca-based coupling agent, an aluminum-based coupling agent, or the like is preferably used. For example, silane coupling It is preferable to use an organosilicon compound such as dimethyldichlorosilane as the agent to introduce a lipophilic group such as a methyl group into the silanol group. In this case, it is preferable that about 10% or more, especially 30% or more of the silanol groups be subjected to a hydrophobic treatment with an organosilicon compound. By using such lipophilic silica as a dispersant for reverse phase suspension polymerization, aggregation It is possible to reliably produce a bead-shaped or elliptical (capsule-shaped) granular polymer by preventing the generation of the polymer and stably suppressing the generation of the fine-particle polymer.

The same treatment can be applied to aluminum oxide-based particles and titanium oxide-based particles.

As described above, as a commercial product in which a methyl group is introduced into the silanol group on the surface of silica to make it hydrophobic, trade name R-972, R
-974 (manufactured by Nippon Aerosil Co., Ltd., containing approximately 7 silanol groups on the surface)
5% of which was subjected to lipophilic treatment with CH ₃ group),
Commercially available products obtained by hydrophobizing aluminum oxide include trade names H-32ST, H-42STV, and H-320ST (manufactured by Showa Denko KK).

Another method for increasing the affinity of various inorganic fine powders (hydrophilic) for hydrophobic solvents is to modify by coating (for example, to make a transparent positive hydrated metal oxide hydrosol, and then Lipophilic conversion of colloidal particles in hydrosol by adding ionic surfactant), topochemical modification (eg silica, metal oxides such as aluminum oxide, titanium oxide, zinc oxide, magnesium oxide, iron oxide or silica) -A method of treating a complex oxide such as alumina with alcohol, a method of treating with a coupling agent, or calcium carbonate, barium sulfate, calcium sulfate,
A method of treating aluminum hydroxide, magnesium hydroxide, talc, etc. with a coupling agent), modification utilizing reaction active points that appear on the crushed surface of the inorganic powder (for example, a method of graft polymerization on the powder surface), capsules Examples include, but are not limited to, modification by oxidization, modification by using high energy such as ultraviolet rays, radiation, and plasma (for example, a method of radiation graft polymerization of styrene on alumina), and modification by precipitation reaction. Instead, any method that can make the inorganic fine powder lipophilic can be employed.

In the reverse phase suspension polymerization method of the present invention, one type of the above-mentioned dispersant comprising the lipophilic inorganic fine powder is used alone or in combination of two or more types, and usually 0.01 to 15 with respect to the water-soluble monomer. It can be added and used in the range of wt%, preferably 0.05 to 8 wt%. If the addition amount is less than 0.01% by weight, the desired dispersion effect cannot be obtained, while if the addition amount is more than 15% by weight, the physical properties of the polymer produced may be adversely affected.

In the reverse phase suspension polymerization method of the present invention, a conventionally known dispersant may be used in combination within a range that does not impair the dispersing effect of the lipophilic inorganic fine powder described above.

In the reverse phase suspension polymerization method of the present invention, a water-soluble monomer can be polymerized in a hydrophobic solvent by a usual method except that the above-mentioned dispersant is used.

For example, as the hydrophobic solvent, it is possible to use all hydrophobic solvents which are inactive in polymerization and do not dissolve water, but in consideration of removal of heat of polymerization and drying step of the resulting polymer, the boiling point is It is preferable to use an aliphatic hydrocarbon, an alicyclic hydrocarbon or an aromatic hydrocarbon or a mixed solvent thereof having a temperature of 30 to 200 ° C., especially heptane, octane, n-hexane, cyclohexane, methylcyclohexane, benzene, toluene, Xylene or a mixed solvent thereof is preferably used.

On the other hand, as the water-soluble monomer, any water-soluble monomer that can be polymerized by the reverse phase suspension polymerization method can be used. For example, acrylic acid or methacrylic acid or their alkali metal salts, ammonium salts, amine salts, acrylamides or methacrylamides, water-soluble N-substituted acrylamides or methacrylamides, vinylimidazoles, vinylpyridines, vinylpyrrolidones, sulfonated styrenes, and Examples thereof include vinyl sulfonic acid and alkali metal salts thereof, and one of these monomers may be copolymerized alone or two or more of them may be arbitrarily combined and copolymerized. Further, other water-soluble monomers such as acrylic acid ester may be copolymerized within a range (homogeneous solution) that does not impair the solubility of the aqueous monomer solution.

Furthermore, if necessary, a crosslinking reaction can be carried out with a water-soluble crosslinking agent having two or more polymerizable unsaturated groups during (co) polymerization of the above-mentioned monomer or after the polymerization. Examples of the cross-linking agent include methylenebisacrylamide and water-soluble cross-linking agents having two or more functional groups capable of reacting with the functional groups of the ethylenically unsaturated monomer, such as ethylene glycol diglycidyl ether. However, the present invention is not limited to these.

The above water-soluble monomer is generally used as an aqueous solution in reverse phase suspension polymerization, but in this case, the monomer concentration can be changed within a wide range, and generally 10 to 80% by weight. it can.

Further, the ratio of the aqueous monomer solution and the hydrophobic solvent can be changed over a wide range, but the volume ratio is usually 1: 1.
A range of up to 1:10 is preferred.

Further, as the polymerization initiator, known water-soluble radical initiators such as persulfates and azo compounds can be used alone or in combination of two or more at a usual dose, and In addition to the above, chromium ion, sulfite, hydroxylamine, hydrazine and the like can be added to be used as a redox polymerization disclosure agent.

〔The invention's effect〕

According to the present invention, by using the lipophilic inorganic fine powder as a dispersant as a dispersant for reverse phase suspension polymerization,
A water-soluble monomer can be stably dispersed in a hydrophobic solvent, and a granular polymer that is easy to handle can be selectively obtained, and the particle size can be controlled in a wide range, and it can be used in a polymerization device or a stirrer. It is possible to suppress the adhesion of the polymer of the polymer as much as possible, whereby the workability throughout the entire process of polymer production,
The productivity can be remarkably improved. Therefore, it is possible to convert the conventional batch system from a conventional batch system to a continuous system, and the reverse phase suspension polymerization method of the present invention is a thickener obtained by the conventional reverse phase suspension polymerization method. It can be suitably applied to the production of coagulants, cross-linking polymers and the like.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

In addition, in the following examples, the degree of hydrophobicity of the lipophilic compound was evaluated based on the following method.

Hydrophobicity evaluation test method In a 200 cc beaker, 50 cc of distilled water was added, and 0.2 g of a sample of lipophilic fine powder was added (in this case, if the sample was sufficiently hydrophobic, it completely floated on the water surface). Next, methanol was added to the floating water of this sample while stirring with a small magnetic stirrer from a burette with the tip placed in water. As methanol is added, the sample powder floating on the water surface gets wet and disperses in water, but the amount of methanol dropped at the point where the floating sample disappeared and became completely wet was measured, and this measured value was used as Acc The degree of hydrophobicity was calculated from the formula.

It should be noted that the larger the value of the degree of hydrophobicity, the higher the degree of hydrophobicity, because the higher the concentration of the aqueous methanol solution is, the more the water does not get wet.

Example 1 14 equipped with a stirrer, a reflux condenser and a nitrogen gas introduction pipe
Cyclohexane 357 g and lipophilic silicon dioxide 2 g were charged into a two-necked separable flask, nitrogen gas was blown in to expel dissolved oxygen, and the mixture was heated to 73 ° C. As lipophilic silicon dioxide, hydrophilic silicon dioxide aerosol (particle Diameter 10
~ 40nm) The product of chemically reacting the surface silanol groups with dimethyldichlorosilane.
% _Of CH ₃ hydrophobic silicon dioxide which has been subjected to the parent oil processing in the group (trade name: R-972, manufactured by Nippon Aerosil Co., Ltd., average particle size of about
16 nm, hydrophobicity 45) was used.

On the other hand, 100 g of acrylic acid was charged into another flask and partially neutralized with an aqueous sodium hydroxide solution while cooling from the outside. At this time, the molar ratio of sodium hydroxide / acrylic acid was 0.75, and the concentration of the aqueous monomer solution was 40% by weight. Next, 0.395 g of ammonium persulfate was added and dissolved therein, and nitrogen gas was blown into the solution to remove oxygen existing in the aqueous solution.

The partially neutralized aqueous solution of acrylic acid was added dropwise to the content of the separable flask at a stirring speed of 500 rpm for 60 minutes for polymerization. After the completion of the polymerization, the temperature was maintained at 73 ° C. and the reaction was continued for another 60 minutes. Next, 0.06 g of a crosslinking agent (ethylene glycol diglycidyl ether) was added and stirring was continued for 60 minutes. Then, 140 g of water was distilled off by azeotropic dehydration, the solvent cyclohexane was distilled off under reduced pressure, and the remaining polymer portion was removed by 100 to 110.
When dried under reduced pressure at ℃, average particle size is 420μm and particle size is 1
A crosslinked sodium acrylate bead-shaped polymer having a proportion of 80 μm or less at 4.2% by weight was obtained. The amount of deposits in the reaction vessel at this time was extremely small at 0.15 g.

Example 2 In Example 1, the lipophilic silicon dioxide (R-97
Polymerization was carried out according to Example 1 except that the amount of 2) used was changed from 2 g to 0.45 g. The average particle size was 680 μm and the particle size was 180 μm.
A crosslinked beaded polymer having a ratio of less than μm of 1.1% by weight was obtained. When the slurry after the completion of the polymerization was observed, no agglomerates were observed, and the amount of adhesion to the reaction tank was 0.30 g.

Example 3 Instead of the partially neutralized acrylic acid aqueous solution in Example 1, 153.5 g of a 15 wt% acrylic acid aqueous solution and 2,2′-
Azobis- (2-amidinopropane) dichloric acid 0.23g is used as a cross-linking agent ethylene glycol diglycidyl ether.
Polymerization was carried out according to Example 1 except that 0.06 g was not used. Next, 115.2 g of water was distilled off by azeotropic dehydration and then dried under reduced pressure to obtain a bead-shaped polyacrylic acid polymer having an average particle size of 500 μm. In addition, the amount of adhesion to the reaction tank was 0.25 g.

When 1 g of this polymer was added to 100 g of ion-exchanged water and mixed with stirring, a viscous liquid was obtained.

Example 4 In Example 1, 2 g of lipophilic silicon dioxide (R-972)
Instead of R-972, the surface is oleophilized with CH ₃ group, and the average particle size is about 12 nm.
Polymerization was carried out according to Example 1 except that 2 g was used (trade name, manufactured by Nippon Aerosil Co., Ltd.), and the average particle size was 460 μm.
As a result, a cross-linked sodium polyacrylate was obtained. In addition, the adhesion amount in the reaction tank was 0.2 g.

Example 5 Polymerization was carried out in the same manner as in Example 1 except that 2 g of acrylamide was added to the partially neutralized acrylic acid aqueous solution. As a result, a crosslinked acrylamide-acrylic acid having an average particle size of 430 μm was obtained. A soda copolymer was obtained. The amount attached to the reaction tank was 0.18 g.

[Example 6] In Example 1, 2 g of lipophilic silicon dioxide (R-972)
According to Example 1, except that 1 g of the same silicon dioxide (R-972) and 0.1 g of silicon dioxide (trade name R-202, manufactured by Nippon Aerosil Co., Ltd.) surface-treated with silicone oil to make it lipophilic were used instead of The average particle size was 430μ.
A polymer of m was obtained. Note that no agglomeration was observed in the slurry after the completion of polymerization, and the amount attached to the reaction vessel was 0.
It was 3 g.

[Example 7] In Example 1, 2 g of lipophilic silicon dioxide (R-972)
Instead of 1 g of silicon dioxide (R-972) and trimethylsilyl group on the surface of lipophilic silicon dioxide (trade name R-
812, manufactured by Nippon Aerosil Co., Ltd.) Example 1 except that 0.1 g was used.
Polymerization was carried out according to the above procedure to obtain a polymer having an average particle size of 410 μm. It should be noted that almost no aggregate was observed in the slurry after the completion of polymerization, and the amount attached to the reaction tank was 0.43 g.

[Example 8] In Example 1, 2 g of lipophilic silicon dioxide (R-972) was used.
Instead of 1.5 g of the same silicon dioxide (R-972) and alumina lipophilicized by the esterification method [The reaction product (AlOH + ROH of alumina gel hydrophobized under the reflux of ethanol
→ AlOR + H ₂ O ↑, R: ethyl group), (average particle size 1 μm or less)] Polymerization was carried out in the same manner as in Example 1 except that 0.1 g was used. Crosslinked polyacrylic acid having an average particle size of 460 μm. I got soda. The amount attached to the reaction tank was 0.42.
It was g.

Example 9 In Example 3, 153.5 g of a 15% by weight acrylic acid aqueous solution
Instead of 15 wt% acrylamide aqueous solution and 2 g of lipophilic silicon dioxide (R-972) was changed to 0.8 g, the reaction was carried out in the same manner as in Example 1 to obtain an elliptical shape (average major axis about 760 μm, average short axis). A water-soluble acrylamide polymer having a diameter of about 380 μm) was obtained. A micrograph (50 times magnification) of this polymer is shown in the reference figure. Note that the amount attached to the reaction tank was 0.1 g, which was very small.

Example 10 In Example 1, with respect to the partially neutralized aqueous solution of acrylic acid
Polymerization was carried out in the same manner as in Example 1 except that 6 g of 10% polyvinyl alcohol (trade name: GH-17, manufactured by Nippon Gosei Co., Ltd.) and 100 g of cyclohexane were added to prepare an O / W emulsion-type monomer emulsion, A beaded polymer of crosslinked porous sodium acrylate having an average particle diameter of 230 μm was obtained. In addition,
The amount attached to the reaction tank was 0.42 g.

Example 11 380 g of cyclohexane and a dispersant R- were added to the polymerization apparatus of Example 1.
0.62 g of 972 was charged and the temperature was raised to 75 ° C. Separately, dissolve 30 g of acrylic acid and 65.5 g of dimethylaminoethyl methacrylate in 175 g of ion-exchanged water in an Erlenmeyer flask to give 35%
12.5 g of hydrochloric acid was added. Furthermore, 10% partially saponified polyvinyl alcohol (GH-17, manufactured by Nippon Gosei Co., Ltd.) 6 g, cyclohexane 10
After adding 0 g and emulsifying the monomer aqueous solution under stirring (O / W emulsion), 0.05 g of ammonium persulfate as a polymerization initiator was added and dissolved, and this O / W type monomer liquid was added to the above polymerization apparatus. The mixture was added dropwise under nitrogen atmosphere over 60 minutes for polymerization and then left at 70 to 75 ° C. for 30 minutes to complete the polymerization.

After this, the water contained in the copolymer was azeotropically dehydrated to 20% under the reflux of cyclohexane, cyclohexane was further removed, and the copolymer was dried under reduced pressure at 80 to 100 ° C. A porous copolymer having a diameter of 300 μm was obtained. This copolymer 1
When g was added to 100 ml of ion-exchanged water with stirring, a viscous aqueous solution was obtained over time. The amount of deposits on the tank is 0.
It was 27 g.

Example 12 0.05 g of ethylene glycol diglycidyl ether was added to 2 ml of water.
Example except that an aqueous solution dissolved in was added after azeotropic dehydration
In the same manner as in 11, a crosslinked porous copolymer having an average particle size of 280 μm was obtained. The amount of the deposit on the tank at that time was 0.3 g.

Example 13 A cross-linked copolymer having an average particle size of 600 μm was obtained in the same manner as in Example 12 except that 6 g of 10% GH-17 and 100 g of cyclohexane were not added. The amount of deposits in the bath at that time is 0.25g
Met.

[Example 14] In the same manner as in Example 10 except that 4 g of white carbon (Tokushiru N manufactured by Tokuyama Soda Co., Ltd.) was used instead of 6 g of 10% polyvinyl alcohol to prepare an O / W emulsion type monomer emulsion. The polymerization was completed, 0.09 g of ethylene glycol diglycidyl ether was added, and a crosslinking reaction (I) was carried out for 60 minutes. Next, 20% of the water in the polymer was distilled off by azeotropic dehydration, and ethylene glycol diglycidyl ether 0.12
g was added, a crosslinking reaction (II) was carried out for 60 minutes, and the mixture was dried by a conventional method to obtain a beaded porous polymer having an average particle size of 320 μm. The deposit on the bath at that time was 0.15 g.

[Example 15] 6 g of polyvinyl alcohol instead of 4 g of white carbon
The same as in Example 14 except that the average particle size of 360μ
A bead-shaped porous polymer of m was obtained. The deposit on the bath at that time was 0.26 g.

Example 16 In Example 1, 2 g of lipophilic silicon dioxide (R-972)
Instead of aluminum hydroxide as a dispersant (trade name: H
−43, Showa Denko KK 10 g and coupling agent (isopropyltriisostearoyl titanate, trade name: KR-TTS,
Ajinomoto Co.) 3 g and cyclohexane 30 g are mixed at room temperature for 30 minutes, then cyclohexane is distilled off, and 110 g under reduced pressure.
When heat-treated for 3 hours, a fine powder (lipophilic aluminum hydroxide) having a hydrophobicity of 53 was obtained.

A bead-like polymer was obtained in the same manner as in Example 1 except that 5 g of this lipophilic aluminum hydroxide was used. The obtained bead-shaped polymer had an average particle size of 290 μm and a deposition amount in the tank of 0.4 g.

Example 17 In Example 1, 2 g of lipophilic silicon dioxide (R-972)
Instead of titanium oxide as a dispersant (trade name: MT-150A,
Reverse phase suspension polymerization was carried out in the same manner as in Example 1 except that 3 g of lipophilic titanium oxide (hydrophobicity 58) obtained by subjecting Teika Co., Ltd.) to hydrophobic treatment in the same manner as in Example 16 was used. As a result, a bead-like polymer having an average particle size of 410 μm was obtained,
The amount deposited on the reaction vessel was 0.5 g.

Example 18 In Example 16, 10 g of aluminum hydroxide (H-43)
And a coupling agent (alumina oxide (trade name: Aluminum Oxide C, manufactured by Nippon Aerosil Co., Ltd.) in place of 3 g of KR-TTS) 1
Hydrophobizing treatment was performed in the same manner as in Example 16 except that 0 g and a coupling agent (acetoalkoxyaluminum diisopropylate, trade name: AL-M, manufactured by Ajinomoto Co., Inc.) 3 g were used. Reversed phase suspension polymerization was conducted in the same manner as in Example 1 except that 5 g of the obtained lipophilic alumina oxide (hydrophobicity 48) was used as a dispersant, and a bead-like polymer having an average particle size of 430 μm was obtained. The amount adhering to the reaction vessel was 0.5 g, which was extremely small.

Comparative Example 1 In Example 1, 2 g of lipophilic silicon dioxide (R-972)
Instead of hydrophilic silicon dioxide (trade name Aerosil
200 g, manufactured by Nippon Aerosil Co., Ltd.) was polymerized in the same manner as in Example 1. As a result, the polymerization system gelled and no particulate polymer was obtained.

Comparative Example 2 In Example 1, 2 g of lipophilic silicon dioxide (R-972)
Polymerization was carried out in the same manner as in Example 1 except that 4 g of sorbitan monostearate was used in place of
Only a fine particle polymer of 30 to 70 μm was obtained. In addition, the adhesion amount in the reaction tank was as large as 3.1 g.

Comparative Example 3 In Example 1, 2 g of lipophilic silicon dioxide (R-972)
When 2 g of talc (natural hydrous anhydrous magnesium silicate, first-class reagent, manufactured by Showa Kagaku Co., Ltd.) was used in place of to carry out the polymerization according to Example 1, the polymerization system gelled and a stable suspension was obtained. No slurry was obtained.

[Comparative Example 4] In Example 1, 2 g of lipophilic silicon dioxide (R-972)
Polymerization was carried out in the same manner as in Example 1 except that 2 g of kaolin (one kind of viscosity, first-class reagent, manufactured by Kanto Kagaku Co., Ltd.) was used instead of, and the polymerization system gelled and a bead-shaped polymer was not obtained. .

Claims (2)

[Claims] 1. A dispersant for reverse phase suspension polymerization for water-soluble monomers, which comprises an inorganic fine powder subjected to lipophilic treatment. 2. A reverse phase suspension polymerization method, which comprises using, as a dispersant, an inorganic fine powder subjected to lipophilic treatment when reverse phase suspension polymerization of a water-soluble monomer in a hydrophobic solvent.