JP2002332358A - Method for adjusting solubility of water-in-oil emulsion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a safe and efficient dissolving process which may inhibit the generation of bulk, non-dissolved particles generated by rapid solution and viscosity increase of water-in-oil emulsions when adding emulsifiers with high HLB as phase inversion agents at high proportions. SOLUTION: When dissolving a water-in-oil polymer emulsion containing a hydrophobic liquid as a continuous phase and an aqueous solution of a water- soluble polymer as a dispersed phase, a combination of an oil-soluble emulsifier and a water-soluble emulsifier is added to and mixed with the water-in-oil polymer emulsion before dissolving the emulsion in water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the solubility of a water-in-oil emulsion, and more particularly to a water-in-oil emulsion having a continuous phase of a hydrophobic liquid and a dispersed phase of an aqueous solution of a water-soluble polymer. Upon dissolving in water, an oil-soluble emulsifier and a water-soluble emulsifier are added to the water-in-oil emulsion,
The present invention relates to a method for adjusting the solubility of a water-in-oil emulsion, which is characterized by dissolving in water after mixing.

[0002]

2. Description of the Related Art A water-in-oil emulsion of a water-soluble polymer can store a water-soluble polymer in a high-concentration product form, and since the viscosity of the dispersion is very low, a high molecular weight such as a polymer flocculant is used. It is a liquid product suitable for applications requiring For example, Japanese Patent Publication No. 54-37986 discloses a monomer aqueous solution 30.
A method of producing a water-in-oil emulsion by emulsifying and dispersing 70 to 30% by weight of a hydrophobic organic liquid and 70 to 30% by weight of a hydrophobic organic liquid using a surfactant is disclosed. However, since it is a water-in-oil type, when it is dispersed in water at the time of dissolution, oil is present around water droplets and dissolution does not proceed as it is. For this reason, a method of adding a hydrophilic emulsifier called a so-called "phase inversion agent" to an emulsion or dissolved water to promote dissolution has been adopted (JP-A-50-43189).

[0003] Depending on the properties of the dissolved water, this dissolving operation is also one of the points that determines the performance of the water-in-oil emulsion type flocculant. That is, if the amount of the phase change agent is increased, the solubility is improved, but the storage stability of the emulsion product is lowered, and the aggregation performance or the environment is affected. A certain amount of an emulsifier having a certain HLB value is previously added to the dissolving water so that the time until complete dissolution can be set, and a certain amount of a water-in-oil emulsion is added thereto, and the mixture is dissolved under stirring. A method for preparing a liquid has been disclosed (Japanese Patent Publication No. 3-75568). Further, depending on the user's use site, the water-in-oil emulsion to which the phase change agent has been added is dissolved in water to form an aqueous solution. In some cases, an aqueous solution is additionally prepared. In such a case, it is very difficult to select the type of the transfer agent or to determine the amount of the transfer agent because of the viscosity.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to rapidly dissolve a water-in-oil emulsion due to the addition of an emulsifier having a high HLB added as a phase change agent and its high addition rate.
An object of the present invention is to develop a safe and efficient dissolving method capable of preventing generation of coarse undissolved particles caused by an increase in viscosity.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the following inventions have been reached. That is, the invention according to claim 1 of the present invention provides a method for converting a hydrophobic liquid into a continuous phase,
When dissolving a water-in-oil polymer emulsion having a water-soluble polymer aqueous solution as a disperse phase in water, an oil-soluble emulsifier and a water-soluble emulsifier are used in combination with the water-in-oil polymer emulsion, mixed, and then mixed with water. A method for controlling the solubility of a water-in-oil emulsion characterized by dissolving in water.

According to a second aspect of the present invention, the water-soluble polymer is
5 to 100 mol% of a cationic monomer represented by the following general formula (1) and / or (2), 0 to 40 mol% of an anionic monomer represented by the following general formula (3) and 0 to acrylamide 2. The composition according to claim 1, comprising 95 mol%.
The method for adjusting the solubility of a water-in-oil emulsion described in the above item.

Embedded image R1 is hydrogen or a methyl group; R2 and R3 are alkyl or alkoxy groups or benzyl groups having 1 to 3 carbon atoms; R4 is hydrogen or an alkyl or alkoxy group or benzyl group having 1 to 3 carbon atoms; . X1 represents an anion, respectively.

Embedded image R5 represents hydrogen or a methyl group; R6 and R7 represent alkyl or alkoxy groups or benzyl groups having 1 to 3 carbon atoms; X2 represents an anion, respectively.

Embedded image R8 is hydrogen, methyl or carboxymethyl, R9
Is hydrogen or carboxyl group, A is SO3, C6H4S
O3, CONHC (CH3) 2CH2SO3 or C
OO and Y each represent hydrogen or a cation

[0007] The invention of claim 3 is that the water-soluble polymer is:
Anionic monomers 2 to 6 represented by the general formula (3)
2. The method for controlling the solubility of a water-in-oil emulsion according to claim 1, wherein 0 mol% and acrylamide comprise 40 to 98 mol%.

According to a fourth aspect of the present invention, a nonionic oil-soluble emulsifier is added to and mixed with the water-in-oil polymer emulsion, and then a nonionic water-soluble emulsifier is added, mixed and dissolved in water. The method for controlling the solubility of a water-in-oil emulsion according to claim 1, characterized in that:

The invention of claim 5 is that the nonionic oil-soluble emulsifier has an HLB number (hydrophobic lipophilic balance) of 2 to 9, and the nonionic water-soluble emulsifier has an HLB number of 8 to 9 The method for adjusting the solubility of a water-in-oil emulsion according to claim 1 or 4, wherein the solubility is 20.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The method of synthesizing a water-in-oil emulsion is the same as the conventional one. First, a water-soluble vinyl monomer, water, an oily substance composed of at least one kind of hydrocarbon, an amount effective for forming a water-in-oil emulsion and HL
After mixing at least one surfactant having B and forming a water-in-oil emulsion under strong stirring, the mixture is synthesized by adding a polymerization initiator and polymerizing in a nitrogen atmosphere. Examples of the water-soluble vinyl monomer include the following. Examples of the anionic monomer include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, vinylsulfonic acid, vinylbenzenesulfonic acid, and acrylamide 2-methylpropanesulfonic acid. Non-ionic monomers (meth) acrylamide, N, N-dimethylacrylamide, vinyl acetate, acrylonitrile, methyl acrylate, 2-hydroxyethyl (meth) acrylate, diacetone acrylamide, N-vinylpyrrolidone, N-vinyl Formamide, N-vinylacetamide and the like.

In order to synthesize an amphoteric water-soluble copolymer, a cationic monomer is copolymerized in addition to the anionic monomer and the nonionic monomer. For example, examples of the tertiary amino group-containing monomer include dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, methyldiallylamine, and ethyldiallylamine. Examples of the quaternary ammonium group-containing monomer include (meth) acryloyloxyethyltrimethylammonium chloride, which is a quaternary compound of the tertiary amino group-containing monomer with (meth) methyl chloride or benzyl chloride.
(Meth) acryloyloxy 2-hydroxypropyltrimethylammonium chloride, (meth) acryloylaminopropyltrimethylammonium chloride, (meth)
Acryloyloxyethyldimethylbenzylammonium chloride, (meth) acryloyloxy 2-hydroxypropyldimethylbenzylammonium chloride, (meth) acryloylaminopropyldimethylbenzylammonium chloride and the like can be mentioned. Further, dimethyldiallylammonium chloride, methylbenzyldiallylammonium chloride and the like are included.

In the case of cationic or amphoteric polymers, the copolymerization molar ratio of these monomers is from 5 to 100 mol% of the cationic monomers represented by the general formulas (1) and / or (2). 0 to 40 mol% of the anionic monomer represented by the general formula (3) and acrylamide in an amount of 0 to 9
5 mol%, preferably 10 to 100 mol%, 0 to 30 mol% of anionic monomer and 0 to acrylamide.
90 mol%. In the case of an anionic polymer,
Anionic monomers 2 to 5 represented by the general formula (3)
0 mol% and 50 to 98 mol% of acrylamide,
Preferably, 5 to 50 mol% of the anionic monomer and 50 to 95 mol% of acrylamide.

Examples of oily substances consisting of hydrocarbons include:
Examples include paraffins, mineral oils such as kerosene, light oil, and medium oil, hydrocarbon-based synthetic oils having substantially the same range of boiling point and viscosity, and mixtures thereof.

Examples of at least one type of surfactant having an HLB and an effective amount for forming a water-in-oil emulsion are nonionic surfactants of HLB 3 to 6, and specific examples thereof include: Sorbitan monooleate, sorbitan monostearate, sorbitan monopalmitate
And others. The addition amount of these surfactants is 0.5 to 10% by weight, preferably 1 to 5% by weight, based on the total amount of the water-in-oil emulsion.

After neutralizing the anionic monomer, the above components are mixed, and a water-in-oil emulsion is formed by an emulsifying machine or the like, followed by purging with nitrogen and keeping the water-in-oil emulsion at a certain polymerization temperature. Is set, polymerization is started by a radical polymerization initiator. As an initiator, any of an azo type, a peroxide type, and a redox type can be polymerized. Examples of the oil-soluble azo initiator include 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexanecarbonitrile), and 2,2′-azobis (2
-Methylbutyronitrile), 2,2'-azobis (2-
Methylpropionate), 4,4'-azobis (4-methoxyl2,4-dimethyl) valeronitrile and the like.

Examples of the water-soluble azo initiator include 2,
2′-azobis (amidinopropane) dichloride,
2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 4, 4 ′
-Azobis (4-cyanovaleric acid) and the like. Examples of the redox system include a combination of ammonium or potassium peroxodisulfate with sodium sulfite, sodium hydrogen sulfite, trimethylamine, tetramethylethylenediamine, or the like. Further examples of peroxides are ammonium peroxodisulfate,
Examples include hydrogen peroxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, succinic peroxide, t-butylperoxy 2-ethylhexanoate and the like.

The polymerization temperature can be from 0 to 80 ° C, preferably from 20 to 60 ° C. The polymerization concentration is generally from 10 to 60% by weight, preferably from 20 to 5% by weight.
0% by weight facilitates the control of the polymerization reaction and has good production efficiency.

The water-in-oil emulsion of the present invention can be used in addition to the above-mentioned monomers, that is, anionic monomers, nonionic monomers, tertiary amino groups or quaternary ammonium base-containing monomers, as well as crosslinkable monomers. , A multifunctional monomer such as methylenebisacrylamide or ethylene glycol di (meth) acrylate, or a thermally crosslinkable monomer such as N, N-dimethylacrylamide. However, it is also possible to improve the performance by modifying the copolymer to cope with various wastewaters.

A phase change agent is added to the water-in-oil emulsion synthesized as described above to promote dissolution in water. Conventionally, a phase-change agent uses a water-soluble emulsifier having an HLB of 8 to 20. However, when the phase inversion agent is added too much, undissolved particles are generated due to a rapid increase in viscosity during dissolution, and environmental concerns arise. On the other hand, if the amount is too small, the solubility decreases. Therefore, in the present invention, an oil-soluble emulsifier is used in addition to a water-soluble emulsifier. Particularly, the emulsifier used in the present invention is a nonionic water-soluble emulsifier and a nonionic oil-soluble emulsifier. By using them together in this manner, the viscosity of the solution increases in proportion to the time, and the generation of undissolved particles can be suppressed. The addition ratio of the nonionic water-soluble emulsifier and the nonionic oil-soluble emulsifier is as follows: a: b, where a and b are weight percentages of the water-soluble emulsifier and the oil-soluble emulsifier, respectively.
= 9: 1 to 5: 5, preferably a: b = 8: 2
5: 5. As the addition method, a method in which both emulsifiers are mixed and added, or a method in which an oil-soluble emulsifier is added and mixed, and then a water-soluble emulsifier is added and mixed is conceivable. Add in. If the water-soluble emulsifier is added first, the water-in-oil emulsion may be broken, which is not preferable.

The nonionic water-soluble emulsifier as referred to in the present invention means a substance which produces a transparent liquid when dissolved in pure water as a 1% by weight solution. When used as a dispersing medium, particularly when it is dissolved in a 1% by weight solution with respect to a refined light oil, a transparent liquid is produced. This property is not necessarily HL
Since the influence of the chemical structure is large, regardless of B,
There is a range that partially crosses oil-soluble emulsifiers 2 to 9 and water-soluble emulsifiers 8 to 20.

As specific examples of these emulsifiers, nonionic water-soluble emulsifiers include polyoxyethylene nonylphenyl ether, polyoxyethylene stearyl ether, polyoxyethylene lauryl ether, and polyoxyethylene cetyl ether. Ter, polyoxyethylene tridecyl ether
And polyoxyethylene oleyl ether. The nonionic oil-soluble emulsifier is sorbitan monooleate, sorbitan dioleate, sorbitan monostearate, sorbitan distearate, sorbitan monolaurate, sorbitan dilaurate, sorbitan monopalmiate. And sorbitan dipalmitate.

The water-soluble polymer comprising the water-in-oil emulsion of the present invention is used for dewatering pulp sludge in the paper industry, other wastewater treatments in the food industry, metals and petroleum refining, and treatment of gravel washing wastewater related to building materials. Applicable to The amount of addition varies depending on the type of wastewater, the concentration of suspended matter, etc.
It is about 00 ppm.

[0023]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. However, the present invention is not limited to the following Examples unless it exceeds the gist thereof.

(Synthesis Example 1) A reaction vessel equipped with a stirrer and a temperature controller was charged with 230.0 g of isoparaffin having a boiling point of 190 ° C to 230 ° C and 17.0 g of sorbitan monooleate. Separately, 200.0 g of 60% aqueous acrylic acid (AAC) and 360.0 g of 50% aqueous acrylamide (AAM) were mixed, and 155.4 g (equivalent to acrylic acid) of 43% aqueous sodium hydroxide solution was heated at 30 ° C. The mixture was cooled and neutralized to prevent the above. The molar ratio of acrylamide to acrylic acid after infiltration of the monomer is 60:40. Thereafter, the oil phase and the aqueous monomer solution were combined and emulsified with stirring at 1000 rpm for 5 minutes using a homogenizer. 1.0 g of a 10% aqueous solution of isopropyl alcohol (based on 0.033
Wt.), And after nitrogen replacement, 2,2′-
Azobis [2- (5-methyl-2-imidazoline-2-
Il) propane] 10% aqueous solution of hydrogen dichloride 1.0
g (based on 0.033% by weight of the monomer) and a temperature of 33 ± 1.
The polymerization reaction was started while controlling at ° C, and after 5 hours, 1.0 g of the initiator was added, and the reaction was continued for another 5 hours to complete the polymerization (referred to as Sample-1). A part of the obtained water-in-oil emulsion was collected, a polymer was precipitated with acetone, and dried at 25 ° C. under reduced pressure for 48 hours to obtain a dry polymer. After dissolution, the weight average molecular weight was measured by a molecular weight measuring device (DLS-7000 manufactured by Otsuka Electronics Co., Ltd.) by a static light scattering method. Table 1 shows the results.

(Synthesis Example 2) In the same manner as in Example 1, a water-in-oil emulsion composed of a copolymer of acrylamide / acrylic acid = 90/10 (hereinafter referred to as Sample-2) was synthesized. Table 1 shows the results.

(Synthesis Example 3) In a reaction vessel equipped with a stirrer and a temperature controller, 230.0 g of isoparaffin having a boiling point of 190 to 230 ° C and 17.5 g of sorbitan monooleate, acryloyloxyethyltrimethylammonium chloride in an 80% aqueous solution were used. 320.7 g, 188.2 g of a 50% aqueous acrylamide solution and 196. deionized water.
1 g was poured. The molar ratio of acryloyloxyethyltrimethylammonium chloride to acrylamide after infiltration of the monomer is 50:50. Thereafter, the oil phase and the aqueous monomer solution are combined, and the mixture is treated with a homogenizer at 1000 rpm for 7 minutes.
The mixture was stirred and emulsified for minutes. 1.0 g of 10% aqueous solution of isopropyl alcohol (0.03
3% by weight), and after nitrogen replacement, 2, 2 ′ as an initiator.
-Azobis [2- (5-methyl-2-imidazoline-2
-Yl) propane] 10% aqueous solution of hydrogen dichloride.
6 g (based on the monomer 0.02% by weight), and the temperature was 33 ± 1.
The polymerization reaction was started while controlling the temperature at ° C., and after 5 hours, 0.6 g of the initiator was added, and the reaction was continued for another 5 hours to complete the polymerization (sample-3). After the polymerization, the weight average molecular weight was measured in the same manner. Table 1 shows the results.

(Synthesis Example 4) A water-in-oil emulsion composed of a copolymer of acryloyloxyethyltrimethylammonium chloride / acrylamide = 20/80 (referred to as Sample-4) was synthesized in the same manner as in Example 1. did. Table 1 shows the results.

Synthesis Example 5 230.0 g of isoparaffin having a boiling point of 190 ° C. to 230 ° C. and 25.0 g of sorbitan monooleate were charged into a reaction vessel equipped with a stirrer and a temperature controller. Separately 60% aqueous acrylic acid 2
8.6 g and 65.9 g of a 50% aqueous solution acrylamide were mixed, and 37.0 g (equivalent to acrylic acid) of a 43% aqueous solution of sodium hydroxide was added thereto while cooling so that the liquid temperature did not become 30 ° C. or more, and neutralized. Add 80% of acryloyloxyethyltrimethylammonium chloride to the neutralized solution.
320.5 g of a 30% aqueous solution was added. The molar ratio of acrylamide / acrylic acid / acryloyloxyethyltrimethylammonium chloride after monomer infiltration is 35: 15: 5.
0. Thereafter, the oil phase and the aqueous monomer solution were combined and emulsified with a homogenizer at 1000 rpm for 7 minutes. Add 10% of isopropyl alcohol to the obtained emulsion
After adding 0.6 g of an aqueous solution (0.02% by weight to the monomer) and replacing with nitrogen, 2,2′-azobis [2- (5
-Methyl-2-imidazolin-2-yl) propane], 1.2 g of a 10% aqueous solution of dihydrochloride (based on 0.04% by weight of monomer), and the polymerization reaction while controlling the temperature at 33 ± 1 ° C. After 5 hours, 1.0 g of the initiator was added, and the reaction was continued for another 5 hours to complete the polymerization (sample-
5). Table 1 shows the results.

(Synthesis Example 6) By the same operation as in Example 1, acrylamide / acrylic acid / acryloyloxyethyltrimethylammonium chloride = 40/20/4
0 water-in-oil emulsion comprising the copolymer (Sample-6)
) Was synthesized. Table 1 shows the results.

[0030]

Examples 1-2 A phase change agent having the composition shown in Table 2 was added to the water-in-oil emulsion synthesized in Synthesis Examples 1-2 in the order of an oil-soluble emulsifier and a water-soluble emulsifier. Thereafter, using a three-one motor, 10 g was sampled and dissolved 200 times in pure water, and the viscosity was measured at regular intervals to test the solubility in water. The solution was filtered through a 60-mesh sieve, and the weight of the insoluble particles was measured. Further, 200 ml of a water-in-oil emulsion one month after the addition of the phase change agent was collected and stored in a sample bottle having a diameter of 5 cm, and the separation stability was tested. Table 2 shows the results.

[0031]

Comparative Examples 1-2 When the water-in-oil emulsions synthesized in Synthesis Examples 3-6 were added with only a water-soluble emulsifier,
Solubility and separation stability were tested. Table 3 shows the results.

[0032]

Examples 3 to 6 To a water-in-oil emulsion synthesized in Synthesis Examples 3 to 6, a phase change agent having a composition shown in Table 2 was added in the order of an oil-soluble emulsifier and a water-soluble emulsifier. Thereafter, using a three-one motor, 10 g was collected and dissolved 100 times in pure water, and the viscosity was measured at regular intervals to test the solubility in water. The solution was filtered through a 60-mesh sieve, and the weight of the insoluble particles was measured. Further, 200 ml of a water-in-oil emulsion one month after the addition of the phase change agent was collected and stored in a sample bottle having a diameter of 5 cm, and the separation stability was tested. Table 4 shows the results.

[0033]

Comparative Examples 3 to 6 In the case where only the water-soluble emulsifier was added to the water-in-oil emulsion synthesized in Synthesis Examples 3 to 6,
Solubility and separation stability were tested. Table 5 shows the results.

[0034]

[Table 1] AAC: acrylic acid, AAM: acrylamide, DM
Q: acryloyloxyethyltrimethylammonium chloride, emulsion viscosity: mPa · s Molecular weight: unit is 10,000

[0035]

[Table 2] (A): Sovitan monooleate (a) -1; 0.6%, (a) -2; 0.6% (b): Polyoxyethylene nonylphenyl ether (polyoxyethylene chain; molecular weight 500) ( b) -1; 2.3%, (b) -2; 2.3% Insolubles: Both solutions were almost zero.

[0036]

[Table 3] (B): polyoxyethylene nonylphenyl ether (polyoxyethylene chain; molecular weight 500) (b) -3; 2.3%, (b) -4; 2.3% Separation stability: * 1; 0.5 cm, * 2; supernatant 0.3 cm, insoluble matter upon dissolution: wet weight of swollen particles (g)

[0037]

[Table 4] (A): Sovitan monooleate (a) -3; 1%, (a) -4; 1%, (a) -5; 1
%, (A) -6; 1% (b): polyoxyethylene oleyl ether (polyoxyethylene chain; molecular weight 600) (b) -5; 3.0%, (b) -6; 3.3 %, (B)
-7; 3.8%, (b) -8; 3.8% Insolubles: All solutions were almost 0.

[0038]

[Table 5] (B) -9; 3.0%, (b) -10; 3.3%,
(B) -11; 3.8%, (b) -12; 3.8% Separation stability: * 1: supernatant 0.8 cm, * 2: supernatant 0.5 cm, * 3: supernatant 1.1 cm, * 4: supernatant 1.1 cm, insoluble matter upon dissolution: wet weight of swollen particles (g)

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Claims (5)

[Claims] When a water-in-oil polymer emulsion containing a hydrophobic liquid as a continuous phase and a water-soluble polymer aqueous solution as a dispersion phase is dissolved in water, the non-ionic oil-soluble polymer is dissolved in the water-in-oil polymer emulsion. A method for adjusting the solubility of a water-in-oil emulsion, comprising adding and mixing an emulsifier and a nonionic water-soluble emulsifier in combination, followed by dissolving in water. 2. The water-soluble polymer according to the following general formula (1)
And / or the cationic monomer 5-1 represented by (2)
2. The water-in-oil emulsion according to claim 1, comprising 0 mol%, 0 to 40 mol% of an anionic monomer represented by the following general formula (3) and 0 to 95 mol% of acrylamide. Solubility control method. Embedded image R1 is hydrogen or a methyl group; R2 and R3 are alkyl or alkoxy groups or benzyl groups having 1 to 3 carbon atoms; R4 is hydrogen or an alkyl or alkoxy group or benzyl group having 1 to 3 carbon atoms; . X1 represents an anion, respectively. R5 is hydrogen or a methyl group, R6 and R7 are alkyl or alkoxy groups having 1 to 3 carbon atoms or benzyl group;
X2 may be the same or different, and X2 represents an anion, respectively. R8 is hydrogen, methyl or carboxymethyl, R9
Is hydrogen or carboxyl group, A is SO3, C6H4S
O3, CONHC (CH3) 2CH2SO3 or C
OO, Y represents hydrogen or a cation 3. The water-soluble polymer according to the general formula (3)
2. The method for controlling the solubility of a water-in-oil emulsion according to claim 1, comprising 2 to 60 mol% of an anionic monomer represented by the formula: and 40 to 98 mol% of acrylamide. 4. A non-ionic oil-soluble emulsifier is added to and mixed with the water-in-oil type polymer emulsion, and then a non-ionic water-soluble emulsifier is added and mixed, and dissolved in water. Item 4. The method for adjusting the solubility of a water-in-oil emulsion according to Item 1. 5. The nonionic oil-soluble emulsifier having an HLB number (hydrophobic lipophilic balance) of 2
5. The method for adjusting the solubility of a water-in-oil emulsion according to claim 1, wherein the nonionic water-soluble emulsifier has an HLB number of 8 to 20. 6.