JP3091831B2 - Water-in-oil microemulsion of water-soluble vinyl polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a water-in-oil microemulsion. More specifically, the present invention relates to a water-in-oil microemulsion of a water-soluble vinyl polymer useful as a wastewater treatment agent, a papermaking agent, a thickener, a drilling mud additive, and the like.

[0002]

2. Description of the Related Art As water-in-oil emulsions of water-soluble vinyl polymers, for example, the following are known. Water-in-oil emulsion containing a water-soluble vinyl polymer, water, an aliphatic hydrocarbon liquid such as isoparaffin, and an emulsifier, and having a specific range of transmittance and viscosity (JP-A-54-1544).
No. 37, JP-A-54-102388, etc.). It contains a water-soluble vinyl polymer, a water-soluble water-in-oil emulsifier, a hydrocarbon liquid such as kerosene, and an aqueous phase, wherein the aqueous phase is 25 to 70% by weight, preferably 34 to 3% by weight of the whole emulsion.
Water-in-oil emulsions occupying 5% by weight
127302). A water-in-oil emulsion of a polyacrylamide polymer using a polyalkenyl succinic anhydride derivative as an emulsifier (JP-A-63-69531). A water-in-oil emulsion of a polyacrylamide polymer obtained by adding amines described in JP-A-54-154439 during the polymerization (JP-A-57-6544).
No. 5706). A water-in-oil emulsion of a water-soluble copolymer in which a hydrocarbon liquid such as isoparaffin is used and the amount of an emulsifier used is specified (Japanese Patent Application Laid-Open No. 61-12706).

[0003]

However, these conventional water-in-oil emulsions of water-soluble vinyl polymers are
There are drawbacks that the viscosity changes over time and that phase separation occurs significantly.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to obtain a water-in-oil emulsion which has solved the above problems, and as a result, have reached the present invention. That is, the present invention relates to a water-in-oil microemulsion of a water-soluble vinyl polymer comprising a water-soluble vinyl polymer (a), water (b), a hydrocarbon liquid (c) and a surfactant (d). A water-in-oil microemulsion comprising an oil-soluble polyoxyalkylene compound (e) represented by the formula (1) and having an average particle diameter of an aqueous phase of 700 mμ or less. R ¹ -[(OR ² ) _n -OR ³ ] _m (1) [wherein R ¹ is a residue obtained by removing an OH group from a compound having ¹ to 6 valent hydroxyl groups, or an OH group from a 1 to 6 valent carboxylic acid. residues excluding the group; R ² is an alkylene group having 2 to 4 carbon atoms (provided that at least a portion of the n R ² is an alkylene group having 3-4 carbon atoms); R ³ is H, the number of carbon atoms N is an integer of 1 to 120; m is an integer of 1 to 6; ]

[0005]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, the water-soluble vinyl monomer (a ') constituting the water-soluble vinyl polymer (a) is a nonionic, anionic or cationic water-soluble vinyl monomer. And at least one monomer selected from the group consisting of: Among them, examples of the nonionic vinyl monomer include acrylamide and methacrylamide.

Examples of the anionic vinyl monomer include a carboxylic acid (salt) group-containing anionic vinyl monomer and a sulfonic acid (salt) group-containing anionic vinyl monomer. Specific examples of the carboxylic acid (salt) group-containing anionic vinyl monomer include unsaturated monocarboxylic acids such as (meth) acrylic acid, unsaturated dicarboxylic acids such as maleic acid, and salts thereof (alkali metal salts, ammonium salts). Salts, amine salts and the like). Examples of the sulfonic acid (salt) group-containing anionic vinyl monomer include vinyl sulfonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid and salts thereof (alkali metal salt, ammonium salt, amine salt) Etc.).

[0007] Examples of the cationic water-soluble vinyl monomer include the following [1] to [4]. [1] Cationic (meta) represented by the following general formula (2)
Acrylic vinyl monomer (In the formula, R ¹ is H or CH _3; R ² and R ³ hydroxyalkyl group having 2 to 4 alkyl groups or carbon atoms having 1 to 4 carbon atoms are each independently; R ⁴ is H, 1 to 4 carbon atoms A is an oxygen atom or NH; Z is a C 1-4 alkyl group, a hydroxyalkyl group having 2 to 4 carbon atoms or a benzyl group;
An alkylene group or a hydroxyalkylene group having 2 to 4 carbon atoms; X represents an anion. )

Specific examples of the cationic (meth) acrylic vinyl monomer represented by the general formula (2) include a quaternary nitrogen-containing (meth) acrylate [2- (meth) acryloyloxyethyltrimethylammonium chloride. , 2
(Meth) acryloyloxyalkyltrialkylammonium salts such as (meth) acryloyloxyethyldimethylbenzylammonium chloride and 2- (meth) acryloyloxyethyltrimethylammonium methosulfate], tertiary nitrogen-containing (meth) acrylate [Sulfates of 2-dimethylaminoethyl (meth) acrylate, salts of dialkylaminoalkyl (meth) acrylates such as hydrochloride of 2-diethylaminoethyl (meth) acrylate], and quaternary nitrogen-containing (meth) acrylamide [ (Meth) acryloylaminoalkyltrialkylammonium salts such as 2- (meth) acryloylaminoethyltrimethylammonium sulfate], tertiary nitrogen-containing (meth) acrylamide salts [2-dimethylaminoethyl (meth) Hydrochloride acrylamide, 2-dimethylaminoethyl (meth) dialkylaminoalkyl (meth) salts of acrylamide, such as acetates acrylamide], and the like.

[2] Cationic vinylbenzyl monomers such as vinylbenzyltrimethylammonium chloride. [3] Cationic dialkyl diallyl-based vinyl monomers Dialkyl diallyl ammonium salts such as dimethyl diallyl ammonium chloride. [4] Other cationic vinyl monomers such as vinyl imidazoline, vinyl pyridine, and vinyl dimethyl amino acetate hydrochloride.

[0010] Of the above-mentioned water-soluble vinyl monomers (a '), preferred ones are acrylamide and acrylic acid, considering that an emulsion having better stability can be obtained and from an industrial viewpoint. And a salt thereof, 2- (meth) acryloyloxyethyltrimethylammonium chloride, and a combination of two or more of these.

The monomers constituting the water-soluble vinyl polymer (a) include, if necessary, a water-soluble vinyl monomer (a ') exemplified above and a water-insoluble vinyl monomer copolymerizable therewith. [Styrene, vinyl acetate, butyl (meth)
Acrylate and acrylonitrile, etc.] in an amount within a range in which the resulting vinyl polymer maintains water solubility (usually 30% by weight or less, preferably 1% by weight of all vinyl monomers).
5% by weight or less).

Specific examples of the water-soluble vinyl polymer (a) include the following. Nonionic water-soluble vinyl polymer: poly (meth) acrylamide and the like. Anionic water-soluble vinyl polymer: (meth) acrylamide- (meth) acrylic acid sodium copolymer, (meth) acrylamide- (meth) acryloylamino-2,2-
Sodium dimethylethanesulfonate-sodium (meth) acrylate copolymer and the like. Cationic water-soluble vinyl polymer: (meth) acrylamide- (meth) acryloyloxyethyltrimethylammonium chloride copolymer, (meth) acrylamide- (meth) acryloyloxyethyldimethylbenzylammonium chloride copolymer and the like. Amphoteric water-soluble vinyl polymer: (meth) acrylamide-
(Meth) acrylic acid- (meth) acryloyloxyethyltrimethylammonium chloride copolymer, (meth)
Acrylamide-itaconic acid-dimethylaminoethyl (meth) acrylate sulfate copolymer and the like.

Although the molecular weight of the water-soluble vinyl polymer (a) is not particularly limited, it has an intrinsic viscosity of usually 3 to 30 dl / g,
Preferably it is 5-25 dl / g. When the intrinsic viscosity is within the usual range, it is preferable in terms of both practical performance and workability. The intrinsic viscosity is a value measured at 30 ° C. in a 1N aqueous sodium nitrate solution.

The water (b) in the water-in-oil microemulsion of the present invention is preferably distilled water or ion-exchanged water, but may be tap water depending on the water quality.

[0015] The hydrocarbon liquid (c) in the present invention has an initial boiling point of usually 150 ° C or higher, preferably 200 ° C or higher. Those having an initial boiling point in a normal range are preferable from the viewpoint of the stability over time of the emulsion. The (c) is obtained mainly as a by-product of petroleum refining, and is obtained by extracting a hydrocarbon liquid satisfying this condition or blending a plurality of hydrocarbon liquids in a petroleum refining process.

The surfactant (d) in the present invention includes a nonionic surfactant, an anionic surfactant, a cationic surfactant or an amphoteric surfactant. Examples of nonionic surfactants include higher alcohol ethylene oxide adducts such as lauryl alcohol polyoxyethylene ether; higher fatty acid esters such as sorbitan diester stearate and sorbitan monoester; polyoxyethylene nonylphenyl ether such as polyoxyethylene nonyl phenyl ether Oxyethylene alkyl ether;
Long-chain alkyl alkanolamides such as N, N dihydroxyethyl lauramide; fatty acid sorbitan ester ethylene oxide adducts such as oleic acid sorbitan ester ethylene oxide adduct; Of these, fatty acid sorbitan ester ethylene oxide adduct, higher alcohol ethylene oxide adduct, higher fatty acid ester and long-chain alkyl alkanolamide are preferable, and fatty acid sorbitan ester ethylene oxide adduct (d1) is particularly preferable. Fatty acids of fatty acid sorbitan ester ethylene oxide adducts have 8 to 30 carbon atoms, such as lauric acid,
Oleic acid, stearic acid and the like can be mentioned.

Examples of anionic surfactants include carboxylate type such as soap oleate; sulfate type such as higher alcohol sulfate; sulfonate type such as sulfosuccinic diester; higher alcohol phosphate Phosphate ester salts such as ester salts may be mentioned.
Of these, sulfonate type is preferred, and sulfosuccinic acid diester type (d2) is particularly preferred.
Examples of the cationic surfactant include amine salts such as aliphatic amine ethylene oxide adducts or aromatic amine ethylene oxide adducts and salts of higher aliphatic amines; and quaternary ammonium salts such as higher alkylamine ammonium salts. Is mentioned. Of these, amine salt type is preferred, and amine ethylene oxide adduct (d3) is particularly preferred. Examples of the amphoteric surfactant include an amino acid type such as a higher alkylaminocarboxylate; and a betaine type such as a higher alkyldimethyl betaine.

The surfactant (d) may be added during the polymerization of (a) or may be added after the polymerization. In the present invention, when the water-soluble vinyl polymer (a) is a nonionic or anionic water-soluble polymer, the surfactant (d) is preferably a combination of (d1) and (d2). When (d1) and (d2) are used in combination, the weight ratio of (d1) to (d2) is usually 99/1 to 1/99, preferably 70/30.
~ 30/70, more preferably 60/40 ~ 40/6
0. When the water-soluble vinyl polymer (a) is a nonionic or cationic water-soluble polymer, the surfactant (d) is preferably a combination of (d1) and (d3). When (d1) and (d3) are used in combination, the weight ratio is usually 99/1 to 1/99, preferably 90/10 to 5
0/50, more preferably 85/15 to 60/40.

The oil-soluble polyoxyalkylene compound (e) in the present invention is a compound represented by the aforementioned general formula (1). In the general formula (1), R ¹ represents a residue obtained by removing an OH group from a compound having ¹ to 6 valent hydroxyl groups, or 1 to 6
It is a residue obtained by removing an OH group from a polyvalent carboxylic acid. Examples of the monovalent to hexavalent hydroxyl group-containing compound include a monovalent hydroxyl group-containing compound such as butanol; a divalent hydroxyl group-containing compound such as ethylene glycol; a trivalent hydroxyl group-containing compound such as glycerin; a tetravalent hydroxyl group-containing compound such as pentaerythritol; Pentavalent hydroxyl group-containing compounds such as fructose; and hexavalent hydroxyl group-containing compounds such as sorbitol.

Examples of the monovalent to hexavalent carboxylic acids include monovalent carboxylic acids such as octylic acid; divalent carboxylic acids such as succinic acid; trivalent or higher carboxylic acids such as trimellitic acid, pyromellitic acid and other polycarboxylic acids. Carboxylic acids.

R ² is an alkylene group having 2 to 4 carbon atoms (at least part of which is an alkylene group having 3 to 4 carbon atoms). The ratio of the alkylene group having 3 to 4 carbon atoms to the alkylene group having 2 carbon atoms is usually 100/0 to 70/30 by weight.
, Preferably 100/0 to 80/20, more preferably 100/0 to 90/10. Carbon number 2
If the weight ratio of the alkylene group exceeds 30, the hydrophilicity becomes strong and the oil-soluble feature is lost. R ³ is H or an alkyl group, an alkenyl group, an alkylloyl group or an alkenyl group having usually 1 to 26, preferably 2 to 20 carbon atoms. n represents an integer of usually 1 to 120, preferably 2 to 90, more preferably 5 to 50. m represents an integer of usually 1 to 4, preferably 1 to 3.

The weight average molecular weight of (e) is usually from 90 to 7000, preferably from 200 to 5,000, more preferably from 300 to 3,000 from the viewpoint of the stability of the emulsion.
It is.

The water-soluble vinyl polymer (a), water (b), hydrocarbon liquid (c), surfactant (d) and oil-soluble polyoxyalkylene compound (e) in the microemulsion of the present invention The weight ratio is expressed by the following formulas 1-3
Is preferable. Formula 1: 0.40 ≦ (a) / [(a) + (b)] (weight ratio) ≦ 0.65 Formula 2: 0.30 ≦ (c) / [(a) + (b)] (weight Ratio) ≦ 0.50 Formula 3: 0.15 ≦ [(d) + (e)] / (c) (weight ratio) ≦ 0.40 Formulas 1 to 4 for further improving the stability of the emulsion.
The more preferable range of 3 is as follows. More preferable range in Formula 1: 0.40 ≦ (a) / [(a) + (b)] ≦ 0.63 More preferable range in Formula 2: 0.30 ≦ (c) / [(a) + (b) )] ≦ 0.49 More preferable range in the formula 3: 0.16 ≦ [(d) + (e)] / (c) ≦ 0.38

In the microemulsion of the present invention,
If necessary, a known pH buffer, a polymer deterioration inhibitor, a deodorant, a preservative, a rust inhibitor, a decoloring agent, and the like may be contained. These amounts are usually 5 to the weight of the emulsion.
% By weight or less. Further, when the water-in-oil microemulsion of the present invention is diluted and used, a high HLB surfactant may be added to the microemulsion so that the microemulsion rapidly changes phase when poured into water. However, in this case,
It is preferred that the total amount of surfactant in the microemulsion falls within the normal range of Formula 3. The more preferable range of the total amount of the surfactant in this case from the viewpoint of maintaining stability is also the same as the more preferable range in the above formula 3.

The average particle size of the water phase of the water-in-oil microemulsion of the present invention is 700 mμ or less, preferably 500 mμ or less. Average particle size of aqueous phase is 700m
If it exceeds μ, the stability over time deteriorates and separation occurs. The average particle diameter is a value measured by an electrophoretic light scattering photometer “ELS-800” manufactured by Otsuka Electronics Co., Ltd.

As an example of the method for producing the water-in-oil microemulsion of the present invention, a monomer (a '), a water (b), a hydrocarbon liquid (c), which is a constitutional unit of the water-soluble vinyl polymer (a), ) The surfactant (d) and the oil-soluble polyoxyalkylene compound (e) are obtained by W / O type emulsion and emulsion polymerization. This emulsion polymerization method is a known method, for example, JP-A-54-154439,
It can be carried out by the method described in JP-A-54-102388. If necessary, a chain transfer agent such as mercaptan, a pH buffer, a chelating agent and the like may be added to the polymerization system. After the emulsion polymerization, low volatile components such as water are distilled off under reduced pressure, and the water-soluble vinyl polymer (a), water (b), hydrocarbon liquid (c), surfactant (d) and oil-soluble The proportion of the polyoxyalkylene compound (e) may be adjusted so as to fall within the range of the above formulas 1 to 3.

The water-in-oil microemulsion of the present invention is used as a papermaking agent such as a wastewater treatment agent, a thickener, an antistatic agent, a fiber treatment agent, and a drainage improver, and a crude oil recovery agent. When using the emulsion of the present invention, if necessary, with water or other solvent at an appropriate concentration, for example, 100 to 100
It is used after being diluted 5,000 times.

[0028]

EXAMPLES The present invention will be further described with reference to the following examples, but the present invention is not limited to these examples. In addition, the test described in the Example was implemented by the following method. Test method (1) Stability test Repeating 5 ° C. × 1 week and 40 ° C. × 1 week is performed for 3 months, and the separation rate and change in viscosity of the emulsion are examined. (2) Polymer intrinsic viscosity Measured in a 1N aqueous sodium nitrate solution at 30 ° C. (3) Aqueous phase average particle size Electrophoretic light scattering photometer “ELS-8” manufactured by Otsuka Electronics Co., Ltd.
00 "at 25 ° C.

Example 1 In a 1 L 4-neck separable flask equipped with a stirrer, a reflux tube, a nitrogen inlet tube and a thermometer, (c) component: 250 g of oil (d) component: 5 g of pentaoxyethylene oleyl alcohol ether (〃) ) Ingredient: 15 g of sorbitan oleate (d1) Ingredient: 15 g of sorbitan oleate ethylene oxide 20 mol adduct (e) Ingredient: 25 g of polyoxypropylene butyl ether (molecular weight: 1200) was charged and stirred and mixed. The oil used was a mixture of 97% normal paraffin and a total of 3% of naphthene and aromatics (initial boiling point: 203 ° C.). Then, a mixed solution of (a ′) component: 300 g of a 40% aqueous solution of sodium acrylate and 240 g of acrylamide (b) component: 150 g of water was adjusted to pH 7 with sodium hydroxide, and added to the above mixture to emulsify. This was adjusted to 50 ° C. with stirring, and nitrogen gas was blown into the liquid for 30 minutes. Then, while flowing nitrogen in the gas phase, 2,2′-azobis (2,4,
1 g of a toluene solution containing 6% by weight of (dimethylvaleronitrile) was added, followed by polymerization at 45 to 55 ° C. for 8 hours. The obtained emulsion was a translucent stable emulsion. The intrinsic viscosity of this polymer was 21.9 dl / g.
Table 1 shows the stability test results and the like of this emulsion.

Examples 2 and 3 The proportions of the water-soluble vinyl polymer (a), water (b), hydrocarbon liquid (c), surfactant (d) and oil-soluble polyoxyalkylene compound (e) are shown in Table 1. Example 2 and Example 3 were obtained in the same manner as in Example 1 except that the emulsion was changed as shown in FIG. Table 1 shows the stability test results and the like of each emulsion.

[0031]

[Table 1]

Example 4 In a 1 L 4-neck separable flask equipped with a stirrer, a reflux tube, a nitrogen inlet tube and a thermometer, (c) component: 250 g of oil (d) component: 5 g of pentaoxyethylene oleyl alcohol ether (〃) ) Ingredient: 15 g of sorbitan oleate (d1) Ingredient: 20 g of sorbitan oleate ethylene oxide 20 mol adduct (d2) Ingredient: 10 g of sodium dioctylsulfosuccinate (e) Ingredient: 20 g of polyoxypropylene butyl ether (molecular weight 1200) is charged and stirred. Mixed. The oil used was a mixture of 97% normal paraffin and a total of 3% of naphthene and aromatics (initial boiling point: 203 ° C.). Then, a mixed solution of (a ′) component: 300 g of a 40% aqueous solution of sodium acrylate and 240 g of acrylamide (b) component: 150 g of water was adjusted to pH 7 with sodium hydroxide, and added to the above mixture to emulsify. This was adjusted to 50 ° C. with stirring, and nitrogen gas was blown into the liquid for 30 minutes. Thereafter, while flowing nitrogen in the gas phase, 2,2′-azobis (2,4,-
1 g of a toluene solution containing 6% by weight of (dimethylvaleronitrile) was added, and polymerization was carried out at 45 to 55 ° C. for 8 hours. The obtained emulsion was a translucent stable emulsion. The intrinsic viscosity of this polymer was 20.6 dl / g. Table 2 shows the stability test results and the like of this emulsion.

Examples 5 and 6 The water-soluble vinyl polymer (a), water (b), hydrocarbon liquid (c) surfactant (d) and oil-soluble polyoxyalkylene compound (e) d1) and (d
Example 4 except that the weight ratio of 2) was changed as shown in Table 2.
In the same manner as in Example 5, emulsions of Examples 5 and 6 were obtained. Table 2 shows the stability test results and the like of each emulsion.

[0034]

[Table 2]

Example 7 In a 1 L four-neck separable flask equipped with a stirrer, a reflux tube, a nitrogen inlet tube and a thermometer, (c) component: 250 g of oil (d) component: 5 g of pentaoxyethylene oleyl alcohol ether (〃) ) Component: Sorbitan oleate 15 g (d1) Component: Sorbitan oleate triester ethylene oxide 17 g 20 mol adduct (d3) Component: oleylamine ethylene oxide 15 mol adduct 6 g (e) Component: 17 g of polyoxypropylene butyl ether (molecular weight 1200) With stirring. As the oil, a mixture (initial boiling point: 155 ° C.) of 90% of normal paraffin and 10% of total of naphthene and aromatic was used. Next, a mixed solution of (a ′) component: 150 g of 80% aqueous solution of 2-acryloyloxyethyltrimethylammonium chloride and 240 g of acrylamide (b) component: 300 g of water was adjusted to pH 4 with diluted sulfuric acid, and added to the above mixture to emulsify I let it. This was adjusted to 50 ° C. with stirring, and nitrogen gas was blown into the liquid for 30 minutes. Then, while flowing nitrogen into the gaseous phase, 1% of a toluene solution containing 6% by weight of 2,2′-azobis (2,4, -dimethylvaleronitrile) was added.
g was added and polymerized at 45-55 ° C. for 8 hours. The resulting emulsion was a translucent stable emulsion. The intrinsic viscosity of this polymer was 14.8 dl / g. Table 3 shows the stability test results and the like of this emulsion.

Examples 8, 9 The ratio of each component of the water-soluble vinyl polymer (a), water (b), hydrocarbon liquid (c), surfactant (d) and oil-soluble polyoxyalkylene compound (e) and ( d1) and (d
Example 7 except that the weight ratio of 3) was changed as shown in Table 3.
In the same manner as in Example 8, emulsions of Examples 8 and 9 were obtained. Table 3 shows the stability test results and the like of each emulsion.

[0037]

[Table 3]

Examples 10 to 12 Emulsions of Examples 10 to 12 were obtained in the same manner as in Example 1 except that the kind of the polyoxyalkylene compound (e) was changed. Table 4 shows the type of the polyoxyalkylene compound (e) used in each of the examples and the results of the stability test of the obtained polymer.

[0039]

[Table 4]

(Note) (1) Polyoxypropylene butyl ether, molecular weight 190 (2) Polyoxypropylene glycerin ether, molecular weight 6000 (3) Polyoxyethylene propylene glycol butyrate, molecular weight 1200, ethylene / propylene weight ratio = 10/90

[0041]

The water-in-oil microemulsion of the present invention has better stability over time, better freeze stability, better fluidity and easier handling than conventional ones. Because of the above effects, the emulsion of the present invention is useful as a papermaking agent such as a wastewater treatment agent, a thickener, an antistatic agent, a fiber treatment agent, a drainage improver, and a crude oil recovery agent.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI C08L 33/02 C08L 33/02 33/26 33/26 // (C08L 33/02 71:02) (C08L 33/26 71: 02) (C08L 57/06 71:02) (56) References JP-A-8-41114 (JP, A) JP-A-2-64105 (JP, A) JP-A-47-12431 (JP, A) ( 58) Field surveyed (Int.Cl. ⁷ , DB name) C08F 2/32 C08F 20/00-20/70 C08F 120/00-120/70 C08F 220/00-220/70 C08L 23/00-57 / 12 C08K 5/06

Claims (7)

(57) [Claims] 1. A water-soluble vinyl polymer (a), water (b),
A water-in-oil microemulsion of a water-soluble vinyl polymer comprising a hydrocarbon liquid (c) and a surfactant (d) contains an oil-soluble polyoxyalkylene compound (e) represented by the following general formula (1). A water-in-oil microemulsion characterized by having an average particle diameter of an aqueous phase of 700 mμ or less. R ¹ -[(OR ² ) _n -OR ³ ] _m (1) [wherein R ¹ is a residue obtained by removing an OH group from a compound having ¹ to 6 valent hydroxyl groups, or an OH group from a 1 to 6 valent carboxylic acid. residues excluding the group; R ² is an alkylene group having 2 to 4 carbon atoms (provided that at least a portion of the n R ² is an alkylene group having 3-4 carbon atoms); R ³ is H, the number of carbon atoms N is an integer of 1 to 120; m is an integer of 1 to 6; ] 2. (a) is an acrylamide homopolymer or a polymer containing acrylamide and another water-soluble vinyl monomer as constituent units, and has an intrinsic viscosity measured at 30 ° C. in a 1N aqueous sodium nitrate solution. Is 3 to 30 dl / g. 3. The microemulsion according to claim 1, wherein (d) contains a fatty acid sorbitan ester ethylene oxide adduct (d1) as an essential component. (A) is a nonionic or anionic water-soluble polymer, and (d) is a fatty acid sorbitan ester ethylene oxide adduct (d1) and a sulfosuccinic acid diester type anionic surfactant (d2) as essential components. The microemulsion according to claim 1, which is contained as: 5. The method according to claim 1, wherein (a) is a nonionic or cationic water-soluble polymer, and (d) contains fatty acid sorbitan ester ethylene oxide adduct (d1) and amine ethylene oxide adduct (d3) as essential components. 3. The microemulsion according to 1 or 2. 6. The micrometer according to claim 1, wherein the weight relationship among the components (a), (b), (c), (d) and (e) satisfies the following formulas (1) to (3). Emulsion. Formula 1: 0.40 ≦ (a) / [(a) + (b)] (weight ratio) ≦ 0.65 Formula 2: 0.30 ≦ (c) / [(a) + (b)] (weight Ratio) ≦ 0.50 Formula 3: 0.15 ≦ [(d) + (e)] / (c) (weight ratio) ≦ 0.40 7. The microemulsion according to claim 1, wherein the initial boiling point of (c) is 150 ° C. or higher.