JP2002233744A - Emulsifier for aqueous resin dispersion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an emulsifier for an aqueous resin dispersion which enables obtaining an emulsion showing high polymerization stability during emulsion polymerization and superb mechanical stability and low foaming properties and significantly improves the water resistance of a polymer film obtained from the emulsion. SOLUTION: This emulsifier for the aqueous resin dispersion is composed of a compound (I) represented by formula (1). In formula (1), R1 is an 8-30C alkyl group; R2 is hydrogen or methyl group; R3, R4 and R5 are each independently a 1-8C hydrocarbon group; A is a 2-4C alkylene group or a substituted alkylene group; n is an integer of 0 to 200; and X- is a univalent anion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an emulsifier for an aqueous resin dispersion, and more particularly to a novel and useful reactive emulsifier used for aqueous emulsion polymerization of an ethylenically unsaturated monomer.

[0002]

2. Description of the Related Art Conventionally, emulsifiers for emulsion polymerization include, in addition to various anionic surfactants, alkyl imidazoline salts, alkyl hydroxyethyl imidazoline salts, alkyl pyridinium salts, alkyl trimethyl ammonium salts, dialkyl dimethyl ammonium salts, Alkoxyethyl ammonium salt, 3-alkoxy-2-hydroxypropyl ammonium salt, benzalkonium chloride,
Cationic surfactants such as benzethonium chloride and nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, and polyoxyethylene polyoxypropylene block polymer are used alone. Or two or more of them are used in combination.

[0003] However, when emulsion polymerization is carried out using a conventional cationic emulsifier, the stability of the obtained emulsion and the properties of the film produced from the emulsion are not always sufficiently satisfactory. ,
Many problems remain to be solved.

That is, there are problems with the polymerization stability of the emulsion, the foaming properties of the obtained emulsion, mechanical stability, chemical stability, pigment miscibility, freeze-thaw stability, storage stability and the like. There is a need for improvements in foamability, foamability, and mechanical stability.

Further, when a polymer film is prepared from an emulsion, the used emulsifier remains in the polymer film in a free state, which causes problems such as poor water resistance and adhesiveness of the film. When applied, it is a serious drawback.

Further, when the polymer is taken out by destroying the emulsion by means of salting out or the like, a large amount of emulsifier is contained in the waste water, which causes river pollution. Become.

[0007] To solve the above problems, many reactive emulsifiers having a copolymerizable unsaturated group have been proposed. For example, JP-B-53-47275 and JP-A-55-98201 describe cationic reactive emulsifiers. JP-A-56-28208 and JP-A-50-98484 disclose non-reactive cationic emulsifiers. Each of the ionic reactive emulsifiers is described, and emulsion polymerization of various monomers is attempted. However, at present, none of these problems has been sufficiently solved.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above, and has high polymerization stability during emulsion polymerization.
It is another object of the present invention to provide an emulsifier for an aqueous resin dispersion capable of obtaining a low-foam emulsion having good mechanical stability and capable of significantly improving the water resistance of a polymer film obtained from the emulsion.

[0009]

According to a first aspect of the present invention, there is provided an aqueous resin dispersion emulsifier comprising a compound (I) represented by the following general formula (1).

[0010]

Embedded image (Where, in the general formula (1), R ¹ is an alkyl group having 8 to 30 carbon atoms, R ² is a hydrogen or methyl group, R ³ , R ⁴ , R
⁵ each independently represent a hydrocarbon group having 1 to 8 carbon atoms;
Represents an alkylene group or a substituted alkylene group having 2 to 4 carbon atoms, n represents an integer of 0 to 200, and X ⁻ represents a monovalent anion. The emulsifier for an aqueous resin dispersion according to claim 2 comprises a compound (II) represented by the following general formula (2).

[0011]

Embedded image (Where, in the general formula (2), R ¹ is an alkyl group having 8 to 30 carbon atoms, R ² is a hydrogen or methyl group, and A is ^{2 to} 30 carbon atoms.
4 alkylene group or substituted alkylene group, n is 0 to 2
And an integer Y is hydrogen or a substituent represented by the following general formula (3). In the general formula (3), R ³ , R ⁴ , R
⁵ is each independently a hydrocarbon group having 1 to 8 carbon atoms, m
Represents an integer of 0 to 5, and X ⁻ represents a monovalent anion. )

Embedded image

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION [Compounds (I) and (II)] Formula (1) showing compounds (I) and (II), respectively.
And R ¹ in (2) is an alkyl group having 8 to 30 carbon atoms, specifically, octyl, nonyl, decyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl. Group, octadecyl group, eicosyl group and the like. When the number of carbon atoms in R ¹ is less than 8 or more than 30, there arises a problem that stability during emulsion polymerization is deteriorated. The preferred carbon number is 10-20.

R ² is hydrogen or a methyl group.

A is an alkylene group having 2 to 4 carbon atoms or a substituted alkylene group substituted by methyl, ethyl or the like. For example, a single ethylene group, a propylene group,
It may be a butylene group, an isobutylene group, or a homopolymer, a block polymer, or a random polymer thereof, or a mixture thereof.

N is an integer of 0 to 200, preferably an integer of 0 to 100. When n exceeds 200, there arises a problem that the surface activity decreases.

In the general formula (2), Y is hydrogen or a substituent represented by the general formula (3).

In the general formulas (1) and (3), R ³ ,
R ⁴ and R ⁵ are each a hydrocarbon group having 1 to 8 carbon atoms, and examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a pentyl group,
Hexyl group, octyl group, alkyl group such as 2-ethylhexyl group, allyl group, butenyl group, isobutenyl group, alkenyl group such as pentenyl group, hexenyl group, benzyl group, aralkyl group such as methylbenzyl group, and methyl group. , An ethyl group and a benzyl group are preferred.

In the general formula (3), m is an integer of 0 to 5, preferably 0 to 2. When m exceeds 5, there arises a problem that the surface activity decreases.

Further, in the general formulas (1) and (3), X⁻
Represents a monovalent anion, for example, Cl⁻, Br⁻, I
⁻Halogen anions such as CH₃SO₄ ⁻, C₂H₅S
O₄ ⁻Alkyl sulfate ions such as Cl.⁻, C
H₃SO₄ ⁻Is preferred.

[Emulsifier for Aqueous Resin Dispersion] The emulsifier for an aqueous resin dispersion of the present invention is one or more of the compounds (I) or (II) represented by the above general formula (1) or (2). It consists of

The method for obtaining the emulsifier for an aqueous resin dispersion of the present invention is not particularly limited.
-An olefin oxide (for example, AOE-X24 [manufactured by Daicel Chemical Industries, Ltd.], having 12 and 14 carbon atoms) and allyl alcohol are subjected to an addition reaction in the presence of a catalyst, and the obtained addition product is converted to epihalohydrin in the presence of a catalyst. , And further reacted with a tertiary amine.

Alternatively, an alkylene oxide is added to an addition product of α-olefin oxide and allyl alcohol by a conventional method. Then, in the presence of a catalyst, glycidyltrimethylammonium chloride (for example, Cation Master G
[Made by Yokkaichi Gosei Co., Ltd.]) or by adding epihalohydrin and further reacting with a tertiary amine, or by reacting with an alkali and epoxidizing the terminal, and then reacting with a secondary amine. The emulsifier of the present invention can also be obtained by quaternization.

[Application of Emulsifier of the Present Invention to Emulsion Polymerization] The emulsifier of the present invention can be applied to emulsion polymerization of various monomers, and the type of monomer is not particularly limited. Examples thereof include methyl acrylate and acrylic acid. Acrylic monomers such as ethyl, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, butyl methacrylate, acrylonitrile, acrylamide, hydroxyethyl acrylate, acrylic acid and methacrylic acid, and aromatic monomers such as styrene and divinyl benzene Monomers, vinyl ester monomers such as vinyl acetate, vinyl chloride, halogenated olefin monomers such as vinylidene chloride, butadiene, isoprene, conjugated diolefin monomers such as chloroprene, etc., ethylene, maleic anhydride,
And methyl maleate. These monomers are
One or more kinds can be used.

The emulsifier of the present invention is used in an amount of usually 0.1 to 20% by weight, preferably 0.2 to 5% by weight, based on the total amount of monomers.

For the emulsion polymerization using the emulsifier of the present invention, conventionally known polymerization initiators can be used without any particular limitation. Representative examples include hydrogen peroxide, potassium persulfate, sodium persulfate, ammonium persulfate, benzoyl peroxide,
2,2′-azobisisobutyronitrile, 2,2′-azobis (2-amidinopropane) dihydrochloride and the like can be mentioned.

Redox polymerization can be carried out using sodium hydrogen sulfite, ferrous ammonium sulfate or the like as a polymerization accelerator.

With the emulsifier of the present invention, a good aqueous resin dispersion can be obtained even when used alone, but if necessary,
Other emulsifiers or protective colloids may be used in combination.

The aqueous resin dispersion obtained by using the emulsifier of the present invention includes, for example, binders for printing inks, paints (for construction, home use, cans, electrodeposition coating, etc.), binders for ink jet media, and the like. It can be applied to wood, metal, paper, cloth, plastic, ceramic, other concrete, and the like as an adhesive, a pressure-sensitive adhesive, a coating agent, an impregnation reinforcing agent, and the like.

[0029]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Synthesis Example 1 Synthesis of Emulsifier (A) In a reaction vessel equipped with a stirrer, a thermometer and a reflux tube, 106 g of allyl alcohol and 0.3 g of caustic soda as a catalyst were charged, and then AOE-X24 (carbon Α-olefin oxide having the number of 12 or 14, manufactured by Daicel Chemical Industries, Ltd.) 196
g was added dropwise, and the mixture was stirred and reacted at 90 ° C. for 10 hours. Thereafter, the mixture was heated to 110 ° C., and excess allyl alcohol was removed under reduced pressure.

Next, after reacting 93 g of epichlorohydrin for 10 hours at a temperature of 90 ° C. with a boron trifluoride ether complex as a catalyst to 257 g of the obtained reaction composition, 197 g of a 30% aqueous solution of trimethylamine was added. 90 ° C
At the same temperature for 10 hours. The contents were transferred to a separating funnel, diluted with 500 ml of water / isopropyl alcohol = 1/1 (volume ratio), washed twice with 200 ml of hexane, and then concentrated to obtain a reaction composition (emulsifier (A)). Was. The obtained reactive emulsifier (A) has a structure represented by the following formula (4).

[0032]

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Synthesis Example 2 Synthesis of Emulsifier (B) A reaction vessel equipped with a stirrer, a thermometer and a reflux tube was charged with 106 g of allyl alcohol and 0.3 g of potassium hydroxide as a catalyst. Then, AOE-X24 (carbon Α-olefin oxide having the number of 12 or 14, manufactured by Daicel Chemical Industries, Ltd.) 196
g was added dropwise, and the mixture was stirred and reacted at 90 ° C. for 10 hours. Thereafter, the mixture was heated to 110 ° C., and excess allyl alcohol was removed under reduced pressure.

Next, 257 g of the obtained reaction composition was transferred to an autoclave, and the pressure was 2.0 kg / cm ² and the temperature was 13
At 0 ° C., 440 g of ethylene oxide was reacted to obtain an ethylene oxide 10 mol adduct.

Next, 697 g of the ethylene oxide 10 mol adduct was reacted with 93 g of epichlorohydrin at 90 ° C. for 10 hours at a temperature of 90 ° C. using a boron trifluoride ether complex as a catalyst.
g was added, and the mixture was further stirred at a temperature of 90 ° C. for 10 hours.
The contents were transferred to a separating funnel, diluted with 500 ml of water / isopropyl alcohol = 1/1 (volume ratio), and diluted with hexane 2/1.
After washing twice with 00 ml, the mixture was concentrated to obtain a reaction composition (emulsifier (B)). The obtained reactive emulsifier (B) has a structure represented by the following formula (5).

[0036]

Embedded image

[Synthesis Example 3—Synthesis of Emulsifier (C)] Ethylene oxide 10 which is an intermediate of the synthesis example of Emulsifier (B)
After reacting 185 g of epichlorohydrin for 10 hours at a temperature of 90 ° C. with 697 g of the molar adduct using a boron trifluoride ether complex as a catalyst, 394 g of a 30% aqueous solution of trimethylamine was added, and the mixture was further stirred at a temperature of 90 ° C. for 10 hours. did. The content was transferred to a separating funnel, diluted with 500 ml of water / isopropyl alcohol = 1/1 (volume ratio), washed twice with 200 ml of hexane, and then concentrated to obtain a reaction composition (emulsifier (C)). Was. The obtained reactive emulsifier (C) has a structure represented by the following formula (6).

[0038]

Embedded image

Synthesis Example 4 Synthesis of Emulsifier (D) In a reaction vessel equipped with a stirrer, thermometer and reflux tube, 106 g of allyl alcohol and 0.3 g of caustic soda as a catalyst were charged, and then AOE-X68 (carbon Α-Olefin oxides of formulas 16 and 18 (manufactured by Daicel Chemical Industries, Ltd.) 252
g was added dropwise, and the mixture was stirred and reacted at 90 ° C. for 10 hours. Thereafter, the mixture was heated to 110 ° C., and excess allyl alcohol was removed under reduced pressure.

Next, 310 g of the obtained reaction composition was transferred to an autoclave, and the pressure was 2.0 kg / cm ² and the temperature was 13
At 0 ° C., 360 g of butylene oxide was reacted with 2200 g of ethylene oxide to obtain a block adduct of 5 mol of butylene oxide and 50 mol of ethylene oxide.

Next, 5 moles of the above butylene oxide
Ethylene oxide 50 mol block adduct 2870 g
After reacting 185 g of epichlorohydrin for 10 hours at a temperature of 90 ° C. using a boron trifluoride ether complex as a catalyst, 394 g of a 30% aqueous solution of trimethylamine was added, and the mixture was further stirred at a temperature of 90 ° C. for 10 hours. Transfer the contents to a separatory funnel and add water / isopropyl alcohol = 1 /
1 (volume ratio) diluted with 500 ml, hexane 200 ml
, And concentrated to obtain a reaction composition (emulsifier (D)). Obtained reactive emulsifier (D)
Has a structure represented by the following formula (7).

[0042]

Embedded image

Synthesis Example 5 Synthesis of Emulsifier (E) In a reaction vessel equipped with a stirrer, thermometer and reflux tube, 106 g of allyl alcohol and 0.3 g of caustic soda as a catalyst were charged, and then AOE-X68 (carbon Α-Olefin oxides of formulas 16 and 18 (manufactured by Daicel Chemical Industries, Ltd.) 252
g was added dropwise, and the mixture was stirred and reacted at 90 ° C. for 10 hours. Thereafter, the mixture was heated to 110 ° C., and excess allyl alcohol was removed under reduced pressure.

Next, 310 g of the obtained reaction composition was transferred to an autoclave, and the pressure was 2.0 kg / cm ² and the temperature was 13
Under the condition of 0 ° C., 880 g of ethylene oxide was reacted to obtain an adduct of 20 mol of ethylene oxide.

Next, 1190 g of the above ethylene oxide 20 mol adduct was reacted with 90 g of epichlorohydrin at 90 ° C. for 10 hours at a temperature of 90 ° C. using a boron trifluoride ether complex as a catalyst to give 20 mol of ethylene oxide and epichlorohydrin addition. I got a body.

Next, 280 g of a 20% aqueous solution of caustic soda was charged into a reaction vessel equipped with a stirrer, thermometer and reflux tube.
While maintaining the temperature at 50 ° C., the above ethylene oxide 20 mol / epichlorohydrin adduct (1283 g) was added dropwise, and the mixture was allowed to react for 1 hour. The mixture was added dropwise and reacted for another 1 hour. The contents were transferred to a separating funnel, and after removing the aqueous layer, the mixture was diluted with 150 g of diethyl ether.
This was washed twice with 200 g of water. The ether layer from which water was well separated and removed was concentrated to obtain a tertiary amine composition.

Next, the tertiary amine composition is quaternized with benzyl chloride, and the resulting composition is subjected to an ion exchange treatment to remove unreacted substances, thereby obtaining a reaction composition (emulsifier (E)). Obtained. Obtained reactive emulsifier (E)
Has a structure represented by the following formula (8).

[0048]

Embedded image

[Synthesis Example 6—Synthesis of Emulsifier (F)] The tertiary amine composition obtained in the synthesis example of Emulsifier (E) was quaternized with dimethyl sulfate, and the obtained composition was subjected to ion exchange treatment. Then, an unreacted substance was removed to obtain a reaction composition (emulsifier (F)). The obtained reactive emulsifier (F) is
It has a structure represented by the following formula (9).

[0050]

Embedded image

Synthesis Example 7 Synthesis of Emulsifier (G) In a reaction vessel equipped with a stirrer, a thermometer and a reflux tube, 106 g of allyl alcohol and 0.4 g of caustic soda as a catalyst were charged, and then AOE-Y08 (carbon Equations 20, 22, 24,
342 g of α-olefin oxides of 26, 28 and 30 (manufactured by Daicel Chemical Industries, Ltd.) were added dropwise at 90 ° C.
The mixture was stirred for 0 hours to react. Then heat to 110 ° C,
Excess allyl alcohol was removed under reduced pressure.

Next, 464 g of the obtained reaction composition was transferred to an autoclave, and the pressure was 2.0 kg / cm ² and the temperature was 13
At 0 ° C., 360 g of butylene oxide was reacted with 2200 g of ethylene oxide to obtain a block adduct of 5 mol of butylene oxide and 50 mol of ethylene oxide.

Next, 5 moles of the above butylene oxide
Ethylene oxide 50 mol block adduct 3024 g
Cation master G using caustic soda as a catalyst
(Glycidyl trimethyl ammonium chloride 73%
208 g of an aqueous solution (Yokkaichi Gosei Co., Ltd.)
The mixture was stirred for 8 hours to react. Transfer the contents to a separatory funnel, water / isopropyl alcohol = 1/1 (volume ratio)
The mixture was diluted with 500 ml, washed twice with 200 ml of hexane, and then concentrated to obtain a reaction composition (emulsifier (G)). The obtained reactive emulsifier (G) has a structure represented by the following formula (10).

[0054]

Embedded image

[Examples 1 to 7] In a reactor equipped with a stirrer, a reflux condenser, a thermometer and a dropping funnel, ion-exchanged water 2 was added.
94 g and each 6 g of the emulsifiers (A to G) of the present invention obtained by the above Synthesis Examples 1 to 7 were charged as shown in Table 1,
The temperature was raised to 70 ° C. After removing the dissolved oxygen in the polymerization system with nitrogen gas, 20 g of butyl methacrylate and 0.5 g of ammonium persulfate were added to pre-polymerize, and the polymerization was started.
After 0 minute, 180 g of butyl methacrylate over 3 hours
Was dropped and polymerized to obtain an emulsion.

At this time, the stability of the emulsion polymerization, the mechanical stability of the emulsion, the foamability, and the water resistance of the polymer film produced from this emulsion were evaluated by the following methods. Table 1 shows the results.

Polymerization stability: The emulsion was filtered through a 150-mesh wire gauze, the residue was washed with water and dried, and the weight of the coagulated product obtained was expressed as a percentage of the weight of the charged monomers. Mechanical stability: 50 g of the emulsion was subjected to a Marlon-type test. The mixture was stirred for 5 minutes at a load of 10 kg and a rotation speed of 1000 rpm with a machine, and the formed aggregates were filtered through a 150-mesh wire gauze. The residue was washed with water and dried, and the weight was expressed in% of the solid content of the emulsion. Foaming: dilute the emulsion 2 times with water, 100ml
Place 30 cc in the Nessler tube, invert 30 times, and leave still
Water resistance: A 0.5 mm thick polymer film was prepared on a glass plate and immersed in water until the 4.5 point characters could not be read through the film.時間: 1 day or more, ： １: 1 hour or more, ×: less than 1 hour.

Comparative Example 1 An emulsion was obtained in the same manner as in Examples 1 to 7, except that lauryltrimethylammonium chloride was used as an emulsifier. Regarding this, Example 1
Evaluation was performed in the same manner as in Examples 7 to 7. The results are also shown in Table 1.

[0059]

[Table 1]

Examples 8 to 14 Stirrer, reflux condenser,
Ion-exchanged water was added to a reactor equipped with a thermometer and a dropping funnel.
90 g was charged, and the inside of the polymerization system was replaced with nitrogen gas. 100 g of butyl acrylate, 100 g of methyl methacrylate
And 10 g of each of the emulsifiers of the present invention shown in Table 2 were mixed, and 21 g of the emulsifier and 0.5 g of 2,2'-azobis (2-amidinopropane) dihydrochloride were added to the reactor, and prepolymerized at 80 ° C. . From 10 minutes after the start of the polymerization, 189 g of a mixture of the remaining monomer and the emulsifier was added dropwise over 3 hours, and after completion of the addition, the mixture was aged for 3 hours to obtain an emulsion.

The emulsion polymerization stability, the mechanical stability of the emulsion, and the water resistance of the polymer film produced from the emulsion were evaluated in the same manner as in Examples 1 to 7. The contact angle was evaluated by the following method. Table 2 shows the results.

Contact angle: A 0.5 mm thick polymer film was formed on a glass plate, and the contact angle with a water droplet was measured.

Comparative Example 2 Examples 8 to 14 were repeated except that lauryltrimethylammonium chloride was used as an emulsifier.
An emulsion was obtained in the same manner as described above. This was evaluated in the same manner as in Examples 8 to 14. The results are also shown in Table 2.

[0064]

[Table 2]

[Examples 15 to 21] Vinyl acetate 140
g, VeoVa10 (manufactured by Shell Japan Co., Ltd.) 60
g, 290 g of ion-exchanged water, 0.5 g of potassium persulfate and 10 g of each of the emulsifiers of the present invention shown in Table 3 to prepare a mixed monomer emulsion, and dissolved oxygen was removed with nitrogen gas. Next, 100 g of the mixed monomer emulsion was placed in a reactor equipped with a stirrer, a reflux condenser, a thermometer and a dropping funnel.
It was charged and heated to 85 ° C. for polymerization. Subsequently, 400.5 g of an emulsion of the remaining mixed monomer was added dropwise over 2 hours. After completion of the addition, the mixture was aged for 2 hours to obtain an emulsion.

The emulsion polymerization stability, the foaming property of the emulsion, the contact angle and the water resistance of the polymer film produced from the emulsion were evaluated in the same manner as in Examples 8 to 14. Table 3 shows the results.

Comparative Example 3 Examples 15 to 2 were repeated except that lauryltrimethylammonium chloride was used as an emulsifier.
An emulsion was obtained in the same manner as in Example 1. This was evaluated in the same manner as in Examples 5 to 21. The results are also shown in Table 3.

[0068]

[Table 3]

[0069]

As described above, according to the emulsifier for aqueous resin dispersion of the present invention, an emulsion having high polymerization stability during emulsion polymerization, good mechanical stability and low foaming can be obtained. In addition, the water resistance of the polymer film obtained from the emulsion can be remarkably improved.

Claims (2)

[Claims] A compound (I) represented by the following general formula (1)
An emulsifier for an aqueous resin dispersion comprising: Embedded image (Where, in the general formula (1), R ¹ is an alkyl group having 8 to 30 carbon atoms, R ² is a hydrogen or methyl group, R ³ , R ⁴ , R
⁵ each independently represent a hydrocarbon group having 1 to 8 carbon atoms;
Represents an alkylene group or a substituted alkylene group having 2 to 4 carbon atoms, n represents an integer of 0 to 200, and X ⁻ represents a monovalent anion. ) 2. A compound represented by the following general formula (2):
An emulsifier for an aqueous resin dispersion comprising I). Embedded image (Where, in the general formula (2), R ¹ is an alkyl group having 8 to 30 carbon atoms, R ² is a hydrogen or methyl group, and A is ^{2 to} 30 carbon atoms.
4 alkylene group or substituted alkylene group, n is 0 to 2
And an integer Y is hydrogen or a substituent represented by the following general formula (3). In the general formula (3), R ³ , R ⁴ , R
⁵ is each independently a hydrocarbon group having 1 to 8 carbon atoms, m
Represents an integer of 0 to 5, and X ⁻ represents a monovalent anion. )