JP2003012797A - Emulsifying agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new high-molecular emulsifying agent which is water-soluble, and biodegradable or alkali decomposable, especially, an emulsifying agent exhibiting excellent characteristics as an emulsifying agent in emulsion polymerization and capable of controlling the particle sizes of formed particles by the amount of its addition, and further an emulsifying agent capable of being hydrolyzed when remains on the surface of the formed particles after the finish of emulsifying polymerization and capable of expectably improving the properties of an obtained latex, and the like. SOLUTION: A polyaspartic acid derivative having a hydrophilic group such as an amphoteric ion structure or a carboxylic group, and a hydrophobic group such as a long chain alkyl group at the same time in its structure.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a biodegradable emulsifier composed of a polyaspartic acid derivative.

[0002]

2. Description of the Related Art The emulsion polymerization method is basically a method in which an emulsifier is dissolved in water, a water-insoluble or sparingly soluble monomer is added to the emulsion to emulsify, and polymerization is carried out using a water-soluble initiator. Since the produced polymer is obtained as an emulsion or latex, it is often used as it is as a paint or an adhesive. Further, in order to obtain a solid polymer,
The emulsion is broken by a method such as salting out or freezing, and the emulsion is filtered out. The polymer thus obtained was in the form of fine powder, but had the drawback that it contained impurities such as emulsifiers.

It has been pointed out that the emulsifier remaining in the polymer produced by emulsion polymerization greatly changes the surface properties of the polymer, which hinders the development of the characteristics as fine polymer particles. However, it has been difficult to remove an emulsifier such as sodium dodecylbenzenesulfonate (SDS) usually used in emulsion polymerization from the polymer after the polymerization.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polymeric emulsifier which is water-soluble, biodegradable or alkali-degradable and can be suitably used for emulsion polymerization and the like.

[0005]

Means for Solving the Problems The inventors of the present invention have made earnest studies in view of the above-mentioned problems of the prior art, and as a result, a zwitterionic structure in the structure, a hydrophilic group such as a carboxyl group, a long-chain alkyl group, etc. The present inventors have found that a polyaspartic acid derivative having both of the hydrophobic groups described above is excellent as an emulsifier, and completed the present invention.

That is, the present invention is an emulsifier comprising a polyaspartic acid derivative having both a hydrophilic group and a hydrophobic group, and preferably the polyaspartic acid derivative is represented by the following formulas (1) and (2).

[0007]

[Chemical 6]

(In the formulas (1) and (2), R ¹ represents a hydrogen atom or a lower hydrocarbon group having 1 to 6 carbon atoms, and R ² and R ⁵ each independently represent the number of carbon atoms. 1 to 24 saturated or unsaturated hydrocarbon group, R ³ and R ⁴ each independently represent a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms,
R ³ and R ⁴ may combine to form a 6-membered ring containing a nitrogen atom. 1) at least one kind of repeating unit selected from the group consisting of repeating units represented by
It has not less than mol% and not more than 99 mol%, and further has the following formula (3) and formula (4)

[0009]

[Chemical 7]

(In the formulas (3) and (4), R ⁶ and R ⁷ each independently represent a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms, and
R ⁶ and R ⁷ may combine to form a 6-membered ring containing a nitrogen atom. ) An emulsifier made of a polymer having at least one kind of repeating unit selected from the group consisting of repeating units represented by the formula 1) in the molecule in an amount of 1 mol% or more and 99 mol% or less. Further, the present invention preferably contains at least 1 type of repeating unit selected from the group consisting of repeating units represented by the formulas (3) and (4) in the molecule in an amount of 1 mol%.
It is an emulsifier made of a polymer having 50 mol% or less and 50 mol% or more and 99 mol% or less in the molecule of at least one kind of repeating unit selected from the following formulas (8) and (9).

[0011]

[Chemical 8]

(In equations (8) and (9), Y is
A hydrogen atom, an alkali metal atom or an alkaline earth metal atom is shown. ) Further, the present invention is an emulsion polymerization method characterized by using the above-mentioned emulsifier.

[0013]

DETAILED DESCRIPTION OF THE INVENTION The term "polyaspartic acid" used in the claims and the specification of the present application includes a polymer in which aspartic acid is subjected to peptide polycondensation. The concept of the term "hydrocarbon group" used in the claims and specification of the present application includes not only straight-chain, but also branched and cyclic ones.
Atoms other than C and H such as O and S may be contained.

The polyaspartic acid derivative as referred to in the present invention is a polymer having an aspartic acid unit or an aspartic acid derivative unit as a repeating unit. Preferably, polysuccinimide is added to amines, alcohols,
A polymer having a polyaspartic acid skeleton in its main chain, which is obtained by reacting a nucleophilic substance such as water. The polyaspartic acid derivative may contain a small amount of a structure other than the aspartic acid skeleton such as an aspartic acid unit or an aspartic acid derivative unit in the main chain as long as the effect as the emulsifier of the present invention is not significantly impaired. The amount is about 20 mol% or less. The method for producing the polyaspartic acid derivative of the present invention is not limited, but it is preferably produced by the method disclosed in JP-A-10-25344.

The substituents in the formulas (1) and (2) are as follows. R ¹ represents a hydrogen atom or a lower hydrocarbon group having 1 to 6 carbon atoms. As a specific example of R ¹ ,
Examples thereof include a hydrogen atom, an alkyl group such as a methyl group, an ethyl group, a propyl group and a butyl group, and a hydroxyalkyl group such as a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group and a hydroxybutyl group. Among these,
From the physical properties of the emulsifier, a hydrogen atom, a methyl group and an ethyl group are more preferable, and a hydrogen atom is the most preferable.

R ² and R ⁵ each independently represent a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms. Specific examples of R ² and R ⁵ include alkylene groups such as methylene group, ethylene group, trimethylene group, tetramethylene group and pentamethylene group, cycloalkylene groups such as cyclobutylene group, cyclopentylene group and cyclohexylene group, Examples thereof include hydroxyalkylene groups such as hydroxyethylene group, hydroxytrimethylene group, hydroxytetramethylene group and hydroxypentamethylene group, and alkenylene groups such as vinylene group and propenylene group. Other specific examples include, for example, an azaalkylene group such as an azatetramethylene group and an azapentamethylene group, an azaalkenylene group, an oxaalkylene group, an oxatetramethylene group, an oxaalkylene group such as an oxapentamethylene group, and an oxaalkylene group. Examples thereof include alkenylene groups, thioalkylene such as thiotetramethylene group and thiopentamethylene group, and thioalkenylene groups.

Among these, as R ² and R ⁵ , for example, an alkylene group having 1 to 18 carbon atoms, a hydroxyalkylene group, an alkenylene group or the like is preferable. Further, R ² is more preferably an alkylene group having 1 to 5 carbon atoms, a hydroxyalkylene group, an alkenylene group or the like, and a trimethylene group is most preferable from the viewpoint of emulsifying properties. Further, as R ⁵ , an alkylene group having 1 to 18 carbon atoms, a hydroxyalkylene group, an alkenylene group or the like is more preferable, and a methylene group is most preferable from the viewpoint of emulsifying properties.

R ³ and R ⁴ each independently represent a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms, and R ³ and R ⁴ are bonded to each other to form a nitrogen atom-containing hexagonal group. You may form a member ring. Specific examples of R ³ and R ⁴ include a hydrogen atom, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a dodecyl group, an octadecyl group, and other alkyl groups, a hydroxymethyl group, a hydroxyethyl group, Examples thereof include hydroxyalkyl groups such as hydroxypropyl group and hydroxybutyl group, propenyl groups, butenyl groups, pentenyl groups, hexenyl groups, alkenyl groups such as heptenyl, and the like. Other specific examples include an azaalkenyl group, an oxaalkenyl group and a thioalkenyl group. Of these, an alkyl group having 1 to 6 carbon atoms, a hydroxyalkyl group, and an alkenyl group are preferable, and a methyl group and an ethyl group are more preferable, and a methyl group is most preferable, from the viewpoint of emulsifier properties. When R ³ and R ⁴ are combined to form a 6-membered ring containing a nitrogen atom, the 6-membered ring obtained by combining the groups listed above is preferred. The 6-membered ring may contain a heteroatom other than the nitrogen atom. The 6-membered ring is more preferably a piperazine ring, a piperidine ring or a morpholine ring, and particularly preferably a morpholine ring.

The substituents in the formulas (3) and (4) are as follows. R ⁶ and R ⁷ each independently represent a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms, and R ⁶ and R ⁷ are bonded to each other to form a 6-membered ring containing a nitrogen atom. You may form. Specific examples of R ⁶ and R ⁷ include a hydrogen atom, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a dodecyl group, an octadecyl group, and other alkyl groups, a hydroxymethyl group, a hydroxyethyl group, Examples thereof include hydroxyalkyl groups such as hydroxypropyl group and hydroxybutyl group, alkenyl groups such as propenyl group, butenyl group, pentenyl group, hexenyl group and heptenyl group. Other specific examples include an azaalkenyl group, an oxaalkenyl group and a thioalkenyl group. Among these, carbon atoms of 7 to 1
The alkyl group, hydroxyalkyl group and alkenyl group of 8 are preferable from the viewpoint of emulsifier properties, and particularly, octyl group, lauryl (dodecyl) group and stearyl (octadecyl) group are more preferable, and lauryl group is most preferable.

Y in the formulas (8) and (9) represents a hydrogen atom, an alkali metal atom or an alkaline earth metal atom.
Specific examples of Y include a hydrogen atom, sodium, potassium, lithium, calcium, magnesium and the like, and among these, a hydrogen atom, sodium, potassium and calcium are preferable.

The polyaspartic acid derivative of the present invention comprises a group consisting of repeating units represented by the formulas (1) and (2), or a group consisting of repeating units represented by the formulas (8) and (9). To at least 1 mol% as a hydrophilic group, at least 1 mol% or more, and at least one repeating unit from the group consisting of the repeating units represented by the formulas (3) and (4) is a hydrophobic group. As at least 1 mol% or more, and as the remaining repeating units, the following formulas (5) to (7),

[0022]

[Chemical 9]

(In the formulas (6) and (7), R
¹ represents a hydrogen atom or a lower hydrocarbon group having 1 to 6 carbon atoms, R ² represents a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms, and R ³ and R ⁴ are each independently Represents a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms, and R ³ and R ⁴ may combine with each other to form a 6-membered ring containing a nitrogen atom. ) And the following formulas (10) and (11)

[0024]

[Chemical 10]

(In equations (10) and (11), R
¹ represents a hydrogen atom or a lower hydrocarbon group having 1 to 6 carbon atoms, R ² represents a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms, and R ³ and R ⁴ are each independently Represents a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms, and R ³ and R ⁴ may combine to form a 6-membered ring containing a nitrogen atom, and R ⁸ represents hydrogen. It represents an atom or a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms, and Z ⁻ represents an anion derived from an organic or inorganic acid. It is also preferable to have in the molecule a repeating unit selected from the group consisting of the repeating units represented by

Specific examples of R ¹ , R ² , R ³ and R ^{4 in} the formulas (6), (7), (10) and (11) are the corresponding formulas (1) and (). The same as R ¹ , R ² , R ³ and R ^{4 in} 2) can be mentioned. Also,
Specific examples of R ⁸ in formulas (10) and (11) also include hydrogen atoms of R ³ and R ⁴ in formulas (1) and (2) or saturated or unsaturated hydrocarbons having 1 to 24 carbon atoms. The same groups as those exemplified as the group can be mentioned. However, the most preferable specific examples of R ³ and R ⁴ in formula (6), formula (7), formula (10) and formula (11) also include a hydrogen atom. Z ⁻ in the formulas (10) and (11) represents an anion derived from an organic or inorganic acid. Specifically, OH ⁻ , Cl ⁻ , Br ⁻ , F ⁻ , I ⁻ , CO ₃ ²⁻ , PO
Anions derived from inorganic acids such as ₃ ²⁻ and SO ₄ ²⁻ , carbanion of aliphatic carboxylic acid, carbanion of aromatic carboxylic acid, sulfoanion of aliphatic sulfonic acid, sulfoanion of aromatic sulfonic acid, etc. And anions derived from the organic acids mentioned above.

The molecular weight of the polyaspartic acid derivative according to the present invention is not particularly limited as long as the desired action and effect are substantially exhibited. If the molecular weight is too low, a problem may occur in the conformation peculiar to the polymer, and the effect of being a polymer may be diminished, so that the effect as a polymer emulsifier may be reduced.

If the molecular weight is too high, the solubility in the solvent may decrease, or the solution viscosity may become too high, which may make handling difficult. The molecular weight of the polyaspartic acid derivative according to the present invention is generally in terms of weight average molecular weight in terms of GPC (for example, chloroform solvent system),
The amount is preferably 1,000 or more and 500,000 or less, more preferably 2000 or more and 300,000 or less.

The number average of all repeating units in the polyaspartic acid derivative of the present invention is preferably 10 to 50.
00. The number average of all repeating units of this polyaspartic acid derivative is determined by the raw material polysuccinimide. The emulsifier comprising the polyaspartic acid derivative of the present invention can be used in the same manner as conventional emulsifiers.

When the emulsifier of the present invention is used as an emulsifier for emulsion polymerization, the method of use is not particularly limited. The amount used is not particularly limited, but it is preferable to use about 0.1% by weight or more with respect to the aqueous phase (continuous phase) in order to exert a preferable effect. Particularly preferably, it is 1% by weight or more. Since the emulsifier of the present invention has a polyaspartic acid skeleton in the main chain, it is essentially biodegradable and hydrolyzable. When necessary, the main chain can be cleaved and cleaved under known hydrolysis conditions that are usually used. Preferably, it can be hydrolyzed by the action of an alkaline aqueous solution having a pH of 8 or more. It is also possible to biodegrade under the presence of microorganisms such as compost.

[0031]

EXAMPLES The contents of the present invention will be described in detail below by showing experimental examples.

[Preparation Example] The weight average molecular weight of the raw material polysuccinimide was determined by gel permeation chromatography (GPC) using polystyrene as the standard.
It was 55,000 when evaluated under the following conditions. Apparatus: JASCO 880-PU Detector: Shodex RID-300 Column: Shodex KD-804 + KD-80M Solvent: 0.01M LiBr / DMF Concentration: 0.5 wt% Injection amount: 20 μL Flow rate: 1.0 mL / min

As a reactor, a separable flask equipped with a stirrer, a heater, a thermometer and a nitrogen line was used, and the reaction system was sufficiently stirred during the reaction. After dissolving 97 g of the raw material polysuccinimide in 400 g of DMF at room temperature,
27.8 g of laurylamine (15 mol% based on succinimide units) were added. While keeping the internal temperature of the reactor at 60 ° C., the reaction was carried out for 4 hours. When the reactor was cooled and the internal temperature fell below 40 ° C, N, N-dimethyl-1,3
-Propanediamine 86.9 g (85 mol% based on succinimide unit) was added dropwise, and the mixture was further reacted at room temperature for 4 hours. After completion of the reaction, the reaction solution was discharged into 3 L of acetone with stirring to precipitate the produced polyaspartic acid derivative, which was collected by filtration.

As a reactor, a separable flask equipped with a stirrer, a heater, a thermometer and a nitrogen line was charged with the above-mentioned isolated polyaspartic acid derivative and dissolved in 500 mL of ethanol. Next, the N, used above,
100 mL of potassium monochloroacetate ethanol solution in which N-dimethyl-1,3-propanediamine and an equimolar amount of potassium monochloroacetate were dissolved was added dropwise to the flask with a dropping funnel, and after completion of dropping, the mixture was further refluxed under a nitrogen stream. The reaction was carried out for 6 hours. After completion of the reaction, the reaction solution was concentrated, the precipitate was filtered off by suction filtration, and the filtrate was discharged into acetone to precipitate the polyaspartic acid derivative. The polyaspartic acid derivative suspension having the zwitterion thus produced was isolated by suction filtration.

[Example 1] 85 mol% of a zwitterionic (betaine) structure as a hydrophilic group obtained in the above Preparation Example,
Emulsion polymerization of styrene was carried out using a polyaspartic acid derivative having 15 mol% of lauryl group as a hydrophobic group. Continuous phase (water phase) 1 in a 50 mL three-necked flask
To 5 g, 0.02 g of potassium persulfate as an initiator and a predetermined amount of the above polyaspartic acid derivative (0.1 to the aqueous phase)
(Wt% to 10 wt%) was dissolved and 1.7 g of styrene was dispersed. The inside of the reactor was filled with nitrogen gas, and polymerization was carried out in an oil bath at 70 ° C. while stirring with a magnetic stirrer. About 0.5 g of the solution during the polymerization was collected from the nitrogen sealing port with a Pasteur pipette, and rapidly added to 25 mL of methanol containing 0.1 mol / L of 4-t-butylpyrocatechol. Unreacted styrene dissolved in methanol was measured by reverse phase liquid chromatography. Emulsion polymerization proceeded rapidly regardless of the amount of the polyaspartic acid derivative used. For example, when the polyaspartic acid derivative was used in an amount of 2% by weight, a polymerization rate of nearly 100% was reached within 1 hour after the initiation of polymerization.

A part of the emulsion after the polymerization was dispersed in a large amount of water, and the particle size was measured by the dynamic light scattering method.
The particle size decreased as the amount of emulsifier used increased. For example, the amount of polyaspartic acid derivative used is 1% by weight,
At 2% by weight, 4% by weight, 6% by weight and 10% by weight, the diameter of the obtained polystyrene particles was 164 nm,
It was 156 nm, 141 nm, 120 nm, and 96 nm. The dependence of the amount of the polyaspartic acid derivative used as an emulsifier on the particle size was -0.23 power, and the Smith-Ewart theory in emulsion polymerization (Langmuir, 1997).
Year, 13 volumes, p4988). From this, it was shown that the present polymerization process proceeds with a typical emulsion polymerization mechanism.

Further, when the emulsifier comprising the polyaspartic acid derivative of the present invention was used, good emulsification stability equal to or higher than conventional emulsifiers was exhibited regardless of the amount of the emulsifier used. However, when the amount of the polyaspartic acid derivative used as the emulsifier was a small amount of less than 1% by weight, the degree of aggregation of the produced particles increased and the emulsion stability tended to decrease as the amount used decreased. After the completion of emulsion polymerization, a sodium hydroxide aqueous solution was added to the polystyrene particle emulsion to adjust the pH to 12, and the emulsifier was hydrolyzed by stirring at 50 ° C. After washing with water and neutralization, the collected polystyrene was subjected to elemental analysis. It was confirmed that the nitrogen atom composition was smaller than that of the particles not subjected to the hydrolysis treatment, and the emulsifier was effectively removed.

[0038]

According to the present invention, a novel biodegradable emulsifier is provided. The emulsifier of the present invention exhibits excellent properties especially as an emulsifier for emulsion polymerization, and the particle size of the produced particles can be controlled by the amount added. When emulsion polymerization is performed using an emulsifier composed of the polyaspartic acid derivative of the present invention, the emulsifier remaining on the surface of the produced particles can be hydrolyzed after the completion of the polymerization reaction, and the physical properties of the obtained latex and the like can be improved. it can.

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) C08L 79/08 C08L 79/08 AF Term (Reference) 4D077 AB14 AC01 BA07 BA12 DD28X DD42X DD70X 4J001 DA01 DB01 EA36 FA03 FB01 FC01 GE02 JA20 JC01 4J002 CM04W CM04X GD00 4J011 KA15 KA25 KB29 4J043 PA02 PC166 QB06 RA06 SA05 SA62 SB01 UA761 YB32 ZB60

Claims (12)

[Claims] 1. An emulsifier comprising a polyaspartic acid derivative having both a hydrophilic group and a hydrophobic group. 2. A polyaspartic acid derivative having a hydrophilic group as the following formula (1) and formula (2): (In the formulas (1) and (2), R ¹ represents a hydrogen atom or a lower hydrocarbon group having 1 to 6 carbon atoms, and R ² and R ⁵
Each independently represents a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms, and R ³ and R ⁴ each independently represent a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms. It represents a hydrocarbon group, and R ³ and R ⁴ may combine to form a 6-membered ring containing a nitrogen atom. ) Having at least one type of repeating unit selected from the group consisting of repeating units represented by the formula 1) in the molecule in an amount of 1 mol% or more and 99 mol% or less, and as a hydrophobic group, the following formulas (3) and (4) ) [Chemical 2] (In the formulas (3) and (4), R ⁶ and R ⁷ each independently represent a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms, and R ⁶ and R ⁷ May combine to form a 6-membered ring containing a nitrogen atom), and 1 mol% or more and 99 mol% or less in the molecule of at least one kind of repeating unit selected from the group consisting of repeating units represented by An emulsifier consisting of a polymer having. 3. A polyaspartic acid derivative is further represented by the following formulas (5) to (9): (In the formulas (6) and (7), R ¹ represents a hydrogen atom or a lower hydrocarbon group having 1 to 6 carbon atoms, and R ² represents a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms. R ³ and R ⁴ each independently represent a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms, and R ³ and R ⁴ are bonded to each other to form a hexagonal group containing a nitrogen atom. A member ring may be formed.) (In the formulas (8) and (9), Y represents a hydrogen atom, an alkali metal atom or an alkaline earth metal atom.)
The emulsifier according to claim 2, which is a polymer having 99 mol% or less in the molecule of at least one kind of repeating unit selected from the group consisting of repeating units represented by: 4. A polyaspartic acid derivative is further represented by the above formulas (5) to (9), and the following formulas (10) and (11): (In the formulas (10) and (11), R ¹ represents a hydrogen atom or a lower hydrocarbon group having 1 to 6 carbon atoms;
² represents a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms, R ³ and R ⁴ each independently represent a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms. R ³ and R ⁴ may combine to form a 6-membered ring containing a nitrogen atom, R ⁸ represents a hydrogen atom or a saturated or unsaturated hydrocarbon group having 1 to 24 carbon atoms, and Z ⁻ Represents an anion derived from an organic or inorganic acid. The emulsifier according to claim 2, which is a polymer having at least one kind of repeating unit selected from the group consisting of repeating units represented by the formula (1) in the molecule. 5. In formula (1) and / or formula (2),
The emulsifier according to claim 2, wherein R ¹ is a hydrogen atom, R ² is a propylene group, R ³ and R ⁴ are methyl groups, and R ⁵ is a methylene group. 6. In formula (3) and / or formula (4),
The emulsifier according to claim 2, wherein R ⁶ is a hydrogen atom and R ⁷ is an alkyl group having 6 to 18 carbon atoms. 7. The polyaspartic acid derivative has 1 mol of at least one repeating unit selected from the group consisting of repeating units represented by the formulas (3) and (4) as a hydrophobic group in the molecule. % Or more and 50 mol% or less, and at least one kind of repeating unit selected from the above formulas (8) and (9) as a hydrophilic group in the molecule is 5
The emulsifier according to claim 1, which is a polymer having 0 mol% or more and 99 mol% or less. 8. In formula (3) and / or formula (4),
The emulsifier according to claim 2, wherein R ⁶ is a hydrogen atom and R ⁷ is a lauryl group. 9. The polyaspartic acid derivative has the formula (3):
And / or at least one type of repeating unit selected from the group consisting of repeating units represented by formula (4) is 1
The emulsifier according to claim 2, which is a polymer contained in an amount of not less than mol% and not more than 40 mol%. 10. The emulsifier according to claim 1, wherein the polyaspartic acid derivative is a polymer in which the number average of all repeating units in the molecule is 10 to 5,000. 11. An emulsion polymerization method, which comprises using the emulsifier according to any one of claims 1 to 10. 12. The use amount of the emulsifier according to claim 1, which is 1% by weight or more and 20% by weight or less with respect to the aqueous phase.
Emulsion polymerization method.