JP6713329B2 - Polymer particles - Google Patents

Description

The present invention relates to polymer particles and a method for producing polymer particles.

A hair treatment agent is required to have excellent feeling such as cohesion, smoothness, and softness of hair after washing and drying, and excellent durability. At this time, if the hair is set using a perm, a curling iron, or a hair styling agent, although the settability is excellent, the hair is damaged by heat or a chemical treatment agent, and as a result, the tips of the hair spread and the styling continues. There was a case that the sex was impaired.

From such a background, a cationized cellulose derivative has been used as a conditioning agent in shampoos to prevent electrostatic charge of hair. However, even if a cationized cellulose derivative is used, there is a problem in that a build-up action is observed by shampooing several times, the hair is charged, and the tips of the hair spread.
Patent Document 1 discloses a hair having excellent styling performance, which prevents electrostatic chargeability after shampooing, and a crosslinked cationic conditioning agent for shampoo having no build-up action does not impair the feel of hair. It is disclosed as a cosmetic product.

On the other hand, in Patent Document 2, as a method for producing a microgel comprising an electrolyte containing a cationic monomer, a polymer gel comprising a synthetic polymer electrolyte produced by a homogeneous polymerization method or a reverse phase suspension polymerization method, Disclosed is a thickener and a cosmetic containing the thickener prepared by synthesizing a polymer by a specific reverse-phase emulsion polymerization (reverse-phase microemulsion polymerization), which solves the drawbacks of carboxyvinyl polymer.

Further, as a hydrophilicity-imparting agent other than the cationic polymer for preventing electrostatic charge, there is a method using an amphoteric polymer containing a nonionic monomer and an anionic monomer. As a production method, a method of obtaining an amphoteric polymer with few impurities by a simple solution polymerization method without performing a post-treatment step of an oil-soluble surfactant such as conventional reverse phase suspension polymerization is mentioned.

In addition, the amphoteric copolymer containing a molar excess of cation-forming groups/cationic groups compared with anion-forming groups/stainless styling properties without stickiness, and at the same time, perceptually perceptible performance such as elasticity and pleasant feel to hair. Patent Document 4 discloses that

Further, as an improvement of the cationic polymer, Patent Document 5 discloses an example in which a cationic gel is applied to hair care as a crosslinkable microgel by reverse phase microemulsion polymerization.

JP, 11-79957, A JP, 2005-298831, A JP-A-63-90521 Japanese Patent Publication No. 2010-503744 JP, 2007-238575, A

However, none of the polymers described in these patent documents have sufficient hydrophilicity of hair, and stickiness increases when the blending amount is increased in order to improve performance, and an amphoteric polymer also has anionic monomer and cationic monomer. When was mixed and polymerized, a gel-like polymer was produced, and the particle shape could not be maintained, so that uniform adhesion to hair was not achieved and satisfactory results were not obtained.

The present invention provides a polymer particle and a method for producing the polymer particle, in which the polymer particle adheres to the hair to improve the cohesiveness and smoothness of the hair.

The present invention relates to polymer particles containing a structural unit A represented by the following general formula (a) and a structural unit B represented by the following general formula (b).

[In the formula, R ^1a , R ^2a and R ^3a are the same or different and each is a hydrogen atom or a methyl group, and X ^1a represents an oxygen atom or NH. R ^4a represents an alkylene group having 1 to 4 carbon atoms which may have a hydroxy group, and R ^5a and R ^6a are the same or different and represent a hydrocarbon group having 1 to 4 carbon atoms. ]

[In formula, R ^<1b> , R ^<2b> , R ^<3b> is the same or different and is a hydrogen atom or a methyl group, and X ^<1b> shows an oxygen atom or NH. R ^4b and R ^7b are the same or different and each represents an alkylene group having 1 to 4 carbon atoms which may have a hydroxy group. R ^5b and R ^6b are the same or different and each represents an alkyl group having 1 to 4 carbon atoms, and Z ^1b- represents SO ₃ ⁻ or COO ⁻ . ]

The present invention also relates to a method for producing polymer particles, which comprises the following steps (1) and (2).
Step (1): A step of polymerizing a monomer A′ represented by the following general formula (a′) to produce polymer particles (a)

[In formula, R ^<1a> , R ^<2a> , R ^<3a> is the same or different and is a hydrogen atom or a methyl group, and X ^<1a> shows an oxygen atom or NH. R ^4a represents an alkylene group having 1 to 4 carbon atoms which may have a hydroxy group, and R ^5a and R ^6a are the same or different and represent a hydrocarbon group having 1 to 4 carbon atoms. ]

Step (2): The polymer particles (a) obtained in the step (1) are reacted with a betaine agent to betain, thereby forming a structural unit A represented by the following general formula (a) and the following general unit: Process for producing polymer particles containing structural unit B represented by formula (b)

[In the formula, R ^1a , R ^2a and R ^3a are the same or different and each is a hydrogen atom or a methyl group, and X ^1a represents an oxygen atom or NH. R ^4a represents an alkylene group having 1 to 4 carbon atoms which may have a hydroxy group, and R ^5a and R ^6a are the same or different and represent a hydrocarbon group having 1 to 4 carbon atoms. ]

[In formula, R ^<1b> , R ^<2b> , R ^<3b> is the same or different and is a hydrogen atom or a methyl group, and X ^<1b> shows an oxygen atom or NH. R ^4b and R ^7b are the same or different and each represents an alkylene group having 1 to 4 carbon atoms which may have a hydroxy group. R ^5b and R ^6b are the same or different and each represents an alkyl group having 1 to 4 carbon atoms, and Z ^1b- represents SO ₃ ⁻ or COO ⁻ . ]

The present invention also relates to a hair cosmetic containing the above polymer particles. The present invention also relates to a hair cosmetic containing the polymer particles obtained by the above production method.

Advantageous Effects of Invention According to the present invention, it is possible to provide a polymer particle and a method for producing the polymer particle, in which the polymer particle adheres to the hair to improve the cohesiveness and smoothness of the hair.
Since the polymer particles of the present invention include a polymer chain containing a monomer having a sulfobetaine group on the particle surface, when the polymer particles are attached to the hair, a hydrophilic surface having an area exceeding the surface area of the hair is Since it is generated on the hair, the hair is moisturized and the feeling of cohesion is improved. Further, by attaching to the hair as polymer particles, the friction between the hairs is reduced and the smoothness can be improved.

<Polymer particles>
[Structural unit A]
The polymer particle of the present invention contains a structural unit A represented by the following general formula (a), which is derived from a nonionic unsaturated monomer.

[In the formula, R ^1a , R ^2a and R ^3a are the same or different and each is a hydrogen atom or a methyl group, and X ^1a represents an oxygen atom or NH. R ^4a represents an alkylene group having 1 to 4 carbon atoms which may have a hydroxy group, and R ^5a and R ^6a are the same or different and represent a hydrocarbon group having 1 to 4 carbon atoms. ]

The structural unit A represented by the general formula (a) is a structural unit derived by polymerizing a monomer A′ represented by the following general formula (a′), and includes the general formula (a) and the general formula (a) R ^1a , R ^2a , R ^3a , X ^1a , R ^4a , R ^5a and R ^6a in formula (a′) have the same meaning.

In formulas (a) and (a′), R ^1a and R ^2a are preferably hydrogen atoms from the viewpoint of availability of monomers and polymerizability. From the same viewpoint, R ^3a is preferably a methyl group.
X ^1a is preferably O from the viewpoint of the polymerizability of the monomer.
From the viewpoint of particle formation and adhesion to hair, R ^4a is preferably an alkylene group having 1 to 4 carbon atoms, and more preferably an alkylene group having 2 to 4 carbon atoms. From the same viewpoint, R ^5a and R ^6a are preferably alkylene groups having 1 to 4 carbon atoms, and more preferably alkylene groups having 2 to 4 carbon atoms.

Specific examples of the monomer A′ include 2-(diethylamino)ethyl (meth)acrylate, 2-(dimethylamino)ethyl (meth)acrylate, and 2-(dipropylamino)ethyl (meth)acrylate. , (Meth)acrylic acid esters such as 2-(dibutylamino)ethyl (meth)acrylate, N-(3-dimethylaminopropyl)(meth)acrylamide, N-(3-diethylaminopropyl)(meth)acrylamide, Examples thereof include (meth)acrylamides such as N-(3-dipropylaminopropyl)(meth)acrylamide and N-(3-dibutylaminopropyl)(meth)acrylamide.
In addition, in this specification, "(meth)acryl" means acryl, methacryl, or both of them.

Monomer A′ is preferably 2-(diethylamino)ethyl (meth)acrylate, N-(3-diethylaminopropyl)(meth)acrylamide, N-(3-dipropylaminopropyl) from the viewpoint of particle forming property. ) (Meth)acrylamide and N-(3-dibutylaminopropyl)(meth)acrylamide, and more preferably, (meth)acrylic acid 2-(diethylamino)ethyl, and further preferably methacrylic acid. The acid is 2-(diethylamino)ethyl.

[Structural unit B]
The polymer particle of the present invention contains a structural unit B represented by the following general formula (b), which is derived from a dipolar unsaturated monomer.

[In formula, R ^<1b> , R ^<2b> , R ^<3b> is the same or different and is a hydrogen atom or a methyl group, and X ^<1b> shows an oxygen atom or NH. R ^4b and R ^7b are the same or different and each represents an alkylene group having 1 to 4 carbon atoms which may have a hydroxy group. R ^5b and R ^6b are the same or different and each represents an alkyl group having 1 to 4 carbon atoms, and Z ^1b- represents SO ₃ ⁻ or COO ⁻ . ]

R ^1b and R ^2b are preferably hydrogen atoms from the viewpoint of availability of monomers and polymerizability. From the same viewpoint, R ^3b is preferably a methyl group.
X ^1b is preferably O from the viewpoint of polymerizability of the monomer.
From the viewpoint of particle formation and adhesion to hair, R ^4b is preferably an alkylene group having 1 to 4 carbon atoms, and more preferably an alkylene group having 2 to 4 carbon atoms. From the same viewpoint, R ^5b and R ^6b are preferably an alkylene group having 1 to 4 carbon atoms, and more preferably an alkylene group having 2 to 4 carbon atoms. From the viewpoint of particle formation and adhesion to hair, R ^7b is preferably an alkylene group having 1 to 3 carbon atoms.
Z ^{1b −} is preferably SO ₃ ⁻ from the viewpoint of smoothness of hair.

[Structural unit C]
From the viewpoint of adhesiveness to hair, the polymer particles of the present invention preferably contain a structural unit C represented by the following general formula (c).

〔式中、Ｒ^１ｃ、Ｒ^２ｃ、Ｒ^３ｃは、同一又は異なって、水素原子又はメチル基であり、Ｘ^１ｃは酸素原子又はNHを示す。Ｒ^４ｃはヒドロキシ基を有しても良い炭素数１以上４以下のアルキレン基を示す。Ｒ^５ｃ、Ｒ^６ｃ、Ｒ^７ｃは、同一又は異なって、炭素数1以上４以下のアルキル基を示し、Ｚ^１ｃ−はハロゲンイオン又はＣ_２Ｈ_５ＳＯ_４ ⁻を示す。〕

[In formula, R ^<1c> , R ^<2c> , R ^<3c> is the same or different and is a hydrogen atom or a methyl group, and X ^<1c> shows an oxygen atom or NH. R ^4c represents an alkylene group having 1 to 4 carbon atoms which may have a hydroxy group. R ^5c , R ^6c and R ^7c are the same or different and each represents an alkyl group having 1 to 4 carbon atoms, and Z ^1c- represents a halogen ion or C ₂ H ₅ SO ₄ ^— . ]

R ^1c and R ^2c are preferably hydrogen atoms from the viewpoint of availability of monomers and polymerizability. From the same viewpoint, R ^3c is preferably a methyl group.
From the viewpoint of the polymerizability of the monomer, X ^1c is preferably O.
From the viewpoint of particle formation and adhesion to hair, R ^4c is preferably an alkylene group having 1 to 4 carbon atoms, and more preferably an alkylene group having 2 to 4 carbon atoms. From the same viewpoint, R ^5c , R ^6c, and R ^7c are preferably an alkylene group having 1 to 4 carbon atoms, and more preferably an alkylene group having 2 to 4 carbon atoms.
Z ^{1c −} is preferably Cl ⁻ or C ₂ H ₅ SO ₄ ⁻ from the viewpoint of particle formation and adhesion to hair.

[Structural unit D]
From the viewpoint of particle formability and particle shape retention, the polymer particles of the present invention preferably include a structural unit D derived from a crosslinking agent.

The structural unit D is preferably a structural unit represented by the following general formula (d).

[In the formula, R ^1d , R ^2d , R ^3d , R ^5d , R ^6d and R ^7d are the same or different and each represents a hydrogen atom or a methyl group. X ^1d and X ^2d are the same or different and each represents an oxygen atom or NH. R ^4d represents an alkylene group having 1 to 10 carbon atoms, or _{- ((CH 2) p O} (CH 2) q) n - (n is a number from 1 to 10, p, q is 2 or 3 It is a number.) ]

R ^1d , R ^2d , R ^5d and R ^6d are preferably hydrogen atoms from the viewpoint of availability of monomers and polymerizability. From the same viewpoint, R ^3d and R ^7d are preferably methyl groups.
From the viewpoint of the polymerizability of the monomer, X ^1d and X ^2d are preferably O.
From the viewpoint of polymerizability and optimization of particle size, R ^4d is preferably an alkylene group having 1 to 4 carbon atoms.

The structural unit D may be a structural unit derived from a crosslinking agent other than the general formula (d). Examples of the raw material cross-linking agent serving as a constituent unit include divinylbenzene and alkylenebisacrylamide. The raw material cross-linking agent serving as the constitutional unit may be one kind or a combination of two or more kinds thereof.

The average particle size of the polymer particles is preferably 0.01 μm or more, more preferably 0.05 μm or more, still more preferably 0.1 μm or more, and the smoothness of the hair, from the viewpoint of easy production of hair cosmetics. In view of the residual whiteness when the hair and particles adhere to the hair, the thickness is preferably 20 μm or less, more preferably 10 μm or less, still more preferably 1 μm or less.

The average particle size of the polymer particles is a value measured by diluting the polymer particles with ion-exchanged water to a solid content of 0.3 wt% and using a particle size/zeta potential measuring device Zetasizer Nano ZS (manufactured by Malvern Instruments Ltd.). is there.

The shape of the polymer particles of the present invention is preferably spherical. The shape of the polymer particles can be confirmed by a field emission scanning electron microscope (SEM). Specifically, it can be confirmed by the method described in Examples.

The content of the structural unit A in the polymer particles is preferably 10% by mass or more, more preferably 15% by mass or more, from the viewpoint of the reaction efficiency of the quaternization reaction and the betaine reaction in the production process of the polymer particles. , More preferably 20% by mass or more, and from the viewpoint of adhesion to hair, preferably 90% by mass or less, more preferably 80% by mass or less, and further preferably 70% by mass or less.

The content of the structural unit B in the polymer particles is preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 15% by mass or more, and the betaine reaction from the viewpoint of adhesion to hair. From the viewpoint of reaction efficiency, the content is preferably 80% by mass or less, more preferably 75% by mass or less, and further preferably 70% by mass or less.

The content of the structural unit C in the polymer particles is preferably 0% by mass or more, more preferably 0.1% by mass or more, further preferably 1% by mass or more, and 4 from the viewpoint of adhesion to hair. From the viewpoint of reaction efficiency of the grading reaction, it is preferably 80% by mass or less, more preferably 75% by mass or less, and further preferably 70% by mass or less.

The content of the structural unit D in the polymer particles is preferably 0.05% by mass or more, more preferably 0.5% by mass or more, further preferably 2% by mass or more, from the viewpoint of particle formation and smoothness of hair. From the viewpoint of reaction efficiency of quaternization and betaine formation, the amount is preferably 30% by mass or less, more preferably 20% by mass or less, and further preferably 15% by mass or less.

In the polymer particles, the total content of constituent units containing a cationic group, that is, the total content of constituent units B and C, is preferably 30% by mass or more, more preferably from the viewpoint of adhesion to hair. 35 mass% or more, more preferably 37 mass% or more, and from the viewpoint of manufacturability, preferably 90 mass% or less, more preferably 85 mass% or less, and further preferably 80 mass% or less.
The constitutional unit containing a cationic group includes the constitutional unit B and the constitutional unit C.

The polymer particle of the present invention is a polymer containing a polymer chain containing the structural unit A inside the polymer particle and a polymer chain containing the structural unit B on the surface of the polymer particle from the viewpoint of adhesion to hair. It is preferably a particle.

<Method for producing polymer particles>
The present invention is a method for producing polymer particles, which comprises the following step (1) and step (2).
Step (1): Step of polymerizing the monomer A′ represented by the general formula (a′) to produce polymer particles (a) Step (2): Polymer obtained in step (1) Step of producing polymer particles containing constitutional unit A and constitutional unit B by reacting particles (a) with a betaine agent to form betaine, and the method for producing polymer particles of the present invention is the polymer of the present invention. The matters described for particles can be applied as appropriate.

[Step (1)]
The step (1) is a step of producing the polymer particles (a) by polymerizing the monomer A′ represented by the general formula (a′). That is, the step (1) is a step of producing the polymer particles (a) containing the structural unit A derived by polymerizing the monomer A′ represented by the general formula (a′).
As the polymerization method, a known method can be used as long as the polymer particles (a) can be obtained. The polymerization method is preferably emulsion polymerization, suspension polymerization, miniemulsion polymerization, or microemulsion polymerization from the viewpoint of polymer particle formation, and a method of polymerizing in the presence of a surfactant in a mixed solvent of water and an organic solvent. Miniemulsion polymerization is more preferable from the viewpoints of the crosslinking reaction rate of the polymer particles and control of the average particle size.

The organic solvent used for the polymerization is not particularly limited as long as it dissolves the monomer. The solvent may be used alone or in combination of two or more kinds. Specifically, hexadecane, heptadecane, octadecane, cetyl alcohol, isopropyl laurate, isopropyl palmitate, hexyl laurate, isopropyl myristate, isopropyl myristate, cetyl myristate, 2-octyldecyl myristate, isopropyl palmitate, palmitin. Acid 2-ethylhexyl, butyl stearate, decyl oleate, 2-octyldodecyl oleate, glycol ester oils (eg polypropylene glycol monooleate), neopentyl glycol 2-ethylhexanoate and glycol ester oils, isostearic acid, Triglycerides and coco fatty acid triglycerides, almond oil, almond oil, avocado oil, cacao butter, carrot seed oil, castor oil, orange seed oil, coconut oil, corn oil, cottonseed oil, cucumber oil, egg oil, jojoba oil, lanolin oil, Flax oil, mineral oil, mink oil, olive oil, coconut oil, human milk, peach seed oil, peanut oil, rapeseed oil, safflower oil, sesame oil, shark liver oil, soybean oil, sunflower oil, sweet almond oil, beef tallow, sheep fat, turtle oil , Vegetable oils, whale oil, and wheat germ oil, organic silicon, siloxane, alkyl mercaptans (eg, n-dodecyl mercaptan, t-dodecyl mercaptan, etc.), fluorinated alkanes (eg, hexafluorobenzene, etc.). However, one or more selected from hexadecane, heptadecane, and octadecane are preferable, and hexadecane is more preferable.

The surfactant used for polymerization is not particularly limited as long as it emulsifies water and an organic solvent. The surfactants may be used alone or in combination of two or more. As the surfactant, a reactive surfactant which becomes a constitutional unit of polymer particles by reacting the surfactant itself may be used.

The polymerization initiator used for the polymerization is not particularly limited, and 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis- Azo-based initiators such as 2-amidinopropane dihydrochloride, lauroyl peroxide, benzoyl peroxide, peroxide-based initiators such as t-butyl peroxyneodecanoate, persulfate-based initiators such as ammonium persulfate Etc. From the viewpoint of polymerizability and availability, 2,2'-azobis(2,4-dimethylvaleronitrile), lauroyl peroxide and benzoyl peroxide are preferable, and 2,2'-azobis(2,4-dimethylvaleronitrile) is preferable. Is more preferable. If necessary, a chain transfer agent or the like can also be used. Examples of the chain transfer agent include mercaptans such as dodecyl mercaptan, mercaptoethanol and mercaptopropionic acid.

In the step (1), from the viewpoint of maintaining the particle shape, it is preferable to further add a monomer D′ which is a crosslinking agent and polymerize.

The monomer D'is preferably a monomer represented by the following general formula (d').

[In the formula, R ^1d , R ^2d , R ^3d , R ^5d , R ^6d and R ^7d are the same or different and each represents a hydrogen atom or a methyl group. X ^1d and X ^2d are the same or different and each represents an oxygen atom or NH. R ^4d represents an alkylene group having 1 to 10 carbon atoms, or _{- ((CH 2) p O} (CH 2) q) n - (n is a number from 1 to 10, p, q is 2 or 3 It is a number.) ]

The monomer D′ represented by the general formula (d′) is a monomer that induces the structural unit D represented by the general formula (d) by polymerizing, and is represented by the general formula (d′) and R ^1d , R ^2d , R ^3d , R ^4d , R ^5d , R ^6d , R ^7d , X ^1d and X ^2d in formula (d) are all synonymous.

R ^1d , R ^2d , R ^5d and R ^6d are preferably hydrogen atoms from the viewpoint of availability of monomers and polymerizability. From the same viewpoint, R ^3d and R ^7d are preferably methyl groups.
X ^1d and X ^2d are preferably O or NH from the viewpoint of polymerizability of the monomer.
From the viewpoint of polymerizability and optimization of particle size, R ^4d is preferably an alkylene group having 1 to 4 carbon atoms.

The amount of the organic solvent used for the polymerization is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and preferably 200 parts from 100 parts by mass of the monomer A′, from the viewpoint of the efficiency of the polymerization reaction. It is not more than 100 parts by mass, more preferably not more than 100 parts by mass.

The amount of the surfactant used for the polymerization is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, with respect to 100 parts by mass of all the monomers, from the viewpoint of polymer particle formation. And it is preferably 20 parts by mass or less, more preferably 10 parts by mass or less.
In addition, all the monomers include all the monomers that are the raw materials of the constituent units of the polymer particles. That is, all monomers are the sum of the monomer A′, the monomer D′, and the reactive surfactant when the surfactant is reactive.

The amount of the polymerization initiator used for the polymerization is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and 100 parts by mass of all the monomers from the viewpoint of the efficiency of the polymerization reaction. , Preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

The amount of the monomer D′ used for the polymerization is preferably 0.05 parts by mass or more, more preferably 0.5 parts by mass or more, with respect to 100 parts by mass of all the monomers, from the viewpoint of particle forming property. It is more preferably 1 part by mass or more, preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and further preferably 15 parts by mass or less.

The average particle size of the polymer particles (a) obtained in the step (1) is preferably 0.01 μm or more, more preferably 0.05 μm or more, and further preferably 0, from the viewpoint of easy production of the hair cosmetic. From 1 μm or more, and from the viewpoint of reducing the softness of hair and white residue of particles on hair, it is preferably 20 μm or less, more preferably 10 μm or less, and further preferably 1 μm or less.

The average particle diameter of the polymer particles (a) is obtained by diluting the polymer particles (a) with ion-exchanged water to a solid content of 0.3 wt% and measuring the particle diameter/zeta potential measuring device Zetasizer Nano ZS (manufactured by Malvern Instruments Ltd.). It is the value measured by using.

The shape of the polymer particles (a) is preferably spherical. The shape of the polymer particles can be confirmed by a field emission scanning electron microscope (SEM). Specifically, it can be confirmed by the method described in Examples.

[Step (2)]
The step (2) is a step of producing a polymer particle containing the structural unit A and the structural unit B by reacting the polymer particle (a) obtained in the step (1) with a betaine-forming agent and converting it into betaine. Is.
In the step (2), in the polymer chain on the surface of the polymer particle (a) containing the structural unit A, the structural unit A is converted into the structural unit B by betaine, so that the structural unit A which is hydrophobic is contained. A polymer particle containing a polymer chain inside the polymer particle and containing a hydrophilic structural unit B on the surface of the polymer particle can be produced.

As a method of reacting an amino group with a quaternizing agent to form betaine, a known method can be used, and examples thereof include the method described in JP-A 2006-514150.

Examples of the betaine agent include 1,3-propane sultone, 1,4-butane sultone, sodium 3-chloro-2-hydroxypropane sulfonate, and the like. From the viewpoint of reactivity, at least one selected from 1,3-propane sultone and sodium 3-chloro-2-hydroxypropane sulfonate is preferable, and 1,3-propane sultone is more preferable.

The solvent is not particularly limited as long as it can suspend the polymer particles. The solvent may be used alone or in combination of two or more kinds. Specific examples include ethanol, 2,2,2-trifluoroethanol, ethyl acetate, isopropyl alcohol, acetone and methyl ethyl ketone. From the viewpoint of reactivity, at least one selected from ethanol and trifluoroethanol is preferable, and ethanol is more preferable.

From the viewpoint of reactivity, the amount of the betaine agent charged is preferably 75 parts by mass or more, more preferably 85 parts by mass or more, relative to 100 parts by mass of the charged amount of the monomer A′ derived from the structural unit A. And, it is preferably 95 parts by mass or less, more preferably 92 parts by mass or less.

In the method for producing polymer particles of the present invention, from the viewpoint of adhesion to hair, the polymer particles (a) obtained in step (1) or the polymer particles obtained in step (2) are quaternized. A method of producing a polymer particle containing the structural unit A, the structural unit B and the structural unit C by reacting the agent is preferable, and the polymer particle (a) obtained in the step (1) is reacted with a quaternizing agent. Then, it is more preferable than the method of producing a polymer particle containing the structural unit A, the structural unit B and the structural unit C by carrying out the step (2) after quaternization.
By including the step of reacting the polymer particles (a) or the quaternizing agent with the polymer particles, in the polymer chain on the surface of the polymer particles (a) containing the constituent unit A, the constituent unit A is replaced with the constituent unit B. And the structural unit C is changed so that the polymer chain containing the hydrophobic structural unit A is contained inside the polymer particle and the hydrophilic polymer chain containing the structural unit B and the structural unit C is provided on the surface of the polymer particle. It is possible to produce polymer particles containing.

A known method can be used for the quaternization method, and examples of the quaternization agent include dialkyl sulfuric acid and alkyl halides. From the viewpoint of reactivity, at least one selected from dimethyl sulfate, diethyl sulfate, methyl chloride and methyl iodide is preferable, and diethyl sulfate is more preferable.
The solvent is not particularly limited as long as it does not cause hydrolysis of the polymer particles. The solvent may be used alone or in combination of two or more kinds. Specific examples thereof include ethanol and isopropanol. Ethanol is more preferable from the viewpoint of reactivity.

In the case where the polymer particles (a) are cationized and then betained, the amount of the quaternizing agent charged is the monomer A′ derived from the structural unit A from the viewpoint of uniformly betaining the polymer particle surfaces. The amount of the polymer particles (a) is preferably 7 parts by mass or more, more preferably 8 parts by mass or more, and preferably 10 parts by mass or less, more preferably 9 parts by mass or less, relative to 100 parts by mass of the charged amount of the polymer particles (a). When not betaining after cationization, is preferably 60 parts by mass with respect to 100 parts by mass of the amount of the monomer A′ derived from the structural unit A, from the viewpoint of uniformly quaternizing the surface of the polymer particles. Parts by mass or more, more preferably 70 parts by mass or more, and preferably 90 parts by mass or less, more preferably 80 parts by mass or less.

The reaction temperature for the quaternization can be appropriately selected depending on the type of organic solvent used for the mixed solvent, etc., but from the viewpoint of reaction rate, preferably 30° C. or higher, more preferably 50° C. or higher, and from the viewpoint of yield, It is preferably 80°C or lower, more preferably 60°C or lower.

<Hair cosmetics>
The present invention is a hair cosmetic containing the above-mentioned polymer particles. Further, the present invention is a hair cosmetic containing the polymer particles obtained by the above production method. For the hair cosmetic composition of the present invention, the matters described in the polymer particles and the method for producing polymer particles of the present invention can be appropriately applied.

The content of the polymer particles in the hair cosmetic is preferably 0.5% by mass or more, more preferably 3% by mass or more, and preferably 20% by mass or less, more preferably 10 from the viewpoint of hair modification. It is not more than mass %.

The hair cosmetic composition of the present invention may contain the following components.

[Surfactant]
The hair cosmetic composition of the present invention may contain a surfactant. As the surfactant, any of anionic surfactant, nonionic surfactant, cationic surfactant and amphoteric surfactant can be used.

Two or more surfactants may be used in combination, and the content in the hair cosmetic is preferably 0.1% by mass or more, more preferably 0.5% by mass, from the viewpoint of the stability of the hair cosmetic. As described above, the content is more preferably 1% by mass or more, preferably 30% by mass or less, more preferably 25% by mass or less, further preferably 20% by mass or less, further preferably 15% by mass or less.

[Higher alcohol]
The hair cosmetic composition of the present invention preferably contains a higher alcohol having 12 or more carbon atoms from the viewpoint of improving the feel and stability. These have the effects of forming a structure with the surfactant to prevent separation and improving the feel during rinsing.

[Other optional ingredients]
In addition to the above components, the hair cosmetic composition of the present invention may contain other components usually used as a raw material for cosmetics. Such optional components include thickeners, preservatives, chelating agents, stabilizers, antioxidants, botanical extracts, crude drug extracts, protein hydrolysates, vitamins, coloring agents such as dyes, and fragrances. , UV absorbers, pearlizing agents such as ethylene glycol difatty acid esters, setting polymers other than the polymer particles of the present invention, amphipathic amide lipids and the like.

[Medium]
Water is used as a medium in the hair cosmetic composition of the present invention. The content of water in the hair cosmetic composition is preferably 10% by mass or more, more preferably 20% by mass or more, further preferably 30% by mass or more, and preferably 90% by mass or less, more preferably 80% by mass or less. , And more preferably 75 mass% or less.

If necessary, an organic solvent is used as a medium other than water in the hair cosmetic composition of the present invention. As the organic solvent, benzyl alcohol, aromatic alcohols such as benzyloxyethanol, ethanol, lower alkanols such as 2-propanol, propylene glycol, 1,3-butanediol, diethylene glycol, polyols such as glycerin, ethyl cellosolve, Examples thereof include cellosolves such as butyl cellosolve and benzyl cellosolve, and carbitols such as ethyl carbitol and butyl carbitol.

[PH]
The pH of the hair cosmetic composition of the present invention at 25° C. is preferably 2 or more, more preferably 4.5 or more, still more preferably 5.5 or more, and preferably 12 or less, more preferably 11.5 or less, further It is preferably 11 or less. A pH adjuster can be used for this adjustment.

As a pH adjuster, as an alkaline agent,
(1) Ammonia or its salt,
(2) Alkanolamines such as monoethanolamine, isopropanolamine, 2-amino-2-methylpropanol and 2-aminobutanol, or salts thereof,
(3) Alkanediamine such as 1,3-propanediamine or a salt thereof,
(4) Carbonates such as guanidine carbonate, sodium carbonate, potassium carbonate, sodium hydrogen carbonate and potassium hydrogen carbonate,
(5) Hydroxides such as sodium hydroxide and potassium hydroxide can be used.
Also, as an acid agent,
(I) Inorganic acids such as hydrochloric acid and phosphoric acid, hydrochlorides such as monoethanolamine hydrochloride,
(Ii) Phosphates such as monopotassium dihydrogen phosphate and disodium monohydrogen phosphate can be used.

These pH adjusters may be used alone or in combination with both an acid agent and an alkali agent, and the content thereof is preferably 0.1% in hair cosmetics from the viewpoint of reducing hair damage and scalp irritation. The amount is 01% by mass or more, more preferably 0.1% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less.

[Formulation]
The hair cosmetic composition of the present invention may be in the form of liquid, emulsion, cream, gel, paste, mousse, aerosol or the like. In the case of an aerosol, the content of each component described above and the pH of the hair cosmetic composition are the content in the undiluted solution containing no propellant and the pH of the undiluted solution.

The hair cosmetic composition of the present invention is a hair cosmetic composition other than a depigmenting composition and a hair dye composition, that is, an in-bath agent such as pre-shampoo treatment, shampoo, hair rinse, hair conditioner, hair treatment, after-shampoo treatment; non-aerosol foam. , Outer bath agents such as aerosol foam, hair gel, hair mousse, hair mist, hair lotion, hair oil, and styling agents.

[Usage method (hair treatment method)]
The treatment of the hair with the hair cosmetic composition of the present invention is carried out by bringing the hair cosmetic composition into contact with the hair directly or with a tool. As a method of contact, a method which is generally widely used in the hair cosmetic type can be applied.For example, in the case of pre-shampoo treatment, an appropriate amount is brought into contact with dry or wet hair before shampoo treatment, For a few seconds to several tens of minutes, wash it off with running water, in the case of shampoo, contact an appropriate amount with hair, massage for several minutes while foaming and then rinse with running water, hair rinse, hair conditioner, hair treatment, after shampoo treatment, etc. In this case, after shampooing, an appropriate amount is brought into contact with the hair, and then left for several seconds to several tens of minutes and then rinsed with running water. .. Here, the appropriate amount is an amount such that the bath ratio relative to the mass of hair becomes about 1:0.005 to 1:10. The hair to be treated may be all or a part thereof. The temperature when applied to the hair is preferably from room temperature to body temperature, but may be heated up to about 50° C. to promote penetration.

In the following production examples, examples and comparative examples, "%" means "mass%". Various physical properties and the like were measured by the following methods.

(1) Average Particle Diameter of Polymer Particles The average particle diameter of each polymer particle obtained in the following production example is calculated by diluting each polymer particle with ion-exchanged water to a solid content of 0.3 wt%. It measured using the electric potential measuring device Zetasizer Nano ZS (made by Malvern).

(2) Shape of polymer particles The shape of each polymer particle obtained in the following production examples was observed by the following method.
Approximately 20 mg of each polymer particle emulsion diluted with ion-exchanged water to a solid content of 100 mg/L on a silicon wafer (manufactured by Niraco Co., Ltd., diameter 100 mm, thickness 0.5 mm) cut into 5 mm square pieces. Was added. Then, the silicon wafer piece containing the polymer particles was dried at room temperature (about 25° C.) for 6 hours in a desiccator filled with silica gel. After sticking the dried silicon wafer piece to the sample stand with a carbon double-sided tape, osmium was vapor-deposited on the sample, and this was used with a field emission scanning electron microscope (SEM) (S-4800 manufactured by Hitachi High-Technologies Corporation). Then, the particle shape was observed at an acceleration voltage of 5 kV.

(3) Content of Each Structural Unit in Polymer Particles The content of each structural unit in the polymer particles is calculated based on the molar ratio and the molecular weight of each structural unit in the polymer particles. The mass of the structural unit was calculated and calculated. In the following production examples, polyoxyethylene polyoxybutylene (3-methyl-3-butenyl) ether (hereinafter, also referred to as a reactive surfactant) and ethylene glycol dimethacrylate (structural unit D ) Is used, the content of each structural unit was calculated in consideration of these molar ratios and molecular weights.
Specifically, the molar ratio of the structural unit A in the polymer particles was determined by titration under the following conditions, and the molar ratios of the structural units B, C, D and the reactive surfactant were calculated from the results. For the polymer particles of Production Example 4, the titration was performed twice after the quaternization reaction with diethyl sulfate and the betaine reaction with 1,3-propane sultone, and the first titration. From the results, a part of the molar ratio of structural unit A and the molar ratio of structural unit C were calculated, and from the second titration result, the other part of the molar ratio of structural unit A and the molar ratio of structural unit B were calculated.
More specifically, the procedure was as follows. About 0.1 g of each polymer particle obtained in the following production example was placed in a beaker, diluted with about 50 g of ion-exchanged water, and about 0.1 g of concentrated sulfuric acid was added under stirring with a stirrer to make it acidic, and then ultrasonically shaken. Deaeration was performed for 3 minutes with a stirrer. About 0.1 g of 1.0 M sodium hydroxide aqueous solution was added thereto to adjust the pH to 11 or more, and titration was performed with 0.1 M hydrochloric acid aqueous solution using an automatic titrator (AUT-701: manufactured by Toa DKK Co., Ltd.). It was The amount of unreacted tertiary amine is calculated from the difference between the drop amount at the inflection point near pH 10 and the drop amount at the inflection point near pH 6 using the following formula.
Unreacted tertiary amine amount (mol) = 0.1 (mol/L) x [drop amount near pH 6 (mL)-drop amount near pH 10 (mL)]/1000
The total molar ratio of the structural units is 100 mol %, and the molar amount of the structural unit A in the total molar ratio of the structural units A, B, and C is calculated from the amount of unreacted tertiary amine obtained by titration. Considering that the ratio (mol %) can be calculated, the mass of the structural unit A per unit mass of the polymer particles, that is, mass %, was calculated. Further, the molar ratio of the other structural units was calculated in consideration of the molar ratio of the structural unit A, and the mass% was calculated in the same manner.

Production example 1
In a 1 L beaker, weigh 600 g of ion-exchanged water, and then 4.0 g of polyoxyethylene polyoxybutylene (3-methyl-3-butenyl) ether (Laomu PD-450, reactive surfactant manufactured by Kao Corporation). Add and dissolve. There, 90 g of diethylaminoethyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.), 10 g of ethylene glycol dimethacrylate (manufactured by Shin Nakamura Chemical Co., Ltd.), 5 g of hexadecane (manufactured by Wako Pure Chemical Industries, Ltd.), 2,2′-azobis( 2,4-Dimethylvaleronitrile) (Wako Pure Chemical Industries, Ltd.: V-65) 1.0 g of an aqueous solution was added, and an ultrasonic homogenizer was stirred for 20 minutes (Nippon Seiki Seisakusho: US-600E). Was emulsified. The obtained emulsion was transferred to a 2 L flask equipped with a condenser and stirred at room temperature at 200 rpm for 5 minutes, and the inside of the flask was replaced with nitrogen for 20 minutes. Then, the flask was heated in a 72° C. water bath to carry out polymerization. After the temperature inside the flask reached 70° C., the reaction was further continued for 3 hours. Then, aging was carried out at a flask internal temperature of 75° C. for 3 hours to obtain a polymer emulsion. The average particle size of the polymer particles (a) in the emulsion was 0.17 μm. The shape of the polymer particles (a) was spherical.

Production example 2
The emulsion obtained in Production Example 1 was transferred to a metallic vat and freeze-dried for 8 hours using a freeze vacuum dryer (DFR-5N-B manufactured by ULVAC, Inc.) to obtain a solid. 15 g of the obtained solid was weighed in a 500 mL flask equipped with a condenser and a dropping funnel, 150 g of acetone (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and then the content in the flask was changed to 20 while stirring at 25° C. and 200 rpm for 5 minutes. The atmosphere was replaced with nitrogen. Then, the flask was heated in a water bath at 52° C., and after the temperature inside the flask reached 50° C., 10.1 g of diethyl sulfate (manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise over 10 minutes, and stirring was continued for further 3 hours. It was made to react. After cooling, the emulsion was transferred to a 1 L eggplant flask, 135 g of ion-exchanged water was added, acetone was removed by an evaporator, and the obtained emulsion was purified according to the following purification method.
The average particle size of the polymer particles in the purified emulsion was 0.21 μm. The cation content was 50.2% by mass. The shape of the polymer particles was spherical.

Production Example 3
180 g of the emulsion obtained in Production Example 1 was weighed in a 500 mL separable flask equipped with a condenser and a dropping funnel, 150 g of ethanol (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the mixture was stirred at 25° C. and 200 rpm for 5 minutes. Meanwhile, the inside of the flask was replaced with nitrogen for 20 minutes. Then, the flask was heated in a water bath of 52° C., and after the temperature inside the flask reached 50° C., 20.4 g of 1,3-propane sultone (manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise over 10 minutes, and further 3 hours. The reaction was continued with stirring. After cooling, the emulsion was transferred to a 1 L eggplant flask, ethanol was removed by an evaporator, and the obtained emulsion was purified according to the following purification method.
The average particle size of the polymer particles in the purified emulsion was 0.22 μm. The betaine content was 57.1% by mass. The shape of the polymer particles was spherical.

Production Example 4
The emulsion obtained in Production Example 1 was transferred to a metallic vat and freeze-dried for 8 hours using a freeze vacuum dryer (DFR-5N-B manufactured by ULVAC, Inc.) to obtain a solid. After weighing 10 g of the obtained solid in a 500 mL flask equipped with a condenser and a dropping funnel and adding 40 g of ethanol (super dehydration) (manufactured by Wako Pure Chemical Industries, Ltd.), the mixture was stirred at 25° C. and 200 rpm for 5 minutes, The inside of the flask was replaced with nitrogen for 20 minutes. Then, the flask was heated in a water bath at 72° C., and after the temperature inside the flask reached 70° C., 0.75 g of diethyl sulfate (manufactured by Wako Pure Chemical Industries, Ltd.) and ethanol (super dehydration) (manufactured by Wako Pure Chemical Industries, Ltd.) ) 10 g of the mixed solution was added dropwise over 10 minutes, and the reaction was continued by further stirring for 3 hours. Next, after adding 50 g of ion-exchanged water and lowering the temperature inside the flask to 50° C., 7.91 g of 1,3-propane sultone (manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise over 10 minutes, and the mixture was further stirred for 3 hours. Was continuously reacted. After cooling, the emulsion was transferred to a 500 mL eggplant flask, 100 g of ion-exchanged water was added, ethanol was removed by an evaporator, and the obtained emulsion was purified according to the following purification method.
The average particle size of the polymer particles in the purified emulsion was 0.21 μm. The cation content was 9.3 mass% and the betaine content was 39.3 mass %. The shape of the polymer particles was spherical.

Purification method Purification of each polymer particle obtained in Production Examples 2 to 4 was carried out by the following method.
150 g of an emulsion of each polymer particle was weighed in a centrifuge PA bottle (500 mL), and ion-exchanged water was added so that the total amount of the bottle including the emulsion was 450 g. This bottle was centrifuged at 12,000 rpm for 3 hours with a high-speed cooling centrifuge (CR21GIII manufactured by Hitachi Koki Co., Ltd.). Then, the supernatant of the obtained separated product was removed, 100 g of ion-exchanged water was added to the same bottle, and the polymer was precipitated using a desktop ultrasonic cleaner (Sharp Co., Ltd.: UT-206) while mixing with a spatula. The particles were redispersed in water. Ion-exchanged water was added to this so that the amount including the bottle was 450 g, and centrifugation was performed again at 12,000 rpm for 3 hours. This operation was repeated twice.
Finally, the supernatant of the obtained separated product was removed, 100 g of ion-exchanged water was added to the same bottle, and the mixture was mixed with a spatula and settled using a tabletop ultrasonic cleaner (Sharp Co., Ltd.: UT-206). By redispersing the coalesced particles in water, an emulsion of purified polymer particles was obtained.

Content (% by mass) of the structural units A to D and the reactive surfactant in the polymer particles obtained by Production Examples 1 to 4, the average particle diameter (μm) of each polymer particle, and the content in each emulsion. Table 1 shows the polymer particle content (% by mass) and the amount charged (g) in the production of each polymer particle.

*The polymer particle content in Production Examples 2 to 4 represents the polymer particle content in the emulsion after purification.

[sensory evaluation]
Example 1, Comparative Example 1
Example 1 was prepared by adding ion-exchanged water to the purified emulsion obtained in Production Example 4 to prepare 10% by mass. 5 g of this cosmetic was applied to 1 g of hair bundle (length 20 cm), and evenly spread over the entire hair bundle, and then thoroughly rinsed with 1 L of ion-exchanged water. After this hair bundle was dried with a dryer for 5 minutes, the smoothness when touched with a finger and the cohesiveness of the hair were sensory evaluated according to the following evaluation criteria. In Comparative Example 1, the hair bundle was not rinsed with the cosmetic material, rinsed thoroughly with 1 L of ion-exchanged water, dried with a dryer for 5 minutes, and then evaluated in the same manner. The results are shown in Table 2.

Evaluation criteria for smoothness ◎: No catch on fingers
◯: It may get caught on the finger, but it does not bother me △: It gets caught in the finger and is uncomfortable ×: It does not get caught in the finger

Evaluation criteria for unity
Cohesion: Hair does not spread and is uncomfortable spreading: Whole hair spreads and is uncomfortable

[sensory evaluation]
Examples 2, 3 and Comparative Examples 2, 3
The rinse components shown in Table 3 were added to each of the purified emulsions obtained in Production Examples 2 to 4, and ion-exchanged water was further added to adjust the contents to give the content shown in Table 3. 3 and Comparative Example 2. 5 g of each cosmetic was applied to a hair bundle of 1 g (length 20 cm) and spread evenly over the entire hair bundle, and then thoroughly rinsed with 1 L of ion-exchanged water. After this hair bundle was dried with a dryer for 5 minutes, the smoothness when touched with a finger and the cohesiveness of the hair were sensory evaluated according to the following evaluation criteria. In Comparative Example 3, the hair bundle was not rinsed with the cosmetic material, rinsed thoroughly with 1 L of ion-exchanged water, dried with a dryer for 5 minutes, and then evaluated in the same manner. The results are shown in Table 4.

Evaluation criteria for smoothness ◎: Not caught on the finger 〇: May be caught on the finger but do not bother △: Caught on the finger and uncomfortable ×: Not caught on the finger

Evaluation criteria for unity
Cohesion: Hair does not spread and is uncomfortable spreading: Whole hair spreads and is uncomfortable

Claims (11)

The structural unit A represented by the following general formula (a), the constituent unit B represented by the following general formula (b), and comprising a structural unit D derived from a crosslinking agent, the polymer particles.

[In formula, R ^<1a> , R ^<2a> , R ^<3a> is the same or different and is a hydrogen atom or a methyl group, and X ^<1a> shows an oxygen atom or NH. R ^4a represents an alkylene group having 1 to 4 carbon atoms which may have a hydroxy group, and R ^5a and R ^6a are the same or different and represent a hydrocarbon group having 1 to 4 carbon atoms. ]

[In formula, R ^<1b> , R ^<2b> , R ^<3b> is the same or different and is a hydrogen atom or a methyl group, and X ^<1b> shows an oxygen atom or NH. R ^4b and R ^7b are the same or different and each represents an alkylene group having 1 to 4 carbon atoms which may have a hydroxy group. R ^5b and R ^6b are the same or different and each represents an alkyl group having 1 to 4 carbon atoms, and Z ^1b- represents SO ₃ ⁻ or COO ⁻ . ] Furthermore, the polymer particle of Claim 1 containing the structural unit C represented by the following general formula (c).

[In formula, R ^<1c> , R ^<2c> , R ^<3c> is the same or different and is a hydrogen atom or a methyl group, and X ^<1c> shows an oxygen atom or NH. R ^4c represents an alkylene group having 1 to 4 carbon atoms which may have a hydroxy group. R ^5c , R ^6c and R ^7c are the same or different and each represents an alkyl group having 1 to 4 carbon atoms, and Z ^1c- represents a halogen ion or C ₂ H ₅ SO ₄ ^— . ] The polymer particle according to claim 1 or 2 , wherein the structural unit D is represented by the following general formula (d).

[In the formula, R ^1d , R ^2d , R ^3d , R ^5d , R ^6d and R ^7d are the same or different and each represents a hydrogen atom or a methyl group. X ^1d and X ^2d are the same or different and each represents an oxygen atom or NH. R ^4d represents an alkylene group having 1 to 10 carbon atoms, or _{- ((CH 2) p O} (CH 2) q) n - (n is a number from 1 to 10, p, q is 2 or 3 It is a number.) ] Comprises a polymer chain containing a constitutional unit A in the interior of the polymer particles containing a polymer chain containing a constitutional unit B on the surface of the polymer particles, the polymer particles according to any one of claims 1-3. The total content of the constitutional unit containing a cationic group is not less than 30 wt%, the polymer particles according to any one of claims 1-4. Containing polymer particles according to any one of claim 1 to 5 hair cosmetics. A method for producing polymer particles, which comprises the following step (1) and step (2).
Step (1): A step of polymerizing a monomer A′ represented by the following general formula (a′) to produce polymer particles (a)

[In formula, R ^<1a> , R ^<2a> , R ^<3a> is the same or different and is a hydrogen atom or a methyl group, and X ^<1a> shows an oxygen atom or NH. R ^4a represents an alkylene group having 1 to 4 carbon atoms which may have a hydroxy group, and R ^5a and R ^6a are the same or different and represent a hydrocarbon group having 1 to 4 carbon atoms. ]
Step (2): The polymer particles (a) obtained in the step (1) are reacted with a betaine agent to betain, thereby forming a structural unit A represented by the following general formula (a) and the following general unit: Process for producing polymer particles containing structural unit B represented by formula (b)

[In the formula, R ^1a , R ^2a and R ^3a are the same or different and each is a hydrogen atom or a methyl group, and X ^1a represents an oxygen atom or NH. R ^4a represents an alkylene group having 1 to 4 carbon atoms which may have a hydroxy group, and R ^5a and R ^6a are the same or different and represent a hydrocarbon group having 1 to 4 carbon atoms. ]

[In formula, R ^<1b> , R ^<2b> , R ^<3b> is the same or different and is a hydrogen atom or a methyl group, and X ^<1b> shows an oxygen atom or NH. R ^4b and R ^7b are the same or different and each represents an alkylene group having 1 to 4 carbon atoms which may have a hydroxy group. R ^5b and R ^6b are the same or different and each represents an alkyl group having 1 to 4 carbon atoms, and Z ^1b- represents SO ₃ ⁻ or COO ⁻ . ] The method for producing polymer particles according to claim 7 , wherein in step (1), the monomer D′ which is a crosslinking agent is further used for polymerization. The method for producing polymer particles according to claim 8 , wherein the monomer D′ is represented by the following general formula (d′).

[In the formula, R ^1d , R ^2d , R ^3d , R ^5d , R ^6d and R ^7d are the same or different and each represents a hydrogen atom or a methyl group. X ^1d and X ^2d are the same or different and each represents an oxygen atom or NH. R ^4d represents an alkylene group having 1 to 10 carbon atoms, or _{- ((CH 2) p O} (CH 2) q) n - (n is a number from 1 to 10, p, q is 2 or 3 It is a number.) ] The method for producing polymer particles according to any one of claims 8 to 10 , wherein the step (1) further comprises miniemulsion polymerization in the presence of a dispersant. The method for producing polymer particles according to any one of claims 7 to 10 , wherein the polymer particles (a) obtained in step (1) are reacted with a quaternizing agent to be quaternized.