JP2002212211A - Process for producing polymer particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an efficient and simple process for producing polymer particles containing a coloring material in the core part and useful for cosmetics, particularly, hair cosmetics. SOLUTION: The process for producing polymer particles having a core part and a shell part comprises dissolving or dispersing a coloring material in a hydrophobic monomer, and emulsifying and dispersing the solution or dispersion in water in the presence of a chitosan and a hydrophilic monomer to effect polymerization. Polymer particles obtained by the process and hair cosmetics containing the polymer particles are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD [0001] The present invention is useful for cosmetics,
The present invention relates to a polymer particle having a core portion and a shell portion, a method for producing the same, and a hair cosmetic containing the polymer particle.

[0002]

2. Description of the Related Art Techniques for selectively coloring a hydrophilic surface or coloring both hydrophilic and hydrophobic surfaces in an aqueous liquid are well known, and are used for, for example, hair dyes. ing. However, few techniques are known for selectively coloring a hydrophobic surface in an aqueous liquid by a simple physical force such as friction.

[0003] Since the surface of the hair is more hydrophobic than the surface of the skin, the use of the above-mentioned technique makes it possible to easily dye the hair in an aqueous system without soiling the skin.

[0004] One of the methods for achieving this technique is a method of enclosing a pigment in the core of core-shell particles having a hydrophilic shell and a hydrophobic core. When used as a hair cosmetic by designing the core-shell particles so that they can be deformed by a certain amount of physical force, they are deformed when applied to the hair surface by hand, exposing hydrophobic parts, and the particles coat the hair And sticks to the hair. On the other hand, particles that have not undergone deformation are less likely to adhere to hair because of their hydrophilic surface, and can be easily removed by rinsing.

[0005] As a method of incorporating a coloring material into the core portion,
JP-A-07-146585 and JP-A-11-84726 describe a method in which particles are formed by performing polymerization, and then mixed with a dispersion of the pigment in water to attach the pigment to the particles. . In this method, when coloring hair, such free pigments flow down at the time of rinsing, and not only do not contribute to coloring, but also are not washed away, because there is a free pigment that does not bind to the particles. If it remains on the hair, it may adhere to clothes, pillows, etc., and contaminate those fibers.

As another method, Japanese Patent Application Laid-Open No. 2000-53545 describes a method in which a coloring material is added to hydrophobic and hydrophilic monomers and then polymerized. In this method, when particles are used as a coloring agent, in order to improve coloring performance,
It is necessary to disperse the coloring material to a certain particle size. However, also in this method, there is a possibility that some free pigment which does not bind to the particles may be present, and there is a possibility that clothes and fibers such as pillows are contaminated.

An object of the present invention is to provide an efficient and simple method for producing polymer particles containing a coloring material in a core portion, which are useful as cosmetics, especially hair cosmetics.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a colorant is dissolved or dispersed in a hydrophobic monomer, and then emulsified and dispersed in water in the presence of chitosan and a hydrophilic monomer. And a method for producing polymer particles having a core portion and a shell portion, a polymer particle obtained by the production method, and a hair cosmetic containing the polymer particles.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION [Polymer particles] The polymer particles produced according to the present invention comprise a hydrophobic polymer as a constituent, a core containing a coloring material, chitosan and a hydrophilic polymer as constituents. It consists of a shell part. The average particle size of the polymer particles is preferably 3 from the viewpoint of performance and stability.
0 μm or less, more preferably 0.01 to 30 μm, particularly preferably 0.1 to 10 μm, and still more preferably 0.5 to
10 μm. In the present invention, the average particle size of the polymer particles is measured by a laser diffraction particle size distribution analyzer (LA-
910, manufactured by HORIBA).

[Core] The core of the polymer particles of the present invention contains a polymer of a hydrophobic monomer as a constituent, and contains a coloring material and, if necessary, a non-polymerizable hydrophobic substance.

<Hydrophobic monomer> The hydrophobic monomer used in the present invention is not particularly limited as long as it can be copolymerized with the hydrophilic monomer and is hydrophobic. Less than 0.1 g is preferred. Such hydrophobic monomers include, for example, styrene, divinylbenzene,
Butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, decyl acrylate, dodecyl acrylate, dodecenyl acrylate, tetradecyl acrylate, hexadecyl acrylate, hexadecenyl acrylate, octadecyl acrylate, octadecenyl acrylate, behenyl acrylate, etc. Acrylates, butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, decyl methacrylate, dodecyl methacrylate, dodecenyl methacrylate, tetradecyl methacrylate, hexadecyl methacrylate, hexadecenyl methacrylate, octadecyl methacrylate, octadecenyl methacrylate , Methacrylates such as behenyl methacrylate, and fluorine-based units such as trifluoroethyl methacrylate. Monomer, silicone macromer and the like. These hydrophobic monomers can be used alone or in combination of two or more.

<Coloring Material> Examples of the coloring material used in the present invention include water-insoluble pigments, oil-soluble dyes, vat dyes, and lake pigments. As pigments, inorganic pigments such as carbon black, talc, kaolin, mica, mica titanium, mung bean, magnesium silicate, titanium oxide, red 202
No. 204, red 205, red 206, red 219, red 228, red 404, yellow 401, orange 403, blue 404, etc. 501
No., Red No. 505, Red No. 225, Yellow No. 404, Yellow No. 405, Yellow No. 204, Orange No. 403, Blue No. 403, Green No. 202, Purple
No. 201, and as vat dyes, red 226, blue
No. 204 and Blue No. 201, and examples of lake pigments include those obtained by lakes of various acidic dyes with aluminum or barium.

Among these coloring materials, at least one selected from the group consisting of carbon black, red 202, red 226, red 404, blue 201, blue 404, yellow 401 and titanium oxide Is preferred.

One or more of such coloring materials can be used in combination, and the compounding amount of the coloring material in the polymer particles is preferably 1 to 3.
-50% by weight, more preferably 2-30% by weight, particularly preferably 2-15% by weight.

In the present invention, it is preferable to use a non-polymerizable hydrophobic substance such as a wax, an oil agent, a fragrance, a cooling agent, a warming agent, a plasticizer, and a skin and hair protecting agent together with the coloring material.

Examples of the wax include natural wax, processed natural wax, and synthetic wax. Examples of the oil include silicone oil, hydrocarbon oil, ester oil, higher alcohols and derivatives thereof, and natural animal and vegetable oils. Examples of the fragrance include limonene. Examples of the plasticizer include esters, benzoates, phosphates, and diethylbenzene. Examples of the skin and hair protection agents include ceramide and its structural substances, squalane, squalene, dialkyl ethers having 24 to 44 carbon atoms, lauroyltaurine calcium salt and the like.

The compounding amount of these non-polymerizable hydrophobic substances is as follows:
The amount is preferably 0 to 90 parts by weight, more preferably 2 to 50 parts by weight, particularly preferably 2 to 15 parts by weight, based on 100 parts by weight of the hydrophobic monomer forming the core.

[Shell Part] The shell part of the polymer particles of the present invention comprises a polymer of chitosan and a hydrophilic monomer as a constituent.

<Chitosan> Chitosan used in the present invention is (1 → 4) -2-acetamido-2-deoxy-
A deacetylated product of chitin having a β-D-glucan structure, comprising (1 → 4) -2-amino-2-deoxy-β
In the present invention, a part of a deacetylated amino group or a part of a hydroxyl group in the same molecule has an acylation reaction, an etherification reaction, an esterification reaction, and other reactions. And chitosan derivatives chemically modified by the method described above. In general, naturally occurring chitin has a degree of deacetylation of 30% or more as chitosan used in the present invention because a part of an acetamido group is an amino group which is not acetylated.

The amount of the chitosan is preferably 1 to 80 parts by weight based on 100 parts by weight of the hydrophobic monomer from the viewpoint of sufficiently exhibiting the performance of the chitosan and not impairing the stability of the polymer particles. preferable.

<Hydrophilic monomer> The hydrophilic monomer is 100 g of water.
The solubility in water at 20 ° C. is preferably 0.1 g or more,
More preferably, it is an organic acid having a reactive unsaturated group or a salt thereof.

The organic acid having a reactive unsaturated group used in the present invention can be dissolved in chitosan to form an aqueous solution. One or more reactive unsaturated groups and one or more acidic groups are contained in the molecule. It is a water-soluble organic acid having at least one. For example, carboxylic acids having a reactive unsaturated group such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, and maleic acid and salts thereof, styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 3- Sulfonic acid having a reactive unsaturated group such as sulfopropyl (meth) acrylate, bis (3-sulfopropyl) itaconic acid ester and salts thereof, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl- 2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, dibutyl-2-methacryloyloxyethyl phosphate, dioctyl-2- (meth) acryloyloxyethyl phosphate Having a reactive unsaturated group such as Like salt of.

In addition, methyl acrylate, hydroxyethyl acrylate, polyethylene glycol monoacrylate, glycidyl acrylate, methyl methacrylate,
Hydroxypropyl methacrylate, polyethylene glycol monomethacrylate, methacrylamide, N, N-dimethylacrylamide, vinyl acetate and the like can also be used. These can be used alone or in combination of two or more.

Of these, carboxylic acids having a reactive unsaturated group having a relatively low acidity are preferable, and methacrylic acid having a low acidity of the polymer is particularly preferable. Examples of the salts of these organic acids having a reactive unsaturated group include alkali metal (Na, K, etc.) salts and ammonium salts.

The amount of the hydrophilic monomer is desirably in the range of 0.5 to 10 times mol per monosaccharide unit of chitosan.

It is also possible to arbitrarily mix various acids together with these hydrophilic monomers. At this time, the kind of the acid to be mixed includes inorganic acids such as hydrochloric acid, sulfuric acid and phosphoric acid, formic acid, acetic acid, lactic acid, citric acid, tartaric acid, succinic acid,
Organic acids such as malic acid, oxalic acid, glycolic acid, dichloroacetic acid, trifluoroacetic acid and the like can be mentioned.

[Method for Producing Polymer Particles] A preferable method for producing the polymer particles of the present invention is as follows:
3 is a method including: Step 1: a step of adding a coloring material and an oil-soluble polymerization initiator to a hydrophobic monomer and dissolving or dispersing the same. Step 2: a step of dissolving or dispersing the hydrophilic monomer and chitosan in water. Step 3: The solution or dispersion prepared in Step 1 is added to the aqueous solution or water dispersion prepared in Step 2, and after emulsification and dispersion, a hydrophobic monomer is polymerized to form a core portion. A step of forming a shell portion by polymerizing a hydrophilic monomer in the presence of a water-soluble polymerization initiator.

<Step 1> In this step, the hydrophobic monomer is
Add a colorant, an oil-soluble polymerization initiator, and if necessary, a non-polymerizable hydrophobic substance and an emulsifier. To dissolve or disperse, preferably at 0 to 30 ° C. for about 1 hour.

The oil-soluble polymerization initiator comprises a hydrophobic monomer 100
It is preferably used in the range of 0.05 to 10.0 parts by weight based on parts by weight. Here, the oil-soluble polymerization initiator is one that initiates addition polymerization of a monomer by radical decomposition in the presence of heat or a reducing substance, and oil-soluble peroxides, azobis compounds, and the like are generally used. . For example, organic peroxides such as lauroyl peroxide and benzoyl peroxide, 2,2'-azobisisobutyronitrile, 2,2 '
Azobis (2,4-dimethylvaleronitrile), 2,
An azo compound such as 2'-azobis (2-methylbutyronitrile) is exemplified. One or more of these oil-soluble polymerization initiators can be used.

At this time, a surfactant can be used as an emulsifier. Surfactants used include cationic, nonionic, anionic and amphoteric surfactants. Among them, a polymer type surfactant is preferable from the viewpoint of polymerization stability. Examples of the cationic surfactant include polyethyleneimine, amino-modified silicone, and examples of the nonionic surfactant include a polyethylene oxide polypropylene oxide copolymer. The amount of the surfactant used is not particularly limited, but may be 0.1 to the hydrophobic monomer.
It is desirable to use in the range of ~ 20% by weight.

<Step 2> In this step, the hydrophilic monomer, chitosan and, if necessary, the emulsifier are dissolved or dispersed in water, but it is preferable to dissolve it. The amount of water is preferably 5 to 50 times the weight of chitosan.

At this time, a surfactant can be used as the emulsifier, and examples thereof include general anionic, cationic, nonionic and amphoteric surfactants. For example, examples of the anionic surfactant include dodecyl sulfate, dodecyl benzene sulfonate, and sulfate salt of polyoxyethylene nonyl phenyl ether. Examples of the nonionic surfactant include polyethylene oxide alkyl ether, polyethylene oxide alkyl phenyl ether, and a polyethylene oxide-polypropylene oxide block copolymer. Examples of the cationic surfactant include octadecyltrimethylammonium chloride. Examples of the amphoteric surfactant include betaine alkyldimethylaminoacetate,
2-alkyl-N-carboxy-N-hydroxyimidazolinium betaine and the like. However, since amphoteric ions are present in the polymer particles, a nonionic surfactant is preferable in consideration of the stability of the polymer particles. The use amount of the surfactant is not particularly limited, but it is preferable to use the surfactant in a range of 0.1 to 20% by weight based on the hydrophilic monomer.

Further, a water-soluble polymer can be used as an emulsifier. Examples of the water-soluble polymer include polyvinyl alcohol and derivatives thereof, starch and derivatives thereof, and cellulose derivatives. One or more of these surfactants and water-soluble polymers can be used in combination.

<Step 3> In this step, first, the solution or dispersion prepared in Step 1 is added to the aqueous solution or dispersion prepared in Step 2, and emulsified and dispersed. For emulsification, ultrasonic homogenizer, homomixer, milder, attritor,
Using an (ultra) high pressure homogenizer, a nanomizer system, a film emulsifying device, or the like, the O / W droplets having an average particle diameter of preferably 10 μm or less are formed.

Next, the core portion is formed by polymerizing a hydrophobic monomer to form a core portion, and subsequently polymerizing a hydrophilic monomer in the presence of a water-soluble polymerization initiator to form a shell portion. And polymer particles having a shell portion.

The polymerization temperature varies depending on the type of the initiator, but is suitably in the range of about 40 ° C. to 90 ° C. The polymerization time varies depending on the type of the monomer, the type of the polymerization initiator, and the reaction temperature. In order to polymerize the hydrophilic monomer in water, the water-soluble polymerization initiator is added during the polymerization of the core portion or after the polymerization of the core portion is completed. In order to increase the content of chitosan, an aqueous solution of chitosan and a hydrophilic monomer may be further added during the polymerization.

The water-soluble polymerization initiator is one which decomposes radically in the presence of heat or a reducing substance to start addition polymerization of a monomer, and is a water-soluble peroxodisulfate, peroxide, azobis compound or the like. Are generally used. For example,
Peroxodisulfates such as potassium persulfate and ammonium persulfate; peroxides such as hydrogen peroxide and t-butyl hydroperoxide; 2,2'-azobis-2-amidinopropane salts (V-50); Azo compounds such as' -azobis-4-cyanopentanoic acid; If necessary, it can be used as a redox initiator in combination with a reducing agent. The amount of the water-soluble polymerization initiator used is 0.05 to 20 parts by weight based on 100 parts by weight of the hydrophilic monomer.
A range of parts by weight is preferred.

The polymer particles obtained by the above-mentioned production method can be neutralized with a base. As the base, ammonia, methylamine, ethylamine, propylamine, butylamine, isobutylamine, hexylamine, octylamine, amino-modified silicone, ethylenediamine, propylenediamine, butylenediamine, sodium hydroxide, potassium hydroxide, calcium hydroxide, carbonated carbonate Sodium, sodium alkoxide, potassium alkoxide and the like can be mentioned.

The amount of the base added is preferably 0.1 to 2.0 mol% with respect to the hydrophilic polymer in the polymer particles, and is preferably 0.6 to 2.0 mol%.
-1.2 mol% is particularly preferred.

[Hair Cosmetic] The hair cosmetic of the present invention contains the polymer particles obtained by the above-mentioned production method. One or more kinds of polymer particles can be blended, and it is effective to blend 0.05 to 40% by weight, particularly 0.1 to 30% by weight, more preferably 0.5 to 10% by weight in hair cosmetics. It is preferable in such points. In particular, in order to obtain a hair cosmetic of an arbitrary color, two or more kinds of polymer particles containing different polymer particles may be mixed or used.

In the hair cosmetic composition of the present invention, in addition to the above-mentioned ingredients, the ingredients used in ordinary hair cosmetic compositions, such as cationic surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants Higher alcohols; hydrocarbons such as liquid paraffin and vaseline; lanolin derivatives such as liquid lanolin and lanolin fatty acids; phospholipids such as lecithin; sterols and derivatives thereof such as cholesterol; Fluoropolyethers; Fats and oils such as higher alcohol higher fatty acid esters and higher fatty acids; Animal and plant fats and oils such as mink oil and olive oil; Anti-dandruff agents, bactericides, and medicinal agents such as vitamins; Glycerin, propylene glycol and the like Polyols; Preservatives such as parabens; Thickeners such as water-soluble polymers; Dyes and face Colorant etc., ultraviolet absorbers, vegetable extracts, astringents, perfumes, dyes and the like, within a range that does not impair the effects of the present invention can be encapsulated in appropriate formulation or particles.

The hair cosmetic of the present invention can be produced according to a usual method, and the dosage form is not particularly limited, and examples thereof include a hair rinse, a hair treatment, a hair conditioner, a hair pack, a hair lotion, a hair shampoo and the like. It is particularly suitable as a dosage form to be applied to hair such as a hair rinse, a hair treatment, a hair conditioner, and a hair pack, and then rinsed and used.

[0043]

According to the process for producing the polymer particles of the present invention, the colorant is dispersed in advance in a hydrophobic monomer as a component of the core portion, and then polymerized using a hydrophilic monomer and chitosan. It is intended to be polymer particles. Therefore, the polymer particles can minimize the amount of the free coloring material other than the core. The hair cosmetic containing the polymer particles is excellent in coloring performance because it selectively colors hair, which is a hydrophobic surface, has little color transfer to non-hair, and has little coloring to skin, which is a hydrophilic surface. It is also something.

[0044]

Example 1 In a 100 ml glass beaker, lauryl methacrylate 42.9 g,
7.2 g of carbon black (# 45L, manufactured by Mitsubishi Chemical Corporation) was added, and the mixture was treated with an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho) for 5 minutes while stirring. 0.45 g of 2,2′-azobis- (2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd.) was further added and dissolved at room temperature to obtain a carbon black dispersion.

In a 500 ml glass beaker, commercially available chitosan
(SK-10, manufactured by Koyo Chemical Co., Ltd., Deacetylation degree 85-88%,
(Weight average molecular weight 130000) 16.5 g and 330 g of water were added, and methacrylic acid 3.0 g (0.4 to the monosaccharide unit of chitosan) was added.
(5 moles) and 2.5 g of acrylic acid (0.45 moles relative to the monosaccharide unit of chitosan) were added and dissolved with stirring at room temperature to prepare an aqueous solution of chitosan / acrylic acid / methacrylic acid. The carbon black dispersion prepared above was added thereto, and the mixture was treated with an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho) for 10 minutes while stirring to obtain an emulsion having an average particle size of 9.0 μm. This emulsion was transferred to a 500-ml glass reactor equipped with a stirrer, a cooler, and a nitrogen inlet tube, and after purging with nitrogen, the mixture was heated with stirring to bring the internal temperature to 70 ° C. Under stirring 2
After polymerization for 2 hours, 0.32 g of 2,2'-azobis- (2-methylpropionamide) dihydrochloride (manufactured by Wako Pure Chemical Industries, Ltd.) dissolved in 10 g of water was added, and then the reaction was further performed for 1 hour. Was. After adjusting the internal temperature to 75 ° C., 0.3 g of 2,2′-azobis- (2-methylpropionamide) dihydrochloride was added to 10 g of water.
Was added, and the reaction was further performed for 1 hour. After adjusting the internal temperature to 80 ° C, a solution prepared by dissolving 0.6 g of 2,2'-azobis- (2-methylpropionamide) dihydrochloride in 10 g of water was added, and then the reaction was further performed for 2 hours, and the pigment was included. A colored fine particle emulsion a having a particle size of 10.0 μm was obtained.

Example 2 The carbon black used in Example 1 was replaced with Statutory Dye Red 404
A colored fine particle emulsion b was obtained under the same conditions as in Example 1 except that the amount was changed to 3.6 g (manufactured by Kishi Kasei).

Comparative Example 1 Lauryl methacrylate 42.9 g in a 500 ml glass beaker
1.0 g of 2,2'-azobis- (2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries) was added and dissolved, and Emulgen 2025G (Kao Corporation)
(Nonionic surfactant) 41.8 g of a 20% aqueous solution, an aqueous solution of chitosan / acrylic acid / methacrylic acid prepared in the same manner as in Example 1 were added, and the mixture was stirred with an ultrasonic homogenizer.
The mixture was treated for 5 minutes to obtain an emulsion having an average particle size of 0.14 μm. 13.9g of carbon black (# 45L), 8.4g of Emulgen 2025G
Was dispersed in 66.88 g of ion-exchanged water, treated with an ultrasonic homogenizer for 1 minute while stirring, and mixed with monomer droplets.

This emulsion was transferred to a 500 ml glass reactor equipped with a stirrer, a cooler, and a nitrogen inlet tube, and polymerized in the same manner as described in Example 1 to obtain a particle size containing pigment.
A 2.0 μm colored fine particle emulsion c was obtained.

Comparative Example 2 In place of the carbon black dispersion used in Comparative Example 1, 7.0 g of Statutory Dye Red No. 404 (manufactured by Kishi Kasei), Emulgen 2
Colored fine particle emulsion d was obtained under the same conditions as in Comparative Example 1, except that a pigment dispersion in which 8.4 g of 025G was dispersed in 74.6 g of ion-exchanged water was used.

Example 3 A hair rinse having the composition shown in Table 1 was produced by a conventional method, and the hair coloring performance and the color transfer to a cloth were evaluated by the following methods.
Table 1 shows the results.

<Evaluation method>-Hair coloring performance A hair bundle of 1 g of goat hair is shampooed and each hair rinse agent is 0.2 g.
Was spread evenly with a finger and immediately rinsed thoroughly with warm water and dried. After repeating this operation three times, the degree of coloring was measured with a color difference meter CR-300 manufactured by Minolta Co., Ltd., and the color difference (ΔE) from the color of the original goat hair was determined. The larger the value of ΔE, the higher the coloring effect.

Color transfer Goat hair colored in the evaluation of hair coloring performance is wound horizontally around a drum having a diameter of 10 cm in the direction of rotation, and rotated at 10 revolutions per minute. A cotton cloth of 10 cm × 10 cm is fixed on a flat plate, and applied to the previous drum, and fixed until the drum rotates 5 times while adjusting so that a force of 10 N is applied. Find the color difference between the darkest part of the cotton cloth and the cotton cloth before evaluation. The larger the value of ΔE, the higher the color transfer.

[0053]

[Table 1].

As is clear from the results shown in Table 1, the product of the present invention had good hair coloring performance and improved color transfer.

Continued on front page F term (reference) 4C083 AB131 AB241 AC072 AC122 AC172 AC302 AC352 AC692 AC791 AC851 AC861 AC931 AD011 AD012 AD282 AD321 AD322 BB24 4J011 KA15 KB29 PA53 PC02 4J026 AA04 BA05 BA07 BA20 BA25 BA27 DB30 BA04 BA04 FA07 GA01

Claims (6)

[Claims] A core and a shell, wherein a colorant is dissolved or dispersed in a hydrophobic monomer, and then emulsified and dispersed in water in the presence of chitosan and a hydrophilic monomer to carry out a polymerization reaction. A method for producing polymer particles having the formula: 2. The method according to claim 1, comprising the following steps 1 to 3. Step 1: a step of adding a coloring material and an oil-soluble polymerization initiator to a hydrophobic monomer and dissolving or dispersing the same. Step 2: a step of dissolving or dispersing the hydrophilic monomer and chitosan in water. Step 3: The solution or dispersion prepared in Step 1 is added to the aqueous solution or water dispersion prepared in Step 2, and after emulsification and dispersion, a hydrophobic monomer is polymerized to form a core portion. A step of forming a shell portion by polymerizing a hydrophilic monomer in the presence of a water-soluble polymerization initiator. 3. The method according to claim 1, wherein the hydrophilic monomer is an organic acid having a reactive unsaturated group or a salt thereof. 4. The coloring material is carbon black, red 202
The method according to any one of claims 1 to 3, which is at least one selected from the group consisting of No. 226, Red No. 226, Red No. 404, Blue No. 201, Blue No. 404, Yellow No. 401 and titanium oxide. 5. A polymer particle obtained by the method according to claim 1. 6. A hair cosmetic containing the polymer particles according to claim 5.