JP2022161634A - Solid surface hydrophilizing method - Google Patents

Abstract

To provide a solid surface hydrophilizing method having a high hydrophilizing effect.SOLUTION: A solid surface hydrophilizing method includes a step 1 of bringing an aqueous medium into contact with a solid surface to which a surface treatment composition is applied, wherein the surface treatment composition comprises the following components (A) to (C): (A) a betaine polymer containing at least a constitutional unit (a1) having a betaine group and a constitutional unit (a2) having an ionic group; (B) a polymer containing at least a constitutional unit (b1) having an ionic group of an opposite charge to the charge of the ionic group of the constitutional unit (a2); and (C) an electrolyte, and in the surface treatment composition, the equivalents of the betaine group of the constitutional unit (a1), the ionic group of the constitutional unit (a2), and the ionic group of the constitutional unit (b1) satisfy the following condition 1. Condition 1: {[equivalent of betaine group of constitutional unit (a1)]+[equivalent of ionic group of constitutional unit (a2)]}/[equivalent of ionic group of constitutional unit (b1)]>0.10.SELECTED DRAWING: None

Description

The present invention relates to a solid surface hydrophilization method.

Conventionally, methods for controlling the wettability of a solid surface, such as hydrophilization and water repellency, are known as solid surface treatment methods. Above all, the hydrophilization treatment of the solid surface reduces the contact angle of the solid surface with water and makes the solid surface more wettable with water. In addition to the effect of making it easier to remove when washing and the effect of preventing re-adhesion of dirt, it is also expected to prevent fogging and static electricity on glass and mirrors, prevent frost formation on the aluminum fins of heat exchangers, and prevent the surfaces of bathtubs and toilets from forming. Since it can be expected to have effects such as imparting staining properties, it has been used in various industrial fields, and studies have been made on solid surface treatment and methods.

For example, in Patent Document 1, for the purpose of providing a hydrophilization treatment composition containing a hydrophilization treatment agent that exerts excellent hydrophilization ability for a long period of time, a structural unit containing a betaine group and a structural unit having an aromatic group are combined. A hydrophilizing agent composition containing a copolymer containing the above, an anionic surfactant and water, and a hydrophilizing method of applying the hydrophilizing agent composition to a solid surface are disclosed.

JP 2019-94434 A

However, although the technique of Patent Document 1 can impart hydrophilicity to various solid surfaces, the hydrophilization effect is still insufficient, and further improvement in the hydrophilization effect of the surface treatment composition is desired. .
An object of the present invention is to provide a solid surface hydrophilization method having a high hydrophilization effect.

The present inventors have found that the surface treatment composition comprises a step of contacting an aqueous medium with a solid surface to which a surface treatment composition has been applied, wherein the surface treatment composition comprises a structural unit having a betaine group and a structural unit having an ionic group. A first polymer containing at least, a second polymer containing at least a structural unit having an ionic group opposite in charge to the charge of the ionic group of the structural unit having the ionic group, and an electrolyte, containing the betaine group The equivalent of the betaine group of the structural unit having, the ionic group of the structural unit having the ionic group of the first polymer, and the ionic group of the structural unit having the ionic group of the second polymer satisfies a predetermined condition The inventors have found that the above problems can be solved by doing so.

That is, the present invention is a solid surface hydrophilization method comprising a step 1 of bringing an aqueous medium into contact with a solid surface to which a surface treatment composition has been applied,
The surface treatment composition contains the following components (A) to (C):
(A) a betaine polymer containing at least a structural unit (a1) having a betaine group and a structural unit (a2) having an ionic group; (B) an ion opposite to the charge of the ionic group of the structural unit (a2); polymer containing at least a structural unit (b1) having a functional group (C) an electrolyte,
A solid surface in which the equivalents of the betaine group of the structural unit (a1), the ionic group of the structural unit (a2), and the ionic group of the structural unit (b1) in the surface treatment composition satisfy the following condition 1: A hydrophilization method is provided.
Condition 1: {[equivalent of betaine group in structural unit (a1)]+[equivalent of ionic group in structural unit (a2)]}/[equivalent of ionic group in structural unit (b1)]>0.10

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a solid surface hydrophilization method having a high hydrophilization effect.

FIG. 4 is an explanatory diagram of a method of calculating a shrink coefficient in measuring a shrink rate;

[Solid Surface Hydrophilization Method]
The solid surface hydrophilization method of the present invention (hereinafter also referred to as "hydrophilization method") includes a step 1 of bringing an aqueous medium into contact with the solid surface to which the surface treatment composition has been applied,
The surface treatment composition contains the following components (A) to (C):
(A) a betaine polymer containing at least a structural unit (a1) having a betaine group and a structural unit (a2) having an ionic group; (B) an ion opposite to the charge of the ionic group of the structural unit (a2); polymer containing at least a structural unit (b1) having a functional group (C) an electrolyte,
The equivalents of the betaine group of the structural unit (a1), the ionic group of the structural unit (a2), and the ionic group of the structural unit (b1) in the surface treatment composition satisfy Condition 1 below.
Condition 1: {[equivalent of betaine group in structural unit (a1)]+[equivalent of ionic group in structural unit (a2)]}/[equivalent of ionic group in structural unit (b1)]>0.10

According to the present invention, a high hydrophilization effect can be exhibited. Although the reason why such an effect is produced is not clear, it is considered as follows.
Component (A) is a betaine polymer containing at least a structural unit having a betaine group and a structural unit having an ionic group, and component (B) is a structure having the ionic group contained in component (A). A polymer containing a structural unit having an ionicity opposite to the charge of the ionic group of the unit, the betaine group of the structural unit having the betaine group, and the ionic group of the structural unit having the ionic group of component (A) , and the equivalent weight of the ionic groups of the constituent units having ionic groups of the component (B) satisfy the predetermined conditions. Therefore, by bringing an aqueous medium into contact with the solid surface to which the surface treatment composition has been applied, the concentration of the component (C) on the solid surface decreases, and the ionic groups of the component (A) and the ions of the component (B) Polyion complexes are formed by the action of the functional groups, and it is believed that the polyion complexes can be effectively adsorbed onto the solid surface. It is believed that the hydrophilic betaine group of component (A) can improve the hydrophilic effect on the solid surface.

Step 1 is the step of contacting the solid surface to which the surface treatment composition has been applied with an aqueous medium.

<Solid surface>
In the present invention, "solid surface" means the interface between a solid and the atmosphere.
The solids are not particularly limited, and include glass, earthenware, porcelain, enamel, tiles, ceramics, wood; metals such as aluminum, stainless steel, and brass; polycarbonate, polyethylene, polypropylene, melamine resin, polyamide resin, ABS resin, FRP, and the like. synthetic resins; natural fibers such as cotton, silk and wool; synthetic fibers such as polyester, nylon and rayon; hair, nails and teeth. The shape of the solid surface is not particularly limited.
Among these, said solid surface is preferably a hydrophobic hard surface or a hair surface.

In the present invention, a "hydrophobic hard surface" means a contact angle of 70° or more, and a "hydrophilic hard surface" means a contact angle of less than 70°. The contact angle can be measured by the method described in Examples.
The hydrophobic hard surface preferably includes one or more selected from ceramics, metals, and synthetic resins.

Moreover, when the solid surface is the surface of hair, the surface of hair can be imparted with high hydrophilicity.
In the field of hair cosmetics, hair shrinkage in the length direction accompanying drying of the hair sometimes poses a problem of difficulty in handling the hair, such as difficulty in combing the hair.
Especially when the hair is wet immediately after washing, even if the desired hairstyle is maintained, shrinkage in the length direction of the hair occurs as the hair dries, resulting in the ideal length and volume of the hair. Sometimes it doesn't work.
According to the studies of the present inventors, when the hair is wet, water existing between the hairs generates a meniscus force that attracts the hairs, and this meniscus force suppresses shrinkage. It was found that shrinkage occurs when the meniscus force between the layers becomes smaller. The meniscus force between hairs can be increased by lowering the contact angle of the hair surface to water to render the hair surface hydrophilic. In order to impart hydrophilicity to the hair surface, while the hair surface has a structure in which highly hydrophobic cuticle pieces are laminated, the vicinity of the edge of the cuticle pieces is hydrophilic, so the hair surface has a hydrophobic site. and hydrophilic sites are mixed, and it is required to make both of these sites hydrophilic.
In the present invention, when the solid surface is hair, the polyion complex effectively adsorbs to the surface of the hair as described above, and the hydrophilic betaine group of component (A) imparts high hydrophilicity to the surface of the hair. As a result, the meniscus force between the hairs is increased, and it is thought that the effect of suppressing the shrinkage of the hairs can be exhibited. From this point of view, the hydrophilic method of the present invention is preferably a hair treatment method in which the solid surface is a hair surface.

<Surface treatment composition>
The surface treatment composition according to the present invention contains the components (A) to (C).
The surface treatment composition satisfies the following condition 1, preferably further satisfies the following condition 2 or condition 3, and more preferably satisfies the following condition from the viewpoint of enhancing the hydrophilization effect and enhancing the effect of suppressing shrinkage of hair. All conditions 1 to 3 are satisfied.
In the present invention, the equivalents of the betaine group of the structural unit (a1), the ionic group of the structural unit (a2), and the ionic group of the structural unit (b1) in the surface treatment composition are the component (A ), the content of the structural unit (b1) in all the structural units of the component (B), and the components in the surface treatment composition It can be calculated from the contents or blending amounts of (A) and component (B).

[Condition 1]
The equivalents of the betaine group of the structural unit (a1), the ionic group of the structural unit (a2), and the ionic group of the structural unit (b1) in the surface treatment composition satisfy Condition 1 below.
Condition 1: {[equivalent of betaine group in structural unit (a1)]+[equivalent of ionic group in structural unit (a2)]}/[equivalent of ionic group in structural unit (b1)]>0.10

The value of {[equivalent of betaine group in structural unit (a1)] + [equivalent of ionic group in structural unit (a2)]}/[equivalent of ionic group in structural unit (b1)] satisfies Condition 1. By the action of the ionic group of component (A) and the ionic group of component (B), a polyion complex is formed, and the polyion complex can be effectively adsorbed on the solid surface, and the hydrophilicity of component (A) The betaine group can impart high hydrophilicity to the solid surface. From this viewpoint, {[equivalent of betaine group in structural unit (a1)] + [equivalent of ionic group in structural unit (a2)]}/[equivalent of ionic group in structural unit (b1)] in Condition 1 The value is preferably 0.5 or more, more preferably 1 or more, still more preferably 1.5 or more, and preferably 1000 or less, more preferably 500 or less, even more preferably 100 or less, even more preferably 70 Below, more preferably 50 or less, still more preferably 30 or less.

[Condition 2]
The equivalent amount of the betaine group of the structural unit (a1) and the ionic group of the structural unit (a2) in the surface treatment composition is preferably Furthermore, the following condition 2 is satisfied.
Condition 2: [equivalent of betaine group in structural unit (a1)]/[equivalent of ionic group in structural unit (a2)]>1

When the value of [equivalent of betaine group of structural unit (a1)]/[equivalent of ionic group of structural unit (a2)] satisfies condition 2, the amount of hydrophilic betaine group of component (A) is sufficient. As a result, the effect of imparting hydrophilicity to the solid surface by the betaine group can be improved. From this point of view, the value of [equivalent of betaine group in structural unit (a1)]/[equivalent of ionic group in structural unit (a2)] in Condition 2 is preferably 3 or more, more preferably 5 or more, and still more preferably is 7 or more, more preferably 9 or more, still more preferably 10 or more, still more preferably 15 or more, and preferably 50 or less, more preferably 40 or less, even more preferably 30 or less, and even more preferably 20 or less.

[Condition 3]
The equivalent amount of the ionic group of the structural unit (a2) and the ionic group of the structural unit (b1) in the surface treatment composition according to the present invention is from the viewpoint of enhancing the hydrophilization effect and from the viewpoint of enhancing the effect of suppressing shrinkage of hair. Therefore, the following condition 3 is preferably further satisfied.
Condition 3: The value of [equivalent of ionic group of structural unit (a2)]/[equivalent of ionic group of structural unit (b1)] is 0.01 or more and 50 or less.

When the value of [equivalent of ionic group of structural unit (a2)]/[equivalent of ionic group of structural unit (b1)] satisfies condition 3, the ionic group of component (A) and the ionic group of component (B) A polyion complex is well formed by the action of the ionic group of (A), and the polyion complex can be effectively adsorbed on the solid surface, and the hydrophilic betaine group of component (A) imparts hydrophilicity to the solid surface. You can improve the effect. From this viewpoint, it is preferably 0.05 or more, more preferably 0.1 or more, still more preferably 0.3 or more, still more preferably 0.5 or more, even more preferably 0.7 or more, and still more preferably 0 .9 or more, and preferably 40 or less, more preferably 30 or less, even more preferably 10 or less, even more preferably 7 or less, even more preferably 5 or less, even more preferably 3 or less, and even more preferably 2 or less, more preferably 1.5 or less, even more preferably 1.3 or less, and even more preferably 1.1 or less.

[Component (A)]
Component (A) is a betaine containing at least a structural unit (a1) having a betaine group and a structural unit (a2) having an ionic group, from the viewpoint of enhancing the hydrophilization effect and the effect of suppressing shrinkage of hair. A structural unit (a1) which is a polymer and preferably has a betaine group, and a structural unit (a2-I) having a cationic group as a structural unit (a2) having an ionic group (hereinafter referred to as "structural unit (a2-I )”) and at least a cationic betaine polymer AI (hereinafter also referred to as “cationic betaine polymer AI”), or a structural unit (a1) having a betaine group and a structural unit having an ionic group ( an anionic betaine polymer AII (hereinafter, "anionic betaine polymer AII") containing at least a structural unit (a2-II) having an anionic group as a2) (hereinafter also referred to as "structural unit (a2-II)"); Also called).
In the present invention, an "anionic polymer" is a polymer having an anionic group and exhibiting anionic properties as a whole.
In the present invention, the "cationic polymer" is a polymer having a cationic group and exhibiting cationic properties as a whole.

[Structural unit (a1)]
The component (A) contains a structural unit (a1) having a betaine group from the viewpoint of enhancing the hydrophilization effect and enhancing the shrink-suppressing effect of hair.
In the present invention, the term "betaine group" means a functional group having a cationic site and an anionic site and having no charge as a whole.
The cationic site of the betaine group is a positively charged atomic group, preferably a cationic group.
In the present invention, the term "cationic group" refers to a cationic group or a group that can be ionized to become a cationic group. Cationic groups include primary amino groups, secondary amino groups, tertiary amino groups, and quaternary ammonium groups. Among these, the cationic site of the betaine group is preferably a quaternary ammonium group from the viewpoint of enhancing the hydrophilization effect and enhancing the effect of suppressing shrinkage of hair.
The anionic site of the betaine group is a negatively charged atomic group, preferably an anionic group.
In the present invention, an "anionic group" refers to an anionic group or a group that can be ionized to become an anionic group.
Examples of the anionic group include a carboxy group (--COOM), a sulfonic acid group (--SO ₃ M) and a phosphoric acid group (--OPO ₃ M ₂ ). In the chemical formula, M represents a hydrogen atom, alkali metal, ammonium or organic ammonium.

The betaine group of the structural unit (a1) is preferably a sulfobetaine group, a phosphobetaine group, or a carbobetaine group, more preferably sulfobetaine, from the viewpoint of enhancing the hydrophilization effect and enhancing the effect of suppressing shrinkage of hair. or phosphobetaine groups, more preferably sulfobetaine groups, the cationic sites of these betaine groups being preferably quaternary ammonium groups.
One type of betaine group may be used, or two or more types may be used.

The structural unit (a1) is preferably a structural unit represented by the following formula (1) from the viewpoint of enhancing the hydrophilization effect and enhancing the effect of suppressing shrinkage of hair.

〔式（１）中、
Ｒ¹～Ｒ³は、同一又は異なって、水素原子、又は炭素数１もしくは２のアルキル基を示し、
Ｒ⁴は、炭素数１以上４以下のアルキレン基、又は－Ｙ¹－ＯＰＯ₃ ^-－Ｙ²－を示し、Ｙ¹及びＹ²は、同一又は異なって、炭素数１以上４以下のアルキレン基を示し、
Ｒ⁵及びＲ⁶は、同一又は異なって、炭素数１以上４以下の炭化水素基を示し、
Ｘ¹は、酸素原子又はＮＲ⁷基を示し、Ｒ⁷は、水素原子又は炭素数１以上４以下の炭化水素基を示し、
Ｘ²は、Ｒ⁴が炭素数１以上４以下のアルキレン基のとき、Ｒ¹⁷ＳＯ₃ ^-、又はＲ¹⁷ＣＯＯ^-を示し、Ｒ¹⁷は水酸基を有してもよい炭素数１以上４以下のアルキレン基を示し、Ｘ²は、Ｒ⁴が－Ｙ¹－ＯＰＯ₃ ^-－Ｙ²－のとき、水素原子、又は炭素数１以上４以下の炭化水素基を示す。〕

[In formula (1),
R ¹ to R ³ are the same or different and represent a hydrogen atom or an alkyl group having 1 or 2 carbon atoms,
R ⁴ represents an alkylene group having 1 to 4 carbon atoms, or -Y ¹ -OPO ₃ ^- -Y ² -, and Y ¹ and Y ² are the same or different and are alkylene groups having 1 to 4 carbon atoms. shows
R ⁵ and R ⁶ are the same or different and represent a hydrocarbon group having 1 to 4 carbon atoms,
X ¹ represents an oxygen atom or an NR ⁷ group, R ⁷ represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms,
X ² represents R ¹⁷ SO ₃ ^- or R ¹⁷ COO ^- when R ⁴ is an alkylene group having 1 to 4 carbon atoms, and R ¹⁷ may have 1 to 4 carbon atoms and may have a hydroxyl group. represents an alkylene group, and X ² represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms when R ⁴ is -Y ¹ -OPO ₃ ^- -Y ² -. ]

Structural unit (a1) is preferably a structural unit having a sulfobetaine group, a phosphobetaine group, or a carbobetaine group.
The structural unit (a1) may be one type, or two or more different types of structural units.
The structural unit (a1) is, for example, a structural unit derived from a monomer (a1') represented by the following formula (1').

〔式（１’）中、Ｒ¹～Ｒ⁶、Ｘ¹、Ｘ²は前記と同じである。〕

[In formula (1′), R ¹ to R ⁶ , X ¹ and X ² are the same as above. ]

Specific examples or preferred embodiments of R ¹ to R ⁶ , X ¹ and X ² in the formulas (1) and (1′) are as follows from the viewpoint of enhancing the hydrophilization effect and enhancing the effect of suppressing shrinkage of hair. That's right.
R ¹ and R ² are preferably hydrogen atoms.
R ³ is preferably a hydrogen atom or a methyl group, more preferably a methyl group.
X ¹ is preferably an oxygen atom.
R ⁴ is preferably an alkylene group having 1 to 4 carbon atoms, more preferably an alkylene group having 2 or 3 carbon atoms, and still more preferably an alkylene group having 2 carbon atoms.
R ⁵ and R ⁶ are preferably methyl or ethyl groups, more preferably methyl groups.
X ² represents R ¹⁷ SO ₃ ^- or R ¹⁷ COO ^- , preferably R ¹⁷ SO ₃ ^- when R ⁴ is an alkylene group having 1 to 4 carbon atoms. R ¹⁷ represents an alkylene group having 1 to 4 carbon atoms which may have a hydroxyl group, preferably an alkylene group having 1 to 3 carbon atoms or a hydroxyalkylene group having 2 to 4 carbon atoms, more preferably It is an alkylene group having 1 to 3 carbon atoms, more preferably an alkylene group having 2 or 3 carbon atoms, and even more preferably an alkylene group having 3 carbon atoms.
X ² is a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms, preferably a hydrocarbon group having 1 to 4 carbon atoms when R ⁴ is -Y ¹ -OPO ₃ ^- -Y ² - and more preferably a methyl group.

Structural unit (a1) is preferably N-(3-sulfopropyl)-N-(meth)acryloyloxyethyl-N,N-dimethylammonium betaine, N-(3-sulfopropyl)-N-(meth) Monomers having a sulfobetaine group such as acryloylamidopropyl-N,N-dimethylammonium betaine; monomers having a phosphobetaine group such as 2-methacryloyloxyethylphosphorylcholine; N-carboxymethyl-N-(meth)acryloyloxyethyl-N , N-dimethylammonium betaine, N-carboxymethyl-N-(meth)acryloylamidopropyl-N,N-dimethylammonium betaine, a structural unit derived from at least one selected from monomers having a carbobetaine group, and more It is preferably a structural unit derived from at least one selected from a monomer having a sulfobetaine group and a monomer having a phosphobetaine group, more preferably a structural unit derived from a monomer having a sulfobetaine group, still more preferably N- (3-Sulfopropyl)-N-(meth)acryloyloxyethyl-N,N-dimethylammonium betaine and N-(3-sulfopropyl)-N-(meth)acryloylamidopropyl-N,N-dimethylammonium betaine is a structural unit derived from at least one selected from, and more preferably a structural unit derived from N-(3-sulfopropyl)-N-(meth)acryloyloxyethyl-N,N-dimethylammonium betaine.

The content of the structural unit (a1) in all the structural units of the component (A) is preferably 50 mol% or more, more preferably 55 mol% or more, from the viewpoint of enhancing the hydrophilization effect and the viewpoint of enhancing the hair shrinkage suppressing effect. , more preferably 60 mol% or more, still more preferably 70 mol% or more, still more preferably 85 mol% or more, still more preferably 90 mol% or more, still more preferably 93 mol% or more, and preferably 99 mol% or less, It is more preferably 98 mol % or less, still more preferably 97 mol % or less.
The content of each structural unit in all the structural units of component (A) can be measured by analysis such as NMR. Alternatively, it can be calculated from the charge ratio of each monomer when the component (A) is produced.

[Structural unit (a2)]
The structural unit (a2) is preferably a structural unit (a2-I) having a cationic group or a structural unit (a2-II) having an anionic group. The cationic group and anionic group are as described above.

〔式（２）中、
Ｒ⁸～Ｒ¹⁰は、同一又は異なって、水素原子又は炭素数１もしくは２のアルキル基を示し、
Ｘ³は、酸素原子又はＮＲ¹⁸基を示し、Ｒ¹⁸は、水素原子又は炭素数１以上４以下の炭化水素基を示し、
Ｒ¹¹は、炭素数１以上４以下のアルキレン基を示し、
Ｘ⁴は、Ｎ⁺Ｒ¹²Ｒ¹³Ｒ¹⁴Ｘ⁵又はＮＲ¹⁵Ｒ¹⁶を示し、Ｒ¹²～Ｒ¹⁶は、同一又は異なって、水素原子又は炭素数１以上４以下の炭化水素基を示し、Ｘ⁵は陰イオンを示す。〕 (Structural unit (a2-I))
When the component (A) is a cationic betaine polymer AI containing a structural unit (a2-I) having a cationic group, the structural unit (a2-I) is preferably a cationic group-containing polymerizable unsaturated monomer It is a structural unit derived from the above, and more preferably a structural unit having a cationic group represented by the following formula (2).
The structural unit (a2-I) may be one type, or two or more different types of structural units.

[In formula (2),
R ⁸ to R ¹⁰ are the same or different and represent a hydrogen atom or an alkyl group having 1 or 2 carbon atoms,
X ³ represents an oxygen atom or an NR ¹⁸ group, R ¹⁸ represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms,
R ¹¹ represents an alkylene group having 1 to 4 carbon atoms,
X ⁴ represents N ⁺ R ¹² R ¹³ R ¹⁴ X ⁵ or NR ¹⁵ R ¹⁶ , R ¹² to R ¹⁶ are the same or different and represent a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms, X ⁵ denotes an anion. ]

The structural unit (a2-I) is, for example, a structural unit derived from a monomer (a2-I') represented by the following formula (2').

〔式（２’）中、Ｒ⁸～Ｒ¹¹、Ｘ³、Ｘ⁴は前記と同じである。〕

[In formula (2′), R ⁸ to R ¹¹ , X ³ and X ⁴ are the same as above. ]

Specific examples or preferred embodiments of R ⁸ to R ¹¹ , X ³ and X ⁴ in the formulas (2) and (2′) are from the viewpoint of efficiently forming a polyion complex to enhance the hydrophilization effect and hair shrinkage. From the viewpoint of enhancing the suppression effect, it is as follows.
R ⁸ and R ⁹ are preferably hydrogen atoms.
R ¹⁰ is preferably a hydrogen atom or a methyl group, more preferably a methyl group.
^X3 is preferably an oxygen atom.
R ¹¹ is preferably an alkylene group having 2 or 3 carbon atoms, more preferably an alkylene group having 2 carbon atoms.
X ⁴ is preferably N ⁺ R ¹² R ¹³ R ¹⁴ X ⁵ , and R ¹² , R ¹³ and R ¹⁴ are each preferably a methyl group or an ethyl group from the same viewpoint as above, more preferably R ¹² , R ¹³ , and R ¹⁴ is an ethyl group.
R ¹⁵ and R ¹⁶ are preferably a methyl group or an ethyl group, more preferably a methyl group, from the viewpoint of enhancing the hydrophilicity effect and facilitating the quaternization reaction.
^X5 is preferably a _{halogen ion} ^or _C2H5SO4- ^, _{more preferably C2H5SO4-} .

Structural unit (a2-I) is preferably a structural unit derived from N,N-(dialkylamino)alkyl(meth)acrylic acid or its quaternary product, more preferably 2-(dialkyl(meth)acrylate Structural unit derived from quaternized amino)alkyl, more preferably quaternized 2-(dimethylamino)ethyl (meth)acrylate, quaternized 2-(diethylamino)ethyl (meth)acrylate , and a structural unit derived from at least one selected from quaternized products of 3-(dimethylamino)propyl (meth)acrylate, more preferably diethyl sulfate of 2-(dimethylamino)ethyl (meth)acrylate It is a structural unit derived from salt.
As used herein, "(meth)acrylic acid" means acrylic acid or methacrylic acid.

When the component (A) is the cationic betaine polymer AI, the component (A) may contain other structural units other than the structural unit (a1) and the structural unit (a2-I) within a range that does not impair the effects of the present invention. may contain. Other structural units include nonionic monomers such as (meth)acrylic acid esters, alkyl (meth)acrylamides, vinylpyrrolidone, and styrenic monomers; structural units derived from other monomers such as anionic-containing polymerizable unsaturated monomers. are mentioned.
As used herein, "(meth)acrylamide" means acrylamide or methacrylamide.

(Meth) acrylic esters include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, (meth) ) sec-butyl acrylate, t-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-(meth)acrylate Decyl, lauryl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, behenyl (meth) acrylate, etc. (meth) having a linear or branched alkyl group ) acrylic acid ester; (meth) acrylic acid ester having an alicyclic alkyl group such as cyclohexyl (meth) acrylate; aromatic group-containing (meth) acrylic acid ester such as benzyl (meth) acrylate, etc. 1 carbon number (Meth) acrylic acid ester having a hydrocarbon group of 30 or less; Polyalkylene glycol (meth) acrylic acid ester such as polyethylene glycol (meth) acrylic acid ester (the average number of added moles of alkylene oxide is preferably 2 or more and 30 or less ); Methoxy polyethylene glycol (meth) acrylate, methoxy polypropylene glycol (meth) acrylate, alkoxypolyalkylene glycol (meth) acrylic acid ester (alkylene oxide is preferably 2 or more and 30 or less.); Phenoxypolyalkylene glycol such as phenoxyethylene glycol (meth)acrylate, phenoxy (polyethylene glycol/polypropylene glycol copolymer) (meth)acrylate (meth)acrylic acid Esters (the average number of added moles of alkylene oxide is preferably 2 or more and 30 or less), and the like.
As used herein, "(meth)acrylate" means acrylate or methacrylate.

Alkyl (meth)acrylamides include N-ethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, Nt-butyl (meth)acrylamide, N,N-dimethylacrylamide, N,N-diethyl (meth)acrylamide N-alkyl (meth)acrylamides having an alkyl group having 1 to 22 carbon atoms such as
Styrenic monomers include styrene, α-methylstyrene, 2-methylstyrene and the like.
Examples of the anionic group-containing polymerizable unsaturated monomers include carboxy group-containing polymerizable unsaturated monomers, sulfonic acid group-containing polymerizable unsaturated monomers, and phosphoric acid group-containing polymerizable unsaturated monomers exemplified for the structural unit (a2-II). etc.

(Structural unit (a2-II))
When the component (A) is an anionic betaine polymer AII containing a structural unit (a2-II) having an anionic group, the structural unit (a2-II) is preferably an anionic group-containing polymerizable unsaturated monomer. It is a structural unit of origin.
Examples of the anionic group-containing polymerizable unsaturated monomers include carboxy group-containing polymerizable unsaturated monomers, sulfonic acid group-containing polymerizable unsaturated monomers, and phosphoric acid group-containing polymerizable unsaturated monomers.
The structural unit (a2-II) may be one type, or two or more different types of structural units.

Carboxy group-containing polymerizable unsaturated monomers include (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, 2-methacryloyloxymethylsuccinic acid and the like.
Sulfonic acid group-containing polymerizable unsaturated monomers include styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 3-sulfopropyl (meth)acrylate and the like.
Phosphate group-containing polymerizable unsaturated monomers include vinyl phosphonic acid, vinyl phosphate, bis(methacryloyloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate and the like.

Among these, the structural unit (a2-II) is preferably a carboxy group-containing polymerizable unsaturated polymer from the viewpoint of efficiently forming a polyion complex to enhance the hydrophilization effect and the shrinkage-suppressing effect of hair. A structural unit derived from at least one selected from a monomer, a sulfonic acid group-containing polymerizable unsaturated monomer, and a phosphoric acid group-containing polymerizable unsaturated monomer, more preferably a carboxy group-containing polymerizable unsaturated monomer and a sulfonic acid group A structural unit derived from at least one polymerizable unsaturated monomer containing, more preferably a structural unit derived from a carboxy group-containing polymerizable unsaturated monomer, still more preferably (meth)acrylic acid, crotonic acid, It is a structural unit derived from at least one selected from itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethylsuccinic acid, and more preferably a structural unit derived from (meth)acrylic acid.

When the component (A) is an anionic betaine polymer AII, the component (A) may contain other structural units other than the structural unit (a1) and the structural unit (a2-II) within a range that does not impair the effects of the present invention. may contain. Other structural units include nonionic monomers such as the aforementioned (meth)acrylic acid esters, alkyl (meth)acrylamides, vinylpyrrolidone, and styrenic monomers; cationic group-containing polymerizable unsaturated monomers and other monomers derived from A structural unit of
Examples of cationic group-containing polymerizable unsaturated monomers include monomers represented by formula (2′) exemplified by the structural unit (a2-I) described above.

The content of the structural unit (a2) in all the structural units of the component (A) is determined from the viewpoint of efficiently forming a polyion complex to enhance the hydrophilization effect and the effect of suppressing shrinkage of hair, and the surface treatment composition. From the viewpoint of compounding stability and adsorptivity of substances, it is preferably 1 mol% or more, more preferably 2 mol% or more, still more preferably 3 mol% or more, and preferably 50 mol% or less, more preferably 45 mol% or less, and further. It is preferably 40 mol % or less, still more preferably 30 mol % or less, still more preferably 15 mol % or less, still more preferably 10 mol % or less, still more preferably 7 mol % or less.

The content of structural units other than structural unit (a1) and structural unit (a2) in all structural units of component (A) is preferably 30 mol% or less, more preferably 20 mol% or less, still more preferably 10 mol%. Below, it is more preferably 5 mol % or less, still more preferably 3 mol % or less, still more preferably 1 mol % or less, and the content of other structural units may be 0 mol %.
Component (A) contains, as structural units other than the structural units (a1) and (a2), aromatic group-containing (meth)acrylic acid esters, styrene-based monomers, and phenoxypolyalkylene glycol (meth)acrylic acid esters. However, the content of the structural unit derived from the aromatic group-containing monomer in all the structural units of the component (A) is determined from the viewpoint of the hydrophilization effect. Therefore, it is preferably 1 mol% or less, more preferably 0.5 mol% or less, still more preferably 0.1 mol% or less, still more preferably 0.05 mol% or less, and still more preferably component (A) is an aromatic It is preferred not to contain a structural unit derived from a group-containing monomer.

The total content of structural units (a1) and structural units (a2) in all structural units of component (A) is preferably 70 mol% or more, more preferably 80 mol% or more, still more preferably 90 mol% or more, and even more preferably is 95 mol% or more, more preferably 97 mol% or more, still more preferably 99 mol% or more, and the total content of structural units (a1) and structural units (a2) in all structural units of component (A) is It may be 100 mol %.

(Production of component (A))
The method for producing component (A) is not particularly limited, and examples thereof include the following methods (x1) and (y1).
(x1) A method of copolymerizing a raw material monomer containing the monomer (a1′) represented by the formula (1′) and the cationic group-containing polymerizable unsaturated monomer or the anionic group-containing polymerizable unsaturated monomer ( y1) After copolymerizing a raw material monomer containing a monomer represented by the following formula (1′-1) and the cationic group-containing polymerizable unsaturated monomer or the anionic group-containing polymerizable unsaturated monomer, a betaining agent Among these, the method (y1) is preferable from the viewpoint of the availability of the monomer and the ease of production.

〔式（１’－１）中、Ｒ¹～Ｒ⁶、Ｘ¹は式（１）と同じであり、好ましい態様も式（１）と同じである。〕

[In formula (1′-1), R ¹ to R ⁶ and X ¹ are the same as in formula (1), and preferred embodiments are also the same as in formula (1). ]

When the method (y1) is used, for example, when the structural unit (a1) is a structural unit derived from a monomer having a sulfobetaine group, a raw material containing a monomer represented by the formula (1'-1) After the monomer is polymerized, a compound represented by the following formula (1′-2) or a compound represented by the following formula (1′-3) can be reacted as a betaining agent to betainize. A compound represented by the following formula (1'-2) is preferred.

〔式（１’－２）中、ｎは１又は２であり、好ましくは１である。〕

[In the formula (1′-2), n is 1 or 2, preferably 1. ]

Z—R ¹⁷ —SO ₃ M (1′-3)
[In formula (1′-3), Z is Cl or Br, preferably Cl, R ¹⁷ is an alkylene group having 2 to 4 carbon atoms which may have a hydroxyl group, preferably a 2-hydroxypropylene group, M represents Na or K; ]

The weight-average molecular weight of component (A) is preferably 3,000 or more, more preferably 5,000 or more, and still more preferably 10,000 or more, from the viewpoint of enhancing the hydrophilization effect and the viewpoint of enhancing the effect of suppressing shrinkage of hair. And, from the viewpoint of blending stability and adsorptivity of the surface treatment composition, it is preferably 1,000,000 or less, more preferably 500,000 or less, even more preferably 300,000 or less, and even more preferably 200 , 000 or less. The weight average molecular weight of component (A) can be measured by the method described in Examples.

When component (A) is a cationic betaine polymer AI, the cationic charge density of component (A) is preferably 0.01 meq/g or more, more preferably 0.05 meq/g or more, and still more preferably 0.1 meq. /g or more, more preferably 0.15 meq/g or more, and preferably 1.0 meq/g or less, more preferably 0.8 meq/g or less, even more preferably 0.6 meq/g or less, and even more preferably 0.6 meq/g or less. It is preferably 0.4 meq/g or less, more preferably 0.2 meq/g or less.
In this case, the cationic charge density of component (A) is calculated from the number of mols of cationic groups in component (A)/g×1000 (cationic charge density; meq/g) to the mol of anionic groups in component (A). It refers to the value obtained by subtracting the number/g×1000 (anion charge density; meq/g).
The cationic charge density of component (A) can be calculated from the types and molar ratios of structural units constituting the polymer. The types and molar ratios of structural units constituting the polymer can be measured by analysis such as NMR.
When the component (A) is a cationic betaine polymer AI, the component (A) is a cationic polymer as a whole. may have an anionic group other than the anionic group contained in the betaine group.
Moreover, two or more kinds of polymers exhibiting cationic properties as a whole may be used for the component (A). The cationic charge density in this case can be obtained by calculating a weighted average from the cationic charge density and blending amount of each polymer.

When component (A) is the anionic betaine polymer AII, the anionic charge density of component (A) is preferably −5 meq/g or more, more preferably −3 meq/g or more, and still more preferably −2 meq/g or more. , more preferably −1 meq/g or more, still more preferably −0.5 meq/g or more, still more preferably −0.3 meq/g or more, and preferably −0.05 meq/g or less, more It is preferably -0.1 meq/g or less, more preferably -0.15 meq/g or less.
In this case, the anionic charge density of component (A) is calculated from the mol number of anionic groups in component (A)/g×1000 (anionic charge density; meq/g) to the mol of cationic groups in component (A). It refers to the value obtained by subtracting the number/g×1000 (cation charge density; meq/g).
The anionic charge density of component (A) can be calculated from the types and molar ratios of structural units constituting the polymer. The types and molar ratios of structural units constituting the polymer can be measured by analysis such as NMR.
When the component (A) is an anionic betaine polymer AII, the component (A) is an anionic polymer as a whole, and contains betaine groups in the polymer to the extent that the effect of the present invention is not impaired. It may have a cationic group other than the cationic group.
In addition, two or more kinds of polymers exhibiting anionic properties as a whole may be used for the component (A). The anion charge density in this case can be determined by calculating a weighted average from the anion charge density and blending amount of each polymer.

[Component (B)]
Component (B) is a polymer containing at least a structural unit (b1) having an ionic group having a charge opposite to that of the ionic group of structural unit (a2).

[Constituent unit (b1)]
(Structural unit (b1-I))
When the ionic group of the structural unit (a2) is a cationic group, the component (B) is a structural unit (b1-I) having an anionic group as the structural unit (b1) (hereinafter referred to as "structural unit (b1- I)”) is an anionic polymer BI (hereinafter also referred to as “anionic polymer BI”).
Here, the "anionic group" refers to an anionic group or a group that can be ionized to become an anionic group, as described above.
The anionic polymer BI is preferably one or more selected from synthetic polymers or naturally occurring polymers having anionic groups, and salts thereof.

Synthetic polymers having anionic groups include polymers having carboxy groups, polymers having sulfonic acid groups, and polymers having phosphoric acid groups.
Examples of polymers having carboxyl groups include poly(meth)acrylic acid, (meth)acrylic acid/maleic acid copolymer, (meth)acrylic acid/itaconic acid copolymer, and (meth)acrylic acid/fumaric acid copolymer. , (meth)acrylic acid/vinyl acetate copolymer, (meth)acrylic acid/2-hydroxyethyl methacrylate copolymer, maleic acid/diisobutylene copolymer, maleic acid/styrene copolymer, benzoic acid formaldehyde condensate , benzoic acid/phenol/formaldehyde condensates and salts thereof.
Polymers having a sulfonic acid group include polystyrene sulfonic acid, styrene sulfonic acid/styrene copolymer, 2-acrylamido-2-methylpropanesulfonic acid/(meth)acrylic acid copolymer, 2-acrylamido-2-methylpropane. Sulfonic acid/(meth)acrylic acid/acrylamide copolymer, naphthalenesulfonic acid-formaldehyde condensate, methylnaphthalenesulfonic acid-formaldehyde condensate, dimethylnaphthalenesulfonic acid-formaldehyde condensate, poly[2-hydroxyethyl (meth)acrylate sulfate] , 2-hydroxyethyl (meth)acrylate/2-hydroxyethyl (meth)acrylate sulfate ester copolymer, poly[2-hydroxyethyl (meth)acrylate] sulfate and salts thereof.
Polymers having a phosphoric acid group include poly[(meth)acryloyloxyethylphosphonic acid], (meth)acryloyloxyethylphosphonic acid/2-hydroxyethyl(meth)acrylate copolymer, naphthalenephosphonic acid formaldehyde condensate, poly [2-hydroxyethyl (meth) acrylate phosphate], 2-hydroxyethyl (meth) acrylate / 2-hydroxyethyl (meth) acrylate phosphate copolymer, poly [2-hydroxyethyl (meth) acrylate] Phosphoric acid esters and salts thereof and the like are included.

A vinyl-based polymer is preferable as the polymer backbone of the synthetic polymer.
The vinyl polymer preferably contains a structural unit derived from an anionic group-containing polymerizable unsaturated monomer.
Examples of the anionic group-containing polymerizable unsaturated monomers include the carboxy group-containing polymerizable unsaturated monomers, sulfonic acid group-containing polymerizable unsaturated monomers, and phosphoric acid group-containing polymerizable unsaturated monomers exemplified above. Among these, preferably a carboxy group-containing polymerizable unsaturated monomer, more preferably (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid and 2-methacryloyloxymethylsuccinic acid One or more selected, more preferably (meth)acrylic acid.

The vinyl-based polymer may be a copolymer containing structural units derived from monomers other than the anionic group-containing polymerizable unsaturated monomer, as long as the effects of the present invention are not impaired. Other monomers include (meth)acrylamide, 2-hydroxyethyl (meth)acrylate, etc., in addition to the (meth)acrylic acid esters, alkyl (meth)acrylamides, and aromatic group-containing monomers exemplified in component (A) above. hydroxyalkyl (meth)acrylate; vinyl acetate; N-vinyl-2-pyrrolidone and the like.
The aforementioned monomers can be used either alone or in combination of two or more.

The vinyl-based polymer is preferably a vinyl-based polymer having a carboxy group, and more preferably poly(meth)acrylic acid, (meth)acrylic acid/maleic acid copolymer, (meth)acrylic acid/itaconic acid copolymer. Polymer, (meth)acrylic acid/fumaric acid copolymer, (meth)acrylic acid/vinyl acetate copolymer, (meth)acrylic acid/2-hydroxyethyl methacrylate copolymer, maleic acid/diisobutylene copolymer , maleic acid/styrene copolymers, and salts thereof, and more preferably at least one selected from poly(meth)acrylic acid and poly(meth)acrylic acid salts.

A naturally occurring polymer having an anionic group is a polymer obtained from a natural product by operations such as extraction and purification, and a chemically modified polymer.
Examples of the naturally-derived polymer include cellulose derivatives such as carboxymethylcellulose, carboxymethylmethylcellulose, and carboxymethylethylcellulose, or salts thereof; hyaluronate; colominate; dextran sulfate; and salts of heparin derivatives.
Among these, at least one selected from cellulose derivatives and salts thereof is preferred, and carboxymethyl cellulose or salts thereof are more preferred.

As described above, when the component (B) is an anionic polymer BI, the component (B) is used from the viewpoint of enhancing the hydrophilization effect, from the viewpoint of the blending stability and adsorption properties of the surface treatment composition, and from the viewpoint of hair shrinkage. From the viewpoint of enhancing the inhibitory effect, it is preferably one or more selected from a polymer having a carboxy group, a polymer having a sulfonic acid group, and a polymer having a phosphoric acid group, more preferably a polymer having a carboxy group, and further It is preferably at least one selected from vinyl polymers having a carboxy group, cellulose derivatives, and salts thereof, and more preferably poly(meth)acrylic acid, (meth)acrylic acid/maleic acid copolymer, ( meth)acrylic acid/itaconic acid copolymer, (meth)acrylic acid/fumaric acid copolymer, (meth)acrylic acid/vinyl acetate copolymer, (meth)acrylic acid/2-hydroxyethyl methacrylate copolymer, At least one selected from maleic acid/diisobutylene copolymer, maleic acid/styrene copolymer, carboxymethylcellulose, carboxymethylmethylcellulose, carboxymethylethylcellulose, and salts thereof, more preferably poly(meth)acrylic It is at least one selected from acids, carboxymethylcellulose, and salts thereof, and more preferably at least one selected from poly(meth)acrylic acid and poly(meth)acrylic acid salts.

(Structural unit (b1-II))
When the ionic group of the structural unit (a2) is an anionic group, the component (B) is preferably a structural unit (b1-II) having a cationic group as the structural unit (b1) (hereinafter referred to as "structural unit ( b1-II)”) (hereinafter also referred to as “cationic polymer BII”).
Here, the "cationic group" refers to a cationic group or a group that can be ionized to become a cationic group, as described above.
Cationic polymer BII is preferably one or more selected from synthetic polymers or naturally-derived polymers having cationic groups, and salts thereof.

Specific examples of synthetic polymers having cationic groups include poly[2-(dimethylamino)ethyldiethyl methacrylate], 2-(dimethylamino)ethyldiethyl methacrylate/vinylpyrrolidone copolymer, Quaternized dialkylaminoalkyl (meth)acrylate polymers such as 2-(dimethylamino)ethyldiethyl methacrylate/N,N-dimethylacrylamide/polyethylene glycol dimethacrylate copolymer; polydiallyldimethylammonium diallyl quaternized ammonium salt polymers such as chloride, diallyldimethylammonium chloride/acrylic acid copolymer, diallyldimethylammonium chloride/acrylamide copolymer, diallyldimethylammonium chloride/acrylic acid/acrylamide copolymer; Trichloride/vinylpyrrolidone copolymer; vinylpyrrolidone/alkylamino (meth)acrylate copolymer; vinylpyrrolidone/alkylamino (meth)acrylate/vinylcaprolactam copolymer; vinylpyrrolidone/(meth)acrylamidopropyl trimethylammonium chloride copolymer Polymer; alkylacrylamide/(meth)acrylate/alkylaminoalkylacrylamide/polyethylene glycol (meth)acrylate copolymer; dimethylaminohydroxypropylethylenetriamine/adipic acid copolymer; cationized polyvinyl alcohol, and JP-A-53- Examples thereof include cationic polymers described in JP-A-139734 and JP-A-60-36407, and one or more of these can be used.

Among them, the structural unit (b1-II) of the synthetic polymer is preferably a structural unit derived from a cationic-containing polymerizable unsaturated monomer, and more preferably has a cationic group represented by the following formula (2). It is a building block.

〔式（２）中、Ｒ⁸～Ｒ¹¹、Ｘ³、Ｘ⁴は、前記と同じである。〕

[In formula (2), R ⁸ to R ¹¹ , X ³ and X ⁴ are the same as defined above. ]

The structural unit (b1-II) is, for example, a structural unit derived from a monomer (b1-II') represented by the following formula (2').

〔式（２’）中、Ｒ⁸～Ｒ¹¹、Ｘ³、Ｘ⁴は前記と同じである。〕

[In formula (2′), R ⁸ to R ¹¹ , X ³ and X ⁴ are the same as above. ]

Specific examples or preferred embodiments of R ⁸ to R ¹¹ , X ³ and X ⁴ in formulas (2) and (2′) are as follows from the viewpoint of enhancing the hydrophilization effect and enhancing the effect of suppressing shrinkage of hair. That's right.
R ⁸ and R ⁹ are preferably hydrogen atoms.
R ¹⁰ is preferably a hydrogen atom or a methyl group, more preferably a methyl group.
^X3 is preferably an oxygen atom.
R ¹¹ is preferably an alkylene group having 2 or 3 carbon atoms, more preferably an alkylene group having 2 carbon atoms.
X ⁴ is preferably N ⁺ R ¹² R ¹³ R ¹⁴ X ⁵ , and R ¹² , R ¹³ and R ¹⁴ are each preferably a methyl group or an ethyl group from the same viewpoint as above, more preferably R ¹² , R ¹³ , and R ¹⁴ is an ethyl group.
R ¹⁵ and R ¹⁶ are preferably a methyl group or an ethyl group, more preferably a methyl group, from the viewpoint of enhancing the hydrophilicity effect and facilitating the quaternization reaction.
^X5 is preferably a _{halogen ion} ^or _C2H5SO4- ^, _{more preferably C2H5SO4-} .

The structural unit (b1-II) is preferably N,N-(dialkylamino)alkyl (meth ) is a structural unit derived from acrylic acid or a quaternized product thereof, more preferably a structural unit derived from a quaternized product of N,N-(dialkylamino)alkyl (meth)acrylic acid, still more preferably (meth) quaternized product of 2-(dimethylamino)ethyl acrylate, quaternized product of 2-(diethylamino)ethyl (meth)acrylate, and quaternized product of 3-(dimethylamino)propyl (meth)acrylate It is a structural unit derived from at least one species, and more preferably a structural unit derived from diethylsulfate of 2-(dimethylamino)ethyl (meth)acrylate.

Component (B) is preferably a homopolymer consisting only of the structural unit (b1-II) or a copolymer containing structural units derived from monomers other than the structural unit (b1-II). When the component (B) is a copolymer containing the structural unit (b1-II), it may be a block copolymer, random copolymer or alternating copolymer. Other monomers include nonionic monomers such as (meth)acrylic acid esters, alkyl (meth)acrylamides, vinylpyrrolidone, and styrenic monomers exemplified in component (A); anionic group-containing polymerizable unsaturated monomers. etc.

Naturally-derived polymers having cationic groups include polymers obtained from natural products by operations such as extraction and purification, as well as those obtained by chemically modifying such polymers, and those having glucose residues in the polymer backbone. Specific examples include cationized guar gum; cationized tara gum; cationized locust bean gum; cationized cellulose; cationized hydroxyalkyl celluloses such as cationized hydroxyethyl cellulose and cationized hydroxypropyl cellulose;

[Constituent unit (b2)]
Component (B) is a betaine polymer containing at least a structural unit (b1) having an ionic group having a charge opposite to that of the ionic group of the structural unit (a2) and a structural unit (b2) having a betaine group. There may be.
That is, when the component (B) is a betaine polymer, the anionic polymer BI preferably has an anionic The cationic polymer BII is preferably a cationic betaine polymer containing at least a structural unit (b1-II) having a cationic group and a structural unit (b2) having a betaine group.
The cationic site of the betaine group of the structural unit (b2) is preferably a quaternary ammonium group from the viewpoint of enhancing the hydrophilization effect and enhancing the effect of suppressing shrinkage of hair.
The betaine group of the structural unit (b2) is preferably a sulfobetaine group, a phosphobetaine group, or a carbobetaine group, more preferably sulfobetaine, from the viewpoint of enhancing the hydrophilization effect and enhancing the effect of suppressing hair shrinkage. or phosphobetaine groups, more preferably sulfobetaine groups, the cationic sites of these betaine groups being preferably quaternary ammonium groups.
One type of betaine group may be used, or two or more types may be used.

The structural unit (b2) is preferably a structural unit represented by the following formula (1) from the viewpoint of enhancing the hydrophilization effect and enhancing the effect of suppressing shrinkage of hair.

〔式（１）中、Ｒ¹～Ｒ⁶、Ｘ¹、Ｘ²は前記と同じである。〕

[In Formula (1), R ¹ to R ⁶ , X ¹ and X ² are the same as above. ]

Structural unit (b2) is preferably a structural unit having a sulfobetaine group, a phosphobetaine group, or a carbobetaine group.
The structural unit (b2) may be one type, or two or more different types of structural units.
The structural unit (b2) is, for example, a structural unit derived from a monomer (b2') represented by the following formula (1').

〔式（１’）中、Ｒ¹～Ｒ⁶、Ｘ¹、Ｘ²は前記と同じである。〕

[In formula (1′), R ¹ to R ⁶ , X ¹ and X ² are the same as above. ]

Specific examples or preferred embodiments of R ¹ to R ⁶ , X ¹ and X ² in formulas (1) and (1′) are as follows from the viewpoint of enhancing the hydrophilization effect and enhancing the effect of suppressing shrinkage of hair. That's right.
R ¹ and R ² are preferably hydrogen atoms.
R ³ is preferably a hydrogen atom or a methyl group, more preferably a methyl group.
X ¹ is preferably an oxygen atom.
R ⁴ is preferably an alkylene group having 1 to 4 carbon atoms, more preferably an alkylene group having 2 or 3 carbon atoms, and still more preferably an alkylene group having 2 carbon atoms.
R ⁵ and R ⁶ are preferably methyl or ethyl groups, more preferably methyl groups.
X ² represents R ¹⁷ SO ₃ ^- or R ¹⁷ COO ^- , preferably R ¹⁷ SO ₃ ^- when R ⁴ is an alkylene group having 1 to 4 carbon atoms. R ¹⁷ represents an alkylene group having 1 to 4 carbon atoms which may have a hydroxyl group, preferably an alkylene group having 1 to 3 carbon atoms or a hydroxyalkylene group having 2 to 4 carbon atoms, more preferably It is an alkylene group having 1 or more and 3 or less carbon atoms, more preferably an alkylene group having 2 or 3 carbon atoms, and even more preferably an alkylene group having 3 carbon atoms.
X ² is a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms, preferably a hydrocarbon group having 1 to 4 carbon atoms when R ⁴ is -Y ¹ -OPO ₃ ^- -Y ² - and more preferably a methyl group.

Structural unit (b2) is preferably N-(3-sulfopropyl)-N-(meth)acryloyloxyethyl-N,N-dimethylammonium betaine, N-(3-sulfopropyl)-N-(meth) Monomers having a sulfobetaine group such as acryloylamidopropyl-N,N-dimethylammonium betaine; monomers having a phosphobetaine group such as 2-methacryloyloxyethylphosphorylcholine; N-carboxymethyl-N-(meth)acryloyloxyethyl-N , N-dimethylammonium betaine, N-carboxymethyl-N-(meth)acryloylamidopropyl-N,N-dimethylammonium betaine, a structural unit derived from at least one selected from monomers having a carbobetaine group, and more It is preferably a structural unit derived from at least one selected from a monomer having a sulfobetaine group and a monomer having a phosphobetaine group, more preferably a structural unit derived from a monomer having a sulfobetaine group, still more preferably N- (3-Sulfopropyl)-N-(meth)acryloyloxyethyl-N,N-dimethylammonium betaine and N-(3-sulfopropyl)-N-(meth)acryloylamidopropyl-N,N-dimethylammonium betaine is a structural unit derived from at least one selected from, and more preferably a structural unit derived from N-(3-sulfopropyl)-N-(meth)acryloyloxyethyl-N,N-dimethylammonium betaine.

When the component (B) is a betaine polymer containing at least the structural unit (b1) and the structural unit (b2) having a betaine group, the content of the structural unit (b1) in all the structural units of the component (B) is From the viewpoint of enhancing the hydrophilization effect and the viewpoint of enhancing the effect of suppressing shrinkage of hair, the content is preferably 1 mol% or more, more preferably 2 mol% or more, still more preferably 3 mol% or more, and preferably 50 mol% or less, more preferably. is 45 mol% or less, more preferably 40 mol% or less, even more preferably 30 mol% or less, still more preferably 15 mol% or less, even more preferably 10 mol% or less, and even more preferably 7 mol% or less.
When the component (B) is a betaine polymer containing at least the structural unit (b1) and the structural unit (b2) having a betaine group, the content of the structural unit (b2) in all the structural units of the component (B) is From the viewpoint of enhancing the hydrophilization effect and enhancing the effect of suppressing shrinkage of hair, the content is preferably 50 mol% or more, more preferably 55 mol% or more, still more preferably 60 mol% or more, still more preferably 70 mol% or more, and even more preferably 85 mol % or more, more preferably 90 mol % or more, still more preferably 93 mol % or more, and preferably 99 mol % or less, more preferably 98 mol % or less, still more preferably 97 mol % or less.
The content of each structural unit in all the structural units of component (B) can be measured by analysis such as NMR. Alternatively, it can be calculated from the charge ratio of each monomer when the component (B) is produced.

The value of [equivalent of betaine group in structural unit (b2)]/[equivalent of ionic group in structural unit (b1)] is preferably greater than 1, more preferably 3 or more, still more preferably 5 or more, and even more preferably is 7 or more, more preferably 9 or more, still more preferably 10 or more, still more preferably 15 or more, and preferably 50 or less, more preferably 40 or less, even more preferably 30 or less, and even more preferably 20 or less.

(Production of component (B))
When the component (B) is a betaine polymer containing at least the structural unit (b1) and the structural unit (b2) containing a betaine group, the method for producing the component (B) is not particularly limited. ) and (y2).
(x2) A method of copolymerizing the monomer (b2') represented by the formula (1') and the raw material monomer containing the anionic group-containing polymerizable unsaturated monomer or the cationic-containing polymerizable unsaturated monomer (y2) ) After copolymerizing the raw material monomer containing the monomer represented by the formula (1′-1) and the anionic group-containing polymerizable unsaturated monomer or the cationic group-containing polymerizable unsaturated monomer, using a betaining agent Method of Betaining Among these, the method (y2) is preferable from the viewpoint of the availability of monomers and the ease of production.

In the case of using the method (y2), for example, when the structural unit (b2) is a structural unit derived from a monomer having a sulfobetaine group, a raw material containing a monomer represented by the formula (1'-1) After the monomer is polymerized, the compound represented by the above formula (1′-2) or the compound represented by the above formula (1′-3) can be reacted as a betaining agent to betainize. A compound represented by the above formula (1'-2) is preferred.

Examples of commercially available cationic polymers of component (B) include the following.
(2-(dimethylamino)ethyl diethyl methacrylate/vinylpyrrolidone copolymer)
Polyquaternium-11: For example, Gafcat 734 (ISP Japan Co., Ltd.), Gafcat 755N (ISP Japan Co., Ltd.), etc. (2-(dimethylamino)ethyl diethyl methacrylate/N,N-dimethylacrylamide/polyethylene dimethacrylate glycol copolymer)
Polyquaternium-52: For example, Softcare KG-101W-E: Cationic charge density (literature value) 0.8 meq / g (Kao Corporation), etc. (polydiallyldimethylammonium chloride)
Polyquaternium-6: For example, MERQUAT100: Cationic charge density (literature value) 6.2 meq/g (Lubrizol Advanced Materials), etc. (diallyldimethylammonium chloride/acrylic acid copolymer)
Polyquaternium-22: For example, MERQUAT280: cationic charge density 2.2 meq/g, MERQUAT295: cationic charge density: 5.7 meq/g (above, Lubrizol Advanced Materials), etc. (diallyldimethylammonium chloride/acrylamide copolymer)
Polyquaternium-7: For example, MERQUAT550: Cationic charge density (literature value) 3.1 meq/g (Lubrizol Advanced Materials), etc. (diallyldimethylammonium chloride/acrylic acid/acrylamide copolymer)
Polyquaternium-39: for example MERQUAT3331PR: cationic charge density 0.42 meq/g (Lubrizol Advanced Materials), etc. (cationized polyvinyl alcohol)
Gohsenex K-434 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), CM318: cationic charge density 0.35 meq / g (Kuraray Co., Ltd.), etc. (cationized guar gum)
Jaguar Excel: cationic charge density 1.1 meq/g (manufactured by Solvay (Novecare)), etc. (cationized tara gum)
Catinal CTR-100: Cationic charge density 1.3 meq / g (manufactured by Toho Chemical Industry Co., Ltd.) etc. (cationized locust bean gum)
Catinal CLB-100 (manufactured by Toho Chemical Industry Co., Ltd.), etc. (cationized hydroxyethyl cellulose)
Polyquaternium-10 (chloride o-[2-hydroxy-3-(trimethylammonio)propyl]hydroxyethyl cellulose): for example U-Care Polymer JR-400: Cationic charge density 1.3 meq/g (Dow Chemical Co.), Poise C- 60H: Cationic charge density 1.1 to 1.8 meq / g (manufactured by Kao Corporation), Poise C-150L: Cationic charge density 0.7 to 1.1 meq / g (manufactured by Kao Corporation), Poise C- 80M: Cationic charge density 0.9 to 1.2 meq/g (manufactured by Kao Corporation)
(cationized hydroxypropyl cellulose)
Sofcare C-HP2: Cationic charge density 0.5 meq / g (Kao Corporation), etc.

The weight-average molecular weight of component (B) is preferably 1,000 or more, more preferably 3,000 or more, from the viewpoints of enhancing the hydrophilization effect, the adsorption property of the surface treatment composition, and enhancing the effect of suppressing shrinkage of hair. 000 or more, more preferably 5,000 or more, and even more preferably 10,000 or more, and from the viewpoint of the blending stability of the surface treatment composition, preferably 3,000,000 or less, more preferably 2,000, 000 or less. The weight average molecular weight of component (B) can be measured by the method described in Examples.

When component (B) is an anionic polymer BI and said anionic polymer BI is an anionic polymer other than an anionic betaine polymer, the anionic charge density of said component (B) is preferably -15 meq/g above, more preferably −14 meq/g or more, more preferably −13 meq/g or more, and preferably −1 meq/g or less, more preferably −3 meq/g or less, still more preferably −5 meq/g or less, Even more preferably -7 meq/g or less, and even more preferably -10 meq/g or less.
When the anionic polymer BI is an anionic betaine polymer, the anionic charge density of component (B) is preferably −5 meq/g or more, more preferably −3 meq/g or more, still more preferably −2 meq/g or more, Even more preferably −1 meq/g or more, still more preferably −0.5 meq/g or more, still more preferably −0.3 meq/g or more, and preferably −0.05 meq/g or less, more preferably is -0.1 meq/g or less, more preferably -0.15 meq/g or less.
In this case, the anionic charge density of component (B) is calculated from the mol number of anionic groups in component (B)/g×1000 (anionic charge density; meq/g) to the mol of cationic groups in component (B). It refers to the value obtained by subtracting the number/g×1000 (cation charge density; meq/g).
The anionic charge density (meq/g) of component (B) can be calculated from the type and molar ratio of structural units derived from monomers having anionic groups in the polymer. The types and molar ratios of structural units constituting the polymer can be measured by analysis such as NMR.
When the component (B) is an anionic polymer BI, the component (B) is a polymer that exhibits anionic properties as a whole, but has cationic groups in the polymer within a range that does not impair the effects of the present invention. may be
Further, two or more kinds of polymers exhibiting anionic properties as a whole may be used as the component (B). The anion charge density in this case can be determined by calculating a weighted average from the anion charge density and blending amount of each polymer.

When the component (B) is a cationic polymer BII and the cationic polymer BII is a cationic polymer other than a cationic betaine polymer, the cationic charge density of the component (B) is preferably 0.1 meq/ g or more, more preferably 0.5 meq/g or more, still more preferably 1.0 meq/g or more, still more preferably 2.0 meq/g or more, still more preferably 3.0 meq/g or more, and preferably is 6.0 meq/g or less, more preferably 5.0 meq/g or less, still more preferably 4.0 meq/g or less.
When the cationic polymer BII is a cationic betaine polymer, the cationic charge density of component (B) is preferably 0.01 meq/g or more, more preferably 0.05 meq/g or more, still more preferably 0.1 meq/g. g or more, more preferably 0.15 meq/g or more, and preferably 1.0 meq/g or less, more preferably 0.8 meq/g or less, even more preferably 0.6 meq/g or less, still more preferably is 0.4 meq/g or less, more preferably 0.2 meq/g or less.
In this case, the cationic charge density of component (B) is calculated from the number of mols of cationic groups in component (B)/g×1000 (cationic charge density; meq/g) to the mol of anionic groups in component (B). It refers to the value obtained by subtracting the number/g×1000 (anion charge density; meq/g).
The cationic charge density of component (B) can be calculated from the types and molar ratios of structural units constituting the polymer.
The types and molar ratios of structural units constituting the polymer can be measured by analysis such as NMR.
When the component (B) is a cationic polymer BII, the component (B) is a cationic polymer as a whole, but has an anionic group in the polymer within a range that does not impair the effects of the present invention. may be
Further, two or more kinds of polymers exhibiting cationic properties as a whole may be used for the component (B). The cationic charge density in this case can be obtained by calculating a weighted average from the cationic charge density and blending amount of each polymer.

[Component (C)]
The surface treatment composition according to the present invention contains an electrolyte as component (C). The surface treatment composition can be applied to a solid surface in a state in which component (A) and component (B) are dissolved by component (C) in the surface treatment composition, and components in the surface treatment composition is suppressed, the solid surface can be uniformly treated, and the hydrophilization effect can be improved. In addition, by reducing the concentration of component (C) in the surface treatment composition on the solid surface in step 1, the ionic groups of component (A) and the ionic groups of component (B) formed by the action of A polyion complex is precipitated, the polyion complex can be effectively adsorbed on a solid surface, the adsorbability of the surface treatment composition is further improved, and the hydrophilic betaine group improves the hydrophilization effect on the solid surface. is considered possible.
When the solid surface to be treated is the hair surface, the polyion complex is effectively adsorbed to the hair surface as described above, and the hydrophilic betaine group can improve the hydrophilization effect on the hair surface. It is thought that the meniscus force between the hairs is increased by this, and the effect of suppressing the shrinkage of the hairs can be further improved.

In the present invention, "electrolyte" means a compound that dissociates ions in water.
As the component (C), the component (A) and the component (B) are dissolved in the system by the component (C) to suppress the precipitation of the components in the surface treatment composition and improve the blending stability. organic acids, inorganic acids, organic bases, inorganic bases, and salts thereof.
Examples of organic acids include monocarboxylic acids such as formic acid, acetic acid, propionic acid, and benzoic acid; dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, and phthalic acid; and polyglutamic acid. polycarboxylic acids; hydroxycarboxylic acids such as glycolic acid, lactic acid, hydroxyacrylic acid, glyceric acid, malic acid, tartaric acid, citric acid; acidic amino acids such as glutamic acid and aspartic acid; methanesulfonic acid, N-methyltaurine, sulfamic acid , xylenesulfonic acid, p-toluenesulfonic acid and benzenesulfonic acid; sulfuric acid esters such as lauryl sulfate; organic phosphoric acid esters such as methylphosphoric acid and ethylphosphoric acid.
Examples of inorganic acids include hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, carbonic acid, thiocyanic acid, phosphoric acid and the like.
Examples of organic bases include alkanolamines such as monoethanolamine, diethanolamine and triethanolamine.
Inorganic bases include hydroxides of alkali metals such as potassium, sodium and lithium. Ammonia may also be used as the inorganic base.
Salts include sodium chloride, potassium chloride, magnesium chloride, sodium citrate, potassium benzoate, ammonium chloride, sodium carbonate, dipotassium phosphate, monoethanolamine sulfate and the like.
These can each be used individually by 1 type or in combination of 2 or more types.
When the surface treatment composition is produced, the component (C) is mixed with the above organic acid or inorganic acid and the organic base or inorganic base so as to form a salt in the surface treatment composition. good too.

Among these, component (C) is preferably a salt, more preferably a water-soluble inorganic salt, from the viewpoint of the stability of the surface treatment composition. The solubility of the water-soluble inorganic salt in 100 g of water at 20° C. is preferably 10 g or more, more preferably 20 g or more, still more preferably 30 g or more.
If the component (C) is a water-soluble inorganic salt, after applying the surface treatment composition to the solid surface, the concentration of the component (C) in the system is reduced by washing with water, and the above-mentioned polyion complex is effectively applied to the solid surface. can be adsorbed onto the solid surface to impart high hydrophilicity to the solid surface, and in particular when applied to the surface of hair, the effect of suppressing shrinkage of hair can be improved. From this point of view, component (C) is more preferably one or more selected from alkali metal salts and metal salts of Group 2 elements, and still more preferably one selected from sodium chloride, potassium chloride, and magnesium chloride. more preferably one or more selected from sodium chloride and potassium chloride, and still more preferably sodium chloride.

[Aqueous medium]
The surface treatment composition according to the invention preferably contains an aqueous medium. Examples of the aqueous medium include water; lower alcohols such as ethanol and isopropyl alcohol; low-molecular-weight diols and triols having 6 or less carbon atoms such as 1,3-butylene glycol, glycerin, ethylene glycol and propylene glycol. Above all, the surface treatment composition preferably contains water.

[Other ingredients]
The surface treatment composition according to the present invention may contain components other than components (A) to (C) as long as the effects of the present invention are not impaired. Other components include, for example, amphoteric surfactants, antioxidants, silicones, aromatic alcohols, polymers other than components (A) and (B), oils, vitamins, bactericides, anti-inflammatory agents, and anti-dandruff agents. , preservatives, chelating agents, moisturizing agents, pearl agents, ceramides, fragrances, ultraviolet absorbers, and the like.

The surface treatment composition according to the present invention can be produced by, for example, blending components (A) to (C) and other components as necessary, and mixing using a known stirring device or the like.

The content or blending amount of the component (A) in the surface treatment composition is determined from the viewpoint of enhancing the hydrophilization effect, the stability of the surface treatment composition and its adsorption properties, and the viewpoint of enhancing the effect of suppressing hair shrinkage. , preferably 0.01% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, still more preferably 0.7% by mass and is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, even more preferably 5% by mass or less, even more preferably 3% by mass or less, and even more preferably is 2% by mass or less, more preferably 1.5% by mass or less.

The content or blending amount of the component (B) in the surface treatment composition is determined from the viewpoint of enhancing the hydrophilization effect, the stability of the surface treatment composition and its adsorptivity, and the viewpoint of enhancing the effect of suppressing hair shrinkage. , preferably 0.0001% by mass or more, more preferably 0.001% by mass or more, still more preferably 0.005% by mass or more, still more preferably 0.01% by mass or more, and preferably 30% by mass Below, more preferably 20% by mass or less, still more preferably 15% by mass or less, even more preferably 10% by mass or less, even more preferably 5% by mass or less, even more preferably 3% by mass or less, still more preferably 2% by mass or less % by mass or less, and more preferably 1% by mass or less.

The total content or total blending amount of the components (A) and (B) in the surface treatment composition is selected from the viewpoint of enhancing the hydrophilicity effect, the viewpoint of the adsorption property of the surface treatment composition, and the effect of suppressing shrinkage of hair. From the viewpoint of increasing the % or more, and from the viewpoint of the blending stability and handling properties of the surface treatment composition, it is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, and even more preferably 30% by mass. % by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, even more preferably 5% by mass or less, and even more preferably 3% by mass or less.

The content or blending amount of the component (C) in the surface treatment composition is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and still more preferably 0.2% by mass or more, from the viewpoint of blending stability. 3% by mass or more, more preferably 0.5% by mass or more, still more preferably 0.7% by mass or more, and even more preferably 1% by mass or more, and from the viewpoint of enhancing the hydrophilic effect, the surface treatment composition From the viewpoint of adsorption of substances and the viewpoint of enhancing the effect of suppressing shrinkage of hair, preferably 15% by mass or less, more preferably 10% by mass or less, even more preferably 7% by mass or less, and even more preferably 5% by mass or less, More preferably 3% by mass or less, and even more preferably 2% by mass or less.

When water is used as the aqueous medium, the content or blending amount of the aqueous medium in the surface treatment composition is preferably 50% by mass or more, more preferably 60% by mass or more, and still more preferably 70% by mass or more. More preferably 80% by mass or more, still more preferably 90% by mass or more, and preferably 99% by mass or less.

When component (A) is a cationic betaine polymer AI and component (B) is an anionic polymer BI, the cation amount of component (A) represented by the following formula (II) and the following formula ( The equivalent ratio of the amount of the anion of component (B) represented by II-I) [(the amount of cation of component (A))/(the amount of anion of component (B))] is from the viewpoint of enhancing the hydrophilization effect, surface treatment From the viewpoint of the composition stability and adsorptivity of the composition, and the viewpoint of enhancing the effect of suppressing shrinkage of hair, the 0.3 or more, more preferably 0.5 or more, still more preferably 0.7 or more, still more preferably 0.9 or more, and preferably 50 or less, more preferably 30 or less, still more preferably 10 or less, more preferably 7 or less, even more preferably 5 or less, still more preferably 3 or less, still more preferably 2 or less, even more preferably 1.5 or less, still more preferably 1.3 or less, more More preferably, it is 1.1 or less.
Cationic amount of component (A)=[cationic charge density of component (A) (meq/g)]×[content or amount (g) of component (A) in surface treatment composition] (II)
Anion amount of component (B) = [anion charge density of component (B) (meq/g)] x [content or amount (g) of component (B) in surface treatment composition] (II-I)

When component (A) is an anionic betaine polymer AII and component (B) is a cationic polymer BII, the following formula ( The equivalent ratio of the cation amount of component (B) represented by II-II) [(cation amount of component (B))/(anion amount of component (A))] is from the viewpoint of enhancing the hydrophilization effect and hair From the viewpoint of enhancing the shrinkage suppression effect of the Still more preferably 0.7 or more, still more preferably 0.9 or more, and preferably 50 or less, more preferably 30 or less, still more preferably 10 or less, still more preferably 7 or less, still more preferably It is 5 or less, more preferably 3 or less, still more preferably 2 or less, still more preferably 1.5 or less, still more preferably 1.3 or less, and even more preferably 1.1 or less.
Anion amount of component (A) = [anion charge density (meq/g) of component (A)] x [content or amount (g) of component (A) in surface treatment composition] (I-II)
Cationic amount of component (B) = [cationic charge density of component (B) (meq/g)] x [content or amount (g) of component (B) in surface treatment composition] (II-II)

<Step 1>
Step 1 is a step of bringing an aqueous medium into contact with the solid surface to which the surface treatment composition has been applied.

[Step 1-1]
Before step 1, it is preferable to further include step 1-1 of applying the surface treatment composition to a solid surface.
The method of applying the surface treatment composition to the solid surface in step 1-1 is not particularly limited, and includes, for example, the following methods (i-1) to (iii-1).
(i-1) A method of immersing a solid in a surface treatment composition (ii-1) A method of spraying or applying a surface treatment composition to a solid surface (iii-1) A solid surface using a surface treatment composition in a conventional manner The ambient temperature when applying the surface treatment composition to a solid surface is preferably 5° C. or higher, more preferably 10° C. or higher, from the viewpoints of enhancing the hydrophilic effect and ease of work. It is more preferably 15° C. or higher, and preferably 50° C. or lower, more preferably 40° C. or lower, and still more preferably 30° C. or lower.
The immersion time in the method (i-1) is preferably 0.1 minute or longer, more preferably 0.3 minute or longer, and still more preferably 0.5 minute or longer, from the viewpoint of enhancing the hydrophilization effect and from the viewpoint of economy. minutes or more, more preferably 1 minute or more, and preferably 60 minutes or less, more preferably 50 minutes or less.
The method of spraying or coating in the method (ii-1) can be appropriately selected according to the size (area) of the solid surface. Further, after spraying, a sponge or the like may be used to apply a thin layer.
The amount of the surface treatment composition applied to a solid surface is, for example, 20 mL or more and 1,000 mL or less per 1 m ² in the case of a hydrophobic hard surface.

In step 1, the contact of the aqueous medium with the solid surface to which the surface treatment composition has been applied is preferably carried out so as to dilute the surface treatment composition on the solid surface with the aqueous medium. That is, step 1 is preferably a step of bringing an aqueous medium into contact with the solid surface to which the surface treatment composition has been applied, and diluting the surface treatment composition on the solid surface with the aqueous medium.
The dilution reduces the concentration of the component (C) contained in the surface treatment composition adhering to the solid surface, forming a polyion complex that precipitates and effectively adsorbs to the solid surface, and is contained in the component (A). The betaine group can impart high hydrophilicity to the solid surface.
The dilution ratio in step 1 is preferably 1.5 times or more, more preferably 2 times or more, still more preferably 5 times or more, and even more preferably, from the viewpoint of enhancing the hydrophilization effect and the viewpoint of enhancing the hair shrinkage suppression effect. is 10 times or more, more preferably 15 times or more, and is preferably 100 times or less, more preferably 70 times or less, even more preferably 50 times or less, and even more preferably 30 times or less.
In the present invention, the “dilution ratio” means the volume α of the surface treatment composition applied to the solid surface in step 1-1 relative to the volume α of the surface treatment composition applied to the solid surface in step 1-1 and step 1 is the ratio [(α+β)/α] of the total volume β of the aqueous medium used for dilution.

In step 1, the method of contacting the aqueous medium with the solid surface to which the surface treatment composition has been applied is not particularly limited, and examples thereof include the following methods (i) to (iii).
(i) A method of immersing a solid to which a surface treatment composition has been applied in an aqueous medium (ii) A method of spraying or coating an aqueous medium onto a solid surface to which a surface treatment composition has been applied (iii) A surface treatment composition is applied A method of washing the solid surface treated with an aqueous medium according to a conventional method

Examples of the aqueous medium used in step 1 include water; lower alcohols such as ethanol and isopropyl alcohol; low-molecular-weight diols and triols having 6 or less carbon atoms such as 1,3-butylene glycol, glycerin, ethylene glycol and propylene glycol. Among them, it is preferable to contain water.
The water used as the aqueous medium in step 1 is not particularly limited, and tap water, distilled water, ion-exchanged water, hard water, soft water, etc. can be used.
The content of water in the aqueous medium used in step 1 is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, still more preferably 95% by mass or more, and The upper limit is 100% by mass.

[Hair treatment method]
As described above, the hydrophilization method of the present invention can be used as a hair treatment method in which the solid surface is the hair surface from the viewpoint of imparting high hydrophilicity to the hair surface and suppressing shrinkage of the hair.
The hair treatment method preferably includes a step of applying the surface treatment composition to the hair surface as step 1-1, and a step of contacting the hair surface to which the surface treatment composition has been applied with an aqueous medium as step 1. .

The surface treatment composition in step 1-1 is preferably used by incorporating the surface treatment composition into a hair treatment agent. In this case, since the surface treatment composition is excellent in the effect of suppressing shrinkage of hair, the hair treatment agent can be used as a hair shrinkage suppressant.
Examples of the hair treatment agents include hair cleansers such as shampoos, hair cosmetics such as conditioners, treatments, and hair dyes. Among these, conditioners are preferred from the standpoint of obtaining the effects of the present invention and from the standpoint of easily suppressing hair shrinkage through daily hair care actions. There are no particular restrictions on the dosage form of the hair treatment agent, and any dosage form such as liquid, foam, paste, or cream may be used. Among these dosage forms, the hair treatment agent is preferably liquid.
Examples of the method of applying the hair treatment agent to the surface of the hair in step 1-1 include a method of coating, spraying or casting the hair treatment agent on the hair, and a method of immersing the hair in the hair treatment agent.
The hair may be dry or wet when the hair treatment agent is applied.
The ambient temperature at which the hair treatment agent is applied is preferably 5 to 50°C, more preferably 15 to 45°C, from the viewpoint of efficient surface treatment.
The application time of the hair treatment agent is preferably 5 seconds to 60 minutes, more preferably 5 seconds to 20 minutes. The application time of the hair treatment agent means the time during which the hair treatment agent is applied, sprayed or cast onto the hair, or the time during which the hair is immersed in the hair treatment agent.

As the method of contacting the aqueous medium in step 1, a method of applying the surface treatment composition to the hair surface in step 1-1 and then washing the hair surface to which the surface treatment composition has been applied with water is preferred. This causes the surface treatment composition on the hair surface to be diluted with water. Since the surface treatment composition contains the component (C), the concentration of the component (C) contained in the surface treatment composition is reduced, and a polyion complex is formed, deposited and adsorbed on the hair surface. , the betaine group contained in the component (A) can impart high hydrophilicity to the surface of the hair. As a result, the meniscus force between the hairs increases, and the effect of suppressing the shrinkage of the hairs can be enhanced.
The method of washing the hair in step 1 is not particularly limited, and for example, it can be performed by rinsing the hair with water by a known method.

As a specific method of the hair treatment method, for example, when the hair treatment agent is a hair cleansing agent such as shampoo, the hair cleansing agent is applied to the hair, foamed to wash the hair, and then rinsed with water. Method: When the hair treatment agent is a hair cosmetic such as a conditioner, a treatment, or a hair dye, the hair cosmetic is applied to the hair and left for a short period of time (about 0.1 to 5 minutes) as necessary. A method of washing away with water later can be mentioned. By routinely repeating the steps described above, shrinkage of hair can be easily suppressed in a short period of time.

EXAMPLES The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples. In addition, various measurements were performed by the following methods.

(Weight average molecular weight of cationic betaine polymer AI and cationic polymer BII)
It was measured under the following measurement conditions using a gel permeation chromatography method.
〔Measurement condition〕
Column: Two "TSKgel α-M" (manufactured by Tosoh Corporation) connected in series Column temperature: 40 ° C.
Eluent: 0.15 mol/L Na ₂ SO ₄ /1% by mass CH ₃ COOH aqueous solution Flow rate: 1.0 mL/min
Detector: Differential refractive index detector Sample size: 5 mg/mL
Reference material: pullulan

(Weight average molecular weight of anionic polymer BI and anionic betaine polymer AII)
It was measured under the following measurement conditions using a gel permeation chromatography method.
〔Measurement condition〕
Column: "TSKgel G4000PW _XL " + "TSKgel G2500PW _XL " (Tosoh Corporation)
Column temperature: 40°C
Eluent: 0.2 M phosphate buffer/CH ₃ CN=9/1 (volume ratio)
Flow rate: 1.0 mL/min
Detector: Differential refractive index detector Sample size: 5 mg/mL
Reference material: pullulan

Production Example 1 (Production of Cationic Betaine Polymer 1)
(Step 1)
126.30 g of ethanol (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was placed in a four-necked flask with an internal volume of 1000 mL, heated to 78° C. and refluxed. Thereto were added 181.12 g of 2-(dimethylamino)ethyl methacrylate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 23.60 g of a 90% aqueous solution of 2-(dimethylamino)ethyl methacrylate diethylsulfate, and 53 g of ethanol. A solution obtained by mixing 20 g, and a solution obtained by mixing 5.83 g of 2,2'-azobis(2-methylbutyronitrile) (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) and 10.00 g of ethanol, respectively. The reaction was carried out by adding dropwise over a period of time. After completion of dropping, the mixture was aged at 78° C. for 4 hours and then cooled to obtain a polymer solution.
A 90% aqueous solution of 2-(dimethylamino)ethyl diethyl methacrylate is composed of 2-(dimethylamino)ethyl methacrylate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) and diethyl sulfate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.). Co., Ltd.) were mixed at a molar ratio (1:1).
(Step 2)
94.70 g of the polymer solution obtained in step 1, 3.15 g of sodium hydrogen carbonate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), and 150.00 g of water were added to a four-necked flask with an internal volume of 1000 mL. °C. 38.70 g of 1,3-propanesultone (manufactured by Tokyo Kasei Kogyo Co., Ltd.) was added dropwise over 1 hour to carry out a reaction. After completion of the dropwise addition, after aging at 50° C. for 3 hours, ethanol is distilled off by heating under reduced pressure at 90° C./20 kPa for 2 hours, and cationic betaine polymer 1 (N-(3-sulfopropyl)-N-methacryloyl Oxyethyl-N,N-dimethylammonium betaine/2-(dimethylamino)ethyldiethyl methacrylate copolymer) (N-(3-sulfopropyl)-N-methacryloyloxyethyl-N,N-dimethylammonium betaine An aqueous solution containing 95 mol % of structural units derived from methacrylate and 5 mol % of structural units derived from 2-(dimethylamino)ethyldiethyl methacrylate) was obtained. The weight average molecular weight and charge density of Polymer 1 are shown in Tables 1 and 2.

Production Example 2 (Production of Cationic Betaine Polymer 2)
In Production Example 1, 133.76 g of 2-(dimethylamino)ethyl methacrylate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) and 73.60 g of 90% aqueous solution of 2-(dimethylamino)ethyldiethyl methacrylate sulfate. , 2.04 g of 2,2′-azobis(2-methylbutyronitrile) (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 7.15 g of sodium hydrogen carbonate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), and 1,3-propanesultone (manufactured by Tokyo Chemical Industry Co., Ltd.) was changed to 111.2 g, and cationic betaine polymer 2 (N-(3-sulfopropyl)-N-methacryloyloxyethyl-N,N-dimethyl Ammonium betaine/2-(dimethylamino)ethyldiethyl methacrylate sulfate copolymer) (N-(3-sulfopropyl)-N-methacryloyloxyethyl-N,N-dimethylammonium betaine-derived structural unit content: An aqueous solution containing 80 mol % of structural units derived from 2-(dimethylamino)ethyldiethyl methacrylate: 20 mol %) was obtained. The content, weight average molecular weight and charge density of Polymer 2 are shown in Tables 1 and 2.

Production Example 3 (Production of Anionic Betaine Polymer 3)
(Step 1)
Ethanol (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) 155.38 g, 2-(dimethylamino)ethyl methacrylate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) 77.76 g, and 2.24 g of methacrylic acid (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was added, and the temperature was raised to 65° C. and refluxed. A solution obtained by mixing 1.29 g of 2,2′-azobis(2,4-dimethylvaleronitrile) (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) and 30.00 g of ethanol was added thereto and aged for 6 hours. After cooling, a polymer solution was obtained.
The resulting polymer solution was reprecipitated using hexane (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) to recover the polymer. The solvent was distilled off by heating under reduced pressure at 50° C./20 kPa for 12 hours to obtain a dried polymer.
(Step 2)
20.00 g of the dried polymer obtained in step 1, 1.59 g of sodium hydrogen carbonate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), ethanol (Fujifilm Wako Pure Chemical Industries, Ltd. ) and 40.00 g of water were added, and the temperature was raised to 50°C. 16.61 g of 1,3-propanesultone (manufactured by Kanto Kagaku Co., Ltd.) was added dropwise over 40 minutes to carry out a reaction. After completion of dropping, the mixture was aged at 50° C. for 5 hours and then cooled to obtain a polymer solution. The resulting polymer solution was reprecipitated using acetone (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) to recover the polymer. Anionic betaine polymer 3 (N-(3-sulfopropyl)-N-methacryloyloxyethyl-N,N-dimethylammonium betaine/methacrylic acid copolymer) (N-(3-sulfopropyl)-N-methacryloyloxyethyl -N,N-dimethylammonium betaine-derived structural unit content: 95 mol%, methacrylic acid-derived structural unit content: 5 mol%). The weight average molecular weight and charge density of Polymer 3 are shown in Tables 1 and 2.

(Preparation of surface treatment composition)
Preparation Examples 1-17, Comparative Preparation Examples 1-5
According to the composition shown in Tables 1 and 2, component (A), component (B), sodium chloride as component (C), and water were mixed to prepare each surface treatment composition.
The amount of each component in the table is the active ingredient amount (% by mass).

(Hydrophilization treatment of solid surface)
Examples 1-3, 7-17 and Comparative Examples 1-3, 5
Using the prepared surface treatment composition, a solid surface was hydrophilized by the following method.
(Step 1-1)
10 mL of the prepared surface treatment composition was added to a beaker with a content of 200 mL, and a substrate (15 mm long x 25 mm wide x 1 mm thick polypropylene plate) was immersed for 1 minute to apply the surface treatment composition to the surface of the substrate.
(Step 1)
Then, 190 mL of ion-exchanged water was added, and the surface of the substrate to which the surface treatment composition was applied was diluted by contacting an aqueous medium (dilution ratio: 20 times). Next, the substrate was taken out of the liquid and washed with deionized water for 20 seconds. Thereafter, the substrate was immersed in ultrapure water without being dried to obtain a hydrophilized substrate.

Examples 4-6
A hydrophilized substrate was obtained in the same manner as in Example 1, except that the amount of ion-exchanged water added in step 1 was changed and the dilution ratio was changed as shown in Table 1.

Comparative example 4
In Example 1, the substrate to which the surface treatment composition was applied in step 1-1 was used for evaluation without performing step 1.

(Evaluation of hydrophilization effect)
Each of the substrates treated in Examples and Comparative Examples was attached to a ternary system sample stage and placed in a ternary system cell containing ultrapure water. The cell in which the measurement substrate is set is placed on the stage of a fully automatic contact angle measurement meter (manufactured by Kyowa Interface Science Co., Ltd. "DM-701"), and 1 μL of air is attached. After 0.2 seconds, the contact angle in water is measured. was obtained by the tangent method.
As the contact angle value, a value obtained by subtracting the obtained underwater contact angle value from 180° is used. The smaller the contact angle value, the higher the hydrophilization effect.

(Evaluation of blending stability)
The state of the surface treatment composition immediately after preparation of 10 mL of the prepared surface treatment composition was visually observed, and the formulation stability was evaluated as the property of the surface treatment composition according to the following evaluation criteria. A score of 3 on the following evaluation criteria indicates excellent blending stability. A score of 3 on the following evaluation criteria is particularly suitable for practical use, and a score of 2 on the following evaluation criteria is practically suitable.
〔Evaluation criteria〕
3: A uniform and transparent state with no deposit observed.
2: Although precipitates are observed, they are fine, uniformly dispersed, and cloudy.
1: Deposits are observed and locally aggregated (separated) or precipitated.

(Evaluation of adsorptivity)
190 mL of ion-exchanged water was added to 10 mL of the prepared surface treatment composition for dilution. The state of the diluted surface treatment composition was visually observed, and the adsorptivity was evaluated according to the following evaluation criteria. If the score is 3 in the following evaluation criteria, the adsorbability of the surface treatment composition is excellent, so that a treatment that imparts a high hydrophilic effect to the solid surface can be performed. A score of 3 on the following evaluation criteria is particularly suitable for practical use, and a score of 2 on the following evaluation criteria is practically suitable.
〔Evaluation criteria〕
3: Fine and uniformly dispersed precipitates are observed, and cloudiness is observed.
2: No precipitate was observed, and the state was uniform and transparent.
1: Coarse aggregates or precipitates are observed.
Here, in the present invention, when an aqueous medium is brought into contact with a solid surface to which the surface treatment composition is applied, a polyion complex is formed and precipitated, and the polyion complex is adsorbed on the solid surface to make it hydrophilic. It is considered that the effect of For this reason, a score of 3 was given when the precipitates were fine and uniformly dispersed throughout the dilution and were in a cloudy state. In addition, a score of 1 was given to those in which aggregates or precipitates were observed due to deposition of the polyion complex, because it is presumed that the solid surface could not be treated uniformly.

(Evaluation of handling performance)
50 mL of the prepared surface treatment agent composition was placed in a screw tube (No. 7, manufactured by Maruem Co., Ltd.) and shaken up and down five times. evaluated. The shorter the time until defoaming, the lower the viscosity of the surface treatment composition and the easier it is to handle. Therefore, if it is A in the following evaluation criteria, it means that it is excellent in the handleability at the time of performing the hydrophilization treatment of the solid surface.
〔Evaluation criteria〕
A: Time until defoaming is less than 600 seconds B: Time until defoaming is 600 seconds or more The viscosity of the surface treatment composition used in Example 14, which is evaluation B, was measured by a B-type viscometer (Toki Sangyo It was 68 mPa·s when measured using a model "TVB-10" manufactured by Co., Ltd.). The measurement conditions were sample volume: 50 mL, SPINDLE No. : M2, number of revolutions: 30 rpm.

Each component in Tables 1 and 2 is shown below.
Polymer 4: Partially neutralized polyacrylic acid ("ACUSOL 445G Polymer" manufactured by The Dow Chemical Company, molecular weight: 4,500 (catalog value))
Polymer 5: sodium carboxymethyl cellulose ("Celogen F-5A" manufactured by Daiichi Kogyo Co., Ltd.)
Polymer 6: Polyacrylic acid ("Jurimer AC-10LHPK" manufactured by Toagosei Co., Ltd.)
Polymer 7: cationized hydroxyethyl cellulose (manufactured by Kao Corporation "Poise C-80M")

From Tables 1 and 2, it can be seen that the method of the example has a smaller contact angle and a higher hydrophilization effect than the comparative example.

The effect of suppressing shrinkage when the method of the present invention is used as a hair treatment method was evaluated by measuring the shrinkage ratio by the method described below.
(Evaluation of effect of suppressing shrinkage of hair)
10 mL of each of the treatment solutions prepared in Examples 1, 17, and Comparative Example 1 was applied to 1 g of African American hair tresses, allowed to stand for 1 minute, and then rinsed with tap water while running fingers 20 times. A tress for evaluation was obtained. The obtained tresses were immersed in a plastic cup filled with tap water for 30 seconds, then pulled out at once, and allowed to stand in the atmosphere for 30 minutes. After 30 minutes, the maximum length (Lmax) and maximum width (Wmax) of the tress shown in FIG. 1 were measured, and the shrink coefficient (=Wmax/Lmax) was calculated.
Here, the tress washed with plain shampoo having the composition shown below is immersed in a plastic cup filled with tap water, and the shrink coefficient immediately after being lifted is assumed to be 0, and after washing with the plain shampoo, The tress treated with a commercially available conditioner (“Essential Hair Conditioner” manufactured by Kao Corporation) was immersed in a plastic cup filled with tap water, and the shrink coefficient was measured 30 minutes after being lifted, assuming that the “shrink rate” was 100. , and the normalized shrinkage coefficient was defined as the shrinkage ratio. Table 3 shows the results.
<Composition of plain shampoo>
(Plain shampoo) (% by mass)
Sodium polyoxyethylene lauryl ether sulfate (Emal E-27C (active ingredient 27% by mass), manufactured by Kao Corporation) 42
Coconut oil fatty acid N-methylethanolamide (Aminone C-11S, manufactured by Kao Corporation) 3
Citric acid 0.2
Methylparaben 0.3
Purified water Remainder
Total 100

From Table 3, it can be seen that the lower the contact angle, the lower the shrinkage value. From this, it can be seen that the method of the present invention can impart high hydrophilicity to the surface of hair, and as a result, can improve the shrinkage suppression effect.

According to the method of the present invention, it is possible to impart high hydrophilicity to a solid surface, and particularly in application to hair, it is possible to obtain a high anti-shrink effect.

Claims (13)

A solid surface hydrophilization method comprising a step 1 of contacting an aqueous medium with a solid surface to which a surface treatment composition has been applied,
The surface treatment composition contains the following components (A) to (C):
(A) a betaine polymer containing at least a structural unit (a1) having a betaine group and a structural unit (a2) having an ionic group; (B) an ion opposite to the charge of the ionic group of the structural unit (a2); polymer containing at least a structural unit (b1) having a functional group (C) an electrolyte,
A solid surface in which the equivalents of the betaine group of the structural unit (a1), the ionic group of the structural unit (a2), and the ionic group of the structural unit (b1) in the surface treatment composition satisfy the following condition 1: Hydrophilization method.
Condition 1: {[equivalent of betaine group in structural unit (a1)]+[equivalent of ionic group in structural unit (a2)]}/[equivalent of ionic group in structural unit (b1)]>0.10 The method according to claim 1, further satisfying condition 2 below.
Condition 2: [equivalent of betaine group in structural unit (a1)]/[equivalent of ionic group in structural unit (a2)]>1 3. The method according to claim 1, further satisfying condition 3 below.
Condition 3: The value of [equivalent of ionic group of structural unit (a2)]/[equivalent of ionic group of structural unit (b1)] is 0.01 or more and 50 or less. The method according to any one of claims 1 to 3, further comprising step 1-1 of applying said surface treatment composition to a solid surface before said step 1. 5. The method according to claim 4, wherein step 1 is a step of contacting an aqueous medium with the solid surface to which the surface treatment composition has been applied to dilute the surface treatment composition on the solid surface with the aqueous medium. . 6. The method according to claim 5, wherein the dilution ratio in step 1 is 1.5 times or more. 7. The method according to any one of claims 1 to 6, wherein the content of the structural unit (a1) having a betaine group in all the structural units of the component (A) is 50 mol% or more. A cationic betaine polymer AI in which the component (A) contains at least a structural unit (a1) having a betaine group and a structural unit (a2-I) having a cationic group as the structural unit (a2) having an ionic group. and
8. The anionic polymer BI according to any one of claims 1 to 7, wherein the component (B) is an anionic polymer BI containing at least a structural unit (b1-I) having an anionic group as the structural unit (b1) having an ionic group. Method. An anionic betaine polymer AII wherein the component (A) contains at least a structural unit (a1) having a betaine group and a structural unit (a2-II) having an anionic group as the structural unit (a2) having an ionic group. and
8. The cationic polymer BII according to any one of claims 1 to 7, wherein the component (B) comprises at least a structural unit (b2-II) having a cationic group as the structural unit (b1) having an ionic group. Method. The method according to any one of claims 1 to 9, wherein the structural unit (a1) having a betaine group is a structural unit represented by the following formula (1).

[In formula (1),
R ¹ to R ³ are the same or different and represent a hydrogen atom or an alkyl group having 1 or 2 carbon atoms,
R ⁴ represents an alkylene group having 1 to 4 carbon atoms, or -Y ¹ -OPO ₃ ^- -Y ² -, and Y ¹ and Y ² are the same or different and are alkylene groups having 1 to 4 carbon atoms. indicates
R ⁵ and R ⁶ are the same or different and represent a hydrocarbon group having 1 to 4 carbon atoms,
X ¹ represents an oxygen atom or an NR ⁷ group, R ⁷ represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms,
X ² represents R ¹⁷ SO ₃ ^- or R ¹⁷ COO ^- when R ⁴ is an alkylene group having 1 to 4 carbon atoms, and R ¹⁷ may have 1 to 4 carbon atoms and may have a hydroxyl group. represents an alkylene group, and X ² represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms when R ⁴ is -Y ¹ -OPO ₃ ^- -Y ² -. ] The method according to any one of claims 1 to 10, wherein the content of component (C) in the surface treatment composition is 0.1% by mass or more and 10% by mass or less. The method according to any one of claims 1 to 11, wherein the weight average molecular weight of component (B) is 1,000 or more and 3,000,000 or less. The method according to any one of claims 1 to 12, wherein the total content of component (A) and component (B) in the surface treatment composition is 0.1% by mass or more and 30% by mass or less.

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