WO2025225527A1 - Hydrophilization treatment composition - Google Patents

Abstract

The present invention addresses the problem of providing a hydrophilization treatment composition which is capable of forming a hydrophilized layer that has good hydrophilicity, water sliding properties, and hydrophilicity sustainability. A hydrophilization treatment composition according to the present invention contains a copolymer (A) which has: at least one constituent unit (A1) that is selected from among a constituent unit (A11) which is derived from a polymerizable monomer having a carboxyl group and a constituent unit (A12) which is derived from a polymerizable monomer having a hydroxyl group; and a constituent unit (A2) that is derived from a monomer in which a polyoxyalkylene group and a hydrocarbon group having a polymerizable double bond are linked via an ether bond.

Description

Hydrophilic treatment composition

The present invention relates to a hydrophilic treatment composition.

Heat exchangers have heat exchange plates such as aluminum fins (aluminum fins) that exchange heat between the heat transfer medium and the air. When the heat exchanger is in operation, moisture in the air can condense on the surface of the aluminum fins. If this condensation turns into droplets and forms bridges between the fins, problems such as increased power consumption due to ventilation resistance and water droplets scattering can occur. To prevent such bridging caused by condensed water, the surface of the fin material is often treated to make it hydrophilic.

A known method of hydrophilization involves applying a resin composition containing hydrophilic particles to the surface of the fin material to form a hydrophilic coating. Conventionally, inorganic particles such as silica and organic particles such as acrylic particles have been used as hydrophilic particles. Patent documents 1 and 2 also describe the use of hydrophilic cross-linked polymer microparticles composed of a copolymer of (a) 2 to 50% by weight of a hydrophilic monomer having a polymerizable double bond and a polyoxyalkylene chain or a polyvinylpyrrolidone chain, (b) 20 to 97% by weight of a (meth)acrylamide monomer, (c) 1 to 30% by weight of a cross-linkable unsaturated monomer, (d) 2 to 50% by weight of a carboxyl group-containing polymerizable unsaturated monomer, and (e) 0 to 50% by weight of other polymerizable monomers.

Furthermore, if the aluminum fin surface remains wet due to condensed water, it can cause various problems such as reduced heat exchange efficiency, corrosion of the aluminum fin, proliferation of bacteria, frost formation, etc. To solve these problems, it is important to make it easier for the condensed water on the aluminum fin surface to drain, that is, to increase the water slippage of the aluminum fin surface.
It is also known to treat the aluminum fin surface with a water-repellent treatment to improve the drainage (water sliding) of this condensed water. For example, Patent Document 3 discloses that a super-water- and oil-repellent heat exchanger component with excellent water sliding properties can be obtained by providing a plurality of confetti-shaped protrusions made of silica or the like on the surface of a substrate, and then forming a water-repellent, oil-repellent, and antifouling thin film on the surface of the substrate on which the confetti-shaped protrusions have been formed. Patent Document 4 also discloses that a heat exchanger component with excellent water repellency and water sliding properties can be obtained by applying a structure having a water-repellent layer containing a polymer having a polyethyleneimine skeleton, a fluorine-containing compound, and silica to a substrate.

On the other hand, Patent Document 5 describes that by using a treatment agent composed of a specific water-soluble resin (A), colloidal silica (B), organoalkoxysilane and/or its hydrolyzate (C), a crosslinking agent (D) capable of crosslinking with the water-soluble resin (A), and water (E) blended in a specified ratio as a surface treatment agent for aluminum-containing metal heat exchangers, it is possible to make the aluminum fin surface hydrophilic, prevent bridging caused by condensed water, and also improve drainage.

Japanese Patent Application Publication No. 9-87576 Japanese Patent Application Laid-Open No. 2000-328038 JP 2013-92289 A International Publication No. 2020/213485 International Publication No. 2014/147782

The present invention aims to solve the following first and/or second problems.
(First issue)
Surface hydrophilicity (initial hydrophilicity) is sometimes required not only for the fin material in a heat exchanger and the coating film applied to the surface thereof but also for various other applications, and there are cases where a coating film is required to have high hydrophilicity (initial hydrophilicity) immediately after formation and good drainage properties (water sliding properties) for droplets.
Therefore, a first object of the present invention is to provide a new hydrophilic treatment composition capable of forming a hydrophilic layer (for example, a coating film) having good hydrophilicity and water sliding properties.

(Second issue)
The hydrophilic coating film is required to have high hydrophilicity immediately after the coating film is formed (initial hydrophilicity) and also to maintain the hydrophilicity. In particular, the fin material of a heat exchanger will repeatedly undergo a wet state in which condensed water is present on the surface of the fin material and a dry state in which the condensed water evaporates over a long period of use. Therefore, a hydrophilic layer such as a hydrophilic coating film applied to the fin material of a heat exchanger may be required to maintain its hydrophilicity even after repeated adhesion and drying of condensed water.
Therefore, a second object of the present invention is to provide a hydrophilic treatment composition capable of forming a hydrophilic layer (e.g., a coating film) that has good hydrophilicity retention even after repeated application and drying of low-ion water such as pure water (hereinafter sometimes referred to as "after wet/dry cycles").

The present invention aims to solve at least one of the first and second problems, and in a preferred embodiment, to solve both the first and second problems.

As a result of extensive research to solve the above problems, the present inventors have found that the use of a specific polymer can enhance both hydrophilicity and water sliding properties.
The present inventors have also found that by using the polymer, it is possible to improve the durability of hydrophilicity after wet/dry cycles.

That is, the present invention includes the following inventions.
[1] at least one structural unit (A1) selected from a structural unit (A11) derived from a polymerizable monomer having a carboxyl group and a structural unit (A12) derived from a polymerizable monomer having a hydroxyl group;
A hydrophilization treatment composition, characterized by containing a copolymer (A) having a structural unit (A2) derived from a monomer in which a polyoxyalkylene group and a hydrocarbon group having a polymerizable double bond are linked via an ether bond.
[2] The hydrophilic treatment composition according to [1], wherein the hydrocarbon group contained in the structural unit (A2) is an aliphatic hydrocarbon group.
[3] The hydrophilic treatment composition according to [1] or [2], wherein the structural unit (A2) is derived from a monomer represented by the following formula:
(In the formula, R ¹ and R ² each independently represent a hydrogen atom or a methyl group. R ³ represents an alkylene group having 1 to 4 carbon atoms. R ⁴ represents an alkylene group having 2 to 4 carbon atoms. a is 0 or 1, and b represents the average number of moles added of 2 to 500.)
[4] The hydrophilic treatment composition according to any one of [1] to [3], further comprising hydrophilic particles (B) having at least one group selected from an acid group, a hydroxyl group, a polyoxyalkylene chain, and a polyvinylpyrrolidone chain.
[5] The hydrophilic treatment composition according to any one of [1] to [4], further comprising a crosslinking agent.
[6] The hydrophilic treatment composition according to [5], wherein the crosslinking agent has two or more oxazoline groups in one molecule.
[7] The hydrophilic treatment composition according to [4], wherein the volume average particle diameter of the hydrophilic particles is 10 nm to 10 μm.
[8] The hydrophilic treatment composition according to any one of [1] to [7], wherein the object to be hydrophilically treated is a fin of a heat exchanger.
[9] The hydrophilic treatment composition according to any one of [1] to [8], wherein the structural unit (A11) derived from a polymerizable monomer having a carboxyl group is a structural unit derived from an unsaturated monocarboxylic acid or a salt thereof.
[10] The hydrophilic treatment composition according to [9], wherein the unsaturated monocarboxylic acid or its salt is acrylic acid, methacrylic acid, or its salt.
[11] The hydrophilization treatment composition according to any one of [1] to [10], wherein the structural unit (A12) derived from a polymerizable monomer having a hydroxyl group is a structural unit derived from a (meth)acrylic acid hydroxyalkyl ester.
[12] The hydrophilization treatment composition according to any one of [1] to [11], wherein the structural unit (A2) is a structural unit derived from an ethylene oxide adduct of 2-methyl-2-propen-1-ol or an ethylene oxide adduct of 3-methyl-3-buten-1-ol.
[13] The hydrophilic treatment composition according to any one of [1] to [12], wherein the content of the structural unit (A2) is 30 to 99 parts by mass, based on 100 parts by mass of the total of the structural unit (A1) and the structural unit (A2).
[14] The hydrophilic treatment composition according to any one of [1] to [13], wherein the total content of the structural unit (A1) and the structural unit (A2) is 70 to 100 parts by mass per 100 parts by mass of the copolymer (A).
[15] The hydrophilic treatment composition according to [4], wherein the hydrophilic particles (B) are hydrophilic particles (B1) containing a hydrophilic polymer (b2) having an acid group and a hydroxyl group.

[16] at least one structural unit (A1) selected from a structural unit (A11) derived from a polymerizable monomer having a carboxyl group and a structural unit (A12) derived from a polymerizable monomer having a hydroxyl group;
A heat exchanger fin having a hydrophilized layer formed on its surface, the hydrophilized layer including a copolymer (A) having a structural unit (A2) derived from a monomer in which a polyoxyalkylene group and a hydrocarbon group having a polymerizable double bond are linked via an ether bond.
[17] The fin according to [16], wherein the thickness of the hydrophilic layer is 0.1 to 80 μm.

The present invention can achieve the following first and/or second effects.
First effect: By using the hydrophilic treatment composition of the present invention, it is possible to impart hydrophilicity and water-slip property to the obtained hydrophilic layer.
Second effect: By using the hydrophilic treatment composition of the present invention, the hydrophilicity of the resulting hydrophilic layer can be improved after wet/dry cycles.

FIG. 1 is a schematic diagram showing a method for measuring the sliding angle.

[Hydrophilic treatment composition]
The hydrophilic treatment composition of the present invention contains a copolymer (A) having at least one structural unit (A1) selected from the structural unit (A11) derived from a polymerizable monomer having a carboxyl group and the structural unit (A12) derived from a polymerizable monomer having a hydroxyl group, and a structural unit (A2) derived from a monomer in which a polyoxyalkylene group and a hydrocarbon group having a polymerizable double bond are linked via an ether bond.
The copolymer (A) constituting the hydrophilic treatment composition of the present invention is able to exhibit excellent hydrophilic properties (initial hydrophilicity, sustained hydrophilicity after wet/drying, and water sliding properties) due to the carboxyl group and/or hydroxyl group contained in the structural unit (A1) and the polyoxyalkylene group ether-bonded to a specific hydrocarbon group contained in the structural unit (A2).
[Structural Unit (A1)]
The structural unit (A1) of the present invention is at least one selected from the structural unit (A11) derived from a polymerizable monomer having a carboxyl group and the structural unit (A12) derived from a polymerizable monomer having a hydroxyl group.

As used herein, a "structural unit derived from a polymerizable monomer" refers to a structural unit having the same structure as the structure formed by polymerizing a specified monomer, and typically has a structure in which the carbon-carbon double bond contained in the specified monomer is replaced with a carbon-carbon single bond and two bonds bonded to each carbon.
It should be noted that the constituent unit derived from a specified monomer does not necessarily have to be a constituent unit formed by actually polymerizing the specified monomer, and even a constituent unit formed by a method other than polymerizing the specified monomer (for example, a constituent unit formed through a reaction such as hydrolysis or neutralization after polymerization) is included in the constituent unit derived from the specified monomer, as long as it has the same structure as the structure formed by polymerizing the specified monomer.

[Structural Unit (A11) Derived from Polymerizable Monomer Having a Carboxyl Group]
The number of carboxyl groups contained in the polymerizable monomer having a carboxyl group is preferably 1 to 3, and more preferably 1.
The polymerizable group contained in the polymerizable monomer having a carboxyl group is preferably an ethylenically unsaturated bond-containing group such as a vinyl group, an allyl group, or a (meth)acryloyl group, and more preferably a (meth)acryloyl group.

Examples of polymerizable monomers having a carboxyl group include carboxyl group-containing monofunctional monomers and salts of carboxyl group-containing monofunctional monomers.

Specific examples of carboxyl group-containing monofunctional monomers include unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid; and unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; of which unsaturated monocarboxylic acids are preferred, (meth)acrylic acid is more preferred, and acrylic acid is particularly preferred.

Examples of the salt of the carboxyl group-containing monofunctional monomer include alkali metal salts of the carboxyl group-containing monofunctional monomer, ammonium salts of the carboxyl group-containing monofunctional monomer, etc. Salts of unsaturated monocarboxylic acids are preferred, and salts of acrylic acid are more preferred.
In the salt of the carboxyl group-containing monofunctional monomer, specific examples of the alkali metal atom or ammonium that forms a salt with the carboxyl group-containing monofunctional monomer are as follows:

Examples of alkali metal atoms include lithium, sodium, and potassium, with sodium and potassium being preferred, and sodium being more preferred.

Ammonium is not limited to NH ⁴⁺ and is defined to include organic ammonium. Examples of organic ammonium include quaternary ammonium such as tetraalkylammonium (preferably tetra-C _1-10 alkylammonium) such as tetramethylammonium and tetrabutylammonium; and ammonium (primary to tertiary ammonium) formed by protonating an amine. Examples of the amine include trialkylamine (preferably tri-C _1-10 alkylamine) such as trimethylamine, triethylamine, and tributylamine; and hydroxyalkylamine (preferably mono-, di-, or tri-(hydroxy-C _1-10 alkyl)amine) such as monoethanolamine, diethanolamine, and triethanolamine.
That is, examples of ammonium include NH ⁴⁺ and primary to quaternary ammonium, and preferred are tetraalkylammoniums such as tetramethylammonium and tetrabutylammonium (preferably tetra-C _1-10 alkylammonium), trialkylammoniums such as trimethylammonium, triethylammonium and tributylammonium (preferably tri-C _1-10 alkylammonium), hydroxyalkylammoniums such as monoethanolammonium, diethanolammonium and triethanolammonium (preferably mono-, di- or tri-(hydroxy-C _1-10 alkyl)ammonium), and NH ⁴⁺ .

[Structural Unit (A12) Derived from Polymerizable Monomer Having a Hydroxyl Group]
The number of hydroxyl groups contained in the polymerizable monomer having a hydroxyl group is preferably 1 to 3, and more preferably 1.
The polymerizable group contained in the polymerizable monomer having a hydroxyl group is preferably an ethylenically unsaturated bond-containing group such as a vinyl group, an allyl group, or a (meth)acryloyl group, and more preferably a (meth)acryloyl group.

Specific examples of the polymerizable monomer having a hydroxyl group include (meth)acrylic acid hydroxyalkyl esters such as hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-1-methylethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and hydroxypentyl (meth)acrylate; 3-(meth)allyloxy-1,2-dihydroxypropane and 1-allyloxy (meth)acrylic acid C _1-8 hydroxyalkyl esters are preferred, and (meth)acrylic acid C _1-4 hydroxyalkyl esters are more preferred.

[Structural unit (A2)]
The structural unit (A2) of the present invention is a structural unit derived from a monomer in which a polyoxyalkylene group and a hydrocarbon group having a polymerizable double bond are linked via an ether bond.

[Polyoxyalkylene group]
The polyoxyalkylene group preferably has a structure shown in the following formula:
In the formula, R ⁴ represents an alkylene group represented by C _m H _2m , and the alkylene group may be either linear or branched, but is preferably linear.
^R4 may be the same or different in the b repeating units.
m is preferably an integer of 2 to 4, more preferably 2 or 3, and even more preferably 2.
Examples of the oxyalkylene group having 2 to 4 carbon atoms include an oxyethylene group, an oxypropylene group, and an oxybutylene group.
b represents the average number of moles of oxyalkylene groups added, and is preferably from 2 to 500, more preferably from 5 to 300, and even more preferably from 10 to 200.
^R5 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. ^R5 is preferably a hydrogen atom.

[Hydrocarbon group having a polymerizable double bond]
The hydrocarbon group having a polymerizable double bond has at least one polymerizable double bond per molecule. The number of carbon atoms in the hydrocarbon group having a polymerizable double bond is not particularly limited, but may be 2 to 20, preferably 2 to 10, and more preferably 2 to 5. The hydrocarbon group having a polymerizable double bond may be linear, branched, or cyclic, and is preferably an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group, and more preferably an aliphatic hydrocarbon group. The hydrocarbon group having a polymerizable double bond preferably has a substituent linked to a polyoxyalkylene group via an ether bond.

Aliphatic hydrocarbon groups having a polymerizable double bond include, for example, alkenyl groups such as vinyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, dodecenyl, hexadecenyl, and icosenyl groups, with vinyl, 2-propenyl (allyl), 2-methyl-2-propenyl (methallyl), and 3-methyl-3-butenyl (isoprenyl) groups being preferred.

Examples of alicyclic hydrocarbon groups having a polymerizable double bond include cycloalkenyl groups such as cyclohexenyl, cycloheptenyl, cyclooctenyl, cyclononadecaenyl, and cyclodecaenyl.

Examples of aromatic hydrocarbon groups having a polymerizable double bond include alkenylaryl groups such as styrene groups, vinylphenyl groups, allylbenzene groups, isoprenylbenzene groups, and chlorostyrene groups.

Among the above, the hydrocarbon group having a polymerizable double bond is preferably an aliphatic hydrocarbon group, and particularly preferably an aliphatic hydrocarbon group having 4 or 5 carbon atoms.

The structural unit (A2) is preferably a structural unit derived from a monomer represented by the following formula:
In the formula, R ¹ and R ² each independently represent a hydrogen atom or a methyl group.
^R3 represents an alkylene group having 1 to 4 carbon atoms. Examples of the alkylene group having 1 to 4 carbon atoms include a methylene group, an ethylene group, a propylene group, and a butylene group.
^R4 represents an alkylene group having 2 to 4 carbon atoms.
a is 0 or 1, and b represents the average number of moles of oxyalkylene groups added, preferably 2 to 500, more preferably 5 to 300, and even more preferably 10 to 200.

Specific examples of the structural unit represented by the above formula include those listed below.
ethylene oxide adducts, propylene oxide adducts, and butylene oxide adducts of vinyl alcohol;
ethylene oxide adducts, propylene oxide adducts, and butylene oxide adducts of 2-propen-1-ol;
ethylene oxide adducts, propylene oxide adducts, and butylene oxide adducts of 3-buten-1-ol;
ethylene oxide adducts, propylene oxide adducts, and butylene oxide adducts of 4-penten-1-ol;
ethylene oxide adducts, propylene oxide adducts, and butylene oxide adducts of 5-hexen-1-ol;
ethylene oxide adducts, propylene oxide adducts, and butylene oxide adducts of 2-propen-ol;
2-methyl-2-propen-1-ol (methallyl alcohol) adducts with ethylene oxide, propylene oxide, and butylene oxide;
ethylene oxide adducts, propylene oxide adducts, and butylene oxide adducts of 3-methyl-3-buten-1-ol (isoprenol);
ethylene oxide adduct, propylene oxide adduct, and butylene oxide adduct of 4-methyl-4-penten-1-ol;
ethylene oxide adduct, propylene oxide adduct, and butylene oxide adduct of 5-methyl-5-hexen-1-ol;
ethylene oxide adducts, propylene oxide adducts, and butylene oxide adducts of 1-propen-1ol;
ethylene oxide adducts, propylene oxide adducts, and butylene oxide adducts of 2-buten-1-ol;
ethylene oxide adducts, propylene oxide adducts, and butylene oxide adducts of 3-penten-1-ol;
ethylene oxide adducts, propylene oxide adducts, and butylene oxide adducts of 4-hexen-1-ol;
ethylene oxide adducts, propylene oxide adducts, and butylene oxide adducts of 5-hepten-1-ol;
ethylene oxide adducts, propylene oxide adducts, and butylene oxide adducts of 2-buten-2-ol;
ethylene oxide adduct, propylene oxide adduct, and butylene oxide adduct of 2-methyl-2-buten-1-ol;
ethylene oxide adduct, propylene oxide adduct, and butylene oxide adduct of 3-methyl-3-penten-1-ol;
ethylene oxide adduct, propylene oxide adduct, and butylene oxide adduct of 4-methyl-4-hexen-1-ol;
ethylene oxide adduct, propylene oxide adduct, and butylene oxide adduct of 5-methyl-5-hepten-1-ol;
Of the above, preferred are ethylene oxide adducts, propylene oxide adducts and butylene oxide adducts of 2-methyl-2-propen-1-ol (methallyl alcohol); and ethylene oxide adducts, propylene oxide adducts and butylene oxide adducts of 3-methyl-3-buten-1-ol (isoprenol); and more preferred are ethylene oxide adducts of 2-methyl-2-propen-1-ol and ethylene oxide adducts of 3-methyl-3-buten-1-ol.

Copolymer (A) may have one or more types of structural units corresponding to structural unit (A1) and one or more types of structural units corresponding to structural unit (A2).

From the perspective of further improving hydrophilicity, the content of the structural unit (A2) is preferably 30 to 99 parts by mass, more preferably 50 to 95 parts by mass, and even more preferably 55 to 95 parts by mass, per 100 parts by mass of the total of the structural units (A1) and (A2).

The total content of the structural unit (A1) and the structural unit (A2) is preferably 70 to 100 parts by mass, more preferably 75 to 100 parts by mass, and even more preferably 80 to 100 parts by mass, per 100 parts by mass of copolymer (A), and may even be 100 parts by mass.

The weight average molecular weight of the copolymer (A) is preferably 2,000 to 1,000,000, more preferably 3,000 to 500,000, and even more preferably 4,000 to 250,000.
The weight average molecular weight is measured by GPC (gel permeation chromatography) under the conditions described in the examples.

Copolymer (A) may contain one or more structural units (hereinafter "other structural units (A3)") derived from monomers having a carbon-carbon double bond (hereinafter "other monomers") other than structural units (A1) and (A2).

The other monomers are not particularly limited as long as they can be copolymerized with the structural units (A1) and (A2), but examples include 3-(meth)allyloxy-2-hydroxypropanesulfonic acid, 2-(meth)allyloxyethylenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, p-styrenesulfonic acid, α-methyl-p-styrenesulfonic acid, vinylsulfonic acid, vinylsulfamic acid, (meth)allyl sulfonic acid, isoprene sulfonic acid, 4-(allyloxy)benzenesulfonic acid, 1-methyl-2-propene-1-sulfonic acid, 1,1-dimethyl-2-propanesulfonic acid, unsaturated sulfonic acids and salts thereof, such as propene-1-sulfonic acid, 3-butene-1-sulfonic acid, 1-butene-3-sulfonic acid, 2-acrylamido-1-methylpropanesulfonic acid, 2-acrylamidopropanesulfonic acid, 2-acrylamido-n-butanesulfonic acid, 2-acrylamido-2-phenylpropanesulfonic acid, and 2-((meth)acryloyloxy)ethanesulfonic acid; N-vinyl lactam monomers, such as N-vinylpyrrolidone; methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and silyl (meth)acrylate; (Meth)acrylic acid esters such as cyclohexyl, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, iso-nonyl (meth)acrylate, dodecyl (meth)acrylate, and stearyl (meth)acrylate; N-substituted or unsubstituted (meth)acrylamides such as (meth)acrylamide, N-monomethyl(meth)acrylamide, N-monoethyl(meth)acrylamide, and N,N-dimethyl(meth)acrylamide; vinyl aryl monomers such as styrene, α-methylstyrene, vinyltoluene, indene, vinylnaphthalene, phenylmaleimide, and vinylaniline. vinyl carboxylates such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether and butyl vinyl ether; vinyl ethylene carbonate and its derivatives; unsaturated amines such as N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylamide, vinylpyridine, vinylimidazole, and their salts or quaternized products; vinyl cyanide monomers such as acrylonitrile and methacrylonitrile.

The content of structural units (A3) derived from other monomers in the copolymer (A) is, for example, 40% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less or 10% by mass or less, and even more preferably 5% by mass or less or 3% by mass or less.

It is preferable that the hydrophilic treatment composition further contains a crosslinking agent. By including a crosslinking agent, the strength of the hydrophilic layer containing the hydrophilic treatment composition of the present invention can be increased. Furthermore, by including a crosslinking agent, the durability of the hydrophilic layer is improved, thereby improving the hydrophilicity retention effect and the water slippage of the hydrophilic layer after heat cycling, as shown in the examples described below. One type of crosslinking agent may be used alone, or two or more types may be used in combination. The crosslinking agent is preferably a compound having two or more groups per molecule that can react with the polar functional group contained in the hydrophilic treatment composition. Examples of groups that can react with polar functional groups include epoxy groups, oxazoline groups, carbodiimide groups, and isocyanate groups, and can be selected appropriately depending on the hydrophilic treatment composition to be used.

Examples of crosslinking agents include at least one selected from melamine resins, urea resins, polyaldehyde compounds, phenolic resins, polyepoxy compounds, blocked polyisocyanate compounds, metal compounds (metal salts, metal complexes, metal oxides, metal hydroxides, etc.), oxazoline compounds, carbodiimide compounds, hydroxyalkylamide compounds, hydrazide compounds, semicarbazide compounds, and silicate compounds. It is particularly preferable to use a crosslinking agent having two or more oxazoline groups per molecule, as combining it with the hydrophilic treatment composition of the present invention tends to further enhance the durability-improving effect described above.

As a crosslinking agent having two or more oxazoline groups per molecule, a water-soluble oxazoline compound is preferred from the viewpoint of excellent crosslinking performance, and an oxazoline group-containing polymer is also preferred. The above oxazoline group-containing polymer can be produced by a conventionally known production method. For example, there is a method of polymerizing a monomer component containing one or more addition-polymerizable oxazolines, or an addition-polymerizable oxazoline and a monomer copolymerizable with the addition-polymerizable oxazoline.

Examples of the above-mentioned addition-polymerizable oxazolines include compounds having a polymerizable unsaturated group and an oxazoline group in the molecule, such as 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline. Monomers copolymerizable with addition-polymerizable oxazolines are preferably monomers that do not have a functional group that reacts with the oxazoline group and are copolymerizable with addition-polymerizable oxazolines. Examples include (meth)acrylic monomers such as alkyl (meth)acrylates; styrene-based monomers such as styrene, α-methylstyrene, and chloromethylstyrene; vinyl-based monomers such as vinyl acetate, vinyl chloride, and vinyl benzoate; acrylonitrile; (meth)acrylamide-based monomers such as acrylamide; and olefin-based monomers such as ethylene and propylene.

Among the oxazoline group-containing polymers, water-soluble oxazoline group-containing polymers are preferred, and can be produced by the same method as the above-mentioned oxazoline group-containing polymer. Examples of the above-mentioned water-soluble oxazoline group-containing polymers include polymers that have a (meth)acrylic resin or the like as a main chain and contain oxazoline groups in the side chains.

Commercially available oxazoline group-containing polymers can also be used. Examples include water-soluble polymers such as Epocross WS-500 and Epocross WS-700, manufactured by Nippon Shokubai Co., Ltd., and emulsion-type polymers such as Epocross K-2010E, Epocross K-2020E, and Epocross K-2035E.

The content of the crosslinking agent is not particularly limited, but is preferably 0.1 to 50 parts by mass, more preferably 1 to 40 parts by mass, and even more preferably 5 to 30 parts by mass, per 100 parts by mass of the copolymer (A).

The hydrophilic treatment composition may further contain a solvent. By containing a solvent, the coatability of the hydrophilic treatment composition is improved. From the viewpoint of reducing the environmental load, an aqueous solvent is preferred as the solvent. The aqueous solvent includes water alone or a mixed solvent of water and a water-miscible organic solvent. The aqueous solvent typically refers to a solvent having a water content of more than 50% by volume. As the water, ion-exchanged water (deionized water), distilled water, pure water, etc. can be used. As the water-miscible organic solvent, an organic solvent that can be uniformly mixed with water (for example, a lower alcohol such as a _C1-4 alkyl alcohol) can be used.

The solvent content in the hydrophilic treatment composition may be 0% by mass, but is preferably 0.1% by mass or more, more preferably 40% by mass or more, even more preferably 60% by mass or more, and particularly preferably 80% by mass or more, and is preferably 99.9% by mass or less, and more preferably 99% by mass or less.

[Method for producing copolymer (A)]
The production of the copolymer (A) of the present invention is not particularly limited, and it can be produced by polymerizing the monomer components, specific examples and preferred examples of which are as described above. The proportion of each structural unit in the copolymer obtained by the polymerization reaction can be calculated based on the proportion of each monomer used as a reaction raw material and the amount of remaining monomer measured by high performance liquid chromatography.

In producing the above copolymer, a chain transfer agent can be used to adjust the molecular weight of the resulting polymer. Examples of chain transfer agents include thiol-based chain transfer agents such as mercaptoethanol, thioglycerol, thioglycolic acid, 3-mercaptopropionic acid, thiomalic acid, and 2-mercaptoethanesulfonic acid; secondary alcohols such as isopropyl alcohol; and hydrophilic chain transfer agents such as lower oxides and salts of phosphorous acid, hypophosphorous acid, and salts thereof (sodium hypophosphite, potassium hypophosphite, etc.), sulfurous acid, hydrogen sulfite, dithionous acid, metabisulfite, and salts thereof (sodium sulfite, sodium hydrogen sulfite, sodium dithionite, sodium metabisulfite, etc.).

Hydrophobic chain transfer agents can also be used as the chain transfer agent. Suitable hydrophobic chain transfer agents include thiol-based chain transfer agents with a hydrocarbon group containing three or more carbon atoms, such as butanethiol, octanethiol, decanethiol, dodecanethiol, hexadecanethiol, octadecanethiol, cyclohexyl mercaptan, thiophenol, octyl thioglycolate, and octyl 3-mercaptopropionate. Furthermore, to adjust the molecular weight of the copolymer, it is also effective to use monomers with high chain transfer properties, such as (meth)allylsulfonic acids (salts).

The amount of the chain transfer agent used may be set appropriately, but is preferably 0.1 mol or more, more preferably 0.25 mol or more, and even more preferably 0.5 mol or more, per 100 mol of the total amount of monomer components, and is preferably 20 mol or less, more preferably 15 mol or less, and even more preferably 10 mol or less.

The above polymerization reaction can be carried out by a method such as solution polymerization or bulk polymerization, using a radical polymerization initiator as necessary. Solution polymerization can be carried out batchwise or continuously, or a combination of both. Examples of solvents used in this process include water; alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol; aromatic or aliphatic hydrocarbons such as benzene, toluene, xylene, cyclohexane, and n-hexane; ester compounds such as ethyl acetate; ketone compounds such as acetone and methyl ethyl ketone; and cyclic ether compounds such as tetrahydrofuran and dioxane. Among these, aqueous solution polymerization is preferred.

When the aqueous solution polymerization is carried out, a water-soluble polymerization initiator is used as the radical polymerization initiator, for example, a persulfate such as ammonium persulfate, sodium persulfate, or potassium persulfate; hydrogen peroxide; azoamidine compounds such as 2,2'-azobis-2-methylpropionamidine hydrochloride; cyclic azoamidine compounds such as 2,2'-azobis-2-(2-imidazolin-2-yl)propane hydrochloride; or azonitrile compounds such as 2-carbamoylazoisobutyronitrile. In this case, an accelerator such as an alkali metal sulfite such as sodium hydrogensulfite, metabisulfite, sodium hypophosphite, Fe(II) salts such as Mohr's salt, sodium hydroxymethanesulfinate dihydrate, hydroxylamine hydrochloride, thiourea, L-ascorbic acid (salt), or erythorbic acid (salt) may also be used in combination. Among these, a combination of a persulfate such as ammonium persulfate, sodium persulfate, or potassium persulfate, or a combination of hydrogen peroxide with an accelerator such as L-ascorbic acid (salt), is preferred. These radical polymerization initiators and accelerators may be used alone or in combination of two or more.
Furthermore, when solution polymerization is carried out using a lower alcohol, an aromatic or aliphatic hydrocarbon, an ester compound, or a ketone compound as the solvent, or when bulk polymerization is carried out, peroxides such as benzoyl peroxide, lauroyl peroxide, and sodium peroxide; hydroperoxides such as t-butyl hydroperoxide and cumene hydroperoxide; and azo compounds such as azobisisobutyronitrile are used as radical polymerization initiators. In this case, accelerators such as amine compounds can also be used in combination. Furthermore, when a water-lower alcohol mixed solvent is used, an appropriate radical polymerization initiator or combination of a radical polymerization initiator and an accelerator can be selected and used from the various radical polymerization initiators described above.

The amount of the radical polymerization initiator used is preferably 0.001 mol or more, more preferably 0.01 mol or more, even more preferably 0.1 mol or more, and particularly preferably 0.2 mol or more, per 100 mol of the total amount of the monomer components; it is also preferably 20 mol or less, even more preferably 10 mol or less, particularly preferably 7 mol or less, and most preferably 5 mol or less.

In the above polymerization reaction, polymerization conditions such as polymerization temperature are determined appropriately depending on the polymerization method, solvent, polymerization initiator, and chain transfer agent used, but the polymerization temperature is preferably 0°C or higher and 150°C or lower. It is more preferably 30°C or higher, and even more preferably 50°C or higher. It is also more preferably 120°C or lower, and even more preferably 100°C or lower.

The method for adding each monomer component to the reaction vessel is not particularly limited, and examples include adding the entire amount to the reaction vessel all at once at the beginning; adding the entire amount to the reaction vessel in portions or continuously; or adding a portion to the reaction vessel initially and then adding the remainder to the reaction vessel in portions or continuously. Furthermore, by continuously or stepwise changing the rate at which each monomer is added to the reaction vessel during the reaction and continuously or stepwise changing the weight ratio of each monomer added per unit time, two or more copolymers with different monomer ratios can be synthesized simultaneously during the polymerization reaction. The radical polymerization initiator may be charged to the reaction vessel from the beginning, or added dropwise to the reaction vessel, or a combination of these methods may be used depending on the purpose.

Each polymer obtained as described above can be used as is to prepare a hydrophilic treatment composition, but if necessary, it may be further neutralized with an alkaline substance before use. Suitable alkaline substances include inorganic salts such as hydroxides and carbonates of monovalent or divalent metals; ammonia; and organic amines. Furthermore, the concentration can be adjusted, if necessary, after the reaction is complete.

The method for producing the hydrophilic treatment composition of the present invention is not particularly limited, but may include, for example, a step of mixing copolymer (A) with a crosslinking agent, solvent, hydrophilic particles, and other additives that are used as needed (also referred to as mixing step (A)). In mixing step (A), mixing may be performed, for example, in the presence of a solvent (preferably an aqueous solvent) or in the absence of a solvent.

The hydrophilic treatment composition preferably further contains hydrophilic particles (B). By containing the hydrophilic particles (B), it is possible to improve the durability of hydrophilicity after wet/dry cycles. The hydrophilic particles (B) may be used alone or in combination of two or more types.
The hydrophilic particles (B) are preferably hydrophilic particles containing a hydrophilic polymer (b1) having at least one group selected from an acid group, a hydroxyl group, a polyoxyalkylene chain, and a polyvinylpyrrolidone chain, more preferably hydrophilic particles (B1) containing a hydrophilic polymer (b2) having an acid group and/or a hydroxyl group, or hydrophilic particles (B2) containing a hydrophilic polymer (b3) having a polyoxyalkylene chain and a polyvinylpyrrolidone chain, and even more preferably hydrophilic particles (B1) containing a hydrophilic polymer (b2) having an acid group and a hydroxyl group.

The hydrophilic polymer (b2) having an acid group and/or a hydroxyl group is preferably at least one structural unit selected from the structural unit (B11) derived from a polymerizable monomer having a carboxyl group and the structural unit (B12) derived from a polymerizable monomer having a hydroxyl group, and more preferably a hydrophilic crosslinked polymer (b4) that further contains a structural unit (C1) derived from a monomer (C) (hereinafter referred to as monomer (C)) having two or more polymerizable groups in one molecule. The structural units (B11) and (B12) contained in the hydrophilic particle (B1) are the same as the structural units (A11) and (A12) described above for the structural unit (A1), and therefore further description is omitted.

The hydrophilic particles (B1) may be structural units (B13) derived from polymerizable monomers having a carboxyl group and a hydroxyl group, and for example, hydroxymethylacrylic acid-based monomers are preferred.

The content of the structural units (B11) to (B13) in the hydrophilic particles (B1) is, for example, 5 to 99.9 mass%, and preferably 40 to 99.9 mass%.

As mentioned above, the hydrophilic particles (B1) preferably have a structural unit (C1) derived from the monomer (C). It is more preferable that the hydrophilic polymer (b2) contained in the hydrophilic particles (B1) is crosslinked with the monomer (C) (hereinafter referred to as the hydrophilic crosslinked polymer (B1-1)). The monomer (C) is preferably a polyfunctional ethylenically unsaturated monomer having two or more ethylenically unsaturated bond-containing groups, such as a hydrocarbon crosslinkable monomer, a divinyl ether monomer, a diallyl ether monomer, or a polyvalent (meth)acrylic acid ester.

Examples of hydrocarbon cross-linking monomers include aromatic hydrocarbon cross-linking monomers such as divinylbenzene, trivinylbenzene, divinylnaphthalene, divinyltoluene, and divinylxylene; alicyclic hydrocarbon cross-linking monomers such as trivinylcyclohexane; and linear hydrocarbon cross-linking monomers such as 1,3-butadiene.

Preferred divinyl ether monomers include diC1-4 alkylene glycol divinyl ether; polyC1-4 alkylene glycol divinyl ether (the number of repeating alkylene glycol units is not particularly limited, but 3 to 10 is preferred); and the like.

Preferred examples of the diallyl ether monomer include di-C _1-4 alkylene glycol diallyl ether; poly-C _1-4 alkylene glycol diallyl ether (the number of repeating alkylene glycol units is not particularly limited, but is preferably 3 to 10); and the like.

As polyvalent (meth)acrylic acid esters, polyvalent methacrylic acid esters such as methacrylic acid diesters of mono-, di-, or polyalkylene glycols, methacrylic acid triesters of polyols, methacrylic acid tetraesters of polyols, methacrylic acid pentaesters of polyols, and methacrylic acid hexaesters of polyols are preferred, as they are highly resistant to hydrolysis, tend to prevent the elution of particle components such as hydrophilic components, and enhance sustained hydrophilicity and/or water slip properties.

Among the polyfunctional ethylenically unsaturated monomers, hydrocarbon cross-linking monomers and polyvalent (meth)acrylic acid esters are preferred. Hydrocarbon cross-linking monomers and polyvalent methacrylic acid esters are more preferred because they are particularly resistant to hydrolysis and tend to further enhance sustained hydrophilicity and/or water slip properties, with aromatic hydrocarbon cross-linking monomers and methacrylic acid diesters of mono-, di-, or polyalkylene glycols being even more preferred, and divinylbenzene being particularly preferred.

The hydrophilic particles (B1) may contain one type of structural unit (C1) derived from the monomer (C) alone, or two or more types.

The content of the structural unit (C1) derived from the monomer (C) in the hydrophilic particles (B1) is preferably 0.01 to 70 mass%.

Furthermore, in the hydrophilic particles (B1), the content of the structural unit (C1) derived from the monomer (C) per 100 parts by mass of the structural units (B11 to B13) is preferably 0.1 to 45 parts by mass. The total content of the structural units (B11 to B13) and the structural unit (C1) in the hydrophilic particles (B1) is preferably 50 to 100% by mass, and the upper limit of this total content may be 99.9% by mass or 99% by mass.

The polymerizable group contained in monomer (C) is preferably an ethylenically unsaturated bond-containing group, more preferably a vinyl group or a methacryloyl group, and particularly preferably a vinyl group.

The molecular weight of the monomer (C) is preferably 50 or more and 1,000 or less, and more preferably 100 or more and 400 or less.

The hydrophilic particles (B1) may contain one or more structural units (hereinafter "other structural units (B3)") derived from monomers having a carbon-carbon double bond (hereinafter "other monomers") other than the structural units (B11-13) and the structural unit (C1).

Other monomers include, but are not limited to, (meth)acrylic monomers, styrene monomers, vinyl ester monomers, silane group-containing monomers, nitrogen atom-containing monomers, oxo group-containing monomers, fluorine atom-containing monomers, epoxy group-containing monomers, light-stabilizing monomers, and ultraviolet absorbing monomers.

Examples of the (meth)acrylic monomer include (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate. Among these, (meth)acrylic acid _C1-10 alkyl esters are preferred, and (meth)acrylic acid _C1-5 alkyl esters are more preferred.

Examples of styrene-based monomers include styrenes which may have one or more substituents such as halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms) and alkyl groups (e.g., C _1-4 alkyl groups such as methyl groups, ethyl groups, n-propyl groups, isopropyl groups, n-butyl groups, and tert-butyl groups). Specific examples of styrene-based monomers include styrene, α-methylstyrene, p-methylstyrene, tert-butylstyrene, chlorostyrene, and vinyltoluene, with styrene being preferred.

Examples of vinyl ester monomers include esters of saturated fatty acids such as vinyl acetate and vinyl propionate with vinyl alcohol, and among these, esters of _C1-5 saturated fatty acids with vinyl alcohol are preferred.

Examples of silane group-containing monomers include alkoxysilyl group-containing silane coupling agents such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(methoxyethoxy)silane, γ-(meth)acryloyloxypropyltrimethoxysilane, and 2-styrylethyltrimethoxysilane; halogenated silyl group-containing silane coupling agents such as vinyltrichlorosilane; and silanol group-containing silane coupling agents such as γ-(meth)acryloyloxypropylhydroxysilane and γ-(meth)acryloyloxypropylmethylhydroxysilane.

Examples of nitrogen atom-containing monomers include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, dimethylaminoethyl(meth)acrylamide, N-vinylpyrrolidone, and (meth)acrylonitrile.

Examples of oxo group-containing monomers include ethylene glycol methoxy(meth)acrylate.

Examples of fluorine atom-containing monomers include (meth)acrylic acid fluorinated alkyl esters such as trifluoroethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, and octafluoropentyl (meth)acrylate. Among these, (meth)acrylic acid C _1-10 fluorinated alkyl esters are preferred, and (meth)acrylic acid C _1-5 fluorinated alkyl esters are more preferred.

Examples of epoxy group-containing monomers include glycidyl (meth)acrylate.

Examples of light-stabilizing monomers include 2,2,6,6-tetramethylpiperidine-4-(meth)acrylate.

Examples of ultraviolet absorbing monomers include benzotriazole-based ultraviolet absorbing monomers and benzophenone-based ultraviolet absorbing monomers.

As the other monomer, (meth)acrylic monomers, styrene-based monomers, carboxy group-containing monomers, salts of carboxy group-containing monomers, and hydroxy group-containing monomers are preferred, (meth)acrylic acid alkyl esters, (meth)acrylic acid, salts of (meth)acrylic acid, and styrene-based monomers are more preferred, acrylic acid alkyl esters, acrylic acid, and salts of acrylic acid are even more preferred, and acrylic acid and salts of acrylic acid are particularly preferred.
In particular, the total content of the structural units derived from acrylic acid and the structural units derived from a salt of acrylic acid may be 0 to 40% by mass in the hydrophilic particles (B1).

The content of the structural unit (B3) derived from other monomers in the hydrophilic particles (B1) is, for example, 40 mass% or less.

Preferred embodiments of the hydrophilic particles (B1) will be described below.
The hydrophilic particles (B1) may be entirely composed of the hydrophilic particles (B1) (preferably hydrophilic crosslinked polymer particles (B1-1), the same applies hereinafter), or the hydrophilic particles (B1) may be partially composed of another polymer (hereinafter, referred to as the second polymer (D)).
That is, the hydrophilic particles (B1) may have a single-layer structure or a multilayer structure. Making the hydrophilic particles (B1) into a multilayer structure, preferably a core-shell structure, is also effective in further enhancing hydrophilic properties and water sliding properties. For example, by forming the outermost shell layer such as the shell portion from the hydrophilic polymer (b1) (preferably a hydrophilic crosslinked polymer, the same applies hereinafter) constituting the hydrophilic particles (B1), the particles can be made highly hydrophilic, or by reducing the hydrophilicity of the inner layer such as the core portion, the particles can be given low solubility and low swelling in water, and as a result, deterioration and elution of the resulting hydrophilized layer can be suppressed.

The following describes the case where the hydrophilic particles (B1) have a multilayer structure. For ease of explanation, the multilayer hydrophilic particles composed of the hydrophilic polymer (b1) and second polymer (D) that constitute the hydrophilic particles (B1) described above will be referred to as "hydrophilic particles (B1D) having a multilayer structure." In the hydrophilic particles (B1D) having a multilayer structure, the second polymer (D) that constitutes layers other than the outermost layer (for example, the core portion in the case of core-shell particles) is preferably different from the hydrophilic polymer (b1).

The second polymer (D) preferably has one or more structural units composed of a non-aqueous monomer that does not have an acidic proton-containing group such as a carboxy group, a hydroxyl group, a thiol group, or a silanol group, or an amino group. This reduces the hydrophilicity of the inner layer, such as the core portion. The non-aqueous monomer is preferably a monomer composed of a hydrocarbon that may have one or more groups selected from an ester group, an ether group, an amide group, and a halogeno group, and more preferably a monomer composed of a hydrocarbon that may have an ester group.

Specific examples of the non-aqueous monomer include (meth)acrylic monomers, styrene-based monomers, vinyl ester-based monomers, oxo group-containing monomers, fluorine atom-containing monomers, and epoxy group-containing monomers. Examples of these (meth)acrylic monomers, styrene-based monomers, vinyl ester-based monomers, oxo group-containing monomers, fluorine atom-containing monomers, and epoxy group-containing monomers are the same as the other monomers described above in relation to the other structural unit (A3), and preferred aspects of each monomer are also the same.

The non-aqueous monomer is preferably a (meth)acrylic monomer or a styrene monomer, more preferably a (meth)acrylic acid alkyl ester or a styrene monomer, and even more preferably a (meth)acrylic acid C _1-5 alkyl ester or styrene.

The content of structural units derived from non-aqueous monomers in the second polymer (D) is 40 to 99 mass%.

It is preferable that the second polymer (D) further contains one or more structural units derived from a polyfunctional ethylenically unsaturated monomer. This is expected to have the effect of further enhancing the initial hydrophilicity, sustained hydrophilicity, and water slippage of the hydrophilized layer surface. Examples of the polyfunctional ethylenically unsaturated monomer include the same monomers as the polyfunctional ethylenically unsaturated monomers described above for monomer (C). Among these, hydrocarbon crosslinkable monomers and polyvalent (meth)acrylic acid esters are preferred, aromatic hydrocarbon crosslinkable monomers and (meth)acrylic acid diesters of mono-, di-, or polyalkylene glycols are more preferred, and divinylbenzene is even more preferred.

The content of the structural units derived from the polyfunctional ethylenically unsaturated monomer in the second polymer (D) is preferably 1 to 50% by mass, more preferably 10 to 45% by mass, and even more preferably 20 to 40% by mass. Furthermore, in the second polymer (D), the content of the structural units derived from the polyfunctional ethylenically unsaturated monomer per 100 parts by mass of the structural units derived from the non-aqueous monomer is preferably 10 to 70 parts by mass, more preferably 20 to 60 parts by mass, and even more preferably 20 to 50 parts by mass. Furthermore, in the second polymer (D), the total content of the structural units derived from the non-aqueous monomer and the structural units derived from the polyfunctional ethylenically unsaturated monomer is preferably 60 to 100% by mass, more preferably 80 to 100% by mass, and even more preferably 90 to 100% by mass. Furthermore, the upper limit of the total content may be 99.9% by mass or 99% by mass.

The second polymer (D) may contain one or more of the aforementioned structural units (B11 to B13), but preferably does not contain any. The content of the structural units (B11 to B13) in the second polymer (D) is preferably less than the content of the structural units (B11 to B13) in the hydrophilic polymer (b1); specifically, it is preferably 10% by mass or less, and more preferably 5% by mass or less.

The second polymer (D) may contain one or more structural units (D11) derived from a non-aqueous monomer, a polyfunctional ethylenically unsaturated monomer, and a monomer having one polymerizable group per molecule, such as a carbon-carbon double bond-containing group, other than the structural units (B11 to B13) (hereinafter referred to as the "second other monomer").

The second other monomer includes a monomer having a carboxy group, a thiol group, a silanol group, an amino group, etc., such as a carboxy group-containing monomer, a silane group-containing monomer, a hydroxy group-containing monomer, a nitrogen atom-containing monomer, a light-stabilizing monomer, and an ultraviolet absorbing monomer. These carboxy group-containing monomers, silane group-containing monomers, hydroxy group-containing monomers, nitrogen atom-containing monomers, light-stabilizing monomers, and ultraviolet absorbing monomers are the same as the other monomers in the other structural unit (B3) described above, and therefore further description is omitted.

The content of the structural unit (D11) derived from the second other monomer in the second polymer (D) is preferably 30% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less or 3% by mass or less.

The volume average particle diameter of the hydrophilic particles (B1) (including multilayered hydrophilic particles (B1D)) is, for example, 10 nm to 10 μm, preferably 10 nm to 5 μm, more preferably 20 nm to 1 μm, and even more preferably 30 nm to 500 nm. The volume average particle diameter can be measured, for example, by dynamic light scattering.

<Method of producing hydrophilic particles>
The method for producing the hydrophilic particles (B1) is not particularly limited, and any conventionally known method may be used, but it is preferable to produce the hydrophilic particles (B1) by polymerizing the monomers constituting the polymer particles (hereinafter, these may be collectively referred to as "raw material monomer components") in an aqueous solvent and, if necessary, partially or completely hydrolyzing them. Examples of the polymerization method include suspension polymerization, emulsion polymerization, and dispersion polymerization. Among these, emulsion polymerization, in which the raw material monomer components are dispersed in an aqueous solvent in the presence of an emulsifier and subjected to a (radical) polymerization reaction, is preferred. In emulsion polymerization, for example, a non-aqueous monomer, a polyfunctional ethylenically unsaturated monomer used as needed, a polymerizable monomer that constitutes the structural units (B11 to B13), and a second other monomer are polymerized in an aqueous solvent in a first stage to synthesize seed particles that become the core (i.e., the second polymer (D)), and then monomers that constitute the hydrophilic polymer (b1) (preferably a hydroxymethyl acrylic acid ester, a polyfunctional ethylenically unsaturated monomer, and other monomers used as needed) are polymerized in a second stage to synthesize the shell (i.e., the hydrophilic polymer (B1D)), thereby producing polymer particles (B1D) having a core-shell structure.

One or more types of emulsifiers can be used, and they may be non-reactive surfactants or reactive surfactants.

The amount of emulsifier used is preferably 0.05 to 20 parts by mass per 100 parts by mass of the total raw material monomer components.

The aqueous solvent is the same as the aqueous solvent explained above in connection with the solvent for the hydrophilic treatment composition, and the preferred embodiments thereof are also the same.
From the viewpoint of minimizing the amount of water-miscible organic solvent remaining in the hydrophilic particles (B1), an aqueous solvent containing water at 80% by volume or more is preferred, and water alone is most preferred.

When polymerizing the raw material monomer components, methods such as using a polymerization initiator, irradiating with ultraviolet or radiation, or applying heat are used. It is preferable to use a polymerization initiator, and a polymerization initiator that combines an oxidizing agent and a reducing agent (redox polymerization initiator) is preferred. Examples of the oxidizing agent include persulfates such as ammonium persulfate and potassium persulfate, and peroxide-based polymerization initiators such as hydrogen peroxide, benzoyl peroxide, parachlorobenzoyl peroxide, lauroyl peroxide, and ammonium peroxide. Examples of the reducing agent include soluble sulfites and ascorbic acid.

If necessary, additives such as chain transfer agents, pH buffers, and chelating agents may be added in appropriate amounts to the reaction system during the above emulsion polymerization. The amount of additive varies depending on the type of additive and cannot be determined in general, but is typically preferably 0.01 to 5 parts by mass per 100 parts by mass of the raw monomer components.

Hydrophilic particles (B1) can be hydrolyzed by adding, for example, an aqueous solution of an alkali metal hydroxide such as an aqueous sodium hydroxide solution, an aqueous solution of an amine such as an aqueous cyclohexylamine solution, or an aqueous solution containing a basic substance such as an aqueous ammonia solution. Furthermore, partial or complete neutralization can be achieved by adding an appropriate amount of acid to the solution after hydrolysis. By carrying out hydrolysis and neutralization, the group corresponding to R in the -COOR group contained in the polymer particles can be converted to a hydrogen atom, an alkali metal atom, or ammonium.

The content of the hydrophilic particles (B1) in the hydrophilic treatment composition of the present invention may be, for example, 0.01% by mass or more, preferably 10% by mass or more, and more preferably 30% by mass or more.

The hydrophilic particles (B) are preferably hydrophilic particles (B2) having a structural unit derived from at least one group selected from a polyoxyalkylene chain and a polyvinylpyrrolidone chain.
The hydrophilic particles (B2) preferably have a group having a polyoxyalkylene chain, such as a constituent unit derived from a polyalkylene glycol monomethacrylate, such as polyethylene glycol monomethyl ether or methoxypolyethylene glycol monomethacrylate, or a group having a polyvinylpyrrolidone chain, such as a constituent unit derived from a polyvinylidone macromonomer.
Furthermore, the hydrophilic particles (B2) may contain, in addition to (1) a structural unit derived from at least one group selected from a polyoxyalkylene chain and a polyvinylpyrrolidone chain, (2) a structural unit derived from a (meth)acrylamide-based monomer such as (meth)acrylamide or N-methyl(meth)acrylamide, (3) a unit derived from a crosslinkable unsaturated monomer such as N-methylolacrylamide, methylenebisacrylamide, glycidyl methacrylate, γ-methacryloxypropyltrimethoxysilane or N-butoxymethylacrylamide, (4) a structural unit derived from a carboxyl group-containing polymerizable unsaturated monomer such as acrylic acid, methacrylic acid or maleic acid, or (5) a structural unit derived from a monomer having one polymerizable unsaturated group in one molecule, such as an alkyl ester such as methyl(meth)acrylate or a hydroxyalkyl ester of (meth)acrylic acid such as 2-hydroxyethyl(meth)acrylate, and the hydrophilic particles (B2) may also be composed of a copolymer of these (1) to (5), preferably a copolymer of (1) to (4).
The above monomers may be polymerized by various known methods, for example, in a solvent such as propylene glycol monomethyl ether in the presence of a polymerization initiator such as 2,2'-azobis(2-methylbutyronitrile).
The volume average particle size of the hydrophilic particles (B2) is preferably 10 nm to 10 μm.
In the present invention, by incorporating the hydrophilic particles (B2) into the hydrophilic layer containing the hydrophilic treatment composition, the hydrophilic layer can be endowed with good hydrophilicity as well as a sustained hydrophilicity effect and/or water slipping property.

In addition to the hydrophilic particles mentioned above, silica particles may also be used. Examples of silica particles include silica sol and finely powdered silica.

The hydrophilic treatment composition of the present invention may contain other additives to the extent that the effects of the present invention are not impaired. Examples of other additives that can be used include additives commonly used in this technical field, such as L-ascorbic acid, gallic acid, and tannic acid, which are water-soluble low-molecular-weight compounds having hydroxyl groups, and polymeric compounds having hydroxyl groups, such as polyvinyl alcohol.

A preferred embodiment of the hydrophilic treatment composition of the present invention will now be described.
[Hydrophilic layer formed using hydrophilic treatment composition]
The hydrophilic layer, such as a hydrophilic coating film, formed from the hydrophilic treatment composition of the present invention contains the above-mentioned hydrophilic treatment composition, and therefore has not only good hydrophilicity but also a sustained hydrophilic effect and/or good water-slip property. Therefore, the hydrophilic treatment composition is suitably applied to tangible objects (i.e., objects to be hydrophilized) that require not only hydrophilicity but also sustained hydrophilicity and/or water-slip property, and is particularly suitably used for hydrophilic coating films applied to fin materials (heat exchanger fins) of heat exchangers.

A preferred embodiment of the hydrophilic treatment composition of the present invention is a heat exchanger fin having a hydrophilic layer (e.g., a hydrophilic coating film) containing the copolymer (A) formed on its surface. The thickness of the hydrophilic layer formed on the fin is preferably, for example, 0.1 to 80 μm.

In addition, when the hydrophilic layer exhibits a hydrophilicity sustaining effect, it is preferable that the following (a) and (b) are satisfied, for example.
(a) The initial contact angle (θ0) measured by the method described in the <Evaluation of Initial Hydrophilicity> in the Examples is less than 40°. (b) The contact angle (θ5) after wet/dry cycling measured by the method described in the <Evaluation of Hydrophilicity Sustaining Effect After Wet/Dry Cycle> in the Examples is less than 40°.

The initial contact angle of the hydrophilic layer is preferably less than 35°, more preferably 30° or less, even more preferably 20° or less, and particularly preferably 15° or less or less than 15°. There is no particular lower limit to the initial contact angle, but it is, for example, 5° or more.

The contact angle (θ5) of the hydrophilic layer is preferably less than 35°, more preferably 30° or less, even more preferably 26° or less, even more preferably 20° or less, and particularly preferably 15° or less or less than 15°. There is no particular lower limit to the contact angle, but it is, for example, 8° or more.

In a more preferred embodiment, the relationship between the initial contact angle (θ0) and the contact angle (θ5) in the hydrophilized layer satisfies the following (c) or (d).
(c) Contact angle (θ5)≦Initial contact angle (θ0)
(d) Contact angle (θ5) > initial contact angle (θ0), and the absolute value of the difference between the contact angle (θ5) and the initial contact angle (θ0) is 20° or less. When the relationship between the initial contact angle (θ0) and the contact angle (θ5) in the hydrophilized layer satisfies (c) above, the absolute value of the difference between the contact angle (θ5) and the initial contact angle (θ0) is preferably any value, more preferably 1° or more, and even more preferably 3° or more. The upper limit of the absolute value of the difference is not particularly limited, but is, for example, 15° or less.
When the relationship between the initial contact angle (θ0) and the contact angle (θ5) in the hydrophilic layer satisfies the condition (d), the smaller the absolute value of the difference between the contact angle (θ5) and the initial contact angle (θ0) is, the better. Specifically, the absolute value is 20° or less, preferably 15° or less, and more preferably 10° or less.

Furthermore, when the hydrophilized layer exhibits both hydrophilicity and water-slip properties, for example, it is preferable that the hydrophilized layer satisfies the above-mentioned initial contact angle (θ0) and the following (i).
(i) The sliding angle (θs) measured by the method described in the <Evaluation of water sliding property> in the Examples is less than 30°

The sliding angle (θs) of the hydrophilic layer is preferably 20° or less, more preferably 15° or less or less than 15°, even more preferably 12° or less, and particularly preferably 10° or less.
Conventional sliding angle measurements did not take into account the influence of droplet wetting and spreading due to the hydrophilicity of the measurement substrate surface. Therefore, for hydrophilic tangible objects (i.e., hydrophilized layers), a good sliding angle measured using conventional measurement methods did not necessarily mean good water-slip properties. In other words, conventional methods measured the sliding angle as the inclination angle of the hydrophilized layer when a water droplet was placed on it and the water droplet moved a certain distance in the sliding direction. However, when a water droplet was placed on the hydrophilized layer, the wetting and spreading motion of the water droplet was observed. Measuring the sliding angle under this condition resulted in simultaneous observation of both sliding and wetting motions, which sometimes made it difficult to accurately evaluate water-slip properties. While it was possible to measure the sliding angle after the wetting and spreading motion reached an equilibrium point, this was undesirable because the water in the droplet could evaporate before reaching the equilibrium point. Therefore, in order for a hydrophilized layer with hydrophilic properties to have good water-slip properties, a small sliding angle is required in a measurement system that takes into account the influence of wetting and spreading of the water droplet.
On the other hand, in the evaluation of water sliding property of the present invention, as will be described later, an evaluation method is adopted that aims to extract the end point movement due to sliding by excluding the influence of the end point movement due to wetting and spreading from the end point movement of the water droplet in the sliding direction. In this evaluation method, the hydrophilized layer of the present invention, which can reduce the sliding angle, can be said to have good water sliding property while being hydrophilic.

The shape of the hydrophilic layer is not particularly limited, but examples include a coating film, a surface (film, sheet, plate), granules, powder, lumps, particle aggregates, spheres, ellipsoids, lenses, columns, rods, cones, cylinders, needles, fibers, fiber aggregates (e.g., woven fabric, nonwoven fabric, etc.), hollow fibers, and porous shapes. Of these, a coating film is preferred.

The thickness of the hydrophilic layer is not particularly limited, but is, for example, 0.1 to 80 μm, preferably 0.1 to 50 μm, more preferably 0.1 to 10 μm, and even more preferably 0.3 to 5 μm.

The method for producing the hydrophilic layer is not particularly limited, and any conventionally known method may be used as appropriate. For example, the hydrophilic layer can be obtained by molding or forming the hydrophilic treatment composition described above.

Furthermore, according to the present invention, by providing a hydrophilic layer containing the hydrophilic treatment composition of the present invention on the surface of a substrate, which is the object of hydrophilic treatment, it is possible to impart a sustained hydrophilic effect and/or water slippage to the surface of the substrate. That is, according to the present invention, by providing a hydrophilic layer containing the hydrophilic treatment composition on the surface of the substrate, it is possible to provide sustained hydrophilicity and/or water slippage to the surface of the substrate. In either the case of forming a hydrophilic layer containing the hydrophilic treatment composition or the case of forming a hydrophilic layer containing the hydrophilic treatment composition on the surface of the substrate, the method of forming or shaping is not particularly limited, and may be appropriately selected depending on the type of composition used and the shape of the desired substrate.
Examples of the molding or forming method include a method of forming a film by applying the hydrophilic treatment composition to a substrate by a method such as coating, spraying, printing, or impregnation; a method of forming a molded article from the hydrophilic treatment composition by injection molding, extrusion molding, vacuum molding, compression molding, or blow molding; and a method of laminating the hydrophilic treatment composition on the surface of a substrate. Among these, it is preferable to form a hydrophilic layer containing the hydrophilic treatment composition on the surface of the substrate by applying the hydrophilic treatment composition to the substrate.

The object to be hydrophilized, such as a substrate, may be made of a resin, and examples thereof include polyester, polyethylene, polypropylene, triacetyl cellulose, polystyrene, polycarbonate, polyether sulfone, cellophane, polyamide, polyvinyl alcohol, polyacetal, polyphenylene ether, polyphenylene sulfide, polyimide, polyamideimide, polyetherimide, polyetheretherketone, fluororesins such as polytetrafluoroethylene, ABS resin, Noryl resin, acrylic resin, epoxy resin, and cellophane.
In addition to the above-mentioned resins, examples of the material include inorganic materials such as glass, slate, and mortar; metals such as stainless steel plate, iron, copper, aluminum, magnesium, and zinc, and alloys thereof; but the present invention is not limited to these examples.
The object to be hydrophilized may be composed of only a single layer, or may have a laminated structure in which a plurality of layers are laminated. In particular, the object to be hydrophilized is preferably a fin material of a heat exchanger, and more preferably, the fin material is made of aluminum.

When a hydrophilic treatment composition is applied to an object to be hydrophilic treated by coating, spraying, printing, impregnation or other methods to form a coating film (hereinafter referred to as a hydrophilic coating film), if a crosslinking agent is to be applied to the hydrophilic coating film, the crosslinking agent may be mixed in advance with the hydrophilic treatment composition or may be added after the film is formed.
When the hydrophilic layer containing the hydrophilic treatment composition of the present invention is applied to a fin material (particularly an aluminum fin material) of a heat exchanger, the hydrophilic layer may be formed directly on the surface of the fin material (particularly an aluminum plate constituting the aluminum fin material) (i.e., the fin material (particularly an aluminum plate constituting the aluminum fin material) and the hydrophilic layer may be directly laminated), or the hydrophilic layer may be formed via an underlayer such as a chemical conversion treatment layer and/or a resin coating layer provided on the surface of the fin material (particularly an aluminum plate constituting the aluminum fin material) for the purpose of preventing corrosion of the fin material (particularly the aluminum constituting the aluminum fin material) (i.e., the hydrophilic layer is laminated on the fin material (particularly an aluminum plate constituting the aluminum fin material) via an underlayer).

As the chemical conversion treatment layer, a conventionally known layer can be used, for example, a layer made of an inorganic oxide or an inorganic-organic composite compound.
The inorganic material constituting the inorganic oxide or inorganic-organic composite compound preferably contains chromium, zirconium or titanium as a main component.
The layer made of an inorganic oxide can be formed, for example, by subjecting the fin material (particularly the aluminum plate that constitutes the aluminum fin material) to a chromate phosphate treatment, a zirconium phosphate treatment, a zirconium oxide treatment, a chromate chromate phosphate treatment, a zinc phosphate treatment, a titanic acid phosphate treatment, or the like.
Furthermore, a layer made of an inorganic-organic composite compound can be formed, for example, by subjecting a fin material (particularly an aluminum plate constituting an aluminum fin material) to a coating type chromate treatment, a coating type zirconium treatment, etc. Specific examples of such inorganic-organic composite compounds include an acrylic-zirconium composite.

The resin coating layer can be formed, for example, by applying a resin-containing resin paint to the fin material (particularly onto the aluminum plate or chemical conversion coating layer that constitutes the aluminum fin material) and solidifying it by drying or the like.
The resin may be a conventionally known resin, such as a polyester-based, polyolefin-based, epoxy-based, urethane-based, or (meth)acrylic resin, and a mixture of one or more of these may be used. Among these, a (meth)acrylic resin is preferred, and a polymer having a (meth)acrylic resin or the like as a main chain and an oxazoline group in a side chain may be used.

In addition to the above, the resin coating layer may contain other optional components as long as the effects of the present invention are not impaired.
Optional components include various paint additives for improving coatability, workability, film properties, etc., such as aqueous solvents, crosslinking agents, surfactants, film-forming aids, surface conditioners, wetting and dispersing agents, anti-settling agents, antioxidants, anti-foaming agents, rust inhibitors, antibacterial agents, anti-fungal agents, etc. These paint additives may be used alone or in combination of two or more.

The method for producing the hydrophilic layer is not particularly limited, but may include a drying process or a curing process after the film-forming process such as coating, spraying, printing, or impregnation.

This application claims the benefit of priority from Japanese Patent Application No. 2024-070007, filed April 23, 2024. The entire contents of the specification of Japanese Patent Application No. 2024-070007, filed April 23, 2024, are incorporated herein by reference.

The present invention will be explained in more detail below using examples, but the present invention is not limited to the examples below, and it is of course possible to make appropriate modifications within the scope of the intent described above and below, all of which are within the technical scope of the present invention. In the following, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass."

<Gel Permeation Chromatography (GPC)>
The weight average molecular weight of the copolymers produced in the following Production Examples was measured by the following method.
Apparatus: Alliance (e2695) (manufactured by Waters)
Analysis software: Empower2 Professional + GPC option (Waters)
Columns used: TSKguard columns SWXL (inner diameter: 6.0 mm x 40 mm) + TSKgel G4000SWXL (inner diameter: 7.8 mm x 300 mm) + G3000SWXL (inner diameter: 7.8 mm x 300 mm) + G2000SWXL (inner diameter: 7.8 mm x 300 mm) (all manufactured by Tosoh Corporation)
Detector: differential refractometer (RI) detector (Waters 2414, manufactured by Waters Corporation)
Eluent: A solution prepared by dissolving 115.6 g of sodium acetate trihydrate in a mixed solvent of 10,999 g of ion-exchanged water and 6,001 g of acetonitrile, and further adjusting the pH to 6.0 with acetic acid.
Flow rate: 1 mL/min Column temperature: 40°C
Measurement time: 45 minutes Sample solution injection amount: 100 μL (eluent solution with a sample concentration of 0.5% by mass)
GPC standard sample: polyethylene glycol manufactured by Tosoh Corporation, Mp=255,000, 200,000, 107,000, 72,750, 44,900, 31,400, 21,300, 11,840, 6,450, 4,020, 1,470
Calibration curve: Prepared using a cubic equation using the Mp values of the above polyethylene glycol.

<High-Performance Liquid Chromatography (LC)>
In the following production examples, the remaining amounts of various monomers used as reaction raw materials were measured under the following conditions and used to calculate the composition of the copolymer.
Apparatus: Alliance 2695 (manufactured by Waters)
Analysis software: Empower Professional (Waters)
Column: Atlantis dC18 5 μm (inner diameter 4.6 mm × length 250 mm) × 2 (Waters)
Detector: differential refractometer (RI) detector (Waters 2414), multi-wavelength visible-ultraviolet (PDA) detector (Waters 2996)
Solvent: 100 mM sodium acetate aqueous solution and acetonitrile mixed in a ratio of 6:4 Flow rate: 1 mL/min Column temperature: 40°C
Measurement time: 30 minutes Sample solution injection amount: 100 μL (sample concentration: 1% by mass)

<Evaluation of initial hydrophilicity>
Using an automatic contact angle meter ("CA-X" manufactured by Kyowa Interface Science Co., Ltd.), a 2 μL droplet of pure water was prepared at 25° C. and applied to the surface of the coating film (hydrophilized layer) of the film-formed sample prepared as described below, and the contact angle was calculated by the θ/2 method.
The contact angle value 30 seconds after contact with the liquid was taken as the measured value, and five measurements were taken. The average of the three measurements excluding the maximum and minimum values was taken as the initial contact angle of the coating film (hydrophilized layer).
The initial hydrophilicity of the coating film (hydrophilized layer) was quantitatively evaluated according to the following criteria.
◎: Initial contact angle is less than 15° ○: Initial contact angle is 15° or more and less than 40° ×: Initial contact angle is 40° or more

<Evaluation of hydrophilicity retention effect after wet/dry cycle>
The coating film (hydrophilized layer) of a film-formed sample prepared as described below was immersed in pure water for 6 hours, and then, in an environment of 25°C and 50% humidity, the film-formed sample was taken out and placed on a Kimwipe so that the surface to be measured for contact angle (the coated surface of the sample) faced upward, and then covered with another Kimwipe and maintained in this state for 5 seconds.
Thereafter, the sample was removed, and excess water was removed by blowing air onto the contact angle measurement surface until no visible water droplets remained. The sample was then dried in an air-blowing constant temperature incubator ("DNF400" manufactured by Yamato Scientific Co., Ltd.) at 80°C for 2 hours in an air atmosphere to obtain a sample after the wet/dry cycle.
Using an automatic contact angle meter ("CA-X" manufactured by Kyowa Interface Science Co., Ltd.), a 2 μL droplet of pure water was prepared at 25° C. and allowed to adhere to the coating surface of the sample after the wet/dry cycle, and the contact angle was calculated by the θ/2 method.
The contact angle measured 30 seconds after application of the liquid was taken as the measured value, and five measurements were taken. The average of the three measurements, excluding the maximum and minimum values, was taken as the contact angle after the wet/dry cycle. The hydrophilicity retention effect of the coating film after the wet/dry cycle was quantitatively evaluated according to the following criteria.
◎: Contact angle after wet/dry cycle is less than 15° ○: Contact angle after wet/dry cycle is 15° or more and less than 40° ×: Contact angle after wet/dry cycle is 40° or more

<Evaluation of water sliding properties>
To evaluate the sliding property, the sliding angle of a water droplet relative to the coating surface of the film-formed sample was measured.
After the above wet/dry cycle was repeated five times, the water sliding property of the sample was evaluated.
Specifically, using an automatic contact angle meter ("CA-X" manufactured by Kyowa Interface Science Co., Ltd.), a 10 μL droplet of pure water was prepared at 25°C and deposited on the horizontally placed coating surface after a heat cycle (5C) (the coating surface of the sample after the heat cycle). 0.1 seconds after deposition, the sample was gradually tilted at a rate of 2°/sec in 0.5° increments, and the angle at which the droplet began to move was recorded as the measured value. Five measurements were taken, and the average of the three points excluding the maximum and minimum values was taken as the sliding angle θs. The water sliding property of the coating was then quantitatively evaluated according to the following criteria:
◎: sliding angle θs less than 15° ○: sliding angle θs 15° or more and less than 30° ×: sliding angle θs 30° or more Note that, as shown in Figure 1, the movement of the water droplet was determined as follows: R0 was the end point of the water droplet (2a) on the opposite side to the sliding direction 0.1 seconds after it landed on the coating surface of the formed sample 1, and L0 was the end point on the sliding direction side; Rθ was the end point of the water droplet (2b) on the opposite side to the sliding direction at an inclination angle θ, and Lθ was the end point on the sliding direction side; the movement distance of the end point on the opposite side to the sliding direction of the water droplet dR = -|Rθ - R0|, and the movement distance of the end point on the sliding direction side of the water droplet dL = |Lθ - L0|. The water droplet was determined to have moved when dR + dL > 1.00 mm was first satisfied, and the inclination angle θ at that time was defined as the sliding angle θs.
This definition is an evaluation method intended to extract the end point movement due to sliding by excluding the influence of the end point movement due to wetting and spreading from the end point movement of the water droplet in the sliding direction.

[Copolymer (A)]
Production Example 1
Ion-exchanged water was charged into a glass reaction vessel equipped with a thermometer, a stirrer, a dropping device, a nitrogen inlet tube, and a reflux condenser. Subsequently, the atmosphere inside the reaction vessel was replaced with nitrogen while stirring, and the temperature was raised to 60°C under a nitrogen atmosphere, after which an aqueous hydrogen peroxide solution was added.
Next, an aqueous solution of acrylic acid (AA), an unsaturated polyalkylene glycol monomer (IPN-10) in which an average of 10 moles of ethylene oxide was added to 3-methyl-3-buten-1-ol, and 3-mercaptopropionic acid dissolved in ion-exchanged water was added dropwise over 4 hours, and an aqueous solution of L-ascorbic acid dissolved in ion-exchanged water was added dropwise over 4.5 hours at a constant rate. The temperature during this period was kept constant at 60°C, and after completion of the addition, the temperature was maintained at 60°C for 1 hour to terminate the polymerization reaction. Thereafter, the pH of the reaction solution was neutralized to pH = 6 using an aqueous sodium hydroxide solution at a temperature below the polymerization reaction temperature, and an aqueous solution containing copolymer (1) was obtained.

Production Examples 2 to 6, 11, and 12
Copolymers (2) to (6), (11), and (12) were produced in the same manner as in Production Example 1, except that the proportions of the structural units were changed as shown in Table 1, and in Production Examples 11 and 12, the structural unit (A2) was further changed.

Production Examples 7, 8, and 13
Copolymers (7), (8), and (13) were produced in the same manner as in Production Example 1, except that acrylic acid (AA) was replaced with 2-hydroxyethyl acrylate (HEA), the proportions of the various structural units were changed, and in Production Example 13, the structural unit (A2) was changed, as shown in Table 1.

Production Examples 9, 10, and 14
Copolymers (9), (10), and (14) were produced in the same manner as in Production Example 1, except that acrylic acid (AA) and 2-hydroxyethyl acrylate (HEA) were used in combination and the proportions of each structural unit were changed as shown in Table 1, and in Production Example 14, the structural unit (A2) was changed.

Production Examples 15 and 16
Copolymers (15) and (16) were produced in the same manner as in Example 1, except that the structural unit (A2) was not used.

Production Example 17
(Hydrophilic particles (1))
To a stainless steel first reaction vessel equipped with a stirrer, a thermometer, and a cooler, 1,128 parts by mass of deionized water and 1.05 parts by mass of ADEKA REASOAP SR-20 (active ingredient 100% by mass, manufactured by ADEKA Corporation) diluted with ion-exchanged water to 10% by mass of the active ingredient (hereinafter referred to as "SR-20 (active ingredient 10% by mass)") were added, and the internal temperature was raised to 75°C and maintained at that temperature.
On the other hand, in a second reaction kettle different from the first reaction kettle, 70 parts by mass of methyl methacrylate (MMA) and 30 parts by mass of divinylbenzene (DVB810 manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.) were mixed to prepare 100 parts by mass of monomer composition A. Furthermore, in a third reaction kettle different from the first and second reaction kettle, 80 parts by mass of methyl 2-hydroxymethylacrylate (RHMA), 10 parts by mass of divinylbenzene (DVB810 manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.), and 10 parts by mass of methoxypolyethylene glycol monomethacrylate (BLEMMER PME400 manufactured by NOF Corporation) were mixed to prepare 100 parts by mass of monomer composition B.
Next, the atmosphere inside the first reaction vessel was replaced with nitrogen gas, and then 100 parts by mass of the monomer composition A, 20 parts by mass of hydrogen peroxide solution (concentration: 3.35% by mass), and 20 parts by mass of an L-ascorbic acid aqueous solution (concentration: 5.0% by mass) were added to the first reaction vessel, and the internal temperature was maintained at 75°C, and an initial polymerization reaction was carried out over 2 hours.
Subsequently, 100 parts by mass of the monomer composition B, 100 parts by mass of aqueous hydrogen peroxide (concentration: 0.83% by mass), 100 parts by mass of an aqueous L-ascorbic acid solution (concentration: 1.25% by mass), and 100 parts by mass of a mixed composition of 7.04 parts by mass of SR-20 (active ingredient: 10% by mass), 0.36 parts by mass of an aqueous ammonia solution (concentration: 28% by mass), and 92.6 parts by mass of ion-exchanged water were uniformly added dropwise to the first reaction kettle from different inlets over a period of 3 hours.
After the dropwise addition was completed, the internal temperature of the first reaction vessel was maintained at 75° C. and the mixture was aged at this temperature for 2 hours, and then the reaction solution was cooled to obtain an aqueous dispersion of polymer particles (a1).
10 parts by mass of the aqueous dispersion of polymer particles (a1) obtained above and 1.2 parts by mass of an aqueous sodium hydroxide solution (concentration: 20%) as a basic aqueous solution were added to a first reaction kettle and stirred overnight at 25° C. to obtain an aqueous dispersion of hydrolyzed hydrophilic particles (1) shown in Table 2. The volume average particle diameter of the obtained hydrophilic particles (1) was 302 nm.

[Hydrophilic treatment composition]
Hydrophilic treatment composition 1
The copolymer (1) prepared in Production Example 1 was used to prepare a hydrophilic treatment composition 1.
Copolymer (1) and an aqueous crosslinking agent ("Epocross WS-700" manufactured by Nippon Shokubai Co., Ltd.; solid content 25% by mass) were blended to a solid content ratio of 100:18 (by mass), and the mixture was diluted with pure water to a final solid content of 5.5% by mass, thereby obtaining a hydrophilic treatment composition 1.

Hydrophilic treatment compositions 2 to 14, 18, and 19
Hydrophilic treatment compositions 2 to 14, 18 and 19 were produced in the same manner as in Example 1, except that the copolymer (1) was changed as shown in Table 3.

Hydrophilic treatment composition 15
A hydrophilic treatment composition 15 was produced using the copolymer (5) and the hydrophilic particles (1).
A hydrophilic resin copolymer (5), hydrophilic particles (1), and an aqueous crosslinking agent ("Epocross WS-700" manufactured by Nippon Shokubai Co., Ltd.; solid content 25% by mass) were blended in a solid content ratio of 100:100:18 (by mass), and the mixture was diluted with pure water to a final solid content of 5.5% by mass, thereby obtaining a hydrophilic treatment composition 15.

Hydrophilic treatment compositions 16 and 17
Hydrophilic treatment compositions 16 and 17 were prepared in the same manner as in Example 15, except that the copolymer was changed as shown in Table 1.

[Film-formed sample]
Film-formed sample 1
A film-formed sample 1 was prepared using the hydrophilic treatment composition 1. Specifically, the hydrophilic treatment composition (1) was applied to the undercoat layer-coated surface of an aluminum plate using a bar coater so that the film thickness after coating would be 1.0 μm, and the composition was dried at 200° C. for 60 seconds in an automatic discharge dryer ("AT-101 (standard type)" manufactured by Tojo Netsugaku Co., Ltd.), to obtain a film-formed sample 1 having a laminated coating film.

Film-formed samples 2 to 19
Film-formed samples 2 to 19 were prepared in the same manner as film-formed sample 1, except that the hydrophilic treatment composition was changed.

In the table,
AA: acrylic acid HEA: 2-hydroxyethyl acrylate IPN-10: ethylene oxide adduct of 3-methyl-3-buten-1-ol (average number of moles added: 10 moles)
IPN-50: ethylene oxide adduct of 3-methyl-3-buten-1-ol (average number of moles added: 50 moles)
MLA-200: ethylene oxide adduct of methallyl alcohol (average number of moles added: 200 moles)
The amount of the basic aqueous solution added represents the number of moles of the added base when the number of moles of RHMA in the polymer particles (hydrophilic particles) is taken as 100 mol %, that is, corresponds to the ionization rate and hydrolysis rate.

The results in Table 4 show that by using the hydrophilic treatment composition of the present invention, it is possible to impart good hydrophilicity to a coating film while also imparting good water-slip properties. Furthermore, it is possible to improve the durability of the hydrophilicity of the resulting coating film after wet/dry cycles.

1. Film-formed sample 2a. Water droplet 0.1 seconds after landing 2b. Water droplet at tilt angle θ R0. End point on the opposite side of the sliding direction of the water droplet 0.1 seconds after landing L0. End point on the sliding direction side of the water droplet 0.1 seconds after landing Rθ. End point on the opposite side of the sliding direction of the water droplet at tilt angle θ Lθ. End point on the sliding direction side of the water droplet at tilt angle θ

Claims (17)

at least one structural unit (A1) selected from a structural unit (A11) derived from a polymerizable monomer having a carboxyl group and a structural unit (A12) derived from a polymerizable monomer having a hydroxyl group;
A hydrophilization treatment composition, characterized by containing a copolymer (A) having a structural unit (A2) derived from a monomer in which a polyoxyalkylene group and a hydrocarbon group having a polymerizable double bond are linked via an ether bond. The hydrophilic treatment composition according to claim 1, wherein the hydrocarbon group possessed by the structural unit (A2) is an aliphatic hydrocarbon group. 2. The hydrophilic treatment composition according to claim 1, wherein the structural unit (A2) is derived from a monomer represented by the following formula:
(In the formula, R ¹ and R ² each independently represent a hydrogen atom or a methyl group. R ³ represents an alkylene group having 1 to 4 carbon atoms. R ⁴ represents an alkylene group having 2 to 4 carbon atoms. a is 0 or 1, and b represents the average number of moles added of 2 to 500.) The hydrophilic treatment composition according to claim 1, further comprising hydrophilic particles (B) having at least one group selected from an acid group, a hydroxyl group, a polyoxyalkylene chain, and a polyvinylpyrrolidone chain. The hydrophilic treatment composition according to claim 1, further comprising a crosslinking agent. The hydrophilic treatment composition according to claim 5, wherein the crosslinking agent is a crosslinking agent having two or more oxazoline groups per molecule. The hydrophilic treatment composition according to claim 4, wherein the volume average particle diameter of the hydrophilic particles is 10 nm to 10 μm. The hydrophilic treatment composition according to claim 1 or 5, wherein the object to be hydrophilically treated is a heat exchanger fin. The hydrophilic treatment composition according to claim 1, wherein the structural unit (A11) derived from a polymerizable monomer having a carboxyl group is a structural unit derived from an unsaturated monocarboxylic acid or a salt thereof. The hydrophilic treatment composition according to claim 9, wherein the unsaturated monocarboxylic acid or its salt is acrylic acid, methacrylic acid, or a salt thereof. The hydrophilic treatment composition according to claim 1, wherein the structural unit (A12) derived from a polymerizable monomer having a hydroxyl group is a structural unit derived from a (meth)acrylic acid hydroxyalkyl ester. The hydrophilic treatment composition according to claim 1, wherein the structural unit (A2) is a structural unit derived from an ethylene oxide adduct of 2-methyl-2-propen-1-ol or an ethylene oxide adduct of 3-methyl-3-buten-1-ol. The hydrophilic treatment composition according to claim 1, wherein the content of the structural unit (A2) is 30 to 99 parts by mass per 100 parts by mass of the total of the structural unit (A1) and the structural unit (A2). The hydrophilic treatment composition according to claim 1, wherein the total content of the structural unit (A1) and the structural unit (A2) is 70 to 100 parts by mass per 100 parts by mass of the copolymer (A). The hydrophilic treatment composition according to claim 4, wherein the hydrophilic particles (B) are hydrophilic particles (B1) containing a hydrophilic polymer (b2) having an acid group and a hydroxyl group. at least one structural unit (A1) selected from a structural unit (A11) derived from a polymerizable monomer having a carboxyl group and a structural unit (A12) derived from a polymerizable monomer having a hydroxyl group;
A heat exchanger fin having a hydrophilized layer formed on its surface, the hydrophilized layer including a copolymer (A) having a structural unit (A2) derived from a monomer in which a polyoxyalkylene group and a hydrocarbon group having a polymerizable double bond are linked via an ether bond. The fin according to claim 16, wherein the thickness of the hydrophilic layer is 0.1 to 80 μm.