CN118974103A - Method for producing fluorinated polymer, fluorinated polymer, coating material and substrate with coating film - Google Patents

Abstract

Provided are a method for producing a fluorine-containing polymer capable of forming a coating film having excellent weather resistance, a fluorine-containing polymer, a coating material, and a substrate with a coating film. The method for producing a fluorine-containing polymer of the present invention comprises polymerizing at least one fluorine-containing monomer selected from the group consisting of _CF2 = _CF2 , _CF2 =CFCl, _CF2 =CHF, and _CH2 = _CF2 with a vinyl ether having no fluorine atom and no reactive group and a monomer having a reactive group in the presence of at least one organic solvent selected from the group consisting of methyl ethyl ketone, acetone, n-butyl acetate, and tetrahydrofuran and in the absence of a vinyl ester to obtain a fluorine-containing polymer.

Description

Method for producing fluorinated polymer, fluorinated polymer, coating material and substrate with coating film

Technical Field

The present invention relates to a method for producing a fluorine-containing polymer, a fluorine-containing polymer, a coating and a substrate with a coating film.

Background Art

Coating materials containing fluorine-containing polymers are widely used because they can form coating films having excellent weather resistance, etc. Patent Document 1 discloses a method of using xylene as a polymerization solvent when producing a fluorine-containing polymer used in a coating material.

Prior art literature

Patent Literature

Patent Document 1: International Publication No. 2017/094861

Summary of the invention

Problem that the invention aims to solve

In recent years, coating materials containing fluorine-containing polymers have been used in various environments, and therefore, there is a demand for further improvement in the weather resistance of coating films obtained using coating materials containing fluorine-containing polymers.

The present inventors: As described in Patent Document 1, a fluorinated polymer was produced using xylene as a polymerization solvent, and found that there is room for improvement in the weather resistance of a coating film obtained using the fluorinated polymer.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing a fluorinated polymer capable of forming a coating film having excellent weather resistance, a fluorinated polymer, a coating material, and a substrate with a coating film.

Solutions for solving problems

The present inventors have conducted intensive studies on the above-mentioned problems and have found that a coating film having excellent weather resistance can be formed by using a fluorinated polymer obtained by polymerizing a specific monomer in the presence of a specific organic solvent and the absence of a vinyl ester, thereby arriving at the present invention.

That is, the inventors have found that the above-mentioned problems can be solved by the following configuration.

[1] A method for producing a fluorinated polymer, comprising: producing a fluorinated polymer in the presence of at least one organic solvent selected from the group consisting of methyl ethyl ketone, acetone, n-butyl acetate and tetrahydrofuran and in the absence of a vinyl ester.

At least one fluorine-containing monomer selected from the group consisting of _CF2 = _CF2 , _CF2 =CFCl, _CF2 =CHF and _CH2 = _CF2 , a vinyl ether having neither a fluorine atom nor a reactive group, and a monomer having a reactive group are polymerized to obtain a fluorine-containing polymer.

[2] The method for producing a fluorinated polymer according to [1], wherein the organic solvent is at least one organic solvent selected from the group consisting of methyl ethyl ketone, acetone and n-butyl acetate.

[3] The method for producing a fluorinated polymer according to [1] or [2], wherein the fluorinated monomer is at least one monomer selected from the group consisting of CF ₂ ═CF ₂ and CF ₂ ═CFCl.

[4] The method for producing a fluorinated polymer according to any one of [1] to [3], wherein the reactive group is at least one group selected from the group consisting of a hydroxyl group, an amino group, an epoxy group, an oxetanyl group, a hydrolyzable silyl group, a sulfone group and a carboxyl group.

[5] A fluorine-containing polymer, characterized in that it has:

a fluorine-containing unit based on at least one fluorine-containing monomer selected from the group consisting of CF ₂ ═CF ₂ , CF ₂ ═CFCl, CF ₂ ═CHF and CH ₂ ═CF ₂ ,

A non-fluorinated unit based on a vinyl ether having no fluorine atom and no reactive group, and

Units based on monomers having reactive groups,

The fluoropolymer has no vinyl ester-based units,

The light transmittance of a film obtained by using the fluorinated polymer in the wavelength region of 260 nm to 300 nm is 50% or more when the thickness of the film is set to 40 μm.

[6] A coating comprising the fluorine-containing polymer described in [5].

[7] A substrate with a coating film, comprising a substrate and a coating film formed of the coating material according to [6] and disposed on the substrate.

Effects of the Invention

According to the present invention, there can be provided a method for producing a fluorine-containing polymer capable of forming a coating film having excellent weather resistance, a fluorine-containing polymer, a coating material, and a substrate with a coating film.

DETAILED DESCRIPTION

The terms used in the present invention are explained below.

The numerical range represented by "～" refers to a range containing the numerical values recorded before and after "～" as the lower limit and the upper limit. In the numerical range recorded in stages in this specification, the upper limit or lower limit recorded in a certain numerical range can be replaced by the upper limit or lower limit of the numerical range recorded in other stages. In addition, in the numerical range recorded in this specification, the upper limit or lower limit recorded in a certain numerical range can also be replaced by the value shown in the embodiment.

In this specification, each component may be used alone or in combination of two or more substances that meet the requirements of each component. Here, when two or more substances are used in combination, the content of the component refers to the total content of the substances used in combination unless otherwise specified.

In the present specification, a combination of two or more preferred aspects is a more preferred aspect.

Unit refers to the general term for the atomic group based on one molecule of the above monomer directly formed by polymerization of the monomer and the atomic group obtained by chemical conversion of a part of the above atomic group. The content (mol %) of each unit relative to all units contained in the polymer is obtained by analyzing the polymer by nuclear magnetic resonance spectroscopy, and can also be determined by the input amount of the components used in the production of the polymer.

“(Meth)acrylic acid” is a general term for “acrylic acid” and “methacrylic acid”, and “(meth)acrylate” is a general term for “acrylate” and “methacrylate”.

The hydrolyzable silyl group refers to a group that can undergo a hydrolysis reaction to form a silanol group.

The acid value and the hydroxyl value are values measured by the method according to JIS K 0070-3 (1992), respectively.

The glass transition temperature (Tg) is the midpoint glass transition temperature of a polymer as measured by differential scanning calorimetry (DSC).

The number average molecular weight (Mn) is a value measured by size exclusion chromatography (gel permeation chromatography) using polystyrene as a standard substance.

The method for producing a fluorine-containing polymer of the present invention (hereinafter also referred to as the present production method) is a method comprising polymerizing at least one fluorine-containing monomer selected from the group consisting of _CF2 = _CF2 , _CF2 =CFCl, CF2=CHF and _CH2 = _CF2 with a vinyl ether having neither a fluorine atom nor a reactive group and _a monomer having a reactive group in the presence of at least one organic solvent selected from the group consisting of methyl ethyl ketone, acetone, n-butyl acetate and tetrahydrofuran (hereinafter also referred to as a specific organic solvent) and in the absence of a vinyl ester to obtain a fluorine-containing polymer.

The fluorine-containing polymer obtained by the present production method can form a coating film having excellent weather resistance. The reason for this is not necessarily clear, but it is considered as follows.

As the solvent used when polymerizing the monomer used in manufacturing the fluoropolymer (hereinafter also referred to as the polymerization solvent), when an organic solvent other than a specific organic solvent is used, a structure that easily absorbs ultraviolet rays from the polymerization solvent is sometimes introduced into the fluoropolymer. For example, when xylene is used as the polymerization solvent, benzene rings, etc. are sometimes introduced into the fluoropolymer in trace amounts. In view of such a problem, in this manufacturing method, a specific organic solvent is used as the polymerization solvent, and therefore, a structure that reduces weather resistance from the polymerization solvent becomes difficult to be introduced into the fluoropolymer. It is thus inferred that the weather resistance of the coating film obtained using the fluoropolymer is improved.

The specific organic solvent is used as a polymerization solvent in the present production method.

The specific organic solvent is at least one organic solvent selected from the group consisting of methyl ethyl ketone, acetone, n-butyl acetate and tetrahydrofuran. From the viewpoint of more excellent effects of the present invention, at least one organic solvent selected from the group consisting of methyl ethyl ketone, acetone and n-butyl acetate is preferred.

Two or more specific organic solvents may be used in combination.

The amount of the specific organic solvent used is preferably from 1 to 60 parts by mass, more preferably from 30 to 50 parts by mass, based on 100 parts by mass of the total amount of monomers charged to produce the fluorinated polymer.

In the present production method, an organic solvent other than the specific organic solvent (hereinafter also referred to as other organic solvent) may be used. However, since the effects of the present invention are more excellent, it is preferred that substantially no other organic solvent is used.

Substantially no other organic solvent is used means that the amount of other organic solvent used is 1 part by mass or less based on 100 parts by mass of the total mass of the monomers used for producing the fluorinated polymer.

Specific examples of other organic solvents include xylene, toluene, and ethylbenzene.

The polymerization of each monomer in the present production method is carried out in the absence of vinyl ester. Therefore, the fluorinated polymer obtained by the present production method does not have units derived from vinyl ester.

Specific examples of the vinyl ester include vinyl acetate, vinyl pivalate, vinyl neononanoate (trade name VevoVa 9 from HEXION), vinyl neodecanoate (trade name VevoVa 10 from HEXION), vinyl versatate, vinyl benzoate, and vinyl tert-butylbenzoate.

The fluorine-based monomer is at least one monomer selected from the group consisting of CF ₂ ═CF ₂ , CF ₂ ═CFCl, CF ₂ ═CHF and CH ₂ ═CF ₂ (hereinafter also referred to as monomer a11), and is used as a monomer for producing a fluorine-containing polymer.

From the viewpoint of more excellent effects of the present invention and polymerizability with monomers other than the monomer a11, the monomer a11 is preferably at least one selected from the group consisting of CF ₂ ═CF ₂ and CF ₂ ═CFCl, and more preferably CF ₂ ═CFCl.

Two or more types of the monomer a11 may be used in combination.

The amount of the monomer a11 charged is preferably 20 to 70 mol %, more preferably 30 to 60 mol %, further preferably 45 to 55 mol %, based on the total amount of monomers charged to produce the fluorinated polymer, because the effect of the present invention is more excellent.

Vinyl ether having neither a fluorine atom nor a reactive group (hereinafter also referred to as monomer a12) is used as a monomer for producing a fluorine-containing polymer.

Specific examples of the monomer a12 include ethyl vinyl ether, tert-butyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexyl vinyl ether, and cyclohexyl methyl vinyl ether.

Two or more monomers a12 may be used in combination.

The amount of the monomer a12 charged is preferably 5 to 60 mol %, more preferably 10 to 50 mol %, based on the total amount of monomers charged to produce the fluorinated polymer, because the effect of the present invention is more excellent.

A monomer having a reactive group (hereinafter also referred to as monomer a13) is used as a monomer for producing a fluorinated polymer. Monomer a13 does not have a vinyl ester structure (CH ₂ =CHOC(O)-).

The monomer a13 preferably has no fluorine atom.

The reactive group may be at least one group selected from the group consisting of a hydroxyl group, an amino group, an epoxy group, an oxetanyl group, a hydrolyzable silyl group, a sulfo group, and a carboxyl group. The sulfo group and the carboxyl group may be ionized to form -SO ₃ - or -COO-, or may be salted to form -SO ₃ ^- Na ⁺ or -COO-Na ⁺ .

The monomer a13 preferably has a hydroxyl group or a carboxyl group as a reactive group, and more preferably has a hydroxyl group, because the strength of the coating film obtained with the fluorinated polymer is more excellent.

Examples of the monomer a13 having a hydroxyl group include vinyl ethers, allyl ethers, allyl esters, (meth)acrylates, and allyl alcohols having a hydroxyl group. The monomer a13 having a hydroxyl group is preferably hydroxy vinyl ether or hydroxy allyl ether.

As the monomer a13 having a hydroxyl group, a monomer represented by the formula X ¹ -Z ¹ is preferred.

X ¹ is CH ₂ =CHC(O)O-, CH ₂ =C(CH ₃ )C(O)O-, CH ₂ =CHCH ₂ OC(O)-, CH ₂ =CHO- or CH ₂ =CHCH ₂ O-, preferably CH ₂ =CHO- or CH ₂ =CHCH ₂ O-.

^Z1 is a monovalent organic group having 2 to 42 carbon atoms and having a hydroxyl group. The organic group may be linear or branched. In addition, the organic group may consist of only a ring structure or may include a ring structure.

As the organic group, an alkyl group having 2 to 6 carbon atoms and having a hydroxyl group, an alkyl group having a cycloalkylene group having 6 to 8 carbon atoms and having a hydroxyl group, or a polyoxyalkylene group having a hydroxyl group is preferred.

Specific examples of the monomer a13 having _a hydroxyl group include _CH2 =CHO- _{CH2 - cycloC6H10} - _CH2OH , _{CH2 = CHCH2O} - _{CH2 -} cycloC6H10 _{- CH2OH} , _{CH2 =} CHO- _{CH2 -} cycloC6H10 _{- CH2- ( OCH2CH2} ) _15OH , _{CH2 = CHOCH2CH2OH , CH2 = CHCH2OCH2CH2OH , CH2 = CHOCH2CH2CH2CH2OH ,} and _{CH2 = CHCH2OCH2CH2CH2CH2OH} .

In addition, "-cycloC ₆ H ₁₀ -" represents a cyclohexylene group, and the bonding site of "-cycloC ₆ H ₁₀ -" is usually 1,4-.

Examples of the monomer a13 having a carboxyl group include unsaturated carboxylic acid, (meth)acrylic acid, and monomers obtained by reacting a hydroxyl group of the above-mentioned monomer having a hydroxyl group with a carboxylic anhydride.

Specific examples of the monomer a13 having a carboxyl group include monomers represented by _CH2 =CHCOOH, CH( _CH3 )=CHCOOH, _CH2 =C( _CH3 )COOH, HOOCCH=CHCOOH, _CH2 =CH( _CH2 ) _n11COOH (wherein n11 represents an integer of 1 to 10) and _CH2 =CHO( _CH2 ) _n12OC (O _{)CH2CH2COOH (} wherein n12 represents an integer of 1 to 10).

Two or more monomers a13 may be used in combination.

The amount of the monomer a13 charged is preferably 0.1 to 45 mol %, more preferably 1 to 30 mol %, further preferably 5 to 20 mol %, based on the total amount of monomers charged to produce the fluorinated polymer, because the effect of the present invention is more excellent.

In the present production method, monomers other than monomer a11, monomer a12 and monomer a13 (excluding monomers having a vinyl ether structure) may be used, but in order to achieve better effects of the present invention, it is preferred to use only monomer a11, monomer a12 and monomer a13.

The order of adding the monomers may be appropriately set. The monomers may be added simultaneously or continuously in batches.

The present production method is preferably carried out in the presence of a radical polymerization initiator.

Specific examples of free radical polymerization initiators include azo initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobiscyclohexanecarbonitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(2-methylbutyronitrile); and peroxide initiators such as ketone peroxides (e.g., cyclohexanone peroxide), hydroperoxides (e.g., tert-butyl hydroperoxide), diacyl peroxides (e.g., benzoyl peroxide), dialkyl peroxides (e.g., di-tert-butyl peroxide), peroxyketals (e.g., 2,2-di-(tert-butylperoxy)butane), and alkyl peroxyesters (e.g., tert-butyl peroxypivalate).

In the present production method, conventionally known components used for production of fluorinated polymers (hereinafter also referred to as other components) may be used.

Specific examples of other components include chain transfer agents, polymerization inhibitors (such as hydroquinone monomethyl ether), stabilizers (such as bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and methyl-1,2,2,6,6-pentamethyl-4-piperidinyl sebacate), and acid absorbers (such as potassium carbonate and hydrotalcite).

The polymerization form of the fluorinated polymer in the present production method is preferably solution polymerization in which each monomer is dissolved in a specific organic solvent from the viewpoint of polymerization stability.

In the present production method, the polymerization conditions may be appropriately set. For example, the polymerization temperature is usually 50 to 90° C., and the polymerization time is usually 3 to 50 hours.

The fluorinated polymer obtained by the present production method is a copolymer having no units based on vinyl ester but having units based on monomer a11, units based on monomer a12 and units based on monomer a13. In order to achieve a more excellent effect of the present invention, a copolymer composed of units based on monomer a11, units based on monomer a12 and units based on monomer a13 is preferred.

The fluorine-containing polymer of the present invention (hereinafter also referred to as the present fluorine-containing polymer) is a fluorine-containing polymer having a fluorine-based unit based on the above-mentioned monomer a11 (hereinafter also referred to as unit A11), a non-fluorine-based unit based on the above-mentioned monomer a12 (hereinafter also referred to as unit A12) and a unit based on the above-mentioned monomer a13 (hereinafter also referred to as unit A13), and having no unit based on vinyl ester. In addition, the light transmittance of the film obtained using the present fluorine-containing polymer in the wavelength region of 260nm to 300nm is 50% or more when the thickness of the film is 40μm.

The present fluorinated polymer is preferably a fluorinated polymer obtained by the present production method described above, because it is easy to obtain a fluorinated polymer satisfying the above light transmittance when formed into a film.

The present fluorine-containing polymer can form a coating film having excellent weather resistance. The reason for this is not necessarily clear in detail, but it is considered as follows.

The film obtained by using the fluorinated polymer has a high light transmittance in a specific wavelength region (wavelength region of 260nm to 300nm). As a result, the film obtained by using the fluorinated polymer becomes less susceptible to the influence of light in the specific wavelength region, so it is speculated that the weather resistance of the film itself obtained by using the fluorinated polymer is improved.

Unit A11 is a fluorine-based unit based on monomer a11. Monomer a11 is the same as monomer a11 in the above-mentioned method for producing a fluorinated polymer, and therefore, description thereof is omitted. Two or more monomers a11 may be used in combination.

The content of the units A11 is preferably 20 to 70 mol %, more preferably 30 to 60 mol %, further preferably 45 to 55 mol % based on all units contained in the fluorinated polymer, because a film obtained using the fluorinated polymer has better weather resistance.

Unit A12 is a non-fluorine-based unit based on monomer a12. Monomer a12 is the same as monomer a12 in the above-mentioned method for producing a fluorinated polymer, and therefore, description thereof is omitted. Two or more monomers a12 may be used in combination.

The content of the unit A12 is preferably from 5 to 60 mol%, more preferably from 10 to 50 mol%, based on all the units contained in the present fluorinated polymer.

The unit A13 is a unit based on the monomer a13. The monomer a13 is the same as the monomer a13 in the above-mentioned method for producing a fluorinated polymer, and therefore, the description thereof is omitted. Two or more monomers a13 may be used in combination.

The content of the unit A13 is preferably from 0.1 to 45 mol %, more preferably from 1 to 30 mol %, further preferably from 5 to 20 mol %, based on all the units contained in the present fluorinated polymer.

The present fluorinated polymer does not have a unit based on vinyl ester. Specific examples of vinyl ester are as given in the above-mentioned method for producing the fluorinated polymer, and therefore, description thereof is omitted.

The present fluorine-containing polymer preferably consists of the unit A11, the unit A12 and the unit A13 in order to form a coating film having more excellent weather resistance.

The Tg of the present fluorine-containing polymer is preferably 0 to 120°C, more preferably 10 to 70°C, from the viewpoint of scratch resistance.

The Mn of the present fluorinated polymer is preferably from 3,000 to 50,000, more preferably from 5,000 to 30,000, further preferably from 10,000 to 20,000, from the viewpoint of film-forming properties and weather resistance.

When the present fluorinated polymer has a hydroxyl value, the hydroxyl value of the specific fluorinated polymer is preferably 1 to 200 mgKOH/g, more preferably 5 to 100 mgKOH/g, further preferably 40 to 60 mgKOH/g, from the viewpoint of water resistance.

When the present fluorinated polymer has an acid value, the acid value of the specific fluorinated polymer is preferably from 1 to 30 mgKOH/g, more preferably from 1 to 10 mgKOH/g, from the viewpoint of pigment dispersibility.

The light transmittance of a film obtained using the present fluorinated polymer in the wavelength region of 260 nm to 300 nm is 50% or more when the film thickness is 40 μm. The upper limit of the light transmittance is usually 100%.

Here, in the present invention, the light transmittance value being X% or more means that when the transmittance is calculated at every 0.5 nm in the wavelength range of 260 nm to 300 nm, the transmittance at each wavelength is X% or more.

The detailed method for measuring the light transmittance is described in the Examples section below.

The coating material of the present invention (hereinafter also referred to as the present coating material) comprises the above-mentioned present fluorine-containing polymer.

The content of the present fluorinated polymer is preferably 5 to 100% by mass, more preferably 30 to 100% by mass, further preferably 40 to 100% by mass, based on the total mass of the present coating material.

The present coating material may contain components other than the present fluorinated polymer. Examples of such components include additives.

Examples of the additives include curing agents, curing catalysts, non-fluorinated polymers ((meth)acrylic resins, polyurethane resins, epoxy resins, polyester resins, silicone resins, etc.), colorants (dyes, organic pigments, inorganic pigments, bright pigments using metals or mica, etc.), ultraviolet absorbers, light stabilizers, matting agents, leveling agents, surface conditioners, degassing agents, fillers, heat stabilizers, thickeners, dispersants, surfactants, antistatic agents, rust inhibitors, silane coupling agents, antifouling agents, low-pollution treatment agents, plasticizers, adhesives, and the like.

In terms of durability of the coating film (water resistance, chemical resistance, weather resistance, etc.), the present coating preferably contains a curing agent among the above-mentioned additives. The curing agent preferably has two or more reactive groups that can react with the reactive groups contained in the present fluorinated polymer in one molecule, and more preferably has 2 to 30 reactive groups.

When the present fluorinated polymer has a reactive group, when the reactive group of the curing agent reacts with the reactive group of the fluorinated polymer, the present fluorinated polymer is crosslinked by the curing agent to form a crosslinked fluorinated polymer.

Specific examples of the reactive group possessed by the curing agent include an isocyanate group, a blocked isocyanate group, an epoxy group, an oxazoline group, and a β-hydroxyalkylamide group.

In particular, when the reactive group of the fluorinated polymer is a hydroxyl group, the reactive group of the curing agent is preferably an isocyanate group or a blocked isocyanate group. In this case, the curing agent is preferably a polyisocyanate that is a curing agent having two or more isocyanate groups or blocked isocyanate groups in one molecule.

As the polyisocyanate, a polyisocyanate monomer and a polyisocyanate derivative are preferred.

As the polyisocyanate monomer, alicyclic polyisocyanate, aliphatic polyisocyanate, and aromatic polyisocyanate are preferred. As the polyisocyanate derivative, a polymer or a modified form (adduct, allophanate, biuret, isocyanurate, etc.) of the polyisocyanate monomer is preferred.

Specific examples of the aliphatic polyisocyanate include tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethyl-1,6-diisocyanatohexane, aliphatic diisocyanates such as lysine diisocyanate, lysine triisocyanate, 4-isocyanatomethyl-1,8-octamethylene diisocyanate, and bis(2-isocyanatoethyl)2-isocyanatoglutarate.

Specific examples of the alicyclic polyisocyanate include alicyclic diisocyanates such as isophorone diisocyanate, 1,3-bis(isocyanatomethyl)-cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, norbornene diisocyanate, and hydrogenated xylylene diisocyanate.

Specific examples of the aromatic polyisocyanate include aromatic diisocyanates such as xylylene diisocyanate.

The polyisocyanate may be a compound in which two or more isocyanate groups of the above-mentioned polyisocyanate monomer or polyisocyanate derivative are blocked with a blocking agent.

The blocking agent is a compound having active hydrogen, and specific examples thereof include alcohols, phenols, active methylene groups, amines, imines, acid amides, lactams, oximes, pyrazoles, imidazoles, imidazolines, pyrimidines, and guanidines.

When the present fluorinated polymer has an acid value, for example, a curing agent having two or more groups reactive with a carboxyl group (epoxy group, carbodiimide group, oxazoline group, β-hydroxyalkylamide group, etc.) in one molecule may be used.

Two or more curing agents may be used in combination.

The content of the curing agent in the present coating material is preferably 1 to 80 parts by mass, more preferably 15 to 75 parts by mass, based on 100 parts by mass of the content of the present fluorinated polymer in the present coating material.

The present coating material may be a coating material in which the present fluorinated polymer is dissolved or dispersed in a liquid medium, or may be a coating material (powder coating material or the like) substantially containing no liquid medium.

As the liquid medium, organic solvents and water can be cited, and as the coating dissolved or dispersed in the liquid medium, coatings dissolved in organic solvents (solvent-based coatings, etc.) and coatings dispersed in water (water-based coatings, etc.) can be cited. From the aspect of excellent weather resistance of the coating film, this coating is preferably a solvent-based coating.

The fact that the present coating material contains substantially no liquid medium means that the content of the liquid medium is 0.1% by mass or less relative to the total mass of the present coating material.

Examples of the organic solvent include ketone solvents, ester solvents, hydrocarbon solvents, alcohol solvents, glycol ether solvents, and glycol ester solvents.

Specific examples of the ketone solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, and diacetone alcohol.

Specific examples of the ester solvent include ethyl acetate and butyl acetate.

Specific examples of the hydrocarbon solvent include hexane, heptane, cyclohexane, and xylene.

A specific example of the alcohol solvent is butanol.

Specific examples of the glycol ether-based solvent include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and propylene glycol monopropyl ether.

Specific examples of the glycol ester-based solvent include 1-methoxypropyl-2-acetate.

When the present coating material contains a liquid medium, the content of the liquid medium is preferably 10 to 95% by mass, more preferably 20 to 90% by mass, based on the total mass of the present coating material.

The present coating material can be produced, for example, by mixing the present fluorinated polymer with an optional component. The liquid medium may be a polymerization solvent (for example, the above-mentioned specific organic solvent) used when producing the present fluorinated polymer.

The substrate with a coating film of the present invention (hereinafter also referred to as a substrate with the present coating film) comprises a substrate and a coating film formed of the present composition and disposed on the substrate (hereinafter also referred to as the present coating film).

Specific examples of the material of the substrate include inorganic substances, organic substances, and organic-inorganic composite materials.

Specific examples of inorganic substances include concrete, natural stone, glass, and metals (iron, stainless steel, aluminum, aluminum alloys, copper, brass, titanium, and the like).

Specific examples of organic substances include plastics, rubber, adhesives, and wood.

Specific examples of the organic-inorganic composite material include fiber-reinforced plastics, resin-reinforced concrete, and fiber-reinforced concrete.

The substrate may be subjected to a known surface treatment (chemical conversion treatment, etc.) The substrate may also have a resin layer (polyester resin layer, acrylic resin layer, silicone resin layer, etc.) formed by applying a primer, etc., on its surface.

The shape, size, etc. of the substrate are not particularly limited.

Specific examples of the substrate include structures (for example, road structures such as bridges, piers, and tunnels), buildings, aircraft, ships, vehicles (for example, railway vehicles and automobiles), traffic signs, signal lights, and power transmission lines.

The thickness of the present coating film is preferably 1 to 200 μm, more preferably 10 to 100 μm, and even more preferably 20 to 60 μm, because the weather resistance of the substrate with the present coating film is more excellent.

The method for producing the substrate with the present coating film is a method of applying the present coating material on the substrate to form the present coating film. The present coating film can be formed by applying the present coating material on the substrate and drying and heating and curing it as required.

This coating can be directly applied to the surface of the substrate, and can also be applied on the basis of known surface treatment (substrate treatment, etc.) implemented to the surface of the substrate. And then, it is also possible to be applied on the primer layer after the substrate forms the primer layer. In addition, this coating can also be applied to the article with the above-mentioned substrate.

When the present coating is a water-based coating or a solvent-based coating, examples of the coating method include spray coating, blade coating, flow coating, rod coating, spin coating, dip coating, screen printing, gravure printing, die coating, inkjet, curtain coating, and methods using a brush or a spatula.

When the coating material is a powder coating material, examples of the coating method include electrostatic coating, electrostatic blowing, electrostatic dipping, spraying, fluid dipping, blowing, spraying, thermal spraying, plasma spraying and the like.

When the coating material contains a liquid medium, it is preferably dried after application to remove the solvent. The drying temperature is usually 0 to 50° C., and the drying time is usually 1 minute to 2 weeks.

When the coating material contains a curing agent, it is preferably cured by heating after application. The curing temperature is usually 50° C. to 300° C., and the curing time is usually 1 minute to 24 hours.

Example

Hereinafter, the present invention will be described in detail by giving examples. Examples 1 to 5 are working examples, and Examples 6 to 8 are comparative examples. However, the present invention is not limited to these examples.

＜Number average molecular weight (Mn)＞

The Mn of the fluorinated polymer was determined by size exclusion chromatography, using tetrahydrofuran as a developing solvent and a polystyrene standard product with a known molecular weight as a standard substance for molecular weight conversion.

<Example 1>

In a stainless steel pressure-resistant reactor with an internal volume of 400 ml equipped with a stirrer, 217 g of butyl acetate, 10 g of ethyl vinyl ether, 6 g of 4-hydroxybutyl vinyl ether, 10 g of cyclohexyl vinyl ether, 0.45 g of a mixture of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and methyl-1,2,2,6,6-pentamethyl-4-piperidinyl sebacate (mass ratio 3:1) (manufactured by BASF Corporation, trade name; TINUVIN292) as a stabilizer, and 0.26 g of tert-butyl peroxypivalate as a polymerization initiator were placed, and the dissolved oxygen in the liquid was removed by degassing with nitrogen. 33 g of chlorotrifluoroethylene was introduced into the reactor, and the temperature was slowly raised to 65° C. to allow polymerization to proceed.

20 hours after the addition of the polymerization initiator was started, the reactor was water-cooled to stop the reaction. After the reaction solution was cooled to room temperature, the unreacted monomers were purged, and the concentration of the obtained reaction solution was adjusted to obtain a base solution having a solid content concentration of 60.6% by mass containing fluoropolymer 1. The Mn of fluoropolymer 1 was 16,800.

<Example 2>

In a stainless steel pressure-resistant reactor with an internal volume of 400 ml equipped with a stirrer, 99 g of methyl ethyl ketone, 33 g of ethyl vinyl ether, 21 g of 4-hydroxybutyl vinyl ether, 34 g of cyclohexyl vinyl ether, 1.5 g of a mixture of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and methyl-1,2,2,6,6-pentamethyl-4-piperidinyl sebacate (mass ratio 3:1) (manufactured by BASF Corporation, trade name; TINUVIN292) as a stabilizer, and 0.26 g of tert-butyl peroxypivalate as a polymerization initiator were placed, and the dissolved oxygen in the liquid was removed by degassing with nitrogen. 107 g of chlorotrifluoroethylene was introduced into the reactor, and the temperature was slowly raised to 65° C. to allow polymerization to proceed.

20 hours after the addition of the polymerization initiator was started, the reactor was water-cooled to stop the reaction. After the reaction solution was cooled to room temperature, the unreacted monomers were purged, and the concentration of the obtained reaction solution was adjusted to obtain a base solution having a solid content concentration of 60.8% by mass containing fluoropolymer 2. The Mn of fluoropolymer 2 was 24700.

<Example 3>

In a stainless steel pressure-resistant reactor with an internal volume of 400 ml equipped with a stirrer, 102 g of acetone, 32 g of ethyl vinyl ether, 20 g of 4-hydroxybutyl vinyl ether, 32 g of cyclohexyl vinyl ether, 1.4 g of a mixture of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and methyl-1,2,2,6,6-pentamethyl-4-piperidinyl sebacate (mass ratio 3:1) (manufactured by BASF Corporation, trade name; TINUVIN292) as a stabilizer, and 0.26 g of tert-butyl peroxypivalate as a polymerization initiator were placed, and the dissolved oxygen in the liquid was removed by degassing with nitrogen. 103 g of chlorotrifluoroethylene was introduced into the reactor, and the temperature was slowly raised to 65° C. to allow polymerization to proceed.

20 hours after the addition of the polymerization initiator was started, the reactor was water-cooled to stop the reaction. After the reaction solution was cooled to room temperature, the unreacted monomers were purged, and the concentration of the obtained reaction solution was adjusted to obtain a base solution having a solid content concentration of 59.3% by mass containing fluoropolymer 3. The Mn of fluoropolymer 3 was 46700.

<Example 4>

In a stainless steel pressure-resistant reactor with an internal volume of 400 ml equipped with a stirrer, 102 g of tetrahydrofuran, 35 g of ethyl vinyl ether, 22 g of 4-hydroxybutyl vinyl ether, 35 g of cyclohexyl vinyl ether, 1.5 g of a mixture of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and methyl-1,2,2,6,6-pentamethyl-4-piperidinyl sebacate (mass ratio 3:1) (manufactured by BASF Corporation, trade name; TINUVIN292) as a stabilizer, and 0.26 g of tert-butyl peroxypivalate as a polymerization initiator were placed, and the dissolved oxygen in the liquid was removed by degassing with nitrogen. 111 g of chlorotrifluoroethylene was introduced into the reactor, and the temperature was slowly raised to 65° C. to allow polymerization to proceed.

20 hours after the addition of the polymerization initiator was started, the reactor was water-cooled to stop the reaction. After the reaction solution was cooled to room temperature, the unreacted monomers were purged, and the concentration of the obtained reaction solution was adjusted to obtain a base solution having a solid content concentration of 60.1% by mass containing fluoropolymer 4. The Mn of fluoropolymer 4 was 5900.

<Example 5>

Into a stainless steel pressure-resistant reactor having an internal volume of 2500 ml and equipped with a stirrer were placed 865 g of butyl acetate, 57 g of 4-hydroxybutyl vinyl ether, 220 g of cyclohexyl vinyl ether, 18 g of a mixture of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and methyl-1,2,2,6,6-pentamethyl-4-piperidinyl sebacate (mass ratio 3:1) (manufactured by BASF, trade name: TINUVIN 292) as a stabilizer, and 24 g of hydrotalcite (manufactured by Kyowa Chemical Industry Co., Ltd., trade name "KW500", particle size 45 μm or less: 38%, 45 to 75 μm: 35%, 75 to 106 μm: 21%, 106 to 500 μm: 6%), and dissolved oxygen in the liquid was removed by degassing with nitrogen. 261 g of chlorotrifluoroethylene was introduced into the reactor, and the reactor was heated until the temperature inside the reactor reached 65° C. Then, 6 ml of a 20% butyl acetate solution of t-butyl peroxypivalate was added to the reactor as a polymerization initiator to initiate the reaction.

While maintaining the reaction rate, additional monomers of 171 g of chlorotrifluoroethylene, 144 g of cyclohexyl vinyl ether and 38 g of 4-hydroxybutyl vinyl ether were continuously added to the reactor, and a 20% butyl acetate solution of tert-butyl peroxypivalate was intermittently added to the reactor to allow polymerization to proceed. After the start of polymerization, the total amount of 20% butyl acetate solution of tert-butyl peroxypivalate intermittently added to the reactor was 12 ml. After 16 hours, the reactor was water-cooled to stop the reaction. After the reaction solution was cooled to room temperature, the unreacted monomers were purged, and the insoluble components of the obtained reaction solution were removed by filtration. The concentration of the obtained reaction solution was adjusted to obtain a base solution containing a solid content concentration of 60.5% by mass of the fluorinated copolymer 5. The Mn of the fluorinated polymer 5 is 13500.

<Example 6>

In a stainless steel pressure-resistant reactor with an internal volume of 2500 ml equipped with a stirrer, 850 g of xylene, 196 g of ethyl vinyl ether, 123 g of 4-hydroxybutyl vinyl ether, 198 g of cyclohexyl vinyl ether, and 1.5 g of a mixture of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and methyl-1,2,2,6,6-pentamethyl-4-piperidinyl sebacate (mass ratio 3:1) (manufactured by BASF Corporation, trade name; TINUVIN292) as a stabilizer were placed, and dissolved oxygen in the liquid was removed by degassing with nitrogen. 629 g of chlorotrifluoroethylene was introduced into the reactor, and the temperature was slowly raised. When the temperature reached 65° C., 8.8 g of tert-butyl peroxypivalate was intermittently added as a polymerization initiator to allow polymerization to proceed.

20 hours after the addition of the polymerization initiator was started, the reactor was water-cooled to stop the reaction. After the reaction solution was cooled to room temperature, the unreacted monomers were purged, and the concentration of the obtained reaction solution was adjusted to obtain a base solution having a solid content concentration of 60.3% by mass containing fluoropolymer 6. The Mn of fluoropolymer 6 was 14600.

<Example 7>

As the solution of the fluorinated polymer 7, Zeffle GK-570 (butyl acetate solution of a copolymer of tetrafluoroethylene and a vinyl monomer, solid content concentration: 65 mass %) manufactured by DAIKIN INDUSTRIES, LTD. was used.

＜Light transmittance＞

Each base solution containing a fluorine-containing polymer in Examples 1 to 7 was applied to a polypropylene plate without any surface treatment using an applicator so that the dry film thickness was about 40 μm or about 60 μm, and then heated and dried at 60° C. for 60 minutes to form a coating film. The coating films were peeled off from the polypropylene plate to form a thin film. The film was used as a sample, and the absorbance A in the wavelength range of 200 nm to 800 nm of the film was measured using an ultraviolet-visible spectrophotometer (manufactured by Shimadzu Corporation, UV-3600MPC-3100). The transmittance T (%) in the wavelength range of 260 nm to 300 nm was calculated using the following formula (1). It should be noted that as the transmittance T (%), the lowest value of the transmittances obtained every 0.5 nm in the wavelength range of 260 nm to 300 nm is recorded in Table 1.

A＝-log ₁₀ T

Formula (1)

The absorbance of the absorbing substance is proportional to the optical path length (film thickness) according to the following equation (2) based on the Lambert-Beer's law, and the transmittance T' (%) when the film thickness is corrected to 40 μm is calculated using the film thickness L (μm) of the film shown in Table 1 and the transmittance T values shown in Table 1. The transmittance T' values are shown in Table 1.

It should be noted that the film thickness L of the thin film was measured using a vernier caliper and was the arithmetic mean value of nine arbitrary locations on the thin film.

＜Weather resistance＞

Based on the above light transmittance value, weather resistance was evaluated. The evaluation criteria are as follows, and the evaluation results are shown in Table 1.

(Evaluation Criteria)

A: The light transmittance in the wavelength region of 260 nm to 300 nm is 50% or more when the film thickness is 40 μm, resin destruction due to ultraviolet absorption is suppressed, and weather resistance is good.

B: The light transmittance in the wavelength region of 260 nm to 300 nm was less than 50% when the film thickness was 40 μm, and resin destruction due to ultraviolet absorption occurred, resulting in insufficient weather resistance.

[Table 1]

As shown in Table 1, it was confirmed that a coating film having excellent weather resistance can be formed when a fluorine-containing polymer obtained by polymerizing the monomer a11, the monomer a12 and the monomer a13 in the presence of a specific organic solvent and in the absence of a vinyl ester is used.

It should be noted that the entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2022-062388 filed on April 4, 2022 are incorporated herein as a disclosure of the specification of the present invention.

Claims (7)

1. A process for producing a fluoropolymer, characterized in that in the presence of at least 1 organic solvent selected from the group consisting of methyl ethyl ketone, acetone, n-butyl acetate and tetrahydrofuran and in the absence of a vinyl ester,

At least 1 fluorine-based monomer selected from the group consisting of CF ₂＝CF₂、CF₂＝CFCl、CF₂ =chf and CH ₂＝CF₂ is polymerized with a vinyl ether having no fluorine atom and reactive group and a monomer having a reactive group to obtain a fluorine-containing polymer.

2. The method for producing a fluorine-containing polymer according to claim 1, wherein the organic solvent is at least 1 organic solvent selected from the group consisting of methyl ethyl ketone, acetone, and n-butyl acetate.

3. The method for producing a fluorine-containing polymer according to claim 1 or 2, wherein the fluorine-based monomer is at least 1 monomer selected from the group consisting of CF ₂＝CF₂ and CF ₂ =cfcl.

4. The method for producing a fluorine-containing polymer according to claim 1 or 2, wherein the reactive group is at least 1 group selected from the group consisting of a hydroxyl group, an amino group, an epoxy group, an oxetanyl group, a hydrolyzable silyl group, a sulfo group and a carboxyl group.

5. A fluoropolymer characterized in that it has:

Fluorine-based units based on at least 1 fluorine-based monomer selected from the group consisting of CF ₂＝CF₂、CF₂＝CFCl、CF₂ =chf and CH ₂＝CF₂;

a non-fluorine-based unit based on a vinyl ether having no fluorine atom and reactive group; and

Based on units of monomers having reactive groups,

The fluoropolymer does not have vinyl ester-based units,

The film obtained from the fluoropolymer has a light transmittance in a wavelength region of 260nm to 300nm of 50% or more when the film has a thickness of 40 [ mu ] m.

6. A coating is characterized in that, comprising the fluoropolymer according to claim 5.

7. A substrate with a coating film comprising a substrate and a coating film formed from the coating material according to claim 6 disposed on the substrate.