JPH1053622A - Fluorine-containing copolymer and composition using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fluorine-containing copolymer which can give coating film and cured film excellent in resistance to heat, whether, chemical and the like by copolymerizing a fluoro-olefin structure unit in a specific proportion. SOLUTION: This copolymer comprises (A) 20-80mol% of one or more kinds of fluoro-olefin structures of formula I (X<1> to X<3> are each H, Cl, F, trifluoromethyl), (B) 0.5-50mol% of one or more kinds of structures of formula II [R is H, R<1> is a 1-10C aliphatic alkyl, a 2-9C fluoroalkyl)] and (C) 0-70mol% of monomer structure copolymerizable with the component (A) and the component (B), and has a number-average molecular weight of 1,000-20,000. For example, a copolymer containing 90-98mol% of tetrafluoroethylene as a component (A) and 2-10mol% is isoprenol as a component (B) gives a tough film excellent in thermal resistance by firing it at an elevated temperature to cause cross- linking.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel fluorine-containing copolymer, and a coating composition and a curable composition containing the same.

[0002]

2. Description of the Related Art Although various fluorine-containing copolymers containing a fluoroolefin structural unit are known, one-quarter of the carbon atoms in the main chain of most copolymers contain tertiary hydrogen (bonded to a carbon atom). A hydrogen atom when only one of the four groups is a hydrogen atom). For example, JP-A-57-
No. 34107 (JP-B-60-21686) discloses a chlorotrifluoroethylene / cyclohexyl vinyl ether / ethyl vinyl ether / 4-hydroxybutyl vinyl ether copolymer, and JP-A-61-57609 discloses chlorobenzene. A trifluoroethylene / vinyl acetate / ethylene glycol monoallyl ether copolymer is described.

[0003] Such a fluorinated copolymer having a tertiary hydrogen bonded to its main chain has a halogen atom (a fluorine atom or a chlorine atom) bonded to the carbon adjacent to the carbon to which the tertiary hydrogen is bonded, and the tertiary hydrogen. Grade hydrogen tends to cause a dehydrohalogenation reaction under alkaline conditions. As a result, there is a problem that the copolymer is easily decomposed and the copolymer is colored by the generated hydrogen halide. Further, in the dehydrohalogenation reaction, chlorine atoms are more likely to occur, and the coloring of the copolymer is remarkably exhibited.

Further, since the dissociation bond energy between tertiary hydrogen and the carbon atom in the main chain is small, there is also a problem that the copolymer is easily cut by heat or light and the stability of the copolymer is poor.

[0005] Therefore, even when a coating composition or a curable composition is prepared using such a fluorine-containing copolymer, there remains a problem to be improved in heat resistance, weather resistance, alkali resistance and the like.

[0006]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a fluorine-containing copolymer capable of providing a coating film and a cured film having excellent heat resistance, weather resistance, chemical resistance, etc., and a composition containing the copolymer. Is to provide.

[0007]

According to the present invention, there is provided a compound of formula (I):

[0008]

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(Wherein X ¹ , X ² and X ³ are the same or different and all are a hydrogen atom, a chlorine atom, a fluorine atom or a trifluoromethyl group) Or two or more of 20 to 80 mol% of the formula (II):

[0010]

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Wherein R is a hydrogen atom, -R ¹ or

[0012]

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(R ¹ is a linear or branched aliphatic alkyl group having 1 to 10 carbon atoms, a fluoroalkyl group having 2 to 9 carbon atoms or an aromatic group which may be substituted)) One or more structural units (II)
50 mol%, and one or two of structural units (III) derived from monomers copolymerizable with structural units (I) and (II)
A number average molecular weight of 0 to 70 mol% of at least 1,000 species
To 20,000 fluorocopolymers.

The present invention also relates to the above-mentioned copolymer containing 50 mol% or less of a structural unit having a hydroxyl group.

The present invention also relates to a coating composition containing the above-mentioned fluorine-containing copolymer and an organic solvent.

When the fluorine-containing copolymer containing 50 mol% or less of the hydroxyl-containing structural unit is used, a curable composition can be provided by using a hydroxyl-curable curing agent in combination.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention can take the following embodiments, but is not limited thereto.

(1) Embodiment 1 (Fluorine-Containing Copolymer) The fluorine-containing copolymer of the present invention comprises one or more kinds of fluoroolefin structural units (I) and one or more kinds of structural units. (II) and one or more structural units (III) as an arbitrary structural unit.

The fluoroolefin structural unit (I) is represented by the above formula (I) wherein at least one fluorine atom is bonded to a carbon atom of the main chain. Examples of the fluoroolefin that provides the structural unit (I) include perhaloolefins such as tetrafluoroethylene, hexafluoropropylene, and chlorotrifluoroethylene; and hydrofluoroolefins such as trifluoroethylene, vinylidene fluoride, and vinyl fluoride. can give. After copolymerization of these, tetrafluoroethylene, hexafluoropropylene,
Vinylidene fluoride is preferred.

The content of the structural unit (I) is from 20 to 80 mol%. If it is less than 20 mol%, it is inferior in weather resistance and chemical resistance. If it exceeds 80 mol%, it dissolves in an organic solvent. Poor sex.

The structural unit (II) is a unit represented by the formula (II), wherein the carbon atoms constituting the main chain do not contain a tertiary hydrogen atom. In the structural unit (II), R is a hydrogen atom, -R ¹ or

[0022]

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## EQU1 ## R ¹ is a linear or branched aliphatic alkyl group having 1 to 10 carbon atoms, a fluoroalkyl group having 2 to 9 carbon atoms (which may be all substituted with a fluorine atom), or unsubstituted It is an aromatic group.

Preferred R is, for example, a hydrogen atom;
Aliphatic alkyl groups such as methyl, ethyl, propyl and cyclohexyl; 2 ′, 2 ′, 2′-trifluoroethyl, 2 ′,
2 ', 3', 3'-tetrafluoropropyl, 2 ', 2', 3 ',
Fluoroalkyl groups such as 3 ', 3'-pentafluoropropyl; aromatic groups such as phenyl and benzyl; and acyl groups such as acetyl. Examples of the monomer giving the structural unit (II) include isoprenol and 2-methyl-4-
Methoxy-1-butene, 2-methyl-4-ethoxy-1-butene, 2
-Methyl-4-propyloxy-1-butene, 2-methyl-4-cyclohexyloxy-1-butene, 2-methyl-4- (2 ′, 2 ′, 2 ′
-Trifluoro) ethoxy-1-butene, 2-methyl-4- (2 ',
2 ', 3', 3'-tetrafluoro) propyloxy-1-butene, 2-methyl-4- (2 ', 2', 3 ', 3', 3'-pentafluoro) propyloxy-1-butene , 2-methyl-4-phenoxy
1-butene, 2-methyl-4-benzoyloxy-1-butene, 2
-Methyl-4-acetyloxy-1-butene, 2-methyl-4-cyclohexyloxy-1-butene, and the like. Isoprenol and 2-methyl-4-methoxy-1-butene are particularly easy to obtain. preferable.

The structural unit (II) does not contain tertiary hydrogen bonded to the carbon atom of the main chain after copolymerization, so that it has heat resistance,
It has the effect of improving weather resistance and chemical resistance.

The structural unit (III) is an optional component, and is a unit derived from a monomer copolymerizable with the monomer giving the structural units (I) and (II). Such copolymerizable monomers include, for example, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether, n-pentyl vinyl ether, n-hexyl vinyl ether, n-octyl vinyl ether, 2-ethylhexyl vinyl ether And alkyl vinyl ethers such as 2-chloroethyl vinyl ether; cycloalkyl vinyl ethers such as cyclopentyl vinyl ether, cyclohexyl vinyl ether, methylcyclohexyl vinyl ether, and cyclooctyl vinyl ether; 2,2,2-trifluoroethyl vinyl ether and 2,2,3,3 -Tetrafluoropropyl vinyl ether, 2,2,3,3,3-pentafluoropropyl vinyl ether, 2,2,3,3,4,4,5,5-octafluoropentyl vinyl ether, Fluoroalkyl vinyl ethers such as 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononyl vinyl ether; perfluorohexyl ethylene, Fluoroalkyl ethylenes such as fluoropentyl ethylene; vinyl acetate, vinyl propylate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caproate, vinyl versatate, vinyl laurate,
Vinyl carboxylate such as vinyl stearate, vinyl benzoate, vinyl p-tert-butyl benzoate, vinyl salicylate, vinyl cyclohexanecarboxylate; ethylene, propylene, isobutylene, 1-heptene, 1-octene, vinyl chloride, chloride Olefins such as vinylidene, allyl chloride, allyl acetate; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, maleic acid, crotonic acid, and cinnamic acid or esters thereof; acrylonitrile; styrene; Hydroxybutyl vinyl ether, 6-hydroxyhexyl vinyl ether, 4-hydroxy-2-methyl vinyl ether, 1,4-cyclohexanedimethanol monovinyl ether, allyl alcohol, 2-hydroxyethyl allyl ether, glycerol monoallyl ether, etc. Hydroxyl group-containing (preferably 1) one or more monomers and the like.

The structural unit (III) can be contained, if necessary, to impart other properties such as heat resistance, weather resistance and chemical resistance to the copolymer of the present invention and the composition thereof. The amount is an amount which does not reduce the effects of the structural units (I) and (II). When a hydroxyl group-containing monomer among the structural units (III) is used, a curing reaction site is given to the copolymer, and a crosslinking reaction occurs by using a curing agent that reacts with the hydroxyl group, and heat resistance, weather resistance, and chemical resistance are obtained. And a cured film having excellent solvent resistance is produced.

Among the structural units (III), ethylene or isobutylene, which is a monomer that does not give tertiary hydrogen to carbon atoms in the main chain of the copolymer after copolymerization, has heat resistance, weather resistance,
Preferred from the viewpoint of chemical resistance.

The copolymer of the present invention comprises structural units (I) and (II)
The ratio (mol%) of the case consisting of only (I) / (II)
= 50-99.5 / 50-0.5, preferably 70-9
5/5 to 30. Structural unit (II) accounts for 5
If it exceeds 0 mol%, the polymerization rate is undesirably reduced.
If it is less than 0.5 mol%, the effect of improving heat resistance, weather resistance and chemical resistance cannot be obtained. When the structural unit (III) is incorporated, the ratio (mol%) is 20 to 80 / 0.5 to 50 /.
0.5 to 70, preferably 35 to 60/5 to 25/15
~ 40.

Next, preferred compositions of the copolymer of the present invention will be exemplified, but the present invention is not limited to these. In addition, the total of each structural unit is 100 mol%.

(Preferred Embodiment 1-A) Structural Unit Type Ratio (mol%) (I) Tetrafluoroethylene 90 to 98 (II) Isoprenol 2 to 10 This polymer is crosslinked by baking at a high temperature and has heat resistance. Gives an excellent tough film.

(Preferred Embodiment 1-B) Structural Unit Type Ratio (mol%) (I) Tetrafluoroethylene 45-60 (II) 2-Methyl-4-methoxy-1-butene 40-55 Excellent weather resistance and chemical resistance.

(Preferred Embodiment 1-C) Structural Unit Type Ratio (mol%) (I) Tetrafluoroethylene 45-65 (II) Isoprenol 5-15 (III) Ethylene 20-50 This copolymer is chemically resistant. It has weather resistance, heat resistance and flexibility.

(Preferred Embodiment 1-D) Structural Unit Type Ratio (mol%) (I) Tetrafluoroethylene 45 to 70 (II) 2-Methyl-4-methoxy-1-butene 3 to 20 (IIIa) Ethylene 30 -50 (IIIb) 1-octene 2-10 This copolymer has weather resistance, chemical resistance, heat resistance and flexibility.

(Preferred Embodiment 1-E) Structural Unit Type Ratio (mol%) (I) Tetrafluoroethylene 40 to 60 (II) Isoprenol 5 to 15 (IIIa) 4-Hydroxybutyl vinyl ether 5 to 15 (IIIb) Pivalin Vinyl acid 5-25 (IIIc) isobutylene 5-25 This copolymer cures to give a film having weather resistance, chemical resistance and heat resistance.

In the copolymer of the present invention, tetrafluoroethylene and other monomers are almost alternately copolymerized except for Embodiment 1-A, and the number average molecular weight measured by gel permeation chromatography (GPC) is 1,000 to 20,000.

The production of the copolymer of the present invention is usually carried out by an emulsion polymerization method, a suspension polymerization method or a solution polymerization method. The polymerization temperature is usually 0 to 150 ° C., preferably 5 to 95 ° C. in any of the polymerization methods. The polymerization pressure is usually 1 to 100 Kg / cm ² G in any polymerization method.

As the polymerization medium, water is used in the emulsion polymerization method, and water, tert-butanol, perfluorocyclobutane or a mixture thereof is used in the suspension polymerization method. In the solution polymerization method, esters such as ethyl acetate, propyl acetate and butyl acetate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; hydrocarbons such as hexane, cyclohexane and octane; benzene, toluene, xylene and naphthalene Aromatic hydrocarbons such as methanol; ethanol, tert-butanol, iso-propanol, and alcohols such as ethylene glycol monoalkyl ether; cyclic ethers such as tetrahydrofuran and dioxane;
Examples thereof include dimethyl sulfoxide and the like, and a mixture thereof.

As the polymerization initiator, in the emulsion polymerization method, for example, persulfates such as ammonium persulfate and potassium persulfate (and, if necessary, reducing agents such as sodium hydrogen sulfite, sodium pyrosulfite, cobalt naphthenate, dimethylaniline). Redox initiators consisting of an oxidizing agent (eg, ammonium peroxide, potassium peroxide, etc.), a reducing agent (eg, sodium sulfite, etc.) and a transition metal salt (eg, iron sulfate, etc.), and can be used as a suspension or solution. In the polymerization method, for example, acetyl peroxide, benzoyl peroxide, isopropoxycarbonyl peroxide, tert-butoxycarbonyl peroxide, methyl ethyl ketone peroxide,
Cyclohexanone peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, isobutyryl peroxide, octanoyl peroxide, di-tert-butyl peroxide, dicumyl peroxide, tert-butylperoxyacetate, tert-butylperoxide Organic peroxides such as oxypivalate, di-n-propylperoxydicarbonate and diisopropylperoxydicarbonate; 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvalero Nitrile), 2,2'-azobis (2-methylvaleronitrile),
2,2'-azobis (2-cyclopropylpropionitrile), dimethyl 2,2'-azobisisobutyrate, 2,2'-azobis [2- (hydroxymethyl) propionitrile],
Azo compounds such as 4,4'-azobis (4-cyanopentenoic acid) can be used.

In any of the polymerization methods, during the polymerization, hydrogen fluoride or hydrogen chloride is eliminated from the monomer or the polymer, so that the polymerization medium becomes acidic and the polymer may be gelled. Inorganic salts such as sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, sodium phosphate, metal oxides, hydrotalcites; organic amines such as diethylamine, dibutylamine, triethylamine; basic anion exchange A resin may be added to neutralize the desorbed hydrogen fluoride or hydrogen chloride.

As will be described later, the fluorine-containing copolymer of the present invention can be used as a lacquer type coating by dissolving it in a solvent as it is, but can be made into a two-part curable composition by adding a curing agent. .

(2) Embodiment 2 (Composition) The fluorinated copolymer of the present invention is used alone or in combination with other resins as a resin component to form molded articles such as pipes, tubes, sheets, films, blocks and the like. Molding composition; can be prepared in the form of a composition for powder coating, lining or electric wire coating by a conventional method.

Further, the composition for coatings can be made into a form dispersed or dissolved in an organic solvent or water, and the curable composition can be made into a form containing a curing agent.

(Preferred Embodiment 2-A) The coating composition of the present invention essentially contains the above-mentioned fluorinated copolymer and an organic solvent.

When the copolymer of the present invention is used, the types and conditions of the solvents used are greatly reduced. Therefore, as the solvent of the coating composition of the present invention, ethyl acetate, butyl acetate, isopropyl acetate, isobutyl acetate,
Esters such as cellosolve acetate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; cyclic ethers such as tetrahydrofuran and dioxane; N, N-dimethylformamide, N, N-
Amides such as dimethylacetamide; aromatic hydrocarbons such as toluene and xylene; mixed solvents thereof and the like can be used.

The copolymer concentration is 5 to 90% by weight, preferably
10-70% by weight.

The coating composition of the present invention may further contain other resins and various additives. Examples of the additives include a curing accelerator, a pigment, a pigment dispersant, a leveling agent, an antifoaming agent, an anti-gelling agent, an ultraviolet absorber, and an antioxidant.

Specific examples of the pigment include, for example, inorganic pigments such as titanium oxide, calcium carbonate and carbon black; and organic pigments such as phthalocyanine, quinacridone and azo, but are not limited thereto. Absent. The amount of pigment added is usually up to about 200% by weight, based on the copolymer.

Examples of various resins that can be blended include (meth) acrylic resins which may contain styrene, polyester resins, alkyd resins, and melamine resins.
Formaldehyde resin, polyisocyanate resin, epoxy resin, vinyl chloride resin (for example, vinyl chloride
-Vinyl acetate copolymer), ketone resin, petroleum resin,
Chlorinated products of polyolefins such as polyethylene and polypropylene, inorganic resins such as silica gel and silicic acid, various fluorine resins other than the fluorine-containing copolymer of the present invention (for example, homopolymers of tetrafluoroethylene and chlorotrifluoroethylene or One or two or more such as copolymers of these and other monomers),
However, it is not limited only to these.

The composition of the present invention can be prepared by thoroughly mixing the above components.

The composition of the present invention is excellent in solvent solubility, the formed coating film is excellent in gloss retention, weather resistance and stain resistance,
Excellent in chemical resistance, mechanical properties, adhesion to base materials, heat-resistant yellowing, etc., as well as ordinary coating compositions, such as building materials, interior materials and other indoor or building materials, automobiles, aircraft, ships It can be applied directly to metals, concrete, plastics and the like as paints for outdoor use such as trains, or overlaid on primer paints such as wash primers, rust preventive paints, epoxy paints, acrylic resin paints and polyester resin paints. Further, it can be used as a sealing agent or a film forming agent.

(Preferred Embodiment 2-B) When the fluorinated copolymer of the present invention contains a structural unit containing a hydroxyl group or an epoxy group, a curable composition can be obtained by using a curing agent in combination. .

When a curable composition is used, the proportion of the structural unit containing a hydroxyl group or an epoxy group in the fluorinated copolymer is 50 mol% or less, preferably 2 to 35 mol%. If the content is more than 50 mol%, the stability of the composition becomes poor, which is not preferable.

As the curing agent, a compound having two or more groups which crosslink by reacting with a hydroxyl group or an epoxy group of the copolymer, for example, isocyanates, amino resins, acid anhydrides, epoxy resins, silicic acids, ladders Silicones and the like are usually used.

Specific examples of the isocyanates include:
For example, 2,4-tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, lysine methyl ester diisocyanate, methylcyclohexyl diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, n-pentane-1,4
-Diisocyanates, their trimers, their adducts and burettes, their polymers having two or more isocyanate groups, and further blocked isocyanates, but are not limited thereto. Not something.

Specific examples of the amino resins include, for example, urea resin, melamine resin, benzoguanamine resin,
In addition to glycoluril resins, methylolated melamine resins obtained by converting melamine to methylol, alkyl etherified melamine resins obtained by etherifying methylolated melamine with alcohols such as methanol, ethanol, and butanol, and the like, include, but are not limited to, is not.

Specific examples of the acid anhydrides include, for example, phthalic anhydride and pyromellitic anhydride.
It is not limited to these.

The compounding amount of the curing agent is 0.1 to 5 equivalents, preferably 0.5 to 1.5 equivalents, per equivalent of the functional group (—OH group) in the fluorinated copolymer. The composition of the present invention usually has 0
Curing can be performed at ~ 200 ° C for several minutes to about 10 days.

When it is desired to cure in a short time, it is preferable to use a curing accelerator.

Examples of the curing accelerator include organotin compounds such as dibutyltin dilaurate, acidic phosphoric acid esters, reactants of acidic phosphoric acid esters with amines, saturated or unsaturated polycarboxylic acids or acid anhydrides thereof, and organic acids. Examples include titanate compounds, amine compounds, lead octylate, and the like.

As the curing accelerator, one type may be used alone, or two or more types may be used in combination.

The compounding ratio of the curing accelerator is preferably about 1.0 × 10 ^{−6 to} 1.0 × 10 ⁻² parts by weight, more preferably about 5.0 × 10 ^{−5 to} 1.0 × 10 ⁻³ parts by weight based on 100 parts by weight of the copolymer. Is more preferred.

In addition, the various organic solvents, additives, and other blended resins described in the coating composition can also be used for the curable composition, can be prepared by the same method, and can be applied by the same method as in the prior art. Can be used.

The curable composition of the present invention has excellent crosslinking reactivity, and the cured coating film has weather resistance, heat yellowing resistance, solvent resistance,
It has excellent coating strength, chemical resistance, especially alkali resistance, and like ordinary coating compositions, it is used for indoor or building materials such as building materials and interior materials, or for outdoor applications such as automobiles, aircraft, ships, and trains. It can be applied directly to metal, concrete, plastic, etc., or overlaid on an undercoat such as wash primer, rust preventive paint, epoxy paint, acrylic resin paint, polyester resin paint. Further, it can be used as a sealing agent or a film forming agent.

[0065]

Next, the present invention will be explained based on examples, but the present invention is not limited to these examples.

Example 1 In a stainless steel autoclave having an internal volume of 6 liters, 2214 g of butyl acetate as a solvent, 117 g of isoprenol as a structural unit (II), and 190 g of isobutylene as a structural unit (III)
g and 261 g of vinyl pivalate were charged, and after purging with nitrogen and degassing, 680 g of tetrafluoroethylene was introduced as a structural unit (I), and the inside of the autoclave was heated with stirring. When the internal temperature reached 65 ° C., 20 g of octanoyl peroxide was added, and polymerization was started.

The reaction was stopped when the internal pressure of the reactor, which was 19.6 kg / cm ² G at the start of the polymerization, dropped to 5.0 kg / cm ² G after 16 hours. Meanwhile, 20g of octanoyl peroxide
Added. After returning the autoclave to room temperature, unreacted monomers were purged, and the autoclave was opened. The contents were poured into n-hexane, and the obtained product was washed and dried to obtain a fluorinated copolymer (1113 g, polymerization yield 8).
9%). The number average molecular weight of the obtained copolymer measured by GPC (polystyrene standard, developing solvent THF) was 6,50.
The copolymer composition analyzed by the 0, ¹⁹ F-NMR method, H-NMR method and elemental analysis method was as follows: tetrafluoroethylene / isoprenol / isobutylene / vinyl pivalate = 49/10
/ 25/16 (mol%).

Examples 2 to 7 Polymerization was carried out in the same manner as in Example 1 except that the solvents, the amounts of charged monomers and the polymerization conditions shown in Table 1 were used, to obtain copolymers having the compositions shown in Table 2.

[0069]

[Table 1]

[0070]

[Table 2]

[0071]

[Table 3]

Comparative Example 1 A 200 ml autoclave equipped with a stirrer was charged with 116 g of tert-butanol, 11.7 g of cyclohexyl vinyl ether, 11.1 g of ethyl vinyl ether, 7.17 g of hydroxybutyl vinyl ether, 0.69 g of potassium carbonate and 0.06 g of AIBN.
After nitrogen substitution and degassing, tetrafluoroethylene 31.0
g was added. The internal temperature of the autoclave was adjusted to 65 ° C., the reaction was carried out for 8 hours with stirring (initial polymerization pressure: 75 kg / cm ² G), the reaction was stopped at a termination polymerization pressure of 1.2 kg / cm ² G, and the mixture was treated to obtain a copolymer. (35 g, 57% yield).

The number average molecular weight of this copolymer determined by the GPC method was 36,000. The composition (mol%) is tetrafluoroethylene / cyclohexyl vinyl ether /
Ethyl vinyl ether / hydroxybutyl vinyl ether = 51/17/23/9.

[0074] Comparative Example 2 isoprenol polymerized in a similar manner but using 2-hydroxyethyl allyl ether 138g to Example 1 instead of the (initial polymerization pressure 19.2 kg / cm ² G, termination polymerization pressure 5.8 kg / cm ² G ) To give a copolymer. The yield of the copolymer was 10.85 g, the yield was 86%,
The number average molecular weight was 5,500, and the composition (mol%) was tetrafluoroethylene / 2-hydroxyethylallyl ether / isobutylene / vinyl pivalate = 47/11/24/18.

Example 8 The copolymers obtained in Examples 1 to 4 and Comparative Examples 1 and 2
10 g was dissolved in butyl acetate to a concentration of 30% by weight. A curable composition was prepared by mixing an isocyanate curing agent (Takenate D140N) manufactured by Takeda Pharmaceutical Co., Ltd. so that NCO / OH was 1.1. This composition was coated on an aluminum plate (JIS H 4000A-1050PA).
M-712) and heated at 80 ° C. for 1 hour to cure, thereby forming a cured film. This cured film was tested for heat yellowing resistance, water yellowing resistance, alkali resistance, weather resistance, and curability described later. Table 3 shows the results. For the copolymers (containing no hydroxyl groups) obtained in Examples 5 to 7, the average particle size was measured using an impact hammer mill.
As a powder of 0.5 to 1 μm, the powder was electrostatically applied to the substrate and baked at 220 ° C. for 15 minutes to form a coating film.

[Heat-resistant yellowing] The coating is treated at 170 ° C for 1 hour, and the degree of coloring (yellowing) is visually observed.

[Water-resistant yellowing] After the coating film is immersed in boiling water for 24 hours, the degree of coloring (yellowing) is visually observed.

[Alkali Resistance] After the coating film is immersed in a 10% aqueous solution of sodium hydroxide for 7 days at room temperature, the degree of coloring is visually observed.

[Weather Resistance] Sunshine Weatherometer Ducycle (Light / Dew =) manufactured by Suga Test Instruments Co., Ltd.
After conducting an accelerated weathering test for 4000 hours at 60 minutes / 60 minutes as one cycle), the contact angle with water was measured with a CA-A type manufactured by Kyowa Kagaku Co., Ltd., and the contact angle retention rate (% ).

[0080]

(Equation 1)

[Curability] The weight retention after immersing the coating film in xylene overnight.

[0082]

[Table 4]

[0083]

The fluorinated copolymer of the present invention has excellent chemical stability and also has improved reactivity with a curing agent.

Claims (4)

[Claims] 1. A compound of formula (I): (Wherein X ¹ , X ² and X ³ are the same or different, and all are a hydrogen atom, a chlorine atom, a fluorine atom or a trifluoromethyl group). More than 20 to 80 mol% of the formula (I
I): (Wherein R is a hydrogen atom, -R ¹ or (R ¹ is a linear or branched aliphatic alkyl group having 1 to 10 carbon atoms, a fluoroalkyl group having 2 to 9 carbon atoms, or an aromatic group which may be substituted)) II) one or more kinds of 0.5 to 50 mol%,
And one or more structural units (III) derived from monomers copolymerizable with the structural units (I) and (II).
0 mol% of number average molecular weight of 1,000 to 20,000
0 fluorine-containing copolymer. 2. The copolymer according to claim 1, which contains 50 mol% or less of a structural unit having a hydroxyl group. 3. A coating composition comprising the copolymer according to claim 1 and an organic solvent. 4. A curable composition comprising the copolymer according to claim 2, an organic solvent, and a curing agent capable of reacting with a hydroxyl group in the copolymer.