JPH06122730A - Fluorocopolymer and coating composition based on the same - Google Patents

Abstract

PURPOSE:To obtain a fluorocopolymer having a high Tg and suited for a coating material. CONSTITUTION:This fluorocopolymer comprises 30-65mol% repeating units derived from chlorotrifluoroethylene or tetrafluoroethylene, 5-45mol% repeating units derived from optionally substituted norbornadiene, 5-50mol% repeating units derived from an aliphatic carboxylic acid/vinyl ester or alkyl vinyl ether, 1-25mol% repeating units derived from a hydroxylated vinyl monomer and 0-20mol% repeating units derived from other vinyl monomers, and has a number- average molecular weight of 1000-200000.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel fluorine-containing copolymer and a coating composition containing the polymer as a main component. The fluorine-containing copolymer obtained by the present invention has a high glass transition temperature as compared with known fluorine-containing copolymers, and further has various physical properties required as a resin for coatings, and thus has a high temperature in summer. It is suitable for exterior coating of buildings and automobiles.

[0002]

2. Description of the Related Art In recent years, in the field of coating materials, there has been a strong demand for materials having excellent properties such as weather resistance and chemical resistance. As a response to these requirements, various polymers containing a fluorine-based monomer as a component have been demanded. Proposed. Among them, a fluorine-containing copolymer composed of chlorotrifluoroethylene, cyclohexyl vinyl ether, alkyl vinyl ether and hydroxyalkyl vinyl ether (JP-A-57-34107), or containing chlorotrifluoroethylene, aliphatic vinyl ester and hydroxyl group A resin having a hydroxyl group in the molecule and soluble in an organic solvent, such as a fluorine-containing copolymer composed of allyl ether (Japanese Patent Laid-Open No. 61-57609), is noted as a curable weather resistant coating resin. Has been done.

However, the glass transition temperature of the fluorine-containing copolymer is at most about 30 ° C., and the glass transition temperature of the cured resin obtained by reacting them with a curing agent is also about 50 ° C. In the summer, when it is used for automotive exterior paints, which may increase in temperature to 60 ° C. or higher, there is a problem in that it is a step in stain resistance. Specifically, in the case of a coating material comprising a fluorocopolymer having the above glass transition temperature, when the temperature of the coated plate reaches 60 ° C. or higher, the copolymer softens and contaminants adhere to it. It became easier.

The present inventors have proposed a method of copolymerizing a monomer containing an aromatic ring such as vinyl benzoate, styrene or phenyl vinyl ether with a fluorine-based monomer in order to increase the glass transition temperature of the fluorocopolymer. I considered
The copolymer obtained by such a method has a high glass transition temperature, but has a defect of poor weather resistance. It is also known that chlorotrifluroethylene is copolymerized with norbornadiene to give a copolymer having a high glass transition temperature and soluble in an organic solvent (USP3287).
327), it was found from experiments that a large number of cracks were generated in a thermal cycle test when the binary copolymer was used as a coating resin.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a fluorine-containing copolymer having the following constitution having a specific amount of norbornadiene or substituted norbornadiene monomer units in a polymer molecule. The inventors have found that the polymer is soluble in an organic solvent, has a high glass transition temperature, and is excellent in thermal cycle resistance and weather resistance, and has completed the present invention.

That is, the first aspect of the present invention is (a)
Chlorotrifluoroethylene or tetrafluoroethylene monomer units, (b) norbornadiene or substituent-containing norbornadiene monomer units, (c) aliphatic carboxylic acid vinyl ester or alkyl vinyl ether monomer units and (d) hydroxyl groups Proportion of each component based on the total amount of all the monomer units, which consists of the vinyl monomer units contained, or (a) to (d) and (e) other vinyl monomer units. , (A); 30 to 65 mol%, (b); 5 to 45 mol%, (c); 5 to 50 mol%, (d); 1 to 25 mol% and (e); 0 to 20 mol %, The fluorine-containing copolymer having a number average molecular weight of 1,000 to 200,000, and the second invention is a coating composition comprising the fluorine-containing copolymer and a curing agent.

The present invention will be described in more detail below. The fluorine-based monomer used in the present invention is chlorotrifluoroethylene or tetrafluoroethylene, and chlorotrifluoroethylene is preferable from the viewpoint of easy handling.

Examples of norbornadiene or a norbornadiene having a substituent include 2,5-norbornadiene,
Examples thereof include ethyl norbornadiene 2-carboxylate, methyl norbornadiene 2-carboxylate, 2-methoxynorbornadiene and 7-cyanonorbornadiene. 2,5-norbornadiene is preferable in terms of excellent polymerizability.

Regarding the aliphatic carboxylic acid vinyl ester or the alkyl vinyl ether, either one of them may be used, or both may be used in combination.
Aliphatic carboxylic acid vinyl ester is more preferable because it is excellent in storage stability of the resulting organic solvent solution of the fluorine-containing copolymer. Incidentally, the aliphatic carboxylic acid vinyl ester in the present invention includes an alicyclic carboxylic acid vinyl ester,
The alkyl vinyl ether includes cycloalkyl vinyl ether.

Examples of the aliphatic carboxylic acid vinyl ester in the present invention include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl laurate, vinyl stearate, vinyl pivalate, vinyl versatate and cyclohexane. Examples thereof include vinyl carboxylate. With vinyl esters of aromatic carboxylic acids such as vinyl benzoate, the resulting fluorocopolymer has poor weather resistance. Examples of the alkyl vinyl ether include methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether, lauryl vinyl ether, stearyl vinyl ether and cyclohexyl vinyl ether.

As the vinyl monomer containing a hydroxyl group,
Examples thereof include hydroxyethyl crotonate, hydroxybutyl vinyl ether, hydroxyethyl allyl ether and hydroxyethyl methacrylate. From the viewpoint of weather resistance and adhesion to a substrate, hydroxyethyl crotonate or hydroxybutyl vinyl ether is preferable, and hydroxyethyl crotonate is particularly preferable.

In the present invention, other vinyl monomers other than the above-mentioned monomers may be optionally used. Examples of the vinyl monomer include α-olefins such as ethylene, propylene and isobutylene; vinyl chloride. Partially halogenated olefins such as vinylidene chloride, vinyl fluoride and vinylidene fluoride; (meth) acrylic acid esters such as methyl methacrylate and methyl acrylate; allyl compounds such as allyl acetate and allyl butyrate; ethyl crotonate, propyl crotonate, etc. Crotonic acid esters of crotonic acid,
Examples include α, β-unsaturated carboxylic acids such as (meth) acrylic acid and vinylacetic acid.

The fluorine-containing copolymer of the present invention can be obtained by radically copolymerizing the above-mentioned monomer by the polymerization method described later. The ratio of each monomer unit in the fluorocopolymer of the present invention, as described above,
(A) Chlorotrifluoroethylene or tetrafluoroethylene monomer unit; 30 to 65 mol%, (b) norbornadiene or norbornadiene monomer unit having a substituent; 5 to 45 mol%, (c) aliphatic carboxylic acid Vinyl ester or alkyl vinyl ether monomer unit; 5 to 50 mol%, (d) hydroxyl group-containing vinyl monomer unit; 1 to 25 mol% and (e) other vinyl monomer unit; 0 to 20 mol %, And more preferably,
(A) 40 to 55 mol%, (b) 10 to 40 mol%,
(C) 10 to 40 mol%, (d) 3 to 20 mol%, and (e) 0 to 10 mol%.

The preferred glass transition temperature of the fluorinated copolymer of the present invention having the above structure is 40 to 120 ° C. As described above, since it has a higher glass transition temperature as compared with the conventionally known fluorine-containing copolymers for paints, the fluorine-containing copolymer of the present invention has a high glass transition temperature, for example, at a high temperature exceeding 60 ° C. A coating film having excellent stain resistance can be obtained.
A more preferable glass transition temperature is 50 to 100 ° C.

When the content of the chlorotrifluoroethylene or tetrafluoroethylene monomer unit is less than 30 mol%, the weather resistance is poor, and when it exceeds 65 mol%, the solubility in an organic solvent is poor. When the content of norbornadiene or the norbornadiene monomer unit having a substituent is less than 5 mol%, the glass transition temperature is too low and the stain resistance at high temperature is poor, while when it exceeds 45 mol%, the physical properties of the coating film obtained. Is inferior and many cracks are generated in the thermal cycle test. When the content of the aliphatic carboxylic acid vinyl ester or alkyl vinyl ether monomer unit is less than 5 mol%, the solubility of the fluorine-containing copolymer in an organic solvent is poor, while 5
If it exceeds 0 mol%, the weather resistance is poor. When the vinyl monomer unit containing a hydroxyl group is less than 1 mol%, the crosslink density in the cured resin obtained by reacting with the curing agent is too low, and when it exceeds 25 mol%, the crosslink density is too high and the processing is performed. Inferior in sex.

The fluorinated copolymer of the present invention is produced by a method of copolymerizing in the presence of a radical-generating polymerization initiator. As the polymerization method, suspension polymerization in an aqueous medium, emulsion polymerization, solution polymerization, or the like can be adopted. Regarding the method of charging each monomer to obtain a polymer having a desired monomer composition, for example, when an alkyl vinyl ether is used as the component (c), the total amount of all the charged monomers is Since they are copolymerized, it is sufficient to charge them in a batch at a rate corresponding to the monomer composition of the desired polymer. On the other hand, when the aliphatic carboxylic acid vinyl ester is used as the component (c), chlorotrifluoroethylene or tetrafluoroethylene is used as the chlorotrifluoroethylene or tetrafluoroethylene monomer in the target polymer. About 1.2 to 5 times the amount of the unit is charged, and the aliphatic carboxylic acid vinyl ester and other monomers are preferably charged in an amount corresponding to the monomer composition in the polymer.

Organic solvents preferably used when solution polymerization is employed include cyclic ethers such as tetrahydrofuran and dioxane; aromatic hydrocarbon compounds such as benzene, toluene and xylene; esters such as ethyl acetate and butyl acetate; Ketones such as acetone, methyl ethyl ketone, cyclohexanone; 1,1,2-trichloro 1,
Fluorocarbons such as 2,2-trifluoroethylene can be used, and one or more of these can be used.

Examples of radical-generating type polymerization initiators include peroxides such as diisopropyl peroxydicarbonate, tertiary butyl peroxypivalate, benzoyl peroxide and lauroyl peroxide, azobisisobutyronitrile and azobisisovalero. Azo compounds such as nitrile and inorganic peroxides such as ammonium persulfate and potassium persulfate can be used. Examples of emulsifiers in the case of employing emulsion polymerization include perfluorooctanoic acid potassium salt, ammonium salt, perfluorooctanesulfonic acid ammonium salt, higher alcohol sulfate sodium salt, polyethylene glycol ether and the like.

The polymerization temperature is preferably about 20 to 100 ° C., the polymerization pressure is suitably 1 to 200 kg / cm ² , and the polymerization is completed by conducting the polymerization in a pressure autoclave for 3 to 40 hours. If necessary, a pH adjusting agent such as potassium carbonate, sodium hydrogen carbonate, hydrotalcite and anion exchange resin may be added to the polymerization system.

According to the above polymerization method, the number average molecular weight in terms of polystyrene by gel permeation chromatography (hereinafter referred to as GPC) is 1,000 to 200,000.
A fluorine-containing copolymer of 0 is obtained. The more preferable number average molecular weight of the fluorocopolymer in the present invention is 3,000.
It is about 100,000. If the number average molecular weight is less than 3,000, the polymer becomes brittle, while if it exceeds 100,000, the viscosity is too high when used as a varnish, and it becomes difficult to coat.

The above-mentioned fluorine-containing copolymer is useful as a component of a room temperature or heat-curable coating material, and in that case, a curing agent is used in combination. The curing agent used in combination is a compound having two or more functional groups that react with hydroxyl groups in the molecule, and examples of such a compound include a polyvalent isocyanate compound or an aminoplast compound. Examples of the polyvalent isocyanate compound include hexamethylene diisocyanate, isophorone diisocyanate or a dimer or trimer thereof, and a blocked isocyanate. Examples of the aminoplast compound include melamine such as methylated melamine and butylated melamine, urea resin and benzoguanamine.

The proportion of the fluorine-containing copolymer and the polyvalent isocyanate compound used is such that the amount of isocyanate groups in the polyvalent isocyanate compound is approximately equal to the amount of hydroxyl groups in the copolymer. When an aminoplast compound is used, it is preferable that the amount of the reactive functional group is about 20 to 40% with respect to the amount of the hydroxyl group. A curing accelerator such as dibutyltin dilaurate or p-toluenesulfonic acid may be used in combination with the above curing agent.

Further, pigments such as titanium oxide, iron oxide, phthalocyanine blue, benzidine yellow, and quinacridone, metal powders such as stainless steel powder, aluminum powder, and bronze powder, dispersants, ultraviolet absorbers, and surfaces are used for forming paints. Additives such as regulators and thickeners can be added. The coating material thus obtained can be applied to a base material such as steel plate, stainless steel, aluminum, concrete, mortar, plastic, and wood by a spray, brush, roll, bar coater or the like. Hereinafter, the present invention will be specifically described with reference to examples.

[0024]

Example 1 In a 1 liter autoclave equipped with a stirrer, 300 g of butyl acetate, 100 g of 2,5-norbornadiene (hereinafter referred to as ND), 100 g of vinyl caproate (hereinafter referred to as VCp) and hydroxyethyl crotonate (hereinafter referred to as HECR). After charging 45 g and repeating deaeration and nitrogen replacement three times, 300 g of chlorotrifluoroethylene (hereinafter referred to as CTFE) was charged. Then, after raising the temperature to 64 ° C., 1 g of tertiary butyl peroxypivalate was press-fitted to start the polymerization. 10
Polymerization was carried out for a time, and when the pressure reached 7 kg / cm ² , unreacted CTFE was purged and the autoclave was opened to obtain a copolymer solution. The obtained solution was put into methanol, washed and dried to obtain 200 g of a copolymer. A 50% solids xylene solution of the obtained copolymer was a colorless and transparent solution, and no increase in viscosity was observed even when it was stored at room temperature for 6 months.

The number average molecular weight of the obtained copolymer is 12,
000 (polystyrene equivalent value by GPC),
The glass transition temperature (hereinafter referred to as Tg) of the copolymer was 55 ° C. The fluorine content of this copolymer was found by fluorine analysis to be 25.4% by weight, and the hydroxyl value was 24 (mg-KOH / g-resin).
Further, the composition of the polymer was analyzed together with the measurement results of ¹ H-NMR and ¹³ C-NMR. As a result, the composition of the copolymer was CTFE / ND / VCp / HECR = 52/1.
It was 9/23/6 (mol%).

[0026]

Example 2 A monomer to be copolymerized was CTFE / ND /
Vinyl propionate (hereinafter referred to as VPr) / HECR =
Polymerization was carried out in the same manner as in Example 1 except that the monomer was changed to 300 g / 40 g / 125 g / 55 g and the solvent was changed to xylene to obtain 250 g of a copolymer. A 50% solids xylene solution of the obtained copolymer was a colorless and transparent solution, and no increase in viscosity was observed even when it was stored at room temperature for 6 months.

The number average molecular weight of the above copolymer is 14,000.
The Tg was 58 ° C., the fluorine analysis value was 24.1%, and the hydroxyl value was 40. The composition of the polymer was analyzed in the same manner as in Example 1, and as a result, CTFE /
It was found that ND / VPr / HECR = 46/18/28/8 (mol%).

[0028]

Example 3 A monomer to be copolymerized was CTFE / ND /
VCp / HECR = 250g / 150g / 100g / 1
Polymerization was performed in the same manner as in Example 1 except that the monomer was changed to 00 g and the solvent was changed to xylene to obtain 230 g of a copolymer. A 50% solids xylene solution of the obtained copolymer is a colorless and transparent solution, which is used at room temperature for 6%.
No increase in viscosity was observed even after storage for months.

The number average molecular weight of the above copolymer is 11,000.
The Tg was 81 ° C., the fluorine analysis value was 24.5%, and the hydroxyl value was 51. And the composition of the copolymer is CTFE / ND / VCp / HE
CR = 49/27/13/11 (mol%).

[0030]

Example 4 The same autoclave used in Example 1 was charged with 250 g of xylene, 68 g of ND, 60 g of ethyl vinyl ether (hereinafter referred to as EVE), 48 g of hydroxybutyl vinyl ether (hereinafter referred to as HBVE) and 10 g of potassium carbonate, and degassed. After repeating nitrogen substitution 3 times, 300 g of CTFE was charged. Then 6
After raising the temperature to 4 ° C, azobisisobutyronitrile 2.
A xylene solution in which 5 g was dissolved was press-fitted to initiate polymerization. Polymerization was carried out for 20 hours, and when the pressure reached 6 kg / cm ² , unreacted CTFE was purged and the autoclave was opened to obtain a copolymer solution. The obtained solution was put into methanol, washed and dried to obtain 300 g of a copolymer. A 50% solids xylene solution of the obtained copolymer is
Although it was a colorless transparent solution, an increase in viscosity occurred when it was allowed to stand at room temperature for 6 months.

The number average molecular weight of the above copolymer is 13,000.
Its Tg is 63 ° C. and its fluorine analysis value is 27.
It was 8% and the hydroxyl value was 63. The composition of the copolymer is CTFE / ND / EVE / HBVE =
It was 50/15/23/12 (mol%).

[0032]

Example 5 Instead of the monomer used in Example 4, CT
FE / ND / VCp / Veova 9 [Vinyl ester consisting of carboxylic acid having 9 carbon atoms of Shell Chemical Co., Ltd.] / HB
Example 4 except that a monomer having a composition of VE = 300 g / 68 g / 50 g / 50 g / 55 g was used, and IRS94S (manufactured by Organo Corporation, ion exchange resin) was used as a deoxidizing agent instead of potassium carbonate. 270 g of a copolymer was obtained by the same procedure as described above. A 50% solids xylene solution of the obtained copolymer was a colorless and transparent solution, but when it was left at room temperature for 6 months, the viscosity increased.

The number average molecular weight of the above copolymer is 16,000.
Its Tg is 61 ° C., and its fluorine analysis value is 23.
It was 3% and the hydroxyl value was 58. The composition of the copolymer is CTFE / ND / VCp / Veova 9 /
HBVE = 49/17/11/10/13 (mol%).

Comparative Example 1 According to the polymerization method of Example 4, CTFE / cyclohexyl vinyl ether (hereinafter referred to as CHVE) / EVE / HB
Using monomers having a composition of VE = 260 g / 85 g / 81 g / 52 g, CTFE / CHVE / EVE / HBVE =
400 g of a copolymer having a composition of 50/14/26/10 (mol%) was obtained. The number average molecular weight of the obtained copolymer was 9,8.
00, its Tg was 21 ° C., and the hydroxyl value was 52.

Comparative Example 2 By the polymerization method of Example 1, CTFE / paratertiarybutyl vinyl benzoate (hereinafter referred to as tBVBz) / H
CTFE / tBVBz / HECR = 45/44 using a monomer having a composition of ECR = 140 g / 108 g / 29 g
170 g of a copolymer having a composition of / 11 (mol%) was obtained. The number average molecular weight of the obtained copolymer was 21,000, its Tg was 85 ° C., and the hydroxyl value was 50.

Next, a coating composition was prepared by using a 50 wt% xylene solution (hereinafter referred to as varnish) of the fluorocopolymer obtained in each of the above examples, and the coating film physical properties were evaluated. The physical properties of the coating film were measured by the following methods. a. 60 degree gloss: the method specified in JIS-K5400. b. Pencil hardness: The method specified in JIS-K5400. c. Cross-cut peeling: 100 cuts were made in a 1 cm ² square and the residual rate when peeled with cellophane tape was evaluated. Further, the peeling residual ratio after immersing the notched coated plate in boiling water for 1 hour and the appearance of the coating film after boiling water are also shown. d. Weather resistance: Using a fluorescent UV weather resistance tester manufactured by Q Panel Co., continuous irradiation with light rays was performed, and ion exchange water was sprayed from the back side of the coated surface for 4 hours out of each 8 hours. The 60-degree gloss retention (%) was evaluated after the 4000-hour test.

E. Thermal cycle test: Room temperature water (16
Time) → 130 ° C. constant temperature bath (3 hours) → −30 ° C. constant temperature bath (3 hours) as one cycle, and the state of the coated surface after 50 cycles was observed. f. Contamination test: After a 0.1% aqueous solution of carbon black was sprayed on the coated surface and the cycle of heating at 90 ° C. for 15 minutes was repeated 6 times, the coated plate was washed with water and the stain condition was visually observed. The symbols of the evaluation results have the following meanings. ○: Dirt is not noticeable. Δ: Some dirt remains. X: Stain remains clearly.

[0038]

Example 6 To 100 parts of a varnish composed of the fluorine-containing copolymer of Example 1, 45 parts of a mixed solution of xylene and methyl isobutyl ketone in an equal amount as a thinner, Tybak CR-9 was used.
0 [Titanium oxide manufactured by Ishihara Sangyo Co., Ltd.] (26.9 parts) and glass beads (150 parts) were added, and the resulting mixture was dispersed with a paint conditioner. Then, the glass beads were removed with a filter cloth, and the resulting solution was added with Coronate H as a curing agent.
X [Nippon Polyurethane Co., Isocyanate] 4.3
Parts (amount of hydroxyl value / NCO value = 1.0 of fluorine-containing copolymer) and 1.0 part of a 0.1 wt% xylene solution of dibutyltin dilaurate as a curing accelerator were added to prepare a coating composition. . Apply the resulting paint on a chromate-treated galvanized steel sheet (thickness: 0.6 mm) that has been coated and baked with an epoxy-based undercoating paint so that the film thickness after drying will be 40μ,
It was dried at room temperature for one week. Table 1 shows the evaluation results of the physical properties of the obtained coating film.

[0039]

Examples 7 to 10 By the same method as in Example 6, using the varnish made of the fluorine-containing copolymer obtained in Examples 2 to 5, coated plates were prepared and coating films were tested. The results are shown in Table 1.
It is as follows. Comparative Examples 3 to 4 Other than using the fluorocopolymer varnish of Comparative Examples 1 and 2,
A coated plate was prepared and tested in the same manner as in Example 6. The results are shown in Table 1.

[0040]

[Table 1]

[0041]

INDUSTRIAL APPLICABILITY According to the present invention, a novel fluorine-containing copolymer suitable as a coating resin can be obtained, and a curable coating composition comprising the fluorine-containing copolymer and a curing agent has a temperature of, for example, 60 ° C. It has a characteristic that conventional fluorine-containing resin coatings do not have, such as excellent stain resistance at high temperatures exceeding 100 ° C.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location C08F 218/04 MLH 6904-4J 220/26 MMN 7242-4J 232/08 MNW 7242-4J C09D 123 / 18 PER 7107-4J 127/02 PFC 9166-4J 127/18 PFG 9166-4J 129/10 PFP 6904-4J 131/02 PFR 6904-4J 145/00 PGM 7921-4J (72) Inventor Tatsuo Nishio Nagoya, Aichi Prefecture 1 Toa Synthetic Chemical Industry Co., Ltd. Nagoya Research Institute, 1 Funa-cho, Minato-ku, Japan

Claims (2)

[Claims] 1. A unit of (a) chlorotrifluoroethylene or tetrafluoroethylene monomer unit, (b) norbornadiene or norbornadiene monomer unit having a substituent, (c) aliphatic carboxylic acid vinyl ester or alkyl vinyl ether monomer Body unit and (d) a hydroxyl group-containing vinyl monomer unit, or (a) above
~ (D) and (e) consisting of other vinyl monomer units,
The ratio of each component based on the total amount of all monomer units,
(A); 30 to 65 mol%, (b); 5 to 45 mol%,
(C); 5 to 50 mol%, (d); 1 to 25 mol% and (e); 0 to 20 mol% and having a number average molecular weight of 1,000.
A fluorine-containing copolymer having a viscosity of about 200,000. 2. A coating composition comprising the fluorine-containing copolymer according to claim 1 and a curing agent.