JP2746412B2 - Fluorine-containing resin for paint - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fluorine-containing resin for coatings, and more particularly, to a curable curable resin containing a fluoroolefin, an alkene, and a hydroxy group-containing allyl ether as essential components. The present invention relates to a fluorine-containing resin for paint.

(Conventional technology) Conventionally, paints using fluoropolymers are made of weather resistance, heat resistance,
Because of its excellent chemical resistance, it is widely used in the fields of chemical industry, architecture, food, machinery and the like.

In particular, a solvent-soluble fluororesin paint with improved workability has recently been spotlighted. These are paints that increase the solubility in organic solvents, allow them to be dissolved in common paint solvents, and allow them to be cured at room temperature from what had to be baked at high temperatures. As well as hydrocarbon-based solvent-based paints, they can be used on site as well as long-term maintenance-free paints that take advantage of their weather resistance and chemical resistance, and are growing for construction, civil engineering and machine metal applications.

(Problems to be solved by the invention) In order to make fluororesin soluble in organic solvents,
Usually, the crystallinity of the fluororesin is disturbed by a method such as copolymerization,
Needs internal plasticization. Furthermore, in order to make these paints, the problem of how to maintain the rigidity, which is the original property of the resin, the problem of the molecular weight of the resin to adjust the viscosity of the paint, or the maintenance of chemical resistance and overcoating In order to make it possible, it is necessary to introduce a functional group into the resin and to cure the resin. In this case, there are problems such as how to select the type and amount of the functional group, and further, a problem in terms of price.

From these viewpoints, fluorine resins for paints proposed from the viewpoint include copolymers containing fluoroolefins, cyclohexyl vinyl ethers, alkyl vinyl ethers and hydroxyalkyl vinyl ethers as essential components (JP-A-57-3410).
7) a copolymer containing fluoroolefin, vinyl carboxylate, and hydroxy-containing allyl ether as essential components (Japanese Patent Application Laid-Open No. 61-57609) or a fluoroolefin, vinyl carboxylate, alkyl vinyl ether, and hydroxyalkyl vinyl ether as essential components. (JP-A-61-275311). All of these copolymers are soluble in organic solvents, and are made difficult to dissolve in the initial solvent by crosslinking with isocyanate-based curing agents and melamine curing agents using functional groups. It is specified that a coating film having excellent properties and chemical resistance can be obtained.

The superiority of the weather resistance of the coating film is judged in a comprehensive manner by the type and amount of the resin, curing agent, solvent, pigment or additive, which affect each other. There is no doubt that the resin present in plays an important role. Light, water, oxygen, heat, and the like are mainly cited as factors for the deterioration of the resin. In order to improve the weather resistance, it is important to use a resin that is as inert as possible to these factors. For example, with respect to deterioration due to light, it is important not to have a part that absorbs light in the structure, and for deterioration due to water, it is important to minimize parts having poor water resistance. Similarly, it is important to make the structure less susceptible to attack by oxygen and the structure having heat resistance against deterioration due to oxygen or heat.

The present inventors have conducted intensive studies on a resin that can be a base resin of a solvent-soluble coating fluororesin from the above viewpoint, and as a result, it has been found that a copolymer of a fluoroolefin and an alkene is extremely resistant to the above-mentioned deterioration factors. It turned out to be stable, and I had been paying more attention. That is, it has been reported that a chlorotrifluoroolefin (CTFE) and alkene copolymer can be obtained as a transparent and highly crystalline resinous material as described in British Patent No. 949,422 and US Patent No. 2,753,328. ing. The same is true for tetrafluoroethylene (TFE) and ethylene [N. Sakai, Organofluorine Chemistry (II), P517, Gihodo (197
3)]. In addition, all of the produced resins have excellent alternating properties.
It is known that a resin containing CTFE and having excellent alternating properties is produced.

Thus, CTFE-ethylene (UK Patent 949,422), C
Among resins such as TFE-isobutylene (US Patent 2,753,328) and CTFE-vinyl ether (US Patent 2,834,767),
Ethylene series and propylene series are characterized by high fluorine content per structural unit. However, when used as a paint, it is necessary to dissolve it in a solvent, and in order to obtain a recoating property, it is necessary to put a site which reacts with a curing agent in the resin.

As proposed from such a viewpoint, Japanese Patent Laid-Open Publication No.
There are 19372. This is a copolymer obtained by adding hydroxyalkyl vinyl ether or vinyl ester as a curing site to a fluoroolefin and an α-olefin, and reacting with a curing agent such as isocyanate or melamine using the OH group in the copolymer to cure. Obtaining a coating film. However, when alkyl vinyl ether is used as the curing site, compatibility with the curing agent is not always satisfactory, and gelation proceeds due to a decrease in the pH of the liquid during production, and it is difficult to become a resin soluble in the intended solvent. There is a problem. Therefore, it is necessary to add a large amount of acid acceptor at the time of polymerization in order to prevent the pH from dropping during the production, and a small amount of this acid remains in the final resin liquid production process, resulting in turbidity of the liquid and gloss when the film is formed. Contribute to closing. In order to further use as a paint, it is necessary to improve the dispersibility of the color pigment. Usually, a polar group such as a carboxyl group is introduced into a polymer chain. In the case where is used, since it reacts with a monomer having a carboxyl group, there is a problem that it is difficult to directly introduce it in the form of a monomer during polymerization.

Also, as described above, vinyl monomers are difficult to polymerize in the presence of an acid, as described in Synthetic Organic Chemistry, vol. 42, p. 842-84.
3 (1984), concerning the copolymerization of vinyl ether, vinyl ether is a cationically polymerizable monomer, radical polymerization is not easy, and it is easily hydrolyzed to acetoaldehyde and alcohol in the presence of proton.
Furthermore, it is difficult to introduce a carboxyl group by copolymerization because vinyl ether is unstable in an acidic atmosphere. Therefore, it is described that a small amount of a carboxyl group is introduced by using a polymer reaction as necessary for a resin after polymerization by utilizing the reactivity of a hydroxyl group.

For these reasons, it is difficult to directly copolymerize a carboxyl group-containing monomer in vinyl ether copolymerization, so that a carboxyl group is introduced by a polymer reaction.For example, in JP-A-58-136605, After polymerization of a hydroxyl group-containing fluororesin, a technique of reacting the resin with succinic anhydride to introduce a carboxyl group is employed.

Means for Solving the Problems The present inventors have conducted intensive studies on the cure site for solving the above-mentioned disadvantages, and as a result, have found that a desired copolymer can be obtained by using a hydroxy group-containing allyl ether, and have completed the present invention. .

That is, a resin obtained by copolymerizing a hydroxy-containing allyl ether with a fluoroolefin or alkene has excellent compatibility with various isocyanates and melamines as curing agents, and can be produced without special use of an acid acceptor during the production of the resin. It is possible to produce it in one step even when a carboxyl group-containing monomer for improving the dispersibility of the pigment is added. Further, since the hydroxy group-containing allyl ether retains an allyl bond which is easily chain-transferred in the molecule, the use of a chain transfer agent is not particularly required for applications where a resin having a relatively low molecular weight is required, such as a paint. Also has the advantage that the molecular weight can be reduced.

The copolymer of the present invention is a fluoroolefin, alkene,
The content of the carboxyl group-containing unit based on the hydroxy co-containing allyl ether and the carboxyl group-containing monomer is 25 to 75 mol%, 10 to 70 mol%, 3 to 40 mol% and 0 to 20 mol%, respectively. And preferably in the range of 30 to 60 mol%, 20 to 50 mol%, 5 to 30 mol% and 0 to 10 mol%.

Here, the content of the fluoroolefin can be arbitrarily changed depending on the amount of each monomer at the time of charging.However, if the content is too high, the solubility of the copolymer in an organic solvent is reduced, and the copolymer is difficult to manufacture. This results in a reduced yield. Conversely, if the amount is small, it is not preferable from the viewpoint of physical properties such as weather resistance and chemical resistance. Further, a copolymer having an alkene content that is too high is not preferable in terms of physical properties such as weather resistance and chemical resistance, and a copolymer that is too low results in a decrease in copolymer yield in terms of production. If the content of the hydroxy-containing allyl ether is too high, the molecular weight is reduced, and a problem arises in production. On the other hand, when the content of the hydroxy group-containing allyl ether is too low, the solubility in the organic solvent is deteriorated, and the crosslinking density is reduced, which causes problems in weather resistance and chemical resistance, making it difficult to perform recoating or the like. Become. If the units based on other monomers are too high, disadvantageous problems arise in terms of solubility and production.

As the fluoroolefin used in the present invention, tetrafluoroolefin, chlorotrifluoroolefin,
Hexafluoropropylene and the like can be used, but chlorotrifluoroethylene or tetrafluoroethylene is preferred from the viewpoint of practical resin properties such as the coating film type and the adhesion between the underground substrate and the coating film.

Examples of the alkene include ethylene, propylene, n-butene, iso-butene, n-hexane, iso-octene, vinylcyclohexene, 1-octene, and vinylcyclohexane.Ethylene, propylene, n-Butene and iso-butene are preferred or these alkenes can be used in combination.

As the hydroxy group-containing allyl ether, CH ₂ CHCH—C
H ₂ -OR (provided that n = 0 to 6, X = H or CH ₃ ], allyl alcohol, ethylene glycol monoallyl ether, diethylene glycol monoallyl ether, triethylene glycol monoallyl ether, hydroxypropyl allyl ether, etc. can be used, Those having a unit of n = 0 to 2 are preferred. As the carboxyl group-containing monomer, acrylic acid, methacrylic acid, vinyl acetic acid, allyloxyacetic acid, itaconic acid and the like can be used, but acrylic acid, methacrylic acid and vinyl acetic acid are preferred. The hydroxy-containing allyl ether of the present invention may be used in combination with a hydroxy-containing vinyl ether such as hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, and hydroxybutyl vinyl ether.

Further, the fluorine-containing resin for a coating material of the present invention is solely soluble in a low-polarity organic solvent such as xylene and toluene. However, if necessary, another organic solvent may be mixed and used. Other organic solvents include cyclic ethers such as tetrahydrofuran and dioxane, aromatic hydrocarbons such as benzene, toluene, and xylene; esters such as ethyl acetate and bityl acetate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. , Dimethylformamide, dimethylacetamide, pyridine and the like; and nitrogen-containing solvents such as 1.1.1-trichloroethane and trichloroethylene.

The fluoroolefin, alkene, hydroxy-containing allyl ether of the present invention, and a fluorine-containing resin for coating obtained by further copolymerizing a monomer containing a carboxyl group-containing monomer can be prepared by a solution in the presence of a usual radical initiator. It can be produced by polymerization, the polymerization temperature varies depending on the type of polymerization initiator, is -30 ~ 130 ℃, preferably 0 ~ 100 ℃
Is appropriate.

Examples of the radical initiator include oil-soluble radical initiators such as diisopropyl peroxydicarbonate, dinormal propyl peroxydicarbonate, tertiary butyl peroxypivalate, di-2-ethylhexylperoxydicarbonate, benzoyl peroxide, lauroyl peroxide. Peroxides such as oxide, propionyl peroxide, trichloroacetyl peroxide, perfluorobutyl peroxide, perfluorooctanoyl peroxide, azobisisobutyronitrile, azobis-
An azo compound such as 2.4-dimethylparenitrile, or an organic boron-based compound such as triethylboron-oxygen or a peroxide is exemplified.

The purity of the co-weight may be 98% or more as long as it does not contain impurities that do not interfere with ordinary radical polymerization.

Since the resin for a fluorine-containing coating material thus obtained has active hydrogen in the molecular chain, it can be cured by a compound having a functional group that reacts with active hydrogen. That is, a polyvalent isocyanate is added to a solution obtained by dissolving the resin for a fluorine-containing paint in the solvent described above, and the solvent is scattered so that the reaction proceeds at room temperature. By treating at a temperature higher than the temperature at which the dissociation occurs, the curing reaction proceeds, and each cured coating film is obtained. Also melamine, urea resin,
It reacts with polybasic acids or their anhydrides at high temperatures to form cured coatings. Furthermore, the solution of the resin for a fluorine-containing paint includes
It is also possible to add a pigment, an ultraviolet absorber, a dispersion stabilizer and the like, and in each case, good dispersibility is exhibited.

Next, the present invention will be described more specifically with reference to Examples, but it should not be construed that the invention is limited thereto.

Examples 1 to 7 and Comparative Examples 1 and 2 In a 1.0 L SUS product autoclave equipped with a magnetic stirrer, the amounts of hydroxy-containing allyl ether, hydroxy-containing vinyl ether, vinyl acetic acid (VA
A), 7.3 g of Parloyl NPP (trade name of Nippon Oil & Fat), xylene or butyl acetate were charged, and the inside of the autoclave was replaced with nitrogen gas three times and degassed. Thereafter, a fluoroolefin (CTFE and TFE) and an alkene were charged, and the temperature was gradually raised. After polymerization at 40 ° C. for 24 hours, unreacted fluoroolefin and gaseous alkene were removed, and the autoclave was opened. Then, after the polymerization liquid was filtered, the solid component concentration was measured. A part of the polymerization solution was put into n-hexane to cause reprecipitation, and the resin obtained after drying was used for evaluation of various physical properties. The molecular weight is the number average molecular weight (Mn) in terms of polystyrene determined by GPC, and the glass transition temperature (Tg) is a value determined from dynamic viscoelasticity by the TBA method. The OH value was determined by an acetylation method using acetic anhydride.

Using the resin liquids obtained in Examples 1, 2, and 6 and Comparative Example 2, a compatibility comparison test with various curing agents was performed. That is, various curing agents were added to the resin solution adjusted to 50% concentration.
Add 0 parts, add 30 parts solids and mix well, drop it on a glass plate, leave it for 24 hours at 140 ° C
Was determined by the turbidity of the coating film after baking for 30 minutes. Table 2 shows the results.

From Tables 1 and 2, a gelation phenomenon was observed in Comparative Examples (using an alkyl vinyl ether as a curing site), and it was difficult to copolymerize a carboxyl group-containing monomer in one step under the same conditions. Care must also be taken in the selection of a combination with a curing agent.
In addition, the molecular weight of the formed resin is large, which makes it difficult to maintain the smoothness of the coating film.

In the resin solution adjusted to 50% concentration of the resin obtained in each example,
A titanium oxide pigment (manufactured by Ishihara Sangyo; Taipaque CR-90) was added so as to be 50 parts by weight with respect to the resin content, and mixed with a ball mill to produce a white mill base. An isocyanate-based curing agent ("Coronate EH" manufactured by Nippon Polyurethane Co., Ltd.) was added to this in an amount equivalent to the hydroxyl value of each example, and the mixture was applied on a chromate-treated aluminum plate degreased with acetone using an applicator. After baking and hardening at 1 ° C. for 1 hour, it was left to stand for 2 days and subjected to a physical property test. The thickness of the coating film was 30 to 35 μm, and the results shown in Table 3 were obtained. The evaluation of the physical properties of the coating film was mainly performed according to JISK5400.

(Effect of the Invention) The fluororesin of the present invention has a low molecular weight, is soluble in ordinary organic solvents, has good compatibility with various effect agents, and has a coating film made of weather resistance and chemical resistance. It is suitable as a paint exhibiting performance such as the above and further, pigment dispersibility.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08F 214: 18 216: 14 220: 04) (C08F 214/18 210: 00 216: 14 220: 04)

Claims (6)

(57) [Claims] A fluoroolefin, an alkene and a compound of the formula CH ₂ CHCH—CH ₂ —O—R wherein R is n is an integer of 0 to 6, X represents a H or CH _3. Wherein the content of the unit based on the fluoroolefin, the alkene and the hydroxy group-containing allyl ether is 25 to 75%, 10 to 70 mol% and 3 to 40 mol, respectively. % Of fluorine-containing resin for paint. 2. The fluorine-containing resin for paint according to claim 1, further comprising up to 20 mol% of a carboxyl group-containing unit based on the carboxyl group-containing monomer. 3. The fluorine-containing resin for paint according to claim 1, wherein the unit based on fluoroolefin is a unit based on chlorotrifluoroethylene or tetrafluoroethylene. 4. The fluororesin for coatings according to claim 1, wherein the unit based on alkene is a unit based on ethylene, propylene, n-butene or iso-butene. 5. The fluorine-containing resin according to claim 1, wherein the unit based on the hydroxy group-containing allyl ether is a unit based on allyl alcohol, ethylene glycol monoallyl ether or diethylene glycol monoallyl ether. 6. The fluorine-containing resin for paint according to claim 2, wherein the carboxyl group-containing monomer is acrylic acid, methacrylic acid, vinyl acetic acid, allyloxy acetic acid or itaconic acid.