JP3206794B2 - Method for producing cold-curable coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a fluororesin paint having excellent weather resistance. According to the present invention, a composition for a room temperature curable paint having significantly improved stain resistance is provided. Obtained easily.

[0002]

2. Description of the Related Art Fluororesin paints are used in a wide range of industrial fields as highly durable paints, and on-site construction, which was impossible with conventional dispersion type fluororesin paints, This has become possible with the advent of solvent-soluble fluororesin paints. Room-temperature-curable paints composed of polyvalent isocyanate as a curing agent and a solvent-soluble fluororesin are generally used for on-site construction.However, conventional fluororesin-based cold-curable paints have poor weather resistance. Although excellent, there was a problem in stain resistance, and there were restrictions on applications.

[0003] That is, not only in an environment with a lot of pollutants such as along an expressway, in a factory area, but also in an outer wall of a building having a structure to which dirt easily adheres, a curtain wall in which the temperature of a painted surface tends to rise, and an automobile. With respect to painted steel sheets and the like, the conventional fluororesin-based room-temperature-curable paints are significantly contaminated, and improvements have been required. As means for improving the stain resistance of a fluororesin-based paint, Japanese Patent Application Laid-Open No.
In JP-A No. 1 (1993), a silane compound having a hydrolyzable group such as tetraalkoxysilane is added to an organic solvent solution of a fluorine-containing copolymer having a functional group such as a hydroxyl group or a carboxyl group. A silane-modified fluorinated copolymer obtained by reacting the functional group with a silane compound has been proposed.

The above-mentioned silane-modified fluorine-containing copolymer is a self-condensing type curable polymer which is cured by a condensation reaction of silanol groups generated by hydrolysis of a silane compound introduced therein. By heat-curing the copolymer in the presence or absence of a catalyst, a coating film having excellent mechanical strength and stain resistance can be obtained. However, the silane-modified fluorine-containing copolymer is used in combination with a polyvalent isocyanate, and the coating film obtained by curing at room temperature has low hardness and insufficient weather resistance,
There is a technically unsolved problem in using the silane-modified fluorinated copolymer alone as a cold-setting resin for coatings.

[0005] Further, in the case of a hard coat composition comprising a fluororesin, a polyvalent isocyanate and a metal oxide sol disclosed in Japanese Patent Application Laid-Open No. 4-211482, as will be apparent from Comparative Example 2 described later, the anti-hard coat composition is hardened. Contamination was equivalent to a fluororesin-based paint to which no metal alkoxide such as alkoxysilane was added, and was not particularly good.

The present inventors have studied to obtain a fluororesin-based coating composition which can be cured at room temperature with a polyvalent isocyanate, and which forms a coating film having high hardness and excellent stain resistance. For a room-temperature-curable coating composition, a silane-modified fluorine-containing copolymer obtained by adding a hydrolyzable silane compound to a solvent-soluble fluorine-containing copolymer having 10 to 20 mol% of a monomer unit. A patent application has been filed for the composition (Japanese Patent Application No. 5-271195).

[0007]

Means for Solving the Problems In addition to the invention according to the above-mentioned patent application, the inventors of the present invention have added a hydroxyl-containing monomer unit as a starting material of the silane-modified fluorinated copolymer. It has been found that a solvent-soluble fluorine-containing copolymer containing more than 20 mol% and up to 50 mol% exhibits the same excellent action and effect, and has completed the present invention.

That is, the present invention relates to an organic solvent solution of a solvent-soluble fluorinated copolymer containing more than 20 mol% and up to 50 mol% of a hydroxyl group-containing monomer unit. Per part, a silane compound having two or more hydrolyzable groups or a low condensate thereof is added at a ratio of 5 to 100 parts by weight, and then water is added to obtain a silane-modified fluorine-containing copolymer (B). A solvent-soluble fluorine-containing copolymer (A) containing 3 to 20 mol% of a hydroxyl group-containing monomer unit in an organic solvent solution has a weight ratio of the copolymer (B) to the copolymer (A) of 1 to 1. 2.0 or less,
A method for producing a composition for a room temperature-curable coating material, which comprises mixing a polyvalent isocyanate into the obtained polymer solution.

Hereinafter, the present invention will be described in detail. First, the fluorine-containing copolymer (A) will be described. As described above, the fluorinated copolymer (A) in the present invention is a solvent-soluble fluorinated copolymer containing 3 to 20 mol% of a hydroxyl group-containing monomer unit, and is preferably a fluorinated copolymer constituting the copolymer. As the fluorine monomer, vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene,
Examples thereof include fluoroolefins such as chlorotrifluoroethylene and hexafluoropropylene, more preferably tetrafluoroethylene and chlorotrifluoroethylene, and particularly preferably chlorotrifluoroethylene. The preferred ratio of the fluoroolefin monomer unit in the fluorinated copolymer (A) is from 35 to 6
0 mol%, and more preferably 40 to 55 mol%.
It is. When the proportion of the fluoroolefin monomer unit is 35,
If it is less than mol%, the weather resistance tends to be insufficient, while if it exceeds 60 mol%, it becomes difficult to dissolve in an organic solvent.

As the hydroxyl group-containing monomer, crotonic acid 2
-Hydroxyethyl, 3-hydroxypropyl crotonic acid, 2,2-dimethyl crotonic acid 3-hydroxypropyl, 4-hydroxybutyl crotonic acid, 5-crotonic acid 5-
Hydroxyalkyl crotonates such as hydroxypentyl and 6-hydroxyhexyl crotonate; 2-
Hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether and 4-hydroxybutyl vinyl ether; allyls such as 2-hydroxyethyl allyl ether, 3-hydroxypropyl allyl ether, 4-hydroxybutyl allyl ether and diethylene glycol monoallyl ether Ethers; methallyl ethers such as 2-hydroxyethyl methallyl ether, 3-hydroxypropyl methallyl ether and 4-hydroxybutyl methallyl ether; If the proportion of the hydroxyl group-containing monomer unit in the fluorinated copolymer (A) is less than 3 mol%, the curing reaction with the polyvalent isocyanate becomes insufficient, and the chemical resistance and water resistance of the coating film are poor. If it exceeds 20 mol%, the weather resistance of the coating film will be poor.

In order to obtain the fluorine-containing copolymer (A), it is preferable to use another copolymerizable monomer together with the above-mentioned fluorine-containing monomer and hydroxyl group-containing monomer. , Methyl vinyl ether, ethyl vinyl ether, n-butyl vinyl ether, cyclohexyl vinyl ether and other vinyl ethers; vinyl carboxylate such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl caproate, vinyl versatate, vinyl stearate, etc. Esters; acrylic acid,
Unsaturated carboxylic acids such as crotonic acid, maleic acid, itaconic acid, and vinyl acetic acid, and anhydrides thereof, and the like. The preferred ratio of the above-mentioned comonomer unit in the fluorinated copolymer (A) is from 20 to 62 mol%.

The fluorinated copolymer (A) can be produced by copolymerizing the monomers by a solution polymerization method described in, for example, JP-A-3-231906.
That is, as a polymerization solvent, toluene, xylene or butyl acetate or the like, and as a polymerization initiator t-butyl peroxypivalate, t-butyl peroxyacetate, a radical-generating compound such as azobisisobutyronitrile,
The mixture of the monomers may be polymerized at a temperature of 40 to 80 ° C. for about 5 to 20 hours, respectively.

The silane-modified fluorinated copolymer (B) is a modified polymer synthesized by the above-mentioned method, and is used as a starting material for the fluorinated copolymer (hereinafter referred to as a fluorinated copolymer for modification). Is a solvent-soluble fluorinated copolymer containing more than 20 mol% and up to 50 mol% of hydroxyl-containing monomer units, as described above. The ratio of the hydroxyl group-containing monomer unit in the fluorinated copolymer for modification is 5
If it exceeds 0 mol%, the weatherability of the coating composition obtained will be poor.

The structural units in the modifying fluorine-containing copolymer are the same monomer units as in the above-mentioned fluorine-containing copolymer (A), and the preferred constitution of the modifying fluorine-containing copolymer is 35 to 60 mol% of a fluoroolefin monomer unit and 2 of a hydroxyl group-containing monomer unit based on the total amount of the
More than 0 mol% and 50 mol% or less and 0 to 45 mol% of other copolymerizable monomer units.

In the present invention, the fluorinated copolymer for modification is dissolved in an organic solvent, a silane compound described later is added to the copolymer solution, and then a small amount of water is added, whereby the solution in the solution is dissolved. The silane-modified fluorocopolymer (B) modified by means of hydrolyzing part or all of the silane compound is used.

Examples of the organic solvent used in the above operation include ethyl acetate, butyl acetate, xylene, cyclohexanone, ethyl cellosolve acetate, methyl ethyl ketone, methyl isobutyl ketone, ethyl cellosolve, butyl cellosolve, isopropanol and cyclohexanol. Alternatively, two or more kinds are used in combination. A more preferred organic solvent is a solvent containing 10 to 50% by weight of an alcohol in that the silane-modified fluorinated copolymer (B) produced by adding water is stably present in a solution. The preferred concentration of the modifying fluorine-containing copolymer in the organic solvent solution is 10 to 40% by weight.

In the present invention, as described above, a silane compound having two or more hydrolyzable groups or a low condensate thereof is used, and a preferred hydrolyzable group is an alkoxy group. Specific examples of such silane compounds having two or more alkoxy groups include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane and tetrabutoxysilane; methyltrimethoxysilane, ethyltriethoxysilane, methyltriethoxysilane. Alkyltrialkoxysilanes such as silane, ethyltrimethoxysilane, propyltrimethoxysilane and butyltrimethoxysilane; and dialkyldialkoxysilanes such as dimethyldimethoxysilane, diethyldiethoxysilane, dipropyldimethoxysilane and dibutyldimethoxysilane. . Examples of the low condensate that can be used in the same manner as the above silane compound include dimers, trimers, tetramers, and pentamers of each of the silane compounds exemplified above, and mixtures thereof. Hereinafter, it is generically referred to as a silane compound including a low-condensate. More preferably,
It is a silane compound having a highly hydrolyzable methoxy group or an ethoxy group, particularly preferably tetramethoxysilane, tetraethoxysilanesilane and low-condensates thereof.

In addition to the above silane compounds, silane compounds usable in the present invention include vinyltrimethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, γ-chloropropyltrimethoxysilane, γ -Aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-hydroxypropyltrimethoxysilane and the like.

The amount of the silane compound to be added to the modifying fluorine-containing copolymer is 5 to 100 parts by weight of the copolymer.
100 parts by weight, more preferably 30 to 100 parts by weight. If the amount of the silane compound exceeds 100 parts by weight, precipitation occurs in the solution, and a stable silane-modified fluorine-containing copolymer solution cannot be obtained. On the other hand, if the amount of the silane compound is less than 5 parts by weight, the coating composition obtained will have poor stain resistance of the coating film. The above silane compound is at room temperature
It is preferable to add to the organic solvent solution of the fluorine-containing copolymer for modification maintained at 80 ° C.

Water can be added to the organic solvent solution of the modifying fluorine-containing copolymer to which the silane compound has been added immediately after the addition of the silane compound is completed. It is preferable to add an acidic compound such as an acid, acetic acid and p-toluenesulfonic acid as a catalyst for hydrolyzing the silane compound. By using an acid catalyst, hydrolysis proceeds smoothly, and a stable silane-modified fluorine-containing copolymer solution can be obtained. As a method for adding water, a method of gradually dropping water into a polymer solution maintained at room temperature to 80 ° C. is preferable. With the addition of water, the silane compound present in the solution undergoes a condensation reaction along with the hydrolysis, and a part of the silane compound reacts with a hydroxyl group in the fluorinated copolymer for modification to form a side chain of the copolymer. I do.

The theoretical amount of water in the above hydrolysis reaction is:
Water is 1 mol per 2 mol of the hydrolyzable group of the silane compound. In the present invention, it is preferable to add 0.1 to 3 mol of water per 2 mol of the hydrolyzable group in the added silane compound. . When the amount of water added is less than 0.1 mol, the stain resistance of the coating film obtained by the coating composition is inferior,
On the other hand, if it exceeds 3 mol, precipitation occurs, and a stable silane-modified fluorine-containing copolymer solution cannot be obtained.

In the silane-modified fluorine-containing copolymer solution obtained by the above-mentioned operation, a fluorine-containing copolymer having a silane compound chemically bonded and having a functional group derived therefrom, a condensate of the silane compound and an unreacted It is presumed that the fluorine-containing copolymer for modification is mixed. In the present invention, such components are collectively referred to as a silane-modified fluorine-containing copolymer (B). Components and functional groups derived from the silane compound in the copolymer are collectively referred to as introduced silane components.

In the above-mentioned silane-modifying operation, as described later, a hydrolysis reaction of the silane compound, that is, a reaction of releasing a hydrolyzable group from the silane compound is involved, so that the introduced silane in the silane-modified fluorocopolymer (B) is involved. The amount of the component is smaller than the weight of the silane compound added to the modifying fluorine-containing copolymer. The preferred content of the introduced silane component in the silane-modified fluorine-containing copolymer (B) is 3 to 60% by weight, more preferably 15 to 6%.
0% by weight.

In the present invention, by using the above-mentioned fluorine-containing copolymer (A) and the silane-modified fluorine-containing copolymer (B) in a specific ratio in combination, a paint excellent in both stain resistance and weather resistance can be obtained. The composition for use is obtained, and the weight ratio of the silane-modified fluorinated copolymer (B) to the fluorinated copolymer (A) is 1.0 or less. If the weight ratio of (B) to (A) exceeds 1.0, a paint having excellent weather resistance cannot be obtained.

The preferred ratio of (A) and (B) in the composition of the present invention varies depending on the amount of the introduced silane component in the silane-modified fluorocopolymer (B).
The ratio of the introduced silane component in the composition is 3 to 20% by weight based on the total amount of the fluorine-containing copolymer for modification and the fluorine-containing copolymer (A) used in the synthesis of the copolymer (B). When the silane-modified fluorine-containing copolymer (B) in which the content of the introduced silane component is 15 to 60% by weight is used, for example, the fluorine-containing copolymer (A It is preferred to use 20 to 100 parts by weight of the silane-modified fluorine-containing copolymer (B) per 100 parts by weight.

In the present invention, when synthesizing the silane-modified fluorine-containing copolymer (B), an alkoxyaluminum such as triethoxyaluminum and tripropoxyaluminum, tetraethoxyzirconium, tetrapropoxyzirconium may be used together with the above-mentioned silane compound. And a hydrolyzable metal alkoxide such as alkoxyzirconium, tetramethoxytitanium, tetraethoxytitanium, and tetrapropoxytitanium. The preferred amount is about 1/10 or less of the silane compound. These metal alkoxides have higher hydrolyzability than alkoxysilane, and when used in combination with alkoxysilane, the yield of hydrolysis of the silane and subsequent condensation reaction is improved.

The polyvalent isocyanate used in the present invention includes hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate, and 4,4'-diphenylmethane diisocyanate. Further, low condensates such as dimers and trimers of the polyvalent isocyanate, and burettes and ureas made of the polyvalent isocyanate can also be used. More preferred are non-yellowing polyvalent isocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate and isophorone diisocyanate. A preferred amount is 5 to 2 per 100 parts by weight of the fluorinated copolymer (A).
5 parts by weight. If the amount of the polyvalent isocyanate is less than 5 parts by weight, the curing is insufficient and the stain resistance is hardly improved. On the other hand, if the amount exceeds 25 parts by weight, the urethane bond increases in the cured coating film and the weather resistance is deteriorated. descend. A more preferred amount is 8 to 20 parts by weight.

The composition for a room temperature-curable coating composition in the present invention contains an organic solvent accompanying the silane-modified fluorine-containing copolymer (B). The used organic solvent may be included, and a solvent may be added for adjusting the solution viscosity. Examples of such a solvent include toluene, xylene, ethyl acetate, butyl acetate, isobutyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone.

The paint is prepared by blending various ordinary paint additives into the cold-curable paint composition of the present invention. As paint additives, pigments such as titanium oxide, iron oxide, carbon black, quinacridone red, phthalocyanine blue, benzophenone-based, benzotriazole-based ultraviolet absorbers, hindered phenol-based, hindered amine-based antioxidants, Examples include a curing catalyst, a surface conditioner, a silane coupling agent, and a matting agent.

[0030]

EXAMPLES The present invention will be described more specifically below with reference to examples and comparative examples. The contents of the abbreviations used in each example are as follows. CTFE: Chlorotrifluoroethylene VPr: Vinyl propionate VV-9: Veova 9 [C9 vinyl versatate manufactured by Shell Chemical Co., Ltd.] HEC: Hydroxyethyl crotonate EVE: Ethyl vinyl ether HBVE: Hydroxybutyl vinyl ether

<Example 1> As the fluorine-containing copolymer (A), CTFE / VPr / VV-9 / HEC = 45/33
/ 11/11 (mol%), a weight average molecular weight of 12,000, a weight average molecular weight of 40,000 (both average molecular weight in terms of polystyrene by GPC), and a glass transition temperature of 35 ° C. Combined (hereinafter referred to as polymer A-1)
And the polymer obtained by the following method was used as the silane-modified fluorine-containing copolymer (B).

That is, the structure is CTFE / VPr / HE
C = 45/30/25 (mol%), a polymer having a number average molecular weight of 5,000, a weight average molecular weight of 14,000 and a glass transition temperature of 30 ° C. was used as a polymer for modification. 25 g of a polymer for use in a mixed solvent of xylene and butyl cellosolve (xylene 42 g + butyl cellosolve 18)
g), and the resulting solution was charged into a flask and heated to 70 ° C. in a nitrogen stream. While stirring the flask, 13 g of tetraethoxysilane, 10 g of methyltriethoxysilane and 0.01 g of p-toluenesulfonic acid were added dropwise. Further, a mixed solution of 3.9 g of water and 3 g of butyl cellosolve was slowly dropped, and then stirring was continued for 3 hours.
The reaction was terminated. By the above operation, the solid content concentration becomes 33
% By weight of a silane-modified fluorinated copolymer (hereinafter referred to as polymer B-
1)). The content of the solid content is as follows: 22% by weight of the fluorinated copolymer (the amount of the modifying polymer charged) and 11% by weight of the introduced silane component (the measured value of the solid content minus the amount of the modifying polymer charged). Met.

A 60% xylene solution of the polymer A-1 8
0 g, titanium oxide [CR-97 manufactured by Ishihara Sangyo Co., Ltd.] 30
g, lubricant (Disperbyk-10, manufactured by BYK)
1) 0.6 g, 45 g of xylene and 80 g of glass beads
Was placed in a glass bottle and dispersed and mixed for 1 hour with a paint shaker. Thereafter, only the glass beads were separated to produce a titanium oxide dispersion (hereinafter referred to as MB-1).

The above titanium oxide dispersion and polymer B-1
Using the solution, a paint was produced according to the following formulation. Titanium oxide dispersion (MB-1) ────30 g (concentration of polymer A-1; 31% by weight) Polymer B-1 solution ────4.5 g hexamethylene diisocyanate ────2 g [Coronate HX manufactured by Nippon Polyurethane Industry Co., Ltd.] 0.1% solution of dibutyltin dilaurate ──── 0.4 g xylene ４ 4 g Introduced silane component 5 per 100 parts by weight of total
Parts by weight and 20 parts by weight of the polyvalent isocyanate.

The paint was evaluated for stain resistance by the following method. The paint was applied to an A4 size aluminum plate subjected to chromate conversion treatment with a # 50 bar coater and cured at 23 ° C. and 50% RH for one week. After the initial L value was measured with a color difference meter, it was exposed outdoors for 6 months from August to February of the following year at an angle of 45 degrees on the south side in a place with much smoke and dust in the southern industrial zone of Nagoya City. After the end of exposure,
The L value was measured again, and the difference (ΔL) from the initial L value was determined (the smaller the absolute value of ΔL, the better the stain resistance). The ΔL value obtained for the paint was -2.5.

<Example 2> As the fluorinated copolymer (A), CTFE / EVE / HBVE = 48/12/40
(Mol%) and a number average molecular weight of 18,000
With a weight average molecular weight of 70,000 and a glass transition temperature of 3
Using the polymer at 0 ° C., a transparent solution of a silane-modified fluorine-containing copolymer (hereinafter referred to as polymer B-2) having a solid content of 33% by weight was obtained in the same manner as in Example 1. The content of the solid content is as follows: 22% by weight of the fluorine-containing copolymer (the amount of the modifying polymer charged) and 11% by weight of the introduced silane component (the measured value of the solid content minus the amount of the modifying polymer charged). Met.

Hereinafter, when the production of paint and the stain resistance were evaluated in the same manner as in the examples, the ΔL value was -2.0.

Comparative Example 1 A coating material was prepared by uniformly mixing the following materials without using the silane-modified fluorine-containing copolymer (B). Titanium oxide dispersion (MB-1) ────30 g hexamethylene diisocyanate ────1.8 g [Coronate HX manufactured by Nippon Polyurethane Industry Co., Ltd.] 0.1% solution of dibutyltin dilaurate ────0 0.4 g xylene ５ 5 g The results of measuring the stain resistance of the above paint were as follows: ΔL =-
It was 12.

<Comparative Example 2> In the production of the silane-modified fluorine-containing copolymer (B) in Example 1, after mixing the fluorine-containing copolymer and the silane compound, without adding water,
A fluorinated copolymer solution containing a silane compound was obtained. The above fluorinated copolymer solution and titanium oxide dispersion (MB-1)
Was used to produce a paint in the same manner as in Example 1. The measurement result of the stain resistance of the obtained paint was ΔL = −1
It was one.

[0040]

According to the present invention, a room-temperature-curable fluororesin paint having extremely excellent stain resistance while maintaining the high weather resistance inherent to the fluororesin paint can be obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-281664 (JP, A) JP-A-63-117073 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09D 127/12

Claims (1)

(57) [Claims] 1. An organic solvent solution of a solvent-soluble fluorinated copolymer containing more than 20 mol% and up to 50 mol% of a hydroxyl group-containing monomer unit, per 100 parts by weight of the fluorinated copolymer, A silane compound having two or more decomposable groups or a low condensate thereof is added at a ratio of 5 to 100 parts by weight,
Then, 3 parts of a hydroxyl-containing monomer unit are added to an organic solvent solution of the silane-modified fluorine-containing copolymer (B) obtained by adding water.
Solvent-soluble fluorinated copolymer containing up to 20 mol% (A)
Wherein a weight ratio of the copolymer (B) to the copolymer (A) is 1.0 or less, and a polyisocyanate is added to the resulting polymer solution. A method for producing a composition for a mold paint.