JPH08120212A - Fluororesin coating composition - Google Patents

Abstract

PURPOSE: To provide a fluororesin coating compsn. as a film-forming component of a coating material capable of forming a coating film so excellent in weatherability and stain resistance as to undergo neither deterioration nor discoloration even through such long-term outdoor exposure as suffered by buildings, outdoor structures, etc., while having a freedom from rain marks even just after application and even through long-term outdoor exposure. CONSTITUTION: 100 pts.wt. fluorocopolymer (A) having an OH no. of 80 to 200mg-KOH/g and obtd. by copolymerizing 40-65mol% chlorotrifluoroethylene with 14-50mol% copolymerizable vinyl ester compd., 12-25mol% polymerizable hydroxylic compd. 0.1-3mol% polymerizable carboxylic compd. and 0.1-12mol% other copolymerizable compd. is blended with 0.1-20 pts.wt. alkyl silicate (B) such as a partial hydrolyzate of tetraethoxysilane, and 0.05-3 pts.wt. water-soluble polyether-modified silicone oil (C) having dimethylsiloxane structural units and ethylene oxide structural units in the molecule thereof to prepare a fluororesin coating compsn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluororesin coating composition having stain resistance.

[0002]

2. Description of the Related Art Conventionally, fluororesin paints utilizing the excellent weather resistance of fluorocopolymers have been industrialized. Particularly recently, solvent-soluble fluorine-based copolymers having a curing site have been synthesized (for example, JP-A-57-34107 and JP-A-61-57609), and are used for construction, automobiles, and chemistry. It is widely applied as a weather resistant paint in the industrial field. In addition, water-based and powder-type paints, which place importance on the environment and suppress the emission of organic solvents, have been put into practical use. The main components of these coating resins are fluorine-based raw materials such as chlorotrifluoroethylene, tetrafluoroethylene, or vinylidene fluoride, and the use of hydrocarbon-based monomers such as vinyl esters and vinyl ethers as copolymerization components makes them It has increased solubility.

However, these solvent-soluble fluororesin coatings have the drawback of being easily soiled although they are excellent in weather resistance. As a solution to this, an attempt to increase the surface hardness by increasing the glass transition point of the resin and an attempt to increase the soil release by creating a hydrophilic / water-repellent surface (monthly building finishing technology, VO
L19, No219, 74 (1993)) and so on. Fluorocarbon resin paints with increased surface hardness show stain resistance effects in carbon black adhesion tests and stain tests with magic ink, but in actual exposure tests they are still susceptible to stains, and to improve clear stain resistance. I haven't arrived.

[0004]

SUMMARY OF THE INVENTION According to the present invention, a building, an outdoor structure, or the like is deteriorated even during a long outdoor exposure period.
Provided is a composition for a fluororesin coating, which is a film-forming component of a coating capable of forming a coating film which is not discolored and has no rain stripes and which is excellent in weather resistance and stain resistance.

[0005]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted a detailed stain test of various coated fluororesin coating films, and as a result, chlorotrifluoroethylene, vinyl ester, and a hydroxy group-containing polymerizable compound. , A fluorine-based copolymer having a specific high OH value obtained by copolymerizing a carboxyl group-containing polymerizable compound as an essential monomer, an alkyl silicate and a water-soluble polyether-modified silicone oil having a specific structure The inventors have found that the compounded composition exhibits stain resistance and weather resistance, and reached the present invention.

That is, the present invention comprises at least 40 to 65 mol% of chlorotrifluoroethylene, 14 to 50 mol% of a copolymerizable vinyl ester compound, 12 to 25 mol% of a hydroxy group-containing polymerizable compound, and a carboxyl group of 100 parts by weight of the fluorine-based copolymer [A] having an OH value of 80 to 200 mgKOH / g obtained by copolymerizing 0.1 to 3 mol% of the polymerizable compound (hereinafter, referred to as "part"). To alkyl silicate [B] of 0.1 to
0.0 parts of a water-soluble polyether-modified silicone oil [C] having 20 parts and at least a dimethylsiloxane structural unit and an ethylene oxide structural unit in the molecule.
A composition for a fluororesin coating, which comprises 5 to 3 parts,
The fluorocopolymer [A] is a fluororesin coating composition which may be a fluorocopolymer obtained by further copolymerizing 0.1 to 12 mol% of vinyltrialkoxysilane.

The present invention will be described in detail below. In the fluorocopolymer [A] according to the present invention, chlorotrifluoroethylene accounts for 40 to 65 mol% of all monomers. If it is less than 40 mol%, the weather resistance is poor and 65 mol%
If it exceeds the range, the solubility in the solvent decreases, which is not preferable.

The copolymerizable vinyl ester compound used in the fluorocopolymer [A] of the present invention is not particularly limited, but it is polymerizable and has an ester compound having a carbonyl group in the molecule. , For example, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl caproate, vinyl caprylate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl versatate 9 vinylate, versatic vinyl 10 acid. , Vinyl benzoate, etc.
The composition ratio of these vinyl ester compounds is 14 to 50 mol% of all monomers. Depending on the balance with other copolymerization components, if it is less than 14 mol%, the solubility of the fluorocopolymer in the solvent may be poor, and if it exceeds 50 mol%, the weather resistance of the coating film is impaired. This is not preferred because it may occur.

As the hydroxy group-containing polymerizable compound used in the fluorocopolymer [A] of the present invention, hydroxy group-containing allyl ethers, hydroxy group-containing vinyl ethers, crotonic acid-modified compounds and the like can be used. Examples of the hydroxyl group-containing polymerizable compound include glycerin monoallyl ether, ethylene glycol monoallyl ether, propylene glycol monoallyl ether, diethylene glycol monoallyl ether, polyethylene glycol monoallyl ether,
Alkylene glycol monoallyl ethers such as hydroxybutyl allyl ether, hydroxymethyl vinyl ether, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, hydroxypentyl vinyl ether, hydroxyalkyl vinyl ethers such as hydroxyhexyl vinyl ether, polyethylene glycol monovinyl ethers such as diethylene glycol monovinyl ether, Examples thereof include crotonic acid-modified compounds such as hydroxyethyl crotonic acid. In this,
Glycerin monoallyl ether having a secondary hydroxy group that is less likely to participate in crosslinking is particularly preferably adopted. By introducing a hydroxy group that is less likely to participate in this crosslinking, it becomes possible to maintain the low contact angle of the coating film with water for a longer period of time. The OH value of the secondary hydroxy group that is less likely to participate in such crosslinking is preferably in the range of 1 to 60 mgKOH / g. If the OH value exceeds 60 mgKOH / g, the coating film will exhibit water absorption and the weather resistance will decrease.

The composition ratio of these hydroxy group-containing polymerizable compounds is 12 to 25 mol%, and the OH value of the fluorine-based copolymer [A] obtained at that time is 80 to 200.
It is preferably in the range of mgKOH / g. If the OH value is less than 80, dirt easily penetrates into the coating film, resulting in 200
If it exceeds the range, the solubility in the solvent and the weather resistance are deteriorated. Further, it is not always necessary that the hydroxy group is involved in all cross-linking, and the OH value is 10 to 100.
It is also preferable to add a curing agent so that it remains in the range of mgKOH / g.

The carboxyl group-containing polymerizable compound used in the fluorine-based copolymer [A] of the present invention is not particularly limited, but vinyl acetic acid, decenoic acid, undecylenic acid, crotonic acid and the like can be mentioned. This carboxyl group-containing polymerizable compound is useful, for example, for improving pigment dispersibility and pot life, but if it is less than 0.1 mol%, it is not effective, and if it exceeds 3 mol%, the pot life becomes short. It is not desirable because it will end up.

The preferred vinyltrialkoxysilane used in the fluorocopolymer [A] according to the present invention makes the coating film more densely crosslinked and improves the compatibility with the alkylsilicate [B]. Is adopted for. The alkoxy group of such vinyl trialkoxysilane preferably has about 1 to 8 carbon atoms, and methoxy group, ethoxy group, isopropoxy group, n-butoxy group and the like are preferably exemplified. These are alone in one molecule,
Alternatively, it may be present as a mixture. Specific examples of the preferred vinyltrialkoxysilane in the present invention include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, vinyltrin-butoxysilane, vinyldimethoxyethoxysilane, and vinylmethoxydiethoxysilane. To be A hydroxy group generated by hydrolysis of an alkoxy group derived from vinyltrialkoxysilane is a curing agent added to the coating composition of the present invention, for example, an isocyanate compound, a site curable by a melamine compound, and the like, Alkyl silicate [B]
It has the effect of improving the compatibility with. That is, when the fluorine-based copolymer [A] does not have an alkoxy group derived from vinyltrialkoxysilane, there may be a problem in compatibility with the alkyl silicate [B], and the alkyl silicate [B] Since it is localized on the surface of the coating film, there are portions where contaminants are likely to adhere and portions where it is difficult to deposit in the long term. For this reason, contamination may be conspicuous. The copolymerization ratio of the vinyltrialkoxysilane according to the present invention can be used in the range of 0.1 to 12 mol%. If it is less than 0.1 mol%, the effect of stain resistance is small, and if it exceeds 12 mol%, the stability and weather resistance of the varnish are adversely affected.

As the method for polymerizing the fluorocopolymer [A] of the present invention, a usual radical polymerization method can be adopted in the production thereof, and the polymerization form thereof can be solution polymerization, suspension polymerization or emulsion polymerization. . The temperature of the polymerization step depends on the radical polymerization initiator used, but is usually 0 to 130 ° C.
Examples of the solvent include water, alcohols such as t-butanol and ethyl alcohol, saturated hydrocarbons such as n-hexane and n-heptane, aromatic hydrocarbons such as toluene and xylene, trichlorotrifluoroethane, dichlorotetra. Fluorine-based and other fluorine-based compounds, acetone,
Ketone-based compounds such as methyl ethyl ketone and methyl isobutyl ketone, and ester-based compounds such as ethyl acetate and butyl acetate can be used alone or as a mixed system. Examples of the radical initiator include dicarbonates such as diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate and di-2-ethylhexyl peroxydicarbonate, or n-heptafluorobutyric peroxide, lauroyl. Diacyl peroxides such as peroxypivalate and t-butyloxy neodecanoate, alkyl peroxides such as di-t-butyl peroxide and t-butylcumyl peroxide, t-butylperoxypivalate and t- Conventional radical initiators such as peroxyesters such as butyl peroxy neodecanoate can be used.

The molecular weight of the fluorocopolymer [A] according to the present invention is not particularly limited, but it may be in the range of 1,000 to 30,000 (number average molecular weight; polystyrene conversion) depending on the required strength and flexibility of the coating film. It is desirable to use within the range, and more preferably about 3,000 to 18,000. If it is less than 1,000, the weather resistance and flexibility of the coating film will be deteriorated, and if it is more than 30,000, it will have a high viscosity when it is made into a coating material, resulting in a drawback that it is difficult to handle.

The alkyl silicate used in the present invention has the following general formula:

[0016]

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(R is an alkyl group having 1 to 8 carbon atoms, n is 0
Alternatively, it represents an integer of 11 or less. ) Is a tetraalkoxysilane or a condensate thereof, and specifically, for example, tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetra n-propoxysilane, tetra n-butoxysilane, tetra 2-methoxyethoxy silane, tetra 2-ethylhexyloxy silane, etc., or these partial hydrolysis products can be mentioned. Although the structure of these partial hydrolysates is not clear, it is a polysilicate ester composed of a skeleton composed of Si—O bonds and an alkoxy group, and the skeleton is shown as a straight chain in Chemical formula 1, but has a branch. There is also
It may have a ring structure. Any method may be used for its production, and for example, it can be obtained by partially hydrolyzing and condensing tetraalkoxysilane with water, an acid and / or a solvent. Such partially hydrolyzed alkyl silicates are commercially available in various types having different degrees of condensation, structures, and types of alkoxy groups.
About 28 to 52% by weight of effective silica content such as silicate 51, ethyl silicate 40, ethyl silicate 45 (above, product of Tama Chemical Industry Co., Ltd.), ethyl silicate 40 (product of Colcoat Co., Ltd.), or these HAS-1, H dissolved in ethanol or isopropanol
Examples include AS-6 and HAS-10 (product of Colcoat Co., Ltd.). It is also possible to use an alkyl silicate obtained by further hydrolyzing these and concentrating the silica content to 57% by weight. These alkyl silicates have the effect of reducing the contact angle on the surface of the coating film by the synergistic effect with the structure derived from vinyltrialkoxysilane in addition to the fluorine-based copolymer [A], and making rain streaks less likely to form. It is considered to be a thing.

The polyether-modified silicone oil [C] used in the present invention is blended for the purpose of reducing the water contact angle immediately after coating. When this polyether-modified silicone oil [C] is not blended, the contact angle immediately after coating is relatively high, and rain streaks occur immediately after outdoor exposure. For this purpose, the polyether-modified silicone oil [C] of the present invention has at least a dimethylsiloxane structural unit and an ethylene oxide structural unit in the molecule, and is water-soluble. The degree of polymerization is not particularly limited as long as it is water-soluble, but the viscosity at 25 ° C. is 20 to
It is about 10,000 cps and 50 to 3,000
It is preferably about 0 cps.

The polyether-modified silicone oil according to the present invention has a polyalkylene oxide structure introduced into one end, both ends or side chains of polydimethylsiloxane. As the polyalkylene oxide structure, an ethylene oxide structural unit is essential, and optionally 3 to 8 carbon atoms.
These oxyalkylene structural units can be used alone or in combination of two or more. When two or more kinds of alkylene oxide structural units are contained together, each structural unit may be randomly polymerized or block polymerized. The terminal group of the polyalkylene oxide introduced into the terminal or side chain of the polydimethylsiloxane is not particularly limited, but it may be a functional group involved in curing such as a hydroxy group, and these can also be preferably used.

The polyether-modified silicone oil [C] that can be used in the present invention is not particularly limited as long as it meets the above-mentioned conditions, and is specifically represented by the following general formula (1) or (2). What is done is mentioned as a suitable example.

[0021]

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(In the formula, PAG is a polyalkylene oxide chain containing an ethylene oxide structural unit, R'is an alkylene group, Me is a methyl group, and m is an integer.)

[0023]

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(In the formula, Me represents a methyl group, and the terminal Si
Other than an arbitrary number of one or more methyl groups bonded to -R'-
It may be substituted with PAG. PAG is a polyalkylene oxide chain containing ethylene oxide structural units,
R'represents an alkylene group. Further, m represents an integer. )
When the polyether-modified silicone oil according to the present invention is enumerated without limitation for commercial products, it is represented by the general formula (1): SF8427, BY16-005, B
Y16-006, BY6-007, BY16-008,
As represented by the general formula (2), SH3746, S
F8428, SH3771, BY16-036, BY1
6-027, BY16-038, SH8400, SH3
749, SH3748, SF8410 (these are products of Toray Dow Corning Silicone Co., Ltd.). Needless to say, other companies' products corresponding to these products also have similar effects.

In the fluororesin coating composition of the present invention, 0.1 to 20 parts of alkyl silicate [B] and polyether modified silicone oil [C] are added to 100 parts of fluorocopolymer [A]. It is necessary to mix in the range of 0.05 to 3 parts. The reason for this is that if the amount of alkyl silicate [B] added is less than 0.1 part, there is no effect, and if it exceeds 20 parts, the change over time in the contact angle with respect to acid rain and heat becomes large, and long-term fouling occurs. It becomes easier.
Furthermore, if the amount of [C] added is less than 0.05 part, it is not effective enough to reduce the water contact angle, and if it exceeds 3 parts, the weather resistance is reduced, which is not preferable. Therefore, in the present invention, the three components [A], [B], and [C] are essential, and it becomes possible to achieve a stain-resistant coating film surface for a long time immediately after coating.

The solvent for the fluororesin coating composition of the present invention is an aromatic solvent, an ester solvent, an ether solvent, a ketone solvent, an alcohol solvent, or the like, which is a solvent generally used in the field of coating, or a mixed solvent thereof. is there. In any case, it can be made into a paint like an ordinary paint, and a pigment or a dye can be appropriately added. Further, other additives such as an ultraviolet absorber, a light stabilizer, a rust preventive and a dispersant can be added depending on the use.

The fluororesin coating composition of the present invention can be used as the curing agent without any particular limitation, including ordinary urethane type or polyvalent isocyanate type curing agents, melamine type curing agents and blocked isocyanate type curing agents. Although possible, for example, when an isocyanate-based curing agent is used, NCO / OH = 0.3 to 1.0 is preferable.
In addition, the resin OH value is 100 to 200 mg KOH / g
In the case of NCO / OH = 0.4 to 1.0 is preferable. Alkyl titanates, carboxylic acid metal salts such as tin octylate and dibutyltin laurate, and dibutylamine-2 for the purpose of promoting the hydrolysis of alkoxysilanes.
It is also possible to add amine salts such as hexoates, acid catalysts, basic catalysts and the like.

The present invention will be specifically described below with reference to examples, but the embodiments are not limited to these.

[0029]

【Example】

[Synthesis Examples 1 to 6] 44.6 g of vinyl acetate (8 mol%; ratio to all monomers; the same applies hereinafter) and 141.3 g of versatic vinyl acetate 9 were added to an autoclave made of SUS having an internal capacity of 2 liter and equipped with a magnetic stirrer. .8 mol%), hydroxybutyl allyl ether 152.3 g (18 mol%), undecylenic acid 2.4 g (0.2 mol%), xylene 240 g, t-butyl peroxypivalate (manufactured by NOF Corporation) 13 g were charged. After repeating degassing and replacement with nitrogen gas three times, 439 g (5
(8 mol%) was charged, and polymerization was carried out at 55 ° C. for 20 hours in the presence of 1.4 g of sodium carbonate (Synthesis Example 1).

In the same manner, polymerization was carried out with the composition shown in Table 1 (Synthesis examples 2 to 6). In each case, after the polymerization was completed, the contents were taken out, filtered, and adjusted to a solid content concentration of 60% by weight with xylene to prepare a varnish of the fluorocopolymer [A]. Here, the synthesis example 5 is O
This is a synthesis example of a copolymer having an H value of 80 mgKOH / g or less, and Synthesis Example 6 is a synthesis example of a copolymer in which the copolymerization ratio of vinyltrimethoxysilane exceeds 12 mol%. Table 1 shows the OH value, acid value, and molecular weight (converted to styrene, number average) of these copolymer resins.

[0031]

[Table 1]

Examples 1 to 6 In the varnish of the fluorine-based copolymer [A] prepared in Synthesis Examples 1 to 4, the compound [C] was added at a ratio shown in Table 2 to 100 parts of the solid content. It was added to give a main varnish for the fluorine-based paint. The compound [C] used was polyether modified silicone SF8427, SH37 manufactured by Toray Dow Corning Silicone Co., Ltd.
46, a polyether-modified silicone BYK333 manufactured by Big Chemie. These are water-soluble silicones having at least a dimethylsiloxane moiety and an ethylene oxide moiety in the molecule.

Next, 10 parts to 100 parts of the fluorine-based copolymer [A] was added to the base varnish containing [A] and [C].
0 part of titanium oxide was uniformly mixed with a dispersion mill to prepare a main component of a white paint. Further, the compound [B] was added to the main component of the white paint in an amount shown in Table 2 with respect to 100 parts of the fluorocopolymer [A]. The compound [B] used was M silicate 51, manufactured by Tama Chemical Industry Co., Ltd.
Ethyl silicate 45, ethyl silicate partial hydrolyzate HAS-6 manufactured by Colcoat Co., Ltd. Then, a 1: 1 mixture of Coronate HX (manufactured by Nippon Polyurethane Industry Co., Ltd.) in xylene was blended in such a manner that the NCO / OH ratio became the ratio shown in Table 2, and mixed uniformly to obtain a white paint. . About 40 parts of this white paint on aluminum plate
It was spray coated to a thickness of micron and dried and cured at room temperature for 2 days.

[0034]

[Table 2]

Using the coated plate produced as described above,
A static contact angle of water, a soil test for 6 months of outdoor exposure, and a weather resistance test were conducted. The stain was judged by the color difference of the part without the rain streak and the generation condition of the rain streak. Table 3 shows the results. Here, [A] and [C]
After mixing, the pigment is added to form a paint, and then [B] and a curing agent are blended. After adding the pigment to [A] alone to form a paint, add [B], [C], and a curing agent. The results were not different from the results of the different procedures in Table 2.

[0036]

[Table 3]

[Comparative Examples 1 to 6] Varnishes of the fluorinated copolymer [A] prepared in Synthesis Examples 2 to 6
White paints having the composition shown in Table 2 were prepared in the same manner as in 1., and the same various tests as in Example 1 were carried out on the coated plate on which the coating films were formed. Table 3 shows the results.

The compounds [B] and [C] used in each comparative example are the same products as those used in the examples. Here, in Comparative Example 1, the OH value of the fluorine-based copolymer [A] is 80 mgKO.
When the amount is less than H / g, Comparative Example 2 has a vinyltrialkoxysilane copolymerization ratio of more than 12 mol% in the fluorine-based copolymer [A], and Comparative Example 3 has a polyether-modified silicone oil [C]. When not containing, Comparative Example 4 does not contain alkyl silicate [B], Comparative Example 5 contains 20 parts or more of alkyl silicate [B], Comparative Example 6 contains 3 parts or more of polyether-modified silicone oil [C]. It is an example of including.

[0039]

EFFECT OF THE INVENTION A coating material comprising the composition for a fluororesin coating material of the present invention does not cause deterioration of the coating film in a weather resistance test corresponding to long-term outdoor exposure as shown in Examples, and
Even in an actual long-term outdoor exposure test, it is clear that the coating film does not discolor and does not show rain streaks. It also has excellent weather resistance and stain resistance, and it is clear that no rain streaks adhere immediately after coating. The coating composition is extremely useful as a film-forming component of a coating used for buildings and outdoor structures.

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Claims (4)

[Claims] 1. At least chlorotrifluoroethylene 4
0-65 mol%, copolymerizable vinyl ester compound 14-50 mol%, hydroxy group-containing polymerizable compound 1
2 to 25 mol%, carboxyl group-containing polymerizable compound 0.1 to 3 mol%, other copolymerizable compound 0.1
OH value obtained by copolymerizing ~ 12 mol% is 80-2
1 of the fluorine-based copolymer [A] which is 00 mgKOH / g
0.1 to 20 parts by weight of alkyl silicate [B], and at least dimethylsiloxane structural unit and ethylene oxide structural unit in the molecule, and water-soluble polyether-modified silicone oil [C ] 0.05 to 3 parts by weight of a fluororesin coating composition. 2. The fluororesin coating composition according to claim 1, wherein the other copolymerizable compound is vinyltrialkoxysilane. 3. At least a part of the hydroxy group-containing polymerizable compound is glycerin monoallyl ether, and the OH value of the secondary hydroxy group is 1 to 60 mgKOH /.
The composition for fluororesin coatings according to claim 1 or 2, which is g. 4. A paint comprising at least the composition for a fluororesin paint according to claim 1, a curing agent and a solvent.