JP2945949B2 - Room-temperature-curable coating sol composition and method for producing fluorocopolymer / silica glass hybrid using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the modification of a fluororesin for coatings comprising an organic solvent-soluble fluorocopolymer used for highly weather-resistant coatings.

[0002]

2. Description of the Related Art Organic solvent-soluble fluorine-containing copolymers (fluororesins for paints) have excellent weather resistance and have recently been used as bases for maintenance-free high-performance paints in high-rise buildings.
It is widely used in large fields such as large structures, ships and vehicles. Such a fluorine resin for an organic solvent-soluble coating material mainly includes a fluoroolefin component such as chlorotrifluoroethylene and tetrafluoroethylene and an alkyl vinyl ether component such as an alkyl vinyl ether such as cyclohexyl vinyl ether or an alkyl vinyl ester component such as a higher carboxylic acid vinyl ester. As a component, a fluorinated copolymer obtained by copolymerizing a specific amount of a monomer component having a hydroxyl group such as hydroxyalkyl vinyl ether or hydroxyalkyl crotonate is known, and is marketed by each company (Special Features). Kaihei 3-231906, JP-B-60-21686, JP-B61-49323). Such an organic solvent-soluble fluorocopolymer gives a transparent film by volatilization of an organic solvent such as xylene, and can be used as it is as a lacquer type paint. In order to reach a certain level, a cross-linking treatment is required, and usually an aminoplast resin-based curing agent such as an isocyanate compound or a methylated melamine resin is blended and used. However, room temperature curing with an isocyanate compound or the like is rather slow and usually takes one week or more, and baking with a melamine resin-based curing agent also requires a considerably high temperature (180 ° C. for 30 minutes, 280 ° C. for 3 minutes). Further, even when cured, the hardness of the coating film is not sufficient, and in many cases, the pencil hardness is H to 2H, and the 60-degree specular gloss is 81 to 83% (20-degree specular gloss is 65 to 72%). ,
Still further improvements are desired.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a fluororesin paint capable of forming a coating film having excellent weather resistance and the like in view of the above prior art, and to achieve a higher performance even at room temperature. Long-term maintenance-free paint material that has improved durability, such as large construction machinery, bridges, structures such as chemical plants, or tunnel inner walls, floor coatings, building outer walls, etc. To provide coating materials with improved hardness, water resistance, solvent resistance, glossiness, weather resistance, corrosion resistance, etc. for various substrates such as metal, glass, cement, concrete, plastic, and wood. It is in.

[0004]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventor has proposed that a commercially available organic solvent-soluble fluorinated copolymer for a hydroxyl group-containing paint is used as a precursor of silica glass precursor. Commercially available alkoxide compounds such as ethoxysilane, tetramethoxysilane or a partial condensate thereof such as ethyl silicate 40 (trade name, manufactured by Colcoat) and methyl silicate 51 (trade name, manufactured by Mitsubishi Kasei Co., Ltd.) may be used in a small amount as necessary. As a result of intensive research on the introduction of siloxane bonds by hybridization with nanometer-sized silica particles in the presence of a trace amount of an acid catalyst, a sol composition obtained by mixing the above components at a specific ratio was obtained. With good wettability during coating, easy application and impregnation, and extremely fast drying and curing speed燥 found that only possible very high high glossiness and good adhesion coating hardness is formed, have accomplished the present invention.

That is, the present invention firstly comprises (A) a copolymer of a fluoroolefin component and an alkyl vinyl ether or an alkyl vinyl ester component as a main component and a fluorine-containing copolymer containing a hydroxy group in the molecule. An organic solvent solution of the polymer (fluororesin varnish for paint)
(B) The hydrolyzable alkoxysilane or its partially hydrolyzed condensate is mixed with ethanol, isopropanol, and ethanol so that the weight ratio of the solid component A and the component B is A / B = 1/3 to 4/1. -Dissolve using butanol and the like, and further add (C) 0.1 to 0.1 wt.
Coating containing 2.5% by weight of an acid catalyst and containing no water as a component thereof to form a fluorinated copolymer / silica glass hybrid.
The present invention relates to a sol composition for use . Secondly, the present invention relates to a method for producing a fluorinated copolymer / silica glass hybrid, which comprises applying the above sol composition to a substrate, followed by air drying. In the sol composition of the present invention, the use of an acid catalyst of the C component is indispensable. If the amount of the catalyst is too small, the wettability may be poor, or phase separation may occur. It was impossible to cure at room temperature because it was tacky. On the other hand, when the amount of the catalyst was too large, the coating film became satin-like, and transparency, glossiness, and adhesion to the substrate were significantly impaired. When the sol composition is applied to a base material, the alkoxide compound such as tetraethoxysilane is rapidly hydrolyzed and polycondensed by moisture in the air while volatilizing an organic solvent such as xylene, whereby the composition is rapidly dried and cured. To form a colorless, transparent and high gloss hard coating. The hardness of the coating film varies depending on the content of the silica component.
A coating film having a considerably high hardness of 0 to 34 (corresponding to a pencil hardness of 2H to 6H) was formed.

As the fluorinated copolymer used as the component A in the present invention, commercially available ones can be used, and specific examples thereof are described in JP-B-60-21686 and JP-A-63-2304. The fluorinated copolymers containing specific amounts of the units based on fluoroolefin, cyclohexyl vinyl ether, alkyl vinyl ether and hydroxyalkyl vinyl ether, respectively, are mentioned. Further, based on the total amount of all monomers described in JP-A-3-231906, (a) fluoroolefin monomer unit: 30 to 60 mol% (b)
Fluorinated copolymers containing hydroxyalkyl crotonate monomer units: 3 to 30 mol% (c) vinyl monomer units other than the above: 10 to 67 mol%. As the organic solvent of the fluorinated copolymer, various solvents can be used, such as xylene, aromatic hydrocarbons such as toluene, alcohols such as n-butanol, esters such as butyl acetate, and methyl isobutyl ketone. In addition to ketones, glycol ethers such as ethyl cellosolve, and the like, various commercially available thinners can also be used, and these can be used in a mixture at various ratios. Such an organic solvent can be appropriately selected in consideration of the state of the object to be coated, the evaporation rate, the working environment, and the like, and the amount used can be set. Usually, the solid content concentration in the varnish is not particularly limited, but is preferably about 40 to 70% by weight, and more preferably 50 to 60% by weight. The organic solvent solution (fluorine resin varnish for paint) of the fluorine-containing copolymer as the component A used in the present invention is more preferably a fluoroolefin such as chlorotrifluoroethylene or tetrafluoroethylene, or an alkyl such as cyclohexyl vinyl ether. Alkyl vinyl esters such as vinyl ethers and higher carboxylic acid vinyl esters were alternately copolymerized as the main component, and hydroxyalkyl crotonates and hydroxyalkyl vinyl ethers were copolymerized to contain hydroxyl groups in the molecule. It is obtained by dissolving a fluorine-containing copolymer in xylene or another organic solvent. The hydroxyl value of this type of copolymer is not particularly limited, and is preferably from 20 mgKOH / g-resin to 120 mgKOH / g-resin, but the present invention can be applied outside this range. As such a copolymer, Lumiflon LF-100 (having a hydroxyl value of 2) manufactured by Asahi Glass Co., Ltd. is commercially available.
6 mg KOH / g-resin), Lumiflon LF-200
(Hydroxyl value 32 mgKOH / g-resin), Lumiflon LF-400 (hydroxyl value 24 mgKOH / g-resin),
Lumiflon LF-600 (hydroxyl value 31 mgKOH /
g-resin), Zaflon F manufactured by Toagosei Chemical Industry Co., Ltd.
C-110 (hydroxyl value 44 mgKOH / g-resin), Zaflon FC-220 (hydroxyl value 53 mgKOH / g-resin)
Resin), Zaflon XFC640 (hydroxyl value 100mg)
KOH / g-resin). The hydrolyzable alkoxysilane as the component B used in the present invention includes a general formula Si (OR) _n (where R represents a carbon number of 1 to 1).
4 is a saturated hydrocarbon group, and n is an integer of 2 to 4). Specific examples of such alkoxysilanes include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane; trialkoxyalkylsilanes such as trimethoxymethylsilane and triethoxymethylsilane; and zinc-rich paint. Silicates 40 and methyl silicates 51 of alkyl silicates (partially hydrolyzed polycondensates of tetramethoxysilane or tetraethoxysilane (having siloxane bonds)) used for industrial purposes as binders for casting and casting are more preferably used. Is done.

In the present invention, a small amount of an acid catalyst is required as the component C in order to promote the hydrolysis and polycondensation of the component B. As the catalyst, a strong organic acid such as p-toluenesulfonic acid, benzenesulfonic acid, decanesulfonic acid and perfluorosulfonic acid is preferably used. 5-10
Methanol containing% hydrogen chloride can also be used.
The amount used is generally about 0.1 to 2.5% by weight, preferably 0.25 to 1% by weight, based on the total weight of both components A and B for the reasons described above. In the sol composition of the present invention, the mixing ratio of the component A, which is an organic polymer component, and the component B, which is an inorganic glass component, is important, and the weight ratio of both solids is A / B = 1/3 to It should be 4/1. If the amount of the component (B) exceeds three times the amount of the component (A), streaks or cracks are formed in the resulting coating film, and the adhesion is significantly reduced. When the amount of the component B is less than 1/4 the amount of the component A, the hardness of the film is reduced. The mixing ratio of both the A and B components is slightly different depending on the type of the B component. For example, when tetraethoxysilane is used as the B component, A
/ B = 2/3 to 3/1, A / B = 1/1 when using methyl silicate 51 as a condensate of tetramethoxysilane
４4/1 is preferred. The coating sol composition of the present invention is obtained by adding a hydrolyzable alkoxysilane of the component B or a partially hydrolyzed condensate of the component B to an organic solvent solution of the fluorine-containing copolymer of the component A, and optionally adding ethanol and isopropanol. , 1-butanol, etc., and uniformly dissolved, and further added with an acid catalyst of component C. There is no limitation on the temperature and time when the components are mixed, as long as the obtained sol composition is in a uniform and transparent solution state. The acid catalyst of the component C may be added immediately before use. However, the sol composition obtained by mixing the component C with both the components A and B in advance can maintain the sol state for a relatively long time if it is sealed. Gelation is low. According to the method of the present invention, after the uniform sol composition thus prepared is applied to various substrates such as a glass plate, it is simply air-dried and, if necessary, forcibly dried at 60 to 150 ° C. A high-gloss colorless and transparent hard coating film having good adhesion can be formed. The coating film is highly crosslinked and no change is seen in the organic solvent, strong alkali, strong acid,
It is stable even in boiling water. Further, a fluorinated copolymer containing chlorotrifluoroethylene as a main component can be expected to have radiation resistance. In order to apply the sol composition to a substrate, a normal coating method using a spray gun, a brush, a roller, a doctor knife or the like can be employed in addition to a dip coating method. The thickness of the film after drying and curing is usually preferably 5 to 50 μm. If the thickness is more than this range, the adhesion to the substrate is reduced, and cracks and peeling are likely to occur. On the other hand, if it is too small, the protective effect of the coating film is reduced and defects such as pinholes are liable to occur. The composition of the present invention can be used as a clear coating, or can be used as a coloring coating by blending a coloring agent such as a pigment. Furthermore, various known additives such as a leveling agent and an ultraviolet absorber can be used as needed.

When the composition of the present invention is used as a paint base, the composition has excellent surface hardness and glossiness, as well as solvent resistance,
It can provide a coating film with excellent stain resistance and weather resistance under mild conditions such as drying and curing at room temperature. It can be used for metals such as color iron plate, aluminum plate, stainless steel, and inorganic materials such as glass and cement. Painted on various plastics such as, FRP resin, polypropylene, acrylic resin, nylon, polyester resin, vinyl chloride resin, polycarbonate and wood, etc. and has high gloss and excellent scratch and wear resistance. Is extremely useful. It is especially useful for outdoor use as a maintenance-free, weather-free paint with good weather resistance that can be installed on site, and is used in bridges, construction machinery, ships / vehicles, tanks, chemical plants, sunrooms, skylights, solar supplies, Fuens,
It is useful for protecting coating materials such as verandas, benches, cooling towers, columns, road signs, and advertising towers, and for protecting substrates that are susceptible to light degradation. The details of the reason why the composition of the present invention forms a hybrid film with silica glass and the resulting film cures at room temperature are not clear yet. Perhaps when the sol composition is coated on a substrate and air-dried or forced-dried, the hydrolyzable alkoxide group of the alkoxysilane is hydrolyzed by the action of moisture in the air and polycondensation proceeds between the sites at the same time. It is considered that silica particles are formed by the reaction, and the silanol groups on the surface of the silica particles are hydrogen-bonded or ester-bonded with the fluorine-containing copolymer having a hydroxyl group to form a hybrid film with silica.

[0009]

EXAMPLE Next, a coating sol composition for forming a fluorine-containing copolymer / silica glass hybrid of the present invention and this sol composition were prepared.
The production method of the hybrid obtained by curing the sol composition will be described more specifically based on Examples, but the present invention is not limited to only these Examples.

Example 1 20 g of Lumiflon LF-200 (a product of Asahi Glass), which is a commercially available fluororesin varnish for paint containing hydroxyl groups in the molecule, containing chlorotrifluoroethylene, tetrafluoroethylene and cyclohexyl vinyl ether as main components. Methyl silicate 51 (Mitsubishi Chemical products)
10 g was mixed with 30 g of 1-butanol, and 0.050 g of p-toluenesulfonic acid was further added as a catalyst to prepare a transparent and low-viscosity sol composition. This composition was stable for a long period of time. The composition was applied to a glass plate, an aluminum plate and the like, and was naturally dried and cured. The coating film is colorless and transparent, has no cracks or streaks, is excellent in adhesion and solvent resistance, and has a Knoop hardness of KH = 35 according to a Terasawa microhardness tester (SM-2 manufactured by Taiyo Tester). 6 in pencil hardness conversion
H equivalent. Also, the glossiness of the coating film is very good,
It was 130% in 0 degree specular reflection gloss, and showed almost the same value as the glass surface before coating (Variable gloss meter Nippon Denshoku Industries V
G-1D type). The cross-cut tape peel test is 100
The adhesion was good at / 100. The solvent resistance of the coating film was good, and it was confirmed that there was no change after immersion in xylene for one week, and that the coating film did not change even if the coating film was impregnated with xylene and rubbed 100 times or more. The water repellency and oil repellency of the coating film were almost the same as those of the fluororesin alone.

Comparative Example 1 In Example 1, when the amount of methyl silicate 51 was 45 to 60 g, which was 1.5 to 2 times the amount of the fluorinated copolymer, fine streaks or network-like cracks were formed in the thick portion of the coating film. And peeling was remarkable, resulting in poor film-forming properties. When the thickness of the coating film was small, there was no crack but the adhesion was poor, so that the coating was easily scratched. Further, in Example 1, methyl silicate 51
When the amount was less than 1/3 of the fluorine-containing copolymer, a good coating film without cracks was formed, but the hardness of the coating film was not sufficient, and the Knoop hardness by a micro hardness tester was KH = 4 to 6, It was equivalent to 2B in terms of pencil hardness. However, since a tack-free coating film with good stain resistance is formed and cured at room temperature, as an architectural elastic paint base that does not require high hardness,
More useful.

Example 2 Chlorotrifluoroethylene, tetrafluoroethylene and cyclohexyl vinyl ether as main components,
25 g of methyl silicate 51 was mixed with 25 g of commercially available fluorinated resin Lumiflon LF-400 (a product of Asahi Glass) containing a hydroxyl group in a molecule, and 20 g of ethanol and 0.050 g of p-toluenesulfonic acid were further added. A colorless, transparent, low-viscosity, uniform sol composition was prepared. This sol composition was cast on a slide glass and dried and cured at room temperature. The coating film was colorless and transparent, had good adhesion, and had high gloss. Knoop hardness by micro hardness tester is KH = 44,
It was 6H or more in terms of pencil hardness. In the same test as in Example 1, no peeling was observed in a cross-cut peeling test, and no change was observed even when the film was immersed in an organic solvent such as xylene or ethanol.

[0013]

[0014]

[0015]

[0016]

[0017]

The fluorine-containing resin for paints is used as a maintenance-free high-performance paint base with excellent weather resistance for use in a wide range of fields such as architecture, large structures, ships and vehicles, outdoor structures, and various industrial products. Although the results have been extended, the hybrid body according to the present invention can provide a material with improved performance for similar applications. In general, fluorine-containing resins for paints have soft coatings and cannot be used as is,
Room-temperature curing with an isocyanate compound and baking and curing with an aminoplast resin are required, and it is necessary to add a curing agent at the time of use. The hybrid according to the method of the present invention comprises:
After coating the prepared sol composition, self-crosslinking proceeds simply by drying at room temperature, and rapidly cures to obtain a high-performance coating film with significantly improved film hardness, weather resistance, solvent resistance, glossiness, etc. Therefore, it can be suitably used as an air-dry lacquer. For this reason, it can be used in a wider field as a fluororesin base for paints with higher performance including on-site construction. Further, since an extremely inexpensive alkyl silicate is used as a component, the amount of expensive fluororesin used is relatively reduced, which is advantageous in terms of cost and practical.

Claims (2)

(57) [Claims] 1. An organic solvent solution of a fluorine-containing copolymer (A) containing a fluoroolefin component and an alkyl vinyl ether or an alkyl vinyl ester component as main components and containing a hydroxyl group in a molecule (fluororesin varnish for paint) And (B) a hydrolyzable alkoxysilane or a partially hydrolyzed condensate thereof, such that the weight ratio of the solid components A and B is A / B = 1/3 to 4/1. And (C) an acid catalyst comprising an organic strong acid in an amount of 0.1 to 2.5% by weight based on the total weight of both components A and B, and not containing water as a component thereof. A sol composition for coating which forms a fluorine-containing copolymer / silica glass hybrid, characterized by the following . 2. A method for producing a fluorinated copolymer / silica glass hybrid, comprising applying the sol composition according to claim 1 to a substrate and then air drying.