JP2003206436A - Top coat composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a top coat composition containing an organic solvent type coating composition comprising a hydroxy group-containing acrylic resin and a (blocked) polyisocyanate compound crosslinking agent and forming coating film excellent in weather resistance, pollution resistance and recoat property. <P>SOLUTION: This top coat composition is obtained by compounding the organic solvent type coating composition comprising the hydroxy group- containing acrylic resin and the (blocked) polyisocyanate compound crosslinking agent with an organosilane represented by the general formula: R<SP>1</SP>Si(OR<SP>2</SP>)<SB>3</SB>[wherein R<SP>1</SP>is a 1-8C organic group; R<SP>2</SP>is a 1-5 alkyl group] and/or a condensate of the organosilane having 2-60 of degree of condensation with a surfactant having 1-20 HLB value, and the compounding amount of the organosilane is 0.1-10 pts.wt. based on 100 pts.wt. resin solid content of the organic solvent type coating composition and the compounding amount of the surfactant is 0.01-5 pts.wt. based on 100 pts.wt. resin solid content of the organic solvent type coating composition. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a top coating composition which is used for coating various materials such as metal, glass, concrete, plastic, and wood, and which forms a coating film excellent in weather resistance, stain resistance and recoatability. Regarding things.

[0002]

2. Description of the Related Art Conventionally, outdoor structures, steel towers, bridges, displays, guard fences, etc. have been painted with an outdoor paint for the purpose of protection and design. If the formed coating film is poor in weather resistance, the stains adhering to the coating film surface will be removed with rainwater and the like along with the deterioration of the coating film surface over time. The problem of contamination of the film surface was small.

However, acrylic urethane resin-based paints, fluororesin-based paints, acrylic silicone resin-based paints, etc., which are currently used for outdoor use form a coating film having excellent weather resistance, and the deterioration of the coating film surface also progresses. Very late. Therefore, when dust particles floating in the air or pollutants contained in exhaust gas from automobiles adhere to the coating film, only part of it is removed by rainwater, resulting in conspicuous rain streaks and the coating film appearance is poor. There is a drawback that Further, a method of adding a low condensate of alkyl silicate has been adopted for the purpose of improving the stain resistance, but this method has a problem in long-term maintenance of stain resistance and recoatability.

[0004]

The conventional alkoxysilane-containing resin coating composition has a drawback that it takes more than half a year for the effect of stain resistance to be exhibited, resulting in contamination for the period until then. In addition, when an alkyl silicate-containing resin-based coating is applied, the alkyl silicate rapidly moves to the surface of the coating film and undergoes hydrolysis, and the effect of stain resistance develops within a few days after application, but conversely. Several days after application
There is a drawback that the recoatability for one month deteriorates and delamination occurs. Further, in the case of a low-condensation alkyl silicate, it disappears quickly from the surface due to rainwater, etc., and there is a problem in maintaining weather resistance for a long period of time.

The present invention is an organic solvent type coating composition containing a hydroxyl group-containing acrylic resin as a reaction-curable organic resin component and a (blocked) polyisocyanate compound cross-linking agent, which has weather resistance, stain resistance and recoating. It is an object of the present invention to provide a top coating composition which forms a coating film having excellent properties.

[0006]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors in order to achieve the above-mentioned object, a specific organosilane and / or a condensate of the organosilane having a condensation degree of 60 or less is compared with an alkyl silicate. And has a high compatibility with the hydroxyl group-containing acrylic resin and the (blocked) polyisocyanate compound cross-linking agent, the migration to the coating film surface after application is slow, and the recoatability is good even within several days to one month after application. I found a thing. Further, it was found that the addition of the surfactant makes it possible to maintain the stain resistance in the initial stage (about 1 day to 4 weeks later).

That is, the top coating composition of the present invention is an organic solvent type coating composition containing a hydroxyl group-containing acrylic resin as a reaction-curable organic resin component and a (blocked) polyisocyanate compound cross-linking agent. wherein R ¹ Si (OR ²⁾ ₃ [wherein, R ¹ is an organic group having 1 to 8 carbon atoms, R ² is an alkyl group having 1 to 5 carbon atoms. ] The organosilane and / or the condensate of the organosilane having a condensation degree of 60 or less and a surfactant having an HLB value of 1 to 20 are blended, and the blending amount of the organosilane is the organic solvent type coating composition. 0.1 to 10 parts by mass per 100 parts by mass of resin solid content, and the compounding amount of the surfactant is 0.01 to 5 per 100 parts by mass of resin solid content of the organic solvent type coating composition.
It is characterized by being a mass part.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The top coating composition of the present invention is an organic solvent type coating composition containing a hydroxyl group-containing acrylic resin and a (blocked) polyisocyanate compound crosslinking agent as a reaction-curable organic resin component. .

The hydroxyl group-containing acrylic resin used in the present invention is one or more kinds of monomers having a polymerizable ethylenic unsaturated bond and a hydroxyl group, and other ethylene which is polymerizable with these monomers. It is obtained by polymerizing one or more monomers having a polyunsaturated bond.

Examples of the above-mentioned monomer having an ethylenically unsaturated bond and a hydroxyl group include 2-hydroxyethyl (meth).
Examples thereof include hydroxyalkyl esters of (meth) acrylic acid having 2 to 24 carbon atoms such as acrylate, hydroxypropyl (meth) acrylate, and hydroxybutyl (meth) acrylate, and lactone-modified hydroxyalkyl esters.

Other monomers that can be polymerized with the above monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, tert-butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate,
Alkyl or cycloalkyl esters having 1 to 24 carbon atoms such as lauryl (meth) acrylate and stearyl (meth) acrylate; glycidyl (meth) acrylate; γ-methacryloxypropyltrimethoxysilane,
γ-methacryloxypropylmethyldimethoxysilane,
γ-methacryloxypropyltriethoxysilane, γ-
Monomers having an alkoxysilyl group such as methacryloxypropylmethyldiethoxysilane; carboxylic acids having an ethylenically unsaturated bond such as (meth) acrylic acid, itaconic acid, crotonic acid; styrene, vinyltoluene, α-
Styrene-based monomers such as methylstyrene; or (meth) acrylonitrile.

The hydroxyl group-containing acrylic resin used in the present invention preferably has a hydroxyl value of 5 to 200 mgKOH.
/ G, and the number average molecular weight is preferably 1,000 to 2
10,000, more preferably 2,000 to 15,000
What is is suitable. Hydroxyl value is 5mgKOH / g
When using a hydroxyl group-containing acrylic resin of less than less than, weather resistance, solvent resistance tends to decrease, and when a hydroxyl group-containing acrylic resin having a hydroxyl value of more than 200 mgKOH / g is used, acid resistance, Moisture resistance tends to decrease. Further, when a hydroxyl group-containing acrylic resin having a number average molecular weight of less than 1,000 is used, low-temperature curability and solvent resistance tend to decrease, and the number average molecular weight is 20,0.
When a hydroxyl group-containing acrylic resin exceeding 00 is used, the smoothness of the coated surface and the fineness of particles during spray coating tend to deteriorate.

The polyisocyanate compound used in the present invention is a compound having at least two isocyanate groups in one molecule. As the polyisocyanate compound, hexamethylene diisocyanate (HMDI), trimethylhexamethylene diisocyanate (TMDI)
Aliphatic diisocyanates such as isophorone diisocyanate (IPDI); Aromatic aliphatic diisocyanates such as xylylene diisocyanate (XDI); Tolylene diisocyanate (TDI), 4,4-diphenylmethane diisocyanate (MDI) ) Etc. aromatic diisocyanates; dimer acid diisocyanates (DDI), hydrogenated TD
I (HTDI), hydrogenated XDI (H6XDI),
Hydrogenated diisocyanates such as hydrogenated MDI (H12MDI); dimers, trimers and higher molecular weight polyisocyanates of these diisocyanate compounds;
Examples thereof include polyhydric alcohols such as trimethylolpropane or water, or an adduct with a low molecular weight polyester resin.

The polyisocyanate compound used in the present invention may be a blocked polyisocyanate compound, and examples of the blocking agent include oximes such as methylethylketoxime, acetoxime, cyclohexanone oxime, acetophenone oxime and benzophenone oxime; m-cresol, xylenol and the like. Phenols; alcohols such as methanol, ethanol, butanol, 2-ethylhexanol, cyclohexanol, ethylene glycol monoethyl ether; lactams such as ε-caprolactam; diketones such as diethyl malonate and acetoacetate; thiophenol Mercaptans such as can be brought in. Other examples include ureas such as thiourea; imidazoles; carbamic acids and the like.

The blocked polyisocyanate compound can be obtained by reacting the above polyisocyanate compound with a blocking agent by a conventional method until free isocyanate groups are exhausted. Oxime- or lactam-blocked polyisocyanate compounds are preferred as crosslinkers.

Regarding the mixing ratio of the hydroxyl group-containing acrylic resin and the (block) polyisocyanate compound, the number of hydroxyl groups in the hydroxyl group-containing acrylic resin and the (block)
The ratio with the number of isocyanate groups in the polyisocyanate compound is preferably 1: 0.6 to 1.5, more preferably 1 :.
The range of 0.8 to 1.2 is preferable. If the above ratio of the compounding ratio is less than 1: 0.6, the weather resistance, stain resistance, water resistance, etc. of the coating film will tend to decrease, while if the above ratio exceeds 1: 1.5 The stain resistance and weather resistance of the film tend to decrease.

As the organic solvent used in the present invention, an organic solvent which is inert to the above reaction-curable organic resin component and which can dissolve or disperse the reaction-curable organic resin component is appropriately selected. Can be used. Specifically, for example, toluene, hydrocarbon solvents such as xylene, methyl ethyl ketone, ketone solvents such as methyl isobutyl ketone, ethyl acetate, ester solvents such as butyl acetate, dioxane, ether solvents such as ethylene glycol diethyl ether, Aliphatic hydrocarbons such as pentane, hexane, heptane and the like can be mentioned. The mixing ratio of the organic solvent is preferably 10 to 95% by mass, more preferably 20 to 90% by mass based on the total amount of the reaction-curable organic resin component.
It is preferably in the range of mass%.

The organosilane used in the present invention is represented by the general formula R ¹ Si (OR ² ) ₃ [wherein R ¹ is an organic group having 1 to 8 carbon atoms, and R ² is an alkyl group having 1 to 5 carbon atoms]. It is a base. ] And / or a condensate of the organosilane having a condensation degree of 60 or less, wherein the organosilane is used in an amount of 0.1 to 10 parts by mass per 100 parts by mass of the resin solid content of the organic solvent-based coating composition. Blend with.

Examples of the organic group R ¹ in the organosilane represented by the above general formula include an alkyl group, a cycloalkyl group, an aryl group and a vinyl group. This alkyl group may be linear or branched. Examples of the alkyl group include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group, t-butyl group, pentyl group, hexyl group and heptyl group. And alkyl groups such as octyl group. Preferred alkyl groups are those with 1 to 4 carbon atoms. Examples of the cycloalkyl group include a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group. Examples of the aryl group include a phenyl group.

Each of the above functional groups may optionally have a substituent. Examples of such a substituent include a halogen atom (eg, chlorine atom, bromine atom, fluorine atom).
And (meth) acryloyl group, mercapto group, alicyclic group and the like.

The alkyl group R ² in the organosilane represented by the above general formula may be linear or branched.
Examples of such an alkyl group include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, an s-butyl group, a t-butyl group and a pentyl group. And a preferred alkyl group has 1 to 1 carbon atoms.
There are two.

As the organosilane used in the present invention,
Methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, i-propyltrimethoxysilane, i-propyltriethoxysilane, γ- Chloropropyltrimethoxysilane, γ-chloropropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, Cyclohexyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-
Examples thereof include mercaptopropyltriethoxysilane, phenyltrimethoxysilane, and phenyltriethoxysilane. Preferred organosilanes are methyltrimethoxysilane and methyltriethoxysilane.

In the present invention, the general formula R ¹ Si (OR ² ) ₃ [wherein R ¹ is an organic group having 1 to 8 carbon atoms and R ² is an alkyl group having 1 to 5 carbon atoms]. ] And / or a condensate of the organosilane having a condensation degree of 60 or less is used.
A low condensation degree of less than 0, a medium condensation degree of 10 or more and less than 20, a 20
The above 60 or less can be classified as a high condensation degree, and in the present invention, it is preferable to use a condensation product having a high condensation degree.

The surfactant used in the present invention has the effect of reducing the contact angle of water in the coating film. In the present invention, a surfactant having an HLB value of 1 to 20, preferably H
A high HLB surfactant having an LB value of 10 to 20 is used. Surfactants that can be used include alkyl allyl ether type, alkyl ether type, alkyl ester type, alkyl amine type, polycyclic phenyl ether type, and silicone ether type. A surfactant which is a silicone polymer having an ethylene glycol and / or propylene glycol skeleton and is soluble in the above solvent is preferable. In the present invention, a surfactant is added in an amount of 0.0 per 100 parts by mass of the resin solid content of the organic solvent type coating composition.
It is mixed in an amount of 1 to 5 parts by mass.

The top coating composition of the present invention can be applied to a substrate and then cured at room temperature or under heating conditions to form a coating film. By using a surfactant having a high solubility of the reaction-curable organic resin component, recoatability is improved, and the surfactant improves hydrophilicity of the coating film surface. Further, when exposed to the outdoors and contacted with acid components such as acid rain, the alkoxy group of the organosilane is hydrolyzed to gradually reduce the contact angle with water to prevent the coating surface from being soiled. You can

The top coating composition of the present invention is an inorganic substrate such as glass, slate, concrete, etc .; metal such as aluminum, steel, zinc, tin, copper, stainless steel, etc., steel surface plated with zinc, tin, chromium, etc. Metals, steels, etc. Metal substrates such as metals whose surfaces have been treated with chromic acid, phosphoric acid, etc .; plastic substrates such as polyethylene, polyvinyl chloride, ABS, etc .; on polyvinyl chloride, polyethylene terephthalate, aluminum etc. substrate films It can be applied to a wide range of base materials such as a tape having an adhesive or a pressure-sensitive adhesive provided thereon and, if necessary, a well-known primer, an intermediate coating composition or a top coating composition.

The top coating composition of the present invention can be applied to the surface of the substrate by means such as brush coating, spray coating, roller coating, dip coating, electrostatic powder coating and the like. The coating amount varies depending on the type of coating material, coating means, etc., but generally the coating film thickness is 5 to 500 μm, preferably 10 to 200.
An amount in the μm range is considered sufficient. The conditions for drying the coating film can be selected according to the type of the top coating composition.

For example, in the case of an overcoating coating composition containing a hydroxyl group-containing acrylic resin as a base resin and a polyisocyanate compound as a crosslinking agent, it takes about 2 to 12 hours at room temperature, and the hydroxyl group-containing acrylic resin is used as a base resin. In the case of a top coating composition containing a blocked polyisocyanate compound as a cross-linking agent, about 10 to 60 minutes at 100 to 200 ° C is considered to be sufficient.

In the coating film formed from the top coating composition of the present invention, the surface layer is composed of the alkyl siloxane or its condensate component and the surfactant, and the inside thereof is composed of the organic coating film, so that it is resistant to contamination. The property is achieved by the alkyl siloxane or its condensate component and the surfactant, and the durability, processability, adhesion and the like are achieved by the organic coating film, so that it is possible to satisfy the requirements of stain resistance and durability. The effect is recognized.

[0030]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. Examples 1 to 7 and Comparative Examples 1 to 5 DNT Urethane Mild White (trade name, manufactured by Dainippon Paint Co., Ltd., acrylic polyisocyanate curing type organic solvent type coating material, resin solid content, which is a reaction curing type organic solvent type coating material composition. 35%) to 286 parts by mass (100 parts by mass of resin solid content), and the type and amount (parts by mass) of the alkyltrialkoxysilane condensate or tetraalkoxysilane condensate shown in Table 1 or 2, A coating composition was obtained by mixing the types and amounts (parts by mass) of the surfactants shown in Table or Table 2 with each other.

<Test Method><Evaluation of Outdoor Exposure Contamination> 300 mm × 150 mm × 0.
Mighty Eposealer (Dainippon paint) Co., Ltd .: epoxy resin-based sealer) was spray-coated so that the dry film thickness was about 30 μm, and dried in an atmosphere of 20 ° C. for 24 hours.
Then, the exposed plate was spray-coated with the above coating composition so that the dry film thickness was about 50 μm, and dried in an atmosphere of 20 ° C. for 3 days to obtain a test body.

The above-mentioned test piece was tested in Otawara City, Tochigi Prefecture on a surface having a large area (one-third from one end in the longitudinal direction described above).
The part from the place to the other end) was vertical, and it was installed outdoors in the south direction and exposed outdoors. One month later, 3
The stains on the rain streaks after months, 6 months and 12 months were visually evaluated according to the following criteria. The results are shown in Table 1 or 2. ⊚: No rain streak stain on vertical surface, ○: Slight rain streak stain on vertical surface, Δ: Rain streak stain on vertical surface, ×: Significant rain streak stain on vertical surface

<Measurement of static contact angle with water> Using the test piece used for outdoor exposure contamination evaluation, 0.1 cc of distilled water was dropped on the surface of the coating film after 1, 7, and 30 days of outdoor exposure. Then, the contact angle after 1 minute of dropping in an atmosphere of 20 ° C. was measured by a Kyowa Interface Science Co., Ltd. CA-X contact angle measuring device. The results are shown in Table 1 or 2.

<Evaluation of Interlayer Adhesion> Mighty Eposealer (manufactured by Dainippon Paint Co., Ltd .:
An epoxy resin-based sealer) was applied by brush coating so that the dry film thickness was about 30 μm, and dried in an atmosphere of 20 ° C. for 24 hours. Then, the above coating composition is applied so that the dry film thickness is about 25 μm, and the temperature is 20 ° C. and the humidity is 50%.
It was dried under the conditions of. 14 hours after painting, 1 day later,
After 3 days, 7 days, 15 days and 30 days, a coating composition having the same compounding ratio was applied by brush coating so that the dry film thickness was about 25 μm to prepare a test body. The total dry film thickness at this time is about 50 μm. 20
Dry under conditions of ℃ and humidity of 50% for 7 days, JIS K
Adhesion (interlayer adhesion) of the coating film was evaluated according to the adhesion test of 5400 8.5 (2001). The results are shown in Table 1 or 2.

[0035]

[Table 1]

[0036]

[Table 2]

Note 1) Methyltrimethoxysilane [CH
₃ Si (OCH ₃ ) ₃ ] condensate having Mw of 4000. Note 2) Mw is 1 with a condensate of methyltrimethoxysilane.
500 things. Note 3) Condensation product of methyltrimethoxysilane with Mw of 1
50 things. Note 4) Tetraethoxysilane condensate with Mw of 100
0 thing. Note 5) HLB13 surfactant containing ethylene glycol and propylene glycol. Note 6) HLB7 surfactant containing ethylene glycol and propylene glycol.

[0038]

EFFECTS OF THE INVENTION The top coating composition of the present invention can form a coating film having excellent weather resistance, stain resistance, and recoatability, and can be applied to outdoor structures, steel towers, bridges, displays, guard fences, etc. Useful for coating substrates.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Akira Iwasawa             1-232 Tayutsuka, Nishinasuno Town, Nasu District, Tochigi Prefecture             -457 Ken Heights E-102 (72) Inventor Tamio Mizuno             Osaka Prefecture Osaka City Konohana Ward Nishikujo 6-1-124 (72) Inventor Kenichi Nishikawa             8-15 Asahi-cho, Nishinasuno-cho, Nasu-gun, Tochigi Prefecture             Ji heim 102 (72) Inventor Masashi Sakurada             3-1172 Shimonagata, Nishinasuno Town, Nasu District, Tochigi Prefecture             4 A-103 F-term (reference) 4J038 CG001 DG191 DG262 DL032                       GA03 JC32 KA09 NA03 NA05

Claims (2)

[Claims] 1. An organic solvent-based coating composition containing a hydroxyl group-containing acrylic resin as a reaction-curable organic resin component and a (blocked) polyisocyanate compound crosslinking agent, further comprising:
Formula R ¹ Si (OR ²⁾ ₃ wherein, R ¹ is an organic group having 1 to 8 carbon atoms, R ² is an alkyl group having 1 to 5 carbon atoms. ] The organosilane and / or the condensate of the organosilane having a condensation degree of 60 or less and a surfactant having an HLB value of 1 to 20 are blended, and the blending amount of the organosilane is the organic solvent type coating composition. 0.1 to 10 parts by mass per 100 parts by mass of resin solid content, and the compounding amount of the surfactant is 0.01 to 5 per 100 parts by mass of resin solid content of the organic solvent type coating composition.
A top coating composition, characterized in that it is part by mass. 2. The topcoat coating composition according to claim 1, which comprises an organosilane condensate having a condensation degree of 20 to 60 and a surfactant having an HLB value of 10 to 20.