JPH09227794A - Clear coating material and its coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a clear coating material excellent in weather resistance and having good interlaminar adhesiveness to adjacent undercoating film and provide its coating method. SOLUTION: This clear coating material contains both components of a benzotriazole-based ultraviolet light absorbent and a triazine-based ultraviolet light absorbent. This coating method comprises applying the clear coating material to colored coating film surface or applying a colored coating material containing chlorinated polyolefine to a polyolefine raw material and applying a clear coating material to the coated surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a clear coating having excellent weather resistance and good interlayer adhesion to an adjacent lower layer coating, and a coating method therefor.

[0002]

2. Description of the Related Art In order to protect metals, wood materials, plastic materials, etc. and enhance aesthetics, it is widely practiced to successively apply colored paint and clear paint. However, especially in the outdoors or the like, since the clear coating film is likely to transmit sunlight, peeling is likely to occur in the interlayer portion between the colored coating film and the clear coating film. For example, in the case of a multilayer coating film in which a colored paint containing a chlorinated polyolefin is applied to a polyolefin material and then a clear paint is applied, the ultraviolet rays transmitted through the clear coating film cause the dechlorination reaction of the chlorinated polyolefin in the colored coating film. It is considered that the interlayer adhesion of both coatings is reduced by promoting the decomposition and the like.

Conventionally, it is known that a clear coating material contains an ultraviolet absorber in order to improve such defects, but in many cases, it is often blended as a single product, and the decomposition of the chlorinated polyolefin cannot be prevented. However, it has not been possible to improve the interlayer adhesion.

[0004]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors to solve the above-mentioned deficiencies, the present inventors have formulated a clear coating by using a specific ultraviolet absorber in combination.
The present invention has been completed by finding that the interlayer adhesion to the adjacent lower colored coating film does not deteriorate even when exposed to sunlight for a long time.

That is, the present invention is a clear coating characterized by containing both components of a benzotriazole-based UV absorber and a triazine-based UV absorber, and coating the above-mentioned clear paint on a colored coating film surface. And a coloring material containing a chlorinated polyolefin on a polyolefin material (object to be coated), and the clear coating material is applied to the colored coating surface.

The benzotriazole-based ultraviolet absorber and the triazine-based ultraviolet absorber used in the present invention have different ultraviolet absorption wavelength ranges. When both are used together, the ultraviolet absorption wavelength range is widened and the ultraviolet rays from sunlight or the like are increased. It is believed that most of them were absorbed, and as a result, deterioration due to ultraviolet rays could be significantly prevented.

The present invention will be described in more detail below.

The clear coating composition of the present invention contains both components of a benzotriazole type ultraviolet absorber and a triazine type ultraviolet absorber. Specifically, the vehicle component and the both ultraviolet absorbers are combined with an organic solvent and an organic solvent. (Or) Dissolved or dispersed in water.

Examples of the benzotriazole type ultraviolet absorber include 2- (2'-hydroxy-5'-methyl-
Phenyl) benzotriazole, 2- [2'-hydroxy-3 ', 5'-di- (1,1-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (2'-hydroxy-3', 5 ' -Di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-te
rt-Butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-
Amylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl)-
5-chlorobenzotriazole, 2- (2'-hydroxy-3 ', 5'-di-isoamylphenyl) benzotriazole, 2- (2'-hydroxy-5'-tert-butylphenyl) benzotriazole and the like can be mentioned. , These can be used alone or in combination.

As the triazine-based ultraviolet absorber, 2,
4-bis (2,4-dimethylphenyl) -6- (2-hydroxy-4-isooctyloxyphenyl) -1,
3,5-triazine, 2- [4 ((2-hydroxy-
3-dodecyloxypropyl) -oxy] -2-hydroxyphenyl) -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine, 2- [4-((2
-Hydroxy-3-tridecyloxypropyl) -oxy] -2-hydroxyphenyl] -4,6-bis (2,2
4-Dimethylphenyl) -1,3,5-triazine
Etc., and these can be used alone or in combination.

The vehicle component in the clear coating is the main component for forming a coating film of the clear coating film, and a usual coating resin composition can be applied. Specifically, a hydroxyl group, an epoxy group, an isocyanate group, a carboxyl group, an acid anhydride group,
Acrylic resins, polyester resins, alkyd resins, fluororesins, urethane resins, etc. that have one or more crosslinkable functional groups selected from methylol groups, half-esters of acid anhydride groups, silanol groups, alkoxysilane groups, etc. Examples thereof include a crosslinkable curable resin composition obtained by mixing a base resin with a crosslinking agent capable of reacting with these functional groups. The mixing ratio of these is not particularly limited, but the base resin is 50 to 95%, particularly 60 to 8% based on the total weight of the both components.
5%, the cross-linking agent is preferably 50 to 5%, and particularly preferably 40 to 15%. The cross-linking agent may be methylolated and / or
Examples thereof include alkoxylated melamine resins, urea resins and benzoguanamine resins, polyisocyanate compounds, blocked polyisocyanate compounds, epoxy group-containing compounds, and carboxyl group-containing compounds.

It is also possible to use a self-curing resin in which two or more kinds selected from the above-mentioned crosslinkable functional groups and capable of reacting with each other coexist in the same molecule. Further, a resin composition which contains a polymerizable unsaturated double bond in the above resin and which is optionally combined with a polymerizable unsaturated monomer and which is crosslinked and cured by irradiation with ultraviolet rays or electron beams can also be used. .

As the base resin, cross-linking agent, self-curing resin and the like, those known per se can be used.

The clear coating material of the present invention is prepared by dissolving or dispersing the above-mentioned vehicle component in an organic solvent and / or water together with both components of the benzotriazole type ultraviolet absorber and the triazine type ultraviolet absorber. First, the composition ratio of the benzotriazole-based UV absorber and the triazine-based UV absorber can be arbitrarily selected according to the purpose. For example, based on the total weight of the both UV absorbers, the benzotriazole-based UV absorber is 10 ~
90%, especially 40 to 60%, triazine-based UV absorber 90 to 10%, especially 60 to 40% are preferable. Further, the both ultraviolet absorbers are preferably 1 to 4 parts by weight, particularly preferably 2 to 3 parts by weight, based on 100 parts by weight of the solid content of the vehicle component.
The clear coating composition of the present invention may further contain a hindered amine light stabilizer and the like, if necessary.

The present invention also includes applying the clear coating composition to the surface of the colored coating film.

The colored coating film is formed by coating and curing a colored coating material obtained by mixing and dispersing a vehicle component and a colorant in an organic solvent and / or water, and the vehicle component is the above clear coating material. It can be appropriately selected and used from those described. As the colorant, one kind or two or more kinds selected from a color pigment, a dye, a metallic pigment, an interference color pigment and the like can be appropriately used. That is, the colored coating film includes a solid color coating film and a metallic coating film.

As a specific example of applying the clear paint of the present invention to the surface of a colored coating film, the following coating system can be mentioned.

A) The above-mentioned colored paints and the above-mentioned clear paints are used in the electrodeposition coating, the intermediate coating (which may be omitted), the colored coating and the clear coating on the outer panel of the automobile.

B) After appropriately subjecting the wood portion to a base treatment, the colored paint and the clear paint are sequentially applied.

C) A plastic material (object to be coated) such as polyolefin is coated with a primer, if necessary, and then the above-mentioned coloring paint and clear paint are sequentially applied.

In particular, in c), it is unexpected that the technical effect of the present invention can be more remarkably exhibited by using a paint containing a chlorinated polyolefin as the coloring paint and applying the clear paint on the coloring coated surface. Since there is, a specific example will be described.

The polyolefin resin used in the preparation of the chlorinated polyolefin used in the colored paint is a polymer of one or more olefins selected from ethylene, propylene, pentene, hexene, octene and decene, and the like. And a copolymer with another polymerizable monomer containing 30% by weight or more of the above olefins. The weight average molecular weight of these polyolefin resins is 20,0.
00 to 200,000, especially 50,000 to 150,000
00 is preferable. And the chlorination is about 50-12
It is carried out by blowing chlorine gas into an organic solvent solution of the polyolefin resin at 0 ° C. Chlorination is
It is preferable that the chlorine content in the chlorinated polyolefin is 15 to 28% by weight, particularly 18 to 25% by weight.

The colored paint used in the above item c) needs to contain a chlorinated polyolefin, and may further contain an acrylic resin, a polyester resin, an alkyd resin, a fluororesin, a urethane resin and the like. Further, hydroxyl groups, epoxy groups, isocyanate groups, carboxyl groups, acid anhydride groups, methylol groups, half ester groups of acid anhydride groups, silanol groups, alkoxysilane groups, etc., on both or either of these chlorinated polyolefins and other resins. A cross-linking curable resin composition having one or more cross-linking functional groups selected from the above and mixing a cross-linking agent capable of reacting with these functional groups is preferable. The mixing ratio of the both components is not particularly limited, but based on the total weight of the both components, the base resin is 50 to 95%, particularly 60 to 85%, the crosslinking agent is 50 to 5%, and particularly 40 to 15%. preferable. Examples of the cross-linking agent include methylol- and / or alkoxylated melamine resins, urea resins, benzoguanamine resins, polyisocyanate compounds, blocked polyisocyanate compounds, epoxy group-containing compounds, and carboxyl group-containing compounds.

Further, one or both of the above-mentioned chlorinated polyolefin and other resins contain a polymerizable unsaturated double bond, and if necessary, a polymerizable unsaturated monomer is used in combination with ultraviolet rays or electrons. A resin composition that is crosslinked and cured by irradiation with rays or the like can also be used.

In the coating step of c), it is preferable to use a two-pack type paint containing a hydroxyl group-containing resin and a polyisocyanate compound as the colored paint and the clear paint; the colored paint contains a hydroxyl group-containing resin and a melamine resin. A two-pack type paint containing a hydroxyl group-containing resin and a polyisocyanate compound is used as a clear paint; a colored paint containing a hydroxyl group-containing resin but not a polyisocyanate compound, and a clear paint containing a hydroxyl group-containing resin and a polyisocyanate compound And a method of using a two-component type coating material contained therein to cure the colored coating film by soaking in the polyisocyanate compound; and the like. It is clear that these colored paints contain chlorinated polyolefin, and the clear paint contains both components of benzotriazole type ultraviolet absorber and triazine type ultraviolet absorber.

In the multilayer coating film obtained by coating the plastic material such as polyolefin of c) with a coloring paint containing chlorinated polyolefin, and coating the above-mentioned clear paint on the colored coating surface, benzotriazole of the clear coating film is used. Since the absorption wavelength range of the UV absorbers consisting of the system and triazine is wider than each, it absorbs most of the UV rays contained in sunlight and suppresses the dechlorination reaction of the chlorinated polyolefin in the colored coating film. It was possible to prevent ultraviolet deterioration.

Examples of the present invention and comparative examples will be described below.

I sample (1) object to be coated A product obtained by degreasing and cleaning polypropylene for automobile bumpers with an organic solvent.

(2) Colored paint Chlorinated polypropylene (weight average molecular weight of about 70,000)
0, chlorine content 21% by weight) 100 parts by weight of aluminum pigment mixed with an organic solvent (toluene / xylene = 1/1 weight ratio) to adjust the coating viscosity to a metallic level. Got the paint.

II Examples 1 to 3 and Comparative Examples 1 to 3 The components shown in Table 1 below were mixed to prepare an organic solvent (toluene /
(Xylene = 1/1 weight ratio) was added to adjust the viscosity suitable for coating to prepare the clear coating material (two-pack type) of the present invention.

[0031]

[Table 1]

III Examples 4 to 6 and Comparative Examples 4 to 6 The above coating material was spray coated with a colored coating material (cured film thickness: 15
μ) and apply the clear paints of Examples 1 to 3 and Comparative Examples 1 to 3 on a wet-on-wet basis (cured film thickness: 40).
μ) and then heated at 80 ° C. for 20 minutes to cure both coating films. Table 2 shows these coating processes and coating film performance.

[0033]

[Table 2]

(1) Weather resistance (accelerated weather resistance) Accelerated weather resistance: Q using an accelerated weather resistance tester manufactured by Q Panel Co.
According to UV accelerated baculo test.

[0035] The coating film after 480 hours (125 cycles) of testing was evaluated.

◯: The gloss is maintained almost unchanged from the initial stage.

Δ: Decrease in gloss and whitening phenomenon are recognized.

X: Remarkably decreased gloss, cracks and whitening phenomena were observed, and it was unacceptable.

(2) Interlayer Adhesion Interlayer Adhesion: After the weather resistance test in the same manner as described above, a cutter knife is used to reach the substrate, and approximately 11 centers of vertical and horizontal parallel lines of 1 mm are crossed at approximately the center of the test piece. 1cm ² pulled at intervals
Cut into scratches and scratches so that 100 eyes can be made inside, and stick adhesive cellophane tape on the coated surface,
The surface of the painted burdock after it was rapidly peeled off was evaluated. O indicates that no peeling of the coating film was observed, Δ indicates that slight peeling was observed between the metallic coating film and the clear coating film, and X indicates that a large amount of delamination was observed.

Moisture resistance: The coated plate was placed in a moisture resistance test box at 50 ° C. and 100% RH for 5 days and then taken out, and the state of the coated surface was observed and evaluated. If there was no abnormality, it was marked as ○.

◯: No cracks or blisters were generated.

Δ: The occurrence of cracks and blisters is slightly clear.

X: Significant cracking and blistering occurred.

Claims (3)

[Claims] 1. A clear paint comprising both components of a benzotriazole type ultraviolet absorber and a triazine type ultraviolet absorber. 2. A coating method, characterized in that the clear coating composition according to claim 1 is applied to the surface of a colored coating film. 3. A coating method comprising coating a polyolefin material with a colored coating material containing a chlorinated polyolefin, and coating the coated surface with the clear coating material according to claim 1.