JPH059430A - Paint composition - Google Patents

Abstract

PURPOSE:To provide a coating composition which does not cause any cohesive failure of an aluminum pigment when a melamine-crosslinkable one-pack base coating material is used in the form of a metallic coating material. CONSTITUTION:A coating composition prepared by adding 15wt.%, based on the solid matter of the coating material, aluminum pigment coated with a urethane resin to a melamine-crosslinkable one-pack base coating material component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a melamine cross-linking type one-pack metallic base paint which can be used as a top coat paint for bumpers and the like.

[0002]

2. Description of the Related Art Conventionally, isocyanate / polyol-based urethane paints have been mainly used as a top coat paint for bumpers, which is excellent in compatibility with bumper materials, along with the weight reduction and color coating of bumpers. However,
Not only is the cost of the isocyanate high, but it is a two-part type, so poor handling is a problem. Therefore,
It has been proposed to use a melamine cross-linking type one-pack type base paint as a paint replacing the urethane paint.

[0003]

However, since the above-mentioned melamine cross-linking type one-pack base paint is used as a metallic paint, when an ordinary aluminum paste for paint is blended, aggregation of the aluminum pigment in the base coat,
The phenomenon of breakage (peeling) occurs, which causes a new problem that it cannot be used as a metallic paint. Therefore, in order to solve such a problem, the present inventor diligently searched for the cause of the aggregation and peeling phenomenon of the aluminum pigment in the base coat, and as a result, in the aluminum paste for normal coating, the aluminum pigments were aggregated in the coating composition. In order to prevent this, an amine compound is added for the purpose of adsorbing a fatty acid and neutralizing it. Therefore, the above fatty acid has poor wettability with the coating resin component and easily causes cohesive failure, and in the case of urethane coating, the amine compound acts as a catalyst during isocyanate curing, but in the case of melamine curing it acts as a negative catalyst. However, it leads to a decrease in cross-linking and promotes the cause of cohesive failure. In particular, since the top coating for bumpers is designed to be soft, cohesive failure is likely to occur. Therefore, an object of the present invention is to provide a coating composition that does not cause cohesive failure of aluminum pigments when a melamine cross-linking type one-pack base coating is used as a metallic coating.

[0004]

Means for Solving the Problems The present invention has been made paying attention to the fact that when an aluminum pigment is coated with a urethane resin, the aggregation and peeling phenomena of the aluminum pigment in the base coat do not occur. A coating composition comprising an aluminum pigment obtained by coating a mold base coating component with a urethane resin in an amount of 15% by weight or less based on the coating solid content.

The melamine cross-linking type one-pack type base coating composition used in the present invention is mainly composed of an acrylic resin or a polyester resin which is a resin constituting a solid base coat and a melamine resin as a cross-linking agent, together with an appropriate additive. A known coating composition can be used which is formed by adding and mixing with a solvent.

On the other hand, as the aluminum pigment coated with urethane resin, aluminum powder used as a pigment for metallic paint is used, and it is produced by coating urethane paint. The aluminum pigment coated with the urethane resin may be added and mixed as it is to the above base paint components, or may be added and mixed as an aluminum paste.

The addition amount of the urethane resin-coated aluminum pigment is determined by the metallic degree of the metallic paint, but when the amount exceeds 15% by weight of the solid content of the coating resin, the phenomenon of cohesive failure tends to occur. It is preferable to stop. The coated aluminum pigment may be used in combination with an uncoated aluminum pigment, but the coated aluminum pigment is required to be at least 50% or more of all pigments from the viewpoint of compensating the cohesive failure due to the pigment.

[0008]

[Function] It is not clear why uncoated aluminum pigment and acrylic resin-coated aluminum pigment undergo cohesive failure in the base coat, and only urethane resin-coated aluminum pigment does not cause cohesive failure in the base coat. It seems that the compatibility (wettability) with the resin is improved by the urethane resin forming the surface coating layer and the synergistic effect of suppressing the curing inhibition of the amine compound with respect to melamine.

Hereinafter, the present invention will be described in detail based on examples.

EXAMPLES (Preparation of base coat coating composition) 10 parts by weight of styrene (hereinafter, simply referred to as "part"), 10 parts of methyl methacrylate, 30 parts of hydroxyethyl acrylate
Parts, ε-caprolactone 50 parts, and acrylic acid 3 parts were polymerized in xylene using a polymerization initiator α, α′-azobisisobutyronitrile to obtain an acrylic resin solution A having a resin content of 50%. A predetermined amount of the aluminum pigments shown in Tables 3 and 4 prepared in the above Preparation Example are added to and mixed with the acrylic resin solution A to prepare base coat paints with the formulations shown in Tables 1 and 2. This base coat paint is diluted with a 30/30/40 mixed solvent of xylene, butyl acetate and sorbet 100 in Ford cup No. 4 for 13 seconds and used.

Table 1 Example No. 1 2 3 4 Acrylic resin solution A (part) 50 50 50 50 CAB381-2 (10% solution) (part) 15.5 15.5 15.5 15.5 U-VAN 122 (60) % Solution) (part) 10.4 10.4 10.4 10.4 aluminum A (part) 1.6 4.9 aluminum B (part) 1.6 4.9 butyl acetate (part) 5 10 5 10 xylene (Parts) 10 10 10 10 butanol (parts) 7.5 7.5 7.5 7.5 7.5 BYK301 (parts) 0.5 0.5 0.5 0.5 CAB 381-2 (manufactured by Eastman) Butyl) U-VAN 122 (Melamine resin manufactured by Mitsui Toatsu) Aluminum A (Asahi Kasei CR-601: paste containing aluminum pigment coated with urethane resin) Aluminum B (Asahi Kasei CR-51: urethane resin coated a) Containing Miniumu pigment paste) Byk 301 Leveling agent (silicone additive BYK chemie Japan production)

Table 2 Comparative Example No. 1 2 3 Acrylic resin solution A (part) 50 ← ← CAB381-2 (part) 15.5 ← ← U-VAN 122 (part) 10.4 ← ← Aluminum A (part) 5.5 Aluminum C (parts) 1.6 Aluminum D (parts) 1.6 Butyl acetate (parts) 5 ← ← Xylene (parts) 10 ← ← Butanol BYK301 (parts) 0.5 0.5 0.5 Aluminum C (Showa Denko) Sap561ps: Paste containing aluminum pigment coated with acrylic resin) Aluminum D (non-coated with Asahi Kasei M-601 pigment)

Table 3 Example No. 1 2 3 4 Resin type Urethane Urethane Urethane Urethane Pigment CR-601 CR-601 CR-51 CR-51 Addition amount (%) 5 15 5 15 Cohesive failure property ○ ○ ○ ○ Addition amount above Is the weight% with respect to the resin solid content.

Table 4 Comparative Example No. 1 2 3 Resin type Acrylic urethane Non-coated Pigment CR-601 CR-601 CR-51 Addition amount (%) 5 17 None Cohesive failure Δ Δ × However, the cohesive failure is the following test method. It was judged by.

(Preparation of clear coat coating composition) 10 parts by weight of styrene (hereinafter simply referred to as "part") 15 parts of 2-hydroxyethyl methacrylate, 50 ε-caprolactone
Parts and 25 parts of ethylhexyl methacrylate were polymerized in xylene using a polymerization initiator α, α′-azobisisobutyronitrile to obtain an acrylic resin solution B having a resin content of 60%. Uban 122 is added to 60 parts of this acrylic resin solution B.
25 parts, Tinuvin 900 (Ciba Geigy benzotriazole UV absorber) 0.5 part, Sanol LS29
2 (Sand's light stabilizer) 0.3 parts, BYK344 1
Part, Solvesso 100 (aromatic solvent) 8.2 parts, and xylene 5 parts are mixed to prepare a clear coat paint, which is diluted with Solvesso 100 ford cup No. 4 at 20 ° C. for 20 seconds and used.

(Test method) An epoxy-based cationic electrodeposition coating composition was electrodeposited to a dry coating film thickness of about 20 μ on a 0.8 mm thick dull steel sheet which had been subjected to zinc phosphate chemical conversion treatment, and was then subjected to 170 ° C.
After baking for 20 minutes, sharpen with # 400 sandpaper electrodeposition, wipe with petroleum benzine to degrease, and then air-spray an automobile width coat surfacer to a dry coating thickness of about 25μ, and at 140 ° C for 30 minutes. After baking, sharpen with # 400 sandpaper, drain,
Then, it was degreased with petroleum benzine and used as a test material. The base coat paints of Examples 1 to 4 and Comparative Examples 1 to 3 prepared on this material with a viscosity of 13 seconds were air spray gun F.
5 (manufactured by Meiji Kikai Seisakusho) was applied to give a dry film thickness of about 15μ, left at room temperature for 3 minutes, and then viscous to a viscosity of about 30 seconds. Approximately 30μ in dry film thickness using gun F5
After painting to the thickness of 10 minutes, set at room temperature for 10 minutes. Then, this was baked and cured at 140 ° C. for 30 minutes in an electric hot air dryer. The obtained coated plate is marked with a mark by a cutter, and a peeling test is performed 5 times with cellophane tape. The test results are shown in Table 4. The greater the cohesive failure of the aluminum pigment, the more marked the peeling of the coating film. However, ○
Indicates no peeling, Δ indicates slight peeling, and x indicates remarkable peeling.

[0017]

As is clear from the above results, when the aluminum pigment is blended with the melamine cross-linking type one-component base paint component, if an uncoated aluminum pigment is used, the cohesive failure is remarkable and the coating is present. Also, even if a non-urethane resin is used, or if a urethane resin-coated aluminum pigment is contained in a specified amount or more, its cohesive failure prevention performance is low, whereas the urethane resin-coated aluminum pigment is used for the solid content of the paint. It can be seen that the coating composition containing 15% by weight or less is excellent in the cohesive failure prevention performance of the aluminum pigment.

Claims (1)

Claims: 1. A melamine cross-linking type one-pack base paint component containing an urethane pigment coated with an aluminum pigment in an amount of 15% by weight or less based on the solid content of the paint. Composition.