JPH07187B2 - Method of forming coating film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for forming a coating film having excellent adhesion and weather resistance on a chrome plated surface formed on various substrates such as metals and plastics.

[Conventional technology]

It is well known that chrome plating is performed on various substrates. It is also known to coat such a chrome plated surface with paint.

However, in general, when chrome plating is performed, when the surface of the chrome plating surface is coated with a paint film, stains are likely to remain on the surface or the activity deteriorates due to aging of the plating.
It is difficult to form a coating film having excellent adhesion to the chrome-plated surface, and the adhesion tends to vary.

The chrome-plated material is often used in a portion exposed directly to the outside in an automobile or the like, and a coating film is further applied on the chrome-plated material to further improve durability.

When chrome plating is applied to a conventional substrate such as a plastic substrate and the chrome plating surface is coated, a normal racker is coated or a two-component polyurethane resin coating is coated within a short time after the chrome plating. The method of doing is generally done. The reason for this is that a relatively stable coating film can be formed by coating after the chrome plating has been performed and the chrome plating surface formed has little change over time.

[Problems to be Solved by the Invention]

The conventional chromium plated surface may have a large amount of stains due to cleaning water or other contaminants depending on its forming conditions, or a plated surface with a different thickness of the plated layer or a plated surface that has been formed for more than 5 days. In such cases, the adhesiveness to the paint is lowered, and the coating film often peels off at the interface between the matte surface and the coating film.

Originally, the surface of the chrome plated surface has a small surface tension, and the state of the surface of the plated surface has not been sufficiently clarified. Therefore, the coating film tends to be difficult to adhere. Among the conventional coating film forming methods using a paint, in the two-component polyurethane resin paint, by changing the structure of the polyol component, the adhesion of the paint film is improved at a relatively early stage after the formation of chrome plating.
Peeling is less. However, if there is a large change such as aging of the chrome-plated surface, or if the polyurethane resin coating film is prone to deterioration, the coating film also peels off, making it unsuitable for use in severe conditions such as outdoor applications. It was enough.

[Means for Solving the Problems]

As a result of intensive studies on the adhesion of the paint film to the chrome-plated surface, the present inventors have undercoated a paint containing a resin having a specific surface tension, a specific elongation and a specific acid value as described below. It was found that the above-mentioned conventional problems can be solved by using as a paint and coating the chrome plated surface.

The present invention has a surface tension of 20 to 32 dyne / c on the chrome plated surface.
m, a coating film is formed by coating a base coat containing a resin having a coating elongation of 80% or more and an acid value of 20 or more, and then coating a two-component polyurethane resin coating as a top coat.

In coating the chrome plated surface, the present invention focuses on the fact that the surface tension of the chrome plated surface is small, and uses a resin having a surface tension close to the surface tension, and further, to alleviate the curing stress strain of the coating film, By using an undercoating paint whose elongation rate is higher than that of an undercoating paint required for a normal hard material, the adhesion of the chrome plating surface, especially even if there is a change over time on the surface, does not decrease. I did so.

Further, as described above, various contaminants such as water, other metallic foreign matters, and acidic components used for forming the matte surface may be present on the chrome matte surface. It is a factor that reduces the adhesion. On the other hand, in the present invention, by setting the acid value of the resin used for the undercoat paint to 20 or more, even if the above contaminants are present, the binding force to the chrome plating surface is not lowered, and a stable adhesive force is exerted. I did.

According to the present invention, after the above-mentioned specific undercoat paint is applied, a two-component polyurethane resin paint is used as an overcoat to impart weather resistance to the formed coating film.

The chrome plating surface targeted by the present invention is, of course, an ordinary metal base material, as well as a resin base material of a variety for plating, such as ABS.
It is an arbitrary chrome-plated surface formed on a plastic substrate such as a resin, a polycarbonate resin or a nylon resin by an ordinary method known to those skilled in the art, for example, an electroless plating method.

The undercoat paint used in the present invention can be any resin as long as it has the above-mentioned surface tension, elongation and acid value,
For example, there are polyvinyl, polyolefin, and polyester resins.

The surface tension is in the range of 20 to 30 dyne / cm, and further 24 to 2
8 dyne / cm is preferred. Since the resin has such a surface tension, it is possible to adjust the resin to have the above-mentioned surface tension by adding a silicon-based additive and a fluorine-based additive as an additive to the resin.

Further, the coating film elongation rate may be 80% or more. The undercoat paint used in the present invention contains the above-mentioned resin and organic solvent as main components, and may further contain a color pigment, an extender pigment, and other commonly used additives, if desired.

The undercoat paint can be applied by a commonly used coating method.

According to the present invention, after the above-mentioned undercoat paint is applied, the two-component polyurethane paint is applied on the formed undercoat paint film in a wet state or usually after drying at 40 to 100 ° C for 20 to 60 minutes.

As the top coating material, a generally used two-component polyurethane coating material may be used, and a two-component polyurethane coating material containing one component of polyacrylic polyol or polyester polyol is particularly preferable. For coating, any commonly used coating method can be used. 2 at 50-100 ° C after painting
Dry for 0 to 100 minutes.

The surface tension of the resin used in the undercoat paint of the present invention is 20 dyne / cm
The smaller it is, or the more it exceeds 32 dyne / cm, the larger the difference between the surface tension of the chrome plated surface and the loss of affinity with the chrome plated surface of the coating film, resulting in deterioration of adhesion. Not preferable.

On the other hand, if the elongation is less than 80%, the internal stress at the time of forming the coating film is increased and the adhesion is deteriorated, which is not preferable.

When the acid value is less than 20, when the contaminants are present on the chrome plated surface, especially when the acid used for the plating remains, the wettability of the undercoating material on the chrome plated surface deteriorates and the uniform adhesion occurs. It is not preferable because it disappears.

The undercoat paint according to the present invention contains a vehicle component and an organic solvent as main components, and a color pigment, an extender pigment, an additive, and the like can be further added to the main component.

The vehicle component is suitable as long as it is within the above range whether it is a thermoplastic resin or a two-component urethane system having an OH group and using polyisocyanate as a curing agent. Polyisocyanate used at this time is toluene diisocyanate, diphenylmethane diisocyanate,
Also suitable are methylene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, triphenylmethane triisocyanate, phenylene diisocyanate, lysine diisocyanate and the abovementioned methylol adducts or 3-pentamers and mixtures thereof.

Furthermore, the undercoat paint should be in a wet state after coating or at 40 ° C.
After drying at -100 ° C for 20 to 60 minutes, the top-coat paint may be applied.

〔Example〕

 The present invention will be described below with reference to examples.

Example I Preparation of sample (1) Chrome plating plate (a) Chrome plating plate on ABS 5 days or more (manufactured by Japan Test Panel Co., Ltd.) (b) Chrome plating plate on ABS was sprayed with a plating solution at a concentration of 1% on the entire surface. Plate (2) Undercoat paint (all parts by weight are shown) (a) Acrylic resin (I) (AV30, surface tension: 30 dyne / c
m: 100% elongation) 100 parts titanium oxide 20 parts, xylol 60
(B) Acrylic resin (II) (AV80, surface tension: 28 dyne / cm elongation: 85 instead of acrylic resin (I) in (a) above)
%) (C) Acrylic resin (III) (AV30, surface tension: 30 dyne / cm, elongation: 30) in place of acrylic resin (I) in (a) above.
%) (D) Polyester resin (Toyobo: Byron 300, AV 0, surface tension: in place of acrylic resin (I) in the above (a):
26dyne / cm, elongation: 500%) (3) Topcoat paint 2-component polyurethane paint: Porin No.1 black (manufactured by Shinto Paint Co., Ltd.) (4) Composition of acrylic resin (I), (III) (5) Manufacturing method of undercoat paint After stirring each resin, titanium oxide and solvent uniformly for 20 minutes, disperse for 30 minutes with a paint conditioner and confirm that the particle size is 10μ or less, then glass beads And use as paint.

II Examples and Comparative Examples Using the samples prepared in the above I, chrome plating plate → primer (10 μ) → 5 minute interval → top coating (30 μ) → drying was applied in the combination shown in Table-1 in the process of 80 ° C. × 30 minutes. .

III Performance Test Results Table 2 shows the results of performance tests performed using the coated plates coated in the above Examples and Comparative Examples.

(Test method) Adhesiveness: 1m / m ruggedness test Warm water: Adhesion test after hot water immersion test at 80 ℃ × 120Hr Weather resistance: Adhesion test after hot water immersion test at 80 ℃ × 48Hr after SWOM400Hr (Evaluation) ◎ : No abnormality ×: There is peeling

Claims (1)

[Claims] 1. A surface tension of 20 to 32 dyne on a chrome plated surface.
/ cm, a coating film elongation rate of 80% or more and an acid value of 20 or more are applied as a base coat, and then a top coat of 2
A method for forming a coating film, which comprises applying a liquid polyurethane resin paint.