JPS63319085A - Coating method for chipping resistant paint film - Google Patents

Abstract

PURPOSE:To obtain a low-cost lightweight chipping resistant paint film by coating the surface of a paint film as an undercoat with a foamable paint to form a first layer, coating the surface of the first layer with a paint contg. no foaming component by a wet-on-wet process to form a second layer and carrying out baking. CONSTITUTION:A paint film (c) is formed as an undercoat on a substrate (steel sheet) (d) by electrodeposition. The surface of the paint film (c) is coated with a foamable paint to form a first layer (b) and the surface of the first layer (b) is coated with a paint contg. no foaming component by a wet-on-wet process to form a second layer (a). Foaming and curing are then carried out in a second coat baking furnace at 140 deg.C to form a foamed film of >=150mum thickness having a smooth skin of several ten mum thickness as a surface layer.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention forms a lightweight, high-thickness film at low cost,
The present invention relates to a coating method that provides a good chipping-resistant coating without impairing the finished appearance, and in particular to a coating method for a chipping-resistant coating that is effective for protecting the underfloor and lower parts of a vehicle body.

(Conventional technology) Conventional techniques for applying chimping-resistant coatings include methods of forming coatings called undercoat and stone guard coating, which provide coatings with excellent elasticity and abrasion resistance on the lower part of the car body and under the floor. A coating film of 150 to 500 μm was applied.

(Problems to be Solved by the Invention) However, in such conventional coating methods, the coating film formed is extremely thick and may sag during application or crack during drying, resulting in poor workability. It was difficult. Furthermore, in order to reduce the weight of the car body, the weight increase due to the thick paint film could not be ignored. To solve these problems, foaming chipping-resistant paints have been proposed, but because the foaming components are uniformly dispersed in the sample and foamed, the surface strength is low and the abrasion resistance is poor. Therefore, there was a problem that it was difficult to maintain performance over a long period of time. In addition, if there is a chance that an intermediate coat or top coat is applied on top of the chipping-resistant paint on the outside of the side sill, etc., the pores caused by foaming that occur on the surface layer of the chipping-resistant paint film will cause cracks and blisters in the paint film. Therefore, there was a problem in that it was extremely difficult to put it into practical use.

(Means for Solving the Problems) The present invention was made by focusing on the above problems, and by forming a non-foaming skin on the surface of the foam layer,
It takes advantage of the cheap, lightweight, and good workability of foam materials without sacrificing it, and ensures abrasion resistance. Also, a certain degree of smoothness is required, such as on the outside of the side sills, and a top coat is applied. The present invention relates to a method for applying a chipping-resistant coating film that can be applied to areas where it is difficult to apply the coating.

In the coating method of the present invention, a foamable paint is first applied as a first layer to the surface of the undercoat film, that is, the surface of the undercoat film coated on the surface of the object to be coated by electrodeposition, etc., and then the foamable paint is applied as a first layer. A second layer of paint that does not contain a foaming component is applied wet-on-wet to the surface of the coating film, and then baked to form a film according to a conventional method.

Next, the composition of the paint used in the present invention will be described.

First, the first layer of foaming paint basically consists of a resin component and a foaming component. As for the resin component, vinyl chloride resin, which is usually used for car body undercoating, is preferred from the viewpoint of cost and low-temperature physical properties, but styrene-butadiene rubber (SBR), urethane, polyester, etc. can also be used. In the case of vinyl chloride resin, the basic composition is a vinyl chloride resin and a plasticizer plus a heat-curable resin system such as an epoxy resin and its curing agent. Vinyl chloride resin may be a polymer of vinyl chloride alone, a known copolymer of vinyl acetate, acrylic acid, methacrylic acid, acrylic ester, or a mixture thereof. . The plasticizer is
Esters such as dioctyl phthalate, dibutyl phthalate-1., tricresyl phosphate, chlorinated paraffins, alkylbenzenes, etc. can be used. As the epoxy resin, a commonly known glycidyl ether ring type epoxy resin can be used. The curing agent can be arbitrarily selected from among imidazur derivatives such as dicyandiamide and acid anhydrides such as tetrahydrophthalic anhydride, which react at around 140°C.

As the foaming component, organic foaming agents such as diazocarbonamide, azobisisobutyronitrile, and dinitrosopentamethylenetetramine are preferred in order to obtain a stable foamed film. However, since the decomposition temperature may not necessarily match the baking temperature in the process, the decomposition temperature may be adjusted, if necessary, using a foaming aid such as zinc white or zinc stearate.

In addition to these basic ingredients, extender pigments such as calcium carbonate and talc, coloring and antirust pigments, etc. can also be added.

Further, in order to ensure workability, a viscosity control component such as a solvent can be added.

Next, regarding the composition of the non-foaming second layer, it is basically the composition of the first layer with the foaming component removed, but it is used to increase surface hardness and provide wear resistance. There is no problem in improving the vinyl chloride resin or changing the ratio of each component.

Next, this invention will be explained based on the drawings. FIG. 1 is a diagram showing an embodiment of the present invention, in which a is the chipping-resistant coating second layer (non-foaming layer), b is the chipping-resistant coating No. 11 (foaming layer), C is the electrodeposition coating, and d indicates the substrate (steel plate). Applying a foaming undercoat as a first layer using air spray or airless spray to a thickness of several tens of microns to no more than 100-odd microns on a steel plate that has been electrocoated in the normal car body painting process, and then hardening by baking. 20 to 50 microns of non-foaming second layer is applied.

However, the amount of the foamable first layer applied can be adjusted appropriately in order to obtain the desired chipping resistance.

After that, it undergoes the usual painting processes such as sealing and intermediate coating, and is then foamed and hardened in an intermediate coating baking oven at 140°C.As shown in Figure 1, the surface layer is over 150μ with a smooth skin of several tens of micrometers. Forms a thick foam film.

(Experimental Example) A detailed explanation will be given below according to Examples, Comparative Examples, and Test Examples.

Adjustment of paint> Paint No. 1 to 4 with the composition shown in Table 1
adjusted. Incidentally, the dispersion was carried out for 4 hours by charging the raw materials excluding the curing agent according to the recipe into an outwriter.

Table 1 *1 Zeon 121 (manufactured by Nippon Zeon ■, product name) Book 2
Epicort 1828 (manufactured by Yuka Shell Epoxy ■, trade name) Book 3 Dicyandiamide (manufactured by Nippon Carbide ■, trade name) *4 Cellular GX (manufactured by Hyuwa Kagaku Kogyo ■, trade name) Book 5 Calcium carbonate, NS-400 (Nitto Powderization■
(manufactured by Mitsubishi Carbon ■, product name) carbon black ULO00 (manufactured by Mitsubishi Carbon ■, product name) - 70mmX 150mmX0.8 +mt+ (J'J
The base material was a cold-rolled steel sheet obtained by chemical conversion treatment and further cationic electrodeposition coating. Paint No. 1, which is a foaming paint, was applied to the base material using a bar coater to a thickness of approximately 60μ, and after being left at room temperature for 15 minutes, non-foaming paint No. 2 was further applied to a thickness of 30μ. Coated. The coating was then dried at 140°C for 30 minutes to foam cure.

As a result, a dry coating film of about 300μ was obtained.

Paint No. 1 was applied to a film thickness of about 60μ in the same manner as in Example 1, and then foamed and cured to obtain a dry coating film of about 300μ.

Approximately 5 Side Notes - 1 Paints No. 3, No. 4, and Paints No. 3, No. 4 were applied in the same manner as in Example 1, with a thickness of approximately 300 μm, and after curing, a dry coating of approximately 300 μm was applied.
I got it.

Test sample - The performance of the paint-coated steel sheets obtained in Example 1 and Comparative Examples 1 to 3 was evaluated using the following measurement method, and the obtained results are shown in Table 2.

side (a) Chipping resistance was evaluated by a nut drop test.

The test piece was worn down by dropping an M6 nut from a height of 2 m, and the amount of the nut was recorded until the base steel plate was exposed.

(b) The appearance of the coating film was evaluated visually.

(c) To examine the appearance after topcoating, a topcoat paint (manufactured by Kansai Paint ■, Amirac White) was applied to a film thickness of about 40μ, and the presence or absence of defects after baking was examined.

(d) Workability was determined by applying twice the amount stated in each Example and Comparative Example with the test piece in an upright position, assuming that the application patterns overlap during spray painting on an actual painting line. It was dried and checked for defects.

Table 2 Paint film performance The following can be seen from the results in Table 2.

That is, a material without a skin formed on the surface layer, such as Comparative Example 1, has poor abrasion resistance and cannot withstand long-term use. In addition, the surface layer has numerous pores due to incomplete air bubbles, giving it a rough appearance and causing wrinkles when a top coat or the like is applied.

Furthermore, conventional undercoat materials such as Comparative Example 2 have good chipping resistance, but sag occurs when applied thickly. Furthermore, in Comparative Example 3, in which the viscosity was increased to prevent sagging, the finished skin was unsightly but smooth. Furthermore, Comparative Example 2,
No. 3 uses a large amount of material, which is extremely disadvantageous from the viewpoint of cost and weight reduction of the vehicle body.

(Effects of the invention) As described above, the present invention involves applying a foaming paint as a first layer to the surface of the undercoat film and then applying a non-foaming paint wet-on-wet. Baking, hardening,
By employing a foaming structure, it is possible to obtain a coating film that is inexpensive, lightweight, and satisfies chipping resistance and appearance at the same time.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of a steel plate on which a chipping-resistant coating is applied by the method of the present invention on the electrodeposition coating of the steel plate. a...Chipping-resistant paint second layer (non-foaming layer) b...
Chipping-resistant paint 1st layer (foaming layer) C... Electrodeposition coating film
d...Base material (steel plate) Figure 1 d-Base material (Sekbin)

Claims (1)

[Claims] 1. A foaming paint is applied as a first layer to the surface of the undercoat film, and then a paint that does not contain foaming components is applied wet-on-wet as a second layer, and then baked to form a film. How to apply chipping paint film.