JPS6075369A - Intermediate painting method - Google Patents

Abstract

PURPOSE:To paint an automotive body to excellently finished appearance without requiring a water polishing operation in the stage of painting said body in three stages; primer coating, intermediate coating and finish coating by executing the intermediate coating stage dividedly in two times with and by specific paints and methods. CONSTITUTION:A primer is first painted on the surface of the steel plate for a vehicle body and the 1st intermediate coating layer 12 of 65-85% nonvolatile content, 0.4-0.8:1.0 weight ratio between a resin and a pigment and 30-50sec/ 20 deg.C viscosity with Ford cup No.4 is coated on the surface 11a of the primer coating film 11 in such a way that the thickness when dried attains 35+ or -5mu. The 2nd intermediate coating layer 13 of 20-40% nonvolatile component, 2-3:1 weight ratio between the resin and the pigment and 10-18sec/20 deg.C viscosity with Ford cup No.4 is coated thereon without drying the same in such a way that the film thickness when dried attains 15+ or -5mu. Said layer is baked for 20min at 140 deg.C. A finish paint is finally coated thereon. The painting to satisfactorily finished appearance is thus possible without requiring a water polishing operation after the 1st intermediate paint coating.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an intermediate coating method in a painting process for, for example, an automobile body.

(Prior art) Generally, in the painting process for automobile bodies, etc., in order to improve the appearance or finish after painting, three stages of painting are applied to the surface of the car body, etc.: undercoating, intermediate coating, and top coating. Furthermore, as for the intermediate coating, a method is usually adopted in which the same paint is applied in two coats in order to achieve a good finish within a limited time.

However, as for the paint for the above-mentioned intermediate coating, conventionally, the resin type is melamine-cured oil-free polyester, the non-volatile content is 45 to 55% by weight, and the ratio of resin and pigment is 0.8 to 1.2:1.
．． A product that is formulated in such a way that the weight ratio of For example, the coating was applied so that the thickness was 30μ in the first application and 20μ in the second application.

However, such conventional intermediate coating methods have the following problems. That is, as shown in FIG.
A is uneven, and there may be unevenness on the surface of the vehicle body. Therefore, when a first intermediate coat is applied on top of the paint 2, the surface 2a becomes smooth immediately after application, as shown in Figure 1 (I), but the paint 2 contains solvents. As the volatile components such as thinner contained in the paint thinner are gradually diluted, the paint 2 thins out as shown in the same figure (1' [), and the surface 2a is coated along the unevenness of the undercoat film surface 1a. Similar unevenness occurs. Therefore,
Immediately after applying the paint 3 as a second intermediate coat, as shown in (1) in the same figure, the surface 3a becomes smooth, but especially after the second intermediate coat, the volatile components are extracted and the paint film is formed. Since baking is carried out at, for example, 140° C. for 20 minutes for curing, both paints 2.3 become thinner and the unevenness of the surface 3a becomes more noticeable, as shown in FIG.

In addition, especially in the first intermediate coating, if there is a problem with atomization during spraying or poor fluidity of the paint after application, as shown in Figure 2 (I), In addition to this, the coating film of the paint 2' itself becomes uneven, and in addition to this, as shown in FIG. The unevenness on the surface 28' of the paint 2' becomes more pronounced due to the application of the paint 2', and therefore, the second intermediate coat 3' is applied as shown in the same figure (I[>, (IV)). At the time of baking, the unevenness of the surface 3a' of the paint 3' becomes more significant than in the case shown in Fig. 1.Therefore, conventionally, after the first intermediate coating, that is, the steps shown in Figs. (II) and (II
I> and the surface 2a of the paint 2, 2'.

2a' required ice work, which required a large amount of manpower and man-hours.

(Object of the Invention) The present invention is intended to address the above-mentioned problems in the prior art, and to provide a paint with an optimal blend for each of the two intermediate coats in the painting process for automobile bodies. By using this method, a smooth intermediate coating film is achieved, which makes it possible to obtain a good appearance finish without having to perform ice work after the first intermediate coat, thereby reducing the number of personnel required for ice work. , the purpose is to reduce the number of processes.

(Structure of invention) In order to achieve the above object, the present invention is configured as follows.

In other words, in a three-coat system of undercoat, intermediate coat, and top coat (in an intermediate coating method in which the intermediate coat is applied in two steps, the non-volatile content is 65 to 85% by weight in the first intermediate coating process). , the weight blending ratio of resin and pigment is 0.4 to 0.8:1
．． 0, viscosity is Ford Cup No. 4, 30-50 seconds/20
℃ paint, put it in a drying oven without drying, and apply a second intermediate coat on top of it with a non-volatile content of 20 to 40% by weight and a weight blending ratio of resin or pigment of 2.゜0
~3. 'O: 1.0, viscosity is) A-Dokatsubu No. 4 is 10
Apply paint at ~18 seconds/20°C.

Here, as the type of resin component in the paint, melamine-cured oil-free polyester is suitable. In addition, as for the coating machine that applies the paint, a rotary atomizing electrostatic type is used for one-time application, and a rotary atomizing electrostatic type or an air atomizing type is used for the second coating. A paint machine is used. Furthermore, after performing the first intermediate coating mentioned above,
Without actively drying using a drying oven, the coated material is allowed to stand naturally at 20° C. for 2 to 30 minutes, and then a second intermediate coat is applied. In addition, the application period of the paint is adjusted so that the first intermediate coat has a dry coating thickness of, for example, 35±5μ, and the second intermediate coat has a dry coating thickness of, for example, 15±5μ. It is adjusted to be 5μ.

The above configuration is summarized in Table 1. This table also includes the previously mentioned conventional example (77) for comparison.

In addition, after the second intermediate coating, for example, 140℃, 2
Baking is performed for 0 minutes.

(The following is a blank space) According to such a configuration, as shown in Fig. 3 (I),
Even if the surface 11a of the undercoat film 11 formed in advance by the undercoat is uneven, the first paint 12 of the intermediate coat applied on the surface 11a has a high proportion of non-volatile matter and pigments, and Since the viscosity is increased accordingly and the paint film is thick, the unevenness on the surface 11a of the undercoat film is completely hidden by the paint 12. Since this paint 12 has a low proportion of volatile components, as shown in the same figure (Jl), it hardly causes any creases even after application, and therefore, the unevenness of the lower surface almost never appears on the surface 12a. , the surface 12a is kept smooth. Furthermore, as shown in FIG. 3 (■), a paint 13 is applied as a second intermediate coat from above the paint 12.
Since it has a large resin content and volatile component and a low viscosity, it has excellent atomization and fluidity, and thus the surface 13a of the paint 13 can be applied smoothly. Then, baking is performed after the second intermediate coating is performed as described above, and at that time, the volatile components contained in the second intermediate coating 13 are absorbed and the paint 13 becomes thinner. Since the surface 12a of the first intermediate coating 12 is smooth, the third
As shown in Figure (IV), the surface 13a of the second intermediate coating 13 remains smooth even after thinning.

On the other hand, during the first application of the intermediate coating, due to poor atomization and poor fluidity of the coating, as shown in FIG. 4(I), the intermediate coating 12' applied for the first time is surface 1
28' may be uneven. However, even in this case, as shown in Figure (II), since the paint 12' has a small amount of 11, which is a volatile component, almost no thinning occurs. Furthermore, before the first intermediate coating 12' dries and hardens, the same figure (I[
Since the second intermediate coat l3113' is applied on the paint 12' as shown in I-1>, the volatile components contained in this paint 13' are applied to the underside of the paint II.
By penetrating into 12', the same figure (I[I-2
As shown in >, the boundary between the paints 13' and 12', that is, the surface 128' of the first intermediate coat 12' is smoothed. Therefore, during subsequent baking, the volatile components in the paints 12' and 13' are reduced by drying and the paints 12' and 13' are dried.
When 13' is cured, an intermediate coating film having a smooth surface 138' is formed as shown in FIG. 13(IV).

(Effects of the Invention) As described above, according to the present invention, since the first and second intermediate coats are configured to use paints with optimal blends,
A good appearance can be achieved without requiring the daffodil work after the first intermediate coating, which was conventionally required, and it is therefore possible to reduce the number of personnel or man-hours involved in the daffodil work.

(Example) Examples of the present invention will be described below.

First, in Example 2, as the first intermediate coating, the resin type was melamine-cured oil-free polyester, the non-volatile content was 78% by weight, and the weight blending ratio of resin and pigment was 0.
5:1.0, a paint with a viscosity of 43 seconds/20°C measured using Ford Cup 4@, a film thickness of 38μ when dry.
It was applied so that After this was left to stand naturally under the specified conditions, a second intermediate coating was applied on top of it, using the same resin type as above, with a non-volatile content of 32% by weight, and a weight blending ratio of resin and pigment of 2.6:1. .0. Viscosity is Ford Cup 4
No. 12 seconds/20℃ paint, dry film thickness is 16μ
I applied it like crazy. Furthermore, after baking and drying these, a specified top coat is applied to a film thickness of 35 μm when dry.
It was applied and dried.

Next, in Example H, as the first intermediate coating, the non-volatile content was 66% and the weight blending ratio of resin and pigment was 0.5%.
7:1.0, viscosity is Ford Cup No. 4, 34 seconds/20
℃ paint so that the film thickness when dry is 32μ, and a second intermediate coat is applied, resulting in a non-volatile content of 38% by weight.
The weight mixing ratio of resin and pigment is 2.2/1. A paint with an O1 viscosity of 12 seconds/20°C was applied using Ford Cup No. 4 so that the dry film thickness was 14μ.Then, a topcoat was applied in the same manner as in Example T above. Also in ■,
The same resin type paint was used as in Example II above, and the PGD value and flow comparator value were calculated for the final coating film formed in Example LII using a sharpness gloss meter and a coating smoothness monitor. The exterior finish was evaluated based on these values in comparison with conventional examples. Here, regarding the PGD value, the larger the value, the
Furthermore, as for the flow comparator value, the smaller the value, the better the finish.

In addition, as a conventional example, the same resin type as in Examples 1 and 2 above, the non-volatile content was 52% by weight, the weight mixing ratio of resin and pigment was 0.9:1.0, and the viscosity was Ford Cup No. 4. 24
sec/20°C, and the film thickness (dry) is 1
The coating was applied at 15μ for the first time and 25μ for the second time (conventional example), and the product was applied at 20μ for the first time and 35μ for the second time (conventional example ■). Ta. Of these, the daffodil work between the first and second intermediate coats was performed only in the conventional construction.

The above conditions and results are shown in Table 2.

As a result, in both Examples I and II, the external finish was superior to the one in which daffodils were not grown using the conventional method (Conventional example ■), and the appearance was superior to that in which daffodils were grown in the conventional method (Conventional example). A similar finish was made on 1q.

[Brief explanation of the drawing]

Fig. 1.2 is a schematic sectional view of a coating film obtained in each step in the conventional intermediate coating method, and Fig. 3.4 is a schematic sectional view of a coating film obtained in each step in the intermediate coating method of the present invention. Applicant: Toyo Kogyo Co., Ltd. No. 1 (I) (■) No. 2 (1) (■) (II[) (N) Figure (III) (N)

Claims (1)

[Claims] (1) An intermediate coating method in which the intermediate coating in a three-coat system of undercoating, intermediate coating, and top coating is applied in two times, and the first intermediate coating contains a non-volatile content of 65 to 85% by weight and a resin. The weight blending ratio of and pigment is 0.4 to o, s:i,
o1 viscosity is Ford Cup No. 4, 30-50 seconds/20℃
The non-volatile content is applied as a second intermediate coating process without drying it in a drying oven.
0-40% by weight, weight blending ratio of resin and pigment is 2.0-40% by weight
3.0+1.0, viscosity is Ford Cup No. 4, 10-1
An intermediate coating method characterized by applying paint at 8 seconds/20°C.