JP4830561B2 - Coating method and coating system - Google Patents

Description

  The present invention relates to a coating method and a coating system for coating a solid paint that does not contain a luster pigment on an object to be coated such as an automobile body or an automobile part.

  Automobile body coating systems are mainly priming for the purpose of rust prevention, intermediate coating for the purpose of improving the adhesion and smoothness of the top coating film as well as rust prevention, and improving design as well as rust prevention. A three-coat coating system composed of a top coat for the purpose of is generally used.

  The paint used in the top coating includes a metallic paint containing a bright pigment such as aluminum flakes and a solid paint containing a coloring pigment without such a bright pigment. The intermediate coating is a solid coating that contains a coloring pigment but does not contain a glittering pigment, like the top coating solid coating.

  In the present specification and claims, a paint that does not contain a bright pigment is referred to as a solid paint regardless of the painting process used, such as intermediate coating and top coating.

  By the way, when applying a solid paint in the top coat, it is necessary to secure a film thickness sufficient to conceal the intermediate coating film (often a light gray color) that is the base, and a red system with a weak hiding power. The coating color must be at least 15 μm. Similarly, in the intermediate coating, it is necessary to secure a film thickness sufficient to hide the electrodeposition coating film (often dark gray or dark green), which is a base, and the intermediate coating is a light gray color. In that case, it must be coated with a film thickness of at least 25 μm.

However, the film thickness for securing the coating film properties such as coating film deterioration due to UV transmission is, for example, about 8 μm for the top coating film, and the above-described film thickness of 15 μm must be ensured simply because the hiding power is weak. Therefore, the development of a coating technique that has a strong hiding power even with a thin film is desired.
JP 2002-256216 A

  An object of this invention is to provide the coating method and coating system which can improve the concealment power of a solid coating material, and can be thinned.

In order to achieve the above object, the coating method of the present invention is characterized in that the average particle size of the paint when the paint containing the glitter pigment in the solid paint not containing the glitter pigment is applied to the painted surface is A first stage for atomizing and coating so that the average particle size of the glitter pigment is less than or equal to a second stage, and a second stage for atomizing and painting a solid paint not containing the glitter pigment on the coating film formed in the first stage. And a stage.

The coating system of the present invention includes a paint supply system for supplying paint to the bell cup, a peripheral speed adjuster for adjusting the peripheral speed of the bell cup, and a control means for controlling the paint supply system and the peripheral speed adjuster. The average particle size of the paint is less than the average particle size of the glitter pigment when the paint containing the glitter pigment in the solid paint not containing the glitter pigment is applied to the painted surface. And a rotary atomizing coating apparatus provided on a first stage for atomizing and coating the paint, and a solid paint not containing the glitter pigment on the coating film formed on the first stage. And a coating device provided on the second stage.

In the present invention, when applying a solid paint that does not contain a glitter pigment, this solid paint contains a glitter pigment, and in the first stage, this paint is coated with an average particle diameter of the glitter pigment. Since the coating is atomized so as to be smaller than the diameter, the glitter pigment is oriented almost in parallel on the painted surface. Thereby, the hiding power of the ground is improved. Then, by applying a solid paint that does not contain the original bright pigment on the coating film, the concealing power of the solid coating film is improved, and a thin film can be realized.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<< First Embodiment >>
FIG. 1 is a cross-sectional view of a coating film showing an example of a multilayer coating film applied by the coating method of the present invention, and FIG. 2 is a flowchart showing a coating process of the multilayer coating film shown in FIG. FIG. 5 is a front view and a side view showing an example of the glitter pigment according to the coating method of the present invention, and FIG. 6 is a schematic diagram for explaining the coating mechanism in the first stage according to the coating method of the present invention. It is.

  This embodiment is an example in which the coating method of the present invention is applied to an intermediate coating process of a three-coat coating system for an automobile body.

  First, the outline of the painting process of the automobile body will be explained. The white body assembled in the body line is first carried into the electrodeposition painting process. In this electrodeposition coating process, the oil and iron powder adhering to the white body are washed, then the surface is adjusted and a chemical conversion film treatment such as zinc phosphate is applied. The electrodeposition coating process of FIG. 2).

  A body coated with an electrodeposition coating material having an epoxy resin such as a polyamine resin as a base resin is carried into an electrodeposition drying furnace and baked at 160 to 180 ° C. for 15 to 30 minutes, for example. An electrodeposition coating film 12 having a film thickness of 10 μm to 35 μm is formed on the surface of the body steel plate 11 (electrodeposition baking process of FIG. 2). The electrodeposition coating film 12 is colored in gray or green so that the distortion of the body steel plate 11 and the defects of the electrodeposition coating film 12 itself can be easily recognized.

  The body on which the electrodeposition coating film 12 is formed is sent to a sealing process (not shown) (including an undercoat process and a stone guard coat process) for the purpose of rust prevention or sealing at the steel plate joints and the steel plate edge portions. The vinyl chloride resin sealing material is applied. In the undercoat process, a vinyl chloride resin-based chipping-resistant material is applied to the tire house and floor, and in the stone guard coat process, a polyester-based or polyurethane-based resin chipping is applied to the lower part of the body outer plate such as a sill or fender. The material is applied. In addition, these sealing materials and chipping-resistant materials are cured in a dedicated drying furnace or an intermediate coating drying furnace described below.

  The body on which the sealing material and the chipping-resistant material are applied and the electrodeposition coating film 12 is formed on the inner and outer plates is then carried into the intermediate coating process.

  In the intermediate coating process, an acrylic resin, an alkyd resin, a polyester resin, etc. are used as a base resin, and an intermediate coating material obtained by diluting a paint stock solution to which a coloring pigment or additive is added with a solvent (water in the case of a water-based coating material) Although it is a process of coating on the surface of the electrodeposition coating film 12, the intermediate coating process of this example is composed of a first stage and a second stage.

  First, in the first stage, the above-mentioned original intermediate coating material containing no bright pigment contains bright pigments such as aluminum flakes and mica foil, preferably 14 parts by weight or more with respect to 100 parts by weight of the resin component. It is added at a ratio, and this glittering pigment-containing intermediate coating is applied using a rotary atomizing coating gun.

  At this time, the coating condition of the glittering pigment-containing intermediate coating is such that the average particle diameter of the intermediate coating particles when applied to the surface of the electrodeposition coating film 12 is equal to or less than the average particle diameter of the glittering pigment. is there.

  Here, the luster pigment 1 contained in the intermediate coating material according to this example has a scaly shape as shown in FIG. 5, and the radius R when the real area in a plan view is converted into a circle 2 is the main pigment. It is defined as the average particle size referred to in the invention. That is, the average particle diameter of the glitter pigment according to the present invention means not the thickness t shown in the figure but the average diameter R of the main surface. Generally, the average particle diameter R of the glitter pigment contained in the top coat base paint for automobiles is about 10 to 30 μm, and the thickness is about 0.2 to 1 μm. Therefore, when the average diameter of the main surface of the scale-like glittering pigment contained is 20 μm, the particle size at the time of application of the intermediate coating is atomized to 20 μm or less and applied.

  By the way, the average particle diameter of the paint particles can be controlled by the discharge amount of the paint, the rotational speed of the rotary atomizing coating gun (atomizing head), and the diameter of the atomizing head. Since the discharge rate of paint has a certain limitation in relation to the film thickness, in this example, the above atomization is controlled by controlling the rotation speed of the bell cup of the rotary atomizing paint gun, strictly speaking, the peripheral speed. Is realized. That is, in the first stage of this example, the peripheral speed of the bell cup is set to 180 to 240 m so that the average particle diameter of the bright pigment-containing intermediate coating at the time of application is equal to or less than the average particle diameter of the scaly bright pigment. / Sec (corresponding to a rotational speed of 70,000 to 90,000 rpm when a bell cup with a diameter of 50 mm is used).

  The particle size at the time of coating can be measured using a laser light scattering type particle size measuring device. An image processing measurement system that takes this measurement and calibration can also be used. In the latter method, a fluorosurfactant is applied to a thin film on a glass plate, and the plate is exposed to the surface of the object to be coated for about 1 second. The coating particles collected in this manner can be easily measured by enlarging them with a microscope and measuring the particle diameter. In the present invention, the weight average particle diameter of the paint particle diameters thus measured is used as the average particle diameter of the paint particles.

  In this example, scaly glittering pigments such as aluminum flakes and mica foil are included in the intermediate coating, and this coating is applied to a thickness of 5 ± 2 μm on the first stage. Thus, by making the average particle size of the paint particles at the time of coating (or just before coating) smaller than the average particle size of the bright pigment, the bright pigment can be formed without forming a large quantity or high-speed air flow. Can be oriented parallel to the painted surface, thereby enhancing the base concealing power.

  Thus, in the absence of high-speed air flow, the relationship between the particle size of the paint and the orientation of the glitter pigment has not been known so far, but the paint particle diameter is small, especially the average particle diameter of the glitter pigment. When the particle diameter is equal to or less than the above, a remarkable effect is exhibited, so that the present inventors have a special effect on the orientation of the glitter pigment when the paint particle diameter is small. I came to a conclusion.

  That is, it is concluded that the surface tension when the coating particles are applied is a factor governing the orientation of the glitter pigment. In other words, the direction of the glitter pigment is not fixed inside the paint particles that are atomized and in the middle of flight, and are expected to be random with respect to the object to be coated. However, when paint particles are applied, there is an effect of smoothing the surface by surface tension when fusing with the paint already applied and covering the surface of the object to be coated. According to the above, since the coated paint particles contain scaly glitter pigments of approximately the same size, it is assumed that the glitter pigments are pulled parallel to the paint surface by surface tension. In this orientation by surface tension, it is considered that the same force is applied as when the paint particles are crushed on the surface of the object by increasing the collision speed of the paint particles.

  In contrast, when the paint particles are coated with paint particles having an average particle size larger than the average particle size of the glitter pigment, even if the paint particles flow so as to be smooth due to the surface tension, the glitter within the paint particles. Since the luminescent pigment has a certain degree of freedom in orientation, it is considered that it is not completely parallel to the surface of the object to be coated, and it is assumed that the orientation of the glitter pigment is insufficient.

  In addition, when the average particle diameter of the paint particles is much smaller than the average particle diameter of the glitter pigment, it can be regarded as the glitter material being applied alone, so that the orientation is considered to be good. That is, when the glitter pigment is applied alone to the object to be coated, the glitter pigment is most preferably applied to the object to be coated on the widest surface, that is, the main surface (planar portion) of the scaly glitter pigment. This is considered to be stable, and the main surface of the scale is oriented parallel to the object to be coated, and the glittering pigment is placed on the entire surface of the paint and exhibits excellent hiding power. .

  This state is shown in FIGS. In the figure, reference numeral 1 is a scaly glitter pigment, reference numeral 3 is a paint particle, reference numeral 4 is an object to be coated, and FIG. 4A shows two paint particles 3 each containing a scaly glitter pigment 1. The state which is flying toward the to-be-coated object 4 is shown. When the lower coating particles 3 arrive at the surface of the article 4 to be coated (A), the coating particles 3 are smoothed by the surface tension along the surface of the article 4 as shown in FIG. It will flow and spread radially. At this time, the glitter pigment 1 contained in the paint particle 3 cannot have a degree of freedom inside the paint particle 3 because the particle diameter of the paint particle 3 is smaller than its own particle diameter. The main surface moves along the surface of the article 4 to be coated. As shown in FIG. 3C, when the paint particles 3 spread on the surface of the object 4 to be coated, the glitter pigment 1 is also included in the paint particles 3 in a state of being oriented parallel to the surface of the object 4 to be coated. Will be. By such a coating mechanism, each coating particle 3 is deposited on the surface of the object 4 to form a coating film, so that a coating film in which the glitter pigment 1 is oriented parallel to the surface of the object 4 is obtained. Can do.

  Returning to FIG. 1 and FIG. 2, when the bright pigment-containing intermediate coating is applied in the first stage of the intermediate coating process under the above-described conditions, the original intermediate coating is 15 ± 2 μm thick by wet on wet. Paint to become. In this second stage, an original intermediate coating material that does not contain a luster pigment, for example, using a rotary atomizing paint gun, the peripheral speed of the bell cup is smaller than that of the first stage described above, for example, 50 to The coating is carried out while controlling at 110 m / sec (when a bell cup having a diameter of 50 mm is used, it corresponds to a rotational speed of 20,000 to 40,000 rpm).

  The second stage is not limited to the rotary atomizing paint gun because it is sufficient if the original function of the intermediate coating film, that is, the rust prevention performance and the adhesion performance of the top coating film are exhibited. In addition, even when the coating is performed using a rotary atomizing paint gun, the rotation speed of the bell cup described above is not an essential coating condition.

  Alternatively, after the glitter pigment-containing paint is applied in the first stage, this may be baked and the second stage intermediate paint may be applied to the surface of the cured coating film.

  When the first stage and the second stage are completed, as shown in FIG. 1, the surface of the electrodeposition coating 12 has a 5 ± 2 μm bright pigment-containing intermediate coating 13A and a 15 ± 2 μm bright pigment. The intermediate coating film 13B that does not contain is formed, and then the body is transported to an intermediate coating drying furnace and passed through, for example, 130 to 150 ° C. for 15 to 30 minutes, so that an intermediate coating thickness of 20 ± 4 μm is formed. The coating film 13 is formed (intermediate baking process in FIG. 2).

  As described above, in the conventional intermediate coating method, a film thickness of at least 25 μm is required to hide the electrodeposition coating film which is dark gray or dark green. The covering power is improved by applying an intermediate coating containing a glittering pigment to ultrafine particles under the above conditions, thereby making it possible to reduce the film thickness to about 5 μm.

  In addition, after finishing the intermediate coating baking process, the body is transported to the top coating booth and coated with the top coating (the top coating process in FIG. 2), and then transported to the top coating drying furnace, whereby the top coating film 14 is formed. (Topcoat baking process of FIG. 2).

<< Second Embodiment >>
FIG. 3 is a cross-sectional view of a coating film showing another example of the multilayer coating film applied by the coating method of the present invention, and FIG. 4 is a flowchart showing a coating process of the multilayer coating film shown in FIG.

  The present embodiment is an example in which the coating method of the present invention is applied to a topcoat process of a three-coat coating system for an automobile body, but the electrodeposition coating film 12 shown in FIG. 3 and the electrodeposition coating process and electrodeposition shown in FIG. Since the embodiment up to the baking step is the same as the first embodiment described above, a description thereof will be omitted.

  In the intermediate coating process of this example, an acrylic resin, an alkyd resin, a polyester resin, etc. are used as a base resin, and an intermediate coating solution obtained by diluting a paint stock solution to which a color pigment or additive is added with a solvent (in the case of water-based paints) A paint is applied to the surface of the electrodeposition coating film 12. Then, the intermediate coating film 13 having a film thickness of 25 ± 2 μm is formed by transporting the body to an intermediate coating drying furnace and passing the body at 130 to 150 ° C. for 15 to 30 minutes, for example.

  Instead of the intermediate coating film 13, the above-described intermediate coating films 13A and 13B of the first embodiment may be employed.

  In this example, the top coat process uses a base resin of acrylic resin, alkyd resin, polyester resin, etc., and a solid color solution obtained by diluting a paint stock solution to which a color pigment or additive is added with a solvent (water for water-based paints). In this process, the top coating is applied to the surface of the intermediate coating film 13. The top coating process in this example includes a first stage and a second stage.

  First, in the first stage, the original topcoat solid paint that does not contain the above-mentioned glittering pigment contains a glittering pigment such as aluminum flake or mica foil, preferably 14 parts by weight or more with respect to 100 parts by weight of the resin component. It is added at a ratio, and this glittering pigment-containing top coat is applied using a rotary atomizing paint gun.

  At this time, the coating condition of the glitter pigment-containing top coat is such that the average particle diameter of the top coat particles when applied to the surface of the intermediate coating film 13 is equal to or less than the average particle diameter of the glitter pigment. As described in the first embodiment, generally, the average particle diameter R of the glitter pigment contained in the automotive topcoat base paint is about 10 to 30 μm, and the thickness is about 0.2 to 1 μm. Therefore, when the average diameter of the main surface of the scale-like glittering pigment contained is 20 μm, the particle size at the time of application of the top coating is reduced to 20 μm or less and applied. In addition, when painting using a rotary atomizing paint gun, the average particle size of the glittering pigment-containing topcoat at the time of application is the scaly in the first stage of this example for the same purpose as in the first embodiment. The peripheral speed of the bell cup is 180 to 240 m / sec so as to be equal to or less than the average particle diameter of the bright glitter pigment (corresponding to a rotational speed of 70,000 to 90,000 rpm when a bell cup having a diameter of 50 mm is used). Paint while controlling with.

  In this example, scaly glitter pigments such as aluminum flakes and mica foil are included in the top-coated solid paint, and this paint is applied on the first stage so as to have a film thickness of 7 ± 2 μm. Thus, by making the average particle size of the paint particles at the time of coating (or just before coating) smaller than the average particle size of the bright pigment, the bright pigment can be formed without forming a large quantity or high-speed air flow. Can be oriented parallel to the painted surface, thereby enhancing the base concealing power.

  Returning to FIG. 3 and FIG. 4, when the glitter pigment-containing top coat is applied in the first stage of the top coat process under the above-described conditions, the original top coat solid paint has a thickness of 3 ± 2 μm by wet-on-wet. Paint like so. In this second stage, an original top-coated solid paint containing no glittering pigment, for example, using a rotary atomizing paint gun, the peripheral speed of the bell cup is smaller than that of the first stage described above, for example 50- The coating is carried out while controlling at 110 m / sec (when a bell cup having a diameter of 50 mm is used, it corresponds to a rotational speed of 20,000 to 40,000 rpm).

  This second stage is not limited to the rotary atomizing paint gun because it is sufficient if the original function of the top coat film, that is, the design (color) and rust prevention performance is exhibited. Even in the case of painting using a rotary atomizing paint gun, the rotation speed of the bell cup described above is not an essential painting condition.

  Alternatively, after the glitter pigment-containing paint is applied in the first stage, this may be baked and the second-stage top-coated solid paint may be applied to the surface of the cured coating film.

  When the first stage and the second stage are completed, as shown in FIG. 3, a 7 ± 2 μm bright pigment-containing topcoat film 14A and a 3 ± 2 μm bright pigment are applied to the surface of the intermediate coating film 13. Since the top coating film 14B that does not contain is formed, the top coating film 14 having a film thickness of 10 ± 4 μm is formed by transporting the body to a top coating drying furnace and passing the body at 130 to 150 ° C. for 15 to 30 minutes, for example. It is formed (top coat baking process of FIG. 4).

  As described above, in the conventional top coating method, a film thickness of at least 15 μm is required to hide the gray intermediate coating film. As in this example, the glitter pigment is used in the first stage. When the top coating composition containing is superfinely coated under the above conditions, the hiding power is improved, and thereby a thin film of about 5 μm can be obtained.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

It is coating film sectional drawing which shows an example of the laminated coating film coated with the coating method of this invention. It is a flowchart which shows the coating process of the laminated coating film shown in FIG. It is coating film sectional drawing which shows the other example of the laminated coating film coated with the coating method of this invention. It is a flowchart which shows the coating process of the laminated coating film shown in FIG. It is the front view and side view which show an example of the luster pigment which concerns on the coating method of this invention. It is a schematic diagram for demonstrating the coating mechanism in the 1st stage which concerns on the coating method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Bright pigment 3 ... Paint particle 4 ... Coating object 11 ... Steel plate 12 ... Electrode coating 13 ... Intermediate coating 13A ... Bright pigment containing intermediate coating 13B ... Intermediate coating 14 ... Top coating 14A: Top coating film containing glitter pigment 14B: Top coating film

Claims (8)

A paint containing a glitter pigment in a solid paint not containing a glitter pigment is atomized so that the average particle diameter of the paint when applied to a painted surface is equal to or less than the average particle diameter of the glitter pigment. The first stage to paint,
And a second stage for atomizing the solid paint not containing the glitter pigment on the coating film formed in the first stage. 2. The coating method according to claim 1, wherein in the second stage, the solid paint is atomized so as to have an average particle size larger than the average particle size of the first stage. A rotary atomizing paint gun is used in the first and second stages, a peripheral speed of a bell cup of the rotary atomizing paint gun in the first stage is 180 to 240 m / sec, and in the second stage The coating method according to claim 1 or 2, wherein a peripheral speed of the bell cup of the rotary atomizing coating gun is 50 to 110 m / sec. The coating method according to any one of claims 1 to 3, wherein a content ratio of the bright pigment to 100 parts by weight of the resin component of the bright pigment-containing paint in the first stage is 14 parts by weight or more. The solid paint is an intermediate paint, and the film thickness of the coating film formed in the first stage is 5 ± 2 μm, and the film thickness of the coating film formed in the second stage is 15 ± 2 μm. The coating method according to any one of claims 1 to 4. The solid coating is a top coating, and the film thickness of the coating film formed in the first stage is 7 ± 2 μm, and the film thickness of the coating film formed in the second stage is 3 ± 2 μm. The coating method according to any one of claims 1 to 4. The coating of the first stage, the wet-on-wet coating of the second stage, and then the coating of the first and second stages is simultaneously baked. The coating method in any one. A paint supply system for supplying paint to the bell cup;
A peripheral speed adjuster for adjusting the peripheral speed of the bell cup;
Control means for controlling the paint supply system and the peripheral speed controller, and the average particle size of the paint when the paint containing the glitter pigment in the solid paint not containing the glitter pigment is applied to the painted surface A rotary atomizing coating device provided in a first stage for atomizing and coating the paint so that the diameter is equal to or less than the average particle diameter of the glitter pigment;
A coating system, comprising: a coating device provided in a second stage that atomizes and paints a solid paint that does not include the glitter pigment on the coating film formed in the first stage.

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