JP2007196110A - Coating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating method which enables formation of a coating film having a good metallic feel without large amounts of shaping air. <P>SOLUTION: The coating method is used to atomize and coat a coating containing a flaky brightening pigment 1 and comprises atomizing and coating a coating 3 in such a manner that the average particle size of the coating on being spread on a to-be-coated material will be equal to or smaller than that of the flaky brightening pigment. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a coating method for spraying a paint containing a scaly glitter pigment on an object to be coated such as an automobile body or an automobile part.

  In order to improve the appearance finish of paints containing scaly glittering pigments such as aluminum flakes and mica foil, especially the flip-flop property called metallic feeling, a coating method that increases the flying speed of paint particles has been proposed. (Patent Documents 1 and 2).

  To increase the flying speed of paint particles, increase the flow rate of atomizing air or pattern air for air atomizing paint guns, and increase the flow rate of shaping air for rotary atomizing paint guns. Thus, a method is generally used in which a large amount of air flow toward the object to be coated is formed to impart speed to the paint particles.

  This is a coating method based on the knowledge that the larger the collision speed of paint particles, the easier the scaly glittering pigment is oriented in parallel to the substrate, thereby making it easier to obtain a coating film with excellent flip-flop properties. .

  However, in the conventional coating method using a large amount of air, an excessive air flow is formed on the surface of the object to be coated, and a relatively fine and lightweight paint particle is carried away. was there.

  For example, the application efficiency of an air atomizing paint gun is about 30 to 45%, and even when a metallic base paint is applied even with a rotary atomizing paint gun which is said to have high application efficiency. There is still room for improvement compared to the coating efficiency of about 80% in the case of applying a clear paint or solid paint containing no scaly glittering pigment.

  For this reason, in the process of applying the metallic base paint, after applying a relatively thick film in the first stage under a coating condition that emphasizes the coating efficiency, a relatively thin film is applied in the second stage together with the above-mentioned large amount of air. A two-stage coating method is used in which finish is ensured by painting.

  In this case, a rotary atomizing paint gun with excellent coating efficiency is used for the first stage, but the coating conditions are such that the shaping air flow rate is reduced so that the coating efficiency is high, thereby reducing the coating efficiency. Increase to 70-80%. In the second stage, an air atomizing paint gun or a rotary atomizing paint gun set to a large amount of shaping air flow is used, but as a result of the large amount of air flow, the coating efficiency is limited to about 60%. It becomes.

  In addition, if the two-stage coating method is used, the number of coating equipment (painting guns) will inevitably increase, which causes a problem of increased equipment costs. As a result, there is a problem that the amount of paint to be discarded at the time of color change and the cleaning liquid also increase.

Furthermore, since the effective pattern width is inevitably narrow in the painting method using a large amount of air, the number of times of painting must be increased, and the painting gun must be moved to paint a predetermined area within a limited painting time. I had to increase the speed. As a result, there is a problem that the failure rate of the robot equipped with the paint gun is increased.
JP 2003-93965 A Japanese Patent No. 2560421

  An object of this invention is to provide the coating method which can obtain the coating film which exhibits a favorable metallic feeling, without using a lot of shaping air.

  In order to achieve the above object, the coating method of the present invention is a coating method in which a paint containing a scaly glittering pigment is atomized and applied to an object to be coated. The coating material is atomized and applied so that the average particle size of the coating material is equal to or less than the average particle size of the scaly glittering pigment.

  In the present invention, when the paint containing the scaly glitter pigment is atomized, the average particle size at the time of application is not more than the average particle diameter of the scaly glitter pigment, so regardless of the shaping air flow rate, The scaly glittering pigment is oriented almost in parallel on the surface of the object to be coated. Thereby, the coating film which exhibits a favorable metallic feeling can be obtained, without using a lot of shaping air.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the outline of the car body painting line will be explained. The white body assembled in the car body line is first carried into the undercoating process. In this undercoating process, the oil and iron powder adhering to the white body are washed, and then surface adjustment and chemical conversion film treatment such as zinc phosphate are applied (the above is the cleaning and pretreatment process), and the undercoating film is further formed Electrodeposition coating is performed. A body coated with an electrodeposition coating material having an epoxy resin such as polyamine resin as a base resin is carried into an electrodeposition drying furnace and baked at, for example, 160 to 180 ° C. for 15 to 30 minutes. An electrodeposition coating film having a thickness of 10 μm to 35 μm is formed on the plate and the bag structure (electrodeposition process).

  The body on which the electrodeposition coating has been formed is sent to the sealing process (including the undercoat process and the stone guard coat process), and vinyl chloride is used for the purpose of rust prevention or sealing at the steel plate joints and steel plate edges. A resin-based sealing material is applied. In the undercoat process, a vinyl chloride resin-based chipping-resistant material is applied to the tire house and the back of the floor, and in the stone guard coat process, a polyester-based or polyurethane-based resin-resistant 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 is formed on the inner and outer plates is then carried into the intermediate coating process. The intermediate coating process has an intermediate coating booth and an intermediate coating drying furnace. In the intermediate coating booth, an inner panel coating paint corresponding to the outer panel color of the vehicle is applied to the inner panel of the body, and then wet. An intermediate coating is applied to the outer plate part on wet. This body is conveyed to an intermediate coating drying furnace, and an intermediate coating film having a film thickness of 15 μm to 35 μm is formed on the outer plate by passing through the intermediate coating drying furnace at 130 to 150 ° C. for 15 to 30 minutes, for example. A coating film for inner plate coating having a film thickness of 15 μm to 30 μm is formed on the inner plate portion. The inner coating paint and the intermediate coating paint are paints using an acrylic resin, alkyd resin, polyester resin, or the like as a base resin.

  After finishing the intermediate coating, the body is sanded as necessary and then transported to the top coating process. When the outer color is metallic, the top coating base paint and clear paint are applied wet-on-wet. Is done. In the case of a solid-type outer plate color, a top-coated solid paint is applied in the clear coating process. The topcoat base paint, clear paint, and topcoat solid paint are paints that use acrylic resin, alkyd resin, polyester resin, or the like as a base resin.

  Then, the body to which the top coat is applied is conveyed to a top coat drying furnace, where it is baked at, for example, 130 to 150 ° C. for 15 to 30 minutes, thereby forming a top coat film. The film thickness of the top coat base coating film is, for example, 10 μm to 20 μm, the film thickness of the clear coating film is, for example, 15 μm to 30 μm, and the film thickness of the top coating solid coating film is, for example, 15 μm to 35 μm. Finally, the coated body is subjected to an inspection and rework process, and then conveyed to an assembly line on which automobile parts are assembled.

  The above is the outline of the painting line of the automobile body, and the coating method of the present invention is suitably used in the top coating base coating process of the top coating process.

  The coating method of this example is a method in which a metallic base paint containing aluminum flakes or a pearl base paint containing mica foil as a paint containing scaly glitter pigment is applied to the surface of the intermediate coating film. The paint is atomized and applied so that the average particle diameter of the paint when applied to the surface of the coating film is equal to or less than the average particle diameter of the scaly glitter pigment.

  In this case, either a rotary atomizing paint gun or an air atomizing paint gun can be used as a paint gun for atomizing the paint, but a rotary atomizing paint gun is used from the viewpoint of coating efficiency. It is preferable.

  In addition, the coating flight speed is not particularly limited as long as the particle size of the base coating when applied to the surface of the intermediate coating film is approximately equal to or less than the average particle size of the scaly glitter pigment, but the coating efficiency is not particularly limited. From this point of view, it is preferable that the flight speed at the time of applying the paint is less than 5 m / sec.

  In addition, when the above-mentioned predetermined film thickness of 10 μm to 20 μm is formed on the surface of the intermediate coating film, it may be applied by two or more stages of coating, but from the viewpoint of coating efficiency, the base paint is applied in one stage. It is preferable to do.

  The metallic paint and the pearl base paint may be organic solvent-based paints, but the effect of the present invention is particularly great when they are water-based paints. This is because the organic solvent-based paint evaporates during the flight and the particle size just before coating is slightly reduced, but the water-based paint does not change much.

  By the way, the luster pigment 1 contained in the base paint according to this example has a scaly shape as shown in FIG. 1, and the radius R when the real area in a plan view is converted into a circle 2 is defined as the present invention. Is defined as the average particle size. That is, the average particle diameter of the scaly glittering pigment referred to in the present invention means not the thickness t shown in the figure but the average diameter R of the main surface. The average particle diameter R of the glitter pigment contained in the base paint according to this example is generally about 10 to 30 μm, and the thickness is about 0.2 to 1 μm. Therefore, when the average diameter of the principal surface of the scale-like glitter pigment contained is 20 μm, the particle diameter at the time of application of the paint is reduced to 20 μm or less for coating.

  Here, 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.

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 uses a weight average particle diameter D ₄₃ of the paint particle size measured in this way as an average particle size of the paint particles.

  According to this example, when applying a base paint containing scaly bright pigments such as aluminum flakes and mica foil, the average particle diameter of the paint particles at the time of application (or immediately before application) is the average of the bright pigments. By making it smaller than the particle size, it is possible to improve the orientation of the glitter pigment without forming a large amount or high-speed air flow, thereby improving the finished appearance of the coating film and improving the coating efficiency. .

  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, it is inferred that the glitter pigment is pulled in parallel with the paint surface by the surface tension because the scaled glitter pigment having almost the same size is contained in the deposited paint particles. 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, whereby the main surface of the scale is oriented in parallel with the object to be coated, and a finished appearance of the coating film exhibiting a good metallic feeling can be obtained.

  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.

  FIG. 3 shows the relationship between the average particle diameter of paint particles and metallic feeling (IV value) when a base paint containing scaly bright pigment having an average particle diameter of 22 μm is applied using a rotary atomizing paint gun. It is the verified graph, and the shaping air flow rate of the rotary atomizing paint gun is 100 to 500 NL / min. According to this, it is understood that even if the shaping air flow rate is 200 NL / min, the metallic sensation IV value can be increased to 200 or more if the average particle size of the paint particles is 22 μm or less.

  Of course, if the shaping air flow rate is 400 NL / min or more, a metallic IV value of 200 or more can be obtained even if the average particle size of the paint particles is as large as 30 μm. However, if the shaping air flow rate is increased, the coating efficiency is improved. There is a problem of lowering.

  FIG. 4 is a graph that verifies the relationship between the shaping air flow rate and the coating efficiency when a base paint containing scaly glittering pigment having an average particle size of 22 μm is applied using a rotary atomizing paint gun. The amount of paint discharged is 50 to 200 cc / min. According to this, if the shaping air flow rate is suppressed to 200 NL / min, the coating efficiency can be increased to 80% or more at a discharge rate of 100 to 200 cc / min. On the other hand, when the above-described shaping air flow rate is 400 NL / min, it is less than 80% even when the discharge rate is 200 cc / min.

  As described above, according to this example, since the click feeling can be easily revealed without depending on the shaping air flow rate, it is easy to obtain high coating efficiency by suppressing the shaping air flow rate. Therefore, it is possible to achieve a coating efficiency almost equal to that of clear coating or intermediate coating.

  In addition, when painting with a rotary atomizing electrostatic coating machine, it is possible to select an arbitrary shaping air flow rate while painting a paint containing a glittering pigment, and the accompanying effect that the coating pattern width can be set freely. There is.

  Furthermore, as an incidental effect of this example, the pattern distribution can be made relatively flat by reducing the shaping air flow rate of the rotary atomizing paint gun. The pattern distribution here refers to the film thickness distribution in the direction perpendicular to the traveling direction of the coating gun when the coating gun is moved along the surface of the workpiece. Then, as shown by the dotted line in FIG. 5, the film thickness distribution generally has a so-called two-cobra-clad type film thickness distribution in which two film thickness peaks appear. The trend appears prominently.

  However, according to the present example, as shown by the solid line in the figure, the trapezoidal pattern with a substantially flat pattern distribution can be obtained by suppressing the shaping air flow rate. ), The so-called meclick unevenness is substantially eliminated.

  Furthermore, as another effect of this example, when the metallic base paint is used, the base concealment film thickness can be reduced. This is because, in the case of opaque glittering pigments such as aluminum flakes, the orientation of the glittering pigment not only improves as the atomization progresses and the average particle diameter decreases, but it is also applied uniformly to the surface of the object to be coated. This is because they tend to wear.

  This means that as the average particle size of the paint particles decreases, the number of particles increases and the number of coatings increases, resulting in the elimination of uneven coating amount due to the surface area of the object to be coated. Means that you can plan. If this effect is used, the discharge amount of the metallic base paint itself can be reduced, and the coating cost can be reduced.

  By using these effects in a composite manner, it is possible to apply the mekki-base paint, which has been conventionally applied in two stages, in one stage and reduce the number of color changes.

  FIG. 6 verified the relationship between the average particle diameter of paint particles and the black and white concealment film thickness when a base paint containing scaly bright pigment having an average particle diameter of 22 μm was applied using a rotary atomizing paint gun. In the graphs and micrographs, when the average particle size of the paint particles is reduced to 20 μm, the black-and-white concealment film thickness is reduced to almost half compared to the case where the average particle size of the paint particles is 56 μm.

  The embodiment described above is described in order to facilitate understanding of the present invention, and is not described in order to limit 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 the front view and side view which show an example of the scaly glittering pigment which concerns on the coating method of this invention. It is a schematic diagram for demonstrating the coating mechanism which concerns on the coating method of this invention. It is a graph which shows the relationship between the average particle diameter of paint particle | grains and metallic feeling (IV value) when the base coating material containing a scaly glittering pigment is applied using the rotary atomization type painting gun. It is a graph which shows the relationship between the shaping air flow rate and coating efficiency when the base coating material containing a scaly glittering pigment is applied using a rotary atomizing paint gun. It is a figure which shows film thickness distribution when it paints using a rotary atomization type painting gun. It is the graph and micrograph which show the relationship between the average particle diameter of a coating particle when a base coating material containing a scaly glittering pigment is applied using a rotary atomizing coating gun, and the black-and-white concealment film thickness.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Scale-like luster pigment 3 ... Paint particle 4 ... Coated object

Claims (6)

A coating method for atomizing and painting a paint containing a scaly glittering pigment on an object to be coated, wherein the average particle diameter of the paint when applied to the object is an average particle of the scaly glittering pigment A coating method, wherein the paint is atomized so as to be equal to or smaller than the diameter. 2. The coating method according to claim 1, wherein a flight speed at the time of applying the paint is less than 5 m / sec. The coating method according to claim 1 or 2, wherein the paint is a metallic base paint or a pearl base paint, and after the paint is applied, a clear paint is applied. 4. The coating method according to claim 3, wherein the metallic paint or the pearl base paint is a water-based paint. The coating method according to claim 1, wherein the coating is applied in one stage. The coating method according to claim 1, wherein the paint is atomized by using a rotary atomizing paint gun.

Images