JP3521761B2 - Coating method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a step (means) for simply heating an electrodeposition coating film in an automobile coating process so that the cationic electrodeposition coating material and the intermediate coating material are wet-on. The present invention relates to a novel method for forming a multilayer coating film in which both coating films are wet coated and then both coating films are simultaneously cured by heating.

[0002]

2. Description of the Related Art Conventionally, in the automobile painting process, after degreasing and chemical conversion treatment of the body conveyed from the car body process, a cationic electrodeposition coating is electrodeposition-coated and heat-cured, followed by sealing, stone guard coating, undercoating. After the steps of coating a coat, heat-curing it, and setting an insulator, it is often practiced to coat the coating surface with an intermediate coating paint, heat-cure it, further coat a topcoat paint, and heat-cure it.

FIG. 1 shows a typical conventional automobile coating process 1
An example is briefly shown. As shown in FIG. 1, the automobile painting process 10
In 0, first, in the degreasing step 101, the body conveyed from the vehicle body step is degreased for the purpose of completely removing oils adhering to the vehicle body. Next, in the chemical conversion step 103, by forming a chemically stable inorganic film on the steel plate surface (film formation), the steel plate surface is inactivated and rust preventive power is given,
Chemical conversion treatment is carried out for the purpose of helping the adhesion between the steel plate and the coating film. After that, in the electrodeposition step 105, a cationic electrodeposition coating (for example, an electrodeposition coating mainly composed of an epoxy resin) capable of obtaining high rust prevention is electrodeposited for the purpose of forming a coating film excellent in rust prevention. To paint. Then, in a baking step 107, heat curing is performed under normal baking conditions (170 ° C. × about 20 to 30 minutes). Then, in a sealing step 109, for the purpose of preventing the intrusion of water and the outside air, the joints of the steel plates are sealed with a polyvinyl chloride (PVC) or bituminous sealing material by a flow gun or a tube. Next, in the undercoat process 111, in order to buffer unpleasant noise (high-frequency sound) due to stone splashes, splashes, etc., and to prevent damage to the coating film due to stone splashes, the floor back surface, the inside of the wheel house, and the vehicle body outer surface lower part (bumper). Apply the stone guard coat and undercoat to the lower part). Insulator process 113
Insulators (heat-bondable bituminous sheets; fusible insulators) for the purpose of damping steel plates
Set (or attach) to the floor surface, dash surface (inside the room), or the inner surface of the door outer. Then, in the baking step 115,
The stone guard coat and the undercoat are heated and cured under normal baking conditions (140 ° C x 10 to 15 minutes) (at the same time, the sealing and insulator are also fused, or 120 ° C x 10 to 15 in the sealing and insulator process). Fuse each in about a minute). Next, in the electrodeposition sharpening step 117, the unevenness of the electrodeposited undercoat surface, dust adhesion, etc. are checked and corrected, and the undercoat surface is finished to be smooth, and by making fine grinds, the adhesion of the next intermediate coating film can be improved. For the purpose of improving (anchoring effect), sanding is used to perform electropolishing (sanding) by water-polishing or air-polishing without water. Next, in the intermediate coating step 119, electrodeposition (in the present specification,
Also called undercoat. ) In addition to filling pinholes and small irregularities on the coated surface to adjust the surface to improve the appearance of the finished topcoat, protect the undercoat film from external impacts, and to protect it from the moisture that permeates the topcoat film. For the purpose of preventing invasion and improving the adhesion between topcoat and undercoat, an intermediate coating is applied to the electrodeposition coated surface by air spraying or electrostatic coating. Then, in the baking step 121, the normal baking conditions (1
It is heated and cured at 40 to 150 ° C. for about 20 to 25 minutes. After that, in the intermediate coating polishing step 123, the final correction step aimed at completely correcting the defects that have been missed up to the previous step, and the content is the same as the above-mentioned electrodeposition polishing,
Medium sanding is performed using fine sandpaper. Furthermore, taking the example of the top coating process that uses the 2-coat 1-bake method, which does not expose aluminum particles in the paint to the surface and is excellent in appearance and chemical resistance, first, the base process
125 and clear process 127 use top coat paint (base paint and clear paint) with air spray or electrostatic coating method for the purpose of imparting aesthetics and environmental durability, chemical resistance, abrasion resistance and durability. To paint. Then
In the baking step 129, normal baking conditions (140 to 150
It is heat-cured at a temperature of about 20 to 25 minutes. Finally, in the inspection step 131, after checking and correcting the top coating surface,
Take the prescribed inspection. Vehicle bodies that pass this inspection are sent to the next assembly process. The above is the process procedure often performed in the conventional automobile coating process.

[0004]

However, in recent years,
From the viewpoint of shortening the coating process, saving resources and preventing pollution, the cationic electrodeposition coating film is coated with an intermediate coating material without being cured by heating, and then the cationic electrodeposition coating film and the intermediate coating film are coated. There is a strong demand for a coating film formation method that simultaneously cures and is heated, but when coating wet-on-wet, a large amount of basic substances and low-molecular substances that volatilize from the uncured cationic electrodeposition coating film during heating are obtained. There is a problem that the coating composition is transferred to the upper layer coating film, and bleeding, curing inhibition, etc. occur, and smoothness and sharpness of the coating film cannot be sufficiently obtained.
Not yet in practical use.

Therefore, the present invention has as its object to eliminate the above-mentioned defects in the step of coating the cationic electrodeposition coating composition and the intermediate coating composition by the two-coat one-bake system.

More specifically, the present invention has been made in order to solve such various conventional problems, and bleeding, inhibition of curing, etc. occur in the automobile coating process, and the smoothness and smoothness of both coating films are improved. It is possible to heat-cure both coating films at the same time after applying an intermediate coating composition on the coating surface of the cationic electrodeposition coating film without causing a problem such as insufficient image clarity. An object of the present invention is to provide a coating film forming method capable of achieving shortening, resource saving, and low pollution.

[0007]

Therefore, the present inventors have
In order to achieve the above object, as a result of intensive research aimed at eliminating the above-mentioned defects in the step of coating a cationic electrodeposition paint and an intermediate coating paint by a two-coat one-bake method, as a result, a cationic electrodeposition coating film can be easily prepared. By warming the
More preferably, the inventors have found that the object can be achieved by providing a step of heat-flowing an electrodeposition coating film and a step of removing moisture and a heating loss amount in a cationic electrodeposition coating composition, and have arrived at the present invention.

That is, the present invention for achieving the above object is constructed as follows for each claim.

According to a first aspect of the present invention, there is provided a method for forming a coating film in an automobile coating process in which a cationic electrodeposition coating and an intermediate coating are carried out in a two-coat, one-bake system. The method for forming a coating film is characterized in that the cationic electrodeposition coating film is simply heated before the application of.

The invention according to claim 2 is an automobile in which a cationic electrodeposition coating composition and an intermediate coating composition are applied wet-on-wet, and both the cationic electrodeposition coating film and the intermediate coating film are simultaneously cured by heating. In the coating film forming method in the coating step, the cationic electrodeposition coating film is simply heated before applying the intermediate coating composition.

The invention according to claim 3 is the method for forming a coating film according to claim 1 or 2, wherein as a step for simply heating the cationic electrodeposition coating film, the electrodeposition coating film is mainly applied. In order to provide smoothness and sharpness, the process of heat-flowing the electrodeposition coating film, and mainly to evaporate the water on the electrodeposition coating film and volatilize basic substances and low-molecular substances from the electrodeposition coating film. And a step of removing the amount of heat and the amount of heating loss in the cationic electrodeposition coating composition are provided.

According to a fourth aspect of the present invention, in the automobile coating process, after the electrodeposition coating of the cationic electrodeposition coating, the step of heat-flowing the electrodeposition coating, water and the heating loss in the cationic electrodeposition coating are controlled. Equipped with a process to fly, then apply sealing, stone guard coat, undercoat,
After the step of setting the insulator, the intermediate coating material is applied, baked at once, the top coating material is applied, and baked.

According to a fifth aspect of the present invention, in the automobile coating process, the step of heat-flowing the electrodeposition coating after the electrodeposition coating of the cationic electrodeposition coating, the water content and the heating loss in the cationic electrodeposition coating are controlled. Equipped with a step of flying, followed by applying an intermediate paint, baking at once, then applying a ceiling, stone guard coat, undercoat, and a step of setting an insulator, then applying a top coat paint,
It is a coating film forming method characterized by baking.

According to a sixth aspect of the present invention, in the coating film forming method according to any one of the third to fifth aspects, the step of heat-flowing the electrodeposition coating film is performed by heating means of 50 to 120.
It is characterized in that it is carried out at a temperature of 1 to 10 minutes.

According to a seventh aspect of the present invention, in the coating film forming method according to any one of the third to fifth aspects, the step of removing moisture and the amount of heating loss in the cationic electrodeposition coating is an infrared heating means. Is performed for 1 to 7 minutes.

The invention according to claim 8 is the coating film forming method according to any one of claims 1 to 7, wherein the intermediate coating material is selected from the group consisting of solvent-based, water-based and powder-based coating materials. It is characterized by being at least one kind of

According to a ninth aspect of the present invention, in the coating film forming method according to any one of the fourth to eighth aspects, the topcoat paint is selected from the group consisting of solvent-based paints, water-based paints and powder-based paints. It is characterized by being at least one kind of

The invention described in claim 10 is the invention according to claims 3 to 9.
In the coating film forming method as described in any one of 1 above, the heating means in the step of heat-flowing the electrodeposition coating film is hot air blow.

The invention according to claim 11 is the invention according to claims 3 to 9.
In the coating film forming method as described in any one of 1 above, the infrared heating means is a means that uses infrared rays in the near red to mid red line region.

[0020]

According to the invention described in claim 1, in the method for forming a coating film in an automobile coating process in which the cationic electrodeposition coating and the intermediate coating are carried out by a two-coat one-bake system, the cationic electrodeposition coating is applied. The feature is that the cationic electrodeposition coating film is simply heated before the intermediate coating is applied, so the uncured cationic electrodeposition coating film before baking is baked. To make it smooth and clear,
Furthermore, the water content on the electrodeposition coating film can be removed to vaporize basic substances and low-molecular substances from the electrodeposition coating film, and when both coatings are baked, the intermediate coating film on the upper layer can be changed to the basic layer from the lower layer. The substance and the low molecular weight substance do not migrate in a large amount, and there is no problem that bleeding, curing inhibition, etc. occur, and the smoothness and sharpness of the coating film are impaired. In addition, the cationic electrodeposition coating and the intermediate coating can be performed by the 2-coat 1-bake method, which is different from the conventional method in which the cationic electrodeposition coating and the intermediate coating are performed by the 2-coat 2-bake method. The coating process can be shortened, resources can be saved, and pollution can be reduced (see FIGS. 1 to 3).

According to the second aspect of the present invention, the cationic electrodeposition coating composition and the intermediate coating composition are applied wet-on-wet, and both the cationic electrodeposition coating film and the intermediate coating film are simultaneously heated by heating. In the method for forming a coating film in an automobile coating process for curing, the cationic electrodeposition coating film is simply heated by the time the intermediate coating material is applied. It can produce an effect. That is, the uncured cationic electrodeposition coating film before being simultaneously cured by heating both coating films can be made smooth and clear by heating, and further, the water content on the electrodeposition coating film is evaporated,
Basic substances and low-molecular substances can be volatilized from the electrodeposition coating film, and when baking both coating films, a large amount of basic substances and low-molecular substances are not transferred from the lower layer to the intermediate coating film of the upper layer. However, problems such as bleeding, inhibition of curing, and deterioration of smoothness and sharpness of the coating film do not occur. In addition, the cationic electrodeposition coating and the intermediate coating are applied wet-on-wet, and both the cationic electrodeposition coating and the intermediate coating are simultaneously cured by heating. Compared with a coating method in which an intermediate coating film is formed on a film and baked, the coating process can be shortened, resources can be saved, and pollution can be reduced.

In the invention described in claim 3, in the method for forming a coating film according to claim 1 or 2, as a step for simply heating the cationic electrodeposition coating film, the electrodeposition is mainly performed. In order to impart smoothness and sharpness to the coating film, a step of heating the electrodeposition coating film for heat flow, and mainly removing water on the electrodeposition coating film to remove basic substances and In order to volatilize the low molecular weight substance, at least a step of heating the electrodeposition coating film to remove water and the heating loss in the cationic electrodeposition coating material is provided. That is, it defines a more specific and suitable means (step) of the method according to claims 1 and 2, wherein the heat flow step ensures smoothness and sharpness of the coating film, In the process of removing the above moisture and heat loss,
The water on the electrodeposition coating film is evaporated to vaporize a basic substance or a low molecular weight substance from the electrodeposition coating film.
In order to easily heat the cationic electrodeposition coating film and obtain the useful action and effect described in claim 1 or 2, it can be carried out by any one arbitrary heating means (one step). . However, the means (heating conditions, heating devices,
And their control, etc., becomes more complex (ie,
Since it is necessary to consolidate the operations of the two steps defined in this claim into one step, it is necessary to set the heating conditions and the heating means (apparatus) for that purpose, so find the optimum conditions. It is necessary to carry out many tests, and also expensive capital investment is required. Therefore, in the present claims, it is necessary to understand the essence (technical idea) of the present invention sufficiently without complicating the technical problem solving means, and to simplify the heating conditions and heating conditions. It has been found that the same action and effect can be achieved by highly combining heating means (devices). That is,
In the present claim, two or more steps having different heating purposes are combined in an appropriate order (further, the optimum heating condition and heating means (device) corresponding to each heating purpose are combined. Etc.), the useful effects described in claims 1 and 2 can be achieved by using a simpler and easier method. Therefore, there is an advantage that it is extremely easy to put into practical use (industrialization).

In the invention according to claim 4, in the automobile coating process, after the cationic electrodeposition coating is electrodeposition coated, a step of heat-flowing the electrodeposition coating, heating of water and heating in the cationic electrodeposition coating are carried out. Equipped with a process to skip the weight loss, followed by the process of painting the ceiling, stone guard coat, undercoat, and setting the insulator,
4. So-called, characterized in that the intermediate coating material is applied, baked at one time, the top coating material is applied, and baked.
It defines one more specific embodiment of the coating film forming method described in (1), and achieves the effects of the above-mentioned claims (1) to (3). By providing the preheating step 206 as shown, it is not necessary to perform the baking step 107 after the electrodeposition step, the baking step 115 after the insulator step and the electrodeposition sharpening step 117 in the conventional method shown in FIG. 1) In addition to the above, except that the cationic electrodeposition coating film was not simply baked until the intermediate coating material was applied, but the cationic electrodeposition coating film was simply heated, as shown in FIG. It is carried out without changing the order of, and has an advantage that existing equipment can be used without being significantly changed.

According to a fifth aspect of the present invention, in the automobile coating process, after the cationic electrodeposition coating is electrodeposition coated, a step of heat-flowing the electrodeposition coating, heating of water and heating in the cationic electrodeposition coating are carried out. Equipped with a process to skip the weight loss, followed by applying an intermediate paint, baking once, then applying a sealing, stone guard coat, undercoat,
After passing through the step of setting the insulator, a top coat paint is applied and baked, so to speak, to define another more specific embodiment of the coating film forming method according to claim 3. The operation and effects of the above-described claims 1 to 3 are achieved (for shortening the process, for example, FIG.
By providing the preheating step 306 as shown in FIG. 1, it is not necessary to perform the baking step 107 and the electrodeposition sharpening step 117 after the electrodeposition step in the conventional method shown in FIG. 1).
Compared to the embodiment of the above, the steps of coating the ceiling, stone guard coat, and undercoat, and setting the insulators are performed after the step of applying the intermediate coating paint and baking at once, and the cationic electrodeposition coating and By shortening the process until the coating material is wet-on-wet, it is possible to reduce the risk of dust and dirt adhering to the object to be coated during the process between these steps and the transport route between the steps. It is possible to provide a clean appearance (finished coating surface) with less dust and pinholes due to dust on the surface of the film (finished coating surface), and to reduce the size of dust collectors etc. for removing such dust from the air. Have the advantage of

According to the invention of claim 6, in the coating film forming method of claims 3 to 5, the step of heat-flowing the electrodeposition coating film is 1 to 10 at 50 to 120 ° C. by a heating means.
The electrodeposition coating is one of two steps having different heating purposes, in addition to the effects of the above-mentioned claims 1 to 5. It specifies the optimum heating conditions and heating means / devices according to the heating purpose of the process of heat-flowing, so that the heat flow does not occur or the coating film starts to harden and the viscosity increases. Therefore, the optimum heat flow can be performed without failing to obtain sufficient smoothness and sharpness, and extremely excellent smoothness and sharpness can be obtained.

In the invention according to claim 7, in the coating film forming method according to claims 3 to 5, the step of removing moisture and the heating loss in the cationic electrodeposition coating composition is 1 to 7 by infrared heating means. It is carried out for a minute, and in addition to exhibiting the effects of the above-mentioned claims 1 to 6, it is one of two steps having different heating purposes, that is, water and cation charge. It specifies the optimum heating conditions and heating means / devices according to the heating purpose in the process of removing the heating loss in the coating material, and this allows sufficient removal of water and heating loss. It is possible to remove basic substances and low molecular weight substances from the electrodeposition coating film very well, without being able to do it, or conversely overbaking to cause poor adhesion, and to bleed the coating film after baking. Or There is no possibility that problems such as of inhibition occurs.

According to the invention of claim 8, in the coating film forming method of claims 1 to 7, the intermediate coating material is at least one selected from the group consisting of solvent-based, water-based and powder-based coating materials. It is characterized in that it is of a kind, has the effects of the above-mentioned claims 1 to 7, and defines an intermediate coating composition which can be particularly preferably used in the present invention. It should be noted that, as defined above, an extremely wide range of intermediate coating materials is the target, and the method of the present invention is also a very useful method which can be widely applied from this point of view.

In the invention according to claim 9, in the coating film forming method according to claims 3 to 8, at least one kind of the top coating material is selected from the group consisting of solvent-based, water-based and powder-based coating materials. The present invention provides the effects of the above-mentioned claims 1 to 8 and defines a topcoat paint which can be particularly preferably used in the present invention. It should be noted that, as defined above, an extremely wide range of top-coat paints is the subject, and it can be seen from this that the method of the present invention is an extremely useful method that can be applied to an extremely wide range.

According to a tenth aspect of the present invention, in the coating film forming method according to the third to ninth aspects, the heating means in the step of heat-flowing the electrodeposition coating film is hot air blow. In addition to the effects of the above-described claims 1 to 8, the process of heat-flowing the electrodeposition coating film, which is one of two processes having different heating purposes, is added. It specifies the optimum heating means (apparatus) according to the purpose of heating, and this makes it possible to perform the optimum heat flow as a substantially uniform heating condition for the entire object to be coated,
It is possible to impart extremely excellent smoothness and sharpness to the entire article to be coated.

According to the invention of claim 11, in the coating film forming method of claims 3 to 9, the infrared heating means comprises:
It is characterized in that it is a means using infrared rays in the near-red to mid-red line region, and has two different heating purposes in addition to the action and effect described in the above 1 to 10. One of the steps is to define the optimum heating means (apparatus) according to the heating purpose in the step of removing water and the amount of heating loss in the cationic electrodeposition coating composition. The basic substances and low-molecular substances remaining in the coating film of the product can be volatilized very well from the electrodeposition coating film, and problems such as bleeding and curing inhibition may occur in the coating film during subsequent baking. There is no.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a coating film forming method in an automobile coating process in which a cationic electrodeposition coating and an intermediate coating are carried out in a two-coat one-bake system. In other words, the cationic electrodeposition coating and the intermediate coating are applied. In the coating film forming method in the automobile coating process, where the coating material is applied wet-on-wet and both the cationic electrodeposition coating film and the intermediate coating film are simultaneously cured by heating, the intermediate coating is applied after the cationic electrodeposition coating material is applied. Before applying the paint, the cationic electrodeposition coating film should be simply heated, preferably as a step for simply heating the cationic electrodeposition coating film. Process to heat-flow the electrodeposition coating film in order to provide good image clarity and sharpness, and mainly to evaporate water on the electrodeposition coating film and volatilize basic substances and low-molecular substances from the electrodeposition coating film. , Moisture and A step of blowing the heating loss content of the thione electrodeposition coating, but is characterized by comprising provided with at least.

In the present invention, the steps of heat-flowing the above-mentioned electrodeposition coating film and the step of removing the above-mentioned water content and the heating loss in the cationic electrodeposition coating material are performed after the application of the cationic electrodeposition coating material. It suffices that it is provided by the time the coating material is applied, and the other steps are not limited at all, and various steps in the conventionally known automobile painting step as described in FIG. 1 can be performed as necessary. Needless to say, it can be used in combination with application, for example, (1) a step of heat-flowing the electrodeposition coating film after the electrodeposition coating of the cationic electrodeposition coating material, moisture and the amount of heating loss in the cationic electrodeposition coating material. It is equipped with a process to skip, then apply sealing, stone guard coat, undercoat,
After going through the process of setting the insulator, apply the intermediate paint, bake it once, apply the top coat paint, and bake it. (2) After electrodeposition coating the cationic electrodeposition paint, heat the electrodeposition paint film. It is equipped with a process of flowing, a process of removing moisture and the amount of heat loss in the cationic electrodeposition paint, followed by applying an intermediate paint, baking once, and then applying a sealing, stone guard coat, and undercoat,
After the step of setting the insulator, a method of coating and baking a topcoat paint, and the like can be exemplified, as well as a method in which the steps shown in FIGS. 2 and 3 described later are further added, but the scope of the present invention is , By no means limited to these.

Further, in the present invention, the step of heat-flowing the above electrodeposition coating film after the application of the cationic electrodeposition coating material to the application of the intermediate coating material, and the above-mentioned water content and heating in the cationic electrodeposition coating material It is desirable that a step of skipping the weight loss is provided, but more desirably, the step of heat-flowing the above electrodeposition coating film is 1 to 50 to 120 ° C. by a heating means, preferably by hot air blow. 1
It is carried out in the range of 0 minutes, preferably at 70 to 90 ° C. for 1 to 5 minutes, and the step of removing the water content and the heating loss in the cationic electrodeposition coating is preferably carried out by infrared heating means. ~ It is carried out for 1 to 7 minutes, preferably 2 to 4 minutes by means of using infrared rays in the middle red line region.

The step of heat-flowing the above-mentioned electrodeposition coating film is the step of heat-flowing the electrodeposition coating film,
If the heating is carried out for less than 1 ° C or for less than 1 minute, the electrodeposition coating film does not flow through heat, and sufficient smoothness and sharpness cannot be obtained. On the other hand, when the temperature of the electrodeposition coating exceeds 120 ° C or is higher than 10 minutes (heating), curing of the electrodeposition coating starts and the viscosity increases, so sufficient smoothness and sharpness are obtained. I can't.

Further, in the step of removing the above-mentioned water content and heating loss in the cationic electrodeposition coating, if the infrared heating is carried out for a time shorter than 1 minute, the temperature does not rise sufficiently,
It is not possible to remove the water content and the heating loss in the cationic electrodeposition coating. On the other hand, when infrared heating is performed for a time longer than 7 minutes, the temperature rises excessively, resulting in overbaking and poor adhesion.

The intermediate coating composition to be applied by the wet-on-wet coating with the cationic electrodeposition coating composition is not particularly limited, but is at least one selected from the group consisting of solvent-based coating compositions, water-based coating compositions and powder-based coating compositions. The above can be preferably applied. Similarly, the top coating material is not particularly limited, but at least one coating material selected from the group consisting of solvent-based, water-based and powder-based coating materials can be preferably applied.

Further, since the cationic electrodeposition coating and the intermediate coating are carried out by the two-coat one-bake system, the baking (baking) conditions, in other words, the cationic electrodeposition coating and the intermediate coating are wet on wet. After coating, the conditions for simultaneously curing both the cationic electrodeposition coating film and the intermediate coating film by heating are simple heating, so the conditions for baking conventional electrodeposition coating films and medium It may be performed under conditions intermediate to the baking conditions of the coating film, but it may change depending on the type of paint and simple heating conditions, so it is necessary to select the optimum conditions according to such conditions. desirable.
In addition, the provisional guideline for intermediate conditions is 160 to 170 ° C.
It can be said that it takes about 20 to 25 minutes, but there is no particular need to be caught by this.

The method for forming a coating film of the present invention in which the cationic electrodeposition coating and the intermediate coating are carried out by a two-coat one-bake system, in other words, the cationic electrodeposition coating and the intermediate coating are applied wet-on-wet. 2 and FIG. 3 are two typical examples of the automobile coating process by the coating film forming method in which both the cationic electrodeposition coating film and the intermediate coating film are simultaneously cured by heating.
Will be briefly described using.

FIG. 2 is an example of an automobile painting process showing the embodiment of claim 4 in more detail. As shown in FIG. 2, an automobile coating process by the coating film forming method of the present embodiment.
In 200, first, in a degreasing process 201, the body conveyed from the vehicle body process is degreased for the purpose of completely removing oils adhering to the vehicle body. Next, in the chemical conversion step 203, a chemically stable inorganic film is formed on the surface of the steel sheet (film formation) to inactivate the steel sheet surface and provide rust prevention, and at the same time, to improve the adhesion between the steel sheet and the coating film. Chemical conversion treatment for the purpose of helping. After that, in the electrodeposition step 205, a cationic electrodeposition coating (for example, an electrodeposition coating mainly composed of an epoxy resin) capable of obtaining high rust prevention is formed for the purpose of forming a coating film excellent in rust prevention.
Is electro-deposited. Then, in the preheating step 206, for the purpose of simply heating the cationic electrodeposition coating film, first of all, mainly for the purpose of imparting smoothness and sharpness to the electrodeposition coating film, the electrodeposition coating is performed. Water and cationic electrodeposition coatings are mainly used to remove the water on the electrodeposition coating film and to volatilize basic substances and low-molecular substances from the electrodeposition coating film by performing a step of heat-flowing the coating film. Perform the step of removing the heating loss. The details of these are as described above. Then, in the sealing step 209,
For the purpose of preventing the invasion of water and the outside air, the seam of the steel plates is sealed with a PVC sol (PVC) or a bituminous sealing material by a flow gun or a tube. Next, in the undercoat process 211, for the purpose of buffering unpleasant noise (high-frequency noise) due to stone splashes, water splashes, etc., and preventing damage to the coating film due to stone splashes, the underside of the floor, the inside of the wheel house, the bottom of the outside of the vehicle body (bumper). Apply the stone guard coat and undercoat to the lower part). In the insulator process 213, an insulator (heat-fusible bituminous sheet; fusible insulator) is set (or attached) to the floor surface, dash surface (inside the room), or the inner surface of the door outer for the purpose of damping the steel sheet. . After that, in the intermediate coating step 219, in addition to filling the pinholes and small irregularities of the electrodeposition coating film after preheating to adjust the surface to improve the finish appearance of the topcoat, protect the electrodeposition coating film against external impact. , Prevents the penetration of moisture that permeates the top coat,
Wet-on-wet intermediate coating is applied to the uncured electrodeposition coating by air spraying or electrostatic coating for the purpose of improving the adhesion between topcoat and undercoat (so-called 2 coat 1 bake coating system). It is.) Next, in the baking step 221, the baking conditions are set to 160 to 170 ° C.
It is cured by heating for 20 to 25 minutes. After that, in the intermediate coating polishing step 223, it is the final correction step that aims to completely correct the defects while checking and correcting the unevenness of the coating surface, dust adhesion, etc. (Sanding) is performed. further,
Taking the example of the top coating process that employs the 2-coat 1-bake method, in which aluminum particles in the paint do not appear on the surface and is excellent in appearance and chemical resistance, first, the base process 225 and the clear process 227 are:
Topcoat paints (base paints and clear paints) are applied by air spraying or electrostatic coating methods for the purpose of imparting an aesthetic appearance and weather resistance, chemical resistance, abrasion resistance and durability to the environment. Next, in a baking step 229, heat curing is performed under normal baking conditions (140 to 150 ° C. × about 20 to 25 minutes). Finally, in the inspection step 231, the top coating surface is checked and corrected, and then a predetermined inspection is performed. Vehicle bodies that pass this inspection are sent to the next assembly process.

On the other hand, FIG. 3 is an example of an automobile painting process showing the embodiment of claim 5 in more detail. Figure 3
As shown in FIG. 1, in the automobile coating process 300 according to the coating film forming method of the present embodiment, first, in the degreasing process 301, the body conveyed from the car body process is subjected to the purpose of completely removing oils attached to the car body. Then, degrease. Next, in the chemical conversion step 303,
By chemically forming an inorganic film that is chemically stable on the surface of the steel sheet (formation of the coating film), the surface of the steel sheet is inactivated, rust-preventive force is given, and chemical conversion treatment is performed for the purpose of assisting the adhesion between the steel sheet and the coating film. After that, in the electrodeposition step 305, a cationic electrodeposition coating (for example, an electrodeposition coating mainly composed of an epoxy resin) capable of obtaining high rust prevention is formed for the purpose of forming a coating film excellent in rust prevention.
Is electro-deposited. Subsequently, in the preheating step 306, first, for the purpose of simply heating the cationic electrodeposition coating film, first of all, mainly for the purpose of imparting smoothness and sharpness to the electrodeposition coating film, Water and cationic electrodeposition coatings are mainly used to remove the water on the electrodeposition coating film and to volatilize basic substances and low-molecular substances from the electrodeposition coating film by performing a step of heat-flowing the coating film. Perform the step of removing the heating loss. The details of these are as described above. Immediately thereafter, in the intermediate coating step 319, pinholes and small irregularities in the electrodeposition coating film after preheating are filled in to minimize the adhesion of dust and the like, and surface adjustment is performed to improve the finish appearance of the top coating. In addition, for the purpose of protecting the electrodeposition coating film from external impacts, preventing the penetration of moisture that permeates the topcoat coating film, and improving the adhesion of the topcoat and undercoat, the uncured electrodeposition coating film Wet-on-wet coating of intermediate coating by air spray or electrostatic coating method (so-called 2-coat 1-bake method). Next, in the baking step 321, the baking conditions are set to 160 to 170 [deg.] C. for 20 to 25 minutes to heat and cure. After that, in the intermediate coating polishing step 323, it is the final correction step that aims to completely correct the defects while checking and correcting the unevenness of the coating surface, dust adhesion, etc. (Sanding) is performed. In the present embodiment, after forming such a value or a coating film, in the sealing step 309, the seam of the steel sheet is made of PVC sol (PV) for the purpose of preventing the intrusion of water and the outside air.
C) or bituminous sealing material is placed on the steel sheet joint with a flow gun or tube and sealed. Then
In the undercoat process 311, in order to buffer unpleasant noise (high-frequency noise) due to stone splashes, splashes, etc., and to prevent damage to the coating film due to stone splashes, the bottom floor, the inside of the wheel house, and the bottom of the vehicle exterior (below the bumper) Part) etc., apply stone guard coat and under coat. Further, in the insulator process 313, an insulator (heat-bonding bituminous sheet; fusible insulator) is set (or attached) on the floor surface, the dash surface (inside the room), or the inner surface of the door outer for the purpose of damping the steel plate. ) Do. Then, in a baking step 315, the stone guard coat and the undercoat are heated and cured under normal baking conditions (140 ° C. × about 10 to 15 minutes) (at the same time, the sealing and the insulator are also fused, or the sealing and the insulator step). At 120 ° C. for about 10 to 15 minutes, respectively). Furthermore, taking the example of the top coating process that uses the 2-coat 1-bake method, which does not expose aluminum particles in the paint to the surface and is excellent in appearance and chemical resistance, first, the base process
325 and clear process 327 use topcoat paints (base paints and clear paints) with air spray or electrostatic coating methods for the purpose of imparting aesthetics and environmental durability, chemical resistance, abrasion resistance and durability. To paint. Then
In the baking step 329, normal baking conditions (140 to 150
It is heat-cured at a temperature of about 20 to 25 minutes. Finally, in the inspection process 331, after checking and correcting the top coating surface,
Take the prescribed inspection. Vehicle bodies that pass this inspection are sent to the next assembly process.

[0041]

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

Example 1 Door parts (Cefiro) were degreased, subjected to zinc phosphate conversion treatment, washed with water, and then cationic electrodeposition paint Power Top U-60.
(Manufactured by Nippon Paint Co., Ltd.) was electrodeposited at a voltage of 250 V for 3 minutes, washed with water, and then set at room temperature for 5 minutes (dry film thickness 20 μm). Next, hot air blowing was performed at 50 ° C. for 1 minute, and further heating was performed for 1 minute at a distance of 400 mm by a transparent quartz tube infrared heater made by Heraeus. Thereafter, a sealing coating, a stone guard coating coating, and an undercoat coating were applied. Further, an intermediate coating paint OP-61 (manufactured by Nippon Paint Co., Ltd.) was applied so as to have a dry film thickness of 25 to 30 μm, and baked at 160 ° C. for 20 minutes. Then, the top coating silver metallic base super rack M-18
0 and Kuriya Super Rack O-130 (both manufactured by Nippon Paint Co., Ltd.) were applied wet-on-wet, and 1
Baking at 40 ° C. for 20 minutes.

Example 2 The same as Example 1 except that the hot air blow for 1 minute at 50 ° C. in Example 1 was changed to 5 minutes.

Example 3 The same as Example 1 except that the hot air blow at 50 ° C. for 1 minute in Example 1 was changed to 10 minutes.

Example 4 Example 4 is the same as Example 1 except that the hot air blow at 50 ° C. in Example 1 was changed to 80 ° C.

Example 5 The same as Example 2 except that the hot air blow at 50 ° C. of Example 2 was changed to 80 ° C.

Example 6 The same as Example 3 except that the hot air blow at 50 ° C. of Example 3 was changed to 80 ° C.

Example 7 The same as Example 1 except that the hot air blow at 50 ° C. in Example 1 was changed to 120 ° C.

Example 8 The same as Example 2 except that the hot air blow at 50 ° C. in Example 2 was changed to 120 ° C.

Example 9 The same as Example 3 except that the hot air blow at 50 ° C. of Example 3 was changed to 120 ° C.

Example 10 The same as Example 1 except that the infrared heater of Example 1 was heated for 1 minute to 4 minutes.

Example 11 Example 11 is the same as Example 2 except that the infrared heater of Example 2 was heated for 1 minute to 4 minutes.

Example 12 Example 12 is the same as Example 3 except that the heating for 1 minute of the infrared heater was changed to 4 minutes.

Example 13 The same as Example 4 except that the infrared heater of Example 4 was heated for 1 minute to 4 minutes.

Example 14 Example 14 is the same as Example 5 except that the infrared heater of Example 5 was heated for 1 minute to 4 minutes.

Example 15 The same as Example 6 except that the heating of the infrared heater of Example 5 for 1 minute was changed to 4 minutes.

Example 16 Example 16 is the same as Example 7 except that the infrared heater of Example 7 was heated for 1 minute to 4 minutes.

Example 17 The same as Example 8 except that the heating of the infrared heater of Example 8 for 1 minute was changed to 4 minutes.

Example 18 The same as Example 9 except that the heating of the infrared heater of Example 9 for 1 minute was changed to 4 minutes.

Example 19 The same as Example 1 except that the heating of the infrared heater of Example 1 for 1 minute was changed to 7 minutes.

Example 20 The same as Example 2 except that the heating of the infrared heater of Example 2 for 1 minute was changed to 7 minutes.

Example 21 The same as Example 3 except that the heating of the infrared heater of Example 3 for 1 minute was changed to 7 minutes.

Example 22 Example 22 is the same as Example 4 except that the heating for 1 minute of the infrared heater was changed to 7 minutes.

Example 23 The same as Example 5 except that the infrared heater of Example 5 was heated for 1 minute to 7 minutes.

Example 24 Example 6 is the same as Example 6 except that the heating for 1 minute of the infrared heater was changed to 7 minutes.

Example 25 The same as Example 7 except that the heating for 1 minute of the infrared heater of Example 7 was changed to 7 minutes.

Example 26 Example 26 is the same as Example 8 except that the infrared heater of Example 8 was heated for 1 minute to 7 minutes.

Example 27 The same as Example 9 except that the heating of the infrared heater of Example 9 for 1 minute was changed to 7 minutes.

Example 28 The same as Example 13 except that the infrared heater of Example 13 was changed from mid infrared to near infrared.

Example 29 The same as Example 13 except that the intermediate coating composition of Example 13 was changed to an aqueous intermediate coating composition.

Example 30 The same as Example 13 except that the intermediate coating material of Example 13 was changed to the powder type intermediate coating material.

Comparative Example 1 Hot air blow for 1 minute at 50 ° C. of Example 1 was conducted at 45 ° C.
The same as Example 1 except that it was changed to.

Comparative Example 2 The same as Example 1 except that the hot air blow for 1 minute at 50 ° C. in Example 1 was changed to 50 seconds.

Comparative Example 3 The same as Example 1 except that the heating for 1 minute of the infrared heater of Example 1 was changed to 50 seconds.

Comparative Example 4 The hot air blow of Example 7 at 120 ° C. for 1 minute was performed for 12 minutes.
Same as Example 7 except that the temperature was changed to 5 ° C.

Evaluation method Appearance of coating film: The state of the coating film was visually evaluated according to the following evaluation criteria.

⊚: Very good smoothness ○: Very good smoothness Δ: Slightly good smoothness ×: Poor smoothness Adhesion: 2 mm square on the coating surface with a cross cut cutter of 100
Individual pieces were made, a cellophane tape was adhered to the surface, and the state after strongly peeling off was evaluated according to the following criteria.

⊚: 100% no peeling ○: 95% no peeling Δ: 90% no peeling ×; less than 90% peeling occurred Sealing suitability: The state of the surface coated with the sealing was visually evaluated as follows. It was evaluated according to the standard.

⊚: Very good smoothness ◯: Very good smoothness Δ: Slightly good smoothness ×: Poor smoothness Stone guard coat suitability: The condition of the stone guard coat coating surface is visually checked as follows. It evaluated according to the evaluation criteria.

[0080] ⊚: Very smooth ○: Very smooth Δ: Smoothness is slightly good ×: Poor smoothness

[0081]

[Table 1]

[0082]

[Table 2]

[Brief description of drawings]

FIG. 1 is an automobile coating process chart showing a typical example of a conventional coating film forming method.

FIG. 2 is a method for forming a coating film of the present invention in which the cationic electrodeposition coating and the intermediate coating are carried out in a two-coat one-bake system, in other words, the cationic electrodeposition coating and the intermediate coating are applied wet-on-wet. Fig. 5 is an automobile coating process chart showing a typical example of a coating film forming method in which both the cationic electrodeposition coating film and the intermediate coating film are simultaneously cured by heating. It is a motor vehicle coating process drawing showing embodiment.

FIG. 3 is a method of forming a coating film of the present invention in which the cationic electrodeposition coating and the intermediate coating are carried out by a two-coat one-bake system, in other words, the cationic electrodeposition coating and the intermediate coating are applied wet-on-wet. FIG. 6 is an automobile coating process chart showing a typical example of a coating film forming method in which both the cationic electrodeposition coating film and the intermediate coating film are simultaneously cured by heating. It is a motor vehicle coating process drawing showing embodiment.

[Explanation of symbols]

100, 200, 300 ... Automotive coating process, 101, 201, 301 ...
Degreasing process, 103, 203, 303 ... Chemical conversion process, 105,
205, 305 ... Electrodeposition process, 107 ... Electrodeposition coating baking process,
109, 209, 309 ... Sealing process, 111, 211, 311
... Undercoat process, 113, 213, 313 ... Insulator process, 115,315 ... Baking process such as undercoat, 11
7 ... Electrodeposition sharpening process, 119, 219, 319 ...
Intermediate coating process, 121 ... Baking process of intermediate coating film 12
3, 223, 323 ... Intermediate coating polishing process, 125, 225, 325 ... Base process, 127, 227, 327 ... Clear process, 129, 22
9,329 ... Baking process of top coating film (base coating and clear coating film), 131, 231, 331 ... Inspection process, 206, 30
6 ... Pre-heating process, 221, 321: Baking process of both electrodeposition coating film and intermediate coating film.

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) C25D 13/00 308 B05D 7/14

Claims (7)

(57) [Claims] 1. A cationic electrodeposition coating composition and an intermediate coating composition are coated on a wafer.
Coated with wet-on-wet, cationic electrodeposition coating and intermediate coating
A car that can simultaneously cure both coatings by heating
In the method of forming a coating film in the coating process, after the cationic electrodeposition coating is applied, the intermediate coating is applied.
Then, as a step for simply heating the cationic electrodeposition coating film, mainly in order to impart smoothness and sharpness to the electrodeposition coating film, in the range of 70 to 90 ° C. for 1 to 5 minutes. The process of heat-flowing the electrodeposition coating film, mainly to remove water on the electrodeposition coating film and to heat basic materials and low-molecular substances from the electrodeposition coating film by infrared heating
Method for forming a coating film comprising the steps of blowing the heating loss content in water and cationic electrodeposition coating in the range of 2-4 minutes, but you characterized by being provided at least by means. 2. An automobile coating process, which comprises a step of heat-flowing the electrodeposition coating after the electrodeposition coating of the cationic electrodeposition coating, a step of removing moisture and a heating loss in the cationic electrodeposition coating, and subsequently. A method for forming a coating film, which comprises coating a ceiling, a stone guard coat, an undercoat, and setting an insulator, then applying an intermediate paint, baking at one time, applying a topcoat paint, and baking. 3. An automobile coating process, comprising a step of heat-flowing the electrodeposition coating film after the electrodeposition coating of the cationic electrodeposition coating material, a step of removing moisture and a heating loss in the cationic electrodeposition coating material, and subsequently. After applying the intermediate coating, baking at once, then applying the sealing, stone guard coat, and undercoat, and setting the insulator, then applying the top coating and baking. Method. Wherein the intermediate coating is solvent-based, according to any one of claims 1 to 3, characterized in that at least one comprising selected from the group consisting of aqueous and powder systems paints Coating film forming method. 5. The topcoat paint is at least one kind selected from the group consisting of solvent-based paints, water-based paints and powder-based paints, according to any one of claims 2 to 4 . Coating film forming method. Heating means 6. A electrodeposition coating in the step of thermally flows, a coating film forming method according to any one of claims 1 to 5, characterized in that a hot air blowing. 7. The method of claim 1 in which the infrared heating means, and feature to be a means using infrared in the near to mid infrared ray region
The method of forming a coating film according to any one of items 1 to 5 .