JP2002282778A - Method of repairing film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a repairing method to easily grind a hard or soft film, which is suitable especially for a scuffing and wear resistant film. SOLUTION: In the hard film, the grinding work is carried out after hot air is blown to change the film hardness and in the soft film, the grinding work is carried out after cold air is blown to change the film hardness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for repairing a coating film, and more particularly to a method for repairing a hard or soft coating film, which is particularly suitable for a scratch-resistant coating film.

[0002]

2. Description of the Related Art Automobile bodies and parts are finished by providing a clear coating layer on a glittering coating layer containing a metallic pigment or a mica pigment or a colored coating layer containing a coloring pigment. There are many. In the process of a coating line such as a car body that forms such a coating film, if fiber dust etc. are mixed into the clear coating film that is the outermost layer and coating defects such as lumps occur, polishing and repair of that portion, if necessary Need to be painted and repaired. Conventionally, such a portion is polished and repaired by the following steps. First, a step of removing buttocks with a knife or the like, or polishing with a grindstone (a polishing agent containing about 10 μm of silicon carbide in polyvinyl alcohol / melamine resin) added with a lubricant, and then removing the buttocks. A process of polishing a grindstone mark or the like with a polishing cloth such as a towel buff driven by a rotary sander and using a coarse abrasive containing abrasive grains such as silicon carbide of 6 to 7 μm, and finally a sponge buff driven by a rotary sander Using a fine polishing agent containing abrasive grains such as silicon carbide having a thickness of 3 to 4 μm, the polishing cloth is polished to a smooth finish, and the repair is completed.

In recent years, as a clear coating film to be the outermost layer,
A very hard or soft coating film with abrasion resistance is being adopted, and if the above-mentioned polishing process is applied to repair it, it takes more than twice as long as the conventional method and the workability is reduced. was there.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the hardness of the coating film is changed by heating or cooling the coating film in the portion to be repaired. It has been found that repairing can be completed without increasing the working time even in the conventional polishing work by setting the coating film hardness, and the present invention has been completed.

That is, the present invention provides a method for repairing a coating film, which comprises blowing hot air onto a hard coating film to change the hardness of the coating film, and then performing a polishing operation. The present invention provides a method for repairing a coating film, which comprises performing a polishing operation after spraying to change the coating film hardness.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a hard coating usually has a two-cone hardness of 11 or more, preferably 12 or more, and more preferably 13 or more.
The two-cone hardness is 7 or less, preferably 6 or less, and more preferably 5 or less. Here, the two-cone hardness is 20 ° C.
, A needle having a rhombus-shaped tip (a quadrangular pyramid-shaped tip) is pressed against the surface of a coating film to be measured under conditions of a load of 25 gf and a speed of 20 sec / μm to remove a flaw (diamond) formed by the needle. It measures the length of the longer diagonal and is a numerical value represented by an index that is inversely proportional to that length.
Therefore, the harder the steel, the harder it is to be damaged, and the higher the two-cone hardness.

As the hard coating film, for example, an acid anhydride group is hardened.
A carboxyl group, an epoxy group, a hydroxyl group and an alkoxysilyl group, which have been esterified, a paint containing a resin composition containing the same molecule or separately in a vehicle component as a vehicle component, or a compounding ratio of a curing agent to a base resin is increased. A coating film formed by using a paint obtained by a method such as increasing the pigment content or further increasing the amount of crosslinkable functional groups to increase the number of crosslinking points can be exemplified. As the soft coating, for example, polyester resin,
The mixing ratio of a curing agent such as melamine to a base resin such as an acrylic resin or a urethane resin may be reduced, or an aliphatic polyhydric alcohol such as hexanediol or adipic acid may be used as a polyester resin for the base resin. Use a paint obtained by a method such as using a basic acid, using an aliphatic acrylate as an acrylic resin or modifying with a lactone, or reducing the number of crosslinkable points by reducing the amount of crosslinkable functional groups. Can be exemplified.

[0008] In the present invention, hot air is blown on the hard coating film,
After the hardness of the coating film is changed, or the soft coating film is blown with cold air to change the hardness of the coating film, a polishing operation is performed.

Heating or cooling of the coating film is performed by blowing air to the portion to be repaired for a predetermined time using, for example, a hot air / cold air generator. The temperature of hot air / cold air and the time of blowing the air are appropriately selected depending on the material / hardness of the coating film in the portion to be repaired, the heat capacity of the object to be coated, and the like. It is preferable to measure the change in the hardness of the coating with respect to the change in the temperature of the coating due to heating and cooling, depending on the material (hard or soft) of the coating in the portion to be repaired. In addition, it is desirable that the temperature of the hot air and the cold air and the time of the air blowing be appropriately selected so that the coating hardness of the repair target portion is usually within the range of the two-cone hardness of 7 to 11, preferably 8 to 10. .

[0010] The polishing operation of the present invention as described above is performed in a polishing step in a normal coating line, that is, by cutting off lumps with a knife or the like, or using a grindstone (for example, about 10 μm in polyvinyl alcohol / melamine resin).
Polishing process using a polishing agent with a lubricant added to silicon carbide, etc.) to remove bumps, etc., with a polishing cloth such as a towel buff driven by a rotary sander, and polishing of 6-7 μm silicon carbide etc. Using a coarse abrasive containing grains, a step of polishing a whetstone mark or the like, using a polishing cloth such as a sponge buff driven by a rotary sander, using a fine abrasive containing abrasive grains such as 3 to 4 μm of silicon carbide. The step of polishing and smoothing the grinds with the polishing cloth. The heating or cooling of the coating film is desirably performed before or in parallel with these operations, whereby the operation time of each step can be reduced, and the surface roughness of the polished surface after polishing is also reduced. It is possible to reduce the working time of the next step.

[0011]

According to the method of the present invention, the hardness of the coating film is changed by heating or cooling the coating film in the portion to be repaired,
By setting the coating film hardness to the same level as before, the polishing operation can be performed without increasing the operation time even in the conventional polishing operation, and the polishing time can be reduced even for hard or soft coating films such as scratch-resistant films. The performance is improved. Therefore, the present invention can be applied not only to spot repair in a coating line but also to skin adjustment and glossing in general repair painting.

[0012]

The present invention will be described in more detail with reference to the following examples.

Example 1 An acrylic resin-based base coat ("Magical Black", manufactured by Kansai Paint Co., Ltd.) was dried on a coated plate on which a chemical conversion treated steel plate (thickness: 0.35 mm) was subjected to electrodeposition coating and intermediate coating. It is applied to a thickness of 15 μm, and then an acrylic resin clear coat (manufactured by Kansai Paint Co.) is applied to a dry thickness of 40 μm, and both coating films are baked and dried at 140 ° C. for 30 minutes. A test coated plate was prepared. The two-cone hardness of this clear coat layer is measured using an ultra-micro hardness tester “M
XT-70UL type ”(manufactured by Matsuzawa Seiki Co., Ltd.) at 20 ° C.
30 RH%, needle load 25 gf, speed 20 sec / μ
It was 13.9 when measured under the condition of m. The 20-degree gloss of this test plate was 83.7, and the surface roughness (R
a) was 0.016 μm. This Ra is a surface roughness profile measuring device "Surfcom 130A" (Tokyo Seimitsu Co., Ltd.)
It was measured according to.

While blowing hot air at 50 ° C. on the test coated plate, the bumps (projections having a height of about 3 μm) of the coated surface of the test coated plate are firstly removed with a grindstone (approximately 10 μm in a polyvinyl alcohol / melamine resin). Polishing "Super Cleaner" (a lubricating agent for shoes made by Columbus Co., Ltd.) on an abrasive containing silicon carbide and the like to remove bumps (process), and then about 6 μm
Using a polishing agent using silicon carbide as abrasive grains and a towel buff as a polishing cloth, the rotating sander is rotated at 1500 rpm.
-It was driven with a pressing load of 3.0 kgf to grind the grind in the previous process (process). Further, a sponge buff is made into a polishing cloth using a fine abrasive having silicon carbide of 3 to 4 μm as abrasive grains, and a rotary sander is driven at a rotation speed of 1000 rpm and a pressing load of 2.0 kgf to polish the abrasive in the previous process. , And finished smoothly as a glossing process (process). The time required for these three steps is: // is 10/60/1
It was a total of 80 seconds at 0 seconds. R of the polished surface after another process
a was 0.027 μm.

Example 2 and Comparative Examples 1 and 2 A polishing operation was performed in the same manner as in Example 1 except that the material of the clear coat, the presence / absence of air flow during the polishing operation and the air temperature were as shown in Table 1. Did. The required time for each operation and Ra of the polished surface are shown in the same table. If there is no blast, 20
Indicates that the work was performed in an atmosphere of ° C.

From the results of Examples and Comparative Examples shown in Table 1,
Polishing work with hard or soft coatings as it is takes time and also reduces the finish after polishing.However, by heating or cooling these coatings, the coating hardness is changed, and it is the same as before. By setting the coating film hardness to, the polishing operation could be performed without increasing the operation time in the conventional polishing operation.

Further, as a clear coat of the test coated plate, a test coated plate was prepared using a paint (acrylic resin clear, manufactured by Kansai Paint Co., Ltd.) having a normal coating hardness of 20.degree. Assuming that the standard test plate (Comparative Example 3) is polished by the above steps (1) to (3), the time required for these three steps in a 20 ° C. atmosphere is 10/30/10 seconds, for a total of 50 seconds. Since the Ra of the polished surface later was 0.021 μm, it was confirmed that the means for varying the coating film hardness was effective.

[0018]

[Table 1]

Claims (4)

[Claims] 1. A method for repairing a coating film, comprising blowing hot air onto the hard coating film to change the hardness of the coating film and then performing a polishing operation. 2. A method for repairing a coating film, comprising blowing cold air onto a soft coating film to change the hardness of the coating film and then performing a polishing operation. 3. The method according to claim 1, wherein the hard coating has a two-cone hardness of 11 or more. 4. The method for repairing a coating film according to claim 1, wherein the soft coating film has a two-cone hardness of 7 or less.