JPS609874B2 - Automotive repair painting method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for repair painting an automobile body.

Repair painting of automobile bodies involves preparing the surface of the repaired area and its surroundings, polishing the old paint film, correcting distortions, degreasing, applying putty,
A method is used in which a top coat is applied after previous paint film treatments such as polishing, primer surfacer painting, and polishing and base treatment.

Traditionally, metallic and solid color paints have been used as top coats. However, since the polishing process is usually performed using sandpaper, the metallic paint flows into the vapor scratched area from the repair painting area and spreads along the paper scratches, resulting in a phenomenon where the top coat color is not lost. There was a drawback that the finish of the interface between the two surfaces was poor. For this reason, measures have been taken to apply metallic paint not only to the repaired area but also around the repaired area, or to apply lacquer clear or two-component urethane clear paint before applying the metallic paint. However, if you apply metallic paint to the area around the repaired area, that amount of metallic paint will be wasted.
On the other hand, when a lacquer clear paint is applied before applying a repair coat to a metallic paint, there is a drawback in that the base coat is dissolved and swelled by the strong solvent in the paint, resulting in a sagging phenomenon.

In addition, when using a two-component urethane clear paint, drying is slow with conventional two-component urethane clear paint, and if metallic paint is applied on a clear coat that has not dried sufficiently, metal migration is likely to occur, causing metal unevenness. Therefore, there was a problem in terms of painting workability that the interval between applying the metallic paint had to be long. Furthermore, even when a solid color paint is used as a top coat, the paint smudges and builds up on the paper scratches as described above, making it impossible to obtain a glossy paint film.Therefore, it is necessary to increase the number of coats of the top coat. There were some drawbacks. In view of the prior art as described above, the present invention has been developed to provide an automotive refinishing method for obtaining a uniform, high-gloss refinishing paint film that is free from poor paint finish appearance due to metal flow and loss of gloss due to paint smearing and inclusions. The purpose is to provide the following.

That is, in the present invention, after the old paint film treatment and base treatment, the entire surface of the repaired area and the periphery of the repaired area is covered with (a) Styrene...20-4
5% by weight {b) Hydroxy group-containing acrylic monomer...
...10-25% by weight {c} Acrylic acid ester, methacrylic acid ester, maleic acid monoester, maleic acid ester, fumaric acid monoester or fumaric acid gester (however, the ester contains an alkyl group having 1 to 4 carbon atoms) )...acrylic polyol resin with a number average molecular weight of 5,000 to 50,000 consisting of 30 to 55% by weight, and a hexamethylene diisocyanate conductor and an isophorone diisocyanate derivative in a weight ratio of 50/50 to 50
10/90, and the ratio of the isocyanate groups of the polyisocyanate compound to the hydroxyl groups of the acrylic polyol resin is in the range of NCO group number/OH group number = 0.6 to 1.5. Apply a urethane clear paint made by dissolving 10% to 9% by weight in an organic solvent, and after drying the paint to the touch at least, apply a two-component urethane enamel paint over the entire surface of the repaired area,
The present invention then relates to an automobile refinish painting method, which is characterized by drying.

In the present invention, after treating the old paint film and surface treatment, and before applying the two-component urethane enamel paint, apply a urethane clear paint that dries quickly even in low temperatures such as winter, not only on the repaired area but also on the repaired area. By painting the periphery as well, an excellent repair coating as described above can be obtained.

In other words, since the far-drying urethane clear paint is also applied around the repaired area, paper scratches are covered, and a paint film that is dry to the touch can be obtained in just a few minutes even at low temperatures. Enamel paint can be applied over and over again in a short time, which not only improves painting workability, but also has the advantage of preventing dirt and dust from adhering to the painted surface. The urethane clear paint used in the present invention contains an acrylic polyol resin, a polyisocyanate compound, and an organic solvent as main components. The acrylic polyol resin is composed of [a' styrene, 'b) a hydroxy group-containing acrylic monomer, and {c-acrylic acid ester, methacrylic acid ester, maleic acid mono- or diester, or fumaric acid mono- or gestal (however, the ester has a carbon number It is a copolymer synthesized from (containing 1 to 4 achyl groups) by a conventional solution polymerization method using a polymerization initiator and an organic solvent.

The acrylic polyol resin has a number average molecular weight of 5000~
50,000 is suitable; if the molecular weight is too low, the film resistance will be poor, and if it is too high, the coating workability will be poor, so neither is preferable. The {a} component used in the production of the acrylic polyol resin is suitably 20 to 45% by weight.

If it is less than 2% by weight, the hardness of the coating film will not be obtained, and the drying properties and water resistance will be poor, while if it exceeds 45% by weight, the film resistance will be poor.

In addition, a suitable amount of component {b) is 10 to 25% by weight.

If the amount is less than 1% by weight, the curing properties of the coating film will be insufficient;
On the other hand, if it exceeds 25% by weight, the viscosity of the resin increases.

In addition, {b} component is 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, N-methylolacrylamide. , N-methylolmethacrylamide, allyl alcohol and the like are three representative examples. Also, {c) component is 30
~5% by weight is suitable.

If it is less than 3% by weight, the resin will become hard and its physical properties will deteriorate;
On the other hand, if it exceeds 55% by weight, the resin becomes soft and the coating performance and drying properties deteriorate.

It is appropriate that the ester of component (c) contains an alkyl group having 4 or less carbon atoms, and if the alkyl group has 5 or more carbon atoms, delamination is likely to occur, which is not preferable. The polyisocyanate compound is composed of a hexamethylene diisocyanate derivative and an isophorone diisocyanate derivative. In the present invention, both of the above polyisocyanate compounds act as crosslinking agents for the acrylic polyol resin.

However, acrylic urethane resin compositions using only hexamethylene diisocyanate derivatives as a crosslinking agent have a slow curing speed at low temperatures but are slow to dry to the touch; The acrylic urethane resin composition used as a crosslinking agent has the disadvantage that it dries quickly to the touch, but has a slow curing speed.
However, by using a crosslinking agent in which both are mixed in a specific quantitative ratio as described below, only the advantages of both can be brought to light.
The hexamethylene diisocyanate derivative in the present invention is a biuret bond product and a polyol adduct of hexamethylene diisocyanate, and the isophorone diisocyanate derivative is a polyol adduct of isophorone diisocyanate.

The above polyols include ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,6
- Dihydric alcohols such as hexanediol, diethylene glycol, dipropylene glycol, neobentyl glycol, triethylene glycol, hydrogenated peacephenol A, bisphenol dihydroxypropyl ether, glycerin, trimethylolethane, trimethylolpropane, etc. Examples include hydrohydric alcohols and tetrahydric alcohols such as pentaerythritol and diventaerythritol.

These diisocyanate derivatives are obtained as a mixture of compounds having two or more isocyanate groups in the molecule, but in the present invention, the NCO% of the mixture (parts by weight of NCO groups in 10 parts by weight of the diisocyanate derivative compound) 10 to 30%.

If the NCO% is less than 10%, fewer urethane bonds are formed and a film with sufficient hardness, solvent resistance, etc. cannot be obtained. Also, those with an NCO% of more than 30% have a high content of non-conductorized isocyanate monomer and generate toxic monomer vapor, so they cannot be used. The hexamethylene diisocyanate derivative and the isophorone diisocyanate derivative are mixed in a weight ratio of 50/50 to 10/90. If the amount of hexamethylene diisocyanate is greater than this range, the dryness to the touch will be slowed down, and conversely, if the amount of isophorone diisocyanate derivative is increased, the curing rate will be slowed down. Particularly preferred is a range of 40/60 to 20 to 80. The above polyisocyanate compound and acrylic polyol resin have a ratio of isocyanate groups to hydroxyl groups of NCO
Mix within the range of base number/OH base number = 0.6 to 1.5.
If the amount of the polyisocyanate compound exceeds the above range, the initial drying time will be longer and the cost will be higher.
On the other hand, if the amount of acrylic polyol resin exceeds the above range, fewer urethane bonds will be formed and the coating film will not exhibit sufficient properties as a urethane resin.

In particular, it is preferable that the ratio of the number of functional groups is 0.8 to 1.2.

In the present invention, organic solvents for dissolving the polyisocyanate compound and acrylic polyol resin include ester solvents such as ethyl acetate, isobutyl acetate, and butyl acetate, and ether solvents such as ethylene glycol monoethyl ether acetate. Sterol solvents, aromatic solvents such as xylene, toluene, etc. can be used.

The combined concentration of polyj isocyanate compound and acrylic polyol resin in the solution is between 10 and 9% by weight.
If the above concentration is less than 1% by weight, a sufficient film thickness cannot be obtained, and if it is more than 9% by weight, the viscosity becomes high and coating workability decreases.

Additives such as an IJ agent, an anti-cissing agent, and an anti-settling agent may be added to the above-mentioned urethane clear paint, if necessary.

This urethane clear paint is used by mixing an acrylic polyol resin solution as a main ingredient and a polyisocyanate compound solution as a curing agent immediately before use. The urethane clear paint thus obtained is applied to the entire surface of the repaired area and around the repaired area using means such as air spraying, airless spraying, electrostatic spraying, etc. to a dry film thickness of about 3 to 50 mm. After the urethane clear paint film is at least dry to the touch, coat the entire surface of the repaired area and its surroundings with a two-component urethane enamel paint that is commonly used for automotive repair.

The two-component urethane enamel paint contains a polyol resin, a polyisocyanate compound, a colored pigment and/or metallic powder, and an organic solvent as main components.

Examples of the polyol resin include the aforementioned acrylic polyol resin, polyester polyol resin, and acrylic modified polyester polyol resin.

Furthermore, non-yellowing polyisocyanate compounds are suitable as the polyisocyanate compound. Specific examples include the aforementioned hexamethylene diisocyanate derivatives and isophorone diisocyanate derivatives, which may be used alone or in combination. The ratio of the isocyanate groups of the polyisocyanate compound which is a curing example and the hydroxyl group of the polyol resin which is the main ingredient is the number of NCO groups to the number of OH groups = 0.5 to 1.
．． Within the range of 5, the curing agent and main agent are mixed immediately before use.

The above colored pigments include titanium oxide, carbon black,
Red iron, yellow lead, navy blue, ultramarine, etc. can be used, and these are suitably in the range of 4 to 9% by weight based on the solid content of the resin.
In addition, aluminum powder, copper powder, mica powder, etc. can be used as metallic powder, and these powders have a ratio of 1 to 1
A range of 6% by weight is suitable. The above-mentioned two-component urethane enamel paint is further added with additives such as ultraviolet absorbers, leveling agents, anti-cissing agents, and anti-settling agents as necessary, and dissolved in the above-mentioned organic solvents to improve coating strength. 20
~6% by weight.

This two-component urethane enamel paint is applied by the above-mentioned coating means. In the case of a solid color finish using a two-component urethane enamel paint containing colored pigments, apply a thin layer of paint to the repaired area in several coats, then gradually expand the area to ensure that the repaired area and topcoat color are not lost. It is desirable to paint around the repaired area while filling in the boundaries of the paint film (old paint film) to blur the boundaries.

Further, if necessary, a paint obtained by mixing the two-component urethane enamel paint with a two-component urethane clear paint or a two-component urethane clear paint can be applied thereon. Also, metallic finishes using two-component urethane enamel paints containing metallic powder are applied in the same manner as solid color finishes, but after this is applied, a wet-on-wet two-component urethane clear paint is applied. It is preferable to apply a wet-on-wet mixture of a two-component urethane clear paint and a metallic paint, and then apply a wet-on-wet two-component urethane clear paint.

The dry film thickness of these top coat paints is suitably 10 to 100 degrees. The present invention will be explained below with reference to Examples.

Note that "parts" and "%" are expressed on a weight basis.

<Production of acrylic polyol resin solution {a}> From the ratio of styrene, 2-hydroxyethyl methacrylate and butyl acrylate (35:20:45) in a mixed organic solvent of xylene/butyl acetate (1:1) A mixed monomer of
0% solution 'a] was prepared.

<Production of acrylic polyol resin solution (b)> A mixture of styrene, 2-hydroxyethyl methacrylate and butyl acrylate in a ratio of (55:20:25) was prepared in the same manner with a number average molecular weight of 3000 and a hydroxyl value. (solid content) 50% solution of 100 acrylic polyol resin (
b} was prepared.

<Production of acrylic polyol resin solution {c}> From a monomer mixture consisting of styrene, 2-hydroxyethyl methacrylate and monobutyl fumarate in a ratio of (40:20:40), a number average molecular weight of 8000 and a hydroxyl value are prepared in the same machine. A 50% solution {b} of an acrylic polyol resin (solid content) of 100 was prepared.

<Production of acrylic polyol resin solution (d)> In the same manner, from a mixed monomer consisting of styrene, hydroxypropyl acrylate, and dibutyl maleate in a ratio of (35:20:45), a number average molecular weight of 13,000 and a hydroxyl value (
A 50% solution 'd} of an acrylic polyol resin with a solid content of 100 was prepared. Production of paint base agent example> Acrylic polyol resin solution [Acrydic A-80
1 (trade name manufactured by Dainippon Ink Chemical Industry Co., Ltd.): number average molecular weight 16,600, hydroxyl value (solid content) 100, 50% xylene solution] 7 anchors, 3 titanium oxides, and 0 staining agents
．． Five parts were kneaded in a roll mill to prepare a base paint base.

<Production of paint main ingredient [B]> Acrylic polyol resin solution [Hitaroid 3018 (trade name, manufactured by Hitachi Chemical Co., Ltd.): number average molecular weight 30,000, hydroxyl value (solid content) 50, 50
% toluene/butyl acetate mixed solution], 0.5 parts of a suspending agent, 10 parts of non-leafing type aluminum pigment paste, 5 parts of xylene, and 5 parts of butyl acetate were mixed uniformly to form the paint main ingredient [B-]. Prepared.

<Manufacture of paint base 'C}> Acrylic polyol resin solution [Acrydic A-85
1 (trade name manufactured by Dainippon Ink Chemical Industries, Ltd.): hydroxyl value (solution content) 7 or more 70% butyl acetate solution] 75 parts, xylene 1
2.5 parts and 12.5 parts of butyl acetate were uniformly mixed to prepare a paint base 'C}.

<Manufacture of paint pans> Acrylic resin solution [Acrylic A
-135 (trade name manufactured by Dainippon Ink Chemical Industries, Ltd.)] 78.
3 parts, 1/4 second nitrocellulose (30% isopropyl alcohol wet) 16.1 parts, dibutyl phthalate 5
．． Clear lacquer paint {D
} was prepared.

<Production of polyisocyanate compound solution A> Hexamethylene diisocyanate derivative (NCO% 16.7) 7
7 parts of a 5% ethyl acetate solution [Burnock DN950 (trade name, manufactured by Dainippon Ink & Chemicals), a polyol adduct mainly composed of trimethylolpropane] was mixed with 11 parts of toluene and 1 part of ethyl acetate to form a polyisocyanate compound. Solution A was prepared.

<Polyisocyanate compound solution port> Isophorone diisocyanate derivative (NCO% 13.4
) 67% ethylene glycol monoethyl ether acetate/xylene (equal weight mixture) solution [Dismodur L2267 (product name manufactured by Bayer AG), polyol adduct mainly composed of trimethylolpropane] Table 1
Urethane clear paint Note: A mixed solvent consisting of 50 parts of xylene, 35 parts of butyl acetate, and 15 parts of ethylene glycol monoethyl ether acetate is used to reduce the viscosity.

#2) Adjusted. Table 2 Urethane enamel paint Note 2) Viscosity adjusted with the same mixed solvent as in Table 1 Note 1).

Examples and Comparative Examples The damaged parts of automobile door panels and their surrounding areas were prepared using the usual methods, applied with poly putty, painted with primer surfacer, and polished with #280 sandpaper as shown in Table 1. Apply the paint to the damaged area and its surroundings by air spraying to a dry film thickness of approximately 15cm, and
After 0 minutes (2000), paint No. 2 in Table-2 was applied. 7 and 8 were painted with air spray.

In addition, the paint base. 7 and no. The dry film thickness of 8 is 3
I painted it so that there were 0 mountains and 15 mountains. In addition, paint No.
8 is used as wet-on-wet paint No.
．． 9 was overcoated to a dry film thickness of about 30 mm. The above coating system and coating performance results are shown in Table 3.

Table-3 Note 3) 20 minutes after applying clear undercoat (20℃)
, press firmly with finger pressure and judge how much index remains Note 4) Apply the top coat and visually judge the appearance of the paint film such as metal unevenness, gloss, and wrinkles after drying Note 5) Sunshine Weather - 2 The appearance of the paint film after ,000 hours was visually judged. ◎:
Very good ○: Good △: Slightly poor ×: Poor As is clear from Table 3, in Comparative Example 1, in which only the hexamethylene diisocyanate derivative was used as a curing agent for the acrylic polyol resin, the drying property and coating condition were poor. Comparative Example 2, which used an acrylic polyol resin with a high styrene content, had poor drying properties, poor coating surface condition, and poor weather resistance, while Comparative Example 3, which used a conventional acrylic lacquer as an undercoat, had poor coating surface condition, weather resistance, and Comparative 4, which did not use an undercoat, had poor coating surface condition and gloss, but Examples 1 to 3 of the present invention had even better properties.

Claims (1)

[Claims] 1. In an automobile repair painting method, after old paint film treatment and base treatment, the entire surface of the repaired area and the periphery of the repaired area is coated with (a) styrene...20 to 45% by weight (b) hydroxy group-containing acrylic System monomer...10~
25% by weight, and (c) acrylic acid ester, methacrylic acid ester, maleic acid monoester, maleic acid diester, fumaric acid monoester, or fumaric acid diester (however, the ester contains an alkyl group having 1 to 4 carbon atoms)... ...acrylic polyol resin with a number average molecular weight of 5,000 to 50,000 consisting of 30 to 55% by weight, and a hexamethylene diisocyanate derivative and an isophorone diisocyanate derivative in a weight ratio of 50/50 to 10/~
90, and the ratio of the isocyanate groups of the polyisocyanate compound to the hydroxyl groups of the acrylic polyol resin is the number of NCO groups/O
A urethane clear paint prepared by dissolving a urethane resin-forming component having an H radical number in the range of 0.6 to 1.5 in an organic solvent at a concentration of 10 to 90% by weight was applied, and the paint was allowed to dry at least to the touch. An automobile repair painting method characterized by applying two-component urethane enamel paint over the entire surface of the repaired area and then drying it.