JPS5969178A - Coating method of car body of automobile - Google Patents

Abstract

PURPOSE:To prevent stone-chipping, by applying a prescribed painting material between intermediate coating and finish coating, with respect to a part which is apt to be subjected to the stone chipping caused by a fact that a pebble, etc. hit against a car body of an automobile and damage it. CONSTITUTION:A foundation coating film and an intermediate coating film are formed on an automobile car body. Subsequently, a coating film of an oil free alkyd resin compound painting material, which has the same color as the finish coating film or an approximate color, and by which a glass transition temperature of the coating film is 15-50 deg.C is formed on a part which is apt to be subjected to stone-chipping, such as a hood tip part of the car body, a tire house circumferential part, etc. As for said painting material, a binder component consisting of oil free alkyd resin and amino aldehyde resin, and a pigment are necessary components. Subsequently, in the end, the finish coating film is formed. In this way, stone-chipping is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention prevents the paint film applied to the surface of an automobile body from being damaged by flying collisions with pebbles, gravel, rock salt, frozen snow, etc. while the automobile is running. The present invention relates to a method for painting an automobile body, which makes it possible to maintain the beauty of the exterior appearance of the vehicle body without making the damaged part noticeable even when the body is damaged.

By the way, the painting of automobile bodies is generally carried out by the following steps: undercoating - (baking) - intermediate coating - (baking) - topcoat - (baking).

The top coat film is composed of various solid colors or metallic colors, but the base coat film and intermediate coat film are painted in a single color such as gray thread or rust color.

Conventionally, in order to prevent the paint film from being damaged by stones thrown up by wheels while driving (i.e., stone chipping), stone chipping primers, rockers, etc. were used.
The method used was to apply a gunner primer. These stone chipping primers or lonocano? The flannel primer prevents scratches from reaching the base steel plate of the car body, and is intended to further prevent the formation of rust.

However, there are many cases where pebbles, etc. collide with the paint film at a shallow angle, causing scratches between the intermediate and top coats (i.e., cracks). This is not a problem, but because the colors of the intermediate and top coats are different, the scars are noticeable, making the car body look very unsightly, and resulting in a significant drop in product value.

As mentioned above, the Sl-7 chimping primer or rocker panel primer has been shown to be effective as a measure to prevent scratches that reach the base material, but it is not effective as a measure to maintain the aesthetic appearance of the car body caused by the peeling phenomenon. I couldn't say it was enough.

The present inventors have overcome the drawbacks of the prior art described above, discovered a coating method that has good peeling resistance, and is also capable of maintaining the aesthetic appearance of the vehicle body even if peeling occurs, and has developed the present invention. It has been completed.

That is, the present invention provides a method for painting an automobile body in which a base coat film is formed on the car body, an intermediate coat film is formed, and a top coat film is further formed on the car body. The color between the intermediate coat film and the top coat film is the same or similar to that of the top coat film, and the resulting paint film has a glass transition temperature of 15 to SOC.
(a) a binder component consisting of an oil-free alkyd resin, a (bl amino aldehyde 1) resin, and (C
1) A method for painting an automobile body characterized by forming an oil-free alkyd resin paint film containing a pigment as an essential component.

The oil-free alkyd resin paint used in the present invention includes (a) oil-free alkyd resin and (1))
A binder component consisting of aminoaldehyde resin and (C)
Pigment is an essential ingredient.

The oil-free alkyd resin can be produced by any known method. Examples include neotakutin glycol, ethylene glycol, hexanodiol, diethylene glycol, propylene glycol, nopropylene glycol, pentanol, trimethyl tannediol, trimethylol prono'P, glycerin, interaerythritol, cyclohexane dimetatool. Polyhydric alcohols such as phthalic acid, isophthalic acid, terephthalic acid, asopic acid, sepacic acid, itaconic acid,
It can be produced by linear polymerization reaction with a polybasic acid such as azelaic acid or maleic acid, generally at a temperature of from /gO to 2SOC for about S to 72 hours.

In order to make the glass transition temperature of the oil-free alkyd resin paint film 75 to 50°C, at least a portion of the polyhydric alcohol should be a dihydric alcohol, and at least a portion of the polybasic acid should be a dihydric alcohol. It can be obtained by partially using an aliphatic dibasic acid.

In addition, oil-free alkyd resin has an acid value of 10 or less and a hydroxyl value of 700 or more. 200, number average molecular weight 2.000~B,
The reaction conditions are adjusted so that θ00 is achieved. If the acid value exceeds 70, the paint tends to thicken, becoming less stable, and also tends to cause wrinkles when applied wet-on-wet on an intermediate coat, which is undesirable. Also, the hydroxyl value is 7
If it is less than 00, the adhesion of the coating film will be poor;
If it exceeds 0, the water resistance etc. of the coating film will deteriorate, so both are not preferred. Further, if the number average molecular weight is less than 2.000, the coating film becomes brittle, while if it exceeds 6,000, the coating workability deteriorates, so both are not preferred.

Furthermore, aminoaldehyde resin can be used as a crosslinking agent for the oil-free alkyd resin.

Typical examples of the aminoaldehyde resin include melamine formaldehyde resin, urea formaldehyde resin, and benozoguanamine formaldehyde resin.

Further, as the crosslinking agent, a part of the aminoaldehyde resin may be replaced with a blocked isocyanate compound. The blocked isocyanate compounds include trilenonoisocyanate-1, metaphenylenediisonane-1-, quinrylenenoisocyanate, -\xamethylenenoinoisocyanate, isophoronenoisocyanate, nocyclohequinylmethane diiso/anate, etc. In the incyanate group of aromatic, aliphatic or alicyclic polyisonanates or adducts of these polyisonanates and polyhydric alcohols, lactams such as caprolactam, monoalcohols, oximes such as methyl ethyl ketoquine, etc. Free incyanate groups are eliminated by reacting with a blocking agent.

Further, as the pigment, it is possible to use a pigment that is usually used for automobiles and has the same color or a color similar to that of the top coat, but it is particularly preferable to use a pigment that is the same as the top coat.

The weight ratio (in terms of solid content) of the oil-free alkyd resin, crosslinking agent, and pigment is usually 10θ:, 20~5:
ri~55 is a suitable drawing.

Other components constituting the oil-free alkyd resin paint used in the present invention include hydrocarbons such as xylene and trubet naphtha, alcohols such as methyl alcohol and butyl alcohol, and ketones such as methyl isobutyl keto 7. organic bath agents such as esters, ethers such as ethyl acetate and ethylene glycol motubutyl ether; extender pigments such as clay, carbonate, talc, silica, alumina, leveling agents, anti-sagging agents, surfactants, and ultraviolet absorbers. Various auxiliary agents such as agents can be added as necessary.

The oil-free alkyd resin paint used in the present invention has a glass transition temperature of 75 to 5 when formed into a coating film.
A temperature of 0°C is required.

If the glass transition temperature exceeds 50°C, the effect of mitigating the destructive force when struck by pebbles, etc. will be reduced, resulting in poor peeling resistance, while if it is below 15°C, water resistance and moisture resistance will not only deteriorate. Both of these are undesirable because they tend to cause the shear star phenomenon.

In addition, although an oil-free alkyd resin paint is used in the present invention, if an oil-modified alkyd resin paint is used instead, the paint film will be inferior in weather resistance, so replacing the top coat will not sufficiently block sunlight. Otherwise, the coating film will deteriorate due to sunlight reaching the lower layer, reducing the adhesion between the surface coatings and easily causing defects such as blistering and delamination.

On the other hand, since the oil-free alkyd resin paint has excellent weather resistance, there is almost no risk of causing the above-mentioned defects.

Next, the coating method will be explained.

The means for forming an undercoat film on an automobile body, then forming an intermediate coat film, and further forming a top coat film can be performed in exactly the same manner as known methods. That is, a car body that has undergone chemical conversion treatment is coated by means such as electrodeposition coating or dipping coating, and baked to form an undercoat film of 75 to 2 Sμ in film thickness, and then coated with oil-free alkyd-aminoaldehyde resin paint or Epoquin. Apply an ester melamine resin paint or the like using air spray or airless spray paint and burn it out to form an intermediate coating film with a film thickness of about 25 to θμ, and then oil-free alkyd resin or acrylic resin solvent-based paint. Then, a water-based or powder type paint is applied by air spraying or airless spraying, and then baked to form a top coat film having a film thickness of 30 to qOμ.

It should be noted that the resin used for the intermediate coating should be the same as the resin used for the oil-free alkyd/resin-based paint that is coated on top of it in order to ensure good adhesion between the coatings and stonotisoping resistance. Particularly desirable from this point of view.

Further, the top coat may be either a solid color or a metallic color, but in the case of a metallic color, it is desirable to further layer a clear paint.

In the present invention, after the intermediate coating is applied and set, the oil-free alkyd resin thread paint is applied by air spray or airless spray only to areas that are susceptible to stone chipping, such as the tip of the hood, the area around the tires, etc. After painting and setting by means such as 0-ray,
The intermediate coat film and the oil-free alkyd resin paint film are baked at the same time, usually at 720-/gO<0>C for 75-30 minutes. Thereafter, a top coat film is formed by the above-mentioned known method.

Therefore, parts of the motor vehicle body that are susceptible to stone chipping require an additional process of painting with the oil-free alkyd resin paint and coating than other parts.

The film thickness of the oil-free alkyd resin paint film is suitably 75 to 30 microns; if it is less than 75 microns, the 4-peeling effect will be diminished, and if it exceeds 30 microns, the coating film is likely to sag or wrinkle.

As explained above, the coating film obtained by the coating method of the present invention has good peeling resistance, and the glass transition temperature of the oil-free alkyd resin paint film is lower than the glass transition temperature of the ordinary intermediate coating film (approximately 70 to 90 C) Because it is lower, it is especially effective in cold regions where the road surface is covered with a mixture of rock salt and gravel to prevent freezing. Furthermore, in the present invention, even if peeling occurs, an oil-free alkyd resin paint film of the same color or similar color is formed under the top coat, so the peeling phenomenon is not noticeable and the appearance of the car body is improved. It has the characteristic of being able to hold.

Next, the present invention will be explained in more detail with reference to Examples. In addition, in the examples, "part" and "section" are based on weight.

The following oil-free alkyd resin paints and intermediate coatings were used in Examples and Comparative Examples.

Oil-free alkyd resin paint pressure/) Paint A > Oil-free alkyd row) pal l varnish (solids content: 60) 60 parts Melamine resin varnish (solids content: 0)
%) i31 20 parts Benozimida/Ron series orange, 5- =++ Carbon black 0. Otobe iron oxide red
Yu, part 3
0゜lI part butyl cellosolve
9 parts xylene 7 parts surface conditioner 0.07 parts Note/)
The resulting coating film is a brown paint with a glass transition temperature of 75°C (measured with a vibro/viscoelasticity meter), 2+ polyhydric alcohol (neo-intyl alcohol, tol) methylol glonomano, ethylene glycol,
A resin 'PE3) synthesized from polybasic acids (phthalic acid, anopic acid) and a water resistance value/2g1 acid value S and an O1 number average force particle weight 2S0θ.Product name: Super Betsucamino L-//
7-60'' (manufactured by Nihon Ink Kago Kogyo Co., Ltd.) <Paint B> In the composition of paint A, the composition is the same except that the following Oil Ref IJ-alkyd resin is used, and the resulting coating film is Brown paint with a glass transition temperature of 115C.

Oil-free alkyd resin> Synthesized from polyhydric alcohols (neo-inthyl glycol, trimethylolprono-E7, 'l-rethanediol, ethylene glycol, benitaerythritol) and polybasic acids (phthalic acid, anopic acid) , hydroxyl value/25,
Resin with acid value S, 2, number average molecular weight 2S00 (Paint C) Same composition as Paint A except that the following oil-free alkyd resin is used, and the resulting coating film has a glass transition temperature of 23 °C plow/color paint.

<Oil-free alkyd <'FB fat> Polyhydric alcohol (neo-ethyl glycol, trimethylolpronogne, 1%-butanol, ethylene glycol,
K) and taerythritol) and polybasic acids (phthalic acid, anopic acid), hydroxyl value/20,
A resin with an acid value of 5° and a number average molecular weight of 3000 - <Paint D> The composition of paint A is the same except that the following oil-free alkyd resin is used, and the resulting coating film has a glass transition temperature g °C brown color paint.

<Oil-free alkyd resin> Synthesized from polyhydric alcohols (neo-inthyl glycol, trimethylolpropano, /'l-butanol, ethylene glycol) and poly[J acids (phthalic acid, adipic acid, sebacic acid), Hydroxyl value // Otsu, acid value Ge, 5,
A resin with a number average molecular weight of 2 goo (Paint E) In the composition for the paint, 52 parts of the same oil-free alkyd resin face used in Paint B, 15 parts of melamine resin varnish, and a block incyanate compound [trade name Takenate B- g, 2O-NS-U, Takeda Pharmaceutical Co., Ltd.]
A brown paint with the same composition except that all 73 parts were used, and the resulting coating film had a glass transition temperature of 3C.

Intermediate paint (Intermediate paint A) Oil-free alkyd resin varnish q)
qo, 5 parts melamine resin face (solid content O θ%)
73.5 parts titanium oxide 7
3Ω, 9 parts carbop rack 0.05
Part Gutil Cellosolve Q Part Kinren 9 Parts Shog) Oil-free alkyd used in the paint A (resin face used) <Intermediate paint B> Used in the paint B as an oil-free alkyd resin varnish in the intermediate paint A L 7j Oil-free The composition was the same except that an alkyd resin varnish was used.

Intermediate Paint C> Intermediate paint A had the same composition except that the oil-free alkyd resin varnish used in paint C was used as the oil-free alkyd resin varnish.

<Intermediate coating D> Intermediate coating A had the same composition except that the oil-free alkyd resin varnish used in the above coating was used as the oil-free alkyd resin varnish.

Example: A cationic electrodeposition paint [Emaguchi/cED'70HJ (trade name manufactured by Inu Nippon Toyo Co., Ltd.)] was electrodeposited on a zinc phosphate-treated steel plate, and baked at 7gO'cX for 20 minutes to reduce the dry film thickness. 20
A μ primer coating film was obtained. Then, apply intermediate paint B on top of it using air spray to a dry film thickness of 35μ, and after cenoting at room temperature for - minutes, apply paint B again using air spray to a dry film thickness of 20μ. After setting for λ minutes at room temperature/SO0, baking was performed for 20 minutes.

Next, a brown metallic paint [Akrose≠'7300J (trade name manufactured by Inu Nippon Toyo Co., Ltd.)] was applied on top of it using an air sprayer to a dry film thickness of 3Sμ.
After setting for 2 minutes at room temperature, apply clear paint ["Acrose 4'/100" (trade name, manufactured by Inu Nippon Toyo Co., Ltd.)] with air spray to a dry film thickness of 75μ, and then leave for 2 minutes at room temperature. After setting, it was baked for /Sac, 2θ minutes.

Example 3 Coating was carried out in the same manner as in Example 1, except that intermediate coat C was used instead of intermediate coat B, and paint C was used instead of paint B.

Example 3 Painting was carried out in the same manner as in Example/, except that paint E was used instead of paint B.

Comparative Example/Example/Coating was performed in the same manner as in Example/, except that intermediate coating paint A was used instead of intermediate coating paint B, and paint A was used instead of paint B.

Comparative Example: Coating was carried out in the same manner as in Example/, except that intermediate coating paint was used instead of intermediate coating paint B, and paint coating was used instead of paint B.

Comparative Example 3 Coating was carried out in the same manner as in Example except that the coating step of paint B was omitted.

The peeling resistance and blister resistance of the coating films obtained in Examples 7 to 3 and Comparative Examples 3 to 3 were tested, and the results are shown in Table 1.

＼ ＼ ＼ ＼ Table 1; Example: Comparative Example 1 Sho) A copper ingot with an air pressure of 7.3K97cm2t7) and a width angle of 2 was injected from a horizontally installed injection pipe with an inner diameter of 5 sides and a length of 90cm. , at a position 30 cm from the tip of the injection tube.
The scratches were examined by colliding with the painted steel plate, which was set at an angle of .

Evaluation criteria: ○: Very small scratches were made on the paint film, but the scratches were hardly noticeable.

Δ: Small scratches may occur on the paint film. The scratches are noticeable.

×...There are large scratches on the paint film, and The scratches are noticeable.

Sedge) 4tThe sedge was left in an atmosphere at 0°C for 0 hours, and the state of the painted surface was examined.

○: No abnormalities ×: Original blister on coated surface As is clear from Table 1, the coating film obtained by the method of the present invention had good peeling resistance and good blister resistance.

On the other hand, in Comparative Example 2, which used a paint with a high glass transition temperature, the peeling resistance was poor, and on the contrary, in Comparative Example 2, which used a paint with a low glass transition temperature, the blister resistance was poor.

Furthermore, in Comparative Example 3, in which no oil-free alkyd resin paint having a color similar to that of the top coat was applied, the peeling phenomenon was noticeable.

Showa year month [1 Director General of the Japan Patent Office 1 Display of case Showa Tough year patent application No. 09/03
No. 2 Title of the invention Method for painting automobile bodies 3 Relationship with the case of the person making the amendment Name of the applicant (332) Dainippon Toyo Co., Ltd. 4 Agent 5 Date of amendment order February 22, 1949 6 Target of amendment: Specification 7, Contents of amendment: As shown in the attached sheet, Table 1 Note 5) From an injection pipe with an inner diameter of 5 questions and a length of 0cm installed horizontally, /,! ; 1 at an air pressure of K9/cm2
．． A copper ingot of two angles was injected, and the state of the damage was examined by colliding with the above-mentioned painted wing plate, which was installed at an angle of 30 degrees at a position 1 cm from the tip of the injection tube.

Evaluation criteria: ○: Very small scratches were made on the paint film, but the hot water was hardly noticeable.

△・・・There are small scratches on the paint film. The scratches are noticeable.

×...There are large scratches on coating H. The scratches are noticeable.

'cEt, left in an atmosphere of +tio℃ for 290 hours,
The condition of the paint surface was examined.

O...No abnormality X...Blister helmet on painted surface

Claims (1)

[Claims] (1) In the car body painting method, which forms a base coat, then an intermediate coat, and then a top coat, stone chipping occurs at the tip of the hood, around the tire house, etc. Between the intermediate coat film and the top coat film in areas where it is easy to coat, the coating film has the same color or a similar color to the top coat film, and the glass transition temperature of the resulting paint film is 75 to 30C, (aJ oil-free alkyd resin and ( b) A method for painting an automobile body, which comprises forming an oil-free alkyd resin paint film containing a binder component consisting of an aminoaldehyde resin and (C) a pigment as essential components.