JPS61114780A - Method for painting outer panel part of automobile - Google Patents

Abstract

PURPOSE:To enhance the capacity of a paint film, by applying a barrier coat based on a modified polyolefin resin, which forms a film having static glass transition temp. of -30--60 deg.C, to the outer panel part of a car to which a cationic electrodeposition paint was applied. CONSTITUTION:A metal member, to which a cationic electrodeposition paint was applied, and a plastic member are assembled and united to form an automobile outer panel part. A barrier coat, in which a modified polyolefin resin (e.g., a propylene/ethylene copolymer) forming a film having static glass transition temp. of -30--60 deg.C is compounded as a main component, is applied to the outer panel part. Then, an alkyd resin and a polyester resin are applied to the barrier coat as an intermediate coat and an aminoacrylic resin paint is further applied as a top coat.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of painting an outer panel of an automobile formed by assembling a metal member and a plastic member.

Automobile bumpers, 7Asia, 7ENGU, door panels, and panels 7-, which until now were mostly made of metal materials.
In recent years, some or all of automobile exterior panels, such as panels, panel roofs, and panel trunk lids, are being replaced with plastic materials. For example, instead of metal, plastics such as polyurethane, polypropylene, and polycarbonate are used in the bumper and 7Asia, and only the lower parts of the 7Asia, door panels, etc. are replaced with the above plastics. In the future, it is inevitable that the range of plastics used in automobile exterior panels will further increase, and this trend can be seen in panel roofs, panel trunk lids, etc. By doing so, you can reduce the weight of the vehicle and reduce fuel consumption, it is easy to process and can be molded into any shape, and it improves the corrosion resistance and impact resistance of the vehicle body.
This is because it has been shown to have effects such as improving sexual performance.

However, despite this current situation, there is no established method for painting automobile exterior panels, which are made up of metal and plastic parts. After applying different types of paint that were suitable for each part on separate painting lines, both parts were assembled onto the exterior of the car. According to this method, since the paints used for both parts (particularly colored base coats) are different, it is extremely difficult to make the color tone of both parts the same when assembled and integrated. This has the disadvantage that the assembly process of parts is complicated.

Furthermore, in the field of automotive coatings, emphasis is being placed on the durability of coating films, particularly the reduction in corrosion resistance of coating films due to impact peeling and the progress of corrosion of steel materials.

In particular, in cold regions of Europe and America, gravel mixed with a large amount of relatively coarsely crushed rock salt is often laid down to prevent road surfaces from freezing during the winter, and vehicles driving on these types of roads are often covered with gravel mixed with large amounts of rock salt. Rock salt particles and pebbles thrown up by the wheels collide with the paint surface, and the impact often causes the paint film to peel off locally from the car body, so-called "chipping." Due to the phenomenon,
The metal surface of the impact area on the outer surface of the car body is exposed, and rust quickly develops and corrosion progresses. Paint peeling due to chipping usually occurs on the bottom of the car body and around the suspension, but it is also known to occur on the bottom and roof, and localized corrosion becomes quite noticeable after about six months to a year. ing.

In order to prevent this chipping and the progression of corrosion caused by it, various studies have been conducted on chemical conversion treatments on the surface of the external metal base of the car body, as well as electrodeposition primers, intermediate coats, and top coats. We have not yet found a suitable solution.

Therefore, in view of the second situation, the inventors of the present invention have realized that an automobile exterior panel made by assembling a metal part and a plastic part can be finished in the same color using a simplified process. They conducted extensive research into methods of forming coatings with excellent chipping resistance. the result,
After assembling and combining the metal member and the plastic member, the above defects are eliminated by coating both members with Barrier Two Y having a specific composition and properties, and then applying an intermediate coat and a top coat. Therefore, the object of the present invention was achieved.

That is, the present invention is a method for painting an automobile exterior panel formed by combining a metal member and a plastic member, in which the metal member and the plastic member, which have been previously coated with a cationic electrodeposition paint, are assembled and combined. After forming the outer panel, the static glass transition temperature of the formed coating film is -30 to
The present invention relates to a method for painting an exterior panel of an automobile, characterized in that a barrier foot containing a modified polyolefin resin as a main component at -60°C is coated, and then an intermediate coat and a top coat are coated.

A feature of the present invention is that when applying an intermediate coat paint and a top coat paint to an automobile exterior panel made by assembling metal members and plastic members, before applying both paints,
A barrier foot having a specific composition and properties is coated on the outer panel in advance. the result,
It has become possible to paint the metal parts and one plastic part of an automobile exterior panel with a single intermediate coat and top coat, thereby eliminating the inconsistency in color tone between the two parts. Moreover, the chipping resistance, corrosion resistance, and physical performance of the formed coating film were also significantly improved.

That is, a barrier coat coating film whose static glass transition temperature is adjusted to -30 to -60°C (more preferably, as described below, the tensile strength elongation rate of the coating film is adjusted to -20°C).
C1 (adjusted by 200 to 1000%) is more flexible than intermediate and top coats for automobile exterior panels, and also has unique viscoelasticity due to modified polyolefin resin. are doing. Therefore, if a coating film with the physical property of bending is applied to the entire surface of the metal and plastic parts of the automobile exterior panel, physical properties such as thermal elasticity and flexibility when the two parts are opened can be improved. Most or all of the "distortion" between the intermediate coating film and the top coating film caused by the difference is absorbed into the barrier neat coating film, so that "distortion" etc. is absorbed into the intermediate coating film and the top coating film. Most of the spread could be prevented. As a result, it has become possible to apply intermediate and top coat paints of a single composition to the entire surface of both parts of the exterior of an automobile, making it possible to finish both parts in the same color tone. Furthermore, even if a strong impact force is applied by rock salt, pebbles, etc. to the surface of the coating film consisting of the intermediate coating and top coating formed through the barrier coating film, most or all of the impact energy is absorbed by the barrier coating film. Since the paint film is absorbed into the interior, there is almost no impact peeling of the paint film, and most of the occurrence of physical damage to the top coat film has been eliminated, so peeling of both the top coat and intermediate paint films due to chipping and occurrence of peeling on metal parts can be avoided. Rust, corrosion, etc. could be prevented.

The coating method of the present invention will be specifically explained below.

First, in the present invention, the automobile outer panel is an outer panel formed by assembling and combining a metal member and a plastic member. For example, parts such as the bumper, 7Asia, fender 1R Abanel, panel 7-door, panel roof, and panel trunk lid are made by combining two or more types of these parts. Tsuma (), individual parts themselves consisting of plastic parts and metal parts, parts made of metal parts and parts made of plastic parts combined and integrated, etc.

Further, the metal part is mainly made of iron, copper, aluminum, zinc, or an alloy containing these, and the plastic part is made of, for example, polyurethane, polypropylene, polycarbonate, or the like.

In the present invention, the term "automobile" in the outer panel of an automobile is not limited to so-called passenger cars, but should be understood to include motorcycles, trucks, safari vehicles, and the like.

Among the above two parts, metal parts should be treated with zinc phosphate, iron phosphate, or chromate according to the usual method as necessary, and then painted with cationic electrodeposition paint. is preferred.

The cationic electrodeposition paint is an electrodeposition paint for coating the above-mentioned metal member, and any known per se can be used. The cationic electrodeposition paint is a basic water-dispersible resin that is neutralized with an organic or inorganic acid, such as a resin containing a large number of 7
It is a water-based paint using a resin such as epoxy, acrylic, or polybutadiene (resin is not limited to these) having a convex/convex shape, and the resin-2 neutralizer, pigment (coloring pigment, extender pigment, antirust pigments, etc.), hydrophilic solvents, water,
If necessary, a curing agent, crosslinking agent, additives, etc. may be added to form a coating by a conventional method. The above basic water-dispersed resin (usually
Neutralizing agents used to neutralize and water-soluble (disperse) (used by dissolving with a hydrophilic solvent) are acetic acid, hydroxyl acetic acid,
Organic acids such as propionic acid, butyric acid, lactic acid, and glycine, and inorganic acids such as sulfuric acid, hydrochloric acid, and phosphoric acid can be used. The appropriate amount of the neutralizing agent is within the range of a neutralization equivalent of about 0.1 to 0.4 relative to the base number (about 50 to 200) of the υ1 fat. The solid content is diluted with deionized water to a concentration of about 5 to 40% by weight, the pH is maintained within the range of 5.5 to 8.0, and the steel plate is electrodeposited using a conventional method. The thickness of the electrocoated film is not particularly limited, but it is preferably 10 to 40 μm based on the cured film, and the film is cured by heating to about 140 to 21°C.

On the other hand, the plastic part undergoes solvent vapor degreasing, polishing, acid treatment,
It is preferable to perform surface treatment by corona discharge or the like.

In the present invention, after the electrodeposited metal member and plastic member are assembled to form an integrated automobile exterior panel, a barrier coat is applied over the entire surface of both parts.

The barrier coat has a static glass transition temperature of -
It is a paint whose main component is a modified polyolefin resin having a temperature of 30 to -60°C (preferably -40 to -55°C). That is, as the modified polyolefin resin, for example, propylene-ethylene copolymer (in molar ratio, 40 to 8
C: 1 to 50 parts by weight, preferably 10 to 20 parts by weight, of chlorinated polyolefin (chlorination rate of about 1 to 60%) (preferably 60 to 20%) per 100 parts by weight of the copolymer. ), or a resin graft-polymerized with 0.1 to 50 parts by weight, preferably 0.3 to 20 parts by weight, of maleic acid or maleic anhydride per 100 parts by weight of the above propylene-ethylene copolymer. etc. In the present invention, if these modified polyolefin resins themselves have a static lath transition temperature within the above range, they can be used as barrier coats by themselves.
If it is desired to change the static lath transition temperature outside the above range or even within the range, a viscosity imparting agent can be added as necessary.

The viscosity imparting agent includes, for example, rosin, petroleum resin (coumaron), which has good compatibility with the modified polyolefin resin.
, artificial chill, polybutanoene, epoxy-modified polybutanoene, low-molecular-weight aliphatic epoxy resin, low-molecular-weight aliphatic bis7J-/-rutaib epoxy resin, polyoxytetramethylene glycol, vinyl acetate-modified polyethylene, etc., and their blending amounts is preferably 1 to 50 parts by weight per 100 parts by weight of the modified polyolefin resin. In addition, in order to improve the coating properties of the barrier foot, it is preferable to dissolve or disperse the above components in an organic solvent. Examples of organic solvents include aromatic hydrocarbons such as benzene, toluene, and xylene, hexane, heptane, etc. Examples include aliphatic hydrocarbons such as octane and decane, and chlorinated hydrocarbons such as tricopyrethylene, perchlorethylene, dichloroethylene, nochloroethane, and dichlorobenzene.

In the present invention, regarding the formed coating film of the barrier coat,
Although it is essential that the static glass transition temperature is within the above range, it is further preferable that the tensile strength elongation at break of the coating film is 200 to 1000% in an atmosphere of 120°C. In addition, the static glass transition temperature of the formed coating film is -3
If the temperature is higher than 0°C, the above object of the present invention cannot be achieved, and if the temperature is higher than -60°C, the coating film performance, especially water resistance,
This is not preferable because it reduces adhesion.

In particular, for the purpose of improving electrostatic coating on plastic parts, a conductive substance is added to the barrier coat to increase the volume-specific resistance value of the coating film to 107 Ωcm or less, particularly 103 to 10'
It is preferable to adjust it to -Ωcm. Examples of the conductive substance include powders such as conductive carbon, silver, nickel, aluminum, zinc oxide, tin dioxide, and tungsten oxide, and the blending amount of these materials does not cause a decrease in the physical performance of the barrier foot coating. As long as it is within the range,
Specifically, the amount is preferably 100 parts by weight or less per 100 parts by weight of the modified polyolefin resin. Furthermore, extender pigments, coloring pigments (excluding anticorrosive pigments), etc. may be added to the barrier foot. The blending amount of these pigments is 100 parts by weight of modified polyolefin resin.
~100 parts by weight is preferred.

In the present invention, these barrier coats are applied to the surfaces of metal parts and plastic parts coated with cationic electrodeposition, but the coating method is not limited, and examples include spray painting, brush painting, dipping painting, melt painting, and static coating. There are electric coatings, etc., and the coating film thickness is 1 to 20μ, depending on the coating film formed.
Particularly preferred is 5 to 10μ.

Note that the static glass transition temperature of the formed coating film of the barrier coat used in the present invention was determined using a differential scanning calorimeter (Daini Seikokin DS).
C-10 type).

The tensile strength elongation at break is a value measured using a universal tensile tester equipped with a constant temperature bath (Shimadzu Autograph Model S-D), the length of the sample was 201, and the tensile speed was 20 mm/min. The samples used for these measurements were coated with the barrier coat on a tin plate to a thickness of 25μ based on the formed coating, baked at 20°C for 30 minutes, and then isolated using the water root amalgam method. I used something.

When applying the following intermediate coat paint to the barrier foot coating surface, it is preferable to bake the barrier foot in advance, but it is also possible to apply the intermediate coat paint wet-on-wet without baking at a certain baking temperature. may be within a range that does not deform or deform the plastic member, for example 60 to 140°C, particularly 80 to 120°C is suitable.

Intermediate Coat 2 As a paint to be applied to the above-mentioned barrier coated surface, any known intermediate paint with excellent adhesion, smoothness, sharpness, overbake resistance, weather resistance, etc. can be used. Specifically, an organic solution-type thermosetting intermediate coating material whose main components are a short-wave or short-wave alkyd resin or an oil-free polyester resin with an oil length of 30% or less and a 7-mino resin is mentioned. These alkyd resins and polynistrul resins have a hydroxyl value of 60 to 140 and an acid value of 5.
~20, and it is preferable to use unsaturated oil (or unsaturated fatty acid) as the modified oil, and suitable amino/resin is etherified melamine resin (having 1 to 5 carbon atoms), urea resin, benzoguanamine resin, etc. ing. These compounding ratios are based on the solid content weight of alkyd resin and (or) oil-free polyester resin 65 to 85.
%, especially 70 to 80%, and 35 to 15%, especially 30 to 20%. Furthermore, the above amino/resin can be replaced with a polyisocyanate compound or a blocked polyisocyanate compound. Further, the form of the intermediate coating is most preferably an organic solution type, but it may also be a non-aqueous drinking liquid using the above vehicle component, a high solid type, an aqueous solution type, an aqueous dispersion type, or the like. In the present invention, the hardness (pencil hardness) of the intermediate coating film is 3B to 2H.
Further, extender pigments, coloring pigments, other paint additives, etc. can be blended into the intermediate coating paint as necessary.

In the present invention, the intermediate coating paint can be applied to the barrier coat surface by the same method as the barrier coat, and the coating film thickness is in the range of 10 to 50 μm, particularly 20 to 30 μm for the cured paint film. is preferable, and the coating film is cured by baking depending on its composition, but the plastic member to be coated is deformed,
Conditions that do not cause deterioration should be adopted;
It is desirable to bake at C (preferably 80 to 140 C) for 10 to 40 minutes.

Top coat paint: A paint applied to the intermediate coat surface,
It imparts cosmetic properties to the object to be coated.

Specifically, the finished appearance (sharpness, smoothness, gloss, etc.)
, coatings that are known in themselves and form coating films with excellent weather resistance (glossy retention, color retention, chalking resistance, etc.), chemical resistance, water resistance, moisture resistance, hardening properties, etc. can be used. For example, Ami/acrylic resin system, Ami7 alkyd resin system,
Examples include paints whose main vehicle components are Ami 7, polyester resin, etc. The form of these paints is not particularly limited, and organic solution type, non-aqueous dispersion type, aqueous (dispersion) liquid distillate type, powder type, high solid type, etc. can be used. The coating film is formed by drying at room temperature, heating, irradiating with active energy rays, etc. In the present invention, the paint film formed by these top coats preferably has a pencil hardness within the range of 2B to 3H.

The top coat used in the present invention is a metallic paint or a solid color finishing paint, which is a paint that uses the above-mentioned vehicle main component and a metallic pigment and/or a colored pigment, and a clear paint that contains almost no pigment at all. Classified as paint (including color clear paint). Then, methods for forming a top coat using these paints include, for example: ■ Painting with metallic pigments, metallic paints containing colored pigments as necessary, or solid color paints containing colored pigments. , heated and cured (metallic or solid color finish by one batch one bake method)
.

■ After applying metallic paint or solid color paint and heating and curing, apply clear paint and heat and harden again (metallic or solid color finish using 2-coat, 2-bake method).

(2) After applying a metallic paint or a solid color paint and then a clear paint, both coatings are cured at the same time by heating (metallic or solid color finish using a 2 foot 1 coat method).

These top coat paints are preferably applied by spray painting, electrostatic painting, etc. Also, the coating film thickness is 25 to 40μ in the above 1 and 25 to 40μ in the above 2.3, based on the dry coating film.
10-3 for metallic paints and solid color paints
0μ and clear paint preferably have a thickness of 25 to 50μ. Heating conditions can be arbitrarily adopted depending on the vehicle components and the plastic member to be coated, but heating conditions are 60 to 140°C,
Particularly preferably at 80 to 140°C for 10 to 40 minutes, the metal parts and plastic parts coated with cationic electrocoating paint are assembled as described above, and the combined automobile outer panel is coated with a barrier coat, an intermediate paint, and a top coat. r) The coating film formed by applying the paint has good color matching between the metal part and the plastic part, and has significantly improved chipping resistance, corrosion resistance, physical performance, etc. .

Next, examples and comparative examples related to the present invention will be described.

Ii & Materials (1) Metal parts: Galvanized steel plate chemically treated with Bonderai #3030 (manufactured by Nippon Parker Linong Co., Ltd., zinc phosphate type) (size 300x90x0.8mm)
) (2) Plastic member: Polyamide resin plate steamed and degreased with trichloroethane (size 300 x 90 x 0.
8mm) (3) Cationic electrodeposition paint: Nireclone #9200 (
r4 Nishi Paint Co., Ltd., epoxy polyamide cationic electrodeposition paint, gray color) (4) Barrier coat (A): Printex L-6 is a resin made by graft polymerizing maleic acid to a propylene-ethylene copolymer.
Organic liquid (static glass transition temperature -43°C, -20°C) of a mixture obtained by dispersing 25 parts by weight (per 100 parts by weight of the graft polymerization port) of conductive carbon (manufactured by Jigusa Co., Ltd.)
tensile strength elongation at break 410%, volume resistivity 2.3 x 101 Ωcm).

(B) 2 An organic liquid of a resin prepared by mixing 100 parts by weight of the resin (A) with 10 parts by weight of Adarironone and 10 parts by weight of Printex L-6.
Tensile strength elongation at C1-20℃ 700%
, volume resistivity value 4.5 x 104 Ωcm).

(C): Maleic acid was graft-polymerized to propylene-ethylene co-ffi polymer (A (fat 100ffLf
An organic liquid (static glass transition temperature +5
°C1 volume resistivity value 5.2X1t1'Ωcm).

(5) Intermediate paint = Amilac N-2 Sealer (manufactured by Kansai Paint Co., Ltd., Ami/polyester resin intermediate paint) (6) Top coat (A): Amilac White (manufactured by Kansai Paint Co., Ltd., Ami/Polyester resin intermediate paint) /Alkyd resin topcoat, 1 coat 1bake white paint, pencil hardness HB) (B): Manocron Silver (manufactured by Kansai Paint Co., Ltd., Ami/Acrylic oil-based topcoat, 2 feet 1bake) Silver metallic paint, pencil hardness H) (C): Manocron Clear (manufactured by Kansai Paint Co., Ltd., Ami/Acrylic 444 oil-based topcoat paint, 2-coat 1-bake clear paint, pencil hardness) +) I+ Examples and comparisons Example: Apply cationic electrodeposition paint Elecron #9 to the above metal member.
2 f) 0 by the usual method, and 30 at 70"C.
It was cured by heating for 20 minutes (cured coating thickness: 20 μm).

Next, a barrier coat is applied by air spraying, and an intermediate coat and a top coat are applied by electrostatic coating to the object to be coated, which is a combination of the metal member coated with the cationic electrodeposition paint and the plastic member. As shown in Table 1 (painted).

In Table 1, (1) All film thicknesses should be reduced to dry, cured coatings.

(2) The top coats of Examples 2.3 and 5 and Comparative Examples 2 and 5 were all wet-on-wet two-coat one-bake systems, and the top coat (B) was coated with (E) at room temperature. After leaving it for 15 minutes, a top coat (C) or (F) was applied and baked.

(3) In Comparative Example 4, (D): So7 Rex #2500 Primer (manufactured by Kansai Paint Co., Ltd., undercoat paint for plastics, polyolefin-urethane system) (G): So7 Rex l$ 1400 Silver Metallic (Kansai (manufactured by Paint Co., Ltd., metallic paint for plastics, aminopolyester type) (F): So7 Rex #500 Clear (manufactured by Kansai Paint Co., Ltd., clear paint for plastics, urethane acrylic type) (4) Examples 1 to 5 In Comparative Examples 1 to 3, a single barrier coat, an intermediate coat, and a top coat were applied to both sides of the metal member and the plastic member, and in Comparative Example 4, gold!
The J4 member was coated with cationic electrodeposition paint, intermediate coat paint, and top coat paints (B) and (C), and the plastic member was coated with paints (D), (E), and (F).

III Performance Test Results A coating film performance test was conducted using the coated plates coated in the above Examples and Comparative Examples. The results are shown in Table 2.

Test method (Book 1) Chipping resistance: (1) Test equipment: Q-G-R Gravelometer (product of Q Panel Company) (2) Stone to be sprayed: Crushed stone with a diameter of about 15 to 20 mm (3) Capacity of stone to be sprayed: Approximately 50 On + 1 (4) Air pressure for spraying: Approximately 4 kg/cm2 (5) Temperature during test: Approximately 20"C Mount the test piece on a holder, and spray approximately 4 kg/cm" using air. Approximately 500 ml of crushed stone particles were shot onto the test piece under pressure, and then the coated surface condition and salt water spray resistance were evaluated.

The condition of the painted surface was visually observed and evaluated using the following criteria. For salt spray resistance, test pieces were subjected to a salt spray test for 240 hours according to JIS 22371, and the presence or absence of rust from the impact area and the state of corrosion were observed. did.

◎ (Good) Only a few scratches due to impact were observed on a part of the double-walled coating, and no peeling of the electrodeposited coating was observed at all.

Δ (slightly poor): Many scratches due to impact were observed on the top coat and intermediate coat, and peeling of the electrodeposited film was also observed here and there.

× (Poor) Most of the double chamber and intermediate coating peeled off, and the electrodeposited coating on the impacted area including the impacted area and its surroundings peeled off.

(Tree 2) Impact resistance: Tested in accordance with JIS K5400-19796.13.3 B method in an atmosphere at 0°C. Weight 500
Damage to the coating film was examined by dropping a weight of 501 g from a height of 501 g.

(Book 3) Adhesion: In accordance with JIS K5400-1979 6.15, we made gongs on the paint film, stuck adhesive top tape on the surface, and evaluated the painted surface after abruptly peeling it off. .

(Tree 4) Water resistance: The coated surface of the metal member was evaluated after being immersed in water at 40°C for 10 days.

(Tree 5) Color difference: The color difference between the metal member and the plastic member was measured according to JIS Z 8730.

In the table, S is the performance of the coating film formed on the metal member, and P is the performance of the coating film formed on the plastic member.

Claims (1)

[Claims] A method for painting an automobile exterior panel consisting of a metal component and a plastic component, which involves assembling a metal component and a plastic component coated with a cationic electrodeposition paint in advance to form an automobile exterior panel, and applying a coating to both components. An automobile exterior panel characterized in that a barrier coat mainly composed of a modified polyolefin resin whose static glass transition temperature is -30 to -60°C is applied, and then an intermediate coat and a top coat are applied. How to paint parts.