JP2587853B2 - Coating method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a composite coating film having excellent chipping resistance, corrosion resistance, physical properties, and the like on a steel plate, particularly an outer plate such as an automobile body.

Conventional technology and its problems
In particular, problems are being emphasized in terms of deterioration of aesthetics due to impact peeling and progress of corrosion of the steel plate as the outer slope base material. For example, in cold regions of Europe and the United States, in order to prevent freezing on the road surface in winter, roads are often laid with gravel mixed with a large amount of relatively coarsely crushed rock salt. The phenomenon of rock salt particles and pebbles bounced up by wheels colliding with the surface of the coating film, causing the coating film to peel off entirely from the steel plate surface due to the impact, so-called "chipping is removed"
Often occurs. Due to this phenomenon, the steel plate surface of the impacted portion of the vehicle body outer plate surface is exposed, and rust is quickly generated and corrosion proceeds. It is generally known that the peeling of the coating film due to chipping is large on the bottom of the vehicle body and around the feet, and the local corrosion becomes considerably noticeable in about half a year to one year.

Composite coatings for automobile outer panels are generally applied to the surface of a chemically treated steel sheet by electrodeposition coating-intermediate coating (sometimes omitted).
-It is formed of a top coat. Various studies have been made on the improvement of the chipping resistance in each of these chemical conversion treatment, electrodeposition, intermediate coating and top coating films, but a satisfactory method has not yet been found. Recently, an SGC (Stone Guard Coat) coating is sometimes applied between the electrodeposition and the intermediate coating to improve the chipping property. SGC paint up to about 100μ
Although it can be applied to a film thickness of the order, a flexible coating film is formed, but the chipping resistance is not practically sufficient, and a coating process of the coating material itself is required, and the number of processes is increased as a whole. have. Further, even if the SGD paint is applied to 100 μm or more to further improve the chipping resistance, it cannot be expected because of cracks and sagging.

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, a pressure-sensitive adhesive film having specific physical properties has been applied between any of the layers of the composite coating film. It has been found that the chipping resistance can be remarkably improved by the wearing, and furthermore, the anticorrosion property, the physical performance and the like are also improved.

That is, the present invention is an electrodeposition paint and a top coat, or an electrodeposition paint, an intermediate coat and a composite coat formed by applying a top coat, between any of these coating layers,
The present invention relates to a method for forming a coating film, characterized by interposing a pressure-sensitive adhesive film having an elongation of 100 to 1000% and a film thickness of 80 to 500 μm (micron).

The feature of the present invention is that the pressure-sensitive adhesive film (hereinafter, referred to as "pressure-sensitive film") is present between any of the coating layers of the electrodeposition coating film, the intermediate coating film (sometimes omitted) and the top coating film. In some cases), that is, sandwiching a pressure-sensitive film between the two coatings. As a result, the chipping resistance of the composite coating film formed by the ordinary coating system was remarkably improved as compared with the composite coating film coated with the SGC paint. Although the reason is not clear, the pressure-sensitive film used in the present invention,
This is probably due to the fact that the elongation is higher than that of the SGC coating film and that the adhesive layer is provided on one side.

That is, the pressure-sensitive film is composed of the base film and the pressure-sensitive adhesive layer, and the base film has a larger elongation percentage and a higher flexibility than the SGC coating film. It is presumed that the base film functions to repel the colliding pebbles even if the pebbles collide at a furious speed, and that the collision energy is absorbed by the adhesive layer. Therefore, the object of the present invention cannot be achieved by using the base film alone or the pressure-sensitive adhesive layer alone instead of the pressure-sensitive film.

As described above, the chipping resistance has been remarkably improved. As a result, defects such as deterioration in aesthetic appearance and deterioration in rust prevention caused by chipping peeling are almost eliminated, and physical performance such as impact resistance is also improved. Was done.

In addition, since the present invention uses a pressure-sensitive film, compared to a conventional SGC paint or the like, there is no need for a new coating device, no need for masking (shading off parts that are not coated), and a reduction in the number of coating steps. It became possible and cost was reduced. Although an organic solvent is essential for the SGC paint, the pressure-sensitive film contains little or no organic solvent, which is advantageous in terms of pollution, safety and health.

Next, the method for forming a coating film of the present invention will be described in detail.

Steel sheet: The steel sheet (object to be coated) capable of forming a composite coating film by the method of the present invention is any type of conductive metal as long as it has a metal surface that can be electrodeposited. No restrictions. For example, iron, copper, aluminum, tin,
Examples include materials such as zinc and alloys containing these metals, and plated or vapor-deposited products of these metals and alloys. More specifically, car bodies such as passenger cars, trucks, buses, and motorcycles using these materials. Tohsaka and its parts and electrical products, building materials and the like are included. It is preferable that the surface of the steel sheet is subjected to a chemical conversion treatment with a phosphate or a chromate before coating the electrodeposition paint.

Electrodeposition paint: As the electrodeposition paint for coating on the steel material, any known cationic and anion type electrodeposition paints can be used.

Examples of cationic electrodeposition paints include epoxy-based paints,
Urethane-based, acrylic-based, and polyolefin-based polymers having a main skeleton are exemplified. Examples of anionic electrodeposition coatings include maleated oil-based resins, polybutadiene-based resins, epoxy ester-based resins, and acrylic-based resins. The main component is that of

Pressure-sensitive film: An adhesive is applied to one side of a base film. The base film has an elongation of 100 to 1000%, preferably 200 to 800%.
%, And the film thickness is 80 to 500 μm, preferably 100 to 500 μm.
It is necessary to use a synthetic resin film of ~ 400μ. The elongation rate has the function of repelling pebbles that collide, and is an important factor in preventing the occurrence of scratches reaching steel plates.
If the elongation is less than 100%, the effect of improving chipping resistance is small. On the other hand, if it exceeds 1000%, the effect of improving chipping resistance is obtained, but it is too stretched, so that it is difficult to stick at a predetermined position on the surface to be stuck. Becomes 80μ thickness
When the thickness is smaller, the impact energy absorbing ability of pebbles and the like is small, and scratches reaching the steel sheet base are likely to occur, and the effect of improving chipping resistance is small. On the other hand, when it is larger than 500 μm, it becomes thick even after overcoating, which is not preferable in terms of finished appearance.

The base film may have any composition as long as it has the above-mentioned characteristic values, and examples thereof include polyolefin (for example, polyethylene and polypropylene), polycarbonate, polystyrene, polyester, nylon, vinylidene chloride, polyvinyl chloride, and polyurethane. Of these, urethane-based and vinyl chloride-based films are particularly preferred.

The pressure-sensitive adhesive is used to form a pressure-sensitive adhesive layer on one side of the base film, and exhibits tackiness at room temperature, and specifically includes rubber, acrylic, silicone, and vinyl, and particularly includes rubber, Acrylic is preferred.

The thickness of the pressure-sensitive adhesive layer formed on one side of the base film is
A range of 10 to 80μ, especially 20 to 50μ is preferred.

The pressure-sensitive film may be a transparent film that is not colored, or a colored film containing a pigment or the like. It is also conceivable that the pressure-sensitive film is colored by printing.

The thickness of the substrate film was measured using a Newmate Digital Micrometer M-30 (trade name, manufactured by Sony Magnescale Co., Ltd.).

Base film elongation is 80-500
μ, width 25 mm, length 100 mm, and a universal tensile tester (Shimadzu Autograph SD
(Type) at a tensile speed of 300 mm / min in the length direction.

Intermediate paint: A paint which is already known per se prior to the application of the top coat and is, for example, a basic resin such as an acrylic resin, an alkyd resin or a polyester resin, and an amino resin or a polyisocyanate compound (block). A coating containing a thermosetting resin composition in which a curing agent is used in combination with an organic solution type.
It is used in the form of a non-aqueous dispersion type, an aqueous type, a powder type and the like.

Top coating: A coating to be applied to the top layer, which can have excellent smoothness, sharpness, weather resistance, etc. For example, amino resin or polyisomia is used for base resin such as acrylic resin, polyester resin or alkyd resin. Organic solution type, non-aqueous dispersion type, aqueous type, and powder type, which are already known per se, are mainly composed of a thermosetting resin composition containing a curing agent such as a nitrate compound (including a blocked product). Paint can be used.

Regarding the topcoat paint, it can be classified into a solid color type containing a coloring pigment, a metallic type containing a metallic pigment, and a clear type containing no or almost no such pigment. Are used in combination.

Coating paint forming method: The following paints can be used as a composite paint having excellent chipping resistance and the like, which is the object of the present invention, using each of the above paints and the pressure-sensitive film.

(1) Electrodeposition coating → baking → sticking of pressure-sensitive film → topcoating → baking (2) electrodeposition coating → baking → sticking of pressure-sensitive film → intermediate coating → baking → painting → baking (3) electrodeposition coating → baking → intermediate coating → baking → sticking of pressure-sensitive film → top coating → baking In the present invention, (2) is particularly preferred among the above methods.

Electrodeposition coating can be performed under normal conditions for both anionic type and cationic type, and it is preferable to wash with water after coating. The film thickness is suitably 15-35μ based on the cured coating,
The coating is baked and hardened by heating to 150 to 180 ° C.

As is clear from the above process, the pressure-sensitive film is adhered to the cured coating surface of the electrodeposition coating film and / or the intermediate coating film, and the film is applied to a portion of the vehicle body where chipping and peeling is likely to occur, for example, the body. It is preferable to adhere to parts such as the bottom, the underbody, the side sill, the rear fender, and the front apron.

In pasting the pressure-sensitive film, in order to facilitate the operation, in advance, release paper on the pressure-sensitive adhesive layer surface of the pressure-sensitive film obtained by applying an adhesive on one side of the base film, one base film It is preferable that application films are adhered to the surfaces. That is, the sheet is cut into a predetermined shape based on the shape and size of the part to which the release paper and the pressure-sensitive film to which the application film is adhered are adhered, and then the release paper is peeled off and adhered to the target part. It is preferable that the sticking is performed so that bubbles do not enter or wrinkles are generated. After the attachment, the application work is completed by peeling off the application film.
Known release papers and application films can be used.

Intermediate coating may be omitted, but it is applied to the surface of the pressure-sensitive film or the cured electrodeposition coating surface. The coating method is not particularly limited, for example, spray coating or electrostatic coating is preferable, and the film thickness is preferably 15 to 35 μm based on the cured coating film.
It is preferred that the composition be cured by heating to 0 to 160 ° C.

The top coat is applied on the coated surface during curing or on the surface of the pressure-sensitive film adhered. The coating method is not particularly limited, and for example, spray coating and electrostatic coating are suitable.

There are solid color finish and metallic finish in the top coat. First of all, the solid color finish is generally painted with a solid color paint as the top coat and baked, but it is also possible to apply a clear paint further after baking or without baking and then bake and finish. It is. In addition, the metallic finish is to apply a metallic paint as a top coat and apply a clear paint without baking or after baking, and bake.
A coat finish is preferred.

In these top coat finishes, solid color paints, metallic paint paint films of 15 to 30μ are suitable, clear paint film thicknesses of 20 to 40μ are suitable, and the baking temperature is 120 to 1
50 ° C is suitable.

Examples Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

I Sample preparation (1) Steel plate: Bonderite # 3030 (Nippon Parker Lysine Co., Ltd.)
(Size: 300 x 90 x 0.8 mm) treated with zinc phosphate metal surface treating agent.

(2) Electrodeposition paint: (A) Cationic electrodeposition paint: Polyamide-modified epoxy resin / blocked isocyanate compound as a vehicle component, neutralized with acetic acid, has a nonvolatile content of 20% by weight, pH
Is 6.5 cationic electrodeposition paint.

(3) Pressure-sensitive film An acrylic resin adhesive is applied to one side of a urethane resin base film (thickness: 30μ), release paper is on the adhesive layer side, and application film is on the base film side. Is attached in advance. Table 1 shows the thickness of the base film and the elongation thereof.

(4) Intermediate coating: (A) short-oil alkyd resin-based coating A soybean oil-modified alkyd resin mainly using phthalic anhydride and terephthalic acid as polybasic acid components (oil length: 15%, hydroxyl value: 80, acid value) : 15) An intermediate coating composition comprising 100 parts by weight of a pigment (titanium white) per 100 parts by weight of a vehicle component consisting of 75% by weight and 25% by weight of butyl etherified methyl melamine resin (solid content ratio).

(5) Topcoat paint: (A) Oil-free alkyd resin solid color paint Oil-free alkyd resin mainly using phthalic anhydride and trimellitic anhydride as polybasic components (hydroxyl value: 8
0, acid value: 10) 100 parts by weight of a pigment (titanium white) per 100 parts by weight of a vehicle component consisting of 70% by weight and 30% by weight of a butyl etherified methyl melamine resin.

(B) Acrylic resin-based metallic paint methyl methacrylate, ethyl methacrylate, n-
75% by weight of a copolymer composed of butyl methacrylate and hydroxyethyl methacrylate (number average molecular weight: about 30,000, hydroxyl value: 100) and 25% by weight of a butylated melamine resin
An organic solution type metallic paint obtained by adding an aluminum powder paste to a vehicle component consisting of:

(C) acrylic resin clear paint ethyl methacrylate, isobutyl methacrylate,
Copolymer of styrene and hydroxyethyl acrylate (number average molecular weight: about 15,000, hydroxyl value: 100) 70
An organic solution type clear coating composition containing, as a main component, 30% by weight and 30% by weight of a butylated melamine resin.

II Examples and Comparative Examples Using the sample prepared in the above I, a coated plate was prepared by the following method.

Cathode-type electrodeposition paint on steel sheet bath temperature 28 ° C, load voltage approx.
Energization was performed at 250 V for 180 seconds, and the film was coated to a thickness of 20 μm. After washing with water, baking was performed at 170 ° C. for 20 minutes.

Then, the above-mentioned pressure-sensitive films (A) to (F) are attached.

Next, the intermediate coating is applied with a thickness of 25 to 30 μm by air spray and baked at 140 ° C. for 20 minutes. (Adjust the viscosity of the intermediate paint in 23 seconds with Ford Cup No. 4 using a thinner.) Then apply the top coat. The top coat (A) is adjusted to a viscosity of 23 to 30 seconds with Ford Cup No. 4 using a thinner, then applied to a thickness of 25 to 30 microns by air spray and baked at 140 ° C. for 20 minutes.

For the topcoat paints (B) and (C), adjust the viscosity of (B) to 18 seconds with Ford Cup No. 4 using a thinner, apply it to 15 microns with an air spray, and use a thinner without baking. (C), the viscosity of which was adjusted in 23 seconds with Ford Cup No. 4, was applied by air spray so as to have a thickness of 25 to 30 microns, and both coating films were simultaneously baked at 140 ° C. for 20 minutes.

These specific painting processes and performance test results
It is as shown in the table.

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

[Test method] (* 1) Chipping resistance: Test equipment: QGR Graperometer (Q panel company product) Blowing stone: crushed stone with a diameter of about 15 to 20 m / m Blowing stone volume: about 500ml spray air pressure: about 4 kg / cm ² test time temperature: the temperature was set to put methanol and dry ice at about -10 ° C. heat-insulating container -10 ° C. or less, put inside a test piece thereof −10
Adjusted to ° C. Attach the test piece to the holder, about 4 kg / cm ²
Approximately 500 ml of crushed stone was sprayed on the test piece at a spraying air pressure of, and the state of the coated surface and the salt spray resistance were evaluated. The painted surface state is the result of visual observation of the painted surface after the end of crushed crushed stone particles, and evaluated according to the following criteria.In addition, salt water spray resistance is performed on the test piece for 1080 hours according to JIS Z2371, a salt water spray test, Then, the cellophane tape adhered to the coated surface was adhered, and after the abrupt peeling, the presence or absence of rust from the impacted portion and the peeling of the coating film were observed.

Coating surface state 良 (good): The scratches due to the impact of the crushed stone particles are very slight in a part of the top coating film, and no peeling of the electrodeposition coating film is observed.

Δ (Slightly poor): Many scratches due to the impact of crushed stones are observed in the top coat and the intermediate coat, and peeling of the electrodeposited coat is also scattered.

X (poor): Most of the topcoat and intermediate coating films peeled off, and the electrodeposition paint on the impacted portion including the impacted portion and its surroundings peeled off.

 Salt spray resistance ◎: No rusting. A slight peeling of the top coat has occurred.

Δ: Slight rusting. Intermediate coating peeling occurred.

X: The rust is remarkable. Steel plate exposure.

(* 2) Finishability Visually observe the finish appearance.

（(Good) Even when the film was attached, there was no coating film defect and the appearance was good.

△ There are some skin spots.

× (poor) The skin is noticeable. Further, defects such as cissing, pinholes, and color unevenness are recognized.

(* 3) Adhesion: 1 mm x 1 mm on coating film according to JIS K5400-1979 6.15
Then, 100 sticks are made, and an adhesive cellophane tape is stuck on the surface, and the coated surface after sharply peeling off is evaluated.

◎ (good) No peeling at all △ Peeled about 20% to 49% × (Poor) Peeled 50% or more.

(* 4) Impact resistance: Conducted at 0 ° C in accordance with JIS K5400-1979 6.13.3B method. A 500 g weight is dropped from a height of 30 cm to examine the coating for damage.

◎ (Good) No peeling including sharpness.

△ There are some sharps.

X (poor) Cracks and peeling are observed.

Claims (1)

(57) [Claims] (1) In an electrodeposition paint and a top coat, or in a composite coating film obtained by applying an electrodeposition paint, an intermediate coat and a top coat, the elongation is between any of these coating layers.
A method for forming a coating film, characterized by interposing a pressure-sensitive adhesive film having a thickness of 100 to 1000% and a thickness of 80 to 500 µ.