JPH07316485A - Air drying coating composition and method of coating body of automobile - Google Patents

Abstract

PURPOSE:To obtain the title composition which can be applied with good adhesiveness even to the surface of a highly water-repellent substrate having stable surface properties, such as a coating film of a fluororesin. CONSTITUTION:This composition comprises 40-60wt.% fluoropolymer, 0.5-10wt.% epoxy compound, 0.1-2wt.% phosphoric ester and the balance of a (meth)acrylic ester polymer having a glass transition temperature of 5-35 deg.C and a weight- average molecular weight of 30000-70000. After a topcoating film 4b is formed in the coating of the body of an automobile, this composition is applied to an area such as a wheel house to form a black coating film 5 excellent in adhesion and weathering resistance. Therefore, the design properties of an automobile can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a room temperature dry coating composition and a method for coating an automobile body, and particularly to a room temperature dry coating capable of coating a substrate having stable surface properties and high water repellency with good adhesion. The present invention relates to a dry coating composition and an automobile body painting method using this composition.

[0002]

2. Description of the Related Art The body of an automobile is painted mainly for the purpose of preventing rust and giving a beautiful appearance. Generally, one paint
It is not possible to satisfy all performances with one material,
BACKGROUND ART Conventionally, as a coating film structure of an automobile body, generally, an undercoat layer, an intermediate coating layer, and an overcoat coating layer are sequentially laminated on a pretreated steel plate base surface. Furthermore, the top coat is composed of a single layer such as in so-called solid coating using amino / alkyd resin coating, or in so-called metallic coating or pearl tone coating using thermosetting acrylic resin coating. There is a two-layer type consisting of a base coat and a clear coat provided on top of it.

Recently, a clear coat made of a fluororesin having excellent weather resistance, chemical resistance and water repellency and having a high gloss retention rate is used as a clear coat in the above metallic coating or as a protective coat in solid coating. It is also used as a two-layer structure with a color base and a clear coat.

By the way, for example, the wheel house seen from the gap between the fender opening and the tire, the hood lock stay seen from the gap between the radiator grill and the bumper, the first cross member, the radiator core, the sill outer, etc. However, the part that is difficult to see is the design surface, especially,
This is one of the relatively important factors in considering the color balance of the vehicle body. That is, if these parts have the same color as the vehicle body color, the observer often looks as if the entire vehicle body is out of focus, which deteriorates the design. Therefore, in order to give a tight and sharp impression to the entire vehicle body, there is a demand to paint these parts in a dark color such as black to improve the appearance.

When a vehicle body color is applied to the entire vehicle body by the above-mentioned method and then parts such as the wheel house are to be painted in a dark color, the parts other than these parts have a high coating film height. It is necessary to maintain the sharpness, and the usable paints are necessarily limited to room temperature dry type.

Room temperature dry acrylic lacquer paints are known as those usable for such applications.
As a conventional room-temperature-drying acrylic lacquer coating composition, a thermoplastic acrylic resin, or a thermoplastic acrylic resin and a nitrocellulose, a fibrin derivative such as cellulose acetate, etc. are used as a main vehicle solid content, and various kinds of plasticizers and the like are added thereto. There are some that contain additives.

[0007]

However, when such a conventional room-temperature-drying acrylic lacquer coating is applied on the surface of a substrate (coating film) having stable surface properties and high water repellency, poor adhesion occurs. In addition, the coating film is deteriorated at the portion receiving the ultraviolet rays, and there is a problem in that appearance retention is deteriorated (discoloration, gloss reduction) and peeling of the coating film due to impact occurs.

Therefore, the object of the present invention is to provide a novel room temperature dry coating composition. A further object of the present invention is to provide a room temperature dry type coating composition capable of coating a substrate surface having stable surface properties and high water repellency with good adhesion. Another object of the present invention is to provide a room-temperature-drying-type coating composition which can be applied on the top coating film for automobile body painting, and an automobile body painting method using this composition.

[0009]

Means for Solving the Problems The above-mentioned objects are as follows: 40-60% by weight of a fluorine atom-containing polymer, 0.5-10% by weight of an epoxy group-containing compound, 0.1-2% by weight of a phosphoric acid ester, and the balance being And a glass transition temperature of 5 to 35 ° C. and a weight average molecular weight of 30,000 to 70,000 (meth) acrylic acid ester-based polymer.

In the room temperature dry coating composition of the present invention, the fluorine atom-containing polymer has a weight average molecular weight of 10,000 to 30,000 having a repeating unit represented by the following general formula (I). desirable.

[0011]

[Chemical 2]

According to the present invention, in the coating of an automobile body, after forming an overcoating film, a coating film is formed at a predetermined portion partially on the topcoating film by using the above-mentioned room temperature dry type coating composition. It is a car body painting method characterized by In the automobile body painting method of the present invention, the top coat film is preferably a fluororesin-based paint film.

[0013]

Since the room-temperature-drying type coating composition of the present invention contains a predetermined amount of the above-mentioned components as vehicle solids, it can be spread in a solvent, coated and dried to obtain various cross-linked structures. A coating film having excellent characteristics can be formed, and a chemically and physically good bonding force can be exhibited even on the surface of a substrate. Therefore, a coating film that exhibits good adhesion and is excellent in various properties such as weather resistance and solvent resistance is formed even on the surface of a substrate (coating film) having stable surface properties and high water repellency.

Further, in the method for coating an automobile body of the present invention, after forming a top coating film, a room temperature dry coating composition according to the present invention as described above is partially applied on the top portion of the top coating film at a predetermined portion. Since it is to form a coating film on top, the top coating film, various coatings conventionally used, for example,
Thermosetting acrylic resin clear paint, fluorine resin clear paint, acrylic-silicone resin clear paint, amino
Regardless of whether it is formed of an alkyd resin paint or a thermosetting oil-free alkyd resin paint, a coating film can be formed on top of it with good adhesion. Therefore, after the overcoating, for example, a part such as a wheel house can be partially coated to improve the design of the automobile body.

In particular, the coating film formed by the coating composition according to the present invention has affinity with the fluororesin coating film due to containing a similar chemical structure, hydrogen bonding force due to the phosphate ester, and the like. It was expected to exhibit, and actually exhibited extremely good adhesion as described later. Therefore, since the surface properties are stable and the water repellency is extremely high,
It is effective as a coating technology on fluororesin coating films, which was difficult in the past.

The operation of the present invention will be described below in more detail with reference to specific embodiments. The room temperature dry type coating composition of the present invention has a fluorine atom-containing polymer, an epoxy group-containing polymer, a phosphoric acid ester, a glass transition temperature of 5 to 35 ° C., and a weight average molecular weight (Mw) of 30,000 as main components.
Up to 70,000 poly (meth) acrylic acid ester-based polymers are contained.

The fluorine atom-containing polymer is a solvent-soluble type or a solution type (prepolymer),
What is necessary is that it can be formed into a film by evaporation of the solvent and can be cross-linked and cured at room temperature, but from the viewpoint of reactivity with an epoxy group and affinity with a poly (meth) acrylic acid ester-based polymer, in particular, Those having a carboxyl group (—COOH) as a functional group in the olefin are desirable, and specifically, for example, those having a repeating unit represented by the following general formula (I) are mentioned as preferable examples. it can.

[0018]

[Chemical 3]

The weight molecular weight is 10,000.
It is preferably about 30,000. Molecular weight is 1000
If it is less than 0, the hardness of the obtained coating film may be lowered, while if it has a molecular weight of more than 30,000, the coating operation may be difficult.

In the coating composition of the present invention, the above-mentioned fluorine atom-containing polymer has a vehicle solid content of 40%.
It is desired to be ˜60% by weight. That is, when the content of the fluorine-containing polymer is less than 40% by weight, physical properties such as solvent resistance and glossiness of the resulting coating film may be deteriorated, while it exceeds 60% by weight. If so, the resulting coating film may become too hard and the impact resistance may be reduced, and in either case, desired coating film performance cannot be obtained.

The epoxy group-containing compound is not particularly limited, and is epichlorohydrin-bisphenol A type (epi-bis type), novolac type, glycidyl ether type, glycidyl ester type, polyglycol ether type, glycol ether type. Various known epoxy group-containing polymers such as epoxidized fatty acid ester type, polyvalent carboxylic acid ester type, aminoglycidyl type, chlorinated type and resorcin type can be used. Further, monoepoxy type ones such as phenyl glycidyl ether, n-butyl glycidyl ether, allyl glycidyl ether, phenoxy ether type glycidyl ether, versatic oxalic acid glycidyl ester, α-olefin oxide, epichlorohydrin, and styrene oxide can also be used. is there.

In the coating composition of the present invention, the epoxy group-containing compound as described above has a vehicle solid content of 0.5.
It is desired to be 10% by weight. That is, when the content of the epoxy group-containing compound is less than 0.5% by weight,
There is a possibility that a sufficient crosslinked structure cannot be introduced into the obtained coating film, the adhesion to the substrate may be deteriorated and the solvent resistance may not be sufficient, while it exceeds 10% by weight. If so, the solvent resistance of the obtained coating film may be significantly lowered, and in any case, desired coating film performance cannot be obtained.

The phosphoric acid ester improves the adhesion to the surface of the substrate (coating film) by the hydrogen bonding force of its polar group, and also functions as a curing accelerator during the curing reaction of the coating composition. . Specific examples of the phosphoric acid ester include phenyl dihydrophosphate, triphenyl phosphate, butyl acid phosphate, and the like, of which phenyl dihydrophosphate is particularly preferable.

In the coating composition of the present invention, it is desirable that the above-mentioned phosphoric acid ester is 0.1 to 2% by weight of the vehicle solid content. That is, if the content of the phosphoric acid ester is less than 0.1% by weight, the adhesion between the obtained coating film and the substrate will be decreased, while if it exceeds 2% by weight, the hydrophilicity will be high. This is because there is a risk that the adhesiveness with the substrate will be deteriorated, and the moisture resistance and weather resistance will be significantly deteriorated, and neither of them will reach the desired coating film performance.

Further, the (meth) acrylic acid ester-based polymer compounded in the coating composition of the present invention has a glass transition temperature (Tg) of 5 to 35 ° C., more preferably 15 in view of solvent resistance. Those in the range of -25 ° C are used. That is, if the Tg is less than 5 ° C, the heat resistance stability of the obtained coating film may decrease, while if it exceeds 35 ° C, the obtained coating film becomes hard and the impact resistance is poor. This is because it becomes something. Also this (meta)
The weight average molecular weight of the acrylate polymer is preferably about 30,000 to 70,000. If the molecular weight is less than 30,000, the hardness of the resulting coating film will be reduced, while if the molecular weight is more than 70,000, the adhesion to the base material will be reduced and the coating operation may be difficult.

The (meth) acrylic acid ester-based polymer is a homopolymer as long as it contains a (meth) acrylic acid ester monomer as exemplified below and has a predetermined glass transition temperature as described above. Or a copolymer. Like this (meta)
Examples of the (meth) acrylic acid ester monomer serving as a main component that constitutes the acrylic acid ester-based polymer include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, and methacrylic acid. Examples thereof include methyl, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, and lauryl methacrylate. Other monomers that can be copolymerized with these (meth) acrylic acid ester monomers include, for example, other vinyl monomers such as styrene and its derivatives, or acrylic acid, methacrylic acid,
Examples thereof include monomers having a functional group such as acrylamide, methacrylamide, glycidyl acrylate, glycidyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, and propyl hydroxypropyl methacrylate.

Examples of homopolymers having a glass transition point within the above range include polymethyl acrylate and poly (n-butyl methacrylate). Further, the (meth) acrylic acid ester-based polymer to be blended in the coating composition of the present invention is a copolymer with a monomer having a functional group as described above and has a functional group in the molecule and a crosslinking reaction. It is also possible to adopt a configuration capable of causing An example of such a preferred copolymer is n-butyl acrylate / 2-hydroxyethyl methacrylate / acrylic acid / styrene copolymer.

The pigment to be incorporated in the coating composition of the present invention is not particularly limited, and conventionally known inorganic pigments and organic pigments can be used alone or in combination of two or more kinds. Examples of the inorganic pigment include titanium dioxide, zinc white, yellow lead (G, 5G, 10G), yellow iron oxide, ocher, titanium yellow, molybdate orange, red iron oxide, purple red iron oxide, dark blue, ultramarine blue, cobalt blue, chrome green. , Chromium oxide, carbon black, iron black and the like, and examples of organic pigments include Hansa Yellow (G, 10G), Permanent Yellow FGL, Permanent Yellow HP, Chromophthal Yellow 3G,
Hosta Palm Yellow (H3G, H4G, HLR), Irgadine Yellow (3RLTN, 3GLT), Resor Fast Yellow 1840, Chromophthal Yellow A2
R, Paliogen Yellow 1560, Green Gold,
Azomethine-based copper complex pigment, Pariotor Yellow L09
60HD, Nova Palm Orange (HL, HL-70),
Hosta Palm Orange GR, Watching Red (M
n), Rake Red 4R, Permanent Carmine FB,
Quinacridone Red, Perylene Red, Bordeaux 10
B, thioindigo red, quinacridone maroon, perylene maroon, quinacridone violet, dioxane diviolet, copper phthalocyanine, metal-free phthalocyanine, indanthrone blue, chlorinated copper phthalocyanine, brominated copper phthalocyanine, etc. can be exemplified, but of course, these It is not limited.

In the embodiment in which the coating composition of the present invention is applied to a portion such as a wheel house for improving design after the overcoating step in the coating of automobile body as described later, for example, carbon black, iron black Such a black pigment, or a pigment composition in which a small amount of another pigment is added to these as a base, and the like is desirable to be a dark color.

In the coating composition of the present invention, if necessary, a drying agent, a wetting agent, a thickening agent, a pigment dispersant, a leveling agent, a defoaming agent, an anti-repellent agent, an anti-blocking agent,
It is also possible to add other known additives such as an ultraviolet absorber. Further, as a diluent medium for the coating composition of the present invention, an organic solvent such as toluene or xylene can be used.

When such a coating composition of the present invention is applied to the surface of a substrate by a coating method such as spraying, roller coating, brush coating, solvent evaporation and addition polymerization of vehicle solid matter occur at room temperature thereafter. By doing so, a film can be formed and a cured film can be formed. In particular,
In order to be able to coat a substrate or coating film surface with stable surface properties and high water repellency with good adhesion, for example, after forming a top coating film in automobile body painting, further coating on this top coating film It is suitable for use in the case of partially applying some pattern or coloring.

That is, in the present invention, in the coating of an automobile body, after forming an overcoating film, a coating film is formed at a predetermined portion partially above the overcoating film by using the above coating composition according to the present invention. It is a car body painting method characterized by Specifically, for example, the wheel house seen from the gap between the fender opening and the tire as described above, the hood lock stay seen from the gap between the radiator grill and the bumper, the first cross member, the radiator core, or the sill outer part is black or the like. The aspect of painting in a dark color, or the aspect of drawing some characters, figures, etc. on the front body, side body, and the like.

In this coating method, the formation of an overcoat coating film is not limited at all, and various conventionally known methods can be used. For example, an undercoat ( Electrodeposition coating), intermediate coating, top coating coating (coating) / baking (baking) respectively
From the most common ones that are laminated in order through the steps, those that omit the above-mentioned middle coat, those that perform two coats of the above-mentioned middle coat, and the base coat and the clear coat provided on the top as the above-mentioned top coating film. It is possible to adopt various modes such as two layers consisting of two coats and one bake, two coats and two bake, and three top coats.

Further, the paint constituting the top coating film (outermost surface coating film) for applying the coating composition according to the present invention is not particularly limited, and conventionally used thermosetting acrylic resin clear paint. It can be applied to any of the following: fluororesin clear paint, acrylic-silicone resin clear paint, amino alkyd resin paint, thermosetting oil-free alkyd resin paint, etc., and good for any of these types However, when the top coat film is made of a fluororesin coating, a better adhesion property can be expected, which is desirable.

The coating composition according to the present invention is applied by coating the above-mentioned top coating film at room temperature after completion of the baking and curing operation, and then drying and curing.

[0036]

EXAMPLES The present invention will be described in more detail below with reference to examples. Examples 1 to 9 and Comparative Examples 1 to 8 Test piece of cold rolled steel sheet (70 × 150 × 0.8 m
m) is treated with zinc phosphate (Granozine DP4000,
Chemical conversion treatment with Nippon Paint Co., Ltd., and electrodeposition coating (Power Top U-600, Nippon Paint Co., Ltd.) thickness 2
After coating so as to have a thickness of 0 μm, it was baked at 170 ° C. for 30 minutes. Intermediate coating (High Epico No. 1
Nippon Oil & Fats Co., Ltd. is coated to a film thickness of 35 μm,
It was baked at 140 ° C. for 30 minutes. Further, an acrylic resin-based base coat (Superlac M-80, manufactured by Nippon Paint Co., Ltd.) was applied thereon to set the film thickness to 20 μm, and setting was carried out for 3 minutes, followed by a fluorine atom-containing vinyl polymer. Fluorine resin-based clear (Super Clon 0-10 clear, manufactured by Nippon Paint Co., Ltd.) was applied to a film thickness of 30 μm, and baked at 140 ° C. for 30 minutes.

Then, a room temperature dry type coating composition prepared so as to have a predetermined composition as shown in Table 1 is applied thereon to a film thickness of 15 μm, and the temperature is set to room temperature (25
The coating was dried and cured by leaving it at 8 ° C for 8 hours.

Incidentally, FIG. 1 schematically shows the constitution of the coating film formed in this example. As shown in the figure, on the steel plate 1, an electrodeposition coating film 2 and an intermediate coating film are successively formed. 3,
This means that the topcoat base coat 4a, the topcoat clear coat (fluorine resin-based) 4b, and the room temperature dry coating film (black) 5 are laminated and formed.

The coated article thus obtained was used as a test plate to evaluate gloss retention, adhesion, solvent resistance, impact resistance, adhesion after humidification, and adhesion after outdoor exposure. . The results obtained are shown in Table 1.

In all of Examples 1 to 9 and Comparative Examples 1 to 8, the room temperature drying type coating composition was Lumiflon (produced by Asahi Glass Co., Ltd.) as the fluorine atom-containing resin.
As the epoxy group-containing substance, versatic acid glycidyl ester, as phosphoric acid ester phenyldihydrophosphate, and as poly (meth) acrylic acid ester-based polymer, n-butyl acrylate / 2-hydroxyethyl methacrylate / acrylic acid Acid / styrene copolymers were used respectively. However, regarding the (meth) acrylic acid ester-based polymer, the compounding ratio of each comonomer component was set to be different in each Example and Comparative Example so that a predetermined glass transition temperature was obtained.

The above evaluations were carried out under the following conditions. (1) Gloss retention Gloss is measured at 60 ° specular gloss.

(2) Adhesion Evaluation A test film is cut with a cutter knife at approximately the center of the test plate to draw eleven vertical and horizontal parallel lines at a distance of 2 mm to form square squares. A cellophane tape having a width of about 18 mm to 30 mm was closely adhered to the coarse-grained coating film, and was peeled off at a stretch to observe the number of the left-eye cells which had not peeled off and the state of peeling and scratches. The value shown in Table 1 is (the number of eyes left without peeling / the total number of eyes).

(3) Evaluation of solvent resistance Soak benzine in a cloth and reciprocate 10 times on the coated surface of the test plate.
It was rubbed and its peelability was observed.

(4) Impact resistance evaluation Using an impact deformation tester (Dupont type) placed horizontally on a solid base such as concrete, a weight of 500 g is collided by natural fall. The weight for dropping and the height of the test plate were changed, and the adhesiveness when the coating film cracked was observed by the method (2).

(5) Evaluation of Adhesion after Humidification After leaving for 24 hours in an environment of 50 ° C. and 95% RH, the adhesion was observed by the method (2).

(6) Adhesion after outdoor exposure After outdoor exposure (Yokohama city, Kanagawa prefecture) for 3 months, the adhesion was observed by the method (2).

[0047]

[Table 1]

[0048]

As described above, the room temperature dry type coating composition of the present invention comprises 40 to 60% by weight of a fluorine atom-containing polymer, 0.5 to 10% by weight of an epoxy group-containing compound, and 0.1 to 10% of a phosphoric acid ester. 2% by weight and the balance glass transition temperature 5 to 35 ° C., weight average molecular weight 30,000 to 7,000
It is characterized by comprising a poly (meth) acrylic acid ester-based polymer of 0, so that it can be applied on a substrate surface having stable surface physical properties and high water repellency with good adhesion, and for a long period of time. Since a film excellent in weather resistance can be formed, it can be suitably used, for example, in the case of further applying a coating on the top coating film of an automobile body.

In such a composition, the fluorine atom-containing polymer has a repeating unit represented by the general formula (I) and has a weight average molecular weight of 10,000 to 3,000.
When it is 0, the resulting coating has more excellent properties such as adhesion and weather resistance.

Further, if such a composition is prepared so as to contain a dark pigment, for example, a portion of a wheel body or the like of an automobile body which is painted in a car body color is painted in a darker color to make the car body look better. It can be suitably used in a coating process performed for the purpose of improvement.

The present invention also provides that after forming the topcoat,
A coating method for an automobile body, characterized in that the coating composition is partially formed on an upper portion of the top coating film at a predetermined portion, which is further designed after the entire automobile body is coated in a body color. When additional partial coating is performed for the purpose of improving the adhesiveness, adhesion is achieved by extremely simple construction without the need for a baking process that deteriorates the quality of the top coating film of other parts. This is an extremely effective technique because it can form a partially-painted film with excellent weather resistance.

Further, in such a car body coating method, when the top coating film is a fluororesin-based coating film, the partial coating film of the coating composition has extremely good adhesion and weather resistance to the top coating film. Therefore, when a fluororesin-based coating material is used for such a top coating film, it has a great technical meaning in that it can provide an effect of improving the designability in coloring the vehicle body, which has been particularly difficult in the past. Is. That is, by such a coating method, parts such as a wheel house, a hood lock stay, a first cross member, a radiator core, and a sill outer are painted in a dark color, thereby enhancing the design of the vehicle body and increasing the commercial value. Is.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing a coating film configuration in an example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Steel plate, 2 ... Electrodeposition coating film, 3 ... Intermediate coating film, 4a ... Topcoat base coat, 4b ... Topcoat clear coat (fluorine resin type), 5 ... Room temperature dry paint film (black).

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area // (C08F 214/26 220: 06)

Claims (6)

[Claims] 1. A fluorine atom-containing polymer (40 to 60% by weight), an epoxy group-containing compound (0.5 to 10% by weight), a phosphoric acid ester (0.1 to 2% by weight), and the balance having a glass transition temperature of 5 to 35 ° C. Weight average molecular weight 30,000 to 7,000
A room-temperature-drying type coating composition comprising 0 (meth) acrylic acid ester-based polymer. 2. The room temperature dry type coating composition according to claim 1, wherein the fluorine atom-containing polymer has a repeating unit represented by the following general formula (I) and has a weight average molecular weight of 10,000 to 30,000. [Chemical 1] 3. The room temperature dry type coating composition according to claim 1, which contains a dark pigment. 4. After forming an overcoating film, a coating film is partially formed on a predetermined portion of the topcoating film by using the coating composition according to any one of claims 1 to 3. Characteristic automobile body painting method. 5. The automobile body painting method according to claim 4, wherein the top coat film is a fluororesin-based paint film. 6. The predetermined part is selected from the group consisting of a wheel house, a hood lock stay, a first floor member, a radiator core and a sill outer.
5. The automobile body painting method according to claim 4, which is a part or more of the part.