JPH0765016B2 - Paint for metal plate, coated metal plate using the same, and method for producing coated metal plate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel coating material for metal plates, a coated metal sheet produced using the coating material, and a method for producing such a coated metal sheet.

More specifically, for example, a finish paint that is applied to a metal plate used for electrical equipment, indoor equipment, vehicle interiors, building interiors and exteriors, etc. to give a unique appearance, and a coated metal plate produced using the paint, And its manufacturing method.

[Conventional technology]

A coated metal sheet that is widely used for parts such as roofs and building exteriors that require long-term durability, electrical equipment, indoor equipment, vehicle interiors, building interiors, etc. is generally called pre-coated steel sheet.

As a material of the coated metal plate, a hot dip galvanized steel plate, a zinc / aluminum alloy plated steel plate, an aluminum plated steel plate, a stainless steel plate, an aluminum plate, etc. are generally used.

In recent years, market demands for coated metal sheets used for roofs, building exteriors, etc. have become more severe, and long-term durability and even long-term guarantees have been required. As a coating material corresponding to this, a fluororesin coating material containing 70% by weight or more of polyvinylidene fluoride is becoming mainstream, and its quality standard is that the discoloration of the color is NBS in the accelerated weather resistance test 1500 hours.
Color difference (△ E) is 7 or less, AST after 2,000 hours of salt spray test
At present, it must have the performance of M8F or higher and is obligated to have a long-term guarantee.

[Problems to be Solved by the Invention]

However, the current fluororesin coating materials have potential problems such as pressure marks being formed during winding (coiling) and scratches during molding and construction.

In Japanese Patent Laid-Open No. 61-236869, an inorganic aggregate (such as glass fiber) is blended with the above fluororesin coating to improve the strength and hardness of the coating film, and to improve workability such as scratch resistance and abrasion resistance. A coating having excellent water resistance and other properties is disclosed. However, in the case of the coating material, since hard aggregate is used, there is a risk of new problems such as abrasion of the forming roll and abrasion of the shirring blade during the forming process.

An object of the present invention is that there is almost no pressure mark at the time of winding or scratches on the coating surface at the time of molding and processing and wear of a molding roll or a shearing blade, and at the same time, it is excellent in a new warm and soft design. A paint for a metal plate, a coated metal plate coated with the same, and a method for producing such a coated metal plate, which have a finished finish and further have the moldability and long-term durability of a conventional coated metal plate. To provide.

[Means for Solving the Problems]

The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, have good molding processability, and without any loss of durability, a finish having a unique design property can be obtained. It was found that the present invention has been completed.

That is, the present invention is a coating material containing a resin component composed of polyvinylidene fluoride and an acrylic resin as a main component, wherein the solid content of the coating material is 0.1 to 20% by weight of acrylic polymer beads containing a crosslinking agent in an amount of 2 to 20% by weight. In order to obtain a paint for metal plates, which is characterized by containing 30% by weight.

Further, the present invention is to obtain a coated metal plate having a top coating film formed by applying the above-mentioned coating material on the plate surface.

Further, the present invention provides a method for producing a coated metal plate, which comprises applying the above-mentioned coating material to a metal plate, heating the metal plate so that the temperature of the metal plate reaches 100 ° C. or higher, and baking and curing the metal plate.

Polyvinylidene fluoride has a weight average molecular weight of 400,00
It is preferably 0 or more and has a melting point of 150 to 180 ° C. For example, there is Kainer 500 (trade name of Japan Penwalt Co., Ltd., weight average molecular weight 650,000, melting point 160 to 165 ° C.) and the like.

As the acrylic resin, 70% by weight or more of its polymerized units are C1-C10 (meth) acrylic acid alkyl ester monomers such as methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate. , (Meta)
It is composed of one or more of propyl acrylate, amyl (meth) acrylate, hexyl (meth) acrylate, and octyl (meth) acrylate, and has a weight average molecular weight of 50,000 to 200,000. More preferably, 50% by weight or more of the polymerized units constituting the acrylic resin is methyl methacrylate.

Similarly, the monomer that constitutes 30% by weight or less of the polymerized units of the acrylic resin may be any monomer that is copolymerizable with the above acrylic monomer. Examples of such a monomer include (meth) acrylic acid, styrene, vinyltoluene, (meth) acrylonitrile, (meth) acrylic acid amide, and vinyl chloride. The mixing ratio of the above polyvinylidene fluoride and acrylic resin is preferably 90:10 to 40:60 by weight.

In the present invention, the acrylic polymer beads to be mixed with the conventional paint must first have a quality that does not impair the excellent properties of the conventional paint and the coating film. Specifically, it is required that it is hardly dissolved in the solvent in the conventional paint, that the storage stability of the paint is not deteriorated, and that it has an affinity with the acrylic resin in the paint.

Therefore, regarding the monomer composition and crosslink density of the acrylic polymer that forms the beads, MMA (methyl methacrylate) is 80 to 98% by weight, the monomer group that can be copolymerized with MMA is 18% by weight or less, and the crosslinking agent (ethylene glycol dimethacrylate). ) Is 2 to 20% by weight, preferably 5 to 10
Weight% is desirable.

If the cross-linking agent exceeds 20% by weight, the beads are too hard, and there is a risk that the back surface may be scratched when winding the coated metal plate or other problems may occur, which is not preferable.

The particle size of acrylic polymer beads is 10-50 μmφ,
It is preferably 20 to 40 μmφ. If it is less than 10 μmφ, the unique designability that is the object of the present invention cannot be obtained, and if it exceeds 50 μmφ, the settling property of the beads in the paint is remarkable, which is not preferable.

Acrylic polymer beads may be mixed in the paint as they are, but after the surface treatment of the beads with a coupling agent for the purpose of improving the affinity and dispersibility in the paint and reducing the risk of sedimentation. It can also be mixed in paint.
As a specific surface treatment method, an aluminum-based coupling agent, for example, Plenact ALM [trade name of Ajinomoto Co., Inc., chemical name: acetoalkoxyaluminum diisopropylate, general formula (I)] Was dissolved in isophorone in an amount of 3% by weight with respect to the acrylic polymer beads, and the beads were put into the solution to bring them into good contact with each other.

The mixing ratio of the acrylic polymer beads in the paint is 0.1 to 30% by weight, preferably 5 to 20% by weight in the coating film.
If it is less than 0.1% by weight, the unique design property which is the object of the present invention is inadequate, and if it exceeds 30% by weight, the paint properties are deteriorated, the coating workability is impaired, and the finish of the coating surface is deteriorated, which is unsatisfactory.

As a conventional method for incorporating the acrylic polymer beads into the coating material, the acrylic polymer beads may be added to and uniformly mixed with the coating material while gently stirring the coating material.

In the coating material for a metal plate of the present invention, an inorganic or organic aggregate, a coloring pigment, an extender pigment, a solvent, an additive and the like can be blended as necessary in addition to the above essential components.

Examples of the inorganic aggregate include glass beads, glass fibers, alumina fibers, alumina particles, silica, and pyrogenic silica.

Examples of the organic aggregate include polyacrylonitrile beads, benzoguanamine beads, nylon beads and the like.

Examples of the color pigment include titanium oxide, carbon black, iron oxide, lead chromate, metal powder (Al, Cu), calcined pigment (cobalt blue, green), pearl pigment, and the like. The pearl pigment is a pigment in which a scale-like mica surface is coated with titanium oxide or the like, and is preferably added to the coating material for a metal plate of the present invention because it has an effect of improving the design. Examples thereof include Exterior Marlin Bright White (trade name of Marl Co., Ltd.) and Iriodin 103W2 (trade name of Merck Japan Co., Ltd.).

Examples of extender pigments include calcium carbonate, clay, talc, antimony trioxide, barium sulfate and kaolin.

Examples of the solvent include toluene, xylene, ethyl acetate, butyl acetate, cellosolve-based solvent, methyl isobutyl ketone, methyl ethyl ketone, diisobutyl ketone, isophorone, cyclohexanone and the like.

Examples of the additive include an antifoaming agent, a pigment dispersant, an anti-sagging agent, and an anti-scratch agent. Among them, a polytetrafluoroethylene powder resin having a melting point of 300 ° C. or higher is effective as a remarkable scratch preventive agent. For example, Fostaflon TF-9205 (trade name of Hoechst Japan KK) and the like can be mentioned.

Next, a method for producing a coated metal plate using the metal plate coating material prepared as described above will be described. As the metal plate to be coated, for example, a hot dip galvanized steel plate, a zinc / aluminum alloy plated steel plate, an aluminum plated steel plate, a cold rolled steel plate, a stainless steel plate, an aluminum plate, etc. are generally used.

These metal plates are usually subjected to degreasing treatment before coating, and if necessary, chemical rust removal such as pickling or electrolytic pickling, and then chemical conversion coating treatment such as chromate treatment or phosphoric acid treatment. To be done.

The coating material for a metal plate of the present invention can be directly coated on the chemical conversion film thus formed, but in order to improve performance such as corrosion resistance and adhesion, it is usually applied to a coated metal plate. It is desirable to coat and bake the used undercoat paint, for example, an epoxy resin-based undercoat paint, and then apply.

Further, the viscosity of the paint at the time of coating may be a commonly used viscosity, and in the case of roll coating, Ford Cup # 4 (25
C.) is preferably 40 to 180 seconds.

The coating method is not particularly limited, and a method commonly used for coating a conventional solvent-based paint, such as brush coating, tampo coating, roll coating, or spray coating, can be used. Roll coating is the most common method of painting. The coating film thickness is in the range of 5 to 80 μm, preferably 10 to 50 μm before baking and curing.

The baking and curing conditions are heating for 15 to 180 seconds to bring the temperature of the metal plate to 100 ° C. or higher. If the baking time is less than 15 seconds, the curing of the resin component is insufficient, and if it exceeds 180 seconds, the curing of the resin component becomes excessive, and in either case, the original performance of the coating material is not exhibited, which is not preferable.

The heating method is not particularly limited, and any method can be used, for example, an external heating method such as a convection heating method or a radiant heating method, or an internal heating method using high frequency.

[Action]

The coated metal plate in the present invention is a polymer having a low cross-linking structure in which the acrylic polymer beads used for the paint contain 2 to 20 wt% of a cross-linking agent, hardly dissolves in a solvent, and also not too hard, It has intermediate desirable properties. Therefore, without reducing the stability of the paint,
In addition, when the coating film is formed, the surface layer of the acrylic polymer beads swells, albeit slightly, and has affinity with the coating resin component to strengthen the integrity, thus making the coating film robust, abrasion-resistant, scratch-resistant, and durable. It is considered that they also contribute to moisture resistance and the like.

〔The invention's effect〕

The metal plate coated with the coating material of the present invention can obtain a unique finished surface which has not been found in the conventional coated metal plate. That is, by blending acrylic polymer beads, it gives a matte-like flesh-like feel and an excellent appearance with a soft design, and during molding processing, the painted surface is tough, scratch-resistant, and wear-resistant. It is also excellent in workability, and the degree of wear of the molding roll surface and shirring blade is also very slight.

〔Example〕

Next, the present invention will be specifically described with reference to Examples and Comparative Examples. All% and parts in the examples are based on weight.

Examples 1 to 6 and Comparative Examples 1 to 3 (Preparation of Topcoat Paint) Each topcoat paint was prepared according to the formulation shown in Table 1 by the following method. As a coating material, Precolor No. 8000 Brown (trade name of NOF CORPORATION) was placed in a container, and other components were added to the mixture while stirring and uniformly mixed to prepare each top coating composition.

* 1: Pre-color No. 8000 Brown (trade name of NOF CORPORATION) The coating composition and properties are as follows.

(1) Resin composition (solid content: 100 in total) Polyvinylidene difluoride (Kiner 500 Nippon Penfort Co., Ltd. product name, weight average molecular weight: 650000,
Melting point 160-165 ° C) 70% Acrylic resin (methyl methacrylate / ethyl acrylate = 70/30, weight average molecular weight: 63000) 30% (2) Pigment composition (total 100) Titanium oxide 3% Firing brown 49% Firing black 43 % Antimony trioxide 5% (3) Pigment / resin (solids) ratio 0.35 (4) Paint solids (% by weight) 55% (5) Paint viscosity (Ford cup # 4, 25 ° C) 105 seconds * 2: Tech Polymer MBX-30 (trade name of Sekisui Plastics Co., Ltd., cross-linking agent: 5% by weight, particle size: 30 μmφ) * 3: Exterior Merlin Bright White (trade name of Marl Co., Ltd.) * 4: Foster Freon TF-9205 (Hoechst Japan Ltd.)
* 5: Micro-Glass Surface TRAND REV-9 (trade name of Nippon Sheet Glass Co., Ltd.) (Preparation of test pieces) The plate to be coated is gallium barium: 55% Al / Zn plated steel plate, and the back side is prepared in advance. The back surface coating is applied to a dry film thickness of 5μ
What was painted m was used.

As a method of forming a coating film on the front surface, first, an epoxy resin-based paint (trade name: pre-color primer F-1, manufactured by NOF CORPORATION) was used as an undercoat paint for the plate to be coated.
No. 12 was used to apply a dry coating film thickness of 5 μm, and the plate was dried at an ultimate plate temperature of 210 ° C. Next, each of the above-mentioned top coating materials was applied using a bar coater # 46 so that the dry coating film thickness would be 25 μm, and dried at an ultimate plate temperature of 250 ° C.

The test pieces produced as described above were tested by the following test items and methods. The results are shown in Table 2.

Test method and evaluation method a: Appearance of coating film: A product having a matte finish, softness, warmth and a poor metallic feel of the coating film was given a high designability (5). On the other hand, a product having hardness and coldness and a metallic feel was designated as having low designability (1). Evaluation was made by this 5-point method, and 4 points or more were passed.

b Pressure mark test: After setting the temperature of the press machine to 40 ° C, stacking the front and back surfaces of two test pieces together, and sandwiching them with a load of 100 kg / cm ^{2 for} 96 hours with the press machine. The change in gloss of the front surface of the test piece was visually observed. In this test method, the flatter the coating film is, the more the gloss is increased. The evaluation method was as follows.

A: No increase in visual gloss O: A slight increase in visual gloss is observed.

Δ: An increase in visual gloss is clearly recognized.

c Coin scratch resistance: Apply an edge to the coated surface of the test piece so that a ten-yen coin is pressed against the coated surface with a finger at an angle of about 45 degrees. While pressing it against the coated surface as it is, pull it in a direction perpendicular to the plane of the ten-yen coin to scratch the coated surface. From the scratching method, the scratch resistance and slipperiness of the coating film were observed. It was evaluated by the following 5-point method.

⊚: Slightly scratched.

○: The scratch is only after rubbing.

Δ: The scratch reached the undercoat paint film only after rubbing.

X: The scratch is scraped and peels off more than after.

d Workability: Each test piece was tested for workability in a room at 20 ° C. 2T in the table means the same coated plate 2 as the test piece to be processed
Insert the pieces inside (3T-6T inserts 3-6 pieces)
It is a 180 degree close contact bend. 10 bent tip
Observation with a double magnifying glass showed a crack-free processing level. 2T to 5T was passed.

e Abrasion resistance of forming roll: 30 pieces of 30 × 100 cm test pieces were formed by a roll forming machine 30 times, and the plated surface of the forming roll was observed after passing 30 pieces. The test pieces of Example 2 and Comparative Examples 1 and 3 were used. The evaluation method was as follows.

⊚: No change is observed in the gloss of the plated surface.

◯: The gloss of the plated surface is slightly reduced.

B: It is recognized that the gloss of the plated surface is reduced.

f Pencil hardness: The pencil hardness was tested based on JIS-D-0202.

g Tapered wear: Tapered wear is JIS-K-690
Based on 2, a wear wheel CS-10 was used to measure the wear loss after 1,000 rotations with a load of 1 kg. The wear loss was evaluated at mg / 1,000 revolutions.

h Sandfall test: The sandfall test was conducted by measuring the sandfall test until the base material was exposed based on ASTM-D968-51.

i Salt spray: A test piece processed for 2T according to JIS-Z-2371 was tested for 2,000 hours, and the degree of rust in the processed portion was visually determined.

j Chemical resistance: 3T processed test pieces were immersed in a 10% hydrochloric acid aqueous solution, a 10% sulfuric acid aqueous solution and a 10% sodium hydroxide aqueous solution at 20 ° C for 10 days each, and then the normal coating film of the processed part was used. The presence or absence was visually determined.

k Accelerated weathering resistance: A test piece subjected to 3T processing was tested for 1,500 hours under the following tester and test conditions (commonly known as Ducycle sunshine weatherometer) Tester: WEL-Sunshine-DC, manufactured by Suga Test Instruments Co., Ltd. Test condition: Light source carbon arc Black panel temperature 63 ℃ Observe the coated surface condition after the test, color difference ΔE before and after the test,
The gloss retention percentage was measured.

As is clear from Table 2, Comparative Examples 1 and 2 which are out of the scope of the present invention have dissatisfaction with respect to the appearance of the coating film, the pressure mark, or the abrasion resistance of the forming roll. In Comparative Example 3 in which the glass fiber is mixed, the abrasion property of the molding roll is somewhat uneasy, and the designability is poor as compared with the Examples. In Examples 1 to 6 according to the present invention, it is apparent that the coating film appearance, design, coating film toughness, durability, etc. all show extremely good results.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A 64-66261 (JP, A) JP-A 2-228377 (JP, A) JP-A 3-203973 (JP, A) JP-A 2- 174977 (JP, A)

Claims (3)

[Claims] 1. A paint comprising a resin component composed of polyvinylidene fluoride and an acrylic resin as a main component, wherein the solid content of the paint is 80 to 98% by weight of methyl methacrylate.
A paint for a metal plate, comprising 18% by weight or less of a monomer group copolymerizable with methyl methacrylate, and 0.1 to 30% by weight of acrylic polymer beads containing 2 to 20% by weight of a crosslinking agent. 2. A coated metal plate having a top surface coated with the coating composition according to claim 1. 3. A method for producing a coated metal plate, which comprises applying the coating composition according to claim 1 to a metal plate, heating the metal plate to a temperature of 100 ° C. or higher, and baking and curing the metal plate.