JP2850795B2 - Metallic material coated with resin coating and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal material coated with a resin film having a beautiful appearance and a beautiful appearance without unevenness (scratch, dirt, etc.), and a method for producing the same. The metal material coated with the resin coating film of the present invention can provide a good appearance even without being subjected to a topcoating treatment, so that it is suitably used for automobiles, household electric appliances, outer panel materials such as steel furniture, building materials, and the like. Can be

In the following description, a metal plate will be mainly described as a typical example of a metal material, but is not limited thereto.
It goes without saying that the present invention can be applied to a metal material such as a metal tube and a metal rod.

[0003]

2. Description of the Related Art Metal sheets used for automobiles, household electric appliances, building materials and the like include plated metal sheets (for example, zinc and zinc alloy plated steel sheets, aluminum and aluminum alloy plated steel sheets, copper-based plated steel sheets, nickel-based plated steel sheets). Steel plates, chromium-plated steel plates, etc.), various metal plates such as mild steel plates and stainless steel plates, and chemical conversion treatment (phosphate treatment, chromate treatment, etc.) metal plates. Of these, zinc-plated steel plates are widely used. ing. However, the galvanized steel sheet has insufficient corrosion resistance and paintability as it is, and is usually subjected to a chemical conversion treatment such as a chromate treatment or a phosphate treatment, or has a higher corrosion resistance or a higher resistance. When chemical properties or the like are required, a coating treatment is applied over a further thickness of several tens μm from above. By performing such a treatment, slight defects in appearance (uneven plating, etc.) on the surface of the zinc-based plating can be masked, so that no major problems have been encountered so far.

However, in recent years, there has been an increasing demand for users to omit the coating process, and corrosion resistance, fingerprint resistance,
For the purpose of improving lubricity etc., special chemical conversion treated steel sheets, which have been subjected to chromate treatment and transparent organic resin coating on zinc-based plated steel sheets, are often used without coating (unpainted) without coating. Has become. In such special chemical conversion treated steel sheets, the appearance of the galvanized steel sheet becomes remarkable as it is in the final product as it is, so the quality requirements for the appearance of the galvanized surface become even more severe. I have.

For such bare use, electrogalvanizing, which provides a particularly beautiful surface among zinc-based platings, is frequently used. It has become impossible to sufficiently cope with strict surface quality levels. That is, when the electro-zinc plating treatment is performed, there is a problem that portions having different color tones are present irregularly on the surface, and as a result, the appearance of the plating surface is significantly deteriorated. This is thought to be because the size and arrangement regularity of the zinc-based plating crystals are partially different, and the amount of light reflected on the plating surface changes according to such a partial change of the plating crystals. Arises
It is perceived by human vision as a color difference. Such a color tone difference is observed through the transparent resin layer even if the above-mentioned transparent thin film resin coating is applied from the plating surface, and the color tone difference is further emphasized depending on the light reflection direction. There is also.

[0006] In order to improve the appearance of the electrogalvanized plating surface, a method of adding a brightener to a plating bath is well known. Among them, low molecular compounds such as thiourea, aromatic aldehyde, coumarone, amine, imino compounds, dextrin, and gluconic acid are known as brighteners added to the acidic zinc-based plating bath. Other examples of brighteners added to the plating bath include JP-B-46-388.
No. 88 discloses polyacrylamide and JP-A-61-12.
Japanese Patent No. 7887 discloses a polyacrylamide obtained by copolymerizing a cationic monomer with polyacrylamide as a main component.

[0007] When such a brightening agent is added, the whole zinc-based plating crystal is made finer and smoother, so that a beautiful appearance with metallic luster can be obtained. However, since the action of these brighteners is extremely large, the appearance of plating changes drastically before and after the addition of the brightener. That is, even if the amount of the brightener added to the plating bath is slightly changed, the glossiness is significantly changed. Therefore, if the plating bath is continuously electrolyzed for a long time during continuous operation, even if the content of the brightener is controlled to an appropriate range at the start of plating, the content changes over time, It is very difficult to maintain the proper content range for a long time.

As a method of improving the plating appearance without adding the brightener, there is disclosed a method of controlling the surface crystal grain size of the material to be plated to a diameter of ferrite crystal grains: 10 μm or more and 35 μm or less (Japanese Patent Application Laid-open No. Sho. 61-166992
No.). This method utilizes the phenomenon that the zinc-based plating crystal grows epitaxially along the surface crystal grains of the material to be plated. By reducing the surface crystal grain size of the material to be plated, the zinc-based plating crystal is reduced. Is a method of making finer and smoother. However, it is difficult to control the crystal grain size of the material to be plated to a specific range for all applications. There is a problem that a system-plated steel sheet is generated.

In the method of controlling the plating layer or the material to be plated, it is very difficult to uniformly adjust the appearance of the plating surface. Various studies have been conducted on the types of paints added to the paint. Specifically, there is a method in which a pigment is added to a coating solution for forming a coating film, the coating solution is applied to a plating metal plate, and coloring is applied to shade the plating unevenness. Among these pigments, inorganic pigments such as titanium oxide, zinc oxide, and zinc oxide are affected by the color of the plated metal plate because the refractive index of the component substances is large (that is, the effect of scattering light is large). And it can be colored to the color of the pigment itself.

However, these inorganic pigments generally have a large specific gravity, and depending on the viscosity of the resin coating solution used, the pigment sediments, so that the pigment is inferior in dispersibility and it is difficult to apply the coating uniformly on the surface of the plated metal plate. Such a phenomenon is particularly noticeable when the above-mentioned inorganic pigment is added to the aqueous resin coating solution. Further, there is a problem that the color tone changes remarkably due to the addition of the inorganic pigment, and when the above-mentioned inorganic pigment is added to the resin coating film, the appearance of the resin-coated steel sheet is greatly different from the original appearance.

As described above, galvanized steel sheets are taken up as typical examples of metal materials used for automobiles and the like, and problems with the galvanized steel sheets are raised. These problems are not limited to the zinc-based steel sheets. It is found in all metal materials. In these metal materials, abrasion, chemical conversion unevenness, pre-plating unevenness, since various stain patterns and the like based on unevenness in water washing after plating also occur, while eliminating the color tone difference caused by the plating crystals and the like described above, There is an urgent need to provide a metal material coated with a novel resin coating film that can also mask such surface unevenness (scratch, dirt, etc.).

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and its object is to be performed without being affected by the type of metal material to be used or the viscosity of a coating solution. Another object of the present invention is to provide a metal material coated with a resin coating film having a uniform appearance and a beautiful appearance capable of masking unevenness (scratch, dirt, etc.) on the surface of the metal material, and a method for producing the same.

[0013]

Means for Solving the Problems A metal material coated with a resin coating film according to the present invention, which can solve the above problems, includes:
The point is that the surface of the metal material is covered with a resin coating film containing resin particles that scatter light.

Here, the shape of the resin particles is preferably at least one of a hollow shape, a donut-shaped flat shape, and a fine particle aggregate shape. The average particle size of the resin particles is preferably from 0.05 to 1.0 μm, more preferably from 0.1 to 0.7 μm. In the present invention, it is recommended that at least two kinds of resin particles having different average particle diameters included in such a range are contained. In addition, the concentration of the resin particles is 1 to 1 in the total weight of the dried coating film.
It is preferably 30% by weight, more preferably 5 to 5% by weight.
20% by weight. Further adhesion amount of the resin coating, a dry coating weight in terms of a 0.2 to 3.0 g / m ^2, more preferably from 0.3 to 1.0 g / m ^2.

The method for producing a metal material coated with a resin coating according to the present invention has a gist in that a coating solution containing the resin particles, more preferably an aqueous coating solution, is applied to the metal material. is there.

[0016]

The greatest feature of the present invention is that resin particles capable of scattering light are added to the resin coating film. As a result, the light reaching the metal material surface and the light reflected from the metal material surface are scattered, and unevenness existing on the metal material surface is hardly visually recognized, so that an excellent shading effect can be obtained. Further, the resin particles have very good dispersibility in the resin coating film, and also have excellent adhesion to a coating film to be overcoated as required on the coating film.
Therefore, the corrosion resistance obtained by applying resin coating,
Good performance such as workability can be exhibited.

The resin particles used in the present invention are not particularly limited as long as they have a function of scattering light. For example, styrene resins, styrene copolymer resins, polyester resins, melamine resins and the like can be used. No.

Of the above resin particles, styrene resins, especially the styrene-acrylic copolymer resin particles, are recommended as preferred. The reason is that the refractive index of the styrene resin is higher than that of the ordinary resin constituting the coating film, and the amount of light scattering on the surface of the resin particles increases. Acrylic monomers have polar groups, whereas styrene monomers are non-polar, and by copolymerizing them, greatly increase the affinity and dispersibility with the resin constituting the coating film. It is thought to contribute. Here, the copolymerization ratio of the styrene monomer and the acrylic monomer is preferably from 1:50 to 50: 1 by weight. As the copolymer monomer having a polar group instead of the acrylic monomer, for example, methyl methacrylate, vinyl acetate, vinyl chloride or the like may be used.

In the present invention, the characteristics of the resin particles to be blended in the coating film are specified as described above, and the resin system constituting the vehicle component is not particularly limited. Any portion may be used as long as the portion where a difference in refractive index occurs between the surfaces forms an optical interface, and light is reflected at the interface to scatter light on the surface of the resin particles. Hereinafter, preferred embodiments of the resin particles used in the present invention will be described.

Regarding the shape of the resin particles: The shape of the resin particles includes a true sphere, a hollow shape, a donut-shaped flat shape, an aggregated fine particle shape, and a flake shape. Fine particle aggregates are preferred.
The reason is that these shapes are more excellent in the light scattering action on the particle surface than the true spherical shape. The resin particles having such a shape may be present alone in the resin coating film, or two or more particles having different shapes may be mixed.

Of these, hollow resin particles have a hollow inside, and the inner diameter of the particles is about 1/5 to 1/2 of the total diameter of the particles. When such hollow resin particles are used, light is scattered not only on the outer surface but also on the inside of the resin particles, so that the scattering effect is larger than that of true spherical particles having no cavities. In addition, the donut-shaped flat resin particles have an elliptical particle cross section and a concave shape at the center thereof. It has a shape in which fine particles further adhere to the surface. The flake-shaped resin particles have a fish-scale shape. As described above, since the surface of each of these resin particles has a unique shape, the scattering effect on the particle surface is larger than that of the spherical resin particles, and the uneven portion existing in the metal material is optically deformed. This makes it difficult to recognize the color difference.

These resin particles are usually synthesized by an emulsion polymerization method or the like, and the synthesized resin usually exists in a spherical form in the resin emulsion liquid. In order to make such a spherical resin hollow, a method of forming a cavity by evaporating water contained therein when drying the resin emulsion is adopted. In addition, in order to prepare a donut-shaped flat or aggregated resin particle, a desired shape can be obtained by appropriately controlling various conditions such as a temperature in a polymerization process of the resin.

Since the resin particles of the present invention can be dispersed as an emulsion in an aqueous coating solution as will be described in detail in the production process described later, the dispersibility in the coating film is extremely high as compared with conventional inorganic pigments, It has the advantage that it is hardly affected by the viscosity of the liquid.

Regarding the average particle size of the resin particles: The average particle size of the resin particles is preferably 0.05 to 1.0 μm, and more preferably 0.1 to 0.7 μm. When comparing only the average particle diameter by equalizing the volume concentration of the resin particles contained in the coating film, when the average particle diameter is smaller than 0.05 μm, the number of particles increases, but without scattering on the particle surface. The proportion of transmitted light is increased and the shading is poor. On the other hand, when the average particle size is larger than 1.0 μm, the ratio of light scattered on the particle surface increases, but the number of particles is small, so that the scattering rate is disadvantageously low. For these reasons,
It is recommended that the average particle size of the resin particles capable of efficiently scattering light be set within the above range. Further, in order to efficiently scatter light in the visible light region that can be recognized by human eyes over all wavelengths, it is preferable to mix two or more kinds of resin particles having different average particle diameters within the above range.

Concentration of resin particles added: The preferred concentration of the resin particles is 1 to 30% by weight, more preferably 5 to 20% by weight, based on the total weight of the dried coating film. If the addition concentration of the resin particles is less than 1% by weight, the shading effect is reduced, the ratio of light that is transmitted without being scattered on the particle surface is increased, and the unevenness of the surface becomes more conspicuous. The higher the additive concentration, the greater the scattering effect, but the adhesion between the resin particle-containing coating and the plated metal material is reduced, and the corrosion resistance inherent in the resin-coated metal material is deteriorated. Since the color tone of the coating film is greatly changed, it is preferable to set the upper limit to 30% by weight or less.

Regarding the adhering amount of the resin coating film: The adhering amount of the resin coating film is preferably 0.2 to 3.0 g / m ^{2 by} weight after drying. When the amount of the coating film is smaller than 0.2 g / m ² , the effect of hiding the resin coating film is reduced, and it is difficult to uniformly apply the coating liquid on the surface of the metal material.
The properties such as chemical resistance, corrosion resistance, and scratch resistance due to the formation of the resin coating film cannot be sufficiently exhibited. On the other hand, the greater the amount of coating, the greater the effect of concealing the unevenness of the plating surface. However, if the amount of coating exceeds 3.0 g / m ² , the amount of peeling of the coating during pressing increases. In addition, the peeled film accumulates in the mold and causes troubles during press forming.In addition, the cost increases, the drying time after applying the resin liquid decreases, the speed in the continuous coating line decreases, Problems such as an increase in manufacturing costs arise. From the standpoint of practical operation, the more preferable adhesion amount of the resin coating film is 0.3 to 1.0 g / m ² .

Regarding the base resin component constituting the coating film: The resin system of the base resin constituting the resin coating film is not particularly limited, but is preferably a polyethylene resin, a polyurethane resin, a polyester resin, an epoxy resin, an acrylic resin. And the like. For the purpose of further improving the coating film performance, a partial cross-linking agent, a diluent, an anti-skinning agent, a leveling agent, a defoaming agent as long as the appearance and color of the metal material coated with the resin coating of the present invention are not significantly changed. Various additives such as an agent, a penetrant, a film-forming aid, a thickener, and a pigment can also be added. Of these, the pigment has a large specific gravity and poor dispersibility, as described above. Therefore, the pigment is preferably added at a ratio of 10% by weight or less of the resin particles so that the dispersibility is not impaired by the addition of the pigment. Alternatively, fine powdered silica, colloidal silica, a silane coupling agent and the like can be appropriately added for the purpose of improving adhesion and corrosion resistance.

Next, a method for producing a metal material coated with a resin coating according to the present invention will be described. First, in preparing a coating solution for a resin coating film, it can be easily obtained by mixing a base resin dispersed in an aqueous dispersion medium in the form of an emulsion with the resin particle-containing emulsion according to the present invention. If necessary, the above-mentioned additives are added to the thus-obtained coating solution, and then applied to the surface of the metal material using an arbitrary coating method and dried to obtain the metal material of the present invention.

Here, the method of applying the coating solution to the surface of the metal material is not particularly limited. For example, the surface is cleaned in advance, or pre-coating treatment (for example, phosphate treatment, chromate treatment, etc.) is performed. A method of applying to the surface of the long metal strip by using a roll coater method, a spray method, a curtain flow coater method, or the like is used. Among these, the roll coater method is the most practically preferable in terms of comprehensive evaluation from the viewpoints of uniformity of coating film thickness, processing cost, coating efficiency and the like. The resin coating film may be formed on only one side of the metal material, or may be formed on both sides.

In the drying step, it is preferable to dry the resin particles at a temperature lower than the softening point of the resin particles so that the shape of the added resin particles does not change and the scattering effect on the surface does not decrease. Further, for the purpose of improving the adhesion or corrosion resistance with the resin coating, the metal material surface, phosphate treatment,
A pre-coating treatment such as a chromate treatment may be performed.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples do not limit the present invention, and all changes and implementations without departing from the spirit of the present invention will be described. Within the technical scope of

[0032]

EXAMPLES Example 1 Evaluation of Dispersibility Resin coating liquids A to G applied to the surface of electrogalvanized steel sheet
(The composition is shown in Table 1) was prepared, and its dispersibility was evaluated. Specifically, a water-dispersed polyethylene resin emulsion is used as a base resin constituting the coating film, and polyethylene resin, styrene-acrylic copolymer and polyacrylonitrile resin particles are used as resin particles for the base resin; and Fine powdered silica, titanium oxide, zinc white and lead white were added as inorganic pigments. The average particle diameter of the resin particles and the inorganic pigment was 0.05 to 1.0 μm, and the addition concentration was in the range of 1 to 30% by weight based on the weight of the dried coating film.

[0033]

[Table 1]

After the thus obtained coating solution was allowed to stand for 12 hours, it was observed whether precipitation of resin particles or pigment was observed. The evaluation criteria for the dispersibility are as follows, and the results are also shown in Table 1. <Dispersibility> ：: Excellent (no precipitation) ○: Good (precipitation, but immediately dispersed by light stirring) ×: Poor (precipitation, strong stirring required for re-dispersion)

As shown in Table 1, the coating solutions A to C containing the resin particles were excellent in dispersibility, and did not precipitate even after standing for 12 hours. Further, among the inorganic pigments, the coating liquid D using a pigment having a low specific gravity caused precipitation after standing for 12 hours, but did not settle because it was immediately dispersed by mild stirring. On the other hand, the coating solutions E to G using the inorganic pigments having a large specific gravity were inferior in dispersibility, and the particles settled after standing for 12 hours.

Example 2 Evaluation of Shading Property and Corrosion Resistance Of the coating solutions A to G used in Example 1, A and B satisfying the requirements of the present invention, and C not satisfying the requirements of the present invention. And D, particle shape, particle addition concentration,
The concealing properties and the corrosion resistance when the average particle diameter and the coating film adhesion amount were variously changed were evaluated in the following manner.

(1) Concealment Concealment was measured as an index for evaluating the degree of making the appearance unevenness of the base steel sheet inconspicuous. That is, in order to evaluate the concealment ratio of the coating film, a coating concealment ratio measurement test defined by JIS-K5400 was performed. Specifically, the particle shape, average particle diameter and addition concentration of the added particles in each of the coating solutions (A to D) used in Example 1 were variously changed as shown in Tables 2 to 8, and the opacity test paper ( Nippon Test Panel Kogyo Co., Ltd.) and apply the resin coating film at a predetermined plate temperature (drying temperature) while transferring it in a hot air drying oven so that the desired coating film adhesion amount is obtained. Let dry.

Next, using a color difference meter (manufactured by Nippon Denshoku Co., Ltd.), the Y value of the coating film on a white surface (one of three functions XYZ of the color for obtaining the color tone of the coating film specified in JIS-Z8701)
And the Y value of the coating film on the black surface were measured, and the hiding ratio was determined according to the following equation. Hiding ratio = Y value of coating film on black surface / Y value of coating film on white surface The evaluation criteria of the hiding ratio calculated as described above are as follows. ：: excellent (concealment ratio more than 0.06) ○: good (〃 more than 0.04 to 0.06) ×: poor (〃 0.04 or less)

(2) Corrosion resistance (white rust resistance) Chromate-treated electrogalvanized steel sheet (zinc adhesion: 20 g / m ² , chromate adhesion: 20 mg / m
² ) Various coating liquids (A to D) shown in Table 1 are applied to the surface of the coating in a predetermined thickness by a roll coater method, and then transferred in a hot air drying furnace to a predetermined plate temperature (drying temperature). ) To dry the resin coating.

The corrosion resistance (white rust resistance) of the various resin-coated steel sheets obtained as described above was measured in accordance with JIS-Z2371.
It was evaluated according to the weight% salt spray test. That is, the evaluation was performed by measuring the time during which the electrogalvanized layer located below the coating film was corroded and 1% white rust was generated. The evaluation criteria are as follows. <White rust resistance> ：: Excellent (white rust occurs after 241 hours or more) ○: Good (white rust occurs from 121 to 240 hours) Δ: Slightly poor (white rust occurs from 49 to 120 hours) ×: Poor (48 (White rust occurs within hours.) The results are also shown in Tables 2 to 8.

[0041]

[Table 2]

[0042]

[Table 3]

[0043]

[Table 4]

[0044]

[Table 5]

[0045]

[Table 6]

[0046]

[Table 7]

[0047]

[Table 8]

The following can be considered from these results. Among the coating liquids A and B containing the resin particles specified in the present invention, those having the shape, average particle diameter, addition concentration and coating weight of the resin particles satisfying the preferred ranges of the present invention are concealing properties and corrosion resistance. Both were excellent. Among them, those containing two or more kinds of resin particles having different average particle diameters and different particle shapes have remarkably excellent effects. On the other hand, the coating solutions C and D have excellent dispersibility,
Since the refractive index was smaller than that of A or B, it was found that there was no light scattering effect and the concealing property was poor.

[0049]

Since the present invention is constructed as described above, the color tone of the surface is uniform and the surface roughness of the metal material is not affected by the type of metal material used and the viscosity of the coating solution. , Dirt, etc.) can be efficiently provided with a resin material coated with a resin coating having a beautiful appearance.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C09D 7/12 C09D 5/00

Claims (7)

(57) [Claims] 1. A metal material coated with a resin coating having a beautiful appearance, wherein the surface of the metal material is coated with a coating containing resin particles that scatter light. 2. The metal material coated with a resin coating according to claim 1, wherein the shape of the resin particles is at least one of a hollow shape, a donut-shaped flat shape, and a fine particle aggregate shape. 3. The resin particles having an average particle size of 0.05 to
The resin coating film according to claim 1 or 2, which has a thickness of 1.0 µm.
Coated metal material . 4. The resin coating film according to claim 3, wherein the resin particles contain two or more kinds of particles having different average particle diameters.
Coated metal material. 5. The method according to claim 1, wherein the concentration of the resin particles is 1 to 30% by weight based on the total weight of the dried coating film.
A metal material coated with the resin coating film according to any one of the above. 6. The metal material coated with a resin coating according to claim 1, wherein the amount of the coating applied is 0.2 to 3.0 g / m ² in terms of dry coating weight. 7. A gold coated with a resin film having a beautiful appearance according to claim 1 by applying a coating solution containing resin particles that scatter light to a metal material. > A method for producing a metal material coated with a resin coating , characterized in that a metal material is obtained.