JPH08337742A - Resin-coated metallic material and its production - Google Patents

Abstract

PURPOSE: To produce the subject metallic material, having a uniform color tone on the surface without being influenced with the kind of the metallic material used, the viscosity, etc., of a coating liquid and having a beautiful appearance capable of hiding the unevenness of the metallic material surface by adding resin particles capable of scattering light into a resin film. CONSTITUTION: This resin-coated metallic material is obtained by coating the metallic material with a coating liquid containing resin particles capable of scattering light. Furthermore, the particles contain two or more kinds of particles having at least one of hollow, doughnut type flat and fine particle aggregatelike shapes and 0.05-1.0μm average particle diameter and different average particle diameters and, e.g. styrene-acrylic copolymer resin particles are used. The concentration thereof added is preferably 1-30wt.% expressed in terms of the ratio thereof occupied in the total weight of the dried film and the amount of the sticking film is preferably 0.2-3.0g/m<2> expressed in terms of the weight of the dried film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-coated metal material having a uniform surface color tone and no unevenness (scratches or stains) and a beautiful appearance, and a method for producing the same. INDUSTRIAL APPLICABILITY The resin-coated metal material of the present invention has a good appearance without being subjected to a top-coating treatment, and is therefore suitably used for outer panels such as automobiles, household electrical appliances, steel furniture, and building materials.

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

[0003]

2. Description of the Related Art Metal plates used for automobiles, household appliances, building materials, etc. are plated metal plates (for example, zinc and zinc alloy plated steel sheets, aluminum and aluminum alloy plated steel sheets, copper-based plated steel sheets, nickel-based plated sheets). Steel plates, chrome-based plated steel plates, etc.), various metal plates such as mild steel plates and stainless steel plates, and metal plates for chemical conversion treatment (phosphate treatment, chromate treatment, etc.), among which zinc-based plated steel plates are widely used. ing. However, since the above-mentioned zinc-based plated steel sheet is insufficient in corrosion resistance and paintability as it is, it is usually subjected to chemical conversion treatment such as chromate treatment or phosphate treatment, or higher corrosion resistance or corrosion resistance. When chemicals and the like are required, a coating process is further applied to a thickness of several tens of μm. By performing such a treatment, it is possible to conceal a slight visual defect (unevenness of plating, etc.) on the surface of the zinc-based plating, and so far no serious problem in use has occurred.

However, in recent years, there has been an increasing demand for the omission of the coating process on the user side, and corrosion resistance, fingerprint resistance, and
For the purpose of improving lubricity etc., we often use special chemical conversion treated steel sheets that are chromate-treated and have a transparent organic resin coating on the zinc-based plated steel sheet without being coated (unpainted). Has become. In such a special chemical conversion treated steel sheet, the appearance of the zinc-based plated steel sheet will appear as it is in the final product, so the quality requirements for the appearance of the zinc-based plated surface will become even more severe. There is.

Among such zinc-based plating, electrozinc-based plating, which gives a particularly beautiful surface, is frequently used for such bare use. It is becoming difficult to sufficiently cope with the strictness of the surface quality level in Japan. That is, when the electrogalvanizing treatment is performed, there are irregular portions on the surface where the color tone is partially different, resulting in a problem that the appearance of the plated surface is significantly deteriorated. It is considered that this is because the size and the regularity of the arrangement of the zinc-based plating crystal are partially different, and the amount of light reflected on the plating surface changes depending on such a partial change of the plating crystal. Occurs,
It is perceived by the human eye as a color difference. When such a color 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 difference is further emphasized depending on the light reflection direction. There is also.

In order to improve the appearance of such an electrogalvanized plating surface, a method of adding a brightening agent to the plating bath is well known. Among these, low molecular compounds such as thiourea, aromatic aldehydes, coumarone, amines, imino compounds, dextrin, and gluconic acid are known as brighteners added to the acidic zinc-based plating bath. Other examples of brightening agents added to the plating bath include Japanese Patent Publication No. 46-388.
No. 88, polyacrylamide, JP-A-61-12
Japanese Patent No. 7887 discloses a polyacrylamide obtained by copolymerizing a cationic monomer containing polyacrylamide as a main component.

When such a brightening agent is added, the entire zinc-based plated crystal is made finer and smoother, so that a beautiful appearance with metallic luster can be obtained. However, the effect of these brighteners is so great that the appearance of the plating changes drastically before and after the addition of the brightener. That is, the gloss level changes significantly only by slightly changing the amount of the brightening agent added to the plating bath. Therefore, if the plating bath is continuously electrolyzed for a long time during continuous operation, even if the content of the brightening agent is controlled to be in an appropriate range at the start of plating, the content will change as time passes, It becomes very difficult to maintain the proper content range for a long time.

As a method for improving the plating appearance without adding the above-mentioned brightening agent, there has been disclosed a method for controlling the surface crystal grain size of a material to be plated to a ferrite crystal grain diameter of 10 μm or more and 35 μm or less (Japanese Patent Laid-Open Publication No. Sho. 61-166992
Issue). This method utilizes the phenomenon that zinc-based plated crystals grow epitaxially along the surface crystal grains of the plated material, and the zinc-based plated crystal is reduced by reducing the surface crystal grain size of the plated material. It is a method of making fine and smooth. However, it is difficult to control the grain size of the material to be plated within a specific range for all applications, and in the case of the material to be plated having a partially different grain size, as a result, electrolytic zinc with a different color tone is obtained. There is a problem that a galvanized steel sheet is produced.

In such a 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. Specifically, there is a method in which a pigment is added to a coating liquid for forming a coating film, and the coating liquid is applied to a plated metal plate for coloring so as to conceal uneven plating. Among these pigments, inorganic pigments such as titanium oxide, zinc oxide, zinc white, etc. are affected by the color of the plated metal plate due to the large refractive index of the component substances (that is, the large effect of scattering light). It is possible to color the color that the pigment itself does not have.

However, these inorganic pigments generally have a large specific gravity, and the pigment is precipitated depending on the viscosity of the resin coating solution used, so that the dispersibility is poor and it becomes difficult to uniformly coat the surface of the plated metal plate. Such a phenomenon is particularly noticeable when the above inorganic pigment is added to the aqueous resin coating liquid. 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 largely different from the original appearance.

The zinc-based plated steel sheet has been taken up as a typical example of the metal material used in automobiles and the like, and the problems in the plated steel sheet have been mentioned above. However, these problems are not limited to the zinc-based plated steel sheet, and have been described above. It is found in all metal materials. In these metal materials, since scratches, chemical conversion treatment unevenness, pre-plating uneven treatment, various stain patterns and the like due to uneven washing after plating, etc. occur, while eliminating the color tone difference caused by the above-mentioned plating crystals, etc., It has been earnestly desired to provide a novel resin-coated metal material capable of concealing such surface irregularities (scratches, stains, etc.).

[0012]

The present invention has been made in view of the above circumstances, and its purpose is not affected by the type of metal material used, the viscosity of the coating liquid, or the like. It is an object of the present invention to provide a resin-coated metal material having a uniform color tone and a beautiful appearance capable of concealing unevenness (scratches, stains, etc.) on the surface of the metal material, and a method for producing the same.

[0013]

The resin-coated metal material according to the present invention which has been able to solve the above-mentioned problems is obtained by coating the surface of a metal material with a resin coating film containing resin particles for scattering light. The point is that

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

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

[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 surface of the metal material and the light reflected from the surface of the metal material are scattered, and it becomes difficult for the unevenness present on the surface of the metal material to be visually recognized, so that an excellent concealing effect is obtained. Further, the resin particles have very good dispersibility in the resin coating film, and also have excellent adhesion to the coating film to be overcoated as needed on the coating film.
Therefore, corrosion resistance obtained by applying resin coating,
Performances such as workability can be exhibited well.

The resin particles used in the present invention are not particularly limited as long as they have a function of scattering light, and examples thereof include styrene resin, styrene copolymer resin, polyester resin, melamine resin and the like. Can be mentioned.

Among the above resin particles, styrene resin, especially the styrene-acrylic copolymer resin particles are recommended as preferable ones. The reason is that the refractive index of the styrene resin is higher than that of the ordinary coating film-constituting resin, and the amount of light scattering on the surface of the resin particles is large. In addition, acrylic monomers have polar groups, whereas styrene monomers are non-polar, and by copolymerizing these, it is possible to increase the affinity and dispersibility with the resin constituting the coating film. It is thought to contribute. Here, the copolymerization ratio of the styrene-based monomer and the acrylic-based monomer is preferably 1:50 to 50: 1 by weight. As the copolymerizable monomer having a polar group, for example, methyl methacrylate, vinyl acetate, vinyl chloride or the like may be used instead of the acrylic monomer.

In the present invention, the characteristics of the resin particles blended in the coating film as described above are defined, and the resin system constituting the vehicle component is not particularly limited. Any resin-based material may be used as long as it is an optical interface at which a difference in refractive index is generated, 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: Examples of the shape of the resin particles include a spherical shape, a hollow shape, a donut type flat shape, a fine particle aggregate shape, a flake shape, and the like. Among them, a hollow shape, a donut type flat shape, Fine particle aggregate form is preferred.
The reason is that these shapes are superior to the spherical shape in light scattering action on the particle surface. The resin particles having such a shape may be present alone in the resin coating film, or two or more kinds of particles having different shapes may be mixed.

Among them, the hollow resin particles are hollow particles, and the inner diameter of the particles is about 1/5 to 1/2 of the total particle diameter. When such hollow resin particles are used, light is scattered not only on the outer surface of the resin particles but also on the inside thereof, so that the scattering effect becomes larger than that of the spherical particles having no void. Further, the donut-shaped flat resin particles are those in which the particle cross section has an elliptical shape and the central part thereof has a concave shape, while the fine particle aggregated resin particles have a spherical resin particle as a core, It has a shape in which fine particles are further attached to its surface. The flake-shaped resin particles have a fish-like shape. As described above, since the surface of each of these resin particles has a unique shape, the scattering effect on the particle surface becomes larger than that of the spherical resin particles, and as a result, the uneven portion existing in the metal material is optically dispersed. It is difficult to recognize as a large color difference.

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

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 very high as compared with the conventional inorganic pigments, and thus the coating can be performed. It has an advantage that it is hardly affected by the viscosity of the liquid.

Regarding the average particle diameter of the resin particles: The average particle diameter of the resin particles is preferably 0.05 to 1.0 μm, more preferably 0.1 to 0.7 μm. When the volume concentration of the resin particles contained in the coating film is made equal and only the average particle diameter is compared, if the average particle diameter is smaller than 0.05 μm, the number of particles increases, but the particles are not scattered on the surface. The ratio of transmitted light becomes large and the hiding property becomes poor. On the other hand, when the average particle size is larger than 1.0 μm, the proportion of light scattered on the particle surface increases, but the number of particles is small, which causes a disadvantage that the scattering rate is low. For this reason
It is recommended to set the average particle size of the resin particles capable of efficiently scattering light within the above range. Further, in order to efficiently scatter light in the visible light region which 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.

Concerning the addition concentration of the resin particles: The preferable addition 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 dry coating film. If the addition concentration of the resin particles is less than 1% by weight, the hiding effect becomes small, the proportion of light that is transmitted without being scattered on the particle surface becomes high, and the unevenness of the surface becomes conspicuous. As the added concentration increases, the scattering effect increases, but the adhesion between the resin particle-containing coating and the plated metal material decreases, and the original corrosion resistance of the resin-coated metal material deteriorates. Since the color tone of the coating film changes greatly, the upper limit is preferably 30% by weight or less.

Regarding the adhesion amount of the resin coating film: The adhesion amount of the resin coating film is preferably 0.2 to 3.0 g / m ^{2 as} the weight after drying. If the amount of coating film adhered is less than 0.2 g / m ² , the hiding effect of the resin coating film will be reduced, and it will be difficult to apply the coating liquid evenly to 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, as the coating amount increases, the effect of concealing the unevenness of the plating surface increases, but if the coating amount exceeds 3.0 g / m ² , the amount of peeling of the coating during pressing increases. , The peeled film accumulates in the mold, which causes troubles during press formation, increases in cost, decreases the speed in the continuous coating line due to the prolonged drying time after resin liquid application, and the resulting decrease in productivity. Problems such as increased manufacturing costs arise. From the viewpoint of practical operation, the more preferable amount of the resin coating film deposited 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 above resin coating film is not particularly limited, but preferred are polyethylene resin, polyurethane resin, polyester resin, epoxy resin, acrylic resin. Examples of such resins include resin. For the purpose of further improving coating film performance, a partial cross-linking agent, within a range that does not significantly change the appearance and color tone of the resin-coated metal material of the present invention,
Various additives such as a diluent, an anti-skinning agent, a leveling agent, a defoaming agent, a penetrating agent, a film-forming aid, a thickener, and a pigment can also be added. Of these, the pigment generally has a large specific gravity and poor dispersibility as described above. Therefore, it is preferable to add the pigment at a ratio of 10% by weight or less of the resin particles so that the addition of the pigment does not impair the dispersibility. Or fine powder silica, colloidal silica, for the purpose of improving adhesion and corrosion resistance,
It is also possible to appropriately add a silane coupling agent or the like.

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

Here, the method of applying the coating liquid to the surface of the metal material is not particularly limited, and for example, the surface is previously cleaned, or pretreatment (for example, phosphate treatment, chromate treatment, etc.) is performed. Examples of the method include coating on the surface of the long metal strip by using a roll coater method, a spray method, a curtain flow coater method, or the like. Among them, the roll coater method is most practically preferable from the viewpoint of comprehensive evaluation of coating film thickness uniformity, treatment 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 below the softening point of the resin particles so that the shape of the resin particles to be added does not change and the scattering effect on the surface does not decrease. Furthermore, for the purpose of improving the adhesion or corrosion resistance with the resin coating film, the metal material surface is treated with phosphate,
Pre-painting treatment such as chromate treatment may be applied.

The present invention will be described in more detail with reference to the following examples, but the following examples are not intended to limit the present invention, and any modification or implementation is within the scope of the present invention without departing from the gist thereof. It is included in 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 thereof is shown in Table 1) was prepared and its dispersibility was evaluated. Specifically, a water-dispersed polyethylene-based resin emulsion is used as a base resin forming the coating film, and a polyethylene-based, styrene-acrylic copolymer and polyacrylonitrile-based resin particles are added to the base resin as resin particles; Finely divided silica, titanium oxide, zinc white and lead white were added as inorganic pigments. The average particle size of these resin particles and 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 dry coating film weight.

[0033]

[Table 1]

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

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

Example 2: Evaluation of concealing property and corrosion resistance Among the coating liquids A to G used in Example 1, A and B satisfying the constitutional requirements of the present invention, and C not satisfying the constitutional requirements of the present invention. And D, particle shape, particle addition concentration,
The hiding property and corrosion resistance when the average particle diameter and the coating film coating amount were variously changed were evaluated in the following manner.

(1) Concealability The concealability was measured as an index for evaluating the extent to which the uneven appearance of the base steel sheet is made inconspicuous. That is, in order to evaluate the hiding ratio of the coating film, a hiding ratio measurement test of the coating film specified in JIS-K5400 was performed. Specifically, the particle shape, average particle size and addition concentration of the additive particles in each coating liquid (A to D) used in Example 1 were variously changed as shown in Tables 2 to 8, and the hiding ratio test paper ( (Japan Test Panel Industry Co., Ltd.) was applied by the bar coating method so that the desired coating amount could be obtained, and then the resin coating film was transferred at the specified plate temperature (drying temperature) while being transferred in the hot air drying oven. Dried.

Next, using a color difference meter (manufactured by Nippon Denshoku Co., Ltd.), the Y value of the coating film on the white surface (one of the three color XYZ functions 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 calculated according to the following formula. Concealment ratio = Y value of coating film on black surface / Y value of coating film on white surface The evaluation criteria of the concealment ratio thus calculated are as follows. ⊚: Excellent (Hiding rate over 0.06) ○: Good (〃 over 0.04 to 0.06) ×: Inferior (〃 0.04 or less)

(2) Corrosion resistance (white rust resistance) Chromate-treated electrogalvanized steel sheet (zinc coverage: 20 g / m ² , chromate coverage: 20 mg / m 2).
^After coating various coating liquids (A to D) shown in Table 1 to a predetermined film thickness on the surface of ² ) by a roll coater method, the coating liquid is transferred in a hot air drying oven to a predetermined plate temperature (drying temperature). The resin coating film was dried in step (1).

The corrosion resistance (white rust resistance) of various resin-coated steel sheets thus obtained was determined according to JIS-Z2371.
Evaluation was performed according to the weight% salt spray test. That is, it was evaluated by measuring the time when the electrogalvanized layer located under the coating film corroded and 1% white rust was generated. The evaluation criteria are as follows. <White rust resistance> ⊚: excellent (white rust occurs in 241 hours or more) ◯: good (white rust occurs in 121 to 240 hours) Δ: somewhat inferior (white rust occurs in 49 to 120 hours) x: inferior (48 White rust occurs within time) The results are also shown in Tables 2-8.

[0041]

[Table 2]

[0042]

[Table 3]

[0043]

[Table 4]

[0044]

[Table 5]

[0045]

[Table 6]

[0046]

[Table 7]

[0047]

[Table 8]

From these results, the following can be considered. Among the coating liquids A to B containing the resin particles defined in the present invention, those in which the shape of the resin particles, the average particle diameter, the addition concentration and the amount of the coating film adhered satisfy the preferred ranges of the present invention are those having hiding property and corrosion resistance. Was excellent for both. Among these, those containing two or more kinds of resin particles having different average particle diameters or particle shapes are remarkably excellent in the above-mentioned action. On the other hand, although the coating liquids C and D have excellent dispersibility,
It was found that the refractive index was smaller than those of A and B, so that there was no effect of scattering light and the hiding property was poor.

[0049]

EFFECTS OF THE INVENTION Since the present invention is constituted as described above, the color tone of the surface is uniform and the surface of the metal material is free from unevenness (defects) without being affected by the kind of the metal material used, the viscosity of the coating liquid, and the like. It was possible to efficiently provide a resin-coated metal material having a beautiful appearance capable of concealing dirt, stains, etc.).

Claims (7)

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