KR20120005038A - Process for producing multilayer-coated metal sheet - Google Patents

Abstract

The present invention provides a method for producing a multilayer coated metal sheet having high adhesion without coating defects. The method for producing a multilayer-coated metal sheet according to the present invention is a multilayer simultaneous coating step in which a metal sheet is curtain-coated on at least one surface simultaneously with an upper layer paint and a lower layer paint in a wet state, and simultaneously drying the upper layer film and the lower layer film in the stacked wet state. In the method for producing a multilayer-coated metal sheet comprising a, the dynamic surface tension and the static surface tension of the upper layer paint and the lower layer paint satisfy a certain relationship.

Description

Manufacturing method of multilayer coating metal plate {PROCESS FOR PRODUCING MULTILAYER-COATED METAL SHEET}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a multilayer-coated metal plate, wherein a coating defect due to a mixed layer is applied in a multi-layer simultaneous coating process in which an upper layer paint and a lower layer paint are simultaneously applied on a metal plate in a wet state, and the laminated wet film is simultaneously dried. The present invention relates to a method for producing a multilayer-coated metal sheet which can be painted without causing agglomeration defects or the like.

Recently, the coated metal plate is used under severe conditions for many uses, and at the same time, many functions such as corrosion resistance, design, processability, corrosion resistance of the processed part, solvent resistance, alkali resistance, conductivity, wet adhesion, scratch resistance, etc. It is required to give.

As one of the solutions, performance is provided by multilayer coating.

As a general method of producing a multilayer coating film, the method of repeating application | coating and drying is mentioned. However, the problem is the equipment cost of a coating line, production time, etc., which need to repeat application and drying by the number of coating films. When producing a multilayer coating film, in the case of a multilayer simultaneous coating system (for example, patent document 1), drying of a coating film can be performed at once, the installation cost of a coating line can be reduced, and energy saving is carried out. In addition, productivity can be improved by shortening the running time. As a multi-layer simultaneous coating method, the method of apply | coating by discharging so that another paint may be laminated | stacked from two or more parallel slits etc. which are represented by a slide hopper type curtain coater can be used. This technique has conventionally been used in the field of photosensitive materials having a multilayer structure (for example, Patent Document 2), but has recently been applied in the paper industry (for example, Patent Document 3) and metal industry (for example, Patent Document 7) have.

In the case of using the multi-layer simultaneous coating method, the biggest problem is that the interface of the upper and lower paint layers (which should be generally flat) is disturbed before the laminated paint cures, and the lower paint enters the upper layer and protrudes to the surface of or near the upper layer. The mixed layer phenomenon, which is a discarding phenomenon, occurs, resulting in coating defects.

In patent document 2, the method of defining the dynamic surface tension and static surface tension of a coating liquid with respect to the curtain application | coating of a photosensitive material is mentioned.

Patent Documents 3 to 6 disclose a method of preventing coating defects such as mixed layers by controlling the difference between the dynamic surface tension of the upper layer paint and the dynamic surface tension of the lower layer paint in connection with multi-layer simultaneous coating.

In patent document 7, the method of controlling and applying the difference between the static surface tension of a lower layer paint and the dynamic surface tension of an upper layer paint with respect to simultaneous middle layer application of the multilayer by a slide bead system or a slide curtain system is mentioned.

Patent Document 8 relates to simultaneous middle layer coating of a plurality of ink absorbing layer coating liquids in the manufacture of an ink jet recording sheet, and a method of controlling and applying static surface tension and dynamic surface tension of upper and lower coating materials.

Moreover, also in the metal field, patent document 9 and patent document 10 control the surface tension of an upper coating material and a lower coating material, and apply | coat multiple layers simultaneously, and patent document 11 barrier of an ultraviolet curable resin to the interface of an upper layer and a lower layer. The method of preventing the mixed layer at the time of multilayer simultaneous application is mentioned by producing a layer.

Patent Document 1: Japanese Unexamined Patent Publication No. 49-24133 Patent Document 2: Japanese Unexamined Patent Publication No. 2001-252612 Patent Document 3: Japanese Unexamined Patent Publication No. 2003-71373 Patent Document 4: Japanese Unexamined Patent Publication No. 2008-162155 Patent Document 5: Japanese Unexamined Patent Publication No. Hei 3-94871 Patent Document 6: Japanese Unexamined Patent Publication No. 2002-274020 Patent Document 7: Japanese Unexamined Patent Publication No. 2008-178848 Patent Document 8: Japanese Unexamined Patent Publication No. 2006-192589 Patent Document 9: Japanese Unexamined Patent Publication No. Hei 6-190335 Patent Document 10: Japanese Unexamined Patent Publication No. 2008-254313 Patent Document 11: Japanese Unexamined Patent Publication No. 2006-320785

In multilayer simultaneous coating using a slide hopper type curtain coater, it is necessary that the upper and lower layers are not mixed on the slide surface, and when the curtain falls, the curtain is stably formed, and the upper and lower layers are not mixed even after being applied to the metal plate.

In the technique disclosed in Patent Literature 2, mixed layers on a slide surface, a curtain cannot be formed, or coating defects due to mixed layers of an upper layer and a lower layer occur after application or during drying. Moreover, the problem was that a base defect was easy to produce when apply | coating on a metal plate.

In the techniques disclosed in Patent Documents 3 to 6, coating defects due to mixed layers were a problem. Moreover, the coating defect which caused a mixed layer generate | occur | produces even during drying, and when it apply | coated on a metal plate was a problem that agglomeration defect was easy to produce.

Patent document 7 does not describe a method of stably forming a curtain film in a multilayer when a curtain coater is used. Therefore, the curtain film may not be stably formed under the provisions of Patent Document 7. In addition, in the technique disclosed in Patent Document 7, the problem is that coating defects due to the mixed layer occur on the slide surface or between the application and the drying furnace after application or during drying.

In the technique disclosed in Patent Document 8, the occurrence of coating defects was a problem when applied to a metal plate. Moreover, the drying temperature was high temperature and generation | occurrence | production of the coating defect by a mixed layer was a problem. In the techniques disclosed in Patent Document 9 and Patent Document 10, generation of agglomeration defects and generation of coating defects due to a mixed layer of an upper layer and a lower layer were problems.

In the technique disclosed in Patent Literature 11, it is necessary to introduce an ultraviolet irradiation device in order to cure ultraviolet rays, but ultraviolet rays are difficult to penetrate due to the difficulty of penetrating a colored layer or a thick layer of film thickness, and the ultraviolet cured resin hardly deteriorates workability. There was a problem.

Accordingly, the present invention has been made in view of the above-described state of the art, and is simple and inexpensive without coating defects due to mixed layers from immediately after application by a simultaneous multilayer coating apparatus such as a slide hopper type curtain coater to after drying by high temperature heating. It is an object to provide a method for producing a multilayer-coated metal sheet that can be produced.

MEANS TO SOLVE THE PROBLEM The present inventors earnestly examined in order to solve the said subject, For example, when it demonstrates the case of multilayer simultaneous application | coating using a slide hopper type curtain coater, a coating liquid is discharged on a slide surface, and a coating liquid is formed after a surface is formed. It was found that the dynamic surface tension was dominant at the time of 1 second or less until it was applied to the coated object, and the static surface tension was dominant for several minutes from being applied to the coated object and then drying. Specifically, by controlling the dynamic surface tension of the lower layer paint and the upper layer paint, it is possible to suppress coating defects due to the mixed layer immediately after the application, and to control the static surface tension of the lower layer paint and the upper layer paint. It turned out that the coating defect by can be suppressed. Moreover, it turned out that improving wettability of a metal plate and an undercoat is effective for suppressing the coating defect by the mixed layer immediately after application | coating. Further, it was found that, in coating film drying, the surface tension of the coating changes due to temperature rise, but the coating defect due to the mixed layer can be suppressed by controlling the static surface tension at 60 ° C. According to the method of the present invention, since only the surface tension is controlled, it is confirmed that there is little influence on the performance of the formed coating film. This invention is completed based on this knowledge, and what this invention makes the summary is as follows.

(1) Fabrication of a multilayer-coated metal plate comprising a multi-layered simultaneous coating step of simultaneously applying curtains on the at least one surface of the metal plate in a wet state at the same time, and simultaneously drying the stacked upper and lower coats in a wet state. In the method, the dynamic surface tension at 20 ° C. of the upper layer paint is γ _{D phase} (mN / m), and the dynamic surface tension at 20 ° C. of the lower layer paint is γ _{D below} (mN / ml). When the static surface tension at 20 ° C. of the paint is γ _{S phase} (mN / m) and the static surface tension at 20 ° C. of the lower layer paint is γ _{S under} (mN / m), the following equation (A1) To (A6) are satisfied, the method for producing a multilayer-coated metal sheet.

30 ≤ γ _{D phase} ≤ 60 ... (Al)

30 ≤ γ _D ≤ 60 ... (A2)

20 ≤ γ _{S phase} ≤ 50 ... (A3)

20 ≤ γ _S ≤ 50 ... (A4)

γ _{D phase} ≤ γ _{D lower} (A5)

γ _{S phase} ≤ γ _{S bottom} (A6)

(2) (static surface tension at 60 ° C of the lower layer paint)> (static surface tension at 60 ° C of the upper layer paint) The method for producing a multilayer-coated metal sheet according to the above (1), wherein .

(3) The viscosity at 20 degrees C of the said lower layer paint is made _into (mu) Pa (mPa * s), and the viscosity in 20 degrees C of the said upper layer paint is made into (mu) _phase (mPa * s),

μ _to ≥μ _phase

The manufacturing method of the multilayer coating metal plate as described in said (1) or (2) characterized by the above-mentioned.

(4) The method for producing a multilayer-coated metal sheet according to any one of (1) to (3), wherein the upper layer paint and the lower layer paint are water-based paints.

(5) The contact angle at 20 degrees C of the said metal plate and the said lower layer coating material is 50 degrees or less, The manufacturing method of the multilayer coating metal plate in any one of said (1)-(4) characterized by the above-mentioned.

(6) The metal plate on which the metal plate is plated, wherein the plating and the multilayer simultaneous coating of the metal plate are successively performed, and the multilayer coating is performed within 300 seconds after the completion of the plating, followed by drying. The manufacturing method of the multilayer coating metal plate in any one of (1)-(5).

(7) The roughness of the to-be-coated surface of the said metal plate is 0.02 micrometer or more as centerline average roughness Ra, The manufacturing method of the multilayer coating metal plate in any one of said (1)-(6) characterized by the above-mentioned.

(8) The method for producing a multilayer-coated metal sheet according to any one of (1) to (7), wherein the µ _phase and the µ _{lower phase} are both 5 mPa · s to 10000 mPa · s.

ADVANTAGE OF THE INVENTION According to this invention, the multilayer coating metal plate which can be manufactured easily and inexpensively without the coating defect by a mixed layer from immediately after application | coating to after drying by high temperature heating can be obtained. When the method of the present invention is applied to the continuous coating equipment of the surface-treated metal plate represented by the plated metal plate, it becomes possible to efficiently manufacture the surface-treated metal plate subjected to the multilayer coating.

In the multi-layer simultaneous coating process which coat | covers an upper coating film and a lower coating film simultaneously in the wet state on at least one surface of a metal plate, the dynamic surface tension of the upper coating material at 20 degreeC is made into (gamma) _{D phase} (mN / m), The dynamic surface tension of the lower layer paint at 20 ° C is γD _below (mN / m), and the static surface tension of the upper layer paint at 20 ° C is γ _{S phase} (mN / m) of the lower layer paint at 20 ° C. When static surface tension is made _into (gamma) _S (mN / m), it is characterized by following Formula (A1)-(A6).

30 ≤ γ _{D phase} ≤ 60 ... (Al)

30 ≤ γ _D ≤ 60 ... (A2)

20 ≤ γ _{S phase} ≤ 50 ... (A3)

20 ≤ γ _S ≤ 50 ... (A4)

γD phase ≤γ _D ... (A5)

γS phase ≤ γ _{S bottom} (A6)

If the dynamic surface tension at 20 ° C. of the paint is more than 60 mN / m or the static surface tension at 20 ° C. is more than 50 mN / m, after coating on the metal plate, the coating liquid shrinks and does not sufficiently cover the lower limbs. It is easy to cause defects. When the dynamic surface tension at 20 ° C of the paint is less than 30 mN / m or the static surface tension at 20 ° C is less than 20 mN / m, bubbles are likely to occur in the coating liquid, and paint defects are likely to occur.

When the dynamic surface tension of the upper layer paint is greater than the dynamic surface tension of the lower layer paint, or when the static surface tension of the upper layer paint is greater than the static surface tension of the lower layer paint, coating defects due to the mixed layer are likely to occur.

The upper surface paint and the lower layer paint have a dynamic surface tension of 35 mN / m to 55 mN / m at 20 ° C., and a static surface tension of 25 mN / m to 45 mN / m at 20 ° C., in particular painting It is more suitable because it is difficult for defects to occur.

Moreover, it is good that the static surface tension in 60 degreeC of a lower layer paint exceeds the static surface tension in 60 degreeC of an upper layer paint. When the static surface tension at 60 ° C of the upper layer paint is equal to or greater than the static surface tension at 60 ° C of the lower layer paint, coating defects due to the mixed layer are likely to occur during drying.

The dynamic surface tension according to the present invention refers to the dynamic surface tension of the coating liquid in a time of 1 second or less after the surface of the coating liquid to be coated with the coating is formed and applied to the coated object. It is defined as dynamic surface tension in 20 degreeC of the paint of each layer to become. As a method of the dynamic surface tension which concerns on this invention, it can measure by a well-known method. Examples include a meniscus method, a dropping method, a maximum bubble pressure method, a curtain coater method, and the like, but in the embodiment of the present invention, the time from the minimum bubble pressure to the maximum bubble pressure is measured using the maximum bubble pressure method. This 100 ms value was taken as the dynamic surface tension value.

The static surface tension according to the present invention is the static surface tension of the coating liquid from the coating liquid to the to-be-coated object by drying the curtain, and specifically, the static surface tension at 20 ° C. of the coating material of each layer. It is defined as As a method of the static surface tension which concerns on this invention, it can measure by a well-known method, For example, a platinum plate method, a platinum ring method, the pendant drop method etc. are mentioned, In this invention, it measured using the platinum ring method. .

Since the paint used by this invention is easy to adjust surface tension, an aqueous paint (liquid paint which melt | dissolved or disperse | distributed the necessary component in water) is good. The water-based paint may be any known water-based dispersion paint, water-based emulsion paint, or water-soluble paint, and specifically, one or two or more paints such as polyester resins, epoxy resins, urethane resins, olefin resins, and acrylic resins may be used. It can be used in combination. As the paint in the present invention, a commercially available one can be used. For example, in the polyester resin system, the "Bironal (trademark) series" by Toyo Boseki Co., etc. can be used. As an epoxy resin type, "jER (trademark)" etc. made from Japan epoxy resin company can be used. As a urethane resin type, "Takerak (registered trademark) series" by Mitsui Chemicals, Inc., etc. can be used. As an olefin resin system, the "high-tech (trademark) series" by Toho Kagaku Co., Ltd. can be used. As an acrylic resin system, the acrylic resin "Acrystal (trademark) series" made from Nippon Shokubai Co., etc. can be used.

Water-based paints are well suited for providing better corrosion resistance if they contain rust inhibitors. As the inorganic rust inhibitor, generally known ones can be used, for example, silica particles, phosphate compounds, vanadium compounds, niobium compounds, zirconium compounds, oxide fine particles (for example, silicon oxide, aluminum oxide, zirconium oxide, titanium oxide, Cerium oxide, antimony oxide, etc.), phosphate (for example, zinc phosphate, aluminum dihydrogen phosphate, zinc phosphite, etc.), molybdate, phosphomolybdate (aluminum phosphate), vanadate. As organic rust inhibitors, organic phosphoric acid and salts thereof (e.g., phytic acid, phytic acid salts, phosphonic acid, phosphonic acid salts and metal salts, alkali metal salts), organic inhibitors (e.g., hydrazine derivatives, thiol compounds, dithiocarbamine Acid salts), organic compounds (polyethylene glycol), and the like. Moreover, you may use 1 type, or 2 or more types in mixture among these. As the fine silica particles, either wet silica or dry silica may be used. Examples of the phosphoric acid compound include condensed phosphates such as phosphoric acid, monophosphate, diphosphate, tertiary phosphate, pyroic acid, pyrophosphate, tripolyphosphate and tripolyphosphate, phosphorous acid, phosphite, hypophosphite, hypophosphite and the like. . Moreover, 1 type or 2 or more types may be mixed and used in some cases. Examples of vanadium compounds include oxides of vanadium, hydroxides, sulfides, sulfates, carbonates, halides, nitrides, fluorides, carbides, cyanides (thiocyanides), salts thereof, and the like. Moreover, 1 type, or 2 or more types may be mixed and used among them.

It is preferable to use surfactant (including an antifoamer and a leveling agent) for adjustment of the surface tension of paint. Surfactant should just be a well-known thing, As commercially available things, BYK-333, BYK-307, etc. of BYK, Ermagen, such as Kao Corporation, Supinol, etc. of Neo Products, Pentants of Neos, etc. are known, but many others As it is, it is added according to paint. Moreover, adjustment methods other than addition of surfactant may be sufficient, such as dilution (change of the quantity of water which is a solvent), and mixing other solvents other than water.

The viscosity in 20 degreeC of an upper coat and a lower coat is especially suitable as it is 5 mPa * s-10000 mPa * s, and is excellent in coating workability. If it is less than 5 mPa * s, coating defects, such as sagging, tend to arise between after application | coating to drying, and when it exceeds 10000 mPa * s, the leveling property after application | coating will be bad, and coating defects will arise easily. It is more preferable that the viscosity of the lower layer paint is higher than that of the upper layer paint. This is because the higher the viscosity, the more the movement of the lower coating layer is suppressed, and the confusion of the interface with the upper coating layer is reduced, which is effective for the prevention of coating defects due to the mixed layer. More preferable viscosity in 20 degreeC of an upper coat and a lower coat is 5-5000 mPa * s, Most preferably, it is 5-1000 mPa * s.

Multi-layer simultaneous coating is the method of carrying out curtain coating simultaneously to a base material in the state which laminated | stacked several layers of coating materials, using the curtain coater of a slide hopper method, etc., and carrying out dry baking simultaneously after that.

The metal plate used as a base material in this invention can use a well-known metal material generally. The metal material may be an alloy material. For example, a steel plate, a stainless steel plate, an aluminum plate, an aluminum alloy plate, a titanium plate, etc. are mentioned. The metal plate may be a surface-treated metal plate, for example, plating may be performed on the surface of the material. If it is a plated metal plate, since corrosion resistance is good, it is very suitable. As a kind of plating, zinc plating, aluminum, copper plating, nickel plating, etc. are mentioned, These alloy plating may be sufficient. For example, as a plated steel plate, generally a well-known steel plate and steel plate, such as a hot dip galvanized steel plate, an electro galvanized steel plate, a zinc- nickel-alloy plated steel plate, a hot-dip galvanized steel plate, an aluminum plated steel plate, an aluminum- zinc alloyed plated steel plate, etc. Can be applied. Generally the well-known chemical conversion treatment is given to the surface of a metal plate, and since adhesiveness of a metal plate and a coating film layer improves, it is more suitable. The chemical conversion treatment may be zinc phosphate chemical conversion treatment, coating chromate treatment, electrolytic chromic acid treatment, reaction chromate treatment, chromate free chemical conversion treatment, or the like. As the chromate-free chemical conversion treatment, treatment with an aqueous solution containing a silane coupling agent, a zirconium compound, a titanium compound, tannin or tannic acid, a resin, silica, or the like is known, and JP-A-53-9238 and JP-A Japanese Patent Laid-Open No. 9-241576, Japanese Laid-Open Patent Publication No. 2001-89868, Japanese Laid-Open Patent Publication No. 2001-316845, Japanese Laid-Open Patent Publication 2002-60959, Japanese Laid-Open Patent Publication 2002-38280, Japanese Laid-Open Patent Publication The well-known technique described in 2002-266081, Unexamined-Japanese-Patent No. 2003-353464, etc. may be used. For such chemical conversion treatment, a commercial chemical treatment agent such as chromate-free chemical conversion agent "CT-E300N" manufactured by Nippon Park Caring Co., Ltd., a trivalent chromium chemical conversion treatment agent "Surcoat NRC1000" manufactured by Nippon Paint, etc. can be used.

In the case of manufacturing the metal plate plated with the multilayer-coated metal plate by the method of the present invention as the original plate, the production is improved by producing a continuous plating line in which the coating step is followed by the coating step. The continuous plating line is generally a continuous electroplating line and a continuous hot dip plating line.

In the continuous electroplating line, after the plating cell in the line is manufactured in a line having a multi-layer simultaneous coating equipment, the baking process of the lower layer coating film can be omitted, the productivity of the coating line can be improved, and the manufacturing cost can be reduced. Further, immediately after plating, the wettability of the surface of the metal plate does not deteriorate due to an oxide film or the like, and coating defects are less likely to occur. In particular, it is very suitable to install a coating apparatus at a position that can be applied within 300 seconds after plating.

In a continuous hot-dip plating line, the baking process of a lower layer coating film can be skipped by manufacturing into the line which has a multilayer simultaneous coating equipment after the melting pot in a line, and productivity of a coating line can be improved and manufacturing cost can also be reduced. . Further, immediately after plating, the wettability of the metal plate surface does not deteriorate due to an oxide film or the like, and coating defects are less likely to occur. In particular, it is very suitable to install the coating device in a position where the coating can be performed within 300 seconds after plating.

It is preferable that the contact angle in 20 degreeC of a metal plate and an undercoat is 50 degrees or less. If necessary, the contact angle can be made 50 degrees or less by adding an additive (surfactant, etc.) to a lower layer paint, and making surface tension small, for example. In particular, in the case where the metal plate is a plated metal plate, by coating within 300 seconds after plating, the formation of an oxide film on the surface of the metal plate can be suppressed and the contact angle can be reduced. In addition, when the relative roughness of the metal plate surface is increased, the contact angle can be reduced. If the contact angle between the metal plate and the lower layer paint is more than 50 degrees, the wettability is poor, and agglomeration defects (defects that expose the surface of the metal plate due to recesses in the coating film) occur or poor adhesion occurs. If the contact angle is 40 degrees or less, the adhesiveness is particularly excellent and is very suitable.

As a hardening method of resin in the coating material used, generally well-known dry baking methods, such as a hot air oven, a direct type oven, a near-infrared oven, an induction heating type oven, can be used.

The heating temperature of the to-be-coated object is 50-250 degreeC, Preferably it is 70-220 degreeC. If the heating temperature is less than 50 ° C., the evaporation rate of the water is slow, and sufficient film formation cannot be obtained. On the other hand, when it exceeds 250 degreeC, thermal decomposition of resin will arise, the performance deterioration of the formed coating film will occur, and appearance, such as yellowing, will worsen. As for the drying time in the case of heat drying after application | coating, 1 second-5 minutes are good.

1.0 micrometer-400.0 micrometers are preferable for a film thickness to apply | coat. If it is less than 1.0 micrometer, it will become difficult to control a mixed layer, and the coating defect by a mixed layer will arise. Moreover, when it becomes thicker than 400.0 micrometers, coating defects, such as 튐, generate | occur | produce.

Roughness of the to-be-coated surface of a metal plate is 0.02 micrometer or more as centerline average roughness Ra. Ra is measured as 0.8 mm of cutoff values based on JISB0601. When Ra is less than 0.02 micrometer, agglomeration defect will arise easily. When Ra is 0.1 micrometer or more, since adhesiveness improves by an anchor effect, it is more suitable. It is difficult for Ra of a metal plate surface to be substantially larger than 2.0 micrometers, and this becomes a practical upper limit.

In the case of simultaneously applying three layers in multiple layers, the dynamic surface tension at 20 ° C. of the paint of the upper and lower coating films, which is a requirement of (1), (2), (3), and (8) of the above-mentioned subject matter of the present invention. And the relationship between the static surface tension, the relationship between the static surface tension at 60 ° C and the viscosity at 20 ° C for the two adjacent layers. For example, when the coating layer laminated | stacked by apply | coating on a metal plate is made into the 1st layer, 2nd layer, and 3rd layer from directly on a metal plate, between the paint of a 1st layer and a 2nd layer, and a 2nd layer and a 3rd layer Among the paints, the requirements of (1), (2), (3) and (8) are established respectively. Moreover, the relationship of the contact angle in 20 degreeC of a metal plate and the coating material which contact | connects it which is a requirement of (5) of the summary of this invention mentioned above is established between a metal plate and a 1st layer. These are also the same in the case of multilayer simultaneous coating of four or more layers.

<Examples>

Below, the detail of an Example is described. This invention is not limited only to an Example.

1. Production of trial

The test piece (plate thickness 0.8mm) of the electrogalvanized steel sheet was cut and cold-rolled steel plate into 10 cm x 10 cm, and was produced by electroplating. Plating conditions were ZnSO ₄ H ₇ O 300 g / l, NaSO ₄ 50 g / l, H ₂ SO ₄ 25 g / l, and the bath temperature was 50 ° C., pH 1.2, and the plating time was 30 seconds. The density was 15 A / dm <2> and the plating adhesion amount was 15 g / m <2>. After plating, the test piece was cooled to room temperature by water cooling. The coating liquid was apply | coated multilayered simultaneously to the test piece after cooling with the slide hopper-type curtain coater, and it dried on the conditions which the highest achieved board temperature will be 200 degreeC in the induction heating furnace which blown hot air. The centerline average roughness Ra of the test piece surface of the electrogalvanized steel sheet was 0.3 µm.

The test piece (plate thickness 0.8mm) of the hot-dip galvanized steel sheet was cut | disconnected the cold rolled steel sheet to 10 cm x 10 cm, and was plated and produced by Lesca's batch hot dip galvanization test apparatus. In the plating conditions, the bath temperature was 500 ° C, the Al concentration in the bath was 0.10%, and the immersion time was in the range of 5 s. The adhesion amount was adjusted by air wiping, and the plating adhesion amount was 40 g / m <2>. After plating, the test piece was cooled to room temperature with N ₂ gas. The coating liquid was apply | coated multilayered simultaneously to the test piece after cooling with the slide hopper-type curtain coater, and it dried on the conditions which the highest achieved board temperature will be 200 degreeC in the induction heating furnace which injected hot air. The centerline average roughness Ra of the test piece surface of the hot-dip galvanized steel sheet was 0.5 µm.

Simultaneous multilayer coating of the coating liquid with a slide hopper type curtain coater on a test piece of a cold rolled steel sheet having a roughness Ra of 0.1, 1.0, 2.0 µm and a stainless steel sheet (SUS430) having a roughness Ra of 0.01, 0.02, 0.05 µm, cut into 10 cm x 10 cm. It apply | coated and dried in the conditions which the highest achieved board temperature will be 200 degreeC in the induction heating furnace in which hot air was blown.

The film thickness at the time of coating film drying of each test piece was calculated | required from the electron microscope photograph, and the wet film thickness T (micrometer) of the coating liquid was calculated | required from solid content concentration. In the case of the plated test piece, the time from the point at which the test piece became normal temperature after plating to the time point at which the coating liquid was applied on the metal plate was set to t seconds, and this time was changed.

2. Undercoat Paint

Coating A: Silica "AEROSIL (registered trademark) 200" made by Nippon Aerosil Co., Ltd. (average particle diameter: about 12 nm) is made of polyurethane paint "bihydrol PR135" made by Sumika Bayer Urethane Co., Ltd. as a rust inhibitor. It produced by adding it by the mass part with respect to 100 mass of solid content.

Paint B: Silica "AEROSIL (registered trademark) 200" (average particle diameter: approximately 12nm) by Nippon Aerosol Co., Ltd. made of Nippon Aerosil Co., Ltd. as a rust preventive agent to polyester paint "Bironal MD-1400" made by Toyo Boseki Co., Ltd. Produced by adding in parts by mass relative to mass.

3. Upper layer paint

Coating C: Produced by adding 5 carbon blacks, AF Black, manufactured by Daiichi Seika Co., Ltd. to a mass part relative to 100 parts by mass of resin to polyurethane paint "Bihydro Roll PR135" manufactured by Sumika Bayer Urethane Co., Ltd. It was.

Coating D: To black polyolefin paint "Hi-tech AR-2300" manufactured by Toho Kagaku Kogyo Co., Ltd., carbon black "AF Black" made by Daiichi Seika Co., Ltd. was added 5 by mass part to 100 masses of resin solids. Produced.

4. Adjustment of paint

BYK-333 (manufactured by BYK), Hermagen 108 (manufactured by Cao Corporation) and thickener BYK-425 (manufactured by BYK) were added to the paints A to D of the upper and lower layers, and the surface tension and viscosity were changed, and the lower layer paints shown in Table 1 were used. -1 to 23, upper coating material-1 to 19 were produced. The mass part of an additive is a mass part when the coating materials A-D are 100 mass. The static surface tension at 20 degreeC and 60 degreeC was measured by the dynamometer (platinum ring pulling method) by a BYK company. The dynamic surface tension at 20 ° C. was measured by Kyowa Kaimen Kagaku Co., Ltd. BP-D5 (maximum bubble pressure method), and the time from the minimum bubble pressure to the maximum bubble pressure was 100 ms. The viscosity in 20 degreeC was measured with the Brookfield viscometer (made by Tokyo Keiki Co., Ltd.). The contact angle between the test piece and the lower layer paint was measured by dropping the lower layer paint on the test piece using DM100 (manufactured by Kyowa Kaimen Kagaku Co., Ltd.). In the case of the plated test piece, after plating, 60 second after, the lower layer paint was dripped at the plating surface using DM100 (made by Kyowa Kaimen Kagaku Co., Ltd.), and the contact angle between the plating surface and the lower layer paint was measured. The stylus roughness meter (the Mitsutoyo company, surf test SV-3100S4) was used for the measurement of the surface roughness of a metal plate. Center line average roughness was calculated | required as cut-off value 0.8mm based on JISB0601.

The prepared test plate was put together in Table 2 and Table 3. The abbreviation of the metal plate was "EG" for the galvanized steel sheet, "GI" for the hot-dip galvanized steel sheet, "cold rolled sheet" for the cold-rolled steel sheet, and "SUS" for the stainless steel sheet.

In the test plate produced in this manner, the following evaluation test was performed.

1. Adhesion Test

In order to reach a base material (metal plate surface), 100 1-mm square checker scales are drawn on a coating surface, and it peels off with a cello tape (registered trademark). The result was evaluated by the following criteria.

◎: Number of remaining checkerboard scales 100

○: number of remaining checkerboard scale 95 or more and less than 100

△: number of remaining checkerboard scale 80 or more and less than 95

×: number of remaining checkerboard scale less than 80

2. Evaluation of coating defects due to mixed layer

The visual appearance evaluated the thing with a beautiful external appearance, (circle), a little non-uniform thing (circle), a thing with a stain, (triangle | delta), and a thing with agglomeration defect as x.

3. Bundling defect evaluation

By visual observation, the thing with a beautiful appearance was evaluated as (circle), (the thing with a little bunching defect) (triangle | delta), and the thing with the appearance defect by a bunching defect as x.

Details of the test results are described. Table 4 and Table 5 show the results of the evaluation. In the metal plate (Invention Examples 11-40) of this invention, the beautiful external appearance which was excellent in adhesiveness and without the coating defect and aggregation defect by a mixed layer was obtained. In particular, both the upper layer paint and the lower layer paint had a dynamic surface tension of 35 mN / m to 55 mN / m and a static surface tension of 25 mN / m to 45 mN / m. 1, 2, 4, 6, 10, 12, 14, 16, 18, 19, 21, 24 to 40). Moreover, the contact angle was 40 degrees or less, and especially the adhesiveness was excellent (example of this invention-1-35, 38-40). When center line average roughness Ra of a metal plate is 0.1 micrometer or more, adhesiveness improved by the anchor effect (Invention example-38-40). When the center line average roughness Ra of the metal plate was less than 0.02 µm, agglomeration defects slightly occurred (Invention Example-41). When the static surface tension of the upper layer paint at 60 ° C. is greater than the static surface tension of the lower layer paint at 60 ° C., coating defects due to the mixed layer slightly occur during drying (Invention Example 9) and at 60 ° C. It was more suitable if the static surface tension of the upper coating material was smaller than the static surface tension of the lower coating material at 60 degreeC. When the coating viscosity was less than 5 mPa · s, some coating defects such as sagging occurred after application to drying (invention examples-45, 47). When it exceeded 10000 mPa * s, leveling property fell and the coating defect a little generate | occur | produced (this invention example-46, 48).

When the contact angle between the metal plate and the lower layer paint exceeded 50 degrees, the wettability was poor, agglomeration defects slightly occurred, and the adhesiveness slightly decreased (Invention Example-44). If wet film thickness was less than 1.0 micrometer, mixed layer control might fall and some coating defect could be seen (Invention example-42). Moreover, when it became thicker than 400 micrometers, some coating defects, such as 튐, could be seen (Invention example-43). If the time from the time of normal temperature after plating to the time of application of the coating liquid on the metal plate is more than 300 seconds, the wettability deteriorates due to the formation of an oxide film, so that a slight agglomeration appearance can be seen (Invention Example 41). .

If the dynamic surface tension at 20 ° C. is greater than 60 mN / m or the static surface tension at 20 ° C. is more than 50 mN / m, after coating on the metal plate, shrinkage of the coating liquid occurs and the coating defects are not sufficiently concealed. Comparative example-2, 4, 6, 8). When the dynamic surface tension was less than 30 mN / m or the static surface tension was less than 20 mN / m, bubbles were generated in the coating liquid, and paint defects were observed (Comparative Examples-1, 3, 5, 7).

When the dynamic surface tension of the upper layer was greater than the dynamic surface tension of the lower layer or the static surface tension of the upper layer was greater than the static surface tension of the lower layer, coating defects due to the mixed layer occurred (Comparative Examples-9, 10).

Industrial availability

According to the present invention, it is possible to obtain a multilayer-coated metal sheet which can be easily and inexpensively manufactured without coating defects due to mixed layers from immediately after application to after drying by high temperature heating, and thus has high industrial applicability. When the method of this invention is applied to the continuous coating installation of the surface-treated metal plate especially represented by a plated metal plate, the surface-treated metal plate which gave multilayer coating can be manufactured efficiently.

Claims (8)

In the manufacturing method of the multilayer coating metal plate which includes the multilayer simultaneous coating process which simultaneously apply | coats an upper coating material and a lower coating material to the at least one surface of a metal plate in a wet state, and simultaneously dries the upper coating film and the lower layer coating film of the laminated wet state. , The dynamic surface tension at 20 ° C of the upper layer paint is γ _{D phase} (mN / m), and the dynamic surface tension at 20 ° C of the lower layer paint is γD _below (mN / ml). When the static surface tension at ° C is γ _{S phase} (mN / m) and the static surface tension at 20 ° C of the lower layer paint is γ _{S under} (mN / m), the following formulas (A1) to (A6) ) Is a method for producing a multilayer-coated metal sheet.
30 ≤ γ _{D phase} ≤ 60 ... (Al)
30 ≤ γ _D ≤ 60 ... (A2)
20 ≤ γ _{S phase} ≤ 50 ... (A3)
20 ≤ γ _S ≤ 50 ... (A4)
γ _{D phase} ≤ γ _{D lower} (A5)
γ _{S phase} ≤ γ _{S bottom} (A6) The method for producing a multilayer-coated metal sheet according to claim 1, wherein (static surface tension at 60 ° C of the lower layer paint)> (static surface tension at 60 ° C of the upper layer paint). According to claim 1 or 2, and the viscosity at 20 ℃ of the lower layer paint in μ _and (mPa · s), _μ-phase (mPa · s) the viscosity at 20 ℃ of the upper layer paint, The method of producing a multilayer-coated metal sheet, characterized by having a _phase of 상 _to 상. The method for producing a multilayer-coated metal sheet according to any one of claims 1 to 3, wherein the upper layer paint and the lower layer paint are water-based paints. The method for producing a multilayer-coated metal sheet according to any one of claims 1 to 4, wherein a contact angle at 20 ° C between the metal plate and the lower layer paint is 50 degrees or less. The metal plate plated with the metal plate according to any one of claims 1 to 5, wherein the metal plate is plated and the plating and the multi-layer simultaneous coating of the metal plate are successively performed. The manufacturing method of the multilayer coating metal plate containing the process of implementing and drying after that. The method for producing a multilayer-coated metal sheet according to any one of claims 1 to 6, wherein the roughness of the surface to be coated of the metal plate is 0.02 µm or more as a center line average roughness Ra. The method for producing a multilayer-coated metal sheet according to any one of claims 1 to 7, wherein the viscosity of the upper layer paint and the lower layer paint is 5 mPa · s to 10000 mPa · s.