JP5987683B2 - Thermoreversible color-changing precoated metal plate and method for producing the same - Google Patents

Description

  The present invention relates to a pre-coated metal plate that is reversibly discolored according to environmental temperature, which is used for home appliances, building materials, automobiles, interior materials, cover materials, and the like.

  Pre-coating pre-coated with an organic coating instead of so-called post-coating products that are painted and used after processing a metal plate as in the past for home appliances, building materials, automobiles, interiors, and exteriors Metal plates have been used. Advantages of using a pre-coated metal plate include cost reduction by omitting the process. In recent years, pre-coated metal sheets have attracted attention from an economical viewpoint, and the invention of pre-coated metal sheets having press workability, design properties, and the like is undeniable.

  In recent years, thermoreversible color-changing products have attracted attention. For example, Patent Documents 1 to 4 describe a technique for visually recognizing the temperature of stored items by bringing a thermoreversible color-changing temperature indicating sheet into contact with a cold storage member of a refrigerator. Patent Document 5 describes that a metal may be used for a base material of a thermochromic interior article.

JP 2006-57909 A JP 2006-57910 A JP 2006-57911 A JP 2006-162088 A JP-A-7-125130

  When the techniques described in Patent Documents 1 to 4 are used, the temperature indicating sheet must be fixed to the cold storage material. Patent Document 1 describes that the regenerator member is preferably a metal lump, and more preferably an iron lump. That is, by using a pre-coated metal plate having a thermoreversible color change function, the step of fixing the temperature indicating sheet to the cold storage material can be omitted, and productivity can be improved.

  In the case of Patent Document 5, the base material of the thermochromic interior article described in the examples and comparative examples is a polyester fabric, wallpaper, or table, and technical studies on the precoated metal plate have not been made.

Thus, the precoat metal plate which has thermoreversible color-change property has not been proposed until now. Thermoreversible discoloration is achieved using thermoreversible discoloration microcapsules, but when thermoreversible discoloration microcapsules are added to coatings that require workability, such as pre-coated metal plates, a water-cooling process after baking However, there was a problem that the thermoreversible color-changing microcapsules were eluted.
In order to visually recognize that the color has changed, ΔE * defined by JIS Z 8729 is preferably 5 or more.

  The present invention has been made to overcome such problems and achieve thermoreversible color change imparting to a precoated metal sheet, and to provide a thermoreversible color change precoated metal sheet and a method for producing the same. And

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies. As a result, the thermoreversible color-changing microcapsule content rate capable of obtaining a thermoreversible color-changing pre-coated metal plate is found, and further, the metal resin type, the crosslinking agent type and content rate, and the metal arrival temperature (PMT) in the paint drying process are adjusted As a result, the inventors have found a technique for suppressing the elution of microcapsules and exhibiting the workability and thermoreversible discoloration necessary for a pre-coated metal plate, thereby completing the present invention.

That is, the present invention has at least one resin film on at least one surface of the metal plate,
The resin film contains reversibly colored or colorless microcapsules at a color change temperature Tc in a ratio of 2 to 30 parts by mass with respect to 100 parts by mass of the resin solid content in the resin film, and It contains a melamine resin as a polyester resin and a crosslinking agent in a proportion of 15 to 35 parts by mass of the melamine resin with respect to 100 parts by mass of the polyester resin solid content,
The resin film has a thickness of 2 μm or more,
The color difference ΔE ^* described in JIS Z 8729 when the temperature of the metal plate is less than Tc-5 ° C. or more than Tc + 5 ° C. is 5 or more, and is reversibly changed.
The present invention relates to a thermoreversible color-changing pre-coated metal plate.

  On the layer 1 of the microcapsule-containing resin film, it is preferable to have at least one layer 2 of the film that does not contain microcapsules that are reversibly colored or colorless depending on the environmental temperature.

  When the average particle diameter of the microcapsules is D, the thickness of the layer 1 is T1, and the thickness of the layer 2 is T2, it is preferable to improve work adhesion by satisfying D <T1 + T2.

  It is preferable that the layer 2 is a colored layer, and the layer 1 and the layer 2 exhibit two or more colors depending on the environmental temperature due to the effect of overcoating.

The present invention also provides
Applying at least one layer of a coating containing thermoreversible color-changing microcapsules reversibly colored or colorless at a color change temperature Tc on at least one surface of a metal plate;
The metal plate coated with the paint is heated to a metal arrival temperature that is 10 ° C. or more higher than the curing start temperature of the paint and 10 ° C. or less lower than the melting temperature of the shell material of the microcapsule, Curing the paint and water cooling to form a film;
The present invention relates to a method for producing a thermoreversible color-changing pre-coated metal plate, wherein the color difference ΔE ^* described in JIS Z 8729 reversibly changes 5 or more when the temperature of the metal plate is less than Tc-5 ° C. and more than Tc + 5 ° C.

Wherein the coating steps, wherein the color change temperature Tc in reversibly paint formulated with thermochromic microcapsules exhibiting colored or colorless at least one layer and said paint without blending microcapsules at least one layer, wherein At least one layer 2 of the film not containing the microcapsules may be formed on the layer 1 of the microcapsule-containing resin film by simultaneously applying multiple layers on one surface of the metal plate.

  According to the present invention, the thermoreversible discoloration that has been produced by post-coating has been realized with a pre-coated metal plate. That is, compared with the prior art, since a thermoreversible color-changing material can be manufactured more industrially, the manufacturing cost can be reduced as compared with a post-coating material. Moreover, since it is a precoat metal plate, it can be applied to applications where strength and large area are required for materials such as housings and wall materials of home appliances. Therefore, the present invention has extremely great industrial value.

Details of the present invention will be described below.
The present invention has one or more resin films on at least one surface of the metal plate,
The resin film contains microcapsules that are reversibly colored or colorless at a color change temperature Tc in a ratio of 2 to 30 parts by mass with respect to 100 parts by mass of the resin solid content in the resin film.
The thickness of the resin film is 2 μm or more, and the color difference ΔE ^* described in JIS Z 8729 is 5 or more reversibly when the temperature of the metal plate is less than Tc-5 ° C. and more than Tc + 5 ° C. The present invention relates to a thermoreversible color-changing pre-coated metal plate.

  Examples of the coating original plate used in the present invention include hot dip galvanized steel sheet, electrogalvanized steel sheet, alloyed hot dip galvanized steel sheet, zinc / aluminum alloy plated steel sheet, aluminum plated steel sheet, zinc / aluminum / silicon / magnesium composite plated steel sheet, etc. Various plated steel sheets, stainless steel sheets, cold-rolled steel sheets, copper plates, aluminum plates, and the like. These metal plates may be used after being subjected to various commonly performed treatments such as chromate treatment, phosphate treatment, and other various non-chromate pretreatments as necessary, as necessary.

  If necessary, these metal plates may be used by applying a primer coating to the lower layer on the design coating film side. The paint used for primer coating is not particularly limited, and any paint may be used. For example, any paint used for general pre-coated metal plates, such as chromate-based rust preventive pigments, non-chromate rust preventive pigments, polyester-based paints including extender pigments, epoxy-based, acrylic-based, urethane-based paints, etc. What is necessary is just to give and use it by the coating method and hardening conditions suitable for a coating material.

  In the case where the thermoreversible discoloration coating film is applied only to one surface of the metal plate, these metal plates may be used after the back surface is coated as necessary. The paint used for the back surface coating is not particularly limited, and an arbitrary one may be used. For example, including chromate rust preventive pigments, non-chromate rust preventive pigments, extender pigments, colored pigments, wax, and other general additives, polyester resin, epoxy resin, alkyd resin, acrylic resin, urethane What is necessary is just to use what is used for a general precoat metal plate, such as a resin-type paint, with the coating method and hardening conditions suitable for the paint. In addition, when a special function such as adhesion to other substances is required on the back surface, the back surface coating according to the request may be selected and used as appropriate.

  The shape of the metal plate used in the present invention may be a coil shape or a cut plate shape. Further, the metal plate is not limited to a smooth metal plate, and may be a metal plate after being subjected to molding or stamping such as embossing or pressing. However, when using such a non-smooth metal plate, when painting after the colored film layer, if there is no unpainted part, the painting method is spray painting, brush painting, Limited to slit curtain coaters, roller curtain coaters, die coaters and the like. This is not the case when unpainted parts are allowed to occur.

  The coating layer containing the microcapsules of the present invention is a central coating layer for developing thermoreversible discoloration. A well-known thing can be used for the said microcapsule contained in this membrane | film | coat layer. Specifically, for example, “Sakura TC slurry” or “Sakura TC powder” manufactured by Sakura Crepas Co., Ltd. can be used.

  The coating preferably contains the microcapsule in a proportion of 2 to 30 parts by mass, and more preferably 10 to 30 parts by mass with respect to 100 parts by mass of the resin solid content in the coating. When the amount is less than 2 parts by mass, the discoloration effect is small and it is difficult to visually recognize the discoloration. On the other hand, when the addition amount exceeds 30 parts by mass, the coating adhesion becomes brittle, so that the processing adhesion tends to be lowered. On the other hand, when the addition amount exceeds 30 parts by mass, the storage stability decreases due to the thickening of the paint, and thus the paintability decreases. In the case of 10 to 30 parts by mass, it becomes easy to achieve both stable thermoreversible color change, processing adhesion, and coating storage stability.

  The coating resin with which the microcapsules are blended is not particularly limited, and may be arbitrarily selected from those commonly used for pre-coated metal plates. For example, resin components such as polyester resins, acrylic resins, epoxy resins, urethane resins, fluorine resins, or modified resins thereof may be mixed with butylated melamine, methylated melamine, butylmethyl mixed melamine, urea resin, isocyanate, What is necessary is just to use what was bridge | crosslinked by the crosslinking agent component of these mixed systems. In particular, a film containing a polyester resin is preferable. Moreover, it is preferable that it is a film | membrane containing a melamine resin as a crosslinking agent. Since the polyester resin is excellent in processability, it is suitable for a precoat film that undergoes processing after coating, and can improve processing adhesion. As addition amount of a melamine resin, it is preferable to set it as 15-35 mass parts with respect to 100 mass parts of polyester resins, and also it is preferable to set it as 20-30 mass parts. When the melamine resin is less than 15 parts by mass, the microcapsules are eluted during water cooling. Moreover, when the melamine resin is more than 30 parts by mass, the processing adhesion of the film is lowered. When the melamine resin is 20 to 30 parts by mass with respect to 100 parts by mass of the polyester resin, it is possible to easily achieve both microcapsule elution and processing adhesion.

  The film thickness of the microcapsule-containing resin is preferably 2 μm or more. If it is less than 2 μm, the thermoreversible color change is insufficient. Further, the microcapsules cannot be covered, and the processing adhesion of the film is lowered. On the other hand, the upper limit of the microcapsule-containing resin film thickness is preferably 30 μm or less, and more preferably 20 μm or less. In the case of more than 30 μm, cracking due to bumping of the solvent (water or solvent) tends to occur in the baking process, and it becomes difficult to obtain a beautiful appearance. On the other hand, if it exceeds 20 μm, many relatively expensive microcapsules are used, which is not economically preferable.

  The coating material in which the microcapsules are blended can be prepared by any method. For example, in the case of a water-based paint, the paint composition for forming a coating film includes an organic resin (A) shown in Table 1, a thermoreversible color-changing pigment (B) shown in Table 2, and a crosslinking agent shown in Table 3. (C) and silicon oxide (D) shown in Table 4 were blended in the blending amounts (mass% of solid content) shown in Table 5 and prepared using a dispersion machine for coating. In the coating, the viscosity of the paint was adjusted by appropriately diluting with ion exchange water.

  In the case of a solvent-based paint, the paint composition for forming a coating film includes an organic resin (F) shown in Table 6, a thermoreversible color-changing pigment (G) shown in Table 7, and a crosslinking agent shown in Table 8. (H) was blended in a blending amount (mass% of solid content) shown in Table 9, and prepared by stirring using a dispersing machine for paint. At the time of coating, the viscosity of the paint was adjusted by appropriately diluting with an organic solvent (using a mass ratio of cyclohexanone: solvesso 150 = 1: 1).

  What is necessary is just to apply | coat the coating material with which a microcapsule is mix | blended to a metal plate by arbitrary coating methods. Examples thereof include a coating method using a roll coater, spray coating, brush coating, bar coater, overflow curtain coater, slit curtain coater, roller curtain coater, die coater, slide curtain coater and the like.

  However, in order to apply a paint containing microcapsules having a large particle size with a low film thickness, it is necessary to select an appropriate coating method. In a roll coater, the microcapsules cannot pass between the roll and the object to be coated and are eliminated, so when trying to coat microcapsules with a large particle size with a thin film, a rope-like appearance defect called roping occurs. Occur. In spray coating, it is difficult to reduce the coating thickness. However, these problems are all cleared by a coating method using an overflow curtain coater, slit curtain coater, roller curtain coater, die coater, or slide curtain coater. The curtain coater is a system in which paint is dropped into a thin curtain shape, and an object to be coated such as a metal plate is passed under the paint. Since it is a non-contact coating method, even a microcapsule having a relatively large particle size is not excluded, and the content in the coating is surely applied as it is onto the object to be coated. Moreover, thin film coating can be easily performed by increasing the speed of passing the object to be coated. In order to stably produce the precoated metal sheet of the present invention, it is very useful to use these curtain coaters.

  The drying (curing) method of the coating material containing the microcapsules is preferably heat drying such as hot air heating or high frequency induction heating. In natural drying, the production efficiency is low, and in curing by irradiation with electron beams or ultraviolet rays, an expensive curing agent must be used, which is unsuitable because the production cost increases. The number of coating layers containing microcapsules is not limited as long as it is one or more.

  It is preferable to have at least one film (layer 2) that does not contain microcapsules on the film (layer 1) in which the microcapsules are dispersed. When the surface of the layer 1 is rubbed with absorbent cotton impregnated with a solvent, depending on the type of the solvent, the microcapsules may be eluted and thermoreversible discoloration may not be exhibited. By forming a film that does not contain microcapsules on the outermost surface of the pre-coated metal plate, the solvent resistance can be improved.

  When the average particle diameter of the microcapsules is D, the thickness of the layer 1 is T1, and the thickness of the layer 2 is T2, it is preferable that D <T1 + T2. When the layer 2 is not present, it is preferable that D <T1. When the above formula is satisfied, since the microcapsule does not cue from the coating film, the work adhesion is improved. Furthermore, for the reasons described above, the solvent resistance is further improved.

  When the layer 2 is a colored layer, it is preferable that the layer 1 and the layer 2 exhibit two or more colors depending on the environmental temperature due to the effect of overcoating. For example, when a film containing a thermoreversible color-changing pigment that exhibits red in layer 1 further contains a blue coloring pigment that does not contain a thermoreversible color-changing pigment in layer 2, purple (red + blue) depending on the environmental temperature It functions as a pre-coated metal plate exhibiting blue and blue (when the upper layer is clear, it exhibits red and colorless (color of layer 1 when the thermoreversible coloring pigment is colorless)). Thus, by combining with the colored layer of the layer 2, a precoated metal plate exhibiting two or more colors according to the environmental temperature is obtained, and the thermoreversible discoloration is improved as compared with the case where the layer 2 is clear.

Further, the present invention is a step of applying at least one layer of a coating containing thermoreversible color-changing microcapsules reversibly colored or colorless at a color change temperature Tc on at least one surface of a metal plate;
Heating, cooling and drying the metal plate to which the paint has been applied at or above the curing start temperature of the paint and below the melting temperature of the shell material of the microcapsule to form a film;
The present invention relates to a method for producing a thermoreversible color-changing pre-coated metal plate, wherein the color difference ΔE ^* described in JIS Z 8729 reversibly changes 5 or more when the temperature of the metal plate is less than Tc-5 ° C. and more than Tc + 5 ° C.

Furthermore, the present invention provides at least one layer of a paint containing thermoreversible color-changing microcapsules reversibly colored or colorless at a color change temperature Tc, and at least one layer of a paint not containing the microcapsules, a metal plate Applying multiple layers simultaneously on at least one side of
A step of forming a film by heating, cooling and drying the metal plate coated with the paint at the same time in multiple layers at a temperature not lower than the curing start temperature of the paint and not higher than the melting temperature of the shell material of the microcapsule;
And a method for producing a thermoreversible color-changing pre-coated metal sheet having a color difference ΔE ^* reversibly changing 5 or more according to JIS Z 8729 when the temperature of the metal sheet is less than Tc-5 ° C. and more than Tc + 5 ° C. .

  When heating the metal plate to which the paint has been applied, it is necessary that the metal arrival temperature (PMT) be equal to or higher than the curing start temperature of the paint and less than the melting temperature of the microcapsule shell material. Moreover, it is preferable to make PMT 10 degreeC or more higher than the hardening start temperature of resin, and it is preferable to make it 10 degreeC or more lower than the melting temperature of a microcapsule shell material. When PMT is lower than the resin curing start temperature, elution of microcapsules occurs in the water-cooled section, so thermoreversible discoloration cannot be expressed. When PMT is higher than the melting temperature of the microcapsule shell material, Since it melts, thermoreversible discoloration cannot be guaranteed. When PMT is 10 ° C. or more higher than the curing start temperature of the resin and 10 ° C. or more lower than the melting temperature of the microcapsule shell material, thermoreversible discoloration can be expressed particularly easily.

  The present invention will be described below with reference to examples, but the present invention is not limited to the following examples. Preparation of the test plate, examples and comparative examples, and a method for applying the surface treatment agent for metal materials will be described below.

(1) Metal plate The commercially available metal plate shown below was used.
-Hot dip galvanized steel sheet (GI): Thickness 0.8 mm, basis weight 30/30 (g / m ² )
・ Electrogalvanized steel sheet (EG): Thickness 0.8mm, weight per unit area 20/20 (g / m ² )
・ Alloyed hot-dip galvanized steel sheet (GA): Plate thickness 0.8mm, basis weight 45/45 (g / m ² )
- molten zinc -11% aluminum -3% magnesium -0.2% silicon-plated steel sheet (SD): sheet thickness 0.8 mm, basis weight 60/60 (g / m ²⁾
・ SUS430 (SUS): Plate thickness 0.8mm
・ Copper plate (Cu): Thickness 0.8mm

(2) Pretreatment agent The following was prepared as a chemical conversion treatment solution used for the test material.
An aqueous solution containing 5 g / l of a silane coupling agent, 1.0 g / l of water-dispersed silica, 0.5 g / l of a zirconium compound with zirconium ions, and 25 g / l of an aqueous acrylic resin was prepared as a chemical conversion treatment solution. The silane coupling agent is γ-glycidoxypropyltrimethoxysilane, the water-dispersed silica is “Snowtech-N” manufactured by Nissan Chemical Co., the zirconium compound is zirconyl ammonium carbonate, and the aqueous acrylic resin is polyacrylic acid. Was used.

(3) Primer paint A clear paint of FL641EU primer, which is a polyester-based primer for PCM manufactured by Japan Fine Coatings Co., Ltd., is prepared. -WHITE # 105 "was added in an amount of 30 parts by mass with respect to 100 parts by mass of the solid content of the clear paint, and the mixture was stirred using a paint disperser to prepare a primer paint used as a test material.

(4) Thermoreversible color-changing coating material (water-based)
The organic resin (A) (Table 1), thermoreversible color-changing pigment (B) (Table 2), curing agent (C) (Table 3), silicon oxide (D) (Table 4) in the amounts shown in Table 5. A water-based coating solution for forming a thermoreversible color-changing film used for the test material was prepared by mixing and stirring with a dispersion machine for paint.

(5) Thermoreversible color-changing coating material (solvent type)
An organic resin (F) (Table 6), a thermoreversible color-changing pigment (G) (Table 7), and a curing agent (H) (Table 8) are blended in the blending amounts shown in Table 9, and a paint disperser is used. Stir. Thereafter, 5 parts by mass of an acidic catalyst “Catalyst 600” manufactured by Mitsui Cytec Co., Ltd. was added and stirred to prepare a solvent-based coating solution for forming a thermoreversible color-changing film used for the test material.

(6) Coating paints that do not have thermoreversible discoloration (water-based)
A melamine resin “Cymel 303” manufactured by Mitsui Cytec Co., Ltd. was added as a curing agent to “Vylonal MD1100” which is a polyester resin manufactured by Toyobo Co., Ltd., to prepare a clear paint. The addition amount of melamine resin was added so that it might be 30 mass parts with respect to 100 mass parts of polyester resin solid content. Furthermore, if necessary, 30 parts by mass of water-based colorants “RED HR (red)” and “BLUE HG (blue)” manufactured by Toyo Ink Co., Ltd. with respect to 100 parts by mass of the polyester resin solid content, respectively. A colored paint was prepared by adding the mixture so as to be and stirring with a disperser for paint.

(7) Coating paints that do not have thermoreversible discoloration (solvent type)
Toyobo's amorphous polyester resin “Byron (registered trademark) 270” is mixed with an organic solvent (using a mass ratio of cyclohexanone: solvesso 150 = 1: 1), and the resin solids concentration is It melt | dissolved so that it might become 30 mass%, and also the melamine resin "Cymel (trademark) 303" by Mitsui Cytec was added as a hardening | curing agent, and the clear coating material was produced. The addition amount of melamine resin was added so that it might be 30 mass parts with respect to 100 mass parts of polyester resin solid content. Furthermore, if necessary, 30 parts by mass of the colorant “CAB-440 red (red)” and “CAB714 blue (blue)” manufactured by Toyo Ink for 100 parts by mass of the polyester resin solid content are added to the clear paint, respectively. And stirred using a disperser for paint. Thereafter, 5 parts by mass of an acidic catalyst “Catalyst 600” manufactured by Mitsui Cytec Co., Ltd. was added and stirred to prepare a solvent-based coating material having no thermoreversible discoloration.

(8) Preparation of pre-coated metal plate (pretreatment)
Each metal plate was spray-treated for 2 minutes under the conditions of a concentration of 20 g / L and a temperature of 60 ° C. using a fine cleaner 4336 manufactured by Nihon Parkerizing Co., Ltd., washed with pure water for 30 seconds and dried to obtain a test plate. . And the chemical conversion liquid was apply | coated to the metal plate with the roll coater, and it dried with the hot-air drying furnace, and obtained the chemical conversion treatment film layer. The amount of the chemical conversion treatment was applied so that the amount of the entire dry film was 100 mg / m ² . The ultimate plate temperature during the chemical conversion treatment drying was set to 60 ° C. The adhesion amount of the chemical conversion film was measured by fluorescent X-ray.

(9) Preparation of thermoreversible color-changing pre-coated metal sheet (aqueous)
On the metal plate that has been subjected to chemical conversion treatment, the water-based paint for forming the thermoreversible color-changing film produced in (4) is applied with a roll coater so as to have a predetermined film thickness, and then dried and baked in a hot air oven. Then, a pre-coated metal plate as a test material was obtained by cooling with water (the pre-coated metal plate produced by this method is hereinafter referred to as [1 coat 1 bake] or “1C1B”). Here, the temperature rising time from 25 ° C. to the metal arrival temperature was 10 seconds. The coating amount was measured by a gravimetric method.

  If necessary, a water-based paint for forming a film having no thermoreversible discoloration produced in (6) is applied with a roll coater, dried and baked in a hot air oven, and water-cooled. (The precoated metal plate produced by this method is hereinafter referred to as “2 coat 2 bake” or “2C2B”). Here, the temperature rising time from 25 ° C. to the metal arrival temperature was 8 seconds. The coating amount was measured by a gravimetric method.

(10) Preparation of thermoreversible color-changing pre-coated metal plate (solvent type)
The primer was coated on the metal plate subjected to the chemical conversion treatment with a roll coater so as to have a thickness of 5 μm, baked and dried in a hot air oven, and cooled with water to obtain a primer plate.

  On the primer plate, apply a solvent-based paint for forming the thermoreversible color-changing film produced in (5) so as to have a predetermined film thickness using a roll coater, roller curtain coater or slide curtain coater, and A pre-coated metal plate as a test material was obtained by drying and baking at 1 and cooling with water (hereinafter, the pre-coated metal plate produced by this method is referred to as “1 coat 1 bake” or “1C1B”). Here, the temperature rising time from 25 ° C. to the metal arrival temperature was 40 seconds. The coating amount was measured by a gravimetric method.

  If necessary, apply a solvent-based paint to form a film without thermoreversible discoloration prepared in (7) with a roll coater, roller curtain coater or slide curtain coater, and dry in a hot air oven. The pre-coated metal plate as the test material was obtained by baking and water cooling (the pre-coated metal plate produced by this method is hereinafter referred to as “2 coat 2 bake” or “2C2B”). Here, the temperature rising time from 25 ° C. to the metal arrival temperature was 40 seconds. The coating amount was measured by a gravimetric method.

  Further, if necessary, a solvent-based paint for forming the thermoreversible color-changing film produced in (5) on the primer plate and a film having no thermoreversible color-changing characteristic produced in (7) are formed. The solvent-based paint was coated with multiple layers at the same time using a slide curtain coater, and the laminated paint was dried and baked at the same time in a hot air oven and cooled with water to obtain a pre-coated metal plate as a test material (by this method). The prepared precoat gold plate is hereinafter referred to as [2 coats 1 bake] or “2C1B”). Here, the temperature rising time from 25 ° C. to the metal arrival temperature was 40 seconds. Further, the coating amount was measured by a gravimetric method.

  The following evaluation test was carried out on the precoated metal sheet produced in this way.

<1. Thermoreversible discoloration test>
Hereinafter, the method for evaluating the present invention will be described in detail.
Metal plate temperature is 10 ° C. (below the discoloration temperature), 30 ° C. (intermediate temperature (when the color by the thermoreversible color-changing pigment is red, the color change temperature is higher than the color change temperature, and when the color by the thermoreversible color change pigment is blue, the color change temperature) Less))), and the relationship of the color tone in the state kept at 50 ° C. (above the discoloration temperature). The color tone (L ^* , a ^* , b ^* ) at each temperature was measured with a color difference meter (“CR-400” manufactured by Konica Minolta).

Using the color difference ΔE ^* described in JIS Z 8729, the thermoreversible color change was evaluated as follows. A score of 3 or higher was preferred. ΔE ^* was calculated by the following equation.
_{^{ΔE * = ((L * 2}} -L * 1) 2 + (a * 2 -a * 1) 2 + (b * 2 -b * 1) 2) 0.5
L ₁ *, a ₁ *, b ₁ *: Colorimetric value at metal plate temperature <Tc-5 ° C
L ₂ *, a ₂ *, b ₂ *: Metal plate temperature> Color measurement value at Tc + 5 ° C
5: ΔE ^* is 20 or more 4: ΔE ^* is 10 or more and less than 20 3: ΔE ^* is 5 or more and less than 10 2: ΔE ^* is 1 or more and less than 5 1: ΔE ^* is less than 1

<2. Coating film processability test>
The prepared pre-coated metal sheet is subjected to 180 ° bending (generally called T-bending) with a plurality of spacers of the same thickness sandwiched between them, and Nichiban's cellophane tape is applied onto the coating film of the T-bending part. (Registered trademark) was applied, and the degree of peeling of the coating film after the cellotape (registered trademark) was peeled was examined. The bending process was performed in an atmosphere of 20 ° C. with 0, 1, 2, and 4 spacers (referred to as 0T, 1T, 2T, and 4T bending, respectively).

When the coating film peeling area in the coating film processed part was 5% or more, peeling was evaluated, and when the peeling area was less than 5%, it was evaluated that there was no peeling. The coating film processability was evaluated as follows depending on whether or not the processed part coating film was peeled off. A score of 3 or higher was preferred.
[Score]
5: No peeling at 0T bending 4: No peeling at 0T bending, no peeling at 1T bending 3: No peeling at 1T bending 2: No peeling at 2T bending 2: No peeling at 4T bending 1: 4T bending With peeling

<3. Solvent resistance (chemical resistance) test>
After placing the test material on a “rubbing tester” manufactured by Taihei Rika Kogyo, the absorbent cotton impregnated with ethanol, toluene, n-hexane and cyclohexanone was rubbed 5 times (reciprocating) at a pressure of 0.5 kgf / cm ² . The appearance of the precoated metal plate was observed and evaluated according to the following criteria. A score of 3 or higher was preferred.
[Score]
5: No discoloration with all solvents 4: Discoloration with one solvent 3: Discoloration with two solvents 2: Discoloration with three solvents 1: Discoloration with all solvents

<4. Corrosion resistance>
(I) Flat plate part corrosion resistance About the flat plate test piece which sealed the end surface and the back surface, the salt spray test (SST) prescribed | regulated to JISZ2371 was implemented, and it evaluated by the incidence rate of the white rust 240 hours after. Corrosion resistance evaluation criteria are shown below. A score of 3 or higher was preferred.
[Score]
5: No white rust generated 4: White rust generated less than 1% 3: White rust generated 1% or more but less than 5% 2: White rust generated 5% or more but less than 20% 1: White rust generated 20% or more

(Ii) Corrosion resistance after processing For a flat plate test piece whose end face and back surface are sealed, the center portion is subjected to 7 mm Erichsen processing, and then subjected to a salt spray test (SST) defined in JIS Z 2371, after 120 hours. Evaluation was made based on the white rust generation rate of the Erichsen processed part. Corrosion resistance evaluation criteria are shown below. A score of 3 or higher was preferred.
[Score]
5: No white rust generated 4: White rust generated less than 1% 3: White rust generated 1% or more but less than 5% 2: White rust generated 5% or more but less than 20% 1: White rust generated 20% or more

  Details of the evaluation results will be described below.

  Table 10 shows pre-coated metal sheets produced in Examples and Comparative Examples of the present invention, and Table 11 shows the evaluation results. In Examples 40 to 77 and Comparative Examples 8 to 14 and Comparative Example 16, the effects of the present invention are described using the specimens with the primer coating applied, but the primer coating is not applied. Also, the same performance as that obtained by applying the primer coating is obtained.

(1) Effect of thermoreversible color-changing microcapsule amount and film thickness (aqueous)
Examples 1 to 8 and 11 and Comparative Examples 1 to 4 show the effects of the thermoreversible color-changing microcapsule amount and film thickness in the water-based paint.

  All of the precoated metal sheets (Examples 1 to 6) of the present invention had excellent thermoreversible discoloration, work adhesion, solvent resistance, and corrosion resistance.

  Since the amount of microcapsules in the resin film is 2 parts by mass with respect to the resin solid content (Examples 1 to 3), the thermoreversible discoloration tends to slightly decrease, so the amount of microcapsules in the film is 10-30 mass parts is more suitable with respect to resin solid content.

  When the film thickness of the microcapsule-containing film was 2 μm (Examples 1 and 5), the thermoreversible discoloration and work adhesion were slightly decreased. The thickness of the microcapsule-containing film is more preferably 3 μm or more.

  Those having a microcapsule content in the resin film of less than 2 parts by mass relative to the resin solid content (Comparative Example 1) are unsuitable due to poor thermoreversible discoloration. Moreover, since the process adhesiveness is inferior (Comparative Examples 3-5) whose microcapsule content in a resin film is more than 35 mass parts with respect to resin solid content, it is unsuitable.

  A microcapsule-containing film having a film thickness of less than 2 μm (Comparative Example-2) is inadequate due to poor thermoreversible discoloration and processing adhesion.

(2) Types of microcapsule-containing resin (aqueous)
Examples 1 to 24 show the influence of the resin type of the microcapsule-containing resin film. All of them had excellent thermoreversible discoloration, work adhesion, solvent resistance and corrosion resistance.

  The microcapsule-containing resin film using an acrylic resin or an epoxy resin (Examples 17 to 24) was slightly inferior in film processing adhesion than that of a polyester resin (Examples 1 to 16). The type of the microcapsule-containing resin is preferably a polyester resin.

(3) Crosslinking agent ratio Examples 1 to 4, Example 12, and Example 13 show the influence of the melamine resin ratio used as the crosslinking agent for the polyester resin. All of them had excellent thermoreversible discoloration, work adhesion, solvent resistance and corrosion resistance.

  Those having a melamine resin content of less than 15 parts by mass (Examples 1-3) in 100 parts by mass of polyester resin solids are slightly less than those having an melamine resin content of 15 parts by mass or more (Examples 4, 12, and 13). It was inferior in solvent resistance.

  The melamine resin with a solid content of 100 parts by mass of polyester resin is more than 30 parts by mass (Example-14), and the process adhesion is slightly less than that with a melamine resin of 30 parts by mass or less (Examples 1-4 and 12). It was inferior.

  As a melamine resin in 100 mass parts of polyester resin solid content, 15-30 mass parts is more suitable.

(4) Influence of metal temperature (PMT) (aqueous)
The influence of PMT is shown in Examples 8 to 10, Examples 22 to 24 and Comparative Examples 6 and 7. The precoated metal plates of the present invention (Examples 8 to 10 and Examples 22 to 24) all had excellent thermoreversible color change, work adhesion, solvent resistance, and corrosion resistance.

In Example 10, ΔE ^* was slightly smaller than in Examples 8 and 9, and the chemical resistance was slightly inferior. If the PMT is low, the degree of cross-linking of the film is low, and it is considered that the elution of the microcapsules and the chemical resistance are reduced.

  In Examples 22-24, the same result as Examples 8-10 was obtained.

On the other hand, Comparative Examples 6 and 7 are not suitable because ΔE ^* is less than 5. In Comparative Example 6, sufficient PMT cannot be obtained, so that elution of microcapsules occurs. In Comparative Example 7, since the PMT is too high, the microcapsule shell material is melted, so that ΔE ^* is considered to be small.

(5) Effect of film that does not have thermoreversible discoloration (aqueous)
Examples 6, 7, 15 and 26 to 29 show the influence of the film having no thermoreversible discoloration. All of them had excellent thermoreversible discoloration, work adhesion, solvent resistance and corrosion resistance.

  Examples 6, 7, and 15 containing only microcapsules and having a thermoreversible discoloration property (Layer 1) were not coated with Layer 1 and microcapsules and did not have thermoreversible discoloration property (Layer 2). The working adhesion and solvent resistance tended to be slightly inferior to those of Examples 26 to 29. As described above, the work adhesion and solvent resistance are slightly inferior due to the inclusion of the microcapsules, but it is considered that the addition of the layer 2 has improved the work adhesion and solvent resistance significantly. It is more preferable to provide a film (layer 2) that does not have thermoreversible discoloration.

(6) Effect of colored film having no thermoreversible color change The effects of a colored film having no thermoreversible color change are shown in Examples 26 to 29 and 30 to 33. All of them had excellent thermoreversible discoloration, work adhesion, solvent resistance and corrosion resistance.

Those in which layer 2 was a clear film (Examples 26 to 29) were slightly inferior in thermoreversible discoloration than those in which layer 2 was a colored film (Examples 30 to 33). Thermoreversible color change is more effective as the color difference ΔE ^* between layer 1 and layer 2 is larger. It is more preferable when the coating (layer 2) having no thermoreversible discoloration is a colored layer.

(7) Influence of PMT when there is a colored film not having thermoreversible discoloration The effects of PMT when there is a colored film not having thermoreversible discoloration are shown in Examples 33 and 34. In Example 34, ΔE ^* slightly decreased as compared with Example 33. On the other hand, chemical resistance did not decrease. It is thought that the chemical resistance at low PMT was improved by the influence of the colored layer having no thermoreversible discoloration.

(8) Influence of the original plate (water system)
Examples 31 and 35 to 39 show the influence of the original plate. The original plate is considered to have the most influence on the corrosion resistance, but no difference was seen with any of the original plates in the evaluation method investigated this time.

(9) Effects of paint types (water-based and solvent-based)
Examples 1 to 39 and Examples 40 to 77 show the influence of the paint type. All have excellent thermoreversible discoloration, work adhesion, solvent resistance and corrosion resistance, and those using water-based paints (Examples 1 to 39) use solvent-based paints (Example 40). ˜77) and the thermoreversible discoloration, work adhesion, and solvent resistance showed almost the same tendency.

Claims (6)

Having at least one layer of resin film on at least one surface of the metal plate;
The resin film contains microcapsules reversibly colored or colorless at a color change temperature Tc in a ratio of 2 to 30 parts by mass with respect to 100 parts by mass of resin solids in the resin film, and A melamine resin as a polyester resin and a cross-linking agent is contained in a proportion of 15 to 35 parts by mass of the melamine resin with respect to 100 parts by mass of the polyester resin solid content,
The resin film has a thickness of 2 μm or more,
A thermoreversible color-changing pre-coated metal sheet, characterized in that the color difference ΔE ^* described in JIS Z 8729 is reversibly changed when the temperature of the metal sheet is less than Tc-5 ° C. and more than Tc + 5 ° C. is 5 or more. On the layer 1 of the microcapsule-containing resin film, and having at least one layer 2 of the film not containing microcapsules exhibiting reversibly colored or colorless according to the environmental temperature, in claim 1 The thermoreversible color-changing precoated metal plate described. The average particle size of the microcapsules D, and the thickness of the layer 1 T1, if the thickness of the layer 2 was set to T2, characterized in that it is a D <T1 + T2, thermochromic according to claim 2 Pre-coated metal plate. The thermoreversible discoloration according to claim 2 or 3 , wherein the layer 2 is a colored layer, and the layer 1 and the layer 2 exhibit two or more colors according to an environmental temperature due to the effect of overcoating. Pre-coated metal plate. Applying at least one layer of a coating containing thermoreversible color-changing microcapsules reversibly colored or colorless at a color change temperature Tc on at least one surface of a metal plate;
The metal plate coated with the paint is heated to a metal arrival temperature that is 10 ° C. or more higher than the curing start temperature of the paint and 10 ° C. or less lower than the melting temperature of the shell material of the microcapsule, Curing the paint and water cooling to form a film;
A method for producing a thermoreversible color-changing pre-coated metal plate, wherein the color difference ΔE ^* described in JIS Z 8729 reversibly changes 5 or more when the temperature of the metal plate is less than Tc-5 ° C. and more than Tc + 5 ° C. Wherein the coating steps, wherein the color change temperature Tc in reversibly paint formulated with thermochromic microcapsules exhibiting colored or colorless at least one layer and said paint without blending microcapsules at least one layer, wherein The multilayer coating is simultaneously applied on one surface of the metal plate, and at least one layer 2 of the film not containing the microcapsule is formed on the layer 1 of the resin film containing the microcapsule. A method for producing a thermoreversible color-changing pre-coated metal plate.