JP2007237460A - Resin coated metal sheet excellent in corrosion resistance and surface properties - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin coated metal sheet containing a polyphenol compound as a rustproof component, excellent in corrosion resistance and also excellent in surface properties not producing discoloration or irregularity even if preserved under a constant temperature and humidity condition for a long time. <P>SOLUTION: In the resin coated metal sheet wherein a resin film obtained from a resin composition is provided at least on one side of a metal sheet, a microcapsule having the polyphenol compound encapsulated therein is added to a water soluble acidic resin with a number average molecular weight of 1,000-100,000 and porous fine particles with an average particle size of 5 μm or below. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a resin-coated metal plate having excellent corrosion resistance and surface properties, and more particularly to a resin-coated metal plate provided with a resin film obtained from a resin composition containing a predetermined resin and a polyphenol-containing microcapsule. is there. Since the resin-coated metal plate of the present invention is excellent in corrosion resistance and surface properties, it can be suitably used, for example, in fields such as household electric products, building materials, and automobile parts.

  For parts such as home appliances and automobiles, for the purpose of improving corrosion resistance, resin-coated metal plates that have been subjected to chemical treatments such as chromate treatment and phosphate treatment on zinc-based plated steel plates have been widely used. . However, recently, in order to avoid the problem of environmental pollution due to harmful chromium, a chromium-free surface treatment technique using a rust preventive agent that can be substituted for chromate treatment has been proposed.

  For example, Patent Documents 1 and 2 propose a resin-coated metal plate using a polyphenol compound such as tannic acid as a rust inhibitor.

  However, the demand for corrosion resistance is increasing and further improvements are required.

  In addition, since polyphenol compounds are easily oxidized, if a resin-coated metal plate containing a polyphenol compound in a resin film is left for a long period of time under constant temperature and humidity, the surface changes color and yellow spot-like unevenness occurs. There is also.

On the other hand, Patent Documents 3 to 5 describe microcapsules containing a rust preventive agent as a core substance (core), but nothing is described about polyphenol compounds.
JP 2000-45079 A JP 2001-89868 A Japanese Patent Laid-Open No. 56-113382 JP-A 61-272391 JP 2003-286196 A

  The present invention has been made in view of the above circumstances, and its purpose is to include a polyphenol compound as a rust preventive component, which has excellent corrosion resistance and does not cause discoloration or unevenness even when stored for a long time under constant temperature and humidity. The object is to provide a resin-coated metal plate having excellent properties.

  The resin-coated metal plate excellent in corrosion resistance and surface properties according to the present invention that has solved the above problems is a resin-coated metal plate provided with a resin film obtained from a resin composition on at least one side of the metal plate, It has a gist in that it contains a water-soluble acidic resin having a number average molecular weight of 1000 to 100,000 and microcapsules in which a polyphenol compound is encapsulated in porous fine particles having an average particle size of 5 μm or less.

  In preferable embodiment, the ratio of the said water-soluble acidic resin and the said microcapsule exists in the range of 60-95 mass parts: 5-40 mass parts with respect to 100 mass parts of solid content of a resin composition.

  In a preferred embodiment, the water-soluble acidic resin has a pH of 6 or less, and examples thereof include an acrylic resin.

  In a preferred embodiment, the polyphenol compound contained in the microcapsule is at least one selected from the group consisting of tannic acid, gallic acid, and catechin.

  In a preferred embodiment, the porous fine particles are inorganic fine particles.

  In a preferred embodiment, the resin composition further includes acidic colloidal silica, and the acidic colloidal silica is 5 to 100 parts by mass of a solid content of the resin composition including the water-soluble acidic resin and the microcapsules. It is contained within the range of 40 parts by mass.

  In a preferred embodiment, the resin composition does not contain Cr or an acidic substance (for example, phosphoric acid, nitric acid, fluorine compound, etc.) used for surface etching.

  The resin-coated metal plate of the present invention that has solved the above-described problems includes a resin film obtained from any of the resin compositions described above on at least one surface of the metal plate.

In preferable embodiment, the adhesion amount of the said resin film is 0.3-3 g / m < ² > by dry weight.

  In a preferred embodiment, the resin film is substantially free of Cr.

  Since the resin-coated metal plate of the present invention is obtained from a resin composition containing a predetermined resin and microencapsulated polyphenol, the resin-coated metal plate is excellent in corrosion resistance and has a yellow stain even when stored for a long time under constant temperature and humidity. No surface irregularities occur and the surface properties are excellent.

  ADVANTAGE OF THE INVENTION According to this invention, even if it does not use chromium, the metal plate which can exhibit the corrosion resistance equivalent to or more than chromium continuously over a long period of time is obtained. Further, a metal plate having an extremely excellent surface property can be obtained without using phosphoric acid or the like that is usually used as a surface etching agent. Furthermore, the metal plate of the present invention is also excellent in paintability (adhesion with a film applied on a resin film if necessary) and tape peel resistance (adhesion between a resin film and a metal plate). Yes.

  Further, if a resin composition further containing acidic colloidal silica is used, a resin-coated metal plate with further improved corrosion resistance, paintability, and tape peel resistance can be obtained.

  In order to provide a composition for a resin-coated metal sheet that can exhibit the corrosion resistance of a polyphenol compound to the maximum while preventing the coloring of the surface, the present inventor has paid much attention to the microcapsule technology in particular. Has been repeated. As a result, the inventors have found that the intended purpose can be achieved by using a resin-coated metal plate containing a microcapsule filled with a polyphenol compound and a predetermined acidic resin, thereby completing the present invention.

  This point will be explained in a little more detail.

  Since polyphenol compounds easily oxidize, there are problems such as yellowing of the surface when conventional resin-coated metal plates (that is, polyphenolphenol compounds are not microencapsulated) are stored for a long time under constant temperature and humidity. . Further, depending on the storage environment, there is a problem that the surface treatment liquid containing the polyphenol compound is gelled and it becomes difficult to paint.

  Accordingly, the present inventor has attempted microencapsulation of a polyphenol compound that has not been proposed so far, with the aim of further improving corrosion resistance and improving surface properties. However, using the known microencapsulation technology to produce polyphenol-filled microcapsules does not provide the desired properties, and gelation occurs during the preparation of microcapsule-containing treatment solutions, and the resin film is stored for a long period of time. It has become clear from the experimental results of the present inventors that problems such as surface discoloration occur due to the above.

  In view of such circumstances, the present inventor has further studied. As a result, a resin-coated metal that exhibits the corrosion resistance of polyphenol compounds effectively and continuously, and is stable even when stored for long periods in harsh environments by preventing oxidation of polyphenol compounds (surface does not change color) In order to obtain a plate, it was not sufficient to microencapsulate the polyphenol compound, and it was found that it was extremely important to use a predetermined acidic resin, and the present invention was reached.

  The resin-coated metal plate of the present invention has a further enhanced corrosion resistance compared to the case where the polyphenol is not encapsulated because the polyphenol compound is encapsulated in the capsule wall (here, porous fine particles). Furthermore, since a predetermined resin is used in the present invention, gelation does not occur even when the treatment liquid is stored for a long period of time, as well as during the preparation of the resin composition (treatment liquid) and the resin film. Therefore, according to the present invention, it is possible to obtain a resin-coated metal sheet that exhibits good corrosion resistance continuously over a long period of time and is excellent in surface properties (discoloration resistance) (see Examples described later).

  The yellowing prevention effect by microencapsulation of a polyphenol compound will be described with reference to FIG.

FIG. 1 shows a metal plate containing tannic acid-containing microcapsules (□ in the figure) or non-microencapsulated tannic acid (■ in the figure) in a film at a temperature of 50 ° C. and a relative humidity of 98%. The result of having investigated temporally the change of the color tone (b value) when preserve | saved under constant temperature and humidity is shown. The tannic acid content in the film is 1.03 g / m ² in all cases. For reference, the results of the chromate-treated steel sheet (in the figure, x) are also shown.

  Here, the degree of yellow increases as the b value increases (+), and the degree of blue increases as the b value decreases (−). If b value is 0 or less, yellowishness is not conspicuous when observed with the naked eye.

  As shown in FIG. 1, in the case of a conventional metal plate that does not microencapsulate tannic acid (in the figure, ■), the b value increases rapidly after 5 days from the test, and on the 7th day, the b value increases. About 1.3, the yellowish color became stronger.

  In contrast, in the metal plate of the present invention (□ in the figure) in which tannic acid was microencapsulated, even when stored for 7 days under constant temperature and humidity, the b value hardly changed, and the chromate-treated steel plate (in the figure) , X), yellowing was not observed.

The change in color tone is generally evaluated by ΔE (color difference) calculated by the following formula. Here, the degree of yellowing caused by tannic acid was evaluated by b value instead of ΔE. The reason is that in the case of tannic acid, the change in ΔE is mainly due to the change in the b value.
ΔE = (Δa ² + Δb ² + ΔL ² ) ^1/2
The L value is a lightness index, the a value is a red index, and the b value is a yellow index.
is there.

  In addition, although the result of tannic acid was shown in FIG. 1, it has confirmed by experiment that the same result is obtained also when another polyphenol compound is used.

(Resin composition)
First, the resin composition characterizing the present invention will be described. The resin composition of the present invention contains a water-soluble acidic resin having a number average molecular weight of 1000 to 100,000 and microcapsules in which a polyphenol compound is encapsulated in porous fine particles having an average particle diameter of 5 μm or less. .

(Resin used in the present invention)
In this specification, “acidic resin” means a resin having a pH of about 6 or less (preferably, pH 1 to 3). As shown in the examples to be described later, when the pH of the resin exceeds the above range, the stability of the treatment liquid containing the resin composition (hereinafter sometimes referred to simply as the treatment liquid) is lowered, and long-term storage is performed. To gel. The smaller the pH, the better.

  Examples of the water-soluble acidic resin used in the present invention include acrylic resins such as polyacrylic acid and polymaleic acid, vinyl acetate, and urethane resins. These resins may include not only a homopolymer but also a copolymer (copolymer) obtained by copolymerizing another copolymerizable monomer. In view of alkali resistance, corrosion resistance and the like, an acrylic resin is preferable. Examples of acrylic resins include (meth) acrylic acid (salts), (meth) acrylic esters, and monomer components copolymerizable therewith (for example, unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid). Acids: Unsaturated monocarboxylic acids such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, glycidyl (meth) acrylate, methyl crotonate, ethyl crotonate, propyl crotonate and the number of carbon atoms And copolymers with esters of 1 to 30 alcohols).

  Said resin may have a hydrophilic functional group (hydrophilic group), and water solubility is further improved by this. As the hydrophilic group, both an anionic group and a cationic group are used. For example, an anionic group such as a carboxyl group, a sulfonic acid group, a sulfate ester group, a phosphate ester group, a hydroxyl group, an ammonium base (for example, Quaternary ammonium bases, etc.), and cationic groups such as amino groups and imino groups.

  Moreover, the number average molecular weight (Mn) of the said acidic resin used for this invention exists in the range of 1000-100,000. When the number molecular weight exceeds 100,000, the fluidity of the resin is deteriorated, so that gelation is likely to occur with time (see Examples described later). On the other hand, when the number molecular weight is less than 1000, the resin film-forming ability (film-forming ability) is insufficient and the alkali resistance is inferior. The number average molecular weight of the acidic resin is preferably 3000 or more and 70000 or less, and more preferably 20000 or more and 50000 or less.

  The number average molecular weight of the resin is determined in terms of polystyrene using a gel permeation chromatography (GPC) method.

  As the resin that satisfies all of these requirements, a commercially available product can be used as shown in the examples described later. Specifically, in addition to acrylic resins A to H shown in Table 1 to be described later, acrylic resin (pH 2.5 to 3.5, Mn 30,000 to 5) of Nippon Pure Chemical Co., Ltd. “Jurimer 5H-8”. Acrylic resin of Nippon Shokubai "Polyment NK-100PM" (pH 4-5, 5, Mn 10,000-30,000).

(Micro capsule)
FIG. 2 schematically shows an example of a microcapsule used in the present invention.

  As shown in FIG. 2, the polyphenol compound 3, which is a rust preventive component, exists in the form of microcapsules 1 encapsulated (filled) in porous fine particles 2. The polyphenol compound 3 is positioned as the core material of the microcapsule 1, and the porous fine particles 2 are positioned as the microcapsule wall.

  The polyphenol compound 3 will not be specifically limited if it is normally used as a rust preventive agent, For example, a tannic acid, a gallic acid, catechin etc. are illustrated typically. These may be used alone or in combination of two or more. In consideration of corrosion resistance and the like, it is preferable that at least tannic acid is included.

  The porous fine particles 2 are produced using an inorganic compound or an organic compound usually used for producing the microcapsules 1 (the production method will be described later). Specifically, as inorganic compounds, silica, titanium oxide, iron oxide, cobalt oxide, zinc oxide, nickel oxide, manganese oxide, alumina, and other metal oxides, iron hydroxide, nickel hydroxide, aluminum hydroxide, hydroxide Metal hydroxides such as calcium and chromium hydroxide, carbonates such as calcium carbonate and barium carbonate, silicates such as calcium silicate, barium silicate and magnesium silicate, calcium phosphate, barium phosphate, magnesium phosphate and phosphorus Examples thereof include phosphates such as zirconium acid and apatite. As organic compounds, various polymers (resins) such as fully saponified polyvinyl alcohol, polyacrylonitrile, polyvinylidene chloride, polystyrene, polyethylene, urea resin, melamine resin, polyamide, urethane resin, epoxy resin, and their copolymers, These include various modified products thereof. In view of solvent resistance and the like, inorganic compounds are preferable, and silica is most preferable.

The average particle size of the porous fine particles 2 is preferably about 5 μm or less. When the average particle diameter exceeds the above range, it is difficult to coat the porous fine particles with the above-described acidic resin film, and it has been confirmed by experiments that the corrosion resistance and tape peel resistance deteriorate. Considering the relationship with the preferable adhesion amount of the resin film (in the range of 0.3 to 3 g / m ^{2 by} dry weight. Details will be described later), the smaller the average particle size of the porous fine particles 2 is, the better. For example, it is more preferably 1.5 μm or less. The lower limit of the average particle size of the porous fine particles is not particularly limited from the relationship with characteristics such as corrosion resistance, but is preferably about 0.5 μm in view of the ease of producing the porous fine particles.

  The average particle diameter of the porous fine particles can be obtained, for example, by calculating the average value of the porous fine particles observed in the visual field using a scanning electron microscope (magnification 5000 times). Alternatively, “SA-P3” manufactured by Shimadzu Corporation can be used to calculate by the centrifugal sedimentation method.

  Such porous fine particles can be produced using, for example, an interfacial polymerization method or an interfacial reaction method. Specifically, for example, the interface reaction method described in JP-A-6-234650 and JP-A-7-173452 can be employed.

Commercially available products may be used as the porous fine particles. Specifically, for example, non-hollow type inorganic porous silica fine particles (“God Ball E-2C” manufactured by Suzuki Oil & Fat Co., Ltd., average particle size 1.0 μm), hollow type inorganic porous silica fine particles (Suzuki fat and oil) “Godball E-6C” manufactured by Kogyo Co., Ltd. “average particle size 2.2 μm”, porous silica particles (“SE MCB-FP / 2” manufactured by Enex Co., Ltd.), average particle size 3.2 μm, specific surface area 242 m ² / g) and the like can be used.

  The ratio of the water-soluble acidic resin and the microcapsules used in the present invention is preferably 100 parts by mass of the resin composition 60-95 parts by mass: 5-40 parts by mass, and 70-90 parts by mass: 10-30. It is more preferable that it is a mass part, and it is still more preferable that it is 75-85 mass part: 15-25 mass%. Below the above ratio (the content of the microcapsules is small), the microcapsules cannot be uniformly dispersed in the resin film, and the corrosion resistance action by the polyphenol compound is not effectively exhibited. On the other hand, if it exceeds the above ratio (the content of the microcapsules is large), the film-forming property of the resin film is lowered, the corrosion resistance and the tape peelability are remarkably deteriorated, and the paintability is also lowered.

  The resin composition of the present invention basically comprises the above porous fine particles and a predetermined acidic resin, and does not contain Cr. Such a resin composition is excellent in all of corrosion resistance, discoloration resistance, paintability, and tape peel resistance, as shown in the examples described later. This is because a resin film excellent in corrosion resistance more than that can be obtained.

  Moreover, the resin composition of the present invention does not contain an etching agent. Since the surface of a metal plate is often covered with an oxide film, the surface of the oxide film is usually roughened using an acidic substance (etching agent) such as phosphoric acid, nitric acid, or a fluorine compound (HF, etc.). The adhesion between the oxide film and the resin film is improved. On the other hand, since the resin composition of the present invention is excellent in adhesion with an oxide film, it is not necessary to use an etching agent (see Examples described later). Of course, an etching agent may be contained for the purpose of further improving the adhesion to the metal plate including the oxide film.

(Other ingredients)
The resin composition of the present invention may contain acidic colloidal silica for the purpose of further improving characteristics such as corrosion resistance. As a result, the strength of the resin film is increased, and in a corrosive environment, the silica is concentrated in the collar portion of the resin film, and the corrosion of the metal is suppressed and the corrosion resistance is further enhanced.

  The colloidal silica needs to be acidic. If colloidal silica other than acid is used, gelation occurs during the preparation of the treatment liquid. Further, when pulverized silica or vapor phase method silica is used, it is inactive unlike colloidal silica, so that no silica is concentrated in the buttocks or the like in a corrosive environment, and an effect of improving corrosion resistance cannot be obtained.

  As the acidic colloidal silica, commercially available products may be used. For example, “Snowtex ST-O” (pH 2 to 4, particle diameter 10 to 20 nm), “Snowtex ST-OL” (manufactured by Nissan Chemical Industries, Ltd.) pH 2-4, particle diameter 40-50 nm), “Snowtex ST-OUP” (pH 2-4, particle diameter 40-100 μm, chain state) and the like.

  The acidic colloidal silica is preferably contained within a range of 5 to 40 parts by mass with respect to 100 parts by mass of the solid content of the resin composition comprising the water-soluble acidic resin and the microcapsules described above (Examples described later). See). When the content of acidic colloidal silica is less than 5 parts by mass, the effect of improving the corrosion resistance is not exhibited effectively. On the other hand, when the content exceeds 40 parts by mass, cracks occur in the film, resulting in corrosion resistance, paintability, and tape peel resistance. descend. As for content of acidic colloidal silica, it is more preferable that it is 5-30 mass parts with respect to 100 mass parts of solid content of the said resin composition, and it is still more preferable that it is 10-20 mass parts.

  The resin composition of the present invention further comprises components usually added to the resin film (for example, surfactants, conductive additives for imparting conductivity, thickeners, antifoaming agents, dispersants, drying agents). , Stabilizers, anti-skinning agents, antifungal agents, preservatives, antifreezing agents, etc.). These are included in the range which does not impair the effect | action of this invention.

  The existence form of the above-mentioned “other components” (whether or not to microencapsulate) is not particularly limited as long as desired properties are effectively exhibited. Therefore, the above-described components may be included in the porous fine particles or may not be included.

(Method for producing microcapsules)
A method for producing a microcapsule by encapsulating polyphenol in porous fine particles is not particularly limited. For example, the following methods (1) to (3) can be appropriately selected and produced. These detailed methods are described, for example, in “Microcapsules—Production, Properties, and Applications—” issued by Sankyo Publishing Co., Ltd.
(1) Chemical production method: a) interfacial polymerization method, b) in situ polymerization method,
(2) Physicochemical production method: a) Coacervation method, b) In-liquid drying method,
(3) Mechanical and physical manufacturing methods: a) Orifice method, b) Spray drying method,
c) air suspension coating method, d) hybridizer method, etc.

  Specifically, for example, microcapsules can be produced as follows.

  First, porous fine particles obtained by the above-described method and an aqueous solution of a polyphenol compound are prepared.

  The concentration of the polyphenol compound in the aqueous solution is preferably in the range of about 50% to 100%. Thereby, the corrosion resistance by a polyphenol compound is exhibited effectively. Examples of the solvent include water, a mixed solution of water and a hydrophilic solvent (for example, alcohol, ketone, ester, glycol), and a water-soluble polymer (for example, polyvinyl alcohol, carboxymethyl cellulose, gelatin, gum arabic, etc.). ), A solution obtained by adding a surfactant (anionic surfactant, cationic surfactant, nonionic surfactant) to water, a solution obtained by mixing these, or the like is used.

  Next, the porous fine particles are immersed in an aqueous solution of a polyphenol compound and stirred to impregnate the porous fine particles with the polyphenol compound. Here, in order to facilitate filling of the polyphenol compound, the temperature of the aqueous solution is preferably about 20 to 40 ° C. Specifically, for example, it is preferable to immerse at the above temperature for about 1 to 3 hours.

  Next, the solution is filtered, and the resulting residue is dried using, for example, a vacuum drier to evaporate water. The drying conditions are preferably, for example, at a temperature of 40 to 80 ° C. for about 1 to 3 hours. As a result, a microcapsule in which a polyphenol compound is encapsulated in porous fine particles is obtained.

  In addition to the above, for example, the method described in JP-A-6-234650 described above (a method using a pressure difference) can be employed. Specifically, after the porous fine particles were put into the vacuum chamber described in FIG. 1 of the above publication and the pressure was reduced, an aqueous solution of a polyphenol compound was introduced into the vacuum chamber at normal pressure, and the solution was introduced into the vacuum chamber. The polyphenol compound penetrates into the porous fine particles due to the pressure difference. Subsequently, after returning the inside of a vacuum chamber to atmospheric pressure and filtering, a desired microcapsule will be obtained.

  In addition, when it is desired to enclose other components such as colloidal silica oxide in addition to the polyphenol compound in the porous fine particles, the same method as described above may be employed.

(Resin-coated metal plate of the present invention)
FIG. 3 shows an example of the resin-coated metal plate of the present invention. As shown in FIG. 3, the resin-coated metal plate 7 of the present invention includes a resin film 6 obtained from the above-described resin composition on one side of the metal plate 5. The microcapsule 1 is dispersed in the resin film 6. Although FIG. 3 shows an example in which the resin film 6 is provided on one side of the metal plate 5, the present invention is not limited to this, and the resin film 6 may be provided on both sides of the metal plate 5. Further, another film may be further provided on the resin film 6.

The content of the polyphenol compound contained in the resin film 6 can vary depending on the pore volume of the porous fine particles and the like, and is not easily determined uniquely. Here, the total pore volume of the porous fine particles is 0.3 to 1.7 mL / g, the specific gravity of the polyphenol is 1, and the content of the microcapsules contained in the resin composition (in the present invention, about 5 to 40). Based on the weight part) and the adhesion amount of the resin film (in the present invention, about 0.3 to 3 g / m ² ), the preferable content (calculated value) of the polyphenol compound is 0.005 g / m ² or more and 2.0 g / m ^2. m ² or less. The total pore volume of the porous fine particles differs mainly in relation to the average particle diameter of the particles, but in the case of the porous fine particles (average particle diameter of 5 μm or less) used in the present invention, the value is generally in the above range. It is because it can take.

For example, in Table 3 of Example 2 which will be described later, the resin film adhesion amount (dry weight) is 1 g / m ² , the total pore volume of the porous fine particles is 1.03 mL / g, and the specific gravity of polyphenol is 1. The content of the polyphenol compound contained in the film was calculated. In the present invention, the content of the microcapsules contained in the resin composition is preferably 5 to 40 parts by mass, and the preferred polyphenol content in the resin film corresponding thereto is based on the above calculation method. It is in the range of 0.052 to 0.412 g / m ² . As shown in Table 3, when the content of the polyphenol compound exceeds the upper limit, all of the corrosion resistance, paintability, and tape peel resistance are lowered, and when the content is lower than the lower limit, the corrosion resistance is lowered.

The adhesion amount of the resin film 6 is preferably in the range of 0.3 to 3 g / m ² by dry weight. When the adhesion amount of the surface treatment film is below the above range, it has been confirmed by experiments that the porous fine particles cannot be covered and the corrosion resistance is lowered. On the other hand, the upper limit of the adhesion amount is not particularly limited in relation to the corrosion resistance and the like, but is preferably about 3 g / m ² considering workability and the like. For example, when a resin film is produced using a coating method such as a roll coater or a spray ringer, the aqueous composition has a low viscosity, unlike the solvent-based one, so that it is difficult to apply and is not practical. The adhesion amount of the resin film is preferably in the range of 0.5 to 1.5 g / m ² by dry weight.

  Said resin film does not contain Cr substantially. “Substantially free” means, for example, that the amount of Cr that can be included as an inevitable impurity in the metal plate invades into the film is acceptable during the production of the resin film.

  The kind of the metal plate used in the present invention is not particularly limited, and includes a metal plate of a steel plate or a non-ferrous metal plate, a plated metal plate obtained by plating these with a single metal or various alloys, and the like. Specifically, for example, steel sheets such as hot-rolled steel sheets, cold-rolled steel sheets, and stainless steel sheets; plated steel sheets such as hot-dip galvanized steel sheets, alloyed hot-dip galvanized steel sheets, electrogalvanized steel sheets, and electrical Zn-Ni alloy-plated steel sheets; Examples thereof include non-ferrous metal plates such as aluminum, titanium, and zinc, and plated non-ferrous metal plates obtained by plating them. Furthermore, the surface treatment metal plate by which surface treatment was given to said metal plate is also contained. Examples of the surface treatment include phosphate treatment, chromate treatment, pickling treatment, alkali treatment, electrolytic reduction treatment, silane coupling treatment, and inorganic silicate treatment.

  The resin-coated metal plate of the present invention may further have another film on the above-described resin film. Examples of other coatings include organic resin coatings, organic / inorganic composite coatings, inorganic coatings, electrodeposition coatings, and the like, which may be appropriately selected according to the application. By forming these films, the corrosion resistance is further improved, and film characteristics such as fingerprint resistance and paintability can be imparted.

  Here, as the organic resin film, for example, urethane resin, epoxy resin, acrylic resin, polyethylene, polypropylene, olefin resin such as ethylene-acrylic acid copolymer, styrene resin such as polystyrene, polyester, or these Examples thereof include a film formed by combining a known resin for coatings such as a copolymer or a modified product with colloidal silica, a solid lubricant, a crosslinking agent, or the like, if necessary.

  A typical example of the organic / inorganic composite film is a film formed by combining the organic resin and a water glass forming component such as sodium silicate.

  Typical examples of the inorganic film include a water glass film and a film formed from lithium silicate.

(Production method of resin-coated metal plate)
Next, a method for producing a resin-coated metal plate using the resin composition of the present invention will be described.

  The method for coating the resin composition on the metal plate is not particularly limited, and a known method can be appropriately selected. For example, an aqueous coating agent (film treatment solution) prepared by dissolving and dispersing a resin composition in an aqueous solvent is applied to a roll coating method, a spray coating method, a knife coater method, a bar coating method, a dip coating method, a brush coating method. It may be applied to the surface of the metal plate using, for example. Thereafter, when heated and dried, a resin-coated metal plate provided with a desired resin film is obtained.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. It is also possible to implement, and they are all included in the technical scope of the present invention.

〔Test method〕
The test methods used in the following examples are as follows.

(1) Flat plate corrosion resistance A salt spray test was performed based on JIS Z2371, and the time until white rust was generated by 5% was measured. Here, the evaluation of flat plate corrosion resistance depends on the type of metal plate to be used (electrogalvanized steel plate or other metal plate) and the composition of the resin film (whether or not acidic colloidal silica is added) (a) to ( c) Different criteria were used. This is because the corrosion resistance of the electrogalvanized steel sheet takes into account that the corrosion resistance tends to be lower than other metal plates represented by hot-dip Zn-plated steel sheets (see Example 4 described later).
(A) A metal plate other than the electrogalvanized steel plate is used, and acidic colloidal silica is contained in the resin film.
When it does not contain mosquitoes (Examples 1 to 3), 96 hours or more are considered acceptable.
(B) Use a metal plate other than the electrogalvanized steel sheet, and use acidic colloidal silica in the resin film.
When containing mosquitoes (Example 4), 168 hours or more are considered acceptable.
(C) When using an electrogalvanized steel sheet (Example 5), 72 hours or more
To do.

(2) Corrosion resistance of the cross cut In order to investigate the corrosion resistance of the buttocks, a cross cut is put into the test material with a cutter knife, a salt spray test is performed based on JIS Z2371, and the time until 10% of white rust is generated is measured. It was measured. The evaluation of the cross-cut corrosion resistance was performed according to the following different criteria (d) to (f) according to the type of the metal plate used and the composition of the resin film, similarly to the flat plate corrosion resistance of (2) described above.
(D) When a metal plate other than the electrogalvanized steel sheet is used and acidic colloidal silica is not contained in the resin film (Examples 1 to 3), 72 hours or more are considered acceptable.
(E) When a metal plate other than the electrogalvanized steel plate is used and acidic colloidal silica is contained in the resin film (Example 4), 96 hours or more are deemed acceptable.
(F) When using an electrogalvanized steel sheet (Example 5), 48 hours or more
To do.

(3) Paintability (coating adhesion)
A specimen was bar-coated with an acrylic paint (“Magicron 1000” manufactured by Kansai Paint Co., Ltd.) (coating thickness 20 μm), and then baked at a temperature of 160 ° C. for 20 minutes for post-coating. Next, this test material was immersed in boiling water for 1 hour, then taken out and allowed to stand for 1 hour, and 100 mm squares of 1 mm square were cut with a cutter knife. After a tape was affixed to this test material, a tape peeling test was carried out, and the paintability was evaluated according to the following criteria based on the ratio of the number of residual meshes of the coating film (coating film residual ratio). Here, an evaluation standard of “◎” or “○” was regarded as acceptable (example of the present invention).
A: Coating film remaining rate 100%
○: Less than 99% to 90% or more Δ: Less than 89% to 80% or more X: Less than 79% to 70% or more XX: Less than 70%

(4) Tape peel resistance Filament tape (# 9510, manufactured by Sliontic Co., Ltd.) was applied to the surface of the test material, stored in an atmosphere of 40 ° C. × RH 98% for 168 hours, the filament tape was peeled off, and the film remained. The area ratio (residual rate) was measured. Here, tape peel resistance was evaluated on the basis of the following criteria, and those with ◎ or ◯ were accepted (examples of the present invention).
A: Residual rate 100%
○: Residual rate 90% or more and less than 100% △: Residual rate 80% or more and less than 90% ×: Residual rate less than 80

(5) Discoloration resistance The test material is placed in a constant temperature and humidity tester and allowed to stand for 186 hours in an atmosphere at a temperature of 50 ° C. and a relative humidity of 98%, and the color tone (color difference ΔE) before and after the test is measured by a color difference meter It measured using SZS- (Sigma) 90 by Corporation | KK. A smaller ΔE means that the color tone is less likely to change, that is, it has better resistance to discoloration. For example, when ΔE is 2 or more, the color tone change of the test material is easily observed with the naked eye. Here, discoloration resistance was evaluated on the basis of the following criteria, and those with ◎ or ○ were regarded as acceptable (examples of the present invention).
A: Less than ΔE = 1 (very good)
○: ΔE = 1 or more and less than 2 (good)
Δ: ΔE = 2 or more and less than 3 (bad)
×: ΔE = 3 or more (very bad)

(6) Measurement of amount of polyphenol compound contained in resin film Here, as described in detail below, the content of the polyphenol compound was indirectly calculated from the total organic carbon amount (TOC) in the resin film.

  First, the area of the test material is measured in advance (the area of one side when a resin film is formed on only one side and the area of both sides when a resin film is formed on both sides).

Next, this test material was immersed in a 0.1 mol alkaline solution (sodium hydroxide) at a temperature of 20 to 25 ° C. for 20 to 24 hours to elute the polyphenol compound. The total amount of organic carbon (TOC) in the eluate was analyzed using a combustion oxidation / infrared color TOC analyzer (POC500A type) manufactured by Shimadzu Corporation. Based on the following formula (1), the polyphenol compound in the resin film The amount (W1) was determined. For example, in the case of tannic acid (C ₁₄ H ₁₀ O ₉ , MW = 322), M1 = 322 and M2 = 168 in the formula (1).
W1 (g / m ² ) = W2 (g / m ² ) × (M1 / M2) (1)
Where
M1 = molecular weight of the polyphenol compound,
M2 = total molecular weight of carbon in the polyphenol compound,
W2 (g / m ² )
= TOC (mg / L) x amount of eluate (L) / (1000 x area of test material (m ² ))
Means.

The area of the test material is the area of one side when the resin film is formed only on one side,
When the resin film is formed on both sides, it means the area of both sides.

  According to this method, the amount of TOC can be quantified generally with an accuracy of measurement error ± 2 mg / L.

Example 1 (examination of resin)
Here, tannic acid was used as the polyphenol compound, and various resins (A to L) shown in Table 1 were used to examine the effects on corrosion resistance and the like.

(Production of microcapsules)
As the porous fine particles, non-hollow type inorganic porous silica fine particles (“God Ball E-2C” manufactured by Suzuki Oil & Fat Co., Ltd., average particle size: 1.0 μm) were used, and tannic acid-encapsulated silica was used as follows. Fine microcapsules were prepared.

  The above silica fine particles were added to a saturated tannic acid aqueous solution heated to 50 ° C. to prepare a solution containing about 50% silica fine particles, which was stirred for 1 hour. After stirring, the mixture was filtered, and the resulting residue was dried at 50 ° C. for 2 hours using a vacuum dryer to obtain microcapsules.

(Preparation of treatment liquid)
Each resin shown in Table 1 and tannic acid-containing porous fine particles (microcapsules) were added at a ratio of 90 parts by mass: 10 parts by mass, stirred with a homogenizer, and dispersed to obtain each resin composition. . This resin composition was diluted with pure water to obtain a film treatment solution having a solid content concentration of tannic acid of about 15%.

(Production of test materials)
The above-mentioned treatment liquid is applied to the surface of a hot-dip galvanized steel sheet (Zn adhesion amount 45 g / m ² ) by the bar coating method (# 3), and dried at a plate temperature of 90 ° C. for 1 minute, whereby the adhesion amount 1 g / m ^2. Resin-coated metal plates (test materials 1 to 12 in Table 2) provided with the above resin film were obtained. The amount of tannic acid in the resin film is 0.103 g / m ² . This amount is a value calculated assuming that the total pore volume of the porous fine particles is 1.03 mL / g and the specific gravity of polyphenol is 1.

For comparison, a conventional resin-coated metal plate (test materials 13 to 21 in Table 2) containing a polyphenol compound (polyphenol compound is not microencapsulated) in the resin film was prepared, and various properties were obtained. Examined. Specifically, a treatment liquid in which 1 part by mass of tannic acid was added to 100 parts by mass of the solid content of each resin shown in Table 1 was prepared, and a resin-coated metal plate was produced in the same manner as described above (resin coating film 1 g / m ² ). The amount of tannic acid in the resin film is about 0.1 g / m ² .

  These test materials were examined for the various characteristics described above.

  Furthermore, in this example, in order to examine the stability of the coating solution, the state when the treatment solution prepared as described above was stored at room temperature for 12 hours was observed with the naked eye.

  These results are shown in Table 2. For reference, Table 2 shows the molecular weight and pH of the resins (A to L) used.

  No. 1 to 8 are examples of the present invention prepared using resins A to H that satisfy the scope of the present invention, and as shown in Table 2, flat plate corrosion resistance, cross-cut corrosion resistance, paintability, tape peel resistance, and Excellent in all color fastness.

  On the other hand, No. using resins I and J having very large molecular weights. In Comparative Examples 9 and 10, gelation occurred 12 hours after the preparation of the treatment liquid.

  No. 1 using alkaline resins K and L. In Comparative Examples 11 and 12, gelation occurred during preparation of the treatment liquid (adding resin and microcapsules and stirring).

  On the other hand, no. In the conventional examples 13 to 18, the corrosion resistance was lowered and the discoloration resistance was also significantly lowered. When the treatment solution was stored under the above conditions, gelation did not occur, but No. 1 using a resin H having a molecular weight of 10,000. In 15, 18, and 21, the viscosity of the treatment liquid increased. An increase in viscosity means that it becomes difficult to produce a resin film.

  In this example, an experiment was performed using tannic acid, but it was confirmed by experiment that similar results were obtained with other polyphenol compounds (not shown in the table).

Example 2 (Examination of composition ratio of resin composition)
Here, various polyphenol compounds were used, and the influence of the content ratio of the resin and the microcapsules (polyphenol compound-containing porous fine particles) in the resin composition on properties such as corrosion resistance was examined.

  Except that the content ratio of the resin and the microcapsules in the resin composition was changed as shown in Table 3 using the resin C in Table 1 and the polyphenol compounds a to b shown in Table 3, Microcapsules were obtained in the same manner as in Example 1 described above.

  Next, a resin-coated metal plate was produced in the same manner as in Example 1, and various characteristics were evaluated. These results are also shown in Table 3.

  No. using tannic acid (a in Table 3) as a polyphenol compound. Considering 1-8, 10 and 12. No. in which the content ratio of the resin and the microcapsule satisfies the scope of the present invention. When the present invention examples 1 to 8 were used, all the characteristics were enhanced. On the other hand, when the amount of microcapsules added was large and the tannic acid content in the resin film was increased (No. 10), both the plate corrosion resistance and the cross cut corrosion resistance were reduced. Furthermore, the paintability was slightly lowered and the tape peel resistance was also lowered. On the other hand, when the amount of microcapsules added was small and the tannic acid content in the resin film was reduced (No. 12), both the plate corrosion resistance and the cross-cut corrosion resistance were lowered.

  The above experimental results were also observed when other polyphenol compounds were used. That is, No. 1 in which the content ratio of the resin and the microcapsule satisfies the requirements of the present invention. In No. 9 (catechin), a resin-coated metal plate excellent in all properties was obtained, but the amount of microcapsules added was large (the amount of resin added was small). In No. 11, the corrosion resistance, paintability, and tape peel resistance decreased.

  Table 3 does not show the results when gallic acid was used, but it was confirmed by experiments that the same tendency as tannic acid and catechin was observed when gallic acid was used. Yes.

Example 3 (Influence of acidic colloidal silica)
Here, the effect of acidic colloidal silica on corrosion resistance and the like was examined.

  In the test material 3 of Table 2 of Example 1 described above, various acidic colloidal silicas (X to Z) shown in Table 4 in the treatment liquid are shown in Table 4 (ratio to 100 parts by mass of the resin composition). Added at.

  Next, a resin-coated metal plate was produced in the same manner as in Example 1, and various characteristics were evaluated. These results are also shown in Table 4.

  No. 1 to 10 are examples in which the addition amount of acidic colloidal silica satisfies the preferred range of the present invention. As shown in Table 4, the plate corrosion resistance was further improved, and the paintability / tape peel resistance improvement effect Was also recognized.

  In contrast, no. No. 11 is an example in which the amount of acidic colloidal silica added is small, and no effect of improving the above characteristics was observed.

  No. No. 12 is an example in which the amount of acidic colloidal silica added is large, and the flat plate corrosion resistance, cross-cut corrosion resistance, paintability, and tape peel resistance decreased.

Example 4 (Influence of metal plate)
Here, an electrogalvanized steel plate was used as the metal plate, and various characteristics were examined.

Specifically, No. in Table 3 of Example 2 described above. Nos. 1 to 9 in the same manner as in Example 2 except that an electrogalvanized steel sheet (Zn adhesion amount 20 g / m ² ) was used instead of the hot-dip Zn-plated steel sheet. 1 to 9 resin-coated metal plates were prepared and their characteristics were evaluated. These results are also shown in Table 5.

  In general, electrogalvanized steel sheets tend to have lower corrosion resistance than hot dip galvanized steel sheets. However, using the resin composition of the present invention, as shown in Table 5, even when using an electrogalvanized steel sheet, it was confirmed that excellent characteristics were obtained as in the case of using a hot dip galvanized steel sheet. It was.

  Table 5 does not show the results when gallic acid was used, but it was confirmed by experiments that the same tendency as tannic acid and catechin was observed when gallic acid was used. Yes.

It is a graph which shows a time-dependent change of the color tone (b value) when a metal plate is preserve | saved under constant temperature and humidity. It is a schematic sectional drawing which shows an example of the microcapsule used for this invention. It is a schematic sectional drawing which shows an example of the resin coating metal plate of this invention.

Explanation of symbols

1 Microcapsule 2 Porous fine particle (microcapsule wall)
3 Polyphenol (core material)
4 Water-soluble acidic resin 5 Metal plate 6 Resin film 7 Resin coated metal plate

Claims (11)

A resin-coated metal plate provided with a resin film obtained from the resin composition on at least one side of the metal plate,
The resin composition contains a water-soluble acidic resin having a number average molecular weight of 1000 to 100,000, and microcapsules in which a polyphenol compound is encapsulated in porous fine particles having an average particle diameter of 5 μm or less. Resin-coated metal plate with excellent corrosion resistance and surface properties.   2. The resin according to claim 1, wherein the ratio of the water-soluble acidic resin to the microcapsule is in the range of 60 to 95 parts by mass to 5 to 40 parts by mass with respect to 100 parts by mass of the solid content of the resin composition. Painted metal plate.   The resin-coated metal sheet according to claim 1 or 2, wherein the water-soluble acidic resin has a pH of 6 or less.   The resin-coated metal sheet according to claim 3, wherein the water-soluble acidic resin is an acrylic resin.   The resin-coated metal sheet according to any one of claims 1 to 4, wherein the polyphenol compound contained in the microcapsule is at least one selected from the group consisting of tannic acid, gallic acid, and catechin.   The resin-coated metal plate according to claim 1, wherein the porous fine particles are inorganic fine particles.   It further contains acidic colloidal silica, and the acidic colloidal silica is contained within a range of 5 to 40 parts by mass with respect to 100 parts by mass of the solid content of the resin composition comprising the water-soluble acidic resin and the microcapsules. The resin-coated metal plate according to any one of claims 1 to 6.   The resin-coated metal sheet according to any one of claims 1 to 7, wherein the resin composition does not contain Cr.   The resin-coated metal plate according to claim 1, wherein the resin composition does not contain an acidic substance used for etching a surface. The resin-coated metal sheet according to any one of claims 1 to 9, wherein an adhesion amount of the resin film is 0.3 to 3 g / m ² or more by dry weight. The resin-coated metal sheet according to any one of claims 1 to 10, wherein the resin film does not substantially contain Cr.

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