JP5161164B2 - Coating composition with excellent corrosion resistance - Google Patents

Description

  The present invention relates to a non-chromium coating composition having excellent corrosion resistance and a coated metal plate using the same, and more specifically, it is effective not only for improving the corrosion resistance of a flat portion of a coated metal plate, but also for improving the corrosion resistance of a processed portion and an end surface portion. The present invention relates to a typical coating composition and a painted metal plate using the same.

  Conventionally, pre-coated metal sheets such as pre-coated steel sheets painted by coil coating, etc., building materials such as roofs, walls, shutters, garages, various household appliances, switchboards, refrigerated showcases, steel furniture, kitchen appliances, etc. Widely used as a housing related product.

  In order to manufacture these housing-related products from a pre-coated metal plate, the pre-coated steel plate is usually cut, press-molded and joined. Therefore, these housing-related products often have a metal exposed portion that is a cut surface and a crack generating portion due to press working. The exposed metal part and cracking part are more likely to have a lower corrosion resistance than other parts, so it is common to include a chromium-based rust-preventive pigment in the precoat steel base coat to improve corrosion resistance. Has been done.

  However, chromium-based anticorrosive pigments contain or produce hexavalent chromium having excellent antirust properties, and this hexavalent chromium is a problem from the viewpoint of human health and environmental protection. .

  To date, many non-chromium anticorrosive pigments such as zinc phosphate, aluminum tripolyphosphate, and zinc molybdate have been put on the market, and various primers have been proposed as a combination of non-chromium pigments. ing. For example, Patent Document 1 discloses a combination of epoxy resin and phenol resin vehicle components, a combination of calcium silicate and phosphorus vanadate, and a combination of calcium carbonate, calcium silicate, aluminum phosphate, and phosphorus vanadate as antirust pigments. A paint containing a rust preventive pigment is described. Patent Document 2 describes a paint in which polyester is combined with a combination of a second magnesium phosphate and a fired product of manganese oxide / vanadium oxide or a fired product of calcium phosphate and vanadium oxide as a rust preventive pigment. Yes. However, the coating film formed from the paint described in Patent Documents 1 and 2 is inferior in corrosion resistance as compared with a paint using a chromium pigment, and in particular, the corrosion resistance in the processed part and the end face part is insufficient. . In addition, chemical resistance such as alkali resistance and acid resistance is often inferior. Further, when a large amount of rust preventive pigment is used, the water resistance is often inferior, and it has not yet been replaced by chromium-based rust preventive pigments in the production of precoated metal sheets.

  Patent Document 3 discloses that a vehicle component composed of an organic resin containing a hydroxyl group or an epoxy group and a curing agent has an oil absorption of 30 to 200 ml / 100 g and a pore volume of 0.05 to 1.2 ml / g. A coating composition containing a silica fine particle and having a glass transition temperature of 40 to 125 ° C. of a cured coating film formed from the coating is described. However, although the coating film formed from the paint described in Patent Document 3 shows considerable corrosion resistance, it is still inferior in corrosion resistance and chemical resistance compared to a paint using a chromium-based pigment. Insufficient corrosion resistance.

Japanese Patent Laid-Open No. 11-61001 JP 2000-199078 A JP 2000-129163 A

  An object of the present invention is to provide a non-chromium coating composition capable of forming a coating film excellent in corrosion resistance of a processed part and an end face part as well as a general part of a coated metal sheet, and a coated metal sheet using the same. It is to be.

  Therefore, as a result of intensive studies to solve the above-mentioned conventional problems, the present inventors have added specific vanadium compounds, calcium compounds and specific phosphorus as anticorrosive pigments to the hydroxyl group-containing film-forming resin system. In order to complete the present invention, it is found that a coating composition containing a predetermined amount of an acid-based metal salt can form a coating film excellent not only in corrosion resistance of a flat surface portion but also in processed portions and end surface portions of a coated metal plate. It came.

That is, the present invention provides a coating composition containing “1. (A) a hydroxyl group-containing film-forming resin, (B) a crosslinking agent, and (C) a rust preventive pigment mixture, wherein the rust preventive pigment mixture (C)”. (1) at least one vanadium compound of vanadium pentoxide, calcium vanadate and ammonium metavanadate, (2) a calcium compound selected from calcium oxide and calcium carbonate , and (3) a metal phosphate, phosphoric acid A resin comprising at least one of a hydrogen metal salt and a metal metal salt of tripolyphosphate, and the metal of each metal salt is Zn, Al, or Mg, the resin (A) And 100 parts by mass of the total solid content of the crosslinking agent (B),
3 to 50 parts by mass of the vanadium compound (1),
The amount of the calcium compound (2) is 3 to 50 parts by mass, the amount of the phosphate metal salt (3) is 3 to 50 parts by mass, and the amount of the rust preventive pigment mixture (C) is 10 to 10 parts by mass. A coating composition characterized by being 150 parts by mass.

2. The coating composition according to Item 1, wherein the hydroxyl group-containing film-forming resin (A) is at least one of a hydroxyl group-containing epoxy resin and a hydroxyl group-containing polyester resin,
3. Item 3. The coating composition according to Item 1 or 2, wherein the crosslinking agent (B) is at least one crosslinking agent selected from an amino resin, a phenol resin, and a polyisocyanate compound which may be blocked.
4). Furthermore, the coating composition as described in any one of said item | term 1-3 containing the at least 1 sort (s) of pigment component among a rust preventive pigment other than a rust preventive pigment mixture (C), a titanium dioxide pigment, and an extender pigment. object,
5. Furthermore, the coating composition as described in any one of said claim | item 1-4 containing at least 1 sort (s) of a ultraviolet absorber and a ultraviolet stabilizer.
6). The vanadium compound (1), the calcium compound (2) and the phosphoric acid compound constituting the rust preventive pigment mixture (C) blended with respect to 100 parts by mass of the total solid content of the resin (A) and the crosslinking agent (B). A mixture of metal salt (3) in an amount of parts by mass within each quantitative range was added to 10000 parts by mass of a 5% strength by weight sodium chloride aqueous solution at 25 ° C., stirred for 6 hours, and allowed to stand at 25 ° C. for 48 hours. The pH of the filtrate which filtered the liquid is 3-10, The coating composition as described in any one of said claim | item 1-5 characterized by the above-mentioned.

7). A coated metal plate in which a cured coating film based on the coating composition according to any one of the above items 1 to 6 is formed on a metal plate that may be subjected to chemical conversion treatment on the surface;
8). A cured coating film based on the coating composition according to any one of the above items 1 to 6 is formed on a metal plate that may be subjected to chemical conversion treatment on the surface, and an overcoat coating is formed on the cured coating film. A coated metal plate having a multilayer coating film formed with a film . Is provided.

  The coating composition of the present invention does not contain a chromium-based rust preventive pigment and is a coating composition that is advantageous in terms of environmental hygiene. By the coating composition of the present invention, not only is the corrosion resistance of the flat part improved, It exhibits the effect of being able to form a coating film with excellent corrosion resistance at the processed and end surfaces of a coated metal plate that has been difficult to achieve with non-chromium anticorrosive paints.

  The coated metal plate on which the cured coating film based on the coating composition of the present invention is formed has excellent corrosion resistance at the flat portion, processed portion and end face portion, and uses a conventional chromate rust preventive pigment such as strontium chromate. It has a corrosion resistance equal to or higher than that of a coated metal plate on which a cured coating film based on a paint is formed.

  A coated metal plate in which a cured coating film based on the coating composition of the present invention is formed, and a top coating film is formed on the cured coating film, is excellent in the corrosion resistance of the flat portion, the processed portion, and the end surface portion. When a galvanized steel plate or an aluminum-zinc alloy plated steel plate is used as the metal plate to be coated, it is excellent not only in the flat portion but also in the end face portion and the processed portion by applying the coating composition of the present invention. Corrosion resistance can be obtained.

  The coating composition of this invention is a coating composition containing the following hydroxyl-containing film-forming resin (A), a crosslinking agent (B), and a rust preventive pigment mixture (C).

Hydroxyl-containing film-forming resin (A)
The hydroxyl group-containing coating film-forming resin in the coating composition of the present invention can be used without particular limitation as long as it is a hydroxyl group-containing resin having a coating film-forming ability that can be usually used in the paint field. , Polyester resin, epoxy resin, acrylic resin, fluororesin, vinyl chloride resin and the like can be used. As the film-forming resin, among them, at least one organic resin selected from a hydroxyl group-containing polyester resin and an epoxy resin can be preferably used.

  Examples of the hydroxyl group-containing polyester resin include oil-free polyester resins, oil-modified alkyd resins, and modified products of these resins such as urethane-modified polyester resins, urethane-modified alkyd resins, epoxy-modified polyester resins, and acrylic-modified polyester resins. Is done. The hydroxyl group-containing polyester resin has a number average molecular weight of 1,500 to 35,000, preferably 2,000 to 25,000, a glass transition temperature (Tg point) of 10 to 100 ° C., preferably 20 to 80 ° C., and a hydroxyl value. Those having 2-100 mg KOH / g, preferably 5-80 mg KOH / g are suitable.

  In the present specification, the “number average molecular weight” of the resin is a value calculated based on the molecular weight of standard polystyrene from a chromatogram measured by gel permeation chromatograph (“HLC8120GPC” manufactured by Tosoh Corporation). The column used was “TSKgel G-4000HXL”, “TSKgel G-3000HXL”, “TSKgel G-2500HXL”, “TSKgel G-2000HXL” (both manufactured by Tosoh Corporation, trade name), and moved. Phase: Tetrahydrofuran, Measurement temperature: 40 ° C., Flow rate: 1 cc / min, Detector: Under the conditions of RI. Moreover, in this specification, the glass transition temperature (Tg) of resin is based on a differential thermal analysis (DSC).

  The oil-free polyester resin is an esterified product of a polybasic acid component and a polyhydric alcohol component. Examples of the polybasic acid component include one or more selected from phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, succinic acid, fumaric acid, adipic acid, sebacic acid, maleic anhydride, and the like. Dibasic acids and lower alkyl esterified products of these acids are mainly used, and if necessary, monobasic acids such as benzoic acid, crotonic acid, pt-butylbenzoic acid, trimellitic anhydride, methylcyclohexentricarboxylic acid , Tribasic or higher polybasic acids such as pyromellitic anhydride are used in combination. Examples of the polyhydric alcohol component include bivalent compounds such as ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 3-methylpentanediol, 1,4-hexanediol, and 1,6-hexanediol. Alcohol is mainly used, and a trihydric or higher polyhydric alcohol such as glycerin, trimethylolethane, trimethylolpropane, pentaerythritol can be used in combination as necessary. These polyhydric alcohols can be used alone or in admixture of two or more. The esterification or transesterification reaction of both components can be carried out by a method known per se. As the acid component, isophthalic acid, terephthalic acid, and lower alkyl esterified products of these acids are particularly preferable.

  In addition to the acid component and alcohol component of the oil-free polyester resin, the alkyd resin is obtained by reacting an oil fatty acid by a method known per se. Examples of the oil fatty acid include coconut oil fatty acid, soybean oil fatty acid, Examples thereof include linseed oil fatty acid, safflower oil fatty acid, tall oil fatty acid, dehydrated castor oil fatty acid, and kiri oil fatty acid. The oil length of the alkyd resin is preferably 30% or less, particularly about 5 to 20%.

  As the urethane-modified polyester resin, the oil-free polyester resin or the low-molecular weight oil-free polyester resin obtained by reacting an acid component and an alcohol component used in the production of the oil-free polyester resin, a polyisocyanate compound and Examples thereof include those reacted by a method known per se. The urethane-modified alkyd resin is obtained by reacting the alkyd resin or a low molecular weight alkyd resin obtained by reacting each component used in the production of the alkyd resin with a polyisocyanate compound by a method known per se. Things are included. Polyisocyanate compounds that can be used in the production of urethane-modified polyester resins and urethane-modified alkyd resins include hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4. Examples include '-methylenebis (cyclohexyl isocyanate) and 2,4,6-triisocyanatotoluene. In general, as the urethane-modified resin, those having a modification degree such that the amount of the polyisocyanate compound forming the urethane-modified resin is 30% by weight or less with respect to the urethane-modified resin can be preferably used.

  As an epoxy-modified polyester resin, a polyester resin produced from each component used in the production of the polyester resin is used, a reaction product of a carboxyl group of the resin and an epoxy group-containing resin, a hydroxyl group in the polyester resin and an epoxy resin. The reaction product by reaction, such as addition of a polyester resin and an epoxy resin, condensation, grafting, etc., such as the product which couple | bonded the hydroxyl group in it through the polyisocyanate compound, can be mentioned. In general, the degree of modification in such an epoxy-modified polyester resin is preferably such that the amount of the epoxy resin is 0.1 to 30% by weight based on the epoxy-modified polyester resin.

  As the acrylic-modified polyester resin, a polyester resin produced from each component used in the production of the polyester resin is used, and a group having reactivity with these groups on the carboxyl group or hydroxyl group of the resin, for example, carboxyl group, hydroxyl group or epoxy. Reaction products obtained by graft polymerization of a (meth) acrylic acid or (meth) acrylic acid ester to a polyester resin using a peroxide polymerization initiator are listed. be able to. In general, the degree of modification in the acrylic-modified polyester resin is preferably such that the amount of the acrylic resin is 0.1 to 50% by weight based on the acrylic-modified polyester resin.

  Of the polyester resins described above, among them, oil-free polyester resins and epoxy-modified polyester resins are preferable from the viewpoint of balance such as processability and corrosion resistance.

  Examples of the epoxy resin suitable as the hydroxyl group-containing coating film-forming resin include bisphenol-type epoxy resins, novolac-type epoxy resins; and modified epoxy resins in which various modifiers are reacted with epoxy groups or hydroxyl groups in these epoxy resins. be able to. In the production of the modified epoxy resin, the modification time with the modifier is not particularly limited, and it may be modified in the middle of the epoxy resin production or in the final stage of the epoxy resin production.

  The bisphenol-type epoxy resin is, for example, a resin obtained by condensing epichlorohydrin and bisphenol to a high molecular weight in the presence of a catalyst such as an alkali catalyst, if necessary, epichlorohydrin and bisphenol, and if necessary, an alkali catalyst or the like. Any of resins obtained by condensing into a low molecular weight epoxy resin in the presence of a catalyst and polyaddition reaction of the low molecular weight epoxy resin and bisphenol may be used.

  Examples of the bisphenol include bis (4-hydroxyphenyl) methane [bisphenol F], 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) propane [bisphenol A], 2, 2-bis (4-hydroxyphenyl) butane [bisphenol B], bis (4-hydroxyphenyl) -1,1-isobutane, bis (4-hydroxy-tert-butyl-phenyl) -2,2-propane, p- (4-hydroxyphenyl) phenol, oxybis (4-hydroxyphenyl), sulfonylbis (4-hydroxyphenyl), 4,4′-dihydroxybenzophenone, bis (2-hydroxynaphthyl) methane and the like can be mentioned among others. Bisphenol A and bisphenol F are preferably used . The bisphenols can be used alone or as a mixture of two or more.

  As commercial products of bisphenol type epoxy resins, for example, Epicoat 828, 812, 815, 820, 834, 1001, 1004, 1007, 1009, 1010 manufactured by Japan Epoxy Resin; Asahi Ciba Examples include Araldite AER6099 manufactured by the company, and Epomic R-309 manufactured by Mitsui Chemicals.

  Examples of the novolac type epoxy resin which is an epoxy resin suitable as a hydroxyl group-containing coating film-forming resin include, for example, phenol novolac type epoxy resins, cresol novolac type epoxy resins, and phenol glyoxal type epoxy having a large number of epoxy groups in the molecule. Various novolak-type epoxy resins such as resins can be mentioned.

  Examples of the modified epoxy resin include an epoxy ester resin obtained by reacting, for example, a dry oil fatty acid with the bisphenol type epoxy resin or the novolac type epoxy resin; and a polymerizable unsaturated monomer component containing acrylic acid or methacrylic acid. Epoxy acrylate resin; Urethane-modified epoxy resin reacted with isocyanate compound; Amino group or quaternary by reacting amine compound with epoxy group in bisphenol type epoxy resin, novolac type epoxy resin or various modified epoxy resins An amine-modified epoxy resin obtained by introducing an ammonium salt can be used.

Cross-linking agent (B)
The crosslinking agent (B) reacts with the hydroxyl group-containing coating film forming resin (A) to form a curing film, and reacts with the hydroxyl group-containing coating film forming resin (A) by heating or the like to be cured. However, amino resins, phenol resins and polyisocyanate compounds which may be blocked are particularly suitable. These crosslinking agents can be used alone or in combination of two or more.

  Examples of the amino resin include methylolated amino resins obtained by reacting an amino component such as melamine, urea, benzoguanamine, acetogranamamine, steroguanamine, spiroguanamine, and dicyandiamide with an aldehyde. Examples of the aldehyde used in the reaction include formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde. Moreover, what etherified the said methylolated amino resin with suitable alcohol can also be used as an amino resin. Examples of alcohols used for etherification include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, 2-ethylbutanol, 2-ethylhexanol and the like.

  The phenol resin that can be used as the cross-linking agent is one that undergoes a cross-linking reaction with the hydroxyl group-containing coating film-forming resin (A). The phenol component and formaldehyde are heated in the presence of a reaction catalyst to cause a condensation reaction, and methylol. Examples thereof include a resol type phenol resin obtained by alkylating a part or all of the methylol group of a methylolated phenol resin obtained by introducing a group with an alcohol.

  In the production of a resol-type phenol resin, a bifunctional phenol compound, a trifunctional phenol compound, a tetrafunctional or higher functional phenol compound, or the like can be used as the phenol component as a starting material.

  Examples of the phenol compound include, for example, bifunctional phenol compounds such as o-cresol, p-cresol, p-tert-butylphenol, p-ethylphenol, 2,3-xylenol, and 2,5-xylenol. Examples of the trifunctional phenol compound include carboxylic acid, m-cresol, m-ethylphenol, 3,5-xylenol, and m-methoxyphenol. Examples of the tetrafunctional phenol compound include bisphenol A and bisphenol F. Can be mentioned. Among them, in order to improve scratch resistance, it is preferable to use a trifunctional or higher functional phenol compound, in particular, carboxylic acid and / or m-cresol. These phenol compounds may be used alone or in combination of two or more.

  Examples of formaldehydes used in the production of phenol resins include formaldehyde, paraformaldehyde, trioxane, and the like, which can be used alone or in combination of two or more.

  As the alcohol used for alkyl etherifying a part of the methylol group of the methylolated phenol resin, a monohydric alcohol having 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms, can be suitably used. Suitable monohydric alcohols include methanol, ethanol, n-propanol, n-butanol, isobutanol and the like.

  The phenol resin has an average of 0.5 or more, preferably 0.6 to 3.0 alkoxymethyl groups per benzene nucleus from the viewpoint of reactivity with the hydroxyl group-containing film-forming resin (A). What you have is suitable.

  Examples of the non-blocked polyisocyanate compound in the optionally-blocked polyisocyanate compound that can be used as the crosslinking agent include aliphatic diisocyanates such as hexamethylene diisocyanate or trimethylhexamethylene diisocyanate; hydrogenated xylylene diisocyanate or Cycloaliphatic diisocyanates such as isophorone diisocyanate; organic diisocyanates per se such as tolylene diisocyanate, xylylene diisocyanate or 4,4'-diphenylmethane diisocyanate, aromatic diisocyanates such as crude MDI, or each of these organic diisocyanates and polyvalent Adducts with alcohol, low molecular weight polyester resin or water, or as described above Cyclic polymerization of an organic diisocyanate comrades, further include isocyanate-biuret, or the like.

  The blocked polyisocyanate compound is obtained by blocking free isocyanate groups of the polyisocyanate compound with a blocking agent. Examples of the blocking agent include phenols such as phenol, cresol and xylenol; ε-caprolactam; lactones such as δ-valerolactam and γ-butyrolactam; methanol, ethanol, n-, i- or t-butyl alcohol, ethylene Alcohols such as glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, and benzyl alcohol; oximes such as formamidoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime System: Active methylene such as dimethyl malonate, diethyl malonate, ethyl acetoacetate, acetylacetone It can be suitably used blocking agent, such as. By mixing the polyisocyanate compound and the blocking agent, free isocyanate groups of the polyisocyanate compound can be easily blocked.

  The blending ratio of the hydroxyl group-containing film-forming resin (A) and the crosslinking agent (B) is based on the total solid content of 100 parts by weight of the components (A) and (B), and the hydroxyl group-containing film-forming resin. (A) is 55 to 95 parts by weight, more preferably 60 to 95 parts by weight, and the crosslinking agent (B) is in the range of 5 to 45 parts by weight, further 5 to 40 parts by weight. It is suitable in terms of boiling water, processability, curability and the like.

  In order to increase the curability of the coating composition of the present invention, a curing catalyst can be blended as necessary. When the crosslinking agent (B) contains an amino resin, particularly a low molecular weight, methyl etherified or mixed etherified melamine resin of methyl ether and butyl ether, sulfonic acid compound or amine neutralization of sulfonic acid compound as a curing catalyst A thing is used suitably. Representative examples of the sulfonic acid compound include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, dinonylnaphthalenedisulfonic acid, and the like. The amine in the amine neutralized product of the sulfonic acid compound may be any of primary amine, secondary amine, and tertiary amine. Among these, the amine neutralized product of p-toluenesulfonic acid and / or the amine neutralized product of dodecylbenzenesulfonic acid is preferable from the viewpoints of the stability of the coating, the reaction promoting effect, and the physical properties of the obtained coating film. .

  When the crosslinking agent (B) is a phenol resin, the sulfonic acid compound or an amine neutralized product of the sulfonic acid compound is preferably used as the curing catalyst.

  When the crosslinking agent (B) is a blocked polyisocyanate compound, a curing catalyst that promotes dissociation of the blocking agent of the blocked polyisocyanate compound, which is a curing agent, is suitable. As a suitable curing catalyst, for example, octyl Tin oxide, dibutyltin di (2-ethylhexanoate), dioctyltin di (2-ethylhexanoate), dioctyltin diacetate, dibutyltin dilaurate, dibutyltin oxide, dioctyltin oxide, lead 2-ethylhexanoate And organometallic catalysts such as

  When the crosslinking agent (B) is a combination of two or more kinds of crosslinking agents, an effective curing catalyst can be used in combination with each crosslinking agent.

Antirust pigment mixture (C)
In the coating composition of the present invention, the rust preventive pigment mixture (C) is composed of the following (1) vanadium compound, (2) calcium-containing material, and (3) phosphate metal salt.

Vanadium compound (1)
The vanadium compound (1) is at least one vanadium compound selected from vanadium pentoxide, calcium vanadate, and ammonium metavanadate. Vanadium pentoxide, calcium vanadate and ammonium metavanadate are excellent in elution of pentavalent vanadium ions into water, and the pentavalent vanadium ions released from the vanadium compound (1) react with the material metal, It works effectively to improve corrosion resistance by reacting with ions from other antirust pigment mixtures.

Calcium compound (2)
Examples of the calcium compound (2) include calcium compounds other than calcium vanadate and phosphoric acid compounds, such as calcium oxide, calcium hydroxide, calcium orthosilicate, calcium metasilicate, calcium carbonate, calcium sulfate, and calcium nitrate. , Calcium sulfide, calcium chloride, calcium fluoride, calcium bromide, calcium nitride, calcium acetate, calcium azide, calcium cyanamide, calcium amide, calcium imide, calcium silicon and the like. Of these, calcium carbonate, calcium oxide, and calcium metasilicate are suitable from the viewpoint of corrosion resistance, and calcium metasilicate is particularly preferable from the viewpoint of corrosion resistance.

Phosphate metal salt (3)
The phosphate metal salt (3) is at least one of a phosphate metal salt, a hydrogen phosphate metal salt, and a tripolyphosphate metal salt, and the metal of each metal salt is Zn, Al, or Mg. It is an acid metal salt.

  Examples of the phosphate metal salt include zinc phosphate, aluminum phosphate, magnesium phosphate, zinc hydrogen phosphate, aluminum phosphate, magnesium phosphate, aluminum hydrogen phosphate, magnesium hydrogen phosphate, magnesium ammonium phosphate. And aluminum dihydrogen tripolyphosphate.

  Zn, Al or Mg metal ions and phosphate ions released from the phosphate metal salt (3) effectively work to improve the corrosion resistance.

In the coating composition of the present invention, with respect to 100 parts by mass of the total solid content of the resin (A) and the crosslinking agent (B), the rust preventive pigment mixture (C) contains the vanadium compound (1) and the calcium compound (2 ) And the phosphoric acid metal salt (3) are within the following range, and the amount of the anticorrosive pigment mixture (C) is 10 to 150 parts by mass, preferably 15 to 90 parts by mass from the viewpoint of corrosion resistance. Is preferred.
Vanadium compound (1): 3 to 50 parts by mass, preferably 5 to 30 parts by mass,
Calcium compound (2): 3 to 50 parts by mass, preferably 5 to 30 parts by mass,
Phosphate metal salt (3): 3 to 50 parts by mass, preferably 5 to 30 parts by mass.

  In the coating composition of the present invention, the corrosion resistance can be synergistically improved by combining a predetermined amount of these (1), (2) and (3) as an antirust pigment mixture.

  Moreover, the vanadium compound (1), the calcium compound (2), and phosphoric acid which comprise the antirust pigment mixture (C) mix | blended with respect to 100 mass parts of total solids of the said resin (A) and a crosslinking agent (B). A part by mass of the metallic metal salt (3) in a quantitative range is added to 10000 parts by mass of a 5% strength by weight sodium chloride aqueous solution at 25 ° C., stirred for 6 hours, and allowed to stand at 25 ° C. for 48 hours. The pH of the filtrate obtained by filtering the supernatant liquid is 3 to 10, preferably 5 to 9, so that the solubility of the vanadium compound (1), the calcium compound (2) and the phosphate metal salt (3) due to moisture and It is suitable from the viewpoint of the reactivity between the solution of the rust preventive pigment and the metal plate, and is preferably in this range from the viewpoint of corrosion resistance.

  That is, the filtrate for measuring the pH is an amount of any one of vanadium compound (1) in the range of 3 to 50 parts by mass with respect to 10000 parts by mass of a 5% by mass sodium chloride aqueous solution at 25 ° C. In the filtrate of the dissolved solution in which (2) is added in any amount within the range of 3-50 parts by mass, and the phosphate metal salt (3) is added in any amount within the range of 3-50 parts by mass. is there.

  In addition to the hydroxyl group-containing coating film-forming resin (A), the crosslinking agent (B), the rust preventive pigment mixture (C), and a curing catalyst blended as necessary, the coating composition of the present invention is used in the coatings field. Usable coloring pigments, extender pigments, UV absorbers, UV stabilizers, organic solvents; additives such as antisettling agents, antifoaming agents, coating surface modifiers, and the like can be blended as necessary.

  Examples of the colored pigment include organic colored pigments such as cyanine blue, cyanine green, organic red pigments such as azo and quinacridone; and inorganic colored pigments such as titanium white, titanium yellow, bengara, carbon black, and various fired pigments. Among them, titanium white can be preferably used.

  Examples of the extender pigment include talc, clay, mica, alumina, calcium carbonate, barium sulfate and the like.

  Examples of the ultraviolet absorber include 2- (2-hydroxy-3,5-di-t-amylphenyl) -2H-benzotriazole, isooctyl-3- (3- (2H-benzotriazol-2-yl)- 5-t-butyl-4-hydroxyphenylpropionate, 2- [2-hydroxy-3,5-di (1,1-dimethylbenzidine) phenyl] -2H-benzotriazole, 2- [2-hydroxy-3- Dimethylbenzyl-5- (1,1,3,3-tetramethylbutyl) phenyl] -2H-benzotriazole, methyl-3- [3-t-butyl-5- (2H-benzotriazol-2-yl)- Benzotriazole derivatives such as condensates with 4-hydroxyphenyl] propionate / polyethylene glycol 300; 2- [4- (2-hydroxy -3-dodecyloxypropyl) oxy] -2-triazine derivatives such as 2-hydroxyphenyl-4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine; ethanediamide-N- (2-ethoxy Succinic acid anilide such as phenyl) -N ′-(2-ethylphenyl)-(oxalic amide), ethanediamide-N- (2-ethoxyphenyl) -N ′-(4-isododecylphenyl)-(oxalic amide) System derivatives and the like.

  Examples of the ultraviolet stabilizer include, for example, hindered amine compounds, hindered phenol compounds; CHIMASORB 944, TINUVIN 144, TINUVIN 292, TINUVIN 770, IRGANOX 1010, IRGANOX 1098. Product)).

  By blending UV absorbers and UV stabilizers in the paint, it is possible to suppress the deterioration of the coating surface due to light. Even when this paint is used as a primer, it passes through the upper coating film and becomes a primer. Since the deterioration of the primer surface due to the light reaching the coating surface can be suppressed, delamination between the primer coating and the upper coating due to the deterioration of the primer coating surface can be prevented, and excellent corrosion resistance can be maintained.

  The said organic solvent which can be mix | blended with this invention coating composition is mix | blended as needed for the coating property improvement of this invention composition, etc., and a hydroxyl-containing film-forming resin (A) and a crosslinking agent ( B) which can dissolve or disperse can be used. Specifically, for example, hydrocarbon solvents such as toluene, xylene and high boiling petroleum hydrocarbons, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and isophorone Ester solvents such as ethyl acetate, butyl acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether acetate, alcohol solvents such as methanol, ethanol, isopropanol, butanol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, And ether alcohol-based solvents such as ethylene glycol monobutyl ether can be cited, which may be used alone or in combination of two or more.

  In the coating composition of the present invention, the glass transition temperature of the cured coating film obtained from the composition of the present invention is 40 to 115 ° C, preferably 50 to 105 ° C, such as the corrosion resistance, acid resistance and workability of the coating film. To preferred. The glass transition temperature of the coating film is tan δ by temperature dispersion measurement at a frequency of 110 Hz using a DINAMIC VISCOELASTOMETER MODEL VIBRON (Dynamic Visco Elastometer Model Vibron) DDV-IIEA type (manufactured by Toyo Baldwin, automatic dynamic viscoelasticity measuring machine). It is the maximum temperature obtained from the change in.

The coating film formed by coating the coating composition of the present invention on a metal plate exhibits excellent corrosion resistance. The reason for this is that the present inventors have dissolved the raw metal by chloride ions and the like in a corrosive environment. Metal ions generated from the above, or zinc ions and aluminum ions eluted from the anti-preventive mixture and pentavalent vanadium ions (VO ₃ ^- and VO ₄ ³ -vanadate ions) directly without redox reaction A stable precipitating salt, and calcium ions and other metal ions dissolved from the rust preventive mixture have the action of suppressing the anodic dissolution reaction of the raw metal, and oxidation of the pentavalent vanadium ion and the raw metal The trivalent vanadium ions and calcium ions produced by the reduction reaction effectively coat the exposed material surface by forming phosphate ions and precipitates. On the galvanized steel sheet, not only calcium ions but also zinc ions and vanadate ions migrate to the exposed iron part as a charged body of corrosion current due to the formation of different metal batteries and react to produce salt, thereby producing cathodic polarization of the iron part. In addition, it has the effect of reducing the potential difference between dissimilar metals, and the zinc hydroxide produced near the cathode site in the corrosion under the coating film is dehydrated. I think that it may have the effect of suppressing the reaction to become zinc oxide. Moreover, by using together said (1), (2) and (3) which comprise a rust preventive pigment mixture, each of said (1), (2) and (3) has acid resistance, alkali resistance, and water resistance It can effectively counter the weakness of sex. Furthermore, since calcium ions have an action of suppressing the dissolution of the material metal in a strong alkaline atmosphere in which the material metal having a pH exceeding 10 is easily dissolved, excellent chemical resistance and water resistance can be achieved at the same time. It is considered that the synergistic effect of the action based on these rust preventive pigment mixtures worked greatly and achieved excellent corrosion resistance.

Painted metal plate The coating composition of the present invention can obtain a painted metal plate by coating and curing on a metal plate. As the metal plate to be coated, cold rolled steel plate, hot dip galvanized steel plate, electrogalvanized steel plate, iron-zinc alloy plated steel plate (galvanyl steel plate), aluminum-zinc alloy plated steel plate (containing about 55% aluminum in the alloy) Metal plate such as “galvanium steel plate”, “galfan” containing about 5% aluminum in the alloy), nickel-zinc alloy plated steel plate, stainless steel plate, aluminum plate, copper plate, copper plated steel plate, tin plated steel plate, etc. The surface of the metal plate may be subjected to chemical conversion treatment. Examples of the chemical conversion treatment include phosphate treatment such as zinc phosphate treatment and iron phosphate treatment, composite oxide film treatment, chromium phosphate treatment, and chromate treatment.

  The composition of the present invention can be coated on the metal plate by a known method such as a roll coating method, a curtain flow coating method, a spray method, a brush coating method, or a dipping method. Although the cured film thickness of the coating film obtained from this invention composition is not specifically limited, Usually, 2-10 micrometers, Preferably it is used in the range of 3-6 micrometers. Curing of the coating film may be appropriately set according to the type of resin used, etc., and when the material coated by the coil coating method is continuously baked, the material reached maximum temperature is usually 160 to 250 ° C. It is preferably baked for 15 to 60 seconds under the condition of 180 to 230 ° C. In the case of baking in a batch system, it can be carried out by baking at 80 to 200 ° C. for 10 to 30 minutes. In addition, when a non-blocked polyisocyanate is used as the crosslinking agent (B), or when a bisphenol type epoxy resin is used as the resin (A) and an amine compound is used as the crosslinking agent (B), a coating film forming process In the case of a combination that does not particularly require heating for the crosslinking reaction in, it can be cured by drying at room temperature according to a conventional method.

  The coated metal plate of the present invention has a coating film formed of the above-described coating composition of the present invention on a metal plate which may be subjected to chemical conversion treatment, and the coated metal plate formed with the coating film of the present coating composition The coating itself can be used, but a top coating film can also be provided on this coating film. The film thickness of the top coat film is usually 8 to 30 μm, preferably 10 to 25 μm.

  Examples of the top coating for forming the top coating film include, for example, top coatings such as polyester resin-based, alkyd resin-based, silicon-modified polyester resin-based, silicon-modified acrylic resin-based, and fluororesin-based coatings that are known for pre-coated steel sheets. Can do. When workability is particularly important, a coated steel sheet having particularly excellent workability can be obtained by using a polyester-based top coat for advanced processing. The coated metal plate of this invention can show the coating-film performance excellent in corrosion resistance.

  When using a galvanized steel plate or an aluminum-zinc alloy plated steel plate as the metal plate to be coated, the corrosion resistance of the flat surface has been considerably improved. Although the corrosion resistance was insufficient, by applying the coating composition of the present invention, excellent corrosion resistance can be obtained also in the end face part and the processed part.

  Moreover, the coating film by this invention coating composition may be provided in both surfaces of to-be-coated article, and the said top coating film is further formed on the coating film by this invention coating composition as needed. May be. By forming the coating composition of the present invention on both sides, that is, on the back side, it is possible to obtain a coated metal plate that does not contain a chromium-based rust preventive pigment and is advantageous in terms of environmental hygiene and excellent in corrosion resistance.

  Hereinafter, the present invention will be described more specifically with reference to production examples and examples. The present invention is not limited to the following examples. Hereinafter, “parts” and “%” are based on mass.

Production Example 1 Production of resol type phenolic resin crosslinker solution In a reaction vessel, 100 parts of bisphenol A, 178 parts of 37% formaldehyde aqueous solution and 1 part of sodium hydroxide were blended and reacted at 60 ° C. for 3 hours. Dehydrated at 0 ° C. for 1 hour. Then, 100 parts of n-butanol and 3 parts of phosphoric acid were added and reacted at 110 to 120 ° C. for 2 hours. After completion of the reaction, the resulting solution was filtered to remove sodium phosphate, which was obtained to obtain a resol type phenolic resin crosslinking agent solution B1 having a solid content of about 50%. The obtained resin had a number average molecular weight of 880, an average number of methylol groups per benzene nucleus of 0.4, and an average number of alkoxymethyl groups of 1.0.

Production Example 2 Production of Back Surface Paint Epicoat # 1009 (Japan Epoxy Resin, Bisphenol A Epoxy Resin, Hydroxyl-Containing Resin) 80 parts mixed solvent 1 [cyclohexanone / ethylene glycol monobutyl ether / solvesso 150 (Esso Petroleum Corporation, High-boiling aromatic hydrocarbon solvent) = 3/1/1 (mass ratio)] In an epoxy resin solution dissolved in 120 parts, titanium white 40 parts, barita 40 parts and mixed solvent 2 [Solvesso 150 (Esso Petroleum) A suitable amount of high boiling point aromatic hydrocarbon solvent) / cyclohexanone = 1/1 (mass ratio)] was mixed, and pigment dispersion was performed until the tube (particle diameter of the coarse pigment particles) became 20 microns or less. It was. Next, 26.7 parts (20 parts by solid content) of Desmodur BL-3175 (manufactured by Sumika Bayer Urethane Co., Ltd., HDI isocyanurate type polyisocyanate compound solution blocked with methyl ethyl ketoxime, solid content of about 75%) was added to this dispersion. ), Takenate TK-1 (manufactured by Takeda Pharmaceutical Co., Ltd., organotin blocking agent dissociation catalyst, solid content of about 10%), and uniformly mixed, and further mixed solvent 2 and viscosity of about 80 seconds (Ford Cup # 4/25 ° C.) to obtain a back coating material.

Manufacture of anti-corrosion paint composition
Reference example 1
Epicote # 1009 (Japan Epoxy Resin, bisphenol A type epoxy resin, hydroxyl group-containing resin) 85 parts mixed solvent 1 [cyclohexanone / ethylene glycol monobutyl ether / Sorvesso 150 (Esso Petroleum, high boiling aromatic hydrocarbon solvent) ) = 3/1/1 (mass ratio)] In 225 parts of the epoxy resin solution dissolved in 135 parts, 5 parts of vanadium pentoxide, 3 parts of calcium metasilicate, 3 parts of aluminum phosphate, 20 parts of titanium white, 20 parts of barita And an appropriate amount of mixed solvent 2 [Solvesso 150 (manufactured by Esso Petroleum Corporation, high-boiling aromatic hydrocarbon solvent) / cyclohexanone = 1/1 (mass ratio)] is mixed to obtain a tube (particle diameter of coarse pigment particles). The pigment dispersion was carried out until it became 20 microns or less. Next, Desmodur BL-3175 (manufactured by Sumika Bayer Urethane Co., Ltd., HDI isocyanurate type polyisocyanate compound solution blocked with methyl ethyl ketoxime, about 75% solid content) in this dispersion was 20 parts (15 parts in solid content), Takenate TK-1 (manufactured by Takeda Pharmaceutical Co., Ltd., organotin blocking agent dissociation catalyst, solid content of about 10%) is added and mixed uniformly. Further, the above mixed solvent 2 is added and the viscosity is about 80 seconds (Ford Cup # 4/25 ° C.) to obtain a rust preventive coating composition.

Examples 1 and 2, Reference Examples 2 to 21 and Comparative Examples 1 to 8
In Reference Example 1, the same procedure as in Reference Example 1 was conducted except that the hydroxyl group-containing resin, the crosslinking agent, the rust preventive pigment, and other pigments used were as shown in Table 1 below, thereby obtaining each rust preventive coating composition. Reference examples 20 and 21 are rust preventive coating compositions containing conventional chromate rust preventive pigments. The amounts of the hydroxyl group-containing resin, the crosslinking agent, and the pigment component in Table 1 are all expressed in terms of solid content. However, in Reference Example 14 , Takenate TK-1 was not blended, and in Reference Examples 17 and 18 , instead of 2 parts of Takenate TK-1, Nure Cure 5225 (manufactured by King Industries, Inc., dodecyl) 1 part of an amine neutralized solution of benzenesulfonic acid) is blended.

In Table 1, the total amount of each rust preventive pigment relative to the resin component (total solid mass of hydroxyl group-containing resin and crosslinking agent is 100 parts by mass) is added to 10000 parts by mass of a 5% by mass sodium chloride aqueous solution at 25 ° C. The pH of the filtrate obtained by filtering the supernatant liquid stirred for 6 hours and allowed to stand at 25 ° C. for 48 hours is also described. For example, the pH of the anticorrosive pigment solution of Reference Example 1 is 10000 parts by mass of a 5% by mass sodium chloride aqueous solution at 25 ° C., 5 parts by mass of vanadium pentoxide, 3 parts by mass of calcium metasilicate, and 3 parts by mass of aluminum phosphate. It is pH of the filtrate which filtered the supernatant liquid which added the part and was dissolved on the said conditions.

In Table 1 above, (Note) in the table has the following meanings.
(Note 1) Epokey 837: manufactured by Mitsui Chemicals, Inc., trade name, urethane-modified epoxy resin, hydroxyl group-containing resin, primary hydroxyl value of about 35, acid value of about 0.
(Note 2) Byron 296: manufactured by Toyobo Co., Ltd., trade name, epoxy-modified polyester resin, hydroxyl group-containing resin, hydroxyl value 7, acid value 6.
(Note 3) Arachid 7018: manufactured by Arakawa Chemical Co., Ltd., trade name, polyester resin, hydroxyl group-containing resin, hydroxyl value of about 10, acid value of 3 or less.
(Note 4) Sumidur N3300: manufactured by Sumika Bayer Urethane Co., Ltd., isocyanurate type polyisocyanate compound, solid content 100%.
(Note 5) Cymel 303: Nihon Cytec Industries, Ltd., trade name, methyl etherified melamine resin.
(Note 6) sandvor 3058: Clariant, trade name, hindered amine UV stabilizer.

Preparation of test coating plate Using the anticorrosion coating compositions and top coatings obtained in Examples 1 and 2 above , Reference Examples 1 to 21 and Comparative Examples 1 to 8 , each material was coated with the following coating specifications. Baking was performed to obtain a test plate for each test.

Paint specification 1:
Chemically treated galvalume steel sheet (thickness 0.35 mm, aluminum-zinc alloy plated steel sheet, containing about 55% aluminum in alloy, alloy plating basis weight 150 g / m ² , indicated as “GL steel sheet” in Table 2 )), The back coating material obtained in Production Example 2 was applied with a bar coater to a dry film thickness of 8 μm, and the back coating film was baked for 30 seconds so that the maximum material temperature reached 180 ° C. Formed. On the steel plate surface opposite to the back surface coating film of the coated plate on which this back surface coating film was formed, each rust preventive coating composition obtained in each of the above examples was coated with a bar coater so as to have a dry film thickness of 5 μm. Each primer coating was formed by baking for 40 seconds so that the maximum temperature reached 220 ° C. After cooling, KP color 1580B40 (trade name, polyester-based top coating, blue, glass transition temperature of cured coating about 70 ° C.) is applied to these primer coatings with a bar coater. The coating was applied to a thickness of about 15 μm, and baked for 40 seconds so that the maximum material temperature reached 220 ° C., to obtain a test plate for each test.

Paint specification 2:
On the hot-dip galvanized steel sheet subjected to chemical conversion treatment (plate thickness 0.35 mm, galvanized basis weight 250 g / m ² , indicated as “GI steel sheet” in Table 2), the coating for the back surface obtained in Production Example 2 Was coated with a bar coater so as to have a dry film thickness of 8 μm, and baked for 30 seconds so that the maximum material reaching temperature was 180 ° C. to form a back coating film. On the steel plate surface opposite to the back surface coating film of the coated plate on which this back surface coating film was formed, each rust preventive coating composition obtained in each of the above examples was coated with a bar coater so as to have a dry film thickness of 5 μm. Each primer coating plate was obtained by baking for 40 seconds so that the maximum temperature reached 220 ° C. After cooling, KP color 1580B40 (trade name, polyester-based top coating, blue, glass transition temperature of cured coating film of about 70 ° C.) is dried on these primer coating plates with a bar coater. The coating was applied to a thickness of about 15 μm, and baked for 40 seconds so that the maximum material temperature reached 220 ° C., to obtain a test plate for each test.

Paint specification 3:
On the cold-rolled steel sheet (having a thickness of 0.8 mm, indicated as “SPC steel sheet” in Table 2) subjected to the zinc phosphate chemical conversion treatment, the back coating material obtained in Production Example 2 has a dry film thickness of 8 μm. In this way, the coating was applied with a bar coater, and the back surface coating film was formed by baking for 30 seconds so that the maximum material temperature reached 180 ° C. On the steel plate surface opposite to the back coating film of the coated plate on which this back coating film was formed, each rust preventive coating composition obtained in each of the above examples was applied with a bar coater so as to have a dry film thickness of 20 μm, and dried. Baking was carried out at a temperature of 180 ° C. for 30 minutes to obtain a test plate for each test.

Paint specification 4:
Chemically treated galvalume steel sheet (thickness 0.35 mm, aluminum-zinc alloy plated steel sheet, containing about 55% aluminum in alloy, alloy plating basis weight 150 g / m ² , indicated as “GL steel sheet” in Table 2 )) Was coated with a bar coater so that the dry film thickness was 8 μm, and baked for 30 seconds so that the maximum material temperature reached 180 ° C. Formed. On the steel plate surface opposite to the back surface coating film of the coated plate on which this back surface coating film was formed, each rust preventive coating composition obtained in each of the above examples was coated with a bar coater so as to have a dry film thickness of 5 μm. Each primer coating was formed by baking for 40 seconds so that the maximum temperature reached 220 ° C. After cooling, KP color 1580B40 (trade name, polyester-based top coating, blue, glass transition temperature of cured coating about 70 ° C.) is applied to these primer coatings with a bar coater. The coating was applied to a thickness of about 15 μm, and baked for 40 seconds so that the maximum material temperature reached 220 ° C., to obtain a coated plate for each test.

Coating Film Performance Test A coating film performance test was carried out according to the following test method for each test coated plate obtained in Examples 1 and 2, Reference Examples 1 to 21 and Comparative Examples 1 to 8. The test results are shown in Table 2 below.

Test method Boiling-resistant water: Each test coating plate cut to a size of 5 cm × 10 cm is immersed in boiling water at about 100 ° C. for 2 hours, and then pulled up to evaluate the appearance of the coating film on the surface side, and a cross-cut tape An adhesion test was performed and evaluated. The cross-cut tape adhesion test is based on JIS K-5400 8.5.2 (1990) cross-cut tape method. And the number of grids remaining on the coated surface after abrupt peeling was examined.

A: There is no abnormality such as blistering or whitening in the coating film, and there are 100 remaining grids,
○: There are no abnormalities such as blistering and whitening in the coating film, and a residual grid number of 91 to 99,
Δ: Slightly abnormalities such as blistering or whitening were observed in the coating film, and the residual grid number was 91 to 99, or the coating film had no abnormality such as blistering or whitening, but the residual grid number was 71 to 99. 90 pieces
X: Generation | occurrence | production of the swelling of a coating film is recognized fairly or remarkably, or the number of remaining grids is 70 or less.

  Alkali resistance: The back surface and the cut surface of each test paint plate cut to a size of 5 cm × 10 cm were sealed with a rust-proof paint, and a cross cut reaching the substrate was put in the center of the front side of the paint plate. This coated plate was immersed in a 5% aqueous sodium hydroxide solution at 20 ° C. for 48 hours, then taken out, washed, and evaluated for the appearance of the coating on the surface side of the coated plate dried at room temperature. Was peeled off, and the peel width (one side) from the cut portion in the coating film after peeling off was evaluated.

A: There is no occurrence of swelling, and the tape peeling width from the cut part is 1.5 mm or less.
○: There is no occurrence of blisters, and the tape peeling width from the cut part exceeds 1.5 mm, 3 mm or less,
Δ: Slight occurrence of swelling is observed, but tape peeling width from the cut portion is 3 mm or less, or occurrence of swelling is not recognized, but the tape peeling width from the cut portion exceeds 3 mm,
X: Generation | occurrence | production of a swelling is recognized and the tape peeling width from a cut part exceeds 3 mm.

  Acid resistance: The back surface and cut surface of each test paint plate cut to a size of 5 cm × 10 cm were sealed with a rust-proof paint, and a cross cut reaching the substrate was put in the center of the front side of the paint plate. This coated plate was immersed in a 5% sulfuric acid aqueous solution at 20 ° C. for 48 hours, then taken out, washed, and evaluated for the appearance of the coating on the surface side of the coated plate dried at room temperature. The peel width (one side) from the cut portion in the coating film after being peeled off rapidly was evaluated.

A: There is no occurrence of swelling, and the tape peeling width from the cut part is 1.5 mm or less.
○: There is no occurrence of swelling, and the tape peeling width from the cut part exceeds 1.5 mm and is 3 mm or less.
Δ: Slight occurrence of swelling is observed, but tape peeling width from the cut portion is 3 mm or less, or occurrence of swelling is not recognized, but the tape peeling width from the cut portion exceeds 3 mm,
X: Generation | occurrence | production of a swelling is recognized and the tape peeling width from a cut part exceeds 3 mm.

  Scratch resistance: Using a coin scratch tester (manufactured by Kayaku Giken Kogyo Co., Ltd.) at a room temperature of 20 ° C., keep the edge of the 10-yen copper coin at a 45 ° angle on the surface of each test coating plate, 3 kg The degree of scratching when the coated surface was scratched by pulling a 10-yen copper coin at a speed of 10 mm / second for about 30 mm while being pressed with a load of was evaluated according to the following criteria.

A: No metal substrate is seen on the scratched part.
○: A slight metal base is seen on the scratched part.
△: A considerable amount of metal base is seen in the scratched part,
X: A coating film is hardly left on the scratched part, and the metal base is clearly seen.

  As the corrosion resistance test, the following combined cycle corrosion test (CCT test) was performed on the GL steel plate and the GI steel plate coated plate, and the following salt spray test was performed on the SPC steel plate coated plate.

  Combined cycle corrosion test: Conforms to JIS K-5621 (1990). For each test, cut to a size of 6 cm x 12 cm so that the burrs at the edge of the long side of each test coating plate face the front side on the right side toward the front side and the back side on the left side. Insert a cross cut with a narrow angle of 30 degrees and a line width of 0.5 mm into the center of the surface side of the paint board using the back of the cutter knife, and seal the top edge of the paint board with anticorrosive paint. Is provided with a 4T bending portion (processing to bend with the surface side of the coated plate facing outward, sandwiching four plates of the same thickness as the painted plate inside, and bending the painted plate 180 degrees in a vise) About the coated plate (5% saline sprayed at 30 ° C. for 0.5 hour)-(Test for 1.5 hours in a humidity tester of RH 95% or higher at 30 ° C.)-(Dry at 50 ° C. for 2 hours)-(30 Drying at 2 ° C for 2 hours is one cycle and 300 cycles (total Was 1800 hours) test. The state of the edge part, cross cut part, and 4T bending process part of the coating board after this test was evaluated.

(4T process part) The total length of the rust part in a 4T process part was evaluated.
A: No occurrence of rust,
○: White rust is observed, but less than 20 mm,
Δ: White rust is 20 mm or more and less than 40 mm,
X: Generation | occurrence | production of white rust 40 mm or more or red rust is recognized.

(Edge part) The average value of the edge creep widths of the left and right long sides of the coated plate was determined and evaluated according to the following criteria.
A: Less than 5 mm
○: 5 mm or more and less than 10 mm,
Δ: 10 mm or more and less than 20 mm,
X: 20 mm or more.

(Cross cut part) Corrosion state of the cross cut part, by the average value of the white rust occurrence length ratio in the bare metal exposed part of 0.5mm cut width, and the left and right swelling width (sum of both sides) of the cut part, Evaluation was made according to the following criteria.
A: White rust generation length ratio in exposed metal portion is less than 50% and swelling width is less than 3 mm,
○: The white rust generation length ratio in the bare metal exposed portion is 50% or more and less than 3 mm, or the white rust occurrence length ratio in the bare metal exposed portion is less than 50% and the swelling width is 3 mm or more and less than 5 mm,
Δ: White rust generation length ratio in exposed metal portion is 50% or more and swelling width is 5 mm or more and less than 10 mm,
X: The white rust generation length ratio in the bare metal exposed part is 50% or more and the swelling width is 10 mm or more.

  Salt spray test: The back and cut surfaces of each test coating plate (SPC steel plate coating plate) cut to a size of 5 cm x 10 cm are sealed with anti-corrosion paint, and a cross cut that reaches the substrate at the center of the surface of the coating plate is performed. I put it in. The coated plate is subjected to a salt spray test (JIS Z-2371) with 5% saline at 35 ° C. for 500 hours to evaluate the occurrence of red rust on the coated surface after the test, and the cellophane adhesive tape is adhered to the crosscut portion. The tape peeling width (one side) from the cut part in the coating film after abrupt peeling was evaluated.

A: There is little or no red rust, and the tape peeling width from the cut part is less than 5 mm.
○: The occurrence of red rust is considerably recognized, and the tape peeling width from the cut portion is less than 5 mm, or the occurrence of red rust is not or slight, but the tape peeling width from the cut portion is 5 mm or more and less than 10 mm,
Δ: generation of red rust is observed in the entire cut portion, but the tape peeling width from the cut portion is 5 mm or more and less than 10 mm, or the occurrence of red rust is not recognized in the entire cut portion but is considerably recognized, and the tape peeling width from the cut portion Is 10 mm or more,
X: The occurrence of red rust was observed in the entire cut part, and the tape peeling width from the cut part was 10 mm or more.

  Weather-resistant salt spray test: Long-term durability of coating film specified in JIS K 5600 7.7, accelerated weathering test (xenon lamp method) Based on the method A, irradiation was continued for 500 hours with a xenon weatherometer under repeated cycle conditions (wet 18 minutes-dry 102 minutes). Next, the back surface and the cut surface were sealed with a rust preventive paint, and a cross cut reaching the substrate was put in the center of the surface of the painted plate. About this coating board, after performing the salt spray test (JIS Z-2371) for 500 hours, the external appearance of the plane part was evaluated by the following reference | standard.

A: The swelling / rust progression width from the cut part is 3 mm or less on average across the cut, and no other abnormalities are observed.
○: The bulge / rust progression width from the cut part exceeds 3 mm and is 5 mm or less, and no abnormality is observed in the flat part or the like, or slight blistering is observed in the flat part, but from the cut part The swelling / rust progression width is 3 mm or less.
Δ: The swelling / rust progression width from the cut part exceeds 3 mm and is 5 mm or less, and slight swelling is observed in the flat part.
X: The swelling / rust progression width from the cut portion exceeds 5 mm, or significant swelling is observed in the flat portion.

Claims (8)

(A) A coating composition containing a hydroxyl group-containing coating film-forming resin, (B) a crosslinking agent, and (C) a rust preventive pigment mixture, wherein the rust preventive pigment mixture (C) is (1) vanadium pentoxide , At least one vanadium compound of calcium vanadate and ammonium metavanadate, (2) a calcium compound selected from calcium oxide and calcium carbonate , and (3) a metal phosphate, a metal hydrogen phosphate, and a metal tripolyphosphate And a phosphate metal salt in which the metal of each metal salt is Zn, Al, or Mg, the resin (A) and the crosslinking agent (B) For 100 parts by mass of the total solid content,
3 to 50 parts by mass of the vanadium compound (1),
The amount of the calcium compound (2) is 3 to 50 parts by mass, the amount of the phosphate metal salt (3) is 3 to 50 parts by mass, and the amount of the rust preventive pigment mixture (C) is 10 to 10 parts by mass. A coating composition characterized by being 150 parts by mass. The coating composition according to claim 1, wherein the hydroxyl group-containing film-forming resin (A) is at least one of a hydroxyl group-containing epoxy resin and a hydroxyl group-containing polyester resin. The coating composition according to claim 1 or 2, wherein the crosslinking agent (B) is at least one crosslinking agent selected from an amino resin, a phenol resin, and a polyisocyanate compound which may be blocked. Furthermore, the coating composition as described in any one of Claims 1-3 which contains at least 1 sort (s) of pigment component in a rust preventive pigment other than a rust preventive pigment mixture (C), a titanium dioxide pigment, and an extender pigment. object. Furthermore, the coating composition as described in any one of Claims 1-4 containing at least 1 sort (s) of a ultraviolet absorber and a ultraviolet stabilizer. The vanadium compound (1), the calcium compound (2) and the phosphoric acid compound constituting the rust preventive pigment mixture (C) blended with respect to 100 parts by mass of the total solid content of the resin (A) and the crosslinking agent (B). A mixture of metal salt (3) in an amount of parts by mass within each quantitative range was added to 10000 parts by mass of a 5% strength by weight sodium chloride aqueous solution at 25 ° C., stirred for 6 hours, and allowed to stand at 25 ° C. for 48 hours. The pH of the filtrate which filtered the liquid is 3-10, The coating composition as described in any one of Claims 1-5 characterized by the above-mentioned. The coated metal plate by which the cured coating film based on the coating composition of any one of Claims 1-6 is formed on the metal plate which may be subjected to chemical conversion treatment on the surface. A cured coating film based on the coating composition according to any one of claims 1 to 6 is formed on a metal plate that may be subjected to chemical conversion treatment on the surface, and an overcoat coating is formed on the cured coating film. A coated metal plate having a multilayer coating film formed with a film.