TWI443158B - Resistant to white rust excellent coating to form galvanized steel - Google Patents

Description

Coating film with excellent white rust resistance to form galvanized steel sheet Field of invention

The present invention relates to a galvanized steel sheet in which a coating film having a plurality of coating films using a non-chromium-based coating composition is formed on both surfaces of the front and back surfaces and having excellent rust preventive properties. Further, in more detail, a galvanized steel sheet is formed in a coating film which is excellent in white rust resistance particularly in a processed portion and an end surface portion.

Background of the invention

In the past, a galvanized steel sheet was used as a coating material for a precoated steel sheet or the like which was coated with a coil coating, and was widely used as a building material for roofs, walls, shutters, garages, etc. of buildings. Home-related products such as home appliances, switchboards, refrigerated display cases, steel furniture, and kitchen appliances.

When a galvanized steel sheet is formed from a coating film to produce such a house-related product, a coating film such as a precoated steel sheet is usually cut into a galvanized steel sheet, and press-molded and joined. Therefore, most of these house-related products have a cut surface, that is, a metal exposed portion and a crack generating portion due to press working. In the above-mentioned metal exposed portion and the crack generating portion, the corrosion resistance is likely to be lowered, and in order to improve the corrosion resistance, a chrome-based rust preventive paint is usually contained in the undercoat film of the galvanized steel sheet formed by the coating film. However, the chromium-based rust-preventive pigment contains or produces hexavalent chromium having excellent rust resistance, and this hexavalent chromium has a problem in terms of a human health surface and an environmental protection surface.

Conventionally, as a coating composition in which a non-chromium-based pigment is combined, and a metal material having good corrosion resistance of a coating film by coating with the coating composition, it has been proposed to disclose various materials.

For example, Patent Document 1 describes a coating composition in which a specific vanadium compound, a specific metal citrate, and a specific metal hydrogen phosphate are formulated as a rust preventive pigment in a predetermined amount in a hydroxyl group-containing coating film-forming resin. to make.

For example, Patent Document 2 describes a method of forming a metal material by forming a coating film of a rust-preventive coating film using a rust-preventive coating composition on both sides of a metal material, and the rust-preventing coating composition is formed on a hydroxyl group-containing coating film. The resin is prepared by mixing a specific vanadium compound, a specific cerium-containing material, and a ceric acid-based calcium salt as a rust preventive pigment in a predetermined amount. However, the metal material formed by using the coating film of the coating composition described in Patent Documents 1 and 2 has substantially good corrosion resistance, but particularly when the metal material is a galvanized steel sheet, compared with the case where a chromium-based pigment is used. In the coating film formed by the coating composition, particularly in the initial stage of use, the end surface portion is conspicuously produced white rust, and there is a problem that the suppression system is insufficient.

Prior technical literature Patent literature

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2008-291160

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2000-266444

An object of the present invention is to provide a coating film for forming a galvanized steel sheet which is formed by forming a plurality of coating films using non-chromium-based coating compositions on both sides of the front and back surfaces, not only the corrosion resistance of the flat portion but also In particular, it is excellent in white rust resistance of the processed portion and the end surface at the beginning of use.

In order to solve the problem, the inventors of the present invention have found that a coating film is formed on both sides of the front and back sides, and at least one of the lowermost layers of the front and back surfaces is used in a resin-containing coating film-forming resin to contain rust prevention in a predetermined amount. A coating film formed by forming a coating film of a pigment forms a galvanized steel sheet, and a coating film is formed by using a coating composition on at least one of the uppermost layers of the front and back surfaces, and the coating composition is formed on a hydroxyl group-containing coating film. The resin is contained in a predetermined amount: at least one compound selected from the group consisting of gold metal ruthenate and metal ion-exchanged cerium oxide; and is selected from a film-forming resin containing a phosphoric acid group and a coating film containing a phosphate group. At least one resin of the group consisting of the resin; and/or an azole compound; the above problems can be solved, and the present invention has been completed.

That is, the present invention provides the following items.

Item 1. A galvanized steel sheet formed by forming a coating film on a surface of a galvanized steel sheet and forming a single layer or a plurality of layers on the back surface, which is formed on at least one of the lowermost layers of the front and back surfaces. a coating layer of the coating composition (I), and a coating layer of the following coating composition (II) is formed on at least one of the uppermost layers of the front and back surfaces; a coating composition (I): one containing (A) a hydroxyl group a coating composition of a coating film-forming resin, (B) a crosslinking agent, and (C) a rust-preventing pigment, and a total of 100 parts by mass of the total solid content of the resin (A) and the crosslinking agent (B) The amount of the rust pigment (C) is 10 to 150 parts by mass; the coating composition (II): a coating composition comprising (A) a hydroxyl group-containing coating film-forming resin and (B) a crosslinking agent, and further containing ( Da) is selected from at least one compound selected from the group consisting of metal ruthenate and metal ion-exchanged cerium oxide, and the total solid content of the resin (A) and the crosslinking agent (B) is 100% by mass. The compound (Da) is used in an amount of 3 to 50 parts by mass or more (Db) selected from the group consisting of a coating film-forming resin containing a phosphoric acid group and a phosphate-containing coating film. The amount of the resin (Db) is 5 to 30 parts by mass based on 100 parts by mass of the total solid content of the resin (A) and the crosslinking agent (B), and at least one resin in the group of the resin. In addition, the amount of the (Dc) azole compound is 2 to 30 parts by mass based on 100 parts by mass of the total solid content of the resin (A) and the crosslinking agent (B).

Item 2. The coating film according to Item 1 forms a galvanized steel sheet, wherein a zinc content in the plating layer of the galvanized steel sheet is 10% by mass or more.

Item 3. The coating film according to Item 1 or 2, wherein the hydroxyl group-containing coating film-forming resin (A) is selected from the group consisting of a hydroxyl group-containing polyester resin and a hydroxyl group-containing epoxy resin. At least one resin in the middle.

Item 4. The coating film according to Item 3, which forms a galvanized steel sheet, wherein the hydroxyl group-containing coating film of the coating composition (II) forms a resin (A) which is a hydroxyl group-containing polyester resin.

Item 5. The coated film according to any one of items 1 to 4, wherein the crosslinking agent (B) is selected from the group consisting of an amine resin, a phenol resin, and a polyisocyanate compound which may also be blocked. At least one crosslinker in the group.

Item 6. The coated film according to any one of items 1 to 5, wherein the rust preventive pigment (C) is (1) selected from the group consisting of vanadium pentoxide, calcium vanadate, ammonium metavanadate and vanadic acid At least one vanadium compound, (2) a ruthenium-containing compound, and (3) a phosphate-based metal salt in the group consisting of magnesium.

Item 7. The coating film of item 6 forms a galvanized steel sheet, wherein the phosphate metal salt (3) is selected from the group consisting of calcium phosphate, calcium monohydrogen phosphate, calcium dihydrogen phosphate, and metal elements of magnesium, aluminum, zinc or At least one metal salt of the group consisting of calcium tripolyphosphate metal salts.

Item 8. The galvanized steel sheet according to any one of Items 1 to 7, wherein 1 part by mass of the compound (Da) is added to 25 parts by mass of the 5% by mass aqueous sodium chloride solution at 25 ° C. After stirring at ° C for 6 hours, the mixture was allowed to stand at 25 ° C for 24 hours, and then the pH of the filtrate obtained by filtering the upper clear liquid was 10 to 13.

Item 9. The galvanized steel sheet according to any one of Items 1 to 8, wherein the resin (Db) has a mass fraction of a component having a molecular weight of 1,000 or less in a molecular weight distribution of 5 to 30% by mass.

Item 10. The galvanized steel sheet according to any one of Items 1 to 9, wherein 1 part by mass of the compound (Db) is added to 25 parts by mass of the 5% by mass aqueous sodium chloride solution at 25 ° C. After stirring at ° C for 6 hours, the mixture was allowed to stand at 25 ° C for 24 hours, and then the pH of the filtrate obtained by filtering the supernatant liquid was 3 to 7.

Item 11. The coating film according to any one of Items 1 to 10, wherein the azole compound (Dc) is an azole compound having a triazolyl group or a thiadiazolyl group.

Item 12. The coated film according to any one of Items 1 to 11, wherein the coating composition (I) further contains one pigment selected from the group consisting of cerium oxide and a filler pigment.

Item 13. The coating film according to any one of items 1 to 12, wherein the coating composition (II) further contains an antirust pigment selected from the group consisting of (Da), cerium oxide, and a filler pigment. Form one of the pigments in the group.

Item 14. The coating film according to Item 6 or 7, wherein a coating layer of the coating composition (I) is formed on the lowermost layer of the surface (face facing outward), and the uppermost layer of the back side of the opposite side is formed. A coating layer of the coating composition (II) is formed.

Item 15. The coating film according to Item 14 forms a galvanized steel sheet which forms a coating layer of the coating composition (I) on the lowermost layer on both sides of the front and back, and forms a coating composition on the uppermost layer of the back surface (the surface used toward the inside). The coating layer of the substance (II).

Item 16. A method of forming a plurality of coating films on a surface of a galvanized steel sheet and forming one or a plurality of coating films on the back surface, comprising: coating the lowermost layer of at least one of the front and back surfaces of the galvanized steel sheet with the following coating a step of the composition (I); a step of curing the coating film obtained by coating the coating composition (I); and coating the following coating composition on the uppermost layer of at least one of the front and back surfaces (step of II; Step of hardening the coating film obtained by coating the coating composition (II); coating composition (I): a coating film-forming resin containing (A) hydroxyl group-containing resin, (B) crosslinking agent, and (C) rust prevention The paint composition of the pigment, wherein the amount of the rust preventive pigment (C) is 10 to 150 parts by mass based on 100 parts by mass of the total solid content of the resin (A) and the crosslinking agent (B); and the coating composition (II) A coating composition comprising (A) a hydroxyl group-containing coating film-forming resin and (B) a crosslinking agent, and further comprising (Da) selected from the group consisting of metal citrate and metal ion-exchanged cerium oxide At least one compound in the group, and the amount of the compound (Da) is 3 based on 100 parts by mass of the total solid content of the resin (A) and the crosslinking agent (B). 50 parts by mass or more (Db) at least one resin selected from the group consisting of a coating film-forming resin containing a phosphoric acid group and a film-forming resin containing a phosphate group, and 100 parts by mass of the total solid content of the resin (A) and the crosslinking agent (B), the amount of the resin (Db) is 5 to 30 parts by mass, or more (Dc) of the azole compound, and relative to the resin (A) And 100 parts by mass of the total solid content of the crosslinking agent (B), and the amount of the (Dc) azole compound is 2 to 30 parts by mass.

The coating film for forming a galvanized steel sheet of the present invention is formed by forming a coating film of a non-chromium-based coating composition which is advantageous in environmental hygiene on both surfaces of a galvanized steel sheet, and is excellent not only in the flat portion but also in corrosion resistance. In the past, it is difficult to achieve a non-chromium rust-resistant paint to form a galvanized steel sheet, and in particular, it is effective in forming a coating film having excellent white rust resistance in a processed portion and an end surface portion which are conspicuous at the beginning of use.

The galvanized steel sheet is formed on the coating film of the present invention, and the corrosion resistance of the flat portion can be a coating layer formed of the coating composition (I) containing the rust-preventing pigment formed on the lowermost layer of at least one of the front and back surfaces. The anti-corrosion effect is achieved, and the white rust resistance of the processed portion and the end surface portion can be formed by a group consisting of metal citrate and metal ion-exchanged cerium oxide formed on at least one of the uppermost layers on the front and back surfaces. The rust-preventing effect of the coating layer formed by the coating composition (II) of at least one compound is achieved.

The white rust of the galvanized steel sheet is produced by the zinc (ion) in the plating being zinc oxide. White rust is white or a large amount of zinc oxide which is accompanied by a part of pale brown spots in white, which is formed on the surface of the zinc plating surface and has an appearance such as a state in which white ink powder adheres. In particular, when the plating layer is exposed to an environment that is not easily dried by rain or dew, and the plating layer is easily wetted by rain or dew, the processed portion and the end surface portion are likely to be generated. White rust parts. Because white rust is a bulky zinc oxide, even if the actual corrosion is a little, it can be observed to be significantly corroded, which is very conspicuous.

In the galvanized steel sheet according to the present invention, the coating layer formed using the coating composition (II) containing the components (Da) (Db) and/or (Dc) is formed on the uppermost layer of at least one of the front and back surfaces. Before the cause of white rust, that is, the formation of zinc oxide, the zinc ions generated in the processed portion and the end surface are exchanged with the metal citrate and the metal ion for the cerium ion of the cerium oxide; the coating film containing the phosphoric acid group is formed. The phosphate group and/or the phosphate group of the resin-forming resin and/or the phosphate-containing coating film-forming resin; and/or the azole compound can efficiently capture zinc ions and suppress the formation of zinc oxide. The white rust resistance of the processed portion and the end surface portion is extremely excellent.

Form for implementing the invention

In the galvanized steel sheet of the present invention, a galvanized steel sheet is formed by forming a plurality of coating films on the surface and forming a coating film of one or more layers on the back surface, and a galvanized steel sheet is formed on at least one of the front and back surfaces. A) a coating composition containing a hydroxyl group-containing coating film-forming resin, (B) a crosslinking agent, and (C) an anti-rust pigment coating composition (I), and a coating composition for at least one of the uppermost layers of the front and back surfaces (II) A coating film layer is formed, and the coating composition (II) contains a hydroxyl group-containing coating film-forming resin (A), (B) a crosslinking agent, and a metal silicate and/or metal ion-exchanged dioxide. Da (Da), a coating film-forming resin containing a phosphoric acid group, and/or a phosphate-containing coating film-forming resin (Db) and/or an azole compound (Dc).

Hereinafter, the galvanized steel sheet for forming a coating film of the present invention (hereinafter referred to as "the galvanized steel sheet of the present invention") will be described in detail.

Coating composition (I)

The coating composition (I) is a coating composition containing a hydroxyl group-containing coating film-forming resin (A), a crosslinking agent (B), and a rust-preventing pigment (C).

Hydroxyl-containing coating film-forming resin (A)

The hydroxyl group-containing coating film-forming resin to be used in the coating composition (I) is not particularly limited as long as it is a resin having a coating film shape which can be used in the coating material field, and can be used as a representative. For example, one or a mixture of two or more kinds of a hydroxyl group-containing polyester resin, an epoxy resin, an acrylic resin, a fluororesin, and a vinyl chloride resin may be mentioned. As the coating film-forming resin, at least one organic resin selected from the group consisting of a hydroxyl group-containing polyester resin and a hydroxyl group-containing epoxy resin can be suitably used.

The hydroxyl group-containing polyester resin includes an oil-free polyester resin, an oil-modified alkyd resin, and a modified product of the resins, for example, a urethane-modified polyester resin, a urethane modification. Alkyd resin, epoxy modified polyester resin, acrylic modified polyester resin, and the like. The hydroxyl group-containing polyester resin has a number average molecular weight of 1,500 to 35,000, preferably 2,000 to 25,000, and a glass transition temperature (Tg) of 10 to 100 ° C, preferably 20 to 80 ° C, preferably a hydroxyl value. It is suitable for 2 to 100 mgKOH/g, preferably 5 to 80 mgKOH/g.

In the present specification, the number average molecular weight and the weight average molecular weight are maintained by gel permeation chromatography (GPC) using a retention time (holding capacity), and the retention of standard styrene of known molecular weight measured under the same conditions. The time (holding capacity) is converted into a molecular weight obtained by polystyrene.

Specifically, for example, as a gel permeation chromatography device, "HLC-8120GPC" (trade name, manufactured by TOSOH Co., Ltd.) is used, and as a column, "TSKgel G4000HXL" and "TSKgel G3000HXL" are used. One of the "TSKgel G2000HXL" (trade name, either manufactured by TOSOH Co., Ltd.) has a total of four, and the detector uses a differential refractometer and is capable of moving phase: tetrahydrofuran, measuring temperature: 40 ° C, flow rate : Measured under conditions of 1 mL/min.

Further, in the present specification, the glass transition temperature (Tg) of the resin is obtained by using differential thermal analysis (DSC).

The above oil-free polyester resin is an esterified product of a polybasic acid component and a polyol component. The polybasic acid component can be selected, for example, from the group consisting of phthalic anhydride, isophthalic acid, p-nonanoic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, succinic acid, fumaric acid, adipic acid, sebacic acid, and cis. One or more kinds of dibasic acids such as butenedic anhydride and lower alkyl esters of the same are used, and if necessary, a monobasic acid such as benzoic acid, crotonic acid or p-tert-butylbenzoic acid may be used in combination. A tribasic or higher polybasic acid such as 1,2,4-benzenetricarboxylic anhydride, methylcyclohexenetricarboxylic acid or pyrogallic anhydride. These polyvalent carboxylic acids may be used singly or in combination of two or more. As the acid component, isodecanoic acid, p-citric acid, and a lower alkyl ester of these acids are particularly preferred. As the polyol component, for example, ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 3-methylpentanediol, 1,4-hexanediol, 1 can be used. A glycol such as 6-hexanediol is used as a main component, and a trihydric or higher polyhydric alcohol such as glycerin, trimethylolethane, trimethylolpropane or neopentyl alcohol may be used in combination as necessary. These polyols can be used singly or in combination of two or more kinds. The esterification or transesterification reaction of the two components can be carried out by a method known per se.

The alkyd resin is obtained by adding an acid component and an alcohol component of the oil-free polyester resin, and reacting the oil fatty acid by a method known per se. Examples of the oil fatty acid include coconut oil fatty acid and soybean oil fatty acid. Linseed oil fatty acid, safflower oil fatty acid, tall oil fatty acid, dehydrated castor oil fatty acid, eucalyptus oil fatty acid and the like. The oil length of the alkyd resin is 30%, and it is particularly preferable for about 5 to 20%.

The urethane-modified polyester resin may be an oil-free polyester resin or a low molecular weight oil-free polymer obtained by reacting an acid component and an alcohol component used in the production of the oil-free polyester resin. The ester resin is obtained by reacting a polyisocyanate compound and a method known per se. Further, the urethane-modified polyester resin also includes a low molecular weight alkyd resin obtained by reacting the above alkyd resin or each component used in the production of the above alkyd resin, and using a polyisocyanate compound and A method known per se makes it a reaction. Examples of the polyisocyanate compound which can be used in the production of the urethane-modified polyester resin and the urethane-modified alkyd resin include hexamethylene diisocyanate, isophorone diisocyanate, and benzodimethyl group. Diisocyanate, toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 2,4,6-triisocyanate, and the like. The above-mentioned urethane-modified resin is generally suitably used in an amount such that the amount of the polyisocyanate compound forming the urethane-modified resin is 30% by weight or less based on the amount of the urethane-modified resin.

The epoxy-modified polyester resin is obtained by reacting a carboxyl group of the resin with an epoxy group-containing resin using a polyester resin obtained from each component used in the production of the above polyester resin. a reaction product; a polyester resin in which a hydroxyl group in a polyester resin and a hydroxyl group in an epoxy resin are bonded to each other by a polyisocyanate compound, and an epoxy resin, which is added, condensed, grafted, or the like The reaction product obtained by the reaction. The degree of modification of such an epoxy-modified polyester resin is usually from 0.1 to 30% by weight based on the amount of the epoxy-modified polyester resin.

The acrylic modified polyester resin may be a polyester resin obtained by using each component used in the production of the above polyester resin, and a carboxyl group or a hydroxyl group of the resin may be reacted with the group. For example, a reaction product obtained by reacting an acrylic resin containing a carboxyl group, a hydroxyl group or an epoxy group; and grafting a polyester resin with a polymerization initiator such as (meth)acrylic acid or (meth)acrylate A reaction product obtained by polymerization. The degree of modification of such an acrylic modified polyester resin is usually from 0.1 to 50% by weight based on the amount of the acrylic resin modified with respect to the acrylic modified polyester resin.

Among the polyester resins described above, in terms of balance of workability, corrosion resistance, and the like, an oil-free polyester resin or an epoxy polyester resin is particularly preferable.

Examples of suitable epoxy resins for the hydroxyl group-containing coating film-forming resin include bisphenol epoxy resins and novolak epoxy resins; and various modifiers for the epoxy resins. A modified epoxy resin obtained by reacting an oxy group or a hydroxyl group. In the production of the modified epoxy resin, the modification period of the modifier is not particularly limited, and it may be modified in the middle of the production of the epoxy resin, or may be modified in the final stage of the production of the epoxy resin.

The bisphenol type epoxy resin is a resin obtained by condensing epichlorohydrin and a bisphenol compound in the presence of a catalyst such as a basic catalyst, to a high molecular weight, and making epichlorohydrin and bisphenol. The compound is condensed in the presence of a catalyst such as a basic catalyst to form a low molecular weight epoxy resin, and the resin obtained by polyaddition reaction of the low molecular weight epoxy resin and bisphenol is used. Either.

Examples of the bisphenol compound include bis(4-hydroxyphenyl)methane [bisphenol F], 1,1-bis(4-hydroxyphenyl)ethane, and 2,2-bis(4-hydroxyphenyl). Propane [bisphenol A], 2,2-bis(4-hydroxyphenyl)butane [bisphenol B], bis(4-hydroxyphenyl)-1,1-isobutane, bis(4-hydroxyl) -T-butyl-phenyl)-2,2-propane, p-(4-hydroxyphenyl)phenol, bis(4-hydroxyphenyl)oxy, sulfonylbis(4-hydroxyphenyl), 4, 4'-dihydroxydiphenyl ketone, bis(2-hydroxynaphthyl)methane or the like, among which bisphenol A and bisphenol F are suitably used. These bisphenols may be used alone or in combination of two or more.

As a commercial item of the bisphenol type epoxy resin, for example, EPICOAT 828, the same 812, the same 815, the same 820, the same 834, the same 1001, the same 1004, the same 1007, the same 1009, the same 1010 manufactured by JAPAN EPOXY RESINS. ; ARALDITE AER6099 manufactured by Asahi CIBA Co., Ltd.; and EPOMIK R-309 manufactured by Mitsui Chemicals Co., Ltd.

Further, the epoxy resin-based epoxy resin which is a suitable epoxy resin-containing coating film-forming resin, for example, a phenol novolac type epoxy resin or a cresol novolac type epoxy resin, Various novolac type epoxy resins, such as a phenol glyoxal type epoxy resin having a large number of epoxy groups.

Examples of the modified epoxy resin include the bisphenol epoxy resin or the novolac epoxy resin, for example, an epoxy ester resin obtained by reacting a dry oil fatty acid; and containing acrylic acid or methacrylic acid. An epoxy acrylate resin obtained by reacting a polymerizable unsaturated monomer component, a urethane-modified epoxy resin obtained by reacting an isocyanate compound, and an amine compound for the above bisphenol epoxy resin or novolac The epoxy resin or the amine-modified epoxy resin obtained by reacting an epoxy group in the above-mentioned various modified epoxy resins to introduce an amine group or a 4- to ammonium group.

Crosslinking agent (B)

The crosslinking agent (B) reacts with the hydroxyl group-containing coating film-forming resin (A) to form a cured coating film, and can be reacted with the hydroxyl group-containing coating film-forming resin (A) by heating or the like. The hardener can be used without particular limitation, and an amine-based resin, a phenol resin, and a polyisocyanate compound which can also be blocked are preferred. These crosslinking agents can be used alone or in combination of two or more.

Examples of the amine-based resin include an amine component such as melamine, urea, benzoguanamine, acetamide, steroguanamine, spiroguanamine, or dicyanodiamide reacted with an aldehyde. The resulting methylolated amine based resin. Examples of the aldehyde used in the above reaction include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde, and the like. Further, the above-mentioned methylolated amine-based resin can also be used as an amine-based resin by etherification with an appropriate alcohol. Examples of the alcohol used for the etherification include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, 2-ethylbutanol, and 2-ethylhexanol.

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

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

Examples of the phenol compound include o-cresol, p-cresol, p-tert-butylphenol, p-ethylphenol, 2,3-xylenol, and 2,5-dimethyl. Examples of the trifunctional phenol compound such as phenol include carbolic acid, m-cresol, m-ethylphenol, 3,5-xylenol, m-methoxyphenol, and the like, and a tetrafunctional phenol compound. Bisphenol A, bisphenol F, etc. are mentioned. In terms of improving the scratch resistance, it is preferred to use a trifunctional or higher phenol compound, particularly carbolic acid and/or m-cresol. These phenol compounds can be used alone or in combination of two or more.

As the formaldehyde used in the production of the phenol resin, formaldehyde, trioxane or tris may be mentioned. An alkane or the like can be used alone or in combination of two or more.

As the alcohol to be used for the alkylation of 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. Examples of suitable monohydric alcohols include methanol, ethanol, n-propanol, n-butanol, and isobutanol.

The phenol resin has an average of alkoxymethyl groups per nucleus of benzene nucleus having 0.5 or more, preferably a reactivity with a hydroxyl group-containing coating film-forming resin (A). 0.6 to 3.0 are suitable.

An unblocked polyisocyanate compound which can be used as the crosslinking agent in the polyisocyanate compound which can be blocked, for example, an aliphatic diisocyanate such as hexamethylene diisocyanate or trimethylhexamethylene diisocyanate; a cyclic aliphatic diisocyanate of benzoyl diisocyanate or isophorone diisocyanate; toluene diisocyanate, benzodimethyl diisocyanate or 4,4'-diphenylmethane diisocyanate itself, or An addition product of each of an organic diisocyanate and a polyhydric alcohol, a low molecular weight polyester resin or water, or a cyclized polymer between the above organic diisocyanates, and an isocyanate-biuret or the like.

The blocked polyisocyanate compound is obtained by blocking a free isocyanate group of the above polyisocyanate compound using a blocking agent. As the above-mentioned blocking agent, for example, a phenolic blocking agent such as phenol, cresol or xylenol; ε-caprolactam; δ-valeramidine or γ-butylide; Endoleamide-based blocking agent; methanol, ethanol, n-, iso- or tert-butanol, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, propylene glycol An alcohol-based blocking agent such as methyl ether or hexanediol; foramidoxime, acetaldehyde oxime, acetamidine, methyl ethyl ketone oxime, diethyl hydrazine mono guanidine, diphenyl ketone An anthracene blocking agent such as hydrazine or cyclohexane hydrazine; an active methylene blocking agent such as dimethyl malonate, diethyl malonate, ethyl acetate or ethyl acetonate; Blocking agent. By mixing the above polyisocyanate compound with the above blocking agent, the free isocyanate group of the above polyisocyanate compound can be easily blocked.

The ratio of the hydroxyl group-containing coating film-forming resin (A) to the crosslinking agent (B) is based on (A) and (B) in terms of corrosion resistance, boiling water resistance, workability, and hardenability. 100 parts by mass of the total solid content of the component, the hydroxyl group-containing coating film-forming resin (A) is 55 to 95 parts by mass, preferably 60 to 95 parts by mass, and the crosslinking agent (B) is 5 to 45 parts by mass. It is preferably in the range of 5 to 40 parts by mass.

In order to improve the hardenability of the coating composition (I), the curing catalyst may be blended as necessary. The crosslinking agent (B) is an amine-based resin, particularly a low molecular weight methyl etherification or a mixed etherified melamine resin of a methyl ether and an ethyl ether, and is used as a hardening catalyst to use a sulfonic acid compound or a sulfonic acid. Amine neutralizers of the compounds are preferred. Typical examples of the sulfonic acid compound include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and dinonylnaphthalene disulfonic acid. The amine which is an amine neutralizer in the sulfonic acid compound may be any of a primary amine, a secondary amine, and a tertiary amine. Among these, the amine neutralization of p-toluenesulfonic acid and/or the amine neutralization of dinonylnaphthalene disulfonic acid are used for the stability of the coating material, the reaction promoting effect, and the physical properties of the obtained coating film. Things are better.

When the crosslinking agent (B) is a phenol resin, it is preferred to use an amine neutralizing agent using the above sulfonic acid compound or sulfonic acid compound as the curing catalyst.

When the crosslinking agent (B) is a blocked polyisocyanate compound, it is preferably a hardening catalyst which promotes dissociation of the blocking agent. Examples of a preferred curing catalyst include tin octylate and dibutyltin di(2-ethyl). Caproic acid ester), dioctyltin bis(2-ethylhexanoate), dioctyltin diacetate, dibutyltin dilaurate, dibutyltin oxide, dioctyltin oxide, 2-ethyl An organic metal catalyst such as lead hexanoate.

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

Anti-rust pigment (C)

As the rust-preventing pigment (C), any one of a chrome-based pigment and a non-chromium-based pigment can be used as long as it is a rust-preventing pigment, and a non-chromium-based pigment is used from the viewpoint of human health and environmental protection. good.

Examples of the chromium antirust pigment include strontium chromate, zinc chromate, zinc potassium chromate, barium chromate, chromic anhydride, chromium chromate, and chromium phosphate.

Examples of the non-chromium antirust pigment include antimony compounds such as vanadium pentoxide, calcium vanadate, ammonium metavanadate, and phosphorus vanadate; ruthenium-containing compounds such as metal ruthenate and ruthenium dioxide microparticles; zinc phosphate and phosphoric acid; a phosphate metal salt such as aluminum, calcium phosphate, magnesium secondary phosphate or aluminum tripolyphosphate; a zinc molybdate, a calcined product of magnesium oxide and vanadium oxide, or a calcined product of calcium phosphate and vanadium oxide. These rust preventive pigments can be used singly or in combination of two or more.

In the coating composition (I), as the rust preventive pigment (C), a combination of the following (1) vanadium compound, (2) ruthenium-containing compound, and (3) phosphate metal salt can be suitably used.

Vanadium compound (1)

The vanadium compound (1) is a vanadium compound selected from the group consisting of vanadium pentoxide, calcium vanadate, ammonium metavanadate and magnesium vanadate. Vanadium pentoxide, calcium vanadate, ammonium metavanadate and magnesium vanadate, the pentavalent vanadium ion is excellent in water dissolution, and reacts with the material metal by the pentavalent vanadium ion discharged from the vanadium compound (1), or The ionic reaction from other rust preventive pigments can effectively act to improve corrosion resistance.

Antimony-containing compound (2)

The ruthenium-containing compound (2) is at least one selected from the group consisting of metal ruthenate and cerium oxide microparticles. The metal ruthenate is a salt composed of cerium oxide and a metal oxide, and may be any of a protopinate or a polysilicate. Examples of the citrate include calcium citrate, magnesium citrate, zinc citrate, aluminum citrate, aluminum orthosilicate, aluminum hydrated citrate, calcium aluminum citrate, sodium aluminum citrate, and aluminum bismuth citrate. Sodium citrate, calcium orthosilicate, calcium bismuth citrate, sodium calcium citrate, zirconium citrate, magnesium orthosilicate, magnesium metasilicate, calcium magnesium citrate, manganese citrate, strontium citrate, olivine, pomegranate Stone, thorveitite, hemimorphite, benitoite, neptunite, beryl, diopside, wollastonite, Rhodamine, tremolite, xonotlite, talc, apophyllite, aluminosilicate, borosilicate, strontium, feldspar, zeolite (zeolite) and so on. As the metal citrate, calcium citrate, calcium orthosilicate, and calcium metasilicate are preferred.

The cerium oxide microparticles are not particularly limited as long as they are cerium oxide microparticles, and examples thereof include cerium oxide microparticles having no surface treatment, cerium oxide microparticles having a surface treated, and calcium ion exchange. Cerium oxide microparticles, organic solvent dispersible colloidal cerium oxide, and the like.

Examples of the cerium oxide fine particles having no surface treatment or having been treated with an organic material include cerium oxide fine powder having an average particle diameter of 0.5 to 15 μm, preferably 1 to 10 μm, and organic solvent-dispersible colloidal cerium oxide. As the cerium oxide fine powder, a range of 30 to 350 ml/100 g, preferably 30 to 150 ml/100 g, can be suitably used, and as a commercial product, SAILISIA 710, SAILISIA 740, SAILISIA 550, AEROSIL R972 can be cited. (Either of the above is Fuji SILYSIA Chemical Co., Ltd.), MIZUKASIL P-73 (manufactured by Mizusawa Chemical Industry Co., Ltd.), GASIL 200DF (manufactured by Crossfield Co., Ltd.), and the like.

The calcium ion-exchanged cerium oxide microparticles are cerium oxide microparticles obtained by introducing calcium ions into a fine porous cerium oxide carrier by ion exchange. Commercial products of the calcium ion-exchanged cerium oxide microparticles include SHIELDEX (registered trademark) C303, AC-3, and AC-5 (all of which are manufactured by W. R. Grace & Co.). The calcium ion system emitted from the calcium ion-exchanged ceria microparticles is associated with electrochemical action and various salt formation effects, and functions effectively for improving corrosion resistance. Moreover, the cerium oxide which is fixed in the coating film can effectively function to suppress peeling of the coating film in a corrosive environment.

The organic solvent-dispersible colloidal cerium oxide system is also called an organic cerium oxide sol, and the cerium oxide fine particles having a particle diameter of about 5 to 120 nm are stably dispersed in organic substances such as alcohols, glycols, and ethers. Among the commercially available products, the OSCAL series (made by Nikko Chemical Co., Ltd.) and ORGANOSOL (Nissan Chemical Co., Ltd.), etc., among them, especially calcium ion exchange ruthenium dioxide Microparticles are preferred.

The ruthenium-containing compound (2) may be used alone or in combination of two or more.

Phosphate metal salt (3)

The phosphate metal salt (3) is at least one selected from the group consisting of a metal phosphate, a metal hydrogen phosphate, and a metal triphosphate. It is not particularly limited, and examples of preferred metals include Ca, Zn, Al or Mg, with Ca being particularly preferred.

Examples of the phosphate metal salt include calcium phosphate, ammonium calcium phosphate, calcium monohydrogen phosphate, calcium dihydrogen phosphate, calcium fluoride phosphate, zinc phosphate, aluminum phosphate, magnesium phosphate, magnesium hydrogen phosphate, and hydrogen phosphate. Zinc, aluminum phosphate, magnesium phosphate, aluminum hydrogen phosphate, magnesium hydrogen phosphate, magnesium ammonium phosphate; metal elements such as aluminum tripolyphosphate or aluminum dihydrogen phosphate are magnesium, aluminum, zinc, or calcium tripolyphosphate metal salts . Among these, in terms of corrosion resistance, it is particularly preferable to use calcium phosphate, calcium monohydrogen phosphate, calcium dihydrogen phosphate, and a metal triphosphate metal such as magnesium, aluminum, zinc or calcium. The metal ions such as phosphate ions, Ca, Zn, Al, or Mg emitted from the phosphate metal salt (3) can effectively contribute to the improvement of corrosion resistance.

In the coating composition (I), 100 parts by mass of the total solid content of the hydroxyl group-containing coating film-forming resin (A) and the crosslinking agent (B), from the viewpoint of corrosion resistance, the rust-preventing pigment (C) The amount is preferably 10 to 150 parts by mass, preferably 15 to 90 parts by mass, and the anti-rust pigment (C) is the above-mentioned vanadium compound (1) and a compound containing ruthenium (see) from the viewpoint of improving corrosion resistance. 2) and the phosphate metal salt (3) are preferably in the following range.

Vanadium compound (1): 3 to 50 parts by mass, preferably 5 to 30 parts by mass, ruthenium-containing compound (2): 3 to 50 parts by mass, preferably 5 to 30 parts by mass, and a phosphate metal salt (3) ): 3 to 50 parts by mass, preferably 5 to 30 parts by mass.

In the coating composition (I), as the rust preventive pigment (C), by combining the above (1), (2), and (3) in a predetermined amount, the corrosion resistance can be multiplied.

Further, when the above-mentioned (1), (2), and (3) are used in combination as a predetermined amount in the rust preventive pigment (C), the solubility in water based on the above (1), (2), and (3) is used. From the viewpoint of the reactivity of the solution of the rust preventive pigment and the metal plate, 1 part by mass of the above (1), (2) and 1 part by mass of the sodium chloride aqueous solution having a concentration of 5 mass% at 25 ° C is added. (3) a mixture of mass parts in the range of each amount, and after stirring at 25 ° C for 6 hours, after standing at 25 ° C for 48 hours, the pH of the filtrate after filtering the upper clear liquid is 3 to 10, preferably It is suitable from 5 to 9, and in terms of corrosion resistance, it is more preferable in this range.

In the coating composition (I), in addition to the hydroxyl group-containing coating film-forming resin (A), the crosslinking agent (B), the rust-preventing pigment (C), and if necessary, the curing catalyst can be blended as necessary. Coloring pigments, filler pigments, ultraviolet absorbers, ultraviolet stabilizers, organic solvents, additives such as anti-settling agents, antifoaming agents, coating surface modifiers, etc., which can be used in the coating field. The form of the coating composition (I) may be any of an organic solvent type coating material, an aqueous coating material, and a powder coating material.

Examples of the above-mentioned coloring pigment include organic coloring pigments such as an anthocyanin blue, an anthocyanin green, an azo pigment, and an organic red pigment such as a quinophthalone pigment; titanium white, titanium yellow, and iron oxide red. Inorganic coloring pigments such as carbon black and various calcined pigments, among which titanium white can be suitably used.

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

The ultraviolet absorber may, for example, be 2-(2-hydroxy-3,5-di-third-pentylphenyl)-2H-benzotriazole or isooctyl-3-(3-(2H-). Benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenylpropionate, 2-[2-hydroxy-3,5-di(1,1-dimethylphenyl)phenyl -2H-benzotriazole, 2-[2-hydroxy-3-dimethylbenzyl-5-(1,1,3,3-tetramethylbutyl)phenyl]-2H-benzotriene Azole, methyl-3-[3-t-butyl-5-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]propionate/condensate with polyethylene glycol 300, etc. Benzotriazole compound; 2-[4-(2-hydroxy-3-dodecyloxypropyl)oxy]-2-hydroxyphenyl-4,6-bis(2,4-dimethyl Phenyl)-1,3,5-three Three Compound; ethane diamine-N-(2-ethoxyphenyl-N'-(2-ethylphenyl)-(petromethamine), ethane diamine-N-(2-ethoxyl) A oxalic acid anilide compound such as phenyl)-N'-(4-isododecylphenyl)-(chlorinamide).

Examples of the ultraviolet absorber include a hindered amine compound and a hindered phenol compound; CHIMASORB 944, TINUVIN 144, TINUVIN 292, TINUVIN 770, IRGANOX 1010, and IRGANOX 1098 (all of the above-mentioned product names are products of CIBA SPECIALTY CHEMICALS). )Wait.

By blending the ultraviolet ray absorbing agent and/or the ultraviolet ray stabilizer in the coating material, it is possible to suppress the light reaching the surface of the coating film formed by using the coating composition (I) by the above coating film, causing the use of the coating composition (I). The surface of the formed coating film is deteriorated, and peeling between the coating film formed using the coating composition (I) and the upper coating film can be prevented, and excellent corrosion resistance can be maintained.

The organic solvent which can be blended in the coating composition (I) can be used as needed to improve the coating property of the coating composition (I), and a resin-containing coating film-forming resin (A) can be used. When the crosslinking agent (B) is dissolved or dispersed, specific examples thereof include hydrocarbon solvents such as toluene, xylene, and high-boiling petroleum hydrocarbons, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. a ketone solvent such as isophorone; an ester solvent such as ethyl acetate, butyl acetate, ethylene glycol monoethyl ether acetate or diethylene glycol monoethyl ether acetate; methanol or ethanol An alcohol solvent such as isopropyl alcohol or butanol; an ether alcohol solvent such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether or diethylene glycol monobutyl ether; One type or a mixture of two or more types is used.

The coating composition (I) is a glass transition temperature of the cured coating film obtained from the coating composition (I) of 40 to 115 ° C, preferably 50 to 105 ° C, from the corrosion resistance, acid resistance and processability of the coating film. Etc., it is suitable. In the present specification, the glass transition temperature of the coating film is obtained by using a DINAMIC VISCOELASTOMER MODEL VIBRON DDV-IIEA type (automatic dynamic viscoelasticity measuring machine manufactured by Toyo Baldwin Co., Ltd.) and measuring the change in tan δ measured at a temperature of 110 Hz. The maximum temperature.

When the coating composition (I) and the rust preventive pigment (C) are a combination of the above (1) vanadium compound, (2) cerium-containing compound, and (3) phosphate metal salt, the coating composition (I) is applied. The coating film formed on the galvanized steel sheet exhibits excellent corrosion resistance. The inventors of the present invention thought that the metal ions generated by the dissolution of the material metal by chloride ions or the like in a corrosive environment and the vanadium ions of five-valent vanadium ions (VO ₃ ^- , VO ₄ ^3-, etc.) Ion) directly forms a precipitating salt without redox; and a trivalent vanadium ion formed by a redox reaction between a pentavalent vanadium ion and a material metal, and a metal ion system and a niobate ion to form a precipitated salt Or a compound, which effectively covers the surface of the material, and the corrosion-removed portion and its peripheral system are adjusted to a suitable pH region in which the 5-valent vanadium ion and the material metal are subjected to a redox reaction, by simultaneously eluting the phosphate ions. reason. In particular, a zinc-plated steel sheet of a type having a low alloy content of a metal having a strong non-conducting action of aluminum is formed in a zinc-iron dissimilar metal battery forming portion such as an edge portion or a deep-cut portion to prevent rust. It is preferable that the component in which the pigment is eluted is formed into a film to form a film, and it is considered that the hydrogen phosphate metal salt is an important task as a component that strongly stabilizes the eluted environmental pH on the acidic side. Further, as the rust preventive pigment (C), by using the above (1), (2), and (3) in combination, it is possible to eliminate the salt tolerance and alkali resistance of each of (1), (2), and (3). And the shortcomings of water resistance. It is considered that the synergistic effect based on these rust preventive pigments strongly acts, and excellent corrosion resistance can be achieved.

Coating composition (II)

The coating composition (II) is a coating composition which is contained in a specific ratio: a hydroxyl group-containing coating film-forming resin (A), a crosslinking agent (B), and a metal niobate and/or metal ion-exchanged dioxide. Da (Da); a film-forming resin containing a phosphate group and/or a phosphate-containing coating film-forming resin (Db); and/or an azole compound (Dc).

Hydroxyl-containing coating film-forming resin (A)

The hydroxyl group-containing coating film-forming resin used in the coating composition (II) is a hydroxyl group-containing resin having a coating film-like energy property which can be generally used in the coating material, similarly to the coating composition (I). The resin can be used without any particular limitation. Typical examples of the resin include a hydroxyl group-containing polyester resin, an epoxy resin, an acrylic resin, a fluororesin, and a vinyl chloride resin. As the coating film-forming resin, at least one organic resin selected from the group consisting of a hydroxyl group-containing polyester resin and a hydroxyl group-containing epoxy resin can be suitably used.

The hydroxyl group-containing polyester resin includes an oil-free polyester resin, an oil-modified alkyd resin, and a modified product of the resins, for example, a urethane-modified polyester resin, a urethane modification. Alkyd resin, epoxy modified polyester resin, acrylic modified polyester resin, and the like. The hydroxyl group-containing polyester resin has a number average molecular weight of from 2,000 to 20,000, particularly from 3,000 to 15,000, a glass transition temperature (Tg) of from 0 to 70 ° C, particularly from 10 ° C to 50 ° C, and a hydroxyl value of from 5 to 80 mg KOH. /g, particularly in the range of 10 to 50 mgKOH/g is preferred.

Examples of the above oil-free polyester resin, alkyd resin, urethane-modified polyester resin, urethane-modified alkyd resin, epoxy-modified polyester resin, and acrylic-modified polyester resin include Illustrated in the coating composition (I). Among these polyester resins, in terms of balance of workability, corrosion resistance, and the like, an oil-free polyester resin or an epoxy-modified polyester resin is particularly preferable.

Preferred epoxy resins for the hydroxyl group-containing coating film-forming resin include bisphenol epoxy resins and novolak epoxy resins; and various modifiers for the epoxy resins in the epoxy resins. A modified epoxy resin obtained by reacting a base or a hydroxyl group. In the production of the modified epoxy resin, the modification period of the modifier is not particularly limited, and it may be modified in the middle of the production of the epoxy resin, or may be modified in the final stage of the production of the epoxy resin.

The bisphenol type epoxy resin, the novolak type epoxy resin, and the modified epoxy resin are exemplified as the coating composition (I).

Crosslinking agent (B)

In the same manner as the coating composition (I), the crosslinking agent (B) is formed by reacting the hydroxyl group-containing coating film-forming resin (A) to form a cured coating film, and can be combined with the above-mentioned hydroxyl group-containing resin by heating or the like. The coating film-forming resin (A) can be used without any particular limitation, and it can be used. Among them, an amine-based resin, a phenol resin, and a polyisocyanate compound which can also be blocked are preferred. These crosslinking agents can be used alone or in combination of two or more.

The amine-based resin, the phenol resin, and the polyisocyanate compound which may be blocked may be exemplified as the coating composition (I).

The ratio of the hydroxyl group-containing coating film-forming resin (A) to the crosslinking agent (B) is based on (A) and (B) in terms of corrosion resistance, boiling water resistance, workability, and hardenability. 100 parts by mass of the total solid content of the component, the hydroxyl group-containing coating film-forming resin (A) is 50 to 95 parts by mass, particularly 70 to 90 parts by mass, and the crosslinking agent (B) is 5 to 50 parts by mass, particularly It is preferably in the range of 10 to 30 parts by mass.

In order to improve the hardenability of the coating composition (II), the curing catalyst may be blended as necessary. As the curing catalyst, those exemplified in the coating composition (I) can be similarly exemplified.

When the crosslinking agent (B) is a combination of two or more kinds of crosslinking agents, it can be used by combining a curing catalyst effective for each crosslinking agent.

Compound (Da)

The compound (Da) is a compound selected from the group consisting of metal citrate and metal ion-exchanged cerium oxide.

The metal ruthenate is a salt composed of cerium oxide and a metal oxide, and may be any of a protopinate or a polysilicate. Examples of the citrate include calcium citrate, magnesium citrate, zinc citrate, aluminum citrate, aluminum orthosilicate, aluminum hydrated citrate, calcium aluminum citrate, sodium aluminum citrate, and aluminum bismuth citrate. Sodium citrate, calcium orthosilicate, calcium bismuth citrate, sodium calcium citrate, zirconium citrate, magnesium orthosilicate, magnesium metasilicate, calcium magnesium citrate, manganese citrate, strontium citrate, olivine, pomegranate Stone, vermiculite, heteropolar ore, blue cone, pillar, stone, beryl, diopside, ash, rhodochro, tremolite, hard strontium, talc, fisheye, aluminosilicate Boron citrate, citrate, feldspar, zeolite, and the like. As the metal citrate, it is preferred to contain calcium or magnesium. These metal silicates can be used alone or in combination of two or more.

Metal ion exchange cerium oxide

The metal ion-exchanged cerium oxide is a cerium oxide fine particle obtained by introducing a metal cation such as calcium ion into a fine porous cerium oxide carrier by ion exchange. Examples of the metal ion-exchanged cerium oxide include calcium ion-exchanged cerium oxide, magnesium ion-exchanged cerium oxide, and cobalt ion-exchanged cerium oxide.

As the metal ion-exchanged cerium oxide, cerium oxide fine particles having an average particle diameter of 0.5 to 15 μm, preferably 1 to 10 μm, and an oil absorption amount of 30 to 300 ml/100 g, preferably 30 to 150 ml/100 g, can be suitably used. Within the scope of the person.

As the metal ion-exchanged cerium oxide, in particular, calcium ion-exchanged cerium oxide can be suitably used. The commercially available product of the calcium ion-exchanged cerium oxide is, for example, SHIELDEX (registered trademark) C303, the same AC-3, and the same AC-5 (all of which are manufactured by W. R. Grace & Co.).

Metal ions such as calcium ions emitted from metal ion-exchanged ceria are related to electrochemical action and various salt formation actions, and are effective for improving corrosion resistance. Further, the ruthenium ion discharged from the metal ion-exchanged ceria plays a role in improving the white rust resistance of the plurality of layer coating films and suppressing peeling.

The metal ion-exchanged cerium oxide system may be used alone or in combination of two or more.

In the coating composition (II), from the viewpoint of white rust resistance, 100 parts by mass of the total solid content of the hydroxyl group-containing coating film-forming resin (A) and the crosslinking agent (B), the compound (Da) The amount is preferably from 3 to 50 parts by mass, preferably from 5 to 30 parts by mass. When the amount of the compound (Da) exceeds 50 parts by mass, the white rust resistance tends to be low, and this is considered to be because when the amount of the compound (Da) exceeds 50 parts by mass, the water resistance of the coating film is lowered.

In addition, from the viewpoint of the solubility of the water of the compound (Da) and the reactivity of the solution of the compound (Da) with the metal plate, it is added to 100 parts by mass of a 5 mass% aqueous solution of sodium chloride at 25 ° C. 1 part by mass of the compound (Da) was stirred at 25 ° C for 6 hours, and after standing for 24 hours, the pH of the filtrate after filtering the upper clear liquid was preferably 10 to 13. In terms of white rust resistance, it is more preferable in this range.

Film-forming resin containing a phosphate group and/or a film-forming resin (Db) containing a phosphate group

Among the coating film-forming resins (Db) containing a phosphoric acid (salt) group, the coating film-forming resin containing a phosphoric acid group contains a phosphate group [-OPO(OH)(OR ₁ )] (here, R ¹ -based hydrogen) The atom, the phenyl group or the alkyl group having 1 to 20 carbon atoms, particularly preferably a hydrogen atom or a 2 to 10 alkyl group, and the type of the resin is a resin-forming resin (A) which is a hydroxyl group-containing coating film. The crosslinking agent (B) is not particularly limited, and examples thereof include an acrylic resin, an epoxy resin, and a polyester resin.

The phosphoric acid group-containing acrylic resin can be obtained, for example, by copolymerizing a phosphoric acid group-containing unsaturated monomer with another polymerizable unsaturated monomer.

Examples of the phosphoric acid group-containing unsaturated monomer include acidic phosphoric acid (2-propenyloxyethyl) ester, acidic phosphoric acid (2-methylpropenyloxyethyl) ester, and acidic phosphoric acid (2-propene). Acidity of methoxypropyl)ester, acidic (2-methylpropenyloxypropyl) phosphate, 10-phosphomethoxydecyl acid phosphate, 10-methylpropenyl oxime acid phosphate Phosphate (meth) propylene decyl oxide (carbon number 2 to 20); epoxy resin such as glycidyl (meth) acrylate added to orthophosphoric acid or acid phosphate (carbon number: 1 to 20) The base is unsaturated monomer; KAYAMER PM-2, same as PM-21 (above, manufactured by Nippon Kayaku Co., Ltd., trade name). Here, examples of the acidic phosphate ester include acidic methyl phosphate, acid butyl phosphate, acid 2-ethylhexyl phosphate, acid isodecyl phosphate, acid lauryl phosphate, and acid tridecyl phosphate. Oleoyl acid phosphate and acid phenyl phosphate.

Examples of the other polymerizable monomer which is copolymerized with the phosphoric acid group-containing unsaturated monomer constituting the phosphoric acid group-containing acrylic resin include 2-hydroxyethyl (meth)acrylate and 2-methyl (meth)acrylate. a hydroxyl group-containing unsaturated monomer such as hydroxypropyl ester, 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether or 2-hydroxyethyl allyl ether; acrylic acid , methacrylic acid; vinyl aromatic compounds such as styrene, α-methylstyrene, vinyl toluene, α-chlorostyrene; methyl (meth)acrylate, ethyl (meth)acrylate, (a) Base) n-propyl acrylate, isopropyl (meth) acrylate, (meth)acrylic acid (n-, iso-, third) butyl ester, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, ( 2-ethylhexyl methacrylate, n-octyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, stearic acid (meth) acrylate, (methyl) An alkyl or cycloalkyl ester having 1 to 24 carbon atoms of acrylic acid or methacrylic acid such as isodecyl acrylate; vinyl acetate; vinyl chloride, vinyl ether, acrylonitrile, methacrylonitrile . In the present invention, "(meth)acrylic" means "acrylic acid or methacrylic acid".

Further, the phosphoric acid group-containing acrylic resin can be added with a phosphoric acid compound by a copolymerized resin having an epoxy group-containing unsaturated monomer such as glycidyl (meth)acrylate and the above other polymerizable unsaturated monomer. The method to get. As the additional phosphoric acid compound, orthophosphoric acid, acid phosphate or the like is suitable, and examples of the acidic phosphate ester include those exemplified as the acidic phosphate.

The phosphoric acid group-containing epoxy resin can be obtained by adding a phosphoric acid compound to an epoxy resin. Examples of the epoxy resin to which the phosphoric acid compound is added include a bisphenol type epoxy resin, a novolak type epoxy resin, and a modification in which various modifiers react with an epoxy group or a hydroxyl group in the epoxy resin. Epoxy resin, etc. The type of the phosphoric acid compound to be added can be similarly used in the description of the phosphoric acid group-containing acrylic resin, and is a phosphate compound added to a copolymerized resin having an epoxy group-containing unsaturated body and another polymerizable unsaturated monomer. Out.

The phosphoric acid group-containing polyester resin can be obtained, for example, by reacting a phosphoric acid compound with a hydroxyl group of the polyester resin. The type of the phosphoric acid compound to be reacted can be similarly used in the description of the phosphoric acid group-containing acrylic resin, and is exemplified as the phosphoric acid compound.

Among the coating film-forming resin containing a phosphate group or the phosphate-containing coating film-forming resin (Db), the phosphate-containing coating film-forming resin can be formed by using the above-mentioned phosphate-containing coating film. The phosphate group in the forming resin is obtained by reacting with a metal compound to form a ceric acid salt. Examples of the metal compound which reacts with the phosphoric acid group include calcium oxide, magnesium oxide, cobalt oxide, nickel oxide, zinc oxide, cerium oxide, cerium oxide, and the like.

The coating film-forming resin containing a phosphate group and/or the phosphate-containing coating film-forming resin can be suitably used, and has a number average molecular weight of 1,000 to 20,000, particularly 3,000 to 15,000, and a glass transition temperature (Tg) of 0. ～100°C, particularly 20°C to 60°C, an acid value of 20 to 120 mgKOH/g, particularly 30 to 100 mgKOH/g, and a hydroxyl value of 0 to 50 mgKOH/g, particularly 5 to 30 mgKOH/g.

The coating film-forming resin containing a phosphate group or the phosphate-containing coating film-forming resin (Db) is a coating film property such as white rust resistance (collection of zinc ions) and water resistance of the obtained coating film. In view of the above, the mass fraction of the component having a molecular weight distribution of 1,000 or less in the molecular weight distribution is 5 to 30% by mass, and particularly preferably 5 to 20% by mass from the viewpoint of having both the elution property of the resin component and the water resistance of the coating film. The range is better.

The phosphate group or the phosphate group of the coating film-forming resin (Db) containing a phosphoric acid (salt) group not only captures zinc ions, but also functions to enhance adhesion imparting property in an acidic environment and to improve corrosion resistance.

In the coating composition (II), a coating film-forming resin containing a phosphate group and/or a total of 100 parts by mass of the total solid content of the hydroxyl group-containing coating film-forming resin (A) and the crosslinking agent (B) The solid content of the phosphate-containing coating film-forming resin (Db) is 5 to 30 parts by mass, and is particularly preferably 10 to 20 parts by mass from the viewpoint of the water resistance and white rust resistance of the coating film.

In addition, a coating film-forming resin containing a phosphate group and/or a phosphate-containing coating film having a solid content of 1 part by mass per 100 parts by mass of a sodium carbonate aqueous solution having a concentration of 5 mass% at 25 ° C is added. The forming resin (Db) was stirred at 25 ° C for 6 hours, and then allowed to stand at 25 ° C for 24 hours, and then the pH of the filtrate after filtering the upper clear liquid was 3 to 7, from a film-forming resin based on a phosphate group-containing coating film. And/or the solubility of the phosphate-containing coating film-forming resin (Db) and the reactivity of the solution of the resin (Db) with the metal plate, particularly preferably 3 to 6, and from whitening resistance In terms of rust, this range is more preferable.

Azole compound (Dc)

The azole compound is a compound having a heterocyclic ring of 5 members, and the heterocyclic ring system contains one or more nitrogen atoms.

Examples of the azole compound include a thiazolyl group, a pyrazolyl group, a triazolyl group, a thiadiazolyl group, a tetrazolyl group, a benzotriazole group, and an imidazolyl group. Azolyl, carbazolyl, iso Azyl, isothiazolyl, Diazolyl, A compound such as a triazolyl group, a thiatriazole group, a bentazol group, a carbazolyl group, a benzimidazolyl group or the like.

Examples of the compound having a thiazolyl group include 2-N,N-diethylthiobenzothiazole, 2-hydrothiobenzothiazole, and the like.

Examples of the compound having a pyrazolyl group include pyrazole, 3,5-dimethylpyrazole, 3-methyl-5-pyrazole, and 3-amino-5-methylpyrazole.

Examples of the compound having a triazolyl group include 1,2,4-triazole, 3-amino-1,2,4-triazole, 3-hydrothio-1,2,4-triazole, and 5 - Amino-3-hydrothio-1,2,4-triazole, 2,3-dihydro-3-o-oxy-1,2,4-triazole, and the like.

Examples of the compound having a thiadiazolyl group include 5-amino-2-hydrothio-1,3,4-thiadiazole and 2,5-dihydrothio-1,3,4-thiazide. Diazole and the like.

Examples of the compound having a tetrazolyl group include 5-phenyl-1,2,3,4-tetrazole, 5-hydrothio-1-phenyl-1,2,3,4-tetrazole, and the like. .

Examples of the compound having a benzotriazole group include 1H-benzotriazole and 1-hydroxybenzotriazole (1 hydrate).

Among the above, from the viewpoint of white rust resistance, an azole compound having a triazolyl group or a thiadiazolyl group can be suitably used.

In the coating composition (II), the amount of the azole compound (Dc) is 2 to 30 parts by mass based on 100 parts by mass of the total solid content of the hydroxyl group-containing coating film-forming resin (A) and the crosslinking agent (B). From the viewpoint of the water resistance and white rust resistance of the coating film, it is particularly preferable from 3 to 20.

Further, the above azole compound (Dc) is also used in combination of two or more types.

Furthermore, from the viewpoint of solubility of water based on the azole compound (Dc) and reactivity of the solution of the azole compound (Dc) with the metal plate, the sodium carbonate aqueous solution having a concentration of 5 mass% at 25 ° C is contained in 100 parts by mass. 1 part by mass of the azole compound (Dc) was added, and the mixture was stirred at 25 ° C for 6 hours, and then allowed to stand at 25 ° C for 24 hours, and then the pH of the filtrate after filtering the upper clear liquid was 3 to 8, particularly 4 to 7. In terms of white rust resistance, it is more preferable in this range.

The above components (Da) to (Dc) may be used alone or in combination of two or more. For example, the component (Db), the component (Dc), the component (Da), the component (Dc), and the like can be used in combination.

In the coating composition (II), in addition to the hydroxyl group-containing coating film-forming resin (A), the crosslinking agent (B), the above components (Da) to (Dc), and the necessary curing catalyst, It is necessary to mix anti-rust pigments (other than (Da)), coloring pigments, filler pigments, UV absorbers, UV stabilizers, organic solvents, anti-settling agents, antifoaming agents, coating surface conditioners, etc., which can be used in the coating field. Additives, etc. The form of the coating composition (II) may be any of an organic solvent type coating material, an aqueous coating material, and a powder coating material.

The colored pigment, the filler pigment, the ultraviolet absorber, and the ultraviolet stabilizer can be similarly exemplified in the coating composition (I).

By disposing the ultraviolet absorber and/or the ultraviolet stabilizer in the coating material, it is possible to suppress the light reaching the surface of the coating film formed by using the coating composition (II) and causing the surface of the coating film formed by using the coating composition (II). Deterioration can prevent peeling between the coating film formed using the coating composition (II) and the upper coating film, and can maintain excellent corrosion resistance.

The organic solvent which can be blended in the coating composition (II) can be used as needed to improve the coating property of the coating composition (II), and a resin-containing coating film-forming resin (A) can be used. The crosslinking agent (B) and the components (Da), (Db) and/or (Dc) are dissolved or dispersed, and can be similarly exemplified in the coating composition (I), which can be used alone or in combination 2 Use more than one species.

The coating composition (II) is a glass transition temperature of the cured coating film obtained from the coating composition (I) of 10 to 80 ° C, and is 20 to 50 from the viewpoints of corrosion resistance, acid resistance, and processability of the coating film. °C is especially good.

A galvanized steel sheet is formed on a coating film formed by forming a plurality of coating films, and a coating film formed by forming a coating layer of the coating composition (II) on the uppermost layer forms an galvanized steel sheet exhibiting excellent white rust resistance. The inventors of the present invention consider the following as the reason.

The white rust of the galvanized steel sheet is particularly likely to be generated in the processed portion and the end surface portion and is caused by the formation of zinc oxide.

In order to prevent generation of white rust, it is only necessary to suppress zinc ions in the galvanized steel sheet from becoming zinc oxide. When the component (Da) is used, the coating film of the present invention forms a galvanized steel sheet by using at least 1 group selected from the group consisting of metal citrate and metal ion exchange cerium oxide which are selected from a source of phthalic acid ions. The coating layer formed of the coating composition (II) of the compound is formed on the uppermost layer of at least one of the front and back surfaces, and the ceric acid ions can be more efficiently generated from the plurality of coating films. When zinc ruthenate (ZnSiO ₃ , Zn ₂ SiO ₄ or the like) is formed by reacting the phthalic acid ion with zinc ions, generation of zinc oxide can be suppressed, and it is considered that the coating film of the present invention forms a galvanized steel sheet which is resistant to white rust. Very good sex.

When the component (Db) is used, the coating film of the present invention forms a galvanized steel sheet by using a coating film-forming resin containing a phosphate ion, that is, a phosphate-containing coating film-forming resin and/or a phosphate-containing coating film. The coating layer formed of the resin coating composition (II) is formed on the uppermost layer of at least one of the front and back surfaces, and the resin component having a phosphate (salt) group can be more effectively produced from the plurality of coating films. When the resin component containing the phosphoric acid (salt) group is reacted with zinc ions to form a resin component having a zinc phosphate group, generation of zinc oxide can be suppressed, and it is considered that the coating film of the present invention forms a galvanized steel sheet resistant to white rust. Very good sex.

When the component (Dc) is used, the coating film forming the galvanized steel sheet of the present invention can be formed on the uppermost layer of at least one of the front and back surfaces by using the coating composition (II) containing the azole compound. The azole compound is more efficiently produced from a plurality of layers of the coating film. When the azole compound is reacted with zinc ions to form a conjugated compound, the formation of zinc oxide can be suppressed, and it is considered that the galvanized steel sheet of the present invention is excellent in white rust resistance.

Coating film forming galvanized steel sheet and coating film forming method thereof

In the coating film of the present invention, the galvanized steel sheet is formed by forming a plurality of coating films on the surface of the galvanized steel sheet and forming a coating film of one or more layers on the back surface to form a galvanized steel sheet, and at least one of the front and back surfaces can be formed. The lowermost layer forms a coating layer of the coating composition (I), and the uppermost layer of at least one of the front and back surfaces is formed by forming a coating layer of the coating composition (II).

For example, a method of the following steps can be carried out to form a plurality of coating films on the surface of a galvanized steel sheet and to form one or a plurality of coating films on the back surface, and to coat the lowermost layer of at least one of the front and back surfaces of the galvanized steel sheet. a step of coating the composition (I); a step of curing the coating film obtained by using the coating composition (I); a step of applying the coating composition (II) on the uppermost layer of at least one of the front and back surfaces, and a coating to be used The step of hardening the coating film obtained by the composition (II).

The galvanized steel sheet having a zinc content of 10% by mass or more in the galvanized steel sheet-based plating layer may, for example, be a galvanized steel sheet, an galvanized steel sheet, or an aluminum-zinc alloy steel sheet containing about 5% of aluminum in the alloy. (eg "Galfan" (registered trademark)), galvanized steel such as galvanized steel-made parts; iron-zinc alloy steel plate (Galvanyl steel plate), aluminized-zinc alloy steel plate (the alloy contains about 55% aluminum) A galvanized alloy steel such as Galvalume steel plate, alloy containing approximately 5% of aluminum "Galfan", and galvanized alloy steel-made parts may be chemically treated on these surfaces. The chemical treatment may, for example, be a phosphate treatment such as zinc phosphate treatment or iron phosphate treatment, a composite oxide film treatment composed of a zirconium salt or the like, a chromium phosphate treatment, or a chromate treatment.

In the galvanized steel sheet for forming a coating film of the present invention, the coating composition (I) is applied to at least one of the front and back surfaces of the galvanized steel sheet to form a coating layer of the lowermost layer. The above coating composition (I) may also be applied to both sides of the front and back sides. When the coating composition (I) is applied to one side, the coating composition (I) is preferably applied to the surface (used on the outer surface) from the viewpoint of durability of the coated steel sheet and the like.

When the coating composition (I) is applied to one side, any (primer) coating may be applied to the other side. The (primer) coating material other than the coating composition (I) may, for example, be a (primer) coating material such as a polyester resin coating composition, an alkyd resin coating composition, or an acrylic resin coating composition.

After the formation of the lowermost coating layer, the coating layer of the lowermost layer may be formed into one or more coating layers as necessary in addition to the coating layer of the uppermost layer. Examples of the coating material for forming the coating layer of any of the coating materials include a polyester resin coating composition, an alkyd resin coating composition, and an acrylic resin coating composition.

After the lowermost coating layer is formed (or further, one or more coating layers are formed on the lowermost coating layer), the coating film layer of the uppermost layer is formed on the coating layer. On the back side, there is also a case where the uppermost coating layer is only one layer.

In the case where the coating composition (II) contains the component (Da) or the component (Db), it is preferred to form a galvanized steel sheet by forming a coating film having a plurality of coating films on both sides of the front and back surfaces of the galvanized steel sheet. Therefore, in the preferred embodiment, the coating film layer of the lowermost layer is formed on both sides of the front and back sides (or further, the coating film layer of one or more layers is formed on the coating film layer of the lowermost layer), and then the two sides are formed. A coating film layer of the uppermost layer is formed on the coating layer.

At least one of the back surface of the front surface is formed into the coating film layer of the uppermost layer by using the above coating composition (II). The above coating composition (II) can also be used to form the uppermost coating layer on both sides of the front and back. When the coating composition (II) is used to form the coating film layer of the uppermost layer, the coating layer formed using the coating composition (II) is formed on the back side from the viewpoint of weather resistance of the surface of the coated steel. (Used on the inward side) is preferred.

When the coating composition (II) is applied to one side, the coating layer may be formed by using any of the top coating materials on the other side.

Examples of the top coating material include a polyester resin coating composition, an alkyd resin coating composition, an acrylic resin coating composition, a cerium modified polyester resin coating composition, and a cerium modified acrylic resin coating. A coating material such as a composition or a fluororesin. When the use of a pre-coated steel sheet or the like is particularly important in terms of workability, a galvanized steel sheet having a particularly excellent workability can be obtained by using a polyester-based top coat for high-grade processing.

By forming each of the above-mentioned coating layers, it is possible to use a roll coating method, a curtain flow coating method, a spray method, a brush coating method, and a dipping method for each coating material including the coating composition (I) and the coating composition (II). It is carried out by a known method of coating and hardening it.

In the formation of each of the above-mentioned coating layers, only one side is coated and cured, and the other side is coated and hardened; and any method of simultaneously curing both sides of the front and back sides after coating both sides of the front and back sides To form a coating layer.

The thickness of the cured film of each of the coating layers is not particularly limited, and the thickness of the cured film of the coating composition using the coating composition (II) is preferably 2 to 20 μm, more preferably 3 to 10 μm, and any desired one. The thickness of the cured film of the coating layer of the primer coating is preferably 2 to 20 μm, more preferably 3 to 7 μm, and the thickness of the cured film using the coating layer of any of the top coatings is preferably 8 to 30 μm. More preferably, in the range of 10 to 25 μm, when a metal silicate and/or a metal ion-exchanged cerium oxide (Da) is used as a raw material of the coating composition (II), a coating layer of the coating composition (I) is used. The thickness of the cured film is preferably 2 to 20 μm, more preferably 3 to 7 μm. When a coating film-forming resin containing a phosphoric acid group and/or a phosphate-containing coating film-forming resin (Db) or an azole compound (Dc) is used as the coating composition (II), coating with the coating composition (I) is used. The thickness of the cured film of the film layer is preferably 2 to 10 μm, more preferably 3 to 7 μm.

The curing of the coating film may be appropriately set according to the type of the resin used in each of the above-mentioned coating materials, and when the coating is performed continuously by a coating method such as a coil coating method, the maximum temperature of the material is usually 160. Baking for 15 to 60 seconds at -250 ° C, preferably 180 to 230. When batch baking is used, it can usually be baked at 80 to 200 ° C for 10 to 30 minutes.

In the curing of the coating film, depending on the type of the resin used in the coating material and the like, when the crosslinking reaction in the coating film formation process does not require special heating, it can be cured in accordance with a usual method and using a normal temperature drying.

In the coating film of the present invention, a galvanized steel sheet is formed, and a galvanized steel sheet is formed as a coating film having a preferable coating film structure, and the following two types are exemplified.

1. The coating composition is formed using the coating composition (I) on the lowermost layer of the surface (the surface to be used outward), and the coating layer is formed by using the coating composition (II) on the uppermost layer on the opposite side of the back side. The film forms a galvanized steel sheet.

In the above 1, the bottom layer (the surface to be used inwardly) is formed by using any primer coating material to form a coating layer. Further, at least one of the front and back surfaces may be formed into one or more coat layers by using any coating material as necessary.

By forming the coating film layer of the lowermost layer on both sides (and further forming at least one of the front and back surfaces by using any coating material), the uppermost layer of the back surface is coated with the coating composition (II). The film layer and the uppermost layer of the surface are formed into a coating film layer using any coating material containing the coating composition (II).

In the above 1, the back surface layer may be a coating layer using only the coating composition (II).

2. The coating layer using the coating composition (I) is formed on the lowermost layer on both sides of the front and back, and the coating layer using the coating composition (II) is formed on the uppermost layer of the back surface (the surface to be used inward). The film forms a galvanized steel sheet.

After the formation of the coating film of the lowermost layer, at least one of the front and back surfaces may be formed into one or more coating layers by using any coating material as necessary.

After the coating film layer of the lowermost layer is formed on both sides (and at least one of the front and back surfaces is formed into one or more coating layers by using any coating material), the coating layer of the coating composition (II) is formed on the uppermost layer of the back surface. And at the uppermost layer of the surface, it is formed into a coating layer using any coating material containing the coating composition (II).

Hereinafter, the present invention will be more specifically described by way of production examples, examples, and comparative examples. However, the present invention is not limited by the terms. In each case, "parts" and "%" are based on quality unless otherwise specified. Further, the film thickness of the coating film is based on a cured coating film.

[Examples] Production of polyester resin 1 Production example a1 Synthesis of polyester resin Aa1 solution

In a reaction tank equipped with a stirrer, a thermometer, a reflux condenser or the like, the following raw material mixture was added, and the temperature was raised from 160 ° C to 230 ° C over 3 hours, and the produced water was distilled off through a rectification column. After maintaining at 230 ° C for 1 hour, xylene was added thereto, and xylene was dehydrated while refluxing at 230 ° C to carry out an esterification reaction.

Ethylene glycol 0.9mol

Neopentyl glycol 0.1mol

Isophthalic acid 0.95mol

When the acid value was approximately 0, it was cooled to 140 ° C and kept for 2 hours. After cooling, SWAZOL 1500 (available from Maruzen Petrochemical Co., Ltd., a high-boiling aromatic petroleum solvent) was added to obtain a solid content of 35%. Ester resin Aa1 solution. The obtained resin had a number average molecular weight of 3,800, a glass transition temperature of 45 ° C, a hydroxyl value of 30 mgKOH/g, and an acid value of about 0 mgKOH/g.

Manufacture of phenolic resin 1 Production Example a2 Production of Soluble-Form Phenolic Resin Ba1 Solution

In the reaction vessel, 100 parts of bisphenol A, 178 parts of 37% aqueous formaldehyde solution and 1 part of sodium hydroxide were added, and the mixture was reacted at 60 ° C for 3 hours, and then dehydrated at 50 ° C for 1 hour under reduced pressure. Subsequently, 100 parts of n-butanol and 3 parts of phosphoric acid were added, and the reaction was carried out at 110 to 120 ° C for 2 hours. After completion of the reaction, the sodium phosphate produced by filtering the obtained solution was separated by filtration to obtain a resol type phenol resin Ba1 solution having a solid content of 50%. The obtained resin coefficient had an average molecular weight of 880 and the average number of methylol groups per nucleus of the benzene nucleus was 0.4 and the average number of alkoxymethyl groups was 1.0.

Manufacturing of coating composition (I) 1 Manufacturing example a3

90 parts of EPICOAT #1009 (manufactured by JAPAN EPOXY RESINS, bisphenol A type epoxy resin, hydroxyl group-containing resin) was dissolved in 135 parts of mixed solvent 1 [cyclohexanone / ethylene glycol monobutyl ether / Solveso 150 ( 225 parts epoxy resin solution made by ESSO Petroleum Co., Ltd., high boiling point aromatic hydrocarbon solvent) = 3/1/1 (mass ratio), mixing 20 parts of vanadium pentoxide, 20 parts of calcium phosphate, 20 parts of citric acid Calcium, 20 parts of titanium dioxide, 20 parts of barium oxide (baryta) and a suitable amount of mixed solvent 2 [Solveso 150 (manufactured by ESSO Petroleum Co., Ltd., high-boiling aromatic hydrocarbon solvent) / cyclohexanone = 1 / 1 (mass ratio)] Further, the pigment is dispersed until the particles (particle diameter of the pigment fine particles) are 20 μm or less. Subsequently, 13.3 parts (10 parts by weight of solid content) of DESMODUR BL-3175 (manufactured by BAYER URETHANE Co., Ltd., and blocked with methyl ethyl ketoxime) was added to the dispersion to form HDI isocyanurate. Type of polyisocyanate compound solution, solid content of about 75%), and 1 part (solid content: 0.1 part) TAKENATE TK-1 (manufactured by Takeda Pharmaceutical Co., Ltd., organotin-based capping agent dissociation catalyst, solid content about 10%) The mixture was uniformly mixed, and adjusted to a viscosity of about 80 seconds (Ford-cup #4/25 ° C) by adding the above mixed solvent 2 to obtain a coating composition (I-1a).

Manufacturing example a4 to a10

In the production example a3, except for the hydroxyl group-containing resin, the crosslinking agent, the rust preventive pigment, the other pigment, and the catalyst, as shown in the following Table 1, the coating composition was obtained in the same manner as in Production Example a3 (I- 2a) to (I-8a). The amount of each component of Table 1 is expressed by the mass of the solid component.

In Tables 1 and 2, the (note) in the table has the following meanings.

(Note 1) SYMEL 303: manufactured by Sytec Industries Co., Ltd., Japan, trade name, methyl etherified melamine resin;

(Note 2) K-White G105: Magnesium oxide treated product of TAYCA, trade name, and aluminum dihydrogen phosphate;

(Note 3) Shieldex C303: manufactured by W. R. Grace & Co., trade name, calcium ion exchange cerium oxide;

(Note 4) Co ion-exchanged cerium oxide: cobalt ion-exchanged cerium oxide, and 10 parts by mass of SAILISIA 710 (Fuji SILYSIA Chemical Co., Ltd., product) in 10,000 parts by mass of a 5 mass% cobalt chloride aqueous solution Name, cerium oxide microparticles, oil absorption of about 105ml / 100g) stirred and mixed for 5 hours, filtered to remove the solid component, the solid component is fully washed with water and dried to obtain Co ion exchange cerium oxide;

(Note 5) Nacure 5225: manufactured by King Industries, trade name, amine neutralizer of dodecylbenzenesulfonic acid;

(Note 6) Mg ion-exchanged cerium oxide: magnesium ion-exchanged cerium oxide, and 10 parts by mass of SAILISIA 710 (Fuji SILYSIA Chemical Co., Ltd., product) in 10,000 parts by mass of a 5 mass% aqueous magnesium fluoride solution Name, cerium oxide microparticles, oil absorption of about 105ml / 100g) stirred and mixed for 5 hours, filtered to remove the solid component, the solid component is fully washed with water and dried to obtain Mg ion-exchanged cerium oxide;

Further, the coating composition (I-8a) is a coating composition containing a conventional chromium-based rust-preventive pigment, and is used for reference.

Manufacturing of coating composition (II) 1 Manufacturing example a11

214.3 parts (75 parts of resin solid content) was used to produce the polyester resin Aa1 solution prepared in Example a1, and 15 parts of calcium citrate, 30 parts of titanium dioxide, 40 parts of barium oxide, and an appropriate amount of mixed solvent 2 were mixed (made with In the same manner as in Example a3, the pigment was dispersed to the particles (particle diameter of the pigment coarse particles) to be 20 μm or less.

Subsequently, 25 parts of SYMEL 303 (Note 1) was added to the dispersion and uniformly mixed, and the viscosity was adjusted by adding 3 parts (solid content: 1 part) Nacure 5255 (Note 5, refer to the above) and the above mixed solvent 2 The coating composition (II-1a) was obtained in about 80 seconds (Ford-cup #4/25 ° C).

Manufacturing example a12 to a20

In the production example a11, except that the hydroxyl group-containing resin, the crosslinking agent, the rust preventive pigment, the other pigment, and the catalyst were as shown in the following Table 2, the same procedure as in Production Example a11 was carried out to obtain each coating composition (II- 2a) ~ (II-10a). The amount of each component of Table 2 is expressed by the mass of the solid component.

In Table 2, 1 part of the compound (Da) of each coating composition (II) was added to 100 parts by mass of a 5 mass% aqueous sodium chloride solution at 25 ° C, and the mixture was stirred at 25 ° C for 6 hours, and then allowed to stand at 25 ° C. The pH of the filtrate (the pH of the compound (Da) solution) after filtering the upper clear liquid after 24 hours was also shown.

Further, the coating compositions (II-8a) and (II-9a) are used in comparative examples. Further, the coating composition (II-10a) is a coating composition containing a conventional chromium-based rust-preventive pigment, and is used for reference.

Manufacture of coating composition (III) 1 Manufacturing example a21

In the polyester resin Aa1 solution produced in the production example a1, 214.3 parts (resin solid content: 75 parts), 30 parts of titanium dioxide, 40 parts of barium oxide, and an appropriate amount of the mixed solvent 2 (the same as the production example a3) were mixed and carried out. The pigment is dispersed until the particles (particle diameter of the pigment fine particles) are 20 μm or less.

Subsequently, 25 parts of SYMEL 303 (Note 1) was added to the dispersion and uniformly mixed, and the viscosity was adjusted by adding 3 parts (1 part of solid content) of Nacure 5225 (Note 5; refer to the above) and the above mixed solvent 2 The coating composition (III-1a) was obtained in about 80 seconds (Ford-cup #4/25 ° C).

Production of galvanized steel sheet by coating film 1 Example a1

In the chemical treatment of Galvalume steel plate (plate thickness 0.4mm, aluminized-zinc alloy steel plate, alloy containing about 55% aluminum, plating alloy weight per unit area 150g / m ² ), using a bar coater to dry the film The coating composition (I-1a) obtained in Production Example a3 was applied to a thickness of 5 μm, and baked at a maximum temperature of 180 ° C for 30 seconds to form a lower back coating film. The coating composition obtained in Production Example a3 was applied to the steel sheet surface on the surface opposite to the lower back coating film of the coating sheet on which the lower back surface coating film was formed by using a bar coater so that the dried film thickness was 5 μm. (I-1a), and baked at a maximum temperature of 220 ° C for 40 seconds to form a lower surface coating film.

Subsequently, on the undercoat film of the lower layer, the coating composition (II-1a) obtained in Production Example a10 was applied in a dry film thickness of 10 μm using a bar coater, and the material reached a maximum temperature of 200 ° C. Baking was performed for 30 seconds to form an upper back coating film.

After cooling, KP COLOR 1580B40 (manufactured by Kansai PAINT Co., Ltd., trade name, polyester resin coating, blue, hardened coating film) was applied to the lower surface coating film by a bar coater at a dry film thickness of 15 μm. The glass transition temperature was about 70 ° C), and baking was performed for 40 seconds so that the material reached the maximum temperature of 220 ° C to obtain a coating film to form a galvanized steel sheet No. 1a.

Examples a2 to a17, Comparative Examples a1 to a2, and Reference Example a1

In the example a1, the galvanized steel sheets No. 2a to 20a were formed in the same manner as in the example a1 except that the coating composition used for the surface and the back surface was as shown in Table 3 below.

Moreover, in Table 3, it means that the coating composition of the ○ mark is apply|coated to each layer of the back surface.

Film performance test 1

Each of the coating films obtained in the above Examples a1 to a17, Comparative Examples a1 to a2, and Reference Example a1 was used as a test plate for forming galvanized steel sheets No. 1a to 20a, and the properties of the respective coating films were carried out in accordance with the following Test Method 1. test. The test results are shown in Table 3 below.

Test method 1 Production of test strips

Each of the test panels was cut to have a size of 6 cm × 12 cm so that the burrs on the side of the long side were coated toward the front side, and the right side was toward the front side and the left side was toward the back side. Each test piece was obtained by cutting the center of the surface of each test plate after cutting with a cross-cut of the ridge of the dicing blade to an angle of 30 degrees and a line width of 0.5 mm.

For each test piece, a composite corrosion test (CCT: JIS K5621) was performed for 200 cycles, and the following criteria were used to evaluate the corrosion;

Edge rust appearance: use visual inspection and evaluation according to the following criteria;

A: It is almost impossible to observe the production of white rust.

B: the same degree as the reference example containing chromium

C: A little white rust was observed.

D: The generation of white rust is significant, or a little observed, but red rust can also be observed.

Evaluation of edge expansion: The average value of the degree of expansion from the left and right edges of the front and back sides is judged according to the following;

A: less than 5mm

B: 5mm or more and less than 10mm

C: 10mm or more and less than 20mm

D: More than 20 mm.

The cutting portion: the ratio of the length of the white rust generated by cutting the wide exposed portion at 0.5 mm, and the expansion width extending to both sides across the cut portion, and evaluated according to the following criteria;

A: The white rust generation length ratio at the exposed portion of the texture is less than 50% and the expansion width is less than 3 mm.

B: The white rust generation length ratio in the exposed portion of the texture is 50% or more and the expansion width is less than 3 mm, or the white rust generation length ratio in the exposed portion of the texture is less than 50% and the expansion width is 3 mm or more and less than 5 mm.

C: The white rust generation length ratio in the exposed portion of the texture is 50% or more and the expansion width is 5 mm or more and less than 10 mm.

D: The white rust generation length ratio in the exposed portion of the texture is 50% or more and the expansion width is 10 mm or more.

The moisture resistance test (50 ° C, relative humidity 98%, 500 hours) was carried out, and the corrosion was evaluated according to the following criteria;

Edge rust appearance: use visual inspection and evaluation according to the following criteria;

A: It is almost impossible to observe the production of white rust.

B: the same degree as the reference example containing chromium

C: A little white rust was observed.

D: The generation of white rust is significant, or a little observed, but red rust can also be observed.

Evaluation of the edge expansion: the average value of the degree of expansion from the left and right edges of the front and back, according to the following evaluation;

A: less than 2mm

B: 2mm or more and less than 4mm

C: 4mm or more and less than 7mm

D: More than 7 mm.

Comprehensive evaluation: It is important to form a galvanized steel sheet on the coating film, and the white rust resistance of the processed portion and the end surface portion is high. Therefore, use the following benchmarks for comprehensive evaluation:

A: The evaluation of the edge rust appearance, the edge expansion appearance and the cut portion after the above composite corrosion test, and the edge rust appearance and the edge expansion appearance after the moisture resistance test are all A or B, and at least one is A.

B: All the above 5 project lines are B

C: All of the above 5 items are A, B or C, and at least one is C

D: At least one of the above five items is D.

Production of polyester resin 2 Production Example b1, Synthesis of Polyester Resin Ab1 Solution

The polyester resin Aa1 obtained in Production Example a1 was used as the polyester resin Ab1 in the following examples.

Manufacture of phenolic resin 2

Production Example b2, Production of Solvent Novolak Phenolic Resin Bb1 Solution The novolac type phenol resin Ba1 obtained in Production Example a2 was used as the resol type phenol resin Bb1 in the following examples.

Production of a resin containing a phosphate (salt) group 1

In the production example b3, the phosphoric acid group-containing resin Db1 was added to the reaction vessel, and 100 parts of butanol was added thereto, and while maintaining the temperature in the reaction vessel at 110 ° C, the following composition was added dropwise to the monomer raw material in advance for 3 hours. mixture;

Styrene 50 parts

2-ethylhexyl methacrylate 35 parts

Glycidyl methacrylate 15 parts

2,2'-azobisisobutyronitrile 3 parts

Subsequently, 0.5 part of 2,2'-azobisisobutyronitrile was further added and the reaction was carried out at 110 ° C for 2 hours. Subsequently, the temperature in the reaction vessel was 80 ° C, and 12.2 parts of 85% orthophosphoric acid and 10.4 parts of butanol were slowly added, and the reaction was carried out for 1 hour until the turbidity in the reaction vessel disappeared, thereby obtaining a solid content of 50%. Phosphate-based acrylic resin Db1 solution. The obtained phosphoric acid group-containing acrylic resin Db1 has an acid value of 54 mgKOH/g (phosphoric acid group concentration: 0.096 equivalent/100 g resin), and a mass ratio of a component having a molecular weight distribution and a molecular weight of 1,000 or less is 20% (from the GPC chart area). The ratio is calculated. The following, the same).

Production Example b4, Production of Phosphate Group-Based Acrylic Resin Db2

Adding 100 parts of butanol to the reaction vessel, and maintaining a temperature in the reaction vessel at 110 ° C for 3 hours, dropping a premixed monomer raw material or the like into a mixture of the following composition;

Styrene 40 parts

2-ethylhexyl methacrylate 30 parts

Glycidyl methacrylate 30 parts

2,2'-azobisisobutyronitrile 3 parts

Subsequently, 0.5 part of 2,2'-azobisisobutyronitrile was further added and the reaction was carried out at 110 ° C for 2 hours. Subsequently, the temperature in the reaction vessel was 80 ° C, and 25 parts of 85% orthophosphoric acid and 17 parts of butanol were slowly added, and the reaction was carried out for 1 hour until the turbidity in the reaction vessel disappeared, thereby obtaining a solid content of 50%. Phosphate-based acrylic resin Db2 solution. The obtained phosphoric acid group-containing acrylic resin Db2 had an acid value of 98 mgKOH/g (phosphoric acid group concentration: 0.17 equivalent/100 g of resin), and a mass ratio of a component having a molecular weight distribution and a molecular weight of 1,000 or less was 27%.

Production Example b5, Production of Phosphate-Based Acrylic Resin Db3

In a sturdy glass container, 100 parts (solid content: 50 parts) of a 50% phosphoric acid-containing acrylic resin Db1 solution obtained in the production example b3, and 5 parts of calcium oxide which has been ground using a mortar are prepared. The glass beads were filled and dispersed to a resin solution using a Skandex disperser to be transparent. Then, it was allowed to stand at room temperature for 48 hours. Subsequently, a phosphate (calcium salt)-containing acrylic resin Db3 having a solid content of 53% was obtained by removing the glass beads.

Manufacture of coating composition (I) 2 Manufacturing example b6

The coating composition (I-1a) produced in Production Example a3 was used as the coating composition (I-1b) in the following examples.

Manufacturing example b7 to b13

In the production example b6, except that the hydroxyl group-containing resin, the crosslinking agent, the rust preventive pigment, the other pigment, and the catalyst were as shown in the following Table 4, each coating composition was obtained in the same manner as in Production Example b6 (I- 2b) ~ (I-8b). The amount of each component of Table 4 is expressed by the mass of the solid component.

In Tables 4 and 5, the (Note) in the table are as described in Tables 1 and 2 above.

Further, the coating composition (I-8b) is a coating composition containing a conventional chromium-based rust-preventing pigment, and is used in the reference example.

Manufacture of coating composition (II) 2 Manufacturing example b14

214.3 parts (75 parts of resin solid content), the polyester resin Ab1 solution produced in the production example b1, and 20 parts (resin solid content: 10 parts) of the phosphoric acid group-containing acrylic resin Db1 solution produced in the production example b3, and 30 parts of titanium dioxide were mixed. 40 parts of barium oxide and an appropriate amount of mixed solvent 2 (the same as in the production example b6) were used to disperse the pigment to particles (particle diameter of the pigment coarse particles) of 20 μm or less.

Subsequently, 25 parts of SYMEL 303 (Note 1) was added to the dispersion and uniformly mixed, and adjusted to a viscosity of about 80 seconds by adding 3 parts (1 part of solid content) of Nacure 5255 (Note 5) and the above mixed solvent 2 (Ford-cup #4/25 ° C) to obtain a coating composition (II-1b).

Manufacturing example b15 to b23

In the production example b14, except that the hydroxyl group-containing resin, the crosslinking agent, the rust preventive pigment, the other pigment, and the catalyst were as shown in the following Table 5, the same procedure as in Production Example b14 was carried out to obtain each coating composition (II- 2b) ~ (II-10b). The amount of each component of Table 5 is expressed by the mass of the solid component.

In Table 5, 1 part by weight of a phosphoric acid (salt) group-containing resin (Db) of each coating composition (II) was added to 100 parts by mass of a 5 mass% aqueous sodium chloride solution at 25 ° C, and stirred at 25 ° C. After the lapse of 24 hours, the pH of the filtrate (the pH of the compound (Db) solution) after filtering the upper clear liquid was also shown.

Further, the coating compositions (II-8b) and (II-9b) were used as comparative examples.

Further, the coating composition (II-10b) is a coating composition containing a conventional chromium-based rust-preventive pigment, and is used for reference.

Manufacture of coating composition (III) 2 Manufacturing example b24

In the following examples, the coating composition (III-1a) produced in Production Example a20 was used as the coating composition (III-1b).

Production of galvanized steel sheet by coating film 2 Example b1

The same operation as in Example a1 was carried out except that the coating composition (II-1b) obtained in Production Example b14 was used instead of the coating composition (II-a) to obtain a coating film to form a galvanized steel sheet No. 1b.

Examples b2 to b17, Comparative Examples b1 to b2, and Reference Example b1

In the example b1, except that the coating composition used for the surface and the back surface was set to Table 6 to be described later, the same operation 1 as in Example b1 was carried out to obtain galvanized steel sheets No. 2b to 20b for each coating film.

Further, in Table 6, it means that the coating composition containing the ○ mark is applied to each layer on the back surface of the front and back.

Film performance test 2

A coating film performance test was carried out in the same manner as in Test Method 1 except that each of the coating films obtained in the above Examples b1 to b17, Comparative Examples b1 to b2, and Reference Example b1 was used to form galvanized steel sheets No. 1b to 20b. The test results are shown in Table 6 below.

Production of polyester resin 3 Production Example c1 Synthesis of Polyester Resin Ac1 Solution

The polyester resin Aa1 obtained in Production Example a1 was used as the polyester resin Ac1 in the following examples.

Manufacture of phenolic resin 3

Production Example c2 Production of Solvable Phenolic Resin Bc1 Solution The novolac type phenol resin Ba1 obtained in Production Example a2 was used as the resol type phenol resin Bc1 in the following examples.

Production of a phosphate group-containing resin 2 Production Example c3 Production of Phosphate-Based Acrylic Resin Db1

As the phosphoric acid group-containing acrylic resin Db1, the phosphoric acid group-containing acrylic resin Db1 produced in Production Example b3 was used.

Manufacture of coating composition (I) 3 Manufacturing example c4

The coating composition (I-1a) produced in Production Example a3 was used as the coating composition (I-1c) in the following examples.

Manufacturing example c5 to c11

In the production example c4, except for the hydroxyl group-containing resin, the crosslinking agent, the rust preventive pigment, the other pigment, and the catalyst, as shown in the following Table 7, the same coating composition was obtained in the same manner as in Production Example c4 (I- 2c) ~ (I-8c). The amount of each component of Table 7 is expressed by the mass of the solid component.

In Tables 7 and 8, the (Note) in the Table are as described in Tables 1 and 2 above.

Further, the coating composition (I-8c) is a coating composition containing a conventional chromium-based rust-preventive pigment, and is used as a reference example.

Production of coating composition (II) 3 Manufacturing example c12

In 214.3 parts (75 parts of resin solid content), the polyester resin Ac1 solution produced in Example c1 was mixed, and 10 parts of 3-amino-1,2,4-triazole, 30 parts of titanium dioxide, and 40 parts of barium oxide (baryta) were mixed. An appropriate amount of the mixed solvent 2 (the same as in Production Example c4) was used to carry out pigment dispersion to particles (particle diameter of the pigment coarse particles) of 20 μm or less.

Subsequently, 25 parts of SYMEL 303 (Note 1) was added to the dispersion and uniformly mixed, and adjusted to a viscosity of about 80 seconds by adding 3 parts (1 part of solid content) of Nacure 5255 (Note 5) and the above mixed solvent 2 (Ford-cup #4/25 ° C) to obtain a coating composition (II-1c).

Manufacturing examples c13 to c23

In the production example c12, the hydroxyl group-containing resin, the crosslinking agent, the rust preventive pigment, the other pigment, and the catalyst (and, if necessary, the phosphoric acid group-containing resin) are as shown in the following Table 8, and the same as in Production Example c12. Each of the coating compositions (II-2c) to (II-12c) was obtained. The amount of each component of Table 8 is expressed by the mass of the solid component.

In Table 8, after adding 1 part of the azole compound (Dc) of each coating composition (II) in 100 parts by mass of a 5 mass% aqueous sodium chloride solution at 25 ° C and stirring at 25 ° C for 6 hours, After standing at 25 ° C for 24 hours, the pH of the filtrate after filtration of the supernatant liquid (pH of the solution of the azole compound (Dc)) was also shown.

Further, the coating compositions (II-10c) and (II-11c) are used as comparative examples.

Further, the coating composition (II-12c) is a coating composition containing a conventional chromium-based rust-preventive pigment, and is used as a reference example.

Manufacture of coating composition (III) 3 Manufacturing example c24

In the following examples, the coating composition (III-1a) produced in Production Example a20 was used as the coating composition (III-1c).

Production of galvanized steel sheet by coating film 3 Example c1

In the chemical treatment of Galvalume steel plate (plate thickness 0.4mm, aluminized-zinc alloy steel plate, alloy containing about 55% aluminum, plating alloy weight per unit area 150g / m ² ), using a bar coater to dry the film The coating composition (I-1c) obtained in Production Example c4 was applied in a thickness of 5 μm, and baked at a maximum temperature of 180 ° C for 30 seconds to form a lower back coating film. The coating composition obtained in Production Example c4 was applied to the steel sheet surface on the surface opposite to the lower back coating film of the coating sheet on which the lower back coating film was formed by using a bar coater so that the dried film thickness was 5 μm. (I-1c), and baked at a maximum temperature of 220 ° C for 40 seconds to form a lower surface coating film.

Subsequently, on the undercoat film of the lower layer, the coating composition (II-1c) obtained in Production Example c12 was applied in a dry film thickness of 10 μm using a bar coater, and the material was brought to a maximum temperature of 200 ° C. Baking was performed for 30 seconds to form an upper back coating film.

After cooling, KP COLOR 1580B40 (manufactured by Kansai PAINT Co., Ltd., trade name, polyester resin coating, blue, hardened coating film) was applied to the lower surface coating film by a bar coater at a dry film thickness of 15 μm. The glass transition temperature was about 70 ° C), and baking was performed for 40 seconds so that the material reached the maximum temperature of 220 ° C to obtain a coating film to form a galvanized steel sheet No. 1c.

Examples c2 to c20, Comparative Examples c1 to c3, and Reference Example c1

In the same manner as in Example a1 except that the coating composition used for the surface and the back surface was as shown in Table 9 below, the coating film was formed into galvanized steel sheets No. 2c to 24c.

Further, in Table 9, it means that the coating composition of the ○ mark is applied to each layer on the back surface of the front and back.

Film performance test 3

Each of the coating films obtained in the above Examples c1 to c20, Comparative Examples c1 to c3, and Reference Example c1 was used as a test plate for forming galvanized steel sheets No. 1c to 24c, and the properties of the respective coating films were carried out in accordance with the following Test Method 1. test. The test results are shown in Table 9 below.

Claims (14)

A coating film forms a galvanized steel sheet which is formed by forming a plurality of coating films on the surface of a galvanized steel sheet and forming one or a plurality of coating films on the back surface, and forming the following coating composition on at least one of the lowermost layers of the front and back surfaces. a coating layer of the material (I), and a coating layer of the following coating composition (II) is formed on the uppermost layer of at least one of the front and back surfaces; a coating composition (I): a coating film containing (A) a hydroxyl group-containing coating film a coating composition of a forming resin, (B) a crosslinking agent, and (C) a rust-preventing pigment, and an anti-rust pigment (100 parts by mass based on the total solid content of the resin (A) and the crosslinking agent (B) The amount of C) is 10 to 150 parts by mass; the coating composition (II): a coating composition comprising (A) a hydroxyl group-containing coating film-forming resin and (B) a crosslinking agent, and further containing (Db) At least one resin selected from the group consisting of a coating film-forming resin containing a phosphoric acid group and a coating film-forming resin containing a phosphate group, and the resin (A) and the crosslinking agent (B) 100 parts by mass of the total solid content, the amount of the resin (Db) is 5 to 30 parts by mass, or more (Dc) of the azole compound, and the combination with the resin (A) and the crosslinking agent (B) 100 parts by mass of the solid component, the amount of the (Dc) azole compound is 2 to 30 parts by mass, and the (Dc) azole compound is at least 1 selected from the group consisting of a triazole compound and a compound having a thiadiazolyl group. And the triazole compound is selected from the group consisting of 1,2,4-triazole, 3-amino-1,2,4-triazole, 3-hydrothio-1,2,4-triazole, At least one of the group consisting of 5-amino-3-hydrothio-1,2,4-triazole and 2,3-dihydro-3-oxo-1,2,4-triazole . For example, the coating film of the first application of the patent scope forms a galvanized steel sheet, wherein galvanizing The zinc content in the plating layer of the steel sheet is 10% by mass or more. The coating film of the first aspect of the patent application form a galvanized steel sheet, wherein the hydroxyl group-containing coating film-forming resin (A) is selected from the group consisting of a hydroxyl group-containing polyester resin and a hydroxyl group-containing epoxy resin. At least one resin. The coating film of the third application of the patent application form a galvanized steel sheet, wherein the hydroxyl group-containing coating film forming resin (A) of the coating composition (II) is a hydroxyl group-containing polyester resin. The coating film of claim 1 is formed into a galvanized steel sheet, wherein the crosslinking agent (B) is selected from the group consisting of an amine resin, a phenol resin, and a polyisocyanate compound which may also be blocked. 1 kind of crosslinking agent. The coating film according to claim 1 of the patent scope forms a galvanized steel sheet, wherein the rust preventive pigment (C) is (1) selected from the group consisting of vanadium pentoxide, calcium vanadate, ammonium metavanadate and magnesium vanadate. At least one of a vanadium compound, (2) a ruthenium-containing compound, and (3) a phosphate-based metal salt. The coating film of claim 6 forms a galvanized steel sheet, wherein the phosphate metal salt (3) is selected from the group consisting of calcium phosphate, calcium monohydrogen phosphate, calcium dihydrogen phosphate, and metal elements such as magnesium, aluminum, zinc or The calcium tripolyphosphate metal salt constitutes at least one metal salt in the group. The coating film according to the first aspect of the patent application form a galvanized steel sheet in which the mass fraction of the component having a molecular weight of 1000 or less in the molecular weight distribution of the resin (Db) is 5 to 30% by mass. The galvanized steel sheet is formed by coating a coating film according to the first aspect of the invention, wherein 1 part by mass of the compound (Db) is added to 100 parts by mass of a 5 mass% aqueous sodium chloride solution at 25 ° C and stirred at 25 ° C for 6 hours. At 25 ° C After standing for 24 hours, the pH of the filtrate obtained by filtering the upper clear liquid was 3-7. The coating film of the first application of the patent application form a galvanized steel sheet, wherein the coating composition (I) further contains one pigment selected from the group consisting of cerium oxide and a filler pigment. The coating film of claim 1 is formed into a galvanized steel sheet, wherein the coating composition (II) further comprises a group selected from the group consisting of (Da) selected from the group consisting of metal ruthenate and metal ion-exchanged cerium oxide. One of the group consisting of a rust preventive pigment other than at least one compound, cerium oxide, and a filler pigment. The coating film of the sixth application of the patent application form a galvanized steel sheet, which forms a coating layer of the coating composition (I) on the lowermost layer of the surface (the surface to be used outward), and forms a coating on the uppermost layer on the opposite side of the back side. The coating layer of the composition (II). The coating film of the 12th application of the patent application form a galvanized steel sheet, which forms a coating layer of the coating composition (I) on the lowermost layer on both sides of the front and back, and forms a coating on the uppermost layer of the back surface (the surface used toward the inside). The coating layer of the composition (II). A method for forming a plurality of coating films on a surface of a galvanized steel sheet and forming one or a plurality of coating films on the back surface, comprising the steps of: coating the lowermost layer of at least one of the front and back surfaces of the galvanized steel sheet with the following coating a step of composition (I); a step of hardening the coating film obtained by coating the coating composition (I); and a step of applying the following coating composition (II) to the uppermost layer of at least one of the front and back surfaces; and a step of hardening a coating film obtained by coating a coating composition (II); a coating composition (I): a coating film-forming resin containing (A) a hydroxyl group-containing resin, (B) a crosslinking agent, and (C) an anti-corrosion agent a coating composition of a rust pigment, wherein the amount of the rust preventive pigment (C) is 10 to 150 parts by mass based on 100 parts by mass of the total solid content of the resin (A) and the crosslinking agent (B); and a coating composition ( II): a coating composition comprising (A) a hydroxyl group-containing coating film-forming resin and (B) a crosslinking agent, and further comprising (Db) selected from the group consisting of a phosphate-containing coating film-forming resin and phosphoric acid-containing The amount of the resin (Db) is at least one resin in the group consisting of the salt-based coating film-forming resin, and the total solid content of the resin (A) and the crosslinking agent (B) is 100 parts by mass. 5 to 30 parts by mass, or more (Dc) azole compound, and the amount of the (Dc) azole compound is 2% based on 100 parts by mass of the total solid content of the resin (A) and the crosslinking agent (B). 30 parts by mass, the (Dc) azole compound is at least one selected from the group consisting of a triazole compound and a compound having a thiadiazolyl group, and the triazole compound is selected from 1, 2, 4-triazole, 3-amine 1,2-,4-triazole, 3-hydrothio-1,2,4-triazole, 5-amino-3-hydrothio-1,2,4-triazole and 2,3- At least one of the group consisting of dihydro-3-oxooxy-1,2,4-triazole.