JP2000199071A - Precoated steel sheet excellent in corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a precoated steel sheet excellent in adhesion of a coating film, workability of the coating film and corrosion resistance without using environmentally harmful chromium. SOLUTION: At least one side of a steel sheet or a plated steel sheet is provided with at least one layer among (1) a film layer contg., as solid contents, 30 to 500 pts.wt. resin, 0.2 to 50 pts.wt. thiocarbonyl group-contg. compd. and a phosphoric compd. of 0.1 to 5 pts.wt. (expressed in terms of PO4), (2) a film layer contg., as solid contents, 10 to 500 pts.wt. particulate silica in addition to the above described (1) and (3) a film layer contg., as solid contents, 30 to 500 pts.wt. resin, 0.2 to 50 pts.wt. thiocarbonyl group-contg. compd. and 50 to 500 pts.wt. particulate silica and contg. no phosphoric compds. as a substrate treating layer, and, the sheet is provided with a rust preventive film layer contg. an ion source emitting vanadic acid ions and an ion source emitting phosphoric acid ions in the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-coated steel sheet having excellent corrosion resistance, and more particularly to a pre-coated steel sheet containing no toxic hexavalent chromium.

[0002]

2. Description of the Related Art Pre-coated steel coated with a colored organic coating has been increasingly used for home appliances, building materials, automobiles, and the like, instead of post-painted products which have been conventionally coated after processing. . This steel sheet is obtained by coating an organic coating on a steel sheet and a plated steel sheet that have been subjected to rust prevention treatment, and has characteristics of having good workability, good workability, and good corrosion resistance.

For example, Japanese Patent Application Laid-Open No. Hei 8-168723 discloses a technique for obtaining a precoated steel sheet having excellent workability, stain resistance and hardness by defining the structure of a film. On the other hand, Japanese Unexamined Patent Publication No. Hei 3-100180 discloses a precoated steel sheet having improved end face corrosion resistance by using a specific chromate treatment solution.

[0004] These pre-coated steel sheets have not only corrosion resistance, but also workability and paint adhesion due to the combined effect of an organic coating to which a chromate treatment and a chromium-based rust-preventive pigment have been added. It is intended for quality improvement and is currently used universally. On the other hand,
JP-A-51620 discloses a precoated steel sheet having good corrosion resistance by providing a coating layer in which a pigment for supplying phosphate ions and a pigment for supplying vanadate ions are mixed on a surface-treated steel sheet subjected to a zinc phosphate treatment. However, the corrosion resistance is inferior to that of a precoated steel sheet having a coating film layer which has been subjected to a chromate treatment and further added with a chromium-based rust preventive pigment.

[0005]

Hexavalent chromium contained in chromate-treated and chromium-based pigments is water-soluble,
By dissolving this, there is a property of repairing the damage of the coating film generated on the coating film. Therefore, it has been used to date to impart corrosion resistance. However, due to the toxicity problem of hexavalent chromium which may be eluted from the chromate treatment and the organic film containing the chromium-based rust preventive pigment, recently, there has been an increasing demand for a chromium-free rust preventive treatment and a chromium-free organic film.

Accordingly, it is an object of the present invention to provide a non-chromium-based precoated steel sheet having excellent corrosion resistance in response to such a demand.

[0007]

According to the present invention, (1) 30 to 500 parts by weight of a resin as a solid content, a thiocarbonyl group-containing compound 0.1 at least on one side of a steel sheet or a plated steel sheet.
A coating layer containing 2 to 50 parts by weight and 0.1 to 5 parts by weight of phosphoric acid compound (as PO ₄ );
A coating layer containing 10 to 500 parts by weight of finely divided silica as a solid content, and (3) a resin 30 to 500 as a solid content.
Parts by weight, 0.2 to 50 parts by weight of a thiocarbonyl group-containing compound, and 50 to 500 parts by weight of fine silica, and at least one of the coating layers containing no phosphoric acid compound as a base treatment, A precoated steel sheet is characterized by having a rust-preventive coating layer containing a vanadate ion source for releasing vanadate ions and a phosphate ion release source for releasing phosphate ions in a resin.

The resin constituting the rust-preventive coating layer is (A) a polyester polyol having at least 3 functional groups,
(B) a product obtained by adding a lactone compound or an alkylene oxide to an epoxy resin having at least one secondary hydroxyl group; and (C) a blocked product of an organic polyisocyanate or a reaction of an organic polyisocyanate with an active hydrogen compound. A resin obtained from a blocked prepolymer having an NCO group at a terminal is preferable.

It is preferable that the precoated steel sheet of the present invention further has a colored film layer as an upper film on the rust preventive film layer.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The rust preventive treatment of a precoated steel sheet according to the present invention has been developed for the purpose of preventing rust of steel sheets and plated steel sheets, and includes cold rolled steel sheets, hot rolled steel sheets, hot-dip galvanized steel sheets, and electrogalvanized steel sheets. Steel sheet, hot dip galvanized steel sheet,
Commonly known steel sheets and plated steel sheets such as an aluminum-plated steel sheet, an aluminum-zinc alloy-plated steel sheet, and a stainless steel sheet can be applied.

[0011] The steel sheet and the plated steel sheet can be subjected to ordinary treatments such as hot water washing and alkali degreasing before the base treatment. The underlying treatment layer for the purpose of the rust prevention treatment of the present invention,
It is characterized by containing a thiocarbonyl group-containing compound based on an aqueous resin. The undercoating layer is preferably a coating layer based on an aqueous resin. Here, the term "aqueous resin" includes not only a water-soluble resin but also a resin (a water-dispersible resin) which is originally water-insoluble but can be in a finely dispersed state in water, such as an emulsion or a suspension. Examples of the resin that can be used as such a water-soluble resin include polyolefin resin, acrylic olefin resin, polyurethane resin, acrylic resin, polycarbonate resin, epoxy resin, polyester resin, phenol resin, and other thermosetting resins. Can be illustrated,
More preferably, the resin is a crosslinkable resin. Particularly preferred resins are acrylic olefin resins, polyurethane silicic resins, and mixed resins of both. Two or more of these water-soluble resins may be used as a mixture.

The thiocarbonyl group-containing compound is a sulfide, is easily adsorbed on the metal surface, and has excellent oxidizing power, so that the metal surface is passivated and exhibits an antirust effect. In particular, it is considered that thiol group ions in the thiocarbonyl group-containing compound are adsorbed to active sites on the surface of the steel sheet and the plated steel sheet and exhibit a rust-preventive effect. Further, the thiocarbonyl group-containing compound also has an effect of efficiently blocking harmful ions such as water and chloride ions, which is also considered to contribute to the rust prevention effect.

In the present invention, the thiocarbonyl group-containing compound is a thiocarbonyl group (formula 1)

[0014]

Embedded image A compound having the following formula: Typically,

[0015]

Embedded image And derivatives thereof, for example, methylthiourea, dimethylthiourea, ethylthiourea, diethylthiourea, thiopental, thiocarbide, thiocarbansosos, thiocyanuric acids, thiohydantoin,
-Thiouramil, 3-thiourazole and the like;

[0016]

Embedded image A thioamide compound represented by, for example, thioformamide, thioacetamide, thiopropionamide, thiobenzamide, thiocarbostyril, thiosaccharin and the like;

[0017]

Embedded image A thioaldehyde compound represented by, for example, thioformaldehyde, thioacetaldehyde and the like;

[0018]

Embedded image Carbothioic acids represented by, for example, thioacetic acid, thiobenzoic acid, dimethioacetic acid;

[0019]

Embedded image And thiocarbonates represented by the following formulas; and other compounds having the structure of Formula 1, for example, thiocoumazone, thiocumothiazone, thionin blue J, thiopyrone, thiopyrine, thiobenzophenone and the like.

The content of the thiocarbonyl group-containing compound is as follows:
0.2 to 500 parts by weight is preferable for 30 to 500 parts by weight of the resin. When the content of the thiocarbonyl group-containing compound is 0.
If the amount is less than 2 parts by weight, the rust-preventing effect cannot be sufficiently exhibited, while
If the amount exceeds 00 parts by weight, the rust-preventive effect is reduced,
In some cases, the resin gels in the state of the coating solution, causing a problem.

The base treatment of the present invention contains a phosphoric acid compound together with a thiocarbonyl group-containing compound, whereby the rust-preventing effect thereof is remarkably improved. As described above, the thiocarbonyl group-containing compound is adsorbed to active sites on the surface of the steel sheet and the plated steel sheet and exhibits a rust preventive effect, but phosphoric acid acts on the inactive surface of the steel sheet and the plated steel sheet. It is considered that an active surface is formed, and the thiocarbonyl group-containing compound is adsorbed on the active surface, so that the rust-preventing effect is exerted on the entire surface of the steel sheet and the plated steel sheet, and the rust-preventing effect is improved. Phosphoric acid compounds also act as a cross-linking accelerator for the resin film, reducing micropores in the resin coating and effectively blocking harmful ions such as water and chloride ions, which also contributes to the rust prevention effect. It is thought that.

As the phosphate compound, phosphate ions may be included, and for example, orthophosphoric acid, condensed phosphoric acid (metaphosphoric acid, polyphosphoric acid, etc.), or ammonium salts and metal salts thereof can be used. The amount of the phosphate compound in the base treatment is in the range of 0.1 to 5 parts by weight as phosphate ions based on 30 to 500 parts by weight of the resin. If the phosphoric acid compound is less than 0.1 part by weight, the rust-preventing effect cannot be sufficiently exerted, while if it exceeds 5 parts by weight, the rust-preventing effect is rather reduced, or the resin is gelled in the state of the coating solution. There may be.

In addition to the excellent rust preventive action due to the coexistence of the thiocarbonyl group-containing compound and the phosphoric acid compound, the addition of finely divided silica further promotes the rust preventive action (corrosion resistance). Moreover, in addition to corrosion resistance, drying, abrasion resistance,
Coating adhesion can also be improved. In the present invention, fine-particle silica is a generic term for silica having characteristics such that when it is dispersed in water, it has a fine particle size and can stably maintain a water-dispersed state, and semi-permanently no sedimentation is observed. It is. The finely divided silica is not particularly limited as long as it has a small amount of impurities such as sodium and is weakly alkaline. For example, "Snowtex N", "Snowtex NS", "Snowtex NXS" (manufactured by Nissan Chemical Industries), "Adelite AT-20N" (manufactured by Asahi Denka Kogyo).
For example, commercially available silica gel or commercially available Aerosil (powder silica, manufactured by Degussa) can be used.

The content of fine silica is 30 to 500
It is preferably 10 to 500 parts by weight based on parts by weight. If it is less than 10 parts by weight, the effect of addition is small, and
On a heavy part, the effect of improving corrosion resistance is saturated, which is uneconomical. Furthermore, according to the present invention, it has been confirmed that when the thiocarbonyl group-containing compound and the finely divided silica coexist, a sufficient rust-preventing effect can be obtained without the presence of a phosphoric acid compound. However, in this case, the content of the fine silica is preferably 50 to 500 parts by weight based on 30 to 500 parts by weight of the resin. Further, the undercoat layer of the present invention may contain other components. For example, pigments, surfactants and the like can be mentioned. Further, a silane coupling material may be blended to improve the affinity between the aqueous resin and the silica fine particles and the pigment, and further improve the adhesion between the aqueous resin and the zinc or iron phosphate compound layer.

Examples of such pigments include titanium oxide (TiO ₂ ), zinc oxide (ZnO), zirconium oxide (ZrO ₂ ), calcium carbonate (CaCO ₃ ), barium sulfate (BaSO ₄ ), and alumina (Al
₂ O _3), it may be used kaolin clay, carbon black, and organic pigments such as iron oxide _{(Fe 2 O 3, Fe 3} O 4), and various coloring pigments such as organic pigments.

Examples of the silane coupling agent include γ-aminopropyltrimethoxysilane, γ-aminopropylethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylethoxysilane, N- [2- (vinylbenzylamino) ethyl] -3-aminopropyltrimethoxysilane and the like can be mentioned.

In order to form a base treatment layer on a steel sheet, a base treatment agent (coating agent) containing the above components is prepared in water, applied to the steel sheet, and the coating film is heated and dried. When the resin is crosslinkable or curable, the resin is crosslinked and cured by this heating.
The heating and drying of the coating film may be performed by applying a base treatment agent and drying. The heating temperature is preferably 50 to 250C. 5
If the temperature is less than 0 ° C., the evaporation rate of water is too slow to obtain a sufficient film-forming property, so that the rust-preventing ability is insufficient. On the other hand, when the temperature exceeds 250 ° C., thermal decomposition of the aqueous resin occurs, so that the SST property,
There is a problem that the water resistance is reduced and the appearance is yellowed. 7
0-160 degreeC is more preferable. In hot air drying, drying for 1 second to 5 minutes is preferable.

It is preferable that the film thickness of the underlayer treatment when dried is 0.1 μm or more. If it is less than 0.1 μm, the rust-preventing ability is insufficient. On the other hand, if the film thickness is too thick, it is uneconomical as a base treatment layer and is inconvenient for painting. Therefore, the upper limit of the film thickness is preferably 40 μm or less. The application method of the base treatment
There is no particular limitation, and generally known coating methods such as roll coating, air spray, airless spray, immersion, and the like can be employed.

In the precoated steel sheet of the present invention, the coating layer coated on the undercoating layer is characterized in that it simultaneously contains an ion source for releasing vanadate ions and an ion source for releasing phosphate ions as rust preventive pigments. . The rust preventive pigment may release both phosphate ions and vanadate ions in an environment where water and oxygen are present. Phosphate ions rarely exist alone in water and exist in various forms such as polycondensates, but it is understood that such cases are also included in the concept of “phosphate ions”. It is understood that the vanadate ion also includes a polymerized vanadate ion. The rust preventive pigment used in the present invention is obtained by calcining a mixture containing a phosphate compound as a phosphate ion release source, a vanadium compound as a vanadate ion release source, and, if necessary, a network modifying ion source and / or a glassy substance, Those obtained by grinding are preferred,
A rust preventive pigment that releases vanadate ions and a rust preventive pigment that releases phosphate ions may be separately contained in the resin.

The phosphoric acid compound used here is preferably one that acts on the vanadium compound by heating to produce a baked product that is not a mere mixture. As such, orthophosphoric acid, condensed phosphoric acid, orthophosphates or condensed phosphates of various metals, phosphorus pentoxide, phosphate minerals, commercially available complex phosphate pigments, or mixtures thereof No. Specific examples of the phosphate compound include phosphate minerals, for example, monetite, tolfillite, witrockite, xenotime, starkolite, struvite, ornite, and the like. Specific examples of commercially available composite phosphoric acid pigments include, for example, silica polyphosphate. Examples of the condensed phosphoric acid include polyphosphoric acid and metaphosphoric acid. Examples of the condensed phosphate include metaphosphate, tetrametaphosphate, hexametaphosphate, pyrophosphate, acid pyrophosphate, tripolyphosphate, and a mixture thereof. The metal species forming the phosphate is not particularly limited, and examples thereof include alkali metals, alkaline earth metals, metal species of other typical elements, and transition metals. Examples of preferred metals include magnesium, calcium, strontium, barium, titanium,
Examples include zirconium, manganese, iron, cobalt, nickel, zinc, and aluminum.

As the vanadium compound used in the present invention, any one or more compounds having a vanadium valence of 0, 2, 3, 4, and 5 can be used, and among them, one or more pentavalent vanadium compounds can be used. desirable. The form is metal,
Examples include oxides, hydroxides, metal oxyacid salts, halides, sulfates, vanadyl compounds, and the like. Specific examples of the vanadium compound include a vanadium (II) compound, for example,
Vanadium (III) compounds such as vanadium (II) oxide and vanadium (II) hydroxide, for example, vanadium (III) oxide
(V ₂ O ₃ ) and other vanadium (IV) compounds such as vanadium (IV) oxide (V ₂ O ₄ ) and vanadyl halide (V
Vanadium (V) compounds, such as OX ₂ ), for example, vanadium oxide (V) (V ₂ O ₅ ), etc., vanadates, for example, orthovanadate, metavanadate or pyrovanadate of various metals, vanadyl halide (VOX ₃ )
And the like, and mixtures thereof. The metal species of vanadic acid are the same as those shown for phosphate.

A coloring pigment may be added to the film containing the rust-preventive pigment in order to enhance the design. Examples of the coloring pigment include titanium oxide (TiO ₂ ), zinc oxide (ZnO), zirconium oxide (ZrO ₂ ), calcium carbonate (CaCO ₃ ),
Barium sulfate (BaSO ₄ ), alumina (Al
Commonly known coloring pigments such as inorganic pigments such as ₂ O ₃ ), kaolin clay, carbon black, iron oxide (Fe ₂ O ₃ , Fe ₃ O ₄ ) and organic pigments can be used.

The thickness of the film containing the rust preventive pigment is 1 to 25 μm
Is preferred, and if it is less than 1 μm, the corrosion resistance becomes poor,
If it exceeds 25 μm, the workability of the coating film is poor. As the base resin of the film containing the rust preventive pigment, a generally known resin, for example,
Polyester resin, urethane resin, acrylic resin, epoxy resin, melamine resin and the like can be used. (A) Polyester polyol having at least 3 functional groups and (B) Epoxy resin having at least one secondary hydroxyl group Resin obtained from a product obtained by adding a lactone compound or an alkylene oxide and a blocked product of (C) a blocked product of an organic polyisocyanate or a prepolymer having a terminal NCO group obtained by reacting an organic polyisocyanate with an active hydrogen compound In this case, the processability and chemical resistance of the coating film are improved, which is still more preferable.

The polyester polyol (A) having at least three functional groups can be obtained by esterifying a dicarboxylic acid, a glycol and a polyol having at least three OH groups. Examples of the dicarboxylic acid used for producing the polyester polyol include succinic acid, succinic anhydride, adipic acid, azelaic acid, sebacic acid, dodecane diacid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, dimer acid, and the like. Aliphatic system,
For example, phthalic acid, phthalic anhydride, isophthalic acid, dimethyl isophthalate, terephthalic acid, dimethyl terephthalate, 2,6-naphthalenedicarboxylic acid, hexahydrophthalic anhydride, cyclohexanedicarboxylic acid, tetrahydrophthalic anhydridecyclohexanedicarboxylic acid dimethyl ester Examples thereof include aromatic and alicyclic compounds such as esters, methylhexahydrophthalic anhydride, hymic anhydride, and methylhymic anhydride. Examples of glycols include ethylene glycol, diethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, dipropylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, hydroxy Neopentyl glycol ester of vivalic acid, triethylene glycol, 1,9-nonanediol, 3-methyl-1,5 pentanediol,
2,2,4-trimethyl-1,3-pentanediol,
2-ethyl-1,3-hexanediol, 2,4-diethyl-1,5-pentanediol, polycaprolactone diol, polypropylene glycol, polytetramethylene ether glycol, polycarbonate diol,
2-n-butyl 2-ethyl l, 3-propanediol,
Aliphatic ones such as 2,2-diethyl-1,3-propanediol, for example, cyclohexanedimethanol,
Cyclohexanediol, 2-methyl-1,1-cyclohexanedimethanol, xylylene glycol, bishydroxyethyl terephthalate, 1,4 bis (2-hydroxyethoxy) benzene, hydrogenated bisphenol A, ethylene oxide adduct of bisphenol A, bisphenol Aliphatic or aromatic compounds such as the propylene oxide adduct of A are mentioned.

Examples of the polyol having at least three OH groups include glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, pentaerythritol, diglycerin, and ethylene using these polyols as an initiator. Oxide adducts, propylene oxide adducts and ε-caprolactone adducts are exemplified.

The product (B) obtained by adding a lactone compound or an alkylene oxide to an epoxy resin having at least one secondary hydroxyl group can be obtained by adding a lactone compound or an alkylene oxide to an epoxy resin represented by the following general formula. Those added by means are mentioned.

[0037]

Embedded image In this formula, X represents a phenylene group or a cyclohexylene group which may be substituted with halogen, and n represents 0.5 to 1
2.0 is shown.

The lactone compound or alkylene oxide is added in an amount of about 5 to 40 parts by weight based on about 95 to 60 parts by weight of the epoxy resin. In particular, the lactone compound or alkylene oxide is preferably used in an amount of about 10 to 30 parts by weight based on about 90 to 70 parts by weight of the epoxy resin. In the epoxy resin represented by the above general formula, X is preferably a p-phenylene group, and n is preferably 2 to 9. Examples of the halogen include bromine and chlorine. The number of the substituents is usually about 1 to 3, and the position may be any position of a phenylene group or a cyclohexylene group.

Examples of the lactone compound include β-propiolactone, butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone, δ-caprolactone, ε-caprolactone, and among them, particularly ε-caprolactone. Caprolactone is preferred. Examples of the alkylene oxide include ethylene oxide, propylene oxide, styrene oxide, glycidyl methacrylate, epichlorohydrin and the like, with ethylene oxide being particularly preferred.

The proportion of the epoxy resin having at least one secondary hydroxyl group to which a lactone compound or an alkylene oxide is added is about 10% in the polyol component.
About 70% by weight, especially about 10 to 60% by weight.
It is preferable to use in the range of. When the compounding ratio is less than 10% by weight, among the stain resistances, particularly the mustard resistance may deteriorate. On the other hand, if the content exceeds 70% by weight, the stain resistance is improved, but the hardness may be extremely reduced.

As the blocked product (C), compounds having at least two NCO groups, for example, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3- Butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4- or 2,2,4
Aliphatic diisocyanates such as trimethylhexamethylene diisocyanate, dodecamethylene diisocyanate, 2,6-diisocyanatomethylcaproate; for example, 1,3-cyclopentane diisocyanate,
4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, 4,4'-methylenebis (cyclohexyl isocyanate), methyl-2,4-cyclo Hexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 1,2-bis (isocyanatomethyl) cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane, 1,3-bis (isocyanatomethyl) ) Cycloalkylene diisocyanates such as cyclohexane and trans-cyclohexane-1,4-diisocyanate; for example, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, - naphthalene diisocyanate,
4,4'-diphenylmethane diisocyanate, 2,4
-Or 2,6-tolylene diisocyanate, 4,4 '
Aromatic diisocyanates such as toluidine diisocyanate, dianisidine isocyanate, 4,4'-diphenyl ether diisocyanate;
Diisocyanate-1,3-dimethylbenzene, ω,
ω'-diisocyanate 1,4-dimethylbenzene,
aromatic aliphatic diisocyanates such as ω, ω′-diisocyanate-1,4-diethylbenzene, α, α, α ′, α′tetramethylmetaxylylene diisocyanate, α, α, α ′, α ′ tetramethyl paraxylylene diisocyanate For example, trifphenylmethane-4,4 ',
Triisocyanates such as 4 "-triisocyanate, 1,3,5-triisocyanatebenzene, 2,4,6-triisocyanatetoluene, .omega.-isocyanateethyl-2,6-diisocyanatocaproate, for example, 4,4 '-Diphenyldimethylmethane-2,2',
Blocked products of tetraisocyanates such as 5,5'-tetraisocyanate and blocked products of prepolymers having an NCO group at a terminal obtained by reacting them with an active hydrogen compound are exemplified.

When used as a precoated steel sheet, weather resistance is required. Therefore, among the aforementioned compounds having an NCO group, hexamethylene diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, 1,4- Bis (isocyanatomethyl)
It is preferable to use isocyanate compounds such as cyclohexane, 1,3-bis (isocyanatomethyl) cyclohexane, 4,4'-methylenebis (cyclohexyl isocyanate), and α, α, α ', α'-tetramethylmet-xylylene diisocyanate. .

The prepolymer having an NCO group at the terminal obtained by the reaction between the isocyanate compound and the active hydrogen compound can be obtained by reacting the isocyanate monomer with the active hydrogen compound in an excess of isocyanate groups. . Active hydrogen compounds used to produce this prepolymer include, for example, ethylene glycol, propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, Dihydric alcohols such as neopentyl glycol, neopentyl glycol hydroxybivalate, triethylene glycol, hydrogenated bisphenol A, xylylene glycol, 1,4-butylene glycol, for example, glycerin, trimethylolethane, trimethylolpropane, Low molecular weight polyols such as trihydric alcohols such as 2,2,6-hexanetriol, for example, tetrahydric alcohols such as pentaerythritol, and propylene oxide of the above polyols. Are high molecular weights such as polyether polyols such as ethylene oxide adducts, polytetramethylene ether glycol, polyester polyols obtained by reacting the aforementioned low molecular weight polyols with dicarboxylic acids, and those modified with fatty acids when producing polyester polyols. Polyols. These polyols may be used alone or as a mixture.

The prepolymer is generally composed of NCO groups / OH
The equivalent ratio with the group is about 2.0-15, preferably about 4-8
After the reaction is carried out usually at 40 to 140 ° C., preferably 70 to 100 ° C., if necessary, unreacted isocyanate monomer is obtained by removing it by a thin film distillation method or an extraction method which is usually carried out. Can be. In this reaction, an organometallic catalyst such as a tin-based, lead-based, zinc-based, or iron-based catalyst may be used.

The above-mentioned blocked isocyanate monomer or prepolymer thereof can be obtained by reacting the isocyanate monomer or prepolymer thereof with a blocking agent by a known method. As the blocking agent used in this reaction, there are known blocking agents that can be used for blocking an isocyanate, for example, phenol-based, lactam-based, active methylene-based, alcohol-based, mercaptan-based, acid amide-based, and imide-based blocking agents. ,
Amine-based, imidazole-based, urea-based, carbamate-based, imine-based, oxime-based, or sulfite-based blocking agents can be used, and in particular, phenol-based, oxime-based, lactam-based, imine-based, etc. Blocking agents are advantageously used. The following are specific examples of the blocking agent.

Phenolic blocking agents: phenol, cresol, xylenol, nitrophenol, chlorophenol, ethylphenol, p-hydroxydiphenyl, t-butylphenol, o-isopropylphenol, o-sec-butylphenol, p-nonylphenol, pt -Octylphenol, hydroxybenzoic acid, hydroxybenzoic acid esters and the like.

Lactam blocking agents: ε-caprolactam, δ-valerolactam, γ-butyrolactam, β-propiolactam and the like. Active methylene blocking agents: diethyl malonate, dimethyl malonate, ethyl acetoacetate, methyl acetoacetate, acetylacetone and the like. Alcohol blocking agent: methanol, ethanol, n
-Propyl alcohol, isopropyl alcohol, n-
Butyl alcohol, isobutyl alcohol, t-butyl alcohol, n-amyl alcohol, t-amyl alcohol, lauryl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, distyrene glycol monoethyl ether , Glycolic acid esters such as propylene glycol monomethyl ether, benzyl alcohol, methoxymethanol, glycolic acid, methyl glycolate, ethyl glycolate, and butyl glycolate; lactic acid esters such as lactic acid, methyl lactate, ethyl lactate, and butyl lactate; methylol urea; Methylol melamine,
Diacetone alcohol, ethylene chlorohydrin, ethylene bromhydrin, 1,3-dichloro-2-propanol, ω-hydroperfluoroalcohol, acetocyanhydrin and the like.

Mercaptan blocking agents: butyl mercaptan, hexyl mercaptan, t-butyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, methylthiophenol,
Ethylthiophenol and the like. Acid amide blocking agents: acetanilide, acetanisidide, acetoloid, acrylamide, methacrylamide, acetate amide, stearamide, benzamide and the like.

Imide blocking agent: succinimide,
Phthalic imide, maleic imide and the like. Amine-based blocking agents: diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine, butylphenylamine and the like.

Imidazole blocking agents: imidanol, 2-ethylimidazole and the like. Urea-based blocking agents: urea, thiourea, ethylene urea, ethylene thiourea, 1,3-diphenyl urea and the like. Carbamate-based blocking agents: phenyl N-phenylcarbamate, 2-oxazolidone and the like.

Imine blocking agents: ethyleneimine, propyleneimine and the like. Oxime blocking agents: formamidoxime, acetoaldoxime, acetoxime, methyl ethyl ketoxime,
Diacetyl monooxime, benzophenone oxime, cyclohexanone oxime and the like. Bisulfite blocking agents: sodium bisulfite, potassium bisulfite, etc. As a specific method of the above-mentioned reaction between the isocyanate monomer or their prepolymer and the blocking agent, for example, the isocyanate monomer or their prepolymer and the blocking agent are converted into NCO groups / active hydrogen groups in the blocking agent. Equivalent ratio of about 0.9 to 1.0, preferably about 0.95 to
1.0, a reaction of an isocyanate monomer and a blocking agent in an NCO group / equivalent ratio of active hydrogen groups in the blocking agent = about 1.1 to 3.0, preferably about 1.2 to 2.0. After reacting, a low-molecular-weight polyol, a high-molecular-weight polyol, a method of reacting water or a lower amine as described above in the production of the prepolymer, or an isocyanate monomer and a low-molecular-weight polyol, a high-molecular-weight polyol, Equivalent ratio of water or lower amine to NCO group / active hydrogen group = about 1.6 to 10.0, preferably about 2.
After reacting at 0 to 7.0, a method of reacting a blocking agent with the reaction may be used. Each of the above reactions is carried out in a solvent having no active hydrogen group (eg, aromatic solvents such as benzene, toluene, and xylene, Solvesso-100, Solvesso-20).
Petroleum-based solvents such as ethyl acetate, butyl acetate, etc., for example, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethers such as tetrahydrofuran, etc.) or in the absence of such solvents. This is performed by a known method. In the reaction, a known catalyst such as a tertiary amine or an organic metal may be used. The film-forming resin raw materials used in the present invention are the above-mentioned polyols (A) and (B) and the blocked product (C), and the mixing ratio of the polyol and the blocked product is such that the equivalent ratio of OH group / regenerated NCO group is about 1/2 to 2/1, particularly preferably 1 / 0.8 to 1 / 1.2.

The resin used in the present invention and the rust preventive pigment have been described above. A paint made by mixing these,
By applying to a precoated metal plate, low toxicity and high corrosion resistance can be obtained. The compounding amount is preferably 0.1 to 50 parts, more preferably 0.5 to 20 parts, for both the phosphate ion source and the vanadate ion source, based on 100 parts by weight of the total solid content of the paint. If the amount is less than 0.1 part by weight, a sufficient rust-preventing effect is not exhibited. If the amount exceeds 50 parts by weight, the cohesive strength of the cured coating film is reduced and sufficient coating film strength cannot be obtained.

The film-forming resin raw material used in the present invention can be sufficiently formed by heating as it is. However, in forming a coating, in addition to the polyol and the blocked product, for example, ethyl acetate, butyl acetate, methyl acetoacetate, Esters such as 2-ethoxyethyl acetate, aromatics such as xylene and toluene, ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, ethers such as diethylene glycol dimethyl ether,
Petroleum-based organic solvents such as Solvesso-100 and Solvesso-200, for example, color pigments and extender pigments, silicon-based, amine-based, polyether-based, polyester-based,
Castor oil-based, synthetic wax-based, pentonite-based dispersants, defoamers, leveling agents, thixotropic agents, benzotriazole-based, hindered amine-based, hindered phenol-based stabilizers, tin-based, lead-based, zinc If necessary, reaction catalysts such as iron-based and iron-based catalysts, and UV inhibitors may be added. After the coating material of the present invention thus obtained is applied to a metal plate, the reached plate temperature is about 150 to 350 ° C., and the heating time is about 20 to
By heating for about 120 seconds, the blocking agent contained in the blocked product is dissociated to regenerate NCO groups, and the regenerated NCO groups react with OH groups in the polyol to give a cured coating film.

The coating method of the film containing the rust-preventive pigment can be performed by a generally known coating method, for example, roll coating, curtain flow coating, air spray, airless spray, immersion, bar coating, brush coating and the like. On the coating layer containing the rust-preventive pigment in the pre-coated steel sheet of the present invention,
When the upper layer film containing the coloring pigment is coated, the corrosion resistance is further improved, and the design property is further increased, which is more preferable. As the base resin of the film, generally known resins, for example, polyester resin, urethane resin, acrylic resin, epoxy resin, melamine resin and the like can be used. As coloring pigments, titanium oxide (TiO ₂ ), zinc oxide (Zn
O), zirconium oxide (ZrO ₂ ), calcium carbonate (CaCO ₃ ), barium sulfate (BaSO ₄ ), alumina (Al ₂ O ₃ ), kaolin clay, carbon black, iron oxide (Fe ₂ O ₃ , Fe ₃ O ₄₎ ) And generally known coloring pigments such as organic pigments.

The coating method of the film can be performed by a generally known coating method, for example, roll coating, curtain flow coating, air spray, airless spray, dipping, bar coating, brush coating and the like.

[0056]

Example: The amount of galvanized steel sheet adhered to 20 g / side
0.6 mm thick electrogalvanized steel sheet plated on both sides with m ² , and the galvanized coating weight is 60 g / m per side
FC-364S (made by Nippon Parkerizing Co., Ltd.) with a 0.6 mm thick hot-dip galvanized steel sheet plated on both sides with ²
Was degreased by immersion in an aqueous solution having a concentration of 2% by weight and a temperature of 60 ° C. for 10 seconds, washed with water and dried. Next, a base material having the composition shown in Table 1 was applied by a roll coater and dried in a hot air drying oven. The ultimate plate temperature during drying is 150
° C.

Next, the components shown in Table 2 were mixed to produce a rust preventive pigment, and the components shown in Table 3 were baked under the conditions shown in the same table and then pulverized to obtain a phosphate ion source. A rust-preventive pigment containing both a vanadate and a vanadate ion source was prepared. Next, the prepared primer paint containing the rust preventive pigment was applied by a roll coater, and was cured and dried in an induction heating furnace into which hot air was blown so that the reached plate temperature was 220 ° C.

As the primer coating, a commercially available polyester-based primer coating, epoxy resin-based primer coating, or urethane resin-based primer coating was used, and the chromium-based rust-preventive pigment added thereto was changed to the rust-preventive pigment prepared above. What was done was used. In addition to the above, a resin described below was prepared, and a resin obtained by adding the above-prepared rust-preventive pigment was used as a rust-preventive pigment-containing coating layer.

Depending on the experimental conditions, FL100HQ (polyester resin, white) made by Nippon Paint was further applied on the coating layer containing the rust-preventive pigment, and the plate temperature reached in an induction heating furnace blown with hot air. Was dried at 220 ° C. After each curing and drying step, the plate was water-cooled. The details of the prepared resin will be described below.

The following [Polyols 1 to 7] and [Block compounds 1 to 7] were prepared, and a paint was prepared by adding the rust preventive pigment prepared above to a combination of these. However, the present invention is not limited to these examples. In addition, the part or% shown without a reference shows a weight part or weight%, respectively. [Polyol 1] 364.9 parts (1.52 mol) of hydrogenated bisphenol A, 441.6 parts of adipic acid (3.02 parts)
Mol) in a reaction vessel, heated to 220 ° C. and blown with nitrogen gas to react while distilling off the condensed water generated. When the acid value reached 250.0, trimethylolpropane (hereinafter referred to as TMP) 304 was prepared. .1 copy (2.27
Mol) and reacted similarly while distilling off condensed water to obtain a polyester polyol having an acid value of 2.6, a hydroxyl value of 187.2, a number of functional groups of 5, and a number average molecular weight of 1478. A product obtained by adding 20 parts by weight of ε-caprolactone to 600 parts by weight of this polyester polyol and 80 parts by weight of an epoxy resin of the following formula (1) (Placcel G-402 (manufactured by Daicel Chemical Industries, Ltd.); 400 parts of epoxy equivalent (1250) was dissolved in 1500 parts of cyclohexanone to obtain a solution having a solid content of 40%.

[0061]

Embedded image [Polyol 2] A product obtained by adding 20 parts by weight of ε-caprolactone to 800 parts by weight of the polyester polyol used for polyol 1 and 80 parts by weight of an epoxy resin represented by the following formula (2) (Placel G-702 (Daicel Chemical Industries, Ltd.) )
20) having a hydroxyl value of 140 and an epoxy equivalent of 2710)
0 parts was dissolved in 1500 parts of cyclohexanone, and the solid content was 4 parts.
A 0% solution was obtained.

[0062]

Embedded image [Polyol 3] 1,6-hexanediol 205.8
Parts (1.74 mol), dimethyl isophthalate 670.
1 part (3.45 mol) and 0.1 g of zinc acetate were charged into a reaction vessel, heated to 220 ° C. and blown with nitrogen gas to cause a reaction while distilling off generated methanol. When 121 ml of methanol was distilled off, TMP347 was distilled off. .2 parts (2.
59 mol), and reacted similarly while distilling off methanol to obtain a polyester polyol having an acid value of 1.4, a hydroxyl value of 193.6, a number of functional groups of 5, and a number average molecular weight of 1438. 600 parts of this polyester polyol and 400 parts of Praxel G-402 used for Polyol 1 were dissolved in 1500 parts of cyclohexanone to obtain a solution having a solid content of 40%. [Polyol 4] 24-5.3 parts (2.08 mol) of 3-methyl-1,5 pentanediol, 541.6 adipic acid
Parts (3.71 mol) were charged into a reaction vessel, heated to 220 ° C. and blown with nitrogen gas to cause a reaction while distilling off the condensed water generated. When the acid value reached 280.0, TMP was obtained.
372.9 parts (2.78 mol) and 0.1 part of dibutyltin dilaurate were charged and reacted while distilling off condensed water in the same manner to give an acid value of 1.6, a hydroxyl value of 216.0, and a number of functional groups of 5,
A polyester polyol having a number average molecular weight of 1289 was obtained. 800 parts of this polyester polyol and 200 parts of Praxel G-402 used for polyol 1 were dissolved in 1500 parts of cyclohexanone to obtain a solution having a solid content of 40%. [Polyol 5] 151.8 parts (2.45 mol) of ethylene glycol and 550.0 parts (4,66 mol) of succinic acid were charged and reacted under the same conditions as for polyol 1 to obtain an acid value of 420.0. By the way, pentaerythritol 1
59.3 parts (1.17 mol) were charged, and the esterification reaction was continued. When the acid value reached 165.0, 159.3 parts (1.17 mol) of pentaerythritol and T were further added.
MP (157.0 parts, 1.17 mol) was charged, and the condensation water was distilled off to obtain a polyester polyol having an acid value of 3.8, a hydroxyl value of 447.8, a number of functional groups of 7, and a number average molecular weight of 870. 800 parts of this polyester polyol and 200 parts of Praxel G-402 of Reference Example 1 were mixed with cyclohexanone 1
It was dissolved in 500 parts to obtain a solution having a solid content of 40%. [Polyol 6] 325.9 parts (1.28 mol) of bishydroxyethyl terephthalate, 513.8 parts of sebacic acid
Parts (2.54 mol), and reacted under the same conditions as for polyol 1. When the acid value reached 184.4, TMP was added.
256.7 parts (1.91 mol) were charged, and condensed water was distilled off to obtain a polyester polyol having an acid value of 8.0, a hydroxyl value of 168.3, a number of functional groups of 5, and a number average molecular weight of 15,91. 800 parts of this polyester polyol and Reference Example 1
Was dissolved in 1500 parts of cyclohexanone to give a solution having a solid content of 40%. [Polyol 7] 183.4 parts (2.95 mol) of ethylene glycol and 664.7 parts (5.63 mol) of succinic acid were charged and reacted under the same conditions as for polyol 1 to obtain an acid value of 420.0. By the way, 89.4 parts (1.41 mol) of TMP was charged and the esterification reaction was continued. When the acid value reached 170.0, 183.4 parts (2.95 mol) of ethylene glycol were further charged and the condensed water was distilled. Then, a polyester polyol having an acid value of 1.5, a hydroxyl value of 215,5, a number of functional groups of 3, and a number average molecular weight of 776 was obtained. 800 parts of this polyester polyol and 702200 parts of Placcel G-702 used for polyol 2 were added to cyclohexanone 1
It was dissolved in 500 parts to obtain a solution having a solid content of 40%. [Block compound 1] 241.6 parts of 1,3-bis (isocyanatomethyl) cyclohexane was dissolved in Solvesso-10
0 (trade name of a solvent having a high aromatic content made of Nikko Paint) dissolved in 400.0 parts of methyl ethyl ketoxime 1
80.6 parts are added dropwise in one hour. After completion of the dropwise addition, the mixture is heated to 75 to 80 ° C. for another hour. Next, 0.6 parts of dibutyltin dilaurate and polyester polyol (adipic acid 87
6.6 parts, ethylene glycol 186.3 parts, TMP
An acid value of 3.5 and a hydroxyl value of 1 obtained by condensing 201.2 parts and 402.3 parts of dipropylene glycol by a conventional method.
72.0, solid content 100%)
React at 80 ° C for 6 hours. Thus, a blocked solution having a regenerated isocyanate group content of 8.5% and a solid content of 60% was obtained. [Block Compound 2] TM in a 2-liter 4-neck flask
Solution of P-3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate adduct (Takenate D-140N, manufactured by Takeda Pharmaceutical Co., Ltd.) solid content 7
80% of 5%, isocyanate content 10.78%, ethyl acetate solution) and cellosolve acetate 31
6.1 parts are charged, and the internal temperature is 60 to
182. Add methyl ethyl ketoxime to maintain 70 ° C.
7 parts was gradually added dropwise, and after the addition was completed, the temperature was maintained at the above-mentioned temperature for about 4 hours.
A 4% blocked solution was obtained. [Block compound 3] ω, ω'-diisocyanate-
307.5 parts of 1,3-dimethylbenzene were dissolved in Solvesso
100 519.1 parts and methyl ethyl ketone 12
Dissolved in 9.7 parts, methyl ethyl ketoxime 237.2
Drop in about 2 hours. 1 hour after dropping 75
Heat to ~ 80 ° C. Next, dibutyltin dilaurate was added.
3 parts and 232.4 parts of the polyester polyol used for the block compound 1 are added and reacted at 75 to 80 ° C. for 6 hours. Thus, a blocked solution having a regenerated isocyanate group content of 8.02% and a solid content of 55% was obtained. [Block Compound 4] TM in a 2-liter 4-neck flask
P-hexamethylene diisocyanate adduct (Takenate D-160N, manufactured by Takeda Pharmaceutical Co., Ltd.) solid content 75
%, Isocyanate content 13.2%), 760.7 parts and cellosolve acetate 325.6 parts were charged, and 213.7 parts of methyl ethyl ketoxime was added under a nitrogen gas atmosphere so that the internal temperature was maintained at 60 to 70 ° C. Slowly dripping,
When the temperature is maintained for about 2 hours after the addition is completed, the solid content is 60%,
A blocked product solution having a regenerated isocyanate group content of 7.77% was obtained. [Block Compound 5] 228.6 parts of 4,4'-methylenebis (cyclohexyl isocyanate) was added to toluene 16
It is dissolved in 0.0 part and 160.0 parts of cyclohexanone, and 126.5 parts of methyl ethyl ketoxime is added dropwise in about 1 hour. After completion of the dropwise addition, the mixture is heated to 75 to 80 ° C. for another hour. Next, l, l, 3,3-tetra-n-butyl-1,3
-Add 0.48 part of diacetoxydistannoxane and 123.92 parts of polyester polyol (same as polyester polyol used for block compound 1) and add 75 to 80 ° C.
For 8 hours. Thus, a blocked solution having a regenerated isocyanate group content of 7.6% and a solid content of 60% was obtained. [Block Compound 6] A stirrer, a thermometer, a nitrogen gas inlet tube, and a condenser for reflux cooling were attached to a 2-liter 4-neck flask, and an adduct of TMP and α, α, α ′, α ′ tetramethylmetaxylylene diisocyanate was added. (Solid at room temperature, isocyanate content 13.3%)
427.1 parts of ethyl acetate and 1,1,3,3-tetra-n-butyl-1,3-diacetoxydistannoxane 0.
19 parts were charged, and the internal temperature was 60 to 70 in an atmosphere of nitrogen gas.
140.5 parts of methyl ethyl ketoxime was gradually added dropwise while maintaining the temperature at 0 ° C., and after the addition was completed, the temperature was maintained at the above temperature for about 4 hours. The solid content was 60% and the regenerated isocyanate group content was 6.
A 20% blocked solution was obtained.

The following evaluation was performed on the pre-coated steel sheet manufactured in this manner. 1. Coating film adhesion The coated plate was cut into a 1 mm square grid on the coated surface with a cutter knife, extruded 7 mm with an Erichsen tester so that the coated surface was convex, and then subjected to a tape peeling test. JIS-K5400.8.2 and J.K.
It carried out according to the method of IS-K5400.08.5. The evaluation after peeling off the tape was performed according to JIS-K5400.
The evaluation was performed according to the figures of the evaluation examples described in 8.5. When the score was 10 points, the evaluation was ○, when the score was 6 or more and less than 10 points, the evaluation was Δ; Further, the precoated steel sheet was immersed in boiling water according to JIS-K5400.8.20, taken out, left for 24 hours, and then subjected to cross-cut Ericksen and tape peeling by the above-mentioned method, and similarly evaluated. 2. Bending test of coating film The coated plate was bent at 180 °, and the coating film in the processed portion was observed with a 10-fold loupe to check for cracks in the coating film. Further, an adhesive tape was stuck to the processed portion, and the remaining state of the coating film when the adhesive tape was vigorously peeled was visually observed. The bending was performed in a 20 ° C. atmosphere with a 0.6 mm spacer interposed therebetween. The evaluation of coating film cracking was evaluated as follows: ○ when there was no coating film cracking, △ when there was some cracking in the coating film,
When the coating film had a clear crack visually, it was evaluated as x. In addition, the evaluation of the remaining state of the coating film after peeling off with the tape was evaluated as follows: ○ when the coating film remained on the plated steel sheet without peeling at all; Δ when the coating film was partially peeled; The case where peeling was observed over the entire surface was evaluated as x.
Further, the coated steel sheet is heated in boiling water according to JIS-K5400.8.
In accordance with the description in No. 20, after immersion, removal, and left standing for 24 hours, the above-mentioned bending was performed, and similarly, the peeling of the coating film and the remaining state of the coating film after the tape peeling test of the processed portion were evaluated.

As a low temperature processability, in an atmosphere of 0 ° C.,
A 180 ° bending test with a 0.6 mm spacer interposed was also performed, and the coating film crack was evaluated according to the same evaluation criteria as at 20 ° C. 3. Corrosion resistance The coated plate was subjected to a salt spray test according to the method described in JIS-K5400.9.1. The test time was 240 hours for an electrogalvanized steel sheet and 360 hours for a galvanized steel sheet. The evaluation method of the coating film of the cross cut part is as follows.
When the maximum swelling width on one side of the cross cut was less than 1 mm, it was evaluated as ○, when it was 1 mm or more and less than 3 mm, and when it was 3 mm or more, it was evaluated as x. In addition, the above-mentioned salt spray test was also performed on a flat plate manufactured so that the return (burr) at the time of cutting was on the evaluation surface side of the coated steel sheet (to be the upper burr),
The swollen width of the coating film from the end face was observed. The evaluation method of the end face portion is as follows: ○ when the swollen width from the end face is within 3 mm, 3 mm
If it is not less than 5 mm, it is x.
Was evaluated.

Hereinafter, Examples 1 to 18 will be described in detail. On the electrogalvanized steel sheet, the base treatment layer No.
Table 4 shows the evaluation results of the coated steel sheets provided with No. 1 and further provided with a coating layer using a commercially available primer coating containing each of the rust preventive pigments shown in Tables 2 and 3. Tables 4 and 5 also show details of the amount of the base treatment layer in the dry state, the dry film thickness of the coating layer containing the rust preventive pigment, and the amount of the rust preventive pigment added. In addition, the coated steel plate of Comparative Example-1 to Comparative Example-6 in Tables 4 and 5 was used as a comparative material.

The precoated steel sheet of the present invention (Examples 1 to 1)
8) has excellent coating film adhesion, bending workability, and corrosion resistance, and has the same coating film performance as a conventional precoated steel sheet (Comparative Examples 1 and 2) using a chromium-based base treatment and a rust-preventive pigment. On the other hand, when no rust-preventive pigment was added to the coating layer (Comparative Example 3), or only the phosphoric acid-based rust-preventive pigment (Comparative Example 4) or only the vanadic acid-based rust-proof pigment (Comparative Example 5) was used. When it is used for a layer, the corrosion resistance of the cut part and the end face part is poor and is unsuitable. It should be noted that Comparative Examples 1 and 2 are also unsuitable because they use environmentally toxic chromium.

[0067]

[Table 1]

[0068]

[Table 2]

[0069]

[Table 3]

[0070]

[Table 4]

[0071]

[Table 5] Hereinafter, details of Examples 19 to 34 will be described.

On the hot-dip galvanized steel sheet, the base treatment layer No. Tables 6 and 7 show the evaluation results of the coated steel sheets provided with No. 1 and further provided thereon with a coating layer using a commercially available primer coating containing each of the rust preventive pigments shown in Tables 2 and 3. Tables 6 and 7 also show details of the amount of the base treatment layer in the dry state, the dry film thickness of the coating layer containing the rust preventive pigment, and the amount of the rust preventive pigment added. In addition, the coated steel plate of Comparative Example 6 in Tables 6 and 7 was used as a comparative material.

The precoated steel sheet of the present invention is excellent in coating film adhesion, bending workability and corrosion resistance even when a hot-dip galvanized steel sheet is used as an original sheet (Examples 19 to 34). It has the same coating performance as the conventional precoated steel sheet used (Comparative Example 6). In addition, Comparative Example 6 is unsuitable because chromium, which is environmentally toxic, is used.

[0074]

[Table 6]

[0075]

[Table 7] Hereinafter, details of Examples 35 to 60 will be described.

Precoating in which each of the base treatments shown in Table 1 was provided on the electrogalvanized steel sheet and the hot-dip galvanized steel sheet, and a coating layer using a commercially available primer paint containing the rust-proofing pigment a shown in Table 2 was provided thereon. Tables 8 and 9 show the evaluation results of the steel sheets. Table 6 also shows details of the amount of the base treatment layer in the dry state, the dry film thickness of the coating layer containing the rust preventive pigment, and the amount of the rust preventive pigment added.
Shown in In addition, Comparative Examples 7 to 11 in Tables 8 to 9 were used as comparative materials.
Was used.

The precoated steel sheet of the present invention (Examples 35 to 6)
0) is excellent in coating film adhesion, bending workability, and corrosion resistance.
On the other hand, in Comparative Example 7, the amount of the thiocarbonyl group-containing compound added was small and the corrosion resistance and the coating film adhesion were poor, which was not preferable. In Comparative Example 8, the amount of the base treatment layer adhered was small, and the corrosion resistance and adhesion were poor, which is also not preferable. In Comparative Example 9, the amount of ammonium phosphate added was too large, and the solution gelled, so that it could not be coated on a plated steel sheet, which was also unsuitable. In Comparative Examples 10 and 11, the thiocarbonyl group-containing compound was not added, so that the coating film adhesion and the corrosion resistance were inferior and were not preferred.

[0078]

[Table 8]

[0079]

[Table 9] Hereinafter, details of Examples 61 to 76 will be described.

Examples 19 to 34 and Comparative Example 6 shown in Table 5
Tables 10 to 11 show the evaluation results of the precoated steel sheet further provided with the overcoat film on the coating film of the precoated steel sheet. The pre-coated steel sheet of the present invention is a case where a coating containing a rust-preventive pigment is used as a lower coating and an upper coating is further provided thereon (Examples 61 to 61).
76) has excellent coating film adhesion, bending workability, and corrosion resistance, and has the same coating film performance as a conventional coated steel plate using a chromium-based base treatment and a rust-preventive pigment (Comparative Example 12). In addition,
Comparative Example 12 is unsuitable because it uses environmentally toxic chromium.

[0081]

[Table 10]

[0082]

[Table 11] Hereinafter, details of Examples 77 to 87 will be described.

On the hot-dip galvanized steel sheet, the base treatment layer No. 1 and the above-mentioned [Polyol 1 to
7] and [Block Compounds 1 to 6] were provided with a coating layer formed by adding a rust-preventive pigment a shown in Table 2 to a resin blended in a combination shown in Tables 12 and 13. Tables 12 and 13 show the evaluation results of the precoated steel sheet provided with the overcoat film.

The precoated steel sheets of the present invention were prepared in Examples 77 to
As shown in 87, the resin constituting the coating layer containing the rust-preventive pigment is (A) a polyester polyol having at least 3 functional groups, (B) an epoxy resin having at least one secondary hydroxyl group, and a lactone compound or an alkylene oxide. And (C) a blocked product of an organic polyisocyanate or a blocked prepolymer having a terminal NCO 2 group obtained by the reaction of an organic polyisocyanate with an active hydrogen compound,
It is excellent in low-temperature workability and more suitable.

[0085]

[Table 12]

[0086]

[Table 13]

[0087]

According to the present invention, it has become possible to provide a precoated steel sheet which is excellent in the adhesion of the coating film, the workability of the coating film and the corrosion resistance without using chromium which is environmentally toxic.
Therefore, it can be said that the present invention is an invention having extremely high industrial value.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiromasa Nomura 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (72) Inventor Hiroshi Kanai 20-1 Shintomi, Futtsu-shi, Chiba Made in New Japan (72) Inventor Hiroyasu Furukawa 1 Kimitsu, Kimitsu City, Chiba Prefecture Nippon Steel Corporation Kimitsu Works (72) Inventor Motoo Kabeya 4-1-1 Minamishinagawa, Shinagawa-ku, Tokyo 15 Japan Paint Co., Ltd. (72) Inventor Toshiaki Shimakura 4-1-1, Minamishinagawa, Shinagawa-ku, Tokyo Japan F Co., Ltd. F-term (reference) 4D075 CA33 DA06 DB02 DC10 DC12 DC18 EB33 EB35 EC01 EC03 EC15 4F100 AA04B AA04C AA17B AA20B AB03A AB18 AH02B AH04B AK01B AK01C AK41C AK51C AK53C AK54C AR00D BA03 BA04 BA05 BA07 BA10A BA10C BA10D CA13B CA13C CA14B CA14C DE01B EH71A GB90 JB02 JK06 JL10D 4K026 AA02 AA11 BA03 BB08 CA23 CA26 CA30 CA37 CA39 CA41 DA02 DA03 DA06

Claims (3)

[Claims] 1. At least one side of a steel sheet or a plated steel sheet, (1) 30 to 500 parts by weight of a resin as a solid content, 0.2 to 50 parts by weight of a thiocarbonyl group-containing compound, and 0.1 to 5 parts by weight of a phosphoric acid compound Part (as PO ₄ ), (2) fine particles of silica (10)
(3) 30 to 500 parts by weight of resin as solids, 0.2 to 50 parts by weight of thiocarbonyl group-containing compound, and 50 parts by weight of fine silica
A coating layer containing no more than 500 parts by weight and not containing a phosphate compound, having at least one layer as a base treatment layer, and further releasing a vanadate ion source and releasing phosphate ions thereon A precoated steel sheet having a rust preventive film layer containing a phosphate ion source contained in a resin. 2. The resin constituting the rust preventive film layer,
(A) a polyester polyol having at least three functional groups, (B) a product obtained by adding a lactone compound or an alkylene oxide to an epoxy resin having at least one secondary hydroxyl group, and (C) a blocked product of an organic polyisocyanate or an organic compound. The precoated steel sheet according to claim 1, which is a resin obtained from a blocked product of a prepolymer having an NCO group at a terminal obtained by reacting a polyisocyanate with an active hydrogen compound. 3. The precoated steel sheet according to claim 1, further comprising a colored upper coating layer on the rust prevention coating layer.