JP2003213202A - Coating resin composition and coated metal plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a primer coating resin composition for coating metal plates excellent in corrosion resistance, acid resistance, processability, boiling water resistance, or the like, even when using a non-chromium rust preventing agent and a coated metallic plate in which the composition is laminated and cured. <P>SOLUTION: The coating resin composition is obtained by compounding a polyester resin composed of an acid component containing 50-100 mol% aromatic dicarboxylic acid and a glycol component containing a ≥5C alkylene glycol and/or an alicyclic glycol with a curing agent and the non-chromium rust preventing agent. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition for coatings using a chromium-free rust preventive agent and a coated metal plate obtained by laminating and curing the composition. More specifically, the present invention, even when using a chromium-free rust inhibitor,
A resin composition for a primer coating for a coated metal plate that has excellent corrosion resistance, acid resistance, processability, boiling water resistance, etc., or a resin composition for a one-coat coating that doubles as a primer and a primer, and the composition is laminated and cured. The present invention provides a painted metal plate.

[0002]

2. Description of the Related Art Among coated metal plates, so-called pre-coated metal plates are used for roofing materials, wall materials and other building materials fields, storerooms, outdoor units such as radiator units, VTRs, etc. by taking advantage of their economic efficiency, productivity and workability. Widely used in home appliances such as washing machines and refrigerators. The paint used for the pre-coated metal plate includes a binder resin, a curing agent, a pigment, a rust preventive agent, a catalyst, a solvent, etc. Among them, currently used paint resins include alkyd resin and acrylic. There are resins, epoxy resins, and the like, but these have problems in processability, and high molecular weight polyesters are used in fields requiring high processability.

At present, the resin used for the primer coating of a coated metal plate is mainly an epoxy resin, but since the epoxy resin lacks flexibility, it cannot withstand high-level processing,
There is a drawback that cracks occur in the coating film of the processed part and the metal is easily corroded from there. Epoxy resin is generally recognized as having good corrosion resistance, but it has poor impact resistance and the problem of poor corrosion resistance of the end face due to the formation of a small coating film on the end face when cutting a coated metal plate. There is. Therefore, when an epoxy resin is used as a resin for a primer coating for a highly processed metal plate, there is a serious drawback that the advantage cannot be utilized due to the above problems. Moreover,
Even if a high-molecular-weight polyester resin having good processability is used for the topcoat paint, the interlayer adhesion between the primer and the topcoat is poor, and high processability cannot be exhibited.

As a solution to such a problem,
Japanese Patent Publication No. 62-5467, Japanese Patent Laid-Open No. 3-217471.
JP-A-6-256721, JP-A-8-8
No. 1651 and the like are known, and the workability and the moisture resistance,
Almost compatible with corrosion resistance and chemical resistance.

However, although the rust preventives used in these resin compositions for coating materials are all chrome-based, the use of heavy metals such as the problem of hexavalent chromium contained in the chrome-based rust preventives can be reduced. In view of this, there is an increasing demand for the use of chromium-free rust preventives. However, when a chromium-free rust preventive is used, the corrosion resistance and boiling water resistance are largely inferior to when a chromium rust preventive is used. In particular, there are no known primer coatings and resins used therefor, which have poor corrosion resistance and use a chromium-free rust preventive.

[0006]

In view of the above circumstances, the present invention is directed to a resin composition for a primer coating which has excellent corrosion resistance, workability, boiling water resistance and the like even when a chromium-free rust preventive agent is used, and a laminate thereof. -It is intended to provide a cured coated metal plate.

[0007]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that an aromatic dicarboxylic acid is essential and an alkylene glycol having a main chain of 5 or more carbon atoms has a special ratio. By blending a polyester resin containing in and a curing agent capable of reacting with these, it has been surprisingly found that end face corrosion resistance, cross-cut portion corrosion resistance, boiling water resistance, acid resistance and processability can be highly compatible, and the present invention has been achieved. did.

That is, the present invention has the following features. (1) 100 mol% of each of acid component and glycol component
Then, the acid component is 50 to 100 aromatic dicarboxylic acid.
A polyester resin (A) containing mol% and an alkylene glycol and / or alicyclic glycol having a main chain of 5 or more carbon atoms in the glycol component, a curing agent (B), and a chromium-free rust preventive agent (C). A resin composition for paints, characterized by:

(2) As the glycol component of the polyester resin (A), an alkylene glycol having 5 or more carbon atoms in the main chain and / or an alicyclic glycol component of 20 to 8 is used.
The resin composition for coating according to (1), which contains 0 mol%.

(3) A coated metal plate characterized in that the resin composition for coating composition comprising (1) or (2) is laminated and cured on the metal plate.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the polyester resin (A) used in the present invention, when the acid component and the glycol component are each 100 mol%, the acid component to be copolymerized is preferably 50 to 100 mol% of an aromatic dicarboxylic acid. The lower limit is preferably 70 mol% or more, more preferably 80 mol% or more. When the aromatic dicarboxylic acid is less than 50 mol%, good acid resistance, chemical resistance, corrosion resistance and scratch resistance may not be obtained. On the other hand, the glycol component contains aliphatic and / or
Alternatively, it is preferable to copolymerize 0 to 50 mol% of an alicyclic dicarboxylic acid. The upper limit is preferably 40 mol% or less,
It is more preferably 30 mol% or less. .

In the polyester resin (A) used in the present invention, the aromatic dicarboxylic acid to be copolymerized is terephthalic acid, isophthalic acid, orthophthalic acid,
2,6-naphthalenedicarboxylic acid and the like can be mentioned. As the aromatic dicarboxylic acid, it is particularly preferable to use terephthalic acid and isophthalic acid together from the viewpoint of coating film physical properties and solubility.

In the polyester (A), the aliphatic dicarboxylic acid content is preferably less than 30 mol%, more preferably less than 20 mol%. If the aliphatic dicarboxylic acid content is 30 mol% or more, the acid resistance may deteriorate.

Examples of the aliphatic dicarboxylic acid copolymerizable with the polyester resin (A) used in the present invention include succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedioic acid and azelaic acid. Examples of the alicyclic dicarboxylic acid to be copolymerized with the polyester resin (A) include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4 cyclohexanedicarboxylic acid and alicyclic dicarboxylic acid such as dimer acid. Can be mentioned. Of these, adipic acid, sebacic acid, 1,4-
Cyclohexanedicarboxylic acid and dimer acid are preferable from the viewpoint of processability, and the content is preferably 30 mol% or less from the viewpoint of acid resistance.

The glycol component to be copolymerized with the polyester resin (A) contains an alkylene glycol and / or alicyclic glycol having a main chain of 5 or more carbon atoms, so that good end face corrosion resistance, processability and acid resistance can be obtained. Can be given. Examples of the alkylene glycol having 5 or more carbon atoms in the main chain include 1,5-pentanediol and 1,6-
Hexanediol, 1,8-octanediol, 1,9
Examples thereof include linear glycols such as nonanediol and side chain glycols such as 3-methyl-1,5-pentanediol and 3-methyl-8-methyl-1,8-octanediol. 1,4 as the alicyclic glycol
-Cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, hydrogenated bisphenol A, and its ethylene oxide / propylene oxide adduct, dimer diol,
Examples thereof include TCD (tricyclodecane) group-containing glycol. Of these, from the viewpoint of corrosion resistance, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,
5-pentanediol and 1,4-cyclohexanedimethanol are preferred. The alkylene glycol and / or alicyclic glycol having 5 or more carbon atoms in the main chain is 20 to 20.
It is preferable to contain 80 mol%. The upper limit is preferably 75 mol% or less, more preferably 70 mol% or less.
The lower limit is preferably 25 mol% or more, more preferably 30 mol% or more.

Other glycols include ethylene glycol, diethylene glycol, neopentyl glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, polyethylene glycol, polypropylene glycol, bisphenol A and / or bisphenol F
And ethylene oxide and / or propylene oxide adducts thereof. Other glycols are appropriately selected from the viewpoints of economy and coating film physical properties, but ethylene glycol, diethylene glycol, bisphenol A
And / or it is preferable to use an adduct of ethylene oxide and / or propylene oxide of bisphenol F within a range not impairing the content of the invention.

Further, polyvalent carboxylic acids such as trimellitic acid and pyromellitic acid or polyhydric polyols such as trimethylolethane, trimethylolpropane, glycerin and pentaerythritol are added in an amount of 0.1 to 3 with respect to all acids or all glycols. The use of mol% can further improve the corrosion resistance and the acid resistance.

The polyester resin (A) used in the present invention is a direct polymerization method in which a dicarboxylic acid and a glycol are directly esterified under normal pressure or pressure, and then polymerized. It is synthesized by a known method such as a transesterification method for polymerization or a method in which a small amount of xylene is added to dicarboxylic acid and glycol to carry out a dehydration reaction under normal pressure. As the polymerization catalyst, known catalysts such as a titanium compound such as tetrabutyl titanate, a zinc compound, an antimony compound, a lead compound and a germanium compound are used.

The glass transition temperature of the polyester resin (A) used in the present invention is 0 to 8 from the viewpoint of processability.
0 ° C is preferred. The upper limit is preferably 70 ° C. or lower, and 60
C. or less is more preferable. The lower limit is preferably 10 ° C or higher, more preferably 20 ° C or higher. When the temperature is lower than 0 ° C, the workability is good, but scratch resistance, chemical resistance, boiling water resistance, etc. may decrease. If it exceeds 80 ° C, the acid resistance is good, but the workability may be lowered.

The reduced viscosity of the polyester resin (A) used in the present invention is preferably 0.2 to 0.7 dl / g. The upper limit is preferably 0.65 dl / g or less, and 0.
It is more preferably 6 dl / g or less. The lower limit is 0.3 dl /
It is preferably at least g, more preferably at least 0.35 dl / g. If the reduced viscosity is less than 0.2 dl / g, the workability may decrease. On the other hand, if it exceeds 0.7 dl / g, the curability may be lowered or the solvent solubility may be lowered. The number average molecular weight is preferably 5,000 to 25,000. The upper limit is preferably 20,000 or less, more preferably 18,000 or less. The lower limit is 700
It is preferably 0 or more, more preferably 8000 or more. If the number average molecular weight is less than 5,000, the processability may decrease. On the other hand, if it exceeds 25,000, the curability may be lowered, or the solvent solubility may be lowered.

In the polyester resin (A) used in the present invention, a dicarboxylic acid containing a sulfonic acid metal base or glycol may be used in an amount of 5 mol% or less. Examples of the dicarboxylic acid containing a metal sulfonate group include sulfoterephthalic acid, 5-sulfoisophthalic acid,
4-sulfonaphthalene-2,7-dicarboxylic acid, 5-
Mention may be made of metal salts such as [4-sulfophenoxy] isophthalic acid. As the glycol containing a metal sulfonate group, 2-sulfo-1,4-butanediol,
Examples include metal salts such as 2,5-dimethyl-3-sulfo-2,5-hexanediol. Li as the metal salt,
Examples thereof include salts of Na, K, Mg, Ca, Fe and the like.

Polyester resin used in the present invention
As a method for determining the composition and composition ratio of (A), for example,
Dissolve the polyester resin in a solvent such as deuterated chloroform
taking measurement ¹H-NMR and¹³C-NMR, polyester resin
Gas chromatography measurement after fat methanolysis
And the like. Of these,¹H-NM
R is simple and preferred.

The polyester resin (A) used in the present invention may be modified with a vinyl polymerizable monomer, an epoxy resin, or a urethane compound with an isocyanate compound. When the polyester resin is modified with a vinyl polymerizable monomer, the polyester resin is copolymerized with a dicarboxylic acid containing an unsaturated double bond such as fumaric acid or oleic acid to introduce an unsaturated double bond into the polyester resin. , A method of radically polymerizing this unsaturated double bond and a vinyl compound such as (meth) acrylic acid ester, styrene, vinyl acetate in a solution, or a hydroxy compound at one end synthesized from (meth) acrylic acid ester, styrene, etc. It is synthesized by a known method such as directly copolymerizing a macromonomer containing two groups with polyester.

The epoxy resin-modified polyester resin is obtained by adding an acid anhydride such as trimellitic anhydride or phthalic anhydride to the terminal hydroxy group of the polyester resin to modify the terminal carboxy, and then to remove the carboxyl group and the epoxy resin from each other. It can be synthesized by a known method such as a method of modifying with epoxy in the presence of a catalyst such as phenylphosphine. Alternatively, a carboxyl group may be introduced by using a carboxyl group-containing glycol such as dimethylolpropionic acid as a chain extender.

The urethane-modified polyester resin is synthesized by a known method such as mixing a polyester diol having a low molecular weight with a chain extender if necessary and reacting it with a diisocyanate compound. Alternatively, a carboxyl group-containing diol such as dimethylolpropionic acid may be used as the chain extender to introduce a carboxyl group into the side chain.

The coating resin composition of the present invention must contain a polyester resin (A), a curing agent (B) capable of reacting with the polyester resin (A), and a chromium-free rust preventive agent (C). The compounding amount of the curing agent (B) is (A) / (B) = 95/5 to 60 when the sum of (A) and (B) is 100 by weight ratio.
/ 40 is preferable. The upper limit of (A) is more preferably 9
0, most preferably 85. The lower limit is more preferably 65, and most preferably 70. When the compounding amount of (A) exceeds 95, the coating film physical properties such as chemical resistance, corrosion resistance and scratch resistance may be poor, and when it is less than 60, good processability may not be obtained. The content of the chromium-free rust preventive agent (C) is (A), (B),
When the sum of (C) is 100, (C) / ((A) +
(B)) = 50/50 to 1/99 is preferable. The upper limit of (C) is preferably 30 or less, and the lower limit is preferably 5 or more.
When (C) exceeds 50, boiling water resistance, processability and gloss may be poor, and when it is less than 5, good corrosion resistance may not be obtained.

Examples of the curing agent (B) capable of reacting with the polyester resin (A) include alkyl etherified amino formaldehyde resins, epoxy compounds and isocyanate compounds, and phenol resins. Of these, alkyl etherified aminoformaldehyde resins and isocyanate compounds are preferable in terms of processability. Further, an isocyanate compound is preferable from the viewpoint of acid resistance, and it is preferable to use the isocyanate compound in a blocked state in view of storage stability.

As the isocyanate compound, there are aromatic and aliphatic diisocyanates and polyisocyanates having a valence of 3 or more, which may be low molecular weight compounds or high molecular compounds. For example, tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate or a trimer of the above isocyanate compounds, and these isocyanate compounds Excess amount and for example ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine,
Examples thereof include a terminal isocyanate group-containing compound obtained by reacting a low molecular weight active hydrogen compound such as diethanolamine and triethanolamine or a high molecular weight active hydrogen compound such as various polyester polyols, polyether polyols and polyamides.

It is preferable to use a blocked isocyanate as the isocyanate compound. Examples of the isocyanate blocking agent include phenols such as phenol, thiophenol, methylthiophenol, ethylthiophenol, cresol, xylenol, resorcinol, nitrophenol and chlorophenol,
Oximes such as acetoxime, methyl ethyl ketoxime, cyclohexanone oxime, alcohols such as methanol, ethanol, propanol, butanol, erylene chlorohydrin, 1,3-dichloro-2-
Halogen-substituted alcohols such as propanol, t-butanol, tertiary alcohols such as t-pentanol, ε-caprolactam, σ-valerolactam, γ-butyrolactam, lactams such as β-propyrolactam, and the like. In addition, aromatic amines, imides, acetylacetone, acetoacetic acid esters, malonic acid ethyl ester compounds, sodium bisulfite and the like can be mentioned.
The blocked isocyanate is obtained by subjecting the above isocyanate compound and an isocyanate blocking agent to an addition reaction by a conventionally known appropriate method.

Alkyl etherified amino aldehyde resin is, for example, formaldehyde or paraformaldehyde alkylated with an alcohol having 1 to 4 carbon atoms such as methanol, ethanol, n-propanol, isopropanol, n-butanol and urea, and urea, N, N-ethylene urea, dicyandiamide,
It is a condensate with aminotriazine and the like, and is methoxylated methylol N, N, -ethylene urea, methoxylated methylol dicyandiamide, methoxylated methylol benzoguanaine, butoxylated methylol benzoguanemine, methoxylated methylol melamine, butoxylated methylol melamine. , Methoxylated / butoxylated mixed methylol melamine, butoxylated methylol benzoguanamine, and the like, but from the viewpoint of processability, methoxylated methylol melamine and butoxylated methylol melamine are used individually or in combination. can do.

As the epoxy compound, diglycidyl ether of bisphenol A and its oligomer, diglycidyl ether of hydrogenated bisphenol A and its oligomer, orthophthalic acid diglycidyl ester, p
-Oxybenzoic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, succinic acid diglycidyl ester, adipic acid diglycidyl ester, sebacic acid diglycidyl ester, ethylene glycol diglycidyl ether, propylene glycol Diglycidyl ether, 1,4-butanediol diglycidyl ether,
1,6-hexanediol diglycidyl ether and polyalkylene glycol diglycidyl ethers, trimellitic acid triglycidyl ester, triglycidyl isocyanurate, 1,4-diglycidyloxybenzene, diglycidyl propionurea, glycerol triglycidyl ether, triglycidyl ether Examples thereof include methylol elan triglycidyl ether, trimelitol propane triglycidyl ether, pentaerythritol tetraglycidyl ether, and triglycidyl ether of glycerol alkylene oxide adduct.

Further, examples of the phenol resin include a resol type resin obtained by reacting a phenol with an aldehyde in the presence of an alkali catalyst, and a novolak type resin obtained by reacting a phenol with an aldehyde in the presence of an acidic catalyst. Is preferable, and a resole type resin is particularly preferable. Phenols used for these phenolic resins include phenol, o-cresol, p-cresol,
Examples thereof include m-cresol, m-methoxyphenol, 2,3-xylenol, 2,5-xylenol, p-tert-butylphenol, p-ethylphenol, bisphenol A and bisphenol F. These mono-trimethylol compounds and The condensate, or an alkyl ether thereof, or those obtained by subjecting these to various modifications such as epoxy modification, oil modification, melamine modification, and amide modification can be used.

These curing agents are preferably used in combination with known curing catalysts or accelerators selected according to their type.

The chromium-free rust preventive agent (C) used in the present invention includes, for example, phosphoric acid rust preventive pigments such as zinc phosphate, iron phosphate, aluminum phosphate, zinc phosphite and aluminum tripolyphosphate. Molybdate anticorrosion pigments such as calcium molybdate, aluminum molybdate, barium molybdate, vanadium anticorrosion pigments such as vanadium oxide, silicate pigments such as calcium silicate, water-dispersed silica, fine silica such as fumed silica. Etc. can be used. Further, it is also possible to use polyaniline, polythiophene, polypyrrole, etc., which are rust preventive conductive polymers. The non-chrome rust preventives shown here are a part and are not particularly limited, but among these, silicate rust preventive pigments,
Phosphoric acid-based rust preventive pigments are preferred from the viewpoint of rust resistance.

The baking temperature of the coating resin composition of the present invention is arbitrarily selected depending on the size and thickness of the metal plate, the ability of the baking furnace, the curability of the coating, and the like. A mixing machine such as a roll kneader, a ball mill, a sand mill, and a blender is used for producing the coating composition. For coating, roller coating, roll coater, spray coating, electrostatic coating, etc. are appropriately selected.

The coating resin composition of the present invention comprises extenders such as titanium oxide, talc, barium sulfate and clay, known colorants, additives such as silica and wax, and glass fibers depending on the purpose and use. It can be blended.

In the coating resin composition of the present invention, the polyester (A) and the curing agent (B) are used in the form of being dissolved in an organic solvent. Examples of the organic solvent include toluene, xylene, Solvesso 100, 150, ethyl acetate, butyl acetate, methyl cellosolve, ethyl cellosolve, ethyl carbitol, butyl carbitol, methyl cellosolve acetate, ethyl cellosolve acetate, methyl carbitol acetate, butyl carbyl. Tall acetate, methyl ethyl ketone, cyclohexanone, isophorone, N
-Methylpyrrolidone is appropriately selected in consideration of solubility and evaporation rate from dibasic acid ester and the like.

The chrome-free rust preventive has a weaker rust preventive power than the chrome preventive rust. Chromium-based rust preventives provide good rust preventive effect due to the self-healing effect of hexavalent chromium, but non-chromium-based rust preventives do not have that effect.
Rises. Therefore, it is considered that the primer coating film is hydrolyzed and the rust prevention property is deteriorated. However, by using the polyester resin (A) having good alkali resistance and hydrolysis resistance, it is considered that good corrosion resistance can be obtained even with a chromium-free anticorrosive agent.

The coating resin composition of the present invention exhibits sufficient performance just by coating and baking the coating composition itself, and is therefore suitable for the backside coating of a metal plate, etc., but is also preferably used as a primer. In addition, a separately known topcoat paint may be separately applied for the purpose of improving weather resistance, stain resistance, alkali resistance and the like.

[0040]

EXAMPLES The present invention will be described below with reference to examples. In the examples, "parts" means "parts by weight". Moreover, each measurement item followed the following method.

Reduced viscosity ηsp / c (dl / g) 0.10 g of a polyester resin was dissolved in 25 cc of a mixed solvent of phenol / tetrachloroethane (weight ratio 6/4) and measured at 30 ° C. using an Ubbelohde viscosity tube.

The glass transition temperature was measured using a differential scanning calorimeter (DSC) at a temperature rising rate of 20 ° C./min. As a sample, 5 mg of the sample was placed in an aluminum pressing lid type container and crimped before use.

An acid value sample of 0.2 g was precisely weighed and dissolved in 20 ml of chloroform. Then, it was determined by titration with 0.01 N potassium hydroxide (ethanol solution). Phenolphthalein was used as the indicator.

The number average molecular weight was measured by gel permeation chromatography (GPC) using a polystyrene standard sample for calibration.

Workability The coated steel sheet was bent 180 degrees, and cracks generated at the bent portion were observed and judged with a 10 times magnifying glass. 3T refers to the case where the coating film does not break even if three sheets having the same plate thickness are sandwiched in the bent portion, and 0T refers to the case where the plate does not crack even if it is bent 180 degrees without sandwiching the plate at all.

The acid-resistant coated steel sheet was immersed in 5% HCl at 40 ° C. for 48 hours, and the state of occurrence of blisters on the coated surface was determined according to ASTM D714-56.
It was evaluated according to. When there was no abnormality, it was set to 10.

Scratchability A 10-yen coin was attached and evaluated using a coin scratch tester manufactured by Tester Sangyo Co., Ltd. The load attached to the coin was 1 kg. The evaluation criteria are shown below. ◎: Almost no primer surface is visible ○: Primer surface is visible, but metal base is not visible ×: Metal base is visible XX: Metal base is visible

The alkali-resistant coated steel sheet was immersed in 5% NaOH at 40 ° C. for 48 hours,
The appearance of blisters on the coated surface is determined by ASTM D714-5.
Evaluation was made according to 6. When there was no abnormality, it was set to 10.

The corrosion-resistant coated steel sheet was subjected to a 5% NaCl salt spray test at 35 ° C. for a predetermined time, and the occurrence of blisters was visually judged. Corrosion resistance is evaluated for the cross cut part, 2T processed part for 1000 hours,
The end face (cutting part) was implemented for 500 hours. The evaluation criteria are shown below. 2T processed part ◎: No abnormality ○: Almost no blisters △: Blister occurrence ×: Remarkably blister occurrence Cross cut part (blister blister width) ◎: 1 mm or less ○: 1 to 5 mm △: 5 to 10 mm ×: 10 mm or more End surface ( Blister blister width) ◎: 1 mm or less ○: 1 to 5 mm △: 5 to 10 mm ×: 10 mm or more

After immersing the boiling water resistant coated steel sheet in boiling water for 2 hours, the following tests were conducted. Gloss 60 degree reflectance was measured (JIS K
5400). Erichsen (6mm) cross-cut (gap 1
mm, the number of squares is 100), Erichsen was applied for 6 mm to the cross section, and finally cellophane tape was peeled off. (100/100 is excellent, and 0/100 indicates that all are peeled off) Gloss retention rate: Gloss after boiling water / Gloss before boiling water (%). Appearance It was judged visually according to ASTM-D714. 10: No change in appearance 8F: Blisters with a diameter of about 1 mm were slightly observed 9D: Blisters were smaller than 8F and number density was 8F
Peeling much more than 2T tape After folding two steel plates (2T) having the same thickness as the steel plate coated with the coating film, the folded portion was peeled with cellophane tape, and the degree of peeling was visually judged. ⊚: Excellent (no peeling): Good Δ: Slightly bad ×: Poor (peeling over the entire surface) 0T tape peeling Bending the steel plate without sandwiching the tape, peeling the tape at the bent portion, and visually judging the degree of peeling.
The evaluation criteria were the same as the 2T tape peeling. Scratch A 10-yen coin was attached and evaluated using a coin scratch tester manufactured by Tester Sangyo Co., Ltd. The load attached to the coin was 1 kg. The evaluation criteria are shown below. ◎: Excellent (scratches stay on top): Good (scratches stay on primer layer) △: Somewhat bad ×: Poor (scratches reach the steel plate))

Synthesis Example (A) In a reaction vessel equipped with a stirrer, a condenser and a thermometer, 389 parts of terephthalic acid, 389 parts of isophthalic acid, 167 parts of 3-methyl-1,3-propanediol, 1,5-
449 parts of pentanediol, an ethylene oxide adduct of bisphenol A (BPE-20 manufactured by Sanyo Kasei Co., Ltd.)
F) 412 parts and tetrabutyl titanate 0.41 part were charged, and the esterification reaction was carried out from 160 ° C. to 240 ° C. for 4 hours. Next, the system pressure is gradually reduced to 5
Reduce the pressure to 5 mmHg over 0 minutes, then 0.3 mmHg
A polycondensation reaction was performed at 260 ° C. for 60 minutes under a vacuum of g or less. As a result of NMR composition analysis, the obtained copolyester (A) was found to have an acid component in a molar ratio of terephthalic acid / isophthalic acid = 50/50 and a glycol component in a molar ratio of 3-methyl-1,3-propane. The ethylene oxide adduct of diol / 1,5-pentanediol / bisphenol A was 20/50/30. The reduced viscosity was measured to be 0.45 dl / g and the glass transition temperature was 31 ° C. The results are shown in Table 1.

Hereinafter, Table 1 was obtained by the method according to the above synthesis example.
Polyester resins (B) to (F) having the compositions shown in Table 1 were synthesized. (E) and (F) are comparative polyesters. The numerical values showing the composition in Table 1 represent the molar ratio.

[0053]

[Table 1]

Example 1 100 parts of polyester resin (A) and cyclohexanone 75 were placed in a reaction vessel equipped with a stirrer, a reflux condenser and a thermometer.
Parts, Solvesso 150, 75 parts were charged and stirred at 80 ° C. for 3 hours to obtain a polyester resin (A) solution having a solid content concentration of 40%. Polyester resin (A) solution 100
50 parts titanium oxide, 5 parts calcium silicate, melamine (trade name: Sumimar M40ST,
Nonvolatile matter 80%, Sumitomo Chemical Co., Ltd.) 20 parts, 10% benzyl alcohol solution of p-toluenesulfonic acid 2.5
Parts were mixed and dispersed for 3 hours with a glass bead type high-speed shaker to obtain a coating composition.

Preparation of Topcoat Paint High molecular weight polyester Byron 300 and Byron 200 manufactured by Toyobo Co., Ltd., which were previously dissolved (cyclohexanone / Solvesso 150 = 1/1 at a solid content concentration of 40%), were used in a solid content ratio of 60, respectively. / 40 parts, Sumimar M40 which is a methyl etherified methylol melamine
S (nonvolatile content 80%, Sumitomo Chemical Co., Ltd.) 31 parts,
2.5 parts of a 10% benzyl alcohol solution of p-toluenesulfonic acid and 125 parts of titanium oxide were added and dispersed for 5 hours with a glass bead type high-speed shaker to prepare an overcoat paint.

Preparation of Coated Steel Sheet (Test Piece) A hot-dip galvanized steel sheet having a zinc basis weight of 60 g / m ² of 0.5 mm thickness and subjected to chromate treatment was used as a base material. A predetermined primer was applied to this substrate so that the dry film thickness was 5 μm, and baking was performed for 50 seconds after the plate temperature reached 210 ° C. Next, the top coating material was applied so that the dry film thickness was 15 μm, and baked at a plate temperature of 230 ° C. for 50 seconds to prepare a coated steel plate.

In the following, the composition shown in Table 2 was similarly used.
The coating compositions of Examples 2 to 6 and Comparative Examples 1 to 4 were prepared, applied and baked. Table 2 shows the test results of the obtained coated steel sheet. However, the composition of the paint was shown in terms of solid content.

[0058]

[Table 2]

In Table 2, Comparative Examples 1, 2 and 4 use polyester resins containing no alkylene glycol having 5 or more carbon atoms in the main chain and / or alicyclic glycol in the glycol component. It is out of range.
Since Comparative Example 3 uses a chromium-based rust preventive, it is outside the scope of the claims.

The evaluation results in Table 2 show that in Comparative Example 4 in which a polyester resin containing no alkylene glycol and / or alicyclic glycol having 5 or more carbon atoms in the main chain and a chromium-based rust preventive agent are combined, corrosion resistance and There is room for improvement in boiling water resistance. Comparative Example 3 using a polyester resin containing an alkylene glycol having 5 or more carbon atoms in the main chain and a chromium-based anticorrosive agent showed excellent results in each measurement item, but it may give a load to the environment and is preferable. Absent. Comparative Example 1 in which a non-chromium type rust preventive agent is combined with a polyester resin containing no alkylene glycol having 5 or more carbon atoms in the main chain and / or alicyclic glycol.
It can be seen that in No. 2, the corrosion resistance and boiling water resistance are remarkably inferior. In comparison with them, Examples 1 to 6 using the coating resin composition of the present invention have excellent properties in each measurement item.

[0061]

EFFECTS OF THE INVENTION The resin composition for coating material and the coated metal plate of the present invention do not contain a chromium-based rust preventive, and are therefore environmentally friendly. Further, the resin composition for paints of the present invention is used as an anticorrosion paint exhibiting an excellent anticorrosion effect. The coated metal plate formed on the metal surface by a simple method of applying the coating composition to a substrate and drying the substrate has excellent stability, strength, solvent resistance and boiling water resistance.

Claims (3)

[Claims] 1. An acid component and a glycol component each of 10
When it is 0 mol%, the aromatic dicarboxylic acid is 50 as the acid component.
˜100 mol%, a polyester resin (A) containing an alkylene glycol and / or an alicyclic glycol having a main chain of 5 or more carbon atoms in the glycol component, a curing agent (B), and a non-chrome rust preventive agent (C). A resin composition for a coating material, comprising: 2. The glycol component of the polyester resin (A) contains 20 to 80 mol% of an alkylene glycol having a main chain of 5 or more carbon atoms and / or an alicyclic glycol component. A resin composition for a paint as described. 3. A coated metal plate, comprising the resin composition for paint according to claim 1 laminated or cured on the metal plate.