JP2003201446A - Resin composition for coating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin composition for a coating material, providing excellent appearance of the coated film after drawing processing, and providing excellent adhesion, boiling water resistance and corrosion resistance after the drawing processing and ironing processing. <P>SOLUTION: The resin composition for the coating material comprising a resin and a curing agent as main components, is regulated so that an organic coated film obtained only from the resin and the curing agent, or optionally with a curing catalyst added thereto has ≤35 mJ/mm<SP>2</SP>elastic strain energy at 100°C, or ≤60% proportion of the elastic strain energy. Preferably, the resin composition for the coating material contains a polyester resin having ≥3,000 number average molecular weight as the resin. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention has excellent processability and hardness, exhibits a coating film appearance excellent in gloss and sharpness, and has excellent squeezing or ironing processability. Of the resin composition for a coating, which has excellent appearance, adhesion, boiling water resistance, or corrosion resistance.

[0002]

2. Description of the Related Art As paints currently used as resins for coated metal plates, there are many paints such as copolyester resins, alkyd resins, vinyl resins, and silicone resin paints, which are used as solvent-based, water-dispersed, and powder paints. Has been done. However, none of them satisfy all the required performances, and focusing on one performance inevitably causes defects in the other performances, and is restricted in use. Is the current situation. Furthermore, not only in the field of two-piece food and beverage cans, but also in recent years, painted metal sheets are required to have squeezing or ironing workability as a high added value.

For example, JP-A-57-57746,
As disclosed in Japanese Patent Laid-Open No. 63-108081, it has been studied to make hardness and workability compatible with each other, but in any case, a sufficient effect is not obtained. In addition, Japanese Patent Publication
In 21830, a resin composition for coatings containing terephthalic acid and alkylene glycol as main components is examined, but when it is drawn, the gloss retention is poor and it has not been put to practical use.
Japanese Patent Publication No. 61-34754 also discloses a resin composition for coatings containing terephthalic acid and alkylene glycol as main components, but similarly, the drawability is insufficient, and the hardness, scratch resistance, and abrasion resistance are similar. Poor pollution. JP-A 1-2
In 45065, a system using polyester and an amino resin as a curing agent containing terephthalic acid and propylene glycol as main components is examined for compatibility between high degree, workability, and stain resistance, but poor drawing workability. There is a problem of poor boiling water resistance and adhesion after processing.

Japanese Patent Laid-Open No. 7-18169 discloses a resin composition for coatings containing isophthalic acid or orthophthalic acid and a long-chain glycol as a main component, but it has good weather resistance, alkali resistance and processability. Since the film strength is insufficient, the drawability is insufficient, and the hardness, stain resistance, and scratch resistance are poor. Also, JP-A-56-4664
In the publication, a polyester containing terephthalic acid and propylene glycol as a main component is studied as a can paint with a thermoplastic system (without a curing agent), but it has poor drawability and poor boiling water resistance after drawing. In addition, this resin system cannot satisfy the strict requirements for pre-coated steel sheets for home appliances and building materials.

As described above, in a polyester resin composition for a coated metal plate, a low Tg polyester resin having good workability causes scratches and peeling during drawing or ironing, resulting in poor stain resistance and hardness. On the other hand, a polyester resin having a high Tg often allows squeezing or ironing, but the adhesiveness and boiling water resistance after processing are poor, and none of them can achieve both.

[0006]

SUMMARY OF THE INVENTION In view of these problems, the present invention is for a coating having an excellent coating film appearance after drawability and also having adhesion, boiling water resistance and corrosion resistance after drawing or ironing. An object is to provide a resin composition.

[0007]

Means for Solving the Problems As a result of earnest analysis and examination in view of these problems, the present inventors have found that among resin compositions for paints mainly composed of a resin and a curing agent, an organic film containing only the resin and the curing agent is 100%. The resin composition for coatings having a low elastic strain energy at ℃ and its ratio has excellent squeezing or ironing processability even in the case of a polyester having a high Tg, which has been difficult in the past. It has been found that the coating film has a surprising coating film physical property having various properties such as corrosion resistance and corrosion resistance, and has arrived at the present invention.

That is, the present invention has the following features. (1) Of the resin composition for coating material containing mainly resin and curing agent, the elastic strain energy at 100 ° C. at 100 ° C. of the resin and the curing agent alone, or the organic film to which a curing catalyst is further added, is 35 mJ / mm ² The following is a resin composition for coatings.

(2) 100 ° C. of an organic film in which a resin and a curing agent alone are contained in a resin composition for coating containing mainly a resin and a curing agent, or a curing catalyst is further added if necessary.
The resin composition for paints, characterized in that the elastic strain energy ratio is 60% or less.

(3) The resin composition for coating according to (1) or (2), wherein the resin is a polyester resin having a number average molecular weight of 3000 or more.

(4) When the total amount of each of the acid component and the glycol component of the polyester in the resin is 100 mol%, the acid component is 10 to 100 mol% and the total amount of terephthalic acid and other aromatic dicarboxylic acid is 80 ~
100 mol%, other dicarboxylic acid 0 to 20 mol%
And a glycol component contains 50 mol% or more of any one or more of ethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, and 1,4-cyclohexanedimethanol. A polyester resin having a glass transition temperature of 10 to 80 ° C., wherein (1) to (3).
A resin composition for a paint as described.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to an elastic strain energy (hereinafter simply referred to as elastic strain energy U) at 100 ° C. of an organic film containing only a resin and a curing agent in a resin composition for coating containing mainly a resin and a curing agent. Shows) is 35 mJ / mm
^It should be ² or less, or the elastic strain energy ratio (hereinafter simply referred to as elastic strain energy ratio U%) should be 60% or less.

The elastic strain energy U and the elastic strain energy ratio U% are parameters measured using a tensile tester and indicate the residual stress of the coating. The measuring method will be described below. The film thickness after drying the resin composition containing the resin and the curing agent with an applicator is 20 to 30μ.
Apply it to the tin plate so that it becomes m. This is 3 at 80 ℃
After setting for 0 minutes, it is baked at 230 ° C. for 50 seconds, and the coated plate is peeled off by a mercury amalgam method to obtain a test piece. Using a Tensilon-type tensile tester that can be heated, the chuck distance is 30 mm, the width is 15 mm, the pulling speed is 5 mm / min, the elongation is 100% at 100 ° C., and then the elongation reaches 100% at the same time. A return is applied at the same speed to obtain a chart pattern as shown in FIG. 1, for example.

The elastic strain energy U is the X-axis shown in FIG.
The area of (II) surrounded by a straight line connecting the X axis corresponding to the elongation of 100% and the corresponding strength and the trajectory at the time of return is divided by the cross-sectional area of the coating film. The unit is mJ / mm ² .

The elastic strain energy ratio U% is surrounded by a straight line connecting the strengths corresponding to the X axis shown in FIG. 1, the X axis corresponding to the elongation of 100%, and the locus at the time of pulling (I) and the above (II). Calculate the area, {area (II) / area (I)}
Calculate with x100. The unit is expressed in%.

The smaller the elastic strain energy U or the elastic strain energy ratio U%, the smaller the residual stress of the organic film. Therefore, since an organic film having a large elastic strain energy U or a large elastic strain energy ratio U% has a large residual stress, a stress that tends to shrink during a boiling water test is developed, and peeling is caused due to a decrease in adhesion to the substrate due to boiling water. Occur.

The elastic strain energy U in the coating composition of the present invention, in order to obtain a good throttling or ironing workability is required to be not more than 35 mJ / mm ^2, preferably 25 mJ / mm ² or less, more Preferably 20 mJ
/ Mm ² or less. The lower limit is not particularly limited, but is preferably 5 mJ / mm ² or more from the viewpoint of scratch resistance and the like. When the elastic strain energy U exceeds 35 mJ / mm ² , the physical properties of the coating film after drawability deteriorate, and especially the boiling water resistance, moisture resistance and corrosion resistance (salt spray test) deteriorate. Here, the test piece that breaks before the elongation reaches 100% is outside the scope of the present invention.

The elastic strain energy ratio U% in the coating composition of the present invention must be 60% or less, preferably 50% or less, and more preferably, in order to obtain good drawability or ironing workability. It is 40% or less. The lower limit is not particularly limited, but is preferably 5% or more. If the elastic strain energy ratio U% exceeds 60%, the physical properties of the coating film after drawability deteriorate, and especially the boiling water resistance, moisture resistance, and corrosion resistance (salt spray test) deteriorate. Here, the test piece that breaks before the elongation reaches 100% is outside the scope of the present invention.

In the resin composition of the present invention, the kind of resin and curing agent for obtaining a low elastic strain energy U or elastic strain energy ratio U% is not limited, but a high molecular weight polyester resin is used as the resin. Is most preferred. The number average molecular weight of the polyester resin is preferably 3,000 or more, more preferably 8,000 or more,
Most preferably, it is 10,000 or more. The upper limit is low elastic strain energy U or elastic strain energy ratio U
The higher the percentage, the better. However, considering the viscosity of the paint, it is preferably 30,000 or less, and more preferably 2 or less.
It is 5,000 or less.

The squeezing and ironing processes are quite severe because they are rubbed with a punch or a die. Therefore, it is preferable that the glass transition temperature (hereinafter referred to as Tg) of the polyester resin is high, and the preferable Tg is 30 ° C or higher, more preferably 45 ° C or higher, and most preferably 60 ° C or higher. The upper limit is not particularly limited, but 110 ° C. or lower is preferable in consideration of adverse effects such as an increase in paint viscosity. Tg
Is less than 30 ° C., problems such as blocking, swelling, and scratches may occur during drawing or ironing.

The breaking elongation of the clear film or the coating film containing the pigment at room temperature is preferably 50% or less, more preferably 30% or less, and further preferably 15% or less. The breaking elongation is preferably 3% or more, more preferably 5% or more. If the breaking elongation at room temperature exceeds 50%,
The coating film becomes too soft and tends to be scratched or blocked during drawing or ironing.

In the resin composition of the present invention, it is preferable to add a curing agent capable of reacting with the polyester resin or other resin. The compounding amount of the curing agent with respect to 100 parts of the resin component is preferably 0.1 part by weight or more, more preferably 1 part by weight or more. If the amount is less than 0.1 part by weight, the effect may not be recognized. If the amount of the curing agent is too large, the elastic strain energy U or the elastic strain energy ratio U% tends to increase, so the upper limit is preferably 30 parts or less, more preferably 20 parts or less, and most preferably 5 parts or less.

As the acid component to be copolymerized with the polyester resin used in the present invention, an aromatic dicarboxylic acid is
Terephthalic acid, isophthalic acid, orthophthalic acid, 2,6
-Naphthalenedicarboxylic acid and the like. Of these, it is particularly preferable to use terephthalic acid alone or in combination with terephthalic acid and isophthalic acid from the standpoint of drawing or ironing processability, processability, impact resistance and hardness balance. The content of these aromatic dicarboxylic acids in all the acid components is preferably 80 mol% or more, more preferably 90 mol% or more,
The upper limit is preferably 100 mol%.

Other carboxylic acids copolymerizable with the polyester resin used in the present invention include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedicarboxylic acid and azelaic acid, 1,2-
Examples thereof include alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid, with alicyclic dicarboxylic acids being preferred. Further, a polyvalent carboxylic acid such as trimellitic anhydride or pyromellitic dianhydride may be used in combination as long as the content of the invention is not impaired.

The glycol component copolymerizable with the polyester resin used in the present invention is ethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 1, 4-butanediol, 2-ethyl-2-butyl-propanediol, 1,5-pentanediol, 1,
6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,5-pentanediol,
Alkylene glycols such as 1,9-nonanediol and 1,10-decanediol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol,
Examples thereof include 1,2-cyclohexanedimethanol, alicyclic glycols such as hydrogenated bisphenol A, alkylene oxide adducts of bisphenol A, alkylene oxide adducts of bisphenol F, and alkylene oxide adducts of bisphenol S.

Among them, ethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3 from the viewpoint of physical properties of the coating film such as drawing or ironing workability.
It is particularly preferable that 50 mol% or more of at least one of propanediol and 1,4-cyclohexanedimethanol is contained.

In the resin composition of the present invention, preferred polyester resins include the following. That is, the acid component is 10 to 100 mol% and the total amount of terephthalic acid and other aromatic dicarboxylic acid is 80 to 100%.
100 mol%, other dicarboxylic acid 0 to 20 mol%
And a glycol component containing at least 50 mol% of ethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, or 1,4-cyclohexanedimethanol. It is a polyester resin having a transition temperature of 10 to 80 ° C.

Further, polyhydric polyols such as trimethylolethane, trimethylolpropane, glycerin and pentaerythritol may be used in combination within a range not impairing the content of the invention. Further, metal salts such as 5-sulfoisophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, 5 [4-sulfophenoxy] isophthalic acid, or 2-sulfo-1,4-butanediol, 2,5- Dimethyl-3-
Dicarboxylic acid or glycol containing sulfonic acid metal base such as metal salt such as sulfo-2,5-hexanediol
May be used in the range of 5 mol% or less of the total acid or glycol components.

Polyester tree used in the present invention
Examples of methods for determining the composition and composition ratio of fat include poly
Measured by dissolving the ester resin in a solvent such as deuterated chloroform
Do ¹H-NMR and¹³C-NMR, polyester resin
By gas chromatography measured after methanolysis
Quantification, etc. Of these,¹H-NMR
It is simple and preferable.

The polyester resin used in the present invention preferably has an acid value of 20 equivalents / 10 ⁶ from the viewpoint of curability and physical properties of the coating film.
g or more, more preferably 50 equivalents / 10 ⁶ g
That is all. The upper limit is preferably 350 equivalents / 10 ⁶ g or less, more preferably 250 equivalents / 10 ⁶ g or less. By giving an acid value, the curability is improved, the hardness,
Scratch resistance, stain resistance, etc. are further improved. Acid value is 35
If it exceeds 0 equivalent / 10 ⁶ g, the workability is deteriorated, which is not preferable. The method for imparting an acid value to the polyester resin is not particularly limited, but for example, after polymerizing the polyester resin, trimellitic anhydride, phthalic anhydride, pyromellitic anhydride, succinic anhydride, 1,8-naphthalic anhydride are obtained under normal pressure. , 1,2-cyclohexanedicarboxylic acid anhydride and the like are post-added to give an acid value.

The polyester resin used in the present invention has a reduced viscosity of 0.2 dl / g or more, preferably 0.3 dl / g.
g, more preferably 0.4 dl / g or more. If the reduced viscosity is less than 0.2 dl / g, good drawability or ironing workability, bending workability, and impact resistance may not be obtained. The upper limit is not particularly limited, but it is preferably 1.0 dl / g or less, and more preferably 0.8 dl / g or less in order to adjust the viscosity of the coating having excellent coating suitability.

Examples of the curing agent capable of reacting with the polyester resin or other resin used in the present invention include alkyl etherified amino formaldehyde resins, epoxy compounds and isocyanate compounds. The alkyl etherified amino formaldehyde resin is, for example, formaldehyde or para formaldehyde alkylated with an alcohol having 1 to 4 carbon atoms such as methanol, ethanol, n-propanol, isopropanol, and n-butanol, and urea, N,
It is a condensation product with N-ethylene urea, dicyandiamide, aminotriazine, etc., and is methoxylated methylol-
N, N-ethylene urea, methoxylated methylol dicyandiamide, methoxylated methylol benzoguanamine, butoxylated methylol benzoguanamine, methoxylated methylol melamine, butoxylated methylol melamine, methoxylated / butoxylated mixed methylol melamine, butoxylated methylol benzoguanamine and the like can be mentioned. But,
From the viewpoint of processability and stain resistance, it is particularly preferable to use a methoxylated methylol melamine or a methoxylated / butoxylated mixed methylol melamine and a butoxylated methylol melamine in combination.

Bisphenol A as an epoxy compound
Diglycidyl ether and its oligomer, hydrogenated bisphenol A diglycidyl ether and its oligomer, orthophthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, p-oxybenzoic acid diglycidyl ester, tetrahydrophthalic acid 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 di Glycidyl ether, 1,6-hexanediol diglycidyl ether and polyalkylene glycol diglycidyl ethers, trime Butyric acid triglycidyl ester, triglycidyl isocyanurate, 1,4-diglycidyloxybenzene, diglycidyl propylene urea, glycerol triglycidyl ether, trimethylolethane triglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether , Triglycidyl ether of glycerol alkylene oxide adduct, and the like.

Further, as the isocyanate compound, there are aromatic and aliphatic diisocyanates and polyisocyanates having 3 or more valences, which may be low molecular 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 trimer of these isocyanate compounds, and excess of these isocyanate compounds. The amount of the low molecular weight active hydrogen compound such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine or various polyester polyols, polyether polyols, polyamides Conflicts with high molecular weight active hydrogen compounds It includes terminal isocyanate group-containing compounds obtained by.

The isocyanate compound may be a blocked isocyanate. Examples of the isocyanate blocking agent include phenol, thiophenol,
Phenols such as methylthiophenol, ethylthiophenol, cresol, xylenol, resorcinol, nitrophenol, and chlorophenol, acetoxime, methylethylketoxime, cyclohexanone oxime and its oximes, alcohols such as methanol, ethanol, propanol, butanol, ethylene chlorohydride Phosphorus, halogen-substituted alcohols such as 1,3-dichloro-2-propanol, t-butanol, t-
Tertiary alcohols such as pentanol, ε-caprolactam, δ-valerolactam, γ-butyrolactam,
Examples include lactams such as β-propyrolactam, and other active methylene compounds such as aromatic amines, imides, acetylacetone, acetoacetate, and malonic acid ethyl ester, mercaptans, imines, ureas, and diaryls. Compounds such as sodium bisulfite are also included. The blocked isocyanate is obtained by subjecting the above-mentioned isocyanate compound and an isocyanate blocking agent to an addition reaction by a conventionally known appropriate method.

A publicly known curing agent or accelerator selected depending on its type may be used in combination with these crosslinking agents.

The coating composition of the present invention shows sufficient performance even if it is applied to a metal plate and baked.
When it is required to further improve the corrosion resistance, epoxy resin, polyester resin, urethane resin or the like may be used as the primer coating agent. Further, the resin composition for coating material of the present invention can be used as a primer, or can be used as both a primer and a top.

The baking temperature of the coating composition of the present invention is arbitrarily selected depending on the size and thickness of the steel sheet, the ability of the baking furnace, the curability of the coating, and the like. A mixer such as a roll kneader, a ball mill and a blender is used for producing the coating composition. For coating, roller coating, roll coater, spray coating, electrostatic coating, etc. are selected as appropriate.

The coating composition of the present invention is a pigment such as titanium oxide, carbon black, an organic coloring pigment or an inorganic coloring pigment, a dye, an aluminum flake, silica, talc, barium sulfate or the like extender pigment depending on the purpose and application. Additives such as glass fiber, colloidal silica and wax can be added.

[0040]

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

1. 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.

2. The number average molecular weight was measured by gel permeation chromatography (GPC) using a polystyrene standard sample as a reference. Tetrahydrofuran was used as the solvent.

3. Using a glass transition temperature differential scanning calorimeter (DSC), -100 to 250
It was measured at a temperature rising rate of 20 ° C / min up to ° C. As a sample, 5 mg of the sample was placed in an aluminum pressing lid type container and crimped before use.

4. 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.

5. Gloss The 60-degree reflectance of the coated surface of the steel plate was measured.

6. The coated surface of the hardened steel plate was measured according to JIS K-5400 using a high-grade pencil specified in JIS S-6006, and judged by the presence or absence of scratches.

7. A line was written on the coated surface of the steel plate resistant to magic marker with a red marker, left for 2 hours and then wiped off with ethanol, and the mark of the marker was evaluated on a 5-point scale. (5: No trace, 1: Complete trace remains)

8. The workable coated steel sheet was bent 180 degrees, and cracks generated in the bent portion were observed and judged with a 10 times magnifying glass. 3T refers to the case where three bent sheets with the same plate thickness are not broken even if they are sandwiched.
OT means a case where the plate is not cracked even if it is bent 180 degrees without sandwiching the plate.

9. Wax was applied to the surface of the drawn steel sheet, and a square can having a side of 60 mm and a depth of 45 mm was press-molded using a press machine. The side surface gloss of the molded can was visually compared with the bottom surface gloss and judged. (5: Almost no change in gloss, 4: Slight polish, 3: Scratch and scratches, 1: Significant polish, partial peeling)

10. Boiling water resistance after drawing 9. A cross-cut was put on the side surface of the molded product drawn in step 2, and a boiling water test was performed for 2 hours. After the test, the peeled state of the coating film on the cross cut portion and the end surface (skirt portion) was visually observed. (5: almost no change, 4: slight peeling occurred, 3: peeling occurred, 2: considerable peeling occurred, 1: significant peeling occurred)

11. Measurement of elastic strain energy U or elastic strain energy ratio U% Preparation of test piece Membrane after drying resin composition for coating only with resin and curing agent or curing catalyst if necessary, and dissolving in solvent with applicator It was applied to a tin plate so that the thickness was 20 to 30 μm. This was set at 80 ° C. for 30 minutes and then baked at 230 ° C. for 50 seconds. The coated plate was peeled off by a mercury amalgam method to obtain a test piece.

Tensile test Using a Tensilon type tensile tester capable of heating, chuck distance 30 mm, width 15 mm, pulling speed 5 m
The elongation was pulled up to 100% at a temperature of 100 ° C. at m / min. Then, at the same time when the elongation reached 100%, a return was applied at the same speed to obtain the chart pattern shown in FIG.

Calculation of elastic strain energy U The area of (II) surrounded by the straight line connecting the X-axis shown in FIG. 1, the X-axis corresponding to the 100% elongation portion and the corresponding strength, and the trajectory at the time of return is the cross-sectional area of the coating film. Divided by. The unit is m
It was expressed in J / mm ² .

Calculation of elastic strain energy ratio U% Enclosed by the straight line connecting the X axis shown in FIG. 1, the X axis corresponding to the strength at the elongation 100% portion, and the locus at the time of pulling (I) and the above ( II) area is calculated, {area (II) /
It was calculated by the area (I)} × 100. The unit is expressed in%.

Synthesis Example (A) 155 parts of dimethyl terephthalate and 6 parts of dimethyl isophthalate were placed in a reaction vessel equipped with a stirrer, a condenser and a thermometer.
13 parts, 2-methyl-1,3-propanediol 576
Part, 1,4-cyclohexanedimethanol 230 parts, and tetrabutyl titanate 0.41 part were charged, and transesterification was carried out from 160 ° C. to 230 ° C. over 4 hours. Then, the pressure in the system was gradually reduced to 5 over 20 minutes.
The pressure was reduced to mmHg, and a polycondensation reaction was performed at 260 ° C. for 40 minutes under a vacuum of 0.3 mmHg or less. Then, the mixture was cooled to 200 ° C. under a normal pressure nitrogen atmosphere, 7.68 parts of trimellitic anhydride was charged, and post addition was performed. As a result of composition analysis such as NMR, the obtained copolyester (A) has a molar ratio of acid components of terephthalic acid / isophthalic acid /
Trimellitic acid (post-addition) = 20/79/1 and the glycol component in molar ratio is 2-methyl-1,3-propanediol / 1,4-cyclohexanedimethanol = 65.
It was / 35. The reduced viscosity was measured to be 0.
58 dl / g, glass transition temperature 58 ° C, acid value 80
The equivalent weight was 10 ⁶ g and the number average molecular weight was 18,000.

Hereinafter, the polyester resins (B) to (G) having the compositions shown in Tables 1 and 2 were prepared by the method according to the above synthesis example.
Was synthesized. These resins were used after being dissolved in cyclohexanone / Solvesso 150 = 50/50 (weight ratio).

Blending of paint resin and measurement result of elastic strain energy U or elastic strain energy ratio U% 100 solid parts of polyester resin (A), methylated melamine (trade name: Sumimar M40ST, manufactured by Sumitomo Chemical Co., Ltd.)
8 solid parts and 2.5 parts of a 10% benzyl alcohol solution of dodecylbenzene sulfonic acid were added, sufficiently stirred with a glass rod, and left sufficiently for defoaming so that the coating resin (A-
1) was obtained. The elastic strain energy U of (A-1) measured by the above method was 20 mJ / mm ² , and the elastic strain energy ratio U% was 42%. The results are shown in Table 3. Similarly, coating resins (B-1) to (G-1) were prepared for the polyester resins (B) to (G). The results are shown in Table 3.

Preparation of primer paint (1) Coating resin (B-1) solution 104 Titanium oxide 4 on solid part
2 parts and 42 parts of strontium chromate were mixed and dispersed for 5 hours with a glass bead type high-speed shaker to obtain a primer coating composition.

Preparation of primer paint (2) Titanium oxide 4 in solid part of solution 105 of paint resin (G-1)
2 parts and 42 parts of strontium chromate were mixed and dispersed for 5 hours with a glass bead type high-speed shaker to obtain a primer coating composition.

Preparation of white top-coat paint A predetermined amount of each paint resin solution, titanium oxide, Polyflow S
(Manufactured by Kyoeisha Yushi Kagaku Kogyo Co., Ltd.) was added and dispersed for 5 hours with a glass bead type high-speed shaker to obtain a coating composition. The formulations are shown in Tables 4 and 5.

Examples 1 to 5 The primer paints shown in Table 4 were applied to a coating type chromate-treated zinc iron plate having a thickness of 0.5 mm to a thickness of 5 μm and baked at 210 ° C. for 50 seconds. Then, Table 4
After applying the white top-coat paint shown in (3) to a film thickness of 18 μm, baking was performed at 230 ° C. for 1 minute. The evaluation results are shown in Table 4.

Comparative Examples 1 to 4 The coated plates of Comparative Examples 1 to 4 were prepared and evaluated in the same manner as in the examples.
The results are shown in Table 5.

From Tables 4 and 5, in Examples 1 to 4 in which the top coating composition using the coating resin composition of the present invention was applied, the coating resin composition outside the scope of the present invention was used as the top coating composition. It can be seen that, as compared with Comparative Examples 1 to 4, particularly, the drawability and the boiling water resistance after the draw processing are excellent. Especially overcoat,
In Example 5 in which both the undercoat layers were coated with the coating composition using the resin composition for coating composition of the present invention, both properties were further improved.

Example 6 100 solid parts of polyester resin (B), 4 solid parts of methylated melamine (Cymel 303 manufactured by Mitsui Cytec Co., Ltd.), 2.5 parts of a 10% benzyl alcohol solution of dodecylbenzenesulfonic acid, and 1 part of polyethylene wax as a lubricant. Parts and mixed well with a glass rod. This clear paint was applied to an aluminum plate having a plate thickness of 0.5 mm so that the film thickness would be 20 μm, and baked at 230 ° C. for 1 minute. This operation was repeated twice and applied on both sides. This coated plate was drawn twice by a known method and then subjected to ironing (ironing) to obtain a DI can. The resulting DI can was free of scratches and had a slight decrease in gloss. Also, the adhesion to the can body was good, and there was no peeling even after the boiling water test, and the film was good.
Moreover, the corrosion resistance to an aqueous solution of acetic acid, salt, etc. was also good.

[0065]

[Table 1]

[0066]

[Table 2]

[0067]

[Table 3]

[0068]

[Table 4]

[0069]

[Table 5]

[0070]

EFFECT OF THE INVENTION The coating resin composition of the present invention can achieve a high degree of compatibility between hardness, workability, and stain resistance, and, surprisingly, good drawing or ironing workability is obtained. Excellent secondary properties such as boiling water and corrosion resistance after squeezing or ironing, which could not be obtained conventionally, can be obtained, and it can meet the high required quality in the fields of various home appliances, vehicle panels, food and beverage cans, etc. it can. Further, the polyester resin used in the present invention is not only used as a coating composition, but alone or in combination with a known curing agent, various base materials, for example, plastic films such as polyethylene terephthalate, iron, tinplate, etc. It can also be used as an adhesive for a metal plate or the like, or as a binder for various pigments.

[Brief description of drawings]

FIG. 1 is a chart showing the results of a tensile test obtained for measuring elastic strain energy U or elastic strain energy ratio U%.

Claims (4)

[Claims] 1. The elastic strain energy at 100 ° C. of a resin composition for a coating material, which mainly contains a resin and a curing agent, of the resin and the curing agent alone, or an organic film to which a curing catalyst is further added, is 35 mJ / A resin composition for a coating, which is less than or equal to mm ² . 2. The elastic strain energy ratio at 100.degree. C. of an organic coating containing a resin and a curing agent alone, or an organic coating to which a curing catalyst is further added, if necessary, is 60. % Or less, a resin composition for coating material. 3. The resin according to claim 1, which is a polyester resin having a number average molecular weight of 3000 or more.
A resin composition for a paint as described. 4. When the total amount of each of the acid component and glycol component of the resin is 100 mol%, the acid component is 10 to 100 mol% and the total amount of terephthalic acid and other aromatic dicarboxylic acid is 80 mol%. ~ 100
Mol%, other dicarboxylic acid 0 to 20 mol%, the glycol component is ethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-
Contains 50 mol% or more of one or more of 1,3-propanediol and 1,4-cyclohexanedimethanol,
The resin composition for coating according to claim 1, which is a polyester resin having a glass transition temperature of 10 to 80 ° C.