JP3287428B2 - Resin composition for paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition for a coated metal sheet. More specifically, the present invention provides a primer coating composition for a coated metal plate which is excellent in workability and is excellent in acid resistance, corrosion resistance and the like.

[0002]

2. Description of the Related Art Painted metal sheets, that is, so-called pre-coated metal sheets, take advantage of their economical efficiency, productivity, workability, etc., in the field of building materials such as roofing materials and wall materials, outdoor equipment such as storage, radiator units, and the like. Widely used for home appliances such as VTRs, washing machines, refrigerators, etc. The first required property of the coated metal plate is that it has excellent bending workability. Alkyd resins, acrylic resins, epoxy resins, etc. are currently used as paint resins, but these have problems in workability, and high-molecular-weight polyesters are used in fields requiring high workability. That is the current situation.

[0003] At present, epoxy resin is mainly used as a primer resin for a coated metal plate. However, since epoxy resin lacks flexibility, it cannot withstand advanced processing, and cracks occur in the coating film of the processed portion. It has the disadvantage of easily corroding. In addition, epoxy resin is generally recognized as having good corrosion resistance, but is poor in impact resistance, and has a problem of poor corrosion resistance of the end face because a small coating is formed on the end face when cutting a coated metal plate. There is. Due to the above problem, there is a serious disadvantage that the advantage cannot be used as a high processing primer, and when a high molecular weight polyester resin with good workability is used for the overcoat, the interlayer adhesion between the primer and the overcoat is poor. There is also a problem.

[0004] As a solution to such a problem,
JP-B-62-5467, JP-A-3-217471, and the like are known, and are compatible with workability, moisture resistance, corrosion resistance, chemical resistance, and the like.

[0005]

However, the required properties are becoming severer year by year, and the properties of coatings such as workability and hardness, various stain resistance, chemical resistance, weather resistance, corrosion resistance, etc. are high regardless of building materials and home appliances. Is required. Further, it has been required to guarantee the corrosion resistance of the end face or the processed portion and to draw the workability, and the above-described conventional technology has not satisfied the workability, the corrosion resistance of the end face, and the drawability. Although overcoating resins have also been eagerly studied for such required properties, compatibility between workability and other coating film properties is insufficient, and satisfactory properties can still be obtained in combination with a conventional primer. Therefore, there has been a demand for the development of an excellent primer resin that has never existed before.

[0006]

In view of these problems, the present inventors have conducted intensive studies on a resin for a primer coating material having excellent workability, corrosion resistance and chemical resistance. As a result, 30 to 80 mol of an aliphatic dicarboxylic acid was obtained. %, 20 to 70 mol% other dicarboxylic acids, glycol component comprises the adduct of 10 to 100 mole% of ethylene o-side or / and propylene oxide of bisphenol a, and a glass transition temperature of 30 ° C. or less, 25 When measured at ° C
Elongation at break when the tension of the high-speed (500mm / min) 10
It has been found that 0% or more of the polyester resin has excellent workability, and surprisingly, the corrosion resistance of the processed portion and the end face is remarkably excellent, and furthermore, it also has an excellent chemical resistance. did.

That is, the present invention relates to (A) 30 to 80 mol% of an aliphatic dicarboxylic acid and 20 to 7 other dicarboxylic acids.
0 mol%, and the glycol component is represented by the following general formula (I)
At the time of high-speed pulling (500 m 2 ) when measured at 25 ° C. at a glass transition temperature of 30 ° C. or lower at a temperature of 30 ° C. or less and an ethylene oxide or / and propylene oxide adduct of bisphenol A represented by
m / min) with a polyester resin having a breaking elongation of 100% or more, (A) / (B) =
It is a resin composition for coatings characterized by being blended at a ratio of 95/5 to 60/40 (weight ratio).

Embedded image (Wherein R _{1 and} R ₂ are hydrogen or a methyl group, m, n
Is a number of 1 or more and 2 ≦ m + n ≦ 8 at the same time. )

In the polyester resin (A) of the present invention, the acid component to be copolymerized is an aliphatic dicarboxylic acid containing 30 to 8
0 mol%, preferably 30 to 50 mol%. If the amount of the aliphatic dicarboxylic acid is less than 30 mol%, good workability and good corrosion resistance of the processed portion and the end face cannot be obtained, and if it exceeds 80 mol%, the corrosion resistance and chemical resistance are reduced.

The aliphatic dicarboxylic acid copolymerized with the polyester resin (A) of the present invention includes succinic acid, glutaric acid, adipic acid, sebacic acid, dodecandionic acid, azelaic acid, dimer acid and the like. Of these, adipic acid and sebacic acid are particularly preferred in view of workability, corrosion resistance, and chemical resistance.

Other dicarboxylic acids copolymerized with the polyester resin (A) include terephthalic acid, isophthalic acid,
Aromatic dicarboxylic acids such as orthophthalic acid and 2,6-naphthalenedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4
Alicyclic dicarboxylic acids such as -cyclohexanedicarboxylic acid; Other dicarboxylic acids are appropriately selected from economics and physical properties of the coating film, but terephthalic acid and isophthalic acid are preferred.

The glycol component copolymerized with the polyester resin (A) is bisphenol A represented by the general formula (I).
Of ethylene oxide or / and propylene oxide of 10 to 100 mol%, preferably 20 to 80 mol%
It is essential that it consists of mol%. If it is less than 10 mol%, good corrosion resistance, chemical resistance, water resistance, adhesion to a metal plate, etc. cannot be obtained.

Other glycols include ethylene glycol, diethylene glycol, neopentyl glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 2-glycol. Butyl-2-ethyl-propanediol, 1,4-cyclohexanedimethanol, TCD glycol, polyethylene glycol,
Examples include polypropylene glycol. Other glycols are appropriately selected from economical properties and coating film properties,
Ethylene glycol, diethylene glycol, 1,4-
Cyclohexanedimethanol is particularly preferred.

Further, within the scope of the invention, a polycarboxylic acid such as trimellitic acid and pyromellitic acid or trimethylolethane, trimethylolpropane,
Polyhydric polyols such as glycerin and pentaerythritol may be used in combination. By copolymerizing an appropriate amount of such a trivalent or higher polycarboxylic acid or polyol, chemical resistance can be further improved.

In the polyester resin (A) of the present invention, an acid anhydride such as trimellitic anhydride or phthalic anhydride may be added after polymerization to give an acid value.

In the polyester resin (A) of the present invention, a dicarboxylic acid or a glycol containing a sulfonic acid metal base may be used in a range of 5 mol% or less. Examples of the dicarboxylic acid containing a sulfonic acid metal base include metal salts such as sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, and 5 [4-sulfophenoxy] isophthalic acid. it can.
Examples of the glycol containing a sulfonic acid metal base include 2-sulfo-1,4-butanediol and 2,5-dimethyl-3-
Metal salts such as sulfo-2,5-hexanediol are exemplified. As metal salts, Li, Na, K, Mg, Ca,
Salts such as Cu and Fe are included.

The polyester resin (A) of the present invention has a temperature of 25 ° C.
The elongation at break during high-speed pulling (500 mm / min) as measured at 100% or more, preferably 200 to 500%
It is necessary to be. If it is less than 100%, the workability, the drawing workability and the corrosion resistance of the cut end face of the coated metal plate deteriorate. Further, the polyester resin (A) of the present invention
Has a glass transition temperature of 30 ° C. or lower, preferably -10 to
It needs to be 20 ° C. Glass transition temperature 3
If the temperature exceeds 0 ° C., a good high-speed pulling (500 mm /
Min) elongation at break cannot be obtained. Further, the polyester resin (A) of the present invention has a reduced viscosity of 0.3 to 0.7 dl / g,
The number average molecular weight is preferably from 5,000 to 25,000.

The resin composition for coatings of the present invention comprises a polyester resin (A) and a curing agent (B) capable of reacting with the polyester resin (A).
(B) = 95/5 to 60/40 (weight ratio). The amount of (A) is 95 (A) /
If it exceeds 5 (B), the coating film properties such as good chemical resistance, corrosion resistance, workability and the like become poor. If it is less than 60 (A) / 40 (B), good workability cannot be obtained.

Examples of the curing agent capable of reacting with the polyester resin (A) include an alkyl etherified aminoformaldehyde resin, an epoxy compound and an isocyanate compound.

Alkyl-etherified aminoformaldehyde resins include, for example, formaldehyde or paraformaldehyde alkyletherified with an alcohol having 1 to 4 carbon atoms such as methanol, ethanol, n-propanol, isopropanol and n-butanol, and urea; Condensation products with N, N-ethylene urea, dicyandiamide, aminotriazine, etc., methoxylated methylol-N, N-ethyleneurea, methoxylated methylol dicyandiamide, methoxylated methylol benzoguanamine, butoxylated methylol benzoguanamine, methoxylated methylol melamine Butoxylated methylol melamine, mixed methoxylated / butoxylated methylol melamine, butoxylated methylol benzoguanamine, and the like. It preferred from the viewpoint of workability, methoxylated methylolmelamine, butoxy methylol melamine or methoxylated / butoxylated mixed melamine, may be used alone, or in combination.

As the epoxy compound, bisphenol A
Diglycidyl ethers and oligomers thereof, diglycidyl ethers of hydrogenated bisphenol A and oligomers thereof, diglycidyl orthophthalate, diglycidyl isophthalate, diglycidyl terephthalate, diglycidyl p-oxybenzoate, tetrahydrophthalate 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, Triglycidyl citrate, triglycidyl isocyanurate, 1,4-diglycidyloxybenzene, diglycidyl propylene urea, glycerol triglycidyl ether, trimethylolethane triglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether And glycerol alkylene oxide adduct triglycidyl ether.

Further, as the isocyanate compound, there are aromatic and aliphatic diisocyanates, and polyisocyanates having a valency of 3 or more. Either a low molecular compound or a high molecular compound may be used. For example, tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate or trimers of these isocyanate compounds, and excess of these isocyanate compounds And the amount of low molecular active hydrogen compounds such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine or various polyester polyols, polyether polyols, polyamides Anti-polymer active hydrogen compounds It includes terminal isocyanate group-containing compounds obtained by.

The isocyanate compound may be a blocked isocyanate. As the isocyanate blocking agent, for example, phenol, thiophenol,
Phenols such as methylthiophenol, ethylthiophenol, cresol, xylenol, resorcinol, nitrophenol, chlorophenol, acetoxime, methylethylketoxime, cyclohexanone oxime and its oximes, alcohols such as methanol, ethanol, propanol and butanol, ethylene chlorohydroxide 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,
lactams such as β-propyrolactam; and other active amines 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 can be obtained by subjecting the above isocyanate compound to an isocyanate blocking agent to undergo an addition reaction by a conventionally known appropriate method.

Known crosslinking agents or accelerators selected according to the type can be used in combination with these crosslinking agents.

The baking temperature of the resin composition for paint of the present invention is arbitrarily selected depending on the size and thickness of the metal plate, the capability of a baking furnace, the curability of the paint, and the like. A mixer such as a roll mill, a ball mill, and a blender is used for the production of the coating composition. For coating, roller coating, roll coater, spray coating, electrostatic coating and the like are appropriately selected.

The resin composition for a coating material of the present invention may be provided with an extender such as titanium oxide, talc, barium sulfate, zinc chromate, strontium chromate, etc.
Anticorrosive pigments such as calcium chromate, known colorants, additives such as silica and wax, glass fibers and the like can be blended.

The coating resin composition of the present invention is used in the form dissolved in an organic solvent. As an organic solvent,
For example, toluene, xylene, Solvesso 100, Solbec 150, ethyl acetate, butyl acetate, methyl cellosolve, ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, methyl cellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, methyl carbitol acetate, butyl carbitol It is appropriately selected from carbitol acetate, methyl ethyl ketone, cyclohexanone, isophorone, N-methylpyrrolidone and the like in consideration of solubility and evaporation rate.

Although the coating resin composition of the present invention exhibits sufficient performance even when coated and baked, it is necessary to apply a top coat known as a top coat for the purpose of further improving weather resistance and stain resistance. Can also.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. In the examples, “parts” means “parts by weight”. 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.

2. Glass transition temperature Measured at a heating rate of 20 ° C./min using a differential scanning calorimeter (DSC). The sample was prepared by placing 5 mg of the sample in an aluminum holding lid type container and crimping it.

3. Acid value 0.2 g of sample 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.

4. Elongation at break A varnish obtained by dissolving a polyester resin in cyclohexanone is applied to a polypropylene film and dried, and a thickness of about 50
A μm film was obtained. Using a Tensilon type tensile tester, the sample length is 30 mm, the tensile speed is 500 mm / min,
It was measured at 25 ° C.

5. Workability The coated steel sheet was bent at 180 degrees, and cracks generated at the bent portions were observed and judged with a 10-fold loupe. 3T indicates a case where three sheets having the same plate thickness are sandwiched in the bent portion, and 0T indicates a case where the sheet is bent 180 degrees without sandwiching the plate.

6. Alkali Resistance The coated steel sheet was immersed in 5% NaOH for 48 hours, and the state of blister formation on the coated surface was evaluated according to ASTM D714-56. When there was no abnormality, it was set to 10.

7. The acid-resistant coated steel sheet was immersed in 5% HCl for 48 hours, and the state of blister formation on the coated surface was evaluated according to ASTM D714-56. When there was no abnormality, it was set to 10.

8. Corrosion resistance The coated steel sheets were subjected to a 5% NaCl salt spray test at 35 ° C. for a predetermined time, and the occurrence of blisters was visually determined. The corrosion resistance was measured for the cross cut portion, the end face (cut portion), and the 2T processed portion. The salt spray time was evaluated at 1000 hours for the cross cut portion and the 2T processed portion, and at 500 hours for the end face. The evaluation criteria are shown below. Cross cut part and processed part ◎: No abnormality ○: Almost no blister △:
Blister generation ×: Many blisters generated End face (blister width) ：: 5 mm or less ○: 5 to 10 mm △: 10 to 20 m
mx: 20 mm or more

9. Drawability After drawing a painted steel plate at D / L (diameter / depth) = 0.6, the side surface portion was subjected to a cellophane tape peeling test. The evaluation criteria are shown below. ：: No abnormality △: Stripping ×: Marked stripping

10. Preparation of Top Coating Paint Commercially-dissolved high-molecular-weight polyester Byron 300 60 solid parts, Byron 200 40 solid parts (all manufactured by Toyobo Co., Ltd.), methyl etherified methylol melamine Sumimar M40S (80% non-volatile content,
Sumitomo Chemical Co., Ltd.) (31 parts), 2.5 parts of a 10% benzyl alcohol solution of p-toluenesulfonic acid, and 125 parts of an acid value titanium were added, and the mixture was mixed with a glass bead-type high-speed shaker.
After time dispersion, a top coat was prepared. The solvent used was an appropriate amount of a cyclohexanone / solvesso 150 = 50/50 mixture.

11. Preparation of Painted Steel Sheet (Specimen) A 0.5 mm thick hot-dip galvanized steel sheet subjected to a chromate treatment was used as a base material. A predetermined primer is applied to this base material so that the dry film thickness becomes 5 μm, and 210 ° C. × 5
Bake for 0 seconds. Then, as described in 10. The top coat prepared in the above was applied so that the dry film thickness became 20 μm, and 230 ° C.
The coated steel plate was prepared by baking for 60 seconds.

Synthesis Example (A) 68 parts of dimethyl terephthalic acid and 47 parts of dimethyl isophthalic acid were placed in a reaction vessel equipped with a stirrer, a condenser and a thermometer.
Parts, 1.9 parts of trimellitic anhydride, 118 parts of ethylene glycol, 96 parts of DA-350 (manufactured by NOF Corporation), which is an ethylene oxide adduct of bisphenol A,
0.102 parts of tetrabutyl titanate was charged, and 160
The transesterification reaction was carried out from 4 to 240 ° C. for 4 hours. Then, the mixture was cooled to 200 ° C., charged with 58 parts of adipic acid, and gradually heated to 240 ° C. to perform an esterification reaction. Then, the pressure inside the system was gradually reduced, and the pressure was reduced to 5 mmHg over 50 minutes, and the polycondensation reaction was further performed at 260 ° C. for 60 minutes under a vacuum of 0.3 mmHg or less.
As a result of composition analysis such as NMR, the obtained copolymerized polyester (A) was found to have an acid component in a molar ratio of terephthalic acid / isosophthalic acid / adipic acid / trimellitic acid = 35/22/42.
/ 1, and the glycol component was ethylene glycol / DA-350 = 68/32 in molar ratio. The measured reduced viscosity was 0.35 dl / g, and the glass transition temperature was 15 ° C. Table 1 shows the results.

Hereinafter, Table 1 was obtained by the method according to the above synthesis example.
Polyester resins (B) to (N) having the compositions shown in Table 3 were synthesized. (F) to (N) are comparative polyesters.

Example 11 1) Preparation of Primer Paint 50 parts of titanium oxide, 50 parts of zinc chromate, and methyl / butyl mixed etherified methylolmelamine (trade name: Cymel 25) were added to 100 parts of polyester resin (A) solution.
4. Non-volatile content 80%, manufactured by Mitsui Cyanamid Co., Ltd.)
25 parts and 2.5 parts of a 10% benzyl alcohol solution of p-toluenesulfonic acid were added, and dispersed with a glass bead-type high-speed shaker for 5 hours to prepare a primer coating.

The coating composition was used for the above 10. A coated steel plate was prepared by applying and baking according to the method described in (1), and a predetermined test was performed. Table 4 shows the results.

Hereinafter, coating compositions of Examples 2 to 7 and Comparative Examples 1 to 9 were prepared in the same manner with the compositions shown in Tables 4 to 7, and applied and baked. Tables 4 to 7 show the test results of the obtained coated steel sheets. However, the mixing ratio of the paint was shown in terms of solid content.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

[Table 3]

[0048]

[Table 4]

[0049]

[Table 5]

[0050]

[Table 6]

[0051]

[Table 7]

[0052]

Industrial Applicability The resin composition for coating of the present invention has an aliphatic dicarboxylic acid as an acid component of a polyester resin, and ethylene glycol or / and propylene oxide of bisphenol A represented by the general formula (1) added to a glycol component. Because of containing materials, excellent workability and corrosion resistance,
Particularly, as compared with a conventional polyester resin or epoxy resin, a resin excellent in bending workability and drawing workability and excellent in corrosion resistance of a processed portion and an end face can be obtained. By using the coating resin of the present invention as a primer for a coated metal plate, the workability of the topcoat paint is remarkably improved, so that the range of use of the topcoat paint is broadened, and the workability and other properties of the coating film can be highly compatible. It becomes possible. In addition, it can be widely used not only for building materials and outdoor equipment, but also for household appliances that require corrosion resistance, such as refrigerators, washing machines, and air conditioner outdoor units, because of the excellent corrosion resistance of the processed parts and end faces, especially for building materials and outdoor equipment. it can. In addition, the polyester resin used in the present invention is used not only as a coating composition but also alone or in combination with a known curing agent to form various base materials, for example, plastic films such as polyethylene terephthalate, iron, tinplate, etc. Can also be used as an adhesive for metal plates and the like, or as a binder for various pigments.

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C09D 167/02

Claims (1)

(57) [Claims] (A) aliphatic dicarboxylic acid 30 to 80
Mol%, other dicarboxylic acid 20 to 70 mol%, and glycol component 10 to 100 mol% of an adduct of bisphenol A with ethylene oxide or / and propylene oxide represented by the following general formula (I). ,
And measured at 25 ° C with a glass transition temperature of 30 ° C or less
(A) / (B) = 95 / 5-60 / a polyester resin having a breaking elongation of 100% or more at the time of high-speed stretching (500 mm / min).
A resin composition for a paint, which is blended at a ratio of 40 (weight ratio). Embedded image (Wherein R _{1 and} R ₂ are hydrogen or a methyl group, m, n
Is a number of 1 or more and 2 ≦ m + n ≦ 8 at the same time. )