JPH0987583A - Copolymerized polyester resin for paint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the hardness, processibility, water resistance, adhesive properties, and wet-ink suitability of a copolyester resin for a coating material by reacting a specific acid component with a specific alcohol component. SOLUTION: A copolyester resin for a coating material having a number average mol.wt. of 3,000-50,000 is obtd. by subjecting an acid component comprising 80-100mol% arom. dicarboxylic acid and 20-0mol% nonarom. polycarboxylic acid and an alcohol component comprising 0-50mol% diol represented by formula I (wherein R1 is a 3C or lower alkylene; and (m) and (n) are each a natural number provided 2<=m+n<=7), 0.5-20mol% compd. represented by formula II [wherein R2 is a 3C or higher noncyclic hydrocarbon group. an alicyclic hydrocarbon group, an aryl group, or a deriv. group (e.g. an ester or ether group) of these groups], 1-50mol% cyclohexanedimethanol, 20-98.4mol% other diol, and 0.1-10mol% trihydric or higher alcohol to esterification or transesterification and then to polycondensation in a vacuum of 150mmHg or lower.

Description

Detailed Description of the Invention

The present invention relates to a copolyester resin, and more specifically, it is useful as a base resin for paints, particularly overcoat clear paints for metal plates used for drinking cans, beauty cans, etc., having hardness, processability and water resistance. , A copolyester resin excellent in adhesion and suitability for wet ink.

[0002]

2. Description of the Related Art A coating film is formed on the surface of a metal processed product used for packaging beautiful cans such as chocolate, biscuits, seaweed, and petroleum cans for the purpose of preventing rust and aesthetics.
Usually, these coating films are formed by first applying an undercoat (white coat) or the like on a metal plate, then printing characters and patterns, and then applying a transparent overcoat clear paint.

Conventionally, baking is carried out at each step of the coating,
Curing was performed, but today, in order to improve productivity, after printing ink is applied, the printing ink remains uncured, and the overcoat clear paint of the next step is applied and baked. It has become to. But,
When the overcoat clear paint is applied on the uncured ink layer, the ink flows with the overcoat clear paint, especially at the edges of the printed part, the ink flows like a "whisker", the so-called "bleed phenomenon". Also, a problem of suitability for wet ink, which is so-called "embossing phenomenon", in which a step is formed at the edge of the printing portion, is likely to occur.

Further, for example, a metal plate used for a can is coated with ink and overcoat clear paint, and after being hardened, it is processed into a metal processed product suitable for each purpose, so that the overcoat clear paint is required to have high workability. To be done.

Generally, these overcoat clear paints are mainly composed of an acrylic or epoxy ester resin, which is relatively suitable for wet ink, but these resins have poor processability. To be inferior
It has a drawback that the coating film is apt to cause the "cracking / peeling" problem. On the other hand, in recent years, a polyester resin has come to be used as an overcoat clear coating which is excellent in processability, but it has a drawback that its suitability for wet ink is insufficient.

[0006]

DISCLOSURE OF THE INVENTION The object of the present invention is to provide hardness, processability and water resistance which are useful as a base resin for paints, particularly overcoat clear paints for metal plates used for drinking cans, beauty cans and the like. It is intended to provide a copolyester resin having excellent adhesion and suitability for wet ink.

[0007]

Means for Solving the Problems As a result of intensive studies aimed at achieving the above object, the present inventors have used a specific amount of a specific component for an acid component and an alcohol component and have a molecular weight within a specific range. The inventors have found that a copolyester resin can achieve the object, and completed the present invention.

That is, according to the present invention, 80 to 100 mol% of (A) aromatic dicarboxylic acid (a-1) and a divalent or higher polyvalent carboxylic acid (a-2) 0 other than aromatic dicarboxylic acid.
To 20 mol% of acid component, and (B) 0 to 50 mol% of diol (b-1) represented by the following general formula (1):
Compound (b-2) represented by the following general formula (2) 0.5 to
20 mol%, cyclohexanedimethanol (b-3) 1
˜50 mol%, other diol (b-4) 20-98.4
Mol% and trihydric or higher polyhydric alcohol (b-5) 0.
A copolyester resin for paints, which comprises an alcohol component of 1 to 10 mol% and has a number average molecular weight of 3,000 to 50,000.

[0009]

Embedded image

In the formula, R ₁ is an alkylene group having 3 or less carbon atoms,
m and n are natural numbers, and 2 ≦ m + n ≦ 7.

[0011]

Embedded image

In the formula, R ₂ is an acyclic hydrocarbon group having 3 or more carbon atoms, an alicyclic hydrocarbon group, an aryl group, or a derivative thereof such as an ether or ester.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The acid component (A) used for obtaining the copolyester resin of the present invention is an aromatic dicarboxylic acid (a-1) and a divalent or higher polyvalent carboxylic acid other than the aromatic dicarboxylic acid. The acid (a-2) (hereinafter, abbreviated as other polyvalent carboxylic acid (a-2)).

The aromatic dicarboxylic acid (a-1) used as the acid component (A) is a component for imparting hardness, stain resistance and water resistance to the coating film. ~ 1
It is used in the range of 00 mol%. When the amount of the aromatic dicarboxylic acid (a-1) is less than 80 mol%, the hardness, stain resistance and water resistance of the coating film deteriorate. Aromatic dicarboxylic acid (a-
Examples of 1) include terephthalic acid, isophthalic acid,
Phthalic acid, 1,4-naphthalenedicarboxylic acid, 2,6-
Examples thereof include naphthalenedicarboxylic acid, and acid anhydrides, acid halides or lower alkyl esters thereof. Examples of the lower alkyl ester of the aromatic dicarboxylic acid include esters such as methyl, ethyl, propyl and butyl, and the methyl ester is preferably used in terms of cost and handling. These aromatic dicarboxylic acids (a-1) can be used alone or in combination of two or more.

Further, the other polyvalent carboxylic acid (a-2) used as the acid component (A) is used by appropriately selecting it according to need, and it is 0 to 0 in the acid component (A). Used in the range of 20 mol%. Other polycarboxylic acid (a-2)
When the amount of the above exceeds 20 mol%, the hardness of the coating film, stain resistance,
Water resistance decreases. Examples of the other polycarboxylic acid (a-2) include sebacic acid, succinic acid, maleic acid, fumaric acid, adipic acid, azelaic acid and other aliphatic dicarboxylic acids and their acid anhydrides, hexahydrophthalic acid. ,
Alicyclic dicarboxylic acids such as hexahydroisophthalic acid and hexahydroterephthalic acid and their acid anhydrides, dicarboxylic acids such as acid halides or lower alkyl esters, trimellitic acid, 1,2,4-cyclohexanetricarboxylic acid, 2 , 5,7-naphthalene tricarboxylic acid, 1,2,4-naphthalene tricarboxylic acid, 1,2,
Tricarboxylic acids such as 5-hexanetricarboxylic acid and their acid anhydrides, pyromellitic acid, 1,2,7,8-
Examples include tetracarboxylic acids such as octane tetracarboxylic acid and 1,2,3,4-butane tetracarboxylic acid, and acid anhydrides thereof. These can be used alone or in combination of two or more.

The alcohol component (B) used to obtain the copolyester resin of the present invention includes a diol (b-1) represented by the general formula (1) and a compound (b) represented by the general formula (2). b-2), cyclohexanedimethanol (b-3), another diol (b-4) and a polyhydric alcohol having 3 or more valences (b-5).

The diol (b-1) represented by the above general formula (1) used in the present invention is a component that imparts water resistance and corrosion resistance to the coating film, and is 0 to 50 mol in the alcohol component (B). %, Preferably 5-40 mol%,
More preferably, it is contained in the range of 10 to 30 mol%.
If the content of the diol (b-1) exceeds 50 mol%, the processability of the resin will deteriorate. Examples of the diol represented by the general formula (1) include aromatic diols such as ethylene oxide or propylene oxide adducts of bisphenol A. These can be used alone or in combination of two or more.

The compound (b-2) represented by the above general formula (2) used in the present invention is a component equivalent to a diol in the reaction with the above component (A), and has a processability of a coating film, It is a component that imparts water resistance, adhesiveness, and suitability for wet ink, and is 0.1% in the alcohol component (B).
It is contained in the range of 5 to 20 mol%. This is because when the content of the compound (b-2) is less than 0.5 mol%, the effect of improving the coating film performance is low, and when it exceeds 20 mol%, the polymerization stability of the polyester resin of the present invention decreases. This is because it becomes difficult to obtain a desired molecular weight. It is preferably in the range of 0.5 to 15 mol%, more preferably 1 to 10 mol%.

The compound represented by the general formula (2) (b-
Examples of 2) include glycidyl such as allyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, phenol glycidyl ether, sec-butylphenol glycidyl ether, 2-methyloctyl glycidyl ether, and o-butylphenol glycidyl ether. Ether, styrene oxide, α-pentene oxide, α-hexene oxide, α-heptene oxide, α-octene oxide, α-decene oxide, α-undecene oxide, α-dodecene oxide and the like, among which 2- Ethylhexyl glycidyl ether, phenol glycidyl ether, sec-butylphenol glycidyl ether, 2-methyloctyl glycidyl ether, Ji alkylene oxide, alpha-dodecene oxide is particularly preferred. These can be used alone or in combination of two or more.

The cyclohexanedimethanol (b-3) used in the present invention is a component that imparts hardness, weather resistance, chemical resistance, water resistance and suitability for wet ink to the coating film, and the alcohol component (B ) In the range of 1 to 50 mol%. This is because when the content of the diol (b-3) is less than 1 mol%, the effect of improving the coating film performance is low.
This is because if the amount exceeds 0 mol%, the processability of the coating film decreases. Preferably 5-45 mol%, more preferably 10-
It is in the range of 40 mol%.

Examples of cyclohexanedimethanol (b-3) include 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol, among which 1,4 -Cyclohexanedimethanol is preferred.

The cyclohexanedimethanol (b-3) used in the present invention is a mixture of cis and trans isomers, and the ratio thereof is in the range of 50: 50≤cis isomer: trans ≤10: 90. Is preferred.

The other diol (b-4) used in the present invention is appropriately selected and used as necessary, and is used in the range of 20 to 98.4 mol% in the alcohol component (B). used. 20 other diols (b-4)
If it is less than mol%, the processability of the coating film will be deteriorated, or it will be difficult to obtain a resin having a target molecular weight. If it exceeds 98.4 mol%, the hardness, processability, water resistance, adhesion and The suitability for wet ink becomes insufficient.

Examples of the other diol (b-4) used as the alcohol component (B) include ethylene glycol, neopentyl glycol, 1,2-propanediol, 1,3-propanediol and 1,4-butane. Diol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, diethylene glycol, triethylene glycol, Polyethylene glycol, 2-methyl-2-ethyl-1,3-propanediol, 2,2-diethyl-
1,3-propanediol, 2-butyl-2-ethyl-
Aliphatic diols such as 1,3-propanediol, 1,2
Examples thereof include cycloaliphatic diols such as cyclohexanediol and 1,4-cyclohexanediol. These are 1
They may be used alone or in combination of two or more.

The trihydric or higher polyhydric alcohol (b-5) used in the present invention is a component for imparting processability to the resin, and is 0.1 to 10 mol% in the alcohol component (B).
It is contained in the range. This is because when the content of the diol (b-5) is less than 0.1 mol%, the effect of improving the workability is low, and when it exceeds 10 mol%, the resin gels and becomes difficult to dissolve in the solvent. . The range is preferably 0.5 to 8 mol%, more preferably 1 to 6 mol%.

3 used as alcohol component (B)
As the polyhydric alcohol (b-5) having a valency or higher, for example, sorbitol, 1,2,3,6-hexanetetralol,
1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose,
1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,
3,5-trihydroxymethylbenzene, or polycaprolactone triol having three hydroxyl groups at terminals,
For example, Plaxel 30 manufactured by Daicel Chemical Industries, Ltd.
3, 305, 306, 308, 312, 320 and the like. These can be used alone or in combination of two or more.

In the copolyester resin for coating composition of the present invention having the above constitution, the number average molecular weight is 3,000.
It is necessary to be 0 to 50,000, preferably 4,000 to 40,000, and more preferably 5,000.
Is in the range of ˜30,000. Number average molecular weight of 3,000
If it is less than 0, the performance of the obtained coating film is low overall,
On the other hand, when it exceeds 50,000, the viscosity of the obtained coating composition becomes high and the handling becomes difficult.

The method for producing the copolyester resin of the present invention is not particularly limited, but known polymerization methods described below can be applied. For example, first, the monomer is charged into a reaction kettle and heated to raise the temperature to carry out an esterification reaction or a transesterification reaction to remove water or alcohol produced in this reaction. At this time, if necessary, an esterification catalyst such as sulfuric acid, titanium butoxide, dibutyltin oxide, magnesium acetate, manganese acetate, and zinc acetate, which is used in a normal esterification reaction or transesterification reaction, can be used.

Next, a polycondensation reaction is subsequently carried out, at which time the polymerization is carried out under a vacuum of 150 mmHg or less while distilling off the diol component. In the polymerization, known polymerization catalysts such as titanium butoxide, dibutyltin oxide, tin acetate, zinc acetate, tin disulfide, antimony trioxide, and germanium dioxide can be used. Further, the polymerization temperature and the amount of the catalyst are not particularly limited, and may be arbitrarily set as needed.

When the copolymerized polyester resin of the present invention is produced by the above-mentioned polymerization method, it is preferable to add the above-mentioned component (b-2) at the time of the condensation reaction. This is because if the component (b-2) is used during the esterification reaction or transesterification reaction, the component (b-2) tends to decompose.

The copolymerized polyester resin obtained by the present invention is useful as a base resin for paints, particularly overcoat clear paints for metal plates used for drinking cans, beauty cans, etc. Correspondingly, a cross-linking agent such as a melamine resin, an isocyanate compound and a block isocyanate compound, an epoxy resin, a phenol resin, a urethane resin, a vinyl chloride resin, a fibrin resin and the like can be blended and used.

Further, rust preventive pigments such as strontium chromate and zinc chromate, a surface smoothing agent, a defoaming agent and the like, and a coupling agent such as titanium and silicon type can be blended.

The copolyester resin of the present invention is used by being dissolved in an organic solvent, and usable organic solvents include benzene, toluene, xylene, mineral terpene, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate. , Methyl cellosolve,
Various solvents such as butyl cellosolve, cellosolve acetate, isophorone, methanol, ethanol, butanol, Solvesso 100, 150 can be used, but one or a mixture of two or more of them may be selected in consideration of solubility and evaporation rate. It can be selected and used.

[0034]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The performance evaluation in the following examples and comparative examples was performed using the following method.

(1) Resin composition analysis Composition analysis was carried out by NMR.

(2) Number average molecular weight The number average molecular weight in terms of GPC polystyrene was determined.

(3) Pencil Hardness The hardness of the coating film was measured in accordance with JIS K-5400 using a high-grade pencil defined in JIS S-6006.

(4) Suitability for wet ink The degree of ink bleeding and embossing was evaluated on a scale of 5 points.

1: An extremely large change was found in the ink,
Poor 2: A large change was found in the ink and could not be used. 3: A change was found in the ink, but it could be used. 4: Some change was found in the ink, but good. 5: No change was found in the ink. Very good. (5) Workability A plate having the same thickness as the evaluation coated plate was clamped in the evaluation coated plate with a vise and bent, and the workability was judged by whether or not cracks were generated in the coating film at the bent portion (number of test sheets 5
Sheet). The numbers in the table indicate the number of cracks.

(6) Water resistance The state of the coating film after the coated plate was immersed in warm water at 50 ° C. for 1 week was evaluated.

◯: No abnormality Δ: Swelling slightly S: Swelling, whitening The abbreviations in the table represent the following compounds.

IPA: isophthalic acid TPA: terephthalic acid ADA: adipic acid SA: sebacic acid EG: ethylene glycol NPG: neopentyl glycol CHDM: 1,4-cyclohexanedimethanol (cis isomer: trans isomer = 32: 68) DEG: Diethylene glycol BPE: Methylene oxide average 2.3 mol adduct of bisphenol A BPP: Propylene oxide average 2.3 mol adduct of bisphenol A TMP: Trimethylolpropane PEN: Pentaerythritol Praxel 308: Polycaprolactone triol, Daicel Chemical Co., Ltd. PLACSEL 303: Polycaprolactone triol, Daicel Chemical Industries, Ltd. Epoxy A: 2-ethylhexyl glycidyl ether Epoxy B: Phenol glycidyl ete Epoxy C: sec-butylphenol glycidyl ether Epoxy D: 2-methyloctyl glycidyl ether Epoxy E: Styrene oxide Epoxy F: α-dodecene oxide [Example 1] 1.83 mol parts of isophthalic acid and 1.83 mol parts of terephthalic acid , Ethylene glycol 2.12 mol parts, 1,4-cyclohexanedimethanol 1.47 mol parts, Praxel 308 (manufactured by Daicel Chemical Industries, Ltd .: polycaprolactone triol) 0.04 mol parts, bisphenol A ethylene oxide (average) (2.3 mol) 0.37 mol part of an adduct and 0.01 part mol of zinc acetate were charged into a reaction vessel, and an esterification reaction was carried out while distilling water at an internal temperature of 230 ° C to 265 ° C. After confirming that the esterification reaction product became transparent, 0.40 parts by mol of 2-ethylhexyl glycidyl ether and 0.0016 parts by mol of antimony trioxide were added, and the internal temperature was controlled to 255 ° C or higher and 260 ° C or lower. The pressure in the reaction system was reduced to 1.0 mmHg over 30 minutes, and the condensation reaction was carried out for 1.5 hours while distilling the excess glycol component. The composition of the obtained copolyester resin (A-1) was analyzed by NMR. As a result, isophthalic acid / terephthalic acid = 50/5
0 (mol%), ethylene glycol / 1,4-cyclohexanedimethanol / Plaxel 308 / ethylene oxide adduct of bisphenol A (average 2.3 mol) /
2-ethylhexyl glycidyl ether = 39/40 /
It was 1/10/10 (mol%).

This copolyester resin (A-1) was dissolved in a mixed solvent of Solvesso 150 / cyclohexanone = 50/50 (weight ratio) and adjusted so that the nonvolatile content was 40%.

The obtained resin solution was blended so that polyester / benzoguanamine = 80/20 (solid content ratio), and p-toluenesulfonic acid as a curing catalyst was added to polyester + benzoguanamine (solid content) in an amount of 0. 1
It was blended so as to be wt%.

The following tests were performed on the obtained clear paint. A 0.3 mm thick tin plate is coated with a polyester-based white coating agent to a film thickness of 10 μm, dried at 180 ° C. for 10 minutes, and then a drying oil alkyd resin is used as the main component of the vehicle. 2μ
m was printed, and the above clear paint was applied in an uncured state (without baking) to a film thickness of 8 μm to prepare a test panel. The evaluation results of the coating film performance are shown in Table 3.

[Examples 2 to 6] Copolymerization polyester resins (A-2) to (A-6) were obtained in the same manner as in Example 1 except that the composition for polymerization was changed as shown in Table 1. It was Table 1 shows the polymer charging compositions of the copolymerized polyester resins (A-2) to (A-6), and Table 2 shows the resin composition analysis results and the number average molecular weight measurement results.

Test panels were prepared from these copolymerized polyesters in the same manner as in Example 1 and evaluated. Table 3 shows the evaluation results.

[0048]

[Table 1]

Numerical values in the table are molar parts

[0050]

[Table 2]

Numerical values in the table are mol%

[0052]

[Table 3]

[Comparative Examples 1 to 6] Copolymerized polyester resins (A-7) to (A-13) were obtained in the same manner as in Example 1 except that the composition for polymerization was as shown in Table 4. It was
The copolyester resin (A-9) gelled during production and could not be taken out from the reactor.

Copolymerized polyester resin (A-7) to (A
The composition of the polymer prepared in -13) is shown in Table 4, and the resin composition analysis result and the number average molecular weight measurement result are shown in Table 5.

Test panels were prepared from these copolyesters in the same manner as in Example 1 and evaluated. The evaluation results are shown in Table 6.

[0056]

[Table 4]

Numerical values in the table are molar parts

[0058]

[Table 5]

Numerical values in the table are mol%

[0060]

[Table 6]

[0061]

EFFECT OF THE INVENTION The copolyester resin for paint of the present invention is excellent in hardness, processability, water resistance, adhesiveness and suitability for wet ink, and is very useful industrially.

Claims (1)

[Claims] (A) Aromatic dicarboxylic acid (a-1) 8
An acid component consisting of 0 to 100 mol% and 0 to 20 mol% of a divalent or higher polyvalent carboxylic acid (a-2) other than an aromatic dicarboxylic acid; and (B) a diol represented by the following general formula (1) ( b-1) 0 to 50 mol%, compound (b-2) 0.5 to 20 mol% represented by the following general formula (2), cyclohexanedimethanol (b-3) 1 to 50 mol%, other diol (B-4) 20 to 98.4 mol% and a trihydric or higher polyhydric alcohol (b-5) consisting of 0.1 to 10 mol% of an alcohol component having a number average molecular weight of 3,000 to.
A copolymerized polyester resin for paints, which is 50,000. Embedded image In the formula, R ₁ is an alkylene group having 3 or less carbon atoms, m and n are natural numbers, and 2 ≦ m + n ≦ 7. Embedded image In the formula, R ₂ is an acyclic hydrocarbon group having 3 or more carbon atoms, an alicyclic hydrocarbon group, an aryl group, or a derivative thereof such as an ether or ester.