JPH09302075A - Copolyester resin for coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a copolyester resin excellent in water resistance by reacting an acid component contg. an arom. dicarboxylic acid and an alicyclic dicarboxylic acid with a diol component contg. a diol represented by a specific formula and 1,4-cyclohexanedimethanol. SOLUTION: A copolyester resin for a coating material with a number- average mol.wt. of 3,000-5-,000 is prepd. by feeding an acid component comprising 80-99mol% arom. dicarboxylic acid (e.g. isophathalic acid), 1-20mol% alicyclic dicarboxylic acid (e.g. hexahydrophthalic acid), and 0-20mol% other dicarboxylic acid, a diol component comprising 0.5-20mol% diol represented by formula I (wherein R1 is 14C or higher alkylene), 0-50mol% diol represented by formula II (wherein R2 is 3C or lower alkylene; and 2<=m+n<=7), 1-50mol% 1,4-cyclohexanedimethanol, 0-98.4mol% other diol, and 0.1-10mol% polyhydric alcohol, and a zinc acetate catalyst into a reactor, heating the reactants to cause transesterification, adding a polymn. catalyst to the reaction system, and heating it under a reduced pressure to cause polycondensation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copolyester resin for paints, and more particularly to paints, especially drinking cans,
The present invention relates to a copolymerized polyester resin for coatings, which is useful as a base resin for overcoat clear coatings for metal plates used for beauty cans and the like and has excellent hardness, processability, water resistance, adhesion and wet ink properties.

[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.

However, when the overcoat clear paint is applied on the uncured ink layer, the ink flows together with the overcoat clear paint, and the ink flows like "whiskers" at the edges of the printed portion. So-called "bleeding phenomenon" or a problem of wet ink suitability called "embossing phenomenon" in which a step is formed at the edge of the printed portion is likely to occur.

Further, for example, since a metal plate used for a can is coated with an ink and an overcoat clear paint, and after being cured, it is processed into a metal processed product suitable for each use,
Overcoat clear paint requires high workability.

Generally, these overcoat clear paints are mainly composed of an acrylic resin or an epoxy ester resin having relatively good wet ink suitability, but these resins have poor processability. In addition, it has a drawback that the coating film tends to have a problem of "breakage / peeling".

On the other hand, in recent years, a polyester resin has come to be used as an overcoat clear coating material which is excellent in processability, but it has a drawback that its suitability for wet ink is insufficient. As described above, there is no known overcoat clear paint that fully satisfies all performances.

[0008]

DISCLOSURE OF THE INVENTION The object of the present invention is to obtain hardness, processability, water resistance, useful as a base resin for paints, particularly overcoat clear paints for metal plates used for drinking cans, beauty cans, etc. An object of the present invention is to provide a copolyester resin for coatings, which has excellent adhesion and wet ink properties.

[0009]

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 99 mol% of (A) aromatic dicarboxylic acid (a-1), 1 to 20 mol% of alicyclic dicarboxylic acid (a-2) and other dicarboxylic acid (a)
-3) 0 to 20 mol% of an acid component, and (B) 0.5 to 20 diol (b-1) represented by the following general formula (I).
Mol%, a diol represented by the following general formula (II) (b-
2) 0 to 50 mol%, 1,4-cyclohexanedimethanol (b-3) 1 to 50 mol%, other diol (b-
4) an alcohol component comprising 0 to 98.4 mol% and a polyhydric alcohol (b-5) having a valence of 3 or more (b-5) and having a number average molecular weight of 3,000 to 50,000.
It is a copolyester resin for paints, which is characterized by 0.

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[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The acid component (A) used to obtain the copolyester resin for paints of the present invention is an aromatic dicarboxylic acid (a-1) and an alicyclic dicarboxylic acid (a-2).
And another dicarboxylic acid (a-3).

The aromatic dicarboxylic acid (a-1) used as the acid component (A) includes terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid,
2,6-naphthalenedicarboxylic acid, and their acid anhydrides, acid halides, lower alkyl esters and the like. 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.

As the alicyclic dicarboxylic acid (a-2) used as the acid component (A), hexahydrophthalic acid,
Examples thereof include hexahydroisophthalic acid, hexahydroterephthalic acid, and acid anhydrides, acid halides or alkyl esters thereof, with hexahydroterephthalic acid being particularly preferred. These alicyclic dicarboxylic acids (a-2) can be used alone or in combination of two or more.

The other dicarboxylic acid (a-3) used as the acid component (A) is, for example, sebacic acid,
Examples thereof include aliphatic dicarboxylic acids such as succinic acid, maleic acid, fumaric acid, adipic acid and azelaic acid, and acid anhydrides, acid halides or lower alkyl esters thereof. These can be used alone or in combination of two or more.

The proportion of the aromatic dicarboxylic acid (a-1), the alicyclic dicarboxylic acid (a-2) and the other dicarboxylic acid (a-3) in the acid component (A) is such that the aromatic dicarboxylic acid (a- 1) is in the range of 80 to 99 mol%, alicyclic dicarboxylic acid (a-2) is 1 to 20 mol%, and other dicarboxylic acid (a-3) is 0 to 20 mol%. When the amount of the dicarboxylic acid (a-2) is less than 1 mol%, no improvement in wet ink properties is observed, and when the amount of the dicarboxylic acid (a-1) is 20 mol% or more, that is, the amount of the aromatic dicarboxylic acid (a-1) is less than 80 mol%, coating is not performed. The hardness, stain resistance, and water resistance of the film are reduced.

The alcohol component (B) used to obtain the copolyester resin for paints of the present invention is represented by the diol (b-1) represented by the general formula (I) and the general formula (II). Compound (b-2), 1,4-cyclohexanedimethanol (b-3), other diol (b-
4) and a trihydric or higher polyhydric alcohol (b-5).

The diol (b-1) represented by the above general formula (I) used in the present invention is a component which imparts processability, water resistance, adhesion and wet ink property to a coating film, and an alcohol component. It is contained in the range of 0.5 to 20 mol% in (B). This is because when the content of the diol (b-1) 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 is difficult to obtain the target molecular weight. Preferably 0.5-
It is in the range of 15 mol%, more preferably 1 to 10 mol%. Specific examples of the diol (b-1) represented by the general formula (I) include, for example, a mixture of diols represented by the following formulas (III) and (IV).

[0018]

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[0019]

[Chemical 6]

The above general formula (I
The diol (b-2) represented by I) is water resistant to the coating film,
It is a component that imparts corrosion resistance and is contained in the alcohol component (B) in an amount of 0 to 50 mol%, preferably 5 to 40 mol%, and more preferably 10 to 30 mol%. If the content of the diol (b-2) exceeds 50 mol%, the processability of the resin will deteriorate.

Specific examples of the diol represented by the above general formula (II) 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 1,4-cyclohexanedimethanol (b-3) used in the present invention is a component that imparts hardness, weather resistance, chemical resistance, water resistance and wet ink resistance to the coating film, and is an alcohol component. It is contained in the range of 1 to 50 mol% in (B). 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 50 mol%, the processability of the coating film decreases. Preferably 5-45 mol%, more preferably 10-
It is in the range of 40 mol%.

The 1,4-cyclohexanedimethanol (b-3) used in the present invention is a mixture of cis isomer and trans isomer, and the ratio thereof is 50: 50≤cis isomer: trans ≤10: 90. Those in the range are preferable.

The other diol (b-4) used in the present invention is appropriately selected and used according to need, and is used in an amount of 0 to 98.4 mol% in the alcohol component (B).
Used in the range. Another diol (b-4) was 98.
If it exceeds 4 mol%, the hardness, processability, water resistance, adhesion and wet ink properties of the coating film will be 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 can be used alone or in combination of two or more, and among them, 2,2-diethyl-1,3
-Propanediol and 2-butyl-2-ethyl-1,3
-Propanediol is particularly preferred. This is 2,2-
Diethyl-1,3-propanediol and 2-butyl-2
This is because the use of -ethyl-1,3-propanediol improves the weather resistance, water resistance and wet ink resistance of the resulting coating film. In this case, the amount used is preferably in the range of 1 to 50 mol% in the alcohol component (B). This is because in this range, the effect of improving the physical properties of the coating film described above is obtained, and good polymerization stability of the resin tends to be obtained. The range is more preferably 5 to 45 mol%, and further preferably 10 to 40 mol%.

Further, 2,2-diethyl-1,3-propanediol and / or 2-butyl-2-ethyl-
When 1,3-propanediol is used and the other component (b-4) is used, the amount used is 20 to 9
It is preferably in the range of 7.4 mol%. Within this range, the productivity of the resin and the processability of the resulting coating film tend to be good.

The trihydric or higher polyhydric alcohol (b-5) used in the present invention is a component that imparts 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 and 320 and the like. These can be used alone or in combination of two or more.

The method for producing the copolyester resin for paints of the present invention is not particularly limited, but the following known polymerization methods can be applied. For example, first, by charging the above monomer into a reaction kettle and heating to raise the temperature,
An esterification reaction or a transesterification reaction is performed, and water or alcohol generated in the reaction is removed. 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 and removing 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.

In the copolyester resin for coating composition of the present invention having the above constitution, the number average molecular weight is 3,000.
0-50,000, preferably 4,000-40,000
It is important that the range is 0, more preferably 5,000 to 30,000. When the number average molecular weight is less than 3,000, the performance of the obtained coating film is low overall, while
When it exceeds 50,000, the viscosity of the obtained coating composition becomes high and the handling becomes difficult.

The copolyester resin for paints obtained by the present invention is useful as a base resin for paints, especially overcoat clear paints for metal plates used for drinking cans, beauty cans, etc. A crosslinking agent such as a melamine resin, an isocyanate compound, or a block isocyanate compound, an epoxy resin, a phenol resin, a urethane resin, a vinyl chloride resin, a fibrin resin, or the like can be blended and used depending on the performance.

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 for paints of the present invention is used by being dissolved in an organic solvent, and usable organic solvents include benzene, toluene, xylene, mineral terpenes, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, Butyl acetate, methyl cellosolve, butyl cellosolve, cellosolve acetate, isophorone, cyclohexanone, methanol, ethanol,
Various solvents such as butanol and Solvesso 100 and 150 can be used, and one or a mixture of two or more thereof can be selected from these and used in consideration of solubility and evaporation rate.

[0036]

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 The composition was analyzed 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) Wet ink property The degree of ink bleeding phenomenon and embossing phenomenon is shown in 6 below.
The evaluation was based on a perfect score. 1: Extremely large change in ink was found, poor 2: Large change in ink was found, unusable 3: Ink changed, but usable 4: Ink slightly changed, but good 5: Very little change in ink, very good 6: No change in ink, very good

(5) Workability A plate having the same thickness as the evaluation coated plate was sandwiched between the evaluation coated plates and clamped with a vise to be bent, and the workability was judged by whether or not cracks were generated in the coating film at the bent portion ( 5 for each test).
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 △: Swelling slightly ×: Swelling, whitening

The abbreviations in the table represent the following compounds. IPA: isophthalic acid TPA: terephthalic acid SA: sebacic acid HPAA: hexahydrophthalic anhydride HTPA: hexahydroterephthalic acid EG: ethylene glycol NPG: neopentyl glycol CHDM: 1,4-cyclohexanedimethanol (cis form: trans form = 32 : 68) DEG: diethylene glycol DEPG: 2,2-diethyl-1,3-propanediol BEPG: 2-butyl-2-ethyl-1,3-propanediol BPE: average ethylene oxide 2.3 mol adduct of bisphenol A BPP: average propylene oxide 2.3 mol adduct of bisphenol A diol b-1: mixture of diols represented by the above general formulas (III) and (IV) (composition; formula (III) / (IV) = 75)
/ 25 (weight ratio)). TMP: Trimethylolpropane PEN: Pentaerythritol Praxel 308: Polycaprolactone triol (Product of Daicel Chemical Industries, Ltd.) Praxel 303: Polycaprolactone triol (Product of Daicel Chemical Industries, Ltd.)

Example 1 1.46 mole parts of isophthalic acid, 1.83 mole parts of terephthalic acid, 0.37 mole part of hexahydrophthalic anhydride, 2.12 mole parts of ethylene glycol, 1,4-cyclohexanedimethanol 1 .47 mole parts, PLAXEL 308 (manufactured by Daicel Chemical Industries, Ltd .:
0.04 mol part of polycaprolactone triol, ethylene oxide of bisphenol A (average 2.3 mol)
0.37 mol part of an adduct and 0.001 mol part 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. or higher and 265 ° C. or lower. After confirming that the esterification reaction product was transparent, 0.37 parts by mole of diol b-1 and 0.00 of antimony trioxide were added.
016 mol parts was added to control the internal temperature to 255 ° C or higher and 260 ° C or lower, and the inside of the reaction system was 1.0 mm over 30 minutes.
The pressure was reduced to Hg, and the condensation reaction was performed for 1.5 hours while distilling excess glycol component. Table 2 shows the resin composition and the measurement results of the number average molecular weight of the obtained copolyester resin (A-1).

Then, this copolymerized polyester resin (A
-1) to Solvesso 100 / Butyl cellosolve (50 /
50 (weight ratio)) is dissolved in a mixed solvent, and the nonvolatile content is 40
%.

Next, benzoguanamine was added to the resulting resin solution in an amount of 80% polyester / benzoguanamine.
20% (solid content ratio), and p-toluenesulfonic acid as a curing catalyst was added to the total amount (solid content) of polyester and benzoguanamine to be 0.1% by weight, and a clear paint. Got

Then, a test panel was prepared in the following manner to evaluate the coating performance of the clear paint. Table 3 shows the evaluation results. Preparation of test panel: A 0.3 mm thick tin plate is coated with a polyester white coating agent to a film thickness of 10 μm, dried at 180 ° C. for 10 minutes, and a drying oil alkyd resin is applied to the main vehicle as a vehicle. Print the ink as a component to a thickness of 2 μm, apply the above clear paint to a thickness of 8 μm with the ink uncured (no baking), and bake at 180 ° C for 10 minutes. Then, a test panel was prepared.

[Examples 2 to 6] Copolymerized 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 The copolymerized polyester resins (A-2) to (A-2 obtained in Table 2
Table 2 shows the resin composition analysis results and the number average molecular weight measurement results for -6).

Next, using the above-mentioned copolymerized polyester resin, a test panel was prepared in the same manner as in Example 1 and the coating film physical properties were evaluated. Table 3 shows the evaluation results.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

[Table 3]

[Examples 7 to 12] Table 4 shows the composition of polymerization.
The same operation as in Example 1 was carried out except that the above procedure was carried out to obtain copolymer polyester resins (A-7) to (A-12). Copolyester resin (A-7) obtained in Table 5
The resin composition analysis results and the number average molecular weight measurement results of (A-12) are shown.

Then, using the above-mentioned copolymerized polyester resin, a test panel was prepared in the same manner as in Example 1 and the physical properties of the coating film were evaluated. The evaluation results are shown in Table 6.

[0055]

[Table 4]

[0056]

[Table 5]

[0057]

[Table 6]

Comparative Examples 1 to 7 Copolymerization polyester resins (A-13) to (A-19) were obtained in the same manner as in Example 1 except that the composition for polymerization was as shown in Table 7. It was However, the copolymer polyester resin (A-15) is
It gelled during manufacture and could not be removed from the reactor. The copolymerized polyester resin (A-1 obtained in Table 8
3) to (A-14) and (A-16) to (A-19)
The resin composition analysis result and the number average molecular weight measurement result of are shown.

Next, using the above-mentioned copolymerized polyester resin, a test panel was prepared in the same manner as in Example 1 and the physical properties of the coating film were evaluated. Table 9 shows the evaluation results.

[0060]

[Table 7]

[0061]

[Table 8]

[0062]

[Table 9]

[0063]

EFFECT OF THE INVENTION The copolyester resin for paints of the present invention is excellent in hardness, processability, water resistance, adhesiveness and wet ink property, and is a metal plate used for paints, especially beverage cans, beauty cans and the like. It is useful as a base resin for overcoat clear paints.

Claims (3)

[Claims] (A) Aromatic dicarboxylic acid (a-1) 8
0-99 mol%, alicyclic dicarboxylic acid (a-2) 1-2
0 mol% and other dicarboxylic acid (a-3) 0 to 20 mol% acid component, (B) diol (b-1) represented by the following general formula (I) 0.5 to 20 mol%, Diol (b-2) represented by the following general formula (II) 0 to 50 mol%, 1,4-cyclohexanedimethanol (b-3) 1
˜50 mol%, other diol (b-4) 0 to 98.4 mol% and trihydric or higher polyhydric alcohol (b-5) 0.1
A copolymerized polyester resin for paints, which comprises an alcohol component consisting of 10 to 10 mol% and has a number average molecular weight of 3,000 to 50,000. Embedded image Embedded image 2. The copolyester resin for coating composition according to claim 1, wherein the alicyclic dicarboxylic acid (a-2) is hexahydroterephthalic acid. 3. As the diol (b-4), 2,2-diethyl-1,3-propanediol and / or 2-
1-butyl-2-ethyl-1,3-propanediol
50 mol% is used, The copolymer polyester resin for paints of Claim 1 characterized by the above-mentioned.