JPH0812751A - Polyester resin for can gloss varnish - Google Patents

Abstract

PURPOSE:To obtain a polyester resin which has excellent low-temperature curability and can give a coating film excellent in ink adaptability to wet-on-wet coating, processability, gloss, retorting resistance, and blocking resistance by modifying the terminal hydroxyl groups of a polyester resin with a lactone compound. CONSTITUTION:A direct addition reaction is effected between the terminal hydroxyl groups of a polyester resin comprising 20-70mol% isophthalic acid, 0-50mol% other aromatic dicarboxylic acids, 1-80mol% 6-12 C aliphatic and/or alicyclic dicarboxylic acids and 60-100mol%, based on the whole glycol component, aliphatic glycol having an alkyl side chain, and 1-60mol%, based on the whole acid component of the polyester, lactone compound after the polycondensation to obtain a polyester resin having a reduced viscosity of 0.2-0.6dl/g, a glass transition temperature of 0-50 deg.C, a resin specific viscosity of 1.20 or below, and a contact angle of 60 deg. or below as measured by contacting the varnish dissolved in a butyl Cellosolve/Solvesso #150 (1/4 by weight) mixture to form a solution of a solid content of 40wt.% with polytetrafluoroethylene.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cannish resin excellent in wet ink properties, image clarity, processability, retort properties, and low temperature curability, and a resin composition thereof.

[0002]

2. Description of the Related Art Conventionally, metal cans have been widely used as one kind of beverages, foods, and other packaging containers. The outer surface of these cans is printed and painted for the purpose of anticorrosion property of metal, aesthetics, and display of contents. For general printing and painting on the outer surface of the can, size coating on a surface-treated metal plate,
Alternatively, an undercoat referred to as a white coating is applied, and several colors are printed with an oil-based or UV ink.
Furthermore, a varnish coating is applied on it to protect the surface and improve the finished appearance. At this time, the method of coating the ink on the wet state (wet-on-wet method) by omitting the drying process of the oil-based ink for the glossy varnish has recently been performed.

For this reason, the main requirements for the gloss coating are: (1) When the gloss-on-wet method is used to coat the varnish, there is no bleeding or agglomeration of the ink layer and no dents or repellency of the varnish. (Wet ink property), (2) Complex processability, sufficient processability to withstand processing (processability), (3) Gloss of appearance and excellent image clarity, (4) Ink effect conditions However, it can be cured (low temperature curability), (5) does not deteriorate by retort sterilization during food container coating (retort resistance), (6) coatings do not stick to each other when stacked coated plates ( Blocking property) and the like. However, there is still no resin for a varnish coating which gives these coatings a well-balanced performance at a high level.

[0004]

Conventionally, an epoxy ester type has been used as a varnish coating, but it has a good wet ink property, but has poor workability and is complicated by recent bead processing, neck-in, spin necking and the like. There is a drawback that it cannot withstand various processing and drawing processing.

As a resin system that withstands the above-mentioned complicated processing, epoxy resin, epoxy acrylic resin, epoxy amino resin, or epoxy phenol resin, which is a thermosetting paint, and a polyester resin is added to the paint for a metal can (Japanese Patent Laid-Open No. 50-32).
No. 230 and JP-A-55-5396) are known.
However, even in this system, satisfactory performances regarding wet ink resistance and retort resistance are not obtained. In particular, if the cohesive force of the resin is high, wet ink properties are likely to attack the ink layer, and satisfactory performance cannot be obtained. Therefore, good performance cannot be obtained with ethylene glycol or polyester containing a large amount of aromatic components.

On the other hand, a polyester-based thermosetting paint which is said to have excellent processability is disclosed in JP-A-1-315472, but in order to satisfy wet ink properties, a glycol having a side chain as a glycol component in the polyester, for example, Neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, 2,2'-diethyl-
A lot of 1,3-propanediol is used. For this reason, the steric hindrance of the terminal OH group becomes remarkable, and the low temperature curability, which is a condition for wet coating, is poor and a sufficiently cured coating cannot be obtained, so that the retort property, blocking property, and processability are insufficient. . Further, if ethylene glycol, 1,4-butanediol, or the like is used to improve the reactivity, the wet ink property is poor, and it is difficult to balance the performance.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that lactone modification of a polyester resin does not reduce wet ink properties and causes steric hindrance of terminal OH groups. The present invention succeeded in improving the low temperature curability, and succeeded in finding a canning paint resin composition for cans having excellent wet ink property, processability, gloss, low temperature curability, retortability and blocking property, and reached the present invention. did.

That is, according to the present invention, the terminal O of the polyester resin is
H group is modified with a lactone compound in an amount of 1 to 60 mol% with respect to the total dicarboxylic acid component of the polyester resin, and has a reduced viscosity of 0.2 to 0.6 dl / g and a glass transition temperature of 0 to 5
Can-tunish varnish having a resin specific gravity of 1.20 or less at 0 ° C., a varnish dissolved in butyl cellosolve / solvesso 150 = 1/4 (weight ratio) and a solid content of 40% by weight and having a contact angle with polytetrafluoroethylene of 60 ° or less. Of the dicarboxylic acid component, wherein the isophthalic acid is 20 to 70 mol%, the other aromatic dicarboxylic acid is 0 to 50 mol%, and the carbon number is 6 to 6.
Up to 12 aliphatic and / or alicyclic dicarboxylic acid components are 1 to 80 mol%, and all glycol components are 60 to 100 mol% of aliphatic glycol having a side chain alkyl group, and other glycol components are 0 to 40 mol% and preferably 0.1 to 5 mol% of trivalent or higher polyvalent carboxylic acid and / or polyglycol with respect to the total acid component or total glycol component, more preferably a side chain alkyl group. Among the total glycol components, the aliphatic glycol having 60% to 100% by mol of one type or two or more types of side chain alkyl group-containing aliphatic glycol represented by the following chemical formula 1, and the other glycol components are 0 to 40 mol. %, And the other glycol is an alicyclic glycol, which is a polyester resin for can varnish.

Embedded image Furthermore, the polyester resin is preferably used in combination with a curing agent capable of reacting with the polyester resin, and the curing agent is preferably an amino resin.

The polyester resin for can varnish of the present invention contains isophthalic acid of 20 to 70 out of dicarboxylic acid components.
Mol%, preferably 30 to 50 mol%, and other dicarboxylic acid components are 0 to 50 mol%. If the amount of isophthalic acid is less than 20 mol%, the solubility will be poor, and the clearness of the coating film will not be obtained. If it exceeds 70 mol%, the stability of the varnish cannot be obtained. In addition, other dicarboxylic acid is 5
If it exceeds 0 mol%, the stability of the varnish will be reduced, or the cohesive force will be too large and the wet ink properties will be poor. Examples of other aromatic dicarboxylic acids include terephthalic acid, orthophthalic acid, naphthalenedicarboxylic acid and the like.

The polyester resin for can varnish of the present invention contains 1-80 mol% of aliphatic and / or alicyclic dicarboxylic acid components having 6 to 12 carbon atoms among dicarboxylic acid components, preferably 10 It consists of 40 mol%. 1 mol% of aliphatic and / or alicyclic dicarboxylic acid component
If it is less than 60%, the cohesive force is not lowered and sufficient performance as wet ink properties cannot be obtained, and if it exceeds 80 mol%, the cohesive force of the coating film becomes low and the processability becomes insufficient.

Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid and dimer acid, and the alicyclic dicarboxylic acid includes hexahydrophthalic anhydride, methylhexahydrophthalic anhydride and cyclohexane. -1,4-dicarboxylic acid,
Examples thereof include cyclohexane-1,3-dicarboxylic acid and tetrahydrophthalic anhydride, and one or more of these can be selected and used.

The polyester resin for can varnish according to the present invention comprises 60 to 100 mol%, preferably 70 to 100 mol% of one or more side chain alkyl group-containing aliphatic glycols among all glycol components. . Examples of the side chain alkyl group-containing glycol include neopentyl glycol, 2,2-diethyl-1,3-propanediol, and 2
-N-butyl-2-ethyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, 2-n-hexyl-2-ethyl-1,3-propanediol, 2,2-di-n-hexyl-1,3-propanediol, 2,4-dimethyl-2-ethylhexane-
1,3-diol, 2-ethyl-2-isobutyl-1,
3-propanediol, 2,2,4-trimethyl-1,
6-hexanediol, 2,2,4-trimethyl-1,
3-pentanediol, 1,3,4-trimethyl-1,
5-pentanediol, 1,2,4-trimethyl-1,
Examples include 5-pentanediol.

More preferably, 1 represented by the following chemical formula 2
60 to 100 mol%, preferably 70 to 100 mol%, of one type or two or more types of side chain alkyl group-containing glycol. Neopentyl glycol, 2,2-diethyl-1,3-propanediol as the glycol of (I),
2-n-butyl-2-ethyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, 2-n-hexyl-2-ethyl-1,3-propanediol , 2,2-di-n-hexyl-1,3-propanediol and the like.

Embedded image

Other glycol components used in the polyester resin for can varnish of the present invention include ethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,
4-butanediol, 1,5-pentanediol, 1,
6-hexanediol, 1,9-nonanediol, 3-
Methyl-1,5-pentanediol, 3-ethyl-1,
5-pentanediol, 3-propyl-1,5-pentanediol, 3-methyl-1,6-hexanediol,
Glycols such as 4-methyl-1,7-heptanediol, 1-methyloctanediol, 4-methyl-1,8-octanediol, 4-propyl-1,8-octanediol, polytetramethylene glycol and the like can be mentioned.

Further, in the polyester resin for can varnish of the present invention, an alicyclic glycol may be used in the range of 0 to 40 mol% of all glycol components. When the alicyclic glycol is used, the wettability of the resin is improved and the wet ink property is improved. 1,2- as the alicyclic glycol
Cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol,
Examples thereof include tricyclodecane glycols and hydrogenated bisphenols. Among these, one kind or two or more kinds can be selected and used.

The polyester resin for can varnish of the present invention has a content of 0.1 to 0.1 with respect to all acid components or all glycol components.
It contains 5 mol% of a trivalent or higher polycarboxylic acid and / or a polyhydric alcohol. Trivalent or higher polycarboxylic acid,
And / or if the polyhydric glycol is less than 0.1 mol%, the strength of the coating film cannot be obtained and the workability is poor, and if it exceeds 5 mol%, the flexibility of the coating film is lost and the workability cannot be obtained. . Examples of the trifunctional or higher polyvalent carboxylic acid include trimellitic acid, pyromellitic acid, and benzophenonetetracarboxylic acid. Examples of the trifunctional or higher polyvalent alcohol include glycerin, trimethylolethane, trimethylolpropane,
Mannitol, sorbitol, pentaerythritol,
α-methylglycoside and the like can be mentioned, among which 1
One kind or two or more kinds can be selected and used. Preferred is trimellitic acid or trimethylolpropane.

In the polyester resin for can varnish of the present invention, immediately after the completion of the polymerization of the polyester, the lactone compound is completed in the range of 1 to 60 mol%, preferably 5 to 40 mol% with respect to the total acid component of the polyester. Immediately after that, it is obtained by directly adding. 1 lactone compound
If it is less than mol%, no improvement in low temperature curability is observed, and 6
If it exceeds 0 mol%, the resin Tg becomes too low and the blocking property and retort property deteriorate.

As the lactone compound, β-propiolactone, β-2,2-dimethylpropiolactone, δ-valerolactone, β-methyl-δ-valerolactone, ζ-
Examples thereof include enanthlactone, ζ-caprylolactone, ε-caprolactone, γ-caprolactone, δ-caprolactone, and the like. Primary O 2 from the viewpoint of reactivity, stability and economy.
Epsilon-caprolactone which provides the H group is preferred.

The polyester resin for can varnish of the present invention has a reduced viscosity of 0.2 to 0.6 dl / g, preferably 0.1.
3-0.5 dl / g is required. Reduced viscosity is 0.2d
If it is less than 1 / g, the coating film becomes brittle and processability cannot be obtained, and if it exceeds 0.6 dl / g, the viscosity of the coating becomes high and gloss and coating suitability cannot be obtained.

The polyester resin for can varnish of the present invention has a glass transition temperature of 0 to 50 ° C, preferably 5 to 40 ° C.
Is. When the glass transition temperature is lower than 0 ° C, the coating film is too soft and poor in blocking property, and when it exceeds 50 ° C, the coating film becomes hard and processability is poor.

The polyester resin for can varnish of the present invention has a resin specific gravity of 1.20 or less, preferably 1.19, and a lactone-modified polyester resin is butyl cellosolve /
Solvesso is dissolved in a mixed solvent of 150 = 1/4 (weight ratio) at a solid content of 40% by weight, and the contact angle of this varnish to PTFE (polytetrafluoroethylene) is 60 degrees or less, preferably 55 degrees in an atmosphere of 20 ° C. It is the following. If the resin specific gravity exceeds 1.20 or the contact angle exceeds 60 degrees, the cohesive force of the resin becomes large and wet ink properties cannot be obtained.

The polyester resin for can varnishes of the present invention may be subjected to lactone modification and then acid value addition by further adding a polyvalent carboxylic acid anhydride. 20 to 12 as the acid value
0 eq / 10 ⁶ g, preferably 30 to 60 eq / 10 ⁶
g. By imparting an acid value, the low-temperature curability can be further improved, but if it is less than 20 eq / 10 ⁶ g, there is no significant difference with the non-addition product, and if it exceeds 120 eq / 10 ⁶ g, hydrolysis of the polyester during retort is caused. Acceleration and retort resistance cannot be obtained.

Examples of the polycarboxylic acid anhydride used for such acid value addition include phthalic anhydride, tetrahydrophthalic anhydride, succinic anhydride, trimellitic anhydride, pyromellitic anhydride and hexahydrophthalic anhydride. Of these, trimellitic acid is preferred.

The polyester resin for can varnish of the present invention is dissolved in an organic solvent and used as a resin solution. As the solvent, any solvent that can dilute the polyester resin can be used without limitation. For example, aromatic hydrocarbons such as toluene, xylene, Solvesso # 100 and Solvesso # 150, aliphatic hydrocarbons such as hexane, heptane, octane and decane, methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, amyl acetate, Ethyl formate,
Butyl ester such as butyl propionate, alcohol such as methanol, ethanol, propanol, butanol, 2-ethylhexanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, ketone such as cyclohexanone, dioxane, diethyl ether, ether such as tetrahydrofuran, There are various cellosolve-based solvents such as cellosolve acetate, ethyl cellosolve, and butyl cellosolve. Considering solubility, evaporation rate, etc., one kind,
Alternatively, two or more kinds are selected and used. Generally, in the case of glossy varnish, a poor solvent system that does not attack the ink layer is used because wet ink properties are required. For example, Solvesso # 100,
Solvesso # 150, Swazol 1500 and the like, alcohols such as butanol and octanol, and cellosolves such as ethyl cellosolve and butyl cellosolve are preferably used.

In the resin composition for a varnish coating for cans of the present invention, a curing agent capable of reacting with the polyester resin is used,
Examples include amino resins and isocyanate resins. Amino resins are preferred.

Examples of the amino resin compound include formaldehyde adducts such as urea, melamine and benzoguanamine, and alkyl ether compounds of these alcohols having 1 to 6 carbon atoms. Specifically, methoxymethylol urea, methoxymethylol-
N, N-ethylene urea, methoxylated methylol dicyandiamide, methoxylated methylol melamine, methoxylated methylol benzoguanamine, butoxylated methylol melamine, butoxylated methylol benzoguanamine and the like are preferable, but methoxylated methylol melamine, butoxylated methylol melamine, butoxylated are preferable. Methylolbenzoguanamine, which can be used alone or in combination. Also, polyester resin 1
The compounding amount is generally 1 to 50 parts by weight with respect to 00 parts by weight, but it is preferably 10 to 40 parts by weight. If the compounding ratio of the amino resin is out of the above range, the workability tends to decrease, which is not preferable.

Examples of the isocyanate compound include aromatic and aliphatic diisocyanates and polyisocyanates having a valence of 3 or more. For example, tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated Xylylene diisocyanate, isophorone diisocyanate or trimers of these isocyanates, and excess amounts of these isocyanate compounds and, for example, ethylene glycol, propylene glycol,
Trimethylolpropane, glycerin, sorbitol,
Terminal isocyanate group-containing compounds obtained by reacting low molecular weight active hydrogen compounds such as ethylenediamine, monoethanolamine, diethanolamine and triethanolamine or various polyester polyols, polyether polyols, high molecular weight active hydrogen compounds of polyamides, etc. Can be mentioned. Each can be used alone or in combination. In addition, it is common to add 1 to 50 parts by weight to 100 parts by weight of the polyester resin,
It is preferably 10 to 40 parts by weight. If the compounding ratio of the amino resin is out of the above range, the workability tends to decrease, which is not preferable.

In the resin composition for a varnish coating for cans of the present invention, known inorganic pigments such as silica, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, a curing catalyst for phosphoric acid and its esterification, a surface smoothing agent, Defoamer, dispersant,
Known additives such as wax can be blended.

[0029]

EXAMPLES The present invention will be specifically described with reference to the following examples. In the examples, "parts" means "parts by weight". Each measurement evaluation item followed the following method. (1) Measurement of resin composition The molar ratio of the acid component and the alcohol component was determined by nuclear magnetic resonance spectroscopy and analysis by gas chromatography after alcoholysis. (2) Measurement of reduced viscosity (dl / g) 0.1 g of polyester was dissolved in 25 cc of phenol / tetrachloroethane (weight ratio 6/4) mixed solvent and measured at 30 ° C. using an Ubbelohde viscometer. (3) Measurement of glass transition temperature It was measured at a temperature rising rate of 20 ° C./min using a differential scanning calorimeter (DSC). (4) Measurement of acid value 0.2 g of resin was dissolved in 20 ml of chloroform,
Titration was performed with a 1N KOH ethanol solution to determine the equivalent weight (eq / 10 ⁶ g) per 10 ⁶ g of the resin. (5) Measurement of Specific Gravity The specific gravity of the resin was determined at 30 ° C. by a float-sink method using a density gradient tube. (6) Measurement of contact angle Resin was butyl cellosolve / solveso 150 (weight ratio 1
/ 4) dissolved in a mixed solvent of 40% by weight of solid content at 25 ° C.
In the atmosphere described above, this was dropped into PTFE (polytetrafluoroethylene, manufactured by Freon Chemical Co., Ltd.) and measured with a contact angle measuring device.

Evaluation items (5) Preparation of white test piece TFS measuring 150 mm in length × 70 mm in width × 0.3 mm in thickness
Polyester white paint on (Tin Free Steel) plate (Polyester Byron 600: Toyobo Co., Ltd., Melamine resin M-40S: Sumitomo Chemical Co., Ltd.)
Curing catalyst p-toluenesulfonic acid, acid number titanium Typaque R-930: Ishihara Sangyo Co., Ltd., dispersed in beads) was applied to a dry film thickness of 10 to 15 μm, and 2
It was dried at 30 ° C. for 1 minute and used as a white test piece (base material).

(6) Wet Ink Property An ink layer (Matsuikagaku Co., Ltd.) was formed on a white test piece so as to have a film thickness of 2 μm, and the paint for varnish of the present invention was applied thereto by a wet-on-wet method. After curing and baking this at 150 ° C for 10 minutes, 3
It was observed with a magnifying glass of 0 times and the presence or absence of bleeding, repelling, deterioration of gloss, etc. of the ink layer was determined. ◯: Good Δ: Slight bleeding, repellency, gloss deterioration X: Significant bleeding, repellency, gloss deterioration (7) Preparation of gloss test piece The gloss paint of the present invention was applied to a white test piece in a film thickness of 6
It was provided so as to have a thickness of up to 8 μm, and was cured and baked at 150 ° C. for 10 minutes to obtain a gloss test piece.

(8) Low Temperature Curability The varnish test piece was rubbed 50 times with a gauze impregnated with methyl ethyl ketone while applying a load of 0.5 kg, and the degree of peeling or elution of the coating film was visually judged. ◯: Good Δ: Slight elution was observed X: Peeling or marked elution (9) Workability A 0.3 mm-thick base material of the varnish test piece was sandwiched between the two pieces and bent 180 degrees, and they were generated at the bent portion. The crack of the coating film was observed and judged with a magnifying glass of 30 times. ◯: Good Δ: Some cracks were found ×: Significant cracks were found (10) Gloss The gloss of the coated surface of the gloss test piece was measured with a gloss meter.

(11) Retort resistance The gloss test piece was treated with steam at 130 ° C. for 30 minutes, and then the whitening and blistering of the coating film was visually evaluated. ◯: Good Δ: Some whitening or slight blistering X: Significant whitening or significant blistering Further, the gloss after retort was measured with a gloss meter and the gloss retention rate was calculated by the following formula. (Gloss after retort / Initial gloss) × 100 = Gloss retention rate [%]

(12) Retort processability A varnish test piece was sandwiched between three 0.3 mm thick base materials and bent at 180 degrees, and this was heated at 130 ° C. under steam for 30 days.
After processing for 3 minutes, cracks and blisters that occur in the curved part are 3
It was observed and judged with a magnifying glass of 0 times. ◯: Good Δ: Some cracks and blisters X: Significant cracks and blisters (13) Blocking property Two gloss test pieces were stacked on the front and back sides, 50 Kg / c
The presence or absence of blocking was determined by applying a load of m ² and leaving it in an atmosphere of 50 ° C. for 5 hours. ◯: Good Δ: Some blocking was observed ×: Significant blocking was observed

Synthesis Example (a) 330 parts of isophthalic acid, 240 parts of phthalic anhydride, 60 parts of adipic acid, 8 parts of trimellitic acid, 475 parts of neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol 250 parts and 0.5 part of titanium butoxide were charged into a 3 L four-necked flask, and the temperature was gradually raised to 230 ° C. over 4 hours for transesterification. Then, the reduced pressure initial polymerization was carried out to 10 mmHg over 30 minutes, the temperature was raised to 250 ° C., and the latter polymerization was carried out at 1 mmHg or less for 90 minutes to obtain a base polyester. Subsequently, this was cooled to 220 ° C. under a nitrogen atmosphere, and the plaque
Add 120 parts of M (Daicel Chemical Co., Ltd.) under nitrogen atmosphere,
The mixture was maintained at 220 ° C. and stirred for 30 minutes to obtain the lactone-modified polyester (a) of the present invention.

Synthesis Example (b) After completion of the lactone modification of the lactone-modified polyester (a), 10 parts of trimellitic anhydride was further added, and the mixture was maintained at 220 ° C. under nitrogen atmosphere and stirred for 20 minutes to obtain the lactone-modified polyester of the present invention. (B) was obtained. Synthesis Examples (c) to (f) In the same manner as in Synthesis Example (a) or (b), lactone-modified polyester resins (c) to (h) of the present invention having resin compositions shown in Table 1 were synthesized. .

[0037]

[Table 1]

Comparative Synthetic Examples (i) to (p) The base polyester of Synthetic Example (a), or a comparative polyester resin having a resin composition shown in Table 2 in the same manner as in Synthetic Examples (a) and (b). , And lactone-modified polyesters (i) to (p) were obtained.

[0039]

[Table 2]

Example 1 100 parts of the lactone-modified polyester (a) of the present invention was dissolved in 30 parts of butyl cellosolve and 120 parts of Solvesso # 150 in a resin solution, and Cymel 303 which is an amino resin.
(Mitsui Cyanamid Co., Ltd.) 30 solid parts and Catalyst 600 (Mitsui Siana Mid Co., Ltd.) 1 solid part were mixed and stirred to obtain a varnish coating composition. This was applied and cured by the method described above to obtain a gloss test piece. When this gloss test piece was evaluated, all the items were good. The results are shown in Table 3.

Examples 2 to 10 A coating composition and a varnish test piece were prepared and evaluated in the same manner as in Example 1 and good results were obtained. The results are shown in Table 3.

Comparative Examples 11 to 16 A coating composition and a gloss test piece were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 4.

[0043]

[Table 3]

[0044]

[Table 4]

As is apparent from Tables 3 and 4, the resin for can coating a varnish for cans and the coating composition of the present invention are coatings excellent in wet ink property, processability, gloss, low temperature curing property, retort property and blocking property. Give a membrane.

[0046]

EFFECTS OF THE INVENTION Conventional polyesters for glossy varnishes require a wet ink property, so that they are used as a raw material having a large steric hindrance that hinders curability, so that low temperature curing is difficult and sufficient performance cannot be obtained. In the present invention, by modifying the polyester resin with a lactone, the wet ink property is not lowered, and the curing reactivity is improved by removing the steric hindrance of the terminal OH group, and the wet ink property, processability, luster, and low temperature curability are obtained. It is possible to provide a varnish coating resin composition for cans having excellent retort properties and blocking properties.

Claims (1)

[Claims] 1. A terminal OH group of a polyester resin is modified with 1 to 60 mol% of a lactone compound with respect to the total dicarboxylic acid component of the polyester resin, and a reduced viscosity is 0.2.
˜0.6 dl / g, glass transition temperature 0 to 50 ° C., resin specific gravity 1.20 or less, and varnish polytetra dissolved in butyl cellosolve / solveso # 150 = 1/4 (weight ratio) with a solid content of 40% by weight. Polyester resin for can varnish having a contact angle with fluoroethylene of 60 degrees or less.