JP2002338881A - Coating material for metallic package and metallic package using the coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating material for a metallic package which does not contain an endocrine disrupter such as bisphenol A, polyvinyl chloride to generate dioxins on combustion and the like and excels in retortability, flavor properties, corrosion resistance and the like, a metallic package using the coating material. SOLUTION: The coating material for a metallic package comprises (A) 60-90 wt.% polyester resin derived from a polycarboxylic acid component having terephthalic acid as the major component and a polyalcohol component, (B) 5-30 wt.% resol type phenolic resin derived from phenols having carbolic acid and/or m-cresol as the major component, and (C) 0.5-10 wt.% amino resin derived from melamine or benzoguanamine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paint for a metal package and a metal package using the paint. More specifically, the present invention does not contain bisphenol A and vinyl chloride, and is resistant to retort, flavor, and adhesion. The present invention relates to a paint for a metal package and a metal package having excellent coating properties such as resistance and corrosion resistance.

[0002]

2. Description of the Related Art Paints for metal packaging such as metal cans, metal lids and metal caps are used for the purpose of preventing corrosion of metal materials and the like, and are required to have good workability and adhesion of coating films to metals. ing. In particular, the paint used for the inner surface is required not to impair the flavor and flavor of the contents, to be free of toxicity, and not to elute the paint components, in addition to the workability. Conventionally, as these paints, epoxy solvent-based paints such as epoxy-phenol paints, epoxy-amino paints, and epoxy-acryl paints and water-based paints have been widely used, but epoxy paints are environmental hormones. To contain bisphenol A, one of
The elution is concerned. Vinyl chloride-based paints are also used as paints for cans, but vinyl chloride has a problem of stabilizers and a problem of generating dioxin during incineration. From this viewpoint, paints containing neither bisphenol A nor vinyl chloride are used. Is desired.

As a paint for cans that does not contain bisphenol A and vinyl chloride, a polyester paint that has excellent adhesion to metals and does not generate toxic components when incinerated has already been used. For example, JP-B-60-36548 discloses that terephthalic acid 80 to 1 is used as a dicarboxylic acid component.
00 mol% and dicarboxylic acids other than terephthalic acid 20 to
0 mol%, and a reduced viscosity of 0.1 to 100 mol% of propylene glycol as a glycol component and 40 to 0 mol% of glycol other than propylene glycol.
A coating agent for the inner surface of a metal can, which is characterized by being 4 or more polyesters, is described.

[0004]

The above-mentioned polyester-based paints which have been conventionally used have excellent workability, but the polyester resin alone does not have blister resistance and whitening resistance during heat sterilization. However, there is a problem that the adhesion and corrosion resistance are poor. Accordingly, an object of the present invention is to provide a paint for metal packaging which does not contain environmental hormones such as bisphenol A or vinyl chloride which generates dioxin when incinerated, and is excellent in retort properties, flavor properties, corrosion resistance and the like. An object of the present invention is to provide a used metal package.

[0005]

According to the present invention, (A)
Polyester resin 60 derived from a polycarboxylic acid component mainly composed of terephthalic acid and a polyalcohol component
To 90% by weight, (B) 5 to 30% by weight of a resol-type phenol resin derived from phenols mainly composed of carboxylate and / or meta-cresol, and (C) amino resin derived from melamine and / or benzoguanamine 0 0.5 to 10% by weight is provided.

In the paint for metal packaging of the present invention,
(1) A polyester resin (A) comprising a carboxylic acid component composed of 60 to 100 mol% of terephthalic acid and 0 to 40 mol% of a polycarboxylic acid other than terephthalic acid, and an alicyclic polyalcohol and / or a polyether having a side chain. 50-100 mol% of alcohol and alicyclic polyalcohol and / or
Or a polyester resin derived from a polyalcohol component consisting of 0 to 50 mol% of a polyalcohol other than a polyalcohol having a side chain. (2) The polyester resin (A) is based on all acid components and all alcohol components. (3) the polyester resin (A) has a number average molecular weight (Mn) of 10,000 to 30,000, and 0.01 to 3 mol% of a trifunctional or higher polycarboxylic acid and / or polyalcohol component. Glass transition point (Tg) of 50 ° C. or more and acid value of 4.0 or less (mgKOH
/ G) is preferable.

According to the present invention, there is further provided a metal package comprising a cured coating film formed of the above-mentioned paint for a metal package. In the metal package of the present invention, (1) the cured coating film has a glass transition point (T
g), and (2) the MEK extraction rate of the cured coating film is 4
It is preferably 0% by weight or less.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the coating material for a metal package of the present invention, (A) a polyester resin derived from a polycarboxylic acid component mainly composed of terephthalic acid and a polyalcohol component, 60 to 90% by weight, (B 5) 30% by weight of resole type phenolic resin derived from phenols mainly composed of carboxylate and / or metacresol, and (C) 0.5 to 10% by weight of amino resin derived from melamine and / or benzoguanamine. Becoming an important feature.

As described above, the polyester resin has excellent processability. However, in the paint for metal packaging of the present invention, the polyester resin (A) is used as the base of the coating film and the resol type phenol resin is mainly used. To form a coating film by curing. That is, the polyester resin and the resol-type phenol resin are substantially non-reactive, and the curing of the resin in this paint proceeds by the reaction of the resol-type phenol resin, forming an interpenetrating network structure (IPN) in the coating film. It is possible. The interpenetrating network (IPN) is defined as a structure in which two or more types of three-dimensional polymer networks are entangled with each other without being connected by a covalent bond. A network associated with the curing of the resol-type phenolic resin is formed, and the polyester resin penetrates in a form entangled with the network. This structure maintains excellent adhesion and processability, while maintaining curability and resistance. This is considered to be the reason for improving retortability.

[0010] The polyester resin (A) used in the present invention has a high glass transition point mainly composed of terephthalic acid. Therefore, when the metal package is a metal can, retort sterilization of the canned product is performed. In addition to improving the moist heat resistance and dent resistance necessary for heat sterilization such as, and improving the barrier property against corrosive components,
Corrosion resistance can be improved.

Such features of the present invention are apparent from the results of the embodiments described later. That is, when a polyester resin composed of a polycarboxylic acid having a terephthalic acid content of 45 mol% is used as the polyester resin, the glass transition point is as low as 45 ° C. (Production Example 2). Is inferior in retort resistance and dent resistance as compared with the present invention using a polyester resin composed of a polycarboxylic acid mainly composed of terephthalic acid (Comparative Example 7).

The resol type phenol resin (B) used in the present invention is a self-curing resin derived from phenols and formaldehyde or a functional derivative thereof in the presence of an alkali catalyst. Among the phenolic resins, in particular, by using those mainly composed of phenolic acid and / or meta-cresol as phenols, it is possible to obtain excellent curability and to obtain a coating film having excellent retort resistance and corrosion resistance. You can do it.

Such features of the present invention are apparent from the results of the embodiments described later. That is, even when a monovalent monocyclic phenol is used, when a resol type phenol resin mainly composed of phenols mainly composed of paracresol is used, a resol type phenol resin composed mainly of phenol mainly composed of carboxylate and / or metacresol is used. The curability and corrosion resistance of the coating film are inferior to those of the present invention using (Comparative Example 8). Further, the resol-type phenolic resin (B) should be contained in an amount of 5 to 30% by weight, particularly 10 to 25% by weight, and if it is more than the above range, the flavor and corrosion resistance are deteriorated. On the other hand, when the amount is less than the above range, the curability and the retort resistance are inferior (Comparative Example 5).

In the present invention, it is also important to use an amino resin (C) derived from benzoguanamine and / or melamine. That is, by using the amino resin (C) derived from benzoguanamine and / or melamine, the compatibility between the polyester resin and the resole-type phenol resin is improved, and a fine network structure is formed by reacting with the resole-type phenol resin. To prevent phase separation between the resol-type phenolic resin and the polyester resin, and to form a good interpenetrating network structure in the coating film, without increasing the dissolution property in retort sterilization. This makes it possible to improve the adhesion and corrosion resistance of the film. This is clear from the results of the examples described later. That is, when the above-mentioned amino resin is not blended and is composed only of a polyester resin and a resol-type phenol resin, the amino resin (C)
Is inferior in adhesion and corrosion resistance as compared with the case of containing (see Comparative Example 1).

It is also important that the amino resin (C) is contained in an amount of 0.5 to 30% by weight, especially 1 to 10% by weight. And inferior dissolution (Comparative Example 4)

In the coating material for a metal package of the present invention, the polyester resin (A) and the thermosetting resin (B)
One of the resin components (C) does not have a heterogenous dispersed structure such as a continuous phase and the other resin component has a dispersed phase, but has a more homogeneous dispersed structure. That is, in the paint for a metal package of the present invention, two or more three-dimensional polymer networks are not connected by a covalent bond,
An interpenetrating network structure (I
PN) is considered to be formed in the coating film, and a network accompanying the mutual curing of the thermosetting resins (B) and (C) is formed in the form of incorporating the polyester resin (A), and the network is involved in this network. The thermoplastic polyester penetrates in an elliptical form, and this structure has improved curability and retort resistance while maintaining excellent adhesion and workability.

(Polyester Resin) In the present invention, as described above, the polyester resin serving as the base of the paint for metal packaging is a polyester resin derived from a polycarboxylic acid component mainly composed of terephthalic acid and a polyalcohol component. It is important that Polycarboxylic acids other than terephthalic acid that can be used in the present invention include isophthalic acid, aromatic dicarboxylic acids such as orthophthalic acid, and aliphatic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, and dimer acid. Dicarboxylic acid,
In addition, alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,2-cyclohexanedicarboxylic acid can be used.

Examples of the polyalcohol include propylene glycol, ethylene glycol, 1,3-propanediol, 1,5-pentanediol and the like, and alicyclic polyhydric polymers such as 1,4-cyclohexanedimethanol and p-xylylene glycol. Examples thereof include alcohols and polyalcohols having a side chain such as 1,2-propylene glycol, 1,2-butanediol, 1,3-butanediol, neopentyl alcohol, and neopentyl glycol.

As the polyester resin used in the present invention, a carboxylic acid component comprising 60 to 100 mol% of terephthalic acid and 0 to 40 mol% of a polycarboxylic acid other than terephthalic acid, and an alicyclic polyalcohol and / or a side chain are used. It is particularly preferable that the polyalcohol is derived from a polyalcohol component comprising 50 to 100 mol% of polyalcohol and 0 to 50 mol% of alicyclic polyalcohol and / or polyalcohol other than polyalcohol having side chain. Further, in the polyester resin used in the present invention, 0.01 to 3 mol%, particularly 0.1 to 2 mol%, of the trifunctional or higher polycarboxylic acid and / or polyalcohol component relative to the total acid component and the total alcohol component. Is preferable. Examples of the trifunctional or higher polycarboxylic acid include trimellitic acid or anhydride thereof, and pyromellitic acid or anhydride thereof. Examples of the trifunctional or higher polyalcohol include glycerin, trimethylolethane, and trimethylol. Propane, pentaerythritol and the like can be mentioned.

The polyester resin used in the present invention comprises 10
000 to 30,000, especially 11,000 to 20,000
Number average molecular weight (Mn) of 50 ° C. or higher, especially 60 to 9
It is desirable to have a glass transition point (Tg) of 5 ° C. and an acid value (mgKOH / g) of 4.0 or less. That is, when the glass transition point (Tg) of the polyester resin is lower than the above range, the wet heat resistance and dent resistance required for heat sterilization such as retort sterilization of canned products and the like tend to decrease, and the barrier property against corrosive components. And the corrosion resistance of the can becomes insufficient.

When the number average molecular weight (Mn) of the polyester resin is lower than the above range, the curability, retort resistance, workability, dent resistance and elution properties are lower than those in the above range. On the other hand, when the number average molecular weight of the polyester resin exceeds the above range, the viscosity of the coating material becomes significantly higher than in the case where the number average molecular weight is within the above range, the coating workability is poor, and an appropriate coating film can be formed. It becomes difficult. Furthermore, when the acid value of the polyester resin exceeds the above range, it is difficult to form an interpenetrating network structure between the phenolic resin and the amino resin used in combination, and while maintaining excellent adhesion and workability, curing is performed. It becomes difficult to improve the resistance, retort resistance and dent resistance. The polyester resin is produced by a usual method for producing a high molecular weight polyester by a transesterification method or a direct esterification method.
However, in consideration of food applications, use of heavy metals or compounds that pose hygiene problems as catalysts and additives should be avoided.

(Phenol resin) The phenol resin is a resin derived from phenols and formaldehyde or a functional derivative thereof. In the present invention, phenols mainly composed of carboxylate and / or meta-cresol are used as the phenols. It is an important feature that a resol type phenol resin is used. In the present invention, the phrase "mainly composed of carboxylate and / or meta-cresol" means that it contains more than 50% of carboxylate and / or meta-cresol, and that it contains nearly 100% qualitatively, and is 100%. Of course, it may contain less than 50% of other phenols. The phenols other than phenolic acid and meta-cresol are not particularly limited, but monocyclic monohydric phenols can be suitably used. For example, phenols such as m-ethylphenol, 3,5-xylenol, and m-methoxyphenol can be used. Functional phenols: o-cresol, p-cresol, p-tertbutylphenol, p-ethylphenol, 2,3-xylenol, 2,5-xylenol, p-tert-amylphenol, p-nonylphenol, p-phenylphenol And bifunctional phenols such as p-cyclohexylphenol; monofunctional phenols such as 2,4-xylenol and 2,6-xylenol.

On the other hand, the formaldehyde used for the reaction is generally available as a formalin solution.
On the other hand, examples of the functional derivative of formaldehyde include paraformaldehyde and trioxane.

The resol type phenol resin used in the present invention can be obtained by a method known per se, that is, by reacting the above-mentioned phenols with formaldehyde in the presence of a basic catalyst. There is no particular limitation on the amount of the aldehyde to phenol, and the aldehyde can be used in the amount ratio conventionally used for the production of resole type resins. For example, the amount ratio is 1 mol or more, especially 2 to 6 mol per 1 mol of phenols. Can be suitably used, but even if less than 1 mole of aldehyde is used,
There is no particular disadvantage even if more than 6 moles of aldehyde are used.

The condensation is generally carried out in a suitable reaction medium, in particular in an aqueous medium. As the basic catalyst, any of the basic catalysts conventionally used in the production of resole-type resins can be used. Among them, ammonia, magnesium hydroxide, calcium hydroxide, barium hydroxide, magnesium oxide, basic Hydroxides, oxides or basic salts of alkaline earth metals such as magnesium carbonate, basic magnesium chloride and basic magnesium acetate are preferably used. These basic catalysts may be present in the reaction medium in a catalytic amount, especially in an amount of 0.01 to 0.5 mol%.
The condensation conditions are not particularly limited, and are generally 80 to 130 ° C.
The heating may be performed at the above temperature for about 1 to 10 hours. The resulting resin can be purified by a means known per se,
For example, the resin component as a reaction product is extracted and separated from the reaction medium with, for example, a ketone, alcohol, hydrocarbon solvent or a mixture thereof, and if necessary, washed with water to remove unreacted substances. By removing water by a sedimentation method, it is possible to obtain a resol-type phenol resin which can be mixed with a polyester resin. Further, a resol type phenol resin obtained by alkyl etherifying a methylol group can be used. As the alcohol used for the alkyl etherification, an alcohol having 1 to 4 carbon atoms can be suitably used. Examples of suitable alcohols include methanol, ethanol, propanol, n-butanol, isobutanol and the like. Can be mentioned. The alkyl etherification of the resole type phenol resin is generally performed by heating at a temperature of 100 to 130 ° C. in the presence of a resole type phenol resin, an alcohol and an acid catalyst, and performing a reaction for about 1 to 10 hours while removing condensed water. . The phenolic resin used in the present invention has a number average molecular weight (Mn) of 4
It is preferably in the range of 00 to 2000. Particularly preferred resol-type phenolic resins are those in which an excess of formaldehyde is reacted in an amount of 3 to 6 mols per mol of carboxylic acid and / or m-cresol, and further alkyl etherified to have a number average molecular weight (Mn) in the range of 500 to 1500. ,
The concentration of methylol groups or etherified methylol groups per benzene ring nucleus is in the range of 1 to 3, especially 1.2 to 2.
2 is a resol type phenol resin.

(Amino Resin) In the present invention, an amino resin (C) derived from melamine and / or benzoguanamine is used in combination with the polyester resin (A) and the phenol resin (B).

The amino resin used in the present invention has the following formula (1)

Embedded image Or a compound of the following formula (2)

Embedded image And a resin obtained by condensing formaldehyde with formaldehyde. Particularly, an etherified amino resin etherified with methanol, ethanol, n-butanol, iso-butanol or the like is preferably used. These amino resins are commercially available in the form of a solution dissolved in a solvent such as methanol, butanol, xylol, and the like, and this solution is added to use in forming a paint.

In the present invention, as the amino resin, a benzoguanamine resin or a melamine resin may be used alone, or a blend of a benzoguanamine resin and a melamine resin may be used. Particularly, the benzoguanamine resin is an essential component. Is preferred. The amino resin has a basic nitrogen atom concentration of 7 to 15 gram atoms, particularly 8 to 13 gram atoms, and a methylol group and an etherified methylol group concentration of 0.5 to 1.5 mmol per 100 gram of the resin. In particular, those in the range of 0.7 to 1.2 mmol are advantageous in view of the above characteristics.

(Acid Catalyst) In the coating material for a metal package of the present invention, as described above, it is important that the blended resole type phenol resin (B) and amino resin (C) are cured to form a network. It is. For the purpose of this curing,
It is preferable to mix an acid catalyst in the paint. By incorporating the acid catalyst, it is possible to improve the coating film performance such as curability and retort resistance without being affected by the baking conditions. The amount of the acid catalyst greatly affects the physical properties of the coating film.
It is desirable to contain it in an amount of 1 to 0.7 part by weight, particularly 0.1 to 0.5 part by weight. If the amount of the acid catalyst is less than the above range, the corrosion resistance and heat resistance of the coating film are insufficient, while if the amount of the acid catalyst is more than the above range, the corrosion resistance also decreases, Workability tends to decrease.

As the acid catalyst for curing the thermosetting resin, known acid catalysts are used, for example, inorganic acids such as phosphoric acid, and organic acids such as dodecylbenzenesulfonic acid and toluenesulfonic acid. You. Of course, these can be used alone or in combination of two or more.
Further, it may be used in the form of a neutralized amine.

(Lubricant) In the coating material for a metal package of the present invention, a lubricant is added in an amount of 0.5 to 0.5% per resin component in addition to the above components.
It is preferable that the compounding agent is blended in an amount of 1 to 3 parts by weight, particularly 1 to 2 parts by weight. By adding a lubricant, the coefficient of kinetic friction on the surface of the coating film can be reduced, and the coating film can be effectively prevented from being damaged during processing. As a lubricant to be blended to reduce the dynamic friction coefficient of the coating film,
(A) Fluid, natural or synthetic paraffin, hydrocarbon wax such as micro wax, polyethylene wax, chlorinated polyethylene wax, carnauba wax, etc. (b)
Fatty acid compounds composed of esters of higher fatty acids such as stearic acid and lauric acid, and (c) stearic acid amide, palmitic acid amide, oleic acid amide, esylic acid amide, methylenebisstearamide, ethylenebisstearamide, etc. Fatty acid monoamide or bisamide type, (d) butyl stearate, hydrogenated castor oil, ester type such as ethylene glycol monostearate, (e) alcohol type such as cetyl alcohol, stearyl alcohol, (f) Metal soaps such as lead stearate, calcium stearate and the like, and (g) a mixed system thereof can be mentioned. In particular, lanolin, carnauba wax and the like can be preferably used.

(Solvent) The paint for metal packaging of the present invention is preferably used as a solvent-type paint. The solvent is preferably contained in an amount of 180 to 400 parts by weight per 100 parts by weight of the resin component. That is, when the amount of the solvent is less than the above range, the coating workability is reduced, or it is difficult to form a coating film having excellent adhesion and corrosion resistance.
On the other hand, when the amount of the solvent exceeds the above range, it is difficult to form a coating film having a sufficient thickness, and a large amount of the solvent is required. Not preferred. As the solvent, any known solvent can be used as long as it can dissolve the resin component described above. The following can be suitably used, but is not limited to this example. Isopropyl alcohol (IPA), isobutyl acetate, n-butanol, ethylene glycol monoisopropyl ether (GIP), methoxypropyl acetate, cyclohexanone, Solvesso 100, DBE (dibasic acid ester), diethylene glycol monobutyl ether (BDG), butyl diglycol acetate Such solvents having different boiling points are mixed and used. In the present invention, it is particularly preferable to use a mixture of two or more solvents having different boiling points so that a coating film defect such as a pinhole does not occur in the coating film.

(Paint) The paint of the present invention contains the above components. It is preferable that the content ratio of each component in the paint is in the above-mentioned range. The viscosity of the paint is preferably in the range of 20 to 150 seconds at # 4 Ford cup viscosity (25 ° C.). If the paint viscosity is less than 20 seconds, the occurrence of paint defects such as sagging, sagging and repelling on the painted surface becomes remarkable. When the viscosity becomes higher than 150 seconds, the flow after coating deteriorates, and it becomes difficult to obtain a smooth coated surface.

(Metal Packing Body) The coating material for a metal packing body of the present invention is, for example, applied to the surface of a metal material and baked to form a cured coating film having the above-described interpenetrating network structure on the surface of the metal material. Can be formed. The existence of an interpenetrating network structure in the cured coating film can be confirmed by the dependence of MEK extraction rate on paint baking time. In the case of an epoxy / phenol-based paint, which is the most typical thermosetting paint for cans, there is a negative correlation that the MEK extraction rate decreases as the baking time increases. This is recognized as a matter of course because the longer the baking time, the more the reticulation proceeds. On the other hand, in the paint having the interpenetrating network structure, the MEK extraction rate shows a minimum value in a very short baking time, and the MEK extraction rate increases with time in a baking time exceeding this minimum value. Shows the correlation.

As already pointed out, in the present invention, a network accompanying the mutual curing of the phenolic resin and the amino resin is formed in a form incorporating the thermoplastic polyester resin (A). The rate is
Although suppressed to a considerably low level, if the degree of heating during the curing of the paint is excessive, phase separation occurs due to the melting of the network of the thermosetting resin and the thermoplastic polyester, thereby causing MEK. It is recognized that the extraction rate increases. Of course, in the paint of the present invention, the time required for curing may be extremely short, the energy for curing may be extremely small, and the process for baking the paint can be significantly simplified and shortened. It also has various advantages. Further, as the network accompanying the mutual curing of the phenol resin and the amino resin becomes denser, the phase separation accompanying the melting of the thermosetting resin network and the thermoplastic polyester becomes less likely to occur, and the MEK extraction rate tends to increase due to the baking time. Become smaller. As a result, a preferable property that a coating film exhibiting constant performance can be obtained in a wide range of baking conditions can be obtained.

The coating material for a metal package of the present invention is, for example, 3
Apply by any means to metal plate for cans used for piece cans
be able to. The application amount is 10 to 200 mg / d
m², Especially 30 to 150 mg / dm ²Amount of coating film
It is preferable to apply under the baking conditions described above.
The coating film is cured by heating to a thickness of 1 to 20 μm.
It is preferably in the range of 3 to 15 μm. The present invention
Paints for metal packaging are also dependent on the amount of each component.
No, it cannot be stipulated in general, but generally speaking, 160
Baking at a temperature of ~ 300 ° C for 10 seconds to 20 minutes
Is preferred.

As the metal plate, various surface-treated steel plates and aluminum plates are used. As the surface-treated steel sheet, cold-rolled steel sheet is annealed and then subjected to secondary cold rolling, and one or two kinds of surface treatment such as zinc plating, tin plating, nickel plating, nickel tin plating, electrolytic chromic acid treatment, and chromic acid treatment What has been described above can be used. Further, an aluminum-coated steel sheet subjected to aluminum plating, aluminum compression bonding, or the like is used. As the aluminum plate, industrial pure aluminum (# 1000 series), aluminum / manganese alloy (# 3000 series), aluminum / magnesium alloy (# 5000 series), or the like is used, and a surface treatment such as chromate phosphate or zirconium phosphate is used. Is used. The thickness of the metal plate varies depending on the type of the metal, the use or the size of the container, but is generally 0.1 mm.
It preferably has a thickness of 10 to 0.50 mm, especially 0.10 to 0.30 mm.

The cured coating film of the metal package of the present invention has a temperature of 60 ° C.
As described above, it is particularly preferable to have a glass transition point of 70 ° C. or higher. The MEK extraction rate determined by the method described below is
It is preferably at most 40%, particularly preferably at most 20%.

As the metal package coated with the coating material for a metal package of the present invention, a three-piece can formed by welding a coated metal plate coated with the coating material for a metal package, drawing and deep drawing, Conventionally known can bodies, such as a seamless can formed by thinning draw forming and a seamless can which is subjected to painting after drawing and ironing, can be mentioned. In addition, conventionally known metal packages such as an easy open end provided with a score for forming an opening for discharging contents and a tab for opening, a metal cap, and the like can be given.

[0040]

The present invention will be specifically described below with reference to examples. “Parts” used in the present embodiment are based on weight unless otherwise indicated.

[Production of Polyester Resin] (Production Examples 1 and 2) Polyester resins of Production Example 1 (Example) and Production Example 2 (for comparison) were produced as follows. In a stainless steel autoclave equipped with a stirrer, a thermometer and a partial reflux condenser, polybasic acids as raw materials,
Polyhydric alcohols and a catalyst are appropriately charged, and the temperature is raised to a reaction temperature of 210 to 250 ° C, a reduced pressure of 2 mmHg or less, and a
Various polyester resins were synthesized in a range of about 6 hours. Table 1 shows the resin composition, glass transition temperature (Tg), number average molecular weight (Mn), and acid value of the obtained polyester resin.

The composition of the polyester resin was determined by NMR. Tg of the polyester resin and the coating film was determined by differential thermal analysis (DSC) using a differential scanning calorimeter. The measurement conditions at this time were a heating rate of 10 ° C./min and a measuring temperature range of 20 to 300 ° C. Mn of polyester resin
Was determined by GPC (gel permeation chromatography). Chloroform was used as a developing solvent at this time, and styrene-converted Mn was determined from a calibration curve using a styrene standard sample. The acid value of the polyester resin was measured according to the method specified in JIS K0070. If the sample did not dissolve, a solvent such as dioxane or tetrahydrofuran was used as the solvent.

[Production of resol type phenolic resin] (Production Examples 3 to 5) Production Examples 3 and 4 as described below.
(Example) A resol type phenol resin of Production Example 5 (for comparison) was prepared. 37% to phenols as raw material
Formaldehyde aqueous solution and caustic soda are added as appropriate,
Heat at 50-60 ° C for 3-6 hours. Thereafter, n-butanol and hydrochloric acid were appropriately added, and the mixture was stirred at 60 ° C. for 10 minutes and allowed to stand. When separated into two layers, the water in the lower layer was removed.
Further, the remaining organic layer was washed with water and refluxed while boiling at the boiling point of n-butanol for 2 hours to obtain a resol-type phenol resin. The number average molecular weight (Mn), weight average molecular weight (Mw), and benzene 1
Table 2 shows the number of methylol groups and etherified methylol groups per nucleus.

[Test / Evaluation Method of Paint for Metal Packaging] (Measurement of MEK Extraction Rate) As an evaluation of the curability of the coating for metal packaging, the MEK extraction rate was measured. An aluminum plate (5052 for a can lid, 0.30 mm in thickness) was coated with the polyester paint of each example by a bar coating method in an amount of 60 mg.
/ dm ² and baked at 205 ° C. for 10 minutes. The coated plate was cut out to obtain a sample. After measuring the weight (W1), extraction was performed at the boiling point for 1 hour using 1 ml of MEK (methyl ethyl ketone) per 2 cm ^{2 of} the coating film.
The coated plate after the extraction was dried at 130 ° C. for 1 hour, and the weight (W2) of the coated plate after the extraction was measured. Further, the coating film was peeled off by a decomposition method using concentrated sulfuric acid, and the weight (W3) of the plate was measured. The MEK extraction rate of a painted plate is obtained by the following equation. (MEK extraction rate%) = (W1-W2) / (W1-W3)
* 100 Evaluation ○: Less than 20%, Δ: 20-40%, ×: 40%
that's all

(Evaluation of retort resistance) The retort resistance of the produced polyester paint was evaluated. The paint of each example was tinplated (plating amount # 25 standard), coated with a bar coat on the surface, baked at 205 ° C. for 10 minutes, and then retorted in distilled water at 125 ° C. for 30 minutes. At this time, the coating amount was 60 mg / dm ² . After the retort treatment, the coating was dried and the surface state of the coating film was visually observed to evaluate the degree of whitening and the presence of blisters. Evaluation ：: good, Δ: slight whitening, blister, and flakes ×: significant whitening, blister, and flakes

(Evaluation of Adhesiveness) Using the same coated plate as that produced in the above evaluation of retortability, 125
A retort treatment was performed at 30 ° C. for 30 minutes. After the retort treatment, a cross-cut tape peel test was performed on the dried coating film to evaluate the adhesion. As a method of the peeling test, first, reach the metal substrate with a cutter knife on the coating film surface,
Eleven vertical and horizontal parallel linear scratches are made at 1 mm width intervals to make a total of 100 1 mm square cells. Thereafter, a cellophane tape (3M scotch tape # 600) was closely adhered so as to cover the grid, and the cell was peeled off sharply. Evaluation ：: Less than 10 peeled squares, Δ: 10 to 40
Pcs, ×: 40 or more

(Evaluation of Flavor Property) The prepared polyester paint was coated on an aluminum foil surface in an amount of 60 mg / dm.
^2, and the water flavor was evaluated using this as a sample. Prepare sampled aluminum painted foil and distilled water, put it in a heat-resistant glass bottle so that the coating area: distilled water is 1 cm ² : 1 ml, cover it,
A retort treatment was performed at 25 ° C. for 30 minutes. The evaluation was conducted using a test water after the retort, and a sensory test of flavor was conducted by 10 or more panelists, and the result was obtained with a majority of the answers. Evaluation ○: No change from distilled water, △: Slight discomfort compared to distilled water ×: Feel a clear difference from distilled water

(Evaluation of Elution Property) The elution property of the coating film by retort treatment was evaluated. Like the flavor evaluation,
The prepared polyester paint is applied on the aluminum foil surface so that the coating amount is 60 mg / dm ^2, and the coated area: distilled water is 1 cm ² : put into a heat-resistant glass bottle such that the water becomes 1 ml, and the lid is closed. And then in a retort kettle at 125 ° C, 30
Heat sterilization for minutes. The evaluation was performed by using distilled water after retort as a sample and measuring the consumption of potassium permanganate. This measurement was performed by the method specified in the Ministry of Health and Welfare Notification No. 20. Evaluation ：: less than 5 ppm, Δ: 5 to 10 ppm, ×: 1
0 ppm or more

(Corrosion resistance)
NS plate (Toyo Kohan Co., Ltd., tin-nickel plated steel plate,
(0.18 mm thick), and the corrosion resistance was evaluated.
In the evaluation method, first, using a cutter knife on the coated plate, scratches that are perpendicular to each other and reach the metal base were given.
This was stored in distilled water at 37 ° C. for 2 weeks, and the under-film corrosion was evaluated based on the progress of the corrosion. Evaluation ：: Corrosion under coating film less than 1 mm △: Corrosion under coating film less than 2 mm ×: Corrosion under coating film 2 mm or more

(Evaluation of Impact Resistance (Dent)) The TNS coated plate used for the corrosion resistance evaluation described above was used as a sample.
The impact resistance (dent property) of the coating film was evaluated. As an evaluation method, the sample was subjected to a retort treatment in distilled water at 125 ° C. for 30 minutes, and then, in a humid atmosphere at 25 ° C., with the coated surface of the sample facing down and a load of 1 k
g, an iron ball having a diameter of 1/2 inch is dropped from a height of 4 cm to give a dent scratch. Thereafter, a current was applied to the dent scratched portion of the painted surface at a voltage of 6 V for 5 seconds, and a current value after 5 seconds was measured. Evaluation ：: less than 5 mA, Δ: 5 to 40 mA, ×: 40 m
A or more

(Evaluation of bending workability) In the same manner as described above, a TNS plate was coated with a polyester paint, and the coated plate was used as a sample to evaluate the bending workability. After bending the painted plate so that the painted surface of this sample is on the outside and sandwiching two plates of the same thickness as the painted plate, a 2 kg weight is dropped from a height of 50 cm and bent at 180 degrees. (2T bending test). An electric current was applied to the 1 cm width of the processed portion at a voltage of 6 V for 4 seconds, and a current value after 4 seconds was measured. Evaluation ：: less than 5 mA, Δ: 5 to 40 mA, ×: 40 m
A or more

(Example 1) 80 parts of a polyester resin (Production Example 1) shown in Table 1 in detail, 15 parts of a phenol resin (Production Example 3) shown in Table 2 in detail, and mycoat 106
(Benzoguanamine resin manufactured by Mitsui Cytec Co., Ltd.) 5 parts was prepared and dissolved in a mixed solvent of cyclohexanone and Solvesso 100. Further, 0.3 parts of dodecylbenzenesulfonic acid as an acid catalyst and 1.5 parts of lanolin as a lubricant were mixed to prepare a paint for a metal package. The mixed solvent is
The amount was adjusted so that the solid content concentration in the paint was 25%. Using the paint, each coating film evaluation described above was performed. As a result, the curability was evaluated by MEK extraction rate of 10.4%,
The evaluation of the retort property was a favorable surface state without whitening, flaking and the like. Adhesion evaluation: 0% peeling, flavor evaluation: no problem, elution: 3.2 ppm elution amount, good corrosion resistance, dent resistance: 0.33 mA, workability evaluation: 0.15
A good result of mA was obtained. In addition, in Examples 2 to 6 and Comparative Examples 1 to 8 described below, the composition list of the prepared coating materials is shown in Table 3 together with Example 1. further,
Table 4 summarizes the results of the evaluation of the performance of each coating film.

(Example 2) 80 parts of the polyester resin obtained in Production Example 1, 15 parts of the phenol resin obtained in Production Example 4,
Five parts of Mycoat 106 (a benzoguanamine resin manufactured by Mitsui Cytec Co., Ltd.) were prepared, and a coating material for a metal package was produced in the same manner as in Example 1 (see Table 3). Using this coating material, each coating film was evaluated in the same manner as in Example 1. The results are summarized in Table 4 and all were good.

Example 3 70 parts of the polyester resin obtained in Production Example 1, 10 parts of the phenol resin obtained in Production Example 3,
15 parts of phenolic resin obtained in Production Example 4, Mycoat 10
5 (benzoguanamine resin manufactured by Mitsui Cytec Co., Ltd.) was prepared, and a coating material for a metal package was produced in the same manner as in Example 1 (see Table 3). Using this coating material, each coating film was evaluated in the same manner as in Example 1. The results are summarized in Table 4 and all were good.

Example 4 80 parts of the polyester resin obtained in Production Example 1, 10 parts of the phenol resin obtained in Production Example 3,
4 parts of Mycoat 106 (benzoguanamine resin manufactured by Mitsui Cytec) and 1 part of Mycoat 508 (melamine resin manufactured by Mitsui Cytec) were prepared, and a coating material for a metal package was produced in the same manner as in Example 1 (see Table 3). . Using this coating material, each coating film was evaluated in the same manner as in Example 1. The results are summarized in Table 4 and all were good.

Example 5 85 parts of the polyester resin obtained in Production Example 1, 14 parts of the phenol resin obtained in Production Example 3,
One part of Mycoat 106 (benzoguanamine resin manufactured by Mitsui Cytec Co., Ltd.) was prepared, and a coating material for a metal package was produced in the same manner as in Example 1 (see Table 3). Each coating film was evaluated in the same manner as in Example 1 using this paint. The results are summarized in Table 4 and all were good.

Example 6 85 parts of the polyester resin obtained in Production Example 1, 14 parts of the phenol resin obtained in Production Example 3,
Mycoat 508 (Melamine resin manufactured by Mitsui Cytec)
One part was prepared, and a coating material for a metal package was produced in the same manner as in Example 1 (see Table 3). Using this coating material, each coating film was evaluated in the same manner as in Example 1. The results are summarized in Table 4 and all were good.

(Comparative Example 1) 80 parts of a polyester resin (Production Example 1) shown in Table 1 and 20 parts of a phenol resin (Production Example 3) shown in Table 2 were prepared. A mixed solvent of cyclohexanone and Solvesso 100 was prepared. Dissolved. Further, 0.3 parts of dodecylbenzenesulfonic acid as an acid catalyst and 1.5 parts of lanolin as a lubricant were mixed to prepare a polyester paint. The mixed solvent has a solid content concentration of 25% in the paint.
The amount was adjusted to be%. Comparative Example 1 is an example in which the composition of the polyester resin and the phenol resin is appropriate, but does not contain an amino resin. As a result of the evaluation of the performance of each coating film, the adhesion and the corrosion resistance became poor.
The results are shown in Table 4 together with the examples.

Comparative Example 2 90 parts of the polyester resin obtained in Production Example 1 and 10 parts of Mycoat 106 (benzoguanamine resin manufactured by Mitsui Cytec Co., Ltd.) were prepared, and a polyester coating was prepared in the same manner as in Example 1 (Table 1). 3). Comparative Example 2 is an example in which the composition of the polyester resin and the amino resin is appropriate, but the phenol resin is not contained.
As a result of the evaluation of the performance of each coating film, the organic elution amount increased, and the flavor property and the retort resistance became inferior. The results are shown in Table 4 together with the examples.

Comparative Example 3 60 parts of the polyester resin obtained in Production Example 1, 35 parts of the phenol resin obtained in Production Example 3,
Then, 5 parts of Mycoat 106 (benzoguanamine resin manufactured by Mitsui Cytec Co., Ltd.) were prepared, and a polyester paint was prepared in the same manner as in Example 1 (see Table 3). Comparative Example 3 is an example in which the composition of the polyester resin and the amino resin is appropriate, but the phenol resin is contained in excess of an appropriate amount. As a result of the evaluation of the performance of each coating film, the adhesion and the corrosion resistance became poor. The results are shown in Table 4 together with the examples.

Comparative Example 4 60 parts of the polyester resin obtained in Production Example 1, 25 parts of the phenol resin obtained in Production Example 3,
Then, 15 parts of Mycoat 106 (a benzoguanamine resin manufactured by Mitsui Cytec Co., Ltd.) were prepared, and a polyester paint was produced in the same manner as in Example 1 (see Table 3). In Comparative Example 4, the compositions of the polyester resin and the phenol resin are appropriate,
This is an example of a case where the amino resin is contained in excess of an appropriate amount. As a result of each coating film performance evaluation, the flavor property was inferior and the elution amount increased. The results are shown in Table 4 together with the examples.

Comparative Example 5 95 parts of the polyester resin obtained in Production Example 1, 4 parts of the phenol resin obtained in Production Example 3, and 1 part of Mycoat 106 (benzoguanamine resin manufactured by Mitsui Cytec Co., Ltd.) were prepared. A polyester paint was prepared in the same manner as in Example 1 (see Table 3). Comparative Example 5 is an example in which the amount of the polyester resin exceeds the proper amount and the amount of the phenol resin is less than the proper amount. As a result of each coating film performance evaluation, the curability and the retort resistance became inferior. The results are shown in Table 4 together with the examples.

Comparative Example 6 55 parts of the polyester resin obtained in Production Example 1, 35 parts of the phenol resin obtained in Production Example 4,
Then, 15 parts of Mycoat 106 (a benzoguanamine resin manufactured by Mitsui Cytec Co., Ltd.) were prepared, and a polyester paint was produced in the same manner as in Example 1 (see Table 3). Comparative Example 5 is an example in which the content of the polyester resin is smaller than the appropriate amount, the content of the phenol resin is higher than the appropriate amount, and the content of the amino resin is higher than the appropriate amount. As a result of each coating film performance evaluation, the adhesiveness, flavor, and dissolution were inferior. The results are shown in Table 4 together with the examples.

Comparative Example 7 80 parts of the polyester resin obtained in Production Example 2, 15 parts of the phenol resin obtained in Production Example 3,
Then, 5 parts of Mycoat 106 (benzoguanamine resin manufactured by Mitsui Cytec Co., Ltd.) were prepared, and a polyester paint was prepared in the same manner as in Example 1 (see Table 3). In Comparative Example 7, the components of the polyester resin were as follows: the carboxylic acid component was 45 mol% of terephthalic acid, the isophthalic acid component was 55 mol%, the polyalcohol component was 1,2-propylene glycol 50 mol%, ethylene glycol 50 mol%, and 3 This is an example in the case where the component having a functionality higher than or equal to 1 mol% of trimethylolpropane. The composition of the polyester resin, phenol resin and amino resin is set to an appropriate amount. As a result of the evaluation of the performance of each coating film, the terephthalic acid component in the polyester resin was reduced, resulting in inferior retort resistance, corrosion resistance, and dent resistance. The results are shown in Table 4 together with the examples.

(Comparative Example 8) 80 parts of the polyester resin obtained in Production Example 1, 15 parts of the phenol resin obtained in Production Example 5,
Then, 5 parts of Mycoat 106 (benzoguanamine resin manufactured by Mitsui Cytec Co., Ltd.) were prepared, and a polyester paint was prepared in the same manner as in Example 1 (see Table 3). Comparative Example 8 is an example in which a phenol resin using p-cresol as a raw material was used, and the compositions of the polyester resin, the phenol resin, and the amino resin were adjusted to appropriate amounts. As a result of each coating film performance evaluation, curability and corrosion resistance became poor. The results are shown in Table 4 together with the examples.

(Examples 7 to 9) Three kinds of polyester resins of Production Examples 6 to 8 shown in Table 5 were produced in the same manner as in Production Example 1. For 80 parts of each polyester resin of Production Examples 6 to 8, 15 parts of the phenolic resin of Production Example 4 and 1 part of Mycoat 106 (benzoguanamine resin manufactured by Mitsui Cytec Co., Ltd.) were prepared, and mixed with cyclohexanone and Solvesso 100 in a mixed solvent. Dissolved. Further, 0.2 parts of dodecylbenzenesulfonic acid was mixed as an acid catalyst to prepare paints for metal packaging bodies of Examples 7 to 9. The amount of the mixed solvent was adjusted such that the solid content concentration in the coating material became 25%. Using this coating material, each coating film was evaluated in the same manner as in Example 1. The results are summarized in Table 4 and all were good. Each coating film was evaluated in the same manner as in Example 1 using these paints. The results are summarized in Table 6 and all were good.

Comparative Example 9 The polyester resin of Production Example 9 shown in Table 5 was prepared in the same manner as in Production Example 1. To 80 parts of this polyester resin, a phenol resin, an amino resin, and an acid catalyst were blended in the same manner as in Example 7 to prepare a polyester paint of Comparative Example 9. The polyester resin used in this comparative example is mainly composed of a carboxylic acid other than terephthalic acid, and the content of the alicyclic polyalcohol and / or the polyalcohol having a side chain is lower than 60 mol%. Further, the number average molecular weight is smaller than 10,000, and Tg
Was less than 50 ° C. The acid number is greater than 4.0 mg KOH / g. Table 6 shows the results of the coating film performance evaluation.
Curability due to the use of polyester resin as described above,
As a result, retort resistance, adhesion, corrosion resistance, dent resistance, and workability were remarkably inferior.

[0068]

[Table 1]

[0069]

[Table 2]

[0070]

[Table 3]

[0071]

[Table 4]

[0072]

[Table 5]

[0073]

[Table 6]

[0074]

According to the paint for metal packaging of the present invention,
(A) 60 to 90% by weight of a polyester resin derived from a polycarboxylic acid component mainly composed of terephthalic acid and a polyalcohol component; and (B) a phenol derived mainly from phenolic acid and / or meta-cresol. By containing 5 to 30% by weight of a resole type phenolic resin and 0.5 to 10% by weight of an amino resin (C) derived from melamine and / or benzoguanamine, it does not contain bisphenol A and vinyl chloride, has curability, Retort resistance, flavor, adhesion, corrosion resistance,
A coating material for a metal package having excellent coating properties such as dent resistance and workability can be provided.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 161/06 C09D 161/06 161/26 161/26 161/28 161/28 F-term (Reference) 3E086 AD04 AD23 BA13 BA15 BA24 BB41 BB57 BB77 DA01 4D075 CA04 CA13 CA18 CA33 CA42 CA44 CA47 DA03 DA06 DB02 DB05 DB07 DC36 DC42 EA07 EB32 EB35 EB51 EB52 EB53 EB55 EB56 4F100 AB01A AB10A AB40A AH02B AB08B AH04B AB04B AB04AJB JA07B JB02 JB11 JB20B JJ03 JK06 JL00 JL08B YY00B 4J038 DA032 DA162 DA172 DD071 DD131 GA06 KA03 MA13 MA14 NA03 NA04 NA12 NA14 PB04 PC02

Claims (7)

[Claims] (A) 60 to 90% by weight of a polyester resin derived from a polycarboxylic acid component mainly composed of terephthalic acid and a polyalcohol component; and (B) a phenol mainly composed of carbonic acid and / or meta-cresol. A paint for metal packaging, comprising 5 to 30% by weight of a resole-type phenol resin derived from phenols and (C) 0.5 to 10% by weight of an amino resin derived from melamine and / or benzoguanamine. 2. A polyester resin (A) comprising a carboxylic acid component comprising 60 to 100 mol% of terephthalic acid and 0 to 40 mol% of a polycarboxylic acid other than terephthalic acid, and an alicyclic polyalcohol and / or a side chain. A polyester resin derived from a polyalcohol component comprising 50 to 100 mol% of a polyalcohol and 0 to 50 mol% of an alicyclic polyalcohol and / or a polyalcohol other than a polyalcohol having a side chain. The paint for a metal package according to claim 1 to be applied. 3. The polyester resin (A) is used in an amount of 0.01 to 3 mol% based on all acid components and all alcohol components.
The coating material for a metal package according to claim 1, comprising a polycarboxylic acid and / or a polyalcohol component having a functionality of at least one. 4. A polyester resin (A) having a number average molecular weight (Mn) of 10,000 to 30,000, a glass transition point (Tg) of 50 ° C. or more, and an acid value (mgKOH) of 4.0 or less.
/ G), the coating material for a metal package according to any one of claims 1 to 3. 5. A metal package comprising a cured coating film formed of the coating material according to claim 1. 6. The metal package according to claim 5, wherein the cured coating film has a glass transition point (Tg) of 60 ° C. or higher. 7. The metal package according to claim 5, wherein the MEK extraction ratio of the cured coating film is 40% by weight or less.