JP2001311039A - Coating resin composition for can and metal plate coated with the same and used for can - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating resin composition which is applied on metal cans for foods and drinks or the like to give the coating films having excellent processability, adhesion, retort resistance, content resistance, extraction resistance, overbaking resistance, deterioration resistance with the passage of time, and denting resistance, and is especially suitable for the inner surfaces of the cans, and to provide a metal plate coated with the coating resin composition and used for the inner surfaces of cans. SOLUTION: This coating resin composition for cans, characterized by comprising (A) a polyester resin having a number-average mol.wt. of 5,000 to 100,000, (B) a resol type phenolic resin cross-linking agent containing 50 to 100 wt.% of a difunctional phenol compound and 0 to 50 wt.% of a trifunctional or more phenolic compound as a phenolic component, and (C) an acid catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating resin composition containing a saturated copolymerized polyester resin as an active ingredient, which is applied to metal cans for food and beverages, and has processability, overbaking property, retort resistance, Resistant contents (acid, salt, etc.)
TECHNICAL FIELD The present invention relates to a coating resin composition excellent in properties, dent resistance, extractability, and deep drawing processability, and particularly suitable for can coating, and a coated metal sheet for cans coated with the coating resin composition.

[0002]

2. Description of the Related Art Among can paints, paints for inner surfaces of cans are used particularly for the purpose of not impairing the flavor and flavor of the contents and preventing the corrosion of can materials due to various foods. First, it has no toxicity, withstands heat sterilization (retort) treatment, and then has excellent workability at the time of molding (workability, deep drawing workability). Blister resistance and whitening resistance (acid resistance), corrosion prevention by acids and sulfur compounds (blackening of sulfur) contained in the contents, no deterioration in workability due to excessive baking during can-making (overbake resistance ), Impact resistance after retort (dent resistance), and the like.
Particularly in recent years, the use of substances such as bisphenol-type epoxy resins containing extrinsic factor endocrine disrupting substances (hereinafter referred to as environmental hormones) is being avoided.

[0003] Polyvinyl chloride resins and epoxy-phenol resins are currently widely used as paint resins for the inner surface of cans, but the following serious problems have been pointed out at present. .

[0004] First, a polyvinyl chloride resin has excellent retort resistance, content resistance, and processability, but is a substance having serious hygiene problems such as carcinogenicity due to the vinyl chloride monomer remaining in the resin. It has been pointed out that. In addition, when incinerating cans when recycling or disposing of cans, polyvinyl chloride resin generates toxic and corrosive chlorine gas, hydrogen chloride gas, and highly toxic dioxin, which leads to corrosion of incinerators and environmental pollution. There is. Further, the polyvinyl chloride-based resin has an insufficient adhesion to metal as a can material, and requires a coating after being treated with an epoxy resin, so that the coating process is complicated.

Next, an epoxy-phenol resin has a high baking temperature, and tends to cause poor appearance such as foaming during baking. Also, as described above, it has been announced that bisphenol-A contained in an epoxy resin acts as an environmental hormone, and it is desired to develop an alternative inner surface coating agent. In addition, in addition to the workability and retort resistance required for the can paint on the outer surface as well as the inner paint described above,
Environmental hormone measures are also needed.

Further, DI (Draw & Ironin)
g) In order to precoat a two-piece can obtained by processing or DRD (Draw & Reddraw) processing, hardness, lubricity, elongation (extensibility) of the coating film, and adhesion after retorting are required. In addition to the above-mentioned performances and requirements, a coating composition which gives a coating film satisfying these processes has not been obtained.

[0007]

In order to solve the above problems, coating and baking are easy, and excellent in workability, adhesion to metal, and retort resistance, and no toxic and corrosive gas is generated during incineration. Attempts have been made to apply polyester resins that do not contain environmental hormones such as bisphenol-A in coatings to internal coating agents for cans, but in addition to these, content resistance, extractability, overbake resistance A paint resin and a paint resin composition suitable for cans having excellent aging resistance, dent resistance, DI processing and DRD workability have not been obtained.

[0008] That is, the coating resin for the inner surface of a can made of a saturated polyester resin alone as disclosed in JP-B-60-42829 and JP-B-61-36548 is resistant to heat treatment (retort resistance) using only boiling water or steam. Excellent blister and whitening resistance, but still insufficient performance, causing deterioration of surface condition and gloss of coating film, and retort treatment in salt solution or acidic atmosphere (content resistance In (2), blistering and whitening occur, resulting in poor appearance.

[0009] Japanese Patent Application Laid-Open No. Hei 7-13058,
In JP-A-113059 and JP-A-8-325513, bisphenol-A type or phenol novolak type epoxy resin is blended with polyester resin, blended, or retort resistance is obtained by using amino resin in combination.
Proposals have been made to provide a coating film having excellent content resistance, but this coating lacks overbake resistance and dent resistance. In addition, some epoxy resins contain bisphenol-A, which is an environmental hormone, and are therefore difficult to use.

In Japanese Patent Application Laid-Open Nos. 1-245065 and 5-112755, a coating composition comprising a saturated polyester resin mainly composed of propylene glycol and an alkyl etherified aminoformaldehyde resin is used as a coating agent for the inner surface of a can. It proposes to provide a coating film having excellent workability and retort resistance by applying the method. However, these are the overbake resistance required for the paint inside the can,
The aging resistance and the dent resistance cannot be sufficiently satisfied. Further, Japanese Patent Application Laid-Open No. 5-112755 describes adaptation to DI and DRD cans, but there are insufficient points regarding the strength of the coating film, retort resistance after processing, and adhesion.

Japanese Unexamined Patent Publication (Kokai) No. 11-315251 proposes a coating composition for cans comprising a polyester resin and a resol-type phenol resin obtained by using a trifunctional phenol compound as a main component. This is because phenolic resin has excellent properties such as retort resistance and acid resistance, but the phenolic resin uses a lot of trifunctional components, so residual stress remaining in the coating after processing DI cans, DRD cans, etc. It is large and may be peeled off from the substrate by performing the retort treatment.

[0012]

SUMMARY OF THE INVENTION The present inventor has found that among these problems, in particular, the overbake resistance, aging resistance, dent resistance,
As a result of intensive studies on acid resistance and further studies to enable the pre-coating of DI cans and DRD cans, these problems were solved by curing polyester resin with the specific resol type phenol resin described below. The inventors have found that a coating film that can be solved is obtained, and arrived at the present invention.

That is, the present invention relates to (A) a number average molecular weight of 5,000
A polyester resin of 0 to 100,000 and a bifunctional phenol compound 50 to 10 as a phenol component (B).
A resole-type phenolic resin crosslinking agent containing a phenol component of 0 to 50% by weight of a phenol compound having 0 to 50% by weight of a trifunctional or higher phenolic compound, (C) a paint resin composition for cans, characterized by containing an acid catalyst; This is a coated metal plate for a can coated with this.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION As the polycarboxylic acid component used in the polyester resin (A) used in the present invention, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid and naphthalenedicarboxylic acid, succinic acid and glutaric acid , Adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, aliphatic dicarboxylic acids such as dimer acid,
Alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, tetrahydrophthalic acid, hexahydroisophthalic acid and 1,2-cyclohexenedicarboxylic acid, and unsaturated dicarboxylic acids such as fumaric acid, maleic acid and terpene-maleic acid adducts And the like, and one or more of these can be used. From the viewpoint of hygiene, terephthalic acid, isophthalic acid, orthophthalic acid, adipic acid, sebacic acid, dimer acid, 1,4-cyclohexanedicarboxylic acid, fumaric acid and maleic acid are preferred. Preferably, terephthalic acid is contained in an amount of 40 to 100 mol%, more preferably 60 to 100 mol%, particularly preferably 80 to 10 mol%.
0 mol%.

The polyalcohol component used in the polyester resin (A) used in the present invention includes, for example, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,2-butane Diol, 2-methyl-1,3-propanediol, 1,3-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-
Pentanediol, 1,4-pentanediol, 1,3
-Pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 1-methyl-1,8-octanediol, 3-methyl-1,6-hexanediol, 4-methyl- Aliphatic glycols such as 1,7-heptanediol, 4-methyl-1,8-octanediol, 4-propyl-1,8-octanediol, 1,9-nonanediol, diethylene glycol, triethylene glycol, polyethylene glycol, Polyether glycols such as polypropylene glycol and polytetramethylene glycol; 1,4-cyclohexane dimethanol; 1,3-cyclohexane dimethanol; 1,2-cyclohexane dimethanol; tricyclodecane glycols; Alicyclic polyalcohol It can be mentioned, one from among them, or more select available. Among these, propylene glycol, 2-methyl-1,3-propanediol, 1,4-butanediol, 3-methyl-1,
5-pentanediol, 1,5-pentanediol,
1,4-cyclohexanedimethanol and the like. Further, those preferable for hygiene include ethylene glycol, propylene glycol, 1,2-butanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,3-butanediol, neopentyl glycol, , 4-butanediol, diethylene glycol,
1,4-cyclohexanedimethanol and the like.

As the polyester resin (A) used in the present invention, a polycarboxylic acid component and / or a polyalcohol component may contain a trifunctional or higher functional polycarboxylic acid and / or polyalcohol as long as the processability is not reduced. Examples of the trivalent or higher polycarboxylic acid component include trimellitic acid, pyromellitic acid, and benzophenone tetracarboxylic acid. Examples of the trifunctional or higher polyalcohol include glycerin, trimethylolethane, trimethylolpropane, and the like.
Mannitol, sorbitol, pentaerythritol,
α-methyl glucoside and the like. From the viewpoint of hygiene, trimellitic acid, trimethylolethane, trimethylolpropane and glycerin are preferred. Preferably 0.1 to
When the amount of these trifunctional components exceeds 3 mol%, the flexibility of the polyester resin is lost and the processability is reduced.

The polyester resin (A) used in the present invention has a number average molecular weight of 5,000 to 100,000, preferably 8,000 to 30,000. When the number average molecular weight is less than 5,000, there is a problem that workability is deteriorated due to insufficient flexibility, and when the number average molecular weight is more than 100,000, the suitability for coating as a paint is remarkably reduced. (A) The glass transition temperature (Tg) of the polyester resin is preferably from 0 to 120 ° C, more preferably from 10 to 120 ° C.
The temperature is 100 ° C, more preferably 30 to 100 ° C. When the glass transition temperature is less than 0 ° C., the retort resistance is poor. In particular, for contents requiring flavor, T
g is desirable. If Tg exceeds 120 ° C., workability and coating workability may be reduced. The number average molecular weight mentioned here is determined by gel permeation chromatography (GPC).
And the glass transition temperature (Tg) was measured by differential thermal analysis (D
SC).

The (A) polyester resin used in the present invention may be given an acid value by any method. The purpose of giving an acid value is to promote curing with a cross-linking agent, to improve adhesion to a metal material for cans, and the like. For these purposes, the preferred acid value range is 40 to 200 eq / 10 ⁶ g.
If it exceeds 200 eq / 10 ⁶ g, the retort resistance may decrease or the acid addition component may elute into the contents. Examples of the method for imparting an acid value include a depolymerization method in which a polycarboxylic acid anhydride is added at a later stage of polycondensation, a high acid value at the stage of a prepolymer (oligomer), and a polycondensation of the acid value. Although there is a method of obtaining a polyester resin having the same, the former depolymerization method is preferred because the operation is easy and a target acid value is easily obtained.

Examples of the polycarboxylic anhydride used for the acid addition in such a depolymerization method include phthalic anhydride, tetrahydrophthalic anhydride, succinic anhydride, trimellitic anhydride, pyromellitic anhydride, and hexahydrophthalic anhydride. And the like. Preferred is trimellitic anhydride.

(B) used in the coating composition for cans of the present invention
The phenolic resin crosslinking agent is a phenolic component (B-
1) 50 to 100% by weight of a bifunctional phenol compound,
(B-2) A phenol component having a trifunctional or higher phenol compound content of 0 to 50% by weight. Preferably (B-
1) / (B-2) = 50-80 / 50-20 weight ratio. As the compound (B-1), o-cresol, p
-Cresol, p-tert-butylphenol, p-
There are ethylphenol, 2,3-xylenol, 2,5-xylenol and the like, and as the compound of (B-2), phenol, m-cresol, m-ethylphenol,
Examples include 3,5-xylenol, m-methoxyphenol, bisphenol-A, and bisphenol-F. These are phenol compounds that can form two or more methylols per phenol compound molecule when converted to methylol with formaldehyde or the like. One or two or more of these may be selected and used. As a method of compounding the compound (B-1) and the compound (B-2), a method of forming the compound into a methylol by mixing it in the above-mentioned range before forming the methylol, or a method of separately forming the compound into the methylol,
Although there is a method of compounding in the above range, any method may be adopted.

The formaldehydes used when converting these phenolic compounds into phenolic resins include formaldehyde, paraformaldehyde and trioxane, and they can be used alone or as a mixture of two or more.

As the alcohol used for alkyl etherifying a part of the methylol group of the methylolated phenol resin, a monohydric alcohol having 1 to 8, preferably 1 to 4 carbon atoms is used. It is possible,
For example, methanol, ethanol, n-propanol, n
-Butanol, isopropanol, isobutanol, t
ert-butanol and the like. N-Butanol is preferred from the viewpoint of curing reactivity with polyester and compatibility.

The (B) phenolic resin crosslinking agent has an average of 0.3 or more, preferably 0.1 or more, alkoxymethyl groups per phenolic nucleus in view of the reactivity and compatibility with the (A) polyester resin. It has five or three. If it is less than 0.3, the curability with the polyester resin will be poor and the workability will be reduced.

(B) The phenolic resin crosslinking agent is preferably 5 to 40 parts by weight based on 100 parts by weight of the polyester resin (A).
Parts by weight, more preferably 10 to 30 parts by weight. If it is less than 5 parts by weight, a sufficiently cured coating film cannot be obtained,
Performance such as workability and retort properties may not be satisfied. If it exceeds 40 parts by weight, flexibility is lost, and performances such as workability and dent resistance may not be satisfied.

(B) As an optional crosslinking agent other than the phenolic resin crosslinking agent, an amino resin, an isocyanate compound, an epoxy resin and the like can be mentioned, but from the viewpoint of hygiene, an amino resin is preferred. These crosslinking agents can be blended and used to such an extent that the performance of the coating film is not deteriorated.

The above-mentioned amino resin is prepared by reacting an amino component such as melamine, urea, benzoguanamine, acetoguanamine, steroganamin, spiroguanamine, dicyandiamide and an aldehyde component such as formaldehyde, paraformaldehyde, acetaldehyde and benzaldehyde. The resulting methylolated amino resin is exemplified. Those obtained by etherifying a methylol group of the methylolated amino resin with an alcohol having 1 to 6 carbon atoms are also included in the amino resin. Of these, they can be used alone or in combination. From the viewpoint of hygiene, an amino resin using melamine or benzoguanamine is preferable, and an amino resin using benzoguanamine which is excellent in retort resistance and extractability is more preferable.

Examples of the amino resin using benzoguanamine include a methyletherified benzoguanamine resin in which part or all of the methylol group of the methylolated benzoguanamine resin is etherified with methyl alcohol, a butyletherified benzoguanamine resin in which butylether is butyletherified, or A mixed etherified benzoguanamine resin with methyl ether and butyl ether etherified with both methyl alcohol and butyl alcohol is preferred. As the butyl alcohol, isobutyl alcohol and n-butyl alcohol are preferable.

As amino resins using melamine,
Part or all of the methylol group of the methylolated melamine resin was etherified with a methyl etherified melamine resin etherified with methyl alcohol, a butyl etherified melamine resin butyl etherified with butyl alcohol, or both methyl alcohol and butyl alcohol. Mixed etherified melamine resins with methyl ether and butyl ether are preferred.

(C) used in the coating composition for cans of the present invention
Examples of the acid catalyst include sulfuric acid, p-toluenesulfonic acid,
Dodecylbenzenesulfonic acid, naphthalenesulfonic acid,
Dinonyl naphthalene sulfonic acid, dinonyl naphthalene disulfonic acid, camphor sulfonic acid, phosphoric acid, and those obtained by amine-blocking (partially neutralized by adding an amine) and the like. Alternatively, two or more kinds can be used in combination, but dodecylbenzenesulfonic acid and a neutralized product thereof are preferable in terms of compatibility with the resin and hygiene.

The resin composition for a can coating composition of the present invention is preferably blended in such a manner that the ratio of (A) a polyester resin, (B) a phenolic resin crosslinking agent, and (C) an acid catalyst is within the following range. . (A) / (B) / (C) = 100 / 5-40 / 0.1-
5 [weight ratio] If the weight ratio of the (B) phenolic resin crosslinking agent exceeds 40 parts by weight with respect to (A) 100 parts by weight of the polyester resin, the processability may be poor. Retort resistance and dent resistance may decrease. More preferably 10 to 30 parts by weight, even more preferably 15 to 25 parts by weight.
It is within the range of parts by weight. Further, (C) the amount of the acid catalyst is 0.1
If the amount is less than 5 parts by weight, the curability becomes insufficient, and the workability and retort resistance may be inferior. Dent resistance may be reduced. More preferably, it is in the range of 0.2 to 1 part by weight.

Further, the resin composition for can coating of the present invention can contain 0.1 to 10 parts by weight of the lubricant (D) based on 100 parts by weight of the polyester resin (A). This has the effect of suppressing damage to the coating film during can making and improving the slip of the coating film during molding. Especially DI processing, DRD
Effective during processing. (D) If the amount of the lubricant is less than 0.1 part by weight, the coating film becomes severely damaged during deep drawing, and the corrosion of the base material may become remarkable. Workability may not be satisfied due to a decrease in mechanical strength or the like. More preferably, it is in the range of 0.3 to 5 parts by weight.

The lubricant (D) used in the present invention is, for example, a fatty acid ester wax, which is an esterified product of a polyol compound and a fatty acid, a silicone wax, a fluorine wax, a polyolefin wax such as polyethylene,
Lanolin-based wax, montan wax, microcrystalline wax, carnauba wax and the like can be mentioned. Lubricants can be used alone or as a mixture of two or more.

The coating resin composition for cans of the present invention contains known inorganic pigments such as titanium oxide and silica, phosphoric acid and its esterified compounds, curing catalysts such as organic tin compounds, surface smoothing agents, and defoaming. Known additives such as agents, dispersants, and lubricants can be blended.

The resin composition for paint for cans of the present invention is formed into a paint in a state of being dissolved in a known organic solvent. Examples of the organic solvent used for coating include toluene, xylene, aromatic hydrocarbon compounds, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, methyl cellosolve, butyl cellosolve, ethylene glycol monoethyl ether acetate, Diethylene glycol monoethyl ether acetate, ethylene glycol monoacetate, methanol,
Ethanol, butanol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether,
One type or two or more types are selected from diethylene glycol monobutyl ether and the like in consideration of solubility, evaporation rate and the like.

In the resin composition for can coating of the present invention, other resins for the purpose of improving the flexibility and adhesion of the coating film can be used. Other resins include an ethylene-polymerizable unsaturated carboxylic acid copolymer, and an ethylene-polymerizable carboxylic acid copolymer ionomer, and are effective by blending at least one resin selected from these. Flexibility and adhesion of the target coating film.

The coating composition for cans of the present invention can be used by coating the inner and outer surfaces of any metal plate which can be used for beverage cans, cans for cans, lids, caps, etc. , Tin free steel, aluminum and the like. For these metal plates, use those that have been subjected to a surface treatment for the purpose of anti-corrosion treatment such as phosphoric acid treatment, chromate chromate treatment, phosphoric acid chromate treatment, and other rust preventive agents, and to improve the adhesion of the coating film. May be.

The coating composition of the present invention can be applied by a known coating method such as roll coater coating or spray coating to obtain the coated metal sheet of the present invention. Although the coating film thickness is not particularly limited, the dry film thickness is 3 to 18
μm, and more preferably 3 to 10 μm. The baking condition of the coating film is usually in the range of about 100 to 300 ° C. for about 5 seconds to about 30 minutes, and further about 150 to 2 minutes.
It is preferred that the heating time be in the range of about 1 to about 15 minutes in the range of 50 ° C.

The present invention will be specifically described below with reference to examples. In the examples, “part (s)” means “part (s) by weight”. Each measurement item followed the following method.

(1) Measurement of Resin Composition The molar ratio of an acid component and an alcohol component was determined by nuclear magnetic resonance spectroscopy and analysis by gas chromatography after alcoholysis.

(2) Measurement of Number Average Molecular Weight The molecular weight was measured by gel permeation chromatography (GPC) using a standard polystyrene calibration curve.

(3) Measurement of reduced viscosity 0.10 g of a polyester resin was dissolved in 25 cc of a mixed solvent of phenol / tetrachloroethane (weight ratio: 6/4) and measured at 30 ° C.

(4) Measurement of glass transition temperature The glass transition temperature was measured at a heating rate of 20 ° C./min using a differential scanning calorimeter (DSC).

(5) Measurement of acid value 0.2 g of polyester was dissolved in 20 ml of chloroform, and titrated with a 0.1N KOH ethanol solution.
0 per ⁶ g was determined equivalents (eq / 10 ⁶ g).

Evaluation Items (6) Preparation of Test Pieces The coating composition was applied to an aluminum metal plate (# 5025, 70 m
m × 150 mm × 0.3 mm) with a bar coater so that the film thickness becomes 4 to 8 μm, and bake hardening,
This was used as a test piece. The baking condition is 250 ° C (PM
(T, maximum temperature at which the material reached) × 1 minute.

(7) Workability One metal plate having the same thickness as the test piece is sandwiched and bent in the direction of 180 degrees. The processed portion was brought into contact with a sponge immersed in a 1% aqueous solution of NaCl, and evaluated by a current value when a voltage of 5.5 V was applied. The smaller the energization value (≦ 1.5 mA), the better.

(8) Overbake Property The test piece was again heat-treated at 210 ° C. × 10 minutes, and the workability was evaluated by the same method as in (7).

(9) Retort resistance A test piece is set up in a stainless steel cup, and ion-exchanged water is poured into the stainless steel cup to half the height of the test piece. This is set in a pressure cooker, and retort processing is performed at 125 ° C. for 30 minutes.
The evaluation after the treatment is performed for the underwater part and the vapor part, and the degree of whitening is visually determined as follows. ：: good ○: slight whitening but no blisters △: slight whitening or slight blistering ×: significant whitening or significant blistering

(10) Resistance to Contents The test piece was immersed in an aqueous solution containing 3 wt% of sodium chloride and 3 wt% of lactic acid, treated at 125 ° C. for 30 minutes, and the whitening of the coating film and the state of the blister were visually determined. ：: good ○: slight whitening but no blisters △: slight whitening or slight blistering ×: significant whitening or significant blistering

(11) Resistance to acid workability The test piece was immersed in an aqueous solution containing 1 wt% of citric acid,
After treating at 30 ° C. for 30 minutes, the workability was evaluated and judged by the same method as in (7).

(12) Dent Resistance The coated surface of the test piece subjected to the retort treatment shown in (11) was placed face down, and a Dupont impact tester was used.
An impact is applied under the condition of ２ inch × 1 kg × 5 cm height. Next, the protruding portion was brought into contact with a sponge immersed in a 1% aqueous NaCl solution, and evaluated by a current value when a voltage of 5.5 V was applied. Smaller current value (≦ 1.5mA)
Is good.

(13) Extractability The extract after the retort test shown in (10) was titrated with potassium permanganate to quantify the amount of organic matter extracted from the coating film. The smaller the value, the better. (14) Deep drawing workability L / D (diameter / depth) = 1/1 was formed using a deep drawing machine so that the painted surface of the test piece was on the outside. The state of peeling of the coating film on the side surface of the test piece was visually observed and judged. ◎: good ○: the coating film has slight scratches. Δ: Slight peeling is observed in the coating film. X: Severe peeling and damage are observed in the coating film.

(15) Adhesion L / D (diameter / depth) = 1/1 was formed using a deep drawing machine so that the painted surface of the test piece was on the inside. This test piece was treated under the same retort conditions as in (9), and the peeled state of the coating film was visually determined. ：: Good ：: Slight peeling of the coating film was observed at the end of the test piece. Δ: Peeling of the coating film was observed at the end and the bottom of the test piece. X: Intense peeling of the coating film is observed.

(16) Lubricity On the painted surface of the test piece, the dynamic friction coefficient was measured under the condition of a tensile speed of 10 cm / min. The smaller the coefficient of dynamic friction, the better the lubricity, and the evaluation was made according to the following criteria. ：: dynamic friction coefficient <0.10 ○: 0.10 ≦ dynamic friction coefficient <0.15 Δ: 0.15 ≦ dynamic friction coefficient <0.2 ×: dynamic friction coefficient ≧ 0.2

Synthesis of Polyester Resin Used in the Invention Synthesis Example by Transesterification (a) 890 parts of dimethyl terephthalic acid, 4.4 of trimellitic acid
Parts, 700 parts of propylene glycol, 100 parts of 1,4-cyclohexanedimethanol, and 0.5 part of titanium tetrabutoxide were charged into a 3 L flask, and 220 parts were charged for 4 hours.
The temperature was gradually raised to ° C. to carry out transesterification. Then
The initial polymerization under reduced pressure was performed to 10 mmHg over 30 minutes, and the temperature was increased to 250 ° C.
Late polymerization was carried out at a pressure of not more than mmHg for 90 minutes to obtain a polyester resin (a) used in the present invention.

Synthesis example by direct polymerization method (a) 2660 parts of terephthalic acid, 15.5 parts of trimellitic acid, 2450 parts of propylene glycol, 350 parts of 1,4-cyclohexanedimethanol, titanium tetrabutoxide
Charge 8 parts into a 10 L autoclave, 3.5 kg / c
The temperature was gradually raised to 235 ° C. over 3 hours under a nitrogen pressure of m · G to carry out esterification. Then take 1 hour
The polymerization was carried out under reduced pressure to 0 mmHg and the temperature was raised to 250 ° C., followed by late polymerization at 1 mmHg or less for 90 minutes to obtain the polyester resin (a) used in the present invention. There is no difference in the performance of the resin (a) obtained by the transesterification method and the direct polymerization method, and the composition and characteristic values are shown in Table 1. Further, the obtained resin was dissolved in cyclohexanone / solvesso-150 = 1/1 solvent at a solid content of 40%.
% Resin varnish, and using this, a coating composition of the present invention was prepared.

Synthesis Example (b) 380 parts of dimethyl terephthalic acid, 2-methyl-1,3-
255 parts of propanediol, neopentyl glycol 1
59 parts, 3 parts of trimethylolpropane, and 0.2 parts of titanium butoxide were charged into a 2 L flask, and 2 parts were charged for 4 hours.
The temperature was gradually raised to 20 ° C. to perform transesterification. Then, after cooling to 200 ° C. or lower, 45 parts of sebacic acid was added, and the temperature was raised again to 230 ° C. to carry out an esterification reaction. Next, this was subjected to initial polymerization under reduced pressure to 10 mmHg over 30 minutes, the temperature was raised to 250 ° C., and further late polymerization was performed at 250 ° C. and 1 mmHg or less for 90 minutes. Thereafter, one end of the resin was cooled to 220 ° C. under a nitrogen stream, and 3.4 parts of trimellitic acid was added thereto to obtain a polyester resin (b) used in the present invention. Table 1 shows the composition and characteristic values of the obtained resin. The resin obtained was a resin varnish having a solid content of 40% with a solvent of cyclohexanone / solvesso-150 = 1/1, and the coating composition of the present invention was prepared using this.

Synthesis Examples (c) to (f) In the transesterification method or the direct polymerization method of Synthesis Example (a) and in Synthesis Example (b), the present invention whose resin composition is as shown in Table 1, and Polyester resin (c) used for comparative example
To (f) and a resin varnish having a solid content of 40% were obtained. Among them, polyester (f) is a polyester resin for comparative example.

[0057]

[Table 1] * 1: 1,4-cyclohexanedicarboxylic acid * 2: 1,4-cyclohexanedimethanol

Resol type phenolic resin of the present invention (g)
Synthesis of P-cresol 60 parts, m-cresol 40 parts, 37%
180 parts of an aqueous formaldehyde solution and 1 part of sodium hydroxide were added, and reacted at 60 ° C. for 3 hours.
Dehydrated at 0 ° C. for 1 hour. Then, 100 parts of n-butanol and 6 parts of phosphoric acid were added and reacted at 110 to 120 ° C. for 2 hours. After completion of the reaction, the obtained solution was filtered to obtain a resol-type phenol resin crosslinking agent (g) of a mixed system of P-cresol and m-cresol having a solid content of about 50%. Table 2 shows the synthetic formulations.

Synthesis of other resole type phenolic resin Examples of synthesis as other resole type phenolic resins (g)
The resol type phenolic resins (h), (i) and (j) of the present invention and the resol type phenolic resins (k) and (l) for the comparative example were obtained in the same manner as described above. The composition is shown in Table 2.

[0060]

[Table 2] In the table, m-CS: m-cresol p-CS: p-cresol Xyl: 3,5-xylenol Ph: phenol

Example (1) After mixing 20 parts of resin varnish (a), 2.6 parts of Mycoat-106 (manufactured by Mitsui Cytec Co., Ltd.) and 0.01 part of dodecylbenzenesulfonic acid, cyclohexanone / solvesso was used. The mixture was diluted to a viscosity suitable for coating at 150 = 1/1 to obtain a coating composition (1) of the present invention. This was applied and baked by the method described above to obtain a test piece of the coated metal plate of the present invention. Table 3 shows the composition and the results of evaluating the test pieces.

Examples (2) to (6) The coating resin compositions (2) to (6) of the present invention were obtained in the same manner as in Example (1), and then applied and baked in the same manner as described above. A test piece of the coated metal plate of the present invention was obtained. Table 3 shows the composition and the results of evaluating the test pieces.

[0063]

[Table 3] * 1: Methyl etherified benzoguanamine resin (manufactured by Mitsui Cytec Co., Ltd.) * 2: Methyl etherified melamine resin (manufactured by Mitsui Cytec Co., Ltd.) * 3: Phenol novolak type epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd.) Dodecylbenzenesulfonic acid * 4: Dodecylbenzenesulfonic acid * 5: Dodecylbenzenesulfonic acid curing catalyst (manufactured by King Industries)

Comparative Examples (7) to (12) Coating resin compositions (7) to (12) of Comparative Examples were obtained in the same manner as in Example (1), and then applied and baked in the same manner as described above. A test piece of a comparative example was obtained. Table 4 shows the composition and the results of evaluating the test pieces.
Incidentally, (12) is a reproduction of an epoxy-phenol resin paint.

[0065]

[Table 4] * 1: Methyl etherified benzoguanamine resin (manufactured by Mitsui Cytec Co., Ltd.) * 2: Methyl etherified melamine resin (manufactured by Mitsui Cytec Co., Ltd.) * 3: Phenol novolak type epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd.) Dodecylbenzenesulfonic acid * 4: Bisphenol type epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd.) * 5: Dodecylbenzenesulfonic acid * 6: Dodecylbenzenesulfonic acid-based curing catalyst (manufactured by King Industries)

As is clear from Tables 3 and 4, the metal plate coated with the resin composition for can coating of the present invention has good workability, retort resistance, overbake resistance, content resistance, acid resistance,
Excellent in deep drawing workability, adhesion, extractability and dent resistance.

[0067]

EFFECTS OF THE INVENTION Paints applied to the inner surfaces of food and beverage cans are non-toxic due to their properties, do not emit pollutants during disposal and recycling, and can be used for processing cans, retort steam,
It must be able to withstand heat, its salts and acids.
In recent years, it has been desired to substitute a paint containing a bisphenol compound, which is an external factor endocrine disrupting substance (environmental hormone), such as an epoxy-phenol paint. The paint resin composition for the inner surface of the can of the present invention contains no toxic compound, does not discharge, does not contain environmental hormones, satisfies workability, retort resistance, and content resistance, and further has adhesion and over-resistance. Since it has excellent baking properties and dent resistance, it is suitable for the inner coating of food cans.

Continuation of the front page (72) Inventor Hiroshi Tajika 2-1-1 Katata, Otsu-shi, Shiga F-term in Toyobo Co., Ltd. Research Laboratory (Reference) 4D075 CA44 CA50 DA06 DB01 DC42 EA05 EA37 EB32 EB35 EB45 EB52 EB56 4J038 DA072 DD051 DD061 DD071 DD081 DD191 GA02 HA376 JC13 KA03 KA04 KA07 MA14 NA04 NA12 NA14 NA24 PB04 PC02

Claims (5)

[Claims] (A) a number average molecular weight of 5,000 to 100,
000 polyester resin, and (B) 50 to 100% by weight of a bifunctional phenol compound as a phenol component.
A paint resin composition for cans, comprising: a resol-type phenol resin crosslinking agent containing a phenol component of 0 to 50% by weight of a functional or higher phenol compound; and (C) an acid catalyst. 2. The resin composition for a can coating composition according to claim 1, wherein (A) / (B) / (C) is 100/5 to 5% by weight.
40 / 0.1 to 5 which is a resin composition for can coating. 3. The coating composition for cans according to claim 1, wherein the alkoxymethyl group of the (B) resol type phenol resin crosslinking agent is an n-butyl group. 4. The method of claim 1, wherein (D) the lubricant is (A) a polyester resin 1
The coating composition for cans according to claim 1, wherein the content is 0.1 to 10 parts by weight with respect to 00 parts by weight. 5. A coated metal sheet for a can, wherein the resin composition for a can coating according to any one of claims 1 to 4 is applied and cured.