JP5691010B2 - Coating composition and can lid using the same - Google Patents

Description

  The present invention relates to a coating composition for metal.

Conventionally, BPA type epoxy resin synthesized from bisphenol A (hereinafter also referred to as “BPA”) and epichlorohydrin has a function of forming a coating film excellent in steam sterilization resistance, workability, and adhesion. Therefore, conventionally, it is suitably used for paints for coating the inner and outer surfaces of cans.
However, in recent years, research results have been reported that BPA has endocrine disrupting effects on organisms, and it was listed in the list of 67 substances in the “chemical substances suspected of having endocrine disrupting actions” published by the Ministry of the Environment. In response to this, the elution of BPA from the inner surface coating film of the can into the contents has become a serious problem. From such a background, a water-based paint for coating the inner surface of a can without using any BPA-derived raw material is desired.

A can having a coating film using a paint for cans may be subjected to steam sterilization treatment more severe than boiling depending on the type of contents. However, if the coating film has insufficient resistance, the coating may cause whitening or blistering (dotted peeling).
Furthermore, the beverage can filled with the carbonated beverage is filled with the contents at a low temperature of about 5 ° C. and attached to the lid, and then returned to room temperature. During this process, the carbonic acid volatilizes and the pressure inside the can increases, so the lid portion of the can swells outward due to the pressure from the inside. After this, the volatilization from the filler of carbonic acid and the dissolution in the filler are repeated due to the change in the ambient temperature, and the lid repeats the uneven change. As a result, the lid is deformed in a state where the contents are filled, and corrosion of the deformed portion is likely to occur. Therefore, various processes are performed on the lid portion in consideration of such deformation due to pressure. Since these various processes are performed after the coating film is provided on both sides of the lid material, the coating composition has high processability so as not to cause a coating film defect in various processes, and the lid is uneven after filling the contents. High corrosion resistance is required so that corrosion does not occur even when the state changes are repeated.

  The can lid is usually manufactured by so-called coil coating in which a metal plate coil is continuously coated with a paint and baked (drying and coating film formation). Conventionally, from the viewpoint of process rationalization, the speed of the coating line has been increased, and in order to cope with this, for example, a reverse coating method or the like may be used. Furthermore, as the line speed increases, the baking process is performed at a higher temperature and in a shorter time than in the past.

In general, in continuous coating / baking lines such as coil coating, as the line speed increases, unless the baking oven is expanded, the time spent in the oven will be shortened and the paint will be baked. The amount of heat will tend to be insufficient. In order to compensate for this, the current situation is that the baking temperature itself is set high.
This transition in baking conditions also affects the paintability of the paint, which was not a problem in the conventional process, and the coating speed is increased and the baking conditions are made faster and shorter. The problem of the occurrence of defects has become apparent.

  In addition, a coating defect means that the coating surface has unevenness or repellency when it is applied, or when the coating film is baked, it is cured with the traces of foam remaining on the surface (so-called “WAKI”). This is a problem that a defect occurs in the surface state of the cured coating film and a uniform cured coating film cannot be obtained. Such coating defects often occur when the selection of the solvent type used in the paint is not appropriate.

  As described above, in a can coating used for coating a can lid or the like, it does not contain a component derived from BPA, and has excellent properties of a cured coating film, and is also commonly used in coil coating. It has been an object to provide a coating composition having good coating properties in coater coating.

Patent Document 1 discloses an aqueous coating composition in which an acrylic-modified epoxy resin obtained by reacting an epoxy resin and a carboxyl group-containing acrylic resin is neutralized and dispersed in an aqueous medium. It is described that this composition can form a coating film excellent in T-bend folding workability, corrosion resistance of a processed part, film remaining resistance, retort whitening resistance, flavor property, hygiene, and adhesiveness.
Patent Document 2 discloses an aqueous coating composition in which an acrylic resin-modified epoxy resin, a resol type phenol resin, and an acrylic resin are dispersed in an aqueous medium.
It is described that this composition can form a coating film excellent in bending workability, water whitening resistance and flavor properties.

JP 2007-291221 A JP 2007-284541 A

  However, the coating compositions of Patent Documents 1 and 2 use a BPA type epoxy resin as a raw material, and do not respond to the recent request that no BPA-derived components are used. Furthermore, there is a problem that it is difficult to obtain a good coating surface.

  The present invention does not contain any component derived from BPA, has good paintability and a coating surface, and is excellent in steam sterilization resistance (also referred to as “retort resistance”), workability, and corrosion resistance. It aims at providing the coating composition which can form a coating film.

The present inventors have found that the above-mentioned problems can be solved by a polyester resin, an organic solvent that satisfies a specific condition relating to the SP value with the resin, and a coating composition comprising a phenol resin, thereby completing the present invention. It came to do.
That is, the present invention comprises a polyester resin (A), an organic solvent (B) and a phenol resin (C),
Organic SP value of the solvent (B) SP value (SP _b) and the polyester resin _(A) (SP _{a) is, (SP b -SP a) =} - 0.40~0.60 (cal / cm 3) 1 ^{/ 2} ,
The weight ratio of the polyester resin (A) and the phenol resin (C) is (A) / (C) = 95/5 to 75/25.

In addition, the present invention includes one or more organic solvents (B) selected from the group consisting of aromatic hydrocarbons, aliphatic monohydric alcohols, aliphatic dibasic acid dimethyl esters, and cyclic ketones,
The molecular weight of the aromatic hydrocarbon is 92 to 246, the molecular weight of the aliphatic monohydric alcohol is 60 to 190, the molecular weight of the aliphatic dibasic acid dimethyl ester is 146 to 174, and the molecular weight of the cyclic ketone is 70 to 112. It is related with said coating composition characterized. The molecular weight is a formula weight.

  The present invention also relates to a compound (a) in which an aliphatic monohydric alcohol has one ether bond in the molecule, a compound (b) having two ether bonds in the molecule, and an alkyl alcohol having 3 to 8 carbon atoms. It relates to said coating composition containing (c).

  In the present invention, the total amount of the organic solvent (B) is 100% by weight, the aromatic hydrocarbon is 25 to 85% by weight, the aliphatic monohydric alcohol is 9 to 45% by weight, and the aliphatic dibasic acid dimethyl ester is 3%. It relates to the coating composition as described above, which is ˜35% by weight and the cyclic ketone is 1 to 20% by weight.

  Moreover, this invention relates to said coating composition whose glass transition temperature of a polyester resin (A) is 10-85 degreeC.

  Moreover, this invention relates to said coating composition whose phenol resin is m-cresol type.

  Furthermore, this invention relates to the can lid | cover by which one side of the member for can lid | covers is coat | covered with said coating composition.

  Furthermore, the present invention relates to a coated can comprising the above can lid and a can body member, wherein a covering surface of the can lid is located inside the can.

  According to the present invention, it is possible to provide a coating composition that does not contain any BPA-derived components, has good paintability, and can form a coating film that is excellent in steam sterilization resistance, workability, and corrosion resistance. did it.

  The coating composition of the present invention comprises a polyester resin (A), an organic solvent (B), and a phenol resin (C), and the SP value difference between the organic solvent (B) and the polyester resin (A) is specific. It is preferable that the polyester resin (A) and the phenol resin (C) are included in a specific ratio.

  In this invention, a polyester resin (A) is a main non-volatile component which comprises a coating composition, and is a component which bears formation of a cured coating film. A tough cured coating film that reacts with phenol resin (C), which will be described later, by baking to form a crosslinked structure and is excellent in adhesion to metal, surface hardness, workability, steam sterilization resistance, corrosion resistance, etc. Form.

The polyester resin (A) is a copolymer having an ester bond obtained by condensation or transesterification of dicarboxylic acid or dicarboxylic acid ester and alcohol. The polyester resin (A) can be usually produced by charging dicarboxylic acids and alcohols, reacting them while raising the temperature and stirring and melting them, and determining the end point from the acid value or solubility.
As said dicarboxylic acid, aromatic dicarboxylic acid, aliphatic dicarboxylic acid, alicyclic dicarboxylic acid, etc. are preferable. Examples of the alcohols include, for example, an aliphatic diol having 2 to 10 carbon atoms, an alicyclic diol having 6 to 12 carbon atoms having 2 hydroxyl groups, 2 hydroxyl groups, and an ether bond. A diol to be contained and a compound having 3 or more hydroxyl groups are preferred. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, orthophthalic acid, naphthalene dicarboxylic acid, and biphenyl dicarboxylic acid.
Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, and dimer acid.
Examples of the alicyclic dicarboxylic acid include 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid and its anhydride. Examples of the dicarboxylic acid having a polymerizable double bond include α, β-unsaturated dicarboxylic acids such as fumaric acid, maleic acid, maleic anhydride, itaconic acid and citraconic acid, and other 2,5-norbornene dicarboxylic acids. Anhydride, tetrahydrophthalic anhydride, etc. are mentioned.
Examples of the aliphatic diol having 2 to 10 carbon atoms include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1, Examples of the alicyclic diol having 6 to 12 carbon atoms such as 6-hexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 2-ethyl-2-butylpropanediol, Examples include 4-cyclohexanedimethanol.
Examples of the diol containing an ether bond include diethylene glycol, triethylene glycol, dipropylene glycol and the like, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and the like.

  The end point of the reaction is usually determined by the acid value, but the acid value should be as low as possible from the viewpoint of the temporal stability of the paint. In addition, the acid value may affect the physical properties of the cured coating film.

  The hydroxyl group of the polyester resin (A) becomes a crosslinking point that reacts with the phenol resin (C). This hydroxyl group is preferably a primary hydroxyl group, and preferably has as few secondary and tertiary hydroxyl groups as possible. Since the secondary and tertiary hydroxyl groups have poor reactivity with the phenol resin (C), they may remain unreacted even after the baking step, thereby deteriorating the physical properties of the coating film.

The glass transition temperature of the polyester resin (A) is preferably 10 to 85 ° C. More preferably, it is 40-70 degreeC.
When the glass transition temperature is in the above range, it is easy to form a cured coating film excellent in both retort resistance and workability. When the temperature is less than 10 ° C., the coating film may be easily whitened in the retort treatment. On the other hand, when the temperature exceeds 85 ° C., the cured coating film tends to become brittle and the workability may be deteriorated.

  In addition, the glass transition temperature in this invention is obtained by dynamic viscoelasticity measurement (DMS), and is specifically a measured value obtained by using “DMS210” manufactured by Seiko Denshi Kogyo.

The number average molecular weight of the polyester resin (A) is preferably 10,000 to 30,000. More preferably, it is 15000-25000. When the number average molecular weight is in the above range, the solubility in a solvent can be further improved, and a cured coating film excellent in both retort resistance and workability can be easily formed. If it is less than 10,000, the retort resistance may be insufficient. On the other hand, if it exceeds 30000, the solubility in the solvent tends to be poor, and the cured coating film becomes brittle and the workability may be inferior. .
In addition, the number average molecular weight in this invention is a value of standard polystyrene conversion by GPC (gel permeation chromatography).

In the present invention, commercially available products that can be preferably used as the polyester resin (A) include, for example, Byron 103, Byron 200, Byron 270, Byron 600, Byron GK250, Byron GK330, Byron GK360, Byron GK640, Byron GK880 manufactured by Toyobo Co., Ltd .;
Also, uniteca's ERITER UE3201, ERITER UE3210, ERITER 3215, ERITER UE3216, ERITER UE3240, ERITERUE 3250, ERITER UE9800;
Dynapole L205, Dynapole L206, Dynapole L208, Dynapole L411, Dynapole L460, Dynapole 600;
Further, Skybon ES100, Skybon ES120, Skybon ES240, Skybon ES250, Skybon ES300, Skybon ES350, Skybon ES410, Skybon ES500, Skybon ES660, Skybon ES900, Skybon ES901, Skybon ES955, manufactured by SK Chemical Co., Ltd .;
Etc.

In the present invention, the organic solvent (B) is a fluidity suitable for coating by dissolving the polyester resin (A) and the phenol resin (C), which are constituents of the coating film, and adjusting the concentration to an appropriate nonvolatile content. It bears the function to give
However, in the present invention, the organic solvent (B) is not only responsible for its function, but its selection is extremely important in terms of imparting good paintability in high-speed coating.
In the present invention, the SP value of the organic solvent (B) (SP _b) and the SP value of the polyester resin _(A) (SP _{a) is, (SP b -SP a) =} - 0.40~0.60 (cal / Cm ³ ) ^1/2 is important.
When organic SP value of the solvent (B) (SP _b) and the SP value of the polyester resin (A) the difference between _{(SP a) (SP b -SP} a) is in the above range, the polyester resin in an organic solvent (B) Not only the solubility of (A) is good, but also excellent coating properties can be obtained by a coating method typified by a reverse coating method, and furthermore, a uniform cured coating film in which coating film defects hardly occur can be obtained. is there.

Although the detailed mechanism is unknown, when (SP _b -SP _a ) is in the above range, it is considered that the solubility of the polyester resin in the organic solvent becomes particularly good, and the interaction between the two becomes strong. Therefore, in addition to being in a very stable state as a solution, when coated and baked, the solvent does not instantaneously leave the resin component, but evaporates from the coating film at an appropriate rate. It is speculated that a good coating film can be obtained.
If the resin is not sufficiently soluble in the organic solvent, the stability of the coating will be poor, separation will occur in the painting process, leading to the generation of precipitates and blisters. It is thought that the occurrence of unevenness and the occurrence of remaining foam marks (flakes) are caused by the separation from the resin component.

The SP value in the present invention is also referred to as a solubility parameter, and the SP value of the organic solvent (B) is calculated by the Fedors calculation method [“Polymer Engineering and Science”, Vol. 14, No. 2 (1974), 148 to 154], which is a value calculated based on the molar evaporation energy and the molar volume.
The SP value in the case of the mixed solvent system is a value obtained by multiplying the SP value of each organic solvent constituting the system by the respective component ratio (molar fraction) and adding them up.

In the present invention, the SP value of the polyester resin (A) is determined as follows.
That is, several kinds of organic solvents having arbitrary different SP values are prepared, and a polyester resin is dissolved in each of them at a non-volatile concentration of 21.5% by weight at room temperature (25 ° C.).
When the SP values of the polyester resin and the organic solvent are the same or close to each other, the polyester resin dissolves in the solvent and does not dissolve when it is far away.
In the vicinity of the SP value of the organic solvent in which the dissolution was recognized, the same test was repeated by further finely dividing the range of the SP value, the upper limit value and the lower limit value of the SP value at which the resin could be dissolved were judged, and the average value thereof The SP value of the polyester resin.
That is, the average value of the maximum value (SP _max ) and the minimum value (SP _min ) of the SP value of the organic solvent in which the resin can be dissolved is defined as the SP value of the polyester resin (A).

In the present invention, the organic solvent (B) preferably contains one or more selected from the group consisting of aromatic hydrocarbons, aliphatic monohydric alcohols, aliphatic dibasic acid dimethyl esters, and cyclic ketones. These solvents have a molecular weight (formula weight) of aromatic hydrocarbons of 92 to 246, aliphatic monohydric alcohols of 60 to 190, aliphatic dibasic acid dimethyl ester of 146 to 174, cyclic ketones. The molecular weight of is preferably 70 to 112.
When organic solvent (B) is such a structure, the coating property of the obtained coating composition becomes more favorable.

  Examples of the aromatic hydrocarbon preferably used in the present invention include amylbenzene, isopropylbenzene, ethylbenzene, o-xylene, m-xylene, p-xylene, 1,2-diethylbenzene, 1,3-diethylbenzene, 1,4. -In addition to diethylbenzene, cyclohexylbenzene, 2,6-dimethylnaphthalene, p-cymene, styrene, tetralin, α-pinene, β-pinene, dodecylbenzene, toluene, mesitylene, etc., SWAZOL 1000, SWAZOL 1500 (above, Maruzen Petrochemical) Co., Ltd.), Solvesso 100, Solvesso 150 (above, ExxonMobil Corp.) and the like.

In the present invention, the aliphatic monohydric alcohol means a compound having no aromatic ring in the molecule and one hydroxyl group.
Among these, it is preferable to include the compound (a) having one ether bond in the molecule, the compound (b) having two ether bonds in the molecule, and the alkyl alcohol (c) having 3 to 8 carbon atoms.

Examples of the compound (a) having one ether bond in the molecule include ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether, ethylene glycol monophenyl ether, ethylene glycol monohexyl ether, ethylene glycol monomethyl ether, Examples include ethylene glycol monomethoxymethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, and propylene glycol monomethyl ether.

Examples of the compound (b) having two ether bonds in the molecule include diethylene glycol monoethyl ether, diethylene glycol monobutyl ether,
Examples include diethylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monopropyl ether, and dipropylene glycol monomethyl ether.

  Examples of the alkyl alcohol (c) having 3 to 8 carbon atoms include n-amyl alcohol, s-amyl alcohol, t-amyl alcohol, isoamyl alcohol, isobutyl alcohol, isopropyl alcohol, 2-ethylbutanol, 2-ethylhexanol, 2- Octanol, n-octanol, neopentyl alcohol, n-butanol, s-butanol, t-butanol, 1-propanol, n-hexanol, 2-heptanol, 3-heptanol, n-heptanol, 3-pentanol, 2-methyl Examples thereof include -1-butanol, 3-methyl-2-butanol, 4-methyl-2-pentanol and the like.

  The aliphatic dibasic acid dimethyl ester constituting the organic solvent (B) includes succinic acid dimethyl ester, glutaric acid dimethyl ester, adipic acid dimethyl ester, Flexisolv DBE esters (trade name), Flexisolv DBE-2 esters. (Product name), Flexisolv DBE-3 esters (Product name) Flexisolv DBE-4 esters (Product name), Flexisolv DBE-5 esters (Product name), Flexisolv DBE-6 esters (Product name, above, manufactured by INVISTA) etc. Can be mentioned.

  Furthermore, examples of the cyclic ketone include cyclobutanone, cyclohexanone, methylcyclohexanone, cycloheptanone, cyclopropanone, and the like.

When a plurality of solvents are used, aromatic hydrocarbon is 25 to 85% by weight, aliphatic monohydric alcohol is 9 to 45% by weight, and dimethyl aliphatic dibasic acid in 100% by weight of organic solvent (B). Preferably, the ester is 3 to 35% by weight and the cyclic ketone is 1 to 20% by weight.
When the ratio of each solvent type is in the above range, the solubility of the polyester resin and the paintability of the paint are particularly good.

The phenol resin (C) in the present invention functions as a curing agent for crosslinking the polyester resin (A) during baking of the coating film, and is one component that forms a cured coating film.
The phenol resin (C) is a resin obtained by an addition condensation reaction between phenols and aldehydes such as formaldehyde.
Examples of phenols for obtaining the phenol resin (C) include o-cresol, p-paracresol, p-phenylphenol, p-nonylphenol, 2,3-xylenol, 2,5-xylenol, phenol, m- Examples include m-cresol, 3,5-xylenol, resorcinol, bisphenol A, bisphenol F, bisphenol B, bisphenol E, bisphenol H, bisphenol S, catechol, hydroquinone, and the like.

In phenols, the ortho-position and para-position serve as reaction sites with respect to the phenolic hydroxyl group. Therefore, o-cresol, p-cresol, p-phenylphenol, p-nonylphenol, 2,3-xylenol, 2,5-xylenol, and the like have two reactive sites in one molecule, so the number of equivalents is 2. Phenols with a functional group of 2. In addition, phenol, m-cresol, 3,5-xylenol, resorcinol, and the like have three reaction sites in one molecule, and thus are phenols having an equivalent number of 3 and have a functional group of 3. Also, bisphenols such as bisphenol A, bisphenol F, bisphenol B, bisphenol E, bisphenol H, bisphenol S, catechol, hydroquinone, etc. are phenols with 4 equivalents because there are 4 reactive sites in one molecule. Yes, the functional group is 4.
In the present invention, among these phenols, in consideration of curability and reactivity, phenol, o-cresol, m-cresol, p-cresol and the like are preferable, and m-cresol is more preferable. When phenols with an equivalent number of 4 or more are used, there is a high possibility that a high molecular weight product is formed, and when the phenol resin is used in a paint for can coating, the solubility in a general-purpose solvent for paint is poor. Therefore, the phenol resin is likely to be deposited when applied as a coating composition. As a result, the coating film is likely to be uneven. Phenol monomers other than trifunctional phenols such as monofunctional 2,4-xylenol, 2,6-xylenol; bifunctional p-cresol, p-ter-butylphenol, p-ethylphenol, o-cresol Phenol monomers such as 2,3-xylenol, 2,5-xylenol, and p-nonylphenol can also be used, but when these are used, the functional group concentration is lowered, and the desired reactivity and molecular weight between crosslinks (crosslink (Density) may be difficult to ensure. Moreover, it is not preferable to use a tetrafunctional phenol monomer such as bisphenol A and bisphenol F as the phenol monomer because the self-condensation property of the phenol resin becomes too high. Furthermore, phenol resin self-condensates generally have hard and brittle properties and tend to degrade the processability of the coating. In the present invention, bisphenol A cannot be used from the viewpoint of BPA free.

Moreover, it is important that the weight ratio of the polyester resin (A) and the phenol resin (C) is (A) / (C) = 95/5 to 75/25. Preferably, (A) / (C) = 90/10 to 85/15.
When the weight ratio between the two is in the above range, a wide range of coating film properties such as curability and adhesiveness can be satisfied. When the polyester resin becomes excessive from the above ratio, the curability of the coating film is lowered, causing defects such as poor curing and poor adhesion to the substrate. On the other hand, when the phenol resin becomes excessive from the above ratio, the coating film is excessively cured, resulting in problems such as deterioration in workability.

The coating composition of the present invention can be obtained by mixing the polyester resin (A), the organic solvent (B), and the phenol resin (C).
In the mixing, a conventionally known stirring means such as a disper can be used. However, the polyester resin (A) and the phenol resin (C) may be dissolved in an arbitrary organic solvent in advance and used for mixing. .
The viscosity of the coating composition is usually 15 to 35 seconds (# 4 Ford cup / 25 ° C.), and the nonvolatile content concentration is 15 to 30% by weight.

If necessary, a lubricant such as wax may be added to the coating composition of the present invention for the purpose of preventing the coating film from being scratched in the can-making process.
Examples of waxes include animal and plant waxes such as carnauba wax, lanolin wax, palm oil, candelilla wax, and rice wax, petroleum waxes such as paraffin wax, microcrystalline wax, and petrolatum, polyolefin wax, and Teflon (registered trademark) wax. A synthetic wax or the like is preferably used.
Other additives such as a curing catalyst and a leveling agent can be used as necessary.

The coating composition of the present invention can be widely used not only for the following cans but also for general metal materials or metal products, etc., but is suitably used as a coating for inner and outer surfaces of cans containing beverages and foods, It is particularly suitable for coating the inner surface of a can, particularly for coating the inner surface of a lid member.
As the material of the can, aluminum, tin-plated steel plate, chrome-treated steel plate, nickel-treated steel plate or the like is used, and these materials may be subjected to surface treatment such as zirconium treatment or phosphoric acid treatment.

As a coating method of the coating composition of the present invention, spray coating such as air spray, airless spray and electrostatic spray, roll coater coating, dip coating, electrodeposition coating and the like can be used.
In particular, even when a reverse coat type roll coater coating commonly used in coil coating is used, it is possible to obtain a cured coating film that exhibits excellent paintability and hardly causes coating defects.
The coating composition of the present invention can form a film even after the volatile components are volatilized after being applied, but it is better to add a baking step in order to obtain excellent steam sterilization resistance, workability and adhesion. . As baking conditions, general baking conditions in coil coating for can lid production are preferable, baking is preferably performed at a temperature of 200 ° C. to 300 ° C. for 10 seconds to 2 minutes, and more preferably 20 to 40 seconds. .

  The can lid can be obtained by coating one surface of the can lid member with the coating composition of the present invention, and further, the can lid is joined to the can body member so that the coated surface is inside. Thus, a coated can can be obtained.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to these. In the examples, “part” represents “part by weight” and “%” represents “% by weight”.

[Example 1]
Polyester resin Byron GK360 (number average molecular weight 16000, glass transition temperature 55 ° C. SP value 9.30 (cal / cm ³ ) ^1/2 ) manufactured by Toyobo Co., Ltd. 193.5 parts, aliphatic dibasic acid dimethyl ester solvent as solvent DBE (molecular weight 159, SP value 9.8 (cal / cm ³ ) ^1/2 , 247.7 parts, aromatic hydrocarbon solvent xylene (molecular weight 106, SP value 8.8 (cal / cm ³ ) ^1/2 , 302.1 parts, BDG (molecular weight 162, SP value 10.5 (cal / cm ³ ) ^1/2 , 46.7 parts, butyl cellosolve (molecular weight 118, SP value 9.5) (Cal / cm ³ ) ^1/2 , 35.2 parts, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^1/2 , 27.3 parts, cyclic ketone solvent cyclohexanone (molecular weight 98 , SP Value 9.9 (cal / cm ³ ) ^1/2 , 120.6 parts were charged into a flask, dissolved at a temperature of 80 ° C., then cooled to 50 ° C. or lower, and metacresol phenol resin sumilite resin manufactured by Sumitomo Bakelite Co., Ltd. 43 parts of PR-55317 (n-butanol solution with a non-volatile content of 50%), 1% of dodecylbenzenesulfonic acid as a curing catalyst was added to 100% of the non-volatile content, and the polyester resin / phenol resin ratio was 90/10. A coating composition adjusted to a partial concentration of 21.5% was obtained.
The above-mentioned “DBE” represents Flexisolv DBE esters (trade name) manufactured by Invista, and is a mixture comprising succinic acid dimethyl ester: 21%, glutaric acid dimethyl ester: 59%, and adipic acid dimethyl ester: 20%. Yes, its molecular weight is the weight average molecular weight of the three compounds.
The “BDG” is an abbreviation for butyl diglycol (trade name) manufactured by Nippon Emulsifier Co., Ltd., and corresponds to diethylene glycol monobutyl ether.

[Example 2]
Aliphatic dibasic acid dimethyl ester solvent DBE (molecular weight 159, SP value 9.8 (cal / cm ³ ) ^1/2 ), 179.7 parts, aromatic hydrocarbon solvent xylene (molecular weight 106, SP value) 8.8 (cal / cm ³ ) ^1/2 , 241.2 parts, as aliphatic monohydric alcohol solvent, BDG (molecular weight 162, SP value 10.5 (cal / cm ³ ) ^1/2 , 114.6 Parts, butyl cellosolve (molecular weight 118, SP value 9.5 (cal / cm ³ ) ^1/2 , 125.9 parts, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^1/2 , 61 0.0 part, cyclic ketone solvent cyclohexanone (molecular weight 98, SP value 9.9 (cal / cm ³ ) ^1/2 , 57.2 parts were charged into a flask and dissolved at a temperature of 80 ° C. Cooled and made by Sumitomo Bakelite 43 parts of phenolic resin Sumilite Resin PR-55317 (n-butanol solution with a non-volatile content of 50%), 1% of dodecylbenzenesulfonic acid as a curing catalyst with respect to 100% of non-volatile content, and otherwise, Example 1 In the same manner as above, a coating composition was obtained.

[Example 3]
Aliphatic dibasic acid dimethyl ester solvent DBE (molecular weight 159, SP value 9.8 (cal / cm ³ ) ^1/2 ), 179.7 parts, aromatic hydrocarbon solvent xylene (molecular weight 106, SP value) 8.8 (cal / cm ³ ) ^1/2 , 241.2 parts, as aliphatic monohydric alcohol solvent, BDG (molecular weight 162, SP value 10.5 (cal / cm ³ ) ^1/2 , 160.0 Parts, butyl cellosolve (molecular weight 118, SP value 9.5 (cal / cm ³ ) ^1/2 , 80.5 parts, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^1/2 , 61 0.0 part, cyclic ketone solvent cyclohexanone (molecular weight 98, SP value 9.9 (cal / cm ³ ) ^1/2 , 57.2 parts were charged into a flask and dissolved at a temperature of 80 ° C. Cooled and made by Sumitomo Bakelite 43 parts of a phenolic resin Sumilite resin PR-55317 (n-butanol solution with a non-volatile content of 50%), 1% dodecylbenzenesulfonic acid as a curing catalyst was added to 100% of the non-volatile content. The coating composition was obtained in the same manner.

[Example 4]
Aliphatic dibasic acid dimethyl ester solvent DBE (molecular weight 159, SP value 9.8 (cal / cm ³ ) ^1/2 ), 202.3 parts, aromatic hydrocarbon solvent xylene (molecular weight 106, SP value) 8.8 (cal / cm ³ ) ^1/2 , 279.5 parts, as aliphatic monohydric alcohol solvent, BDG (molecular weight 162, SP value 10.5 (cal / cm ³ ) ^1/2 , 114.7 Parts, butyl cellosolve (molecular weight 118, SP value 9.5 (cal / cm ³ ) ^1/2 , 80.5 parts, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^1/2 , 27 .3 parts, cyclic ketone solvent cyclohexanone (molecular weight 98, SP value 9.9 (cal / cm ³ ) ^1/2 , 75.3 parts were charged into a flask and dissolved at a temperature of 80 ° C. Cooled and made by Sumitomo Bakelite 43 parts of a phenolic resin Sumilite resin PR-55317 (n-butanol solution with a non-volatile content of 50%), 1% dodecylbenzenesulfonic acid as a curing catalyst was added to 100% of the non-volatile content. The coating composition was obtained in the same manner.

[Example 5]
Aliphatic dibasic acid dimethyl ester solvent DBE (molecular weight 159, SP value 9.8 (cal / cm ³ ) ^1/2 ), 193.4 parts, aromatic hydrocarbon solvent xylene (molecular weight 106, SP value) 8.8 (cal / cm ³ ) ^1/2 , 243.1 parts, as aliphatic monohydric alcohol solvent, BDG (molecular weight 162, SP value 10.5 (cal / cm ³ ) ^1/2 , 160.0 Parts, butyl cellosolve (molecular weight 118, SP value 9.5 (cal / cm ³ ) ^1/2 , 80.5 parts, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^1/2 , 27 .3 parts, cyclic ketone solvent cyclohexanone (molecular weight 98, SP value 9.9 (cal / cm ³ ) ^1/2 , 75.3 parts were charged into a flask and dissolved at a temperature of 80 ° C. Cooled and made by Sumitomo Bakelite 43 parts of a phenolic resin Sumilite resin PR-55317 (n-butanol solution with a non-volatile content of 50%), 1% dodecylbenzenesulfonic acid as a curing catalyst was added to 100% of the non-volatile content. The coating composition was obtained in the same manner.

[Example 6]
Aliphatic dibasic acid dimethyl ester solvent DBE (molecular weight 159, SP value 9.8 (cal / cm ³ ) ^1/2 ), 213.7 parts, aromatic hydrocarbon solvent xylene (molecular weight 106, SP value) 8.8 (cal / cm ³ ) ^1/2 , 302.1 parts, as aliphatic monohydric alcohol solvent, BDG (molecular weight 162, SP value 10.5 (cal / cm ³ ) ^1/2 , 92.0 Parts, butyl cellosolve (molecular weight 118, SP value 9.5 (cal / cm ³ ) ^1/2 , 57.8 parts, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^1/2 , 27 .3 parts, cyclic ketone solvent cyclohexanone (molecular weight 98, SP value 9.9 (cal / cm ³ ) ^1/2 , 86.7 parts were charged in a flask and dissolved at a temperature of 80 ° C. Cooled and Sumitomo Bakelite Metacresol 43 parts of phenol resin Sumilite resin PR-55317 (n-butanol solution having a nonvolatile content of 50%), 1% of dodecylbenzenesulfonic acid as a curing catalyst was added to the nonvolatile content of 100%, and the others were the same as in Example 1. To obtain a coating composition.

[Example 7]
Aliphatic dibasic acid dimethyl ester solvent DBE (molecular weight 159, SP value 9.8 (cal / cm ³ ) ^1/2 ) 225.1 parts, aromatic hydrocarbon solvent xylene (molecular weight 106, SP value) 8.8 (cal / cm ³ ) ^1/2 , 336.3 parts, as aliphatic monohydric alcohol solvent, BDG (molecular weight 162, SP value 10.5 (cal / cm ³ ) ^1/2 , 69.3 Parts, butyl cellosolve (molecular weight 118, SP value 9.5 (cal / cm ³ ) ^1/2 , 35.2 parts, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^1/2 , 27 .3 parts, cyclic ketone solvent cyclohexanone (molecular weight 98, SP value 9.9 (cal / cm ³ ) ^1/2 , 86.4 parts were charged into a flask and dissolved at a temperature of 80 ° C. Cooled and Sumitomo Bakelite Metacresol 43 parts of phenol resin Sumilite resin PR-55317 (n-butanol solution having a nonvolatile content of 50%), 1% of dodecylbenzenesulfonic acid as a curing catalyst was added to the nonvolatile content of 100%, and the others were the same as in Example 1. To obtain a coating composition.

[Example 8]
Aliphatic dibasic acid dimethyl ester solvent DBE (molecular weight 159, SP value 9.8 (cal / cm ³ ) ^1/2 ) 40.0 parts, aromatic hydrocarbon solvent xylene (molecular weight 106, SP value) 8.8 (cal / cm ³ ) ^1/2 , 622.8 parts, as aliphatic monohydric alcohol solvent, BDG (molecular weight 162, SP value 10.5 (cal / cm ³ ) ^1/2 , 30.0 Parts, butyl cellosolve (molecular weight 118, SP value 9.5 (cal / cm ³ ) ^1/2 , 25.8 parts, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^1/2 , 31 0.0 part, cyclic ketone solvent cyclohexanone (molecular weight 98, SP value 9.9 (cal / cm ³ ) ^1/2 , 30.0 parts were charged in a flask and dissolved at a temperature of 80 ° C. Cooled and made by Sumitomo Bakelite 43 parts of Enol Resin Sumilite Resin PR-55317 (n-butanol solution with a non-volatile content of 50%), 1% of dodecylbenzenesulfonic acid as a curing catalyst with respect to 100% of the non-volatile content, and otherwise the same as in Example 1 To obtain a coating composition.

[Example 9]
Aliphatic dibasic acid dimethyl ester solvent DBE (molecular weight 159, SP value 9.8 (cal / cm ³ ) ^1/2 ) 225.1 parts, aromatic hydrocarbon solvent xylene (molecular weight 106, SP value) 8.8 (cal / cm ³ ) ^1/2 , 436.3 parts, as aliphatic monohydric alcohol solvent, BDG (molecular weight 162, SP value 10.5 (cal / cm ³ ) ^1/2 , 19.3 Parts, butyl cellosolve (molecular weight 118, SP value 9.5 (cal / cm ³ ) ^1/2 , 35.2 parts, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^1/2 , 27 .3 parts, cyclic ketone solvent cyclohexanone (molecular weight 98, SP value 9.9 (cal / cm ³ ) ^1/2 , 36.4 parts were charged into a flask and dissolved at a temperature of 80 ° C. Cooled and Sumitomo Bakelite Metacresol 43 parts of phenol resin Sumilite resin PR-55317 (n-butanol solution having a nonvolatile content of 50%), 1% of dodecylbenzenesulfonic acid as a curing catalyst was added to the nonvolatile content of 100%, and the others were the same as in Example 1. To obtain a coating composition.

[Example 10]
Aliphatic dibasic acid dimethyl ester solvent DBE (molecular weight 159, SP value 9.8 (cal / cm ³ ) ^1/2 ), 130.0 parts, aromatic hydrocarbon solvent xylene (molecular weight 106, SP value) 8.8 (cal / cm ³ ) ^1/2 , 382.8 parts, as aliphatic monohydric alcohol solvent, BDG (molecular weight 162, SP value 10.5 (cal / cm ³ ) ^1/2 , 30.0 Parts, butyl cellosolve (molecular weight 118, SP value 9.5 (cal / cm ³ ) ^1/2 , 125.8 parts, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^1/2 , 31 0.0 part, cyclic ketone solvent cyclohexanone (molecular weight 98, SP value 9.9 (cal / cm ³ ) ^1/2 , 80.0 parts were charged in a flask and dissolved at a temperature of 80 ° C. Cooled and made by Sumitomo Bakelite 43 parts of a phenolic resin Sumilite resin PR-55317 (n-butanol solution with a non-volatile content of 50%), 1% dodecylbenzenesulfonic acid as a curing catalyst was added to 100% of the non-volatile content. The coating composition was obtained in the same manner.

[Example 11]
Aliphatic dibasic acid dimethyl ester solvent DBE (molecular weight 159, SP value 9.8 (cal / cm ³ ) ^1/2 ), 180.0 parts, aromatic hydrocarbon solvent xylene (molecular weight 106, SP value) 8.8 (cal / cm ³ ) ^1/2 , 228.6 parts, as aliphatic monohydric alcohol solvent, BDG (molecular weight 162, SP value 10.5 (cal / cm ³ ) ^1/2 , 160.0 Parts, butyl cellosolve (molecular weight 118, SP value 9.5 (cal / cm ³ ) ^1/2 , 120.0 parts, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^1/2 , 61 0.0 part, cyclic ketone solvent cyclohexanone (molecular weight 98, SP value 9.9 (cal / cm ³ ) ^1/2 , 30.0 parts were charged in a flask and dissolved at a temperature of 80 ° C. Cooled and made by Sumitomo Bakelite 43 parts of phenolic resin Sumilite Resin PR-55317 (n-butanol solution with a non-volatile content of 50%), 1% of dodecylbenzenesulfonic acid as a curing catalyst with respect to 100% of non-volatile content, and otherwise, Example 1 In the same manner as above, a coating composition was obtained.

[Example 12]
Aliphatic dibasic acid dimethyl ester solvent DBE (molecular weight 159, SP value 9.8 (cal / cm ³ ) ^1/2 ) 30.0 parts, aromatic hydrocarbon solvent xylene (molecular weight 106, SP value) 8.8 (cal / cm ³ ) ^1/2 , 652.8 parts, as aliphatic monohydric alcohol solvent, BDG (molecular weight 162, SP value 10.5 (cal / cm ³ ) ^1/2 , 30.0 Parts, butyl cellosolve (molecular weight 118, SP value 9.5 (cal / cm ³ ) ^1/2 , 25.8 parts, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^1/2 , 31 0.0 part, cyclic ketone solvent cyclohexanone (molecular weight 98, SP value 9.9 (cal / cm ³ ) ^1/2 , 10.0 parts were charged in a flask and dissolved at a temperature of 80 ° C. Cooled and made by Sumitomo Bakelite 43 parts of Enol Resin Sumilite Resin PR-55317 (n-butanol solution with a non-volatile content of 50%), 1% of dodecylbenzenesulfonic acid as a curing catalyst with respect to 100% of the non-volatile content, and otherwise the same as in Example 1 To obtain a coating composition.

[Example 13]
In place of Byron GK360, polyester resin Skybon ES-500 (number average molecular weight 26000, glass transition temperature 10 ° C., SP value 9.67 (cal / cm ³ ) ^1/2 , 193.5 parts, manufactured by SK Chemical Co., Ltd. was used. Was carried out in the same manner as in Example 1 to obtain a coating composition.

[Example 14]
In place of Byron GK360, except that 193.5 parts of Toyobo polyester resin Byron GK330 (number average molecular weight 17000, glass transition temperature 16 ° C., SP value 9.03 (cal / cm ³ ) ^1/2 was used) A coating composition was obtained in the same manner as in Example 1.

[Example 15]
In place of Byron GK360, except that 193.5 parts of Toyobo polyester resin Byron GK880 (number average molecular weight 18000, glass transition temperature 84 ° C., SP value 9.74 (cal / cm ³ ) ^1/2 was used) A coating composition was obtained in the same manner as in Example 1.

[Example 16]
Instead of Byron GK360, polyester resin Skybon ES-660 (number average molecular weight 18000, glass transition temperature 71 ° C., SP value 9.45 (cal / cm ³ ) ^1/2 manufactured by SK Chemical Co., Ltd. was used except 193.5 parts. Was carried out in the same manner as in Example 1 to obtain a coating composition.

[Example 17]
Instead of Byron GK360, polyester resin Skybon ES-900 (number average molecular weight 8000, glass transition temperature 22 ° C., SP value 9.67 (cal / cm ³ ) ^1/2 manufactured by SK Chemical Co., Ltd. was used except 193.5 parts. Was carried out in the same manner as in Example 1 to obtain a coating composition.

[Example 18]
199.9 parts of Toyobo polyester resin Byron GK360 (number average molecular weight 16000, glass transition temperature 55 ° C., SP value 9.30 (cal / cm ³ ) ^1/2 ), aliphatic dibasic acid dimethyl ester as solvent Solvent DBE (molecular weight 159, SP value 9.8 (cal / cm ³ ) ^1/2 ), 250.9 parts, aromatic hydrocarbon solvent xylene (molecular weight 106, SP value 8.8 (cal / cm ³ ) ^{1 / 2} ), 305.3 parts, as aliphatic monohydric alcohol solvent, BDG (molecular weight 162, SP value 10.5 (cal / cm ³ ) ^1/2 ), 46.7 parts, butyl cellosolve (molecular weight 118, SP Value 9.5 (cal / cm ³ ) ^1/2 ), 35.2 parts, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^1/2 ), 20.9 parts, cyclic ketone Solvent cyclohexanone (molecule 98, SP value ^{9.9 (cal / cm 3) 1/2} ), was charged to the flask 120.6 parts, was dissolved at a temperature 80 ° C., then cooled to 50 ° C. or less by Sumitomo Bakelite Co., Ltd. cresol-based phenol Resin Sumilite Resin PR-55317 (n-butanol solution with a non-volatile content of 50%) 64.5 parts, 1% dodecylbenzenesulfonic acid as a curing catalyst with respect to 100% non-volatile content, polyester resin / phenol resin ratio A coating composition adjusted to a non-volatile content concentration of 21.5% on 93/7 was obtained.

[Example 19]
Polyester resin Byron GK360 (number average molecular weight 16000, glass transition temperature 55 ° C., SP value 9.30 (cal / cm ³ ) ^1/2 ) manufactured by Toyobo Co., Ltd., 172.0 parts, aliphatic dibasic acid dimethyl ester as solvent Solvent DBE (molecular weight 159, SP value 9.8 (cal / cm ³ ) ^1/2 ) 236.9 parts, aromatic hydrocarbon solvent xylene (molecular weight 106, SP value 8.8 (cal / cm ³ ) ^{1 / 2} ), 291.3 parts, BDG (molecular weight 162, SP value 10.5 (cal / cm ³ ) ^1/2 ), 46.7 parts, butyl cellosolve (molecular weight 118, SP) Value 9.5 (cal / cm ³ ) ^1/2 ), 35.2 parts, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^1/2 ), 48.6 parts, cyclic ketone Solvent cyclohexanone (molecule 98, SP value ^{9.9 (cal / cm 3) 1/2} ), was charged to the flask 120.6 parts, was dissolved at a temperature 80 ° C., then cooled to 50 ° C. or less by Sumitomo Bakelite Co., Ltd. cresol-based phenol Resin Sumilite Resin PR-55317 (n-butanol solution with a non-volatile content of 50%) 86.0 parts, 1% dodecylbenzenesulfonic acid as a curing catalyst with respect to 100% non-volatile content, polyester resin / phenol resin ratio A coating composition adjusted to a non-volatile content concentration of 21.5% at 80/20 was obtained.

[Example 20]
The same as Example 1 except that 43 parts of Sumitomo Bakelite's metacresol phenol resin Sumilite Resin PR-55893A (n-butanol solution with a non-volatile concentration of 50%) was used in place of Sumireite Resin PR-55317. To obtain a coating composition.

[Comparative Example 1]
Aliphatic dibasic acid dimethyl ester solvent DBE (molecular weight 159, SP value 9.8 (cal / cm ³ ) ^1/2 ), 140.0 parts, aromatic hydrocarbon solvent xylene (molecular weight 106, SP value) 8.8 (cal / cm ³ ) ^1/2 ), 22.8 parts, as aliphatic monohydric alcohol solvent, BDG (molecular weight 162, SP value 10.5 (cal / cm ³ ) ^1/2 ), 205 8 parts, butyl cellosolve (molecular weight 118, SP value 9.5 (cal / cm ³ ) ^1/2 ), 20.0 parts, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^{1 / 2} ), 161.0 parts, cycloketone solvent cyclohexanone (molecular weight 98, SP value 9.9 (cal / cm ³ ) ^1/2 ), 230.0 parts, except that 230.0 parts were used A composition was obtained.

[Comparative Example 2]
Aliphatic dibasic acid dimethyl ester solvent DBE (molecular weight 159, SP value 9.8 (cal / cm ³ ) ^1/2 ) 30.0 parts, aromatic hydrocarbon solvent xylene (molecular weight 106, SP value) 8.8 (cal / cm ³ ) ^1/2 ), 32.8 parts, as aliphatic monohydric alcohol solvent, BDG (molecular weight 162, SP value 10.5 (cal / cm ³ ) ^1/2 ), 375 8 parts, butyl cellosolve (molecular weight 118, SP value 9.5 (cal / cm ³ ) ^1/2 ), 20.0 parts, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^{1 / 2} ), 241.0 parts, cyclic ketone solvent cyclohexanone (molecular weight 98, SP value 9.9 (cal / cm ³ ) ^1/2 ) 80.0 parts, except that 80.0 parts were used A composition was obtained.

[Comparative Example 3]
Aromatic hydrocarbon solvent xylene (molecular weight 106, SP value 8.8 (cal / cm ³ ) ^1/2 ), 268.6 parts as a solvent, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^1/2 ), 31.0 parts, aliphatic ketone solvent methyl isobutyl ketone as other solvent (molecular weight 100.0, SP value 8.4 (cal / cm ³ ) ^1/2 ), except that 480.0 parts were used, a coating composition was obtained in the same manner as in Example 1.

[Comparative Example 4]
215.0.0 parts of Toyobo polyester resin Byron GK360 (number average molecular weight 16000, glass transition temperature 55 ° C., SP value 9.30 (cal / cm ³ ) ^1/2 ), dimethyl aliphatic dibasic acid as solvent Ester solvent DBE (molecular weight 159, SP value 9.8 (cal / cm ³ ) ^1/2 ) 258.4 parts, aromatic hydrocarbon solvent xylene (molecular weight 106, SP value 8.8 (cal / cm ³⁾ ) ^1/2 ), 312.8 parts, as aliphatic monohydric alcohol solvent, BDG (molecular weight 162, SP value 10.5 (cal / cm ³ ) ^1/2 ), 46.7 parts, butyl cellosolve (molecular weight 118) , SP value 9.5 (cal / cm ³ ) ^1/2 ), 35.2 parts, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^1/2 ), 5.8 parts, Cyclic ketone solvent cyclohexanone (min The amount 98, SP value ^{9.9 (cal / cm 3) 1/2} ), was charged to the flask 120.6 parts, was dissolved at a temperature 80 ° C., then cooled to 50 ° C. or less, dodecylbenzenesulfonic as a curing catalyst An acid was added in an amount of 1% with respect to 100% non-volatile content to obtain a coating composition in which the polyester resin / phenol resin ratio was adjusted to 100/0 and the non-volatile content concentration was 21.5%.

[Comparative Example 5]
208.6 parts of Toyobo's polyester resin Byron GK360 (number average molecular weight 16000, glass transition temperature 55 ° C., SP value 9.30 (cal / cm ³ ) ^1/2 ), aliphatic dibasic acid dimethyl ester as solvent Solvent DBE (molecular weight 159, SP value 9.8 (cal / cm ³ ) ^1/2 ) 255.2 parts, aromatic hydrocarbon solvent xylene (molecular weight 106, SP value 8.8 (cal / cm ³ ) ^{1 / 2} ), 309.6 parts, as an aliphatic monohydric alcohol solvent, BDG (molecular weight 162, SP value 10.5 (cal / cm ³ ) ^1/2 ), 46.7 parts, butyl cellosolve (molecular weight 118, SP Value 9.5 (cal / cm ³ ) ^1/2 ), 35.2 parts, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^1/2 ), 12.3 parts, cyclic ketone Solvent cyclohexanone (molecule 98, SP value ^{9.9 (cal / cm 3) 1/2} ), was charged to the flask 120.6 parts, was dissolved at a temperature 80 ° C., then cooled to 50 ° C. or less by Sumitomo Bakelite Co., Ltd. cresol-based phenol Resin Sumilite Resin PR-55317 (n-butanol solution with a non-volatile content of 50%) 12.9 parts, 1% dodecylbenzenesulfonic acid as a curing catalyst to 100% non-volatile content, polyester resin / phenol resin ratio A coating composition having a nonvolatile content concentration of 21.5% was obtained at 97/3.

[Comparative Example 6]
150.5 parts of Toyobo Polyester Resin Byron GK360 (number average molecular weight 16000, glass transition temperature 55 ° C., SP value 9.30 (cal / cm ³ ) ^1/2 ), aliphatic dibasic acid dimethyl ester as solvent Solvent DBE (molecular weight 159, SP value 9.8 (cal / cm ³ ) ^1/2 ) 226.2 parts, aromatic hydrocarbon solvent xylene (molecular weight 106, SP value 8.8 (cal / cm ³ ) ^{1 / 2} ), 280.6 parts, BDG (molecular weight 162, SP value 10.5 (cal / cm ³ ) ^1/2 ), 46.7 parts, butyl cellosolve (molecular weight 118, SP) Value 9.5 (cal / cm ³ ) ^1/2 ), 35.2 parts, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^1/2 ), 70.3 parts, cyclic ketone Solvent cyclohexanone (molecule 98, SP value ^{9.9 (cal / cm 3) 1/2} ), was charged to the flask 120.6 parts, was dissolved at a temperature 80 ° C., then cooled to 50 ° C. or less by Sumitomo Bakelite Co., Ltd. cresol-based phenol Resin Sumilite Resin PR-55317 (n-butanol solution with a non-volatile content of 50%) 129.0 parts, 1% dodecylbenzenesulfonic acid as a curing catalyst with respect to 100% non-volatile content, polyester resin / phenol resin ratio A coating composition adjusted to a non-volatile content concentration of 21.5% at 70/30 was obtained.

[Comparative Example 7]
193.5 parts of Toyobo polyester resin Byron GK360 (number average molecular weight 16000, glass transition temperature 55 ° C., SP value 9.30 (cal / cm ³ ) ^1/2 ), aliphatic dibasic acid dimethyl ester as solvent Solvent DBE (molecular weight 159, SP value 9.8 (cal / cm ³ ) ^1/2 ) 258.8 parts, aromatic hydrocarbon solvent xylene (molecular weight 106, SP value 8.8 (cal / cm ³ ) ^{1 / 2} ), 312.4 parts, BDG (molecular weight 162, SP value 10.5 (cal / cm ³ ) ^1/2 ), 46.7 parts, butyl cellosolve (molecular weight 118, SP) Value 9.5 (cal / cm ³ ) ^1/2 ), 35.2 parts, n-butanol (molecular weight 74, SP value 11.4 (cal / cm ³ ) ^1/2 ), 5.8 parts, cyclic ketone Solvent cyclohexanone (molecular weight 8, SP value ^{9.9 (cal / cm 3) 1/2} ), was charged with 120.6 parts to a flask, and dissolved at a temperature 80 ° C., then cooled to 50 ° C. or less Nippon Cytec benzoguanamine resin Cymel 14.6 (nonvolatile content> 98%) 34.6 parts, 1% dodecylbenzenesulfonic acid as a curing catalyst to 100% non-volatile content, polyester resin / benzoguanamine resin ratio 90/10, non-volatile concentration 21.5 The coating composition adjusted to% was obtained.

<Evaluation of paintability>
Using a reverse coater, the paintability was confirmed. Apply the reverse coater conditions as "peripheral speed ratio: backup roll / application roll / pickup roll = 1 / 1.27 / 0.3" so that the coating amount becomes 120 mg / dm ² at room temperature of 26 ° C. The film state was visually evaluated. The coating was performed using a sheet-like aluminum plate affixed on a backup roll as a base material. The evaluation criteria are as follows.
A: A uniform coating film is good.
○: A uniform coating film with slight unevenness. It is in practical use.
X: Unevenness and streaks occur due to only a part of the uniform coating film. Not practical.
XX: Overall streak / unevenness occurs. Not practical.

<Bending workability>
A coating composition is applied onto an aluminum plate using a bar coater, dried and cured by passing it through a duplex conveyor oven in which the temperature in the first zone is 286 ° C. and the temperature in the second zone is 326 ° C. A coated plate having a coating film thickness of 80 mg / dm ² was produced.
The obtained coated plate was cut into a size of 30 mm × 50 mm (length × width). Next, with the coating film on the outside, the sheet is folded in advance by hand so that the width of 50 mm is 20 mm and 30 mm, and two tin plates with a thickness of 0.23 mm are sandwiched between the two folded test pieces. Mr .. Next, a 1 kg metal hexahedral cuboid was completely bent from a height of 40 cm by dropping the flat surface onto the bent portion. Next, the bending tip of the test piece was immersed in a 1% strength saline solution, and the current when the metal part not immersed in the test sample saline solution and the saline solution was energized at 9.0 V for 6 seconds. The value was measured. When the processability (flexibility) of the coating film is poor, the coating film in the bent portion is cracked, the underlying metal plate is exposed, and the conductivity is increased, so that a high current value can be obtained. Evaluation criteria are shown below.
A: “Less than 20 mA”
○: “20 mA or more and less than 30 mA”
Δ: “30 mA or more and less than 40 mA”
×: “40 mA or more”

<Low-temperature bending workability>
A coated plate similar to that used for evaluation of “bending workability” was cut into a size of 30 mm × 50 mm (length × width). Next, it is immersed in water at a water temperature of 4 ° C., and after 1 hour, with the coating film facing outward in water, bent by hand so that the width of 50 mm is 20 mm and 30 mm, and then the bending tip of the test piece The part was immersed in a 1% strength saline solution, and the current value was measured when the metal part not immersed in the saline solution of the test piece and the saline solution were energized at 9.0 V for 6 seconds. When the processability (flexibility) of the coating film is poor, the coating film in the bent portion is cracked, the underlying metal plate is exposed, and the conductivity is increased, so that a high current value can be obtained. Evaluation criteria are shown below.
A: “Less than 20 mA”
○: “20 mA or more and less than 30 mA”
Δ: “30 mA or more and less than 40 mA”
×: “40 mA or more”

<Openness evaluation>
Make a coated plate similar to the one used for the evaluation of "folding workability" into a 50mm x 50mm (length x width), and use a beverage can on the painted surface to shape the shape of a general steion tab opening with a press Then, the aluminum plate was peeled off along the shape of the opening from the uncoated surface side of the coated plate, and the opening was visually determined using a microscope.
When the opening property is poor, the coating film tends to remain in the peripheral part of the opening, and the width of the film protruding into the opening becomes large. “Openness is good” means that the coating film does not protrude into the opening at all, or even if it protrudes, its protruding width is very small.
As a specific determination method, the width of the protruding coating film was measured and evaluated according to the following evaluation criteria.
○: The maximum width of the protruding coating film is 100 μm or less. It is in practical use.
Δ: The maximum width of the protruding coating film is larger than 100 μm and smaller than 200 μm. It is in practical use.
X: The maximum width of the protruding coating film is 200 μm or more. Not practical.

<Retort resistance test>
Check whether there is any abnormality in the appearance of the coating film after it was exposed to water vapor after being placed in a retort kettle and treated for 30 minutes in a water vapor atmosphere at 125 ° C. Visual judgment was made.
○: “No abnormality”
Δ: “Minor abnormality but within practical range”
X: “Abnormal (coating cloudiness and blistering). Impractical.”

<Heat resistance test>
An abnormality in the appearance of the coating film after a coated plate similar to that used for the evaluation of "folding workability" is placed in a retort kettle, immersed in hot water at 125 ° C for 30 minutes, and exposed to pressurized hot water The presence or absence of was visually determined.
○: “No abnormality”
Δ: “Minor abnormality but within practical range”
X: “Abnormal (coating cloudiness and blistering). Impractical.”

  Tables 1 to 3 show the solvent composition (expressed in weight%) and physical property evaluation results of each coating composition.

Claims (5)

Including a polyester resin (A), an organic solvent (B), and a phenol resin (C) formed by reacting m-cresol and an aldehyde ,
Organic SP value of the solvent (B) SP value (SP _b) and the polyester resin _(A) (SP _{a) is, (SP b -SP a) =} - 0.40~0.60 (cal / cm 3) 1 ^{/ 2} ,
The weight ratio of polyester resin (A) and the phenolic resin (C) is, Ri (A) / (C) = 95 / 5~75 / 25 der,
The glass transition temperature of the polyester resin (A) is 10 to 85 ° C., the number average molecular weight is 10,000 to 30,000,
The coating composition, wherein the organic solvent (B) contains an aromatic hydrocarbon, an aliphatic monohydric alcohol, an aliphatic dibasic acid dimethyl ester, and a cyclic ketone . The molecular weight of the aromatic hydrocarbon contained in the organic solvent (B) is 92 to 246, the molecular weight of the aliphatic monohydric alcohol is 60 to 190, the molecular weight of the aliphatic dibasic acid dimethyl ester is 146 to 174, and the molecular weight of the cyclic ketone is 70. The coating composition according to claim 1, wherein the coating composition is. In a total of 100% by weight of the organic solvent (B), the aromatic hydrocarbon is 25 to 85% by weight, the aliphatic monohydric alcohol is 9 to 45% by weight, the aliphatic dibasic acid dimethyl ester is 3 to 35% by weight, and The coating composition according to claim 1 or 2 , wherein the cyclic ketone is 1 to 20% by weight. Can lid on one surface of the member for can lid is covered by claims 1-3 coating composition according to any one. A coated can comprising the can lid according to claim 4 and a can body member, wherein the coated surface of the can lid is located inside the can.