JP2018172448A - Coating material, coating member and can - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating material capable of forming a coated film, which is excellent in transparency and is excellent in high workability and high corrosion property to a content of a worked part, without using a raw material derived from BPA and BADGE.SOLUTION: A coating material contains a polyester resin (A) having an acid value of 10-40 mgKOH/g, and an epoxy curing agent (B) which is a reactant of aromatic polyol other than bisphenol A and an epoxy group-containing compound. The polyester resin (A) preferably has a glass transition temperature of 20-90°C.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a paint.

  Conventionally, BPA type epoxy resin synthesized from bisphenol A (hereinafter also referred to as “BPA”) and epichlorohydrin forms a coating film with excellent steam sterilization resistance (retort resistance), processability and adhesion. As a result, it has been widely used as a coating for coating the inner and outer surfaces of cans. However, BPA was listed in 67 substances in the list of “chemical substances suspected of having endocrine disrupting action” published by the Ministry of the Environment. There has also been a need for a can coating material that does not use any raw material derived from BPA or its derivative bisphenol A diglycidyl ether (hereinafter also referred to as “BADGE”).

  In addition to flavor resistance, corrosion resistance, retort resistance, etc. that do not impair the flavor of the contents, the paint that covers the inner surface of the can, for example, a lid member with many irregularities, a drawn can that undergoes a punching process The processability to withstand a high degree of molding is required, such as an embossed can in which a concavo-convex pattern is processed on the side wall of the can body. Moreover, the corrosion resistance with respect to the content of the process part to which stress is added is requested | required.

  Patent Document 1 discloses a paint containing a hydroxyl group-containing polyester resin and a resol type phenol resin. Patent Document 2 discloses a paint containing a melamine resin mainly composed of a polyester resin having an acid value of 4 mgKOH / g or less and a benzoguanamine resin.

JP 2001-131470 A JP 2002-179996 A

  An object of the present invention is to provide a coating material that can form a coating film that does not use a raw material derived from BPA, has little coloring, has good workability, has excellent corrosion resistance, and suppresses fumes during coating.

  The paint of the present invention contains the epoxy compound (B) that does not contain a constitution derived from the polyester resin (A) having an acid value of 10 to 40 mgKOH / g, bisphenol A or bisphenol F.

  According to the present invention, a paint, a coating member, and a can that can form a coating film that does not use a BPA or BADGE-derived raw material, has little coloration, has good workability, has excellent corrosion resistance, and suppresses fume during coating. Can provide.

Schematic diagram showing the bending processability test method

Before describing the present invention, terms are defined. The polycarboxylic acid includes a compound in which a carboxyl group in the polycarboxylic acid is esterified with a monoalcohol such as methanol or ethanol, and an acid anhydride of the polycarboxylic acid.
When the above esterified compound is used as the polycarboxylic acid, the “number of carboxyl groups of the polycarboxylic acid” is “—COOH” and “—COOR” (R is an alkyl alcohol used for esterification). If it is, it is the alkyl group of the alkyl alcohol used for the esterification.)
In addition, since an acid anhydride group is generated by dehydration from two carboxyl groups, one acid anhydride group in the present invention corresponds to two carboxyl groups. For example, trimellitic anhydride is regarded as a compound having three carboxyl groups.
The content resistance property refers to the property that the coating film is not easily damaged by the contents of the can, and the main contents that affect the inner surface of the can are acidic food, salt, fish meat, and the like. Acidic foods corrode iron, the material of cans, and salt oxidizes iron. Fish meat also contains trace amounts of sulfur compounds, which react with iron and turn the can black.

  The paint of this invention contains the epoxy compound (B) which does not contain the structure derived from the polyester resin (A) whose acid value is 10-40 mgKOH / g, bisphenol A, or bisphenol F. The coating material of the present invention forms a coating layer in which the polyester resin (A) and the epoxy compound (B) are inhibited from being colored by curing. The epoxy compound (B) that does not contain a structure derived from bisphenol A or bisphenol F (does not use a raw material derived from bisphenol A or bisphenol F) can suppress defects in the coating layer because it does not contain a self-crosslinking component. For example, when it is used for coating the inner surface of a can, the content resistance is improved. In addition, since the epoxy compound (B) is less cured and shrinkage of the coating layer upon curing, the content resistance is improved when used for the above-mentioned purposes.

  The paint of the present invention is preferably used as a coating member in which a coating layer is formed by coating and curing a metal or plastic substrate. The painted member can be used by processing into a flat plate or various shapes. The painted member is preferably used for coating the inner and outer surfaces of the can.

<Polyester resin (A)>
In the present invention, the polyester resin (A) is synthesized by reacting a polyol and a polycarboxylic acid. The polyol and polycarboxylic acid do not contain a compound derived from bisphenol A or bisphenol F.

The polyol can be classified into a polyol having no alkyleneoxy group in the molecule and a polyol having an alkyleneoxy group in the molecule. The polyol having no alkyleneoxy group in the molecule includes, for example, an alicyclic diol, a diol having one primary hydroxyl group and one secondary hydroxyl group, a linear diol having 4 to 6 carbon atoms, a branched diol, Trifunctional or higher functional polyols and other polyols are preferred. The polyol having an alkyleneoxy group in the molecule is preferably, for example, an ethyleneoxy group or a propyleneoxy group as the alkyleneoxy group.
Among these polyols, alicyclic diols and diols having one primary hydroxyl group and one secondary hydroxyl group are preferable.
Polyols can be used alone or in combination of two or more.

  The alicyclic diol is, for example, a diol having a cyclohexane ring, a cyclopentane ring, or a cyclooctane ring, and the folding processability, retort resistance, and acid resistance of the coating layer are further improved.

  Examples of the alicyclic diol include 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,2-cyclopentanediol, and the like. Among these, 1,4-cyclohexanedimethanol is preferable in terms of processability.

  The alicyclic diol is preferably used in an amount of 10 to 45 mol%, more preferably 10 to 40 mol%, in a total of 100 mol% of the polyol. When an appropriate amount of the alicyclic diol is used, the folding processability, retort resistance and acid resistance of the coating layer are further improved.

  The diol having one primary hydroxyl group and one secondary hydroxyl group contributes to the improvement of the synthesis stability of the polyester resin (A). For example, when the paint contains a solvent, the solubility of the polyester resin (A) Will be improved. In addition, a diol having one primary hydroxyl group and one secondary hydroxyl group further improves the content contamination resistance and acid resistance of the coating layer.

  Examples of the diol having one primary hydroxyl group and one secondary hydroxyl group include propylene glycol, 1,2-butanediol, 1,3-butanediol, and the like. Among these, propylene glycol, 1,2-butanediol, and 1,3-butanediol, which are diols having 3 to 4 carbon atoms, are more preferable.

  The diol having one primary hydroxyl group and one secondary hydroxyl group is preferably used in an amount of 5 to 35 mol%, more preferably 5 to 30 mol%, in a total of 100 mol% of the polyol. When a suitable amount of a diol having one primary hydroxyl group and one secondary hydroxyl group is used, the content contamination resistance and acid resistance of the coating layer are further improved.

  The linear diol having 4 to 6 carbon atoms has a linear alkylene group. Examples of the linear diol having 4 to 6 carbon atoms include 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and the like.

  Non-alicyclic diols having 2 to 10 carbon atoms (excluding linear diols having 4 to 6 carbon atoms) are, for example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 2 -Methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 2-ethyl-2-butylpropanediol.

The trifunctional or higher functional polyol can make the polyester resin (A) into a branched structure.
Examples of the trifunctional or higher functional polyol include trimethylolpropane, glycerin, trimethylolethane, mannitol, sorbitol, pentaerythritol, and α-methylglucoside.

  Other polyols include, for example, pentacyclopentadecane dimethanone, 2,6-decalin dimethanol, 1,5-decalin dimethanol, 2,3-decalin dimethanol and the like as glycols having a plurality of alicyclic rings.

  Examples of the polyol having an alkyleneoxy group in the molecule include diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

Polycarboxylic acids are aromatic dibasic acids, aliphatic dibasic acids, alicyclic dibasic acids, α, β-unsaturated dibasic acids, other dibasic acids, and acids with three or more bases and their anhydrides. As well as their alkyl esters. The alkyl ester of the dibasic acid is preferably formed by a reaction with an alcohol having 1 to 3 carbon atoms.
Polycarboxylic acids can be used alone or in combination of two or more.

  Examples of the aromatic dibasic acid include terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, and biphenyldicarboxylic acid.

  Examples of the aliphatic dibasic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, and dimer acid.

  Examples of the alicyclic dibasic acid include 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, and the like.

  Examples of the α, β-unsaturated dibasic acid include fumaric acid, maleic acid, itaconic acid, citraconic acid and the like.

  Examples of other dibasic acids include 2,5-norbornene dicarboxylic acid anhydride and tetrahydrophthalic anhydride.

The acid having three or more bases can make the polyester resin (A) into a branched structure.
The acid having three or more bases is, for example, (anhydrous) trimellitic acid [trimellitic acid and trimellitic anhydride together are referred to as “(anhydrous) trimellitic acid”. The same applies below. ], (Anhydrous) pyromellitic acid, ethylene glycol bis trimellitate dianhydride, etc. are mentioned.

<Synthesis of polyester resin (A)>
The polyester resin (A) can be synthesized by a known method. The polyester resin (A) can be synthesized, for example, by subjecting a polyol and a polycarboxylic acid to a condensation reaction or a transesterification reaction in a high temperature atmosphere. In addition, when using an acid anhydride for polycarboxylic acid, an addition reaction may also occur in part. The end point of the reaction is usually determined by the acid value.

  Since the polyester resin (A) has an acid value of 10 to 40 mgKOH / g, a desired acid value can be obtained by using a polycarboxylic acid anhydride in the condensation reaction or transesterification reaction. Alternatively, after completion of the first stage reaction of the condensation reaction or transesterification reaction, a desired acid value can be obtained by adding polycarboxylic acid anhydride as the second stage reaction. When it has an acid value, adhesiveness with a base material will improve and the reactivity with an epoxy compound will improve. If the acid value is in an appropriate range, the retort resistance, bending workability, openability and acid resistance of the coating layer are improved.

  Examples of the polycarboxylic acid anhydride include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, ethylene glycol bistrimellitic dianhydride, and the like. In addition, as for the acid value of a polyester resin (A), 15-25 mgKOH / g is preferable. If the acid value is within this range, a coating film excellent in retort resistance, bending workability, openability and acid resistance can be formed.

When synthesizing the polyester resin (A), when the polycarboxylic acid does not contain an alkyl ester, the blend ratio of the polycarboxylic acid and the polyol is the number of hydroxyl groups (NB) in the polyol and the number of carboxyl groups in the polycarboxylic acid. The molar ratio with (NA) is preferably NB / NA = 1.1 to 1.5, more preferably 1.15 to 1.4.
Moreover, it is preferable that it is NB / NA = 1.1-2.4, and, as for molar ratio in case polycarboxylic acid (A) contains the alkyl ester, 1.2-2.1 are more preferable. If the ratio of NB and NA is in the above range, the resistance to contamination of contents, acid resistance and processability will be further improved.
For the synthesis of the polyester resin (A), the molecular weight can be appropriately adjusted by using monofunctional alcohol and monobasic acid in combination. In addition, the polycarboxylic acid anhydride added by the 2nd step reaction of polyester resin (A) and the said 1 basic acid are not included in calculation of said NB / NA.

  The glass transition temperature (Tg) of the polyester resin (A) is preferably 20 to 90 ° C, and more preferably 30 to 60 ° C. When the glass transition temperature is within this range, the bending workability is further improved.

  The number average molecular weight of the polyester resin (A) is preferably 5,000 to 30,000, and more preferably 10,000 to 25,000. When the number average molecular weight is within this range, the bending workability, the opening property and the acid resistance are further improved. In addition, the number average molecular weight in this invention is a value of standard polystyrene conversion by GPC (gel permeation chromatography).

  When the commercial item of a polyester resin (A) is given, for example, Unitika's Elitaire UE9885 etc. can be mentioned.

<Epoxy compound (B) that does not contain components derived from bisphenol A or bisphenol F>
In the present invention, the epoxy compound (B) that does not contain a component derived from bisphenol A or F (hereinafter referred to as epoxy compound (B)) is a curing agent for crosslinking the polyester resin, and has an epoxy group in one molecule. The compound which has 2 or more in this. The epoxy compound (B) preferably has a ring structure, and more preferably an aromatic ring.
The epoxy compound (B) is an epoxy compound that does not contain BPA in a free state and an aromatic glycidyl ether compound (for example, BADGE, glycidyl ether of bisphenol F (BFDGE), novolac epoxy). For example, BPA type epoxy resin, BPF type epoxy resin, phenol novolac type epoxy resin obtained by reacting phenol novolac resin and epichlorohydrin.

  The epoxy compound (B) was copolymerized with a monomer capable of copolymerizing glycidyl ether, glycidyl ester, glycidyl amine, linear aliphatic epoxide, alicyclic epoxide, hydantoin type epoxy, glycidyl (meth) acrylate, for example. An acrylic oligomer etc. are mentioned.

Examples of the glycidyl ether include alkylene glycol or glycidyl ether of polyalkylene glycol. Examples of this glycidyl ether of alkylene glycol or polyalkylene glycol include glycidyl ethers of glycols such as polyethylene glycol, polypropylene glycol, and butanediol.
Examples of the glycidyl ester include glycidyl ester of hexahydrophthalic acid and glycidyl ester of dimer acid.

  Examples of the glycidylamine include triglycidylaminodiphenylmethane, triglycidylaminophenol, triglycidyl isocyanurate, and the like.

  Examples of the linear aliphatic epoxide include epoxidized polybutadiene and epoxidized soybean oil. Examples of the alicyclic epoxide include 3,4-epoxy-6-methylcyclohexyl methyl carboxylate and 3,4-epoxy. Examples include cyclohexyl carboxylate.

Hydantoin type epoxy resins include, for example, diglycidyl hydantoin, glycidyl glycidoxyalkylhydantoin, and the like.
The epoxy compound (B) can be used alone or in combination of two or more.

  The blend using the acid value of the polyester resin (A) and the epoxy value of the epoxy compound (B) is preferably an equivalent ratio (A) / (B) = 0.5-2. If the equivalence ratio is in this range, it is easy to form a coating layer excellent in retort resistance and acid resistance.

  The molecular weight of the epoxy compound (B) is preferably a number average molecular weight of 300 to 2,000. When it is within the above range, the content resistance and acid resistance are further improved.

  Examples of commercially available epoxy compounds (B) include Epolite 100MF (trimethylolpropane triglycidyl ether) manufactured by Kyoei Co., Ltd. and Tetrad X (1,3-bis (N, N-glycidylaminomethyl) manufactured by Mitsubishi Gas Chemical Company, Inc. Benzene), tetrad C (1,3-bis (N, N-glycidylaminomethyl) cyclohexane), JP-100 (epoxidized polybutadiene) manufactured by Nippon Soda Co., Ltd., O-130P (epoxidized soybean oil) manufactured by ADEKA, And O-180A (epoxidized linseed oil).

A curing catalyst can be used in combination for the reaction between the polyester resin (A) and the epoxy compound (B).
Examples of the curing catalyst include ammonium salts, phosphonium salts, metal soaps, imidazoles, amines, phosphines, phosphites, Lewis acids, and the like.

The paint of the present invention can contain, as optional components, a lubricant such as wax, an additive such as a leveling agent and a plasticizer, and an organic solvent.
When wax is used, it is easy to prevent the coating layer from being damaged. 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, Teflon (registered trademark) wax, and the like Synthetic wax and the like.

  The painted member of the present invention includes a substrate and a coating layer that is a cured product of the paint of the present invention. The substrate is at least one of metal and plastic. Moreover, after forming a coating layer on a base material, a coating member can be produced by laminating plastic on the coating layer. Alternatively, paint is formed on the base material to form a coating, and then a plastic is laminated on the coating, followed by heat curing to produce a coating member by curing the coating and forming a coating layer. Can do.

  The paint of the present invention can be used regardless of its inner and outer surfaces in terms of can applications, and is preferably used as an inner paint for cans taking advantage of its high workability, especially on the inner surface of can lid members. It is preferable to use it. In addition, it cannot be overemphasized that the coating material of this invention can be used for the outer surface of a can including the outer surface of the member for can lids.

The can lid of the present invention includes a base material and a coating layer that is a cured product of the paint of the present invention.
The substrate is at least one of metal and plastic.

  The can of the present invention includes a base material, a can lid, and a can body member, and has a coating layer that is a cured product of the paint of the present invention on at least one of the can lid and the can body member. The substrate is at least one of metal and plastic. Moreover, it is preferable that the can lid | cover of this invention has the said coating layer.

  The can of this invention can be used also for the use which accommodates non-food, such as machine oil, engine oil, a coating material, ink, for example.

  The food and beverage can according to the present invention is a can including a beverage can and a food can, and can contain a beverage or a food other than a beverage as a content. And it is preferable to provide the can lid | cover which has a coating layer formed from the coating material of this invention. In the food and beverage can of the present invention, the coating layer may be formed not on the can lid but on the can body member. As for the can for food and drink, the content is food and drink, and the other structure is the same as that of the said ring.

  The metal is preferably a metal plate such as aluminum, tin-plated steel plate, chrome-treated steel plate, or nickel-treated steel plate. The thickness of the metal is about 150 to 400 μm.

  The plastic is preferably polyolefin, polyester or the like, more preferably polyethylene terephthalate. The thickness of the plastic is about 10 to 100 μm.

  The coating layer is formed by coating a metal by a known method and heating at about 150 to 300 ° C. for about 10 seconds to 15 minutes. When plastic is used for the base material, damage to the base material can be suppressed when the temperature is 60 ° C. to 120 ° C. and the drying time is about 1 minute.

  Coating is preferably spray coating such as air spray, airless spray, and electrostatic spray, roll coater coating, immersion coating, and electrodeposition coating.

  The thickness of the coating layer is about 1 to 20 μm.

  The food and beverage can of the present invention includes a can lid, a can body member, and a coating layer. Food and drink cans are generally two-piece cans composed of one can lid and one can body member, and three-piece cans composed of two upper and lower can lids and one can body member.

  Among the contents of the can for food and drink, examples of the beverage include drinking water, soft drinks, coffee, tea, beer, Chuhai, sake, whiskey, and whiskey water split. Examples of foods other than beverages include fish meat, livestock meat, vegetables, fruits, oils and sauces, and processed foods thereof.

  Hereinafter, the present invention will be described more specifically with reference to examples. In the examples, “parts” represents “parts by weight” and “%” represents “% by weight” unless otherwise specified. “Mn” represents the number average molecular weight, and “Mw” represents the weight average molecular weight.

(Measurement of molecular weight)
The number average molecular weight and the weight average molecular weight were measured using a high-speed GPC apparatus 8020 series (tetrahydrofuran solvent, column temperature 40 ° C., polystyrene standard) manufactured by Tosoh Corporation. Specifically, it is a measured value obtained by connecting four columns of G1000HXL, G2000HXL, G3000HXL, and G4000HXL manufactured by Tosoh in series and measuring at a flow rate of 1.0 ml / min.

(Measurement of glass transition temperature)
It measured with the temperature increase rate of 10 degree-C / min using the differential scanning calorimeter (DSC) ("DSC6220" Seiko Instruments make).

(Measurement conditions of acid value)
0.2 g of the polyester resin was dissolved in 20 ml of THF (tetrahydrofuran) and titrated with a 0.1N KOH ethanol solution to obtain the acid value (mgKOH / g) of the polyester resin.

Production Example of Polyester Resin A [Production Example A (Direct Polymerization Method)]
59.0 parts of terephthalic acid, 236.0 parts of isophthalic acid, 51.2 parts of 1,4-cyclohexanedimethanol, 33.8 parts of propylene glycol, 120.0 parts of 1,4-butanediol, 0.1% of titanium butoxide. 01 parts were charged into a polymerization reactor, and the temperature was gradually raised from 25 ° C. to 250 ° C. over 6 hours in a nitrogen atmosphere to carry out an esterification reaction. Next, the pressure in the polymerization reactor was reduced to 5 mmHg or less over 30 minutes, and the polymerization reaction was carried out at 250 ° C. for 2 hours while maintaining the reduced pressure state. Then, internal temperature was cooled to 200 degreeC under nitrogen stream, 10.0 parts of trimellitic anhydride was added to this, and reaction was performed for 2 hours. Next, cooling was performed to obtain a polyester resin. The obtained polyester resin was adjusted with a mixed solvent of Flexisolv DBE esters (manufactured by Invista) / xylene = 1/1 (weight ratio) so as to have a nonvolatile content concentration of 40% to obtain a resin varnish. In Table 1, the weight parts of each monomer used in the above polymerization are expressed in molar ratio.

[Production Example B (transesterification method)]
Charge 96.7 parts of dimethyl terephthalic acid, 36.6 parts of propylene glycol, 89.7 parts of 1,4-butanediol, 0.1 part of zinc acetate and 0.01 part of titanium butoxide, and gradually rise to 220 ° C. Warmed and transesterified. After distilling the theoretical amount of methanol, 193.1 parts of isophthalic acid and 83.8 parts of 1,4-cyclohexanedimethanol were added and the temperature was gradually raised to 250 ° C. over 3 hours to continue the esterification reaction. . Next, the pressure was reduced to 5 mmHg or less over 30 minutes, and the polymerization reaction was carried out at 250 ° C. for 3 hours while maintaining the reduced pressure state. Thereafter, the internal temperature was cooled to 200 ° C. under a nitrogen stream, and 6.3 parts of trimellitic anhydride was added thereto and reacted for 2 hours. Next, cooling was performed to obtain a polyester resin. The obtained polyester resin was adjusted with a mixed solvent of Flexisolv DBE esters (manufactured by Invista) / xylene = 1/1 (weight ratio) so as to have a nonvolatile content concentration of 40% to obtain a resin varnish.

[Production Examples C to F, Comparative Production Examples G to H]
A polyester resin was synthesized by carrying out in the same manner as in Production Example A except that the raw material in Production Example A was replaced with the raw material shown in Table 1, and the resin varnishes of Production Examples C to F and Comparative Production Examples GH were used. Obtained. In Table 1, the weight parts of each monomer used in the above polymerization are expressed in molar ratio.

[Example 1]
477.8 parts of polyester resin varnish of Production Example A, 23.9 parts of tetrad X (1,3-bis (N, N-glycidylaminomethyl) benzene, manufactured by Mitsubishi Gas Co.) as a curing agent, Flexisolv DBE esters as a solvent (Invista) 153.4 parts, 216.1 parts of xylene, 23.6 parts of butyl cellosolve, 28.4 parts of n-butanol and 76.8 parts of cyclohexanone were mixed to obtain a paint having a nonvolatile content of 21.5%. .

[Examples 2 to 10, Comparative Examples 1 and 2]
Using polyester resin varnishes obtained in Production Examples C to F and Comparative Production Examples G to H, except that the composition shown in Table 2 below is used, the same procedure is carried out, and Example 2 having a nonvolatile content of 21.5%, respectively. To 10 and Comparative Examples 1 and 2 were obtained.

[Comparative Example 3]
Epoxy resin JER1009 (Mitsubishi Chemical Corporation, nonvolatile content 40% (Anon / Swazole 1000 / methoxybutyl acetate = 2/1/1)) 525.0 parts, phenol resin PHENODUR PR897 (Ornex Corp., nonvolatile content) 169.8 Part, 85% phosphoric acid 0.71 part, as solvent, 152.2 parts of anone and 1000152.2 parts of Swazol were mixed to obtain a paint having a nonvolatile content of 30.0%.

[Production of test panels for evaluation with painted plates]
The obtained paint was applied on an aluminum plate having a thickness of 0.26 mm with a bar coater so that the dry weight was 80 mg / dm ^2, and then the temperature in the first zone was 286 ° C. and the temperature in the second zone was 326 ° C. The test panel provided with the coating film (coating layer) was produced by passing through a double-type conveyor oven and drying and curing in 24 seconds. The obtained test panel was evaluated as follows.

<Appearance of coating film>
The test panel was visually observed for coloration.
A: Transparent (good)
△: Slightly orange (cannot be used)

<Bending workability>
The test panel was prepared in a size of 30 mm in width and 50 mm in length. Next, in a 23 ° C. environment, FIG.
As shown in (A) of Fig. 3, with the coating film of the test panel 1 on the outside, a diameter of 3 at a position of 30 mm in length.
Attach a round bar 2 mm. And then. Test panel 2 along round bar 2 as shown in FIG.
Was folded in half to prepare a test piece 3. A thickness of 0.26 between the test pieces 3 folded in half.
2 mm aluminum plate (omitted) scissors, 15cm wide x 5cm high as shown in Fig. 1 (c)
A 1 kg weight 4 having a rectangular parallelepiped shape with a depth of 5 cm was dropped from a height of 40 cm onto a bent portion of the test piece 3 and completely bent.
Next, after removing the aluminum plate, the bent portion of the test piece 3 was immersed in a saline solution having a concentration of 1%. Subsequently, between the metal part of the plane part of the test piece 3 which is not immersed in the saline solution and the saline solution, a current was measured for 6.0 V × 6 seconds. When the processability of the coating film is poor, the coating film in the bent part is cracked, the underlying metal plate is exposed, and the conductivity increases,
The current value becomes high.
A: Less than 5 mA (good)
○: 5 mA or more and less than 10 mA (usable)
Δ: 10 mA or more and less than 20 mA (unusable)
X: 20 mA or more (defect)

<Retort resistance test>
A test panel prepared in a size of 10 cm in length and 100 cm in width was immersed in water in a retort kettle, subjected to retort treatment at 125 ° C. for 30 minutes, and the appearance of the coating film was visually evaluated. Regarding the retort treatment, the ratio of the area of the test panel (that is, the area of the coating film) to water was 100 mL of water with respect to 100 cm ² of the test panel.
A: No change from the coating film before retort treatment (good)
○: The coating film is very thin and white (can be used)
Δ: Slightly whitened coating (cannot be used)
X: The coating film is markedly whitened (defect)

<Content contamination test>
The water after retort treatment used for the evaluation of the “retort resistance test” was analyzed using “TOC-L CPH” (manufactured by Shimadzu Corporation), and the total organic carbon (TOC) amount was measured. In addition, the amount of TOC is the total amount of organic matter present in water expressed as the amount of carbon in the organic matter.
A: Carbon content is less than 1 ppm (good)
○: Carbon content is 1 ppm or more and less than 1.5 ppm (can be used)
Δ: Carbon content is 1.5 ppm or more and less than 2 ppm (cannot be used)
X: Carbon amount is 2 ppm or more (defect)

<Bisphenol A dissolution test>
In the same manner as in the above “retort resistance test”, 1000 mL of water after performing the retort treatment was distilled off under reduced pressure, and a solution obtained by dissolving the dried solid in 2 mL of tetrohydrofuran (concentration 500 times) was subjected to reverse phase HPLC (CHROMASTER). (Manufactured by Hitachi, Ltd.), and 30 μL was injected, and the fluorescence intensity at 310 nm was measured.
A: No detection (good)
×: 1ppb or more (cannot be used)

<Fume test>
The obtained paint was applied on a 100 cm ² aluminum plate test panel having a thickness of 0.26 mm with a bar coater so that the dry weight was 80 mg / dm ² , so that the coating film was on the 220 ° C. hot plate. Further, a 100 cm ² tin plate was set on the upper side of the coating film using a jig so that the distance from the aluminum plate was 1 cm. For 2 minutes after setting, fumes generated from the coating film were adhered to the tin plate, and then the test panel was removed. Next, the test panel immediately after coating was performed 30 times in total in the same manner as above without changing the tin plate, and the fumes were adhered to the tin plate. Thereafter, the tin plate was removed and dried by heating at 120 ° C. for 10 minutes, and the weight of the deposit on the tin plate was evaluated as the amount of fume. The evaluation criteria are shown below.
A: Fume amount is less than 3 mg (good)
○: Fume amount is 3mg or more and less than 5mg (can be used)
Δ: Fume amount is 5 mg or more and less than 10 mg (unusable)
×: Fume amount is 10 mg or more (defect)

<Formaldehyde dissolution test>
A sample was prepared by mixing 10 g of water after retort treatment and 10 g of acetylacetone indicator after performing the retort treatment in the same manner as in the “retort resistance test”, and the sample was heated in a 65 ° C. constant temperature bath for 10 minutes. Thereafter, the absorbance at 413 nm of this sample was measured with a new spectrophotometer to evaluate the elution amount of formaldehyde.
A: Elution amount is less than 0.01 ppm (good)
○: Elution amount is 0.01 ppm or more and less than 0.2 ppm (can be used)
Δ: Elution amount is 0.2 ppm or more and less than 0.4 ppm (unusable)
×: Elution amount is 0.4 ppm or more (defect)

[Production of test panel for secondary processing evaluation]
The outer surface coating is 50 mg / dm ^{2 on the} surface opposite to the inner surface coating so that the dry weight is 80 mg / dm ² on the 0.26 mm thick aluminum plate. And then dried and cured by passing it through a double-type conveyor oven with the temperature of the first zone being 286 ° C and the temperature of the second zone being 326 ° C in 24 seconds. A panel was produced. The obtained test panel was evaluated as follows.

<Openness test>
A test panel was prepared in a size of 50 mm long × 50 mm wide. Using a press machine, a can was formed on the painted surface of the test panel using a beverage can in the shape of a common steion tub opening to produce a can-lid sample. Next, the aluminum plate was peeled off along the shape of the opening from the surface of the sample where the coating layer was not formed, and the opening was magnified with a microscope and visually judged. 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.
A: The maximum width of the protruding coating film is less than 100 μm (good)
○: The maximum width of the protruding coating is 100 μm or more and less than 200 μm (can be used)
Δ: The maximum width of the protruding coating film is 200 μm or more and less than 400 μm (unusable)
X: The maximum width of the protruding coating film is 400 μm or more (defect)

<Acid resistance test>
A 350g DI can (aluminum can) was filled with 345g of an aqueous solution of about pH 2 containing 2% by weight of citric acid and 1% by weight of sodium chloride, and then a can-lid sample prepared in the same manner as in the "opening test" was wrapped with a lid. Processed and sealed. The obtained sample can was subjected to a retort treatment at 125 ° C. for 30 minutes in a retort kettle, and then stored at 37 ° C. for 1 week, and then the can lid was cut from the sample can and the inner surface was observed. The observation was performed using a stereomicroscope and a metallographic microscope, and the corrosion resistance was evaluated in terms of acid resistance in terms of the corrosion points on the inner surface of the lid and the presence or absence of perforations.
A: No abnormality on the inner surface of the lid (good)
○: There was slight rust on the processed part on the inner surface of the lid (can be used)
Δ: Clear rust was present on the inner surface of the lid (unusable)
X: Rust occurred on the entire inner surface of the lid (defect)

  Table 2 shows the physical property evaluation results of each paint. The paint shows the blending ratio of the polyester resin and the curing agent in weight ratio.

1 Test panel 2 Round bar 3 Test piece 4 Weight

Claims (7)

  The coating material containing the epoxy resin (B) which does not contain the structure derived from the polyester resin (A) whose acid value is 10-40 mgKOH / g, bisphenol A or bisphenol F.   The coating material of Claim 1 whose glass transition temperature of a polyester resin (A) is 20-90 degreeC.   The coating material of Claim 1 or Claim 2 whose number average molecular weights of a polyester resin (A) are 5000-30000.   The coating material of any one of Claims 1-3 whose number average molecular weights of an epoxy compound (B) are 300-2000.   The polyester resin (A) is a coating material according to any one of claims 1 to 4, which is a reaction product of a polyol containing an alicyclic diol and a linear diol and a polybasic acid.   The coating member provided with the base material and the coating layer which is a hardened | cured material of the coating material of any one of Claims 1-5.   A can comprising a substrate, a can lid having a coating layer that is a cured product of the paint according to any one of claims 1 to 5, and a can body member.

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