JP6932069B2 - Resin composition, paint, metal can inner surface paint - Google Patents

Description

The present invention relates to resin compositions, paints, and metal can inner surface paints having excellent solvent resistance and corrosion resistance.

Metal cans and metal containers are widely used as packaging containers for filling foods, beverages, cosmetics, chemicals and the like. A protective coating film is provided on the inner surface side of the metal can to prevent metal from elution into the contents and to prevent corrosion of the can due to the contents. Various paint compositions for providing such a protective coating film are known according to the purpose thereof, and when packaging cosmetics, chemicals, etc., amideimide resin-based or epoxy having excellent solvent resistance and corrosion resistance. Resin-based coating compositions are used (References 1 and 2).

Amidoimide resin-based paints are superior in solvent resistance and corrosion resistance to epoxy resin-based paints, but in general, the solvents that can dissolve amideimide resins are N-methylpyrrolidone (NMP) and N, N-dimethylacetamide (DMAc). , N, N-Dimethylformamide and other amide solvents, and some solvents such as γ-butyrolactone (GBL). Amide solvents have been reported to be reproductive toxic, and some are REACH regulated substances enacted by the European Union. In addition, these solvents are also concerned about skin irritation.

Japanese Unexamined Patent Publication No. 2-067374 Japanese Unexamined Patent Publication No. 7-145345

Due to such concerns, amide imide resins that are soluble in non-amide solvents have been studied in recent years, but when trying to ensure solubility in non-amide solvents, solvent resistance, which is a characteristic of amide imide resin paints, and Corrosion resistance may decrease.
The present invention has been made in view of such circumstances, and an amide imide resin-based resin capable of obtaining a cured coating film having excellent solvent resistance and corrosion resistance even when an amide-based solvent such as NMP is not used. It is an object of the present invention to provide a composition, a paint, and a paint on the inner surface of a metal can.

The present invention contains a urethane-modified amideimide resin, a silane coupling agent containing an epoxy group or a methacryl group, and an alkoxy group, and a solvent, and the content of the silane coupling agent is 100 parts by mass of the urethane-modified amideimide resin. On the other hand, the present invention relates to a resin composition having 1 part by mass or more and 45 parts by mass or less.

The resin composition, coating material, and metal can inner surface coating material of the present invention include amide-based solvents such as N-methylpyrrolidone (NMP), N, N-dimethylacetamide (DMAc), N, N-dimethylformamide, and γ-butyrolactone (γ-butyrolactone). Even when GBL) is not used, it can be stably stored, and a cured coating film having excellent solvent resistance and corrosion resistance can be obtained.

<Resin composition>
The resin composition of the present invention contains a urethane-modified amideimide resin, a silane coupling agent containing an epoxy group or a methacryl group, an alkoxy group, and a solvent. Hereinafter, the resin composition of the present invention will be described in detail.

(Urethane modified amidoimide resin)
The urethane-modified amideimide resin used in the resin composition of the present invention is used for the reaction of the diol compound and the diisocyanate compound with the amideimide moiety derived from the reaction of the trivalent aromatic carboxylic acid derivative and the diisocyanate compound in one molecule. It is a resin having a urethane moiety from which it is derived. Since such an amide-imide resin dissolves in a non-amide solvent, for example, cyclohexanone or cyclopentanone, the resin composition does not contain an amide solvent such as NMP.

Examples of the trivalent aromatic carboxylic acid derivative used for adjusting the amidimide moiety include trimellitic acid and trimellitic acid anhydride, and these can be used alone or in combination. It is preferable to use trimellitic acid anhydride.

Examples of the diisocyanate compound used for adjusting the amidimide moiety include diphenylmethane-2,4'-diisocyanate, 3,2'-dimethyldiphenylmethane-2,4'-diisocyanate, and 3,3'-dimethyldiphenylmethane-2,4'-diisocyanate. , 4,2'-dimethyldiphenylmethane-2,4'-diisocyanate, 4,3'-dimethyldiphenylmethane-2,4'-diisocyanate, 5,2'-dimethyldiphenylmethane-2,4'-diisocyanate, 5,3' -Dimethyldiphenylmethane-2,4'-diisocyanate, 6,2'-dimethyldiphenylmethane-2,4'-diisocyanate, 6,3'-dimethyldiphenylmethane-2,4'-diisocyanate, 3,2'-diethyldiphenylmethane-2 , 4'-Diisocyanate, 3,3'-diethyldiphenylmethane-2,4'-diisocyanate, 4,2'-diethyldiphenylmethane-2,4'-diisocyanate, 4,3'-diethyldiphenylmethane-2,4'-diisocyanate , 5,2'-diethyldiphenylmethane-2,4'-diisocyanate, 5,3'-diethyldiphenylmethane-2,4'-diisocyanate, 6,2'-diethyldiphenylmethane-2,4'-diisocyanate, 6,3' -Diethyldiphenylmethane-2,4'-diisocyanate, 3,2'-dimethoxydiphenylmethane-2,4'-diisocyanate, 3,3'-dimethoxydiphenylmethane-2,4'-diisocyanate, 4,2'-dimethoxydiphenylmethane-2 , 4'-diisocyanate, 4,3'-dimethoxydiphenylmethane-2,4'-diisocyanate, 5,2'-dimethoxydiphenylmethane-2,4'-diisocyanate, 5,3'-dimethoxydiphenylmethane-2,4'-diisocyanate , 6,2'-dimethoxydiphenylmethane-2,4'-diisocyanate, 6,3'-dimethoxydiphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-3,3'-diisocyanate, diphenylmethane -3, 4'-diisocyanate, diphenyl ether-4,4'-diisocyanate, benzophenone-4,4'-diisocyanate, diphenylsulfone-4,4'-diisocyanate, trilen-2,4-diisocyanate, trilen-2,6- Di Isocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, naphthalene-2,6-diisocyanate, 4,4'-[2,2 bis (4-phenoxyphenyl) propane] diisocyanate, 3,3'-dimethylbiphenyl- 4,4'-diisocyanate, 2,2'-dimethylbiphenyl-4,4'-diisocyanate, 3,3'-diethylbiphenyl-4,4'-diisocyanate, 2,2'-diethylbiphenyl-4,4'- Aromatic diisocyanates such as diisocyanates, 3,3'-dimethoxybiphenyl-4,4'-diisocyanates, 3,3'-diethoxybiphenyl-4,4'-diisocyanates,

Aliphatic diisocyanates such as hexamethylene diisocyanate and lysine diisocyanate,
Examples thereof include alicyclic diisocyanates such as isophorone diisocyanate, cyclohexane diisocyanate, and dicyclohexylmethane diisocyanate, and these can be used alone or in combination of two or more.
From the viewpoint of the balance of impact resistance, processability and corrosion resistance, it is preferable to use aromatic diisocyanate, and 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, dimethylbiphenyl diisocyanate and the like are preferably used.

If the content of the amideimide moiety in the urethane-modified amideimide resin is too small, the solubility in a non-amide solvent is excellent, but the polymerization reaction is difficult to proceed, and the solvent resistance and corrosion resistance of the coating film may be lowered. When the total constituent components of the urethane-modified amideimide resin for this purpose are 100 mol%, the content of the amideimide moiety is preferably 30 mol% or more, more preferably 35 mol% or more, and 40 mol% or more. Is more preferable. Further, if the content of the amidimide moiety is too large, it becomes difficult to dissolve in a non-amide solvent, and the storage stability of the non-amide solvent-based paint may decrease. Therefore, the content may be 90 mol% or less. It is more preferably 85 mol% or less, and even more preferably 80 mol% or less.

Examples of the diol compound used for adjusting the urethane moiety include polyalkylene glycols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, poly (neopentyl glycol / tetramethylene glycol), polyalkylene oxide adducts of bisphenol, and tricyclode. Examples thereof include candimethanol, 9,9-bis (hydroxyalkoxyphenyl) fluorene, and the like, and one type alone or two or more types can be used in combination.

As the polyalkylene glycol, those having a number average molecular weight of 500 or more and 3000 or less are preferable, and those having a number average molecular weight of 800 or more and 2000 or less are more preferable. In particular, it is preferable to use polytetramethylene glycol.

The polyalkylene oxide used for preparing the polyalkylene oxide adduct of bisphenol is not particularly limited, and examples thereof include polyethylene oxide, polypropylene oxide, and polytetramethylene oxide. When a polyalkylene oxide adduct of bisphenol is used as the diol compound used for adjusting the urethane moiety, it is preferable to use one having a number average molecular weight of 200 or more and 2000 or less.

As the diisocyanate compound used for adjusting the urethane moiety, the same diisocyanate compound as that used for adjusting the amidoimide moiety described above can be used alone or in combination of two or more. It is preferable to use aromatic diisocyanate.

The urethane moiety in the urethane-modified amideimide resin is a polyalkylene oxide adduct of bisphenol, tricyclodecanedimethanol, from the viewpoint of improving the solubility in non-amide solvents such as cyclohexanone and cyclopentanone without impairing the characteristics of the amideimide resin. It preferably contains a urethane moiety derived from the reaction of at least one selected from the group consisting of 9,9-bis (hydroxyalkoxyphenyl) fluorene with an aromatic diisocyanate. At least one selected from the group consisting of a polyalkylene oxide adduct of bisphenol, tricyclodecanedimethanol, and 9,9-bis (hydroxyalkoxyphenyl) fluorene when all the constituents of the urethane-modified amidimide resin are 100 mol%. The content of the urethane moiety derived from the reaction with the aromatic diisocyanate is preferably 10 mol% or more, more preferably 15 mol% or more, still more preferably 20 mol% or more.

Further, in order to suppress deterioration of heat resistance, corrosion resistance, and abrasion resistance of the coating film, a polyalkylene oxide adduct of bisphenol and tricyclodecanedimethanol when all the constituents of the urethane-modified amideimide resin are 100 mol%. The content of the urethane moiety derived from the reaction of at least one selected from the group consisting of 9,9-bis (hydroxyalkoxyphenyl) fluorene with aromatic diisocyanate is preferably 70 mol% or less, preferably 65 mol%. It is more preferably less than or equal to 60 mol% or less.

By introducing a urethane moiety derived from the reaction between polyalkylene glycol and diisocyanate into the urethane-modified amideimide resin, the solubility in a non-amide solvent can be improved, and the flexibility of the cured coating film can be improved. Can be made to.
When polyalkylene glycol is used for adjusting the urethane moiety, the content of the urethane moiety derived from the reaction between the polyalkylene glycol and the diisocyanate compound is 100 mol% when all the constituents of the urethane-modified amideimide resin are 100 mol%. It is preferably 50 mol% or less, more preferably 40 mol% or less, and even more preferably 30 mol% or less.

The urethane-modified amideimide resin used in the resin composition of the present invention is an imide derived from the reaction of a tetravalent carboxylic acid derivative and a diisocyanate compound in addition to the above-mentioned amideimide moiety and urethane moiety as long as the desired performance is not impaired. The site may be introduced.

Examples of the tetravalent carboxylic acid used for adjusting the imide moiety include aromatic polyvalent carboxylic acid, aliphatic polyvalent carboxylic acid, alicyclic polyvalent carboxylic acid, and acid anhydrides and acid dianhydrides thereof. It can be used alone or in combination of two or more.

Examples of the tetravalent aromatic carboxylic acid derivative include pyromellitic dianhydride, ethylene glycol bisamhydrotrimethylate, propylene glycol bisuanhydrotrimerite, 1,4-butanediol bisamhydrotrimerite, and hexa. Alkylene glycol bisanhydrotrimeritate, such as methylene glycol bisanhydrotrimerite, polyethylene glycol bisanhydrotrimerite, polypropylene glycol bisanhydrotrimerite, 3,3', 4,4'-benzophenonetetracarboxylic Acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, 1,2,5,6-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic Acid dianhydride, 2,3,5,6-pyridinetetracarboxylic acid dianhydride, 3,4,9,10-perylenetetracarboxylic acid dianhydride, 3,3', 4,4'-diphenylsulfonetetra Carboxyl dianhydride, m-terphenyl-3,3', 4,4'-tetracarboxylic hydride, 4,4'-oxydiphthalic hydride, 1,1,1,3,3,3 -Hexafluoro-2,2-bis (2,3- or 3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3- or 3,4-dicarboxyphenyl) propane dianhydride 2,2-Bis [4- (2,3- or 3,4-dicarboxyphenoxy) phenyl] propane dianhydride, 1,1,1,3,3,3-hexafluoro-2,2- Bis [4- (2,3- or 3,4-dicarboxyphenoxy) phenyl] Propane dianhydride, 1,3-bis (3,4-dicarboxyphenyl) -1,1,3,3-tetramethyl Disiloxane dianhydride and the like can be mentioned.

Examples of the tetravalent aliphatic polycarboxylic acid derivative or alicyclic polycarboxylic acid derivative include butane-1,2,3,4-tetracarboxylic dianhydride and pentane-1,2,4,5-tetracarboxylic acid. Dianhide, cyclobutanetetracarboxylic dianhydride, hexahydropyrimellitic dianhydride, cyclohexa-1-ene-2,3,5,6-tetracarboxylic dianhydride, 3-ethylcyclohexa-1- En-3- (1,2), 5,6-tetracarboxylic dianhydride, 1-methyl-3-ethylcyclohexane-3- (1,2), 5,6-tetracarboxylic dianhydride, 1 -Methyl-3-ethylcyclohexa-1-ene-3- (1,2), 5,6-tetracarboxylic dianhydride, 1-ethylcyclohexane-1- (1,2), 3,4-tetra Carcarboxylic dianhydride, 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic dianhydride, 1,3-dipropylcyclohexane-1- (2,3), 3- (2) , 3) -Tetracarboxylic dianhydride, dicyclohexyl-3,4,3', 4'-tetracarboxylic dianhydride, bicyclo [2.2.1] heptane-2,3,5,6-tetracarboxylic Acid dianhydride, 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic dianhydride, 1,3-dipropylcyclohexane-1- (2,3), 3- (2, 3) -Tetracarboxylic dianhydride, dicyclohexyl-3,4,3', 4'-tetracarboxylic dianhydride, bicyclo [2.2.1] heptane-2,3,5,6-tetracarboxylic acid Dihydride, bicyclo [2.2.2] octane-2,3,5,6-tetracarboxylic dianhydride, bicyclo [2.2.2] octo-7-ene-2,3,5,6 -Examples include tetracarboxylic dianhydride and hexahydrotrimeric dianhydride.

Considering heat resistance, adhesion to metals, solubility in cyclohexanone and cyclopentanone, cost, etc., pyromellitic dianhydride, ethylene glycol bisuanhydrotrimeritate, 3,3', 4, 4'-benzophenonetetracarboxylic dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride are preferable, and ethylene glycol bisanehydrotrimeritate is more preferable among them.

As the diisocyanate compound used for adjusting the imide moiety, the same diisocyanate compound as that used for adjusting the amide imide moiety described above can be used alone or in combination of two or more. It is preferable to use an aromatic diisocyanate, and it is more preferable to use only an aromatic diisocyanate.

If the content of the imide moiety is too large, it becomes difficult to dissolve in the non-amide solvent, and the storage stability of the non-amide solvent-based paint may decrease. When all the constituents of the urethane-modified amideimide resin for this purpose are 100 mol%, the content of the amideimide moiety is preferably 60 mol% or less, more preferably 50 mol% or less, and 40 mol% or less. Is more preferable.

In addition to the above-mentioned amidimide moiety, urethane moiety, and imide moiety, the urethane-modified amideimide resin is further copolymerized with aliphatic, alicyclic, and aromatic polycarboxylic acids as necessary within a range that does not impair the desired performance. It may be a thing.
Examples of the aliphatic dicarboxylic acid include succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedioic acid, dodecanedioic acid, eikosandioic acid, 2-methylsuccinic acid, 2-methyladipic acid, 3 -Methyladipic acid, 3-methylpentanedicarboxylic acid, 2-methyloctanedicarboxylic acid, 3,8-dimethyldecandicarboxylic acid, 3,7-dimethyldecandicarboxylic acid, 9,12-dimethyleicosanedioic acid, fumaric acid, Examples thereof include maleic acid, dimeric acid and hydrogenated dimeric acid.

Examples of the alicyclic dicarboxylic acid include 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, and 4,4'-dicyclohexyldicarboxylic acid. Examples of the aromatic dicarboxylic acid include isophthalic acid, terephthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, oxydibenzoic acid, stillbenzicarboxylic acid and the like. These dicarboxylic acids may be used alone or in combination of two or more. Considering heat resistance, adhesion, solubility, cost, etc., 1,4-cyclohexanedicarboxylic acid and isophthalic acid are preferable.

The urethane-modified amideimide resin may be obtained by copolymerizing other flexible components in addition to the above-mentioned amideimide moiety, urethane moiety, and imide moiety, if necessary, as long as the desired performance is not impaired. .. For example, aliphatic / aromatic polyesterdiols (manufactured by Toyo Spinning Co., Ltd., trade name VYLON (registered trademark) 220, etc.), aliphatic / aromatic polycarbonate diols (manufactured by Daicel Chemical Industry Co., Ltd., trade name PLACCEL) Registered trademark) -CD220, manufactured by Kuraray Co., Ltd., trade name C-2015N, etc.), polycaprolactone diols (manufactured by Daicel Chemical Industry Co., Ltd., trade name PLACCEL (registered trademark) -220, etc.), carboxy-modified acrylonitrile butadiene rubber Species (manufactured by Ube Kosan Co., Ltd., trade name HyproCTBN 1300 × 13, etc.), polysiloxane derivatives such as polydimethylsiloxane diol, polymethylphenylsiloxane diol, and carboxy-modified polydimethylsiloxanes.

When extremely high solvent resistance and corrosion resistance are required, it is preferable to use a urethane-modified amideimide resin that does not contain an amideimide moiety, a urethane moiety, or a moiety other than the imide moiety.

The elastic modulus of the urethane-modified amidimide resin used in the present invention is preferably 2500 MPa or less.

The logarithmic viscosity of the urethane-modified amidimide resin used in the present invention is preferably 0.1 dl / g or more, and more preferably 0.2 dl / g or more. Further, it is preferably 2.0 dl / g or less, and more preferably 1.5 dl / g or less. The logarithmic viscosity is defined as (Inηrel) / C, where In is the natural logarithm, ηrel is the viscosity ratio of the solution to the pure solvent by measuring the solvent drop time, and C is the concentration of the solution (g / dl).

The glass transition temperature of the urethane-modified amidimide resin used in the present invention is preferably 200 ° C. or higher, more preferably 210 ° C. or higher. The glass transition temperature of the urethane-modified amideimide resin used in the present invention is preferably 260 ° C. or lower, more preferably 250 ° C. or lower. If the glass transition temperature of the urethane-modified amideimide resin is too low, sufficient corrosion resistance may not be obtained even if a silane coupling agent described later is added. On the other hand, if the glass transition temperature is too high, the cured coating film may become too hard, and the impact resistance and workability may decrease.

As a method for producing such a urethane-modified amideimide resin, the above-mentioned amideimide moiety, the trivalent aromatic carboxylic acid derivative used for forming the urethane moiety, the diisocyanate compound, and the diol compound are collectively charged into the solvent. , Heating, stirring and reacting all at once while removing the gas generated by the reaction. A diol compound is added after synthesizing an amidimide prepolymer at the isocyanate terminal by reacting a trivalent aromatic carboxylic acid derivative with a diisocyanate compound. To form a urethane bond, a diisocyanate compound and a diol compound are reacted to synthesize an isocyanate-terminated urethane prepolymer, and then a trivalent aromatic carboxylic acid derivative is added to obtain a urethane-modified amideimide resin. Can be mentioned. In order to suppress the introduction of a site due to a side reaction between the polycarboxylic acid and the diol compound, a method of adding a trivalent aromatic carboxylic acid derivative after synthesizing an isocyanate-terminated urethane prepolymer is preferable.

Generally, the reaction temperature is preferably about 60 ° C. to 150 ° C.
The solvent used in the reaction is preferably at least one selected from the group consisting of cyclohexanone and cyclopentanone. Hydrocarbon solvents such as xylene and toluene, ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone, ether solvents such as tetrahydrofuran and dioxane, alcohol solvents such as methanol, ethanol, isopropyl alcohol and butyl alcohol, if necessary. Etc. may be used together.

When synthesizing a urethane-modified amidimide resin, the total amount of the trivalent aromatic carboxylic acid derivative and the diol compound that the diisocyanate compound reacts with is 1.0 mol, and the amount is 0.8 mol or more and 1.1 mol or less. Is preferable.

To promote the reaction, amines such as triethylamine, rutidin, picolin, undecene, triethylenediamine (1,4-diazabicyclo [5.4.0] -7-undecene), lithium methylate, sodium methylate, sodium ethylate. , Alkali metals such as potassium butoxide, potassium fluoride and sodium fluoride, alkaline earth metal compounds or metals such as titanium, cobalt, tin, zinc and aluminum, and catalysts such as semi-metal compounds may be used.

(Silane coupling agent)
The silane coupling agent used in the resin composition of the present invention includes an alkoxy group and a reactive group, and examples of the alkoxy group include a methoxy group and an ethoxy group.
As the reactive group contained in the silane coupling agent, it is preferable to use one having either an epoxy group or a methacryl group because it is excellent in storage stability, solvent resistance of the cured coating film, and corrosion resistance, and includes an epoxy group. It is more preferable to use a silane coupling agent.

Examples of the silane coupling agent having an epoxy group include 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-. Examples thereof include glycidoxypropylmethyldiethoxysilane and 3-glycidoxypropyltriethoxysilane.
Examples of the silane coupling agent having a methacryl group include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane and the like. Be done.
These silane coupling agents can be used alone or in combination of two or more.

In order to surely improve the solvent resistance and corrosion resistance, the content of the silane coupling agent in the resin composition of the present invention should be 1 part by mass or more with respect to 100 parts by mass of the solid content of the urethane-modified amidimide resin. It is preferably 5 parts by mass or more, and more preferably 5 parts by mass or more. Further, if the content of the silane coupling agent is too large, the workability is deteriorated, and when it is applied to a can having a complicated shape or a large amount of deformation, a problem may occur during molding. It is preferably 45 parts by mass or less, and more preferably 40 parts by mass or less with respect to 100 parts by mass.

When such a silane coupling agent is not contained, the corrosion resistance to the aqueous solution of acid or alkali may be sufficient, but the corrosion resistance to the actually encapsulated product may be insufficient. In such a case, it is necessary to provide an inner bag in order to prevent corrosion of the can, but in the present invention, by including the above-mentioned silane coupling agent, corrosion resistance can be reliably ensured.

(solvent)
Examples of the solvent used in the resin composition of the present invention include amide solvents such as N-methylpyrrolidone, N, N-dimethylacetamide, and N, N-dimethylformamide, which are usually used for dissolving amideimide resins, and γ-butyrolactone. In addition, cyclohexanone and cyclopentanone can be mentioned. These can be used alone or in combination, and there is no particular limitation, but cyclohexanone and cyclopentanone are preferably used alone or in combination.

Further, alkylene glycol alkyl ethers, aromatic hydrocarbons such as xylene and toluene, ketones such as methyl ethyl ketone and methyl isobutyl ketone, alcohols such as ethanol and 2-propanol, and diethyl ether as long as the desired effect is not impaired. Etc. may be used in combination.

(Additive)
By containing the above-mentioned urethane-modified amideimide resin and the silane coupling agent, the resin composition of the present invention can secure sufficient solvent resistance and corrosion resistance, but if necessary, a curing agent and urethane-modified amideimide can be ensured. Even if a resin other than a resin or a curing agent, a rocking modifier, a pigment, a filler, an antistatic agent, a flame retardant, a polymerization inhibitor, a lubricant, a defoaming agent, a leveling agent, a surface conditioner, a rheology control agent, etc. are added. good.

As the curing agent that may be added to the resin composition of the present invention, conventionally known curing agents can be used, and there is no particular limitation. Examples thereof include epoxy resins, amino resins, polyfunctional isocyanate compounds, and phenol resins.

More specifically, as the epoxy resin, bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, amine type epoxy resin, alicyclic epoxy resin, brominated Epoxy resins and the like can be mentioned, and examples of the amino resin include melamine resins such as trimethylol melamine, hexamethylol melamine and these alkoxy ether compounds, methylated benzoguanamine resins and butylated benzoguanamine resins.

Examples of the polyfunctional isocyanate compound include a bifunctional isocyanate compound used for preparing the urethane-modified amidimide resin described above, a 2,4-tolylene diisocyanate adduct of trimethylpropan, hexamethylene diisocyanate, diphenylmethane diisocyanate, and isophorone diisocyanate. Examples thereof include trifunctional isocyanate compounds such as trimers and blocks in which these are protected with phenol or alcohol.

Examples of the phenol resin include trifunctional phenol compounds such as coalic acid, m-cresol, m-ethylphenol, 3,5-xylenol, and m-methoxyphenol, p-cresol, o-cresol, p-tert-butylphenol, and p. Examples thereof include a resol-type phenol resin obtained by synthesizing bifunctional phenol such as −ethylphenol, 2,3-xylenol, 2,5-xylenol, and m-methoxyphenol and formaldehyde in the presence of an alkali catalyst. Further, it is also possible to use a form in which a part or all of the methylol groups contained in the phenol resin are etherified with alcohols having 1 to 12 carbon atoms.

These curing agents may be used alone or in combination of two or more. Bisphenol A type epoxy resin, phenol novolac type epoxy resin, phenol resin of coal acid, phenol resin of m-cresol, and phenol resin of o-cresol can be preferably used. In particular, it is preferable to use a bisphenol A type epoxy resin or a phenol novolac type epoxy resin because the corrosion resistance can be effectively improved by using it in combination with the above-mentioned silane coupling agent.

The content of the curing agent in the resin composition of the present invention is not particularly limited and may be appropriately adjusted according to the amount of the silane coupling agent and the required properties. As an example, the solid content of the urethane-modified polyamide-imide resin is 100% by mass. It is 1 part by mass or more, more preferably 3 parts by mass or more, and further preferably 10 parts by mass or more. Further, as an example, the content of the curing agent is 40 parts by mass or less, more preferably 30 parts by mass or less, and preferably 15 parts by mass or less with respect to 100 parts by mass of the solid content of the urethane-modified amideimide resin. .. If the content of the curing agent is too large, the cured coating film becomes too hard, and the coating film may be easily cracked or the workability may be deteriorated when an impact is applied.

Examples of the rocking denaturing agent include silica, organic bentonite, and organic polymer particles.
Examples of pigments and fillers include iron oxide, titanium oxide, aluminum oxide, barium sulfate, calcium carbonate, magnesium carbonate, talc, clay, silica and the like.

The resin composition of the present invention can be applied to various uses such as paints and screen inks for circuit boards, and is not particularly limited, but can be suitably used as paints, particularly inner surface paints for metal cans. Various additives, viscosities, etc. may be adjusted according to the application.

<Paint on the inner surface of metal cans>
The coating composition of the present invention can be applied to a can material at any stage. For example, black plate; plated steel plate whose surface is plated with tin, chromium, aluminum, zinc, etc., and various coated steel plates such as steel plate whose surface is chemically treated with chromic acid, phosphoric acid, etc. Light metal plate; The paint of the present invention is applied in advance to a material for a can of a composite metal material in which an aluminum foil or the like is adhered and laminated on the surface of a resin film such as polyolefin or an organic substrate such as a paper board, and then baked.

In the case of a three-piece can, the obtained painted metal plate is soldered, welded, joined with an adhesive, or the like to form a can body. In the case of a two-piece can, the baked painted metal plate is deep-drawn or thinned and deep-drawn to obtain a painted can body. The painted metal plate may be punched, press-molded, and if necessary, score molding, button molding, tab attachment, and the like may be performed to form a can lid or an easy-open can lid.
Further, the coating composition may be applied and baked after the can body, the can body, and the can lid are first molded. The coating composition of the present invention may be provided as a single coat or may be double coated.

The paint of the present invention can be applied to a can material, a can body, a can lid, or the like by any means such as immersion coating, roller coating, wire coating, flow coating, doctor coating, spray coating, and brush coating. As an example, the coating film is coated so that the film thickness after drying is about 1 μm or more and 20 μm or less.

The baking conditions vary depending on the characteristics of the urethane-modified amideimide resin used in the coating material of the present invention, the content of the silane coupling agent, and the like, but for example, it is 1 to 20 minutes at 150 ° C. to 250 ° C. It may be appropriately adjusted according to the physical characteristics required for the coating film.

Hereinafter, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited thereto. The composition and other values are based on mass unless otherwise specified.

<Urethane-modified amidoimide resin>
In a 4-neck flask equipped with a stirrer, a cooling tube, a nitrogen gas introduction tube, and a thermometer, trimellitic anhydride: 67.2 parts, ethylene glycol bisamhydrotrimerite: 123 parts, tricyclodecanedimethanol: 58. .9 parts, polypropylene glycol (average molecular weight 1000): 50 parts, diphenylmethane-4,4'-diisocyanate: 250 parts, 1,8-diazabicyclo [5,4,5] -7-undecene (DBU): 1.5 Part, cyclohexane was added, and the temperature was raised with stirring to carry out the reaction. Cyclohexanone was further added while cooling to obtain a urethane-modified amideimide resin solution having a solid content concentration of 30%.

<Paint adjustment>
(Example 1)
100 parts of the urethane-modified amidimide resin solution (solid content 30%) obtained above, 2 parts of 3-glycidoxypropylmethoxysilane as a silane coupling agent, and 0.1 part of a surface conditioner were dispersed with a disper, and 25 parts were dispersed. Cyclohexanone was further added to adjust the viscosity so that the flow time in Ford Cup # 4 measured at ° C. was 60 to 70 seconds, and the coating material of Example 1 was obtained.

(Examples 2 to 9)
The paints of Examples 2 to 9 were obtained in the same manner as in Example 1 except that the composition of the raw materials was changed as shown in Table 1.
(Comparative Examples 1 to 15)
The paints of Comparative Examples 1 to 15 were obtained in the same manner as in Example 1 except that the composition of the raw materials was changed as shown in Tables 2 and 3.

The blending amount in Tables 1 to 3 is the amount of solid content. The details of the novolak type epoxy resin, the resol type phenol resin, and the surface conditioner used in Examples and Comparative Examples are as follows.
(Novolac type epoxy resin)
N-740-80 (manufactured by DIC Corporation, solid content 80%) was used.
(Resol type phenol resin)
BKS-355 (manufactured by Aica Kogyo Co., Ltd., solid content 80%) was used.
(Surface conditioner)
BYK-310 (25% solution of polyester-modified polydimethylsiloxane, manufactured by Big Chemie) was used.

<Creation of test coating board>
Examples 1 to 9 and Comparative Examples 1 and 8 to 15 were prepared using a bar coater so that the weight of the dry coating film was 70 mg / dm ^{2 on a 5182 aluminum plate having a thickness of 0.26 mm.} Each of the paints was applied and baked under oven conditions where the PMT was 230 ° C. with an oven passage time of 10 minutes, and then cooled to room temperature to prepare a test coating plate.

<Evaluation>
The storage stability of the paints of Examples 1 to 9 and Comparative Examples 1 to 15 was evaluated as follows. In addition, the solvent resistance, impact resistance, workability, and corrosion resistance of the test coated plate were evaluated as follows, and the results are summarized in Table 1-3. No other evaluation was performed for those with a storage stability of ×.
(Storage stability)
◎… Liquid and non-sticky, retains liquid even when left unattended ×… Gels and becomes pudding when left unattended

(Solvent resistance)
The coated surface of the test coating plate was impregnated with cotton wool with NMP and a load of 2 kg was applied to perform rubbing (reciprocating rubbing). The number of rubbing required until 10% of the base of the coating film was exposed was evaluated in the following four stages.
◎… No damage to the coating film after 300 times 〇… Slight change in the coating film after 300 times △… Less than 10% background exposure on the coating film after 300 times ×… 10% background exposure after less than 300 times

(Impact resistance)
The test coating plate was set in the DuPont impact test, a weight of 500 g was dropped from a height of 30 cm, and the coating film surface was processed with a 1/2 inch diameter punch. A cellophane tape was pressure-bonded to the processed portion, and peeling of the coating film after peeling at 90 ° was observed and evaluated in the following four stages.
◎… No peeling 〇… Slight peeling △… A little less than half peeled ×… All processed parts peeled

(Workability)
Bending tester A test coating plate bent 180 ° with a 4 mm mandrel is placed on a 1/10 tilting cradle placed on the weight drop part of the DuPont impact tester, and a 1 kg weight is dropped from a height of 50 cm to tilt it. Crushed to. The test coating plate was immersed in a hydrochloric acid / copper sulfate solution, and the cracks in the crushed portion were evaluated in the following four stages.
◎… No cracks 〇… Cracks 0 to 2 mm
Δ… Crack 2-5 mm
×… Crack 5 mm or more

(Corrosion resistance: acidic)
A test coating plate was placed in a glass cup containing a 10% benzalkonium chloride solution (manufactured by Showa Pharmaceutical Co., Ltd.) so that the coated surface touched the solution, and fixed with a vise so that the solution did not leak. The fixed sample was placed in an oven at 60 ° C. and left for 4 days, and then the state of the coating film portion of the test coating plate taken out was observed and evaluated in the following 4 stages.
◎… No blister or spots 〇… No blister but slight spots on the coating film △… No blister but clearly visible spots on the coating film ×… Peeling of blister or coating film

(Corrosion resistance: alkaline)
Venezel Wave Permanent Liquid A test coating plate was placed in a glass cup containing the first liquid for damaged hair (manufactured by Dariya Co., Ltd.) so that the coating film surface touched the solution, and fixed with a vise so that the liquid would not leak. .. The fixed sample was placed in an oven at 60 ° C. and left for 4 days, and then the state of the coating film portion of the test coating plate taken out was observed and evaluated in the following 4 stages.
◎… No blister or spots 〇… No blister but slight spots on the coating film △… No blister but clearly visible spots on the coating film ×… Peeling of blister or coating film

As is clear from Tables 1 to 3, all the paints of the present invention exhibited excellent properties.
On the other hand, the paints of Comparative Example 1 in which the silane coupling agent was not added and Comparative Example 14 in which the content of the silane coupling agent was small lacked corrosion resistance to alkali.
Further, among the paints of Comparative Examples 2 to 11 using the silane coupling agent having a reactive group other than the epoxy group or the methacryl group, the paints of Comparative Examples 2 to 7 gelled and were not suitable for coating. No improvement in corrosion resistance to alkali was observed in the paints of Comparative Examples 8 to 11.
The paint of Comparative Example 15 in which the content of the silane coupling agent was too large had sufficient corrosion resistance to alkali, but the impact resistance and processability were deteriorated.

The resin composition of the present invention can be applied to various uses such as paints and screen inks for circuit boards. In particular, it can be suitably used as a paint that requires solvent resistance and corrosion resistance, and as an inner paint for metal cans.

Claims (8)

Urethane-modified amidoimide resin and
A silane coupling agent comprising an epoxy group or a methacrylic group and an alkoxy group,
Contains solvent,
A resin composition characterized in that the content of the silane coupling agent is 1 part by mass or more and 45 parts by mass or less with respect to 100 parts by mass of the urethane-modified amidimide resin. It contains at least one curing agent selected from the group consisting of epoxy resin, amino resin, polyfunctional isocyanate compound, and resol type phenol resin.
The resin composition according to claim 1, wherein the content of the curing agent is 1 part by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the urethane-modified amidimide resin. The resin composition according to claim 1 or 2, wherein the curing agent contains an epoxy resin. The resin composition according to any one of claims 1 to 3, wherein the curing agent contains a resol type phenol resin. The resin composition according to any one of claims 1 to 4, wherein the urethane-modified amideimide resin has a glass transition temperature of 200 ° C. or higher and 260 ° C. or lower. The resin composition according to any one of claims 1 to 5, wherein the solvent contains at least one selected from the group consisting of cyclohexanone and cyclopentanone. A coating material comprising the resin composition according to any one of claims 1 to 6. A coating material on the inner surface of a metal can, which comprises the resin composition according to any one of claims 1 to 7.