JPH09169949A - Coating material for manufacturing can - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject coating material, comprising a copolymerized epoxy resin derived from bisphenol A and bisphenol F, excellent in coating operating efficiency at a low solvent content, having short-time curability at low temperatures and capable of highly processing a coating film after curing. SOLUTION: This coating material for manufacturing cans comprises (A) a copolymerized epoxy resin, derived from (i) bisphenol A and (ii) bisphenol F at (5:5) to (8:2) molar ratio and having 8000-15000 number-average molecular weight and (B) a methylol group-containing thermosetting resin curing agent. Furthermore, the component (A) is derived from a mixture of the component (i) with (iii) a glycidyl ether and the component (ii) or the component (ii) and the component (A). The component (ii) contains >=60mol% o-o and o-p methylene bonds and further a component having <=1000 molecular weight in an amount of <2wt.%. The average number of epoxy groups based on one molecule is 0.6-1.5. The component (B) is preferably a resol type phenol resin derived from the component (ii) and formaldehyde and present in an amount of 1-10 pts.wt. based on 100 pts.wt. component (A).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin-based coating material for cans, and more specifically, it contains a copolymerized epoxy resin derived from bisphenol A and bisphenol F and has a low solvent content. The present invention relates to a coating material for cans having excellent workability in coating, curability at a low temperature for a short time, and a coating film after curing having high processability, high corrosion resistance, and low elution into contents.

[0002]

2. Description of the Related Art In the can manufacturing industry, an organic coating film that protects metal is subjected to severe mechanical processing such as advanced drawing processing, multiple neck-in processing and bead processing in the case of a can body. Required to have. Also, Easy
Even open-ended can lids are subjected to severe processing such as score processing and rivet processing, so excellent workability and corrosion resistance are required.

Epoxy paints have hitherto been widely used as can-coating paints having excellent workability and satisfying practical performances such as corrosion resistance and chemical resistance.

Japanese Patent Publication No. 6-21 concerning the proposal by the present inventors
No. 270, obtained by polycondensation of bisphenols with epihalohydrin and having a number average molecular weight of 11,000.
A highly workable epoxy-based coating composition is described, which comprises a mixture of an epoxy resin having a branching degree (N _BR ) of 2 to 15% and a curing agent resin.

Further, in order to improve the processability of the epoxy-based coating film, measures such as increasing the molecular weight of the epoxy resin and decreasing the usage ratio of the curing agent resin to the epoxy resin have been adopted.

[0006]

However, the above countermeasures still have problems to be solved in view of the quality of the coating film. That is, in the former method, if the molecular weight of the epoxy resin is increased, the adhesion of the coating film is lowered, the coating film floats due to heat sterilization, etc., and the corrosion resistance of the coating can is easily lowered. In the latter method, when the ratio of the epoxy resin component is increased, moisture or corrosive components from the contents to the metal is easily transmitted, and the corrosion resistance of the paint can is reduced. Furthermore, a low molecular weight epoxy resin component remains in an uncured state in the final cured coating film, which is eluted into the contents, which is not preferable from the viewpoint of hygienic properties and flavor retention.

Further, in the case of solvent-based paint, the higher the molecular weight of the epoxy resin is, the higher the viscosity of the paint is, which deteriorates the coating workability. In order to maintain good coating workability, use of an organic solvent is required. A large amount must be added, the solvent cost and the energy cost for baking the coating film increase, and the problem of environmental pollution occurs, and in order to prevent this, the cost for exhaust treatment increases.

Further, it is desirable that the coating film on the metal plate can be baked at a temperature as low as possible. That is, the baking of the coating film at a high temperature is likely to damage the metal such as aluminum.

Therefore, an object of the present invention is to have excellent workability in coating with a low solvent content, to have curability at a low temperature for a short time, and the coating film after curing has high workability, high corrosion resistance, An object is to provide an epoxy-based coating material for cans having a low dissolution property.

Another object of the present invention is to provide an epoxy paint which can be applied to coil coating on a can lid and has a high degree of workability.

[0011]

According to the present invention, the number average molecular weight derived from bisphenol A and bisphenol F in a molar ratio of 5: 5 to 8: 2 is 8000 to 150.
And a copolymerization epoxy resin of No. 00 and a methylol group-containing thermosetting resin curing agent are provided.

The copolymerized epoxy resin is preferably a copolymerized epoxy resin derived from diglycidyl ether of bisphenol A and bisphenol F or a mixture of bisphenol F and bisphenol A.

Bisphenol F used is o-o and o-
It is preferable that the content of p-methylene bond is 60 mol% or more.

The copolymerized epoxy resin has a molecular weight of 1
It is preferably a copolymerized epoxy resin containing less than 000 components in an amount less than 2% by weight.

The copolymerized epoxy resin preferably has an average number of epoxy groups per molecule in the range of 0.6 to 1.5.

The methylol group-containing thermosetting resin curing agent is
It is preferable to use a resol type phenol resin, particularly a resol type phenol resin derived from bisphenol F and formaldehyde.

The resol type phenolic resin is preferably present in an amount of 1 to 10 parts by weight per 100 parts by weight of the epoxy resin.

[0018]

The epoxy-based coating composition of the present invention contains a copolymerized epoxy resin having a number average molecular weight of 8,000 to 15,000 derived from bisphenol A and bisphenol F in a molar ratio of 5: 5 to 8: 2. It is a remarkable feature.By using this copolymerized epoxy resin, excellent coating workability with a low solvent content, low-temperature short-time curability, and high workability, high corrosion resistance, and content of the coating film after curing are achieved. A low dissolution property into the inside can be obtained.

That is, as shown in an example to be described later, in the coating material in which the bisphenol component in the epoxy resin is all bisphenol A (Comparative Example 9), the solid content concentration is 15%, and it is already 115 seconds (# 4 cup, 25 ° C.). The coating composition showing a viscosity and having a molar ratio of bisphenol F in the bisphenol component in the epoxy resin below the range of the present invention (Comparative Example 1) shows a viscosity of 120 seconds at a solid content concentration of 19%. In the coating composition in which the molar ratio of bisphenol A: bisphenol F in the bisphenol component in the epoxy resin is within the range of the present invention, even if the solid content concentration is 23% or more,
Since it has a viscosity similar to or lower than the above, it is clear that the coating material of the present invention has excellent coating workability and exhibits the effect of reducing the amount of solvent used.

Further, in the paints in which the molar ratio of bisphenol F in the bisphenol component is below the range of the present invention (Comparative Examples 1 and 9), the maximum temperature (PMT) reached is 250 ° C.,
Under the condition of 20 seconds, the coating film formed is whitened during retort sterilization, it is difficult to cure at low temperature for a short time, and the coating components are eluted into the contents during retort, and the corrosion resistance of the processed part is still insufficient. Is. This tendency is PMT27
Even curing at 0 ° C. for 20 seconds is still visible.

On the other hand, a paint in which the molar ratio of bisphenol F in the bisphenol component exceeds the range of the present invention (Comparative Example 1
In 0), in terms of keeping the viscosity of the paint in a low range,
Even if it can be satisfied, the low temperature short-time curability is insufficient, and at the ultimate temperature (PMT) of 250 ° C for 20 seconds, the formed coating film is whitened during retort sterilization, and the coating components are contained during retort. Tends to elute in the product. This coating reaches the maximum temperature (PMT) of 270 ° C, 30
When baked under the condition of second, the above whitening of the coating film and the tendency of elution into the contents are eliminated, but with such high temperature baking, processing of the coated plate on the can lid, that is, score processing However, the corrosion resistance of the coating film tends to decrease during riveting.

The copolymerized epoxy resin used in the present invention is derived from bisphenol A and bisphenol F in a molar ratio of 5: 5 to 8: 2 and has a number average molecular weight of 8,000 to 15,000. It is also important regarding the combination properties.

When the number average molecular weight of the copolymerized epoxy resin is less than the above range (Comparative Example 4), whitening of the coating film and tendency to elute into the contents occur during retort, and further to the can lid of the coated plate. There is a large tendency for the corrosion resistance of the coating film to decrease during the processing of 1, that is, score processing, rivet processing, and the like.

On the other hand, when the number average molecular weight of the copolymerized epoxy resin exceeds the above range, there is no problem in whitening of the coating film and the tendency of elution into the contents, but the processing of the coated plate into the can lid is possible. That is, the corrosion resistance of the coating film tends to decrease during score processing, rivet processing and the like.

The copolymerized epoxy resin contains a component having a molecular weight of 1000 or less in an amount of 2% by weight or less, and has high processability, high corrosion resistance of the coating film after curing and low elution property in the content. Important in terms. When the content of the low molecular weight component is increased, these characteristics are deteriorated (Comparative Examples 4 to 6 and 10).

Bisphenol F, which is a raw material for the copolymerized epoxy resin, is a bisphenol F having oo and op methylene bonds.
The content of 0 mol% or more is important for ensuring excellent coating workability with a low solvent content and achieving low-temperature short-time curability. The copolymerized epoxy resin derived from bisphenol F having less than 60 mol% of the oo and o-p methylene bonds has high paint viscosity and lacks low temperature curability (Comparative Example 5).

The copolymerized epoxy resin used in the present invention has, unlike ordinary bisepoxides, less than 2 epoxy groups per molecule, particularly in the range of 0.6 to 1.5. Those having less than 0.6 or more than 1.5 epoxy groups per molecule are inferior in any of the combination characteristics as compared with those in the above range (Comparative Examples 4, 6 and 10).

The above copolymerized epoxy resin is preferably used in combination with a methylol group-containing thermosetting resin, particularly a resole-type phenol resin, most preferably a resole-type phenol resin derived from bisphenol F and formaldehyde. The curing agent resin is preferably used in an amount of 1 to 10 parts by weight per 100 parts by weight of the copolymerized epoxy resin.

When the amount of the curing agent resin used is less than the above range, the coating film formed has low hot water resistance and insufficient corrosion resistance after processing, and the lid using this coating is feathered. It easily occurs (Comparative Example 8). On the other hand, when the amount of the curing agent resin is larger than the above range, the paint components are largely eluted into the content and the corrosion resistance after processing is poor (Comparative Example 7).

The copolymerized epoxy resin of the present invention may be any copolymerized epoxy resin as long as it is derived from bisphenol A and bisphenol F in a molar ratio of 5: 5 to 8: 2. Is preferably a copolymerized epoxy resin derived from a diglycidyl ether of bisphenol A and bisphenol F or a mixture of bisphenol F and bisphenol A.

First, bisphenol F used as a raw material will be described.

[Bisphenol F] Bisphenol F is derived from the reaction of phenol with formaldehyde. The reaction has a phenol / formaldehyde molar ratio of 3
It is carried out in the presence of an excess of phenol such as Nos. 6 to 6, and a strong acid such as oxalic acid, hydrochloric acid, sulfuric acid, paratoluenesulfonic acid or phosphoric acid, a divalent metal salt or oxide, etc. is used as a catalyst. The reaction temperature is suitably from 40 to 120 ° C., and the reaction time is suitably from about 30 minutes to 4 hours. As formaldehyde, a 30 to 55% aqueous solution (formalin) is usually used, and phenol having a melting point of 40.9 ° C. is usually mixed with a small amount of water and handled in a liquid state. The pH during the reaction is adjusted to an appropriate pH of 1 to 7,
Bisphenol F having a high p-methylene bond content is produced under acidic conditions of 1 to 4, and Mn, Ca, Mg, Zn, Cd, Pb, Cu and C are produced in a weak acidic region of pH 4 to 7.
When a divalent metal salt or oxide such as o or Ni is used as a catalyst, bisphenol F having a high o-methylene bond content can be obtained. Particularly suitable divalent metal salts for obtaining o-methylene bonds are acetates such as Zn, Mn and Mg.

Water is separated and removed from the reaction suspension, and if necessary, the catalyst is neutralized and the product is washed with water. It is then generally dehydrated by atmospheric distillation and the residual phenol is removed by vacuum distillation. The obtained bisphenol F contains 2,
In addition to the three types of binuclear phenols, 2′-, 2,4′-, and 4,4′-dihydroxydiphenylmethane, polynuclears such as trinuclear and tetranuclear are included. Is purified by a vacuum distillation method. Furthermore, it is also possible to isolate each of the three binuclear phenols using a distillation method or a recrystallization method from a solvent. Bisphenol F
For purification of, a distillation purification method is usually used, but a recrystallization method from a solvent may be used. Alcohols such as butanol, acetone, benzene,
Toluene or the like, or a mixed solvent thereof is used.
A dimethylene ether bond by-produced in a small amount during the production of bisphenol F can be converted to a methylene bond by providing a heating stage at 150 to 160 ° C. during purification.

By analyzing the obtained bisphenol F by high performance liquid chromatography (HPLC), three types of binuclear phenols can be separated from polynuclears such as trinuclear and quadrinuclear, and the binuclear purity and oo, op, pp
Can be determined respectively. Silica or the like treated with dichlorodibutylsilane is used for the stationary phase, and methanol /
Water, acetonitrile / water, a mixture of methanol / acetonitrile / water and the like are used. Ultraviolet absorption (UV) is used as a detector, and the content of each component in bisphenol F is determined on the assumption that each peak area is proportional to the weight concentration of each component. In addition, bisphenol F
The ratio of oo, op, and pp methylene bonds therein can be quantitatively evaluated.

Bisphenol F is represented by the following chemical formula (1) HO-Φ-CH ₂ -Φ-OH (1) In the formula, Φ represents a phenylene group.
And those containing 60 mol% or more of those having an o-p methylene bond are preferable. Bisphenol F, which is easily available and is preferably used for the purpose of the present invention, has an ortho-para-methylene bond content of 40 to 60 mol%, and a para-para-methylene bond content of 20 to 50 mol%. 10 to 20 mol% of ortho-ortho-methylene bond
It is a mixture containing.

[Copolymerized Epoxy Resin] The epoxy resin used in the present invention is a copolymerized epoxy resin derived from bisphenol A, bisphenol F and epichlorohydrin, and a suitable copolymerized epoxy resin has a molar ratio of 5: 5 to 8 :. 2, particularly preferably a number average molecular weight derived from bisphenol A and bisphenol F of 5: 5 to 7: 3 is 8,000 to 15,000, particularly preferably 1,000.
It is a copolymerized epoxy resin in the range of 0 to 14000.
When the content of bisphenol F in the copolymerized epoxy resin exceeds the above range, the viscosity of the coating material decreases, but the glass transition point (Tg) of the resin decreases and the heat resistance and water resistance of the coating film deteriorate. become. The tendency of the coating film to be whitened by the retort treatment is increased, and the corrosion resistance of the coating film is reduced because water and ions are easily transmitted. When the bisphenol F content is smaller than the above range, the viscosity of the resin solution is remarkably increased, and the amount of solvent used for obtaining a proper coating viscosity is increased. Also, when the number average molecular weight exceeds the above range, it causes a significant increase in the amount of the solvent used for obtaining the proper viscosity for coating, and when it is less than the above range, the workability of the coating film becomes insufficient and the work corrosion resistance is inferior. become.
In addition, the low-temperature short-time curing property of the coating material becomes inferior as the number average molecular weight decreases, and if the amount of the curing agent added is increased to compensate for the insufficient curability, the workability and the elution property deteriorate.

The copolymerized epoxy resin is bisphenol A.
And one-step polymerization method of bisphenol F and epichlorohydrin (Tuffy method), two-step polymerization method of bisphenol F or diglycidyl ether of bisphenol F and bisphenol A and bisphenol A (fusion method)
However, in order to obtain a high molecular weight copolymerized epoxy resin having a number average molecular weight in the above range, a diglycidyl ether of bisphenol A and bisphenol F or a mixture of bisphenol F and bisphenol A can be used. It is preferable to induce by a two-step polymerization method (fusion method). Copolymerized epoxy resin polymerized by the one-step polymerization method tends to have a wide molecular weight distribution expressed by weight average molecular weight / number average molecular weight, and since it contains a large amount of low molecular weight components, it has poor elution properties. Since a large amount is contained, the viscosity of the resin solution becomes high, resulting in an increase in the amount of solvent used. Even in the former case of the above two-step polymerization method, the copolymerized epoxy resin contains a large amount of low molecular weight components, and the elution property tends to be poor. Regarding this cause, compared to the reaction product of the diglycidyl ether of bisphenol A and bisphenol F or the mixture of bisphenol F and bisphenol A, the former diglycidyl ether of bisphenol F or the mixture of bisphenol F and bisphenol A and bisphenol A It is considered that the reaction product is likely to form a cyclic dimer or a cyclic trimer in the initial stage of the reaction. This can be analogized by considering the structural features of the diglycidyl ether of 2,2'-dihydroxydiphenylmethane and 2,4'-dihydroxydiphenylmethane.

In order to obtain a high molecular weight copolymerized epoxy resin having a number average molecular weight of 8,000 to 15,000, the purity of raw materials used in the two-step polymerization method is important. As bisphenol A, a high-purity product having a melting point of 155 to 157 ° C. is preferably used, and as the diglycidyl ether of bisphenol A, a high-purity product is preferably used.
30 poise (25 ° C), epoxy equivalent 175 to 190
Liquid bisphenol A type epoxy resin is preferred. The binuclear purity of the bisphenol F used is more important, and a suitable bisphenol F has a binuclear purity of 98% or more, preferably 99% or more. When the purity of the raw material used is poor, the molecular weight distribution becomes large, and even if the weight average molecular weight becomes large, it contains a considerably low degree of polymerization component and the number average molecular weight often does not reach the above range.

Further, in order to obtain a copolymerized epoxy resin having a number average molecular weight in the above range, the diglycidyl ether of bisphenol and bisphenol are mixed at about 1: 1 (10: 10).
It is also an important requirement to polymerize by using a molar ratio of 9 to 9:10). If the molar ratio of the raw materials deviates from the above range, the number average molecular weight often does not reach the above range.

The copolymerized epoxy resin used in the present invention contains less than 2% of a component having a molecular weight of 1000 or less, and the coating film obtained from this has excellent elution and flavor properties. Conventional paint for cans requires a high-temperature, long-term curing reaction to suppress dissolution, but using a resin with a small amount of dissolution components enables low-temperature, short-time baking. Was.

The copolymerized epoxy resin used in the present invention has a narrow molecular weight distribution represented by weight average molecular weight / number average molecular weight,
The following is one of the important requirements. When the molecular weight distribution exceeds 6, the viscosity of the coating material becomes high, and the effect of reducing the viscosity by blending bisphenol F is offset.

The average number of epoxy groups per epoxy resin molecule, which is obtained by dividing the number average molecular weight by the epoxy equivalent, is in the range of 0.6 to 1.5, particularly in the range of 0.7 to 1.3. There is also a feature of the copolymerized epoxy resin used in the present invention, if the above range is exceeded, the adhesiveness to the base of the coating film,
Inconvenience arises in terms of workability and dissolution.

In order to obtain a high molecular weight copolymerized epoxy resin having a low viscosity when dissolved in the solvent used in the present invention, the ratio of the three isomers of bisphenol F used is important,
It is preferable that the content of the o-o and o-p methylene bond is 60% or more, particularly 68% or more (the content of the p-p methylene bond is 40% or less, particularly 32% or less).
When the content of the o-o and o-p methylene bond is below the above range (when the content of the p-p methylene bond is above the range), the effect of decreasing the solution viscosity is insufficient and the conventional bisphenol is not used. It is not possible to expect a drastic reduction in the amount of solvent used for paints using A-type epoxy resin.

Another reason why the coating composition for a can according to the present invention exhibits excellent low-temperature short-time curability is the copolymerized epoxy resin. The copolymerized epoxy resin has a high molecular weight, and not only for obvious reasons that the film performance is remarkably improved only by a small amount of crosslinking reaction, but also for the copolymerized epoxy resin, oo and op There is another reason that this is involved in the curing reaction because bisphenol F having a high content of methylene complex is used and the p-position showing high reactivity is vacant. Vacant p on the skeleton of the copolymerized epoxy resin
The −-position appears to react directly with a methylol group or an etherified methylol group, as well as via formaldehyde produced as a by-product during the curing reaction.

The reason why the copolymerized epoxy resin used in the present invention contains bisphenol A and bisphenol F in a molar ratio of 5: 5 to 8: 2 has been described above, but there is another reason for controlling the reactivity. When bisphenol F is contained more than the above range, it reacts sensitively to a slight difference in the baking conditions of the paint, and it is difficult to obtain a coated film of a constant quality. The distortion is large, and the adhesiveness and workability become poor. When the content of bisphenol F is lower than the above range, the low-temperature short-time curability becomes insufficient.

The polymerization reaction is carried out in a continuous system using an extruder or a batch system using a reaction kettle. In the case of the continuous system, a suitable polymerization temperature is 170 to 250 ° C., and a suitable reaction time is 0.01 to 0.06 hours. In the case of a batch type, a temperature range of 140 to 220 ° C. and a reaction time of 1 to 8 hours are preferable.

The polymerization reaction can be carried out without solvent or in the presence of a solvent. Suitable solvents for use in the polymerization include, for example, glycol ethers, alcohols, ketones, acetates, aromatic hydrocarbons, and any combination thereof. Particularly suitable solvents are, for example, acetone, methyl ethyl ketone, methyl isobutyl ketone,
Methyl amyl ketone, diacetate alcohol, C ₁ -C ₄ alkyl ether of mono- or dialkylene glycol, for example, n-methyl ether of ethylene glycol, methyl ether of ethylene glycol, n-butyl ether of propylene glycol, methyl ether of propylene glycol, N-butyl ether of diethylene glycol, methyl ether of diethylene glycol,
N-butyl ether of dipropylene glycol or methyl ether of dipropylene glycol, 3-methyl-3-methoxybutanol, n-butanol, sec-
Includes butanol, isopropanol, butyl acetate, toluene, xylene and any combination thereof.

The solvent in the polymerization system is preferably used in an amount of 0.1 to 20 parts, particularly 1 to 10 parts, per 100 parts of the raw material mixture of the epoxy resin, particularly when the desired copolymerized epoxy resin is prepared. In the batch method, the reaction can be stopped by diluting with a solvent. When stirring becomes difficult, the reaction can be further advanced by diluting with a solvent to lower the viscosity.

Suitable catalysts used in the polymerization reaction are, for example:
Included are phosphonium compounds such as phosphonium carboxylates, phosphonium carboxylate carboxylic acid complexes, phosphonium halides, phosphonium biscarbonates, phosphonium phosphates, and any combination thereof. Particularly suitable catalysts include, for example, ethyltriphenylphosphonium acetate-acetic acid complex, ethyltriphenylphosphonium acetate, tetrabutylphosphonium acetate-acetic acid complex, tetrabutylphosphonium phosphate and any combination thereof.

A catalyst represented by the following formula (2) is also suitable. ^{- ZR 1 R 2 R 3 P} + -Z-P + R 1 R 2 R 3 Z'- ‥ (2) ( In the formula, each of R ^1, R ² and R ³ are independently an aromatic group or an inert a substituted aromatic group; Z is _{^{- (C (R 4) 2}} ) 2
Each R ⁴ is independently hydrogen or a hydrocarbyl group or an inert substituted hydrocarbyl group containing 1 to 20, more preferably 1 to 10, most preferably 1 to 4 carbon atoms; Z ′ Is any suitable anion; a is at least 4, preferably 4-20, more preferably 4-1
0, most preferably having a value of 4-6). Suitable inert substituents for Z are, for example, -CO-Cl, -CN.
And -OH.

Particularly suitable catalysts for use in the present invention are:
For example, tetramethylenebis (triphenylphosphonium chloride), tetramethylenebis (triphenylphosphonium iodide), tetramethylenebis (triphenylphosphonium bromide), pentamethylenebis (triphenylphosphonium chloride), pentamethylenebis (triphenyl Phosphonium iodide), pentamethylene bis (triphenylphosphonium bromide), hexamethylene bis (triphenylphosphonium iodide),
Hexamethylenebis (triphenylphosphonium chloride), hexamethylenebis (triphenylphosphonium bromide), heptamethylenebis (triphenylphosphonium chloride), heptamethylenebis (triphenylphosphonium bromide), tetramethylenebis (triphenylphosphonium acetate) -Acetic acid complex), pentamethylene bis (triphenylphosphonium acetate-acetic acid complex), hexamethylene bis (triphenylphosphonium acetate-acetic acid complex), heptamethylene bis (triphenylphosphonium acetate-acetic acid complex), tetramethylene bis (triphenyl) Phosphonium phosphate), pentamethylene bis (triphenylphosphonium phosphate), hexamethylene bis (triphenylphosphonium phosphate) ), Heptamethylenebis (triphenylphosphonium) phosphate, tetramethylenebis (triphenylphosphonium) bicarbonate, pentamethylenebis (triphenylphosphonium) bicarbonate, hexamethylenebis (triphenylphosphonium) bicarbonate, heptamethylenebis (Triphenylphosphonium) bicarbonate, tetramethylenebis (triphenylphosphonium) oxalate, pentamethylenebis (triphenylphosphonium) oxalate, hexamethylenebis (triphenylphosphonium)
Oxalates, heptamethylenebis (triphenylphosphonium) oxalates, and combinations thereof.

Also preferably used as the catalyst is a phosphonium compound having three phenyl groups bonded to the phosphorus atom and one cycloalkyl group bonded to the phosphorus atom. It does not matter what the anion part of the phosphonium compound is. Particularly suitable such anions are
For example, halides such as chloride, bromide or iodide; carboxylates such as formates, acetates, oxalates, trifluoroacetates, carboxylate-carboxylic acid complexes such as acetate-acetic acid complexes; conjugated bases of inorganic acids such as bicarbonates, tetrafluoroborate. Or biphosphates; and conjugated bases of phenols, such as phenates or anions derived from bisphenols or biphenols (eg bisphenol A or bisphenol F), combinations thereof and the like. This cycloalkyltriphenylphosphonium catalyst has the following formula (3)

Embedded image (Wherein Q is preferably 3-8 in the cycloalkyl ring,
More preferably, it is a cycloalkyl, alkyl or halo-substituted cycloalkyl group having 4-7, most preferably 5-6 carbon atoms; each R is independently hydrogen, halogen, or preferably 1-12 More preferably a hydrocarbyl group having 1 to 6, most preferably 1 to 3 carbon atoms;
Z is an anion such as chloride, bromide or iodo, carboxylate such as formate, acetate, oxalate, trifluoroacetate, or carboxylate-carboxylic acid complex such as acetate-acetic acid complex, a conjugate base of an inorganic acid such as bicarbonate or tetra. Fluoroborate or biphosphate;
And conjugate bases of phenol, such as phenate or anions derived from bisphenol or biphenol (eg, bisphenol A or bisphenol F) and combinations thereof.

Particularly suitable such catalysts are, for example, cyclopropyltriphenylphosphonium iodide, cyclopropyltriphenylphosphonium bromide, cyclopropyltriphenylphosphonium chloride, cyclopropyltriphenylphosphonium acetate, cyclopropyltriphenylphosphonium acetate. Acetic acid complex,
Cyclopropyltriphenylphosphonium phosphate, cyclopropyltriphenylphosphonium heptanoate, cyclopropyltriphenylphosphonium oxalate, cyclobutyltriphenylphosphonium iodide, cyclobutyltriphenylphosphonium bromide, cyclobutyltriphenylphosphonium chloride,
Cyclobutyltriphenylphosphonium acetate, cyclobutyltriphenylphosphonium acetate / acetic acid complex, cyclobutyltriphenylphosphonium phosphate, cyclobutyltriphenylphosphonium heptanoate, cyclobutyltriphenylphosphonium oxalate, cyclopentyltriphenylphosphonium iodide, cyclopentyltrinium Phenylphosphonium bromide, cyclopentyltriphenylphosphonium chloride, cyclopentyltriphenylphosphonium acetate, cyclopentyltriphenylphosphonium acetate / acetic acid complex, cyclopentyltriphenylphosphonium phosphate, cyclopentyltriphenylphosphonium heptanoate, cyclopentyltriphenylphosphonium oxalate , Cyclopropyltriphenylphosphonium iodide, cyclopropyltriphenylphosphonium bromide, cyclopropyltriphenylphosphonium chloride, cyclopropyltriphenylphosphonium acetate, cyclopropyltriphenylphosphonium acetate / acetic acid complex, cyclopropyltriphenylphosphonium phosphate, cyclopropyl Triphenylphosphonium heptanoate, cyclopropyltriphenylphosphonium oxalate, cyclohexyltriphenylphosphonium iodide, cyclohexyltriphenylphosphonium bromide, cyclohexyltriphenylphosphonium chloride, cyclohexyltriphenylphosphonium acetate, cyclohexyltriphenylphosphonium acetate / acetic acid complex , Cyclohexyltriphenylphosphonium phosphate, cyclohexyltriphenylphosphonium oxalate, cycloheptyltriphenylphosphonium iodide, cycloheptyltriphenylphosphonium bromide, cycloheptyltriphenylphosphonium chloride, cycloheptyltriphenylphosphonium acetate, cycloheptyltriphenylphosphonium acetate・ Acetic acid complex, cycloheptyltriphenylphosphonium phosphate, cycloheptyltriphenylphosphonium heptanoate, cycloheptyltriphenylphosphonium oxalate, cyclooctyltriphenylphosphonium iodide, cyclooctyltriphenylphosphonium bromide, cyclooctyltriphenylphosphonium chloride , Shiku Includes cyclooctyltriphenylphosphonium acetate, cyclooctyltriphenylphosphonium acetate / acetic acid complex, cyclooctyltriphenylphosphonium phosphate, cyclooctyltriphenylphosphonium heptanoate, cyclooctyltriphenylphosphonium oxalate and combinations thereof.

The catalyst is used in an amount sufficient to catalyze the reaction of diglycidyl ether of bisphenol with bisphenol, and is 0.0 per 100 parts of the raw material mixture of epoxy resin.
It is preferably used in an amount of 3 to 2 parts, especially 0.04 to 1 part.

[Resol-Type Phenolic Resin] The resol-type phenol resin used in the present invention is obtained by reacting phenols with formaldehyde or a functional derivative thereof in the presence of a basic catalyst and, if necessary, etherification with alcohol. .

Examples of suitable phenols are as follows, including any combination of the following phenolics:
lower alkyl-substituted bifunctional phenols such as o-cresol, p-cresol, p-tert-butylphenol, p-ethylphenol, 2,3-xylenol, 2,5-xylenol; p-tert-amylphenol, p-cresol Other bifunctional phenols such as nonylphenol, p-phenylphenol and p-cyclohexylphenol; trifunctional such as phenol (phenyl carbonate), m-cresol, m-ethylphenol, 3,5-xylenol and m-methoxyphenol Phenols; monofunctional phenols such as 2,4-xylenol and 2,6-xylenol; 2.2'-bis (4-hydroxyphenyl) propane (bisphenol A), 2,2'-bis (4-hydroxy Phenyl) butane (bisphenol B), bisphenol F, 1,1'-bi (4-hydroxyphenyl)
Ethane, 4-hydroxyphenyl ether, P- (4-
Polycyclic polyphenols such as hydroquine) phenol;

The most preferable phenol constituting the resol type phenol resin used in the present invention is bisphenol F. Bisphenol F may be a purified product having a high binuclear content or a crude product containing polynuclear bodies. When special attention is required for the dissolution property, a phenol / novolak having a high polynuclear content such as trinuclear or tetranuclear may be preferably used.

For applications in which low-temperature short-time curability is particularly required, o
Bisphenol F having a high content of -o and op methylene bonds is preferable, and preferably, the amount of oo and op methylene bonds in all methylene bonds of bisphenol F is 60% or more, more preferably 68%. The above is used.
This is because when the ratio of the o-bond is high, the p-position showing higher reactivity to formaldehyde than the o-position is vacant, and the methylol group coordinated to the p-position shows high reactivity. .

In order to further improve the curability at a low temperature for a short time, bisphenol F having a high o-o methylene bond content.
Preferably, the amount of o-o methylene bond in the total methylene bond of bisphenol F is 10% or more, more preferably 17% or more, and most preferably 23% or more. The reason why the o-o methylene conjugate is highly reactive is that one hydrogen of the phenolic OH group forms a strong intramolecular hydrogen bond to dissociate the other hydrogen, exhibiting a very high acidity, and This is because the phenol resin itself has autocatalytic curing.

It is considered that a structure similar to the resol type phenolic resin obtained from the reaction of bisphenol F and formaldehyde can be directly derived from phenol and formaldehyde in the presence of an alkali catalyst. The resin contains a large amount of a methylol compound of a low molecular weight monocyclic phenol, and results in poor elution when used as a can-making coating material.

Formaldehyde is generally used in the form of an aqueous solution such as formalin, but functional derivatives such as paraformaldehyde, polyoxymethylene and trioxane can also be used.

The methylolation reaction is generally carried out using 1 to 10 mol, especially 3 to 7 mol of formaldehyde per mol of phenol, although it depends on the composition of the phenol.

As the basic catalyst, sodium hydroxide,
Alkali metal hydroxides such as potassium hydroxide, alkali carbonates such as sodium carbonate and potassium carbonate, alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide, and ammonia are used. These basic catalysts are preferably used in an amount of 0.2 to 3 mol, particularly 0.5 to 2 mol, per mol of phenols.

The methylolation reaction is preferably carried out in an aqueous medium, and the reaction conditions are not particularly limited, but it is generally room temperature to 100 ° C., particularly 40 to 80 ° C., 0.5 to 10 hours, particularly 1 to 5 hours. Some reaction is desirable. The concentration of phenols in the reaction system is suitably from 10 to 50%.

To separate the resol type phenolic resin from the final reaction product, the reaction mixture is neutralized with an acid such as hydrochloric acid, sulfuric acid, phosphoric acid, p-toluenesulfonic acid, oxalic acid, acetic acid, and the product is obtained. Precipitate, and if necessary, filter, wash with water,
Dry and collect in solid form. Also, as an alternative,
The reaction mixture after the neutralization, methyl ethyl ketone, ketones such as cyclohexanone, alcohols such as butanol,
Alternatively, the desired product can be recovered by extracting the mixture with a mixed solvent such as toluene and xylene.

The alkyl etherification of the methylol group of the resol type phenol resin is carried out by subjecting the methylol group in the resin to a condensation reaction with an alcohol in the presence of an etherification catalyst, particularly an acid catalyst.

Examples of alcohols include methanol, ethanol, n- or iso-propanol, n- and iso.
Although-, tert-butanol and the like can be used, alcohols having 3 to 6 carbon atoms, particularly butanol, are preferable.

As the etherification catalyst, phosphoric acid, sulfuric acid,
Hydrochloric acid, aromatic sulfonic acid (for example, p-toluenesulfonic acid), oxalic acid, acetic acid and the like can be used. In synthesizing this resin, a dissolved methylol group-containing thermosetting resin and an alcohol are reacted in an appropriate solvent in the presence of the catalyst. The amount of the catalyst used is such that the pH of the reaction system is 4-6.
The reaction temperature is preferably in the range of 70 to 90 ° C. As the solvent, an excess of alcohol, toluene, xylene or the like is used alone or in combination.
It is advantageous to carry out the reaction while removing water by-produced in the above-mentioned reaction. For this purpose, the reaction is carried out while removing water in the reaction system from the system in the form of azeotropic distillation with a solvent. It is desirable. Of course, if the amount of alcohol in the system is insufficient, it may be added to the reaction system.

The production of the phenolic resin and the alkyl etherification can be carried out in the same step or in separate steps. For example, the reaction between phenols and formaldehyde is carried out in a medium containing alcohol in the presence of an alkali catalyst, and after the desired methylolated resin is obtained, an acid catalyst is added to the system and the pH is adjusted to the above-mentioned range. The alkyl etherification reaction can be performed while maintaining. Alternatively, the formed methylolated resin may be separated by a means known per se, and this may be subjected to alkyl etherification in another system.

The obtained alkyl etherified resin may be neutralized, washed with water and dried to form a coating film forming resin component,
The salt or the like generated by the neutralization may be removed by any means and used as it is in the form of a resin solution.

[Coating resin composition] In the present invention, 1 to 10 parts by weight of the methylol group-containing curing agent resin is combined with 100 parts by weight of the copolymerization epoxy resin to prepare a coating material. The copolymerized epoxy resin and the curing agent resin may be simply mixed, or both resins may be precondensed in advance. It is common to use solvent-based paints in which both resins are dissolved in an organic solvent, but use as a powder paint in which both resins are pulverized or as an aqueous paint in which both resins are dispersed in water using a dispersant. You can also

In the case of an organic solvent type paint, the solvent is an aromatic solvent such as toluene and xylene, an alcohol solvent such as ethanol and butanol, a ketone solvent such as methyl ethyl ketone and cyclohexanone, and a cellosolve solvent such as methyl cellosolve and butyl cellosolve. One or two or more ester solvents such as butyl acetate can be used. The coating material of the present invention is characterized in that it has a low viscosity even though the copolymerized epoxy resin used has a high molecular weight and can be used with a low solvent content. For example, as a coating material having a solid content of 25% or more, Can be used. Generally, in consideration of coating workability and the like, it is preferable to use it as a paint in the form of a solution having a solid content of 20 to 30%.

The coating composition may contain a modifier or a compounding agent known per se, for example, a modifier such as a fatty acid, a polymerized fatty acid, a rosin, a drying oil or a xylene resin by mixing or precondensation. An acetal resin, a leveling agent such as silicone oil, a lubricant such as wax, a curing accelerator for phosphoric acid or a metal salt of naphthenic acid, and the like may be added.

[Use] The coating material of the present invention is useful as a coating material for various substrates, but is particularly useful as a coating material for cans. This paint can be applied to the can material at any stage.

This coating material can be applied to coil coating on a can lid, and is coated on pure aluminum or aluminum alloy to obtain a coated metal material having a high workability. The material for painted cans is punched, press-molded, or scored, button-formed, tabs are attached, and the like to form can lids or easy open can lids. Of course, the order is reversed, and the paint is applied to a can body, a can lid or a can after can-making,
The paint may be baked, and the paint may be provided as a single coat or a double coat.

Of course, this paint can also be used for painting the body of a can. In the case of a three-piece can having a side seam, a black plate, various coated steel plates such as tin, chrome,
Plated steel plate whose surface is plated with aluminum, zinc, etc., steel plate whose surface is chemically or cathodically treated with chromic acid and / or phosphoric acid, etc .; light metal plate such as aluminum; resin film such as polyolefin, paper board, etc. A material for cans such as a composite metal material in which aluminum foil or the like is adhered and laminated on the surface of an organic substrate is applied in advance with the paint, then baked, and then joined by means such as soldering, welding, or joining with an adhesive, It will be a can body. In the case of a two-piece can, a painted metal plate is subjected to deep drawing or thinning deep drawing to obtain a painted can body.

In the case of a seamless can body, the can material may be subjected to a squeezing process or a squeezing-ironing process, and the paint may be applied to the molded can body and baked.

The coating material of the present invention can be coated with a can material, a can by any means such as dip coating, roller coating, spray coating, brush coating, electrostatic coating, electrodeposition coating, wire coating, flow coating and doctor coating. It can be applied to the barrel, can lid or can. The paint thickness is generally 1 on a dry basis.
It can be in the range of from 15 to 15 microns, in particular 3 to 10 microns.

The baking condition of the paint is characterized in that it can be baked at a low temperature for a short time, and it varies depending on the compounding amount of the above-mentioned copolymerized epoxy resin or resol-type phenol resin in the paint, but generally 180 It is only necessary to select conditions from the temperature of ˜270 ° C. and the baking time of 10˜180 seconds that can achieve sufficient curing in terms of chemical resistance and hot water resistance.

[0080]

The present invention is described in detail in the following examples. The percentages and parts used in this example are percentages by weight and parts by weight.

[Measurement of Molecular Weight] Tetrahydrofuran (TH
The molecular weight of the epoxy resin was measured by GPC method (gel permeation chromatography) using F) as a developing solvent. The calibration curve is based on Tosoh polystyrene standard samples (F-128, F-40, F-10, F-
4, F-2, F-1, A-2500, A-500), and the molecular weight of the epoxy resin is 20.
The number average molecular weight (Mn),
Weight average molecular weight (Mw) and molecular weight distribution (Mw / M
n) was calculated. Epoxy resin 4mg portion 1ml THF
The sample solution was adjusted at such a rate that it was dissolved in the solution, and the measurement was performed under the conditions of a sample injection amount of 100 μl, a solvent flow rate of 1 ml / min, and 40 ° C. GPC and column are Tosoh's HLC-
8020 and TSK-GEL (G1000HXL, G20
00HXL, G3000HXL, G4000HXL) was used, and the analysis time was 50 minutes. When the sample to be measured contains a large amount of solvent other than THF, most of the solvent was dried and removed before preparation of the sample solution.
Furthermore, from the area ratio of the GPC chart, M in the epoxy resin
A low molecular weight fraction (%) of n = 1000 or less was determined.

[Epoxy equivalent: EEW] 3 to 4 g of an epoxy resin is precisely weighed to a 0.1 mg unit in a 100 ml Erlenmeyer flask, and 20 ml of methylene chloride is added and dissolved. Tetraethylammonium bromide (TEAB) reagent (TEAB 1g / 4ml glacial acetic acid solution)
10 ml and crystal violet (CV) indicator (C
V1g / l glacial acetic acid solution) 2-3 drops, and titrated with 0.1N perchloric acid acetic acid solution. A blank test was conducted in the same manner, and the epoxy equivalent was calculated from the following formula. W: Sample weight (g) V: Titration amount of 0.1N perchloric acid acetic acid solution (ml) B: Titration amount of blank test 0.1N perchloric acid acetic acid solution (m
l) N: Normality of 0.1N perchloric acid acetic acid solution (eq / l) F: Factor of 0.1N perchloric acid acetic acid solution

[Viscosity Measurement] The viscosity of the paint was measured at 25 ° C. with a # 4 Ford cup for measuring the outflow time (seconds) of the paint and with a Brookfield (B type) viscometer at 60 revolutions using a # 2 rotor. . The coating composition for a can of the present invention was developed mainly for the purpose of coating a metal plate by natural or reverse roll coating, and the suitable coating viscosity range is # 4 Ford cup viscosity of 30 to 150 seconds, 100
To 600 cps. When the viscosity is higher than the proper viscosity range for coating, it causes poor transfer of the coating material to the plate material and poor leveling, and it becomes difficult to adjust the coating amount. If the viscosity is lower than the above range, problems such as dripping and sagging of the coating material and scattering of the coating material from the roll edge become difficult, and it becomes difficult to secure the film thickness.

[Evaluation of coating film performance] "Retort dissolution: potassium permanganate consumption" was used to evaluate the coating film performance.
The four items of "retort whitening", "feathering", and "processing corrosion resistance" were performed. Details of each test are given in Example 1.

"Retort elution" is an evaluation of the total amount of organic substances that may elute in the beverage from the coating film, and is a very important test from the viewpoint of hygiene and flavor (flavor preservation). Yes, potassium permanganate consumption is 1
It is preferably less than 0 ppm.

"Retort whitening" refers to the appearance of the coating film after retort. A coating film that is whitened by the retort is generally insufficiently cured, and the heat resistance and water resistance of the coating film are insufficient. Indicates. In the case of paints using high molecular weight epoxy resin, if the curing is considered to be insufficient, the processability will be good and the coating film will have good continuity after lid molding, but in the case of such a lid, the corrosiveness of the contents However, in many cases, the corrosion resistance of the coating film is insufficient and corrosion occurs relatively early.

The "feathering property" is an evaluation of the adhesion between the coating film and the base metal. In recent years, the can lid has been changed from the pull-tab type to the Stein-tab type, and thus the occurrence of feathering, which is a fatal defect in the pull-tab type, has become less practical. However, coatings with poor adhesion generally have poor corrosion resistance and are still an important test in predicting long term corrosion resistance performance.

"Processing corrosion resistance" is obtained by actually performing lid molding,
It is an accelerated aging test that evaluated corrosion resistance with a corrosion model liquid,
It is very important for practical use. Using a mixed solution of salt and citric acid as the corrosion model liquid, the corrosion resistance to acidic drinks and drinks containing salts was evaluated.

[Bisphenol F] phenol and 37%
F-1 to F- shown in Table 1 from formalin by a conventional method
4 kinds of 4 bisphenol F were synthesized. The molar ratio of phenol to formaldehyde is 4: 1 and the reaction time is 2.5.
Time, reaction temperature 100 ℃, catalyst used and pH
Was changed to synthesize various bisphenol F, and binuclear purity and content of three isomers were determined by HPLC measurement. F
-3 and F-4 are examples in which the degree of purification of bisphenol F is changed.

[Liquid Epoxy Resin] A reactor equipped with a stirrer, a thermometer, a dropping funnel, and a device for condensing and separating the azeotropic mixture of epichlorohydrin and water to return epichlorohydrin to the reactor is charged with bisphenol and epichlorohydrin. The mixture was charged at a molar ratio of 1:10 and heated to reflux with stirring. A 2.5-fold molar amount of sodium hydroxide was added dropwise to the bisphenol in the form of a 40% aqueous solution for 3 hours for reaction. After completion of the dropwise addition of sodium hydroxide, heating was continued for 15 minutes to completely remove water, and then unreacted epichlorohydrin was collected and removed by distillation.
Further, the product was repeatedly washed in hot water to remove sodium chloride and sodium hydroxide, and then heated to about 120 ° C. to completely remove water by drying. The properties of the obtained liquid epoxy resin are shown in Table 2.

[Copolymerized Epoxy Resin] From various bisphenol F shown in Table 1 or a mixture of bisphenol F and bisphenol A or bisphenol A, and a liquid epoxy resin (LER-1 or LER-2) shown in Table 2 by a conventional method. The copolymerized epoxy resin was polymerized. LE
R and bisphenol are 1.00: 1.00 to 1.0
Used at a molar ratio of 8: 1.00. Ethyltriphenylphosphonium acetate / acetic acid complex catalyst and diethylene glycol n-butyl ether were used in an amount of 0.1 part and 10 parts, respectively, per 100 parts of resin raw material (LER + bisphenol) and heated to 175 ° C. for 1.5 hours, and then 1
Hold at 75 ° C for 1 to 3.5 hours to grow to the desired molecular weight, and 140 parts of mixed solvent (butyl cellosolve 50%
+ Butyl carbitol 50%) to stop the reaction,
A resin solution having a solid content of 40% was prepared. The molecular weight and epoxy equivalent of the obtained copolymerized epoxy resin were determined by the GPC method and titration and are summarized in Table 3. The bis A / F ratio in the table is the molar ratio of the bisphenol A component and the bisphenol F component in the copolymerized epoxy resin.

[Resol type phenol resin] Various resol type phenol resins were synthesized from phenols and formaldehyde using a sodium hydroxide catalyst. Formaldehyde was used as 37% formalin and sodium hydroxide was used as a 40% aqueous solution. To the reaction product, 10-fold molar amount of n-butanol of phenols was added, sodium hydroxide was neutralized with an excess amount of 20% hydrochloric acid aqueous solution, and the mixture was stirred for several minutes and allowed to stand to remove the separated aqueous layer. Thus, an organic layer containing a resol type phenol resin was obtained. The obtained organic layer was washed and neutralized with water and ammonia water, and after removing water by distillation, further concentrated to obtain a solid content of 40%.
A resol type phenol resin solution was prepared. Table 4 shows the synthesis conditions and molecular weight of the resol-type phenol resin.
The molecular weight of the resol type phenolic resin was measured according to the method described in [Molecular weight measurement]. A polystyrene standard sample for a calibration curve was added with a styrene monomer to prepare a calibration curve, and a molecular weight of 100 or more was calculated. And Mn and Mw were determined.

Example 1 40% copolymer epoxy resin solution of CE-2 and RP-1
40% resol type phenolic resin solution of bisphenol F of is mixed in a weight ratio of 95: 5 and diluted with a mixed solvent of butyl carbitol: butyl cellosolve: xylene: MIBK (methyl isobutyl ketone) = 1: 1: 1: 1. To a solid content of 23%. The obtained resin solution was maintained at 80 ° C. for 1 hour with stirring to improve miscibility, and then filtered to prepare a can-making coating material.

The thus-obtained can coating composition had a viscosity of 25 seconds at a # 4 Ford cup viscosity of 110 seconds and a viscosity of 386 cps as measured by a B-type viscometer, showing a value within a suitable coating viscosity range.

Aluminum 5 0.28 mm thick with no external coating
182 materials, and the same aluminum material with a coating film of 5 μm on the outer surface, the dry coating amount on the inner surface was 110 mg / dm
Roll coating was performed so that it became ^2, and it was baked by passing through a conveyor-conveying hot air oven. The baking condition is a mountain-shaped temperature curve in which the passing time of the hot air zone in the furnace (hereinafter referred to as "pass time") is 20 seconds and the maximum attainable temperature (PMT: peak metal temperature) is actually 250 ° C. Is the condition for drawing.

The retort dissolution property of the coating film was evaluated using a coating material having no outer surface. Using 1 ml of distilled water per 1 cm ^{2 of} coating,
Retort extraction was performed at 125 ° C. for 30 minutes, and the extract and the blank test solution were subjected to the potassium permanganate consumption test method described in “Ministry of Health and Welfare Notification No. 20, Test method for general equipment or container packaging”. The consumption amount of potassium permanganate was calculated by the following formula. a: Titration amount of 0.01N potassium permanganate solution in this test (ml) b: Titration amount of 0.01N potassium permanganate solution in blank test (ml) The obtained potassium permanganate consumption was 6 0.6 ppm
Therefore, it was found that the excellent retort dissolution property was exhibited despite the low temperature and short time baking.

Next, a pull tab type can lid having a nominal diameter of 206 was molded using the coating material for the inner and outer surfaces. The formed can lid was subjected to retort treatment (125 ° C. for 30 minutes) in tap water, opened, and the presence or absence of feathering at the opening was evaluated. The occurrence of feathering was 0 in 10 can lids. When the adhesion between the coating film and the aluminum base is poor, the coating film on the tab side is peeled off and remains at the opening score portion, and a jagged coating film sticks out from the opening end, and a feathering phenomenon occurs. The whitening of the coating film after retort was evaluated at the same time as the feathering test, but the whitening was 0 in 10 sheets.

Next, using the coating material on the inside and outside, a nominal 206
Diameter canister tab type can lid is molded, and the can lid curl is lined with an SBR-based aqueous compound at 100 ° C-
It was dried for 10 minutes. 5% salt + in a 350 ml seamless can with a nominal diameter of 211 and a neck-in diameter of 206
50 ml of a 5% citric acid aqueous solution was filled, and the can lid obtained here was double-wound to produce a sample can for corrosion resistance evaluation. When the sample cans for corrosion resistance evaluation were stored upside down at 50 ° C. for 1 month, the corrosiveness of the inner surface of the can lid was evaluated, and it was found that corrosion was 0 in 10 cans.

Example 2 40% copolymer epoxy resin solution of CE-3 and RP-1
A 40% resol type phenolic resin solution of bisphenol F in Example 2 was mixed at a weight ratio of 95: 5, and a can-making coating composition having a solid content of 23% was prepared in the same manner as in Example 1. The resulting can coating composition had a viscosity of 25 seconds at a # 4 Ford cup viscosity of 92 seconds and a viscosity by a B-type viscometer of 320 cps.
The values in the proper coating viscosity range are shown in Table 1. Further, a coated plate was prepared in the same manner as in Example 1 and evaluated for retort elution property, feathering property, retort whitening property, and corrosion resistance. The results are summarized in Table 5, and it was found that they exhibited excellent coating performance and low-temperature short-time bakeability as a paint for can lids.

Comparative Example 1 40% copolymer epoxy resin solution of CE-1 and RP-1
A 40% resol type phenolic resin solution of bisphenol F in Example 2 was mixed at a weight ratio of 95: 5, and a paint having a solid content of 23% was prepared in the same manner as in Example 1. 25 of the resulting paint
The # 4 Ford cup viscosity at ° C was 300 seconds or longer, and the viscosity on a B type viscometer was 1500 cps.
(Hereinafter, the viscosity in seconds is the viscosity of # 4 Ford cup at 25 ° C, and the viscosity in cps is the value measured by B-type viscometer, # 2 rotor.) The solid content of the mixed solvent used in Example 1 was 1
When it was diluted to 9% and the viscosity was measured again, it was 120
The second was 413 cps. No coating on outer surface 0.28
mm 5182 aluminum with a dry coating thickness of 11 on the inner surface
Attempts were made to roll coating to 0 mg / dm ² , but the solid content was low and the limit was to secure a film thickness of 90 mg / dm ² . When the retort dissolution property and retort whitening were evaluated by baking at a PMT of 250 ° C. and a pass time of 20 seconds in the same manner as in Example 1, the whitening tendency was 12.3 ppm.
Furthermore, aluminum 5182 with an unpainted outer surface and a plate thickness of 0.28 mm
Material, and the same aluminum material with a 5 μm coating on the outer surface,
Each of the inner surfaces was roll-coated so that the dry coating amount was 70 mg / dm ² , and baked at PMT of 250 ° C. and a pass time of 20 seconds. When the retort dissolution and retort whitening were evaluated, the retort dissolution was 9.8 ppm, and no coating whitening was observed. This is understood to be the result of reducing the film thickness and increasing the heating efficiency during baking. Then, a Stein tab type can lid having a nominal diameter of 206 was prepared in the same manner as in Example 1 and the corrosion resistance was evaluated. Corrosion appeared in 5 out of 10 cans.

Comparative Example 2 CE-4 40% copolymerized epoxy resin solution and RP-1
A 40% resol type phenolic resin solution of bisphenol F of was mixed in a weight ratio of 95: 5, and a coating material having a solid content of 25% was prepared in the same manner as in Example 1. The viscosity of the obtained paint was 73 seconds and 254 cps. Aluminum 5182 with unpainted 0.28 mm thickness and 5 μm on the outside
Roll coating was applied to the same aluminum material with the coating film of No. 1 on the inner surface side so that the dry coating film amount was 110 mg / dm ^2.
It was baked at MT 250 ° C. and a pass time of 20 seconds. When the retort dissolution and retort whitening were evaluated, the retort dissolution was 9.4 ppm, and no coating whitening was observed. Then, a Stein-tab type can lid having a nominal diameter of 206 was prepared in the same manner as in Example 1 and its corrosion resistance was evaluated.
Corrosion appeared in 4 out of 0 cans.

Comparative Example 3 40% copolymer epoxy resin solution of CE-5 and RP-2
A 40% resol type phenolic resin solution of bisphenol F was mixed at a weight ratio of 95: 5, and the resin solution was diluted with the mixed solvent of Example 1 so that the proper viscosity range for coating was obtained to prepare a coating material. The resulting coating had a solids content of 15% and a viscosity of 118 seconds and 412 cps. A coating of 70 mg / dm ^{2 of} dry film thickness is roll-coated on the inner surface of an aluminum 5182 material having an uncoated outer surface and a thickness of 0.28 mm, and on the outer surface of the aluminum material having a coating film of 5 μm. PMT250 Baking was carried out at 20 ° C. for 20 seconds.
The film thickness of 70 mg / dm ² was the limit of roll coating because the solid content of the coating was low. Retort dissolution, retort whitening,
When the feathering property was evaluated, all were good, and the retort elution property was 3.1 ppm, which was a very excellent value. Further, the result of evaluating the corrosion resistance in the same manner as in Example 1 was 1
Corrosion was observed in 3 out of 0 cans. The copolymerized epoxy resin used in this comparative example has a very high molecular weight and was excellent in processability and elution properties, but the molecular weight was too large, and therefore the paint solid content had to be lowered from the viewpoint of coatability, As a result, it is understood that it was difficult (or impossible) to secure a sufficient film thickness, and as a result, the coating film could not withstand the lid molding.

Examples 3 and 4 40% solution of CE-6 copolymerized epoxy resin and RP-2
40% resol type phenolic resin solution of bisphenol F was mixed in a weight ratio of 95: 5 and 97: 3, and can coating materials for cans of Examples 3 and 4 were prepared in the same manner as in Comparative Example 3. . The solid content of each of the obtained coating materials for cans was 23%, and the viscosity was 97 seconds and 332 cps for the coating material of Example 3, and 107 seconds and 375 cps for the coating material of Example 4. A coated plate was prepared in the same manner as in Example 1, and the retort elution property, retort whitening property, feathering property, and corrosion resistance were evaluated for each paint, and good results were obtained in all cases. The retort dissolution property was 3.5 ppm in Example 3 and 3.2 pp in Example 4.
m was a very excellent value.

Examples 5, 6 and Comparative Examples 4, 5, 6 CE-7, CE-8, CE-9, CE-10, and CE
A 40% copolymerized epoxy resin solution of -11 and a 40% resol type phenolic resin solution of bisphenol F of RP-2 were mixed at a weight ratio of 95: 5, and each of Examples 5 and 6 was carried out in the same manner as in Comparative Example 3. Paints for can manufacturing, Comparative Examples 4, 5, and 6
A paint was prepared. In the same manner as in Example 1, the solid content and viscosity of the obtained coating material, the performance of the coating film and the coated plate were evaluated, and the results are summarized in Table 5.

In Comparative Example 4, the paint can be highly solidified and the amount of solvent used can be expected to be greatly reduced, but the molecular weight of the copolymerized epoxy resin is low, and the retort elution, retort whitening and corrosion resistance are insufficient. It was a result. PMT270
Even when the curing was promoted by reviewing the baking conditions of 30 ° C. and the pass time of 30 seconds, evaluation was made, but no satisfactory result was obtained.

Comparative Example 5 is a case where a bisphenol F component of a copolymerized epoxy resin having a large pp methylene bond content was used. The paint viscosity was high, and it was necessary to keep the solid content low during painting, which made it impossible to secure the film thickness. Also, the reactivity between the resin and the curing agent seems to drop,
Insufficient results were obtained in retort dissolution and retort whitening.

Comparative Example 6 is a case where a liquid epoxy resin of bisphenol F and a copolymerized epoxy resin from bisphenol A are polymerized and used in a paint. In terms of paint solids and viscosity, there was not much difference from the can-making paint shown in the examples,
The retort dissolution property was insufficient. It is considered that this is because the low molecular weight fraction of the resin was high.

Examples 7 and 8 40% copolymerized epoxy resin solution of CE-7 and RP-3
40% resol type phenolic resin solution of bisphenol F was mixed at a weight ratio of 95: 5 and 93: 7 and diluted with the mixed solvent used in Example 1 to obtain a solid content of 24.
% And 25% of the canning coatings of Examples 7 and 8 were prepared. The viscosity of the obtained can coating composition was 50 seconds and 172 cps in Example 7, and 83 seconds and 291 cps in Example 8. No coating on the outer surface 0.28 mm
Of aluminum 5182 material and the same aluminum material with a coating film of 5 μm on the outer surface side, and a dry coating film amount of 110 on the inner surface side.
Roll coated to give mg / dm ² and PMT250
Baking was carried out at 20 ° C. for 20 seconds. Table 5 shows the test results of the retort dissolution property, retort whitening, feathering property and corrosion resistance of the coating film. Good results were obtained in all tests.

Comparative Example 7 40% copolymer epoxy resin solution of CE-7 and RP-3
Was mixed with a 40% resol type phenol resin solution of bisphenol F in a weight ratio of 85:15 and diluted with the mixed solvent used in Example 1 to prepare a coating material having a solid content of 25%. The viscosity of the resulting paint was 63 seconds and 222 cps. Aluminum 518 with an unpainted outer surface and a thickness of 0.28 mm
Two materials, and the same aluminum material with a coating film of 5 μm on the outer surface, each having a dry coating film amount of 110 mg / dm ² on the inner surface.
The roll coating was carried out so as to obtain a temperature of PMT of 250 ° C., a pass time of 20 seconds and a PMT of 270 ° C. for 30 seconds. The performance of the coating film and the coated plate was evaluated, but no satisfactory result was obtained under any baking condition. Table 5 summarizes the evaluation results.

Comparative Example 8 A copolymer epoxy resin solution of CE-3 and a resol type phenol resin of bisphenol F of RP-3 were prepared as 99.
A coating material of Comparative Example 8 was prepared by combining in a weight ratio of 5: 0.5 and diluting with the mixed solvent of Example 1. The solid content of the paint was 23%, and the viscosity at that time was 119 seconds and 413 seconds.
cps. When a coated plate was prepared in the same manner as in Example 1 and the coating film performance was evaluated, the retort dissolution property was 2.7 ppm, which was very excellent, but the coating film was whitened by the retort, and feathering and corrosion resistance were observed. In the test all samples showed feathering and corrosion. The baking condition is P
Even if the MT 270 ° C. and the pass time were changed to 30 seconds, the above tendency did not change.

Example 9 The copolymerized epoxy resin of CE-3, the bisphenol A of RP-4 and the resole type phenolic resin of p-cresol were mixed in a weight ratio of 92: 8 and diluted with the mixed solvent of Example 1. To prepare a coating composition for cans having a solid content of 23%. In addition, in order to improve the miscibility of each component in the paint, heat treatment was performed at 80 ° C. for 1 hour. The viscosity of the obtained paint is 116 seconds, 400
cps. Aluminum 5182 with 0.28 mm plate thickness without coating on the outside and the same aluminum with 5 μm coating on the outside have a dry coating amount of 110 mg /
It was roll coated to dm ² and baked at PMT 270 ° C. and a pass time of 30 seconds. From the coating film performance test, the retort dissolution property was 9.3 ppm, and good results were also obtained in the retort whitening, feathering, and corrosion resistance tests.

Comparative Example 9 Phenoxy resin (trade name: PKHH) manufactured by Phenoxy Associates (Mn: 12400, Mw: 6580)
0, EEW: 26000 g / eq) and a resole type phenol resin of RP-4 were combined at a weight ratio of 92: 8 and dissolved in the mixed solvent of Example 1 to prepare a coating material having a solid content of 15%. The viscosity of the obtained paint is 115 seconds, 40
It was 6 cps. We tried roll coating on the inner surface of aluminum 5182 material with a thickness of 0.28 mm with no outer surface coating and the same aluminum material with a 5 μm coating film on the outer surface.
70 mg / dm as dry coating amount due to low paint solids
² was the limit. The coating performance was evaluated by baking at PMT 270 ° C. and a pass time of 30 seconds. The retort dissolution property was 22.3 ppm, which showed a tendency of retort whitening. Feathering was observed in 3 out of 10 sheets in the feathering test, and corrosion was observed in all 10 cans in the corrosion resistance test. PKHH resin is a high molecular weight epoxy resin obtained from bisphenol A and epichlorohydrin by a one-step polymerization method (Tuffy method).

Comparative Example 10 CE-12 bisphenol F type epoxy resin and RF-
3 bisphenol F resol type phenolic resin 9
A coating material having a solid content of 23% was prepared in the same manner as in Example 1 by combining the components in a weight ratio of 5: 5. The viscosity of the obtained paint is
It was 362 cps in 103 seconds. Aluminum 5182 with unpainted 0.28 mm thickness and 5 μm on the outside
Roll coating on the inner surface of the same aluminum material with a dry coating amount of 110 mg / dm ² ,
PMT250 ℃, pass time 20 seconds and PMT27
Baking was performed under conditions of 0 ° C. and a pass time of 30 seconds. PMT2
At 50 ° C. for 20 seconds, the retort dissolution property was poor, and 17.
2 ppm and a slight tendency to retort whitening were seen, but good results were obtained in terms of feathering and corrosion resistance. In the case of PMT270 ° C. for 30 seconds, the retort elution property was 9.3 ppm, and the retort whitening and feathering properties were also good, but the corrosion resistance test showed 7 out of 10 cans.
Corrosion was found in the can. As a result of strengthening the baking, although the retort dissolution and whitening of the retort were improved, it seems that the workability was greatly impaired and the corrosion resistance was deteriorated.

[0114]

[Table 1]

[0115]

[Table 2]

[0116]

[Table 3]

[0117]

[Table 4]

[0118]

[Table 5]

The following table is shown as a reference material.

[Table 6]

[0120]

According to the present invention, a copolymerized epoxy resin having a number average molecular weight of 8,000 to 15,000 derived from bisphenol A and bisphenol F having a molar ratio of 5: 5 to 8: 2 and a methylol group-containing thermosetting resin. By combining it with a water-soluble resin curing agent to form a coating for cans, it has excellent workability with a low solvent content, low-temperature short-time curability, and the coating film after curing has high processability and high It has been possible to provide an epoxy-based coating material for cans having corrosion resistance and low elution into the contents. This paint can be applied to coil coating on can lids.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display area C08G 59/62 NJS C08G 59/62 NJS

Claims (8)

[Claims] 1. A copolymerized epoxy resin having a number average molecular weight of 8,000 to 15,000 derived from bisphenol A and bisphenol F in a molar ratio of 5: 5 to 8: 2 and a methylol group-containing thermosetting resin curing agent. A coating material for cans characterized by being contained. 2. The copolymerized epoxy resin is bisphenol A.
The can coating composition according to claim 1, which is a copolymerized epoxy resin derived from the diglycidyl ether and the bisphenol F or a mixture of bisphenol F and bisphenol A. 3. The can-making coating composition according to claim 1, wherein the bisphenol F contains 60 mol% or more of o-o and o-p methylene bonds. 4. The can coating composition according to any one of claims 1 to 3, wherein the copolymerized epoxy resin is a copolymerized epoxy resin containing a component having a molecular weight of 1,000 or less in an amount of less than 2% by weight. 5. The can according to claim 1, wherein the copolymerized epoxy resin is a copolymerized epoxy resin having an average number of epoxy groups per molecule in the range of 0.6 to 1.5. Paint. 6. The can-making coating composition according to claim 1, wherein the methylol group-containing thermosetting resin curing agent is a resol-type phenol resin. 7. The can coating composition according to claim 6, wherein the resol-type phenol resin is a resol-type phenol resin derived from bisphenol F and formaldehyde. 8. The can-making coating composition according to claim 6, wherein the resol-type phenol resin is present in an amount of 1 to 10 parts by weight per 100 parts by weight of the epoxy resin.