JPH10310683A - Epoxy resin and coating composition containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an epoxy resin that has a reduced content of components to be extracted in thermal sterilization and is useful for coating the inside of beverage cans, by subjecting a bisphenol epoxy resin having a specified epoxy equivalent and a dihydric phenol to addition polymn. to give a bisphenol epoxy resin having a specified epoxy equivalent and number average mol.wt. SOLUTION: This epoxy resin is a bisphenol epoxy resin which has an epoxy equivalent of 1,500-60,000 g/eq and a number average mol.wt. of 3,000-15,000 and is obtd. by the addition polymn. of a bisphenol epoxy resin of formula I (wherein X is a bisphenol residue; and n is a positive integer) having an epoxy equivalent of 450-2,000 and a dihydric phenol. A bisphenol and/or a phenolic- hydroxyl-terminated bisphenol epoxy resin of formula II having a phenolic hydroxyl equivalent of 300-1.200 is used as the dihydric phenol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bisphenol type epoxy resin and a coating composition comprising the resin and a curing agent component, and is particularly useful for coating the inner surface of a beverage can for storing a beverage. High-molecular-weight bisphenol-type epoxy resin and a coating composition thereof.

[0002]

2. Description of the Related Art Metal materials such as aluminum, tinplate, and tin-free steel are used as materials for so-called "food cans" such as edible cans and beverage cans, and these metals prevent corrosion due to the contents thereof. In general, coating with a paint is carried out for the purpose of cleaning. Usually, the food can is filled with the contents and sealed, and then subjected to a high-temperature heating treatment (retort treatment). At this time, a problem arises in that some of the coating film components are eluted. If the amount of the eluted components is large, it is not preferable from the viewpoint of hygiene, and even if the amount is very small, there is a problem that the taste and flavor of the contents (flavor retention) are impaired. In recent years, the contents of beverage cans have become diversified, especially among food cans. In particular, the content of low-sugar or sugar-free products such as Japanese tea, oolong tea, and black tea is increasing, and beverage cans used for these are particularly important in flavor retention.

Conventionally, epoxy / phenol resin-based paints, epoxy / amino resin-based paints, epoxy / urea resin-based paints and the like, which are excellent in adhesion, workability, corrosion resistance, etc., have been used as paints for the inner surface of food cans. The epoxy resins used for these are polycondensates of bisphenols and epihalohydrin (direct synthesis method) or polyaddition products of epoxy resins having a number average molecular weight of 1,000 or less and bisphenols (indirect polymerization method). In any of the above methods, the obtained high-molecular-weight epoxy resin having a molecular weight suitable for the resin viscosity range usually used in the coating composition cannot avoid the remaining of low-molecular components not directly involved in the curing reaction. For this reason, there has been a problem that uncured low molecular components remain in the baked coating film and are eluted into the contents to lower the flavor retention.

As a method for solving this problem, for example, Japanese Patent Publication No. 6-78498 discloses a method using a bisphenol-type epoxy resin characterized in that most of the terminal groups are phenolic hydroxyl groups. However, although this method improves the flavor retention, there is a problem that the adhesion, workability and retort resistance of the coating film are inferior. Japanese Patent Publication No. 3-12113 discloses that the number average molecular weight is 2,000 to 8,000, the dispersion ratio between the number average molecular weight and the weight average molecular weight is 1.8 to 2.6, and the molecular weight is 600 or more and one molecule. A bisphenol A type epoxy resin containing at least 99.4% by weight of an epoxy resin component containing at least one secondary hydroxyl group per one and having an average number of epoxy groups per molecule of at least 1.2. And an agent for coating the inside of a can. Further, JP-A-1-230678 discloses a purified bisphenol in which an epoxy resin having a number average molecular weight of 2,000 to 6,000 is brought into contact with a lower alcohol by being melted in a parent solvent or by heating to reduce a component having a molecular weight of 800 or less. A water-based paint for the inner surface of a can using a mold epoxy resin is disclosed. However, the former requires several times of purification of the epoxy resin by distillation under reduced pressure, and the latter also requires several times of contact with a lower alcohol, which is industrially disadvantageous and such a method. In the epoxy resin obtained in the above, there were components extracted from the coating film when the contents were heat-sterilized, and the flavor retention was not satisfactory. On the other hand, JP-A-7-310047 discloses that the α-glycol group content is 1 meq / 100 g or less, the hydrolyzable chlorine content is 150 ppm or less, and the number average molecular weight is 3000 to 800.
A coating composition using a No. 0 epoxy resin is disclosed. This epoxy resin is obtained in an industrially advantageous manner,
Excellent coating film adhesion, workability, retort resistance, etc.
The flavor retention was not satisfactory as described above.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and to provide an epoxy resin in which components extracted during heat sterilization treatment are reduced, an adhesiveness, workability, retort resistance and flavor. An object of the present invention is to provide a coating composition capable of forming a coating film having excellent holding properties and the like.

[0006]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a high molecular weight obtained by a polyaddition reaction between a specific bisphenol type epoxy resin and a specific bifunctional phenol. Bisphenol type epoxy resin substantially does not contain a low molecular component of n = 0,
The present inventors have found that a coating composition comprising the resin and the curing agent component can form a coating film having excellent adhesion processability, retort resistance, flavor retention, and the like, and have completed the present invention.

That is, the present invention is obtained by an addition polymerization reaction between a bisphenol type epoxy resin (a) having an epoxy equivalent of 450 to 2,000 g / eq represented by the following general formula (1) and a bifunctional bisphenol (b). A bisphenol type epoxy resin [A] having an epoxy equivalent of 1,500 to 60,000 g / eq and a number average molecular weight of 3,000 to 15,000, wherein the bifunctional phenol (b) is a bisphenol ( b-1) and / or a modified bisphenol-type epoxy resin (b-2) containing a terminal phenolic hydroxyl group having a phenolic hydroxyl equivalent of 300 to 1,200 g / eq represented by the following general formula (2). Wherein the bisphenol-type epoxy resin (a) contains a phenolic hydroxyl group represented by the general formula 2 A bisphenol-type epoxy resin obtained by epoxidizing a phenolic hydroxyl group of a phenolic epoxy resin (b-2), and an adhesive comprising the resin [A] and a curing agent [B]. An object of the present invention is to provide a coating composition capable of forming a coating film having excellent properties, workability, retort resistance and flavor retention.

[0008]

Embedded image

(In the formula (1), X is a residue of a bisphenol, and a plurality of Xs may be the same or different. Also, n is an integer of 1 or more which does not include 0 in the number of repeating units. )

[0010]

Embedded image

(In the formula (2), X is a residue of a bisphenol, a plurality of Xs may be the same or different, and n is an integer of 0 or more in the number of repeating units.)

The modified bisphenol type epoxy resin (b-2) having a terminal phenolic hydroxyl group can be prepared by a so-called direct synthesis method in which a bisphenol is reacted with epichlorohydrin, or a low molecular weight bisphenol type epoxy resin and a bisphenol Can be synthesized by any of the so-called indirect synthesis methods. In the case of the direct synthesis method, it can be obtained by reacting epichlorohydrin with an excess of bisphenols in the presence of a sodium hydroxide catalyst, and then removing unreacted bisphenols. In the case of the indirect synthesis method, it can be obtained by reacting a low-molecular bisphenol type epoxy resin with an excess of bisphenols and then removing the remaining unreacted bisphenols. The modified bisphenol type epoxy resin obtained by the indirect synthesis method and the direct synthesis method has a phenolic hydroxyl equivalent of 300 to 1,200 g / eq.
1% of unreacted bisphenols remaining
It is desirable to be less than. Hydroxyl equivalent is 300g / eq
In the following, bifunctional phenols remaining during the production increase, which is industrially disadvantageous. If it is 1,200 g / eq or more, it is difficult to form a high molecular weight substance and to solidify it. Preferably it is in the range of 400 to 800 g / eq. Further, if the amount of the remaining unreacted bisphenol exceeds 1%, the hygiene and flavor retention of the cured coating film are deteriorated due to the influence of low molecular components, and the content is preferably 0.5% or less.

As a method for removing unreacted bisphenols remaining after the reaction, there are a solvent extraction method, a recrystallization method, a molecular distillation method, a treatment method using a separation membrane, and a method of dissolving and removing in an aqueous alkali solution. Etc., but industrially, a molecular distillation method and an aqueous alkali solution dissolution method are preferred. As a method for dissolving an alkaline aqueous solution, after the reaction is completed in both the direct synthesis method and the indirect synthesis method, the above-mentioned solvent is added and diluted so that the solid content becomes 20 to 50% by weight, and a phenolic hydroxyl group is added to the generated terminal. An alkali metal hydroxide is added and reacted in an equimolar amount with respect to 1 mole of the phenolic hydroxyl group of the unmodified bisphenol-type epoxy resin and the unreacted bisphenol to generate an alkali metal phenolate. The reaction is carried out at 30 to 100 ° C. for 10 minutes to 5 minutes.
It can be implemented in about an hour. Next, from the high molecular weight product dissolved in the solvent, only the alkali metal phenolate of bifunctional phenol is separated and removed as an aqueous solution. Most of the remaining bisphenols can be removed by one separation operation. After removing the bisphenols, neutralization and washing with an acid such as phosphoric acid or sodium phosphate, and then distilling off the solvent, the phenolic hydroxyl equivalent is 300 to 1,200 g / eq and the monomeric bisphenols are substantially eliminated. Thus, it is possible to obtain a solid phenolic hydroxyl group-containing modified bisphenol type epoxy resin (b-2) which does not remain.

The bisphenols (b-1) include bisphenol A, bisphenol F, bisphenol S, tetrabromobisphenol A, bisphenol A
D, bisphenol C, etc., and these can be used alone or as a mixture of several kinds, but bisphenol A and bisphenol F are particularly preferable. The bisphenol type epoxy resin (a) having an epoxy equivalent of 450 to 2,000 g / eq is a phenolic hydroxyl group of a modified bisphenol type epoxy resin (b-2) having a terminal phenolic hydroxyl group represented by the above general formula (2). Is a solid epoxy resin obtained by epoxidation with an epihalohydrin in the presence of an alkali metal hydroxide, and can be represented by the same formula as the general formula (1).

The bisphenol-type modified epoxy resin (b)
The bisphenol type epoxy resin (a) obtained by epoxidizing -2) can be obtained by a known method of epoxidizing the modified bisphenol type epoxy resin with epihalohydrin in the presence of an alkali metal hydroxide. Those having an epoxy equivalent of 450 g / eq or less have poor productivity in producing phenol as a raw material, and 2,000 g / eq.
Those having eq or more make it difficult to remove the solvent after epoxidation.

The bisphenol type epoxy resin [A] of the present invention is obtained by reacting the bisphenol type epoxy resin (a) with the bisphenol (b) at a temperature of usually 80 to 220 ° C. for 30 minutes to 20 hours. Let me get it. Bisphenols and the same reaction catalyst as described above are desirable. The amount of catalyst used is the same as above. Further, at the time of producing the bisphenol type epoxy resin [A] of the present invention, a solvent can be used. Solvents that can be used include aromatic hydrocarbons such as toluene, xylene and benzene, ketones such as methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone and acetone, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether and ethylene glycol. Glycol ethers such as monomethyl ether, aliphatic ethers such as diethyl ether, dibutyl ether and ethylpropyl ether, alicyclic ethers such as dioxane and tetrahydrofuran, methanol, ethanol, propanol, n-butanol, isobutanol and pentanol , Hexanol, heptanol and other alcoholic solvents, ethyl acetate, butyl acetate, methyl cellosolve acetate, ethyl cello Lube acetate, although ester solvents such as butyl cellosolve acetate may be used but not limited thereto. These solvents may be used alone or as a mixture of two or more as necessary.

The epoxy equivalent of the bisphenol type epoxy resin [A] of the present invention is from 1,500 to 60,000 g.
/ Eq is desirable. 1,500 g of epoxy equivalent
If it is less than / eq, sufficient workability cannot be obtained when a film is formed, and if it is more than 60,000 g / eq, it is difficult to obtain industrially. When the number average molecular weight is less than 3,000, sufficient workability cannot be obtained when a film is formed, and
It is difficult to obtain more than 000 products industrially.

[0018] The curing agent component [B] of the coating composition of the present invention.
As the resin, those generally used as a curing agent for an epoxy resin can be used, and a resol resin and an amino resin are particularly desirable. Examples of the resole resin include condensates of phenols such as phenols, alkylphenols and bisphenols with aldehydes such as formaldehyde and acetaldehyde in the presence of a basic catalyst and alcohols such as methanol, n-butanol and isobutanol. And the like. On the other hand, examples of the amino resin include condensates of urea, melamine, benzoguanamine and the like with formaldehyde in the presence of a basic catalyst, and alkyl ethers thereof with alcohols.

In the coating composition of the present invention, one or more of these curing agent components may be used as a mixture. The compounding amount is in the range of 1 to 50% by weight based on the total amount of the composition. When the amount is less than 1% by weight, crosslinking is insufficient and the retort resistance of the coating film is poor, and when it exceeds 50% by weight, the bending property of the coating film is poor. The coating composition of the present invention can be used without solvent or, if necessary, dissolved in a solvent. The solvent that can be used is not particularly limited as long as it can dissolve the composition uniformly.

The coating composition of the present invention can be prepared by a known method, for example, by partially esterifying the bisphenol type epoxy resin [A] with an acrylic resin having a carboxyl group in the presence of an esterification catalyst, or The aqueous dispersion can be used as an aqueous coating by dispersing in water by a method of copolymerizing in the presence of an unsaturated monomer and a free radical generator.

In the coating composition of the present invention, a reaction accelerator such as phosphoric acid, p-toluenesulfonic acid and the like can be used as required.

The coating composition of the present invention may optionally contain various additives usually used in epoxy resin coatings, such as fillers, reinforcing agents, pigments, and flow control agents. As a method for applying the coating composition of the present invention, known methods such as spraying, roll coating, brush coating, and flow coating can be used.

The coating composition of the present invention is usually used in an amount of from 120 to 3
The coating can be obtained by baking at a temperature of 00 ° C. for 30 seconds to 20 minutes.

[0024]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the technical scope of the present invention is not limited to the examples. In addition, the compounding number of each component in Examples and Comparative Examples indicates parts by weight unless otherwise specified. The analysis of the epoxy resin and the evaluation of the coating film are described below 1) to 8).
Was performed in the manner described above.

1) Epoxy equivalent: measured by a perchloric acid titration method according to JIS K7236. 2) Number average molecular weight; measured by the GPC method under the following conditions. Apparatus: HLC-8020 (manufactured by Tosoh Corporation) Column: 2 GMHXL + 1 G2000XL (manufactured by Tosoh Corporation) Temperature: 35 ° C., Eluent / flow rate: THF 1 ml / min Detector: RI, calibration method: Conversion with standard polystyrene 3) Dissolution viscosity 25 ° C. using a Gardner-Holtz viscometer
Was measured. 4) Softening point: Measured according to JIS K-7234.

5) Phenolic hydroxyl group equivalent: Tetramethylammonium hydroxide is allowed to act on phenolic hydroxyl groups in a mixed solution of tetrahydrofuran and methanol at 3% by weight to form a color, and 305 n using a spectrophotometer.
The absorbance at m was measured and converted by a calibration curve prepared in advance by the same operation using bisphenol A as a standard. 6) Consumption of potassium permanganate: A sample was dissolved in cyclohexanone to prepare a varnish having a solid content of 25 wt%. This varnish was applied to an aluminum plate having a thickness of 0.3 mm with a bar coder so that the dry coating film became 10 μm,
The sample was dried in an oven for 10 minutes to prepare a test plate. The test plate was placed in a pressure-resistant glass bottle, and the contact ratio between the coating surface area and water was 1 m.
Activated carbon-treated tap water was added to a volume of 1/5 cm ² and sealed, followed by treatment with a retort sterilizer at 125 ° C. for 1 hour. After cooling, the consumption of potassium permanganate in the treated water was measured by the method described in the Food Sanitation Law. 7) Adhesion: 100 pieces of 1 mm × 1 mm grid were cut into the coating film with a cutter knife at a depth reaching the substrate, and then a cellophane tape was applied and instantaneously peeled off. The number of grids of the coating film remaining on the substrate was visually measured.

8) Bending workability: The coated plate was bent so that the coated surface was on the outside, and pressed at 20 ° C. under a pressure of 20 kg / cm ² . Next, the bent portion was measured for the current value using an enamel meter (electricity tester), and the degree of damage to the coating film was evaluated in the following three stages. ：: Current value is less than 1 mA, Δ: Current value is 1 mA or more and less than 5 mA X: Current value is 5 mA or more 9) Retort resistance: After the coated plate is retorted at 125 ° C. for 30 minutes, the degree of whitening of the coating film is visually observed. Was evaluated in the following three stages. ：: no whitening, Δ: partial whitening, ×: whitening of the entire surface

10) Flavor Retention: Put a test plate coated on both sides into a pressure-resistant glass bottle, add tap water treated with activated carbon so that the contact ratio between the surface area of the coating film and water becomes 1 ml / 5 cm ^2, and seal it. It processed at 125 degreeC by sterilizer for 1 hour. After cooling, the flavor of the treated water was compared with water treated without a test plate by a sensory test according to the following evaluation. ：: no change at all, △: slight change, ×: significant change

REFERENCE EXAMPLE 1 YD-128 (manufactured by Toto Kasei; epoxy equivalent: 186 g / eq, viscosity: 12,500 mPa · S / 2) was used as an epoxy resin in a 2 l reactor equipped with a stirrer, thermometer and cooling tube.
150 ° C. of 5 ° C. and 183 parts of bisphenol A were charged,
After heating and melting at 120 ° C., 0.2 part of triphenylphosphine was added and reacted at 150 ° C. for 5 hours. Thereafter, 550 parts of methyl isobutyl ketone was charged and dissolved,
700 parts of 5.5% aqueous sodium hydroxide solution
After stirring at 0 ° C. for 30 minutes, the mixture was allowed to stand and liquid was separated. The resin solution layer was neutralized with phosphoric acid, washed with water, and then methyl isobutyl ketone was distilled off to remove the modified bisphenol type epoxy resin (b-2-
1) was obtained. The resulting modified resin has a hydroxyl equivalent of 653 g.
/ Eq, the softening point was 107 ° C., and the amount of residual bisphenol A was 0.08% from the GPC analysis value.

REFERENCE EXAMPLE 2 130 parts of the resin obtained in Reference Example 1, 220 parts of epichlorohydrin and 44 parts of diethylene glycol dimethyl ether were charged into a reactor equipped with a stirrer, a thermometer, a dropping device and a reaction water recovery device. The resin was dissolved. Next, the pressure inside the system was reduced to 220 torr, and then the system was heated to 80 ° C., and 18.53 parts of a 49% aqueous sodium hydroxide solution was added dropwise over 1 hour. At this time, the temperature in the system is maintained at 80 to 85 ° C., and water produced by the reaction and water of the aqueous caustic soda solution are removed from the reaction system in the form of an azeotrope with epichlorohydrin. Phosphorus was returned to the system. Next, after completion of the dropping of the aqueous solution of caustic soda, the system was returned to normal pressure and aged for 2 hours. Then, excess epichlorohydrin was removed by evaporation, and 275 of methyl isobutyl ketone was added to the mixture of the produced epoxy resin and sodium chloride. And 200 parts of water were added and dissolved by stirring. Thereafter, the mixture was allowed to stand still to separate and remove the lower layer aqueous solution of sodium chloride, and 9.45 parts of a 20% aqueous sodium hydroxide solution was added thereto to carry out a purification reaction at 80 to 85 ° C for 2 hours. After the reaction, 200 parts of water was added, and the mixture was heated to 80 ° C. and allowed to stand for 30 minutes to separate an aqueous layer. Then 10%
5 parts of a sodium phosphate aqueous solution and 200 parts of water were added for neutralization and liquid separation, followed by washing with 100 parts of water, liquid separation, and dehydration. Next, after filtration, methyl isobutyl ketone was removed by evaporation to obtain a solid epoxy resin (a-1) having an epoxy equivalent of 846 g / eq, a softening point of 95 ° C, and a glass transition temperature (Tg) of 58 ° C. The glass transition temperature (Tg) is measured by a differential scanning calorimeter (D
SC) at a heating rate of 10 ° C./min.

Reference Example 3 Epichlorohydrin was added to the same reactor as Reference Example 1
0 parts and 444 parts of bisphenol A were charged and dissolved by heating to 90 ° C. Then, after cooling to 70 ° C., 10% Na
450 parts of an OH aqueous solution was added over 30 minutes while paying attention to heat generation, and the solution was reacted at 90 ° C. for 90 minutes. After the completion of the reaction, 822 parts of methyl isobutyl ketone was added and dissolved, and 1706 parts of a 5% aqueous NaOH solution was added to obtain 9
Stirred at 0 ° C. for 30 minutes. Next, the mixture was allowed to stand and separated, the resin solution layer was neutralized with phosphoric acid, and further washed with water. Then, methyl isobutyl ketone was distilled off, and the phenolic hydroxyl group equivalent was 503 g / eq.
Modified bisphenol epoxy resin having a softening point of 95 ° C (b
-2-2) was obtained.

REFERENCE EXAMPLE 4 The charged amount of the modified bisphenol type epoxy resin (b-2
Epoxidation was carried out in the same manner as in Reference Example 2 except that 390 parts of -2), 660 parts of epichlorohydrin and 44 parts of diethylene glycol dimethyl ether were used, and a solid having an epoxy equivalent of 653 g / eq and a softening point of 79 ° C was obtained. An epoxy resin (a-2) was obtained.

Example 1 The epoxy resin (a-1) obtained in Reference Example 2 was equipped with a stirrer, a thermometer, a nitrogen inlet tube and a condenser.
423.1 parts of bisphenol A (manufactured by Nippon Bisphenol) in a liter glass separable flask (b-
1) 31.2 parts and methyl isobutyl ketone 50.5
And 0.5 parts of triethylamine, and the mixture was heated to 160 ° C. while stirring under a nitrogen atmosphere, and further reacted at 150 to 160 ° C. for 2 hours. After completion of the reaction, the temperature was raised to 200 ° C. over 2 hours while removing xylene outside the system.
When the internal temperature reached 200 ° C., the contents were taken out, and the epoxy equivalent was 2,140 g / eq (solid content) and the nonvolatile content was 9
9.8%, solid epoxy resin having a melt viscosity of Z2 to Z3 [A
-1] was obtained.

Example 2 The charged amount of the epoxy resin (a-1) obtained in Reference Example 2 was
423.1 parts of bisphenol A (b-1) 36.1
Parts, 51.0 parts of methyl isobutyl ketone, and 0.5 parts of triethylamine, except that the epoxy equivalent was 2,680 g / eq (solid content),
A solid epoxy resin [A-2] having a nonvolatile content of 99.5% and a dissolution viscosity of Z4 to Z5 was obtained.

Example 3 The charged amounts were 423.1 parts of the epoxy resin (a-1), 38.2 parts of bisphenol A (b-1), 51.3 parts of methyl isobutyl ketone, and 0.5 part of triethylamine. Except for the above, the same procedure as in Example 1 was carried out to obtain an epoxy equivalent of 3,180 g / eq (solid content) and a nonvolatile content of 99.4.
Parts, solid epoxy resin [A-3] having a dissolution viscosity of Z6. FIG. 1 shows a GPC chart of the obtained epoxy resin.
FIG. 3 shows an infrared absorption spectrum chart.

Example 4 142.0 parts of the phenolic hydroxyl group terminal-modified bisphenol type epoxy resin (b-2-1) and 423.1 parts of the epoxy resin (a-1) obtained in Reference Example 1 were stirred. Methyl isobutyl ketone in a 1 liter separable flask equipped with a thermometer, a nitrogen inlet tube and a condenser.
The mixture was added together with 8 parts, and the temperature was raised to 120 ° C. to dissolve completely. Then, 0.5 parts of triethylamine was added and the reaction was carried out in the same manner as in Example 1 to obtain an epoxy equivalent of 1,960.
A solid epoxy resin [A-4] having g / eq (solid content), a nonvolatile content of 99.6%, and a dissolution viscosity of Z3 was obtained.

Example 5 The charged amount of the modified epoxy resin (b-
2-1) was changed to 171.3 parts, the epoxy resin (a-1) obtained in Reference Example 2 was changed to 423.1 parts, methyl isobutyl ketone was changed to 66.0 parts, and triethylamine was changed to 0.5 part. The reaction was carried out in the same manner as in Example 1 to obtain an epoxy equivalent of 2,440 g / eq (solid content) and a nonvolatile content of 99.5.
%, A solid epoxy resin having a melt viscosity of Z4 to Z5 [A-5]
I got

Example 6 The amount of the modified epoxy resin (b-2-1) was 184.
8 parts, 423.1 parts of epoxy resin (a-1), 67.5 parts of methyl isobutyl ketone, 0.5 parts of triethylamine
Parts, except that the epoxy equivalent was 2,750 g / eq (solid content) and the nonvolatile content was 9
9.4%, solid epoxy resin with melt viscosity Z6 [A-6]
I got

Example 7 400 parts of the solid epoxy resin (a-2), 49.3 parts of bisphenol A (b-1), and 4 parts of xylene were charged.
9.9 parts, except that n-butyltriphenylphosphonium bromide was changed to 0.5 part, in the same manner as in Example 1 to obtain an epoxy equivalent of 2,720 g / eq (solid content value).
A solid epoxy resin [A-7] having a nonvolatile content of 98.0% and a dissolution viscosity of Z5 to Z6 was obtained.

Example 8 The charged amount of the modified bisphenol type epoxy resin (b-2
The reaction was carried out in the same manner as in Example 1 except that 142.1 parts of -2), 300 parts of the solid epoxy resin (a-2), 49.1 parts of xylene, and 0.5 parts of triethylamine were used. A solid epoxy resin [A-8] having an epoxy equivalent of 2,650 g / eq (solid content), a nonvolatile content of 98.5%, and a dissolution viscosity of Z5 to Z6 was obtained.

Comparative Example 1 Epototo YD-909 (a product of Toto Kasei Co., Ltd.
PA type epoxy resin; epoxy equivalent 2,200 g / e
q, number average molecular weight 6,100) was taken as the solid epoxy resin [C-1] of the comparative example. GPC of the obtained epoxy resin
The chart is shown in FIG.

Comparative Example 2 YD-8125 (Molecularly distilled BPA type liquid epoxy resin manufactured by Toto Kasei Co., Ltd .; epoxy equivalent 172 g / eq, α-diol content 0.8 meq / 1) was prepared in the same reactor as in Example 1.
00g, hydrolyzable chlorine content 0.01 wt%) 1,720
Parts, 992 parts of BPA, 300 parts of xylene and 0.4 part of triethylamine, and the mixture was heated to 160 ° C. with stirring in a nitrogen atmosphere, and further reacted at 160 to 170 ° C. for 2 hours. After completion of the reaction, the content was taken out when the temperature reached 200 ° C. while removing xylene outside the system, and the epoxy equivalent was 2,450 g / eq (solid content value) and the nonvolatile content was 96.
%, A melt viscosity of Z3 to Z4 and a number average molecular weight of 7,100 were obtained as a solid epoxy resin [C-2].

Comparative Example 3 YD-019 (BPA type epoxy resin manufactured by Toto Kasei; epoxy equivalent: 2800 g / eq, number average molecular weight: 4000) was placed in a 2-liter glass separable flask having the same functions as in Example 1. 450 parts and 150 parts of xylene were charged and heated to 120 ° C. to dissolve over 90 minutes. Next, after cooling the system to below 100 ° C,
The mixture was stirred for 30 minutes, transferred to a 2-liter separating funnel and allowed to stand until completely separated into two layers. After separation into two layers, only the lower layer xylene solution was returned to the original separable flask. Further, the same washing operation with methanol was performed 5 times.
I went there. Finally, xylene was removed with a rotary evaporator to obtain a solid epoxy resin [C-3] having an epoxy equivalent of 3,500 g / eq (solid content), a nonvolatile content of 99%, a softening point of 140 ° C, and a number average molecular weight of 5,700.

Examples 9-16 Solid epoxy resins [A-1] obtained in Examples 1-8
[A-8]; 599 parts of xylene and 600 parts of cyclohexanone were dissolved in 401 parts of each to prepare a solution having a resin concentration of 25% by weight. To this resin solution, 100 parts of Hitachil 4010 (a resol type phenol resin manufactured by Hitachi Chemical Co., Ltd.) and 2 parts of 85% phosphoric acid were added and stirred to obtain a uniform coating. The obtained paint was applied to an aluminum plate having a thickness of 0.3 mm with a bar coater and baked at 200 ° C. for 10 minutes to obtain a film pressure of 10 μm.
m of Examples 9 to 16 were obtained.

Comparative Examples 4 to 6 The solid epoxy resins [C-1] to [C-
3]; 583 parts of xylene and 600 parts of cyclohexanone were dissolved in 417 parts of each to prepare a solution having a resin concentration of 25% by weight. To this resin solution were added 100 parts of Hitanol 4010 and 2 parts of 85% phosphoric acid, followed by stirring to obtain a uniform coating. The obtained paint was applied to an aluminum plate having a thickness of 0.3 mm with a bar coater and baked at 200 ° C. for 10 minutes to obtain Comparative Examples 4 to
6 was obtained with a thickness of 10 μm.

Table 1 shows the properties of the bisphenol-type epoxy resins of Examples 1 to 9 and Comparative Examples 1 to 3, and Table 2 shows the physical properties of the coating films of Examples 9 to 16 and Comparative Examples 4 to 6.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

The epoxy resin of the present invention does not substantially contain a low molecular component of n = 0 or less, which is a repeating unit of the epoxy resin, so that the consumption of potassium permanganate by retort extraction can be significantly reduced. Can be. In addition, a coating film having excellent flavor retention can be formed without impairing the adhesiveness, bending workability, and retort resistance, and a coating composition particularly useful for the inner surface of a can can be provided.

[Brief description of the drawings]

FIG. 1 is a GPC chart of an epoxy resin obtained in Example 3.

FIG. 2 is a GPC chart of the epoxy resin obtained in Comparative Example 1.

FIG. 3 is an infrared absorption spectrum chart of the epoxy resin obtained in Example 3.

[Explanation of symbols]

1 and 2, the vertical axis indicates the response amount, and the horizontal axis indicates the elution time. FIG. 1 is a plot of the elution time (horizontal axis) and the logarithm of the molecular weight (vertical axis; logM) in the calibration curve. In FIG. 3, the vertical axis indicates the transmittance, and the horizontal axis indicates the wavelength.

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[Procedure amendment]

[Submission date] July 2, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 2

[Correction method] Change

[Correction contents]

Embedded image (In the formula (2), X is a residue of a bisphenol, and a plurality of Xs may be the same or different. Further, n is an integer of 0 or more in the number of repeating units.)

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

[0010]

Embedded image

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yasuyuki Takeda 3-17-14 Higashikasai, Edogawa-ku, Tokyo Inside the Tokyo Metropolitan Chemical Research Laboratory

Claims (5)

[Claims] 1. An addition polymerization reaction of a bisphenol type epoxy resin (a) having an epoxy equivalent of 450 to 2,000 g / eq represented by the following general formula (1) and a bifunctional phenol (b). Bisphenol type epoxy resin [A] having an epoxy equivalent of 1,500 to 60,000 g / eq and a number average molecular weight of 3,000 to 15,000. Embedded image (In the formula (1), X is a residue of a bisphenol, and a plurality of Xs may be the same or different. Further, n is an integer of 1 or more that does not include 0 in the number of repeating units.) 2. The bifunctional phenol (b) has a bisphenol (b-1) and / or a phenolic hydroxyl equivalent of 300 to 1,200 represented by the following general formula (2).
The bisphenol type epoxy resin according to claim 1, which is a modified bisphenol type epoxy resin (b-2) containing g / eq terminal phenolic hydroxyl groups. Embedded image (In the formula (2), X is a residue of a bisphenol, and a plurality of Xs may be the same or different. Further, n is an integer of 0 or more in the number of repeating units.) 3. The bisphenol-type epoxy resin (a) according to claim 1 is obtained by epoxidizing a modified bisphenol-type epoxy resin having a terminal phenolic hydroxyl group represented by the general formula (2) according to claim 2. The bisphenol-type epoxy resin according to claim 1, wherein: 4. A coating composition comprising the bisphenol epoxy resin [A] according to claim 1 and a curing agent component [B]. 5. The solvent-type or water-based coating composition according to claim 4, wherein the curing agent component [B] is a resol type phenol resin or an amino resin, and at least one of them is blended.