JPH0717874B2 - Thermosetting paint - Google Patents

Description

TECHNICAL FIELD The present invention relates to a thermosetting coating material suitable for an inner surface coating material of a metal container, and more specifically, to water-extractability, curability, adhesion and adhesiveness. And to a thermosetting paint excellent in processability.

(Prior Art) As a conventional inner surface paint for a metal container, a thermosetting paint made of a combination of a resol-type phenol formaldehyde resin and another resin such as an epoxy resin is widely used.

The resol-type phenol-formaldehyde resin that has been put to practical use has a phenol raw material of p-cresol, bisphenol A, pt-butylphenol, etc., and most of the reaction catalyst is ammonia. Resole-type phenol-formaldehyde resin (ammonia resol) has a relatively slow curing rate and is inferior in flavor retention, so that the re-sol-type phenol-formaldehyde resin (alkali resol) using an alkali metal component or alkaline earth metal component as a catalyst It has come to be considered for use.

Japanese Patent Laid-Open No. 63-6063 related to the proposals of the present inventors,
A resol type phenol formaldehyde resin obtained by reacting a bisphenol A type epoxy resin derived from epichlorohydrin and bisphenol A with a phenol and formaldehyde in the presence of an alkali metal catalyst or an alkaline earth metal catalyst, which comprises benzene Methylol group or etherified methylol group per ring is approximately 0.3 to
A low temperature curable can coating composition is disclosed which comprises 1.0 and about 1 to 30 meq of acid catalyst per solid content of the coating.

(Problems to be Solved by the Invention) However, even when a conventional resole-type phenol-formaldehyde resin is obtained as a composition composed of a mixture of different molecular weight components and a certain average molecular weight is produced, Inevitably, low molecular weight components having a low degree of condensation are mixed. In addition, a water-soluble decomposition component may occur during the curing reaction of the coating film or the retort of the inner surface-coated metal container.

These low molecular weight components and water-soluble components may migrate from the coating film into the food, which is the content of the metal container, over time, impairing the flavor of the food, or causing food hygiene problems.

Also, the presence of a low molecular weight component other than the resin network in the coating film adversely affects the adhesion or the adhesion between the coating film and the metal plate, and also adversely affects the workability and corrosion resistance of the coated metal container. It is possible.

Therefore, an object of the present invention is to improve the water-extracting resistance, curability, adhesiveness or adhesiveness, and processability of a thermosetting coating material for metal containers containing a resol-type phenol-formaldehyde resin resin component.

Another object of the present invention is to provide a paint in which low molecular weight components and water-soluble components that are not involved in curing are significantly reduced as compared with conventional thermosetting paints for metal containers.

(Means for Solving Problems) According to the present invention, p-, in which the substituent has 2 to 3 carbon atoms,
Derived from phenols mainly composed of substituted phenols, the number of methylol groups and etherified metrol groups per phenol ring is 0.25 to 2.0 on average, and 250 to
An alkaline resole-type phenol formaldehyde resin having a number average molecular weight of 1000 and a molecular weight distribution in which the content of components having a molecular weight of 200 or less is 30% by weight or less; and a resin having at least 4 alcoholic hydroxyl groups on average per resin molecule. Is provided in a weight ratio of 3:97 to 50:50.

(Function) The thermosetting coating material of the present invention is characterized by the resol-type phenol formaldehyde resin used, and this resol resin is characterized by the combination of the following requirements.

(I) The raw material phenol has a substituent having 2 to 3 carbon atoms.
And (ii) the number of methylol groups and etherified methylol groups per phenol ring is 0.25 to 2.0 on average, particularly 0.4 to 1.
5 pieces, (iii) having a number average molecular weight of 250 to 1000, particularly 280 to 900, (iv) a molecular weight distribution in which the content of components having a molecular weight of 200 or less is 30% by weight or less, particularly 20% by weight or less, and (v) the resol type phenol formaldehyde resin is an alkali resol, that is, a resol type phenol formaldehyde resin using an alkali metal catalyst or an alkaline earth metal catalyst.

The above-mentioned (i) p-substituted phenol used in the present invention, for example, p-ethylphenol, is a component generally known as a p-substituted phenol in a conventional resol-type phenol formaldehyde resin, but specifically ( Examples) are components that have not been used yet. Conventionally, the p-substituted phenol component used in most cases is p-cresol in most cases, and pt-butylphenol and p-phenylphenol are also used in some other amounts. In the present invention, the p-substituted phenol having a p-substituent having 2 to 3 carbon atoms is used for the following reason. That is, p-
Cresol tends to dissolve in the alkaline reaction catalyst as methylolation proceeds, and thus tends to precipitate in the form of a mononuclear dimethylol compound, which makes it difficult to increase the molecular weight of the resole phenol formaldehyde resin. . Of course, this mononuclear dimethylol compound can be reacted at a high temperature to obtain a binuclear dimethylol compound (Japanese Patent Publication No. 62-41544), but in this case, a two-step reaction and isolation and purification of the product are carried out. It is inevitable that means will be needed and costs will be high. On the other hand, when the number of carbon atoms of the p-substituent is 4 or more, such as p-t-butylphenol and p-phenylphenol, the reactivity of addition condensation becomes low, and the thermosetting reactivity with, for example, an epoxy resin also becomes low. Get lower. Thus, as a p-substituted phenol, both when the carbon number of the p-substituent is smaller than 2 and when it is larger than 3, the monomer (phenol) tends to remain in the resol resin as it is.

It is also important that the resol-type phenol formaldehyde resin used in the present invention has the concentration of the methylol group and the etherified methylol group of (ii) (hereinafter simply referred to as the concentration of the methylol group). That is, when the methylol group concentration is lower than the above range, the curing rate is low and thus short-time curability cannot be obtained. The amount of water extracted from the membrane also tends to increase.

It is also important that the resol-type phenol-formaldehyde resin used in the present invention has a number average molecular weight in the range of (iii) above, and if it is lower than the above range, the amount of water extracted from the cured coating film tends to increase. However, if it is higher than the above range, the thermosetting reactivity becomes poor.

Furthermore, the resol-type phenol formaldehyde resin used in the present invention is also markedly characterized by having the molecular weight distribution shown in (iv) above. FIG. 1 of the accompanying drawings is a resole-type phenol formaldehyde resin of the present invention using p-ethylphenol, FIG. 2 is a conventional resole-type phenol formaldehyde resin using p-cresol, and FIG. 3 is p-phenylphenol. The gel permeation chromatogram about the used resol type phenol formaldehyde resin used is shown. These first to third
From the comparison of the figures, it is clear that the resol-type phenol-formaldehyde resin of the present invention has a surprisingly low content of components having a molecular weight of 200 or less, particularly a monomer content.
This feature shows that the coating material for a metal container of the present invention can remarkably reduce the low molecular weight component remaining in the cured coating film, and can remarkably improve the water extraction resistance.

Furthermore, it is important that the resol-type phenol-formaldehyde resin is an alkaline resole, as described in the above feature (v), in terms of the curing rate and the water-extracting resistance (flavor retention). Resol-type phenol-formaldehyde resin using ammonia catalyst has a low curing rate, cannot obtain curability in a short time, and the polymer chain is easily decomposed during coating curing baking or retort sterilization, leading to an increase in water-soluble components. Although easy, according to the present invention, these drawbacks are eliminated by using an alkali metal catalyst or an alkaline earth metal catalyst.

According to the present invention, by integrating the above, low molecular weight components and water-soluble components that are not involved in coating film curing are significantly reduced compared to conventional ones, and when used as a coating for a metal container, its water-extracting resistance It is possible to remarkably improve the combination of curability, adhesiveness or adhesiveness and workability.

(Preferred embodiment of the invention) As the p-substituted phenol having a p-substituent having 2 to 3 carbon atoms, p-ethylphenol, p-iso-propylphenol and pn-propylphenol are used. P-Ethylphenol is the most preferable from the standpoint of ease of application and coating performance. In the production of the resol type phenol formaldehyde resin, it is preferable to use the p-substituted phenol alone, but under the condition that the p-substituted phenol accounts for 60 mol% or more, particularly 80 mol% or more of the total phenol. Other phenols can be used in combination.

Examples of such other phenols include o-cresol, p-cresol, p-tert-butylphenol, p-phenylphenol, 2,3-xylenol and 2,5.
-Bifunctional phenol such as xylenol; 2,2'-bis (4-hydroxyphenyl) propane <bisphenol A>, 2,2'-bis (4-hydroxyphenyl) butane <bisphenol B>, 1,1'- Screw (4
-Hydroxyphenyl) ethane, bis (4-hydroxyphenyl) methane <bisphenol F>, 4-hydroxyphenyl ether, polycyclic phenols such as p- (4-hydroxy) phenyl; phenol (carboxylic acid), m-cresol, m Examples include trifunctional phenols such as ethylphenol, 3,5-xylenol, and m-methoxyphenol.

The amount of formaldehyde used is such as to bring about the above-mentioned methylol group concentration, and although the amount of formaldehyde is related to the functionality and molecular weight of the phenols, it is generally 0.8 to 4 moles, especially 1 to 1 mole per 1 mole of the phenols. From the range of 3 mol, an amount may be used so as to bring about the above-mentioned concentration of the methylol group.

The condensation reaction is carried out in a suitable reaction catalyst, especially in an aqueous catalyst, in the presence of an alkali metal catalyst or an alkaline earth metal catalyst. Examples of the catalyst include caustic soda, caustic
Alkali metal hydroxides and salts such as sodium carbonate, alkaline earth metals such as magnesium hydroxide, calcium hydroxide, barium hydroxide, calcium oxide, basic magnesium carbonate, basic magnesium chloride, basic magnesium acetate The hydroxides, oxides or basic salts of the above are preferably used. These basic catalysts may be present in the reaction catalyst in a catalytic amount, particularly in an amount of 0.01 to 0.5 mol%. The condensation conditions are not particularly limited as long as the above-mentioned molecular weight and molecular weight distribution are provided, and generally heating at a temperature of 80 to 130 ° C. for about 1 to 10 hours may be performed. The resulting resin can be purified by a means known per se, and for example, the resin component as a reaction product can be converted into, for example, ketone, alcohol,
Extraction and separation from the reaction medium with a hydrocarbon solvent or a mixture thereof, and if necessary, washing with water to remove unreacted substances, and further removing water by an azeotropic method or a precipitation method to obtain an epoxy resin or the like. It can be a resol type phenol formaldehyde resin which can be mixed.

Of course, at least a part of the methylol group in the resol-type phenol-formaldehyde resin may be reacted with an alcohol such as butyl alcohol to preliminarily modify it into an etherified methylol group.

According to the present invention, the above-mentioned resol-type phenol formaldehyde resin is combined with another resin having at least 4 and preferably at least 5 or more alcoholic hydroxyl groups per resin molecule to prepare a coating material. In this case, the other resin to be combined with the resol-type phenol formaldehyde resin, it is important to have an alcoholic hydroxyl group as a reactive group from the viewpoint of rapid thermosetting and physical properties of the coating film during short-time thermosetting, The number of reactive groups in the molecule must also be in the range given above. That is, when a resin having a number of alcoholic hydroxyl groups smaller than the above range, for example, a bisphenol A type epoxy resin having a molecular weight of less than 1400 is used, the heat curing rate is considerably slower than that within the range of the present invention, and the coating film The characteristics of are also unsatisfactory.

Further, the ratio of the resol type phenol formaldehyde resin and the alcoholic hydroxyl group-containing resin is 3:97 to 50: 5.
It is also important to be in the range of weight ratios of 0, especially 5:95 to 40:60. That is, when the amount of the resol-type phenol-formaldehyde resin is less than the above range, it becomes unsatisfactory in terms of rapid thermosetting property, and hot water resistance, corrosion resistance and the like tend to decrease, while the resol-type phenol When the amount of the formaldehyde resin is more than the above range, the workability and adhesion of the coating film tend to deteriorate. According to the present invention, the ratio of the two may be adjusted within the above range depending on the performance required for the coating film.

As the alcoholic hydroxyl group-containing resin, those which can be dissolved or dispersed in an organic solvent are preferably used. Of course, in the case of powder coating, it may be meltable at a relatively low temperature. This resin may have other reactive groups in addition to the alcoholic hydroxyl group, such as epoxy resin and carboxyl group. Examples of the resin suitable for the purpose of the present invention include, but are not limited to, epoxy resin, acrylic resin, alkyd resin, vinyl resin, acetal resin, phenoxy resin, and epoxy ester resin.

As the epoxy resin, any resin having an average of 4 or more hydroxyl groups on the molecular chain and an average of 1 or more epoxy groups at the terminal of the molecular chain, particularly an epoxy group-terminated resin obtained by condensation of a dihydroxy compound and epihalohydrin Is used, most preferably an epoxy resin obtained by condensation of bisphenols with epihalohydrin.
Suitable epoxy resin has a number average molecular weight of 1400 to 7000,
Especially 2000 to 5500.

As the acrylic resin, a water-insoluble acrylic copolymer having a hydroxyl group or a carboxyl group in the molecular chain is used. These hydroxyl groups or carboxyl groups are
For example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic anhydride, acrylic acid in the form of units such as acrylic acid-2-hydroxyethyl ester, acrylic acid-3-hydroxypropyl ester, and methacrylic acid-2-hydroxyethyl ester. It is incorporated into the polymer chain with other monomers such as ethyl acidate, methyl methacrylate, and 2-ethylhexyl acrylate. The average content of the hydroxyl group-containing monomer in the acrylic resin is preferably in the range of 4 to 30 mol%, and the number average molecular weight thereof is 2000 to 50.
It is desirable to be in the range of 000.

As the alkyd resin, a resin obtained by condensation of a polyhydric alcohol and a polybasic acid and having a hydroxyl group or a carboxyl group in the molecular chain is used, for example, phthalic acid resin, maleic acid resin, etc. are preferable. is there. These alkyds may be so-called pure alkyds or fatty acid-modified or resin-modified alkyds. The average hydroxyl value of these resins is 10 to
It is desirable that the acid number is 500 and the acid value is in the range of 0.5 to 50, and the number average molecular weight thereof is in the range of 1000 to 10,000.

As the vinyl-based resin, a copolymer of vinyl chloride and a hydroxyl group or a carboxyl group-containing monomer is used, and examples thereof include vinyl chloride / hydroxyalkyl acrylate copolymer, vinyl chloride / maleic anhydride / acrylic acid. Examples thereof include partially saponified products or partially saponified and partially acetalized products of hydroxyalkyl ester copolymers and vinyl chloride / vinyl acetate copolymers. The average content of the hydroxyl group monomer component in these vinyl resins is 1 to 30 mol%
It is desirable that the number average molecular weight is 5000
It is desirable to be in the range of 50000.

Examples of the acetalized resin include partially saponified products of polyvinyl acetate or acetalized products of polyvinyl alcohol with formaldehyde, acetaldehyde, butyraldehyde, benzaldehyde and the like, and those having an acetalization degree of 50 to 90 mol% are generally preferable.

As the phenoxy resin, a polymer resin obtained by condensation of epihalohydrin and bisphenols, particularly one having a number average molecular weight of 8,000 to 50,000 is used.

As the epoxy ester resin, a resin obtained by reacting the epoxy terminal group of the above-mentioned epoxy resin with a fatty acid, a semi-drying oil, a drying oil or the like is used.

Both of these resin components can be used in the paint in the form of a simple mixture or in the form of a precondensate. As a solvent,
Aromatic solvents such as toluene and xylene, alcohol solvents such as ethanol and butanol, methyl ethyl ketone,
One or more of ketone solvents such as cyclohexanone and ester solvents such as butyl acetate can be used,
The paint is applied in the form of a solution having a solid content of 10 to 60%. The coating composition may contain a modifier or a compounding agent known per se, for example, a modifier such as fatty acid, polymerized fatty acid, rosin, drying oil or xylene resin by mixing or precondensation, and further silicone-oil or the like. Leveling agents, lubricants such as wax, and curing accelerators such as phosphoric acid and metal salts of naphthenic acid.

In addition to the solution type paint described above, the composition of the present invention can be used as a so-called powder paint. For example, both components described above are dry-blended with an auxiliary agent if necessary, kneaded at a relatively low temperature, and pulverized after or during cooling to obtain a powder coating material. Instead of kneading, they can be mixed in a solvent to give a homogeneous composition.

Furthermore, the coating material of the present invention is also used as an aqueous coating material, particularly as an aqueous emulsion coating material. That is, by adding water to the solution or melt of both resins to perform phase inversion, and by removing the organic solvent from the obtained phase inversion product (O / W type emulsion) by azeotropic distillation or the like, if necessary, Use water-based emulsion paint. Upon emulsification by phase inversion, an anionic or nonionic surfactant can be used in combination. Further, in this case, a carboxyl group-containing acrylic resin is used as at least a part of the alcoholic hydroxyl group-containing resin, and the phase inversion proceeds smoothly by neutralizing the acrylic resin with ammonia or amines. The dispersed particle size of this water-based paint is preferably in the range of 0.1 to 10 μm, particularly 0.3 to 5 μm.

The coating material of the present invention is characterized in that it can be cured at a relatively low temperature of 170 to 220 ° C. in a short time. For example
Heating at a relatively low temperature such as 195 ° C. is sufficient for 20 to 60 seconds, and at a relatively high temperature such as 250 ° C., curing is completed by heating for a significantly short time such as 5 to 30 seconds.

The paint of the present invention is particularly useful as a paint for metal containers, and can be applied as a coating film at any stage from the stage of metal material to the stage of metal container. However, since the coating material of the present invention has the above-mentioned rapid curing property, continuous coating is applied to a coiled metal plate or metal foil, or spray coating and baking on the inner surface of a re-squeezed can or a squeezed can are shortened. It has the great advantage that it can be done in time.

For example, in the case of a three-piece can having a side seam, a black plate, various coated steel plates such as tin, chrome,
A plated steel sheet having a surface plated with aluminum, zinc or the like, or a steel sheet or foil having the surface chemically treated or anodic electrolytically treated with chromic acid and / or phosphoric acid; a light metal sheet or foil such as aluminum; a resin film such as polyolefin or the like. By applying the above-mentioned paint beforehand to a material for a can such as a composite metal material in which an aluminum foil or the like is adhesively laminated on the surface of an organic substrate such as a paper board, and then baking it, by means such as soldering, welding, bonding with an adhesive, etc. Join to form a can body.

Alternatively, the material for a painted can is punched, press-molded, or scored, button-processed, tabs are attached, etc. to form a can lid or an easy open can lid. Of course, the above coating composition may be applied to the can body, can lid or can after baking, and baked in the reverse order. This coating composition may be provided as a single coat or as a double coat. Good.

In the case of a seamless can body, the can material is subjected to squeezing processing or squeezing-ironing processing, and the coating material is applied to the can body after molding and baked. Alternatively, the order may be reversed, and the coating material may be applied to the can material before processing and baked.

The solution type coating material of the present invention can be used as a can material, a can body, by any means such as dip coating, roller coating, spray coating, brush coating, electrostatic coating, electrodeposition coating, wire coating, flow coating, doctor coating and the like. , Can lids or cans. The paint thickness is generally 1 to 50μ on a dry matter basis.
m, especially 2 to 40 μm.

The heating for bake hardening of the paint is, for example, an electric heating oven,
In addition to atmosphere heating methods such as gas burning obon, hot air ovens generated from various heat sources, resistance heating by heating from the substrate side of the coating object, induction heating method or heating by conduction heat to press the coating object on the hot plate, Any method such as a method of directly heating the coating film by a flame generated by burning gas or heating by infrared rays or far infrared rays may be used.

The baking conditions for paint vary depending on the type and combination of the thermosetting resins in the above-mentioned paint, but generally 130
From the temperature of to 350 ° C. and the baking time of 1 second to 20 minutes, the condition that the gel fraction is 70% or more may be selected.

(Effects of the Invention) According to the present invention, in a paint comprising a combination of a resol type phenol formaldehyde resin and an alcoholic hydroxyl group-containing resin, the resol type phenol formaldehyde has a substituent having 2 to 3 carbon atoms.
-Derived from phenols mainly composed of substituted phenols, the number of methylol groups and etherified methylol groups per phenol ring is an average of 0.25 to 2.0, a number average molecular weight of 250 to 1000, and a molecular weight of 200 or less. By using an alkaline resole-type phenol formaldehyde resin having a molecular weight distribution in which the content of the components is 30% by weight or less, the low molecular weight components and water-soluble components that are not involved in coating film curing can be remarkably compared with conventional ones. Can be reduced,
As a result, the water resistance of the coating film was improved, and as a result, the flavor retention and hygienic properties of the contents could be improved.

Further, this coating material has a quick-curing property or a short-time curing property in combination with the above-mentioned properties, so that the coating film can be cured by heating at a relatively low temperature for a short time. For this reason, not only the painting line can be shortened, but also continuous painting of the container metal material on the continuous coil is possible, and spray painting and baking on the seamless can body are also facilitated.

Furthermore, this coating film has an additional advantage that it is excellent in adhesion and adhesion to a metal substrate, and is also excellent in workability and corrosion resistance.

(Example) -Manufacturing of phenol resin In the examples, the phenol resin was manufactured in the following manner.

A predetermined amount of phenols and 37% formalin are placed in a reactor, and a predetermined amount of catalyst is added with heating and stirring at 40 ° C.
Then, the reaction system is heated to a predetermined temperature and reacted for a predetermined time. When an alkali metal compound or an alkaline earth metal compound is used as the above reaction catalyst, the liquid temperature should be adjusted.
After lowering to 60 ° C, 10% phosphoric acid aqueous solution is added for neutralization, but when ammonia or amines is used as the reaction catalyst, the neutralization operation is not performed. Next, methyl isobutyl ketone 40
Part, toluene 20 parts, cyclohexanone 20 parts, cellosolve acetate 20 parts was added to extract the resulting resin, the lower layer water and catalyst were separated and removed, and the water remaining in the resin solution was azeotropically dehydrated. I removed it by law. Then, a phenol resin solution was obtained by adjusting the mixed solvent so that the coating solid content was 30%.

The number average molecular weight of these resins and the ratio of the specific phenol resin to the total amount of the resins were obtained from gel permeation chromatography (hereinafter abbreviated as GPC). Further, the methylol group concentration of these resins was measured by the NMR method and shown as the number of methylol groups or etherified methylol groups per phenol ring.

Table 1 shows the measurement results of the charging conditions of various phenol resins, reaction conditions, number average molecular weight, and the ratio of the specific phenol resin to the entire resin.

-GPC measurement method A THF solution having a measurement sample concentration of 0.3 wt% was prepared, and a GPC chart was obtained using the following measurement device and measurement conditions. The number average molecular weight of the resin was calculated in terms of polystyrene.

GPC measuring device: TOYO SODA HLC-8020 column: TOYO SODA TSK-GEL G4000HXL, G3000HXL, G2000HXL, G1000HXL 1 each column temperature: 40 ° C solvent: THF solvent flow rate: 1.0 ml / min Sample injection rate: 100 μl ・ Epoxy resin Manufacturing of Epicort 828 (trade name of Yuka Shell Epoxy Co., Ltd.): 64
0 g, bisphenol A: 353 g, reaction catalyst (ethyltriphenylphosphonium chloride): 0.3 g and Solvesso 15
0: 150 g was mixed and reacted at 155 ° C. for 2.5 hours. The number average molecular weight of the obtained epoxy resin was 5100 as determined by GPC measurement in terms of polystyrene.

・ Production of paint Epoxy resin is dissolved in a mixed solvent of 50 parts of butyl cellosolve and 50 parts of xylene to prepare a 30% resin solution, which is mixed with a 30% phenol resin solution at a predetermined ratio. At this time, when precondensation was required, the test paint was prepared after 2 hours at 110 ° C.

-Evaluation of paints In the examples, paints were evaluated as follows.

Using a coating machine such as a roll coater or gravure coater, apply a dry coating film to the base material (aluminum plate, electrolytic chromic acid treated steel plate (TFS plate), aluminum foil, rolled steel foil with chromate surface treatment, etc.) Coat to a thickness of about 10 micrometers and in a gas oven at 200-230 ℃
The coated plate was baked for 20 to 60 seconds and subjected to the evaluation of coating film performance described below.

(1) Measurement of gel fraction A coated plate is cut into 10 cm × 10 cm to prepare a test piece, and the initial weight (W ₀ ) of this test piece is measured. After extracting these test pieces in methyl ethyl ketone at 75 ° C. for 60 minutes, the test pieces are taken out and dried at 150 ° C. for 30 minutes to measure the weight% (W ₁ ). Next, the extraction residue on the plate is decomposed and removed with concentrated sulfuric acid, and the weight (W ₂ ) of the dried test piece is measured. The gel fraction was calculated by the following formula.

Gel fraction = (W ₁ −W ₂ ) / (W ₀ −W ₂ ) × 100 The gel fraction was evaluated according to the following criteria.

◎: 85% or more ○: 70 to 85% △: 50 to 70% ×: 50% or less (2) Retort whitening resistance A coated plate was cut into 4 cm × 8 cm to obtain a test piece. The test piece was immersed in a beaker containing distilled water, the mouth of the beaker was covered with an aluminum foil, and then the retort treatment was performed at 125 ° C. for 30 minutes. The retort whitening resistance was evaluated by the following criteria by visually judging the degree of whitening of the coating film after retort.

⊚: No whitening ○: Slight whitening Δ: Significant whitening ×: Significant whitening (3) Processing adhesion A coated plate was cut into 3 cm × 3 cm to prepare a test piece. Pre-bend the test piece so that the coating surface is on the outside, sandwich two metal plates with the same plate thickness as the test piece as a spacer, and then bend by dropping a 3 kg iron block from a height of 40 cm. did. Both ends of this bending test piece were covered with wax and subjected to bending workability evaluation. The bending workability was evaluated by immersing the bent part of the test piece in 1% saline solution, measuring the current value flowing through the test piece when a 7v DC voltage was applied using the test piece as an anode, and the following criteria were used for evaluation. did.

◎: 0mA to 20mA ○: 20mA to 40mA △: 40mA to 60mA ×: 60mA or more (4) Water extraction amount Make the ratio of the amount of distilled water put into a pressure bottle with a screw cap and the coating area of the sample 1/1. After plugging, it was subjected to retort treatment at 120 ° C for 30 minutes. The extract after retort is transferred to an eggplant-shaped flask and concentrated by an evaporator. At the end, the tar-like residue on the wall of the eggplant-shaped flask is dissolved with ethyl alcohol. This liquid was transferred to a glass evaporation dish of known weight, evaporated to dryness, and then weighed, and the amount of water extracted was determined from the weight difference between them.

(5) Potassium permanganate consumption Potassium permanganate consumption was calculated based on the potassium permanganate consumption measurement method listed in Ministry of Health and Welfare Notification No. 20.

(6) Heating loss The solvent is removed by pre-drying the coated plate just coated with the trial paint at 100 ° C for 30 minutes, and the weight is measured.
(W ₀ ). After that, baking is performed under predetermined heating conditions, cooling is performed, and the weight is measured (W ₁ ). The weight loss on heating was determined from this weight difference (W ₁ −W ₀ ).

Examples 1 to 5 and Comparative Examples 1 to 6 Eleven kinds of coating materials shown in Table 2 were prepared by using epoxy resins and various phenolic resins and setting the charging ratio to epoxy resin / phenolic resin = 80/20 (weight ratio). These paints
It was applied to a 0.22 mm thick TFS plate or 50 μm aluminum foil, baked and dried at 230 ° C. for 30 seconds, and the performance of the coating film was evaluated. The results are shown in Table 2.

From the results of Table 2, in the alkaline resole type phenol formaldehyde resin using p-substituted phenol, the carbon number of the p-substituent, the content (mol%) of the p-substituted phenol as the main raw material, and the methylol per phenol ring. Number of groups and etherified methylol groups, number average molecular weight,
Furthermore, it can be seen that the contents of components having a molecular weight of 200 or less are interrelated and have a great influence on the properties of the paint for metal containers.

Examples 6 to 9 and Comparative Examples 7 to 8 Six kinds of coating materials shown in Table 3 were prepared using epoxy resin and phenol resin No. 3. These paints were applied to an aluminum plate having a thickness of 0.2 mm, baked and dried at 200 ° C. for 60 seconds, and then the performance of the coating film was evaluated. The results are shown in Table 3.

From the results of Table 3, it can be seen that in the coating material according to the present invention, the epoxy resin / phenolic resin (weight ratio) is greatly involved in the properties of the coating material for metal containers, and there is a suitable range.

Example 10 and Comparative Example 9 Two kinds of paints were prepared by using epoxy resin and phenol resin Nos. 3 and 12 with the charging ratio being epoxy resin / phenol resin = 80/20 (weight ratio). These paints were applied to a 75 μm thick steel foil, baked and dried at 230 ° C. for 20 to 40 seconds, and the performance of the coating film was evaluated. The results are shown in Table 4.

From the results in Table 4, the paint according to the present invention cures in about half the time or less as compared with the conventionally used paint, and the heating loss at that time is also small, so that the generation of fumes during coating baking is suppressed. You can see that it is done.

[Brief description of drawings]

1 is a resol-type phenol formaldehyde resin of the present invention using p-ethylphenol, FIG. 2 is a conventional resol-type phenol formaldehyde resin using p-cresol, and FIG. 3 is a conventional method using p-phenylphenol. 3 is a gel permeation chromatogram of the resol type phenol formaldehyde resin of FIG.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area C09D 171/00 PLQ // C08G 8/12 NBU (56) Reference JP-A-62-59618 (JP , A) JP-A-58-219251 (JP, A) JP-A-54-135892 (JP, A) JP-A-55-27338 (JP, A) JP-B-49-13232 (JP, B1)

Claims (1)

[Claims] 1. A derivative derived from a phenol containing a p-substituted phenol having a carbon number of 2 to 3 as a main component and having an average of 0.25 to 2.0 methylol groups and etherified methylol groups per phenol ring. Individual, 250 to 10
The number average molecular weight of 00 and the content of components with a molecular weight of 200 or less are 3
Containing a weight ratio of 3:97 to 50:50 of an alkali resol-type phenol formaldehyde resin having a molecular weight distribution of 0% by weight or less and a resin having at least 4 alcoholic hydroxyl groups per resin molecule on average. A thermosetting paint characterized by.