JP2903989B2 - Coated metal plate and manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated metal sheet and a method for producing the same, and more particularly, to a method for producing a seamless can or the like having a combination of excellent adhesion, workability and corrosion resistance. TECHNICAL FIELD The present invention relates to a coated metal plate useful for a method and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, cans for cans include so-called three-piece cans in which a top and bottom can lid is wound around a can body provided with a seam formed by soldering, bonding, and welding on a side surface, a drawing process, and a drawing depth. It is formed by drawing or drawing and ironing, etc., and is a so-called two-tool made by winding a can lid around a can body having no seams on the side.
Piece cans (seamless cans) are commonly used,
Each of these forms of can has a protective coating on its inner surface to suppress metal elution to the contents and to prevent corrosion of the can.

[0003] As such a paint for cans, a mixture or an initial condensate of an epoxy resin component and another thermosetting resin component such as a resol-type phenol resin and an amino resin is generally widely used. In the production of cans, this paint is applied to a can material before or after can making, and then the paint is baked to form a thermosetting coating film.

It is already known to use a metal material laminated with a resin film for a can in place of a paint,
For example, a resin film is laminated on a metal material such as an aluminum plate, a tin plate or a tin-free steel plate, and the laminate is subjected to at least one stage of drawing between a drawing die and a punch to form a side seam. Forming a cup consisting of a body without a body and a bottom integrally connected to the body without a seam, and then, if desired, ironing the body with an ironing punch and a die to form a container body; A thinner part is known. It is also known that instead of ironing, the side wall is thinned by bending and stretching at the curvature corner of the redrawing die (Japanese Patent Publication No. 56-501442).

[0005] Japanese Patent Publication No. 59-34580 describes the use of a metal material laminated with a polyester film derived from terephthalic acid and tetramethylene glycol. It is also known to use a coated metal plate of vinyl organosol, epoxy, phenolics, polyester, acrylic or the like when producing a redrawn can.

[0006]

However, when the above-mentioned paint for cans is used, the organic solvent-based paint has good coverage on a metal substrate and is excellent in corrosion resistance.
Since organic solvents are released into the environment during painting and baking, extra facilities and costs are required to recover or burn off the organic solvents. In order to prevent this, the development of water-based paints and powder paints has been promoted, but even water-based paints containing no organic solvent have not been put to practical use, and painting workability has been reduced. It is still worse than organic solvent-based ones, and there are still problems to be solved in terms of coverage and corrosion resistance. Powder coatings are excellent in that they do not completely contain an organic solvent, but the melt fluidity and film forming properties of powders are still unsatisfactory for coatings with thin coatings such as cans. It is enough and has not been put to practical use.

On the other hand, a metal material previously coated with an organic coating such as a plastic film is susceptible to damage by a tool in a draw forming process, and in such a damaged portion of the coating, obvious or potential metal exposure occurs. This causes metal elution and corrosion from this portion. In the production of seamless cans, plastic flow occurs such that the dimension increases in the height direction of the can and decreases in the circumferential direction of the can. As the adhesion decreases, the adhesion between the two also tends to decrease over time due to residual strain in the organic coating, etc., and this tendency is caused by hot filling the contents for canning or changing the temperature of cans from low to high temperature. This is particularly noticeable when sterilizing with heat.

In particular, in the case of a thermoplastic resin film, it is often difficult to achieve a good balance between adhesion and workability to metal and barrier properties to corrosive components. On the other hand, if the corrosion resistance is improved, the adhesion and processability are reduced, and therefore, in a can laminated with the above-mentioned film, under-film corrosion (under-film corrosion) and the like often occur.
In addition, in the case where a thermoplastic resin film is laminated, there is a problem in heat resistance and hot water resistance as compared with the thermosetting resin coating film, and the dent resistance after retort treatment is lower than that of the thermosetting resin coating film. Seems to be inferior.

Accordingly, an object of the present invention is to provide a coated metal plate coated with a high molecular weight epoxy resin in the form of a continuous film, and a method for producing the same. Another object of the present invention is to provide a coated metal sheet excellent in the combination of adhesion to metal, workability, and corrosion resistance, and a method for producing the same.

[0010]

According to the present invention, a bisphenol-type epoxy resin (A) having a weight-average molecular weight of 70,000 or more and a methylol group-containing resin curing agent (B) are combined with (A) :( B ) = 99: 1 to 70:30 by weight in the form of a film containing a meltable resin composition (C).
In coated metal plate characterized by comprising by thermal bonding to a metal substrate is provided.

According to the present invention, the weight average molecular weight is 7
Bisphenol-type epoxy resin of more than 000 (A)
And a methylol group-containing resin curing agent (B), (A):
(B) = contained in a weight ratio of 99: 1 to 70:30
The meltable resin composition (C) and the resin (D) having a film forming ability were prepared by mixing (C) :( D) in a ratio of 3:97 to 50:
A coated metal plate is provided, wherein a composite film having a thickness ratio of 50 is thermally bonded to a metal substrate so that the resin composition (C) is in contact with the metal surface.

According to the present invention, further, the weight average molecular weight is 7
Bisphenol-type epoxy resin of more than 000 (A)
And a methylol group-containing resin curing agent (B), (A):
(B) = 99: 1 to dissolve containing a weight ratio of 70:30
A film of the fusible resin composition (C) or a laminated film containing the resin (D) having a film forming ability is produced, and the film is placed in a positional relationship where the resin composition (C) is in contact with the metal base material, There is provided a method for producing a coated metal sheet, which is characterized by being thermally fused to a metal substrate.

According to the present invention, further, a bisphenol-type epoxy resin (A) having a weight average molecular weight of 70,000 or more and a methylol group-containing resin curing agent (B) are used.
(A): (B) = 99: 1 to 70:30 by weight ratio, the meltable resin composition (C) or the resin (D) having a film forming ability, A method for producing a coated metal sheet is provided, wherein the metal sheet is extrusion-coated on a metal substrate in a positional relationship in contact with the metal substrate.

The epoxy resin (A) is bisphenol A
The epoxy resin (A) used in the present invention is preferably obtained by solution polymerization of a liquid epoxy resin derived from bisphenol and epihalohydrin with bisphenol. On the other hand, the methylol group-containing resin curing agent is particularly preferably a resol-type phenol-aldehyde resin. The epoxy resin (A) and the methylol group-containing resin curing agent (B) are in a weight ratio of 99: 1 to 70:30, especially 9
It is preferable to contain from 8: 2 to 90:10. The composition (C) of the epoxy resin and the methylol group-containing resin curing agent has a thickness of 0.5 to 30 μm, particularly 2 to 25 μm.
It is good to exist as a layer of. The metal substrate is not particularly limited, but is generally a surface-treated steel plate or an aluminum plate or a foil thereof. The resin (D) having a film forming ability used in combination with the composition (C) is preferably an olefin resin, a thermoplastic polyester resin or a polyamide resin.

[0015]

According to the present invention, the weight average molecular weight is 70,0.
It is remarkable that a meltable resin composition of a bisphenol type epoxy resin (A) of at least 00 and a methylol group-containing resin curing agent (B) is thermally bonded to a metal substrate in the form of a film. It is a characteristic.

Conventionally, when an epoxy resin is polymerized, its viscosity becomes too high, so that fluidity and film-forming properties are reduced, and it cannot be handled as a paint. The upper limit of the weight average molecular weight is at most 4,5. However, in the present invention, by using the epoxy resin having a weight average molecular weight increased to 70,000 or more in a solid form, melt extrusion becomes possible and excellent film forming ability is obtained. It is possible to coat a metal substrate as a film.

In the present invention, it is also important to combine the high molecular weight epoxy resin (A) with a methylol group-containing resin curing agent (B). The excellent adhesion of the epoxy resin to the metal and the excellent corrosion resistance are exhibited when the epoxy resin is appropriately cured, but when the epoxy resin contains a curing agent, melt kneading and extrusion are required. At this time, there is a tendency that the epoxy resin gels at an early stage, that is, a so-called premature formation, and if the gelation can be avoided, the final curing of the epoxy resin tends to be insufficient. When a methylol group-containing resin is used as a curing agent, satisfactory gelling performance can be obtained while preventing early gelation during melt-kneading and extrusion. In addition, the resulting coating has excellent adhesion to metal, workability, and corrosion resistance, and peels off or produces coating defects even when subjected to severe impacts such as dents. No dent resistance.

Epoxy resins are a generic term for resins made from compounds having more than one epoxy group in the molecule and which can be converted into useful thermoset products by this epoxy group (Herman F. Mark, Encyclopedia). of Polymer Sci
ence and Technology). Usually, this resin is obtained by condensation of a dihydroxy compound and epihalohydrin, and the terminal of the molecular chain is an epoxy group, that is, a group represented by the following formula (1). This terminal epoxy group was considered to have an important role in curing the resin.

On the other hand, the epoxy resin (A) used in the present invention has a remarkably high weight average molecular weight of 70,000 or more. Repeating unit, In the formula, Y is a bisphenol residue, which has a considerably smaller concentration than the glyoxyl hydroxyl group. The methylol group-containing resin curing agent (B) used in the present invention has a high selectivity of the reaction to the above glyoxyl hydroxyl group, and this reaction hardly occurs at the melt kneading temperature of the resin.
Since it is effectively generated under higher-temperature fusion conditions, excellent adhesion, corrosion resistance, heat resistance, hot water resistance, and the like can be obtained while preventing early gelation.

Further, since the epoxy resin is amorphous and has a remarkably high molecular weight, it is particularly excellent in workability. Even when the coated metal plate is subjected to a high drawing-redrawing process or a further ironing process. No coating defects such as peeling of the coating and pinholes and cracks occur, and the trouble does not occur even when the seamless can is subjected to a high degree of neck-in processing. Moreover, since the epoxy resin has a remarkably high molecular weight, even when the epoxy resin is brought into contact with the content at a high temperature or for a long time, there is little tendency for the coating film component to be extracted into the content, and the flavor retention of the content (flavor retention) ) Is remarkably excellent.

In the present invention, it is also important that the epoxy resin (A) and the methylol group-containing resin curing agent (B) are used in the above-mentioned ratio, and when the epoxy resin is in a lower ratio than the above-mentioned range. In addition, satisfactory film forming ability cannot be obtained, and a tendency to cause early gelation during melt kneading is observed. On the other hand, when the methylol group-containing resin curing agent is lower than the above range, the curing of the epoxy resin component tends to be insufficient, compared with the case where the adhesion and corrosion resistance are within the above range. Become inferior.

The epoxy resin (A) is bisphenol A
It is preferable from the viewpoints of obtaining a sufficiently high-molecular-weight epoxy resin or a bisphenol F-type epoxy resin from the viewpoint of processability, adhesion and corrosion resistance of the coating. It is also particularly excellent in content resistance.

The epoxy resin (A) used in the present invention can be obtained relatively easily by solution polymerization of a liquid epoxy resin derived from bisphenol and epihalohydrin with bisphenol.

On the other hand, the resin curing agent containing a methylol group is particularly preferably a resol type phenol / aldehyde resin. This resol-type phenol / aldehyde resin forms a cured film having excellent adhesiveness and workability as compared with other methylol group-containing resin curing agents.

The layer of the composition (C) of the epoxy resin and the methylol group-containing resin curing agent should preferably be in the above-mentioned thickness range. If the thickness is smaller than this range, it becomes difficult to form a uniform continuous film. On the other hand, corrosion resistance is insufficient. On the other hand, if it is thicker than this range, workability tends to decrease, which is economically disadvantageous.

The metal substrate is not particularly limited, but is preferably a surface-treated steel plate or an aluminum plate or a foil thereof in view of workability to a seamless can and adhesion of a coating.

In the present invention, the epoxy resin composition (C) is extruded alone or in the form of a laminate with the resin (D) having film forming ability. This laminate is formed into a film in advance and heat-fused to a metal substrate or directly extrusion-coated on the metal substrate to form a coating layer of an epoxy resin composition having a uniform thickness and a thin thickness completely continuously. Can be formed. According to the present invention, since no solvent is used, there is no pollution of the environment, no equipment for preventing pollution is required, and no heat energy for volatilization of the solvent is required. It will be clear that the benefits are also significant.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 showing an example of a coated metal plate of the present invention, this coated metal plate 1 comprises a metal substrate 2, an inner coating layer 3 which is formed on the inner side when formed into a container, And layer 4. The inner surface coating layer 3 is formed from a film of a composition of a specific epoxy resin and a methylol group-containing resin curing agent. The outer surface coating layer 4 may be the same as the inner surface coating layer, or may be formed from another film or coating.

In FIG. 2 showing another example of the coated metal plate of the present invention, this coated metal plate 1 is made up of a metal substrate 2 and a metal-side epoxy formed on the inner surface when molded into a container. Resin composition layer 3 and film-forming resin layer 5 thereon
And The outer surface coating layer 4 is provided on the opposite surface. The outer surface coating layer 4 may be the same as the inner surface side coating layers 3 and 5, or may be formed from another film or coating.

[Epoxy resin] The epoxy resin used in the present invention has a weight average molecular weight of 70,000 or more, preferably 90,000 to 120,000.
Its glass transition point (Tg) is at least 70 ° C., especially in the range of 80 to 100 ° C. Its softening point is generally 15
It is in the range of 0 to 250 ° C. and has excellent workability. This epoxy resin is generally, but not necessarily, produced by solution polymerization of a liquid epoxy resin derived from bisphenol and epihalohydrin with bisphenol.

The bisphenols are represented by the following formula (3): HO-ARA-OH ‥‥ (3) In the formula, R is a direct bond or a divalent bridging group, particularly one having 1 carbon atom.
0 following alkylidene group, -O -, - S -, - SO 2 -
Wherein A is a phenylene group and ring A may be substituted with a halogen atom such as Br or Cl, and 2,2-bis (4-hydroxyphenyl) propane
-Bisphenol A, 2,2-bis (4-hydroxyphenyl) butane --- bisphenol B, 1,1-bis (4-hydroxyphenyl) ethane, bis (4-hydroxyphenyl) ethane --- Bisphenol F, 4,
4'-dihydroxybiphenyl 4-hydroxyphenyl ether tetrabromobisphenol A and the like. Among these, bisphenol A,
Bisphenol F is preferred.

The epoxy resin used for the production of the high molecular weight epoxy resin of the present invention has the following formula (4) obtained from the above bisphenols and epihalohydrin In the formula, Y is a bisphenol residue, which is generally represented by the following formula:
It has an epoxy equivalent of 0 to 500.

A stoichiometric ratio of the liquid epoxy resin and bisphenol to the molecular weight of the final epoxy resin,
In general, the reaction is carried out in an organic solvent at a molar ratio of 1: 0.5 to 1:10, especially 1: 0.8 to 1: 1.2.

Examples of the catalyst for the above addition polymerization (ring opening etherification) include tertiary amines such as trimethylamine and triethylamine; tertiary phosphines such as triphenylphosphine and tributylphosphine; tetramethylammonium chloride and tetramethylammonium bromide , Quaternary ammonium salts such as tetratyrylammonium chloride, tetraethylammonium bromide, choline chloride; tetramethylphosphonium bromide;
Quaternary phosphonium salts such as tetramethylphosphonium iodide and triphenylpropylphosphonium bromide; tertiary sulfonium salts such as benzyldibutylsulfonium chloride and benzyldimethylsulfonium chloride; alkalis such as sodium hydroxide, potassium hydroxide and lithium hydroxide Metal hydroxide and the like can be exemplified. In particular, a quaternary phosphonium salt is preferable as the polycondensation catalyst.

The polymerization catalyst is used in an amount of 0.001 to 5 per equivalent of the phenolic hydroxyl group of the bisphenol used.
Preferably it is mol%.

The organic solvent may be any solvent capable of dissolving the high molecular weight epoxy resin, such as toluene,
Xylene, Solvesso (product of Esso Standard)
Aromatic solvents such as Shelsol (products of Shell); ketone solvents such as cyclohexanone, methyl amyl ketone, butylhexyl ketone, diacetone alcohol, and isophorone; alcohol solvents such as amyl alcohol, hexyl alcohol, and cyclohexyl alcohol; methylcellulose , Ethylcellulose, butylcellulose, hexylcellulose, ethylcellulose acetate and the like; sorbitol solvents such as diethylene glycol diethyl ether, diethylene glycol dibutyl ether and the like are used alone or in combination.

At the time of the reaction, an epoxy resin, bisphenols, a solvent and a catalyst are charged into a reaction vessel, and a polyaddition reaction is generally performed at a temperature of 90 to 280 ° C., particularly 170 to 250 ° C. The reaction can be carried out in a closed system such as an autoclave, but can also be carried out under normal pressure and under reflux. The reaction atmosphere may be air, but it is preferable to use an inert atmosphere such as a nitrogen stream in order to prevent deterioration of the resin. The polymerization time varies depending on the molecular weight of the target epoxy resin, but generally about 1 to 10 hours of polymerization is sufficient.

In general, the polymerization is carried out so that the resin solid content concentration is 50 to 80% by weight. For example, it should be understood that polymerization at very high concentrations, such as 95% by weight, where the resin solids concentration is greater than 80% by weight, is possible. That is, in the polyaddition reaction, since the reaction rate is proportional to the synergistic product of the nuclear reaction components, the polymerization rate can be increased by increasing the solid content concentration. In addition, if the concentration is high, the amount of solvent to be removed after the polymerization for separating the resin solids can be reduced.

After reaching a predetermined degree of polymerization, the solvent is distilled off, and the desired epoxy resin having a high degree of polymerization is recovered. The stripping of the solvent is preferably performed under reduced pressure. In order to promote the evaporation, the evaporation can be performed while flowing an inert gas such as nitrogen.

[Methylol Group-Containing Resin Curing Agent] In the present invention, as mentioned above, a methylol group-containing resin curing agent is used as a curing agent for a high molecular weight epoxy resin. This curing agent resin may be any resin as long as it contains a methylol group. Here, the methylol group may be free or may be etherified with an alcohol such as ethanol or butanol. There may be.

Suitable examples of the resin curing agent include resol-type or novolak-type phenol-aldehyde resins, urea-aldehyde resins, melamine-formaldehyde resins, benzoguanamine-aldehyde resins, xylene-formaldehyde resins, and the like. It may be modified with an acrylic resin, an alkyd resin or the like.

For the purpose of the present invention, the resole type phenol
Aldehyde resins are particularly preferred. The phenol-aldehyde resin is obtained by polycondensing various phenols and formaldehyde in the presence of an alkali catalyst. As the phenol, a monocyclic monohydric phenol or a polycyclic dihydric phenol can be used, or a combination thereof can be used. In phenols, a methylol group can be introduced at the ortho-position or para-position of the phenolic hydroxyl group, and its functionality is determined by whether or not these positions are substituted. Is as follows.

O-cresol, p-cresol, p-te
rt-butylphenol, p-ethylphenol, 2,3
Lower alkyl-substituted bifunctional phenols such as -xylenol and 2,5-xylenol; p-tert-amylphenol, p-nonylphenol,
Other bifunctional phenols such as p-phenylphenol and p-cyclohexylphenol; trifunctional phenols such as phenol (carbonic acid), m-cresol, m-ethylphenol, 3,5-xylenol, and m-methoxyphenol ; 2,4-xylenol, monofunctional phenols such as 2,6-xylenol; 2, 2'-bis (4-hydroxyphenyl) propane (bisphenol a), 2,2'-bis (4-hydroxyphenyl) butane (bisphenol B), 1,1'-bis (4-hydroxyphenyl) ethane, bis (4-hydroxyphenyl) methane (bisphenol F), 4-hydroxyphenyl E vinyl ether, p - (4-hydroxy Shi) phenol, And other polycyclic polyphenols.

The phenol resin used is generally from 200 to 2,
It is desirable to have a number average molecular weight of 000, especially 250 to 1,000. Phenolic resins in which at least 10 mol% of the phenol component comprises a bifunctional phenol or bisphenol are particularly suitable.

[Epoxy Resin Composition] According to the present invention,
The high molecular weight epoxy resin and the methylol group-containing resin curing agent are mixed in the above-described ratio, and the mixture is melt-kneaded and then extruded from an extruder, formed into a film, or used for extrusion coating.

The mixing of the epoxy resin and the methylol group-containing resin curing agent is generally carried out by dry blending of solid powders, but may be carried out by melt blending. In the case of the latter blending method, more uniform blending can be performed using a master batch of a methylol group-containing resin curing agent. As a special blending method,
Before subjecting the solution of the high molecular weight epoxy resin to stripping, a methylol group-containing resin curing agent is added in the form of a powder or a solution, the solution is desolvated, and the solid composition in which the above components are mixed is removed. You can also get.

[Film-forming resin]
Examples of film-forming resins that can be used in combination with the epoxy resin composition include polypropylene, low-, medium- or high-density polyethylene, linear low-density polyethylene, propylene-ethylene copolymer, propylene-ethylene-
Olefinic resins such as butene copolymer, ethylene-1-butene copolymer, ethylene-acrylate copolymer, polyolefin / ionomer, acid-modified olefin resin; polyethylene terephthalate, polytetramethylene terephthalate, polyethylene terephthalate / isophthalate, polyethylene / Polyester resins such as butylene terephthalate and polyethylene naphthoate; nylon 6,
Nylon 66, nylon 6/66 copolymer, nylon 1
2, polyamide resins such as nylon 11, nylon 66/610 copolymer and nylon 6/11 copolymer.

[Metal Substrate] In the present invention, various metal plates, particularly various surface-treated steel plates, light metal plates such as aluminum, and metal foils thereof are used as the metal substrate.

As the surface-treated steel sheet or foil, one or two kinds of surface treatment such as galvanizing, tin plating, nickel plating, electrolytic chromic acid treatment, chromic acid treatment, etc. What has been described above can be used. An example of a suitable surface-treated steel sheet or foil is an electrolytic chromic acid-treated steel sheet or foil, particularly 10 to 200 mg / m
² and a chromium oxide layer of 1 to 50 mg / m ² (in terms of chromium metal), which is excellent in combination of coating film adhesion and corrosion resistance. Another example of the surface-treated steel sheet or foil is 0.6 to 11.2 g /
A hard tin plate or foil having a tin plating amount of m ² .
The tin plate or foil is desirably subjected to chromic acid treatment or chromic acid / phosphoric acid treatment in which the amount of chromium is 1 to 30 mg / m ^{2 in} terms of chromium metal.
As still another example, an aluminum-coated steel sheet subjected to aluminum plating, aluminum pressure welding, or the like is used.

As the light metal plate or foil, an aluminum alloy plate is used in addition to a so-called pure aluminum plate or foil.
An aluminum alloy plate excellent in corrosion resistance and workability is as follows: Mn: 0.2 to 1.5% by weight, Mg: 0.8 to 5% by weight, Zn: 0.25 to 0.3% by weight. , And C
u: 0.16 to 0.26% by weight, with the balance being Al. It is desirable that these light metal plates have also been subjected to a chromic acid treatment or a chromic / phosphoric acid treatment such that the chromium amount becomes 20 to 300 mg / m ^{2 in} terms of chromium metal.

The thickness of the metal plate or foil varies depending on the type of metal, the use or size of the container, but is generally 0.1 mm.
005 to 1.0 mm, especially 0.009 to 0.5 mm
It is preferable to have a thickness of 0.10 to 0.30 mm in the case of a surface-treated steel sheet and 0.15 to 0.40 mm in the case of a light metal plate. .

[Lamination] In the present invention, the epoxy resin composition (C) is extruded alone or in the form of a laminate with the resin (D) having a film forming ability. This extrudate is formed into a film in advance and heat-fused to a metal substrate, or is directly extrusion-coated on the metal substrate to form a single or multiple coating layer of the epoxy resin composition on the metal substrate. Let it.

A single screw or twin screw extruder can be used for extruding the epoxy resin composition, and a T-die method or an inflation film forming method can be used for film formation. The extrusion temperature of the epoxy resin composition varies depending on the softening point of the epoxy resin, but is generally preferably in the range of 150 to 300 ° C. The obtained film or sheet can be used in an unstretched state, or can be used after being stretched uniaxially or biaxially. The thickness of the film should be in the range of 0.5 to 30 μm, especially 2 to 25 μm.

The film of the epoxy resin composition formed in this manner is used as the softening point (T _s ) of the epoxy resin component.
Or higher, thermally fusing the metal substrate, particularly in softening point (T _S) + 20 ℃ to the softening point (T _S) + 100 ℃ temperature.
In the present invention, the heat-sealing of the epoxy resin composition film to the metal substrate and the curing of the epoxy resin composition may be carried out simultaneously or separately. It can be performed at a temperature of from about 350 ° C. to about 350 ° C. for a time of from 2 to 30 seconds. Of course, if heating is performed under these curing conditions, it is needless to say that thermal fusion can be performed simultaneously with curing. For this purpose, the surface of the metal base is maintained at the above-mentioned temperature, and the metal base and the film are pressure-bonded with a roller or the like to perform thermal bonding.

For heating the metal substrate, a heating means known per se such as electric heating, high-frequency induction heating, infrared heating, hot stove heating, roller heating and the like can be used. The film to be heat bonded can be preheated.

The laminate after the completion of the heat bonding may be left to cool naturally, but it is preferable to cool it as quickly as possible to prevent oxidative deterioration. This cooling is performed by blowing cold air, spraying cooling water, immersing in cooling water, contacting with a cooling roller, or the like.

Extrusion coating can be carried out in the same manner as the above-mentioned heat bonding of the film, except that the thin film of the epoxy resin composition extruded from the die is spread and applied to the surface of the metal substrate.

The co-extrusion with another film-forming resin (D) is carried out by using an epoxy resin composition (C) extruder, an extruder of this film-forming resin, and a multi-layer die. It can be carried out in the same manner as in the case of the composition single layer. The extruded laminate is preliminarily formed into a multilayer film, and then heat-sealed to a metal substrate or directly extrusion-coated on the metal substrate in multiple layers to form an epoxy resin composition (C) on the metal substrate. The film layer of another resin (D) can be formed via the thin layer of (1). The extrusion temperature of the film-forming resin (D) is a temperature not lower than the melting point of the resin, and an appropriate temperature is generally selected from the range of 150 to 300 ° C. The obtained laminated film or sheet can be used in an unstretched state, or can be used after being stretched uniaxially or biaxially. In the case of a stretched laminated film, the outer surface resin (D) can be selected by selecting the heat bonding temperature.
It should be understood that the molecular orientation can be left in the film layer. The thickness of the upper resin (D) film is
It is preferably in the range of 2 to 50 μm, especially 5 to 20 μm.

As another method for producing a coated metal plate having an outer surface layer of a film-forming resin (D), an epoxy resin composition (C) is provided between an outer surface resin (D) film and a metal substrate.
Can be extruded into a layer, and the film-forming resin (D) and the metal substrate can be bonded and fixed via the epoxy resin composition.

[Outer Surface Protective Layer] In the present invention, the coating layer (C) or (D) may be provided on both sides of the metal base material. C) or (D) may be provided, and the other side may be provided with another resin protective coating. The formation of another protective coating is performed by providing a protective coating.

Other protective coatings include any protective coating consisting of thermosetting and thermoplastic resins: for example phenol-
Modified epoxy coatings such as epoxy coatings and amino-epoxy coatings: for example, vinyl chloride-vinyl acetate copolymer, partially saponified vinyl chloride-vinyl acetate copolymer, vinyl chloride-
Vinyl acetate-maleic anhydride copolymer, epoxy-modified, epoxyamino-modified or epoxyphenol-modified vinyl or modified vinyl paint such as vinyl paint: acrylic resin paint: synthetic rubber such as styrene-butadiene copolymer A single paint or a combination of two or more paints is used. These paints are in the form of an organic solvent solution such as enamel or lacquer, or in the form of an aqueous dispersion or solution.
Roll coating, spray coating, dip coating, electrostatic coating, electrophoretic coating, etc. are applied to metal materials. Of course, if the resin coating is thermosetting, the coating is baked if necessary. The protective coating preferably has a thickness (in a dry state) of generally 2 to 30 μm, particularly 3 to 20 μm, from the viewpoint of corrosion resistance and workability. Further, in order to improve workability, various lubricants can be contained in the coating film.

[Use] The coated metal sheet according to the present invention is useful as a blank for producing seamless cans such as drawn cans, drawn-deep drawn cans, and drawn-ironed cans. Further, the one using a metal foil as a base is useful as a container with a flange by drawing. The coated metal plate is useful for manufacturing a can lid, particularly an easy-open lid, and can be used as a blank for manufacturing a two-piece can such as an adhesive can or a welding can. Further, by utilizing the above-mentioned characteristics, it can be used in the field of exterior materials of various articles, building materials, and the like.

[0063]

The present invention is further described by the following examples.

Example 1 A high-molecular-weight epoxy resin was obtained by a solution polymerization method using a liquid epoxy resin (Epicoat 828 manufactured by Yuka Shell Epoxy Co., Ltd.), bisphenol A, and a quaternary phosphonium-based polymerization catalyst. . The solvent was removed from the obtained resin solution using a thin film evaporator to obtain a solid epoxy resin. The weight average molecular weight of this epoxy resin was 105,000.

The above epoxy resin and solid phenol resin (Tamanol 903 manufactured by Arakawa Chemical Industry Co., Ltd.) were mixed with 97:
The mixture was dry-blended at a ratio of 3 and formed into a sheet having a thickness of about 0.5 mm using an extruder equipped with a T-die, and further biaxially stretched to obtain a film having a thickness of about 20 μm. Next, the above film was pressed by pressing between a rubber and a roll together with a 0.17 mm-thick electrolytic chromic acid-treated steel sheet (hereinafter referred to as TFS) preheated to about 150 ° C.
After heat-sealing on both sides of the FS, heat treatment was performed at 200 ° C. for 1 minute to obtain a coated metal plate.

A deep-drawn can body of 202 diamonds was manufactured from the coated metal plate. No defects such as cracking and peeling of the coating occurred in the manufacturing process of the can body. This can body was filled with pickled tuna oil, the can lid was double-tightened, and then retorted at 115 ° C. for 90 minutes to produce a canned tuna oil. When this canned with tuna oil was stored in an indoor atmosphere for 6 months and opened and evaluated, no abnormalities such as corrosion were observed on the inner and outer surfaces of the can body.

Example 2 Five kinds of epoxy resins were prepared according to the method shown in Example 1, and these epoxy resins and amino resin (Cymel 303 manufactured by Mitsui Cyanamid Co., Ltd.) were mixed at a ratio of 99: 1. Then, using an extruder equipped with a T-die, extrusion coating was performed on the TFS so as to have a thickness of about 25 μm, and the other side of the TFS was similarly extrusion coated, followed by heat treatment at 220 ° C. for 30 seconds. Thus, five types of coated metal plates were produced. Table 1 shows the weight average molecular weight of the obtained epoxy resin.

As a result of evaluating these coated metal plates according to the method shown in Example 1, no abnormality such as corrosion was found on the inner and outer surfaces of the can even after storage for 6 months.

[0069]

[Table 1]

[Comparative Example 1] Weight average molecular weight 45,000
97: 3 with the epoxy resin of Example 1 and the phenolic resin of Example 1.
An attempt was made to form a sheet by using an extruder equipped with a T-die using the composition blended in the above, but a uniform sheet could not be produced. Extrusion coating on TFS was attempted as in Example 2, but could not be extruded to the desired thickness.

Example 3 The epoxy resin and the phenol resin of Example 1 were blended at a ratio of 70:30, and extruded to a thickness of about 5 μm on TFS using an extruder equipped with a T-die. After coating and extrusion coating on the opposite side of TFS in the same manner, this is preheated to 150 ° C., and a biaxially stretched polyester film having a thickness of about 20 μm is pressure-bonded to both sides between rubber and roll. And heat fused,
Further, a heat treatment was performed at 220 ° C. for 30 seconds to produce a coated metal plate. As a result of evaluating the coated metal plate according to the method described in Example 1, no abnormality such as corrosion was observed on the inner and outer surfaces of the can even after storage for 6 months.

Example 4 The epoxy film of Example 1 was heat-sealed on the other side of the TFS coated on one side with a vinyl paint by the method shown in Example 1, and further, After heat-sealing the polyester-based film shown in Example 3, it was heat-treated at 220 ° C. for 30 seconds to produce a coated metal plate. The coated metal plate was evaluated in accordance with the method described in Example 1 so that the surface on which the film was heat-sealed was the inner surface of the can. As a result, no abnormality such as corrosion was observed on the inner and outer surfaces of the can even after storage for 6 months.

Example 5 An epoxy resin E-2 of Example 2 and a phenolic resin of Example 1 were mixed at various ratios on another surface of an aluminum plate having a thickness of 0.3 mm with one surface coated with a vinyl paint. Was extruded to a thickness of about 25 μm using an extruder equipped with a T-die, and then heat-treated at 220 ° C. for 30 seconds to produce seven types of coated metal plates. Table 2 shows the mixing ratio of the epoxy resin and the phenol resin.

These coated metal plates were processed so that the surface coated and extruded was the inner surface of the can, thereby producing an easy-open can lid having a diamond of 200 diamonds. A can body of 202 diamonds (the tightening portion is necked in to 200 diamonds) is filled with sprite, and the can lid is double-tightened to produce a can of carbonated beverage, which is stored for 6 months in an indoor atmosphere. saved. After a lapse of time, the can was disassembled and the condition of the inner surface of the lid was evaluated. As a result, no abnormality such as corrosion was found in any of the lids.

[0075]

[Table 2]

Example 6 A composition (A) containing the epoxy resin of Example 1 and the phenol resin of Example 1 in a ratio of 98: 2, and polyethylene terephthalate / isophthalate (terephthalic acid / isophthalic acid = 95/5) A resin (B) was prepared, and one side of the TFS coated with a vinyl-organo-based paint was coated on the other side with a thickness shown in Table 3.
The layer A is positioned at the interface with TFS,
The layers were coextruded to form two layers of coating on TFS. This coated TFS was heat-treated at 220 ° C. for 30 seconds to produce five types of coated metal plates. The coated metal plate was evaluated according to the method described in Example 1 so that the surface coated with extrusion was the inner surface of the can. As a result, no abnormality such as corrosion was observed on the inner surface of the can even after storage for 6 months.

[0077]

[Table 3]

Example 7 A mixture of the epoxy resin and phenolic resin of Example 1 (C) and maleic anhydride-modified polypropylene (D) were applied to another side of TFS coated on one side with a vinyl organosol paint. , Unmodified polypropylene (E) in order of C, D, and E from the TFS side, and the film thicknesses of the C, D, and E layers are 2, 0.5,
After co-extrusion to 23 μm, the coating T
The FS was heat-treated at 220 ° C. for 30 seconds to produce a coated metal plate. The coated metal plate was evaluated according to the method described in Example 1 so that the surface coated with extrusion was the inner surface of the can. As a result, no abnormality such as corrosion was observed on the inner surface of the can even after storage for 6 months.

Example 8 Five kinds of resole phenolic resins were synthesized using paracresol, bisphenol A and formalin as raw materials using an ammonia catalyst. Table 4 shows the methylol group concentration per benzene ring and the weight average molecular weight of the obtained phenol resin.

The epoxy resin E-3 of Example 2 and the above-mentioned phenol resin were mixed at a solid content of 97: 3, and the solvent in which the phenol resin was dissolved was removed by vacuum drying. It was formed into a sheet having a thickness of about 0.5 mm using an extruder equipped with a die, and further biaxially stretched to obtain a film having a thickness of about 20 μm. This film was heat-sealed on the other surface of a 0.3 mm-thick aluminum plate coated on one side with a vinyl paint according to the method shown in Example 1 to produce a coated metal plate.

The coated metal plate was processed such that the surface on which the film was heat-sealed became the inner surface of the can, thereby producing an easy-open can lid having a diamond of 200 diamonds. Fill a cider into a 202-diameter can body (the winding-up portion is necked in to 200-diameter) and double-tighten the can lid to produce a can of carbonated beverage, and then store for 6 months in an indoor atmosphere. saved. After time,
As a result of disassembling the can and evaluating the state of the inner surface of the lid, no abnormality such as corrosion was observed on the inner surface of the lid.

[0082]

[Table 4]

[Comparative Example 2] Weight average molecular weight of 45,000
Epoxy resin of Example 8 and phenolic resin P-5 of Example 8
Attempts to form a sheet with an extruder equipped with a T-die using the composition blended at 0:20 resulted in gelation of the composition in the extruder and failure to extrude.

[0084]

According to the present invention, melt-extrusion becomes possible and excellent film-forming ability is obtained by using an epoxy resin whose weight average molecular weight is increased to 70,000 or more in a solid form. This makes it possible to coat a metal substrate as a film.

In the present invention, the high molecular weight epoxy resin (A) is combined with the methylol group-containing resin curing agent (B) and used as a film for coating on a metal substrate, so that an early gel during melt kneading and extrusion can be obtained. While preventing
In addition, satisfactory curing performance is finally obtained. Also,
The resulting coating has excellent adhesion to metal, workability, and corrosion resistance, and can be peeled or produce coating defects even when subjected to severe impacts such as dents. And excellent in dent resistance.

Further, since this epoxy resin is amorphous and has a remarkably high molecular weight, it is particularly excellent in workability. Even when the coated metal plate is subjected to high drawing-redrawing or further ironing. No coating defects such as peeling of the coating and pinholes and cracks occur, and the trouble does not occur even when the seamless can is subjected to a high degree of neck-in processing. Moreover, since the epoxy resin has a remarkably high molecular weight, even when the epoxy resin is brought into contact with the content at a high temperature or for a long time, there is little tendency for the coating film component to be extracted into the content, and the flavor retention of the content (flavor retention) ) Is remarkably superior to the above.

According to the present invention, since no solvent is used, the environment is not polluted, no equipment for preventing pollution is required, and no heat energy for volatilizing the solvent is required. The manufacturing benefits are also significant.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a coated metal plate of the present invention.

FIG. 2 is a sectional view showing another example of the coated metal plate of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coated metal plate 2 Metal substrate 3 Inner surface coating (epoxy resin composition) layer 4 Outer surface coating layer 5 Film-forming resin layer

Claims (16)

(57) [Claims] 1. A bisphenol-type epoxy resin (A) having a weight-average molecular weight of 70,000 or more and a methylol group-containing resin curing agent (B) are mixed with (A) :( B) = 99: 1 to 70:30. A coated metal plate obtained by thermally bonding a meltable resin composition (C) contained in a weight ratio to a metal substrate in the form of a film . 2. A bisphenol type epoxy resin (A) having a weight average molecular weight of 70,000 or more and a methylol group-containing resin curing agent (B) are mixed with (A) :( B) = 99: 1 to 70:30. A meltable resin composition (C) contained in a weight ratio, and a resin (D) having a film forming ability,
(C) :( D) is closed with a film thickness ratio 3:97 to 50:50
A coated metal plate obtained by thermally bonding a composite film to a metal substrate such that the resin composition (C) is in contact with a metal surface. 3. The epoxy resin (A) is bisphenol A
3. The coated metal plate according to claim 1, wherein the coated metal plate is a type or bisphenol F type epoxy resin. 4. The coated metal plate according to claim 1, wherein the epoxy resin (A) is an epoxy resin obtained by solution polymerization of a liquid epoxy resin derived from bisphenol and epihalohydrin with bisphenol. 5. The resin curing agent containing a methylol group is a resol type phenol-aldehyde resin.
The coated metal plate as described in the above. 6. The coated metal plate according to claim 1, wherein the composition (C) of the epoxy resin and the methylol group-containing resin curing agent is present as a layer having a thickness of 0.5 to 30 μm. 7. The coated metal sheet according to claim 1, wherein the metal substrate is a surface-treated steel sheet, an aluminum sheet, or a foil thereof. 8. The resin (D) having a film forming ability,
The coated metal sheet according to claim 2, wherein the metal sheet is an olefin resin, a thermoplastic polyester resin, or a polyamide resin. 9. A bisphenol-type epoxy resin (A) having a weight-average molecular weight of 70,000 or more and a methylol group-containing resin curing agent (B) are mixed with (A) :( B) = 99: 1 to 70:30. A film of a meltable resin composition (C) or a laminated film containing a resin (D) having a film forming ability, which is contained in a weight ratio, is produced.
A method for producing a coated metal plate, wherein a resin composition (C) is thermally fused to a metal substrate in a positional relationship in contact with the metal substrate. 10. A bisphenol-type epoxy resin (A) having a weight-average molecular weight of 70,000 or more and a methylol group-containing resin curing agent (B) in a ratio of (A) :( B) = 99: 1 to 70:30. meltable resin composition in a weight ratio (C) or more resins having a film-forming ability (D)
In the positional relationship where the resin composition (C) is in contact with the metal substrate,
A method for producing a coated metal sheet, comprising extrusion coating on a metal substrate. 11. The method for producing a coated metal sheet according to claim 9, wherein the epoxy resin (A) is a bisphenol A type or bisphenol F type epoxy resin. 12. The method for producing a coated metal sheet according to claim 9, wherein the epoxy resin (A) is an epoxy resin obtained by solution polymerization of a liquid epoxy resin derived from bisphenol and epihalohydrin with bisphenol. 13. The method for producing a coated metal sheet according to claim 9, wherein the resin curing agent containing a methylol group is a resol-type phenol-aldehyde resin. 14. The method for producing a coated metal plate according to claim 9, wherein the composition (C) of the epoxy resin and the methylol group-containing resin curing agent is present as a layer having a thickness of 0.5 to 30 μm. 15. The method for producing a coated metal plate according to claim 9, wherein the metal substrate is a surface-treated steel plate or an aluminum plate or a foil thereof. 16. A resin (D) capable of forming a film.
11. The method for producing a coated metal sheet according to claim 9 or 10, wherein is a olefin resin, a thermoplastic polyester resin or a polyamide resin.