JPH0530696B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is directed to a 5-gallon can that can prevent metal leaching into the contents and deterioration of the contents due to corrosion, and has excellent contents resistance performance. Regarding large metal containers such as, in more detail, the inner surface of the can is made of a metal plate laminated with a biaxially stretched polyester film mainly composed of ethylene terephthalate units. The joints, such as the seaming part between the end and the top and bottom of the can body, are bonded with nylon adhesive, resulting in high joint strength, excellent airtightness, chemical resistance, corrosion resistance, heat resistance, etc., and excellent can strength. This relates to large metal containers such as 5-gallon cans. (Prior art) In the case of containers for food use, exposure of metal on the inner surface of the container, such as liquid contents or highly corrosive contents that are heated and sterilized at high temperatures, has a significant effect on container performance and the shelf life of the contents. Increasingly, thermoplastic resin films are laminated onto metal plates and used as metal can materials. 5-gallon cans include polyolefin coated metal cans (Japanese Unexamined Patent Publication No. 58-87038) whose inner surface is coated with polyolefin film;
58-99345). However, polyolefin film has the property of being easily stretched and distorted by stress, and when impact or external force is applied to the can, distortion occurs in the polyolefin, which can reduce the strength of the joints of the can and reduce airtightness. . Furthermore, it is not satisfactory in terms of heat resistance such as high-temperature hydrothermal treatment. Steel sheets laminated with polyester film have also been tried for metal cans, but even if initial adhesion is secured, the adhesive strength decreases when subjected to high-temperature hot water treatment, resulting in insufficient bonding strength. (Problems to be Solved by the Invention) The present invention solves the problems of the above-mentioned polyester-coated metal cans, etc., and an object of the present invention is to strongly adhere a biaxially stretched polyester film to a metal plate and further By applying a paint layer on the inside and outside surfaces and bonding the can joints with a nylon adhesive, the joint strength of the can joints is large and stable, and has excellent chemical resistance, corrosion resistance, and heat resistance. The purpose of the present invention is to provide large metal containers such as 5-gallon cans that have significantly superior can strength compared to polyolefin-coated cans. Furthermore, another object of the present invention is acidic, alkaline,
It does not corrode when storing relatively corrosive contents such as salt-containing contents, does not elute metal ions, and has little effect on the storage stability of the contents, especially for foods that require preservation of flavor etc. Large metal containers, such as 5-gallon cans, that have satisfactory storage stability and have little effect on the properties of the contents, even if It provides: (Means for Solving the Problems) In order to achieve the above object, the metal container of the present invention includes a can body member having a seam on the side surface, and a top and bottom can end member wrapped around both ends of the can body member. In the metal container, each of the can body member and the can end member includes a metal, an adhesive primer layer located on the side of the metal plate that becomes the inner surface of the can, and an ethylene terephthalate unit located on the primer layer. (hereinafter simply referred to as polyester)
It is formed of a laminate of a biaxially stretched film, an inner paint top layer located on the film surface, and an outer paint layer located on the outer surface of the metal plate, and the seams and seams are formed between the top layers. It is formed by bonding with a nylon adhesive interposed between the top layer and the outer coating layer. (Function) The metal container of the present invention has a metal plate (for example, Tein).
A biaxially oriented polyester film is strongly adhered to the inner surface of the can (free steel, etc.) via an adhesive primer layer, and a top layer of inner paint (adhesive primer layer of nylon adhesive and polyester film) is applied to the surface of the can. (acts as a protective layer)
and the use of a laminated board as the can material, with an external paint layer (which acts as a protective layer on the can's external surface and a primer layer for adhesion of nylon adhesive) on the surface that should become the can's external surface, and the can body. A nylon-based adhesive is used to firmly join the joints such as the joints on the sides of the can body and the seams between both ends of the can body and the top and bottom can end members (lid plate and bottom plate). It is characterized by highly stable strength and perfect airtightness. The biaxially stretched polyester film used in the present invention has a constant thickness and is completely continuous in the plane direction, has no defects such as pinholes, blisters, and sag, and has higher tensile strength and tensile strength than polyolefin films. It has a high elastic modulus, a high yield point, and a low elongation at the yield point. Excellent dimensional stability due to small distortion due to stress. It has excellent properties such as much higher impact strength. It also has excellent physical and mechanical properties over a wide temperature range. It also has excellent processability, and even when can members are cut, formed, lock-seamed, double-sealed, etc., the film does not produce pinholes or blisters, and maintains a continuous coating state. The same applies to stress such as impact applied to the can during use, and a good continuous coating state is maintained. Furthermore, polyester is one of the resins with the best barrier properties (impermeability) against moisture and various corrosive components, and by using this material as the inner material, corrosion of metal plates can be advantageously prevented. be able to. Moreover, the flavor preservation property of the contents is also good. However, polyester has the property of easily thermally crystallizing at temperatures considerably lower than its melting point, for example from 80°C to 150°C, and this thermal crystallization tends to be significantly accelerated by the presence of water. If thermal crystallization occurs, the inner layer itself becomes extremely brittle, and there is a risk that the protective layer itself will peel off due to impact or external force, and there is also a risk that the protective layer will peel off due to internal stress due to volumetric shrinkage accompanying crystallization. In the present invention, a biaxially stretched film is used as the polyester film, and by oriented crystallization of the film itself, thermal crystallization during heat sterilization is prevented, and the excellent physical properties of the film are maintained virtually unchanged. It is something that is maintained. Furthermore, due to the molecular orientation of the polyester film, the barrier properties against corrosive components are significantly improved compared to non-oriented films, and various physical properties such as strength and rigidity can also be improved. Biaxially oriented polyester film exhibits the above-mentioned excellent properties as an inner surface material, but it is one of the most difficult resin films to adhere to, and it adheres strongly to metal plates such as stain-free steel. The problem is that it is difficult to do so.
In one embodiment of the invention, an epoxy-phenolic adhesive primer is selected as the adhesive layer and
By setting the thickness to a limited range of 3μm to 3μm, biaxially stretched polyester film and stain-free
Sufficient adhesive strength can be obtained between metal plates such as steel. The adhesive primer layer not only significantly improves the adhesion of the polyester film to the metal plate, but is also effective in preventing corrosion under the coating film. The top layer of the inner paint is mainly made of epoxy-phenol resin, which improves the adhesion of nylon adhesives, increases bonding strength, and has hot water resistance.
It not only improves stability over time, but also serves as a protective coating for biaxially stretched polyester films. Epoxy-phenol resin and epoxy-urea resins are mainly used for the can exterior paint layer, which acts as a protective coating for metal plates such as tain-free steel and provides good adhesion to nylon adhesives. Acts as a primer layer. The nylon adhesive used is in the form of a film, which is applied to the can joint in a molten state and then cooled and solidified to provide both adhesive and sealing properties. Adhesive strength due to adhesive primer layer,
It is possible to obtain stable properties in terms of hot water resistance and changes over time. In this way, the metal container of the present invention has a stable biaxially stretched polyester film coating on the inner surface of the can, and also has high and stable joint strength at the joints of the can, good airtightness, chemical resistance, and corrosion resistance. , a metal container with excellent heat resistance can be obtained. In addition, the metal container of the present invention has a can material that is tain-free. Because the can itself has a laminate structure in which metal plates such as steel and biaxially oriented polyester film are laminated and a protective coating is applied, the strength of the can itself is improved, and the strength is far superior to that of polyolefin-coated cans. The strength of the container against impact and other external forces has been significantly improved. (Embodiments of the invention) Embodiments of the invention will be described in detail below based on the drawings. FIG. 1 is a perspective view showing an outline of an embodiment of a 5-gallon can as a representative example of the metal container of the present invention, and FIG. 2 is a composite biaxial stretching of the can material of the 5-gallon can shown in FIG. FIG. 2 is a cross-sectional view of a polyester-coated metal plate. FIG. 3 is a cross-sectional view taken along the line A-A in FIG. 1, and shows an example of a joint structure of a joint on the side surface of a can body member. FIG. 4 is a longitudinal sectional view taken along the line BB in FIG. 1, and shows an example of a joint structure of the seaming portion between the end of the can body member and the top and bottom can end members. And Figure 5 is
2 is a plan view of an example of a body blank used in manufacturing the 5 gallon can of FIG. 1; FIG. In FIG. 1, 1 is a 5-gallon can, 2 is a can body member, 3a is a lid plate, 3b is a bottom plate, and lid plate 3a and bottom plate 3b are top and bottom can end members. Reference numeral 4 indicates a side seam of the can body, and reference numeral 5 indicates a seaming portion of the joint between both ends of the can body member 2 and the top and bottom can end members 3a and 3b. In FIG. 2, reference numeral 6 denotes a metal plate coated with a composite biaxially stretched polyester film that forms the can material such as the can body member 2, the lid plate 3a of the top and bottom can end members, and the bottom plate 3b. A biaxially stretched polyester film 9 is adhesively laminated on the surface that is to become the inner surface of the can through an adhesive primer layer 8, and an inner surface paint top layer 10 is formed on the surface of the film 9, and the surface of the metal plate 7 that is to become the outer surface of the can is laminated with adhesive. has an outer paint layer 11
is formed. As the metal plate 7, tain-free steel (electrolytic chromic acid treated steel plate), tin-plated steel plate, phosphate-treated steel plate, aluminum alloy plate, etc. are used, but the most suitable one is tain-free steel. . As the adhesive primer layer 8, an epoxy-phenolic resin primer, an epoxy resin-based primer, or a polyester resin-based primer is used, and an epoxy-phenolic resin-based primer is particularly preferred. The biaxially stretched polyester film 9 is a biaxially stretched polyester film mainly composed of ethylene terephthalate units, and has a thickness of 8 to 60 μm, particularly 10 to 60 μm.
40 μm is used. For the inner surface paint top layer 10, an epoxy-phenol resin paint, an epoxy-urea resin paint, an epoxy resin paint, or the like is used. External paint layer 1
As 1, paints such as epoxy-phenol resin, epoxy-urea resin, and epoxy resin are used, but epoxy-phenol resin is particularly preferred, and the baked coating film is formed. FIG. 3 shows an example of a joint structure in which the seam 4 on the side surface of the can body member is composed of a lock seam 12, in which 14 is a nylon adhesive. As shown in the figure, the joints are coated with the top layer of paint on the inside.
There are a part 12a where the inner paint top layer 10 and the outer paint layer 11 contact each other, a part 12b where the inner paint top layer 10 and the outer paint layer 11 contact each other, and a part 12c where the outer paint layers 11 contact each other. It is heat-sealed and adhered to the opposite contact surface to form an airtight joint. The inner surface paint top layer 10 and the outer surface paint layer 11 serve as adhesive primer layers to ensure the adhesion of the nylon adhesive 14 and to strengthen the bonding strength. FIG. 4 shows a joining structure of the double seam portion 13 of the seam portion 5 between both ends of the can body member 2 and the top and bottom can end members 3a, 3b. As shown in the figure, the joint part of the double seaming part 13 is from part 13a to part 13b.
Here, the inner surface top layers 10 are bonded to each other, the inner surface paint top layer 10 and the outer surface paint layer 11 are bonded to each other in a portion 13c, and the outer surface paint layers 11 are bonded to each other in a portion 13d with a nylon adhesive 14 interposed therebetween. The nylon adhesive 14 is heat-sealed and adhered to the opposing surfaces to form an airtight connection. The inner surface paint top layer 10 and the outer surface paint layer 11 serve as adhesive primer layers to ensure the adhesion of the nylon adhesive 14 and to strengthen the bonding strength. The 5-gallon can 1 having the lock seam portion 11 and the double seam portion 13 is manufactured, for example, as follows. Both sides 16 and 16 of a fuselage blank 15 (see FIG. 5) are formed by cutting a composite biaxially stretched polyester-coated metal plate (hereinafter referred to as a composite polyester laminate plate) 6 into a predetermined size, usually in the form of a strip. A tape-shaped nylon adhesive film 14 is adhered to both sides of both edges 17 using a hot adhesive roll. The width of the nylon adhesive film is usually 3 to 20 mm, and the thickness is 20 to 100 μm. A molded can body is formed by a conventional method with the polyester film side of the composite polyester laminate plate 6 inside, and the lock seam portion 11 is heated to a temperature higher than the melting point of the nylon adhesive film 14 to thermally fuse it, and after cooling, both open ends are sealed. A flange portion is formed at the portion to form the body portion 2. Next, the bottom plate 3b, which has a peripheral curl portion formed so that the polyester film side is the inner surface of the composite polyester laminate plate 6, is double-sealed to the body portion 2, and the double-sealed portion 13 is wrapped with a nylon adhesive film. Heat fusion is performed by heating to a temperature higher than the melting point of No. 14. Next, a lid plate 3a having a structure similar to that of the bottom plate 3b (usually provided with a mouthpiece and a hanger, not shown) is double-sealed to the can body, and the double-sealed portion 13 is bonded with nylon adhesive. Heat fusion is performed to a temperature higher than the melting point of the agent film 14. In this way, a 5-gallon can having the lock seam portion 12 and the double seam portion 13 having a high joint strength is obtained. In FIG. 5 above, the nylon adhesive 14 is bonded to both side edges 16 and both end edges 17. It is also possible to bond to one side or only one side edge as necessary, but strong bonding strength is required. In this case, it is necessary that the nylon adhesive 14 be interposed between the facing composite polyester laminate plates 6. Further, the nylon adhesive film 14 may be folded back and bonded to the front and back surfaces so as to cover the cut opening of the composite polyester laminate board 6. Large metal containers such as 5 gallon cans of the present invention are
It is possible to obtain a can with excellent joint strength between the side seam joint and the double seam part, and also with excellent chemical resistance and corrosion resistance on the inner surface of the can. Next, the materials used for the can material will be explained. A typical example used for the metal plate 7 is tain-free steel, which has a metal chromium layer on the steel plate.
It has a chromium hydrated oxide layer on the outermost surface on the primer coating side, and a chromium oxide layer having a structure that is compatible with the metallic chromium layer is mixed in between. The composition and structure of each of these layers, as well as the presence of trace elements, etc., are deeply related to the bonding strength with the primer, hot water resistance, changes over time, and workability such as double seaming of the bonded portion. However, the steel plate 7 is not limited to stain-free steel, and various surface-treated steel plates can also be used. In addition, from the viewpoint of corrosion resistance, the aluminum alloy plate used is an alloy plate containing at least one of magnesium and manganese and subjected to surface treatment with chromic acid, phosphoric acid, zirconium, acrylic acid, alumite, etc. The biaxially stretched polyester film 9 is a polyester mainly composed of ethylene terephthalate units, and usually 80 mol% or more of the acid component, preferably 90 mol% or more of terephthalic acid, and 80 mol% of the glycol component, preferably 90 mol%. % or more of ethylene glycol, and the remaining acid components include isophthalic acid, diphenyl ether 4,4'-dicarboxylic acid, naphthalene 1,4-
or 2,6-dicarboxylic acid, adipic acid, sepacic acid, decane 1,10-dicarboxylic acid, hexahydroterephthalic acid, and other glycol components such as propylene glycol, 1,4-butanediol, neopentyl glycol, diethylene glycol, 1 , 6-hexylene glycol, cyclohexanedimethanol, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyethoxyphenyl)propane, or p-oxybenzoic acid as the oxyacid, It means a polyester containing p-hydroxyethoxybenzoic acid or the like. Further, a polyfunctional component having trifunctionality or more may be copolymerized within a range that does not impair moldability. Further, it may be a mixed polyester of two or more types such that polyethylene terephthalate is mixed with another thermoplastic polyester so that the content of ethylene terephthalate is 80 mol% or more. The molecular weight of the polyester used is such that it has film-forming ability, and the intrinsic viscosity "η"
It is preferably 0.7 or more. As already pointed out, it is important that this film is oriented and crystallized by biaxial stretching, and the presence of oriented crystals
It can be easily confirmed by X-ray diffraction method, density method, birefringence method, polarized fluorescence method, etc. The thickness of the polyester film used is 8 to 60 μm, preferably 10 to 40 μm. For the adhesive primer layer 8, an epoxy-phenolic resin adhesive primer or an epoxy resin-based adhesive primer is used, but an epoxy-phenolic resin adhesive primer is particularly preferred.
A primer that has particularly excellent adhesiveness between a polyester film and a metal plate is a primer made of an epoxy resin a and a phenolic resin b containing a polycyclic polyhydric phenol. As the epoxy resin component a, all those conventionally used as epoxy resin components in so-called phenol-epoxy paints can be used without restriction, but representative ones include epihalohydrin and bisphenol A [2 ,2′-bis(4
-hydroxyphenyl)propane] and has an average molecular weight of 800 to 5,500, particularly preferably 1,400 to 5,500, and is preferably used for the purpose of the present invention. This epoxy resin has the following general formula: In the formula, R is a condensed residue of 2,2'-bis(4-hydroxyphenyl)propane, and n is a number selected such that the average molecular weight of the resin is 800 to 5500. . The molecular weight of the epoxy resin mentioned above is the average molecular weight, and therefore, the epoxy resin for paints with a relatively low degree of polymerization and the linear epoxy resin with a high molecular weight, that is, the phenoxy resin, have an average molecular weight within the above range. There is no problem in using them in combination so that As the phenol resin component b used in combination with the epoxy resin component a, any resin can be used as long as it contains a polycyclic phenol in its resin skeleton. As used herein, polycyclic phenol refers to phenols having a plurality of rings to which phenolic hydroxyl groups are bonded, and representative examples of such polycyclic phenols include the formula In the formula, R represents a direct bond or a divalent bridging group. Divalent phenols represented by the following are known, and such phenols are preferably used for the purpose of the present invention. In the divalent phenol of the formula (), 2
As the valent bridging group R, an alkylidene of the formula -CR ¹ R ² - (in the formula, each of R ¹ and R ² is a hydrogen atom, a halogen atom, an alkyl group having 4 or less carbon atoms, or a perhaloalkyl group) group, -O-, -S-, -SO
-, _-SO2- , ^NR3- (in the formula, ^R3 is a hydrogen atom or an alkyl group having 4 or less carbon atoms), and the like. Generally, an alkylidene group or an ether group is preferred. Such divalent phenols
Suitable examples for (a) are: 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 ether, p-(4-hydroxy)phenol, etc., but bisphenol A and bisphenol B are most preferred. These polycyclic phenols, alone or in combination with other phenols, are subjected to a condensation reaction with formaldehyde to form a resol type phenolic resin. As for other phenols, all monohydric phenols conventionally used in the production of this type of resin can be used, but in general, the following formula is used: In the formula, R ⁴ is a hydrogen atom or an alkyl group or alkoxy group having 4 or less carbon atoms, and two of the three R ⁴ are hydrogen atoms and one is an alkyl group or an alkoxy group. , R ⁵ is a hydrogen atom or an alkyl group having 4 or less carbon atoms. One or two difunctional phenols represented by, for example, o-cresol, p-tert-butylphenol, p-ethylphenol, 2,3-xylenol, 2,5-xylenol, etc.
A combination of more than one species is most preferred. Of course, in addition to the bifunctional phenol of the above formula (), trifunctional phenols such as phenol (carbolic acid), m-cresol, m-ethylphenol, 3,5-xylenol, and m-methoxyphenol; 2,4 - Monofunctional phenols such as xylenol and 2,6-xylenol; other difunctional phenols such as p-tert aluminum phenol, p-nonylphenol, p-phenylphenol, and p-cyclohexylphenol, either alone or In combination with the difunctionality of formula () above, it can be used for the preparation of phenolic resins. In the present invention, as already mentioned above, the use of a paint containing a phenolic resin containing a polycyclic phenol and an epoxy resin as an adhesive primer makes it possible to withstand retort sterilization and to withstand aging during storage after retort sterilization. This is extremely important for preventing leakage, and when using an adhesive primer layer made of phenolic resin and epoxy resin that do not contain polycyclic phenols, it is difficult to form a joint that can withstand retort sterilization. , shell breakage and microleakage often occur. The amount of polycyclic phenol in the phenolic resin is at least 10% by weight of the total phenol component,
In particular, the weight ratio of the polycyclic phenol (a) and the monovalent phenol (b) is 98:2 to 65:35, especially 95:5 to 75:25, although it may be 30% by weight or more. The combination is advantageous in terms of retort resistance. Further, as the aldehyde component of the phenolic resin, formaldehyde (or paraformaldehyde) is particularly suitable, but other aldehydes such as acetaldehyde, butyraldehyde, and benzaldehyde can be used alone or in combination with formaldehyde. The resol type phenolic resin used in the present invention is
It is obtained by reacting the above-mentioned phenol and aldehyde in the presence of a basic catalyst. There is no particular restriction on the amount of aldehyde to be used with respect to phenol, and it can be used in the ratio conventionally used in the production of resol type resins, for example, a ratio of 1 mol or more, particularly 1.5 to 3.0 mol, per 1 mol of phenol. aldehydes can be suitably used, but there is no particular disadvantage in using less than 1 mol of aldehydes. It is generally desirable to carry out the condensation in a suitable reaction medium, especially an aqueous medium. As a basic catalyst,
Any of the basic catalysts conventionally used in the production of resol type resins can be used, including ammonia, magnesium hydroxide, calcium hydroxide, barium hydroxide, calcium oxide, basic magnesium carbonate, and basic chloride. Alkaline earth metal hydroxides such as magnesium and basic magnesium acetate;
Oxides or basic salts are preferably used. These basic catalysts are present in the reaction medium in catalytic amounts, especially
It may be present in an amount of 0.01 to 0.5 mol%. Condensation conditions are not particularly limited and are generally 80 to 130°C.
Heating may be performed at a temperature of 1 to 10 hours. The resulting resin can be purified by means known per se, for example by extracting the resin component of the reaction product from the reaction medium with, for example, a ketone, an alcohol, a hydrocarbon solvent or a mixture thereof and, if necessary, washing with water. By removing unreacted substances and further removing water by an azeotropic method or a precipitation method, a resol type phenolic resin that can be mixed with an epoxy resin can be obtained. The above-mentioned epoxy resin component (a) and phenol resin component (b) can be used in combination in any ratio and are not particularly limited. From the viewpoint of water resistance of the adhesive part, (a):(b) = 95:5 to 5:95, especially a paint that combines both at a weight ratio of 90:10 to 10:90, is used to form the adhesive primer layer. It is desirable to use it for In the present invention, the epoxy resin and phenolic resin are mixed in a dissolved state in ketones, esters, alcohols, hydrocarbon solvents, or mixed solvents thereof, and used directly as a paint for the adhesive primer layer. However, in general, these mixed resin solutions are
It is desirable to pre-condense the mixture at a temperature of 130° C. for about 1 to 10 hours and then use it as a paint for the adhesive primer layer. Furthermore, epoxy resin and phenolic resin are 2
Instead of using it in the form of a component-based paint, the phenolic resin can be pretreated with modifiers known per se, such as fatty acids, polymerized fatty acids, resin acids (or rosins), drying oils, After being modified with one or more alkyd resins, it is combined with an epoxy resin, or both resins are optionally modified with vinyl acetal (butyral) resin,
It goes without saying that it may be modified with a modifier such as an amino resin, xylene resin, acrylic acid, or phosphoric acid. This adhesive primer has a thickness of 0.1 to 3 μm, especially
It is also important to provide the polyester film with a thickness of 0.2 to 2.0 μm; if it is thicker than the above range, the adhesion will be reduced, and if it is smaller than the above range, it will be difficult to apply it uniformly. As expected, the adhesion will decrease. For the inner surface paint top layer 10, the same material as that used for the adhesive primer layer 8 is used. In addition, epoxy-phenol resin paints, epoxy-urea resin paints, epoxy resin paints, etc. are used. For the external paint layer 11, a baked coating film such as an epoxy-phenol resin paint, an epoxy-urea resin paint, an epoxy resin paint, etc. is used. The nylon adhesive 14 used is in the form of a film. For example, nylon 6, nylon 66, nylon 610, nylon 11, nylon 12, copolymers thereof, etc. are used. Nylon adhesives are advantageous in that their melt viscosity is highly temperature dependent and can be melted and solidified within a relatively narrow temperature range. When manufacturing the laminated composite material, an external paint layer 11 is formed by applying an external paint to the outer surface of the metal plate 7 and performing a baking or printing operation. A biaxially stretched polyester film 9 is prepared, and an adhesive primer layer 8 is provided on the surface of this film to be bonded. When the adhesive primer layer 8 is provided on a film layer rather than on a metal plate, uniform coating is possible even when the thickness of the primer layer is small, since the film layer has superior smoothness. Next, the polyester film coated with an adhesive primer and a metal plate are overlapped and bonded together under heating. During this heat bonding process, it is important to ensure that the molecular orientation effect of the biaxially stretched polyester film is not substantially impaired, and for this purpose, this bonding process should be performed within 1 second. Further, it is desirable that the temperature of the metal plate reaches 230 to 250°C. This short-time thermal bonding process is performed by, for example, high-frequency induction heating and forced cooling by, for example, water cooling. (Effects of the Invention) Since the large metal container such as a 5-gallon can of the present invention is constructed as described above, the joint strength of the can joint is large and stable, and the container has excellent airtightness. Excellent chemical resistance and corrosion resistance against contents. Because it has excellent hydrothermal properties, it can be treated with hot water to store foods, etc., and can also store foods that are heated to a high temperature. It also has excellent flavor preservation properties for foods, etc. It is also stable over time. In addition, the can strength is high and can withstand shock and other external forces, such as large metal containers such as ordinary 5 gallon cans, and polyolefin-coated 5
It has superior effects such as being stronger than gallon cans. The large metal containers such as 5-gallon cans of the present invention have such excellent effects, so they can be used to prevent relatively corrosive contents such as acidic, alkaline, and salt-containing contents, elution of metal ions, and deterioration of flavor etc. It is suitable as a storage can for food, medicine, and a wide range of other products and raw materials, including contents that must not affect the shelf life of the contents. (Example) Example 1 Biaxially stretched polyester film (thickness 38 μm)
m) An epoxy-phenol resin adhesive primer (solid content epoxy resin/phenol resin (weight ratio) = 60/40) was applied to one side at a solid content of 1 g/m ² and dried. This polyester film is laminated with a laminating roll on one side of a 0.32 mm thick stain-free steel plate heated to 240°C via an adhesive primer layer, and then cooled. Next, 5 g/m ² of epoxy-phenol resin paint (solid content of epoxy resin/phenol resin (weight ratio) = 85/15) was applied to the surface of the laminated polyester film as a top layer of internal paint, and the atmosphere was applied. Bake at a temperature of 205℃ for 10 minutes, cool, and then apply epoxy-phenolic resin paint (solid content epoxy resin/phenolic resin (weight ratio) = 90/10) to the non-laminated surface of the tain-free steel.
6 g/m ² of the can material is applied, baked and cooled at an ambient temperature of 205°C for 10 minutes to produce a composite laminate plate of can material. A body blank measuring 914.4 mm x 353.3 mm was formed from this composite laminate plate, and a lid plate with a curled portion and a polyester film having a square rounded corner with a side length of 243 mm were formed so as to face the inside of the can. A thickness of
Tape-shaped nylon film 14 with a diameter of 40μm and a width of 10mm
Thermal adhesive is applied using a pressure roll. Next, the fuselage blank was cut into corners, formed into a square shape (square cross section with rounded corners), and the outer paint layer was placed on the outside to form the lock seam part shown in Figure 3. Heat to ℃ to thermally fuse. A bottom plate is double-sealed to the resulting body, and the double-sealed portion is heated to 240°C and heat-sealed. A lid plate having a mouthpiece was double-sealed to this, and the double-sealed portion was heated to 240° C. and heat-sealed to produce a 5-gallon can of the present invention. Example 2 A composite laminate plate manufactured in the same manner as in Example 1 (however, the thickness of the polyester film was 25 μm) was used to coat the outer paint layer surfaces of both side edges 16 and both end edges 17 of the fuselage blank, as well as one side edge 16 and both end edges 17. A 5-gallon can of the present invention was manufactured in the same manner as in Example 1, except that the tape-shaped nylon film 14 was adhered to the inner surface of the paint top layer. Example 3 The composite laminate plate of Example 2 was used to coat the outer paint layer surface of one side edge 16 and both end edges 17 of a fuselage blank, as well as both side edges 16 and both end edges 1.
A 5-gallon can of the present invention was manufactured in the same manner as in Example 1, except that the tape-shaped nylon film 14 was attached on the inner surface paint layer of No. 7 in the same manner as in Example 1. Comparative Example 1 A 5-gallon can was manufactured in the same manner as in Example 2, except that the top layer of inner paint was not applied to the polyester surface. Comparative Example 2 The composite laminate plate of Example 2 was used, except that the tape-shaped nylon film 14 was pasted on the outer paint layer on one side edge 16 and both end edges 17 of the fuselage blank in the same manner as in Example 1. A 5-gallon can was manufactured in the same manner as in Example 1. Comparative Example 3 A baked coating film of 5 μm thick epoxy-urea resin paint was formed on one side of a 0.32 mm thick stain-free steel plate, and a 60 μm thick polypropylene coating was thermally bonded to the other side (modified polyolefin fine particles). The body blank, lid plate, and bottom plate were made using polyolefin-coated steel plates coated with an adhesive consisting of a solvent suspension containing epoxy resin, and a width of 10 mm.
A 5-gallon can was manufactured in the same manner as in Example 1 by thermally bonding a modified polypropylene film having a thickness of 60 μm to both sides and both ends (inner and outer sides) of the body blank. The temperature during thermal bonding and thermal fusion of the joints was 200°C. Regarding the 5 gallon cans of the above examples and comparative examples,
A joint strength and airtightness test of the can joint, a drop leakage test of the can, and a joint strength and airtightness test of the can joint after the hot water resistance test were conducted. The results of these tests are shown in Table 1. The test method is as follows. (1) Bonding strength: Cut into 20 mm width strips so that the lock seam part and double seam part are perpendicular to the tensile direction, and then pull them at a tensile speed of 40 mm/min using a tensile testing machine. , measure the maximum tensile strength. (2) Airtightness test: Submerge a metal can in water and test from the mouthpiece.
Blow in compressed air of 0.2Kg/cm ² (gauge pressure),
Check for leaks by the appearance of air bubbles. For each exam
100 cans are provided, and the number of cans that leaked is shown. (3) Drop leakage test: After filling a 5-gallon can with colored water, it was dropped onto concrete from a height of 120cm, and leakage over time was visually observed. Twenty cans of each were used in the test. The number of leaking cans is shown. (4) Hot water resistance test: Fill a 5-gallon can with water at 50°C, treat it with boiling water at 100°C for 1 hour, then apply cold water treatment, remove the water from the can, and perform the bonding strength and airtightness tests described above. . 【table】

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an outline of one embodiment of a 5-gallon can, which is a representative example of the metal container of the present invention;
The figure is a sectional view of a metal plate (composite polyester laminate plate) coated with a composite biaxially stretched polyester film, which is a can material for the 5-gallon can shown in FIG. 1. Figure 3 shows
FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1, showing an example of the joint structure of the joint on the side of the can body member;
It is a longitudinal cross-sectional view taken along the line BB in the figure, and shows the joint structure of the seaming part. FIG. 5 is a plan view of an example of a body blank used in manufacturing the 5-gallon can shown in FIG. 1...5 gallon can, 2...body, 3a...lid plate, 3b
... Bottom plate, 4... Side seam, 5... Sealing part, 6... Composite polyester laminate plate, 7... Metal plate, 8...
Adhesive primer layer, 9... Biaxially stretched polyester film, 10... Inner surface paint top layer, 11... Outer surface paint layer, 12... Lock seam portion, 13... Double seam portion, 14... Nylon adhesive.

Claims (1)

[Scope of Claims] 1. A metal container comprising a can body member having a seam on the side surface and a top and bottom can end member wrapped around both ends of the can body member, wherein each of the can body member and the can end member is , a metal plate, an adhesive primer layer located on the side of the metal plate that becomes the inner surface of the can, a biaxially stretched polyester film mainly composed of ethylene terephthalate units located on the primer layer, and a polyester biaxially stretched film mainly composed of ethylene terephthalate units, and It is formed of a laminate of an inner paint top layer located on the can and an outer paint layer located on the outer surface of the metal plate can, and the seams and seams are between the top layers or between the top layer and the outer paint layer. A metal container characterized in that it is formed by bonding with a nylon adhesive interposed between. 2. The metal container according to claim 1, wherein the adhesive primer layer is made of an epoxy phenol resin primer and has a thickness of 0.1 to 0.3 μm.