JP2532002B2 - Resin coated metal plate for thin-walled deep drawing - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a resin-coated metal plate for a thin-walled deep-drawing can, more specifically, a surface of a polyester resin film coated on the metal plate and a surface of a portion in contact with the metal plate. The present invention relates to a resin-coated metal plate for a thin-walled deep drawing can, which is coated with a polyester resin film having a different orientation coefficient.

[0002]

2. Description of the Related Art Conventionally, food and beverage cans include a three-piece can consisting of a can body, a can lid and a bottom lid, and a can body and a can in which the can body and the bottom lid are integrated. A two-piece can consisting of two parts of the lid is used. The tin barrel of this three-piece can is made of tinplate that has been painted once or several times, and electrolytic chromic acid treated steel plate (generally called tin-free steel, abbreviated as TFS hereafter) is used for soldering. Adhesion with nylon, or resistance welding is used. Such coating not only complicates the baking process, but also requires long-time heating for baking. Further, since a large amount of solvent components in the paint are discharged in the baking process, there is a drawback that the discharged solvent must be guided to a special incinerator and incinerated from the viewpoint of pollution. Two-piece cans are drawn cans and draw cans.
RD cans, squeezed and squeezed cans (Drawn and Iro)
edcan, DI can), but cans with a relatively small drawing ratio, such as squeezed cans and DRD cans, are coated with tinplate or TFS similar to the materials for the above three-piece cans. . Therefore, similar to the above, there are problems in terms of process and environmental pollution. Although tin and aluminum are used for squeezing cans and DI cans, lubricating oil is used at the time of molding for the manufacture of DI cans. After molding, this lubricating oil is removed by washing, and after drying, The inner and outer surfaces are painted. In the manufacturing process of this DI can, there are problems in terms of pollution, such as treatment of lubricating oil and treatment of solvent components volatilized from the paint during baking. In recent years, a manufacturing technology for a thin-walled deep-drawing can in which a coated TFS is drawn and then stretched is developed, and the painted TFS has been studied as a material thereof. However, when the coated TFS undergoes such severe processing, numerous cracks are formed in the coating film, and a thin-walled deep-drawing can having good characteristics has not yet been put to practical use.

The manufacturing technology of this thin-walled deep-drawing can is compared with the manufacturing technology of DI can, for example, the manufacturing equipment is compact and the equipment cost is low, the equipment installation area is small, and the number of operating personnel can be reduced. It has many advantages such as that it can be used as a material, no pollution measures are required, and TFS that is cheaper than tinplate can be used. However, when TFS coated with a paint is applied to a thin-walled deep drawing can, The corrosion resistance after processing is insufficient, so it is not yet widely used. On the other hand, as an alternative to the paint, a method of laminating a polyester resin film on a metal plate without using an adhesive (Japanese Patent Publication No. 60-47103, etc.), a polymerization composition comprising an epoxy resin and its curing agent, etc. are previously prepared. A method of laminating the coated polyester resin film on a metal plate (Japanese Patent Publication No. 63-13829, JP-A-1-249331).
And Japanese Patent Application No. 1-154523) have been developed. The polyester resin-coated steel sheet obtained by the method described in JP-B-63-13829 is a steel sheet whose steel sheet surface is coated with a biaxially stretched polyethylene terephthalate film via an epoxy-based polymerization composition. The following properties are inferior to the processability of the copolyester resin film and can be used for squeezing cans, DRD cans, and can lids with a relatively small degree of processing, but a deeper wall thickness that requires more severe processability. Cannot be used for squeezers. The reason for this is that if such a severe process is applied, the polyester resin film peels off or countless cracks are formed in the film, and it is not possible to fill the contents with strong corrosiveness. In addition, JP-A 1-2
The polyester resin-coated metal plate obtained by the method described in Japanese Patent No. 49331 limits the softening start temperature, crystal melting temperature, and elongation at break of the copolymerized polyester resin film to be laminated, and Japanese Patent Application No. 1-154523. The polyester resin-coated metal plate obtained by the method described in the publication limits the in-plane refractive index and crystal melting temperature of the copolymerized polyester resin film to be laminated. The films used in these methods have better workability than the films used in the method described in JP-B-63-13829, but when applied to a thin-walled deep drawing can, the laminated film peels from the metal surface. I have something to do. This is because the plane orientation coefficient of the polyester resin layer that is in contact with the metal surface and the plane orientation coefficient of the outermost polyester resin layer are not adjusted, so that the moldability and the adhesion to the metal plate surface, especially the thinning depth. This is due to the poor adhesion after severe forming such as a squeeze can.

[0004]

As described above, the manufacturing technique of the thin-walled deep-drawing can has many advantages as compared with the conventional can-making technology, but there is no material suitable for the thin-walled deep-drawing can. The present invention is to develop a resin-coated metal plate suitable for a thin-walled deep-drawing can and having excellent workability and corrosion resistance.

[0005]

A resin-coated metal plate for a thin-walled deep-drawing can of the present invention comprises a heated metal plate coated with a polyester resin film having a melting point of 190 to 250 ° C. on at least one side of the metal plate, When the surface orientation coefficient of the portion of the resin that is in contact with the metal plate is n ₁ and the surface orientation coefficient of the outermost portion that is not in contact with the metal plate is n ₂ , n ₁ is 0.
0.10 or less, n ₂ is 0.01 or more, 0.15
It is characterized by the following. Furthermore, a metal plate obtained by heating a biaxially stretched polyester resin film having a melting point of 190 to 250 ° C. and a plane orientation coefficient of 0.12 to 0.17 on at least one surface of the metal plate to a temperature equal to or higher than the melting point of the resin. The surface orientation coefficient of the portion of the resin after coating that is in contact with the metal plate is n _1, and the surface orientation coefficient of the outermost portion that is not in contact with the metal plate is n ₂ Then, n ₁ is more than 0 and 0.10 or less, and n ₂ is 0.01 or more and 0.15 or less. In these resin-coated metal plates, it is desirable that an adhesive layer be interposed between the metal plate and the resin film.

The contents of the present invention will be described in detail below. First, it is important that the polyester resin film used in the present invention has an oriented portion at least in the polyester resin layer. As a polyester resin,
A copolymerized polyester resin in which 75 to 95% of the ester repeating units consist of ethylene terephthalate units and the remaining 5 to 25% of the ester repeating units consist of ethylene isophthalate units is preferred. Acid components other than terephthalic acid and isophthalic acid used to synthesize esters other than ethylene terephthalate and ethylene isophthalate include phthalic acid, succinic acid, azelaic acid, adipic acid, sebacic acid, dodecanedioic acid and diphenyl. Examples thereof include one or more acid components of carboxylic acid, 2,6 naphthalenedicarboxylic acid, 1,4 cyclohexanedicarboxylic acid, and trimellitic anhydride. As alcohol components other than ethylene glycol, 1,4 butanediol, 1,5 pentanediol,
1,6 hexanediol, propylene glycol, polytetramethylene glycol, trimethylene glycol,
Triethylene glycol, neopentyl glycol,
One or more saturated polyhydric alcohols such as 1,4 cyclohexanedimethanol, trimethylolpropane and pentaerythritol may be mentioned. The ester unit other than the ethylene terephthalate unit may be any one or both of the acid component and the alcohol component as long as it is an acid component other than terephthalic acid and a polyhydric alcohol other than ethylene glycol. It can be used to obtain a copolyester resin. Such a copolymerized polyester resin can also be obtained by a method in which a polyester comprising a copolymerization component is blended with an ethylene terephthalate resin, melted, and copolymerized by a partition reaction. These copolyester resins are produced by forming a film by a known extruder, biaxially stretching in the longitudinal and transverse directions, and heat fixing.
When a metal plate laminated with an unstretched film that has not been stretched after film formation is used, the coefficient of friction with a can-making tool becomes high, and the can-making property is extremely reduced, and the barrier property against the contents is also poor. come. Therefore, in the present invention, it is essential that the outermost surface portion of the polyester resin film retains the orientation due to the stretching applied during the film formation even after the film is heated and laminated on the metal plate. In some cases, stabilizers, antioxidants, antistatic agents, pigments,
The addition of additives such as lubricants and corrosion inhibitors does not hinder the present invention.

The thickness of the polyester resin film used in the present invention is not particularly limited, but is preferably 5 to 50 μm. When the thickness is 5 μm or less, the laminating workability is remarkably deteriorated and sufficient working corrosion resistance cannot be obtained. Further, when the thickness is 50 μm or more, it is not economical as compared with an epoxy resin paint which is widely used as a material for a can.

The plane orientation coefficient of the biaxially stretched polyester resin film before being laminated on the metal plate and the portion of the polyester resin-coated metal plate in contact with the metal plate, which are important factors in the present invention. The surface orientation coefficient (n ₁ ) and the surface orientation coefficient (n ₂ ) of the outermost surface portion that is not in contact with the metal plate are determined by the following method. That is, in the case of a biaxially stretched polyester resin film before being laminated on a metal plate, the refractive index in each of the longitudinal direction, the lateral direction and the thickness direction on one side of the film is measured by an Abbe refractometer, Calculate from the formula. Plane orientation coefficient = (A + B) / 2-C A: Refractive index in the longitudinal direction B: Refractive index in the lateral direction C: Refractive index in the thickness direction Further, in the case of the polyester resin film of the polyester resin-coated metal plate, it is obtained. The polyester resin-coated metal plate was immersed in hydrochloric acid to chemically dissolve the metal plate surface, and only the polyester resin film was peeled off, and the top surface side of the obtained film and the vertical side of the side that was in contact with the metal plate The refractive index in the transverse direction, the transverse direction and the thickness direction is measured with an Abbe refractometer, and is determined in the same manner as in the case of the biaxially stretched polyester resin film using the above formula. The orientation of the biaxially stretched polyester resin film is brought into contact with a metal plate heated to a temperature equal to or higher than the melting point of the polyester resin and pressure-bonded to the metal plate, and the heat conduction from the metal plate causes a collapse in a portion closer to the metal plate. When the plane orientation coefficient of the biaxially stretched polyester resin film obtained by the method exceeds 0.17, the plane orientation coefficient (n ₂ ) is 0.15 or less and the plane orientation coefficient (n ₁ ) is 0.10 or less. Becomes extremely difficult. On the other hand, when the plane orientation coefficient of the biaxially stretched polyester resin film is less than 0.12, the orientation of the polyester resin film after contacting with a metal plate heated to a temperature equal to or higher than the melting point of the polyester resin and pressure bonding is almost lost. Therefore, it becomes extremely difficult to set the surface orientation coefficient (n ₂ ) to 0.01 or more and to exceed the surface orientation coefficient (n ₁ ) of the portion in contact with the metal plate to 0. Furthermore, when the plane orientation coefficient (n ₁ ) of the polyester resin film obtained from the polyester resin-coated metal plate exceeds 0.10, the polyester resin film is easily removed from the surface of the metal plate when processed into a thin-walled deep drawing can. Peel off. The plane orientation coefficient (n ₁ ) is 0.1
If it is 0 or less, the polyester resin film is difficult to peel off, but more preferably 0.05 or less. The refractive index measured by the above method is an average value of the portion from the outermost surface of the resin film to a depth of about 5 μm, and the plane orientation coefficient (n ₁ ) obtained from that value is the same as that of the metal plate surface. The surface orientation coefficient of the outermost surface portion that was in contact with 0 is 0, that is, even if there is no orientation, the surface orientation coefficient exceeds 0 if the oriented portion exists within a depth of 5 μm. In the present invention, the fact that the plane orientation coefficient (n ₁ ) exceeds 0 and is 0.10 or less is a result of such consideration, and the plane orientation coefficient (n ₁ ) of the polyester resin film is 0. Specifically, it means that the surface orientation coefficient of the portion up to the depth of 5 μm from the contact surface with the metal plate is 0, that is, there is no orientation. If the surface orientation coefficient of the outermost surface that is not in contact with the metal plate is 0.01 or less, the coefficient of friction with the wrinkle holding tool, the punch and other can-making tools becomes high in the drawing process as described above. Too much, the processing is not performed uniformly, and the polyester resin film and the metal plate are remarkably roughened, which is not preferable. In addition, the barrier property of the resin layer itself constituting the polyester resin film to the contents is remarkably inferior, and when the contents are highly corrosive and stored for a long time, the surface of the metal plate is corroded, which is not preferable. On the other hand, when the plane orientation coefficient (n ₂ ) exceeds 0.15, even if the plane orientation coefficient (n ₁ ) is 0.10 or less,
When processed into a thin-walled deep-drawn can, countless cracks are formed in the entire polyester resin film, making it unusable as a can. That is, the plane orientation coefficient (n ₂ ) is 0.
It must be in the range of 01 to 0.15. Further, the surface orientation coefficient (n ₁ ) is particularly important in order for the polyester resin film to follow the metal plate without being separated even when subjected to severe drawing, stretching, necking and the like.

Next, the case where the adhesive layer is interposed between the metal plate and the polyester resin film will be described. A metal plate without an adhesive layer and covered with a polyester resin film having a surface orientation coefficient in the range limited by the present invention has excellent workability, work corrosion resistance, and scratch resistance as described above. However, when it comes into contact with a more corrosive content, the surface of the metal plate may be corroded through the polyester resin film, and the polyester resin film may peel off from the metal plate. The adhesive layer interposed between the metal plate and the polyester resin film is effective in preventing corrosion of the metal plate surface and peeling of the polyester resin film from the metal plate in such a case.
Known adhesives can be used as the adhesive, but a polymerization composition having an epoxy group in the molecule is more preferable, and the adhesive is applied to the surface of the polyester resin film in contact with the metal plate, dried, and then laminated on the metal plate. Alternatively, the polyester resin film may be laminated on the surface of the metal plate after coating and drying. As a method for applying the adhesive, a known method such as a roll coating method may be used and is not particularly limited.

To obtain the polyester resin film-coated metal plate of the present invention, for example, the following methods are available. 190-
It has a melting point of 250 ° C., is biaxially stretched and then heat set to 0.
A polyester resin film having a plane orientation coefficient of 12 to 0.17 is heated and laminated at a temperature around the melting point of the polyester resin, and the plane orientation coefficient (n ₂ ) is 0.01 or more and 0.
15 or less, there is a method of adjusting so that the plane orientation coefficient (n ₁ ) exceeds 0 and becomes 0.10. When the polyester resin film is laminated on a metal plate heated to a temperature around its melting point, the crystal structure stretched and oriented by heating is destroyed, and the polyester resin film after lamination has a plane orientation coefficient (n ₁ ) before lamination. It can be made lower than the plane orientation coefficient. Further, the higher the heating temperature of the metal plate and the temperature of the laminating roll and the shorter the time required to cool to room temperature, the lower the plane orientation coefficient after lamination. In particular, since heat is transferred from the heated metal plate to the laminated polyester resin film, the plane orientation coefficient (n ₁ ) becomes the smallest,
As the distance from the metal plate increases, the plane orientation coefficient of that portion increases, and the plane orientation coefficient (n ₂ ) becomes the largest.

Next, as the metal plate used in the present invention,
A sheet-shaped or strip-shaped steel plate, or an aluminum alloy plate having a chromium hydrate oxide film on its surface is preferable in order to ensure excellent adhesion to the laminated polyester resin film. In particular, TFS having a double-layered coating of a lower layer of metallic chromium and an upper layer of chromium hydrated oxide is preferable, and one or more multi-layer plating of tin, nickel, zinc, aluminum, etc. on the surface of the steel sheet, Alloy plating was performed and the above-mentioned two-layer structure film was formed on it, or aluminum alloy plate was subjected to electrolytic chromic acid treatment and immersion chromic acid treatment to form a chromium hydrate oxide film on the surface. It is possible to use a thing etc.
The amount of the hydrated chromium oxide film formed on the surface of the metal plate is less than 3 mg / m ² as chromium, or 50 mg / m ²
If it exceeds, the adhesiveness to the laminated polyester resin film, particularly the adhesiveness after processing is deteriorated. Therefore, the amount of chromium hydrate oxide film is 3 to 50 mg / chromium.
It is preferably in the range of m ² , and more preferably 7 to
25 mg / m ² . The amount of metallic chromium is not particularly limited, but is preferably in the range of 10 to 200 mg / m ² from the viewpoint of corrosion resistance after processing and adhesion of the polyester resin film.

Examples of the method for heating the metal plate include known hot air circulating electric heating method, resistance heating method, induction heating method, heat roll method and the like, and these methods may be used alone or in combination. good.

[0013]

EXAMPLES Next, the present invention will be described in more detail with reference to Examples. Electrolytic chromic acid treated steel plate (TFS) with a plate thickness of 0.17 mm and a temper degree of DR-10 (amount of metal chromium: 110 m
g / m ² , chromium content in hydrated chromium oxide: 23 mg /
m ² ), or an aluminum alloy having a plate thickness of 0.30 mm (3004, H38, the amount of chromium in the hydrated chromium oxide film formed on the surface: 18 mg / m ² ) on both sides of Table 1.
2 to 2 are shown in Tables 3 to 4.
By heating and laminating under the conditions shown in Table 3, a polyester resin film-coated metal plate shown in Tables 3 to 4 was prepared. After laminating, a test piece was cut out from each polyester resin-coated metal plate, and the plane orientation coefficient (n ₁ ) and (n ₂ ) of the polyester resin film were measured by the method described in the detailed description. Tables 3 and 4 show the structure of the polyester resin-coated metal plate and the plane orientation coefficient measured after lamination. These coated metal plates were molded into thin-walled deep-drawn cans under the processing conditions shown below, the upper ends of the cans were trimmed, and then doming, neck-in, and flanging were performed by a conventional method.

[Molding processing conditions] A. Drawing process Blank diameter: 187 mm Drawing ratio: 1.50 B. Redrawing process Primary redrawing ratio: 1.29 Secondary redrawing ratio: 1.24 Third redrawing ratio: 1.20 Curvature radius of corner of die: 0.4 mm Wrinkle holding load (metal plate Is TFS): 6000 kg (when the metal plate is an aluminum alloy): 2000 kg) C.I. Average thinning rate of the body of the can -20% of the thickness of the polyester resin-coated metal plate before molding

The characteristics of the thin-walled deep-draw cans formed from the polyester resin-coated metal plates shown in Tables 3 to 4 were evaluated by the methods described below. The evaluation results are shown in Table 5. [Characteristics Evaluation] (1) Processing Adhesion of Polyester Resin Film The film cracking and peeling state of the polyester resin film in the flanging portion were visually observed and evaluated by the following 5 grades. Rating 5: No film cracking or peeling is observed. 4: A slight film peeling was observed at the end of the flanging portion, but there was no practical problem. 3: Film cracking and peeling are recognized at the end of the flanging portion. 2: A film crack reaching the neck-in portion from the flanging portion and peeling are recognized. 1: Complete peeling of the film is observed from the flanging portion to the neck-in portion.

(2) Exposed degree of metal surface on the inner surface of the can The thin-walled deep-formed can that has been molded is filled with 3% saline, and a stainless rod is immersed therein, and the can is used as an anode and the stainless rod is used as a cathode. A direct current voltage of 6.3 V was applied to the bipolar cans, and the value of the flowing current was used to evaluate the degree of exposure of the metal surface.

(3) Hot water resistance The formed thin-walled deep drawing can is put in a retort kettle at 125 ° C.
The state of peeling of the polyester resin film from the flanging portion to the neck-in portion after hot water treatment for 30 minutes in water vapor was visually observed, and evaluated by the following 5 grades. Rating 5: No film cracking or peeling is observed. 4: A slight film peeling was observed at the end of the flanging portion, but there was no practical problem. 3: Peeling of the film, which is a practical problem, is observed at the end of the flanging portion. 2: Film peeling from the flanging portion to the neck-in portion is recognized. 1: Complete peeling of the film is observed from the flanging portion to the neck-in portion.

(4) Heat resistance The squeezed can formed up to the third redrawing is heated for 5 minutes at a temperature of 205 ° C., which corresponds to the baking temperature for external printing, and then the polyester resin film of the body of the can is formed. discoloration,
The film cracking and peeling were visually observed, and those without any defects were evaluated as 5 points, and the degree of any defect was increased as 4 to 1 points, and the evaluation was made with 5 grades.

(5) Corrosion resistance A molded thin-walled deep drawing can was filled with a 3% acetic acid aqueous solution, and
After being stored at 0 ° C. for 3 months, the can was opened, and the corrosion state of the inner surface of the can was visually observed, and the corrosion was evaluated as 5 points, and the degree of corrosion increased as 4 to 1 points.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

[Table 4]

[0024]

[Table 5]

[0025]

INDUSTRIAL APPLICABILITY As described above, the resin-coated metal plate for a thin-walled deep-drawn can of the present invention is a material excellent in workability and work corrosion resistance, and has various advantages as compared with conventional can bodies. Not only used for thinning deep drawing cans,
It is also widely applicable as a container material such as a can lid, an easily openable can lid, a crown, and a cap.

Claims (3)

(57) [Claims] 1. A melting point of 190 on at least one side of a metal plate.
A heated metal plate is coated with a polyester resin film at a temperature of up to 250 ° C., and the surface orientation coefficient of the portion of the resin that is in contact with the metal plate is n _1, and the outermost surface portion that is not in contact with the metal plate is used. The resin coating for a thin-walled deep-drawing can, wherein n ₁ is more than 0 and 0.10 or less, and n ₂ is 0.01 or more and 0.15 or less when the plane orientation coefficient of n is ₂ Metal plate. 2. A melting point of 190 on at least one side of the metal plate.
A biaxially stretched polyester resin film having a surface orientation coefficient of 0.12 to 0.17 at ˜250 ° C. is brought into contact with a metal plate heated to a temperature equal to or higher than the melting point of the resin and pressure-bonded thereto, and the resin after coating. When the surface orientation coefficient of the portion in contact with the metal plate is n ₁ and the surface orientation coefficient of the outermost portion not in contact with the metal plate is n ₂ , n ₁ exceeds 0 and 0 .1
A resin-coated metal plate for a thin-walled deep drawing can, which is 0 or less and n ₂ is 0.01 or more and 0.15 or less. 3. The adhesive layer is interposed between the metal plate and the resin film.
The resin-coated metal plate for a thin-walled deep-drawing can described in (4).