JP2532002C - - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-coated metal plate for a thin-walled deep-drawing can, and more particularly, to a polyester resin film coated on a metal plate. The present invention relates to a resin-coated metal plate for a thin-drawing deep drawn can covered with a polyester resin film in which a surface portion and a portion in contact with the metal plate have different plane orientation coefficients. 2. Description of the Related Art Conventionally, a food or beverage can has a three-piece can consisting of a can body, a can lid and a bottom lid, and a can in which the can body and the bottom lid are integrated. A two-piece can consisting of two parts, a body and a can lid, is used. The three-piece can body is made of tinplate that has been painted once or several times, and is made of electrolytic chromic acid-treated steel sheet (generally called tin-free steel, hereinafter abbreviated as TFS). Adhesion with nylon or resistance welding is used. Applying the coating in this manner 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.
In addition, drawn and redrawn cans (Drawn and redra) can be used for two-piece cans.
wn can, DRD can), drawn and ironed can (Drawn and Ironed)
can, DI can), but for tins with a relatively small drawing ratio, such as drawn cans and DRD cans, painted tin or TFS is used in the same manner as the above-mentioned three-piece can material. . Therefore, there is a problem in terms of process and environmental pollution as in the above.
Tin and aluminum are used for drawn cans and DI cans, but lubricating oil is used in the manufacture of DI cans during molding. After forming, the lubricating oil is removed by washing, and after drying, the cans are dried. The interior and exterior are painted. The manufacturing process of this DI can has problems in terms of treatment of lubricating oil from the viewpoint of pollution, treatment of a solvent component volatilized from paint during baking of paint, and the like. In recent years, a technique for manufacturing a thin-walled deep-drawn can that performs stretching after painting TFS has been developed has been developed, and painted TFS has been studied as a material thereof. However, when the painted TFS is subjected to such severe processing, countless 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. [0003] The manufacturing technology of the thinned deep drawn can is compared with the manufacturing technology of the DI can. For example, the manufacturing equipment is compact, 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 the use of materials and no pollution countermeasures, and the use of TFS, which is cheaper than tinplate, has many advantages, but when TFS pre-coated with paint is applied to thin-walled deep drawn cans, Due to insufficient corrosion resistance after processing, it has not been widely used yet. On the other hand, as a method of replacing the paint, a method of laminating a polyester resin film on a metal plate without using an adhesive (such as Japanese Patent Publication No. 60-47103) and a polymer composition comprising an epoxy resin and a curing agent thereof are used in advance. A method of laminating the applied polyester resin film on a metal plate (Japanese Patent Publication No. 63-13829,
331, Japanese Patent Application No. 1-154523, etc.) have been developed. The polyester resin-coated steel sheet obtained by the method described in JP-B-63-13829 is a steel sheet whose surface is coated with a biaxially stretched polyethylene terephthalate film via an epoxy-based polymer composition. It is inferior to the processability of the copolyester resin film described below, and can be used for draw cans, DRD cans, and can lids with a relatively small degree of processing. Cannot be used for drawn cans. The reason for this is that when such severe processing is performed, the polyester resin film is peeled off or countless cracks are formed in the film, so that highly corrosive contents cannot be filled. Further, the polyester resin-coated metal plate obtained by the method described in JP-A-1-249331 is one in which the softening start temperature, crystal melting temperature, and elongation at break of the laminated polyester resin film are limited. The polyester resin-coated metal plate obtained by the method described in Japanese Patent Application No. 1-154523 is one in which the in-plane refractive index and the crystal melting temperature of the laminated polyester resin film are limited.
The film used in these methods has better workability than the film used in the method described in JP-B-63-13829, but when applied to a thinned deep drawing can, the laminated film peels off from the metal surface. May be. This is because the plane orientation coefficient of the polyester resin layer in contact with the metal surface and the plane orientation coefficient of the outermost polyester resin layer are not adjusted, so that moldability and adhesion to the metal plate surface,
In particular, the adhesion after severe forming such as a thinned deep drawn can is poor. [0004] As described above, the technique of manufacturing a thinned deep-drawn can has many advantages as compared with the conventional can-making technique, but a material suitable for the thinned deep-drawn can is used. There is no. An object of the present invention is to develop a resin-coated metal plate having excellent workability and work corrosion resistance suitable for a thinned deep drawn can. [0005] The resin-coated metal plate for a thin-walled deep-drawing can of the present invention is formed by heating a polyester resin film having a melting point of 190 to 250 ° C on at least one surface of the metal plate. Coated,
The plane orientation coefficient of the metal plate and the phase contact with that portion of the resin and n _1, when the plane orientation coefficient of a portion of the outermost surface which is not in contact the metal plate and the phase was n _2, n ₁ is greater than zero 0.10
Hereinafter, n ₂ is 0.01 or more state, and are 0.15 or less and characterized in that it is a n ₁ ≦ n _2. Furthermore, 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,
Crimp in contact with the metal plate is heated to a temperature above the melting point of the resin, the plane orientation coefficient of the metal plate and the phase contact with that portion of the resin after coating and n _1, a metal plate and a phase contact when the plane orientation coefficient of a portion of the outermost surface is not set to n _2, 0.10 or less n ₁ is beyond 0, n ₂ is 0.01 or more state, and are 0.15 or less, and n ₁ ≦ n It is characterized by being ₂ . In these resin-coated metal plates, it is desirable that an adhesive layer is interposed between the metal plate and the resin film. Hereinafter, the contents of the present invention will be described in detail. First, it is important that the polyester resin film used in the present invention has at least an oriented portion in the polyester resin layer. As the polyester resin, 75 to 9 of ester repeating units are used.
It is preferred that 5% is an ethylene terephthalate unit and the remaining 5 to 25% of the ester repeating unit is, for example, a copolymerized polyester resin consisting of ethylene isophthalate units. Ethylene terephthalate and terephthalic acid used to synthesize esters other than ethylene isophthalate, and acid components other than isophthalic acid include phthalic acid, succinic acid, azelaic acid, adipic acid, sebacic acid, dodecanedioic acid, diphenyl One or more acid components of carboxylic acid, 2,6 naphthalenedicarboxylic acid, 1,4 cyclohexanedicarboxylic acid, and trimellitic anhydride are cited, and alcohol components other than ethylene glycol include 1,4 butanediol, 1,5 pentanediol, 1,6 hexanediol, propylene glycol, polytetramethylene glycol, trimethylene glycol, triethylene glycol, neopentyl glycol, 1,4 cyclohexane dimethanol, trimethylolpropane Alone or in combination of two or more saturated polyhydric alcohols pentaerythritol. The ester unit other than the ethylene terephthalate unit may be any one or both of the acid component and the alcohol component, provided that the acid component is other than terephthalic acid and the polyhydric alcohol is other than ethylene glycol. Can be used to obtain a copolymerized polyester resin. Such a copolymerized polyester resin can be obtained by a method in which a polyester comprising a copolymerized component is blended with an ethylene terephthalate resin, melted, and then copolymerized by a distribution reaction. These copolyester resins are produced by forming a film with a known extruder, then biaxially stretching in two directions, and heat-setting. After film formation, when using a metal plate laminated with an unstretched film that is not stretched, the coefficient of friction with the can-making tool becomes high, and the can-making property is extremely reduced, and the barrier property to the contents is also inferior. come. For this reason, in the present invention, it is essential that the outermost surface portion of the polyester resin film retain the orientation provided by the stretching imparted at the time of film forming even after the film is heated and laminated on a metal plate. In some cases, when the film is formed, if necessary, additives such as a stabilizer, an antioxidant, an antistatic pigment, a lubricant, and a corrosion inhibitor do not interfere with 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, laminating workability is remarkably reduced, and sufficient working corrosion resistance cannot be obtained. On the other hand, when the thickness is 50 μm or more, it is not economical as compared with an epoxy resin paint widely used as a material for cans. The important factors in the present invention are the plane orientation coefficient of the biaxially stretched polyester resin film before lamination on the metal plate, and the portion of the polyester resin coated metal plate in contact with the metal plate of the polyester resin film. plane orientation coefficient of (n _1), and the plane orientation coefficient of the portion of the metal plate and a phase not in contact with the uppermost surface (n ₂₎ is obtained by the following method. In other words, in the case of a biaxially stretched 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 of any one side of the film is measured by Abbe's refractometer, It is obtained from the following equation. Plane orientation coefficient = (A + B) / 2-CA A: vertical refractive index B: horizontal refractive index C: refractive index in the thickness direction Also, in the case of a polyester resin film of a polyester resin coated metal plate, it is obtained. The polyester resin-coated metal plate is immersed in hydrochloric acid, the surface of the metal plate is chemically dissolved, only the polyester resin film is peeled off, and the respective vertical surfaces of the outermost surface of the obtained film and the side in contact with the metal plate are obtained. The refractive indices in the direction, the transverse direction and the thickness direction are measured with an Abbe refractometer, and are determined in the same manner as in the case of the biaxially stretched stretched polyester resin film using the above formula. The orientation of the biaxially stretched stretched polyester resin film is brought closer to the metal plate due to heat conduction from the metal plate by being brought into contact with and pressed against a metal plate heated to a temperature equal to or higher than the melting point of the polyester resin. The plane orientation coefficient of the biaxially stretched polyester resin film determined by the method of 0.1 is 0.1
If it exceeds 7, the plane orientation coefficient (n ₂ ) is 0.15 or less and the plane orientation coefficient (n ₁ )
Is extremely difficult to be 0.10 or less. On the other hand, when the plane orientation coefficient of the biaxially stretched stretched polyester resin film is less than 0.12, the orientation of the polyester resin film after being brought into contact with a metal plate heated to a temperature equal to or higher than the melting point of the polyester resin and crimped is almost zero. Since it is lost, it is extremely difficult to set the plane orientation coefficient (n ₂ ) to 0.01 or more and to make the plane orientation coefficient (n ₁ ) of the portion in contact with the metal plate exceed 0. Further, 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 can be easily removed from the metal plate surface when processed into a thinned deep drawn can. Peel off. Plane orientation coefficient (n
_{If 1} ) is 0.10 or less, the polyester resin film is difficult to peel off, but more preferably 0.05 or less. Refractive index measured by the method described above is an average value of the portion to a depth of 5μm approximately from the outermost surface of the resin film, plane orientation coefficient obtained from the value (n ₁₎ is actually the metal plate surface The surface orientation coefficient of the outermost surface portion that is in contact with is 0, that is, even if it is non-oriented, the plane orientation coefficient exceeds 0 if the oriented portion exists within a depth of 5 μm. In the present invention, the reason that the plane orientation coefficient (n ₁ ) is set to more than 0 and equal to or less than 0.10 is a result in consideration of such a fact, and the plane orientation coefficient (n ₁ ) of the polyester resin film is 0. To be more specific, the depth is 5 μm from the contact surface with the metal plate.
The plane orientation coefficient of the portion up to 0 means 0, that is, no orientation. When the plane orientation coefficient of the outermost surface portion not in contact with the metal plate is 0.01 or less,
As described above, in the drawing step, the coefficient of friction with a can-making tool such as a wrinkle holding tool or a punch becomes too high, whereby the processing is not performed uniformly, and the polyester resin film and the metal plate are unfavorably roughened. Further, the barrier property of the resin layer itself constituting the polyester resin film itself to the content is remarkably poor, and if the corrosive content is filled and stored for a long period of time, the metal plate surface is corroded, which is not preferable. On the other hand, if the plane orientation coefficient (n ₂ ) exceeds 0.15, even if the plane orientation coefficient (n ₁ ) is 0.10 or less, innumerable cracks occur in the entire polyester resin film when processed into a thinned deep drawn can. And cannot be put to practical use as a can. That is, the plane orientation coefficient (n ₂₎ is required to be in the range of 0.01 to 0.15. Furthermore, even if severe drawing, stretching, necking, or the like is performed, the plane orientation coefficient (n ₁ ) is particularly important in order for the polyester resin film to follow the metal plate without peeling off. Next, a case where an adhesive layer is interposed between the metal plate and the polyester resin film will be described. A metal plate covered with a polyester resin film having no adhesive layer and having a plane orientation coefficient in the range limited by the present invention has excellent workability, work corrosion resistance, and scratch resistance as described above. Has, but when in contact with more corrosive contents, the metal plate surface is corroded through the polyester resin film,
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 surface of the metal plate 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 polymer composition having an epoxy group in the molecule is more preferable.The adhesive is applied to the surface of the polyester resin film which is in contact with the metal plate, dried, and then laminated on the metal plate. Alternatively, a polyester resin film may be laminated after coating and drying on the surface of a metal plate. A known method such as a roll coating method may be used for applying the adhesive, and is not particularly limited. In order to obtain the metal sheet coated with the polyester resin film of the present invention, for example, there is the following method. It has a melting point of 190-250 ° C.
A polyester resin film having a plane orientation coefficient of about 0.17 is laminated by heating to a temperature around the melting point of the polyester resin, and the plane orientation coefficient (n ₂ ) is 0.01 or more and 0
. There is a method of adjusting the plane orientation coefficient (n ₁ ) to be not more than 15 and not more than 0 to not more than 0.10. When a polyester resin film is laminated on a metal plate heated to a temperature around its melting point, the crystalline structure stretched and oriented by heating is broken, and the plane orientation coefficient (n ₁ ) of the polyester resin film after lamination is determined before lamination. It can be lower than the plane orientation coefficient. Also, the higher the heating temperature of the metal plate and the temperature of the laminating roll and the shorter the time required for cooling 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, and as the distance from the metal plate increases, the plane orientation coefficient of the portion becomes larger. The orientation coefficient (n ₂ ) is the largest. Next, the metal plate used in the present invention has excellent adhesion to a polyester resin film in which a sheet-like or belt-like steel plate or an aluminum alloy plate having a chromium hydrate oxide film on the surface is laminated. It is preferable to secure the property. In particular, TFS having a two-layered film of a lower layer of metallic chromium and an upper layer of chromium hydrated oxide is preferable, and further, tin, nickel, zinc, one or two or more kinds of multi-layer plating such as aluminum, An alloy plating was applied, and a film having the above-mentioned two-layer structure was formed thereon, or an aluminum alloy plate was subjected to electrolytic chromic acid treatment and immersion chromic acid treatment to form a chromium hydrated oxide film on the surface. It is possible to use such things. 3 mg / m less than ² amount as chromium metal plate surface formed hydrated chromium oxide film, or exceeds 50 mg / m ^2, adhesion between the polyester resin film to be laminated, particularly adhesion after working Decrease. Therefore, the amount of the chromium hydrated oxide film is preferably in the range of 3 to 50 mg / m ² as chromium, and more preferably 7 to 25 mg / m ² . Although there is no particular limitation on the amount of chromium metal, it is more 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. As a method for heating the metal plate, there are 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. Next, the present invention will be described in more detail with reference to examples. Electrolytic chromic acid treated steel sheet (TFS) with a thickness of 0.17 mm and a temper degree of DR-10
(Amount of chromium metal: 110 mg / m ² , amount of chromium in hydrated chromium oxide: 23 mg
/ M ² ) or a 0.30 mm-thick aluminum alloy (3004, H38, the amount of chromium in the chromium hydrated oxide film formed on the surface: 18 mg / m ² ). Various polyester resin films were heat-laminated under the conditions shown in Tables 3 and 4 to prepare metal sheets coated with polyester resin films shown in Tables 3 and 4. After lamination, a test piece was cut out from each of the polyester resin-coated metal plates, and the plane orientation coefficient (n ₁ ) and (n ₂ ) of the polyester resin film were determined by the method described in the detailed description.
) Was measured. Tables 3 and 4 show the structure of the polyester resin-coated metal plate and the plane orientation coefficient measured after lamination. After forming these coated metal plates into thinned deep-drawing cans under the processing conditions shown below and trimming the upper end of the can, doming by a conventional method,
Neck-in and flanging were applied. [Molding Processing Conditions] Drawing process Blank diameter: 187 mm Drawing ratio: 1.50 Redrawing step Primary redrawing ratio: 1.29 Secondary redrawing ratio: 1.24 Tertiary redrawing ratio: 1.20 Curvature radius at 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) Average Thinning Rate of Can Body -20% of Thickness of Polyester Resin-Coated Metal Sheet Before Molding Characteristics of Thin-Walled Deep-Draw Cans Formed from Polyester Resin-Coated Metal Sheets as Shown in Tables 3 and 4 Was evaluated by the following method. Table 5 shows the evaluation results. [Characteristic Evaluation] (1) Processing Adhesion of Polyester Resin Film The film cracking and peeling state of the polyester resin film in the flanged portion were visually observed, and evaluated according to the following five grades. Rating 5: Film cracking and peeling were not observed. 4: Slight film peeling was observed at the end of the flanged portion, but there was no practical problem. 3: Film cracking and peeling were observed at the end of the flanged portion. 2: A film crack reaching the neck-in portion from the flanged portion and peeling are observed. 1: From the flanged portion to the neck-in portion, complete film peeling is observed. (2) Extent of Exposing Metal Surface Inside Can Body A 3% saline solution is filled in a molded thin-walled deep-drawing can, a stainless steel bar is immersed in the solution, and the can body is used as an anode and the stainless steel bar is used as a cathode. A DC voltage of 6.3 V was applied to the bipolar can and the degree of exposure of the metal surface was evaluated based on the flowing current value. (3) Hot Water Resistance The molded thin-walled deep-drawing can is put into a retort pot, and subjected to hot water treatment in steam at 125 ° C. for 30 minutes, and then the polyester resin film is peeled from the flanged portion to the neck-in portion. The state was visually observed and evaluated according to the following five-point scale. Rating 5: Film cracking and peeling were not observed. 4: Slight film peeling was observed at the end of the flanged portion, but there was no practical problem. 3: Film peeling to an extent that would cause a problem in practice is observed at the end of the flanged portion. 2: Film peeling from the flanged portion to the neck-in portion is observed. 1: From the flanged portion to the neck-in portion, complete film peeling is observed. (4) Heat Resistance The drawn can formed up to the above-mentioned third redrawing is heated at 205 ° C. corresponding to the baking temperature of the outer surface printing for 5 minutes. Discoloration, film cracking, and peeling were visually observed, and five points where no defect was generated were evaluated as five points, and the degree of any one of the points increased as the number of points reached 4-1. (5) Corrosion Resistance A 3% acetic acid aqueous solution is filled in a molded thin-walled deep-drawing can, stored at 50 ° C. for 3 months, opened, and the corrosion state of the inner surface of the can is visually observed. The score was evaluated on a five-point scale in which the degree of corrosion increased as the score reached 4 to 1. [Table 1] [Table 2] [Table 3] [Table 4] [Table 5] As described above, the resin-coated metal sheet for a thin-walled deep drawn can according to the present invention is a material excellent in workability and corrosion resistance, and has various properties as compared with conventional can bodies. Not only can it be used for thin-walled deep-drawing cans that have advantages, but it can also be widely applied as container materials for drawn cans, can lids, easy-open can lids, crowns, caps, and the like.

Claims (1)

Claims: 1. A heated metal plate is coated with a polyester resin film having a melting point of 190 to 250 ° C. on at least one surface of the metal plate, and a portion of the metal plate which is in contact with the metal plate is heated. When the plane orientation coefficient is n ₁ and the plane orientation coefficient of the outermost surface portion not in contact with the metal plate is n ₂ , n ₁ exceeds 0 and is 0.10 or less, and n ₂ is 0.01 or more. , 0
. 15 Ri der less and thinner deep-drawing a resin-coated metal sheet for cans, characterized in that a n ₁ ≦ n _2. 2. 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 a metal plate was heated to a temperature not lower than the melting point of the resin. crimp in contact with the metal plate, the plane orientation coefficient of the metal plate and the phase contact with that portion of the resin after coating and n _1, the plane orientation coefficient of a portion of the outermost surface which is not in contact the metal plate and the phase When n ₂ , n ₁ exceeds 0 and is 0.10 or less;
₂ is 0.01 or more, 0.15 or less der is, and thin deep drawn resin-coated metal sheet for cans, characterized in that a n ₁ ≦ n _2. 3. The resin-coated metal plate for a deep-drawn thin drawing can according to claim 1, wherein an adhesive layer is interposed between the metal plate and the resin film.