JP2802355B2 - Resin-coated metal sheet for thinned deep drawn cans with excellent denting resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-coated metal plate for a thin-drawing deep drawn can, and more particularly, to a can body formed by coating a metal plate with a polyester resin layer having a limited IV value. The present invention relates to a resin-coated metal plate for a deep-drawn deep-drawing can having excellent denting resistance (impact resistance) in a portion.

[0002]

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, a can body in which the can body and the bottom lid are integrated, and a can body and a can lid. A two-piece two-piece can 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 step, there is a drawback that the discharged solvent must be led to a special incinerator and incinerated from the viewpoint of pollution. For two-piece cans, drawn cans, drawn redrawn cans (Dr
awn and reduce can, DRD
Cans), drawn and ironed cans (Drawn and Irone)
d 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 material for the above three-piece cans. I have. 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 the DI can has problems in terms of pollution, such as treatment of lubricating oil and treatment of a solvent component volatilized from the paint during baking of the paint. 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 this thinned deep-drawing can is compared with the manufacturing technology of DI cans. For example, precoating is possible because the manufacturing equipment is compact and the equipment cost is low, the equipment installation area is small, and the number of operators can be reduced. It has many advantages, such as the use of materials, no need for pollution countermeasures, and the use of TFS which is less expensive than tinplate.However, when TFS pre-coated with paint is applied to thinned deep drawn cans However, because of insufficient corrosion resistance after processing, it has not been widely used yet. On the other hand, as an alternative to painting, a method of laminating a polyester resin film on a metal plate without using an adhesive (Japanese Patent Publication No. 60-47103), a method of preparing a polymer composition comprising an epoxy resin and a curing agent thereof in advance. A method of laminating a coated polyester resin film on a metal plate (JP-B-63-13829, JP-A-1-249331, and JP-A-2-15498) has been developed.
The polyester resin-coated steel sheet obtained by the method described in JP-B-63-13829 is a steel sheet coated with a biaxially stretched polyethylene terephthalate film via an epoxy polymer composition, and the workability of the polyethylene terephthalate film Can be used for drawn cans, DRD cans, and can lids, which are inferior to the processability of the copolyester resin film described below and have a relatively small degree of processing. Cannot be used for 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. Also, Japanese Patent Application Laid-Open No. 1-249331
The polyester resin-coated metal plate obtained by the method described in Japanese Patent Application Laid-Open Publication No. H11-15083 is one in which the softening start temperature, crystal melting temperature, and elongation at break of the copolymerized polyester resin film to be laminated are limited. Further, the polyester resin-coated metal plate obtained by the method described in Japanese Patent Application No. 2-154098 is one in which the in-plane refractive index and crystal melting temperature of the laminated copolymerized 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 thin-walled deep-drawing can, the laminated film is more likely to have a lower surface than the metal plate surface. May peel off. Even if these known polyester resin-coated metal plates are used for thinning deep-drawing cans, after filling the thinned deep-drawing cans formed in the can-making process or the contents of the cans, the cans are processed at high speed. During continuous and continuous transportation, the cans may collide with each other and cause dents in one of the cans. The portion where the dent is formed is deformed into a convex shape when viewed from the inner surface side of the can, and countless cracks may enter the polyester resin layer in this portion, which may cause local corrosion. That is, the conventional polyester resin-coated metal sheet is formed into a can in a normal state, and if it is conveyed in a normal state, there are some which can be applied to a thin-wall deep-drawing can, but the abnormal can-making as described above. Since practical work and abnormal filling work are not taken into consideration, the utility is poor.

[0004]

As described above, the technique of manufacturing a thinned deep-drawing can has many advantages as compared with the conventional can-making technique. No suitable material has been developed. The present invention has excellent workability suitable for a thin-walled deep-drawing can in consideration of such abnormal work, and also has a work corrosion resistance, particularly, a denting resistance in a can body after being formed into a thin-walled deep-drawing can. An object of the present invention is to develop a metal sheet coated with a polyester resin having excellent performance.

[0005]

According to the present invention, as a result of various studies, a metal plate having an IV value of 0.50 to 0.70 on one or both surfaces of a metal plate with or without an adhesive is used. By coating with a thermoplastic polyester resin, it is not necessary to take measures against pollution, which is a problem to be solved by the present invention, and strict workability and work corrosion resistance, particularly, anti-denting in a can body after being formed into a thin deep drawn can. It is possible to obtain a polyester resin-coated metal sheet suitable for a thin-drawing deep-drawing can requiring the property.

Hereinafter, the contents of the present invention will be described in detail. First, as the polyester resin used in the present invention, it is preferable that 75 to 95% of the ester repeating units are composed of ethylene terephthalate units, and the remaining 5 to 25% of the ester repeating units are composed of ester units other than ethylene terephthalate units. . Acid components other than terephthalic acid include phthalic acid, isophthalic acid, succinic acid, azelaic acid, adipic acid, sebacic acid, dodecanedioic acid,
One or more acid components of diphenylcarboxylic acid, 2,6 naphthalenedicarboxylic acid, 1,4 cyclohexanedicarboxylic acid, and trimetic anhydride can be mentioned. As the alcohol component other than ethylene glycol, 1,4
1 of butanediol, 1,5 pentanediol, 1,6 hexanediol, propylene glycol, polytetramethylene glycol, trimethylene glycol, triethylene glycol, neopentyl glycol, 1,4 cyclohexanedimethanol, trimethylolpropane, and pentaerythritol One or more kinds of saturated polyhydric alcohols are mentioned. 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. 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 copolymerized polyester resins can be used as they are in the form of a film formed by a known extruder, or, after the film is formed, stretched in two directions in the vertical and horizontal directions. Can be used. It is also possible to directly laminate the molten polyester resin extruded from the extruder on the surface of the metal plate. In general, a metal plate on which an unstretched film is laminated is inferior to a metal plate on which a stretched film is laminated, but has an inferior canning property. It is possible to obtain a polyester resin-coated metal sheet having excellent denting resistance in the body portion of the thin-drawing deep-drawing can as the object. Further, if necessary, additives such as a stabilizer, an antioxidant, an antistatic agent, a pigment, a lubricant, and a corrosion inhibitor do not interfere with the present invention.

Although the thickness of the polyester resin film used in the present invention is not particularly limited,
5 to 50 μm is preferred. When the thickness becomes 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.

An important factor in the present invention is an IV value (Intrinsic value) of a polyester resin for coating a metal plate.
c Viscosity, intrinsic viscosity) is determined by the following method. That is, the obtained 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, 0.6 g of the film is collected, and 50 ml of orthochlorophenol is added. After heating for 30 minutes to dissolve the collected polyester resin film, and after cooling, the viscosity is measured using an Ostwald viscometer in a thermostat at 35 ° C., and the viscosity is determined by the following equation. η _SP / C = [η] + κ [η] ² C where η _SP : specific viscosity [η]: intrinsic viscosity, equivalent to IV value κ: constant (0.247) C: volume concentration (g / 100 ml) The IV value of the polyester resin obtained from the equation is 0.
When it is 50 or less, it is processed into a thin-walled deep-drawn can, filled with contents, and further given a dent from the outer surface to the can body, countless cracks enter the polyester resin layer laminated on the inner surface side of the can, It is not preferable because the metal surface is corroded from that portion. Polyester resins having an IV value of 0.70 or more are difficult to form industrially, and are not suitable as the resin for metal surface coating of the present invention. That is, the IV value is 0.50 to 0.70, more preferably 0.55 to 0.5.
Polyester resin No. 65 is suitable for thin-walled deep-drawing cans that are easy to form industrially and are required to have strict workability and corrosion resistance as described above.

Next, a case where an adhesive layer is interposed between the metal plate and the polyester resin layer will be described. As described above, a metal plate coated with a polyester resin layer having no adhesive layer and having an IV value within the range defined in the present invention has excellent workability, work corrosion resistance, and especially denting resistance. However, when it comes into contact with more corrosive contents, the surface of the metal plate is corroded through the polyester resin layer, and the polyester resin layer may peel off from the metal plate. The adhesive layer interposed between the metal plate and the polyester resin layer is effective in preventing corrosion of the metal plate surface and peeling of the polyester resin layer in such a case.
Known adhesives can be used, but a polymer composition having an epoxy group in the molecule is more preferable. The adhesive can be applied to a surface of a polyester resin in contact with a metal plate and dried, or applied to the surface of the metal plate. It may be dried, and its application method is not particularly limited.

To obtain the polyester resin-coated steel sheet of the present invention, for example, there is the following method. That is, an unstretched or biaxially stretched polyester resin film having an IV value of 0.50 to 0.70 is laminated on a metal plate heated to around its melting point, and part or all of the polyester resin surface in contact with the metal surface is removed. Known methods such as a method of melting and bonding to a metal plate, a method of temporarily bonding to a metal surface at a temperature equal to or lower than the melting point thereof, and then increasing the temperature to completely fuse the metal surface and the film are used.

Next, the metal plate used in the present invention has excellent adhesion to a polyester resin laminated with a chromium hydrated oxide film on the surface layer of a sheet-like or belt-like steel plate and an aluminum plate. Useful for securing. In particular, TFS having a two-layer structure of a lower layer of metallic chromium and an upper layer of chromium hydrated oxide is preferable, and furthermore, tin, nickel, zinc, aluminum, etc.
Kind of multi-layer plating or alloy plating of two or more types,
A TFS film or a chromium hydrated oxide film having the above two-layer structure is formed on the upper layer, or aluminum is subjected to electrolytic chromic acid treatment and immersion chromic acid treatment,
A chromium hydrate oxide film formed on the surface layer is used. When the amount of the chromium hydrated oxide film on the surface layer is 3 mg / m ² or less or 50 mg / m ² or more as chromium, the adhesion to the laminated polyester resin layer, particularly the adhesion after processing is reduced. Therefore, the amount of the hydrated chromium 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 . The amount of chromium metal does not need to be particularly limited, but is preferably 10 from the viewpoint of corrosion resistance after processing and adhesion of the polyester resin layer.
More preferably, it is in the range of 200 to 200 mg / m ² .

As a method for heating the metal plate, there are known hot air circulation heat transfer system, resistance heating system, induction heating system, heat roll system and the like, and these systems may be used alone or in combination.

[0013]

EXAMPLES Example 1 Isophthalic acid was applied to both sides of a TFS having a plate thickness of 0.17 mm and a temper degree of DR-10 (110 mg / m ² of chromium metal, 14 mg / m ² of chromium in a chromium hydrated oxide film). 1
A biaxially oriented polyester resin film (IV value 0.68, thickness 25 μm) obtained by polymerization of 2 mol%, terephthalic acid 88 mol% and ethylene glycol 100 mol% was treated with 24
Laminated at 2 ° C. The obtained polyester resin-coated steel sheet was processed into a thin-walled deep drawn can under the processing conditions shown below.
Furthermore, doming, necking,
Flanging was applied. [Molding conditions] Drawing process Blank diameter: 187 mm Drawing ratio: 1.50 Redrawing process Primary redrawing ratio: 1.29 Secondary redrawing ratio: 1.24 Tertiary redrawing ratio: 1.20 Curvature radius of corner of die in redrawing process: 0.4 m
m Wrinkle holding load in the redrawing process: 6000 kg Average thinning rate of can body part -2 with respect to thickness of polyester resin coated steel sheet before molding
0%

Comparative Example 1 12 mol% of isophthalic acid, 88 mol% of terephthalic acid and ethylene glycol 10 were added to both surfaces of the TFS shown in Example 1.
A biaxially oriented polyester resin film (IV value 0.48, thickness 25 μm) obtained by polymerization of 0 mol% was laminated at 242 ° C. The obtained polyester resin-coated steel sheet was subjected to molding under the same conditions as in Example 1.

Example 2 0.5 g / m ^{2 of an} epoxy-phenol-based paint was previously applied as a primer to both surfaces of the TFS shown in Example 1,
After drying at 150 ° C., an acid component of 15 mol% of isophthalic acid, 15 mol% of adipic acid and 70 mol% of terephthalic acid, 60 mol% of ethylene glycol, and 1,4 butanediol 40
Unstretched polyester resin film obtained by polymerization of mol% alcohol component (IV value 0.53, thickness 30 μm)
At 210 ° C. The obtained polyester resin-coated steel sheet was subjected to molding under the same conditions as in Example 1.

Example 3 30 mol% of isophthalic acid, 70 mol% of terephthalic acid and ethylene glycol 10 were added to both surfaces of the TFS shown in Example 1.
An unstretched polyester resin film (IV value 0.64, thickness 30 μm) obtained by polymerization of 0 mol% was laminated at 215 ° C. Example 1 was applied to the obtained polyester resin-coated steel sheet.
Molding was performed under the same conditions as described above.

Comparative Example 2 An unstretched polyester resin film having the same resin composition as in Example 3 (IV value: 0.4) was formed on both surfaces of the TFS shown in Example 1.
7, thickness 30 μm) at 215 ° C. The obtained polyester resin-coated steel sheet was subjected to molding under the same conditions as in Example 1.

Example 4 A polyester resin obtained by polymerization of 12 mol% of isophthalic acid, 88 mol% of terephthalic acid and 100 mol% of ethylene glycol on both sides of a 0.30 mm-thick aluminum (Al-Mg alloy) and isophthalic Bilayer biaxially oriented polyester resin film obtained by co-extrusion of a polyester resin obtained by polymerization of 18 mol% of an acid, 82 mol% of terephthalic acid and 100 mol% of ethylene glycol (a polyester resin layer containing 12 mol% of isophthalic acid) IV value 0.61, thickness 1
5 μm, a polyester resin layer containing 18 mol% of isophthalic acid having an IV value of 0.56 and a thickness of 5 μm) were laminated at 220 ° C. The obtained polyester resin-coated aluminum plate was subjected to molding under the same conditions as in Example 1 except that the molding conditions in the redrawing step were changed as described below. [Conditions Different from Example 1 in Redrawing Step] Curvature radius of corner of die in redrawing step: 0.4 m
m Wrinkle holding load in redrawing process: 2000kg

Example 5 The same biaxially oriented polyester resin film as in Example 1 previously coated with 0.38 g / m ^{2 of an} epoxy-phenol paint and dried was applied on one side of the TFS shown in Example 1 and on the other side. Contains 12 parts by weight of titanium oxide and isophthalic acid 1
A white polyester resin film (IV value 0.56, thickness 20 μm) obtained by polymerization of 2 mol%, terephthalic acid 88 mol% and ethylene glycol 100 mol% was heated at 250 ° C.
Was laminated. The obtained polyester resin-coated steel sheet was subjected to molding under the same conditions as in Example 1.

Comparative Example 3 A polyester resin film having the same composition as in Example 5 (IV value: 0.48, thickness: 25) was formed on one side of the TFS shown in Example 1.
μm) and the same white polyester resin film as in Example 5 was laminated on the other side at 250 ° C. The obtained polyester resin-coated steel sheet was subjected to molding under the same conditions as in Example 1.

The polyester-coated steel sheet and the aluminum sheet obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were subjected to thinning deep drawing, and the properties of the obtained thinned deep drawn cans were evaluated by the following methods. did. The results are shown in Tables 1 and 2. (1) Denting resistance of the inner surface of the can A circle is placed at a position 10 mm in the height direction of the can from the bottom of the can body of the obtained thinned deep drawn can and at a position 10 mm in the can bottom direction from the necked portion. 5. A steel ball of 1/2 inch in diameter and 1 kg was dropped from a height of 50 mm from the outer surface of the can at four positions in the circumferential direction, and a sponge impregnated with 3% saline was applied to the convex portion of the inner surface. A direct current voltage of 5 V was applied, the flowing current was measured, and the denting resistance (impact processing resistance of the laminated polyester resin) was evaluated by the average value of the current at each position. (2) Denting resistance of inner surface of can after hot water treatment The obtained thinned deep drawn can was placed in a retort pot, and heated at 130 ° C.
Was subjected to a hot water treatment with water vapor for 1 hour, and then the method of (1) was used to evaluate the anti-denting property of the inner surface body of the can after the hot water treatment. (3) Corrosion resistance of the inner surface of the can A carbonated beverage (trade name: Coca-Cola) is filled in a can with a dent given to the body of the can by the method shown in (1), and stored at 37 ° C for 3 months. The amount of aluminum was measured, and the state of corrosion at the protrusions on the inner surface of the can body was visually observed.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

As described above, the polyester resin-coated metal sheet for a thin-walled deep drawn can of the present invention is excellent in workability and corrosion resistance, especially impact resistance (denting resistance) of the can body. It is a material that is not only used for thin-walled deep-drawn cans that have various advantages compared to conventional can bodies,
It can be widely applied as a container material such as squeezed cans, can lids, easy-open can lids, crowns and caps.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tsuneo Inui 7417-7417, Nishikitayama, Tokuyama City, Yamaguchi Prefecture (56) References JP-A-2-242738 (JP, A) ) JP-A-52-65588 (JP, A)

Claims (1)

(57) [Claims] 1. A can-resin-coated metal plate for a thin-drawing deep-drawing can formed by a stretch processing method for making the thickness of a can body thinner than the thickness of an original plate. A resin-coated metal plate for a deep drawn can with excellent denting resistance, which is entirely biaxially oriented and is coated with a thermoplastic polyester resin having an IV value of 0.50 or more and 0.70 or less and having excellent denting resistance.