JPH0379252B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a drawing and ironing can, and more particularly to a drawing and ironing can that is provided with a polyester coating mainly composed of molecularly oriented ethylene terephthalate units in close contact with the inner surface of the can.
The present invention particularly relates to an inner-coated drawn and ironed can with excellent inner coating adhesion, corrosion resistance, and flavor characteristics. Conventionally, it has already been possible to thermally bond a thermoplastic polyester film such as polybutylene terephthalate to a metal material such as a steel plate, and then subject this covered metal structure to drawing or drawing ironing to make container lids or containers. Are known. However, drawn containers manufactured by known methods are shallow drawn containers in the shape of plates or cups with a drawing ratio of about 1.5, and even those called ironed containers are processed with an ironing rate of about 20%. The degree of ironing is generally low, and it is applicable to the production of squeezed ironing cans with a can height of 100 to 230mm and a high ironing rate of 30% or more, such as those currently used for beer cans and carbonated beverage cans. That was extremely difficult. Furthermore, in containers made by drawing and ironing such film-coated metal materials, the adhesion between the film layer and the metal material decreases significantly over time, and peeling at the interface between the two easily progresses. . This tendency becomes more pronounced as the degree of ironing increases. Thermoplastic polyesters mainly composed of ethylene terephthalate units are not used as coated metal materials for drawing and ironing, although they have superior mechanical properties compared to other polyesters such as polybutylene terephthalate. It seems very strange that there is no resin, but this is because no consideration was given to the orientation of the resin during harsh processing such as ironing, so sufficient barrier properties and adhesion over time cannot be obtained. It is thought that The inventors have discovered that the metal material and the ester repeating unit
A polyester film of which 70% or more consists of ethylene terephthalate units,
When subjected to drawing and ironing, by positively imparting molecular orientation to the film, the adhesion between the metal material and the film over time is significantly improved, and an inner-coated drawing and ironing can with excellent properties can be obtained. I discovered that. That is, it is an object of the present invention to provide a drawing and ironing can having an inner coating of polyester in which 70% or more of the molecularly oriented ester repeating units are ethylene terephthalate units. Another object of the present invention is to improve the adhesion of the inner surface coating over time;
To provide a drawing and ironing can with an inner surface coated and excellent in corrosion resistance and flavor characteristics. Still another object of the present invention is that the polyester coating layer, in which 70% or more of the ester repeating units on the inner surface of the can are ethylene terephthalate units, is molecularly oriented as the metal is thinned by drawing and ironing, and as a result, it has excellent properties over time. An object of the present invention is to provide a drawing and ironing can which provides excellent coating adhesion and corrosion resistance. According to the present invention, there is provided a drawing and ironing can formed by drawing and ironing a resin-coated metal material,
This can has a thermoplastic polyester coating in which 70% or more of the ester repeating units are ethylene terephthalate units, which is closely adhered to at least the inner surface of the can via an adhesive base layer, and on the side wall of the can, The metal material is determined by the following formula: R = t ₀ − _{t 1} /t ₀ ×100 where t ₀ is the thickness of the metal material covering the bottom of the can, and t ₁ is the thickness of the metal material covering the side wall. The polyester coating on the side wall is thinned so that R) is 30 to 85%, and the polyester coating on the side wall has the following formula fc = 180-H/180 x 100, where H is when the coating is subjected to X-ray diffraction. The degree of orientation (fc) defined by represents the half-value width obtained from the ring diffraction intensity curve of the crystal plane (100) interference obtained by irradiating X-rays in the can circumferential direction and parallel to the polyester coating surface. Provided is a drawing and ironing can with excellent corrosion resistance, characterized in that the molecules are oriented so that the Regarding the degree of orientation in the present invention, a rotating anticathode type strong X-ray generator (Cu-Ka, Ni-filter) is used to determine the output.
Photographs were taken at 40KV and 50mA under conditions that reflect X-ray diffraction intensity well. The present invention will be explained in detail below based on specific examples shown in the accompanying drawings. In FIG. 1 showing the coated metal material used in the present invention, the coated metal material 1 consists of a metal material 2 and a thermoplastic polyester resin layer (hereinafter simply referred to as a polyester resin layer) in which 70% or more of the ester repeating units are ethylene terephthalate units. ) consists of 3. This polyester resin layer 3 is thermally bonded to the metal material 2, and in the specific example shown in FIG. ing. Also,
In this specific example, the polyester resin layer 3 is provided only on the surface of the metal material 2 that should become the inner surface of the container, but the polyester resin layer 3 may also be provided on the surface that should become the outer surface of the container. As the metal material 2, all the metal materials conventionally used for manufacturing drawn and ironed cans can be used, such as black plates (untreated steel plates), surface-treated steel plates, or light metal plates such as aluminum plates. . Suitable examples of surface-treated steel sheets include steel sheets subjected to chemical treatments such as phosphoric acid treatment and/or chromic acid treatment; chemically treated steel sheets such as electrolytic chromic acid treated steel sheets; tin-plated steel sheets, galvanized steel sheets, nickel-plated steel sheets, and aluminum. Examples include plated steel plates such as plated steel plates. Further, the tin-plated steel sheet may be a no-reflow plate (matte plate) that has been electrolytically plated, or a reflow plate (bright plate) that has been subjected to melting treatment after electrolytic plating.
The thickness of the metal material varies depending on the size of the can and the degree of ironing, but generally speaking it is 0.05
It is preferable to have a thickness of 2.5 mm to 2.5 mm, particularly 0.1 to 1.0 mm. In the present invention, a thermoplastic polyester (hereinafter sometimes simply referred to as polyester) in which 70% or more of the ester repeating units are ethylene terephthalate units is used as the resin coating layer. In addition to polyethylene terephthalate, this polyester may contain at least 70% of the ester repeating units, especially 90%
% or more consists of ethylene terephthalate units,
In addition, isophthalic acid, naphthalene dicarboxylic acid,
Other dibasic acids such as 2,2-bis(4-carboxyphenyl)propane, hexahydroterephthalic acid, adipic acid, sebacic acid; propylene glycol, butanediol, neopentyl glycol,
Other glycols such as xylylene glycol, hexahydroxylylene glycol, diethylene glycol, triethylene glycol, and hexamethylene glycol; Contains modifying ester units derived from oxycarboxylic acid components such as p-oxybenzoic acid and caprolactone. Copolyesters are used. The polyester resin should have a molecular weight capable of forming a film, and it is generally desirable to have an intrinsic viscosity in the range of 0.1 to 2.8, measured at a concentration of 1.0 g/100 ml in orthochlorophenol and at 30°C. The polyester resin used in the present invention has several characteristics not found in other coating resins. First, this polyester resin itself has excellent mechanical properties such as strength and elongation, and the effect of molecular orientation by stretching is the greatest. That is, molecular orientation significantly improves rigidity, barrier properties, and heat resistance. In addition, this polyester has excellent barrier properties against metal corrosive components, and despite being composed of repeating ester units, it has a low water absorption rate for this type of resin, meeting ASTM D570-63 (24°C at 23°C).
The water absorption rate measured in hours) is 1.5% or less. Furthermore, polyester resin has excellent flavor characteristics among various resins, does not impart any off-taste or odor to the contents of the can, and unlike polyolefin, does not absorb malodorous components during the manufacturing process. do not have. Moreover, this polyester resin has a uniform molecular weight distribution, and unlike thermosetting resin paints, low molecular weight components in the resin are not eluted or extracted into the contents, and it has outstanding hygienic properties. ing. The thickness of the polyester resin layer varies depending on the degree of ironing, but generally speaking, the thickness is 5 to 5.
Preferably it has a thickness of 1000 microns, especially 10 to 500 microns. The adhesion base layer 4 improves the adhesion of the polyester resin layer 3 to the metal material 2, and includes, for example, an inorganic oxide layer such as a chromate layer, a phosphoric acid treatment layer, or a titanate layer applied to the metal material 2 itself. Examples include a urethane adhesive layer, an epoxy adhesive layer, a copolyester adhesive layer or a polyester ether adhesive layer, and a combination of an inorganic oxide layer and an adhesive layer. In order to manufacture coated metal material 1, metal material 2
The polyester resin layer 3 is adhered to. This adhesion can be performed by directly thermally adhering the polyester resin layer itself through an inorganic oxide layer as an adhesion base, or it can be performed through the above-mentioned adhesive layer. In this coated metal material, it is necessary that the polyester resin layer is firmly adhered to the metal material, and generally speaking, the adhesive strength is 0.5
Kg/cm or more, especially 1.0Kg/cm or more,
It is necessary for performing advanced ironing processing. Another point that must be taken into account when manufacturing coated metal materials is to minimize the growth of spherulites in the polyester resin during this manufacturing process in order to enable molecular orientation by stretching the polyester resin layer. It is to suppress. That is, if excessive spherulites of polyester resin are generated in this step,
It becomes difficult to stretch the resin layer during the ironing process, leading to problems such as breakage, peeling, and cracking. For this purpose, for example, the coating material after thermal bonding is preferably cooled rapidly so that the resin layer is in a supercooled state. Also, the resin layer rapidly passes through the crystallization temperature during the melting-solidification stage. In the present invention, T as the polyester resin layer
- It is possible to use an unoriented film with low crystallinity produced by the die method. Further, as this polyester resin layer, it is also possible to use a material in which microcrystals are formed due to orientation, such as a polyester film that has already been oriented by uniaxial stretching or biaxial stretching. For example, if a polyethylene terephthalate film oriented by biaxial stretching is used as this resin layer, the degree of in-plane orientation will decrease and uniaxial orientation in the ironing direction will occur more greatly. According to the present invention, the coated metal material 1 for molding manufactured in this manner is coated with the polyester resin layer 3.
The material is drawn and ironed between a punch and a die at an appropriate stretching temperature. In this drawing and ironing process, the coated metal material is drawn into the shape of a cup-shaped seamless cylinder, and the side wall portion is thinned, thereby performing the ironing process. In the present invention, by maintaining the resin layer at an appropriate stretching temperature, remarkable molecular orientation is imparted to the resin layer, and this molecular orientation significantly improves various physical properties of the resin layer. Moreover, not only the adhesiveness or adhesion of the resin layer to the metal material over time is significantly improved, but also the corrosion resistance of the can is significantly improved. This improvement in adhesion and corrosion resistance over time is remarkable. For example, in iron forming at room temperature, peeling of the film already occurs after leaving it for about one minute, whereas in forming according to the present invention, the film peels off after being left for about one minute. Even after filling and long-term storage, such peeling is hardly observed. In FIG. 2-A of the attached drawing for explaining the processing order of a drawn and ironed can, that is, a seamless side metal can, first, the above-mentioned molding material 1 is punched into a disc shape (first step - shear). The size of the coated metal material 1 is determined in consideration of the drawing ratio and ironing rate, which will be described later, so that the metal material necessary for the final container is secured. Next, in a drawing process shown in FIG. 2-B, the sheared material is drawn between a drawing die 5 and a punch 6 to form a shallowly drawn cup-shaped product 7. The clearance between the drawing die 5 and the punch 6 is approximately equal to or slightly larger than the thickness of the coated metal material 1 described above. When using the coated metal material of the present invention, the drawing ratio R D is defined by the following formula: R _D = D/d, where D is the minimum diameter of the sheared coated metal material, and d is the minimum diameter of the _punch . varies considerably depending on the type of metal material, but in practical terms
It is preferably in the range of 1.1 to 3.0, preferably 1.2 to 2.8. Next, in the re-drawing step shown in FIG. 2-C, the cup-shaped molded product 7 obtained in the first-stage drawing step is passed through a re-drawing die 8 having a smaller diameter and a re-drawing punch 9.
The product is re-drawn between the two and formed into a deep-drawn cup-shaped molded product 10. Of course, in many cases, the drawing ratio in this re-drawing step, that is, the ratio of the diameter of the cup-shaped molded product 7 to the diameter of the re-drawing punch 9, is also required to be within the above-mentioned value range in the drawing step. The clearance between the re-drawing punch 9 and the re-drawing die 8 can be made substantially equal to the thickness of the coated metal material 1 to avoid straining the material, or the clearance can be made substantially equal to the thickness of the coated metal material 1 to avoid straining the material. It is also possible to make the thickness smaller than the thickness of , so that the material is slightly strained. A commonly used lubricant can also be used for this drawing or re-drawing. Further, the drawn product formed by the re-drawing process can be subjected to a third drawing process to obtain a more deeply drawn product. The cup-shaped molded product 7 obtained in the drawing process shown in Fig. 2-B and the cup-shaped molded product 1 obtained in Fig. 2-C
Add 0 to ironing process. That is, in FIG. 2-D, a plurality of ironing dies 12 (only one is shown in the drawing) are arranged along the movement path of the ironing punch 11, and the side walls of the cup-shaped molded product 7 or 10 are arranged. The parts are ironed between an ironing punch 11 and an ironing die 12. Shigoki dice 1
2 and the ironing punch 11 is smaller than the wall thickness of the coated metal material, so the side wall 13 of the cup-shaped molded product is stretched and thinned by meshing with the ironing die 12. In this case, the following formula R = t ₀ − _{t 1} /t ₀ ×100 In the formula, t ₀ is the thickness of the metal material covering the bottom of the can, and t ₁
is the thickness of the metal material covering the side wall portion.The ironing rate (R) defined by: differs depending on the type of metal material and the thickness of the oriented resin coating layer, but generally speaking, it is one step of ironing. So, 10 to 50
%, preferably in the range of 30 to 85% as a whole. In the present invention, at least this ironing step,
Preferably, the drawing step and the ironing step are all carried out at an appropriate stretching temperature in order to impart molecular orientation to the polyester resin film layer. The appropriate stretching temperature for polyester film is 40 to 100
Temperatures of 0.degree. C. are preferred, especially temperatures of 45 to 90.degree. As already pointed out, when the ironing temperature is lower than the stretching temperature of the polyester film, such as room temperature, it is more difficult to impart effective molecular orientation to the film layer itself than in the case of the present invention. At the same time, adhesion to metal materials and corrosion resistance become significantly inferior. Furthermore, even when this ironing process is performed at a temperature higher than the appropriate stretching temperature of the polyester film, it is difficult to impart effective molecular orientation to the film layer itself, and processability may deteriorate due to crystallization etc. , causing problems such as breakage and peeling. In the present invention, the molecular orientation imparted to the polyester film layer is uniaxial molecular orientation in the ironing direction, and the degree of orientation is largely related to the ironing rate and stretching temperature. The degree of molecular orientation is determined by the following formula: fc=180-H/180×100, where H is the amount of X-ray irradiation in the can circumferential direction when the coating is subjected to X-ray diffraction and parallel to the surface of the polyester coating. The degree of orientation (fc) defined by is 25 to 90%, especially 35%, which represents the half-width obtained from the ring diffraction intensity curve of the crystal plane (100) interference obtained by
It is desirable that it be ~90%. According to the present invention, not only is it possible to easily obtain an inner-coated drawn and ironed can with excellent film adhesion and corrosion resistance, but also rusting of the metal material during and after molding is effectively prevented. Furthermore, there are many advantages, such as eliminating the trouble of post-processing the cans after molding to improve the adhesion of the paint film or spray painting the inside of each can. The invention is illustrated by the following example. Example 1 Mild steel plate (thickness: 0.123 mm, temper: T-1,
Nickel plating of 5g/ ^m2 is applied to both sides of the steel (aluminum killed), and one side (film-covered side)
310 plated metal material with chromate treatment
℃ to form a film (thickness: 31 μm, degree of orientation: 0) of polyethylene terephthalate resin (molecular weight: 25,000) on the heated metal material.
%) was laminated and rapidly cooled, and using the coated metal material obtained, drawing and ironing was performed under the following forming conditions to obtain a drawing and ironing can. A storage test was conducted on the squeezed and ironed can under the following conditions, and the results were good as shown in Table 1. <Molding conditions> (1) Stretching temperature (resin temperature immediately before molding): 65℃ (2) Blank diameter: 139mm (3) Drawing conditions: 1st drawing ratio: 1.85, 2nd drawing ratio:
1.42 (4) Ironing punch diameter: 52.65mm (5) Total ironing rate: 35% <Storage test conditions> After degreasing and cleaning the squeeze ironing can, dry it at 180℃ for 5 minutes, and after processing the flange, put the contents (sprite) into the can. Fill the container to 90% of its height, wrap it with an aluminum lid coated with epoxyphenol paint to a dry thickness of 10 μm, and leave it face down in an atmosphere at 37°C for 6 months. Example 2 The thickness of the mild steel plate is 0.25mm and the thickness of the coating material is 62μ
Using a coated metal material obtained in the same manner as in Example 1 except that m was used, drawing and ironing was performed under the following forming conditions to obtain a drawn and ironed can. A storage test was conducted on this squeezed and ironed can in the same manner as in Example 1. The results are shown in Table 1 and were good. <Molding conditions> (1) Stretching temperature (resin temperature just before molding): 65℃ (2) Blank diameter: 105mm (3) Drawing conditions: 1st drawing ratio: 1.40, 2nd drawing ratio:
1.42 (4) Ironing punch diameter: 52.65mm (5) Total ironing rate: 68% Example 3 Mild steel plate thickness is 0.40mm and coating material thickness is 100μ
Using a coated metal material obtained in the same manner as in Example 1 except that m was used, drawing and ironing was performed under the following forming conditions to obtain a drawn and ironed can. A storage test was conducted on this squeezed and ironed can in the same manner as in Example 1. The results are shown in Table 1 and were good. <Molding conditions> (1) Stretching temperature (resin temperature immediately before molding): 65℃ (2) Blank diameter: 89mm (3) Drawing conditions: 1st drawing ratio: 1.69 (4) Ironing punch diameter: 52.65mm (5) Total Ironing rate: 80% Example 4 A film (thickness: 31 μ
A drawn and ironed can was obtained using the same coated metal material and molding conditions as in Example 1, except for the following: m, degree of orientation: 16%). A storage test was conducted on this squeezed and ironed can in the same manner as in Example 1. The results are shown in Table 1 and were good. <Molding conditions> (1) Stretching temperature (resin temperature just before molding): 65℃ (2) Blank diameter: 139mm (3) Drawing conditions: 1st drawing ratio: 1.85, 2nd drawing ratio:
1.42 (4) Ironing punch diameter: 52.65mm (5) Total ironing rate: 35% Example 5 The thickness of the mild steel plate is 0.25mm and the thickness of the covering material is 62μ
Using a coated metal material obtained in the same manner as in Example 4 except that m was used, drawing and ironing was performed under the following forming conditions to obtain a drawn and ironed can. A storage test was conducted on this squeezed and ironed can in the same manner as in Example 1. The results are shown in Table 1 and were good. <Molding conditions> (1) Stretching temperature (resin temperature just before molding): 65℃ (2) Blank diameter: 105mm (3) Drawing conditions: 1st drawing ratio: 1.40, 2nd drawing ratio:
1.42 (4) Ironing punch diameter: 52.65mm (5) Total ironing rate: 68% Example 6 Mild steel plate thickness is 0.40mm and coating material thickness is 100μ
Using a coated metal material obtained in the same manner as in Example 4 except that m was used, drawing and ironing was performed under the following forming conditions to obtain a drawn and ironed can. A storage test was conducted on this squeezed and ironed can in the same manner as in Example 1. The results are shown in Table 1 and were good. <Molding conditions> (1) Stretching temperature (resin temperature immediately before molding): 65℃ (2) Blank diameter: 89mm (3) Drawing conditions: 1st drawing ratio: 1.69 (4) Ironing punch diameter: 52.65mm (5) Total Ironing rate: 80% Comparative example 1 Mild steel plate thickness is 0.10mm and coating material thickness is 25μ
Using a coated metal material obtained in the same manner as in Example 1 except that m was used, drawing and ironing was performed under the following forming conditions to obtain a drawn and ironed can. A storage test was conducted on this squeezed and ironed can in the same manner as in Example 1. The results are shown in Table 1, and the container was unsuitable. <Molding conditions> (1) Stretching temperature (resin temperature just before molding): 65℃ (2) Blank diameter: 152mm (3) Drawing conditions: 1st drawing ratio: 2.02, 2nd drawing ratio:
1.42 (4) Ironing punch diameter: 52.65mm (5) Total ironing rate: 20% Comparative example 2 Mild steel plate thickness is 0.115mm and coating material thickness is 28μ
Using a coated metal material obtained in the same manner as in Example 1 except that m was used, drawing and ironing was performed under the following forming conditions to obtain a drawn and ironed can. A storage test was conducted on this squeezed and ironed can in the same manner as in Example 1. The results are shown in Table 1, and the container was unsuitable. <Molding conditions> (1) Stretching temperature (resin temperature just before molding): 65℃ (2) Blank diameter: 143mm (3) Drawing conditions: 1st drawing ratio: 1.90, 2nd drawing ratio:
1.42 (4) Ironing punch diameter: 52.65mm (5) Total ironing rate: 30% Comparative example 3 Mild steel plate thickness is 0.66mm and coating material thickness is 170μ
Using a coated metal material obtained in the same manner as in Example 1 except that m was used, drawing and ironing was performed under the following forming conditions to obtain a drawn and ironed can. A storage test was conducted on this squeezed and ironed can in the same manner as in Example 1. The results are shown in Table 1, and the container was unsuitable. <Molding conditions> (1) Stretching temperature (resin temperature in molding conditions): 65℃ (2) Blank diameter: 77mm (3) Drawing conditions: 1st drawing ratio: 1.46 (4) Ironing punch diameter: 52.65mm (5) Total Ironing rate: 88% Comparative example 4 Mild steel plate thickness is 0.10mm and coating material thickness is 25μ
Using a coated metal material obtained in the same manner as in Example 4 except that m was used, drawing and ironing was performed under the following forming conditions to obtain a drawn and ironed can. A storage test was conducted on this squeezed and ironed can in the same manner as in Example 1. The results are shown in Table 1, and the container was unsuitable. <Molding conditions> (1) Stretching temperature (resin temperature just before molding): 65℃ (2) Blank diameter: 152mm (3) Drawing conditions: 1st drawing ratio: 2.02, 2nd drawing ratio:
1.42 (4) Ironing punch diameter: 52.65mm (5) Total ironing rate: 20% Comparative example 5 Mild steel plate thickness is 0.50mm and coating material thickness is 125μ
Using a coated metal material obtained in the same manner as in Example 4 except that m was used, drawing and ironing was performed under the following forming conditions to obtain a drawn and ironed can. A storage test was conducted on this squeezed and ironed can in the same manner as in Example 1. The results are shown in Table 1, and the container was unsuitable. <Molding conditions> (1) Stretching temperature (resin temperature just before molding): 65℃ (2) Blank diameter: 83mm (3) Drawing conditions: 1st drawing ratio: 1.58 (4) Ironing punch diameter: 52.65mm (5) Total Shigo rate: 84%

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the structure of the coated metal material used in the present invention, and FIGS. It is a sectional view showing a process of manufacturing a drawn and ironed can. The reference numbers are: 1 is the coated metal material, 2 is the metal material, 3 is the resin layer, 4 is the adhesive base layer, 5 is the drawing die, 6 is the drawing punch, 7 is the cup-shaped molded product, 8 is the re-drawing die, 9 is re-squeezing punch, 10
Reference numeral 11 indicates a cup-shaped molded product, 11 a barring punch, 12 a barring die, and 13 a side wall portion of the cup-shaped molded product.

Claims (1)

[Scope of Claims] 1. A drawn and ironed can formed by drawing and ironing a resin-coated metal material, wherein the can has an ester repeating material adhered to at least the inside surface of the metal material through an adhesive base layer. At least 70% of the unit has a thermoplastic polyester coating consisting of ethylene terephthalate units, and the metal material on the side wall of the can is expressed by the following formula: R = t ₀ - _{t 1} / t ₀ ×100 t ₀ is the metal covering the bottom of the can The thickness of the material, _t1 , indicates the thickness of the metal material covering the side wall.The material is thinned so that the total ironing rate (R) defined by The following formula f _c = 180 - H / 180 × 100 In the formula, H is the crystal plane ( 100) Corrosion resistance characterized by molecular orientation such that the degree of orientation (f _c ) defined by is 25 to 90%, which represents the half-value width determined from the interference ring diffraction intensity curve. Excellent squeezing can.