JPH0270430A - Metallic plate coated with polyester resin for use in draw-forming can - Google Patents

Abstract

PURPOSE:To improve the resistance to thread-like rust, processing and adhering readiness and resistance to cracks of a layer of a metallic plate of an inner surface of a can by laminating a specific polyester resin on said metallic plate. CONSTITUTION:A polyester resin coated on a metallic plate of an inner surface of a draw-forming can is such that at least 75-95% of the ester repeating unit is formed of an ethylene terephthalate unit. a Film molded by an extruder has a softening starting temperature of 170-235 deg.C, a crystal melting temperature of 190-250 deg.C, a surface orientation coefficient of 0-0.1, an elongation at break of 150-500% and a strength at break of 3-18kg/mm<2>. For the metallic plate of the can, a steel plate or an aluminum plate is employed as is or after it is subjected to the surface treatment. Even when the metallic plate is done with a hard draw-forming process, the polyester resin layer generates no cracks, with showing superior resistance to corrosion. Accordingly, the metallic plate can be used for a can of carbonated or other kinds of beverages.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a Drawn & Ironed can.
Can.

Polyester resin-coated metal plate (hereinafter abbreviated as DI can) (hereinafter referred to as DI can). Something.

This invention relates to a polyester resin-coated metal plate for drawn and ironed cans with excellent processing adhesion and processing corrosion resistance.

[Conventional technology]

Currently, a large amount of beer cans and carbonated drink cans (DI cans made of tin-plated steel plates, so-called tin plates, or aluminum plates) are in use.These DI cans are made by drawing tin or aluminum plates.

After re-drawing and ironing two or three times,
The lubricating oil used in processing is washed away, a phosphoric acid-based or zirconium-based surface treatment is applied, and after washing and drying, the inner surface of each can is spray-painted once or multiple times, and then the outer surface of the can is printed. (Manufactured from 2.

These methods of manufacturing DI cans have the disadvantage that the process is complicated and the cost of manufacturing the cans is high. In recent years, active efforts have been made to develop pre-coated materials in order to produce inexpensive I-cans.

For example, steel plates coated with vinyl chloride-based organosol (Japanese Patent Laid-open No. 61-92850), metal plates coated with paints containing hydrocarbon wax as an internal lubricant (Japanese Patent Laid-Open No. 62-1998), and thermosetting paints (2). 275172), a steel plate laminated with a polyester film (Japanese Patent Application Laid-Open No.
168643) etc. have been disclosed.

[Problems to be solved by the present invention]

Using the precoat material as a material for DI cans
Simplifying the can manufacturing process and reducing the cost per can is one method, but known precoating materials have not been able to reach the quality level of current DI cans.

JP 61-92850 and JP 62275172
Although it is possible to form DI cans with the coated metal sheet disclosed in 2003, the coating film that can become the inner surface of DI cans has numerous small cracks during DI forming, making it impossible to fill the contents as is. This is not economical as it requires a top coat on the inner surface after DI molding.

On the other hand, the polyethylene terephthalate resin-coated steel sheet disclosed in JP-A No. 60-168643 has the following properties:
It has the disadvantage that when it is heated after printing on the outer surface of a DI can, its characteristic C decreases considerably.

That is, when an empty can with its outer surface printed is stored, countless reddish-brown filamentous rust forms on the inner surface of the can from the end surface of the empty can.

This is polyethylene terephthalate resin.

After DI molding from an amorphous, non-oriented state (to knee-axis-plane orientation), polyethylene terephthalate resin tends to crystallize when post-heated to 160°C or higher. As a result, the adhesion between the surface of the 9w4 board and the polyethylene terephthalate resin deteriorates, and it is thought that the interface between the polyethylene terephthalate resin and the surface of the single board (two-thread rust is likely to occur).

[Means to solve the problem]

As a result of various studies to apply Precoat H as a material for DI cans, the present invention is a scale that has excellent thread rust resistance and processing adhesion by laminating a specific polyester resin on a metal plate (two layers). It has been found that a polyester resin coating layer (2) on the inner surface of the can yields a DI can with almost no cracks.

Hereinafter, one aspect of the present invention will be explained in detail.

First, the polyester resin to be used as the inner surface of the DI can consists of at least 75 to 9596 ester repeating units consisting of ethylene terephthalate units.

The remaining 5-2596 ester repeating units are phthalic acid, isophthalic acid, terephthalic acid, succinic acid, azelaic acid, adipic acid, cepatenoic acid, dodecanedioic acid,
One or more acid components of diphenylcarboxylic acid, 2.6-naphthalene dicarboxylic acid, 1.4-cyclohexanedicarboxylic acid, and trimethic anhydride, and ethylene glycol, 1.4-butane Qt-ol, and 1,5-bentanediol. , 1.6 +-+ diol, propylene glycol,
Polytetramethylene glycol, trimethylene glycol.

Synthesis of one or more saturated polyhydric alcohols of triethylene glycol, 1.4-cyclohexane dimetatool, trimethylolpropane, and pentaerythritol (obtained by two or more methods).

This polyester resin is formed into a film using a known extruder, and can also be provided as an unstretched polyester resin film, but after the film is formed, it is not stretched vertically.

It is preferable that the polyester film undergoes a heat setting process after being stretched in two transverse directions (two directions) because it improves the barrier properties of the polyester film.The thickness of the polyester film is not particularly limited, but is preferably 10 to 50 μm.Thickness If the diameter is less than 10 μm, the lamination work will be significantly reduced.

The coating film on the inside of the DI can is defect-free.

Furthermore, if the thickness is 50 μm or more, it is not economical compared to epoxy paints widely used in the field of can manufacturing.

Such a polyester resin film has a softening start temperature of 17
Preferably, the temperature is within the range of 0 to 235°C.

The softening start temperature here refers to the thermomechanical analyzer (TM)
A 100. 10°
When the temperature is raised at a heating rate of C/min, the temperature at which the needle begins to penetrate into the polyester film (=temperature at which the needle begins to penetrate into the polyester film). Even if it becomes easier (
=, When post-heat treatment such as external printing is performed, the polyester resin tends to crystallize and the processing adhesion tends to decrease (=).On the other hand, if the softening start temperature is 170°C or lower (=, the external printing after DI processing When baking is performed, the baking temperature is usually higher than the softening temperature of the polyester film, resulting in a significant decrease in workability, making it impractical.

(2) The crystal melting temperature of the polyester film is also important, preferably within the range of 210 to 250°C.
10, manufactured by Seiko Electronics Co., Ltd.) (Secondly, when the temperature was raised at a rate of 10°C/min, an endothermic peak was observed,
It refers to the temperature at which the maximum endothermic peak is found.

When the crystal melting temperature of the polyester resin film is 250°C or higher (250°C or higher), the polyester resin film itself becomes extremely
It becomes rigid and straight, resulting in a significant decrease in workability.

If the crystal melting temperature is below 190'C, the heat resistance of the polyester film itself will drop significantly, and when heated during external printing after DI processing, the mechanical strength will drop significantly (1
Polyester film rank may occur during the subsequent necking and flange processes.

Next (=, the orientation of the polyester film is also an important factor in determining the processability of the polyester film.

That is, it is very important that the plane orientation coefficient is within the range of 0 to 0100.

The planar orientation coefficient here is determined by using a refractometer C2 and is defined as (longitudinal refractive index + transverse refractive index) + 2 - Jl transverse refractive index.

Planar orientation coefficient is 0. 100 or more (2), the processability of the polyester film is greatly reduced, and countless cracks occur in the polyester film during ironing, making it unable to withstand practical C1.

Furthermore, the mechanical properties of the polyester film are also important devices, and in particular, the elongation at break of the polyester film is 150 to 500%, and the strength at break is 3 to 18 kg/mm.
It is desirable that C2 be within the range of ``.

Here, the elongation at break strength of the polyester resin film is determined by conducting a tensile test at a constant temperature of 25° C. and a tensile speed of 100 mm/min using a normal tensile test tI&-2.

When the elongation at break of the polyester film becomes 15096 or less, the processability of the polyester film decreases significantly.
When a severe ironing process such as DI process is applied, film ≦ Nikrack tends to occur.

On the other hand, if the elongation at break is 50096 or more (=), thickness unevenness is likely to occur during film forming, and the thickness unevenness is
The film tends to be easily damaged during ironing processes such as molding (there are two types).

A similar phenomenon occurs with the breaking strength of polyester film.
If the breaking strength exceeds 18 kg/mm, the processability and adhesion of the polyester film will be significantly reduced, and the film will easily crack when subjected to ironing.
It becomes easier to peel off.

When the breaking strength is less than 3 kg/mm', the polyester film itself loses its strength and becomes susceptible to scratches during the can manufacturing process.

When the final ironing process is applied, scratches become a starting point and the polyester film is likely to be damaged.

Such a polyester film can be used as it is to form a metal plate 1.
:Can be laminated, but it is also possible to have an interface between the polyester film and the metal plate (=adhesive).

Adhesives include epoxy groups, hydroxyl groups, amide groups, ester groups, carboxyl groups, and urethane groups.

A polymer composition having one or more of an acrylic group and an amino group in the molecule is preferred.

The amount of adhesive is preferably 0.01 to 5.0 g/m". If it is less than 0.1 g/m", the uniformity of the adhesive layer will decrease, so the adhesion of the polyester film during DI can molding will be reduced. Characteristics become unstable. On the other hand, 5.0 g/m
2 or more (if it is 2, the polyester film will easily peel off during DI can molding), which is undesirable.

This adhesive forms the interface between the polyester film and the metal plate (
The presence of C2 is preferable because it can prevent filamentous rust that tends to occur when a DI can is left under high temperature and high humidity for a long period of time.

Next, the present invention (= as a metal plate used).

Examples include steel plates, aluminum plates, and their metal plates (those with dual surface treatment).

Particularly (2) As for the surface treatment of the steel plate or aluminum plate on the surface to be coated with polyester resin, the upper layer is coated with chromium hydrated oxide, and the lower layer is coated with metal chromium, tin, nickel, zinc, or aluminum. A steel plate coated with two or more types of plating layer or alloy plating layer, or an aluminum plate coated with one or more types of chromium hydrated oxide, phosphate, siliconium salt, or metallic chromium, is coated with polyester resin. This is preferable in terms of ensuring processing adhesion.

On the other hand, as for the surface treatment of the steel plate to be the outer surface of the DI can, it is preferable that the steel plate be coated with ductile tin, nickel, zinc, aluminum, or two or more metals. A chemical conversion film such as chromate treatment or phosphate treatment may be applied to these metal platings within a range that does not interfere with drawing and ironing.

The surface of the aluminum plate, which is to become the outer surface of the DI can, should be drawn and ironed (2, although it is not particularly necessary, as long as it does not cause any problems), since the aluminum plate is originally a malleable metal.
A chemical conversion film such as chromate or phosphate may also be applied.

Next, one possible method for obtaining a polyester resin-coated metal plate is, for example, the following method. In order to laminate a polyester film to a metal plate without using a specific adhesive, it is necessary to heat the metal plate within the range of the crystal melting temperature of the polyester film to the crystal melting temperature + 50°C. . If the temperature of the metal plate is below the crystal melting temperature of the polyester film, the polyester film will be strong with the metal plate (without contact, the polyester film will easily peel off when DI processing is performed).

Furthermore, if the temperature of the metal plate exceeds the crystal melting temperature of the polyester film + 50°C, the laminated polyester film will be susceptible to thermal deterioration.

The barrier properties against the contents of the can also deteriorate and the can body becomes more susceptible to corrosion.

On the other hand, as a method of laminating a specific polyester film to a metal plate using an adhesive, one side of the polyester film (-2 in advance, 0.1 to 5.
Using a polyester film coated with a polymer having one or more of 0 g/m'' of epoxy groups, hydroxyl groups, amide groups, ester groups, carboxyl groups, urethane groups, acrylic groups, and amino groups (1), polyester It is preferable to laminate the metal plate heated within the range of the crystal melting temperature of the film from 50°C to the crystal melting degree +50°C.When the temperature of the metal plate is below the crystallographic melting temperature of the polyester film -50°C, The adhesive did not show good adhesion to either the polyester film or the metal plate.
Polyester film easily peels off when processed.

On the other hand, if the temperature of the metal plate is higher than the crystal melting temperature of the polyester film plus 50° C., the barrier properties of the polyester film will deteriorate for the reasons mentioned above.

The cooling conditions after laminating the polyester film may be either rapid cooling or slow cooling.

In order to suppress recrystallization of the polyester film (second, it is preferable to rapidly cool it).

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to the following examples.

Example 1 Plate thickness 0.30 mm, f y par T -2.5, width 3
One side of a 00mm cold-rolled steel sheet was subjected to a known electrolytic chromic acid treatment (the second layer had a chromium content of 0.015 g/m).
"Chromium hydrated oxide, lower I11 is 0.12 g/m"
Metal chrome! - was formed, and then the other side was plated with 5.6 g/m" of tin by a known method. This strip-shaped surface-treated steel sheet was heated at 220°C (= = 220°C) using a heater roll. 25 μm biaxially oriented polyester film (polycondensate of ethylene glycol and terephthalic acid 8096/isophthalic acid 2096, softening onset temperature 176°C)
Crystal melting temperature 215℃, elongation at break 330%, strength at break K
8.2 kg/mm", plane orientation coefficient 0.024) and quenched with Dadachi C. The obtained polyester resin-coated steel sheet was laminated with a polyester resin-coated surface (2, Drawing and ironing was performed under the following molding conditions.

(Molding 1 conditions) 1 Blank diameter: 123.5 mm 2 N41 stage drawing conditions Drawing ratio: 1.82 3 2nd stage re-drawing conditions Drawing ratio: 1.29 4 Ironing punch diameter during tightening 5 2, 6 4 mm 5 Total ironing rate: 64% Example 2 A strip-shaped cold-rolled steel sheet similar to Example 1 was plated with 2.8 g/m'' tin on both sides by a known method, and then plated with chromic acid. It was treated to form a chemical conversion film with a chromium content of 0.006 g/m'' and washed with water and dried. One side of this strip-shaped tin-plated steel sheet (2) was laminated using the polyester film described in Example 1 under the same lamination conditions as in Example 1.

The obtained polyester film laminate A plate was processed under the drawing and ironing processing conditions shown in Example 1 to obtain l) I cans.

Example 3 A surface-treated steel sheet similar to that in Example 1 was heated to 240°C (240°C) using a heater roll, and a 30 μm polyester film (ethylene glycol and terephthalic acid/isophthalic acid) having chromium hydrated oxide I- Acid 8596/
Polycondensate of 1596, softening start temperature 192°C, crystal melting temperature 239°C, elongation at break 210! %, breaking strength 12.3
kg/mm", plane orientation coefficient 0.065) and immediately quenched. The obtained polyester film laminated steel plate was processed under the same processing conditions as in Example 1 to obtain a DI can.

Example 4 Example 2 (=One side of the surface-treated steel plate shown in C1 was laminated using the polyester film shown in C1 under the conditions shown below.

Polyester film Thickness: 30 μm Polycondensate of ethylene glycol and terephthalic acid 8596/Isophthalic acid 1596 Softening start temperature 192°C Crystal melting temperature 239°C Elongation at break 21096 Breaking strength 12.3 kg/mm” Planar orientation coefficient 0065 Epoxy on the above polyester film A polyester film coated with a 20% solids solution of 80 parts of 3000 epoxy resin and 20 parts of Baracresol resol at a dry weight of 0.2 g/m was laminated onto a tin-plated steel plate heated to 220°C. Chi (= quenched.

The obtained polyester resin-coated steel sheet was processed under the drawing and ironing conditions shown in Example 1 (2) to obtain a DI can.

Comparative Example 1 Example IC - The steel plate shown was heated to 300°C (
Heat the surface with the chromium hydrated oxide layer (two 25μ
A biaxially oriented polyethylene terephthalate film (softening start temperature 242°C, crystal melting temperature 260°C, WL breaking elongation 131%, breaking strength 23.2kg/mm", plane orientation coefficient 0.147) was laminated.

The resulting polyester resin-coated steel sheet was then processed under the drawing and ironing conditions of Example 1 so that the inner surface of the DI can became the polyester resin-coated surface.

Comparative Example 2 The steel plate shown in Example 1 was heated to 240 mm using a heater roll.
30μ on the surface with chromium hydrated oxide by heating to °C.
m polyester film (polycondensate of ethylene glycol and terephthalic acid/isophthalic acid 8596/1596, softening start temperature 194°C, crystal melting temperature 241°C
2. Elongation at break 190%, strength at break 13.6 kg/mm”
, plane orientation coefficient 0, 129) were laminated and immediately quenched.

The obtained polyester film laminate) M plate was processed under the drawing and ironing conditions shown in Example 1 to obtain a DI can.

Comparative Example 3 Example 2L = 22 using the shown steel plate as a heater roll
A double-layer polyester film was laminated on one side by heating at 0'CC and immediately quenched.

Polyester film Thickness: 30 μm Polycondensate of ethylene glycol and terephthalic acid 9696/isophthalic acid 496 Softening onset temperature: 235°C Crystal melting temperature: 250°C Elongation at break
15596 breaking strength 20.6
kg/mm” plane orientation coefficient 0.131
The above polyester film (two polymer compositions shown in Example 4) was coated in a similar formulation.

The obtained polyester film laminated steel plate was processed under the drawing and ironing conditions shown in Example 1 (:) to obtain a DI can.

As described above, the DI cans whose inner surfaces were made of polyester resin-coated steel sheets obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were degreased, washed, dried, and subjected to a heat treatment assuming external surface painting and printing. After heating at 190° C. for 15 minutes, flanging was performed.

The obtained DI cans were then evaluated using the double cell test method.

The results are shown in Table 1 (duplicated).

+ Extent of metal exposure on the inner surface of the II DI can The current flowing when a DI can is filled with 196 sodium chloride solution, the can body is the anode, the stainless steel rod is the cathode, and a constant voltage of 6.3 V is applied between the two poles (mA) The degree of exposure of the metal surface was evaluated.

(2) Test for filamentous rust during storage Empty DI cans were stored for 3 months in an atmosphere of 27°C and relative humidity of 92%, and the filamentous rust generated on the inner surface of the can from the vicinity of the flange was evaluated as 5 (good) and 1 (poor). Evaluation was made on a five-point scale.

(3) Test for seaming of flange portion Empty DI cans (2) After double seaming with a regular painted aluminum lid, the aluminum lk was removed and the degree of cracking in the polyester film near the seaming was observed.

(4) Contents filling test DI can (= Filled with Coca-Cola and double-sealed with a painted aluminum lid, stored at 37℃ under royal conditions (aluminum lid on top) for 3 months, and measured the amount of iron eluted. The state of corrosion on the side wall of the can was observed.

〔Effect of the invention〕

The polyester resin-coated metal plate obtained in this manner does not develop cracks in the polyester resin layer even when subjected to severe drawing and ironing, and exhibits excellent corrosion resistance.
It can be applied to various beverages including carbonated drinks, and is highly effective in reducing the cost of cans.

Patent applicant: Toyo Kohan Co., Ltd.

Claims (4)

[Claims] (1) The softening start temperature on the inner surface of the drawn and ironed can is 170~2
35°C, a crystal melting temperature of 190-250°C, a plane orientation coefficient of 0-0.1, an elongation at break of 150-500%, a breaking strength of 3-18 kg/mm^2, and at least 75 ester repeating units. A polyester resin-coated metal plate for a drawing and ironing can, which is coated with a polyester resin containing ~95% ethylene terephthalate units. (2) A polymer unit or mixture having one or more of epoxy groups, hydroxyl groups, amide groups, ester groups, carboxyl groups, urethane groups, acrylic groups, and amino groups in the molecule at the interface between the polyester resin and the metal plate. 2. The polyester resin-coated metal plate for drawn and ironed cans according to claim 1, wherein the metal plate is coated with a polyester resin. (3) The metal plate is a steel plate, and the surface of the steel plate on the inside of the can has an upper layer of hydrated chromium oxide layer and a lower layer of one or more of metal chromium, tin, nickel, zinc-aluminum plating layer or alloy plating layer. A polyester resin-coated metal plate for a drawn and ironed can according to claim 1 or 2, wherein the steel plate on the outer surface of the can is coated with one or more metals selected from tin, nickel, and zinc-aluminum. (4) Claim 1 or 2, wherein the metal plate is aluminum and the aluminum surface on the inner surface of the can is coated with one or more films of hydrated chromium oxide, phosphate, zirconium salt, and metallic chromium. Polyester resin-coated metal plate for drawn and ironed cans as described.