JPH05200961A - Production of polyethylene resin coated metal plate excellent in hot water resistance - Google Patents

Abstract

PURPOSE:To continuously produce a thermoplastic resin coated metal plate for a can at a high speed by thermal welding by laminating a polyethylene resin film composed of an ethylene repeating specific unit of which the single surface or both surfaces is subjected to the irradiation with specific radiation to a metal plate having a specific hydrated chromium oxide film and heated to the m.p. of a laminated film by thermal welding to quench the same. CONSTITUTION:In order to ensure the adhesion of a metal plate to be used to a laminated polyethylene resin layer, the surface of the metal has a hydrated chromium oxide film of 5-25mg/m<2> based on chromium as the uppermost layer. Further, the temp. of the metal plate immediately before the lamination of a polyethylene resin film is controlled to the range of the m.p. (Tm1) of the resin film - Tm1+240 deg.C when the laminated film is composed only of the resin film. Next, the quantity of the radiation applied to the polyethylene resin film before the lamination to the metal plate or the same resin layer after lamination is pref. set to the range of 1-25kc/kg. As the polyethylene resin containing 70-100mol% of an ethylene repeating unit, low density polyethylene, linear low density polyethylene or a mixture thereof is pref.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyethylene resin-coated metal sheet for cans having excellent hot water resistance. More specifically, one side or both sides of a metal plate having a specific surface treatment layer is laminated with a polyethylene resin film irradiated with radiation and then rapidly cooled, or a polyethylene resin layer is laminated and rapidly cooled and then irradiated with radiation. The present invention relates to a method for producing a polyethylene resin-coated metal plate for cans having excellent hot water resistance, which provides a material suitable for applications requiring sterilization treatment at high temperature which is widely performed in the can industry field, for example, retort treatment. ..

[0002]

BACKGROUND OF THE INVENTION food cans or Te _Lee emission-free steel is a metal can for materials used in beverage cans (hereinafter, referred to as TFS) and the metal plate such as aluminum is decorated with one or a plurality of times of coating It was To apply this painting,
Not only the paint baking process is complicated, but it also requires a long baking time and discharges a large amount of solvent, so the discharged solvent must be guided to a special incinerator and burned from the perspective of pollution. Had. In order to solve these problems, many methods of laminating a thermoplastic resin film on a heated metal plate have been proposed. For example, a method in which a polyethylene resin film is heat-sealed to a so-called TFS, which is a steel sheet having a double-layer coating of chromium hydrate oxide in the upper layer and metallic chromium in the lower layer (JP-A-46-6142).
No.), a method of laminating a polyester resin film on a metal plate without using an adhesive (Japanese Patent Publication No. 60-47103).
No. 2, Japanese Patent Application No. 2-6342), a method of laminating a polyester resin film on a metal plate using a specific adhesive (Japanese Patent Publication No. 63-13829), a two-layer polyester resin film and a polyolefin containing an adhesive component. and a method of the _Lee Nfuirumu laminated simultaneously on each side of the metal plate (Kohyo 2-Patent 501 644) is disclosed.

The polyethylene resin film-laminated TFS obtained by the method disclosed in JP-A-46-6142 is inferior in hot water resistance, and after being molded into a can, it is filled with food contents.
Sterilization treatment with pressurized steam at a temperature of 20 to 130 ° C (hereinafter,
When abbreviated as retort treatment), the laminated polyethylene resin film on the outer surface of the can comes into contact with pressurized steam and hot water in a molten state, resulting in a non-uniform surface appearance with surface irregularities and a remarkable commercial value. Therefore, it cannot be applied to the material for cans that are subjected to retort processing because it damages.

The polyester resin-coated metal plate obtained by the method disclosed in Japanese Examined Patent Publication No. 47103/1985 is one of the methods for obtaining a laminate by heat fusion. When the retort treatment is applied, the polyester resin layer on the outer surface of the can discolors into milky white spots, and the commercial value is remarkably reduced. Therefore, it cannot be used as a material for a can subjected to the retort treatment. In particular, when the polyester resin layer in which water vapor is evenly laminated does not reach the polyester resin layer during the retort treatment, it becomes more speckled and opalescent, which is not preferable. The reason for this is that when a biaxially oriented polyester resin film is laminated on a metal plate at a temperature above the melting point of the polyester resin film,
It is believed that this is due to recrystallization of the formed amorphous polyester resin layer. The method disclosed in Japanese Patent Application No. 2-6342 prevents opacification of a laminated polyester resin layer during retort treatment, which is a drawback of the polyester resin-coated metal sheet obtained by the method of Japanese Patent Publication No. 60-47103. For,
Laminate a specific copolyester resin film on a metal plate at a temperature lower than the melting point of the resin to minimize the amount of the amorphous polyester resin layer generated during lamination to prevent opacification due to recrystallization of the amorphous polyester resin. It is characterized by doing. However, the copolyester resin film having specific physical properties used in this Japanese Patent Application No. 2-6342 is more expensive than the polyethylene resin film used in the present invention, and is not preferable from the viewpoint of reduction in can cost.

The polyester resin-coated TFS obtained by the method disclosed in Japanese Examined Patent Publication No. 63-13829 is a biaxially oriented polyester resin film coated with an adhesive in advance and laminated at a temperature below the melting point of the film. However, since an amorphous polyester resin layer such as a polyester resin-coated metal plate obtained by the method of Japanese Patent Publication No. 60-47103 is hardly formed, even if a retort treatment is applied,
Although the surface does not become opalescent, it is essential that the polyester resin film be evenly and thinly coated with an adhesive and dried, which requires a coating device, solvent, drying oven, exhaust solvent incinerator, etc. It is not an economical method and is not preferable as a material for cans.

[0006] The two-layer polyester resin film obtained by the method disclosed in JP-A-2-501644 and the olefin resin film containing the adhesive component coated on each side of the metal plate are two-layer polyester. When the retort treatment is performed in the same manner as above with the metal surface laminated with the resin film as the outer surface of the can, the lower amorphous polyester resin layer is formed in the same manner as the polyester resin-coated metal plate obtained by the method of JP-B-60-47103. It recrystallizes, and the surface changes to milky white with spots. Further, when a metal surface laminated with an olefin resin film containing an adhesive component is used as an outer surface of a can, for example, in the case of an olefin resin film mainly containing polyethylene, the film is partially melted during retort treatment, As in the case of the polyethylene resin-coated TFS obtained by the method of JP-A-46-6142, it has a non-uniform surface appearance with surface irregularities and impairs the commercial value, so it is not suitable as a can material for retort treatment. Further, when an adhesive component is applied to an olefin resin film, it has the same drawbacks as the polyester resin-coated TFS obtained by the method of Japanese Patent Publication No. 63-13829, and it is not an economical can material. .. In addition, special table flat 2-5016
The method disclosed in No. 44 is a method of laminating two kinds of resin films on a metal plate heated to a specific temperature, and then 230-27.
It is characterized in that it is reheated at a temperature of 0 ° C., but since it is reheated at a high temperature, there is a risk that the laminated two-layer polyester resin film and the olefin resin layer containing the adhesive component are re-melted, It may not be possible to obtain a resin film-coated metal plate having an excellent surface appearance. Further, considering the temperature of the laminating roll, it is not necessary to use a two-layer polyester resin film, which is economically inferior, and a single-layer polyester film can be favorably laminated on a metal plate, which is not economical. .. Like this special table flat 2
The method disclosed in U.S. Pat. No. 5,011,644 is complicated in the manufacturing process and the film preparation process, and cannot be said to be an economical method for manufacturing a can material.

On the other hand, many attempts have been made to improve the resin properties by electron beam irradiation. For example, a method in which a polyolefin film is laminated on the surface of a metal plate through acrylic acid or a mixture of this and a radiation-curable monomer and then irradiated with radiation to bond the two with excellent adhesive strength (JP-A-63-63). No. 150330), a method of improving the surface hardness and heat resistance of a rust-preventing steel sheet by gluing a polyolefin film on the surface of a metal plate with a specific polymer adhesive and then irradiating the surface with an electron beam or γ-rays Sho 6
No. 2-156944), a thread that is decomposed by electron beam irradiation is spirally wound on the outer circumference of the conductor, and the outer circumference of the thread is covered with an electron beam irradiation cross-linking type insulator to irradiate the electron beam, so that the insulated wire is covered. Method for facilitating (Japanese Patent Application Laid-Open No. 55-126
48), etc. are disclosed.

JP-A-63-150330 and JP-A-6-150330
The coated metal sheet obtained by the method disclosed in JP-A-2-156944 is not preferable because it is indispensable to interpose an adhesive for laminating the film on the metal sheet and the economy is poor.
Further, the present invention is different in use and purpose. On the other hand, the method disclosed in JP-A-55-12648 is considered to be one technique in the field of electric wire production to which the electron beam irradiation technique is widely applied, but the form and the application are different from the present invention. Not only that, but also good adhesion between the metal and the film cannot be ensured.

[0009]

As described above, the thermoplastic resin-coated metal sheet obtained by the method disclosed as an alternative to painting has not only the mottled opalification on the surface at the time of retort treatment but also the economy. There is also a problem with sex. Further, the adhesion between the metal plate and the resin layer cannot be ensured only by the electron beam irradiation technique widely applied to the electric wire field. The problem to be solved by the present invention is to solve the above problems, corrosion resistance required as a material for cans, processing adhesion of laminated resin film, especially adhesion of laminated thermoplastic resin film during retort treatment. The object of the present invention is to develop a method for producing a thermoplastic resin-coated metal sheet for cans, which also has good properties, at high speed and continuously by heat fusion.

[0010]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention has made various investigations and as a result, at least a metal plate having a hydrated chromium oxide film is used as an inexpensive polyethylene film in a thermoplastic resin film. Before stacking with resin film,
Alternatively, after stacking, a can body, which is the main object of the present invention, is formed by causing a crosslinking reaction of a polyethylene resin by irradiation with radiation, and the outer surface of the can is opalified in spots by retort treatment after filling the contents. It was found that a polyethylene resin-coated metal plate for cans, which does not peel off during retort treatment and has excellent adhesion, can be obtained.

The present invention will be described in detail below. First, the ethylene repeating unit 70-100 used in the present invention is used.
Suitable for mol% polyethylene resin (hereinafter abbreviated as polyethylene resin) is low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene or a mixture thereof which is generally widely used as a packaging material. There is. Further, it is possible to blend ionomer, which is an ionic salt of α / β unsaturated carboxylic acid such as methacrylic acid, acrylic acid, and maleic acid containing metal ions such as sodium, potassium, zinc, magnesium, calcium, and aluminum, and maleic acid. Polyethylene modified with acid, acrylic acid or the like or copolymerized with polypropylene or the like is also applicable as the polyethylene resin used in the present invention. However, if the ethylene repeating unit is less than 70 mol%, that is, if the above-mentioned components other than ethylene exceed 70 mol%, the crosslinking reaction of polyethylene due to irradiation does not proceed and the effect of irradiation may not be obtained. Not only is it expensive, but it is also not economical. Adequate amounts of these components improve the adhesion of the polyethylene resin layer to the metal plate, but since the economic efficiency is lower than that of the polyethylene resin alone, the amounts of these components are determined in consideration of economic efficiency and its effect. It is necessary to do so, and if the effect is sufficiently obtained, the smaller the amount is, the more preferable. From the viewpoint of workability, the resin preferably has a breaking elongation of 80% or more as measured by the test method according to ASTM D638.

In the present invention, to coat a metal plate with a polyethylene resin, a method of continuously laminating a polyethylene resin film on a heated metal plate, a method of directly heating a molten polyethylene resin extruded by a known extruder to a metal heated Any method of continuously laminating on the plate surface may be used. In the method of irradiating polyethylene resin with radiation before laminating on a metal plate, it is preferable to use a polyethylene resin film for high-speed and continuous production of the polyethylene resin-coated metal plate of the present invention. Any of the above methods may be used in the method of irradiating with radiation after being laminated. The thickness of the polyethylene resin layer to be laminated on the metal plate is preferably 7 to 250 μm in consideration of properties required for can materials such as economy, corrosion resistance, and processing adhesion. If the thickness is less than 7 μm, it is not preferable in terms of corrosion resistance. Further, when the film is laminated on the metal plate, there is a risk of significantly lowering workability. On the other hand, if the thickness exceeds 250 μm, not only the economical efficiency is deteriorated but also the processing adhesion is deteriorated, which is not preferable as a can material.

Next, the amount of radiation applied to the polyethylene resin film before being laminated on the metal plate or the polyethylene resin layer after being laminated, which is an important condition in the present invention, is the international unit of irradiation dose of kilocoulomb / When expressed in kilograms (hereinafter abbreviated as Kc / Kg), the range of 1 to 25 Kc / Kg is preferable, and the more preferable range is 2 to 20 Kc / Kg. When the irradiation dose is less than 1 Kc / Kg, the cross-linking reaction of the polyethylene resin does not proceed so much, so the hot water resistance during retort treatment is not improved, and the appearance of the polyethylene resin-coated metal sheet is partially affected by the retort treatment. It is not preferable because the resin layer is melted and the surface has many irregularities.
Further, if the radiation dose exceeds 25 Kc / Kg, not only the improvement of the effect due to the radiation is not recognized but the economical efficiency is deteriorated, and the film shape is adversely affected, which is not preferable. The radiation dose to this polyethylene resin is not as remarkable as the polyethylene resin film before laminating on the metal plate and the polyethylene resin layer after laminating on the metal plate. The effect of radiation irradiation is slightly reduced when laminated on the metal plate. Therefore, it is preferable that the polyethylene resin film before being laminated on the metal plate is irradiated with a slightly large amount of radiation. This radiation includes electron rays, γ rays,
Although X-rays are included, the radiation intensity per unit time should be determined in consideration of the production rate and economic efficiency of the polyethylene resin-coated metal sheet of the present invention, and is not particularly limited.

Further, the surface of the polyethylene resin film used in the present invention in contact with the metal plate surface is subjected to surface oxidation treatment such as corona discharge, plasma treatment, flame treatment, etc., so that the wetting index is 38 to 54 dynes. It is preferable from the viewpoint of processing adhesion to the plate. In particular, when the heating temperature of the metal plate is limited by the equipment or the film structure, or in the case of tin-plated steel sheet coated with a hydrated chromium oxide film, nickel-plated steel sheet, etc., the polyethylene subjected to the above surface oxidation treatment is used. It is preferable to use a resin film. Wetting index 3
If it is less than 8 dynes, the effect of the surface oxidation treatment is small, and even if the surface oxidization treatment having a wetting index of more than 54 dynes is applied, the effect is not improved, and not only the economical efficiency but also the coloring There is a risk and it is not preferable. The wetting index here is a value measured according to JIS K6768-1977.

When the resin film is laminated on both sides, it may be laminated on each side, or both sides may be laminated simultaneously. Further, the temperature of the metal plate immediately before the lamination of the polyethylene resin film, which is important in the present invention, must be controlled within the range of the melting point (Tm1) to Tm1 + 240 ° C. of the polyethylene resin when the laminated film is only the polyethylene resin film. Is. When a polyethylene resin film is laminated on one side and a polyester resin film is laminated on the other side, the temperature of the metal plate immediately before the polyethylene resin film is laminated is the melting point (T) of the polyethylene resin.
m1) to Tm1 + 240 ° C., the temperature of the metal plate immediately before the polyester resin film is laminated is in the range of the melting point of the polyester resin (Tm2) to Tm2 + 160 ° C., and T
It is necessary to control the temperature below m1 + 240 ° C. When the temperature of the metal plate is lower than Tm1, the surface of the laminated polyethylene resin film which is in contact with the metal plate does not melt,
Sufficient adhesion cannot be obtained. Further, when the temperature of the metal plate immediately before the polyester resin film is laminated is less than Tm2 during the lamination of the polyester resin film, the surface of the laminated polyester resin film which is in contact with the metal plate is not melted and sufficient adhesion is obtained. Can't get In addition, the temperature of the metal plate immediately before the polyethylene resin film is laminated is Tm1.
If the temperature exceeds + 240 ° C, even if the pair of laminating rolls are sufficiently cooled, the heat transfer in the laminated polyethylene resin film is fast, the outermost layer is notably melted and the surface appearance is impaired, and it also adheres to the laminating rolls. Comes to
It is not preferable because it hinders productivity. The temperature of the laminating roll is preferably not higher than the melting point of the laminating film in consideration of the adhesion of the film to the roll, the surface appearance of the coated metal plate and the like. Furthermore, when laminating polyester resin,
When the temperature of the metal plate just before the polyester resin film is laminated exceeds Tm2 + 160 ° C, even if the pair of laminating rolls are sufficiently cooled, the heat transfer in the laminated polyester resin film is fast and the outermost layer is remarkable. Not only is it melted and the surface appearance is impaired, but it also becomes attached to the laminating rolls, which hinders productivity and heat history adversely affects the resin, and sufficient corrosion resistance cannot be obtained. Furthermore, in the production of polyethylene resin-coated metal plates used for cans that are filled with highly corrosive contents and subjected to retort treatment, the metal plate surface that is the inner surface of the can has a barrier property against contents that is superior to polyethylene resin. Laminated with a biaxially oriented polyester resin film, the surface of the metal plate to be the outer surface of the can is preferably laminated with a polyethylene resin layer subjected to irradiation before or after lamination,
When laminating these different types of resin films on a metal plate at the same time, the metal plate is heated to a temperature near the melting point of the polyethylene resin film and the melting point of the polyester resin film. The temperature of the laminating roll in contact with the film is determined below the melting point of the polyethylene resin film, the temperature of the laminating roll in contact with the polyester resin film is below the melting point of the polyester resin film, and is determined considering the amount of formation of the amorphous polyester resin layer. What is important in continuous production of the polyethylene resin-coated metal sheet of the present invention. Further, when the molten polyethylene resin extruded from the extruder is directly laminated on the metal plate directly, the temperature of the metal plate is the melting point (Tm1) of the polyethylene resin-50 to Tm1 + 200 ° C.
It is necessary to control within the range. If the temperature of the metal plate is less than Tm1-50 ° C, the surface shape of the coating film becomes poor. Further, even if the temperature of the metal plate exceeds Tm1 + 200 ° C., no improvement in adhesion is observed and the economy is poor, which is not preferable. On the other hand, the melting temperature of polyethylene resin is Tm1 + 20
The range of to Tm1 + 150 ° C is preferred. If Tm1 + 20 ° C or less, it is difficult to form a uniform film.
If the temperature exceeds ℃, not only is the economy inferior, but also the decomposition of polyethylene may proceed, which is not preferable. The melting point mentioned here is obtained from the endothermic peak of a differential scanning calorimeter (DSC) at a heating rate of 10 ° C./min., And refers to the temperature indicating the maximum depth of the endothermic peak. When two or more resins are used, it is determined from the peak of the main resin.

Cooling after forming the polyethylene resin layer or the polyester resin layer on the surface of the metal plate is an important condition, and must not be heated at a temperature higher than the proper temperature range of the metal plate immediately before the film is laminated. Needless to say, it is preferable that the film is cooled to a temperature of -30 ° C. within the melting point of the film within 6 seconds. If cooled too slowly, spherulites are formed in the laminated resin layers and the workability of the resin layers deteriorates.

In the present invention, a biaxially oriented polyester resin film is preferably used as the polyester resin film laminated on the surface of the metal plate which is the inner surface of the can body which is filled with a highly corrosive content and is subjected to retort treatment. In the case where strict processability is not required, a biaxially oriented polyethylene terephthalate film is sufficient, but when stricter processability is required, a copolymerized polyester resin film mainly composed of ethylene terephthalate, particularly ethylene isophthalate, It is preferable to use a copolymerized polyester resin film with butylene terephthalate, ethylene sebacate or the like. Structurally, it has a biaxially oriented structure before being laminated on a metal plate, and it is preferable that the biaxially oriented structure remains as much as possible after laminating from the viewpoint of the content resistance. It is essential to form an amorphous polyester resin layer at the interface between the metal plate and the metal plate in order to secure strong processing adhesion.

Next, the metal plate used in the present invention ensures excellent processing adhesion with the laminated polyethylene resin layer, so that the surface layer of the metal plate is at least 5 to 25 mg / m ² of chromium hydrate. It is essential to have an oxide coating on the top layer. If the amount of the hydrated chromium oxide film is out of this range, the work adhesion is significantly deteriorated, which is not preferable. Electrolytic chromic acid treatment is applied to mild steel sheets, aluminum sheets, tin-plated steel sheets, and nickel-plated steel sheets, which are widely used as materials for cans, and chromium hydrate oxide or lower layer is metallic chromium, and upper layer is chromium hydrate oxide. A two-layer coating composed of a so-called TFS coating, such as a surface-treated steel sheet, is applicable to the present invention, but it is necessary to apply it in consideration of required properties such as corrosion resistance and economical efficiency. In addition, the value in terms of chromium referred to here is based on a commonly used method. First, the chromium count of the sample is measured by fluorescent X-ray, and then the sample is measured at 100 ° C. in 7.5N NaOH solution. It is the amount of chromium obtained by immersing in the inside for 5 minutes to remove the hydrated chromium oxide, again measuring the chromium count, and using the calibration curve from the difference between the two.

Further, as a method for heating the metal plate in the present invention, there are known hot air circulation heat transfer method, resistance heating method, induction heating method, heat roll method and the like, and these methods may be used alone or in combination. ..

[0020]

EXAMPLES Examples and comparative examples of the present invention will be described below.

Example 1 Chromic acid treated films on both sides (amount of metallic chromium: 120 mg /
m ^2, hydrated chromium oxide content: strip TFS that having a 20 mg / m ²⁾ as a chromium (thickness ₀ · 17 mm, Itahaba 250m
m, temper degree DR-10) 2 by induction heating roll
It is heated to 90 ° C and a low-density polyethylene resin film (Tama Poly Co., Ltd., trade name: AJ-1, thickness 4) is provided on one side.
0 μm) was laminated at a line speed of 60 m / min using a pair of laminating rolls having a surface temperature of 80 ° C., rapidly cooled in water, dried, _and irradiated with an electron beam of 1.2 Kc / Kg to obtain a coated metal plate. ..

Example 2 A coated metal plate was obtained in the same manner as in Example 1 except that after drying, irradiation with an electron beam of 23 Kc / Kg was performed.

Example 3 A low density polyethylene resin film similar to that of Example 1 was subjected to surface oxidation treatment by corona discharge to obtain a surface oxidation treatment film having a wetting index of 38 dynes. The surface oxidation-treated surface of this film was used as a metal plate laminating surface, and these films were degreased and pickled by a known method on a cold-rolled steel plate having a plate thickness of 0.21 mm, a plate width of 250 mm, and temper DR-10, Tin sulfate 80g / l, phenolsulfonic acid (65% aqueous solution) 60g
/ l, ethoxylated α-naphthol 0.06 g / l tin plating bath, 1.5 g / m ² tin plating on both sides under conditions of bath temperature 45 ° C and cathode current density 20 A / dm ² , and after washing with water , chromic anhydride 50 g / l, using a chromic acid solution of sulfuric acid 0.5 g / l, bath temperature 50 ° C., cathode current density 40A / dm TFS film on both sides with ^second condition (metallic chromium amount: 95 mg / m ^2, Chromium hydrated oxide amount: 13 mg / m ² ) was formed as chromium, and the tin-plated steel sheet washed with hot water and dried was heated to 200 ° C.,
A coated metal plate was obtained in the same manner as in Example 1 except that the films were laminated.

Example 4 A coated metal plate was obtained in the same manner as in Example 3 except that the surface-oxidized film having a wetting index of 54 dynes was used.

Example 5 The amount of chromium hydrated oxide of band-shaped TFS was 25 as chromium.
A coated metal plate was obtained in the same manner as in Example 1 except that the amount was mg / m ² .

Example 6 Chromium hydrated oxide of band-shaped TFS was 5 mg as chromium.
A coated metal plate was obtained in the same manner as in Example 1 except that / m ² was used.

Example 7 A linear low-density polyethylene resin film (manufactured by TamaPoly Co., Ltd., trade name: NB-1, thickness 40 μm) was applied to one side of a strip-shaped TFS similar to that used in Example 1 on the other side. Axial oriented polyethylene terephthalate resin film (Toray Industries, Inc.)
Lumirror S10 (thickness: 25 μm), and a pair of laminating rolls having different surface temperatures (surface temperature of laminating roll in contact with polyethylene resin film: 80 ° C., surface temperature of laminating roll in contact with polyethylene terephthalate resin film: 120 ° C.). At the same time, they were laminated at a line speed of 60 m / min, rapidly cooled and dried. Thereafter, the surface coated with the polyethylene resin film was irradiated with an electron beam of 10 Kc / Kg to obtain a coated metal plate.

Example 8 A low density polyethylene resin film similar to that of Example 1 was used.
The film which had been irradiated with an electron beam of 0 Kc / Kg before lamination was laminated, quenched and dried under the same metal plate and conditions as in Example 1, and then a coated metal plate was obtained without electron beam irradiation.

Example 9 The same band-shaped TFS as in Example 1 was heated to 10 by high frequency heating.
It was heated to 0 ° C., and a low-density polyethylene resin having the same composition as that of the film of Example 1 was melt-extruded on one surface thereof at a line speed of 60 m / min by a T-die extruder (melt resin temperature =
220 ° C., resin thickness = 10 μm), quenched in water, dried, and then subjected to electron beam irradiation of 6 Kc / Kg to obtain a coated metal plate.

Comparative Example 1 A polyethylene resin film similar to that used in Example 1 was laminated on one side of a strip-shaped TFS similar to that used in Example 1 under the same conditions as Example 1, quenched and dried, and then irradiated with an electron beam. Without a coated metal plate was obtained.

Comparative Example 2 A polyethylene resin film similar to that of Example 1 was used.
Laminated, quenched, and dried under the same conditions as. Then, 0 _· 8K
An electron beam of c / Kg was applied to obtain a coated metal plate.

Comparative Example 3 A coated metal plate was obtained in the same manner as in Comparative Example 2 except that electron beam irradiation of 28 Kc / Kg was performed.

Comparative Example 4 The same polyethylene resin film as in Example 1 was subjected to surface oxidation treatment by corona discharge treatment to obtain a surface oxidation treatment film having a wetting index of 35 dynes. This film was laminated, quenched and dried under the same metal plate and conditions as in Example 3, and a coated metal plate was obtained without electron beam irradiation.

Comparative Example 5 The procedure of Example 1 was repeated except that the amount of chromium hydrate oxide film was a band-shaped TFS having a chromium content of 3 mg / m ² .
A coated metal plate was obtained.

Comparative Example 6 A coated metal plate was obtained in the same manner as in Example 1 except that it was a band-shaped TFS having a chromium hydrate oxide coating amount of 28 mg / m ² as chromium.

The characteristics of the samples prepared in Examples 1 to 9 and Comparative Examples 1 to 6 were evaluated by the methods described below. (1) punching processability adhesion samples polyethylene resin layer into a circular plate having a diameter of 80 mm, a polyethylene resin-coated surface as the outer surface, draw ratio deep-drawn in _2-0, the side surfaces of the deep drawn cup of a polyethylene resin layer The degree of peeling was evaluated with the naked eye, 5 without peeling and 1 with almost all peeling.
And displayed in 5 steps. (4 or more is good characteristic) (2) Retort resistance The cylindrical deep-drawing cup obtained by the method of (1) is put in a retort kettle and treated with pressurized steam at 130 ° C for 30 minutes to The degree of peeling of the polyethylene resin layer was evaluated with the naked eye, and displayed in 5 levels as in the case of (1), and the change in the surface appearance was observed with the naked eye. It is displayed in five levels. (4 or more is good in characteristics) (3) Impact processing resistance According to the bending property test method of JIS K-6744 (1977), the polyethylene resin coated surface becomes the outer surface,
It was folded on an axis with a radius of 2 mm. On the inside of the bent sample, insert the steel sheet having a thickness of ₀ · 34 mm, 2 kg
Was dropped from a height of 50 cm, and the presence or absence of cracks in the polyethylene resin layer of the processed portion was observed with a microscope. .. (4 or more are good characteristics)

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

As described above, according to the present invention, as shown in Tables 1 and 2, the processing adhesion, the impact resistance, and the adhesion of the polyethylene resin layer after the retort treatment are excellent. The surface appearance is good even after retort treatment,
It is possible to provide a material for a can that is also highly economical. In particular, the product of the present invention is suitable as a material for a can, which is formed by molding a can so that the polyethylene resin-coated surface is the outer surface, filling the contents, and then performing a retort treatment. Widely applicable to can lids, squeezed cans, crowns, caps, etc. The inner surface of the can body is coated with a biaxially oriented polyester resin film, which has better corrosion resistance to the contents to be filled than the polyethylene resin layer, so that the polyethylene resin-coated metal plate for a can according to the method of the present invention can be used. The application as a material can be further expanded.

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Claims (5)

[Claims] 1. A metal plate having a hydrated chromium oxide film of 5 to 25 mg / m ² as chromium is heated to a melting point (Tm1) to Tm1 + 240 ° C. of a laminated film and 1 to 25 kg on one side or both sides thereof. A method for producing a polyethylene resin-coated metal sheet excellent in hot water resistance, which comprises laminating a polyethylene resin film having ethylene repeating units of 70 to 100 mol% irradiated with coulomb / kg of radiation by heat fusion and then rapidly cooling. 2. A metal plate having, as chromium, a hydrated chromium oxide film of 5 to 25 mg / m ² is heated to a melting point (Tm1) to Tm1 + 240 ° C. of a laminated film, and an ethylene repeating unit is provided on one or both sides thereof. A method for producing a polyethylene resin-coated metal sheet excellent in hot water resistance, comprising laminating 70 to 100 mol% of a polyethylene resin film, quenching, and further irradiating with radiation of 1 to 25 kilocoulombs / kilogram. 3. As chromium, a metal plate having a hydrated chromium oxide film of 5 to 25 mg / m ² is heated to a melting point (Tm1) of polyethylene of −50 to Tm1 + 200 ° C., and Tm1 to Tm1 to both sides thereof are heated. Polyethylene excellent in hot water resistance, characterized by extruding and laminating a polyethylene resin containing 70 to 100 mol% of a repeating ethylene unit at a temperature of Tm1 + 150 ° C, quenching, and then irradiating with radiation of 1 to 25 kilocoulombs / kilogram. A method for producing a resin-coated metal plate. 4. A polyethylene resin film having excellent hot water resistance according to claim 1 or 2, wherein a polyethylene resin film having an ethylene repeating unit of 70 to 100 mol% is subjected to surface oxidation treatment with a wetting index of 38 to 54 dynes. A method for manufacturing a coated metal plate. 5. A polyethylene resin layer according to claim 1, 2 or 3 is laminated on one surface of the metal plate, and a polyester resin film is laminated on the other surface of the metal plate, the melting point (Tm2) to T of the polyester resin.
The method for producing a polyethylene resin-coated metal plate excellent in hot water resistance according to claim 1, wherein the metal plate is laminated on a metal plate heated to m2 + 160 ° C.