JP2007076240A - Laminate metal plate and laminating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminate metal plate which reduces entrained bubbles which can cause defects such as film peeling in carrying out a severe forming work to a laminate metal band, and a high-speed laminating technique. <P>SOLUTION: The resin film laminate metal plate in which a metal plate surface projection area of the largest bubble present on a resin-metal plate boundary face is 300 μm<SP>2</SP>or less is provided. Further, in a method of thermal-laminating a resin film on a metal band at speeds of 150 m/min or more, after the resin film is thermal-laminated on the metal band in an atmosphere containing a gas having a molecular weight of less than 45 except nitrogen, for example, a carbon dioxide gas, helium gas, or oxygen gas at an amount of 90 vol% or more, a surface pressure of ≥1×10<SP>6</SP>Pa and ≤6×10<SP>7</SP>Pa is given by a roll within 1.5 s for ≥0.002 s and ≤0.04 s. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a laminate material used in cans, home appliances, and construction fields, that is, a material in which a resin film is laminated on a metal strip, and in particular, effectively reduces the volume of gas entrained between the resin film and the metal strip. The present invention relates to a laminated metal plate and a method thereof.

  In the cans, home appliances, and construction fields, plates coated with plated steel plates or aluminum plates have been used in many cases, but there is a growing voice from society that environmental pollution due to solvent discharge should be prevented. In addition, there is a limit in improving productivity and energy saving in the painting and baking process, and the production volume of resin film laminates is increasing instead of painting.

  Resin film lamination is a process in which a resin layer can be applied on a metal strip at a rate several times faster than coating, and the production cost is reduced as the speed is increased. However, when the resin film is supplied toward the surface of the metal strip at a high speed, the air in the vicinity of the surface of the metal strip or the resin film is entrained in the traveling and is caught in the crimping portion. The entrained air enters the molten layer of the resin film or adhesive and remains as bubbles even after solidifying. When the area ratio is large, when the laminated metal strip is subjected to drawing / ironing processing, the resin film layer may cause a defect such as peeling or tearing. Even when not subjected to drawing and ironing, if the resin is subjected to severe bending, a defect will occur in the resin film layer.

  As a method of preventing entrainment of bubbles, Patent Document 1 discloses a method in which the resin film is fed toward the steel strip while maintaining the angle between the steel strip and the resin film at 30 to 90 degrees, and is crimped by a crimping roll. It is disclosed. Patent Document 2 discloses a method in which heated gas is blown into a space sandwiched between a resin film and a metal strip immediately before pressure bonding. This method uses the principle that the gas taken in as air bubbles contracts due to cooling after lamination and the air bubble volume decreases.

  In Patent Document 3, a metal box is laminated with a seal box around the crimping part where a resin film is laminated, and the internal atmosphere is controlled to a volume ratio of 50% or more with a gas having a molecular weight of 44 or less excluding air. A laminating device for controlling the pressure in the range of 50 to 750 Torr is disclosed. This is aimed at laminating in a gas atmosphere with high permeability of the resin film, so that even if a gas is involved, the resin film is permeated and discharged out of the system. Furthermore, there is an aim to reduce the amount of gas entrained by reducing the pressure of the laminate atmosphere.

  Patent Document 4, similar to Patent Document 3, aimed at being exhausted out of the system through the resin film, even when gas is involved, by laminating in a gas atmosphere with high permeability of the resin film Lamination method.

Japanese Unexamined Patent Publication No. 63-233824 JP-A-7-125169 Japanese Patent Laid-Open No. 9-52286 Japanese Laid-Open Patent Publication No.9-141741

  However, the method disclosed in Patent Document 1 is understood to prevent the wedge effect of air fluid, but when the laminating speed is 150 m / min or more, the bubble area due to air entrainment also increases, This measure is not enough. The method disclosed in Patent Document 2 does not appear as an effect of reducing bubbles unless the temperature of the entrained gas is made very high, but when a gas having a temperature exceeding the temperature suitable for the laminate is blown onto the crimping part, It becomes difficult to control the laminating temperature to be constant, the resin film is extremely softened or expanded, and the shape deteriorates, making it difficult to obtain a good laminated metal band.

  The apparatus disclosed in Patent Document 3 requires a large amount of equipment such as a pump in order to reduce the pressure so that the effect of reducing entrained gas appears, and the initial cost and running cost become enormous. The method of laminating in a gas atmosphere with high resin film permeability disclosed in Patent Document 3 and Patent Document 4 is effective in reducing the bubble area ratio. However, after the application, the usage environment of the laminated metal strip becomes more severe, and further reduction of bubbles is required. For example, laminated steel sheets made by laminating polyester film on electrolytic chrome-plated steel sheets (tin-free steel) are becoming increasingly used in can manufacturers for extremely severe ironing, and the importance of reducing entrained bubbles Is increasing.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method and a laminated metal plate that can further reduce bubbles generated in high-speed lamination.

  The inventors of the present invention diligently studied the above problems, heat laminating in an atmosphere having a high resin film permeability, and repressurizing immediately thereafter to significantly reduce the bubble area ratio or individual bubbles. The inventors have found that the area is small and have arrived at the present invention.

That is, the main point of the present invention is that
(1) A resin film laminated metal plate, wherein the projected area of the metal plate surface of the largest bubble existing at the resin-steel interface is 300 μm ² or less,
(2) In the method of thermally laminating a resin film on a metal strip at a speed of 150 m / min or more, after laminating the resin film on the metal strip in an atmosphere containing 90 vol% or less of a gas with a molecular weight of less than 45 excluding nitrogen, 1.5 seconds Laminating method characterized by applying a surface pressure of 1 × 10 ⁶ Pa or more and 6 × 10 ⁷ Pa or less with a roll within 0.002 seconds or more and 0.04 seconds or less,
(3) The laminating method according to (2), wherein the atmospheric gas is any one of carbon dioxide gas, helium gas, oxygen gas, or a mixed gas of two or more kinds,
It is.

  According to the resin laminating method of the present invention, it is possible to stably produce a resin-laminated metal band with extremely few entrained bubbles at a high speed. In addition, the laminated metal strip manufactured by the method of the present invention hardly contributes to defects such as peeling of the resin film layer even if it is subjected to strong processing, and thus greatly contributes to the improvement of yield and productivity of processed product manufacture. .

  The present invention is described in detail below.

  When laminating a resin film on a metal band, more atmospheric gas is involved as the speed increases, but the amount of gas entrained increases at 150 m / min or more, and bubbles remain between the resin film and the metal band. . Therefore, the basic idea of the present invention is to reduce the area and area ratio of the bubbles in the laminated metal strip by discharging as much gas as possible out of the system through the resin film.

  Gases with a molecular weight of 45 or more, such as cyclohexane, benzene, toluene, and carbon tetrachloride vapor, have high resin permeability, but these have problems such as safety during production, food hygiene, effects on flavor, and odor. Should be avoided. Therefore, it is preferable to control the pressure-bonding portion atmosphere with a gas having a molecular weight of less than 45 and a permeation rate in the laminate resin larger than that of nitrogen.

  The apparatus for controlling the atmosphere of the crimping part is not limited in the present invention. Only the crimping section or the entire crimping roll section may be covered with a box-type seal box, or the entire laminate section may be used as an atmosphere control chamber, but the former is preferable from the viewpoint of economy and work safety.

  The effect of reducing the bubble area begins to appear when the concentration of the atmospheric gas in the laminated crimping portion is 50 vol% or more. However, since the ratio of nitrogen is large, a sufficient bubble reduction effect cannot be obtained. The important thing is to reduce the proportion of nitrogen, and it is necessary to keep it below 10 vol%. Therefore, it is necessary to heat laminate the resin film on the metal strip in an atmosphere containing 90 vol% or less of a gas having a molecular weight of less than 45 excluding nitrogen. Theoretically, 100 vol% is preferable, but since the sealing mechanism for maintaining a high concentration is a complicated and expensive facility, it is preferable that the concentration be about 90 to 99 vol% that is possible with more economical facilities.

  The atmospheric temperature is not limited in the present invention. The higher the ambient temperature, the greater the volume shrinkage after lamination, which is more advantageous, but the effect is not as great as compared with the effects of gas species and repressurization. For example, if it is heated to about 400 ° C., it is considered that the effect of reducing bubbles due to volume shrinkage is increased.

  As for the pressure of the atmospheric gas, it is advantageous to reduce the pressure because the amount of gas involved is reduced. However, the equipment for reducing the pressure is very large and is not economical.

  Re-pressurization after thermocompression bonding of the resin film needs to be performed within 1.5 seconds. When the resin film is heat-laminated, it is not performed at a temperature at which the resin film is completely melted. Usually, the resin film is bonded at a temperature slightly exceeding the melting point of the resin, so that the resin film is solidified within a short time after the bonding. The entrained gas enters the melted part of the resin film at the time of pressure bonding, but if the resin film cools and solidifies, the shape of the bubbles due to the entrained gas is determined, and even if re-pressurization is applied, its area Can no longer be reduced. As a result of various studies by the present inventors, the time from thermocompression bonding to repressurization is within 1.5 seconds. When the time exceeding 1.5 seconds elapses, the effect of reducing bubbles is not recognized even when repressurization is performed.

  The roll used for re-pressurization is not limited, but a metal roll with silicon rubber with high heat resistance is desirable. This makes it possible to obtain an appropriate nip length and surface pressure.

For re-pressurization, it is necessary to apply a surface pressure of 1 × 10 ⁶ Pa to 6 × 10 ⁷ Pa for 0.002 seconds to 0.04 seconds. If it is less than 1 × 10 ⁶ Pa, the effect of reducing bubbles is insufficient. On the other hand, when the surface pressure exceeds 6 × 10 ⁷ Pa, the tension of the metal strip varies greatly, making it difficult to keep the lamination conditions constant. In addition, rubbing wrinkles easily enter the film surface. The surface pressure referred to here is defined as a value obtained by dividing the total force applied to the bearing of the laminate roll by the area where the roll and the metal plate are in contact. The area where the roll and the metal plate are in contact may be, for example, an area where discoloration of the pressure-sensitive paper is recognized when the line is stopped and the steel strip and the pressure-sensitive paper are overlapped and pressed with a laminate roll. If the surface pressure is not applied for 0.002 seconds or more, the gas is too short to permeate the film, and the effect of reducing bubbles cannot be obtained sufficiently. On the other hand, in a high-speed laminate of 150 m / min or more, in order to secure a pressurization time exceeding 0.04 seconds, the roll diameter must be very large, which is not practical.

  The permeability coefficient of the atmospheric gas to the resin film is preferably at least 3 times the permeability coefficient of nitrogen gas, and more preferably one of carbon dioxide gas, helium gas, oxygen gas, or a mixed gas of two or more kinds It is to be. By performing thermocompression bonding in such a gas atmosphere and applying the above-described re-pressurization, the area ratio of bubbles remaining in the laminated metal strip can be made extremely small.

  In Patent Document 4, water vapor is also mentioned as an example of the gas to be sealed. However, when water vapor becomes very high, it is dangerous, and when the resin to be laminated is polyester, it may be hydrolyzed. Is big.

  As the metal strip used in the present invention, steel plate, tin-plated steel plate, thin tin-plated steel plate (LTS), nickel-plated steel plate, electrolytic chrome-plated steel plate, galvanized steel plate, alloyed galvanized steel plate, lead-tin plated steel plate, aluminum plating Steel strips such as steel plates and alloy-plated steel plates, aluminum strips of aluminum plates (for example, No. 3000 series and No. 5000 series alloys), and the like can be used. As a resin film that can be thermocompression bonded, polyester resin (polyethylene terephthalate, polybutylene terephthalate, these isophthalate copolymers, etc.), acid-modified polyolefin resin (polyethylene, polypropylene, or acid-modified products such as copolymers thereof), Polyamide resin (such as nylon), polyvinyl alcohol, polyacrylonitrile, polystyrene, or the like may be used.

  The thickness of the resin film is not particularly limited, but is preferably in the range of 5 to 200 μm. If it is less than 5 μm, pinholes are likely to occur, and sufficient corrosion resistance cannot be obtained. On the other hand, if it exceeds 200 μm, it is not economical.

  The temperature of the metal band at the time of thermocompression bonding is set to a temperature 2 to 20 ° C. higher than the melting point of the resin film defined as the endothermic peak appearing in the measurement using the differential scanning calorimeter, and the thermocompression bonding method is directed from the metal band to the resin film. Ordinary method of giving heat. In addition, so-called dry lamination in which lamination is performed via an adhesive is also within the scope of the present invention.

Of the bubbles generated when the atmosphere gas is involved in the resin-metal plate interface, the largest metal plate surface projection area must be 300 μm ² or less. A resin film on air bubbles having an area of more than 300 μm ² is easily broken when subjected to a severe forming process such as a draw and ironing (drawing-handling) process, and a defect occurs in the coating of the metal plate processed product. More preferably, it is 100 μm ² or less. If it is 100 μm ² or less, there is an advantage that moisture and other corrosive factors hardly enter through the film and the metal plate is hardly corroded or discolored. The projected area of the metal plate surface of the bubble at the resin-metal plate interface is, for example, by cutting a laminated steel plate into an appropriate size, capturing a 50x optical microscope image from the resin film side through a CCD camera, and using image processing software. Can be calculated.

  Hereinafter, the present invention will be described based on examples.

As the metal band, an electrolytic chromium-plated steel band having a thickness of 0.24 mm and having a metal chromium plating of 100 mg / m ² and an upper layer of chromium hydrated oxide of 15 mg / m ² was used. A clear film (melting point 240 ° C., thickness 25 μm) made of a copolymer resin of polyethylene terephthalate and polyethylene isophthalate was used as the resin film.

  Electrolytic chrome-plated steel strip was run at a speed of 150 to 500 m / min, heated to 245 ± 2 ° C. during lamination using induction heating and a jacket roll, and then thermally laminated by supplying the resin film on both sides. . The pressure roll was a steel roll coated with silicon rubber, and an atmosphere seal box was installed on the entrance side, and the internal atmosphere was controlled by measuring pressure and oxygen concentration. The types and concentrations of gases in the seal box are as shown in Table 1.

  Re-pressurization was applied to the electrolytic chromium-plated steel sheet immediately after heat lamination. The re-pressurizing roll was a steel roll coated with silicon rubber.

  Table 1 shows the time from thermal lamination to re-pressing, the surface pressure of re-pressing, and the time of re-pressing.

  The obtained laminated steel sheet was cut out to an appropriate size, a 50-fold optical microscope image was taken into a computer through a CCD camera, and image processing was performed to calculate the bubble area and the bubble area ratio. A bubble area ratio of 0.3% or less was regarded as an acceptable level.

  In addition, the laminated steel sheet was drawn and ironed into a cylindrical shape having a diameter of 65 mm and a height of 127 mm so that the thickness of the thinnest part was 1/3 of the original plate thickness, and subjected to the ERV test. In the ERV test, a voltage of 6 V was applied between the platinum electrode and the sample via 0.5% saline, and the current value flowing at that time was measured. Since ERV represents a defect penetrating the film, it needs to be 0 mA.

  These results are shown in Table 1.

  In all of Examples 1 to 19 of the present invention, the area ratio of entrained bubbles was small, there was no defect in the ironing process, and the ERV was 0 mA.

  Comparative Examples 1 to 3 are examples in which re-pressurization was not performed after thermal lamination in a carbon dioxide atmosphere. The area ratio of entrained bubbles exceeded 0.3%, and ERV after ironing was detected.

  Comparative Example 4 was also an example in which re-pressurization was not performed after heat lamination in a carbon dioxide atmosphere. However, since the speed was as high as 500 m / min, the bubble area ratio was large, and film peeling occurred during ironing.

  Comparative Example 5 is an example in which the repressurization time was short. The bubble area ratio exceeded 0.3%, and ERV after ironing was detected.

  Comparative Example 6 is an example in which the surface pressure during re-pressurization is low. The bubble area ratio exceeded 0.3%, and ERV after ironing was detected.

  Comparative Example 7 is an example in which the time from heat lamination to re-pressurization was long. The bubble area ratio exceeded 0.3%, and ERV after ironing was detected.

  Comparative Example 8 is an example in which the carbon dioxide concentration in the atmosphere is low, that is, the proportion of air is high. The bubble area ratio exceeded 0.3%, and ERV after ironing was detected.

  Comparative Example 9 is an example in which the carbon dioxide concentration in the atmosphere is lower than that of Comparative Example 10. The bubble area ratio was large, and film peeling occurred during the ironing process.

  Comparative Examples 10 to 12 are examples of lamination in air. The bubble area ratio was large, and film peeling occurred during the ironing process.

  Comparative Example 13 was also an example of laminating in the air, but because the speed was as high as 500 m / min, the bubble area ratio was very large, and the can body was broken by ironing.

In addition to the comparative examples listed in Table 1, production conditions for taking a re-pressurization time of 0.1 seconds were also planned, but for this purpose, the re-pressurization roll had to be enlarged, which was not feasible. In addition, although it was tried even under manufacturing conditions where the surface pressure of re-pressurization was 1 × 10 ⁸ Pa, fluctuations in the tension of the electrolytic chromium-plated steel strip were large, and the manufacturing conditions of the laminated steel sheet could not be kept constant. It was. In addition, many scratches were found on the film surface, making it impossible to produce a sample for evaluation.

  In addition, although it is referred to as can manufacturing as an example of processing, this is not limited to the field of can manufacturing, but since it is used through the same processing process in the field of home appliances and building materials, the processing described above Will receive as well.

  In the above examples, a copolymer resin of polyethylene terephthalate and polyethylene isophthalate was obtained at a pressure of 260 ° C., but polybutylene terephthalate, nylon 6, acid-modified polypropylene, acid-modified low-density polyethylene, polyacrylonitrile. As for isotactic polystyrene, the same results as in Table 1 were obtained by heat laminating at a pressing temperature in the vicinity of each melting point. Furthermore, in the above example, an electrolytic chromium-plated steel strip was used as the metal strip, but the unplated steel strip, tin-plated steel strip, nickel-plated steel strip, galvanized steel strip, alloyed galvanized steel strip, lead-tin plated The same results as in Table 1 were obtained even when steel strip, aluminum plated steel strip, zinc-iron alloy plated steel strip, zinc-nickel alloy plated steel strip or aluminum strip was used.

Claims (3)

A resin film-laminated metal plate, wherein the projected area of the metal plate surface of the largest bubble existing at the resin-metal plate interface is 300 μm ² or less. In the method of heat laminating a resin film on a metal strip at a speed of 150 m / min or more, after laminating the resin film on the metal strip in an atmosphere containing 90 vol% or more of a gas with a molecular weight of less than 45 excluding nitrogen, roll within 1.5 seconds. A laminating method characterized in that a surface pressure of 1 × 10 ⁶ Pa to 6 × 10 ⁷ Pa is applied for 0.002 seconds to 0.04 seconds.   3. The laminating method according to claim 2, wherein the atmospheric gas is any one of carbon dioxide gas, helium gas, oxygen gas, or a mixed gas of two or more kinds.