JP4710433B2 - LAMINATED METAL CAN, METHOD FOR PRODUCING THE SAME, AND METHOD FOR PRODUCING LAMINATED METAL PLATE - Google Patents

Description

  The present invention relates to a laminated metal can for beer and sparkling liquor, a method for producing the same, and a method for producing a metal plate for a laminated metal can for beer and sparkling liquor.

  In recent years, froth-conscious beer and sparkling liquor products are on the market. For example, a glass that produces creamy foam when poured or a server for home use. The foam of beer and happoshu has given great appeal to products called beer and happoshu. In the metal can field for beer and sparkling liquor, there are some products that are devised for foam. For example, there is a device with a spout that can easily generate bubbles when poured, and a can filled with an item that induces foaming when opened.

  Metal cans have the function of preserving the contents and the function of using them as glasses, but these functions are limited to one time until the contents are drunk. Finish the role. Therefore, an inexpensive can is more preferred.

  In a beer / sparkling liquor can with foaming properties, a can in which a foam-inducing item is enclosed is generally not widespread and is applied only to specific contents. On the other hand, cans that easily generate bubbles when pouring are only cheaply devised because the shape of the spout is devised, but if you use this function, the function of the can as a glass In addition to being abandoned, since it is greatly affected by the pouring container and the pouring method, a stable and good foaming property cannot be obtained.

  As a technique for imparting foaming properties without causing a significant increase in can cost, Patent Document 1 provides a large number of convex portions by baking a paint added with granules on the inner surface of an aluminum can. Disclosed is a technique for improving the foaming property of carbonated beverages by forming a large number of recesses having a substantially V-shaped cross section by pressing protrusions by applying ridge lines between portions or after applying paint. ing.

  Further, Patent Document 2 discloses a biaxially stretched laminated polyester film having two or more layers, in which polyester of the non-metal plate side layer contains particles that are relatively close to a spherical shape, and has a uniform roughness on the surface to provide a rough surface. A technique for improving the foamability of a laminated metal can by making the degree uniform is disclosed.

However, when the present inventors evaluated the foaming properties of beer / happoshu based on the description of Examples in Patent Documents 1 and 2, considering the actual use environment, good foaming properties were not obtained. It was.
Japanese Patent Laid-Open No. 05-97149 JP-A-11-254625

  An object of the present invention is to provide a laminated metal can that exhibits good foaming properties in an actual use environment when filled with beer and sparkling liquor without significantly increasing the can cost, a method for producing the metal can, and It is providing the manufacturing method of this metal plate for metal cans.

  Means of the present invention for solving the above problems are as follows.

[1] A metal can having a laminate resin layer on a metal plate on the inner surface of the can, wherein a substantially spherical object having a diameter of 0.5 μm or more and 3 μm or less is 1/3 or less of the diameter of the sphere on the surface of the laminate resin. Embedded in the base resin layer, and the number density of the substantially spherical objects existing in the surface of the laminate resin layer is 500 / mm ² or more and 3000 / mm ² or less. Metal cans.

  [2] The laminated metal can according to [1], wherein at least the outermost layer of the laminated resin layer is made of a resin mainly composed of a thermoplastic polyester.

[3] The thermoplastic polyester resin is obtained by condensation polymerization of a dicarboxylic acid component and a diol component, the dicarboxylic acid component is composed of terephthalic acid, or terephthalic acid and isophthalic acid, and the diol component is composed of ethylene glycol and / or butylene glycol. And a repeating unit composed of ethylene terephthalate or butylene terephthalate is any resin selected from the following (1) to (5) having a molar ratio of 85% or more [2] A laminated metal can described in 1.
(1) Polyethylene terephthalate-polyethylene isophthalate copolymer (2) Polyethylene terephthalate (3) Polybutylene terephthalate-polyethylene terephthalate copolymer (4) Polyethylene terephthalate-polyethylene isophthalate-polybutylene terephthalate copolymer (5) Polybutylene The laminated resin layer of terephthalate [4] [2] has at least the outermost layer as a main component of a thermoplastic polyester whose main phase is the resin of claim 3 as a main skeleton, and the subphase is made of polyolefin. The laminated metal can according to [2], which comprises a mixed resin.

  [5] The laminated metal can according to [4], wherein the polyolefin comprises one or more of polyethylene, polypropylene, and ionomer.

[6] Any one of [1] to [5], wherein the laminate resin layer is formed by an extrusion method or is formed by thermocompression bonding of an unstretched film. The laminated metal can described.
The laminate metal can according to [1], wherein the laminate resin layer is formed by an extrusion method or is formed by thermocompression bonding of an unstretched film.

  [7] A substantially spherical material having a diameter of 0.5 μm or more and 3.0 μm or less is sprayed on a laminated metal plate having a resin film layer on the metal plate, and then heat treatment is performed, so that the substantially spherical material has a diameter of the sphere part. 1/3 or less of the above is embedded in the base resin layer and adhered to the base resin layer. The method for producing a metal plate for a laminate can according to [1].

  [8] After a substantially spherical object having a diameter of 0.5 μm or more and 3.0 μm or less is sprayed on the inner surface of the metal can body, heat treatment is performed to reduce the approximately spherical object to 1/3 or less of the diameter of the spherical part. The method for producing a laminated metal can according to [1], wherein the method is embedded in a base resin layer and adhered to the base resin layer.

  [9] Using a laminated metal plate in which a resin layer contains a substantially spherical product having a diameter of 0.5 μm or more and 3.0 μm or more, and by deforming the resin around the substantially spherical product in a can molding process, The method for producing a laminated metal can according to [1], wherein 2/3 or more of the diameter of the part is projected from the resin surface around the part.

  According to the present invention, it is possible to obtain a laminated metal can that exhibits good foaming properties simply by opening beer / happoshu without significantly increasing the can cost.

  The present invention will be described below together with the background to the invention.

  In the beer / happoshu can, the inside of the can before opening the lid is in a positive pressure state, and the vapor-liquid equilibrium is maintained in this state. However, when the lid is opened, the pressure becomes atmospheric pressure, the equilibrium is lost, and supersaturated carbon dioxide dissolved in the liquid becomes carbon dioxide and diffuses into the atmosphere. This is the source of bubbles. However, normally, just by opening the lid, the rate of carbon dioxide gas generation is slow and sufficient foaming cannot be achieved. For this reason, in order to make generation | occurrence | production of a bubble remarkable, a device is needed.

  The inventors poured beer / happoshu into a glass by various pouring methods to generate various bubbles, and investigated the amount of foam generated and its size. When beer / happoshu was poured into a glass vigorously, a large amount of large foam was generated, but the foam immediately disappeared. Next, when moderately slowly poured, fine bubbles having a diameter of 1 mm or less were deposited on the upper layer to form an ideal bubble portion. When poured more slowly, no bubble accumulation was observed on the upper layer, and no bubble accumulation was observed even after standing for a while. In the observed range, the bubble size tends to increase when pouring vigorously, and the bubble size tends to decrease when pouring slowly, and the accumulation of bubbles in the upper layer is observed whether it is too vigorous or too slow. From this, it was considered that there was an appropriate bubble size for the deposition of bubbles on the upper layer. That is, it was considered that there was an appropriate bubble size when the bubbles were released into the liquid from the bubble generation point.

  As for the generation point of bubbles, it is said that the wall portion, particularly the hole portion, is advantageous. This is because, when bubbles are generated, the surface energy of the newly generated gas-liquid interface is smaller in the wall than in the liquid and requires fewer holes than in the wall. In order to obtain bubbles having a size suitable for foam accumulation, various foam sizes may be adjusted to obtain good foamability. Therefore, the inventors formed hemispherical holes of sub-micron to millimeter order size on the surface of the laminated steel plate, and investigated the foaming property in beer / happoshu.

  However, as a result, sufficient foamability could not be obtained at any size. Furthermore, although the foamability of a film having a sub-micron or smaller sub-micron surface that was not hemispherical on the film surface was investigated, no improvement in foamability was observed.

  Although the above-mentioned investigation was an investigation on a wide range of pore sizes, it was not possible to find a hole size or irregularity size suitable for forming a foam layer of about 1 mm in the upper layer. The inventors reasoned that this was because bubbles of a size suitable for deposition on the upper layer were generated, but because the number of bubbles of that size was small, the deposition of bubbles on the upper layer was insufficient. Thought.

  Therefore, the inventors examined various methods for generating a large number of bubbles having a size suitable for deposition on the upper layer. As a result, bubbles that are smaller than the size of the bubbles suitable for deposition on the upper layer are generated at the starting point of the bubbles, and the bubbles are grown into bubbles of a size suitable for deposition on the upper layer and then released into the liquid. I got a new idea to make it happen. Since it is possible to have a large number of generation points of fine bubbles, according to this idea, a large number of fine bubbles are generated at the generation point of bubbles, and the bubbles are of a size suitable for deposition on the upper layer. It is possible to generate a large number of bubbles having a size suitable for the deposition of the bubbles on the upper layer by releasing them into the liquid after they are grown.

  Paying attention to the fact that the recesses present on the wall surface can be the starting point of bubbles, the case of attaching a sphere to the film surface was examined. When the sphere is brought into point contact with the film surface having a flat surface, a narrow gap is formed between the sphere and the film surface. This gap becomes narrower as it approaches the contact point between the sphere and the film surface, and gradually increases as it moves further away.If the size of the sphere is appropriately selected, minute bubbles are generated in the space between the sphere and the film surface. A large number of bubbles were generated, and the bubbles were grown into bubbles of a size suitable for deposition, and then released into the liquid. Thus, it was considered that good foamability could be expected. Actually, since it is difficult to attach the sphere to the film surface by point contact, it is necessary to adhere the sphere so that it has a certain contact area on the film surface. Even in such an adhesive state, if the sphere is not deeply embedded in the film surface, the distance between the sphere and the film surface becomes narrower as it approaches the contact point between the sphere and the film surface, and gradually increases with increasing distance. I thought that there was no problem because of the gap.

  As a trial, a sample was prepared in which silica particles of 1 μmφ were adhered to the surface of the laminated steel plate. Specifically, the silica particles are dispersed on the surface of the laminated steel plate, then the laminated steel plate is heated to near the melting point of the film, and then passed between a pair of rolls so that part of the silica particles are buried in the film, A gap was formed between the film surface and the contact point between the sphere and the film surface that became narrower and gradually increased with distance from the film surface, and then rapidly cooled with water. In water, it was rinsed well to remove unadhered silica particles. When this sample was molded into a welded can and examined for foamability, it was found that the creamy foam covered the liquid upper layer immediately after opening, and the good foamability expected by the inventors was obtained.

  Further, when zinc oxide grains having a diameter of 1 μm were added to the film, this film was laminated on a steel plate, and after heat treatment, deep drawing was performed, the zinc oxide grains were exposed in the severely processed portion. In the exposed part of the zinc oxide particles, the zinc oxide particles and the film are attached in a state close to point contact, and a gap is formed that becomes narrower as it gets closer to the contact part between the zinc oxide and the film, and gradually increases as it goes away. . When a foaming test was conducted using this can, good foamability was confirmed.

  Subsequently, investigation and examination were conducted to arrive at the present invention. The invention and the reasons for limitation will be described below. First, a laminated metal can for beer / happoshu will be described.

The laminated metal can for beer and sparkling liquor of the present invention is a metal can having a laminate resin layer on a metal plate on the inner surface side of the can, and on the surface of the laminate resin, a substantially spherical product having a diameter of 0.5 μm or more and 3 μm or less, The number of the substantially spherical objects that are embedded in the base surface at a depth of 1/3 or less of the diameter of the sphere is 500 / mm ^{2 to} 3000 / It must be present at a density of mm ² or less.

The reason why the diameter of the substantially spherical object is defined as 0.5 μm or more and 3 μm or less is that if the diameter is less than 0.5 μm, even if bubbles are generated, there is not enough space to reach an appropriate size. This is because when the diameter exceeds 3 μm, it is easily detached from the surface in the manufacturing process. The reason why the number of substantially spherical objects is defined as 500 / mm ² or more and 3000 / mm ² or less is that the foamability is not expressed when the number is less than 500 / mm ² and the content is more than 3000 / mm ^2. This is because the amount of foaming becomes too large when a product is filled in a can, which causes a practical problem.

In addition, if the substantially spherical object is embedded in the base surface exceeding 1/3 of the diameter of the sphere, good foamability cannot be obtained. This is presumed to be because bubbles do not grow to a sufficient size because the space formed by the sphere and the base interface becomes narrow. When a substantially spherical object coexists as a material that is buried 1/3 or less of the diameter of the sphere and a material that is buried more than 1/3, the number density of the material that is buried 1/3 or less of the diameter of the sphere is 500. if pieces / mm ² or more 3000 / mm ² or less, good foamability can be obtained even coexist those buried beyond the 1/3. In the present invention, the reason for defining the substantially spherical object is that the above-mentioned narrow space exists between the protrusion on the resin surface and the base surface, and there is a space in which bubbles grow to an appropriate size. This is because the effect of the present invention is exhibited even if it is not a sphere. Therefore, a substantially spherical object is a shape that forms a space between the protrusion and the film surface that is narrower as it approaches the contact point between the protrusion and the film surface, and in which bubbles generated here are sufficiently grown. This means that the protrusion is included. Examples of the projection having such a shape include agglomerated silica in which spheres of about 0.1 μm aggregate to form a substantially spherical aggregate. The diameter of the substantially spherical object is a diameter when the protrusion is converted as a sphere having the same volume. Furthermore, even when the groundwork is not flat, it is sufficient if there is a narrow space between the protrusions and sufficient space for the bubble size to grow to an appropriate size. For example, when a film having a structure in which olefin grains are dispersed in polyester is processed, a gap is formed between the olefin grains exposed on the surface layer and the polyester base layer surrounding the olefin grains, and good foaming is achieved. Sex is expressed. However, the diameter and density of the olefin particles in this case are determined within the prescribed range of the present invention.

  The substantially spherical material may be either inorganic or organic. Examples of inorganic materials include zinc powder and silica. Examples of the organic system include polypropylene and polyethylene. Of these, zinc powder, silica and the like can be suitably used.

  The resin layer is preferably one in which at least the outermost layer is made of a resin having a thermoplastic polyester as a main component from the viewpoint of surface modification and easy adhesion of particulate matter.

  Moreover, the following are more preferable from a viewpoint on cost and food hygiene. The reason why the repeating unit composed of ethylene terephthalate or butylene terephthalate is defined as 85% or more is that film formation becomes difficult and the production cost is increased below this.

(A) The thermoplastic polyester is obtained by condensation polymerization of a dicarboxylic acid component and a diol component, the dicarboxylic acid component is made of terephthalic acid, or terephthalic acid and isophthalic acid, and the diol component is made of ethylene glycol and / or butylene glycol. In addition, any of the resins selected from the following (1) to (5) in which the repeating unit composed of ethylene terephthalate or butylene terephthalate is 85% or more by mole percentage is preferable.
(1) Polyethylene terephthalate-polyethylene isophthalate copolymer (2) Polyethylene terephthalate (3) Polybutylene terephthalate-polyethylene terephthalate copolymer (4) Polyethylene terephthalate-polyethylene isophthalate-polybutylene terephthalate copolymer (5) Polybutylene The terephthalate (ii) laminate resin layer is preferably a resin whose main phase is a thermoplastic polyester whose main component is the resin (a) as a basic skeleton, and whose secondary phase is a mixed resin made of polyolefin.

  (Iii) It is preferable that the polyolefin comprises at least one of polyethylene, polypropylene, and ionomer.

  The resin layer may have a single layer structure made of the aforementioned resin, or may have a multilayer structure and the outermost layer may be made of the aforementioned resin. In the case of a multilayer structure, the resin other than the outermost layer is not particularly limited. The resin on the outer surface side of the can is not limited. A known resin layer may be used. The thickness of the resin layer may be selected according to the application, but generally a thickness of 15 μm or more and 30 μm or less is used. The metal plate is preferably a steel plate or an aluminum plate. As the orientation crystal component increases in the resin, the generation of the groove tends to be suppressed. Therefore, the resin layer of the laminated metal plate is formed by an extrusion method or formed by thermocompression bonding of an unstretched film, or a stretched film. It is preferable to sufficiently melt the oriented crystals by giving a sufficiently high amount of heat when using and laminating.

  Next, the manufacturing method of the metal can of this invention is demonstrated.

The first method is a method in which a substantially spherical object is dispersed on a laminated metal plate, and then a heat treatment is performed so that a part of the approximately spherical object is buried and adhered in the resin layer. In this production method, a substantially spherical object of 0.5 μm or more and 3.0 μm or less is sprayed on a laminated metal plate, and then heat treatment is performed to embed and adhere the approximately spherical object in a base resin, and the resin surface has a diameter of 0. A substantially spherical object having a diameter of 5 μm or more and 3 μm or less is embedded in the base surface at a depth of 1/3 or less of the diameter of the sphere part. , 500 / mm ^{2 to} 3000 / mm ² in density.

  The laminated metal plate may be manufactured by a usual method. After the approximately spherical object of 0.5 μm or more and 3.0 μm or less is sprayed on the laminated metal plate, the laminated steel sheet is heat-treated, and then passed between a pair of rolls so that the approximately spherical object is 1/3 or less of its diameter. It is buried in the base resin surface to the depth, and the substantially spherical object and the resin film are bonded. From the viewpoint of good adhesion and prevention of fusion of the mother layer, the heat treatment conditions are preferably in the range of the melting point of the resin to −30 ° C. or higher and the melting point to −10 ° C. From the viewpoint of preventing fusion of the mother layer, the pair of rolls is preferably a cooling roll. Moreover, it is preferable to cool with water immediately after passing between the rolls, and it is preferable to remove the substantially spherical substance not adhered to the resin film by washing the surface with running water or the like. You may spray a substantially spherical thing in the middle of a heat treatment process.

  By adjusting the heat treatment conditions and the roll gap between the pair of rolls, the burying depth of the substantially spherical object can be adjusted. Moreover, the number (density) of the substantially spherical thing of a laminated metal plate can be adjusted by adjusting the application | coating amount of a substantially spherical thing.

  The step of spraying the substantially spherical object on the laminated metal plate may be performed subsequent to the laminating step of forming the resin layer on the surface of the metal plate, or may be performed by equipment other than the equipment for performing the laminating process.

  The second method does not use a laminated metal plate in which a part of a sphere is embedded on the surface of the resin layer, but after a can manufacturing process in which a laminated metal plate having no sphere is formed into a can body having a required shape. Then, the can body may be heated, and a substantially spherical object of 0.5 μm or more and 3.0 μm or less may be sprayed and dispersed on the inner surface side of the can to embed and adhere the substantially spherical object to the resin film. In this case, the heating temperature of the can is preferably from the melting point of the resin to the melting point + 10 ° C. or less.

  In the third method, a laminated metal plate is prepared by laminating a resin composition obtained by previously kneading a substantially spherical material of 0.5 μm or more and 3.0 μm or more onto a metal plate. When manufacturing a can body using this laminated metal plate, for example, after heat treatment, drawing is performed. The heat treatment reduces the flexibility of the resin, and in the drawing process, the resin around the substantially spherical object becomes difficult to deform in accordance with the shape of the approximately spherical object. 2/3 or more can be protruded from the surrounding resin surface, or a sufficient space in which a narrow space and bubbles grow can be secured.

  Or the same effect is acquired also by adjusting the plane orientation coefficient of the film produced by the biaxial stretching method. In this case, if the plane orientation coefficient is high, the flexible deformability of the resin is impaired, and the spherical object tends to be exposed, but if it is too high, the film reaches the base metal plate, which is preferable in terms of corrosion resistance. Absent. For this reason, it is necessary to adjust the plane orientation coefficient appropriately. Furthermore, the same effect can be expected by means for adjusting the aperture ratio of the can body. That is, the higher the aperture ratio, the more easily the spherical body is exposed.

  The addition amount of the substantially spherical material is preferably appropriately adjusted so that the density of the spherical material exposed on the surface falls within the range specified in the present invention. The heat treatment needs to be performed at a temperature at which crystallization of the film proceeds. The drawing process is preferably deep drawing with a drawing ratio of 1.5 or more.

"Production of laminated steel sheet"
(Test laminated steel sheets 1-18)
T4CA, TFS (metal chromium layer: 100 to 120 mg / m ² , chromium hydrated oxide layer: 14 to 18 mg / m ² (converted to metal chromium) having a thickness of 0.23 mm was extruded on the surface of a metal plate by an extrusion method. A resin layer of terephthalate-butylene terephthalate copolymer (butylene terephthalate ratio 60 wt%, melting point: 247 ° C.) was formed, and 0.1 to 5.0 μm of granular silica was sprayed on the laminated metal plate, and the resin melting point-30. A laminated steel sheet for test 1 in which a part of the granular silica was embedded in a resin on the surface of the laminated metal plate by heating to a temperature of from ℃ to melting point to -5 ℃ and immediately cooling with a cooling roll. -18 were produced.

  When the plane orientation coefficient of the laminated steel plate produced above was measured, the plane orientation coefficient was 0.01. The plane orientation coefficient was measured by the following procedure.

Using an Abbe refractometer, light source: sodium / D line, intermediate solution: methylene iodide, temperature: 25 ° C., longitudinal refractive index Nx of the film surface, lateral refractive index Ny of the film surface, The refractive index Nz in the thickness direction was measured, and the plane orientation coefficient Ns was calculated by the following formula.
Planar orientation coefficient (Ns) = (Nx + Ny) / 2−Nz
The laminated steel plates 1 to 18 for test were embedded in a resin and subjected to cross-sectional polishing, and then observed with an electron microscope to investigate how much the granular material was buried in the ground plane. At this time, 10 spheres were measured, and the arithmetic average was taken as the burial depth. In addition, planar observation of the test laminated steel sheets 1 to 18 was performed with an electron microscope, and observed at a magnification of × 2000, and the number density of the granular materials was measured. Measurement was performed for any five visual fields, and the arithmetic average was taken as the number density.
The heat treatment temperature and the measurement results of the granular materials are shown in Table 1.

(Test laminated steel sheet 19)
On the surface of a metal plate having a thickness of 0.23 mm, T4CA, TFS (metal chromium layer: 100 to 120 mg / m ² , chromium hydrated oxide layer: 14 to 18 mg / m ² (converted to metal chromium), by a film lamination method, A resin layer of polyethylene terephthalate (melting point 257 ° C.) was formed.

  When the plane orientation coefficient of the laminated steel sheet produced above was measured in the same procedure as described above, the plane orientation coefficient was “0”.

The surface of the laminated steel plate produced above was polished with # 400 abrasive paper to produce a test laminated steel plate 19 in which a number of substantially V-shaped grooves were formed on the surface. The dimension and shape of the groove of the laminated steel sheet 19 for test and the total length (groove density) of the groove were measured. For the measurement, an electron beam three-dimensional roughness analyzer ERA-8800FE manufactured by Elionix was used. Measurement was performed at an acceleration voltage of 5 kV and a WD of 15 mm, and the sampling interval in the in-plane direction during measurement was 4 nm. For the calibration in the height direction using this device, the SHS thin film level standard for stylus type and optical surface roughness measuring instruments of VLSI Standard, traceable to NIST, a national research institution in the United States ( Steps of 18 nm, 88 nm, and 450 nm were used. Based on this measurement method, the cross-sectional shape of the groove was determined, and each groove width was measured.
The measurement results of the grooves are shown in Table 2.

"Can manufacturing"
Each of the test laminated steel plates 1 to 19 produced above was subjected to bending and seam welding, and the bottom lid was tightened to produce a 350 cc welding can.

"Bubbling test"
About the metal can obtained above, foaming property was evaluated as follows.
The inner surface of the can body subjected to the heat treatment for strain relief is washed and filled with beer (Kirin lager), and then filled with carbon dioxide gas so that the internal pressure becomes 1 kg / cm ^2. After cooling for 120 hours, the container was opened in a room at 20 ° C., and the foamability of the beer surface after 15 seconds was evaluated according to the following criteria.
Test result: Evaluation foam does not completely cover the liquid level: ×
Foam completely covers the liquid level: ○
The survey results are shown in Table 3.

  All the test cans A1 to A12 satisfying the configuration of the invention according to claim 1 were able to obtain good foamability. On the other hand, the test cans A13 to A19 that do not satisfy the configuration of the invention according to claim 1 have poor foamability.

"Production of laminated steel sheet"
(Laminated steel plates for test 21-25)
On the surface of a metal plate having a thickness of 0.23 mm, T4CA, TFS (metal chromium layer: 100 to 120 mg / m ² , chromium hydrated oxide layer: 14 to 18 mg / m ² (in terms of metal chromium), The film was laminated with a polyethylene terephthalate film (melting point 254 ° C.) to which zinc oxide was added, to prepare test laminated steel plates 21 to 25 having a zinc oxide-containing resin layer with a weight ratio of 10 wt%. It heated so that it might become melting | fusing point -30 degreeC or more and melting | fusing point +15 degreeC or less, and it laminated | stacked, pressing and cooling the resin film on the surface with a cooling roll.

  When the plane orientation coefficient of the laminated steel plate produced above was measured in the same procedure as described above, the plane orientation coefficient was 0.01.

  Table 4 shows the particle size of zinc oxide contained in the resin layer.

"Can manufacturing"
The test laminated steel plates 21 to 25 prepared above were subjected to heat treatment at 180 ° C. for 10 minutes and then subjected to drawing to produce a drawn can having a can diameter of 67 mm. In order to obtain a can with a target drawing ratio, one to three drawing processes were continuously performed.
Blank diameter: 112-186mm
Final aperture ratio: 1.67-2.74
Laminated steel sheets collected from cans using the test laminated steel sheets 21 to 25 were embedded in resin and subjected to cross-sectional polishing, and then observed with an electron microscope to investigate how much the granular material was buried in the ground plane. At this time, 10 spheres were measured, and the arithmetic average was taken as the burial depth. Moreover, the plane observation of the laminated steel plate extract | collected from the produced can was performed with the electron microscope, it observed with the magnification of * 2000, and the number density of the granular material was measured. Measurement was performed for any five visual fields, and the arithmetic average was taken as the number density. Table 5 shows the drawing ratios and measurement results of the manufactured cans.

"Bubbling test"
About the metal can obtained above, foaming property was evaluated as follows.
The inner surface of the can body subjected to the heat treatment for strain relief is washed and filled with beer (Kirin lager), and then filled with carbon dioxide gas so that the internal pressure becomes 1 kg / cm ^2. After cooling for 120 hours, the container was opened in a room at 20 ° C., and the foamability of the beer surface after 15 seconds was evaluated according to the following criteria.
Test result: Evaluation foam does not completely cover the liquid level: ×
Foam completely covers the liquid level: ○
Table 5 shows canning process conditions and survey results.

  All of the test cans A21 to A26 satisfying the configuration of the invention according to claim 1 were able to obtain good foamability. On the other hand, the test cans A27 to A29 not satisfying the configuration of the invention according to claim 1 were inferior in foamability.

The metal can of the present invention can be used as a metal can for beer / happoshu that can exhibit good foaming properties when filled with beer / happoshu. The manufacturing method of the metal can of this invention can be utilized as a method of manufacturing the said metal can. The manufacturing method of the laminated metal plate of this invention can be utilized as a method of manufacturing the said metal plate.

Claims (9)

A metal can having a laminate resin layer on a metal plate on the inner surface of the can, the surface of the laminate resin having a substantially spherical product having a diameter of 0.5 μm or more and 3 μm or less, and 1/3 or less of the diameter of the sphere is a base resin A laminated metal can characterized by being embedded in a layer and having a number density of substantially spherical objects embedded in the surface of the laminate resin layer of 500 / mm ^{2 to} 3000 / mm ² .   2. The laminated metal can according to claim 1, wherein at least the outermost layer of the laminate resin layer is made of a resin mainly composed of a thermoplastic polyester. The thermoplastic polyester resin is obtained by condensation polymerization of a dicarboxylic acid component and a diol component, the dicarboxylic acid component is composed of terephthalic acid, or terephthalic acid and isophthalic acid, the diol component is composed of ethylene glycol and / or butylene glycol, and The repeating unit consisting of ethylene terephthalate or butylene terephthalate is any resin selected from the following (1) to (5) having a molar ratio of 85% or more. Laminated metal can.
(1) Polyethylene terephthalate-polyethylene isophthalate copolymer (2) Polyethylene terephthalate (3) Polybutylene terephthalate-polyethylene terephthalate copolymer (4) Polyethylene terephthalate-polyethylene isophthalate-polybutylene terephthalate copolymer (5) Polybutylene Terephthalate   The laminate resin layer according to claim 2 is a resin whose main phase is a resin whose main phase is a thermoplastic polyester whose main skeleton is the resin according to claim 3 and whose subphase is a mixed resin made of polyolefin. The laminated metal can according to claim 2, wherein   The laminated metal can according to claim 4, wherein the polyolefin is one or more of polyethylene, polypropylene, and ionomer.   The laminate according to any one of claims 1 to 5, wherein the laminate resin layer is formed by an extrusion method or is formed by thermocompression bonding of an unstretched film. Metal cans. After a substantially spherical material having a diameter of 0.5 μm or more and 3.0 μm or less is sprayed on a laminated metal plate having a resin film layer on the metal plate, heat treatment is performed, and the diameter is 0.5 μm or more and 3.0 μm or less. the substantially spherical objects, so the number density present buried 1/3 or less of the diameter of the spherical portion to the base resin layer is 500 / mm ² or more 3000 / mm ² or less in the laminated resin layer surface preparation The method for producing a metal plate for a laminated metal can according to claim 1, wherein the metal plate is embedded in a resin layer and adhered to the underlying resin layer. After a substantially spherical object having a diameter of 0.5 μm or more and 3.0 μm or less is sprayed on the inner surface of the metal can body, heat treatment is performed to obtain a substantially spherical object having a diameter of 0.5 μm or more and 3.0 μm or less. 1/3 or less of the diameter of the sphere is embedded in the base resin layer so that the number density existing in the base resin layer is 500 / mm ² or more and 3000 / mm ² or less on the surface of the laminate resin layer. The method for producing a laminated metal can according to claim 1, wherein the laminated metal can is adhered to a base resin layer. With diameter laminated metal sheet which contains a 3.0μm or more substantially spherical object than 0.5μm in the resin layer, the deformation of the resin around the substantially spherical product in can forming step, the diameter of 0.5μm or more 3 The number density of the sphere portion of a substantially spherical object having a diameter of 0.0 μm or less protrudes from the resin surface around the sphere portion and 1/3 or less of the diameter of the sphere portion is buried in the base resin layer. The method for producing a laminated metal can according to claim 1, wherein the surface of the laminated resin layer is 500 pieces / mm ² or more and 3000 pieces / mm ² or less .