JP2020104925A - Method of manufacturing metal can, and metal can - Google Patents

Abstract

To provide a method of manufacturing a metal can that includes shaping a metal plate having a resin film laminated into members of the metal can such as a can body, a lid, a cap, etc., and then seaming the members and heating and welding seamed parts, and that can tightly weld the seamed parts to suppress contents from leaking from the seamed part.SOLUTION: The present invention relates to a method of manufacturing a metal can that includes shaping metal plates 3c, 5c having films 3a, 3b and 5a, 5b of crystalline resin laminated into members of the metal can, then seaming the members, and heating and welding the seamed part 10, wherein the seamed part is cooled by using cooling means after the seamed part is heated and welded so as to increase a low-temperature crystallization rate of the films at the seamed part.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a metal can and a metal can in which a metal plate laminated with a film of a crystalline resin is fastened and the fastened portion is heated and welded.

Conventionally, metal cans such as rectangular metal cans have been used as means for transferring and storing various liquid or solid contents.

The metal can is required to have a sealing property such that the contents are not leaked when the contents are pressed by heating, dropped, or shocked by an external force during transportation or storage.

The metal can includes, for example, a can body and a top plate and/or a base plate as a lid that is wound around at least one of the top and bottom of the can body. For example, a cap, which is a stopper that closes the outlet of the stored contents, is fixed to the lid.

Leakage of the contents from the metal can occurs from the portions where the winding-fastened portion between the base and the lid and the winding-fastened portion between the lid and the can body are insufficient. Conventionally, a metal plate laminated with a resin film may be used for the mouthpiece, lid, and can body. In a metal can using the metal plate laminated with this resin film, double seam, single seam (caulking), etc. In order to bond the winding-fastened portion more firmly, a sealing material such as rubber or compound, which is a sealant mainly made of resin or the like, is applied, and the winding-fastened portion is sealed with the sealing material.

The sealing material is excellent in sealing the wound portion. On the other hand, shortening the manufacturing process, cost reduction, from the viewpoint of environmental problems, and from the viewpoint of solvent resistance in the case of using dangerous substances such as solvents as contents, technology without using sealing materials is also being considered, For example, a technique has been proposed in which a winding-up portion is heated by high frequency or the like, and a resin film laminated on a metal plate is directly welded (Patent Documents 1 and 2).

JP 2000-6978 A JP, 2005-160351, A

However, in the conventional method of winding a metal plate laminated with a resin film and heating and welding the winding portion, leakage of the contents cannot be sufficiently suppressed, the resin film is also limited, and further improvement is desired. Was there.

The present invention has been made in view of the above circumstances, and after forming a metal plate laminated with a resin film into a member of a metal can, winding the member, heating the winding portion, and welding the metal. In a can manufacturing method, it is an object to provide a metal can manufacturing method and a metal can in which a winding portion is firmly welded and leakage of contents from the winding portion can be suppressed.

As a result of earnest studies to solve the above-mentioned problems, the present inventor has found that, after welding the winding-fastened portion, from the DSC chart (1st run measurement chart) of the film of the wound-fastened portion, the heat generation amount ΔHc and the melting endothermic amount ΔHm due to low-temperature crystallization are obtained. Was measured, and the ratio ΔHc/ΔHm was multiplied by 100 to define as the low temperature crystallization rate. As a result of investigating the relationship between the low temperature crystallization rate ΔHc/ΔHm and the adhesive strength and sealing property, this DSC 1st run measurement chart It was found that when the low-temperature crystallization rate at 1 is increased, the adhesive strength is increased and the sealing property of the metal can is also improved. In particular, it has been found that the adhesive strength is increased and the sealing property of the metal can is improved when the low temperature crystallization rate is increased by the forced cooling after the welding of the winding tightening portion, and the present invention has been completed.

In DSC measurement, when measuring a target sample, the heat capacity change in the temperature raising process of the target substance in the temperature range is measured. The measurement in the first temperature raising process is called 1st run, and the same sample is used as it is for the second time. However, in this case, it is referred to as a 2nd run and is distinguished, but it should be additionally noted that the 1st run is shown in the expression of DSC thermal analysis thereafter.

That is, the method for producing a metal can of the present invention is a method of producing a metal can in which a metal plate laminated with a film of a crystalline resin is molded into a member of a metal can, and the member is wound and the winding portion is heated and welded. Method,
The low-temperature crystallization rate of the film obtained by DSC thermal analysis (1st run chart) in the winding portion is obtained by heating and welding the winding portion and then cooling the winding portion using a cooling means. Is characterized by increasing.

The method for producing a metal can of the present invention is a method for producing a metal can in which a metal plate laminated with a film of a crystalline PET resin is formed into a member of a metal can, which is then wound and the wound portion is heated and welded. Method,
The low-temperature crystallization rate of the film obtained by DSC thermal analysis (1st run chart) can be improved by heating and welding the winding portion, and then cooling the winding portion using a cooling means if necessary. It is characterized in that the winding tightening portion is 4% or more.

The metal can of the present invention is a metal can obtained by molding a metal plate laminated with a film of a crystalline PET resin into a member of the metal can, winding the member, heating the winding portion, and welding.
The low temperature crystallization rate of the film obtained by DSC thermal analysis (1st run chart) in the winding portion is 4% or more.

According to the present invention, after molding a metal plate laminated with a resin film into a member of a metal can, the member is wound, and the winding part is heated and welded, in the method of manufacturing a metal can, the winding part is firmly fixed. It can be welded and the leakage of the contents from the winding portion can be suppressed.

It is a perspective view of a square metal can which shows an example to which the method of the present invention is applied. It is a longitudinal cross-sectional view which partially shows the base and lid in a metal can showing an example to which the method of the present invention is applied. It is a longitudinal cross-sectional view showing a fitting state of a cap and a cap in a metal can. It is a longitudinal cross-sectional view which partially shows a lid and a can body in a metal can showing an example to which the method of the present invention is applied. It is a cross-sectional photograph which shows another example of a winding fastening part. It is a photograph explaining the pressure resistance test in an example.

Hereinafter, embodiments of the present invention will be described.
(Embodiment 1)
In the method for manufacturing a metal can according to this embodiment, a metal plate laminated with a crystalline resin film is formed into a member of a metal can, and then the member is wound and the tightened portion is heated and welded.

The metal can is not particularly limited, and examples thereof include a square metal can and a round metal can.

The member of the metal can is not particularly limited, but examples thereof include a can body, a lid, and a base. The winding portion is not particularly limited, but examples thereof include a winding portion between the base and the lid, a winding portion between the lid and the can body, and the like.

The form of the tightening is not particularly limited, but examples thereof include a double seam and a single seam (caulking), and examples of the caulking portion between the mouthpiece and the lid include upper caulking and lower caulking.

In this embodiment, the pair of metal plates to be fastened may be both metal plates laminated with a crystalline resin film, or only one may be a metal plate laminated with a crystalline resin film. .. The crystalline resin film may be laminated on one side of the metal plate or may be laminated on both sides.

In this embodiment, the crystalline resin refers to a resin having a high ratio of the amount of crystal regions (a resin having a high degree of crystallinity) in a state where molecular chains are regularly arranged. On the other hand, the amorphous resin is a polymer having extremely low crystallinity or being unable to be in a crystallized state, and includes an amorphous polymer and an amorphous polymer. The crystalline resin film is not particularly limited, and examples thereof include polyethylene terephthalate (PET) resin, polyethylene resin, and polypropylene resin.

In this embodiment, the metal plate may be a film obtained by laminating a film of a crystalline resin alone, or the film of the crystalline resin may be the outermost surface layer, and between the outermost surface layer and the surface of the metal plate. In addition, a film in which a single layer or a plurality of layers of a crystalline resin and/or a layer of an amorphous resin are laminated may be used.

In this embodiment, the film thickness of the crystalline resin film, which is the outermost surface layer, is not particularly limited, but is preferably 50 μm or less, and more preferably 30 μm or less in view of material cost.

An example of a square metal can among the metal cans will be described with reference to FIGS. 1 to 4. As shown in FIG. 1, a rectangular metal can 1 has a rectangular parallelepiped can body 2 formed by processing a metal plate and having a cavity for containing contents therein, and an open end of the can body 2 from above and below. It is equipped with a lid for a rectangular metal can that covers each edge. In the figure, the lid of the top plate is indicated by reference numeral 3. A square metal can lid is double-wound around the top and bottom of the can body 2 by winding two top and bottom lids for a square metal can around the top and bottom of the can body 2. Can 1 is obtained. On the lid 3 for the rectangular metal can of the top plate, a cap 4 for sealing the outlet of the stored contents may be fixed to the base.

FIG. 2 shows a state in which the base 5 is fastened (in the case of upper caulking), and FIG. 3 shows a state in which the base 5 and the cap 4 are fitted. As shown in FIG. 2, the base 5 and the lid 3 form a winding portion 10 with the crystalline resin films 5a and 3a as inner surfaces. The base 5 has a crystalline resin film 5a laminated on the inner surface of a metal plate 5c such as TFS (tin-free steel) or tin plate, and a crystalline resin film 5b laminated on the outer surface. In the lid 3, a crystalline resin film 3a is laminated on the inner surface of a metal plate 3c such as TFS or tin plate, and a crystalline resin film 3b is laminated on the outer surface. The inner and outer surfaces of the metal plates 5c and 3c are plain as long as a crystalline resin film laminated on either the mouthpiece 5 or the lid 3 is interposed between the mouthpiece 5 and the lid 3. It may be a coated surface coated with a coating material. The winding tightening portion 10 shown within the dotted line in FIG. 2 may have a rounded curl at the tip as shown in the photograph of FIG.

FIG. 4 shows a state in which the lid 3 and the can body 2 are tightly wound. In this manner, the lid 3 and the can body 2 can form the winding portion 10 with the laminated crystalline resin film (not shown) interposed.

As the rectangular metal can, for example, 18 liter cans, half cans (half cut cans) and 5 liter cans are representative, but cans having a capacity of 4 to 22 liters are also exemplified. The rectangular metal can of this embodiment includes not only those conforming to the JIS standard such as JIS Z 1602 but also general cans (variable cans) that are not unified by the JIS standard. The material thereof is not particularly limited, and examples thereof include tinplate and tinplate original plate conforming to the JIS standard, tin-free steel, new materials (various special surface-treated steel plates), laminate materials and the like. The thickness of the lid and the body of the rectangular metal can is not particularly limited.

In this embodiment, the content of the metal can is not particularly limited to food use, industrial use, and the like, but as a dangerous substance in industrial use, for example, it is handled from the viewpoint of safety such as firefighting and ship safety. Legally regulated primary petroleum such as toluene, hexane, MEK, ethyl acetate, acetone, alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, secondary petroleum such as styrene, xylene, gas oil, ethylene glycol, etc. Examples include ternary petroleum such as cresol and nitrobenzene, quaternary petroleum such as gear oil, cylinder oil, lubricating oil, machine oil and motor oil.

The means for heating and welding the winding portion is not particularly limited, and examples thereof include a method of heating the winding portion by high frequency heating, infrared rays, hot air, open flame, and the like, contact heating by a heater, and the like.

In this embodiment, the winding portion is heated and welded, and then the winding portion is cooled by using a cooling means to increase the low temperature crystallization rate of the film obtained by DSC thermal analysis in the winding portion. If the low temperature crystallization rate measured by DSC thermal analysis is small, the residual strain becomes large due to crystallization, the welding resin itself becomes brittle, and the adhesive strength of the welded part decreases, contributing to the improvement of the winding strength of the metal can. However, if pressure such as internal pressure or impact is applied, the adhesive strength will be reduced and the sealing performance will be reduced. As the low-temperature crystallization rate increases, the amorphous part increases in the temperature decrease history from heating for welding, the toughness improves and the residual strain in the welding part decreases, so the metal can is tightened. Strength is improved. Further, even if pressure such as internal pressure or impact is applied, the sealing function can be secured and the contents can be sealed so as not to leak.

In this embodiment, the measurement of the low temperature crystallization rate is performed with reference to the following conditions. It is considered that each condition such as the model of the differential scanning calorimeter is appropriately changed within a range in which a significant difference does not occur in the measurement result.
<Measurement of low temperature crystallization rate>
A 5 mg sample was taken from the welded portion in the winding tightened portion after melting, and measured with a differential scanning calorimeter (DSC-7200 manufactured by Hitachi Technos Co., Ltd.) at a temperature rising rate of 10° C./min to obtain a DSC chart (low temperature). Crystallization and melting endotherm curve). Specifically, an exothermic peak of low temperature crystallization near 130° C. and an endothermic peak of melting around 250° C. were measured, and a tangent line was drawn at the lower end of each of the low temperature crystallization peak and the melting peak. Measure the area (peak area) defined by two contact points and peaks, and multiply the ratio ΔHc/ΔHm of heat of crystallization (ΔHc (J/g)) and heat of fusion (ΔHm (J/g)) by 100 to obtain a low temperature. The crystallization rate (%).

Generally, in a crystalline polymer, a crystal part is generated in addition to an amorphous part in the process of cooling after heating and melting. For example, when PET is melted and then rapidly cooled by immersion in water, a glass transition is observed at around 70°C, an exothermic peak due to crystallization is observed around 130°C, and an endothermic peak due to melting is observed around 250°C. After PET was melted, it was slowly cooled (gradual cooling) by allowing it to cool in the air, etc., and DSC measurement showed that it was slowly cooled (gradual cooling), so no peak of low-temperature crystallization was observed at around 130°C. , Only an endothermic peak due to melting around 250° C. is observed (see Industrial Chemistry Magazine, Vol. 73, No. 11, (1970), pages 217-222, etc.). This indicates that the low temperature crystallization peak does not occur at around 130° C. in the DSC chart because the crystallization progressed by gradually cooling the PET melted at the temperature rise.

That is, as compared with the case of slow cooling, the amorphous region can be increased in the case of rapid cooling, so that the amorphous region is crystallized at a low temperature when the temperature is raised during DSC measurement, and the amount of heat generated by this low temperature crystallization is By measuring the ratio of the entire resin to the heat of fusion, it can be used as an index of the cooling history.

That is, in the case of slow cooling (cooling), low temperature crystallization is not observed because crystallization proceeds, but as the temperature is rapidly cooled, the low temperature crystallization peak becomes more prominent and the low temperature crystallization heat value increases. In this embodiment, after the winding portion is heated and welded, the winding portion is cooled by using the cooling means, so that the low temperature crystallization rate is increased, and the amorphous material is used in the temperature decrease history from the heating for welding. Since the number of flexible portions is increased, the toughness is improved and the residual strain in the welded portion is reduced. Therefore, the winding strength of the metal can is improved and leakage of the contents from the winding portion can be suppressed.

In this embodiment, the cooling means is not particularly limited, but in consideration of application to the production line, in addition to a method of directly cooling the winding tightening portion with cold air or cold water, a cooling jig through which cooling water passes is contacted. Examples of the method include cooling by cooling. The use of the cooling means mainly accelerates the cooling rate after heating and welding the winding portion, as compared with cooling in the air.
(Embodiment 2)
The method for manufacturing a metal can in this embodiment is a method of manufacturing a metal can in which a metal plate laminated with a film of a crystalline PET resin is molded into a member of a metal can, and then the member is wound and the winding portion is heated and welded. In this method, the winding tightening portion is heated and welded, and then the winding tightening portion is cooled if necessary by using a cooling means so that the low temperature crystallization rate of the film obtained by DSC thermal analysis is 4% or more. , Preferably 5% or more.

The metal can according to this embodiment is a metal can in which a metal plate laminated with a film of a crystalline PET resin is molded into a member of the metal can, and the member is wound, and the wound portion is heated and welded. The low temperature crystallization rate of the film obtained by DSC thermal analysis in the winding tightening portion is 4% or more, preferably 5% or more.

The detailed description of the same parts as those in the first embodiment will be omitted.

This embodiment is characterized by using a metal plate laminated with a film of a crystalline PET resin, and forming a winding part having a low temperature crystallization rate of 4% or more obtained by DSC thermal analysis. There is. As a result, the amorphous part increases in the temperature decrease history from the heating for welding, the toughness is improved and the residual strain in the welded part is reduced. Therefore, the winding strength of the metal can is improved and the winding tightening is improved. Leakage of contents from parts can be suppressed. Therefore, as in the first embodiment, the winding fastening portion can be cooled by using the cooling means after heating and welding the winding fastening portion. On the other hand, in the case of the crystalline homo-PET resin that has been conventionally used for the resin-laminated metal plate of the metal can, the low temperature crystallization rate of the film obtained by DSC thermal analysis is the slow cooling in which PET is melted and then allowed to cool in the air. Although it is 0% under the condition, for example, when the low temperature crystallization rate of the film obtained by DSC thermal analysis is 4% or more in the copolymer PET resin having crystallinity lower than that of the homo PET resin, a cooling means is used. It is not necessary to use and cool the tightening portion.

When the low temperature crystallization rate measured by DSC thermal analysis becomes small, the residual strain becomes large due to crystallization and the adhesive strength of the welded part decreases, so the welding resin itself becomes brittle and contributes to the improvement of the winding strength of the metal can. However, if pressure such as internal pressure or impact is applied, the adhesive strength will be reduced and the sealing performance will be reduced. When the low temperature crystallization rate is 4% or more, the amorphous portion increases due to crystallization, the toughness is improved, and the residual strain in the welded portion is reduced, so that the winding strength of the metal can is improved. Therefore, the sealing function can be secured even when pressure such as internal pressure or impact is applied.

The crystalline PET resin is not particularly limited. The PET resin used for a laminated steel sheet for can manufacturing and the like is generally PET containing terephthalic acid and ethylene glycol as monomer components, particularly a crystalline homo-PET resin. In this embodiment, in addition to the crystalline homo-PET resin, a copolymerized PET resin having crystallinity lower than that of the homo-PET resin can be used. The copolymerized PET resin, which has a higher crystallinity than the homo-PET resin, is obtained by copolymerizing terephthalic acid and ethylene glycol with another monomer component as the third component. And a PET resin copolymerized by adding an acid (isophthalic acid or the like) or an alcohol (CHDM or the like). In the case of a copolymerized PET resin having crystallinity lower than that of the homo-PET resin, the low-temperature crystallization rate of the film obtained by DSC thermal analysis is 4% or more under a slow cooling condition of cooling in air after melting. Does not require cooling the winding portion by using a cooling means.

The present invention has been described above based on the embodiments, but the present invention is not limited to these embodiments, and various modifications can be made without departing from the scope of the invention.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

The lid of the rectangular metal can (18 liter can) with a material of TFS (tin-free steel) is formed by laminating a crystalline homo-PET resin with a film thickness of 12 μm on the welding surface of the tightening part of the base ( Using a metal plate having a thickness of 0.32 mm) and a spinneret (thickness of the metal plate of 0.30 mm) laminated with a crystalline homo-PET resin having a film thickness of 12 μm on the welding surface, both laminate plates are wound (caulked). ), melted at 270° C. for 20 seconds, and immediately cooled by the cooling method described in Table 1.

As a cooling method after melting to 270°C, cold air was used when submerged cooling, a cold cooler (simple spot cooler manufactured by Sanwa Enterprise) and a spot cooler (spot air conditioner manufactured by Suiden Co., Ltd.) were used. Samples having different low-temperature crystallization rates were prepared by changing the distance from the outlet of the blowing nozzle.
<Measurement of low temperature crystallization rate>
A 5 mg sample was taken from the welded portion in the winding tightened portion after melting, and measured with a differential scanning calorimeter (DSC-7200 manufactured by Hitachi Technos Co., Ltd.) at a temperature rising rate of 10° C./min to obtain a DSC chart (low temperature). A crystallization and melting endotherm curve) was obtained. Specifically, an exothermic peak of low temperature crystallization near 130° C. and an endothermic peak of melting around 250° C. were measured, and a tangent line was drawn at the lower end of each of the low temperature crystallization peak and the melting peak. Measure the area (peak area) defined by two contact points and peaks, and multiply the ratio ΔHc/ΔHm of heat of crystallization (ΔHc (J/g)) and heat of fusion (ΔHm (J/g)) by 100 to obtain a low temperature. The crystallization rate (%) was used.
<T-peel adhesion strength>
A PET laminated plate was cut into a 10 mm width×40 mm square, two PET films were stacked, and an area of 10 mm×10 mm was heated at 290° C. for 20 seconds, and then a predetermined cooling treatment was performed, and after one day, a tensile tester was used. The T peel strength was measured.
<Voltage test>
The cap is fitted and closed on the mouthpiece part, the jig for pressure resistance test is attached to the flat part of the rectangular metal can, and the inner pressure of the can is pressurized with water pressure of 100 Kpa x 5 minutes to check for leakage from the mouthpiece tightening part. did. The photograph of FIG. 6 shows the state of this pressure resistance test (internal pressure test). It was judged that there was leakage even if it spilled out from the mouthpiece tightening portion, and in the examples and comparative examples of Table 1, the number of passing tests out of 10 cans was described.

The results of the above measurement and evaluation are shown in Table 1.

1 Square Metal Can 2 Can Body 3 Lid 3a Crystalline Resin Film 3b Crystalline Resin Film 3c Metal Plate 4 Cap 5 Cap 5a Crystalline Resin Film 5b Crystalline Resin Film 5c Metal Plate 10 Winding Part

Claims (3)

A method of manufacturing a metal can, comprising forming a metal plate laminated with a film of a crystalline resin into a member of a metal can, and then tightening the member, heating and welding the tightening portion,
After heating and welding the winding portion, and then cooling the winding portion using a cooling means, to increase the low temperature crystallization rate of the film obtained by DSC thermal analysis in the winding portion, metal Can manufacturing method. A method for producing a metal can, comprising forming a metal plate laminated with a film of a crystalline PET resin into a member of a metal can, winding the member, heating the winding portion, and welding.
The low-temperature crystallization rate of the film obtained by DSC thermal analysis is 4% or more by heating and welding the winding-up portion and then cooling the winding-up portion using a cooling means as needed. A method of manufacturing a metal can, wherein the winding portion is formed. A metal can obtained by molding a metal plate laminated with a film of a crystalline PET resin into a member of a metal can, winding the member, heating the winding portion, and welding.
A metal can in which the low temperature crystallization rate of the film obtained by DSC thermal analysis in the winding portion is 4% or more.