JPH0128021Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) This invention relates to a three-piece foil can.
More specifically, the present invention relates to a three-piece steel foil can that has a shape-retaining structure that can withstand handling in a vending machine, can be disposed of by incineration, and has excellent strength, light weight, and corrosion resistance.

(Technical issues of prior art and inventions) In the case of a can generally called a three-piece can, a metal material for the can made of a tin plated steel plate or an electrolytic chromic acid treated steel plate is rolled into a cylindrical shape, and both ends are soldered and bonded. A seam is formed by joining by means such as adhesive or welding, and top and bottom lids are secured to both ends of the resulting cylindrical body.

This three-piece container is structurally strong and can withstand rough handling by vending machines, etc., but it is generally difficult to dispose of, so it is recommended to manufacture containers with a three-piece structure using other materials instead of steel plates. Various proposals have been made. One method uses a laminate consisting of inner and outer layers of a paper substrate, aluminum foil, and heat-sealable olefin resin, but this laminate lacks rigidity and is easily deformed by pressure differences inside and outside the container. Since aluminum foil has poor rigidity and is easily corroded by salts, it has not yet been used in place of a three-piece steel can. The other type is a so-called plastic can, in which a laminated film made of aluminum foil and resin film is wrapped and thermally bonded to the surface of a rigid cylindrical plastic molded body, but the manufacturing process is slow. It is complex and has not been commercially successful.

(Gist and purpose of the invention) The present inventors have developed a steel foil substrate, a surface treatment layer consisting of a metal plating layer or a chromate layer provided on the surface of the substrate, and a thermoplastic resin provided through this surface treatment layer. It has been found that when a laminate of film layers is used to form the cylindrical body, a three-piece foil can is obtained which is fully satisfactory with respect to various properties.

In other words, the purpose of the present invention is to create a three-piece steel foil can that maintains its shape to withstand handling in vending machines, is easy to dispose of by incineration, and has an excellent combination of strength, lightness, and corrosion resistance. is to provide.

The purpose of the present invention is to provide a three-piece can in which corrosion and rust of steel foil are effectively suppressed.

Still another object of the present invention is to provide a three-piece steel foil can with excellent corrosion resistance and safety of the cut edges present in the cylindrical body.

(Structure of the invention) According to the invention, in a three-piece can consisting of a cylindrical part with openings at both ends and a lid sealingly engaged with both ends of the cylindrical body, the cylindrical body has a thickness of 30 to 30 mm.
A surface treatment layer consisting of a 120 μm steel foil substrate, a metal plating layer or a chromate layer provided on the surface of the substrate, and a thickness provided through the surface treatment layer.
A three-piece foil can is provided, characterized in that it is formed of a laminate sheet consisting of a thermoplastic resin film layer with a thickness of 10 to 200 μm.

(Characteristics and effects of the invention) In FIG. 1 showing the cross-sectional structure of an example of a laminate used in the invention, the laminate sheet 10 has a thickness of 30 to 30 mm.
A 120 μm steel foil 1, surface treatment layers 2a and 2b consisting of a metal plating layer or a chromate layer applied to the inner and outer surfaces of the foil 1, and adhesive layers 3a and 3b are applied to the surface treatment layers 2a and 2b as necessary. It has organic resin inner and outer surface coatings 4a and 4b provided thereon.

In this invention, steel foil is used because it has a significantly lower pitting rate for contents containing salt than aluminum foil, and this makes it easier to use as a packaging material. Corrosion resistance,
Gas barrier properties can be significantly improved. Also,
Steel foil has a Young's modulus approximately 2.5 times that of aluminum foil, and can provide sufficient strength and shape retention with a relatively thin thickness. Furthermore, steel foil is available relatively cheaply compared to aluminum foil, and can also reduce the cost of packaging materials.

It is also important that this iron or steel foil has a thickness of 30 to 120 μm, in particular 50 to 100 μm. If the thickness is less than the above range, the rigidity of the laminate will be insufficient and it will be difficult to obtain shape retention that can withstand handling in a vending machine, and it will be difficult to obtain foil without defects such as pinholes. It is difficult to obtain sufficient barrier properties against various gases, water vapor, etc. Further, if the above range is exceeded, the final container becomes too rigid, which tends to make disposal difficult or to cause problems with cut edge covers as described below.

In the present invention, it is extremely important to provide the steel foil 1 with a surface treatment layer consisting of a metal plating layer or a chromate layer thereon from the viewpoint of corrosion resistance and adhesion of the organic resin coating. . Although the organic resin coating is effective in preventing direct contact between the contents and the steel foil, the resin coating can considerably absorb hydrogen ions from organic acids contained in the highly corrosive contents. It has the property of being easily permeable, and anions such as chloride ions contained in salts are also permeable to some extent. For this reason, the coating tends to peel off at the interface between the organic resin coating and the foil, and once such peeling occurs, corrosion such as rust, iron leaching, and pitting easily progresses in this area. Become.

According to the present invention, by providing a surface treatment layer consisting of a metal plating layer or further a chromate layer on the steel foil, this metal plating layer acts as a barrier layer against the above-mentioned corrosive components, and furthermore, the organic resin coating layer It acts to increase the adhesion with. At this time, when a chromate layer is provided on the metal plating layer, the adhesion with the organic resin coating is further improved.

For the metal plating layer, metals that are softer than iron and have anticorrosive effects on iron, such as Ni, Sn,
Metals such as Zn and Al are advantageously used. The plating layer made of these metals not only has an excellent corrosion-preventing effect, but when cutting the steel foil, the plating layer metal flows to the cut edge, protects the cut edge, and prevents rust from coming from the cut edge. It shows an unexpected and novel effect of suppressing the outbreak. The fact that the plating layer metal flows and exists at the cut edge of the steel foil with the plating layer is confirmed by the presence of the plating layer metal when the cut edge is observed with an X-ray microanalyzer. .

In the metal plating layer, a metal having a hardness of Vickers hardness of Hv500 or less, more preferably Hv400 or less is present in a coating amount of 0.1 to 15 g/m ² , particularly 0.2 to 12 g/m ² . That is, if the metal has a hardness exceeding the above range, the plating layer metal will not flow to the cut edge when cutting the steel foil, and the effect of preventing rust from occurring at the cut edge will not be obtained. Further, if the amount of metal plating is at the end of the above range, the effect of blocking corrosive components or preventing corrosion will be unsatisfactory, and in particular, the effect of preventing rust from forming on cut edges will not be obtained. Further, it is economically disadvantageous to provide the plating layer beyond the above range, which cancels out the advantage of using steel foil.

A nickel plating layer is particularly effective in shielding corrosive components, and an example of an easily available plated steel foil is tin plated foil, that is, tin foil. In this tin foil, sufficient corrosion resistance and organic film adhesion can be obtained even when the amount of tin coated is relatively small, for example in the range of 0.5 to 10 g/m ² , and in this case, the tin layer exists as a metallic tin layer. However, from the viewpoint of resin adhesion, it is preferable that the Sn/Fe metal atomic ratio be present in the form of a tin-iron alloy layer having a metal atomic ratio of 2 to 1.

Examples of the chromate layer include a chromium oxide layer mainly composed of hydrated chromium oxide having a coating amount of Cr in the range of 1 to 50 mg/m ² , particularly 3 to 35 mg/m ² . This chromate layer can be formed on the plating layer described above by a chemical conversion treatment and/or chemical treatment that is known per se.

In the present invention, for applications in which rust formation at cut edges is not a problem, for example in the case of three-piece cans with curled edges, the plating layer is a metallic chromium layer and a chromate layer is applied on top of the metal chromium layer. - May be steel foil. This metallic chromium layer has a thickness of 0.03 to 0.5 g/m ² , especially
It is preferably present in a coverage of 0.05 to 0.3 g/m ² .

Further, the metal plating layer is not limited to being composed of a single metal layer, but can also be composed of a plurality of different types of metal layers. For example, the base plating layer is the above-mentioned soft metal layer such as nickel, the top plating layer is a chromium metal layer formed by electrolytic chromic acid treatment, and further has a chromium oxide layer thereon. good.

In the present invention, an organic resin coating is provided on the above-mentioned surface-treated steel foil, and in this case, the total thickness of the organic resin coating layer is 10 to 200 μm, particularly 20 to 180 μm, and more preferably 30 to 160 μm.
It is also extremely important from the viewpoint of workability and moldability safety. As already pointed out, iron or steel foils have sharp cutting edges that can easily cause damage to fingers, etc. if touched, but according to the present invention, it is possible to provide a resin coating layer with the thickness described above. As a result, the above-mentioned dangers were completely eliminated, and it became possible to establish the safety of three-piece cans using steel foil. That is, if the thickness is less than the above range, it is difficult to eliminate the risk of cut edges, while if it exceeds the above range, the moldability and processability into a three-piece can will be reduced.

The three-piece can of the present invention is formed into a three-piece can by a method known per se, except for using the above-mentioned laminate.

(Preferred embodiment of the invention) In FIG. 2 for explaining the structure of the cylindrical body, the above-mentioned laminate 10 is rolled and molded into a cylindrical shape, and both ends 11a and 11b are formed on the surface of the laminate. Existing thermoplastic resin layer (Fig. 1 4a, 4b)
The side seam 12 is formed by integrating them by heat fusion using the heat sealability of the two. This side seam 1
The cut edges 13 of the laminate are exposed on the inside of the laminate 2, and in order to protect them, a seam protection coating resin layer 14 is provided, for example, by heat fusion or the like to cover the seams.

In the specific example shown in FIG. 2, the seam is formed by overlapping and joining both ends of the laminate 10;
- As shown in FIG.
After they are engaged, they may be heat fused to form a side seam. Moreover, as shown in FIG. 3-B, both ends 11a and 11b on the inner surface side of the laminate 10
are overlapped and joined, and the joint end 16 is bent laterally to create a seam 1 that is not exposed inside the cut edge.
2 may be formed. Furthermore, as shown in FIG. 3-C, the end edges 11a located inside the seam 12 may be coated in advance with a cut edge coating resin layer 17 which also serves as an adhesive layer, and then both ends may be bonded.

In FIG. 4 showing an example of the structure of a three-piece can, flanges 21a and 21b are formed at both open ends of the cylindrical body 20 formed through the above-mentioned seam, and lids are attached to these flange parts 21a and 21b, respectively. The bodies 22a and 22b are applied, and heat sealing is performed between the peripheral edges of the lids 22a and 22b and the flanges 21a and 21b to form the final three-piece can.
The lids 22a and 22b may be made of the same type of laminate 10 as the laminate forming the cylindrical body 20, or may be made of other known metal foil-resin bodies. . An easy-to-open mechanism 23, which is known per se, may be provided on one of the lids 22a, 22b. Appropriate examples of easy-to-open lids are described in JP-A-59-152161, JP-A-59-115241, etc., and the former is a score breaking type and the latter is an existing opening type. be.

In addition to the flange lid-seal type shown in FIG. 4, as shown in FIG.
4a, 24b and the lids 22a, 22b may be heat sealed. Further, as shown in Fig. 5-B, both open ends 25a, 25b of the body 20 are shaped like a cylinder, and the lid is provided with circumferential grooves 26a, 26b around the cylindrical ends 25a, 25b. body 22
It may be inserted into the grooves of a and 22b and sealed by heat sealing. Furthermore, as shown in Fig. 5-C, sealing can be achieved by using an ordinary can lid which is itself rigid and forming double seams 27a and 27b between the can lid and the can lid. good.

According to the present invention, the cylindrical body 20 itself has much higher rigidity than that made of a normal aluminum foil-plastic film laminate;
By heat-sealing or seaming this material to the lid, the cylindrical structure is fixed or reinforced, and the container as a whole has excellent shape retention and deformation resistance.

In addition, since it is made of steel foil, it is easier to compress and deform after use compared to ordinary steel plate cans, and when incinerated, the resin layer becomes a heat source and the steel foil is disposed of as a heat source, converting it into iron oxide. is easily carried out.

Both ductile and full hard steel foils are used. For pre-rolled steel sheets, cold rolled steel sheets are annealed and then subjected to secondary cold rolling, and if necessary, one or more of galvanizing, tin plating, nickel plating, electrolytic chromic acid treatment, or chromic acid treatment is performed. It can be obtained by For the latter type, cold-rolled steel sheets are annealed and then subjected to secondary cold rolling, followed by galvanizing, tin-plating,
It can be obtained by performing post-treatments such as nickel plating, electrolytic chromic acid treatment, and chromic acid treatment. A fully hard-type steel plate with a metal plating layer can also be manufactured by annealing a cold rolled steel plate, subjecting it to tempering treatment, applying metal plating thereto, and then subjecting it to secondary cold rolling.

An example of the mechanical properties of soft steel foil, hard steel foil, and iron foil is as follows.

Tensile strength and elongation are generally in the range of 30 to 50 Kg/mm ² and 15 to 35%, respectively, for soft steel foils, and 40 to 60 Kg/mm ² and 1 to 15%, respectively, for hard steel foils.

The organic resin coating used is a thermoplastic resin or a combination of a thermosetting resin and a thermoplastic resin, which can be applied in the form of a preformed film or in the form of a paint. Suitable examples of such resins include, but are not limited to:

(a) Polyolefins: polypropylene, polyethylene, polybutene-1, propylene-ethylene copolymer, propylene-butene-1 copolymer, ethylene-vinyl acetate copolymer, ionically crosslinked olefin copolymer (ionomer).

(b) Polyamides; especially general formula or In the formula, n is a number from 3 to 13, and m is a number from 4 to 11.

Polyamides consisting of repeating units represented by

For example, poly-ω-aminocaproic acid, poly-ω-aminoheptanoic acid, poly-ω-aminocaprylic acid, poly-ω-aminopelagoic acid, poly-ω-aminodecanoic acid, poly-ω-aminoundecanoic acid, poly-ω -Aminododecanoic acid, poly-ω-aminotridecanoic acid, polyhexamethylene adipamide, polyhexamethylene sebamide, polyhexamethylene dodecamide, polyhexamethylene tridecamide, polydecamethylene adipamide, polydeca Methylene sebamide, polydecamethylene dodecamide, polydecamethylene tridecamide, polydodecamethylene adipamide,
Polydodecamethylene sebacamide, polydodecamethylene dodecamide, polydodecamethylene tridodecamide, polytridecamethylene adipamide,
Polytridecamethylene sebamide, polytridecamethylene dodecamide, polytridecamethylene tridecamide, polyhexamethylene azeramide, polydecamethylene azeramide, polydodecamethylene azeramide, polytridecamethylene azeramide, or these Copolyamide.

(c) Polyesters; especially general formulas Or In the formula, R ₁ is an alkylene group having 2 to 6 carbon atoms,
R ₂ is an alkylene group or arylene group having 2 to 24 carbon atoms.

A polyester consisting of repeating units represented by

For example, polyethylene terephthalate, polyethylene terephthalate/isophthalate, polytetramethylene terephthalate, polyethylene/tetramethylene terephthalate, polytetramethylene terephthalate/isophthalate,
Polyethylene terephthalate/isophthalate, polytetramethylene/ethylene terephthalate, polyethylene/tetramethylene terephthalate/isophthalate, polyethylene/oxybenzoate, or blends thereof.

(d) Polycarbonates; especially general formula A polycarbonate represented by the following formula, where R ₃ is a hydrocarbon group having 8 to 15 carbon atoms.

For example, poly-p-xylene glycol biscarbonate, poly-dioxydiphenyl-methane carbonate, poly-dioxydiphenyl ethane carbonate, poly-dioxydiphenyl 2,2-propane carbonate, poly-dioxydiphenyl 1 , 1-ethane carbonate.

(e) Vinyl chloride resins such as polyvinyl chloride, vinyl chloride-butadiene copolymer, and vinyl chloride-styrene-butadiene copolymer.

(f) vinylidene chloride-vinylidene chloride copolymer,
Vinylidene chloride resin such as vinylidene chloride-vinylpyridine copolymer.

(g) High nitrile resins such as high nitrile content acrylonitrile-butadiene copolymers, acrylonitrile-styrene copolymers, acrylonitrile-styrene-butadiene copolymers.

(h) Polystyrene resin, styrene-butadiene copolymer, etc.

These resins are generally formed into a film shape and adhered to the above-mentioned steel foil by thermal fusion or bonded using an adhesive. Adhesives that are excellent for a wide range of thermoplastic resin films and steel foils are urethane adhesives, and for polyolefin films, acids graft-modified with ethylenically unsaturated carboxylic acids or their anhydrides are suitable for use with polyolefin films. Modified olefin resins can be used, and low-melting copolyamides can be used as adhesives for polyamide films, and low-melting copolyesters can be used for polyester films.

An organic resin paint can also be used as an undercoat layer for the above-mentioned thermoplastic resin film. Such coatings include any protective coatings consisting of thermosetting and thermoplastic resins; for example phenolic.
Modified epoxy paints such as epoxy paints and amino-epoxy paints; for example, vinyl chloride-vinyl acetate copolymer, partially saponified vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, epoxy modification -, epoxyamino-modified, or epoxyphenol-modified vinyl paints are used.

In the present invention, a metal or pigment that has an effect of improving processability, and has a blocking effect and a hiding effect against corrosive components can be blended into the resin. Such metals or pigments include:
Examples include aluminum flakes, tin oxide, titanium white, and zinc oxide.

The invention will be explained with the following example.

Example 1 A rolled steel foil with a thickness of 70 μm was subjected to cathode electrolysis in an electrolytic chromic acid treatment bath (aqueous solution of chromic anhydride 60 g/, sulfuric acid 0.2 g/, and sodium silicofluoride 0.2 g/),
After obtaining metallic chromium with a thickness of 0.1 g/m ² and chromate layer with a thickness of 15 mg/m ² on both sides, a 70 μm thick layer containing 10 g/m ² of titanium white was applied to the inner surface of the container using urethane adhesive. A 40 μm thick polypropylene film containing 5 g/m ² of titanium white was laminated on the outer surface of the container. A blank is cut out from the steel foil laminate material obtained in this way, and a third
A straight cylindrical body having an inner diameter of 52 mm and a height of 140 mm was formed by preliminarily coating the cut edge with a polypropylene layer such as 17 in Fig. C, and then gluing both ends. At one end edge of this cylindrical body,
60μm thick with inner layer containing 10g/ ^m2 titanium white
No. 6-A, which was molded from a laminate consisting of polypropylene, an intermediate layer of steel foil with a thickness of 70 μm, which is the same as the body material, and an outer layer of epoxy phenol paint with a thickness of 5 μm.
A lid body equipped with a score-type easy opening mechanism shown in Figure 6-B was fitted, and the fitted portion was heat-sealed by heating by high-frequency induction heating.

Next, add 250 ml of coffee to this three-piece can container.
ml and heat-sealed the other end edge of the lid body shown in FIGS. 7-A and 7-B formed from a laminate similar to the lid body by high-frequency induction heating method,
Heat sterilization treatment was performed in a differential pressure hot water retort at 120°C for 40 minutes.

50 three-piece cans filled with this coffee
After storage at ℃ for 6 months, the internal and external conditions of the body and lid of the three-piece can were examined, and no corrosion was observed.

Example 2 Metallic chromium and chromate layers were provided on both sides of rolled steel foil with a thickness of 70 μm using the same method as in the example, and then urethane-based adhesive was used to coat the inner surface of the container with a layer of 10 μm.
A 70 μm thick polyethylene film containing titanium white at g/m ² was laminated on the outside of the container, and a 12 μm printed biaxially oriented polyester film was laminated on the outside of the container. A blank is cut out from the steel foil laminate material obtained in this way, and both long side edges are
A straight cylindrical body with an inner diameter of 52 mm and a height of 150 mm was formed by bonding as shown in Figure -B. Next, the both end edges of this cylindrical body are
curled outwards like this.

At one end edge of this cylindrical body, an inner layer with a thickness of
No. 6 molded from a laminate consisting of 50 μm polyethylene, an intermediate layer of 100 μm thick soft aluminum foil, and an outer layer of 5 μm thick epoxyphenol paint.
A lid body equipped with a score-type easy opening mechanism shown in Figures A and 6-B was fitted, and the fitted portion was heat-sealed by heating using a high-frequency induction heating method.

Next, this three-piece can container body is sterilized with hydrogen peroxide gas, and coffee that has been previously heated and sterilized is filled in an aseptic environment. 7th -
The other edge of the lid shown in Figures A and 7-B was heat-sealed under sterile conditions by high-frequency induction heating.

50 three-piece cans filled with this coffee
After storage at ℃ for 6 months, the internal and external conditions of the body and lid of the three-piece can were examined, and no corrosion was observed.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional structural diagram of an example of a laminate used in the present invention, Fig. 2 is a perspective view showing the structure of a cylindrical body of a specific example of the present invention, Fig. 3-A, Fig. 3- Figures B and 3-C are cross-sectional views showing the structure of the side joint of the cylindrical body, Figure 4 is a cross-sectional view showing the structure of the three-piece can, Figures 5-A, 5-B, and 5th-C
The figure is a cross-sectional view showing the sealing method of a three-piece can.
Figures 6-A and 6-B are a perspective view and a sectional view of a lid body equipped with a score type easy opening mechanism, and Figures 7-A and 7-B are a specific example of a lid body. They are a perspective view and a sectional view. 1...Steel foil, 2a, 2b...Surface treatment layer, 3
a, 3b... adhesive layer, 4a, 4b... organic resin coating layer, 10... laminate, 11a, 11b... end, 12... side seam, 13... cut edge of laminate, 14... Seam protection coating resin layer, 15a,
15b...Hook, 16...Joining end, 17...
Cut edge coating resin layer, 20... Cylindrical body, 2
1a, 21b... flange, 22a, 22b...
Lid body, 23... Easy opening mechanism, 24a, 24b...
Curled portion, 25a, 25b... Trunked end portion, 27
a, 27b...Double seaming part.

Claims (1)

[Scope of Claim for Utility Model Registration] A three-piece can consisting of a cylindrical body with openings at both ends and a lid sealingly engaged with both ends of the body, wherein the cylindrical body is made of steel foil with a thickness of 30 to 120 μm. A surface treatment layer consisting of a substrate and a metal plating layer or a chromate layer provided on both surfaces of the substrate, and a thickness of 10 to 200 μm provided through the surface treatment layer.
A three-piece foil can, characterized in that it is formed of a laminate sheet consisting of thermoplastic resin film layers of m.