JPH0329666B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION The present invention relates to an easy-to-open can lid, and more specifically, the lid is made of a chromate surface-treated steel plate and has an excellent combination of easy-to-open ability, corrosion resistance, and pressure deformation resistance. This invention relates to an easy-to-open can lid that is easy to manufacture and easy to reuse resources. Conventional technology and problems to be solved by the invention Conventionally, easy-open lids used for cans containing beverages such as cola, beer, and youth have been divided by scores (partial cutting lines). An opening part is provided, a rivet is formed on the opening part, a tension tab is fixed by the rivet, and by pulling the tab, the score is broken and the opening part is removed. Widely used. Although this score-break type easy-open container lid has an excellent combination of sealing reliability and easy-openability, it has several problems that need to be solved. In other words, in manufacturing this type of container lid, harsh processing such as score processing and riveting processing must be performed, so the metal materials used are limited to materials with excellent workability such as aluminum. Become. In this way, the main body of the can is
Even when made of surface-treated steel sheets such as free steel (TFS), there is a restriction that the easy-open container lid must be made of aluminum. On the other hand, collecting and reusing used cans is desirable from the standpoint of preventing can pollution and conserving resources, but it is not possible for the can body and lid to be made of different materials. This makes it extremely difficult to reuse used housings. Furthermore, the inner coating of the can lid is easily damaged by harsh processing such as riveting, and applications such as edible canners, which are filled with corrosive contents and subjected to harsh processing such as heat sterilization, However, it is impossible to obtain satisfactory results in terms of corrosion resistance. This tendency is particularly noticeable in easy-to-open can lids made of aluminum. Publication No. 51-524 of the Publication states that an opening section is formed on the top of the can by a score, and a primer is applied to a part of this opening section, which is then heated and cured to form a painted section that will become an adhesive section. However, an easy-to-open can is described in which a tensile piece is layered on the coated area, and the two pieces are bonded together by heating and rapidly cooling the piece. However, when applying this easy-to-open can lid with adhesive structure to a highly rigid material such as steel plates, it is not possible to tear the score by just pulling up the tension piece, and the adhesive part is This tends to cause the inconvenience of peeling off and making it impossible to open the package. Purpose of the Invention The present inventors have developed a chromate-treated steel sheet, such as an electrolytic chromic acid-treated steel sheet, a chromate-treated nickel-plated steel sheet, a chromate-treated iron/tin alloy-plated steel sheet, and a chromate-treated tin alloy as a metal material for an easy-to-open can lid.・Choose a nickel alloy plated steel plate, chromate treated iron/tin nickel alloy plated steel plate, chromate treated aluminum plated steel plate, etc., and attach an opening tab with a specific structure to this lid material with a specific adhesive structure. It has been found that when provided, an easy-to-open can lid can be obtained that has an excellent combination of easy-to-open properties, corrosion resistance, and pressure deformation resistance, is easy to manufacture, and allows resource reuse. The present invention further provides that this easy-to-open can lid can withstand sterilization treatments such as retort sterilization and hot filling, and is useful as a can lid for edible cans containing saline and other corrosive ingredients. It was also found that Structure of the Invention According to the present invention, the sealing compound applied portion is wrapped around the can body flange and is applied so as to reach partway in the thickness direction of the lid material so as to define a portion to be opened inwardly. score set for,
and an easy-to-open can lid with an opening tab adhered to the portion to be opened, wherein the lid material has a surface treatment layer containing no free metallic tin layer on the surface, and the entire surface of the treatment layer has a surface treatment layer containing no free metallic tin layer. It is made of a steel plate on which a primer coating layer is formed through a chromate surface treatment layer with a chromate content of 3 to 200 mg/ ^m2 , and the opening tab has a score tearing tip on one end and a gripping part on the other end. and an opening tab which is provided with a tongue-shaped adhesion fulcrum between the two, and the connection part of the tongue-shaped adhesive fulcrum is located on the score tearing tip side, and the opening tab is When the tearing tip is located almost on the score and the adhesive width at the edge of the connection part side of the fulcrum for tongue-like adhesive is the following formula: W ≥ K・d・σ _B・t ² ...(1) In the formula, K is a constant with a value of 4Kg ^-1 , d represents the distance (mm) from the score part to be torn to the edge of the connection part of the adhesive fulcrum, and σ _B is the tensile strength of the chromate-treated steel plate (Kg /mm ² ), t represents the score remaining thickness (mm) of the lid material, and W represents the width (mm) of the adhesive layer at the distance d from the score. There is provided an easily openable can lid which is bonded via a thermoplastic adhesive comprising repeating units or repeating ester units. Function All score-type easy-open can lids that have been used in practical use have been made of aluminum plates or tinplate. This is because aluminum plates and tinplates have excellent workability in score engraving, riveting, etc. In contrast, in the present invention, the lid material has a surface treatment layer that does not contain free metallic tin, and the amount of chromium on the entire surface of the treatment layer is 3 to 200 mg/m ^{2 .}
The first feature is the use of a chromate surface-treated steel sheet having a chromate layer. In other words, the chromate surface-treated steel sheet has excellent adhesion with thermoplastic adhesives through the primer coating, and
It also has the advantage of being excellent in corrosion resistance at the score processed part, and these advantages are shown in Table 1 below, compared to chromate-treated tinplate with free tin on the surface (Comparative Example 1) and chromate-treated tinplate with free tin on the surface. Steel sheets having no surface treatment layer or having a surface treatment layer less than the scope of the present invention (Comparative Examples 2 to 3)
6), all of them cause poor opening, rusting, and pitting on the score part, whereas in the cases that satisfy the above condition () (Examples 1 to 6), there was no failure during opening and the score part However, it is clear that no abnormality is observed. By the way, although the primer-coated surface-treated steel sheet has the above-mentioned advantages, it has high rigidity, and therefore, when applied to an easy-to-open lid, a considerably large force is required to shear the score, making it difficult to easily attach the opening tab. The problem is that it is easily destroyed. In the present invention, an opening tab equipped with a tongue-shaped adhesion fulcrum is used as the opening tab, and the opening tab is arranged such that the tip for pushing and tearing is located on the score and the connecting portion of the tongue-shaped fulcrum is located on the score. The second feature is that it is provided on the can lid so that the base portion is located on the tearing tip side. The adhesive fulcrum is tongue-shaped, and this tongue-shaped adhesive fulcrum is connected to the opening tab at its base, allowing the opening tab to perform operations such as pushing, tearing, and pulling up with a considerable degree of freedom. At the same time, it is possible to ensure a wide adhesive area between the can lid and the opening tab, and it is also possible to correct the tendency of the opening tab to tilt to the left or right during the tearing operation. In the present invention, the tongue-shaped adhesive fulcrum and the can lid are adhered via a thermoplastic resin adhesive having an amide repeating unit or an ester repeating unit, and the edge of the tongue-shaped adhesive fulcrum on the connection part side Another notable feature is that the adhesive width (W) is determined to satisfy the above formula (1). When pushing the tearing tip into the score of the lid to start opening, it is important that the tearing tab is firmly adhered as close as possible to the tearing tip (score). As the distance d between the score and the adhesive fulcrum increases, as shown in equation (1) above, the peeling force applied to the adhesive fulcrum increases in proportion to this distance d, so the adhesive peels off on the side of the adhesive fulcrum near the score. When this occurs, the peeling force applied to the adhesion fulcrum becomes larger and larger, and as a result, adhesion failure tends to progress and the opening of the package by pushing and tearing becomes uncertain. In the lid of the present invention, a tongue-shaped adhesive fulcrum is used, and the adhesive width (W) at the edge of the tongue-shaped adhesive fulcrum on the connection side, that is, the edge closest to the score, is expressed by the formula ( By setting 1) to be satisfied, it is possible to prevent the adhesive fulcrum from being destroyed when opening the package, and to ensure that the package can be opened by tearing. Taking the above into account, according to the present invention, easy opening,
An easy-to-open can lid for general food cans having an excellent combination of corrosion resistance and pressure deformation resistance is provided. Preferred embodiments of the invention The present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings. Lid Structure As shown in FIGS. 1, 2 and 3, one feature of the easy-open can lid 1 of the present invention is that it is made of a surface-treated steel plate 3 provided with a primer coating 2.
This surface-treated steel sheet 3 is a chromate-treated steel sheet among various surface-treated steel sheets, especially an electrolytic chromic acid treated steel sheet, a chromate-treated nickel-plated steel sheet, a chromate-treated iron/tin alloy-plated steel sheet, and a chromate-treated tin-nickel alloy-plated steel sheet. Steel plate, chromate treated iron/
Only tin-nickel alloy-plated steel sheets and chromate-treated aluminum-plated steel sheets can be used. The reason why the above-mentioned surface-treated steel sheet is particularly selected as the lid material for the easy-to-open can lid in the present invention is that this surface-treated steel sheet has a high rigidity characteristic of steel, and the interior of the can can has a high rigidity like an edible can lid. This is because it can withstand external pressure deformation caused by being in a vacuum, and it has both excellent corrosion resistance and excellent coating film adhesion. This lid 1 includes a circumferential groove 4 on the outer periphery and a panel portion 6 connected to the groove through an annular rim portion 5. A layer 7 of sealing compound is provided in sealing engagement therewith. Inside the annular rim portion 5 there is a portion 9 to be opened, which is defined by a steer 8 . This opening portion 9 may substantially coincide with most of the panel portion 6, or a portion of the panel portion 6 may be the opening portion. As shown in the enlarged cross-sectional view of FIG. 3, the score 8 is provided so as to reach the middle of the surface-treated steel plate 3 in the thickness direction, and is easily sheared when the package is opened by the mechanism described in detail below. . According to the invention, this opening portion 9 is also provided with an opening tab 10 in a particular arrangement as described below. This opening tab 10 has a score tearing tip 11 at one end, a gripping part (ring) 12 at the other end, and a fulcrum part 13 located between these parts and joined to the lid. In this embodiment, the fulcrum portion 13 has a cut 14, generally U-shaped in shape, in the tab between the tip 11 and the ring 12, such that a connection 15 exists between the fulcrum portion 13 and the tip 11. It is formed by providing a tongue-like shape. The tearing tip 11 of the opening tab 10 is attached to the opening portion 9 of the lid and the thermoplastic resin adhesive layer at the tongue-shaped fulcrum portion 13 so that its position almost matches the score 8 of the lid. It is thermally bonded via 16. In the present invention, a thermoplastic adhesive consisting of an amide repeating unit and/or an ester repeating unit is used as the adhesive layer 16, and the adhesive fulcrum is provided with a width (W) that satisfies the above formula (1). In the can lid of the present invention, when the ring 12 of the opening tab 10 is picked up with a finger and lifted upward, this force is transmitted as a downward force to the tearing tip 11 via the fulcrum portion 13, At the same time as a downward tearing force is applied to the score 8, a tearing force is applied to the adhesive layer 16 between the fulcrum part 13 and the opening part 9. The above formula (1) shows that this peeling force increases as the distance d from the score 8 to the adhesive fulcrum 13 increases, and () the tensile strength σ _B of the surface-treated steel sheet 3 increases. This is an empirical formula derived from the fact that the larger the value, the larger the value, and is proportional to the square of the residual thickness t of () score 8. For a smooth opening operation, it is important to determine the width (W) of the adhesive layer at the adhesive fulcrum so that it satisfies this formula (1), as shown in the graph in Figure 4. It becomes immediately obvious. Figure 4 shows the use of epoxy-phenol coated electrolytic chromic acid treated steel plate and nylon-12 adhesive.
The experimental results are plotted with the distance d being 6 mm, the horizontal axis representing the score residual thickness (t), and the width (W) of the adhesive layer representing the vertical axis. In the figure, curve 1' is a curve corresponding to W≧K・d・σ _B・t ² , and the white circle (○) mark in the plot indicates that the adhesive layer 16 has reached a score of 8 without substantially peeling. This is an example in which the cut was inserted smoothly, and the cross mark (x) is an example in which peeling of the adhesive layer 16 occurred before the cut was inserted to a score of 8. From the results shown in Figure 4 above, it is clear that the width (W) of the adhesive layer at the adhesive fulcrum can be set to a width that satisfies formula (1).
It can be seen that it is extremely critical to provide easy-opening properties to a lid made of a highly rigid surface-treated steel plate. In this way, in order to break a lid made of a rigid surface-treated steel plate at the score part, an opening tab is thermally bonded to the opening part, as described in Japanese Utility Model Publication No. 51-524. It is difficult to even make a cut in the score by simply pulling this opening tab, and it is absolutely necessary to first make a cut in the score by pressing downwards on the score with the pointed tip, and then to remove the score. In order to withstand the peeling force applied to the adhesive layer when inserting the cut, the width (W) of the adhesive layer must be
It is important to determine so that the above equation (1) is satisfied. In this case, the metal material is electrolytic chromic acid treated steel plate, chromate treated nickel plated steel plate,
Chromate-treated iron/tin alloy plated steel sheet, chromate-treated tin/nickel alloy plated steel plate, chromate-treated iron/tin/nickel alloy plated steel plate, chromate-treated aluminum plated steel plate, adhesives made from amide and/or ester repeating units It is also absolutely necessary to use a thermal adhesive other than an amide or ester, such as a tin plate that has a free metallic tin layer, which will cause adhesive failure when inserting the score cut, and a thermal adhesive other than an amide or ester such as an acid-modified olefin resin. Even when using the adhesive, there is a tendency for adhesive failure to occur when inserting the cut. Note that once the score 8 of the lid is cut, the score 8 will easily break along the score 8 due to the tension of the tab, so only the first cut in the score 8 is the problem. It becomes. Each component material As mentioned above, the surface-treated steel sheets include chromate surface-treated steel sheets, especially electrolytic chromic acid treated steel sheets,
Chromate-treated nickel-plated steel sheet, chromate-treated iron and tin alloy-plated steel sheet, chromate-treated tin and
Nickel alloy plated steel plate, chromate treated iron/
Tin/nickel alloy plated steel plates and chromate-treated aluminum plated steel plates are preferably used. Electrochromic acid treated steel sheets consist of a metallic chromium layer on a cold rolled steel substrate and a non-metallic chromium layer thereon. The thickness of the steel plate substrate is determined by the balance between pressure deformation resistance, workability, and ease of opening, and is generally
It is preferably in the range of 0.10 to 0.40 mm, particularly 0.12 to 0.35 mm. The thickness of the metal chromium layer is determined by the balance between corrosion resistance and workability, and the amount is 30
It is preferably in the range of 50 to 250 mg/m ² , particularly 50 to 250 mg/m ² . The thickness of the non-metallic chromium layer is related to paint film adhesion and adhesive peel strength, and is expressed as a chromium content of 4 to 40 mg/m ² .
In particular, it is desirable that the content be in the range of 7 to 30 mg/m ² . Chromated nickel-plated steel sheets consist of a nickel layer and a chromate layer on top of a cold-rolled steel substrate. The thickness of the nickel layer is related to corrosion resistance, and the amount is 30 to 3000mg/
m ² , preferably in the range of 100 to 1000 mg/m ² . The chromate layer may also include a non-metallic single layer or a metallic chromium layer. The thickness of the chromate layer is related to coating film adhesion and adhesive peel strength, and the chromium content is preferably in the range of 3 to 200 mg/m ² , particularly 5 to 150 mg/m ² . Chromate-treated iron-tin alloy coated steel sheet consists of a cold-rolled steel sheet substrate with an iron-tin alloy layer and a chromate layer thereon. The thickness of the iron-tin alloy layer is related to corrosion resistance, and its amount is 30% as the amount of tin.
It is desirable that the amount is in the range of 800 mg/m ² to 800 mg/m ² , particularly 200 to 700 mg/m 2 . Further, the chromate layer may include a single nonmetallic chromium layer or a metallic chromium layer. The thickness of the chromate layer is related to coating film adhesion and adhesive peel strength, and the chromium content is preferably in the range of 3 to 200 mg/m ² , particularly 5 to 150 mg/m ² . A chromate-treated tin/nickel alloy plated steel sheet consists of a tin/nickel alloy layer and a chromate layer thereon on a cold rolled steel sheet substrate. The thickness of the tin-nickel alloy layer is related to corrosion resistance, and the amount of tin is preferably 30 to 800 mg/m ² , particularly 50 to 500 mg/m ² . The chromate layer may include a single layer of non-metallic chromium or a layer of metallic chromium. The thickness of the chromate layer is related to coating film adhesion and adhesive peel strength, and the chromium content is preferably in the range of 3 to 200 mg/m ² , particularly 5 to 150 mg/m ² . Further, a small amount of iron, manganese, zinc, molybdenum, copper, etc. can be added to the tin/nickel alloy layer to improve corrosion resistance.
A nickel layer or a tin layer can also be provided between the tin/nickel alloy layer and the steel plate. Chromate-treated iron/tin/nickel alloy plated steel sheets consist of a cold-rolled steel plate substrate, an iron/tin/nickel alloy plating layer, and a chromate layer above the iron/tin/nickel alloy plating layer.
The thickness of the iron-tin-nickel alloy plating is related to corrosion resistance, and the amount of tin is preferably 10 to 800 mg/m ² , particularly 30 to 400 mg/m ² . The chromate group may also include a non-metallic chromium single layer or a metallic chromium layer. The thickness of the chromate layer is related to paint film adhesion and adhesive peel strength, and the chromium content is 3 to 200 mg/m ² .
In particular, it is desirable that the content be in the range of 5 to 150 mg/m ² . Further, a small amount of manganese, zinc, molybdenum, copper, etc. can be added to the iron-tin-nickel alloy layer to improve corrosion resistance. A chromate-treated aluminum-plated steel sheet consists of an aluminum layer on a cold-rolled steel sheet substrate and a chromate layer thereon, and an iron-aluminum alloy layer may be provided between the steel sheet and the aluminum layer.
The thickness of the aluminum layer is related to corrosion resistance, and the amount is 30 to 3000 mg/ ^m2 , especially
It is desirable that the content be between 100 and 2500 mg/m ² . or,
The chromate layer may include a single non-metallic chromium layer or a metallic chromium layer. Further, the chromate layer may be a phosphoric acid chromate layer. The thickness of the chromate layer is related to paint adhesion and adhesive peel strength, and the chromium content is preferably in the range of 3 to 200 mg/m ² , particularly 5 to 150 mg/m ² . As the primer coating, any primer coating known per se that exhibits excellent adhesion to the above-mentioned surface-treated steel sheet and also to thermoplastic adhesives consisting of amide and/or ester repeating units may be used. is used. Examples of this paint include thermosetting or thermoplastic resin paints, such as modified epoxy paints such as phenol epoxy paints, amino epoxy paints, and epoxy ester paints; for example, vinyl chloride-vinyl acetate copolymers, vinyl chloride-acetic acid copolymers, etc. Vinyl or modified vinyl paints such as partially saponified vinyl copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers, epoxy-modified, epoxyamino-modified, or epoxyphenol-modified vinyl resin paints; acrylic resin paints; Oil-based paints; alkyd paints; polyester paints; synthetic rubber-based paints such as styrene-butadiene copolymers, etc. are used. Typical primer paints with excellent adhesion and corrosion resistance are resol-type phenols derived from various phenols and formaldehyde.
It is a phenol-epoxy paint consisting of an aldehyde resin and a bisphenol type epoxy resin.
It is a paint containing a weight ratio of 10 to 5:95. This paint also has excellent workability, and even when subjected to score processing, it has the advantage that the score processing portion has good corrosion resistance. This type of coating is particularly suitable for use with polyamide adhesives. Another typical example of a primer paint with excellent adhesion and corrosion resistance is a vinyl chloride copolymer resin paint having a polar group. This paint has a carboxyl group,
Add polar groups such as acid anhydride groups and epoxy groups to resin 100%.
It contains acrylic acid, methacrylic acid, maleic anhydride, hydroxy-propyl or ethyl ester of acrylic acid or methacrylic acid, glycidyl acrylate (methacrylate), etc. in acetic acid if necessary. It is a paint containing a resin obtained by copolymerizing vinyl chloride with other comonomers such as vinyl. Hydroxyl groups can also be supplied by saponifying vinyl acetate units in the copolymer, and epoxy groups can also be supplied by modifying the copolymer with an epoxy resin or epoxyphenol paint. Of course, these primer coatings may have a single layer structure, or may have a multilayer structure such as a combination of a base coat and a top coat. The thickness of the primer coating is not particularly limited as long as the above-mentioned purpose is achieved, but it is generally desirable to have a thickness in the range of 0.2 to 30 μm, particularly 1 to 20 μm. The opening tab may be formed from the stain-free surface-treated steel plate that constitutes the can lid, or may be formed from a light metal plate such as aluminum or aluminum alloy. It may also be made of plastic material as long as it has sufficient rigidity. The resin containing amide repeating units and/or ester repeating units used as a thermoplastic adhesive has a melting point or softening point of 50 to 300°C, particularly 80 to 270°C.
Homo to copolyamides, copolyesters, or blends of two or more of these are used. As a homo- or copolyamide, carbon number is 100
Homo- to copolyamides in which the number of amide repeat units per unit ranges from 4 to 17, especially from 5 to 17, are suitable, especially in the case of copolyamides in which at least 3 mol % of the amide repeat units are the main amide repeats. Preferably it consists of different amide repeating units. Examples of suitable materials include, but are not limited to, nylon 13, nylon 12, nylon
11, nylon 6-12, nylon 6-10, nylon 6-6, nylon 6, nylon 12/nylon 6,
These include nylon 12/nylon 10/nylon-12 nylon 6/nylon 6-6 or dimer acid-based polyamides. Copolyesters include, but are not limited to, polyethylene terephthalate/isophthalate, polytetramethylene, and copolyesters in which 3 to 70 mol% of the total ester units are composed of ester repeating units different from the main ester repeating unit.・Terephthalate/Isophthalate,
Examples include polyethylene terephthalate/adipate, polytetramethylene terephthalate/adipate, polytetramethylene/ethylene terephthalate/dodecanoate, and the like. Of course, these adhesives should have a molecular weight sufficient to form a film, and may be polyamides, copolyesters, or blends of polyamides and copolyesters, and may also be used for purposes of modification, etc. Other resins such as ionomers,
There is no problem even if xylene resin, epoxy resin, etc. are blended. Furthermore, these adhesives may contain well-known compounding agents such as fillers, heat stabilizers, antioxidants, nucleating agents, pigments, plasticizers, and lubricants according to known formulations. Manufacturing method In manufacturing the easy-to-open can lid of the present invention,
First, a primer paint is applied to the above-mentioned surface steel plate in the form of an organic solvent solution, an aqueous dispersion, or an aqueous solution by means such as spray painting, roller coating, dipping painting, electrostatic painting, electrophoretic painting, etc., and the coating film is dried. Or, it is formed by baking. This painted board is punched out to the specified size of the can lid.
It is formed into a can lid of a predetermined shape by press molding, and score processing is performed at the same time or in a separate process.
In score processing, the residual thickness at the score part is 1/8 to 1/2 of the base plate thickness, and the absolute thickness is 0.02 to 1/2.
It is desirable that the thickness be 0.09 mm, particularly in the range of 0.03 to 0.08 mm. Prior to or after this scoring process, a sealing compound composition made of a synthetic rubber latex such as styrene-butadiene rubber latex, a tackifier, and a filler is applied to the circumferential groove of the can lid, and then dried. Make it a compound layer. The above-mentioned thermoplastic adhesive layer is provided on the supporting point of a separately manufactured opening tab, or a thermoplastic adhesive layer is provided on the portion of the can lid where the opening tab is to be provided. Of course, it is also possible to do both. The adhesive layer can be formed by any method other than applying an adhesive film cut to a predetermined size, such as applying the adhesive in the form of powder, melt, suspension, or solution. can. The thickness of the adhesive resin layer is 3 to 150 μm, especially 10 to 100 μm.
It is appropriate that the value be within the range of . Next, the opening tab is positioned on the can lid, and the thermoplastic resin located between the fulcrum part of the tab and the can lid is melted and then cooled and solidified to complete adhesion between the two. In the case of an edible can, it is preferable that the score be provided close to the annular rim and over the entire circumference, as shown in the attached drawing, in a so-called full open format. It is also possible to provide a portion of the can lid with an arbitrary shape such as a raindrop shape or a semicircular shape. Effects and Applications The easy-to-open can lid of the present invention is made of a rigid, stain-free surface-treated steel plate, so it is suitable for heat sterilization at high temperatures, and even after the passage of time, the inside of the can lid is Even when applied to the field of canning food cans where vacuum is applied, there is a significant advantage in that deformation is prevented. Moreover, since this can lid does not require harsh processing such as riveting, it is possible to use a very inexpensive surface-treated steel sheet instead of aluminum, and it is also possible to use this surface-treated steel sheet for the lid. This has the advantage that the can body and can lid are made of the same material, making it easier to reuse resources. In addition, this surface-treated steel sheet has excellent corrosion resistance,
It has sufficient corrosion resistance even for contents containing salt, and can be used to fill various foods, such as livestock products and processed livestock products, marine products, vegetables, vegetable juice, and various fruits. Useful as a can lid. The following examples specifically explain the effects of the present invention. Tests were conducted in the following manner throughout each Example and Comparative Example. (1) Openability test Open the can by pulling up the tab on the easy-open can lid to break the score. The state in which the part that should be opened separated by the score is separated from the can lid is considered to be openable, and is expressed as the number of lids that could be opened out of 100 test lids. (2) Openability test for actual storage cans () A No. 7 can with an easy-to-open can lid that was one-sidedly tightened was filled with bonito seasoning, the lid was vacuum-sealed, and the lid was sealed at 116°C.
After the cans that have been heat sterilized for 90 minutes are stored at room temperature for one year, the same openability test as in (1) is conducted. It is expressed as the number of cans that could be opened out of 100 test cans. (3) Openability test of actual storage cans () A No. 7 can with an easy-to-open can lid that was tightened one-sidedly was filled with mandarin oranges, the lid was vacuum-sealed, and then heat sterilized at 82°C for 20 minutes. After storing the mature can at room temperature for one year, perform the opening test in the same manner as in (1).
It is expressed as the number of cans that could be opened out of 100 test cans. (4) Observation of the inner surface of the easy-open can lid For the cans of Tests (2) and (3), the corrosion status of the inner surface of the easy-open lid before opening was observed using a stereomicroscope. In Examples 1 to 6 and Comparative Examples 1 to 6, the type of primer and adhesive, the residual thickness of the score, the distance from the score to the adhesive fulcrum, the width of the adhesive layer at that position, and the tensile strength of the steel plate used were kept constant. Tests were conducted using different types of surface-treated steel sheets. Example 1 A commercially available electrolytically chromic acid treated steel plate (thickness 0.23 mm, tensile strength 42.5 Kg/mm ² ) with a metallic chromium content of 100 mg/m ² and a non-metallic chromium layer containing 15 mg/m ² of chromium.
Epoxy/phenol paint was applied to both sides of the board to a dry thickness of 5 μm, and baked at 210°C for 10 minutes. This coated electrolytic chromic acid treated steel plate was formed into a 211-diameter lid using a press, and then a sealing compound was applied to the curled portion by a conventional method and dried. Next, a score was processed on the inner surface of the lid in a circular shape with a diameter of 58 mm so that the remaining score thickness was 45 μm. A tab made from the same coated electrolytic chromic acid treated steel plate was assembled to the lid material thus obtained as shown in FIGS. 1 and 2. That is, the distance from the score to the edge of the tongue-like adhesive fulcrum on the connection side is 6 mm, and the width of the adhesive layer at the same position is 5 mm.
Bonding was carried out at 220°C using the film adhesive described in No. 2.
An opening test was performed on the easy-open can lid obtained in this way.
We conducted an openability test on actual storage cans and observed the inner surface of the easy-open can lid. The results are shown in Table 1. Comparative Example 2 A cold-rolled steel plate with a thickness of 0.23 mm and a tensile strength of 42.5 Kg/mm ² was subjected to alkaline degreasing and pickling pretreatment in the usual manner, and then treated in a Watts bath at 50°C (nickel sulfate 250 g/mm).
Nickel plating was carried out in 40 g of nickel chloride and 40 g of boric acid at a current density of 5 A/dm ² to obtain a nickel-plated steel plate with a thickness of 300 mg/m ² . Next, this nickel-plated steel sheet was subjected to cathodic electrolysis treatment in an aqueous solution of 30 g of sodium dichromate to obtain a chromate film with a chromium content of 8 mg/m ² . The chromate-treated nickel-plated steel plate thus obtained was painted, lid-formed, tab-formed, and tab-adhered in the same manner as in Example 1 to create an easy-to-open can lid.
An openability test, an openability test of actual storage cans, and corrosion observation of the scoring area were conducted. The results are shown in Table 1. Example 3 The same cold-rolled steel sheet as in Example 2 was subjected to alkali degreasing and pre-pickling treatment in a conventional manner, and then placed in the following tin plating bath: 60 g of stannous sulfate / 60 g of phenol sulfonic acid / 10 g of sulfuric acid / Under the conditions of bath temperature 45℃ and current density 30A/dm ² in water 1.
Tin plated to a thickness of 500mg/ ^m2 , then 250℃, 5
After heat treatment for seconds, an iron/tin alloy plated steel plate was obtained. Next, this iron-tin alloy plated steel sheet was subjected to cathodic electrolysis treatment in an aqueous solution containing 30 g of sodium dichromate to obtain a chromate film with a chromium content of 7 mg/m ² . The chromate-treated iron/tin alloy plated steel sheet thus obtained was painted, lid-formed, and
An easy-to-open can lid was created by tab molding and tab adhesion, and an openability test, an openability test of an actual can storage can, and corrosion observation of the scoring area were conducted. The results are shown in Table 1. Example 4 The same cold rolled steel plate as in Example 2 was tinned to a thickness of 500 mg/m ² in the same manner as in Example 3, and then
300 mg/m ² under the nickel plating conditions shown in Example 2
Nickel plating is performed to the thickness of , then 180℃,
Heat treatment was performed for 1 second to obtain a tin/nickel alloy plated steel plate. Next, this tin-nickel alloy plated steel sheet was subjected to cathodic electrolysis treatment in an aqueous solution containing 30 g of sodium dichromate to obtain a chromate film with a chromium content of 8 mg/m ² . Using the chromate-treated tin/nickel alloy plated steel plate thus obtained, an easy-to-open can lid was prepared in the same manner as in Example 1, and the same tests as in Example 1 were conducted. The results are shown in Table 1. Example 5 Using the same cold-rolled steel sheet as in Example 2, an iron-tin-nickel alloy plated steel sheet was prepared in the same manner as in Example 4, except that the heat treatment conditions after nickel plating were 250°C and 2 seconds. Obtained. Next, this iron-tin-nickel alloy plated steel sheet was subjected to cathodic electrolysis treatment in an aqueous solution containing 30 g of sodium dichromate to obtain a chromate film with a chromium content of 10 mg/m ² . Using the thus obtained chromate-treated iron-tin-nickel alloy plated steel plate, an easy-to-open can lid was prepared in the same manner as in Example 1, and the same tests as in Example 1 were conducted. The results are shown in Table 1. Example 6 The same cold-rolled steel plate as in Example 2 was pretreated with alkali degreasing and pickling using the usual method, then immersed in a 350°C flux, preheated, and immersed in a molten aluminum bath to produce a flux of 1000 mg/m2. An aluminum-plated steel plate with a thickness of ² was obtained. Next, this aluminum-plated steel sheet was cathodic electrolyzed in an aqueous solution containing 30 g of sodium dichromate to obtain a chromate film with a chromium content of 15 mg/m ² . Using the chromate-treated aluminum-plated steel sheet thus obtained, an easy-to-open can lid was prepared in the same manner as in Example 1, and the same tests as in Example 1 were conducted. The results are shown in Table 1. Comparative Example 1 A ^commercially available tin plate ( ^thickness
0.23 mm, tensile strength 42.5 Kg/mm ² ), an easy-to-open can lid was prepared in the same manner as in Example 1.
The same tests were conducted. The results are shown in Table 1. Comparative Example 2 Using the same cold-rolled steel sheet as in Example 2, it was subjected to alkaline degreasing and pickling pretreatment in the usual manner, and then subjected to electric current in the following chromium plating chromic anhydride 250g/sulfuric acid 2.5g/water 1 bath. A chromium-plated steel plate with a thickness of 250 mg/m ² was obtained by cathodic electrolytic treatment at a density of 30 A/dm ² and a temperature of 40°C. Using the chromium-plated steel plate thus obtained, an easy-to-open can lid was prepared in the same manner as in Example 1, and the same tests as in Example 1 were conducted. The results are shown in Table 1. Comparative Example 3 Using the same cold rolled steel plate as in Example 2,
In the same manner as above, a nickel-plated steel plate with a thickness of 300 mg/m ² was obtained. Using the nickel-plated steel plate thus obtained, an easy-to-open can lid was prepared in the same manner as in Example 1, and the same tests as in Example 1 were conducted. The results are shown in Table 1. Comparative Example 4 Using the same cold rolled steel plate as in Example 2, Example 3
In the same manner as above, an iron-tin alloy coated steel plate with a tin content of 500 mg/m ² was obtained. Using the thus obtained iron-tin alloy plated steel plate, an easy-to-open can lid was prepared in the same manner as in Example 1, and the same tests as in Example 1 were conducted. The results are shown in Table 1. Comparative Example 5 Using the same cold rolled steel plate as in Example 2, Example 4
Similarly, the amount of tin is 500 mg/m ² and the amount of nickel is 300 mg/m 2
A tin/nickel alloy coated steel plate with mg/m ² was obtained. Using the thus obtained tin-nickel alloy plated steel plate, an easy-to-open can lid was prepared in the same manner as in Example 1,
The same tests as in Example 1 were conducted. The results are shown in Table 1. Comparative Example 6 Using the same cold rolled steel plate as in Example 2, Example 6
In the same manner as above, an aluminum-plated steel plate with an aluminum content of 1000 mg/m ² was obtained. Using the thus obtained aluminum plated steel plate, an easy-to-open can lid was prepared in the same manner as in Example 1, and the same tests as in Example 1 were conducted. Table 1 shows the results.
Shown below. From Examples 1 to 6 and Comparative Examples 1 to 6, among the many surface-treated steel sheets, electrolytic chromic acid treated steel sheet, chromate treated nickel plated steel sheet, chromate treated iron/tin alloy plated steel sheet, chromate treated tin/nickel plated steel sheet Alloy plated steel plate, chromate treated iron/tin/
It can be seen that nickel alloy-plated steel sheets and chromate-treated aluminum-plated steel sheets are superior. In Examples 7 to 14 and Comparative Examples 7 and 8, tests were conducted while keeping everything other than the type of adhesive and the bonding temperature constant. Example 7 Using the same electrolytic chromic acid treated steel plate as in Example 1,
Example 1 except that film-shaped nylon 6-10 was used as the adhesive and the bonding temperature was 260°C.
An easy-to-open can lid was prepared in the same manner as above, and an openability test and an openability test of an actual storage can were conducted. The results are shown in Table 2. Example 8 Example 7 except that film-like nylon 6-6 was used as the adhesive and the bonding temperature was 300°C.
An easy-to-open can lid was prepared in the same manner as above, and an openability test and an openability test of an actual storage can were conducted. The results are shown in Table 2. Example 9 An easy-to-open can lid was prepared in the same manner as in Example 7 except that a film-like nylon 12/nylon 6 copolymer was used as the adhesive and the bonding temperature was 240°C, and an opening test was conducted. We conducted an openability test on actual storage cans. The results are shown in Table 2. Example 10 Polyamide polycondensed from dimer acid, polyalkylene polyamine, and hexamethylene diamine was used as the adhesive, and it was applied to the tab side in advance to a thickness of 50 μm using a hot melt applicator equipped with a gear pump, and the adhesive temperature was set to 240°C. An easy-to-open can lid was prepared in the same manner as in Example 7, and an openability test and an openability test of an actual storage can were conducted. The results are shown in Table 2. Example 11 Polyamide polycondensed from dimer acid and polyalkylene polyamine was used as the adhesive. It was applied to the tab side in advance to a thickness of 50 μm with a hot melt applicator equipped with a gear pump, and the adhesive temperature was set at 140 µm.
An easy-to-open can lid was prepared in the same manner as in Example 7 except that the temperature was changed to 0.degree. C., and an openability test and an openability test of an actual storage can were conducted. The results are shown in Table 2. Example 12 Terephthalic acid, sebacic acid,
Using a copolyester film containing 1,4-butanediol triethylene glycol as a component,
An easy-to-open can lid was prepared in the same manner as in Example 7, except that the bonding temperature was 240° C., and an opening test and an opening test on an actual storage can were conducted. The results are shown in Table 2. Example 13 An easy-to-open can lid was prepared in the same manner as in Example 7, except that a blend copolyester film of polyethylene terephthalate copolyester and polybutylene terephthalate copolyester was used as the adhesive, and the bonding temperature was 230°C. Then, an openability test and an openability test of actual storage cans were conducted. The results are shown in Table 2. Example 14 A copolyester containing terephthalic acid, isophthalic acid, sebacic acid, and 1,4-butanediol was used as an adhesive. It was applied to the tab side in advance to a thickness of 50 μm using a hot melt applicator equipped with a gear pump, and the adhesive temperature was An easy-open can lid was prepared in the same manner as in Example 7, except that the temperature was 120°C, and an opening test and an opening test of an actual storage can were conducted. The results are shown in Table 2. Comparative Example 7 An easy-to-open can lid was prepared in the same manner as in Example 7 except that a maleic anhydride-modified polypropylene film was used as the adhesive and the bonding temperature was 210°C. An openness test was conducted. The results are shown in Table 2. Comparative Example 8 Using ethylene/vinyl acetate copolymer as the adhesive, it was applied in the same manner as Example 7, except that it was applied to the tab side in advance to a thickness of 50 μm using a hot melt applicator equipped with a gear pump, and the bonding temperature was set to 140°C. An easy-to-open can lid was created, and an opening test and an opening test on an actual storage can were conducted. The results are shown in Table 2. It can be seen from Examples 7 to 14 and Comparative Examples 7 and 8 that thermoplastic adhesives containing amide repeating units and/or ester repeating units are superior among other adhesives.

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【table】 [Brief explanation of the drawing]

FIG. 1 is a top view of the easy-to-open can lid of the present invention, FIG. 2 is a sectional view of the can lid shown in FIG. Fig. 4 shows the score residual pressure (t) on the horizontal axis and the width of the adhesive layer (W) on the vertical axis, and whether the adhesive peels off when opening the package (○) or not. It is a diagram plotting (x). 2 is the primer coating film, 3 is the chromate surface treated steel plate, 8 is the score, 9 is the part to be opened, 1
0 is an opening tab, 11 is a tearing tip, 13 is a fulcrum, 14 is a cut, and 16 is an adhesive layer.

Claims (1)

[Scope of Claims] 1. A sealing compound applied part that is tightened between the can body flange provided around the can body, and reaches halfway in the thickness direction of the lid material so as to define the part that should be opened inward. In the easy-to-open can lid, which has a score provided as shown in FIG. It is made of a steel plate on which a primer coating layer is formed via a chromate surface treatment layer with a chromate content of 3 to 200 mg/m ² on the entire surface of the treatment layer, and an opening tab is attached to one end for score tearing. An opening tab having a tip, a gripping portion at the other end, and a tongue-shaped adhesive fulcrum between the two, and a connecting portion of the tongue-shaped adhesive fulcrum located on the score tearing tip side;
In addition, the tearing tip of the opening tab is located almost on the score, and the adhesive width at the edge of the connection side of the fulcrum for tongue-like adhesive is as follows: W≧K・d・σ _B・t In Equation ² , K is a constant with a value of 4Kg ^-1 , d represents the distance (mm) from the score part to be torn to the edge of the connection part side of the adhesive fulcrum, and σ _B is the distance of the chromate-treated steel plate. represents the tensile strength (Kg/mm ² ), t represents the score remaining thickness of the lid material (mm), W represents the width of the adhesive layer at the distance d from the score (mm), and the width that satisfies the following. 1. An easily openable can lid, characterized in that the can lid is bonded via a thermoplastic adhesive comprising an amide repeating unit or an ester repeating unit.