JPH0451425B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an easy-to-open can lid for a sealed can, and more specifically, an opening tab for shearing the score of the can lid is fixed to the can lid via an adhesive. However, the present invention relates to an easy-to-open can lid in which the opening tab is securely fixed to the can lid even after retort sterilization until the opening operation is completed. (Prior Art) Conventionally, easy-open lids used for cans containing beverages such as cola, beer, youth, etc. have been provided with opening portions demarcated by scores (partial cutting lines). Widely used devices include a rivet formed in the opening portion, a tension tab fixed by the rivet, and the score broken by pulling the tab to remove the opening portion. However, with this easy-to-open lid, the inner coating film of the can lid is easily damaged due to harsh processing such as riveting. For applications involving severe treatment, satisfactory results in terms of corrosion resistance cannot be obtained. This tendency is particularly noticeable in easy-to-open can lids made of aluminum. Furthermore,
Contents with a high salt concentration cause pitting corrosion, and there is a problem of leakage of contents from through holes and contamination by bacteria. Japanese Utility Model Publication No. 51-524 proposes an easy-to-open can lid in which an opening piece is adhesively fixed to an opening section defined by a score. (Problem to be Solved by the Invention) In this type of easy-to-open lid, by lifting the grip part of the opening piece upward, the adhesive part becomes a fulcrum and the tip of the opening piece (tab) is pushed into the score. Shearing of the score is started by pulling the tab, and shearing is performed across the entire score by pulling the tab, but in this case, the force necessary to tear the score acts as a moment on the adhesive part, The problem is that the parts are likely to break. Particularly in the case of cans, the cans with easy-to-open lids are subjected to so-called retort sterilization under high temperature and pressure, so joints can deteriorate due to attack by high temperatures and hot water or hot steam. Therefore, the bonded portion is more likely to break. Such a tendency for adhesive deterioration also occurs due to the thermal history when a correction paint is applied and baked to correct paint film cracks in the score processed area. Furthermore, the method of opening an easy-open lid varies depending on the purchaser of the can. , a relatively large moment acts on the adhesive fulcrum between the tab and the lid, making it easy for the adhesive fulcrum to break. Furthermore, if the tab is not pulled correctly in the tab direction, a moment will still act on the adhesive fulcrum, making it easy for the adhesive fulcrum to break. Therefore, the technical problem of the present invention is that the adhesive fixation of the opening tab to the can lid for shearing the score of the can lid is effective against the moment applied during the opening operation, regardless of retort sterilization or other thermal history. To provide an easy-to-open lid that can be reliably opened until the completion of the opening operation without peeling off due to (Means for Solving the Problems) The present invention provides a lid member made of a rigid metal material with a score that defines a portion to be opened so as to reach halfway in the thickness direction of the metal material, and an opening tab. In an easy-to-open can lid that is fixed to a can body by seaming, which is provided in the vicinity of the score shearing start point via an adhesive fulcrum, the adhesive constituting the adhesive fulcrum has an average main chain carbon per amide group. The crystallinity is in the range of 15% to 40%, and the dynamic elastic modulus is in the range of 0.8 × 10 ¹⁰ to 3.5 × 10 ¹⁰ dynes/cm at 25°C and relative humidity of 20% or less. It is characterized by being made of a polyamide adhesive within the range of ² . (Function) The adhesive for bonding and fixing the opening piece to the lid material is required to have properties completely different from those of the adhesive used for forming the side seam of a normal can body. That is,
Adhesives in side seams are subjected exclusively to shear forces, so adhesives that withstand high shear forces are good seam adhesives. On the other hand, when using an adhesive to fix the opening piece to the lid, a moment acts on the adhesive fulcrum, so it is important that the adhesive used can withstand such an opening moment. The present invention provides that among various polyamide adhesives, a polyamide adhesive whose average main chain carbon number per amide group, degree of crystallinity, and dynamic elastic modulus are within the above-mentioned certain ranges has a high moment-induced breaking force. This is based on the knowledge that it can serve as an excellent adhesion fulcrum between the active lid material and the opening piece. Generally, in polyamides, the average number of carbon atoms in the main chain per amide group is related to the strength of intermolecular hydrogen bonds, and also has a significant effect on cohesive force, hardness, and affinity for water. . If the average number of carbon atoms in the main chain per amide group is less than 6.1, the melting point will be too high and the possible bonding temperature will be too high, making the bonding operation difficult. Inconveniences such as scorching of the coating film occur, and it becomes difficult to control the cooling of the adhesive, which tends to make it difficult to control the degree of crystallinity, which will be described later. In addition, this polyamide is extremely sensitive to water, and its mechanical properties vary greatly depending on the moisture content, and furthermore, the moisture content tends to cause defects such as foaming in the bonded area. In addition, amide group 1
If the average number of carbon atoms in the main chain exceeds 15.0, the cohesive force of the polyamide itself tends to decrease, resulting in decreased heat resistance and decreased adhesion of the correction paint to the score area during baking or retort sterilization. In severe cases, the adhesive fulcrum may even become misaligned. Furthermore, the adhesion to the primer coating also decreases. In the present invention, polyamide with the above-mentioned molecular chain structure is selected, but it alone is insufficient as an adhesion fulcrum between the lid material and the opening piece, and the degree of crystallinity is
It is also important to maintain it within the range of 15-40%.
Here, the crystallinity is the crystallinity of the polyamide that actually serves as the adhesive fulcrum, and in more detail,
It means the degree of crystallinity measured by line diffraction method. Of course, in addition to the X-ray diffraction method, methods such as the density method and the heat of fusion method are known for measuring the degree of crystallinity, and there is a difference of 1 Since there is a one-to-one correspondence, the degree of crystallinity referred to in the present invention may be obtained by correcting this correspondence. This crystallinity is 40%
If it is higher than , the elastic modulus becomes too large and the mechanical properties tend to become brittle, making it unsuitable as an adhesive fulcrum. In addition, in polyamide adhesive fulcrums with such a high degree of crystallinity,
Since the shrinkage during the solidification process after welding is large, residual stress is generated internally or at the interface, and the adhesion tends to deteriorate over time. On the other hand, polyamide adhesive fulcrums with a crystallinity of less than 15% have extremely low heat resistance and hot water resistance, as well as low elastic modulus.
It is not possible to sufficiently increase the initial opening force. In the present invention, it is also important to select a polyamide whose dynamic modulus at 25° C. and 20% relative humidity is in the range of 0.8×10 ¹⁰ to 3.5×10 ¹⁰ dynes/cm ² . Here, the dynamic elastic modulus is an elastic modulus measured when a periodic strain of a constant frequency is applied, and more specifically refers to an elastic modulus measured by a method of an example described later. The unsealing performance of an easy-to-open lid using an adhesive fulcrum can be evaluated based on the relationship between the peeling force (Kg) in a 90 degree direction and the displacement (cm) at a pulling speed of 200 mm/sec. FIG. 1 shows polyamides whose dynamic elastic modulus is within the range of the present invention (curve A, 1.5×10 ¹⁰ dyne/cm ² , curve B,
2.7×10 ¹⁰ dyne/cm ² ), a polyamide whose dynamic elastic modulus is lower than the range of the present invention (curve C, 0.68×10 ¹⁰ dyne/cm 2 )
cm ² ) and dynamic elastic modulus higher than the range of the present invention (curve D, 4.8×10 ¹⁰ dyne/cm ² ),
This is a plot of the relationship between the above peeling force (Kg) and displacement (mm). This figure 1 shows that the larger the initial opening force is obtained as the final peeling force at the rise is larger, and the larger the integral value of these curves, that is, the 90 degree peeling work, the stronger the adhesive fulcrum. Show that. If the dynamic elastic modulus is smaller than the above range,
An initial opening force sufficient to start shearing the score may not be obtained, or the moment applied to the fulcrum may easily cause the adhesive fulcrum to shift position.
Furthermore, if the dynamic elastic modulus is larger than the above range, even if a high initial opening force is obtained, the adhesive fulcrum cannot follow the displacement, stress is concentrated at one point, and the adhesive fulcrum is destroyed. According to the present invention, by using a polyamide adhesive that satisfies all the above-mentioned requirements as an adhesive fulcrum, the initial peeling force required for initial opening can be increased.
8.0Kg or more, and 90 per ^cm2 of unit bonding area
It is possible to increase the amount of work required for peeling to a value greater than 2.5 kg cm, which is required for complete opening. (Operations and Effects of the Invention) According to the present invention, not only is there provided an easy-to-open lid with an adhesive-fixed opening tab that is resistant to correction paint application and baking and retort sterilization, but also the lid material is secured to the can body by seaming. Even though it is made of a rigid metal material used in the packaging, it effectively prevents the joint fulcrum from breaking during opening, and has the advantage that the opening operation can be performed stably even after a long period of time. (Description of Preferred Embodiments of the Invention) Lid Structure As shown in Figures 2, 3 and 4, the easy-to-open can lid 1 of the present invention is made of a rigid metal material 3 provided with a primer coating 2. . This lid material 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 which engages sealingly during tightening. Inside the annular rim portion 5 there is a portion 9 to be opened, demarcated by scores 8 . This opening portion 9 may substantially coincide with a large portion of the panel portion 6;
A portion of the panel portion 6 may be an opening portion.
As shown in the enlarged sectional view of FIG. 3, the score 8 is provided so as to reach the middle of the metal material 3 in the thickness direction, and is easily sheared when the package is opened by a 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 polyamide 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 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 peeling force (moment) is applied to the adhesive layer 16 between the fulcrum part 13 and the opening part 9. According to the invention, adhesive layer 1
By using the specific polyamide adhesive mentioned above as No. 6, it is made to be able to withstand the above-mentioned peeling force. Next, this opening tab 10
By pulling at an angle of approximately 90 degrees to the lid 1, the score 8 is sheared from the location where the cut was made. Metal materials Metal materials for the lid include light metal plates such as aluminum, various surface steel plates, such as steel plates plated with zinc, tin, chromium, alumium, etc., or chemically coated surfaces with chromic acid, phosphoric acid, etc. It is made of a material on which a treated film is formed, and any metal material having pressure deformation resistance and rigidity that can withstand seaming can be used. The thickness of the material is generally 0.10 to 0.40mm, especially
It is desirable that it be within the range of 0.12 to 0.35 mm.
Further, the opening tab is also made of the various metal materials mentioned above, especially aluminum. The lid material of the present invention is suitable for metal materials that are difficult to rivet, such as chromate surface-treated steel sheets, especially electrolytic chromic acid treated steel sheets, chromate-treated nickel-plated steel sheets, chromate-treated iron/tin alloy-plated steel sheets, chromate-treated tin/nickel plates. It is suitably applied to alloy-plated steel sheets, chromate-treated iron/tin/nickel alloy-plated steel sheets, and chromate-treated aluminum-plated steel sheets. 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 metallic chromium layer is determined by the combination of corrosion resistance and workability, and the amount is between 30 and 300 mm.
mg/m ² , preferably in the range of 50 to 250 mg/m ² . The thickness of the nonmetallic chromium layer is related to paint film adhesion and adhesive peel strength, and is preferably in the range of 4 to 40 mg/m ² , particularly 7 to 30 mg/m ² in terms of chromium content. . Primers These metal materials are typically coated with an adhesive primer that also serves as a protective base coat for use in the manufacture of can lids. As such a primer coating, any primer coating known per se that exhibits excellent adhesion to the aforementioned metal plate and also to thermoplastic adhesives composed of amide repeating units may be used. be done. 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 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 phenol-epoxy paints made of resol-type phenol-aldehyde resins derived from various phenols and forlarbite, and bisphenol-type epoxy resins. In particular, it is a paint containing a phenolic resin and an epoxy resin in a weight ratio of 90:10 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. 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. Polyamide Adhesive In the present invention, the first condition is to use a polyamide having an average number of main chain carbon atoms per amide group in the range of 6.1 to 15.0, particularly 7.0 to 14.0. The polyamide may be a homopolyamide, a copolyamide, or a blend thereof, in which the starting monomer component is ω-aminocarboxylic acid and/or diamine dicarboxylic acid salt. Examples of suitable polyamides are:

[Evaluation of adhesive physical properties]

1 Average number of main chain carbon atoms per unit amide group Here, the value calculated from the amount of monomer charged during polymerization is shown, but it is also possible to determine it by gas chromatography etc. after directly hydrolyzing the adhesive resin itself, and both values can be calculated. The difference is at most 5
It was %. In addition, when a resin other than polyamide such as polyolefin was contained, the resin was excluded from the calculation. 2 Crystallinity The crystallinity is measured mainly by wide-angle X using standard samples with known crystallinity for each polyamide resin.
This was done by line diffraction method. In addition, it is possible to use the latter method after confirming the compatibility between wide-angle X-ray diffraction and other density methods or calorimetry methods such as differential thermal analysis for standard samples, from the viewpoint of accuracy in measuring crystallinity. It was hot. Samples are mainly collected from actual can tests by removing the metal by melting or scraping, and in the case of the density method or calorimetry method, the weight or volume of the attached primer is corrected when calculating the density. I did it. Three sample pieces were measured for each sample number, and the arithmetic mean value of these was taken as the measured value. 3 Dynamic Modulus of Elasticity There are various principles and methods for measuring dynamic modulus of elasticity, and they are used depending on the shape of the sample, etc. Here, although the measurement method is not limited thereto, measurements were carried out at 110 Hz using a Leovibron DDV-type manufactured by Toyo Baldwin. Sample pieces were mainly taken from the lids used in the actual can tests, as in the previous crystallinity test, but the influence of the adhering primer on the measured dynamic elastic modulus was evaluated using the following parallel model: I made a correction. E=x _p E _p + (1-x _p ) E _a where xp is the ratio of the thickness of the primer layer when the total thickness of the sample piece is 1, and E is the dynamic elastic modulus of the sample piece actually measured. , Ep is the dynamic elastic modulus of the primer, and Ea is the dynamic elastic modulus of the adhesive layer. Each sample was left in an atmosphere with a relative humidity of 20% or less for a sufficiently long time before being subjected to measurement. The dynamic elastic modulus measured in this way showed a tendency to be slightly higher by 5 to 20% compared to the original film before adhesion, but this was different from when the original film was heated in a predetermined oven, which is post-heating after adhesion. The agreement was approximately within the measurement accuracy. Three sample pieces were measured for each sample number, and the arithmetic mean value of these was taken as the measured value. [Evaluation of Adhesive Properties] 1. Peel Strength After the tab was adhered under predetermined adhesive conditions, the peel strength of this lid was measured by the following method. In other words, if the tab is lifted up and the initial opening of the score section is performed, and the tab is raised vertically to the lid panel surface, the adhesive part will be peeled at 90 degrees when the tab ring is perpendicular to the lid panel surface. A tensile test was conducted as follows. For the tensile test, an Instron type tensile testing machine was used, and the measurement was carried out at room temperature at a tensile speed of 200 mm/min to evaluate the initial strength and peeling work. Peeling work is calculated by integrating the area within the peel strength curve on the chart using an automatic integrator, and then calculating the adhesive area of 1 cm ^2.
It was calculated by converting it into a hit. Measurements were performed five times for each sample number, and the arithmetic mean value of these measurements was taken as the measured value. 2 Lid openability The openability of the lid is measured immediately after adhesion, after applying correction paint to the score on the inner and outer surfaces of the lid, and after performing the prescribed oven baking, and after double-sealing the lid to the 211 diameter flange can body. After tightening the flat lid filled with dressing tuna.
When retort sterilization was performed at 116°C for 90 minutes, 20 panelists were asked to open 5 cans each immediately after retorting and after 6 months at 37°C, for a total of 100 cans. As a result, the number of cans that could not be opened because the tab came off during opening, and the number of cans that could not be opened initially among these opening failures are shown in the box. Example 1 Plate thickness 0.20 mm, surface nonmetallic chromium amount 15 mg/m ² ,
Epoxy/phenol paint was applied to both sides of a regular tain-free steel (TFS) plate with a metallic chromium content of 100 mg/ ^m2 to a thickness of 5 μm after baking, and baked at 210°C for 10 minutes. . This painting
Form the TFS plate into a 211 diameter lid using a press,
Next, a sealing compound was applied to the curled portion by a conventional method and dried. Then add a diameter of 58 to the outside of the lid.
Score processing was performed in a circular shape of mm so that the score residual thickness/steel plate thickness was 0.23. On the other hand, on the adhesive side of a 0.46-thick aluminum coil (#5082) material, epoxy urea paint was coated on the opposite side of the epoxy phenol paint so that the thickness after baking was 5 μm. Slit to 30mm. On the other hand, a 50 μm thick film having the composition shown in Table 1,
A microslit film with a width of 8 mm was laminated by high-frequency induction heating and then press-molded into a tab having the shape shown in the figure. The tab created like this,
Each adhesive was heated to a temperature at least 30° C. higher than the melting point of each adhesive using high-frequency heating to adhere to the previously formed lid so that the distance from the score to the adhesive fulcrum was 6 mm. In this case, the width of the adhesive layer at the adhesive fulcrum portion was approximately 7 mm, and the area of the adhesive portion was approximately 40 mm ² . Note that when adhesives No. 2 and No. 9 were used for bonding, after heating the bond, a rapid cooling operation was performed by hitting with a cooling body in which a refrigerant of about -30° C. was circulated. After adhesion, samples No. 1 to No. 7 were coated with epoxy phenol paint on the inner and outer score portions, and then baked at 200°C for 4 minutes, and samples No. 8 to No. 13 were coated with epoxy After applying water-based paint
Baking was performed at 170°C for 4 minutes. Table 1 shows the results of evaluating the adhesive properties of the lids prepared in this way, together with the physical properties of each adhesive. According to these results, when the average number of carbon atoms in the main chain per unit amide group of polyamide adhesives is low and is less than 6.0, although the initial peel strength is relatively high, sufficient peel work cannot be obtained, and the opening of the lid becomes difficult. Even though some initial opening is achieved,
It is difficult to shear the score area and the tab tends to separate from the adhesive fulcrum. Furthermore, if the average number of main chain carbon atoms per unit amide group is more than 15.0, the initial peel strength is low, making initial opening extremely difficult, resulting in tab displacement and peeling, and as a result, tab detachment tends to increase. It is in. When the average main chain carbon number per unit amide group is 6.1 or more and 15.0 or less, the peel strength is well-balanced, the lid opening is good in all cases, and the opening performance is stable even after storage in actual cans. showed that. Example 2 A tab device lid was prepared in the same manner as in Example 1, except that the adhesive shown in Table 2 was used, and various evaluations were conducted in the same manner as before. In addition, sample No. 15
and No. 17 are samples in which a nucleating agent is added as an additive to the adhesive, and the crystallization properties are significantly different from that of the base resin. For sample Nos. 14 and 15, the above-mentioned epoxy/phenol paint was used as the score correction paint.
Baked at 200℃ for 4 minutes. Samples No. 17 to 22 were baked at 170℃ for 4 minutes using the same epoxy water-based paint. Sample No. 16 was baked at 170℃ for 4 minutes using epoxy acrylic paint.
Baking was performed at 175°C for 10 minutes to obtain each prescribed correction lid. Table 2 shows the results of evaluating the adhesive properties of the lids prepared in this way, together with the physical properties of each adhesive. According to these results, if the crystallinity of the polyamide adhesive exceeds 40%, even if a certain degree of high initial peel strength is obtained, sufficient peeling work cannot be obtained, and initial opening may not occur during opening. However, when the score part is sheared and opened, the tab is often detached, making it extremely difficult to open the lid. Furthermore, if the crystallinity is lower than 15%, a sufficiently high initial peel strength cannot be obtained, and initial opening tends to be difficult, and the tab may come off due to misalignment or peeling. Moreover, this tendency is further promoted after retort sterilization. When the crystallinity was 15% or more and 40% or less, the peel strength was well-balanced and the opening property was good, and the lid maintained good opening property even after retort sterilization or storage. Example 3 A tab adhesive lid was made in the same manner as in the previous example except that 0.35 aluminum material (#5082) was used as the lid material and the adhesive listed in Table 3 was used as the adhesive, and various evaluations were performed. Ta. Samples No. 25 and 26 were made by mixing glass fiber with the base resin to change the dynamic elastic modulus of the adhesive itself. Samples No. 23 to 28 were baked at 200℃ for 4 minutes using the epoxy/phenol paint as the score correction paint, and samples No. 29 to 31 were baked at 170℃ for 4 minutes using the same epoxy water-based paint. Each of them obtained a predetermined correction lid. In Table 3,
The results of evaluating the adhesive properties of the lids made in this way are shown together with the physical properties of each adhesive. According to this result, the temperature of polyamide adhesive at 25℃
Dynamic modulus of elasticity at relative humidity of 20% or less is 3.5×
If it exceeds 10 ¹⁰ dyne/cm ² , sufficient peeling work will not be obtained in terms of peel strength, and the tab will often come off when shearing the score area, and the initial opening property will also tend to be poor because the initial strength is low. The opening of the lid is significantly inferior. In addition, the dynamic elastic modulus is
When breaking 0.8×10 ¹⁰ dyne/cm ² , initial opening tends to be difficult due to a significant drop in initial peel strength, resulting in tab misalignment,
More detachment occurs due to peeling. Dynamic modulus is 0.8
In the range of ×10 ¹⁰ to 3.5 × 10 ¹⁰ dyne/cm ² , initial strength and peeling work above a certain level are ensured in terms of peel strength, so initial opening of the lid can be performed stably. Furthermore, even when opening the score part by shearing, stable opening was possible without the adhesive fulcrum being dislodged. Example 4 Using a 0.23 tin tin plated steel plate and a 0.23 thin nickel plated steel plate as the lid material, spot coat an epoxy/urethane adhesive around the outer tab adhesive area in advance and dry it, then apply the spot coat on the inner and outer surfaces. Epoxy on the entire surface except for
A phenol-based paint was applied so that the film thickness after baking was 5 μm, and baking was performed at 210°C for 10 minutes. Forming the lid The following steps are the same as in the previous example. After the tabs using the adhesives of samples No. 5 and 18 are heat-bonded under the specified conditions, the score parts are coated with the epoxy/phenol paint described above. Then, correction baking was performed with an epoxy water-based paint to obtain a correction lid. When various adhesive properties of these tabs were evaluated, sample No. 5 had an initial peel strength of 12.6 kg and a peeling work of 4.8 kg cm, while sample No. 18 had a stable peel strength of 11.6 kg and 11.6 kg cm, respectively. The strength achieved was as follows, and no problems occurred in the opening characteristics of the lid.

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【table】 [Brief explanation of the drawing]

FIG. 1 is a graph plotting the relationship between the peeling force in the 90-degree direction and the amount of displacement for various polyamide adhesives, and FIG. 2 is a top view of the easy-open can lid of the present invention. Figure 3 is line A- of the can lid in Figure 2.
4 is an enlarged sectional view of essential parts of the can lid of FIG. 2; FIG. 1 is an easy-to-open can lid, 2 is a primer coating film, 3 is a metal material, 6 is a panel part, 8 is a score, 9 is a part to be opened, 10 is a tab for opening, 11 is a tip for tearing a score, 12 13 is the gripping part, 13 is the fulcrum part, 16
indicates a polyamide adhesive layer.

Claims (1)

[Claims] 1 A score is provided on a lid made of a rigid metal material to define the part to be opened, reaching halfway in the thickness direction of the metal material, and an opening tab is provided near the score shearing start point via an adhesive fulcrum. In an easy-to-open can lid that is fixed to a can body by seaming, the adhesive constituting the adhesive fulcrum has an average number of main chain carbon atoms per amide group in the range of 6.1 to 15.0, and has a high crystallinity. is in the range of 15 to 40% and 25℃
and dynamic elastic modulus of 0.8 at relative humidity of 20% or less.
An easy-open can lid characterized in that it is made of a polyamide adhesive in the range of ×10 ¹⁰ to 3.5 × 10 ¹⁰ dynes/cm ² .