cap

Abstract

To provide a cap with excellence in plug openability.SOLUTION: A cap has a disk-shaped top plate part and a cylindrical skirt part provided on the peripheral edge part of the top plate part, the top plate part includes a substrate and a resin coating provided on the inner surface side of the cap of the substrate, the resin coating includes a cap body containing a polyester resin and a lubricant, and a sealing member that is separately from the cap body and is provided in the cap body so as to face the top plate part and has an outer diameter smaller than an inner diameter of the skirt part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cap for closing a can container. [Background technology]

[0002] Conventionally, paints mainly containing epoxy resins such as epoxy phenolic resins have been widely used as inner surface paints for metal caps that seal the mouths of can containers (see, for example, Patent Documents 1 and 2). On the other hand, there is known a cap that includes a metal cap body and a resin sealing member provided separately within the cap body in order to reduce the opening torque required when opening the cap (see, for example, Patent Documents 3 and 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-208795 [Patent Document 2] Patent No. 6534377 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-217295 [Patent Document 4] Japanese Patent Application Publication No. 2017-178421 Summary of the Invention [Problem to be solved by the invention]

[0004] In the caps described in Patent Documents 3 and 4, friction between the inner surface of the top plate of the cap body and the sealing member is thought to have a significant effect on the openability. Therefore, the present inventors attempted to reduce this friction by adding a lubricant to the inner coating of the cap body. Specifically, when the present inventors added a lubricant to a coating made of epoxy phenol resin as the inner coating of the cap body, they encountered the problem that the friction-reducing effect of the lubricant was not exerted and the cap opening torque could not be sufficiently reduced (see Example 8 in the Examples section below).

[0005] Therefore, an object of the present invention is to solve the above problems and provide a cap with excellent openability. [Means for solving the problem]

[0006] The inventors newly discovered that adding a lubricant to a coating made of polyester resin exerts the friction-reducing effect of the lubricant, thereby reducing the torque required to open the cap, and thus completed the present invention.

[0007] That is, according to the present invention, a cap body having a disk-shaped top plate portion and a cylindrical skirt portion provided on the peripheral edge of the top plate portion, the top plate portion including a substrate and a resin coating that coats the substrate on the inner surface side of the cap, the resin coating including a polyester resin and a lubricant; a sealing member that is formed separately from the cap body, that is provided within the cap body facing the top plate portion, that has an outer diameter smaller than the inner diameter of the skirt portion, and that is not adhered to the cap body; Equipped with 、 The lubricant contains a hydrocarbon wax and a fatty acid ester wax. A cap is provided. [Effects of the Invention]

[0008] According to the present invention, a cap with excellent openability is provided. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a side view showing, in partial cross section, the configuration of a cap and a mouth portion of a can container according to an embodiment of the present invention. [Figure 2] FIG. 3 is a side view showing the configuration of the cap, partially in cross section. [Figure 3] FIG. [Figure 4] FIG. [Figure 5] 4 is a flowchart showing a method for manufacturing the cap. [Figure 6]4 is a flow chart schematically illustrating a part of the manufacturing method of the cap. DETAILED DESCRIPTION OF THE INVENTION

[0010] A cap 1 according to one embodiment of the present invention will be described below with reference to Figures 1 to 4. The following description is intended to explain the present invention in detail and is not intended to limit the present invention.

[0011] Fig. 1 is a side view, partially in cross section, showing the configuration of a cap and the mouth of a can container according to one embodiment of the present invention. Fig. 2 is a side view, partially in cross section, showing the configuration of the cap 1. Fig. 3 is a cross-sectional view showing the configuration before the cap 1 is seamed and fixed to the can container 100. Fig. 4 is a cross-sectional view showing the configuration after the cap 1 has been seamed and fixed to the can container 100.

[0012] As shown in Fig. 1, the cap 1 is attached to the mouth 110 of the can container 100, and is sealed by being drawn and seamed to the mouth 110 of the can container 100 while the cap 1 is in the crowning state, thereby sealing the can container 100. By sealing the can container 100, the cap 1, together with the can container 100, constitutes a bottle-type can sealed and filled with a liquid such as a beverage.

[0013] Here, the can container 100 is a so-called bottle-shaped container for containing beverages or the like. For example, the can container 100 is made of a metal material such as an aluminum alloy or a surface-treated steel plate with resin films laminated on both sides. The can container 100 is formed into a cylindrical shape with different outer diameters, one end of which is reduced in diameter. The can container 100 has a mouth 110 at one end for discharging the contained beverage. The mouth 110 has a jaw portion 111, a male screw portion 112, and a curl portion 113 on its outer circumferential surface, from the bottom side of the can container 100 toward the end.

[0014] The jaw portion 111 is configured to protrude in an annular shape. The curled portion 113 is formed to have a smaller diameter than the male thread portion 112. The curled portion 113 is also configured to be smaller than the inner diameter of the cap 1. The curled portion 113 is configured by folding the end of the mouth portion 110 one or more times. The curled portion 113 forms an opening for discharging the beverage stored in the can container 100.

[0015] As shown in FIGS. 1 to 4, the cap 1 includes a cap body 11 and a sealing member 12 provided separately within the cap body 11.

[0016] The cap body 11 is made of a material in which a resin coating is formed on a metal material such as an aluminum alloy. In this embodiment, a specific resin coating is provided on the inner surface of the cap body 11. This resin coating will be described in detail later. The cap body 11 is formed by drawing a thin, flat plate-shaped material into a cup shape, followed by various forming processes such as knurling and roll-on forming.

[0017] The cap body 11 includes a disk-shaped top plate portion 21 and a cylindrical skirt portion 22 that is integrally provided on the peripheral edge of the top plate portion 21. The cap body 11 is configured such that the top plate portion 21 and the skirt portion 22 are integrally connected by annular, curved corner portions 23.

[0018] The top plate 21 is disk-shaped and has a flat main surface. One end of the skirt 22 is continuous with the top plate 21 via a corner 23, and the other end is open. The skirt 22 is provided with a plurality of knurls 31 with vent slits 31a, a plurality of recesses 32, a female screw 33, and a tamper-evident band 34 from the end on the top plate 21 side to the open end.

[0019] The top plate portion 21 includes a substrate and a resin coating (hereinafter also referred to as the inner resin coating) provided on the inner surface of the substrate facing the cap, and the inner resin coating includes a polyester resin and a lubricant. Specifically, the inner resin coating mainly includes a polyester resin and includes a lubricant as an additive. The inner resin coating may further include additives other than the lubricant, as necessary. The resin coating can be formed on the substrate by a known method, for example, by baking. The top plate portion 21 may include a known resin coating, such as an epoxy phenol resin or a polyester resin, on the outer surface of the substrate facing the cap. Furthermore, the outer surface of the substrate facing the cap may be printed.

[0020] As mentioned above, the substrate is typically a metal substrate such as an aluminum alloy.

[0021] The polyester resin for forming the inner resin coating may be a commercially available polyester resin that is commonly used to form resin coatings for bottle-shaped cans. The polyester resin refers to a resin made of polyester.

[0022] The inner resin coating contains a lubricant in addition to a polyester resin. The lubricant preferably contains a hydrocarbon wax. The hydrocarbon wax is present in the resin coating in the form of dispersed solid particles, and therefore can also be called a "dispersed wax" or "particulate wax." The hydrocarbon wax is preferably a polyethylene wax. The hydrocarbon wax is added in an amount of, for example, about 2 to about 7% by mass, preferably about 3 to about 7% by mass, relative to the polyester resin. Using a hydrocarbon wax as a lubricant can significantly reduce the opening torque of the cap 1 and significantly improve the openability of the cap 1.

[0023] The mechanism by which hydrocarbon waxes exert such remarkable effects is considered below. Hydrocarbon waxes have a high melting point, and even when heated during cap production, they are believed to remain dispersed in the resin coating in the form of solid particles. Therefore, the hydrocarbon wax can form irregularities on the surface of the inner resin coating, which is primarily composed of polyester resin. These irregularities are believed to improve the contact between the inner resin coating and the can container 100, resulting in point contact rather than surface contact, thereby improving the smoothness between the inner resin coating and the can container 100. Furthermore, because the polyester resin has a low crosslink density, the polyester resin flexibly conforms to the solid particles of the hydrocarbon wax during cap formation, presumably enabling the solid particles of the hydrocarbon wax to be stably held without falling off the surface of the resin coating.

[0024] On the other hand, when an inner resin coating is formed by adding a hydrocarbon-based wax to an epoxy phenolic resin, the crosslink density of the epoxy phenolic resin is higher than that of the polyester-based resin, and therefore the flexibility of the epoxy phenolic resin is low. In particular, it is difficult to stably retain the solid particles of the hydrocarbon wax on the surface of the resin coating during cap molding, and the solid particles of the hydrocarbon wax are likely to fall off from the surface of the resin coating.

[0025] When a hydrocarbon wax is used as a lubricant, the hydrocarbon wax may be used alone or in combination with other lubricants. Fatty acid ester waxes can also be used as other lubricants. Fatty acid ester waxes exist in either a molten or solidified state in the resin coating depending on the temperature, and therefore can also be referred to as "molten waxes." The fatty acid ester wax is preferably lanolin. The fatty acid ester wax is added to the polyester resin in an amount of, for example, about 2 to about 7% by mass, preferably about 3 to about 7% by mass. When a hydrocarbon wax is used in combination with a fatty acid ester wax as a lubricant, the second torque (i.e., the torque at the time of breaking the breaking portion 34a of the tamper-evident band portion 34 of the cap, as described below) can be further reduced compared to when a hydrocarbon wax is used alone, thereby further improving the ease of opening the cap. Fatty acid ester waxes tend to exist in a molten state and have the effect of reducing the coefficient of dynamic friction, thereby reducing the second torque by reducing the frictional resistance during the cap opening operation.

[0026] The mechanism by which the fatty acid ester wax, when used in combination with a hydrocarbon wax, can achieve the above-mentioned effects is discussed below. Fatty acid ester waxes have a low melting point, e.g., 40°C, and can volatilize from the surface of the resin coating when heated during cap production (e.g., when drying in an oven after printing on the outer surface of the cap). Even if the fatty acid ester wax volatilizes from the surface of the resin coating, the low crosslink density of the polyester resin that makes up the resin coating allows the fatty acid ester wax present inside the resin coating to seep out to the surface, further improving the slip between the inner resin coating and the can container 100 when opening the lid. Furthermore, the fatty acid ester wax contributes to the dispersion of solid particles of the hydrocarbon wax in the resin coating and to preventing the solid particles of the hydrocarbon wax from falling off the surface of the resin coating during cap molding.

[0027] On the other hand, when an inner resin coating is formed by adding a fatty acid ester wax to an epoxy phenolic resin, the crosslink density of the epoxy phenolic resin is higher than that of the polyester resin, so the fatty acid ester wax present inside the resin coating is less likely to seep out to the surface, and it is thought that it is unable to exert its effect as a lubricant.

[0028] As shown in Figures 1 and 2, the multiple knurl portions 31, multiple recesses 32, female screw portions 33 and tamper evidence band portions 34 are formed by processing a cup-shaped molded product consisting of a top plate portion 21, a cylindrical skirt portion 22 in which the multiple knurl portions 31, multiple recesses 32, female screw portions 33 and tamper evidence band portions 34 are not molded, and a corner portion 23, such as by knurling molding or roll-on molding.

[0029] The knurl portion 31 has a vent slit 31a and protrudes from the inner peripheral surface of the skirt portion 22. In other words, the knurl portion 31 forms a protrusion with a portion cut out from the inner peripheral surface of the skirt portion 22 by recessing a portion of the skirt portion 22 radially inward.

[0030] The multiple knurl portions 31 are provided in the circumferential direction of the skirt portion 22. The vent slit 31a is a cut that allows gas and the like to be released from inside the can container 100 when the can container 100 is opened. The vent slit 31a is formed by cutting the end of the knurl portion 31 on the top plate portion 21 side.

[0031] The diameter of the tangent circle connecting the ends of the plurality of knurl portions 31 on the vent slit 31a side, in other words, the ends of the plurality of knurl portions 31 on the top plate portion 21 side, is set to be smaller than the outer diameter of the sealing member 12. Therefore, the plurality of knurl portions 31 form a locking portion that restricts the movement of the sealing member 12 arranged on the top plate portion 21 in a direction away from the top plate portion 21.

[0032] The recess 32 is formed by a portion of the skirt portion 22 being recessed from the outer peripheral surface side to the inner peripheral surface side. Specifically, the recess 32 is formed by a portion of the skirt portion 22 being recessed inward in the radial direction of the skirt portion 22, thereby forming a protrusion on the inner peripheral surface of the skirt portion 22.

[0033] The recess 32 has an inclined surface 32a on the inner side of the skirt portion 22. The inclined surface 32a is inclined in the axial direction away from the top plate portion 21 and radially inward. In other words, the height of the recess 32 from the inner circumferential surface of the skirt portion 22 increases as the recess 32 moves away from the top plate portion 21, and therefore the inner surface of the recess 32 is inclined.

[0034] A plurality of recesses 32 are provided, preferably three or more; in this embodiment, four recesses 32 are provided. For example, the recesses 32 are arranged at approximately equal intervals along the circumferential direction of the skirt portion 22. The diameter of a tangent circle connecting the inclined surfaces 32a of the recesses 32 is configured to be the same as the outer diameter of the sealing member 12 at least in a portion of the axial direction. In other words, the inclined surfaces 32a are configured to be able to abut against the outer peripheral edge of the sealing member 12 in a portion of the axial direction, and are restricting portions that restrict radial movement of the abutted sealing member 12 and position the sealing member 12 in the radial direction. In other words, the recesses 32 center the sealing member 12 abutting against the inclined surfaces 32a relative to the cap body 11. The diameter of a tangent circle connecting the axially lowest ends of the inclined surfaces 32a is set larger than the diameter of a tangent circle connecting the radially innermost ends of the ends of the knurl portions 31 on the vent slit 31a side.

[0035] Furthermore, at least the portions of the inclined surface 32a of the plurality of recesses 32 that have the same diameter as the outer diameter of the sealing member 12 are arranged closer to the top plate 21 in the axial direction of the skirt portion 22 than the locking portion, which is the end of the knurl portion 31 on the vent slit 31a side. For example, the plurality of recesses 32 are arranged together with the plurality of knurl portions 31 in the circumferential direction of the skirt portion 22, and are arranged closer to the top plate 21 in the axial direction of the skirt portion 22 than the plurality of knurl portions 31.

[0036] In this embodiment, the multiple knurled portions 31 are provided at 13 locations, and the multiple recessed portions 32 are provided at four locations. For example, in the circumferential direction of the skirt portion 22, three knurled portions 31 are lined up at three locations, and four knurled portions 31 are lined up at one location, with one recessed portion 32 disposed between each row of knurled portions 31. In this embodiment, the multiple recessed portions 32 are disposed closer to the top plate portion 21 than the multiple knurled portions 31 of the skirt portion 22.

[0037] The female screw portion 33 is configured to be able to screw into the male screw portion 112 of the can container 100. The female screw portion 33 is molded together with the can container 100. In other words, the female screw portion 33 is not formed in the cap 1 before it is attached to the can container 100, but is formed when it is combined integrally with the can container 100.

[0038] The tamper evidence band portion 34 engages with the jaw portion 111 of the can container 100 in the direction in which the cap 1 moves away from the can container 100 and in the axial direction of the cap 1. The tamper evidence band portion 34 also has a breaking portion 34a that breaks when the cap 1 is opened and detaches from the skirt portion 22. That is, the tamper evidence band portion 34 is configured by forming a slit on the end side of the skirt portion 22, leaving the breaking portion 34a, and similar to the female screw portion 33, when combined integrally with the can container 100, it is shaped to the shape of the jaw portion 111 of the can container 100, thereby engaging with the jaw portion 111.

[0039] The corner portion 23 is, for example, an annular corner portion whose cross-sectional shape is curved at one center of curvature before the cap body 11 is seamed and fixed to the mouth portion 110 of the can container 100. During the drawing process for seaming and fixing the cap body 11 to the mouth portion 110 of the can container 100, a part of the corner portion 23 is pressed in the axial direction into a ring shape along the circumferential direction, thereby forming, for example, an annular corner portion whose cross-sectional shape is curved at at least two centers of curvature.

[0040] The sealing member 12 is configured separately from the cap body 11. That is, the sealing member 12 is disposed opposite the top plate portion 21 and the skirt portion 22, and is not bonded to the cap 1. Specifically, the sealing member 12 is configured in a disk shape and has an outer diameter larger than the diameter of the inscribed circle of the knurl portion 31 provided on the skirt portion 22 of the cap body 11. The sealing member 12 also has an outer diameter equal to the diameter of the inscribed circle of at least a portion of the inclined surface 32a of the recess 32 that protrudes radially from the inner circumferential surface of the skirt portion 22, specifically, the central portion in the axial direction of the inclined surface 32a.

[0041] The sealing member 12 is provided integrally with the cap body 11 by engaging, in the axial direction of the cap body 11, with an end portion provided with a vent slit 31a of a knurl portion 31 that protrudes radially from the inner peripheral surface of the skirt portion 22. In addition, the sealing member 12 is centered so that its center is located on the axis of the cap body 11 by engaging, in the radial direction of the cap body 11, with an inclined surface 32a of a recess 32 that protrudes radially from the inner peripheral surface of the skirt portion 22.

[0042] The sealing member 12 includes a disk-shaped sliding layer 41 and a disk-shaped sealing layer 42 laminated integrally with the sliding layer 41. The sealing member 12 is configured by integrally molding the sliding layer 41 and the sealing layer 42 using different resin materials. The sealing member 12 includes a flat plate portion 12a with a uniform thickness and a curved surface portion 12b whose outer surface on the outer periphery on the top plate portion 21 side is configured as a curved surface.

[0043] In other words, the sealing member 12 is formed in a disk shape, and the ridge portion on the top plate portion 21 side is configured as a curved surface with a predetermined curvature. In addition, the sealing member 12 is configured so that the curved surface portion 12b configuring the outer periphery side is thinner than the flat plate portion 12a, and the thickness of the curved surface portion 12b gradually decreases from the center side toward the outer periphery, with the tip of the curved surface portion 12b, i.e., the outer periphery, being configured to be the thinnest compared to the other portions.

[0044] A part of the flat plate portion 12a on the curved surface portion 12b side forms a sealing portion that abuts against the mouth portion 110 of the can container 100. The flat plate portion 12a is configured so that the sealing portion that abuts against the mouth portion 110 of the can container 100 is thicker than other portions.

[0045] The sliding layer 41 is made of a resin material that is relatively harder (harder) than the sealing layer 42. The sliding layer 41 is also made of a resin material that is not adhesive or tacky to the inner resin coating of the cap body 11. That is, the sliding layer 41 is not adhesive to the top plate portion 21, and slides on the top plate portion 21 while in contact with the top plate portion 21.

[0046] Examples of resin materials used for the sliding layer 41 include olefin-based resins such as polypropylene resin and polyethylene resin, polyester-based resins such as polyethylene terephthalate, styrene-based resins, and acrylic-based resins. In this embodiment, the sliding layer 41 is made of, for example, polypropylene resin. Note that pigments, lubricants, softeners, and the like can be added to the resin material used for the sliding layer 41 as appropriate.

[0047] 1 to 4, the sliding layer 41 is provided separately from the cap body 11 and faces the top plate portion 21 of the cap body 11. The sliding layer 41 is configured to be slidable with the top plate portion 21 of the cap body 11 depending on the resin material used. The sliding layer 41 is configured in a disk shape. The outer diameter of the sliding layer 41 is configured to be smaller than the inner diameter of the skirt portion 22, larger than the inscribed circle of the multiple knurled portions 31, and larger than the outer diameter of the curled portion 113 of the mouth portion 110.

[0048] The sliding layer 41 has a first flat plate portion 41a, a first curved surface portion 41b having a curved outer surface on the outer periphery of the top plate portion 21 side, a protrusion portion 41c provided on the first curved surface portion 41b on the sealing layer 42 side, and a thin portion 41d provided on the first flat plate portion 41a. The thickness of the first flat plate portion 41a from the center of the sliding layer 41 to the outer periphery side of the portion facing the curled portion 113 of the mouth portion 110 is uniform except for the thin portion 41d.

[0049] First curved surface portion 41b is curved on the top plate 21 side, so that the thickness of the portion from the outer periphery side to the outer periphery of the portion facing curled portion 113 of mouth portion 110 gradually decreases toward the outer periphery. Also, for example, first curved surface portion 41b has a portion adjacent to first flat plate portion 41a that is the same thickness as first flat plate portion 41a and is thicker than thin portion 41d.

[0050] The protrusion 41c is provided on the outer peripheral edge of the first curved surface portion 41b on the opening side of the skirt portion 22. The protrusion 41c is configured in the shape of an annular protrusion that is inclined with respect to the axial direction of the sliding layer 41 and the surface direction of the top plate portion 21 and curved or inclined toward the open end side of the skirt portion 22. The thickness of the protrusion 41c gradually decreases from the first curved surface portion 41b toward the tip.

[0051] The thin-walled portion 41d is provided on the main surface of the first flat plate portion 41a on the opening side of the skirt portion 22. The thin-walled portion 41d is an annular recess configured such that the main surface on the opening side of the skirt portion 22 is parallel to the main surface of the first flat plate portion 41a on the opening side of the skirt portion 22. The thin-walled portion 41d is continuous with the first flat plate portion 41a and the first curved surface portion 41b by inclined surfaces 41d1 and 41d2 that are inclined with respect to the main surfaces of the thin-walled portion 41d.

[0052] That is, the thin-walled portion 41d is continuous with adjacent portions on the inner and outer sides in the radial direction of the thin-walled portion 41d through the inclined surfaces 41d1 and 41d2, and therefore the adjacent portions on the inner and outer sides in the radial direction of the thin-walled portion 41d are thicker than the thin-walled portion 41d. In this embodiment, the adjacent portions on the inner and outer sides in the radial direction of the thin-walled portion 41d are portions of the first flat plate portion 41a excluding the thin-walled portion 41d and the first curved surface portion 41b.

[0053] Specifically, the thin-walled portion 41d has a main surface that is continuous with the main surface of the first flat plate portion 41a via an annular inclined surface 41d1. The inclination angle of the inclined surface 41d1 can be set as appropriate as long as the inclined surface 41d1 can guide the resin material of the sealing layer 42 to the thin-walled portion 41d.

[0054] The thin-walled portion 41d has a main surface that is continuous with the main surface of the first curved surface portion 41b via an annular inclined surface 41d2. The inclination angle of the inclined surface 41d2 can be set appropriately as long as the inclined surface 41d2 can guide the resin material of the sealing layer 42 to the thin-walled portion 41d.

[0055] The thin-walled portion 41d is provided on the main surface of the first flat plate portion 41a opposite to the top plate portion 21, i.e., on the main surface on which the sealing layer 42 is laminated. When the sealing member 12 is arranged on the cap body 11, the thin-walled portion 41d is provided at a position facing the base point of deformation of the top plate portion 21 when the cap 1 is attached to the can container 100 and the corner portion 23 of the cap body 11 is drawn. The thin-walled portion 41d is also provided at a position axially adjacent to a portion of the sealing layer 42 that faces the mouth portion 110 when the cap 1 is attached to the can container 100.

[0056] The radial width of the thin-walled portion 41d is set to a width that allows it to be located at a position facing the base point of deformation of the top plate portion 21 during drawing and at a position axially facing the mouth portion 110 when the sealing member 12 is placed on the cap body 11 and the cap 1 is fitted onto the mouth portion 110 of the can container 100. Here, the radial width of the thin-walled portion 41d is set appropriately in consideration of the difference between the inner diameter of the cap body 11 and the outer diameter of the sealing member 12, the shrinkage rate of the resin material constituting the sliding layer 41 and the sealing layer 42 of the sealing member 12, the amount of deformation of the sliding layer 41 due to an external force, dimensional accuracy, etc.

[0057] The sealing layer 42 is made of a resin material that is relatively lower in hardness (softer) than the sliding layer 41. Examples of resin materials used for the sealing layer 42 include olefin resins, polyester resins, styrene resins, and acrylic resins, and more preferably, a blend of a styrene elastomer and a polypropylene resin, a blend of low-density polyethylene and a styrene elastomer, and a polyester elastomer. In this embodiment, the sealing layer 42 is made of, for example, a mixed material of a styrene elastomer and a polypropylene resin. Note that pigments, lubricants, softeners, and the like can be added to the resin material used for the sealing layer 42 as appropriate.

[0058] 1 to 4, the sealing layer 42 is integrally provided on the main surface of the sliding layer 41 facing the mouth portion 110. The sealing layer 42 is configured to be disk-shaped. The outer diameter of the sealing layer 42 is configured to be larger than the outer diameter of the curled portion 113 of the mouth portion 110 and to be approximately the same as the outer diameter of the sliding layer 41.

[0059] 3, the sealing layer 42 has a second flat plate portion 42a having a thickness greater than that of other portions facing the mouth portion 110, a second curved surface portion 42b having a curved outer surface on the outer periphery of the top plate portion 21 side, an annular recess 42c provided on the main surface of the second curved surface portion 42b opposite the sliding layer 41 side, and a thick portion 42d provided on the second flat plate portion 42a. The main surface of the second flat plate portion 42a facing the curled portion 113 is flat. For example, the second flat plate portion 42a has the same diameter as the first flat plate portion 41a of the sliding layer 41. The second flat plate portion 42a, together with the first flat plate portion 41a, constitutes the flat plate portion 12a of the sealing member 12.

[0060] The second curved surface portion 42b has, for example, a main surface flush with the main surface of the second flat plate portion 42a that faces the curled portion 113. The second curved surface portion 42b is configured such that the thickness of the portion from the outer periphery of the portion facing the curled portion 113 of the mouth portion 110 to the outer periphery gradually decreases toward the outer periphery. The second curved surface portion 42b is layered on the first curved surface portion 41b and the protrusions 41c. The second curved surface portion 42b, together with the first curved surface portion 41b and the protrusions 41c, constitutes the curved surface portion 12b of the sealing member 12.

[0061] The recess 42c is, for example, an annular recess having a semicircular cross section. When the sealing member 12 is placed in the cap body 11, the recess 42c abuts, for example, against the end of the knurl portion 31 on the vent slit 31a side.

[0062] The thick portion 42d is made up of annular protrusions 42d1 and 42d2 protruding from both main surfaces of the second flat plate portion 42a. An annular first protrusion 42d1 protruding from the main surface of the thick portion 42d facing the slide layer 41 of the second flat plate portion 42a is disposed on the thick portion 42d. An annular second protrusion 42d2 protruding from the main surface of the thick portion 42d facing away from the slide layer 41 of the second flat plate portion 42a covers the first protrusion 42d1 in the axial direction and has a width wider than that of the first protrusion 42d1 in the radial direction.

[0063] The thick-walled portion 42d, together with the thin-walled portion 41d, constitutes a sealing portion that abuts against the mouth portion 110 of the can container 100. The thickness of the thick-walled portion 42d is set to a thickness such that the difference between its own thickness and the thickness of the second flat plate portion 42a is greater than the depth of the thin-walled portion 41d from the first flat plate portion 41a. That is, by setting the thickness of the first protrusion 42d1 to the same depth as the thin-walled portion 41d and by configuring the thick-walled portion 42d to further have the second protrusion 42d2, the sealing portion of the flat plate portion 12a of the sealing member 12 that abuts against the mouth portion 110 is configured to be thicker than the rest of the flat plate portion 12a.

[0064] Specifically, the radial width of the first protrusion 42d1 is the same as the width of the thin-walled portion 41d. That is, the radial width of the first protrusion 42d1 is formed to be a width that allows the first protrusion 42d1 to be located at a position facing the base point of deformation of the top plate portion 21 during drawing and at a position facing the mouth portion 110 in the axial direction when the sealing member 12 is arranged on the cap body 11 and the cap 1 is fitted onto the mouth portion 110 of the can container 100. Furthermore, specifically, the radial width of the second protrusion 42d2 is formed to be a width that allows the first protrusion 42d1 to be located at a position facing the mouth portion 110 in the axial direction when the sealing member 12 is arranged on the cap body 11 and the cap 1 is fitted onto the mouth portion 110 of the can container 100.

[0065] Here, the radial width of the first protrusion 42d1 and the radial width of the second protrusion 42d2 are appropriately set taking into consideration the difference between the inner diameter of the cap body 11 and the outer diameter of the sealing member 12, the shrinkage rate of the resin material constituting the sliding layer 41 and the sealing layer 42 of the sealing member 12, the amount of deformation of the sliding layer 41 due to external force, dimensional accuracy, etc.

[0066] When the cap 1 is placed with the top plate 21 facing upward, the sealing member 12 comes into contact with the end of the knurl 31 on the vent slit 31a side when it drops below the top plate 21, and is thereby locked by the knurl 31, restricting downward movement in the direction of gravity. When the cap 1 is placed on the mouth 110 of the can container 100, the thick-walled portion 42d of the sealing member 12 comes into contact with the mouth 110, and the thin-walled portion 41d is positioned opposite the base point of deformation of the top plate 21 when the corner portion 23 is drawn.

[0067] A method for manufacturing the cap 1 configured as above will be described below with reference to Figures 5 and 6. Note that the female screw portion 33 provided on the cap body 11 is formed when the cap 1 is capped onto the can container 100, and therefore the method for manufacturing the cap 1 will also be described as a method for manufacturing a bottle-shaped can, in which the cap 1 is attached to the can container 100 and the can container 100 is sealed.

[0068] First, for example, a metal plate material having the above-described inner resin coating formed on one main surface is processed to form a cup-shaped molded product from the metal plate material (step ST11). This molded product is a cap body 11 without the multiple knurls 31, multiple recesses 32, female screw portion 33, and tamper evidence band portion 34. That is, the molded product is composed of a top plate portion 21, a cylindrical skirt portion 22 without the multiple knurls 31, multiple recesses 32, female screw portion 33, and tamper evidence band portion 34, and corner portions 23.

[0069] Next, the sliding layer 41 is molded (step ST12). As a specific example, for example, the cap body 11 is placed on the lower mold in an orientation in which the top plate portion 21 is positioned downward in the direction of gravity. Next, a molten or softened resin material for the sliding layer 41 is supplied onto the top plate portion 21, and the supplied resin material is compression molded by the upper mold to form the sliding layer 41.

[0070] Next, the sealing layer 42 is molded (step ST13). As a specific example, for example, a molten or softened resin material for the sealing layer 42 is supplied onto the sliding layer 41, and the supplied resin material is compression molded using an upper mold to mold the sealing layer 42 on the sliding layer 41. Through these steps, the sealing member 12 in which the sliding layer 41 and the sealing layer 42 are laminated is manufactured in a molded product.

[0071] Next, the molded product is processed to form the cap body 11 (step ST14). As a specific example, the knurl portion 31, the vent slit 31a, the recess 32, the tamper-evident band portion 34, etc. are formed in the skirt portion 22 of the molded product. This process produces the cap body 11. When molding the cap body 11, the sealing member 12 is removed from inside the molded product.

[0072] Next, the sealing member 12 is inserted into the manufactured cap body 11 to manufacture the cap 1 (step ST15). Through these steps, the cap 1 is manufactured.

[0073] Next, a beverage or the like is filled into a separately manufactured can container 100. At this time, the can container 100 is in an upright position with the mouth portion 110 at the top. Next, the cap 1 is placed on the can container 100 (step ST16). Specifically, the cap 1 is placed in a position with the top plate portion 21 facing upward and is placed on the mouth portion 110 of the can container 100.

[0074] When the cap 1 is oriented with the top plate 21 facing upward, the sealing member 12 descends a certain distance away from the top plate 21, whereupon the sealing member 12 is supported by the end of the knurl portion 31, restricting its downward movement. When the cap 1 is placed over the mouth 110 in this state, the thick portion 42d of the sealing layer 42 of the sealing member 12 faces the mouth 110, and the mouth 110 and the thick portion 42d come into contact with each other, as shown in ST16 of FIG. 6 .

[0075] Next, the cap 1 is capped onto the can container 100 using the mold 200 of the molding device (step ST17). As a specific example of capping, with the cap 1 placed on the mouth portion 110, the corner portions 23 are drawn and the skirt portion 22 is rolled on.

[0076] Here, the mold 200 includes a first mold 210 that draws the corner portions 23, a second mold 220 that rolls onto the skirt portion 22, and a drive mechanism that drives the first mold 210 and the second mold 220. The first mold 210 also includes a fixed mold 211 that abuts against the top plate portion 21, and a movable mold 212 that applies a load to the corner portions 23 in the axial direction.

[0077] As shown in ST17 of FIG. 6 , a specific example of capping using a mold 200 will be described. First, the fixed mold 211 presses the top plate 21 to bring the mouth 110 into close contact with the sealing member 12. At this time, the sealing member 12 is in a state where the thick-walled portion 42d of the sealing layer 42 is compressed by the mouth 110. With the top plate 21 and the sealing member 12 positioned between the mouth 110 and the fixed mold 211, the movable mold 212 applies a downward load in the axial direction to the corner portion 23, thereby shaping the corner portion 23 and squeezing it into a predetermined shape. In addition, the skirt portion 22 is roll-formed by the second mold 220, thereby forming a female screw portion 33 in the shape of the male screw portion 112 of the can container 100 into the skirt portion 22.

[0078] After these moldings, the mold 200 is retracted from the cap 1, whereby the cap 1 is tightly fastened to the mouth 110 of the can container 100, completing the capping of the cap 1 (step ST18 in Figure 6), and a bottle-shaped can filled with a beverage is produced.

[0079] According to the cap 1 configured in this manner, the inner resin coating of the cap body 11 contains a polyester resin and a lubricant. This configuration can improve the openability of the cap 1. Using a hydrocarbon wax as the lubricant can significantly reduce the opening torque of the cap 1, thereby significantly improving the openability of the cap 1. Furthermore, using a hydrocarbon wax in combination with a fatty acid ester wax as the lubricant can further reduce the second torque of the cap 1 (i.e., the torque at the time of breaking the breaking portion 34a of the tamper evidence band portion 34 of the cap) compared to using a hydrocarbon wax alone, thereby further improving the openability of the cap 1. [Example]

[0080] The present invention will be described below based on examples.

[0081] [Experiment 1] In Experiment 1, the effect of adding a lubricant to the inner surface coating of the cap, which mainly contains polyester resin, was investigated.

[0082] [1] Manufacturing of bottle-shaped cans The bottle-shaped cans of Examples 1 to 6 were produced as follows: The caps of the produced bottle-shaped cans had the structure shown in FIG.

[0083] (Example 1) The inner surface of the cap was coated with a polyester resin paint containing polyethylene wax and lanolin as a lubricant. The inner surface paint was applied to one main surface (the inner surface of the cap) of an aluminum alloy plate (thickness: 0.23 mm) at a concentration of 50 mg / dm 2 The coating was baked on with a coating amount of 1000 ppm. The other main surface (the outer surface of the cap) was printed. The resulting metal plate was formed into a cup-shaped cap body having a top plate portion and a skirt portion by drawing. The cap body was approximately 18 mm high and weighed approximately 2.1 mg.

[0084] The sealing member was manufactured using the cap body as a mold as follows: A resin material for forming a sliding layer was supplied to the inner surface of the top plate of the cap body, the sliding layer was molded using the mold, a resin material for forming a sealing layer was supplied on top of the sliding layer, and the sealing layer was molded using the mold, thereby manufacturing a sealing member consisting of the sliding layer and the sealing layer.

[0085] The sealing member was removed from the cap body, and a knurl portion (reference numeral 31 in Figure 1), a recess (reference numeral 32 in Figure 1), and a tamper-evident band portion (reference numeral 34 in Figure 1) were molded on the skirt portion of the cap body, and the sealing member was inserted into the cap body to manufacture the cap.

[0086] The cap was capped onto the mouth of the container as follows: With the cap placed on the mouth of the container so that the tip (curl portion) of the mouth of the container came into contact with the sealing layer of the sealing member, a load was applied to the top plate of the cap body, and the corners were drawn downward while the skirt was rolled on. This resulted in the cap being tightly attached to the mouth of the container, producing the bottle-shaped can of Example 1.

[0087] (Example 2) A bottle-shaped can of Example 2 was produced in the same manner as in Example 1, except that a polyester resin paint containing no lubricant was used as the inner surface paint.

[0088] (Example 3) A bottle-shaped can of Example 3 was produced in the same manner as in Example 1, except that a polyester resin paint containing only lanolin as a lubricant was used as the inner surface paint.

[0089] (Example 4) A bottle-shaped can of Example 4 was produced in the same manner as in Example 1, except that a polyester resin paint containing only polyethylene wax as a lubricant was used as the inner surface paint.

[0090] (Example 5) A bottle-shaped can of Example 5 was produced in the same manner as in Example 1, except that a polyester resin paint containing polyethylene wax and lanolin as a lubricant, but with the amount of lanolin added reduced by 25% compared to Example 1, was used as the inner surface paint.

[0091] (Example 6) A bottle-shaped can of Example 6 was produced in the same manner as in Example 1, except that a polyester resin paint containing polyethylene wax and lanolin as lubricants was used as the inner surface paint, but the amounts of polyethylene wax and lanolin added were reduced by 25% compared to Example 1.

[0092] [2] Evaluation method The openability of the caps was evaluated for the bottle-shaped cans of Examples 1 to 6. The evaluation method was as follows.

[0093] (1) 1st torque and 2nd torque To measure the 1st torque, the body of the bottle-shaped can is fixed to a torque meter (Nidec-Shimpo Corporation TNK-50B-1), and the cap is held and rotated in the opening direction. The peak torque value when the cap starts to move from the origin is defined as the "1st torque."

[0094] To measure the second torque, reset the torque meter's reading after measuring the first torque, then rotate the cap in the opening direction again, sequentially breaking the breaking portions of the tamper-evident band. The peak torque value from the first torque until the cap is removed from the can is defined as the "second torque."

[0095] (2) Opening angle To measure the opening angle, rotate the cap from the closed position in the opening direction. The rotation angle of the cap when all the breaking portions of the tamper-evident band break is defined as the "opening angle."

[0096] [3] Evaluation results The evaluation results are shown in Table 1.

[0097] [Table 1]

[0098] In Table 1, the amount of each lubricant added is expressed as a relative value when the amount (mass) of each lubricant added in Example 1 is set to 100. In Table 1, the 1st torque refers to the peak torque value when the cap starts to rotate, and the 2nd torque refers to the peak torque value when the breaking portion of the tamper-evident band portion of the cap breaks.

[0099] When the inner resin coating of the cap body contained a polyester resin and a lubricant, the openability of the cap could be improved (see Examples 1 to 6). When polyethylene wax was used alone as a lubricant, the torque was significantly reduced, and the openability of the cap was significantly improved (see Examples 2 and 4). Furthermore, when polyethylene wax was used in combination with lanolin as a lubricant, the second torque was further reduced, and the openability of the cap was further improved, compared to when polyethylene wax was used alone (see Examples 1 and 4 to 6).

[0100] [Experiment 2] In Experiment 2, the effect of adding a lubricant to a cap inner surface coating mainly containing polyester resin is compared with the effect of adding a lubricant to a cap inner surface coating mainly containing epoxy phenol resin.

[0101] A bottle-shaped can of Example 7 was produced using a polyester resin paint containing polyethylene wax and lanolin as a lubricant as the inner coating material for the cap according to the same method as in Experiment 1. A bottle-shaped can of Example 8 was produced using an epoxy phenol resin paint containing polyethylene wax and lanolin as a lubricant as the inner coating material for the cap according to the same method as in Experiment 1.

[0102] The openability of the caps of the bottle-shaped cans of Examples 7 and 8 was evaluated in the same manner as in Experiment 1. In Experiment 2, the produced bottle-shaped cans were stored at 55°C for one day before evaluation. The evaluation results are shown in Table 2.

[0103] [Table 2]

[0104] When the inner resin coating of the cap body contained a lubricant together with a polyester resin, the openability of the cap could be improved (see Example 7). On the other hand, when the inner resin coating of the cap body contained a lubricant together with an epoxy phenol resin, the open torque of the cap could not be sufficiently reduced (see Example 8). As discussed above, this difference is thought to be due to the fact that the polyester resin has a lower crosslink density than the epoxy phenol resin, which allows the particulate wax to be stably held on the surface of the resin coating and allows the molten wax present inside the resin coating to seep out to the surface. The invention as originally claimed is set forth below. [1] a cap body having a disk-shaped top plate portion and a cylindrical skirt portion provided on the peripheral edge of the top plate portion, the top plate portion including a substrate and a resin coating provided on the cap inner surface side of the substrate, the resin coating including a polyester resin and a lubricant; a sealing member provided separately from the cap body and facing the top plate portion within the cap body, the sealing member having an outer diameter smaller than the inner diameter of the skirt portion; A cap comprising: [2] The cap of claim 1, wherein the lubricant comprises a hydrocarbon-based wax. [3] 3. The cap according to claim 2, wherein the hydrocarbon wax is a polyethylene wax. [4] 4. The cap according to claim 2, wherein the lubricant further contains a fatty acid ester wax. [5] 5. The cap according to claim 4, wherein the fatty acid ester wax is lanolin. [Explanation of symbols]

[0105] 1...cap, 11...cap body, 12...sealing member, 12a...flat plate portion, 12b...curved surface portion, 21...top plate portion, 22...skirt portion, 23...corner portion, 31...knurl portion, 31a...vent slit, 32...recess, 32a...inclined surface, 33...female screw portion, 34...tamper evidence band portion, 34a...break portion, 41...sliding layer, 41a...first flat plate portion, 41b...first curved surface portion, 41c...projection portion, 41d...thin-walled portion, 41d1...inclined surface, 41d2...inclined surface, 42...sealing layer, 42a...second flat portion, 42b...second curved portion, 42c...depression, 42d...thick-walled portion, 42d1...first protrusion, 42d2...second protrusion, 100...can container, 110...mouth portion, 111...jaw portion, 112...male screw portion, 113...curl portion, 200...mold, 210...first mold, 211...fixed mold, 212...movable mold, 220...second mold.

Claims

1. a cap body having a disk-shaped top plate portion and a cylindrical skirt portion provided on the peripheral edge of the top plate portion, the top plate portion including a substrate and a resin coating that coats the substrate on the inner surface side of the cap, the resin coating including a polyester resin and a lubricant; a sealing member that is formed separately from the cap body, that is provided within the cap body facing the top plate portion, that has an outer diameter smaller than the inner diameter of the skirt portion, and that is not adhered to the cap body; Equipped with The cap, wherein the lubricant contains a hydrocarbon wax and a fatty acid ester wax.

2. 2. The cap according to claim 1, wherein the hydrocarbon wax is a polyethylene wax.

3. 3. The cap according to claim 1, wherein the fatty acid ester wax is lanolin.

Images