JP4896095B2 - Container lid manufacturing method - Google Patents

Description

  The present invention relates to a container lid for a pail can or drum can, and more particularly to a method for manufacturing a container lid in which a fitting groove formed on the periphery is filled with a packing made of a thermoplastic resin, and a container lid.

  Storage cans such as pail cans and drum cans have been widely used. This storage can is used for storage and transportation of various liquids including chemicals, paints, oils and the like. Moreover, this storage can is normally comprised by the cross-sectional circular shape, has an opening part in the upper part, and can make the said opening part sealed with a circular container lid.

  By the way, this container lid is formed with an annular fitting groove for fitting the storage can body, and this fitting groove is made of resin to maintain airtightness and liquid tightness inside the container. Often made of rubber and rubber packing. Such packing of the container lid is usually fitted into a fitting groove provided in the container lid manually after being made into an annular shape by connecting both ends of a molded body formed in a linear shape in advance. . For this reason, in the process of producing container lids in large quantities, particularly the labor burden related to the fitting of the packing has increased, which has become a barrier to shortening the manufacturing period. For this reason, there existed a problem that control of the manufacturing cost of the container lid with packing became difficult.

  Conventionally, a method of manufacturing a container lid with packing that can easily form a packing in a fitting groove provided in the container lid and can also realize space saving and energy saving of the manufacturing equipment has been proposed (for example, (See Patent Document 1).

In the container lid disclosed in Patent Document 1, a thermoplastic resin to which a foaming agent has been added is heated and melted inside an extruder, and the heated and melted thermoplastic resin is foamed immediately after being discharged from a nozzle. As shown in FIG. 4, the fitting groove 111 is filled with a foam constituting the packing 120.
JP 2008-100452 A

  However, the container lid 101 disclosed in Patent Document 1 has a configuration in which a large number of microscopic voids 122 constituting the foam constituting the packing 120 are exposed to the surface 120a. For this reason, there is a possibility that the liquid may enter such a microscopic gap 122. Therefore, there is a possibility of causing the cause of liquid leakage particularly in the storage can in which the liquid is sealed.

  Further, in the configuration in which a large number of microscopic voids 122 are exposed on the surface 120a of the packing 120, the voids 122 exposed on the surface 120a are microscopically connected to the internal voids 124. The internal air will be exhausted through. In particular, the packing 120 can be elastically deformed and can exhibit its intended function by exhibiting its resilience to pressing, but this resilience is the elasticity of the air contained in each gap 124 constituting the foam. It is based on shrinkage. For this reason, it was necessary to confine the air inside the packing 120 and prevent the air from being discharged to the outside so that the restoring property can be exhibited over a long period of time. In particular, when the storage cans sealed by the container lid 101 are stacked in a plurality of stages and stored for a long period of time, the packing 120 is subjected to a pressing force for a long period of time. There is also a need to prevent the restoring force from being lost due to discharge through the gap 122 exposed on the surface.

  Furthermore, since the disclosed technique disclosed in Patent Document 1 has a structure in which the gap 122 is exposed on the surface 120a, the surface 120a has a large number of irregularities, and the smoothness is low. For this reason, even if it is going to seal the opening of a storage can through such a packing 120, a clearance gap arises between packing 120 and a storage can by such low smoothness, and it is perfect by improving mutual adhesiveness. There is a problem that it is difficult to ensure a good sealing property.

  Further, the cross-sectional shape of the packing 120 is not limited to a substantially circular shape as shown in FIG. 11, but may be formed in various shapes such as a semicircular cross-section and a crescent-shaped cross-section. There was also a need to improve.

  Therefore, the present invention has been devised in view of the above-mentioned problems, and exhibits the restoring force of the packing for a long time, improves the adhesion with the storage can to be closed, and is optional. An object of the present invention is to provide a method for manufacturing a container lid and a container lid that can be easily formed into a cross-sectional shape.

  The manufacturing method of a container lid to which the present invention is applied is a manufacturing method of a container lid for a pail can or a drum can. In the container lid in which a fitting groove formed on the periphery is filled with a thermoplastic resin, A bottom surface heating step of heating from the bottom surface above the melting point of the thermoplastic resin, and a top surface heating step of pressing the thermoplastic resin from above with a mold and heating through the mold above the melting point of the thermoplastic resin. The bottom surface heating step and the top surface heating step are executed sequentially from either one or at the same time.

  A container lid to which the present invention is applied is a container lid for a pail can or a drum can, and a packing groove made of a thermoplastic resin is filled in a fitting groove formed on the periphery, and the packing is formed at least inside the cross section. And a smooth layer having a smooth surface formed on the outer periphery of the foam layer.

  In this invention which consists of an above-described structure, it becomes possible to form a smooth layer so that the circumference | surroundings of the foaming layer which comprises packing may be covered. As a result, it is possible to prevent liquid from entering the microscopic voids that constitute the foam layer. In particular, since this pail can encloses a liquid in many cases, it is possible to prevent liquid leakage through the packing more firmly.

  Moreover, in the manufacturing method of the container lid to which the present invention is applied, it is possible to prevent the air contained in the foam layer from being discharged outside. For this reason, it becomes possible to exhibit the restoring property based on the elastic contraction of the air for a long period of time by confining the air contained in each void of the foam layer and not discharging it to the outside. If the pail can sealed by this container lid is piled up over a plurality of stages and the contents are stored for a long period of time, a pressing force is applied to the packing for a long period of time. However, even in such a case, since the air gap is not formed in the smooth layer, it is possible to prevent the internal air from being discharged from the packing surface and thus the loss of the restoring force. .

  In the present invention, since the surface of the packing can be covered with a smooth layer, it is possible to increase the smoothness by eliminating surface irregularities. For this reason, when trying to close a pail can with a container lid, it is possible to improve the mutual adhesion without causing a gap between the fixed edge located at the top of the pail can and the packing. It becomes possible. As a result, it is possible to ensure a more complete sealing property when the pail can is closed.

  Furthermore, in the present invention, the surface shape of the smooth layer of the packing can be formed in accordance with the shape of the pressing surface in the mold because the heating is performed to a temperature equal to or higher than the melting point of the thermoplastic resin while pressing with the mold. Become. For this reason, when it is desired to make the smooth layer of the packing into a desired shape, this can be realized by preparing a pressing surface in the mold in advance according to the desired shape.

  For this reason, the cross-sectional shape of the packing is not limited to the so-called crescent shape surrounded by curves having different radii of curvature. This can be realized by preparing the shape of the surface in advance according to this.

  Hereinafter, as a best mode for carrying out the present invention, a container lid for a pail can or a drum can and a manufacturing method thereof will be described in detail with reference to the drawings.

  FIG. 1 shows a container lid 1 to which the present invention is applied and a pail can 2 closed by the container lid 1. The pail can 2 has a circular cross section and has an opening at the top, and the opening can be sealed with a circular container lid 1. The pail can 2 is used for storage and transportation of various liquids including chemicals, paints, oils, etc., and a fixed edge 21 formed outside the opening located at the top, and a fixed edge 21 The lower stage includes a curved bead 22 projecting outward, and a base plate 23 is wound around the bottom of the can.

  As shown in FIG. 2, the fixed edge portion 21 is formed so as to be wound outward and has a curved shape. The bead 22 similarly has a curved shape. The pail can 2 is coated with anticorrosion coating on the surface, for example, an epoxy inner surface coat or the like.

  Further, as shown in FIG. 3, the container lid 1 is formed with an annular fitting groove 11 for fitting into the body of the pail can 2, and the fitting groove 11 has an airtightness and liquid inside the container. In order to maintain the tightness, a resin packing 12 is provided.

  FIG. 4 shows an enlarged cross-sectional view of the fitting groove 11 and the packing 12. The fitting groove 11 is configured by bending an iron plate constituting the container lid 1 into a curved shape. The packing 12 is filled in close contact with the fitting groove 11. The cross-sectional shape of the packing 12 will be described by taking as an example a case of a so-called crescent shape surrounded by curves having different curvature radii, but is not limited to this, for example, a substantially circular cross-section, It may be configured in any shape such as a semicircular cross section. The material of the packing 12 is made of a thermoplastic resin. The thermoplastic resin used for the packing 12 may be composed of any kind, but may be, for example, polyolefin, polyvinyl chloride, polyvinyl acetate, polyester, polyamide or the like. In addition, a thermoplastic elastomer can be used as the material of the packing 12, and various thermoplastic elastomers such as polyurethane, polyolefin, polystyrene, polyester, and polyamide can also be used. As a material for the packing 12, it is particularly desirable to apply polyolefin. This is because polyolefin is generally excellent in flexibility, chemical resistance and moldability, is low in cost, and does not generate harmful gas even when incinerated upon disposal.

  Note that a foaming agent may be further added to the thermoplastic resin constituting the packing 12. As this foaming agent, for example, an organic chemical foaming agent such as azodicarboxylic acid amide or an inorganic chemical foaming agent such as bicarbonate, which is in a powder form, may be used.

  Next, a method for manufacturing the container lid 1 having the above-described configuration will be described.

  First, as shown in FIG. 5 (a), a packing 12 is filled in a fitting groove 11 formed on the periphery of the container lid 1. By the way, at the time of filling, after placing the bottom surface 11a bent in the curved shape in the fitting groove 11 on the lower side, the molten thermoplastic resin is poured into the fitting groove 11 and cooled and solidified. You may make it fill by. Further, at the time of filling, a thermoplastic resin previously formed in a linear shape may be filled by fitting into the fitting groove 11.

  Next, heating is performed from the bottom surface 11 a of the fitting groove 11 to a temperature equal to or higher than the melting point of the thermoplastic resin constituting the packing 12. As a result, the contact portion of the packing 12 with respect to the bottom surface 11a of the fitting groove 11 is once melted by being heated to the melting point or more of the thermoplastic resin and then cooled and solidified. When using polyolefin as a thermoplastic resin which comprises the packing 12, it will heat to 100 degreeC or more. Through this process, the smooth layer 15a is formed at the contact portion of the packing 12 with respect to the bottom surface 11a as shown in FIG.

  Next, as shown in FIG. 5 (c), the packing 12 is pressed from above through the pressing surface 19 a by the mold 19. At the same time, the packing 12 is heated via the mold 19. Similarly, the heating temperature at this time is also heated to the melting point of the thermoplastic resin constituting the packing 12 or higher. As a result, the portion of the packing 12 that contacts the mold 19 is once melted by being heated to the melting point or higher of the thermoplastic resin, and then cooled and solidified. Thereafter, the pressed mold 19 is separated and the process ends. Through this process, the smooth layer 15b is formed at the contact portion of the packing 12 with the mold 19 as shown in FIG.

  As a result, the packing 12 is composed of two layers of a foam layer 16 formed in the cross section and smooth layers 15 a and 15 b formed on the outer periphery of the foam layer 16. Incidentally, the foam layer 16 is formed by a large number of small bubbles and is composed of voids containing air. In addition, the smooth layers 15a and 15b are very smooth to touch, have little surface irregularities, and voids that exist in the foamed layer 16 have disappeared in the course of melting and solidifying. The smooth layers 15a and 15b are formed so as to cover the periphery of the foam layer 16 so as to prevent the air contained in the foam layer 16 from being discharged to the outside. That is, the surface of the packing 12 after the heat treatment is entirely composed of the smooth layer 15 and the foamed layer 16 is not directly exposed to the surface. In other words, the periphery of the foam layer 16 where the voids exist is sealed by the smooth layer 15 through which air cannot pass.

  Actually, in order to achieve complete sealing of the foamed layer 16, the shape of the bottom surface 11a of the fitting groove 11 and the shape of the pressing surface 19a of the mold 19 so that at least the smooth layers 15a and 15b are connected to each other. Is preferably adjusted in advance. Incidentally, although the shape of the pressing surface 19a assumes the case where it consists of a downward convex curved surface, it is not limited to this, You may comprise in any shape.

  Thus, in the manufacturing method of the container lid 1 to which the present invention is applied, the smooth layer 15 can be formed so as to cover the periphery of the foam layer 16 constituting the packing 12. As a result, it is possible to prevent liquid from entering the microscopic voids constituting the foam layer 16. In particular, since this pail can 2 has many cases in which liquid is sealed, it is possible to prevent liquid leakage through the packing 12 more firmly.

  In particular, by providing the smooth layer 15a, the packing 12 can be closely attached to the fitting groove 11 without any gaps, liquid leakage can be prevented firmly, and further, the packing 12 can be prevented from coming off. It becomes possible. In particular, in the present invention, no adhesive is required to achieve the two purposes of preventing the liquid leakage and preventing the leakage from the packing 12, and it can be realized at a lower cost.

  Moreover, in the manufacturing method of the container lid 1 to which the present invention is applied, it is possible to prevent the air contained in the foam layer 16 from being discharged outside. For this reason, by setting it as the structure which does not discharge | emit outside contained in each space | gap of the foaming layer 16, it becomes possible to exhibit the restoring property based on the elastic contraction of the air over a long period of time. In particular, when the pail cans 2 sealed by the container lid 1 are stacked in a plurality of stages and the contents are stored for a long period of time, a pressing force is applied to the packing 12 for a long period of time. Even in such a case, since the air gap is not formed in the smooth layer 15, the internal air is not discharged from the surface of the packing 12, thereby preventing the restoring force from being lost. It becomes possible.

  Further, in the present invention, since the surface of the packing 12 can be covered with the smooth layer 15, the smoothness can be increased by eliminating the surface irregularities. For this reason, when trying to close the pail can 2 with the container lid 1, there is no gap between the fixed edge portion 21 positioned at the top of the pail can 2 and the packing 12, and the mutual adhesion Can be improved. As a result, it is possible to ensure a more complete sealing property when the pail can 2 is closed.

  Furthermore, in the present invention, the surface shape of the smooth layer 15b of the packing 12 is molded in accordance with the shape of the pressing surface 19a of the mold 19 because the mold 19 is pressed and simultaneously heated to a temperature equal to or higher than the melting point of the thermoplastic resin. It becomes possible to do. For this reason, when it is desired to make the smooth layer 15b of the packing 12 into a desired shape, this can be realized by preparing the pressing surface 19a in the mold 19 in advance according to the desired shape. .

  For this reason, the cross-sectional shape of the packing 12 is not limited to the so-called crescent shape surrounded by curves having different radii of curvature. For example, the mold 19 may have a substantially circular cross-section or semi-circular cross-section. This can be realized by preparing the shape of the pressing surface 19a in advance in accordance with this.

  FIG. 6 shows an example of a cross-sectional shape of the packing 12. The cross-sectional shape of the packing 12 is controlled so that a substantially horizontal upper surface 15c is formed in addition to the smooth layers 15a and 15b having different curvature radii. By making the packing 12 have such a cross-sectional shape, the surface contact with the fixed edge portion 21 can be improved by the smooth layer 15b having a small radius of curvature. In addition, by pressing the fixed edge portion 21 against the smooth layer 15b, the smooth layer 15b bends in the α direction in the figure, and accordingly, the portion constituting the upper surface 15c is in the β direction in the figure. It will be deformed towards. This bending of the upper surface 15c in the β direction presses the fixed edge 21 that contacts the smooth layer 15b, and as a result, the adhesion between the packing 12 and the fixed edge 21 can be further improved.

  In addition, the manufacturing method of the container lid 1 to which this invention is applied is not limited to embodiment mentioned above. FIG. 7 shows an example of a time chart of heat treatment. In FIG. 7A, as described above, the bottom surface heating is performed first, in which the bottom surface 11a is heated to a temperature equal to or higher than the melting point of the thermoplastic resin constituting the packing 12. Next, the packing 12 is pressed from above with a mold 19. At the same time, so-called upper surface heating is performed in which the packing 12 is heated through the mold 19. Incidentally, the timing of the pressing and the upper surface heating may be performed in advance, as long as the pressing is performed at least while the upper surface is heated to the melting point of the thermoplastic resin or higher.

  FIG. 7B shows a time chart when the top surface heating and pressing and bottom surface heating are performed simultaneously. FIG. 7 (c) shows that top surface heating and pressing are performed in advance, and then bottom surface heating is sequentially performed.

  As described above, in the present invention, the bottom surface heating, the top surface heating, and the pressing may be sequentially performed from any one of them, or may be simultaneously performed. Regardless of the order, the same effects as described above can be obtained.

  Further, in the present invention, for example, as shown in FIG. 8, at least a part of the packing 12 has a curved surface that can be brought into surface contact with the curved fixed edge portion 21 formed so as to be wound around the outside of the opening. It is desirable that it is molded. If this surface contact can be realized, the adhesion can be further improved, the airtightness inside the pail can 2 can be secured, and the liquid leakage can be firmly prevented. In order to make the cross-sectional shape of the packing 12 actually come into a surface-contactable shape with the fixed edge 21, the curved surface constituting the pressing surface 19 a in the mold 19 is made to have at least part of the surface contact with the fixed edge 21. It is necessary to shape in advance to a possible shape.

  Incidentally, in the present invention, as shown in FIG. 5 (c), when the mold 19 is cooled or insufficiently cooled, if the gasket 19 is separated from the packing 12, the packing adheres to the mold 19. In other words, it can be a factor in reducing the manufacturing yield. For this reason, a measure may be taken to coat the mold with a release agent such as silicon or Teflon (registered trademark). Furthermore, when the packing 12 is pressed by the mold 19, a material having high thermal conductivity may be sandwiched between the mold 19 and the packing 12. As an example of the material having high heat conductivity, it is desirable to select a thin and easily deformable material, for example, a metal foil or a metal thin plate made of aluminum or copper. In such a case, it is necessary to make such a metal foil or metal thin plate in advance so as to have the same shape as the mold. Thereby, it becomes suitable when using metal foil or a metal thin plate repeatedly in the same shape.

  Thereby, the packing 12 is heat-molded from the pressed mold 19 through the metal foil or the metal thin plate. The mold 19 can be separated from the metal foil or the metal thin plate without cooling. This mold can be used repeatedly and can improve thermal efficiency and work efficiency. If the metal foil or the metal thin plate is cooled or insufficiently cooled, the packing may stick to the metal foil or the metal thin plate, which causes a reduction in manufacturing yield. . For this reason, a measure for coating the contact surface between the metal foil or metal thin plate and the packing 12 with a release agent such as silicon or Teflon (registered trademark) is also suitable.

  Furthermore, the container lid 1 to which the present invention is applied is not limited to the case where the pail can 2 is closed, and may be used when the drum can is closed.

  Moreover, this invention may heat-process the packing produced through the indication technique of patent document 1. FIG. In the disclosed technique of Patent Document 1, for example, as shown in FIG. 9, the thermoplastic resin 40 is extruded from the nozzle 30 in a linear shape and poured into the fitting groove 11 provided in the container lid 1, thereby fitting the fitting groove 11. The packing 12 is integrally formed along the. The thermoplastic resin 40 is charged into the thermoplastic resin charging unit 31 in the form of pellets, and is heated and melted inside the extruder 32. A gas or liquid foaming agent 41 is added to the thermoplastic resin 40 heated and melted inside the extruder 32. The foaming agent 41 is added by pressing the foaming agent 41 into the extruder 32 from the foaming agent press-fitting portion 34.

  The thermoplastic resin 40 heated and melted inside the extruder 32 and added with the foaming agent 41 is discharged from the nozzle 30 and poured into the fitting groove 11 of the container lid 1. The melting temperature of the thermoplastic resin 40 is usually 150 to 300 ° C. At this time, since the foaming agent 41 added to the thermoplastic resin 40 is foamed immediately after being discharged from the nozzle 30, the thermoplastic resin 40 becomes a foam and is filled in the fitting groove 11. Form. In this embodiment, the thermoplastic resin 40 is poured into the fitting groove 11 while the container lid 1 is rotated around the central axis of the fitting groove 11 by the container lid moving means 60.

  Thus, after passing through the process of filling the resin into the fitting groove 11, the above-described heat treatment is performed. In particular, as shown in FIG. 10, the packing 12 filled through the process of Patent Document 1 described above overlaps both ends of the thermoplastic resin 40 that is filled in an annular shape by making the fitting groove 11 go around once, and this is cooled. The raised portion 48 is formed after solidifying. If the raised portion 48 is formed, the pail can 2 cannot be actually closed with the container lid 1 in a stable state. However, in the manufacturing method of the container lid 1 to which the present invention is applied, the raised portion 48 is melted in the process of performing the top surface heating, pressing, and bottom surface heating, and thus can be removed.

  As described above, the method for manufacturing the container lid 1 to which the present invention is applied effectively removes the raised portion 48 when combining the resin filling process described in the technology disclosed in Patent Document 1 described above in the previous stage. This is useful in that

It is a figure which shows the container lid to which this invention is applied, and the pail can closed. It is a figure which shows about the detail of the fixed edge part which is wound up and formed in the outer side, and has a curved shape. It is a perspective view of a container lid in which a fitting groove is formed in an annular shape. It is an expanded sectional view of a fitting groove and packing. It is a figure for demonstrating the manufacturing method of the container lid to which this invention is applied. It is a figure which shows an example of the cross-sectional shape of packing. It is a figure which shows the example of the time chart of heat processing. It is a figure which shows the example which makes packing contact surface on a fixed edge part. It is a figure for demonstrating the indication technique of patent document 1. FIG. It is a figure which shows the protruding part formed in packing. It is a figure for demonstrating the problem of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Container lid 2 Pail can 11 Fitting groove 12 Packing 15 Smooth layer 16 Foam layer 19 Mold 21 Fixed edge part 22 Bead 23 Base plate 30 Nozzle 31 Thermoplastic resin input part 32 Extruder 34 Foaming agent press-in part 40 Thermoplastic resin 41 Foam 48 ridge

Claims (7)

In the method of manufacturing a container lid for a pail or drum can,
About a container lid filled with a thermoplastic resin in a fitting groove formed on the periphery, a bottom surface heating step of heating from the bottom surface of the fitting groove above the melting point of the thermoplastic resin,
An upper surface heating step of pressing the thermoplastic resin from above with a mold and heating at a temperature equal to or higher than the melting point of the thermoplastic resin through the mold;
The method of manufacturing a container lid, wherein the bottom surface heating step and the top surface heating step are sequentially performed from either one or simultaneously. The method for producing a container lid according to claim 1, wherein in the bottom surface heating step and the top surface heating step, a container lid filled with polyolefin as the thermoplastic resin is heated at a temperature equal to or higher than the melting point of the polyolefin. The method for producing a container lid according to claim 1 or 2, wherein, in the upper surface heating step, the mold having a downwardly convex curved surface as a pressing surface to the thermoplastic resin is pressed. In the upper surface heating step, the gold consisting of the curved surface that can be brought into surface contact with at least a part of the curved fixed edge that is wound around and formed outside the opening located at the top of the pail or drum can to be closed. The method for producing a container lid according to claim 3, wherein the mold is pressed. The outer periphery of the thermoplastic resin is melted through the bottom surface heating step and the top surface heating step, and is cooled and solidified to form a smooth layer having a smooth surface around the foam layer. Item 5. The method for producing a container lid according to any one of Items 1 to 4. A resin filling step of filling the fitting groove with a thermoplastic resin;
The resin filling step
This is a process in which a thermoplastic resin heated and melted by an extruder is linearly extruded from a nozzle and poured into the fitting groove to integrally form a packing along the fitting groove, and a foaming agent is added. The thermoplastic resin is heated and melted inside the extruder, and the molten thermoplastic resin is foamed immediately after being discharged from the nozzle, and the foam is filled in the fitting groove without heating the entire container lid. The method for producing a container lid according to any one of claims 1 to 5, wherein: In a container lid for a pail or drum,
Packing made of thermoplastic resin is filled in the fitting groove formed on the periphery,
The packing is a foam layer formed at least inside the cross section;
A container lid, comprising: a smooth layer formed on an outer periphery of the foam layer and having a smooth surface.

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