JPS6326025B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing an easy-to-open container lid, and more specifically, the present invention relates to a lid material body made of a metal foil-resin laminate and a knob of a resin molded product integrated therein. The present invention relates to a method for efficiently manufacturing an easy-to-open container lid that is excellent in both easy-to-open properties and airtightness and storage stability. (Prior Art) Conventionally, as a lid body having an easy-to-open function, a score is engraved on the area to be opened, a rivet is formed on a part of the score, and a knob piece having a push-in tip that comes into contact with the score is attached to the rivet. The most widely used method is to fix it through metal foil.
In the case of a flexible material such as a resin laminate, there is a problem in that it is difficult to form such rivets and to fix the tab piece with the rivets. In addition, an opening is provided in the lid in advance, a thermoplastic resin film is pasted on the side of the lid that will become the inner surface of the container, and a knob piece is integrally formed with the cover for the opening by resin injection molding. An easily openable container lid in which a resin film and the cover are bonded together by heat sealing is also already known. However, in this type of easy-to-open container lid, only resin is present in the opening, so gas barrier properties are low.
The storage stability of the contents is still unsatisfactory. Furthermore, as a lid with a structure different from that described above, Japanese Patent Application Laid-Open No. 48-79085 discloses a metal lid with a riveted hole drilled in the vicinity of the opening start part, and a small piece of the handle made of thermoplastic resin with riveted holes. It is described that the legs of a product with a head and legs attached are inserted into the rivet holes, and the legs are heat-fused while being compressed in a mold to be riveted to the lid. (Problems to be Solved by the Invention) However, in this method, the operation of manufacturing a resin molded product consisting of a small pull piece, etc., the operation of inserting this resin molded product into the rivet hole of the lid, and the heating of the legs of the molded product are required. It requires an operation of melting and crimping, and there are problems in that the operation is complicated and the number of steps is large. In order to solve this problem, it is possible to install the lid in an injection mold and manufacture the above-mentioned molded product as one unit with the lid, but in this case, the molded product itself must be molded, that is, in-mold. Although molding would be possible, there would still be problems with the sealing and opening performance of the lid. That is, in the above-mentioned type of container lid, the amount of resin injected onto the inner surface of the lid is relatively small, and the laminate that makes up the lid body contains metal foil with high thermal conductivity. The heat of the injected resin dissipates to the surroundings through the metal foil, making it difficult to fuse at the interface. Moreover, in this type of container, the contact area between the lid and the resin molded product around the small hole is extremely small, so even if there is a joint defective area around the small hole, this joint defect will occur. Leakage or poor airtightness cannot be ignored from the perspective of preserving the contents, and furthermore, if there is a poor connection, the molded product that forms the knob may tear off from the lid body, making it difficult to open. There is a tendency that Therefore, the present invention makes it possible to manufacture easy-to-open container lids with a reduced number of steps and at a high production rate in the conventional manufacturing of this type of easy-to-open container lids, and also to manufacture an openable molded product. The area around the small hole in the lid body and the molded body are completely fused and integrated using only the heat of the injected resin, and as a result, excellent sealing performance, storage stability, and easy opening are ensured. An object of the present invention is to provide an openable container lid. (Means for Solving the Problems) According to the present invention, a small hole is provided in the vicinity of the opening opening part of the lid body made of a laminate of a metal foil and a thermoplastic resin film layer, and the lid body is injected. A mold is held between the molds, and a thermoplastic resin is injected from a portion corresponding to the small hole in the lid body of the injection mold to form a knob on the opposite side of the film layer of the laminate and a fixing part of the knob on the film layer side. is molded as a thermoplastic resin molded product together with a connecting portion penetrating the small hole in a relationship that seals the small hole and integrally with the lid body, and here, the resin constituting the film layer is mixed with the molded product. The constituent resin and the main constituent monomer are the same, but the melting point is at least 2°C lower than that of the resin constituting the molded article, and the film layer and the molded article are thermally fused only by the heat of the injected resin. have them do it. (Function) In FIGS. 1 to 3, the container lid according to the present invention consists of a lid body, generally designated 1, and a resin molded part, generally designated 2. This lid body 1
consists of a metal foil substrate 3 and a thermoplastic resin film layer 4 applied to one surface thereof, and a protective coating 5 may be formed on the other surface of the metal foil substrate 3 if desired. good. The lid main body 1 has an unsealing portion 6, and a small hole 7 passing through the opening portion near the opening start portion (the end with a large curvature in FIG. 2) of this portion is provided. The lid main body 1 made of this laminate has a film layer 4
In this regard, the resin molded product 2 has a knob 8 located on the opposite side of the film layer 4, that is, on the outside of the lid, and a knob 8 that is located on the side opposite to the film layer 4, that is, on the outside of the lid. A fixing part 9 of the knob is located inside the small hole 7, and these parts are integrated with each other via a connecting part 10 extending through the small hole 7. In the present invention, the above-mentioned knob 8, knob fixing part 9, connecting part 10, or other parts integrated with the knob fixing part are connected to the lid main body 1 provided with the small hole 7.
is sandwiched between a split mold part equipped with a cavity corresponding to the knob 8 and a split mold part equipped with a cavity corresponding to the knob fixing part 9, etc., and integrally molded by injecting thermoplastic resin into the cavity. Ru. As shown in FIG. 1, the bases of the knob 8 and the knob fixing part 9 have a larger diameter or cross-sectional dimension than the small hole 7 of the lid body 1, and thus the small hole 7 has a larger diameter or cross-sectional dimension than the small hole 7 of the lid body 1. The fixing portion 9 is in a sealed relationship. In the present invention, the thermoplastic resin A constituting the laminate, that is, the inner film layer 4 of the lid body 1, is
Although the main constituent monomer is common to the thermoplastic resin B that constitutes the molded product such as the knob 8, the fixing part 9, and the connecting part 10, the temperature is at least 2°C, preferably 5°C lower than that of the molded product constituent resin B. Use one with a low melting point (melting point determined by differential scanning calorimetry). As a result, the resin A forming the inner surface film layer of the lid laminate is reliably melted only by the heat of the injected resin B, and the resin A and the resin B are reliably thermally fused. Furthermore, since both resins A and B have the same main constituent monomer, a strong bond can be obtained. The fact that one resin has a higher melting point than the other even though the main monomers are the same type means that the heat of fusion of one resin is also higher than the heat of fusion of the other resin. In the present invention, by using a high melting point resin as the injected resin and a low melting point resin as the inner surface film layer of the lid, conditions are provided in which the injected resin is easily melted.
The inner film layer melts and the two resins are easily fused and integrated. Moreover, according to the present invention, the heat fusion of both resins A and B is performed only with the heat of the injected resin B, so there is no need for operations such as preheating the lid body attached to the mold. Various operations such as molding, positioning, and fusing of the molded product are performed all at once. (Operations and Effects of the Invention) In the easy-to-open lid according to the present invention, the knob fixing portion 9
Since the heat fusion between the cap and the inner film layer 4 of the lid main body is completely performed, highly reliable sealing performance and easy-to-open performance are achieved, and the lid can be manufactured with a small number of steps and at a high production rate. Can be done. (Description of preferred embodiments of the invention) In the present invention, the resin used to form the molded product 2 such as a knob may be low-, medium-, or high-density polyethylene, crystalline polypropylene, or crystalline ethylene-propylene copolymer. and polyester resins such as polyethylene terephthalate and polybutylene terephthalate. On the other hand, as the resin constituting the film layer of the laminate, a resin whose main constituent monomer is the same as that of the above-mentioned resin and whose melting point is at least 2° C. lower than that of the above-mentioned resin is used. In order to lower the melting point of the resin constituting the film layer, (a) means for lowering the melting point by copolymerizing a comonomer;
(b) A means of reducing the crystallinity or polymerization degree of the resin, or (c) a combination thereof is employed. Thus, combinations of copolymers for homopolymers, such as ethylene-vinyl acetate copolymers for polyethylene, propylene-ethylene copolymers for homopolypropylene, and copolyester combinations for polyester. is used. Additionally, combinations of low crystallinity resins to high crystallinity resins are also used, such as low density polyethylene to high density polyethylene. Regarding various thermoplastic resins, the relationship between the comonomer content and the melting point of the copolymer is well known. What is necessary is to set the content of the comonomer. In the present invention, the resin for forming the film layer may be obtained by blending the resin constituting the molded article with another resin to lower the overall melting point. For example, the film layer may be made of a blend of polypropylene, polyethylene, or an ethylene-propylene copolymer, and the polypropylene may be injection molded to fuse the two. Metal foil for laminates has a thickness of 7 to 100 mm.
Micron aluminum foil is preferably used, but other metal foils such as tin foil, steel foil, iron foil, etc. can also be used. The thickness of the film layer is such that it protects the metal foil and facilitates heat sealing with the container body, and is generally desired to have a thickness of 10 to 100 microns. In terms of ease of opening, it is desirable that the metal foil and film layer are firmly bonded, and from this point of view, the above-mentioned film layer and metal foil may be bonded using an isocyanate adhesive, an acid-modified olefin resin adhesive, etc. It is desirable that they be joined via a. In the preferred embodiment shown in FIGS. 1 to 3, on the inside of the lid, that is, on the side of the film layer 4, in addition to the knob fixing part 9, there is also a knob fixed part 9 on the inner peripheral side of the contour of the intended opening part 6. an inner circumferential rib 11 provided along
An outer circumferential rib 13 is provided along the outer circumferential side of the contour of the scheduled opening portion 6 that is connected to the inner circumferential rib 11 via bridging portions 12, 12, and maintains the shape of the lid main body by integrating with the outer circumferential rib 13. A ring portion 14 is formed. This ring portion 14 is connected to the sealing engagement flange 16 of the container body 15 in FIG.
When the lid body 1 is engaged with the lid body 1, the dimensional relationship is such that the engaging portion is located slightly on the inner circumferential side of the engaging portion. In the specific example containers shown in FIGS. 1 to 3,
The inner film layer 4 of the lid body 1 also serves as a heat sealant, and the container lid is sealed to the flange of the container 15 by heat sealing. To open the container lid, hold the knob 8 with your fingers and lift it upwards, and the end of the fixing part 9- (the right end in Figure 1) will be lifted upwards by the lever action. The laminate forming the lid body 1 is broken approximately in a semicircular shape. Subsequently, by lifting the knob 8 upward, the laminate progresses to break between the inner circumferential rib 11 and the outer circumferential rib 13 formed on the inside of the lid using resin, and the lid opens along the planned opening section 12. The main body 1 will be opened. In the specific example shown in FIGS. 1 to 3, the inner circumferential rib 11 and the outer circumferential rib 13 serve as guides to accurately break the laminate. It is also possible to engrave a score that reaches halfway in the thickness direction of the metal foil. In FIGS. 4 to 6 showing such aspects,
A score 17 is provided on the lid main body 1 on the inside of the heat seal portion over the entire circumference thereof. A tip 18 for pushing and cutting is provided at one end of the knob 8, and this tip 18 for pushing and cutting is provided so as to substantially match the score 17. When opening, lift the knob 8 upwards.
The tip 18 is pushed down by the lever action, resulting in a score of 1.
A portion of the score 7 is first broken, and then the entire score 17 is broken by lifting the knob 8 to open the container lid. The invention is illustrated by the following example. Example 1 A 50 μ thick aluminum foil with printing on one side, vinyl acetate content of 12% by weight, melt index of 2.0 g/10 min (ASTM P 1238),
A 40 μm thick film made of an ethylene-vinyl acetate copolymer having a density of 0.927 g/cm ² and a melting point of 98° C. was laminated with an isocyanate adhesive. Next, a circular blank having an outer diameter of 90 mmφ and a small hole with a diameter of 5 mmφ in the center was punched out of this laminated sheet. From this blank, a molding die and a curler are used to form a drop-lid-like piece with an outer diameter of 76 mmφ and a curled part on the outer periphery, and a concentric circle shape with a diameter of 65 mmφ and a depth of 3 mm so that the aluminum foil printing surface is concave. was molded. Next, the molded and curled lid intermediate is loaded into the mold of an injection molding machine, and the melt index is 40g/10 minutes and the density is 0.919 from the small hole of the lid intermediate.
A lid body as shown in FIGS ^. 1 to 3 was obtained by injecting low-density polyethylene having a melting point of 109° C. and a melting point of 109° C. The heat of fusion of the ethylene-vinyl acetate copolymer, which is the inner material, is 101 KJ/kg, and the heat of fusion of the low-density polyethylene, which is the injection molding resin, is 152 KJ/kg.
It was kg. The difference in heat of fusion between the ethylene-vinyl acetate copolymer layer on the inner surface of the lid and the injected low-density polyethylene on the inner surface is 51 KJ/kg, so the adhesive strength between them is sufficient to allow them to separate. That is difficult. Next, a bottom part with a diameter of 50 mmφ made of low density polyethylene with a melt index of 1.5 g/10 minutes, a density of 0.921 g/cm ² and a melting point of 110°C, a tapered side wall part with a height of 80 mm, and Diameter is 76mm and width is 3
A cup having a flange portion of mm was filled with sake, and the lid was sealed to the flange portion of the cup using a heat sealer. When the spout was opened by pulling up the low-density polyethylene knob ring on the lid of the container filled with contents, it was easy to open, and there was a feather ring at the opening, and peeling between the aluminum foil and the ethylene-vinyl acetate copolymer layer. Also, no peeling between the ethylene vinyl acetate copolymer layer and the low density polyethylene on the inner surface was observed. Examples 2 to 7 and Comparative Examples 1 to 3 Laminated sheets having the configurations shown in Table 1 were laminated using the materials shown in Table 1, respectively. Next, a lid intermediate body was produced from these laminated sheets in the same manner as in Example 1, in which a small hole was punched in the center, the lid was formed into a drop lid shape, and the peripheral edge was curled. Next, these lid intermediate bodies are loaded into a mold of an injection molding machine, and resin of the injection molding grade shown in Table 2 is injected from the small holes of the lid intermediate body, thereby producing a lid body similar to that in Example 1. I got it. The heat of fusion of the resin serving as the inner surface material and the injection molding resin were as shown in Table 3. In Examples 2 to 7, the adhesive strength between the inner surface resin layer of the lid body and the injected inner surface side resin portion was sufficient and it was difficult to separate the resin layer. Next, a container having the same size as in Example 1 and molded from the resin material shown in Table 2 was filled with the contents shown in Table 2, and the lid was heat-sealed to the flange of the container. When opening the drinking spout by pulling up the opening ring on the lid of these containers, the opening was easy, and there was no feathering at the opening, separation between the aluminum foil and the inner resin layer, and separation between the inner resin layer and the inner surface. No peeling from the injection molded resin was observed. On the other hand, when the melting point of the resin layer on the inner surface of the lid is higher than the melting point of the injection-molded resin as in Comparative Example 1, the adhesive strength between the high-density polyethylene on the inner surface and the low-density polyethylene on the injection-molded inner surface is insufficient and easily peels off. did. Furthermore, when the low-density polyethylene ring on the lid of the container was pulled up, the inner high-density polyethylene and the injection-molded inner low-density polyethylene peeled off, making it difficult to open the container smoothly. Furthermore, in the case of Comparative Example 2, as in Comparative Example 1, the melting point of the resin layer on the inner surface of the lid was higher than the melting point of the injection molding resin, so the adhesion between the two resins was insufficient. Furthermore, even if the melting point of the resin layer on the inner surface of the lid is lower than the melting point of the injection molding resin as in Comparative Example 3, if the main constituent monomers of both resins are different, the adhesion between the two resins may be insufficient. Ta. Example 8 Isotactic polypropylene is crafted with maleic anhydride and the average carbonyl group concentration is
140meq/100g polymer, melting point 163℃, MI 40
g/10 min modified polypropylene and melting point 156℃,
93% by weight ethylene-propylene random copolymer with density 0.90g/cc, MI 20g/10min, ethylene content 5mol%, melting point 109℃, density
A blend of 0.919 g/cc and 7% by weight of low density polyethylene with an MI of 12 g/10 min was coated on a 100 μ thick aluminum foil coated with epoxyphenol on one side by two-layer coextrusion method. Co-extrusion coating was applied to the aluminum foil so that the non-painted surface and the modified polypropylene were in contact with each other. Next, this laminate is heat-treated with a heat roll at a temperature of 200°C to thermally bond the aluminum foil and modified polypropylene, resulting in a composition of 100μ aluminum foil/
A laminate of a 5μ modified polypropylene layer/10μ ethylene-propylene random copolymer blend layer was obtained. Next, a circular blank having an outer diameter of 90 mmφ and a small hole with a diameter of 5 mmφ in the center was punched out from this laminated sheet. This blank is formed into a concentric concave shape with an outer diameter of 76 mmφ and a curled part on the outer periphery, and a diameter of 65 mmφ and a depth of 3 mm using a punch, die, and curler.
A drop-lid-like product with a score of φ was molded. Next, this lid intermediate body is loaded into the mold of an injection molding machine, and the melt index is released from the small hole of the lid intermediate body.
A lid body as shown in FIGS. 4 to 6 was obtained by injecting polypropylene having a density of 0.90 g/cm ² and a melting point of 164° C. at 8 g/10 minutes. The heat of fusion of the ethylene-propylene random copolymer that is the inner material is 172 KJ/kg, and the heat of fusion of the polypropylene that is the injection molding resin is:
It was 209KJ/kg. Inner surface of the resulting lid - ethylene-propylene
The difference in heat of fusion between the random copolymer blend layer and the injection molded inner polypropylene is 37 KJ/kg.
Therefore, the adhesive strength between them was sufficient and it was difficult to separate them. Next, the melt index is 2g/10 minutes, the density is 0.90g/cc, the melting point is 163℃
A cup consisting of a 60 mmφ bottom, a tapered side wall with a height of 50 mm, and a flange with a diameter of 76 mm and a width of 3 mm was filled with potato salad, and the lid was heat-sealed to the flange of the container body. The polypropylene knob ring on the lid of this content-filled container was pulled up and opened along the circumference of the score. In this case, the opening was very easy because the adhesive between the knob ring and the lid was sufficient.

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[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a sectional view showing the structure of a container according to an embodiment of the present invention, FIG. 2 is a plan view of the lid shown in FIG. 1, and FIG. is an exploded perspective view of the lid shown in FIG. 1, FIG. 4 is a sectional view showing the structure of a container according to another embodiment of the present invention, and FIG. 5 is an exploded perspective view of the lid shown in FIG. FIG. 6 is an exploded perspective view of the lid shown in FIG. 4, and reference numeral 1 indicates the lid main body;
2 is a resin molded part, 3 is a metal foil substrate, 4 is a thermoplastic resin film layer, 5 is a protective coating, 6 is a portion to be opened, 7 is a small hole, 8 is a knob, 9 is a fixing part of the knob, 10 is a 11 is an inner peripheral rib, 12 is a bridge portion, 13 is an outer peripheral rib, 14 is a ring portion, 15 is a container body, 16 is a sealing engagement flange, 17 is a score, and 18 is a tip for pushing and cutting, respectively. .

Claims (1)

[Claims] 1. A small hole is provided in the vicinity of the opening start part of the lid body made of a laminate of metal foil and a thermoplastic resin film layer, and the lid body is sandwiched between injection molds, and the injection mold A thermoplastic resin is injected from a portion of the lid body of the mold corresponding to the small hole, and a knob is attached to the film layer of the laminate on the opposite side, and a fixing part of the knob is attached to the film layer side along with a connecting part that passes through the small hole. A thermoplastic resin molded product is molded integrally with the lid main body and in a relationship that seals the small hole, and the resin constituting the film layer has the same main constituent monomer as the resin constituting the molded product. but at least 2°C lower than the resin constituting the molded product.
A method for manufacturing an easily openable container lid, characterized in that the lid has a low melting point and the film layer and the molded product are thermally fused only by the heat of the injected resin.