Plastic containers

Abstract

Provided is a plastic container that is lightweight, has excellent environmental friendliness and leak prevention properties, and has excellent sealing properties during storage and transportation. In particular, the plastic container is suited to holding, storing, and transporting high-density, high-viscosity solutions such as CMP slurries, and meets UN specifications. A first screw portion 8 is formed in an inner surface of a cylindrical body 7. A second screw portion 16 capable of screwing into the first screw portion 8 is formed on an outer surface of a top member 13 of a plug 12. A gasket 21 is interposed between an outer surface of the plug 12 and an inner surface of an opening 5 so as to abut the outer surface of the plug 12 and the inner surface of the opening 5. A protrusion 25 is formed in the inner surface of the opening 5 in a manner allowing contact with the gasket 21.　

Description

[Technical field]

[0001] The present invention relates to a plastic container that is suitable for filling, storing, and transporting a solution such as a CMP slurry and that satisfies UN standards. [Background technology]

[0002] Conventionally, paper containers, glass containers, metal containers, plastic containers and the like have been widely used for storage and transportation due to the required container properties such as light weight, mechanical strength, cleanliness, etc.

[0003] In recent years, with the development of industry, it has become common to fill highly viscous solutions such as highly viscous foods, chemicals, CMP slurries, photoresists, and developers in containers for storage and transportation for industrial use. These highly viscous solutions are heavy due to their high specific gravity, and are generally discharged using a dispenser, so the containers must have high mechanical strength.

[0004] For this reason, various proposals have been made for containers for the above-mentioned high-viscosity solutions. For example, Patent Document 1 describes a container for a dustproof container, as shown in the cross-sectional view of FIG. 11, in which "a drum mouth 41 has an internal thread 42 and is threadedly engaged with a plug 44 having an external thread 43. A gasket 45 is disposed below the threads, and a sealing surface is formed by a protruding end face 46 of the drum mouth 41 and a horizontal end face 47 of the plug 44. Two annular protrusions 48a and 48b are formed on the outer periphery of the drum mouth 41. As shown in the cross-sectional view of FIG. 12, a dustproof container is described. When the dust cap 49 is attached, the protrusion 48b fits into the protrusion 50 of the dust cap 49 and acts as a retainer, and when the safety seal cap 51 is attached, the protrusion 48a fits into the protrusion 52 of the seal cap 51 and acts as a retainer, and as shown in the cross-sectional view of FIG. 11, the upper end surface 53 of the drum mouth 41 is higher than the upper end surface 56 of the L-ring 55 of the resin drum 54 and lower than the drum top surface 57.

[0005] The mouth plug of the resin drum is provided with a gasket 45 between the resin drum 54 and the plug 44. On the other hand, since a high-viscosity solution such as a CMP slurry contains fillers with high specific gravity such as abrasives, metal powders, and inorganic fillers, the fillers settle during storage or transportation, making it unusable as is. Therefore, before use, the resin drum is fed to a rotating device or a vibrating device and rotated or vibrated to uniformly mix the high-viscosity solution before use. However, simply providing the gasket 45 has the drawback that the high-viscosity solution leaks out during rotation or vibration. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 11-342962 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above problems, an object of the present invention is to provide a plastic container which is lightweight, has excellent cleanliness and resistance to leakage of the contents, and has excellent sealing properties during storage and transportation, in particular a plastic container which is suitable for filling, storing and transporting a high specific gravity, high viscosity solution such as CMP slurry and which satisfies UN standards. [Means for solving the problem]

[0008] The first invention of the present application to achieve the above-mentioned object is a plastic container comprising a container body having a mouth formed therein, and a plug for sealing the mouth, wherein a first threaded portion is formed on the inner surface of the mouth, and a second threaded portion capable of being screwed into the first threaded portion is formed on the outer surface of the plug, and a gasket is interposed between the outer surface of the plug and the inner surface of the mouth so as to abut against the outer surface of the plug and the inner surface of the mouth, and wherein a raised portion is formed on the inner surface of the mouth so as to be able to come into contact with the gasket. The second invention of the present application is a plastic container according to the first invention of the present application, characterized in that a protrusion is formed below the second screw portion on the outer surface of the plug. A third invention of the present application is a plastic container according to the first invention of the present application, characterized in that a protrusion is formed below the first screw portion on the inner surface of the mouth portion. A fourth invention of the present application is a plastic container according to the second invention of the present application, characterized in that a protrusion is formed below the first screw portion on the inner surface of the mouth portion. The fifth invention of the present application is a plastic container according to any one of the first to fourth inventions of the present application, characterized in that a groove is formed on the outer surface of the plug and the inner surface of the mouth at the location where the gasket comes into contact. A sixth aspect of the present invention is a plastic container according to the fifth aspect of the present invention, characterized in that a protrusion is formed on the inner surface of the mouth at a position where the gasket comes into contact. A seventh aspect of the present invention is a plastic container according to the fifth aspect of the present invention, characterized in that a protrusion is formed on the outer surface of the plastic at a location where the gasket comes into contact. The eighth invention of the present application is a plastic container according to the sixth invention, characterized in that a protrusion is formed on the outer surface of the plastic at a location where the gasket comes into contact. A ninth aspect of the present invention is a plastic container according to the eighth aspect of the present invention, characterized in that the gasket is an O-ring. The tenth aspect of the present invention is a plastic container according to the ninth aspect of the present invention, characterized in that the opening is covered with a cap. An eleventh aspect of the present invention is a plastic container according to the tenth aspect of the present invention, characterized in that the circularity of the mouth portion is 1.0 mm or less. Effect of the Invention

[0009] The plastic container of the present invention has the configuration described above, is lightweight, has high mechanical strength, is highly clean and airtight, has excellent resistance to leakage of the contents, and has excellent sealing properties during storage and transportation, and is particularly suitable for filling with high specific gravity, high viscosity solutions such as CMP slurry and storing and transporting them. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1(A) is a side view showing an example of a plastic container of the present invention, and FIG. 1(B) is a plan view thereof. [Diagram 2] FIG. 2 is a cross-sectional view showing an example of the mouth of the plastic container of the present invention. [Diagram 3] FIG. 3(A) is a cross-sectional view showing an example of a plug in a plastic container of the present invention, and FIG. 3(B) is a bottom view thereof. [Figure 4] FIG. 4 is a cross-sectional view showing an example of a plastic container of the present invention with its mouth sealed. [Diagram 5] FIG. 5 is a cross-sectional view showing a different example of the state in which the mouth of the plastic container of the present invention is sealed. [Figure 6] 6(A) and 6(B) are cross-sectional views showing still another example of the plastic container of the present invention with the mouth part sealed. [Figure 7] 7(A) and 7(B) are diagrams for explaining the gap between the protrusion and the opposing member. [Figure 8] FIG. 8 is a cross-sectional view showing still another example of the plastic container of the present invention with its mouth portion sealed. [Figure 9] FIG. 9 is a cross-sectional view showing still another example of the plastic container of the present invention with its mouth portion sealed. [Figure 10] FIG. 10 is a cross-sectional view showing still another example of the plastic container of the present invention with its mouth portion sealed. [Figure 11] FIG. 11 is a partial cross-sectional view showing details of a spout portion of a resin drum described in Patent Document 1. [Figure 12] FIG. 12 is a cross-sectional view showing a state in which a dustproof cap is attached to the mouth plug portion of the resin drum described in Patent Document 1. [Figure 13] FIG. 13 is a cross-sectional view showing a state in which a safety seal cap is attached to the mouth plug portion of the resin drum described in Patent Document 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The plastic container of the first invention of this application is a plastic container comprising a container body having a mouth formed therein, and a plug for sealing the mouth, wherein a first threaded portion is formed on the inner surface of the mouth, and a second threaded portion capable of being screwed into the first threaded portion is formed on the outer surface of the plug, and a gasket is interposed between the outer surface of the plug and the inner surface of the mouth so as to abut against the outer surface of the plug and the inner surface of the mouth, and wherein a raised portion is formed on the inner surface of the mouth so as to be able to come into contact with the gasket.

[0012] The shape of the plastic container is not particularly limited, but is preferably substantially cylindrical, barrel-shaped or prismatic. The plastic container is preferably made of plastic.

[0013] The above-mentioned plastic may be any known resin that has traditionally been used as a material for liquid containers, such as a natural resin, a thermoplastic resin, or a thermosetting resin. However, a thermoplastic resin that has excellent thermoformability, high mechanical strength, and excellent cleanliness is preferred, and among these, an olefin-based resin is preferred.

[0014] The olefin resin is a polymer polymerized using olefin monomers such as ethylene monomers and propylene monomers as the main raw material, for example, ethylene homopolymers such as high density polyethylene resins, medium density polyethylene resins, and low density polyethylene resins, copolymers of ethylene with α-olefins such as propylene, 1-butene, 1-pentene, 1-hexene, and 1-heptene, propylene homopolymers such as homopolypropylene resins and random polypropylene resins, copolymers of propylene with α-olefins such as ethylene, 1-butene, 1-hexene, and 1-heptene, etc., etc., and high density polyethylene resins, medium density polyethylene resins, homopolypropylene resins, and random polypropylene resins that have high mechanical strength and excellent self-supporting properties are preferred, and high density polyethylene resins and polypropylene resins are more preferred. Moreover, these olefin resins may be used alone, or two or more types of olefin resins may be used in combination.

[0015] Next, the plastic container of the present invention will be described with reference to the drawings. In each drawing, the same or similar components are designated by the same reference numerals.

[0016] FIG. 1(A) is a side view showing an example of the plastic container of the present invention, and FIG. 1(B) is a plan view thereof. In FIG. 1(A), 1 is a barrel-shaped container body consisting of an upper wall portion 2, a side wall portion 3, and a bottom wall portion 4, and a mouth portion 5 and an air port 6 are formed on the upper wall portion 2. The air port 6 is an opening connected to a pressurizing device for injecting air so that the pressure inside the container is reduced when the stored liquid is discharged and the discharge speed of the stored liquid does not decrease, or for pressurizing the inside of the container in order to easily discharge the stored liquid. Of course, the air port 6 is closed during storage and transportation after filling the container body 1 with the stored liquid. Note that a plurality of air ports 6 may be provided. The structure of the air port 6 is not particularly limited, and may be simply open, cylindrical, or the same shape as the mouth portion in the present invention.

[0017] The method for producing the container body is not particularly limited, but when the container body is made of an olefin resin, it is preferable to mold the olefin resin by a blow molding method. As the blow molding method, any conventionally known blow molding method may be used, and examples of the blow molding method include extrusion blow molding, injection blow molding, stretch blow molding, and multilayer blow molding.

[0018] FIG. 2 is a cross-sectional view showing an example of a mouth portion 5 formed on the container body 1 of the plastic container. The mouth portion 5 has a cylindrical body 7 located above the upper wall portion 2 of the container body 1, and can inject and discharge the stored liquid. A first screw portion 8 is formed near the upper portion of the inner surface of the cylindrical body 7, and a substantially flat protruding portion 10 is formed at the lower portion of the first screw portion 8, which protrudes inward in a substantially horizontal direction via an inclined portion 9. Furthermore, the tip of the protruding portion 10 faces vertically downward, and its lowest end is connected to the upper wall portion 2 to form the mouth portion 5. A groove 11 having a substantially arc-shaped cross section is formed on the upper surface of the protruding portion 10, and a part of a gasket, which is an O-ring, described later, can be fitted into the groove 11, which is slightly recessed inward from the upper surface of the protruding portion 10.

[0019] Fig. 3(A) is a cross-sectional view showing an example of the plug 12 in the plastic container of the present invention, and Fig. 3(B) is a bottom view thereof. The plug 12 is composed of a disk-shaped upper member 13 and a disk-shaped lower member 14. The diameter of the upper member 13 is longer than that of the lower member 14, and the upper member 13 and the lower member 14 are laminated concentrically and molded integrally. A reinforcing rib is erected on the side of the upper member 13 to form a side wall 15, and the side wall 15 is formed with a second screw portion 16 that can be screwed into the first screw portion 8 formed on the inner surface of the cylindrical body 7. A groove 18 having a cross section of a substantially arc shape is formed on the lower surface 17 of the outer peripheral edge of the upper member 13, and a part of a gasket, which is an O-ring, described later, can be fitted into the groove 18 that is slightly recessed inward from the lower surface 17 of the outer peripheral edge.

[0020] FIG. 4 is a cross-sectional view showing an example of a state in which the mouth of the plastic container of the present invention is sealed. The second screw portion 16 formed on the side wall 15 of the upper member 13 of the plug 12 is screwed into the first screw portion 8 formed on the inner surface of the cylindrical body 7. By screwing the second screw portion 16 into the first screw portion 8, the gasket 21, which is an O-ring, comes into contact with the side surface 20 of the outer circumferential wall 19 of the lower member 14 of the plug 12 and the inner surface 9a of the inclined portion 9 of the cylindrical body 7, and a part of the gasket 21, which is an O-ring, fits into the recessed grooves 11 and 18. Thus, the gasket 21 is sandwiched and pressed against the outer surface of the plug 12 and the inner surface of the mouth 5 at four points, so that the mouth 5 can ensure excellent sealing. By making the gasket 21 out of a plastic material, the gasket 21 may be compressed and deformed when it is sandwiched and pressed. In order to improve sealing performance, it is preferable that the inner diameter of gasket 21 is the same as or slightly smaller than the outer diameter of lower member 14, and it is preferable that the diameter of gasket 21 is slightly larger than the height of side surface 20 of outer wall 19 of lower member 14, as long as a portion of gasket 21 can fit into grooves 11 and 18.

[0021] Reference numeral 22 denotes a plastic cap that is placed over the sealed mouth portion 5 to protect and strengthen it. The cap 22 may have a structure that covers the mouth portion 5 by pressing it to come into close contact with the cylindrical body 7 and the inclined portion 9, and when a threaded portion th is formed on the outer surface of the mouth portion 5, the cap 22 may have a structure that a threaded portion that can be screwed into the threaded portion th is formed on the inner surface of the cap 22.

[0022] If the cylindrical body 7 is distorted and not a perfect circle, the sealing performance will decrease, liquid leakage will occur, and the plug may fall off, so it is preferable that the planar shape of the cylindrical body 7 is a perfect circle. That is, the higher the circularity of the cylindrical body 7, the more preferable it is, and it is more preferably 1.0 mm or less, and even more preferably 0.8 mm or less.

[0023] In the present invention, the circularity is the difference between the length of the major axis and the length of the minor axis of the upper surface of the cylindrical body 7, and is expressed in mm. When a plastic container is manufactured by blow molding, it has an elliptical shape with the major axis being the PL (parting line) direction, so the length in the PL direction and the direction perpendicular thereto may be measured, and the difference between these lengths may be taken as the circularity, with a smaller difference meaning a higher circularity.

[0024] Since the second screw portion 16 formed on the side wall 15 of the upper member 13 is screwed into the first screw portion 8 formed on the inner surface of the cylindrical body 7, the upper member 13 is distorted and cannot ensure airtightness unless it is a perfect circle. This can reduce the sealing performance, cause liquid leakage, or cause the plug 12 to fall off, so it is preferable that the planar shape of the upper member 13 is also a perfect circle. In other words, it is preferable that the roundness of the upper member 13 is high, and more preferably, it is 1.0 mm or less, and even more preferably, it is 0.8 mm or less.

[0025] In this specification, an O-ring refers to a solid or hollow ring-shaped body, the cross-sectional shape of which is not particularly limited and may be, for example, circular, elliptical, rectangular, hexagonal, etc., but a circular shape is preferred so that it does not wear down or deform over time. Therefore, the O-ring is preferably a solid or hollow ring-shaped body having a circular cross-sectional shape.

[0026] By screwing the second screw portion 16 into the first screw portion 8, a part of the gasket 21, which is an O-ring, fits into the grooves 11 and 18, and the gasket 21 contacts the outer surface of the plug 12 and the inner surface of the mouth portion 5 at four points and is sandwiched and pressed, thereby ensuring excellent sealing performance of the mouth portion 5. Therefore, if the gasket 21, which is an O-ring, is too hard, its toughness decreases and its sealing performance is likely to decrease over time, and if it is too soft, it is likely to become worn or its abrasion resistance decreases, resulting in a decrease in sealing performance. Therefore, the hardness (durometer D) of the gasket 21 is preferably 40 to 48. In the present invention, the hardness (durometer D) is a value measured in accordance with JIS K 7215-1986.

[0027] Since an O-ring gasket 21 is sandwiched between the upper surface of the protrusion 10 protruding from the inner surface of the cylindrical body 7 and the lower surface 17 of the outer peripheral edge of the upper member 13 of the plug 12 to improve the sealing performance of the container body 1, it is preferable that the upper surface of the protrusion 10 and the lower surface 17 of the outer peripheral edge of the upper member 13 are both approximately horizontal and parallel.

[0028] In order to improve the sealing performance of the container body 1 by sandwiching an O-ring gasket 21 between the upper surface of the protrusion 10 protruding from the inner surface of the cylindrical body 7 and the lower surface 17 of the outer peripheral edge of the upper member 13 of the plug 12, it is preferable that the protrusion 10, the upper member 13 and the O-ring gasket 21 are in closer contact with each other.

[0029] If the surface smoothness of the upper surface of the protrusion 10 and the lower surface 17 of the outer peripheral edge of the upper member 13 with which the O-ring gasket 21 comes into contact becomes high, the surface pressure applied to the surface of the O-ring gasket 21 will not be uniform, and the sealing performance will decrease, so it is preferable that the above surface smoothness be small.

[0030] Therefore, the surface smoothness of the upper surface of the protrusion 10 and the lower surface 17 of the outer circumferential edge of the upper member 13 is preferably 0.30 mm or less, and more preferably 0.25 mm or less. For the same reason, the surface smoothness of the surface of the gasket 21 is also preferably 0.30 mm or less, and more preferably 0.25 mm or less.

[0031] Furthermore, since the protrusion 10 on the inner surface of the cylindrical body 7 has an O-ring gasket 21 located on its upper surface, in order to improve sealing performance, it is preferable that the surface smoothness of the upper surface of the protrusion 10 is smaller, preferably 0.20 mm or less, and it is preferable that the surface smoothness of the upper surface of the protrusion 10 is 0.05 mm or more smaller than the surface smoothness of the lower surface 17 of the outer peripheral edge of the upper member 13 and the surface of the gasket 21.

[0032] In the present invention, the "surface smoothness" is a value measured by a three-dimensional measuring device (manufactured by Mitutoyo Corporation, product name "Quick Vision PRO").

[0033] As described above, if a groove (11, 18) having a cross-sectional shape such as an arc-shaped groove into which a portion of a gasket 21, which is an O-ring, can be fitted is formed on the upper surface of the protrusion 10 formed on the inner surface of the cylindrical body 7 and / or the lower surface 17 of the outer peripheral edge of the upper member 13 of the plug 12, this is preferable because when the first threaded portion 8 formed on the inner surface of the cylindrical body 7 and the second threaded portion 16 formed on the side wall 15 of the plug 12 are screwed together, the plug 12 and the gasket 21, which is an O-ring, will adhere more strongly to each other, improving sealing performance.

[0034] Furthermore, for the same reason, a recessed groove having a cross-sectional shape such as an arc shape may be formed on the side surface 20 of the outer peripheral wall 19 of the lower member 14 of the plug 12 into which part of the gasket 21, which is an O-ring, can be fitted.

[0035] The material constituting the plug 12 and gasket 21 is preferably an olefin-based resin, more preferably a high-density polyethylene resin or a polypropylene resin, and when the plug 12 and the O-ring gasket 21 are made of an olefin-based resin, they are preferably molded by injection molding.

[0036] 5 is a cross-sectional view showing another example of a state in which the mouth of the plastic container of the present invention is sealed. The second screw portion 16 formed on the side wall 15 of the upper member 13 of the plug 12 is screwed into the first screw portion 8 formed on the inner surface of the cylindrical body 7a.

[0037] Gasket 21, which is an O-ring, is fitted so as to surround side surface 20 of outer peripheral wall 19 of lower member 14 of plug 12. On the upper surface of a substantially flat protrusion 23 that protrudes inwardly in a substantially horizontal direction from the inner surface of cylindrical body 7a, an upward protrusion 24 is formed concentrically with cylindrical body 7a, and cylindrical body 7a is tapered inwardly toward the bottom to form a protrusion 25 that protrudes inwardly.

[0038] In addition, the upward protrusion 24 may be formed concentrically and upwardly on the upper surface of the protrusion 23, and its position is not particularly limited, but it is preferable that it is formed on the upper surface of the protrusion 23 between directly below the center of the gasket 21, which is the O-ring, and the side surface 20 of the outer wall 19 of the lower member 14.

[0039] The cross-sectional shape of the upward protrusion 24 is not particularly limited, but is preferably, for example, a triangular, semicircular, elliptical, etc. In order to improve the sealing performance, the gasket 21 which is an O-ring and / or the upward protrusion 24 may be compressed and deformed when the gasket 21 which is an O-ring abuts against the tip of the upward protrusion 24, the raised portion 25, the lower surface 17 of the outer peripheral edge portion of the upper member 13, and the side surface 20 of the outer peripheral wall 19 of the lower member 14, and is clamped and pressed.

[0040] By screwing the second screw portion 16 formed on the side wall 15 of the plug 12 into the first screw portion 8 formed on the inner surface of the cylindrical body 7a, the gasket 21, which is an O-ring, is clamped and pressed by the underside 17 of the outer peripheral edge of the upper member 13 of the plug 12, the side surface 20 of the outer peripheral wall 19 of the lower member 14, and the tip and raised portion 25 of the upward protrusion 24, thereby sealing the mouth 5.

[0041] Since gasket 21, which is an O-ring, is clamped by raised portion 25, the surface smoothness of raised portion 25 is preferably 0.30 mm or less, more preferably 0.25 mm or less, and even more preferably 0.20 mm or less, and the surface smoothness of raised portion 25 is preferably 0.05 mm or more smaller than the surface smoothness of gasket 19, which is an O-ring.

[0042] Furthermore, a protrusion may be formed on one or more of the underside 17 of the outer periphery of the upper member 13, the side surface 20 of the outer periphery wall 19 of the lower member 14, or the raised portion 25. When such a protrusion is formed, the gasket 21, which is an O-ring, is clamped and pressed by more fulcrums, so that it is held more firmly and the container body 1 is more reliably sealed. The cross-sectional shape of this protrusion may be the same as the upward protrusion 24.

[0043] Furthermore, as shown in FIG. 6(A), a raised portion 26 can be provided on the side surface 20a of the outer peripheral wall 19a of the lower member 14, and as shown in FIG. 6(B), a raised portion 28 can be provided on the side surface 27 of the protruding portion 23. By providing such raised portions 26 and 28, the following effects can be expected. That is, since the gasket 21 is set on the plug 12 and then attached to the mouth portion 5, if the gasket 21 is not attached in the appropriate position when it is screwed, the surface of the mouth portion 5 or the surface of the plug 12 may be damaged, or the first screw portion 8 or the second screw portion 16 may be deformed. Therefore, by providing raised portions 26 and 28 on the side surface 20a of the outer peripheral wall 19a of the lower member 14 and the side surface 27 of the protruding portion 23, respectively, the positioning of the gasket 21 becomes easy, and the gasket 21 can be attached in the appropriate position. As a result, the surface of the mouth portion 5 or the surface of the plug 12 is not damaged, and the first screw portion 8 or the second screw portion 16 is not deformed. Therefore, the stored liquid will not leak and the plug 12 will not fall off. It is sufficient that the plastic container of the present invention is provided with either the raised portion 26 or the raised portion 28, and it is of course possible to provide both the raised portions 26 and the raised portions 28 on the same plastic container.

[0044] The gap d1 between the tip of the raised portion 26 and the protrusion 23 as shown in FIG. 7(A), and the gap d2 between the tip of the raised portion 28 and the outer peripheral wall 19 of the lower member 14 as shown in FIG. 7(B) are preferably 1 mm or less, more preferably 0.05 mm or less, and the lower limit of the gaps d1 and d2 is 0.01 mm.

[0045] 8 is a cross-sectional view showing yet another example of the state in which the mouth of the plastic container of the present invention is sealed. An upward protrusion 30 is formed concentrically with the cylindrical body 7b on the upper surface of a substantially flat protrusion 29 that protrudes inwardly in a substantially horizontal direction from the inner surface of the cylindrical body 7b. The cross-sectional shape of the upward protrusion 30 is not particularly limited, but is preferably a triangular, semicircular, elliptical, or other shape.

[0046] An O-ring gasket 21 is sandwiched between the upward projection 30 and the underside 17 of the outer peripheral edge of the upper member 13 of the plug 12 and the side surface 20 of the outer peripheral wall 19 of the lower member 14, and the O-ring gasket 21 is sandwiched and pressed by the outer peripheral edge 17 of the upper member 13 of the plug 12, the side surface 20 of the outer peripheral wall 19 of the lower member 14, and the tip of the upward projection 30, thereby sealing the mouth 5.

[0047] In order to improve sealing performance, the O-ring gasket 21 and / or the upward protrusion 30 may be compressed and deformed when clamped and pressed by the underside 17 of the outer edge of the upper member 13 of the plug 12, the side surface 20 of the outer wall 19 of the lower member 14, and the tip of the upward protrusion 30.

[0048] If the surface smoothness of the upward protrusion 30, the underside 17 of the outer peripheral edge of the upper member 13, and the side surface 20 of the outer peripheral wall 19 of the lower member 14 with which the O-ring gasket 21 comes into contact becomes high, the surface pressure applied to the surface of the gasket 21 will not be uniform, resulting in reduced adhesion and reduced sealing performance. Therefore, the surface smoothness of the upward protrusion 30, the underside 17 of the outer peripheral edge of the upper member 13, and the side surface 20 of the outer peripheral wall 19 of the lower member 14 is preferably 0.30 mm or less, and more preferably 0.25 mm or less.

[0049] In addition, in order to improve sealing performance, it is preferable that the center of gasket 21, which is an O-ring, is located directly above upward protrusion 30, and the surface smoothness of the surface of upward protrusion 30 is preferably smaller, preferably 0.30 mm or less, more preferably 0.25 mm or less, and even more preferably 0.20 mm or less, and it is preferable that the surface smoothness of the surface of upward protrusion 30 is 0.05 mm or more smaller than the surface smoothness of the underside 17 of the outer peripheral edge of upper member 13 and the surface of gasket 21, which is an O-ring.

[0050] 9 is a cross-sectional view showing yet another example of the state in which the mouth of the plastic container of the present invention is sealed. An upward protrusion 32 is formed concentrically with the cylindrical body 7c on the upper surface of a substantially flat protrusion 31 that protrudes inwardly from the inner surface of the cylindrical body 7c in a substantially horizontal direction, and a downward protrusion 33 is formed concentrically with the cylindrical body 7c on the lower surface 17 of the outer circumferential edge of the upper member 13 so as to be located directly above the upward protrusion 32. The cross-sectional shapes of the upward protrusion 32 and the downward protrusion 33 are not particularly limited, but are preferably, for example, triangular, semicircular, elliptical, or the like.

[0051] An O-ring gasket 21 is sandwiched between the upward protrusion 32 and the downward protrusion 33, and the O-ring gasket 21 is sandwiched and pressed by the tip of the upward protrusion 32, the tip of the downward protrusion 33, and the side surface 20 of the outer wall 19 of the lower member 14, thereby sealing the mouth 5.

[0052] In addition, in order to improve sealing performance, the gasket 21, which is an O-ring, the upward protrusion 32 and / or the downward protrusion 33 may be compressed and deformed when clamped and pressed by the tip of the upward protrusion 32, the tip of the downward protrusion 33, and the side surface 20 of the outer wall 19 of the lower member 14.

[0053] If the surface smoothness of the upward protrusions 32 and downward protrusions 33 with which the O-ring gasket 21 comes into contact becomes high, the surface pressure applied to the surface of the gasket 21 will not be uniform, reducing adhesion and sealing performance. Therefore, the surface smoothness of the upward protrusions 32 and downward protrusions 33 is preferably 0.30 mm or less, more preferably 0.25 mm or less, and even more preferably 0.20 mm or less, and the surface smoothness of the upward protrusions 32 and downward protrusions 33 is preferably 0.05 mm or more less than the surface smoothness of the surface of the O-ring gasket 21.

[0054] In order to improve sealing performance, it is preferable to position the upward protrusion 32, the downward protrusion 33 and the O-ring gasket 21 so that the center of the O-ring gasket 21 is located directly above the upward protrusion 32 and the downward protrusion 33 is located directly above the center of the O-ring gasket 21.

[0055] 8, a protrusion may be formed inward on the side surface 20 of the outer peripheral wall 19 of the lower member 14 and / or the inner surface 34 of the cylindrical body 7c. If such a protrusion is formed, the gasket 21, which is an O-ring, is clamped and pressed by more fulcrums, so that it is held more firmly and the mouth of the plastic container is more reliably sealed. The cross-sectional shape of this protrusion may be the same as the upward protrusion 24.

[0056] Furthermore, in Figure 8, if a protrusion is formed on the inner surface 34 of the cylindrical body 7b so as to protrude inward, by screwing the second screw portion 16 formed on the side wall 15 of the plug 12 into the first screw portion 8 formed on the inner surface of the cylindrical body 7b, the gasket 21, which is an O-ring, will be clamped and pressed at four points: the upward protrusion 30, the side surface 20 of the outer wall 19 of the lower member 14, the underside 17 of the outer edge of the upper member 13, and the above-mentioned protrusion, thereby further improving the sealing ability of the mouth of the plastic container.

[0057] In Figure 9, if a protrusion is formed on the inner surface 35 of the cylindrical body 7c so as to protrude inward, by screwing the second screw portion 16 formed on the side wall 15 of the plug 12 into the first screw portion 8 formed on the inner surface of the cylindrical body 7c, the gasket 21, which is an O-ring, will be clamped and pressed at four points: the upward protrusion 32, the side surface 20 of the outer wall 19 of the lower member 14, the downward protrusion 33, and the above-mentioned protrusion, thereby further improving the sealing ability of the mouth of the plastic container.

[0058] Fig. 10 is a cross-sectional view showing yet another example of the state in which the mouth of the plastic container of the present invention is sealed. Fig. 10 differs from the structure shown in Fig. 4 in that a diagonally upward protrusion 37 is formed concentrically with the cylindrical body 7d on the upper surface of a protrusion 36 of the cylindrical body 7d, which is a substantially flat plate-like body protruding inwardly from the inner surface of the cylindrical body 7d in a substantially horizontal direction. By screwing the second screw portion 16 formed on the side wall 15 of the plug 12 into the first screw portion 8 formed on the inner surface of the cylindrical body 7d, the gasket 21, which is an O-ring, is clamped and pressed by the lower surface 17 of the outer peripheral edge of the upper member 13, the side surface 20 of the outer peripheral wall 19 of the lower member 14, the diagonally upward protrusion 37, the protrusion 36, and the inner surface 38 of the cylindrical body 7d, and is firmly held, so that the mouth of the plastic container is sealed more reliably.

[0059] It is preferable that the plastic container of the present invention is provided with an identification information display section, which is a sheet on which identification information of the materials inside the container is printed, at a position on the container wall that can be read from the outside, and which allows the printable and updateable sheet to be affixed and peeled off.

[0060] The identification information display portion is preferably flat so that it can be read from the outside of the container wall, so that the identification information of the materials inside the container can be easily printed and updated, and so that the sheet on which the identification information of the materials inside the container is printed can be easily attached and peeled off, and is preferably installed on the top wall or side wall of the container.

[0061] The upper wall or side wall of a plastic container can be used as it is as an identification information display part, but if the plastic container is a transparent container, it is difficult to print or update the identification information, and the container is likely to peel off during transportation and may be difficult to read from the outside. Also, when a sheet with the identification information printed on it is attached, the attachment strength is weak and it may fall off during transportation, so it is preferable that the identification information display part is colored or has a matte finish or corona treatment, and has an uneven surface and is opaque.

[0062] The method of printing and updating the identification information on the identification information display section may be any conventionally known method, and may be handwritten, but it is preferable to use a printing method that can be managed by a computer, such as laser printing or inkjet printing.

[0063] Furthermore, when printing the identification information on the identification information display portion by laser printing or the like, the printing is performed by a laser involving a chemical reaction such as oxidation, so it is preferable to use an olefin-based resin which is more reactive than polyethylene resin, and it is also preferable that the outer layer contains inorganic pigments, organic pigments, inorganic fillers, and other additives which have been commonly used in the manufacture of olefin-based resin containers.

[0064] As the sheet on which the identification information is printed, a conventionally known adhesive label or adhesive sheet having an adhesive laminated on one surface of a paper or plastic sheet is preferably used.

[0065] The identification information display means is preferably a barcode, a two-dimensional code, a QR code (registered trademark), or an RF1D tag.

[0066] The plastic container of the present invention is lightweight, has high mechanical strength, excellent cleanliness, and has excellent resistance to leakage of the contents and excellent airtightness, and is therefore suitable for use as a container for filling, storing, and transporting beverages and edible liquids such as water, juice, and soy sauce, chemicals such as kerosene, acetic acid, hydrochloric acid, and nitric acid, high-viscosity and high-specific-gravity solutions such as CMP slurries containing high-specific-gravity fillers such as abrasives, metal powders, and inorganic fillers, and special industrial intermediate chemicals, etc. In particular, it meets the UN standards for transportation and is suitable for use as a transport container for high-viscosity and high-specific-gravity solutions. [Explanation of symbols]

[0067] 1 Container body 2 Upper wall 3 Side wall 4 Bottom wall 5 Mouth 6 Air Vent 7, 7a, 7b, 7c, 7d Cylindrical body 8 First screw part 9 Slope 10 Protrusion 11 Groove 12 Plug 13 Upper member 14 Lower member 15 Side wall 16 Second screw part 17 Underside of outer periphery 18 Groove 19, 19a outer wall 20, 20a Side 21 Gasket 22 Plastic Cap 23 Protrusion 24 Upward protrusion 25 Ridge 26 Ridge 27 Side 28 Ridge 29 Protrusion 30 Upward protrusion 31 Protrusion 32 Upward protrusion 33 Downward protrusion 34 Inside 35 Inside 36 Protrusion 37 Diagonally upward protrusion 38 Inside

Claims

1. A plastic container is provided with a container body (1) having a mouth (5) and a plug (12) for sealing the mouth, a first screw portion (8) is formed on the inner surface of the mouth, a second screw portion (16) capable of being screwed into the first screw portion is formed on the outer surface of the plug, and a gasket (21) made of an olefin resin is interposed between the outer surface of the plug and the inner surface of the mouth so as to abut against the outer surface of the plug and the inner surface of the mouth. In this plastic container, a cylindrical body (7a) constituting the mouth has a tapered inclined surface (25) whose diameter decreases toward the bottom. a protrusion (23) is formed so as to protrude horizontally inward from a lower end of the portion having the tapered slope, an upward protrusion (24) of triangular cross section is formed on an upper surface of the protrusion, a portion where the plug abuts against the gasket is hollowed out in a stepped shape by a flat horizontal surface (17) and a flat vertical surface (20), and the gasket is sandwiched between the portion having the tapered slope, the upward protrusion of triangular cross section, the flat horizontal surface, and the flat vertical surface.

2. 2. The plastic container according to claim 1, wherein a groove is formed on the outer surface of the plug and the inner surface of the mouth at the portion where the gasket comes into contact.

3. 3. The plastic container of claim 2, wherein the gasket is an O-ring.

4. 4. The plastic container according to claim 3, wherein the opening is covered with a cap.

5. 5. The plastic container according to claim 4, wherein the roundness of the mouth portion is 1.0 mm or less.

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