JP2008094453A - Plastic container with airtightness - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plastic container with airtightness which is easily openable and produced by an easy production process and maintains an airtightness even if it undergoes a temperature change or receives a shock such as falling. <P>SOLUTION: The plastic container is airtightly closed by mounting a screw cap onto a mouth part, is formed with threads on the outer periphery of the mouth part, and is provided with an undercut part whose outer diameter increases toward the top face at least partially between the upper end of the threads and the top face of the mouth part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a plastic container having excellent airtightness, and more particularly to a plastic container that can be sealed by attaching a screw-in type cap to a mouth.

  Conventionally, as one of packaging containers for filling and packaging various articles, there are various types of plastic containers molded by molding methods such as injection molding, extrusion molding, and blow molding. These plastic containers have various advantages such as light weight, resistance to breakage, low cost, easy manufacture, and mass production as compared with glass containers, and are widely used as packaging containers.

  Some of these plastic containers are filled with drinking water and sealed with a screw-on cap. In such a container, if the sealing property is impaired, a sanitary problem may occur, and the contents may leak and contaminate the surroundings. Therefore, a particularly reliable sealing property is required. However, when such a container is used, there are often situations where the sealing performance is liable to be lost, for example, the container filled with the contents is accidentally dropped to give a strong impact to the container. Furthermore, in recent years, it has been widely used to fill warm containers with plastic containers, and the containers and contents are subject to large temperature changes, such as heating, allowing them to cool to room temperature, or cooling them according to taste. A situation has arisen. When such a temperature change is applied, a change in the internal pressure of the container, a change in the physical characteristic value of the container material, a change in the deformation of the container, and the like occur, and there arises a problem that it becomes difficult to maintain the hermeticity of the container.

  On the other hand, if importance is placed only on the sealing property of the container, the ease of opening is impaired, and there is a problem that it becomes difficult for a person with weak power to open the container.

Conventionally, plastic containers filled with warm beverages are made white by crystallization of the mouth of the container (resulting in loss of plastic transparency and whitening) in order to achieve both the sealing performance and the ease of opening. Curing) (Japanese Patent Publication No. 4-13216: Patent Document 1). However, the mouth crystallization requires a heat treatment for a predetermined time, which complicates the process and causes a cost increase.
Japanese Patent Publication No. 4-13216

  The object of the present invention is to provide a hermetic seal that can be easily opened by a simple manufacturing process even though the hermeticity can be maintained even when subjected to an impact such as temperature change or dropping. The object is to provide an excellent plastic container.

  In a plastic container in which a screw is formed on the outer periphery of the mouth and can be sealed by attaching a screw-in type cap to the mouth, the upper end of the screw and the top surface of the mouth It has been found that the above-mentioned problems can be solved by providing an undercut portion whose outer diameter increases as it approaches the top surface in at least part of the space.

  Accordingly, the plastic container of the present invention is a plastic container that can be sealed by attaching a screw-in type cap to the mouth portion, wherein a screw is formed on the outer periphery of the mouth portion, and the upper end of the screw And an undercut portion whose outer diameter increases as it approaches the top surface, at least partly between the top and the top surface of the mouth.

  In a preferred aspect of the present invention, it is the plastic container, and further, a vent slot is not formed in the screw portion on the outer periphery of the mouth.

  In another preferred embodiment of the present invention, in the plastic container, the maximum inclination on the lower side of the thread slope of the screw portion on the outer periphery of the mouth is 15 ° to 19 ° with respect to the diameter direction. Suppose that

  In another preferred embodiment of the present invention, the plastic container is configured such that an increase amount of the outer diameter of the undercut portion is 0.01 mm to 2.00 mm.

  In another preferred embodiment of the present invention, the plastic container is configured such that the increase amount of the outer diameter of the undercut portion is 0.04 mm to 0.40 mm.

  In still another preferred embodiment of the present invention, the plastic container is a PET bottle.

  In still another preferred embodiment of the present invention, the plastic container is a PET bottle for heating.

  In still another preferred embodiment of the present invention, the plastic container is a PET bottle for heating that is not subjected to crystallization treatment at the mouth.

Plastic Container FIG. 1 shows an example of a schematic cross section of a mouth of a plastic container according to the present invention. As shown in FIG. 1, a screw is formed on the outer periphery of the mouth portion of the plastic container according to the present invention in order to attach a screw-in type cap.

  FIG. 2 shows an example of a schematic cross section of the mouth when a screw cap is attached to the plastic container according to the present invention shown in FIG. In the mouth part of FIG. 2, the outer ring contact part 21 which is a contact part with the cap between the upper end of the screw and the top face of the mouth part, and the contact ring which is a contact part between the top face of the mouth part and the cap. In the contact portion 22 and the inner ring contact portion 23 that is a contact portion between the inside of the mouth portion and the cap, the mouth portion and the cap are brought into close contact with each other, whereby the container is sealed.

  The material of the plastic container according to the present invention is not particularly limited as long as it is a resin material. For example, PE (polyethylene), PP (polypropylene), PS (polystyrene), PAN (polyacrylonitrile), PC (polycarbonate), PET (Polyethylene terephthalate), PBT (polybutylene terephthalate), PEN (polyethylene naphthalate), PES (polyethersulfone), COP (cyclic polyolefin), PA (polyamide), and the like, typically PET (polyethylene terephthalate) As a main component.

  The shape of the plastic container according to the present invention is not particularly limited as long as it can be hermetically sealed by attaching a screw-in type cap to the mouth, and typically has a capacity of 100 mL to 2 L. Moreover, it can be set as a 150-500 mL bottle and also a 200-400 mL bottle. The diameter of the mouth portion is not particularly limited, but typically, the diameter of the screw valley portion may be 10 to 100 mm, 15 to 50 mm, or 20 to 40 mm.

  The plastic container according to the present invention can be filled and stored with various contents at various temperature states (for example, refrigeration, room temperature and warming), and can be a container for room temperature and refrigeration, preferably Can be used as a plastic container for a warmed beverage, particularly a PET bottle for warming. Heating-compatible containers such as PET bottles that support heating range from warmed conditions (typically up to 60-70 ° C content temperature, up to 70 ° C at the warmer contact) to room temperature conditions, and consumer preferences Depending on the case, the container may be subjected to a refrigerated state (about 3 to 5 ° C.) and exposed to severe temperature changes. The container of the present invention is characterized in that it can maintain hermeticity even if it is exposed to such a temperature change or receives an impact such as accidental dropping, and nevertheless the opening performance can be secured.

  The plastic container according to the present invention may be any container whose mouth is crystallized or not crystallized, preferably a container whose mouth is not crystallized, It can be set as the PET bottle for heating which is not especially subjected to the mouth crystallization treatment. The container of the present invention is characterized in that it can maintain hermeticity even when subjected to temperature change or impact, and can secure the opening performance even if it is not crystallized to increase the hardness of the mouth. . Therefore, the mouth crystallization step can be omitted in the manufacturing process, cost and labor can be reduced, and the yield rate can be improved.

Undercut Portion A plastic container according to the present invention is provided with an undercut portion. In this specification, the undercut portion is a portion formed between the upper end of the screw formed on the outer periphery of the container mouth portion and the top surface of the mouth portion so that the outer diameter increases as the top surface is approached. Say. The upper end of the screw here means a circular cut line when the mouth is cut in a line passing through the end of the screw thread closer to the mouth, and the screw thread is actually formed at each part of the outer periphery of the mouth. It is not the part that reaches The undercut portion only needs to be formed in a ring shape at least at a part between the upper end of the screw and the top surface of the mouth portion.

  FIG. 3 is an enlarged schematic view of a cross section of the plastic container mouth of the present invention. In FIG. 3, the space between the upper end of the screw and the top surface of the mouth is schematically shown. An outer diameter increasing portion 32 is provided between the top surface 31 and the upper end of the screw 33, and the upper end of the screw 33 and the outer diameter increase. It can be seen that an undercut portion, which is a portion whose outer diameter increases as it approaches the top surface, is formed between the portion 32 (exaggerated in the drawing). The increase in the outer diameter may be a shape that draws a curve as shown in FIG. 3 or may be linear. Further, the undercut portion can be provided at the lower portion between the top surface 31 and the screw upper end 33, and conversely, the outer diameter of the upper portion between the top surface 31 and the screw upper end 33 becomes closer to the top surface. It is also possible to provide an outer diameter decreasing portion that decreases.

  When the undercut portion is provided in this way, the container is heated, and even if the mouth portion is deformed so as to collapse inward (deformation such that it falls to the right side in FIG. 3), contact with the outer ring of the cap is prevented. It can be secured and the sealing property of the container can be maintained. In the present invention, the amount of increase in the outer diameter of the undercut portion is not particularly limited, but if the amount of increase is too large, it may be difficult to open the cap due to friction with the cap due to an increase in the outer diameter of the mouth. Therefore, for example, the amount of increase in the outer diameter of the undercut portion can be 0.01 mm to 1.00 mm, preferably 0.04 mm to 0.40 mm.

Screw part The screw part on the outer periphery of the mouth part of the plastic container according to the present invention preferably has no vent slot. Here, the vent slot is a cutout in the vertical direction (that is, the direction crossing the screw thread) formed in the screw portion. Such a vent slot may be provided to promote drainage of the cleaning water or the like of the screw part, but it tends to impair the roundness of the mouth part and lead to the loss of sealing performance and openability. Therefore, it is preferable not to form a vent slot particularly in the case of a bottle for heating that is assumed to have a large temperature change.

  The screw portion on the outer periphery of the mouth of the plastic container according to the present invention is preferably such that the maximum inclination on the lower side of the thread slope (opposite to the top surface) is 15 ° to 19 ° with respect to the diameter direction. And The maximum inclination on the lower side of the thread slope is an angle of a portion indicated by A in FIG. 3, and is an inclination at which the angle A is “smallest”. This portion is typically 20 °, but this portion is deformed in the direction of thickening the screw thread to be 15 ° to 19 °, so that it is between the mouth screw valley and the cap screw thread. Clearance can be reduced and sealing performance can be increased. In addition, the screw portion on the outer periphery of the mouth of the plastic container according to the present invention is preferably a ratio of the cross-sectional area on the upper side of the screw to the cross-sectional area on the lower side of the screw when the screw thread is divided by a line passing through the top of the screw thread. Can be 1: 1.01-1.10. Thus, by making the cross-sectional area on the lower side of the screw slightly larger than the cross-sectional area on the upper side of the screw, the clearance between the mouth screw valley and the cap screw thread can be reduced and the sealing performance can be improved.

Method for Manufacturing Plastic Container The plastic container according to the present invention can be molded using molding methods such as extrusion molding, injection molding, blow molding, cast molding, thermoforming, etc. It is manufactured by a method of subjecting a molded body (also called a preform) to biaxial stretch blow molding. And preferably, in forming the preform, a gas barrier layer may be formed in the polyethylene terephthalate resin layer by using a co-injection molding method. In addition, preferably, the mouth crystallization step can be omitted.

  Hereinafter, the plastic container according to the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

  Non-crystallized warming PET bottle (280 mL) with mouth as shown in Fig. 1 No vent slot, undercut one side 0.06mm, maximum slope 18 ° below thread slope As an example, the following sealing performance test (instantaneous pressure resistance test, heating / cooling drop test) and the opening performance test were performed.

The cap described in FIG. 1 of JP-A-2002-68282 (manufactured by Nippon Crown Cork Co., Ltd.) was used. The tightening conditions were as follows.
・ Capper: 24H Servo Capper made by Shibuya Industries ・ Temporary tightening torque: 180 N ・ cm
・ Tightening torque: 200 N · cm
・ Meshing torque: 200 N · cm
・ Top load: 150N
・ Rotation speed 180rpm

  On the other hand, tests with other mouth shapes were performed under the same conditions as described above.

<Instantaneous pressure test (SST)>
After being stored at 70 ° C. for 1 week, the pressure was increased to 0.4 MPa in a 70 ° C. water tank for 12 seconds, and the pressure was maintained for 1 minute to check whether bubbles were generated between the mouth and the cap. Tests were performed on 10 samples each.

<Heating / cooling drop test>
After storing at 70 ° C. for 1 week, it was left at 23 ° C. for 1 day. Thereafter, a methylene blue ethanol solution was injected from the bottom of the cap, and the methylene blue ethanol solution was dropped from a height of 50 cm onto an inclined surface of a lump having an inclination of 10 °. The presence or absence of inhalation of methylene blue into the contents liquid was confirmed. Tests were performed on 10 samples each.

<Cooling openability test>
After storage for 1 week at 5 ° C after filling, 1st opening torque (torque when the cap starts to move), 2nd opening torque (torque during opening), leak angle (rotation angle of the cap at the start of air passage), The bridge break angle (the angle at which the tamper epident band (TE band) for confirming whether or not the plug was opened) and the BL angle (the angle obtained by subtracting the bridge break angle from the leak angle) were measured. The preferred ranges were 1st opening torque of 40 to 180 N · cm, 2nd opening torque of 20 to 180 N · cm, no missing band, leak angle of 100 ° or more, and BL angle of 0 ° or more.

<Heating and room temperature openability test>
After filling, the sample was stored at 70 ° C. for 1 week, and measured in the same manner as the cooling-time opening test except that the measurement was performed after leaving at 23 ° C. for 1 day.

The results are shown in Table 1.

It is a schematic sectional drawing of the plastic container opening part of this invention. FIG. 3 is a schematic cross-sectional view of a mouth when a screw-type cap is attached to a plastic container according to the present invention. It is an expansion schematic diagram of the plastic container mouth part cross section of this invention which exaggerated the undercut part.

Explanation of symbols

21 outer ring contact portion 22 contact ring contact portion 23 inner ring contact portion 31 top surface 32 outer diameter increasing portion 33 screw upper end

Claims (8)

A plastic container that can be sealed by attaching a screw-on cap to the mouth,
A screw is formed on the outer periphery of the mouth,
A plastic container, characterized in that an undercut portion whose outer diameter increases as it approaches the top surface is provided at least at a part between the upper end of the screw and the top surface of the mouth portion.   The plastic container according to claim 1, wherein a vent slot is not formed in a screw portion on the outer periphery of the mouth portion.   2. The plastic container according to claim 1, wherein a maximum inclination on a lower side of a thread slope of a screw portion on an outer periphery of the mouth is 15 ° to 19 ° with respect to a diameter direction.   The plastic container according to claim 1, wherein an increase in the outer diameter of the undercut portion is 0.01 mm to 2.00 mm.   The plastic container according to claim 1, wherein an increase amount of the outer diameter of the undercut portion is 0.04 mm to 0.40 mm.   The plastic container according to claim 1, wherein the plastic container is a PET bottle.   The plastic container according to claim 1, wherein the plastic container is a PET bottle for heating.   The plastic container according to claim 1, wherein the plastic container is a heating-compatible PET bottle whose mouth is not crystallized.

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