JPH04242541A - Inner pressure-proof container - Google Patents

Abstract

PURPOSE:To provide an inside pressure-proof container in which detection of a pinhole such as a stress crack of a container can be made correctly and invasion of strangers such as dust and insects into a base cup can be prevented by providing a small diameter ventilation hole opened outward on both walls of a sealed bottom chamber and a sealed leg chamber. CONSTITUTION:An inside pressure-proof container is constituted of a container 1 and a base cup 2. A bottom part of the container 1 inserted into an opening part of the base cup 2 is adhered to the base cup 2 closely. On the other hand, a support wall 6 of the base cup and the bottom part 8 of the container 1 are adhered closely. As a result, a leg chamber 3 and a bottom chamber 4 are sealed from outside. A small diameter ventilation hole 5 which is pierced on a wall of the sealed chambers 3 and 4 communicates the chambers 3 and 4 with outside. As a result, when a pinhole such as a stress crack is produced in the bottom part of the container 1, it is immediately detected. If a connection between the base cup 2 and the container 1 is strong enough, self-standing of the container 1 and protection of the bottom part of the container 1 can be improved. Further, the diameter of the ventilation hole 5 is preferably 1 to 2mm.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an internal pressure resistant container containing contents with high internal pressure, such as gas-containing beverages.

[Prior Art] It has been known for a long time to make the bottom of a container protrude into a hemispherical shell shape in order to improve internal pressure resistance. However, since containers with such a shape are not self-supporting, base cups serving as legs have been installed. Attempts for pinhole detection have also been proposed.

[Problem to be solved by the invention] The base cup has a function of supporting the container,
It must be bonded sufficiently firmly to the bottom of the container. Furthermore, since the container filled with the contents is heavy, it is desired that the container be structurally strong.

For this reason, in conventional gas-containing beverage containers with high internal pressure, the base cup and the bottom of the container are tightly fixed in order to improve self-standing stability and strength.

However, with such a structure, a closed chamber is formed surrounding the bottom of the container and is isolated from the outside by the bottom of the container and the base cup. This makes pinhole testing of the container impossible. In other words, even if there is a pinhole at the bottom of the container, it cannot be detected because it is sealed by the base cup.

[Means for Solving the Problems] The present invention provides: 1. The bottom of a synthetic resin container that protrudes in the shape of a hemispherical shell,
The base cup is made up of a cylindrical leg wall having a substantially vertical outer circumferential wall and a support wall connected to the leg wall. The support wall is fitted into the opening of the base cup and is tightly coupled to the base cup. In an internal pressure-resistant container that is tightly joined to a shaped bottom to form a free-standing leg, there is a sealed bottom chamber surrounded by a support wall and a hemispherical shell-shaped bottom of the container, and a sealed bottom chamber surrounded by a cylindrical leg wall and a hemispherical shell-shaped bottom of the container. A pressure-resistant container with a small-diameter ventilation hole that opens to the outside in a sealed leg chamber.

2. The pressure-resistant container according to claim 1, wherein the hemispherical shell-like protruding bottom of the container and the opening of the cylindrical leg wall of the base cup are tightly joined together using an adhesive.

3. The internal pressure resistant container according to claim 1 or 2, wherein the hemispherical bottom of the container and the support wall are closely joined together using an adhesive.

4. The internal pressure resistant container according to any one of claims 1 to 3, wherein the hemispherical bottom of the container and the support wall are closely joined together using a hot melt adhesive.

5. The internal pressure resistant container according to any one of claims 1 to 4, wherein the vent hole comprises a plurality of small holes having a diameter of 1 mm to 2 mm. ”.

As the container of the present invention, a container made of stretch blow molded synthetic resin is suitable, and a container molded of polyethylene terephthalate resin is most preferable. The base cup is preferably molded from synthetic resin.

The bottom of the container is inserted and fitted into the upper opening of the base cup, and if the two are not only tightly fitted but also joined using an adhesive, the adhesion strength is increased and the self-supporting property is stabilized.

The connection between the support wall of the base cup and the bottom of the container is very important, and if the connection between the two becomes misaligned, the container will tilt and lose its independence. Therefore, it is necessary not only to simply bring them into contact, but also to bond them together with an adhesive. In view of the speed of the bonding process, it is optimal to bond using a polyamide hot melt adhesive. A good bond between the base cup and the container provides good self-support as well as good protection of the bottom of the container. The diameter of the vent hole is most preferably 1 to 2 mm.

[Function] As mentioned above, conventional pressure-resistant containers that can withstand the high internal pressure of gas-containing beverages and the like have been sealed by bringing the base cup into close contact with the bottom of the container, making it impossible to detect pinholes in the bottom of the container. However, in the manufacture of pressure-resistant containers, the shoulders and body are stretched and oriented crystallized, resulting in high strength, but the central portion of the bottom is not stretched and is therefore weak in strength. Therefore, the center of the bottom is thermally crystallized to improve strength. However, since neither thermal crystallization nor orientation crystallization occurs at the boundary between the thermally crystallized portion and the stretch-oriented crystallized portion, the strength is low and the strain is large, so there is a strong tendency for stress cracking to occur after molding.

As mentioned above, when the base cup is installed, the area near the center of the bottom of the container, where cracks are most likely to occur, forms the upper surface of the sealed bottom chamber surrounded by the supporting walls of the base cup, so the bottom of the container is ultimately sealed. It will be sealed by the bottom chamber.

In other words, even if a stress crack exists near the center of the bottom of the container, it is isolated from the outside by the base cup.

Further, since the bottom part slightly away from the center forms a sealed leg chamber with the cylindrical leg part of the base cup, any stress cracks that occur in this bottom part are also in a sealed state.

Therefore, even if a pinhole test is performed on the container, the internal pressure does not change immediately and cannot be detected.

However, if the contents are filled and left unattended, a serious problem arises in that gas gradually escapes.

According to the inventor's research, gas moves from the crack to the sealed bottom chamber, gradually enters the sealed leg chamber through the joint gap between the support wall and the bottom of the container, and gradually escapes to the outside through the gap between the fitting part of the base cup and the container. do. Therefore, as time passes, most of the gas escapes from inside the container, and the internal pressure drops significantly.

The inventor of the present invention has researched the detection of pinholes mainly caused by stress cracking in pressure-resistant containers, and has concluded that there is no other way than to break the seal at the bottom of the container by the base cup.

On the other hand, the integral connection of the base cup and the bottom of the container is absolutely necessary for self-sustaining stability.

As a result of various studies to satisfy these two contradictory requirements, the inventor of the present invention solved the problem by installing small-diameter ventilation holes that open to the outside in both the walls of the sealed bottom chamber and the sealed leg chamber. solved.

Gas leaking from the container is released to the outside through this vent, so pinholes can be easily detected by a pinhole test.

Since the sealed bottom chamber and the sealed leg chamber are each independent, it is necessary to provide ventilation holes in both. The installation position of the ventilation hole is not particularly limited, but it may be provided on the wall.

In order to explain the operation of the present invention in an easy-to-understand manner, a comparison will be made with the above-mentioned conventional technology.

Japanese Utility Model Publication No. 61-129730 discloses a base cup in which a recess is provided in the support wall of the base cup that continues from the center to the inner circumferential wall, and a sealed portion surrounded by the bottom chamber of the base cup communicates with the outside. The bottle with which it is attached is listed. This bottle is said to be capable of detecting pinholes in the bottom of the bottle in a pinhole test because gas is released from the pinhole in the bottom of the bottle through a support wall recess.

However, in actual tests, it is often impossible to detect pinholes.

The reason for this is that when bonding the bottom of the bottle and the support wall of the base cup, the adhesive flows into the recesses of the support wall and fills the grooves.

In particular, it has been found that when hot melt adhesive is used, the adhesive not only flows in during pressure bonding, but also directly fills the groove depending on the position where the adhesive is applied. However, it is difficult to supply adhesive to the support wall of the base cup at a constant position, and controlling the adhesive position reduces the work speed by 1.
There is a drawback that it cannot be avoided that the value decreases to /2 or less.

According to the research of the present inventor, it is necessary that the supporting wall of the bottle bottom and the base cup be firmly fixed with adhesive, and that it is necessary to apply adhesive to the supporting wall and then press it. It was found that it was not possible to prevent the adhesive from flowing into the grooves.

Also, since this method inevitably reduces the bonding area,
The connection with the bottle is weak, and there is a high risk of the bottle tipping.

Next, although a container equipped with a base cup for beverages that does not contain gas is already known, as described in, for example, Japanese Patent Laid-Open No. 2-85151, an explanation will be given to avoid confusion between this container and the present invention. do.

In other words, the container described in JP-A-2-85151 is not a container for storing contents with high internal pressure, but a container for heating and sterilizing the contents, and the purpose and required performance are completely different. In this container, since the sterilizing shower must be introduced into the base cup, a shower inflow gap is provided between the peripheral wall of the bottom of the container inserted into the base cup opening and the inner peripheral wall of the base cup opening, and the base cup The container has a shower mixing gap between the support wall and the bottom of the container so that the shower flows into the bottom chamber on the center side of the support wall, and the shower outlet is arranged in the legs and the bottom chamber. There is.

This container is completely different in purpose, structure, and effect from the container of the present invention.

The first difference is that a gap is provided between the opening of the base cup and the bottom of the container to allow sufficient contact of the sterilizing shower to the bottom of the container. In other words, the leg compartments are not sealed and are open to the outside world.

The second difference is that the sterilizing shower also flows into the bottom chamber surrounded by the supporting walls of the base cup. In other words, the bottom chamber is not sealed and is open to the outside.

The third difference is that the base cup and the container are not tightly bonded and fixed.

This structure is a container that does not have high internal pressure and is a container for sterilizing showers, so it is a necessary structure to provide a shower passage.

I see, there are shower outlets in the legs and bottom chamber, but even without such outlets, the bottom chamber and legs communicate with the outside through the shower inlet gap, so ventilation holes are necessary from the beginning. Not. The shower outlet is not a vent.

However, this container cannot be used for internal pressure resistance. In such a structure in which the base cup and the container do not come into close contact with each other, the container may shift and tilting cannot be prevented. In particular, in the case of a high internal pressure container, if there is a tilt during automatic filling, accidents due to misalignment between the beverage nozzle and the mouth of the container will increase, and this is not suitable.

Furthermore, as mentioned above, the hot water for shower sterilization has surface tension, so the outlet needs to be of sufficient size. Drainage cannot be done through small diameter ports.

However, through such large holes, dirt and insects can get into the bottom chamber and the legs, and when viewed from the outside of the container, it appears as though the dirt and insects are inside the container and are inside the contents. The apparent product value is lost. In particular, since the base cup and container are joined together to ensure self-supporting stability, dirt and insects cannot be removed, which inevitably results in defective products.

The ventilation holes provided in the walls of the bottom chamber and the leg chamber of the base cup of the present invention are small-diameter holes through which gas passes, and are not large-diameter holes such as liquid passage ports. Therefore, there is no danger of dirt or insects entering.

A vent hole with a diameter of 1 to 7 mm is sufficient for pinhole testing of the container. However, in order to prevent foreign matter from entering, it is necessary to have a small opening of 1 to 2 mm, and to provide the ventilation required for the test, it is necessary to arrange a plurality of openings to increase the ventilation.

〔Example〕

Next, the present invention will be specifically explained by showing Examples, Comparative Examples, and Comparative Tests.

FIG. 1 is a partially sectional front view of an internal pressure resistant container equipped with a base cup of the present invention, where 1 indicates the container and 2 indicates the base cup. 3 is the leg chamber of the base cup, and 4 is the bottom chamber of the base cup, both of which are closed rooms shut off from the outside. Reference numeral 5 denotes small-diameter ventilation holes provided in the walls of these closed chambers, and each closed chamber communicates with the outside through this ventilation hole.

FIG. 2 is an enlarged view of the bottom of the container shown in FIG. 1 and the attachment portion of the base cup.

The bottom part of the container inserted into the base cup opening is in tight contact with the base cup at 7, while in tight contact with the supporting wall 6 of the base cup at 8. Therefore, the leg chamber 3 and the bottom chamber 4 are in a sealed state from the outside. Reference numeral 5 indicates a small-diameter ventilation hole provided in the walls of these closed rooms. Each closed chamber communicates with the outside through this ventilation hole.

Therefore, if there is a pinhole such as a stress crack at the bottom of the container, it can be detected immediately.

FIG. 3 is an enlarged view of the bottom of a conventional pressure-resistant container.

It is understood that since there are no ventilation holes in the leg chamber 3 and the bottom chamber 4, pinholes in the container are sealed by these closed chambers and cannot be detected.

FIG. 4 shows the bottom of the container described in JP-A-2-85151. A container bottom 1 is attached to a base cup 2 forming a shower passage 10. A shower passage 11 is also arranged between the support wall 6 of the base cup and the bottom chamber. As is clear from this structure, the leg room 3 is communicated with the outside through the shower passage 10. It is also understood that the bottom chamber 4 communicates with the outside via the shower passage 11 at 10. These shower passages must be sufficiently spaced to prevent flow obstruction due to surface tension of the shower. Of course, the shower drain 9 also needs to have a large diameter, which will allow dirt and insects to enter.

FIG. 5 is a plan view of the bottom of the base cup. It is clear that shower drains 5 are provided in the bottom compartment 4 and the leg compartment 3.

Next, the results of the comparative test are shown.

Comparative Test 1 Pinhole Test The containers of the present invention shown in FIG.
The container shown in the figure was filled with 6 kg/cm2 of air, and pinholes due to a drop in gas pressure were detected. Comparative Example 2 used the container described in the specification of Utility Model Application Publication No. 129730/1983. The resin, volume, etc. are the same as in the present invention. The results are shown in Table 1.

Note: Bottles with even a slight drop in gas pressure were counted as the number of bottles with reduced gas pressure.

It is understood that pinholes cannot be detected in the comparative example.

Comparative Test 2 Next, 4G. V. of carbon water and stored at room temperature, and inspected every 3 months, 6 months, and 12 months. The test results are shown in Table 2.

It is clear that undetectable pinholes will cause gas to escape during storage.

Note: Bottles with even a slight drop in gas pressure were counted as the number of bottles with reduced gas pressure.

Comparative Test 3 1000 polyethylene terephthalate resin biaxially stretched blow-molded bottles each having a resin amount of 50 g and a volume of 1.5 liters were used, and a bottle of the present invention with a base cup shown in FIG. In a comparative example bottle equipped with a base cup, 4G of carbon water was added. V. The bottles were filled and transported from Tokyo to Naha City, Okinawa Prefecture via normal distribution routes, and stored there for 3, 6, and 12 months. We counted the number of bottles that were tilted and the number of foreign objects such as dirt and insects that had entered the bottom chamber and leg chamber of the base cup. The test results are shown in Tables 3 and 4.

Note: A bottle that was even slightly tilted was counted as tilted.

〔effect〕

As described above, the present invention is extremely effective in accurately detecting pinholes such as stress cracks in containers, preventing foreign matter such as dirt and insects from entering the base cup, and preventing containers from tilting. It has a great effect.

[Brief explanation of the drawing]

FIG. 1 is a partially vertical front view of the container of the present invention. Second
The figure is an enlarged view of the bottom of the container of the invention. FIG. 3 is an enlarged view of the bottom of a conventional container, and FIG. 4 is an enlarged view of the bottom of a shower sterilization container. 5 is a bottom plan view of the shower sterilization container of FIG. 4; FIG. 1: Container 2: Base cup 3: Leg chamber 4: Bottom chamber 5: Ventilation hole 6: Support wall 7: Close joint 8: Close joint 9: Drain hole 10: Shower passage 11: Shower passage

Claims (5)

[Claims] Claim 1: The bottom of a container made of synthetic resin, which protrudes into a hemispherical shell shape, is formed by a base cup comprising a cylindrical leg wall having a substantially vertical outer circumferential wall and a support wall connected to the leg wall. In an internal pressure resistant container that is assembled and fixed by fitting into the opening and tightly joining, and the support wall is tightly joined to the hemispherical shell-like bottom of the container to form a self-supporting leg, the container is surrounded by the support wall and the hemispherical shell-like bottom of the container. A pressure-resistant container that is equipped with a small-diameter ventilation hole that opens to the outside in a sealed bottom chamber surrounded by a cylindrical leg wall and a hemispherical bottom of the container. 2. The pressure-resistant container according to claim 1, wherein the hemispherical shell-like protruding bottom of the container and the opening of the cylindrical leg wall of the base cup are tightly joined together using an adhesive. 3. The internal pressure resistant container according to claim 1, wherein the hemispherical bottom of the container and the supporting wall are closely joined together using an adhesive. 4. The internal pressure resistant container according to claim 1, wherein the hemispherical bottom of the container and the support wall are closely joined together using a hot melt adhesive. 5. The pressure-resistant container according to claim 1, wherein the vent hole comprises a plurality of small holes having a diameter of 1 mm to 2 mm.