JPH10305824A - Heat-resistant and pressure-resistant self-supporting type hollow container made of synthetic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hollow container imparted with resistances to heat and pressure and provided with a leg for self-supporting the container by forming the wall thickness of a lower portion of the container so as to be two or more times thicker than that of a body and constituting the weight of the lower portion of the container so as to have about half of the total weight of the container, in a hollow container formed by biaxially stretched blow molding of a polyester resin such as polyethylene terephthalate. SOLUTION: A thermoplastic synthetic resin is molded into a bottle-like hollow container composed of a mouth 1, a shoulder 2, a body 3 and a bottom 4 by biaxially stretched blow molding. The bottom 4 is formed into a semispherical shape in such a state as to protrude outward, and a leg 5 for self-supporting the container is formed at the bottom 4. The wall thickness of a bottom wall 4a of the bottom 4 is formed into the state of a wall thickness having 10-12 times as thick as that of the body 3, and the wall thickness of the leg 5 is formed into the state of a wall thickness having two - three times as thick as that of the body 3. It is so designed that the weight of the bottom of the container has about half of the weight of the mouth and its lower portion of the container.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant and pressure-resistant hollow container having a self-supporting bottom portion formed by biaxially stretch-blowing a thermoplastic synthetic resin, and more particularly to a biaxially stretched polyester resin such as polyethylene terephthalate. Stretch blow molding, forming the lower part of the container to the meat pressure, heat resistance suitable for filling carbon dioxide-containing beverages with self-supporting legs,
The present invention relates to a cylindrical hollow container having pressure resistance.

[0002]

2. Description of the Related Art Polyethylene terephthalate resin (PE)
(T-resin) is obtained by biaxially stretch-blow-molding the bottle, which is lightweight and excellent in transparency, has higher strength than other resin bottles, less change over time, and is safe from food hygiene. , Cider, cola, beer and other beverage containers containing carbon dioxide. However, when the beverage container is formed into a normal cylindrical flat-bottom free-standing bottle, the bottom portion is formed by the internal pressure of carbon dioxide contained in the internal solution due to various environmental conditions after filling the beverage solution. However, there has been a problem in that the container expands and deforms, and the container cannot be stably self-supported as it is.

In order to eliminate the above-mentioned drawbacks and to provide the container with pressure resistance, Japanese Patent Laid-Open Publication No.
As shown in JP-A-53566 and JP-A-58-73710, a method of raising the bottom of the bottle to the inside like a champagne bottle and indenting it into a bottom shape is disclosed in JP-A-59-118729 and JP-A-62-33529. As shown in the publication, the method of bulging the bottom of the bottle to the outside in a hemispherical shape has been frequently used.However, in the case of raising the bottom inward and denting it into a bottom, an annular bottom is formed on the bottom. It is formed and can be self-supported, but the one with the bottom part bulged in a hemispherical shape is the best in terms of strength, but it can not be self-supported as it is, so it was molded separately from the main body It is necessary to mount the base cup on the bottom of the main body, or to integrally form legs for landing on the bottom of the main body.

[0004] However, a bottle in which the base cup is mounted on the bottom of the bottle main body can exhibit high pressure resistance against internal pressure since the bottom is also sufficiently stretched and deformed. Since the base cup is configured as a separate member from the bottle body, a special work process is required to attach the base cup to the bottle body, and the base cup itself is a synthetic resin different from the bottle body. In addition, there is a problem from the viewpoints of resource saving and recycling. Pressure-resistant containers, so-called one-piece bottles, have come to be used.

As shown in FIG. 4, a self-standing pressure-resistant container made of such a one-piece bottle is formed by raising the bottom inward and swelling outward on the bottom wall of the bottle body recessed in the bottom-shaped curved wall. With legs formed (Japanese Patent Publication No. 64-1032)
No. 9, as shown in FIG. 5, or as shown in FIG. 5, a bottom portion of a bottle whose bottom is bulged outward in a hemispherical shape, and which is bulged outward to form a leg (Japanese Patent Laid-Open No. 5-254529). Reference). However, the bottom wall of the container having such a shape tends to be insufficiently biaxially stretched as compared with the upper wall and the body wall, and the biaxial stretching is sufficiently biaxially stretched. It is easy to deform compared to the wall, so it lacks stable independence, and the bottom part swells and deforms due to heat sterilization, transfer and other external environment changes after filling and sealing the contents There is a drawback that a cracking phenomenon easily occurs in the rocker bottom and the bottom.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a one-piece bottle in which a leg is integrally formed on a bottom of a hollow container obtained by biaxially stretch-blow-molding a preform made of a thermoplastic resin, preferably PET resin. After filling and sealing the carbonated beverage in the hollow container, the rocker bottom and cracks are not generated at the bottom of the container even by external environment such as heat sterilization by pasterizer, cooling treatment, impact at the transfer stage, etc. In addition, the present invention provides a pressure-resistant container having a strong bottom portion of the container body and having a stable self-sustainability as a low-cost, easy-to-recycle one.

[0007]

SUMMARY OF THE INVENTION A thermoplastic synthetic resin is biaxially stretch blow-molded into a bottle-shaped hollow container having a mouth, a shoulder, a body, and a bottom, and the bottom is recessed inward. Either a spherical shape so as to be in a state or a hemispherical shape so as to be outwardly convex to increase pressure resistance and form a seating portion or a leg at the bottom for allowing the container to stand on its own. A free-standing bottle-shaped hollow container having a bottom portion having a bottom wall thickness excellent in internal pressure resistance, impact resistance, and the like, wherein the bottom wall thickness is formed to be uniform and thicker than the wall thickness of the shoulder portion and the body portion. And

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described in JP-B-64-10329 and JP-A-5-254529, those having a container bottom formed in a spherical shape and provided with a seating portion or a leg portion are described below. The bottom wall is easy to be formed with uneven thickness,
Since the degree of stretching orientation is smaller than that of the body, the internal pressure is not so large, and there is no problem in the case of a container having an internal volume of 1 liter or less, but the internal pressure is large and the internal volume is 1 liter or more. When used in a container for carbonated drinks, there are drawbacks such as deformation of the legs, resulting in poor self-standing stability, and cracking at the bottom. As means for eliminating these drawbacks, the seating portion or the leg portion is made to have a thick wall as shown in FIG. 6 (see Japanese Patent Application Laid-Open No. 4-72131), or a part of the bottom portion is made thick as shown in FIG. A container in which the bottom of the container is partially reinforced by using a wall (JP-A-6-80132) has been proposed.

The inventors of the present invention have conducted various experiments on the partially reinforced bottom, and as a result,
By simply strengthening the bottom wall in such a way that the bottom wall is partially thickened, a severe carbonated beverage container mixed with a large juice having a volume of 1 liter or more, a milk component, and other components may cause severe pasteurizer conditions. It was found that it was not enough to obtain rocker bottom resistance and impact resistance under (10 minutes at 65 ° C), and to solve the above-mentioned drawbacks by forming the entire bottom of the container with a thick wall. Was completed. That is, a thermoplastic resin is biaxially stretched and blow-molded to form a bottle composed of a mouth portion 1 and a shoulder portion 2, a body portion 3, and a bottom portion 4. The mouth portion 1 is not stretched as it is during preform molding. Crystallize, the shoulder portion 2 and the trunk portion 3 are biaxially stretched uniformly and thinly in a cylindrical shape, and the bottom portion 4 is stretched outwardly and formed into a hemispherical shape, and the spherical wall portion is expanded to form a plurality of leg portions 5. While conducting various experiments on a container formed and having a bottom wall thicker than the body wall, the relationship between the bottom wall thickness and the body wall thickness, heat resistance, pressure resistance, and 1.
When a study was conducted on a container containing 5 liters, the results shown in Appendix 1 were obtained.

[0010] Based on this result, the strength of the bottom part of the container is calculated as a weight ratio of 41% to the total weight under the mouth.
% Or more, it was concluded that heat and pressure resistance could be imparted to the container, so that the weight of the bottom part 4 of the container was about the combined weight of the shoulder part 2 and the trunk part 3. It has been found that blow molding should be performed, that is, the thickness of the bottom wall of the container should be about twice as large as the thickness of the body.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention can be carried out by a usual blow molding method of polyethylene terephthalate (PET) resin. That is, a PET resin is molded into a preform of a predetermined shape by injection molding into a roughly test tube, the preform is heated to a temperature at which stretch molding can be performed, and the preform is set in a blow molding mold and the mouth is closed. Then, after extending in the longitudinal direction and forming into a predetermined shape, the mouth 1 is crystallized and blow-molded, and the bottom 4 is formed to project hemispherically to the outside.
The two or more legs 5 are bulged and formed by biaxial stretching.
It is formed into a self-supporting predetermined bottle having heat resistance, pressure resistance and impact resistance.

In performing the above-mentioned molding step, in order that the thickness of the entire wall forming the bottom 4 of the container is approximately twice or more the thickness of the body 3, the preform is The portion forming the mouth, shoulder, and body of the bottle is formed to have an even thickness, and the portion forming the bottom of the bottle is formed in a predetermined shape so as to have a wall thickness of 65 to 80% of the body. At a predetermined temperature (100 to 100 ° C.) at which the preform can be stretch-molded.
After heating to 120 ° C), the bottle is set in a blow mold maintained at a predetermined temperature (80 to 90 ° C). Is inserted, the bottom of the preform is pushed downward so that the bottom of the container has a predetermined thickness, and a stretching operation in the longitudinal direction is performed. Then, a single blow molding is performed to form a bottle. As a result, of the total weight below the mouth 1 of the container,
The biaxial stretch blow molding could be performed so that the weight ratio of the bottom 4 would be about 50%, and the bottle could be formed into a bottle having a reinforced bottom and provided with a free-standing leg.

Then, when the thickness of the bottom wall 4a of the bottom portion 4 and the body portion 3 of the bottle of the present invention and the conventional product were measured, the relationship shown in Appendix 2 could be obtained. From these results, the thickness of the bottom wall 4a of the bottom 4 in the present invention is 10 to 12 times the thickness of the body 3 (7 to 8 in the conventional product).
The thickness of the leg 5 is 2 times the thickness of the trunk.
Up to 3 times (1.5 times for the conventional product) is sufficient to obtain a container having excellent heat resistance and pressure resistance and stable self-sustainability as compared with the conventional product. You can see that there is. According to the present invention, by making the bottle body as described above, the wall thickness of the shoulder portion 2 and the body portion 3 at the top of the container is made thinner and lighter, and the wall thickness of the bottom portion 4 is made thicker and heavier. As a result, the weight is collected at the bottom of the container, and the rocker bottom phenomenon does not occur even during the pastelizer process.The weight of the body is reduced as much as possible, so the creep characteristics can be improved and the container can be heat resistant. Resistance, pressure resistance and impact resistance.

As described above, an example in which the present invention is applied to a self-standing container having a structure in which a bottom portion of a bottle having a bottom portion bulged outward and a leg portion bulged outward is formed on a bottom wall portion of the bottle body. However, the present invention is not limited to a container having such a bottom shape, but a seating portion is provided on a bottom peripheral portion of a bottle in which the bottom portion is raised inward and recessed in a bottom-shaped curved wall, or It is also possible to apply the present invention to a container in which legs are formed by bulging outward on the bottom wall.

It is needless to say that the present invention can also be applied to a double blow molding method which increases heat resistance. That is, the portions constituting the mouth, shoulder, and body of the bottle are formed to have a uniform thickness, and the portion constituting the bottom of the bottle has a thickness of 65 to 80% of the body. In order to perform blow molding, a PET resin is molded into a preform of a predetermined shape by injection molding, and the preform is heated to a predetermined temperature (100 to 120 ° C.) at which blow molding is possible, and then set in a primary blow molding die. After forming the mouth of the bottle and crystallizing it, insert a stretching push-down rod into the preform, push down the bottom of the preform to perform a stretching operation in the vertical axis direction, and then perform primary blowing. By molding, the bottom part protrudes outward in a hemispherical shape and biaxially stretch-blow-molds into an intermediate molded product similar to the final molded product. At this time, the ratio of the weight occupied by the bottom to the total weight of the portion below the mouth of the container is approximately
In order to mold to 50%, the thickness of the bottom wall is about 2 to 3 times the thickness of the trunk, and the thickness of the leg wall is about 10 to 12 times the thickness of the trunk. And blown into an intermediate bottle with free-standing legs with reinforced bottom wall of the container. Next, the intermediate molded product obtained by the primary blow molding is heated to a predetermined temperature (200 to 230 ° C.) while removing the internal residual stress by opening the mold and thermally shrinking, so that the temperature becomes higher than the maximum use temperature of the bottle. A secondary blow mold is used for the final product bottle by a secondary mold kept a few degrees high, and then heat-set to perform double blow molding for imparting strong heat resistance.

[0016]

The present invention has the following effects by adopting the above-described configuration. In the container of the present invention, since the bottom wall thickness is twice or more the wall thickness of the trunk, even if the internal pressure increases, the bottom wall does not deform due to absorption in the trunk. It has stable autonomy, and the bottom of the container weighs about half of the entire container, so the center of gravity is near the bottom even during processing under bath riser conditions, so that it is stable and generates rocker bottom. Nor. In particular, the heat-resistant, pressure-resistant, and self-standing stability of the double-blow molded container is remarkable. Since the container of the present invention is a one-piece bottle molded using a single resin material, the production cost can be kept low as compared with the base cup method, and the recycling of the raw material resources is easy.

[Brief description of the drawings]

FIG. 1 is a side view showing the entire hollow container of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG. 1 showing the present invention.

FIG. 3 is a bottom view of the present invention.

FIG. 4 is a first conventional example.

FIG. 5 is a second conventional example.

FIG. 6 is an example in which the bottom of the type of the first conventional example is reinforced.

FIG. 7 is an example in which the bottom of the type of the second conventional example is reinforced.

[Table 1]

[Table 2]

Claims (7)

[Claims] 1. A hollow container formed by molding a thermoplastic synthetic resin into a bottle comprising a mouth portion, a shoulder portion, a body portion and a bottom portion by biaxial stretching blow, wherein the bottom portion has a hemispherical shape with an outwardly protruding state. The bottom is formed with legs for allowing the container to stand on its own, and the entire wall thickness of the bottom is formed into a uniform thick state approximately twice or more larger than the wall thickness of the shoulder and the body. A heat-resistant and pressure-resistant self-standing hollow container characterized by the following. 2. The heat-resistant and pressure-resistant self-standing hollow container according to claim 1, wherein the hollow container is formed by biaxial stretching by single blow molding. 3. The heat-resistant and pressure-resistant self-standing hollow container according to claim 1, wherein the hollow container is biaxially stretch-formed by double blow molding and heat-set. 4. The heat-resistant and pressure-resistant self-standing hollow according to claim 1, wherein the weight of the portion constituting the bottom is about 50% of the total weight below the mouth of the container. container. 5. The method of claim 1, wherein the wall thickness of the bottom is about 2-3 times the wall thickness of the sphere and the wall thickness of the legs is 10-12 times the wall thickness of the body. 4. The heat-resistant and pressure-resistant self-standing hollow container described in any one of items 1 to 4. 6. The heat-resistant and pressure-resistant self-standing hollow container according to claim 1, wherein the bottom is formed in a hemispherical shape so as to be concave inward. 7. The heat-resistant and pressure-resistant self-standing hollow container according to claim 1, wherein the thermoplastic synthetic resin is polyethylene terephthalate.