JP3101405B2 - Polyethylene terephthalate resin bottle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyethylene terephthalate resin bottle, and more particularly, to a polyethylene terephthalate resin bottle having a leg at the bottom for imparting self-support to the bottle.

[0002]

2. Description of the Related Art Conventionally, polyethylene terephthalate resin bottles having a bottle body formed by biaxial stretching blow molding have been widely used. This kind of bottle is excellent in transparency, impact resistance, gas barrier property, light weight, etc., because the polyethylene terephthalate resin forming the bottle body is molecularly oriented by biaxial stretching.

[0003] The polyethylene terephthalate resin bottle is also used as a container for an effervescent liquid such as a carbonated beverage. In this case, the inner pressure of the effervescent liquid tends to deform the bottle. Therefore, it has been considered to improve the pressure resistance of the bottle by forming the bottom in a hemispherical shape in order to prevent the deformation of the bottle, so that the internal pressure of the foaming liquid is evenly applied to the bottle. . However, if the bottom of the bottle body is made hemispherical, the bottle body loses its independence, and it is necessary to take measures to give the bottle body its independence.

In order to impart autonomy to the bottle body having the hemispherical bottom, three or more bottles are provided on the hemispherical bottom.
In general, a technique has been proposed in which five to six protrusions are provided so as to protrude downward, and the bottle main body is self-standing using the protrusions as legs. The bottle having the legs is commonly referred to as a petaloid type, for example, disclosed in Japanese Utility Model Publication No. 3-5537.

FIG. 7 is a sectional view of the bottom of the polyethylene terephthalate resin bottle described in the above publication. The polyethylene terephthalate resin bottle body 71 has a bottom portion 73 that swells below the bottle body 72, and the bottom portion 73 has a hemispherical curved bottom surface 76 and a curved bottom surface 76 integrally formed around the curved bottom surface 76. The bottle 71 is provided with the hollow leg 77 so as to be self-supporting.

[0006] The hollow leg portions 77 are provided at five locations at equal equiangular angles around a center 76a, which is the lowermost position of the curved bottom surface 76, and extend obliquely upward from the flat bottom surface 78 toward the center 76a. And an inclined wall surface 79 extending obliquely upward from the inclined bottom surface 78a toward the inside of the bottle main body 2 and connected to the curved bottom surface 76. According to the description of the above publication, when the bottle 71 is filled with the foaming liquid, the bottom portion 73 is slightly deformed by the internal pressure to displace the center portion downward, but the inclined bottom surface 78a is
1 is formed so as to have an inclination angle of about 3 ° with respect to a plane L (shown by a straight line connecting the flat bottom surface 78), and the inclination angle is set to be zero by the deformation. As shown by the imaginary line in FIG.
It is said that the "sitting" of the bottle 1 becomes extremely stable.

On the other hand, in the polyethylene terephthalate resin bottle 71, an inclined wall surface 79 connecting the curved bottom surface 76 and the inclined bottom surface 78a is formed in an arc-shaped cross section. The cross-sectional shape of the inclined wall surface 79 is intended to smoothly connect to the curved bottom surface 76 to improve the flow of the resin during blow molding, and is a general method for blow molding polyethylene terephthalate resin. Have been.

However, the curved bottom surface 76 and the inclined wall surface 7
8a having the above-mentioned shape, the curved bottom surface 76 is formed by blow molding.
In addition, the inclined wall surface 79 tends to be formed to be thick, and tends not to be sufficiently biaxially stretched. The curved bottom surface 76 and the inclined wall surface 79 formed as described above are easily deformed as compared to the bottle body 72 formed by being sufficiently biaxially stretched. Under severe conditions of about 60% humidity, the pressure resistance against the internal pressure of the foamable liquid is insufficient. As a result, in the bottle 71, the curved bottom surface 76 and the inclined wall surface 79 swell further downward from the flat bottom surface 78 as shown by the imaginary line A in FIG. Creep deformation exceeding the deformation that occurs, the "sitting" of the bottle 71 becomes unstable.

In order to maintain the independence of the bottle 71 against the deformation indicated by the imaginary line A, the center 76a of the curved bottom 76 extends from the plane L indicated by a straight line connecting the flat bottom 78.
If the height h is increased to 5.0 mm or more, the curved bottom surface 76 and the inclined wall surface 79 can be prevented from bulging below the flat bottom surface 78 even when the creep deformation occurs. In this case, the protruding amount of the hollow leg 77 increases, so that a decrease in workability cannot be avoided.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned disadvantages and, after filling an effervescent liquid such as carbonated beverage, creep deformation of the bottom and legs is reduced even under severe temperature and humidity conditions. It is an object of the present invention to provide a polyethylene terephthalate resin bottle having excellent self-sustainability and processability.

[0011]

In order to achieve the above object, a polyethylene terephthalate resin bottle of the present invention comprises a biaxially stretched bottle body and a curved surface bulging below the bottle body in a bowl shape. A biaxially-stretched bottom having three or more hollow legs for self-supporting a bottle provided with the curved bottom integrally protruding downward at the bottom and the periphery of the curved bottom; In a polyethylene terephthalate resin bottle comprising a non-stretched mouth having a threaded portion provided on the outer peripheral portion of the bottle, the bottom of the curved surface coincides with the hemisphere having the same diameter as the diameter of the bottle main body at the lowest portion, A hollow having a shape in which a peripheral portion of the curved bottom bulges outward from a hemispherical surface having the same diameter as the diameter of the bottle body, and wherein the peripheral portion of the curved bottom is integrally protruded downward. A flat bottom surface on which the legs support the bottle, and Extending obliquely upward directed towards an inclined wall surface connected to the curved bottom, the inclined wall surface, characterized in that provided in the cross-section linearly.

[0012]

According to the polyethylene terephthalate resin bottle of the present invention, since the inclined wall surface of the hollow leg is provided in a straight line in cross section, the inclined wall surface is formed thin by blow molding and sufficiently biaxially stretched. Is done. Therefore, when the sloping wall surface is filled with an effervescent liquid such as carbonated beverage, a sufficient pressure resistance against the internal pressure is obtained, and the container is placed under severe temperature and humidity conditions after the effervescent liquid is filled. In addition, the creep deformation of the bottom portion due to the internal pressure of the foaming liquid is reduced, and the "sitting" of the bottle becomes stable.

Further, according to the polyethylene terephthalate resin bottle of the present invention, since the creep deformation of the inclined wall surface is reduced, the "leg" of the bottle does not become unstable, and the protrusion of the hollow leg portion does not occur. The amount can be reduced. Further, by reducing the amount of protrusion of the hollow leg, the amount of resin forming the hollow leg increases, so that the processing of the details of the hollow leg becomes easy, and excellent workability is obtained.

[0014]

Next, the bottle made of polyethylene terephthalate resin of the present invention will be described in more detail with reference to the accompanying drawings. 1 is a front view of a polyethylene terephthalate resin bottle of the present embodiment, FIG. 2 is a plan view showing the shape of the bottom of the polyethylene terephthalate resin bottle shown in FIG. 1, and FIG. 3 is a cross-sectional view taken along line III-III of FIG. FIG. 4 is a graph showing the change over time in the amount of creep deformation at the bottom of the bottle made of polyethylene terephthalate resin when the carbonated beverage is filled in the polyethylene terephthalate resin bottle of this embodiment. FIGS. 5 and 6 are made of polyethylene terephthalate resin of this embodiment. It is explanatory sectional drawing which shows the blow molding method of a bottle.

A polyethylene terephthalate resin bottle 1 of the present embodiment shown in FIG. 1 is a bottle for filling a carbonated beverage, and includes a bottle body 2 and a bottom 3 provided below the bottle body 2. And a mouth 4 provided above the bottle body 2. In the polyethylene terephthalate resin bottle 1, the bottle body 2 and the bottom 3 are formed by biaxially stretching the polyethylene terephthalate resin, but the mouth 4 is formed of a non-stretched polyethylene terephthalate resin. A thread forming portion 5 is provided on the outer peripheral portion. The bottom 3 has a curved bottom 6 bulging into a bowl shape below the bottle body 2 and a hollow leg 7 provided around the curved bottom 6 so that the curved bottom 6 is integrally protruded downward. The bottle 1 made of polyethylene terephthalate resin is provided with autonomy by the hollow legs 7.

As shown in FIGS. 2 and 3, the hollow legs 7 are formed at five locations at equal angular intervals around a center 6a, which is the lowest position of the curved bottom 6, and Has a fan-shaped flat bottom surface 8 having an outer diameter and an inner diameter smaller than the outer diameter. The flat bottom surface 8 is flat, and even when the bottle 1 is not filled with contents, the entire flat surface is grounded to support the bottle 1.

The hollow leg 7 is connected to the curved bottom 6 by an inclined wall 9 and a peripheral wall 10 extending obliquely upward from the flat bottom 8 toward the inside of the bottle body 2. The inclined wall surface 9 is provided with a linear cross section. The thickness of the inclined wall surface 9 is thinner than the curved bottom 6 and is formed by biaxial stretching.

The inclined wall surface 9 has an inclination angle α of 10 to a plane L (shown by a straight line connecting the flat bottom surface 8) on which the bottle 1 contacts the ground.
The connecting portion 11 between the flat bottom surface 8 and the inclined wall surface 9 and the connecting portion 12 between the inclined wall surface 9 and the curved bottom surface 6 have a radius of curvature of 1 mm or less, preferably 0.1 mm or less. It has a curved surface of 5 mm and forms a clear corner. With the inclination angle α in the above range, the connection portions 11 and 1
By forming 2 as a clear corner portion as described above, the thickness of the inclined wall surface 9 becomes thin in the blow molding described later, and it becomes easy to be biaxially stretched, so that a sufficient pressure resistance against the internal pressure of the foamable liquid is obtained. Strength is obtained.

Accordingly, the height h from the plane L to the center 6a of the curved bottom 6 (hereinafter, abbreviated as the height h of the curved bottom 6) is 4
mm or less, a creep deformation in which the curved bottom surface 6 and the inclined wall surface 9 bulge below the flat bottom surface 8 due to the internal pressure of the foaming liquid does not occur, and the curved surface is smaller than the conventional petaloid type bottle. The amount by which the hollow leg 7 projects from the bottom 6 is reduced.

In the bottle 1, the curved bottom 6 is formed by rotating a circular arc having a radius r ₁ around a point whose upper part is located away from the axis Z of the bottle 1 around the axis Z. The lower part is formed in the shape of the top of a spherical surface having a radius r ₂ (r ₂ > r ₁ ) centered on a point on the axis Z of the bottle 1, so that the two are smoothly joined. ing. The center 6a, which is the lowermost position of the curved bottom 6, is the bottle 1
And the radius r is equal to the lowermost position of a hemispherical surface having a radius r, and r ₂ > r.

By forming the curved bottom 6 in such a shape, the curved bottom 6 has a shape that bulges out of the bottle 1 beyond the hemisphere S having the radius r, and the curved bottom 6 is formed as a hemisphere S. The projecting amount of the hollow leg 7 can be reduced as compared with the case where it is performed.

Next, the carbonated beverage was filled into the polyethylene terephthalate resin bottle 1 at 4.0 GV (gas volume), and the time-dependent change in the amount of creep deformation of the bottom 3 due to the internal pressure of the carbonated beverage was measured. The amount of creep deformation of the bottom portion 3 is set such that the height h of the curved bottom 6 when the bottle 1 filled with the carbonated beverage is held at room temperature for 1 hour under the above conditions is an initial value. The measurement was performed by measuring the height h of the curved bottom 6 at predetermined time intervals while maintaining the humidity at 60%.

As shown in FIG. 4, the height h of the curved bottom 6 of the bottle 1 is 3.30 when the contents are not filled (empty state).
mm. The initial value was 2.55 mm after filling the carbonated beverage under the above conditions, and 0.23 mm after being stored for 2 weeks under the above temperature and humidity conditions. That is, in the bottle 1, the curved bottom 6 does not reach the plane L even after two weeks have passed under the temperature and humidity conditions after filling the carbonated beverage.

For comparison, a carbonated beverage was hot-filled in a polyethylene terephthalate resin bottle 71 shown in FIG. 7 under the same conditions as described above, and the change over time in the amount of creep deformation of the bottom 73 due to the internal pressure was measured. The height h of the curved bottom 76 of the bottle 71 was 4.28 mm when the contents were not filled, but the curved bottom 76 swells below the flat bottom 78 about one day after the filling of the carbonated beverage. Creep deformation occurred, and the independence of the bottle 71 was lost.

From the above results, according to the polyethylene terephthalate resin bottle 1 of the present embodiment, the pressure resistance of the bottom portion 3 is improved, and even under severe temperature and humidity conditions, the creep due to the internal pressure of the foaming liquid such as carbonated beverages. It is clear that the deformation is reduced.

The polyethylene terephthalate resin bottle 1 of this embodiment can be manufactured as follows.
First, as shown in FIG. 5, a preform 51 obtained by a conventionally known method is heated to 100 ° C., and the outer shape of the bottle 1 is formed in a state where the mouth 4 is sandwiched by a mouth forming die 52. It is installed in a blow molding mold 53 having a concave portion having a matching shape. The temperature of the blow mold 53 is set at 15 to 20 ° C. Next, a stretch pin 54 is inserted into the inner surface of the preform 51, and the preform 51 is stretched in the axial direction by the stretch pin 54, while a gas introduced through the stretch pin 54 blows at a pressure of 15 kg / cm ^2. After stretching in the circumferential direction, primary blow molding is performed. By the primary blow molding, the bottle main body 2 and the curved bottom 6 shown by the imaginary line in FIG. 5 are formed. At this time, the bottle body 2 is biaxially stretched, but the curved bottom 6 is not sufficiently biaxially stretched, and is formed thicker than the bottle body 2.

Next, as shown in FIG. 6, the curved bottom 6 formed in the above step is moved along the bottom forming mold 53a by a gas introduced through the stretch pin 54 at a blowing pressure of 40 kg / cm ² . Then, a second blow molding is performed to form a hollow leg 7 (shown by a phantom line in FIG. 6) projecting from the curved bottom 6. The bottom molding die 53a has a concave portion having a shape corresponding to the external shape of the bottom portion 3 shown in FIG. 2 and FIG. 3, and by molding along the concave portion, a sufficiently biaxially stretched inclined portion is formed. A hollow leg 7 having a wall surface 9 is obtained. At this time, the temperature of the bottom molding die 53a is 15 to
The temperature is set to 20 ° C., and the hollow leg 7 formed by the blow molding is kept in contact with the bottom molding die 53a for 2 to 3 seconds. By doing so, the polyethylene terephthalate resin solidifies, and after the mold release, the curved bottom 6
In addition, the deformation of the hollow leg 7 can be prevented.

In the bottle 1, since the amount of protrusion of the hollow leg 7 is reduced as described above, the amount of resin forming the flat bottom surface 8 during the blow molding is relatively large, and the processing of details is easy. And the degree of freedom in design is increased, for example, by increasing the area of the grounding portion or changing the shape of the flat bottom surface 8.

The shape of the flat bottom surface 8 is flat in the above embodiment, but the flat bottom surface 8 may be any shape that can give the bottle 1 self-sustainability, such as a concave portion protruding inside the hollow leg 7. May be provided. By providing the concave portion on the flat bottom surface 8, the internal pressure applied to the flat bottom surface 8 is absorbed by the creep deformation of the concave portion, and the creep deformation of the flat bottom surface 8 itself can be reduced.

[0030]

As is apparent from the above, according to the present invention, even if the foaming liquid such as a carbonated beverage is placed under severe temperature and humidity conditions after filling, the internal pressure of the foaming liquid is maintained. It is possible to obtain a polyethylene terephthalate resin bottle having reduced bottom and leg creep deformation, stable "sitting", and excellent self-sustainability.

Further, according to the present invention, since the creep deformation of the inclined wall surface is reduced, the self-sustainability of the bottle can be maintained even when the protrusion of the hollow leg is reduced. Further, by reducing the amount of protrusion of the hollow leg, the amount of resin forming the hollow leg is increased, so that the processing of the details of the hollow leg is facilitated. Therefore, a polyethylene terephthalate resin bottle having excellent processability can be obtained.

[Brief description of the drawings]

FIG. 1 is a front view of an embodiment of a polyethylene terephthalate resin bottle according to the present invention.

FIG. 2 is a plan view showing a bottom shape of the polyethylene terephthalate resin bottle shown in FIG.

FIG. 3 is a sectional view taken along line III-III of FIG. 2;

FIG. 4 is a graph showing the change over time in the amount of creep deformation at the bottom when the carbonated beverage is filled in the polyethylene terephthalate resin bottle shown in FIG.

FIG. 5 is an explanatory sectional view showing a blow molding method of the polyethylene terephthalate resin bottle shown in FIG.

FIG. 6 is an explanatory sectional view showing a blow molding method of the polyethylene terephthalate resin bottle shown in FIG.

FIG. 7 is an explanatory sectional view showing a bottom shape of a conventional polyethylene terephthalate resin bottle.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1: Bottle of polyethylene terephthalate resin, 2: Bottle body, 3: Bottom, 6: Curved bottom, 7: Hollow leg, 8
... flat bottom surface, 9 ... inclined wall part.

Claims (1)

(57) [Claims] 1. A bottle body which has been biaxially stretched, a curved bottom which bulges out in a bowl shape below the bottle body, and a curved bottom which is integrally protruded downward from a periphery of the curved bottom. A polyethylene terephthalate resin made of a biaxially stretched bottom having three or more hollow legs for self-supporting a bottle, and a non-stretched mouth having a threaded portion provided on an outer peripheral portion above the bottle body. In a bottle, the curved bottom has the same diameter at the bottom as the diameter of the bottle body
The bottom of the curved surface is the same as the diameter of the bottle body.
A shape that bulges outward from a hemisphere with the same diameter
And the peripheral portion of the curved bottom is integrally formed so as to protrude downward.
The girder hollow leg has a flat bottom surface for supporting the bottle and an inclined wall surface extending obliquely upward from the flat bottom surface toward the inside of the bottle and connected to the curved bottom surface, and the inclined wall surface has a linear cross section. A polyethylene terephthalate resin bottle characterized by being provided in a bottle.