JPH05254529A - Bottle made of polyethylene terephthalate resin - Google Patents

Abstract

PURPOSE:To obtain a bottle made of polyethylene terephthalate resin which is reduced in the creep deformation of the bottom and leg parts even under severe conditions after being filled with foam liquid and which has an excellent standing ability and workability. CONSTITUTION:The bottle has a biaxially stretched bottle body 2, a biaxially stretched bottom part 3 and an undrawn mouth part having a threaded part formed on the upper outer peripheral part of the bottle body 2. The bottom part 3 has a curved bottom 6 extending downwards in the form of a bowl from the lower end of the bottle body 2 and hollow leg parts 7 formed at the peripheral side of the curved bottom 6 extending downwards integrally therewith so as to make the bottle stand. The hollow leg parts are provided at five places equally angularly spaced at the periphery of the curved bottom 6 and has flat bottom surfaces 8 for supporting the bottle body and sloping walls 9 extending inwardly of the bottle body and obliquely and upwardly from the flat bottom surfaces 8 and blending into the curved bottom 6. The sloping walls 9 are formed with linear cross section.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a bottle made of polyethylene terephthalate resin, whose bottle body is biaxially stretch blow molded, has been widely used. This type of bottle is excellent in transparency, impact resistance, gas barrier property, and lightness because the polyethylene terephthalate resin forming the bottle body is molecularly oriented by biaxial stretching.

The polyethylene terephthalate resin bottle is also used as a container for an effervescent liquid such as a carbonated beverage. In this case, the bottle is easily deformed by the internal pressure of the effervescent liquid. Therefore, it has been considered to form the bottom portion in a hemispherical shape in order to prevent the bottle from being deformed and to improve the pressure resistance of the bottle by making the internal pressure of the foaming liquid evenly applied to the bottle. .. However, if the bottom of the bottle body is made hemispherical, the bottle body loses its independence, so it is necessary to take measures to impart independence to the bottle body.

In order to impart self-supporting property to the bottle body having the hemispherical bottom, three or more are provided on the hemispherical bottom.
Usually, a technique has been proposed in which 5 to 6 projecting portions are provided so as to bulge downward, and the projecting portions are used as legs to make the bottle body self-supporting. The bottle having the leg portion is commonly called a petaloid type, and for example, it is disclosed in Japanese Utility Model Publication No. 3-5537.

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

The hollow leg portions 77 are provided at five locations around the center 76a, which is the lowermost position of the curved bottom 76, at equal center angles, 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 body 2 and connected to the curved bottom 76. According to the description of the publication, when the bottle body 71 is filled with the foaming liquid, the bottom portion 73 is slightly deformed by the internal pressure thereof so that the central portion thereof is displaced downward, but the inclined bottom surface 78a has the bottle body 7a.
Since the inclination angle formed by 1 and the plane L (shown by the straight line connecting the flat bottom surfaces 78) to the ground is formed to be about 3 °, and the inclination angle is set to zero by the deformation, the inclination bottom surface 78a is As shown by the phantom line in FIG. 7, the flat surface 78b
It is said that the "sitting" of the bottle 1 will be extremely stable.

On the other hand, in the polyethylene terephthalate resin bottle body 71, an inclined wall surface 79 connecting the curved bottom surface 76 and the inclined bottom surface 78a is formed in an arcuate cross section. The cross-sectional shape of the inclined wall surface 79 is intended to be smoothly connected to the curved bottom 76 to improve the flow of resin during blow molding, and is a common method in blow molding of polyethylene terephthalate resin. Has been done.

However, the curved bottom 76 and the inclined wall surface 7
When 8a has the above-mentioned shape, the curved bottom 76 is formed by blow molding.
In addition, the inclined wall surface 79 is likely to be formed to have a large wall thickness, and tends not to be sufficiently biaxially stretched. The curved bottom 76 and the inclined wall surface 79 formed as described above are more easily deformed than the bottle main body 72 formed by being sufficiently biaxially stretched, and are 40 ° C. during storage after filling the foamable liquid, If it is placed under a severe condition of a humidity of about 60%, the pressure resistance against the internal pressure of the foamable liquid becomes insufficient. As a result, in the bottle body 71, the curved bottom 76 and the inclined wall surface 79 swell further downward from the flat bottom surface 78 as shown by the phantom line A in FIG. There is a disadvantage that creep deformation that exceeds the deformation becomes greater and the "sitting" of the bottle body 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 from the plane L indicated by the straight line connecting the flat bottoms 78
By increasing the height h up to 5.0 mm or more, it is possible to prevent the curved bottom 76 and the inclined wall surface 79 from bulging below the flat bottom surface 78 even if the creep deformation occurs. Since the amount of protrusion of the hollow leg portion 77 is increased, the workability is unavoidably deteriorated.

[0010]

DISCLOSURE OF THE INVENTION The present invention has solved such inconveniences, and after filling a foaming liquid such as a carbonated beverage, the creep deformation of the bottom and legs is reduced even under severe temperature and humidity conditions. The object is to provide a bottle made of polyethylene terephthalate resin having excellent self-supporting property and processability.

[0011]

To achieve the above object, a polyethylene terephthalate resin bottle body of the present invention comprises a biaxially stretched bottle body and a curved surface which bulges like a bowl below the bottle body. A biaxially stretched bottom having three or more hollow legs for making a bottle body self-sustaining, which is provided by integrally projecting the curved bottom on the bottom and a peripheral portion of the curved bottom; In a bottle made of polyethylene terephthalate resin, which comprises an unstretched mouth portion having a screw forming portion provided on an upper outer peripheral portion, a flat bottom surface on which the hollow leg portion supports the bottle body and an inward direction of the bottle body from the flat bottom surface It has an inclined wall surface extending obliquely upward toward and connected to the curved bottom, and the inclined wall surface is provided in a linear shape in cross section.

[0012]

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

Further, according to the bottle body made of polyethylene terephthalate resin of the present invention, the creep deformation of the inclined wall surface is reduced, so that the hollow leg does not project without making the "sitting" of the bottle body unstable. The amount can be reduced. Furthermore, since the amount of resin forming the hollow leg is increased by reducing the amount of protrusion of the hollow leg, it is possible to easily process the details of the hollow leg and obtain excellent workability.

[0014]

The polyethylene terephthalate resin bottle of the present invention will now be described in more detail with reference to the accompanying drawings. 1 is a front view of a polyethylene terephthalate resin bottle of this 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 sectional view taken along line III-III of FIG. 4 and 5 are graphs showing changes over time in the amount of creep deformation at the bottom when the bottle made of polyethylene terephthalate resin of the present example is filled with a carbonated beverage, and FIGS. 5 and 6 are made of polyethylene terephthalate resin of the present example. It is an explanatory sectional view showing a method of blow molding a bottle.

A bottle body 1 made of polyethylene terephthalate resin of this embodiment shown in FIG. 1 is a bottle body for filling a carbonated beverage, and comprises a bottle body 2 and a bottom portion 3 provided below the bottle body 2. , And a mouth portion 4 provided above the bottle body 2. In the bottle body 1 made of polyethylene terephthalate resin, the bottle body 2 and the bottom portion 3 are formed by biaxially stretching polyethylene terephthalate resin, while the mouth portion 4 is formed of unstretched polyethylene terephthalate resin. A screw forming portion 5 is provided on the outer peripheral portion of the. The bottom portion 3 has a curved bottom 6 that bulges like a bowl below the bottle body 2, and a hollow leg portion 7 that is provided around the curved bottom 6 so that the curved bottom 6 integrally projects downward. Therefore, the polyethylene terephthalate resin bottle body 1 is made to be self-supporting by the hollow leg portions 7.

As shown in FIGS. 2 and 3, the hollow leg portions 7 are formed around the center 6a, which is the lowermost position of the curved bottom 6, at five equiangular angles, and the bottle body 2 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 if the bottle body 1 is not filled with contents, the entire flat surface is grounded to support the bottle body 1.

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

The inclined wall surface 9 has an inclination angle α of 10 with a plane L (shown by a straight line connecting the flat bottom surfaces 8) with which the bottle body 1 is in contact with 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 surface bottom 6 are formed to have a radius of curvature of 1 mm or less, preferably 0. It is composed of a curved surface of 5 mm and forms a clear corner portion. The inclination angle α is within the above range, and the connecting portions 11 and 1
By forming 2 as the clear corner portion as described above, the thickness of the inclined wall surface 9 becomes thin in the blow molding described later, and biaxial stretching is facilitated, so that a sufficient pressure resistance against the internal pressure of the foamable liquid is obtained. Strength is obtained.

Therefore, 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.
Even if the thickness is less than or equal to mm, the curved bottom 6 and the inclined wall surface 9 do not undergo creep deformation bulging below the flat bottom surface 8 due to the internal pressure of the foamable liquid, and the curved surface is smaller than that of a conventional petaloid-type bottle. The amount of protrusion of the hollow leg portion 7 from the bottom 6 is reduced.

In the bottle 1, the curved bottom 6 is formed by rotating an arc having a radius r ₁ centered on a point where the upper portion is located away from the axis Z of the bottle 1 around the axis Z. It is formed into a shape, and the lower part is formed into the shape of the top of a spherical surface with a radius r ₂ (r ₂ > r ₁ ) centered on a point on the axis Z of the bottle 1 and a shape in which both are smoothly joined. ing. In addition, the center 6a, which is the lowest position of the curved bottom 6, is the bottle body 1.
It is arranged so as to coincide with the lowest position of a hemisphere having a radius r equal to the radius of, and r ₂ > r.

By making the curved bottom 6 into such a shape, the curved bottom 6 bulges outside the bottle body 1 more than the hemisphere S having the radius r, and the curved bottom 6 is formed as the hemisphere S. It is possible to reduce the amount of protrusion of the hollow leg portion 7 as compared with the case of

Next, the bottle 1 made of polyethylene terephthalate resin was filled with a carbonated beverage at 4.0 GV (gas volume), and the change with time of the creep deformation amount of the bottom portion 3 due to the internal pressure of the carbonated beverage was measured. The creep deformation amount of the bottom portion 3 has an initial value of the height h of the curved bottom 6 when the bottle body 1 filled with a carbonated beverage under the above conditions is held at room temperature for 1 hour, and thereafter, the bottle body 1 is kept at 40 ° C. The height h of the curved bottom 6 was measured at a predetermined time with the humidity kept 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).
It was mm. The initial value was 2.55 mm after filling the carbonated drink under the above conditions, and 0.23 mm after being stored for 2 weeks under the temperature and humidity conditions. That is, in the bottle 1, the curved bottom 6 has not reached the flat surface L even after 2 weeks have passed under the temperature and humidity conditions after the carbonated beverage is filled.

For comparison, a polyethylene terephthalate resin bottle body 71 shown in FIG. 7 was hot-filled with a carbonated beverage under the same conditions as described above, and the change with time of the creep deformation amount of the bottom portion 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 bulges downward from the flat bottom 78 about one day after the carbonated beverage is filled. Creep deformation occurred, and the bottle 71 lost its independence.

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

The polyethylene terephthalate resin bottle body 1 of this embodiment can be manufactured as follows.
First, as shown in FIG. 5, the preform 51 obtained by a conventionally known method is heated to 100 ° C., and the mouth 4 is sandwiched between the mouth forming dies 52 to form the outer shape of the bottle body 1. It is attached to a blow molding die 53 having a recess having a matching shape. The temperature of the blow molding die 53 is set to 15 to 20 ° C. Next, the 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 the gas introduced through the stretch pin 54 applies a blow pressure of 15 kg / cm ^2. It is stretched in the circumferential direction and primary blow molding is performed. By the primary blow molding, the bottle body 2 and the curved bottom 6 shown by phantom lines in FIG. 5 are formed. At this time, the bottle body 2 is biaxially stretched, but the curved surface 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 molding die 53a by the gas introduced through the stretch pin 54 with a blow pressure of 40 kg / cm ² . Thus, the secondary blow molding is performed to form the hollow leg portion 7 (shown by an imaginary line in FIG. 6) protruding from the curved surface bottom 6. The bottom molding die 53a has a recess having a shape that matches the external shape of the bottom 3 shown in FIGS. 2 and 3, and by molding along the recess, a sufficiently biaxially stretched slope is obtained. Hollow legs 7 having wall surfaces 9 are 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 portion 7 formed by the blow molding is held for 2 to 3 seconds while being in contact with the bottom molding die 53a. By doing so, the polyethylene terephthalate resin is solidified, and after the mold is removed, the curved bottom 6
Also, it is possible to prevent the hollow leg portion 7 from being deformed.

In the bottle body 1, since the protruding amount of the hollow leg portion 7 is reduced as described above, the amount of resin forming the flat bottom surface 8 at the time of the blow molding is relatively large, and the fine processing is easy. Therefore, the degree of freedom in design is increased by increasing the area of the ground contact portion or changing the shape of the flat bottom surface 8.

The shape of the flat bottom surface 8 is flat in the above-mentioned embodiment, but the flat bottom surface 8 may be any shape capable of imparting the bottle 1 with self-supporting property, such as a recess protruding inside the hollow leg portion 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 when placed under harsh temperature and humidity conditions after the filling of a sparkling liquid such as a carbonated beverage, the internal pressure of the foaming liquid causes It is possible to obtain a polyethylene terephthalate resin bottle body in which the creep deformation of the bottom portion and the leg portions is reduced, the "sitting" is stable, and which has excellent self-standing property.

Further, according to the present invention, since the creep deformation of the inclined wall surface is reduced, it is possible to maintain the self-supporting property of the bottle body even if the protruding amount of the hollow leg portion is reduced. Furthermore, since the amount of resin forming the hollow legs is increased by reducing the amount of protrusion of the hollow legs, it is easy to process the details of the hollow legs. Therefore, a polyethylene terephthalate resin bottle having excellent workability can be obtained.

[Brief description of drawings]

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

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

3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a graph showing changes over time in the amount of creep deformation at the bottom when the carbonated beverage is filled in the bottle made of polyethylene terephthalate resin shown in FIG. 1.

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

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

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

[Explanation of Codes] 1 ... Polyethylene terephthalate resin bottle body, 2 ... Bottle body, 3 ... Bottom portion, 6 ... Curved bottom portion, 7 ... Hollow leg portion, 8
… Flat bottom, 9… Sloping wall.

Claims (1)

[Claims] 1. A bottle main body that is biaxially stretched, a curved bottom that bulges like a bowl below the bottle main body, and the curved bottom is integrally provided at the peripheral portion of the curved bottom so as to project downward. Made of polyethylene terephthalate resin consisting of a biaxially stretched bottom having three or more hollow legs that make the bottle self-supporting, and a non-stretching mouth having a screw forming portion provided on the outer periphery above the bottle body. In the bottle, the 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. Is a polyethylene terephthalate resin bottle body having a linear cross section.