JPH05147637A - Polyethylene terephthalate resin bottle and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a polyethylene terephthalate resin bottle having excellent pressure tightness and self-supporting stability, also when a sparkling liquid is packed as contents into the bottle. CONSTITUTION:A polyethylene terephthalate resin bottle 1 is composed of a bottle main body 2, bottom 3 and mouth 4. The bottle main body 2 and bottom 3 are biaxially oriented while the mouth 4 is formed in non-oriented manner. The bottom 3 has a curved-face bottom 6 provided below the bottle main body 2 and hollow leg part 7. The bottle main body 3 can be self-supporting by the leg part 7. The lowest part of the curved-face bottom 6 coincides with a virtual spherical surface having the same diameter as that of the bottle main body 3 and the peripheral part of the curved-face bottom 6 above the lowest part is formed into a shape swelling outward of the virtual spherical surface. The leg part 7 is formed so as to be thicker than that formed in the virtual spherical surface because the leg part 7 is formed in the peripheral part of the curved-face bottom 6.

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 a method for producing the same, and more particularly to a polyethylene terephthalate resin bottle having a bottom for supporting the bottle body by itself and a method for producing the same. It is a thing.

[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. In the polyethylene terephthalate resin bottle body, the bottom portion is usually formed into a conical shape projecting on the inner surface of the bottle body, which is commonly referred to as the champagne bottom, and the conical bottom portion and the bottle body are joined as an annular leg portion. I am trying to add independence.

The bottle made of polyethylene terephthalate resin is also used as a container for an effervescent liquid such as a carbonated beverage. In this case, in the bottle having a shape with the champagne bottom, the effervescent liquid is contained in the bottle. As a result, there is a problem that the bottle body is easily deformed by the internal pressure when it is filled. 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, for example, a method of attaching a base (base cup) to the bottom of the bottle has been proposed. However, such a method has a problem that the bottle body is not vertical depending on the joining state of the bottle body and the base cup, and thus the bottle body easily falls.

On the other hand, a hemispherical bottom portion of the bottle is provided with a protruding portion which is bulged downward, and a flat plate-shaped grounding portion is formed on the bottom portion of the protruding portion so that the protruding portion serves as a leg. Techniques for making the main body self-sustaining have been proposed. But,
The protrusion formed by the above technique tends to be thin because it further bulges from the bottom of the bottle. For this reason, the flat grounded portion tends to be easily deformed by the internal pressure of the foamable liquid and further bulges downward to be rounded, and the amount of deformation at the grounded portion of each leg (roundness It is difficult for the bottle body to become uniform, and the bottle itself tends to become unstable.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves such inconveniences and has excellent pressure resistance and self-sustaining stability even when a foaming liquid such as a carbonated beverage is filled as a content. An object is to provide a resin bottle and a method for producing the same.

[0007]

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 portion having a plurality of hollow legs for independently supporting the bottle body, which is provided by integrally projecting the curved bottom toward the bottom and the peripheral portion of the curved bottom, and above the bottle body. In a polyethylene terephthalate resin bottle body consisting of a non-stretched mouth portion having a thread forming portion provided on the outer peripheral portion, the curved bottom matches the virtual true spherical surface having the same diameter as the diameter of the bottle body at the lowest portion, The peripheral portion is characterized by having a shape that bulges outward from the virtual true spherical surface.

Further, the bottle of polyethylene terephthalate resin according to the present invention is characterized in that the leg portions are thick enough to maintain their shape against the internal pressure of the foaming liquid.

Further, in the bottle of polyethylene terephthalate resin according to the present invention, the leg portion has a peripheral wall portion projecting downward from the curved bottom and at least two or more locations along the outer peripheral direction of the bottle main body at the tip of the peripheral wall portion. Is provided, and a recess having an inverted U-shaped cross section that protrudes into the leg is provided in a portion sandwiched by at least two or more grounding portions.

The polyethylene terephthalate resin bottle body of the present invention is obtained by injecting a molten polyethylene terephthalate resin into a die having a predetermined shape to form a mouth portion having a thread forming portion and a bottomed cylindrical bottle main body. An injection molding step of molding a bottle preform composed of a molded body, and holding the mouth of the preform obtained in the injection molding step in a non-stretched state, A blow molding mold having a bowl-shaped concave curved surface at the bottom of a cylindrical hollow portion, wherein the bowl-shaped concave curved surface corresponds to a virtual true spherical surface having the same diameter as the diameter of the hollow portion at the lowest portion, A blow molding step of performing blow molding along a blow molding die having a concave shape deeper than the virtual true spherical surface in the peripheral portion, and providing a plurality of leg forming concave portions in the peripheral portion of the bowl-shaped concave curved surface; A manufacturing method characterized by comprising It can be more advantageously produced.

In the above manufacturing method, the preform is
The cylindrical portion connected to the bottom of the primary molded body of the bottle body is provided with as many thick portions as the leg forming recesses along the axial direction, and in the blow molding step, the preform is provided with the thick portion. Is fixed to the blow-molding die in a state of being aligned with the position of the leg-forming recess, and blow-molding is performed.

Further, in the above-mentioned manufacturing method, the leg forming concave portion provided in the blow molding die is provided at the peripheral wall forming concave portion and at the bottom of the peripheral wall forming concave portion along the outer peripheral direction of the hollow portion. A flat plate portion is provided, and a convex portion having an inverted U-shaped cross section is provided in a portion sandwiched by the two flat plate portions.

[0013]

According to the bottle of polyethylene terephthalate resin of the present invention, the bottom of the curved surface is coincident with the bottom of the virtual true spherical surface having the same diameter as the diameter of the bottle main body at the lowest portion thereof, and the virtual true spherical surface is provided at the peripheral portion thereof. It has a shape that bulges outward from the bottom. By configuring the curved surface bottom as described above, it becomes a shape that substantially matches the virtual true spherical surface bottom in the vicinity of the lowest part, so the internal pressure applied to the curved surface bottom when the bottle is filled with the foaming liquid is equalized. Therefore, it is difficult to deform and excellent pressure resistance can be obtained.

Further, since the curved surface bottom has a shape that bulges outward from the virtual true spherical surface in the peripheral portion, the legs provided in the peripheral portion of the curved surface bottom are formed on the virtual true spherical surface. Compared with the case, the amount of downward projection is reduced, and the amount of resin used for forming the legs is increased. Therefore, in the polyethylene terephthalate resin bottle body of the present invention, the leg portions are unlikely to be deformed by the internal pressure, and excellent self-sustaining stability is obtained.

Further, in the polyethylene terephthalate resin bottle body of the present invention, two flat plate-shaped ground portions are provided at the tip of the peripheral wall portion along the outer peripheral direction of the bottle body, and
A recess having an inverted U-shaped cross section that protrudes into the leg portion is provided in the portion sandwiched by the ground contact portions. Therefore, even when the leg portion is deformed by the internal pressure of the foamable liquid filled in the bottle, the leg portion is deformed so as to form a more enlarged flat plate-shaped grounding portion together with the two grounding portions. However, the self-sustaining stability of the bottle body is maintained.

According to the method for producing a polyethylene terephthalate resin bottle of the present invention, the molten polyethylene terephthalate resin is injected into a mold having a predetermined shape to form a mouth portion having a thread forming portion and a bottomed cylindrical shape. A bottle preform comprising the bottle main body primary molding is molded, and then the bottle main body primary molding of the preform is blow-molded along a blow molding die.

At this time, as a blow molding die, a bowl-shaped concave curved surface is provided at the bottom of a substantially cylindrical hollow portion, and the bowl-shaped concave curved surface has an imaginary diameter which is the same as the diameter of the hollow portion at the lowest portion. A blow molding die is used which has a concave shape deeper than the imaginary true spherical surface in the peripheral portion, and has a plurality of leg-forming concave portions in the peripheral portion of the bowl-shaped concave curved surface. At the bottom, the bottom matches the imaginary true spherical surface having the same diameter as the diameter of the bottle main body, and at the periphery, it has a shape that bulges outward from the imaginary true spherical surface. A polyethylene terephthalate resin bottle having a shape having a plurality of hollow legs for independently supporting a bottle body having a curved bottom integrally projected downward is advantageously manufactured.

According to the above-mentioned manufacturing method, the leg portion is formed thicker than the case where it is formed on the virtual true spherical surface, so that it is formed thicker. However, as the preform, the bottle main body is formed. In the blow molding step, a preform having a same number of thick-walled portions as the leg-forming recesses is provided in a cylindrical portion connected to the bottom of the primary molded body in the blow molding step is used. By fixing to the blow molding die in a state in which is aligned with the position of the leg forming concave portion and performing blow molding, the amount of resin forming the leg portion increases, and a shape having thick leg portions The polyethylene terephthalate resin bottle body of is advantageously manufactured.

Further, according to the manufacturing method of the present invention, as the blow molding die, a peripheral wall forming concave portion is formed in the leg forming concave portion and a bottom portion of the peripheral wall forming concave portion is formed along the outer peripheral direction of the hollow portion. By using a blow molding die in which two flat plate-shaped portions are provided and a convex portion having an inverted U-shaped cross section is provided in a portion sandwiched between the two flat plate-shaped portions, the tip of the peripheral wall portion is A bottle body made of polyethylene terephthalate resin, which has two flat-plate-shaped grounding portions along the outer peripheral direction of the bottle body and has a recess having an inverted U-shaped cross section in a portion sandwiched by the two grounding portions is provided. Advantageously manufactured.

[0020]

The polyethylene terephthalate resin bottle of the present invention and the method for producing the same will now be described in more detail with reference to the accompanying drawings. 1 is a front view of the polyethylene terephthalate resin bottle of this embodiment, FIG. 2 is an explanatory view showing the shape of the curved bottom of the polyethylene terephthalate resin bottle shown in FIG. 1, and FIG. 3 is a III-III line of FIG. Sectional drawing, FIG. 4 is a vertical sectional view of the bottom of the bottle made of polyethylene terephthalate resin shown in FIG. 1, FIG. 5 is a vertical sectional view taken along line VV of FIG. 3, and FIG. 6 is an injection molding process of the manufacturing method of this embodiment. 7 is a front view of the preform obtained in the injection molding step, and FIG. 8 is a VIII-VIII of FIG. 7.
9 is an explanatory sectional view showing a blow molding process of the manufacturing method of the present embodiment, and FIG. 10 is a sectional view taken along line XX of FIG.

As shown in FIG. 1, a polyethylene terephthalate resin bottle body 1 of the present embodiment is provided with a bottle body 2, a bottom portion 3 provided below the bottle body 2, and above the bottle body 2. It consists of the mouth 4. 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 part 3 has a curved bottom 6 that bulges like a bowl below the bottle body 2 and a curved bottom 6 around the curved bottom 6.
And a hollow leg portion 7 that is integrally provided so as to project downward, and the bottle body 1 made of polyethylene terephthalate resin can be self-supported by the leg portion 7.

In this embodiment, the polyethylene terephthalate resin bottle body 1 has a diameter R of 9 as shown in FIG.
It is formed to 3 mm. As shown in FIG. 2, the curved bottom 6 has a shape in which an upper curved bottom 6a and a lower curved bottom 6b are smoothly joined, and the upper curved bottom 6a is made of polyethylene terephthalate. A circular arc having a radius r ₁ centered on a point O ₁ located away from the axis line z of the resin bottle body 1 (the circular arc AB and the circular arc CD shown in FIG. 2).
Is a rotating body that is rotated around the axis z, and the lower curved bottom 6b has a polyethylene terephthalate resin bottle body 1
Of the spherical surface of r ₂ centered on a point O ₂ located on the axis line z and having a radius larger than r ₁ (arc BL ₁ C shown in FIG. 2)
Has become.

The curved bottom 6 having the above-mentioned structure has a virtual true spherical surface 8 having the same diameter as the diameter R of the polyethylene terephthalate resin bottle 1 on the axis z of the polyethylene terephthalate resin bottle 1 and the lower curved bottom 6b. larger r from the center O ₂ r ₁ is the radius centered from the O point located below the
_When represented as a spherical surface with r ₀ smaller than _2, the lowest part L ₁ of the curved surface bottom 6 coincides with the virtual true spherical surface 8, and the lowest part L ₁
The peripheral portion of the curved bottom 6 at the upper side has a shape that bulges outward from the virtual true spherical surface 8.

Polyethylene terephthalate resin bottle 1
When a foaming liquid such as a carbonated beverage is filled in, the internal pressure applied to the polyethylene terephthalate resin bottle body 1 by the foaming liquid becomes highest at the lowest portion L ₁ of the curved bottom 6.
However, in the polyethylene terephthalate resin bottle body 1 of this embodiment, the curved bottom 6 is formed in the above-mentioned shape, and the lowest portion L is formed.
_{In the} vicinity of ₁ , the shape is substantially coincident with the virtual true spherical surface 8 and the internal pressure can be evenly received, so that excellent pressure resistance is obtained and deformation is difficult.

As shown in FIGS. 3 and 4, the leg portions 7 are provided at five locations along the outer circumference of the bottom portion 3 at intervals of 72 °, and project downward from the curved bottom portion 6. It has a triangular frustum-shaped peripheral wall portion 9, and the inside of the peripheral wall portion 9 is hollow. Since the leg portion 7 is integrally formed with the curved bottom 6 around the curved bottom 6 that bulges outward from the virtual true spherical surface 8, it is formed on the curved bottom 6 that matches the virtual true spherical surface 8. In comparison with the above case, the amount protruding downward is small, and the amount of resin forming the peripheral wall portion 9 is correspondingly large. Therefore, the peripheral wall portion 9 is formed thick and has a thickness sufficient to maintain its shape against the internal pressure of the foamable liquid.

A flat plate-shaped grounding portion 10 is provided at the tip of the peripheral wall portion 9.
Are provided at two locations along the outer peripheral direction of the bottle body 2, and the portion sandwiched between the grounding portions 10 and 10 is a recess 11 projecting into the leg portion 7. The recess 11 has an inverted U-shaped cross section as shown in FIG.
Has a shape reduced in a similar manner. When the internal pressure of the foamable liquid increases, the concave portion 11 is pressed downward, as shown in FIG.
As shown by the phantom line, the flattened flat ground portion 10a is formed together with the ground portion 10. Therefore, in the polyethylene terephthalate resin bottle body 1, even when the internal pressure of the foamable liquid is inevitably deformed, the internal pressure is absorbed by the deformation of the recess 11, and the expanded flat-plate-shaped grounding portion 10a is absorbed. As a result, independence stability is maintained.

In this example, the polyethylene terephthalate resin bottle body 1 was manufactured as follows.

In the manufacturing method of this embodiment, first, in an injection molding step for molding a preform, a molten polyethylene terephthalate resin is injected into a mold having a predetermined shape to form a mouth portion having a screw forming portion. The bottle is made of a primary molded body having a bottomed cylindrical bottle body, and the same number of meat as the leg portions 7 provided on the polyethylene terephthalate resin bottle body 1 along the axial direction in the cylindrical portion connected to the bottom of the primary molded body. A preform having a thick portion is formed.

Next, in the blow molding step, the mouth portion of the preform obtained in the injection molding step is held in an unstretched state, and a substantially cylindrical hollow portion has a bowl-shaped concave curved surface at the bottom,
The bowl-shaped concave curved surface corresponds to a virtual true spherical surface having the same diameter as the hollow portion at the lowest portion, and the peripheral portion has a concave shape deeper than the virtual true spherical surface, and the peripheral portion of the bowl-shaped concave curved surface. Then, the primary molded body of the bottle main body is blow-molded along the blow molding die having the same number of leg forming recesses as the leg portions 7 provided in the polyethylene terephthalate resin bottle body 1.

In the blow-molding step, the preform is blow-molded by mounting it on the blow-molding die so that the thick portion matches the position of the leg-forming recess. Further, the leg forming recess provided in the blow molding die is provided with a peripheral wall forming recess and two flat plate-shaped portions at the bottom of the peripheral wall forming recess along the outer peripheral direction of the hollow portion. Cage, in the part sandwiched between these two flat plate-shaped parts,
A convex portion having an inverted U-shaped cross section is provided.

Next, the manufacturing method of this embodiment will be described in detail in the order of steps.

First, in the injection molding process, as shown in FIGS. 6 and 7, a molten polyethylene terephthalate resin 25 is applied to a preform molding die 22 for molding the preform 21 from a cylinder 23 through a hot runner 24.
Is ejected. The preform molding die 22 comprises a mouth molding die 26, a primary molding body molding die 27, and an in-core 28, and the polyethylene terephthalate resin 25 is injected into a cavity 29 constituted by these.

The primary molding die 27 has a cylindrical hollow portion 27a formed at the top and a concave spherical hollow portion 27 at the bottom.
b is formed. Further, the in-core 28 has an upper portion 28a.
Is formed into a cylindrical shape, and the lower portion 28b is formed into a pentagonal shape,
The bottom portion 28c is formed into a convex spherical surface.

The molten polyethylene terephthalate resin 25 injected as described above is filled with the cavity 29.
The preform 21 shown in FIG. 7 is cooled and solidified inside.
Is molded into the shape of. The preform 21 includes a mouth portion 4 having a thread forming portion 5 and a primary molded body 30 of the bottle body 2.

The primary molded body 30 comprises a tubular portion 30a and a hemispherical bottom portion 30b, and the bottom portion 30 of the tubular portion 30a.
As shown in FIG. 8, the portion 30c connected to b has an outer surface 31
A has a circular shape and the inner surface 31b has a pentagonal cross section. The portion sandwiched by the arc of the outer surface 31a and the pentagonal side of the inner surface 31b is the thick portion 32 along the axial direction.

Next, the preform 21 is heated to a state where it can be blow-molded, and then the preform 21 is mounted on the blow-molding mold 34 while the mouth 4 is sandwiched by the support members 33. As shown in FIG. 9, the blow molding die 34 has split shapes 36 a and 36 b having a shape that matches the outer shape of the bottle body 2 and forming a substantially cylindrical hollow portion 35, and the outer shape of the bottom portion 3. It is composed of a bottom die 37 having a matching shape.

The bottom die 37 has a bowl-shaped concave curved surface 38 having a shape matching the outer shape of the curved bottom 6. That is, the lowest portion L ₂ of the bowl-shaped concave curved surface 38 coincides with a virtual true spherical surface 39 (shown by a virtual line in FIG. 9) having the same diameter as the diameter of the hollow portion 35, and the peripheral portion 38 a is closer to the virtual true spherical surface 39. It has a deep concave surface.

The peripheral portion 38a of the bowl-shaped concave curved surface 38 is shown in FIG.
Also, as shown in FIG. 10, a leg forming recess 40 is provided. The leg forming recess 40 is formed as a substantially triangular truncated pyramid-shaped recess, and extends 72 along the outer circumference of the bowl-shaped recessed curved surface 38.
It is provided at five places with a space between each other. A flat plate-like portion 41 is provided at the bottom of the leg forming recess 40, and a hollow portion 35
Are provided at two locations along the outer peripheral direction of the flat plate-shaped portion 4
A convex portion 42 having an inverted U-shaped cross section is provided in a portion sandwiched between the first and the first portions 41.

In this embodiment, when the preform 21 is mounted on the blow molding die 34, the thick portion 32 is fixed so as to match the position of the leg forming recess 40, and blow molding is performed. In blow molding, as shown in FIG. 9, the stretch pin 43 is inserted into the inner surface side of the primary molded body 30 of the preform 21 fixed as described above, and the primary molded body 30 is stretched in the axial direction by the stretch pin 43. On the other hand, the bottle main body 2 and the bottom portion 3 which are stretched in the circumferential direction by the gas introduced through the stretch pin 43 and blow-molded along the shape of the blow molding die 34 and biaxially stretched are obtained. At this time, the mouth portion 4 of the preform 21 has the support member 3
Since it is still sandwiched by 3, it is not stretched even by the blow molding.

In this embodiment, after the blow molding process, the supporting member 33, the split dies 36a and 36b, and the bottom die 3 are formed.
The polyethylene terephthalate resin bottle body 1 is obtained by demolding 7.

In this embodiment, the leg portions 7 are formed at five locations along the outer circumference of the bottom portion 3. However, the leg portions 7 are formed in a number enough to give the polyethylene terephthalate resin bottle body 1 self-supporting property. However, the number is not limited to the above number. The legs 7 are usually formed in three or more places,
It is preferable that the bottle main body 3 is formed at 5 to 6 positions from both sides of the self-sustaining stability and the ease of molding.

When the number of legs 7 is different from that of this embodiment,
In the manufacturing method, the thick portion 32 of the preform 21
Of course, the number of leg forming recesses 40 of the blow molding die 34 may be changed according to the number of leg portions 7 to be formed.

In the manufacturing method of this embodiment, the preform 21 obtained in the injection molding step is mounted on the blow molding die 34 with the mouth portion 4 held by the support member 33. However, a blow molding process is provided subsequent to the injection molding process, and the preform 2 molded in the injection molding process
1 without removing the mouth mold 26, the mouth mold 2
Transferring to the blow molding process with the mouth 4 clamped by 6,
It may be provided in a blow molding. According to such an aspect, the amount of heat in injection molding can be utilized in blow molding, which is thermally advantageous. Further, since the preform 21 is still held by the mouth molding die 26, the thick portion 32 formed by injection molding and the leg forming recess 40 of the blow molding die 34 are set at corresponding positions. If so, the preform 21 can be mounted on the blow molding die 34 without positioning.

[0044]

As is apparent from the above, according to the bottle made of polyethylene terephthalate resin of the present invention, the curved bottom coincides with the virtual true spherical bottom having the same diameter as the diameter of the bottle main body at the lowest portion. Since the peripheral portion has a shape that bulges outward from the virtual true spherical surface bottom, the vicinity of the lowest portion of the curved surface bottom becomes a shape that substantially matches the virtual true spherical surface having the same diameter as the diameter of the bottle body, When the body is filled with the foamable liquid, it is difficult to be deformed by the internal pressure applied to the curved surface bottom, and excellent pressure resistance can be obtained.

The legs of the bottle made of polyethylene terephthalate resin according to the present invention are formed in the peripheral portion of the curved bottom surface which bulges outward from the virtual true spherical surface, so that the legs are thick and Also, it is difficult to deform, and excellent self-sustaining stability can be obtained.

Further, according to the bottle of polyethylene terephthalate resin of the present invention, the inside of the leg portion is located at the portion sandwiched by the two flat grounding portions provided at the tip of the peripheral wall portion of the leg portion projecting downward from the curved bottom. Since it has a recess having an inverted U-shaped cross-section protruding to the inside, when the internal pressure increases, the recess is pressed to form the flat plate-shaped grounding parts which are enlarged together with the flat plate-shaped grounding parts at the two places, and the bottle body is self-supporting. Stability can be maintained.

According to the manufacturing method of the present invention, there is provided a blow molding die having a bowl-shaped concave curved surface at the bottom of a substantially cylindrical hollow portion, wherein the bowl-shaped concave curved surface has the diameter of the hollow portion at the lowest portion. Blow molding in which a peripheral portion has a concave shape deeper than the virtual true spherical surface and has a plurality of leg-forming concave portions in the peripheral portion of the bowl-shaped concave curved surface. A preform obtained in the injection molding process is blow-molded along the blow-molding die using a die, so that the curved bottom has the same diameter as the diameter of the bottle body at the lowest part. Therefore, a polyethylene terephthalate resin bottle having a shape that bulges outward from the virtual true spherical surface in the peripheral portion can be advantageously manufactured.

Further, according to the manufacturing method of the present invention, since the leg portion of the bottle is formed in the peripheral portion of the curved bottom that bulges outward from the virtual true spherical surface, the leg portion formed to be thick Can be obtained. This effect is a preform in which the same number of wall thickness portions as the leg forming recesses of the blow molding die are provided along the axial direction in the tubular portion connected to the bottom of the primary molded body, By fixing to the blow molding die so as to match the position of the leg forming recess and blow molding,
It becomes even more remarkable.

Further, according to the manufacturing method of the present invention, as the blow molding die, two flat plate-shaped portions are formed at the bottom of the peripheral wall forming concave portion of the leg forming concave portion along the outer peripheral direction of the hollow portion. A leg portion protruding downward from a curved bottom by blow molding using a blow molding die provided with a convex portion having an inverted U-shaped cross section in a portion sandwiched between the two flat plate-shaped portions. A polyethylene terephthalate resin bottle having a recess having an inverted U-shaped cross-section protruding into the leg at a portion sandwiched by two flat plate-shaped grounding portions provided at the tip of the peripheral wall can be advantageously manufactured.

[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 an explanatory view showing the shape of a curved bottom of a bottle made of polyethylene terephthalate resin according to this embodiment.

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

FIG. 4 is a vertical cross-sectional view of the bottom portion of the bottle made of polyethylene terephthalate resin according to the present embodiment.

5 is a vertical cross-sectional view taken along line VV of FIG.

FIG. 6 is an explanatory cross-sectional view showing an injection molding process of the manufacturing method of this embodiment.

7 is a front view of a preform obtained in the injection molding process shown in FIG.

8 is a sectional view taken along line VIII-VIII of FIG.

FIG. 9 is an explanatory cross-sectional view showing the blow molding process of the manufacturing method of the present embodiment.

10 is a cross-sectional view taken along line XX of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Polyethylene terephthalate resin bottle body, 2 ... Bottle main body, 3 ... Bottom part, 4 ... Mouth part, 6 ... Curved bottom, 7 ... Leg part, 8 ... Virtual true spherical surface, 9 ... Peripheral wall part, 10 ... Flat plate-shaped grounding part , 11 ... Recesses, 21 ... Preforms, 22 ... Preform molding dies, 30 ... Primary moldings, 32 ... Thick parts, 34 ... Blow molding dies, 38 ... Bowl-shaped concave curved surface,
Reference numeral 39 ... Virtual spherical surface, 40 ... Recess for forming legs, 41 ... Flat plate portion, 42 ... Convex portion.

Claims (6)

[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. Bottle made of polyethylene terephthalate resin consisting of a biaxially stretched bottom portion having a plurality of hollow legs for making the bottle body self-supporting, and an unstretched mouth portion having a screw forming portion provided on the outer peripheral portion above the bottle body. In the body, the curved bottom has a shape in which the bottom of the curved surface coincides with a virtual true spherical surface having the same diameter as the diameter of the bottle main body, and the peripheral portion has a shape bulging outward from the virtual true spherical surface. Bottle body made of polyethylene terephthalate resin. 2. The bottle of polyethylene terephthalate resin according to claim 1, wherein the leg portion has a wall thickness capable of maintaining its shape against the internal pressure of the foaming liquid. 3. The leg portion is provided with a peripheral wall portion projecting downward from the curved bottom and at least two flat plate-shaped ground portions along the outer peripheral direction of the bottle body at the tip of the peripheral wall portion. The bottle body made of polyethylene terephthalate resin according to claim 1, characterized in that a recessed portion having an inverted U-shaped cross section that projects into the leg portion is provided in a portion sandwiched between two or more grounding portions. 4. A bottle mold made of a polyethylene terephthalate resin in a molten state is injected into a mold having a predetermined shape to have a mouth portion having a thread forming portion and a bottomed cylindrical bottle body primary molded body. An injection molding step of molding the reform, and the preform obtained in the injection molding step is held in the non-stretched state of the preform, and the primary molded body of the bottle main body is placed in the bottom of the substantially cylindrical hollow portion. A mold for blow molding having a concave concave curved surface, wherein the concave concave curved surface of the bowl coincides with a virtual true spherical surface having the same diameter as the diameter of the hollow portion at the lowest portion, and is deeper than the virtual true spherical surface at the peripheral portion. A blow molding step of performing blow molding along a blow molding die having a concave shape and having a plurality of leg-forming concave portions provided in the peripheral portion of the bowl-shaped concave curved surface. Method of manufacturing resin bottle body. 5. The blow molding step, wherein the preform comprises a cylindrical portion connected to a bottom portion of the primary molded body of the bottle main body and provided with the same number of thick portions as the leg forming recesses along the axial direction. 5. The polyethylene terephthalate resin according to claim 4, wherein the preform is fixed to the blow molding die in a state where the thick portion is aligned with the position of the leg forming recess, and blow molding is performed. Bottle manufacturing method. 6. A leg forming recess provided in the blow molding die is provided with a peripheral wall forming recess and two flat plate-shaped portions at the bottom of the peripheral wall forming recess along the outer peripheral direction of the hollow portion. The method for producing a polyethylene terephthalate resin bottle body according to claim 4, wherein a convex portion having an inverted U-shaped cross section is provided in a portion sandwiched between the two flat plate-shaped portions.