JP3101375B2 - Polyethylene terephthalate resin bottle and method for producing the same - 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 a method for producing the same, and more particularly to a polyethylene terephthalate resin bottle having a leg at the bottom for allowing the bottle body to stand on its own. Things.

[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. In the polyethylene terephthalate resin bottle, usually, the bottom is formed in a conical shape protruding from the inner surface of the bottle main body commonly referred to as a champagne bottom, and a joint between the conical bottom and the bottle main body is formed as an annular leg. Independence is provided.

The polyethylene terephthalate resin bottle is also used as a container for an effervescent liquid such as a carbonated beverage. In this case, the effervescent liquid is contained in a bottle having a champagne bottom. There is a problem that the bottle is easily deformed due to its internal pressure when filled. 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, for example, a method of attaching a base (base cup) to the bottom of the bottle has been proposed. However, in such a method, there is a problem that the bottle does not become vertical depending on the joining state of the bottle and the base cup, and the bottle easily falls down.

On the other hand, a projecting portion is provided on the hemispherical bottom of the bottle so as to protrude downward, and a flat grounding portion is formed at the bottom of the projecting portion. A technique for making the main body independent has been proposed. But,
Protrusions formed by the technique tend to be thinner because they protrude further from the bottom of the bottle. For this reason, the flat contact portion tends to be easily deformed due to the internal pressure of the foaming liquid and swell further downward to take on a rounded shape. Degree) is difficult to be uniform, and there is a disadvantage that the independence of the bottle body tends to be unstable.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned disadvantages, and has excellent pressure resistance and self-standing stability even when filled with a foaming liquid such as a carbonated beverage. It is an object of the present invention to provide a resin bottle and a method for producing the same.

[0007]

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 a plurality of hollow legs for self-supporting a bottle body provided by projecting the curved bottom integrally downward at the bottom and at the periphery of the curved bottom; In a polyethylene terephthalate resin bottle comprising a non-stretched mouth having a thread forming portion provided on the outer peripheral portion, 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 at the lowest portion, The peripheral portion has a shape bulging outward from the virtual true spherical surface.

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

Further, in the polyethylene terephthalate resin bottle of the present invention, the leg portion projects downward from the bottom of the curved surface, and at least two or more locations are provided at the tip of the peripheral wall portion along the outer peripheral direction of the bottle body. And a concave portion having an inverted U-shaped cross section projecting into the leg portion is provided in a portion sandwiched between the at least two or more ground portions.

[0010] The polyethylene terephthalate resin bottle of the present invention is characterized in that a molten polyethylene terephthalate resin is injected into a mold having a predetermined shape to form a mouth having a threaded portion and a primary cylinder body having a bottomed cylindrical shape. An injection molding step of molding a preform of a bottle 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 coincides with 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 forming a concave shape deeper than the virtual true spherical surface in the peripheral portion, and blow molding along a blow molding die having a plurality of leg forming concave portions provided in the peripheral portion of the bowl-shaped concave curved surface; Manufacturing method characterized by comprising: It can be more advantageously produced.

In the above method, the preform may be:
A cylindrical portion connected to the bottom of the primary molded body of the bottle body is provided with the same number of thick portions as the leg forming recesses along the axial direction along the axial direction. Are fixed to the blow-molding die in a state where they coincide with the positions of the leg-forming concave portions, and are blow-molded.

[0012] In the manufacturing method, the leg forming recess provided in the blow molding die may include two peripheral wall forming recesses and a bottom portion of the peripheral wall forming recess along the outer peripheral direction of the hollow portion. A flat portion is provided, and a convex portion having an inverted U-shaped cross section is provided in a portion sandwiched between the two flat portions.

[0013]

According to the polyethylene terephthalate resin bottle of the present invention, the bottom of the curved surface coincides with the bottom of the imaginary true spherical surface having the same diameter as the diameter of the bottle main body at the lowest part, and the imaginary true spherical surface at the peripheral portion. It has a shape that bulges outward from the bottom. Since the curved bottom is configured as described above, in the vicinity of the lowest portion, it has a shape substantially matching the virtual spherical bottom, so that when the bottle is filled with the foaming liquid, the internal pressure applied to the curved bottom is equalized. And it is hardly deformed, and excellent pressure resistance can be obtained.

Further, since the curved bottom has a shape which bulges outward from the virtual true sphere at the peripheral portion, the legs provided at the peripheral portion of the curved bottom are formed on the virtual true spherical surface. As compared with the case, the amount of protrusion downward is reduced, and the amount of resin used for forming the leg is increased. Therefore, in the polyethylene terephthalate resin bottle of the present invention, the legs are hardly deformed even by the internal pressure, and excellent self-standing stability is obtained.

Further, in the polyethylene terephthalate resin bottle of the present invention, two flat contact portions are provided at the end of the peripheral wall along the outer peripheral direction of the bottle main body.
A concave portion having an inverted U-shaped cross section is provided at a portion sandwiched between the grounding portions, and protrudes into the leg portion. Therefore, even when the legs are deformed due to the internal pressure of the foaming liquid filled in the bottle, the recesses are pressed to form a flattened ground portion with a larger size together with the two ground portions. However, the self-standing stability of the bottle main body is maintained.

According to the method for producing a polyethylene terephthalate resin bottle of the present invention, a molten polyethylene terephthalate resin is injected into a mold having a predetermined shape, and a mouth having a screw forming portion and a bottomed cylindrical shape are formed. A preform of a bottle composed of the primary molded body of the bottle main body is molded, and then the primary molded body of the bottle main body of the preform is blow molded along a blow mold.

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 the same diameter as the diameter of the hollow portion at the lowest portion. Since the blow molding die which has a concave shape that matches the true spherical surface and has a concave shape deeper than the virtual 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 is used, the curved surface At the bottom, the bottom coincides with a virtual spherical surface having the same diameter as the bottle body, and at the peripheral portion, the bottom has a shape that bulges outward from the virtual spherical surface. Advantageously, a bottle made of polyethylene terephthalate resin having a plurality of hollow legs for self-supporting a bottle body provided with a curved bottom integrally projecting downward is advantageously produced.

According to the manufacturing method, the leg portion is formed to be thick because the amount of downward projection is reduced as compared with the case where the leg portion is formed on the virtual true spherical surface. Using a preform in which the same number of thick portions as the leg forming recesses are provided along the axial direction in a cylindrical portion connected to the bottom of the primary molded body, and in the blow molding step, the preform is formed by using the thick portion. Is fixed to the blow molding die in a state where it matches the position of the leg forming recess, and the amount of resin forming the leg is increased, and the shape having the thicker leg is further increased. Is advantageously produced.

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 providing a blow-molding mold having two flat portions and a convex portion having an inverted U-shaped cross section in a portion sandwiched between the two flat portions, the tip of the peripheral wall portion is A polyethylene terephthalate resin bottle having two flat contact portions along the outer peripheral direction of the bottle body and having a concave portion having an inverted U-shaped cross section at a portion sandwiched between the two contact portions. Produced advantageously.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The polyethylene terephthalate resin bottle of the present invention and a method for producing the same will be described in more detail with reference to the accompanying drawings. FIG. 1 is a front view of a polyethylene terephthalate resin bottle of the present 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 line III-III in FIG. FIG. 4 is a vertical sectional view of the bottom of the polyethylene terephthalate resin bottle 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. FIG. 7 is a front view of a preform obtained in the injection molding step, and FIG. 8 is a VIII-VIII of FIG.
9 is an explanatory sectional view showing a blow molding step 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, the polyethylene terephthalate resin bottle 1 of this embodiment is provided with a bottle body 2, a bottom 3 provided below the bottle body 2, and an upper part of the bottle body 2. The mouth 4. 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 in a bowl shape below the bottle body 2 and a curved bottom 6 around the curved bottom 6.
And a hollow leg 7 provided integrally and protruding downward. The polyethylene terephthalate resin bottle 1 can be self-standing by the leg 7.

In this embodiment, the polyethylene terephthalate resin bottle 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. arc of radius r ₁ to the O ₁ point located from the axis z of the resin bottle body 1 away to the left and right and center (arc AB and arc CD shown in FIG. 2)
Is rotated about the axis z, and the lower curved bottom 6b is a polyethylene terephthalate resin bottle 1
The top of the spherical surface of r ₂ having a radius larger than r ₁ centered on the point O ₂ located on the axis z of the circle (arc BL ₁ C shown in FIG. 2)
It has become.

The curved bottom 6 having the above-described configuration is formed by placing 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 a 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 expressed 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 upper curved surface bottom 6 has a shape bulging outward from the virtual true spherical surface 8.

Polyethylene terephthalate resin bottle 1
Is filled with an effervescent liquid such as a carbonated beverage, the internal pressure applied to the polyethylene terephthalate resin bottle 1 by the effervescent liquid becomes highest at the lowest part L ₁ of the curved bottom 6.
However, in the bottle 1 made of polyethylene terephthalate resin of the present embodiment, the curved bottom 6 is formed in the above-described shape, and the minimum portion L
_{In the} vicinity of ₁ , the shape substantially conforms to 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 periphery of the bottom portion 3 at intervals of 72 °, and project downward from the curved bottom portion 6. The peripheral wall 9 has a truncated triangular pyramid shape, and the inside of the peripheral wall 9 is hollow. Since the leg 7 is formed integrally with the curved bottom 6 around the curved bottom 6 bulging outward from the virtual true spherical surface 8, it is formed on the curved bottom 6 that coincides with the virtual true spherical surface 8. The amount of resin that forms the peripheral wall portion 9 is larger than that of the case in which the protrusion is small, and the amount of resin that forms the peripheral wall portion 9 is correspondingly large. Therefore, the peripheral wall portion 9 is formed to be thick and has a thickness sufficient to maintain the shape against the internal pressure of the foamable liquid.

At the end of the peripheral wall portion 9, a flat grounding portion 10 is provided.
Are provided at two places along the outer peripheral direction of the bottle body 2, and a portion sandwiched between the grounding portions 10, 10 is a concave portion 11 protruding into the leg portion 7. The recess 11 has an inverted U-shaped cross section as shown in FIG.
Is reduced in a similar manner. When the internal pressure of the foaming liquid increases, the concave portion 11 is pressed downward, and as shown in FIG.
As shown by the imaginary line, a grounded portion 10a in the form of an enlarged flat plate is formed together with the grounded portion 10. Therefore, in the polyethylene terephthalate resin bottle 1, even if the internal pressure of the foaming liquid has forced the deformation, the internal pressure is absorbed by the deformation of the concave portion 11, and the flattened ground portion 10 a is further enlarged. Thereby, self-sustaining stability is maintained.

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

In the manufacturing method of this embodiment, first, in an injection molding step of molding a preform, a molten polyethylene terephthalate resin is injected into a mold having a predetermined shape to form a mouth having a screw forming portion. It is composed of a primary molded body of a bottle body having a bottomed cylindrical shape, and the same number of meats as the legs 7 provided on the polyethylene terephthalate resin bottle 1 along the axial direction in a 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 of the preform obtained in the injection molding step is held in an unstretched state, and has a bowl-shaped concave curved surface at the bottom of the substantially cylindrical hollow part.
The bowl-shaped concave curved surface coincides with the imaginary true spherical surface having the same diameter as the diameter of the hollow portion at the lowest part, and has a concave shape deeper than the imaginary true spherical surface at the peripheral portion, and the peripheral portion of the bowl-shaped concave curved surface The primary molded body of the bottle main body is blow-molded along a blow molding die provided with the same number of leg forming recesses as the legs 7 provided on the polyethylene terephthalate resin bottle 1.

[0030] In the blow molding step, the preform is mounted on the blow molding die and blow molded so that the thick portion matches the position of the leg forming recess. In the leg forming recess provided in the blow molding die, a peripheral wall forming recess and two flat plate-shaped portions are provided at the bottom of the peripheral wall forming recess along the outer peripheral direction of the hollow portion. And the part sandwiched between these two flat 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 step, as shown in FIGS. 6 and 7, a molten polyethylene terephthalate resin 25 is fed from a cylinder 23 through a hot runner 24 to a preform molding die 22 for molding a preform 21.
Is injected. The preform mold 22 includes a mouth mold 26, a primary molded body mold 27, and an in-core 28, and the polyethylene terephthalate resin 25 is injected into a cavity 29 formed by these.

The primary molded body molding die 27 has a cylindrical hollow portion 27a formed at the upper portion, and a concave spherical hollow portion 27 at the bottom portion.
b is formed. Also, the in-core 28 has an upper part 28a.
Are formed in a columnar shape, and the lower portion 28b is formed in a pentagonal column shape.
The bottom part 28c is formed as a convex spherical surface.

The molten polyethylene terephthalate resin 25 injected as described above is
It is cooled and solidified in the preform 21 shown in FIG.
It is molded in the shape of The preform 21 includes a mouth 4 having a thread forming portion 5 and a primary molded body 30 of the bottle main body 2.

The primary molded body 30 comprises a cylindrical portion 30a and a hemispherical bottom portion 30b, and the bottom portion 30a of the cylindrical portion 30a is formed.
As shown in FIG.
a is circular and the inner surface 31b has a pentagonal cross section. A portion sandwiched between the arc of the outer surface 31a and the pentagonal side of the inner surface 31b is a thick portion 32 along the axial direction.

Next, after the preform 21 is heated to a state where it can be blow-molded, the preform 21 is mounted on a blow-molding mold 34 with the opening 4 held between the support members 33. As shown in FIG. 9, the blow molding mold 34 has a shape matching the outer shape of the bottle body 2, and has split dies 36 a and 36 b forming a substantially cylindrical hollow portion 35, and the outer shape of the bottom 3. It is constituted by a bottom mold 37 having a matching shape.

The bottom mold 37 has a bowl-shaped concave curved surface 38 whose shape matches the outer shape of the curved bottom 6. That is, the minimum unit L ₂ of the cup-shaped concave surface 38 coincides with the virtual true spherical surface 39 having the same diameter as the diameter of the hollow portion 35 (shown in phantom in FIG. 9), the peripheral portion 38a is the virtual true spherical surface 39 It has a deep concave surface.

FIG. 9 shows a peripheral portion 38a of the bowl-shaped concave curved surface 38.
As shown in FIG. 10, a leg forming recess 40 is provided. The leg forming recess 40 is formed as a substantially truncated triangular pyramid-shaped recess, and extends along the outer periphery of the bowl-shaped concave curved surface 38.
It is provided at five places with an interval from each other for every °. At the bottom of the leg forming recess 40, a flat plate-shaped portion 41 is provided.
Are provided at two locations along the outer circumferential direction of the
A convex portion 42 having an inverted U-shaped cross section is provided in a portion sandwiched between 1 and 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 coincide with the position of the leg forming recess 40, and blow molding is performed. In the blow molding, as shown in FIG. 9, a 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 body 2 and the bottom 3 are stretched in the circumferential direction by the gas introduced through the stretch pins 43 and blow-molded along the shape of the blow molding mold 34 and biaxially stretched. At this time, the opening 4 of the preform 21 is
Since it is in the state of being clamped in 3, it is not stretched even by the blow molding.

In this embodiment, after the blow molding step, the support member 33, the split dies 36a and 36b and the bottom die 3
By demolding 7, a polyethylene terephthalate resin bottle 1 is obtained.

In this embodiment, the legs 7 are formed at five places along the outer periphery of the bottom 3, but the legs 7 are formed in such a number that the polyethylene terephthalate resin bottle 1 can be provided with autonomy. And the number is not limited to the above. The legs 7 are usually formed in three or more places,
It is preferable that the bottle body 3 is formed at 5 or 6 places from both the stand-alone 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 is used.
Needless to say, the number of the leg forming recesses 40 of the blow molding mold 34 is changed according to the number of the leg portions 7 to be formed.

Further, 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 opening 4 held by the support member 33. However, a blow molding process is provided following the injection molding process, and the preform 2 molded in the injection molding process is provided.
1 without removing the mouth-forming mold 26 from the mouth-forming mold 2
Transferred to the blow molding process while holding the mouth 4 in 6,
It is good also as a mode provided for blow molding. According to such an embodiment, the amount of heat in injection molding can be used for blow molding, which is thermally advantageous. Further, since the preform 21 is held by the mouth forming die 26, the thick portion 32 formed by injection molding and the leg forming concave portion 40 of the blow molding die 34 are set at corresponding positions. If so, the preform 21 itself can be mounted on the blow molding die 34 without positioning.

[0044]

As is apparent from the above, according to the polyethylene terephthalate resin bottle of the present invention, the curved bottom coincides with the imaginary true spherical bottom having the same diameter as the diameter of the bottle main body at the lowest part. Since the peripheral portion has a shape that bulges outward from the bottom of the virtual spherical surface, the vicinity of the lowest portion of the curved bottom has a shape substantially matching the virtual spherical surface having the same diameter as the diameter of the bottle main body. When the body is filled with the foaming liquid, the body is not easily deformed due to the internal pressure applied to the bottom of the curved surface, and excellent pressure resistance can be obtained.

The legs of the polyethylene terephthalate resin bottle of the present invention are formed around the bottom of the curved surface which bulges outward from the imaginary true spherical surface, so that the thickness is increased by the internal pressure. Is hardly deformed, and excellent self-standing stability can be obtained.

Further, according to the polyethylene terephthalate resin bottle of the present invention, the portion between the two flat grounding portions provided at the tip of the peripheral wall portion of the leg projecting downward from the bottom of the curved surface has the inside of the leg. Since the internal pressure is increased, the concave portion is pressed to form a flattened ground portion that is further enlarged together with the two flat ground portions, and the bottle main body is self-supporting. Stability can be maintained.

According to the production 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 a minimum diameter of the hollow portion. Blow molding, which has a concave shape that is deeper than the virtual 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. Using a mold, the preform obtained in the injection molding step is blow-molded along the blow-molding mold, so that a virtual spherical surface whose curved surface bottom has the same diameter as the diameter of the bottle body at the lowest part. In the peripheral portion, a polyethylene terephthalate resin bottle having a shape bulging outward from the virtual spherical surface can be advantageously produced.

Further, according to the manufacturing method of the present invention, since the legs of the bottle are formed at the periphery of the curved bottom protruding outward from the virtual true spherical surface, the thick legs are formed. Can be obtained. This effect is achieved by forming a preform having the same number of thick portions as the leg forming recesses of the blow molding die along the axial direction in the cylindrical portion connected to the bottom of the primary molded body, By fixing the blow molding die and performing blow molding so as to match the position of the leg forming recess,
It becomes even more significant.

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

[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 an explanatory view showing the shape of the bottom of the curved surface of the polyethylene terephthalate resin bottle of the present embodiment.

FIG. 3 is a sectional view taken along line III-III of FIG. 1;

FIG. 4 is a longitudinal sectional view of the bottom of the polyethylene terephthalate resin bottle of the present embodiment.

FIG. 5 is a vertical sectional view taken along line VV of FIG. 3;

FIG. 6 is an explanatory sectional view showing an injection molding step of the manufacturing method according to the present embodiment.

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

FIG. 8 is a sectional view taken along line VIII-VIII in FIG. 7;

FIG. 9 is an explanatory sectional view showing a blow molding step of the manufacturing method according to the present embodiment.

FIG. 10 is a sectional view taken along line XX of FIG. 9;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Bottle made of polyethylene terephthalate resin, 2 ... Bottle main body, 3 ... Bottom part, 4 ... Mouth part, 6 ... Curved bottom, 7 ... Leg, 8 ... Virtual true spherical surface, 9 ... Peripheral wall part, 10 ... Flat ground part Reference numeral 11: concave portion, 21: preform, 22: preform molding die, 30: primary molded body, 32: thick portion, 34: blow molding die, 38: bowl-shaped concave curved surface,
39: virtual spherical surface, 40: concave portion for leg formation, 41: flat plate portion, 42: convex portion.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B65D 1/02 B29C 49/08 B29D 22/00 B29K 67:00 B29L 22:00

Claims (6)

(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 bottle comprising a biaxially stretched bottom having a plurality of hollow legs for self-supporting the bottle body, and a non-stretched mouth having a threaded portion provided on an outer peripheral portion above the bottle body. In the body, 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 at the lowest part, and has a shape protruding outward from the virtual true spherical surface at the peripheral part. Polyethylene terephthalate resin bottle. 2. The polyethylene terephthalate resin bottle according to claim 1, wherein said 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 bottom of the curved surface and at least two or more flat ground portions at a tip end of the peripheral wall portion along an outer peripheral direction of the bottle main body. 2. The polyethylene terephthalate resin bottle according to claim 1, wherein a concave portion having an inverted U-shaped cross section is provided at a portion sandwiched between two or more grounding portions and protrudes into the leg portion. 4. Injection of a molten polyethylene terephthalate resin into a mold having a predetermined shape to form a bottle formed of a mouth having a threaded portion and a primary molded body of a bottle body having a bottomed cylindrical shape. An injection molding step of molding a reform; holding the mouth of the preform obtained in the injection molding step in a non-stretched state; and placing the primary molded body of the bottle main body at the bottom of a substantially cylindrical hollow portion. A blow molding die having a concave concave surface, wherein the bowl-shaped concave surface 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 having a concave shape and performing blow molding along a blow molding die having a plurality of leg forming concave portions provided in a peripheral portion of the bowl-shaped concave curved surface. A method for manufacturing a resin bottle. 5. The blow molding process according to claim 1, wherein the preform comprises a cylindrical portion connected to the bottom of the primary molded body of the bottle main body, and the same thick portion as the leg forming concave portion is provided 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 coincides with the position of the leg forming recess, and blow molding is performed. Bottle manufacturing method. 6. A leg forming recess provided in said blow molding die is provided with a peripheral wall forming recess and two flat plate-like portions at the bottom of said peripheral wall forming recess along the outer peripheral direction of said hollow portion. 5. The method for producing a polyethylene terephthalate resin bottle according to claim 4, wherein a convex portion having an inverted U-shaped cross section is provided at a portion sandwiched between the two flat plate portions.