JP2996451B2 - Manufacturing method of pressure-resistant self-standing container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic container having good self-sustainability even when a large internal pressure is applied thereto, and a method for manufacturing the same. More specifically, a so-called petaloid-shaped bottom is integrally formed on a base. The present invention relates to a method for manufacturing a plastic container that can stand alone without using a cup.

[0002]

2. Description of the Related Art A biaxially stretched blow-molded container made of a saturated polyester resin represented by polyethylene terephthalate has excellent transparency and surface gloss, is beautiful, and has a gas barrier. Excellent in water resistance, moisture impermeability, content resistance and storage stability. In addition, it has many advantages such as low heat generation during combustion and easy disposal because it does not damage the furnace. Therefore, it is widely used for various drinking water, seasonings, alcoholic beverages and other food containers.

Some of such biaxially stretch blow-molded containers (bottles) have a so-called base cup mounted on the bottom. The base cup is mounted to provide autonomy to the container and, in some cases, to reinforce the bottom, which is often used, for example, for containers whose contents have a high internal pressure, such as carbonated beverages. This is because in such a container, the bottom of the container is generally formed into a rounded convex shape in order to improve the internal pressure resistance.

[0004] Such a container with a base cup has excellent self-standing stability, and the bottom is reinforced. However, the number of steps for manufacturing the base cup in a separate process and then attaching it to the container body increases, thereby increasing productivity. Inferior. Further, since the base cup is usually formed of a different kind of resin from the container body, the container provided with the base cup is inferior in recyclability.

Therefore, a container having a structure in which various irregularities are formed on the bottom of the container to reinforce the bottom of the container and secure independence without a base cup (for example, Japanese Patent Publication No. 48-5 / 78).
708, JP-A-2-57545, etc.) have been developed and put to practical use.

Japanese Patent Publication No. 48-5708 discloses a container as shown in FIG. 10 as a typical example. Of FIG.
10 (a) shows a front view of the container 60, and FIG. 10 (b) shows a bottom view of the container 60. As can be seen from FIG. A plurality of legs 62 are formed at equal intervals in the circumferential direction. The leg portion 62 has an outer surface that smoothly continues from the body of the container 60, and a lower end portion of the leg portion 62 is a ground contact portion 64. Also between the legs 62, (a) in along the line L ₁ showing be smoothly concave container inwardly is also (b) to along a line L ₂ showing smoothly convex container downwardly And a curved surface portion 63 that is generally concave inward from the outer surface of the leg portion 62.
Are formed. Although the container having such a bottom shape is self-supporting, as can be seen from the figure, each leg 62 becomes thinner downward, so that the ground portion 64 is small. Further, since the ground contact portion 64 is located inside the diameter of the container body, the self-standing stability is not good.

Japanese Patent Application Laid-Open No. 2-57545 discloses a container having a bottom shape as shown in FIG. 11 as a typical example. At the bottom 71 of this container 70,
The leg portion 72 is formed large, and the ground contact portion 74 formed at the lower end of the leg portion 72 is located slightly inward of the diameter of the body of the container, thereby improving the self-standing stability. However, also in the container of this example, each leg 7
2, the curved surface 73 is relatively large, and the curved surface 73 is formed so as to spread downward. Therefore, the leg 72 becomes thinner at the lower side, and the size of the grounding portion 74 is sufficient. Not be. For this reason, the independence stability at the time of container filling and the line feedability at the time of filling work etc. are not yet sufficient.

In order to obtain good self-sustaining stability, it is basically preferable to form the grounding portion as large as possible and to make the position of the grounding portion as close as possible to the maximum diameter in the container body. This is difficult to achieve with equipment and manufacturing methods, and some improvement was needed.

Accordingly, an object of the present invention is to provide a method for producing an integrally molded type container (without using a base cup) having good pressure resistance and excellent self-standing stability.

[0010]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that a bottom wall portion formed of a smoothly curved surface that is convex downward, and that the bottom wall portion is alternately formed in the circumferential direction. The bottom of the structure having a plurality of arranged legs, the corner of each surface forming the legs and the corner between the legs and the bottom wall portion are formed as corners having a relatively small radius of curvature, and each leg is formed. If the section is not substantially narrowed downward and the outer corner of the lower end of each leg is configured as a grounding section, the grounding section can be enlarged, thereby providing excellent self-sustaining stability and content. In order to manufacture a container having such a bottom structure, it has been found that the stability at the time of line transport in the step of filling and the like is also good, and to manufacture a container having such a bottom structure, a hole having a hole at a position corresponding to a leg at the bottom is required. And the bottom mold of this first bottom mold And a second bottom mold having a protrusion that can be inserted vertically from below the hole of the first bottom mold when moved upward. Using a blow mold, the parison is stretch blow-molded with the second bottom mold placed on the lower side, and then the second bottom mold is pushed up to form a hole in the first bottom mold. It has been found that the legs can be formed with good shapeability by compression-molding the convex portions of the formed intermediate molded body. The present invention is based on the above findings.

That is, the method of the present invention for producing a pressure-resistant self-standing container having a bottom portion in which a plurality of legs forming a ground contact portion are formed at equal intervals in the circumferential direction is provided as a biaxial stretch blow mold. A torso mold, a first bottom mold fixed to the torso mold, and having a hole at a position corresponding to the plurality of legs, and installed vertically below the first bottom mold and up and down Movable, equipped with a second bottom mold having a projecting portion that can be inserted from below into the hole of the first bottom mold, using the second bottom mold located on the lower side, Performing biaxial stretch blow molding of the parison in a state where the hole portion of the bottom mold is free, and in the hole portion, inflating the end of the stretch-blown intermediate molded body to form a convex portion, Pressing the second bottom mold upward to insert the protrusion into the hole, Swollen by compression molding the protrusion in parts, characterized in that this portion with the leg portion.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

First, the container of the present invention will be described. FIG.
1 shows a pressure-resistant self-standing container 1 according to an embodiment of the present invention, in which (a) is a front view and (b) is a bottom view. The container 1 includes a mouth portion 2 having a support ring 21 and a screw portion 22, a shoulder portion 3 which smoothly expands in diameter from a lower end of the mouth portion 2, a substantially cylindrical body portion 4, and a plurality of legs. And a bottom 5 having a portion 51. In the container 1 of the present embodiment, the reinforcing portion 4a whose diameter is slightly increased is provided at the lower end portion of the body portion 4. In the present invention, the mouth portion 2, the shoulder portion 3, and the body portion 4 are The shape is not limited to the shape shown in FIG. 1 and may be appropriately changed to various shapes found in conventional plastic containers. A feature of the container of the present invention is its bottom shape.

In the embodiment shown in FIG. 1, five legs 51 are formed on the bottom 5 at equal intervals in the circumferential direction. Each leg portion 51 has an outer peripheral surface portion 51a that is smoothly continuous from the outer surface of the body portion 4 and a pair of side surface portions 5 that are formed radially and substantially vertically (in the axial direction of the container) from the bottom center portion side.
1b, 51b, an inner peripheral surface portion 51c formed substantially vertically at the outer end portion of the pole portion 53 formed at the center of the bottom, and these surfaces (the outer peripheral surface portion 51a, the pair of side surface portions 51b, 51).
b and a bottom surface portion 51d continuous with the inner peripheral surface portion 51c).

A bottom wall portion 52 is formed between each leg portion 51 and has a smooth curved surface protruding downward from the container. The bottom wall portion 52 is continuous with the bottom pole portion 53. I have. As can be seen from FIG.
Are formed radially outward from the bottom pole 53 (in the direction of the container body).

The bottom shape will be described in more detail with reference to FIG. 2 which is a sectional view taken along the line AA in FIG. 1 (b).
The outer peripheral surface portion 51a of the first portion is formed from the lower end of the enlarged-diameter reinforcing portion 4a formed at the lower end portion of the body portion 4 toward the lower part of the container slightly toward the inside of the container. Specifically, the angle theta ₁ which the outer peripheral surface 51a forms with the vertical plane P ₁ 0 to 20
It is good to form it small in the range of about °. In addition, the outer peripheral surface part 51a has a cross section approximated by a straight line or a suspension curve. Also, as described above, the bottom surface 51d of the leg 51
Are inclined so as to rise into the container. At this time, the angle theta ₂ between the bottom portion 51d and a horizontal plane P ₂ 5-30
It is good to set to about °. With such a shape,
A ground contact portion is formed at a corner portion at a lower end portion outside the leg portion 51. That is, the outer peripheral surface 51a of the leg 51
And P _{0 of the} corner formed by the bottom part 51 d is the ground contact part,
Actually, when the container is unfilled, the grounding portion is the outer peripheral surface portion 51.
A linear grounding portion (grounding line portion) is formed along the corner between a and the bottom portion 51d. As can be readily seen from previously indicated in FIG. 1 (b), the grounding conductor portion P ₀ is formed along the intermittently circumferentially. When the container is filled (especially when the internal pressure is increased by filling a carbonated beverage or the like), the bottom portion 51d of the leg portion
Although it is somewhat will be pushed downward, at that time, also to the ground portion slightly inward of the bottom surface 51d from the ground line portion P _0.

The inner peripheral surface 51c of the leg 51 is formed substantially perpendicular to the outer end of the bottom pole 53.

In the lower right part of FIG.
Although 1 'is drawn, this shows a cross-sectional shape when a cross-section taken along the line OC of FIG. 1 is taken.

The diameter φ ₃ of the circle including the ground line P ₀ in the circumference of each leg 51 is the maximum diameter of the trunk 4 (in this embodiment, the enlarged reinforcement provided at the lower end of the trunk 4). Diameter φ at part 4a
_It is better to be 70% or more of ₂ ). When the diameter phi ₃ of a circle including the ground line portion P ₀ in the circumferential designed to be less than 70% of the maximum diameter of the body portion 4, freestanding stability of the container obtained is not good.

In addition, the total length of the ground line portion P ₀ (in this embodiment, since five leg portions 51 are formed in the circumferential direction,
Length × 5 of the ground line portion P ₀ where one leg 51 has become the total length of the ground line portion P ₀₎ is, the circumferential length of a circle including the ground line portion P ₀ in the circumferential ([pi · It is preferably at least 30% of φ ₃ ). If the total length of the ground line portions P ₀ is shorter than this ratio, the self-sustaining stability will not be good. More preferably,
And more than 35% of the length of the circumference of a circle including the ground line portion P ₀ of the total length of the ground line portion P ₀ in the circumference.

On the other hand, a bottom wall portion 52 formed between the legs 51 is provided with an enlarged diameter reinforcing portion 4 provided at the lower end of the body portion 4.
a smoothly continues from the bottom pole portion 53 to the bottom pole portion 53, and has a smoothly curved surface portion that is convex downward. This bottom wall portion 52
It is a semi-spherical shape, but it is not always necessary to make the curved surface of the semi-spherical shape exactly. The bottom wall portion 52 and the bottom pole portion 53 are smoothly continuous as shown in FIG. 2, but they do not need to be surfaces having one curvature. Actually, the curvature at the bottom pole portion 53 is changed to the bottom wall portion 5.
It is preferable that the curvature is smaller than the curvature in (2) (the radius of curvature is large).

Also, the side surface of each leg 51
As shown in FIG. 3, which is a cross-sectional view taken along the line BB of FIG. 1B, the pair of side surfaces 51b, 51b of the leg 51 are formed substantially vertically (parallel to the container axis). A curvature radius r ₂ of a corner formed by the side surface portion 51 b and the bottom surface portion 51 d of the leg portion;
The radius of curvature r ₃ of the corner formed by 1b and the bottom wall portion 52 is
Both are formed small, and the leg 51 has a very sharp corner. The side surface portion 51b may be a flat surface or a curved surface whose longitudinal section is approximated by a suspension curve. FIG. 3 schematically shows a cross section taken along the line BB of FIG.

[0023] When the leg portion of the shape as described above, the bottom portion 51d of the leg portion 51 becomes extremely large, therefore it is possible to increase (increase) the ground line portion P _0.
Further, it is possible to position the ground line portion P ₀ radially outward of the container. As a result, good self-sustaining stability can be ensured.

The container having five legs has been described above with reference to the accompanying drawings. However, the number of legs is not limited to this and may be variously changed. However, if the number of legs is two, the self-standing stability is not significantly improved, so the number of legs is preferably three or more. Preferably 3 legs
To 6, which are formed at equal intervals in the circumferential direction of the bottom.

An example of a container having six legs will be described below with reference to the accompanying drawings. FIG. 4 is a bottom view of the container 10 having six legs 51 at the bottom. 6 legs 5
1 are arranged at regular intervals in the circumferential direction of the bottom, and each leg 5
A bottom wall portion 52 formed of a smooth curved surface convex downward is formed between the two. Each leg portion 51 is formed in the same shape as the leg portion of the container 1 described above, and has an outer peripheral surface portion 51a that smoothly continues from the container body portion and a radially and substantially perpendicular (from the bottom center portion side). A pair of side surfaces 51b, 51b formed in the axial direction of the container), an inner peripheral surface 51c formed substantially vertically at the outer end of the pole 53 formed at the center of the bottom, and these surfaces (outer periphery). A surface portion 51a, a pair of side surface portions 51b, 51b, and a bottom surface portion 51d continuous with the inner peripheral surface portion 51c).

As shown in FIG. 5, which is a cross-sectional view taken along the line AA of FIG. 4, the outer peripheral surface 51a slightly extends from the lower end of the enlarged reinforcing portion 4a formed at the lower end of the body of the container 10. It is formed toward the container downward toward the inside of the container (the outer peripheral surface 51a and the vertical plane P ₁ forms an angle theta _1. the angle theta
₁ has a size comparable to the angle in a container with five legs as described above). Further, the bottom surface portion 51d is inclined so as to rise inward of the container. Angle theta ₂ between the bottom portion 51d and a horizontal plane P ₂ also may be set to the same extent as the previous embodiment. The total length of the outer peripheral surface 51a and the ground line portion P _0, which is formed at the corner portions of the bottom surface portion 51d of the leg portion 51, a more than 30% of the circumferential length of a circle including the ground line portion P ₀ ing. The diameter phi ₃ of a circle including the ground line portion P ₀ is equal to or more than 70% of the reinforcing portion 4a diameter phi ₂ of the largest diameter of the body portion.

Next, a method of the present invention capable of manufacturing a container having the above-described bottom shape will be described. In the following description, a method of manufacturing a container having six legs will be described as an example. First, a description will be given of a biaxial stretch blow molding die used in this production method.

FIG. 6 is an exploded perspective view partially showing an example of a bottom mold of a biaxial stretch blow molding mold that can be used in the method of the present invention, and FIG. 7 shows the bottom mold of FIG. It is a fragmentary sectional view showing the state where it was installed in a model.

First, as shown in FIG. 6, the bottom mold used in the present invention comprises two partial molds. First bottom mold 30
Is a central surface 33 corresponding to the bottom pole of the resulting container,
It has an upper end surface having a curved surface portion 32 extending radially from the central surface portion 33. The curved surface portion 32 is a surface corresponding to the bottom wall portion 52 in the container 10 having the six legs described above, and the upper end surface of the first bottom mold 30 formed by the central surface portion 33 and the curved surface portion 32 is a container. A smooth concave curved surface complementary to the bottom pole portion 53 and the bottom wall portion 52 of 10 is formed.

The first bottom die 30 has six holes 31 formed vertically from the upper end surface. The holes 31 penetrate the first bottom mold 30 in the vertical direction, and are formed in the circumferential direction alternately with the above-described radially extending curved surfaces 32. The hole portion 31 has a surface 31a located at the most radially outer side, and a pair of side surfaces 31b, 31 formed radially from the center portion.
b and the surface 31c located at the radially innermost position. The hole 31 is formed at a position corresponding to a leg formed at the bottom of the container as a final product. When a container having six legs is manufactured as in the present embodiment, the hole 31 is formed.
Two holes 31 are formed at equal intervals in the circumferential direction. As will be described in detail later, the surfaces 31b, 31b and 31c are formed substantially vertically (along the axial direction of the first bottom mold).

Further, a flange 35 having a tapered surface is formed on the outer peripheral surface of the first bottom mold so as to be fitted to a concave ridge provided on the body mold of the biaxial stretch blow molding mold. I have. Thereby, the first bottom mold 30 is easily positioned and fixed to the body mold.

Further, a fixing bolt 36 and a spring 37 are provided at a lower portion at the center of the first bottom mold. Although the exact installation state of the fixing bolt 36 and the spring 37 will be described later, the fixing bolt 36 and the spring 37 allow the second state in a free state (with no external force applied to the second bottom mold 40 described below). Is kept away from the first bottom mold 30.

On the upper surface of the second bottom mold 40 attached to the lower part of the first bottom mold 30, the hole 31 of the first bottom mold described above is provided.
Are formed at positions corresponding to. The projecting portion 41 has an outer peripheral surface 41 a and a pair of side surfaces 4.
1b, 41b, an inner peripheral surface 41c, and an upper surface 41d, and have a size that can be inserted from below the first bottom die hole 31 with almost no gap. That is, when a force is applied to the second bottom mold from below, the outer peripheral surface 41a of the protrusion 41
And a pair of side surfaces 41 of the protruding portion 41.
b, 41b are a pair of side surfaces 31b, 31b of the hole 31;
And the inner peripheral surface 41c of the protruding portion 41 is the surface 31c of the hole 31.
The second bottom die moves upward so as to slide.

The upper surface 41d of each protruding portion 41 of the second bottom mold 40 has a lower outer peripheral surface 41a side and is inclined upward in the center direction. The slope has a tilt theta ₂ the same angle of the bottom surface portion 51d of the leg portion 51 shown in FIG. 5 above.

FIG. 7 shows a state in which the bottom dies 30, 40 shown in FIG. First bottom mold 3
0 is fixed to the torso mold 48 so as to be sandwiched from the lateral direction at the lower part of the torso mold 48 that is split into two in the horizontal direction. A concave portion 49 formed at the lower portion and having a shape complementary to that of the lower portion.
And is positioned by fitting.

FIG. 7 shows a vertical cross section of the first bottom mold 30. As can be seen from FIG. 7, the outermost inner surface 31a of the hole 31 becomes slightly smaller as it goes down. an upper surface portion 31a ₁ whose diameter is reduced, substantially vertical lower surface portion 3
It consists 1a ₂ Prefecture, the upper surface portion 31a _1, a corresponding surface shape on the outer wall surface 51a of the leg portion 51 in the finally obtained container. The lower surface portion 31a ₂ is a portion of the outer peripheral surface 41a and the sliding of the protrusion 41 of the second bottom mold 40.

The second bottom mold 40 is attached to a lower portion of the first bottom mold 30 via a fixing bolt 36 and a spring 37.
As shown in FIG. 7, when no external force is applied to the second bottom mold 40, the upper end of the protrusion 41 slightly enters the hole 31 of the first bottom mold 30 due to the presence of the spring 37. State. Also, in the container manufacturing process described below,
When the second bottom mold 40 is pressed and moved upward, the protrusion 41
Outside of the upper end A is a boundary portion between the most upper surface portion 31a ₁ of the outside of the inner surface 31a and the lower surface portion 31a ₂ of the hole 31 B
Rises until it matches.

Although not shown in FIG. 7, the cavity of the biaxial stretching blow mold formed by the body mold 48 and the mouth mold (including the shoulder mold in some cases) is a part other than the bottom part. Has a shape similar to the contour of the container shown in FIG.

Next, a method of manufacturing a container using the above-described apparatus will be described. First, a plastic parison having a bottomed cylindrical shape is placed in a biaxial stretch blow molding mold having the above-described bottom mold (and body mold). At this time, the second bottom mold 40 is kept away from the first bottom mold 30 as shown in FIG. 7, and the hole 31 of the first bottom mold is in a free state (substantially the hole 31). The projection 41 does not enter the
The parison is biaxially stretch-blow-molded in a state where the upper surface 41d is located at the lower end of the hole 31). This biaxial stretch blow molding may be performed according to a known method.

When the parison is blown in the cavity of the biaxial stretch blow mold, the bottom of the molded body immediately after blowing (hereinafter referred to as an intermediate molded body) is molded as shown in FIG. That is, the bottom mold 3 is placed at the tip of the intermediate molded body 44.
The portion facing the 0 hole 31 enters the hole 31 to form a convex portion 46 having a smooth curved surface. By this blow molding, the tip of the convex portion 46 of the intermediate molded body 44 reaches the upper surface 41d of the projection 41 of the second bottom die.

When the intermediate molded body 44 in the state shown in FIG. 8 is obtained, while the intermediate molded body 44 is still hot, the second bottom mold 4 is formed.
0 is pressed from below and moved upward, and the convex portion 46 formed by the hole 31 is compression molded. When the second bottom mold 40 is completely moved upward, as shown schematically in FIG. 9, the convex portion 46 of the intermediate molded body 44 is formed into a target leg shape.

When the state shown in FIG. 9 is obtained, each part of the molded body is heat-set in a biaxially stretched blow molding mold as required, and the mold is opened to obtain a target container.

When the container is manufactured by the above-described method, relatively large irregularities on the bottom of the container having the legs (the corners of the legs are clear, the surface of the legs 51 and the legs 5
(The surface of the bottom wall portion 52 formed between them is formed with a distinct step), and the formation portion of the leg portion 51 can be formed with a large stretch ratio. Therefore, the bottom can have good strength, and not only does it stand alone, but also does not deform or break even when a large internal pressure is applied.

As the resin forming the container, a polyester resin is preferable. As the polyester resin, a thermoplastic resin comprising a saturated dicarboxylic acid and a saturated dihydric alcohol can be used. As the saturated dicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, naphthalene-1,4- or 2,6-dicarboxylic acid, diphenyl ether-
4,4'-dicarboxylic acid, diphenyldicarboxylic acids, aromatic dicarboxylic acids such as diphenoxyethanediethanedicarboxylic acids, adipic acid, sebacic acid, azelaic acid, aliphatic dicarboxylic acids such as decane-1,10-dicarboxylic acid, An alicyclic dicarboxylic acid such as cyclohexanedicarboxylic acid can be used. Examples of the saturated dihydric alcohol include ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, diethylene glycol, polyethylene glycol,
Aliphatic glycols such as polypropylene glycol, polytetramethylene glycol, hexamethylene glycol, dodecamethylene glycol, neopentyl glycol, alicyclic glycols such as cyclohexane dimethanol, 2,2-bis (4'-β-hydroxyethoxyphenyl )
Propane, other aromatic diols and the like can be used. A preferred polyester is polyethylene terephthalate consisting of terephthalic acid and ethylene glycol.

The polyester resin has an intrinsic viscosity of 0.5 to 1.5.
, Preferably in the range 0.55 to 0.8. Also, such polyesters are produced by melt polymerization,
Those subjected to a reduced pressure treatment or a heat treatment in an inert gas atmosphere at a temperature of 250 ° C., or those subjected to solid phase polymerization to reduce the content of oligomers and acetaldehyde, which are low molecular weight polymers, are preferred.

In the polyester resin, additives such as stabilizers, pigments, antioxidants, heat deterioration inhibitors, ultraviolet light deterioration inhibitors, antistatic agents, antibacterial agents, etc., as long as the object of the present invention is not impaired. Can be added in an appropriate amount.

Although the present invention has been described with reference to the accompanying drawings, the present invention is not limited thereto, and various modifications can be made without departing from the spirit of the present invention. For example, the shape and number of the legs are appropriately set in consideration of the purpose of use and design of the container.

[0048]

As described in detail above, in the method of the present invention, a biaxial stretch blow molding die having a bottom die formed by combining a first bottom die and a second bottom die is used. The end of the intermediate molded body formed by the biaxial stretch blow molding is inserted into the hole of the bottom mold to form a projection at the lower end of the intermediate molded body. Pressing into the hole of one bottom mold, compression molding the convex part formed at the end of the intermediate molded body and molding it into a leg shape, so that the leg with relatively clear corners The portion can be reliably formed with a sufficient stretch ratio, and can have a bottom shape that does not deform even when an internal pressure is applied.

Therefore, in the container manufactured by the method of the present invention, the grounding portion formed on the leg provided at the bottom is disposed on the circumference having a diameter close to the maximum diameter of the container body. It will be formed as follows. Also, since the legs of the container manufactured by the method of the present invention have relatively sharp corners and the grounding portion formed at the bottom end of the legs is also large (the grounding wire is long), Independent stability and line feedability are improved. Further, even when the container is filled and an internal pressure is applied to the bottom, the grounding portion is not deformed so as to be distorted, and good autonomy is maintained.

The container produced by the method of the present invention is suitable for containers (bottles) for various foods and beverages such as carbonated beverages.

[Brief description of the drawings]

FIG. 1 shows a container according to one embodiment of the present invention;
(a) is a front view of the container, and (b) is a bottom view of the container.

FIG. 2 is a partial cross-sectional view taken along line AA in FIG. 1 (b).

FIG. 3 is a partial sectional view taken along line BB in FIG. 1 (b).

FIG. 4 is a bottom view showing a container according to another embodiment of the present invention.

FIG. 5 is a partial sectional view taken along line AA in FIG. 4;

FIG. 6 is a partially broken exploded perspective view showing a bottom mold in a biaxial stretch blow mold that can be used in the method of the present invention.

FIG. 7 is a partial cross-sectional view showing a state where the bottom mold shown in FIG. 6 is mounted on a trunk mold.

FIG. 8 is a partial cross-sectional view showing a state in which an intermediate molded body is formed in biaxial stretch blow molding using the biaxial stretch blow molding die shown in FIG.

9 is a partial cross-sectional view showing a state in which a second bottom mold is pushed upward from the state shown in FIG. 8 to form a leg portion.

FIG. 10 shows an example of a conventional self-supporting container, in which (a)
Is a front view of the container, and (b) is a bottom view of the container.

FIG. 11 is a front view showing another example of a conventional self-supporting container.

[Explanation of symbols]

 1, 10 Pressure-resistant self-standing container 4 Body 5 Bottom 30 First bottom mold 31 Hole 36 Fixing bolt 37 Spring 40 Second bottom mold 41 Projection 44 Intermediate molded body 48 Body mold 51, 62, 72 Leg 52 Bottom wall 53 Bottom pole 60, 70 Conventional container

Claims (5)

(57) [Claims] 1. A method of manufacturing a pressure-resistant self-standing container having a bottom portion in which a plurality of legs forming a ground contact portion are formed at equal intervals in a circumferential direction. And a first bottom mold fixed to the body mold, and having a hole at a position corresponding to the plurality of legs, and installed vertically below the first bottom mold and movable up and down,
A second bottom mold having a projection that can be inserted from below into the hole of the first bottom mold, and the second bottom mold is positioned on the lower side, and the first bottom mold is used. The parison is subjected to biaxial stretch blow molding in a state where the hole is free, and in the hole, the end of the stretch-blown intermediate molded body is expanded to form a convex portion. The second bottom die is pressed and moved upward to insert the protruding portion into the hole portion, and the convex portion bulging in the hole portion is compression-molded, and this portion is used as a leg portion. Manufacturing method of self-standing container. 2. The method according to claim 1, wherein the number of the legs is three or more. 3. The method for manufacturing a pressure-resistant self-standing container according to claim 1, wherein the leg portion is smoothly connected to an outer peripheral surface portion from a substantially cylindrical body portion, and a center portion of the bottom portion. A pair of side surfaces that are formed radially and are substantially vertical, an inner peripheral surface formed substantially perpendicular to the outer end of the pole formed at the center of the bottom, the outer peripheral surface, the side surfaces, and In addition to forming the inner peripheral surface portion and a bottom surface portion continuous with the inner peripheral surface portion, the leg portion is inclined so that the bottom surface portion slightly rises inward, so that the corner portion between the outer peripheral surface portion and the bottom surface portion Is a ground line portion when the container is not filled. 4. The method for manufacturing a pressure-resistant self-standing container according to claim 3, wherein a diameter of a circle including the ground wire portion in a circumference thereof is 70% or more of a maximum diameter of the body portion. Manufacturing method for self-standing containers. 5. The method for manufacturing a pressure-resistant self-standing container according to claim 3, wherein a total length of the grounding wire portion is 30% or more of a circumference of a circle including the grounding wire portion in a circumference. A method for producing a pressure-resistant self-supporting container.