JPH0532248A - Plastic blow-molded container - Google Patents

Abstract

PURPOSE:To provide a plastic blow-molded container the bottom part of which is not deformed, and which can maintain a favorable self-standing property even when the internal pressure of the container rises or even under a high temperature exceeding a normal temperature. CONSTITUTION:The subject container substantially has a cylindrical body 13, bottom part 14, and flange 11 which constitutes an opening, and the bottom part 14 consists of a central recessed part 18 and an annular heel part 17 which surrounds the central recessed part 18. On a container wall surface at the central recessed part 18, a plurality of polygonal pyramid shaped recessed parts, of which the vertexes face inward, are formed in such a manner that they are continuously arranged annularly such as surrounding the central part of the central recessed part while sharing a part of the ridges, and an outer wall surface 16 of the heel part is a conical curved surface of which the diameter becomes smaller as it becomes lower.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic blow molding container having a flange-shaped opening having a diameter substantially the same as that of a body, and in particular, it is pressure-resistant by winding a lid made of aluminum or the like around a flange provided in the opening. The present invention relates to a plastic blow-molded container that can be suitably used as a container, its bottom shape does not change even when the pressure inside the container is increased, and that maintains good self-sustainability.

[0002]

2. Description of the Related Art In recent years,
Plastic cans (containers) are receiving attention as alternatives to metal cans. Plastic cans are generally shown in Figure 7.
As shown in FIG. 7, a plastic blow-molded container 7 having a cylindrical body portion 71, a bottom portion 72, a flange portion 73 that constitutes an opening, and a lower region 74 of the flange, and a metal lid 76.
The lid 76 is wound around the flange 73 by the double seam 75, and the can is sealed.

By the way, when used as a container for carbonated drinks or tennis balls, a high internal pressure is applied to the container, so it is necessary to impart strength to the container. In particular, since the bottom of the container cannot be expected to have the stretching effect due to the biaxial stretch blow molding, it is necessary to have a shape capable of ensuring self-supporting property without being deformed by high internal pressure.

As shown in FIG. 7, the bottom portion of such a plastic blow-molded container is so-called that the center portion of the bottom portion is recessed upward and the periphery of the center recess is an annular heel portion. It is often the bottom of a champagne container shape. However, according to the research conducted by the present inventors, if the shape of the container is simply such a shape, when the internal pressure of the container is large, when the container is exposed to a high temperature of room temperature or higher, for example, 60 to 70 ° C. for a long time, It has been found that the recess may be inverted, or the bottom may be deformed and the self-supporting property may be impaired without being inverted.

Therefore, an object of the present invention is to provide a plastic blow-molded container capable of maintaining good self-sustainability without deforming the bottom portion even when the internal pressure of the container is increased or even at a high temperature exceeding normal temperature. Is to provide.

[0006]

As a result of earnest research in view of the above problems, the inventors of the present invention basically have a structure in which the shape of the bottom of a container is composed of a central concave portion and an annular heel portion surrounding the central concave portion. If the outer wall surface of the heel portion is formed into a conical curved surface and a plurality of recesses having a specific structure are formed on the container wall forming the central recess, the bottom of the container is deformed even if the internal pressure of the container is increased. The present invention has been accomplished by finding that a container having excellent self-sustaining property can be obtained without the need.

That is, the plastic blow-molded container of the present invention having a substantially cylindrical body portion, a bottom portion, and a flange portion forming an opening has a ring-shaped bottom portion surrounding the central concave portion and the central concave portion. A plurality of polygonal pyramidal recesses, each having a heel portion and having a vertex directed inward, are formed on a wall surface of the container in the central recess so as to surround a central portion of the central recess by sharing a part of its ridge. And the outer wall surface of the heel portion is a conical curved surface whose diameter is reduced downward.

[0008]

The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a side view showing a blow molded container according to an embodiment of the present invention. The blow-molded container 1 includes a flange portion 11 formed at an open end, a reduced diameter portion 12 formed in a lower region of the flange portion 11, a substantially cylindrical body portion 13, and a bottom portion 14. .

The flange portion 11 formed at the open end is
As will be described later, it becomes a portion to which the lid member is attached, and extends substantially perpendicular to the axial direction of the container. When increasing the internal pressure of the container, it is preferable that the lid member is attached by double tightening, so that the flange portion 11 is formed to have a thickness, strength, and rigidity suitable for double tightening. . Specifically, the draw ratio in the flange portion 11 is preferably 4 to 6 times. If the draw ratio is less than 4 times, the strength of the flange portion 11 is reduced, and good double winding cannot be performed. On the other hand, if the flange portion 11 has a draw ratio of more than 6 times, the thickness is too thin and the rigidity is too high, so that it is also difficult to perform good winding tightening.

In the lower region of the flange portion 11, it is necessary to improve the rigidity in order to prevent cracks or deformation when the flange portion is wound and tightened. For this reason, in this embodiment, the reduced diameter portion 12 is formed in the lower portion of the flange portion 11 to improve the rigid property in the vicinity of the opening portion. The draw ratio in the reduced diameter portion 12 is preferably 3 times or more and less than 6 times. If the draw ratio is less than 3 times, the wall thickness becomes too large, and the elasticity is lowered, and cracks are likely to occur. If the draw ratio is 6 times or more, the wall thickness becomes too thin and the flange portion is tightened. Sufficient rigidness to prevent deformation and the like cannot be obtained. It is preferable that the reduced diameter portion 12 be formed thicker than the body portion 13. As a result, the rigidity of this portion is further improved, and it is possible to prevent the opening portion from being broken or deformed when it is sealed as a can. In addition, in the open state before winding and tightening, the opening, particularly the flange, is less likely to be deformed from the outside, which facilitates transportation or handling during line transportation.

The body portion 13 has a substantially cylindrical shape,
An enlarged diameter portion 15 is provided just above the bottom portion 14. Body 1
The draw ratio of 3 is preferably 6 times or more. Draw ratio is 6
If it is less than twice, the container does not have sufficient pressure resistance. Further, the mechanical strength due to the stretching effect cannot be improved so much, which is not preferable. Further, it cannot be made lighter. In addition,
The enlarged diameter portion 15 provided immediately above the bottom portion 14 is formed for reinforcement, and the diameter of the enlarged diameter portion 15 is substantially the same as the outer diameter of the flange portion 11 provided in the opening portion. Is good. In this way, it is possible to arrange and display a plurality of containers without the expanded diameter portion 15 interfering.

The bottom 14 comprises a central recess 18 and an annular heel 17 surrounding the central recess 18. The outer wall surface 16 of the heel portion 17 has a conical curved surface whose diameter decreases downward, and the lower end portion of the heel portion 17 has an annular grounding portion 19.
Becomes On the other hand, the central recess 18 will be described in detail later,
It is formed inside the annular grounding portion 19 and is basically concave inward. As described above, when the outer wall surface 16 of the heel portion 17 does not have a shape that expands outward in the radial direction but has a conical curved surface that slims down in diameter, it is possible to efficiently arrange a plurality of containers when they are displayed.

FIG. 2 is a plan view of the bottom portion 14 of the container shown in FIG. 1 viewed from below along the axial direction, and FIG. 3 is a sectional view taken along line A--O--B in FIG.

As described above, the lower end portion of the heel portion 17 serves as an annular grounding portion 19, and the inner wall surface 20 of the heel portion 17 is formed.
Has a concave shape and smoothly continues to the central concave portion 18. By thus forming the inner wall surface 20 of the heel portion 17 in a concave shape, the central concave portion will not be inverted even if the container internal pressure is increased.

A plurality of polygonal pyramidal recesses are continuously formed on the container wall of the central recess 18. In this embodiment, as shown in FIG. 2, two types of quadrangular pyramid-shaped recesses are continuously formed. That is, the first concave portion is a concave portion abcd-e (and a congruent concave portion), which is a side surface of a quadrangular pyramid having a square abcd as a bottom surface and an apex of e (the apex e is located inside the container). It is a concave part made of. In this first recess, the surface abe, the surface ade,
The surface bce and the surface dce are substantially flat surfaces (that is, triangles), and the ridge line bc and the ridge line dc are portions protruding below the container. In addition, the portion of the ridge line bad is located outside the central concave portion 18 so as to draw a substantially circular shape.

The second recess is a recess fghi-j (and a recess congruent therewith), which is a quadrangular pyramid having a quadrangle fghi as the bottom and a vertex of j (the vertex j is located inside the container). ) Is a recess formed by the side surface. In this second recess, the surface fgj, the surface fij, the surface ghj, and the surface ih
j is substantially a plane (that is, a triangle), and the ridge line fg and the ridge line fi are portions that overlap the ridge line bc and the ridge line dc of the first recessed portion.

As can be seen from FIG. 2, in the container of this embodiment, the above-mentioned first recesses and second recesses are arranged alternately and continuously, and surround the central portion 21 of the bottom. As can be seen from FIG. 2 and FIG. 3, in this bottom shape, the first concave portion has the innermost convex portion (the portion corresponding to the line aec) and the second convex portion has the innermost convex portion. The portions (the portions corresponding to the line fjh) are alternately arranged in the circumferential direction of the container, and the lines extend radially, so that the container bottom is reinforced isotropically. Further, as described above, since all the concave portions provided on the wall surface of the central concave portion 18 are quadrangular pyramid-shaped concave portions with their vertices facing inward, they do not invert outward even if the internal pressure is large. .

Therefore, when the bottom structure as described above is used, even if the internal pressure of the container is increased and the temperature is higher than room temperature, the central recessed portion 18 is inverted and the grounding portion 19 is distorted and self-supporting. Is not damaged.

As can be seen from FIG. 3, the innermost portion of the second convex portion (the portion corresponding to the apex j of the quadrangular pyramid) is located along the axial direction of the container rather than the central portion 21 of the central concave portion 18. It is located above. Therefore, when this container is used as a container for tennis balls, for example, as shown in FIG.
As shown in FIG. 5, the tennis ball 22 has a plurality of ridges (the line hj and the same part as the ridge) of the second quadrangular pyramid-shaped recess.
Will be accepted well.

In this embodiment, eight first pyramidal recesses and eight second pyramidal recesses are alternately arranged, but the present invention is not limited to this. The size and number of the quadrangular pyramidal recesses may be changed as appropriate. Further, the concave portion provided on the container wall of the central concave portion at the bottom does not have to be a quadrangular pyramid shape as described above, and may be a concave portion having side surfaces such as a pentagonal pyramid and a hexagonal pyramid. Furthermore, a configuration in which quadrangular pyramids, pentagonal pyramids, hexagonal pyramids and the like are appropriately combined may be used.

Next, a method of manufacturing the above-mentioned plastic blow-molded container 1 will be described.

FIG. 4 is a sectional view showing an example of a parison that can be used to manufacture the plastic blow-molded container of the present invention. The parison 4 has a mouth portion 41 having a support ring portion (a in the figure), a body portion 42, and a bottom portion 43.

As can be seen from FIG. 4, the parison body 42
In, the body upper portion 44 following the mouth portion 41 is expanded so as to have the same diameter as the mouth portion 41, and the lower portion is a reduced diameter body portion 45. Further, the wall thickness of the parison is slightly thinner in the mouth portion 41 and the expanded diameter body portion 44 (compared to the reduced diameter body portion 45). The expanded-diameter body portion 44 is a portion to be an expanded-diameter portion formed below the mouth portion in a primary blow-molded body (intermediate molded body) described later.

Further, the parison 4 is formed so that the wall thickness of the bottom portion 43 thereof is slightly thinner than the wall thickness of the body portion 42. By doing so, the bottom portion 43 can be cooled to a temperature lower than that of the body portion 42. Therefore, the body portion can be stretched without breaking through the bottom portion 43 by the longitudinal stretching by the rod during stretching.

In manufacturing the container, first, the parison 4 having the shape shown in FIG. 4 is formed by injection molding. The injection molding can be performed by an ordinary method using an injection molding die having a cavity having a shape corresponding to the parison 4. At this time, after the resin is injected into the cavity, the resin forming the parison is preferably cooled to a temperature not lower than its glass transition temperature and not higher than its solidification temperature by rapidly cooling the injection mold. The injection mold can be rapidly cooled by means such as pouring a refrigerant into a passage provided in the mold.

When the temperature of each part of the parison 4 becomes equal to or higher than the glass transition temperature of the resin used and equal to or lower than the solidification temperature, the parison 4 is taken out of the injection mold and before the temperature of each part of the parison 4 becomes lower than the glass transition temperature. Then, biaxially stretch blow molding is performed.

FIG. 5 is a side view showing an example of a primary blow molded product obtained by biaxially stretch blow molding the parison of FIG.

The primary blow-molded body 5 has a mouth portion 51 in order from the top.
And a diameter expansion portion 52, a diameter reduction portion 53, a body portion 54, and a bottom portion 55.

In such a primary blow-molded product, the draw ratio of each part is such that the mouth part (holding part) 51 is not drawn and the expanded diameter part 52 is
Is a medium stretch of 4 times or more and less than 6 times, the reduced diameter portion 53 is a medium stretch of 3 times or more and less than 6 times, the cylindrical body 54 is a high stretching of 6 times or more, and the bottom 55 is a low stretching of 6 times or less. is there.

In order to obtain such a draw ratio, the process shown in FIG.
Using a parison of the shape shown in Fig. 1, set it in the stretch blow mold having a cavity in the shape of the primary blow molded body, with the mouth of this parison held in the mouth mold, and stretch it by the usual method. Blow molding may be performed.

By this stretch blow molding, the expanded diameter body portion 44 of the parison shown in FIG. 4 is expanded to form the expanded diameter portion 52 of the primary blow molded body.

Further, the reduced diameter portion 53 of the primary blow-molded body is shown in FIG.
The upper portion 45a of the reduced diameter body portion 45 of the parison is stretched. This portion 45a is thicker than the expanded body 44 of the parison, and the diameter of the portion corresponding to the reduced diameter portion 52 of the blow molding die is smaller, so that the diameter of the primary blow molded body is reduced. The portion 53 becomes thick.

The body portion 54 is largely stretched to have a thin wall and has a large strength due to the stretching effect. In addition,
Since the bottom of the parison is regulated at a lower temperature than the barrel, the barrel is more stretched, which stretches the barrel fully while the bottom is not stretched to a high degree. The bottom 55 has a heel 56 and a central recess 57 at the bottom of the container formed by the shape of a mold. Also, the central recess 57
A plurality of quadrangular pyramid-shaped recesses having the shape shown in FIG. 2 are continuously formed in an annular shape on the wall surface of the container. The formation of the quadrangular pyramid-shaped recess can be achieved by forming the surface of the bottom die of the blow molding die into an uneven shape complementary to the shape shown in FIG.

In the bottom die of the blow molding die,
If an air vent is provided at a portion corresponding to the ridgeline b-a-d ... Of the bottom shape shown in FIG. 2, the uneven shape provided in the central concave portion of the bottom can be clearly obtained.

As described above, stretch blow molding is performed by using the parison having the shape shown in FIG. 4 and the mold having the cavity having the shape of the primary blow molding as shown in FIG. It is possible to manufacture a primary blow-molded body in which the diameter-reduced portion is thicker than the body portion (portion to be the main body portion of the container), the body portion is sufficiently stretched, and the bottom portion is thick.

When the primary blow molded product (intermediate molded product) as shown in FIG. 5 is obtained, the bottom wall portion (for example, position C in FIG. 5) of the expanded diameter portion of this primary blow molded product is cut. A blow molded container of the present invention as shown in FIG. 1 is obtained.

Blow-molded container 1 thus obtained
In the same manner as shown in FIG. 7 above, a plastic can with excellent sealing performance can be obtained by applying a double seam with a metal lid while incorporating the flange 11.

In the above description, the manufacturing method using the parison having the shape shown in FIG. 4 has been described, but the plastic blow-molded container of the present invention is not limited to this, and it is substantially the same as shown in FIG. 6, for example. It is also possible to manufacture using a bottomed cylindrical parison 6 having a body portion 62 of a single diameter. At this time, from the mouth portion 61 of the parison 6 to the body portion 62
By making the portion applied to the upper end portion (portion b in FIG. 6) thin inside, it is possible to easily form an intermediate molded body having an enlarged diameter portion in the upper portion as shown in FIG.

In the present invention, the plastic used as the raw material of the container is not particularly limited as long as it is a thermoplastic resin which can be stretch blow molded, but a polyester type is preferable.

As the polyester resin, a thermoplastic resin composed of saturated dicarboxylic acid and saturated dihydric alcohol can be used. A particularly preferred polyester is polyethylene terephthalate composed of terephthalic acid and ethylene glycol.

Further, it is also possible to use a mixture of the above polyester resin with a heat resistant resin, a barrier resin or the like, or a multilayer resin.

The polyester resin used in the present invention may also contain additives such as stabilizers, pigments, antioxidants, heat deterioration inhibitors, UV deterioration inhibitors, antistatic agents, antibacterial agents and other resins. An appropriate amount can be added.

The present invention will be described in more detail with reference to the following specific examples. Example 1 A polyethylene terephthalate resin (Mitsui Petrochemical Industry Co., Ltd., Mitsui PET J125) was used to prepare a parison shown in FIG. 4 by injection molding. The shape and weight of the parison were as follows.

Height: 127mm Mouth: outer diameter 36.5mm, inner diameter 32.5mm Support ring part: outer diameter 39mm Expanded body: outer diameter 36.3 mm, inner diameter 31.9 mm Reduced body: outer diameter 25.8-26.8mm Inner diameter 18.2 to 19.6 mm Bottom: Wall thickness 2.0 mm Weight: 46.9g

After molding the parison having the above-mentioned shape, a primary blow-molded body having a shape as shown in FIG. 5 (total height 240.2 mm, maximum barrel diameter 88 mm) was prepared. As the bottom die of the stretch blow molding die used at this time, a bottom die having irregularities complementary to the irregularities shown in FIG. 2 was used.

The primary blow-molded body thus obtained was cut in the longitudinal direction and the stretching ratio of each part was measured. As a result, the mouth part was unstretched, the expanded diameter part was about 5.5 times, and the reduced diameter part was About 5
Double, the body was about 14.5 times, and the bottom was 1 to 6 times. Also,
The thickness of the body is 0.25 mm, and the thickness of the lower area of the flange is
It was 0.5 mm. Further, the wall surface of the molded body in the central concave portion at the bottom had the shape shown in FIGS. 2 and 3.

Next, the position of C in FIG. 5 of this primary blow-molded product was punched out into a circle with a punching blade and separated to obtain the structure shown in FIG.
A blow molded container as shown in was obtained.

A tennis ball was placed in the container thus obtained, and then, under pressure, the flange portion was rolled up and the container was sealed with a double seam with a metal lid.

The can thus obtained has an internal pressure of 1.2.
Even if the pressure was increased to Kg / cm ² (gauge pressure), the bottom did not deform and had good self-sustaining property. Also, 0.9 kg /
Even after being stored at 60 to 70 ° C. for 1 to 2 hours, what was filled and sealed with 4 tennis balls by applying an internal pressure at room temperature of cm ² at room temperature had self-supporting property. In addition, it had sufficient sealing property, and did not cause cracks or deformation even when subjected to double seam, and had impact resistance and internal pressure resistance that could be practically used.

[0051]

As described above in detail, the blow-molded container of the present invention has a bottom shape capable of withstanding a large internal pressure, so that the self-standing property is impaired even as a plastic can having a large internal pressure. Absent. Further, even if a double seam is applied to the flange portion in the opening, no crack or damage occurs, and a good plastic can can be obtained.

Such a container of the present invention can be suitably used as a pressure resistant container for carbonated drinks, tennis balls and the like by providing a metallic lid member.

[Brief description of drawings]

FIG. 1 is a side view showing a plastic blow-molded container according to an embodiment of the present invention.

FIG. 2 is a plan view showing a bottom shape of the plastic blow-molded container of FIG.

3 is a cross-sectional view taken along the line A-O-B in FIG.

FIG. 4 is a cross-sectional view showing an example of a parison capable of manufacturing the plastic blow-molded container of the present invention.

FIG. 5 is a side view showing an example of an intermediate molded body (primary blow molded body) obtained in the step of manufacturing the plastic blow molded container of the present invention.

FIG. 6 is a cross-sectional view showing another example of the parison capable of manufacturing the plastic blow-molded container of the present invention.

FIG. 7 is a cross-sectional view showing an example of a plastic can using a conventional plastic blow-molded container.

[Explanation of symbols]

1 plastic blow molding container 4, 6 parison 5 Primary blow molding 7 plastic cans 11 Flange 12 Reduced part 13 torso 14 bottom 15 Expanded part 16 Outer wall surface of heel 17 Heel part 18 central recess 19 Ground section 20 Inside wall of heel 21 Bottom center 75 double seams 76 metal lid

Continued front page    (72) Inventor Hiroaki Nose             1-1-1, Ichigaya-Kagacho, Shinjuku-ku, Tokyo             Dai Nippon Printing Co., Ltd.

Claims (6)

[Claims] 1. A plastic blow-molded container having a substantially cylindrical body, a bottom, and a flange forming an opening, wherein the bottom comprises a central recess and an annular heel portion surrounding the central recess. And a plurality of polygonal pyramid-shaped recesses with their vertices directed inward are continuously formed on the container wall surface in the central recessed portion so as to surround a central portion of the central recessed portion by sharing a part of the ridge sides thereof. A plastic blow-molded container characterized in that the outer wall surface of the heel portion has a conical curved surface whose diameter decreases downward. 2. The plastic blow-molded container according to claim 1, wherein the polygonal pyramidal recess comprises two types of quadrangular pyramidal recesses, and the two types of quadrangular pyramidal recesses are alternately arranged in an annular shape. A plastic blow-molded container characterized in that 3. The plastic blow-molded container according to claim 1 or 2, wherein an inner wall surface of the heel portion which is continuous from the lower end portion of the heel portion serving as a ground contact portion to the central recess is a concave curved surface. A plastic blow-molded container characterized by the above. 4. The plastic blow-molded container according to claim 1, wherein a reduced diameter portion is formed in a lower portion of the flange portion. 5. The plastic blow molded container according to claim 1, wherein the container is made of polyethylene terephthalate. 6. The plastic blow-molded container according to any one of claims 1 to 5, wherein the container is formed by cutting a mouth of a primary blow-molded body obtained by biaxially stretch-blow molding a parison. A plastic blow-molded container characterized by being present.