JPH0532247A - Plastic blow-molded container - Google Patents

Abstract

PURPOSE:To provide the above plastic blow-molded container the bottom part of which is not deformed, and which can maintain a favorable standing property, even when the internal pressure of the container rises, or even under a high temperature exceeding a normal temperature. CONSTITUTION:A plastic blow-molded container 1 substantially has a cylindrical body 13, bottom part 14, and a flange 11 which constitutes an opening. The bottom part 14 consists of a central recessed part 18 and an annular heel part 17 which surrounds the central recessed part 18, and an outer wall surface 16 of the heel part 17 is a conical curved surface of which the diameter becomes smaller as it becomes lower. Also, an inner wall surface of the heel part 17 is a recessed curved surface, and at the same time, connects the lower end 19 of the heel part 17, which becomes a ground part, and the central recessed part 18 smoothly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic blow-molded container having a flange-shaped opening having substantially the same diameter 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 6.
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. 6, 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. However, according to the research conducted by the present inventors,
With such a simple 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, a high temperature of 60 to 70 ° C for a long time, the bottom recess may be inverted,
It was also found that the bottom portion may be deformed and the self-supporting property may be impaired without being inverted.

As a means for eliminating such deformation at the bottom portion, Japanese Patent Laid-Open No. 1-222120 discloses a plastic container as shown in FIG. here,
The bottom portion 80 of the container 8 is composed of an annular heel portion 81 and a central recess 85 formed inside the annular heel portion 81.
The outer wall surface 82 of No. 1 forms a curved surface that is convex outward and has a diameter larger than that of the body portion 88. The outer wall surface 82 of the heel portion 81 is reduced in diameter as it goes downward and is continuous with the ground contact portion 83. On the other hand, the inner wall surface 84 of the heel portion 81 is a conical curved surface (the inner wall surface 84 is drawn in a straight line at a partly broken portion in FIG. 7) and is continuous with the central recess 85.

However, according to the study by the present inventors, even when the bottom shape of the container shown in the above-mentioned Japanese Patent Laid-Open No. 1-222120 is applied, when the pressure in the container is increased, especially when the temperature is higher than room temperature, The bottom may be slightly deformed, and the deformation resistance is insufficient. In addition, the outer wall surface of the bottom portion (the outer wall surface 82 of the heel portion 81 described above) needs to be relatively large in diameter to the outside, so that the displayability of the container is poor.

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 even when the internal pressure of the container is increased or even at a high temperature exceeding normal temperature. Is to provide.

[0008]

As a result of intensive studies in view of the above problems, the inventors of the present invention have basically determined that the shape of the bottom of a container is a structure having a central concave portion and an annular heel portion surrounding the central concave portion. , The outer wall surface of the heel portion has a conical curved surface, and the portion between the ground contact portion and the central concave portion of the lower end portion of the heel portion has an inward concave curved surface so that the ground contact portion and the central concave portion are smoothly formed. The present invention has been found out that a continuous structure makes it possible to obtain a container having excellent self-sustainability without causing deformation of the container bottom even if the container internal pressure is increased.

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 bottom portion having an annular shape surrounding the central concave portion and the central concave portion. A heel portion, the outer wall surface of the heel portion is a conical curved surface that reduces in diameter downward, the inner wall surface of the heel portion is a concave curved surface, and the heel portion of the heel portion serving as a ground contact portion is formed. The lower end and the central recess are smoothly continuous.

[0010]

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, cracking or deformation does not occur when the flange portion is wound and tightened, so that it is necessary to improve the rigidity. 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 central concave portion 18 is basically concave inside the container, but at the center thereof, a so-called navel portion 21, which is a portion pushed by a stretch rod in stretch blow molding described later, is formed. A detailed description of the shape of the bottom portion 14 will be described below with reference to an enlarged sectional view of that portion.

FIG. 2 is a partial cross-sectional view of the lower portion of the container 1 shown in FIG. 1 taken along the axis, and is shown from the lower portion of the body portion 13 to the bottom portion 14. As shown in FIG. 2, the heel portion 17 includes the outer wall surface 16, the ground contact portion 19, and the inner wall surface 2.
0, and the central recess 18 is formed continuously inside the inner wall surface 20. The outer wall surface 16 of the heel portion is formed continuously with the enlarged diameter portion 15 provided at the lowermost portion of the body portion 13, and the outer wall surface 16 is a conical curved surface whose diameter is reduced downward. Therefore, in the cross-sectional view, the outer wall surface 16
Is drawn in a straight line. The ground contact portion 19 is a ridge having a small curvature and is formed in an annular shape at the lowermost end of the bottom portion 14. Furthermore, the inner wall surface 20 of the heel portion 17, which is a portion where the ground contact portion 19 and the central recess portion 18 are continuous, is a curved surface that is concave in the upper and outer directions with respect to the container. That is,
As shown in FIG. 2, in its cross section, the inner wall surface 20 of the heel portion 17 is directed almost upward in the vicinity of the ground contact portion 19, but gradually inclines toward the central concave portion 18 and becomes smooth. To the central recess 18.

With the bottom having such a shape, even if the internal pressure of the container is increased, or even at a high temperature of room temperature or higher,
There is no possibility that the central concave portion 18 is inverted and that the grounding portion 19 is distorted to impair the self-supporting property. When the internal pressure is large, the pressure tends to push down the central concave portion 18 at the bottom, but since the inner wall surface 20 of the heel portion 17 is formed into a concave curved surface inside the container, the central concave portion 18 does not invert outward. Further, although a force is applied to the outer wall surface 16 of the heel portion 17 from the inner side in the direction of the outer diameter, the curved surface of the inner wall surface 20 of the heel portion 17 also prevents the outer wall surface 16 from expanding outward.

It should be noted that the wall surface of the container forming the central recess 18 may be provided with a concavo-convex pattern as used in the conventional container of this type.

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

FIG. 3 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. 3, the parison body 4
2, the upper body portion 44 following the mouth portion 41 is the mouth portion 41.
The diameter is expanded so as to have the same diameter as, and the lower portion is a reduced diameter body portion 45. The thickness of the parison is 4 in the mouth.
1 and the expanded diameter body portion 44 are somewhat thinner (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.

The parison 4 is formed so that the thickness of the bottom portion 43 thereof is slightly smaller than the 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. 3 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. 4 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 the mouth portion 5 in order from the top.
1, the expanded diameter portion 52, the reduced diameter portion 53, the body portion 54, and the bottom portion 55.

In such a primary blow-molded product, the stretch ratio of each part is such that the mouth part (holding part) 51 is unstretched, the expanded diameter part 52 is medium stretched from 4 times to less than 6 times, and the reduced diameter part 53 is 3 times. It is a medium stretch of not less than 2 times and less than 6 times, a high stretch of 6 times or more for the cylindrical body portion 54, and a low stretch of 6 times or less for the bottom portion 55.

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. 3 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. Since this portion 45a is thicker than the expanded diameter body portion 44 of the parison and the diameter of the portion corresponding to the reduced diameter portion 52 of the blow molding die is small, 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. In addition, a heel portion 56 and a central concave portion 57 at the bottom of the container are formed in the bottom portion 55 by the shape of a mold.

As described above, if the parison having the shape as shown in FIG. 3 is used and the stretch blow molding is carried out by using the mold having the cavity having the shape of the primary blow molded body 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 body (intermediate molded body) as shown in FIG. 4 is obtained, the bottom wall portion (for example, position C in FIG. 5) of the expanded diameter portion of the primary blow-molded body 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. 6 above, a plastic can with excellent sealing performance can be obtained by applying a double seam with a metal lid in the form of incorporating the flange portion 11.

In the above description, the manufacturing method using the parison having the shape shown in FIG. 3 has been described. However, the plastic blow-molded container of the present invention is not limited to this, and it is substantially the same as shown in FIG. 5, 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 (b portion in FIG. 5) 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 capable of stretch blow molding, 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. 3 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. 4 (total height 240.2 mm, maximum body diameter 88 mm) was prepared.

The primary blow-molded product 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.

Next, the position C of the primary blow-molded body shown in FIG. 4 was punched out in a circular shape by a punching blade to separate it, and 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 by 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, at room temperature 0.
An internal pressure of 9 kg / cm ² was applied and filled with 4 tennis balls, which were then sealed and stored at 60 to 70 ° C. for 1 to 2 hours and found to be self-supporting. 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.

[0047]

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 beverages, tennis balls, etc. 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 partial cross-sectional view showing the bottom shape of the plastic blow-molded container of FIG.

FIG. 3 is a cross-sectional view showing an example of a parison capable of manufacturing the plastic blow-molded container of the present invention.

FIG. 4 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. 5 is a cross-sectional view showing another example of the parison capable of manufacturing the plastic blow-molded container of the present invention.

FIG. 6 is a cross-sectional view showing an example of a plastic can using a conventional plastic blow-molded container.

FIG. 7 is a partial cross-sectional side view showing an example of 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 (5)

[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. The outer wall surface of the heel portion is a conical curved surface that reduces in diameter downward, and the inner wall surface of the heel portion is a concave curved surface,
A plastic blow-molded container characterized in that a lower end portion of the heel portion, which serves as a ground contact portion, and the central concave portion are smoothly continuous. 2. The plastic blow-molded container according to claim 1, wherein a reduced diameter portion is formed below the flange portion. 3. The plastic blow-molded container according to claim 1 or 2, wherein an enlarged diameter portion is formed at a lower end portion of the body portion. 4. The plastic blow molded container according to claim 1, wherein the container is made of polyethylene terephthalate. 5. The plastic blow-molded container according to any one of claims 1 to 4, 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.