JPH04242538A - Plastic blow molded container and manufacture of the same - Google Patents

Abstract

PURPOSE:To provide a plastic blow molded container which can be used as a pressure-proof container and method of manufacture of the container by a method wherein a lid made of aluminium or the like is wound and fastened around a flange-shaped opening. CONSTITUTION:A cylindrical parison is blow molded to make a primary blow molded container which is constituted of a mouth part 21, a large diameter part 22, a small diameter part 23, a container body part 24 and a bottom part 25. In the primary blow molded container, the large diameter part has a draw ratio of more than 4 times and less than 6 times, the small diameter part more than 3 times and less than 6 times, the body part more than 6 times, and the bottom part less than 6 times. Then a bottom wall part C of the large diameter part is cut in a ring to obtain a desired container.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to a plastic blow-molded container having a flange-shaped opening having approximately the same diameter as the body, and a method for manufacturing the same. The present invention relates to a plastic blow-molded container that can be suitably used as a pressure-resistant container, and a method for manufacturing the same.

0002

[Prior art and problems to be solved by the invention] In recent years,
Plastic cans (containers) are attracting attention as an alternative to metal cans.

As shown in FIG. 4, a plastic can is a plastic blower having a cylindrical container body 41, a bottom 42, a flange 43 forming an opening, and a lower region 44 of the flange. It consists of a molded container 4 and a metal lid 46, and the lid 46 is wrapped around the flange portion 43 by a double seam 45 to seal the can.

By the way, when used as a container for carbonated drinks, tennis balls, etc., high internal pressure is applied, so not only must the internal pressure of the entire container be high, but also the opening must have good sealing and mechanical strength. be. In particular, since the lid is tightened with a double seam at the flange part, it is necessary to prevent cracks from occurring at that time.

[0005] In order to prevent such cracks, a method has been proposed in which a primary container is first manufactured by blow molding, and then the primary container is cut at a predetermined position to form a container into a desired shape ( JP-A No. 58-501991).

[0006] However, since the container manufactured by the above method is stretched more than six times as a whole, the wall thickness is not sufficient in the lower region of the flange, and there is a problem that the opening easily deforms when double seaming is performed. be. Furthermore, there is a problem in that other parts such as the body and the bottom do not necessarily have impact resistance or pressure resistance suitable for each part as a plastic can.

[0007] Therefore, an object of the present invention is to provide a plastic can in which the flange portion constituting the opening has sufficient strength to withstand the tightening of a double seam;
The object of the present invention is to provide a plastic blow-molded container in which the lower region of the flange part has excellent deformation resistance (rigidity), and each part has sufficient impact resistance and pressure resistance.

Another object of the present invention is to provide a method for manufacturing the above-mentioned container.

[0009]

[Means for Solving the Problems] In view of the above problems, as a result of intensive research, the present inventors used a bottomed cylindrical parison with an enlarged diameter at the mouth and upper part of the body, and stretch-blow-molded the parison. When making a container, the stretching ratio of each part of the plastic blow-molded container, which consists of a cylindrical container body, a bottom, and a flange that forms the opening, is determined, especially the stretching ratio of the flange and its lower region. We have discovered that by adjusting the thickness within a specific range and making the wall thickness of each part appropriate, it is possible to create a container that is not deformed by tightening the lid and has excellent strength and pressure resistance, and has developed the present invention. I came up with the idea.

That is, the plastic blow-molded container of the present invention is composed of a cylindrical container main body, a bottom, a flange forming an opening, and a reduced diameter portion, such that the stretching ratio of each part of the container is the same as that of the flange. 4 times or more and less than 6 times, 3 times or more and less than 6 times at the reduced diameter part of the lower region of the flange, 6 times or more at the container body, 6 times or less at the bottom, and the lower part of the flange. The container is characterized in that the region is thicker than the container body.

[0011] Furthermore, the method for manufacturing a plastic blow molded container of the present invention includes blow molding a cylindrical parison having a mouth, a body, and a bottom, so that the mouth, the enlarged diameter part, and the reduced diameter part are formed in order from the top. A flange-shaped opening is formed by manufacturing a primary blow-molded container consisting of a container body, a container main body, and a bottom, and cutting the bottom wall of the expanded diameter portion of the primary blow-molded container into an annular shape. Using a parison whose diameter increases at the mouth and the upper part of the body corresponding to the expanded diameter part of the primary blow-molded container, the stretching ratio of each part of the primary blow-molded container is set such that the opening is unstretched and the expanded diameter part is unstretched. 4 times or more and less than 6 times at the reduced diameter part, 3 times or more and less than 6 times at the reduced diameter part, 6 times or more at the container body, and 6 times or less at the bottom, and the lower area of the flange part is made thicker than the container body part. It is characterized by being thick.

0012

[Operation] In the present invention, the stretching ratio of each part of the plastic blow-molded container is set to 4 times to less than 6 times in the flange part, 3 times to less than 6 times in the lower region of the flange part, and 6 times in the cylindrical container body part. It is more than 6 times, and 6 times or less at the bottom. Further, the lower region of the flange portion is made thicker than the container main body portion.

[0013] In the plastic blow-molded container of the present invention, even when a metal lid is attached by tightening, the flange does not develop cracks, and furthermore, the flange does not crack when a double seam is applied. The lower region is not deformed.

In other words, by stretching the flange part to an appropriate magnification and giving it a certain degree of thickness, the strength is such that no cracks will occur even when the flange is tightened, and the stretching ratio of the lower region of the flange can be adjusted to a certain degree. By keeping the stretching ratio lower than that of the main body and thickening the lower region of the flange, which tends to deform, rigidity is improved and deformation, etc. when double seaming is performed, is prevented. Moreover, the main body of the container, which requires impact resistance and pressure resistance, is sufficiently elongated. Therefore, each part has the required strength as a plastic can.

[0015] In the method of the present invention, a parison whose diameter is expanded from the mouth part to the upper part of the body is used.
The enlarged diameter portion and the reduced diameter portion of the upper portion of the primary blow molded container can be formed without difficulty, and can be formed to have a desired wall thickness with good reproducibility.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings.

The plastic used as a raw material in the present invention is not particularly limited as long as it is a thermoplastic resin that can be blow molded, but polyester-based plastics are preferred.

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

It is also possible to use a mixture of the above-mentioned polyester resin with a heat-resistant resin, a barrier resin, etc., or a multilayered one.

[0020] In addition, the polyester resin used in the present invention may contain additives such as stabilizers, pigments, antioxidants, heat deterioration inhibitors, ultraviolet deterioration inhibitors, antistatic agents, antibacterial agents, and other resins. You can add an appropriate amount.

Next, a method for manufacturing a blow-molded container of the present invention using such resin as a raw material will be explained. FIG. 1 is a sectional view showing an example of a parison with which the plastic blow-molded container of the present invention can be manufactured. The parison 1 has a mouth part 11 having a support ring part (a in the figure), and a body part 12.
and a bottom portion 13.

As can be seen from FIG. 1, in the body 12 of the parison used in the present invention, the upper body part 14 following the mouth 11 is enlarged to have the same diameter as the mouth 11, and the lower part 14 is enlarged to have the same diameter as the mouth 11. is a diameter-reduced body portion 15. Further, the wall thickness of the parison is somewhat thinner at the mouth portion 11 and the enlarged diameter body portion 14 (compared to the reduced diameter body portion 15). This enlarged diameter body portion 14 is a portion that becomes an enlarged diameter portion formed below the mouth of a primary blow-molded container to be described later.

Further, the parison 1 is formed so that the wall thickness of the bottom portion 13 is slightly thinner than the wall thickness of the body portion 12. By doing so, the bottom portion 13 can be cooled to a temperature lower than that of the body portion 12. Therefore, the body can be stretched without breaking through the bottom part 13 by longitudinal stretching using the rod during stretching.

The parison 1 having the shape described above is biaxially stretched and blow molded to produce a primary blow molded container having the shape as shown in FIG.

First, a parison 1 having the shape shown in FIG. 1 is formed by injection molding. Injection molding can be carried out by a conventional method using an injection mold having a cavity having a shape corresponding to the parison 1. In the present invention, after the resin is injected into the cavity, the injection mold is rapidly cooled to cool the resin constituting the parison to a temperature above its glass transition temperature and below its solidification temperature. Note that 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 1 becomes higher than the glass transition temperature and lower than the solidification temperature of the resin used, the parison 1 is removed from the injection mold, and before the temperature of each part of the parison 1 becomes lower than the glass transition temperature. Then, biaxial stretch blow molding is performed.

FIG. 2 is a sectional view showing an example of a primary blow molded container obtained by biaxially stretching blow molding the parison shown in FIG.

The primary blow-molded container 2 includes, in order from the top, a mouth portion 21, an enlarged diameter portion 22, a reduced diameter portion 23, and a container body portion 24.
and a bottom portion 25.

[0029] In such a primary blow-molded container,
The stretching ratio of each part is as follows: the mouth part (grip part) 21 is unstretched;
The enlarged diameter part 22 is medium stretched by 4 times or more and less than 6 times, the reduced diameter part 23 is medium stretched by 3 times or more and less than 6 times, the cylindrical container body part 24 is highly stretched by 6 times or more, and the bottom part 25 is stretched by 6 times. Low stretching is as follows.

The reason for limiting the stretching ratio of each part is as follows. If the stretching ratio of the enlarged diameter part 22 is less than 4 times, it is difficult to sufficiently stretch the flange part of the blow-molded container (included in the lower surface of the enlarged diameter part 22), and the strength of the flange part is reduced. descend. Furthermore, if the stretching is 6 times or more, the enlarged diameter portion (flange portion) becomes thin and rigid, which is not preferable for seaming accompanied by deformation. Medium stretching with a stretching ratio of 4 to 6 times is good for stable seaming. Such a stretching ratio is suitable for double seaming, as it has good conformability and strength.

The reduced diameter portion 23 is the lower region of the flange of the blow-molded container, and it is necessary to improve its rigidity in order to prevent cracking, deformation, etc. when the flange portion is tightened. . Therefore, the stretching ratio is set to 3 times or more and less than 6 times. If the stretching ratio is less than 3 times, the wall thickness will become too large, and the elasticity will decrease, causing cracks to easily occur.If the stretching ratio is 6 times or more, the wall thickness will become too thin, causing problems when the flange is wrapped tightly. Sufficient rigidity to prevent deformation etc. cannot be obtained. In the present invention, this reduced diameter portion is formed to be thicker than the container main body. This improves the rigidity of this part and prevents bending and deformation when sealing the can.

Further, if the stretching ratio of the container body 24 is less than 6 times, the container cannot have sufficient pressure resistance. Further, if the stretching ratio of the bottom portion 25 exceeds 6 times, the wall thickness becomes thinner, so that the container cannot have sufficient impact resistance.

In order to obtain such a stretching ratio, specifically, a parison having a shape as shown in FIG.
Place the parison with the mouth part held in the mouth mold,
Stretch blow molding may be performed by a conventional method.

By this stretch blow molding, the expanded diameter body portion 14 of the parison shown in FIG. 1 is stretched to form the expanded diameter portion 22 of the primary blow molded container.

The reduced diameter portion 23 of the primary blow-molded container is
Upper portion 15a of the reduced diameter body 15 of the parison in FIG.
becomes stretched. This portion 15a is thicker than the expanded diameter body portion 14 of the parison, and the diameter of the portion corresponding to the reduced diameter portion 22 of the blow molding mold is smaller, so that the diameter of the primary blow molded container is reduced. The portion 23 is thick.

[0036] The body portion 24 is greatly stretched and has a thin wall, and also has great strength due to the stretching effect. Note that since the bottom of the parison is adjusted to a lower temperature than the body, the body is more easily stretched, so that the body is fully stretched, while the bottom is hardly stretched. In this embodiment, a heel portion 26 and a center portion 27 of the container bottom are formed in the bottom portion 25 depending on the shape of the mold.

As explained above, if a parison having a shape as shown in FIG. 1 is used and stretch blow molding is performed using a mold having a shape of a primary blow molding container as shown in FIG. 2, the diameter can be reduced. It is possible to manufacture a primary blow-molded container in which the part is thicker than the body (the part that becomes the main body of the container), the body is sufficiently stretched, and the bottom is thick.

Once the primary blow-molded container as shown in FIG. 2 is obtained, the bottom wall of the enlarged diameter portion of this container (for example, at position C in FIG. 2) is cut to form a book as shown in FIG. A blow-molded container of the invention is obtained.

The blow-molded container 3 shown in FIG. 3 includes a flange portion 31, a lower region 32 of the flange portion, and a container body portion 3.
3 and a bottom portion 34.

The blow-molded container 3 of the present invention obtained in this manner has excellent sealing performance by forming a double seam 45 with a metal lid 46 that incorporates the flange portion 43, as shown in FIG. It can be a plastic can. In particular, plastic cans using the blow-molded container of the present invention are suitable as pressure-resistant containers for carbonated beverages, tennis ball cans, and the like.

Although the present invention has been described above in detail with reference to the drawings, the present invention is not limited thereto, and it goes without saying that various changes can be made without departing from the spirit of the present invention. . For example, the shape of each part of the primary blow-molded container can be changed as appropriate as long as the shape can achieve the stretching ratio as in the present invention.

The present invention will be explained in more detail with reference to the following specific examples. Example 1 A parison shown in FIG. 1 was made by injection molding using polyethylene terephthalate resin (Mitsui Pet J125, manufactured by Mitsui Petrochemical Industries, Ltd.). The shape and weight of the parison were as follows.

Overall height: 127mm Mouth: Outer diameter 36.5mm, Inner diameter 32.5mm Support ring part: Outer diameter 39mm Expanded diameter body: Outer diameter 36.3mm, Inner diameter 31.9mm
Reduced diameter body: outer diameter 25.8-26.8mm inner diameter 18.2
~19.6mm Bottom: Thickness 2.0mm Weight: 46.9g

After molding the parison of the above shape, a primary blow molded container (total height 240.2 m) as shown in FIG.
m, maximum trunk diameter 88 mm).

[0045] When the primary blow-molded container thus obtained was cut in the longitudinal direction and the stretching ratio of the container was measured, the mouth part was unstretched, the enlarged diameter part was about 5.5 times, and the diameter reduced part was about 5.5 times. Approximately 5
The container body was about 14.5 times larger, and the bottom was 1 to 6 times larger. The thickness of the container body was 0.25 mm, and the thickness of the lower region of the flange was 0.5 mm.

Next, this container was cut into a circular shape with a knife at position C shown in FIG. 2 and separated to obtain a blow-molded container as shown in FIG.

[0047] After the balls were placed in the container thus obtained, the container was sealed under pressure with a double seam with a metal lid so as to incorporate the flange portion.

The can thus obtained has sufficient sealing properties and is free from cracks and cracks even when double seamed.
Impact resistance that can withstand practical use without causing deformation, etc.
and had internal pressure resistance.

[0049]

Effects of the Invention As described above in detail, the blow-molded container of the present invention has a cylindrical container main body, a bottom, a flange, and a lower region of the flange with appropriate stretching ratios for each part. In addition, since the thickness of the lower part of the flange is increased, if this container is made of plastic, there will be no cracks in the flange, and the double seam will prevent deformation. There is no.

[0050] Such a container of the present invention can be suitably used as a pressure-resistant container for carbonated drinks, tennis balls, etc. by being provided with a metal end.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of a parison from which the plastic blow-molded container of the present invention can be manufactured.

2 is a sectional view showing an example of a primary blow-molded container obtained by blow-molding the parison of FIG. 1. FIG.

FIG. 3 is a cross-sectional view showing an example of a blow-molded container of the present invention obtained from the primary blow-molded container of FIG. 2;

FIG. 4 is a sectional view showing an example of a plastic can in which a metal double seam is added to the blow-molded container of FIG. 3;

[Explanation of symbols]

1 parison 11, 2
1 Mouth part 12
Parison body 13, 25, 34, 42
Bottom part 14 Expanded diameter trunk part 15
Reduced diameter body 2
Primary blow molded container 22
Expanded diameter part 23
Reduced diameter portions 24, 33, 41
Container body parts 31, 43
Flange part 33, 44 Lower area of flange 3, 4 Blow-molded container 45 Double seam 46 Metal lid

Claims (3)

[Claims] 1. A plastic blow-molded container consisting of a cylindrical container body, a bottom, a flange forming an opening, and a reduced diameter part, wherein the stretching ratio of each part of the container is 4 times at the flange. at least 3 times and less than 6 times at the reduced diameter part of the lower region of the flange, at least 6 times at the container body, and at most 6 times at the bottom, and the lower region of the flange is at least 6 times A plastic blow-molded container characterized by having a wall thickness greater than that of the container body. [Claim 2] By blow molding a cylindrical parison having a mouth, a body, and a bottom, from the top, the mouth, the enlarged diameter part, the reduced diameter part, the container body, and the bottom are formed. In the method for manufacturing a plastic blow molded container having a flange-shaped opening, the parison The mouth part and the upper part of the body part corresponding to the enlarged diameter part of the primary blow molded container were expanded in diameter. At least 3 times and less than 6 times at the reduced diameter portion, at least 6 times at the container body, and at most 6 times at the bottom, and the lower region of the flange portion is thicker than the container body. A method for manufacturing a plastic blow-molded container, characterized by: 3. The method of manufacturing a plastic blow molded container according to claim 2, wherein the container is made of polyethylene terephthalate.