JP2792013B2 - Plastic blow molded container and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic blow-molded container having a flange-shaped opening having substantially the same diameter as a body, and a method of manufacturing the same. In particular, a lid made of aluminum or the like is wound around the flange-shaped opening. The present invention relates to a plastic blow-molded container that can be suitably used as a pressure-resistant container, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years,
Plastic cans (containers) have attracted attention as alternatives to metal cans.

As shown in FIG. 4, a plastic can includes 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 double-seam
It is wrapped around 43 and the can is sealed.

When used as a container for carbonated drinks, tennis balls, and the like, a high internal pressure is applied. Therefore, not only is the internal pressure of the entire container high, but also the sealing state and mechanical strength of the opening must be good. is there. In particular, since the flange portion is wound around the lid by a double seam, it is necessary to prevent cracks and the like from occurring at that time.

In order to prevent such cracks, a method has been proposed in which a primary container is first manufactured by blow molding, and the primary container is cut at a predetermined position to obtain a container having a desired shape. JP-A-58-501991).

However, since the container according to the above method is stretched 6 times or more as a whole, the thickness is not sufficient in the lower region of the flange, and the opening is easily deformed when performing double seam. is there. Further, there is a problem that other parts such as a body part and a bottom part do not necessarily have a suitable impact resistance and pressure resistance for each part as a plastic can.

Accordingly, an object of the present invention is to provide a plastic can having such a strength that the flange portion constituting the opening can withstand the tightening of the double seam,
An object of the present invention is to provide a plastic blow-molded container in which the lower region of the flange portion has excellent deformation resistance (rigidity) and each portion has sufficient impact resistance and pressure resistance.

It is another object of the present invention 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 studies, the present inventors have used a bottomed cylindrical parison having an enlarged diameter of the mouth and the upper part of the body, and stretch blow molded the parison. In making the container, the draw ratio of each part of the plastic blow-molded container comprising the cylindrical container body, the bottom, and the flange constituting the opening, particularly the draw ratio of the flange and its lower region, By adjusting to a specific range, and by making the thickness of each part appropriate, it was found that a container excellent in strength and pressure resistance can be obtained without deformation due to tightening of a lid, and the present invention. I arrived.

That is, in the plastic blow-molded container of the present invention comprising a cylindrical container main body, a bottom, a flange forming an opening, and a reduced diameter portion, the stretch ratio of each part of the container is defined by the flange. 4 times or more and less than 6 times, 3 times or more and less than 6 times in the reduced diameter portion of the lower region of the flange portion, 6 times or more in the container body portion, 6 times or less in the bottom portion,
The lower region of the flange portion is thicker than the container body.

The method for producing a plastic blow-molded container according to the present invention comprises the steps of blow-molding a cylindrical parison having a mouth, a body, and a bottom so as to form a mouth, a diameter-increasing portion, and a diameter-reducing portion in order from the top. , A container main body, and a primary blow-molded container comprising a bottom portion, and a flange-shaped opening is formed by cutting the bottom wall portion of the enlarged diameter portion of the primary blow-molded container into an annular shape. In the above, using a parison whose diameter is increased at the mouth and at the upper part of the body corresponding to the enlarged diameter of the primary blow-molded container, the stretching ratio of each part of the primary blow-molded container is unstretched at the mouth, and the diameter is increased. 4 times or more and less than 6 times, 3 times or more and less than 6 times in the reduced diameter portion, 6 times or more in the container body portion, and 6 times or less in the bottom portion, and the lower region of the flange portion is thicker than the container body portion. It is characterized by being thick.

[0012]

In the present invention, the stretch ratio of each part of the plastic blow-molded container is 4 to less than 6 in the flange portion, 3 to less than 6 in the lower region of the flange portion, and 6 to 6 in the cylindrical container body. More than twice and less than 6 times at the bottom.
The lower region of the flange is thicker than the container body.

Such a plastic blow-molded container of the present invention does not cause cracks or the like in the flange portion even when the metal lid is attached by tightening, and when the double seam is applied, the flange portion does not crack. The lower region is not deformed.

That is, by stretching the flange portion to an appropriate magnification and giving it a certain thickness, the strength is such that cracks and the like do not occur even when tightening is performed. The rigidity is improved by suppressing the stretching ratio of the main body portion to be lower than the stretching ratio and by increasing the thickness of the lower region of the easily deformable flange portion, thereby preventing deformation when a double seam is formed. Moreover, the container body, which is required to have impact resistance and pressure resistance, is sufficiently stretched. Therefore, each part has the required strength as a plastic can.

In the method of the present invention, since the parison whose diameter is expanded from the mouth to the upper part of the body is used, when producing the primary blow-molded container by biaxial stretch blow molding,
The large diameter portion and the small diameter portion of the upper part of the primary blow molded container can be formed without difficulty, and the desired thickness can be formed with good reproducibility.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below 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 which can be blow-molded, but a polyester-based plastic is preferred.

As the polyester resin, a thermoplastic resin comprising 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.

A mixture of the above-mentioned polyester resin with a heat-resistant resin, a barrier resin, or the like, or a multi-layered resin may be used.

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

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

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

The parison 1 is formed such that the thickness of the bottom 13 is slightly smaller than the thickness of the body 12. By doing so, the bottom 13 can be cooled to a temperature lower than the temperature of the body 12. Therefore, the trunk can be extended without breaking through the bottom 13 by the longitudinal extension by the rod at the time of extension.

Using the parison 1 having the above-described shape, biaxial stretching blow molding is performed to produce a primary blow-molded container having a 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 performed by an ordinary 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 resin constituting the parison is cooled to a temperature equal to or higher than the glass transition temperature and equal to or lower than the solidification temperature by rapidly cooling the injection mold. The quenching of the injection mold can be performed by means such as pouring a coolant into a passage provided in the mold.

When the temperature of each part of the parison 1 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 1 is taken out of the injection mold, and 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 stretch blow molding the parison of FIG.

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

In such a primary blow molded container,
The stretching ratio of each part is as follows.
Medium stretched 4 times or more to less than 6 times, reduced diameter part 23 3 times or more to 6 times
Medium stretching of less than 2 times, high stretching of 6 times or more of the cylindrical container body 24, and low stretching of 6 times or less of the bottom 25.

The reasons for limiting the draw ratio of each part are as follows. If the stretching ratio of the enlarged diameter portion 22 is less than 4 times, it is difficult to sufficiently stretch the flange portion (included in the lower surface of the enlarged diameter portion 22) of the blow molded container, and the strength of the flange portion is reduced. descend. Further, if the stretching is performed six times or more, the enlarged diameter portion (flange portion) becomes thin and has high rigidity, which is not preferable for winding with deformation. For stable winding, medium stretching of 4 to 6 times is preferable. With such a stretching ratio, it is well-adapted when double-sealed and has high strength and is suitable.

The reduced diameter portion 23 is a portion to be a lower region of the flange of the blow-molded container, and it is necessary to improve rigidity in order to prevent cracks, deformation, and the like 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 becomes too large, the elasticity is reduced and cracks are easily generated, and if the stretching ratio is 6 times or more, the wall thickness becomes too thin and the flange portion is tightened. Rigidity sufficient to prevent deformation and the like cannot be obtained. In the present invention, the reduced diameter portion is formed thicker than the container body. This improves the rigidity of this part, breaks when sealing as a can,
Prevent deformation.

If the stretching ratio of the container body 24 is less than 6, the container cannot have sufficient pressure resistance.
Further, when the stretching ratio of the bottom portion 25 exceeds 6 times, the thickness becomes thin, so that a container having sufficient impact resistance cannot be obtained.

In order to obtain such a draw ratio, specifically, a parison having a shape as shown in FIG. 1 is used, and a draw blow mold having the shape of a primary blow mold container is placed in a stretch blow mold.
Install this parison with the mouth held in the mouth shape,
Stretch blow molding may be performed by a conventional method.

By this stretch blow molding, the enlarged barrel portion 14 of the parison shown in FIG. 1 is extended to form the enlarged portion 22 of the primary blow molded container.

The reduced diameter portion 23 of the primary blow molded container is formed by extending an upper portion 15a of the reduced diameter body portion 15 of the parison in FIG. This part 15a is thicker than the parison's enlarged body 14 and the diameter of the part corresponding to the reduced diameter part 22 of the blow mold is smaller, so that the diameter of the primary blow molded container is reduced. The part 23 becomes thick.

The body portion 24 is stretched greatly and is thin, and has a large strength due to the stretching effect. In addition,
Since the bottom of the parison is adjusted to a lower temperature than the trunk, the trunk is easier to stretch, so that the trunk is stretched well while the bottom is barely stretched. In this embodiment, a heel portion 26 and a central portion 27 of the container bottom are formed on the bottom 25 by the shape of a mold.

As described above, if the stretch blow molding is performed using a parison having a shape as shown in FIG. 1 and a mold having the shape of a primary blow molding container as shown in FIG. It is possible to produce a primary blow-molded container in which the portion is thicker than the trunk (the portion to be the main body of the container), the trunk is sufficiently stretched, and the bottom is thick.

When the primary blow-molded container as shown in FIG. 2 is obtained, the bottom wall portion (for example, the position of C in FIG. 2) of the enlarged diameter portion of this container is cut, and the book as shown in FIG. Obtain the blow molded container of the invention.

The blow molded container 3 shown in FIG. 3 includes a flange portion 31, a lower region 32 of the flange portion, a container body portion 33,
And a bottom 34.

As shown in FIG. 4, the blow molded container 3 of the present invention obtained as described above is provided with a double seam 45 with a metal lid 46 in the form of taking in the flange 43, thereby achieving excellent sealing performance. Plastic cans. In particular, a plastic can using the blow-molded container of the present invention is suitable as a pressure-resistant container for carbonated beverages, tennis ball cans, and the like.

As described above, the present invention has been described in detail with reference to the drawings. However, the present invention is not limited thereto, and it is needless to say that various modifications can be made without departing from the spirit of the present invention. . For example, the shape and the like of each part of the primary blow-molded container can be appropriately changed as long as the shape can be set to the draw ratio as in the present invention.

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

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

After the parison having the above shape was formed, a primary blow-molded container (having a total height of 240.2 mm and a maximum body diameter of 88 mm) as shown in FIG. 2 was prepared.

The primary blow-molded container thus obtained was cut in the longitudinal direction, and the stretch ratio of the container was measured. The mouth was unstretched, the enlarged portion was approximately 5.5 times, and the reduced portion was approximately 5 times.
2 times, the container body was about 14.5 times, and the bottom was 1 to 6 times.
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, the position C shown in FIG. 2 of the container was cut into a circle with a knife and separated to obtain a blow-molded container as shown in FIG.

After the balls were put into the container thus obtained, the container was sealed with a metal lid under a pressure so as to incorporate a flange portion under pressure.

The can thus obtained has a sufficient sealing property, and even if a double seam is applied, cracks,
Impact resistance that can withstand practical use without deformation etc.,
And internal pressure resistance.

[0049]

As described in detail above, the blow-molded container of the present invention is preferably configured such that the stretch ratio of the cylindrical container body, the bottom, the flange, and the lower region of the flange is appropriately adjusted for each of the parts. Since this is changed and the thickness of the lower region of the flange is increased, when this container is made of a plastic can, there is no crack etc. in the flange part, and it is deformed by applying a double seam There is no.

The container of the present invention having a metal end can be suitably used as a pressure-resistant container for carbonated drinks, tennis balls and the like.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a parison capable of manufacturing the plastic blow-molded container of the present invention.

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

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

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

[Explanation of symbols]

 1 Parison 11, 21 mouth 12 Parison body 13, 25, 34, 42 Bottom 14 Large diameter body 15 Reduced diameter body 2 Primary blow molded container 22 Large diameter part 23 Reduced diameter part 24, 33, 41 Container Body 31, 43 Flange 33, 44 Lower area of flange 3, 4 Blow-molded container 45 Double seam 46 Metal lid

Continuation of the front page (56) References JP-A-2-155625 (JP, A) Japanese Utility Model Application Sho 60-18927 (JP, U) Tokuyo Sho 58-501991 (JP, A) (58) Fields investigated (Int) .Cl. ⁶ , DB name) B65D ⁶ /00-13/02

Claims (3)

(57) [Claims] 1. A plastic blow-molded container comprising a cylindrical container body, a bottom, a flange forming an opening, and a reduced diameter portion, wherein the stretch ratio of each part of the container is four times that of the flange. The above is less than 6 times, 3 times or more and less than 6 times at the reduced diameter portion of the lower region of the flange portion, 6 times or more at the container body portion, 6 times or less at the bottom portion, and the lower region of the flange portion is A plastic blow molded container characterized by being thicker than the container body. 2. A blow molding of a cylindrical parison having a mouth, a body, and a bottom, from the top, the diameter increasing part, the diameter reducing part, the container body, and the bottom in order from the top. A method for producing a plastic blow-molded container having a flange-like opening by producing a primary blow-molded container, and cutting a bottom wall portion of an enlarged diameter portion of the primary blow-molded container into an annular shape. As the mouth and the upper part of the body corresponding to the enlarged part of the primary blow-molded container having an enlarged diameter, the stretching ratio of each part of the primary blow-molded container is set to be unstretched at the mouth and 4% at the enlarged part. More than double and less than 6 times, 3 times or more and less than 6 times in the reduced diameter portion, 6 times or more in the container body, and 6 times or less in the bottom, and the lower region of the flange portion is made thicker than the container body. Plastic blow molded container characterized by the following: Manufacturing method. 3. The method for producing a plastic blow-molded container according to claim 2, wherein said container is made of polyethylene terephthalate.