JPH04173124A - Plastic blow molding container and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent crack and the like from developing at a flange part when a metal lid is mounted thereto and deformation from developing at the lower region of the flange part when double seaming is applied at the flange part by a method wherein the drawing ratio at each part of a plastic blow-molded container having a flange-like opening is specified. CONSTITUTION:After formation of a parison 1 by injection molding, resin constituting the partison is cooled down to a temperature, which is higher than its glass transition temperature and lower than its solidification temperature, by quenching an injection mold. Next, after being taken out of the injection mold, the parison is blown so as to be biaxially stretched. The drawing ratio at each part of a primarily blown container container obtained as mentioned above is as follows: the mouth part 21 is unstretched, the diametrically enlarged part 22 is 1,200-1,700%, the diametrically reduced part is 400--1,200%, the cylindrical container main body part 24 is 600% or more and the bottom part 25 is 600% or less. The diametrically enlarged part forms the flange part of a blow-molded container. The diametrically reduced part forms the lower region of the flange. In this case, when the parison is blown so as to be stretched with a mold having the shape of a primarily blown container and cut off at the bottom wall part (the positions (c)) of the diametrically enlarged part, a primarily blown container, in which the diametrically enlarged part is thin, the diametrically reduced part is somewhat thick, the cylindrical part is fully stretched and the bottom part is thick, can be manufactured.

Description

Detailed Description of the Invention [Field of Industrial 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, and in particular, to The present invention relates to a plastic blow-molded container that can be suitably used as a pressure-resistant container by wrapping it around a shaped opening, and a method for manufacturing the same.

[Problems to be solved by conventional techniques and inventions] In recent years,
Plastic cans (containers) are attracting attention as an alternative to metal cans.

As shown in FIG. 4, the plastic can is a plastic blow-molded container having a cylindrical container body 4I, a bottom 42, a flange 43 forming an opening, and a lower region 44 of the flange. 4 and a metal lid 46, the lid 46 is wrapped around the flange portion 43 by a double seam 45, and the can is sealed.

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 the opening must also be sealed and have good mechanical strength.

In particular, the flange part needs to be tightened with a double seam to avoid cracks or the like.

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 obtain a container of the desired shape (Japanese Patent Application Laid-Open No. No. 58-501991).

However, since the above container is stretched more than 6 times as a whole, the wall thickness is not sufficient in the lower part of the flange, which causes the problem that the opening easily deforms when double seaming is performed. . Furthermore, other parts such as the body and the bottom do not necessarily have impact resistance or pressure resistance suitable for a plastic can.

Therefore, an object of the present invention is to have a flange forming the opening of a plastic can with sufficient strength to be able to tighten a double seam, and a lower region of the flange to be resistant to deformation. To provide a plastic blow-molded container having excellent rigidity and sufficient impact resistance and pressure resistance in each part.

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

[Means to solve the problem]

As a result of intensive research in view of the above problems, the present inventors have determined the stretching ratio of each part of a plastic blow-molded container consisting of a cylindrical container main body, a bottom, and a flange forming an opening. The present inventors have discovered that by adjusting the stretching ratio of the container and its lower region within a specific range, it is possible to create a container that is free from deformation due to tightening of the lid and has excellent strength and pressure resistance, and has conceived the present invention.

That is, in the plastic blow-molded container of the present invention, which is composed of a cylindrical container main body, a bottom, and a flange forming an opening, the stretching ratio of each part of the container is 12 to 17 times for the flange, and 4 to 12 times in the lower region, 6 times or more in the container body, and 6 times or less in the bottom region.

In addition, by blow molding a cylindrical parison having a mouth, a body, and a bottom, the primary blow molding consists of a mouth, an enlarged diameter part, a reduced diameter part, a container body, and a bottom in order from the top. The method of the present invention for manufacturing a plastic blow-molded container having a flange-shaped opening by manufacturing a container and cutting the bottom wall portion of the enlarged diameter portion of the primary blow-molded container into an annular shape comprises: The stretching ratio of each part of the molded container shall be unstretched at the mouth, 12 to 17 times at the expanded diameter section, 4 to 12 times at the reduced diameter section, 6 times or more at the container body, and 6 times or less at the bottom. Features.

[For production]

In the present invention, the stretching ratio of each part of the plastic blow-molded container is set to 12 to 17 times in the flange part, 4 to 12 times in the lower region of the flange part, 6 times or more in the cylindrical container body part, and 6 times in the bottom part. It is as follows.

Such a plastic blow-molded container of the present invention does not cause cracks or the like in the flange when a metal lid is attached, and furthermore, the lower area of the flange does not deform when a double seam is applied. There is no.

The reason for this effect is that by increasing the stretching ratio of the flange part, the occurrence of cracks, etc. is prevented, and at the same time, the stretching ratio of the lower region of the flange part is kept lower than the stretching ratio of the main body of the container. This is because the lower region of the flange, which is prone to deformation, is thickened to improve rigidity and prevent deformation when double seams are formed. 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.

〔Example〕

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.

Furthermore, a mixture of the above-mentioned polyester resin with a heat-resistant resin, a barrier resin, etc. can also be used.

In addition, the polyester resin used in the present invention includes,
Additives such as stabilizers, pigments, antioxidants, heat deterioration inhibitors, ultraviolet deterioration inhibitors, antistatic agents, antibacterial agents, and other resins can be added in appropriate amounts.

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 I has a mouth portion 11 having a support ring portion (a in the figure), a body portion 12, and a bottom portion I3.

In addition, in this embodiment, from the mouth portion 11 to a portion corresponding to the shoulder portion of the primary blow-molded container (b in the figure), which will be described later,
The wall thickness gradually increases and becomes thinner than the wall thickness of the body portion 12. The reason why the wall thickness is so thin is:
In order to make the mouth part 11, which will not be the final product, as thin as possible, ■ In order to smoothly transition the wall thickness of the body part I2 to the thickness of the tip of the mouth part 11, ■ As will be described later, the diameter of the blow-molded container is expanded at part b. This is the part where the flange part is formed, and corresponds to the part that transitions from the shoulder part to the flange part.In particular, it is necessary to obtain an appropriate stretching ratio and wall thickness to provide strength and flexibility against bending. .

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.

By performing biaxial stretch blow molding using the parison 1 having the shape described above, a primary blow molded container having a shape as shown in FIG. 2 can be manufactured. The manufacturing method will be explained below.

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 molding 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 parison 1 becomes higher than the glass transition temperature and lower than the solidification temperature of the resin used, take out the parison 1 from the injection mold, and before the temperature of each part of the parison 1 becomes lower than the glass transition temperature, Perform axial stretch blow molding.

FIG. 2 is a sectional view showing a primary blow molded container obtained by biaxially stretch blow molding the parison of FIG. 1.

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, a container body portion 24, and a bottom portion 25.
It consists of.

In such a primary blow-molded container, the stretching ratio of each part is 21 or unstretched at the opening (grip), 22 or 12 at the enlarged diameter part.
-17 times, the reduced diameter part 23 is 4 to 12 times, the cylindrical container main body part 24 is 6 times or more, and the bottom part 25 is 6 times or less.

The reason for limiting the stretching ratio of each part is as follows.

If the stretching ratio of the enlarged diameter portion 22 is less than 12 times, it is difficult to sufficiently stretch the flange portion of the blow-molded container (included on the lower surface of the enlarged diameter portion 22), and if the stretching ratio exceeds 17 times. Therefore, it is not possible to obtain an appropriate wall thickness for the flange.

The reduced diameter portion 23 is the lower area of the flange of the blow-molded container, and when the flange is tightened, cracks,
In order to prevent deformation etc., it is necessary to improve rigidity. Therefore, the stretching ratio is set to 4 to 12 times.

If the stretching ratio is less than 4 times, the wall thickness becomes too large, the elasticity decreases, and cracks are likely to occur. If the stretching ratio exceeds 12 times, the wall thickness becomes thinner and deformation occurs when the flange is rolled up. It is not possible to obtain sufficient rigidity to prevent such problems.

Further, if the stretching ratio of the container main body portion 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 particular, it is preferable that the stretching ratio of each part of the primary blow-molded container as described above be in the following relationship: enlarged diameter part 22>container body part 24>reduced diameter part 23>bottom part 25>opening part 21 (unstretched).

In order to achieve such a stretching ratio, specifically, the parison is placed in a stretch blow mold in the shape of a primary blow molding container, with the mouth part 21 held by the mouth mold, and the parison is stretched and blow molded. All you have to do is mold it.

That is, the enlarged diameter portion 22 has a wall thickness that is thinner at a corresponding portion in the parison than a portion corresponding to the container body, and when used as a container, the enlarged diameter portion 22 has a larger outer diameter and has a higher stretching ratio. It becomes.

Normally, after forming a parison, the thinner part becomes colder and is less likely to be stretched, but in order to achieve a thinner wall and a high stretching ratio as mentioned above, a heating and temperature control process using a heater etc. is required before stretch blow molding. may be provided, and the portion corresponding to the expanded diameter portion 22 may be brought to a temperature suitable for stretching.

On the other hand, in the diameter-reduced portion 23 immediately below the mold, the diameter of the mold is smaller than that of the enlarged-diameter portion 22 and the container body 24, so that the stretching ratio can be kept low.

Furthermore, the parison l is longitudinally stretched by inserting a stretching rod, but at this time, the bottom part 13 is slightly thinner than the annular part, so the temperature is correspondingly low, and the stretching rod stretches the bottom part 13. There is no breaking through,
The trunk 12 is being stretched.

At this time, as mentioned above, the temperature of the bottom is lower than that of the body, so the body is easier to stretch. As a result, the trunk is fully stretched and 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 the parison is shaped as shown in Fig. 1 and stretch blow molding is performed using a mold having the shape of the primary blow molded container as shown in Fig. 2, the enlarged diameter portion It is possible to produce a primary blow-molded container that has a thin wall, a slightly thick reduced diameter portion, a sufficiently stretched body, and a thick bottom.

Also, by cutting the bottom wall part of the expanded diameter part of such a primary blow-molded container (for example, at the position C in FIG. 2),
A blow molded container of the present invention as shown in FIG. 3 can be obtained.

In FIG. 3, 3 indicates a blow-molded container, 31 indicates a flange, 32 indicates a lower region of the flange, 33 indicates a container body, and 34 indicates a bottom.

The blow-molded container 3 of the present invention obtained in this way is
By forming a double seam 45 with a metal lid 46 that incorporates the flange portion 43 as shown in FIG. 4, a plastic can with excellent airtightness can be obtained. 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 method of blow molding is also not particularly limited, and may be either the hot parison method, in which the steps from parison molding to primary blow molding are continuous, or the cold parison method, in which the parison molding and primary blow molding steps are separated. good.

The present invention will be explained in more detail by the following specific examples.

Example 1 Polyethylene terephthalate resin (Mitsui PET resin@)
The parison shown in FIG. 1 was made by injection molding using a material manufactured by J. The shape and weight of the parison were as follows.

Overall height: II6.5mm Mouth: Outer diameter 26-25.82mm, Inner diameter 22-16.
17mm Support ring part: Outer diameter 32mm Body part: Outer diameter 25.82-25.14mm, Inner diameter 16.
17-15.24m Bottom: Wall thickness 2.5mm Weight: 43.1g After molding the parison of the above shape, a primary blow-molded container of the shape shown in Figure 2 (total height 234mm, maximum diameter 88mm)
mm) was created.

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 not stretched, the expanded diameter part was approximately 15 times, the diameter reduced part was approximately 9 times, and the container was unstretched. The main body part was approximately 13 times larger, and the bottom part was 1 to 6 times larger.

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. 3.

After putting a tennis ball into the container thus obtained, the flange part is assembled under pressure.
Sealed by double seam with metal lid.

The cans obtained in this way have sufficient sealing properties, do not crack or deform even when double seamed, and have impact resistance and internal pressure resistance that can withstand practical use. Met.

〔Effect of the invention〕

As detailed above, the professionally molded container of the present invention has
Since the stretching ratios of the cylindrical container body, bottom, flange, and lower area of the flange are suitably changed for each part, when this container is made into a plastic can, the flange No cracks or the like will occur, and the double seam prevents deformation.

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 sectional view showing an example of a parison from which the plastic blow-molded container of the present invention can be manufactured, and FIG. 2 is an example of a primary blow-molded container obtained by blow-molding the parison of FIG. 1. FIG. 3 is a cross-sectional view showing an example of the blow-molded container of the present invention obtained from the primary blow-molded container of FIG. 2, and FIG. 4 is a cross-sectional view of the blow-molded container of FIG. FIG. 2 is a cross-sectional view showing an example of a double-seamed plastic can. l... Parison 11.21... Mouth part 12... Body part 13, 25.34.42... Bottom part 2... Primary blow molded container 22... Expanded diameter part 23... Contraction Diameter portions 24, 33.41... Container body portions 31, 43... Flange portions 33, 44... Lower region of the 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 main body, a bottom, and a flange forming an opening, wherein the stretching ratio of each part of the container is 12 to 12 at the flange.
17 times, in the lower region of the flange part 4 to 12 times, in the container body part 6 times or more, and in the bottom part 6 times or less. (2) By blow-molding a cylindrical parison having a mouth, a body, and a bottom, a primary material consisting of a mouth, an enlarged diameter part, a reduced diameter part, a container body, and a bottom in order from the top. In the method of manufacturing a plastic blow molded container having a flange-shaped opening by manufacturing a blow molded container and cutting the bottom wall portion of the enlarged diameter portion of the primary blow molded container into an annular shape, the primary blow molding The stretching ratio of each part of the container is unstretched at the mouth, 12 to 17 times at the expanded diameter section, 4 to 12 times at the reduced diameter section, 6 times or more at the container body, and 6 times or less at the bottom. A method for manufacturing a plastic blow-molded container. (3) The method for manufacturing a plastic blow-molded container according to claim 2, wherein the container is made of polyethylene terephthalate.