JPH09286423A - Biaxial stretching molded container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxial stretching molded container which is made of polyethylene terephtalate base, etc., thermoplastic resin having improved heat resistance, packaging characteristics and strength. SOLUTION: This biaxial stretching molded container 10 is made of thermoplastic resin such as polyethylene terephtalate base, polyethylene 2.6 naphthalate base. Its shell is formed of a spherical shoulder part 15 and a basically cylindrically shaped body part 16. On its cannonball shaped outer peripheral wall, 4 flat walls 18 are formed evenly. A length L of the shorter flat wall 18 side satisfies L<R.2<1/2> when the radius of the body part is R, so a part of the outer peripheral wall of the cylindrical shape remains as a circular arc shaped outer peripheral wall 6b in 4 places. The container of this shape is resistant to heat and negative pressure deformation and suitable for heat set treatment. Therefore, it is possible to realize a light weight container with less deformation by an external force at a low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin biaxially stretch-molded container used for beverage containers and the like. More specifically, the present invention relates to a biaxially stretch-molded container made of a polyethylene terephthalate or polyethylene 2.6 naphthalate type thermoplastic resin having improved heat resistance, wrapping property and strength.

[0002]

2. Description of the Related Art Biaxially stretch-molded containers molded from materials such as thermoplastic polyethylene terephthalate are extremely excellent in transparency and gas barrier property, and have been used in many beverage containers in recent years. .

Polyethylene terephthalate resin has many advantages as a material for forming beverage containers and the like. However, the heat resistance is not sufficient. That is, it does not necessarily have sufficient strength for hot filling of beverages.

The glass transition temperature of polyethylene terephthalate resin, that is, the heat distortion temperature is about 70 ° C. When used beyond this temperature range, the container made of the material is deformed by heat. That is, when a temperature higher than the heat deformation temperature is applied to the container, the entire container contracts / deforms, and particularly in the case where a rib is added to the shape of the container, the rib deforms and the function cannot be fulfilled. .

Generally, a beverage containing fruit juice is heated at 85 to 90 ° C. for sterilization and then hot-filled in a container. After that, the entire container is shower-cooled and finally returned to room temperature. Thus, the beverage container is filled with the beverage as it expands and the actual product is for use at room temperature. By this cycle, the beverage contracts inside the container to a negative pressure (decompression contraction), and it loses external force, in this case atmospheric pressure, causing thin or flat parts of the container, or even deformation or twisting of the whole. .

[0006]

In order to avoid such an adverse effect, conventionally, measures such as making a container heavy to increase the overall wall thickness, and a high temperature heat setting process that takes a long time for molding have been carried out. We are working to increase the strength of the container. However, these measures lead to high container prices.

As described above, in the case of a container requiring high temperature filling, a device for preventing deformation due to heat and a negative pressure deformation due to a decrease in internal pressure of the container, and further, both, that is, a shape and a function to overcome the heat and the negative pressure are required. It is essential to have it. Of course, it is natural that a low price is required.

An object of the present invention is to realize an economical biaxially stretch-formed container in which various strengths are improved in the shape of the container to improve the overall strength.

[0009]

SUMMARY OF THE INVENTION The present inventors have made various tests on the external pressure acting on the container by making containers of various shapes. As a result, they found that the shape most resistant to external pressure (heat and negative pressure) was a “sphere”. This is because the spheres are uniformly subjected to the atmospheric pressure, and in a cubic body having the same volume, the spheres have the smallest surface area and thus the area to receive heat is small. In addition, the weight can be reduced by making the container spherical.

However, the intended container is a bottle.
Therefore, in order to be as faithful as possible to the spherical shape, the shape of the bottle is brought close to it, and the shell shape that combines the spherical zone (the sliced sphere) and the cylinder is adopted. Based on this shape, in order to further avoid the pressure-reduction contraction and negative-pressure deformation to the maximum extent, at least the outer periphery of the cylindrical portion defining the body of the container has four locations evenly distributed on the outer periphery. It uses a structure with a flat wall.

The reason why there are four flat walls is that the area of one surface of the flat wall can be made the largest next to three (when three flat surfaces are used, the bottle shape greatly deviates from the normally required bottle shape. , It is not practical.), Because of the ideal packaging form and acceptance by the industry.

As described above, as the shape of the container, the shape extending from the shoulder portion to the body portion is formed into a shell shape, and at least the body portion is formed with four flat walls on the outer peripheral surface thereof. ing. The inventors of the present invention have found that the container having the shape obtained in this way strongly resists deformation by heat and negative pressure deformation, and arrived at the present invention.

Referring to FIG. 1, the basic shapes of the present invention are a sphere 1 and a cylinder 2 as shown in FIG. 1 (A). By combining these shapes, as shown in FIG. 1 (B), the shape 3A which is the basis of the shape of the container 3 of the present invention
Is getting That is, the container 3 has a cylindrical mouth and neck 4
And a shoulder portion 5 in the shape of a sphere which is continuous with the lower end opening 4a.
And a cylindrical body 6 that is continuous with the circular opening 5a at the lower end of the shoulder 5, and a circular bottom 9 that closes the lower end of the body 6. As described above, the shell shape 7 is formed by the spherical belt-shaped shoulder portion 5 and the cylindrical body portion 6.

In the present invention, based on the shell shape 7, four flat walls 8 are extended in the major axis direction mainly on the outer peripheral wall of the cylindrical body 6 at equal angular intervals (90 degree intervals). It is formed on. FIG. 1C shows the container 3 thus obtained.

Here, in FIG. 1D, the body portion 6 of the container 3 is shown.
The cross section of FIG. As shown in this figure, flat walls 8 are formed at four locations on the cylindrical outer peripheral wall 6a. In the present invention, when the short side length of the flat wall is L and the radius of the cylindrical shape of the body is R, the flat wall is formed so that L <R√2 holds. As a result, arcuate outer peripheral walls 6b remain between the flat walls 8, and the adjacent flat walls 8 are continuous by the outer peripheral walls 6b. It was confirmed that leaving such an arc-shaped outer peripheral wall 6b is important for strengthening the strength and the like of the container.

Incidentally, for example, if L = R√2, the arc-shaped outer peripheral wall 6b is not formed as shown in FIG. 1 (E), which is not preferable.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

Referring to FIG. 2, the container 1 of the present example.
0 is polyethylene terephthalate type, polyethylene 2
A biaxially stretch-molded container made of a thermoplastic resin such as a 6-naphthalate system, which has a cylindrical mouth-neck portion 14, a spherical belt-shaped shoulder portion 15 continuous to the lower end opening 14a, and the shoulder portion 1.
5 is constituted by a body portion 16 which is continuous with the lower end opening 15a and has a cylindrical basic shape, and a bottom portion 19. The shape of the bottom portion 19 is, for example, Japanese Patent Application No. 6-2272.
The shape having the rib-like structure shown in the specification of No. 69 is preferable. As described with reference to FIG. 1, the container 10 basically has a shell shape 17 obtained by combining a spherical shape and a cylindrical shape as a basic shape. The first feature is that four chamfers, that is, the flat walls 18 are evenly provided.

This basic shape (4
Of the shape in which the number of flat walls 18 is formed), a bottom portion 19 and
The second characteristic is that the portion excluding the flat wall 18 has no spherical structure and has a spherical shape that is most resistant to heat and negative pressure deformation.

Further, the short side length L of the flat wall 18 is determined by the body portion 1.
Let R be the radius of the cylindrical shape that is the basic form of 6, then L <R√
It has a length that satisfies 2. That is, a part of the cylindrical outer peripheral wall is left as the arc-shaped outer peripheral wall 16a, which contributes to the strength improvement, and the shoulder portion, which is weak against heat and negative pressure deformation, also has the spherical shape. There are three characteristics.

In the container 10 of this example having the above characteristics,
A flat wall 18 is formed continuously from the shoulder portion 15 to the lowermost end of the body portion 16 without interruption. As a result, a large area corresponding to the reduced pressure contraction can be obtained. Further, in the outer peripheral wall portion of the body portion 16, arcuate outer peripheral walls 16b remain at four positions, and the adjacent flat walls 18 are continuous with each other. As a result, the portion of the outer peripheral wall 16b causes the rib effect to increase the strength of the body portion 16. The existing conventional product has a straight shape between the four peripheral walls of the body.

Here, the flat wall 17 is required to have an area and strength capable of coping with the decompression contraction that occurs when the filling temperature of juice or the like (85 ° C., for example) drops to room temperature (20 ° C., for example). In view of this point and the like, in this example, the flat wall 18
A concave portion 21 is formed at the bottom. This allows the flat wall 1
8 is in a state in which a bank-shaped oblong ring 18A is formed, so that this ring 18A exerts a rib function, and becomes strong against twisting, buckling, etc. of the container 10.

Further, inside the concave portion 21 of the flat wall 18, convex ribs 22 intersecting in an X shape are formed. The ribs evenly distribute the external pressure applied to the container 10 vertically and horizontally. Therefore, the container 10 of this example also has a function of preventing local deformation.

The X-shaped convex rib 22 of the present example is formed so as to be recessed from the surface of the flat wall 18 toward the inside of the container. Therefore, sticking a label on the outer circumference of the container,
It does not get in the way of attaching the label. In particular, the container shape of this example has an excellent effect that a large label covering a wide range from the shoulder portion 15 to the lowermost end of the body portion 16 can be added.

On the other hand, in this example, the four arc-shaped outer peripheral walls 16b remaining between the flat walls 18 each have a width of more than about 10 mm at the middle position in the vertical direction. No concave rib 23 is formed. This concave rib 2
3 is formed in a range that does not block the flat wall 18.

Here, as described above, when hot filling, for example, juice at 85 ° C. is filled, not only the deformation of the container due to the contraction under reduced pressure but also the deformation due to heat is a serious problem. The heat is applied almost uniformly to the entire container, and it is desirable to perform a heat treatment called heat setting during the molding of the container as a deformation preventing measure therefor.

In this method, for example, when a primary molded product called a test tubular preform is blow-molded with high pressure air, the temperature of the container-shaped mold is set to 100 ° C. or higher and the blow-molded container wall is formed. This is a method of thermally fixing the molecules of the resin by rapidly raising the temperature and then rapidly cooling.
The most important thing in heat setting treatment is to uniformly apply a constant amount of heat to the container wall.

In order to efficiently give the heat quantity determined to the container, the heat quantity per unit area may be increased. In other words, since the amount of heat is determined, the surface area of the container should be made as small as possible. As previously mentioned,
The container 10 of this example is set so that its basic shape is as close as possible to a sphere having the smallest surface area. Therefore, the container 10 of this example is extremely suitable even when performing such heat setting treatment.

In the heat treatment at the time of molding, the amount of heat received per unit area is increased, and the residual stress on the wall surface of the blow-molded container, that is, the bottle container tends to return to the preform. It is important to eliminate distortion as much as possible.

In the container 10 of this example, the basic shape is a combination of a shell shape having a spherical shape and a cylindrical shape and a flat surface formed on the outer periphery of the shell shape. Therefore, the distance from the center of the container to the outer peripheral wall surface is not large, and the residual stress varies little depending on the location. That is, there is an advantage that the blow ratio in the circumferential direction does not have a large difference.

On the other hand, most of the heat-resistant containers of the same kind that are generally commercially available have a rectangular cross section or a square cross section, and the advantages of the container shape of this example cannot be obtained.

[0032]

As described above, the container of the present invention is
The basic shape is a combination of a shell shape consisting of a spherical zone and a cylinder, and four flat walls formed on the outer periphery thereof.
Therefore, it is resistant to heat and negative pressure deformation. Also, the shape is suitable for heat setting.

Furthermore, the container of the present invention employs, in addition to the above configuration, a configuration in which a flat wall is provided with a concave portion and an X-shaped rib is provided inside thereof. Therefore, it is possible to realize a container that is resistant to twisting, buckling, and local deformation.

In addition to this, by adopting the container shape of the present invention and adding a heat setting process in the molding process, it is possible to supply a lightweight container which is less deformed by an external force at a low price. can get.

[Brief description of drawings]

FIG. 1A is an explanatory view for explaining a basic container shape of the present invention, FIG. 1B is an explanatory view showing a basic shell shape of the container of the present invention, and FIG. It is explanatory drawing which shows the basic shape of a container, (D) is the cross-sectional view, and (E) is explanatory drawing which shows the limit of the width of a flat wall.

2A and 2B are respectively a side view and a bottom view of a container to which the present invention is applied.

[Explanation of symbols]

3 Container 3A Basic shape of container (combination of shell shape and flat wall) 4 Mouth neck section 5 Shoulder section 6 Body section 6b Arc-shaped outer peripheral wall 7 Shell shape 8 Flat wall 9 Bottom L Flat wall lateral width R Body radius

Claims (9)

[Claims] 1. A container made of a thermoplastic resin having a mouth / neck portion, a shoulder portion, a body portion, and a bottom portion, wherein the shoulder portion has a spherical shape, and the large-diameter bottom portion of the shoulder portion has a cylindrical shape. By connecting to the upper end of the body, it forms a shell shape as a whole from the shoulder to the body, and at least the outer peripheral wall of the body of the shoulder and the body has the outer circumference. Flat walls extending in the major axis direction are formed at positions respectively dividing the circumferential direction of the wall into four parts. The short side length of the flat wall is L, and the radius of the cylindrical shape of the body is R. In this case, the flat wall is formed so that L <R√2 holds, and a biaxially stretch-molded container. 2. The biaxially stretch-molded container according to claim 1, wherein the flat wall is formed in a continuous state from the shoulder to the bottom of the body without interruption. 3. The biaxially stretch-molded container according to claim 1, wherein the flat wall has a concave portion having a function of absorbing reduced pressure. 4. The biaxially stretch-molded container according to claim 3, wherein a bank-shaped elliptical ring is formed around the concave portion formed on the flat wall. 5. The biaxially stretch-molded container according to claim 4, wherein a convex rib structure is formed inside the concave portion. 6. The biaxially stretch-molded container according to claim 5, wherein the convex rib does not protrude from the flat wall. 7. The biaxially stretch-molded container according to claim 5, wherein the convex ribs are formed in an X-shaped cross shape. 8. The concave rib is formed on the arc-shaped outer peripheral wall outside the flat wall where a part of the body surface remains, according to any one of claims 1 to 7. The biaxially stretch-molded container, wherein the concave rib is formed so as not to block the flat wall. 9. A biaxially stretch-molded container according to claim 1, wherein the material of the container is thermoplastic polyethylene terephthalate or thermoplastic polyethylene 2.6 naphthalate.