JP2004331227A - Biaxially stretched blow molded vessel and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biaxially stretched blow molded vessel, which can satisfactorily ensure rigidity and keeps a groove part in the circumferential wall not locally thickened in a wall thickness distribution in an axial direction of the vessel, and a method for manufacturing the same. <P>SOLUTION: In this biaxially stretched blow molded vessel 20, the outer diameter of an annular groove part 26 in the circumferential wall is made 2.15 to 4.5 times larger than the outer diameter of a part near the lower part of a flange 23 provided in the vessel 20. A manufacturing method for the vessel 20 is also provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a biaxially stretch blow-molded container and a method for producing the same. The present invention relates to a biaxially stretch blow-molded container excellent in moldability that does not become meat and a method for producing the same.

  A plastic container, for example, a biaxially stretch blow-molded container of a thermoplastic polyester such as polyethylene terephthalate (PET) has not only excellent transparency and surface gloss but also impact resistance, gas barrier properties, and the like. Widely used as containers for various beverages.

Generally, in the manufacture of a PET container by biaxial stretch blow molding, a preform with a bottom is manufactured by injection molding using PET resin as a material, and the preform is preheated to a predetermined stretching temperature and then held in a split mold. At the same time, the stretching is performed by stretching in the axial direction by the stretching rod and blowing air into the inside to expand and stretch in the circumferential direction.
In the PET container manufactured as described above, in order to increase the rigidity of the container or to ensure that the shrink label indicating the product name or raw material of the contents can be securely fixed to the peripheral wall of the container. An annular groove is formed on the peripheral wall of the container along the circumferential direction.

Conventionally, PET containers having a volume of 1.5 liters or 2.0 liters have been the mainstream, but in recent years, PET containers having a relatively small volume of approximately 350 ml or 500 ml have been used. Demand is growing.
When a relatively small volume PET container having the above-mentioned volume is manufactured by biaxial stretch blow molding, it is necessary to reduce the length and diameter of the preform with a bottom for the reduced volume. However, since the capping machine of the filling line is used together with the conventional 1.5 liter or 2.0 liter container, the mouth and the flange have the same outer diameter as the 1.5 liter or 2.0 liter container. It has dimensions. If the axial dimension of the bottomed preform is simply shortened, the stretching ratio in the circumferential direction becomes small, and in the thickness distribution in the axial direction of the container, the annular groove provided on the body peripheral wall is extremely thick. In addition, there is a problem that sink is generated in the thick portion due to poor appearance and a difference in cooling rate between the thick portion and the peripheral portion.
Also, in the manufacturing method, the blow ratio is the smallest in the annular groove portion of the body portion, and the resin corresponding to the annular groove portion of the container is caught by the convex portion of the mold during biaxial stretch blow molding, and the stretch of the portion is performed. Magnification decreases.
Accordingly, an object of the present invention is to provide biaxial stretch blow molding which can secure sufficient rigidity and is excellent in molding such that the annular groove portion of the peripheral wall does not become locally thick in the axial thickness distribution of the container. An object of the present invention is to provide a container and a method for producing the container.

The present invention has been proposed to achieve the above object, and has the following configuration.
That is, according to the present invention, the peripheral wall has a rectangular cylindrical shape, and is formed at the center of the annular groove portion of each of the opposed peripheral walls so as to be connected to the upper peripheral wall and the lower peripheral wall and project outwardly lower than the annular groove portion. A biaxially stretch blow-molded container, characterized in that the outer diameter of the protrusion is 2.15 to 4.5 times the outer diameter near the lower part of the flange of the container.

  Further, according to the present invention, the peripheral wall has a rectangular cylindrical shape, and is formed at the center of the annular groove of each of the opposed peripheral walls so as to be connected to the upper peripheral wall and the lower peripheral wall, and to protrude outwardly below the annular groove. Wherein the outer diameter of the protrusion is 2.15 to 4.5 times the outer diameter near the lower part of the flange of the container. .

  ADVANTAGE OF THE INVENTION According to this invention, while ensuring sufficient rigidity, in the axial thickness distribution of a container, the annular groove part of a peripheral wall does not become locally thick, and the two-axis which does not produce appearance defects, such as sink, A stretch blow-molded container and a method for producing the same are provided.

  The technical feature of the biaxially stretch blow-molded container according to the invention of claim 1 is that, as shown in FIG. 1, the peripheral wall has a rectangular cylindrical shape, and the upper peripheral wall and the lower A projection is provided which is connected to the peripheral wall and protrudes outward below the annular groove, and the outer diameter of the projection is 2.15 to 4.5 times, preferably 2 times, the outer diameter near the lower part of the flange of the container. .2 to 3.0.

  By setting the projection provided at the center of the annular groove as described above to be 2.15 to 4.5 times the outer diameter near the lower portion of the flange, the thickness distribution in the axial direction of the rectangular cylindrical container is obtained. In the case where the annular groove portion of the side wall does not locally become thick, furthermore, the beverage or the like is hot-filled, and after cooling, if the inside of the container becomes a negative pressure, the negative pressure is also favorably applied to the annular groove portion. Can be absorbed. In other words, the upper and lower sidewalls do not independently absorb the negative pressure at the boundary of the annular groove, but the upper and lower sidewalls simultaneously move inward to absorb the negative pressure satisfactorily as a large surface. In addition, the provision of the protrusion prevents the annular groove from breaking when absorbing negative pressure.

  The radial depth dimension X of the annular groove of each side wall varies depending on the volume of the container and the like, but is preferably 1.0 to 6.0 mm, particularly 2.0 to 4.5 mm. It is desirable in terms of shape and thickness distribution. The width Y in the axial direction of the annular groove is preferably 2.0 to 6.0 mm, particularly preferably 3.0 to 4.0 mm in terms of lateral rigidity. Further, the formation position of the groove varies depending on the bottle height or the like, but is preferably 6 to 13 cm upward from the bottom of the container from the viewpoint of moldability.

  Further, the circumferential length S2 of the protrusion is formed to be shorter than the circumferential length S1 of the annular groove of the side wall facing each other, and the dimension S2 is １ ／ or less of S1 (see FIG. 2). More preferably, S2 / S1 is set to 0.46 or less. If S2 is smaller than 1/3 of S1, the thickness distribution tends to be poor (thickening), and if S2 is larger than 1/2 of S1, the lateral rigidity tends to decrease.

Further, the projection is provided so as to be lower than the radial depth of the annular groove so as not to project outward, and the size of the projection is 30% to 50% of the depth of the annular groove in which the projection is formed. % Is desirable in terms of lateral rigidity. If the size of the protrusion is smaller than 30%, there is a tendency for breakage when absorbing negative pressure, and if it is larger than 50%, there is a tendency for lateral rigidity to decrease.
The circumferential angle α (see FIG. 2) of the projection with respect to the annular groove is set to 150 to 170 degrees, particularly 160 to 165 degrees, from the viewpoint of shaping properties and prevention of breakage during absorption of negative pressure. preferable.

  Further, it is necessary to form at least one protrusion at the center of the annular groove on each of the four side walls forming the peripheral wall, but it is also possible to provide two or more protrusions on each side wall. In the first aspect of the present invention, since the groove is formed in the peripheral wall, the rigidity of the container is sufficiently ensured. Further, the shape of the annular groove is not particularly limited, and a cross-sectional shape cut in the axial direction may be an arc, a U-shape, a concave shape, or the like.

The technical feature of the biaxially stretch blow-molded container according to the second aspect of the present invention is that the peripheral wall has a rectangular cylindrical shape, and protrudes outward from the center of the annular groove on each of the opposed peripheral walls, which is lower than the annular groove. A protrusion is provided, and the inner diameter of the protrusion is set to 2.15 to 4.5 times the outer diameter near the lower part of the flange of the container.
In the present invention, as a material for forming the container, a plastic material capable of being subjected to biaxial stretch blow molding can be used, and examples thereof include polyester resins such as polyethylene terephthalate and copolymerized polyester, and polyolefin resins.
The volume of the biaxially stretched blow-molded container of the present invention is not particularly limited, but the above-mentioned effect is remarkably exhibited by using a container having a volume of 200 to 900 ml, particularly 350 to 500 ml.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Example 1
FIG. 1 shows a biaxially stretch blow-molded container 20 according to the claims.
The biaxially stretch blow-molded container 20 according to the present embodiment is provided with a flange 23 below the mouth 22, an upper peripheral wall 24 for fixing a label below the flange 23, and an annular groove 26 below the upper peripheral wall 24. A lower peripheral wall 25 having a bottom portion 27 is integrally formed, and the peripheral walls 24 and 25 have a rectangular cylindrical shape, and have a rectangular cylindrical shape as a whole. 21 indicates a parison virtual line before blowing.
The annular groove 26 is formed substantially midway between the upper peripheral wall 24 and the lower peripheral wall 25 along the entire circumferential direction. In addition, a projection 28 is provided at the center of the annular groove 26, and the projections 28A to 28D are respectively provided at positions corresponding to the side walls (25A to 25D in FIG. 2) of the upper peripheral wall 24 and the lower peripheral wall 25 in the radial direction. The projection is provided outward so as not to protrude from the annular groove portion 26.

In the present embodiment, in the biaxially stretched blow-molded container 20, the outer diameter L3 between the convex portions 28A and 28C provided in the annular groove 26 is 57.6 mm, and the outer diameter near the lower portion of the flange 23 in the container 20. L4 is formed to be 26.16 mm. That is, in this embodiment, L3 / L4 is set to 2.20.
In this embodiment, the circumferential length S1 of the annular groove 26 is set to 43.7 mm, the radial depth X is set to 2.0 mm, and the axial width Y is set to 3.0 mm. Further, the length S2 in the circumferential direction of the protrusion 28 was set to 20 mm, the protrusion Z in the radial direction was set to 0.8 mm, and the width in the axial direction was set to 4.3 mm. In the biaxially stretched blow-molded container 20 configured as described above, in the axial thickness distribution of the container 20, the annular groove portion 26 was formed well without a locally thick portion being formed.

Comparative Example 1
Except that the outer diameter L3 of the protrusion 28 provided in the annular groove is set to 56.0 mm, that is, L3 / L4 is set to 2.14, the biaxial stretching blow is performed under the same conditions as in Example 1. A molded container was manufactured. In the obtained container, thickness distribution failure occurred in the annular groove portion 26, and it was confirmed that the thick portion was formed.

It is a front view of the biaxial stretch blow molding container of the present invention. It is sectional drawing in the AA line of FIG.

Explanation of reference numerals

20: biaxially stretch blow molded container 23: flange 24: upper peripheral wall 25: lower peripheral wall 26: annular groove 28: convex portion

Claims (2)

The peripheral wall has a rectangular cylindrical shape, and at the center of the annular groove of each of the opposed peripheral walls, a projection is provided which is connected to the upper peripheral wall and the lower peripheral wall and projects outwardly lower than the annular groove. A biaxially stretch blow-molded container, wherein the outer diameter is 2.15 to 4.5 times the outer diameter near the lower part of the flange of the container. The peripheral wall has a rectangular cylindrical shape, and at the center of the annular groove of each of the opposed peripheral walls, a projection is provided which is connected to the upper peripheral wall and the lower peripheral wall and projects outwardly lower than the annular groove. A method for producing a biaxially stretch blow-molded container, wherein the outer diameter is 2.15 to 4.5 times the outer diameter near the lower part of the flange of the container.

Images