JPH07112730A - Heat-resistant plastic container - Google Patents

Abstract

PURPOSE:To provide a heat-resistant plastic container having good shape holdability against an internal pressure and good material yield wherein heat shrinking or deformation under heat due to the weight of contents may not occur even if it is filled with high temperature contents. CONSTITUTION:A heat-resistant plastic container comprises a bottom structure formed with a recess 1 inward the container at a bottom 2 of a drawn-molded plastic container wherein an outer periphery roundness 3 is provided outward from a circular bottom heel in contact with a floor of the recess 1, a ring-like stage 4 raised inward from the bottom is provided, while the container comprises a spherical wall 8 standing like a recess inward from the stage 4 and a spherical wall connected with the spherical wall 8 and protruding toward the bottom, wherein a plurality of recessed and protruding ribs 7 to 9 are formed on the respective spherical, walls.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant plastic container made of saturated polyester resin or the like.

[0002]

2. Description of the Related Art In recent years, biaxially stretched blow containers made of saturated polyester resin have been used as containers for fruit juice drinks. Among them, polyethylene terephthalate resin containers have excellent gas barrier properties, high transparency, toughness that does not break even when dropped, and non-adsorbability that does not transfer the odor of food, and the resin itself produces odors. It has a number of advantages such as low odor which is less likely to occur.

No particular consideration is given to the contents to be filled at ordinary temperature, but the contents to be sterilized and filled at a high temperature are heat-set in order to impart heat resistance in the container manufacturing process. And so on. This heat treatment is extremely effective for a container body that has been sufficiently biaxially stretched, but since the bottom part is not stretched, when filled with high-temperature contents, it is thermally deformed outward due to heat shrinkage and the self-weight of the contents. Occurs, which causes a change in capacity. Therefore, a reinforcing structure has been proposed in which the center of the bottom portion is recessed inward of the container, and the recessed inner wall is provided with uneven ribs, or the inner wall is formed in a stepwise manner.

For example, in Japanese Examined Patent Publication No. 62-29378, as shown in the partial partial sectional view of FIG. 3, a concave spherical wall 8 is formed when viewed from the bottom side, and a plurality of wall surfaces are formed. There is a form in which individual vertical ribs 9 are attached.

In the above case, the shape retention with respect to the internal pressure and the strength of the ribs are improved, but this is not sufficient in consideration of heat resistance and material yield. If the height of the siding from the bottom floor is made large, shape retention and the strength increase by the ribs can be expected, but since the height of the siding from the bottom is high, the longitudinal stretching cannot be made large and the heat resistance is insufficient. However, there is a problem in that the heat resistance and the material yield are deteriorated due to problems such as a decrease in the content capacity of the above. The yield here is
It is the ratio of the internal volume to the raw material of the container.

[0006]

DISCLOSURE OF THE INVENTION According to the present invention, even if a high temperature content is filled, heat shrinkage or heat deformation does not occur outward due to the self weight of the content, and the shape retention property against internal pressure and the material yield are high. It is an object to provide a flexible plastic container.

[0007]

According to the present invention, as shown in FIGS. 1 and 2, by improving the bottom center to a concave shape (convex shape toward the floor), a vertical length for maintaining heat resistance is obtained. The purpose is to secure the degree of stretching and to secure the capacity of the container.The bottom of the stretch-molded plastic container has a recessed part formed in the container inward direction. A ring-shaped step portion having an outer peripheral R portion in the outward direction from the contacting annular bottom heel portion and an inward raised bottom surface from the bottom surface is provided, and a spherical wall rising inward from the step portion in a concave shape and the spherical wall. A heat-resistant plastic container comprising a continuous spherical wall having a convex shape in the bottom direction, and a plurality of concave-convex ribs formed on each spherical wall.

[0008]

In the bottom structure as described above, a ring-shaped step portion 4 which is raised inward from the bottom surface is provided, and a spherical wall 5 which rises inward from the step portion 4 in a concave shape, and a bottom portion which is continuous with the spherical wall 5 are provided. Since the spherical wall 6 has a convex shape in the direction, and the spherical wall 6 comes to the lower surface from the upper end of the raised spherical wall 5, it is possible to secure a vertical stretching degree and to increase the content capacity. It became possible.

The plurality of ribs formed on the raised spherical wall 5 and the spherical wall 6 prevent thermal contraction and thermal deformation of the high-temperature contents, and reduce the pressure generated during the cooling process of the high-temperature contents. The rib reinforcement effect also made it possible to absorb the deformation. Moreover, since the bottom structure is formed based on the uneven spherical wall as a base, it is possible to exert a strong effect against any internal pressure reduction or internal pressure increase.

The degree of stretching of the surface area forming the bottom is almost the same as in the case of FIG. 2, and a considerable portion becomes highly stretched, and heat resistance and strength are secured equally.

[0011]

Embodiments will be described in detail with reference to the drawings. FIG. 1 is a plan view of the bottom of one embodiment of the present invention.
FIG. 2 is a cross-sectional explanatory view taken along the line AA of FIG. 1. According to the bottom structure of the present invention, the recessed portion 1 is formed in the inward direction of the container, and the ring-shaped step 4 recessed inwardly of the container is provided from the bottom heel portion 2 that contacts the floor surface of the recessed portion 1. A concave spherical surface wall 5 and a spherical surface wall 6 which is continuous with the spherical wall 5 and is convex toward the floor surface. The spherical wall 5 and the spherical wall 6 are provided with a plurality of concave and convex ribs 7. It is a thing.

The heat-resistant plastic containers having the bottom shapes of the present invention and the conventional example (Japanese Patent Publication No. 4-20728) shown in FIGS. 1, 2 and 3 were molded under the same conditions, and the heat resistance was evaluated. As a molding material, a polyethylene terephthalate (RT543M) manufactured by Nippon Unipet Co., Ltd. was used to mold a 1.5 L round container by a biaxially stretch blow molding method.
After pouring hot water of 90 ° C. to 90 ° C. and capping and leaving it at room temperature, changes in the bottom height and changes in the full water capacity were examined with the container emptied.

The molding conditions for molding the container are shown in (Table 1), the outline of the container is molded in (Table 2), and the changes in the full water capacity and the bottom height are shown in Table 3 for each filling temperature.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

As is clear from the results of (Table 1), the bottom shape created this time has the effect of minimizing changes in the height of the bottom of the container and changes in the volume of the container.

Further, since the spherical wall 6 at the center of the bottom is formed in a convex shape in the floor direction, the stretching is good and the heat resistance at the bottom is sufficiently secured. Further, the spherical wall 5 and the spherical wall 6
Due to the strength effect of the plurality of uneven ribs 7 formed on the
Since the deformation is hardly reached, the bottom height (in a state where the contents are empty) with the contents open is hardly changed.

[0019]

As described above, in the heat-resistant plastic container of the present invention, the convex spherical wall 6 in the floor direction prevents heat shrinkage and thermal deformation of the bottom portion that occurs when the hot contents are filled. Further, the uneven ribs formed on the spherical wall 5 and the spherical wall 6 maintain rigidity and internal pressure strength, and can be used not only for high-temperature fillings but also for carbonated beverages related to internal pressure.

[0020]

[Brief description of drawings]

FIG. 1 is a plan view of a bottom portion of a heat resistant plastic container according to an embodiment of the present invention.

FIG. 2 is a cross-sectional explanatory view taken along the line AA of FIG.

FIG. 3 is a cross-sectional explanatory view of the bottom of a conventional heat-resistant plastic container.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Recessed part 2 ... Bottom part 3 ... Outer peripheral R part 4 ... Ring-shaped step 5, 6, 8 ... Spherical wall 7, 9 ... Rib

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiko Nakamura 1-5-1 Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd.

Claims (1)

[Claims] 1. A bottom portion of a stretch-molded plastic container,
In a bottom structure in which a recessed portion is formed in the container inward direction, an annular bottom heel portion in contact with the floor surface of the recessed portion has an outer peripheral R portion in an outward direction, and a ring-shaped step portion raised inward from a bottom surface is provided. A spherical wall that is provided in a concave shape rising inward from the step portion, and a spherical wall that is continuous with the spherical wall and that is convex toward the bottom, and each of the spherical walls is provided with a plurality of uneven ribs. Heat resistant plastic container to be.