JP2000229615A - Plastic bottle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress heat distortion at the time of heating without providing a complex form on a bottom. SOLUTION: A recess 3 which protrudes inside the plastic bottle 1 is formed on a bottom of the bottle 1, wherein hollow ribs 6 radially extending from the center of the recess 3 toward its periphery are formed to project outside the plastic bottle. The hollow rib 6 comprises a tip wall 7a standing steeply from a periphery of the center of the recess 3, both side walls 7b extending from both ends of the tip wall 7a toward the periphery of the recess 3 and a lower wall 7c connected with both side walls 7b and the tip wall 7a. The lower wall 7c is formed to extend approximately linearly to the periphery of the recess 3, and a half or more of portions surrounded by the side walls 7b of the hollow ribs 6 adjacent to the recess 3 are formed to be positioned on a plane in parallel with the lower wall 7c.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic bottle, and more particularly to a plastic bottle having a bottom structure suitable for a plastic bottle manufactured by biaxial stretch blow molding.

[0002]

2. Description of the Related Art In recent years, glass bottles have been widely used as containers for soft drinks, natural juice drinks and the like.
Bottles made of polyester resin such as polyethylene terephthalate are being used. Polyester resin bottles are lighter than glass bottles and have advantages in terms of impact resistance and safety in the event of breakage, but are inferior in heat resistance.

[0003] By stretching and blow molding a polyester resin bottle, the transparency and tensile strength are improved, and the oxygen permeability and moisture permeability are reduced to improve the performance as a bottle. Therefore, biaxially stretch blow molded bottles are often used. However, in a biaxially stretched blow-molded bottle, the resin at the bottom of the bottle tends to be insufficiently stretched.
If a high-temperature liquid is filled for sterilization or the like and heat treatment is performed after the filling, the load resistance of the bottom becomes insufficient and the bottle bottom is deformed.

[0004] In the case of a stretch blow-molded bottle, molding distortion remains, and even in a state where no load is applied, deformation occurs in a heated state in an attempt to eliminate the residual distortion. Therefore, various methods for suppressing thermal deformation of the bottom of a blow-molded bottle have been conventionally proposed or implemented. For example, as shown in FIG. 6 and FIG.
And a plurality of hollow ribs 52 protruding outward from the bottom of the plastic bottle are formed in the recess 51 so as to extend radially. The concave portion 51 has a substantially dome shape with a flat center, and the hollow rib 52 has such a shape that the protruding distance L from the peripheral surface of the concave portion 51 becomes maximum at the longitudinal center portion and the distance gradually decreases toward both ends. Is formed.

Further, Utility Model Registration Publication No. 2581837
As shown in FIGS. 8 to 10, as a bottom structure of the polyester resin bottle, a bottom heel portion 61, a concave portion 62 surrounded by the bottom heel portion 61, and a circle in the concave portion 62, as shown in FIGS. A plurality of first bulges 63 arranged in a ring and radially, a second bulge 64 formed between the bulges 63, and a center formed in the recess 62. There has been proposed one having a frusto-conical central recess 65 protruding so as to taper toward the inside of the bottle. First bulge 6
Numeral 2 has a truncated pyramid shape in which the head surface 63a rises from the surface of the recess 62 near the central recess 65. The first bulging portion 63 is formed such that a protruding distance L from the peripheral surface of the concave portion 62 becomes gradually smaller from the head surface 63a side. The second bulge 64 is the first bulge 6
It is formed smaller than 2. The recess 62 is formed in a substantially dome shape with a flat central portion.

[0006]

In the former prior art in which a plurality of hollow ribs 52 are provided radially in the concave portion 51, the load resistance of the bottom portion at the time of filling the liquid at a high temperature is still insufficient.

On the other hand, Japanese Utility Model Registration No. 2581837
In the bottom structure disclosed in the above-mentioned publication, the degree of stretching of the bottle bottom is increased by forming a smaller second bulging portion 64 between the first bulging portions 63, and the first bulging portion is also formed. By further forming the central recess 65 in the region surrounded by the circle, there is an effect of increasing the degree of stretching of the resin at the center of the bottle bottom. However, in this configuration, the structure of the bottle bottom becomes complicated, the processing of the mold becomes complicated, and the moldability (mold fidelity) deteriorates.

In the case of biaxial stretch blow molding of a polyester resin bottle, compressed air is injected while the test tubular preform is stretched in the axial direction with a rod called a stretch rod. However, in the shape having the truncated cone-shaped central recess 65, it is necessary to provide a projection corresponding to the central recess 65 at the center of the bottom of the mold, and the bottom of the preform guided by the extension rod is strongly against the projection. It is easy to wear when hit.

The present invention has been made in view of the above problems, and has as its object the purpose of providing a complicated shape at the bottom without providing a complicated shape at the bottom.
An object of the present invention is to provide a plastic bottle that can suppress thermal deformation during heating.

[0010]

In order to achieve the above object, according to the first aspect of the present invention, a recess is formed at the bottom of the bottle so as to protrude toward the inside of the bottle, and from the center of the recess to the periphery. A radially extending hollow rib is formed so as to protrude to the outside of the bottle, and the angle formed by the hollow rib from the periphery of the central portion of the recess to a plane perpendicular to the central axis of the bottle is a steeply slopeable die. And a side wall extending from both ends of the front end wall toward the periphery of the concave portion, and a lower wall continuous with the front end wall and the both side walls, wherein the lower wall is formed substantially linearly with the concave portion. , And formed so that at least half of the portion of the concave portion sandwiched between the side walls of the adjacent hollow rib is parallel to the lower wall of the hollow rib.

According to a second aspect of the present invention, in the first aspect of the present invention, a concave groove is formed on the entire periphery of a central portion of the concave portion, and a central convex portion that protrudes outward from the bottle is provided. Is formed.

According to a third aspect of the present invention, in the first or second aspect, the hollow rib has a width of 6 mm.
mm or more. Therefore, according to the first aspect of the present invention, the height (the distance between the upper and lower edges) of each side wall of each hollow rib that is continuous from both ends of the tip wall rising from the periphery of the center of the concave portion is equal to the height of the tip wall. The range that is almost the same as the height is larger than that of the conventional structure. as a result,
The degree of stretching of the side wall of the hollow rib is higher than that of the conventional structure, and the heat resistance and load resistance of the entire bottom of the bottle are improved.

According to a second aspect of the present invention, in the first aspect of the present invention, a portion corresponding to the concave groove formed over the entire periphery of the central portion of the concave portion functions as an annular rib. Min, the load resistance is improved.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the hollow rib is formed to have a width, that is, a distance between both side walls of 6 mm or more.
The mold fidelity is improved and the mold is easily removed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment in which the present invention is embodied in a plastic bottle made of polyester resin formed by biaxial stretch blow molding will be described below with reference to FIGS. FIG. 1 is a partial perspective view of a plastic bottle upside down as viewed from the bottom, and FIG. 2 is a bottom view. The plastic bottle 1 is formed to have a circular cross section, and a bottom portion 2 is formed with a concave portion 3 protruding inward of the plastic bottle 1 around the center of the plastic bottle 1.

As shown in FIG. 3, the concave portion 3 is formed in a substantially dome shape, and a central convex portion 4 that protrudes outward from the plastic bottle 1 is formed at the central portion of the concave portion 3. The protrusion amount of the central convex portion 4 is smaller than the depth of the concave portion 3. An annular concave groove 5 extending around the entire periphery of the central convex portion 4 is formed. A plurality (eight in this embodiment) of hollow ribs 6 extending radially around the central convex portion 4 are provided outside the plastic bottle 1 (downward).
It is formed so as to protrude.

The hollow rib 6 has a tip wall 7a rising from the periphery of the central convex portion 4, side walls 7b extending from both ends of the tip wall 7a toward the periphery of the concave portion 3, both side walls 7b and the tip wall 7a.
a and a lower wall 7c that is continuous with a. Side wall 7
b is formed in a linear shape whose upper edge and lower edge extend substantially in parallel. The lower wall 7c of the hollow rib 6 is formed so as to extend substantially linearly to the periphery of the concave portion 3. A portion sandwiched between the side walls 7b of the hollow rib 6 adjacent to the concave portion 3 is a central convex portion 4
The shifted portion is formed so as to be located on a plane parallel to the lower wall 7c, and more than half of the portion sandwiched between the side walls 7b is formed to be a surface parallel to the lower wall 7c.

As shown in FIG. 3, the angle θ between the end wall 7a and a plane orthogonal to the center axis of the plastic bottle 1 is formed.
Reference numeral 1 is formed to have a steep slope that becomes a punching taper that can be die-cut. The value of the angle θ1 is set in a range of 40 degrees or more and less than 90 degrees. The angle θ1 is preferably closer to 90 degrees in terms of heat resistance and load resistance. However, if the angle θ1 is closer to 90 degrees, it is disadvantageous in terms of releasability, and the upper limit is about 88 degrees. A smaller angle is better from the viewpoint of mold fidelity, but if the angle is too small, heat resistance and load resistance become insufficient. Therefore, the angle θ1 is 40 degrees or more and less than 90 degrees,
Preferably it is 60 degrees to 88 degrees. Further, considering that the load resistance and the heat resistance are sufficiently satisfied and that the mold fidelity is easily ensured, a more preferable range is 70 to 85 degrees. Also, the angle between the peripheral edge of the concave portion 3 and the plane perpendicular to the central axis of the plastic bottle 1 at the rising portion is formed larger than that of the conventional one.

As shown in FIG. 4, the hollow ribs 6 are formed so that their peaks 8a and valleys 8b located between the adjacent hollow ribs 6 are equally spaced. The angle θ2 at which the side walls 7b of the hollow rib 6 rise is equal to the angle θ.
As in the case of 1, the closer to 90 degrees, the better the heat resistance and load resistance. However, considering the releasability, about 70 to 88 degrees is appropriate.

The height H (see FIG. 3) and the width W of the hollow rib 6
The appropriate value of (see FIG. 4) varies depending on the size of the plastic bottle 1, but the height H is about 3 mm to 20 mm. For example, when the outer diameter of the plastic bottle 1 is about 85 mm, it is about 5 mm. If the width W is less than 6 mm, the fidelity of the mold is significantly deteriorated. On the other hand, if the width W is too large, the rib effect is impaired, so the upper limit is about 20 mm. That is, the width W is 6 mm or more.
It is preferably about 20 mm. Also, the diameter of the central convex portion 4 is preferably small, but if it is too small, the fidelity of the mold is deteriorated. Therefore, the diameter is preferably about 5 mm to 20 mm. For example, when the outer diameter of the plastic bottle 1 is about 85 mm, 14 m is used.
m.

The bottom heat resistance of the plastic bottle 1 constructed as described above was evaluated by the following evaluation method. Table 1 shows the results. As a comparative example, the same evaluation was performed for the conventional plastic bottles shown in FIGS. 6 and 7 having different shapes of the hollow ribs.

Evaluation method: (1) Measure bottom height Hb before filling. (2) Store at 40 ° C, 90% for 1 week. (3) After filling with warm water (73-76 ° C), let it cool naturally. (4) Measure the bottom height Ha after filling. In addition, the bottom height means a distance (shown by HB in FIG. 3) from the surface of the plastic bottle 1 where the bottom portion contacts to the lower surface of the central convex portion 4.

[0023]

[Table 1] As is evident from Table 1, the ratio (%) of the amount of bottom fall was 11 to 11 in each case in the prior art products evaluated as comparative examples.
In the case of the embodiment of the present invention, even when the temperature is 75 ° C. and 76 ° C., the bottom drop amount is particularly large when the temperature is 75 ° C. and 76 ° C. 7 ~
It was as small as about 8%, and it was confirmed that the heat resistance was significantly improved with respect to the conventional product.

This embodiment has the following effects. (1) The distal end wall 7a of the hollow rib 6 formed radially at the bottom of the plastic bottle 1 and the plastic bottle 1
The angle formed by a plane perpendicular to the center axis of the plastic bottle is steeply inclined so that the die can be removed, so that the function as a reinforcing rib of the front end face 7a is higher than that of a conventional plastic bottle.

(2) Since the height H of both side walls 7b is formed to be substantially the same as the height of the front end wall 7a up to the vicinity of the periphery of the concave portion 3, the side wall 7b is smaller than the conventional plastic bottle.
The area occupied by b increases, and the effect of increasing the degree of stretching at the bottom increases. Further, the height H of the side wall 7b is
Since it is almost constant in the longitudinal direction, stretching can be easily performed uniformly, and moldability is improved.

(3) Due to both the effects (1) and (2), even if the bottom of the plastic bottle 1 is not made to have a complicated shape, the effect of suppressing thermal deformation during heating, for example, the bottom of the plastic bottle 1 when filling a high-temperature liquid, The load resistance and the effect of suppressing thermal deformation when no load is applied are improved as compared with conventional products.

(4) Since the concave groove 5 is formed on the entire periphery of the central convex portion 4 formed at the center of the concave portion 3, the portion corresponding to the concave groove 5 functions as an annular rib,
The load resistance is improved accordingly. Also, the tip of the stretch rod used when manufacturing the plastic bottle 1 by biaxial stretch blow molding fits in a predetermined position corresponding to the central convex portion 4 of the preform, thereby playing a role of preventing displacement.

(5) Since the hollow rib is formed to have a width W of 6 mm or more, the fidelity of the mold is improved and the die is easily removed. (6) Since the diameter of the central convex portion 4 is 5 to 20 mm, the tip end surface 7a of the hollow rib 6 is located near the center of the concave portion 3, and the load resistance at the bottom center of the plastic bottle 1 is reduced. improves.

The embodiment is not limited to the above, and may be embodied as follows, for example. The shape of the plastic bottle 1 is not limited to a circular cross section, but may be a polygon such as a triangle, a quadrangle, a hexagon, or an octagon, or an ellipse. In this case, the shape of the concave portion 3 and the central convex portion 4 may be a truncated cone shape instead of a truncated polygonal pyramid shape corresponding to the outer shape of the plastic bottle 1. For example,
In the case of a plastic bottle 1 having a square cross section, FIG.
The concave portion 3 and the central convex portion 4 may have a truncated cone shape as shown in FIG. 5A, or the concave portion 3 and the central convex portion 4 may have a truncated square pyramid shape as shown in FIG. However, the truncated cone shape has better moldability.

The hollow ribs 6 do not need to be arranged such that the peaks 8a and the valleys 8b are arranged at the same interval, or that all the hollow ribs 6 have the same shape. For example, the pitch of the peaks 8a may be different from the pitch of the valleys 8b, or hollow ribs 6 having different widths may be mixed and provided. When the diameter of the plastic bottle 1 is small, it is preferable that the number of the hollow ribs 6 is smaller than that of the plastic bottle 1 having a large diameter.

The number of the hollow ribs 6 is not limited to eight.
May be appropriately changed to 9 or more or 7 or less depending on the size of. For small plastic bottles, it is preferable to reduce the number of hollow ribs 6 from the viewpoint of mold fidelity.

A concave groove 5 formed around the central convex portion 4
May be omitted. The material of the plastic bottle 1 is not limited to a polyester resin such as polyethylene terephthalate, but may be polypropylene or polyacrylonitrile.

The inventions (technical ideas) other than those described in the claims which can be grasped from the above embodiments will be described below together with their effects. (1) In the invention described in claim 1, the bottle is made of a polyester resin. In this case, when a plastic bottle made of polyester resin, which has been used as a plastic bottle for beverages, is manufactured by biaxial stretch blow molding,
The moldability is improved, the structure of the mold is simplified, and the thermal deformation of the plastic bottle during heating can be suppressed.

(2) In the first aspect of the present invention,
The angle formed between the tip wall and a plane orthogonal to the central axis of the bottle is 70 to 85 degrees. In this case, load resistance and heat resistance are sufficiently satisfied, and mold fidelity is easily ensured.

(3) In the first aspect of the present invention,
The central projection has a diameter of 5 to 20 mm.
In this case, the load resistance at the center of the bottom of the plastic bottle is improved.

[0036]

As described in detail above, claims 1 to 3 are described.
According to the invention described in the above, without providing a complicated shape at the bottom,
Thermal deformation at the time of heating can be suppressed, and the load resistance of the bottom at the time of filling a high-temperature liquid is improved.

According to the second aspect of the present invention, the portion corresponding to the concave groove functions as an annular rib, and the load resistance is improved accordingly. In addition, the stretch rod used when manufacturing plastic bottles by biaxial stretch blow molding,
It also plays a role in preventing the preform from deviating from a predetermined position corresponding to the central convex portion.

According to the third aspect of the present invention, the mold fidelity is improved and the mold is easily removed.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a bottom of a plastic bottle according to an embodiment.

FIG. 2 is a bottom view of a plastic bottle.

FIG. 3 is a vertical cross-sectional view of the bottom of a plastic bottle.

FIG. 4 is a schematic end view taken along line AA of FIG. 2;

FIG. 5 is a bottom view of another embodiment.

FIG. 6 is a perspective view showing the bottom of a conventional plastic bottle.

FIG. 7 is a longitudinal sectional view of the bottom of the same plastic bottle.

FIG. 8 is a perspective view showing the bottom of another conventional plastic bottle.

FIG. 9 is a sectional view of the same.

FIG. 10 is a partially broken perspective view of the same.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Plastic bottle, 2 ... Bottom part, 3 ... concave part, 4 ... Central convex part, 5 ... Concave groove, 6 ... Hollow rib, 7a ... Tip wall, 7b
... side wall, 7c ... lower wall.

Claims (3)

[Claims] 1. A concave portion which protrudes to the inside of the bottle is formed at the bottom of the bottle, and a hollow rib extending radially from the center of the concave portion to the periphery is formed so as to protrude to the outside of the bottle. A tip wall that rises from the periphery of the center of the recess to a plane perpendicular to the central axis of the bottle so as to form a steep slope that can be cut out, and sidewalls extending from both ends of the tip wall toward the periphery of the recess. And a lower wall continuous with the end wall and the side walls, wherein the lower wall is formed so as to extend substantially linearly to the periphery of the concave portion,
A plastic bottle wherein at least half of a portion of the concave portion sandwiched between side walls of the adjacent hollow ribs is formed so as to be parallel to a lower wall of the hollow rib. 2. The plastic bottle according to claim 1, wherein a concave groove is formed around the entire periphery of the central portion of the concave portion, and a central convex portion that protrudes outward from the bottle is formed. 3. The plastic bottle according to claim 1, wherein the hollow rib has a width of 6 mm or more.