JPH11152123A - Drawn resin container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drawn resin container wherein the bottom part can be made light, the bottom part is excellent in heat-resistance, pressure-resistance, stress crack-resistance, and hygroscopicity resistance or the like, and the axial load strength and the anti-impact strength or the like of the container are improved by a method wherein for a self-supporting container having valley-form parts and leg parts which are alternately arranged on the peripheral edge of the bottom, the bottom part is effectively orient-crystalized under a highly drawn- oriented state, including a gate remaining part, and in addition, at least at one part of the bottom valley part, a band-form thicker part under a highly drawn-oriented state which is peripherally arranged is formed, and at the same time, a thickness reduction of the bottom leg part corresponding with the band-form thicker part, is suppressed. SOLUTION: For a self-supporting container equipped with a mouth part 1, a shoulder part 2, a body part 3 and a bottom part 4 having a plurality of leg parts 7 and valley-form parts 6, which are formed of a resin by a biaxial draw-blow-molding, the body part 3 and the bottom part 4 have a highly drawn-oriented layer including a gate remaining part 8 at the bottom center, and also, at least at one part of the bottom valley part 6, a band-form thicker part under a highly drawn-oriented state, which is peripherally arranged, is provided, and at the same time, a reduction of the thickness is suppressed at the bottom leg part 7 which corresponds with the band-form thicker part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a self-standing structure consisting of a valley and a foot at the bottom, has excellent heat pressure resistance, improved rupture strength and axial load strength, and further has impact resistance. And a stretched resin container having excellent stress cracking resistance and moisture absorption resistance.

[0002]

2. Description of the Related Art Polyethylene terephthalate (PET)
The biaxially stretched blow-molded container made of thermoplastic polyester has excellent transparency and surface gloss, and also has the necessary impact resistance, rigidity, and gas barrier properties for bottles. That is, it is used as a bottle.

In this biaxially stretch blow molded container,
The body wall of the body is in a highly stretched orientation, which helps to increase the heat resistance, impact resistance, transparency and gas barrier properties of the container, but the problem is that the bottom is fully stretched However, this causes a decrease in heat resistance, a decrease in pressure resistance, a decrease in impact resistance, and a decrease in self-standing stability of the container.

That is, if there is an unoriented or low-oriented portion at the bottom of the container, this portion will undergo creep deformation under the influence of pressure or further heat, and not only will the heat resistance, pressure resistance, etc. decrease, but also the autonomous container In this case, the bulging deformation of this portion reduces the self-standing stability of the container. In addition, the unoriented or low-oriented portion is naturally brittle as compared with the highly-oriented portion, and reduces the drop impact at the bottom and the like.

[0005] In a biaxially stretched blow-molded container, handling the unoriented or low-oriented portion at the bottom of the container is a troublesome problem. Fixed and thermal crystallization is performed.

[0006] Japanese Patent Application Laid-Open No. 8-267549 discloses a container having a petaloid bottom which has a thick thermal crystallization portion at the center of the bottom, is thinned around the periphery in a highly stretched state, and is heat-fixed. Has been disclosed.

Further, the bottom of the container is stretched as high as possible,
Unaligned portions or low-oriented portions are also made as small as possible.

Japanese Patent Application Laid-Open No. 57-8123 discloses a method for producing a hollow container by forming a preform from polyethylene terephthalate and then biaxially stretch-blowing to reduce the low orientation portion. The preform is
In one or both of a portion corresponding to the shoulder of the container and a portion corresponding to the vicinity of the bottom of the container, the thickness of the portion is determined by the following formula (1), (2) t ₂ ≦ t ₁ ‥ (1) 0.5 ≦ t ₂ / t ₃ ≦ 0.8 ‥ (2) In the formula, the thickness of the preformed body corresponding to the lower end of the mouth of the t ₁ container; or the thickness of the bottom center of the preform, the wall thickness of the preform portion corresponding to the bottom periphery of the site or container which corresponds to the shoulders of the t ₂ containers, the portion corresponding to the barrel of t ₃ containers preliminary A method for producing a hollow container characterized by having a shape satisfying the thickness of a molded article is described.

[0009] Japanese Patent Laid-Open No. Hei 9-118 based on the proposal of the present inventors
No. 322 discloses a self-supporting container having a mouth, a neck, a shoulder, a torso, and a plurality of valleys and a foot formed by biaxial stretch blow molding of a resin. The bottom excluding the bottom center is thinned to a thickness of 1 mm or less, is crystallized in a relatively high stretched state with a crystallinity of 20% or more, and the diameter Dc of the bottom center is the body diameter D0. A self-supporting container having excellent heat and pressure resistance characterized by being within the range of 1 to 20% of the preform, wherein the preform heated to the stretching temperature was inserted into the preform in a mold. The center of the bottom of the preform is sandwiched between the stretching rod and the press rod outside the preform. Then, while driving the stretching rod, high-pressure gas is simultaneously blown into the inside of the preform, and the bottom is kept until just before the stretching process is completed. Central temperature drop of 40 A biaxial stretch blow molding is performed while maintaining the temperature within a temperature of not more than 0 ° C., thereby forming a secondary molded product having a generally dome-shaped bottom portion, which is relatively thin and stretched except for the center portion of the bottom portion. At least a bottom part of the article and a part of a body part connected to the bottom part are heat-shrinked to form a tertiary molded article.
A method for producing a self-supporting container excellent in heat and pressure resistance, characterized in that a secondary molded product is subjected to secondary blow molding in a mold to form a final container.

[0010]

However, in the above-mentioned prior art thermal crystallization method, the thermal crystallization portion at the center of the bottom of the container is
It is obtained by heating and thermally crystallizing the bottom of the preform, and requires a complicated heating step.

A preform used for manufacturing a stretch blow-molded container is manufactured by injection molding of a resin.
A gate is always connected to the center of the bottom of the preform. The gate section performs a trimming operation or a finishing operation of cutting out the surplus. However, such a trimming operation or a finishing operation is a troublesome process, and has a problem in accuracy that it is not always easy to make a cutout size constant. In particular, if the length of the gate portion is made to be as close as possible to zero in consideration of the moldability of the container bottom, a finishing operation such as polishing is required after the trimming operation, and the number of steps is increased, which is more troublesome. On the other hand, if the remaining gate remains in the preform for a little longer time, the remaining gate has a large volume, and this portion becomes significantly embrittled by thermal crystallization, and the embrittled portion occupies a considerable portion of the bottom of the petaloid. There is a problem that the impact resistance is reduced. Further, the bottom portion in the low stretch orientation state is whitened by thermal crystallization, but there is also a problem that if the region becomes too wide, it is not preferable from an aesthetic point of view.

On the other hand, in the prior art bottom high stretching method,
It is possible to stretch a significant portion of the bottom high,
There is a problem that an unoriented or low-oriented portion still exists in the remaining gate at the bottom center. Further, in the above-described method of using the preform in which the portion corresponding to the bottom periphery is thinned, there is also a problem that the axial load strength of the container is reduced due to the thinning around the bottom of the container.

The present inventors have proposed a biaxial stretch blow molding means for making the bottom of a petaloid highly stretched and oriented without thermally crystallizing the bottom of the preform and effectively utilizing the remaining gate of the preform. Was studied diligently. as a result,
It has been found that the stretch forming of the bottom portion in the blow molding is performed remarkably from the time when the gate portion, which is the center of the bottom of the molded product, reaches the bottom of the mold. Then, by adopting means for reducing the temperature drop in the bottom center portion and the vicinity thereof at the time when the bottom center portion of the molded body reaches the mold bottom portion to a certain level or less, the entire bottom portion, including the remaining gate, It has been found that a layer can be formed into a highly stretched orientation state. Furthermore, by using a preform of a specific size and shape, a band-shaped thick portion in a high stretch orientation state arranged circumferentially is formed on at least a part of the bottom valley portion, and the band-shaped thick portion corresponding to the band-shaped thick portion is formed. It has been found that a decrease in the thickness of the sole foot can be suppressed, and thereby various properties of the container can be significantly improved.

That is, an object of the present invention is to provide a self-supporting container having valleys and feet alternately arranged around the bottom, wherein the bottom, including the rest of the gate, is effectively oriented to a high stretch orientation state. Crystallized, furthermore, at least a part of the bottom valley portion is formed with a belt-like thick portion in a high stretch orientation state circumferentially arranged, and a decrease in the thickness of the bottom foot portion corresponding to this belt-like thick portion is suppressed. By doing, it is possible to reduce the weight of the bottom,
An object of the present invention is to provide a stretched resin container excellent in heat-resistant pressure resistance, stress crack resistance, moisture absorption resistance, and the like at the bottom, and having improved axial load strength, impact resistance, and the like.

[0015]

According to the present invention, a mouth, neck, shoulder, and shoulder formed by biaxial stretch blow molding of a resin are provided.
In a self-supporting container having a torso and a bottom having a plurality of feet and a valley, the torso and the bottom have a highly stretched orientation layer including a bottom center gate remainder, and A stretched resin container having a strip-shaped thick portion in a highly stretched orientation state arranged at least in part in a circumferential shape and a decrease in thickness at a bottom foot corresponding to the strip-shaped thick portion is suppressed. Is provided. In the container of the present invention: In a space defined by a virtual frustoconical surface including a perpendicular to the inner peripheral edge of the band-shaped thick portion of the bottom trough and a virtual frustoconical surface including a perpendicular to the outer peripheral edge of the band-shaped thick portion, 1. The band-like thick portion of the bottom valley and the bottom foot are provided in a positional relationship including the tip of the foot. 2. the thickness of the band-shaped thick portion is in the range of 0.45 to 1.1 mm; 3. The decrease in thickness is suppressed so that the thickness of the tip of the sole is maintained at 0.17 mm or more; 4. The degree of crystallinity accompanying the orientation of the highly stretched orientation layer is 20% or more; 5. The thickness of the portion excluding the bottom center gate remaining portion and the vicinity thereof is 1.1 mm or less; 6. the bottom center gate remainder is composed of a high-stretch alignment layer and a low-stretch alignment layer; Preferably, the bottom is heat-set with a crystallinity of at least 25% and substantially transparent except for the bottom center gate remnant.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The stretched resin container of the present invention has a mouth, a neck, a shoulder, a trunk, a bottom having a plurality of feet and a valley formed by biaxial stretch blow molding of resin, and has a self-supporting property. But the body and bottom have a high stretch orientation layer including the bottom center gate remnant, and a high stretch orientation state circumferentially disposed in at least a portion of the bottom valley. It is a remarkable feature that the band-shaped thick portion and the bottom foot corresponding to the band-shaped thick portion are prevented from decreasing in thickness.

In the present specification, the bottom center gate remaining portion means a gate portion projecting from the bottom center at the time of injection molding of a preform, and the thickness of the bottom center of the container corresponding to the gate portion in the thickness direction. Refers to the whole part.

In the container of the present invention, first, since the body and bottom of the container have a highly stretched orientation layer including the bottom center gate residue, the pressure resistance at a high temperature of about 70 ° C., that is, the heat resistance pressure resistance is high. And has excellent heat and pressure resistance. In general,
The heat resistance at the bottom of the container can be evaluated by the yield load at 70 ° C. The container of the present invention measures 25 kgf /
cm, more preferably 30 kgf / cm or more. The yield load value at 70 ° C was calculated by calculating the yield load value when a standard test piece was prepared from the bottom center valley including the rest of the gate, and the standard test piece was subjected to a tensile test at a temperature of 70 ° C per 1 cm width. It can be obtained as a value converted to. This yield load value at 70 ° C. takes into account the thickness of the bottom of the container. By calculating the yield load value at 70 ° C. at the center of the bottom including the rest of the gate where the largest deformation force acts, the heat resistance of the bottom of the container is obtained. Pressure can be evaluated.

Furthermore, in this container, since it is highly stretch-oriented, including not only the trunk, bottom valleys and feet, but also the bottom center gate remnants, it is self-sustaining, impact resistant and stress resistant. It is excellent in cracking properties and the like, and the weight of the bottom can be reduced as compared with conventional containers.

It has been found that the stretch forming of the bottom portion in the blow molding is remarkably performed from the time when the gate portion, which is the center of the bottom of the preform, reaches the bottom of the mold. In the present invention, by adopting a means for reducing the temperature drop in the bottom center portion and the vicinity thereof at the time when the bottom center portion of the molded body reaches the mold bottom portion to a certain level or less, the bottom portion, including the remaining gate, is included. It can be thinned to a highly stretched orientation state.

The remaining gate in the stretch blow-molded container is one of the troublesome problems. If this portion remains in an unstretched thick state, creep deformation occurs under the condition that heat and pressure are applied simultaneously. Therefore, the conventional idea was to thermally crystallize this portion in a preform state, or to make the remaining gate portion as thin as possible to facilitate stretching orientation. Even with meat, a high-stretch orientation layer can be formed at the center by the above-described means, and the above problem has been solved.

In the present invention, the shape of the preform, the thickness of the bottom portion, and the blow molding conditions are adjusted to optimize the stretch ratio of the bottom portion of the preform during blow molding, particularly the stretch ratio of the peripheral portion of the gate in contact with the remaining gate. By doing so, even when the bottom center gate remaining portion of the container is thick, the surrounding gate peripheral portion can be highly stretch-oriented, and a high stretching orientation layer can be formed on the remaining gate.

Further, in the container of the present invention in which the peripheral edge of the bottom center gate is in a high stretch orientation state as described above, surprisingly, the high stretch orientation section or the high stretch orientation section and the low stretch orientation It was found that an oriented portion was present, and that the high stretch oriented portion of the remaining gate was layered, and had a structure continuously connected to the gate periphery in the high stretch orientation state.

The above-mentioned structure of the bottom center gate remaining portion has a structure in which the periphery of the bottom gate portion of the preform corresponding to the bottom center gate remaining portion is made to have a high stretch orientation state at the time of blow molding, so that the bottom gate portion can be formed in the thickness direction. The drawing shows that the portion is stretched by its highly stretched surroundings and locally stretched orientated to form a layered highly stretched orientated portion.

Generally, in the bottom center gate remainder, there is a low stretching orientation part together with the high stretching orientation layer, and this low stretching orientation part exists independently of the high stretching orientation part in the gate remainder. Since the layered structure of the highly stretched orientated portion and the continuous layered structure continuously connected to the gate connection portion and the gate peripheral portion in the highly stretched and aligned state are not broken at all, it does not become a hindrance factor such as heat resistance and pressure resistance.

As described above, the container of the present invention has a body portion and a bottom portion having a highly stretched orientation layer including a bottom center gate remaining portion, and is disposed circumferentially on at least a part of the bottom valley portion. It is a remarkable feature that it has a band-shaped thick portion in a highly stretched and oriented state, and that a decrease in thickness is suppressed at a sole foot portion corresponding to the band-shaped thick portion.

Generally, at the bottom of the self-supporting stretched resin container, the bottom center gate remaining portion has the largest thickness, and the thickness gradually decreases outward in the radial direction, that is, from the center to the connection portion with the body. In particular, in a foot portion formed so as to protrude outward compared to a valley portion, a decrease in the thickness tends to be particularly remarkable.

On the other hand, in the present invention, a high stretching band-like thick portion which is circumferentially arranged is provided in a valley located near the bottom. This band-shaped thick portion is derived from an annular thick portion existing at the bottom of the container at the stage of molding, but at the bottom foot projecting outward from the valley, this annular thick portion is formed. The part acts to suppress a decrease in the thickness of the sole foot. That is, in the bottom foot portion, since the portion of the annular thick portion is blow-extended further outward than the bottom trough portion, the portion corresponding to the annular thick portion is further stretched and thinned. Thus, the decrease in the thickness is suppressed as compared with the case where no is present.

The bottom valley and the foot in the present invention naturally have a molecular orientation due to high stretching. However, the bottom valley has an increased wall thickness, and the bottom valley has a thick wall. Since the decrease is suppressed, the rigidity of the valley and the foot is remarkably improved, so that the burst strength of the container is generally 10 kgf.
/ Cm ² or more, and the axial load strength of the container is 30 kg.
f or more.

The existence of the band-shaped thick portion in the bottom valley portion can be confirmed by obtaining the thickness distribution from the center to the periphery of the bottom valley portion. There is at least one peak where has a maximum value, or there is a shoulder with a relatively flat thickness. FIG. 4 of the accompanying drawings shows the thickness distribution at the bottom of one example of the stretched resin container of the present invention.

Generally, between the remaining bottom center gate and the band-shaped thick portion, which are the thickest, there are portions whose thickness is smaller than these. This is because, as already pointed out, the high stretch around the bottom center gate remnant results in the formation of a high stretch orientation layer in the bottom center gate remnant.

In the present invention, the band-shaped thick portion provided for the bottom valley portion suppresses the thickness of the foot portion, but this band-shaped thick portion is the thinnest portion of the foot tip portion which is most likely to be thinned. It must be able to prevent the conversion. For this,
In a space defined by a virtual frustoconical surface including a perpendicular to the inner peripheral edge of the band-shaped thick portion of the bottom trough and a virtual frustoconical surface including a perpendicular to the outer peripheral edge of the band-shaped thick portion, It is best to provide the band-shaped thick portion of the bottom trough and the bottom foot portion in the positional relationship including the tip portion of the foot portion.

From the viewpoint of preventing the thickness of the tip of the bottom foot portion from becoming thin and performing high stretching orientation, the thickness of the band-shaped thick portion at the bottom valley portion is 0.45 to 1.1 mm. When the thickness of the band-shaped thick portion is less than the above range, the tip portion of the foot tends to be thin, and the axial load and burst strength tend to decrease. On the other hand, if it exceeds the above range, a low-stretch orientation portion will be formed in a part of the band-shaped thick portion, and as a result, the heat-resistant pressure resistance of the valley tends to decrease. Further, the low-stretched oriented portion is not preferable because it tends to whiten by heat setting.

In the present invention, by adopting the above-mentioned means, the thickness of the tip portion of the foot, which is easily reduced in thickness, is generally set to 0.1.
It can be maintained at 17 mm or more, preferably 0.2 mm or more, whereby the axial load and burst strength can be improved to the above-mentioned ranges.

In the present invention, since the body and the bottom have a highly stretched orientation layer including the bottom center gate residue, the thickness of the portion excluding the bottom center gate remainder and the vicinity thereof is 1.1.
mm, preferably 1 mm or less, and this portion has an oriented crystallinity of 20% or more. If the stretch thinning and oriented crystallization have been performed as described above, satisfactory results can be obtained with respect to creep resistance, impact resistance, and stress cracking resistance at high temperatures, and the weight of the container bottom can be reduced. It is possible to do.

In the heat-resistant and pressure-resistant self-standing container of the present invention, the highly stretched orientation layer at the bottom is preferably heat-fixed, and the heat-stretched highly stretched orientation layer generally has a crystallinity of 30 to 55%. Have. The heat set bottom is substantially transparent except for the bottom center gate remnant.

The bottom center gate remainder in the container of the present invention is highly stretched and thinned, and the high stretch orientation layer formed on this gate remainder is different from the high stretch orientation layer formed on other portions of the bottom. It is likewise transparent, generally from 0.4 to 1.
It has a thickness of 1 mm and an oriented crystallinity of 20% or more. In the case of heat setting, the bottom center gate residue is generally 3
Although it has a degree of crystallinity of 0 to 55%, if there is a low-stretch orientation portion in the remaining bottom center gate, this portion tends to whiten.

The container of the present invention is not limited to the above, but includes a step of primary-blowing a bottomed preform into a secondary molded article, and a step of heat-shrinking the secondary molded article to form a tertiary molded article. It is manufactured through a process of forming a molded product and a process of forming a final product having a valley portion and a foot portion alternately around the bottom by subjecting the tertiary molded product to secondary pro-molding and molding, and as a bottomed preform, The preform is manufactured by using a preform in which the bottom shoulder portion is thicker than the gate peripheral portion and the body portion, and furthermore, the above-mentioned band-shaped thick portion is formed in the bottom valley portion. The preform used has a gate portion at the center of the bottom, but the temperature at the center of the bottom is kept within 40 ° C. until immediately before the stretching process is completed, and a high stretch is applied to the remaining bottom gate of the molded article. It is preferable to form an alignment layer.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Container of the Present Invention] In FIGS. 1 (partial sectional side view) and FIG. 2 (enlarged bottom view) showing a heat-resistant pressure-resistant container of the present invention, this container is formed by biaxial stretch blow molding of a resin. It comprises a mouth-neck portion 1, a shoulder portion 2 connected to the mouth-neck portion, a torso portion 3 and a bottom portion 4. In this example, the bottom 4
Is composed of a plurality of valleys 6 and feet 7 alternately arranged around the bottom center valley 5 and the bottom center valley. The lower part of the trunk 3 connected to the bottom 4 has a diameter D ₀ , and at the bottom center,
There is a bottom center gate remnant 8 of diameter Dg. The bottom central valleys 5 and 6 are located on a smooth curved surface that is convex downward. The shoulder portion 2 and the trunk portion 3 are thinned in a highly stretched orientation state except for a connection portion with the mouth and neck portion 1.

The bottom portion 4 has a thick gate remaining portion 8 located at the center of the bottom, a gate connecting portion 9 in contact with the gate remaining portion 8, and a gate around the gate connecting portion and inside the base of the foot portion 7. It comprises a bottom central valley portion 5 constituted by a peripheral portion 10 and a bottom peripheral portion in which a plurality of valley portions 6 and feet 7 are alternately formed. In the container of this specific example,
Each part (10, 6, 7) of the bottom part 4 except the gate remaining part 8 consists substantially only of a layer in a highly stretched orientation state. In addition, except for the gate remaining portion 8 and the gate connecting portion 9, 1.1 m
m or less. These highly stretched orientation layers have an orientation crystallinity of 20% or more.

The foot portion 7 protrudes downward (outward) from the valley portion 6 and has a tip portion 13 and a ground contact portion 14.
The valley portion 6 has a band-shaped thick portion 15 in a highly stretched state arranged circumferentially.

[Bottom Center Gate Remaining] Although the bottom center gate remaining portion 8 of the container of the present invention is relatively thick, as shown in the bottom center enlarged cross-sectional view of FIG. 11 and a combination of a low-stretch orientation unit 12. Normally, the high stretch orientation portion 11 of the gate remainder 8 consists of a continuous layer traversing the gate remainder and is connected to the gate rim 10 extending around the gate remainder. As a result, in the container of the present invention, the bottom 4 is covered with the continuous high-stretch orientation layer.

In a preferred arrangement of the high-stretch alignment layer, the bottom center gate remainder 8 comprises a generally transparent high-stretch alignment layer 11 on the inside surface of the container and a generally whitened low-stretch low-alignment layer 12 on the outside surface of the container. ing. In the bottom center gate remaining portion 8 of the heat-resistant stretched resin container, the high stretch orientation layer 11 is present on the inner surface side, so that the combination of heat resistance and impact resistance is particularly excellent.

In another example of the arrangement of the high-stretch alignment layer, the bottom center gate remainder 8 comprises a generally transparent high-stretch alignment layer located at the center in the thickness direction, and a whitened low-stretch low-alignment layer on both the inner and outer sides. May be provided. This laminated structure is a so-called rigid-soft-rigid laminated structure, and is particularly excellent in dimensional stability at the bottom under high temperature and high pressure.

In addition, even if it has a structure composed of a generally transparent high-stretch alignment layer on the inner surface side of the container and a generally whitened low-stretch low-alignment portion on the outer surface side of the container, the high-stretch alignment layer 11 is very thick. The low-stretch low-orientation portion 12 may be formed thinly at a very limited portion such as the center of the gate or the periphery of the gate. In this structure, the increase in the bottom yield load due to the increase in the thickness of the high stretch orientation layer 11 is remarkable.

High stretch orientation portion 11 of bottom center gate remaining portion 8
In general, it is preferable from the viewpoint of heat-resistant pressure resistance and impact resistance that the crystallized product be oriented at a crystallinity of 20% or more, preferably 25% at the time of blow molding.

By thermally fixing the bottom including the bottom center gate residue, the low-stretch orientation layer 12 of the gate residue 8 is thermally crystallized and whitened to increase the degree of crystallinity. On the other hand, thermal crystallization proceeds while the highly stretched orientation layer 11 of the remaining gate 8 remains substantially transparent. In this case, the low-stretched alignment layer 12 remaining as the whitened gate remains at the center of the bottom of the container, but its size is limited, and there is no particular aesthetic problem.

In the heat-fixed bottom center gate remainder 8, the low-stretch alignment layer 12 has a crystallinity of 20% or more, especially 25% or more, and the high-stretch alignment layer 11 has a crystallinity of 25% or more. Is preferred.

The thickness of the bottom center gate remaining portion 8 is usually preferably about 1.4 to 3.5 mm at the maximum portion. According to the present invention, the bottom portion of the bottom of the preform does not need to be finished. The bottom of the container can be formed with the remaining gate being highly oriented. On the other hand, the thickness of the high-stretch alignment layer 11 in the bottom center gate remaining portion 8 may be any thickness that imparts sufficient heat resistance to the bottom center.
5 mm or more, especially in the range of 0.4 to 1.1 mm,
Preferably, the gate occupies at least 20%, particularly at least 30%, of the total thickness of the remaining gate.

The diameter Dg of the bottom center gate remaining portion 8 is the body diameter D
0.25 times or less of ₀ , especially 0.2 times or less,
The presence of the remaining gate is inconspicuous, which is preferable in terms of the appearance characteristics of the container.

[Band-shaped Thick Portion] At the bottom of the container of the present invention, the thickness and crystallinity of each portion of the bottom 4 are within the ranges described above. And a strip-shaped thick portion 15 in a highly stretched orientation state disposed at the same position.

In FIG. 4 showing the relationship between the positions of the valley central portions 10 and the valley portions 6 of the container of the present invention and the distribution of the thickness, the bottom center gate remaining portion 8 has the largest wall thickness, and the body portion 3 has the largest thickness. Although it is the smallest, there is a portion where the thickness increases at a part of the valley portion 6 and has a maximum value of the thickness.

The strip-shaped thick portion 15 oriented to high stretch orientation provided for the bottom valley 6 has the effect of increasing the heat-resistant pressure resistance of the valley. Further, the band-shaped thick portion 15 suppresses the thinning of the foot 7, particularly the tip 13 of the foot, and is provided in a specific positional relationship described below. That is, FIG.
As shown in FIG. 5, a virtual frustoconical surface including a perpendicular line P to the inner peripheral edge of the band-shaped thick portion 15 of the bottom valley portion 6 and a virtual frustoconical surface including a perpendicular line Q to the outer peripheral edge of the band-shaped thick portion 15 In the space defined by the above, the band-shaped thick portion of the bottom trough and the bottom foot portion are provided in a positional relationship including the tip portion 13 of the bottom foot portion. Since the foot tip 13 is formed of the same thick part located on the same circumference as the belt-shaped thick part 15 of the bottom trough, the thinning of the foot tip 13 is suppressed.

Improving the strength of the bottom trough and the tip 13 of the bottom foot
From the viewpoint of preventing the thickness of the belt-like thick part, the thickness of the belt-like thick part 15 in the bottom trough preferably has a thickness of 0.45 to 1.1 mm, and the thickness of the belt-like thick part 15 is in the above range. When the ratio is less than the above range, the tip of the foot tends to be thin, and the axial load and the burst strength tend to decrease. On the other hand, if it exceeds the above range, a low-stretch orientation portion will be formed in a part of the belt-like thick portion 15, and consequently, the heat-resistant pressure resistance of the valley tends to decrease. Further, the low-stretched oriented portion is not preferable because it tends to whiten by heat setting.

In the present invention, by adopting the above-mentioned means, it is possible to maintain the thickness of the foot tip portion 13 which is easily thinned to generally 0.17 mm or more, preferably 0.2 mm or more. The axial load and burst strength can be improved to the above-mentioned ranges.

The maximum value of the thickness of the band-shaped thick portion 15 of the valley 6 is
T₆, The thickness of the lower part of the trunk 3 connected to the bottom 4 is T_FourAnd
The thickness of the peripheral portion 10 of the_FiveThen, in general, T₆> T_Four And T₆≧ T_Five, Especially T₆> T_Five It is. From the standpoint of improving burst strength and axial load strength,
T₆> T_FourHas a thickness ratio of 1.3 to 3.5, particularly 1.5
To 3, especially 1.6 to 3, and T₆> T
_FiveHas a thickness ratio of 1 to 2.2, particularly 1.1 to 2.
Is preferred.

The width d of the band-shaped thick portion 15, that is, the width between the rising portions of the thickness varies depending on the size and shape of the bottom of the container. This is preferable in terms of improving the heat resistance and the pressure resistance of the valleys.

[Gate Peripheral Part] The gate peripheral part 10 is 1 m
Even when the thickness slightly exceeds m or more, it is possible to maintain a high stretch orientation state. The thickness of the gate connecting portion is preferably in the range of 0.3 to 1.1 mm, particularly preferably 0.35 to 1.0 mm, in order to effectively form the highly stretched orientation layer 11 on the remaining gate 8.

If the thickness of the gate peripheral portion 10 is less than 0.3 mm, the thickness becomes too thin, and the heat resistance at the bottom center is lowered, which is not preferable. On the other hand, when the thickness of the peripheral portion of the gate at the stage of blow molding exceeds 1 mm, it becomes difficult to form a highly stretched orientation layer on the remaining gate. However, in the case where the thickness of the peripheral portion of the gate exceeds 1 mm in a narrow portion where the thickness is extremely limited, it does not prevent the part of the rest of the gate from being highly stretch-oriented.

As described above, the gate peripheral portion 10 having a thickness in a preferable range and being highly oriented and crystallized is particularly excellent in heat and pressure resistance and impact resistance.

[Valley Shape] In the specific example shown in FIG. 5, it has already been pointed out that the valley center portion 5 and the bottom valley portion 6 are located on a curved surface that is convex downward. And a substantially spherical surface having a radius of curvature R ₁ located at the bottom center portion and a generally spherical surface having a radius of curvature R ₂ connected to the body.

The radius of curvature R ₁ of the spherical surface including the bottom center trough 5 is set to an appropriate size, and the perpendicular of the spherical surface is
The distance between the tip 13 and the valley 6 can be made relatively small by setting the distance between the valley surface and the shortest distance. As a result, the blow moldability of the bottom foot portion 13 is improved, and the thickness of the foot tip portion 13 can be made relatively thick, and whitening of the foot tip portion 13 due to overstretching can be prevented.

More specifically, the ratio R ₁ / R _{0 of the} radius of curvature R ₁ of the roughly spherical surface constituting the bottom center trough 5 to the radius R _{0 of the} trunk portion.
Preferably it is 1.25 to 2, the ratio D ₁ / D ₀ between the diameter D ₁ and the barrel diameter D ₀ indicating the range of the spherical 0.
It is preferably 55 to 0.75. When R ₁ / R ₀ exceeds 2, the heat-resistant pressure performance of the valley decreases, and it becomes difficult to ensure the autonomy of the container after filling the contents and performing the heat sterilization treatment. When R ₁ / R ₀ falls below 1.2,
Since the distance between the tip of the foot and the valley becomes too large, it is difficult to secure a preferable thickness of the tip of the foot.

In the specific example shown in FIG. 6, the bottom valley 6 has a relatively small radius of curvature R ₁ including the remaining gate 8, and a substantially spherical surface A that is in contact with the substantially spherical surface A and is larger than an extended virtual surface of the roughly spherical surface A. It comprises a truncated cone-shaped or substantially spherical surface B located on the outer surface side, and a substantially spherical or conical surface C connected to the body from the surface B. At this time, it is preferable that the surface B or the surface C constituting the peripheral portion of the bottom valley be the shortest distance portion from the tip 13 of the foot.

In this embodiment, the bottom central valley 6 including the bottom gate remaining portion 8 on which the largest deformation force acts is made to be a spherical surface A having a relatively small radius of curvature, thereby providing a preferable heat-resistant pressure strength. On the other hand, the distance between the tip 13 and the valley surface can be reduced by greatly expanding the valley surfaces B and C on which a relatively small deformation force acts as compared with the center of the bottom. Thereby, the blow moldability of the sole tip 13 can be improved, and as a result, the thickness of the tip 13 can be made relatively thick and whitening due to overstretching can be prevented. Specifically, the ratio R ₁ / R ₀ of the radius of curvature R ₁ and the radius of the body portion R ₀ of the roughly spherical surface A constituting the bottom central portion is preferably set to 0.9 to 1.4, and It is preferable that the diameter D ₁ indicating the range be 0.18 to 0.5 times the body diameter D ₀ . The surface B connected to the general spherical surface A and extending outward is preferably formed of a conical surface in contact with the general spherical surface A or a general spherical surface having a large radius of curvature close to the conical surface,
0.3 times to 0.8 of the outermost diameter D ₂ is barrel diameter D ₀ of the surface B
Preferably it is 5 times.

Further, it is preferable to secure the heat and pressure resistance by making the bottom center valley portion 5 where the largest deformation force acts and the valley width in the vicinity thereof relatively large. Specifically, the ratio S / S ₀ of the surface area S ₀ of the valley included in the circle having a diameter of 80% of the trunk diameter D ₀ to the surface area S ₀ of the virtual approximate spherical surface composed only of the valley is set to 0. .2 to 0.5. If S / S ₀ is less than 0.2, the area of the bottom center and the valleys in the vicinity thereof is too small and limited,
The deformation at the bottom center becomes large, and it becomes difficult to ensure the independence of the container. On the other hand, when the S / S ₀ exceeds 0.5, since the sites available in the foot too limited during blow molding, ensuring the thickness of a preferred foot tip is difficult.

[Foot] In the present invention, as shown in FIG.
A foot opening angle θ sandwiching the valley in a plane perpendicular to the valley 6 and pointing toward the tip 13 of the foot while traversing between the feet 7 is 65.
It is preferable that the angle be in the range of {90}. In a container in which the foot opening angle θ is less than 65 °, when a relatively severe heat sterilization process is performed, the foot opening angle θ after the heat sterilization process is greatly increased, and the deformation amount of the valley is also increased accordingly. Tend to be. If the foot opening angle θ is increased in advance, it can be considered that the acting direction of the force acting to pull up the valley formed by a part of the spherical surface by the foot approaches the direction of the spherical surface. The force component acting perpendicular to the portion, that is, the force component for deforming the valley, is reduced. As a result, by increasing the foot opening angle θ, the deformation of the valley can be reduced, and the heat and pressure resistance performance is improved. Furthermore, by making the foot opening angle θ relatively large,
It also has an advantageous effect on the formability of the foot. That is, when the foot opening angle θ is increased, the surface area of the foot relatively decreases, and the amount of stretching at the foot can be suppressed relatively low. On the other hand, if the foot opening angle θ is too large, the width of the foot contact portion 14 will be reduced.
If the foot tip contact portion 14 is too thin, it tends to easily fall particularly in an empty container before filling, which is not preferable. Therefore, the foot opening angle θ is preferably set to 90 ° or less.

[Foot Height, Number of Feet] In this specification, the foot height refers to the axial distance between the foot contact portion 14 and the bottom center gate remaining portion 8. Unfilled, foot height 2-8m
m, preferably 3 to 6 mm. When the foot height is less than 2 mm, the foot height after deformation of the bottom center valley after filling the contents and heat sterilization becomes extremely small, or minus, that is, the bottom center part protrudes below the foot part. State, making it difficult to maintain the autonomy of the container.
On the other hand, if the foot height exceeds 8 mm, the distance between the tip of the foot and the valley becomes too large, and it becomes difficult to secure a preferable thickness of the tip of the foot. The number of feet is preferably six to four.

[Resin] In the present invention, any plastic material can be used as the plastic material as long as it is a plastic material that can be stretch blow-molded and thermally crystallized. Thermoplastic polyesters, especially ethylene terephthalate-based thermoplastic polyesters, can be used. Is advantageously used. Of course, polycarbonate, arylate resin or the like can also be used.

The ethylene terephthalate-based thermoplastic polyester used in the present invention contains most of ester repeating units,
In general, the ethylene terephthalate unit accounts for 70 mol% or more, particularly 80 mol% or more, and has a glass transition point (Tg) of 50 to 90 ° C., particularly 55 to 80 ° C., and a melting point (Tm) of 200 to 275 ° C. Especially 220 to 27
Thermoplastic polyesters at 0 ° C. are preferred.

Homopolyethylene terephthalate is preferred in terms of heat and pressure resistance, but a copolymerized polyester containing a small amount of ester units other than ethylene terephthalate units can also be used.

Examples of dibasic acids other than terephthalic acid include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid and naphthalenedicarboxylic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; succinic acid, adipic acid, sebacic acid, dodecane acid One or a combination of two or more aliphatic dicarboxylic acids such as diacids, and diol components other than ethylene glycol include propylene glycol,
1,4-butanediol, diethylene glycol, 1,
One or more of 6-hexylene glycol, cyclohexane dimethanol, an ethylene oxide adduct of bisphenol A and the like can be mentioned.

A composite material obtained by blending about 5% to 25% of ethylene terephthalate-based thermoplastic polyester with, for example, polyethylene naphthalate, polycarbonate or polyarylate having a relatively high glass transition point can be used. Material strength at high temperatures can be increased. Further, polyethylene terephthalate and the above-mentioned material having a relatively high glass transition point can be laminated and used.

The ethylene terephthalate-based thermoplastic polyester to be used should have at least a molecular weight sufficient to form a film, and an injection grade or an extrusion grade is used depending on the application. Its intrinsic viscosity (IV) is generally 0.6 to 1.4 dL / g,
In particular, those in the range of 0.63 to 1.3 dL / g are desirable.

[Manufacturing Method of Container] The stretched resin container of the present invention comprises a preform heated to a stretching temperature and a preform formed by a stretching rod inserted into the inside of the preform in a mold and a press rod outside the preform. When manufacturing a stretched resin container by simultaneously blowing a high-pressure gas into the preform while driving the stretching rod while sandwiching the bottom center portion of the preform, a preform having a gate portion at the bottom center portion is used as the preform. And it is manufactured by maintaining the temperature drop at the center of the bottom within 40 ° C. until immediately before the completion of the stretching, and also performing high stretching at the center of the bottom.

In manufacturing the container, first, a cylindrical preform having a bottom is formed, and if necessary, the mouth and neck of the preform are heated to locally provide a thermal crystallization portion.

The preform used for manufacturing the container of the present invention has a shape as shown in FIG. 8 and includes a neck 21, a body 22 and a closed bottom 2.
The neck 21 is provided with a cap fastening mechanism such as a screw and a support ring for holding the container, and the neck 21 is usually thermally crystallized, that is, spheroidized. This spheroidized neck 21 is the container neck 1 shown in FIG.
It is what becomes. At the center of the closed bottom portion 23, a gate remaining portion 24 exists.

In FIG. 9 showing the bottom of this preform in an enlarged manner, the bottom 23 of this preform has a bottom shoulder 25.
And a gate periphery 26, but the thickness T ₁ of the barrel portion 22, the thickness of the thickness T ₂ and bottom shoulder of the gate periphery T
_3, it is important to form a belt-like thick portion 15 in at least a portion of the trough portion 6 of the container are in a relationship satisfying the following formula T ₃ ≧ T ₁ and T _3> T _2.

That is, in the manufacture of the container of the present invention, the gate portion 24 of the preform 20 is replaced with the bottom center gate remaining portion 8 of the container,
The gate edge 26 of the preform is extended so that the gate edge 10 of the container, the shoulder 25 of the preform corresponds to the valley 6 of the container, and the body 22 of the preform corresponds to the body 3 of the container. By setting the conditions and making the thickness of the wall of the preform satisfy the above-mentioned relationship, at least a part of the valley portion 6 of the container has a band-shaped thick portion 15.
Can be formed.

In the present invention, the preform body 2
2 of the thickness T _1, the thickness T ₂ and the thickness T ₃ of the bottom shoulder of the gate periphery represented by the following formula T ₁ / T ₃ = 0.8~1 and T ₂ / T ₃ = 0.75~0.98 The relationship that satisfies the following conditions is to form a band-shaped thick portion clearly and reliably at least in a part of the valley portion of the container and to suppress a decrease in the thickness of the tip of the bottom foot portion. This is suitable for maintaining the thickness dimension in the above-described range.

For molding the plastic material into the preform 20, injection molding can be used. That is, the plastic is melt-injected into a cooled injection mold to form a supercooled amorphous plastic preform.

As the injection machine, a known injection machine equipped with an injection plunger or a screw is used, and the polyester is injected into an injection mold through a nozzle, a sprue, and a gate. As a result, the polyester or the like flows into the injection mold cavity and is solidified to form a preform for stretch blow molding.

As the injection mold, one having a cavity corresponding to the shape of a container is used, but a one-gate or multi-gate injection mold is preferably used. Injection temperature is 270 ~ 310 ℃, pressure is 28 ~ 110kg / c
m ² is preferable.

The spheroidization of the neck 21 of the preform 20
It can be carried out by selectively heating these parts by means known per se. Since thermal crystallization of polyesters and the like occurs remarkably at an inherent crystallization temperature, generally, the corresponding portion of the preform may be heated to the crystallization temperature. Heating can be performed by infrared heating, dielectric heating, or the like. Generally, it is preferable to selectively heat the body to be stretched by shielding the body from a heat source with a heat insulating material.

The above spheroidization may be performed simultaneously with or separately from the preheating of the preform 20 to the stretching temperature.

In the present invention, the center of the closed bottom portion 23 of the preform 20 is used for biaxial stretch blow molding without thermal crystallization. At the center of the closed bottom portion 23, there is a gate portion 24 formed during injection molding. In the present invention,
The gate portion 24 is used to form the highly stretched orientation layer 11 at the center of the bottom of the container while remaining without being subjected to a finishing step such as cutting.

FIG. 1 for explaining the dimensions of the gate portion.
At 0, the gate portion 24 has a length h and a root diameter d, and is generally tapered (taper angle α). h is preferably 3 mm or less, particularly in the range of 0.1 to 1 mm, d is suitably in the range of 2 to 6 mm, and α is suitably in the range of 0.5 to 6 degrees.

The stretching temperature of the preform 20 is generally 8
A temperature of 5 to 135 ° C., particularly 90 to 130 ° C. is appropriate, and the heating can be performed by a means known per se such as infrared heating, hot air heating furnace, and dielectric heating. In addition, in the mouth spherulization, the preform bottom and the mouth are generally insulated from 140 to 220 in a state of being thermally insulated from other parts.
C., in particular, by heating to a temperature of 160 to 210.degree. Crystallinity of preform mouth is 2
It is good to be 5% or more.

For stretch blow molding from a preform, a method of performing stretch blow molding subsequent to preform molding by utilizing heat given to a preform molded article to be molded, ie, residual heat, can also be used. However, in general, it is preferable to produce a preform molded article in a supercooled state, and then heat the preform to the above-mentioned stretching temperature to carry out stretch blow molding.

The container of the present invention comprises a step of primary blow molding a bottomed preform into a secondary molded article, a step of heat shrinking the secondary molded article to a tertiary molded article, and a step of producing a tertiary molded article. 2
Next, it is manufactured through a process of forming a final product having a valley portion and a foot portion alternately around the bottom by molding, and at this time, the bottom shoulder portion of the preform as a bottomed preform has a gate peripheral portion and It is manufactured by using the above-described preform which is thicker than the body, and by forming the above-mentioned band-shaped thick portion in the bottom trough.

The container of the present invention can be produced by a single biaxial stretch blow molding. However, when blow molding a petaloid bottom having a complicated shape into a high stretch orientation state at a time, the tip of the foot tends to be easily whitened, particularly in an overstretched state. It becomes quite narrow. In addition, in the heat fixing of the bottom using a mold, a relatively long time is required, and there is a problem that the blow molding time becomes long.

As a result of the study, as a means for molding the container of the present invention, a two-stage blow molding method in which a preform is formed into an intermediate molded product by primary blow molding, and the intermediate molded product is subjected to secondary blow molding to obtain a final product. Was found to be suitable.

In the two-stage blow molding method of the present invention, in the primary blow molding, the bottom part and the part of the trunk connected to the bottom part are larger in the height direction or the circumferential direction than the preform molded body than the final container. A molded product is formed, and then at least the bottom portion of the secondary molded product and a body portion connected to the bottom are heated and shrunk to form a tertiary molded product large enough to be accommodated in a secondary blow mold. Preferably, the article is subjected to secondary blow molding to form a final container.

The following effects are obtained by employing the above-described two-stage blow molding method. First, by optimizing the shape of the bottom portion in the primary blow molding, it is easy to make the bottom portion in a preferable high stretch orientation state, and in particular, to optimize the stretch ratio at the peripheral portion of the gate. As a result, the remaining gate at the bottom of the secondary molded product has a large thickness including a highly stretched orientation layer,
The peripheral edge of the gate is in a high stretch orientation state, and can be blow-molded stably so as to maintain a preferable thickness. Second, by heat-shrinking the bottom part of the secondary molded product and a part of the trunk connected to the bottom, the bottom central part of the secondary molded product can be thermally fixed and thermal crystallization can be advanced. This heat setting step can be performed efficiently in a very short time. Third, in the secondary blow molding, the bottom of the tertiary molded product in a high temperature state is stretch blow-molded, so that the foot can be easily molded without being in an overstretched state. In particular, the degree of stretching is small at the bottom center, and the degree of reduction in crystallinity due to blow molding is extremely small. Therefore, while having a foot of favorable properties, in the bottom center where the most heat and pressure resistance is required,
A container having high heat and pressure resistance, in which oriented crystallization and thermal crystallization are sufficiently performed, can be obtained.

In the two-stage blow molding method, the preform 20 which has been preheated for partial thermal crystallization and stretching is biaxially stretch blow-molded in a primary blow mold, and has a size larger than that of the final container. And a portion other than the thermally crystallized portion of the preform is formed into a secondary molded product 36 stretched to a high stretching ratio (FIGS. 11 and 12); the bottom and the bottom of the secondary molded product are connected to each other. A tertiary molded product 44 in which at least a part of the body is heated, and the bottom and a part of the body are shrunk.
(FIG. 13); Then, the tertiary molded product is blow-molded in a secondary blow mold to obtain a final product 5 comprising a plurality of valleys and feet, and having a bottom portion thinned by high stretching.
0 (FIGS. 14 and 15).

At this time, in order to reduce the thickness of the petaloid bottom of the final container in a relatively high orientation state except for the remaining gate, the bottom of the first blow molded secondary molded product including the remaining gate is compared. It is important that the film is oriented at a high stretch.

(1) Primary blow molding The preform 20 used for the primary blow molding is shown in FIG.
However, the shape and thickness distribution are determined in consideration of the stretching ratio of each part of the secondary molded product. At this time, a portion corresponding to the peripheral edge of the gate of the final container spreading around the bottom center gate remaining portion of the secondary molded product has an area stretching ratio of 3.5 to 12.5 times, particularly preferably 5 to 10 times. It is important to determine the profile of the bottom of the preform to be stretched.

In the primary blow molding, the preform 20 is heated to a stretching temperature. The stretching temperature of the preform is generally from 85 to 135 ° C, preferably from 90 to 130 ° C. At this time, it is preferable that the heating temperature difference between the bottom and the body of the preform be within 10 ° C., thereby enabling high stretching of both the bottom and the body.

If the heating temperature of the preform body is higher than the heating temperature of the bottom by more than 10 ° C., the stretching of the bottom having a relatively low temperature is insufficient. If the heating temperature of the bottom is higher than the heating temperature of the body by more than 10 ° C., the bottom is locally stretched too much, which is not preferable.

11 and 12 showing the primary stretch blow molding step, the neck of the preform 20 is supported by a core mold 31, and the closed split molds 32, 3
2. On the opposite side of the core mold, a bottom mold 33 that defines the bottom shape of the secondary molded product is also arranged. The stretch rod is inserted into the preform 20, and the bottom of the preform 23 is pushed up to perform stretch molding. At a certain stage during the stretch molding, a high-pressure gas is blown into the molded body through the stretch rod 34 to perform blow molding to obtain a container along the mold.

In the embodiment shown in FIGS. 11 and 12, a press rod 35 is arranged on the side of the bottom mold 33 so as to be coaxial with the draw rod 34, and the gate portion 24 of the preform is drawn by the draw rod 34 during the tensile drawing. And the press rod 35, the container bottom 4 in which the gate 24 at the bottom of the preform is formed.
The position is regulated so that it is located at the center of. That is, the press rod 35 sandwiches and restrains the gate portion 24 of the preform with the stretching rod 34 at the stage of stretching the preform, and further restrains the remaining bottom gate of the molded body at the stage of blow molding. Use of this press rod has an effect of preventing misalignment of the remaining gate.

At the time of the primary blow, a stretching speed at which the bottom of the preform is pushed up by a stretching rod, a timing at which high-pressure air is blown into the molded body, and a high pressure so as to form a highly stretched orientation layer on the entire bottom of the secondary molded product. It is important to optimize blow molding conditions such as the stretch blow speed determined by the flow rate of air.

Further, the inventors attached a thermocouple to the tip of the press rod and measured the temperature change of the remaining bottom center gate at the time of blow molding. As a result, after the press rod reached the top dead center, 5 to 15 ° C. It was found that a slight temperature rise was observed.
This is because, after the bottom central portion reaches the mold, relatively large stretching is performed on the remaining portion of the gate and in the vicinity thereof, and it is assumed that the temperature has risen due to heat generated during the stretching. At that time, by reducing the temperature drop from the initial heating temperature of the remaining gate of the molded body facing the tip of the press rod at the point when the press rod reaches the top dead center, the amount of temperature increase due to subsequent stretching That is, it was found that the degree of stretching in the remaining portion of the gate and in the vicinity thereof can be increased.

Specifically, the temperature drop at the center of the bottom of the preform just before the completion of the stretching process is set to 40 ° C. or less, more preferably 30 ° C. or less, so that the center of the bottom of the secondary molded product is reduced. It was found that the remaining portion of the gate and its peripheral portion can be in a highly stretched orientation state.

As a means for reducing the temperature drop at the center of the preform bottom during blow molding, it is effective to prevent excessive heat conduction from the stretching rod 34 and the pressing rod 35. Specifically, it is preferable that at least the tip of the stretching rod or the pressing rod is made of a heat-resistant plastic material or a ceramic material having heat insulation performance.

It is also effective to heat the press rod or the stretch rod and control the temperature to a relatively high temperature. It is preferable that the heating of the press rod and the stretching rod is usually performed at 50 ° C. to 130 ° C. corresponding to the stretching temperature of the preform. As the heating method, an electric heating method using an electric heater, high-frequency induction heating, or the like, a fluid heating method using circulation of a high-temperature liquid, or a heat conduction method such as a heat pipe can be used.

The bottom portion 37 of the obtained secondary molded product 36 has a bottom gate remaining portion 42 and a gate connection portion 41 shown in FIG.
Except that the crystallinity is 20% or more, more preferably 25%
As described above, it is preferable that the crystal is oriented and crystallized in a relatively high stretched state and that the thickness is reduced to 1 mm or less, particularly 0.8 mm or less. Normally, the bottom gate remaining part 42 of the secondary molded product 36 is composed of a high stretch orientation layer 42a located on the inner surface side and a low stretch orientation layer 42b located on the outer surface side shown in FIG. At the stage of the secondary molded article, the low-stretch orientation layer of the bottom gate remaining part 42 is usually transparent. The maximum value of the crystallinity of the high stretch orientation layer 42a remaining at the gate is 20%.
It is preferably at least 25%. The diameter D _G of the gate balance, 0.25 times the body diameter D _0, particularly preferably 0.2 times or less. Also, the remaining gate 4
2 has a crystallinity of 20% or more,
More preferably, it is oriented and crystallized in a relatively high stretched state to 25% or more, and is preferably thinned to 1.3 mm or less, more preferably 1.1 mm or less.

In FIG. 16 showing the bottom shape of the secondary molded product obtained by primary blow molding, the height H ₁ of the concave portion 41 from the flat portion 40 in the bottom portion 37 is generally 1 to 8 m.
m, the diameter D _{4 of the} concave portion 41 is desirably in the range of 0.15 to 0.6 times the diameter of the body connected to the bottom of the secondary molded product, in order to effectively perform high stretch orientation at the bottom center.

FIG. 16 also shows the relationship between the position of the bottom and the distribution of thickness for the secondary molded product. The bottom center gate remaining portion 42 has the largest thickness, and the body portion 43 has the smallest thickness. However, the portion where the thickness increases at the bottom corner portion 44a or in the vicinity thereof and takes the maximum value of the thickness, that is, the annular thick portion is It is particularly important to be present. This annular thick part,
It is formed corresponding to the thick bottom shoulder portion 25 of the preform shown in FIG. 9, and a part thereof is finally subjected to secondary blow molding to obtain the final molded product of the container. The band-shaped thick portion 15 is formed at the bottom valley 6 of the petaloid bottom.

[0110] secondary molded article bottom corner 44a of curvature radius R ₁ of the bottom 37 of generally be in the 0.05 to 0.35 times the range of trunk diameter is subsequently performed heat treatment than the final molded article It is preferable to develop a bottom shape close to the bottom shape.

(2) Heat Shrinkage Step In the present invention, in the subsequent heat shrinkage step, the bottom of the secondary molded product and a part of the trunk connected to the bottom are heated and shrunk in the height direction and the radial direction. This is a tertiary molded product having a shape that fits in the secondary blow mold that is the product shape.

In the heat treatment of the bottom part of the secondary molded product, it is preferable that the heat shrinkage be performed by non-contact heating and shrinkage without restriction. In the example shown in FIG. 13, infrared radiators 45 and 46 are provided along the path of movement of the secondary molded product and opposed to the bottom and a part of the body of the secondary molded product. By supporting the secondary molded product 36b in the space enclosed by the core mold 31 and moving the secondary molded product 36b while rotating and heating in the axial direction, the bottom and part of the body of the secondary molded product are As shown in FIG. 13, the tertiary molded product 44 is shrunk by heating. It is recommended that a heat shield plate 47 be provided to prevent unnecessary shrinkage of the trunk.

The infrared radiators 45 and 46 are 400 to 10
It is preferable to use a material heated to about 00 ° C. and having relatively excellent radiation efficiency. Thus, a predetermined portion of the secondary molded article 36 can be irradiated with infrared rays having a relatively high energy density, and the predetermined temperature can be set to a predetermined temperature in a short time of, for example, about 10 seconds or less.

The shape of the bottom 48 of the tertiary molded product 44 is preferably as close as possible to the bottom valley of the secondary blow mold, thereby facilitating the molding of the foot of the final product (FIG. 14).

In order to make the bottom shape of the tertiary molded product 44 a preferable shape, the bottom shape of the secondary molded product 36 is important. Is preferred. Further, since the bottom center gate remaining portion 42 of the secondary molded product 36 is thick when the bottom is heated, the temperature rise is slower than that of the surrounding thin portion. Therefore, if the bottom shape of the secondary molded product is, for example, a hemispherical shape, the thin portion around the remaining gate first thermally contracts in a conical shape, so that the thick gate remaining portion 42 projects to the outer surface side, In the case of such a shape whose center is upwardly convex, it will be far away from the valley shape of the secondary blow bottom type. In the present invention, as shown in FIG. 16, it is effective to adopt a shape in which the bottom 37 of the secondary molded product is flat when viewed as a whole, and a concave portion 41 is provided at the center of the bottom. Thus, it is possible to obtain a tertiary molded product 44 which is slightly concave at the bottom center, but has a substantially flat bottom surface 48 and a shoulder 49 close to the valley of the secondary blow mold. . At this time, if an annular thick portion is formed in the bottom corner portion 44a of the secondary molded product shown in FIG. 16, since the thick portion is thicker than the bottom peripheral portion and the body portion sandwiching the annular thick portion, the temperature during heating is reduced. The temperature rise is small and the degree of heat shrinkage is small. As a result, the annular thick portion of the secondary molded product becomes the bottom shoulder portion 49 of the tertiary molded product that has shrunk by heating, and as shown in FIG. 13, it is possible to obtain a tertiary molded product having a relatively shouldered shape. You can. The bottom shoulder portion 49 of this tertiary molded product is thick, and by the next secondary blow molding, a part thereof is located at the valley and becomes the band-shaped thick part 15 and a part thereof is a foot tip part. 13 to secure a preferable thickness of the foot end portion 13.

The heating temperature of the highly stretched oriented bottom portion of the secondary molded product and a part of the body connected thereto is preferably 130 to 200 ° C., and the obtained tertiary molded product shrinks and is heat-set. Thermal crystallization proceeds. At this time, at the bottom of the tertiary molded product, the low-stretch alignment layer of the remaining gate is whitened, but the high-stretch alignment layer of the remaining gate and the periphery of the gate around it remain substantially transparent without whitening. .

(3) Secondary Blow Molding The tertiary molded product 44 in the heated state is introduced into a secondary blow mold and subjected to secondary blow molding to become a final product (FIGS. 14 and 15).

Referring to FIG. 14 showing the details of the secondary blow molding step, the tertiary molded product 44 has its neck supported by the core mold 31 and is held in the closed split mold 51. On the opposite side of the core mold, a bottom mold 52 that defines the bottom shape of the final container is also arranged. A fluid is blown into the tertiary molded product 44 to perform secondary blow molding of the tertiary molded product to form a bottom shape of the final container 50 having predetermined valleys and feet. The molded container 50 is removed from the opened secondary blow mold 51 to the outside by a removal mechanism (not shown) known per se.

In the tertiary molded product, since the elastic modulus is increased by crystallization due to heat treatment, it is preferable to use a high fluid pressure, and generally use a pressure of 15 to 45 kg / cm ^2. preferable.

At the time of the secondary blow molding, the temperature of the mold is
Cooling may be performed immediately after molding while maintaining the temperature at 5 to 135 ° C., or cooling may be performed by flowing cold air or the like into the final molded product.

The bottom of the final product thus obtained, including the remaining portion of the gate, is composed of a heat-set, high-stretched oriented layer having high heat-resistant pressure strength and high impact strength. Excellent impact performance. At this time, the thickness of the bottom center gate remaining portion, the gate connection portion, and the gate peripheral portion of the container becomes thicker than the thickness of the secondary molded product formed by the primary blow molding by the amount of heat shrinkage at the time of heat fixing. In the secondary blow molding, the bottom center portion is hardly stretched, so that the thickness becomes somewhat thick. In addition, a band-shaped thick portion is formed in the valley corresponding to the bottom corner portion 44a of the secondary molded product or the annular thick portion in the vicinity thereof, and the thinning of the tip of the foot is suppressed. Become.

[Production Example] Using a two-stage blow molding apparatus as shown in FIGS. 11 to 15, the maximum body diameter D ₀ of the final molded product is 91 mm, the total height is 303 mm, and the capacity is 1
A 500 ml container made of polyethylene terephthalate (PET) as shown in FIG. 1 composed of six feet and a valley was prepared.

A preform having a bottom as shown in FIGS. 8 and 9 was prepared. The ratio T1 / T3 of the thickness T1 of the trunk portion of the preform to the thickness T3 of the bottom shoulder portion is 0.95, and the ratio T2 / T3 of the thickness T2 of the gate peripheral portion to the thickness T3 of the bottom shoulder portion is as follows. It was 0.89. Using the above preform, FIG.
315 mm in height, the center of the generally flat bottom is inward, the diameter D1 is 30 mm and the depth H1 is 2
The primary blow molding was performed using a blow mold having a bottom mold having a concave portion having a thickness of 20 mm and a bottom corner having a radius of curvature of 20 mm. In the primary blow molding, first, the preform is heated to a stretching temperature and introduced into a mold, and then the bottom of the preform is sandwiched between a stretching rod provided inside and a press rod provided outside. At the same time, the compressed air of 20 kgf / cm ² is blown into the preform and blow-molded while pushing up the bottom of the preform with a stretching rod.
The following molded article was obtained. The bottom of the obtained secondary molded article had a thickness of 1 mm or less except for the bottom center gate residue, and the crystallinity associated with the stretch orientation was 25% or more. The thickness of the largest thick part of the remaining bottom center gate is 1.5 mm, 0.6 to 0.7 mm
It consisted of a high-stretch orientation layer located on the inner surface side with a thickness of about 10 mm and a low-stretch orientation layer located on the outer surface side with a thickness of about 0.8 mm at the maximum thickness. The maximum crystallinity of the high stretch orientation layer was 25%, and the crystallinity near the outer surface of the low stretch orientation layer was about 1 to 10%. In addition, the obtained 2
At the bottom corner R portion of the next molded product, an annular thick portion thicker than the body and the peripheral edge of the remaining gate was formed.
The thickness of the largest thick part of the annular thick part formed at the bottom corner R is 0.64 mm, and the minimum thickness of the body part and the remaining peripheral part of the gate in the vicinity is 0.35 mm and 0.38 mm, respectively.
mm. The width of the annular thick portion was about 18 mm.

Next, the secondary molded article is moved while rotating in a tunnel-shaped heat treatment apparatus in which a planar infrared heating element in which an electric heater is incorporated in a ceramic is disposed on the top surface and side surfaces while rotating. A tertiary molded product was obtained by heat shrinking the bottom of the molded product and part of the trunk connected to the bottom. The temperature of the infrared heater was 900 ° C. on the top surface and 750 ° C. on the side surface, and the heating time was 6 seconds. As shown in FIG. 13, the heating portion of the obtained tertiary molded body has a relatively elongated shape of an annular bottom shoulder, and the bottom shoulder is relatively formed on the bottom valley curved surface of the final container. Was close. The bottom shoulder of the tertiary molded product is relatively thick, and corresponds to the annular thick portion of the bottom corner R of the secondary molded product. In this case, when the secondary molded product is heated, the temperature rises faster because the relatively thin portion inside the annular thick portion of the bottom corner portion is thin first, and the flat molded product shrinks in a flat shape. . Next, when the temperature of the annular thick portion rises and starts shrinking, the shrinkage of the flat thin portion in the inside is almost finished. Therefore, the degree of contraction of the annular thick portion is suppressed, and a relatively shouldered bottom shoulder is formed. In order to obtain such a preferable tertiary molded product bottom shape, two steps are required.
It is important to form an annular thick part in the next molded product.

Finally, the tertiary molded product in the heated state was compressed with 40 kgf / cm ² of compressed air using a secondary blow mold having a predetermined bottom shape consisting of six feet and valleys.
Next, the container was obtained by blow molding. In the bottom mold of the secondary blow mold at that time, the radius of curvature R ₁ of the valley bottom near the center of the bottom is 67 mm, and the total surface area S ′ of the bottom valley included in the diameter of 40% of the trunk diameter D ₀ is: Ratio S ′ / S with surface area S ₀ ′ of bottom imaginary curved surface included within a diameter of 40% of trunk diameter D _0
0 'is 0.72, the barrel diameter D total surface S and barrel diameter D 80% of the bottom surface area S ₀ of the imaginary curved surface contained within the diameter of ₀ 80% of the bottom valley portions contained within the diameter of the ₀ The ratio S / S ₀ is 0.
31, the foot height H was 4 mm, and the foot angle θ sandwiching the valley in a plane crossing between the feet and perpendicular to the valley was 71 °.
Except for the bottom center gate remaining part, the bottom of the obtained container and a part of the trunk connected to the bottom had a thickness of 1 mm or less and were in a transparent state. The heated bottom part and part of the body part are thermally crystallized, and the degree of crystallinity at the bottom valley is 35 to 45%.
Met. The bottom center gate remainder has a diameter of about 3 mm and, as shown in FIG. 3, comprises a transparent high-stretch alignment layer located on the inner side and a whitened low-stretch alignment layer located on the outer side. Was. The highly stretched orientation layer had a thickness of about 0.8 mm and a crystallinity of about 33%. On the other hand, the whitened low-stretched orientation layer had a maximum thickness of 1.3 mm and a spherulitic crystallinity of about 30%. A band-shaped thick part was formed in the bottom trough of the obtained container. The thickest part of the band-shaped thick part was located at a position about 25 mm from the center of the bottom, and the average value of the thickness at each valley was 0.85 mm. The width of the band-shaped thick part was about 20 mm. Such a band-shaped thick portion is derived from an annular thick portion formed near the bottom corner R of the secondary molded product, and the annular thick portion heats the next bottom portion and a part of the body portion. It was found that the tertiary molded product obtained in the shrinking step became an annular and thick bottom shoulder portion, and was further subjected to secondary blow molding to become a band-like thick portion at the valley portion. On the other hand, in the annular bottom shoulder portion of the tertiary molded product, the portion to be the foot in the secondary blow molding was extended to the vicinity of the tip of the foot. As a result, the minimum thickness of the foot contact portion and the tip portion of the foot was considerably large, 0.22 to 0.3 mm, and a preferable thickness could be obtained.

The obtained five containers were prepared, and the opening of the container was axially compressed by a compression tester to determine the axial load strength. As a result, the axial load strength was 38.6 kgf on average, and a favorable value was obtained with an increase in the thickness of the tip of the foot. Next, 10 containers were prepared, and 3 gas volumes (G
After filling with carbonated water of V) and capping, the contents were heated and sterilized by flowing hot water at 70 ° C. from the upper part of the container for 30 minutes. In the heat sterilization treatment, the temperature at the bottom center increased to a maximum of 68 ° C. The heat disinfection treatment was completed and the amount of deformation of the cooled container bottom was measured, and the foot height (H) was determined. The foot height was 1 mm or more, and all the containers had sufficient autonomy. . In addition, 10
Prepare a book container and place it in a humid environment at 5000 ppm
Water content. The container was filled with 2.8 gas volumes (GV) of carbonated water and capped, and then heat-sterilized under the same conditions as above. The height of the bottom of the container after the treatment was 0.8 mm or more, and all containers had sufficient autonomy. The 20 heat-sterilized containers were vertically dropped from a height of 1.2 m in an upright state, and no cracks were observed in any of the containers.

[0127]

According to the present invention, the bottom portion, including the remaining gate, is effectively oriented and crystallized in a highly stretched orientation state, and further has a highly stretched annular thick portion in the bottom valley portion and a bottom foot. By suppressing the thinning of the part, the bottom can be reduced in weight, and the bottom is excellent in heat and pressure resistance, stress crack resistance, moisture absorption resistance, etc., and the axial load strength, impact resistance, etc. of the container are improved. An improved stretched resin container is provided.

[Brief description of the drawings]

FIG. 1 is a partially sectional side view showing an example of the container of the present invention.

FIG. 2 is an enlarged bottom view showing the bottom of the container of FIG. 1;

FIG. 3 is a partially enlarged cross-sectional view showing an example of the arrangement of the remaining bottom center gate in the container of the present invention.

FIG. 4 is an explanatory diagram showing the relationship between each part of the bottom of the container of the present invention and the distribution of wall thickness.

FIG. 5 is an explanatory diagram for explaining the shape and dimensions of a bottom trough of the container of the present invention.

FIG. 6 is an explanatory diagram for explaining another example of the shape and dimensions of the bottom trough of the container of the present invention.

FIG. 7 is an explanatory diagram for explaining a foot opening angle θ in the container of the present invention.

FIG. 8 is a side view showing an example of a preform used in the method of the present invention.

FIG. 9 is an explanatory view showing the shape and dimensions of the bottom of the preform.

FIG. 10 is an explanatory view showing the shape and dimensions of a gate portion of a preform.

FIG. 11 is a sectional view showing an initial stage of a primary blow molding step in a two-stage blow molding method.

FIG. 12 is a sectional view showing the last stage of the primary blow molding step in the two-stage blow molding method.

FIG. 13 is a cross-sectional view showing an initial stage of an intermediate heating step for obtaining a tertiary molded product in the two-stage blow molding method.

FIG. 14 is a sectional view showing a secondary blow molding step in a two-stage blow molding method.

FIG. 15 is a side view showing a final product in the two-stage blow molding method.

FIG. 16 is an explanatory diagram showing a bottom shape and a thickness distribution of a secondary molded product.

FIG. 17 is a partially enlarged cross-sectional view showing an example of an arrangement of a bottom center gate remaining portion in a secondary molded product.

FIG. 18 is a partial sectional view showing a bottom shape of a tertiary molded product.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mouth and neck part 2 Shoulder part 3 Trunk part 4 Bottom part 5 Center bottom valley part 6 Valley part 7 Foot part 8 Remaining gate 9 Gate connection part 10 Gate peripheral part 11 High stretch orientation part 12 Low stretch orientation part 13 Tip part 14 Ground part DESCRIPTION OF SYMBOLS 15 Belt-shaped thick part 16 Foot tip part 20 Preform 21 Neck part 22 Body part 23 Closed bottom part 24 Gate remaining part 25 Bottom shoulder part 26 Gate peripheral part 31 Core mold 32 Split mold 33 Bottom mold 34 Extension rod 35 Press rod 36 Secondary molded product 36b Secondary molded product 37 Bottom part 38 Convex part 39 Flat part 41 Gate connection part 42 Bottom gate remaining part 42a Highly oriented layer 42b Low oriented layer 43 Body 44 Tertiary article 44a Bottom corner 45, 46 Infrared radiator 48 Flat bottom 49 Bottom shoulder 50 Final product 51 Split mold

[Procedure amendment]

[Submission date] July 21, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0027

[Correction method] Change

[Correction contents]

Generally, at the bottom of the self-supporting stretched resin container, the bottom center gate remaining portion is the thickest , and the thickness gradually decreases outward in the radial direction, that is, from the center to the connection portion with the body. In particular, in a foot portion formed so as to protrude outward as compared to a valley portion, the thickness is likely to be significantly reduced.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction contents]

[0031] Generally, between the most thick-walled bottom central gate remainder and the strip thick portion, there is reduced portion thicker than these. This is because, as already pointed out, the high stretch around the bottom center gate remnant results in the formation of a high stretch orientation layer in the bottom center gate remnant.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0056

[Correction method] Change

[Correction contents]

When the maximum value of the thickness of the band-shaped thick portion 15 of the valley portion ₆ is T ₆ , the thickness of the lower portion of the body portion 3 connected to the bottom portion 4 is T _4, and the thickness of the gate peripheral portion 10 is generally T _5. , T ₆ > T ₄ and T ₆ ≧ T ₅ , especially T ₆ > T ₅ . From the standpoint of improving burst strength and axial load strength,
The thickness ratio of T ₆ > T ₄ is in the range of 1.3 to 3.5 , especially 1.6 to 3, and the thickness ratio of T ₆ > T ₅ is 1 to 2.2, especially 1.1. It is preferably in the range of 2 to 2.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0062

[Correction method] Change

[Correction contents]

The radius of curvature R _{1 of the} spherical surface including the bottom center trough 5
The appropriate size Satoshi, and perpendicular foot tip 1 of the spherical
By setting the shortest distance between 3 and the valley surface, the distance between the foot tip 13 and the valley 6 can be made relatively small. As a result, the blow moldability of the bottom foot portion 13 is improved, and the thickness of the foot tip portion 13 can be made relatively thick, and whitening of the foot tip portion 13 due to overstretching can be prevented.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0110

[Correction method] Change

[Correction contents]

[0110] the bottom corner 44a of curvature radius R ₄ of the bottom 37 of the secondary molded article, generally be in the 0.05 to 0.35 times the range of trunk diameter is subsequently performed heat treatment than the final molded article It is preferable to develop a bottom shape close to the bottom shape.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0123

[Correction method] Change

[Correction contents]

A preform having a bottom as shown in FIGS. 8 and 9 was prepared. The ratio T1 / T3 of the thickness T1 of the trunk portion of the preform to the thickness T3 of the bottom shoulder portion is 0.95, and the ratio T2 / T3 of the thickness T2 of the gate peripheral portion to the thickness T3 of the bottom shoulder portion is as follows. It was 0.89. Using the above preform, FIG.
315 mm in height, the center of the generally flat bottom is inward, the diameter D4 is 30 mm and the depth H1 is 2
The primary blow molding was performed using a blow mold having a bottom mold having a concave portion having a thickness of 20 mm and a bottom corner having a radius of curvature of 20 mm. In the primary blow molding, first, the preform is heated to a stretching temperature and introduced into a mold, and then the bottom of the preform is sandwiched between a stretching rod provided inside and a press rod provided outside. While simultaneously pushing up the bottom of the preform with a stretching rod, simultaneously blow compressed air of 20 kgf / cm ² into the preform to blow-mold,
A secondary molded product was obtained. The bottom of the obtained secondary molded article had a thickness of 1 mm or less except for the bottom center gate residue, and the crystallinity associated with the stretch orientation was 25% or more. The maximum thickness of the remaining bottom center gate is 1.5 mm, 0.6-0.7 m
A high-stretch alignment layer located on the inner surface side with a thickness of about m and a low-stretch alignment layer located on the outer surface side with a thickness of about 0.8 mm in the maximum thickness portion. The maximum crystallinity of the high stretch orientation layer was 25%, and the crystallinity near the outer surface of the low stretch orientation layer was about 1 to 10%. In addition, an annular thick portion thicker than the body and the periphery of the remaining gate was formed at the bottom corner R of the obtained secondary molded product. The thickness of the largest thick part of the annular thick part formed at the bottom corner R is 0.64 mm, and the minimum thickness of the body part near the periphery and the peripheral part of the remaining gate is 0.35 mm and 0.1 mm, respectively.
38 mm. Also, the width of the annular thick part is about 18mm
Met.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0127

[Correction method] Change

[Correction contents]

[0127]

According to the present invention, the bottom, including the gate balance, effectively oriented crystallized to a high stretch orientation state, the bottom together with further having a belt JoAtsu meat portion of the highly oriented state in the bottom valley portions By suppressing the thinning of the feet, the weight of the bottom can be reduced, and the bottom has excellent heat and pressure resistance, stress crack resistance, moisture absorption resistance, etc., and axial load strength, impact strength, etc. of the container. The present invention provides a stretched resin container having improved properties.

[Procedure amendment 8]

[Document name to be amended] Drawing

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG. 16

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuhisa Hamada 2-206 Nishitobe-cho, Nishi-ku, Yokohama-shi, Kanagawa Prefecture (72) Inventor Yutaka Mukai 6-7-27 Shimoodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture

Claims (8)

[Claims] 1. A self-contained container having a mouth, a neck, a shoulder, a trunk, and a bottom having a plurality of feet and valleys formed by biaxial stretch blow molding of a resin, wherein the trunk and the bottom are bottomed. It has a high stretch orientation layer including the center gate remaining portion, and has a high stretch orientation state belt-like thick portion which is circumferentially arranged on at least a part of the bottom valley portion. A stretched resin container characterized in that a decrease in thickness is suppressed at a corresponding bottom foot portion. 2. A frustoconical surface including a perpendicular to the inner peripheral edge of the band-shaped thick portion of the bottom valley portion, and a virtual frustoconical surface including a perpendicular to the outer peripheral edge of the band-shaped thick portion. 2. The stretched resin container according to claim 1, wherein a thick bottom portion and a bottom foot portion of the bottom valley portion are provided in a positional relationship including a tip portion of the bottom foot portion in the space. 3. The thickness of the band-shaped thick portion of the bottom valley portion is 0.45 to 0.45.
The stretched resin container according to claim 1 or 2, which is in a range of 1.1 mm. 4. The method according to claim 1, wherein the thickness of the tip of the sole is maintained at 0.17 mm or more.
4. The stretched resin container according to any one of claims 1 to 3. 5. The stretched resin container according to claim 1, wherein the degree of crystallinity accompanying the orientation of the highly stretched orientation layer is 20% or more. 6. The stretched resin container according to claim 1, wherein a thickness of a portion excluding the remaining bottom center gate and the vicinity thereof is 1.1 mm or less. 7. The stretched resin container according to claim 1, wherein the remaining bottom center gate comprises a high stretch orientation layer and a low stretch orientation section. 8. The method according to claim 1, wherein said bottom portion is heat-set so as to have a crystallinity of 25% or more, and is substantially transparent except for the bottom center gate remainder. Stretched resin container.