JPH11165723A - Oriented resin container and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a weight of a bottom, improve resistance to heat, resistance to stress crack and resistance to moisture-absorbability and increase axial load strength and impact resistance strength by laminating an entire bottom including a gate remaining part in a highly oriented state and further forming a relatively thick highly oriented part on a bottom corner. SOLUTION: A self-supporting container having a recessed bottom formed by biaxially orientation blow-molding resin is manufactured by highly orientation blow-molding a bottom and a body of a preform using the bottomed preform whose bottom shoulder is thicker than a gate periphery and a body, forming a highly oriented annular thick part 13 at a bottom corner 8 of a mold or in the vicinity, and highly orienting the bottom including a bottom center gate remaining part 9 surrounded by the annular thick part 13. At this time, until immediately before orientation processing is completed, drop in temperature at the bottom center is kept at 40 deg.C or less, more preferably at 30 deg.C or less, and a highly oriented layer including the gate remaining part 9 is formed on the entire bottom of the mold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretched resin container, and more particularly, to a resin material capable of reducing the weight of the bottom and having excellent heat resistance, stress crack resistance and moisture absorption resistance at the bottom. The present invention relates to a stretched resin container having significantly improved axial load strength, impact resistance and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Polyethylene terephthalate (PET)
The thermoplastic polyester biaxially stretch blow-molded container has excellent transparency and surface gloss, and also has the necessary impact resistance, rigidity, and gas barrier properties for bottles. It is used as a heat-resistant container made as described above or a container for aseptically filling various types of liquids aseptically. In particular, the above-mentioned heat-resistant container is required to have heat resistance and pressure-resistant deformation resistance to prevent thermal deformation when filling with a high-temperature liquid and reduced-pressure deformation after sealing. On the other hand, in a container for aseptic filling, since a relatively high temperature sterilizing liquid is usually used when an empty container is sterilized, heat resistance corresponding to the sterilizing temperature condition is required.

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. The problem is that it is difficult to perform a high degree of stretch orientation at the bottom, which requires a thick unstretched orientation or a low stretch orientation portion at the bottom of the container, and hinders lightening of the container, This causes a decrease in heat resistance or impact resistance.

[0004] That is, if there is a relatively thin portion of low stretch orientation at the bottom of the container, the portion has lower deformation resistance, particularly heat resistance, than the high stretch orientation portion. Therefore, by increasing the thickness of the low-stretched portion and adopting, for example, a complex shape such as a petal in the center of the bottom, the deformation resistance of the bottom, particularly the heat resistance, is increased. In addition, the heat resistance of the bottom of the container can be increased by heat-setting the low-stretched oriented portion at the bottom, but the low-stretched oriented portion is whitened during the heat-fixing. If the whitened low-stretched orientation portion covers a relatively wide range, it becomes aesthetically pleasing and causes a significant decrease in impact resistance.

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 in a highly stretched state around the bottom, 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 it for the purpose of reducing 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.

Japanese Unexamined Patent Publication No. Hei 9-118 based on the proposal of the present inventors
Japanese Patent No. 322 discloses a relatively low-strength container having a neck portion, a shoulder portion, a torso portion, and a bottom portion including a plurality of valleys and feet formed by biaxial stretch blow molding of a resin. The bottom portion except the bottom center portion in the state 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 portion is the body diameter. A self-standing container excellent in heat and pressure resistance characterized by being within the range of 1 to 20% of D0 is described. Further, the preform heated to the stretching temperature is inserted into the preform in a mold. The center of the bottom of the preform is sandwiched between the stretch rod and the press rod outside the preform, and while the stretch rod is being driven, a high-pressure gas is simultaneously blown into the preform at the same time, and until the stretching process is completed. Lower the temperature at the bottom center by 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.

[0009]

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, the remaining gate becomes large in volume, and this portion becomes significantly embrittled by thermal crystallization, and the embrittled portion occupies a considerable portion of the bottom, resulting in extremely high 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.

[0011] 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 inventors of the present invention have proposed a biaxial stretching blow that makes the bottom of a free-standing structure a highly stretch-oriented state without thermally crystallizing the bottom of the preform and effectively utilizing the remaining gate of the preform. The forming means 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, it is possible to form a relatively thick high-stretch orientation portion at the bottom corner portion,
As a result, it has been found that various properties of the container can be significantly improved.

That is, an object of the present invention is that the bottom portion, including the rest of the gate, is effectively oriented and crystallized in a highly stretched orientation state,
Furthermore, by having a high-stretch annular thick portion at the bottom corner, it is possible to reduce the weight of the bottom, and it is excellent in heat resistance, stress crack resistance, moisture absorption resistance, etc. of the bottom, and the axial load strength of the container. An object of the present invention is to provide a stretched resin container having improved impact resistance and the like. In addition, another object of the present invention is to provide a bottom portion having a high-stretched annular thick portion at a bottom corner portion, a bottom portion having a high-stretched state, and a body portion in a high-stretch state, including a gate remaining portion. Is to provide a stretched resin container in which high heat resistance is secured particularly at the bottom and the body by heat-setting.

[0014]

According to the present invention, a mouth, neck, shoulder, and shoulder formed by biaxial stretch blow molding of a resin are provided.
A self-contained container having a body and a central portion having a concave bottom when viewed from below, wherein the body and the bottom have a high stretch orientation layer including a bottom center gate remainder, and the body and the bottom The stretched resin container is characterized in that the stretched resin container has a highly stretched orientated annular thick portion at least at a part of or near the bottom corner portion connecting the two. According to the present invention also
A method for producing a stretched resin container by biaxially stretch-blowing a bottomed preform, wherein a bottom shoulder of the preform is a thicker preform than a gate peripheral portion and a body portion, Highly stretch blow-molded the bottom and body of the molded part to form a high stretch oriented annular thick part at the bottom corner of the molded product, and the bottom part surrounded by the annular thick part is generally highly stretch oriented. A method for producing a stretched resin container is provided.

In the stretched resin container of the present invention: 1. The thickness of the bottom corner portion and the ground contact portion is greater than the thickness of the trunk portion near the bottom corner portion; 2. the thickness of the annular thick portion is 0.4 to 1 mm; 3. The degree of crystallinity accompanying the orientation of the highly stretched orientation layer is 20% or more; 4. The thickness of the portion excluding the bottom center gate remaining portion and the vicinity thereof is 1 mm or less; 5. the bottom center gate remainder is composed of a high stretch orientation layer and a low stretch orientation section; 6. the bottom is heat set with a crystallinity of 25% or more and is substantially transparent except for the bottom center gate remnant; It is preferable that the entire container is heat-set with a crystallinity of 25% or more, and is substantially transparent except for the mouth, neck, and the rest of the bottom center.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The stretched resin container of the present invention has a neck, a shoulder, a cylindrical portion or a rectangular cylindrical body formed by biaxial stretch blow molding of a resin, and a hollow central portion when viewed from below. It has a bottom and is self-supporting, but the body and the bottom have a high stretch orientation layer including the bottom center gate remnant, and a bottom corner connecting the body and the bottom. It is a remarkable feature that at least a part or the vicinity thereof has an annular thick part which is highly stretched and oriented.

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, the body and the bottom of the container have a highly stretched orientation layer including the bottom center gate residue, and the high stretched orientation layer allows the temperature range up to about 65 ° C. Thus, it can have excellent mechanical properties that combine the required rigidity and flexibility of the container. In particular, at the bottom of the container, it is possible to significantly reduce the weight as the thickness is reduced while maintaining excellent mechanical properties.

By heat-fixing the body and bottom of the container of the present invention, excellent heat resistance can be obtained. That is,
The highly stretched alignment layer covering the entire body and bottom of the container maintains a transparent state even when heat-fixed, has excellent heat-resistant deformation, and has excellent rigidity, impact resistance, stress cracking resistance, etc. I have. In the container of the present invention, the remaining bottom gate is composed of a high-stretched orientation layer and a low-stretched orientation portion, but during heat setting, only the low-stretched orientation portion is whitened, and the high-stretched orientation layer remains transparent. The low-stretch alignment portion of the remaining bottom gate which is whitened is relatively brittle, but is locally laid on a high-stretch alignment layer having excellent mechanical properties, and the size of the low-stretch alignment portion is large. Because of their limited nature, they do not impair the excellent mechanical properties of the bottom at all. In addition, the whitened low-stretch orientation part is usually located in the concave part at the bottom center,
Because of its small diameter, it does not detract from aesthetics.

The present inventors have conducted intensive studies on blow molding. As a result, the stretching of the bottom portion in the blow molding is remarkably started from the time when the gate, which is the center of the bottom of the preform, reaches the bottom of the mold. Turned out to be done. Therefore,
Means for reducing the temperature drop at the bottom center and the vicinity thereof at the point when the bottom center of the molded body reaches the mold bottom to a certain level or less was adopted. It was found that the thickness could be reduced.

In the above blow molding, it has been considered that if the gate length of the preform is too long, it is difficult to reduce the thickness of the remaining gate and its periphery to a sufficiently high stretched state. The remaining gate and its periphery are thermally crystallized, that is, spheroidized, and the bottom part including the vicinity of the spherulized part is highly stretch-oriented, or the gate length of the preform is reduced to almost zero, and the remaining gate is thinned. That was the conventional idea. According to the present invention, even if the gate length of the preform is somewhat longer, it is possible to form a highly stretched orientation layer on the remaining portion of the thick bottom center gate by the above-described means.

In the present invention, the shape of the preform, the thickness of the bottom portion, and the blow molding conditions are adjusted so that the stretch ratio at the bottom of the preform at the time of blow molding, particularly the peripheral portion of the gate including the gate connecting portion in contact with the remaining portion of the gate. By optimizing the stretching ratio, even when the bottom center gate remaining portion of the container is thick, the surrounding gate connection portion and the gate peripheral portion are in a high stretch orientation state, and accordingly, the bottom center gate remaining portion is reduced. Can also be stretched effectively.

Further, in the container of the present invention in which the bottom center gate connection portion and the gate peripheral portion are in a highly stretched orientation as described above, surprisingly, the thick gate remaining portion has a highly stretched orientation portion or a lower stretch portion. The stretch-oriented portion exists, and the high stretch-oriented portion of the remaining gate has a layered structure, and has a structure continuously connected to the gate connection portion and the gate peripheral portion in the high stretch-oriented state. understood.

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 oriented portion and the continuous layered structure continuously connected to the gate connection portion and the gate peripheral portion in the highly stretched oriented state are not divided at all, it does not become a hindrance factor such as heat resistance or impact 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 the bottom center gate residue, and at least one of the bottom corner portions connecting the body portion and the bottom portion. It is a remarkable feature that it has an annular thick portion which is highly stretched and oriented at or near the portion.

Generally, at the bottom of the self-supporting stretched resin container, the bottom center gate remaining portion is the thickest, and the thickness is such that the thickness gradually decreases toward the bottom corner, that is, the connection with the body. The wall thickness tends to be remarkably reduced particularly at the corners where the distribution is made, particularly at the corners where the grounding is performed. On the other hand, in the present invention, an annular thick portion which is highly oriented and oriented is provided at or near the bottom corner portion where the thickness tends to decrease. This annular thick portion, of course, has a molecular orientation due to high stretching, but the rigidity of the bottom corner portion or its vicinity is significantly improved with the increase in thickness,
For this reason, the axial load strength of the container is improved to 30 kgf or more.

The existence of the annular thick portion at or near the bottom corner can be confirmed by obtaining the thickness distribution from the center of the bottom to the periphery of the bottom. In general, the thickness of the annular thick portion is maximized. There is at least one peak that takes a value, or there is a shoulder that is relatively flat in thickness. FIG. 3 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 annular thick portion, which are the thickest, there are portions with a reduced thickness. 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.

Of course, the existence of the reduced thickness portion between the bottom center gate remaining portion and the annular thick portion does not particularly hinder the axial load strength of the container. This is because buckling of the empty container, which is a problem in the distribution process, occurs at the bottom corner or in the vicinity thereof.

The container of the present invention is not limited to this, but as the preform with a bottom, a preform whose bottom shoulder is thicker than the periphery of the gate and the body is used. The bottom and body of this preform are highly stretch blow-molded to form a highly stretch-oriented annular thick portion at or near the bottom corner of the molded product,
It is manufactured by highly stretching orienting the bottom portion surrounded by the annular thick 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.

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 other than the bottom center gate remainder and the vicinity thereof is 1.1.
mm, particularly 0.3 to 1.1 mm, and this portion has an oriented crystallinity of 20% or more. If the stretch thinning and oriented crystallization of the above degree are performed, stiffness, heat resistance, impact resistance, satisfactory results with respect to stress cracking resistance are obtained,
Further, the weight of the container bottom can be reduced.

In the case of a heat-resistant container, the high-stretch orientation layer is generally heat-fixed, and the heat-stretched high-stretch orientation layer generally has a crystallinity of 30 to 55%. And the vessel wall is substantially transparent except for the low stretch orientation at the bottom center gate. In the case of using a sterilizing agent having a relatively high temperature at the time of sterilizing the container in the aseptic filling container, for example, the high-stretched orientation layer can be heat-fixed as in the case of the heat-resistant container to improve the heat resistance.

Further, in the present invention, the annular thick portion in the high stretch orientation state is provided at least in part or in the vicinity of the bottom corner portion, and the annular thick portion generally has a thickness of 0.4 to 1 mm. This portion has an oriented crystallinity of 20% or more. By keeping the above thickness and the oriented crystallinity in the bottom corner portion or the vicinity thereof, the axial load strength of the container can be increased to the above-mentioned range.

The heat-fixed annular thick portion generally has a degree of crystallinity of 30 to 55%, similarly to the highly oriented layer, and the annular thick portion is also substantially transparent.

The bottom center gate remainder in the container of the present invention has a highly stretched and thinned highly oriented layer.
This high-stretch alignment layer is as transparent as the high-stretch alignment layer formed in the other part of the bottom, and is generally 0.3 to 1 m.
m, in particular, a wall thickness of 0.35 to 1 mm and an oriented crystallinity of 20% or more. When heat setting is performed, the bottom center gate residue generally has a crystallinity of 25 to 55%. However, if a low stretching orientation portion exists in the bottom center gate residue,
This part tends to whiten.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Container of the Present Invention] In FIG. 1 showing a stretched resin container of the present invention, this container has a neck and neck portion 1 formed by biaxial stretch blow molding of a resin, and a shoulder connected to the neck and neck portion. It comprises a part 2, a trunk 3 and a bottom 4. In this specific example, the bottom portion 4 includes a bottom center concave portion 5 and a bottom peripheral convex portion 6 around the bottom central concave portion. The bottom peripheral convex portion 6 has a grounding portion 7 and a bottom portion connected to the trunk portion. There is a corner section 8. At the center of the bottom center concave portion 5, a bottom center gate remaining portion 9 is present. The shoulder 2 and the torso 3 except for the connection with the mouth and neck 1
It is thinned in a highly stretched orientation state.

The bottom part 4 connects the thick gate remaining part 9 located at the center of the bottom and the gate remaining part 9 and the bottom peripheral convex part 6.
Approximately frustoconical or tapered gate periphery 10
It consists of In this container, each part (10, 7, 6) of the bottom part 4 except the gate remaining part 9 consists substantially only of a layer in a high stretch orientation state. Except for the remaining gate 9, the thickness is reduced to 1.1 mm or less.

When the stretched resin container of the present invention is used as a heat-resistant container or a container for aseptic filling requiring heat resistance, the body and the bottom are heat-fixed. Means for thermally fixing the body and bottom are not particularly limited in the present invention,
Means for performing heat fixing during blow molding by a normal high-temperature blow mold can be employed. In the heat-resistant container, the mouth and neck 1 is usually heated to be spheroidized, that is, whitened, and the heat resistance of the non-crystallized mouth and neck 1 is improved.

[Bottom Center Gate Remaining] The bottom center gate remaining portion 9 of the container of the present invention is relatively thick, but as shown in the enlarged bottom center sectional view of FIG. 12 in combination. Normally, the high stretch orientation portion 11 of the gate remainder 9 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 FIG. 2, which shows an example of a preferred arrangement of the remaining gate 9, in the case where the bottom is not thermally fixed, the low-stretch alignment layer 12 of the remaining gate 9 is in a transparent state like the high-stretch alignment section 11. At this time, the mechanical properties such as the rigidity, heat resistance, and impact resistance of the gate remaining portion 9 and the vicinity thereof are high in the highly stretched oriented portion 1.
1 and has excellent mechanical properties. Further, in the heat-resistant container, the bottom is heat-fixed. In this case, the low-stretched oriented portion 12 of the remaining gate 9 usually undergoes thermal crystallization and becomes white. On the other hand, the remaining gate 9
The highly stretched orientation layer 11 remains transparent even when heat set.
In the bottom center gate remaining portion 9 of the stretched resin container for heat resistance, the highly stretched alignment layer 11 is present on the inner surface side, so that the combination of heat resistance and impact resistance is particularly excellent.

FIG. 3 showing an example of a preferred arrangement of the high-stretch alignment layer is the same as that of FIG. 2 in that the bottom center gate remainder 9 has a high-stretch alignment layer 12 disposed on the inner surface side of the container. However, a special composite structure exists on the outer surface side of the container. That is, on the outer surface side of the container, a composite layer of the ring-shaped low-stretched oriented portion 12a and the high-stretched oriented layer 11a in the center thereof is formed. When the bottom is heat-fixed, the ring-shaped low-stretch alignment portion 12a is whitened, but the high-stretch alignment layer located at the center thereof remains transparent. In the composite shape, the thickness of the highly stretched orientation layer is particularly increased, and the composite shape is particularly excellent in heat resistance and impact resistance.

Further, even if the structure comprises a generally transparent high-stretch orientation layer on the inner surface side of the container and a generally whitened low-stretch orientation portion on the outer surface side of the container, the high-stretch alignment layer 11 is very thick and low-stretch. The stretched low orientation part 12 may be formed thinly at a very limited part 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 9
It is preferable in terms of heat resistance and impact resistance that the crystallized material be generally crystallized to have a crystallinity of 20% or more, preferably 25% at the time of blow molding.

By heat-fixing the bottom including the bottom center gate residue, the low-stretch orientation layer 12 of the gate residue 9 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 9 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 9, 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 9 is usually preferably about 1 to 3.5 mm at the maximum portion. In the present invention, the bottom center gate remaining portion 9 does not need to be finished in the gate portion of the preform. Can form a container bottom portion with a high stretch orientation. On the other hand, the thickness of the highly stretched alignment layer 12 in the bottom center gate remaining portion 9 may be any thickness that imparts sufficient heat resistance to the bottom center, and is generally 0.35 mm or more, particularly 0.4 to 1 mm. 0.1 mm, and preferably accounts for 20% or more, particularly 30% or more of the entire thickness of the remaining gate.

The diameter Dg of the remaining bottom center gate 9 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.

[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 9.

If the thickness of the gate peripheral portion 10 is less than 0.3 mm, the thickness becomes too thin, and the rigidity at the center of the bottom decreases, which is not preferable. On the other hand, when the thickness of the peripheral portion of the gate exceeds 1.1 mm, it becomes difficult to form a highly stretched alignment layer on the remaining gate. However, in the case where the thickness of the gate peripheral portion exceeds 1.1 mm in a very limited narrow portion, it does not particularly hinder a part of the remaining gate from being highly stretched and oriented.

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

[Circular Thick Part] In the bottom part of the container of the present invention, the thickness and crystallinity of each part in the bottom part 4 are in the ranges already described, but in the present invention, in the bottom corner part 8 or the vicinity thereof, It is important to provide an annular thick portion 13 (FIG. 4).

In FIG. 4 showing the relationship between the position of the bottom portion of the container of the present invention and the distribution of thickness, the bottom center gate remaining portion 9 has the largest wall thickness, and the bottom center peripheral portion 10 has a smaller thickness. In the bottom corner portion 8 and its vicinity, the thickness increases, and there is a portion where the thickness has a maximum value. Annular thick part 1
The thickness of No. 3 is usually in the range of 0.4 to 1 mm, and particularly the thickness of the thickest part is usually in the range of 0.5 to 1 mm.

[0054] When the annular thick portion 13 the maximum value T ₃ of the thickness of the thickness of the bottom portion 4 of the lower part of the thickness of the trunk portion 3 continuing to T ₄ and bottom around the center portion 10 has a T _5, generally, T ₃ > T ₄ and T ₃ ≧ T ₅ , especially T ₃ > T ₅ . From the viewpoint of improving the burst strength and the axial load strength, the thickness ratio of T ₃ > T ₄ is in the range of 1.3 to 3.5, particularly 1.5 to 3, and the thickness ratio of T ₃ > T ₅ The ratio is preferably in the range from 1 to 2.2, especially from 1.1 to 2.

The width d of the annular thick portion 13, that is, the width between the rising portions of the thickness varies depending on the size and shape of the bottom of the container, but is generally in the range of 15 to 30 mm.
It is preferable in terms of improvement in axial load strength and heat resistance.

[Thickness and Crystallinity of Container] In the container of the present invention, the mouth and neck portion 1 and its vicinity, and the bottom center gate remaining portion 9
And the thickness of the container except for the vicinity thereof is 0.2 mm to l.m. 1
mm, preferably in the range of 0.3 mm to 0.9 mm.

The degree of crystallinity associated with the stretching orientation of the container excluding the neck portion 1 and its vicinity, and the remaining portion of the gate 9 is 20%, preferably 25% or more.

In the container of the present invention which requires heat resistance, it is preferable that the whole container is heat-set, and the crystallinity is preferably 25 to 55%. After that heat fixation
The portions of the mouth and neck 1 and the vicinity thereof and the remaining portion of the gate remaining portion 9 except for the low stretch orientation portion substantially maintain a transparent state.

[Resin] In the present invention, as the plastic material, any plastic material can be used as long as it can be stretch blow molded and thermally crystallized. Thermoplastic polyesters, especially ethylene terephthalate 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.

Although homopolyethylene terephthalate is preferred in terms of heat and pressure resistance, a copolymerized polyester containing a small amount of an ester unit other than the ethylene terephthalate unit may 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 and 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.

[Method of Manufacturing Container] The container of the present invention is not limited to this, but as a preform having a bottom, the bottom shoulder portion of the preform is thicker than the gate peripheral portion and the body portion. Using a preform, the bottom and the body of the preform are highly stretch blow-molded to form a highly stretch-oriented annular thick portion at or near the bottom corner of the molded product, and the annular thick portion is formed. It is manufactured by highly stretching orienting the bottom surrounded by the part. The preform used has a gate portion at the center of the bottom.
It is preferable to maintain the temperature within ° C. to form a highly stretched alignment layer on the remaining bottom gate of the molded article.

The preform used for manufacturing the container of the present invention has a shape as shown in FIG. 5 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, a support ring for holding the container, and the like, and the neck 21 is generally thermally crystallized, that is, spherulized. 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. 6 showing the bottom of the preform in an enlarged manner and FIG. 7 showing the correspondence between the bottom of the preform and the bottom of the container, the bottom 23 of the preform is the bottom shoulder 2.
5 and is provided with the gate periphery 26, the thickness T ₁ of the barrel portion 22, the thickness T ₃ of thickness T ₂ and bottom shoulder of the gate periphery
It is important that a relationship satisfying the following formulas T ₃ ≧ T ₁ and T ₃ > T ₂ is satisfied in order to form an annular thick portion at or near the bottom corner portion 8 of the container.

That is, in the manufacture of the container of the present invention, the gate portion 24 of the preform 20 is replaced by the bottom center gate remaining portion 9 of the container,
The gate periphery 26 of the preform is the gate periphery 10 of the container, and the bottom shoulder 25 of the preform is the bottom corner 8 of the container.
The stretching conditions are set so that the bottom convex portion 6 including the and the body 22 of the preform respectively correspond to the body 3 of the container,
Moreover, by making the thickness of the container wall of the preform satisfy the above-described relationship, it is possible to form an annular thick portion at or near the bottom corner of the container.

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 In order to form the annular thick portion clearly and reliably in the bottom corner portion 8 of the container or in the vicinity thereof, and to maintain the thickness dimension of each portion of the bottom bottom of the container within the above-described range, It is suitable.

In the production of the stretched resin container of the present invention, the preform heated to the stretching temperature is pushed up the bottom center of the preform while driving the stretching rod inserted into the preform in the mold. Stretching in the longitudinal direction, it is preferable to manufacture a stretched resin container by blowing a high-pressure gas into the preform in synchronization with the stretching, and in this case, the temperature of the bottom central portion is reduced until immediately before the stretching process is completed. It is most preferable to maintain the temperature within 40 ° C. and to stretch the center of the bottom highly.

In the case of a heat-resistant container, at the time of 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 spherulized portion.

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 the 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 spherulization 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 spheroidizing. At the center of the closed bottom portion 23, there is a gate portion 24 formed during injection molding. In the present invention, in order to form the highly stretched alignment layer 11 (see FIG. 2) at the center of the bottom of the container while leaving the gate portion 24 as it is without being subjected to a finishing step such as further cutting. Use.

Referring to FIG. 8 for describing the dimensions of the gate portion 24, the gate portion 24 has a length h and a root diameter d, and is generally tapered (taper angle α).
It has become. h is 3 mm or less, especially 0.1 to 1 mm
Where d is 2 to 6 mm and α is 0.5
Suitably, it is in the range of 6 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, the mouth spherulization in the heat-resistant container is generally performed by heating the preform bottom and the mouth to a temperature of 140 to 220 ° C., particularly 160 to 210 ° C. while being thermally insulated from other parts. Can be performed. The crystallinity at the mouth of the preform is preferably at least 25%.

For stretch blow molding from a preform, a method of performing stretch blow molding subsequent to preform molding using 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 is characterized in that the entire container except for the mouth and neck is made substantially thinner in a highly stretched state. In particular, the high stretch orientation is applied to the entire bottom including the bottom center including the remaining gate. It is important to provide the layers.

In particular, in the present invention, the gate peripheral portion 10 which is a portion connected to the bottom center gate remaining portion 9 during blow molding.
It is important that (FIG. 1) be in a highly stretched orientation state with an appropriate thickness. Thereby, the bottom center gate remainder 9 (FIG. 1)
Although it is thick, it is possible to form the high stretch orientation part 11 (FIG. 2) in a layer continuous with a part thereof.

At this time, the appropriate thickness of the gate peripheral portion 10 (FIG. 1) is not more than the maximum thickness capable of maintaining the high stretch orientation state and not less than the thickness not excessively thin. It is preferably within the above range. In this case, if the thickness of the gate peripheral portion is too large, it is difficult to form a highly stretched alignment layer on the remaining gate, while if the thickness of the gate peripheral portion is too small, the rigidity of the bottom portion is reduced. Occurs.

In the biaxial stretch blow molding, the above-mentioned gate peripheral portion 10 (FIG. 1) can be brought into a high stretch orientation state with an appropriate thickness by stretching blow molding from the bottom of the preform to the gate peripheral portion. It is important to optimize the stretching ratio of the film. Specifically, the area stretching ratio at the time of stretching the peripheral portion of the gate is 3.5 to 12.5 times, particularly 5 to 1 times.
It is preferable to make it 0 times.

In order to attain the above-mentioned preferred stretching ratio of the bottom center gate peripheral portion 10 by blow molding, first, the shape and thickness distribution of the preform 20, particularly, the preform which finally becomes the gate peripheral portion Thickness T of bottom portion 26
₂ needs to be optimized. Next, the blow molding conditions for performing the blow molding are optimized to obtain a predetermined stretch ratio of the peripheral portion of the gate. The blow molding conditions include the heating temperature and temperature distribution of the preform, the stretching speed at which the bottom of the preform is pushed up by the stretching bar, the timing at which high-pressure air is blown into the molded body from the start of stretching of the stretching bar, and the stretching blow speed determined by the high-pressure air flow rate. It is important to further optimize the temperature level of the molded body when the bottom is substantially stretched.

As a result of the study, the present inventors have found that the bottom is substantially in a highly stretched state in the blow molding after the remaining bottom gate of the molded body reaches the bottom of the mold. It was ascertained that the stretch molding at the bottom was performed until immediately before the end of the blow molding in which the blow shape was substantially determined. At that time, by keeping the temperature at the center of the bottom of the molded body relatively high right before reaching the bottom of the mold and immediately before the end of the blow molding, the bottom, particularly the peripheral edge of the gate, at an appropriate stretching ratio. It has been found that a high stretch orientation state can be obtained. As a result, it became possible to form a layered high-stretched oriented portion in the remaining gate. On the other hand, if the temperature of the center of the bottom of the molded body that has reached the bottom of the mold is too low as compared with the initial preform heating temperature, the peripheral edge of the gate remains in a relatively low stretch orientation state. Accordingly, the entire remaining gate remains in a low stretched orientation state or a non-stretched state.

More specifically, the temperature of the remaining gate of the molded body until reaching the bottom of the mold during the blow molding and immediately before the bottom is almost completely stretched is set at 40 ° C., which is the heating temperature of the preform. It is preferably within 30 ° C.

9 and 10, which show the production of a container by single-stage blow molding, the preform 20 has its neck supported by a core mold 31 and a closed split mold 3.
2, 32. On the opposite side of the core mold, a bottom mold 33 which defines the bottom shape of the molded product, that is, the concave / convex bottom shape is also arranged. By inserting the stretching rod 34 into the preform 20 and pushing up the preform bottom 23,
Stretch molding is performed. At a certain stage during the stretch molding, a high-pressure gas is blown into the molded body through the core mold 31 to perform blow molding to obtain a container having a shape along the mold.

In the embodiment shown in FIGS. 9 and 10, a press rod 35 is arranged on the side of the bottom die 33 coaxially with the draw rod 34, and the gate 2
4 is pinched by the stretching rod 34 and the pressing rod 35 and regulates the position so that it is located at the center of the container bottom 5 where the gate 24 at the bottom of the preform is formed. 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.

Immediately before the completion of the stretching process, the temperature drop of the sandwiched portion at the bottom of the preform should be kept within 40 ° C.
More preferably, the temperature is within 30 ° C.
6 can be made substantially thinner in a highly stretched state over the whole bottom including the bottom center portion which is the sandwiching portion, and a high stretch alignment layer can be formed on the remaining bottom center gate.

In the above blow molding, first, the shape and thickness distribution of the preform are considered in consideration of the stretching ratio so that the portion to be the peripheral edge of the bottom center gate is sufficiently stretched and has an appropriate thickness. It is important to decide. At this time, the height of the gate portion at the center of the bottom of the preform is preferably in the range of 0.1 to 3 mm, particularly 0.5 to 1 mm. Secondly, measures are taken to prevent a temperature drop near the bottom center of the molded body during blow molding. In this case, it is important to reduce the heat conduction from the preform to the stretch bar and the press bar during blow molding. Specifically, it is effective to use a heat-insulating material such as a heat-resistant plastic or ceramic at the tip of the stretching rod or the pressing rod. It is effective to heat at least the tip of the press rod.
When a press rod is not used, a heat insulation layer should be provided on the surface of the center of the mold bottom where the remaining gate of the molded body first contacts during blow molding, or the bottom mold should be heated. Is valid.

In performing the blow molding, the heating temperature and the temperature distribution of the preform are optimized. The heating temperature of the preform is generally 85 to 135 ° C, particularly 90 to 1 ° C.
A temperature of 30 ° C. is suitable. At that time, it is important that the difference between the heating temperature of the bottom of the preform and the heating temperature of the body is within 10 ° C. in order to bring the bottom into a highly stretched orientation state. in this case,
If the heating temperature difference between the bottom and the body of the preform exceeds 10 ° C., only the higher temperature portion tends to be stretched too much, which is not preferable.

A container having a highly stretched orientation layer in which the entire container except for the neck and its vicinity is thinned in a highly stretched orientation state by using the above-described means and method and further optimizing various blow molding conditions. Can be molded. Also,
The peripheral edge portion 10 of the bottom center gate of the formed container has a wall thickness of 0.1 mm.
In the range of 3 to 1.1 mm, the film is in a highly stretched orientation state, and accordingly, a highly stretched orientation layer 11 is formed on the bottom center gate remaining portion 9. In addition, the bottom shoulder 2 of the preform
5 is thickened, it is possible to form an annular thick portion 13 in a high stretch orientation state in the bottom corner portion 8 or in the vicinity thereof.

The heat resistance of the container can be improved by thermally fixing the shoulder, the trunk, and the bottom. During the heat setting, the high-stretch alignment layer keeps a substantially transparent state, but the low-stretch alignment portion 12 of the remaining gate 9 usually becomes spherulite and whitens. Although the low-stretched oriented portion 12 of the remaining whitened gate becomes brittle, the high-stretched oriented layer 11 retains sufficient flexibility, so that the impact resistance indicated by the drop strength is maintained at an extremely high level. I have. As a specific heat fixing means for the container, by setting the temperature of the blow mold, the body mold and the bottom mold to the crystallization temperature of the resin, the molded article can be heated and thermally crystallized in the blow molding step. It is valid. Although the above-mentioned thermal crystallization temperature varies depending on the required heat resistance, heat fixing is usually performed at 110 to 200 ° C. At this time, the degree of crystallinity accompanying thermal crystallization is 20 to 55%. In addition to the above-described heat fixing means using a mold, a means for performing heat fixing in an intermediate step of a two-stage blow molding method in which blow molding is performed twice can be adopted.

[Production Example] Using a blow molding apparatus as shown in FIGS. 9 and 10, a polyethylene terephthalate (PE) having a capacity of 1500 ml as shown in FIG.
A heat-resistant container made of T) was prepared.

A preform having a bottom as shown in FIGS. 5 and 6 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 is 0.85, and the ratio T2 / T3 of the thickness T2 of the gate peripheral portion and the thickness T3 of the bottom shoulder is as follows. 0.9. The diameter d of the gate portion of the preform shown in FIG. 8 is 4 mm, the height h is 0.8 mm, and the angle α
Was 1 ゜. The preform was heated until the mouth and neck became white and spheroidized.

The preform was first heated to about 100 ° C., and as shown in FIG.
Into a mold heated to ℃, and then sandwich the bottom of the preform between a stretching rod installed inside and a press rod installed outside, and simultaneously push up the bottom of the preform with the stretching rod and simultaneously push up to 30 kgf. / Cm ² compressed air is blown into the preform for blow molding, heat-set in a mold for 3 seconds, and then cooled compressed air is introduced to cool the molded product. Was removed from the mold. In the above-mentioned stretch blow molding, the material of the tip of the stretching rod and the press rod is made of polytetrafluoroethylene (TF) having good heat insulating properties, and the temperature decrease of the bottom center gate residue during blow molding is suppressed. A highly stretched orientation layer was formed at the bottom of the container.

The shoulder, trunk and bottom of the obtained container, except for the bottom center gate remainder, were thinned to a high stretch orientation state, had a thickness of 1 mm or less, and were in a transparent state. The vessel wall in the highly stretched orientation state is heat-fixed by contact with a mold in a high temperature state, and the crystallinity of those portions is 33 to 3
8%. The bottom center gate remainder has a diameter of about 5 mm and, as shown in FIG. 2, is composed of 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 0.7 mm and a crystallinity of about 33%. On the other hand, the whitened low-stretched orientation layer had a maximum thickness of 1 mm and a spherulitic degree of crystallinity of about 30%. An annular thick portion was formed at the bottom corner and in the vicinity of the obtained container. The thickest part of the annular thick part in the container longitudinal section is located at the bottom corner R, and the thickness of the largest thick part is 0.6.
０．６0.65 mm. The width of the annular thick portion was about 15 mm. On the other hand, the minimum thickness of the trunk portion close to the annular thick portion was 0.38 mm, and the minimum thickness of the peripheral portion of the gate was 0.4 mm.

When the axial load strength of the above container was measured, it was 40 kgf, indicating that the container had a sufficient axial load strength.
Further, the above container was filled with hot water of 83 ° C., and the degree of thermal deformation of the container was measured.

[0100]

According to the present invention, the bottom portion, including the remaining gate, is effectively oriented and crystallized to a high stretch orientation state, and further has a high stretch state annular thick portion at the bottom corner portion. Provided is a stretched resin container in which the weight of the bottom can be reduced, the bottom has excellent heat resistance, stress crack resistance, moisture absorption resistance, and the like, and the container has improved axial load strength, impact resistance, and the like.

[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 a partially enlarged sectional view showing an example of a structure of a bottom center gate remaining portion in the container of the present invention.

FIG. 3 is an explanatory view showing another example of the structure 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 a partial cross-sectional side view showing an example of a preform used in the method of the present invention.

FIG. 6 is an enlarged sectional view for explaining the dimensions of the bottom of the preform.

FIG. 7 is an explanatory diagram showing the correspondence between each part of the bottom of the preform and each part of the bottom of the container.

FIG. 8 is an explanatory view showing the shape and dimensions of a gate portion of a preform.

FIG. 9 is a cross-sectional view showing a state before the start of blow molding in an example of manufacturing a container by the one-stage blow molding method of the present invention.

FIG. 10 is a cross-sectional view showing a state after the completion of blow molding in an example of manufacturing a container by the single-stage blow molding method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mouth and neck part 2 Shoulder part 3 Body part 4 Bottom part 5 Bottom central concave part 6 Bottom peripheral convex part 7 Ground part 8 Bottom corner part 9 Gate remaining part 10 Gate peripheral part 11 High stretch oriented part 12 Low stretch oriented part 13 Annular thick part Reference Signs List 20 Preform 21 Neck 22 Body 23 Preform bottom 24 Gate remaining 25 Bottom shoulder 26 Gate periphery 31 Core mold 32 Split mold 33 Bottom mold 34 Stretching rod 35 Press rod 36 Molded product

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[Procedure amendment]

[Submission date] July 21, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction contents]

The existence of the annular thick portion at or near the bottom corner can be confirmed by obtaining the thickness distribution from the center of the bottom to the periphery of the bottom. In general, the thickness of the annular thick portion is maximized. There is at least one peak that takes a value, or there is a shoulder that is relatively flat in 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.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0054

[Correction method] Change

[Correction contents]

The maximum value of the thickness of the annular thick portion 13 is represented by T ₆ ,
When the lower portion of the thickness of the trunk portion 3 continuing to the bottom 4 and the thickness of the _{T 4} and bottom around the center portion 10 and _{T 5,} generally, _T 6> _{T 4} and _{T 6} ≧ T _5, especially in _T 6> _{T 5} is there. From the viewpoint of improving the burst strength and the axial load strength, T ₆ > T ₄
Is in the range of 1.3 to 3.5, particularly 1.5 to 3, and the thickness ratio of T ₆ > T ₅ is in the range of 1 to 2.
2, particularly preferably in the range of 1.1 to 2.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0089

[Correction method] Change

[Correction contents]

In the embodiment shown in FIGS. 9 and 10, a press rod 35 is arranged on the side of the bottom die 33 coaxially with the draw rod 34, and the gate 2
4 is held between the stretching rod 34 and the pressing rod 35, and the position is regulated so that the gate 24 at the bottom of the preform is located at the center of the container bottom 5 to be formed . 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.

[Procedure amendment 4]

[Document name to be amended] Drawing

[Correction target item name] Fig. 4

[Correction method] Change

[Correction contents]

FIG. 4

Continued 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 (9)

[Claims] 1. A self-supporting container formed by biaxial stretch blow molding of a resin and having a mouth, neck, shoulder, trunk, and a central portion having a concave bottom when viewed from below. It has a highly stretched orientation layer including the bottom center gate remainder, and has a highly stretched orientated annular thick portion at least in part or in the vicinity of the bottom corner connecting the body and the bottom. A stretched resin container characterized by the above-mentioned. 2. The container according to claim 1, wherein the thickness of the bottom corner portion and the grounding portion is greater than the thickness of the body near the bottom corner portion. 3. The annular thick part has a thickness of 0.4 to 1 mm.
The container according to claim 1 or 2, wherein 4. The stretched resin container according to claim 1, wherein the degree of crystallinity associated with the orientation of the highly stretched orientation layer is 20% or more. 5. The stretched resin container according to claim 1, wherein the thickness of the portion excluding the bottom center gate remaining portion and the vicinity thereof is 1 mm or less. 6. 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. 7. The stretched resin according to claim 1, wherein the bottom is heat-set at a crystallinity of 25% or more, and is substantially transparent except for the bottom center gate remainder. container. 8. The entire container is heat-set with a crystallinity of 25% or more, except for the mouth and neck and the bottom center rest.
The stretched resin container according to any one of claims 1 to 6, which is substantially transparent. 9. A method of manufacturing a stretched resin container by biaxially stretch-blowing a bottomed preform, wherein a bottom shoulder of the preform is a thicker preform than a gate peripheral portion and a body portion. Yes, the preform bottom and body are highly stretch blow-molded to form a high stretch oriented annular thick portion at the bottom corner of the molded article, and the bottom surrounded by the annular thick portion is generally A method for producing a stretched resin container, wherein the stretched resin is highly oriented.