JP3449182B2 - Manufacturing method of heat-resistant stretched resin container - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates, excellent heat resistance or heat pressure resistance and impact resistance, even relates to a process for the production of stretched resin molded container which is excellent in self-supporting.

[0002]

2. Description of the Related Art Polyethylene terephthalate (PET)
Biaxially stretched blow molded containers of thermoplastic polyester such as those have excellent transparency and surface gloss, as well as the impact resistance, rigidity and gas barrier properties required for bottles, and are bottled containers for various liquids. That is, it is used as a bottle.

In general, in the production of bottled products, it is necessary to hot-fill the contents or to heat-sterilize or sterilize the contents after filling them in order to improve the storability of the contents.

The heat-resistant and pressure-resistant self-supporting container is required to have resistance to hot filling and heat sterilization of the contents also from the viewpoint of securing self-supporting property. In particular, at the bottom of the container (hereinafter also referred to simply as the bottom of a petaloid shape) having legs and valleys that are alternately arranged around the bottom, ensure the independence of the contents after hot filling and heat sterilization. Is important, and high heat and pressure resistance is required.

In the heat resistant and pressure resistant self-supporting container currently on the market, the central portion of the bottom of the petaloid is relatively thick in the unstretched or low stretched orientation state. The bottom of such a petaloid is excellent in pressure resistance at normal room temperature, but is 70 ° C.
The heat-resisting pressure strength at a high temperature is about a low level. Therefore, it is used under conditions where the gas pressure of the contents and the temperature during the heat sterilization treatment are limited. Further, when the resin forming the bottom portion of the thick-walled petaloid absorbs excessive moisture, the decrease in heat-resistant pressure strength becomes remarkable, and it is not suitable for a heat-resistant pressure-resistant freestanding container.

By heat fixing the thick bottom portion in such a low stretch orientation state and performing thermal crystallization, the heat and pressure resistance can be increased. However, when the bottom portion in the low stretch orientation state is thermally crystallized to sufficiently increase the heat-resisting pressure strength, the thermally crystallized site becomes significantly brittle. If the embrittled portion occupies a considerable portion of the bottom of the petaloid, there arises a problem that the impact resistance is significantly reduced. Further, due to thermal crystallization, the bottom portion in the low stretch orientation state is whitened, but if the area is too wide, it is aesthetically unfavorable.

In Japanese Patent Laid-Open No. 8-267549, there is disclosed a container having a thick thermal crystallization part in the center of the bottom part, a thin part in the periphery thereof in a highly stretched orientation, and a heat-fixed petaloid bottom part. Disclosure. In such a container, the central thermal crystallization part at the bottom is brittle, but it can be limited to a relatively small area.On the other hand, the thinned part around it in the highly stretched orientation state is softened even if it is heat-fixed. Since it is rich in properties and possesses high impact resistance, the impact resistance of the petaloid bottom can be at a level without problems.

[0008]

However, in the above prior art, the thermal crystallization part at the center of the container bottom is obtained by heating and thermally crystallizing the bottom part of the preform, so that a troublesome heating step is required. Become.

Further, the preform used for producing the stretch blow molded container is produced by injection molding of resin.
The gate is always connected to the center of the bottom of this preform. As is the case with general stretch blow molding,
In the case of a petaloid bottom container, this gate is
Trimming is done to cut this as an extra item.

However, such a trimming operation is a tedious process, and there is a problem in accuracy that it is not always easy to make the cut size constant.
In particular, if the length of the gate portion is made to approach zero as much as possible in consideration of the moldability of the bottom portion of the container, a finishing operation such as polishing is required after the trimming operation, which increases the number of steps and becomes more troublesome.

The present inventors have made a biaxial stretch blow molding means for bringing the bottom of the petaloid into a highly stretched orientation state without thermally crystallizing the bottom of the preform and effectively utilizing the remaining gate of the preform. I diligently studied. as a result,
It has been found that stretch molding of the bottom portion in blow molding is significantly performed from the time when the gate portion, which is the center portion of the bottom of the molded body, reaches the bottom portion of the mold. Then, by adopting a means for reducing the temperature drop of the bottom center and the vicinity thereof at the time when the center of the bottom of the molded body reaches the bottom of the mold to a certain level or less, the bottom including the rest of the gate is highly It has been found that it can be layered in a stretched orientation.

That is, an object of the present invention is to effectively crystallize the bottom portion including the rest of the gate into a highly stretched orientation state,
Heat resistance or excellent in heat pressure resistance and impact resistance, even to provide a manufacturing <br/> method stretched resin molded container which is excellent in self-supporting and appearance characteristics. Another object of the present invention is to provide a process for producing the stretch-molded container with a relatively small number of steps and by effectively utilizing resources.

[0013]

According to the present invention, a preform heated to a drawing temperature is stretched in a mold by a drawing rod inserted inside the preform and a press rod outside the preform to form a bottom of the preform. In a method for producing a stretched resin container comprising sandwiching a central portion and then blowing a high-pressure gas into the preform while driving a stretching rod at the same time, the preform is a preform having a gate portion at the bottom central portion, and Until the end of the stretching process, the temperature drop at the center of the bottom is kept within 40 ° C for the primary blow molding.
The bottom mold used is a curved part around the bottom from the outer circumference to the center.
Outer peripheral projection, circumferential recess, inner peripheral projection and central recess
Part, and the circumferential recess protrudes more inward than the central recess.
Highly stretched at the center of the bottom with a shape such that the thickness of the peripheral edge of the gate is in the range of 0.35 to 1 mm and the area stretch ratio of the peripheral edge of the gate is 3.5 to 12.5 times. ,
As a result, a secondary molded product including a bottom having a highly stretched alignment layer including the center of the bottom is formed, and at least the bottom of the secondary molded product and a part of the body portion connected to the bottom are heated and shrunk.
There is provided a method for producing a heat-resistant resin container, characterized in that a final molded product is obtained by secondary blow molding the tertiary molded product in a mold.

In the manufacturing method of the present invention, 1. The preform gate has a height of 0.1 to 3 mm
Be one having a diameter D ₅ of the circumferential recess of Sokokin type used in 2.1 primary blow molding
Is 0.5 to 0.9 times the body diameter D ₀ of the secondary molded product , and has a circumferentially concave shape
Step H ₂ between the central portion and the central concave portion is 1 to 10 mm, the circumferential concave portion
The step H ₃ between the outer peripheral side concave portion and the outer peripheral side concave portion is 0 to 5 mm,
Is preferred.

[0015]

DETAILED DESCRIPTION OF THE INVENTION Heat-resistant stretched tree obtained by the present invention
The fat container is formed by biaxial stretch blow molding of resin
It has a mouth, neck, shoulders, torso and bottom, but the center of the bottom
The rest of the gate is located at the gate connection and radially outward of it.
It is obvious that it has a high-stretch alignment layer connected to the bottom of the high-stretch alignment.
It is a remarkable feature.

[0016] In the present specification, the gate portion of the preform, called the bottom gate portion protruding from the preform, whereas the gate remainder of the container, the thickness direction of the bottom center corresponding to the gate portion It refers to the whole part.

In this container, the pressure-strength strength at a high temperature of about 70 ° C. exists because the highly-stretched orientation layer integrally connected to the gate connection portion and the highly-stretched orientation bottom portion radially outward of the gate connection portion also exists at the center of the bottom. That is, the heat and pressure resistance is at a high level,
It is possible to maintain preferable heat and pressure resistance. Furthermore, in a container in which the bottom portion of the petaloid shape in the highly stretched and oriented state is heat-fixed, the heat and pressure resistance is further improved, and particularly excellent heat and pressure resistance, independence, impact resistance and the like are provided.

It has been found that the stretch molding of the bottom portion in blow molding is significantly performed from the time when the gate portion, which is the center portion of the bottom of the molded body, reaches the bottom portion of the mold. In the present invention, by adopting a means for reducing the temperature drop of the bottom center and the vicinity thereof at the time when the bottom center of the molded body reaches the die bottom to a certain level or less, the bottom, including the gate remaining part, is included. It is possible to reduce the thickness to a high stretch orientation state.

The remaining gate portion 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 where heat and pressure are simultaneously applied. Therefore, the conventional idea was to thermally crystallize this part in the preform state or to make the gate remainder as thin as possible so that it could be easily stretch-oriented, but in the present invention, the gate remainder is thick. Even with meat, the highly stretched alignment layer can be formed in the central portion by the above-mentioned means, and the above problem is solved.

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 of the preform bottom portion during blow molding, particularly the gate peripheral portion including the gate connecting portion in contact with the rest of the gate. By optimizing the stretching ratio, the bottom center gate remaining portion of the container can be made thick, and the surrounding gate connection portion and gate peripheral portion can be in a highly stretched orientation state and have a preferable thickness.

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 state as described above, surprisingly, the high-stretch orientation portion and the low-stretch orientation are provided in the thick gate remainder. In addition, it is understood that the high stretch orientation portion of the remaining portion of the gate is layered and has a structure in which the gate connection portion and the gate peripheral portion in the high stretch orientation state are continuously connected. It was

The structure of the bottom-bottom gate remaining portion has a structure in which the periphery of the bottom-gate portion of the preform, which corresponds to the bottom-center gate remaining portion, is in a highly stretched orientation state during blow molding, so that the bottom-gate portion is formed in the thickness direction. It is shown that the part is pulled by its highly stretched periphery to locally undergo high stretch orientation, resulting in the formation of a layered high stretch orientation part.

[0023]

【Example】

[Container of the Present Invention] In FIG. 1 showing a heat and pressure resistant container of the present invention, the container is a mouth / neck portion 1 formed by resin biaxially stretch blow molding, a shoulder portion 2 connected to the mouth / neck portion, and a body. It consists of a part 3 and a bottom part 4. In this example, the bottom 4
Is composed of a bottom central valley portion 5 and a plurality of valley portions 6 and foot portions 7 which are alternately arranged around the bottom central valley portion. The lower portion of the body portion 3 connected to the bottom portion 4 has a diameter D ₀ , and at the center of the bottom,
There is a bottom center gate remnant 8 of diameter Dg. The shoulder portion 2 and the body portion 3 are thinned in a highly stretched orientation state except for the connection portion with the mouth / neck portion 1.

The bottom 4, the thick located at the bottom center gate remainder 8, located around the gate connection 9及beauty gate <br/> preparative connection portion in contact with the gate remainder 8 and the base portion 10 of the foot 7 It is composed of a bottom central portion 5 constituted by a gate peripheral portion 11 which is an inner portion, and a bottom peripheral portion in which a plurality of valley portions 6 and foot portions 7 are alternately formed. In the container of this example,
Each part of the bottom part 4 except the gate remaining part 8 is substantially composed of only a layer in a highly stretched orientation state. Also, the gate connection part 9
It is relatively thin except for.

The bottom center gate remaining portion 8 of the container of the present invention is relatively thick and is composed of a high stretch orientation portion or a combination of a high stretch orientation portion and a low stretch orientation portion. Usually, high-stretch orientation of the gate remainder 8 is connected to the gate connection 9及beauty gate periphery 11 extending around the is composed of a continuous layer across the gate remainder and the gate remainder.
As a result, in the container of the present invention, the bottom 4 is covered with the continuous highly stretched alignment layer.

[Gate Remaining] The arrangement of the transparent stretched alignment layer in the bottom center gate remaining 8 will be described below with reference to FIGS. 2 to 5, but the present invention is not limited to these examples.

In FIG. 2 showing an example of the arrangement of the high-stretch alignment layer, the bottom center gate remainder 8 is a generally transparent high-stretch alignment layer 12 on the inner surface of the container and a generally whitened low-stretch low-orientation layer 13 on the outer surface of the container. And consists of. In the bottom center gate remaining portion 8 of this heat resistant stretched resin container, the highly stretched alignment layer 12 is present on the inner surface side, and therefore the combination of heat and pressure resistance and impact resistance is particularly excellent.

In FIG. 3 showing another example of the arrangement of the high-stretch alignment layer, the bottom center gate remnant 8 is a generally transparent high-stretch alignment layer 12 located at the center in the thickness direction, and whitened low layers on both inner and outer sides. It has a laminated structure including the stretched low-orientation layers 13 and 13. This laminated structure is a so-called rigid-soft-rigid laminated structure, and is particularly excellent in dimensional stability of the bottom portion under high temperature and high pressure.

The remaining gate portion 8 shown in FIG. 4 is a modification of that shown in FIG. 2, and is composed of a generally transparent highly stretched orientation layer 12 on the inner surface side of the container and a generally stretched low stretched low orientation portion 13 on the outer surface side of the container. However, it is characterized in that the high-stretch alignment layer 12 is very thick and the low-stretch low-alignment portion 13a is thinly formed in 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 highly stretched orientation layer 12 is remarkable.

In FIG. 5 showing still another example of the arrangement of the highly stretched alignment layer, FIG. 2 shows that the bottom center gate remainder 8 is provided with a generally transparent highly stretched 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-stretch whitening portion 13b and the transparent high-stretch orientation portion 12b located in the center thereof is formed.

Highly stretched orientation portion 12 of bottom center gate remainder 8
In general, it is preferable that oriented crystallized at a crystallinity of 20% or more, preferably 25% at the time of blow molding from the viewpoint of heat and pressure resistance and impact resistance.

By thermally fixing the bottom including the bottom center gate remainder, the low stretch orientation layer 13 of the gate remainder 8 is thermally crystallized and whitened to increase the crystallinity. On the other hand, thermal crystallization proceeds while the highly stretched alignment layer 12 of the remaining gate portion 8 maintains a substantially transparent state. In this case, the whitened low-stretch alignment layer 13 remaining in the gate is present in the center of the bottom of the container, but its size is limited, and there is no particular aesthetic problem.

In the heat-set bottom center gate remainder 8, the low stretch orientation layer 13 has a crystallinity of 20% or more, particularly 25% or more, and the high stretch orientation layer 12 has a crystallinity of 25% or more. Is preferred.

The thickness of the bottom center gate remaining portion 8 is normally about 1 to 3.5 mm at the maximum, and in the present invention, the bottom center gate remaining portion 8 is not necessary to finish the gate portion of the preform. Can form a container bottom having a high stretch orientation. On the other hand, the thickness of the highly stretched alignment layer 12 in the bottom center gate remaining portion 8 may be any thickness that imparts sufficient heat and pressure resistance to the center of the bottom portion, and is generally 0.35 mm or more, particularly 0.4 mm or more. It suffices if it occupies 20% or more, particularly 30% or more of the total thickness of the remaining gate portion.

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

[Gate Connection Portion and Gate Peripheral Portion] In the present invention, the gate connection portion 9 and the gate peripheral edge portion 11 are brought into a high stretch orientation state at an appropriate stretching ratio, so that a part of the thick gate remaining portion 8 is formed. It is possible to form a layered high-stretch alignment portion 12.

The gate connecting portion 9 and the gate peripheral portion 11 surrounding the bottom center gate remaining portion 8 are preferably highly stretched and oriented to have a crystallinity of 20% or more, particularly 25% or more. Furthermore, 30% of the gate connection part and the gate peripheral part after heat fixing
It is preferable to have the above crystallinity.

The gate peripheral portion 11 is located in the periphery of the gate remaining portion and the gate connecting portion, and is located in the center portion of the bottom up to the bottom center foot base portion 10. The thickness of the gate peripheral portion 11 is fixed by heat. If not, generally 0.35 to 1m
m, especially in the range of 0.45 to 0.8 mm,
It is preferable for effectively forming the highly stretched alignment layer 12 on the remaining gate portion 8, while it is 0.35 when heat-fixed.
To 1.1 mm, and preferably 0.45 to 1 mm. The reason why the preferable range of the wall thickness is slightly widened when the heat setting is performed is that the heat contraction causes the wall thickness to increase.

The bottom center gate remaining portion 8 and the gate connecting portion 9 can maintain the high stretch orientation state even if the thickness slightly exceeds 1 mm. The thickness of the gate connection is 0.
It is preferable that the thickness is in the range of 4 to 1.3 mm, particularly 0.5 to 1.1 mm in order to effectively form the highly stretched alignment layer 12 on the remaining gate portion 8.

If the wall thickness of the gate peripheral portion 11 is less than 0.35 mm, it is not preferable because the thickness of the gate peripheral portion 11 becomes too thin and the heat and pressure resistance of the center of the bottom is lowered. On the other hand, if the thickness of the gate periphery of at the stage of blow molding is that many sites of more than 1 mm, it becomes difficult to form a high stretch orientation layer to the gate remainder及beauty gate connection unit. However, when it exceeds 1 mm in a narrow region where the wall thickness of the gate peripheral portion is very limited, it does not particularly prevent a part of the remaining gate portion from being highly stretched.

As described above, the highly oriented crystallized gate connection portion 9 and the gate peripheral portion 11 having a preferable thickness range are particularly excellent in heat resistance and impact resistance. Therefore, the petaloid bottom of the present invention consisting of the above-mentioned thick gate remainder, the bottom central valley having the gate connecting portion and the gate peripheral portion simultaneously has excellent heat and pressure strength and excellent impact resistance. be able to.

[Container Wall Thickness and Crystallinity] In the container of the present invention, the mouth / neck portion 1 and its vicinity, and the bottom center gate remaining portion 8
And the thickness of the container excluding its vicinity is 0.15 mm to l.
It is in the range of 1 mm, preferably 0.2 mm to 0.9 mm.

The crystallinity of the container excluding the mouth / neck portion 1 and its vicinity and the remaining portion of the gate 8 is 20%, preferably 25% or more with the stretched orientation.

The bottom 4 is heat-fixed in a substantially non-whitening state except for the gate remainder 8, and the bottom center including the bottom gate remainder 8 inside the diameter of 50% of the body diameter D _0. The crystallinity of the valley is preferably 25 to 55%.

[Yield load at 70 ° C.] A relatively large deformation force acts on the valley portion of the petaloid-type bottom portion, particularly on the valley portion at the center of the bottom, as compared with the barrel portion. Therefore, the heat resistant pressure strength of the central valley portion of the bottom determines the heat resistant pressure resistance of the bottom portion of the container.

The heat resistant pressure strength of the bottom central valley can be shown by the yield load value at 70 ° C. As for the yield load value at 70 ° C., as shown in FIG. 6, a standard test piece 15 was prepared from the bottom central valley including the remaining gate, and the standard test piece was 70
The yield load value shown in FIG. 7 when the tensile test is performed at a temperature of ° C can be obtained as a value converted per 1 cm of width. This yield load value at 70 ° C takes into account the wall thickness of the bottom of the container, and the yield load value at 70 ° C of the center of the bottom including the gate residue where the largest deformation force acts is calculated to determine the heat resistance of the container bottom. The pressure property can be evaluated.

In the present invention, the temperature of the portion forming the valley is 70 ° C.
It was found that by setting the yield load at 25 kgf / cm or more, preferably at 30 kgf / cm or more, it becomes a container having a petaloid bottom that is self-sustainable after heat sterilization and has excellent heat resistance and pressure resistance.

The container of the present invention has a highly stretched alignment layer having a wall thickness of 0.35 mm or more including the bottom center gate remainder, and is 70 ° C. in the bottom valley portion in a state not heat set.
The yield load is usually about 25 to 30 kgf / cm, and it can have preferable heat resistance and pressure resistance. At that time, if there is a portion where the wall thickness of the bottom central valley is less than 0.35 mm, the yield load at 70 ° C. usually becomes less than 25 kgf / cm, and the heat and pressure resistance decreases. Become.

When the center of the bottom of the above-mentioned container of the present invention is heat-fixed, the bottom valley portion including the bottom center gate residue is thermally crystallized, and the yield load value at 70 ° C. of that portion is 35 to 50.
It becomes about kgf / cm, and can have extremely high heat resistant pressure strength.

On the other hand, in a conventional container having a petaloid bottom portion whose bottom central valley portion is composed of only a relatively thick low-stretch orientation layer, the yield load value at 70 ° C. is 10 to 20 kg.
f / cm and heat and pressure resistance are low. In particular, when the thick low-stretch alignment layer of the conventional container contains water of about 5000 ppm, the yield load value at 70 ° C. is 10 k.
This is lower than gf / cm, and the heat and pressure resistance is extremely reduced.

[Bottom Shape] In the present invention, the container bottom is thinned in a relatively highly stretched state. For this reason, the weight of the bottom is relatively smaller than that of a conventional self-standing container having a thick bottom, and the position of the center of gravity moves to the top of the container. Therefore, the tipping angle of the empty container is small and the tipping is easy. In order to improve the fall resistance, it is necessary to increase the number of legs or to make the diameter and width of the grounding portion relatively large in the container of the present invention. In that case, the formability of the foot becomes a problem. That is, in addition to originally thinning the bottom, in order to improve the tipping resistance, when trying to widen the tip of the foot, the thickness of the tip of the bottom foot, that is, the thickness near the outside of the grounding section becomes extremely thin, The problem of whitening occurs in the overstretched state.

In the present invention, the above problem is solved by devising the shape of the bottom of the container, and the thickness of the tip of the foot is 0.15.
It was possible to obtain a container having a diameter of at least mm, preferably at least 0.2 mm, and substantially free of whitening due to overstretching at the tip of the foot.

[Valley Shape] In the specific example shown in FIG. 8, the bottom valley 6 has a radius of curvature R ₁ located at the center of the bottom including the remaining gate 8 and a radius of curvature R ₂ connected to the body.
And a substantially spherical surface.

The radius of curvature R ₁ of the spherical surface including the bottom center portion 5 is set to an appropriate size, and the perpendicular line of the spherical surface is set to be the shortest distance between the foot tip portion 16 and the valley surface. The distance between and the valley 6 can be made relatively small. As a result, the blow moldability of the tip of the bottom foot is improved, the wall thickness of the tip of the foot can be made relatively thick, and the whitening of the tip of the foot due to overstretching can be prevented.

Specifically, it is preferable that the ratio R ₁ / R ₀ between the radius of curvature R ₁ of the substantially spherical surface forming the center of the bottom and the body radius R ₀ is 1.2 to 2. the ratio D ₁ / D ₀ between the diameter D ₁ and the barrel diameter D ₀ for the range 0.55
It is preferably set to 0.75. When R ₁ / R ₀ exceeds 2, the heat resistance and pressure performance of the valley portion deteriorates, and it becomes difficult to secure the self-supporting property of the container after filling the contents and performing heat sterilization treatment. If R ₁ / R ₀ is less than 1.2, the distance between the foot tip and the valley becomes too large, and it becomes difficult to secure a preferable thickness of the foot tip.

In the specific example shown in FIG. 9, the bottom valley portion 6 has a substantially spherical surface A having a relatively small radius of curvature R ₁ including the remaining gate portion 8 and an extended virtual surface of the substantially spherical surface A which is in contact with the substantially spherical surface A. It is composed of a truncated cone-shaped or substantially spherical surface B located on the outer surface side and a substantially spherical-shaped or conical surface C connected from the surface B to the body. At this time, it is preferable that the surface B or the surface C forming the peripheral part of the bottom valley be the shortest distance from the foot tip 16.

In this example, the bottom central valley portion 6 including the bottom gate remaining portion 8 on which the largest deformation force acts is formed of the spherical surface A having a relatively small radius of curvature to impart a preferable heat resistant pressure strength. On the other hand, the distance between the foot tip portion 16 and the valley surface can be shortened by bulging the valley surfaces B and C on which a relatively small deformation force acts compared to the center of the bottom to the outside. Thereby, the blow moldability of the tip part 16 of the bottom foot can be improved, and as a result, it is possible to make the thickness of the tip part 16 of the foot relatively thick and prevent whitening due to overstretching. Specifically, it is preferable that the ratio R ₁ / R ₀ of the radius of curvature R ₁ of the substantially spherical surface A forming the center of the bottom to the body radius R ₀ is 0.9 to 1.4. The diameter D ₁ indicating the range is preferably 0.18 to 0.5 times the body diameter D ₀ . The surface B which is connected to the substantially spherical surface A and extends outward is preferably a conical surface which is in contact with the substantially spherical surface A or a substantially spherical surface having a large radius of curvature close to the conical surface,
The outermost diameter D ₂ of the surface B is 0.3 to 0.8 times the body diameter D _0.
It is preferably 5 times.

Further, it is preferable to secure the heat resistance and pressure resistance by making the valley width of the bottom central portion 5 and its vicinity where the largest deformation force acts relatively wide. Specifically, the ratio S / S ₀ of the surface area S of the valley portion included in the diameter of 80% of the body diameter D ₀ and the surface area S ₀ of the virtual substantially spherical surface constituted only by the valley portion is 0.2. To 0.5, particularly preferably 0.3 to 0.4. When S / S ₀ is less than 0.2, the area of the bottom central portion and the valley portion in the vicinity thereof is too small, so that the deformation of the bottom central portion becomes large and it becomes difficult to secure the self-supporting property of the container. . On the other hand, S / S ₀
When the value exceeds 0.5, the portion that can be used for the foot portion during blow molding is too limited, and it becomes difficult to secure a preferable wall thickness of the tip portion of the foot.

[Foot Opening Angle] In the present invention, as shown in FIG. 10, the foot opening is such that the foot tip portion 16 is directed while crossing between the foot portions 7 and the valley portion is sandwiched in a plane perpendicular to the valley portion 6. The angle θ is preferably in the range of 65 ° to 90 °.
For containers with a foot opening angle θ of less than 65 °, when subjected to relatively severe heat sterilization, the foot opening angle θ after heat sterilization greatly expands, and the amount of deformation of the valley also increases accordingly. Tends to become. When the foot opening angle θ is increased in advance, it can be considered that the action direction of the force that acts to pull up the valley that is a part of the spherical surface approaches the direction of the spherical surface. The force component that acts perpendicularly to the portion, that is, the force component that deforms 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 resistance and pressure resistance performance is improved. Further, by making the foot opening angle θ relatively large, it acts in an advantageous direction with respect to the moldability of the foot. That is, when the foot opening angle θ is increased, the surface area of the foot is relatively reduced, and the amount of stretching at the foot can be suppressed to be relatively low. On the other hand, if the foot opening angle θ is made too large, the width of the foot tip grounding portion becomes narrow. If the foot tip grounding portion becomes too thin, it tends to fall, especially in an empty container before filling, which is not preferable. Therefore, the foot opening angle θ is preferably 90 ° or less.

[Foot Height, Number of Feet] The initial foot height is 2 to 8 mm, preferably 3 to 6 mm. Foot height is 2m
If it is less than m, the height of the foot after deformation of the bottom central valley after filling the contents and heat sterilization becomes extremely small, or becomes negative, that is, the center of the bottom protrudes below the foot, and the container It becomes difficult to maintain the independence of. on the other hand,
If the foot height exceeds 8 mm, the distance between the foot tip and the valley becomes too large, and it becomes difficult to secure a preferable foot tip thickness. The number of legs is preferably 6 to 4.

[Other Embodiments of Heat-Resistant Container] In addition to the heat-resistant and pressure-resistant container described above, the container of the present invention can be used as a heat-resistant container for heat-filling contents having a high temperature of about 80 to 93 ° C. The heat-resistant container consists of a mouth and neck, a shoulder, a cylindrical or square tube-shaped body and a bottom. The body has a concave panel for absorbing reduced pressure and the center of the bottom has a bottom center gate remainder. An inwardly recessed recessed portion including is included.
At this time, in order to ensure heat resistance to prevent deformation due to heat shrinkage at high temperature, all of the bottom including the center gate of the bottom, the body, shoulders, and mouth / neck are heat-fixed. Is preferable, and the crystallinity of each part of those containers is 25 to 55.
% Is preferable. In particular, the heat-fixed bottom portion can achieve notable weight reduction as the thickness becomes thinner, but also have excellent heat resistance despite the reduction in thickness. In addition, the high stretch orientation portion of the bottom portion, excluding the low extension orientation portion of the remaining bottom gate having a relatively small diameter, retains the transparent state even when it is heat set, which is excellent in appearance.

[Resin] In the present invention, any plastic material can be used as long as it can be stretch blow-molded and thermally crystallized, but thermoplastic polyester, particularly ethylene terephthalate thermoplastic polyester. 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 the ester repeating units,
Generally, ethylene terephthalate units account for 70 mol% or more, particularly 80 mol% or more, and have 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 preferable in terms of heat resistance and pressure resistance, a copolymerized polyester containing a small amount of ester units other than ethylene terephthalate units can also be used.

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. Aliphatic dicarboxylic acids such as dionic acid; and combinations of two or more thereof. As the diol component other than ethylene glycol, propylene glycol,
1,4-butanediol, diethylene glycol, 1,
One or more of 6-hexylene glycol, cyclohexanedimethanol, and an ethylene oxide adduct of bisphenol A can be used.

Further, it is possible to use a composite material obtained by blending ethylene terephthalate type thermoplastic polyester with a relatively high glass transition point, for example, polyethylene naphthalate, polycarbonate or polyarylate in an amount of about 5% to 25%. The material strength at high temperature can be increased. Furthermore, polyethylene terephthalate and the above-mentioned material having a relatively high glass transition point can be laminated and used.

The ethylene terephthalate type thermoplastic polyester 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.

[Production Method of Container] The heat-resistant stretched resin container of the present invention comprises a stretch rod inserted into the preform in a mold and a press rod outside the preform in which the preform heated to the stretching temperature is used. Insert the bottom center of the preform,
Next, when manufacturing a stretched resin container by simultaneously blowing a high-pressure gas into the preform while driving the stretch rod, a preform having a gate portion at the center of the bottom is used as the preform, and the stretching process is completed. It is manufactured by keeping the temperature drop in the center of the bottom within 40 ° C. until just before and stretching the center of the bottom highly.

In manufacturing a container, first, a bottomed cylindrical preform is formed, and if necessary, the mouth and neck of this preform is heated to locally provide a spherulization part.

The preform used for manufacturing the container of the present invention has a shape as shown in FIG. 11 at 20, and this preform 20 comprises a neck portion 21, a body portion 22 and a closed bottom portion 23. The neck 21 is provided with a lid fastening mechanism such as a screw and a support ring for holding the container, and the neck 21 is thermally crystallized, that is, spherulized.
The spherulized neck portion 21 becomes the container neck portion 1 of FIG. Further, the gate remaining portion 24 exists at the center of the closed bottom portion 23.

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

As the injection machine, one known per se 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, polyester or the like flows into the injection mold cavity and is solidified to form a stretch blow molding preform.

As the injection mold, one having a cavity corresponding to the shape of the container is used, but it is preferable to use a one-gate type or a multi-gate type injection mold. Injection temperature is 270 ~ 310 ℃, pressure is 28 ~ 110kgf /
It is preferably about cm ² .

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

The above spherulization may be carried out simultaneously with the preheating of the preform 20 to the drawing temperature or separately.

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 for forming the highly stretched alignment layer 12 (see FIGS. 2 to 5) in the center of the bottom portion of the container without being subjected to a finishing process such as further cutting and leaving it as it is. .

FIG. 1 for explaining the dimensions of the gate portion.
2, the gate portion 24 has a length h and a root diameter d, and generally has a tapered shape (taper angle α). It is preferable that h is 3 mm or less, particularly 0.1 to 1 mm, d is 2 to 6 mm, and α is 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 suitable, and the heating can be carried out by means known per se such as infrared heating, hot air heating furnace, dielectric heating and the like. The spherulization of the mouth is generally 140 to 220 when the bottom of the preform and the mouth are thermally insulated from other parts.
It can be carried out by heating to a temperature of 160 ° C., particularly 160 to 210 ° C. Crystallinity of preform mouth is 2
It is preferably 5% or more.

In the stretch blow molding from the preform, a method of utilizing the heat given to the preform molded article to be molded, that is, residual heat, and performing the stretch blow molding subsequent to the preform molding can also be used. However, in general, a method is preferred in which a preformed product in a supercooled state is once produced, and the preform is heated to the above-mentioned drawing temperature to carry out draw blow molding.

The container of the present invention is characterized in that the entire container except for the mouth and neck is thinned in a highly stretched state, and particularly the entire bottom including the center of the bottom (including the remaining gate) is relatively made. It is important to perform blow molding in a highly stretched state.

Particularly, in the present invention, the gate peripheral portion 11 (FIG. 1) extending around the bottom center gate remaining portion 8 (FIG. 1) and the gate connecting portion 9 (FIG. 1) is made to have an appropriate thickness during blow molding. It is important to obtain a high stretch orientation state. Thereby, although the bottom center gate remaining portion 8 (FIG. 1) is thick, the high stretch orientation portion 12 (FIGS. 2 to 5) can be formed as a continuous layer in a part thereof.

At this time, the proper thickness of the gate peripheral portion 11 (FIG. 1) is a thickness not more than the maximum thickness capable of maintaining the high stretch orientation state and not less than a thickness not extremely thinned. Is preferred. In this case, if the thickness of the gate peripheral portion is too thick, it becomes difficult to form the highly stretched alignment layer on the remaining portion of the gate, while if the thickness of the gate peripheral portion is too small, the heat resistant pressure strength of the petaloid bottom portion decreases. Problem arises. Specifically, the thickness of the gate peripheral portion 11 (FIG. 1), which is a region extending around the remaining portion of the central gate through the gate connection portion and reaching the bottom center foot base, is in the range of 0.35 to 1 mm. In particular, it is preferable to set it in the range of 0.45 to 0.8 mm.

In the biaxial stretch blow molding, in order to bring the above-mentioned gate peripheral portion 11 (FIG. 1) into a highly stretched orientation state with an appropriate wall thickness, when performing stretch blow molding from the bottom of the preform to the gate peripheral portion. It is important to optimize the stretching ratio. 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 preferably 0 times.

In order to achieve the above preferable stretching ratio of the bottom center gate peripheral portion 11 by blow molding, first, the shape and wall thickness distribution of the preform 20, particularly the preform which finally becomes the gate peripheral portion. It is necessary to optimize the thickness of the bottom part. Next, the blow molding conditions for blow molding are optimized to obtain a predetermined stretch ratio of the peripheral portion of the gate. The blow molding conditions are 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 rod, the timing at which high pressure air is blown into the molded body from the start of stretching the stretching rod, and the stretching blow speed determined by the high pressure air flow rate. Further, it is important to optimize the temperature level of the molded body when the bottom is substantially stretched.

As a result of investigations by the present inventors, the bottom portion in the blow molding is substantially in a highly stretched state after the bottom gate residue of the molded body reaches the bottom portion of the mold. It was found that the stretch molding of the bottom portion was performed until just before the end of blow molding, where the blow shape was almost determined. At that time, by keeping the temperature of the center of the bottom of the molded body relatively high until reaching the bottom of the mold and immediately before the blow molding is completed, the bottom, especially the gate peripheral portion, is drawn at an appropriate draw ratio. It has been found that a high stretch orientation state can be achieved. As a result, it became possible to form a high stretch orientation portion in the remaining portion of the 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 compared to the initial preform heating temperature, the peripheral edge of the gate remains in a relatively low stretch orientation state. Along with this, the entire remaining portion of the gate remains in a low stretch orientation state or an unstretched state.

Specifically, the temperature of the gate remaining portion of the molded body until reaching the bottom of the mold during blow molding and immediately before the end of stretch molding of the bottom is 40 ° C. which is the heating temperature of the preform. It is preferably within 30 ° C., in particular.

[ One- Step Stretch Blow Molding] FIGS. 13 and 1 showing production of a container by one- step blow molding.
4, the preform 20 has its neck supported by the core mold 31 and is held in the closed split molds 32, 32. On the opposite side of the core mold, a bottom mold 33 that defines the bottom shape of the molded product, that is, the petaloid bottom is also arranged. Stretching is performed by inserting the stretch rod 34 into the preform 20 and pushing up the preform bottom portion 23. At a stage in the middle of the stretch molding, the timing is measured, and high-pressure gas is blown into the molded body through the stretch rod 34 to perform blow molding to obtain a container having a shape along the mold.

In the embodiment shown in FIGS. 13 and 14, the press rod 35 is arranged coaxially with the stretch rod 34 on the side of the bottom die 33, and the gate portion 2 of the preform is stretched during the stretching.
4 is sandwiched between the drawing rod 34 and the pressing rod 35, and the position of the preform 4 is regulated so as to be located at the center of the container bottom 5 where the gate portion 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 stretch rod 34 at the stage of pulling and stretching the preform, and further restrains the bottom gate remaining portion of the molded body at the stage of blow molding. The use of this press rod has the effect of preventing misalignment of the remaining gate.

Immediately before the stretching process is completed, the temperature drop of the sandwiched portion at the bottom of the preform is kept within 40 ° C.,
More preferably, by setting the temperature to be within 30 ° C., the bottom portion 37 of the secondary molded product 36 can be highly stretched over the entire bottom portion including the center portion of the bottom which is the sandwiched portion.

In the blow molding, first, the shape and thickness distribution of the preform are taken into consideration in consideration of the stretching ratio so that the portion which should become 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 0.1 to 3 mm, and more preferably 0.3 to 1 mm. Secondly, measures are taken to prevent a temperature drop near the center of the bottom of the molded product during blow molding. In this case, it is important to reduce the heat transfer from the preform to the draw bar and the press bar during blow molding. Specifically, it is effective to use a heat insulating material such as heat resistant plastic or ceramic at the tip of the drawn rod or the pressed rod. It is also effective to heat at least the tip of the press rod.
If you do not use a press rod, provide a heat insulating layer on the surface of the center of the bottom of the mold where the remaining gate of the molded product first contacts during blow molding, or heat the bottom mold. Is effective.

When performing blow molding, the heating temperature and temperature distribution of the preform are optimized. The heating temperature of the preform is generally 85 to 135 ° C., especially 90 to 1
A temperature of 30 ° C is suitable. At that time, it is important that the difference in heating temperature between the bottom of the preform and the body is within 10 ° C. in order to bring the petaloid bottom into a highly stretched orientation state.
In this case, the heating temperature difference between the bottom of the preform and the body is 1
If the temperature exceeds 0 ° C, only the portion having the higher temperature tends to be stretched too much, which is not preferable.

[0092] Using the above means及beauty method, by further optimizing the blow molding conditions, molding a container having a high draw layer on the entire container, including the bottom central portion except for the b neck and the vicinity thereof can do.

As shown in FIG. 15, the bottom center gate peripheral portion 11 of the molded container has a high stretch orientation in the range of wall thickness 0.35 to 1 mm and in the degree of crystallinity of 20% or more. The high-stretch alignment layer 12 is formed in the bottom center gate remaining portion 8 accordingly. The highly stretched alignment layer 12 of the remaining gate portion 8 is normally located on the inner surface side, and the gate connecting portion 9 and the peripheral portion 11 of the gate around the gate connecting portion 9 are provided.
And form a continuous layer. The thickness of the bottom center gate remaining portion 8 depends on the height of the bottom center gate portion of the preform, but is usually in the range of 1 to 3.5 mm. The crystallinity associated with the stretch orientation of the remaining gate portion 8 increases from the low stretch orientation portion 13 on the outer surface side to the high stretch orientation portion 12 on the inner surface side, and is 0 in the low stretch orientation portion near the outer surface. Whereas the crystallinity is about 12%, the crystallinity is about 20-35% in the highly stretched orientation portion near the inner surface. Further, the yield load at 70 ° C. is usually about 25 to 35 kgf / cm at the central portion of the bottom valley including the bottom gate remaining portion 8, and it is possible to have preferable heat resistance and pressure resistance.

By heat-fixing the center of the bottom of the container by heat, the heat and pressure resistance can be further increased. At that time, it is preferable that the low stretch orientation layer 13 in the remaining portion of the gate be whitened and thermally crystallized to such an extent that the crystallinity becomes 25% or more. Due to the heat fixing of the bottom of the container, the heat resistant pressure strength is significantly increased. On the other hand, although the low stretch orientation portion 13 in the remaining whitened gate is embrittled, the high stretch orientation layer 12 retains sufficient flexibility, so that the impact resistance represented by the drop strength is kept at a very high level. There is. As a specific heat fixing means for the bottom of the container, the temperature of the blow mold, particularly the bottom mold, is set to the crystallization temperature of the resin, and the bottom of the molded product is heated in the blow molding step to be thermally crystallized. .

By the above-described one- stage blow molding means of the present invention, it is possible to manufacture a heat-resistant container in which a high temperature content of about 80 to 93 ° C. is heat-filled. In this case, the blow molding is performed using a blow mold having a shape that conforms to the product shape including a cylindrical or rectangular tubular body and a bottom having an inwardly recessed recess including the bottom center gate remaining portion. In this heat-resistant container, it is important to heat-fix the entire container, and by molding the parts corresponding to the shoulder, body and bottom of the mold to the crystallization temperature of the resin, the molded product can be molded in the blow molding process. Each part of is heated to be thermally crystallized. Usually, the heating temperature of the blow mold is 120 ° C to 180 ° C. The crystallinity of the bottom including the body and the rest of the gate due to heat setting is 25
% Or more is preferable. In this case, the bottom of the blow-molded product is in a highly stretched orientation, and the body and the wall are thinned except for the remaining gate, so that the time required for heat setting can be shortened to about the body. Further, thermal crystallization can be performed in a state where transparency is maintained, except for the low stretch orientation portion that constitutes the remaining portion of the gate.

[ Two- stage Blow Molding Method] As described above, the container of the present invention can be prepared by a single biaxial stretch blow molding. However, when blow molding a petaloid bottom of a complicated shape into a high stretch orientation state at a time, there is a tendency for whitening to occur easily, especially when the tip of the foot is over stretched. It becomes quite narrow. In addition, heat fixing of the bottom portion using a mold takes a relatively long time, and there is a problem that the blow molding time becomes long.

As a result of the examination, as a molding means of the container of the present invention, a two-stage blow molding method in which a preform is used as 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 portion of the preform molded body and a part of the body portion connected to the bottom portion are larger in the height direction or in the circumferential direction than the final container. A molded product is created, and then at least the bottom of the secondary molded product and the body portion connected to the bottom are heated and shrunk to form a tertiary molded product of a size that can be stored in the secondary blow mold, and finally the tertiary molded product. It is preferable to carry out secondary blow molding of the product into the final container.

By adopting the above-mentioned two-step blow molding method, the following effects are produced. Firstly, by optimizing the shape of the bottom portion by the primary blow molding, it becomes easy to bring the bottom portion into a preferable highly stretched orientation state, and particularly to optimize the stretching ratio of the peripheral portion of the gate. As a result, the remaining gate at the bottom of the secondary molded product has a thick wall including the highly stretched alignment layer,
In addition, the peripheral portion of the gate around it is in a highly stretched orientation state, and can be stably blow-molded so as to maintain a preferable wall thickness. Secondly, by heat-shrinking the bottom of the secondary molded product and a part of the body portion connected to the bottom, the center of the bottom of the secondary molded product is heat-set and thermal crystallization can proceed. This heat setting step can be efficiently performed in an extremely short time. Thirdly, in the secondary blow molding, the bottom portion of the tertiary molded article in a high temperature state is stretch-blow molded, so that the foot portion can be easily molded without being overstretched, and the bottom portion excluding the foot portion, In particular, the degree of stretching is small in the central portion of the bottom, and the degree of decrease in crystallinity due to blow molding is very small. Therefore, it is possible to provide a container having a foot portion having a preferable property and having a high heat and pressure strength in which the oriented crystallization and the thermal crystallization are sufficiently performed in the center of the bottom where the heat and pressure resistance is most required. .

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 the primary blow mold to have a size larger than that of the final container. And a bottom 37 of the preform, and a portion other than the spherulized mouth neck portion of the preform is drawn to a high draw ratio to obtain a secondary molded product 36 (FIGS. 16 and 17);
At least a part of the bottom of the next molded product and the body connected to the bottom are heated to form a tertiary molded product 44 in which the bottom and a part of the body are contracted (FIGS. 19 and 20); The molded product is blow-molded in a secondary blow mold to obtain a final product 50 having a plurality of valleys and feet and a bottom portion thinned by high drawing (FIGS. 22 and 23).

At this time, in order to reduce the thickness of the petaloid bottom of the final container in a relatively high stretch orientation state excluding the remaining gate, the bottom of the primary blow-molded secondary molded product including the remaining gate was compared. It is important that the film is oriented in a highly stretched state.

(1) Primary Blow Molding The preform 20 used in the primary blow molding determines the shape and wall thickness distribution in consideration of the draw ratio of each part of the secondary molded product. At this time, the area corresponding to the gate peripheral portion of the final container spreading around the bottom center gate remaining portion of the secondary molded product is an area stretch ratio of 3.5 to 12.5 times, particularly preferably 5 to 10 times. It is important to determine the bottom profile of the preform so that it will be stretched.

In the primary blow molding, the preform 20 is heated to the stretching temperature. The stretching temperature of the preform is generally 85 to 135 ° C., and preferably 90 to 130 ° C. At that time, it is preferable that the difference in heating temperature between the bottom portion and the body portion of the preform is within 10 ° C., whereby it is possible to increase the stretching of both the bottom portion and the body portion.

When the heating temperature of the preform body is higher than the heating temperature of the bottom by more than 10 ° C., stretching of the bottom having a relatively low temperature is insufficient. Further, when the heating temperature of the bottom portion is higher than the heating temperature of the body portion by more than 10 ° C., the bottom portion is excessively stretched locally, which is not preferable.

In the blow molding, the preform 20 heated to the stretching temperature stretches the bottom of the preform by raising the stretching rod 34 while sandwiching the gate portion 24 at the bottom of the preform with the stretching rod 34 and the press rod 35. Preferably. In the process of stretching, high-pressure gas is blown into the preform to perform blow molding, whereby the secondary molded product 36a is molded (FIGS. 16 and 1).
7). At that time, in order to form a highly stretched orientation layer on the entire bottom of the secondary molded product, the stretching speed for pushing the preform bottom with a stretching rod, the timing of blowing high-pressure air into the molded body, and the stretching determined by the flow rate of high-pressure air. It is important to optimize blow molding conditions such as blow speed.

The inventors attached a thermocouple to the tip of the press rod and measured the temperature change of the bottom center gate remainder during blow molding. As a result, the temperature of the press rod was 5 to 15 ° C. after reaching the top dead center. It was found that the temperature increased to some extent.
This is presumed to be because the relatively large stretching of the remaining portion of the gate and its vicinity is performed after the center of the bottom reaches the mold, and it is presumed that the temperature rises due to the heat generated during the stretching. At that time, by reducing the temperature decrease from the initial heating temperature of the remaining gate of the molded body facing the tip of the press rod at the time when the press rod reaches the top dead center, the amount of temperature increase due to subsequent stretching. , that it was found to be able to increase the degree of gate remainder及beauty its neighboring stretching. Specifically, the temperature decrease of the center part of the bottom of the preform before the end of the stretching process is within 40 ° C., more preferably 30 ° C.
It was found that by setting the temperature within the range of 0 ° C., the bottom center gate remaining portion and the peripheral portion of the secondary molded product 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 draw bar 34 and the press bar 35. Specifically, it is preferable that at least the tip portion of the drawn rod or the pressed rod is made of a heat-resistant plastic material or ceramic material having a heat insulating property. Further, a means for heating the press rod or the drawing rod to control the temperature to a relatively high temperature is also effective. The heating of the press rod and the stretching rod is preferably 50 ° C. to 130 ° C., which usually corresponds to the stretching temperature of the preform. As the heating method, an electric heater,
An electric heating method such as high-frequency induction heating, a fluid heating method by circulating a high-temperature liquid, a heat conduction method such as a heat pipe can be adopted.

In order to promote the higher elongation of the bottom portion of the secondary molded product, the bottom central portion is flat and the bottom central portion and the body portion are connected by an annular curved surface having a relatively small radius of curvature. It is effective to adopt. Further, it is effective to provide a recess 38 on the inner surface side at the center of the bottom (FIGS. 17 and 24).
Bottom center of the recess 39 of the blow Sokokin mold 33, when the blow molding, since it has the effect of delaying the timing of a molded article reaches the mold surface of the peripheral portion from the bottom center, bottom center and Its <br / It is possible to increase the degree of stretching of the peripheral edge of.

The bottom portion 37 of the obtained secondary molded product 36a has a crystallinity of 2 except for the bottom gate remaining portion 8 and the gate connecting portion 9.
0% or more, more preferably 25% or more, is oriented and crystallized in a relatively high stretched state, and is 1 mm or less, and particularly, 0.
It is preferable that the thickness is reduced to 8 mm or less (FIG. 18). Generally, the bottom gate remainder 8 is composed of a high-stretch alignment layer 12 located on the inner surface side and a low-stretch alignment layer 13 located on the outer surface side.
Composed of and. Highly stretched alignment layer 12 remaining on the gate
Then, the maximum value of the crystallinity is preferably 20% or more, and particularly preferably 25% or more. Also, the diameter D of the rest of the gate
_g is preferably 0.25 times or less, and particularly preferably 0.2 times or less of the body diameter D ₀ . In addition, the gate connecting portion 9 that contacts the remaining gate portion 8
Has a crystallinity of 20% or more, more preferably 25% or more and is oriented and crystallized in a relatively high stretched state.
It is preferable that the thickness is reduced to a plate thickness of mm or less, more preferably 1.1 mm or less (FIG. 18).

In FIG. 24 showing the shape of the bottom mold 33 used for the primary blow molding, the height H ₁ of the recess 39 in the bottom mold is generally 1 to 8 mm, and the diameter D ₄ is continuous with the bottom of the secondary molded product. It is desirable that the diameter is in the range of 0.15 to 0.6 times the barrel diameter in order to effectively perform the highly stretched orientation centered on the bottom.

In FIG. 25, which shows an example of a bottom mold particularly suitable for the purpose of the present invention, the bottom mold 33 has an outer peripheral side convex portion 41 which is continuous with the bottom peripheral curved portion 40 from the outer periphery toward the center. The concave portion 42, the inner-side convex portion 43, and the central concave portion 44 are formed, and the circumferential concave portion 41 has a shape projecting inward from the central concave portion 44.

In the primary blow molding using this primary blow bottom mold, abrupt stretching of the center of the bottom is started from the time when the center of the bottom of the stretch-blow molded article reaches the bottom central recess 44. However, at a rather early stage, a part of the molded body comes into contact with the inwardly projecting circumferential recess 42, and the contact portion is cooled. In the subsequent blowing step, stretch blow molding is performed on the central bottom portion and the vicinity of the curved portion around the bottom, which are not yet in contact with the bottom mold. At this time, since the stretch blow molding of the central portion of the bottom and the peripheral portion of the bottom is performed by sandwiching the cooled circumferential recessed portion 42, the two portions are stretch blow molded as separate parts. In particular, in the central portion of the bottom, since the large stretching is performed inside the circumferential recess 42, the degree of stretching of the remaining gate increases, the size of the low stretch orientation portion decreases, and the inside of the circumferential recess 42 increases. The thickness of is more averaged.

High stretch centered on the bottom including the rest of the gate is possible
In order to make the diameter D of the circumferential recess 41 _FiveIs the bottom of the secondary molded product
It is in the range of 0.5 to 0.9 times the diameter of the body connected to the
H between the concave portion 41 and the central concave portion 44₂Is 1 to 10 m
m in the range of the circumferential concave portion 44 and the outer circumferential side convex portion 40.
Difference H₃Is preferably in the range 0 to 5 mm.

[0114] (2) In the thermal shrinkage process the present invention, then with heat shrinking step carried out, a part of the barrel portion continuous to the bottom portion and the bottom portion of the secondary molded article is heated, the height direction <br/>及beauty radially Then, it becomes a tertiary molded product having a shape that fits in the secondary blow mold which is the final product shape.

It is preferable that the bottom of the secondary molded product is heated and contracted by non-contact heating without restraint.
In the example shown in FIG. 19 and FIG. 20, infrared radiators 45 and 46 are provided along the moving path of the secondary molded product 36a so as to face the bottom and a part of the body of the secondary molded product, Secondary molded product 3 in the space surrounded by the infrared radiator
6b is supported by the core mold 31 and is rotated in the axial direction and moved while being heated, whereby the bottom part and the part of the body part of the secondary molded product are heated and contracted as shown in FIG. The next molded product 36b is obtained. It is recommended to provide a heat shield plate 47 to prevent unnecessary shrinkage of the body.

The infrared radiators 45 and 46 are 400 to 10 respectively.
It is preferable to use a material which is heated to about 00 ° C. and has relatively high radiation efficiency. As a result, infrared rays having a relatively high energy density can be applied to a predetermined portion of the secondary molded product 36a, and the temperature can be raised to a predetermined temperature in a short time of, for example, 10 seconds or less.

It is preferable that the shape of the bottom 48 of the tertiary molded product 36b is as close as possible to the bottom valley of the secondary blow mold, which can facilitate the molding of the foot of the final product (see FIG. 20 and FIG. 22).

In order to make the bottom shape of the tertiary molded product 36b a preferable shape, the bottom shape of the secondary molded product 36b is important,
It is preferable to increase the height of the secondary molded product that undergoes heat shrinkage in consideration of heat shrinkage. Further, since the bottom center gate remaining portion 8 of the secondary molded product 36b is thick when the bottom portion is heated, the temperature rise is slower than that of the thin portion around the bottom portion. for that reason,
If the bottom shape of the secondary molded product is, for example, a hemispherical shape, the thin-walled portion around the gate residual portion first undergoes thermal contraction in a conical shape, and the thick gate residual portion 8 is projected to the outer surface side. When the center is convex upward, it is largely separated from the valley shape of the secondary blow bottom type. At this time, as shown in FIG. 24, it is effective to adopt a shape in which the bottom 37 of the secondary molded product is flat as a whole and a recess 38 is further provided at the center of the bottom, as shown in FIG. Has a bottom surface 37 which is slightly concave in the center of the bottom but is substantially flat and has a shoulder 4
It is possible to obtain a tertiary molded product 36b having a shape in which 8 is close to the valley of the secondary blow mold.

The heating temperature of the highly stretch-oriented bottom portion of the secondary molded product and a part of the body portion connected to it 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 orientation layer in the remaining portion of the gate is whitened, but the high stretch orientation layer in the remaining portion of the gate and the peripheral portion of the gate around it remain substantially transparent without being whitened. .

(3) Secondary blow molding The tertiary molded product 36b in the heated state is introduced into the secondary blow mold and is secondary blow molded into the final product (FIGS. 22 and 23).

In FIG. 22 showing the details of the secondary blow molding process, the tertiary molded product 36b has its neck portion supported by the core mold 31 and is held in the closed split mold 51. A bottom mold 52 that defines the bottom shape of the final container is also arranged on the opposite side of the core mold. A fluid is blown into the tertiary molded product 36b to carry out the secondary blow molding of the tertiary molded product to form the bottom shape of the final container 36c having a predetermined trough and foot. The molded container 50 is placed in the opened secondary blow mold 51 by a take-out mechanism (not shown) known per se.
Is taken out from the.

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

At the time of the secondary blow molding, the temperature of the mold is
The temperature may be maintained at 5 to 135 ° C. and cooling may be performed immediately after molding, or cooling may be performed by passing cold air or the like through the final molded product.

The bottom of the final product thus obtained, including the rest of the gate, is composed of a heat-stretched and highly stretched orientation layer having high heat and pressure resistance and high impact resistance. Excellent impact performance. (FIGS. 2 and 3) At this time, the thickness of the bottom center gate remaining portion of the container, the gate connecting portion, and the gate peripheral portion is smaller than that of the secondary blow-molded secondary molded product by heat shrinkage during heat setting. However, since the center part of the bottom is hardly stretched in the subsequent secondary blow molding, the thickness becomes somewhat thick.

The remaining gate portion at the bottom of the container of the present invention is composed of a high stretch orientation layer and a low stretch orientation portion. In the case of the two-step blow molding method, the structure of the remaining gate at the bottom of the container is determined by the structure composed of the high stretch orientation layer and the low stretching orientation portion of the remaining gate of the secondary blow molded product. The structure of the bottom gate residue of the secondary blow molded product is determined by the bottom shape of the primary blow molding die, the bottom shape of the secondary molded product, the stretched state of the bottom of the secondary molded product derived from the primary blow molding conditions, and It is affected by the thickness distribution, the size of the gate portion of the preform, and the thermal history of the gate portion due to the injection conditions of the preform.

When the bottom shape of the primary blow mold is a flat shape having a recess 39 in the center as shown in FIG. 24, a typical container of the present invention molded under the above-mentioned preferable molding conditions of the present invention. As shown in FIG. 2, the remaining bottom gate is composed of a whitened low-stretch alignment portion 13 on the outer surface side and a transparent high-stretch alignment layer 12 on the inner surface side. The high stretch orientation layer 12 of the remaining gate portion 8 is connected to the gate connection portion 9 in the high stretch orientation state and the gate peripheral portion 11 outside thereof.

[0127] Also in the case of using the primary blow bottom type shown in Figure 24, the primary blow molding by adjusting the degree of heating of the preform during the Hare line, heating the inner surface of the bottom portion of the preform Under the condition that the temperature is slightly lowered, the remaining gate at the bottom of the obtained secondary molded product may have a structure in which the high stretch alignment layer located in the center is sandwiched between the low stretch alignment portions on the inner surface side and the outer surface side. At this time, the bottom gate remaining portion of the container finally obtained through the intermediate heat setting step has a transparent high stretch orientation layer 12 as shown in FIG. The structure is sandwiched between the low-stretch alignment layer 13 described above. The heating of the preform in the above primary blowing step is usually performed mainly by infrared rays emitted from the infrared radiator provided on the outer surface side of the preform and the rod-shaped infrared radiator inserted inside the preform. However, the heating temperature on the inner surface side of the bottom of the preform can be lowered by increasing the distance between the rod-shaped infrared radiator inserted inside the preform and the bottom of the preform.

The container having the bottom gate remainder 8 shown in FIG. 5 can also be manufactured by using the primary blow bottom mold shown in FIG. In this case, the reason why the transparent highly stretched orientation portion 12b is formed in the center of the inner surface side of the gate remaining portion 8 at the bottom of the container is not clear, but it is presumed as follows. That is, usually, in the gate portion of the preform, the degree of thermal crystallization tends to be larger in the outer peripheral portion of the gate portion in a ring shape than in the inner portion of the gate portion due to the heat history during injection molding. In particular, when performing primary blow molding using a preform in which the degree of thermal crystallization of the ring-shaped gate outer peripheral portion is relatively large, the ring-shaped outer peripheral portion of the gate portion of the preform is stretched more than the inner portion thereof. It is in a difficult state.
At the time of blow molding, in the bottom gate remainder of the obtained molded product, the inner surface side having a particularly high stretch ratio is in a highly stretched state, and accordingly, the outer surface side of the gate remainder corresponding to the gate portion of the preform is stretched. The outer periphery of the ring-shaped gate, which is difficult to be deformed, remains in a relatively low stretched state despite being deformed, while the inner portion of the gate, which is easily stretched, is stretched locally by the outer periphery of the ring-shaped gate and stretched to a high extent. Become a state. As a result, as shown in FIG. 5, the ring-shaped low-stretch alignment portion 13b and the inner high-stretch alignment portion 12b are present on the outer surface side of the remaining gate, and the inner surface is the high-stretch alignment layer 12 on the inner surface side. It is considered that the balance 8 is formed.

On the other hand, when the primary blow bottom mold having the ring-shaped irregularities as shown in FIG. 25 is used, the center of the bottom of the molded product at the time of blow molding, including the gate remainder, is compared as described above. The degree of stretching can be increased, and the size of the low stretch orientation portion formed in the remaining portion of the gate can be relatively reduced.
As a result, a relatively thick highly stretched alignment layer 12 as shown in FIG.
It is possible to obtain a container having a gate remaining portion 8 composed of a low stretch orientation portion 13 thinly formed in a limited portion on the outer surface side.

[0130]

According to the present invention, by adopting a means for reducing the temperature drop in the center of the bottom and the vicinity thereof at the time when the center of the bottom including the gate reaches the bottom of the mold to a certain level or less, The bottom, including the rest of the gate, can be layered in a highly stretched orientation. According to this method, the operation of trimming (finishing) the gate portion of the preform and the operation of thermally crystallizing the center of the bottom portion prior to the stretch blowing are unnecessary, and the stretch-molded container can be produced with a relatively small number of steps. It can be manufactured with good performance and effective use of resources. Further, in the container of the present invention, the bottom center gate remainder has a high stretch orientation layer continuous to the gate connection portion and a highly stretch orientation bottom portion in a direction radially outward from the gate connection portion, so that the entire bottom has impact resistance and creep resistance. It has a strong structure and is useful for hot-filling the contents, and also has the advantage that it is excellent in the self-supporting property and appearance of the container.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional side view showing an example of a container obtained by the present invention.

FIG. 2 is a partially enlarged cross-sectional view showing an example of the arrangement of a transparent highly stretched alignment layer at the bottom center gate remainder of the container .

FIG. 3 is a partially enlarged cross-sectional view showing another example of the arrangement of a transparent highly stretched alignment layer in the bottom center gate remainder of the container .

FIG. 4 is a partially enlarged cross-sectional view showing an example of the arrangement of a transparent highly stretched alignment layer at the bottom center gate remainder of the container obtained by the present invention.

FIG. 5 is a partially enlarged cross-sectional view showing still another example of the arrangement of the transparent highly stretched alignment layer at the bottom center gate remainder of the container .

FIG. 6 is an explanatory diagram showing dimensions of a standard test piece for measuring a yield load value at 70 ° C.

FIG. 7 is an explanatory diagram showing how to obtain a yield load value.

FIG. 8 is an explanatory diagram for explaining another example of the shape and size of the bottom valley portion of the container obtained by the present invention.

FIG. 9 is an explanatory diagram for explaining another example of the shape and size of the bottom valley portion of the container obtained by the present invention.

FIG. 10 is an explanatory diagram for explaining a foot opening angle θ in the container obtained according to the present invention.

FIG. 11 is a side view showing an example of a preform used in the method of the present invention.

FIG. 12 is an explanatory diagram showing the shape and dimensions of the gate portion of the preform.

FIG. 13 is a cross-sectional view showing a state before the start of blow molding in an example of container production by the one- step blow molding method.

FIG. 14 is a cross-sectional view showing a state after completion of blow molding in an example of container production by the one- step blow molding method.

FIG. 15 is an enlarged cross-sectional view showing the structure of the container bottom formed by the one- step blow molding method.

FIG. 16 is a cross-sectional view showing the first stage of a primary blow molding process in a two-stage blow molding method.

FIG. 17 is a cross-sectional view showing the final stage of the primary blow molding process in the two-stage blow molding method.

FIG. 18 is an enlarged cross-sectional view showing the structure of the bottom portion of the secondary molded product formed by the primary blow molding of the two-stage blow molding method.

FIG. 19 is a cross-sectional view showing the first stage of an intermediate heating step for obtaining a tertiary molded product in the two-stage blow molding method.

FIG. 20 is a cross-sectional view showing the final stage of the intermediate heating step for obtaining a tertiary molded product in the two-stage blow molding method.

FIG. 21 is an enlarged cross-sectional view showing the structure of the bottom of the tertiary molded product.

FIG. 22 is a cross-sectional view showing a secondary blow molding process in the two-stage blow molding method.

FIG. 23 is a side view showing the final product in the two-stage blow molding method.

FIG. 24 is a cross-sectional view showing an example of the structure of a blow mold used for primary blow molding of a two-stage blow molding method.

FIG. 25 is a cross-sectional view showing another example of the structure of the blow mold used for the primary blow molding of the two-stage blow molding method.

[Explanation of symbols]

1 mouth and neck 2 shoulder 3 torso 4 bottom 5 Bottom central valley 6 Tanibe 7 feet 8 remaining gate 9 Gate connection 10 Base 11 Gate periphery 12 High stretch orientation layer 13 Low stretch low orientation layer 15 Standard test pieces 20 preform 21 neck, 22 body 22 23 Blocked bottom 33 blow bottom mold 34 Stretching rod 35 press rod 36a Secondary molded product 36b Secondary molded product 37 bottom 38 Recess to inner surface 39 Bottom center recess 40 Bottom curvature area 41 Outer peripheral convex 42 circumferential recess 43 Inner peripheral side convex part 44 central recess 45 infrared radiators 45 and 46 47 Heat shield plate 48 bottom type

Front page continuation (72) Inventor Kazuhisa Hamada 2-206 Nishitobe-cho, Nishi-ku, Yokohama-shi, Kanagawa Prefecture (72) Inventor Yutaka Mukai 6-7-27 (56) Shimootadanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Reference (56) 9-118322 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B29C 49/00-49/80 B65D 1/02

Claims (3)

(57) [Claims] 1. A preform heated to a stretching temperature is sandwiched between a stretch rod inserted inside the preform and a press rod outside the preform in a mold, and the center of the bottom of the preform is sandwiched between the stretch rod and the stretch rod. In a method for producing a stretched resin container, which comprises simultaneously blowing high-pressure gas into the preform while driving, the preform is a preform having a gate portion in the center of the bottom, and until just before the stretching process is completed. Keeping the temperature drop at the center of the bottom within 40 ° C , the bottom mold used for the primary blow molding is centered from the outer circumference.
Toward the outer peripheral side convex portion, circumferential concave portion, which is continuous with the bottom peripheral curvature portion,
Consists of an inner circumference side convex part and a central concave part, and the circumferential concave part
A shape that is more inwardly projected than that of the above, and that the center of the bottom is highly stretched, and the thickness of the peripheral edge of the gate is in the range of 0.35 to 1 mm and the area stretch ratio of the peripheral edge of the gate is 3.5 to 12. 5
The secondary molded product is composed of a bottom having a highly stretched orientation layer including the center of the bottom, and at least the bottom of the secondary molded product and a part of the body part connected to the bottom are formed. A process for producing a heat-resistant resin container, which comprises heat-shrinking to form a tertiary molded product, which is secondarily blow-molded in a mold to form a final container. 2. A preform having a gate portion of 0.1 to 3
A method according to claim 1, wherein those having a height of mm. 3. A periphery of a bottom mold used for the primary blow molding.
The diameter D _{5 of the} cylindrical recess is 0.5 to the body diameter D ₀ of the secondary molded product.
0.9 times, the step H ₂ between the circumferential recess and the central recess is 1 to 1
0 mm, the step H ₃ between the circumferential concave portion and the outer circumferential concave portion is 0 to 5
The manufacturing method according to claim 1 or 2, which is mm.