JP3835428B2 - Heat-resistant stretched resin container - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a resin stretch-molded container that is excellent in heat resistance, heat-resistant pressure resistance and impact resistance, and is also excellent in self-supporting properties.
[0002]
[Prior art]
A biaxial stretch blow molded container of thermoplastic polyester such as polyethylene terephthalate (PET) has excellent transparency and surface gloss, as well as impact resistance, rigidity and gas barrier properties required for bottles. It is used as a bottled container for various liquids, that is, a bottle.
[0003]
In general, when manufacturing a bottled product, it is necessary to heat sterilize or sterilize the contents after hot filling or filling the contents in order to enhance the storage stability of the contents.
[0004]
The heat-resistant and pressure-resistant self-supporting container is required to have resistance to hot filling of contents and heat sterilization treatment from the viewpoint of ensuring self-supporting property. In particular, in a container bottom portion (hereinafter also simply referred to as a petaloid-shaped bottom portion) provided with foot portions and trough portions arranged alternately around the bottom peripheral portion, ensuring self-supporting after hot filling of the contents and heat sterilization treatment Is important, and high heat and pressure strength is required.
[0005]
In a heat-resistant pressure-resistant self-supporting container currently on the market, the petaloid bottom center is relatively thick in an unstretched or low-stretch orientation state. In such a petaloid bottom, the pressure resistance at normal room temperature is excellent, but the heat pressure resistance at a high temperature of about 70 ° C. is considerably low. Therefore, it is used under conditions where the gas pressure of the contents and the temperature during the heat sterilization treatment are limited. In addition, when the resin constituting the bottom of the thick petaloid excessively absorbs moisture, the decrease in heat-resistant pressure strength becomes remarkable, and it is not suitable for a self-standing container for heat-resistant pressure.
[0006]
The heat-resistant pressure strength can be increased by thermally fixing the thick bottom portion in such a low stretch orientation state and performing thermal crystallization. However, when the bottom of the low-stretch orientation state is thermally crystallized to sufficiently increase the heat-resistant pressure strength, the thermal crystallized portion becomes extremely brittle. When the embrittled portion occupies a considerable portion of the petaloid bottom, there arises a problem that the impact resistance is remarkably lowered. Moreover, although the bottom part of the low stretch orientation state is whitened by thermal crystallization, it is not preferable for aesthetics if the region becomes too wide.
[0007]
Patent Document 1 below discloses a container having a petaloid bottom portion that has a thick thermal crystallization portion in the center of the bottom portion, the periphery thereof is thinned in a highly stretched orientation state, and is heat-set. In such a container, although the bottom center thermal crystallization part is brittle, it can be limited to a relatively small area. On the other hand, the thinned part in the high stretch orientation state around it is flexible even if it is heat-set. Since it is rich in nature and possesses high impact resistance, the impact resistance at the bottom of the petaloid can be brought to a level with no problem.
[0008]
[Patent Document 1]
JP-A-8-267549
[0009]
[Problems to be solved by the invention]
However, in the above prior art, the thermal crystallization portion at the center of the container bottom is obtained by heating and thermal crystallization of the preform bottom portion, which requires a troublesome heating step.
[0010]
In addition, a preform used for manufacturing a stretch blow molded container is manufactured by injection molding of a resin, and a gate portion is always coupled to the center of the bottom of the preform. As in the case of general stretch blow molding, in the case of a petaloid type bottom-shaped container, this gate portion is trimmed to cut it out as an extra.
[0011]
However, such a trimming operation is a troublesome process, and there is a problem in accuracy that it is not always easy to make the trimming dimension constant. In particular, if the length of the gate portion is made as close to zero 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 is further troublesome.
[0012]
  The present inventors diligently studied a biaxial stretch blow molding means for making the petaloid bottom portion in a highly stretched orientation state without effectively crystallizing the bottom portion of the preform and also effectively using the remaining gate of the preform. did. As a result, it was found that the stretch molding of the bottom part in the blow molding is remarkably performed from the time when the gate part which is the bottom center part of the molded body reaches the bottom part of the mold. And means for reducing the temperature drop at the bottom center portion and its vicinity when the bottom center portion of the molded body reaches the bottom of the mold to a certain level or less.And the bottom mold in which the bottom center gate remainder is thick, and the surrounding gate connection and gate periphery are in a highly oriented state.By adopting, it was found that the bottom part, including the gate remainder, can be layered in a highly stretched orientation state.
[0013]
That is, the object of the present invention is that the bottom portion is effectively crystallized in a highly stretched orientation state including the remainder of the gate, and is excellent in heat resistance, heat pressure resistance and impact resistance, and further in self-standing and appearance characteristics. The present invention also provides an excellent stretched resin container.
[0014]
[Means for Solving the Problems]
  According to the present invention, in a self-supporting container provided with a mouth-neck part, a shoulder part, a trunk part, and a bottom part formed by biaxial stretch blow molding of resin, the bottom center gate remainder is a transparent high-stretch orientation on the container inner surface side. Layer and a whitened low-stretch orientation layer on the outer surface side of the container. The high-stretch orientation layer is thick and the low-stretch orientation layer isIn a limited area on the outer surfaceProvided is a heat-resistant stretched resin container, characterized in that it has a thin stretched and highly stretched orientation layer at the bottom center remaining portion, and has a highly stretched orientation layer connected to a gate connection portion and a highly stretched orientation bottom portion in a radially outward direction. Is done.
[0015]
In the present invention,
1. The bottom is formed of a plurality of valleys and legs alternately arranged around the bottom central valley and the bottom central valley, and the container has self-supporting property,
2. Being oriented and crystallized so that the crystallinity of the highly stretched orientation layer is 20% or more,
3. The bottom center gate remainder is heat-set and the highly stretched alignment layer has a crystallinity of 25-55%;
4). The high stretch orientation layer has a thickness of 0.35 mm or more,
5). The bottom center gate remainder is body diameter D₀Having a diameter Dg less than or equal to 0.25 times
6). The bottom center gate remainder has a yield load of 25 kgf / cm or more at a temperature of 70 ° C .;
Is preferred.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The heat-resistant stretched resin container of the present invention is provided with a mouth neck portion, a shoulder portion, a trunk portion, and a bottom portion formed by biaxial stretch blow molding of resin, but the bottom center gate remaining portion is a gate connection portion and more than that. It is a remarkable feature that it has a high stretch orientation layer connected to the bottom of the high stretch orientation in the radial direction. In the present specification, the gate portion of the preform refers to the gate portion protruding from the bottom of the preform, while the remaining gate portion of the container refers to the entire portion in the thickness direction of the bottom center corresponding to the gate portion. Say.
[0017]
In this container, a high-stretch orientation layer integrally connected to the gate connection portion and the high-stretch orientation bottom portion in the radially outward direction is also present at the bottom center. The pressure strength is at a high level, and preferable heat and pressure resistance can be maintained. Furthermore, in a container in which the bottom of the petaloid shape in a highly stretched orientation state is heat-fixed, the heat-resistant pressure strength is further improved and has particularly excellent heat-resistant pressure resistance, self-supporting property, impact resistance, and the like.
[0018]
It has been found that stretch molding of the bottom portion in blow molding is remarkably performed from the time when the gate portion, which is the bottom center portion of the molded body, reaches the bottom portion of the mold. In the present invention, by adopting means for reducing the temperature drop at the bottom center portion and its vicinity when the bottom center portion of the molded body reaches the bottom of the mold to a certain level or less, the bottom portion including the gate remaining portion is included. , It can be thinned to a highly stretched orientation state.
[0019]
The remaining gate in a stretch blow molded container is one of the troublesome problems. If this part remains in an unstretched thick state, creep deformation occurs under conditions where heat and pressure are applied simultaneously. The conventional idea was to thermally crystallize the part in a preform state, or to make the gate remainder as thin as possible to facilitate stretching and orientation, but in the present invention, the gate remainder is thick. However, it becomes possible to form a highly stretched alignment layer at the center by the above-mentioned means, which solves the above problem.
[0020]
In the present invention, by adjusting the shape of the preform, the thickness of the bottom, and the blow molding conditions, the stretch ratio of the preform bottom during blow molding, in particular, the stretch ratio of the gate peripheral part including the gate connection part in contact with the gate remainder By optimizing, the bottom center gate remaining part of the container can be made thick, and the surrounding gate connecting part and gate peripheral part can be in a highly stretched orientation state and have a preferable thickness.
[0021]
Furthermore, 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 portion are formed in the thick gate remainder. In addition, it was found that the highly stretched orientation portion of the remaining gate portion is layered, and has a structure continuously connected to the gate connection portion and the gate peripheral portion in the highly stretched orientation state.
[0022]
The structure of the bottom center gate remaining portion described above is such that a part of the bottom gate portion in the thickness direction is formed by making the periphery of the bottom gate portion of the preform corresponding to the bottom center gate remaining portion in a highly stretched orientation state during blow molding. It is shown that the film is pulled by the highly stretched surrounding area and locally stretched and highly oriented, resulting in the formation of a layered highly stretched and oriented portion.
[0023]
【Example】
[Container of the present invention]
In FIG. 1 which shows the heat-resistant pressure-resistant container of this invention, this container is from the neck part 1 formed by biaxial stretch blow molding of resin, the shoulder part 2 connected to the mouth neck part, the trunk | drum 3, and the bottom part 4. It is made up. In this specific example, the bottom 4 is composed of a plurality of valleys 6 and legs 7 arranged alternately around the bottom central valley 5 and the bottom central valley. The lower part of the body part 3 connected to the bottom part 4 has a diameter D.₀The bottom center gate remaining portion 8 having a diameter Dg exists at the center of the bottom. The shoulder 2 and the body 3 are thinned in a highly stretched orientation except for the connection with the mouth and neck 1.
[0024]
The bottom portion 4 is a thick gate remaining portion 8 located in the center of the bottom, a gate connecting portion 9 in contact with the gate remaining portion 8, and a gate peripheral portion 11 that is around the gate connecting portion and is an inner portion of the base portion 10 of the foot 7. 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 specific example, each part of the bottom part 4 except the gate remainder 8 is substantially composed of a layer in a highly stretched orientation state. Further, it is relatively thin except for the gate connection portion 9.
[0025]
The bottom center gate remainder 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, the highly stretched orientation portion of the gate remainder 8 is composed of a continuous layer that crosses the gate remainder, and is connected to the gate connection portion 9 and the gate peripheral edge portion 11 that extend around the gate remainder. As a result, in the container of the present invention, the bottom 4 is covered with a continuous high stretch orientation layer.
[0026]
[Remaining gate]
The arrangement of the transparent stretched alignment layer in the bottom center gate remainder 8 will be described below with reference to FIGS.
[0027]
In FIG. 2 showing an example of the arrangement of the high stretch orientation layer, the bottom center gate remainder 8 is composed of a generally transparent high stretch orientation layer 12 on the container inner surface side and a generally whitened low stretch low orientation layer 13 on the container outer surface side. ing. In the bottom center gate remaining portion 8 of this heat resistant stretched resin container, the high stretch orientation layer 12 exists on the inner surface side, so that it is particularly excellent in the combination of heat resistance and impact resistance.
[0028]
In FIG. 3 showing another example of the arrangement of the high-stretch alignment layer, the bottom center gate remainder 8 includes a generally transparent high-stretch alignment layer 12 located in the center in the thickness direction, and whitened and low-stretch low-orientation on both the inner and outer sides. It has a laminated structure composed of layers 13 and 13. This laminated structure is a so-called rigid-soft-rigid laminated structure, and is particularly excellent in the dimensional stability of the bottom portion under high temperature and high pressure.
[0029]
The gate remainder 8 shown in FIG. 4 is a modification of that shown in FIG. 2 and comprises a generally transparent high stretch orientation layer 12 on the container inner surface side and a generally whitened low stretch low orientation portion 13 on the container outer surface side. The high stretch orientation layer 12 is very thick, and the low stretch low orientation portion 13a is thinly formed at a very limited portion such as the gate center or the gate periphery. In this structure, the increase in the bottom yield load due to the increase in the thickness of the high stretch orientation layer 12 is significant.
[0030]
In FIG. 5 showing still another example of the arrangement of the high stretch orientation layer, the bottom center gate remainder 8 includes a generally transparent high stretch orientation layer 12 disposed on the inner surface side of the container as in FIG. Similarly, a special composite structure exists on the outer surface side of the container. That is, a composite layer of a ring-shaped low-stretched whitening portion 13b and a transparent high-stretch orientation portion 12b located in the center thereof is formed on the outer surface side of the container.
[0031]
The high stretch orientation portion 12 of the bottom center gate remainder 8 is generally oriented and crystallized at a crystallinity of 20% or more, preferably 25%, at the time of blow molding. This is preferable.
[0032]
By thermally fixing the bottom including the bottom central 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 gate remainder 8 is kept substantially transparent. In this case, the low-stretched alignment layer 13 of the remaining gate that is whitened is present at the center of the bottom of the container, but its size is limited, and there is no particular aesthetic problem.
[0033]
In the heat-fixed bottom center gate remainder 8, it is preferable that the low stretch alignment layer 13 has a crystallinity of 20% or more, particularly 25% or more, and the high stretch alignment layer 12 has a crystallinity of 25% or more.
[0034]
The thickness of the bottom center gate remaining portion 8 should normally be about 1 to 3.5 mm at the maximum portion. In the present invention, the bottom center gate remaining portion is highly stretched without the need to finish the gate portion of the preform. An oriented container bottom can be formed. On the other hand, the thickness of the highly stretched alignment layer 12 in the bottom center gate remainder 8 may be any thickness as long as it provides sufficient heat and pressure resistance to the center of the bottom, and is generally 0.35 mm or more, particularly 0.4 mm or more. As long as it occupies 20% or more, particularly 30% or more of the total thickness of the gate remainder.
[0035]
The diameter Dg of the bottom center gate remainder 8 is the trunk diameter D.₀0.25 times or less, particularly 0.2 times or less, is preferable in view of the appearance characteristics of the container since the presence of the gate remainder is not noticeable.
[0036]
[Gate connection and gate periphery]
In the present invention, by forming the gate connection portion 9 and the gate peripheral portion 11 in a high stretch orientation state at an appropriate stretch ratio, a layered high stretch orientation portion 12 is formed in a part of the thick gate remaining portion 8. I can do it.
[0037]
It is preferable that the gate connection portion 9 and the gate peripheral portion 11 surrounding the bottom center gate remaining portion 8 are highly stretched and oriented to a crystallinity of 20% or more, particularly 25% or more. Furthermore, it is preferable that the gate connection portion and the gate peripheral portion after heat setting have a crystallinity of 30% or more.
[0038]
The gate peripheral edge 11 is located around the gate remainder and the gate connection part, and is located at the bottom central part up to the bottom central foot base 10, but the thickness of the gate peripheral part 11 is not thermally fixed. In general, it is preferably in the range of 0.35 to 1 mm, particularly 0.45 to 0.8 mm, in order to effectively form the highly stretched alignment layer 12 in the gate remainder 8, while when heat-fixed, It is preferably in the range of 0.35 to 1.1 mm, particularly 0.45 to 1 mm. The reason why the preferable wall thickness range is somewhat widened when heat setting is performed is that the heat shrinks during heat setting and the wall thickness increases.
[0039]
The bottom center gate remaining portion 8 and the gate connection portion 9 can maintain a highly stretched orientation state even if they slightly exceed a thickness of 1 mm or more. The thickness of the gate connection portion is preferably in the range of 0.4 to 1.3 mm, particularly 0.5 to 1.1 mm, so that the highly stretched alignment layer 12 is effectively formed in the gate remaining portion 8.
[0040]
When the thickness of the gate peripheral portion 11 is less than 0.35 mm, it is not preferable because it is too thin to reduce the heat pressure resistance of the bottom center portion. On the other hand, if the thickness of the peripheral edge of the gate exceeds 1 mm at the stage of blow molding, it becomes difficult to form a highly stretched alignment layer on the remaining gate and the gate connection. However, in the case where the thickness of the peripheral edge of the gate exceeds 1 mm in a narrow part where the thickness is extremely limited, it does not particularly prevent the part of the remaining gate from being highly stretched and oriented.
[0041]
As described above, the gate connection part 9 and the gate peripheral part 11 having a thickness within a preferable range and highly oriented and crystallized are particularly excellent in heat resistant pressure strength and impact resistance strength. Therefore, the petaloid bottom portion of the present invention consisting of the bottom central valley portion having the thick gate remainder and the gate connection portion and the gate peripheral portion has both excellent heat pressure strength and excellent impact resistance at the same time. be able to.
[0042]
[Thickness of container, crystallinity]
In the container of the present invention, the thickness of the container excluding the mouth / neck portion 1 and the vicinity thereof, and the bottom center gate remaining portion 8 and the vicinity thereof is 0.15 mm to l. 1 mm, preferably in the range of 0.2 mm to 0.9 mm.
[0043]
The degree of crystallinity associated with the stretching orientation of the container excluding the mouth / neck portion 1 and its vicinity and the gate remainder 8 is 20%, preferably 25% or more.
[0044]
The bottom portion 4 is heat-fixed in a state substantially free of whitening except for the gate remaining portion 8, and the body diameter D₀It is preferable that the crystallinity of the bottom central valley portion including the bottom gate remaining portion 8 inside the 50% diameter is 25 to 55%.
[0045]
[Yield load at 70 ° C]
In the valley part of the petaloid type bottom part, in particular, in the bottom central valley part, a relatively large deformation force acts as compared with the trunk part. Therefore, the heat and pressure strength of the bottom central valley determines the heat and pressure resistance of the bottom of the container.
[0046]
The heat-resistant pressure strength of the bottom central valley can be represented by a yield load value at 70 ° C. As shown in FIG. 6, the yield load value at 70 ° C. is obtained when a standard test piece 15 is prepared from the bottom central valley including the gate remainder, and the standard test piece is subjected to a tensile test at a temperature of 70 ° C. The yield load value shown in FIG. 7 can be obtained as a value converted per 1 cm width. The yield load value at 70 ° C. takes into account the thickness of the bottom of the container. By obtaining the yield load value at 70 ° C. at the center of the bottom including the remaining gate where the greatest deformation force acts, the heat resistance of the bottom of the container is obtained. The pressure can be evaluated.
[0047]
In the present invention, by setting the yield load at 70 ° C. of the portion constituting the valley portion to 25 kgf / cm or more, preferably 30 kgf / cm or more, the petaloid bottom portion having excellent heat and pressure resistance that can be self-supported after the heat sterilization treatment is obtained. It turns out that it becomes a container which has.
[0048]
In the container according to the present invention, the bottom trough portion having a highly stretched orientation layer having a thickness of 0.35 mm or more including the remainder of the bottom center gate and not thermally fixed usually has a yield load at 70 ° C. It becomes about 25-30 kgf / cm, and can have preferable heat-resistant pressure property. At that time, if there is a portion where the thickness of the bottom central valley portion is less than 0.35 mm, the bottom valley portion often has a yield load at 70 ° C. usually lower than 25 kgf / cm, and the heat pressure resistance is reduced. Become.
[0049]
When the bottom center of the container of the present invention is heat-fixed, the bottom valley portion including the bottom center gate remainder is thermally crystallized, and the yield load value at 70 ° C. of the portion is about 35 to 50 kgf / cm, It can have extremely high heat and pressure strength.
[0050]
On the other hand, in a conventional container having a petaloid bottom portion whose bottom central valley portion is composed only of a relatively thick and low-stretch orientation layer, the yield load value at 70 ° C. is about 10 to 20 kgf / cm, and the heat and pressure resistance is low. . In particular, when the thick low-stretch orientation layer of the conventional container contains about 5000 ppm of moisture, the yield load value at 70 ° C. is less than 10 kgf / cm, and the heat and pressure resistance is extremely lowered.
[0051]
[Bottom shape]
In the present invention, the container bottom is thinned in a relatively high stretched state. For this reason, compared with the conventional self-standing container having a thick bottom, the weight of the bottom becomes relatively small, and the position of the center of gravity moves to the top of the container. Therefore, an empty container has a small fall angle and is easy to fall. In order to improve the overturning resistance, it is necessary to increase the number of legs in the container of the present invention or to make the diameter and width of the contact portion relatively large. In that case, the moldability of the foot becomes a problem. That is, when the bottom of the foot is originally thinned and the tip of the foot is widened to improve the fall resistance, the thickness of the bottom of the foot of the bottom, that is, the outside of the grounding portion becomes extremely thin, The problem of whitening occurs in the overstretched state.
[0052]
In the present invention, the above problem is solved by devising the bottom shape of the container, the thickness of the foot tip is 0.15 mm or more, preferably 0.2 mm or more, and substantially at the foot tip. A container without whitening due to overstretching could be obtained.
[0053]
[Valley shape]
In the specific example shown in FIG. 8, the bottom valley portion 6 has a curvature radius R located at the bottom center portion including the gate remaining portion 8.₁The approximate spherical surface and the radius of curvature R connected to the body₂It is comprised with the following general spherical surface.
[0054]
The radius of curvature R of the spherical surface including the bottom center 5₁The distance between the foot tip portion 16 and the valley portion 6 is made relatively small by making the size of the sphere an appropriate size and the perpendicular of the spherical surface being the shortest distance between the foot tip portion 16 and the valley surface. be able to. As a result, the blow moldability of the tip of the bottom foot is improved, and the thickness of the tip of the foot is made relatively thick, and whitening of the foot tip due to overstretching can be prevented.
[0055]
Specifically, the radius of curvature R of the substantially spherical surface constituting the bottom center portion₁And trunk radius R₀Ratio R₁/ R₀Is preferably 1.2 to 2, and the diameter D indicating the range of the spherical surface₁And body diameter D₀Ratio D to₁/ D₀Is preferably set to 0.55 to 0.75. R₁/ R₀If it exceeds 2, the heat and pressure performance of the trough is lowered, and it becomes difficult to ensure the self-supporting property of the container after filling the contents and performing the heat sterilization treatment. R₁/ R₀If it is less than 1.2, the distance between the foot tip portion and the valley portion becomes too large, and it becomes difficult to secure a preferable thickness of the foot tip portion.
[0056]
In the example shown in FIG. 9, the bottom valley 6 has a relatively small radius of curvature R including the gate remainder 8.₁A substantially spherical surface A having a truncated cone shape or a substantially spherical surface B which is in contact with the approximate spherical surface A and located on the outer surface side of the extended virtual surface of the approximate spherical surface A, and a substantially spherical shape connected to the body from the surface B. Alternatively, it is composed of a conical surface C. At this time, it is preferable that the surface B or the surface C constituting the bottom valley peripheral portion is the shortest distance portion from the foot tip portion 16.
[0057]
In this example, a preferable heat-resistant pressure strength is imparted by making the bottom central valley portion 6 including the bottom gate remaining portion 8 where the greatest deformation force acts into a spherical surface A having a relatively small curvature radius. On the other hand, the distance between the foot tip 16 and the valley surface can be shortened by inflating the valley surfaces B and C to which a relatively small deformation force acts compared to the center of the bottom. Thereby, the blow moldability of the bottom foot tip portion 16 can be improved, and as a result, the thickness of the foot tip portion 16 can be made relatively thick and whitening due to overstretching can be prevented. Specifically, the radius of curvature R of the approximate spherical surface A constituting the bottom center portion.₁And trunk radius R₀Ratio R₁/ R₀Is preferably 0.9 to 1.4, and the diameter D indicating the range of the spherical surface₁Is body diameter D₀It is preferable to set it to 0.18 times to 0.5 times. The surface B that is connected to the substantially spherical surface A and extends outward is preferably a conical surface that is in contact with the approximately spherical surface A or a substantially spherical surface having a large radius of curvature close to the conical surface, and the outermost diameter D of the surface B.₂Is body diameter D₀Is preferably 0.3 times to 0.85 times.
[0058]
Furthermore, it is preferable to ensure the heat and pressure resistance by making the bottom central portion 5 where the greatest deformation force acts and the valley width in the vicinity thereof relatively wide. Specifically, body diameter D₀The surface area S of a hypothetical spherical surface composed only of the surface area S of the valley and the valley included in the diameter of 80%₀Ratio S / S₀Is preferably 0.2 to 0.5, and more preferably 0.3 to 0.4. S / S₀If it is less than 0.2, the area of the bottom center part and the valley part in the vicinity thereof is too small and limited, so that the deformation of the bottom center part becomes large and it becomes difficult to ensure the self-supporting property of the container. On the other hand, S / S₀If it exceeds 0.5, the portion that can be used for the foot during blow molding is too limited, so that it is difficult to secure a preferable foot tip thickness.
[0059]
[Foot opening angle]
In the present invention, as shown in FIG. 10, the foot opening angle θ between 65 ° and 90 ° is directed to the foot tip 16 while traversing between the feet 7 and sandwiches the valley in the plane perpendicular to the valley 6. It is preferable to be in the range. In a container having a foot opening angle θ of less than 65 °, when a relatively severe heat sterilization treatment is performed, the foot opening angle θ after the heat sterilization treatment is greatly increased, and the deformation amount of the valley portion is accordingly increased. Tend to be. When the foot opening angle θ is increased in advance, it can be considered that the acting direction of the force acting so that the foot pulls up the trough part of the spherical surface is close to the spherical surface direction. The force component that works perpendicularly to the portion, that is, the force component that deforms the valley portion is reduced. As a result, by increasing the foot opening angle θ, the deformation of the valley can be reduced, and the heat and pressure resistance performance is improved. Further, by relatively increasing the foot opening angle θ, it acts in an advantageous direction on the formability of the foot. That is, if 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 kept relatively low. On the other hand, if the foot opening angle θ is excessively increased, the width of the foot tip grounding portion is reduced. If the foot tip grounding portion is too thin, it tends to fall over in an empty container before filling, which is not preferable. Therefore, the foot opening angle θ is preferably 90 ° or less.
[0060]
[Foot height, number of screens]
The initial foot height is 2 to 8 mm, preferably 3 to 6 mm. When the foot height is less than 2 mm, the foot height after deformation of the bottom central valley after filling the contents and heat sterilization becomes extremely small, or minus, that is, the bottom central portion protrudes below the foot. It becomes difficult to maintain the independence of the container. On the other hand, when the foot height exceeds 8 mm, the distance between the foot tip portion and the valley portion becomes too large, and it becomes difficult to ensure a preferable foot tip thickness. The number of legs is preferably 6 to 4.
[0061]
[Other Embodiments of Heat-resistant Container]
In addition to the heat and pressure resistant container described above, the container of the present invention can be used as a heat resistant container for hot-filling high-temperature contents of about 80 to 93 ° C. The heat-resistant container is composed of a mouth and neck, a shoulder, a cylindrical or rectangular tube body, and a bottom part. The body part has a concave panel for absorbing reduced pressure and the bottom center part has a bottom center gate remaining part. An inwardly recessed portion including is provided. At this time, in order to ensure heat resistance to prevent deformation due to heat shrinkage at high temperature, the bottom, body, shoulder, and mouth and neck including the bottom center gate are heat-fixed. It is preferable that the crystallinity of each part of the container is 25 to 55%. In particular, the bottom portion subjected to the above-described heat fixing can achieve a significant weight reduction as the thickness is reduced, and can have excellent heat resistance strength despite the thickness reduction. In addition, the high stretch orientation portion at the bottom, excluding the low stretch orientation portion at the bottom of the bottom gate having a relatively small diameter, retains a transparent state even during heat setting, and is excellent in appearance.
[0062]
[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, etc. can also be used.
[0063]
The ethylene terephthalate-based thermoplastic polyester used in the present invention occupies most of the ester repeating units, generally 70 mol% or more, particularly 80 mol% or more of ethylene terephthalate units, and has a glass transition point (Tg) of 50 to 90. Thermoplastic polyesters having a melting point (Tm) of 200 to 275 ° C., particularly 220 to 270 ° C., at 55 ° C., in particular 55 to 80 ° C., are preferred.
[0064]
Homopolyethylene terephthalate is preferred in terms of heat and pressure resistance, but a copolyester containing a small amount of ester units other than ethylene terephthalate units can also be used.
[0065]
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, dodecanedioic acid, etc. 1 type or combination of 2 or more types of diol components other than ethylene glycol include propylene glycol, 1,4-butanediol, diethylene glycol, 1,6-hexylene glycol, cyclohexane di 1 type, or 2 or more types, such as methanol and the ethylene oxide adduct of bisphenol A, are mentioned.
[0066]
Also, it is possible to use a composite material in which ethylene terephthalate-based thermoplastic polyester is blended with about 5% to 25% of polyethylene naphthalate, polycarbonate, polyarylate, etc. having a relatively high glass transition point, so that it can be used at a relatively high temperature. The material strength can be increased. Further, polyethylene terephthalate and a material having a relatively high glass transition point can be laminated and used.
[0067]
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 extrusion grade is used depending on the application. The intrinsic viscosity (IV) is generally in the range of 0.6 to 1.4 dL / g, particularly 0.63 to 1.3 dL / g.
[0068]
[Container manufacturing method]
The heat-resistant stretched resin container of the present invention sandwiches the bottom center of the preform between the stretched bar inserted into the preform inside the mold and the press rod outside the preform, the preform heated to the stretching temperature, Next, when a stretched resin container is manufactured by blowing a high-pressure gas into the preform at the same time as the stretching rod is driven, 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 maintaining the temperature drop of the bottom center portion within 40 ° C. until just before, and also highly stretching the bottom center portion.
[0069]
In manufacturing the container, a bottomed cylindrical preform is first formed, and if necessary, the neck and neck of the preform are heated to locally provide a spherulitic portion.
[0070]
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 includes a neck portion 21, a trunk portion 22 and a closed bottom portion 23, and the neck portion 21. Are provided with a lid fastening mechanism such as a screw and a support ring for holding the container, and the neck portion 21 is thermally crystallized, that is, spheroidized. The spherulized neck portion 21 is the container neck portion 1 of FIG. Further, a gate remaining portion 24 exists at the center of the closed bottom portion 23.
[0071]
Injection molding can be used for molding the plastic material into the preform 20. That is, the plastic is melt-injected into a cooled injection mold and formed into a supercooled amorphous plastic preform.
[0072]
As the injection machine, a known one having an injection plunger or 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 preform for stretch blow molding.
[0073]
As the injection mold, a mold having a cavity corresponding to the container shape is used, but a one-gate or multi-gate injection mold is preferably used. Injection temperature is 270 to 310 ° C, pressure is 28 to 110 kgf / cm²The degree is preferred.
[0074]
The spherulization of the neck portion 21 of the preform 20 can be performed by selectively heating these portions by means known per se. Since thermal crystallization of polyester or the like occurs remarkably at a specific crystallization temperature, generally a corresponding portion of the preform may be heated to the crystallization temperature. Heating can be performed by infrared heating, dielectric heating, or the like. In general, it is preferable to perform selective heating by blocking a body portion to be stretched from a heat source with a heat insulating material.
[0075]
The above spherulization may be performed simultaneously with the preheating of the preform 20 to the stretching temperature or may be performed separately.
[0076]
In the present invention, the center of the closed bottom 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 at the time of injection molding. In the present invention, the highly stretched alignment layer 12 (see FIGS. 2 to 5) is formed at the center of the bottom of the container in a state where the gate portion 24 is left without being subjected to a finishing process such as further cutting. For use.
[0077]
In FIG. 12 for explaining the dimensions of the gate portion, 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.
[0078]
The stretching temperature of the preform 20 is generally 85 to 135 ° C., particularly 90 to 130 ° C., and the heating can be performed by means known per se such as infrared heating, hot air heating furnace, dielectric heating and the like. it can. The spherulization of the mouth is generally performed by heating the preform bottom and the mouth to a temperature of 140 to 220 ° C., particularly 160 to 210 ° C. in a state of being thermally insulated from other parts. it can. The crystallinity of the preform mouth is preferably 25% or more.
[0079]
In addition, for stretch blow molding from a preform, a method of performing stretch blow molding subsequent to preform molding using heat applied to the preform molded product to be molded, that is, residual heat, can be generally used. Is preferably a method in which a preform molded product once in a supercooled state is produced, and this preform is heated to the aforementioned stretching temperature and stretch blow molding is performed.
[0080]
The container of the present invention is characterized in that the entire container except the neck and neck is thinned in a highly stretched state, and in particular, the entire bottom including the bottom center (including the gate remainder) is relatively highly stretched. It is important to blow-mold.
[0081]
In particular, in the present invention, the gate peripheral portion 11 (FIG. 1) spreading around the bottom center gate remaining portion 8 (FIG. 1) and the gate connection portion 9 (FIG. 1) at the time of blow molding is highly stretched with an appropriate thickness. It is important to have an orientation state. Thereby, although the bottom center gate remaining part 8 (FIG. 1) is thick, the high stretch orientation part 12 (FIGS. 2 to 5) can be formed in a continuous layer form on a part thereof.
[0082]
At this time, the appropriate thickness of the gate peripheral portion 11 (FIG. 1) is equal to or less than the maximum thickness that can maintain a highly stretched orientation state, and within a range that is not excessively thin. Is preferred. In this case, if the thickness of the peripheral edge of the gate is too thick, it becomes difficult to form a highly stretched alignment layer on the remaining gate. On the other hand, if the thickness of the peripheral edge of the gate is too thin, the heat resistant pressure strength of the petaloid bottom is reduced. Problems arise. Specifically, the thickness of the gate peripheral portion 11 (FIG. 1), which extends from the gate connecting portion around the remaining portion of the central gate and reaches the bottom center foot base, is in the range of 0.35 to 1 mm. In particular, the range of 0.45 to 0.8 mm is preferable.
[0083]
In the biaxial stretch blow molding, in order to make the gate peripheral edge portion 11 (FIG. 1) in a highly stretched orientation state with an appropriate thickness, the stretch ratio at the time of stretch blow molding from the bottom of the preform to the gate peripheral edge portion. It is important to optimize. Specifically, the area stretch ratio at the time of stretching the peripheral edge of the gate is preferably 3.5 times to 12.5 times, more preferably 5 times to 10 times.
[0084]
In order to achieve the above-mentioned preferable draw ratio of the bottom center gate peripheral edge 11 by blow molding, first, the shape and thickness distribution of the preform 20, particularly the portion of the preform bottom that finally becomes the gate peripheral edge. It is necessary to optimize the wall thickness. Next, the blow molding conditions for performing the blow molding are optimized to obtain a predetermined stretch ratio of the gate peripheral portion. Blow molding conditions include preform heating temperature and temperature distribution, stretching speed for pushing up the bottom of the preform with a stretching rod, timing for blowing high-pressure air into the molded body from the start of stretching of the stretching rod, stretching blow speed determined by high-pressure air flow rate Furthermore, it is important to optimize the temperature level of the molded body when the bottom is substantially stretched.
[0085]
As a result of the study, the inventors have found that the bottom part is substantially in a highly stretched state by blow molding after the bottom gate remainder of the molded body has reached the bottom part of the mold. It was ascertained that the stretch molding was performed until just before the end of the blow molding in which the blow shape was almost determined. At that time, by maintaining the temperature of the bottom center of the molded body until reaching the bottom of the mold and immediately before the blow molding is completed, the bottom, particularly the gate periphery, at an appropriate stretch ratio. It has been found that a highly stretched orientation state can be achieved. As a result, it became possible to form a highly stretched orientation part in the gate remainder. On the other hand, if the temperature at the bottom center 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 orientation state. As a result, the entire remaining gate remains in a low stretch orientation state or an unstretched state.
[0086]
Specifically, the temperature of the remaining part of the gate of the molded body until reaching the bottom of the mold during blow molding and immediately before the bottom stretch molding is almost finished is within 40 ° C. of the heating temperature of the preform. It is preferable to be within 30 ° C.
[0087]
[One-stage stretch blow molding]
In FIG. 13 and FIG. 14 showing the manufacture of the container by one-stage blow molding, the preform 20 is supported by the core mold 31 and held in the closed molds 32 and 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 disposed. Stretching is performed by inserting a stretching rod 34 into the preform 20 and pushing up the preform bottom 23. The timing is measured in the middle of the stretch molding, and a high-pressure gas is blown into the molded body through the stretching rod 34 to perform blow molding to obtain a container having a shape along the mold.
[0088]
In the embodiment shown in FIGS. 13 and 14, a press bar 35 is disposed on the side of the bottom mold 33 coaxially with the stretching bar 34, and the gate portion 24 of the preform is stretched with the stretching bar 34 and the pressing bar 35 during tensile stretching. The position is regulated so as to be positioned at the center of the container bottom 5 where the gate portion 24 of the bottom of the preform is formed. That is, the press bar 35 sandwiches and restrains the preform gate portion 24 with the stretching rod 34 at the stage of drawing and stretching the preform, and further restrains the remaining bottom gate of the molded body at the stage of blow molding. The use of this press bar has the effect of preventing misalignment of the gate remainder.
[0089]
The temperature of the sandwiched portion at the preform bottom is within 40 ° C., more preferably within 30 ° C. until just before the stretching process is completed, so that the bottom 37 of the secondary molded product 36 is placed in the sandwiched portion. It can be highly stretched over the entire bottom including the bottom center.
[0090]
In the above blow molding, first, the shape and thickness distribution of the preform are determined in consideration of the draw ratio so that the portion to be the bottom center gate peripheral portion is sufficiently stretched and has an appropriate thickness. is important. At this time, the height of the gate portion at the center of the preform bottom is preferably in the range of 0.1 to 3 mm, particularly 0.3 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 draw 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 drawing rod or press rod. It is also effective to heat at least the tip of the press bar. If a press bar is not used, a heat insulating layer should be provided on the surface of the mold bottom center part where the remaining part of the molded body first comes into contact with the blow molding, or the bottom mold should be heated. Is effective.
[0091]
In 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, particularly 90 to 130 ° C. At that time, it is important that the difference in heating temperature between the bottom portion of the preform and the body portion is within 10 ° C. in order to bring the petaloid bottom portion into a highly stretched orientation state. In this case, if the heating temperature difference between the bottom portion and the body portion of the preform exceeds 10 ° C., only the higher temperature portion tends to be stretched too much, which is not preferable.
[0092]
By using the above-mentioned means and methods and further optimizing the blow molding conditions, a container having a highly stretched layer can be formed on the entire container including the mouth and neck part and the bottom center part excluding the vicinity thereof. .
[0093]
As shown in FIG. 15, the bottom center gate peripheral portion 11 of the molded container is in a highly stretched orientation state when the thickness is in the range of 0.35 to 1 mm and the degree of crystallinity accompanying orientation is 20% or more. Accordingly, a highly stretched alignment layer 12 is formed in the bottom center gate remainder 8. The highly stretched alignment layer 12 of the remaining gate portion 8 is usually located on the inner surface side, and forms a layer continuous with the gate connection portion 9 and the peripheral gate peripheral portion 11 around it. The thickness of the bottom center gate remaining portion 8 is usually in the range of 1 to 3.5 mm, although it depends on the height of the bottom center gate portion of the preform. The degree of 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 0 in the low stretch orientation portion near the outer surface. While the crystallinity is about ˜12%, the crystallinity is about 20-35% in the high stretch orientation portion near the inner surface. In addition, the yield load at 70 ° C. is usually about 25 to 35 kgf / cm at the center of the bottom valley including the bottom gate remainder 8 and can have preferable heat and pressure resistance.
[0094]
Heat resistant pressure strength can be further increased by heating and fixing the bottom center of the container. At that time, it is preferable that the low stretch orientation layer 13 of the remaining gate is whitened and thermally crystallized to such an extent that the crystallinity becomes 25% or more. The heat-resistant pressure strength is remarkably increased by heat fixing of the bottom of the container. On the other hand, although the low stretch orientation portion 13 of the remaining gate whitened becomes brittle, the high stretch orientation layer 12 maintains sufficient flexibility, so that the impact resistance indicated by the drop strength is maintained at a very high level. Yes. 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, so that the bottom of the molded product is heated and crystallized in the blow molding process. .
[0095]
By the above-described one-stage blow molding means, a heat-resistant container that is hot-filled with a high-temperature content of about 80 to 93 ° C. can be manufactured. In this case, blow molding is performed using a blow mold having a shape that conforms to a product shape including a cylindrical portion or a rectangular tube-shaped body portion and a bottom portion including an indented portion including the bottom center gate remaining portion. In this heat-resistant container, it is important to heat-fix the entire container, and the parts corresponding to the shoulder part, body part and bottom part of the mold are set to the crystallization temperature of the resin, so that the molded product is formed in the blow molding process. Each part of is heated and crystallized. Usually, the heating temperature of the blow mold is 120 ° C to 180 ° C. It is preferable that the degree of crystallinity of the bottom portion including the trunk portion and the gate remainder accompanying heat fixation is 25% or more. In this case, the bottom of the blow-molded molded product is in a highly stretched orientation state, and since the body and the wall are made thin except for the remaining gate, the time required for heat setting can be reduced to almost the same as the body. Further, thermal crystallization can be performed in a state of maintaining transparency except for the low-stretch orientation portion constituting the gate remainder.
[0096]
[Two-stage blow molding method]
As described above, the container of the present invention can be prepared by one biaxial stretch blow molding. However, when the bottom of a petaloid with a complicated shape is blow-molded into a highly stretched orientation at once, the tip of the foot tends to be whitened, especially when the tip of the foot is overstretched. It becomes quite narrow. In addition, the heat fixing of the bottom using a mold requires a relatively long time, resulting in a problem that the blow molding time becomes long.
[0097]
As a result of the study, a two-stage blow molding method in which a preform is made into an intermediate molded product by primary blow molding and the intermediate molded product is subjected to secondary blow molding to obtain a final product is suitable as a result of the study. I understood.
[0098]
In the two-stage blow molding method, in the primary blow molding, a secondary molded product is produced in which the bottom portion and a part of the body portion connected to the bottom portion are larger than the final container in the height direction or the circumferential direction from the final container, Next, at least the bottom part of the secondary molded product and the body part connected to the bottom are heated and shrunk to obtain a tertiary molded product having a size that can be accommodated in the secondary blow mold, and finally the tertiary molded product is subjected to secondary blow molding. Thus, the final container is preferable.
[0099]
By adopting the above two-stage blow molding method, the following effects are produced. First, by optimizing the shape of the bottom portion by primary blow molding, it becomes easy to make the bottom portion a preferable high stretch orientation state, in particular, to optimize the stretch ratio of the gate peripheral portion. As a result, the remaining gate at the bottom of the secondary molded product is thick with a highly stretched orientation layer, and the peripheral edge of the gate is in a highly stretched orientation, and is stable so as to maintain a desirable thickness. Can be blow molded. Secondly, by heat-shrinking the bottom part of the secondary molded product and a part of the body part connected to the bottom part, heat fixing of the center part of the bottom of the secondary molded product can be performed and the thermal crystallization can proceed. This heat setting step can be performed efficiently in a very short time. Thirdly, in the secondary blow molding, the bottom of the tertiary molded product in a high temperature state is stretch blow molded so that the foot can be easily molded without being overstretched, and the bottom excluding the foot, In particular, the bottom center portion has a small degree of stretching, and the degree of decrease in crystallinity due to blow molding is very small. Therefore, the container can have a foot portion having a preferable property and a high heat-resistant pressure strength in which orientation crystallization and thermal crystallization are sufficiently performed in the bottom center portion where the heat-resistant pressure strength is most required. .
[0100]
In the two-stage blow molding method, a preform 20 that has been preheated for partial thermal crystallization and stretching is biaxially stretched in a primary blow mold to form a bottom 37 having a size larger than that of the final container. And forming a secondary molded product 36 in which the portion other than the spherulized mouth and neck of the preform is stretched at a high stretch ratio (FIGS. 16 and 17); continuous to the bottom and bottom of the secondary molded product At least a part of the body part is heated to form a tertiary molded product 44 in which the bottom part and part of the body part are contracted (FIGS. 19 and 20); To form a final product 50 having a bottom portion made of a plurality of valleys and feet and thinned by high stretching (FIGS. 22 and 23).
[0101]
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 gate remainder, the bottom of the secondary blow molded secondary product including the gate remainder is relatively high. It is important to stretch and align.
[0102]
(1) Primary blow molding
The preform 20 used for the primary blow molding determines the shape and thickness distribution in consideration of the draw ratio of each part of the secondary molded product. At this time, the area corresponding to the peripheral edge of the gate of the final container extending around the bottom center gate remainder 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 profile of the bottom of the preform so that it is stretched.
[0103]
In the primary blow molding, the preform 20 is heated to the stretching temperature. The preform stretching temperature is generally 85 to 135 ° C, particularly 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., which makes it possible to increase both the bottom portion and the body portion.
[0104]
When the heating temperature of the preform body is higher than the heating temperature of the bottom by more than 10 ° C., the stretching of the bottom portion having a relatively low temperature is insufficient. Moreover, when the heating temperature of the bottom part is higher than the heating temperature of the body part by more than 10 ° C., it is not preferable because the bottom part is excessively stretched locally.
[0105]
In blow molding, the preform 20 heated to the stretching temperature can be stretched by lifting the stretching rod 34 while sandwiching the gate 24 at the bottom of the preform between the stretching rod 34 and the press rod 35. preferable. In the process of stretching, high pressure gas is fed into the preform and blow molding is performed to form the secondary molded product 36a (FIGS. 16 and 17). At that time, stretching determined by the stretching speed of pushing the preform bottom with a stretching rod, the timing of blowing high-pressure air into the molded body, and the flow rate of high-pressure air so that a highly stretched orientation layer can be formed on the entire bottom of the secondary molded product. It is important to optimize the blow molding conditions such as the blow speed.
[0106]
In addition, the inventors attached a thermocouple to the tip of the press rod and measured the temperature change of the bottom center gate at the time of blow molding. As a result, the temperature of about 5 to 15 ° C. was reached after the press rod reached top dead center. An increase was found. This is presumed that the relatively large stretching of the gate remainder and the vicinity thereof is performed after the bottom center reaches the mold, and the temperature rises due to heat generated during the stretching. At that time, when the press rod reaches the top dead center, the temperature rise from the initial heating temperature of the remaining gate part of the molded body facing the tip of the press rod is reduced, so that the temperature rise accompanying the subsequent stretching That is, it has been found that the degree of stretching in the gate remainder and the vicinity thereof can be increased. Specifically, the temperature at the center of the preform bottom before the end of the stretching process is within 40 ° C., more preferably within 30 ° C., so that the bottom center gate remainder of the secondary molded product and It was found that the peripheral edge can be in a highly stretched orientation state.
[0107]
As a means for lowering the temperature drop at the center of the preform bottom during blow molding, it is effective to prevent excessive heat conduction from the stretching bar 34 and the press bar 35. Specifically, it is preferable to use at least the tip of the drawing rod or the press rod as a heat-resistant plastic material or ceramic material having heat insulation performance. In addition, a means for heating the press bar or the stretching bar and controlling the temperature to a relatively high temperature is also effective. The heating of the press bar and the stretching rod is usually preferably 50 ° C. to 130 ° C. corresponding to the stretching temperature of the preform. As the heating method, an electric heater, an electric heating method by high-frequency induction heating, a fluid heating method by circulating a high-temperature liquid, a heat conduction method such as a heat pipe, or the like can be adopted.
[0108]
In order to promote high stretching at the bottom of the secondary molded product, a bottom shape is adopted in which the bottom center is flat and the bottom center and the body are connected by an annular curved surface having a relatively small radius of curvature. It is effective. It is also effective to provide a recess 38 on the inner surface side at the center of the bottom (FIGS. 17 and 24). The recess 39 at the bottom center of the blow bottom mold 33 has the effect of delaying the timing of the molded product reaching the mold surface at the peripheral edge from the bottom center during blow molding. Can be increased.
[0109]
The bottom portion 37 of the obtained secondary molded product 36a is oriented and crystallized in a relatively high stretched state to a crystallinity of 20% or more, more preferably 25% or more, except for the bottom gate remaining portion 8 and the gate connection portion 9. In addition, it is preferable that the thickness is reduced to 1 mm or less, particularly 0.8 mm or less (FIG. 18). Usually, the bottom gate remainder 8 is composed of a high stretch orientation layer 12 located on the inner surface side and a low stretch orientation layer 13 located on the outer surface side. In the highly stretched alignment layer 12 of the remaining gate, the maximum value of crystallinity is preferably 20% or more, particularly 25% or more. In addition, the gate diameter Dg Is the body diameter D₀0.25 times or less, especially 0.2 times or less. Further, the gate connection portion 9 in contact with the gate remaining portion 8 has a crystallinity of 20% or more, more preferably 25% or more, which is oriented and crystallized in a relatively high stretched state, and 1.3 mm or less, more preferably 1 It is preferably thinned to a plate thickness of 1 mm or less (FIG. 18).
[0110]
In FIG. 24 showing the shape of the bottom mold 33 used for the primary blow molding, the height H of the recess 39 in the bottom mold is shown.₁Is generally 1-8mm, diameter D_FourIs preferably in the range of 0.15 to 0.6 times the body diameter connected to the bottom of the secondary molded product in order to effectively perform high-stretch orientation at the center of the bottom.
[0111]
In FIG. 25 showing an example of a bottom mold particularly suitable for the object of the present invention, the bottom mold 33 is formed by an outer peripheral convex portion 41 and a peripheral concave portion 42 that are continuous with the bottom peripheral curvature portion 40 from the outer periphery toward the center. The inner circumferential convex portion 43 and the central concave portion 44, and the circumferential concave portion 41 has a shape protruding inward from the central concave portion 44.
[0112]
In the primary blow molding using this primary blow bottom mold, when the bottom center portion of the stretch blow molded molded article reaches the bottom center recess 44, rapid stretching of the bottom center portion is started. At a considerably early stage, a part of the molded body comes into contact with the circumferential recess 42 protruding inward, and the contact portion is cooled. In the next blowing step, stretch blow molding is performed on the bottom center portion and the bottom peripheral curvature portion that have not yet contacted the bottom mold. At this time, since stretch blow molding of the bottom center portion and the bottom peripheral portion is performed with the cooled circumferential recess 42 interposed therebetween, the two portions are stretch blow molded separately. In particular, since large stretching is performed inside the circumferential recess 42 at the bottom center portion, the degree of stretching of the gate remainder increases, the size of the low stretching orientation portion decreases, and the inside of the circumferential recess 42 increases. The wall thickness is more averaged.
[0113]
In order to enable high stretching at the bottom center including the gate remainder, the diameter D of the circumferential recess 41_FiveIs in the range of 0.5 to 0.9 times the body diameter connected to the bottom of the secondary molded product, and the step H between the circumferential recess 41 and the central recess 44 is₂Is in the range of 1 to 10 mm, and the step H between the circumferential concave portion 44 and the outer circumferential side convex portion 40 is_ThreeIs preferably in the range of 0 to 5 mm.
[0114]
(2) Heat shrinkage process
In the present invention, in the subsequent heat-shrinking step, the bottom part of the secondary molded product and a part of the body part connected to the bottom part are heated and shrunk in the height direction and the radial direction, and the secondary blow mold which is the final product shape It becomes a tertiary molded product having a shape that fits in the above.
[0115]
The heat shrinkage of the bottom of the secondary molded product is preferably non-contact heating and heat shrinkage without restriction. In the example shown in FIG. 19 and FIG. 20, infrared radiators 45 and 46 are provided along the path along which the secondary molded product 36 a moves, facing the bottom and part of the barrel of the secondary molded product, The secondary molded product 36b is supported by the core mold 31 in the space surrounded by the infrared radiator, and is rotated in the axial direction and moved while being heated, so that the bottom portion and the barrel portion of the secondary molded product are moved. A part is heated and shrunk as shown in FIG. 20 to form a tertiary molded product 36b. In order to prevent the shrinkage of the body part other than necessary, it is recommended to provide the heat shielding plate 47.
[0116]
The infrared radiators 45 and 46 may be heated to about 400 to 1000 ° C. and relatively excellent in radiation efficiency. Thereby, infrared rays having a relatively high energy density can be irradiated to a predetermined portion of the secondary molded product 36a, and for example, the predetermined temperature can be set in a short time of about 10 seconds or less.
[0117]
The shape of the bottom 48 of the tertiary molded product 36b is preferably as close as possible to the bottom valley of the secondary blow mold, thereby facilitating the molding of the foot of the final product (FIGS. 20 and 20). 22).
[0118]
In order to make the bottom shape of the tertiary molded product 36b preferable, the bottom shape of the secondary molded product 36b is important, and it is necessary to increase the height of the secondary molded product to be subjected to heat shrinkage in anticipation of heat shrinkage. preferable. Further, since the bottom center gate remaining portion 8 of the secondary molded product 36b is thick when the bottom is heated, the temperature rise is slower than that of the surrounding thin portion. Therefore, if the bottom shape of the secondary molded product is, for example, a hemispherical shape, the thin portion around the gate remaining portion is first thermally contracted into a conical shape, and the thick gate remaining portion 8 protrudes to the outer surface side. In such a shape where the center is upwardly convex, it is far 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 provided in the center of the bottom, as shown in FIG. In addition, it is possible to obtain a tertiary molded product 36b that has a slightly concave shape at the center of the bottom but has a substantially flat bottom surface 37 and a shoulder 48 close to the valley of the secondary blow mold.
[0119]
It is preferable that the heating temperature of the bottom part of the secondary molded product that has been highly stretched and the part of the body part connected to the bottom is 130-200 ° C. Progresses. At this time, the low stretch orientation layer of the remaining gate portion is whitened at the bottom of the tertiary molded product, but the high stretch orientation layer of the remaining gate portion and the peripheral edge portion of the gate around the gate stretch portion are not whitened, and substantially remain transparent. .
[0120]
(3) Secondary blow molding
The heated tertiary molded product 36b is introduced into a secondary blow mold and subjected to secondary blow molding to obtain a final product (FIGS. 22 and 23).
[0121]
In FIG. 22 showing the details of the secondary blow molding process, the neck of the tertiary molded product 36 b is 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. Fluid is blown into the tertiary molded product 36b, and the tertiary molded product is subjected to secondary blow molding to form the bottom shape of the final container 36c having a predetermined valley and foot. The molded container 50 is taken out from the opened secondary blow mold 51 by a known take-out mechanism (not shown).
[0122]
Further, since the elastic modulus of the tertiary molded product is increased by crystallization by heat treatment, it is preferable to use a high fluid pressure, and generally 15 to 45 kg / cm.²It is preferable to use a pressure of
[0123]
During secondary blow molding, the mold temperature may be maintained at a temperature of 5 to 135 ° C., and cooling may be performed immediately after molding, or cooling may be performed by flowing cool air or the like through the final molded product. May be performed.
[0124]
The bottom of the final product thus obtained is composed of a heat-stretched highly stretched orientation layer with high heat pressure strength and high impact strength strength, including the remainder of the gate. Excellent. (Fig. 2, Fig. 3)
At this time, the thickness of the remaining bottom center gate of the container, the gate connection portion, and the peripheral edge of the gate becomes thicker than the thickness of the secondary molded product formed by primary blow molding by the amount of heat shrinkage at the time of heat fixation. In the secondary blow molding, the central portion of the bottom is hardly stretched, so that it is somewhat thick.
[0125]
The remaining gate 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-stage blow molding method, the structure of the remaining gate portion at the bottom of the container is determined by the structure composed of the high stretch orientation layer and the low stretch orientation portion of the remaining gate portion of the secondary molded product formed by primary blow molding. The structure of the bottom gate remaining part of the secondary blow-molded product is the bottom shape of the secondary molded product determined by the bottom shape of the primary blow-molding mold, the stretched state of the bottom of the secondary molded product derived from the primary blow molding conditions, and It is influenced by the wall thickness distribution, the size of the gate portion of the preform and the thermal history of the gate portion derived from the injection conditions of the preform.
[0126]
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, the bottom gate of a typical container of the present invention molded under the preferable molding conditions of the present invention described above. As shown in FIG. 2, the remaining portion is composed of a whitened low stretch orientation portion 13 on the outer surface side and a transparent high stretch orientation layer 12 on the inner surface side. The highly stretched alignment layer 12 of the gate remaining portion 8 is connected to the gate connection portion 9 in the highly stretched alignment state and the gate peripheral edge portion 11 outside the gate connection portion 9.
[0127]
Similarly, when the primary blow bottom mold shown in FIG. 24 is used, the heating temperature of the inner surface of the bottom of the preform is slightly lowered by adjusting the degree of heating of the preform when performing the primary blow molding. Under the above conditions, the remaining gate at the bottom of the obtained secondary molded product can have a structure in which the high stretch orientation layer located in the center is sandwiched between the low stretch orientation portions on the inner surface side and the outer surface side. At this time, the bottom gate remaining part of the container finally obtained through the intermediate heat setting step is whitened on the outer surface side and the low-stretched alignment layer 13 which is whitened on the inner surface side of the transparent high-stretched alignment layer 12 as shown in FIG. The structure is sandwiched between the low-stretch orientation layer 13. The heating of the preform in the primary blowing step is usually performed mainly by infrared rays irradiated from an infrared radiator provided on the outer surface side of the preform and a rod-shaped infrared radiator inserted in the preform. However, the heating temperature on the inner surface side of the preform bottom can be lowered by increasing the distance between the rod-shaped infrared radiator inserted into the preform and the preform bottom.
[0128]
The container having the bottom gate remainder 8 shown in FIG. 5 can also be manufactured using the primary blow bottom mold shown in FIG. In this case, although the reason why the transparent high stretch orientation portion 12b is formed at the inner surface side center of the gate remaining portion 8 at the bottom of the container is not clear, it is presumed as follows. That is, normally, in the gate portion of the preform, due to the thermal history during injection molding, the outer peripheral portion of the gate portion tends to have a higher degree of thermal crystallization in a ring shape than the inner portion of the gate portion. In particular, when primary blow molding is performed using a preform having a relatively large degree of thermal crystallization of the ring-shaped gate outer peripheral portion, the ring-shaped outer peripheral portion of the gate portion of the preform is stretched more than its inner portion. It is difficult. At the time of blow molding, the bottom gate remainder of the obtained molded product is in a highly stretched state especially on the inner surface side with a high stretch ratio, and the outer surface side of the gate remainder corresponding to the gate portion of the preform is stretched accordingly. The outer periphery of the ring-shaped gate, which is difficult to be deformed, remains in a relatively low stretched state while being deformed, while the inner portion of the gate that is easily stretched is stretched locally by being pulled by the outer periphery of the ring-shaped gate and is highly stretched. It becomes a shape. As a result, a gate having a ring-shaped low-stretch orientation portion 13b and a high-stretch orientation portion 12b inside the ring-shaped low stretch orientation portion 12b on the outer surface side of the remaining gate as shown in FIG. It is considered that the remaining part 8 is formed.
[0129]
On the other hand, when a primary blow bottom mold provided with 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 is relatively stretched including the remaining gate as described above. Thus, the size of the low stretch orientation portion formed in the remaining gate portion can be made relatively small. As a result, a container having a gate remaining portion 8 composed of a relatively thick high-stretch orientation layer 12 and a low-stretch orientation portion 13 formed thin at a limited portion on the outer surface side as shown in FIG. 4 can be obtained.
[0130]
【The invention's effect】
[0130]
【The invention's effect】
In the container of the present invention, the bottom center gate remainder is composed of a transparent high-stretch orientation layer on the inner surface side of the container and a whitened low-stretch low-orientation layer on the outer surface side of the container. Since the layer is formed thin and the high stretch orientation layer at the bottom center gate is connected to the gate connection portion and the high stretch orientation bottom in the radially outward direction, the entire bottom is impact resistant and creep resistant. It has a strong structure, is useful for applications in which the contents are hot-filled, and has the advantage of being excellent in the self-supporting properties and appearance characteristics of the container.
In addition, by means of reducing the temperature drop in the center of the bottom and its vicinity when the center of the bottom including the gate reaches the bottom of the mold to a certain level or less, the bottom includes the gate and the high stretch orientation. Layered into a state, trimming (finishing) operation of the gate part of the preform and operation of thermally crystallizing the center of the bottom part prior to stretching blow are unnecessary, with a relatively small number of processes and high productivity, Moreover, it is manufactured using resources effectively.
[Brief description of the drawings]
FIG. 1 is a partially sectional side view showing an example of a container of 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 in the remaining portion of the bottom center gate of the container.
FIG. 3 is a partially enlarged cross-sectional view showing another example of the arrangement of the transparent highly stretched alignment layer in the remaining portion of the bottom center gate of the container.
FIG. 4 is a partially enlarged cross-sectional view showing an example of the arrangement of a transparent high-stretch alignment layer in the remaining portion of the bottom center gate of the container.
FIG. 5 is a partially enlarged cross-sectional view showing another example of the arrangement of the transparent highly stretched alignment layer in the remaining portion of the bottom center gate of the container.
FIG. 6 is an explanatory view showing dimensions of a standard test piece for measurement of 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 the shape and dimensions of the bottom valley portion of the container.
FIG. 9 is an explanatory diagram for explaining another example of the shape and dimensions of the bottom valley portion of the container.
FIG. 10 is an explanatory diagram for explaining a foot opening angle θ of a container.
FIG. 11 is a side view showing an example of a preform.
FIG. 12 is an explanatory diagram showing the shape and dimensions of a gate portion of a preform.
FIG. 13 is a cross-sectional view showing a state before the start of blow molding in an example of container production by a one-stage 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 a one-stage blow molding method.
FIG. 15 is an enlarged cross-sectional view showing the structure of a container bottom formed by a one-stage blow molding method.
FIG. 16 is a cross-sectional view showing an initial stage of a primary blow molding process in a two-stage blow molding method.
FIG. 17 is a cross-sectional view showing the last 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 of a secondary molded product formed by primary blow molding in a two-stage blow molding method.
FIG. 19 is a cross-sectional view showing an initial stage of an intermediate heating step for obtaining a tertiary molded product in the two-stage blow molding method.
FIG. 20 is a cross-sectional view showing the last stage of an 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 a two-stage blow molding method.
FIG. 23 is a side view showing a final product in a 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 in a two-stage blow molding method.
FIG. 25 is a cross-sectional view showing another example of the structure of a blow mold used for primary blow molding in the two-stage blow molding method.
[Explanation of symbols]
1 mouth and neck
2 shoulder
3 trunk
4 Bottom
5 bottom central valley
6 Tanibe
7 feet
8 Gate remainder
9 Gate connection
10 Root
11 Gate periphery
12 High stretch orientation layer
13 Low stretch low orientation layer
15 Standard specimen
20 preform
21 neck,
22 trunk 22
23 Blocking bottom
33 Blow bottom mold
34 Stretching rod
35 Press bar
36a Secondary molded product
36b Secondary molded product
37 Bottom
38 Concave to inner surface
39 Recess in the bottom center
40 Bottom peripheral curvature
41 Outer peripheral convex
42 Circumferential recess
43 Inner circumference convex
44 Center recess
45 Infrared emitters 45 and 46
47 Heat shield
48 Bottom type

Claims (7)

In a self-supporting container having a neck, shoulder, body, and bottom formed by biaxial stretch blow molding of resin, the bottom center gate remaining portion is formed of a transparent highly stretched orientation layer on the container inner surface side and a container outer surface side A low-stretched alignment layer that is whitened, the high-stretched alignment layer is thick, the low-stretched alignment layer is thinly formed in a limited portion on the outer surface side , and the high-stretched alignment layer remaining at the bottom center is the gate connection portion and A heat-resistant stretched resin container having a highly stretched alignment layer connected to a bottom of a highly stretched orientation in the radially outward direction. The heat-resistant stretched resin container according to claim 1, wherein the bottom portion is formed of a plurality of valley portions and foot portions alternately arranged around the bottom central valley portion and the bottom central valley portion, and the container has self-supporting properties. The heat-resistant stretched resin container according to claim 1 or 2, wherein the crystallized degree of the highly stretched orientation layer is oriented and crystallized so as to be 20% or more. The heat-resistant stretched resin container according to any one of claims 1 to 3, wherein the bottom center gate remainder is heat-fixed and the highly stretched orientation layer has a crystallinity of 25 to 55%. The heat-resistant stretched resin container according to any one of claims 1 to 4, wherein the highly stretched orientation layer has a thickness of 0.35 mm or more. Heat-resistant stretched resin container according to any one of claims 1 to 5 bottom central gate balance has a 0.25 times the diameter Dg of the barrel diameter D _0. The heat-resistant stretched resin container according to any one of claims 1 to 6, wherein the bottom center gate remainder has a yield load of 25 kgf / cm or more at a temperature of 70 ° C.

Images