JPH05193636A - Preformed molding of resin with hollow wall and method for its manufacture and container produced therefrom by biaxially stretching blow molding - Google Patents

Abstract

PURPOSE:To improve the heat-insulation property and the gas-barrier property by forming a molding in which an alternation of hollow wall parts and solid wall parts, both hollow and solid wall parts being axially extended and the solid wall parts being less thick than the hollow wall parts, constitutes the wall of a barrel and the inner layer and the outer layer having a layer of hollow therebetween constitute the bottom. CONSTITUTION:A preformed molding 1 has a mouth 2, a barrel 3, and a bottom 4: the mouth 2 consists of a solid wall; the barrel 3 consists of an alternation of hollow wall parts 34 and solid wall parts 35, each hollow wall part 34 consisting of an inner layer 32 and an outer layer 33 having a layer of hollow 31 therebetween and each solid wall part 35 being less thick than the hollow wall part 34 and both the hollow and solid wall parts being axially extended. At the bottom 4, the inner layer 32 has a central part 41 at which a stretching rod pushes in biaxially stretching blow molding and the outer layer 33 has a gate 42 having a hole 43 of small diameter which goes into the layers of hollow 31. It is desirable that the hollow wall parts 34 constitute the barrel in a proportion of 50 to 90% with the whole area of the barrel as 100%. Each of the solid wall parts 35 forms a hollow on the inner side and therefore its wall thickness is less than that of the hollow wall part 34.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer plastic preform and a method for producing the preform, and more particularly to a resin preform having hollow walls in a body and a bottom and a method for producing the preform. The present invention also relates to a biaxially stretch blow molded container using such a multilayer plastic preform, and more particularly to a biaxially stretch blow molded container having excellent heat insulation and gas barrier properties.

[0002]

BACKGROUND OF THE INVENTION Resin containers (bottles) for enclosing carbonated drinks, fruit juices, etc. are manufactured by injection molding saturated polyester resins and then stretch blow molding. It is common.

When hot-filling the above-mentioned beverage or the like in such a container, the pressure inside the container may decrease after sealing. Due to this decrease in pressure, the container is deformed, the external shape becomes unsightly, and the deformation resistance against external force decreases.

Therefore, various measures have been taken against the deformation due to the decompression after the container is closed, but the conventional technique is to form a deformable portion in the container and deform the portion. Is the way. However, such a method has a problem in that when the amount of reduced pressure exceeds the volume of the deformable portion, the reduced pressure cannot be completely absorbed.

In addition to the above-mentioned problem of deformation under reduced pressure, since containers such as beverage bottles are formed of solid-layered walls, they have poor heat insulating properties, and there is a problem that the heat retaining properties of the contents are not sufficient.

Further, when juice, beer or the like is enclosed, there is a problem that the properties of the contents are changed due to the influence of oxygen invading from the outside of the container.

Therefore, the present inventors have proposed a biaxially stretch blow-molded container in which the container wall (body and bottom) is a hollow wall and the container main body has a double structure (Japanese Patent Application No. 2). -13
No. 4785, Japanese Patent Application No. 2-134786, Japanese Patent Application No. 2-135574). In this container, the container wall is doubled, and since the reduced pressure deformation after hot filling can be received only by the inner container wall, the outer container wall is not deformed. Further, since the container wall has a hollow portion, the container wall exhibits a good heat insulating property, so that a good heat insulating container can be obtained. Furthermore, if an oxygen scavenger is added to the hollow part of the container wall to seal the hollow part, external oxygen cannot permeate the container wall,
It can also be an oxygen barrier container. However, although the above-mentioned container exerts various effects as described above, as a result of subsequent research, it has been found that the strength of the container is not always sufficient.

Accordingly, it is an object of the present invention to provide a preform which provides a biaxially stretch blow molded container having excellent heat insulation and gas barrier properties, and a method for producing the same.

Another object of the present invention is to provide a biaxially stretched blow molded container which is excellent in heat insulation and gas barrier properties by the above-mentioned preform.

[0010]

As a result of earnest research in view of the above object, the present inventors have made various studies on a container having a hollow wall, and as a result, even if the hollow wall does not exist over the entire body of the container. If there is a hollow wall in about 50% or more of the area of the body, good heat insulation and gas barrier properties can be maintained, and a hollow wall and a solid wall have a structure that alternately extends in the axial direction. It has been found that the strength of the container hardly decreases when the body is used. Further, the present inventors, in order to produce a container having such a hollow wall portion and a solid wall portion having a body portion alternately extending in the axial direction, the solid mouth portion and the hollow layer 3, the hollow wall part consisting of the inner layer and the outer layer, and the body part having a structure in which the solid wall part which is thinner than the hollow wall part alternately extends in the axial direction, and the hollow layer It has been found that it is sufficient to blow-mold a preform composed of an inner layer and a bottom composed of an outer layer. Furthermore, the inventors of the present invention use an injection molding die having a cavity in which the solid wall portion has a thinner layer than the hollow wall portion, and the resin and gas are co-injection-molded to form a solid wall portion cavity. The gas is diverted at the narrowed portion, and hollow wall portions and solid wall portions that are thinner than the hollow wall portions are formed alternately in the axial direction to manufacture the above preform. I have found that I can.
The present invention has been made based on the above findings.

That is, the preform of the present invention made of a resin having a cylindrical shape with a bottom has a solid mouth portion, a hollow wall portion having an inner layer and an outer layer sandwiching a hollow layer, and the hollow wall. A solid wall portion that is thinner than the portion, and a body portion that alternately extends in the axial direction, and a bottom portion that includes an inner layer and an outer layer sandwiching the hollow layer. It is characterized in that it has a small-diameter opening-shaped gate portion at the lower end of the outer layer.

Further, the method of the present invention for producing the above-mentioned preformed body includes (a) a cavity having a ridge corresponding to the solid wall portion of the above-mentioned preformed body and corresponding to the bottom of the above preformed body. Inject the molding resin into the injection mold having the gate at the position to fill the resin up to the middle of the cavity, and (b) Next, inject a small amount of the resin without stopping the injection, or stop the injection. Then, a gas is blown so that a hollow layer is formed in the body portion, the resin and the gas are co-injected, and the gas is diverted at the ridge portion of the cavity, so that the axial direction is increased. It is characterized by forming a plurality of hollow wall portions and a plurality of solid wall portions.

Further, the biaxially stretch blow molded container of the present invention obtained by biaxially stretch blow molding the above preform has a solid mouth and an inner layer and an outer layer sandwiching a hollow layer. A plurality of hollow wall portions consisting of, and a plurality of solid wall portions each axially alternately extending the body portion, consisting of a hollow layer sandwiching the inner layer and the outer layer bottom, It is characterized in that it has a small-diameter opening-shaped gate portion at the lower end of the outer layer of the bottom portion.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a vertical cross-sectional view showing an example of the preform of the present invention. The preform 1, which is a so-called parison, has an inner layer sandwiching a solid mouth 2 and a hollow layer 31.
A hollow wall portion 34 composed of 32 and an outer layer 33, and a solid wall portion 35 having a thinner layer than the hollow wall portion alternately in the axial direction, and a body portion 3 and a bottom portion 4. Further, the inner layer 32 of the bottom portion 4 has a central portion 41 which is a portion pressed by a stretch rod during biaxial stretch blow molding, and the outer layer 33 of the bottom portion 4 has a gate portion 42, and the gate portion 42 is Hollow layer
It has a small-diameter hole portion 43 leading to 31.

FIG. 2 is a cross-sectional view of the body of the preform shown in FIG. Five hollow wall portions 34 and five solid wall portions 35 are alternately arranged in the body portion 3, and the ratio of the hollow wall portions 34 is 50 to 90% with the total area of the body portion being 100%.
Is preferred. If the hollow wall is less than 50%,
Gas barrier, heat insulation, etc. are not sufficiently effective, while 90%
When it exceeds, the strength of the container decreases.

The number of hollow walls is 5 as in this embodiment.
There is no need for the number of pieces, and for example, in the case of a parison having a wall thickness of 5 mm, it may be set appropriately within the range of 3 to 8. When the number of hollow walls is less than 3, the strength of the container is liable to be lowered, while when the number of hollow walls is more than 8, the ratio of the hollow walls is small, and it is difficult to form more than 50%. Further, the hollow wall portion does not have to be provided over the entire region of the body portion in the axial direction, and the upper portion or the lower portion of the body portion may be unevenly distributed. Further, it is not necessary to provide them at equal intervals, and the positions may be set appropriately according to the form of the container.

Further, the thickness of the solid wall portion 35 is made thinner than the thickness of the hollow wall portion 34 by making the inside concave. This is to provide the hollow wall portions alternately in the axial direction as described later, and to provide the hollow wall portions accurately,
It is preferable that the thickness of the solid wall portion is 30 to 70% of the thickness of the hollow wall portion. It should be noted that the thinning is not required to have a concave inside as in the present embodiment,
The outside may be concave as shown in FIG. 3, or both the outside and the inside may be concave as shown in FIG.

Next, the method of the present invention for producing such a preform will be described. First, in the method of the present invention, an injection having a cavity having ridges corresponding to the thin layer state of the solid wall of the preform and having a gate at a position corresponding to the bottom of the preform Use a mold.

The cavity having the ridges corresponding to the thin layer state of the solid wall of the preform is, for example, when the inner side of the solid wall of the preform is concave as in this embodiment. As shown in FIG. 5, a core die 5 having a ridge 51 at a position corresponding to a solid wall portion, and a barrel die (not shown) having a gate at a position corresponding to a bottom portion of a preformed body are cylindrical. ) And an injection mold consisting of

Using the injection molding die as described above, the resin is press-fitted from the gate, filled with the resin halfway into the cavity, and when reaching a predetermined position, the injection of the resin is stopped without stopping a small amount. The resin is co-injected with the gas by flowing in or stopping and blowing gas so that a hollow layer is formed in the body.

At that time, when the gas reaches the start position of the convex portion 51 of the core mold 5, the cavity is narrow at the portion having the convex portion, so that the cavity is substantially blocked by the resin, For this reason, the gas is split and a plurality of hollow wall portions are formed in the axial direction along the thick portion of the cavity. More specifically, the flow resistance of the thinned layer becomes larger than that of the thick layer due to the shape and the progress of cooling of the resin, so that the molten resin selectively flows in the thick layer. Similarly, the gas to be filled will flow into the bed with a small inflow resistance. In order to surely divide the gas in this way, as described above, the thickness of the solid wall portion is 30% of the thickness of the hollow wall portion.
It is preferable to set the size of the ridges 51 so that it is 70%.

The gas co-injection molding is a GIP molding method.
(Gas Injection Process, Mannesmann Demag), AM
P. Molding method (Air Mold Process, Battenfeld Co.), or the method of molding a hollow mold as described in JP-B-57-14968.

In this manner, the solid mouth portion, the hollow wall portion including the inner layer and the outer layer sandwiching the hollow layer, and the solid wall portion are alternately extended in the axial direction. If a preformed body composed of a body portion having a hollow layer and a bottom portion including an inner layer and an outer layer sandwiching a hollow layer is formed, a gate portion having a small diameter opening is formed at the lower end of the outer layer of the bottom portion. At the same time, the solid wall portion becomes thinner than the hollow wall portion.

As shown in FIG. 3, in the case of manufacturing a preformed body having a concave outer side of the solid wall portion, a linear convex portion is provided at a location corresponding to the solid wall portion of the body type. In addition, as shown in FIG. 4, in the case of producing a preformed body in which both the outside and the inside of the solid wall portion are concave, linear protrusions are provided on both the core mold and the body mold. Just do it.

The preformed body thus obtained is biaxially stretch blow molded by a conventional method to obtain the biaxially stretch blow molded container of the present invention having a hollow wall.

FIG. 6 is a longitudinal sectional view showing an example of the container of the present invention obtained by performing biaxial stretch blow molding.

The biaxially stretch blow-molded container 6 of the present invention comprises a solid mouth portion 61, a plurality of hollow wall portions 62 having an inner layer 62b and an outer layer 62c with a hollow layer 62a interposed therebetween, and a plurality of hollow wall portions 62. Solid wall
A hollow body 64, and a body portion 64 that alternately has 63 and an axial direction, respectively.
It has a bottom portion 66 having a hollow wall 62 consisting of an inner layer 62b and an outer layer 62c, sandwiching 62a. Further, a gate portion 66a is provided on the outer layer of the bottom portion 66, and the gate portion 66a has a small diameter hole portion 66b communicating with the hollow layer 62a from the outside of the container.

FIG. 7 is a cross-sectional view of the body of the container shown in FIG. The hollow wall portions 62 and the solid wall portions 63 are alternately arranged in the body portion, and the ratio of the hollow wall portions 62 is almost the same as the ratio in the above-mentioned preformed body, and the total area of the body portion is 100% is preferably 50 to 90%. When the hollow wall portion is less than 50%, the effects such as gas barrier property and heat insulating property are not sufficient, while when it exceeds 90%, the strength of the container decreases. The thickness of the solid wall portion 63 will be thinner than the thickness of the hollow wall portion 62 when a preformed body having a concave shape as shown in FIG. 2 is used. However, the stretching virtually eliminates the difference.

When a preform having a concave portion on the outer side of the solid layer is used as shown in FIGS. 3 and 4, if the body of the biaxially stretched blow mold has a smooth surface. The recess is eliminated. The stretching ratio of the hollow wall portion and the solid wall portion can be changed depending on the heating method of the parison. When heated to almost the same temperature, the draw ratio will differ due to the difference in wall thickness.

With the container having such a structure, even if the inner layer 62b is deformed by the reduced pressure absorption when the contents such as a beverage are enclosed, the volume change of the hollow layer 62a due to the deformation is caused by the change of the gate portion 66a. It is absorbed by the air that can freely move in and out through the small-diameter hole portion 66b. Therefore, the biaxially stretched blow molded container can absorb the reduced pressure without deforming the outer layer 66c.

Further, since the hollow layer 62a between the inner layer 62b and the outer layer 62c acts as a heat insulating layer, the biaxially stretched blow molded container is excellent in heat retention and heat insulation. Further, the small-diameter hole portion 66b of the gate portion 66a can be closed by heat sealing or an adhesive agent. Thus the gate part
Since the air in the hollow layer 62a does not flow in and out through the small-diameter hole portion 66b by closing the 66a, it is possible to obtain a biaxially stretch blow-molded container having further excellent heat retention.

Furthermore, a biaxially stretched blow molded container having an excellent oxygen barrier property can be obtained by injecting an oxygen scavenger into the hollow layer 62a and closing the gate portion 66a.

The resin forming the biaxially stretch blow molded container of the present invention as described above is not particularly limited as long as it can be biaxially stretch blow molded, and polypropylene,
Polystyrene, polycarbonate, nylon, polyacrylonitrile, polyester, polyarylate, etc. can be used. Among these, polyester resin is preferable. As the polyester resin, a thermoplastic resin composed of saturated dicarboxylic acid and saturated dihydric alcohol can be used. As the saturated dicarboxylic acid, terephthalic acid,
Aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, naphthalene-1,4- or 2,6-dicarboxylic acid, diphenylether-4,4'-dicarboxylic acid, diphenyldicarboxylic acids, diphenoxyethanediethanedicarboxylic acids, adipic acid , Sebacic acid, azelaic acid, decane-1,10-dicarboxylic acid and other aliphatic dicarboxylic acids, and cyclohexanedicarboxylic acid and other alicyclic dicarboxylic acids can be used. As the saturated dihydric alcohol, aliphatic glycols such as ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, hexamethylene glycol, dodecamethylene glycol and neopentyl glycol are used. Glycols, alicyclic glycols such as cyclohexanedimethanol, 2,2-bis (4'-β-hydroxyethoxyphenyl) propane, other aromatic diols and the like can be used. A preferred polyester is polyethylene terephthalate consisting of terephthalic acid and ethylene glycol.

Polyester resin has an intrinsic viscosity of 0.5 to 1.5.
, Preferably having a value in the range 0.55 to 0.8. In addition, such polyester is produced by melt polymerization,
Those that have been subjected to reduced pressure treatment or heat treatment in an inert gas atmosphere at a temperature of 250 ° C., or those that have reduced the content of oligomers and acetaldehyde which are low molecular weight polymers by solid-phase polymerization are suitable.

In the polyester resin, additives such as stabilizers, pigments, antioxidants, heat deterioration preventing agents, UV deterioration preventing agents, antistatic agents, antibacterial agents, etc. may be added to the polyester resin within the range not impairing the object of the present invention. An appropriate amount of resin can be added.

Although the present invention has been described in detail with reference to the drawings, the present invention is not limited to this. For example, the number of hollow walls does not have to be five as in the present embodiment, and a bottle is required. The shape and the like can be appropriately changed without departing from the concept of the present invention. In addition, not only the method of inserting an oxygen scavenger into the hollow layer and sealing it, but also various substances can be sealed according to the characteristics required for the biaxially stretch blow molded container. For example, in order to further improve the heat insulating property, a resin or the like having a high heat insulating effect can be enclosed instead of air. Further, water, carbon dioxide gas, oxygen, gas barrier substance, coloring substance and the like can be enclosed.

[0037]

As described above in detail, the resin preform having a hollow wall according to the present invention has a solid mouth portion and a hollow wall portion composed of an inner layer and an outer layer sandwiching the hollow layer. And a body having a structure in which solid wall portions thinner than the hollow wall portion extend alternately in the axial direction, and a bottom portion including an inner layer and an outer layer with the hollow layer sandwiched therebetween. Consists of. Further, the blow-molded container of the present invention obtained by biaxially stretch-blow-molding such a preformed product of the present invention comprises a solid mouth and an inner layer and an outer layer with a hollow layer sandwiched therebetween. A plurality of hollow wall portions,
A plurality of solid wall portions each alternately extending in the axial direction, and a bottom portion having an inner layer and an outer layer with a hollow layer sandwiched between them, and a thin diameter is provided at the lower end of the outer layer of the bottom portion. It has an opening-shaped gate portion.

The biaxially stretched blow molded container of the present invention as described above is excellent not only in heat insulation and gas barrier properties but also in strength.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a preformed body according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a preform according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a preform according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a preform according to another embodiment of the present invention.

FIG. 5 is a plan view showing an example of the position of a core mold used for manufacturing the preform of the present invention.

FIG. 6 is a vertical sectional view showing a biaxially stretch blow molded container according to an embodiment of the present invention.

FIG. 7 is a vertical sectional view showing a biaxially stretch blow molded container according to an embodiment of the present invention.

[Explanation of symbols]

 1 ... Preform 2, 61 ... Mouth 3, 64 ... Body 31, 62a ... Hollow layer 32, 62b ... Inner layer 33, 62c ... Outer layer 34, 62・ ・ ・ Hollow wall 35, 63 ・ ・ ・ Solid wall 4, 66 ・ ・ ・ Bottom 41 ・ ・ ・ Central 42, 66a ・ ・ ・ Gate 43, 66b ・ ・ ・ Pore hole 5 ・ ・ ・Core type 51 ・ ・ ・ Ridge 6 ・ ・ ・ Biaxial stretch blow molding container

Claims (6)

[Claims] 1. A bottomed cylindrical resin preform, comprising a solid mouth portion, a hollow wall portion including an inner layer and an outer layer sandwiching a hollow layer, and the hollow wall portion. Also, the thin walled solid wall portion and the body portion that alternately extend in the axial direction,
A preformed article comprising a bottom portion composed of an inner layer and an outer layer sandwiching the hollow layer, and having a gate portion having an opening with a small diameter at the lower end of the outer layer of the bottom portion. 2. The method for manufacturing a resin preform according to claim 1, further comprising: (a) a cavity having a ridge corresponding to the solid wall of the preform, and the preform. Injecting a molding resin into the injection mold having a gate at a position corresponding to the bottom of the body to fill the resin up to the middle of the cavity, (b) Next, without stopping the injection of the resin, By injecting a gas so that a hollow layer is formed in the body, co-injecting the resin and the gas, and by diverting the gas in the protruding portion of the cavity,
A method for manufacturing a preform, comprising forming a plurality of hollow wall portions and a solid wall portion in the axial direction. 3. Using the preform according to claim 1,
A container formed by biaxial stretch blow molding, comprising a solid mouth portion, a plurality of hollow wall portions including an inner layer and an outer layer sandwiching a hollow layer, and a plurality of solid wall portions. And an axially alternately extending trunk portion, and a bottom portion sandwiching a hollow layer and having an inner layer and an outer layer, and a gate portion having a small opening at the lower end of the outer layer of the bottom portion. A biaxially stretched blow-molded container having. 4. The biaxially stretch blow molded container according to claim 3, wherein the ratio of the hollow wall portion to the total area of the body is 50 to 90%. 5. The biaxially stretched blow-molded container according to claim 3 or 4, wherein gas is prevented from flowing into and out of the hollow wall by closing a small-diameter hole portion existing in the gate portion. A biaxially stretched blow-molded container. 6. The biaxially stretch blow molded container according to claim 5, which has an oxygen barrier property by enclosing a deoxidizer in the hollow wall.