JP3142344B2 - Resin preform having hollow wall, method for producing the same, and biaxially stretch blow molded container using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Resin containers (bottles) for encapsulating carbonated beverages, fruit juice beverages, and the like are manufactured by injection molding of a saturated polyester resin or the like, followed by stretch blow molding. General.

[0003] When hot-filling the above-mentioned beverage or the like in such a container, the pressure in the container may be reduced after sealing. There is a problem that the container is deformed due to the decrease in the pressure, the external shape becomes unsightly, and the deformation resistance to external force is reduced.

Therefore, various countermeasures have been taken against deformation due to reduced pressure after the container is closed. However, conventionally, a deformable portion is formed in a container and the portion is deformed. Is the way. However, such a method has a problem that when the amount of reduced pressure exceeds the volume of the deformable portion, the reduced pressure cannot be absorbed.

In addition to the above-mentioned problem of deformation under reduced pressure, containers such as beverage bottles have a problem that since they are formed of solid layer walls, they are inferior in heat insulation and do not have sufficient heat retention of the contents.

[0006] In addition, when juice, beer or the like is enclosed, there is a problem that the properties of the contents change due to the influence of oxygen entering from outside the container.

Accordingly, the present inventors have proposed a biaxially stretched blow-molded container in which the container walls (body and bottom) are hollow walls and the container body is of a double structure. -13
4785, Japanese Patent Application No. 2-134786, Japanese Patent Application No. 2-135574). In this container, the container wall is doubled, and the reduced pressure deformation after hot filling can be received only by the inner container wall, so that the outer container wall is not deformed. Further, since the container wall has a hollow portion, the container wall exhibits good heat insulating properties, and thus a good heat insulating container can be obtained. Furthermore, if a deoxidizer is put in the hollow part of the container wall and the hollow part is sealed, external oxygen cannot pass through the container wall,
Oxygen barrier containers can also be used. However, although the above-mentioned container exerts various effects as described above, as a result of subsequent studies, it has been found that the strength of the container may not always be sufficient.

[0008] Accordingly, an object of the present invention is to provide a preformed article which provides a biaxially stretched blow molded container having excellent heat insulating properties 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 preformed body.

[0010]

Means for Solving the Problems As a result of intensive studies in view of the above-mentioned objects, the present inventors have conducted various studies on a container having a hollow wall, and have found that even if the hollow wall does not exist over the entire region of the 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 the hollow wall and the solid wall alternately extend in the axial direction. It has been found that if the body is used, the strength of the container hardly decreases. In addition, the present inventors have proposed a method for manufacturing a container having a body in which such hollow walls and solid walls alternately extend in the axial direction, in which a solid mouth and a hollow layer are formed. A hollow wall portion having an inner layer and an outer layer, a body portion having a structure in which solid wall portions thinner than the hollow wall portion alternately extend in the axial direction, and a hollow layer. It has been found that it is sufficient to blow-mold a preform comprising an inner layer and a bottom composed of an outer layer. Further, the present inventors have found that when a resin and a gas are co-injected and molded using an injection mold having a cavity in which the solid wall portion is thinner than the hollow wall portion, the cavity becomes a solid wall portion. The gas is diverted at the narrowed portion, and a hollow wall portion and a thinner solid wall portion are alternately formed in the body in the axial direction, thereby manufacturing the preformed body. I found that I can do it.
The present invention has been made based on the above findings.

That is, a 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, A solid wall portion thinner than the portion and a body portion each extending in the axial direction alternately, and a bottom portion including an inner layer and an outer layer with the hollow layer interposed therebetween, and the bottom portion includes It is characterized in that it has a gate portion having a small-diameter opening at the lower end of the outer layer.

[0012] The method of the present invention for producing the preform may further comprise (a) a cavity having a ridge corresponding to a solid wall portion of the preform, and a cavity corresponding to a bottom of the preform. Injecting a molding resin into an injection mold having a gate at a position to fill the resin to the middle of the cavity, and (b) then injecting a small amount without stopping the injection of the resin or stopping the injection. By blowing a gas so that a hollow layer is formed in the body, co-injecting the resin and the gas, and splitting the gas at the ridge of the cavity, in the axial direction A plurality of hollow walls and a solid wall are formed.

Further, the biaxially stretched blow-molded container of the present invention obtained by biaxially stretch-blow-molding the above preformed body has a solid mouth portion, an inner layer and an outer layer sandwiched by a hollow layer. A plurality of hollow wall portions, and a body portion in which a plurality of solid wall portions each extend alternately in the axial direction, and a bottom portion including an inner layer and an outer layer sandwiching the hollow layer, It is characterized in that it has a gate portion having a small-diameter opening at the lower end of the outer layer at the bottom.

[0014]

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

FIG. 2 is a cross-sectional view of the body of the preform shown in FIG. Five hollow walls 34 and solid walls 35 are alternately arranged in the body 3, and the ratio of the hollow walls 34 is 50 to 90% with the total area of the body being 100%.
It is preferred that If the hollow wall is less than 50%,
Insufficient effects such as gas barrier properties and heat insulation properties, while 90%
If it exceeds, the strength of the container decreases.

The number of hollow walls is 5 as in this embodiment.
It is not necessary to set the number of pieces, and for example, in the case of a parison having a thickness of 5 mm, it may be set appropriately within the range of 3 to 8 pieces. If the number of hollow wall portions is less than three, the strength of the container tends to decrease, while if it exceeds eight, the ratio of the hollow wall portions decreases and it becomes difficult to form the hollow wall portion exceeding 50%. Further, the hollow wall portion does not need to be provided over the entire region in the axial direction of the trunk portion, and may be unevenly distributed at an upper portion or a lower portion of the trunk portion. Further, it is not necessary to provide them at equal intervals, and the positions may be appropriately set according to the form of the container.

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 because the hollow walls are provided alternately in the axial direction as described later, and in order to accurately provide the hollow walls,
Preferably, the thickness of the solid wall is 30-70% of the thickness of the hollow wall. Note that the thinning is not necessary by making the inside concave as in this 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, there is provided an injection molding having a cavity having a ridge corresponding to a thin layer state of a solid wall portion of the preform, and having a gate at a position corresponding to a bottom of the preform. Use a mold.

The cavity having a ridge corresponding to the thin state of the solid wall portion of the preformed body is used, for example, when the inside of the solid wall portion of the preformed body is concave as in this embodiment. As shown in FIG. 5, a core mold 5 having a ridge 51 at a position corresponding to a solid wall portion, and a body mold having a gate at a position corresponding to the bottom of a cylindrical preform (not shown) ) May be used.

Using the injection mold as described above, press-fit the molten resin from the gate, fill the resin to the middle of the cavity, and when it reaches a predetermined position, inject a small amount of the resin without stopping it. A gas is blown in or stopped so as to form a hollow layer in the body, and the resin and the gas are co-injected.

At this time, when the gas reaches the start position of the convex portion 51 of the core mold 5, the cavity is substantially closed at the portion having the convex portion because the cavity is narrowed, and the cavity is substantially closed by the resin. For this reason, the gas is divided, and a plurality of hollow walls 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 progress of the shape and the cooling of the resin, so that the molten resin flows selectively in the thick layer. Similarly, the gas to be filled flows into the layer having a small inflow resistance. As described above, in order to surely divide the gas, the thickness of the solid wall is 30 times the thickness of the hollow wall as described above.
It is preferable to set the size of the ridge 51 so as to be about 70%.

The gas co-injection molding is performed by a GIP molding method.
(Gas Injection Process, Mannesmann Demag), AM
P. Molding method (Air Mold Process, Battenfeld), or a molding method of a hollow mold described in Japanese Patent Publication No. 577-14968.

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

As shown in FIG. 3, in the case of manufacturing a preform in which the outside of the solid wall portion is concave, a linear convex portion is provided at a position corresponding to the solid wall portion of the body type. In the case of manufacturing a preform in which both the outside and the inside of the solid wall are concave as shown in FIG. 4, linear projections are provided on both the core mold and the body mold. Just do it.

By subjecting the thus obtained preform to biaxial stretch blow molding by a conventional method, the biaxial stretch blow molded container having a hollow wall of the present invention can be obtained.

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 stretched 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 sandwiching a hollow layer 62a, Solid wall
And a hollow layer 64 having alternately in the axial direction 63 respectively.
It has a bottom 66 having a hollow wall 62 comprising an inner layer 62b and an outer layer 62c sandwiching 62a. A gate 66a is provided on the outer layer of the bottom 66, and the gate 66a has a small-diameter hole 66b communicating from the outside of the container to the hollow layer 62a.

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-described preformed body, and the entire area of the body portion is reduced. It is preferably 50 to 90% as 100%. If the hollow wall portion is less than 50%, effects such as gas barrier properties and heat insulating properties are not sufficient, while if it exceeds 90%, the strength of the container is reduced. The thickness of the solid wall portion 63 is made thinner than the thickness of the hollow wall portion 62 when a preformed body that is concave inside is used as shown in FIG. However, the difference substantially disappears by stretching.

When a preform having a concave portion outside the solid layer as shown in FIGS. 3 and 4 is used, the body of the biaxial stretch blow mold should have a smooth surface. This eliminates the recess. Further, the stretching ratio of the hollow wall portion and the solid wall portion can be changed depending on the method of heating the parison. When heated to substantially the same temperature, the draw ratio will be different due to the difference in wall thickness.

With the container having such a structure, even if the inner layer 62b is deformed due to the reduced pressure absorption when the contents such as beverages are enclosed, the volume change of the hollow layer 62a due to the deformation is caused by the deformation of the gate 66a. It is absorbed by air that can freely enter and exit through the small-diameter hole 66b. For this reason, a biaxially stretch blow-molded container capable of absorbing reduced pressure without deforming the outer layer 66c.

Further, since the hollow layer 62a between the inner layer 62b and the outer layer 62c functions as a heat insulating layer, a biaxially stretched blow-molded container having excellent heat insulating properties and heat insulating properties can be obtained. Further, the small-diameter hole portion 66b of the gate portion 66a can be closed by a heat seal or an adhesive. Thus, the gate section
By closing the opening 66a, the flow of air into and out of the hollow layer 62a through the small-diameter hole 66b is eliminated, so that a biaxially stretched blow-molded container having more excellent heat retention can be obtained.

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

The resin forming the biaxially stretched blow-molded container of the present invention as described above is not particularly limited as long as it can be biaxially stretched blow-molded.
Polystyrene, polycarbonate, nylon, polyacrylonitrile, polyester, polyarylate and the like can be used. Of these, polyester resins are preferred. As the polyester resin, a thermoplastic resin comprising a saturated dicarboxylic acid and a saturated dihydric alcohol can be used. As saturated dicarboxylic acids, 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, and adipic acid And aliphatic dicarboxylic acids such as sebacic acid, azelaic acid and decane-1,10-dicarboxylic acid, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid. Saturated dihydric alcohols include 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. Glycols, alicyclic glycols such as cyclohexanedimethanol, 2,2-bis (4'-β-hydroxyethoxyphenyl) propane, and other aromatic diols can be used. A preferred polyester is polyethylene terephthalate consisting of terephthalic acid and ethylene glycol.

The polyester resin has an intrinsic viscosity of 0.5 to 1.5.
, Preferably in the range 0.55 to 0.8. Also, such polyesters are produced by melt polymerization,
Those subjected to a reduced pressure treatment or a heat treatment in an inert gas atmosphere at a temperature of 250 ° C., or those subjected to solid phase polymerization to reduce the content of oligomers and acetaldehyde, which are low molecular weight polymers, are preferred.

In the polyester resin, additives such as stabilizers, pigments, antioxidants, heat deterioration inhibitors, ultraviolet light deterioration inhibitors, antistatic agents, antibacterial agents and the like are provided as long as the object of the present invention is not impaired. Can be added in an appropriate amount.

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 need to be five as in the present embodiment. Can be appropriately changed without departing from the spirit of the present invention. In addition, various substances can be enclosed in the hollow layer according to the characteristics required for the biaxially stretch blow-molded container, as well as the method of enclosing the oxygen-absorbing agent in the hollow layer. For example, in order to further improve the heat insulating property, a resin or the like having a high heat insulating effect can be sealed instead of air. In addition, water, carbon dioxide, oxygen, a gas barrier substance, a 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 hollow wall comprising a solid mouth, an inner layer and an outer layer sandwiching the hollow layer. And a body portion having a structure in which solid wall portions thinner than the hollow wall portions alternately extend in the axial direction, and a bottom portion including an inner layer and an outer layer with the hollow layer interposed therebetween. Consists of Further, the blow-molded container of the present invention obtained by biaxially stretch blow-molding such a preformed body of the present invention comprises a solid mouth portion, an inner layer and an outer layer sandwiching a hollow layer. A plurality of hollow walls,
A plurality of solid wall portions each include a body portion extending alternately in the axial direction, and a bottom portion including an inner layer and an outer layer with a hollow layer interposed therebetween. It has an open gate.

Such a biaxially stretched blow-molded container of the present invention is excellent in heat insulation and gas barrier properties and also in strength.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a preform 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 a position of a core mold used for manufacturing a preform of the present invention.

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Preformed body 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 5 Core mold 51 ・ ・ ・ Protrusion 6 ・ ・ ・ Biaxially stretch blow molded container

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B65D 1/00 B29B 11/06 B29C 49/08 B29D 23/02

Claims (6)

(57) [Claims] 1. A resin preform having a bottomed cylindrical shape, comprising: a solid mouth portion; a hollow wall portion having an inner layer and an outer layer sandwiching a hollow layer; A body portion in which the solid wall portions that are also thinned also alternately extend in the axial direction,
A preform comprising a bottom portion having an inner layer and an outer layer sandwiching the hollow layer, and having a gate portion having a small-diameter opening at a lower end of the outer layer at the bottom portion. 2. The method of manufacturing a resin preform according to claim 1, further comprising: (a) a cavity having a ridge corresponding to a solid wall of the preform, and In an injection mold having a gate at a position corresponding to the bottom of the body, a molding resin is injected to fill the resin to the middle of the cavity, (b) Next, without stopping the injection of the resin, By blowing a gas so that a hollow layer is formed in the body, co-injecting the resin and the gas, and dividing the gas at the ridge portion of the cavity,
A method for manufacturing a preform, wherein a plurality of hollow walls and a solid wall are formed in an axial direction. 3. The preform according to claim 1,
A container formed by biaxial stretch blow molding, wherein 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 Each comprises a body portion extending alternately in the axial direction, and a bottom portion having an inner layer and an outer layer with a hollow layer interposed therebetween. A biaxially stretch blow molded container characterized by having: 4. The biaxially stretched blow-molded container according to claim 3, wherein the ratio of the hollow wall portion to the total area of the body portion is 50 to 90%. 5. The biaxially stretched blow-molded container according to claim 3, wherein the small-diameter hole in the gate is closed to prevent gas from flowing into and out of the hollow wall. A biaxially stretch blow-molded container characterized by the above-mentioned. 6. The biaxially stretched blow-molded container according to claim 5, wherein an oxygen barrier property is provided by enclosing a deoxidizer in the hollow wall.