JPH05228925A - Preform for multilayer thin-walled container - Google Patents

Abstract

PURPOSE:To manufacture a preform of multilayer structure without unevenness of thickness of respective layers and of accurately even wall thickness all over of a multilayer thin wall container to be finished even in the case the rate of stretch of the preform is not uniform at the time of molding. CONSTITUTION:A preform 1 is molded into a multilayer container by molding and stretching and constituted by laminating injection resin layers 3 by injection molding on the surface of a sheet material 2 including layers provided with specified function. The finished preform for the multilayer thin wall container is provided with injection resin layers 5 and 6 forming sections stretching larger than other sections at the time of molding and having the thickness of their walls thicker than those of other sections so that said sections are protruded to the opposite side of the sheet material 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preform used as a raw material for a thin container having a plurality of resin layers.

[0002]

2. Description of the Related Art Containers for packaging foods are required to have some or all of various specific functions such as mechanical strength, gas barrier property, moisture resistance, heat resistance, and aroma retention. It It is known that each of these properties is achieved by a specific resin layer. When there are a plurality of properties to be obtained, individual resin materials that achieve those properties are laminated to form one container.

As a method for manufacturing such a multi-layered thin-walled container, first, a material called a preform is prepared, and the preform is subjected to a forming process such as vacuum forming or pressure forming to be stretched. It has already been proposed to manufacture a container having a desired shape. For example, the container manufacturing method disclosed in Japanese Patent Publication No. 57-1415, or Japanese Patent Laid-Open No. 60-178020.
No. 60-244518 and 63-130330.
No. 63-296921 and the like, so-called injection blow method and the like.

In the method disclosed in Japanese Patent Publication No. 57-1415, a rectangular multi-layer sheet material is heated and press-molded to produce a disk-shaped preform, and the disk-shaped preform is vacuum-formed. Is used to manufacture a product container, which is a method of reducing scrap (burrs) generated in conventional sheet molding. However, in this method, it is necessary to heat the sheet material to a high temperature to reduce its viscosity when press forming the multilayer sheet material to form a preform. In this way, the layer structure of the multilayer sheet material is likely to collapse.
That is, the layer is partially thinned or easily divided. A product container formed of a multilayer sheet material having a broken layer structure cannot obtain a specific target function such as gas barrier property.

Further, a good preform cannot be obtained unless a resin having good fluidity is used as a resin in contact with a mold for molding the preform. That is, the resin that can be used as the multilayer sheet material is limited to a narrow range.

The injection blow method disclosed in Japanese Patent Application Laid-Open No. 60-178020 discloses a product container by molding a disc-shaped preform by injection molding and subjecting the preform to molding processing such as plug assist molding. Is manufactured. In this injection blow method, since the injection molding method, that is, the injection molding method is used in the step of molding the preform, it is extremely difficult to form the preform into a multi-layer structure. Is only made. Therefore, there is a problem that a container having a specific function such as gas barrier property cannot be manufactured.

In the case of molding a preform by utilizing injection molding, as shown in, for example, Japanese Patent Application Laid-Open No. 3-176126, if molding is performed using a plurality of injection devices and a multi-layer molding injection nozzle, a multi-layered structure can be obtained. Reforms can be manufactured. In this case, the layer structure is symmetrical, and studies are being conducted toward the practical application of, for example, cup-shaped containers or bottles having a gas barrier resin as an intermediate layer. However, according to this technique, it is extremely difficult to make the thickness of each resin layer uniform, and in many cases, the multilayer structure itself does not hold in the vicinity of the cavity end where the fluidized resin finally reaches. Therefore, it is not possible to provide a uniform multilayer structure throughout the preform. Further, this method cannot be applied when a large number of resins need to be laminated in an asymmetrical layer structure as in the present invention.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems in preforms that have been conventionally used, and has a multi-layer structure, and the thickness of each layer is not disturbed. The present invention aims to provide a preform for a multi-layer thin-wall container.

Another object of the present invention is to manufacture a product container by molding and expanding the preform, and when the elongation rate varies depending on the location of the preform, the finished product is obtained. An object of the present invention is to provide a preform capable of making the wall thickness of a container uniform and uniform throughout.

[0010]

In order to achieve the above object, the preform according to the present invention is a preform which is molded into a multi-layer thin-walled container by being extended and has a specific function. It is formed by stacking an injection resin layer on the surface of a sheet material including a resin layer having And out of this preform
The thickness of the injection resin layer at the portion that extends more than other portions when it is molded into the multilayer thin container is so thick as to project to the opposite side of the sheet material.

In the above structure, the resin layer having a specific function means a resin layer having various functions such as gas barrier property, moisture resistance, heat resistance, and aroma retention (non-adsorption). An adhesive layer, which is provided between the respective layers when the resins having poor adhesiveness are laminated, and which acts as an adhesive, is also considered as a resin layer having a specific function. As the resin layer for achieving each of these functions, the following resin layers can be selected and used.

Gas barrier property: Saponified ethylene-vinyl acetate copolymer (EVOH), polyvinylidene chloride (PV)
DC), polyvinyl alcohol (PVA) Moisture proof: polyamide (nylon), polypropylene (P
P), polyolefin mixed with desiccant Heat resistance: Polyester (PET), Polycarbonate (PC), PP Fragrance retention: PET, EVOH, Polyacrylonitrile (P
AN) Adhesive layer: ionomer, ethylene-vinyl acetate copolymer (EVA)

The sheet material is formed in a single-layer structure or a multi-layer structure in order to obtain the above various specific functions. For example, 2
As a layered structure, PET / EVOH, PET / PVDC, etc. can be considered from the direction corresponding to the inside of the container. As a three-layered structure, PET / EVOH / PP, PP / PVDC / PP, etc. can be considered. Further, an adhesive or an adhesive resin is present between the layers of the sheet material, if necessary.

The method for producing the sheet material is not limited to a special method, and any method can be used. For example, one large sheet having a target layer structure is prepared by an arbitrary sheet forming method such as an adhesive laminating method or a co-extrusion method, and a large number of sheet materials are manufactured from the one sheet by punching. it can.

The resin layer laminated on the sheet material by injection molding is a thermoplastic resin having a mechanical strength capable of imparting a desired shape to the container, such as polypropylene (P
P), polystyrene (PS), polyvinyl chloride (PV
C), polycarbonate (PC), etc. are used.

Further, as the forming process for producing the multi-layer thin-walled container, vacuum forming, pressure forming, plug assist forming and the like can be considered. The vacuum forming is a forming method in which the inside of the cavity is evacuated and the sheet material is deformed so as to be in close contact with the mold and formed. Pneumatic molding is a molding method in which a sheet material is pressed by air and brought into close contact with a mold to mold the sheet material. The plug assist molding is a molding method in which the sheet material is auxiliary pressed by a plug in the above vacuum molding or pressure molding to mold the sheet material.

[0017]

The preform is formed by laminating the injection resin layer on the surface of the sheet material. Therefore, if this is molded and processed to make a product container, a multi-layer structure of at least two layers, or three or more layers can be obtained if the sheet material itself has a plurality of resin layers. Further, since the preform is not formed by press molding, the layer structure of the sheet material, that is, the layer structure of the preform does not collapse. Further, since the preform is formed by the combination of the preformed sheet material and injection molding, even if there is some variation in the thickness of the sheet material, the variation is absorbed by the injection process and the preform as a whole The thickness is extremely accurate and uniform. Furthermore, a part that extends more than other parts when molded into a product container,
For example, the wall thickness of the injection resin layer corresponding to the curved portion of the container is preliminarily formed thicker than other portions. As a result, the entire thickness of the product container including the curved portion can be made uniform.

[0018]

EXAMPLE FIG. 1 shows an example of a preform according to the present invention. This preform 1 is formed by stacking an injection resin layer 3 on the lower surface of a disc-shaped sheet material 2 having a specific function such as gas barrier property by injection molding. The sheet material 2 is composed of one or multiple resin layers depending on the kind of the specific function to be obtained.

The preform 1 is subjected to a forming process such as vacuum forming to produce a product container 4 having a side sectional shape as shown in FIG. The product container 4 shown is 2
The curved portions A and B are provided at some places, and the extension rate of the portions corresponding to these curved portions during the molding process of the preform 1 is higher than the extension rates of the other portions. As shown in FIG. 1, thick portions 5 and 6 are formed in portions of the preform 1 corresponding to the curved portions A and B. Each of these thick-walled portions 5 and 6 is formed by increasing the thickness of the injection resin layer 3 and protrudes in the direction opposite to the sheet material 2.

As described above, since the preform 1 has the thick portions 5 and 6 corresponding to the curved portion at the time of molding, that is, the portion having a large elongation rate, the curved portion of the finished product container 4 is formed. The thickness of A and B does not become too thin as compared with the other portions, and it is possible to finish the overall uniform thickness.

In the case of a retort-compatible container or the like, if the thickness of the container is not uniform, defects such as deformation and damage may occur after the retort sterilization process. On the other hand, in the product container 4 molded from the preform 1 having the thick portions 5 and 6, such a thin portion does not occur,
Therefore, it can be used as a container for retort without any problems.

Hereinafter, a manufacturing method for manufacturing the preform 1 and the product container 4 will be described with reference to an example.
3 shows an injection molding device 24, FIG. 4 shows a preform heating device 25, and FIG. 5 shows a plug assist molding device 26 as a molding processing device. The preform 1 is formed by the injection molding device 24, the preform 1 thus obtained is heated by the heating device 25, and the molding process is performed by the molding device 26, whereby the product container 4 is manufactured.

The injection molding apparatus 24 shown in FIG. 3 has a fixed plate 8 at the uppermost portion, and the core 9 is fixed to the lower surface of the fixed plate 8. Inside the core 9, a cooling liquid passage 10 and an air suction passage 22 are provided. A lip cavity 11 and a lip plate 12 are arranged around the lower portion of the core 9. Further, a cavity 13 held by a holding plate 14 is provided below the core 9, and the cavity 13 is held by the cavity 13.
The tip of the hot runner 15 is exposed inside the gate 16
Is in contact with.

The core 9 together with the fixed plate 8 is adapted to be capable of reciprocating linear movement in the vertical direction as shown by the arrow AA '.
It moves between the illustrated mold clamping position and an open position (not shown) that is far away from the cavity 13. The mold clamping position is a position where a gap G corresponding to a desired preform shape is formed between the core 9 and the cavity 13.

The lip cavity 11 is of a so-called split type, and both left and right types can be reciprocated linearly in the left and right direction as indicated by an arrow BB 'with the central axis L as a boundary. Due to this movement, the lip cavity 11 moves between the illustrated mold clamping position and the open position (not shown) that is largely separated from each other.

The preform heating device 25 shown in FIG. 4 has a heater 17 that can be exposed above the preform 1 formed by the injection molding process which is the previous process. Also,
A heater 30 for heating the injection resin layer 3 is provided below the preform 1. The heater 30 can be omitted when the injection resin layer 3 is laminated and then immediately moved to the molding process of the container.

The plug assist molding apparatus 26 of FIG. 5 has a lower mold 18 connected under the lip cavity 11, a vertically movable core 19, and a vertically movable penetrating core 19. And a plug 20. An air introduction hole 23 is formed in the core 19. Further, the lower mold 18 is provided with a recess 21 having an inner wall surface matching the shape of the product container 4.

The operation of each of the above devices will be described below. In FIG. 3, both the core 9 and the lip cavity 11 are moved to an open position (not shown) that is far away from the cavity 13. As a result, the upper surface of the cavity 13 is largely opened. In this state, as shown in FIG.
The disc-shaped sheet material 2 is attached to the lower end of the core 9. The sheet material 2 is adsorbed and fixed to the lower end of the core by the air flowing through the air suction passage 22. The upper surface of the mounted sheet material 2, that is, the surface in contact with the core 9, is the inner peripheral surface of the product container.

When the sheet material 2 is attached to the lower end of the core 9, as shown in FIG. 3, the core 9 and the lip cavity 1 are
1 is set in the mold clamping position. In this state, the resin is poured into the cavity recess G via the hot runner 15. As a result, the injection resin layer 3 is laminated on the sheet material 2 to form the preform 1 shown in FIG.

When the above injection molding is completed, the core 9 moves from the mold clamping position to the opening position in FIG. The lip cavity 11 continues to hold the preform 1 while remaining in the mold clamping position. Then, the preform 1 is sent to the heating stage shown in FIG. 4 while being held by the lip cavity 11. In this heating stage, the heater 17 is carried out to a position just above the preform 1, and the preform 1 is heated by the heat radiated from the heater 17 and the heater 30 arranged as necessary. By this heating, fusion between the sheet material 2 and the injection resin layer 3 is promoted, and preheating for the next step, the molding process, is performed. Note that this heating step can be omitted in some cases.

During the above heat treatment, the thick portions 5, 6 are closer to the heater 30 than the other portions. As a result, it is possible to reliably heat the thick portion having poor heating efficiency.

The heated preform 1 is then sent to the container forming stage of FIG. 5 while being held by the lip cavity 11. At this container molding stage, the core 19 provided with the plug 20 is set to the illustrated molding position from above the preform 1 and the container molding process is performed. That is, the preform 1 is pressed downward by the downward movement of the plug 20, and at the same time, the preform 1 is extended by the air fed through the air introduction hole 23. The preform 1 thus extended is formed into a wall surface shape of the recess 21 of the lower mold 18, that is, a cup shape,
The product container as shown in FIG. 2 is completed.

Although the preform according to the present invention has been described based on the preferred embodiment, the present invention is not limited to the embodiment. For example, the number of thick-walled parts is not limited to two, but may be smaller depending on the shape of the product container,
Or it can be more.

The preform manufacturing method shown in FIGS. 3 to 6 is an example for manufacturing the preform 1. There is no problem even if the preform 1 is manufactured by a method other than this.

[0035]

According to the present invention, the injection resin layer is preliminarily formed on the surface of the sheet material having the resin layer by injection molding to form a preform. It is possible to obtain a preform with no disorder.

Since the injection resin layer is provided with the thick portion, even if there is a locally greatly extending portion such as a curved portion in the product container, the thickness of the entire finished product container is made uniform. be able to. Further, in the preform of the present invention, since the injection resin layer is formed by injection molding, less resin is used as compared with conventional sheet molding, and it is economical.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing an embodiment of a preform for a multilayer thin container according to the present invention.

FIG. 2 is a side sectional view showing an example of a product container manufactured using the preform.

FIG. 3 is a side sectional view showing an injection molding apparatus which is an example of an apparatus for manufacturing the preform.

FIG. 4 is a side sectional view showing an example of a preform heating device required for manufacturing the product container.

FIG. 5 is a side sectional view showing an example of a forming / processing apparatus required to manufacture the product container.

FIG. 6 is an enlarged sectional view showing a main part of FIG.

[Explanation of symbols]

 2 Sheet material 3 Injection resin layer 4 Product container (multi-layer thin container) 5, 6 Thick part of injection resin layer

Claims (1)

[Claims] 1. A preform that is molded and extended to be molded into a multi-layer thin-walled container, wherein an injection resin layer is superposed on the surface of a sheet material containing a resin layer having a specific function by injection molding. It is characterized in that the thickness of the injection resin layer at the part that extends more than other parts when molded into a multi-layer thin-walled container is made thicker so as to project to the opposite side of the sheet material. Preform for multi-layer thin containers.