JP2002144411A - Method for blow-molding inner face-reinforced hollow container and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a blow-molding method for an inner face-reinforced hollow container by which a plastic bottle or a tube is made thin-walled and lightweight and at the same time, its required strength can be secured and the irregularity of the rib can be prevented from occurring without any disorder in a resin layer as well as a device using the method. SOLUTION: A die core 24 is relatively moved in the axial direction to a die shell 21 having a groove part 22 for forming a thick wall part 16 in a parison 15. In addition, the protruding thick-wall part 16 is formed on the outer peripheral face 15a of the parison 15 corresponding to only the part 12 which needs to be reinforced of the hollow container 10 and a blow-off gas is blown into a flat inner peripheral face 15b of the parison 15 to form the hollow container 10 with an inward rib 13 formed on the inner surface. Thus it is possible to make the blow-off gas uniformly act upon the parison 15 with a flat inner peripheral face, prevent the irregularity of the rib 13 from occurring and blow mold the inner face-reinforced hollow container 10 free from any disorder in the resin layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for blow molding a hollow container having a reinforced internal surface, and to reduce the thickness and weight of a hollow container such as a plastic bottle or a plastic tube, and at the same time, to an arbitrary position on the inner surface. A reinforcing portion is provided to ensure necessary compression strength and the like so that blow molding can be performed.

[0002]

2. Description of the Related Art In recent years, hollow containers such as plastic bottles and plastic tubes have been frequently used as packaging containers for beverages and foods. Such a plastic hollow container is usually formed by blow molding, and the plastic is melt-extruded through a die core and a die shell into a single-layer or multi-layer parison, and cavities of various container shapes are formed. It is introduced between a pair of molds, and after closing the molds, blow gas is blown to form a cavity shape, and then cooled and solidified to be taken out.

[0003] Such a plastic hollow container has made it possible to reduce the weight compared to a conventional glass or metal container.

However, with respect to conventional plastic hollow containers, there has been an increasing demand for resource saving and further weight reduction by reducing the amount of resin used, and the thickness of the container itself has to be reduced. There are conflicting demands to secure them as before.

Therefore, it is conceivable that the thickness of the hollow container is reduced and the reinforcing ribs are formed on the inner surface to achieve both reduction in weight and securing of strength.

As a method of forming inward ribs on the inner surface of such a hollow container, when plastic is melt-extruded into a parison shape through a die, a thick portion which is to be an inward rib is connected to the parison in advance. The parison is blow-molded using this parison to make the body of the container thinner, and is reinforced with inwardly formed ribs to ensure strength.

[0007] However, in the blow molding method using a parison in which a thick portion that becomes an inward rib is continuously formed, a blow gas is blown through a mandrel in an upper blow or a lower blow. Although there is a thick part, the inner circumference of the bottle neck can be constrained by a mandrel to form a perfect circle, but the resin in the thick part is wasted, while blowing the blow gas through the blow pin In the case of horizontal blowing, the thick part remains on the inner periphery of the neck of the bottle as it is, resulting in poor sealing performance as a container and poor heat sealing performance at the bottom of the tube.

Therefore, as a method of forming an inward rib only on a necessary portion of the inner surface of the hollow container, for example, Japanese Patent Publication No.
There is a method for producing a heat-resistant deformable plastic bottle described in Japanese Patent No. 18846, and when a plastic is melt-extruded into a parison shape through a die, as shown in FIGS. A die 3 is formed, and a groove 3b is formed in a part of a die core 3 having a tapered tip 3a constituting the die 2, and the die core 3 is moved axially relative to a die shell 4, FIG.
As shown in FIG. 8B, extrusion is performed to form the thick portion 6a of the parison 6 which is extruded from between the groove 3b of the die core 3 and the die shell 4 and becomes the rib 5a of the hollow container 5, and FIG.
As shown in (c), the rib 5a is extruded from the tapered tip portion 3a of the die core 3 without the groove 3b and the die shell 4 so as to perform normal extrusion without the thick portion 6a. The parison 6 having the thick part 6a formed therein is obtained.

Such a tapered tip portion 3a and groove 3
By moving the die core 3 and the die shell 4 forming the b in the axial direction relative to each other, the thick portion 6a of the parison 6 which becomes the inward rib 5a can be formed at an arbitrary position of the hollow container 5, and the lateral blowing is performed. Even in the case of (1), the problem of the sealing property at the bottle neck and the heat sealing property at the bottom of the tube can be solved.

[0010]

However, when such a thick portion 6a as the rib 5a is formed by protruding inside the parison 6 and blow-molded, as shown in FIG. Does not act uniformly on the inner periphery of the parison 6 and concentrates on the root portion of the thick portion 6a, and the blow ratio of this portion becomes large and becomes thin, or the thick portion 6a
There is a problem that the rib 5a formed by the above is not straightened but is distorted.

In the case of blow molding using a multi-layer parison, each resin layer 8 is shifted inward from the rib 5a at the rib 5a, so that the resin layer 8 is not blow molded in parallel and is disturbed. There is a problem that a part of the barrier layer becomes thin and the barrier effect becomes insufficient.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art, and is intended to reduce the thickness and weight of hollow containers such as plastic bottles and plastic tubes and to provide a reinforcing portion on the inner surface. In order to ensure high compressive strength, etc.
An object of the present invention is to provide a method and an apparatus for blow molding an internally reinforced hollow container capable of preventing irregularities in ribs and preventing the resin layer from being disturbed.

[0013]

SUMMARY OF THE INVENTION In order to solve the problems of the prior art, a blow molding method for an internally reinforced hollow container according to claim 1 of the present invention is a method in which a plastic is melt-extruded through a die into a parison shape and closed. When blowing a blow gas into the inside of the parison to blow-mold a hollow container having a reinforcing portion on the inner surface, a thick wall portion is formed by protruding from the outer peripheral surface of the parison corresponding only to the reinforcing necessary portion of the hollow container. The blow gas is blown into a flat inner peripheral surface of the parison to form a hollow container having a reinforcing portion formed on the inner surface.

According to this method of blow molding a hollow container having a reinforced inner surface, a plastic is melt-extruded into a parison through a die, and blow gas is blown into the closed parison to blow the hollow container having a reinforcing portion on the inner surface. In doing so, a thick portion is formed by protruding on the outer peripheral surface of the parison corresponding only to the necessary reinforcing portion of the hollow container, and the blown gas is blown into the flat inner peripheral surface of the parison to form a reinforcing portion on the inner surface. To form a hollow container,
By forming ribs on the inner surface with the thicker portion of the outer peripheral surface, the inner peripheral surface can act uniformly as a parison with the blow gas as a flat parison, preventing irregularities in the ribs and preventing the resin layer from being disturbed. The reinforced hollow container can be blow molded.

According to a second aspect of the present invention, in the blow molding method for an internally reinforced hollow container according to the first aspect, the thick portion protruding from the outer peripheral surface of the parison is formed on a die shell. The die core is formed by moving the die core relatively in the axial direction with respect to the groove in which the formed thick portion can be formed.

According to the blow molding method for the hollow container having the inner surface reinforced, the thick portion protruding from the outer peripheral surface of the parison is formed by moving the die core relative to the groove which can form the thick portion formed in the die shell. The thick part protruding from the outer periphery of the parison can be easily formed simply by moving the die core relative to the die shell in the axial direction.

Further, the blow molding method for an inner surface reinforced hollow container according to claim 3 of the present invention, in addition to the structure according to claim 1 or 2, wherein the hollow container is a bottle and corresponds to at least a neck portion of the bottle. The blow molding is performed without forming the thick part in the parison.

According to the blow molding method of the hollow container having the inner surface reinforced, the hollow container is formed into a bottle, and the parison corresponding to at least the neck portion of the bottle is blow molded without forming the thick portion. As a result, a plastic bottle without a reinforcing rib at the neck portion can be blow-molded, thereby eliminating waste of resin and improving sealing performance.

According to a fourth aspect of the present invention, there is provided a blow molding method for an internally reinforced hollow container, wherein the hollow container is a tube and the contents of at least the rear end of the tube. The parison corresponding to the heat-sealed portion after filling is blow-molded without forming the thick portion.

According to the blow molding method for an inner surface reinforced hollow container, the hollow container is a tube, and the thick portion is formed on the parison corresponding to the heat-sealed portion of at least the rear end of the tube after filling the contents. The plastic tube without the reinforcing ribs can be blow-molded at the bottom heat-sealed portion without using resin, so that the resin is not wasted and the sealing performance can be improved.

Further, according to a fifth aspect of the present invention, there is provided a blow molding method for an internally reinforced hollow container according to any one of the first to fourth aspects, wherein the parison is a multilayer parison, and The blow molding is performed so that the resin layer in the cross section of the inner surface reinforcing portion of the hollow container is substantially parallel.

According to the blow molding method of the hollow container having the internal reinforcement, the parison is a multi-layer parison, and the multi-layer parison is blow-molded so that the resin layer in the cross section of the internal reinforcing portion of the hollow container is substantially parallel. In this way, the thick part protruding from the outer periphery of the parison is blow-molded so that it can be molded with a uniform blow pressure applied to the inner surface of the parison. It is possible to blow-mold a hollow container which is formed by the above method and has a reinforcing portion protruding from the inner surface, so that the resin layer is not disturbed and the barrier layer and the like can be formed to a uniform thickness.

According to a sixth aspect of the present invention, there is provided a blow molding apparatus for an inner surface reinforced hollow container, wherein a plastic is melt-extruded into a parison shape through a die, and a blow gas is blown into a closed parison to form a reinforcing portion on the inner surface. An apparatus for blow molding a hollow container provided with a die core, a die shell having a groove portion capable of forming a thick portion in the parison, and a die core and a die shell which are relatively axially moved to form a hollow container. A relative movement mechanism that protrudes from the outer peripheral surface of the parison corresponding to only the part requiring reinforcement to form a thick part, and the blow gas is blown into the flat inner peripheral surface of the parison to form a reinforcing part on the inner surface. It is characterized by forming a hollow container.

According to the blow molding apparatus for an internally reinforced hollow container, the plastic is melt-extruded into a parison shape through a die, and a blow gas is blown into the closed parison to blow-mold the hollow container having a reinforced portion on the inner surface. A die core, a die shell having a groove capable of forming a thick part in the parison, and a die core and a die shell which are relatively moved in the axial direction to correspond only to the necessary portions of the hollow container. A relative movement mechanism that protrudes from the outer peripheral surface of the parison to form a thick portion, and blows the blow gas into the flat inner peripheral surface of the parison to form a hollow container having a reinforcing portion formed on the inner surface. The parison can be formed by projecting a thick part on the outer peripheral surface and forming a flat parison on the inner peripheral surface. In that the rib prevents the rib irregularities, the inner surface reinforcing hollow container does not occur disturbance of the resin layer can be blown.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method and an apparatus for blow-molding an internally reinforced hollow container of the present invention will be described below in detail with reference to the drawings. The hollow container formed by the blow molding method for an internally reinforced hollow container or the blow molding apparatus for an internally reinforced hollow container according to the present invention is a plastic bottle 10 or tube 11 as shown in FIGS. The inward rib 13 as a reinforcing portion is integrally formed only in the portion 12 where the inward rib 13 is required, and the inward rib 13 is not integrally formed in a portion where the reinforcement is not necessary or where it is better not to form the inward rib 13. It was made.

For example, in the case of the bottle 10, the portions 12 that need to be reinforced of the hollow container such as the bottle 10 and the tube 11 include four corners 12 a of the body 10 a and a shoulder between the body 10 a and the neck 10 b. As shown in FIG. 1D, the inner surface 12b of the body 10c or the place where the label 14 is to be embedded in the surface of the body 10a so as to be embedded (in the case of an in-mold label attaching method or the like). The rear portion (the rear portion at the boundary between the label-attached portion and the non-label-attached portion) 12c can be mentioned.
In 1, the inner surface 12d of the trunk 11a can be mentioned.

The inward rib 13 as such a reinforcing portion
Is formed integrally with the hollow containers 10, 11 and the like by blow molding a thick-walled portion 16 formed on the outer peripheral surface 15a of the parison 15 when the parison 15 is melt-extruded. It is formed linearly in the axial direction of the tube 11, but the spiral inward rib 13 is formed by extruding the parison 15 while rotating it, or the thick part is formed integrally with the parison 15 by protruding from the outer peripheral surface 15a of the parison 15. The inward rib 13 of another shape may be formed as long as the rib 16 can be formed.

On the other hand, such a bottle 10 or tube 1
The portion of the hollow container such as 1 that does not need to be reinforced includes, for example, a neck portion 1 sealed with a stopper cap or the like in the bottle 10.
0b and a bottom 10d for performing pinch-off of a parison. In the tube 11, a neck 11b for reducing waste of resin, a rear heat-sealing portion 11c for sealing with a heat seal after filling the contents, and the like. Can be mentioned.

Next, a method for blow-molding the thick portion 16 formed by projecting the inward rib 13 as the reinforcing portion on the outer peripheral surface 15a of the parison 15 will be described in detail.

In the conventional method of blow molding an inward rib integrally, a thick portion is formed by protruding from the inner peripheral surface of the parison, and this is used as an inward rib. In this case, as described above, since the blow gas is concentrated on the root of the thick portion, problems such as falling down of the rib and thinning of the rib root occur.

Therefore, in the blow molding method of the inner surface reinforced hollow container, the thick part 16 is formed by projecting from the outer peripheral surface 15a of the parison 15, and the flat parison 1 is formed on the inner peripheral surface 15b.
The hollow containers 10 and 11 provided with the inward ribs 13 are formed by blow molding using the mold 5.

In this blow molding, as shown in FIG.
Grooves 22 for forming the thick portion 16 on the inner peripheral surface of the cylindrical die shell 21 constituting the die 20 are formed at four locations at equal intervals in the circumferential direction, for example, corresponding to the four corners of the bottle 10. .

On the other hand, a die core 24 disposed inside the die shell 21 with a gap serving as a die passage 23 provided therein
A cylindrical portion 26 forming a die lip 25 at the tip and a conical portion 27 located above the cylindrical portion 26 are provided.
By moving the cylindrical portion 26 relative to the die shell 21 in the axial direction and facing the groove 22, the thick portion 16 is formed on the outer peripheral surface 15 a of the parison 15, and the cylindrical portion 26 is opposed to the portion without the groove 22. , Parison 1 of normal uniform thickness
5 is formed.

In order to move the position of the die core 24 relative to the die shell 21, although not shown, the die core 24 is provided with a relative movement mechanism, the position of which is controlled by, for example, a servomotor or the like, and the outer peripheral surface of the die core 24 is moved. 15a
The parison 15 having the thick portion 16 formed thereon and the parison 15 having a normal uniform thickness can be continuously formed, and the length of each parison 15 can be arbitrarily adjusted.

The groove 22 formed in the die shell 21 for forming the thick portion 16 on the outer peripheral surface 15a of the parison 15 is formed, for example, as shown in FIG.
4, or may be formed longer than the lower end as shown in FIG. 4, but it is usually better to form the short groove 22 at the lower end. When the parison 15 having a uniform thickness is extruded, the portion of the die shell 21 where the die core 24 is opposed to the groove 22 is long, and the thin parison 15 is prevented by preventing the resin from swelling inside the die core 24. Can be extruded.

The groove 22 formed in the die shell 21
Is not necessarily shorter than the height of the cylindrical portion 26 at the tip of the die core 24 at the lower end portion of the illustrated example, and is limited to a length longer than that of the cylindrical portion 26 at the tip of the die core 24. Not the thing, reverse the length, die core 24
May be a middle length of about several times the height of the columnar portion 26 at the tip of the above.

Such a die shell 21 and a die core 24
The parison 15 is melt-extruded by relatively moving the die core 24 in the axial direction using
The thick part 16 corresponding to the groove 22 is formed so as to protrude from the outer peripheral surface 15a, so that the parison 15 having a flat inner peripheral surface 15b can be formed. The bottle 10 can be formed at any position in the direction, and the neck 10 b and the bottom 10
d, no thick portion 16 is formed, and only the trunk portion 10a has a thick portion 1
6 can be formed as the parison 15.

Similarly, in the case of the tube 11, the thick portion 1 is added to the neck portion 10b and the heat seal portion 11c at the rear end.
The parison 15 which does not form 6 can be formed.

The method of forming the thick portion 16 by protruding from the outer peripheral surface 15a of the parison 15 is not limited to the case where the groove 22 is formed in the die shell 21 and the die core 24 is relatively moved in the axial direction. As shown in FIG. 5, radial groove portions 22 are formed from the inner peripheral end to the outer peripheral end corresponding to the portion where the thick portion 16 is formed at the tip end of the die shell 21,
A movable shell 28 is mounted in each groove 22 so as to be movable in the radial direction.
It may be fixed at a position facing the one groove 22.

When it is necessary to protrude from the outer peripheral surface 15 a of the parison 15 to form the thick portion 16, the movable shell 28 is moved radially outward to move the die lip 25.
While the groove is formed in the portion, if it is not necessary to form the thick portion 16, the movable shell 28 is moved so as to be flush with the inner peripheral surface of the die shell 21.

It is also possible to form the thick portion 16 by protruding the outer peripheral surface 15a of the parison 15 by moving only the movable shell 28 without relatively moving the die core 24 in the axial direction.

A blow gas is blown into the parison 15 in which the thick portion 16 is formed only in the necessary portion 12 of the bottle 10 or the tube 11, and the parison 15 is blow-molded into the bottle 10 or the tube 11. , Necessary reinforcement 12
The inward rib 13 can be formed integrally with the parison 15. When the blow gas is blown into the parison 15, the inner peripheral surface 15a of the parison 15 is flat.
The inward rib 13 formed by the thick portion 16 does not fall down, and the root portion of the inward rib 13 formed by the thick portion 16 does not become thin.

When the parison 15 having the thick part 16 protruding from the outer peripheral surface 15a is introduced into a pair of molds having flat cavities and blow-molded by blowing a blow gas, For example, even when the multilayer parison 15 is used, as shown in FIG. 6, since the inner peripheral surface 15a of the parison 15 is flat, the blowing pressure acts uniformly to blow the multilayer resin layer 13a substantially in parallel. At the same time as the molding, the inward rib 13 is molded so as to bulge inward corresponding to the thick portion 16. After completion of the molding, although the resin layer 13 a is slightly curved at the inward rib 13, each resin is formed. The layer 13a is substantially parallel, and the intermediate layer such as a barrier layer has a uniform thickness so that its function can be sufficiently exhibited.

On the other hand, when the thick rib 6 is formed by protruding from the inner peripheral surface of the conventional parison and the inward rib 5a is blow-molded, as shown in FIG.
The resin layer 8 may be disturbed due to the rib 5a falling down at the portion a, and the intermediate layer may be folded and overlapped. When a barrier layer is provided in the middle, a part of the intermediate layer may be thinned.

From the resin layer in the case of using such a multilayer parison, it is possible to identify the molding method even if the appearance of the product is the same.

According to the blow molding method of the hollow container having the internally reinforced inner surface, the inward rib 13 can be formed at an arbitrary position such as the hollow containers 10 and 11, and the vertical compressive strength can be improved. The inward rib 13 can be formed into a predetermined shape without bending or falling, and in a multilayer hollow container using a multilayer parison,
Disorder of the resin layer can also be prevented.

As a result, the thickness of the body of the hollow container such as the bottle 10 and the tube 11 can be reduced, and the weight and the amount of resin used can be reduced, and at the same time, the necessary vertical length required for the hollow container is obtained. Compressive strength and drop strength can be ensured, and thermal deformation can be prevented by the inward ribs 13.

Particularly, even in the case of a hollow container in which a label is mounted in a mold by an in-mold labeling method and is affixed flush with the surface of the hollow container during blow molding, the label-applied portion and the label are not attached. The necessary strength can be ensured by forming the inward ribs 13 on the inner surface of the bottle corresponding to the boundary with the portion. That is, in the case of a bottle to which an in-mold label is attached, when the bottle falls, a drop impact is applied. However, elastic deformation hardly occurs in a portion where the label is attached, and conversely, elastic deformation easily occurs in a portion where no label is attached. Due to the difference, the stress concentrates on the boundary between the label affixed portion and the non-label affixed portion, which is the corner portion of the label. This stress can be relaxed by the inward rib 13 and reinforced.

Further, according to the blow molding method for the inner surface reinforced hollow container, the inward rib 13 is not formed on the neck portion 10b of the bottle 10 to which the stopper cap is attached or the bottom portion 10d serving as the pinch-off portion of the parison 15. In addition, the inward rib 13 can be prevented from being formed in the neck portion 11b and the heat seal portion 11c of the tube 11, and the sealing performance of the neck portion and the heat seal portion of the bottle 10 and the tube 11 can be improved. At the same time, it is possible to blow the blow gas by lateral blowing with a blow pin without using a perfect circular mandrel to form the neck and the like, and there is no restriction on the shape of the neck (outlet), and it is possible to make the shape other than a perfect circle I can do it.

Further, according to the blow molding method of the hollow container having the inner surface reinforced, the rib formed on the necessary reinforcing portion 12 is the inward rib 13 and is formed by protruding inside the hollow containers 10 and 11. The outer surface is flat and has the same appearance as conventional bottles and tubes, and decoration such as printing can be applied in the same manner as before.

The plastic used as the material of such a hollow container can be any of those used in blow molding so far. Examples of such plastics include high-density polyethylene, isotactic polypropylene, and crystalline propylene. Olefin resins such as ethylene copolymers and ionomers; Styrene resins such as polystyrene and styrene-butadiene block copolymers; nitrile-butadiene-styrene resins; acrylic resins such as polymethyl methacrylate; hynitrile resins; saturated polyester resins A polyamide resin; a polycarbonate; an ethylene-vinyl alcohol copolymer; a vinyl chloride resin or a mixture thereof.

In addition to the case where these resins are composed of a single layer, the resins may be composed of multiple layers such as 2 to 7 layers.
The layer structure may be an ethylene-vinyl alcohol copolymer / olefin resin, and an adhesive layer such as an acid or acid anhydride-modified olefin resin may be interposed between these layers.

[0053]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

(Example 1) 50 m / m extruder (L / D =
22) and the melt flow rate (MFR) is 0.3
The gap between the die shell and the die core is made of high-density polyethylene having a density of 0.947 g // cm ³ and a gap of 1 mm, and a slit-shaped groove having a depth of 2 mm, a width of 3 mm and a height of 2 mm is formed at the tip of the die shell. The molten parison was formed at four locations around the periphery, the die core was moved up and down, and a thick parison was formed only on the outer peripheral surface of the body of the hollow container. This parison is blow-molded in a mold and has a mass of 15 g and a capacity of 4 g.
A 00 cc hollow container having a flat outer surface and an inward rib formed on the inner surface was obtained. The thickness distribution of the thickness of the obtained hollow container was 0.3 mm in the normal part, 1.0 mm in the thickest part of the inward rib, and the width of the inward rib was 10 mm. To evaluate the compression strength of this hollow container, a compression speed of 50
Empty bottle compressive strength was measured in mm / min. Table 1 shows the results. As is clear from the table, it can be seen that the compressive strength is sufficiently increased by the inward rib.

Example 2 50 m / m extruder (L / D =
22) and the melt flow rate (MFR) is 0.3
g / 10 minutes and a density of 0.947 g // cm ³ of high density polyethylene was supplied to the first extruder to form an innermost and outermost layer of ethylene-vinyl alcohol having an ethylene content of 32 mol% and a melting point of 185 ° C. The polymer (EVOH) was supplied to a second extruder to form an intermediate layer having a carbonyl group concentration of 40 meq / 10.
0 g of maleic anhydride-modified polyethylene was supplied to a third extruder to form an adhesive resin layer between the layers with a distance of 1 mm between the die shell and the die core, a depth of 2 mm and a width of 3 mm on the die shell.
mm, 2 mm high slit-shaped groove with the circumference of the tip 4
The molten parison having the thick part formed only on the outer peripheral surface of the body of the hollow container was extruded by moving the die core up and down. This parison was blow-molded in a mold to obtain a hollow container having a mass of 15 g, a capacity of 400 cc, and a three-type five-layer structure having a flat outer surface and inward ribs formed on the inner surface. The thickness distribution of the thickness of the obtained hollow container is 0.3 m in the normal part.
m, the thickest part of the inward rib is 1.0 mm, the width of the inward rib is 10 mm, and the thickness of each layer of the body is 120 μm for the innermost and outermost layers, 20 μm for the intermediate layer, and 20 μm for the adhesive resin layer. 20 μm (0.3 mm in total).
To evaluate the compressive strength of this hollow container, the empty bottle compressive strength was measured in the same manner as in Example 1, and the results are shown in Table 1. As is clear from the table, it can be seen that the compressive strength is sufficiently increased by the inward rib.

Comparative Example 1 Using the same extruder as in Example 1, a high-density polyethylene having a melt flow rate (MFR) of 0.3 g / 10 minutes and a density of 0.947 g // cm ³ was subjected to die shell and die core. Was set to 1 mm, and a molten parison having no thick portion was extruded. This parison was blow-molded in a mold to obtain a hollow container having a flat inner and outer surface with a mass of 15 g and a capacity of 400 cc. The thickness distribution of the thickness of the obtained hollow container was 0.4 mm in the normal part. In order to evaluate the compressive strength of this hollow container, the empty bottle compressive strength was measured in the same manner as in Example 1, and the results are shown in Table 1.
As is clear from the table, it can be seen that the empty bottle compression strength is less than half that of Examples 1 and 2.

[0057]

[Table 1]

Example 3 Using the same extruder, die shell and die core as in Example 1, a molten parison having a thick portion formed only on the outer peripheral surface of the body of the hollow container was extruded. This parison is blow-molded in a mold equipped with an in-mold label made of OPP having a thickness of 100 μm, and the outer surface having a mass of 15 g and a capacity of 400 cc is flat, and inward ribs are formed on the inner surface at the left and right of the label. The obtained hollow container was obtained. The thickness distribution of the thickness of the obtained hollow container is 0.3 mm at the normal portion, 1.0 mm at the thickest portion of the inward rib on the right and left sides of the in-mold label, and the width of the inward rib is 10 m.
m. To evaluate the drop strength of this hollow container,
Fill the container with tap water, seal the mouth, and place in a 5 ° C environment.
After storing for 4 hours or more, a low-temperature drop strength test was performed. Table 2 shows the results. As is clear from the table, the inward ribs on the left and right sides of the label can sufficiently increase the low-temperature drop strength.

(Comparative Example 2) Using the same extruder as in Example 1, a high-density polyethylene having a melt flow rate (MFR) of 0.3 g / 10 min and a density of 0.947 g // cm ³ was subjected to die shell and die core. Was set to 1 mm, and a molten parison having no thick portion was extruded. This parison is blow-molded in a mold equipped with an in-mold label made of OPP having a thickness of 100 μm, and has a mass of 15 g and a capacity of 400 c.
The hollow container of c was obtained.厚 み The thickness distribution of the thickness of the obtained hollow container was 0.4 mm in the normal part. In order to evaluate the drop strength of the hollow container, a low-temperature drop strength test was performed in the same manner as in Example 3, and the results are shown in Table 2. As is clear from the table, it is found that sufficient low-temperature drop strength cannot be obtained.

[0060]

[Table 2]

[0061]

According to the method for blow-molding an internally reinforced hollow container according to the first aspect of the present invention, plastic is melt-extruded into a parison shape through a die as described above in detail with reference to one embodiment. When blowing a blow gas into the inside of a closed parison to blow-mold a hollow container having a reinforcing portion on the inner surface, a thick portion is formed by protruding from the outer peripheral surface of the parison corresponding only to the reinforcing portion of the hollow container. Then, since the blow gas is blown into the flat inner peripheral surface of the parison to form a hollow container having a reinforcing portion formed on the inner surface, a rib is formed on the inner surface by the thick portion on the outer peripheral surface. As a parison having a flat inner peripheral surface, the blow gas can be uniformly applied, the irregularity of the ribs can be prevented, and the internally reinforced hollow container which does not cause the resin layer to be disturbed can be blow molded. Can.

Thus, the hollow container can be made thinner to reduce the weight and the amount of resin used, and at the same time, the necessary strength can be secured.

Further, since no inward ribs are formed at portions other than the portions requiring reinforcement, there is no need to regulate the shape of the neck portion with a mandrel, and the degree of freedom of the shape can be increased.

Further, according to the blow molding method of the inner surface reinforced hollow container according to the second aspect of the present invention, the thick portion protruding from the outer peripheral surface of the parison is formed into a thick portion formed in a die shell. Since the die core is moved in the axial direction relatively to the groove that can be formed, the thick part protruding on the outer periphery of the parison can be easily formed simply by moving the die core relative to the die shell in the axial direction. Can be formed.

Further, according to the blow molding method for an internally reinforced hollow container according to a third aspect of the present invention, the hollow container is a bottle, and the thick portion is formed on the parison corresponding to at least a neck portion of the bottle. Since the blow molding is performed without performing the above, it is possible to blow mold a plastic bottle having no reinforcing rib at the neck portion, thereby eliminating waste of resin and improving sealing performance.

Further, according to the blow molding method for an inner surface reinforced hollow container according to a fourth aspect of the present invention, the hollow container is a tube, and at least the rear end of the tube corresponds to the heat-sealed portion after filling the contents. Since the parison is blow-molded without forming the thick portion, a plastic tube without a rib for reinforcement can be blow-molded at the bottom heat-sealed portion, eliminating waste of resin and sealing performance. Can be improved.

Further, according to the blow molding method for an internally reinforced hollow container according to the fifth aspect of the present invention, the parison is a multilayer parison, and the resin layer in the cross section of the internal reinforcement portion of the hollow container is formed by the multilayer parison. Since the blow molding is performed so that it is almost parallel, the thick part formed by projecting to the outer peripheral side of the parison can be molded by the uniform blow pressure applied to the inner surface of the parison, and the multilayer resin layer Can be blow-molded into a hollow container having a uniform thickness and a reinforcing portion protruding from the inner surface while being substantially parallel to each other, so that the resin layer is not disturbed and the barrier layer and the like can be formed to a uniform thickness.

Further, according to the blow molding apparatus for an inner surface reinforced hollow container according to the sixth aspect of the present invention, plastic is melt-extruded through a die into a parison shape, and blown gas is blown into the inside of the closed parison to reinforce the inner surface. Apparatus for blow-molding a hollow container provided with a part, a die shell having a groove capable of forming a thick part in the parison, and a die shell and a die shell which are relatively axially moved to form the hollow. A relative movement mechanism that protrudes from the outer peripheral surface of the parison corresponding to only the necessary reinforcement portion of the container to form a thick portion, and the blow gas is blown into the flat inner peripheral surface of the parison to form a reinforcing portion on the inner surface. Since the hollow container formed is molded, a parison having a thick inner portion protruding from the outer peripheral surface and having a flat inner peripheral surface can be formed. Uniformly allowed to act over a gas by forming the ribs on the inner surface, can be prevented ribs irregularities, the inner surface reinforcing hollow container does not occur disturbance of the resin layer can be blown.

[Brief description of the drawings]

FIG. 1 is a perspective view of a bottle which is a hollow container to be molded according to an embodiment of a blow molding method and an apparatus for an internally reinforced hollow container of the present invention, and a partially enlarged view and a partially enlarged sectional view of each part. .

FIG. 2 is a perspective view of a tube, which is a hollow container to be molded, and a partially enlarged view of each part according to an embodiment of a method and an apparatus for blow molding an internally reinforced hollow container of the present invention.

FIGS. 3A and 3B are cross-sectional views of a die shell and a die core according to an embodiment of a method and a device for blow molding an inner surface reinforced hollow container of the present invention, wherein FIG. 3A is a cross section of a groove portion of the die shell, and FIG. When not extruding the thick part, (c)
Indicates a case where a thick portion is extruded.

FIG. 4 is a cross-sectional view of a die shell and a die core according to another embodiment of the blow molding method and the apparatus for the internally reinforced hollow container of the present invention, wherein (a) shows a case where a thick portion is not extruded. b) shows a case where a thick portion is extruded.

FIG. 5 is a cross-sectional view of a die shell and a die core according to still another embodiment of the blow molding method and the apparatus for the internally reinforced hollow container of the present invention, wherein (a) shows a cross section of a groove portion of the die shell; b) shows the case where the thick part is not extruded, and (c) shows the case where the thick part is extruded.

FIG. 6 is an enlarged partial cross-sectional view of a part of the parison and the hollow container according to one embodiment of the method and the apparatus for blow molding an inner surface reinforced hollow container of the present invention.

FIG. 7 is a schematic sectional view of a conventional blow molding apparatus.

8A and 8B are cross-sectional views of a die shell and a die core according to a conventional blow molding method of a hollow container having a reinforcing rib on an inner surface, where FIG. 8A shows a cross section of a groove portion of the die shell, and FIG. (C) shows the case where the thick part is not extruded.

FIG. 9 is an enlarged partial cross-sectional view showing a parison and a part of a hollow container according to a conventional blow molding method for a hollow container having a reinforcing rib on an inner surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Bottle (hollow container) 10a Body 10b Neck 10c Shoulder 10d Bottom 11 Tube (Hollow container) 11a Body 11b Neck 11c Heat seal part 12 Reinforcement required part 12a Inner four corners 12b Shoulder inner surface 12c Label back surface 12d Tube inner surface 13 inward rib 14 label 15 parison 15a outer peripheral surface 15b inner peripheral surface 16 thick portion 20 die 21 die shell 22 groove portion 23 die passage 24 die core 25 die lip 26 cylindrical portion 27 conical portion 28 conical portion 28 movable shell

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29L 22:00 B65D 1/00 C (72) Inventor Tsuyoshi Saito 2-206 Nishitobe-cho, Nishi-ku, Yokohama-shi, Kanagawa F-term (reference) 3E033 AA01 BA13 CA02 DB01 DD01 EA01 EA04 FA03 4F208 AG03 AG07 AG22 AG25 AG28 AH55 LA01 LB01 LB22 LG06 LG14 LG19 LG22

Claims (6)

[Claims] 1. A method in which a plastic is melt-extruded through a die into a parison shape, and a blow gas is blown into a closed parison to blow-mold a hollow container having a reinforcing portion on an inner surface. Only the corresponding parison protrudes from the outer peripheral surface to form a thick portion, and the blow gas is blown into the flat inner peripheral surface of the parison to form a hollow container having a reinforcing portion formed on the inner surface. A blow molding method for a hollow container with a reinforced inner surface. 2. The method according to claim 1, wherein the thick portion protruding from the outer peripheral surface of the parison is formed by moving a die core in an axial direction relatively to a groove portion capable of forming a thick portion formed in a die shell. The blow molding method for an internally reinforced hollow container according to claim 1, wherein: 3. The bottle according to claim 1, wherein the hollow container is a bottle, and the parison corresponding to at least a neck portion of the bottle is blow-molded without forming the thick portion. Blow molding method of hollow container with inner reinforcement. 4. The method according to claim 4, wherein the hollow container is a tube, and the parison corresponding to a heat-sealed portion of at least the rear end of the tube after filling the contents is blow-formed without forming the thick portion. The blow molding method for an internally reinforced hollow container according to claim 1 or 2, wherein: 5. The multi-layer parison according to claim 1, wherein said parison is blow-molded so that a resin layer in a cross section of an inner surface reinforcing portion of said hollow container is substantially parallel. 5. The blow molding method for an internally reinforced hollow container according to any one of items 4 to 4. 6. An apparatus for melt-extruding a plastic into a parison through a die and blowing a blow gas into a closed parison to blow-mold a hollow container having a reinforcing portion on an inner surface, comprising: a die core; A die shell having a groove portion capable of forming a thick portion, and moving the die core and the die shell relative to each other in the axial direction to project on the outer peripheral surface of the parison corresponding only to the reinforcement necessary portion of the hollow container to form a thick portion. And a relative movement mechanism for forming
A blow molding apparatus for an internally reinforced hollow container, wherein the blow gas is blown into a flat inner peripheral surface of the parison to form a hollow container having a reinforcing portion formed on the inner surface.