JPH1128761A - Sprueless container and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sprueless container formed with a flat bottom and uniform thickness in the container obtained by injection orientation blow molding of a hot parison, and a method for manufacturing it. SOLUTION: The container is manufactured by injection molding of a parison 7A with a bottom without sprue, and then orientation blowing of the obtained parison 7A in a high temperature as it is in such a manner that the maximum thickness at the bottom is 100 to 300% of the minimum thickness. And, the method for manufacturing the container uses an injection mold having a nozzle member 4 mounted at a position corresponding to the bottom of the parison 7A of a cavity 15 in a cavity mold 1, a gate 42 provided at a flat end face of the member 4, and a shut-off pin 43 internally mounted in a resin channel 47 of the nozzle member to seal the gate 42 in the same planar state as the end face of the member 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sprueless container and a method for manufacturing the same, and more particularly, to a container manufactured by stretch-blowing an injection-molded hot bottom parison without a sprue. The present invention relates to a sprueless container having almost no trace of resin injected into the sprueless container and having a flat bottom and a uniform thickness, and a method for manufacturing the sprueless container.

[0002]

2. Description of the Related Art For example, certain pharmaceuticals are produced by freeze-drying in a bottle-shaped small container. The container used in such an application is manufactured by further subjecting a bottomed parison obtained by injection molding a transparent resin to stretch blow molding. FIG. 6 is a longitudinal sectional view of a bottomed parison used for conventional stretch blow molding and a container molded from the parison.

In stretch blow molding of a container with a bottomed parison, first, a parison (8A) as shown in FIG. 6A is injection-molded using a usual injection mold. In the manufactured parison (8A), the sprue (84) protrudes from the lower surface of the bottom (82a) by the injection operation from the bottom surface side. Then, in order to improve the finish of the container as the final molded product, the sprue (84)
Are cut or crushed appropriately in a soft state immediately after injection molding. Then the shaped parison (8
A) is charged into a blow mold having a cavity of the final shape, stretch-blown and formed into a container (8B) as shown in FIG. 6 (b).

[0004]

In the container (8B) manufactured by the above manufacturing method, the parison (8A)
Since the part of the sprue (84) remaining at the center of the bottom of the bottom (82b) is forcibly crushed by the stretch rod during blow molding, the thickness of the bottom (82b) is not uniform. The center is thin and the periphery is thick. As a result, when the container (8B) is used for freeze-drying or the like, there is a problem that a uniform frozen state cannot be obtained in the container (8B).

By the way, when a flat and bottom part having a uniform thickness is formed in the final container, it is desirable to previously injection-mold a parison without sprue. A parison without a sprue can be molded to some extent by employing an extension nozzle type injection mold, a well type injection mold, a pin point gate, or the like.

However, in the case of the extended nozzle type or well type injection molding die, a mechanism for performing nozzle touch and a heating mechanism for maintaining the temperature of the gate portion are required, and the structure of the die is further complicated. In addition, there is a problem that the resin adheres to the gate portion. Further, in the case of a pinpoint gate, a problem of clogging occurs with resins other than polyethylene. Therefore, any of these methods has a problem in continuous operation for a long time, and is difficult to use industrially.

The present invention has been made as a result of various studies on a method for continuously producing a sprueless container by using a mold having a simpler structure. Another object of the present invention is to provide a sprueless container having a flat bottom and a uniform thickness, and a method of manufacturing the sprueless container. Another object of the present invention is to provide a sprueless container having excellent heat resistance that can sufficiently withstand heat treatment in pretreatment for freeze-drying or the like.

[0008]

That is, the present invention comprises two aspects. The first aspect is that a parison having no sprue and having a bottom is injection-molded and then the obtained parison is stretched in a high temperature state. A container manufactured by blowing,
A sprueless container characterized in that the maximum thickness at the bottom is 100 to 300% of the minimum thickness.

The above-mentioned container is preferably made of a heat-resistant resin so that it can be used for heat treatment.

[0010] A second aspect of the present invention is the above-mentioned method for manufacturing a container, wherein a cavity mold having the same shape as a parison is formed as a mold for injection molding in cooperation with a core mold. And a nozzle member mounted at a position corresponding to the parison bottom surface of the cavity with respect to the cavity mold, wherein the nozzle member is provided with a gate on a flat end surface, and the nozzle member The present invention provides a method for manufacturing a sprueless container, characterized in that a mold in which a shutoff pin capable of sealing the gate is provided in the same plane as the front end surface is used for the resin flow path.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a main part of an injection molding die used for manufacturing a bottomed parison in an injection molding process. FIG. 2 is a longitudinal sectional view showing a gate portion of the injection molding die in FIG. 1, and FIG. 3 is a longitudinal sectional view similar to FIG. 2 showing an injection operation. FIG. 4 is a longitudinal sectional view showing a main part of a blow molding die used for manufacturing a container in the blow molding step. FIG. 5 is a longitudinal sectional view of a bottomed parison as a precursor and a longitudinal sectional view of a container as a final molded product. Hereinafter, in the description of the embodiment, a sprueless container is abbreviated as a “container”, and a method for manufacturing a sprueless container is abbreviated as a “manufacturing method”.

First, the container of the present invention will be described with reference to FIG. As shown in FIG. 5 (a) by reference numeral (7B), the container of the present invention has a bottomed parison (7
A) (see FIG. 5 (b)) is a container produced by subjecting the obtained parison (7A) to stretch-blowing in a high-temperature state by injection molding after injection-molding (see FIG. 5 (b)), wherein the bottom (72b) is flat and It is formed with a uniform thickness. That is, the container (7
In B), the maximum thickness (t) at the bottom (72b) is 100 to 300% of the minimum thickness.

Specifically, for example, the height of the container (7B) is about 45 to 200 mm, and the diameter of the body (71b) is about 20 mm.
~ 90mm, thickness of bottom (72b) is about 0.5 ~ 1.5
mm, and the maximum thickness of the bottom (72b) is about 1.0 to
3.0 mm and the minimum thickness is about 0.3 to 1.5 mm. Moreover, it is preferable that the bottom part (72b) is recessed inside by 0 to 2.0 mm. These dimensional specifications are set according to the specifications of the mold described later. The state in which substantially no sprue is present on the bottom surface of the parison (7A) refers to a state in which the height of a protrusion as a trace of the gate (42) is 0.5 mm or less.

As the resin constituting the container (7B) of the present invention, general resins such as polypropylene and polyethylene terephthalate may be used, but from the viewpoint of heat resistance, polycarbonate, polybutylene terephthalate,
Heat resistant resins such as polyethylene naphthalate, polyphenylene sulfide, cyclic polyolefin resin, polyphenylene resin or wholly aromatic polyester resin are preferred. Containers (7) made of these heat-resistant resins
B) exhibits excellent heat resistance under a temperature condition exceeding 100 to 120 ° C.

As the polyphenylene resin or wholly aromatic polyester resin, various commercially available resins can be used. As the cyclic polyolefin resin, "Apel" manufactured by Mitsui Petrochemical Co., Ltd., Daikyo Rubber Seiko Co., Ltd. “DAIKYO Resin CZ” manufactured by Nippon Synthetic Rubber Co., Ltd., and “ARTON” manufactured by Nippon Synthetic Rubber Co., Ltd.

Since the container (7B) of the present invention has almost no trace of the resin injected to the bottom side and the bottom (72b) is formed in a flat and uniform thickness, it was used for freeze-drying or the like. In this case, a uniform freezing process can be performed, and a better storage state of the contents can be realized. Furthermore, since the container (7B) of the present invention composed of the above specific resin material has high heat resistance, heat treatment at a higher temperature is possible in sterilization treatment or the like as a pretreatment for freeze-drying. .

Next, the manufacturing method of the present invention will be described. The production method of the present invention is a stretch blow method using a hot parison. In the injection molding step, a bottomed parison (7A) (see FIG. 5 (a)) is formed by an injection molding die as shown in FIG. After the production, in a blow molding step, the parison (7A) is blow-molded with a blow molding die as shown in FIG. 4 to produce a container (7B) (see FIG. 5 (b)). In the hot parison method, usually, a mold for injection molding and a mold for blow molding are arranged in combination in one mold apparatus or a molding line.

First, the parison (7) in the injection molding process
The production method A) will be described. In the production of the parison (7A), a mold for injection molding shown in FIG. 1 is used. Such a mold for injection molding mainly comprises a cavity mold (1), a neck mold (2), a core mold (3) and a nozzle member (4). The neck mold (2) is arranged as a common member of the blow molding mold.

Cavity mold of injection mold (1)
A main body (11) having a substantially cylindrical space for forming a cavity (15) therein, as shown in FIG. 1;
Bottom plate (12) arranged at one end (lower end) of main body (11)
It is composed of One end surface (upper end surface) of the bottom plate (12) on the side of the main body (11) is provided with a flat bottom concave portion having a shape corresponding to the bottom of the parison (7A).

Further, the bottom plate (1) opposite to the main body (11) is provided.
On the other end surface (lower end surface) of 2), a nozzle mounting hole (17) with which the nozzle member (4) is engaged is formed coaxially with the space. The nozzle mounting hole (17) is a space whose diameter is gradually reduced toward the main body (11) side, and has a gate port opening at the deepest end thereof on the upper end surface of the bottom plate (12) on the concave side. (16) An (opening) is provided. In addition, inside the main body (11) and the bottom plate (12), a flow path (13) for the temperature control medium is provided so as to surround the space of the main body (11) and the nozzle mounting hole (17), respectively.

The neck mold (2) is a mold for forming the neck (73) (see FIG. 5) of the parison (7A) and for holding the molded parison (7A), and the body (11).
It is arranged so as to be able to abut on the upper end of the. The neck mold (2) is formed in a substantially bottomed cylindrical shape, and has a bottom portion through which a part of the core mold (3) can be inserted and whose inner peripheral shape matches the outer peripheral shape of the neck portion (73). Neck forming holes (2
3) is opened coaxially with the space of the main body (11).

The neck mold (2) is configured to be able to approach and separate from the main body (11) by a separately provided moving mechanism for transferring the formed parison (7A) to a blow molding mold. Is done. In addition, the neck mold (2) has a two-part structure and is provided with a separately provided cylinder device to move the two members in the left-right direction in order to open the molded container (7B) in a mold opening operation in a blow molding step described later. It can be approached and separated.

The core mold (3) is a mold formed by projecting a core (35) forming the inner surface shape of the parison (7A) from a substantially cylindrical core block (32). An enlarged diameter portion (33) is provided at the base end. Further, inside the core (35), a flow path (14) of a temperature control medium for controlling the temperature of the surface of the core (35) is provided. The core mold (3) is provided by a separately provided cylinder device.
It is configured to be removable in the neck type (2) cylinder.

In the core mold (3), the core block (62) is fitted into the neck mold (2) by the mold closing operation, and the core (35) is connected to the neck at the bottom of the neck mold (2). A cavity (15) for projecting from the forming hole (23), entering the space of the main body (11), and forming a bottom (72a) of the parison (7A) with the bottom plate (12); A cavity (15) for forming the body (71a) of the parison (7A) is formed between the cavity and the inner wall of (11). The enlarged diameter portion (33) of the core (35) is provided with a cavity (15) for forming a neck portion (73) of a parison (7A) between the neck mold (2) and a neck forming hole (23) at the bottom. Is configured.

The cavity (15) is defined by the space of the body (11) and the dimensions of the core (35).
For example, in the case of the above-mentioned specification size of the container (7B), the size of the cavity (15) is about 25 to 130 mm in height and the part corresponding to the trunk (71a) based on the design conditions of the parison (7A). Diameter about 9-50mm, trunk (71a)
Is about 2.5 to 7.0 mm, and the gap distance of the part corresponding to the bottom (72a) is about 1 to 3 mm.
And the diameter of the gate opening (16) is about 3 to
10 mm.

The nozzle member (4) is engaged with a nozzle mounting hole (17) formed in the lower end surface of the bottom plate (12).
It is a flat nozzle whose diameter is reduced stepwise toward the distal end portion (41) and whose distal end surface is formed flat.
The tip (41) of the nozzle member (4) fits into the gate opening (16) of the bottom plate (12).

The tip portion (4) is provided inside the nozzle member (4).
A resin flow path (47) is formed along the axis of the nozzle member toward the gate (42) (nozzle port) opened in 1). The resin flow path (47) is sharply narrowed on the gate (42) side, and a shut-off pin (43) (shut-off mechanism) is provided inside the resin flow path (47) so as to be able to advance and retreat along an axis. Is done.

The distal end side of the shut-off pin (43) is formed in a taper having the same diameter as the constricted portion of the resin flow path (47), and the distal end face of the shut-off pin (43) has a distal end (41). (41)
And a flat surface for sealing the gate (42) in the same plane as the end surface of the gate. As an operation mechanism of such a shut-off pin (43), a mechanism for moving back and forth inside the nozzle member (4) by a separately provided cylinder device to open and close the gate (42) or a resin flow path (47) is provided. A pilot-type mechanism for opening the gate (42) by the applied injection pressure is employed.

The nozzle member (4) is screwed into a cylinder of the nozzle holder (45), and is connected to the nozzle holder (45).
Is held by a cylindrical hot runner block (44) disposed coaxially with the main body at the lower end side of the main body (11). In addition, the tip side of the nozzle member (4) is screwed into a screw portion formed on the inner periphery of the nozzle mounting hole (17) of the bottom plate (12). That is, the nozzle member (4)
The mounting position with respect to the nozzle mounting hole (17) can be finely adjusted. The resin flow path (4) of the nozzle member (4)
7) is connected to an injection device for supplying a molten resin.

Incidentally, a mold for injection molding is designed in consideration of a change in volume due to heat because the temperature of the mold is raised by the injected molten resin. That is, the nozzle member (4)
It needs to be assembled at a specific position with respect to the bottom plate (12). Specifically, as shown in FIG. 2, the nozzle member (4)
Indicates that the tip end surface of the nozzle member (4) has receded a predetermined distance from the position corresponding to the bottom of the cavity (15) (the bottom surface of the concave portion of the bottom plate (12)) with respect to the nozzle mounting hole (17) of the bottom plate (12). It is attached so that it becomes a position (down position).

In other words, the tip portion (41) of the nozzle member (4) is positioned at a position where the step (18) is minimized at the gate opening (16) of the bottom plate (12) in anticipation of the amount of expansion due to thermal expansion. Placed in Such a step (18) is
Based on the melting temperature condition of the injection material, for example, under the above dimensional conditions, it is set in the range of about 0.5 to -1.0 mm. With such a configuration, the swelling amount (swelling height) from the gate port (16) on the bottom surface is -0.5 to 1.0.
mm parison (7A) is molded. The state in which the swelling amount is -0.5 mm refers to a state in which the bulge is recessed by 0.5 mm.

In the above mold for injection molding, FIG.
In a mold closed state as shown in FIG. 2, that is, after forming the cavity (15) by inserting the core (35) of the core mold (3) into the cavity mold (1), FIG.
As shown in the figure, the shut-off pin (4) of the nozzle member (4)
By retracting 3), the gate (42) is opened and the injection operation is performed.

When the molten resin is supplied from the injection device to the nozzle member (4), the tip (41) of the nozzle member (4) is
The cavity (15) is filled with the molten resin through the gate (42), and the tip portion (41) itself thermally expands and extends toward the cavity, and the tip surface of the nozzle member (4) is It reaches the bottom surface of (15) (the bottom surface of the concave portion of the bottom plate (12)). That is, the tip (41)
Due to its thermal expansion, the step (18) is filled and completely enters the gate opening (16), and the central portion at the bottom of the cavity (15) is made as flat as possible.

Next, when the shut-off pin (43) is advanced simultaneously with the end of the injection operation, the tip of the shut-off pin (43) seals the gate (42),
The nozzle member (4) is flush with the tip end surface. That is, when the gate (42) is closed by the tip of the shut-off pin (43), the tip end surface of the nozzle member (4) forms a flat surface. As a result, a parison (7A) having a smooth bottom surface without sprues can be manufactured.

When the parison (7A) is formed in the cavity (15), the periphery of the space (cavity (15)) of the main body (11) is heated by the temperature control medium flowing through the flow path (13). Tuned, body (11)
Cools the surface of the parison (7A) at the same time as molding and shrinks it slightly. Therefore, the parison (7A) can be easily removed from the cavity mold (1) by the retreat operation (elevation operation) of the neck mold (2) and the core mold (3).

That is, in the operation of discharging the parison (7A) from the cavity mold (1), when the neck mold (2) and the core mold (3) are separated from the cavity mold (1), the parison (7) is moved as described above. (7A) slightly shrinks, and the neck forming hole (23) of the neck mold (2) holds the neck of the formed parison (7A). From the cavity mold (1).

On the other hand, the core (35) of the core mold (3) is cooled by the temperature control path 14 provided therein, so that the core (35) simultaneously forms the inner surface of the parison (7A) with the molding. Cool and shrink slightly. Therefore, after pulling out the parison (7A) from the cavity mold (1), the rise of the neck mold (2) is stopped, and when the core mold (3) is further raised, the parison (7A) is pulled out of the core (35). Can be relatively extracted. Next, the neck mold (2) immediately transfers the held parison (7A) to the next blow molding step by rotating the neck mold (2).

Subsequently, the container (7) in the blow molding step
The production method B) will be described. In the blow molding process,
A mold for blow molding shown in FIG. 4 is used. Such a mold for blow molding mainly includes a blow mold (5), the neck mold (2), and a blow core (6).

The blow mold (5) includes a pair of split molds (51, 51) arranged on a pedestal (53) and a pedestal (5).
3) and a bottom mold (52) disposed between the split molds (51, 51). Split mold (51, 51)
When these are integrated, a blow cavity (55) having a shape corresponding to the outer shape of the container (7B) is formed inside. The blow cavity (55) is a portion for molding a portion below the trunk (71b) of the container (7B) shown in FIG. 5B. Inside each split mold (51), a flow path of a temperature control medium is provided (not shown) for cooling a molded product in the blow cavity (55) at the time of blow molding.
The split molds (51, 51) are configured to be able to approach and separate from each other by the cylinder devices arranged on the left and right.

The bottom mold (52) is a cylindrical mold protruding from the pedestal (53) and constituting a part of the bottom of the split molds (51, 51). That is, the bottom mold (52) forms a portion of the blow cavity (55) corresponding to a substantially central portion of the bottom (72b) of the container (7B). The bottom mold (52) is configured to be vertically movable by a separately provided cylinder device in order to adjust the flatness of the bottom surface of the container (7B) to be molded. With such a function of the bottom mold (52), the bottom surface of the container (7B) can be formed flat, or the central portion of the bottom surface can be slightly recessed inside.

The neck mold (2) used in the injection molding mold is mounted on the blow molding mold. Like the mold for injection molding, the neck mold (2) is blow-molded (5) by the moving mechanism separately provided.
It is configured to be able to approach and separate from. Then, the blow core (6) is incorporated in the neck mold (2).

The blow core (6) is a member for extending the parison (7A) vertically and horizontally in the blow cavity (55), and comprises a substantially cylindrical core block (62) and an elongated rod extended from the core block (62). (65). At the lower end of the core block (62), there is provided a projection (63) that fits hermetically with the inner periphery of the neck (73) of the parison (7A) held by the neck mold (2). And inside the core block (62),
A gas supply path (64) for supplying a pressurized gas from the protrusion (63) to the inside of the parison (7A) is provided.

The blow core (6) is configured to be detachable in a neck type (2) cylinder by a separately provided cylinder device. The extension rod (65) is provided with a pressing member having a shape corresponding to the inner surface of the bottom (72a) of the parison (7A) at the tip, and can press the bottom (72a) of the parison (7A) by advancing and retracting the cylinder device. Has been made. The blow core (6) fits inside the neck mold (2) during the mold closing operation, and the protrusion (63).
Abuts against and seals the neck (73) of the parison (7A) and the extension rod (65) is adapted to extend to the bottom (72a) of the parison (7A).

In the blow molding die, FIG.
The blow molding is performed in the mold closed state as shown in FIG. That is, first, after the blow cavity (55) is formed by the blow mold (5), the neck mold (2) is brought into contact with the end face of the blow mold (5), and the parison (7A) is placed in the blow cavity (55). ) Hold. And neck type (2)
The blow core (6) is lowered via the
Against the neck (73) and the extension rod (65) is advanced into the parison (7A).

Next, while extending the stretching rod (65), pressurized gas is supplied into the parison (7A) through the gas supply path (64). The stretching rod (65) presses the bottom (72a) of the parison (7A) and stretches it in the axial direction. The pressurized gas blown from the lower end of the blow core (6) causes the parison (7A) to move in the radial direction. Stretch.
On the other hand, the blow cavity (55) in the blow mold (5)
Regulates a three-dimensionally stretched parison (7A),
The outer shape is made to follow the blow cavity. Further, at the time of stretching, the bottom mold (52) holds the parison (7) to be stretched.
The bottom shape of A) is defined.

As a result, the parison (7A) has a thin body (71b) and a bottom (72b) having a flat and uniform thickness without sprue projections at the center of the lower surface.
B) is formed. When the tip surface of the bottom mold (52) is slightly projected inside the blow cavity (55),
On the bottom surface of the formed container (7B), an annular ground surface is formed in which the center portion is slightly receded inward. Container (7B)
The amount of depression (T) (retreat amount) from the ground surface on the bottom surface of the container is 0 to 2.0 mm, preferably about 0.1 to 0.3 mm for a container having an internal volume of 10 to 30 ml. Is 1.0 for a 300-500 ml container.
It is about 2.0 mm.

When the container (7B) is molded in the blow cavity (55), the periphery of the blow cavity (55) is controlled by the temperature control medium inserted into the flow path of the split molds (51, 51). Cooled and split mold (5
1, 51) simultaneously cools the surface of the container (7B) and fixes the shape.

Therefore, after the blow molding, the split molds (51, 51) are separated from each other to separate the neck mold (2) from the blow mold (5).
From the blow cavity (55). Next, for the neck mold (2), the blow core (6)
Is raised, the protrusion (63) and the extension rod (6)
The container (7B) can be relatively pulled out from 5). Then, when the neck mold (2) is divided, the neck (7) of the container (7B) gripped by the neck mold (2) is moved.
3) is opened, and the container (7B) can be completely removed.

As described above, the mold for injection molding used in the present invention is a parison (7A) which cooperates with the core mold (3).
And a nozzle member (4) mounted at a position corresponding to the bottom surface of the parison (7A) of the cavity (15) with respect to the cavity mold (1). And a nozzle member (4)
Is formed by providing a gate (42) on a flat front end surface, and a gate (42) is provided in the resin flow path (47) of the nozzle member (4) in the same plane as the front end surface. Since the shutoff pin (47) that can be sealed is provided, the parison (7A) having a smooth bottom surface without sprue protrusions can be manufactured in the manufacturing method of the present invention.

Further, in the above-described injection mold, the nozzle member (4) is different from the cavity mold (1) in that
In consideration of expansion and contraction due to temperature change, a predetermined step (18) is provided in advance between a position corresponding to the bottom surface of the parison (7A) of the cavity (15) and the tip end surface of the nozzle member (4). I have.

That is, in the container manufacturing method of the present invention, in the injection molding step, the above-described specific injection molding die is used, and the bottomed parison having a smooth bottom surface from which sprues do not substantially project. 7A), and in the blow molding step, a bottom mold (52) having a flat tip is arranged at the bottom of the blow cavity (55) to form a parison (7).
Since the blow molding of A) is performed, there is almost no trace of the injected resin on the bottom side, and the container (7B) having a flat bottom (72b) and a uniform thickness can be manufactured.

In the injection molding die, when the gate (42) is closed, the nozzle member (4) is separated from the bottom of the cavity (15) by a certain distance due to the contraction of the nozzle member (4). And the inside of the nozzle member (4)
Since the gate (42) is always heated by the molten resin supplied to the resin flow path (47) and the gate (42) is sealed by the high-temperature shut-off pin (43), the resin in the gate (42) is not fixed. And continuous operation for a long time is possible. Therefore, according to the manufacturing method of the present invention, a large number of sprueless containers (7B) can be manufactured continuously.

[0053]

According to the sprueless container of the present invention, since there is almost no trace of the injected resin on the bottom side and the bottom is formed in a flat and uniform thickness, it can be used for freeze-drying or the like. A uniform freezing process can be performed, and a more favorable storage state of the contents can be realized. Furthermore, the container of the present invention composed of the specific resin material described above has a high heat resistance, so that in a sterilization treatment or the like as a pretreatment for freeze-drying,
Heat treatment at a higher temperature is possible.

According to the sprueless container manufacturing method of the present invention, the nozzle member is mounted at a position corresponding to the parison bottom surface of the cavity, and the flat tip surface of the nozzle member is flush with the tip surface. The bottomed parison is manufactured using a specific injection mold with a sealable gate, so that a parison with a smooth bottom without sprue protrusions can be manufactured, resulting in an injection on the bottom side A sprueless container having a flat bottom and a uniform thickness can be manufactured with almost no trace of the resin formed.

According to the method of manufacturing a sprueless container of the present invention, in the above-described injection mold, the tip end surface of the nozzle member is disposed so as to be able to reach a position substantially corresponding to the bottom surface of the parison of the cavity. Since there is no sticking of the resin at the gate and continuous operation for a long time is possible, a large number of sprueless containers can be manufactured continuously.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a main part of an injection mold used for manufacturing a bottomed parison in an injection molding process.

FIG. 2 is a longitudinal sectional view showing a gate portion of the injection molding die in FIG. 1;

FIG. 3 is a longitudinal sectional view similar to FIG. 2 showing an injection operation;

FIG. 4 is a longitudinal sectional view showing a main part of a blow molding die used for manufacturing a container in a blow molding process.

FIG. 5 is a longitudinal sectional view of a bottomed parison as a precursor and a longitudinal sectional view of a container as a final molded product.

FIG. 6 is a longitudinal sectional view of a bottomed parison used for conventional stretch blow molding and a container molded from the parison.

[Explanation of symbols]

 1: Cavity mold 11: Main body 12: Bottom plate 15: Cavity 16: Gate opening 17: Nozzle mounting hole 2: Neck mold 23: Neck forming hole 3: Core mold 32: Core block 35: Core 4: Nozzle member 42: Gate 43 : Shut-off pin 47: resin flow path 5: blow mold 51: split mold 52: bottom mold 55: blow cavity 7A: bottomed parison 7B: sprueless container T: recess amount

Claims (5)

[Claims] 1. A container manufactured by injection-molding a parison having a bottom without a sprue and stretch-blowing the obtained parison in a high temperature state, wherein the maximum thickness at the bottom is 100% of the minimum thickness. -300%. 2. The method according to claim 1, wherein the bottom surface has a concave shape, and the concave amount from the ground contact surface is set to 0 to 2.0 mm.
A sprueless container according to item 1. 3. The method according to claim 1, wherein the heat-resistant resin is used.
Or the sprueless container according to 2. 4. The method for manufacturing a container according to claim 1, wherein a cavity having the same shape as the parison is formed as a mold for injection molding in cooperation with a core mold. And a nozzle member mounted at a position corresponding to the parison bottom surface of the cavity with respect to the cavity mold, wherein the nozzle member is provided with a gate on a flat end surface, and the nozzle member A method for manufacturing a sprueless container, characterized in that a mold having a shut-off pin capable of sealing the gate in the same plane as the front end surface is used for the resin flow path. 5. The amount of swelling from the gate opening on the bottom surface is-
5. A parison of 0.5 to 1.0 mm is injection molded.
3. The method for producing a sprueless container according to item 1.