JPH0449450B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method and apparatus for manufacturing plastic containers by injection blow molding. The present invention relates to a method and apparatus for manufacturing plastic containers having uniform wall thickness and no uneven thickness by using the same apparatus (within the same apparatus).

(Prior Art and Technical Problems of the Invention) Stretch blow-molded containers made of polyethylene terephthalate, etc. have molecular orientation on the container wall, and therefore have excellent impact resistance, moderate rigidity, and transparency. Widely used as plastic bottles for filling contents.

In manufacturing a stretched plastic container, a bottomed preform is first manufactured by injection molding plastic, and this preform is stretched in the axial direction and expanded and stretched in the circumferential direction by blowing fluid. The preform to be formed needs to be in an amorphous state, and at the time of stretch blow molding, it needs to be at the stretch molding temperature.

Conventionally, this has been achieved using a two-stage method, in which the preform is supercooled to an amorphous state during injection molding, then the preform is preheated to the stretch molding temperature, and then blow molded in a separate device; A one-stage method is known in which the temperature of the preform is slightly adjusted without excessively cooling it, and then blow molding is performed in the same device.

Among these methods, the one-stage method requires a small equipment footprint and is advantageous in terms of thermal efficiency and productivity, but it tends to cause temperature unevenness in the preform before stretch blowing, and this temperature unevenness can cause problems in the final plastic. There is a problem in that the bottle tends to have a significant uneven wall thickness.

OBJECTS OF THE INVENTION Accordingly, it is an object of the present invention to provide a method for manufacturing plastic blow-molded containers and an apparatus for the same, which eliminates the above-mentioned drawbacks of the conventional one-stage method.

Another object of the present invention is to provide a method for manufacturing a plastic container that has uniform wall thickness in the circumferential direction and has no uneven thickness by performing plastic injection molding and blow molding in the same device, and an apparatus therefor. There is something to do.

Still another object of the present invention is an improvement for uniformizing the temperature of the preform throughout before blow molding and thus during injection.

(Structure of the Invention) According to the present invention, a process of melting and kneading resin in an injection machine and injecting the molten resin into an injection mold via a hot runner to manufacture a preform, and following the above process, blow molding is performed. The preform at temperature is stretched in the axial direction in a blow mold,
Injection blow molding of a plastic container, which is characterized by imparting a swirling flow to the molten resin in a hot runner to equalize the temperature of the preform vessel wall, in a method of manufacturing a plastic container comprising a step of blow molding by blowing liquid. A manufacturing method is provided.

Further, according to the present invention, there is provided an apparatus for manufacturing plastic containers by injection blow molding, which includes a rotating turret, an injection position, a blow molding position, and a container take-out position arranged along the moving path of the rotating turret, and a A combination of a cavity mold having at least one injection machine disposed and a plurality of vertical cavities corresponding to the injection machine, a core mold, and a block below the cavity mold, provided within the block, The combination of the hot runner, cavity mold and block from the sprue connected to the injection machine to the nozzle connected to the cavity is moved up and down between the upper injection position and the lower mold removal position, and the core mold is moved downward. An elevating mechanism that moves up and down between an injection position and an upper mold removal position, a neck gripping mold that can be opened and closed on a rotating turret, a blow mold that can be opened and closed located at a blow molding position, a fluid blowing mechanism, and the hot runner. An injection blow molding apparatus is provided, which is characterized by comprising a swirling passage provided at any position from the sprue to the nozzle in the mold for imparting swirling flow to the resin flow.

According to the present invention, the injection blow molding apparatus further includes a preform temperature control position between the injection position and the blow molding position, and a stretching rod that is movable up and down at the blow molding position. equipment is provided.

(Characteristics and effects of the invention) In FIGS. 1 and 2 showing the main parts of an injection molding apparatus, an injection mold 1 consists of a cavity mold 2, a neck holding mold 3, and a core mold 4. A vertical cavity 5 corresponding to the preform is formed between them, and a gate 6 is formed at the lower part of the cavity mold 2, that is, at a portion corresponding to the bottom of the preform. In the specific example shown in the drawings, six cavities 5 (see FIG. 2) are formed in a single mold. The cavity 5 of the injection mold is connected to the injection machine 1 via a hot runner nozzle 7, a hot runner block 8, and a sprue 9.
Connected to 0. The injection machine 10 has a heater 11
It consists of a barrel 12 and a screw 13, and a nozzle 14 is formed at the tip of the palace. The sprue 9 is provided with a single hot runner 15 connected to the nozzle 14, and the sprue 9 is equipped with a heater 11 for keeping warm. Similarly, the hot runner block 8 is also provided with a heater 11 for keeping warm, and inside thereof there is a hot runner 16 extending horizontally, and a hot liner 16 corresponding to the six cavities.
There are branched hot liners 17a, 17b, . . . 17f branching from and extending in the vertical direction. A hot runner 18 is also provided in the hot runner nozzle 7 in order to connect each of these branch hot runners 17a and the gate 6.

The cavity mold 2 is provided with a cooling water hole 19 (Fig. 1) for cooling the injected resin, but in the one-stage method to which the present invention is applied, it is possible to cool the injected resin without heating or without heating. Even if it is heated, blow molding can be continued with only slight temperature control, so cooling is only performed to bring the resin temperature within the cavity to 80 to 120°C.

However, it has been found that in the known method, the temperature of the preform thus formed is considerably uneven and non-uniform in the circumferential direction. Figure 3 shows preform 2 made of polyethylene terephthalate (PET).
0, the results of actually measuring the temperature of each part of the central horizontal circumferential cross section of the preform body corresponding to each of the six cavities are shown. In addition, in FIG. 3, the arrow indicates the injection machine side. According to these results, it can be seen that the temperature of the preform body 21 is high on the injection machine side, and low on the opposite side, and the temperature difference reaches 2 to 5°C.

Moreover, FIG. 4 is a cross-sectional view showing the thickness distribution of the container body 22 obtained by blow molding the preform having the temperature distribution in the circumferential direction shown in FIG. 3, and the unit of thickness is mm. . From the results shown in Figure 4, it is clear that the high-temperature part becomes thinner after blow molding, and the temperature difference mentioned above appears as an extremely large variation in thickness, about twice the maximum thickness/minimum thickness ratio. .

The feature of the present invention is that the hot runner 18 described above is
Alternatively, it has a remarkable feature in that the temperature of the preform wall is made uniform in the circumferential direction by imparting a swirling flow to the molten resin in steps 17, 15, or 16.

FIG. 5 shows a product obtained by injection molding in the same manner as in the prior art described above, except that a screw member of an embodiment (FIGS. 7-A and 7-B), which will be described later, is inserted into the passage of the hot runner nozzle 7. It shows the temperature distribution of the preform body 21, and in this case, the temperature unevenness of the preform is approximately 1°C in the circumferential direction.
It can be seen that it can be suppressed within a short period of time. Further, FIG. 6 shows the thickness distribution in the circumferential direction of the container body obtained by blow molding using this preform, and the meanings of the units and arrows are the same as in FIG. 4. From the results shown in FIG. 6, according to the present invention,
The surprising fact that the variation in thickness in the circumferential direction can be suppressed to within about ±5% is revealed.

(Example) The present invention will be specifically explained in the following examples.

Swirling Mechanism Figures 7-A and 7-B show a suitable example of a screw mechanism 30 suitably used for the purpose of imparting a swirling flow to the resin in the hot runner nozzle 7. . The hot runner nozzle 7 is formed from an upper member 25 and a lower member 26. The upper member 25 has an engaging part 27 with the gate 6 at its tip (upper end) and a passage 18a inside, while the lower member 26 has an engaging part 28 with the hot runner block 8 at its rear end (lower end). It has a passage 18b inside. The upper member 25 and the lower member 26 are removably integrated by screws 29 so that the passages 18a and 18b are aligned.

The screw mechanism 30 has a sharpened tip 31 at one end.
and a shaft 33 having a pedestal 32 at the other end, and a single spiral (screw) 34 is integrally provided around the shaft 33. Pedestal 3
2 is provided with arc-shaped passages 35, 35.

At the open end of the upper member 25 opposite to the gate engaging portion, there is a recess 36 for accommodating the pedestal 32 of the screw mechanism 30, and the spiral 34 of the screw mechanism 30 is connected to the hot runner passage 1 of the upper member.
It is adapted to be fitted into 8a.

Thus, the flow of molten resin flowing into the passageway 18 through the passageway 18b and the passageway 35 flows into the spiral 3
It will be understood that the temperature distribution in the circumferential direction of the resin flow is equalized by swirling and stirring of the resin flow by the action of step 4.

The degree of swirling of the resin flow is determined by the resin flow path length of 5 to 30 mm.
If it is something that makes one turn per turn,
Temperature homogenization with satisfactory stirring takes place.

In the embodiment shown in FIG. 8-A and FIG. 8-B,
Except for the fact that two spirals 34a and 34b are provided to swirl the resin flow more violently.
The configuration is similar to that shown in Figures 7-A and 7-B.

In the embodiment shown in FIG. 9-A and FIG. 9-B,
Two spirals 34aa (34ba) and 34ab respectively
The configuration is the same as the example described above, except that consideration is taken to reduce flow resistance while causing intense swirling of the molten resin flow.

In the embodiment shown in FIGS. 10-A and 10-B, nests 40 and 41 are used in place of the screw mechanism 30 described above. That is, nest 40,4
1 consists of a short cylindrical member, and this nest 4
0 and 41 are each provided with a plurality of through holes 44a, 44b, and 44c provided in a spiral shape. In the embodiment shown in the drawings, the first nest 40 has a large diameter, and the open end of the upper member 25 is provided with a recess 42 for accommodating this nest 40. The second nest 41 has a smaller diameter, and the open end of the upper member 25 is provided with a small diameter recess 43 that is smaller in diameter and deeper than the recess 42.
The second nest 41 is inserted into this recess 43,
It is fixed via a spacer 45.

In this example as well, the molten resin flow flows through the nest 40,
41 spiral through holes 44a, 44b, 44
By passing through c, swirling is imparted, and the stirring effect makes the resin temperature uniform.

Overall Arrangement of the Apparatus In FIG. 11, which shows the overall arrangement of the apparatus of the present invention, a rotating turret 52 is provided at the center of a fixed machine base. The moving path of this rotary turret 52 includes an injection molding station P ₁ , a temperature control station P ₂ , and a blow molding station P _{3 .}
and a container removal station _P4 are each provided at an angle of about 90 degrees.

The rotary turret 52 is provided with four sets of neck gripping molds 3 at 90 degrees apart corresponding to each station (see FIG. 12-A). Thus,
It will be clear that the neck gripping mold 3 can be rotated through 90 degrees and rotationally moved from injection molding station P ₁ to each station in turn.

Injection molding equipment No. 12 showing the injection molding station P ₁ in detail
-A and 12-B, below the neck gripping mold 3, the cavity mold 2 and the block 8 are integrated, and a fluid pressure cylinder 53 is used to form the 12th-
It is provided so as to be movable up and down between the upper injection molding position shown in Figure A and the lower preform take-out position shown in the right half of Figure 12-B. On the other hand, above the neck gripping die 3, the core die 4 is moved by a fluid pressure cylinder 54 to the upper preform take-out position shown in the right half of FIGS. 12-A and 12-B.
- It is provided so as to be movable up and down between the injection molding position shown in the left half of Figure B.

During injection molding, the cavity mold 2 and block 8 rise to the position shown in the left half of Fig. 12-B, and the core mold 4 also descends to the position shown in the left half of Fig. 12-B. is combined. In this state, the injection molding apparatus 10 moves to the left in FIG. 12-A and injects resin into the mold cavity through the block 8. After resin injection, 12th-B
As shown in the right half of the figure, the core mold 4 is raised, the cavity mold 3 is lowered, and the preform 55 is cut out while being held by the neck gripping mold 3. In this state, the turret 52 rotates 90 degrees, and the preform 55 moves to the temperature control station _P2 .

Temperature Control Device In FIG. 13 showing the device of the temperature control station _P2 , a temperature control pot 56 is located below the neck holding mold 3 at a position for taking out the preform shown in the right half of FIG. It is provided so that it can be moved up and down by a lifting mechanism 57 between it and the preform temperature control position shown in the left half of the figure. Further, above the neck holding mold 3, a temperature control core 58 is installed between a position for taking out the preform shown in the right half of FIG. 13 and a preform temperature control position shown in the left half of FIG. It is provided so that it can be moved up and down by a lifting mechanism 59. The temperature control pot 56 has a housing section 60 for keeping the preform 55 warm, and a heating mechanism (not shown) such as an electric heater is provided around the housing section 60 for keeping the preform 55 warm. Also, temperature control core 5
8 is inserted into the preform 55 for the purpose of heat retention, and is also provided with a heating mechanism such as an electric heater.

As shown in the right half of FIG. 13, the rotary turret 52 rotates 90 degrees with the temperature control core 58 in the raised position and the temperature control pot 56 in the lowered position, and the preform that has just been injection molded at the injection molding station _P1. 55 is held by the neck gripping mold 3,
The temperature control core 58 and the temperature control pot 56 are moved to be located on the same vertical axis and stopped at this position.

Next, the temperature control core 58 is lowered and the temperature control pot 56 is raised, and the preforms 55 are assembled as shown in the left half of FIG. 13, and the temperature of the preform 55 is controlled.
Upon completion of temperature control, the temperature control core 58 rises again, the temperature control pot 56 descends, and the temperature controlled preform 5
5 is transferred to the next blow molding position _P3 by the rotation of the rotating turret.

Blow Molding Apparatus In FIG. 14 showing the overall arrangement of the blow molding apparatus and FIG. 15 showing an enlarged view of the main parts thereof, below the rotating turret 52, a pair of split molds 61,
62 is a mold clamping mechanism 63, 64 such as a fluid cylinder.
It is provided so that it can be opened and closed horizontally. In this specific example, a bottom mold 65 that can be moved up and down is provided below the position where the split molds 61 and 62 are brought together. The split molds 61 and 62 are provided with a cavity 66 that defines the final shape of the bottle when the molds are matched.

Further, above the rotating turret 52, a blow core 67 and a stretching rod 68 are provided so as to be movable up and down by elevating mechanisms 69 and 70 such as fluid cylinders, respectively. As clearly shown in FIG. 15, the blow core 67 is a hollow body, and the stretching rod 63 is provided inside the blow core 67 coaxially with the blow core 67 so as to be movable relative to each other in the perpendicular direction. A blowing fluid passage 71 having an annular cross section extends vertically between the blowing core 67 and the stretching rod 68. A seal portion 7 is provided at the tip of the blow core 67 to sealingly engage with the mouth portion of the preform 55.
2, and at the tip of the stretching rod 68 there is a smooth stretching tip 7 that engages with the bottom of the preform.
There are 3.

The blow core 67 is movable up and down between a die-cutting raised position shown in the left half of FIG. 14 and a lowered position shown in the right half of FIG. 14 where the core seal portion 71 and the mouth of the preform 55 engage. On the other hand, the stretching rod 68 can be moved up and down between a die-cutting raised position shown in the left half of FIG. 14 and a stretching end position shown in the left half of FIG.

First, prior to the start of stretch blow molding, the split molds 61 and 62 are in an open state, and the blow core 6
7 and extension rod 68 are in the raised position shown in the left half of FIG. In this state, the turret 52
The preform 55 rotated 90 degrees and whose temperature is controlled by the temperature control station P ₂ is transferred while being held by the neck gripping mold 3 to be positioned on the same vertical axis of the blow core 67 and stopped at this position. .

Next, the mold clamping mechanisms 63 and 64 operate to close the split mold 6.
1 and 62 are closed and combined with the core mold 3. The lifting mechanism 69 operates to lower the blow mold 67,
It stops at a position where the seal portion 72 is in sealing engagement with the mouth portion of the preform 55. Furthermore, the lifting mechanism 70
is actuated, the stretching rod 68 begins to descend, the bottom of the preform is pressed against the stretching tip 73, and the preform is pulled and stretched in the vertical direction. At the same time or following the stretching, a blowing fluid is blown into the preform 55 through the flow passage 71 in the blow core 67, and the preform 55 is expanded and stretched in the circumferential direction.

After the stretch blow molding is completed, the stretch rod 68 and the blow core 67 rise to reach the position shown in the left half of FIG. 14, and then the molds 61 and 62 are opened.
Obtained blow-molded bottle 74 (see Figure 16)
The extraction station is rotated by the rotation of the turret 52.
Transferred to P ₁ .

Removal Device In FIG. 16, which shows the ejection device, above the rotating turret 52, there is a release position regulating member 75 for the blow-molded bottle 74, which is in the ascending position shown in the right half of FIG. 16 and in the descending position shown in the left half of FIG. It is provided so that it can be moved up and down between the positions by a lifting mechanism 76. This release position regulating member 75 includes
A tip 77 is provided which is inserted into the bottle 74. In addition, the release position regulating member 75 has a 17th
A core mold opening wedge member 78 shown in the figure is integrally provided in the positional relationship described below. Furthermore, a chute 79 is provided below the rotating turret 52 for discharging the bottles 74 in a positioned manner.

Initially, the discharge position regulating member 75 is in the raised position shown in the right half of FIG. In this state,
With the turret 52 rotated 90 degrees and the blow-molded bottle 74 being gripped by the neck gripping mold 3,
It is moved so as to be positioned on the same vertical axis of the discharge position regulating member 75 and then stopped. Neck gripping mold 3
Although it can be opened and closed in the horizontal direction, it is always urged in the closing direction by an elastic member such as a spring (not shown).

Next, the discharge position regulating member 75 descends, and its tip 77 begins to be inserted into the bottle mouth. At the same time, as shown in FIG.
The neck gripping molds 3, 3 are also lowered and inserted into the cracks of the neck gripping molds 3, 3, and the neck gripping molds 3, 3 begin to open horizontally. The release position regulating member 75 prevents the bottle from moving in the horizontal direction while attached to one of the molds 3, and functions to release the bottle 74 from the mold at the correct position. The bottle 74 discharged from the neck gripping mold 3 is sent through a chute 79 onto a conveyance mechanism (not shown) such as a conveyor in a correctly positioned state.

In the apparatus of the present invention, injection molding of the resin into the preform, temperature control of the preform, stretch blow molding of the preform, and removal of the container are all performed synchronously within a fixed time period.

According to the present invention, an advantage is achieved in that a stretch blow molded container without uneven thickness can be easily manufactured by a one-stage method by a simple operation of applying a swirling flow to the molten resin using a hot runner.

[Brief explanation of drawings]

Fig. 1 is a side sectional layout diagram showing the main parts of the injection molding device, Fig. 2 is a sectional view taken along line A-A of the device in Fig. Fig. 4 is an explanatory diagram showing the temperature distribution actually measured in the horizontal cross section of the center of the body for the preform formed from the preform.
An explanatory diagram showing the thickness distribution of the container body obtained by stretch-blow molding a preform with the temperature distribution shown in the figure. An explanatory diagram showing the temperature distribution of the preform, Fig. 6 is an explanatory diagram showing the thickness distribution of the container body obtained by stretch blow molding the preform in Fig. 5, and Fig. 7-A is an explanatory diagram showing the thickness distribution of the container body obtained by stretch blow molding the preform in Fig. 5. A partially sectional side view showing an example of an applicable screw mechanism for imparting swirling flow;
Fig. 7-B is a sectional view taken along line B-B of the mechanism in Fig. 7-A, Fig. 8-A is a partially sectional side view of the screw mechanism provided with two spirals, Fig. 8-B The figure is a sectional view taken along line B-B of the mechanism in Figure 8-A, Figure 9-A is a partially sectional side view of the screw mechanism provided with two divided spirals, and Figure 9-B is a cross-sectional view of the mechanism shown in Figure 8-A. is the mechanism line B-B in Figure 9-A.
10-A is a partially sectional side view of the nest used to provide a swirling flow of resin, and FIG. 10-B is a sectional view taken along line B-- of the mechanism in FIG. 10-A.
11 is a plan view showing a schematic horizontal arrangement of the apparatus of the present invention, FIG. 12-A is a side view of the injection molding apparatus, and FIG. 12-B is a front view of the apparatus of FIG. 12-A. In the figure, the left half of the figure shows the injection state, the right half of the figure shows the mold cutting state, and FIG. 13 is a front view showing the temperature control device, and the left half of the figure shows the temperature control state, The right half shows the extraction state, and the 14th
The figure is a front view showing a stretch blow molding device,
The right half of the figure shows the stretch molding state, the right half of the figure shows the unloading state, FIG. 15 is an enlarged sectional view showing the main parts of the stretch blow molding device, and FIG. 16 is a front view showing the container unloading device. , the left half of the figure shows the extraction state,
The right half of the figure shows a state in which the transfer is completed, and FIG. 17 is an explanatory view showing the opening of the neck gripping mold in the horizontal direction. 1 is an injection mold, 2 is a cavity mold, 3 is a neck holding mold, 4 is a core mold, 7 is a hot runner nozzle, 10 is an injection machine, 15 and 16 are hot runners, 20 and 55 are preforms, and 21 is a A preform body, 22 a container body, 30 a rotating mechanism,
40 and 41 are nests (swivel mechanism), 52 is a rotating turret 56 and 58 are temperature control mechanisms, 61, 62 and 67 are blow molds, 68 is a stretching rod, and 78 is a neck gripping mold opening mechanism.

Claims (1)

[Scope of Claims] 1. A step of melting and kneading resin in an injection machine and injecting the molten resin into an injection mold through a hot runner to produce a preform; Following the above step, the preform is at blow molding temperature. In the manufacturing method of plastic containers, which consists of the steps of stretching the resin in the axial direction in a blow mold and blow-molding it by blowing fluid, a swirling flow is applied to the molten resin in a hot runner, and the temperature of the preform vessel wall is lowered. A manufacturing method using injection blow molding for plastic containers, which is characterized by uniformity. 2. An apparatus for manufacturing plastic containers by injection blow molding, which includes: a rotating turret; an injection position located along the moving path of the rotating turret; a blow molding position; and a container ejection position; at least one unit located at the injection position. A combination of an injection machine, a cavity mold having a plurality of vertical cavities corresponding to the injection machine, a core mold, and a block below the cavity mold, which is provided in the block and connected to the injection machine. The combination of the hot runner, cavity mold and block from the sprue to the nozzle connected to the cavity is moved up and down between the upper injection position and the lower mold extraction position, and the core mold is moved between the lower injection position and the upper mold extraction position. an elevating mechanism that moves up and down between positions, a neck gripping mold that is openable and closable on the rotating turret, an openable and closable blow mold and fluid blowing mechanism that are located at the blow molding position, and a nozzle from the sprue in the hot runner. 1. An injection blow molding apparatus comprising a swirl passage provided at any position leading to a swirl flow for imparting swirl flow to a resin flow. 3. The apparatus according to claim 2, wherein a preform temperature control position is provided between the injection position and the blow molding position, and a stretching rod that can be moved up and down is provided at the blow molding position.