JP3787423B2 - Method and apparatus for molding synthetic resin container - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a molding method and a molding apparatus for a synthetic resin container, and more particularly, to a molding method and a molding apparatus for a synthetic resin container capable of adjusting a shrinkage amount of a primary molded product heat-treated with a heat treatment mold.
[0002]
[Background Art and Problems to be Solved by the Invention]
As a technique for molding a heat-resistant container made of synthetic resin, the applicant of the present application has previously proposed a method for molding a heat-resistant container disclosed in JP-A-8-187768.
[0003]
This heat-resistant container is formed by heat-treating a primary molded product in a container shape in a heated heat treatment mold, and then blow-molding the primary molded product that has been taken out of the heat treatment mold and shrunk in the final blow mold to form a final container. Like to get.
[0004]
In the case of such a molding method, it is more advantageous in terms of heat resistance that the size of the contracted primary molded product after the heat treatment is closer to the size of the final container.
[0005]
However, if the primary molded product in the contracted state is too large, it may be pinched or scratched when the final blow mold is clamped, so it is necessary to control the amount of shrinkage of the primary molded product after heat treatment. It was.
[0006]
In the molding method, the size of the primary molded product after the heat treatment step can be adjusted by the heat treatment temperature and the heat treatment time in order to approximate the size of the final container as much as possible.
However, since the heat treatment temperature and time are greatly related to heat resistance and productivity, adjustment from other viewpoints is desired.
[0007]
[Means for Solving the Problems]
The method for molding a synthetic resin container according to the invention of claim 1 includes a step of introducing compressed air into a primary molded product in a heat treatment mold,
A step of bringing the primary molded product into contact with the inner wall surface of the heat treatment mold and heat-treating;
After the heat treatment is completed, exhausting the compressed air in the primary molded product to shrink the primary molded product in the heat treatment mold ,
A step of blow molding the primary molded product taken out of the heat treatment mold and contracted into a final container in a final blow mold;
Including
When exhausting the compressed air, the amount of contraction of the primary molded product is controlled by adjusting the flow rate of exhausting the compressed air.
[0008]
According to the first aspect of the present invention, the size of the primary molded product after contraction can be controlled by adjusting the flow rate of exhausting compressed air, and more specifically, by adjusting the flow rate of exhausting less. The amount of shrinkage of the primary molded product after heat treatment can be reduced, and the amount of shrinkage can be increased by increasing the flow rate. As a result, the size of the final container can be approached, and pinching or the like during clamping of the final blow mold can be prevented.
[0009]
The invention of claim 2 is the invention according to claim 1,
The primary molded product is a bottomed cylindrical preform formed by injection molding.
[0010]
According to the second aspect of the invention, in addition to the state of the first aspect, the preform can be blow-molded into the container shape and the heat treatment can be simultaneously performed in the heat treatment mold, so that the cost of the molding apparatus can be reduced.
[0011]
The invention of claim 3 is the invention according to claim 1,
The primary molded product is a primary blow molded product in a container shape subjected to primary blow molding.
[0012]
According to the invention of claim 3, in addition to the state of claim 1, the blow molding mold for blow molding the stretched primary molded product and the heat treatment mold are separately provided, so that the molding cycle can be shortened and the primary The thickness distribution of the molded product can be adjusted.
[0015]
According to a fourth aspect of the present invention, there is provided a molding apparatus for a synthetic resin container, comprising: a heat treatment section for introducing a compressed air into a primary molded product in a heat treatment mold and bringing the primary molded product into contact with the inner wall surface of the heat treatment mold for heat treatment; When,
A blow molding part that blow-molds the primary molded product heat-treated in the heat treatment part into a final container in a final blow molding die,
The heat treatment section has an exhaust circuit for discharging compressed air in the primary molded product after the heat treatment is completed, and an exhaust means for opening the exhaust circuit and returning the pressure in the primary molded product to atmospheric pressure,
An adjusting means capable of adjusting the flow rate smaller than the flow rate of the exhaust means is provided in the middle of the exhaust circuit.
[0016]
According to invention of Claim 4 , the magnitude | size of the primary molded product after heat processing is controllable by adjusting an adjustment means. More specifically, the amount of shrinkage of the primary molded product after heat treatment can be reduced by reducing the flow rate exhausted from the exhaust means by the adjusting means, and the amount of shrinkage can be increased by increasing the flow rate. it can. As a result, the size of the final container can be approached, and pinching or the like during clamping of the final blow mold can be prevented.
[0017]
The invention of claim 5 is, in claim 4 ,
The exhaust means is an on-off valve that opens and closes the exhaust circuit, and the adjusting means is a flow rate adjusting valve.
[0018]
According to the fifth aspect of the present invention, in addition to the state of the fourth aspect , the exhaust flow rate can be easily adjusted by restricting the flow rate by the flow rate adjusting valve with respect to the opening and closing of the exhaust circuit by the open / close valve.
[0019]
The invention of claim 6 is the invention according to claim 4 or 5,
The heat treatment mold is a blow mold for blow molding the primary molded product.
[0020]
According to the invention of claim 6 , in addition to the state of claim 4 or 5, it is possible to reduce the cost of the apparatus by combining the primary blow molding and heat treatment which are molded from the preform state into a container shape. it can.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.
[0022]
FIG. 1 is a schematic circuit diagram of compressed air in a heat treatment part in a synthetic resin container molding apparatus according to an embodiment of the present invention.
[0023]
The heat treatment unit 10 includes an air supply circuit 14 that supplies compressed air into the primary molded product via a compressed air supply block 42 of the heat treatment unit, and an exhaust circuit 16 that discharges compressed air in the primary molded product to the outside. Have.
[0024]
The air supply circuit 14 is connected to the heat treatment mold 12 through a solenoid valve 20 and a check valve 22 for opening and closing the air supply circuit 14 from the compressed air tank 18.
[0025]
The exhaust circuit 16 is connected from the compressed air supply block 42 to the silencer 30 through a flow rate adjusting valve 24 as an adjusting means and an electromagnetic valve 28 as an exhaust means.
[0026]
The solenoid valve 28 opens and closes the exhaust circuit 16 to act as an on-off valve that returns the pressure in the primary molded product to atmospheric pressure, and the flow rate control valve 24 is manually adjustable to a flow rate lower than the flow rate of the solenoid valve 28. Yes.
[0027]
FIG. 2 is a diagram showing a drawing mechanism of the primary blow molding unit in addition to the apparatus configuration in the heat treatment unit.
[0028]
The figure shows a conveying member 32 that conveys the primary molded product, a heat treatment mold 12, a seal piston 34 that moves up and down below the conveying member 32, a stretching unit 36 that moves up and down below the sealing piston 34, and a lifting and lowering unit. Mechanism 38 is shown.
[0029]
The conveying member 32 holds the primary molded product in an inverted state and conveys it to the heat treatment mold 12 position.
[0030]
Further, the conveying member 32 is connected to a conveying chain arranged in a loop shape, receives a preform injection-molded at the receiving portion along the conveying chain, for example, and passes through a heating unit and a primary blow molding unit to form a container. After the primary molded product blow-molded into the shape is transported to the heat treatment section 10 and heat treated, it is transported to the final blow molding section and molded into the final container, and the final container can be transported to the take-out section and taken out To do.
[0031]
Furthermore, the conveying member 32 has a communicating hole penetrating in the vertical direction, and the compressed air can be supplied and discharged through the communicating hole.
[0032]
The heat treatment mold 12 is constituted by a split mold, and can be clamped and opened by a mold clamping mechanism (not shown).
[0033]
The heat treatment mold 12 has an inner wall surface 40 having the same size as that of the primary molded product, and a temperature at which crystallization is promoted by a heating mechanism such as a built-in heater (not shown) (for example, 150 to 220 ° C. in the case of PET). ) To heat-treat the primary molded product.
[0034]
The seal piston 34 is mounted on the compressed air supply block 42, and as shown on the right two in the figure, the seal piston 34 rises and the upper end abuts on the lower surface of the conveying member 32, and the compressed air supply block 42 and the conveying member 32 As shown at the left end of the figure, the seal position that maintains the communication state and the seal release position that lowers and releases the communication state between the conveying member 32 and the compressed air supply block 42 can be moved up and down.
[0035]
The raising / lowering of the seal piston 34 is performed by supplying air to the ascending air supply port 44a or the descending air supply port 44b, as shown in the cross-sectional view seen from the left side of the figure. Yes.
[0036]
The compressed air supply block 42 has a compressed air supply port 46 on the back side, as shown in the cross-sectional view seen from the left side of the figure, and the air supply circuit 14 is connected to the compressed air supply port 46 for conveyance. Compressed air is supplied into the primary molded product in the heat treatment mold 12 via the member 32.
[0037]
Further, an exhaust port 48 is provided on the opposite side of the compressed air supply block 42 from the compressed air supply port 46, and the exhaust circuit 16 is connected to the exhaust port 48 so that the compressed air in the primary molded product can be discharged. It has become. It is preferable that the silencer 30 of the exhaust circuit 16 is disposed in the device base 74 to further reduce noise.
[0038]
The stretching unit 36 and the stretching unit lifting mechanism 38 are not usually required in the heat treatment section. Here, the drawing mechanism is shown as a reference for implementation in which the heat treatment section also serves as the primary blow molding section.
[0039]
The stretching unit 36 includes a stretching rod 50, a stretching rod fixing plate 52, a stretching cylinder 54, and a stretching cylinder fixing plate 56.
[0040]
The stretching rod 50 penetrates the compressed air supply block 42 and the conveying member 32 and is inserted into the heat treatment mold 12 to stretch the injection-molded bottomed cylindrical preform in the axial direction. 52 is attached.
[0041]
The extending rod fixing plate 52 and the extending cylinder fixing plate 56 are supported along the guide rod 58 so as to be movable up and down.
[0042]
The stretching cylinder 54 is attached to the stretching cylinder fixing plate 56, and allows the stretching rod fixing plate 52 to move up and down with respect to the stretching cylinder fixing plate 56.
[0043]
The stretching unit lifting mechanism 38 includes a stretching unit lifting cylinder 60 and a lifting cylinder fixing plate 62.
[0044]
The lifting cylinder fixing plate 62 is fixed to the guide rod 58.
[0045]
The stretching unit lifting cylinder 60 is attached to the lifting cylinder fixing plate 62 and allows the stretching cylinder fixing plate 56 to be lifted and lowered.
[0046]
Accordingly, the stretching cylinder fixing plate 56 and the stretching rod fixing plate 52 are integrally raised to the position shown in the vicinity of the center of the drawing by the stretching unit elevating cylinder 60, and then the stretching rod fixing plate 52 is moved to the position of the machine base 74 by the stretching cylinder 54. The primary molded product is stretched by the stretching rod 50 by moving up to the upper end position.
[0047]
FIG. 3 is a diagram illustrating a state of a molded product in each molding process.
[0048]
With reference to FIG. 3, a method for molding a synthetic resin container of the present invention will be described.
[0049]
First, the injection-molded bottomed cylindrical preform 64 is conveyed to a heating unit while being held on the conveying member 32 shown in FIG. 2 and heated to an appropriate temperature for blow molding. The preform 64 can be either injection-molded by an injection molding machine provided separately or one having a retained heat quantity that is injection-molded by an injection molding unit provided integrally.
[0050]
Next, the preform 64 heated by the heating unit is conveyed to the primary blow molding unit, and blow molded while being stretched by the stretching unit 36 in the primary blow molding die, so that a container shape larger than the final container 72 is formed. The primary molded product 66 is molded.
[0051]
Next, the primary molded product 66 is conveyed to the heat treatment section 10 of FIG. 2, the heat treatment mold 12 is clamped in a state where the primary molded product 66 is accommodated, the seal piston 34 is raised, and the compressed air supply block 42 The conveyance member 32 is communicated in an airtight state.
[0052]
In this state, the electromagnetic valve 28 of the exhaust circuit 16 shown in FIG. 1 is closed, the electromagnetic valve 20 of the air supply circuit 14 is opened, and the compressed air supply port 46 of the compressed air supply block 42 is connected through the communication member communication hole. Compressed air is introduced into the primary molded product 66, and the primary molded product 66 is brought into contact with the inner wall surface 40 of the heat treatment mold 12 to perform heat treatment. In this case, since the primary blow-molded product has already been formed into the same shape as the heat treatment mold, stretching is not necessary.
[0053]
After heat treatment for a predetermined time, for example, 2 to 6 seconds, the electromagnetic valve 20 of the air supply circuit 14 is closed to stop the air supply, the electromagnetic valve 28 of the exhaust circuit 16 is opened, the flow rate is reduced by the flow control valve 24, and the exhaust port is opened. The compressed air in the primary molded product 66 is slowly discharged from 48 over time. This evacuation time is longer than the time evacuated only by opening the solenoid valve 28 without providing the flow rate control valve, and is about 1 to 3 seconds.
[0054]
Then, after a predetermined exhaust time elapses, the seal piston 34 is lowered, and when compressed air remains in the primary molded product, the air is exhausted to atmospheric pressure.
[0055]
In this way, by slowly discharging the compressed air in the primary molded product 66 over time, the amount of shrinkage after the heat treatment can be reduced, and the size of the final container can be approached. Also, in case of contact when closing the final blow mold, the exhaust flow rate is increased by slightly opening the diverting control valve, and the shrinkage of the primary molded product is increased, resulting in damage or pinching. To prevent. FIG. 3 shows, for comparison, a primary molded product 70 after contraction with a large contraction amount when the seal piston 34 is lowered immediately after the electromagnetic valve 28 is opened and exhausted at once.
[0056]
Also, FIG. 4 shows a blow time in which the solenoid valve 20 is open and the solenoid valve 28 is closed, and exhaust until the seal piston 34 is lowered after the solenoid valve 20 is closed and the solenoid valve 28 is opened. The time is shown by comparing the example with the comparative examples 1 and 2.
[0057]
In the embodiment, the blow time is 4.8 seconds and the exhaust time is slowly exhausted by 2.2 seconds by restricting the flow rate with the flow rate control valve 24.
[0058]
On the other hand, in Comparative Example 1, the blow time was 4.8 seconds, in Comparative Example 2, the exhaust time was 6.5 seconds, and in both Comparative Examples 1 and 2, the exhaust time was 0.5 seconds. In Comparative Examples 1 and 2, the flow control valve is fully open.
[0059]
As a result, as shown in FIG. 5, the overall height of the contracted primary molded product 68 is 306.0 mm, the capacity is 1825 ml, the contraction amount with respect to the primary molded product 66 before contraction is 63.26%, and the contraction is In contrast, in Comparative Examples 1 and 2, the total height of the contracted primary molded product 70 is 299.7 mm, 302.8 mm, the capacities are 1679 ml, 1698 ml, the shrinkage amounts are 58.2%, 58.86%, and the shrinkage is large. It is in a state.
[0060]
Then, the primary molded product 68 with a small shrinkage is taken out from the heat treatment mold and conveyed to the final blow molding part, and after the final blow molding is performed to form the final container 72, the final product is advantageous in terms of heat resistance. A container is obtained.
[0061]
The present invention is not limited to the above-described embodiment, and can be changed to various embodiments within the scope of the gist of the present invention.
[0062]
For example, in the above-described embodiment, the primary blow molding part and the heat treatment part are separately described. However, the present invention is not limited to this example, and the primary blow molding part and the heat treatment part can be combined. In this case, the primary molded product is a preform.
[0063]
Moreover, in the said embodiment, although what conveyed the molded article to each part in an inverted state was demonstrated, it is applicable also to what is conveyed to each part in a non-inverted state.
[0064]
[Brief description of the drawings]
FIG. 1 is a schematic circuit diagram of compressed air in a heat treatment section in a synthetic resin container molding apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing an apparatus configuration in a heat treatment section.
FIG. 3 is a diagram showing a state of a molded product in each molding step.
FIG. 4 is a diagram showing the blow time and the exhaust time until the seal piston descends, comparing Example and Comparative Examples 1 and 2;
FIG. 5 is a diagram showing a contracted state of an example and comparative examples 1 and 2 when molded in the state of FIG. 4;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Heat processing part 12 Heat processing type 14 Air supply circuit 16 Exhaust circuit 24 Flow control valve 28 Solenoid valve 64 Preform 66 Primary molded product 68 before shrinking Primary molded product 72 after shrinking Final container

Claims (6)

Introducing compressed air into the primary molded product in the heat treatment mold;
A step of bringing the primary molded product into contact with the inner wall surface of the heat treatment mold and performing a heat treatment;
After the heat treatment is completed, exhausting the compressed air in the primary molded product to shrink the primary molded product in the heat treatment mold ,
A step of blow molding the primary molded product taken out of the heat treatment mold and contracted into a final container in a final blow mold;
Including
A method for molding a synthetic resin container, wherein the amount of contraction of a primary molded product is controlled by adjusting a flow rate of exhausting the compressed air when the compressed air is exhausted. In claim 1,
The method for molding a synthetic resin container, wherein the primary molded product is a bottomed cylindrical preform formed by injection molding. In claim 1,
The method for molding a synthetic resin container, wherein the primary molded product is a primary blow molded product in a primary blow molded container shape. A heat treatment part that introduces compressed air into the primary molded product in the heat treatment mold and brings the primary molded product into contact with the inner wall surface of the heat treatment mold to perform heat treatment;
A blow molding part that blow-molds the primary molded product heat-treated in the heat treatment part into a final container in a final blow molding die,
The heat treatment section has an exhaust circuit for discharging the compressed air in the primary molded product after the heat treatment is completed, and an exhaust means for opening the exhaust circuit and returning the pressure in the primary molded product to atmospheric pressure,
An apparatus for molding a synthetic resin container, characterized in that adjusting means capable of being adjusted to a flow rate smaller than the flow rate of the exhaust means is provided in the middle of the exhaust circuit. In claim 4 ,
The apparatus for molding a synthetic resin container, wherein the exhaust means is an on-off valve that opens and closes the exhaust circuit, and the adjustment means is a flow rate adjustment valve. In claim 4 or 5 ,
The apparatus for molding a synthetic resin container, wherein the heat treatment mold is a blow mold for blow molding the primary molded product.

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