JP6955166B2 - Manufacturing method of molded product - Google Patents

Description

The present invention relates to a method for producing a molded product, a molding machine, and a stretching device.

In Patent Document 1, after the lower end of a tubular parison is sandwiched and sealed with a pinch bar, gas is pre-blown inside the parison to expand the parison, and then the parison is sandwiched in a split mold and main blown. A method for producing a hollow body including a step is disclosed.

Japanese Unexamined Patent Publication No. 6-8313

In the method of Patent Document 1, when the parison is sandwiched between pinch bars, the parison becomes substantially elliptical, and when pre-blow is performed in that state, the parison is not uniformly stretched and the wall thickness of the parison fluctuates along the circumferential direction. In some cases.

The present invention has been made in view of such circumstances, and provides a method for producing a molded product capable of suppressing fluctuations in the wall thickness of the parison in the circumferential direction.

According to the present invention, it is a method for manufacturing a molded product, which includes an extrusion step, a pinch step, and a molding step. In the pinch step, the parison is sandwiched to form a welded portion, and in the molding step, the pair of split dies are molded with the parison placed between the pair of split dies, and the parison is molded. Is provided, and the welded portion is formed so that a vent hole communicating from the inside of the parison to the lower part of the parison is provided.

In the present invention, in the pinch step, the welded portion is formed so that a ventilation hole communicating from the inside of the parison to the lower part of the parison is provided. When air is blown into the parison or the parison is sandwiched between the split molds, the internal pressure of the parison rises, but at the portion adjacent to the vent, the air escapes from the vent, so that the internal pressure does not rise easily. Therefore, it is difficult for the parison to be stretched at the portion adjacent to the ventilation hole. Therefore, it is possible to suppress fluctuations in the wall thickness of the parison in the circumferential direction by providing the ventilation holes at positions adjacent to the portion where the wall thickness of the parison tends to be thin.

Hereinafter, various embodiments of the present invention will be illustrated. The embodiments shown below can be combined with each other.
Preferably, it is the method described above, wherein the vent is provided between the inner surface of the parison and the welded portion.
Preferably, it is the method described above, wherein the welded portion is formed along the width direction of the split mold.
Preferably, the method described above comprises a stretching step, wherein the stretching step is performed between the extrusion step and the pinch step, and in the stretching step, the stretching step is performed along the width direction of the split mold. The method by which the parison is stretched.
Preferably, in the method described above, the stretching step is performed by increasing the distance between the pair of stretching members while the pair of stretching members are in contact with the inner surface of the parison. be.
Preferably, in the method described above, the distance between the pair of stretched members is widened by inclining the stretched member so that the tip end side of the stretched member is outside the proximal end side of the stretched member. , The way.
Preferably, in the method described above, the pinch step is performed by sandwiching the parison between a pair of pinch members, and in the stretching step, the inner surface of the parison is more than the longitudinal end of the pinch member. Is a method in which the parison is stretched so that
According to another aspect of the present invention, it is a molding machine, comprising a head and a stretching device, the head being configured to extrude a tubular parison made of molten resin, the stretching device. The pair of stretching members are brought into contact with the parison, and the distance between the pair of stretching members is widened so that the tip end side of the stretching member is outside the proximal end side of the stretching member. Provided is a molding machine configured so that the distance between the pair of stretched members is widened by inclining the stretched member.
Preferably, the molding machine according to the above description is provided with a pinch device having a pair of pinch members, and the parison is sandwiched between the pair of pinch members to form a welded portion. It is a molding machine configured to extend the parison so that the inner surface of the parison is outside the end in the longitudinal direction of the pinch member.
According to still another aspect of the present invention, in a stretching device having a pair of stretching members, the stretching member is tilted so that the tip end side of the stretching member is outside the proximal end side of the stretching member. Provided is an apparatus configured to widen the distance between the pair of stretched members.

It is a block diagram (cross-sectional view of the split die 19 and the member in the vicinity) of the molding machine 1 that can be used for manufacturing the molded body of one Embodiment of this invention. It is an enlarged view of the split mold 19 in FIG. 1 and the member in the vicinity thereof. It is an enlarged view of the stretching apparatus 4 in FIG. FIG. 2 is a cross-sectional view taken along the line AA in FIG. 2 (the stretching device 4 is a right side view). It is an enlarged view of the stretching apparatus 4 in FIG. 2 is a cross-sectional view having the same cross section as that of FIG. 4, showing a state in which the distance between the pair of stretching members 5 is widened from the state of FIGS. 2 to 5. It is an enlarged view of the stretching apparatus 4 in FIG. It is sectional drawing of the same cross section as FIG. 2 which shows the state which sandwiched the parison 23 by the pinch member 3a from the state of FIG. FIG. 8 is a cross-sectional view taken along the line AA in FIG. 8 (the stretching device 4 is a right side view). It is sectional drawing of the same cross section as FIG. 2 which shows the state after performing the pre-blow process from the state of FIG. 8 to FIG. FIG. 10 is a cross-sectional view taken along the line AA in FIG. 10 (the stretching device 4 is a right side view). 10 is a cross-sectional view of the same cross section as that of FIG. 2, showing a state after the rod 5b is retracted from the state of FIGS. 10 to 11. FIG. 12 is a cross-sectional view taken along the line AA in FIG. 12 (the stretching device 4 is a right side view). 12 is a cross-sectional view of the same cross section as that of FIG. 2, showing a state after the split mold 19 is molded from the state of FIGS. 12 to 13.

Hereinafter, embodiments of the present invention will be described. The various features shown in the embodiments shown below can be combined with each other. In addition, the invention is independently established for each feature.

1. 1. Configuration of Molding Machine 1 The molding machine 1 according to the embodiment of the present invention will be described with reference to FIGS. 1 to 14. The molding machine 1 includes a resin supply device 2, a head 18, a pinch device 3, a stretching device 4, and a pair of split dies 19. The resin supply device 2 includes a hopper 12, an extruder 13, an injector 16, and an accumulator 17. The extruder 13 and the accumulator 17 are connected via a connecting pipe 25. The accumulator 17 and the head 18 are connected via a connecting pipe 27.
Hereinafter, each configuration will be described in detail.

<Hopper 12, extruder 13>
The hopper 12 is used to put the raw material resin 11 into the cylinder 13a of the extruder 13. The form of the raw material resin 11 is not particularly limited, but is usually in the form of pellets. The raw material resin 11 is a thermoplastic resin such as polyolefin, and examples of the polyolefin are low density polyethylene (LDPE), linear low density polyethylene, high density polyethylene (HDPE), polypropylene, ethylene-propylene copolymer and the like. Examples include mixtures. The raw material resin 11 is charged into the cylinder 13a from the hopper 12 and then melted by being heated in the cylinder 13a to become a molten resin. Further, it is conveyed toward the tip of the cylinder 13a by the rotation of the screw arranged in the cylinder 13a. The screw is arranged in the cylinder 13a, and the molten resin is kneaded and conveyed by its rotation. A gear device is provided at the base end of the screw, and the screw is rotationally driven by the gear device.

<Injector 16>
The cylinder 13a is provided with an injector 16 for injecting a foaming agent into the cylinder 13a. When the raw material resin 11 is not foamed, the injector 16 can be omitted. Examples of the foaming agent injected from the injector 16 include a physical foaming agent, a chemical foaming agent, and a mixture thereof, and a physical foaming agent is preferable. As the physical foaming agent, inorganic physical foaming agents such as air, carbon dioxide, nitrogen gas, and water, organic physical foaming agents such as butane, pentane, hexane, dichloromethane, and dichloroethane, and their supercritical fluids are used. be able to. As the supercritical fluid, it is preferable to use carbon dioxide, nitrogen, etc., for nitrogen, the critical temperature is -149.1 ° C, the critical pressure is 3.4 MPa or more, and for carbon dioxide, the critical temperature is 31 ° C, the critical pressure. It is obtained by setting the pressure to 7.4 MPa or more. Examples of the chemical foaming agent include those that generate carbon dioxide gas by a chemical reaction between an acid (eg, citric acid or a salt thereof) and a base (eg, baking soda). The chemical foaming agent may be injected from the hopper 12 instead of being injected from the injector 16.

<Accumulator 17, head 18>
The molten resin 11a to which the foaming agent is added or not added is extruded from the resin extrusion port of the cylinder 13a and injected into the accumulator 17 through the connecting pipe 25. The accumulator 17 includes a cylinder 17a and a piston 17b slidable inside the cylinder 17a, and the molten resin 11a can be stored in the cylinder 17a. Then, by moving the piston 17b after a predetermined amount of the molten resin 11a is stored in the cylinder 17a, the molten resin 11a is pushed out from the die slit provided in the head 18 through the connecting pipe 27 and hung down to form a cylinder. Form the parison 23. The accumulator 17 may be built in the head 18. Further, the head 18 may be provided with a blow nozzle (not shown) for blowing air into the parison 23.

<Pinch device 3>
The pinch device 3 is configured to sandwich (pinch) the parison 23 to form a welded portion 23a (see FIGS. 8 to 9). The welded portion 23a is formed so that a ventilation hole 23b (see FIG. 9) communicating from the inside of the parison 23 to the lower part of the parison 23 is provided. The pinch device 3 is preferably arranged below the cavity 19a of the pair of split dies 19.

The pinch device 3 includes a pair of pinch members 3a. The pinch member 3a is preferably an elongated plate body, and extends along the width direction of the split mold 19. The welded portion 23a is formed by sandwiching the parison 23 with a pair of pinch members 3a.

<Stretching device 4>
As shown in FIGS. 2 to 5, the stretching device 4 includes a pair of stretching members 5 and a drive mechanism 6. The stretching member 5 includes a base 5a and a rod 5b. The rod 5b is configured to be able to move forward and backward (that is, to be slidable in the longitudinal direction) with respect to the base 5a. The rod 5b is configured to be projectable from the tip end side of the base 5a.

The drive mechanism 6 includes a rail 7, a base 8, a pair of slide members 9, and a pair of connecting members 10.

The rail 7 and the base 8 are configured to be immovable with respect to the molding machine 1. The slide member 9 is configured to be slidable along the rail 7. The slide member 9 is rotatably connected to the base 5a on the connecting shaft 32 via the bracket 31. The connecting member 10 is rotatably connected to the base 8 on the connecting shaft 33. Further, the connecting member 10 is rotatably connected to the protruding piece 5c provided at the base end of the base 5a on the connecting shaft 34. The slide member 9 is fixed to the base 5a on the tip end side of the base 5a with respect to the connecting member 10. According to such a configuration, by moving the slide member 9 along the rail 7, the distance between the pair of stretching members 5 is widened, and the tip end side of the stretching member 5 is closer to the proximal end side of the stretching member 5. The stretching member 5 can be tilted so as to be outside of the split die 19 in the width direction (hereinafter, simply referred to as "outside").

Further, the stretching device 4 is configured so that the parison 23 can be stretched so that the inner surface 23c of the parison 23 is outside the end in the longitudinal direction of the pinch member 3a.

<Split mold 19>
The parison 23 is guided between a pair of split molds 19. The pair of split dies 19 are configured so that the parison 23 is formed into a shape along the inner surface of the cavity 19a by molding with the parison arranged between them. As a result, a molded product having a desired shape can be obtained.

2. Method for Producing Molded Product A method for producing a molded product according to an embodiment of the present invention will be described with reference to FIGS. 1 to 14. The method of the present embodiment includes an extrusion step, a stretching step, a pinch step, and a molding step. Hereinafter, a detailed description will be given.

2-1. Extrusion step In the extrusion step, as shown in FIGS. 1 to 5, a tubular parison 23 formed of the molten resin 11a is extruded from the head 18.

2-2. Stretching Step In the stretching step, as shown in FIGS. 6 to 7, the parison 23 is stretched along the width direction of the split mold 19. This step can be performed by widening the distance between the pair of stretching members 5 while the pair of stretching members 5 are in contact with the inner surface 23c of the parison 23, respectively.

In the state of FIGS. 4 to 5, the slide member 9 is located adjacent to the center of the split mold 19 in the width direction. From this state, as shown in FIGS. 6 to 7, when the slide member 9 is slid outward, the base 5a is pushed by the slide member 9, and the tip end side of the base 5a moves outward. The base end side of the base 5a is connected to the connecting member 10 by the connecting shaft 34, and the connecting shaft 34 can be displaced only on the rotation locus of the connecting member 10 centered on the connecting shaft 33. Therefore, as the slide member 9 slides, the stretching member 5 is tilted so that the tip end side of the stretching member 5 is outside the proximal end side of the stretching member 5. Along with this inclination, the position of the tip of the stretching member 5 (that is, the tip of the rod 5b) is arranged outside the slide member 9.

The stretching of the parison 23 can be performed without tilting the stretching member 5, but by tilting the stretching member 5, (maximum distance between the pair of stretching members 5) / (movable range of the slide member 9). The value can be increased. As a result, the movable range of the slide member 9 required to achieve a predetermined stretching can be reduced, so that the required stretching can be achieved even when the installation space of the drive mechanism 6 is limited. Is possible. Further, by inclining the stretching member 5, the value of (amount of change in the interval between the pair of stretching members 5) / (amount of movement of the slide member 9) becomes large, so that if the moving speed of the slide member 9 is the same. , The rate of increase in the interval between the pair of stretching members 5 is increased, and the stretching step can be completed in a shorter time.

The maximum inclination angle α of the stretching member 5 with respect to the vertical direction is preferably 5 to 75 degrees, more preferably 15 to 50 degrees, and specifically, for example, 5, 10, 15, 20, 25, 30, 35, 40. It is 45, 50, 55, 60, 65, 70, 75 degrees, and may be within the range between any two of the numerical values exemplified here.

2-3. Pinch step In the pinch step, as shown in FIGS. 8 to 9, the parison 23 is pinched to form the welded portion 23a. The welded portion 23a is formed so that a ventilation hole 23b (see FIG. 9) communicating from the inside of the parison 23 to the lower part of the parison 23 is provided.

This step can be performed by sandwiching the parison 23 with the pinch member 3a. In the stretching step, the parison 23 is stretched so that the inner surface 23c of the parison 23 is outside the end in the longitudinal direction of the pinch member 3a. Therefore, when the parison 23 is sandwiched between the pinch members 3a, a ventilation hole 23b is formed between the inner surface 23c of the parison 23 and the welded portion 23a.

The length of the welded portion 23a (or the length of the pinch member 3a) is L1, and the length between the facing inner surfaces 23c of the parison at the portion where the welded portion 23a is formed (or the distance between the tips of the pair of rods 5b). When L2, L1 / L2 is preferably 0.70 to 0.99, more preferably 0.99 to 0.98, and specifically, for example, 0.70, 0.75, 0.80, 0. .85, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, which are the numerical values exemplified here. It may be within the range between any two of.

2-4. Molding step In the molding step, the parison 23 is molded by molding the pair of split dies 19 with the parison 23 arranged between the pair of split dies 19. The molding step preferably includes a pre-blow step, a mold clamping step, and a blow step. At least one of the pre-blow step and the blow step can be omitted when it is not necessary.

(1) Pre-blow step In this step, as shown in FIGS. 10 to 11, air is blown into the parison 23 to inflate the parison 23 before the split mold 19 is clamped. As a result, the shape of the parison 23 can be made closer to the inner surface shape of the cavity 19a of the split mold 19. The air can be blown from the blow nozzle provided on the head 18, but it may be blown by another method.

When air is blown into the parison 23, the internal pressure of the parison 23 rises and the parison 23 swells. ..

The wall thickness of the parison 23 tends to be thin at a portion corresponding to the outer side in the width direction of the split mold 19, but since the ventilation hole 23b is provided at a position adjacent to such a portion, the wall thickness of the parison 23 is in the circumferential direction of the parison 23. Fluctuations in wall thickness are suppressed.

(2) Molding Step In this step, as shown in FIGS. 12 to 13, the rod 5b is retracted, and then the split mold 19 is molded as shown in FIG. When the rod 5b is still in contact with the parison 23, the weight of the parison 23 continues to be applied to the rod 5b, so that the parison 23 may be perforated by the rod 5b. If an unintended opening is formed in the parison 23, excessive tension may not be applied to the parison 23 due to excessive air bleeding, resulting in breakage. Therefore, in the present embodiment, the rod 5b is retracted before the mold is fastened so that the tip of the rod 5b does not come into contact with the parison 23. In the present embodiment, since the stretching member 5 is inclined, the tip of the rod 5b can be separated from the parison 23 by slightly retracting the rod 5b.

Further, if the tip of the rod 5b is located inside the parison 23, burrs generated after molding may be caught on the rod 5b and difficult to remove. Therefore, the rod 5b is retracted so that the tip of the rod 5b is not located in the parison 23. When it is not necessary to retract the rod 5b, the split mold 19 may be clamped without retracting the rod 5b.

(3) Blow Step In this step, the parison 23 is shaped into a shape along the inner surface of the cavity 19a by blowing air into the parison 23 in the split mold 19. As a result, a molded product having a desired shape can be obtained.

1: Molding machine 2: Resin supply device 3: Pinch device 3a: Pinch member 4: Stretching device 5: Stretching member 5a: Base 5b: Rod 5c: Protruding piece 6: Drive mechanism 7: Rail 8: Base 9: Slide member 10: Connecting member 11: Raw material resin 11a: Molten resin 12: Hopper 13: Extruder 13a: Cylinder 16: Injector 17: Accumulator 17a: Cylinder 17b: Piston 18: Head 19: Split mold 19a: Cavity 23: Parison 23a: Welded portion 23b: Vent hole 23c: Inner surface 25: Connecting pipe 27: Connecting pipe 31: Bracket 32: Connecting shaft 33: Connecting shaft 34: Connecting shaft α: Maximum inclination angle

Claims (8)

It is a method of manufacturing a molded product.
It has an extrusion process, a pinch process, and a molding process.
Wherein in the extrusion step, extruding a tubular parison made of a molten resin from F head,
In the pinch step, the parison is sandwiched to form a welded portion, and the welded portion is formed.
Wherein in the molding step, performed shaping of the parison in clamping the pair of split molds in a state of arranging the parison between split mold blocks of a pair,
The molding step includes a pre-blow step of blowing air into the parison to inflate the parison before molding the pair of split dies.
The welded portion is formed so as to provide a ventilation hole communicating from the inside of the parison to the lower part of the parison .
The welds, Ru is formed along the width direction of the split molds, methods. The method according to claim 1.
Equipped with a stretching process
The stretching step is performed between the extrusion step and the pinch step.
In the stretching step, the parison is stretched along the width direction of the split mold. It is a method of manufacturing a molded product.
It includes an extrusion process, a stretching process, a pinch process, and a molding process.
Wherein in the extrusion step, extruding a tubular parison made of a molten resin from F head,
In the pinch step, the parison is sandwiched to form a welded portion, and the welded portion is formed.
Wherein in the molding step, performed shaping of the parison in clamping the pair of split molds in a state of arranging the parison between split mold blocks of a pair,
The molding step includes a pre-blow step of blowing air into the parison to inflate the parison before molding the pair of split dies.
The welded portion is formed so as to provide a ventilation hole communicating from the inside of the parison to the lower part of the parison .
The stretching step is performed between the extrusion step and the pinch step.
In the stretching step, the parison is stretched along the width direction of the split mold. The method according to claim 3.
A method in which the welded portion is formed along the width direction of the split mold. The method according to any one of claims 2 to 4.
The stretching step is performed by increasing the distance between the pair of stretching members while the pair of stretching members are in contact with the inner surface of the parison. The method according to claim 5.
A method in which the distance between the pair of stretched members is widened by inclining the stretched member so that the tip end side of the stretched member is outside the proximal end side of the stretched member. The method according to any one of claims 2 to 6.
The pinch step is performed by sandwiching the parison between a pair of pinch members.
A method in which the parison is stretched so that the inner surface of the parison is outside the longitudinal end of the pinch member in the stretching step. The method according to any one of claims 1 to 7.
A method in which the vent is provided between the inner surface of the parison and the welded portion.

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