JP2011251481A - Injection molding machine and method for producing multilayered preform - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection molding machine which can more reliably prevent entrainment of air during injection even in an injection molding machine which uses both an injection mechanism which injects a resin through a storage part which can be decompressed and an injection mechanism which does not have such a storage part and injects the molten resin from each of the injection mechanisms; and to provide a method for producing a multilayered preform using the injection molding machine.SOLUTION: A state is formed, in which a first injection mechanism which injects the molten resin through the storage part which can be decompressed and a third injection mechanism which does not have such a storage part are provided, in a gate part 45 which is opened/closed by a valve gate 80, the respective outlets of the hot runner 14 of the first injection mechanism and the hot runner 34 of the third injection mechanism are opened, and the hot runners 14 and 34 of the respective injection mechanisms are made to communicate with each other even when the gate part 45 is closed by forming a communication groove 85 straddling each of the outlets.

Description

  The present invention relates to an injection molding apparatus suitable for manufacturing a multilayer preform which is a molding intermediate such as a resin bottle, and a method for manufacturing a multilayer preform using such an injection molding apparatus.

  A container made of a thermoplastic resin has excellent impact resistance and is easy to handle. In particular, containers made of a thermoplastic polyester resin such as polyethylene terephthalate are widely used in various containers because they are excellent in transparency, heat resistance and gas barrier properties in addition to impact resistance.

  However, although such a polyester container is excellent in gas barrier properties as a resin container, it passes a non-negligible amount of oxygen and carbon dioxide gas compared to the gas permeability of metal cans and glass containers. Was relatively short and insufficient. Therefore, in order to remedy such drawbacks, it has been proposed that the structure of the container has a multilayer structure, a layer made of a resin having an oxygen barrier property, or a layer of a material that exhibits oxygen absorption is provided. Yes.

As a method for producing a container having a multilayer structure, there is a method in which a preform having a multilayer structure is produced in advance and the preform is shaped by stretch blow molding.
As a method for producing a multilayer preform, for example, there is a method of sequentially injecting different resins into one mold using two injection molding machines in an injection molding method. Specifically, a predetermined amount of the polyester resin forming the outermost layer is supplied into the mold cavity (primary injection), and then an ethylene-vinyl alcohol copolymer is supplied into the polyester resin (secondary injection). (Injection), and further, a method of producing a multilayer preform by supplying a polyester resin (tertiary injection) and pressing and stretching an ethylene-vinyl alcohol copolymer is disclosed (for example, see Patent Document 1).

  In addition, in order to more accurately inject the amount into the mold cavity and reduce defects due to excess or shortage of resin, material is supplied from a material supply device such as an injection molding machine to a measuring instrument (shooting pot). A method of injecting by advancing the injection plunger is disclosed (for example, see Patent Document 2).

  As described above, various methods for manufacturing a multilayer preform have been known in the past. However, the present applicant has found that the multilayer preform manufactured by these methods causes air biting around the mouth and neck. It was found that appearance defects such as a streak pattern were formed on the surface of the preform due to the effect of deaeration in the cavity during molding. And as a result of the present applicant's earnest research, the cause of the air bite is that when the molten resin is supplied to the storage part, the molten resin storage pressure increases, so when the molten resin is injected into the mold Because of the turbulent flow state, it is presumed that the air in the mold is entrained, and when the countermeasures were examined, it was found that it was effective to reduce the molten resin storage pressure before injection. The manufacturing method of the multilayer preform which can improve the appearance defect by air biting etc. was proposed previously (refer patent document 3).

  In the method proposed in Patent Document 3, the first molten resin that forms the outermost layer of the multilayer preform is stored in the first reservoir, and the second melt that forms the intermediate layer of the multilayer preform. The resin is stored in the second storage section, and the storage pressure of the second molten resin and the storage pressure of the first molten resin are reduced in order, and then the first molten resin and the second molten resin are sequentially ordered. The molten resin is injected into a mold, and the molten resin is injected through a storage section that can be decompressed. By doing so, it was possible to prevent the air inside the mold from being caught when the first molten resin was injected from the nozzle, and to improve appearance defects such as air biting.

Japanese Patent Publication No. 4-25848 JP-A-11-314252 JP 2004-130650 A

By the way, Patent Document 3 shows an example in which a third molten resin is injected into a mold following the first and second molten resins when forming a three-kind five-layer multilayer preform. In such an injection molding apparatus that molds the multilayer preform, the third molten resin is injected without going through the storage part because of the installation space and the like.
As a result of further earnest research by the present applicant, a plurality of types of melting can be performed by using an injection mechanism that injects molten resin through a depressurizable storage part and an injection mechanism that does not have such a storage part. It has been found that an injection molding apparatus for injecting resin cannot completely suppress air entrapment, and there is still room for improvement. And in such an apparatus, the resin pressure remains in the runner of the injection mechanism that does not include the reservoir, and the resin in the runner blows out when the valve gate is opened when the resin is injected. I came to think that it might involve air.

  The present invention has been made in view of the circumstances as described above, and uses an injection mechanism that injects resin through a depressurized storage section and an injection mechanism that does not include such a storage section. Providing an injection molding apparatus capable of more reliably suppressing air entrainment during injection and a method for producing a multilayer preform using such an injection molding apparatus even in an injection molding apparatus for molding a multilayer preform With the goal.

  An injection molding apparatus according to the present invention includes an injection mechanism that injects molten resin through a depressurizable storage section, and an injection mechanism that does not include such a storage section, and is opened and closed by a valve gate. In addition, an outlet of the resin flow path of each injection mechanism is opened, and a communication groove extending over each of the outlets is formed, so that the resin flow path of each injection mechanism is closed even when the gate portion is closed. Are configured to communicate with each other.

  The method for producing a multilayer preform according to the present invention is a method for molding a multilayer preform using an injection molding apparatus as described above.

  According to the present invention, an injection mechanism that injects molten resin through a depressurized storage part and an injection mechanism that does not include such a storage part are used together, and the molten resin is injected from each injection mechanism. In doing so, it is possible to more reliably prevent air from being involved during injection.

It is sectional drawing which shows the outline of embodiment of the injection molding apparatus which concerns on this invention. It is sectional drawing which expands and shows the principal part of embodiment of the injection molding apparatus which concerns on this invention. It is AA sectional drawing of FIG.2 (b). It is a time chart which shows each process of embodiment of the manufacturing method of the multilayer preform which concerns on this invention. It is the conceptual diagram which showed the mode of resin in the cavity in the injection process of embodiment of the manufacturing method of the multilayer preform which concerns on this invention. It is a graph explaining the relationship between the storage pressure of the 1st molten resin in the embodiment of the manufacturing method of the multilayer preform concerning the present invention, and the residual pressure of the 3rd molten resin.

  Embodiments of the present invention will be described below with reference to the drawings.

[Injection molding equipment]
First, an embodiment of an injection molding apparatus according to the present invention will be described.
FIG. 1 is a cross-sectional view schematically showing an embodiment of an injection molding apparatus according to the present invention. An injection molding apparatus 1 in the present embodiment has a plurality of injection mechanisms, and has three types and five layers by an injection molding method. It is configured as an injection molding apparatus for molding a preform.

In the example shown in FIG. 1, the injection molding apparatus 1 heats and melts the first thermoplastic resin that forms the outermost layer (first layer, fifth layer) of the multilayer preform and supplies it as the first molten resin. An extruder 10, and an extruder 20 that heats and melts a second thermoplastic resin that forms a first intermediate layer (second and fourth layers) in contact with the inside of the outermost layer and supplies the second molten resin as a second molten resin; And an extruder 30 that heats and melts a third thermoplastic resin that forms a second intermediate layer (third layer) between the first intermediate layers and supplies it as a third molten resin. . Furthermore, the injection molding apparatus 1 cools the resin that is injected from the nozzles 42 of the hot runner unit 40 and the hot runner unit 40 that maintains the resin supplied from the extruders 10, 20, and 30 in a molten state. And a mold part 50 which is shaped into a predetermined shape.
The mold part 50 has an injection mold 51 and a core mold 52, and a cavity 53 corresponding to the shape of the preform to be molded and air in the cavity 53 are formed on the joint surface. A vent 54 is formed to perform extraction.

  The extruder 10 is connected to the hot runner portion 40 via the sprue bush 13 and is supplied to the hot runner 14 while rotating in the cylinder 11 and capable of heating to a desired temperature while melting and kneading the resin. And a screw 12 to be used. Similarly, the extruders 20 and 30 are connected to the hot runner portion 40 via sprue bushes 23 and 33, respectively, and can rotate within the cylinders 21 and 31 that can be heated to a desired temperature, and the cylinders 21 and 31, respectively. Are supplied to the hot runners 24 and 34 while melt kneaded.

  The hot runner portion 40 has a block 41 and a nozzle 42, and the nozzle 42 is attached to the block 41 on the mold portion 50 side. And the hot runner 14 as the flow path of the first molten resin supplied from the extruder 10 passes through the sprue bush 13 connecting the extruder 10 to the hot runner portion 40, the block 41, and the nozzle 42. Is provided. Similarly, the hot runner 24 as a flow path of the second molten resin supplied from the extruder 20 passes through the sprue bush 23 that connects the extruder 20 to the hot runner portion 40, the block 41, and the nozzle 42. The hot runner 34 as a flow path of the third molten resin supplied from the extruder 30 is a sprue bush 33 that connects the extruder 30 to the hot runner section 40, a block 41, It is provided so as to penetrate the nozzle 42.

  Furthermore, the block 41 switches the flow path of the 1st storage part 60 which measures and inject | emits 1st molten resin, the hot runner 64 which connects the 1st storage part 60 to the hot runner 14, and the hot runners 14 and 64. A valve V1, a second reservoir 70 for measuring and injecting the second molten resin, a hot runner 74 for connecting the second reservoir 70 to the hot runner 24, and a valve V2 for switching the flow paths of the hot runners 24, 74, A valve gate 80 for opening and closing the gate portion 45 and a drive cylinder 81 for the valve gate 80 are provided.

  Various valves can be used as the valves V1 and V2. However, it is preferable to use a rotary valve because the stored pressure can be prevented from being transmitted to the hot runners 14 and 24 when the resin is measured.

  In the injection molding apparatus 1 including such a block 41, the first injection for injecting the first molten resin by the extruder 10, the hot runners 14 and 64, the first reservoir 60, and the valve V1. The mechanism is configured. Further, the extruder 20, the hot runners 24 and 74, the second reservoir 70, and the valve V2 constitute a second injection mechanism for injecting the second molten resin. The extruder 30 and the hot runner 34 constitutes a third injection mechanism for injecting the third molten resin.

The first reservoir 60 includes an injection cylinder 61 and an injection piston 62, and the injection piston 62 is connected to a plate 63. The first molten resin supplied from the extruder 10 is filled in the reservoir 60 while pressing the injection piston 62. By sensing and controlling the amount of movement of the plate 63 at this time, the resin filled in the reservoir 60 can be measured. And by retreating the plate 63 to slightly increase the volume of the region filled with the resin in the storage unit 60, the storage pressure of the resin in the storage unit 60 can be reduced, and the plate 63 is advanced. Thus, the resin stored in the storage unit 60 can be injected.
Similarly, the second reservoir 70 has an injection cylinder 71 and an injection piston 72 connected to the plate 73. The storage unit 70 is filled by sensing and controlling the amount of movement of the plate 73 when the storage unit 70 is filled while the second molten resin supplied from the extruder 20 presses the injection piston 72. The measured resin can be measured, and the resin can be injected and decompressed by moving the plate 73 back and forth.
The plates 63 and 73 are connected to a cylinder (not shown) and are configured to advance and retract independently.

  2 is an enlarged cross-sectional view showing the vicinity of the gate portion 45 of the injection molding apparatus 1 shown in FIG. 1, and FIG. 2A shows a state in which the gate portion 45 is closed by moving the valve gate 80 forward. FIG. 2B shows a state in which the valve gate 80 is retracted and the gate portion 45 is opened.

In the example shown in FIG. 2, the gate portion 45 is a cylindrical hollow portion that is coaxially connected to the hot runner 14 via a tapered portion 14 a having a tapered tip end side of the hot runner 14. The outlet of the hot runner 14 opens to one end side in the axial direction of the gate portion 45, and the outlet of the hot runners 24 and 34 opens to the peripheral surface of the gate portion 45. As a result, the molten resin that has passed through each of the hot runners 14, 24, 34 is injected into the cavity 53 of the injection mold 51 through the gate portion 45.
At this time, the valve gate 80 inserted into the central portion of the hot runner 14 advances and retreats and moves in and out of the gate portion 45 so that the gate portion 45 can be opened and closed. The inner diameter of the portion 45 is substantially the same.

Further, as shown in FIG. 2, a communication groove 85 is formed along the axial direction of the gate portion 45 so as to straddle the outlet of the hot runner 14 and the outlet of the hot runner 34. Thus, even when the gate portion 45 is closed by the valve gate 80, the hot runner 14 and the hot runner 34 are in communication with each other.
That is, in the present embodiment, the first injection mechanism including the extruder 10, the hot runners 14 and 64, the first reservoir 60, and the valve V1 injects the molten resin through the depressurized reservoir. The third injection mechanism consisting of the extruder 30 and the hot runner 34 is an injection mechanism that does not have a depressurizable reservoir, and the outlets of the hot runners 14 and 34 as the resin flow paths Is opened in the gate portion 45, and a communication groove 85 extending over each of the outlets is formed, so that the hot runners 14 and 34 communicate with each other even when the gate portion 45 is closed. .
FIG. 3 is a cross-sectional view taken along the line AA in FIG.

By doing in this way, even if there is a residual pressure in the molten resin in the hot runner 34 of the third injection mechanism that does not have a depressurizable storage part, the resin in the storage part 60 is removed in the first injection mechanism. When the pressure is reduced, the third molten resin filled in the hot runner 34 flows in the communication groove 85 toward the hot runner 14, and the third molten resin in the hot runner 34 slightly decreases. Thus, the residual pressure can be released.
Thus, an injection mechanism (a first injection mechanism in the present embodiment) that injects resin through a depressurized reservoir, and an injection mechanism (such as this embodiment) that does not include such a reservoir. Even in the case of an injection molding apparatus that injects a plurality of types of molten resin in combination with the third injection mechanism), air entrainment during injection can be more reliably suppressed.

Further, in forming such a communication groove 85, when a plane orthogonal to the axial direction of the gate portion 45 is used as a projection surface, the total area of the orthogonal projection of the communication groove 85 to the projection surface (the communication groove 85 is defined as When a plurality of the grooves are formed, the area is obtained by combining the orthogonal projections of all the communication grooves 85. In the illustrated example, the area obtained by combining the orthogonal projections of both the communication grooves 85 located above and below in the drawing) The area of the outlet opening in the gate portion 45 of the hot runner 14 is preferably 16.7% or more of the area (this area is substantially equal to the cross-sectional area of the valve gate 80). If the communication groove 85 is smaller than this range, the residual pressure of the molten resin in the hot runner 34 tends not to be sufficiently released.
Further, the shape of the communication groove 85 is not particularly limited, but considering the ease of flow of the molten resin when releasing the residual pressure of the molten resin in the hot runner 34, as shown in FIG. 34 are preferably formed by cutting a portion straddling each of the outlets into a circular arc shape along the axial direction of the gate portion 45.
In the cross-sectional view shown in FIG. 3, the hot runner 34 is viewed from the front side of the paper with respect to the communication groove 85, and the hot runner 14 is viewed from the communication groove 85 by looking into the back side of the paper. It has become.

[Manufacturing method of multilayer preform]
Next, a method for manufacturing a multilayer preform using the injection molding apparatus as described above will be described.
FIG. 4 is a time chart showing the steps of the manufacturing method of the present embodiment.

1. Resin metering / filling process In the resin metering / filling process, the injection pistons 62, 72 in the reservoirs 60, 70 are in the most advanced state, that is, the resins are stored in the reservoirs 60, 70. The first molten resin is filled in the hot runner 14, the second molten resin is filled in the hot runner 24, the third molten resin is filled in the hot runner 34, and the valve gate 80 is closed. The state is an initial state (t0 in FIG. 6). Then, from this initial state, the valve V1 is switched to connect the extruder 10 and the storage unit 60, and the storage unit 60 is weighed and filled with the first molten resin supplied from the extruder 10. The amount of resin filling at this time can be performed by sensing and controlling the amount of movement of the plate 63. Similarly, the valve V <b> 2 is switched to connect the extruder 20 and the storage unit 70, and the second molten resin supplied from the extruder 20 is measured and filled into the storage unit 70. The amount of resin filling at this time can be performed by sensing and controlling the amount of movement of the plate 73.
In addition, there is no restriction | limiting in particular in the order which fills the storage parts 60 and 70 with 1st molten resin and 2nd molten resin, respectively, It can also fill simultaneously.

2. Next, the storage unit 70 is disconnected from the extruder 20 by switching the valve V2. Then, the storage pressure of the 2nd molten resin with which the storage part 70 and the hot runner 24 were filled is pressure-reduced by retracting the plate 73 and slightly increasing the volume of the area | region with which the resin in the storage part 70 is filled. . At this time, the plate 73 may be naturally retracted by the storage pressure of the second molten resin acting on the injection piston 72, or may be forcibly retracted by a cylinder (not shown) connected to the plate 73. Also good.
The resin storage pressure at this time is preferably reduced to a range of 24 to 0 MPa. Further, the retraction amount of the plate 73 can be set as appropriate depending on the properties of the resin to be used, but if the retraction amount is too large, the variation in the shot amount increases and the position of the layer formed by the second molten resin varies greatly. There is a risk of problems such as becoming.

Subsequently, the storage pressure of the first molten resin filled in the storage unit 60 and the hot runner 14 is similarly reduced. That is, the storage unit 60 and the hot runner 14 are switched by switching the valve V1 to disconnect the storage unit 60 from the extruder 10 and retreating the plate 63 to slightly increase the volume of the region filled with the resin in the storage unit 60. The storage pressure of the first molten resin filled in is reduced (t1 in FIG. 6).
At this time, the hot runner 14 is in communication with the hot runner 34 filled with the third molten resin, as described above. For this reason, if there is residual pressure in the third molten resin, the third molten resin filled in the hot runner 34 communicates toward the hot runner 14 when the storage pressure of the first molten resin is reduced. Flowing in the groove 85, the third molten resin in the hot runner 34 is slightly reduced, and the residual pressure of the third molten resin is released.

  In order to prevent leakage of the second molten resin to the hot runner 14, it is important to reduce the storage pressure of the first molten resin after reducing the storage pressure of the second molten resin. is there. That is, normally, the clearance between the valve gate 80 and the gate portion 45 is sealed with the first molten resin. For example, a barrier resin or an oxygen absorbing material is used as the second molten resin. In some cases, the melt viscosity of the resin may be low, and the resin may leak from this clearance. In order to prevent this, it is necessary to make the storage pressure of the first molten resin higher than the storage pressure of the second molten resin. As the first molten resin, a polyester resin or the like that forms the surface layer of the container is used. However, since the melt viscosity is high, the resin does not leak from the clearance.

Here, in contrast to the conventional injection molding apparatus in which the communication groove 85 is not formed and the injection molding apparatus 1 in the present embodiment, the first molten resin in the hot runner 14 is reduced in the storage pressure reducing process. FIG. 6 shows how the pressure and the pressure of the third molten resin in the hot runner 34 fluctuate.
FIG. 6A shows an ideal relationship between the pressure P1 of the first molten resin in the hot runner 14 and the pressure P3 of the third molten resin in the hot runner 34 in the present embodiment. Both vary while showing the same value. At this time, the increase in the pressure of the resin is due to an increase in pressure accompanying the measurement and filling of the first molten resin into the storage unit 60. That is, when the pressure P1 of the first molten resin in the hot runner 14 is increased, the resin moves through a slight gap existing in the valve V1 when the first molten resin is measured and filled in the reservoir 60. The increase in the pressure P3 of the third molten resin in the hot runner 34 is due to the movement of the resin through the communication groove 85.
On the other hand, FIG. 6B shows the first molten resin in the hot runner 14 in the conventional injection molding apparatus configured in the same manner as the injection molding apparatus 1 of the present embodiment except that the communication groove 85 is not formed. The relationship between the pressure P ₀ 1 and the pressure P ₀ 3 of the third molten resin in the hot runner 34 is shown, immediately before opening the gate portion 45 (immediately before t2 in FIG. 6), that is, immediately before the start of injection. , Residual pressure is observed in the third molten resin in the hot runner 34. At this time, the fluctuation of the pressure P ₀ 3 of the third molten resin in the hot runner 34 is caused by the movement of the resin through the clearance existing between the valve gate 80 and the gate portion 45.
In the graph shown in FIG. 6, t0 on the horizontal axis is an initial state in which the valve gate 80 is advanced and the gate portion 45 is closed, and t1 is a state in which the plate 63 is retracted to fill the resin in the storage portion 60. By slightly increasing the volume of the region, the storage pressure of the first molten resin filled in the storage unit 60 and the hot runner 14 is reduced, and t2 is the state in which the gate 45 is opened by retreating the valve gate 80. is there. As can be seen from this graph, in the pressure holding state at t0, in the injection molding apparatus 1 of the present embodiment, the pressure P3 of the third molten resin in the hot runner 34 is caused by the communication groove 85 in the hot runner 14. While the pressure is equal to the pressure P1 of the first molten resin, the pressure P ₀ 3 of the third molten resin in the hot runner 34 is in the hot runner 14 in the conventional injection molding apparatus. It is higher than the pressure P ₀ 1 of the first molten resin.

3. Injection process In the injection process performed subsequently, first, the valve gate 80 is retracted and the gate part 45 is opened (t2 in FIG. 6), and then the injection piston 62 of the first storage part 60 is advanced, A predetermined amount of the first molten resin stored in the storage unit 60 is injected into the cavity 53 through the hot runner 14.
FIG. 5 is a conceptual diagram showing the state of the resin in the cavity in the injection process. FIG. 5A shows a state when the first molten resin is injected, and the middle of the cavity 53 is filled with the first molten resin 91.

  At this time, if the storage pressure of the first molten resin is high, the flow of the resin becomes a turbulent state because the gate portion 45 is vigorously passed when the gate portion 45 is opened. In this case, the first molten resin entrains the air in the cavity 53, and the air stays in the resin to generate bubbles, or a defect such as a trace when the air escapes remains on the surface of the preform. However, in this embodiment, since the storage pressure of the first molten resin 91 is reduced before injection, the above flow does not occur even when the gate portion 45 is opened. Therefore, appearance defects can be improved without entraining air. Moreover, since the residual pressure of the third molten resin in the hot runner 34 is also released when the storage pressure of the first molten resin is reduced, the third molten resin is released when the gate portion 45 is opened. The bubble entrainment due to the blowout to the gate portion 45 is also effectively suppressed.

Next, the injection piston 72 of the second storage unit 70 is advanced, and a predetermined amount of the second molten resin stored in the storage unit 70 is injected into the cavity 53 through the hot runner 24.
FIG. 5B shows a state when the second resin is injected. As shown in FIG. 5B, in the surface portion of the cavity 53, the first molten resin 91 is solidified by contact with the mold, or even if it is not solidified, the viscosity is extremely high. Therefore, the second molten resin 92 flows toward the tip of the cavity 53 along substantially the center surface of the first molten resin 91 filled layer, and forms an intermediate layer of the second molten resin 92. .

Next, a predetermined amount of the third molten resin is supplied from the extruder 30 to the cavity 53 through the hot runner 34.
FIG. 5C shows a state when the third resin is injected. As shown in FIG. 5C, the third molten resin 93 flows into the middle of the second molten resin 92, and the second molten resin 92 and the first molten resin 91 are directed toward the tip of the cavity 53. And move forward while pushing. As a result, a structure of three types and five layers is formed.

Subsequently, the injection piston 62 of the first storage unit 60 is advanced again, and the resin in the storage unit 60 is injected into the cavity 53 through the hot runner 14 to hold the pressure.
FIG. 5D shows a state when the first molten resin is injected again. As shown in FIG. 5D, the third molten resin 93 filling the gate portion 45 is replaced with the first resin. In this step, the third molten resin staying in the gate portion 45 is injected as a part of the second intermediate layer of the preform and discharged from the gate portion 45. Therefore, in the subsequent cycle, Appearance defects caused by mixing the third resin with one resin can be prevented.

  Thereafter, the valve gate 80 is advanced, the gate portion 45 is closed, and after cooling, the mold is opened and the preform is taken out. And after closing the gate part 45, the process after resin measurement and filling demonstrated above is repeated, and a preform is manufactured continuously.

In the present invention, any resin that can be used as the first thermoplastic resin can be used without any problem as long as it is a thermoplastic resin. A thermoplastic polyester is preferred because of its excellent gas barrier properties.
Any thermoplastic polyester can be used as long as it can be stretch blow molded and heat treated (thermally crystallized). For example, thermoplastic polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyarylate, or copolymers thereof, and blends of these resins or other resins can be suitably used. Ethylene terephthalate-based thermoplastic polyester such as can be suitably used.

The ethylene terephthalate-based thermoplastic polyester is composed of an ethylene terephthalate unit in the majority of ester repeating units, generally 70 mol% or more, and has a glass transition point (Tg) of 50 to 90 ° C. and a melting point (Tm) of 200 to 275. Those in the range of ° C are preferred.
These resins are blended with various additives such as colorants, ultraviolet absorbers, mold release agents, lubricants, nucleating agents, antioxidants, antistatic agents and the like within a range that does not impair the quality of the molded product. be able to.

The resin used as the second thermoplastic resin can be appropriately selected according to the function required for the final molded body. For example, oxygen absorbing materials, gas barrier resins, recycled materials, other functional inorganic and / or organic component mixed resins, and the like can be used.
Examples of the gas barrier resin include ethylene-vinyl alcohol copolymer (EVOH). As another example of the gas barrier resin, a cyclic olefin copolymer (COC), particularly a copolymer of ethylene and a cyclic olefin, particularly APEL manufactured by Mitsui Chemicals, Inc. can be used as the moisture barrier resin. .

Another example of the gas barrier resin is a polyamide resin. Examples of the polyamide resin include (a) an aliphatic, alicyclic or semi-aromatic polyamide derived from a dicarboxylic acid component and a diamine component, (b) a polyamide derived from an aminocarboxylic acid or a lactam thereof, or these Copolyamide or blends thereof may be mentioned.
Among these polyamides, xylylene group-containing polyamides are preferable because they have excellent gas barrier properties compared to other polyamide resins.

  As the oxygen absorbing material, any material can be used as long as it absorbs oxygen and prevents permeation of oxygen, but a combination of an oxidizable organic component and a transition metal catalyst, a gas barrier resin, an oxidizable organic Combinations of components and transition metal catalysts are preferably used.

  As the gas barrier resin, when the first molten resin is a thermoplastic polyester, a polyamide resin is preferable from the viewpoint of moldability, and a xylylene group-containing polyamide is more preferable. Among the xylylene group-containing polyamides, those having a terminal amino group concentration of 40 eq / 106 g or more are preferable in that they are not substantially oxidized. The oxidizable organic component is preferably a polymer derived from polyene.

  The transition metal catalyst is preferably a Group VIII metal component of the periodic table such as iron, cobalt, nickel, etc. In addition, a Group I metal such as copper and silver: a Group IV metal such as tin, titanium and zirconium, Examples include V group of vanadium, Group VI such as chromium, and Group VII metal components such as manganese. Among these metal components, the cobalt component is particularly preferable because of its high oxygen absorption rate.

  There is no restriction | limiting in particular as a 3rd thermoplastic resin, For example, said 1st thermoplastic resin and 2nd thermoplastic resin can be used. Since the third thermoplastic resin is used as an intermediate layer, there is no need to worry about the appearance, and therefore a recycled material such as a recycled PET resin can be used.

  Although the present invention has been described with reference to the preferred embodiment, it is needless to say that the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention. .

  For example, in the above-described embodiment, an example is shown in which the communication groove 85 is formed across the outlet of the hot runner 14 of the first injection mechanism and the outlet of the hot runner 34 of the third injection mechanism. The communication groove 85 may be formed so as to straddle the outlet of the hot runner 24 of the second injection mechanism and the outlet of the hot runner 34 of the third injection mechanism. In this case, the second injection mechanism corresponds to an injection mechanism that injects the molten resin through the storage section that can be decompressed.

  Further, in the above-described embodiment, the hot runner 14 of the first injection mechanism, that is, an example in which the resin flow path of the injection mechanism that injects the molten resin through the depressurizable reservoir is connected coaxially with the gate portion 45. Although shown, in the illustrated example, the first injection mechanism and the third injection mechanism are interchanged, and the resin flow path of the injection mechanism that does not include the storage portion is connected to the gate portion 45 coaxially, You may make it the outflow port of the resin flow path of the injection mechanism which injects molten resin through the storage part which can be pressure-reduced open in the surrounding surface of the gate part 45. FIG.

  In the embodiment described above, an example in which an extruder is used as the material supply device is shown, but the present invention is not limited to this. For example, as a material supply device, an injection machine may be used, or a resin supplied from an extruder may be temporarily filled in an injection cylinder and then supplied to a hot runner from the injection cylinder. Good.

  In the above-described embodiment, an example in which a three-kind five-layer preform is manufactured is shown. For example, instead of the third thermoplastic resin, a second thermoplastic resin is supplied to supply two or three kinds of preforms. A two-layer five-layer preform can also be manufactured by supplying the first thermoplastic resin instead of the third thermoplastic resin. Furthermore, the present invention can also be applied to the production of multilayer preforms such as four types and six layers. In this case, the number of extruders and storage units is increased or decreased.

  The present invention as described above can be used as a technique for producing a multilayer preform which is a molding intermediate such as a resin bottle.

DESCRIPTION OF SYMBOLS 1 Injection molding apparatus 10, 20, 30 Extruder 45 Gate part 14, 24, 34 Hot runner (resin flow path)
60, 70 Reservoir 80 Valve gate 85 Communication groove

Claims (5)

An injection mechanism for injecting the molten resin through a depressurizable reservoir, and an injection mechanism that does not include such a reservoir;
In the gate portion that is opened and closed by the valve gate, the outlet of the resin flow path of each injection mechanism opens, and by forming a communication groove across each of the outlets,
An injection molding apparatus, wherein the resin flow paths of the injection mechanisms are in communication with each other even when the gate portion is closed. The resin flow path of one of the injection mechanisms and the gate part are coaxially connected, and the outlet of the resin flow path opens on one end side in the axial direction of the gate part,
While the outlet of the resin flow path of the other injection mechanism among the injection mechanisms is open to the peripheral surface of the gate portion,
The injection molding apparatus according to claim 1, wherein the communication groove is formed along an axial direction of the gate portion.   When a plane orthogonal to the axial direction of the gate portion is a projection plane, the total area of the orthogonal projection of the communication groove onto the projection plane is 16 of the area of the outlet of the resin flow path of the one injection mechanism. The injection molding apparatus according to claim 2, which is 7% or more.   The injection molding apparatus according to claim 2 or 3, wherein the communication groove is formed in a cross-sectional arc shape along the axial direction of the gate portion.   The manufacturing method of a multilayer preform which shape | molds a multilayer preform using the injection molding apparatus as described in any one of Claims 1-4.

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