JPH06285910A - Injection molding method of thermoplastic resin, injection molding nozzle and hot runner - Google Patents

Abstract

PURPOSE:To provide an injection molding method of thermoplastic resin and injection molding nozzle and hot runner wherein stringing phenomenon to be generated at mold opening does not occur. CONSTITUTION:A cylindrical injection molding nozzle 20 having at its tip a melt resin injecting hole 22 is attached to a resin injecting opening 13 of a melt resin supplying machine and is engaged with a nozzle engaging part of a sprue provided in an injection mold so as to inject melted thermoplastic resin into the sprue. At a tip 22b of the melt resin injecting hole 22 of the nozzle 20, a flow dividing plate 24 crossing the hole 22 is provided so as to narrow the area of the hole 22 and enlarge the contact area of the resin in the tip of the hole 22 and the nozzle 20, so that cooling and solidification of the resin in between the nozzle 20 and the sprue in cooling process are accelerated and stringing phenomenon which has conventionally been a problem in releasing process can be eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin injection molding method, an injection molding nozzle and an injection molding hot runner.

[0002]

2. Description of the Related Art An injection molding machine is shown in FIG.
The molten resin supply that melts and injects the thermoplastic resin
Feeder 1 and molten resin injected from the molten resin feeder 1
It is composed of a mold 5 for molding and solidifying fat,
A predetermined amount of molten resin is supplied to the resin injection port 2 of the molten resin feeder 1.
With a resin passage for injection at a pressure of
Has been attached. On the other hand, the molding die 5 is fixed on the injection side.
The fixed mold 5a and the fixed mold 5a in the direction of approaching and separating.
It is composed of a movable mold 5b on the mold clamping side that is movable,
The fixed mold 5a includes a tip portion of the nozzle 3 of the molten resin feeder 1.
A sprue bush 6 having an engaging recess 6a for engaging with
The molten resin injected from the nozzle 3 is
Pass through the sprue bush 6 and define the key defined in the mold 5.
Avity C ₁, C₂Is injected into. And injected into the mold
Pressure-holding process to keep the resin held at a constant pressure, solidify the molded product
After the cooling process to move, as shown in FIG.
The mold 5b is separated from the fixed mold 5a in the release process,
Molded product by the protruding mechanism 7 built in the moving mold 5b
Is pushed and removed from the mold 5.

[0003]

However, in the conventional molding method, at the time of the mold release step (mold opening), as shown by reference numeral 8 in FIG. 17, the resin material forms a thread from the tip of the nozzle 3 to the sprue portion. The so-called stringing phenomenon sometimes occurred. This occurs because the resin is not sufficiently solidified between the nozzle 3 and the sprue bush 6. When this stringing phenomenon occurs, the solidified resin string remains in the mold 5 and damages the parting surface. The occurrence of the stringing phenomenon is a major problem because it leads to the generation of defective products. In order to prevent the stringing phenomenon, the mold releasing step (mold opening) may be delayed until the resin in the nozzle 3 is sufficiently solidified.
The longer the cooling process is, the longer the entire time required for producing the molded product is, which is not preferable.

The present invention has been made in view of the above-mentioned problems of the prior art, and its purpose is to provide a thermoplastic resin injection molding method, an injection molding nozzle, and an injection molding hot method which do not cause a stringing phenomenon during mold opening. To provide a runner.

[0005]

In order to achieve the above object, in the method of injection molding a thermoplastic resin according to claim 1, a molten thermoplastic resin injected from an injection molding nozzle is injected into an injection molding metal. Injection process of injecting into the cavity through the sprue provided in the mold, pressure holding process of maintaining the resin in the mold at a constant pressure, cooling process of cooling and solidifying the resin in the mold, and separating the mold In the injection molding method of the thermoplastic resin, which comprises a mold release step for taking out the molded product by
In the injection step, the branched portion provided in the injection hole of the nozzle is used to inject the molten resin into the sprue in a branched state.

In the thermoplastic resin injection molding method according to the second aspect, the molten thermoplastic resin injected from the injection molding nozzle is introduced into the cavity through the sprue and hot runner provided in the injection molding die. An injection step of injecting, and a pressure holding step of maintaining the resin in the mold at a constant pressure,
In an injection molding method including a cooling step of cooling and solidifying a resin in a mold and a mold release step of separating a mold and taking out a molded product, in the injection step, a resin injection hole to a cavity of a hot runner is formed. With the branching portion provided, the molten resin is injected into the cavity in a branched state.

In the injection molding nozzle according to the third aspect, the sprue is attached to the resin injection port of the molten resin supply machine and engages with the nozzle engaging portion of the sprue provided in the injection molding die. In a cylindrical injection molding nozzle that injects a molten thermoplastic resin into a molten resin injection hole at the tip, a branch portion that crosses the injection hole is provided at the tip of the molten resin injection hole. It is a thing.

In the injection-molding hot runner according to claim 4, the injection molding hot-runner is located between the sprue provided in the injection-molding die and the cavity, and injects the molten resin injected through the sprue into the cavity. In the hot runner, a branch portion that crosses the injection hole is provided at the tip of the resin injection hole of the hot runner.

[0009]

In the first and third aspects of the invention, at the tip of the injection hole of the nozzle, the resin passage is narrowed by the branch portion, and the contact area of the resin with the nozzle is larger than that of the conventional nozzle having no branch portion. In the cooling step, cooling and solidification of the molten resin in the vicinity of the injection hole of the nozzle is promoted.

According to the second and fourth aspects of the present invention, at the tip of the resin injection hole to the cavity of the hot runner, the resin passage is narrowed by the branch portion, and the contact area of the resin with the hot runner is not the conventional hot portion. Since it is larger than the runner, cooling and solidification of the resin in the vicinity of the resin injection hole into the cavity of the hot runner is promoted in the cooling step.

[0011]

Embodiments of the present invention will now be described with reference to the drawings. 1 to 10 show an embodiment of the present invention,
1 is a general view of an injection molding apparatus for carrying out the method of the present invention, FIG. 2 is a sectional view of the apparatus in an injection step, FIG. 3 is a sectional view of the apparatus in a releasing step, and FIG. 4 is a sectional view of the present invention. An enlarged side view of an injection molding nozzle used only for carrying out the method, FIG. 5 is an enlarged cross-sectional view of the nozzle, FIG. 6 is an enlarged perspective view of the tip of the nozzle, and FIG. 7 is an enlarged view of the tip of the nozzle. FIG. 8 is a plan view, FIG. 8 is a perspective view illustrating a state in which a flow dividing plate constituting chip that is a branch portion is fitted in the nozzle, FIG. 9 is a side view in the same state, and FIG. 10 is a sectional view in the same state (shown in FIG. 9). It is sectional drawing which follows the line XX).

In these drawings, an injection molding apparatus includes a molten resin supply machine 10 for injecting a thermoplastic resin material in a molten state, and a molding die 30 for molding the resin injected from the molten resin supply machine 10. It consists of and. The molten resin feeder 10 has a horizontally arranged cylinder 12 in which a screw 14 is capable of advancing and retreating, and a resin supply port 13 provided at a front end of the cylinder 12 has an injection nozzle 20.
Is attached to the outer periphery of the cylinder 12 and the nozzle 20,
A structure is provided in which a band-shaped heater 15 is provided for melting the thermoplastic resin material in the cylinder 12 and keeping it in a constant molten state. The resin material charged from the hopper 16 is melted and stirred in the cylinder 12, and screwed. It is ejected from the nozzle 20 by the advance of 14. Reference numeral 14a is a check valve provided at the front end of the screw 14, reference numeral 17 is a hydraulic motor for rotationally driving the screw 14, and reference numeral 18 is an injection cylinder for moving the screw 14 forward and backward.

The nozzle 20 is made of an iron alloy having a good heat dissipation property, and a resin passage 22 which is an injection hole extending in the axial direction and opening to the spherical tip is formed inside the nozzle 20. The resin supply port 1 of the molten resin supply machine 10 is provided on the outer periphery of the nozzle rear end portion.
A male screw 23 that matches the female screw 13a of No. 3 is formed. An inner region 22a of the resin passage 22 is a tapered hole whose diameter becomes smaller toward the front end side (in the resin flow direction), and this tapered region 22a communicates with a region 22b where the tip side diameter gradually increases. Thus, the structure is such that a high injection pressure and a high injection speed can be obtained. In addition, the front end region 22b of the injection hole
Is provided with a flow dividing plate 24 extending across the hole 22, and the flow of the molten resin is divided into two by the flow dividing plate 24 and injected from the injection hole 22.

The flow dividing plate 24, as shown in FIGS.
In order to reduce the flow resistance and ensure a smooth flow of the molten resin, the side edge portion 24a on the inner side of the hole 22 is formed to have an acute-angled cross section. Further, as shown in FIGS. 8 and 9, the flow dividing plate 24 is press-fitted from the side of the nozzle with the flow dividing plate constituting chip W made of an iron alloy that has been hardened in the flow dividing plate fitting slit 21 formed at the tip of the nozzle. The nozzle 10 is integrated with the tip of the nozzle 10 and then the part of the flow distribution plate constituting chip W protruding from the outer surface of the nozzle is cut to be flush with the outer peripheral surface of the front end of the nozzle.

Further, the nozzle tip side region 21a of the slit 21 formed in the nozzle 20 and the side edge portion on the injection hole opening side (side edge portion on the nozzle front end side) 24b of the flow distribution plate 24 fitted in this region 21a are A wedge-shaped cross section (tapered shape that becomes narrower toward the nozzle tip side) has a retaining effect by a wedge action. Since the flow dividing plate 24 having good heat conductivity is located at the center of the front end portion of the injection hole 22, the opening area of the injection hole 22 is smaller than that of the conventional nozzle, and the resin at the position of the injection hole 22 has good heat conductivity. Since the area in contact with the metal material (the inner wall of the nozzle and the flow dividing plate) is large and the distance from the resin to the metal material is short, the heat dissipation of the resin at the tip of the injection hole 22 is excellent, and the time for the resin to cool and solidify. Is short.

That is, in the cooling step in the injection molding, the resin is cooled in the state where the resin material is filled from the resin passage 22 in the nozzle 20 to the sprue bush 32 of the mold 30 to the cavity C. Since the resin cooling action at the front end position is superior to that of the conventional nozzle, the resin in the vicinity of the nozzle injection hole 22 is surely cooled in the predetermined cooling time required in the cooling step in the conventional injection molding method. There is no risk of stringing occurring during the mold release step (mold opening) after solidification.

On the other hand, the molding die 30 is composed of a fixed die 30A on the nozzle side and a movable die 30B which can move in a direction toward and away from the fixed die 30A.
A cavity C (C ₁ , C ₂ ) is defined by the molding surfaces 31A, 31B on the opposite sides of A, 30B. A cylindrical sprue bushing 32 forming a sprue S communicating with the cavity C is incorporated in the fixed mold 30A, and the end of the sprue bushing 32 on the molten resin feeder 10 side is
A spherical engagement recess 33 that can engage with the tip of the nozzle 20 is formed. Then, the molten resin injected from the injection molding nozzle 20 is injected and filled into the cavity C through the sprue S.

Next, an injection molding method performed by using the injection molding apparatus shown in FIG. 1 will be described. First, the mold 30 (30A, 3
0B) is closely attached and the mold is clamped. Next, after the nozzle 20 is touched on the mold 30 (recess 33 that is the nozzle engaging part), the molten resin in the cylinder 12 is injected into the cavity C of the mold 30 at high pressure (injection step). Next, the resin injected into and filled in the mold 30 is kept under pressure (pressure holding step). After the resin in the mold 30 is solidified and the gate is solidified, the pressure is removed, and the molded product is placed in the mold 30 until the molded product can withstand the protrusion (cooling step). After that, the screw 14 is rotated to heat and plasticize the resin in the cylinder 12, and the screw 14 is retracted, whereby the amount of resin necessary for the next molding is accumulated in front of the screw 14. Next, the mold 30 (30A, 30B) is opened, and the solidified molded product is removed from the mold 30 using the protrusion mechanism 34 (mold release step).

In this way, when injection molding is performed using the molding apparatus shown in this embodiment, in the cooling step, the cooling rate of the resin in the vicinity of the injection hole 22 of the nozzle 20 is the nozzle of the conventional structure (the flow dividing plate 24). Since it is faster than the case of using a nozzle (without a nozzle), the resin at the position between the nozzle 20 and the engagement recess 33 of the sprue bush 32 is surely cooled and solidified during the mold opening in the mold release process. Therefore, the stringing phenomenon that occurs in the conventional injection molding method does not occur.

In the embodiment described above, the injection hole 22 is divided into two by the flow dividing plate 24.
As shown by reference numerals 24A and 24B, the flow dividing plate may have a trifurcated shape, a cross shape, or the like, and the injection hole 22 may have a structure in which it is divided into three or four parts. 13 to 15 show another embodiment of the injection molding apparatus for carrying out the method of the present invention, FIG. 13 is a sectional view of a main part of the injection molding apparatus, and FIG. 14 is an enlarged sectional view of a resin injection hole of a hot runner. FIG. 15 is a cross-sectional view of essential parts showing the mold release process of the same apparatus.

In the injection molding apparatus of this embodiment, the hot runner 40 is provided between the sprue S in the molding die 30 (fixed die 30A, movable die 30B) and the cavity C (C ₁ , C ₂ ).
Are formed. Then, instead of providing the flow dividing plate 24 in the nozzle 20A, the flow dividing plate 24 is provided at the front end portion of the resin injection hole 42 into the cavity C of the cylindrical hot runner bush 41 forming the hot runner 40, and the resin injection is performed in the cooling step. By speeding the cooling and solidification of the resin at the position of the front end portion of the hole 42, the stringing phenomenon is eliminated at the time of mold opening (see FIG. 15) in the mold releasing process.

Reference numeral 44 denotes a rod-shaped heater extending in the hot runner bush 41 so that the molten resin injected into the cavity C from the resin injection hole 42 is kept in a constant molten resin state in the hot runner 40. It has become. Reference numeral 32 is a sprue bush for forming a sprue S that guides the molten resin injected from the nozzle 20A to the hot runner 40. The other points are the same as those in the first embodiment, and the description thereof will be omitted by giving the same reference numerals.

The hot runner 40 in the second embodiment described above has a structure in which a rod-shaped heater 44 is extended in a hot runner bush 41.
Instead of 4, the band-shaped heater may be arranged around the hot runner bush 41.

[0024]

As is apparent from the above description, according to the thermoplastic resin injection molding method and the injection molding nozzle of the present invention, the injection hole tip end portion of the nozzle provided with the branch portion is branched. The part narrows the resin passage,
Since the contact area of the resin with the nozzle is larger than that of a conventional nozzle with no branching portion, the molten resin cools and solidifies quickly in the vicinity of the injection hole of the nozzle in the cooling process, and the stringing phenomenon does not appear in the mold release process. Various problems caused by the pulling phenomenon are eliminated.

Also in the injection molding apparatus having the hot runner and the injection molding method using the same apparatus, since the resin is rapidly cooled and solidified at the position of the resin injection hole into the cavity of the hot runner, the stringing phenomenon occurs in the mold releasing step. It does not appear and eliminates various problems caused by the stringing phenomenon.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of an injection molding apparatus for carrying out the method of the present invention.

FIG. 2 is a sectional view of the device in an injection process.

FIG. 3 is a sectional view of the same device in a mold release process.

FIG. 4 is an enlarged side view of an injection molding nozzle used in the apparatus.

FIG. 5 is an enlarged sectional view of the nozzle.

FIG. 6 is an enlarged perspective view of the tip of the nozzle.

FIG. 7 is an enlarged plan view of the tip of the nozzle.

FIG. 8 is a perspective view illustrating a state in which a flow dividing plate constituting chip that is a branch portion is fitted to the nozzle.

FIG. 9 is a side view of the same nozzle in the same state.

FIG. 10 is a sectional view of the same nozzle in the same state (line X in FIG. 9).
(Cross-section view along X)

FIG. 11 is a plan view of another embodiment of the injection molding nozzle.

FIG. 12 is a plan view of still another embodiment of the injection molding nozzle.

FIG. 13 is a cross-sectional view of an essential part of another embodiment of the injection molding apparatus for carrying out the method of the present invention.

FIG. 14 is a sectional view of a resin injection hole of a hot runner.

FIG. 15 is a cross-sectional view of an essential part of the injection molding device in the mold release process.

FIG. 16 is a sectional view of a main part of a conventional injection molding device.

FIG. 17 is a cross-sectional view of an essential part of the same device in a mold release process.

[Explanation of symbols]

10 Molten Resin Supply Machine 20 Injection Molding Nozzle 22 Injection Hole 24 Flow Dividing Plate 30 (30A, 30B) Mold 32 Sprue Bushing 40 Hot Runner 42 Hot Runner Resin Injection Hole C (C ₁ , C ₂ ) Cavity S Sprue W Split Board component chip

Claims (4)

[Claims] 1. An injection step of injecting a molten thermoplastic resin injected from an injection molding nozzle into a cavity through a sprue provided in an injection molding die, and maintaining the resin in the die at a constant pressure. In the injection molding method of the thermoplastic resin, which comprises a pressure-holding step of, a cooling step of cooling and solidifying the resin in the mold, and a mold releasing step of separating the mold and taking out a molded product, in the injection step, An injection molding method for a thermoplastic resin, characterized in that a molten resin is injected into a sprue in a branched state by a branch portion provided in an injection hole of a nozzle. 2. An injection step of injecting a molten thermoplastic resin injected from an injection molding nozzle into a cavity through a sprue and a hot runner provided in the injection molding die, and a resin in the die is kept constant. A pressure-holding step of maintaining the pressure,
In a thermoplastic resin injection molding method comprising a cooling step of cooling and solidifying a resin in a mold and a mold releasing step of separating a mold and taking out a molded product, in the injection step, a hot runner cavity An injection molding method for a thermoplastic resin, characterized in that the molten resin is injected into the cavity in a branched state by a branch portion provided in the resin injection hole. 3. A molten thermoplastic resin is attached to a resin injection port of a molten resin feeder and engages with a nozzle engaging portion of a sprue provided in an injection molding die to inject a molten thermoplastic resin into the sprue. In a cylindrical injection molding nozzle having a molten resin injection hole at its tip, a branching portion that crosses the injection hole is provided at the tip of the molten resin injection hole. . 4. A hot-runner for injection molding, which is located between a sprue provided in an injection-molding die and a cavity and injects molten resin injected through the sprue into the cavity, wherein a resin injection hole of the hot-runner is provided. A hot runner for injection molding, characterized in that a branch portion that crosses the injection hole is provided at the tip of the.