KR20190010266A - A vacuum injection molding apparatus and method for Teflon mold - Google Patents

Abstract

For vacuum injection of a Teflon resin by an injection machine to improve the flow of molten Teflon, a valve is mounted between a cavity and a vacuum source, a probe is mounted to sense the valve when the molten Teflon overflows through a pipe connected to the opposite side of a runner part of the cavity, and a shielding means for blocking and injecting the molten Teflon is mounted in the nozzle of an injection unit. The flowability of the molten Teflon can be improved to improve the injection speed of the Teflon, and pores in a product can be removed to enhance the strength of a bolt screw. In addition, mass production and cost savings can be possible.

Description

Technical Field [0001] The present invention relates to a vacuum injection molding apparatus and method for a Teflon mold,

The present invention relates to a Teflon mold vacuum injection molding apparatus and method, and more particularly to a Teflon mold vacuum injection molding apparatus including a vacuum source and a valve, more preferably a pressurization line, and a method of vacuum injection molding using the apparatus .

Teflon is polytetrafluoroethylene (PTFE) fluorine resin. Its characteristics are as follows: 1) It has non-adhesive property so that it can be easily separated when all materials do not stick to each other and very sticky material. Low friction coefficient is generally 0.05 to 0.20 Respectively. 2) It is non-oil, and it is easy to clean because it does not get water or oil very well, and in many cases, it is kept clean automatically. 3) Because of heat resistance, continuous use up to 290 ° C is possible. Up to 315 ° C is possible under proper ventilation conditions. The melting point is 327 ° C. 4) Due to its unique electrical properties, it has high insulation, low loss rate and high surface resistance. 5) Because of low temperature stability, physical properties are unchanged at extreme low temperature and minimum temperature is -270 ° C. 6) It has chemical resistance, so it is not affected by chemical environment.

A typical bolt screw may be a metal bolt screw or a plastic bolt screw. The bolt screw consists of a head with a round, flat, square and hexagonal shape that can be used with a screwdriver, and a shank part which is screwed with the screw. And a nut can be inserted there.

Due to the nature of Teflon described above, demand for Teflon products such as bolt threads as a fastening product in semiconductor equipment and chemical equipment is gradually increasing. Another method is coating with Teflon.

At present, Teflon is not flowable even in a molten state, so that it can not be processed by a general injection machine or an extruder. Therefore, for the production of Teflon products, for example, they are produced in the form of rods by machining by milling. Therefore, it consumes a large amount of material, requires a large processing cost, and can not be mass-produced.

In this regard, Earling Klinger of Germany has sold "PTFE resin" as "Moldflon", which can be processed by general extruder and extruder by adjusting Teflon and isolated molecular weight to low. It is much more expensive than regular Teflon.

"Mold Apparatus for Vacuum Forming" of Korean Patent Publication No. 10-0299545 (registered on June 11, 2001) discloses a mold apparatus for bonding a skin material (C) on a base material (P) Upper and lower frames 23 and 24 to which the air pipes 27 and 28 and the cooling water pipes 25 and 26 are connected to allow water and air to flow in and out through the upper and lower frames 23a and 24a, And the cooling holes 21a and 22a and the vacuum holes 21b and 21b which are divided and fixed on the lower frame 24 and communicate with the air pipes 27 and 28 and the cooling water pipes 25 and 26 22b of the upper and lower molds 21 and 22. Accordingly, when the skin material and the base material are bonded to each other, a clear design shape and pattern are uniformly and precisely transferred It has the effect of being processed. "

In the "Method of manufacturing an integral type polymer arrester using vacuum injection molding" of Korean Patent No. 10-0551580 (registered on Feb. 06, 2006), when manufacturing a base module of an integral type polymer arrester by multiaxial filament winding, Treating the body with an epoxy resin and a heat resistant synthetic resin film so that the housing rubber can withstand the vulcanization temperature; After the epoxy resin and the heat-resistant synthetic resin film are cured, the module and the housing are vacuum-injection-molded so as to be bonded to the body of the base module and to the different materials of the upper and lower electrodes, Treating the primers simultaneously; And a step of vacuum injection molding the molded polymer lightning arrester module mounted on a vacuum injection molding die to injection-mold the housing together with the housing, so that the lightning arrester module and the housing are integrally injection-molded so that the interface between the lightning arrester module and the housing is completely bonded Therefore, it is possible to prevent the risk of hygroscopic accident due to poor airtightness.

The above-mentioned conventional patent documents can be used as a reference of the present invention, but the contents of improving the flowability of molten Teflon are not disclosed at all.

As described above, Teflon is not flowable even in the molten state, so that it can not be processed by a general injection machine or an extruder. Accordingly, an object of the present invention is to provide a mold apparatus for improving the flowability in a molten state and vacuum-injecting a Teflon resin by a general injection machine.

It is another object of the present invention to provide a mold apparatus for removing pores in a product.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems and to solve the problems of the related art, and it is an object of the present invention to provide a method of manufacturing a Teflon mold, including a driving cylinder, an eject plate, an eject pin, a movable mold, a die, a fixed mold into which molten resin is injected, In an injection molding apparatus,

Wherein the movable mold and the stationary mold include a molten Teflon injection port, a runner portion, a gate, and a cavity,

A valve is mounted between the cavity and the vacuum source, the valve being connected through a tube opposite the runner of the cavity,

A probe for detecting the overflow of the molten Teflon through the pipe connected to the cavity and blocking the valve is connected to the valve and mounted in the pipe,

The nozzle of the injection unit is equipped with a shielding means for injecting and blocking molten Teflon.

The preferred embodiment further comprises a pressurization line separate from the molten Teflon injection line of the injection unit, wherein the pressurization line includes a piston and a rod for applying pressure to the molten Teflon.

In a preferred embodiment, the nozzle opening and closing means is opened until the pressure in the cavity becomes a desired negative pressure and the pressure of the pressurizing line is below a predetermined pressure, so that the molten Teflon is injected into the mold.

In another embodiment of the present invention, there is provided a Teflon mold vacuum injection molding method comprising: a plasticizing step in which solid Teflon is melted; a filling step in which molten Teflon is injected into the mold; a holding step for replenishing the reduced volume as the Teflon solidifies A step of lowering the temperature of the Teflon in a state where the injection port is solidified and the further external pressure can not be transmitted to the inside of the mold so as to be blocked from the outside, and a discharging step of pushing the product out of the mold; A preheating step of preheating the temperature of the mold to 250 DEG C or higher and a pre-charging step of evacuating air in the cavity by a vacuum source to make the negative pressure and applying the molten Teflon to the predetermined pressure by the pressurizing line. In the filling step, when the nozzle opening / closing means is opened to inject the molten Teflon into the cavity through the runner portion and the gate and overflows through the pipe provided at the opposite side of the runner portion of the cavity, the valve is closed to inject molten Teflon into the cavity . When the injected Teflon shrinks due to curing, it is sensed by the probe of the valve to open the valve to evacuate the gas generated at the time of curing, and inject additional molten tees through the nozzle.

As described above, the flowability of the molten Teflon can be improved, and the Teflon article can be vacuum-injected with an injection machine. The injection speed of the molten Teflon into the mold can be remarkably improved and the pores in the product can be removed to enhance the strength. And mass production and cost savings. In addition, the thickness of the runner portion can be reduced, and the raw material of Teflon can be saved.

Fig. 1 is a perspective view of a mold for injection molding performed by the present inventor.
2 is a perspective view of a bolt screw which is a defron vacuum injection molding product of the present invention.
3 is a perspective view showing a connection between a vacuum source and a valve and a cavity according to the present invention.
4 is a perspective view showing a pressurizing line of the injection unit in the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. In particular, for vacuum injection molding of the Teflon article of the present invention, and for the purpose of better understanding of the present invention, a variety of Teflon products can be used, although bolt threads are shown and described as one product example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the term " comprising "or the like is intended to specify the presence of stated features, integers, steps, operations, elements, parts, or combinations thereof, And does not preclude the presence or addition of one or more other elements, components, components, parts, or combinations thereof.

In the present invention, a thermosetting injection molding technique in which an injection part is cooled and a mold is heated is used. The mold is usually preheated to 180 ° C or higher. In the injection molding apparatus, the injection molding machine is constituted by a mold-shaped portion, an injection portion, and a power control portion. The mold portion is a portion that holds the mold so that it is not opened by the high pressure inside due to the injection of the molten resin and has the same structure as a general press. The injection part is composed of a barrel and a screw which can inject molten resin into the mold after melting the solid resin in a short period of time. The injection part is classified into an inline screw type and a plunger type according to a method of melting a resin. Most modern injection molding machines are designed with inline screw type. The power control unit is a part including a hydraulic pressure generating device for generating a pressure required by the mold-shaped part and the injection part, and a control part for controlling the operation order and degree of each part.

The mold apparatus includes a driving cylinder, an eject plate, an eject pin, a movable mold, a die, a stationary mold into which molten resin is injected, and an injection unit and a screw. A description thereof will be omitted (see FIG. 1).

The applicant's first attempt to manufacture a bolt screw, which is a Teflon vacuum-formed product in such a general injection molding apparatus, is shown in FIG. 1, wherein the molten Teflon inlet 2, the runner 3, the gate 4, And a movable cavity 6 and a corresponding cavity 6 of the head portion. The size of the runner portion 3 is increased in order to rapidly supply a large amount of molten Teflon into the cavities 5 and 6. As shown in FIG. 2, the Teflon bolt screw is composed of a head portion 21 including an engaging groove to which the engaging means is engaged, and a shank 22 having a threaded portion. As can be seen from FIG. 2, in the case of using a general injection molding apparatus, pores 23 are formed in the shank 22. This is because the melting point of Teflon is 327 ° C and it is injected into the mold through the injection port at about 400 ° C, and the gas is generated by the rapid cooling and the pores 23 are generated by the generated gas. Even if a cold slug well is installed to improve the flow of Teflon, porosity is still formed and the strength of the bolt screw is lowered.

In order to eliminate pores in injection-molded Teflon bolt threads, the flow of molten Teflon must be improved and the generated gas must be discharged quickly out of the mold.

To this end, as shown in Fig. 3, a vacuum system including a vacuum source 30 and a vacuum valve 31 is firstly included. A valve 31 is mounted between the corresponding cavity 6 of the head of the bolt and the vacuum source 30. The cavity 6 of the head and the valve 31 are connected through a pipe 33 connected to the mold 1. The valve 31 communicates with the vacuum source 30 through the connection pipe 34. The injection port 2 of the molten Teflon is closed by the opening and closing means of the nozzle in order to set the pressure in the cavities 5 and 6 to a negative pressure (-pressure) before the molten teflon is injected into the cavities 5 and 6, (31) is opened and the gas in the cavities (5, 6) is sucked in the vacuum source (30) by the pipe (33). When the pressure in the cavities 5 and 6 becomes a desired negative pressure state, the opening and closing means of the nozzle is opened to inject molten Teflon. Since the pressure in the cavities 5 and 6 is negative at this time, the molten Teflon moves quickly to the cavities 5 and 6 through the runner 3 and the gate 4. When the valve 31 is opened, the molten Teflon is continuously sucked in the vacuum source 30. When the molten Teflon at a high temperature of 400 degrees is injected into the mold cavity, the gas generated due to the temperature difference passes through the valve 31 and the vacuum source (30). When the molten Teflon overflows through the pipe 33 connected to the cavity 6 at the head, it is sensed by the probe 32 installed on the valve 31. When the molten Teflon is detected by the probe 32, the valve 31 is closed. Thus, molten Teflon can be completely injected into the cavities 5 and 6 within 0.3 seconds. Since the gas generated by the injection into the cavities 5 and 6 into the molten Teflon at such a speed is almost discharged through the valve 31, no pores 23 are formed in the bolt screw in the shank 22. Further, the thickness of the runner portion 3 can be reduced to save the raw material of the discharged teflon.

The valve 31, which can be used here, is of the molten metal type, in which the valve is opened by pneumatic pressure and the valve is closed by the collision of the molten metal in the vacuum exhaust. However, in addition, various valves can be used.

Next, in the filling step in which the molten Teflon is injected into the mold, a pressurization line is added to the injection line separately from the injection line. Figure 4 includes a piston (11) and a rod (12) for injecting molten Teflon into the injection line before charging and applying pressure to the molten teflon injected therefrom. The rod presses the molten Teflon through the piston when connected to external drive means. The nozzle 8 is provided with opening / closing means and is opened / closed in accordance with a predetermined pressure of the molten Teflon and a predetermined pressure of the cavity in the mold. The opening and closing means of the nozzle 8 is not opened until the pressure in the cavities 5 and 6 of the mold becomes a desired negative pressure state by the vacuum source 30 and the pressure of the pressurizing line is below a predetermined pressure, It is not injected. The left side of FIG. 4 illustrates the injection process of the molten Teflon in the injection line, and the right side shows the state in which the Teflon is pressurized by the piston 11 in the pressurization line.

The injection molding method generally includes a plasticizing step in which a solid resin is melted, a filling step in which the molten resin is injected into the mold, a holding step to compensate for the volume that decreases as the injected resin solidifies, The temperature of the resin is lowered in a state in which the pressure can not be transmitted to the inside of the mold so as to be blocked from the outside, and a releasing step of pushing the product out of the mold.

According to a preferred embodiment of the Teflon mold vacuum injection molding method of the present invention, a preheating step of preheating the temperature of the mold to 300 DEG C or higher is carried out. This is to reduce the temperature difference of the molten Teflon at 400 ° C to reduce the generation of gas and improve the flowability of the melt tape.

The air in the cavities 5 and 6 is evacuated by the vacuum source 30 to a negative pressure and the pre-charging step of applying the molten Teflon to the predetermined pressure by the pressurizing line is performed.

Next, the opening and closing means of the nozzle 8 is opened to inject the molten Teflon into the cavities 5 and 6 through the runner portion and the gate, and through the pipe 33 connected to the cavity 6 corresponding to the head portion of the screw When overflowing, the valve 31 is closed and molten Teflon is injected into the cavities 5 and 6 to carry out the filling step. When the injected Teflon shrinks while being hardened, it is sensed by the probe 32 of the valve 31 to open the valve 31 to exhaust the gas generated during curing. And the additional molten tee is injected through the nozzle 8 to carry out the pressure holding step.

Then, the injection port is solidified so that the pressure of the further pressurizing line can not be transferred to the inside of the mold, so that the cooling step is performed in a state of being shut off from the outside, and then a releasing step is performed to separate the product from the mold without deforming.

Although the present invention has been described based on a bolt screw as a preferred embodiment, it is intended to exemplify the present invention. Those of ordinary skill in the art will recognize that the above embodiments may be modified or modified to other products. However, since the scope of the present invention is defined by the appended claims, such variations and modifications can be construed as being included in the following claims.

1: Mold
2: inlet
3: Runner section
5, 6: Cavity
8: Nozzle
11: Piston
12: Load
23: Groundwork
30: Vacuum source
31: Valve
32: Probe

Claims (4)

A Teflon mold vacuum injection molding apparatus comprising a driving cylinder, an eject plate, an eject pin, a movable mold, a die, a stationary mold into which molten resin is injected, and an injection unit and a screw,
Wherein the movable mold and the stationary mold comprise a molten-tapered injection opening, a runner portion, a gate, and a cavity,
A valve is mounted between the cavity and the vacuum source, and the valve is connected through a tube opposite to the runner of the cavity,
A probe for detecting the overflow of the molten Teflon through a pipe provided on the opposite side of the runner portion of the cavity to block the valve is connected to the valve and mounted in the pipe,
Wherein the nozzle of the injection unit is equipped with a shielding means for blocking and injecting molten Teflon. The method according to claim 1,
Further comprising a pressurization line separate from the molten Teflon injection line of the injection unit, wherein the pressurization line includes a piston and a rod for applying pressure to the molten Teflon. The method according to claim 1,
Wherein the nozzle opening and closing means is opened until the pressure in the cavity becomes a desired negative pressure and the pressure of the pressurizing line is not more than a predetermined pressure so that the molten Teflon is injected into the mold. A filling step in which the molten Teflon is injected into the mold, a holding step to compensate for the decrease in volume as the Teflon is solidified, and a further external pressure is transferred to the inside of the mold A step of lowering the temperature of the Teflon in a state of being blocked from the outside, and a releasing step of pushing the product out of the mold. In the Teflon mold vacuum injection molding method,
A preheating step of preheating the temperature of the mold to 250 DEG C or more, and a pre-charging step of evacuating air in the cavity by a vacuum source to make the negative pressure and applying the molten Teflon to the predetermined pressure by the pressurizing line,
In the filling step, when the nozzle opening / closing means is opened to inject the molten Teflon into the cavity through the runner portion and the gate and overflows through the pipe connected to the opposite side of the runner portion of the cavity, the valve is closed to inject molten Teflon into the cavity ,
In the pressure holding step, when the injected Teflon shrinks due to curing, it is sensed by the probe of the valve to open the valve to evacuate the gas generated at the time of curing, and further melt teflon is injected through the nozzle. Injection molding method.

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