KR102429304B1 - A vacuum injection molding apparatus and method for Teflon mold - Google Patents

Abstract

A valve is installed between the cavity and the vacuum source to improve the flowability of the molten Teflon so that the Teflon resin can be vacuum injected with the injection machine. The nozzle of the injection unit is equipped with a shielding means to block the injection of molten Teflon. By improving the flowability of the molten Teflon, the injection speed of the molten Teflon can be improved, and the strength of the bolt screw can be strengthened by removing the pores in the product. And it can bring about mass production and cost reduction.

Description

Teflon mold vacuum injection molding apparatus and method { A vacuum injection molding apparatus and method for Teflon mold}

The present invention relates to a Teflon mold vacuum injection molding apparatus and method, in particular, a Teflon mold vacuum injection molding apparatus including a vacuum source and a valve, and more preferably a pressure line, and a method for vacuum injection molding using the same is about

Teflon is a PTFE (Poly Tetra Fluoro Ethylene) fluororesin, and its characteristics are 1) non-adhesive, so all substances do not stick, and in the case of a very adhesive material, it is easily separated, and a low coefficient of friction is generally 0.05 to 0.20. it is about 2) It is non-oily, and it is easy to clean because it does not adhere well to water or oil. In many cases, the cleanliness is maintained automatically. 3) Because it is heat-resistant, it can be used continuously up to 290°C. Up to 315°C can be achieved under suitable ventilation conditions. The melting point is 327°C. 4) It has unique electrical properties, so it has high insulation, low loss rate and high surface resistance. 5) It has low-temperature stability, so physical properties are unchanged at extremely low temperatures, and the lowest operating temperature is -270°C. 6) It has chemical resistance, so it is not affected by the chemical environment.

A general bolt screw may use a metal bolt screw or a plastic bolt screw. A bolt screw consists of a head having a shape such as round, straight, square, and hexagonal that can be used with a screwdriver and a screwed shank part. through which a nut can be fitted.

Due to the characteristics of Teflon described above, the demand for Teflon products, for example, bolt screws, is gradually expanding as a fastening product in semiconductor equipment or chemical equipment. Another method is coating with Teflon.

At present, Teflon has no flowability even in a molten state, so it is impossible to process it by a general injection machine or an extruder. Therefore, for the production of Teflon products, for example, injection in the form of a rod is produced by machining by milling. Accordingly, material consumption is high, processing cost is high, and large-scale production is impossible.

In contrast, Germany's EarlingKlinger Co., Ltd. regulates Teflon and isolated molecular weight to a low level, and sells "Moldflon", a new material that can be processed with general injection machines and extruders. It is much more expensive than regular Teflon.

Republic of Korea Patent 10-0299545 (registration date June 11, 2001) in "a mold apparatus for vacuum molding" in "in a mold apparatus for bonding the skin material (C) on the substrate (P); each chamber (23a) ) upper and lower frames 23 and 24 to which air pipes 27 and 28 and cooling water pipes 25 and 26 are connected so that water and air enter and exit through 24a, and each of the upper frames 23 ) and the cooling holes 21a, 22a and vacuum holes 21b, respectively, 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), it is characterized in that it includes the upper and lower molds 21 and 22, and thus, when the skin material and the substrate are bonded to produce various interior products including automobiles, the clear design shape and pattern are uniformly and precisely through the transfer. It has the effect of allowing it to be processed.”

In the "Manufacturing method of an integrated polymer arrester using vacuum injection molding" of Korean Patent 10-0551580 (registration date February 06, 2006), when manufacturing the basic module of an integrated polymer arrester by multiaxial filament winding, vacuum injection molding 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 curing the epoxy resin and heat-resistant synthetic resin film, before mounting the module and housing in a mold for vacuum injection molding as an integral part, the body of the base module and the dissimilar materials of the upper and lower electrodes are used for adhesion and performance improvement. simultaneously treating the primers; and vacuum injection molding by mounting the treated polymer arrester module to a vacuum injection molding mold in order to be integrally injection-molded with the housing. Therefore, it is possible to fundamentally prevent the risk of moisture absorption due to poor airtightness.

The above-mentioned prior patent documents may be used as a reference for the present invention, but the content for improving the flowability of Teflon in a molten state is not disclosed at all.

As described above, Teflon does not have flowability even in a molten state, so processing by a general injection machine or an extruder is impossible. Accordingly, it is an object of the present invention to provide a mold apparatus for vacuum injection of Teflon resin with a general injection machine by improving the flowability of the molten state.

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

The present invention is to solve the above object and the problems of the prior art, in a Teflon mold vacuum injection molding apparatus comprising a fixed mold and a movable mold into which the molten resin is injected, and an injection unit for injecting the molten resin,

The movable mold and the fixed mold include a molten Teflon injection hole, a runner part, a gate and a cavity,

A valve is mounted between the cavity and the vacuum source, and the valve is connected through a pipe installed on the opposite side of the runner part of the cavity,

When the molten Teflon overflows through the pipe installed on the opposite side of the runner part of the cavity, a probe that detects this and blocks the valve is connected to the valve and mounted in the pipe,

The nozzle installed in the injection line of the injection unit is equipped with a shielding means to block the injection of molten Teflon.
Increase the size of the runner part, open the shielding means of the nozzle, inject molten Teflon into the cavity through the runner part and the gate, and when the Teflon overflows through the pipe installed on the opposite side of the runner part of the cavity, the valve is closed and Then, molten Teflon is injected into the cavity.

A preferred embodiment further includes a pressure line separate from the melt Teflon injection line of the injection unit, wherein the pressure line includes a piston and a rod for applying pressure to the melt Teflon.

In a preferred embodiment, when the pressure in the cavity reaches a desired negative pressure state and when the pressure in the pressurization line is above a predetermined pressure, the shielding means of the nozzle is opened to inject molten Teflon into the mold.

As another embodiment of the present invention, a Teflon mold vacuum injection molding method, a plasticizing step in which solid Teflon is melted, a filling step in which molten Teflon is injected into the mold through the molten Teflon inlet of the mold, and reduced as the injected Teflon is solidified It includes a holding pressure step to replenish the volume, a step in which the temperature of Teflon is lowered when the inlet is solidified and no more external pressure can be transmitted to the inside of the mold, so that it is blocked from the outside, and a release step to push the product out of the mold and
Before the filling step, pre-heating to preheat the temperature of the mold to 250° C. or higher, exhaust the air in the cavity by a vacuum source to make it a negative pressure, and pressurize the molten Teflon to a predetermined pressure by the pressure line of the injection unit. including more,
In the filling step, the shielding means of the nozzle is opened to inject molten Teflon into the cavity through the runner part and the gate, and when the Teflon overflows through the pipe installed on the opposite side of the runner part of the cavity, the valve is closed and continues into the cavity Inject molten Teflon,
In the holding pressure step, when the injected Teflon contracts while curing, it is sensed by the probe of the valve, opens the valve, exhausts the gas generated during curing, and injects additional molten Teflon through the nozzle of the injection unit.

As described above, by improving the flowability of molten Teflon, the Teflon product can be vacuum-injected with an injection machine. It can significantly improve the injection speed of molten Teflon into the mold, and also enhance strength by removing pores in the product. And it can bring about mass production and cost reduction. In addition, it is possible to save the raw material of Teflon by reducing the thickness of the runner part.

1 is a perspective view of a mold of injection molding performed primarily by the present inventors.
Figure 2 is a perspective view of a bolt screw, which is a Deflon vacuum injection molding product of the present invention.
Figure 3 is a perspective view showing the connection of the vacuum source, the valve and the cavity in the present invention.
4 is a perspective view showing a pressure line of the injection unit in the present invention.

Since the present invention can apply various transformations and can have various embodiments, specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In particular, it relates to vacuum injection molding of the Teflon product of the present invention, wherein, for a good description of the present invention, a bolt screw is shown and described as one product example, but various Deflon products may be used.

In describing the present invention, if it is determined that a detailed description of a related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, the term "comprising" and the like is intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification is present, and includes one or more other features or numbers, steps, It should be understood that the existence or addition of operations, components, parts or combinations thereof is not precluded in advance.

In the present invention, a thermosetting injection molding technique in which the injection part is cooled and the mold is heated is used. The mold is usually preheated to 180°C or higher. The injection molding machine is composed of a clamping unit, an injection unit, and a power control unit. The clamping part is the part that holds the mold from being opened by the high internal pressure caused by the injection of molten resin and has the same structure as the general press. The injection part is composed of a barrel and a screw with a structure that can inject solid resin into the mold after melting it within a short time. The injection part is divided into an inline screw method and a plunger method according to the method of melting the resin. Most modern injection molding machines are designed with an in-line screw method. The power control unit includes a hydraulic pressure generator that generates the pressure required by the clamping unit and the injection unit, and a control unit that controls the order and degree of operation of each part.

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The applicant's first attempt to manufacture a bolt screw, which is a Teflon vacuum molded product in such a general injection molding apparatus, is as shown in FIG. shows a movable mold and a stationary mold 1 comprising a corresponding cavity 5 in the shank and a corresponding cavity 6 in the head. Here, in order to quickly supply a large amount of molten Teflon to the cavities 5 and 6, the size of the runner part 3 is increased. As shown in Fig. 2, the Teflon bolt screw is composed of a head 21 including a coupling groove to which the fastening means is coupled, and a shank 22 having a threaded thread. As can be seen from FIG. 2 , in the case of using a general injection molding apparatus, pores 23 are formed inside the shank 22 . As Teflon having a melting point of 327 degrees is injected into the mold at about 400 degrees through the injection hole, gas is generated by rapid cooling, and pores 23 are formed by the gas generated in this way. Even if a cold slug well is installed to improve the flowability of Teflon, pores are still formed and the strength of the bolt screw is reduced.

In order to eliminate pores in injection-molded Teflon bolt screws, it is necessary to improve the flowability of molten Teflon and to expel the generated gas out of the mold quickly.

For this, first, as shown in FIG. 3 , a vacuum system including a vacuum source 30 and a vacuum valve 31 is included. A valve 31 is mounted between the vacuum source 30 and the corresponding cavity 6 of the bolt head. The cavity 6 of the head and the valve 31 are connected through a tube 33 connected to the mold 1 . The valve 31 communicates with the vacuum source 30 through a connecting pipe 34 . Before the molten Teflon is injected into the cavities 5, 6, the inlet 2 of the molten Teflon is closed with a shielding means of the nozzle of the injection unit in order to set the pressure in the cavities 5, 6 to a negative pressure (-pressure). Then, the valve (31) is opened to suck in the gas in the cavities (5, 6) from the vacuum source (30) through the tube (33). When the pressure in the cavity (5, 6) reaches the desired negative pressure state, the shielding means of the nozzle is opened to inject molten Teflon. At this time, since the pressure in the cavities (5, 6) is negative pressure, the molten Teflon moves rapidly to the respective cavities (5, 6) through the runner part (3) and the gate (4). And while the valve 31 is open, the gas is continuously sucked from the vacuum source 30, and when the high temperature molten Teflon of 400 degrees is injected into the mold cavity, the gas generated due to the temperature difference is the valve 31 and the vacuum source ( 30) to the outside. When the molten Teflon overflows through the tube 33 installed on the opposite side of the runner portion of the cavity 6 of the head, it is detected by the probe 32 installed on the valve 31 . When molten Teflon is detected by probe 32, valve 31 is closed. In this way, molten Teflon can be completely injected into the cavities 5 and 6 within 0.3 seconds. Since the gas generated while injecting the molten Teflon into the cavities 5 and 6 at this rate is almost discharged through the valve 31, no pores 23 are formed in the shank 22 in the bolt screw. In addition, by reducing the thickness of the runner part 3, it is possible to save the raw material of Teflon wasted.

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

Next, in the filling step in which the molten Teflon is injected into the mold, a pressure line is added separately from the injection line. Fig. 4 includes a piston 11 and a rod 12 for pre-injecting molten Teflon into the injection line before filling, and for applying pressure to the injected molten Teflon. The rod presses the molten Teflon through the piston when it is connected to an external drive means. The nozzle 8 is provided with a shielding means, which is shielded according to the prescribed pressure of the molten Teflon and the prescribed pressure of the cavity in the mold. Until the pressure in the cavity (5, 6) of the mold reaches a desired negative pressure state by the vacuum source (30), and when the pressure in the pressure line is below the predetermined pressure, the shielding means of the nozzle (8) is not opened and the molten Teflon is poured into the mold not injected That is, the shielding means of the nozzle 8 is opened when the pressure in the cavities 5 and 6 of the mold is negative and the pressure in the pressure line is higher than the predetermined pressure, and the molten Teflon is injected into the mold. The left diagram of FIG. 4 describes the injection process of the molten Teflon in the injection line, and the right diagram shows the state in which the molten Teflon is pressed by the piston 11 in the pressure line.

Injection molding methods generally include a plasticizing step in which the solid resin is melted, a filling step in which the molten resin is injected into the mold, a holding pressure step to compensate for the volume that is reduced as the injected resin solidifies, and It includes a step of lowering the temperature of the resin in a state in which the pressure cannot be transmitted to the inside of the mold and is blocked from the outside, and a releasing step of pushing the product to the outside of the mold.

According to a preferred embodiment of the Teflon mold vacuum injection molding method of the present invention, preheating is performed to preheat the temperature of the mold to 300° C. or higher. This is to reduce the temperature difference of the molten Teflon of 400 ℃ to reduce the generation of gas and to improve the flowability of the molten Teflon.

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

Next, by opening the shielding means of the nozzle 8 of the injection unit, molten Teflon is injected into the cavities 5 and 6 through the runner part and the gate, and the pipe 33 connected to the cavity 6 corresponding to the head of the screw ), close the valve 31 and continue to inject molten Teflon into the cavities 5 and 6 to carry out the filling step. When the injected Teflon contracts while curing, it is sensed by the probe 32 of the valve 31 and opens the valve 31 to exhaust the gas generated during curing. And through the nozzle (8) an additional molten Tayron is injected to carry out the holding pressure step.

And since the inlet is solidified, the pressure of the pressure line can no longer be transmitted to the inside of the mold, so the cooling step is performed in a state in which it is blocked from the outside, and then the releasing step of separating the product from the mold so that it is not deformed is performed.

The present invention has been described above based on a bolt screw as a preferred embodiment, but this is for illustrating the present invention. Those of ordinary skill in the art will be able to change or modify the above embodiment into other products. However, since the scope of the present invention is defined by the claims, such variations or modifications may be construed as being included in the claims below.

1: mold
2: inlet
3: Runner part
5, 6: Cavity
8: Nozzle
11: piston
12: load
23: Qigong
30: vacuum source
31: valve
32: probe

Claims (4)

It includes a movable mold and a fixed mold, wherein the movable mold and the fixed mold include an injection unit including a molten Teflon injection port, a runner unit, a gate and a cavity, and a molten Teflon injection line connected to the injection port, the cavity A valve is mounted between the and the vacuum source, the valve is connected to the vacuum source through a tube installed on the opposite side of the runner part of the cavity, and the nozzle installed in the injection line has a shielding means for blocking the injection of molten Teflon In a vacuum injection molding apparatus for a Teflon mold, a probe that detects when the molten Teflon overflows through a tube installed on the opposite side of the runner part of the cavity and blocks the valve is connected to the valve and mounted in the tube ,
When the shielding means of the nozzle is opened and the molten Teflon is injected into the cavity through the runner part and the gate, and the Teflon overflows through the pipe installed on the opposite side of the runner part of the cavity, the valve is closed and the molten Teflon is continuously injected into the cavity After that, when the injected Teflon contracts while curing, it is sensed by the probe of the valve, the valve is opened to exhaust the gas generated during curing, and additional molten Teflon is injected through the nozzle of the injection unit. vacuum injection molding equipment. The method of claim 1,
Teflon mold vacuum injection molding apparatus further comprising a pressure line separately from the molten Teflon injection line of the injection unit, wherein the pressure line includes a piston and a rod for applying pressure to the molten Teflon. The method of claim 1,
A Teflon mold vacuum injection molding apparatus, wherein when the pressure in the cavity becomes a desired negative pressure state and when the pressure in the pressure line is higher than a predetermined pressure, the shielding means of the nozzle is opened to inject molten Teflon into the mold. The plasticizing stage in which the solid Teflon is melted, the filling stage in which the molten Teflon is injected into the mold through the molten Teflon inlet of the mold, the holding pressure stage to compensate for the volume that decreases as the injected Teflon solidifies, In a Teflon mold vacuum injection molding method comprising a step of lowering the temperature of Teflon in a state in which external pressure cannot be transmitted to the inside of the mold and being blocked from the outside, and a releasing step of pushing the product to the outside of the mold,
Between the plasticizing step and the filling step, the mold is preheated to a temperature of 250° C. or higher, and the air in the cavity is exhausted by a vacuum source to make a negative pressure, and the molten Teflon is heated to a predetermined pressure by the pressurization line of the injection unit. It further comprises a pre-charging step of pressurizing,
In the filling step, the shielding means of the nozzle is opened to inject molten Teflon into the cavity through the runner part and the gate, and when the Teflon overflows through the pipe installed on the opposite side of the runner part of the cavity, the valve is closed and continues into the cavity Inject molten Teflon,
In the holding pressure step, when the injected Teflon shrinks while curing, it is sensed by the probe of the valve, opens the valve to exhaust the gas generated during curing, and injects additional molten Teflon through the nozzle of the injection unit, Teflon mold vacuum injection molding method.

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