JPS6076324A - Two stage extruder - Google Patents

Abstract

PURPOSE:To minimize the fluctuation of pressure and temperature and the ununiformity of temperature of the resin at the outlet of the second stage extruder by connecting the spouting outlet of the first stage extruder to the feed inlet of the second stage extruder by the connecting pipe having stationary mixers arranged in series. CONSTITUTION:The resin supplied from the feed inlet 3 of the first stage extruder 1 is melted under heating, sending said resin in the direction of a screw shaft by the rotation of said screw 5, and it is extruded into a connecting pipe 11 from a spouting outlet 6. The extruded resin passes through every element 13 arranged in series and is fully mixed, when said resin passes through the stationary mixer 12 arranged in the connecting pipe, whereby the fluctuation of pressure and temperature and the ununiformity of temperature are suppressed. Next, the resin is supplied to the second stage extruder 2, and at the outlet of the second stage extruder 2, the molten resin is extruded in the condition where the fluctuation of pressure and temperature and the ununiformity of temperature are minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an extruder for melt extruding a resin, and in particular, to an extruder for melt extruding a resin, and in particular for a method in which two extruders are arranged in series and a first extruder and a second extruder are connected. It concerns a two-stage extruder connected by a tube.

When melt-extruding a resin using a conventional single-screw extruder, it is difficult to increase the molten resin temperature, that is, the extrusion rate while suppressing the shear heat generation of the resin in the extruder. Regarding low temperature and high discharge, Japanese Patent Application Laid-open No. 48-79864 and Utility Model Application No. 1983
-151-1-,. .

As described in Japanese Patent No. 119, it is generally known that a two-stage extrusion system in which two extruders are connected in series has excellent performance.

In a two-stage extruder, the screw of the first stage extruder is usually a deep groove type and rotates at high speed to melt as much resin as possible in the first stage extruder. When the eel type is rotated at low speed, shear heat generation of the resin is suppressed and the discharge amount per screw rotation speed is increased, resulting in the characteristics of low temperature and high discharge eel.

However, in such a two-stage extruder, in order to suppress the temperature of the molten resin discharged, it is necessary to keep the resin temperature at the outlet of the first stage extruder low. The resin discharged from the machine is a mixed system of molten resin and unmelted resin. If there is unmelted resin, the resin pressure will not propagate as fluid pressure in that part, and the melted part and unmelted part will be separated and mixed, so the resin pressure at the exit of the first stage extruder will be reduced. Fluctuations and Temperature Changes 2- The power becomes larger. As a result of this molten resin having large pressure fluctuations and temperature fluctuations being introduced into the second-stage extruder, pressure fluctuations and temperature fluctuations at the outlet of the second-stage extruder also increase, resulting in pressure and temperature surging. There is a problem with the cause.

Furthermore, in a two-stage extruder, in order to keep the temperature of the resin discharged from the second-stage extruder low, the groove depth of the second-stage screw is reduced in order to reduce the shear force inside the second-stage extruder. Generally, the grooves are deeper than in the case of a single-screw extruder, so if the humidity of the resin supplied from the first-stage extruder varies, there is also the problem that the temperature unevenness in the second-stage extruder becomes larger accordingly. be.

In this way, if the pressure fluctuations, temperature fluctuations, and temperature unevenness of the resin discharged from the second stage extruder are large, although high discharge can be obtained, the discharge amount will fluctuate and the physical properties of the discharged resin will fluctuate. This causes a problem in that it has a negative impact on subsequent processes and it is not possible to obtain a product of the desired quality.

Purpose of the Invention In order to solve the above problems, the present invention suppresses the pressure fluctuations and temperature fluctuations of the resin from the first stage extruder, and suppresses the pressure fluctuations and temperature fluctuations of the resin at the exit of the second stage extruder. The purpose is to keep temperature fluctuations to a minimum.

Structure and operation of the invention The two-stage extruder of the present invention that meets this objective is a two-stage extruder in which the discharge port of the first-stage extruder and the supply port of the second-stage extruder are connected by a connecting pipe. , characterized in that a static mixer is disposed within the connecting pipe.

In such a two-stage extruder, the resin, which is a mixture of molten and unmelted resin discharged from the first stage extruder, is naturally mixed by a static mixer along the flow as it flows through the connecting pipe. By mixing, the unmolten resin is uniformly dispersed, and the pressure distribution is made uniform, and the entire resin is mixed, so that the temperature distribution is made uniform. As a result, fluctuations in the pressure and temperature of the resin supplied to the second-stage extruder are suppressed to a small level, ensuring a high discharge amount while reducing pressure fluctuations in the resin discharged from the second-stage extruder. , temperature fluctuations, and temperature unevenness can be suppressed to a small level.

EXAMPLES Below, preferred examples of the two-stage extruder of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration of a two-stage extruder according to an embodiment of the present invention. In the figure, 1 indicates a first-stage extruder, and 2 indicates a second-stage extruder.

The first stage extruder 1 is supplied with a resin thickness FI (usually pellet-shaped granules) from its supply port 3, and the resin is delivered to the discharge port 6 by rotation of a screw 5 inserted into the cylinder 4.
It is designed to be extruded from Similarly, in the second stage extruder 2, the resin supplied from the supply lower is rotated by the screw 9 inserted into the cylinder 8, and the resin is transferred to the discharge port 1.
Extruded from 0.

The discharge port 6 of the first stage extruder I11 and the supply lower of the second stage extruder 2 are connected by a pipe-shaped connecting pipe 11. A static mixer 12 is disposed within the connecting pipe 11 .

The static mixer 12 consists of a plurality of four elements 13 arranged in series. However, the number of elements 13 is determined in consideration of the desired mixing state, the pressure loss of the passing fluid, etc., and the number may be singular or plural as required.

Various types of static mixer 12 structures are currently known, but in this embodiment, one with an element structure as shown in FIG. 2 (Hi-Mixer, manufactured by Toshi Co., Ltd.) is used. It is used. That is, each element 13 consists of two passages 14, 15 with blades 16 twisted 180 degrees left and right inserted, and an intermediate chamber 17 is provided between the elements 13, so that the adjacent elements 13
They are arranged offset by 0 degrees.

In addition, the groove depth of the screw 5 of the first stage extruder 1 and the screw 9 of the second stage extruder 2 is larger than the groove depth of a normal single screw extruder, so that the discharge amount per rotation speed is large. It is desirable that the Further, 18 and 19 are pressure gauges for measuring the resin pressure inside the pipe, and 20 and 21 are thermometers for measuring the resin humidity. 22 is piping.

The operation of the two-stage extruder configured as described above will be described below.

The resin supplied from the supply port 3 of the first stage extrusion tIl is
The resin is sent in the axial direction of the screw 5 by the rotational drive of the screw 5, and is melted by shear heat generation of the resin or heating from the cylinder 4 side, and is extruded from the discharge port 6 into the connecting pipe 11.

The state of the resin at the exit of the extrusion t11 is a mixture of molten resin and unmelted resin, and the screw 5 has a function of separating the unmolten resin and molten resin to some extent within its groove. The unmelted resin is unevenly distributed within the molten resin. Therefore, within the connecting pipe 11 from the discharge port 6 to the static mixer 12, pressure fluctuations, temperature fluctuations, and temperature unevenness of the resin are considerably large.

However, when the extruded resin passes through the static mixer 12, it sequentially passes through each element 13 arranged in series, and the flow is twisted and the streamlines are exchanged between each element 13, so the extruded resin is mixed. be done. This mixing progresses as the number of elements 13 increases, and the mixing condition improves. Moreover, since the static mixer 12 has no mechanically moving parts, mixing occurs naturally along the flow.

Since the resin passing through the static mixer 12 is sufficiently kneaded and mixed, the unmelted resin is sufficiently dispersed in the molten resin and its distribution is made uniform.

Therefore, pressure fluctuations, temperature fluctuations, and temperature unevenness of the resin in the connecting pipe 11 that has passed through the static mixer 12 can be suppressed to a much smaller extent than before passing through.

This resin with suppressed pressure fluctuations, temperature fluctuations, and temperature unevenness is supplied to the second stage extruder 2, but the second stage extruder l1
From the point of view of the second side, the raw material is stably supplied in a highly molten state and in a uniform state.
This means that the feeding and discharging conditions by the screw 9 can be maintained in a stable constant state. As a result, at the exit of the second stage extruder 2, the molten resin is extruded with pressure fluctuations, temperature fluctuations, and unevenness of dryness and thinning suppressed to a small level.

By the way, for a two-stage extruder in which the diameter of cylinder 4 and screw 5 of extruder 2 in the first stage is 651Illll, and the diameter of cylinder 8 and screw 9 of extruder 2 in the first stage is 9011IIll, using polyester resin, a stationary type mixer 1
2 (number of elements: 10) and cases where they were not provided were tested, and as a result, good results as shown below were obtained.

That is, as shown in FIGS. 3 and 4, which show the results of measuring the pressure just before the second stage extruder 2 using the pressure gauge 18, the pressure fluctuation ΔP1 ranged from ±5 kg/cd to ±1.5 kg.
/c# was suppressed. Moreover, as shown in FIGS. 5 and 6, the temperature fluctuation ΔT1 at the same position is
In the central part of 1, the temperature was suppressed from ±5°C to ±3°C. Also,
The pressure fluctuation △P2 immediately after the second stage extruder 2 varies from ±1 kg/cd to ±0°5, as shown in Figures 7 and 8.
kg/c or less, temperature fluctuation △T2 is
9 1, 8- ±0.5 from 11°C as shown in Figures 9 and 10
temperature was kept below ℃. Furthermore, the resin temperature distribution in the radial direction inside the pipe immediately after the second stage extrusion 1N2 was measured. This can be interpreted as corresponding to the temperature distribution in the radial direction within the groove of the screw 9, since the flow of a high viscosity fluid such as resin is a laminar flow.

As shown in FIGS. 11 and 12, a static mixer 1
The temperature unevenness, which was about 12°C in the case without 2, was suppressed to 4.5°C by providing the static mixer 12.

As described in detail, when using the two-stage extrusion mode of the present invention, a static mixer is disposed between the first-stage extruder and the second-stage extruder, and After the extruded resin is sufficiently mixed, it is supplied to the second stage of extrusion.
Raw material supply in the second stage extruder, feeding by screw,
The extrusion state can be suppressed to a state with few fluctuations, and compared to conventional equipment, pressure fluctuations and temperature fluctuations in the molten resin discharged from the second stage extruder are reduced.6. The effect of suppressing temperature unevenness to a small level while maintaining a high discharge amount can be obtained.

As a result, fluctuations in the discharge amount and physical properties of the discharged resin are suppressed to a small level, making it possible to stabilize the process and obtain stable quality.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of a two-stage extruder according to an embodiment of the present invention, Fig. 2 is an enlarged partial perspective view of a static mixer of the apparatus shown in Fig. 1, and Fig. 3 is a static mixer. Figure 4 is a resin pressure characteristic diagram just before the second extruder without a static mixer, Figure 5 is a resin pressure characteristic diagram just before the second extruder with a static mixer installed, and Figure 5 is a static mixer diagram. Fig. 6 shows the resin temperature characteristics immediately before the second extruder when a static mixer is installed. Fig. 7 shows the resin temperature characteristics immediately before the second extruder when a static mixer is installed. Figure 8 is a resin pressure characteristic diagram immediately after the second extruder without a static mixer, Figure 9 is a resin pressure characteristic diagram immediately after the second extruder with a static mixer installed, and Figure 9 is a static mixer. Fig. 10 is a resin temperature characteristic diagram immediately after the second extruder without a static mixer. Fig. 11 is a resin temperature characteristic diagram immediately after the second extruder with a static mixer. Fig. 12 is a resin temperature distribution diagram in the piping immediately after the second stage extruder when there is no static mixer. . 1......First stage extruder 2......Second stage extruder 4.8...Cylinder 5.9... ...Screw 6...Discharge lower of the first stage extruder...
......Feed port 11 of the second stage extruder...
...Connecting pipe 11-12...Static mixer 13...Element 18.19...Pressure gauge 20.21. ......Thermometer 12- Sparrow bud sea bream- Ki F! ；Regretful dormitory－″゛ゞ

Claims (1)

[Claims] (1) In a two-stage extruder in which the discharge port of the first-stage extruder and the supply port of the second-stage extruder are connected by a connecting pipe,
A two-stage extruder, characterized in that a static mixer is disposed within the connecting pipe.