JP7532705B2 - Extruder, extruder vent device, and extruder vent method - Google Patents

Description

The present invention relates to extruder venting technology suitable for the production of resin composite materials that contribute to the realization of the Sustainable Development Goals (SDGs).

Resin composite materials are being developed in which a liquid medium or a filler having excess moisture is dispersed and compounded in a synthetic resin. Extruders suitable for these resin composite materials are also being developed. A technology has been disclosed in which an extruder is provided with a means for dehydrating excess moisture derived from biomass at a set pressure lower than the saturated vapor pressure at the kneading temperature and higher than atmospheric pressure, suppressing agglomeration of biomass during dehydration and producing a resin composite material (for example, Patent Document 1).

A technology has been disclosed for producing a resin composite material by providing an extruder with a vent device having a filter supported by a support layer at the opening of the cylinder, thereby improving both the performance of water discharge and the effect of suppressing vent-up (e.g., Patent Document 2). Furthermore, a technology has been disclosed for producing a resin composite material in which a filler of a water-absorbing substance that forms hydrogen bonds with water is dispersed in a continuous phase of a synthetic resin, and the moisture content of the resin composite material at the thermal flow temperature is 1% (e.g., Patent Document 3).

Patent No. 4660528 Patent No. 5467796 Patent No. 7061239

However, in vent devices consisting of filters, etc., it was necessary to set the kneading conditions at high temperature and high pressure to achieve stable dehydration. In addition, such filters were prone to clogging, and required frequent maintenance to avoid a decrease in dehydration capacity. For this reason, the above-mentioned circumstances are factors that hinder the efficiency of production when reducing the moisture content of the molten kneaded body of a resin composite material.

The present invention has been made in consideration of these circumstances, and aims to provide an extruder venting technology that can stably dehydrate without restrictions on kneading conditions, requires no special maintenance, and efficiently produces resin composite materials that contribute to the realization of the SDGs.

The vent device of the extruder according to the present invention comprises a cylindrical body having one end connected to an external through hole that opens into the inner peripheral surface of a barrel hole through which the molten kneaded material is extruded in one direction, a helical body that is positioned at the through hole, has a helical groove formed on its outer peripheral surface, and rotates about its axis inside the cylindrical body, a pipe that discharges gas that passes through the helical body and flows into the internal space of the cylindrical body from the barrel hole to the atmosphere , a pressure gauge that is provided in the cylindrical body and measures the internal pressure of the internal space, and a throttle valve that is provided in the pipe to adjust the discharge amount of the gas that is discharged to the atmosphere side .

The present invention provides an extruder venting technology that enables stable dehydration without restrictions on kneading conditions, requires no special maintenance, and efficiently produces resin composite materials that contribute to the realization of the SDGs.

FIG. 2 is a cross-sectional view of a vent device installed in an extruder in an embodiment of the present invention. FIG. 2 is an exploded cross-sectional view of the vent device according to the embodiment. FIG. 2 is a top perspective view of an extruder equipped with a vent device in an embodiment of the present invention. FIG. 2 is a side perspective view of an extruder equipped with a vent device in an embodiment of the present invention. 3 is a flow chart illustrating a method for venting an extruder according to an embodiment of the present invention.

An embodiment of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is an XY cross-sectional view (A-A cross-sectional view in Fig. 3 described later) of a vent device 10 mounted on an extruder 30 in an embodiment of the present invention. Fig. 2 is an exploded cross-sectional view of the vent device 10 according to the embodiment.

Thus, the vent device 10 comprises a cylindrical body 11, one end of which is connected to the outside, and a through hole 36 which opens onto the inner circumferential surface of a barrel hole 32 through which the molten kneaded material is extruded in one direction (the Z-axis direction); a spiral body 12 which is positioned in this through hole 36, has a spiral groove 15 formed on its outer circumferential surface, and rotates on its axis inside the cylindrical body 11; and a pipe 17 which passes through this spiral body 12 and discharges gas or drain liquid which has flowed from the barrel hole 32 into the internal space 16 of the cylindrical body 11 to the outside.

As shown in Figure 2, a single helical groove 15 is formed on the outer peripheral surface of the helical body 12, but two or more helical grooves 15 may be formed. Such a helical body 12 is arranged coaxially inside the cylindrical body 11, thereby communicating the barrel hole 32 of the cylinder 35 with the internal space 16 of the cylindrical body 11 through the gap with the inner peripheral surface of the cylindrical body 11 and the helical groove 15.

The through hole 36 opens on the side of the barrel hole 32 so that the central axis of the cylindrical body 11 faces a direction perpendicular to the screw 31. One end of the cylindrical body 11 is connected to the outside of the through hole 36, and the other end is connected to the bearing part 20 that rotatably supports the shaft 21 with a bearing 22. In the figure, the cylindrical body 11 and the bearing part 20 are directly connected, but the two may be connected via a spacer (not shown). The position of the spiral body 12 in the through hole 36 can be adjusted by adjusting the length of this spacer (not shown).

A motor 25 is connected via a shaft coupling 27 to the base end of the shaft 21 opposite the tip where the helical body 12 is fixed. When the motor 25 rotates, the shaft 21 rotates coaxially with the helical body 12 at the tip about the central axis of the cylindrical body 11. Although the rotating shaft of the motor 25 is directly connected to the shaft 21 of the helical body 12 in the illustrated embodiment, the motor 25 can be laid out in any manner by connecting it to the shaft 21 via various gears.

In this way, the spiral body 12 rotates in the through hole 36, thereby preventing the molten kneaded body from venting up from the barrel hole 32. Furthermore, moisture and gas separated from the molten kneaded body remaining in the barrel hole 32 are passed through the through hole 36 in which the spiral body 12 is arranged, and guided to the internal space 16 of the cylindrical body 11. In addition to traveling along the spiral groove 15, the moisture and gas also travel through the gap between the inner surface of the cylindrical body 11 and the spiral body 12 to move from the barrel hole 32 to the internal space 16.

The piping 17 discharges the gas or drain liquid that has flowed into the internal space 16 of the cylindrical body 11 to the outside. The throttle valve 18 provided in this piping 17 is not an essential component, but by setting the opening degree as desired, it adjusts the amount of drain liquid or gas discharged from the internal space 16 of the cylindrical body 11 to the outside. Note that the illustrated piping 17 has a base end connected to the upper side of the cylindrical body 11 and mainly functions to discharge gas, but there are also cases where a piping (not shown) with a base end connected to the lower side of the cylindrical body 11 has the function of mainly discharging drain liquid.

The throttle valve 18 applies a variable flow resistance to the gas (water vapor) discharged from the internal space 16 to the atmosphere. This allows the throttle valve 18 to arbitrarily set the internal pressure P of the internal space 16 measured by the pressure gauge 19 between the saturated vapor pressure _Pz at the set temperature of the molten kneaded body and the atmospheric pressure _P0 . In other words, if the throttle valve 18 is completely closed, the internal pressure of the internal space 16 is set to the saturated vapor pressure _Pz , and if the throttle valve 18 is completely opened, the internal pressure is set to the atmospheric pressure _P0 . Furthermore, by connecting a pressure reducing device to the tip of the pipe 17, the internal pressure of the internal space 16 can be set to atmospheric pressure _P0 or less, which promotes dehydration of the molten kneaded body.

The frame 26 supports the motor 25 and the bearing unit 20, and is fixed to a stand 41 placed on a foundation 40. As shown in FIG. 2, the components of the vent device 10 are configured so that the vent device 10 can be easily attached and detached to and disassembled and reassembled from the extruder 30 during maintenance.

Figure 3 is a top perspective view of an extruder 30 equipped with a vent device 10 in an embodiment of the present invention. Figure 4 is a side perspective view of the same. The extruder 30 is composed of an input section 37, a drive section 38, a cylinder 35, and the vent device 10. Inside the cylinder 35, a screw 31 is provided which rotates by the driving force of the drive section 38. Note that in Figure 3, the screw 31 is composed of two shafts, but the extruder 30 is not limited to such a two-shaft configuration, and may be composed of a single shaft or multiple shafts of three or more shafts.

The feeding section 37 feeds the mixture of synthetic resin and other compounds into the cylinder 35, which is an airtight container. The cylinder 35 is set to a temperature at which the synthetic resin melts, so that the mixture is heated and kneaded into a molten mixture by the rotation of the screw 31.

The vent device 10 opens the cylinder 35, which is a sealed container, and discharges the moisture contained in the molten kneaded material to the outside. The molten kneaded material that has been dehydrated in the vent device 10 is discharged from the most downstream end of the cylinder 35. The discharged molten kneaded material is then molded into pellets or into a specified bulk product or film product.

In the extruder 30 shown in Figure 3, vent devices 10 (10a, 10b) are installed in two stages along the extrusion direction (Z-axis direction) of the molten kneaded body, but there is no particular limit to the number of stages. The moisture contained in the molten kneaded body is sequentially discharged from the vent devices 10 (10a, 10b) in which the throttle amount of the throttle valve 18 (18a, 18b) is adjusted. Although not shown in the figure, a vent device with a pressure reducing pump at the tip of the pipe 17 can be provided at the most downstream position.

The opening of the throttle valves 18 (18a, 18b) provided in each of the vent devices 10 is adjusted so that the internal pressure (the value of the pressure gauge 19) of the vent device 10 (10a, 10b) is set so that it slopes from the upstream to the downstream in the order of _Pa > _Pb = _P0 . In this case, the throttle valve 18 for setting the internal pressure _Pb is set to full open. Also, when a pressure reducing pump is provided at the end of the pipe 17, the throttle valve 18 is set so that the value _Pc of the pressure gauge ₁₉ in this case is smaller than the atmospheric pressure _P0 ( _P0 > _Pc ). In this way, by first performing dehydration at an internal pressure _Pa higher than the atmospheric pressure P0, and then gradually lowering and setting the internal pressures _Pb and _Pc , it is possible to prevent excessive evaporation of moisture and achieve stable dehydration even when the molten kneaded body contains a large amount of moisture.

A venting method for an extruder 30 according to an embodiment of the present invention will be described with reference to the flow chart of Figure 5 (see Figure 3 as appropriate). First, the vent device 10 is externally connected to the extruder 30, and the cylindrical body 11 and the barrel hole 32 are connected (S11). Then, raw materials are fed into the input section 37, and the screw 31 is rotated axially to extrude from upstream to downstream, while heating and applying shear stress to the raw materials to make them into a molten mixture (S12).

Next, the spiral body 12 of the vent device 10 is rotated on its axis (S13). Then, the pressure of the molten kneaded body pushed out to the opening position of the through-hole 36 drops, and the water contained therein vaporizes and expands all at once. This vaporized and expanded water (water vapor) also engulfs the solid components of the molten kneaded body and attempts to fly out of the through-hole 36. However, these solid components are pushed back by the spiral body 12 rotating on its axis, and are unable to pass through the through-hole 36, and are instead pushed further downstream of the barrel hole 32.

On the other hand, the moisture (water vapor) vaporized and expanded from the molten kneaded body passes through the barrel hole 32, the spiral body 12, and the through hole 36, and is trapped in the vent device 10a set to an internal pressure _Pa (S14). Then, this trapped water vapor (gas component) or the drain liquid in which this water vapor is condensed is discharged to the outside through the pipe 17 (S15).

On the other hand, the molten kneaded material that has passed through the vent device 10a on the upstream side of the barrel hole 32 is further trapped and discharged to the outside in the downstream vent device 10b, which is set to an internal pressure _Pb (< _Pa ) (S16 Yes, S14, S15). The molten kneaded material that has been dehydrated in the vent device 10 (10a, 10b) is discharged from the most downstream of the extruder 30 and formed into pellets or a predetermined bulk product or film product (S16 No, S17, END).

10...vent device, 11...cylindrical body, 12...spiral body, 15...spiral groove, 16...internal space, 17...piping, 18...throttle valve, 19...pressure gauge, 20...bearing portion, 21...shaft, 21...bearing, 25...motor, 26...frame, 27...shaft coupling, 30...extruder, 31...screw, 32...barrel hole, 35...cylinder, 36...through hole, 37...feeding portion, 38...drive portion, 40...foundation, 41...frame, P( _Pa , _Pb )...internal pressure, _P0 ...atmospheric pressure.

Claims (4)

A cylindrical body having one end connected to an external portion of a through hole that opens to an inner peripheral surface of a barrel hole through which the molten kneaded material is extruded in one direction;
a helical body positioned in the through hole, the helical body having an outer peripheral surface formed with a helical groove, and the helical body rotating on an axis inside the cylindrical body;
a pipe for discharging the gas that has passed through the spiral body and flowed into the internal space of the cylindrical body from the barrel hole to the atmosphere ;
a pressure gauge provided in the cylindrical body and configured to measure an internal pressure of the internal space;
a throttle valve provided in the piping for adjusting the amount of gas discharged to the atmosphere ;
1. A vent device for an extruder comprising: The extruder vent device according to claim 1,
a bearing portion that rotatably supports a shaft that is fixed to a tip of the spiral body and is connected to the other end of the cylindrical body;
A vent device for an extruder comprising: a motor that rotates the shaft; and a frame that supports the bearing portion. The vent device for an extruder according to claim 1 or 2,
An extruder in which a plurality of the vent devices are provided along a direction in which the molten kneaded body is extruded. A step of externally connecting one end of a cylindrical body to a through hole that opens to an inner circumferential surface of a barrel hole through which the molten kneaded body is extruded in one direction;
Positioning a spiral body having a spiral groove formed on an outer circumferential surface in the through hole;
rotating the helical body around an axis inside the cylindrical body;
discharging the gas that has passed through the spiral body and flowed into the internal space of the cylindrical body from the barrel hole to the atmosphere through a pipe;
Measuring the internal pressure of the internal space with a pressure gauge provided in the cylindrical body;
and adjusting the amount of the gas discharged to the atmosphere by a throttle valve provided in the piping .

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