JP2011245721A - Venting device for twin screw extruder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently devolatilize and degas devolatilized and degassed products generated in a plastic excruding molding step by a twin screw extruder from a venting port provided in the way of the extruder.SOLUTION: The venting device for twin screw extruder includes a vacuum barrel 20 connected to a side part of a screw space 3 in a barrel 2 of the extruder 1 and a venting screw 30 whose tip part is housed in the vacuum barrel 20 to face the screw space 3 and which can be rotated in the same direction of twin screws. The venting screw 30 includes a decelerator and a rotational motor transmitting rotation force to an end opposite to the extruder 1 side. In the venting screw 30, a front end screw 31 having a twist part to be a pushing direction to the extruder 1 side on rotation is formed, a transfer screw 32 having a twist part having a direction reverse to that of the front end screw 31 is formed between the front end screw 31 and an outlet port from the vacuum barrel 20 and a rear end screw 33 having a twist part having the direction the same as the front end screw 31 is formed at a rear end part.

Description

  The present invention relates to a venting device for a twin screw extruder, and efficiently removes devolatilized and degassed substances generated by melt extrusion of plastic by a twin screw extruder from a vent port provided in the middle of the extruder. The present invention relates to a venting device for a possible twin screw extruder.

  Conventionally, as a venting device for an extruder, a vertical vacuum vent hole is formed in the middle of the extrusion process path, and a block having a shape that prevents the polymer from venting up is attached so as to communicate with the vacuum vent hole. An apparatus for venting devolatilized and degassed substances generated in melt extrusion is used. In this type of vent apparatus, there has been a problem that the devolatilized monomer falls again on the screw in the extruder, causing a deterioration in the quality of the molded resin. Further, when the vent port is blocked by the vent-up that has caused the extrusion fluctuation, the venting effect is lost, so it is necessary to periodically clean the vent portion. During this time, since the operation of the extruder was stopped, there was also a problem that productivity loss occurred.

  In order to solve these problems, an extruder equipped with a horizontal vacuum vent device has also been proposed (see Patent Document 1). Patent Document 1 discloses an extruder having a side vent port connected to a suction box. As described above, by providing the side vent port and the vent box, it is possible to prevent the bent-up polymer or the polymer adhering to the vent block, which has occurred in the vertical type, from falling into and entering the main body screw. Further, since the devolatilized and degassed material is sucked and discharged by suction from the side vent port, re-entry of the vented polymer into the screw in the extruder main body can be prevented.

JP 2001-162671 A

  However, in the invention disclosed in Patent Document 1, there is a problem that the vent opening is blocked by the slight rise of the polymer pool sucked into the vent box, and the vent function is impaired. Therefore, the object of the present invention is to eliminate the problems of the conventional techniques described above, and to prevent the polymer from being re-entered into the extruder side by suppressing the vent-up of the polymer discharged from the vent port. Another object of the present invention is to provide a venting device for a twin screw extruder that can eliminate the hue change and foreign matter contamination of an extruded product.

  In order to achieve the above object, the present invention provides a vacuum barrel connected to a side of a screw space in an extruder barrel and a tip of the vacuum barrel facing the screw space in the barrel of the extruder. A vent screw housed in the same direction and biaxially rotatable, a speed reducer connected to the end of the vent screw opposite to the extruder side and transmitting a predetermined rotational force to the vent screw, and the speed reducer A rotary motor that applies a predetermined rotational driving force to the vent screw, and the vent screw is formed with a tip screw having a twisted portion that is pushed into the extruder during rotation. Between the discharge port, a transfer screw having a twist portion opposite to the tip portion is formed, and a rear end screw having a twist portion in the same direction as the tip screw is formed at the rear end portion. It is characterized in.

  It is preferable that the vent screw includes a member in which the tip screw, the transfer screw, and the rear screw are connected in the axial direction.

  It is preferable that a vacuum pipe is connected to a discharge port formed in the vacuum barrel so that a predetermined vacuum state is maintained in the screw space of the vacuum barrel.

  It is preferable that the vacuum barrel has a flow passage hole for the heating medium so as to surround the vent screw space.

  The lead of the tip screw is preferably set to 0.5 to 2 times the screw diameter.

  The clearance between the screw in the barrel of the extruder and the tip of the vent screw in the vacuum barrel is preferably set to 1 to 3 mm.

  The rotation speed of the vent screw is preferably set to 50 to 300 rpm.

  According to the present invention, the rotation of the vent screw in the vacuum barrel connected through the vent port provided on the side surface of the extruder suppresses the polymer vent-up discharged from the vent port, and deteriorates the polymer, etc. This prevents the re-entry of the resin to the extruder side and eliminates the hue change and foreign matter contamination of the extruded product.

The top view which showed the whole schematic structure of the vent apparatus for twin-screw extruders of this invention. The side view (partial cross section display) of the vent apparatus for a twin-screw extruder shown in FIG. The expanded sectional view which showed the structure of the vacuum barrel and the screw element. Explanatory drawing which showed the structure of the screw element. The schematic explanatory drawing which showed the application range of the attachment position of a vent apparatus.

  Hereinafter, the following examples will be described with reference to the accompanying drawings as modes for carrying out the vent device for a twin screw extruder of the present invention.

  FIG. 1 is a plan view showing a state in which a biaxial extruder vent device 10 (hereinafter referred to as a vent device 10) according to the present invention is attached to a side surface of the biaxial extruder 1. FIG. 2 is a side view showing, in cross section, a vacuum barrel that accommodates a vent screw that is a part of the vent device 10 shown in FIG. As shown in FIGS. 1 and 2, the vent device 10 is installed on the side surface of the front end side block of the extruder body.

  The vent device 10 is attached to the extruder main body, and includes an insert member 11 that accommodates the tip of the vent screw, a vacuum barrel 20 that accommodates the vent screw connected in series to the insert member 11, and a vacuum barrel. A seal member 12 that holds the vacuum in 20, a coupler for rotating the vent screw, a speed reducer that transmits a predetermined number of rotations to the coupler, and an inverter motor 15 as a drive source are arranged in series, It is configured. Note that a graphite gasket (not shown) is applied to the joint between the members, and a vacuum in the vacuum barrel 20 is secured.

  Hereinafter, the configuration of each unit will be described with reference to FIGS. 1 and 2. As shown in FIG. 2, the insert member 11 is inserted into the barrel 2 of the extruder 1 main body in close contact with the inner surface of the support hole 5 formed so as to penetrate from the side surface to the end of the screw space 3. And a cylindrical body 11a having an inner diameter substantially equal to the outer diameter of the screw space 3 of the barrel 2 of the extruder 1 body, and a flange 11b for tightly fixing to the side surface of the extruder 1, The tip of the vent screw 30 is housed inside. The vacuum barrel 20 is coaxially connected through the flange 11 b of the insert member 11.

  The vacuum barrel 20 is a box-like body in which a connecting flange 20a is formed at an end and a connecting flange 20b for connecting to the seal member 12 is formed at the other end, and a vent biaxial screw 30 is rotated inside. A screw space 21 that can be held and a shaft end hole 22 in which the screw end shaft is supported are coaxially formed along the longitudinal direction of the box-like body at a position substantially at the center of the rectangular cross section. Further, a through-hole 23 through which a heat medium for barrel heating or cooling can be circulated is formed in the box-like body in a direction perpendicular to the paper surface (see FIGS. 2 and 3). Further, a vacuum piping port 24 and a devolatilization outlet 25 are formed in communication with the upper and lower surfaces of the vent screw 30 space. An end of a vacuum pipe 26 extended from a vacuum pump (not shown) is connected to the vacuum pipe port 24 and the discharge port 25 via a seal (not shown). In addition, by evacuating from the discharge port 25 below the box-like body, devolatilized substances such as devolatilized monomers transferred in the screw space 21 are discharged.

  The seal member 12 has a bearing portion (not shown) that supports the drive-side shaft end of the vent screw 30 inside, and a plurality of ring-shaped metal bushes and O-rings that are arranged in the bearing in the axial direction. (Not shown) ensures vacuum sealing at the shaft end. A coupler 13 that transmits a driving force from the reduction gear 14 side is connected to the end of the seal member 12. Thus, the vent screw 30 can be operated by appropriately adjusting the number of rotations thereof by a predetermined control operation.

  In FIG. 2, the speed reducer is supported by the fixed portion. However, the speed reducer and the drive motor are installed on a stand that is supported in a state where the position can be secured during operation. You can also.

Hereinafter, the configuration and operation of the screw accommodated in the screw space of the vacuum barrel 20 will be described with reference to FIG.
As described above, the vacuum barrel 20 that accommodates the screw is attached to the side surface of the extruder 1 via the insert member 11 so that the vent port faces the horizontal direction with respect to the screw space of the barrel of the extruder 1. . As a result, the bent-up polymer and the devolatilized devolatilized product are prevented from falling into and entering the screw due to gravity. Further, a rotating twin screw 30 is accommodated in the vacuum barrel 20 in parallel. This biaxial screw 30 is comprised from the some element (a structure is mentioned later) connected with the axial direction. Of the entire configuration, a tip screw element 31 (hereinafter simply referred to as a tip screw 31) is formed with a twisted portion in a pushing direction in which the polymer that vents up when the screw rotates is suppressed. The tip screw 31 composed of the biaxial screw rotates synchronously in the same direction, so that it is possible to forcibly suppress vent-up that occurs due to extrusion fluctuations in the extrusion process. The length of the tip screw 31 is set to the minimum orbital twist length because the deteriorated material adhering to the surface is pushed again into the screw space on the extruder 1 side. Moreover, the lead of a screw is set to the dimension below a screw diameter, and the feed efficiency is ensured. In this embodiment, the clearance between the screw 4 in the screw space 3 of the extruder 1 and the tip of the tip screw 31 of the vent device 10 is set to 1 to 3 mm. Thereby, the monomer returned from the tip screw 31 does not stay between both screws.

  A transfer screw element 32 (hereinafter simply referred to as a transfer screw 32) is coaxially formed at the rear end portion of the tip screw 31. The transfer screw 32 serves to transfer the devolatilized material beyond the screw portion of the tip screw 31 in the vacuum suction direction. Thus, the devolatilized material does not re-enter into the extruder 1 side screw except for the portion pushed back by the tip screw 31. For this reason, the devolatilized material discharged from the vent port can be reliably removed from the extruder 1. As shown in FIG. 3, a devolatilized material discharge port 25 is provided behind the transfer screw 32. A vacuum pipe 26 is connected to the devolatilization outlet 25. Further, a rear end screw element 33 (hereinafter simply referred to as a rear end screw 33) in the same twist direction as that of the front end screw 31 is formed continuously with the transfer screw 32 on the drive side from the devolatilized product discharge port 25. . Thereby, it can prevent that a devolatilized material will be sent to the screw edge part only by the transfer screw 32. FIG.

  The rotation controlled by the speed reducer is transmitted to the single screw element 30 including the front end screw 31, the transfer screw 32, and the rear end screw 33 via the seal member 12 and the coupler 13. The rotational speed of the screw element 30 can be used in the range of 50 to 600 rpm as long as it has a pushing force with respect to the vent-up and the vacuum effect can be exhibited. Moreover, when using a general resin material, it is preferable to set to about 100-300 rpm. Furthermore, it is preferable that the heating medium is circulated using the through holes 23 formed in the vacuum barrel 20 to heat the vacuum barrel 20 to a predetermined temperature. Thereby, it is possible to prevent the devolatilized material that has been devolatilized from becoming highly viscous due to a decrease in temperature and being unable to be discharged from the discharge port 25.

  A vacuum gauge 16 is attached to the tip of the vacuum barrel 20 to measure the degree of vacuum, and it is constantly measured whether the screw space on the extruder 1 side of the vacuum barrel 20 is kept in a vacuum state. When a decrease in the degree of vacuum is confirmed at this portion, the vacuum pipe 26 on the discharge port 25 side may be clogged with monomers or the like. In that case, appropriate measures such as pipe cleaning and parts replacement can be taken quickly.

  Here, the structure of the screw element 30 accommodated in the vacuum barrel 20 will be described with reference to FIG. FIG. 4A is a view showing the screw element 30 shown in FIG. As described above, the screw element 30 can be divided into three block elements, ie, the front screw 31, the transfer screw 32, and the rear screw 33, according to the screw configuration. These blocks are illustrated in FIG. ), A screw element (not shown) is fixed to the end of a transfer screw 32 which is continuously attached integrally with the screw shaft 34 in a cylindrical shape. 30 is configured as a whole.

  As another configuration example, as shown in FIG. 3C, the component is divided into a plurality of parts, and the parts 31, 32, and 33 are connected in the axial direction. Each part can be replaced as appropriate according to the use situation. That is, the tip is exposed to a state where the monomer that has been vented up adheres and the parts are constantly worn so as to push it back. For this reason, the parts are consumed faster than the rear end. Therefore, the maintenance cost can be reduced by exchanging only the tip screw 31. Needless to say, when used for extrusion molding of a soft resin polymer, as shown in FIG. 4D, the screw element 30 formed as a whole can be used.

  The screw shape (twisted shape) of the tip screw 31 will be described with reference to FIGS. As described above, the tip screw 31 has the action of pushing back the monomer. At this time, for example, as shown in FIG. it can. Further, it is preferable to reduce the lead when vent-up from the extruder 1 is likely to occur or the polymer is likely to deteriorate. The lead of the tip screw 31 is preferably about 0.5 to 2 times the screw diameter (D). Further, depending on the material of the extruded resin, as shown in FIG. 5F, the length in the axial direction of various leads can be shortened.

  Next, the position of the vent port formed in the screw space 3 formed in the barrel 2 of the extruder 1 and the angle formed by the insert member installed toward the vent port will be described with reference to FIGS. In the above-described embodiment, as shown in FIGS. 2, 3, and 5 (a), the vent device 10 includes the insert member so that the vent port faces the horizontal direction with respect to the screw space of the barrel of the extruder 1. 11 and attached to the side surface of the extruder 1. The vent device 10 functions as a so-called side vent device positioned laterally with respect to the screw space 3, but if the vent device 10 is installed so as to be orthogonal to the screw space 3, an inclination angle thereof is provided. α ° can be set as appropriate. FIG. 5B shows a state in which the insert member 11 of the vent device 10 is attached in a state where the inclination angle is set downward from α = 20 ° downward. Since the vent device 10 is installed toward a position lower than the screw space 3 in this way, the low viscosity monomer easily flows to the discharge port side (not shown) through the screw element 30 of the vent device 10. There is an advantage that the situation of re-invasion to the side can be prevented. Theoretically, one of the twin screw can be provided with a vent device in a range of 90 ° from horizontal to vertically downward. Therefore, in consideration of providing on the other screw side, the vent device can be installed at any position within the range of 180 ° below the screw space.

  In addition, this invention is not limited to the Example mentioned above, A various change within the range shown to each claim is possible. In other words, embodiments obtained by combining technical means appropriately changed within the scope of the claims are also included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Extruder 2 Barrel 3 Screw space 4 Screw 10 Vent device (vent device) for twin screw extruder
12 Seal member 13 Coupler 14 Reducer 15 Motor 20 Vacuum barrel 23 Heating medium flow hole 25 Volatilized material discharge port 26 Vacuum pipe 30 Vent screw 31 Lead screw element 32 Transfer screw element 33 Trailing screw element

Claims (7)

A vacuum barrel connected to the side of the screw space in the barrel of the extruder, and accommodated in the vacuum barrel so that its tip faces the screw space of the barrel of the extruder, and can rotate in the same direction in two axes. A venting screw, a speed reducer connected to the end of the venting screw opposite to the extruder side, transmitting a predetermined rotational force to the venting screw, and a rotation motor for applying a predetermined rotational driving force to the speed reducer; With
The vent screw is formed with a tip screw having a twisted portion that is pushed into the extruder during rotation. Between the tip and a discharge port from the vacuum barrel, the tip twisted portion is opposite to the tip. A venting device for a twin screw extruder, wherein a rear end screw having a twisted portion in the same direction as the front end screw is formed at a rear end portion.   2. The venting device for a twin screw extruder according to claim 1, wherein the venting screw includes a member in which the tip screw, the transfer screw, and the trailing screw are connected in an axial direction.   The venting device for a twin screw extruder according to claim 1, wherein a vacuum pipe is connected to a discharge port formed in the vacuum barrel, and a predetermined vacuum state is maintained in a screw space of the vacuum barrel. .   The venting device for a twin screw extruder according to claim 1, wherein the vacuum barrel has a flow passage hole for a heating medium so as to surround the vent screw space.   The vent of the twin screw extruder according to claim 1 or 2, wherein a lead of the tip screw is set to 0.5 to 2 times a screw diameter.   The vent device for a twin screw extruder according to claim 1, wherein a clearance between a screw in the barrel of the extruder and a tip of a vent screw in the vacuum barrel is set to 1 to 3 mm.   The venting device for a twin screw extruder according to claim 1, wherein the number of rotations of the venting screw is 50 to 300 rpm.

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