JP5684063B2 - Volatilization apparatus and method in an extruder - Google Patents

Description

  The present invention relates to a devolatilizing apparatus and method in an extruder, and more particularly, to a novel improvement for obtaining additional transportation capacity and preventing overfilling of raw materials inside a cylinder by twisting the chip flight part of each screw segment. .

Examples of the devolatilization apparatus in this type of extruder that has been conventionally used include the conventional configurations of Patent Documents 1 to 4.
That is, in the method of conveying and kneading the screw of the extruder of Patent Document 1 described above, the kneading unit and the devolatilization unit are alternately provided at a plurality of locations, and the devolatilization unit is in a vacuum state, although not illustrated. In this devolatilization section, devolatilization is performed by screw kneading action.

Moreover, in the biaxial screw extruder for devolatilization of the above-mentioned patent document 2, like the case of the structure of the above-mentioned patent document 1, in the devolatilization area | region where the airtightness was hold | maintained by the filling part, the raw material was supplied. An apparatus having kneading flights twisted so as to be transported downstream and separating volatile components by feeding and kneading materials downstream was proposed and configured as shown in FIG.
That is, in FIG. 6, what is indicated by reference numeral 1 is a cylinder whose overall shape is a longitudinal hollow shape, and for the devolatilization for keeping the inside of the cylinder 1 in a negative pressure state on the rear stage side of the cylinder 1. A vacuum vent 2 is formed.

A pair of screws 3 are installed in the cylinder 1 in a state where the screws 3 mesh with each other, and the screw 3 is formed with a kneading portion 4 and a devolatilization region 5 from the upstream side to the downstream side.
In the devolatilization region 5, a surface renewable screw 6 is formed at the upstream side thereof, that is, immediately after the kneading unit 4, and a raw material filling portion 7 is formed at the most downstream position of the devolatilization region 5. Has been.

As shown in FIGS. 7 and 8, the surface renewable screw 6 includes a screw segment 9 attached to the screw shaft 10 in a state where the disks 8 are sequentially shifted by a predetermined rotation angle θ.
Next, in the above-described configuration, when a plastic raw material is supplied from a raw material supply port (not shown) of the cylinder 1, the plastic raw material is transported to the downstream kneading unit 4 by the screw 3 and filled with the kneading unit 4, thereby removing the plastic raw material. The volatile region 5 is transported to the devolatilized region 5 in a state where the airtightness is maintained.

The plastic raw material transported to the devolatilization region 5 is replaced from the surface to the inside by the surface renewable screw 6 and transported downstream while separating and removing volatile components contained in the plastic raw material. After passing through the filling unit 7, the die is sent from a die not shown to the underwater cutter device.
The screw segment 9 of the surface renewable screw 6 is a kneading piece having a transport capability in the downstream direction, and each disk 8 is arranged around the screw shaft 10 at a phase angle θ (45 degrees).

  Further, in the screw kneading extruder disclosed in the above-mentioned Patent Document 3, as shown in FIG. 9, the screw 3 provided in the cylinder 1 has a stirring unit 11, a kneading and transporting unit from upstream to downstream. 12, the surface renewable screw piece 6 and the kneading and transporting portion 12a are provided, and the surface renewable screw piece 6 is disposed between the kneading and transporting portions 12 and 12a.

  Further, in the mixing device and the mixing element disclosed in the above-mentioned Patent Document 4, as shown in FIG. 10, the pair of screw segments 9 meshing with each other has a pair of wings facing each other at 180 degrees at the outer peripheral position. The chip flight part 20 is formed, and the surface flight property is promoted by each chip flight part 20.

JP 11-277604 A JP 2010-179575 A JP 2004-306547 A JP 63-151340 A

Since the devolatilization apparatus in the conventional extruder is configured as described above, the following problems exist.
That is, in the case of the conventional configuration shown in Patent Document 1 described above, devolatilization is performed by causing a part of the molten resin to flow backward at the meshing portion of each screw existing in the devolatilization region and increasing the residence time. In order to promote this, not only the residence time but also the expansion of the exposed area of the resin to be devolatilized is necessary. However, a transport screw connected to a flight has a high transport capacity and sometimes lacks a surface renewal capacity.
Also, in order to prevent the exposed area of the plastic raw material in the devolatilization region from being reduced, it is necessary to consider repositioning the surface by arranging a screw piece having a high transport capability that does not fill the plastic raw material inside the cylinder. However, since the transport capacity is high, the residence time is reduced and the surface renewal efficiency is deteriorated. Therefore, there is a disadvantage that the effect cannot be obtained unless a large number of kneading screws are provided and the devolatilization region is lengthened.
Further, in the case of the conventional configuration shown in Patent Document 2, in order to promote the renewal of the surface, many disks of the segment screw must be laminated in the axial direction with a phase angle, and the segment screw itself is It was supposed to be longer in the axial direction.
In the case of the conventional configuration shown in Patent Document 3, since the surface renewable screw piece is provided between the kneading and transporting portions, it is difficult to shorten the entire length of the screw itself.
Further, in the case of the conventional configuration shown in Patent Document 4, a chip flight part is formed in each screw segment, but since the twist is not applied to the chip flight part, it is difficult to expect the transport capability, and excessive It was difficult to avoid stagnation.

The devolatilization apparatus in the extruder according to the present invention includes a kneading section upstream of the devolatilization area in a devolatilization area of a twin-screw extruder in which a pair of screws mesh with each other in a cylinder having a vacuum vent and rotate in the same direction. Immediately after, in the devolatilization apparatus in the extruder formed by disposing the surface renewable screw, each chip flight part provided on the outer periphery of each screw segment of the surface renewable screw meshes with each other in a non-contact manner through a gap, Each of the chip flight portions is formed with a twist , and is formed at both end portions on the long axis side in the cross section perpendicular to the screw axis of the surface renewable screw via an air gap portion, and the other screw in the air gap portion is formed. a configuration wherein the tip flight portion of the segments are arranged so as to be passed through, also, the tip flight portion is configured to form a trapezoidal sectional shape The devolatilization method in the extruder according to the present invention is a devolatilization region of a twin-screw extruder in which a pair of screws mesh with each other in a cylinder having a vacuum vent port and rotate in the same direction. Using a devolatilizer in an extruder in which a surface renewable screw is arranged immediately after the upstream kneading part, chip flight parts provided on the outer periphery of each screw segment of the surface renewable screw are not mutually connected via a gap. The tip flight portions are engaged with each other and are twisted , and are formed at both ends on the long axis side in the cross section perpendicular to the screw axis of the surface renewable screw via air gap portions. the a method used in a state where the tip flight portion of the other of the screw segments are arranged so as to be passed through, also, the tip flight portion A method of forming a trapezoidal sectional shape.

Since the devolatilization apparatus and method in the extruder according to the present invention are configured as described above, the following effects can be obtained.
That is, in a devolatilization area of a twin screw extruder in which a pair of screws mesh with each other in a cylinder having a vacuum vent port and rotate in the same direction, a surface renewable screw is disposed immediately after the kneading section upstream of the devolatilization area. in devolatilizer in the extruder comprising Te, each chip flight portion provided on the outer periphery of each screw segment of the surface renewability screw, meshes with a non-contact with each other through a gap, said each chip flight portion, twisting Formed and formed at both ends on the long axis side in the cross-section perpendicular to the screw axis of the surface renewable screw via an air gap portion, and the chip flight portion of another screw segment can pass through the air gap portion. by being arranged as the residence of the raw material on the screw by placing the surface renewable screw segment devolatilization region immediately after the kneading portion So, blades of adjacent screw plastic material is thinned by meshing while maintaining a gap, it is possible to accelerate the surface renewal. In addition, twisting is provided in the tip flight part provided in the surface renewable screw segment to suppress excessive stagnation and increase the surface area of the plastic raw material exposed to the reduced pressure atmosphere. Can be removed.
Further, the tip flight part can be easily twisted to the tip flight part by forming a trapezoidal cross section.

It is a schematic block diagram which shows the devolatilization apparatus in the extruder by this invention. It is a schematic block diagram which shows the comparative example of FIG. It is sectional drawing which shows the meshing state of the surface renewable screw segment of FIG. FIG. 4 is a right side view of the screw segment of FIG. 3. It is a schematic block diagram which shows the other form of the devolatilization apparatus in the extruder of FIG. It is a schematic block diagram which shows a conventional structure. It is an enlarged side view which shows the surface renewable screw of FIG. It is the front view seen from the right side of FIG. It is a schematic block diagram which shows another conventional structure. It is sectional drawing of the principal part which shows another conventional structure. It is a characteristic view which shows the devolatilization performance in each screw shape. It is a characteristic view which shows the specific energy in each screw shape. It is a characteristic view which shows the extruder front-end | tip exit resin temperature in each screw shape.

  By twisting the chip flight part of each screw segment, the total exposed area is increased by renewing and thinning the surface while adding transportation capability and preventing overfilling of the raw material inside the cylinder. An object of the present invention is to provide a devolatilization apparatus and method in an extruder that can achieve a devolatilization effect.

Hereinafter, preferred embodiments of a devolatilization apparatus and method in an extruder according to the present invention will be described with reference to the drawings.
In addition, the same code | symbol is demonstrated to the part which is the same as that of a prior art example, or an equivalent part.
A reference numeral 1 in FIG. 1 denotes a cylindrical cylinder having an overall hollow shape, and a vacuum vent port for devolatilization for keeping the inside of the cylinder 1 in a negative pressure state on the rear stage side of the cylinder 1. 2 is formed.

  A pair of screws 3 are installed in the cylinder 1 in a state where they are engaged with each other. The screw 3 is provided with a kneading portion 4 and a devolatilization region 5 from the upstream side to the downstream side. Inside, a surface renewable screw 6 is formed upstream thereof, and a raw material filling portion 7 is formed downstream thereof.

  The surface renewable screw 6 is disposed as a front stage of the devolatilization region 5 immediately after the kneading section 4, and the surface renewable screw 6 is composed of a screw segment having a high surface renewal / thinning ability. The exposure area is enlarged, and the volatile components contained in the raw material are effectively removed.

The surface renewable screw 6 is configured as shown in FIGS.
That is, the surface renewable screw 6 located in the devolatilization region 5 incorporates a pair of screw segments 6A, 6B and 6C, 6D, and both ends on the long axis side in the cross section perpendicular to the screw axis of the screw segments 6B and 6C. A pair of tip flight portions 20 are formed in the portion via the air gap portion 22, and the tip flight portions 20 are configured to engage with each other in a non-contact state via the narrow gap 21 and rotate in the same direction in two axes. Yes. That is, it arrange | positions so that the chip flight part 20 of the other screw segment 6B or 6C can pass the inside of the said air gap part 22 as FIG. 3 shows.
In addition, by rotating each surface renewable screw 6 in a state where the gap 21 by each chip flight part 20 is held, it becomes possible to reduce the thickness of the raw material, promote the surface renewability, and further increase the total exposed area. A higher devolatilizing effect can be obtained.
Each of the chip flight sections 20 has a trapezoidal cross section and is twisted in a spiral shape along the axial direction so as to be able to transport a molten resin as a raw material. Is about 1 to 8.

Next, the operation will be described.
The raw material supplied into the extruder is transported to the kneading unit 4 by the screw 3 inserted into the cylinder 1 and, after being subjected to a shearing action by the kneading unit 4, is brought into a negative pressure state by the transport screw segment. It is transported to the devolatilization area 5. In this devolatilization region 5, screw segments 6A to 6D having surface renewability are installed, and the raw material is transported downstream while being kneaded, thereby efficiently removing contained volatile components. As shown in FIG. 3, the shape of the surface renewable screw segments 6A to 6D is configured by a total of two flight tip portions 20 and air gap portions 22 in the axial center direction of the tips at both ends on the long axis side. The The flight tip portions 20 of the 6A, 6B, 6C, and 6D segments are non-contact when rotating, and the surface exposure is promoted while maintaining a narrow gap 21 between the flight tip portions 20 to each other, thereby increasing the total exposed area. Increases the devolatilization effect. Further, when the raw material is excessively filled in the cylinder 1, the area of the raw material exposed to the reduced pressure atmosphere is reduced and the devolatilization efficiency is lowered. Therefore, the tip flight part 20 is twisted in the axial direction to add transportation capability. As a result, the exposed area is increased without excessively filling the cylinder 1 with the raw material, and a decrease in devolatilization efficiency is suppressed.
The configuration of the comparative example of FIG. 2 and the configuration of the other form of FIG. 5 are modifications of the configuration of FIG. 1. Therefore, the same or equivalent parts as in FIG. Omitted.

Next, an embodiment actually performed by the applicant will be described.
In FIG. 1, a cylinder 1, a screw 3, and a vacuum vent port 2 are shown. Two screws 3 are inserted into the heat-coolable cylinder 1 and rotated in the same direction by a driving machine (not shown) so that the two screws 3 are engaged with each other.
Reference numeral 5 denotes a devolatilization region, 4 denotes a kneading portion that forms a seal portion, and 6 denotes a surface renewal screw. The devolatilization region 5 is sucked by the vacuum device from the vacuum vent port 2 and is filled with the raw material in the raw material filling portion 7 which is a seal portion, so that the airtightness is maintained and is in a negative pressure state. The surface renewable screw 6 is arranged so as to avoid a position directly below the vacuum vent 2.

Experimental conditions are shown below.
Raw material: LDPE (Ml = 50)
Raw material-containing volatile components: n-He x (4000 ppm)
Cylinder inner diameter: φ69mm
Processing capacity: 150kg / h
Screw rotation speed: 100, 150, 200 rpm
Screw shape: FIG. 2 shows a screw configuration of a comparative example, and FIG. 5 shows another screw configuration.
FIG. 2 shows a comparative example. The comparative example- is a conventional screw configuration that does not use a surface renewal screw in the devolatilization region 5, and is configured only by a screw segment (FF: Forwrd Full-flight) having high downstream transport capability.
FIG. 5 shows another embodiment as an embodiment. The embodiment- has a configuration in which four sets of eight surface renewable screws 6 of the present invention having a LEAD number of about 6 are arranged in the devolatilization region 5 (FIG. 5).

[result]
11, 12, and 13 show values obtained by averaging the data of the three conditions with the screw rotation speed changed.
FIG. 11 shows the devolatilization performance in each screw shape. The devolatilization performance was defined as the devolatilization rate in each screw shape. The devolatilization rate is (1−Cout / Cin) * 100.
Cout = Volatile component concentration contained in the raw material discharged from the extruder
Cin = Concentration of volatile components contained in raw material before being supplied to the extruder FIG. 12 shows specific energy in each screw shape.
FIG. 13 shows the extruder tip outlet resin temperature in each screw shape.
The screw of FIG. 5 using the new surface renewal screw 6 having a twisted blade has almost no change in the resin temperature and specific energy compared with the screw of FIG. 2 which is a comparative example, but the devolatilization rate is improved by 11%. did.

The above-described configuration of the present invention is summarized as follows.
That is, in a devolatilization region 5 of a twin-screw extruder in which a pair of screws 3 mesh with each other in a cylinder 1 having a vacuum vent port 2 and rotate in the same direction, the surface immediately after the kneading section 4 upstream of the devolatilization region 5. In the devolatilization apparatus in the extruder in which the renewable screw 6 is arranged, the chip flight portions 20 provided on the outer circumferences of the screw segments 6B and 6C of the surface renewable screw 6 are not in contact with each other through the gap 21. The tip flight portions 20 are twisted and formed at both ends on the long axis side in the cross section perpendicular to the screw axis of the surface renewable screw 6 via the air gap portions 22. said section 22 of the other of said screw segment 6B or 6C is a configuration chip flight portion 20 is disposed so as to pass through, also, the tip Write unit 20 has a configuration which forms a trapezoidal sectional shape.
Therefore, in the present invention, in the devolatilization region 5 adjacent to the kneading part 4 and hermetically sealed by the resin, a surface renewable screw 6 not connected to the flight is provided immediately after the kneading screw of the kneading part 4, and the resin Has the ability to transport so that it does not fill, and since the adjacent chip flight portions 20 mesh with each other, it has a thin film forming ability, increasing the residence time, improving the kneading surface renewal efficiency, and improving the thin film forming ability. Possible devolatilization devices and methods can be obtained.

  The apparatus and method for devolatilization in an extruder according to the present invention is to provide a twist in a chip flight part provided in a screw segment of a surface renewal screw to obtain an increase in residence time, improvement in kneading surface renewal efficiency, and improvement in thin film formation ability. With the goal.

1 Cylinder 2 Vacuum vent 3 Screw 4 Kneading part (seal part)
5 Volatilization area 6 Surface renewable screw 6A-6D screw segment 7 Raw material filling part (seal part)
20 Tip flight part 21 Crevice 22 Air gap part

Claims (4)

In the devolatilization region (5) of the twin-screw extruder in which a pair of screws (3) mesh with each other in a cylinder (1) having a vacuum vent (2) and rotate in the same direction, upstream of the devolatilization region (5) In the devolatilizing apparatus in the extruder formed by arranging the surface renewable screw (6) immediately after the kneading part (4),
Each chip flight part (20) provided on the outer periphery of each screw segment (6B, 6C) of the surface renewable screw (6) meshes with each other in a non-contact manner through a gap (21), and each chip flight part (20) is a torsion formed , and is formed through air gaps (22) at both ends on the long axis side in the cross section perpendicular to the screw axis of the surface renewable screw (6),
A devolatilizer in an extruder, which is arranged so that the tip flight part (20) of another screw segment (6B or 6C) can pass through the air gap part (22) .   The devolatilizer in an extruder according to claim 1, wherein the tip flight part (20) has a trapezoidal shape in cross section. In the devolatilization region (5) of the twin-screw extruder in which a pair of screws (3) mesh with each other in a cylinder (1) having a vacuum vent (2) and rotate in the same direction, upstream of the devolatilization region (5) Using a devolatilizer in an extruder in which a surface renewable screw (6) is arranged immediately after the kneading part (4),
Tip flight portions (20) provided on the outer periphery of each screw segment (6B, 6C) of the surface renewable screw (6) are engaged with each other in a non-contact manner through a gap (21), and each tip flight portion ( 20) is formed with a twist , and is formed via air gaps (22) at both ends on the long axis side in the cross section perpendicular to the screw axis of the surface renewable screw (6),
A devolatilizing method in an extruder, characterized in that it is used in a state where the tip flight part (20) of the other screw segment (6B or 6C) can pass through the air gap part (22). .   The devolatilization method in an extruder according to claim 3, wherein the tip flight part (20) has a trapezoidal shape in cross section.

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