Devolatilization extruder

Abstract

To thoroughly remove a volatile component remaining in a resin composition.SOLUTION: A devolatilization extruder according to one embodiment comprises: a cylinder 2; and a screw 20 disposed within the cylinder 2. The screw 20 includes conveying parts 52 and 53 having a forward helical structure. The screw 20 further includes a resistance part 82 having a reverse spiral structure between the conveying part 52 and the conveying part 53 and downstream of a supply port S1 provided in the cylinder 2.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an extruder for devolatilization.

Background Art

[0002] In a polymerization plant for producing a polymer, a catalyst is added to a monomer dissolved in a solvent for polymerization. Therefore, the polymer produced in the polymerization plant contains volatile components such as residual solvent and residual monomer.

[0003] Patent Document 1 discloses an extruder for devolatilization that removes volatile components contained in a polymer. The extruder for devolatilization disclosed in Patent Document 1 has a conveying section, a melt kneading section, and a devolatilization section arranged along the conveying direction of the polymer. Further, the devolatilization section includes a supply port for a devolatilization aid and a seal ring arranged downstream of the supply port.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] It is desired to sufficiently remove volatile components remaining in the resin composition and produce a resin composition having better properties.

[0006] Other problems and novel features will become apparent from the description of this specification and the accompanying drawings.

Means for Solving the Problems

[0007] According to one embodiment, a devolatilization extruder includes a cylinder having a supply port for supplying a devolatilization aid added to a resin raw material and an exhaust port for exhausting volatile components generated from the resin raw material, and a screw disposed in the cylinder. The screw includes an upstream conveyance section and a downstream conveyance section having a first spiral structure. The screw further includes a resistance section having a second spiral structure opposite to the first spiral structure between the upstream conveyance section and the downstream conveyance section and downstream of the supply port.

Effect of the Invention

[0008] According to one embodiment, volatile components remaining in the resin composition can be sufficiently removed, and a resin composition with better properties can be produced.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8A

Figure 8B

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0010] Hereinafter, one embodiment will be described in detail with reference to the drawings. In all the drawings for explaining the embodiment, members and devices having the same or substantially the same functions are denoted by the same reference numerals. In addition, for members and devices that have been described once, repeated explanations will not be given in principle.

[0011] [Outline of the Extruder for Devolatilization] FIG. 1 is a schematic diagram showing the configuration of the devolatilization extruder 1 according to the present embodiment. The devolatilization extruder 1 has a cylinder 2, a charging port (hopper) 3, a drive mechanism 4, etc.

[0012] A die head 5 is attached to the tip of the cylinder 2. Further, a screw described later is rotatably disposed inside the cylinder 2. Furthermore, the cylinder 2 is provided with supply ports S1, S2 and exhaust ports E1, E2.

[0013] The resin raw material is charged into the hopper 3. For example, a polymer resin raw material (hereinafter abbreviated as "polymer") produced (synthesized) in a polymerization plant is charged into the hopper 3. The polymer charged into the hopper 3 is supplied into the cylinder 2 through the hopper 3.

[0014] Here, the polymer synthesized in the polymerization plant contains a large amount of low-molecular-weight organic components. For example, the polymer contains a large amount of organic solvents, residual monomers, by-products generated during synthesis, etc. used during synthesis. In the following description, the low-molecular-weight organic components as described above may be collectively referred to as "volatile components".

[0015] When molding is performed with a volatile component contained in the polymer, the volatile component elutes or foams during molding. The elution or foaming of the volatile component contributes to molding defects.

[0016] The extruder 1 for devolatilization according to the present embodiment can be used for removing volatile components contained in a polymer or other resin composition. More specifically, the extruder 1 for devolatilization can vaporize and remove the volatile components contained in a polymer or other resin composition.

[0017] The polymer fed into the cylinder 2 through the hopper 3 is kneaded by a screw that is rotationally driven by a drive mechanism 4 and is conveyed from one end side in the longitudinal direction of the cylinder 2 to the other end side. That is, the longitudinal direction of the cylinder 2 is the conveyance direction of the polymer. More specifically, the side where the hopper 3 is disposed is the upstream side in the conveyance direction, and the side where the die head 5 is disposed is the downstream side in the conveyance direction.

[0018] The volatile component contained in the polymer is pressurized and vaporized in the process of the polymer moving from the upstream side to the downstream side in the cylinder 2 as described above. Further, the vaporized volatile component is exhausted from the cylinder 2 through the exhaust ports E1 and E2.

[0019] At this time, a devolatilization aid is injected into the cylinder 2 through the supply ports S1 and S2. In other words, the devolatilization aid is added to the polymer upstream of the exhaust port E1 and upstream of the exhaust port E2, respectively. The devolatilization aid is an additive for improving the devolatilization efficiency, and water is used in the present embodiment.

[0020] The polymer from which the volatile component has been removed is extruded as strands from a plurality of nozzles provided in the die head 5. The strands extruded from each nozzle are cooled in a strand bath 6 and then cut into pellets by a strand cutter (pelletizer) 7.

[0021] Since the pellets produced as described above do not contain additives such as fillers, they may be called "natural pellets". Natural pellets may be secondarily processed into pellets containing additives such as fillers.

[0022] For example, by kneading natural pellets and a filler using the devolatilization extruder 1 according to the present embodiment, pellets containing the filler can be produced. Pellets containing various functional additives including fillers may be called "compound pellets" and distinguished from natural pellets.

[0023] If compound pellets are produced using the devolatilization extruder 1 according to the present embodiment, the volatile components contained in the resin raw material (natural pellets) can be further reduced.

[0024] As described above, the devolatilization extruder 1 according to the present embodiment can be used for the production of natural pellets and can also be used for the production of compound pellets. Hereinafter, on the premise of producing natural pellets using a polymer as a resin raw material, the devolatilization extruder 1 according to the present embodiment will be described in more detail.

[0025] However, the resin compositions that can be produced using the devolatilization extruder 1 according to the present embodiment are not limited to natural pellets and compound pellets. Further, the raw material of the resin composition produced using the devolatilization extruder 1 according to the present embodiment is not limited to polymers.

[0026] [Details of the Devolatilization Extruder] <Cylinder> FIG. 2 is a longitudinal sectional view (vertical sectional view) showing the cylinder 2 and the inside of the cylinder 2. FIG. 3 is a transverse sectional view (horizontal sectional view) showing the cylinder 2 and the inside of the cylinder 2.

[0027] The cylinder 2 is composed of a plurality of cylinder blocks. More specifically, the cylinder 2 is composed of 11 cylinder blocks (cylinder blocks C1 to C11). The cylinder blocks C1 to C11 are arranged in a row in this order from the upstream side to the downstream side. In the following description, when the cylinder blocks C1 to C11 are not particularly distinguished, they may be collectively referred to as "cylinder block C".

[0028] The cylinder block C1 is provided with a supply port 10 to which the hopper 3 is connected. The cylinder block C6 is provided with a supply port S1, and the cylinder block C8 is provided with a supply port S2.

[0029] The cylinder block C7 is provided with an exhaust port E1, and the cylinder block C9 is provided with an exhaust port E2. Note that the cylinder blocks C1, C3 to C5, C10, and C11 have the same or substantially the same structure.

[0030] FIG. 4 is a perspective view showing one of the cylinder blocks C. All the cylinder blocks C are provided with the through holes 11 and the connection flanges 12 shown in FIG. 4. The through hole 11 is composed of two circular holes 11a and 11b that partially overlap.

[0031] The 11 cylinder blocks C are arranged such that the connection flanges 12 of adjacent cylinder blocks C face each other. Further, the opposing connection flanges 12 are fastened by bolts. As a result, the through holes 11 provided in each cylinder block C are connected, and a cylinder 2 having a series of flow paths is formed.

[0032] Pumps P1 and P2 for supplying a devolatilization aid (water) are respectively connected to the supply ports S1 and S2 provided in the cylinder blocks C6 and C8. On the other hand, a pump (vacuum pump) P3 for sucking volatile components is connected to the exhaust ports E1 and E2 provided in the cylinder blocks C7 and C9.

[0033] <Screw> Inside the cylinder 2, two screws 20 that are rotationally driven by the drive mechanism 4 are arranged. The two screws 20 are arranged parallel to each other and mesh with each other. That is, the devolatilization extruder 1 is a twin-screw extruder. More specifically, the devolatilization extruder 1 is an intermeshing twin-screw extruder and has excellent self-cleaning performance.

[0034] Each screw 20 is composed of a screw shaft 30 and a plurality of segments (screw pieces, screw elements) 40 attached to the screw shaft 30. Each segment 40 is non-rotatably attached to the screw shaft 30 and rotates integrally with the screw shaft 30.

[0035] More specifically, each segment 40 has a cylindrical shape into which the screw shaft 30 can be inserted, and internal teeth are formed on the inner peripheral surface. On the other hand, the screw shaft 30 has a cylindrical shape into which the segment 40 can be inserted, and external teeth are formed on the outer peripheral surface. The internal teeth formed on each segment 40 and the external teeth formed on the screw shaft 30 are spline-coupled.

[0036] Therefore, when the rotational driving force output from the drive mechanism 4 is input to the screw shaft 30, the screw shaft 30 and all the segments 40 attached to the screw shaft 30 rotate in the same direction at the same speed. That is, the screw 20 rotates within the cylinder 2.

[0037] <<Configuration of Screw>> A plurality of segments 40 of different types are attached to the screw shaft 30 of each screw 20. As a result, each screw 20 has a plurality of parts with different main roles. Specifically, each screw 20 includes conveying parts 51, 52, 53, 54, a kneading part 61, a devolatilization aid dispersion kneading part 71, 72, and resistance parts 81, 82, 83.

[0038] The above-mentioned respective parts of the screw 20 are arranged in order from the upstream side to the downstream side as follows. That is, the above-mentioned respective parts are arranged in a line in the order of conveying part 51 ⇒ kneading part 61 ⇒ resistance part 81 ⇒ conveying part 52 ⇒ devolatilization aid dispersion kneading part 71 ⇒ resistance part 82 ⇒ conveying part 53 ⇒ devolatilization aid dispersion kneading part 72 ⇒ resistance part 83 ⇒ conveying part 54.

[0039] In the following description, when the conveying parts 51, 52, 53, and 54 are not distinguished, they may be collectively referred to as "conveying part 50". Similarly, the devolatilization aid dispersion kneading parts 71 and 72 may be collectively referred to as "devolatilization aid dispersion kneading part 70", and the resistance parts 81, 82, and 83 may be collectively referred to as "resistance part 80".

[0040] The main role of the conveying part 50 is to convey the polymer in the cylinder from the upstream side to the downstream side, and it has a spiral structure. Among the four conveying parts 50, the conveying part 51 located on the most upstream side is sometimes called the "supply part" and is distinguished from the other conveying parts 52, 53, and 54.

[0041] In relation to the supply port S1, the devolatilization aid dispersion kneading part 71, and the resistance part 82, the conveying part 52 is an upstream conveying part located upstream of these. Also, in relation to the supply port S1, the devolatilization aid dispersion kneading part 71, and the resistance part 82, the conveying part 53 is a downstream conveying part located downstream of these.

[0042] In relation to the supply port S2, the devolatilization aid dispersion kneading part 72, and the resistance part 83, the conveying part 53 is an upstream conveying part located upstream of these. Also, in relation to the supply port S2, the devolatilization aid dispersion kneading part 72, and the resistance part 83, the conveying part 54 is a downstream conveying part located downstream of these.

[0043] The main role of the kneading part 61 is to knead the polymer. The main role of the devolatilization aid dispersion kneading part 70 is to knead the polymer and disperse and distribute the devolatilization aid into the polymer.

[0044] The resistance part 80 mainly serves to prevent the downstream movement of the polymer. Viewed from another perspective, the resistance part 80 mainly serves to maintain or increase the resin pressure to maintain or improve the efficiency and effect of kneading and devolatilization.

[0045] The resistance part 81 does not have a spiral structure, while the resistance parts 82 and 83 have a spiral structure. More specifically, the resistance parts 82 and 83 have a spiral structure opposite to that of the conveying part 50. Therefore, in the following description, the spiral structure of the conveying part 50 may be referred to as a "clockwise spiral structure", and the spiral structure of the resistance parts 82 and 83 may be referred to as a "counterclockwise spiral structure". The details of the clockwise spiral structure and the counterclockwise spiral structure will be described again later.

[0046] Note that the above roles are only the main roles of each part of the screw 20. Therefore, it is not excluded that each part of the screw 20 has other roles according to the above description.

[0047] <<Conveying part>> Most of the conveying part (feeding part) 51 is arranged in the cylinder blocks C1 and C2. However, a part of the conveying part 51 enters the cylinder block C3 beyond the boundary between the cylinder block C2 and the cylinder block C3.

[0048] Most of the conveying part 52 is arranged in the cylinder blocks C4 and C5. However, a part of the conveying part 52 enters the cylinder block C6 beyond the boundary between the cylinder block C5 and the cylinder block C6.

[0049] Most of the conveying part 53 is arranged in the cylinder block C7 where the exhaust port E1 is provided. However, a part of the conveying part 53 enters the cylinder block C8 beyond the boundary between the cylinder block C7 and the cylinder block C8.

[0050] The conveying part 54 is arranged across the cylinder blocks C10 and C11 from the cylinder block C9 where the exhaust port E2 is provided.

[0051] As described above, the conveying unit 50 has a right-handed spiral structure. More specifically, each of the conveying units 51, 52, 53, and 54 has a series of flights extending in a spiral shape.

[0052] FIG. 5 is a perspective view showing the segment 40 constituting the conveying unit 50. In the following description, the segment 40 constituting the conveying unit 50 is referred to as "segment 41" to distinguish it from other segments 40.

[0053] The conveying unit 50 is composed of a plurality of segments 41, and each segment 41 has one or more spiral flights 41a. Further, the flights 41a of adjacent segments 41 are connected in series.

[0054] That is, the conveying unit 50 is a full-flight screw, which generates a conveying force for moving the polymer in the cylinder 2 from the upstream side to the downstream side.

[0055] More specifically, the conveying unit 51 shown in FIGS. 2 and 3 conveys the polymer supplied into the cylinder 2 through the hopper 3 to the downstream side and feeds it around the kneading unit 61.

[0056] Also, the conveying unit 52 conveys the polymer that has passed through the kneading unit 61 and the resistance unit 81 to the downstream side and feeds it around the devolatilization aid dispersion kneading unit 71. The conveying unit 53 conveys the polymer that has passed through the devolatilization aid dispersion kneading unit 71 and the resistance unit 82 to the downstream side and feeds it around the devolatilization aid dispersion kneading unit 72. The conveying unit 54 conveys the polymer that has passed through the devolatilization aid dispersion kneading unit 72 and the resistance unit 83 to the downstream side and feeds it into the die head 5.

[0057] <<Kneading Unit and Devolatilization Aid Dispersion Kneading Unit>> The kneading unit 61 is disposed in the cylinder block C3. The devolatilization aid dispersion kneading unit 71 is disposed in the cylinder block C6 provided with the supply port S1. The devolatilization aid dispersion kneading unit 72 is disposed in the cylinder block C8 provided with the supply port S2.

[0058] Viewed in another way, the supply port S1 provided in the cylinder block C6 is located between the upstream end and the downstream end of the devolatilization aid dispersion kneading section 71. Further, the supply port S2 provided in the cylinder block C8 is located between the upstream end and the downstream end of the devolatilization aid dispersion kneading section 72. That is, the supply port S1 is located within the length range of the devolatilization aid dispersion kneading section 71, and the supply port S2 is located within the length range of the devolatilization aid dispersion kneading section 72.

[0059] FIG. 6 is a perspective view showing a segment 40 constituting the kneading section 61 and the devolatilization aid dispersion kneading section 70. In the following description, the segment 40 constituting the kneading section 61 and the devolatilization aid dispersion kneading section 70 is referred to as "segment 42" to distinguish it from other segments 40.

[0060] The segment 42 includes a plurality of kneading disks 42a having a generally elliptical cross-sectional shape. Adjacent kneading disks 42a are arranged with a phase shift in the screw axis direction. More specifically, adjacent kneading disks 42a are arranged with a 90-degree phase shift in the screw axis direction.

[0061] Referring to FIGS. 2 and 3 again. The kneading section 61 kneads the polymer fed by the conveying section 51. The polymer fed around the kneading section 61 is kneaded by the rotating kneading section 61. Further, the polymer fed around the kneading section 61 is pushed by the subsequent polymer and moves downstream. That is, the polymer is kneaded while being conveyed downstream within the cylinder block C3.

[0062] Due to the kneading by the kneading section 61, the polymer becomes at high temperature and high pressure. As a result, the volatile components contained in the polymer vaporize. That is, the volatile components contained in the polymer are removed.

[0063] The devolatilization aid dispersion and kneading section 71 kneads the polymer fed by the conveying section 52. The polymer fed around the devolatilization aid dispersion and kneading section 71 is kneaded by the rotating devolatilization aid dispersion and kneading section 71. Also, the polymer fed around the devolatilization aid dispersion and kneading section 71 is pushed by the subsequent polymer and moves to the downstream side. That is, the polymer is kneaded while being conveyed to the downstream side within the cylinder block C6.

[0064] Due to the kneading by the devolatilization aid dispersion and kneading section 71, the polymer becomes high temperature and high pressure again. As a result, the volatile components contained in the polymer vaporize. That is, the volatile components contained in the polymer are further removed.

[0065] As described above, the supply port S1 is located within the length range of the devolatilization aid dispersion and kneading section 71. Therefore, the devolatilization aid (water) injected into the cylinder 2 from the supply port S1 is added to the polymer being kneaded by the devolatilization aid dispersion and kneading section 71. As a result, the devolatilization aid (water) added to the polymer is dispersed and distributed in the polymer.

[0066] The devolatilization aid (water) dispersed and distributed in the polymer foams (vaporizes) within the cylinder block C6 and on the downstream side of the cylinder block C6, promoting the removal of the volatile components.

[0067] The volatile components removed from the polymer as described above are exhausted from the cylinder 2 through the exhaust port E1 provided in the cylinder block C7.

[0068] The devolatilization aid dispersion and kneading section 72 kneads the polymer fed by the conveying section 53 again. Due to the kneading by the devolatilization aid dispersion and kneading section 72, the polymer becomes high temperature and high pressure again, and the volatile components contained in the polymer are further removed.

[0069] As described above, the supply port S2 is located within the length range of the devolatilization aid dispersion kneading section 72. Therefore, the devolatilization aid (water) injected into the cylinder 2 from the supply port S2 is added to the polymer being kneaded by the devolatilization aid dispersion kneading section 72. As a result, the devolatilization aid (water) added to the polymer is dispersed and distributed in the polymer.

[0070] The devolatilization aid (water) dispersed and distributed in the polymer foams (vaporizes) within the cylinder block C8 and on the downstream side of the cylinder block C8, promoting the removal of volatile components.

[0071] The volatile components removed from the polymer as described above are exhausted from the cylinder 2 through the exhaust port E2 provided in the cylinder block C9.

[0072] As described above, in the devolatilization extruder 1, the first devolatilization treatment is performed in the cylinder block C3, the second devolatilization treatment is performed in the cylinder blocks C6 and C7, and the third devolatilization treatment is performed in the cylinder blocks C8 and C9.

[0073] ≪Resistance section≫ The resistance section 81 is disposed within the cylinder block C4. More specifically, the resistance section 81 is located at the upstream end of the cylinder block C4. Viewed another way, the resistance section 81 is located between the kneading section 61 and the conveying section 52.

[0074] FIG. 7 is a perspective view showing the segment 40 constituting the resistance section 81. In the following description, the segment 40 constituting the resistance section 81 is referred to as "segment 43" to distinguish it from other segments 40.

[0075] The segment 43 is a seal ring having an annular flange portion 43a. The outer diameter D3 of the segment 43 (flange portion 43a) is larger than the outer diameter D1 of the segment 41 (flight 41a) shown in FIG. 5 and larger than the outer diameter (major axis) D2 of the segment 42 (kneading disk 42a) shown in FIG. 6.

[0076] That is, a resistance portion 81 having a larger diameter than the kneading portion 61 is disposed downstream of the kneading portion 61 shown in FIGS. 2 and 3. In other words, the clearance between the resistance portion 81 and the cylinder 2 is smaller than the clearance between the kneading portion 61 and the cylinder 2.

[0077] Accordingly, the resistance portion 81 prevents the polymer kneaded by the kneading portion 61 from moving downstream. As a result, the resin pressure within the cylinder block C3 in which the kneading portion 61 is disposed increases, and the efficiency and effect of kneading and devolatilization by the kneading portion 61 are improved.

[0078] The resistance portion 82 is disposed within the cylinder block C7. More specifically, the resistance portion 82 is located at the upstream end of the cylinder block C7. In other words, the resistance portion 82 is located downstream of the supply port S1 and upstream of the exhaust port E1. That is, the resistance portion 82 is located between the supply port S1 and the exhaust port E1.

[0079] The resistance portion 83 is disposed within the cylinder block C9. More specifically, the resistance portion 83 is located at the upstream end of the cylinder block C9. In other words, the resistance portion 83 is located downstream of the supply port S2 and upstream of the exhaust port E2. That is, the resistance portion 83 is located between the supply port S2 and the exhaust port E2.

[0080] FIG. 8A is a perspective view showing a segment 40 constituting the resistance portions 82 and 83. In the following description, the segment 40 constituting the resistance portions 82 and 83 is referred to as a "segment 44" to distinguish it from other segments 40.

[0081] The resistance portions 82 and 83 are constituted by one segment 44, and the segment 44 has one spiral flight 44a. In other words, the segment 44 has a single-threaded screw structure.

[0082] As described above, the conveying section 50 has a right-handed spiral structure, and the resistance sections 82 and 83 have a left-handed spiral structure. More specifically, the flight 41a (Fig. 5) of the conveying section 50 and the flight 44a (Fig. 8A) of the resistance sections 82 and 83 are structured to generate conveying forces in opposite directions when rotating in the same direction.

[0083] That is, when the screw 20 shown in Figs. 2 and 3 rotates, the conveying section 50 applies a conveying force from the upstream side to the downstream side to the polymer, while the resistance sections 82 and 83 apply a conveying force from the downstream side to the upstream side to the polymer.

[0084] However, the conveying force generated by the conveying section 50 is greater than the conveying force generated by the resistance sections 82 and 83. Therefore, the polymer does not flow backward due to the conveying force applied by the resistance sections 82 and 83.

[0085] Viewed another way, the resistance section 82 prevents the movement of the polymer downstream where the devolatilization aid injected from the supply port S1 is added and kneaded by the devolatilization aid dispersion kneading section 71. Also, the resistance section 83 prevents the movement of the polymer downstream where the devolatilization aid injected from the supply port S2 is added and kneaded by the devolatilization aid dispersion kneading section 72.

[0086] As a result, the resin pressure in the cylinder block C6 where the devolatilization aid dispersion kneading section 71 is disposed is maintained or increased, and the efficiency and effect of kneading and devolatilization are improved. Similarly, the resin pressure in the cylinder block C8 where the devolatilization aid dispersion kneading section 72 is disposed is maintained or increased, and the efficiency and effect of kneading and devolatilization are improved.

[0087] As described above, the resistance section 80 has a damming ability to improve the efficiency and effect of kneading and devolatilization by preventing the movement of the polymer downstream.

[0088] Furthermore, the resistance part 82, which is disposed between the supply port S1 and the exhaust port E1 and dams up the polymer to which the devolatilization aid is added, is particularly effective in improving the devolatilization efficiency. Similarly, the resistance part 83, which is disposed between the supply port S2 and the exhaust port E2 and dams up the polymer to which the devolatilization aid is added, is particularly effective in improving the devolatilization efficiency.

[0089] Here, the damming ability of the resistance part 81 depends solely on the clearance between the flange part 43a and the cylinder 2 and the width (land length) of the flange part 43a. Viewed another way, the damming ability of the resistance part 81 having no spiral structure does not change even if the rotational speed of the screw 20 increases or decreases.

[0090] On the other hand, when the rotational speed of the screw 20 increases, the temperature of the polymer rises. Then, the viscosity of the polymer decreases, and the polymer easily passes through the gap between the flange part 43a and the cylinder 2. That is, when the rotational speed of the screw 20 is increased to improve the processing efficiency and processing speed, the damming ability of the resistance part 81 relatively decreases.

[0091] In contrast, the damming ability of the resistance parts 82 and 83 having a reverse spiral structure changes according to the rotational speed of the screw 20. More specifically, as the rotational speed of the screw 20 increases, the damming ability of the resistance parts 82 and 83 also increases.

[0092] Therefore, even if the viscosity of the polymer decreases by increasing the rotational speed of the screw 20, the devolatilization efficiency and the devolatilization effect do not decrease. In other words, the devolatilization efficiency and the devolatilization effect are maintained even if the rotational speed of the screw 20 is increased.

[0093] From the viewpoint of increasing the damming ability (pressure boosting ability) of the resistance parts 82 and 83, it is effective to reduce (shorten) the lead length of the flights 44a of the resistance parts 82 and 83.

[0094] FIG. 8B is an explanatory diagram for clarifying the definition of the lead length. The lead length of the flight is the linear distance L parallel to the screw axis between an arbitrary vertex a on a series of flights and the next vertex b adjacent to the vertex a.

[0095] Note that the flights shown in FIG. 8B are different from the flight 44a shown in FIG. 8A. However, the above definition regarding the lead length also applies to the flight 41a of the segment 41 and the flight 44a of the segment 44.

[0096] If the lead length of the flight 44a is decreased (shortened), the conveying capacity per rotation of the resistance portions 82 and 83 decreases, but the boosting capacity improves. On the other hand, as the lead length decreases, the thickness of the flight 44a becomes thinner and the strength decreases. Therefore, from the viewpoint of balancing the blocking capacity (boosting capacity) and the strength of the resistance portions 82 and 83, the lead length of the flight 44a included in the resistance portions 82 and 83 is preferably 0.25 times or more and 1.50 times or less of the inner diameter of the cylinder 2.

[0097] <Comparative Test> FIG. 9 is a table showing the results of a comparative test conducted by the present inventor. In this test, two extruders (TEX65XCT) having substantially the same structure as that shown in FIGS. 2 and 3 were prepared. However, the screw 20 provided in one of the extruders is constituted not only by the resistance portion 81 but also by the resistance portions 82 and 83 with the segment 43 (sealing ring) shown in FIG. 7.

[0098] In the following description, one of the extruders equipped with the screw 20 in which all the resistance portions 81, 82, and 83 are constituted by the segment 43 (sealing ring) is referred to as "extruder 1A", and the other extruder is referred to as "extruder 1B".

[0099] Viewed from another perspective, in extruder 1A, none of the resistance portions 80 of the screw 20 has a spiral structure. In contrast, in extruder 1B, two of the resistance portions 80 of the screw 20 have a spiral structure. More specifically, the resistance portions 82 and 83 of the screw 20 of extruder 1B have a reverse spiral structure.

[0100] Using an extruder (TEX65XCT) different from the extruders 1A and 1B, the POE pellets (polyolefin elastomer pellets) melted were supplied as a resin raw material to the cylinders 2 of the extruders 1A and 1B. The supply amount Q [Kg / h] is as shown in the table of Fig. 9.

[0101] Also, a devolatilization aid (water) was injected into the cylinder blocks C6 and C8 from the supply ports S1 and S2 provided in the cylinders 2 of the respective extruders 1A and 1B. The amount of water injection [phr] is as shown in the table of Fig. 9.

[0102] Under the above conditions, when the rotational speed Ns of the screws 20 of the extruders 1A and 1B was set to 150 [rpm] (No. 1), 200 [rpm] (No. 2), and 250 [rpm] (No. 3), the resin pressure [MPa] and the residual VOC concentration [ppm] were measured. The measurement results are as shown in the table of Fig. 9.

[0103] In the table, the "C6 resin pressure" is the injection pressure of the devolatilization aid by the pump P1 connected to the supply port S1 (cylinder block C6). Also, the "C8 resin pressure" is the injection pressure of the devolatilization aid by the pump P2 connected to the supply port S2 (cylinder block C8). The injection pressure of the devolatilization aid into the cylinder blocks C6 and C8 can be regarded as the resin pressure in these cylinder blocks C6 and C8.

[0104] The "residual VOC concentration" in the table is the ratio of the volatile components in the polymer extruded from the cylinder 2 measured by gas chromatography.

[0105] Fig. 10 is a graph showing the relationship between the screw rotational speed and the resin pressure in the extruder 1A confirmed by this test. Fig. 11 is a graph showing the relationship between the screw rotational speed and the resin pressure in the extruder 1B confirmed by this test.

[0106] As shown in FIGS. 9 and 10, in the extruder 1A, the C6 resin pressure and the C8 resin pressure decrease as the screw rotation speed Ns increases. On the other hand, as shown in FIGS. 9 and 11, in the extruder 1B, the C6 resin pressure and the C8 resin pressure do not change even when the screw rotation speed Ns increases. From this result, it is considered that in the extruder 1B equipped with the screw 20 including the resistance portions 82 and 83 having a reverse spiral structure, the devolatilization efficiency and the devolatilization effect are maintained even when the screw rotation speed Ns increases.

[0107] In fact, the residual VOC concentration of the polymer devolatilized by the extruder 1B was lower than that of the polymer devolatilized by the extruder 1A (see FIG. 9).

[0108] Specifically, when the screw rotation speed Ns is 150 [rpm] (No. 1), the residual VOC concentration of the polymer devolatilized by the extruder 1B was improved by about 40% compared to the residual VOC concentration of the polymer devolatilized by the extruder 1A.

[0109] When the screw rotation speed Ns is 200 [rpm] (No. 2), the residual VOC concentration of the polymer devolatilized by the extruder 1B was improved by about 50% compared to the residual VOC concentration of the polymer devolatilized by the extruder 1A.

[0110] When the screw rotation speed Ns is 250 [rpm] (No. 3), the residual VOC concentration of the polymer devolatilized by the extruder 1B was improved by about 60% compared to the residual VOC concentration of the polymer devolatilized by the extruder 1A.

[0111] As described above, the invention made by the present inventor has been specifically described based on the embodiments and examples. However, the present invention is not limited to the above embodiments or examples, and it goes without saying that various modifications can be made without departing from the gist thereof.

[0112] For example, the supply ports S1 and S2, the exhaust ports E1 and E2, the devolatilization aid dispersion and kneading portions 70, the resistance portions 80, etc. can be increased or decreased as necessary.

[0113] Specifically, in the devolatilization extruder 1 according to the above embodiment, one devolatilization unit (devolatilization unit) was constituted by the supply port S1, the exhaust port E1, the devolatilization aid dispersion and kneading unit 71, and the resistance unit 82. Further, another devolatilization unit (devolatilization unit) was constituted by the supply port S2, the exhaust port E2, the devolatilization aid dispersion and kneading unit 72, and the resistance unit 83.

[0114] However, either one of the above two devolatilization units may be omitted. Further, a devolatilization unit having a similar configuration may be added upstream or downstream of the above two devolatilization units.

[0115] The number of flight strips of the segment 44 constituting the resistance units 82 and 83 may be two or more. However, the weir stopping ability of the resistance units 82 and 83 increases as the width W of the flight 44a shown in FIG. 8A is larger. Therefore, in order to increase the width W of the flight 44a and enhance the weir stopping ability of the resistance units 82 and 83, it is preferable to set the number of flight strips of the segment 44 to one.

[0116] As an example of the resin raw material that can be devolatilized by the devolatilization extruder 1 according to the above embodiment, polyethylene, polypropylene, polyamide, polyethylene terephthalate, polyimide, polyether ether ketone, etc. can be mentioned.

[0117] As an example of the additive (filler) added to the resin raw material, talc can be mentioned. Talc is a mineral mainly composed of magnesium hydrosilicate.

[0118] As an example of additives (fillers) other than talc, fibrous fillers, fullerenes, graphene, boron nitride, colloidal silica, carbon black, alumina, etc. can be mentioned.

[0119] The fibrous fillers include natural fibers such as cellulose (cellulose nanofibers), ramie, jute, kenaf, bamboo, bagasse, etc., carbon-based fibers such as carbon fibers, carbon nanofibers, carbon nanotubes, glass fibers, resin-based fibers, and the like.

[0120] Examples of additives other than fillers include lubricants and pigments. The fillers and other additives may be used alone or in combination of two or more.

Explanation of Reference Signs

[0121] 1... Extruder for devolatilization, 1A, 1B... Extruders, 2... Cylinder, 3... Inlet (hopper), 4... Driving mechanism, 5... Die head, 6... Strand bath, 7... Strand cutter (pelletizer), 10... Supply port, 11... Through hole, 11a, 11b... Round holes, 12... Connecting flange, 20... Screw, 30... Screw shaft, 40, 41, 42, 43, 44... Segments, 41a, 44a... Flights, 42a... Kneading disk, 43a... Flange portion, 50, 51, 52, 53, 54... Conveying parts, 61... Kneading part, 70, 71, 72... Devolatilization aid dispersion kneading parts, 80, 81, 82, 83... Resistance parts, a, b... Vertices, C, C1~C11... Cylinder blocks, E1, E2... Exhaust ports, P1, P2, P3... Pumps, S1, S2... Supply ports

Claims

1. An extruder for devolatilization, comprising: a cylinder having an inlet for introducing a resin raw material, a supply port provided downstream of the inlet for supplying a devolatilization aid, and an exhaust port for exhausting volatile components generated from the resin raw material; and a screw disposed in the cylinder and including an upstream conveying portion and a downstream conveying portion having a first spiral structure, wherein the screw further includes a resistance portion having a second spiral structure opposite to the first spiral structure between the upstream conveying portion and the downstream conveying portion and downstream of the supply port.

2. The extruder for devolatilization according to Claim 1, wherein the resistance portion is provided downstream of the supply port and upstream of the exhaust port.

3. The extruder for devolatilization according to Claim 1, wherein the screw further includes a devolatilization aid dispersion and kneading portion provided between the upstream conveying portion and the downstream conveying portion, and the supply port is located between an upstream end portion and a downstream end portion of the devolatilization aid dispersion and kneading portion.

4. The extruder for devolatilization according to Claim 1, wherein the screw further includes a seal ring provided upstream of the upstream conveying portion, a kneading portion provided upstream of the seal ring, and a conveying portion provided upstream of the kneading portion.

5. The extruder for devolatilization according to Claim 1, wherein the upstream conveying portion, the downstream conveying portion, and the resistance portion have flights extending in a spiral shape, and when the flights of the upstream conveying portion and the downstream conveying portion rotate in the same direction, they can generate conveying forces opposite to each other with respect to the flights of the resistance portion.

6. The extruder for devolatilization according to Claim 5, wherein the lead length of the flights of the resistance portion is not less than 0.25 times and not more than 1.50 times the inner diameter of the cylinder.

7. The extruder for devolatilization according to Claim 5, wherein the resistance portion has one flight.

8. The extruder for devolatilization according to Claim 1, wherein two of the screws are disposed inside the cylinder in parallel and meshing with each other.

9. The extruder for devolatilization according to Claim 1, wherein the resin raw material and an additive are supplied to the cylinder, The screw conveys the resin raw material and the additive supplied to the cylinder from the upstream side to the downstream side while kneading them. Water as the devolatilization aid is supplied to the supply port. The resistance part is an extruder for devolatilization that prevents the resin raw material and the additive with the devolatilization aid added from moving downstream.

10. The extruder for devolatilization according to claim 9, An extruder for devolatilization in which a polymer as the resin raw material and a filler as the additive are supplied to the cylinder.

11. An extruder for devolatilization including the following: An inlet for introducing a polymer resin raw material, a cylinder having a supply port for supplying water and an exhaust port for exhausting volatile components generated from the polymer resin raw material, provided downstream of the inlet; and A screw disposed in the cylinder, including an upstream conveying part and a downstream conveying part having a regular spiral structure. Here, The screw further includes a resistance part having an inverse spiral structure opposite to the spiral structures of the upstream conveying part and the downstream conveying part, between the upstream conveying part and the downstream conveying part and downstream of the supply port.

12. The extruder for devolatilization according to claim 11, The extruder for devolatilization, wherein the resistance part has a single-screw structure.

13. The extruder for devolatilization according to claim 11, The extruder for devolatilization, wherein the polymer resin raw material includes a polyolefin elastomer.

14. The extruder for devolatilization according to claim 11, The extruder for devolatilization, wherein the polymer resin raw material and the additive are introduced into the inlet.

15. The extruder for devolatilization according to claim 14, The extruder for devolatilization, wherein at least one of a filler, a lubricant, and a pigment is introduced into the inlet as the additive.

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