Continuous high-shearing device and method for producing low-molecular-weight polymer using same

Abstract

Provided is a continuous high-shearing device 1 that applies a shearing force to a feedstock polymer 10 by using a screw 21 in a cylinder part 38, thereby reducing the molecular weight of the feedstock polymer, the continuous high-shearing device continuously discharging the polymer as a low-molecular-weight polymer from a die part 37. The continuous high-shearing device 1 is provided with a high-shearing part 3 in which the screw 21 comprises: a conveyance part 31 that has flights 35 on an outer circumferential surface 33 and conveys the feedstock polymer 10 to the die part 37 side; and a collar section 32 that has no flights 35 on the outer circumferential surface 33, is adjacent to the die part 37 side of the conveyance part 31, and applies a shearing force to the feedstock polymer 10. As a result of being provided with the high-shearing part 3, the continuous high-shearing device 1 can control the molecular weight of the low-molecular-weight polymer by the extrusion amount.

Description

Continuous high shear processing device and method for producing low molecular weight polymer using the same

[0001] The present invention relates to a continuous high shear processing apparatus for continuously producing low-molecular-weight polymers by applying shear force to a raw polymer, and a method for producing low-molecular-weight polymers using the same.

[0002] Thermoplastic resins such as polypropylene resin and nylon 6 are used with viscosities adjusted according to various applications. For example, when used in fine fibers, nonwoven fabrics, filter media, etc., the viscosity must be suitable for the meltblown manufacturing process. Therefore, continuous high-shear processing devices are used to produce low-viscosity, low-molecular-weight polymers (hereinafter referred to as low-molecular-weight polymers). Patent Document 1 describes a continuous high-shear processing device that generates shear heat in a raw polymer by high-speed screw rotation, thereby reducing the molecular weight of the raw polymer. The screw in the high-shear processing section of the continuous high-shear processing device described in this document has a blocking section that blocks the raw polymer and a through-hole that connects the upstream side and downstream side of the blocking section.

[0003] Patent No. 6949342

[0004] In the high shear processing section of Patent Document 1, the feed polymer is blocked by a blocking section, and the feed polymer fills the screw in front of the blocking section (upstream in the feed polymer transport direction), thereby applying shear force to the feed polymer. That is, the shear force applied in the region filled with the feed polymer (hereinafter also referred to as the filled region) reduces the molecular weight of the feed polymer to form a low-molecular-weight polymer. However, because the length of the filled region in the screw rotation axis direction (feed polymer transport direction) (hereinafter also referred to as the filled length) varies depending on the extrusion rate (feed rate) of the feed polymer, it is difficult to predict the residence time of the feed polymer in the filled region (hereinafter also referred to as the residence time) and control the molecular weight and viscosity of the low-molecular-weight polymer. Furthermore, due to the large pressure loss in the filled region, it is difficult to increase the extrusion rate of the feed polymer and improve the production efficiency of the low-molecular-weight polymer. An object of the present invention is to provide a continuous high-shear processing apparatus that can control the molecular weight and viscosity of a low-molecular-weight polymer by adjusting the extrusion rate of the raw polymer, and that can efficiently produce a low-molecular-weight polymer with little pressure loss, and a method for producing a low-molecular-weight polymer using the same.

[0005] The continuous high-shear processing device of the present invention is a continuous high-shear processing device that applies shear force to a raw polymer using a screw inside a cylinder section to reduce its molecular weight, and continuously discharges the low-molecular-weight polymer from a die section, and is characterized in that the screw is equipped with a conveying section that has flights on its outer surface and conveys the raw polymer toward the die section, and a collar section that is adjacent to the die section side of the conveying section and does not have flights on its outer surface and applies shear force to the raw polymer.

[0006] The method for producing a low-molecular-weight polymer of the present invention is a method for producing a low-molecular-weight polymer using the above-mentioned continuous high-shear processing device, and is characterized in that the raw material polymer is transported to a collar section by the transport section, shear force is applied to the transported raw material polymer in the collar section to reduce its molecular weight and form a low-molecular-weight polymer, and the low-molecular-weight polymer is continuously discharged from the die section.

[0007] The present invention uses a screw equipped with a conveying section and a collar section, allowing the raw polymer to fill the collar section but not the conveying section, thereby applying shear force to the raw polymer. This suppresses changes in the length of the region filled with the raw polymer, and by adjusting the extrusion rate of the raw polymer, it is possible to adjust the residence time in a state where shear force is applied, thereby controlling the molecular weight and viscosity of the low-molecular-weight polymer. Furthermore, applying shear force to the raw polymer between the outer peripheral surface of the collar section and the inner wall surface of the cylinder section reduces pressure loss, allowing for an increase in extrusion rate and improved productivity of low-molecular-weight polymers.

[0008] 5 is a schematic perspective view of a continuous high shear processing apparatus according to an embodiment of the present invention; FIG. 6 is a partially cutaway cross-sectional view of a twin-screw kneading / extrusion section; FIG. 7 is a perspective view showing a state in which two screws in the twin-screw kneading / extrusion section are intermeshing with each other; FIG. 8 is a partially cutaway cross-sectional view of a degassing section; FIG. 9 is a partially cutaway cross-sectional view schematically showing the configuration of a high shear processing section; FIG. 10 is a cross-sectional view in the XZ plane showing an enlarged schematic view of a collar section in the high shear processing section of FIG. 5; FIG. 11 is a cross-sectional view in the XY plane showing an enlarged schematic view of the collar section in the high shear processing section of FIG. 5; FIG. 12 is a graph showing the relationship between the length of the collar and the viscosity of a low molecular weight polymer in Example 2; FIG. 13 is a graph showing the relationship between the extrusion rate and the viscosity of a low molecular weight polymer in Example 2; FIG. 14 is a graph showing the relationship between the extrusion rate and the viscosity of a low molecular weight polymer in Comparative Example 2; FIG. 15 is a partially cutaway cross-sectional view schematically showing the configuration of a conventional high shear processing section;

[0009]

[0016] The present invention will be described in detail below with reference to the accompanying drawings, in which:

[0017] As shown in Fig. 1, a continuous high shear processing apparatus 1 includes a twin-screw kneading / extrusion section 2 for melting and kneading a raw polymer 10, a high shear processing section 3 for applying a high shear force to the raw polymer 10, and a degassing section 4, which are connected in series in this order.

[0010] The twin-screw kneading / extrusion section 2 melts and kneads the raw material polymer 10, and supplies the melted raw material polymer 10 to the high shear processing section 3. As shown in Figure 2, the twin-screw kneading / extrusion section 2 includes a barrel 6 and two screws 7a, 7b housed inside the barrel 6. The barrel 6 includes a cylinder section 8 having a shape formed by combining two cylinders, and a heater (not shown) for melting the raw material polymer 10. The raw material polymer 10 is continuously supplied to the cylinder section 8 from a supply port 9 provided at one end of the barrel 6.

[0011] The screws 7a and 7b are housed in a cylinder portion 8 in a state where they are meshed with each other, and are rotated in the same direction by torque transmitted from a motor (not shown). By using the screws in the same direction, the raw polymer 10 can be strongly kneaded and melted.

[0012] 3, the screws 7a, 7b each include a feed section 11, a kneading section 12, and a pumping section 13, which are aligned in a line along the axial direction of the screws 7a, 7b. Note that a supply port for supplying fibers or the like to be dispersed in the raw polymer 10 may be provided between the feed section 11 and the kneading section 12 in the cylinder section 8.

[0013] The feed section 11 has spirally twisted flights 14. The flights 14 of the screws 7a, 7b rotate while meshing with each other, and transport the raw polymer 10 supplied from the supply port 9 toward the kneading section 12.

[0014] The kneading section 12 has a plurality of disks 15 arranged in the axial direction of the screws 7 a and 7 b. The disks 15 of the screws 7 a and 7 b rotate facing each other and knead the raw polymer 10 sent from the feed section 11. The kneaded raw polymer 10 is sent to the pumping section 13 by the rotation of the screws 7 a and 7 b.

[0015] The pumping section 13 has spirally twisted flights 16. The flights 16 of the screws 7a, 7b rotate while intermeshing with each other, and extrude the raw polymer 10 from the discharge end of the barrel 6.

[0016] The raw polymer 10 supplied to the supply port 9 of the twin-screw kneading / extrusion section 2 is melted and kneaded by the heat of the heater. The raw polymer 10 is continuously supplied from the discharge end of the barrel 6 to the high shear processing section 3, as shown by arrow A in Figure 1.

[0017] The raw polymer 10 is stably supplied in a predetermined amount with an appropriate viscosity from the twin-screw kneading / extrusion section 2 to the high-shear processing section 3. This reduces the burden on the high-shear processing section 3, which lowers the molecular weight of the raw polymer 10 molten in the twin-screw kneading / extrusion section 2. Note that because the twin-screw kneading / extrusion section 2 is intended to melt-knead the raw polymer 10, it is difficult to produce a low-viscosity, low-molecular-weight polymer having fluidity suitable for, for example, a melt-blown manufacturing method using only the twin-screw kneading / extrusion section 2.

[0018] The degassing section 4 shown in Fig. 4 is an element that sucks and removes gas components contained in the low-molecular-weight polymer discharged from the high-shear processing section 3. The degassing section 4 includes a barrel 22 and a single vent screw 23 housed in the barrel 22. The barrel 22 includes a straight cylindrical cylinder section 24. The low-molecular-weight polymer extruded from the high-shear processing section 3 is continuously supplied from one end thereof to the cylinder section 24 of the barrel 22.

[0019] The barrel 22 has a vent port 25. The vent port 25 is open in the middle of the barrel 22 and is connected to a vacuum pump 26. Furthermore, the other end of the cylinder portion 24 of the barrel 22 is closed by a head portion 27 having a discharge port 28.

[0020] The vent screw 23 has a spirally twisted flight 29, is housed in the cylinder portion 24, and is rotated in one direction by torque transmitted from a motor (not shown). The flight 29 rotates integrally with the vent screw 23 and continuously transports the low-molecular-weight polymer supplied to the cylinder portion 24 toward the head portion 27. When the fiber-reinforced composite material is transported to a position corresponding to the vent port 25, it is subjected to vacuum pressure from the vacuum pump 26. That is, by creating a negative pressure inside the cylinder portion 24 with the vacuum pump 26, gaseous substances and other volatile components contained in the low-molecular-weight polymer are continuously sucked and removed. After the gaseous substances and other volatile components have been removed, the low-molecular-weight polymer is discharged from the discharge port 28 of the head portion 27.

[0021] Before describing the structure of the high shear processing section 3 included in the continuous high shear processing apparatus 1 of the present invention, a conventional high shear processing section 103 will be described. As shown in Figure 9, the conventional high shear processing section 103 is a single-screw extruder that reduces the molecular weight of a raw polymer 10, and includes a barrel 120 equipped with a cylinder section 128 and one screw 121. The cylinder section 128 is straight and tubular, and the screw 121 applies a shearing action to the raw polymer 10 supplied from the twin-screw kneading / extrusion section 2 (see Figure 1). The XYZ coordinates shown in the figure are used to identify directions and will also be shown in other figures as appropriate.

[0022] The screw 121 is provided with a damming portion 122 as a member for damming the raw polymer 10. For example, a kneading disk, an inverted screw, or the like is used as the damming portion 122. Inside the screw 121, through-holes 124a and 124b are provided on both sides (Z1 side and Z2 side) of the damming portion 122, which communicate with the outer circumferential surface 123 of the screw rotation shaft.

[0023] As the rotation speed of the screw 121 increases, the force conveying the raw polymer 10 in the Z1 to Z2 direction increases, reducing the length L3 of the filled region 126 filled with the raw polymer 10 and the filling rate of the cylinder portion 128. The filled region 126, where shear force is applied to the raw polymer 10, is a narrow region on the Z1 side of the dam portion 122 and the die portion 127, and the length of the screw 121 in the axial direction (the conveying direction of the raw polymer 10, the Z direction) is not used effectively.

[0024] Furthermore, because the damming capacity of the damming section 122 in the high shear processing section 103 is high and the pressure loss is large, the length L3 of the filled region 126 increases as the extrusion rate increases. Thus, if the length L3 of the filled region 126 is not constant depending on the extrusion rate, it is difficult to predict the residence time of the raw polymer 10 in the filled region 126. Furthermore, because the screw 121 in the high shear processing section 103 has flights 125 provided over the entire outer circumferential surface 123 of the screw rotation shaft, a force is applied to the raw polymer 10 in the filled region 126 to convey it in the Z2 direction. For these reasons, it has been difficult in conventional high shear processing sections 103 to control the viscosity and molecular weight of low-molecular-weight polymers by the extrusion rate of the raw polymer 10.

[0025] Furthermore, when two through holes 124a and 124b are provided as in the screw 121, it is difficult to predict which of the two divided flow paths the raw polymer 10 will pass through, which makes it difficult to simulate the reduction in molecular weight.

[0026] 5 is a partially cutaway cross-sectional view schematically illustrating the configuration of the high shear processing section 3 included in the continuous high shear processing apparatus 1. As shown in the figure, the screw 21 of the high shear processing section 3 includes a conveying section 31 and a collar section 32. The collar section 32 is provided continuous with the die section 37 in the direction of the rotation axis of the screw 21 (the conveying direction of the raw polymer 10, the Z direction). In the high shear processing section 3, rotation of the screw 21 within the cylinder section 38 of the barrel 20 applies shear force to the raw polymer 10 to reduce its molecular weight, and the raw polymer is continuously discharged from the die section 37 as a low-molecular-weight polymer.

[0027] The conveying section 31 is provided with flights 35 on the outer peripheral surface 33 of the screw rotation shaft, and conveys the raw polymer 10 in the Z1 to Z2 direction by the rotation of the screw 21.

[0028] A collar section 32 without flights 35 is provided on the outer peripheral surface 33 of the screw shaft adjacent to the conveying section 31 on the Z2 side. Because the collar section 32 does not have flights 35, the pressure loss is smaller than that of the filled region 126 (see FIG. 9 ) near the blocking section 122 in the conventional high shear processing section 103. Furthermore, the force conveying the raw polymer 10 in the Z2 direction differs significantly between the collar section 32 without flights 35 and the conveying section 31 with flights 35. Therefore, if the length of the collar section 32 in the conveying direction is set to an appropriate length, the entire collar section 32 will be filled with raw polymer 10 regardless of the extrusion rate, and there is no need to consider the region filled with raw polymer 10 in the conveying section 31 adjacent to the collar section 32 on the Z1 side.

[0029] That is, even if the extrusion rate of the raw polymer 10 changes, the filled region 36 filled with the raw polymer 10 extends from the boundary 39 between the conveying section 31 and the collar section 32 to the die section 37, and the length L2 of this region is substantially constant, so that the state is the same as when the raw polymer 10 is completely filled inside the cylinder section 38. That is, as the extrusion rate of the raw polymer 10 increases, the residence time in the collar section 32 where shear force is applied becomes shorter, and the effect of reducing the molecular weight becomes weaker. Therefore, it is possible to control the physical properties of the low-molecular-weight polymer obtained by the reduction in molecular weight by the extrusion rate of the raw polymer 10. Furthermore, it becomes easier to simulate the reduction in molecular weight of the raw polymer 10 by the collar section 32.

[0030] As described above, by providing the collar portion 32, the filled region 36 of the raw polymer 10 in the axial direction (Z direction) of the screw 21 becomes longer than the conventional filled region 126 (see FIG. 9 ). Therefore, for the same extrusion rate, the residence time in the filled region 36, where shear force is applied to the raw polymer 10, is longer than the residence time in the conventional filled region 126, improving the efficiency of molecular weight reduction. Therefore, when the extrusion rate is the same as that of the conventional high shear processing section 103, the length of the screw 21 in the Z direction can be shortened to reduce the size of the high shear processing section 3. Furthermore, when the size of the high shear processing section 103 is the same as that of the conventional high shear processing section 3, the extrusion rate of the high shear processing section 3 can be increased. Furthermore, since the collar portion 32 does not have a flight 35, there is an advantage in that a measuring device such as a thermocouple can be inserted anywhere in the Z direction.

[0031] The collar portion 32 may be, for example, a collar element that has conventionally been provided at the base (Z1 side) of the screw 21 to adjust the length of the screw 21. In this case, the collar portion 32 has a configuration in which the flight 35 has been removed from the conveying portion 31, and the distance (gap) between the outer circumferential surface 33 and the cylinder portion 38 is approximately the same as the height of the flight 35.

[0032] The length L1 of the conveying section 31 in the Z direction may be any length that provides a conveying force sufficient to fill the collar section 32 with the raw polymer 10, and may be, for example, a length such that L1 / L2 is 1 to 9. By making the length L2 of the collar section 32 in the Z direction equal to or greater than the length L1 of the conveying section 31, the raw polymer 10 can be efficiently reduced in molecular weight. The length L2 of the collar section 32 in the Z direction may be appropriately set depending on the inner diameter D of the cylinder section 38 and the magnitude of the shear force applied to the raw polymer 10. For example, by setting L2 to 160 mm or less, the raw polymer 10 can be filled into the collar section 32, and the viscosity and molecular weight of the low-molecular-weight polymer can be controlled by the extrusion rate of the raw polymer 10.

[0033] 6A and 6B are enlarged schematic cross-sectional views of the collar portion 32 in the high shear processing unit 3 in Fig. 5 , taken along the XZ and XY planes. The feed polymer 10 in the collar portion 32 is transported in the Z1 to Z2 directions as indicated by the arrows in Fig. 6A by the action of the adjacent transport unit 31. During this transport, as indicated by the arrows in Fig. 6B , a shear force is applied to the feed polymer 10 between the outer circumferential surface 33 of the collar portion 32 and the cylinder portion 38, degrading the polymer into a low-molecular-weight polymer.

[0034] The magnitude of the shear force applied to the raw polymer 10 can be adjusted by the inner diameter D of the cylinder portion 38, the gap (distance) G between the outer surface 33 of the screw 21 at the collar portion 32 and the cylinder portion 38, and the rotation speed of the screw 21.

[0035] For example, when the inner diameter D of the cylinder portion 38 is 45 to 50 mm, the gap G is set to 2 to 4 mm and the rotation speed of the screw 21 is set to 1000 to 4000 rpm (revolutions per minute), thereby making the shear force in the collar portion 32 large enough to reduce the molecular weight of the raw polymer 10.

[0036] (Method for producing low-molecular-weight polymer) The present invention can also be implemented as a method for producing a low-molecular-weight polymer using the continuous high-shear processing apparatus 1 according to the embodiment of the present invention described above. In the method for producing a low-molecular-weight polymer of this embodiment, the feed polymer 10 is conveyed to the collar section 32 by the conveying section 31 of the continuous high-shear processing apparatus 1, a shear force is applied to the conveyed feed polymer 10 in the collar section 32 to reduce its molecular weight to form a low-molecular-weight polymer, and the low-molecular-weight polymer is continuously discharged from the die section 37.

[0037] By applying shear force to the raw polymer 10 in the collar section 32 that does not have a flight 35 to reduce the molecular weight, it is possible to increase the extrusion rate of the raw polymer 10. For example, when the inner diameter of the cylinder section 38 in the high shear processing section 3 is 45 to 50 mm, it is possible to efficiently reduce the molecular weight of the raw polymer 10 to produce a low-molecular-weight polymer at an extrusion rate of 20 to 100 kg / hour, which was difficult to achieve with the conventional high shear processing section 103 shown in Figure 9.

[0038] In the present invention, reducing the molecular weight of raw polymer 10 refers to reducing the weight average molecular weight (Mw) of the resin contained in raw polymer 10. For example, when polypropylene is used as the raw polymer, according to the method for producing a low-molecular-weight polymer of the present embodiment, a low-molecular-weight polymer having a weight average molecular weight of about 50,000 to 200,000 can be produced using a raw polymer having a weight average molecular weight of about 250,000 to 1,200,000.

[0039] Examples of the raw polymer 10 include thermoplastic resins such as polypropylene (PP), polysulfone (PSF), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethersulfone (PES), polyphenylene sulfide (PPS), polyetherketone (PEK), polyetheretherketone (PEEK), aromatic polyamide (PA), aromatic polyester, aromatic polycarbonate (PC), polyetherimide (PEI), polyarylene oxide, thermoplastic polyimide, and polyamideimide. These resins may be used alone or in combination of two or more.

[0040] Components that may be contained in the raw polymer 10 include fibers such as glass fiber (GF), carbon fiber (CF, both virgin and recycled), aramid fiber (Kevlar (registered trademark) fiber), and boron fiber, as well as additives such as antioxidants (sulfur-based and phosphorus-based), carboxylic acid anhydride, maleic acid, plasticizers, UV absorbers, flame retardants, and crystal nucleating agents, and various fillers (carbon black, talc, metal powder, CNT, silica particles, mica), etc. These may be added in amounts that do not inhibit the reduction in molecular weight, and one type may be used, or two or more types may be used in combination.

[0041] Example 1 A low-molecular-weight polymer was produced by kneading using the twin-screw kneading / extrusion section 2 of the continuous high-shear processing apparatus 1 shown in Figure 1 and applying high shear force to the raw material polymer using the high-shear processing section 3 shown in Figure 5, and the viscosity of the processed PP was measured near the die. The raw materials used, the configuration of the continuous high-shear processing apparatus, and the production conditions are described below, and Table 1 shows the screw rotation speed of the high-shear processing section and the viscosity of the processed PP.

[0042] <Raw material polymer> Resin: F704NP (trade name, manufactured by Prime Polymer, Mw 451,000, polypropylene (PP), zero shear viscosity 5,906 Pa.s) <Twin-screw kneading extrusion section: TEM26SX (manufactured by Shibaura Machine Co., Ltd.)> Configuration: feed section, first kneading section, first pumping section, second kneading section, second pumping section Rotation speed: 200 rpm (revolutions / minute) Barrel temperature: 195°C Supply rate (extrusion rate): 4.8 kg / hour

[0043] <High shear processing section> Barrel temperature: 195°C Inner diameter (D) of barrel unit cylinder: 48 mm Die section: Diameter 4 mm, length 25 mm Screw collar section: Gap (G) 3 mm, length (L2) 150 mm Screw conveying section: Flight height (groove depth) 3 mm, pitch 15 mm, length (L1) 135 mm Rotation speed: 100 rpm, 200 rpm, 300 rpm, 1000 rpm, 2000 rpm Extrusion rate: 4.8 kg / hour

[0044]

[0045] Comparative Example 1 Instead of the high shear processing section 3 shown in Figure 5 of Example 1, a high shear processing section 103 shown in Figure 9 was used to apply high shear force to a raw material polymer to produce a low molecular weight polymer, and the viscosity was measured near the die. The raw material used, the configuration of the continuous high shear processing device, and the production conditions are described below, and Table 2 shows the screw rotation speed of the high shear processing section and the viscosity of the processed PP.

[0046] <High shear processing section> Barrel temperature: 195°C Inner diameter (D) of barrel unit cylinder: 48 mm Die section: Diameter 4 mm, length 25 mm Screw: Flight height 3 mm, pitch 15 mm, length 285 mm Damming section: One installed at the center of the screw in the conveying direction (length 45 mm) Through hole: Passage length 45 mm, circular cross section, diameter 2 mm, number of passages 2 (installed evenly in parallel), communicating upstream and downstream of the damming section Rotation speed: 500 rpm, 2000 rpm Extrusion rate: 4.8 kg / hour

[0047]

[0048] As shown in Tables 1 and 2, the high-shear processing section equipped with a screw equipped with a collar between the conveying section and the die section was able to further lower the viscosity of PP, i.e., to further lower the zero-shear viscosity of the resulting PP, compared to a conventional high-shear processing section equipped with a screw equipped with a dam section and a through-hole. The results shown in Table 1 show that in a continuous high-shear processing device equipped with a screw having a collar, the viscosity of PP decreases as the rotation speed of the screw section increases, and that a screw rotation speed of 1,000 rpm or more is preferable from the perspective of sufficiently lowering the viscosity of PP.

[0049] Example 2 The effects of the extrusion rate and the length L2 of the collar section were investigated when a low-molecular-weight polymer was produced using a continuous high-shear processing apparatus equipped with a high-shear processing section 3 shown in Figure 5. The raw materials used, the configuration of each section of the continuous high-shear processing apparatus, and the production conditions are described below. The viscosity was measured by sampling the low-molecular-weight polymer emerging from the die section.

[0050] <Raw Materials> Resin: F704NP (trade name, manufactured by Prime Polymer, Mw 451,000, polypropylene (PP), zero shear viscosity 5,906 Pa.s) <Twin-screw kneading extrusion section: TEM26SX (manufactured by Shibaura Machine Co., Ltd.)> Configuration: feed section, first kneading section, first pumping section, second kneading section, second pumping section Rotation speed: 400 rpm (revolutions / minute) Barrel temperature: 195°C Supply rate (extrusion rate): 4.8 kg / hour

[0051] <High shear processing section> Barrel temperature: 300°C Inner diameter (D) of barrel unit cylinder: 48 mm Die section: diameter 4 mm, length 25 mm Screw collar section: gap (G) 3 mm, length (L2) 0, 37.5, 70, 150 mm Screw conveying section: flight height 3 mm, pitch 15 mm, length 135 mm Rotation speed: 3600 rpm Extrusion rate: 30, 50, 70 kg / hour

[0052] The viscosity of low molecular weight polymers produced by changing the extrusion rate using high shear processing sections with different collar lengths (L2) was measured, and the results are shown in Table 3 and Figures 7A and 7B.

[0053] As shown in Figure 7A, the longer the collar length, the smaller the zero shear viscosity of the resulting low molecular weight polymer, indicating that the zero shear viscosity of the low molecular weight polymer can be controlled by the length of the collar. In this example, within the collar length range of 30 to 150 mm, the viscosity of the resulting low molecular weight polymer decreased as the collar length increased. From these results, it can be said that if the collar length is 20 to 160 mm, it is possible to apply shear force to the raw polymer so that the raw polymer fills the entire collar section but does not fill the conveying section.

[0054] As shown in FIG. 7B , the greater the extrusion rate, the greater the zero shear viscosity of the resulting low-molecular-weight polymer, indicating that the zero shear viscosity of the resulting low-molecular-weight polymer can be controlled by the extrusion rate.

[0055] Comparative Example 2: A low-molecular-weight polymer was produced by reducing the molecular weight of a raw material polymer using the conventional high-shear processing section 103 shown in Figure 9. The raw material used, the configuration of the continuous high-shear processing device, and the production conditions are described below. <Raw Material> Resin: F704NP (trade name, manufactured by Prime Polymer, Mw 451,000, polypropylene (PP), zero-shear viscosity 5,906 Pa.s) <Twin-screw kneading / extrusion section: TEM18SX (manufactured by Shibaura Machine Co., Ltd.)> Barrel temperature: 195°C Configuration: feed section, first kneading section, first pumping section, second kneading section, second pumping section Rotation speed: 100 rpm (revolutions / minute) Extrusion rate: 2, 5, 10 kg / hour

[0056] <High shear processing section> Barrel temperature: 195°C Inner diameter (D) of the cylinder section of the barrel unit: 48 mm Die section: Diameter 4 mm, length 25 mm Screw: Flight height 3 mm, pitch 15 mm, length 285 mm Damming section: One installed at the center of the screw in the conveying direction (length 45 mm) Through hole: Passage length 45 mm, circular cross section, diameter 2 mm, number of passages 2 (installed evenly in parallel), communicating the upstream and downstream of the damming section Rotation speed: 1500 rpm Extrusion rate: 2, 5, 10 kg / hour

[0057] Using a continuous high shear processing apparatus equipped with a conventional high shear processing section as shown in FIG. 9, low molecular weight polymers were produced by varying the extrusion rate, and the viscosity was measured. The results are shown in Table 4 and FIG. 8.

[0058] As shown in Table 4 and Figure 8, when a conventional high shear processing unit was used, no correlation was observed between the extrusion rate of the raw polymer and the viscosity of the produced low-molecular-weight polymer. This result indicates that when a conventional high shear processing unit equipped with a dam and a through-hole is used, the viscosity of the low-molecular-weight polymer cannot be controlled by the extrusion rate of the raw polymer.

[0059] The continuous high shear processing apparatus of the present invention can be used to produce low-molecular-weight polymers by lowering the molecular weight of a raw polymer.

[0060] 1: Continuous high shear processing device 2: Twin-screw kneading extrusion section 3: High shear processing section 4: Defoaming section 6: Barrel 7a: Screw 7b: Screw 8: Cylinder section 9: Supply port 10: Raw polymer 11: Feed section 12: Kneading section 13: Pumping section 14: Flight 15: Disk 16: Flight 20: Barrel 21: Screw 22: Barrel 23: Vent screw 24: Cylinder section 25: Vent port 26: Vacuum pump 27: Head section 28: Discharge port 29: Flight 31: Conveying section 32: Collar section 33: Outer periphery 35: Flight 36: Filling region 37: Die section 38: Cylinder section 39: Boundary 103 : High shear processing section 120: Barrel 121: Screw 122: Dam section 123: Outer circumferential surface 124a: Through hole 124b: Through hole 125: Flight 126: Filling area 127: Die section 128: Cylinder section D: Inner diameter G: Gap (distance) L1: Length L2: Length L3: Length

Claims

1. A continuous high-shear processing device that applies shear force to a raw polymer using a screw inside a cylinder section to reduce its molecular weight and continuously discharges the low-molecular-weight polymer from a die section, characterized in that the screw has: a conveying section with flights on its outer circumferential surface that conveys the raw polymer toward the die section; and a collar section without flights on its outer circumferential surface that is adjacent to the die section side of the conveying section and applies shear force to the raw polymer.

2. A continuous high shear processing device according to claim 1, wherein the length of the collar portion in the direction of transport of the raw polymer is 160 mm or less.

3. The continuous high shear processing device according to claim 1, wherein the length of the collar portion in the direction of transport of the raw polymer is 30 to 150 mm.

4. A continuous high shear processing device according to claim 1, wherein the distance (gap) between the outer peripheral surface of the screw at the collar portion and the cylinder portion is 2 to 4 mm.

5. The continuous high shear processing device according to claim 1, wherein the rotation speed of the screw is 1,000 to 4,000 rpm.

6. A method for producing low molecular weight polymers using the continuous high shear processing device described in claim 1, characterized in that the feed polymer is transported to a collar section by the transport section, shear force is applied to the transported feed polymer in the collar section to reduce its molecular weight and form a low molecular weight polymer, and the low molecular weight polymer is continuously discharged from the die section.

7. The method for producing a low-molecular-weight polymer according to claim 6, wherein the inner diameter of the cylinder is 45 to 50 mm, and the extrusion rate of the raw polymer is 20 to 100 kg / hour.

8. The method for producing a low molecular weight polymer according to claim 6, wherein the raw polymer is polypropylene having a weight average molecular weight of 250,000 to 1,200,000.

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