Screw assembly for reactive melt-blowing process and double-screw extruder

Abstract

The utility model discloses a screw assembly and a double-screw extruder for a reactive melt-blowing process, the screw assembly comprises two screws which have the same structure, rotate in the same direction and are meshed with each other, and each screw consists of a mandrel and a thread element; one end of the core shaft is a feeding end, the other end of the core shaft is a discharging end, and the core shaft can rotate under the action of external force; the threaded element is arranged on the mandrel in a sleeving mode and can rotate along with the mandrel. The screw assembly comprises a feeding section, a reaction section and an extrusion section which are connected in sequence, and the types, the leads and the lengths of internal thread elements in all the sections are reasonably arranged; therefore, conveying of low-viscosity raw materials, initiation of polymerization reaction, macromolecule growth and mixing, conveying and extrusion of high-viscosity polymerization products can be rapidly achieved in a continuous process, and a continuous polymer melt which is stable in pressure, constant in flow and easy to draw and thin is provided for a subsequent spinning assembly.

Description

A screw assembly for reactive meltblown processes and a twin-screw extruder Technical Field

[0001] This utility model relates to the field of polymer reaction processing equipment technology, and in particular to a screw assembly and a twin-screw extruder for reactive meltblown processes. Background Technology

[0002] Reactive polymer processing refers to the continuous chemical reaction of polymer monomers, prepolymers, or polymers within specific equipment to produce polymer products with novel properties. Since the 1960s, new processes and technologies belonging to reactive polymer processing have emerged continuously, such as reactive injection molding, pultrusion, and reactive extrusion. The combination of chemical reaction and polymer processing enables product diversification and functionalization, continuous production, and simplified and economical processes. Therefore, research on reactive polymer processing has received widespread attention from academia and industry in recent years.

[0003] Patent CN117966365A discloses a method for preparing polyamide microfiber two-dimensional membranes using reactive meltblown technology. This method uses a mixture of caprolactam monomer and catalyst as starting material. In a twin-screw extruder, the process sequentially completes the feeding of low-viscosity raw materials, initiation of the polymerization reaction, macromolecular growth, and mixing, feeding, and extrusion of the high-viscosity polymer product. Subsequently, the generated polymer melt is stretched and thinned using conventional spinning components. After solidification, a two-dimensional nonwoven fabric composed of polyamide microfibers is formed. Reactive meltblown technology creatively combines the polymerization reaction with spinning, achieving a one-step preparation of polyamide microfiber nonwoven fabric from caprolactam monomer. This technology broadens the application fields of polymer reactive processing and has many advantages, including low process cost, high production efficiency, energy saving and environmental protection, and adjustable fiber structure, and is expected to further develop into a commercially viable manufacturing technology.

[0004] In polymer reactive processing, especially reactive meltblown processes, the twin-screw extruder, as a continuous processing reactor, is a key piece of equipment determining the smooth operation of the entire production process. According to the process design concept of reactive meltblown technology, a twin-screw extruder must complete six basic tasks: feeding, conveying, reaction, mixing, venting, and extrusion. It should possess the following characteristics: ① Easy feeding and effective conveying of initial low-viscosity raw materials and the high-viscosity polymer melt generated from the reaction; ② A suitable screw structure and a high-precision temperature control system to ensure efficient and continuous polymerization.

[0005] ③ Excellent dispersibility and distribution, allowing materials in different states to be fully mixed; ④ Minimizes high shear and long residence time, which would otherwise cause material degradation; ⑤ Removes unreacted monomers and small molecule oligomers, thereby improving spinning efficiency and the quality of the final product.

[0006] Existing technologies, such as the twin-screw extruders for conventional chemical fiber production lines disclosed in patents CN221622714U, CN105473299A, and CN221641727U, and the reactive twin-screw extruders disclosed in patents CN220946593U, CN222178621U, and CN205705220U, cannot meet the above conditions and have at least the following problems during use:

[0007] (1) Since the raw materials used in previous production and processing were mostly solid particles, the existing twin-screw extruder has insufficient capacity to convey low-viscosity liquid raw materials. The material is exposed at the feed port for a long time because it cannot be conveyed forward in time, which reduces its subsequent chemical reaction activity.

[0008] (2) In order to improve the mixing and plasticizing capacity, existing twin-screw extruders use a lot of shearing screw elements, or even reverse conveying screw elements. However, the high shear force and long residence time can easily cause the polymer melt generated by the reaction to turn yellow and carbonize, which in turn affects the subsequent spinning process and the quality of the final product. Summary of the Invention

[0009] To address the aforementioned technical problems in the existing technology, this utility model provides a screw assembly and a twin-screw extruder for reactive meltblown processes.

[0010] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0011] A screw assembly for a reactive meltblown process, the screw assembly comprising two screws with identical structures, rotating in the same direction and meshing with each other, each screw consisting of a mandrel and a threaded element;

[0012] One end of the mandrel is the feed end, and the other end is the discharge end. The mandrel can rotate under the action of external force. The threaded element is fitted on the mandrel and can rotate with the mandrel.

[0013] The threaded elements include two types: feed threaded elements and shear threaded elements. Feed threaded elements with different leads are alternately distributed along the length of the mandrel, and any shear threaded element is located between two feed threaded elements.

[0014] The threaded element is made of nitrided steel.

[0015] Along the direction from the feed end to the discharge end, the functional areas of the screw are, in sequence, the feed section, the reaction section, and the extrusion section. Each of the feed section, the reaction section, and the extrusion section includes multiple threaded elements, and the type, lead, and length of the threaded elements in each section are arranged in a reasonable manner.

[0016] The feeding section is designed to heat the low-viscosity raw material and convey it forward to the reaction section, while preventing the material from accumulating at the feed port. The feeding section includes, in sequence, one forward conveying threaded element, six to eight forward conveying threaded elements, four to six forward conveying threaded elements, six to eight forward conveying threaded elements, and one forward shearing threaded element.

[0017] The lead of the first forward conveying thread element is 30-36 mm and the axial length is 30-36 mm.

[0018] The lead of the second forward conveying threaded element is 40-50 mm and the axial length is 40-50 mm.

[0019] The lead of the forward conveying threaded element three is 18-24 mm and the axial length is 18-24 mm;

[0020] The forward shearing thread element employs 4 to 6 forward kneading blocks with a length of 28 to 38 mm and a staggered angle of 30 to 45°.

[0021] The reaction section is designed to ensure the high-quality polymerization of the raw materials. Therefore, this stage involves not only basic chemical reactions but also numerous physical processes such as flow, heat transfer, and mass transfer. The reaction section comprises, in sequence, 4-6 forward conveying threaded elements (II), 2-4 forward conveying threaded elements (I), 2-4 forward conveying threaded elements (III), and 1 forward shearing threaded element (II).

[0022] The second positive shearing thread element adopts 4 to 6 positive kneading blocks with a length of 40 to 50 mm and a staggered angle of 30 to 45°;

[0023] The positive shearing thread element three uses 4 to 6 positive kneading blocks with a length of 28 to 38 mm and a staggered angle of 60 to 90°.

[0024] The extrusion section further homogenizes the polymer melt generated in the reaction, and then discharges it from the extruder at a constant temperature, pressure, and quantity. The extrusion section includes 4 to 6 forward feed threaded elements (II), 4 to 6 forward feed threaded elements (I), and 2 to 4 forward feed threaded elements (III) connected in sequence.

[0025] Furthermore, the length-to-diameter ratio of the screw is (48-62):1; the length ratio of the feeding section, the reaction section and the extrusion section is (7-10):(8-12):(5-7).

[0026] This invention also provides a twin-screw extruder for reactive meltblown processes, employing the aforementioned screw combination.

[0027] Furthermore, it includes a sleeve and a screw assembly installed inside the sleeve, as well as a drive device, a heating device, and a cooling device;

[0028] The sleeve is divided into 9 to 15 sections, and a feeding port is provided at the position corresponding to the feeding section, and an exhaust port is provided at the position corresponding to the extrusion section;

[0029] The driving device includes a drive motor and a reducer;

[0030] The heating device is a cast aluminum heater or a ceramic heater, and the temperature of each section of the sleeve is individually controlled and adjusted by a temperature controller via a solid-state relay.

[0031] The cooling device is equipped with both air cooling and water cooling methods.

[0032] Compared with the prior art, the outstanding advantages of this utility model are:

[0033] (1) The screw assembly structure of this utility model is relatively simple. By arranging and combining two types of screw elements, namely conveying and shearing, the requirements of the twin-screw extruder for reactive meltblown processes can be met. For example, a large-lead forward screw element is used at the beginning of the feeding section, which can efficiently convey low-viscosity raw materials; then the lead of the forward conveying screw element is gradually reduced to increase the screw channel filling degree, thereby accelerating the heating rate of the raw materials; finally, a set of shearing screw elements is used to further disperse and mix the raw materials. The reaction section adopts a combination of two types of meshing blocks with different angles, which can increase the residence time of the raw materials and make the polymerization reaction more complete and uniform; in addition, forward conveying screw elements are designed at intervals, and the screw channel volume gradually decreases to build up pressure and push the polymer melt generated by the reaction to continue to be conveyed forward. A forward feed thread element with a larger lead is set at the beginning of the extrusion section, followed by a thread element with a smaller lead. This combination not only allows small molecules in the melt to be volatilized as much as possible, but also achieves the purpose of conveying and pressurizing, increasing the melt density at the extruder outlet to a certain extent, and finally extruding it smoothly from the extruder.

[0034] (2) The screw assembly of this utility model can simultaneously ensure that the conveying of low viscosity raw materials, the initiation of polymerization reaction, macromolecular growth, and the mixing, conveying and extrusion of high viscosity polymer products are realized in a continuous process, thereby providing a continuous supply of polymer melt with stable pressure, constant flow and easy stretching for subsequent spinning components.

[0035] (3) The application of the twin-screw extruder of this utility model can reduce the process steps and reduce the difficulty of operation. At the same time, it helps to reduce the construction cost of the production line and has high practical and economic value.

[0036] The screw assembly for reactive meltblown processes and the twin-screw extruder described in this utility model will be further explained below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0037] Figures 1 to 3 are schematic diagrams of the screw assembly of the twin-screw extruder in the embodiments.

[0038] Figure 4 is a schematic diagram of the forward feeding threaded element in the embodiment, where (a) is a side view and (b) is a front view.

[0039] Figure 5 is a schematic diagram of the forward shearing threaded element in the embodiment, where (a) is a side view and (b) is a front view.

[0040] Figure 6 is a front view of the twin-screw extruder in the embodiment.

[0041] Figure 7 is a top view of the twin-screw extruder in the embodiment.

[0042] Figure 8 is a side view of the twin-screw extruder in the embodiment.

[0043] Wherein, 1-screw; 11-feed end; 12-discharge end; 2-mandrel; 3-conveyor threaded element; 4-shearing threaded element; 21-feed section; 22-reaction section; 23-extrusion section;

[0044] 5-Sleeve; 6-Feeding port; 7-Exhaust port; 8-AC asynchronous drive motor; 9-Reducer; 10-Cast aluminum heater; 11-Cooling fan; 12-Cooling water channel; 13-Base. Detailed Implementation

[0045] It should be noted that in this application, 48 / 48×3 indicates a forward feed thread element with a lead of 48mm, an axial length of 48mm, and a quantity of 3; other data follow the same pattern. KB45° / 5 / 32 indicates that the forward shear thread element consists of 5 kneading blocks with a length of 32mm and a staggered angle of 45°; other data follow the same pattern. The forward feed and shear thread elements in this application are made of nitrided steel and are all commercially available products.

[0046] One embodiment of this utility model provides a screw assembly installed in a twin-screw extruder for reactive meltblown processes. The extruder's drive motor is connected to the mandrel of the screw assembly, driving the screw assembly to rotate within the sleeve. In use, low-viscosity monomer raw materials are fed into the twin-screw extruder. Under the action of the screw assembly, the raw materials undergo conveying, shearing, reaction, heat transfer, mixing, and devolatilization within the extruder, ultimately producing a polymer melt suitable for stretching and thinning.

[0047] As shown in Figures 1-5, a screw assembly for a twin-screw extruder used in a reactive meltblown process is provided. The screw assembly comprises two identical, co-rotating, and meshing screws 1. The screw assembly has a feed end 11 and a discharge end 12. Each screw 1 is specifically composed of a mandrel 2 and threaded elements. The threaded elements are mounted on the mandrel 2 and include two types: conveying threaded elements 3 and shearing threaded elements 4, which can rotate with the mandrel 2. Along the direction from the feed end 11 to the discharge end 12, the screw assembly includes a feed section 21, a reaction section 22, and an extrusion section 23 connected in sequence. Each of the feed section 21, reaction section 22, and extrusion section 23 includes multiple conveying threaded elements 3 and shearing threaded elements 4. The types, leads, and lengths of the conveying threaded elements 3 and shearing threaded elements 4 within each section are rationally arranged to meet the requirements of the reactive meltblown process.

[0048] As shown in Figures 1-3, the feeding section 21 includes one forward conveying threaded element 1, seven forward conveying threaded elements 2, six forward conveying threaded elements 1, seven forward conveying threaded elements 3, and one forward shearing threaded element 1 connected in sequence.

[0049] The lead and axial length of the first forward conveying threaded element are 32mm; the lead and axial length of the second forward conveying threaded element are 48mm; the lead and axial length of the third forward conveying threaded element are 22mm; the first forward shearing threaded element uses five 32mm long forward kneading blocks with a staggered angle of 45°. The arrangement of the threaded elements in the feeding section 21 is: 32 / 32, 48 / 48×7, 32 / 32×6, 22 / 22×7, KB45° / 5 / 32. The function of the feeding section 21 is to heat the fed low-viscosity raw material and convey it forward to the reaction section, while preventing the raw material from accumulating at the feed port.

[0050] The reaction section 22 includes six forward conveying threaded elements II, four forward conveying threaded elements I, three forward conveying threaded elements III, one forward shearing threaded element II, three forward conveying threaded elements II, four forward conveying threaded elements I, one forward conveying threaded element III, and one forward shearing threaded element III connected in sequence.

[0051] The second forward shearing threaded element uses five forward kneading blocks, each 40mm long, with a staggered angle of 45°; the third forward shearing threaded element uses four forward kneading blocks, each 32mm long, with a staggered angle of 60°. The arrangement of the threaded elements in reaction section 22 is as follows: 48 / 48×6, 32 / 32×4, 22 / 22×3, KB45° / 5 / 40, 48 / 48×3, 32 / 32×4, 22 / 22, KB60° / 4 / 32. The function of reaction section 22 is to ensure that the raw materials complete the polymerization reaction with high quality; that is, the raw materials undergo polymerization initiation and macromolecular growth reactions sequentially here, ultimately generating a high-viscosity polymer melt.

[0052] The extrusion section 23 comprises five forward-feeding threaded elements (II), five forward-feeding threaded elements (I), and three forward-feeding threaded elements (III) connected in sequence. The arrangement of the threaded elements in the extrusion section 23 is: 48 / 48×5, 32 / 32×5, and 22 / 22×4. The function of the extrusion section 23 is to further homogenize the polymer melt generated in the reaction, and then discharge it from the extruder at a constant temperature, pressure, and quantity.

[0053] The length ratio of the feeding section 21, the reaction section 22, and the extrusion section 23 is 9:10:6. The length-to-diameter ratio of the screw 1 is 58:1.

[0054] As shown in Figures 6-8, a twin-screw extruder for reactive meltblown processes uses the aforementioned screw assembly. Its main structural components include a sleeve 5, a screw assembly, a drive unit, a heating unit, and a cooling unit.

[0055] Sleeve 5: The sleeve 5 is designed with 12 sections according to the actual length of the screw 1, and the sleeve 5 is provided with a feeding port 6 at the position corresponding to the feeding section 21, and an exhaust port 7 at the position corresponding to the extrusion section 23.

[0056] Screw assembly: installed inside sleeve 5.

[0057] Drive unit: mainly composed of AC asynchronous drive motor 8 and reducer 9. When the twin-screw extruder is working, AC asynchronous drive motor 8 drives conveying thread element 3 and shearing thread element 4 to rotate through spindle 2, thereby gradually conveying the material from feed end 11 to discharge end 12.

[0058] Heating device: A cast aluminum heater 10 is used, located below the sleeve 5. The temperature of each section of the sleeve 5 is individually controlled and adjusted by a temperature controller through a solid-state relay.

[0059] Cooling device: Equipped with both air cooling and water cooling to precisely control the temperature of the feeding section 21, reaction section 22, and extrusion section 23, thereby ensuring the continuous production of polymer melt suitable for spinning. The cooling fan 11 is installed on one side of the sleeve 5, and the cooling water channel 12 is installed on the other side of the sleeve 5.

[0060] The bottom of the twin-screw extruder is equipped with a base 13.

[0061] The embodiments described above are merely preferred embodiments of the present utility model and are not intended to limit the scope of the present utility model. They should not be construed as limitations on the present utility model. Any modifications and improvements made to the technical solutions of the present utility model by those skilled in the art without departing from the spirit of the present utility model should fall within the protection scope defined by the claims of the present utility model.

Claims

1. A screw assembly for a reactive meltblown process, characterized in that: The screw assembly includes two screws (1) with the same structure, rotating in the same direction and meshing with each other. Each screw (1) consists of a mandrel (2) and a threaded element. One end of the mandrel (2) is the feed end (11) and the other end is the discharge end (12). The mandrel (2) can rotate under the action of external force. The threaded element is fitted on the mandrel (2) and can rotate with the mandrel (2). The threaded element includes two types: a conveying threaded element (3) and a shearing threaded element (4).

2. The screw assembly for reactive meltblown processes according to claim 1, characterized in that: The feed thread elements (3) with different leads are alternately distributed along the length direction of the mandrel (2), and any shear thread element (4) is located between two feed thread elements (3).

3. The screw assembly for reactive meltblown processes according to claim 2, characterized in that: The threaded element is made of nitrided steel.

4. The screw assembly for reactive meltblown processes according to claim 3, characterized in that: Along the direction from the feed end (11) to the discharge end (12), the functional areas of the screw (1) are, in sequence, the feed section (21), the reaction section (22) and the extrusion section (23), and each of the feed section (21), the reaction section (22) and the extrusion section (23) includes multiple threaded elements.

5. The screw assembly for reactive meltblown processes according to claim 4, characterized in that: The feeding section (21) includes one forward conveying threaded element I, six to eight forward conveying threaded elements II, four to six forward conveying threaded elements I, six to eight forward conveying threaded elements III, and one forward shearing threaded element I connected in sequence; the lead of the forward conveying threaded element I is 30 to 36 mm and the axial length is 30 to 36 mm; the lead of the forward conveying threaded element II is 40 to 50 mm and the axial length is 40 to 50 mm; the lead of the forward conveying threaded element III is 18 to 24 mm and the axial length is 18 to 24 mm; the forward shearing threaded element I uses four to six forward kneading blocks with a length of 28 to 38 mm and a staggered angle of 30 to 45°.

6. The screw assembly for reactive meltblown processes according to claim 4, characterized in that: The reaction section (22) includes 4-6 forward conveying threaded elements II, 2-4 forward conveying threaded elements I, 2-4 forward conveying threaded elements III, and 1 forward shearing threaded element II, 2-4 forward conveying threaded elements II, 4-6 forward conveying threaded elements I, 1 forward conveying threaded element III, and 1 forward shearing threaded element III connected in sequence; the lead of the forward conveying threaded element I is 30-36 mm, and the axial length is 30-36 mm; The lead of the second forward conveying threaded element is 40-50 mm and the axial length is 40-50 mm; the lead of the third forward conveying threaded element is 18-24 mm and the axial length is 18-24 mm; the second forward shearing threaded element uses 4-6 forward kneading blocks with a length of 40-50 mm and a staggered angle of 30-45°; the third forward shearing threaded element uses 4-6 forward kneading blocks with a length of 28-38 mm and a staggered angle of 60-90°.

7. The screw assembly for reactive meltblown processes according to claim 4, characterized in that: The extrusion section (23) includes 4 to 6 forward conveying threaded elements II, 4 to 6 forward conveying threaded elements I, and 2 to 4 forward conveying threaded elements III connected in sequence; the lead of the forward conveying threaded element I is 30 to 36 mm and the axial length is 30 to 36 mm; the lead of the forward conveying threaded element II is 40 to 50 mm and the axial length is 40 to 50 mm; the lead of the forward conveying threaded element III is 18 to 24 mm and the axial length is 18 to 24 mm.

8. The screw assembly for reactive meltblown processes according to any one of claims 4-7, characterized in that: The length-to-diameter ratio of the screw (1) is (48-62):1; the length ratio of the feeding section (21), the reaction section (22) and the extrusion section (23) is (7-10):(8-12):(5-7).

9. A twin-screw extruder for reactive meltblown processes, characterized in that: The screw assembly described in any one of claims 1-8 is adopted.

10. The twin-screw extruder according to claim 9, characterized in that: It includes a sleeve and a screw assembly installed inside the sleeve, as well as a drive device, a heating device and a cooling device; the sleeve is divided into 9 to 15 sections, and a feeding port is provided at the position corresponding to the feeding section, and an exhaust port is provided at the position corresponding to the extrusion section; the drive device includes a drive motor and a reducer; the heating device is a cast aluminum heater or a ceramic heater; the cooling device is equipped with both air cooling and water cooling.

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