A continuous reactor for spandex dry spinning solution and a reaction method

Abstract

The present invention provides a continuous reactor for dry-spinning spandex dope and a reaction method. The reactor comprises a housing and a rotor. The housing is provided with a prepolymer feed inlet, a mixed amine feed inlet, and a polymer outlet. The rotor comprises a main shaft portion and a mixing section. The diameter of the mixing section gradually decreases from the side closest to the prepolymer feed inlet to the side closest to the polymer outlet, and the gap between the side of the mixing section closest to the prepolymer feed inlet and the housing is less than 5 mm. The mixing section is provided with at least a first blade group and a second blade group in the direction of decreasing diameter. The gap between the end of the first blade group distal to the rotor axis and the housing is less than 5 mm. The present invention allows the prepolymer to form a prepolymer liquid film between the housing and the rotor. The liquid film is divided into small units by the blades, enabling more accurate mixing with the mixed amine solution. The conical rotor allows the blades' rotation radius and linear speed to gradually decrease, reducing mechanical heat generation, miniaturizing the equipment, and increasing the rotation speed.

Description

Technical Field

[0001] The present invention relates to the field of elastic fiber production equipment, and in particular to the technical field of a continuous chain extension reactor and a reaction method for reacting a spandex prepolymer with a mixed amine solution. Background Art

[0002] In the dry-spin spandex production process, the preparation of the spinning solution primarily involves two reaction steps: the first reaction produces the prepolymer, and the second reaction produces the polyurethane polymer. In the second reaction, the reagents typically include: 1. the prepolymer produced in the first reaction; 2. a mixed amine solution containing one or more aliphatic monoamine terminators and one or more aliphatic diamine chain extenders.

[0003] The reaction of the prepolymer with the mixed amine solution is typically carried out in a batch or continuous reactor. Due to the rapid reaction between the prepolymer and the mixed amine solution and the high molecular weight of the product, the viscosity of the liquid in the reactor typically increases from 20 poise to 1200-1400 poise within seconds. Furthermore, the reaction produces byproducts, often referred to as "hard segment gels." Technically, these byproducts are not typical "gels," but rather consist of low-solubility polymers resulting from some side reactions. Compared to the desired polyurethane polymer, these polymers have unusually long urea-based hard segments and unusually short polyurethane soft segments, as well as small amounts of cyclic oligomers of MDI molecules and ethylenediamine. These byproducts primarily form when the prepolymer solution and the mixed amine solution flow into contact. At the interface, numerous different polymer entities rapidly form. The most insoluble of these polymer entities precipitate and adhere to the metal surface in contact. These deposits are swollen by the solvent, forming the so-called "hard segment gel."

[0004] In existing continuous polymerization reactors, such as a traditional spandex continuous reactor disclosed in CN102408532A, a mixed amine solution and a prepolymer solution are metered into the reaction chamber through a single through-axis inlet, wherein the mixed amine solution enters through a central tube and the prepolymer solution flows together around the periphery of the central tube. Therefore, at the coaxial inlet, a large amount of prepolymer solution and the mixed amine solution come into contact at the coaxial inlet, and local mis-ratioing is very likely to occur at the contact interface, forming a "hard segment gel".

[0005] In addition, traditional reactors are large and bulky, and the polymers generated by the reaction have high molecular weight and high viscosity. The rotor with a bulky mechanical structure stirs the high-viscosity polymer when it rotates, generating high mechanical shear heat, making it impossible to achieve high speeds. Usually, the maximum speed does not exceed 250 rpm, and the mixing effect is poor. When the prepolymer solution contacts the mixed amine solution, the local ratio may deviate from the theoretical value, causing the molecular weight and viscosity of the reaction product to deviate from the preset values, further causing the content of by-products such as "hard segment gel" to increase.

[0006] The accumulation of these byproducts within the reactor requires shutting down the reactor for cleaning, and the accumulation of byproducts between cleanings can also lead to variations in reactor performance. In some reactor types, a manually operated mechanical cleaning device or scraper is located at the reagent inlet, positioned so that the area surrounding the inlet is periodically cleared of polymer hard segment gel while the reactor continues to operate. However, because the scraper occupies a significant portion of the cross-sectional area of the coaxial inlet's peripheral flow channel during operation, backpressure disturbances and interruptions in the flow of the prepolymer solution can occur. Summary of the Invention

[0007] To address the above technical issues, the present invention provides a continuous reactor for dry-spinning spandex dope, capable of achieving a polymerization reaction with a precisely proportioned prepolymer solution and mixed amine solution, while avoiding the impact of byproducts on equipment and production, and reducing mechanical heat generation at high rotation speeds. The specific solution is as follows:

[0008] A continuous reactor for dry-spinning spandex dope, comprising a shell and a rotor, wherein the shell is provided with a prepolymer feed port, a mixed amine feed port and a polymer outlet, and is characterized in that the shell comprises a circumferential surface and at least one end surface, the rotor comprises a main shaft portion and a mixing portion, the main shaft portion passes through the shell and is connected to a driving device, the mixing portion is the portion of the rotor inside the reactor cavity, the diameter of the mixing portion gradually decreases from the side close to the prepolymer feed port to the side close to the polymer outlet, and the gap between the bottom surface of the mixing portion and the end surface of the shell is less than 5 mm; the mixing portion is sequentially provided with at least a first blade group and a second blade group in the direction in which its diameter decreases.

[0009] The mixing section of the rotor can be roughly considered a "cone." The term "cone" refers to the overall shape of the mixing section being roughly conical or a truncated cone similar to a cone, i.e., the mixing section has a side conical surface and two end surfaces. Specifically, in the direction in which the diameter of the mixing section decreases, the geometric shape of the side conical surface can be a standard cone, i.e., the waistline of the mixing section is a straight line; the side conical surface can also be a smooth curved surface, i.e., the waistline of the mixing section is a curve; or the side conical surface can be stepped, i.e., the waistline of the mixing section is a broken line. Generally speaking, the diameter of the mixing section gradually decreases from the side close to the prepolymer feed inlet to the side close to the polymer outlet. Furthermore, in the present invention, unless otherwise specified, the end surface of the mixing section with the larger diameter is referred to as its "bottom surface," and the portion of the mixing section close to its bottom surface is referred to as its "bottom." Similarly, the end surface of the mixing section with the smaller diameter is referred to as its "top surface," and the portion of the mixing section close to its end surface is referred to as its "top." The reactor "cavity" is a space enclosed by the shell for accommodating the reactor's internal components and the reaction liquid. The shell may include two end surfaces and a circumferential surface. Optionally, the rotation radius of each blade group decreases step by step as it approaches the discharge port.

[0010] Optionally, a gap between the end of the first blade assembly away from the rotor axis and the circumferential surface of the housing is less than 5 mm.

[0011] Optionally, the prepolymer feed port faces the bottom surface of the mixing section.

[0012] In another alternative embodiment, the prepolymer feed port can also be located on the circumferential surface of the housing. In this case, the prepolymer feed port should be positioned on the side of the mixed amine feed port near the bottom of the mixing section to allow the prepolymer solution to form a liquid film between the rotor's mixing section and the housing. Furthermore, the prepolymer and mixed amine solution can be fed coaxially. While maintaining the other features of the present invention, the reactor's reaction performance using coaxial feeding will still be better than that of a conventional reactor. However, since the prepolymer does not pre-form a liquid film, gel may still form at the feed port, resulting in a lower reaction performance than the preferred feeding method of the present invention.

[0013] Optionally, the mixed amine feed port is arranged on the circumferential surface of the shell.

[0014] Optionally, the prepolymer feed ports are multiple feed ports distributed circumferentially on the end surface of the shell.

[0015] Optionally, the mixed amine feed port is directly opposite to the first blade assembly.

[0016] Optionally, the mixed amine feed port is located between the prepolymer feed port and the first blade assembly.

[0017] Optionally, a side of the first blade assembly close to the prepolymer feed inlet partially overlaps with the mixed amine feed inlet in the radial projection of the reactor.

[0018] The above-mentioned optional methods are all designed to ensure that the prepolymer solution and the mixed amine solution are immediately separated and broken up by the first blade group after they come into contact, so as to achieve the purpose of accurately mixing the prepolymer and the mixed amine. Because the mixed amine feed port is close enough to the first blade group, and the gap between the mixing part and the circumferential surface of the shell is small, the liquid linear velocity is fast, so the first blade group can break up the mixed solution in time, avoiding local mixing errors.

[0019] Optionally, the diameter of the mixed amine feed port is smaller than the width of a single blade in the first blade group.

[0020] Optionally, the distance between the first blade assembly and the bottom surface of the mixing portion is greater than 5 mm.

[0021] Optionally, the shell is provided with a thermal insulation interlayer.

[0022] Optionally, a stator group is provided in the reactor cavity, and the stator group is provided between each blade group.

[0023] Optionally, the number of stators in each stator group is 4-16.

[0024] Optionally, the minimum gap between the stator and its adjacent blades is less than 5 mm.

[0025] The "minimum clearance" refers to the minimum distance between the stator and the blade rotation surface.

[0026] Optionally, the minimum gap between the stator and the mixing part is less than 5 mm.

[0027] The minimum gap between the stator and the mixing section refers to the minimum distance between the end of the stator close to the mixing section and the side surface of the mixing section.

[0028] Optionally, the stator is plate-shaped.

[0029] Optionally, the plate-shaped stator is not perpendicular to the rotor axis.

[0030] Optionally, the diameter of the cavity gradually decreases from the prepolymer inlet to the polymer outlet.

[0031] Optionally, the mixing portion is further provided with a third blade set in the direction in which its diameter decreases.

[0032] Optionally, the number of blades in each blade group decreases sequentially.

[0033] Optionally, the number of blades in the first blade group is 4-50, the number of blades in the second blade group is 2-36, and the number of blades in the third blade group is 0-18.

[0034] Optionally, the mixed amine feed port is provided with a self-cleaning device.

[0035] Optionally, two mixed amine feed ports are provided.

[0036] Optionally, the self-cleaning device includes a cleaning device shell, a liquid inlet pipe, a porous tube, and a cleaning rod, wherein the porous tube is provided with multiple openings, the cleaning rod extends from the outside of the cleaning device shell to the inside of the porous tube, and the cleaning rod is provided with a handle outside the cleaning device shell.

[0037] A polyurethane chain extension reaction method using the above reactor is characterized by comprising the following steps:

[0038] 1) The prepolymer enters the reactor cavity through the prepolymer feed port and forms a liquid film with a thickness of less than 5 mm under the action of the shell and the bottom surface of the mixing section;

[0039] 2) As the liquid film moves forward, the mixed amine solution is injected into the reactor cavity from the mixed amine feed port and meets the liquid film;

[0040] 3) After the liquid film meets the mixed amine solution, the first blade group separates the mixture of the prepolymer and the mixed amine solution into a plurality of small units, and simultaneously performs a preliminary reaction in the small units;

[0041] 4) The prepolymer and mixed amine solution are continuously advanced under the push of the metering pump and blades. During the advancement, the prepolymer and mixed amine solution are fully stirred by the blades at each stage and the chain extension reaction and chain termination reaction are completed to obtain a polymer. The rotation speed of the blades is 300-3000 rpm.

[0042] 5) After the reaction is completed, the polymer leaves the reactor through the polymer outlet under the push of the metering pump and blades.

[0043] Beneficial effects:

[0044] The present invention provides a continuous reactor for dry-spinning spandex dope. Compared with traditional reactors, the rotor mixing section in the reactor cavity of the present invention is conical, and a gap is defined between the side of the mixing section close to the prepolymer feed port and the shell. After the prepolymer enters the reactor cavity, a layer of prepolymer liquid film is evenly formed between the shell and the rotor, which can be more accurately proportioned with the mixed amine solution.

[0045] By limiting the gap between the first blade group and the shell, and limiting the relative positional relationship between the mixed amine feed port and the first blade group, when the liquid film advances to the first row of blades installed on the cone, it is divided into a number of small units by the blades and driven to rotate rapidly. At the same time, it encounters the mixed amine solution entering from the mixed amine feed port, and the reaction between the prepolymer and the mixed amine solution is limited to each small unit. The ratio of reactants in each unit is more precise, and the influence of gel polymer generated by local imbalance of ratio in the reactor cavity on subsequent reactions is avoided.

[0046] The conical rotor mixing section reduces the number of blades, the rotation radius and the linear speed of each blade group step by step, thereby reducing the mechanical heat generated by stirring the viscous polymer, miniaturizing the equipment and increasing the rotation speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a schematic diagram of the overall structure of the continuous reactor for the spandex dry spinning solution of the present invention.

[0048] Figure 2 is a cross-sectional view of the reactor of the present invention

[0049] Figure 3 This is a schematic diagram of the three-dimensional structure of the rotor of the present invention.

[0050] Figure 4 This is a schematic structural diagram of the mixed amine feed port of the present invention.

[0051] The following are the descriptions of the reference numerals:

[0052] 1. Shell 11. Shell first end surface 12. Shell second end surface 13. Shell circumferential surface

[0053] 14. First stator assembly 15. Second stator assembly 16. Insulation interlayer 17. Insulation liquid inlet 18. Insulation liquid outlet 2. Rotor 21. Main shaft 22. Mixing section 23. First blade assembly 24. Second blade assembly 25. Third blade assembly 3. Prepolymer feed port 4. Mixed amine feed port 41. Self-cleaning device 42. Cleaning device housing 43. Mixed amine inlet pipe 44. Perforated tube 45. Cleaning rod 46. Handle 5. Polymer outlet 6. Drive device DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be further clearly and completely described below in text combined with the drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments. For the sake of clarity and conciseness, not all the features of the actual implementation are described in the specification. In order to avoid obscuring the present invention due to unnecessary details, only the device structure and processing steps closely related to the solutions according to the present invention are described in the drawings and descriptions, while the representation and description of components and processes that are not closely related to the present invention and are known to ordinary technicians in this field are omitted.

[0055] For the convenience of description, unless otherwise specified, the terms "up", "down", "left" and "right" are based on Figure 1 The relative position description of the prepolymer is as follows. The prepolymer refers to a prepolymer solution obtained by the prepolymer reaction of a diol compound and a diisocyanate compound; the mixed amine solution refers to a substance such as a small molecule diol, or a small molecule diamine, or a mixture of a small molecule diamine and a monoamine that undergoes chain extension and chain termination reactions with the prepolymer in spandex production. The "mixed amine" is a general term for ease of description, which refers to a mixed solution of a chain extender and a chain terminator in a polyurethane polymerization reaction. It can actually also contain alcohol chain extenders and chain terminators; the polymer refers to a high molecular weight polyurethane compound obtained by the reaction of the prepolymer and the mixed amine solution. The gel refers to a high-viscosity byproduct substance produced due to an incorrect local ratio of the prepolymer and the mixed amine solution, or due to mechanical heat generation causing the reaction to be too fast, resulting in an excessively high molecular weight of the reaction product. It also includes the "hard segment gel" mentioned above. The presence of the gel will affect the operation of the equipment and the subsequent reaction.

[0056] Example 1

[0057] This embodiment relates to a continuous reactor for dry-spinning spandex dope, such as Figure 1-2 As shown, the reactor comprises a housing 1, a rotor 2, and the housing is provided with a prepolymer feed port 3, a mixed amine feed port 4, a polymer outlet 5, and a driving device 6. Figure 2As shown, the shell 1 includes a first end surface 11 , a second end surface 12 and a circumferential surface 13 . The prepolymer feed port 3 is provided on the first end surface 11 , and the mixed amine feed port 4 is provided on the circumferential surface 13 . Among them, the diameter of the prepolymer feed port 3 is ф50mm, the inner diameter of the mixed amine feed port 4 is ф15mm, the inner diameter of the polymer outlet 5 is ф200mm, the end inner diameter of the first end face 11 of the shell is ф480mm, the end inner diameter of the second end face 12 of the shell is ф360mm, and the inner cavity length of the shell 1 is 560mm. A cavity is formed inside the shell 1, and its free volume is about 45 liters. The inner diameter of the cavity gradually decreases from left to right. The prepolymer solution at a flow rate of 1700kg / hr and the mixed amine solution at a flow rate of 1100kg / hr continuously enter the cavity through the prepolymer feed port 3 and the mixed amine feed port 4 respectively. After reacting in the cavity to generate polymer, it leaves the reactor through the polymer outlet 5 and enters the next equipment.

[0058] In an optional embodiment, the prepolymer feed port 3 can also be multiple inlets evenly distributed along the circumference on the first end face 11 of the shell. Preferably, the number of the inlets is 4, each with an inner diameter of ф25 mm. The four feed ports can be connected to a one-inlet and four-outlet distribution valve through a pipeline.

[0059] like Figure 2 and Figure 3As shown, the rotor 2 includes a main shaft portion 21 and a mixing portion 22. The main shaft portion 21 passes through the housing 1 from left to right and is connected to the drive device 6. In this embodiment, the drive device 6 is composed of a motor, a coupling, a bearing, and other components. In this embodiment, the motor is a synchronous motor with a power of 160kW and a speed of 1800rpm. The mixing portion 22 is the portion of the rotor 2 within the cavity. The main shaft portion 21 and the mixing portion 22 can be a fixedly connected integral unit or two components that can be detachably connected in any known manner. In this embodiment, they are preferably fixedly connected integrally. The diameter of the mixing section 22 gradually decreases from left to right (i.e., from the side close to the prepolymer feed port 3 to the side close to the polymer outlet 5). Hereinafter, unless otherwise specified, the side of the mixing section 22 close to the prepolymer feed port 3 is referred to as its bottom surface, and the side of the mixing section 22 close to the polymer outlet 5 is referred to as its top surface. The prepolymer feed port 3 is directly opposite to the bottom surface of the mixing section 22, and the prepolymer feed port 3 deviates from the center position of the first end surface. The side conical surface of the mixing section 22 is a continuous smooth curved surface, and the bottom surface of the mixing section 22 is aligned with the first end surface 11 of the shell. The gap between them is 3 mm, which allows the prepolymer solution to form a thin liquid film, so that the amount of prepolymer is small when the prepolymer meets the mixed amine solution, which helps the prepolymer and the mixed amine solution to fully contact each other and avoid the problem of local mismatching between the two. The mixing part 22 is provided with a first blade group 23, a second blade group 24 and a third blade group 25 from left to right. The first blade group 23 has 30 first blades 23', the second blade group 24 has 8 second blades 24', and the third blade group 25 has 8 third blades 25'.The first blade group has an outer diameter of 474 mm and is distributed along the circumference at intervals of 12°. The blade width is 54 mm. The first blade 23' in the first blade group is embedded in the bottom of the rotor mixing section 22. The distance between the left edge of the first blade group 23 and the bottom surface of the mixing section 22 is 50 mm. The gap between the end of the first blade 23' of the first blade group 23 away from the rotor axis and the circumferential surface 13 of the shell is 2 mm. In this embodiment, a certain distance is preferably present between the first blade group 23 and the bottom surface of the mixing section 22 to leave space for setting the mixed amine feed port 4 on the circumferential surface 13 of the shell, so that the prepolymer solution can meet the mixed amine solution in a liquid film state and be absorbed by the first blade group 23. In other optional embodiments, the first blade assembly 23 can also be flush with the bottom surface of the mixing section 22, and the mixed amine feed port 4 can be located on the first end surface 11 of the housing. This can also achieve more uniform material mixing. However, this may cause gel accumulation in the gap between the bottom surface of the mixing section 22 and the first end surface 11 of the housing. Therefore, the solution in this embodiment is most preferred. The second blade assembly 24 is composed of second blades 24' with a width of 54 mm and a rotational outer diameter of φ400 mm, which are evenly distributed around the circumference. The second blades 24' are embedded in the middle of the mixing section 22. The third blade assembly 25 has a blade width of 36 mm and a rotational outer diameter of φ300 mm. The third blades 25' are embedded in the end of the mixing section 22. The power for the rotation of each blade assembly comes from a drive device 6 connected to the rotor 2 (not shown). Because the viscosity of the liquid in the reactor chamber gradually increases from left to right, the inner diameter of the reactor chamber and the rotational outer diameter of each blade assembly decrease from left to right, which to some extent reduces the motor power required by the rotor 2. In an optional embodiment, the third blade assembly 25 may correspond to the center line of the discharge port 5 to assist the polymer solution in flowing out of the polymer outlet 5 .

[0060] In a preferred embodiment, the blades in the first blade group 23 and the second blade group 24 form an angle of 15° with the axis of the rotor 2, and the blades in the third blade group 25 form an angle of 30° with the axis of the rotor 2. The blades in each blade group are angled with the axis so that the blades not only have a stirring effect but also have a certain propulsion effect on the liquid in the cavity, causing the liquid to move forward.

[0061] Within the inner cavity of the housing 1, a first stator assembly 14 is disposed between the first blade assembly 23 and the second blade assembly 24, and a second stator assembly 15 is disposed between the second blade assembly 24 and the third blade assembly 25. The first stator assembly 14 comprises 12 flat stators 14', while the second stator assembly 15 comprises four flat stators 15'. Each stator plate forms a 20° angle with the axis of the rotor 2. The minimum clearance between the rotating surfaces of the stator assembly and adjacent blade assemblies is 1 mm, and the minimum clearance between each stator assembly and the mixing section 22 is 2 mm. The diameter of the cavity gradually decreases from left to right.

[0062] To prevent the reaction from being affected by temperature fluctuations within the chamber, the housing 1 is further provided with an insulating interlayer 16. This interlayer 16 can be heated and cooled using cold water, hot water, hot oil, or other media at a flow rate of 20 L / min to accommodate polymerization reactions with varying polymer ratios. Accordingly, the housing 1 is provided with an insulating liquid inlet 17 and an insulating liquid outlet 18.

[0063] In this embodiment, there are two mixed amine feed ports 4, which are located at higher points on the circumferential surface 13 of the housing. The liquid flow from the mixed amine solution supply pump is divided into two pipes of equal diameter and length to ensure that the flow to each mixed amine feed port is equal. The central axis of each mixed amine feed port 4 on the circumferential surface 13 of the housing is flush with the left edge of the first blade group 23. The mixed amine feed port 14 is also provided with the following Figure 4 The self-cleaning device 41 shown in the figure includes a cleaning device shell 42, a mixed amine solution inlet pipe 43, a porous tube 44, and a cleaning rod 45, wherein the mixed amine solution inlet pipe 43 is connected to the reactor shell 1 through the cleaning device shell 42, the porous tube 44 is arranged in the cleaning device shell 42, one end of the porous tube 44 is connected to the reactor shell 1, and a plurality of openings are provided on the tube body of the porous tube 44. The cleaning rod 45 extends from the outside of the cleaning device shell 42 to the inside of the porous tube 44, and the cleaning rod 45 is provided with a handle 46 on the outside of the cleaning device shell 42. The cleaning rod 45 can be provided with a scraping head in the porous tube 44, or the rod body diameter can be set to be consistent with the inner diameter of the porous tube 44. The handle 46 can push the cleaning rod 45 into the reactor cavity, thereby scraping off the byproduct gel attached to the inner wall of the porous tube 44, thereby cleaning the porous tube 44. The handle 46 can be operated manually or connected to an automated device to automatically push the cleaning rod 45 to clean the porous tube 44 at regular intervals. This regular cleaning operation allows for the scraping of byproduct gel when accumulation is minimal, effectively ensuring smooth feed of the mixed amine solution. Minor gel debris does not materially affect the polymer solution. The aperture of each mixed amine feed port 4 is sufficient to deliver the entire required flow of mixed amine solution into the reactor chamber. While one porous tube 44 is being cleaned, the other is operating normally. The two feed ports alternately clean each other, ensuring that the cleaning action does not cause backpressure disturbances or flow interruptions in the mixed amine solution flow.

[0064] The working process of the reactor of the present embodiment is as follows:

[0065] During operation, the reactor provided by the present invention can be divided into three sections: Region A, Region B, and Region C, based on the direction of liquid flow. Region A, the reactor's feed and premixing area, includes the prepolymer feed port 3, the mixed amine feed port 4, the bottom of the mixing section 22, and the first blade assembly 23. Region B, the reactor's mixing area, includes the first stator assembly 14 and the second blade assembly 24. Region C, the reactor's outlet area, includes the second stator assembly 15 and the third blade assembly 25. During operation, the mixing intensity decreases from Region A to Region B and then to Region C.

[0066] In area A, the prepolymer solution and the mixed amine solution meet and are initially mixed under the action of the first blade group. The specific process is as follows:

[0067] The motor in drive unit 6 drives rotor 2 at high speed through a coupling, bearings, and other transmission devices. A prepolymer solution, one of the reactants, is accurately metered by a metering pump (not shown) and enters the reactor chamber through prepolymer inlet 3 on the first end face 11 of the housing. Driven by the centrifugal force of rotor 2 and the propulsion of the metering pump, the prepolymer solution is continuously and evenly propelled rightward along a smooth mixing section 22. Because the bottom of mixing section 22 occupies the majority of the volume of region A, the prepolymer solution forms a flowing liquid film on the surface of rotor mixing section 22. Simultaneously, the mixed amine solution is injected into the side surface of the bottom edge of mixing section 22 through mixed amine inlet 4. In this region, the prepolymer and mixed amine solution react extremely rapidly. As the flowing prepolymer film meets the jet of mixed amine solution, it is sheared and divided into numerous small units by first blade assembly 23, rotating at 1800 rpm, facilitating precise proportioning of the prepolymer solution and the mixed amine solution. At the same time, driven by the power of the prepolymer metering pump and the mixed amine solution metering pump, the dense first blade group 23 quickly disperses and propels the reactants forward, thereby avoiding the local imbalance of the ratio of the prepolymer solution and the amine solution at the mixed amine feed port 4 to produce by-product gel, thereby preventing the by-product gel from affecting the subsequent reaction.

[0068] The mixed amine feed port 4 occasionally experiences backflow, causing high-viscosity polymer liquid to clog the mixed amine feed port 4. Therefore, a self-cleaning device 41 is provided at the mixed amine feed port 4. The mixed amine solution enters the reactor chamber through a porous tube 44 via a mixed amine inlet pipe 43. An operator or automated equipment can periodically pull a handle 46 to move a cleaning rod 45 back and forth within the porous tube 44, thereby scraping away high-viscosity polymer adhering to the inner wall of the porous tube 44 and ensuring unobstructed flow of the mixed amine feed port 4. While one porous tube 44 is being cleaned, the other is in normal operation. The two feed ports alternately perform cleaning operations, ensuring that the cleaning operation does not cause backpressure disturbances or flow interruptions in the mixed amine solution flow. Preferably, the cleaning operation is performed at least six times per hour to prevent the accumulation of byproduct gel at any one mixed amine feed port.

[0069] After passing through the first blade group 23, the prepolymer solution and the mixed amine solution are initially mixed and reacted, but the reaction is not complete. The nascent polymer obtained by the reaction increases the viscosity of the mixed liquid in the reactor and continues to flow rightward along the surface of the mixing section 22 and enters area B.

[0070] In region B, blending of the nascent polymer occurs and the viscosity of the polymer continues to gradually increase in this region.

[0071] The specific process is as follows:

[0072] As the nascent prepolymer formed in region A passes through the second blade assembly 24 of the mixing section 22, the second blade assembly 24 further stirs the mixed liquid within the cavity, allowing unreacted NCO groups in the prepolymer to fully mix, contact, and react with the NH2 groups in the mixed amine solution. Because the diameter of the mixing section 22 decreases at the second blade assembly 24, the cavity diameter also decreases there, resulting in a smaller stirring radius for the second blade assembly 24. Furthermore, due to the smaller number of blades in the second blade assembly 24, the heat generated by the stirring of the viscous polymer by the second blade assembly 24 is also reduced. This increases the rotor speed, resulting in more uniform mixing and improved mixing efficiency. Furthermore, because the diameter of the mixing section 22 in region B is larger than that in region C, and the cavity inner diameter is reduced, the linear velocity of the liquid flowing from left to right within region B increases, thereby reducing the residence time of the finished polymer traveling from region B to the polymer outlet 5 in region C.

[0073] In region C, the mixed liquid has essentially reacted after passing through the second blade assembly 24, producing a polymer solution. The viscosity of the resulting polymer solution increases further, and the polymer solution continues to flow rightward along the surface of the mixing section 22, passing through the third blade assembly 25. This allows the reaction to proceed further and also helps the polymer solution exit the reactor through the polymer outlet. Furthermore, the polymer reaction in region C is complete, the product viscosity reaches its maximum, and the resistance experienced by the third blade assembly 25 is also the greatest. This also effectively increases the rotational resistance of the rotor 2. The main shaft 21 of the rotor 2 can be connected to a torque measuring device outside the reactor. The measurement results can be considered as the magnitude of the resistance experienced by the third blade assembly 25, and the torque is used to measure the viscosity of the finished polymer solution. A temperature sensor and a pressure sensor are installed at the reactor outlet, along with a polymer removal pump to stabilize the reactor outlet pressure. The temperature sensor monitors the reaction temperature in real time and serves as a metric for the degree of reaction and uniformity.

[0074] Throughout the reaction process, to counteract the tendency of the viscous polymer to follow and "climb" the rotor's rotating axis (known as the Weissenberg effect), a first stator assembly 14 and a second stator assembly 15 are respectively positioned on the inner walls of the chambers in regions B and C. These two stator assemblies are located adjacent to the side surfaces of the mixing section 22, homogenizing the mixed solution, redirecting its flow, and promoting internal recirculation of the polymeric material, thereby achieving more uniform mixing and a more thorough reaction between the prepolymer and the mixed amine solution. Furthermore, the relatively small gaps between the stator and the blades of the rotor 2 ensure that the mixed liquid is adequately squeezed and sheared by the stator and rotor as it passes through the gaps, resulting in more uniform mixing and a more thorough reaction. The stator plates form a certain angle with the axis of the rotor 2. This arrangement not only complicates the flow of the liquid within the chamber but also reduces the stator's volume while ensuring a sufficiently small minimum gap between the stator and rotor blades, thereby reducing the weight of the device.

[0075] The actual use effect of the reactor provided in this embodiment is as follows:

[0076] The prepolymer was dissolved in dimethylacetamide and metered continuously into the reactor every hour. The amine mixture required for polymerization, also dissolved in dimethylacetamide, was also metered into the reactor every hour. The trial run lasted two weeks, with the prepolymer injection port cleaned six times an hour. The final polymer was tested regularly, with the following average results:

[0077] Intrinsic viscosity 1.0;

[0078] primary amine termini 15.0%;

[0079] Solid content 35.0%;

[0080] The bulk viscosity calculated from the melt flow index was 2450 poise.

[0081] At the end of the test, the reactor was disassembled for cleanliness inspection. No signs of hard segment gel deposition were found at the mixed amine feed port or elsewhere in the reaction chamber.

[0082] In summary, the reactor provided in this embodiment, through the cooperation of the shell 1, the mixing part 22 and the first blade group 23, shears and divides the mixed liquid of the prepolymer and the mixed amine solution into a large number of small units, and the ratio of the mixed liquid in each unit is more precise, avoiding the problem of local ratio imbalance; by setting the rotor 2 in the reactor cavity to be conical, the rotation radius of the blade is reduced, and at the same time, the shear linear velocity and shear radius of the viscous polymer are reduced, thereby reducing the heat generated by mechanical stirring of the viscous polymer, so that the rotor speed can be increased and the mixing is more uniform; compared with traditional reactors, since the liquid in the reactor is required to pass through the gaps between the various components in a film-like shape during the flow process, the equipment can be miniaturized and lightweight; at the same time, the smaller blade rotation radius reduces the stirring resistance to the viscous material, so that the rotor speed can be increased to 1800rpm, thereby improving the stirring efficiency and reaction efficiency.

Claims

1. A continuous reactor for dry-spinning spandex dope, comprising a housing and a rotor, wherein the housing is provided with a prepolymer feed port, a mixed amine feed port and a polymer outlet, characterized in that: The shell includes a circumferential surface and at least one end surface, and the rotor includes a main shaft portion and a mixing portion. The main shaft portion passes through the shell and is connected to a driving device. The mixing portion is the portion of the rotor inside the reactor cavity. The diameter of the mixing portion gradually decreases from the side close to the prepolymer feed inlet to the side close to the polymer outlet, and the gap between the bottom surface of the mixing portion and the adjacent shell end surface is less than 5 mm. The mixing portion is sequentially provided with at least a first blade group and a second blade group in the direction in which its diameter decreases.

2. The reactor according to claim 1, characterized in that The gap between the end of the first blade assembly away from the rotor axis and the circumferential surface of the housing is less than 5 mm.

3. The reactor according to claim 1, characterized in that The rotation radius of each blade group decreases step by step in the direction close to the discharge port.

4. The reactor according to claim 1, characterized in that The prepolymer feed port faces the bottom surface of the mixing part.

5. The reactor according to claim 1, characterized in that The relative position relationship between the mixed amine feed port and the first blade assembly satisfies one of the following conditions: 1) The mixed amine feed port is directly opposite to the first blade group; 2) The mixed amine feed port is located between the prepolymer feed port and the first blade group; 3) The side of the first blade assembly close to the prepolymer feed inlet partially overlaps with the mixed amine feed inlet in the radial projection of the reactor.

6. The reactor according to claim 1, characterized in that The diameter of the cavity gradually decreases from the prepolymer inlet to the polymer outlet.

7. The reactor according to claim 1, characterized in that A stator group is arranged in the reactor cavity, and the stator group is arranged between the blade groups.

8. The reactor according to claim 7, characterized in that The minimum gap between the stator and the mixing part is less than 5 mm, and the minimum gap between the stator and its adjacent blades is less than 5 mm.

9. The reactor according to claim 1, characterized in that The mixed amine feed port is provided with a self-cleaning device, which includes a cleaning device shell, a liquid inlet pipe, a porous tube, and a cleaning rod, wherein the porous tube is provided with multiple openings, the cleaning rod extends from the outside of the cleaning device shell to the inside of the porous tube, and the cleaning rod is provided with a handle outside the cleaning device shell.

10. A polyurethane chain extension reaction method according to any one of claims 1 to 9, characterized in that: The steps include: 1) The prepolymer enters the reactor cavity through the prepolymer feed port and forms a liquid film with a thickness of less than 5 mm under the action of the shell and the bottom surface of the mixing section; 2) As the liquid film moves forward, the mixed amine solution is ejected from the mixed amine feed port and meets the liquid film; 3) When the liquid film meets the mixed amine solution, the first blade group separates the mixture of the prepolymer and the mixed amine solution into a plurality of small units, and simultaneously performs a preliminary reaction in the small units; 4) The prepolymer and mixed amine solution continue to move forward under the push of the metering pump and blades. During the forward process, they are fully stirred by the blades at each level and the chain extension reaction and chain termination reaction are completed to obtain a polymer. The blade speed is 300-3000rpm; 5) After the reaction is completed, the polymer leaves the reactor through the polymer outlet under the push of the metering pump and blades.

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