Continuous reactor and reaction method for dry spandex spinning dope

Abstract

To provide a reactor and a reaction method that can prevent uneven mixing of prepolymer and mixed amine and local deviation in the compounding ratio in the continuous reaction of a spinning solution for spandex dry spinning, improve reaction efficiency, and suppress gel generation, thereby enabling stable production of polymer. [Solution] The reactor according to the present invention comprises a casing (1) and a rotor (2), and the casing (1) is provided with a prepolymer supply port (3), a mixed amine supply port (4), and a polymer discharge port (5). The rotor (2) has a main shaft portion (21) and a mixing portion (22), and the diameter of the mixing portion (22) gradually decreases from the prepolymer supply port (3) side toward the polymer discharge port (5) side, and the gap between the prepolymer supply port (3) side of the mixing portion (22) and the casing (1) is less than 5 mm. At least a first set of blades (23) and a second set of blades (24) are sequentially arranged in the mixing portion (22) along the direction in which the diameter decreases, and the gap between the end of the first set of blades (23) remote from the rotor axis and the casing (1) is also less than 5 mm. The reaction method involves forming a liquid film using the prepolymer, bringing the mixed amine solution into contact with the liquid film, shearing the mixture into small units using the first blade group to carry out an initial reaction, and then completing the chain-extending reaction and the terminal reaction while thoroughly stirring the mixture using multiple stages of blades, and discharging the final polymer from the polymer outlet.

Description

[Technical Field]

[0001] The present invention relates to the field of elastic fiber manufacturing equipment, and more particularly to a continuous chain extension reactor and reaction method used for reacting a spandex prepolymer with a mixed amine solution. [Background technology]

[0002] In the dry-laid spandex manufacturing process, the preparation of the spinning dope mainly involves two reaction steps. The first reaction is to produce a prepolymer, and the second reaction is to obtain a polyurethane polymer. In the second reaction step, the reaction reagents usually include: 1. the prepolymer obtained 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 process between the prepolymer and the mixed amine solution is typically carried out in a batch or continuous reactor. The reaction between the prepolymer and the mixed amine proceeds very rapidly, resulting in a high molecular weight product. The viscosity of the liquid often rises from 20 poise to 1200-1400 poise within a few seconds. Furthermore, by-products can be generated during the reaction, commonly referred to as "hard segment gels." Technically, these are not typical "gels," but rather contain poorly soluble polymers produced by side reactions. Compared to the target polyurethane polymer, these 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 by-products are primarily formed upon contact between the prepolymer solution and the mixed amine solution. At the interface, various polymer structures rapidly form, with the least soluble polymer structures precipitating and adhering to the metal surface they contact. These deposits are then swollen by the solvent, forming the so-called "hard segment gels." "Hard segment gel" refers to a poorly soluble polymer produced by reacting a prepolymer with a mixed amine solution, which has unusually long urea-based hard segments and short polyurethane soft segments.

[0004] An example of a conventional continuous polymerization reactor is the conventional spandex continuous reactor disclosed in CN102408532A. In this reactor, a mixed amine solution and a prepolymer solution are supplied at a fixed rate through a single coaxial inlet and introduced into a reaction chamber. The mixed amine solution is supplied through a central tube, and the prepolymer solution flows in from the periphery of the central tube. This results in large amounts of prepolymer solution and mixed amine solution coming into contact at the coaxial inlet, which can easily lead to localized non-uniformity in the blend ratio and the formation of "hard segment gel."

[0005] Furthermore, conventional reactors are large in size and volume, making it difficult for the rotors, with their heavy mechanical structure, to rotate at high speeds when stirring the high-molecular-weight, high-viscosity polymers that are the reaction products. Stirring high-viscosity polymers generates high mechanical shear heating, making high-speed rotation impossible; the typical maximum rotation speed is limited to 250 rpm. This results in insufficient mixing, and when the prepolymer solution and the mixed amine solution come into contact, the local blending ratio deviates from the theoretical value. This causes the molecular weight and viscosity of the reaction product to deviate from the target values, leading to an increase in the content of by-products such as "hard segment gel."

[0006] Accumulation of these by-products in the reactor requires shutting down the reactor and cleaning. Even between cleanings, the accumulation of by-products can cause changes in reactor performance. Some reactors are equipped with manually operated mechanical cleaning devices or scrapers at the reagent inlets to periodically remove the polymer hard segment gel around the inlet while the reactor is running. However, the scrapers occupy a large portion of the cross-sectional area around the coaxial inlet during operation, which can cause backpressure fluctuations and interrupt the flow of the prepolymer solution. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] China Patent Publication CN102408532A Summary of the Invention

[0008] In order to solve the above-mentioned technical problems, the present invention provides a continuous reactor for producing a dope for dry spinning of spandex, which can achieve a polymerization reaction with a precise blending ratio of the prepolymer solution and the mixed amine solution, avoid the influence of by-products on the equipment and production, and reduce mechanical heat generation under high-speed rotation. The specific configuration is as follows:

[0009] A continuous reactor for spandex dry spinning dope includes a casing and a rotor, and the casing is provided with a prepolymer supply port, a mixed amine supply port, and a polymer discharge port. The casing has a peripheral surface and at least one end surface, the rotor includes a main shaft portion and a mixing portion, the main shaft portion penetrates the casing and is connected to a drive device, the mixing portion is a part of the rotor within the reactor cavity, the diameter of the mixing portion gradually decreases from the prepolymer supply port side toward the polymer discharge port side, and the gap between the bottom surface of the mixing portion and the end surface of the casing is less than 5 mm, and the mixing portion is provided with at least a first set of blades and a second set of blades in that order in the direction in which the diameter decreases.

[0010] Here, the mixing section of the rotor can be considered to be roughly "conical," and this "conical" 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 may be a standard cone, i.e., the side line of the mixing section is straight, or the side may be a smoothly curved surface, i.e., the side line is curved, or it may be stepped, i.e., the side line is a broken line. In general, the diameter of the mixing section gradually decreases from the side closer to the prepolymer supply port to the side closer to the polymer discharge port. Furthermore, unless otherwise specified in the present invention, the end surface of the mixing section with a larger diameter will be referred to as the "bottom surface," and the portion of the mixing section close to the bottom surface will be referred to as the "bottom portion." Similarly, the end surface of the mixing section with a smaller diameter will be referred to as the "top surface," and the portion close to the top surface will be referred to as the "top portion." The "cavity" of the reactor is a space surrounded by a casing for accommodating the internal structure of the reactor and the reaction liquid, and the casing may include two end surfaces and one peripheral surface. Optionally, the radius of rotation of each set of blades may be gradually reduced in a direction closer to the outlet.

[0011] Optionally, the gap between the end of the first set of blades remote from the rotor axis and the circumferential surface of the casing is less than 5 mm.

[0012] Optionally, the prepolymer feed port is located directly opposite the bottom surface of the mixing section.

[0013] In another embodiment, the prepolymer supply port may be located on the periphery of the casing. In this case, the prepolymer supply port is located closer to the bottom of the mixing section than the mixed amine supply port, allowing the prepolymer solution to form a liquid film between the mixing section of the rotor and the casing. Furthermore, the prepolymer and mixed amine solution may be supplied coaxially. While the other configurations of the present invention remain unchanged, the coaxial supply method may improve the reaction efficiency of the reactor compared to conventional reactors, since the prepolymer does not form a liquid film beforehand, which may result in gel formation at the supply port, making it less effective than the preferred supply method of the present invention.

[0014] Optionally, a mixed amine feed port is provided on the periphery of the casing. Optionally, the prepolymer feed ports are a plurality of feed ports arranged circumferentially on the casing end face. Optionally, a mixed amine feed port is located directly opposite the first set of blades.

[0015] Optionally, a mixed amine feed port is provided between the prepolymer feed port and the first set of blades. Optionally, the side of the first set of blades near the prepolymer feed inlet and the mixed amine feed inlet partially overlap in radial projection of the reactor.

[0016] The above optional configurations aim to achieve an accurate blending ratio of prepolymer and mixed amine by dividing and dispersing the prepolymer solution and mixed amine solution by the first blade set immediately after they come into contact. Because the mixed amine supply port is sufficiently close to the first blade set, and the gap between the mixing section and the casing surface at this location is small and the linear liquid flow velocity is fast, the first blade set can immediately disperse the mixed solution, avoiding local blending ratio errors.

[0017] Optionally, the diameter of the mixed amine feed port is less than the width of a single blade of the first set of blades. Optionally, the distance between the first set of blades and the bottom surface of the mixing section is greater than 5 mm. Optionally, the casing is provided with an insulating jacket.

[0018] Optionally, stator groups are provided within the reactor cavity, said stator groups being positioned between each of the blade groups. Optionally, the number of stators included in each stator group is between 4 and 16. Optionally, the minimum gap between the stator and the adjacent blades is less than 5 mm.

[0019] Here, the "minimum gap" refers to the shortest distance between the stator and the rotating surface of the blade. Optionally, the minimum gap between the stator and the mixing section is less than 5 mm. The minimum gap between the stator and the mixing section refers to the shortest distance between the end of the stator closest to the mixing section and the side surface of the mixing section.

[0020] Optionally, the stator is plate-shaped. Optionally, the plate-shaped stator is not perpendicular to the rotor axis. Optionally, the diameter of the cavity gradually decreases in the direction from the prepolymer inlet to the polymer outlet. Optionally, the mixing section further comprises a third set of blades in the direction of decreasing diameter.

[0021] Optionally, the number of blades in the first set of blades is 4-50, the number of blades in the second set of blades is 2-36, and the number of blades in the third set of blades is 0-18.

[0022] Optionally, the mixed amine feed port is equipped with an automatic cleaning device. Optionally, there are two mixed amine feed ports.

[0023] Optionally, the automatic cleaning device includes a cleaning device casing, a supply pipe, a perforated pipe, and a cleaning rod, the perforated pipe having a plurality of openings, the cleaning rod extending from the exterior of the cleaning device casing to the interior of the perforated pipe, and the cleaning rod having a handle on the exterior of the cleaning device casing.

[0024] A polyurethane chain extension reaction method using the above reactor, characterized by comprising the following steps:

[0025] 1) The prepolymer is introduced into the reactor cavity through the prepolymer inlet, and forms a liquid film with a thickness of less than 5 mm through the action of the casing and the bottom of the mixing section;

[0026] 2) During the advancement of the liquid film, the mixed amine solution is injected into the reactor cavity through the mixed amine inlet to contact with the liquid film;

[0027] 3) After the liquid film contacts with the mixed amine solution, the first set of blades divides the mixture of prepolymer and mixed amine solution into a plurality of small units, and an initial reaction proceeds in each small unit;

[0028] 4) The prepolymer and mixed amine solution are continuously advanced by the metering pump and impeller, and are thoroughly stirred by the impellers at each stage during the advance, completing the chain extension and termination reactions to obtain the polymer. Here, the impeller rotation speed is 300-3000 rpm;

[0029] 5) After the reaction is completed, the polymer is discharged from the reactor through the polymer outlet by the driving force of the metering pump and impeller. [Effects of the Invention]

[0030] The present invention provides a continuous reactor for spandex dry spinning dope. Compared with conventional reactors, the rotor mixing section disposed in the reactor cavity of the present invention is conical, and the gap between the side of the mixing section close to the prepolymer supply port and the casing is limited. Therefore, after the prepolymer is introduced into the reactor cavity, a uniform prepolymer liquid film is formed between the casing and the rotor, and the blending ratio with the mixed amine solution is more accurately achieved.

[0031] By limiting the gap between the first blade group and the casing, as well as the relative positional relationship between the mixed amine supply port and the first blade group, when the liquid film reaches the first row of blades installed on the cone, it is divided into multiple small units by the blades. At the same time, it is rotated and stirred at high speed, and comes into contact with the mixed amine solution introduced from the mixed amine supply port. As a result, the reaction of the prepolymer and the mixed amine solution is limited to each small unit, the mixing ratio of the reactants in each unit is more accurate, and the impact of gel-like polymer caused by local imbalance in the mixing ratio within the reactor cavity on the subsequent reaction can be avoided.

[0032] The conical rotor mixing section allows the number of blades in each blade group, the rotation radius, and the linear velocity to be gradually reduced, which suppresses the mechanical heat generated by stirring highly viscous polymers, allowing for the device to be made more compact and the rotation speed to be increased. [Brief explanation of the drawings]

[0033] [Figure 1] 1 is a schematic diagram showing a continuous reactor according to the present invention. [Figure 2] 1 is a schematic diagram showing a casing according to the present invention; [Figure 3] 1 is a schematic diagram showing the internal structure of a continuous reactor according to the present invention. [Figure 4] FIG. 1 is a schematic diagram showing a mixed amine feed port of a continuous reactor according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0034] In order to clarify the objectives, technical means, and effects of the embodiments of the present invention, the technical means of the embodiments of the present invention will be described more clearly and completely below with reference to the drawings. Obviously, the described embodiments are only some of the embodiments of the present invention and do not cover all the embodiments. For the sake of clarity and conciseness, not all features of actual embodiments are described in this specification. In order to avoid obscuring the present invention with unnecessary details, the drawings and descriptions only describe device structures and processing steps that are closely related to the technical configuration of the present invention, and omit descriptions and illustrations of structures and processes that are not directly related to the present invention and are well known to those skilled in the art.

[0035] For ease of explanation, unless otherwise specified, "top," "bottom," "left," and "right" refer to relative positions based on Figure 1 in the following description. The term "prepolymer" refers to a prepolymer solution obtained by prepolymerization of a diol compound and a diisocyanate compound. The term "mixed amine solution" refers to a low molecular weight diol, low molecular weight diamine, or a mixture of a low molecular weight diamine and a monoamine, which undergoes chain extension and termination reactions with the prepolymer in spandex production. The term "mixed amine" is a general term for convenience and actually refers to a mixed solution of a chain extender and a terminating agent used in polyurethane polymerization, including alcohol-based chain extenders and terminating agents. The term "polymer" refers to a high molecular weight polyurethane compound obtained by reacting a prepolymer with a mixed amine solution. The term "gel" refers to a high-viscosity by-product produced by excessive reaction due to localized inaccuracies in the blending ratio of the prepolymer and the mixed amine solution or mechanical heat generation, resulting in an excessively high molecular weight of the reaction product. This term also includes the aforementioned "hard segment gel." The presence of gel affects the operation of the equipment and the progress of subsequent reactions.

[0036] Example 1 This embodiment relates to a continuous reactor for producing dry spinning dope for spandex, and as shown in Figures 1 and 2, the reactor includes a casing 1 and a rotor 2. The casing is provided with a prepolymer supply port 3, a mixed amine supply port 4, a polymer discharge port 5, and a driving device 6. As shown in Figure 2, the casing 1 includes a first casing end surface 11, a second casing end surface 12, and a casing circumferential surface 13. The prepolymer supply port 3 is provided at the first casing end surface 11, and the mixed amine supply port 4 is provided at the casing circumferential surface 13. The diameter of the prepolymer inlet 3 is 50 mm, the inner diameter of the mixed amine inlet 4 is 15 mm, the inner diameter of the polymer outlet 5 is 200 mm, the inner diameter of the end of the first end 11 of the casing is 480 mm, the inner diameter of the end of the second end 12 of the casing is 360 mm, and the lumen length of the casing 1 is 560 mm. A chamber is formed within the casing 1, with a free volume of approximately 45 liters. The inner diameter of the chamber gradually decreases from left to right. The prepolymer solution and the mixed amine solution are continuously fed into the chamber through the prepolymer inlet 3 and the mixed amine inlet 4 at flow rates of 1700 kg / hr and 1100 kg / hr, respectively. The prepolymer solution and the mixed amine solution are reacted in the chamber to produce polymer, which then leaves the reactor through the polymer outlet 5 and is sent to the next device.

[0037] In an optional embodiment, the prepolymer supply port 3 may be a plurality of supply ports evenly arranged circumferentially on the first end face 11 of the casing. Preferably, the number of supply ports is four, each with an inner diameter of 25 mm, and the four supply ports may be connected to a one-inlet, four-outlet type distribution valve via piping.

[0038] As shown in Figures 2 and 3, the rotor 2 includes a main shaft 21 and a mixing section 22. The main shaft 21 penetrates the casing 1 from left to right and is connected to a drive unit 6. In this embodiment, the drive unit 6 is composed of components such as a motor, a coupling, and bearings. The motor is a synchronous motor with an output of 160 kW and a rotation speed of 1800 rpm. The mixing section 22 is located within the cavity of the rotor 2. The main shaft 21 and the mixing section 22 may be fixedly connected as an integral structure or may be two parts detachably connected by any known method. In this embodiment, they are preferably fixedly connected as an integral structure. The diameter of the mixing section 22 gradually decreases from left to right, i.e., from the prepolymer supply inlet 3 side to the polymer discharge outlet 5 side. Hereinafter, unless otherwise specified, the side of the mixing section 22 closest to the prepolymer supply inlet 3 will be referred to as the "bottom" and the side closest to the polymer discharge outlet 5 will be referred to as the "top." The prepolymer supply port 3 faces the bottom surface of the mixing section 22 and is offset from the center of the first end face. The side conical surface of the mixing section 22 is a continuous, smoothly curved surface, and there is a 3 mm gap between the bottom surface of the mixing section 22 and the casing first end face 11. This gap allows the prepolymer solution to form a thin liquid film, reducing the amount of prepolymer when it encounters the mixed amine solution. This ensures sufficient contact between the two and prevents localized mixing ratio errors. The mixing section 22 is provided, from left to right, with a first blade group 23, a second blade group 24, and a third blade group 25. The first blade group 23 includes 30 first blades 23', the second blade group 24 includes 8 second blades 24', and the third blade group 25 includes 8 third blades 25'. The first blade group has an outer diameter of 474 mm, is arranged circumferentially at 12° intervals, and has a blade width of 54 mm. The first blade 23' is fitted into the bottom of the rotor mixing section 22, and the distance between the left edge of the first blade group 23 and the bottom of the mixing section 22 is 50 mm. The gap between the end of the first blade 23' far from the rotor axis and the casing circumferential surface 13 is 2 mm. In this embodiment, a certain distance is provided between the first blade group 23 and the bottom of the mixing section 22, ensuring space for the mixed amine supply port 4 on the casing circumferential surface 13. The prepolymer solution meets the mixed amine solution in the form of a liquid film and is separated by the first blade group 23.In another alternative embodiment, the first blade set 23 may be positioned flush with the bottom surface of the mixing section 22, and the mixed amine supply port 4 may be provided on the first end surface 11 of the casing. However, this configuration is most preferred because gel may accumulate in the gap between the bottom surface of the mixing section 22 and the first end surface 11 of the casing. The second blade set 24 is composed of 54 mm wide second blades 24' evenly spaced around a circumference, with an outer rotational diameter of φ400 mm, and the second blades 24' are fitted into the middle of the mixing section 22. The third blade set 25 has a blade width of 36 mm and an outer rotational diameter of φ300 mm, and the third blades 25' are fitted into the end of the mixing section 22. Each blade set is rotated by power from a drive unit 6 connected to the rotor 2 (not shown). As the viscosity of the liquid in the reactor cavity gradually increases from left to right, the inner diameter of the reactor cavity and the outer rotational diameter of each blade group also decrease from left to right, thereby reducing the motor power required for rotor 2. In an optional embodiment, a third blade group 25 is positioned corresponding to the centerline of outlet 5 to assist in discharging the polymer solution from outlet 5.

[0039] In a preferred embodiment, the blades in the first blade group 23 and the second blade group 24 form an angle of 15° with respect to the axis of the rotor 2, and the blades in the third blade group 25 form an angle of 30° with respect to the axis of the rotor 2. The blades in each blade group having a certain angle with respect to the axis not only produce a stirring effect, but also a certain propulsion effect on the liquid in the cavity, promoting the forward movement of the liquid.

[0040] Within the cavity of the casing 1, a first stator group 14 is provided between the first blade group 23 and the second blade group 24, and a second stator group 15 is provided between the second blade group 24 and the third blade group 25. The first stator group 14 includes 12 flat stators 14', and the second stator group 15 includes four flat stators 15'. The plate surface of each stator forms an angle of 20° with respect to the axis of the rotor 2, and the minimum gap between the rotation surface of each stator group and the adjacent blade group is 1 mm, and the minimum gap between each stator group and the mixing section 22 is 2 mm. The diameter of the cavity gradually decreases from left to right.

[0041] To prevent temperature changes in the cavity from affecting the reaction, a thermal insulation jacket layer 16 is installed inside the casing 1. The thermal insulation jacket layer 16 can be heated and cooled using cold water, hot water, hot oil, etc. at a flow rate of 20 L / min, making it possible to accommodate polymerization reactions of different polymer blends. Accordingly, the casing 1 is equipped with a thermal insulation liquid inlet 17 and a thermal insulation liquid outlet 18.

[0042] In this embodiment, two mixed amine supply ports 4 are provided, and are located at a relatively high position on the casing circumferential surface 13. The liquid flow from the mixed amine solution supply pump is divided into two pipes of equal diameter and length, so that the flow rates toward each mixed amine supply port are equal. The central axis of each mixed amine supply port 4 is located at the same position on the casing circumferential surface 13 as the left edge of the first blade set 23. The mixed amine supply port 4 is provided with an automatic cleaning device 41 as shown in FIG. 4 , which includes a cleaning device casing 42, a mixed amine solution inlet pipe 43, a perforated pipe 44, and a cleaning rod 45. The mixed amine solution inlet pipe 43 is connected to the reactor casing 1 via the cleaning device casing 42, and the perforated pipe 44 is located within the cleaning device casing 42, with one end of the perforated pipe 44 communicating with the reactor casing 1. The perforated pipe 44 has a plurality of holes in its tubular body. A cleaning rod 45 extends from the outside of the cleaning device casing 42 into the perforated pipe 44, and a handle 46 is attached to the outside of the cleaning device casing 42. The tip of the cleaning rod 45 may be equipped with a scraper head, or the rod's outer diameter may be adjusted to match the inner diameter of the perforated pipe 44. By operating the handle 46 to push the cleaning rod 45 into the reactor cavity, by-product gel adhering to the inner wall of the perforated pipe 44 can be scraped off and removed, thereby cleaning the perforated pipe 44. The handle 46 can be manually operated or connected to an automatic device to automatically push the cleaning rod 45 out at regular intervals to clean the perforated pipe 44. Periodic cleaning allows the by-product gel to be removed before it accumulates, ensuring smooth supply of the mixed amine solution. Note that even small amounts of gel fragments do not substantially affect the polymer solution. The diameter of each mixed amine supply port 4 is large enough to supply the entire required amount of mixed amine solution into the reactor cavity, and even when one perforated pipe 44 is being cleaned, the other perforated pipe continues normal operation. This allows the two supply ports to be cleaned alternately, without causing back pressure or interruption of the mixed amine solution flow due to the cleaning operation.

[0043] The operation process of the reactor in this embodiment is as follows: During operation of the reactor of the present invention, the interior of the reactor can be divided into three sections, Zone A, Zone B, and Zone C, along the direction of liquid flow during operation. Zone A is the feed and premixing zone of the reactor, and includes the prepolymer feed port 3, the mixed amine feed port 4, the bottom of the mixing section 22, and the first blade group 23. Zone B is the mixing zone of the reactor, and includes the first stator group 14 and the second blade group 24. Zone C is the discharge zone of the reactor, and includes the second stator group 15 and the third blade group 25. During operation of the reactor, the mixing intensity decreases from Zone A to Zone B and then to Zone C.

[0044] In region A, the prepolymer solution and the mixed amine solution come into contact with each other and are initially mixed by the action of the first set of blades. The specific process is as follows:

[0045] A motor in the drive unit 6 rotates the rotor 2 at high speed via a transmission mechanism including couplings and bearings. The prepolymer solution, one of the reaction materials, is accurately metered by a metering pump (not shown) and supplied to the reactor cavity through the prepolymer supply port 3 at the first end face 11 of the casing. The centrifugal force of the rotor 2 and the thrust of the metering pump continuously and uniformly transport the prepolymer solution to the right along the smooth mixing section 22. Because the bottom of the mixing section 22 occupies most of region A, a liquid film of prepolymer solution forms on the surface of the rotor mixing section 22. Meanwhile, the mixed amine solution is injected from the mixed amine supply port 4 onto the side along the bottom edge of the mixing section 22. In this region, the reaction between the prepolymer and the mixed amine solution proceeds very rapidly. As the flowing prepolymer liquid film intersects with the mixed amine solution jet, it is sheared and divided into multiple small-volume units by the first blade set 23, rotating at 1800 rpm, promoting accurate mixing ratios of the prepolymer solution and the mixed amine solution. At the same time, the reactants are quickly dispersed and propelled by the driving force of the prepolymer metering pump and the mixed amine solution metering pump, and by the closely spaced first blade group 23, which prevents the generation of gel by-products due to local deviations in the blending ratio near the mixed amine supply port 4, thereby preventing the gel from affecting subsequent reactions.

[0046] The mixed amine feed port 4 is equipped with an automatic cleaning device 41 to prevent backflow, which can occasionally cause the mixed amine feed port 4 to become clogged with a high-viscosity polymer solution. The mixed amine solution is supplied through the mixed amine inlet pipe 43 and reaches the reactor cavity via the perforated pipe 44. An operator or an automated device periodically operates and pulls the handle 46, causing the cleaning rod 45 to reciprocate within the perforated pipe 44, scraping off the high-viscosity polymer adhering to the inner wall and clearing the clog in the mixed amine feed port 4. While one perforated pipe 44 is being cleaned, the other is in normal operation. This allows the two feed ports to be cleaned alternately, avoiding backpressure and fluid interruptions during cleaning. Preferably, cleaning operations are performed at least six times per hour for each mixed amine feed port to prevent large amounts of by-product gel from accumulating in any of the feed ports.

[0047] After passing through the first blade set 23, the prepolymer solution and the mixed amine solution have completed initial mixing and reaction, but have not yet reached complete reaction. The initial polymer produced by the reaction increases the viscosity of the mixed liquid in the reactor, and the liquid continues to flow to the right along the surface of the mixing section 22 and enters region B.

[0048] When the initial prepolymer formed in region A passes through the second blade set 24 above the mixing section 22, the second blade set 24 again stirs the mixed liquid in the cavity, allowing the NCO groups in the unreacted prepolymer and the NH groups in the mixed amine solution to thoroughly mix, contact, and react. The diameter of the mixing section 22 is narrowed at the position of the second blade set 24, and the diameter of the cavity is also narrowed in this area, resulting in a correspondingly smaller stirring radius of the second blade set 24. Furthermore, because the number of blades in the second blade set 24 is small, heat generation due to stirring of the viscous polymer by the second blade set 24 is reduced, allowing the rotor rotation speed to be increased, resulting in more uniform mixing and improved mixing efficiency. Furthermore, because the diameter of the mixing section 22 in region B is larger than the diameter in region C and the cavity diameter is also narrower, the linear velocity of the liquid in the cavity as it flows from left to right in region B increases, shortening the residence time of the product polymer as it moves from region B to the polymer discharge port 5 in region C.

[0049] In zone C, the mixed liquid after passing through the second blade set 24 has almost completed the reaction, resulting in a polymer liquid. At this point, the viscosity of the resulting polymer liquid has further increased, and the polymer liquid flows to the right along the surface of the mixing section 22. It then passes through the third blade set 25, further completing the reaction and assisting the polymer liquid in being discharged from the polymer outlet. Furthermore, in zone C, the polymer reaction is already complete, and the viscosity of the product is at its maximum, resulting in the greatest resistance experienced by the third blade set 25. The third blade set 25 also serves to increase 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 torque measurement indicates the magnitude of the resistance experienced by the third blade set 25, allowing the viscosity of the resulting polymer solution to be measured. A temperature sensor and a pressure sensor are installed at the reactor outlet and connected to the polymer discharge pump to stably control the pressure at the reactor outlet. The temperature sensor detects changes in the reaction temperature in real time and is used as one of the criteria for evaluating the progress and uniformity of the reaction.

[0050] To counteract the tendency of the viscous polymer to "climb" along the rotor axis (i.e., the Weissenberg effect) throughout the reaction process, the first and second stator groups 14 and 15 are installed on the interior walls of the chambers in Regions B and C, respectively. These stator groups are located close to the sides of the mixing section 22, homogenizing the mixture, redirecting the flow, and promoting internal circulation of the polymer material, resulting in more uniform mixing of the prepolymer and mixed amine solution and a more complete reaction. Furthermore, the small gaps between the stators and each group of blades in the rotor 2 allow the mixed liquid to be sufficiently compressed and sheared by the stators and rotor as it passes through the gaps, resulting in more uniform mixing of the prepolymer and mixed amine solution and a more complete reaction. The faces of each stator are angled relative to the axis of the rotor 2. This arrangement complicates the flow of the liquid within the chamber while minimizing the gap between the stators and the rotor blades, thereby reducing the stator volume and contributing to a lighter device.

[0051] The effects of the reactor according to this embodiment in actual use are as follows. The prepolymer was dissolved in dimethylacetamide, and a fixed amount was measured every hour and continuously fed to the reactor. The mixed amines required for polymerization were also dissolved in dimethylacetamide and fed in a measured amount every hour. The trial run continued for two weeks, and the prepolymer feed port was cleaned six times every hour. The results of periodic measurements of the final polymer produced were the following average values:

[0052] Characteristic viscosity: 1.0; Primary amine end content: 15.0%; Solid content: 35.0%; Volume viscosity calculated from melt flow index: 2450 poise.

[0053] After the test was completed, the reactor was disassembled to check its cleanliness, and no hard gel deposits were found in the mixed amine feed port or other parts of the reaction chamber.

[0054] As described above, the reactor of this embodiment, through the cooperative action of the casing 1, mixing section 22, and first blade set 23, shears and divides the mixture of prepolymer and mixed amine solution into numerous small units, thereby more accurately adjusting the blending ratio of the mixture within each unit and avoiding localized imbalances in the blending ratio. Furthermore, by designing the rotor 2 in the reactor cavity to have a conical shape, the rotational radius of the blades is reduced, reducing the linear shear velocity and shear radius of the viscous polymer and reducing heat generation due to mechanical stirring of the viscous polymer. As a result, the rotor rotation speed can be increased, improving mixing uniformity and reaction efficiency. Compared to conventional reactors, the reactor of this embodiment requires the liquid to pass through the gaps between each component in a film-like form during the flow process, thereby enabling a more compact and lightweight device. At the same time, the small rotational radius of the blades reduces the stirring resistance of the viscous material, allowing the rotor rotation speed to be increased to 1800 rpm, improving stirring and reaction efficiency. [Explanation of symbols]

[0055] 1 casing 11 casing first end face 12 Casing second end face 13 Casing surface 14 1st stator group 15 2nd stator group 16 Thermal jacket 17 Heat retention liquid inlet 18 Heat retention liquid outlet 2 rotors 21 Main shaft section 22 Mixing section 23 First feather group 24 Second group of feathers 25 Third feather group 3 Prepolymer supply port 4. Mixed amine feed port 41 Automatic cleaning device 42 Cleaning device casing 43 Mixed amine supply pipe 44 Porous pipe 45 Cleaning Rod 46 Handle 5 Polymer outlet 6. Drive unit

Claims

1. A continuous reactor for a spandex dry spinning dope, comprising a casing and a rotor, the casing being provided with a prepolymer inlet, a mixed amine inlet, and a polymer outlet; the casing includes a circumferential surface and at least one end surface; the rotor includes a main shaft portion and a mixing portion, the main shaft portion passes through the casing and is connected to a drive device; the mixing section is a portion of the rotor located inside the reactor cavity, the diameter of the mixing section gradually decreases from the side closer to the prepolymer supply port to the side closer to the polymer discharge port, and the gap between the bottom surface of the mixing section and the end surface of the casing is less than 5 mm; A continuous reactor characterized in that the mixing section is provided with at least a first set of blades and a second set of blades in this order along a direction in which the diameter of the mixing section decreases.

2. 2. The continuous reactor according to claim 1, wherein the gap between the end of the first set of blades farther from the rotor axis and the circumferential surface of the casing is less than 5 mm.

3. 2. The continuous reactor according to claim 1, wherein the radius of rotation of each set of blades becomes smaller in stages in a direction approaching the discharge port.

4. 2. The continuous reactor according to claim 1, wherein the prepolymer supply port is provided directly opposite to the bottom surface of the mixing section.

5. (1) (1) The mixed amine supply port is disposed directly opposite the position of the first blade set; (2) the mixed amine supply port is disposed between the prepolymer supply port and the first blade set; (3) The side of the first blade group close to the prepolymer supply port partially overlaps with the mixed amine supply port in a radial projection of the reactor; 2. The continuous reactor according to claim 1, wherein the relative positional relationship between the mixed amine supply port and the first blade group satisfies any one of the above (1) to (3).

6. 2. The continuous reactor according to claim 1, wherein the diameter of the cavity gradually decreases from the prepolymer supply port toward the polymer discharge port.

7. 2. The continuous reactor according to claim 1, wherein a set of stators is provided in the cavity of the reactor, and the set of stators is disposed between each set of blades.

8. 8. The continuous reactor according to claim 7, wherein the minimum gap between the stator and the mixing section is less than 5 mm, and the minimum gap between the stator and the blade adjacent thereto is less than 5 mm.

9. the mixed amine supply port is provided with an automatic cleaning device, the automatic cleaning device including a cleaning device casing, an inlet pipe, a perforated pipe and a cleaning rod; 2. The continuous reactor according to claim 1, wherein the perforated pipe has a plurality of openings, the cleaning rod extends from the outside of the cleaning device casing into the perforated pipe, and a handle for gripping is provided on the outside of the cleaning rod.

10. A method for a continuous chain extension reaction of polyurethane using the continuous reactor according to any one of claims 1 to 9, (1) introducing a prepolymer into the reactor cavity through a prepolymer supply port, and forming a liquid film having a thickness of less than 5 mm by the action of the casing and the bottom surface of the mixing section; (2) a step in which a mixed amine solution is sprayed from a mixed amine supply port and contacted with the liquid film while the liquid film is advancing; (3) when the liquid film contacts with the mixed amine solution, the first set of blades divides the mixture of the prepolymer and the mixed amine solution into a plurality of small units, and an initial reaction occurs within the small units; (4) The prepolymer and the mixed amine solution are continuously advanced by the metering pump and the impeller, and are sufficiently stirred by the impeller at each stage during the advancement process, to complete the chain extension reaction and the termination reaction, thereby obtaining a polymer; Here, the rotation speed of the blade is 300 to 3000 rpm, (5) A step in which the polymer after the reaction is completed is discharged from the reactor through a polymer discharge port by the propulsion of a metering pump and impeller; A method for continuous chain extension reaction of polyurethane, comprising the above steps.

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