CN114481372A

CN114481372A - Method for recovering solvent in fiber spinning process and fiber spinning system

Info

Publication number: CN114481372A
Application number: CN202011148954.9A
Authority: CN
Inventors: 孔凡敏; 赵运生; 于品华; 张叶; 徐莉; 吴小莲; 苏豪
Original assignee: China Petroleum and Chemical Corp; Research Institute of Sinopec Nanjing Chemical Industry Co Ltd
Current assignee: China Petroleum and Chemical Corp; Research Institute of Sinopec Nanjing Chemical Industry Co Ltd
Priority date: 2020-10-23
Filing date: 2020-10-23
Publication date: 2022-05-13
Anticipated expiration: 2040-10-23
Also published as: CN114481372B

Abstract

The invention relates to a method and a spinning system for recovering a solvent in a fiber spinning process, wherein the fiber spinning process comprises the steps of extruding and spinning a spinning solution, sequentially carrying out a cooling forming process, a drying process and a stretching process on fiber precursors obtained by spinning, and recovering the solvent in the cooling forming process and the drying process, and is characterized in that the cooling forming process comprises the steps of contacting the fiber precursors with a fluid with the temperature of not more than-10 ℃, the solvent in the cooling forming process is recovered in a cyclone separation mode, and the solvent in the drying process is recovered in a mode of combining cryogenic separation and adsorption desorption. The invention recovers the solvent in the solution by different processes in different modes, and can realize lower energy consumption and higher solvent recovery rate.

Description

Method for recovering solvent in fiber spinning process and fiber spinning system

Technical Field

The invention relates to the field of fiber spinning, in particular to a method for recovering a solvent in a fiber spinning process and a fiber spinning system.

Background

Since the technology for producing ultra-high molecular weight polyethylene fibers by a gel spinning method is invented by P.Smith and P.J.Lemstra of DSM company in the Netherlands in 1979, two process routes of dry spinning and wet spinning are formed in sequence through development of years, and large-scale industrialization is carried out worldwide.

CN109666976A proposes a method for improving the performance of polyethylene fiber products, which adopts a water bath quenching method to improve the degree of fiber crystal orientation, thereby improving the performance of the fiber.

Disclosure of Invention

The invention aims to overcome the problem of low solvent recovery rate in the prior art, and provides a novel method for recovering a solvent in a fiber spinning process and a fiber spinning system.

In order to achieve the above object, in one aspect, the present invention provides a method for recovering a solvent in a fiber spinning process, the fiber spinning process includes extruding and spinning a spinning solution, sequentially performing a cooling forming process, a drying process and a stretching process on fiber precursors obtained by spinning, and recovering the solvent in the cooling forming process and the drying process, wherein the solvent in the cooling forming process is recovered by a cyclone separation method, and the solvent in the drying process is recovered by a combination of cryogenic separation and adsorption desorption.

The invention provides a fiber spinning system, which comprises a melt extrusion unit, a spinning unit, a cooling and forming unit, a drying unit, a stretching unit, a winding unit and a solvent recovery unit, wherein the melt extrusion unit provides molten spinning raw materials for the spinning unit, the cooling and forming unit and the drying unit are respectively used for cooling and forming fiber precursors spun by the spinning unit and drying and removing solvents, the stretching unit is used for stretching the fiber precursors dried by the drying unit, and the solvent recovery unit is used for recovering the solvents; the device is characterized in that the solvent unit comprises a cyclone separation device, a cryogenic separation device and an adsorption and desorption device, the cyclone separation device is used for recovering the solvent in the cooling and forming unit, and the cryogenic separation device and the adsorption and desorption device are used for recovering the solvent in the drying process.

The invention recovers the solvent in the solution by different processes in different modes, and can realize lower energy consumption and higher solvent recovery rate. The invention can effectively improve the drying efficiency of materials and further improve the effect of fiber yarn products by the cooperation of the drying hot box with the air knife with a specific structure. And because the air output and the air output direction of the air knife air outlet are adjustable, the air knife is more flexible to use and can adapt to various use requirements. By adopting the method, the solvent recovery rate can reach more than 95%.

Drawings

FIG. 1 is a schematic structural view of an embodiment of an air knife according to the present invention;

FIG. 2 is a cross-sectional view of the inner and outer barrels of FIG. 1;

FIG. 3 is a schematic structural view of the movable flange of FIG. 1;

FIG. 4 is a schematic view of the mounting flange of FIG. 1;

FIG. 5 is a schematic diagram of the structure of one embodiment of the fiber spinning system of the present invention.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

In the present invention, unless otherwise specified, the use of directional terms such as "upper, lower, left, and right" generally refers to the orientation as shown in the drawings. "inner and outer" refer to the inner and outer contours of the respective component itself.

In the invention, the cooling forming process adopts a low-temperature quenching mode, so that the solvent volatility is low in the cooling forming process, the gas phase is basically free of the solvent, the mixed gas exists in the form of aerosol, and the gas can be separated from the coolant (especially the gas for cooling) and the solvent only by a simple separation mode of cyclone separation, so that the recycling of the coolant and the solvent is realized. The gas temperature in the drying section is high, the solvent is volatilized in a large amount, and the separation of the drying gas and the solvent can be better realized only by adopting a deep separation mode. Therefore, the invention adopts the mode of carrying out sectional treatment on return air with different temperature points, thereby realizing reasonable distribution of energy consumption in the system and leading the solvent recovery rate to reach more than 95 percent. Preferably, the deep separation mode is an integrated mode of cooling separation, cryogenic separation, compression, cooling separation and adsorption desorption, wherein the cooling separation temperature is controlled to be less than 40 ℃, and the cryogenic separation temperature is controlled to be less than-5 ℃, so that the solvent recovery rate is more than 95%, the gas is recycled, and the solvent is recycled. Therefore, in the present invention, the method of recovering the solvent in the fluid after the cooling molding is a cyclone separation method, and the method of recovering the solvent in the dry gas is a method of combining cryogenic separation and adsorption/desorption.

Preferably, the temperature of the cyclone separation is <40 ℃, preferably 10-30 ℃.

In the invention, the low-temperature quenching mode is to quench the fiber precursor sprayed out of the spinneret orifice by using fluid with the temperature not higher than-10 ℃. In the prior art, the gas with the temperature of more than 0 ℃ is used for cooling in both the dry method and the wet method. The inventor of the invention researches and discovers that although the temperature of the gas above 0 ℃ relative to the spinning (fiber precursor) sprayed by a nozzle is very low and the temperature difference is relatively large, the mechanical property and the product stability of the fiber product can be further improved by using the fluid below-10 ℃. The reason for this is probably because the melt is in a uniform state before entering the spinneret plate for extrusion, and the internal folding chain structure is stable; after extrusion, the surface is cooled and can be rapidly solidified and formed, the stable folding chain structure in the protofilament can not be changed, and after further heating and drawing, the folding chain in the protofilament can be gradually stretched into a stable lattice structure. Therefore, the quenching time of the protofilament is shortened, the internal stable structure of the fiber can be protected to the maximum extent, and the spinnability of the fiber is improved.

In theory, fluids at temperatures below-10 ℃ may be used in the present invention, but it is preferred that the temperature of the fluid used for cooling forming is-10 to-180 ℃, preferably-10 to-50 ℃, more preferably-20 to-30 ℃ in view of the combined energy consumption and fiber product performance.

The low-temperature wind is adopted to accelerate the curing of the gel strand silk, the lower the temperature is, the shorter the curing and forming time is, thereby ensuring that the gel strand silk is not interfered by the wind speed, keeping the stable structure inside the gel strand silk and effectively avoiding the adhesion condition of the gel strand silk.

The fluid may be a gas or a liquid, and any inert fluid that does not react with the filament product and adversely affect the filament product may be used to achieve the objectives of the present invention. For example, it may be one or more of liquid ammonia, liquid nitrogen, air, an aqueous ethylene glycol solution, an aqueous ethanol solution, and the like.

In the present invention, the fluid for cooling molding is preferably a gas. For the dry spinning process, inert gases such as nitrogen and the like are adopted, and air is not used.

The contact is preferably performed by blowing, and the blowing is preferably performed by circular blowing around the blown fiber strand. The so-called circular blowing is to blow a quench fluid formed by cooling around the fiber strand to sufficiently cool the fiber strand.

According to a preferred embodiment of the invention, the blowing time is from 0.1 to 1 second, preferably from 0.5 to 0.7 second, and the pressure is from 0 to 100kPa, preferably from 3 to 10 kPa. The time of blowing is the time period from the start of contact of the filament with the quench fluid to the exit of the quench fluid. The pressure here means the pressure at which the quench fluid flows out, and is a gauge pressure.

In the invention, the blowing process is a continuous and stable process, the blowing effect is related to the stretching speed of the spray head, and the faster the speed is, the shorter the blowing time on the unit filament bundle is. When the stretch ratio of the nozzle is 8 times, the nozzle extrusion rate is preferably 2 to 5m/min, more preferably 3 to 3.5 m/min.

The low-temperature and ring-blowing dry air quenching forming mode provided by the invention can be suitable for the existing wet process and can also be suitable for the dry process. Preferably suitable for dry processes. The combination of the above-described quench molding method with the dry process is further described below.

Preferably, the mode of combining cryogenic separation and adsorption and desorption is to perform cryogenic separation first and then perform adsorption and desorption.

Preferably, the temperature of the cryogenic separation is < -5 ℃, preferably between-20 and-10 ℃.

Preferably, the adsorption is performed by contacting the gas from the drying step with an adsorbent.

In the present invention, the volumetric space velocity of a gas means the volume of gas passing through a unit volume of adsorbent per unit time.

According to a preferred mode of the invention, the adsorbent is one or more of activated carbon, coconut shell carbon and molecular sieve, and cylindrical activated carbon with the diameter of 3-6mm is preferred.

Preferably, the desorption conditions comprise that the desorption temperature is 5-25 ℃ and the pressure is 0.1-5 MPa.

The method of the present invention is applicable to a dry spinning process as well as a wet spinning process, wherein the spinning solution is extruded and spun, and the drying process and the stretching process of the spun fiber precursor are sequentially performed with reference to the prior art.

The spinning dope generally comprises polyethylene, solvent and an auxiliary agent, preferably the weight ratio of polyethylene to solvent is from 1 to 30:100, preferably from 4 to 20:100, and the weight ratio of auxiliary agent to polyethylene is from 0.3 to 3:100, preferably from 0.5 to 2: 100.

The solvent is preferably one or more of decalin, tetralin, toluene, xylene, white oil and paraffin oil.

For convenience of description, the fiber filaments before stretching after spinning are called fiber precursor filaments or gel filaments, and the stretched product is called a fiber filament product.

In the invention, the fiber can be one or more of various plastic silk products, such as polyethylene, acrylic fiber and the like.

The spinning aid can be one or more of various materials that aid in spinning, such as antioxidants, plasticizers, modifiers, and lubricants.

In the present invention, the stretching ratio of the stretching is 160-. The stretching may be carried out once or in a plurality of times, preferably in a plurality of times. When the stretching is carried out in a plurality of times, the above stretching ratio means a total stretching ratio.

The draw ratio is the length of the fiber product after drawing/the length of the fiber strand after cooling molding.

Preferably, the nozzle stretching is 6-9 times, the pre-spinning pre-drafting multiplying power is 3-3.5 times, and the post-spinning drafting multiplying power is 7-8 times.

Preferably, the method of the present invention further comprises winding the drawn filament product for convenient product storage.

In the invention, the cooling and forming mode comprises the step of contacting the fiber strands with a fluid with the temperature not higher than-10 ℃. Preferably, the temperature of the fluid used for cooling shaping is-10 to-180 ℃, preferably-10 to-50 ℃, more preferably-20 to-30 ℃.

Preferably, the fluid is a gas, and the contact is performed by blowing, and the blowing is performed by circular blowing with the fiber strand as a center. Preferably, the blowing time is from 0.5 to 0.7 seconds and the pressure is from 0 to 100kPa, preferably from 3 to 10 kPa.

Preferably, the fluid for cooling and forming is one or more of liquid nitrogen, air and inert gas.

Preferably, the drying means comprises contacting the cooled and shaped fiber strands with a drying gas at a speed of not less than 20 m/s, preferably 30-40 m/s.

Preferably, the temperature of the drying gas is between 0 and 140 ℃, preferably between 40 and 80 ℃.

The invention provides a fiber spinning system, which comprises a melt extrusion unit, a spinning unit, a cooling and forming unit, a drying unit, a stretching unit, a winding unit and a solvent recovery unit, wherein the melt extrusion unit provides molten spinning raw materials for the spinning unit, the cooling and forming unit and the drying unit are respectively used for cooling and forming fiber precursors spun by the spinning unit and drying and removing a solvent, the stretching unit is used for stretching the fiber precursors dried by the drying unit, and the solvent recovery unit is used for recovering the solvent; the device is characterized in that the solvent unit comprises a cyclone separation device, a cryogenic separation device and an adsorption and desorption device, the cyclone separation device is used for recovering the solvent in the cooling and forming unit, and the cryogenic separation device and the adsorption and desorption device are used for recovering the solvent in the drying process.

Preferably, the cryogenic separation device and the adsorption and desorption device are sequentially connected and used for sequentially carrying out cryogenic separation and adsorption and desorption separation on the solvent in the drying procedure; preferably, the cryogenic separation device comprises a cooler, a chiller and a gas-liquid separator which are connected in sequence.

Preferably, the adsorbent in the adsorption and desorption device is one or more of activated carbon, coconut shell carbon and molecular sieve, and cylindrical activated carbon with the diameter of 3-6mm is preferred.

The air knife 60 comprises an inner cylinder 61 and an outer cylinder 62 which are coaxially sleeved, one end of the inner cylinder 61 is in an open shape to form an air inlet 611 of the air knife 60, a first air outlet 612 communicated with the air inlet 611 is formed in the cylinder wall of the inner cylinder 61, a second air outlet 621 (the second air outlet 621 is an air outlet of the air knife 60) is formed in the cylinder wall of the outer cylinder 62, a radial interval is formed between the inner cylinder 61 and the outer cylinder 62 to form a communication channel 63 communicated with the first air outlet 612 and the second air outlet 621, and at least one of the inner cylinder 61 and the outer cylinder 62 is arranged to move along the radial direction of the air knife 60 to adjust the air output and the air outlet direction of the second air outlet 621.

In the above, it can be understood that, in use, the wind can enter the inner barrel 61 through the wind inlet 611, then enter the communication channel 63 through the first wind outlet 612, and finally exit through the second wind outlet 621. When the inner cylinder 61 is moved to gradually approach the second air outlet 621, the air outlet volume of the second air outlet 621 is gradually reduced; when the inner barrel 61 is moved to be gradually away from the second outlet 621, the air outlet volume of the second outlet 621 is gradually increased. When the wall of the inner cylinder 61 partially covers the second outlet 621, the air outlet direction of the second outlet 621 can be changed.

At least one of the inner cylinder 61 and the outer cylinder 62 is provided to be movable in the radial direction of the air knife 60, and includes the following three modes: the first is that the outer cylinder 62 is fixed, and the inner cylinder 61 is arranged to be movable relative to the outer cylinder 62 in the radial direction of the air knife 60; the second is that the inner cylinder 61 is fixed, and the outer cylinder 62 is arranged to be movable relative to the inner cylinder 61 in the radial direction of the air knife 60; the third is to arrange the inner cylinder 61 and the outer cylinder 62 to be movable relative to each other in the radial direction of the air knife 60.

By adopting the technical scheme, the air knife 60 can adjust the air outlet quantity and the air outlet direction of the air knife air outlet, so that the air knife 60 is more flexible to use and can adapt to various use requirements, and when the air knife is applied to a drying hot box, the drying efficiency and the drying effect on materials can be effectively improved.

In the present invention, the first outlet 612 and the second outlet 621 may have any suitable shape and arrangement position as long as the above-mentioned functions can be achieved. For example, the cross-sections of the first air outlet 612 and the second air outlet 621 may be oval, square, and the like, and the first air outlet 612 and the second air outlet 621 may be arranged at intervals in the axial direction and/or the circumferential direction of the air knife 60. Of course, the first air outlet 612 and the second air outlet 621 may be a plurality of air outlets.

According to a preferred embodiment of the present invention, referring to fig. 1 and 2, the first outlet port 612 and the second outlet port 621 are respectively one, the first outlet port 612 is an elongated strip extending in the axial direction of the inner tube 61, and the second outlet port 621 is an elongated strip extending in the axial direction of the outer tube 62. In this case, the first outlet port 612 and the second outlet port 621 are offset from each other in the circumferential direction of the air knife 60, that is, the first outlet port 612 and the second outlet port 621 are preferably not aligned, so that the air entering the inner cylinder 61 is prevented from being discharged from the first outlet port 612 and then directly discharged from the second outlet port 621.

Preferably, as shown in fig. 2, the first outlet 612 and the second outlet 621 are arranged back to back in the circumferential direction of the air knife 60.

In addition, the cross-sections of the first air outlet 612 and the second air outlet 621 are preferably rectangular, and the opening angles of the first air outlet 612 and the second air outlet 621 in the circumferential direction of the air knife 60 are 0 to 90 °, and preferably 25 to 40 °.

In the present invention, in order to prevent the wind entering the wind knife 60 from being discharged from the inner cylinder 61 and/or other ports of the communication channel 63, one end of the inner cylinder 61 facing away from the wind inlet 611 is closed, and both ends of the communication channel 63 are closed. The inner cylinder 61 can be closed by an end wall integral with the wall thereof, or by a mounting assembly (described below) or other structure (such as a hot drying box described below) to which an air knife is to be mounted; the closure of the communication channel 63 may be closed by means of a mounting assembly or other structure to which the air knife is to be mounted.

In the present invention, in order to integrate the inner cylinder 61 and the outer cylinder 62 into a whole and facilitate the integral assembly and disassembly of the air knife 60, the air knife 60 may further include a mounting assembly for mounting the inner cylinder 61 and the outer cylinder 62. The mounting assembly can be any component that can integrate the inner cylinder 61 with the outer cylinder 62 and allow movement of the inner cylinder 61 and/or the outer cylinder 62.

In order to simplify the structure of the air knife 60 and reduce the manufacturing cost of the air knife 60, according to a preferred embodiment of the present invention, the outer cylinder 62 is fixed, and the inner cylinder 61 moves relative to the outer cylinder 62 along the radial direction of the air knife 60, as shown in fig. 1, the mounting assembly may include two movable flanges 64 respectively mounted at two ends of the inner cylinder 61 and two fixed flanges 65 respectively mounted at two ends of the outer cylinder 62, the two movable flanges 64 are respectively connected with the two fixed flanges 65 (i.e., the movable flange 64 and the fixed flange 65 at the same end of the air knife 60 are connected), and the two movable flanges 64 are configured to be lockably movable relative to the corresponding fixed flanges 65 along the radial direction of the air knife 60.

Wherein, the movable flange 64 is hermetically mounted on the inner cylinder 61, and the fixed flange 65 is hermetically mounted on the outer cylinder 62. As shown in fig. 3 and 4, the movable flange 64 has a mounting hole for mounting the inner cylinder 61, and the fixed flange 65 has a mounting hole for mounting the outer cylinder 62, and since the diameter of the inner cylinder 61 is smaller than that of the outer cylinder 62, the diameter of the mounting hole of the movable flange 64 is smaller than that of the mounting hole of the fixed flange 65.

As shown in fig. 1, the movable flange 64 is located outside the fixed flange 65, two ends of the inner cylinder 61 are respectively and sequentially inserted into the mounting holes of the fixed flange 65 and the movable flange 64, and two ends of the outer cylinder 62 are respectively and sequentially inserted into the mounting holes of the fixed flange 65. In this case, both ends of the communication passage 63 may be respectively closed by two movable flanges 64.

In the above description, it should be noted that, referring to fig. 1, the left end face of the inner cylinder 61 may extend out of the left movable flange 64, may be located inside the movable flange 64, or may be flush with the left end face of the movable flange 64. The right end face of the inner cylinder 61 can extend out of the right movable flange 64 and can be flush with the right end face of the movable flange 64, and in the two cases, the right end port of the inner cylinder 61 can be closed by an end wall integrated with the cylinder wall of the inner cylinder or by other structures to be provided with the air knife 60; the right end face of the inner cylinder 61 may also be located in a movable flange 64 on the right side, in which case the right end port of the inner cylinder 61 may be closed by an end wall integral with the cylinder wall thereof, or by the movable flange 64, that is, the mounting hole of the movable flange 64 for mounting the inner cylinder 61 is not a through hole but a semi-closed hole having a right side wall.

Further, as shown in fig. 3 and 4, the movable flange 64 and the fixed flange 65 may be connected by a fastener, the movable flange 64 and the fixed flange 65 are respectively provided with a through hole for the fastener to penetrate through, the through hole on the movable flange 64 is a circular hole 641, and the through hole on the fixed flange 65 is an oblong hole 651.

In the above, it should be noted that the diameter of the circular hole 641 is adapted to the diameter of the fastening member, the oblong hole 651 has a small diameter adapted to the diameter of the fastening member and a large diameter larger than the diameter of the fastening member. The fastener locks and connects the movable flange 64 to the fixed flange 65 by locking the circular hole 641 at a certain position of the oblong hole 651 in the extending direction of the oblong hole 651. The extending direction of the oblong hole 651 is the moving direction of the inner cylinder 61. For example, as shown in fig. 4, the oblong hole 651 extends in a vertical direction, and in this case, the inner cylinder 61 and the movable flange 64 can move up and down in the vertical direction with respect to the outer cylinder 62 and the fixed flange 65, and the first air outlet 612 and the second air outlet 621 are located in the vertical direction.

For strengthening the connection, as shown in fig. 3 and 4, the movable flange 64 may be provided with a plurality of circular holes 641, and the fixed flange 65 may be correspondingly provided with a plurality of oblong holes 651, wherein the plurality of oblong holes 651 extend in the same direction.

In use, the fasteners can be loosened, moved to the desired position with the inner barrel 61 and the movable flange 64, and tightened again to lock the movable flange 64 to the fixed flange 65.

In the present invention, the fastening member may be any member capable of connecting the movable flange 64 to the fixed flange 65. For example, the fasteners are bolts, in which case the round holes 641 and the oblong holes 651 may be threaded holes.

In a second aspect of the present invention, the hot drying box 6 includes a box body and an air knife 60, a drying cavity for drying a material is disposed in the box body, the air knife 60 is disposed in the drying cavity, a second air outlet 621 of the air knife 60 is disposed in alignment with the material, a feed port, a discharge port, a dry gas inlet, and a dry gas outlet which are communicated with the drying cavity are disposed on the box body, an air inlet 611 of the air knife 60 is communicated with the dry gas inlet, and the second air outlet 621 of the air knife 60 is communicated with the dry gas outlet.

When the air drying device is used, the air output and the air outlet direction of the air knife 60 can be adjusted as required, the dry air inlet enters the dry air in the drying cavity to enter the air knife 60 through the air inlet 611, and the dry air is intensively blown to the material by the air knife 60 in a certain air output and air outlet direction, so that the material is quickly dried.

Wherein, referring to fig. 5, the feed port and the discharge port are respectively located at two opposite sides of the box body (referring to the left and right sides of the drying heat box 6 shown in fig. 5), and the drying gas inlet and the drying gas outlet are respectively located at two opposite sides of the box body (referring to the upper and lower sides of the drying heat box 6 shown in fig. 5). A plurality of air knives 60 may be disposed in the drying chamber, and the air knives 60 extend in a direction perpendicular to the material feeding and discharging direction and are arranged at intervals along the material feeding and discharging direction (see the left and right direction shown in fig. 5). This can further improve the drying efficiency and effect.

In case that a plurality of air knives 60 are provided in the drying chamber, referring to fig. 5, a plurality of the dry gas inlets and dry gas outlets may be correspondingly provided on the cabinet. It is understood that the positions corresponding to the black arrows of the hot drying box 6 shown in fig. 5 are the dry gas inlet and the dry gas outlet.

Further, as shown in fig. 5, the drying unit may further include a heated roller-type stretching machine 5 and a non-heated roller-type stretching machine 7 which are respectively provided in front of and behind the hot drying box 6. The heated roller-type drawing machine 5 and the non-heated roller-type drawing machine 7 are preferably each a five-roller drawing machine. It should be noted that the roller drafting machine of the drying unit mainly plays a drying role, and does not apply a large drafting force to draft, and the drafting function thereof is negligible.

In the present invention, as shown in fig. 5, the melt extrusion unit may include a twin screw extruder 1, a booster pump 2, and a static mixer 3, the spinning unit may include a cooling fluid supply device and a spinning beam 4, the drawing unit may include a draw heat beam 8 and a draw machine 9, and the winding unit may include a winder 11.

The double-screw extruder 1 is used for performing melt extrusion on the spinning solution to form a stable melt; the booster pump 2 is used for applying a stable pressure output to the melt so as to ensure the stable output of the melt; the static mixer 3 is used for forming stable and uniform melt; the cooling fluid supply device is used for supplying cooling fluid to the spinning box 4 and carrying out quenching forming on fiber precursors sprayed from spinneret orifices (described below) in the spinning box 4; the spinning beam 4 is used for converting the melt into gel elastic fluid and simultaneously carrying out dry air quenching to form solid gel filaments (namely fiber precursor); the hot drafting box 8 and the drafting machine 9 are used for drafting the dried fiber precursor, wherein the hot drafting box 8 is used for hot drafting so as to realize solvent volatilization while drafting; the winder 11 is used to wind the drafted fiber strands.

In addition, the fiber spinning system may further include a oiling machine 10 for surface-oiling the fiber strands before the winding machine 11.

In the embodiment of the fiber spinning system shown in fig. 5, the black arrows represent the gas flow direction.

In the following examples, the fiber spinning system shown in fig. 1 was used, and included a twin-screw extruder, a spinning box, a hot five-roll drawing machine, a drying hot box, a five-roll drawing machine one, a drawing hot box, a five-roll drawing machine two, and a winding machine, which were connected in this order. Wherein the spinning box is internally provided with an annular pipeline for circular blowing, the opening ratio is 35 percent, the opening size is 5mm, the inner diameter of the spinning box is 1000 multiplied by 1200mm, the drying hot box comprises a box body and a plurality of air knives which are uniformly arranged along the axial direction of the box body (the material inlet and outlet direction), a certain distance is arranged between every two adjacent air knives, a drying cavity for drying materials is arranged in the box body, the air knives are arranged in the drying cavity, a second air outlet of the air knives is aligned with the materials, the box body is provided with a feed inlet, a discharge outlet, a drying gas inlet and a drying gas outlet which are communicated with the drying cavity, an air inlet is communicated with the drying gas inlet, the second air outlet is communicated with the drying gas outlet, the feed inlet and the discharge outlet are respectively positioned at two opposite sides of the box body, and the air knives comprise an inner cylinder and an outer cylinder which are coaxially sleeved, one end of the inner cylinder is in an opening shape to form an air inlet of the air knife, a first air outlet communicated with the air inlet is formed in the cylinder wall of the inner cylinder, the first air outlet is in a long strip shape extending along the axial direction of the inner cylinder, a second air outlet is formed in the cylinder wall of the outer cylinder, the second air outlet is in a long strip shape extending along the axial direction of the outer cylinder, a radial interval is formed between the inner cylinder and the outer cylinder to form a communication channel communicated with the first air outlet and the second air outlet, and the first air outlet and the second air outlet are staggered with each other in the circumferential direction of the air knife; the opening angle of the first air outlet and the opening angle of the second air outlet in the circumferential direction of the air knife are 40 degrees, and the inner barrel and the outer barrel can move along the radial direction of the air knife to adjust the air outlet amount and the air outlet direction of the second air outlet.

Firstly, mixing a solvent, polyethylene powder and a spinning auxiliary agent, pre-swelling the ultra-high molecular weight polyethylene powder, then, feeding the mixture into a double-screw extruder for sufficient dissolution and shearing, then, feeding the mixture into a static mixer through a booster pump, feeding the stabilized solution into a metering pump and a spinning box for extrusion, wherein the extrusion speed is 1-10 m/min, and ensuring the volatilization temperature of the solvent and the stable temperature of a spinneret plate after the extruded gel strips pass through a heat-insulating oil jacket (200 ℃). The gel strips passing through the heat-insulating oil jacket are rapidly formed by quenching through circular blowing dry air, the pressure of the circular blowing air is 0-50kPa, the temperature is-50 ℃ to-10 ℃, the rapidly quenched silk strips are rapidly cured and formed to form a stable folding chain state, the rapidly quenched silk strips enter a five-hot roller through a godet roller, the temperature is 30-100 ℃ through the heating of the five-hot roller, the solvent on the surface of the fiber is volatilized, the silk strips are sent into a drying hot box and rapidly volatilized by an air knife passing through the inside of the drying hot box, and the dry hot air sent out by the air knife is hot nitrogen. The temperature in the hot box is controlled at 40-150 ℃, then pre-drafting, drafting forming and rolling are carried out, and the total drafting multiplying power is 160-300 times.

Example 1

The mass/volume ratio of the raw material (polyethylene with the number average molecular weight of 425) to the solvent (decalin) is 8%, the mass percentage of the auxiliary agent (antioxidant: calcium stearate is 7:3 by weight, the same applies below) to the raw material is 0.8%, the swelling temperature is 98 ℃, the extrusion rate is 3m/min, the heat-insulating oil jacket is 200 ℃, the ring-blowing quenching temperature is-10 ℃ air, the time is 0.64s, the wind pressure is 5kPa, the hot roller temperature is 40 ℃, the drying hot box temperature is 40 ℃ (the wind knife wind temperature is 40 ℃, the wind speed is 30 m/s, and the wind pressure is 0.4MPa), the drawing hot box temperature is 125 ℃, the pre-drawing magnification is 3 times, the multi-stage drawing hot box temperature is 140-145 ℃, and the total drawing magnification is 200 times. The performance testing indexes of different batches of fiber products are shown in the following table 1. The solvent recovery adopts the mode of recovering the solvents at different temperature points in stages, a cyclone separator is adopted in a low-temperature area, an integrated mode of cooling separation, cryogenic separation, cooling separation and adsorption desorption is adopted in a high-temperature area, the temperature of the cyclone separation and the cooling separation is less than 40 ℃, the temperature of the cryogenic separation is less than-5 ℃, and the adsorbent is activated carbon. The solvent recovery was 97.17%.

TABLE 1

Example 2

The mass/volume ratio of the raw material (polyethylene with the number average molecular weight of 425) to the solvent (decahydronaphthalene) is 8 percent, the mass percentage of the auxiliary agent to the raw material is 0.8 percent, the swelling temperature is 98 ℃, the extrusion rate is 3.25m/min, the heat-insulating oil jacket is 200 ℃, the air with the ring-blowing quenching temperature of-15 ℃ is 0.54s, the air pressure is 4kPa, the hot roller temperature is 40 ℃, the drying hot box temperature is 40 ℃ (the air temperature of an air knife is 40 ℃, the air speed is 30 m/s, and the air pressure is 0.4MPa), the drawing hot box temperature is 125 ℃, the pre-multiplying factor drawing is 3 times, the multi-stage drawing hot box temperature is 140-. The fiber performance test indexes of different batches are shown in the following table 2. The solvent recovery adopts the mode of recovering the solvents at different temperature points in stages, a cyclone separator is adopted in a low-temperature area, an integrated mode of cooling separation, cryogenic separation, cooling separation and adsorption desorption is adopted in a high-temperature area, the temperature of the cyclone separation and the cooling separation is less than 40 ℃, the temperature of the cryogenic separation is less than-5 ℃, and the adsorbent is activated carbon. The solvent recovery was 97.22%.

TABLE 2

Example 3

The mass/volume ratio of a raw material (polyethylene with the number average molecular weight of 487) to a solvent (decalin) is 8%, the mass percentage of an auxiliary agent to the raw material is 0.8%, the swelling temperature is 98 ℃, the extrusion rate is 3.25m/min, the temperature of a heat-insulating oil jacket is 200 ℃, air with the ring-blowing quenching temperature of-20 ℃ is subjected to ring-blowing, the time is 0.7s, the wind pressure is 10kPa, the temperature of a hot roller is 50 ℃, the temperature of a drying hot box is 50 ℃ (the wind temperature of a wind knife is 50 ℃, the wind speed is 30 m/s, and the wind pressure is 0.4MPa), the temperature of a drawing hot box is 125 ℃, the pre-multiplying factor is 3 times, the temperature of a multi-stage drawing hot box is 140-145 ℃, and the total drawing multiplying factor is 220 times. The fiber performance test indexes of different batches are shown in the following table 3. The solvent recovery adopts the mode of recovering the solvents at different temperature points in stages, a cyclone separator is adopted in a low-temperature area, an integrated mode of cooling separation, cryogenic separation, cooling separation and adsorption desorption is adopted in a high-temperature area, the temperature of the cyclone separation and the cooling separation is less than 40 ℃, the temperature of the cryogenic separation is less than-5 ℃, and the adsorbent is activated carbon. The solvent recovery was 97.19%.

TABLE 3

Example 4

The mass/volume ratio of a raw material (polyethylene with the number average molecular weight of 487) to a solvent (decalin) is 8%, the mass percentage of an auxiliary agent to the raw material is 0.8%, the swelling temperature is 98 ℃, the extrusion rate is 3m/min, the heat-insulating oil jacket is 200 ℃, air with the quenching temperature of-25 ℃ is blown around, the time is 0.5s, the wind pressure is 0.4MPa, the hot roller temperature is 40 ℃, the drying hot box temperature is 40 ℃ (the wind knife wind temperature is 40 ℃, the wind speed is 30 m/s, and the wind pressure is 0.4MPa), the drawing hot box temperature is 125 ℃, the pre-multiplying factor drawing is 3 times, the multi-stage drawing hot box temperature is 140-145 ℃, and the total drawing multiplying factor is 220 times. The fiber performance test indexes of different batches are shown in the following table 4. The solvent recovery adopts the mode of recovering the solvents at different temperature points in stages, a cyclone separator is adopted in a low-temperature area, an integrated mode of cooling separation, cryogenic separation, cooling separation and adsorption desorption is adopted in a high-temperature area, the temperature of the cyclone separation and the cooling separation is less than 40 ℃, the temperature of the cryogenic separation is less than-5 ℃, and the adsorbent is activated carbon. The solvent recovery was 97.35%.

TABLE 4

Example 5

The mass/volume ratio of a raw material (polyethylene with the number average molecular weight of 487) to a solvent (tetrahydronaphthalene) is 6.5%, the mass percentage of an auxiliary agent to the raw material is 0.7%, the swelling temperature is 98 ℃, the extrusion rate is 3.25m/min, the temperature of a heat-insulating oil jacket is 200 ℃, the ring-blowing quenching temperature is-20 ℃ nitrogen, the time is 0.6s, the wind pressure is 5kPa, the temperature of a hot roller is 40 ℃, the temperature of a drying hot box is 80 ℃ (the wind temperature of a wind knife is 80 ℃, the wind speed is 40 m/s, and the wind pressure is 0.4MPa), the temperature of a drawing hot box is 125 ℃, the pre-drawing multiplying power is 3 times, the temperature of a multistage drawing hot box is 140-145 ℃, and the total drawing multiplying power is 220 times. The fiber performance test indexes of different batches are shown in the following table 5. The solvent recovery adopts the staged recovery mode of different temperature points, the low-temperature zone adopts a cyclone separator, the high-temperature zone adopts an integrated mode of cooling separation, cryogenic separation, cooling separation and adsorption desorption, the temperature of the cyclone separation and the cooling separation is less than 40 ℃, the temperature of the cryogenic separation is less than-5 ℃, and the adsorbent is coconut shell activated carbon. The solvent recovery rate was 98.0%.

TABLE 5

Example 6

The mass/volume ratio of a raw material (polyethylene with the number average molecular weight of 487) to a solvent (toluene) is 6.5%, the mass percentage of an auxiliary agent to the raw material is 0.7%, the swelling temperature is 98 ℃, the extrusion rate is 3.25m/min, the heat-insulating oil jacket is 200 ℃, the air with the ring-blowing quenching temperature of-10 ℃ is 0.6s, the air pressure is 5kPa, the hot roller temperature is 40 ℃, the drying hot box temperature is 60 ℃ (the air knife air temperature is 60 ℃, the air speed is 50 m/s, and the air pressure is 0.4MPa), the drawing hot box temperature is 125 ℃, the pre-magnification drawing is 3 times, the multi-stage drawing hot box temperature is 140-145 ℃, and the total drawing magnification is 300 times. The solvent recovery adopts the mode of recovering the solvents at different temperature points in stages, a cyclone separator is adopted in a low-temperature area, an integrated mode of cooling separation, cryogenic separation, cooling separation and adsorption desorption is adopted in a high-temperature area, the temperature of the cyclone separation and the cooling separation is less than 40 ℃, the temperature of the cryogenic separation is less than-5 ℃, and the adsorbent is a molecular sieve. The solvent recovery rate was 98.5%. The fiber performance test indexes of different batches are shown in the following table 6.

TABLE 6

Comparative example 1

The fiber filaments were prepared according to the method of example 4, except that the circular blowing manner was changed to the side blowing manner described in CN106544741B, the side blowing temperature was 10 ℃, the air knife structure was not installed in the drying hot box, and the performance indexes of the fibers obtained from different batches are shown in table 7 below.

TABLE 7

Comparative example 2

Spinning was carried out according to the method of example 4, except that a conventional drying oven was used, that is, no air knife structure was provided in the drying oven, and the fiber property test index is shown in table 8 below. The solvent recovery was 84%.

TABLE 8

Comparative example 3

Spinning was carried out as in example 4, except that the solvent recovery unit used two cyclones in series, i.e. the solvent of the drying unit was also separated and recovered using a cyclone. The solvent recovery was 55%.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. A method for recovering a solvent in a fiber spinning process comprises the steps of extruding and spinning a spinning solution, sequentially carrying out a cooling forming process, a drying process and a stretching process on fiber precursors obtained by spinning, and recovering the solvent in the cooling forming process and the drying process, and is characterized in that the cooling forming mode comprises the step of enabling the fiber precursors to be in contact with a fluid with the temperature not higher than-10 ℃, the solvent in the cooling forming process is recovered in a cyclone separation mode, and the solvent in the drying process is recovered in a combination mode of cryogenic separation and adsorption desorption.

2. A process according to claim 1, wherein the temperature of the cyclone separation is <40 ℃, preferably 10-30 ℃.

3. The method according to claim 1 or 2, wherein the cryogenic separation and the adsorption desorption are combined in such a way that the cryogenic separation is performed first and then the adsorption desorption is performed.

4. The method according to any one of claims 1-3, wherein the temperature of the cryogenic separation is < -5 ℃, preferably between-20 and-10 ℃.

5. The method according to any one of claims 1 to 4, wherein the adsorption is carried out by contacting the gas from the drying step with an adsorbent.

6. The method according to claim 5, wherein the adsorbent is one or more of activated carbon, coconut shell carbon, molecular sieve, preferably cylindrical activated carbon with a diameter of 3-6 mm.

7. The process according to any one of claims 1 to 6, wherein the desorption conditions comprise a desorption temperature of 5 to 25 ℃ and a pressure of 0.1 to 5 MPa.

8. The process according to any one of claims 1 to 7, wherein the dope comprises polyethylene, solvent and an auxiliary agent, the weight ratio of polyethylene to solvent being from 1 to 30:100, preferably from 4 to 20:100, and the weight ratio of auxiliary agent to polyethylene being from 0.3 to 3:100, preferably from 0.5 to 2: 100.

9. The method of claim 8, wherein the solvent is one or more of decalin, tetralin, toluene, xylene, white oil, and paraffin oil.

10. The method of any of claims 1-9, wherein the cooling and shaping comprises contacting the fiber filaments with a fluid having a temperature of no more than-10 ℃.

11. A method according to claim 10, wherein the temperature of the fluid used for cooling the shape is-10 to-180 ℃, preferably-10 to-50 ℃, more preferably-20 to-30 ℃.

12. A method according to claim 10 or 11, wherein the fluid is a gas and the contacting is by blowing, preferably by ring blowing around the filaments.

13. The process according to claim 12, wherein the blowing time is 0.5 to 0.7 seconds and the pressure is 0 to 100kPa, preferably 3 to 10 kPa.

14. The method according to any one of claims 10-13, wherein the fluid used for cooling the shape is one or more of liquid nitrogen, air, inert gas.

15. The method according to any one of claims 1 to 14, wherein the drying comprises contacting the cooled and shaped fiber strands with a drying gas at a speed of not less than 20 m/s, preferably 30 to 40 m/s,

16. A fiber spinning system comprises a melt extrusion unit, a spinning unit, a cooling forming unit, a drying unit, a stretching unit, a winding unit and a solvent recovery unit, wherein the melt extrusion unit provides molten spinning raw materials for the spinning unit, the cooling forming unit and the drying unit are respectively used for cooling forming and drying and removing solvents for fiber precursors spun by the spinning unit, the stretching unit is used for stretching the fiber precursors dried by the drying unit, and the solvent recovery unit is used for recovering the solvents; the device is characterized in that the solvent unit comprises a cyclone separation device, a cryogenic separation device and an adsorption and desorption device, the cyclone separation device is used for recovering the solvent in the cooling and forming unit, and the cryogenic separation device and the adsorption and desorption device are used for recovering the solvent in the drying process.

17. The system according to claim 16, wherein the cryogenic separation device and the adsorption and desorption device are connected in sequence and are used for carrying out cryogenic separation and adsorption and desorption separation on the solvent in the drying process in sequence; preferably, the cryogenic separation device comprises a cooler, a chiller and a gas-liquid separator which are connected in sequence.

18. The system of claim 16 or 17, wherein the adsorbent in the adsorption desorption device is one or more of activated carbon, coconut shell carbon, molecular sieve, preferably cylindrical activated carbon with a diameter of 3-6 mm.

19. The system according to any one of claims 16 to 18, wherein the drying unit comprises a drying hot box, the drying hot box comprises a box body and an air knife (60), a drying cavity for drying the material is arranged in the box body, the air knife (60) is arranged in the drying cavity, the air knife (60) comprises an inner cylinder (61) and an outer cylinder (62) which are coaxially sleeved, one end of the inner cylinder (61) is open to form an air inlet (611) of the air knife (60), a first air outlet (612) communicated with the air inlet (611) is formed in the wall of the inner cylinder (61), a second air outlet (621) is formed in the wall of the outer cylinder (62), a radial interval is formed between the inner cylinder (61) and the outer cylinder (62) to form a communication channel (63) communicated with the first air outlet (612) and the second air outlet (621), at least one of the inner barrel (61) and the outer barrel (62) is set to be capable of moving along the radial direction of the air knife (60) so as to adjust the air output and the air outlet direction of the second air outlet (621), the second air outlet (621) of the air knife (60) is aligned to the material setting, a feed inlet, a discharge outlet, a dry gas inlet and a dry gas outlet which are communicated with the drying cavity are formed in the box body, the air inlet (611) is communicated with the dry gas inlet, and the second air outlet (621) is communicated with the dry gas outlet.

20. The system according to claim 19, wherein the first air outlet port (612) is elongated in the axial direction of the inner cylinder (61), the second air outlet port (621) is elongated in the axial direction of the outer cylinder (62), and the first air outlet port (612) and the second air outlet port (621) are offset from each other in the circumferential direction of the air knife (60); and/or one end of the inner cylinder (61) departing from the air inlet (611) is closed, and two ends of the communication channel (63) are closed.

The first air outlet (612) and the second air outlet (621) are arranged back to back in the circumferential direction of the air knife (60), and/or

The opening angles of the first air outlet (612) and the second air outlet (621) in the circumferential direction of the air knife (60) are 20-60 degrees.