Flash spinning nozzle and spinning method using same

Abstract

The invention relates to a flash spinning nozzle which comprises a split-phase chamber, a liquid inlet pipeline and a spinning nozzle are arranged at the two ends of the split-phase chamber respectively, homogeneous spinning liquid enters the split-phase chamber from the liquid inlet pipeline and then reaches the spinning nozzle to be sprayed out, an injection port is formed in the peripheral wall of the liquid inlet pipeline, and the injection port is communicated with the liquid inlet pipeline. The injection port is used for injecting a solvent into the liquid inlet pipeline, and the solvent is not dissolved in the homogeneous spinning solution in the state that the homogeneous spinning solution is located. The flash spinning nozzle is provided with the injection port, and the solvent insoluble in the homogeneous spinning solution is injected into the homogeneous spinning solution through the injection port, so that the homogeneous spinning solution is subjected to phase separation, and then spinning is realized; according to the flash spinning nozzle, the homogeneous spinning solution is subjected to phase separation in a solvent injection mode instead of a pressure reduction mode of a throttling valve and a pressure reduction chamber in a traditional nozzle, so that the flash spinning nozzle can be suitable for homogeneous spinning solutions of different formulas, and the flash spinning nozzle is higher in adaptability.

Description

Technical Field

[0001] The invention relates to the field of non-woven fabric preparation, in particular to a flash spinning nozzle and a spinning method using the nozzle. Background Art

[0002] Functional nonwoven materials produced using flash spinning technology boast numerous structural advantages, including fine fiber diameter, large specific surface area, high material crystallinity, and a three-dimensional continuous structure. These materials offer excellent waterproofing, breathability, weather resistance, tear resistance, high reflectivity, and barrier properties against particles and bacteria. DuPont's Tyvek is a commercial product successfully produced using flash spinning. The technology involves dissolving high-density polyethylene (HDPE) in a low-boiling-point solvent, chlorofluorocarbon, under high temperature and pressure to form a homogeneous spinning solution. Prior to spinning, the solution passes through a pressure-reducing chamber, causing phase separation into a two-phase region. The separated two-phase solution is then ejected through a spinneret at near-sonic speed to room temperature and pressure. The chlorofluorocarbon rapidly vaporizes, absorbing heat, while the HDPE precipitates, forming micro- and nanofiber filaments. The fibers are then spread onto a felt and then heat-pressed to form a dense, high-strength nonwoven material. The key to this technology is the phase separation of the homogeneous spinning solution through rapid depressurization, which relies on a flash spinning nozzle. The flash spinning nozzle consists of a throttle valve, a depressurization chamber, and a spinneret. During the flash spinning process, the homogeneous spinning solution passes through the throttle valve and enters the depressurization chamber with an increased volume, causing the homogeneous spinning solution to be rapidly depressurized. After phase separation, the homogeneous spinning solution is ejected from the spinneret to achieve flash spinning.

[0003] In current technology, a homogeneous spinning solution of a certain formulation must be reduced to a specific pressure through a specific flash spinning nozzle to achieve phase separation and complete flash spinning. To flash spin homogeneous spinning solutions of different formulations, the throttle valve, pressure reduction chamber, and spinning nozzle geometry must be modified to adapt the solution to the desired formulation. This adaptation process is complex and inefficient. Summary of the Invention

[0004] The first technical problem to be solved by the present invention is to provide a flash spinning nozzle which can be used for homogeneous spinning solutions with different formulations and has high adaptability in view of the current status of the existing technology.

[0005] The second technical problem to be solved by the present invention is to provide a spinning method using the above-mentioned flash spinning nozzle in view of the current status of the existing technology.

[0006] The technical solution adopted by the present invention to solve the first technical problem mentioned above is: the flash spinning nozzle includes a phase separation chamber, and a liquid inlet pipe and a spinneret are respectively provided at both ends of the phase separation chamber. The homogeneous spinning liquid enters the phase separation chamber from the liquid inlet pipe and then reaches the spinneret for spraying out. It is characterized in that: an injection port is provided on the peripheral wall of the liquid inlet pipe, and the injection port is used to inject a solvent into the liquid inlet pipe, and the solvent is insoluble in the homogeneous spinning liquid when the homogeneous spinning liquid is in the state.

[0007] In order to uniformly inject the solvent into the homogeneous spinning solution, the number of the injection ports is 3 to 8, and they are distributed at equal distances along the circumference of the side wall of the liquid inlet pipe.

[0008] In order to separate the different components of the spinning solution, the solvent is liquid carbon dioxide or liquid nitrogen, and the mass of the solvent is 0.5-5% of the mass of the homogeneous spinning solution. The solvent does not affect the recovery of the organic solvent in the homogeneous spinning solution after spinning is completed.

[0009] In order to control the phase separation process of the homogeneous spinning solution with different components, the injection port is connected to an injection pump, and the volume of the solvent is accurately controlled by the injection pump.

[0010] In order to improve the mixing of various substances in the phase separation chamber, the phase separation chamber is a static mixer, and a mixing element is provided inside the static mixer. The static mixer includes a first conical section, a cylindrical section and a second conical section. The small diameter end of the first conical section is connected to the outlet of the liquid inlet pipe, the large diameter end of the first conical section is connected to the first end of the cylindrical section, the large diameter end of the second conical section is connected to the second end of the cylindrical section, and the small diameter end of the second conical section is connected to the spinneret.

[0011] Furthermore, the diameter of the cylindrical section ranges from 12 to 50 mm, and the length of the cylindrical section is 4 to 40 times the diameter of the cylindrical section. The length of the cylindrical section being much greater than the diameter of the cylindrical section is beneficial to the mixing of various substances in the phase separation chamber.

[0012] Furthermore, the diameter of the liquid inlet pipe is 5 to 10 mm.

[0013] Furthermore, the ratio of the length of the first conical section to the length of the cylindrical section is 1:10 to 1:5.

[0014] Furthermore, the ratio of the length of the second conical section to the length of the cylindrical section is 1:10 to 1:5.

[0015] The technical solution adopted by the present invention to solve the above second technical problem is: a spinning method using the above nozzle is characterized in that it includes the following steps:

[0016] (1) mixing a polymer and a solvent to form a spinning mixture of a first concentration;

[0017] (2) mixing the spinning mixture at a first pressure and a first temperature to form a homogeneous spinning solution;

[0018] (3) the homogeneous spinning solution enters the liquid inlet pipe, and a certain amount of the solvent is injected into the homogeneous spinning solution in the liquid inlet pipe through the injection port, so that the homogeneous spinning solution forms a two-phase spinning mixture;

[0019] (4) The two-phase spinning mixture enters the phase separation chamber and is mixed in the phase separation chamber, and then is ejected from the spinneret to form fiber plexifilaments.

[0020] Compared with the prior art, the advantages of the present invention are: the flash spinning nozzle of the present invention is provided with an injection port, through which a solvent insoluble in the homogeneous spinning solution is injected into the homogeneous spinning solution, so that the homogeneous spinning solution undergoes phase separation, thereby achieving spinning; the present invention uses the method of injecting solvent to cause the homogeneous spinning solution to undergo phase separation, replacing the pressure reduction method of the throttle valve and the pressure reduction chamber in the traditional nozzle to cause the homogeneous spinning solution to undergo phase separation, so that the flash spinning nozzle of the present invention can be suitable for homogeneous spinning solutions of different formulations, so the flash spinning nozzle of the present invention is more adaptable. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 2 is a cross-sectional view of a flash spinning nozzle in Example 1 of the present invention;

[0022] Figure 2 This is a cross-sectional view of the liquid inlet pipe in Example 1 of the present invention. DETAILED DESCRIPTION

[0023] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0024] Existing spinning methods prepare a homogeneous spinning solution at an appropriate temperature, concentration, and pressure. The homogeneous spinning solution is then passed through a decompression chamber, where the pressure is reduced to below the cloud point to form a two-phase spinning mixture. The two-phase spinning mixture is then ejected through a spinneret at room temperature and room pressure. The low-boiling-point solvent rapidly evaporates, and the polymer precipitates and solidifies from the solution while being subjected to high-speed shear and stretching, forming fine-diameter, highly crystallinity, and three-dimensional continuous fiber filaments. In addition to achieving phase separation of the homogeneous spinning solution by rapidly reducing the pressure of the homogeneous spinning solution as described above, a solvent insoluble in the homogeneous spinning solution can also be added to the homogeneous spinning solution, as in the present invention, to cause the homogeneous spinning solution to phase separate and form a two-phase spinning mixture.

[0025] In principle, the cloud point pressure of a spinning mixture of a certain formula is P0. The spinning mixture is pressurized to P1 (greater than the cloud point pressure P0) to form a homogeneous spinning solution. After a solvent insoluble in the homogeneous spinning solution is injected into the homogeneous spinning solution, the cloud point pressure of the new system formed by the homogeneous spinning solution and the solvent becomes P0. ’ , the P0 ’ Greater than P1, so that the solvent causes phase separation of the homogeneous spinning solution.

[0026] Example 1 Structure of the flash spinning nozzle

[0027] like Figures 1-2 The figure shows a preferred embodiment of the flash spinning nozzle of the present invention, which includes a liquid inlet pipe 2, a phase separation chamber 1 and a spinneret 3 from upstream to downstream. The homogeneous spinning liquid in the spinning kettle flows into the liquid inlet pipe 2, then flows into the phase separation chamber 1, and then reaches the spinneret 3 to be ejected to form fiber filaments.

[0028] The diameter of the liquid inlet pipe 2 is 8 mm, and the liquid inlet pipe 2 is provided with four injection ports 21, which are evenly spaced around the circumference of the side wall of the liquid inlet pipe 2. Each injection port 21 is connected to an injection pump (not shown in the figure). The phase separation chamber 1 is a static mixer, and the static mixer has a mixing element 14 inside. The mixing element 14 is one of the types of SK, SH, SV, SX, SL, and SY. The static mixer includes a first conical section 11, a cylindrical section 12 and a second conical section 13 from upstream to downstream. The small diameter end of the first conical section 11 is connected to the outlet of the liquid inlet pipe 2, the large diameter end of the first conical section 11 is connected to the first end of the cylindrical section 12, the large diameter end of the second conical section 13 is connected to the second end of the cylindrical section 12, and the small diameter end of the second conical section 13 is connected to the spinneret 3; the diameter of the cylindrical section 12 is 25 mm, the length of the cylindrical section 12 is 10 times the diameter of the cylindrical section 12, and the ratio of the length of the first conical section 11 and the second conical section 13 to the length of the cylindrical section 12 is 1:8. The diameter of the spinneret is 0.78 mm and the length is 0.78 mm.

[0029] In this embodiment, after the homogeneous spinning solution in a certain state enters the liquid inlet pipe 2, the valve 22 on each injection port 21 is opened, so that each injection pump injects the solvent into the liquid inlet pipe 2 through the injection port 21 in a quantitative manner. The solvent is liquid carbon dioxide or liquid nitrogen, and the mass of the solvent is 0.5 to 5% of the mass of the homogeneous spinning solution.

[0030] Example 2 Structure of the flash spinning nozzle

[0031] Different from Example 1, the diameter of the liquid inlet pipe 2 is 5 mm, three injection ports 21 are provided on the liquid inlet pipe 2, the diameter of the cylindrical section 12 is 12 mm, the length of the cylindrical section 12 is 4 times the diameter of the cylindrical section 12, and the ratio of the length of the first conical section 11 and the second conical section 13 to the length of the cylindrical section 12 is 1:10.

[0032] Example 3 Structure of the flash spinning nozzle

[0033] Different from Example 1, the diameter of the liquid inlet pipe 2 is 10 mm, 8 injection ports 21 are provided on the liquid inlet pipe 2, the diameter of the cylindrical section 12 is 50 mm, the length of the cylindrical section 12 is 40 times the diameter of the cylindrical section 12, and the ratio of the length of the first conical section 11 and the second conical section 13 to the length of the cylindrical section 12 is 1:5.

[0034] Example 4 Preparation of Fiber Plexifilaments

[0035] (1) High-density polyethylene (Sinopec, SH4502; melt flow rate, 45.0 g / min; density 0.960 g / m 3 ) and dichloromethane to form a spinning mixture with a concentration of 13 wt%;

[0036] (2) The spinning mixture was placed in a 4 L spinning kettle and mechanically stirred for 30 min at 12 MPa and 205 °C to form a homogeneous spinning solution;

[0037] (3) The homogeneous spinning solution enters the liquid inlet pipe 2, and the valve 22 on the injection port 21 is immediately opened. 1 wt% of liquid carbon dioxide is injected into the homogeneous spinning solution in the liquid inlet pipe 2 through the injection port 21. The liquid carbon dioxide induces the homogeneous spinning solution to form a two-phase spinning mixture.

[0038] (4) The two-phase spinning mixture enters the phase separation chamber 1 and is mixed in the phase separation chamber 1, and then ejected from the spinneret 3 to form fiber plexiforms. The properties of the obtained fiber plexiforms are listed in Table 1.

[0039] In step (2) of this embodiment, the cloud point pressure of the homogeneous spinning solution at this concentration and temperature is 10.3 MPa, and the system is pressurized to 12 MPa, so that the spinning mixture becomes a homogeneous spinning solution; in step (3) of this embodiment, after liquid carbon dioxide is added to the homogeneous spinning solution, the cloud point pressure of the new system formed by the homogeneous spinning solution and the liquid carbon dioxide becomes 13.3 MPa, so the system pressure of 12 MPa is less than the new cloud point pressure, and the homogeneous spinning solution undergoes phase separation.

[0040] Example 5 Preparation of Fiber Plexifilaments

[0041] (1) High-density polyethylene (Sinopec, SH4502; melt flow rate, 45.0 g / min; density 0.960 g / m 3 ) and dichloromethane to form a spinning mixture with a concentration of 13 wt%;

[0042] (2) The spinning mixture was placed in a 4 L spinning kettle and mechanically stirred for 30 min at 14 MPa and 205 °C to form a homogeneous spinning solution;

[0043] (3) The homogeneous spinning solution enters the liquid inlet pipe 2, and the valve 22 on the injection port 21 is immediately opened. 3 wt% of liquid carbon dioxide is injected into the homogeneous spinning solution in the liquid inlet pipe 2 through the injection port 21. The liquid carbon dioxide induces the homogeneous spinning solution to form a two-phase spinning mixture;

[0044] (4) The two-phase spinning mixture enters the phase separation chamber 1 and is mixed in the phase separation chamber 1, and then ejected from the spinneret 3 to form fiber plexiforms. The properties of the obtained fiber plexiforms are listed in Table 1.

[0045] The difference between this embodiment and embodiment 4 is that the system is pressurized at a different pressure and the amount of liquid carbon dioxide injected is different.

[0046] In step (2) of this embodiment, the cloud point pressure of the homogeneous spinning solution at this concentration and temperature is 10.3 MPa, and the system is pressurized to 14 MPa, so that the spinning mixture becomes a homogeneous spinning solution; in step (3) of this embodiment, after liquid carbon dioxide is added to the homogeneous spinning solution, the cloud point pressure of the new system formed by the homogeneous spinning solution and the liquid carbon dioxide becomes 16.5 MPa, so the system pressure of 14 MPa is less than the new cloud point pressure, and the homogeneous spinning solution undergoes phase separation.

[0047] Example 6 Preparation of Fiber Plexifilaments

[0048] (1) High-density polyethylene (Sinopec, SH4502; melt flow rate, 45.0 g / min; density 0.960 g / m 3 ) and dichloromethane to form a spinning mixture with a concentration of 15 wt%;

[0049] (2) The spinning mixture was placed in a 4 L spinning kettle and mechanically stirred for 30 min at 12 MPa and 205 °C to form a homogeneous spinning solution;

[0050] (3) The homogeneous spinning solution enters the liquid inlet pipe 2, and the valve 22 on the injection port 21 is immediately opened. 1 wt% liquid nitrogen is injected into the homogeneous spinning solution in the liquid inlet pipe 2 through the injection port 21. The liquid nitrogen induces the homogeneous spinning solution to form a two-phase spinning mixture;

[0051] (4) The two-phase spinning mixture enters the phase separation chamber 1 and is mixed in the phase separation chamber 1, and then ejected from the spinneret 3 to form fiber plexiforms. The properties of the obtained fiber plexiforms are listed in Table 1.

[0052] This example differs from Example 4 in that the polymer concentration of the spinning mixture and the composition of the added solvent are different.

[0053] In step (2) of this embodiment, the cloud point pressure of the homogeneous spinning solution at this concentration and temperature is 9.8 MPa, and the system is pressurized to 12 MPa, so that the spinning mixture becomes a homogeneous spinning solution; in step (3) of this embodiment, after liquid nitrogen is added to the homogeneous spinning solution, the cloud point pressure of the new system formed by the homogeneous spinning solution and the liquid nitrogen becomes 12.5 MPa, so the system pressure of 12 MPa is less than the new cloud point pressure, and the homogeneous spinning solution undergoes phase separation.

[0054] Example 7 Preparation of Fiber Plexifilaments

[0055] (1) High-density polyethylene (Sinopec, SH4502; melt flow rate, 45.0 g / min; density 0.960 g / m 3 ) and dichloromethane to form a spinning mixture with a concentration of 15 wt%;

[0056] (2) The spinning mixture was placed in a 4 L spinning kettle and mechanically stirred for 30 min at 13 MPa and 215 °C to form a homogeneous spinning solution;

[0057] (3) The homogeneous spinning solution enters the liquid inlet pipe 2, and the valve 22 on the injection port 21 is immediately opened. 5 wt% of liquid carbon dioxide is injected into the homogeneous spinning solution in the liquid inlet pipe 2 through the injection port 21. The liquid carbon dioxide induces the homogeneous spinning solution to form a two-phase spinning mixture.

[0058] (4) The two-phase spinning mixture enters the phase separation chamber 1 and is mixed in the phase separation chamber 1, and then ejected from the spinneret 3 to form fiber plexiforms. The properties of the obtained fiber plexiforms are listed in Table 1.

[0059] The difference between this embodiment and embodiment 6 is that the pressure at which the system is pressurized is different and the amount of liquid carbon dioxide injected is different.

[0060] In step (2) of this embodiment, the cloud point pressure of the homogeneous spinning solution at this concentration and temperature is 9.5 MPa, and the system is pressurized to 13 MPa, so that the spinning mixture becomes a homogeneous spinning solution; in step (3) of this embodiment, after liquid carbon dioxide is added to the homogeneous spinning solution, the cloud point pressure of the new system formed by the homogeneous spinning solution and the liquid carbon dioxide becomes 13.8 MPa, so the system pressure of 13 MPa is less than the new cloud point pressure, and the homogeneous spinning solution undergoes phase separation.

[0061] Comparative Example 1

[0062] (1) High-density polyethylene (Sinopec, SH4502; melt flow rate, 45.0 g / min; density 0.960 g / m 3 ) and dichloromethane to form a spinning mixture with a concentration of 13 wt%;

[0063] (2) The spinning mixture was placed in a 4 L spinning kettle and mechanically stirred for 30 minutes at 12 MPa and 205°C to form a homogeneous spinning solution; the cloud point pressure of the homogeneous spinning solution at this concentration and temperature was 10.3 MPa;

[0064] (3) The homogeneous spinning solution enters the decompression chamber and is decompressed to 5.1 MPa to form a two-phase spinning mixture, which is maintained in the decompression chamber for 10 seconds;

[0065] (4) The two-phase spinning mixture is ejected from a spinneret to obtain fiber plexiform fibers. The properties of the obtained fiber plexiform fibers are listed in Table 1.

[0066] The nozzles used in Comparative Example 1 are different from those used in Example 4. The nozzle in Comparative Example 1 is a nozzle with a built-in decompression chamber in the prior art, and the pressure reduction effect of the decompression chamber is used to perform phase separation on the homogeneous spinning solution.

[0067] Table 1 Performance parameters of fiber plexifilaments obtained by spinning different homogeneous spinning solutions through different nozzles

[0068]

[0069] The test results show that, compared with Examples 4 to 7, the nozzle of the present invention can be applied to spinning mixtures of different formulations. The spinning mixtures of different formulations are heated and pressurized under different conditions to generate homogeneous spinning solutions of different formulations. The homogeneous spinning solutions of different formulations have different cloud point pressures. The homogeneous spinning solutions of different formulations can all be phase-separated under the action of the solvent through the flash spinning nozzle of the present invention, achieving a good spinning effect. The resulting fiber filaments have a crystallinity of greater than 80%, and the fiber strength is higher and more uniform. In other embodiments, it can also be applied to homogeneous spinning solutions composed of different polymers and different solvents. In the above other embodiments, the polymers used include one or more of polyethylene, polypropylene, polytetrafluoroethylene, and polyvinylidene fluoride, and the solvents used include one or more of methyl chloride, dichloromethane, chloroform, carbon tetrachloride, monofluoro-trichloromethane, ethyl chloride, trifluorodichloroethane, and cis-1,2-dichloroethylene, which are not listed one by one in the present invention.

Claims

1. A flash spinning nozzle, comprising a phase separation chamber (1), wherein both ends of the phase separation chamber (1) are provided with a liquid inlet pipe (2) and a spinneret (3), respectively, wherein a homogeneous spinning liquid enters the phase separation chamber (1) from the liquid inlet pipe (2) and then reaches the spinneret (3) for ejection, characterized in that: An injection port (21) is provided on the peripheral wall of the liquid inlet pipe (2), and the injection port (21) is used to inject a solvent into the liquid inlet pipe (2), wherein the solvent is insoluble in the homogeneous spinning solution when the homogeneous spinning solution is present.

2. The flash spinning nozzle according to claim 1, characterized in that: The number of the injection ports (21) is 3 to 8, and they are distributed at equal distances along the circumference of the side wall of the liquid inlet pipe (2).

3. The flash spinning nozzle according to claim 2, characterized in that: The solvent is liquid carbon dioxide or liquid nitrogen, and the mass of the solvent is 0.5-5% of the mass of the homogeneous spinning solution.

4. The flash spinning nozzle according to claim 3, characterized in that: The injection port (21) is connected to an injection pump, and the volume of the solvent is precisely controlled by the injection pump.

5. The flash spinning nozzle according to claim 4, characterized in that: The phase separation chamber (1) is a static mixer having a mixing element (14) therein. The static mixer comprises a first conical section (11), a cylindrical section (12) and a second conical section (13). The small diameter end of the first conical section (11) is connected to the outlet of the liquid inlet pipe (2), the large diameter end of the first conical section (11) is connected to the first end of the cylindrical section (12), the large diameter end of the second conical section (13) is connected to the second end of the cylindrical section (12), and the small diameter end of the second conical section (13) is connected to the spinneret (3).

6. The flash spinning nozzle according to claim 5, characterized in that: The diameter of the cylindrical section (12) ranges from 12 to 50 mm, and the length of the cylindrical section (12) is 4 to 40 times the diameter of the cylindrical section (12).

7. The flash spinning nozzle according to claim 6, characterized in that: The diameter of the liquid inlet pipe (2) is 5 to 10 mm.

8. The flash spinning nozzle according to claim 7, characterized in that: The ratio of the length of the first conical section (11) to the length of the cylindrical section (12) is 1:10 to 1:

5.

9. The flash spinning nozzle according to claim 8, characterized in that: The ratio of the length of the second conical section (13) to the length of the cylindrical section (12) is 1:10 to 1:

5.

10. A spinning method using the nozzle according to any one of claims 1 to 9, characterized in that: The following steps are involved: (1) mixing a polymer and a solvent to form a spinning mixture of a first concentration; (2) mixing the spinning mixture at a first pressure and a first temperature to form a homogeneous spinning solution; (3) the homogeneous spinning solution enters the liquid inlet pipe (2), and simultaneously a certain amount of the solvent is injected into the homogeneous spinning solution in the liquid inlet pipe (2) through the injection port (21), so that the solvent triggers the homogeneous spinning solution to form a two-phase spinning mixture; (4) The two-phase spinning mixture enters the phase separation chamber (1) and is mixed in the phase separation chamber (1), and then ejected from the spinneret (3) to form fiber plexiform filaments.

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