Spindle-shaped sound-absorbing hollow fiber and method for manufacturing the same

Abstract

The present application belongs to the technical field of sound-absorbing fiber materials, and particularly relates to a spindle-shaped sound-absorbing hollow fiber and a preparation method thereof. By using microfluidic technology, the discontinuous time and flow rate of the spinning fluid are controlled, so that the shell layer spinning fluid continuously flows out and the core layer spinning fluid discontinuously flows out, thereby controlling the longitudinal cavity structure of the hollow fiber to be similar to a continuous spindle shape. The hollow fiber prepared by the present application has a special spindle-shaped hollow structure and high porosity, the internal cavity of the fiber is tortuous, the collision probability of sound waves with the inner wall or the hole wall of the cavity is increased, the consumption of sound energy is increased, the sound-absorbing and noise-reducing properties of the fiber are excellent, and the material TPU used to prepare the hollow fiber has good mechanical properties, so that the prepared hollow fiber can resist external pressure, the porosity of the fiber is stable, and the sound-absorbing effect is maintained during subsequent processing and use.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sound-absorbing fiber materials, and particularly relates to a spindle-shaped sound-absorbing hollow fiber and a preparation method thereof. BACKGROUND

[0002] With the development of contemporary science and technology, human life is becoming more and more mechanized and automated, which brings us convenience but also makes the noise problem more and more serious. Noise pollution has affected people's production and life, and even health, becoming a global environmental problem that cannot be ignored. Therefore, the demand for sound-absorbing and noise-reducing materials is increasing, and the performance and preparation process are also becoming more and more demanding.

[0003] Hollow fibers have always been a hot research topic in the field of sound-absorbing materials due to their high porosity, light weight, and other characteristics. Currently, the hollow fibers used to make sound-absorbing materials more or less have the shortcomings of complicated preparation process, small sound-absorbing range, poor compression resistance, and poor recovery. For example, patent (CN202111404399.6) uses waste feathers and ES fibers (a new type of thermal bonding composite fiber) or PLA (corn fiber) three-dimensional hollow fibers mixed in proportion to prepare a warm sound-absorbing material by wet-laid and hot air reinforcement method. Although it has the advantages of simple process flow, environmental protection, sound absorption and insulation, and high warmth retention rate, it fails to fully utilize the special structure of the hollow fiber to improve the sound-absorbing effect, and the compression resistance is poor, and the stability of the sound-absorbing and insulating effect is poor. Patent (CN202011312492.X) adopts a melt spinning method to prepare polyester hollow fibers with triangular cross-sections that have excellent sound-absorbing performance. Although the recovery of the hollow fibers is good, it can ensure the stability of the hollow rate, but the hollow degree of the hollow fibers itself is not high, and the tortuosity of the internal cavity of the fibers is not enough, and the sound-absorbing effect needs to be improved. In the existing technology, there are also hollow fibers prepared by coaxial wet spinning technology, for example, patent (CN202010017049.3) uses coaxial wet spinning technology, uses PAN solution as the skin layer and PVP (polyvinylpyrrolidone) solution as the core layer, and through a triangular-shaped needle, triangular hollow porous fibers are prepared. Patent (CN202210217600.8) uses coaxial wet spinning technology, uses polyurethane solution as the shell layer and gallium-based liquid metal as the core layer to prepare core-shell structure liquid conductive fibers. Although this traditional coaxial wet spinning technology can obtain hollow fibers with core-shell structure, it does not combine microfluidic technology, and cannot prepare hollow fibers with special hollow structure by controlling the spinning fluid, and thus cannot improve the sound-absorbing effect by changing the hollow structure of the hollow fibers.

[0004] Therefore, if a preparation method capable of stably controlling the longitudinal cavity cross-sectional structure of the fiber and simple in process flow is used to prepare a hollow fiber having excellent sound absorption effect and good mechanical properties, the defects of the hollow fiber used in the existing sound insulation material can be made up for, and the hollow fiber will have a better development prospect in the sound absorption and insulation field. SUMMARY

[0005] To solve the above-mentioned prior art problems, the present application provides a preparation method of a spindle-shaped sound-absorbing hollow fiber, comprising the following steps:

[0006] The water is introduced through the main pipe orifice of the coaxial needle, and the shell layer spinning fluid is introduced through the side pipe orifice of the coaxial needle. The two are converged in the coaxial needle to form a spinning solution, which is introduced into the coagulation bath through the outlet of the coaxial needle for solidification. The spindle-shaped sound-absorbing hollow fiber is obtained by traction and winding.

[0007] The solute of the shell layer spinning fluid comprises a thermoplastic polyurethane.

[0008] The water is intermittently introduced into the coaxial needle by a micro-flow pump, and the intermittent time is 0.1-0.5 s every 0.5-1 s. The flow distance of the water before entering the coaxial needle is 10-50 cm.

[0009] In detail, when the micro-flow controller parameters are set, the shell layer injector is pushed to make the shell layer spinning fluid continuously flow out, and the core layer injector is pushed to make the core layer spinning fluid intermittently flow out. If the pushing of the core layer injector is maintained, the core layer spinning fluid can flow at the set speed. When it reaches the coaxial needle, it will generate pressure on the shell layer spinning fluid in the coaxial needle, so that the hollow degree of the fiber increases. If the pushing of the core layer injector is stopped, the core layer spinning fluid that has been pushed out of the core layer injector cannot maintain the original set speed, and after entering the coaxial needle, the pressure on the shell layer spinning fluid is weakened, so that the hollow degree of the fiber is also reduced.

[0010] When the above two cases are regularly alternated, that is, the shell layer spinning fluid in the injector continuously flows out, and the core layer spinning fluid regularly intermittently flows out, the hollow fiber with the special structure of spindle shape can be continuously prepared. This method of combining micro-fluidic technology and coaxial wet spinning technology to prepare hollow fiber not only has a simple overall process flow, but also can control the internal cavity structure of the hollow fiber, and is an innovation of the traditional coaxial wet spinning technology.

[0011] The method adopts microfluidic coaxial spinning technology, controls the flow rate and intermittent time of the spinning fluid by microfluidic technology, and then controls the longitudinal cavity structure of the hollow fiber, so that the prepared hollow fiber has a special longitudinal cavity structure of spindle shape; the coaxial wet spinning technology is used, a thermoplastic polyurethane (TPU) solution is used as the shell layer spinning fluid, and water is used as the core layer spinning fluid, and the spindle-shaped sound-absorbing hollow fiber is spun.

[0012] By setting the parameters of the micro-flow pump, the micro-flow pump is used to drive the movement of the syringe in the coaxial wet spinning equipment, so that the shell layer spinning fluid in the syringe flows out continuously, and the water flows out intermittently.

[0013] Preferably, the solvent of the shell layer spinning fluid is DMF (N,N-dimethylformamide), DMA (N,N-dimethyl aniline) or DMSO (dimethyl sulfoxide).

[0014] Preferably, in the shell layer spinning fluid, the temperature for dissolving the thermoplastic polyurethane (TPU) is 60-80℃, and the time is 4-5h.

[0015] Preferably, the concentration of the thermoplastic polyurethane in the shell layer spinning fluid is 15-20wt%.

[0016] Preferably, the flow rate ratio of the shell layer spinning fluid to water is 1-5:2, and the flow rate difference is 1-6mL / h.

[0017] Further, the flow rate of the shell layer spinning fluid is 5-10mL / h.

[0018] Further, the flow rate of the water is 4-8mL / h.

[0019] Preferably, the speed of the traction is 20-30mm / s.

[0020] Preferably, the speed of the winding is 15-20mm / s.

[0021] Preferably, the diameter of the coaxial needle head outlet is 10-30μm.

[0022] The present application also provides a spindle-shaped sound-absorbing hollow fiber prepared by the above preparation method.

[0023] The technical scheme of the present application has the following advantages compared with the prior art:

[0024] The present application combines microfluidic technology and coaxial wet spinning technology, and adopts microfluidic coaxial wet spinning technology to prepare hollow fibers. By setting the parameters of the microfluidic controller, the motion of the microflow pump is controlled, and then the flow rate, flow rate ratio, and intermittent time of the shell layer spinning fluid and the core layer spinning fluid are controlled. By using this new technology, on the one hand, the hollow fibers can be stably and controllably prepared, and on the other hand, the longitudinal cavity structure of the hollow fibers can be changed by controlling the shell layer spinning fluid and the core layer spinning fluid (water).

[0025] The longitudinal cavity section of the hollow fiber prepared by the present application is a spindle-like structure with a wide middle and narrow ends. The internal cavity of the fiber is tortuous, and the fiber porosity is high, which can reach more than 50%. When sound waves are incident into the fiber, these characteristics increase the collision probability of sound waves with the pore wall, the inner wall of the cavity, or the fiber. The collision causes vibration, which converts sound energy into heat energy or mechanical energy under the action of friction and air viscosity, thereby increasing the consumption of sound energy. Therefore, the hollow fiber has excellent sound absorption and noise reduction properties.

[0026] The spindle-shaped hollow fiber prepared by the present application adopts thermoplastic polyurethane (TPU) as the solute of the shell layer spinning fluid. Due to the performance characteristics of TPU, such as high toughness, high strength, and good resilience, the fiber can effectively resist external pressure, ensure the stability of the internal porosity of the fiber, and maintain excellent sound absorption and noise reduction effects in the subsequent processing or use process. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The present application is a process flow chart;

[0028] Figure 2 The present application is a cross-sectional view of the coaxial needle in the process flow;

[0029] Figure 3 The present application is a longitudinal section diagram of the spindle-shaped hollow fiber prepared in Example 1;

[0030] Figure 4 The present application is a longitudinal section diagram of the spindle-shaped hollow fiber prepared in Example 2;

[0031] Figure 5 The present application is a longitudinal section diagram of the spindle-shaped hollow fiber prepared in Example 3;

[0032] Figure 6 The present application is a longitudinal section diagram of the ordinary hollow fiber prepared in Comparative Example 1;

[0033] Figure 7 The present application is a longitudinal section diagram of the fiber prepared in Comparative Example 2;

[0034] Figure 8Figure showing the flow of the internal spinning fluid of the coaxial needle in the present application.

[0035] BRIEF DESCRIPTION OF DRAWINGS 1 - first micro flow pump, 2 - core layer syringe, 3 - core layer syringe chamber, 4 - second micro flow pump, 5 - shell layer syringe, 6 - shell layer syringe chamber, 7 - hose, 8 - coaxial needle, 9 - first stretching roller, 10 - second stretching roller, 11 - coagulation bath, 12 - spindle-shaped sound-absorbing hollow fiber, 13 - winding roller, 14 - coaxial needle side orifice, 15 - coaxial needle main orifice, 16 - coaxial needle outlet, 121 - shell layer, 122 - core layer. DETAILED DESCRIPTION

[0036] The present application will be further described in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present application and implement it. However, the embodiments are not intended to limit the present application.

[0037] In the following examples and comparative examples, the method used to test the sound absorption coefficient of the sample is the transfer function method (a method for separating the energy of the incident wave from the energy of the reflected wave by using the transfer function of the sound wave in the impedance tube, and then calculating the sound absorption coefficient of the material, which is the transfer function method). The samples used for testing are large-diameter samples (cylindrical samples with a diameter of 60 mm made from the prepared hollow fibers) and small-diameter samples (cylindrical samples with a diameter of 30 mm made from the prepared hollow fibers). The bulk density of both large-diameter and small-diameter samples is 25 kg / m 3 The sound absorption coefficient in the frequency range of 100-2500 Hz can be measured for large-diameter samples, and the sound absorption coefficient in the frequency range of 1600-6300 Hz can be measured for small-diameter samples. The sound absorption coefficient in the full frequency range (100-6300 Hz) is a combination of the measured values of both samples. Other test methods are conventional methods, and the materials and reagents used can be obtained from commercial sources.

[0038] Example 1

[0039] Step 1: Add thermoplastic polyurethane (TPU) to dimethylformamide (DMF) and stir magnetically at a temperature of 80°C for 4 h to obtain a TPU spinning fluid with a mass fraction of 20% as the shell layer spinning fluid.

[0040] Step two: using microfluidic coaxial wet spinning technology, 10 ml of TPU spinning fluid prepared in step one is taken as the shell spinning fluid by shell injector 5 into shell injector chamber 6, 10 ml of deionized water is taken as the core layer spinning fluid by core layer injector 2 into core layer injector chamber 3, shell injector 5 and core layer injector 2 are respectively installed on second micro flow pump 4 and first micro flow pump 1, the parameters of micro flow controller are set, and second micro flow pump 4 is controlled to continuously push shell injector 5 to make the shell spinning fluid continuously flow out, and core layer injector 2 is intermittently pushed to make the core layer spinning fluid intermittently flow out. Among them, the flow rate of the shell spinning fluid is set to 8 ml / h, the flow rate of the core layer spinning fluid is 4 ml / h, the flow rate ratio of the shell spinning fluid to the core layer spinning fluid is 2:1, and the flow rate difference is 4 ml / h. The deionized water in the core layer injector 2 is intermittently pushed every 0.5 s, and the intermittent time is 0.2 s.

[0041] Step three: set the spinning parameters, set the diameter of the coaxial needle 8 outlet to 15 um, the length of the hose 7 to 30 cm, the drafting speed of the first stretching roller 9 and the second stretching roller 10 to 20 mm / s, and the winding speed of the winding roller 13 to 15 mm / s.

[0042] Step four: start the micro flow controller, control the micro flow pump to move shell injector 5 and core layer injector 2 respectively, and start spinning. The shell spinning fluid, water, flows into the coaxial needle 8, the water flows from the coaxial needle main pipe 15, the shell spinning fluid flows from the coaxial needle side pipe 14, and finally flows out from the coaxial needle outlet 16 and enters the coagulation bath 11 deionized water for solidification. In this process, the core layer spinning fluid is intermittently pushed out from the core layer injector 2, and in this intermittent time, the core layer spinning fluid that has been pushed out from the core layer injector 2 but has not yet entered the coaxial needle 8 continues to flow into the coaxial needle 8 along the hose 7, so that the core layer spinning fluid always flows into the coaxial needle 8. This way, a spindle-shaped hollow fiber can be obtained in the coagulation bath 11. Finally, after being stretched by the first stretching roller 9 and the second stretching roller 10, the hollow fiber is wound and collected on the winding roller 13, and is naturally dried at room temperature. The longitudinal section diagram of the spindle-shaped hollow fiber 12 prepared is as shown in Figure 3

[0043] The spindle-shaped hollow fiber 12 prepared has excellent sound absorption and noise reduction properties and mechanical properties, with a tensile stress of 3.11 MPa, an elongation at break of 575%, an elastic recovery rate of 90%, and a porosity of 72%. The average sound absorption coefficient of the large and small caliber samples is 0.537 at 100-6300 Hz.

[0044] Example 2

[0045] ​The difference from Example 1 is that in Step 1: thermoplastic polyurethane (TPU) is added to dimethylformamide (DMF) and stirred magnetically at a temperature of 80℃ for 4h to obtain a TPU spinning fluid with a mass fraction of 15% as the shell spinning fluid.

[0046] The longitudinal section diagram of the prepared spindle-shaped hollow fiber is shown in Figure 4 .

[0047] The prepared spindle-shaped sound-absorbing hollow fiber has excellent sound-absorbing and noise-reducing properties and mechanical properties, with a tensile stress of 2.69MPa, a breaking elongation of 536%, an elastic recovery rate of 86%, a porosity of 84%, and an average sound absorption coefficient of 0.583 measured for large and small caliber samples at 100-6300Hz.

[0048] Example 3

[0049] The difference from Example 1 is that in Step 2: a microfluidic coaxial wet spinning technology is used, 10ml of the TPU spinning fluid prepared in Step 1 is taken as the shell spinning fluid by shell injector 5 into shell injector chamber 6, 10ml of deionized water is taken as the core spinning fluid by core injector 2 into core injector chamber 3, shell injector 5 and core injector 2 are respectively installed on second micro flow pump 4 and first micro flow pump 1, the parameters of the micro flow controller are set, and second micro flow pump 4 is controlled to continuously push shell injector 5 to make the shell spinning fluid continuously flow out, and core injector 2 is controlled to intermittently push to make the core spinning fluid intermittently flow out. Among them, the flow rate of the shell spinning fluid is set to 8ml / h, the flow rate of the core spinning fluid is set to 4ml / h, the flow rate ratio of the shell spinning fluid to the core spinning fluid is 2:1, the flow rate difference is 4ml / h, and the deionized water in the core injector 2 is intermittently pushed every 0.5s, and the intermittent time is 0.4s.

[0050] The longitudinal section diagram of the prepared spindle-shaped hollow fiber is shown in Figure 5 .

[0051] The prepared spindle-shaped sound-absorbing hollow fiber has excellent sound-absorbing and noise-reducing properties and mechanical properties, with a tensile stress of 3.52MPa, a breaking elongation of 601%, an elastic recovery rate of 93%, a porosity of 64%, and an average sound absorption coefficient of 0.488 measured for large and small caliber samples at 100-6300Hz.

[0052] Comparative Example 1

[0053] Step 1: thermoplastic polyurethane (TPU) is added to dimethylformamide (DMF) and stirred magnetically at a temperature of 80℃ for 4h to obtain a TPU spinning fluid with a mass fraction of 20% as the shell spinning fluid.

[0054] Step two: using microfluidic coaxial wet spinning technology, taking 10 ml of TPU spinning fluid prepared in step one as the shell spinning fluid with the shell injector, and taking 10 ml of deionized water as the core layer spinning fluid with the core layer injector, installing the shell injector and the core layer injector on the second micro flow pump and the first micro flow pump respectively, setting the parameters of the micro flow controller, and controlling the micro flow pump to continuously push the shell injector and the core layer injector to make the shell spinning fluid and water continuously flow out. Among them, the flow rate of the shell spinning fluid is set to 8 ml / h, the flow rate of the water is 4 ml / h, and the flow rate ratio of the shell spinning fluid to the core layer spinning fluid is 2:1, and the flow rate difference is 4 ml / h.

[0055] Step three: set the spinning parameters, set the diameter of the coaxial needle head outlet to 15 um, the length of the hose to 30 cm, the drawing speed of the drawing roller to 20 mm / s, and the winding speed of the winding roller to 15 mm / s.

[0056] Step four: start the micro flow controller, control the micro flow pump to move the shell injector and the core layer injector respectively, and start spinning. The shell spinning fluid and water flow into the coaxial needle head and finally into the coagulation bath deionized water for solidification. Finally, after the drawing of the drawing roller, the hollow fiber is wound and collected on the winding roller, and is naturally dried at room temperature. The longitudinal section of the prepared hollow fiber is spindle-shaped, and the longitudinal section diagram is shown in Figure 6 The tensile stress of the fiber is 2.77 MPa, the elongation at break is 547%, the elastic recovery rate is 88%, the porosity is 81%, and the average sound absorption coefficient of the large and small diameter samples is 0.403 at 100-6300 Hz.

[0057] Comparative example 2

[0058] Step one: add thermoplastic polyurethane (TPU) into dimethylformamide (DMF), and magnetically stir at 80℃ for 4h to obtain TPU spinning fluid with a mass fraction of 20% as the shell spinning fluid.

[0059] Step two: using microfluidic coaxial wet spinning technology, taking 10 ml of TPU spinning fluid prepared in step one as the shell spinning fluid with the shell injector, and not taking any spinning fluid with the core layer injector, installing the shell injector on the second micro flow pump, not installing the core layer injector, setting the parameters of the micro flow controller, and controlling the micro flow pump to continuously push the shell injector to make the shell spinning fluid continuously flow out. Among them, the flow rate of the shell spinning fluid is set to 8 ml / h.

[0060] Step three: set the spinning parameters, set the diameter of the coaxial needle head outlet to 15 um, the length of the hose to 30 cm, the drawing speed of the drawing roller to 20 mm / s, and the winding speed of the winding roller to 15 mm / s.

[0061] Step four: start the micro flow controller, control the micro flow pump to push the shell layer injector to move, start spinning. The shell layer spinning fluid flows into the coaxial needle, and finally enters the coagulation bath deionized water to solidify, and finally, after the drafting of the stretching roller, the hollow fiber is wound and collected on the winding roller, and is naturally dried at room temperature. The prepared fiber has no hollow structure, only a large number of small pores, and the longitudinal section diagram is as shown in Figure 7 The tensile stress of the fiber is 5.49 MPa, the elongation at break is 673%, the elastic recovery rate is 95%, the porosity is 41%, and the average sound absorption coefficient of the large and small diameter samples is 0.311 at 100-6300 Hz.

[0062] Effect evaluation 1

[0063] In order to verify the technical effect obtained by the present application, the fibers obtained in Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2 were tested, and the specific results are shown in Table 1:

[0064] Table 1: Test results of mechanical properties, porosity and sound absorption coefficient of fibers obtained in examples and comparative examples

[0065]

[0066] The longitudinal cavity section of the hollow fiber prepared by the present application is a spindle-like structure with a wide middle and narrow ends. The internal cavity of the fiber is tortuous, and the porosity of the fiber is high, which can reach more than 50%. When sound waves enter the internal cavity of the fiber, these characteristics increase the collision probability of sound waves with the pore wall, the internal wall of the cavity or the fiber. The collision causes vibration, which converts sound energy into heat energy or mechanical energy under the action of friction and air viscosity, thereby increasing the consumption of sound energy. Therefore, the hollow fiber has excellent sound absorption and noise reduction properties.

[0067] The spindle-shaped hollow fiber prepared by the present application uses thermoplastic polyurethane (TPU) as the solute of the shell layer spinning fluid. Due to the performance characteristics of TPU, such as high toughness, high strength and good resilience, it can effectively resist external pressure, ensure the stability of the internal porosity of the fiber, and maintain excellent sound absorption and noise reduction effect during subsequent processing or use.

[0068] Obviously, the above examples are only examples for the purpose of clear illustration, and are not limited to the embodiments. For ordinary skilled persons in the art, other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and impossible to exhaust all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for producing a spindle-shaped sound-absorbing hollow fiber, characterized by, It comprises the following steps: Water is introduced through the main orifice of the coaxial needle, and the shell layer spinning fluid is introduced through the side orifice of the coaxial needle. The two are converged in the coaxial needle to form a spinning solution, which is introduced into a coagulation bath through the outlet of the coaxial needle for solidification, drawing and winding to obtain the spindle-shaped sound-absorbing hollow fiber. The solute of the shell layer spinning fluid comprises thermoplastic polyurethane. The water is intermittently introduced into the coaxial needle by a micro-flow pump, with an interval of 0.5-1 s, and the interval time is 0.1-0.5 s each time. The flow distance of the water before entering the coaxial needle is 10-50 cm. The flow rate ratio of the shell layer spinning fluid to water is 1-5:

2. The flow rate of the shell layer spinning fluid is 5-10 mL / h. The flow rate of the water is 4-8 mL / h. The drawing speed is 20-30 mm / s.

2. The production method according to claim 1, wherein The solvent in the shell layer spinning fluid is DMF, DMA or DMSO.

3. The production method according to claim 1, wherein The concentration of the thermoplastic polyurethane in the shell layer spinning fluid is 15-20 wt%.

4. The production method according to claim 1, wherein The winding speed is 15-20 mm / s.

5. The production method according to claim 1, wherein The diameter of the outlet of the coaxial needle is 10-30 μm.

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