A method for producing a porous polyurethane fiber

Abstract

The present application belongs to the field of textile application, and particularly relates to a preparation method of porous (homogeneous porous) polyurethane fiber, namely, a method for constructing porous polyurethane fiber through a precipitation-induced phase separation method and normal pressure drying. The present application comprises the following steps: using a polyurethane solution as polyurethane spinning solution, using an alcohol / water mixed solution as mixed coagulation bath, and then spraying the polyurethane spinning solution into the mixed coagulation bath at a set injection speed to perform wet spinning, completing phase separation, and finally obtaining porous (homogeneous porous) polyurethane fiber with high elasticity and high thermal insulation through normal pressure drying of the obtained polyurethane gel fiber.

Description

Technical Field

[0001] This invention belongs to the field of textile applications, and particularly relates to a method for preparing porous (homogeneous porous) polyurethane fibers, namely, a method for constructing porous polyurethane fibers by precipitation-induced phase separation and atmospheric pressure drying. Background Technology

[0002] Polyurethane fibers have been widely used in clothing, textiles, and biomedical materials due to their high strength, low modulus, high resilience, and high elongation at break.

[0003] Currently, most methods for preparing porous polyurethane fibers involve wet spinning to obtain polyurethane gel fibers. The pore-forming processes in wet spinning vary; some methods use freeze-drying, while others use precipitation-induced phase separation. Freeze-drying obtains pores through sublimation of ice crystal templates, but this method is energy-intensive (at -75°C) and has a long cycle of 3-7 days. Precipitation-induced phase separation uses water as a non-solvent (the non-solvent in the coagulation bath), resulting in strong interaction forces between the solvent and non-solvent, leading to a fast kinetic diffusion rate and generating more large pores (50-300 micrometer pores) with low porosity.

[0004] When using precipitation-induced phase separation, the presence of numerous gas-liquid and liquid-liquid interfaces within the polyurethane gel causes severe shrinkage and cracking during atmospheric pressure drying. This ultimately leads to deterioration of fiber properties (reduced porosity, lower elongation at break, and loss of thermal insulation), making it impossible to obtain high-quality porous fiber products. To address this critical technical issue, current drying processes typically employ supercritical drying or freeze-drying. However, these methods still have drawbacks, such as expensive equipment, stringent process control, long production cycles, and limitations on large-scale production of porous fiber materials, thus restricting the industrial production of porous polyurethane fibers. Therefore, developing a green, environmentally friendly, low-cost, and simple porous polyurethane fiber preparation technology to obtain high-performance porous fiber products with tunable pore structures is a crucial problem that urgently needs to be solved. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a green, environmentally friendly, low-cost and simple method for preparing porous (homogeneous porous) polyurethane fibers by atmospheric pressure drying.

[0006] To solve the above-mentioned technical problems, the present invention provides a method for preparing porous (homogeneous porous) polyurethane fibers (i.e., a method for preparing porous polyurethane fibers by precipitation-induced phase separation), comprising the following steps:

[0007] S1. Preparation of polyurethane spinning solution:

[0008] The polyurethane masterbatch is added to an organic solvent and stirred until completely dissolved. The resulting polyurethane solution is used as the polyurethane spinning solution.

[0009] S2. Preparation of mixed coagulation bath:

[0010] Alcohol and water are mixed and stirred until homogeneous. The resulting alcohol / water mixture is used as a coagulation bath (i.e., a non-solvent used as a coagulation bath).

[0011] S3, Wet spinning:

[0012] The polyurethane spinning solution obtained in step S1 enters the spinneret at a set injection speed, and then is ejected into the mixing coagulation bath obtained in step S2 for wet spinning to complete phase separation (the solvent in the polyurethane spinning solution is separated from the non-solvent phase in the mixing coagulation bath), thereby obtaining polyurethane gel fiber; the temperature of the mixing coagulation bath is 30-70℃ (preferably 35-65℃).

[0013] Note: The injection speed of the polyurethane spinning solution is controlled by a microfluidic pump, and the spinneret is located in the coagulation bath; this is a conventional technique.

[0014] S4, Drying at atmospheric pressure

[0015] The polyurethane gel fiber obtained in step S3 is dried under normal pressure to produce porous (homogeneous porous) polyurethane fiber.

[0016] As an improvement to the preparation method of the present invention: the mass fraction of polyurethane masterbatch in the polyurethane solution is 5-30% (preferably 10-30%).

[0017] As a further improvement to the preparation method of the present invention:

[0018] In step S1, the organic solvent is at least one of the following: dimethylformamide, dimethylacetamide, and dimethyl sulfoxide, that is, one or more of dimethylformamide, dimethylacetamide, and dimethyl sulfoxide;

[0019] In step S2, the alcohol is at least one of the following: ethanol, isopropanol, tert-butanol, and the mass concentration of the alcohol in the alcohol / water mixture is 10% to 90% (preferably 30% to 60%).

[0020] As a further improvement to the preparation method of the present invention:

[0021] In step S1, the stirring is performed mechanically at 25–80°C (preferably 30–70°C).

[0022] As a further improvement to the preparation method of the present invention:

[0023] In step S3, the diameter of the wet spinning head is 200–800 μm (preferably 300–700 μm).

[0024] As a further improvement to the preparation method of the present invention:

[0025] In step S3, under the flow rate control of the microfluidic pump, the polyurethane spinning solution enters the spinneret at a push rate of 1-10 mL / min (preferably 1.5-5 mL / min) and the collection rate is 20-100 m / min (preferably 10-50 m / min).

[0026] As a further improvement to the preparation method of the present invention:

[0027] In step S4, the atmospheric pressure drying process is to dry at 40-100℃ for 1-5 hours (preferably at 50-80℃ for 2-4.5 hours).

[0028] As a further improvement to the preparation method of the present invention:

[0029] The polyurethane is a thermoplastic polyurethane.

[0030] As a further improvement to the preparation method of the present invention:

[0031] A polyurethane solution with a polyurethane mass fraction of 10% was used as a polyurethane spinning solution.

[0032] A 60% ethanol / water mixture was used as the coagulation bath, and the temperature of the coagulation bath was 65℃.

[0033] This invention employs precipitation-induced phase separation (PEP) to create pores in the wet spinning process; specifically, it provides a method for constructing porous polyurethane fibers using atmospheric pressure drying and PEP. Based on wet spinning technology, this invention regulates the diffusion coefficient of phase separation kinetics by adjusting the ratio of non-solvents in the coagulation bath. After atmospheric pressure drying and setting, porous polyurethane fibers with high elasticity and high thermal insulation properties are prepared. The preparation method of this invention is simple and easy to implement, facilitating industrial production, and the prepared products exhibit good thermal insulation performance. The homogenized pore structure and high porosity within the porous polyurethane fibers endow them with lightweight properties, providing potential applications for lightweight and high-thermal-insulating textiles. Furthermore, this method is simple to implement, easy to control, low-cost, environmentally friendly, and suitable for industrial production.

[0034] The beneficial effects of this invention are:

[0035] 1. This invention constructs porous (homogeneous porous) polyurethane fibers by selecting a non-solvent (ethanol / water mixed solution) with low interaction forces between the solvent and the non-solvent, thereby controlling the kinetic diffusion coefficient during phase separation, reducing the formation of large pores, and increasing porosity. The method of this invention has a short cycle time (5-12 hours) and low energy consumption (drying under normal pressure).

[0036] 2. This invention strengthens the porous network structure of polyurethane by regulating the coagulation bath temperature, thereby resisting capillary stress.

[0037] 3. The present invention obtains a uniform pore structure by changing the non-solvent ratio and non-solvent temperature in precipitation-induced phase separation.

[0038] In summary, this invention provides a method and application for preparing porous polyurethane fibers using precipitation-induced phase separation. Based on wet spinning technology, the pore size during fiber coagulation is controlled by adjusting the kinetic diffusion coefficient during phase separation. High-elasticity and high-thermal-insulation porous (homogeneous) polyurethane fibers are then prepared by pressure drying. This preparation method is simple to implement, easy to control, low-cost, environmentally friendly, and suitable for industrial production. Attached Figure Description

[0039] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0040] Figure 1 Cross-sectional electron microscope images of the porous polyurethane fibers prepared in Examples 1-4;

[0041] Figure 1 In the text: a to d correspond to Examples 1 to 4, respectively;

[0042] Figure 2 Stress-strain curves of porous polyurethane fibers prepared in Examples 1-4;

[0043] Figure 3 The graphs show the temperature rise curves of Examples 1-4 under a heating environment of 35°C. Detailed Implementation

[0044] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0045] The polyurethane masterbatch was BASF (China) Co., Ltd., model 1180A10, with a particle size of 2cm and a specific gravity of 1.11g / cm³. 3 Tensile modulus: 12.4 MPa, flexural modulus: 17.2 MPa. It is thermoplastic polyurethane.

[0046] Example 1: A method for preparing porous polyurethane fibers using precipitation-induced phase separation, comprising the following steps:

[0047] (1) At 30-70℃, 5g of polyurethane masterbatch is added to 45g of N,N-dimethylformamide and stirred until the polyurethane masterbatch is completely dissolved to obtain a polyurethane solution with a polyurethane mass fraction of 10%, which is used as the polyurethane spinning solution.

[0048] (2) Add 150g of ethanol to 350g of water and stir at 35℃ for 1h to obtain a 30% ethanol / water mixture as a mixed coagulation bath (i.e., a non-solvent used as a mixed coagulation bath).

[0049] (3) Wet spinning is used:

[0050] Under the flow rate control of the microfluidic pump, the polyurethane spinning solution enters the spinneret at a push rate of 1.5 mL / min, and then is sprayed into the mixed coagulation bath obtained in step 2) for wet spinning to complete phase separation (the solvent in the polyurethane spinning solution is separated from the non-solvent phase in the mixed coagulation bath), thereby obtaining polyurethane gel fiber.

[0051] The spinneret diameter is 400 micrometers (i.e., the diameter of the formed fibers is 400 micrometers); the collection rate is 20 m / min; and the temperature of the mixing and coagulation bath is set to 35°C.

[0052] (4) The polyurethane gel fiber that has completed phase separation is dried at 50°C and normal pressure for 2 hours to obtain porous polyurethane fiber.

[0053] Example 2: A method for preparing porous polyurethane fibers using precipitation-induced phase separation.

[0054] The following changes were made compared to Example 1:

[0055] (2) Add 200g of ethanol to 300g of water and stir at 45℃ for 1h to obtain a 40% ethanol / water mixture as a mixing coagulation bath.

[0056] In step (3): the temperature of the mixing coagulation bath is set to 45℃;

[0057] The rest is the same as in Example 1.

[0058] Example 3: A method for preparing porous polyurethane fibers using precipitation-induced phase separation.

[0059] The following changes were made compared to Example 1:

[0060] (2) Add 250g of ethanol to 250g of water and stir at 55℃ for 1h to obtain a 50% ethanol / water mixture as a mixing coagulation bath.

[0061] In step (3): the temperature of the mixing coagulation bath is set to 55℃;

[0062] The rest is the same as in Example 1.

[0063] Example 4: A method for preparing homogeneous porous polyurethane fibers using precipitation-induced phase separation.

[0064] The following changes were made compared to Example 1:

[0065] (2) Add 300g of ethanol to 200g of water and stir at 65℃ for 1h to obtain a 60% ethanol / water mixture as a mixing coagulation bath.

[0066] In step (3): the temperature of the mixing coagulation bath is set to 65℃;

[0067] The rest is the same as in Example 1.

[0068] Experiment 1: The cross-sections of the porous polyurethane fibers prepared in Examples 1-4 were analyzed; their electron micrographs are shown below. Figure 1 ,according to Figure 1 It can be seen that: Example 1 ( Figure 1 a) Numerous finger-like pores and large cavitary pores are generated; as the ethanol content in the coagulation bath increases, the number of large pores gradually decreases; when the ethanol content is 60% (Example 4), Figure 1 d) The fiber has no large pores and a uniform pore structure, thus producing a homogeneous porous polyurethane fiber.

[0069] Experiment 2: The porous polyurethane fibers prepared in Examples 1-4 were tested according to GB / T 3923.1-2013, and their stress-strain curves are shown below. Figure 2 ,according to Figure 2 It can be seen that as the number of large pores inside the porous polyurethane fiber decreases, the fiber breaking elongation increases, and the homogeneous porous fiber in Example 4 exhibits the highest breaking elongation of 2865%.

[0070] Experiment 3: The porous polyurethane fibers prepared in Examples 1-4 were heated at 35°C; the heating curves are shown below. Figure 3 ,according to Figure 3 It can be seen that the temperature differences of the porous polyurethane fibers prepared in Examples 1 to 4 are 3.48, 3.59, 3.71 and 3.85℃, respectively, and the homogeneous porous polyurethane fiber prepared in Example 4 has the highest thermal insulation performance.

[0071] The performance comparison of Examples 1 to 4 above is shown in Table 1 below:

[0072] Table 1. Statistics on thermal insulation performance and stress-strain properties of porous polyurethane fibers

[0073]

[0074] Example 5-1: Replace "dimethylformamide" in Example 4 with "dimethylacetamide", keep the amount the same, and the rest are the same.

[0075] Example 5-2: Replace "dimethylformamide" in Example 4 with "dimethyl sulfoxide", keep the amount the same, and the rest are the same.

[0076] Example 6-1: Replace “ethanol” with “isopropanol” in Example 4, keep the amount the same, and the rest are the same.

[0077] Example 6-2: Replace “ethanol” in Example 4 with “tert-butanol”, keep the amount the same, and the rest are the same.

[0078] Example 7-1: Replace “5g polyurethane masterbatch and 45g N,N-dimethylformamide” in Example 4 with “2.5g polyurethane masterbatch and 47.5g N,N-dimethylformamide” to obtain a polyurethane solution with a mass fraction of 5%; the rest are the same.

[0079] Example 7-2: In Example 4, “5g of polyurethane masterbatch and 45g of N,N-dimethylformamide” were replaced with “15g of polyurethane masterbatch and 35g of N,N-dimethylformamide” to obtain a polyurethane solution with a mass fraction of 30%; the rest were the same.

[0080] Example 8-1: In Example 4, "the urethane solution is injected into the spinneret at a rate of 1.5 mL / min" is changed to "the urethane solution is injected into the spinneret at a rate of 2 mL / min"; the rest is the same.

[0081] Example 8-2: In Example 4, "the urethane solution is injected into the spinneret at a rate of 1.5 mL / min" is changed to "the urethane solution is injected into the spinneret at a rate of 3 mL / min"; the rest is the same.

[0082] Example 8-3: In Example 4, "the urethane solution is injected into the spinneret at a rate of 1.5 mL / min" is changed to "the urethane solution is injected into the spinneret at a rate of 5 mL / min"; the rest are the same.

[0083] Example 9-1: Change "collection rate 20 m / min" in Example 4 to "collection rate 10 m / min"; the rest are the same.

[0084] Example 9-2: Change "collection rate 20m / min" in Example 4 to "collection rate 30m / min"; the rest are the same.

[0085] Example 9-3: Change "collection rate 20m / min" in Example 4 to "collection rate 50m / min"; the rest are the same.

[0086] The above-described Examples 5-1 to 9-3 were tested according to the experimental methods described above. The performance comparison of each example is shown in Table 1 below:

[0087] Table 2. Statistics on thermal insulation performance and stress-strain properties of porous polyurethane fibers

[0088]

[0089] Comparative Example 1-1: The “60% ethanol / water mixture” in Example 4 was changed to “90% ethanol / water mixture”, and the rest was the same as in Example 4.

[0090] Comparative Examples 1-2: The “60% ethanol / water mixture” in Example 4 was changed to “20% ethanol / water mixture”, and the rest was the same as in Example 4.

[0091] Comparative Example 2-1: The temperature of the mixing coagulation bath in Example 4 was changed from 65°C to 75°C, and the rest was the same as in Example 4.

[0092] Comparative Example 2-2: The temperature of the mixing coagulation bath in Example 4 was changed from 65°C to 25°C, and the rest was the same as in Example 4.

[0093] All the comparative examples were tested according to the experimental method described above, and the performance comparison with Example 4 is shown in Table 3 below:

[0094] Table 3. Statistics on thermal insulation performance and stress-strain properties of porous polyurethane fibers

[0095]

[0096] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing porous polyurethane fibers, characterized in that... Includes the following steps: S1. Preparation of polyurethane spinning solution: The polyurethane masterbatch is added to an organic solvent and stirred until completely dissolved. The resulting polyurethane solution is used as the polyurethane spinning solution. The mass fraction of polyurethane masterbatch in the polyurethane solution is 10-30%; The polyurethane is thermoplastic polyurethane; The organic solvent is at least one of the following: dimethylformamide, dimethylacetamide, or dimethyl sulfoxide; S2. Preparation of mixed coagulation bath: An alcohol is mixed with water, and the resulting alcohol / water mixture is used as a mixing coagulation bath; the alcohol is at least one of the following: ethanol, isopropanol, tert-butanol, and the mass concentration of the alcohol in the alcohol / water mixture is 30-60%; S3, Wet spinning: The polyurethane spinning solution obtained in step S1 enters the spinneret at a set injection speed, and then is ejected into the mixing and coagulation bath obtained in step S2 for wet spinning to complete phase separation and obtain polyurethane gel fiber; the temperature of the mixing and coagulation bath is 30-70℃; the diameter of the wet spinning head is 300-700μm. S4, Drying at atmospheric pressure The polyurethane gel fiber obtained in step S3 is dried under normal pressure to produce porous polyurethane fiber. The atmospheric pressure drying process involves drying at 40–100°C for 1–5 hours.

2. The method for preparing porous polyurethane fibers according to claim 1, characterized in that: In step S1, the stirring is performed mechanically at a temperature of 30–70°C.

3. The method for preparing porous polyurethane fibers according to claim 2, characterized in that: In step S3, the injection rate is 1–10 ml / min, and the collection rate is 20–100 m / min.

4. The method for preparing porous polyurethane fibers according to claim 3, characterized in that: A polyurethane solution with a polyurethane mass fraction of 10% was used as a polyurethane spinning solution. A 60% ethanol / water mixture was used as the coagulation bath, and the temperature of the coagulation bath was 65℃.

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