A kind of PBO aerogel fiber and preparation method thereof

Abstract

The present invention belongs to the field of high-performance materials, and discloses a PBO aerogel fiber and a preparation method thereof, comprising the following steps: (1) preparing a polyhydroxyamide (PHA) spinning solution; (2) extruding the PHA spinning solution from a spinneret into a coagulation bath to spin a PHA-PBO wet gel fiber; (3) freeze-drying the PHA-PBO wet gel fiber to obtain a PHA-PBO aerogel fiber; (4) heating the PHA-PBO aerogel fiber to obtain a PBO aerogel fiber. The above method uses a precursor PHA spinning and a volatile solvent to avoid solvent residue inside the fiber; secondly, a partial rigid skeleton structure is constructed in the wet gel fiber to avoid the collapse of the fiber structure during the drying process, so that the final aerogel fiber product has a high porosity, has the advantages of light weight, high strength, and high temperature resistance, and has potential application prospects in the fields of thermal insulation protection, sound absorption and vibration reduction, and catalyst carriers.

Description

Technical Field

[0001] The invention belongs to the field of high-performance materials and discloses a PBO aerogel fiber and a preparation method thereof. Background Art

[0002] Poly(p-phenylene benzobisoxazole) (PBO) fiber is currently the world's highest strength and best comprehensive high-performance organic fiber, with high strength, high modulus, high flame retardancy and high heat resistance. At present, conventional PBO fiber has been industrialized and plays an irreplaceable key role in the defense and civilian fields. However, PBO aerogel fiber used in the field of heat-resistant insulation has not achieved a technological breakthrough and is still in the research and development stage.

[0003] The preparation of PBO aerogel fibers faces the following technical problems: Aerogel fibers are usually prepared by first wet spinning a polymer solution at a low speed to obtain wet gel fibers with a gel network structure, and then a special drying method is used to replace the solvent in the wet gel with air while keeping the gel network structure from collapsing. However, PBO fibers use polyphosphoric acid as a spinning solvent, which has high viscosity and low volatility, making it difficult to completely remove the phosphorus from the wet gel fiber no matter what method is used, resulting in an excessively high phosphorus residual rate inside the aerogel fiber, which leads to a serious decrease in the wet heat aging performance and a loss of application value. It can be seen that PBO aerogel fibers cannot be prepared using conventional aerogel preparation methods, and the field of PBO aerogel fibers is currently in a technical gap.

[0004] Therefore, how to obtain PBO aerogel with better performance and apply it to aerospace, weapons and ships, and high-end civilian fields is an urgent problem to be solved by technicians in this field. Summary of the invention

[0005] In view of the many deficiencies in the prior art, the present invention provides a PBO aerogel fiber and a preparation method thereof, comprising the following steps: (1) preparing a spinning solution of polyhydroxyamide (PHA), a precursor of PBO; (2) extruding the PHA spinning solution from a spinneret into a coagulation bath to spin PHA-PBO wet gel fiber; (3) freeze-drying the PHA-PBO wet gel fiber to obtain PHA-PBO aerogel fiber; (4) heating the PHA-PBO aerogel fiber to obtain PBO aerogel fiber. The above method uses the precursor PHA spinning, which has a simple process and can use volatile solvents to avoid solvent residue inside the fiber; secondly, a partial rigid skeleton structure is constructed in the wet gel fiber to avoid the collapse of the fiber structure during the drying process, so that the final aerogel fiber product has high porosity, light weight, high strength, high temperature resistance and other advantages, and has potential application prospects in the fields of thermal insulation protection, sound absorption and vibration reduction, and catalyst carriers.

[0006] The main principles of the present invention are:

[0007] During the preparation of PBO, the flexibility of PHA is significantly increased because the oxazole ring in the macromolecular chain is not closed, and the solubility in solvents such as DMAC and NMP is greatly increased. Therefore, PHA can be polymerized in the above solvents to prepare wet gel fibers. In the subsequent drying process, solvents such as DMAC and NMP have low viscosity and are easy to volatilize, so the drying effect is good and there is no problem of solvent residue. On the other hand, in the process of preparing wet gel fibers, the inventors partially convert the flexible chain PHA into a rigid chain PBO by ring blowing heating, which promotes the sol-gel transition. During the drying process, due to the skeleton support of some rigid chain PBO, the gel network structure is not easily destroyed, so the structure does not collapse and has a high porosity.

[0008] Under the guidance of the above concept, the specific technical solution of the present invention is:

[0009] A method for preparing PBO aerogel fiber comprises the following steps:

[0010] (1) Add a certain amount of solvent to a three-necked flask filled with nitrogen, then add stannous chloride as an antioxidant, then add 4,6-diaminoresorcinol hydrochloride, heat to 120°C and stir for 10-12 hours to remove hydrogen chloride, then cool to 10-30°C, add terephthalic acid, stir for 12 hours, and maintain the temperature at 10-30°C to obtain a polyhydroxyamide (PHA) spinning solution;

[0011] In the step (1), the solvent is one or more of dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), and N,N-dimethylpyrrolidone (NMP);

[0012] (2) The polyhydroxyamide spinning solution is transported to a metering pump, and after being accurately measured, it is extruded from a single-hole spinneret and enters a channel to form filaments. The filaments enter a coagulation bath and are rapidly coagulated to obtain PHA-PBO wet gel fibers;

[0013] (3) The PHA-PBO wet gel fiber is freeze-dried to obtain an internally porous PHA-PBO aerogel fiber, which is then heated and thermally cyclized in a nitrogen atmosphere to obtain a PBO aerogel fiber.

[0014] In the step (1), the amount of stannous chloride added is 1-2% of the mass of 4,6-diaminoresorcinol hydrochloride, the molar ratio of 4,6-diaminoresorcinol hydrochloride to terephthalic acid is 1:1, and the total mass of the two is 14%-18% of the mass of the solution.

[0015] In the step (2), the delivery rate of the spinning metering pump is 0.8-1.2 mL / min, the spinneret is a single hole with a hole diameter of 0.2-0.6 mm, and the spinneret stretching ratio is 2-3; in the step (2), the tunnel height is 15-30 cm, there is an annular blowing in the tunnel, and the annular blowing air volume is 2-3 m 3 / min, the annular air temperature is 70-100℃.

[0016] The ring-blowing heating under the above-mentioned setting conditions causes the PHA polymer in the PHA spinning solution to undergo partial ring closure to generate a small amount of PBO, which reduces its solubility in the solvent, thereby causing a sol-gel transition.

[0017] In step (2), the coagulation bath is one or more of ethanol, acetone or water, the coagulation bath temperature is 40-50° C., and the spinning speed is 5-10 m / min.

[0018] In the step (3), during the freeze-drying process, the temperature is -70°C to -50°C, the time is 36-48 hours, the vacuum degree is 20-30Pa, and after the freeze-drying is completed, the temperature is naturally raised to room temperature.

[0019] In the step (3), the process of heating the thermal cyclization is to increase the temperature from room temperature to 150-200°C at a rate of 3-5°C / min, maintain for 1-2h, and then increase the temperature to 350-400°C and maintain for 1-2h.

[0020] In addition, the present application also claims protection for the PBO aerogel fiber prepared by the above method.

[0021] Compared with the prior art, the technical solution provided by the present invention is characterized in that the precursor PHA is used for spinning. PHA can be dissolved in solvents such as DMAC and NMP. Compared with PPA, a common solvent for PBO, the above solvent has much lower viscosity and good volatility, and is easy to remove during the drying process, thus avoiding solvent residue. In addition, part of PHA is converted into PBO during the spinning process. During the drying process, the rigid chain PBO plays the role of skeleton support, and the gel network structure inside the fiber is not easily destroyed. Therefore, the structure does not collapse and has a high porosity. For the first time in this field, PBO aerogel fibers have been successfully prepared, filling the gap in this field. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the process and equipment for preparing PBO aerogel fibers in this application. DETAILED DESCRIPTION

[0023] In order to better understand the present invention, the contents of the present invention are further illustrated below in conjunction with embodiments. The present invention described herein is only used to explain the present invention and is not used to limit the present invention.

[0024] Example 1 A method for preparing a PBO aerogel fiber, such as Figure 1 As shown, the following steps are included:

[0025] (1) Add 200 g of DMAC into a three-necked flask filled with nitrogen, then add 0.18 g of stannous chloride as an antioxidant, then add 18.33 g of 4,6-diaminoresorcinol hydrochloride, heat to 120°C and stir for 10 h to remove hydrogen chloride, then cool to 10°C, add 14.23 g of terephthalic acid, stir for 12 hours, and maintain the temperature at 10°C to obtain a polyhydroxyamide (PHA) spinning solution;

[0026] (2) The polyhydroxyamide spinning solution is transported to the metering pump. After precise metering, it is extruded from a single-hole spinneret at a speed of 0.8 mL / min. The spinneret hole diameter is 0.2 mm and the spinneret stretch ratio is 2. Then it enters the tunnel. The tunnel height is 30 cm. There is an annular blowing in the tunnel. The annular blowing air volume is 2 m 3 / min, the annular air temperature is 70℃, the spinning solution forms filaments, and then the filaments enter the ethanol coagulation bath for rapid coagulation, the coagulation bath temperature is 40℃, and PHA-PBO wet gel fibers are obtained, and the spinning speed is 5m / min;

[0027] (3) The PHA-PBO wet gel fiber was freeze-dried at -70 °C for 36 h under a vacuum of 20 Pa, and then naturally heated to room temperature to obtain an internally porous PHA-PBO aerogel fiber; then, the temperature was raised from room temperature to 150 °C at a rate of 3 °C / min in a nitrogen atmosphere, maintained for 1 h, and then raised to 350 °C and maintained for 2 h to obtain a PBO aerogel fiber.

[0028] The obtained PBO aerogel fiber density is 0.19 g / cm 3 , tensile strength is 280MPa, Young's modulus is 7.3GPa, and the initial thermal decomposition temperature is 640℃.

[0029] Embodiment 2 A PBO aerogel fiber and a preparation method thereof, comprising the following steps:

[0030] (1) Add 200 g of DMAC into a three-necked flask filled with nitrogen, then add 0.22 g of stannous chloride as an antioxidant, then add 20.11 g of 4,6-diaminoresorcinol hydrochloride, heat to 120°C and stir for 11 h to remove hydrogen chloride, then cool to 20°C, add 15.61 g of terephthalic acid, stir for 12 hours, and maintain the temperature at 20°C to obtain a polyhydroxyamide (PHA) spinning solution;

[0031] (2) The polyhydroxyamide spinning solution is transported to the metering pump. After precise metering, it is extruded from a single-hole spinneret at a speed of 1.0 mL / min. The spinneret hole diameter is 0.4 mm and the spinneret stretch ratio is 3. Then it enters the tunnel. The tunnel height is 15 cm. There is an annular blowing in the tunnel. The annular blowing air volume is 2.5 m 3 / min, the annular air temperature is 90℃, the spinning solution forms filaments, and then the filaments enter the acetone coagulation bath for rapid coagulation, the coagulation bath temperature is 45℃, and PHA-PBO wet gel fibers are obtained, and the spinning speed is 8m / min;

[0032] (3) The PHA-PBO wet gel fiber was freeze-dried at -60 °C for 40 h under a vacuum of 25 Pa, and then naturally heated to room temperature to obtain an internally porous PHA-PBO aerogel fiber. The fiber was then heated from room temperature to 180 °C at a rate of 4 °C / min in a nitrogen atmosphere and maintained for 1.8 h, and then heated to 380 °C and maintained for 1.5 h to obtain a PBO aerogel fiber.

[0033] The obtained PBO aerogel fiber density is 0.17g / cm 3 , tensile strength is 260MPa, Young's modulus is 6.9GPa, and the initial thermal decomposition temperature is 650℃.

[0034] Example 3 A PBO aerogel fiber and a preparation method thereof, comprising the following steps:

[0035] (1) Add 200 g of DMAC into a three-necked flask filled with nitrogen, then add 0.48 g of stannous chloride as an antioxidant, then add 24.71 g of 4,6-diaminoresorcinol hydrochloride, heat to 120°C and stir for 12 h to remove hydrogen chloride, then cool to 30°C, add 19.19 g of terephthalic acid, stir for 12 hours, and maintain the temperature at 30°C to obtain a polyhydroxyamide (PHA) spinning solution;

[0036] (2) The polyhydroxyamide spinning solution is transported to the metering pump. After precise metering, it is extruded from a single-hole spinneret at a speed of 1.2 mL / min. The spinneret hole diameter is 0.6 mm and the spinneret stretch ratio is 2.5. Then it enters the tunnel. The tunnel height is 20 cm. There is an annular blowing in the tunnel. The annular blowing air volume is 3 m 3 / min, the annular blowing temperature is 100℃, the spinning solution forms filaments, and then the filaments enter a coagulation bath with a volume ratio of water and acetone of 1:1 and are rapidly coagulated. The coagulation bath temperature is 50℃ to obtain PHA-PBO wet gel fibers. The spinning speed is 10m / min;

[0037] (3) The PHA-PBO wet gel fiber was freeze-dried at -50 °C for 48 h under a vacuum of 30 Pa, and then naturally heated to room temperature to obtain an internally porous PHA-PBO aerogel fiber. The fiber was then heated from room temperature to 200 °C at a rate of 5 °C / min in a nitrogen atmosphere, maintained for 2 h, and then heated to 400 °C and maintained for 1 h to obtain a PBO aerogel fiber.

[0038] The obtained PBO aerogel fiber density is 0.21g / cm 3 , tensile strength is 310MPa, Young's modulus is 7.5GPa, and the initial thermal decomposition temperature is 660℃.

[0039] Comparative Example

[0040] There is no method for preparing PBO aerogel fibers at present. The inventors tried to prepare PBO aerogel fibers using a conventional method for preparing aerogel fibers. The steps are as follows:

[0041] (1) Add 200 g of polyphosphoric acid to a three-necked flask filled with nitrogen, then add 0.48 g of stannous chloride as an antioxidant, then add 24.71 g of 4,6-diaminoresorcinol hydrochloride, heat to 120°C and stir for 12 h to remove hydrogen chloride, then cool to 30°C, add 19.19 g of terephthalic acid, stir for 10 min, heat to 80°C and stir for 3 h, heat to 110°C and stir for 4 h, heat to 120°C and stir for 4 h, heat to 150°C and stir for 6 h, heat to 180°C and stir for 3 h to obtain PBO spinning solution;

[0042] (2) The PBO spinning solution is delivered to the metering pump. After precise metering, it is extruded from a single-hole spinneret at a speed of 1.2 mL / min. The spinneret hole diameter is 0.8 mm and the spinneret stretch ratio is 2.0. Then it enters the tunnel. The tunnel height is 50 cm. There is an annular airflow in the tunnel. The annular airflow volume is 2 m 3 / min, the annular air temperature is 80℃, the spinning solution forms filaments, and then the filaments enter a coagulation bath with a volume ratio of water and acetone of 1:1 and are rapidly coagulated. The coagulation bath temperature is 60℃ to obtain PBO wet gel fibers. The spinning speed is 6m / min;

[0043] (3) The PBO wet gel fiber was freeze-dried at -60 °C for 36 h at a vacuum degree of 20 Pa to obtain PBO aerogel fiber.

[0044] The obtained PBO aerogel fiber density is 0.52g / cm 3 , tensile strength is 290MPa, Young's modulus is 7.4GPa, and the initial thermal decomposition temperature is 635℃.

[0045] By comparison, it can be seen that the density of the PBO aerogel fiber obtained in the comparative example is much higher than that of the PBO aerogel fiber of the present invention, and no loose porous structure is formed, so the thermal insulation is poor and the effect of using it as an aerogel fiber is not good. The inventor believes that the main reason is that the comparative example uses a completely cyclized PBO polymer for spinning, and can only use strong acid solvents such as polyphosphoric acid; while the present invention uses PHA for spinning, and partially cyclizes during molding, which can take into account the rigidity and solubility of the polymer, so the effect is good; secondly, the solvent of the comparative example is polyphosphoric acid, which is not suitable as a solvent for aerogel fibers, because it has a high viscosity and no volatility, resulting in the inability to form a loose porous structure, and there is a lot of polyphosphoric acid residue in the fiber, resulting in unsatisfactory mechanical properties.

[0046] The above embodiments show and describe the basic principles, product features and advantages of the method of the present invention. The present invention is not limited by the above embodiments. Without departing from the scope of the present invention, the present invention may have various changes and improvements, all of which are required to be included in the scope of protection.

Claims

1. A method for preparing PBO aerogel fiber, characterized in that: The steps include: (1) Add a certain amount of solvent to a three-necked flask filled with nitrogen, then add stannous chloride as an antioxidant, then add 4,6-diaminoresorcinol hydrochloride, heat to 120°C and stir for 10-12 hours to remove hydrogen chloride, then cool to 10-30°C, add terephthalic acid, stir for 12 hours, and maintain the temperature at 10-30°C to obtain a polyhydroxyamide spinning solution; In step (1), the solvent is one or more of dimethylacetamide, dimethyl sulfoxide, and N,N-dimethylpyrrolidone; The amount of stannous chloride added is 1-2% of the mass of 4,6-diaminoresorcinol hydrochloride, the molar ratio of 4,6-diaminoresorcinol hydrochloride to terephthalic acid is 1:1, and the total mass of the two is 14%-18% of the mass of the solution; (2) The polyhydroxyamide spinning solution is transported to a metering pump, and after being accurately measured, it is extruded from a single-hole spinneret and enters a channel to form filaments. The filaments enter a coagulation bath and are rapidly coagulated to obtain PHA-PBO wet gel fibers; The delivery rate of the spinning metering pump is 0.8-1.2mL / min, the spinneret is a single hole with a hole diameter of 0.2-0.6mm, and the spinneret stretch ratio is 2-3; the tunnel height is 15-30cm, and there is an annular blowing in the tunnel with an annular blowing air volume of 2-3m 3 / min, the ring air temperature is 70-100℃; (3) freeze-drying the PHA-PBO wet gel fiber to obtain an internally porous PHA-PBO aerogel fiber, which is then heated and thermally cyclized in a nitrogen atmosphere to obtain a PBO aerogel fiber; During the freeze-drying process, the temperature is -70°C to -50°C, the time is 36-48 hours, and the vacuum degree is 20-30Pa. After the freeze-drying is completed, it is naturally heated to room temperature.

2. The method for preparing the PBO aerogel fiber according to claim 1, characterized in that: In the step (2), the coagulation bath is one or more of ethanol, acetone or water, the coagulation bath temperature is 40-50°C, and the spinning speed is 5-10 m / min.

3. The method for preparing the PBO aerogel fiber according to claim 1, characterized in that: In the step (3), the process of heating the thermal cyclization is to increase the temperature from room temperature to 150-200°C at a rate of 3-5°C / min, maintain for 1-2h, and then increase the temperature to 350-400°C and maintain for 1-2h.

4. PBO aerogel fiber prepared by the method according to any one of claims 1 to 3.

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