High-thermal-conductivity PBO fiber and preparation method thereof

Abstract

The invention belongs to the field of high-performance materials, and discloses a high-thermal-conductivity PBO fiber and a preparation method thereof, and the preparation method comprises the following steps: (1) preparing a PBO polymer solution with a conventional molecular weight; (2) preparing an ultra-high molecular weight PBO polymer solution; (3) mixing the two PBO polymer solutions in a double-screw extruder according to a certain proportion to obtain a PBO spinning solution; (4) preparing as-spun PBO fibers by adopting a dry-wet liquid crystal spinning process and a condensed state structure regulation and control means; and (5) washing, drying, oiling and winding the as-spun PBO fiber to obtain the high-thermal-conductivity PBO fiber. According to the method, a small amount of the ultra-high molecular weight PBO polymer is added into the conventional spinning solution, the heat conduction performance of the PBO fiber is remarkably improved through the induced orientation crystallization effect of an ultra-high molecular weight PBO long chain, and the method has good application prospects in the field of high-power radio frequency microwave circuits with high requirements for heat dissipation capacity.

Description

Technical Field

[0001] This invention belongs to the field of high-performance materials, specifically providing a high thermal conductivity PBO fiber and its preparation method. Background Technology

[0002] With the rapid development of technology, high-power radio frequency (RF) microwave circuits are increasingly used in aerospace, satellite navigation, 5G / 6G communications, and national defense. As the core substrate material for high-power RF microwave circuits, the performance of copper-clad laminates (CCLs) determines the reliability and transmission efficiency of the circuit. Circuit devices generate a large amount of heat during high-power operation, thus requiring the CCL to dissipate this heat quickly. Traditional CCLs typically use a composite of fiber and resin, where the thermal conductivity of the fiber significantly affects the heat dissipation of the CCL substrate. Currently, traditional CCLs mainly use glass fiber, but glass fiber has a high dielectric constant, high dielectric loss, and low thermal conductivity, making it difficult to meet the low-loss and high thermal conductivity requirements of high-power RF microwave circuits.

[0003] Polymer oxide (PBO) fiber is a high-performance organic fiber with excellent overall properties. Its molecular chains are tightly and regularly arranged, exhibiting high crystallinity and orientation, and good thermal conductivity. PBO fiber can be composited with resin to prepare high-performance copper-clad laminate (CCL) matrices that meet the performance requirements of traditional applications. However, for high-power operating environments such as 5G / 6G communications, satellite navigation, high-power integrated chips, and new energy batteries, conventional PBO fiber-based CCLs are insufficient to meet thermal conductivity requirements. Therefore, it is necessary to further improve the thermal conductivity of PBO fibers and prepare novel high-thermal-conductivity PBO fibers to meet the urgent needs of high-tech, high-power fields for high-thermal-conductivity materials. Summary of the Invention

[0004] To address the problems existing in the above-mentioned technologies, this invention provides a high thermal conductivity PBO fiber and its preparation method, comprising the following steps: (1) preparing a PBO polymer solution of conventional molecular weight; (2) preparing an ultra-high molecular weight PBO polymer solution; (3) mixing the two PBO polymer solutions in a twin-screw extruder in a certain proportion to obtain a PBO spinning solution; (4) using a dry-wet liquid crystal spinning process and through condensed-state structure control methods to prepare virgin PBO fibers; (5) washing, drying, oiling, and winding the virgin PBO fibers to obtain high thermal conductivity PBO fibers. The above method adds a small amount of ultra-high molecular weight PBO polymer to the conventional spinning solution, significantly improving the thermal conductivity of PBO fibers through the induced orientation crystallization effect of the ultra-high molecular weight PBO long chain; secondly, by effectively controlling the condensed-state structure of the fiber during the molding process, the thermal conductivity of the fiber in the axial and radial directions is improved, thus preparing high thermal conductivity PBO fibers, which have potential application prospects in the field of high-power radio frequency microwave circuits with high heat dissipation requirements.

[0005] The biggest difference between this invention and the prior art is that: By introducing a small amount of ultra-high molecular weight PBO polymer into a conventional PBO polymer solution, the orientation and crystallinity of PBO fiber segments are improved through the induced orientation and crystallization effect of the long ultra-high molecular weight PBO chains. Secondly, by controlling the temperature of the spinneret individually and using high aspect ratio spinnerets, the chain segments are relaxed during the extrusion process of the PBO spinning solution, forming pre-orientation of the chain segments, reducing outlet bulging, and improving the regularity of molecular chain arrangement. During the channel stretching process, multi-zone individual temperature control technology creates a suitable temperature gradient within the channel, enabling effective thermal stretching over a longer distance. During stretching, the high molecular weight PBO long chains facilitate orientation. The fiber forming process employs a spinning sleeve design, combined with coagulation bath temperature and concentration control, which improves the regularity of the condensed structure of PBO fibers, weakens the core-sheath structure, and optimizes the axial and radial chain segment stacking structure. This tightly and regularly arranged structure is conducive to phonon conduction, thus possessing better thermal conductivity.

[0006] The specific technical solution of the present invention is as follows: A high thermal conductivity PBO fiber is composed of conventional PBO polymer and ultra-high molecular weight PBO polymer, wherein the conventional PBO polymer has a molecular weight of 30,000-50,000; the ultra-high molecular weight PBO polymer has a molecular weight of 70,000-90,000, and the mass ratio of the two is 95:5-90:10.

[0007] The inventors also provided a method for preparing the above-mentioned high thermal conductivity PBO fiber, which specifically includes the following steps: (1) Add polyphosphoric acid solvent and antioxidant stannous chloride to a nitrogen-purified reactor, stir for 10 min, add 4,6-diaminoresorcinol hydrochloride, stir for 30 min, add phosphorus pentoxide, stir for 30 min, add terephthalic acid, stir for 30 min, raise the temperature to 100℃, stir for 4-6 h, raise the temperature to 150℃, stir for 5-7 h, raise the temperature to 180℃, stir for 5-7 h, and obtain PBO polymer with conventional molecular weight; (2) Add polyphosphoric acid solvent and antioxidant stannous chloride to a nitrogen-purified reactor, stir for 10 min, add 4,6-diaminoresorcinol hydrochloride, stir for 30 min, raise the temperature to 100℃, stir for 4 h-6 h, raise the temperature to 120℃, stir for 5 h-8 h, lower the temperature to 50℃, add phosphorus pentoxide, stir for 10 min, add terephthalic acid, stir for 10 min, raise the temperature to 100℃, stir for 6-8 h, raise the temperature to 160℃, stir for 8-10 h, raise the temperature to 190℃, stir for 5-7 h, and obtain ultra-high molecular weight PBO polymer; (3) The two PBO polymer solutions prepared above are added to the twin-screw extruder at a certain ratio and mixed under the strong shearing action of the twin-screw extruder to further increase viscosity. Then, the mixture is degassed, filtered, and then fed into the spinning stage. (4) The PBO polymer solution after degassing and filtration is accurately metered by a metering pump and then delivered to the spinning assembly. It is extruded from the spinneret and enters the channel. It is then subjected to high-ratio stretching in the air layer of the channel and then enters the coagulation device containing the spinning sleeve. The filament comes into contact with the coagulation bath in the spinning sleeve and undergoes double diffusion. Water in the coagulation bath enters the interior of the filament, and the solvent inside the filament enters the coagulation bath. The filament is then coagulated into fiber. (5) The above fibers are washed, dried, oiled and wound to obtain high thermal conductivity PBO fibers.

[0008] Preferably, in step (1) above, the content of stannous chloride is 0.2wt%-0.4wt% of the mass of polyphosphoric acid, the content of phosphorus pentoxide in the final system is 82wt%-84wt%, and the molar ratio of 4,6-diaminoresorcinol hydrochloride to terephthalic acid is 1:1.005-1:1.010. The molecular weight of PBO polymer is controlled to be 30,000-50,000 by the above two monomers. After polymerization, the solid content of PBO polymer in solution is 12%-14%. In step (2), the content of stannous chloride is 0.2wt%-0.4wt% of the mass of polyphosphoric acid, the content of phosphorus pentoxide in the final system is 84wt%-86wt%, and the molar ratio of 4,6-diaminoresorcinol hydrochloride to terephthalic acid is 0.998:1-1:1002. The molecular weight of PBO polymer is controlled to 70,000-90,000 by the above two monomers. After polymerization, the solid content of PBO polymer in solution is 11%-12%.

[0009] In step (3), the mass ratio of polymers in the conventional PBO polymer solution to the ultra-high molecular weight PBO polymer solution is 95:5-90:10; the length-to-diameter ratio of the twin-screw extruder is 36:1-48:1; the rotation speed is 20rpm-40rpm; the temperature is 180℃-200℃; the vacuum degree of the vacuum port is -0.085-0.09MPa; and the filter element is 1000-1500 mesh.

[0010] In step (4), the spinneret is electrically heated, which allows for more precise temperature control at 210℃-230℃. The spinneret has a hole diameter of 0.13mm-0.17mm, a hole length-to-diameter ratio of 5:1-8:1, and a channel length of 600mm-900mm. Four sets of heating jackets are used for zoned heating, with temperature ranges from top to bottom of 180℃-200℃, 150℃-180℃, 120℃-150℃, and 90℃-110℃. The spinneret has a higher aspect ratio than conventional processes, allowing the spinning solution to have a longer residence time in the spinneret. This promotes chain segment relaxation during the PBO spinning solution extrusion process, forming chain segment pre-orientation, reducing outlet bulging, and improving the regularity of molecular chain arrangement. The channel adopts four-zone independent temperature control, which can form a more suitable temperature gradient and can effectively perform thermal stretching over a longer distance. During the stretching process, it is easier to orient under the induction of high molecular weight PBO long chains.

[0011] In step (4), the length of the spinning sleeve is 500mm-800mm, the temperature of the coagulation bath inside the spinning sleeve is 20℃-80℃, the ratio of water to phosphoric acid in the coagulation bath is 80:20-90:10, and the flow velocity of the coagulation bath with the fiber is 120m / min-160m / min. Through the synergistic control of the above parameters, the regularity of the fiber's condensed structure can be improved.

[0012] In step (5), the washing time is 200s-300s, the washing temperature is 30℃-50℃, the drying temperature is 120℃-180℃, the drying time is 150s-250s, and the winding speed is 120m / min-160m / min.

[0013] Compared with existing technologies, the technical solution provided by this invention improves the orientation and crystallinity of PBO fiber segments by introducing a small amount of ultra-high molecular weight PBO polymer into a conventional PBO polymer solution and inducing orientation crystallization through the long chain of ultra-high molecular weight PBO. Secondly, by using high aspect ratio spinnerets and individual temperature control of the spinneret, chain segment relaxation is promoted during the extrusion process of PBO spinning solution, forming chain segment pre-orientation, reducing outlet bulging, and improving the regularity of molecular chain arrangement. During the channel stretching process, multi-region individual temperature control technology creates a suitable temperature gradient within the channel, enabling effective thermal stretching over a longer distance. During stretching, the high molecular weight PBO long chain induces easier orientation. In the fiber forming process, a spinning sleeve design is adopted, combined with coagulation bath temperature and concentration control, which improves the regularity of the condensed structure of PBO fiber, weakens the core-sheath structure, and thus optimizes the axial and radial chain segment stacking structure of the fiber. In a thermal environment, the highly oriented and regularly packed PBO fiber structure facilitates phonon thermal conduction, releasing heat in the form of phonons. Therefore, the PBO fiber prepared by this invention has better thermal conductivity. The thermal conductivity of existing ultra-high molecular weight polyethylene fibers is generally below 10 W / (m•K), while the thermal conductivity of conventional PBO fibers can only reach 55-60 W / (m•K). However, the thermal conductivity of the high thermal conductivity PBO fiber prepared by the above-mentioned scheme in this application can reach more than 70 W / (m•K), which is far superior to the fiber varieties currently on the market. Attached Figure Description

[0014] Figure 1 The WAXD comparison diagrams of the high thermal conductivity PBO fiber prepared in Example 2 and the conventional PBO fiber prepared in Comparative Example 1 show that the high thermal conductivity PBO fiber has clearer and stronger diffraction spots in the equatorial direction, and the diffraction arc in the meridional direction is narrower and clearer. This indicates that the high thermal conductivity PBO fiber has a more regular condensed-state structure, which is more conducive to the transfer of phonon heat conduction. The crystallinity of Example 2 is calculated to be 80% and the orientation degree is 98%, while the crystallinity of Comparative Example 1 is 72% and the orientation degree is 93%. Therefore, the thermal conductivity of the fiber prepared in Example 2 is higher than that of Comparative Example 1. Detailed Implementation

[0015] The present invention will be further described below with reference to specific embodiments, which will enable those skilled in the art to have a more comprehensive understanding of the invention, but will not limit the invention in any way. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0016] Example 1 A high thermal conductivity PBO fiber and its preparation method, comprising the following steps: (1) Add 10 kg of polyphosphoric acid solvent and 20 g of antioxidant stannous chloride to a nitrogen-purified reactor, stir for 10 min, add 1.78 kg of 4,6-diaminoresorcinol hydrochloride, stir for 30 min, add 1.34 kg of phosphorus pentoxide, stir for 30 min, add 1.39 kg of terephthalic acid, stir for 30 min, raise the temperature to 100 °C, stir for 4 h, raise the temperature to 150 °C, stir for 5 h, raise the temperature to 180 °C, stir for 5 h, and obtain a PBO polymer with a conventional molecular weight, with an average molecular weight of 30,000. The solid content of the PBO polymer in the solution is 14%, and the phosphorus pentoxide content in the final solution system is 82%.

[0017] (2) Add 10 kg of polyphosphoric acid solvent and 40 g of antioxidant stannous chloride to a nitrogen-purified reactor, stir for 10 min, add 1.97 kg of 4,6-diaminoresorcinol hydrochloride, stir for 30 min, raise the temperature to 100 °C, stir for 4 h, raise the temperature to 120 °C, stir for 5 h, lower the temperature to 50 °C, add 5.16 kg of phosphorus pentoxide, stir for 10 min, add 1.53 kg of terephthalic acid, stir for 10 min, raise the temperature to 100 °C, stir for 6 h, raise the temperature to 160 °C, stir for 8 h, raise the temperature to 190 °C, stir for 7 h to obtain ultra-high molecular weight PBO polymer with an average molecular weight of 90,000. The solid content of PBO polymer in the solution is 12%, and the phosphorus pentoxide content in the final solution system is 86%.

[0018] (3) The conventional PBO polymer solution with a polymer mass ratio of 95:5 and the ultra-high molecular weight PBO polymer solution are simultaneously added to a twin-screw extruder. The twin-screw extruder has a length-to-diameter ratio of 36:1, a rotation speed of 20 rpm, and a temperature of 180°C. The two PBO materials are mixed under the strong shearing action of the twin-screw extruder to further increase viscosity. Then, the material is degassed. The vacuum degree of the degassed vacuum port is -0.085 MPa. The material is then filtered. The filter element is 1000 mesh. Finally, the material enters the spinning stage.

[0019] (4) The PBO polymer solution after degassing and filtration is precisely metered by a metering pump and then delivered to the spinning assembly. It is extruded from the spinneret, which is electrically heated to a temperature of 210°C. The spinneret orifice diameter is 0.13 mm, and the length-to-diameter ratio is 5:1. The extruded filaments enter the channel and undergo high-ratio drawing in the air layer of the channel. The channel length is 600 mm. Four sets of heating jackets are used for zoned heating, with temperature ranges from top to bottom of 180°C, 150°C, 120°C, and 90°C, respectively. In a coagulation device containing a spinning sleeve, the filament comes into contact with the coagulation bath within the spinning sleeve, resulting in a double diffusion effect. Water from the coagulation bath enters the interior of the filament, while the solvent inside the filament enters the coagulation bath, causing the filament to coagulate into fibers. The spinning sleeve used in the coagulation device is 500 mm long, the temperature of the coagulation bath inside the spinning sleeve is 20°C, the ratio of water to phosphoric acid in the coagulation bath is 80:20, and the flow rate of the coagulation bath with the fiber is 120 m / min. Through the comprehensive and coordinated control of the above parameters, fibers with good shaping and high crystallinity and orientation can be obtained.

[0020] (5) The above fibers are washed, dried, oiled and wound to obtain high thermal conductivity PBO fibers. The washing time is 200s, the washing temperature is 30℃, the drying temperature is 120℃, the drying time is 150s, and the winding speed is 120m / min. The PBO fiber prepared in this embodiment has a crystallinity of 77%, an orientation degree of 97%, and a thermal conductivity of 70 W / (m•K).

[0021] Example 2 A high thermal conductivity PBO fiber and its preparation method, comprising the following steps: (1) Add 10 kg of polyphosphoric acid solvent and 40 g of antioxidant stannous chloride to a nitrogen-purified reactor, stir for 10 min, add 1.63 kg of 4,6-diaminoresorcinol hydrochloride, stir for 30 min, add 2.58 kg of phosphorus pentoxide, stir for 30 min, add 1.28 kg of terephthalic acid, stir for 30 min, raise the temperature to 100℃, stir for 6 h, raise the temperature to 150℃, stir for 7 h, raise the temperature to 180℃, stir for 7 h, and obtain a PBO polymer with a conventional molecular weight, with an average molecular weight of 50,000. The solid content of the PBO polymer in the solution is 12%, and the phosphorus pentoxide content in the final solution system is 84%.

[0022] (2) Add 10 kg of polyphosphoric acid solvent and 20 g of antioxidant stannous chloride to a nitrogen-purified reactor, stir for 10 min, add 1.44 kg of 4,6-diaminoresorcinol hydrochloride, stir for 30 min, raise the temperature to 100 °C, stir for 6 h, raise the temperature to 120 °C, stir for 8 h, lower the temperature to 50 °C, add 2.24 kg of phosphorus pentoxide, stir for 10 min, add 1.12 kg of terephthalic acid, stir for 10 min, raise the temperature to 100 °C, stir for 8 h, raise the temperature to 160 °C, stir for 10 h, raise the temperature to 190 °C, stir for 6 h to obtain ultra-high molecular weight PBO polymer with an average molecular weight of 80,000. The solid content of PBO polymer in the solution is 11%, and the phosphorus pentoxide content in the final solution system is 85%.

[0023] (3) The conventional PBO polymer solution with a polymer mass ratio of 90:10 and the ultra-high molecular weight PBO polymer solution are simultaneously added to a twin-screw extruder. The twin-screw extruder has a length-to-diameter ratio of 48:1, a rotation speed of 40 rpm, and a temperature of 200 ℃. The two PBO materials are mixed under the strong shearing action of the twin-screw extruder to further increase viscosity. Then, the material is degassed. The vacuum degree of the degassed vacuum port is -0.09 MPa. The material is then filtered. The filter element is 1500 mesh. Finally, the material enters the spinning stage.

[0024] (4) The PBO polymer solution after degassing and filtration is precisely metered by a metering pump and then delivered to the spinning assembly. It is extruded from the spinneret, which is electrically heated to a temperature of 230°C. The spinneret orifice diameter is 0.17 mm, and the orifice length-to-diameter ratio is 8:1. The extruded filaments enter the channel and undergo high-ratio drawing in the air layer of the channel. The channel length is 900 mm, and four sets of heating jackets are used for zoned heating. The temperature ranges from top to bottom are 200°C, 180°C, 150°C, and 1... The filaments are heated to 10℃ and then enter a coagulation device containing a spinning sleeve. The filaments come into contact with the coagulation bath in the spinning sleeve, and a double diffusion effect occurs. Water in the coagulation bath enters the interior of the filaments, and the solvent inside the filaments enters the coagulation bath. The filaments are then coagulated into fibers. The length of the spinning sleeve used in the coagulation device is 800mm, the temperature of the coagulation bath in the spinning sleeve is 80℃, the ratio of water to phosphoric acid in the coagulation bath is 90:10, and the flow rate of the coagulation bath with the fibers is 160m / min. Finally, fibers with good shaping and high crystallinity and orientation can be obtained.

[0025] (5) The above fibers are washed, dried, oiled and wound to obtain high thermal conductivity PBO fibers. The washing time is 300s, the washing temperature is 50℃, the drying temperature is 180℃, the drying time is 250s, and the winding speed is 160m / min. The PBO fiber prepared in this embodiment has a crystallinity of 80%, an orientation degree of 98%, and a thermal conductivity of 75 W / (m•K).

[0026] Example 3 A high thermal conductivity PBO fiber and its preparation method, comprising the following steps: (1) Add 10 kg of polyphosphoric acid solvent to a nitrogen-purified reactor, add 32 g of antioxidant stannous chloride, stir for 10 min, add 1.71 kg of 4,6-diaminoresorcinol hydrochloride, stir for 30 min, add 2.12 kg of phosphorus pentoxide, stir for 30 min, add 1.32 kg of terephthalic acid, stir for 30 min, raise the temperature to 100℃, stir for 5 h, raise the temperature to 150℃, stir for 6 h, raise the temperature to 180℃, stir for 6 h, and obtain a PBO polymer with a conventional molecular weight, with an average molecular weight of 40,000. The solid content of the PBO polymer in the solution is 13%, and the phosphorus pentoxide content in the final solution system is 83%.

[0027] (2) Add 10 kg of polyphosphoric acid solvent and 29 g of antioxidant stannous chloride to a nitrogen-purified reactor, stir for 10 min, add 1.68 kg of 4,6-diaminoresorcinol hydrochloride, stir for 30 min, raise the temperature to 100 °C, stir for 5 h, raise the temperature to 120 °C, stir for 7 h, lower the temperature to 50 °C, add 3.38 kg of phosphorus pentoxide, stir for 10 min, add 1.34 kg of terephthalic acid, stir for 10 min, raise the temperature to 100 °C, stir for 7 h, raise the temperature to 160 °C, stir for 9 h, raise the temperature to 190 °C, stir for 5 h, and obtain ultra-high molecular weight PBO polymer with an average molecular weight of 70,000. The solid content of PBO polymer in the solution is 11.5%, and the phosphorus pentoxide content in the final solution system is 84%.

[0028] (3) The conventional PBO polymer solution with a polymer mass ratio of 92:8 and the ultra-high molecular weight PBO polymer solution are simultaneously added to a twin-screw extruder. The twin-screw extruder has a length-to-diameter ratio of 42:1, a rotation speed of 30 rpm, and a temperature of 190°C. The two PBO materials are mixed under the strong shearing action of the twin-screw extruder to further increase viscosity. Then, the material is degassed. The vacuum degree of the degassed vacuum port is -0.089 MPa. The material is then filtered. The filter element is 1200 mesh. Finally, the material enters the spinning stage.

[0029] (4) The PBO polymer solution after degassing and filtration is precisely metered by a metering pump and then delivered to the spinning assembly. It is extruded from the spinneret, which is electrically heated at 220°C. The spinneret has a hole diameter of 0.16 mm and a length-to-diameter ratio of 6:1. The extruded filaments enter the channel and are subjected to high-ratio drawing in the air layer of the channel. The channel is 700 mm long and is heated in four sections by four heating jackets. The temperature ranges from top to bottom are 190°C, 160°C, 140°C, and 190°C, respectively. The filaments are heated to 100°C and then enter a coagulation device containing a spinning sleeve. The filaments come into contact with the coagulation bath in the spinning sleeve, and a double diffusion effect occurs. Water in the coagulation bath enters the interior of the filaments, and the solvent inside the filaments enters the coagulation bath. The filaments are then coagulated into fibers. The length of the spinning sleeve used in the coagulation device is 700 mm, the temperature of the coagulation bath inside the spinning sleeve is 70°C, the ratio of water to phosphoric acid in the coagulation bath is 85:15, and the flow rate of the coagulation bath with the fibers is 130 m / min. This process can produce fibers with good shaping and high crystallinity and orientation.

[0030] (5) The above fibers are washed, dried, oiled and wound to obtain high thermal conductivity PBO fibers. The washing time is 250s, the washing temperature is 40℃, the drying temperature is 160℃, the drying time is 190s and the winding speed is 130m / min. The PBO fiber prepared in this embodiment has a crystallinity of 78%, an orientation degree of 98%, and a thermal conductivity of 72 W / (m•K).

[0031] Comparative Example 1: The preparation steps of conventional PBO fibers are as follows: (1) Add 10 kg of polyphosphoric acid solvent to a nitrogen-purified reactor, add 32 g of antioxidant stannous chloride, stir for 15 min, add 1.82 kg of 4,6-diaminoresorcinol hydrochloride, stir for 60 min, add 2.44 kg of phosphorus pentoxide, stir for 30 min, add 1.41 kg of terephthalic acid, stir for 20 min, raise the temperature to 90 °C, stir for 6 h, raise the temperature to 120 °C, stir for 5 h, raise the temperature to 150 °C, stir for 7 h to obtain PBO polymer solution.

[0032] (2) The above PBO polymer solution is added to a twin-screw extruder with a length-to-diameter ratio of 48:1, a rotation speed of 35 rpm, and a temperature of 195°C. The extruder head is degassed, and the vacuum degree of the degassed vacuum port is -0.08. The solution is then filtered, and the filter element is 1000 mesh. The solution then enters the spinning stage.

[0033] (3) The PBO polymer solution after degassing and filtration is metered by a metering pump and then transported to the spinning assembly. It is extruded from the spinneret. The diameter of the spinneret hole is 0.22 mm and the length-to-diameter ratio of the hole is 3:1. The filaments extruded from the spinneret enter the air layer and are drawn in the air layer. The height of the air layer is 300 mm. Then it enters the coagulation tank and the filaments are coagulated into fibers. The temperature of the coagulation bath in the coagulation tank is 25°C. The ratio of water to phosphoric acid in the coagulation bath is 92:8. The fiber traction speed is 100 m / min.

[0034] (4) The above fibers are washed, dried, oiled and wound to obtain conventional PBO fibers. The washing time is 90s, the washing temperature is 20℃, the drying temperature is 150℃, the drying time is 300s, and the winding speed is 100m / min. The PBO fiber prepared in Comparative Example 1 has a crystallinity of 72%, an orientation degree of 93%, and a thermal conductivity of 55 W / (m·K).

[0035] Comparative Example 2: A PBO fiber and its preparation method, comprising the following steps: (1) Add 10 kg of polyphosphoric acid solvent to a nitrogen-purified reactor, add 36 g of antioxidant stannous chloride, stir for 13 min, add 1.66 kg of 4,6-diaminoresorcinol hydrochloride, stir for 30 min, add 2.62 kg of phosphorus pentoxide, stir for 30 min, add 1.29 kg of terephthalic acid, stir for 30 min, raise the temperature to 90 °C, stir for 6 h, raise the temperature to 155 °C, stir for 7 h, raise the temperature to 180 °C, stir for 6 h, and obtain a PBO polymer with a conventional molecular weight and an average molecular weight of 51,000.

[0036] (2) Add 10 kg of polyphosphoric acid solvent and 20 g of antioxidant stannous chloride to a nitrogen-purified reactor, stir for 10 min, add 1.44 kg of 4,6-diaminoresorcinol hydrochloride, stir for 30 min, raise the temperature to 100 °C, stir for 6 h, raise the temperature to 120 °C, stir for 8 h, lower the temperature to 50 °C, add 2.24 kg of phosphorus pentoxide, stir for 10 min, add 1.12 kg of terephthalic acid, stir for 10 min, raise the temperature to 100 °C, stir for 8 h, raise the temperature to 160 °C, stir for 10 h, raise the temperature to 190 °C, stir for 6.5 h to obtain ultra-high molecular weight PBO polymer with an average molecular weight of 85,000.

[0037] (3) The conventional PBO polymer solution with a polymer mass ratio of 90:10 and the ultra-high molecular weight PBO polymer solution are simultaneously added to a twin-screw extruder. The twin-screw extruder has a length-to-diameter ratio of 48:1, a rotation speed of 40 rpm, and a temperature of 200 ℃. The two PBO materials are mixed under the strong shearing action of the twin-screw extruder to further increase viscosity. Then, the material is degassed. The vacuum degree of the degassed vacuum port is -0.09 MPa. The material is then filtered. The filter element is 1500 mesh. Finally, the material enters the spinning stage.

[0038] (4) The PBO polymer solution after degassing and filtration is precisely metered by a metering pump and then delivered to the spinning assembly. It is extruded from the spinneret, which is electrically heated to a temperature of 190°C. The spinneret orifice diameter is 0.13 mm, and the orifice length-to-diameter ratio is 2:1. The extruded filaments enter the channel and undergo high-ratio drawing in the air layer of the channel. The channel length is 200 mm, and four sets of heating jackets are used for zoned heating, with temperature ranges from top to bottom of 100°C. The fibers are heated to ℃, 80℃, 70℃, and 60℃, and then enter a coagulation device containing a spinning sleeve. The fibers come into contact with the coagulation bath in the spinning sleeve, and a double diffusion effect occurs. Water in the coagulation bath enters the interior of the fibers, and the solvent inside the fibers enters the coagulation bath. The fibers are then coagulated into fibers. The spinning sleeve used in the coagulation device is 200mm long, the temperature of the coagulation bath in the spinning sleeve is 10℃, the ratio of water to phosphoric acid in the coagulation bath is 60:40, and the flow rate of the coagulation bath with the fibers is 70m / min.

[0039] (5) The above fibers are washed, dried, oiled and wound to obtain high thermal conductivity PBO fibers. The washing time is 300s, the washing temperature is 50℃, the drying temperature is 180℃, the drying time is 250s, and the winding speed is 160m / min. The fiber prepared in Comparative Example 2 had a crystallinity of 71%, an orientation degree of 92%, and a thermal conductivity of 54 W / (m•K). This is significantly worse than that of the examples (e.g., ...). Figure 1 As shown in the figure, the reason is that the parameters in the above preparation step (4) were not controlled in accordance with the technical solution of this application, which resulted in a decrease in the regularity of the PBO fiber condensed structure and thus affected its performance.

[0040] Comparisons show that the PBO fibers obtained in Comparative Examples 1 and 2 have significantly lower crystallinity, orientation, and thermal conductivity than the PBO fibers prepared in the embodiments of this invention. Comparative Example 1 uses a conventional spinning process, resulting in weak molecular chain orientation and crystallinity within the fiber, and an incomplete condensed-state structure, thus leading to its low thermal conductivity. While Comparative Example 2 uses essentially the same process as this invention, the parameter control during the spinning and forming stage is not within the scope of this application, resulting in a significant performance degradation. This invention introduces ultra-high molecular weight PBO long chains, utilizing their induced orientation and crystallization effect to improve the regularity of the condensed-state structure and enhance the thermal conductivity of the PBO fiber. Furthermore, precise control of the fiber forming process improves the axial and radial thermal conductivity of the fiber. Therefore, the PBO fibers prepared by this invention have significantly better thermal conductivity than the comparative examples.

[0041] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A high thermal conductivity PBO fiber, characterized in that: It is composed of conventional PBO polymer and ultra-high molecular weight PBO polymer, wherein the conventional PBO polymer has a molecular weight of 30,000-50,000; the ultra-high molecular weight PBO polymer has a molecular weight of 70,000-90,000, and the mass ratio of the two is 95:5-90:

10.

2. The method for preparing the high thermal conductivity PBO fiber according to claim 1, characterized in that, Specifically, the steps include the following: (1) Prepare a PBO polymer solution with a conventional molecular weight; (2) Prepare an ultra-high molecular weight PBO polymer solution; (3) Mix the two PBO polymer solutions in a twin-screw extruder in a certain proportion to obtain a PBO spinning solution; (4) Use a dry-wet liquid crystal spinning process and prepare primary spun PBO fibers by means of condensed state structure control. (5) Wash, dry, oil and wind the virgin PBO fiber to obtain high thermal conductivity PBO fiber.

3. The method for preparing high thermal conductivity PBO fiber according to claim 2, characterized in that, The specific steps for preparing a PBO polymer solution with a conventional molecular weight in step (1) are as follows: Add polyphosphoric acid solvent to a nitrogen-purged reactor, add stannous chloride antioxidant, stir for 10 min, add 4,6-diaminoresorcinol hydrochloride, stir for 30 min, add phosphorus pentoxide, stir for 30 min, add terephthalic acid, stir for 30 min, raise the temperature to 100℃, stir for 4-6 h, raise the temperature to 150℃, stir for 5-7 h, raise the temperature to 180℃, stir for 5-7 h, and obtain a PBO polymer with a conventional molecular weight; The content of stannous chloride is 0.2wt%-0.4wt% of the mass of polyphosphoric acid, the content of phosphorus pentoxide in the final system is 82wt%-84wt%, the molar ratio of 4,6-diaminoresorcinol hydrochloride to terephthalic acid is 1:1.005-1:1.010, and the molecular weight of PBO polymer is controlled to 30,000-50,000 by the above two monomers. After polymerization, the solid content of PBO polymer in solution is 12%-14%.

4. The method for preparing high thermal conductivity PBO fiber according to claim 2, characterized in that, The specific steps for preparing the ultra-high molecular weight PBO polymer solution in step (2) are as follows: add polyphosphoric acid solvent and antioxidant stannous chloride to a nitrogen-purified reactor, stir for 10 min, add 4,6-diaminoresorcinol hydrochloride, stir for 30 min, raise the temperature to 100℃, stir for 4-6 h, raise the temperature to 120℃, stir for 5-8 h, lower the temperature to 50℃, add phosphorus pentoxide, stir for 10 min, add terephthalic acid, stir for 10 min, raise the temperature to 100℃, stir for 6-8 h, raise the temperature to 160℃, stir for 8-10 h, raise the temperature to 190℃, stir for 5-7 h, and obtain ultra-high molecular weight PBO polymer; The content of stannous chloride is 0.2wt%-0.4wt% of the mass of polyphosphoric acid, the content of phosphorus pentoxide in the final system is 84wt%-86wt%, the molar ratio of 4,6-diaminoresorcinol hydrochloride to terephthalic acid is 0.998:1-1:1002. The molecular weight of PBO polymer is controlled to 70,000-90,000 by the above two monomers. After polymerization, the solid content of PBO polymer in solution is 11%-12%.

5. The method for preparing high thermal conductivity PBO fiber according to claim 2, characterized in that, Step (3) The two PBO polymer solutions mentioned above are mixed in a certain proportion in a twin-screw extruder to obtain the PBO spinning solution. The specific steps are as follows: The two PBO polymer solutions are added to the twin-screw extruder in a certain proportion and mixed under the strong shearing action of the twin-screw extruder to further increase viscosity. Then, the solution is degassed, filtered, and enters the spinning stage. The mass ratio of polymers in the conventional PBO polymer solution to the ultra-high molecular weight PBO polymer solution is 95:5-90:10; the length-to-diameter ratio of the twin-screw extruder is 36:1-48:1, the rotation speed is 20rpm-40rpm, the temperature is 180℃-200℃, the vacuum degree of the vacuum port is -0.085-0.09MPa, and the filter element is 1000-1500 mesh.

6. The method for preparing high thermal conductivity PBO fiber according to claim 2, characterized in that, Step (4) The specific steps for preparing primary spun PBO fibers using the dry and wet liquid crystal spinning process and through condensed matter structure control are as follows: After the PBO polymer solution is degassed and filtered, it is accurately metered by a metering pump and then transported to the spinning assembly. It is extruded from the spinneret and enters the channel. It is then subjected to high-ratio stretching in the air layer of the channel and then enters the coagulation device containing the spinning sleeve. The filament comes into contact with the coagulation bath in the spinning sleeve and undergoes double diffusion. The water in the coagulation bath enters the interior of the filament, and the solvent inside the filament enters the coagulation bath. The filament is then coagulated into fibers. The spinneret is electrically heated, with a temperature control range of 210℃-230℃. The spinneret's hole diameter is 0.13mm-0.17mm, the hole length-to-diameter ratio is 5:1-8:1, and the channel length is 600mm-900mm. Four sets of heating jackets are used for zoned heating, with temperature ranges from top to bottom of 180℃-200℃, 150℃-180℃, 120℃-150℃, and 90℃-110℃.

7. The method for preparing high thermal conductivity PBO fiber according to claim 6, characterized in that, The length of the spinning sleeve is 500mm-800mm, the temperature of the coagulation bath inside the spinning sleeve is 20℃-80℃, the ratio of water to phosphoric acid in the coagulation bath is 80:20-90:10, and the flow rate of the coagulation bath with the fiber is 120m / min-160m / min.

8. The method for preparing high thermal conductivity PBO fiber according to claim 2, characterized in that, In step (5), the washing time is 200s-300s, the washing temperature is 30℃-50℃, the drying temperature is 120℃-180℃, the drying time is 150s-250s, and the winding speed is 120m / min-160m / min.

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