High conversion rate boron nitride fibers and continuous methods and systems for making same

Abstract

This invention provides a high-conversion boron nitride fiber and its continuous preparation method and system. The method includes: spinning a boron nitride organic precursor to obtain precursor fiber; guiding the precursor fiber to a coating zone to coat it with protective oil, obtaining precursor fiber with a protective oil layer on its surface; guiding the precursor fiber with the protective oil layer to an oil control zone for oil control, controlling the oil content to a preset value, obtaining oil-controlled precursor fiber; guiding the oil-controlled precursor fiber to an inert atmosphere multi-temperature zone for sequentially performing protective oil layer curing treatment and boron nitride organic precursor fiber thermal stability treatment; guiding the thermally stabilized precursor fiber to a reaction atmosphere multi-temperature zone for sequentially performing degreasing treatment and sintering treatment, obtaining boron nitride fiber. The preparation method of this invention eliminates upstream and downstream disconnection in each process, enabling continuous production; the protective oil combined with the temperature zone design allows for precise control of the timing of fiber protection, improving the conversion rate.

Description

Technical Field

[0001] This invention relates to the field of boron nitride fiber technology, and more specifically, to a high-conversion-rate boron nitride fiber and its continuous preparation method and system. Background Technology

[0002] Boron nitride fibers possess properties such as high temperature resistance, ablation resistance, and good wave transmission, making them promising for a wide range of applications. Currently, the organic precursor conversion method is the most commonly used method for preparing boron nitride fibers. This involves spinning an organic precursor to obtain precursor fibers, followed by sintering to obtain boron nitride fibers. The spinning process typically requires the organic precursor to be in a solution or molten state, and the organic precursor itself must possess good solubility and fusibility. Therefore, the degree of polymerization of organic precursors is usually relatively low, containing a large number of small molecules or oligomers. During the subsequent organic-to-inorganic conversion process in sintering, these small molecules or oligomers are rapidly removed due to their poor thermal stability, resulting in a low conversion rate (ceramic yield). To address this, the existing solution involves transferring the precursor fibers into an electron beam apparatus after spinning. High-energy particles and an active atmosphere are used to cross-link and solidify the precursor fibers before removing them from the electron beam apparatus for sintering. While the above methods have solved the problem of low conversion rate caused by the rapid removal of small molecules or oligomers during sintering to some extent, they have also introduced the following problems: the electron beam treatment is an additional step with a long processing cycle and poor continuity with the previous process (spinning) and the subsequent process (sintering), making it unsuitable for batch continuous production; the heterogeneous elements introduced by the active atmosphere will decompose during the subsequent sintering process, resulting in a significant degradation of fiber structure and performance; and the electron beam equipment is expensive and costly.

[0003] Therefore, there is an urgent need in this field for a low-cost method for preparing boron nitride fibers that can achieve high conversion rates, continuous production, and no introduction of foreign elements. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a high-conversion boron nitride fiber and its continuous preparation method and system, which enables continuous production of boron nitride fiber without the introduction of foreign elements during the production process, resulting in high conversion rate and high ceramic yield.

[0005] On one hand, the present invention provides a continuous preparation method for high-conversion boron nitride fibers, comprising the following steps: S1, spinning a boron nitride organic precursor to obtain boron nitride organic precursor fibers; S2, guiding the spun boron nitride organic precursor fibers to a coating area, coating the boron nitride organic precursor fibers with a protective oil layer to obtain boron nitride organic precursor fibers with a protective oil layer on the surface; S3, guiding the boron nitride organic precursor fibers with a protective oil layer on the surface to an oil control area, and applying a protective oil layer to the boron nitride organic precursor fibers. The boron nitride organic precursor fiber is subjected to an oil control treatment to control the oil content of the boron nitride organic precursor fiber to a preset value, thereby obtaining the oil-controlled boron nitride organic precursor fiber; S4, the oil-controlled boron nitride organic precursor fiber is guided to an inert atmosphere multi-temperature zone and subjected to a protective oil layer curing treatment and a boron nitride organic precursor fiber thermal stability treatment in sequence; S5, the boron nitride organic precursor fiber treated in S4 is guided to a reaction atmosphere multi-temperature zone and subjected to an oil removal treatment and a sintering treatment in sequence to obtain the high conversion rate boron nitride fiber.

[0006] Compared with existing technologies, the present invention has the following advantages: The preparation method of the present invention sequentially performs spinning, oiling, oil control, protective oil layer curing treatment, thermal stability treatment of boron nitride organic precursor fibers, degreasing treatment, and sintering treatment. The protective oil layer is introduced online. Compared with the electron beam equipment introduced in the prior art, it is not necessary to move the boron nitride organic precursor fibers into the electron beam equipment, thus avoiding the problem of disconnection with the corresponding upstream and downstream processes. It has better connection with upstream and downstream processes, and there is no problem of disconnection between upstream and downstream processes. It can realize continuous production, and the batch continuous production is feasible, while reducing equipment costs. The preparation method of the present invention protects the boron nitride organic precursor fibers with protective oil. With the temperature zone design, the protection time of the protective oil is reasonably controlled. During the curing stage of the protective oil layer, a dense film is formed, effectively isolating the boron nitride organic precursor fiber from the external atmosphere. This prevents the fiber from being exposed to the external atmosphere and introducing / expelling water / oxygen, as well as causing defects due to excessive decomposition of small molecules. Especially during the thermal stability treatment stage of the boron nitride organic precursor fiber, it protects the fiber to complete the polymerization of small molecules and oligomers, improving the degree of polymerization and thermal stability. After polymerization, the protective oil layer is removed during the degreasing stage, allowing the thermally stable boron nitride organic precursor fiber to come into full contact with the reaction atmosphere in a timely manner. During the sintering stage, the precursor ceramicization transformation is completed, avoiding the problem of low conversion rate caused by rapid removal of small molecules or oligomers during sintering, thus improving the conversion rate.

[0007] In some embodiments of the present invention, the curing temperature of the protective oil is lower than the softening point of the boron nitride organic precursor, and the decomposition temperature of the protective oil is higher than the polymerization temperature of the boron nitride organic precursor. The present invention cures the protective oil layer during the curing treatment stage to form a dense film. The curing temperature of the protective oil is lower than the softening point of the boron nitride organic precursor, which prevents the boron nitride organic precursor fibers from softening during the curing and densification process, thus affecting the formation of the film on the surface of the boron nitride organic precursor fibers. Furthermore, the present invention polymerizes small molecules and oligomers in the boron nitride organic precursor fibers during the thermal stability treatment stage. The decomposition temperature of the protective oil is higher than the polymerization temperature of the boron nitride organic precursor, which prevents the protective oil from decomposing during the thermal stability treatment stage, thus losing its protective effect on the boron nitride organic precursor fibers and exposing them to the atmosphere, introducing defects.

[0008] In some embodiments of the present invention, the oil control treatment includes a first oil control stage and a second oil control stage performed sequentially; the first oil control stage involves passing boron nitride organic precursor fibers with a protective oil layer on their surface through upper and lower oil pressure rollers, and extruding a portion of the protective oil by means of the cooperation of the upper and lower oil pressure rollers; the second oil control stage involves guiding the boron nitride organic precursor fibers after the first oil control stage into an inert atmosphere channel, evaporating a portion of the protective oil until the oil content of the boron nitride organic precursor fibers is controlled at a preset value; the preset value is 2 to 4%.

[0009] In some embodiments of the present invention, the temperature of the inert atmosphere channel is controlled at 30–50°C, the inert atmosphere is a nitrogen atmosphere, and the nitrogen flow rate is 3–8 m³ / h. 3 / h.

[0010] The first oil control stage of this invention removes a large amount of protective oil, improving removal efficiency. The second oil control stage is a fine oil control stage, where the temperature and nitrogen flow rate are designed to facilitate the evaporation of the protective oil at an appropriate rate, thus enabling accurate control of the oil carryover rate. This invention rationally controls the amount of protective oil adhering, keeping the oil carryover rate between 2% and 4%. This effectively protects the boron nitride organic precursor fibers in subsequent processes while shortening the oil removal cycle and improving production efficiency.

[0011] In some embodiments of the present invention, the inert atmosphere multi-temperature zone is a nitrogen atmosphere multi-temperature zone, and the nitrogen flow rate is 3-8 m³ / h. 3 / h; The inert atmosphere multi-temperature zone includes a first inert atmosphere temperature zone for curing the protective oil layer and a second inert atmosphere temperature zone for thermal stability treatment of boron nitride organic precursor fibers, which are set sequentially; the temperature of the first inert atmosphere temperature zone is controlled at the curing temperature of the protective oil, and the temperature of the second inert atmosphere temperature zone is controlled at the polymerization temperature of the boron nitride organic precursor.

[0012] In some embodiments of the present invention, the reaction atmosphere multi-temperature zone is an ammonia atmosphere multi-temperature zone, and the ammonia flow rate is 2-3 m³ / h. 3 / h; The reaction atmosphere multi-temperature zone includes a first reaction atmosphere temperature zone for degreasing treatment and a second reaction atmosphere temperature zone for sintering treatment, which are set in sequence; the temperature of the first reaction atmosphere temperature zone is controlled at the decomposition temperature of the protective oil; the temperature of the second reaction atmosphere temperature zone is controlled at 1000~1200℃.

[0013] In this invention, the temperature of the first inert atmosphere temperature zone is controlled at the curing temperature of the protective oil, completing the curing of the protective oil layer and forming a dense film that isolates the boron nitride organic precursor fibers from the external atmosphere. Since the curing temperature of the protective oil is lower than the softening point of the boron nitride organic precursor, it prevents the softening of the boron nitride organic precursor fibers during the curing and densification process, thus avoiding interference with film formation on the surface of the boron nitride organic precursor fibers. The temperature of the second inert atmosphere temperature zone is controlled at the polymerization temperature of the boron nitride organic precursor. Under the isolated environment formed by the protective oil layer, it protects the boron nitride organic precursor fibers from completing the polymerization of small molecules and oligomers, thereby improving… The degree of polymerization is improved, thus enhancing thermal stability. Furthermore, since the decomposition temperature of the protective oil is higher than the polymerization temperature of the boron nitride organic precursor, it prevents the protective oil from decomposing and losing its protective effect on the boron nitride organic precursor fibers, which would otherwise be exposed to the atmosphere and introduce defects. The temperature of the first reaction atmosphere zone is controlled at the decomposition temperature of the protective oil, causing it to decompose and be removed. This allows the thermally stable boron nitride organic precursor fibers to come into full contact with the reaction atmosphere in a timely manner, completing the precursor ceramization transformation in the second reaction atmosphere zone. This avoids the problem of low conversion rate caused by the rapid removal of small molecules or oligomers during sintering, thereby improving the conversion rate.

[0014] In some embodiments of the present invention, the boron nitride organic precursor is composed of a mixture of raw materials comprising 30-50 parts of aminoborane, 5-15 parts of aminocycloborane, and 10-20 parts of aniline, by weight; the softening point of the boron nitride organic precursor is 105-120°C, and the polymerization temperature is 160-220°C.

[0015] In some embodiments of the present invention, the protective oil is composed of a mixture of raw materials including 20-30 parts amino silicone oil, 30-50 parts dimethyl silicone oil and 10-20 parts vinyl silicone oil, by weight; the curing temperature of the protective oil is 80-100°C and the decomposition temperature is 260-310°C.

[0016] The protective oil of this invention is a mixture of amino silicone oil, dimethyl silicone oil, and vinyl silicone oil. The degreasing stage completely removes the protective oil, leaving no residue and preventing the introduction of foreign elements into the fibers. Through the design of the formulation and the dosage of each component, this invention achieves the following: the curing and decomposition temperatures of the protective oil, and the softening and polymerization temperatures of the boron nitride organic precursor, satisfy the condition that the curing temperature of the protective oil is lower than the softening temperature of the boron nitride organic precursor, and the decomposition temperature of the protective oil is higher than the polymerization temperature of the boron nitride organic precursor. Combined with temperature control in the first inert atmosphere zone, the second inert atmosphere zone, the first reaction atmosphere zone, and the second reaction atmosphere zone, this controls the curing and densification of the protective oil layer, the polymerization of small molecules and oligomers in the boron nitride organic precursor fibers, and the timing of contact between the boron nitride organic precursor fibers and the reaction atmosphere. Furthermore, the temperature in each zone gradually increases according to the process sequence. The temperature at the sintering stage has reached the required temperature of 1000-1200℃. Compared with the existing technology (which obtains boron nitride fiber by spinning organic precursor fiber and then sintering it), this technology effectively avoids the problems of fiber weight loss and local overheating and melting caused by oligomers and small molecules in boron nitride organic precursor fiber directly participating in the sintering stage (there is a heating process from room temperature to sintering temperature). This improves the conversion rate of boron nitride organic precursor fiber to boron nitride fiber by 10-15%.

[0017] On the other hand, the present invention also provides a high-conversion boron nitride fiber, which is prepared according to the continuous preparation method of high-conversion boron nitride fiber described in any one of the preceding claims. The high-conversion boron nitride fiber prepared by the present invention has an oxygen content of 1.5-1.8%, a fiber density of 1.6-1.9%, and a ceramic yield of 50-55%, exhibiting low oxygen content, high fiber density, and high ceramic yield.

[0018] Furthermore, the present invention also provides a high-conversion-rate boron nitride fiber preparation system, applicable to the continuous preparation method of high-conversion-rate boron nitride fibers described in any of the above claims, comprising: a spinning device, a bundling device, a coating device, an oil control device, an inert atmosphere multi-temperature zone furnace, and a reaction atmosphere multi-temperature zone furnace arranged sequentially; the coating device includes an oil storage tank and an oiling wheel located above the oil storage tank and partially immersed in the protective oil surface stored in the oil storage tank; the oil control device includes a first oil control device and a second oil control device arranged sequentially, the first oil control device including an oil receiving tank and an oil pressing roller group located above the oil receiving tank, the oil pressing roller group including The invention comprises two oil-pressing rollers positioned vertically. The second oil control device includes an inert atmosphere furnace with openings at both ends. The inner cavity of the inert atmosphere furnace has an inert atmosphere channel communicating with these openings. The inert atmosphere multi-temperature zone furnace also has openings at both ends and includes a first inert atmosphere temperature zone near the oil control device and a second inert atmosphere temperature zone near the reaction atmosphere multi-temperature zone furnace. Similarly, the reaction atmosphere multi-temperature zone furnace has openings at both ends and includes a first reaction atmosphere temperature zone near the inert atmosphere multi-temperature zone furnace and a second reaction atmosphere temperature zone away from the inert atmosphere multi-temperature zone furnace. This invention's preparation system can be applied to the preparation method of this invention. The upstream and downstream processes are well-connected, eliminating the problem of upstream and downstream disconnection. It enables continuous production, has good feasibility for batch continuous production, and reduces equipment costs. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be described below.

[0020] Figure 1 This is a flowchart of a continuous preparation method for high-conversion boron nitride fibers according to an embodiment of the present invention;

[0021] Figure 2 This is a simplified structural diagram of a high-conversion boron nitride fiber preparation system according to an embodiment of the present invention;

[0022] Figure 3 This is a microscopic morphology diagram of boron nitride organic precursor fibers with a protective oil layer according to an embodiment of the present invention.

[0023] Figure 4 This is a cross-sectional elemental distribution diagram of boron nitride organic precursor fibers with a protective oil layer according to an embodiment of the present invention; wherein, Figure 4 (a) shows the distribution of Si elements. Figure 4 (b) shows the distribution of element C;

[0024] Figure 5 Thermogravimetric curves of boron nitride organic precursor fibers without protective oil coating and boron nitride organic precursor fibers with protective oil coating according to an embodiment of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions and advantages of the present invention clearer, the various aspects of the present invention will be described in detail below with reference to specific embodiments. However, these specific embodiments are only used to illustrate the present invention and do not constitute any limitation on the scope of protection and the substantive content of the present invention.

[0026] Example 1

[0027] This embodiment provides a continuous preparation method for high-conversion boron nitride fibers, such as... Figure 1 As shown, it includes the following steps:

[0028] S1. Boron nitride organic precursor is spun to obtain boron nitride organic precursor fiber. In this embodiment, the boron nitride organic precursor is spun and extruded by a spinning device to obtain fiber filaments, which are then bundled by a bundling device to obtain boron nitride organic precursor fiber.

[0029] S2. The boron nitride organic precursor fibers obtained by spinning are guided to the coating area, and a protective oil is coated onto the boron nitride organic precursor fibers using a coating device to obtain boron nitride organic precursor fibers with a protective oil layer on the surface. In this embodiment, the curing temperature of the protective oil is lower than the softening point of the boron nitride organic precursor, and the decomposition temperature of the protective oil is higher than the polymerization temperature of the boron nitride organic precursor.

[0030] S3. Guide the boron nitride organic precursor fiber with a protective oil layer on its surface to the oil control zone. Use an oil control device to treat the boron nitride organic precursor fiber with oil, controlling the oil content of the fiber to a preset value, thus obtaining oil-controlled boron nitride organic precursor fiber. In this embodiment, the oil control treatment includes a first oil control stage and a second oil control stage performed sequentially. The first oil control stage involves passing the boron nitride organic precursor fiber with a protective oil layer through upper and lower oil-pressing rollers, squeezing out most of the excess protective oil using the weight of the protective oil layer and the cooperation of the upper and lower oil-pressing rollers. The second oil control stage involves guiding the boron nitride organic precursor fiber after the first oil control stage into an inert atmosphere channel via rollers, evaporating some of the protective oil until the oil content of the boron nitride organic precursor fiber is controlled to a preset value of 2-4%. In this embodiment, the inert atmosphere channel is a channel with circulating inert atmosphere flow, the temperature of the inert atmosphere channel is controlled at 30-50°C, the inert atmosphere is a nitrogen atmosphere, and the nitrogen flow rate is 3-8 m³ / s. 3 / h. In this embodiment, the oil content refers to the percentage of protective oil to the weight of the boron nitride organic precursor fiber.

[0031] S4. The boron nitride organic precursor fiber, after oil control, is guided to an inert atmosphere multi-temperature zone for sequential curing of the protective oil layer and thermal stability treatment of the boron nitride organic precursor fiber. In this embodiment, the inert atmosphere multi-temperature zone is a circulating atmosphere protected zone, specifically a nitrogen atmosphere multi-temperature zone with a nitrogen flow rate of 3-8 m³ / h. 3 / h; The inert atmosphere multi-temperature zone includes a first inert atmosphere temperature zone for curing the protective oil layer and a second inert atmosphere temperature zone for thermal stability treatment of boron nitride organic precursor fibers, which are set sequentially; the temperature of the first inert atmosphere temperature zone is controlled at the curing temperature of the protective oil, and the temperature of the second inert atmosphere temperature zone is controlled at the polymerization temperature of the boron nitride organic precursor.

[0032] S5. The boron nitride organic precursor fibers treated in S4 are guided to a multi-temperature zone in a reaction atmosphere, where they undergo degreasing and sintering processes sequentially to obtain high-conversion boron nitride fibers. In this embodiment, the multi-temperature zone in the reaction atmosphere is a circulating reaction atmosphere multi-temperature zone, specifically an ammonia atmosphere multi-temperature zone, with an ammonia flow rate of 2-3 m³ / h. 3 / h; The reaction atmosphere multi-temperature zone includes a first reaction atmosphere temperature zone for degreasing treatment and a second reaction atmosphere temperature zone for sintering treatment, which are set in sequence; the temperature of the first reaction atmosphere temperature zone is controlled at the decomposition temperature of the protective oil; the temperature of the second reaction atmosphere temperature zone is controlled at 1000~1200℃.

[0033] In this embodiment, preferably, the boron nitride organic precursor is composed of a mixture of 30-50 parts of aminoborane, 5-15 parts of aminocycloborane and 10-20 parts of aniline by weight; the softening point of the boron nitride organic precursor is 105-120°C and the polymerization temperature is 160-220°C.

[0034] In this embodiment, preferably, the protective oil is composed of a mixture of 20-30 parts amino silicone oil, 30-50 parts dimethyl silicone oil and 10-20 parts vinyl silicone oil by weight; the curing temperature of the protective oil is 80-100°C and the decomposition temperature is 260-310°C.

[0035] This embodiment also provides a high-conversion-rate boron nitride fiber, which is prepared according to the continuous preparation method of the high-conversion-rate boron nitride fiber of this embodiment. The preparation method of this embodiment improves the conversion rate of boron nitride organic precursor fiber to boron nitride fiber. Compared with the prior art (spinning organic precursor to obtain precursor fiber and then sintering to obtain boron nitride fiber), the conversion rate of boron nitride organic precursor fiber is increased by 10-15%. The high-conversion-rate boron nitride fiber prepared in this embodiment has an oxygen content of 1.5-1.8%, a fiber density of 1.6-1.9%, and a ceramic yield of 50-55%, exhibiting low oxygen content, high fiber density, and high ceramic yield.

[0036] This embodiment also provides a system for preparing high-conversion boron nitride fibers, which is applied to the continuous preparation method of high-conversion boron nitride fibers in this embodiment. For example... Figure 2 As shown, the high-conversion boron nitride fiber preparation system of this embodiment includes: a spinning device 1, a bundling device 2, a coating device 3, an oil control device 4, an inert atmosphere multi-temperature zone furnace 5, and a reaction atmosphere multi-temperature zone furnace 6 arranged sequentially. In this embodiment, the specific structures of the spinning device 1 and the bundling device 2 are not limited; for example, the bundling device 2 can be a bundling wheel device. In this embodiment, the coating device 3 includes an oil storage tank 31 and an oil coating wheel 32 located above the oil storage tank 31 and partially immersed in the protective oil surface stored in the oil storage tank 31. In this embodiment, the oil control device 4 includes a first oil control device 41 and a second oil control device 42 arranged sequentially. The first oil control device 41 includes an oil receiving tank 411 and an oil pressing roller group located above the oil receiving tank 411. The oil pressing roller group includes two oil pressing rollers 412 arranged vertically. The second oil control device 42 includes an inert atmosphere furnace with openings at both ends. The inner cavity of the inert atmosphere furnace is provided with an inert atmosphere channel communicating with the openings at both ends of the inert atmosphere furnace. In this embodiment, preferably, a roller 8 can be provided between the first oil control device 41 and the second oil control device 42 to draw the boron nitride organic precursor fiber. In this embodiment, the inert atmosphere multi-temperature zone furnace 5 has openings at both ends, and the inert atmosphere multi-temperature zone furnace 5 includes a first inert atmosphere temperature zone 51 near the oil control device 4 and a second inert atmosphere temperature zone 52 near the reaction atmosphere multi-temperature zone furnace 6. In this embodiment, the reaction atmosphere multi-temperature zone furnace 6 has openings at both ends, and the reaction atmosphere multi-temperature zone furnace 6 includes a first reaction atmosphere temperature zone 61 near the inert atmosphere multi-temperature zone furnace 5 and a second reaction atmosphere temperature zone 62 away from the inert atmosphere multi-temperature zone furnace 5. In this embodiment, preferably, a roller can also be provided between the inert atmosphere multi-temperature zone furnace 5 and the reaction atmosphere multi-temperature zone furnace 6 to draw the boron nitride organic precursor fiber. In this embodiment, preferably, the high-conversion-rate boron nitride fiber preparation system may further include a winding device 7. The high-conversion-rate boron nitride fiber obtained after sintering the boron nitride organic precursor fiber in the second reaction atmosphere temperature zone 62 can be drawn to the winding device 7 via rollers 8 for winding. In this embodiment, preferably, when transferring the boron nitride organic precursor fiber in each process, a sealed and insulated / protective atmosphere is provided at the transfer gap to prevent the boron nitride organic precursor fiber from undergoing a sudden drop in temperature or adverse atmosphere when being introduced from the previous process to the next process, which could lead to fiber defects.

[0037] Example 2

[0038] This embodiment provides a high-conversion boron nitride fiber and its continuous preparation method and system. The only differences between this embodiment and Example 1 are in the boron nitride organic precursor, protective oil, second oil control stage, inert atmosphere multi-temperature zone, and reaction atmosphere multi-temperature zone. Here, only the differences will be described; the similarities will not be repeated.

[0039] In this embodiment, the boron nitride organic precursor is composed of a mixture of 50 parts by weight of aminoborane, 5 parts by weight of aminocycloborane and 10 parts by weight of aniline; the softening point of the boron nitride organic precursor is 105°C and the polymerization temperature is 160°C.

[0040] In this embodiment, the protective oil is composed of a mixture of 30 parts amino silicone oil, 30 parts dimethyl silicone oil and 10 parts vinyl silicone oil by weight; the curing temperature of the protective oil is 80°C and the decomposition temperature is 260°C.

[0041] In this embodiment, the second oil control stage involves guiding the boron nitride organic precursor fiber, after the first oil control stage, into an inert atmosphere channel via rollers to evaporate some of the protective oil until the oil content of the boron nitride organic precursor fiber is controlled at a preset value of 2%. In this embodiment, the inert atmosphere channel is a channel with circulating inert atmosphere flow, the temperature of the inert atmosphere channel is controlled at 30°C, the inert atmosphere is a nitrogen atmosphere, and the nitrogen flow rate is 3 m³ / s. 3 / h.

[0042] In this embodiment, the inert atmosphere multi-temperature zone is a circulating atmosphere protected inert atmosphere multi-temperature zone, specifically a nitrogen atmosphere multi-temperature zone, with a nitrogen flow rate of 3m³. 3 / h; The inert atmosphere multi-temperature zone includes a first inert atmosphere temperature zone for curing the protective oil layer and a second inert atmosphere temperature zone for thermal stability treatment of boron nitride organic precursor fibers, which are set sequentially; the temperature of the first inert atmosphere temperature zone is controlled at the curing temperature of the protective oil, 80℃, and the temperature of the second inert atmosphere temperature zone is controlled at the polymerization temperature of the boron nitride organic precursor, 160℃.

[0043] In this embodiment, the reaction atmosphere multi-temperature zone is a circulating reaction atmosphere multi-temperature zone, specifically an ammonia atmosphere multi-temperature zone, with an ammonia flow rate of 2m³ / h. 3 / h; The reaction atmosphere multi-temperature zone includes a first reaction atmosphere temperature zone for degreasing treatment and a second reaction atmosphere temperature zone for sintering treatment, which are set in sequence; the temperature of the first reaction atmosphere temperature zone is controlled at the decomposition temperature of the protective oil, 260℃; the temperature of the second reaction atmosphere temperature zone is controlled at 1000℃.

[0044] In this embodiment, boron nitride organic precursor fibers without a protective oil coating are used as a comparative example. Compared to obtaining boron nitride fibers by spinning organic precursors and then sintering them, the preparation method in this embodiment improves the conversion rate of boron nitride organic precursor fibers to boron nitride fibers, increasing the conversion rate by 10%. The boron nitride fibers prepared in the comparative example have an oxygen content of 5.5%, a fiber density of 1.29%, and a ceramic yield of 40%. The high-conversion boron nitride fibers prepared in this embodiment have an oxygen content of 1.5%, a fiber density of 1.6%, and a ceramic yield of 50%. The reduction in oxygen content and the increase in fiber density result in a higher ceramic yield.

[0045] Example 3

[0046] This embodiment provides a high-conversion boron nitride fiber and its continuous preparation method and system. The only differences between this embodiment and Example 1 are in the boron nitride organic precursor, protective oil, second oil control stage, inert atmosphere multi-temperature zone, and reaction atmosphere multi-temperature zone. Here, only the differences will be described; the similarities will not be repeated.

[0047] In this embodiment, the boron nitride organic precursor is composed of a mixture of 40 parts by weight of aminoborane, 8 parts by weight of aminocycloborane and 15 parts by weight of aniline; the softening point of the boron nitride organic precursor is 108°C and the polymerization temperature is 200°C.

[0048] In this embodiment, the protective oil is composed of a mixture of 25 parts amino silicone oil, 40 parts dimethyl silicone oil and 15 parts vinyl silicone oil by weight; the curing temperature of the protective oil is 90°C and the decomposition temperature is 280°C.

[0049] In this embodiment, the second oil control stage involves guiding the boron nitride organic precursor fiber, after the first oil control stage, into an inert atmosphere channel via rollers to evaporate some of the protective oil until the oil content of the boron nitride organic precursor fiber is controlled at a preset value of 3%. In this embodiment, the inert atmosphere channel is a channel with circulating inert atmosphere flow, the temperature of the inert atmosphere channel is controlled at 40°C, the inert atmosphere is a nitrogen atmosphere, and the nitrogen flow rate is 6 m³ / s. 3 / h.

[0050] In this embodiment, the inert atmosphere multi-temperature zone is a circulating atmosphere protected inert atmosphere multi-temperature zone, specifically a nitrogen atmosphere multi-temperature zone, with a nitrogen flow rate of 6m³. 3 / h; The inert atmosphere multi-temperature zone includes a first inert atmosphere temperature zone for curing the protective oil layer and a second inert atmosphere temperature zone for thermal stability treatment of boron nitride organic precursor fibers, which are set sequentially; the temperature of the first inert atmosphere temperature zone is controlled at the curing temperature of the protective oil, 90℃, and the temperature of the second inert atmosphere temperature zone is controlled at the polymerization temperature of the boron nitride organic precursor, 200℃.

[0051] In this embodiment, the reaction atmosphere multi-temperature zone is a circulating reaction atmosphere multi-temperature zone, specifically an ammonia atmosphere multi-temperature zone, with an ammonia flow rate of 2.5 m³ / s. 3 / h; The reaction atmosphere multi-temperature zone includes a first reaction atmosphere temperature zone for degreasing treatment and a second reaction atmosphere temperature zone for sintering treatment, which are set in sequence; the temperature of the first reaction atmosphere temperature zone is controlled at the decomposition temperature of the protective oil, 280℃; the temperature of the second reaction atmosphere temperature zone is controlled at 1100℃.

[0052] In this embodiment, boron nitride organic precursor fibers without a protective oil coating are used as a comparative example. Compared to obtaining boron nitride fibers by spinning organic precursors and then sintering them, the preparation method in this embodiment improves the conversion rate of boron nitride organic precursor fibers to boron nitride fibers, increasing the conversion rate by 12%. The boron nitride fibers prepared in the comparative example have an oxygen content of 5.6%, a fiber density of 1.31%, and a ceramic yield of 42%. The high-conversion boron nitride fibers prepared in this embodiment have an oxygen content of 1.68%, a fiber density of 1.68%, and a ceramic yield of 54%, demonstrating a decrease in oxygen content, an increase in fiber density, and an increase in ceramic yield.

[0053] Example 4

[0054] This embodiment provides a high-conversion boron nitride fiber and its continuous preparation method and system. The only differences between this embodiment and Example 1 are in the boron nitride organic precursor, protective oil, second oil control stage, inert atmosphere multi-temperature zone, and reaction atmosphere multi-temperature zone. Here, only the differences will be described; the similarities will not be repeated.

[0055] In this embodiment, the boron nitride organic precursor, by weight, is composed of a mixture of 30 parts aminoborane, 15 parts aminocycloborane, and 20 parts aniline; the softening point of the boron nitride organic precursor is 120°C, and the polymerization temperature is 220°C.

[0056] In this embodiment, the protective oil is composed of a mixture of 20 parts amino silicone oil, 50 parts dimethyl silicone oil and 20 parts vinyl silicone oil by weight; the curing temperature of the protective oil is 100°C and the decomposition temperature is 310°C.

[0057] In this embodiment, the second oil control stage involves guiding the boron nitride organic precursor fiber, after the first oil control stage, into an inert atmosphere channel via rollers to evaporate some of the protective oil until the oil content of the boron nitride organic precursor fiber is controlled at a preset value of 4%. In this embodiment, the inert atmosphere channel is a channel with circulating inert atmosphere flow, the temperature of the inert atmosphere channel is controlled at 50°C, the inert atmosphere is a nitrogen atmosphere, and the nitrogen flow rate is 8 m³ / s. 3 / h.

[0058] In this embodiment, the inert atmosphere multi-temperature zone is a circulating atmosphere protection inert atmosphere multi-temperature zone, specifically a nitrogen atmosphere multi-temperature zone, with a nitrogen flow rate of 8m³ / h. 3 / h; the inert atmosphere multi-temperature zone includes a first inert atmosphere temperature zone for curing the protective oil layer and a second inert atmosphere temperature zone for thermal stability treatment of the boron nitride organic precursor fiber, arranged sequentially; the temperature of the first inert atmosphere temperature zone is controlled at the curing temperature of the protective oil, 100℃, and the temperature of the second inert atmosphere temperature zone is controlled at the polymerization temperature of the boron nitride organic precursor, 220℃. For example... Figure 3 The figure shows the microstructure of the boron nitride organic precursor fiber with a protective oil layer after coating the fiber with protective oil, followed by oil control and curing treatment. As can be seen from the figure, after coating, controlling and curing with protective oil, the surface of the boron nitride organic precursor fiber is covered with a uniform and dense protective oil layer. Figure 4 The diagram shows the cross-sectional elemental distribution of the boron nitride organic precursor fiber after coating it with protective oil, followed by oil control and curing treatment. As can be seen from the diagram, after coating, controlling and curing with protective oil, Si and C elements are enriched on the surface of the boron nitride organic precursor fiber, which also indicates that the protective oil layer effectively coats the surface of the boron nitride organic precursor fiber.

[0059] In this embodiment, the reaction atmosphere multi-temperature zone is a circulating reaction atmosphere multi-temperature zone, specifically an ammonia atmosphere multi-temperature zone, with an ammonia flow rate of 3m³. 3 / h; The reaction atmosphere multi-temperature zone includes a first reaction atmosphere temperature zone for degreasing treatment and a second reaction atmosphere temperature zone for sintering treatment, which are set in sequence; the temperature of the first reaction atmosphere temperature zone is controlled at the decomposition temperature of the protective oil, 310℃; the temperature of the second reaction atmosphere temperature zone is controlled at 1200℃.

[0060] like Figure 5 The figure shows the thermogravimetric curves of boron nitride organic precursor fibers without a protective oil coating, and boron nitride organic precursor fibers with a protective oil coating after being coated with protective oil and then subjected to oil control and protective oil layer curing treatment, at temperatures ranging from 0 to 1500°C. As can be seen from the figure, compared to boron nitride organic precursor fibers without a protective oil coating, the boron nitride organic precursor fibers with a protective oil coating of the present invention exhibit better thermal stability. Within the range from the softening point of the boron nitride organic precursor fibers to the decomposition temperature of the protective oil, the boron nitride organic precursor fibers with a protective oil coating of the present invention show lower thermal weight loss, improving temperature resistance and thus achieving a higher ceramic yield.

[0061] In this embodiment, boron nitride organic precursor fibers without a protective oil coating are used as a comparative example. Compared to obtaining boron nitride fibers by spinning organic precursors and then sintering them, the preparation method in this embodiment improves the conversion rate of boron nitride organic precursor fibers to boron nitride fibers, increasing the conversion rate by 15%. The boron nitride fibers prepared in the comparative example have an oxygen content of 5.8%, a fiber density of 1.37%, and a ceramic yield of 40%. The high-conversion boron nitride fibers prepared in this embodiment have an oxygen content of 1.8%, a fiber density of 1.9%, and a ceramic yield of 55%. The reduction in oxygen content and the increase in fiber density result in a higher ceramic yield.

[0062] The present invention has been described above with reference to specific embodiments. These specific embodiments are merely exemplary and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make various modifications, changes, or substitutions without departing from the essence of the present invention. Therefore, various equivalent variations made according to the present invention still fall within the scope of the present invention.

Claims

1. A continuous preparation method for high-conversion boron nitride fibers, characterized in that, Includes the following steps: S1. Boron nitride organic precursor is spun to obtain boron nitride organic precursor fiber; S2. Guide the boron nitride organic precursor fiber obtained by spinning to the coating area, coat the boron nitride organic precursor fiber with protective oil to obtain boron nitride organic precursor fiber with a protective oil layer on the surface. S3. Guide the boron nitride organic precursor fiber with a protective oil layer on its surface to the oil control area, perform oil control treatment on the boron nitride organic precursor fiber, control the oil content of the boron nitride organic precursor fiber to a preset value, and obtain the oil-controlled boron nitride organic precursor fiber. S4. Guide the oil-controlled boron nitride organic precursor fiber to an inert atmosphere multi-temperature zone, and perform protective oil layer curing treatment and boron nitride organic precursor fiber thermal stability treatment in sequence. S5. The boron nitride organic precursor fibers treated in S4 are guided to a multi-temperature zone of the reaction atmosphere and subjected to degreasing and sintering treatments in sequence to obtain the high-conversion boron nitride fibers. in, The inert atmosphere multi-temperature zone is a nitrogen atmosphere multi-temperature zone; The inert atmosphere multi-temperature zone includes a first inert atmosphere temperature zone for curing the protective oil layer and a second inert atmosphere temperature zone for thermal stability treatment of boron nitride organic precursor fibers, arranged sequentially. The temperature in the first inert atmosphere zone is controlled at the curing temperature of the protective oil, and the temperature in the second inert atmosphere zone is controlled at the polymerization temperature of the boron nitride organic precursor. The reaction atmosphere multi-temperature zone is an ammonia atmosphere multi-temperature zone; The reaction atmosphere multi-temperature zone includes a first reaction atmosphere temperature zone for degreasing treatment and a second reaction atmosphere temperature zone for sintering treatment, which are arranged sequentially. The temperature of the first reaction atmosphere zone is controlled at the decomposition temperature of the protective oil; the temperature of the second reaction atmosphere zone is controlled at 1000~1200℃. The protective oil, by weight, is a mixture of raw materials comprising 20-30 parts amino silicone oil, 30-50 parts dimethyl silicone oil and 10-20 parts vinyl silicone oil; The curing temperature of the protective oil is 80~100℃, and the decomposition temperature is 260~310℃.

2. The continuous preparation method of high-conversion boron nitride fiber as described in claim 1, characterized in that, The curing temperature of the protective oil is lower than the softening point of the boron nitride organic precursor, and the decomposition temperature of the protective oil is higher than the polymerization temperature of the boron nitride organic precursor.

3. The continuous preparation method of high-conversion boron nitride fiber as described in claim 1, characterized in that, The oil control treatment includes a first oil control stage and a second oil control stage performed sequentially. The first oil control stage is as follows: the boron nitride organic precursor fiber with a protective oil layer on its surface is passed through the upper and lower oil pressing rollers, and a portion of the protective oil is squeezed out by the cooperation of the upper and lower oil pressing rollers. The second oil control stage is as follows: the boron nitride organic precursor fiber after the first oil control stage is guided into an inert atmosphere channel to volatilize some of the protective oil until the oil content of the boron nitride organic precursor fiber is controlled at a preset value; the preset value is 2~4%.

4. The continuous preparation method of high-conversion boron nitride fiber as described in claim 3, characterized in that, The temperature of the inert atmosphere channel is controlled at 30~50℃, and the inert atmosphere is nitrogen atmosphere with a nitrogen flow rate of 3~8m³. 3 / h.

5. The continuous preparation method of high-conversion boron nitride fiber as described in claim 1, characterized in that, The nitrogen flow rate in the inert atmosphere multi-temperature zone is 3~8m³. 3 / h.

6. The continuous preparation method of high-conversion boron nitride fiber as described in claim 1, characterized in that, The ammonia flow rate in the multi-temperature zone of the reaction atmosphere is 2-3 m³ / h. 3 / h.

7. The continuous preparation method of high-conversion boron nitride fiber as described in claim 1, characterized in that, By weight, the boron nitride organic precursor is composed of a mixture of raw materials including 30-50 parts of aminoborane, 5-15 parts of aminocycloborane and 10-20 parts of aniline; The softening point of the boron nitride organic precursor is 105~120℃, and the polymerization temperature is 160~220℃.

8. A high-conversion boron nitride fiber, characterized in that, The high-conversion boron nitride fiber is prepared by the continuous preparation method according to any one of claims 1-7.

9. A system for preparing high-conversion boron nitride fibers, applied to the continuous preparation method of high-conversion boron nitride fibers according to any one of claims 1-7, characterized in that, include: The spinning device, bundling device, coating device, oil control device, inert atmosphere multi-temperature zone furnace and reaction atmosphere multi-temperature zone furnace are arranged in sequence. The coating device includes an oil tank and an oiling wheel located above the oil tank and partially immersed in the protective oil surface stored in the oil tank; The oil control device includes a first oil control device and a second oil control device arranged in sequence. The first oil control device includes an oil receiving tank and an oil pressing roller group located above the oil receiving tank. The oil pressing roller group includes two oil pressing rollers arranged vertically. The second oil control device includes an inert atmosphere furnace. The inert atmosphere furnace has openings at both ends, and the inner cavity of the inert atmosphere furnace has an inert atmosphere channel communicating with the openings at both ends of the inert atmosphere furnace. The inert atmosphere multi-temperature zone furnace has openings at both ends. The inert atmosphere multi-temperature zone furnace includes a first inert atmosphere temperature zone near the oil control device and a second inert atmosphere temperature zone near the reaction atmosphere multi-temperature zone furnace. The multi-temperature zone furnace for reaction atmosphere has openings at both ends. The multi-temperature zone furnace for reaction atmosphere includes a first reaction atmosphere temperature zone close to the inert atmosphere multi-temperature zone furnace and a second reaction atmosphere temperature zone far away from the inert atmosphere multi-temperature zone furnace.

Images