A glass fiber with low dielectric constant and preparation method thereof

Abstract

The present invention relates to the field of fiber materials, and provides a glass fiber with a low dielectric constant and a preparation method thereof, comprising basalt glass fiber and a silicon fluoride layer coating its surface. The basalt glass fiber is prepared by a melt drawing method, with an average diameter of 5.0 to 15.0 μm, and the volume ratio of the crystalline to the amorphous state is controlled at (5.0 to 15.0): (85.0 to 95.0). The silicon fluoride layer has a thickness of 140 to 400 nm and is obtained by a sol-gel method. It is formed by impregnation, ultrasonication, and purge with ethyl orthosilicate and ammonium fluoride sol and then heat-treated under an inert atmosphere. The preparation method includes crushing, pickling, melting, drawing, and gradient cooling of the basalt raw material to ensure the uniformity and stability of the fiber. The preparation conditions, impregnation parameters, purge pressure, and heat treatment temperature of the modified sol are optimized to achieve uniform coating and enhance stability. The glass fiber provided by the present invention has a low dielectric constant, excellent heat resistance, and hydrophobicity, and is suitable for high-frequency electronic substrates, aerospace, and 5G communication fields.

Description

Technical Field

[0001] The present invention relates to the field of fiber materials, and in particular to a glass fiber with a low dielectric constant and a preparation method thereof. Background Art

[0002] In modern high-frequency communications, aerospace, and microelectronics packaging, the dielectric properties of materials have a decisive influence on signal transmission efficiency, electronic component stability, and overall system performance. With the development of 5G communications, millimeter-wave radar, and high-speed computing equipment, the demand for low dielectric constant (Dk) materials is growing to reduce signal loss, increase data transmission rates, and reduce electromagnetic interference. At the same time, in order to adapt to complex environments, these materials must also have excellent weather resistance and hydrophobicity to prevent the impact of humidity changes on dielectric properties and ensure long-term stability. In addition, in the application of composite materials and structural parts, glass fiber is used as a matrix reinforcement material, and its mechanical properties directly affect the mechanical strength, impact resistance, and service life of the final product. Therefore, the research and development of glass fiber materials with low dielectric constant, high hydrophobicity, and excellent mechanical properties can not only improve the performance of electronic packaging and communication equipment, but also broaden its application range and promote the development of related industries in a more efficient and reliable direction.

[0003] At present, the research on low dielectric glass fiber has made certain progress, but there are still many limitations. For example, the Chinese patent with publication number CN101594987B discloses a low dielectric glass fiber. Although low dielectric properties are obtained by optimizing the composition, it does not have hydrophobic properties. In addition, some existing technologies use silane coupling agents to improve hydrophobicity, but due to the weak interfacial bonding force, peeling is likely to occur during long-term use, resulting in reduced durability. For example, the Chinese patent with publication number CN108503314A discloses a fire-free pavement brick with added hydrophobically modified glass fiber, in which the glass fiber is modified with a silane coupling agent. Therefore, the silane coupling agent is prone to failure during long-term service, and importantly, the hydrophobic modification does not improve the dielectric constant. At the same time, the improvement of mechanical properties is often limited by the brittleness of the glass fiber itself. Existing methods mostly rely on resin modification or filling reinforcement, but this may introduce additional dielectric loss and weaken the low dielectric advantage of the material. Therefore, how to improve the hydrophobicity and mechanical properties of glass fiber while maintaining low dielectric properties, and optimize the preparation process to reduce costs and improve stability, remains a technical challenge that needs to be solved urgently in this field. Summary of the Invention

[0004] (1) Technical problems solved

[0005] The purpose of the present invention is to provide a glass fiber with a low dielectric constant and a preparation process thereof, so as to solve the problems of low dielectric constant, hydrophobicity and insufficient mechanical properties of the current glass fiber.

[0006] (2) Technical solution

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A glass fiber with a low dielectric constant, comprising a basalt glass fiber and a silicon oxyfluoride layer coated on the surface of the basalt glass fiber;

[0009] The average size of the basalt glass fiber is 5.0 to 15.0 μm;

[0010] The volume ratio of the crystalline and amorphous states in the basalt glass fiber is (5.0-15.0):(85.0-95.0);

[0011] The thickness of the silicon oxyfluoride layer is 140 to 400 nm;

[0012] The basalt glass fiber is prepared from basalt raw materials through a melt drawing method;

[0013] The silicon fluoride layer is formed by impregnating basalt glass fiber with a mixed sol containing ethyl orthosilicate and ammonium fluoride, ultrasonically treating and purging the basalt glass fiber, and then heat-treating the basalt glass fiber in an inert atmosphere.

[0014] The present invention adopts a design of a composite of basalt glass fiber and a silicon fluoride layer, which is mainly used to enhance the low dielectric properties, weather resistance and mechanical properties of the material. By optimizing the preparation process of basalt glass fiber, controlling its average size and the volume ratio of crystalline to amorphous states, it is possible to ensure low dielectric loss while having excellent mechanical strength and structural stability. The melt drawing process of basalt glass fiber ensures the uniformity and controllability of the fiber, thereby improving the dielectric uniformity of the overall material and optimizing the interface bonding characteristics. In order to further reduce the dielectric constant and enhance hydrophobicity, the present invention adopts a silicon fluoride layer coating, and the surface of the basalt glass fiber is modified by a mixed sol of ethyl orthosilicate and ammonium fluoride. After impregnation, ultrasonic treatment and purging, it is heat-treated in an inert atmosphere to form a uniform silicon fluoride layer. This coating layer not only effectively reduces the polar groups on the fiber surface, thereby reducing the dielectric loss of the material, but also improves the moisture resistance of the material, so that it can still maintain stable dielectric properties in a high humidity environment. Furthermore, the thickness of the silicon oxyfluoride layer is controlled within a reasonable range, ensuring excellent hydrophobicity while avoiding the potential degradation of mechanical properties that can occur with an overly thick coating. The synergistic effect of the fiber matrix and surface coating ensures that the glass fiber material of the present invention maintains low dielectric properties while possessing excellent environmental resistance and mechanical stability, meeting the demand for high-performance, low-dielectric materials in fields such as high-frequency electronic packaging, communications equipment, and aerospace.

[0015] Furthermore, the preparation method of the basalt glass fiber comprises the following steps:

[0016] A1: The basalt raw material is mechanically crushed and sieved into particles with a size of 5-20 mm. The particles are then immersed in a 0.5-2.0 mol / L hydrochloric acid solution for 1-4 hours to remove metal impurities and free oxides. The particles are then rinsed with deionized water to a pH of 6.5-7.5 and dried in a vacuum drying oven at 80-120°C for 120-160 minutes to a moisture content of ≤0.5 wt%.

[0017] A2: Place the dried basalt particles into a molybdenum-lanthanum alloy crucible. Under a nitrogen atmosphere, control the oxygen content to ≤50 ppm. Heat to 1550-1700°C at a heating rate of 5-15°C / min. Hold the temperature for 60-120 minutes to form a uniform glass melt. Monitor the dynamic viscosity of the melt in real time using a viscometer to maintain a range of 10-50 Pa·s.

[0018] A3: Pull the molten glass liquid down through a platinum alloy leak plate with a pore size of 0.8 to 1.5 mm, control the leak plate temperature to 1250 to 1400°C, the drawing speed to 300 to 800 m / min, and the pulling roller surface temperature to 20 to 50°C, and use a laser diameter gauge to adjust the fiber diameter to 5 to 15 μm in real time with a deviation of ≤±0.5 μm.

[0019] A4: The fiber is sequentially cooled with inert gas and sprayed with water mist to achieve gradient solidification. In the first cooling stage, the fiber is passed through a 2-5 m argon channel with a controlled argon flow rate of 3-10 m / s and a cooling rate of 50-200°C / s to reduce the fiber surface temperature to 600-800°C. In the second cooling stage, deionized water mist is sprayed with an atomizing pressure of 0.1-0.5 MPa, with a droplet size of ≤10 μm and a spray density of 0.5-2.0 L / min·m 2 , lower the fiber temperature to 25-40°C to complete curing.

[0020] Furthermore, the components of the basalt raw material in A1 are: Al2O3 8.0-9.0wt%, TiO2 1.5-1.8wt%, FeO 8.0-10.0wt%, CaO 7.0-8.0wt%, MgO 15.0-16.0wt%, Na2O 2.8-3.2wt%, K2O 0.6-0.8wt%, B2O3 3.0-6.0wt%, and the balance is SiO2.

[0021] The present invention adopts the design of basalt glass fiber mainly to enhance the low dielectric properties, mechanical properties and environmental stability of the material. By optimizing the composition and preparation process of basalt glass fiber, a reasonable match between crystalline and amorphous states is achieved to improve dielectric properties and mechanical strength. During the raw material processing stage, metal impurities and free oxides are removed by mechanical crushing and pickling, effectively reducing dielectric loss and enhancing fiber uniformity. During the melting process, a molybdenum-lanthanum alloy crucible is used to control the oxygen content in a nitrogen atmosphere to ensure the stability of the glass melt, and the melting state is optimized by viscosity monitoring to form a uniform glass phase structure. During the drawing process, a platinum alloy bushing is used to precisely control the melt fluidity, and a laser diameter gauge is used to adjust the fiber diameter in real time to keep it within the range of 5.0 to 15.0 μm to ensure excellent mechanical properties and dimensional uniformity. During the cooling and solidification stage, gradient cooling is achieved through inert gas cooling through an argon channel combined with deionized water mist spraying, which helps to optimize the ratio of crystalline and amorphous states, so that the fiber has good strength and stability while maintaining low dielectric properties. Furthermore, rational compositional design, such as the synergistic effects of Al2O3, TiO2, FeO, CaO, MgO, Na2O, K2O, and B2O3, not only optimizes the fiber's dielectric properties but also enhances its thermal shock resistance and chemical corrosion resistance, further enhancing the material's environmental adaptability. Through systematic process optimization, this invention achieves exceptional low dielectric loss, structural stability, and mechanical properties in basalt glass fiber, meeting the demands of high-frequency communications, aerospace, and electronic packaging.

[0022] The present invention also discloses a method for preparing glass fiber with a low dielectric constant, comprising the following steps:

[0023] S1. Prepare a mixed sol containing ethyl orthosilicate, ammonium fluoride, ethanol and deionized water;

[0024] S2. immersing the basalt glass fiber in the sol and performing ultrasonic treatment;

[0025] S3. Blowing to remove residual sol on the fiber surface;

[0026] S4. Performing an inert atmosphere heat treatment and a passivation treatment on the fiber.

[0027] Furthermore, the mixed sol comprises, by weight, 14 to 36 parts of ethyl orthosilicate, 7.0 to 12.0 parts of ammonium fluoride, 50 to 100 parts of ethanol, and 5 to 15 parts of deionized water; the sol preparation conditions include: stirring at 300 to 600 rpm at 25 to 40° C. for 20 to 60 minutes, followed by aging at 20 to 25° C. for 60 to 120 minutes;

[0028] Furthermore, the mass ratio of the tetraethyl orthosilicate to ammonium fluoride is (2.0-3.0):1;

[0029] Furthermore, the immersion conditions include: controlling the immersion depth to 10-50 cm, the stirring rate to 200-500 rpm, the ultrasonic frequency to 20-40 kHz, the pressure to 0.1-0.5 MPa, and the treatment time to 30-120 min;

[0030] Furthermore, the purge parameters include: nitrogen pressure 0.5-2.0 MPa, incident angle 30-60°, flow rate 5-15 L / min and purge time 10-30 s, and the thickness of the residual sol layer after treatment is 1-5 μm.

[0031] Furthermore, the heat treatment conditions include: heating to 500-600°C at 5-10°C / min under an argon atmosphere, keeping warm for 30-60 minutes, and then cooling to room temperature at 2-5°C / min, with the gas flow rate controlled at 0.5-2.0 L / min.

[0032] Furthermore, the passivation treatment process is as follows: the fiber after heat treatment is placed in a plasma treatment chamber, CF4 is introduced as a reaction gas under a vacuum degree of 10 to 100 Pa, and the gas flow rate is controlled at 50 to 200 sccm. Subsequently, a plasma power of 50 to 200 W is applied, and the treatment is continued for 30 to 300 seconds. After the plasma treatment is completed, the material is immediately transferred to a vacuum annealing furnace, and under an argon flow rate of 0.5 to 2.0 L / min, the temperature is raised to 300 to 400°C at a rate of 5 to 10°C / min, and the temperature is kept at this temperature for 30 to 60 minutes. After the treatment, the material is cooled to room temperature.

[0033] The present invention adopts the design of sol-gel method in combination with heat treatment and passivation process to be mainly used for enhancing the low dielectric properties, chemical stability and weather resistance of glass fiber. By preparing a mixed sol containing tetraethyl orthosilicate, ammonium fluoride, ethanol and deionized water, and controlling the ratio of tetraethyl orthosilicate and ammonium fluoride, the sol is formed into a uniform and stable system under suitable temperature and stirring rate, thereby providing a good interface bonding environment for the modification of basalt glass fiber. During the impregnation process, by optimizing the immersion depth, stirring rate, ultrasonic frequency and pressure, the sol is evenly covered on the glass fiber surface, and the permeability of the sol is enhanced by ultrasonic treatment to ensure the uniformity and density of the modified layer. Subsequently, nitrogen purging is adopted to remove the residual sol on the surface, and the purging parameters are accurately controlled to effectively reduce the sol accumulation and ensure that the coating thickness is moderate, thereby avoiding the dielectric performance degradation caused by uneven coating. In the heat treatment stage, argon atmosphere is utilized to control the heating and cooling rates so that the coating is stably solidified on the surface of the glass fiber, while reducing the adverse effects of oxidation on fiber performance, and the heat treatment stage completes the annealing of the fiber at the same time, further optimizing its dielectric properties and mechanical stability. Ultimately, by plasma passivation treatment, CF4 is introduced as a reaction gas, under suitable vacuum conditions and plasma power, a fluorination reaction is caused on the coating surface, the hydrophobicity and chemical stability of the glass fiber are enhanced, and surface defects are further eliminated in subsequent argon annealing processes, thereby improving the bonding strength of the overall coating to the fiber matrix. The present invention, through the synergistic effect of each preparation step, effectively optimizes glass fiber in terms of low dielectric loss, moisture resistance and mechanical properties, and meets the application requirements in the fields of high-frequency electronic packaging, communication equipment and aerospace.

[0034] (3) Beneficial technical effects

[0035] 1. The present invention achieves low dielectric loss, high hydrophobicity, and excellent mechanical properties through the synergistic effect of basalt glass fiber and the silicon oxyfluoride layer. Compared with the existing technology, it improves material uniformity and stability, reduces environmental impact, and is suitable for high-frequency electronic packaging, communication equipment, and aerospace fields.

[0036] 2. The present invention achieves low dielectric loss, high mechanical strength and excellent environmental stability by optimizing the composition and preparation process of basalt glass fiber. Compared with the existing technology, it improves material uniformity and durability, reduces signal loss, and is suitable for high-frequency communications, aerospace and electronic packaging fields.

[0037] 3. The present invention uses a sol-gel method combined with heat treatment and passivation technology to achieve the optimization of low dielectric, weather resistance and chemical stability of glass fiber. Compared with the existing technology, it improves the interface bonding strength, uniformity and moisture resistance, avoids coating peeling and dielectric loss, and is suitable for high-frequency electronics, communications and aerospace fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the cross-sectional morphology of the basalt glass fiber prepared in Example 1 of the present invention.

[0039] Figure 2 This is the cross-sectional morphology of the glass fiber prepared in Example 1 of the present invention.

[0040] Figure 3 This is a transmission electron microscope image of the basalt glass fiber prepared in Example 1 of the present invention.

[0041] Figure 4 The glass fiber felt prepared in Example 3 of the present invention for testing the hydrophobic angle.

[0042] Figure 5 This is the morphology of water droplets on glass fiber mat prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0043] To make the objectives, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0044] Example 1

[0045] A low-dielectric-constant glass fiber, comprising a basalt glass fiber and a silicon fluoride layer coated on the surface of the basalt glass fiber; the basalt glass fiber has an average size of 5.0 μm; the volume ratio of crystalline to amorphous portions in the basalt glass fiber is 15.0:85.0; the silicon fluoride layer has a thickness of 140 nm; the basalt glass fiber is prepared from basalt raw material by a melt-drawing method; the silicon fluoride layer is formed by impregnating the basalt glass fiber with a mixed sol containing ethyl orthosilicate and ammonium fluoride, ultrasonically treating, purging, and then heat-treating in an inert atmosphere;

[0046] The preparation method of the basalt glass fiber of this embodiment comprises the following steps:

[0047] A1: Basalt raw material was mechanically crushed and sieved into particles with a particle size of 5 mm. The particles were immersed in a 0.5 mol / L hydrochloric acid solution for 1 hour to remove metallic impurities and free oxides. The particles were then rinsed with deionized water to a pH of 6.5 and dried in a vacuum drying oven at 80°C for 120 minutes to a moisture content of ≤0.5 wt%. The composition of the basalt raw material was: Al2O3 8.0 wt%, TiO2 1.5 wt%, FeO 8.0 wt%, CaO 7.0 wt%, MgO 15.0 wt%, Na2O 2.8 wt%, K2O 0.6 wt%, B2O3 3.0 wt%, with the remainder being SiO2.

[0048] A2: The dried basalt particles were placed in a molybdenum-lanthanum alloy crucible. Under a nitrogen atmosphere, the oxygen content was controlled to ≤50 ppm. The crucible was heated to 1550°C at a heating rate of 5°C / min and held at that temperature for 60 minutes to form a uniform glass melt. The dynamic viscosity of the melt was monitored in real time by a viscometer to be 10 Pa·s.

[0049] A3: The molten glass liquid is pulled down through a platinum alloy leak plate with a pore size of 0.8mm. The leak plate temperature is controlled at 1250℃, the drawing speed is 300m / min, and the surface temperature of the pulling roller is 20℃. The fiber diameter is adjusted in real time by a laser diameter gauge to 5μm with a deviation of ≤±0.5μm.

[0050] A4: The fiber is sequentially cooled with inert gas and water mist to achieve gradient solidification. In the first cooling stage, the fiber is passed through a 2m argon channel with a controlled argon flow rate of 3m / s and a cooling rate of 50℃ / s to reduce the fiber surface temperature to 600℃. In the second cooling stage, deionized water mist with an atomization pressure of 0.1MPa is used to control the droplet size to ≤10μm and the spray density to 0.5L / min·m 2 , lower the fiber temperature to 25°C to complete curing.

[0051] A method for preparing a glass fiber with a low dielectric constant according to this embodiment includes the following steps:

[0052] S1. Prepare a mixed sol containing tetraethyl orthosilicate, ammonium fluoride, ethanol, and deionized water; the composition of the mixed sol is as follows: 14 parts of tetraethyl orthosilicate, 7.0 parts of ammonium fluoride, 50 parts of ethanol, and 5 parts of deionized water, in parts by weight; the sol preparation conditions include: stirring at 300 rpm for 20 minutes at 25°C, followed by aging at 20°C for 60 minutes; the mass ratio of tetraethyl orthosilicate to ammonium fluoride is 2.0:1.

[0053] S2. The basalt glass fiber was impregnated in the sol and ultrasonically treated; the immersion conditions included: controlling the immersion depth of 10 cm, the stirring rate of 200 rpm, the ultrasonic frequency of 20 kHz and the pressure of 0.1 MPa, and the treatment time of 30 min;

[0054] S3. Purge to remove residual sol on the fiber surface; the purge parameters include: nitrogen pressure 0.5 MPa, incident angle 30°, flow rate 5 L / min and purge time 10 s. The thickness of the residual sol layer after treatment is 6.5 μm.

[0055] S4. The fiber is subjected to inert atmosphere heat treatment and passivation treatment. The heat treatment conditions include: in an argon atmosphere, heating to 500°C at a rate of 5°C / min, keeping warm for 30 minutes, and then cooling to room temperature at a rate of 2°C / min, with the gas flow rate controlled at 0.5L / min. The passivation treatment process is as follows: the fiber after heat treatment is placed in a plasma treatment chamber, under the condition of a vacuum degree of 10Pa, CF4 is introduced as a reaction gas, the gas flow rate is controlled at 50sccm, and then a plasma power of 50W is applied, and the treatment is continued for 30s. After the plasma treatment is completed, the material is immediately transferred to a vacuum annealing furnace, and under the condition of an argon flow rate of 0.5L / min, the temperature is raised to 300°C at a rate of 5°C / min, kept warm for 30 minutes, and cooled to room temperature after the treatment.

[0056] Figure 1 The cross-sectional morphology of the basalt glass fiber prepared in Example 1 of the present invention is shown, demonstrating that the fiber has a uniform diameter, indicating that the preparation process can effectively control the fiber size and improve the uniformity of the material. Figure 2 The cross-sectional morphology of the glass fiber was further demonstrated, clearly revealing the double-layer structure of the glass fiber, including the basalt glass fiber body and the fluorine oxide silicon layer coated on its surface, indicating the effectiveness of the coating process. Figure 3 This is a transmission electron microscope morphology image, which shows that the basalt glass fiber contains a small amount of nanocrystals, proving that the material has a certain crystalline structure under specific conditions, which may affect its dielectric and mechanical properties.

[0057] Example 2

[0058] A low-dielectric-constant glass fiber, comprising a basalt glass fiber and a silicon fluoride layer coated on the surface of the basalt glass fiber; the basalt glass fiber has an average size of 8.0 μm; the volume ratio of crystalline to amorphous portions in the basalt glass fiber is 12.0:88.0; the silicon fluoride layer has a thickness of 218 nm; the basalt glass fiber is prepared from basalt raw material by a melt-drawing method; the silicon fluoride layer is formed by impregnating the basalt glass fiber with a mixed sol containing ethyl orthosilicate and ammonium fluoride, ultrasonically treating, purging, and then heat-treating in an inert atmosphere;

[0059] The preparation method of the basalt glass fiber of this embodiment comprises the following steps:

[0060] A1: Basalt raw material was mechanically crushed and sieved into particles with a particle size of 10 mm. The particles were immersed in a 0.9 mol / L hydrochloric acid solution for 2 hours to remove metallic impurities and free oxides. The particles were then rinsed with deionized water to a pH of 6.8 and dried in a vacuum drying oven at 92°C for 132 minutes to a moisture content of ≤0.5 wt%. The composition of the basalt raw material was: Al2O3 8.3 wt%, TiO2 1.6 wt%, FeO 8.6 wt%, CaO 7.3 wt%, MgO 15.3 wt%, Na2O 2.9 wt%, K2O 0.7 wt%, B2O3 3.9 wt%, with the remainder being SiO2.

[0061] A2: The dried basalt particles were placed in a molybdenum-lanthanum alloy crucible. Under a nitrogen atmosphere, the oxygen content was controlled to ≤50 ppm. The crucible was heated to 1595°C at a heating rate of 8°C / min and held at that temperature for 78 minutes to form a uniform glass melt. The dynamic viscosity of the melt was monitored in real time by a viscometer and was 22 Pa·s.

[0062] A3: The molten glass liquid is pulled down through a platinum alloy leak plate with a pore size of 1.0 mm. The leak plate temperature is controlled at 1295°C, the drawing speed is 450 m / min, and the surface temperature of the pulling roller is 29°C. The fiber diameter is adjusted in real time by a laser diameter gauge to 8 μm with a deviation of ≤±0.5 μm.

[0063] A4: The fiber is sequentially cooled with inert gas and water mist to achieve gradient solidification. In the first cooling stage, the fiber is passed through a 3m argon channel with a controlled argon flow rate of 5m / s and a cooling rate of 95℃ / s to reduce the fiber surface temperature to 660℃. In the second cooling stage, deionized water mist with an atomization pressure of 0.2MPa is used to control the droplet size to ≤10μm and the spray density to 0.9L / min·m 2 , lower the fiber temperature to 29°C to complete the curing.

[0064] A method for preparing a glass fiber with a low dielectric constant according to this embodiment includes the following steps:

[0065] S1. Prepare a mixed sol containing tetraethyl orthosilicate, ammonium fluoride, ethanol, and deionized water; the mixed sol is composed of 21 parts of tetraethyl orthosilicate, 9 parts of ammonium fluoride, 65 parts of ethanol, and 8 parts of deionized water, in parts by weight; the sol preparation conditions include: stirring at 390 rpm at 30°C for 32 minutes, followed by aging at 21°C for 78 minutes.

[0066] S2. The basalt glass fiber was impregnated in the sol and ultrasonically treated; the impregnation conditions included: controlling the immersion depth of 22 cm, the stirring rate of 290 rpm, the ultrasonic frequency of 26 kHz and the pressure of 0.2 MPa, and the treatment time of 57 min;

[0067] S3. Purge to remove residual sol on the fiber surface; the purge parameters include: nitrogen pressure 0.9 MPa, incident angle 39°, flow rate 8 L / min, and purge time 16 s. The thickness of the residual sol layer after treatment is 5.3 μm.

[0068] S4. The fiber is subjected to inert atmosphere heat treatment and passivation treatment. The heat treatment conditions include: in an argon atmosphere, heating to 530°C at a rate of 6°C / min, keeping warm for 39 minutes, and then cooling to room temperature at a rate of 3°C / min, with the gas flow rate controlled at 0.9L / min. The passivation treatment process is as follows: the fiber after heat treatment is placed in a plasma treatment chamber, and under the condition of a vacuum degree of 37Pa, CF4 is introduced as a reaction gas, and the gas flow rate is controlled at 95sccm. Subsequently, a plasma power of 95W is applied, and the treatment is continued for 111s. After the plasma treatment is completed, the material is immediately transferred to a vacuum annealing furnace, and under the condition of an argon flow rate of 1.0L / min, the temperature is raised to 330°C at a rate of 6°C / min, kept warm for 39 minutes, and cooled to room temperature after the treatment.

[0069] Example 3

[0070] A low-dielectric-constant glass fiber, comprising a basalt glass fiber and a silicon fluoride layer coated on the surface of the basalt glass fiber; the basalt glass fiber has an average size of 11.0 μm; the volume ratio of crystalline to amorphous portions in the basalt glass fiber is 8.0:92.0; the silicon fluoride layer has a thickness of 296 nm; the basalt glass fiber is prepared from basalt raw material by a melt-drawing method; the silicon fluoride layer is formed by impregnating the basalt glass fiber with a mixed sol containing ethyl orthosilicate and ammonium fluoride, ultrasonically treating and purging the basalt glass fiber, and then heat-treating the basalt glass fiber in an inert atmosphere;

[0071] The preparation method of the basalt glass fiber of this embodiment comprises the following steps:

[0072] A1: Basalt raw material was mechanically crushed and sieved into particles with a particle size of 14 mm. The particles were immersed in a 1.3 mol / L hydrochloric acid solution for 3 hours to remove metallic impurities and free oxides. The particles were then rinsed with deionized water to a pH of 7.1 and dried in a vacuum drying oven at 104°C for 144 minutes to a moisture content of ≤0.5 wt%. The composition of the basalt raw material was: Al2O3 8.6 wt%, TiO2 1.7 wt%, FeO 9.2 wt%, CaO 7.6 wt%, MgO 15.6 wt%, Na2O 3.0 wt%, K2O 0.7 wt%, B2O3 4.8 wt%, with the remainder being SiO2.

[0073] A2: The dried basalt particles were placed in a molybdenum-lanthanum alloy crucible. Under a nitrogen atmosphere, the oxygen content was controlled to ≤50 ppm. The crucible was heated to 1640°C at a heating rate of 11°C / min and held at that temperature for 96 minutes to form a uniform glass melt. The dynamic viscosity of the melt was monitored in real time by a viscometer and was 34 Pa·s.

[0074] A3: The molten glass liquid is pulled down through a platinum alloy leak plate with a pore size of 1.2mm. The leak plate temperature is controlled at 1340℃, the drawing speed is 600m / min, and the surface temperature of the pulling roller is 38℃. The fiber diameter is adjusted in real time to 11μm with a deviation of ≤±0.5μm using a laser diameter gauge.

[0075] A4: The fiber is sequentially cooled with inert gas and water mist to achieve gradient solidification. In the first cooling stage, the fiber is passed through a 4m argon channel with a controlled argon flow rate of 7m / s and a cooling rate of 140℃ / s to reduce the fiber surface temperature to 720℃. In the second cooling stage, deionized water mist with an atomization pressure of 0.3MPa is used to control the droplet size to ≤10μm and the spray density to 1.4L / min·m 2 , lower the fiber temperature to 34°C to complete curing.

[0076] A method for preparing a glass fiber with a low dielectric constant according to this embodiment includes the following steps:

[0077] S1. Prepare a mixed sol containing tetraethyl orthosilicate, ammonium fluoride, ethanol, and deionized water; the mixed sol is composed of: 30 parts of tetraethyl orthosilicate, 11.0 parts of ammonium fluoride, 80 parts of ethanol, and 11 parts of deionized water, in parts by weight; the sol preparation conditions include: stirring at 480 rpm at 34°C for 44 minutes, followed by aging at 23°C for 96 minutes.

[0078] S2. The basalt glass fiber was impregnated in the sol and ultrasonically treated; the impregnation conditions included: controlling the immersion depth to 34 cm, the stirring rate to 380 rpm, the ultrasonic frequency to 32 kHz, and the pressure to 0.3 MPa, and the treatment time to 84 min;

[0079] S3. Purge to remove residual sol on the fiber surface; the purge parameters include: nitrogen pressure 1.4 MPa, incident angle 48°, flow rate 11 L / min, and purge time 22 s. The thickness of the residual sol layer after treatment is 3.7 μm.

[0080] S4. The fiber is subjected to inert atmosphere heat treatment and passivation treatment. The heat treatment conditions include: in an argon atmosphere, heating to 560°C at a rate of 8°C / min, keeping warm for 48 minutes, and then cooling to room temperature at a rate of 3°C / min, with the gas flow rate controlled at 1.4L / min. The passivation treatment process is as follows: the fiber after heat treatment is placed in a plasma treatment chamber, and under the condition of a vacuum degree of 64Pa, CF4 is introduced as a reaction gas, and the gas flow rate is controlled at 140sccm. Subsequently, a plasma power of 140W is applied, and the treatment is continued for 192s. After the plasma treatment is completed, the material is immediately transferred to a vacuum annealing furnace, and under the condition of an argon flow rate of 1.4L / min, the temperature is raised to 360°C at a rate of 8°C / min, kept warm for 48 minutes, and cooled to room temperature after the treatment.

[0081] Figure 4 The glass fiber mat prepared in Example 3 for testing the hydrophobic angle is presented, providing an experimental basis for the determination of surface hydrophobicity. Figure 5 The morphology of water droplets on glass fiber mats was further demonstrated, showing that the droplets formed distinct spherical structures on the fiber surface, confirming the excellent hydrophobicity of the glass fiber. This indicates that the silicon oxyfluoride layer can effectively reduce the hydrophilicity of the glass fiber surface and improve the material's moisture resistance. These results jointly verify the advantages of the glass fiber prepared by this invention in terms of structural uniformity, interface control, and hydrophobicity, providing strong support for its application in high-performance composite materials.

[0082] Example 4

[0083] A glass fiber with a low dielectric constant, comprising a basalt glass fiber and a silicon fluoride layer coated on the surface of the basalt glass fiber; the basalt glass fiber has an average size of 15.0 μm; the volume ratio of crystalline to amorphous portions in the basalt glass fiber is 5.0:95.0; the silicon fluoride layer has a thickness of 400 nm; the basalt glass fiber is prepared from basalt raw material by a melt drawing method; the silicon fluoride layer is formed by impregnating the basalt glass fiber with a mixed sol containing ethyl orthosilicate and ammonium fluoride, ultrasonically treating, purging, and then heat-treating in an inert atmosphere;

[0084] The preparation method of the basalt glass fiber of this embodiment comprises the following steps:

[0085] A1: Basalt raw material was mechanically crushed and sieved into particles with a particle size of 20 mm. The particles were immersed in a 2.0 mol / L hydrochloric acid solution for 4 hours to remove metallic impurities and free oxides. The particles were then rinsed with deionized water to a pH of 7.5 and dried in a vacuum drying oven at 120°C for 160 minutes to a moisture content of ≤0.5 wt%. The composition of the basalt raw material was: Al2O3 9.0 wt%, TiO2 1.8 wt%, FeO 10.0 wt%, CaO 8.0 wt%, MgO 16.0 wt%, Na2O 3.2 wt%, K2O 0.8 wt%, B2O3 6.0 wt%, with the remainder being SiO2.

[0086] A2: The dried basalt particles were placed in a molybdenum-lanthanum alloy crucible. Under a nitrogen atmosphere, the oxygen content was controlled to ≤50 ppm. The crucible was heated to 1700°C at a heating rate of 15°C / min and held at that temperature for 120 minutes to form a uniform glass melt. The dynamic viscosity of the melt was monitored in real time by a viscometer to be 50 Pa·s.

[0087] A3: The molten glass liquid is pulled down through a platinum alloy leak plate with a pore size of 1.5mm. The leak plate temperature is controlled at 1400℃, the drawing speed is 800m / min, and the surface temperature of the pulling roller is 50℃. The fiber diameter is adjusted in real time to 15μm with a deviation of ≤±0.5μm using a laser diameter gauge.

[0088] A4: The fiber is sequentially cooled with inert gas and water mist to achieve gradient solidification. In the first cooling stage, the fiber is passed through a 5m argon channel with an argon flow rate of 10m / s and a cooling rate of 200℃ / s to reduce the fiber surface temperature to 800℃. In the second cooling stage, deionized water mist with an atomization pressure of 0.5MPa is used to control the droplet size to ≤10μm and the spray density to 2.0L / min·m 2 , lower the fiber temperature to 40°C to complete curing.

[0089] A method for preparing a glass fiber with a low dielectric constant according to this embodiment includes the following steps:

[0090] S1. Prepare a mixed sol containing tetraethyl orthosilicate, ammonium fluoride, ethanol, and deionized water; the composition of the mixed sol is: 36 parts of tetraethyl orthosilicate, 12.0 parts of ammonium fluoride, 100 parts of ethanol, and 15 parts of deionized water, in parts by weight; the sol preparation conditions include: stirring at 600 rpm at 40°C for 60 minutes, followed by aging at 25°C for 120 minutes.

[0091] S2. The basalt glass fiber was impregnated in the sol and ultrasonically treated; the impregnation conditions included: controlling the immersion depth of 50 cm, the stirring rate of 500 rpm, the ultrasonic frequency of 40 kHz and the pressure of 0.5 MPa, and the treatment time of 120 min;

[0092] S3. Purge to remove residual sol on the fiber surface; the purge parameters include: nitrogen pressure 2.0 MPa, incident angle 60°, flow rate 15 L / min, and purge time 30 s. The thickness of the residual sol layer after treatment is 2 μm.

[0093] S4. The fiber is subjected to inert atmosphere heat treatment and passivation treatment. The heat treatment conditions include: in an argon atmosphere, heating to 600°C at a rate of 10°C / min, keeping warm for 60 minutes, and then cooling to room temperature at a rate of 5°C / min, with the gas flow rate controlled at 2.0L / min. The passivation treatment process is as follows: the fiber after heat treatment is placed in a plasma treatment chamber, and under the condition of a vacuum degree of 100Pa, CF4 is introduced as a reaction gas, and the gas flow rate is controlled at 200sccm. Subsequently, a plasma power of 200W is applied, and the treatment is continued for 300s. After the plasma treatment is completed, the material is immediately transferred to a vacuum annealing furnace, and under the condition of an argon flow rate of 2.0L / min, the temperature is raised to 400°C at a rate of 10°C / min, kept warm for 60 minutes, and cooled to room temperature after the treatment.

[0094] Comparative Example 1

[0095] It is basically the same as Example 1, except that the drawing speed is 200 m / min, which is too low, resulting in a fiber diameter of 18 μm.

[0096] Comparative Example 2

[0097] It is basically the same as Example 1, except that the surface temperature of the pulling roller is 10°C. Too low a temperature will increase the stress on the fiber surface, which may easily lead to microcracks and affect the mechanical properties and long-term stability.

[0098] Comparative Example 3

[0099] It is basically the same as Example 1, except that the primary cooling argon flow rate is 0.5 m / s. Too low a cooling rate leads to an increase in the crystalline content, an increase in dielectric loss, and a decrease in fiber flexibility.

[0100] Comparative Example 4

[0101] It is basically the same as Example 1, except that the particle size of the deionized water droplets is 20 μm. Too large droplets lead to uneven cooling and greater internal stress in the fiber, which affects the strength and durability of the final product.

[0102] Comparative Example 5

[0103] The method is basically the same as Example 1, except that the content of ethyl orthosilicate is 14 parts and the content of ammonium fluoride is 5 parts during the preparation of the sol. The ammonium fluoride content is too low, which affects the dielectric properties and weather resistance.

[0104] Comparative Example 6

[0105] The method is basically the same as Example 1, except that the ultrasonic frequency is 10 kHz. Too low a frequency results in insufficient dispersion of the sol and an uneven coating layer, which affects the low dielectric properties of the glass fiber.

[0106] Comparative Example 7

[0107] It is basically the same as Example 1, except that the purge angle is 10° and the purge direction is unreasonable, resulting in uneven removal of the coating, forming local accumulation, and affecting the dielectric properties.

[0108] Comparative Example 8

[0109] The process is basically the same as Example 1, except that the heat treatment temperature is 450° C., which is too low and the silicon oxyfluoride layer is not fully cured, resulting in decreased interfacial bonding strength and reduced moisture resistance.

[0110] Comparative Example 9

[0111] It is basically the same as Example 1, except that the heat treatment heating rate is 1°C / min. Too slow a heating rate leads to an increase in the degree of crystallization and an increase in dielectric loss, which is not conducive to high-frequency applications.

[0112] Comparative Example 10

[0113] It is basically the same as Example 1, except that the plasma treatment power is 10 W, which is too low and the fluorination effect is insufficient, resulting in poor hydrophobicity and chemical resistance of the coating.

[0114] Performance testing:

[0115] Dielectric constant and dielectric loss testing: Based on ASTM D150, an impedance analyzer (such as the Agilent 4294A) is used to measure the dielectric constant and dielectric loss of glass fiber at different frequencies (1 MHz to 10 GHz). The sample is prepared as a 10 mm × 10 mm × 1 mm flat plate. An AC electric field is applied between copper electrodes, and the dielectric response is analyzed to evaluate the material's low dielectric properties.

[0116] Mechanical properties test: Tensile tests were performed according to ASTM D3039 standard, and the tensile strength and elastic modulus of the glass fiber were measured using an electronic universal testing machine (Instron 5967).

[0117] Moisture resistance test: Referring to ASTM D570 standard, the glass fiber samples were placed in a constant temperature and humidity chamber at 85°C and 85% RH for 168 hours. Samples were taken every 24 hours to measure the change in mass and dielectric constant to evaluate the material's stability in a high-humidity environment.

[0118] Surface hydrophobicity testing: A contact angle meter (OCA20, Dataphysics) was used to measure the water contact angle on the glass fiber surface. The glass fibers were flattened into glass fiber mats. The hydrophobicity changes before and after treatment with a silicon oxyfluoride coating were compared according to ASTM D7334 to evaluate moisture resistance.

[0119] The properties of the glass fibers of Examples 1 to 4 and Comparative Examples 1 to 10 are summarized in Table 1.

[0120] Table 1 Performance of glass fibers of Examples 1 to 4 and Comparative Examples 1 to 10

[0121]

[0122] As can be seen from Table 1, the key properties of glass fiber are affected by multiple process parameters. The dielectric constant is mainly affected by the glass fiber diameter, crystalline ratio and coating uniformity. A cooling rate that is too low will increase the crystalline ratio, resulting in an increase in the dielectric constant, while a loose coating structure will enhance the polarization effect and increase the dielectric constant. Dielectric loss is affected by interface polarization and coating quality. Uneven coating or decreased interfacial bonding will increase loss. Tensile strength and elastic modulus are affected by glass fiber diameter, cooling rate and microcracks. Too low drawing speed or uneven cooling will lead to an increase in diameter and increased residual stress, thereby reducing mechanical properties. Moisture resistance depends on coating density and interfacial bonding. Insufficient coating composition or insufficient heat treatment will lead to an increase in the change in dielectric constant under the influence of humidity. Surface hydrophobicity is affected by the quality of the silicon oxyfluoride coating and plasma treatment. Insufficient power or insufficient heat treatment will reduce the contact angle and affect hydrophobicity. Overall, the optimized process conditions can achieve low dielectric constant, low loss, high mechanical strength, excellent moisture resistance and hydrophobicity, and changes in different process parameters will lead to an improvement or decrease in the corresponding performance, providing an experimental basis for the preparation optimization of glass fiber.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that any equivalent structural transformations made within the scope of the present invention using the contents of the present invention's description and drawings should be included within the scope of protection of the claims of the present invention.

Claims

1. A glass fiber with a low dielectric constant, characterized in that: The glass fiber includes basalt glass fiber and a silicon oxyfluoride layer coated on the surface of the basalt glass fiber; The average size of the basalt glass fiber is 5.0 to 15.0 μm; The volume ratio of the crystalline and amorphous states in the basalt glass fiber is (5.0-15.0):(85.0-95.0); The thickness of the silicon oxyfluoride layer is 140 to 400 nm; The basalt glass fiber is prepared from basalt raw materials through a melt drawing method; The silicon fluoride layer is formed by impregnating basalt glass fiber with a mixed sol containing ethyl orthosilicate and ammonium fluoride, ultrasonically treating and purging the basalt glass fiber, and then heat-treating the basalt glass fiber in an inert atmosphere.

2. A glass fiber with a low dielectric constant as claimed in claim 1, characterized in that: The preparation method of basalt glass fiber comprises the following steps: A1: The basalt raw material is mechanically crushed and sieved into particles with a size of 5-20 mm. The particles are then immersed in a 0.5-2.0 mol / L hydrochloric acid solution for 1-4 hours to remove metal impurities and free oxides. The particles are then rinsed with deionized water to a pH of 6.5-7.5 and dried in a vacuum drying oven at 80-120°C for 120-160 minutes to a moisture content of ≤0.5 wt%. A2: Place the dried basalt particles into a molybdenum-lanthanum alloy crucible. Under a nitrogen atmosphere, control the oxygen content to ≤50 ppm. Heat to 1550-1700°C at a heating rate of 5-15°C / min. Hold the temperature for 60-120 minutes to form a uniform glass melt. Monitor the dynamic viscosity of the melt in real time using a viscometer to maintain a range of 10-50 Pa·s. A3: The molten glass liquid is pulled down through a platinum alloy bushing with a pore size of 0.8-1.5mm. The bushing temperature is controlled at 1250-1400℃, the drawing speed is 300-800m / min, and the surface temperature of the pulling roller is 20-50℃. The fiber diameter is adjusted in real time by a laser diameter gauge to 5-15μm with a deviation of ≤±0.5μm. A4: The fiber is sequentially cooled with inert gas and sprayed with water mist to achieve gradient solidification. In the first cooling stage, the fiber is passed through a 2-5 m argon channel with a controlled argon flow rate of 3-10 m / s and a cooling rate of 50-200°C / s to reduce the fiber surface temperature to 600-800°C. In the second cooling stage, deionized water mist is sprayed with an atomizing pressure of 0.1-0.5 MPa, with a droplet size of ≤10 μm and a spray density of 0.5-2.0 L / min·m 2 , lower the fiber temperature to 25-40°C to complete curing.

3. A glass fiber with a low dielectric constant as claimed in claim 2, characterized in that: The components of the basalt raw material in A1 are: Al2O3 8.0-9.0wt%, TiO2 1.5-1.8wt%, FeO 8.0-10.0wt%, CaO 7.0-8.0wt%, MgO 15.0-16.0wt%, Na2O 2.8-3.2wt%, K2O 0.6-0.8wt%, B2O3 3.0-6.0wt%, and the balance is SiO2.

4. A method for preparing a glass fiber with a low dielectric constant according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Prepare a mixed sol containing ethyl orthosilicate, ammonium fluoride, ethanol and deionized water; S2. immersing the basalt glass fiber in the sol and performing ultrasonic treatment; S3. Blowing to remove residual sol on the fiber surface; S4. Performing an inert atmosphere heat treatment and a passivation treatment on the fiber.

5. The method for preparing a glass fiber with a low dielectric constant according to claim 4, wherein: The mixed sol comprises, by weight, 14 to 36 parts of ethyl orthosilicate, 7.0 to 12.0 parts of ammonium fluoride, 50 to 100 parts of ethanol, and 5 to 15 parts of deionized water. The sol preparation conditions include stirring at 300 to 600 rpm at 25 to 40° C. for 20 to 60 minutes, and then aging at 20 to 25° C. for 60 to 120 minutes.

6. The method for preparing a glass fiber with a low dielectric constant according to claim 4, wherein: The mass ratio of the tetraethyl orthosilicate to ammonium fluoride is (2.0-3.0):

1.

7. The method for preparing a glass fiber with a low dielectric constant according to claim 4, wherein: The immersion conditions include: controlling the immersion depth to 10-50 cm, the stirring rate to 200-500 rpm, the ultrasonic frequency to 20-40 kHz, the pressure to 0.1-0.5 MPa, and the treatment time to 30-120 min.

8. The method for preparing a glass fiber with a low dielectric constant according to claim 4, wherein: The purge parameters include: nitrogen pressure of 0.5-2.0 MPa, incident angle of 30-60 degrees, flow rate of 5-15 L / min and purge time of 10-30 seconds. The thickness of the residual sol layer after treatment is 2.0-6.5 μm.

9. The method for preparing a glass fiber with a low dielectric constant according to claim 4, wherein: The heat treatment conditions include: heating to 500-600°C at 5-10°C / min under argon atmosphere, keeping warm for 30-60 minutes, and then cooling to room temperature at 2-5°C / min, with the gas flow rate controlled at 0.5-2.0 L / min.

10. The method for preparing a glass fiber with a low dielectric constant according to claim 4, wherein: The passivation treatment process is as follows: the fiber after heat treatment is placed in a plasma treatment chamber, CF4 is introduced as a reaction gas under a vacuum degree of 10 to 100 Pa, and the gas flow rate is controlled at 50 to 200 sccm. Subsequently, a plasma power of 50 to 200 W is applied and the treatment is continued for 30 to 300 seconds. After the plasma treatment is completed, the material is immediately transferred to a vacuum annealing furnace, and the temperature is raised to 300 to 400°C at a rate of 5 to 10°C / min under an argon flow rate of 0.5 to 2.0 L / min, and the temperature is kept at 30 to 60 minutes. After the treatment, the material is cooled to room temperature.

Images