Glass fiber with low dielectric constant and preparation method thereof

Abstract

The invention relates to the field of fiber materials, and provides a low-dielectric constant glass fiber and a preparation method thereof, and the low-dielectric constant glass fiber comprises basalt glass fiber and a silicon oxyfluoride layer coating the surface of the basalt glass fiber. The basalt glass fiber is prepared by adopting a melting wire drawing method, the average diameter is 5.0-15.0 microns, and the volume ratio of a crystalline state to an amorphous state is controlled to be (5.0-15.0): (85.0-95.0). The thickness of the silicon oxyfluoride layer is 140-400 nm, and the silicon oxyfluoride layer is obtained through a sol-gel method and is formed by conducting dipping, ultrasonic treatment and purging on tetraethoxysilane and ammonium fluoride sol and then conducting heat treatment in an inert atmosphere. The preparation method comprises the steps of basalt raw material crushing, acid pickling, melting, wire drawing and gradient cooling, and the uniformity and stability of the fibers are ensured. The preparation conditions, impregnation parameters, purging pressure and heat treatment temperature of the modified sol are all optimized, so that uniform coating and stability enhancement are realized. The glass fiber provided by the invention has low dielectric constant and excellent heat resistance and hydrophobicity, and is suitable for the fields of high-frequency electronic substrates, aerospace and 5G communication.

Description

Technical Field

[0001] The 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 microelectronic 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 radars, and high-speed computing equipment, there is an increasing demand for low dielectric constant (Dk) materials 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 influence 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 constants, high hydrophobicity, and excellent mechanical properties can not only improve the performance of electronic packaging and communication equipment, but also broaden its scope of application 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 some 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 through component optimization, it does not have hydrophobic properties. In addition, some existing technologies use silane coupling agents to improve hydrophobicity, but due to weak interfacial bonding, peeling is prone 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, so 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 losses 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 issues 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] To achieve the above object, the present invention provides the following technical solution:

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

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

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

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

[0012] The basalt glass fiber is obtained by preparing from basalt raw materials through the melt drawing method;

[0013] The silicon oxyfluoride layer is formed by impregnating the basalt glass fiber with a mixed sol containing tetraethyl orthosilicate and ammonium fluoride, followed by ultrasonic treatment, purging, and then heat treatment in an inert atmosphere.

[0014] The design of the present invention using the composite of basalt glass fiber and silicon oxyfluoride layer is mainly used to enhance the low dielectric properties, weather resistance, and mechanical properties of the material. By optimizing the preparation process of the basalt glass fiber, controlling its average size and the volume ratio of the crystalline state to the amorphous state, it has excellent mechanical strength and structural stability while ensuring low dielectric loss. The melt drawing process of the basalt glass fiber ensures the uniformity and controllability of the fiber, thereby improving the dielectric uniformity of the overall material and optimizing the interfacial bonding characteristics. To further reduce the dielectric constant and enhance the hydrophobicity, the present invention uses a silicon oxyfluoride layer coating to modify the surface of the basalt glass fiber with a mixed sol of tetraethyl orthosilicate and ammonium fluoride. After impregnation, ultrasonic treatment, and purging, a uniform silicon oxyfluoride layer is formed by heat treatment in an inert atmosphere. 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, enabling it to maintain stable dielectric properties in a high-humidity environment. In addition, the thickness of the silicon oxyfluoride layer is controlled within a reasonable range, which not only ensures excellent hydrophobic performance but also avoids the possible decline in mechanical properties caused by an overly thick coating. The synergistic effect between the fiber matrix and the surface coating enables the glass fiber material of the present invention to have excellent environmental resistance and mechanical stability while maintaining low dielectric characteristics, meeting the requirements for high-performance low-dielectric materials in fields such as high-frequency electronic packaging, communication equipment, and aerospace.

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

[0016] A1: Mechanically crush basalt raw materials and screen them into particles with a particle size of 5 - 20 mm. Immerse the particles in a hydrochloric acid solution with a concentration of 0.5 - 2.0 mol / L for 1 - 4 h to remove metal impurities and free oxides. Then, rinse with deionized water until the pH is 6.5 - 7.5, and place the washed particles in a vacuum drying oven at 80 - 120 °C for 120 - 160 min until the moisture content ≤ 0.5 wt%;

[0017] A2: Load the dried basalt particles into a molybdenum - lanthanum alloy crucible. Under a nitrogen atmosphere, control the oxygen content ≤ 50 ppm, and heat at a heating rate of 5 - 15 °C / min to 1550 - 1700 °C. Hold for 60 - 120 min to form a uniform glass melt, and continuously monitor the dynamic viscosity of the melt with a viscometer to be 10 - 50 Pa·s;

[0018] A3: Pull the molten glass liquid through a platinum - alloy spinneret with a pore diameter of 0.8 - 1.5 mm. Control the spinneret temperature at 1250 - 1400 °C, the drawing speed at 300 - 800 m / min, and the surface temperature of the drawing roller at 20 - 50 °C. And continuously adjust the fiber diameter to 5 - 15 μm with a deviation ≤ ±0.5 μm by a laser diameter gauge.

[0019] A4: Cool the fiber successively by inert gas and water - mist spraying to achieve gradient curing. In the first - stage cooling: Let the fiber pass through an argon channel of 2 - 5 m, control the argon flow rate at 3 - 10 m / s and the cooling rate at 50 - 200 °C / s, so that the surface temperature of the fiber drops to 600 - 800 °C; In the second - stage cooling: Pass deionized water mist with an atomization pressure of 0.1 - 0.5 MPa, control the droplet diameter ≤ 10 μm and the spraying density at 0.5 - 2.0 L / min·m 2 , and reduce the fiber temperature to 25 - 40 °C to complete curing.

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

[0021] The design of this invention using basalt glass fiber is mainly for enhancing the low dielectric properties, mechanical properties, and environmental stability of the reinforcing material. By optimizing the composition and preparation process of basalt glass fiber, a reasonable match between the crystalline state and the amorphous state is achieved to improve the dielectric characteristics and mechanical strength. In the raw material treatment stage, mechanical crushing and pickling are used to remove metal impurities and free oxides, effectively reducing dielectric loss and enhancing the uniformity of the fiber. 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 through viscosity monitoring to form a uniform glass phase structure. During the wire drawing process, a platinum alloy spinneret is used to precisely control the melt fluidity, and a laser diameter gauge is combined to adjust the fiber diameter in real time to keep it within the range of 5.0 - 15.0 μm to ensure excellent mechanical properties and dimensional uniformity. In the cooling and solidification stage, gradient cooling is achieved through inert gas cooling in an argon channel combined with deionized water mist spraying, which helps optimize the ratio of the crystalline state and the amorphous state, enabling the fiber to have good strength and stability while maintaining low dielectric characteristics. In addition, a reasonable composition design, such as the synergistic effect of Al2O3, TiO2, FeO, CaO, MgO, Na2O, K2O, and B2O3, not only optimizes the dielectric properties of the fiber but also improves the thermal shock resistance and chemical corrosion resistance, thereby further enhancing the environmental adaptability of the material. Through systematic process optimization, this invention enables basalt glass fiber to reach an excellent level in terms of low dielectric loss, structural stability, and mechanical properties, meeting the application requirements in fields such as high-frequency communication, aerospace, and electronic packaging.

[0022] This invention also discloses a preparation method for glass fiber with a low dielectric constant, which includes the following steps:

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

[0024] S2. Immerse the basalt glass fiber in the sol and perform ultrasonic treatment;

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

[0026] S4. Perform heat treatment and passivation treatment on the fiber in an inert atmosphere.

[0027] Furthermore, the composition of the mixed sol is as follows: by weight, 14 - 36 parts of tetraethyl orthosilicate, 7.0 - 12.0 parts of ammonium fluoride, 50 - 100 parts of ethanol, and 5 - 15 parts of deionized water; the sol preparation conditions include: stirring at 300 - 600 rpm for 20 - 60 min at 25 - 40 °C, and then standing and aging at 20 - 25 °C for 60 - 120 min;

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

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

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

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

[0032] Furthermore, the process of passivation treatment is as follows: putting the fibers after heat treatment into a plasma treatment chamber, under the condition of a vacuum degree of 10 - 100 Pa, introducing CF4 as the reaction gas, controlling the gas flow rate at 50 - 200 sccm, then applying a plasma power of 50 - 200 W, and continuously treating for 30 - 300 s. After the plasma treatment is completed, immediately transfer the material to a vacuum annealing furnace, under the condition of an argon flow rate of 0.5 - 2.0 L / min, heating to 300 - 400 °C at a rate of 5 - 10 °C / min, holding for 30 - 60 min, and cooling to room temperature after treatment.

[0033] The design of the present invention, which combines the sol-gel method with heat treatment and passivation processes, is mainly used to enhance the low dielectric properties, chemical stability, and weather resistance of glass fibers. By preparing a mixed sol containing tetraethyl orthosilicate, ammonium fluoride, ethanol, and deionized water, and controlling the ratio of tetraethyl orthosilicate to ammonium fluoride, a uniform and stable system is formed for the sol at an appropriate temperature and stirring rate, thereby providing a good interfacial bonding environment for the modification of basalt glass fibers. During the impregnation process, by optimizing the impregnation depth, stirring rate, ultrasonic frequency, and pressure, the sol uniformly covers the surface of the glass fibers, and the permeability of the sol is enhanced by ultrasonic treatment to ensure the uniformity and denseness of the modified layer. Subsequently, nitrogen purging is used to remove the residual sol on the surface, and the purging parameters are precisely controlled to effectively reduce sol accumulation and ensure an appropriate coating thickness, thereby avoiding a decrease in dielectric properties caused by uneven coating. In the heat treatment stage, the heating and cooling rates are controlled using an argon atmosphere to stably cure the coating on the surface of the glass fibers, while reducing the adverse effects of oxidation on the fiber properties. At the same time, annealing of the fibers is completed during the heat treatment stage to further optimize their dielectric characteristics and mechanical stability. Finally, through plasma passivation treatment, CF4 is introduced as a reaction gas, and under appropriate vacuum conditions and plasma power, a fluorination reaction occurs on the surface of the coating to enhance the hydrophobicity and chemical stability of the glass fibers, and surface defects are further eliminated during the subsequent argon annealing process to improve the bonding strength between the overall coating and the fiber matrix. Through the synergistic effect of each preparation step of the present invention, the glass fibers are effectively optimized in terms of low dielectric loss, moisture resistance, and mechanical properties, meeting the application requirements in fields such as high-frequency electronic packaging, communication equipment, and aerospace.

[0034] (3) Beneficial technical effects

[0035] 1. Through the synergistic effect of basalt glass fibers and the silicon oxyfluoride layer, the present invention achieves low dielectric loss, high hydrophobicity, and excellent mechanical properties. Compared with the prior art, it improves the material uniformity and stability, reduces the environmental impact, and is applicable to high-frequency electronic packaging, communication equipment, and aerospace fields.

[0036] 2. By optimizing the composition and preparation process of basalt glass fibers, the present invention achieves low dielectric loss, high mechanical strength, and excellent environmental stability. Compared with the prior art, it improves the material uniformity and durability, reduces signal loss, and is applicable to high-frequency communication, aerospace, and electronic packaging fields.

[0037] 3. Through the sol-gel method combined with heat treatment and passivation processes, the present invention optimizes the low dielectric, weather resistance, and chemical stability of glass fibers. Compared with the prior art, it enhances the interfacial bonding force, uniformity, and moisture resistance, avoids coating peeling and dielectric loss, and is applicable to high-frequency electronics, communication, and aerospace fields. Description of the Drawings

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

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

[0040] Figure 3 Transmission electron microscope morphology diagram of the basalt glass fiber prepared in Example 1 of the present invention.

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

[0042] Figure 5 Morphology of water droplets on the glass fiber felt prepared in Example 3 of the present invention. Detailed implementation manners

[0043] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, 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 glass fiber with a low dielectric constant, the glass fiber includes basalt glass fiber and a fluosilicate layer coated on the surface of the basalt glass fiber; the average size of the basalt glass fiber is 5.0 μm; the volume ratio of the crystalline state to the amorphous state in the basalt glass fiber is 15.0:85.0; the thickness of the fluosilicate layer is 140 nm; the basalt glass fiber is prepared by a melt drawing method from basalt raw materials; the fluosilicate layer is formed by impregnating the basalt glass fiber with a mixed sol containing tetraethyl orthosilicate and ammonium fluoride, followed by ultrasonic treatment, purging, and then heat treatment in an inert atmosphere;

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

[0047] A1: The basalt raw materials are mechanically crushed and screened into particles with a particle size of 5 mm, immersed in a hydrochloric acid solution with a concentration of 0.5 mol / L for 1 h to remove metal impurities and free oxides, then rinsed with deionized water until the pH is 6.5, and the washed particles are placed in a vacuum drying oven at 80 °C for 120 min until the moisture content ≤ 0.5 wt%; the components of the basalt raw materials are: 8.0 wt% of Al2O3, 1.5 wt% of TiO2, 8.0 wt% of FeO, 7.0 wt% of CaO, 15.0 wt% of MgO, 2.8 wt% of Na2O, 0.6 wt% of K2O, 3.0 wt% of B2O3, and the balance is SiO2.

[0048] A2: Load the dried basalt particles into a molybdenum lanthanum alloy crucible. Under a nitrogen atmosphere, control the oxygen content ≤ 50 ppm, heat to 1550 °C at a heating rate of 5 °C / min, hold for 60 min to form a uniform glass melt, and monitor the dynamic viscosity of the melt in real time with a viscometer to be 10 Pa·s;

[0049] A3: Pull down the molten glass through a platinum alloy spinneret with a pore diameter of 0.8 mm. Control the spinneret temperature at 1250 °C, the drawing speed at 300 m / min, and the surface temperature of the traction roller at 20 °C, and adjust the fiber diameter to 5 μm with a deviation ≤ ±0.5 μm in real time with a laser diameter gauge.

[0050] A4: Cool the fiber successively with inert gas and water mist spray to achieve gradient curing. Among them, in the first-stage cooling stage: make the fiber pass through a 2-m argon gas channel, control the argon gas flow rate at 3 m / s and the cooling rate at 50 °C / s, and reduce the surface temperature of the fiber to 600 °C; in the second-stage cooling stage: through deionized water mist with an atomization pressure of 0.1 MPa, control the droplet diameter ≤ 10 μm and the spray density at 0.5 L / min·m 2 , reduce 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: by weight, 14 parts of tetraethyl orthosilicate, 7.0 parts of ammonium fluoride, 50 parts of ethanol, and 5 parts of deionized water; the sol preparation conditions include: stir at 300 rpm for 20 min at 25 °C, and then stand and age at 20 °C for 60 min; the mass ratio of tetraethyl orthosilicate to ammonium fluoride is 2.0:1.

[0053] S2. Immerse the basalt glass fiber in the sol and perform ultrasonic treatment; the immersion conditions include: control the immersion depth at 10 cm, the stirring rate at 200 rpm, the ultrasonic frequency at 20 kHz, and the pressure at 0.1 MPa, and the treatment time is 30 min;

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

[0055] S4. Heat-treat and passivate the fibers in an inert atmosphere. The heat-treatment conditions include: heating to 500 °C at a rate of 5 °C / min in an argon atmosphere, holding for 30 min, and then cooling to room temperature at a rate of 2 °C / min, with the gas flow rate controlled at 0.5 L / min. The passivation process is as follows: place the fibers after heat-treatment into the plasma treatment chamber, introduce CF4 as the reaction gas under a vacuum of 10 Pa, control the gas flow rate at 50 sccm, then apply a plasma power of 50 W and continuously treat for 30 s. After the plasma treatment is completed, immediately transfer the material to a vacuum annealing furnace, heat it to 300 °C at a rate of 5 °C / min under an argon flow rate of 0.5 L / min, hold for 30 min, and cool to room temperature after treatment.

[0056] Figure 1 The cross-sectional morphology of the basalt glass fiber prepared in Example 1 of the present invention is shown, proving that the fiber has a uniform diameter, indicating that the preparation process can effectively control the fiber size and improve the material uniformity. Figure 2 It further shows the cross-sectional morphology of the glass fiber, clearly revealing the double-layer structure of the glass fiber, including the basalt glass fiber main body and the silicon oxyfluoride layer coated on its surface, indicating the effectiveness of the coating process. Figure 3 It is a transmission electron microscopy morphology diagram, showing that there are a small amount of nanocrystals inside the basalt glass fiber, 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 glass fiber with a low dielectric constant, the glass fiber includes a 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 8.0 μm; the volume ratio of the crystalline state to the amorphous state in the basalt glass fiber is 12.0:88.0; the thickness of the silicon oxyfluoride layer is 218 nm; the basalt glass fiber is prepared by a melt spinning method from basalt raw materials; the silicon oxyfluoride layer is formed by impregnating, ultrasonic treating, and purging the basalt glass fiber with a mixed sol containing tetraethyl orthosilicate and ammonium fluoride, and then heat-treating in an inert atmosphere.

[0059] The preparation method of the basalt glass fiber in this example includes the following steps:

[0060] A1: The basalt raw material is mechanically crushed and screened into particles with a particle size of 10 mm, immersed in a hydrochloric acid solution with a concentration of 0.9 mol / L for 2 h to remove metal impurities and free oxides, then rinsed with deionized water until the pH is 6.8, and the washed particles are placed in a vacuum drying oven at 92 °C for 132 min until the moisture content ≤ 0.5 wt%; the components of the basalt raw material are: 8.3 wt% Al2O3, 1.6 wt% TiO2, 8.6 wt% FeO, 7.3 wt% CaO, 15.3 wt% MgO, 2.9 wt% Na2O, 0.7 wt% K2O, 3.9 wt% B2O3, and the balance is SiO2.

[0061] A2: The dried basalt particles are loaded into a molybdenum-lanthanum alloy crucible, and the oxygen content is controlled ≤ 50 ppm under a nitrogen atmosphere, heated to 1595 °C at a heating rate of 8 °C / min, and held for 78 min to form a uniform glass melt, and the dynamic viscosity of the melt is monitored in real time by a viscometer to be 22 Pa·s;

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

[0063] A4: The fiber is sequentially cooled by inert gas and water mist spraying to achieve gradient curing. Among them, in the first-stage cooling stage: the fiber passes through a 3 m argon channel, the argon flow rate is controlled at 5 m / s and the cooling rate is 95 °C / s, so that the surface temperature of the fiber drops to 660 °C; in the second-stage cooling stage: through deionized water mist with an atomization pressure of 0.2 MPa, the droplet diameter is controlled ≤ 10 μm and the spraying density is 0.9 L / min·m 2 , and the fiber temperature is reduced to 29 °C to complete curing.

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

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

[0066] S2. Immerse the basalt glass fiber in the sol and perform ultrasonic treatment; the immersion conditions include: controlling the immersion depth at 22 cm, the stirring rate at 290 rpm, the ultrasonic frequency at 26 kHz and the pressure at 0.2 MPa, and the treatment time at 57 min;

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

[0068] S4. Conduct heat treatment and passivation treatment on the fiber in an inert atmosphere. The heat treatment conditions include: in an argon atmosphere, heating to 530 °C at a rate of 6 °C / min, holding for 39 min, and then cooling to room temperature at a rate of 3 °C / min. The gas flow rate is controlled at 0.9 L / min. The passivation treatment process is as follows: put the fiber after heat treatment into the plasma treatment chamber. Under the condition of a vacuum degree of 37 Pa, introduce CF4 as the reaction gas, control the gas flow rate at 95 sccm, then apply a plasma power of 95 W, and continuously treat for 111 s. After the plasma treatment is completed, immediately transfer the material to a vacuum annealing furnace. Under the condition of an argon flow rate of 1.0 L / min, heat it to 330 °C at a rate of 6 °C / min, hold for 39 min, and cool to room temperature after treatment.

[0069] Example 3

[0070] A kind of glass fiber with low dielectric constant, the glass fiber includes basalt glass fiber and a fluorooxosilicate layer coated on the surface of the basalt glass fiber; the average size of the basalt glass fiber is 11.0 μm; the volume ratio of the crystalline state to the amorphous state in the basalt glass fiber is 8.0:92.0; the thickness of the fluorooxosilicate layer is 296 nm; the basalt glass fiber is prepared by a melting and drawing method from basalt raw materials; the fluorooxosilicate layer is formed by impregnating, ultrasonic treating, and blowing the basalt glass fiber with a mixed sol containing tetraethyl orthosilicate and ammonium fluoride, and then heat-treating in an inert atmosphere.

[0071] The preparation method of the basalt glass fiber in this example includes the following steps:

[0072] A1: Mechanically crush the basalt raw materials and screen them into particles with a particle size of 14 mm, immerse them in a hydrochloric acid solution with a concentration of 1.3 mol / L for 3 h to remove metal impurities and free oxides, then rinse with deionized water until the pH is 7.1, and place the washed particles in a vacuum drying oven at 104 °C for 144 min until the moisture content ≤ 0.5 wt%. The components of the basalt raw materials are: 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%, and the balance is SiO2.

[0073] A2: Load the dried basalt particles into a molybdenum lanthanum alloy crucible. Under a nitrogen atmosphere, control the oxygen content ≤ 50 ppm, heat it to 1640 °C at a heating rate of 11 °C / min, hold for 96 min to form a uniform glass melt, and monitor the dynamic viscosity of the melt in real time with a viscometer to be 34 Pa·s;

[0074] A3: Pull down the molten glass liquid through a platinum alloy spinneret with a pore diameter of 1.2 mm. Control the spinneret temperature at 1340 °C, the drawing speed at 600 m / min, and the surface temperature of the take-up roll at 38 °C, and adjust the fiber diameter to 11 μm with a deviation ≤ ±0.5 μm in real time with a laser diameter gauge.

[0075] A4: Cool the fiber successively with inert gas cooling and water mist spray cooling to achieve gradient curing. Among them, in the first-stage cooling stage: make the fiber pass through a 4 m argon gas channel, control the argon gas flow rate at 7 m / s and the cooling rate at 140 °C / s, and reduce the fiber surface temperature to 720 °C; in the second-stage cooling stage: through deionized water mist with an atomization pressure of 0.3 MPa, control the droplet diameter ≤ 10 μm and the spray density at 1.4 L / min·m 2 , reduce 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 composition of the mixed sol is: by weight, 30 parts of tetraethyl orthosilicate, 11.0 parts of ammonium fluoride, 80 parts of ethanol, and 11 parts of deionized water; the sol preparation conditions include: stir at 480 rpm for 44 min at 34 °C, and then stand for aging at 23 °C for 96 min.

[0078] S2. Immerse the basalt glass fiber in the sol and perform ultrasonic treatment; the immersion conditions include: control the immersion depth at 34 cm, the stirring rate at 380 rpm, the ultrasonic frequency at 32 kHz and the pressure at 0.3 MPa, and the treatment time at 84 min;

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

[0080] S4. Heat-treat and passivate the fibers in an inert atmosphere. The heat-treatment conditions include: heating to 560 °C at a rate of 8 °C / min in an argon atmosphere, holding for 48 min, and then cooling to room temperature at a rate of 3 °C / min, with the gas flow rate controlled at 1.4 L / min. The passivation process is as follows: Place the fibers after heat-treatment into the plasma processing chamber. Under the condition of a vacuum degree of 64 Pa, introduce CF4 as the reaction gas, control the gas flow rate at 140 sccm, then apply a plasma power of 140 W and continuously process for 192 s. After the plasma treatment is completed, immediately transfer the material to a vacuum annealing furnace. Under the condition of an argon flow rate of 1.4 L / min, heat to 360 °C at a rate of 8 °C / min, hold for 48 min, and cool to room temperature after the treatment is completed.

[0081] Figure 4 The glass fiber felt for testing the hydrophobic angle prepared in Example 3 is shown, providing an experimental basis for the determination of surface hydrophobicity. Figure 5 It further shows the morphology of water droplets on the glass fiber felt, indicating that obvious spherical structures are formed on the fiber surface, proving that the glass fiber has excellent hydrophobicity, which shows that the silicon oxyfluoride layer can effectively reduce the hydrophilicity of the glass fiber surface and improve the moisture-proof performance of the material. The above results jointly verify the advantages of the glass fiber prepared by the present 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, the glass fiber includes basalt glass fibers and a silicon oxyfluoride layer coated on the surface of the basalt glass fibers; the average size of the basalt glass fibers is 15.0 μm; the volume ratio of the crystalline state to the amorphous state in the basalt glass fibers is 5.0:95.0; the thickness of the silicon oxyfluoride layer is 400 nm; the basalt glass fibers are prepared by a melt spinning method from basalt raw materials; the silicon oxyfluoride layer is formed by impregnating, ultrasonic treating, and purging the basalt glass fibers with a mixed sol containing tetraethyl orthosilicate and ammonium fluoride, and then heat-treating in an inert atmosphere.

[0084] The preparation method of the basalt glass fibers in this example includes the following steps:

[0085] A1: After mechanically crushing the basalt raw materials, they are screened into particles with a particle size of 20 mm, immersed in a hydrochloric acid solution with a concentration of 2.0 mol / L for 4 h to remove metal impurities and free oxides, then rinsed with deionized water until the pH reaches 7.5, and the washed particles are placed in a vacuum drying oven at 120 °C for 160 min until the moisture content ≤ 0.5 wt%; the components of the basalt raw materials are: 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%, and the balance is SiO2.

[0086] A2: Load the dried basalt particles into a molybdenum lanthanum alloy crucible, control the oxygen content ≤ 50 ppm in a nitrogen atmosphere, heat to 1700 °C at a heating rate of 15 °C / min, and hold for 120 min to form a uniform glass melt, and monitor the dynamic viscosity of the melt in real time through a viscometer to be 50 Pa·s;

[0087] A3: Pull down the molten glass liquid through a platinum alloy spinneret with a pore diameter of 1.5 mm, control the spinneret temperature at 1400 °C, the drawing speed at 800 m / min, and the surface temperature of the traction roller at 50 °C, and adjust the fiber diameter to 15 μm in real time through a laser diameter gauge with a deviation ≤ ±0.5 μm.

[0088] A4: Cool the fiber successively by inert gas cooling and water mist spray cooling to achieve gradient curing. Among them, in the first-stage cooling stage: make the fiber pass through a 5-m argon gas channel, control the argon gas flow rate at 10 m / s and the cooling rate at 200 °C / s, and reduce the surface temperature of the fiber to 800 °C; in the second-stage cooling stage: through deionized water mist with an atomization pressure of 0.5 MPa, control the droplet diameter ≤ 10 μm and the spray density 2.0 L / min·m 2 , and reduce the fiber temperature to 40 °C to complete the curing.

[0089] A method for preparing a glass fiber with a low dielectric constant in 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: by weight, 36 parts of tetraethyl orthosilicate, 12.0 parts of ammonium fluoride, 100 parts of ethanol, and 15 parts of deionized water; the sol preparation conditions include: stirring at 600 rpm for 60 min at 40 °C, and then standing and aging at 25 °C for 120 min.

[0091] S2. Immerse the basalt glass fiber in the sol and perform ultrasonic treatment; the immersion conditions include: controlling the immersion depth at 50 cm, the stirring rate at 500 rpm, the ultrasonic frequency at 40 kHz, and the pressure at 0.5 MPa, and the treatment time is 120 min;

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

[0093] S4. Perform heat treatment and passivation treatment on the fiber in an inert atmosphere. The heat treatment conditions include: in an argon atmosphere, heat up to 600 °C at a rate of 10 °C / min, hold for 60 min, and then cool to room temperature at a rate of 5 °C / min. The gas flow rate is controlled at 2.0 L / min. The process of passivation treatment is: put the fiber after heat treatment into the plasma treatment chamber, under the condition of a vacuum degree of 100 Pa, introduce CF4 as the reaction gas, control the gas flow rate at 200 sccm, then apply a plasma power of 200 W, and continuously treat for 300 s. After the plasma treatment is completed, immediately transfer the material to a vacuum annealing furnace, under the condition of an argon flow rate of 2.0 L / min, heat up to 400 °C at a rate of 10 °C / min, hold for 60 min, and cool to room temperature after treatment.

[0094] Comparative Example 1

[0095] It is basically the same as Example 1, except that the drawing speed is 200 m / min, and the too low speed results 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 traction roller is 10 °C. The too low temperature results in an increase in the surface stress of the fiber, which is likely to cause 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 argon gas flow rate in the first-stage cooling is 0.5 m / s. The too low cooling rate results in an increase in the crystalline content, an increase in the dielectric loss, and a decrease in the fiber flexibility at the same time.

[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. The too large droplets result in uneven cooling and large internal stress in the fiber, affecting the strength and durability of the final product.

[0102] Comparative Example 5

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

[0104] Comparative Example 6

[0105] It is basically the same as Example 1, except that the ultrasonic frequency is 10 kHz. The too low frequency results in insufficient dispersion of the sol and an uneven coating layer, affecting the low dielectric performance of the glass fiber.

[0106] Comparative Example 7

[0107] It is basically the same as Example 1, except that the purging angle is 10°. The unreasonable purging direction leads to uneven removal of the coating, forming local accumulation and affecting the dielectric performance.

[0108] Comparative Example 8

[0109] It is basically the same as Example 1, except that the heat treatment temperature is 450 °C. The too low temperature results in insufficient curing of the silicon oxyfluoride layer, leading to a decrease in the interfacial bonding force and a reduction in moisture resistance.

[0110] Comparative Example 9

[0111] It is basically the same as Example 1, except that the heating rate during heat treatment is 1 °C / min. The too slow 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. The too low power results in insufficient fluorination effect, leading to poor hydrophobicity and chemical resistance of the coating.

[0114] Performance testing:

[0115] Dielectric constant and dielectric loss testing: According to the ASTM D150 standard, an impedance analyzer (such as Agilent 4294A) is used to measure the dielectric constant and dielectric loss of the glass fiber at different frequencies (1 MHz to 10 GHz). The sample is prepared into a flat plate structure of 10 mm × 10 mm × 1 mm, and an alternating electric field is applied between the copper electrodes to analyze its dielectric response to evaluate the low dielectric characteristics of the material.

[0116] Mechanical property testing: Tensile testing is carried out according to the ASTM D3039 standard, and an electronic universal testing machine (Instron 5967) is used to measure the tensile strength and elastic modulus of the glass fiber.

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

[0118] Surface hydrophobicity test: The water contact angle of the glass fiber surface was measured using a contact angle measuring instrument (OCA20, Dataphysics). The glass fiber was made into a flat glass fiber mat, and according to the ASTM D7334 standard, the change in hydrophobicity before and after the treatment with the silicon oxyfluoride coating was compared to evaluate the moisture-proof ability.

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

[0120] Table 1 Summary of the properties of the glass fibers in Examples 1-4 and Comparative Examples 1-10

[0121]

[0122] As can be seen from Table 1, the key properties of glass fibers are affected by multiple process parameters. The dielectric constant is mainly affected by the glass fiber diameter, the proportion of the crystalline state, and the coating uniformity. Too low a cooling rate will increase the proportion of the crystalline state, resulting in an increase in the dielectric constant, while a loose coating structure enhances the polarization effect and increases the dielectric constant. The dielectric loss is affected by the interfacial polarization and the coating quality. Non-uniform coating or a decrease in the interfacial bonding force will increase the loss. The tensile strength and elastic modulus are affected by the glass fiber diameter, the cooling rate, and microcracks. Too low a drawing speed or uneven cooling will cause an increase in diameter and an increase in residual stress, thereby reducing the mechanical properties. The moisture resistance depends on the coating compactness and the interfacial bonding force. Insufficient coating composition or insufficient heat treatment will cause a greater change in the dielectric constant under the influence of humidity. The surface hydrophobicity is affected by the quality of the silicon oxyfluoride coating and the plasma treatment. Insufficient power or insufficient heat treatment will reduce the contact angle and affect the hydrophobicity. Generally speaking, 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 corresponding improvements or decreases in performance, providing an experimental basis for the optimization of glass fiber preparation.

[0123] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the above examples, those of ordinary skill in the art should understand that any equivalent structural transformation made under the concept of the present invention using the content of the specification and drawings of the present invention should be covered by the protection scope 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 fluoride oxide 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 fluorine oxide silicon layer is 140 to 400 nm; The basalt glass fiber is prepared from basalt raw materials by 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 method for preparing basalt glass fiber comprises the following steps: A1: The basalt raw material is mechanically crushed and sieved into particles with a particle size of 5-20 mm, immersed in a hydrochloric acid solution with a concentration of 0.5-2.0 mol / L for 1-4 hours to remove metal impurities and free oxides, then rinsed with deionized water to a pH of 6.5-7.5, and the washed particles are placed in a vacuum drying oven at 80-120°C for 120-160 minutes to a moisture content of ≤0.5wt%; A2: The dried basalt particles are placed in a molybdenum-lanthanum alloy crucible, the oxygen content is controlled to be ≤50ppm under a nitrogen atmosphere, and the crucible is heated to 1550-1700℃ at a heating rate of 5-15℃ / min, and kept at this temperature for 60-120min to form a uniform glass melt, and the dynamic viscosity of the melt is monitored in real time by a viscometer to be 10-50Pa·s; A3: The molten glass liquid is pulled down through a platinum alloy bushing with a hole diameter of 0.8-1.5 mm, and the bushing temperature is controlled to be 1250-1400°C, the drawing speed is 300-800 m / min, and the surface temperature of the pulling roller is 20-50°C. The fiber diameter is adjusted in real time by a laser diameter meter to be 5-15 μm with a deviation of ≤±0.5 μm; A4: The fiber is cooled by inert gas and sprayed with water mist in turn to achieve gradient solidification. In the first cooling stage, the fiber is passed through a 2-5 m argon channel, the argon flow rate is controlled at 3-10 m / s and the cooling rate is 50-200 °C / s, so that the fiber surface temperature drops to 600-800 °C; in the second cooling stage, the deionized water mist with an atomization pressure of 0.1-0.5 MPa is used to control the droplet size to ≤10 μm and the spray density to 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 as claimed in any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Prepare a mixed sol containing tetraethyl orthosilicate, ammonium fluoride, ethanol and deionized water; S2. immersing the basalt glass fiber in the sol and performing ultrasonic treatment; S3. Blowing to remove the residual sol on the fiber surface; S4. The fiber is subjected to an inert atmosphere heat treatment and a passivation treatment.

5. The method for preparing a glass fiber with a low dielectric constant as claimed in claim 4, characterized in that: 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 for 20 to 60 minutes at 25 to 40° C., and then standing and 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, characterized in that: 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 as claimed in claim 4, characterized in that: 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 as claimed in claim 4, characterized in that: The purging parameters include: nitrogen pressure of 0.5-2.0 MPa, incident angle of 30-60°, flow rate of 5-15 L / min and purging time of 10-30 s. 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, characterized in that: The heat treatment conditions include: in an argon atmosphere, heating to 500-600°C at 5-10°C / min, keeping warm for 30-60 minutes, then cooling to room temperature at 2-5°C / min, and controlling the gas flow rate to 0.5-2.0 L / min.

10. The method for preparing a glass fiber with a low dielectric constant according to claim 4, characterized in that: 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, the gas flow rate is controlled at 50 to 200 sccm, and then 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 increased 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, it is cooled to room temperature.

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