Dry forming process and equipment for viscose-based pre-oxidized short fiber solid felt

Abstract

The invention provides a dry forming process and equipment for a viscose-based pre-oxidized short fiber solid felt, and relates to the technical field of solid felt dry forming, and the dry forming process comprises the following steps: placing processed viscose short fibers in a nitrogen reactor through an efficient shredding machine, heating to 240 DEG C at a rate of 10 DEG C / min, keeping for 30 minutes, introducing NOO-containing mixed gas, heating to 280 DEG C, keeping for 15 minutes, and cooling to room temperature to obtain the viscose-based pre-oxidized short fiber solid felt. Epoxy cyclohexyl-polyhedral oligomeric silsesquioxane aerosol is synchronously sprayed, finally, the temperature is raised to 320 DEG C, the temperature is kept for 5 min, and the felt yield of the fibers is increased to 85%. And through gradient pre-oxidation treatment, the felt yield of the fibers is increased to 85%. In the pre-oxidation process, three-stage temperature control is adopted, and specific gas and aerosol are introduced in a matched manner, so that the utilization rate of the fibers in the forming process is increased, the waste of the fibers is reduced, the production cost is reduced, and the problems that the energy consumption is huge and the production cost is increased due to a traditional pre-oxidation multi-stage heating mode are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of dry forming of solid felts, and particularly to a dry forming process and equipment for viscose-based pre-oxidized short fiber solid felts. Background Art

[0002] The viscose-based pre-oxidized short fiber solid felt is a non-woven material made from viscose-based pre-oxidized short fibers through a dry forming process. The dry forming process and equipment for viscose-based pre-oxidized short fiber solid felts are methods for directly processing viscose-based pre-oxidized short fibers into solid felts, and are applicable to industrial scenarios such as high-temperature heat insulation materials and composite reinforcement substrates.

[0003] In the existing forming process of viscose-based pre-oxidized short fiber solid felts, traditional processes usually rely on the soaking solution treatment step, which not only generates a large amount of wastewater, increasing the environmental protection treatment cost and difficulty, but also results in poor fiber orientation, thus affecting the overall performance and quality stability of the solid felt. Although the dry process avoids wastewater discharge, the fiber dispersion uniformity in dry forming is low, and 5% - 15% of organic binders often need to be added, which will have an adverse impact on the temperature resistance of the solid felt. The traditional multi-stage temperature rising method for pre-oxidation not only consumes a large amount of energy, increasing the production cost, but also has a low felt yield. Summary of the Invention

[0004] The present invention relates to a dry forming process and equipment for viscose-based pre-oxidized short fiber solid felts, aiming to solve the problems that traditional processes usually rely on the soaking solution treatment step, which not only generates a large amount of wastewater, increasing the environmental protection treatment cost and difficulty, but also results in poor fiber orientation, thus affecting the overall performance and quality stability of the solid felt. Although the dry process avoids wastewater discharge, the fiber dispersion uniformity in dry forming is low, and 5% - 15% of organic binders often need to be added, which will have an adverse impact on the temperature resistance of the solid felt.

[0005] The present invention provides a dry forming process and equipment for viscose-based pre-oxidized short fiber solid felts, which specifically include the following steps: First, gradient pre-oxidation treatment: The processed viscose short fibers are placed in a nitrogen reactor through a high-efficiency fiber cutting machine, heated to 240°C at a rate of 10°C / min and maintained for 30 min, then a mixed gas containing NO2 is introduced, heated to 280°C and maintained for 15 min, and cyclohexene oxide-caged polyhedral oligomeric silsesquioxane aerosol is sprayed synchronously, and finally heated to 320°C and maintained for 5 min, and the fiber felt yield is increased to 85%; Second, fiber dispersion and forming: After the pre-oxidized fibers are dispersed by an electrostatic fiber separator with a voltage of 10 kV, they enter the Venturi cyclone chamber, and the fibers are collected by a negative pressure adsorption mold with a vacuum degree of -0.09 MPa to form a uniform fiber web with a surface density of 350 g / m²; III. Microwave curing and post-treatment: Through a water spray pipe, a nano-boehmite atomized solution is sprayed onto the fibers in the negative-pressure adsorption mold. The curing component triggers a condensation reaction through microwave radiation. After a power density of 3 W / cm² and a time of 5 min, it is cured into a fiber web. The fiber web is carbonized and graphitized under nitrogen protection. Finally, a viscose-based pre-oxidized short fiber felt product with a thermal conductivity ≤ 0.032 W / (m·K) and a tensile strength ≥ 800 MPa is obtained.

[0006] Further, the viscose staple fibers with a diameter of 5 - 8 mm processed by the high-efficiency fiber cutting machine in Step I are placed in a nitrogen reactor, and a mixed gas containing 3 - 5 vol% of NO2 by volume is introduced. Gradient pre-oxidation is carried out under three-stage temperature control of 240 °C → 280 °C → 320 °C, so that the carboxyl group content on the fiber surface is increased to 12.6 μmol / g, and the fiber volume density gradient changes from 1.38 g / cm³ at the core to 1.42 g / cm³ at the surface layer. At the same time, epoxycyclohexyl-cage-shaped polyhedral oligomeric silsesquioxane aerosol is introduced to promote the in-situ formation of sulfur ether bonds between fibers, replacing the traditional impregnating solution.

[0007] Further, the electrostatic fiber separator in Step II eliminates the electrostatic agglomeration of fibers, and the single-fiber separation degree > 92%. The air flow with a speed of 28 m / s inside the Venturi cyclone chamber and the negative-pressure adsorption mold are used to make the fiber surface density distribution uniform.

[0008] Further, the water spray pipe in Step III sprays an atomized solution containing 0.5% nano-boehmite onto the deposited fibers, and combines with the microwave radiation of the curing component to trigger the surface hydroxyl condensation reaction, forming a three-dimensional network structure with an interlayer bonding strength ≥ 2.4 MPa, so that the viscose-based pre-oxidized short fiber felt is cured and formed.

[0009] Further, the equipment for the dry forming process of the viscose-based pre-oxidized short fiber felt includes: a fixed support, which is composed of rectangular pipes welded together. An operation panel is installed on the side of the fixed support, and a high-efficiency fiber cutting machine is installed at the top of the side end of the fixed support; three feeding pipes are installed at the output end of the bottom of the high-efficiency fiber cutting machine, and control valves are installed on the feeding pipes; a nitrogen reactor is also installed at the top of the fixed support; the top of the side end of the nitrogen reactor is connected to the bottom of the feeding pipe, and a plurality of uniformly distributed shunt pipes are installed at the bottom of the nitrogen reactor; control valves are installed on the shunt pipes, and the bottom of the shunt pipes is connected to a centralized diversion pipe; a diversion hood is installed at the side end of the centralized diversion pipe.

[0010] Further, a servo motor is installed on the side end of the nitrogen reactor, and the output end of the servo motor penetrates through the side end of the nitrogen reactor and is installed with a rotating connecting plate; a rotating dial is installed on the side end of the rotating connecting plate; a receiving cavity is opened on the outer side of the rotating dial; a spring is installed inside the receiving cavity, and a cleaning scraper is installed inside the receiving cavity through the spring. Among them, the outer end of the cleaning scraper is slidably installed on the inner side of the nitrogen reactor; the other end of the nitrogen reactor is installed with a nitrogen storage tank and an aerosol storage tank.

[0011] Further, a driving pump is installed on the side ends of the nitrogen storage tank and the aerosol storage tank, and a diversion air pipe is installed on the output end of the driving pump; a diversion hood is installed on the side end of the diversion air pipe; a rotating block is rotatably installed at the middle position of the other side end of the nitrogen reactor; a nitrogen conduit and an aerosol conduit are installed inside the rotating block; an air inlet hood is installed at the outer end of the nitrogen conduit, and a jet pipe is installed at the inner end of the nitrogen conduit.

[0012] Further, the jet pipe is installed on the inner side surface of the rotating dial, and jet nozzles are installed on the jet pipe; a slot is provided on the outer side of the air inlet hood, and the air inlet hood is rotatably installed inside a diversion hood; a conveying hood is installed at the outer end of the aerosol conduit, and a spraying pipe is installed at the inner end of the aerosol conduit; the spraying pipe is installed on the inner side surface of the rotating dial, and spray heads are installed on the spraying pipe; a slot is provided on the outer side of the conveying hood, and the conveying hood is rotatably installed inside another diversion hood.

[0013] Further, an electrostatic fiber splitting device is supported and installed on the top of the fixed bracket; the input end of the electrostatic fiber splitting device is connected to the diversion hood, and a Venturi cyclone chamber is installed at the output end of the bottom of the electrostatic fiber splitting device; a guide rail is installed inside the bottom of the fixed bracket; the top of the guide rail is connected to the bottom of the Venturi cyclone chamber; a negative pressure adsorption mold is slidably installed inside the guide rail, and a fixed support plate is installed on the guide rail.

[0014] Further, a curing liquid storage tank is installed on the top side end of the fixed support plate; a water spraying pipe is installed at the bottom on one side of the curing liquid storage tank; the water spraying pipe is installed on the top of the fixed support plate, and a nozzle is installed at the bottom of the water spraying pipe. The nozzle penetrates through the fixed support plate and is located above the negative pressure adsorption mold; a curing component is also installed on the guide rail; a microwave curing generator is installed on the curing component, and the curing component is located on the negative pressure adsorption mold.

[0015] The present invention provides a dry forming process and equipment for viscose-based pre-oxidized short fiber solid felt, and has the following beneficial effects: When the present invention is in use, through gradient pre-oxidation treatment, the fiber mat forming rate is increased to 85%. During the pre-oxidation process, three-stage temperature control is adopted: 240°C → 280°C → 320°C, and the introduction of specific gases and aerosols is combined to enable the fibers to react more fully under suitable temperature and chemical environments, thereby improving the utilization rate of the fibers during the forming process, reducing fiber waste, and lowering production costs.

[0016] In the pre-oxidation stage, a mixed gas containing NO2 is introduced for gradient heating treatment, so that the carboxyl group content on the fiber surface is increased to 12.6 μmol / g, and the fiber volume density gradient changes from 1.38 g / cm³ at the core to 1.42 g / cm³ at the surface layer, which helps to improve the physical and chemical properties of the fibers, enabling them to better combine with each other during the subsequent forming process and improving the overall quality of the solid mat. At the same time, cyclohexene oxide-caged polyhedral oligomeric silsesquioxane aerosol is introduced to promote the in-situ formation of thioether bonds between the fibers, replacing the traditional impregnating solution, avoiding the wastewater discharge problem caused by the treatment of the immersion liquid in the traditional process, and also reducing the use of organic binders, improving the heat resistance of the solid mat.

[0017] The pre-oxidized fibers are first subjected to primary dispersion treatment by an electrostatic fiber separator with a voltage of 10 kV. The electrostatic fiber separator can effectively eliminate the electrostatic agglomeration of the fibers and preliminarily disperse the fibers. Subsequently, they enter a Venturi cyclone chamber for secondary dispersion treatment. Under the action of an air flow velocity of 28 m / s, the fibers are further dispersed, and the single-fiber separation degree > 92%, and the porosity is controlled at 65 - 85%, which is beneficial to the formation of a fiber web with uniform areal density, laying a foundation for obtaining a high-quality solid mat in the subsequent curing and forming process.

[0018] By spraying an atomized liquid containing 0.5% nano-boehmite on the deposited fibers and combining with the microwave radiation of the curing component to trigger the surface hydroxyl condensation reaction, the combination between the fibers becomes tighter, improving the mechanical properties of the solid mat. In addition, carbonization and graphitization treatments are carried out under nitrogen protection to further optimize the internal structure of the solid mat, so that its thermal conductivity ≤ 0.032 W / (m·K), having good heat insulation performance. Description of the Drawings

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly introduced below.

[0020] The drawings in the following description only relate to some embodiments of the present invention and do not limit the present invention.

[0021] In the drawings: Figure 1 The block diagram of the forming process flow of the present invention is shown; Figure 2A schematic diagram showing the overall structure of the device applied in the present invention; Figure 3 A schematic three-dimensional structure diagram of the centralized diversion pipe of the present invention; Figure 4 A schematic sectional structure diagram of the nitrogen reactor of the present invention; Figure 5 A schematic sectional structure diagram of the rotary baffle of the present invention; Figure 6 Shows the part A enlarged structure diagram led out from Figure 5 of the present invention; Figure 7 A schematic sectional structure diagram of the shunt cover of the present invention; Figure 8 A schematic three-dimensional structure diagram of the Venturi cyclone chamber of the present invention; Figure 9 A schematic three-dimensional structure diagram of the negative pressure adsorption mold of the present invention.

[0022] List of reference numerals 1. Fixed bracket; 101. High-efficiency wire cutter; 102. Feed pipe; 103. Nitrogen reactor; 104. Shunt pipe; 105. Centralized diversion pipe; 106. Diversion cover; 107. Rotary connecting plate; 108. Rotary baffle; 109. Storage cavity; 1010. Cleaning scraper; 1011. Nitrogen storage tank; 1012. Aerosol storage tank; 1013. Diversion air pipe; 1014. Shunt cover; 1015. Rotary block; 1016. Nitrogen conduit; 1017. Intake hood; 1018. Jet pipe; 1019. Aerosol conduit; 1020. Delivery hood; 1021. Spraying pipe; 2. Electrostatic wire separator; 201. Venturi cyclone chamber; 3. Guide rail; 301. Negative pressure adsorption mold; 302. Fixed support plate; 303. Curing liquid storage tank; 304. Water spray pipe; 305. Curing assembly. Detailed implementation manners

[0023] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0024] Please refer to Figures 1 to 9 : Embodiment 1: The present invention provides a dry forming process and equipment for viscose-based pre-oxidized short fiber solid felt, including the following steps: 1. Place the processed viscose staple fiber in the nitrogen reactor 103 through the high-efficiency fiber cutter 101, heat it to 240 °C at a rate of 10 °C / min and hold for 30 min, then introduce the mixed gas containing NO2, heat it to 280 °C and hold for 15 min, simultaneously spray the epoxycyclohexyl-cage-like polyhedral oligomeric silsesquioxane aerosol, and finally heat it to 320 °C and hold for 5 min. The fiber mat yield is increased to 85%; 2. After the pre-oxidized fiber is dispersed by the electrostatic fiber separator 2 with a voltage of 10 kV, it enters the Venturi cyclone chamber 201, and the fiber is collected by using the negative pressure adsorption mold 301 with a vacuum degree of -0.09 MPa to form a uniform fiber web with a surface density of 350 g / m²; 3. Spray the nano-boehmite atomized liquid onto the fiber in the negative pressure adsorption mold 301 through the water spray pipe 304. The curing component 305 triggers the condensation reaction through microwave radiation. After a power density of 3 W / cm² and a time of 5 min, it is cured into a fiber web. The fiber web is carbonized and graphitized under nitrogen protection. Finally, the viscose-based pre-oxidized short fiber solid mat product is obtained with a thermal conductivity ≤ 0.032 W / (m·K) and a tensile strength ≥ 800 Mpa. In step 1, the viscose staple fiber with a diameter of 5 - 8 mm processed by the high-efficiency fiber cutter 101 is placed in the nitrogen reactor 103, and the mixed gas containing NO2 with a volume percentage of 3 - 5 vol% is introduced. Gradient pre-oxidation is carried out under three-stage temperature control of 240 °C → 280 °C → 320 °C, so that the carboxyl group content on the fiber surface is increased to 12.6 μmol / g, and the fiber volume density gradient changes from 1.38 g / cm³ at the core to 1.42 g / cm³ at the surface layer. At the same time, the epoxycyclohexyl-cage-like polyhedral oligomeric silsesquioxane aerosol is introduced to promote the in-situ formation of thioether bonds between fibers, replacing the traditional impregnating solution. In step 2, the electrostatic fiber separator 2 eliminates the electrostatic agglomeration of the fiber, and the single fiber separation degree > 92%. The air flow with a speed of 28 m / s inside the Venturi cyclone chamber 201 and the negative pressure adsorption mold 301 make the fiber surface density distribution uniform. In step 3, the water spray pipe 304 sprays the atomized liquid containing 0.5% nano-boehmite concentration onto the deposited fiber, and combines with the microwave radiation of the curing component 305 to trigger the surface hydroxyl condensation reaction, forming a three-dimensional network structure with an interlayer bonding strength ≥ 2.4 MPa, so that the viscose-based pre-oxidized short fiber solid mat is cured and formed.

[0025] Equipment for the dry forming process and equipment of viscose-based pre-oxidized staple fiber solid felt, including: a fixed bracket 1, the fixed bracket 1 is composed of welded rectangular tubes, and an operation panel is installed on the side of the fixed bracket 1, and a high-efficiency filament cutter 101 is installed on the top of the side end of the fixed bracket 1; three feed pipes 102 are installed on the output end at the bottom of the high-efficiency filament cutter 101, among which, control valves are installed on the feed pipes 102; a nitrogen reactor 103 is also installed on the top of the fixed bracket 1; the top of the side end of the nitrogen reactor 103 is communicated with the bottom of the feed pipe 102, and a plurality of uniformly distributed shunt pipes 104 are installed at the bottom of the nitrogen reactor 103; control valves are installed on the shunt pipes 104, and the bottom of the shunt pipe 104 is connected to a centralized diversion pipe 105; a diversion hood 106 is installed on the side end of the centralized diversion pipe 105; a servo motor is installed on the side end of the nitrogen reactor 103, and the output end of the servo motor penetrates through the side end of the nitrogen reactor 103 and installs a rotating connecting plate 107; a rotating baffle 108 is installed on the side end of the rotating connecting plate 107; a storage cavity 109 is opened on the outside of the rotating baffle 108; a spring is installed inside the storage cavity 109, and a cleaning scraper 1010 is installed inside the storage cavity 109 through the spring, among which, the outer end of the cleaning scraper 1010 is slidably installed inside the nitrogen reactor 103; a nitrogen storage tank 1011 and an aerosol storage tank 1012 are installed at the other end of the nitrogen reactor 103; a driving pump is installed on the side end of the nitrogen storage tank 1011 and the aerosol storage tank 1012, and a diversion air pipe 1013 is installed on the output end of the driving pump; a diversion hood 1014 is installed on the side end of the diversion air pipe 1013; a rotating block 1015 is rotatably installed at the middle position of the other side end of the nitrogen reactor 103; a nitrogen conduit 1016 and an aerosol conduit 1019 are installed inside the rotating block 1015; an air inlet hood 1017 is installed at the outer end of the nitrogen conduit 1016, and a jet pipe 1018 is installed at the inner end of the nitrogen conduit 1016; the jet pipe 1018 is installed on the inner side surface of the rotating baffle 108, and jet nozzles are installed on the jet pipe 1018; a slot is provided on the outside of the air inlet hood 1017, and the air inlet hood 1017 is rotatably installed inside a diversion hood 1014; the outer end of the aerosol conduit 1019 is a conveying hood 1020, and a spraying pipe 1021 is installed at the inner end of the aerosol conduit 1019; the spraying pipe 1021 is installed on the inner side surface of the rotating baffle 108, and spray nozzles are installed on the spraying pipe 1021; a slot is provided on the outside of the conveying hood 1020, and the conveying hood 1020 is rotatably installed inside another diversion hood 1014.

[0026] In the embodiment of the present invention, when the viscose-based pre-oxidized staple fiber felt is formed by the dry method, the longer fibers are put into the high-efficiency fiber cutter 101. The high-efficiency fiber cutter 101 cuts the fibers into viscose staple fibers with a diameter of 5-8 mm. The control valve on the feed pipe 102 is opened, and the viscose staple fibers are put into the nitrogen reactor 103 through the feed pipe 102. The servo motor at one end of the nitrogen reactor 103 drives the rotating connecting plate 107 to rotate, and the rotating connecting plate 107 drives the two rotating paddles 108 to rotate. The rotating paddles 108 turn over the short fibers, and the nitrogen reactor 103 heats them. The temperature is raised at a rate of 10 °C / min and raised to 240 °C and maintained for 30 min to ensure the temperature uniformity. When the rotating paddle 108 rotates, it drives the rotating block 1015 to rotate through the nitrogen conduit 1016 and the aerosol conduit 1019. Then, by introducing nitrogen, the drive pump on the nitrogen storage tank 1011 at the other end of the nitrogen reactor 103 works. The drive pump diverts the nitrogen through the diversion gas pipe 1013 into the interior of a diversion hood 1014. The airflow inside the diversion hood 1014 enters the nitrogen conduit 1016 through the intake hood 1017, and the nitrogen flows into the nitrogen reactor 103 through the jet nozzles on the jet pipe 1018. The temperature is raised to 280 °C and maintained for 15 min. At the same time, the drive pump on the aerosol storage tank 1012 works. The drive pump extracts the oxacyclohexyl-cage-shaped polyhedral oligomeric silsesquioxane aerosol and enters it into the interior of another diversion hood 1014 through the diversion gas pipe 1013. The aerosol inside the other diversion hood 1014 flows into the aerosol conduit 1019 through the conveying hood 1020, and the aerosol then enters the interior of the spraying pipe 1021 and is sprayed inside the nitrogen reactor 103. During the rotation process, nitrogen or aerosol is sprayed to ensure the spraying uniformity. Finally, the temperature is raised to 320 °C and maintained for 5 min, so that the fiber mat formation rate is increased to 85%, and the fibers are subjected to gradient pre-oxidation treatment. The treated fibers are concentrated and flow into the interior of the diversion hood 106 at the side end of the centralized diversion pipe 105 through the diversion pipe 104. The fibers in the nitrogen reactor 103 are discharged. Then, the servo motor drives the rotating paddles 108 at both ends of the rotating connecting plate 107 to rotate at high speed. Under the action of centrifugal force, the spring at the inner end of the cleaning scraper 1010 contracts, and the cleaning scraper 1010 moves outward inside the storage cavity 109. The outer end of the cleaning scraper 1010 contacts the inner side wall of the nitrogen reactor 103. After the cleaning scraper 1010 rotates, it rotates and cleans the residual fibers, reducing the problem of fiber residue and ensuring that the fibers are completely cleaned out.

[0027] Example 2: On the basis of Example 1, an electrostatic fiber distributor 2 is mounted on the top of the fixed support 1 in a supported manner; the input end of the electrostatic fiber distributor 2 is connected to the flow guide cover 106, and a Venturi cyclone chamber 201 is mounted on the output end at the bottom of the electrostatic fiber distributor 2. When the viscose-based pre-oxidized short fiber solid felt is formed by the dry process, the fibers in the flow guide cover 106 enter the interior of the electrostatic fiber distributor 2. The electrostatic fiber distributor 2 performs primary dispersion treatment on the fibers at a voltage of 10 kV. The dispersed fibers enter the Venturi cyclone chamber 201, and under the action of an air flow velocity of 25 - 30 m / s, the fibers are subjected to secondary dispersion treatment, with a single filament separation degree > 92%, the porosity controlled at 65 - 85%, the thermal conductivity reduced by 50% compared with the traditional process, and the treated fibers enter the negative pressure adsorption mold 301.

[0028] Example 3: On the basis of Example 1, a guide rail 3 is mounted on the inner side of the bottom of the fixed support 1; the top of the guide rail 3 is connected to the bottom of the Venturi cyclone chamber 201; a negative pressure adsorption mold 301 is slidably mounted on the inner side of the guide rail 3, and a fixed support plate 302 is mounted on the guide rail 3; a curing liquid storage tank 303 is mounted on the top side end of the fixed support plate 302; a water spray pipe 304 is mounted on the bottom side of one side of the curing liquid storage tank 303; the water spray pipe 304 is mounted on the top of the fixed support plate 302, and a nozzle is mounted on the bottom of the water spray pipe 304, and the nozzle penetrates through the fixed support plate 302 and is located above the negative pressure adsorption mold 301; a curing assembly 305 is also mounted on the guide rail 3; a microwave curing generator is mounted on the curing assembly 305, and the curing assembly 305 is located above the negative pressure adsorption mold 301. When the viscose-based pre-oxidized short fiber solid felt is formed by the dry process, the negative pressure adsorption mold 301 moves along the guide rail 3, so that the negative pressure adsorption mold 301 moves to the bottom of the Venturi cyclone chamber 201. Under the negative pressure of -0.09 Mpa of vacuum degree, the negative pressure adsorption mold 301 performs adsorption treatment to form a uniform fiber web with a surface density of 350 g / m². The nano-boehmite atomized liquid in the curing liquid storage tank 303 on the top side end of the fixed support plate 302 is sprinkled out through the nozzle on the water spray pipe 304, so that the nano-boehmite atomized liquid is sprinkled on the fibers in the negative pressure adsorption mold 301. The negative pressure adsorption mold 301 drives the fibers to move to the bottom of the curing assembly 305, and the microwave curing generator on the curing assembly 305 emits microwave radiation to trigger a condensation reaction, and the short fiber solid felt is cured. No wastewater is generated throughout the process, realizing zero wastewater discharge, meeting the environmental protection trend of biological waste gas treatment technology, the fiber utilization rate is increased to 96%, and the production cost is reduced by 30%.

[0029] Working principle of this embodiment: Long fibers are put into the high-efficiency fiber cutter 101 and cut into viscose staple fibers. The viscose staple fibers are put into the nitrogen reactor 103 through the feed pipe 102. The nitrogen reactor 103 heats it to 240 °C and maintains it for 30 min. The nitrogen storage tank 1011 guides nitrogen through the diversion gas pipe 1013 into a diversion hood 1014. The air flow in the diversion hood 1014 enters the nitrogen conduit 1016 through the air inlet hood 1017 and then flows into the nitrogen reactor 103 through the spray pipe 1018, and is heated to 280 °C and maintained for 15 min. At the same time, the aerosol storage tank 1012 makes the oxacyclohexyl-cage-shaped polyhedral oligomeric silsesquioxane aerosol enter another diversion hood 1014 through the diversion gas pipe 1013. The aerosol flows into the aerosol conduit 1019 through the conveying hood 1020 and is then sprayed into the nitrogen reactor 103 through the spraying pipe 1021. Finally, it is heated to 320 °C and maintained for 5 min, so that the fiber mat forming rate is increased to 85%. The treated fibers are centrally flowed into the diversion hood 106 at the side end of the central diversion pipe 105 through the diversion pipe 104 and enter the electrostatic fiber separator 2. The electrostatic fiber separator 2 performs primary dispersion treatment on the fibers under a voltage of 10 kV. The dispersed fibers enter the Venturi cyclone chamber 201, and the fibers are subjected to secondary dispersion treatment under the action of an air flow velocity of 25 - 30 m / s. The treated fibers enter the negative pressure adsorption mold 301 to form a uniform fiber web with a surface density of 350 g / m². The nano-boehmite atomized liquid is sprayed on the fibers in the negative pressure adsorption mold 301 through the spray pipe 304. The microwave curing generator on the curing assembly 305 emits microwave radiation to trigger the condensation reaction, and the short fiber solid mat is obtained by curing. No wastewater is generated throughout the process, achieving zero wastewater discharge.

[0030] In this article, the following points need to be noted: 1. The attached drawings of the embodiments of the present invention only relate to the structures involved in the embodiments of the present invention, and other structures can refer to the general design.

[0031] 2. Without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other to obtain new embodiments.

[0032] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. Dry forming process for viscose-based preoxidized staple fiber solid felt, characterized in that, It includes the following steps: First, place the processed viscose staple fiber in a nitrogen reactor (103) through a high-efficiency fiber cutter (101), heat it to 240°C at a rate of 10°C / min and hold for 30 min, then introduce a mixed gas containing NO2, heat it to 280°C and hold for 15 min, synchronously spray epoxycyclohexyl-cage polyhedral oligomeric silsesquioxane aerosol, and finally heat it to 320°C and hold for 5 min; Second, after the pre-oxidized fiber is dispersed by an electrostatic fiber separator (2) with a voltage of 10 kV, it enters a Venturi cyclone chamber (201), and the fiber is collected by a negative pressure adsorption mold (301) with a vacuum degree of -0.09 MPa to form a uniform fiber web with a surface density of 350 g / m²; Third, spray a nano-boehmite atomized liquid onto the fiber in the negative pressure adsorption mold (301) through a water spray pipe (304), and the curing component (305) triggers a condensation reaction through microwave radiation. After a power density of 3 W / cm² and a time of 5 min, it is cured into a fiber web. The fiber web is carbonized and graphitized under nitrogen protection. Finally, a viscose-based pre-oxidized short fiber solid felt product with a thermal conductivity ≤ 0.032 W / (m·K) and a tensile strength ≥ 800 MPa is obtained.

2. The dry forming process of the viscose-based pre-oxidized staple fiber solid felt according to claim 1, characterized in that, In step one, the viscose staple fiber with a diameter of 5 - 8 mm processed by the high-efficiency fiber cutter (101) is placed in a nitrogen reactor (103), and a mixed gas with a volume percentage of NO2 of 3 - 5 vol% is introduced. Gradient pre-oxidation is carried out under temperature control in three stages of 240°C → 280°C → 320°C, so that the carboxyl group content on the fiber surface is increased to 12.6 μmol / g, and the fiber volume density gradient changes from 1.38 g / cm³ at the core to 1.42 g / cm³ at the surface layer. At the same time, epoxycyclohexyl-cage polyhedral oligomeric silsesquioxane aerosol is introduced to promote the in-situ generation of thioether bonds between fibers, replacing the traditional impregnating liquid.

3. The dry forming process of the viscose-based pre-oxidized staple fiber solid felt according to claim 2, characterized in that, In step two, the electrostatic fiber separator (2) eliminates the electrostatic agglomeration of the fiber, and the single fiber separation degree > 92%. The air flow with a speed of 28 m / s inside the Venturi cyclone chamber (201) cooperates with the negative pressure adsorption mold (301) to make the fiber surface density distribution uniform.

4. The dry forming process of the viscose-based pre-oxidized staple fiber solid felt according to claim 3, characterized in that In step three, the water spray pipe (304) sprays an atomized liquid containing 0.5% nano-boehmite onto the deposited fiber, and the microwave radiation of the curing component (305) triggers the surface hydroxyl condensation reaction to form a three-dimensional network structure with an interfacial bonding strength ≥ 2.4 MPa, so that the viscose-based pre-oxidized short fiber solid felt is cured and formed.

5. An apparatus for implementing a dry forming process of the viscose-based pre-oxidized staple fiber felt according to any one of claims 1-4, characterized in that, It includes: Fixed support (1), an operation panel is installed on the side of the fixed support (1), and a high-efficiency slicing machine (101) is installed at the top of the side end of the fixed support (1); three feed pipes (102) are installed at the output end of the bottom of the high-efficiency slicing machine (101), and control valves are installed on the feed pipes (102); a nitrogen reactor (103) is also installed at the top of the fixed support (1); the top of the side end of the nitrogen reactor (103) is communicated with the bottom of the feed pipe (102), and a plurality of uniformly distributed shunt pipes (104) are installed at the bottom of the nitrogen reactor (103); control valves are installed on the shunt pipes (104), and the bottom of the shunt pipe (104) is connected to a centralized diversion pipe (105); a diversion cover (106) is installed at the side end of the centralized diversion pipe (105).

6. The equipment for the dry forming process of the viscose-based pre-oxidized staple fiber solid felt according to claim 5, characterized in that, A servo motor is installed at the side end of the nitrogen reactor (103), and a rotating connecting plate (107) is installed at the output end of the servo motor through the side end of the nitrogen reactor (103); a rotating dial (108) is installed at the side end of the rotating connecting plate (107); a receiving cavity (109) is opened on the outer side of the rotating dial (108); a spring is installed inside the receiving cavity (109), and a cleaning scraper (1010) is installed inside the receiving cavity (109) through the spring. The outer end of the cleaning scraper (1010) is slidably installed inside the nitrogen reactor (103); a nitrogen storage tank (1011) and an aerosol storage tank (1012) are installed at the other end of the nitrogen reactor (103).

7. The equipment for the dry forming process of the viscose-based pre-oxidized staple fiber solid felt according to claim 6, characterized in that, Driving pumps are installed at the side ends of the nitrogen storage tank (1011) and the aerosol storage tank (1012), and a diversion air pipe (1013) is installed at the output end of the driving pumps; a diversion hood (1014) is installed at the side end of the diversion air pipe (1013); a rotating block (1015) is rotatably installed at the middle position of the other side end of the nitrogen reactor (103); a nitrogen conduit (1016) and an aerosol conduit (1019) are installed inside the rotating block (1015); an air inlet hood (1017) is installed at the outer end of the nitrogen conduit (1016), and a jet pipe (1018) is installed at the inner end of the nitrogen conduit (1016).

8. The equipment for the dry forming process of the viscose-based pre-oxidized staple fiber solid felt according to claim 7, characterized in that, The jet pipe (1018) is installed on the inner side surface of the rotating dial (108), and jet nozzles are installed on the jet pipe (1018); a slot is provided on the outer side of the air inlet hood (1017), and the air inlet hood (1017) is rotatably installed inside a diversion hood (1014); a conveying hood (1020) is installed at the outer end of the aerosol conduit (1019), and a spraying pipe (1021) is installed at the inner end of the aerosol conduit (1019); the spraying pipe (1021) is installed on the inner side surface of the rotating dial (108), and spray heads are installed on the spraying pipe (1021); a slot is provided on the outer side of the conveying hood (1020), and the conveying hood (1020) is rotatably installed inside another diversion hood (1014).

9. The equipment for the dry forming process of the viscose-based pre-oxidized staple fiber solid felt according to claim 8, characterized in that, The top of the fixed bracket (1) is supported and installed with an electrostatic fiber splitting device (2); the input end of the electrostatic fiber splitting device (2) is connected to the flow guiding cover (106), and a Venturi cyclone chamber (201) is installed at the output end of the bottom of the electrostatic fiber splitting device (2); the inner side of the bottom of the fixed bracket (1) is installed with a guide rail (3); the top of the guide rail (3) is connected to the bottom of the Venturi cyclone chamber (201); a negative pressure adsorption mold (301) is slidably installed inside the guide rail (3), and a fixed support plate (302) is installed on the guide rail (3).

10. The equipment for the dry forming process of the viscose-based pre-oxidized staple fiber solid felt according to claim 9, characterized in that, A curing liquid storage tank (303) is installed at the top side end of the fixed support plate (302); a water spray pipe (304) is installed at the bottom of one side of the curing liquid storage tank (303); the water spray pipe (304) is installed on the top of the fixed support plate (302), and a nozzle is installed at the bottom of the water spray pipe (304), and the nozzle penetrates through the fixed support plate (302) and is located above the negative pressure adsorption mold (301); a curing component (305) is also installed on the guide rail (3); a microwave curing generator is installed on the curing component (305), and the curing component (305) is located on the negative pressure adsorption mold (301).

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