A layered pitch-based carbon fiber skeleton electrothermal base paper and its preparation process

Abstract

This invention relates to the fields of specialty paper, carbon fiber composite paper, and electrothermal material preparation technology, specifically to a layered structure pitch-based carbon fiber skeleton electrothermal base paper and its preparation process. The preparation method includes surface paper preparation, intermediate layer preparation, layered structure paper preparation, and layered structure paper reinforcement. This invention utilizes a clever combination of carbon fibers of different lengths, aramid pulp, aramid precipitation, and carbon black to form a "sandwich" layered structure. The introduction of carbon black in the surface layer reduces the resistance of the insulating fibers, stabilizes the heating power, prevents electrothermal loss, and improves the uniformity of heating. The long carbon fibers used in the intermediate layer can provide a current conduction path and improve the overall utilization rate of carbon fibers.

Description

Technical Field

[0001] This invention relates to the field of special paper, carbon fiber composite paper, and electrothermal paper preparation technology, specifically to a layered structure pitch-based carbon fiber skeleton electrothermal base paper and its preparation process. Background Technology

[0002] Carbon fiber paper can be traced back to the 1960s, when an American company developed the first batches and used them in special components for the aerospace industry. Carbon fiber itself possesses extremely high strength and modulus; the resulting carbon fiber paper, while remaining thin and lightweight, exhibits excellent durability and bending resistance, making it easy to carry and use. Simultaneously, carbon fiber has excellent electrical conductivity, meeting the requirements of electronic products for electrostatic protection and electromagnetic shielding, and can also be used as an electrode material. Furthermore, its good stability allows it to operate stably in high-temperature environments, making it suitable for insulation and heat preservation materials in high-temperature furnaces, heat exchangers, and other equipment. It is also corrosion-resistant, acid and alkali-resistant, and maintains stable performance under various chemical environments.

[0003] There are two main methods for preparing carbon fiber paper: wet process and dry process. The wet process involves mixing carbon fiber and resin and other raw materials to form a pulp suspension, which is then shaped through processes such as papermaking, pressing, and drying, followed by impregnation, pre-oxidation, carbonization, and graphitization. The dry process involves directly compressing or pyrolyzing carbon fiber and other raw materials under conditions such as hot pressing or pyrolysis to form carbon paper. For example, CN103628350B produces a flame-retardant carbon fiber electric heating paper by mixing carbon fiber with raw materials such as wood glue and gelatin, and then using wet papermaking processes such as papermaking, pressing, and drying. This solves the problems of uneven resistance and heating, and easy breakage and tearing of traditional carbon fiber paper. CN102465475A successfully produces industrial high-temperature carbon fiber electric heating paper by mixing polyacrylonitrile-based carbon fiber with serpentine asbestos wool and using wet papermaking processes. This overcomes the problem of limited heating temperature caused by the low carbonization temperature of the pulp when mixing short-cut carbon fiber with pulp to make paper. CN110129992B produces a carbon fiber paper for fuel cells by graphitizing carbon fiber, dry papermaking to make preforms, and then using carbonization, deposition, and other processes. This solves the problems of carbon fiber not being easy to disperse, slow water filtration, and harmful liquid discharge in wet papermaking.

[0004] Currently, carbon fiber paper is widely used in aerospace, automotive, electronics, medical devices, and sporting goods. In the fuel cell field, it serves as a key substrate material for the gas diffusion layer, playing a vital role in supporting the fuel, collecting current, conducting gas, and removing reactant water. However, the high cost, susceptibility to damage, and poor thermal conductivity of traditional carbon fiber paper have limited the development of the domestic carbon fiber paper industry. Summary of the Invention

[0005] To address the problems of easy damage and poor thermal conductivity of carbon fiber paper in existing technologies, this invention provides a layered structure pitch-based carbon fiber skeleton electrothermal base paper, its preparation process, and its preparation method.

[0006] This invention is achieved through the following technical solution:

[0007] A process for preparing a layered pitch-based carbon fiber skeleton electrothermal base paper includes the following steps:

[0008] S1, Preparation of surface paper web: Weigh aramid pulp, aramid precipitate, conductive carbon black, carbon fiber and PEO dispersion, mix and then dissolve to obtain mixed system pulp A. Then, through pulp dilution, turbulent homogenization and negative pressure dewatering, surface wet paper web B is formed.

[0009] Preparation of intermediate layer paper web: Weigh carbon fiber, aramid precipitate and PEO dispersion, mix and dissolve to obtain mixed slurry C, then dilute and add water, turbulent homogenize and dewater under negative pressure to form carbon fiber intermediate layer wet paper web D;

[0010] S2, the intermediate wet paper web D and the surface wet paper web B are stacked together, and then cold-pressed and dehydrated to obtain the layered structure paper web E;

[0011] S4. Vacuum drying and hot pressing bonding of the layered paper web E are performed to obtain the layered pitch-based carbon fiber skeleton electrothermal base paper F.

[0012] Preferably, in S1, when preparing the surface paper web, the aramid pulp is para-aramid fiber with a freeness of (45-48)°SR, a specific surface area of ​​(9-11) m² / g, and a total dry weight of (0.26-0.27) g.

[0013] Aramid precipitation is a differentiated product of meta-aramid fiber, with a freeness of (42-45)°SR, a moisture content of (70-85)%, and a total dry weight of (3.64-3.65)g;

[0014] The carbon fiber is pitch-based carbon fiber with a fiber length of (3–4) mm, a fiber diameter of (6–10) μm, and a total dry weight of (0.37–0.38) g; the conductive carbon black has a mass of (0.30–0.50) g ​​and an electrical conductivity of (0.20–0.50) S·cm. -1 ;

[0015] The concentration of the PEO dispersion is (10-15) g / L, and the volume is (10.00-11.00) mL.

[0016] Preferably, in S1, the unwinding speed during the preparation of the surface paper web is 25,000 to 30,000 rpm;

[0017] The amount of water added for dilution is (2.0~3.0) L;

[0018] The turbulent homogenization was repeated (8-10) times.

[0019] Vacuum pumping is performed using an 80-100 mesh forming net, with a vacuum degree of 0.080-0.098 MPa and a pumping time of 20-25 seconds.

[0020] Preferably, in S1, when preparing the intermediate layer paper web, the carbon fiber is pitch-based carbon fiber with a fiber length of (7-8) mm, a fiber diameter of (6-10) micrometers, and a total dry weight of (0.87-0.88) g.

[0021] Aramid precipitation is a differentiated product of meta-aramid fiber, with a freeness of (45-50)°SR, a moisture content of (85-92)%, and a total dry weight of (2.18-2.19) g;

[0022] The concentration of the PEO dispersion is (10-15) g / L, and the volume is (10.00-11.00) mL.

[0023] Preferably, in S1, the unwinding speed during the preparation of the intermediate layer paper web is 25,000 to 30,000 rpm;

[0024] The amount of water added for dilution is (2.0~3.0) L;

[0025] The turbulent homogenization was repeated (8-10) times.

[0026] Vacuum pumping is performed using an 80-100 mesh forming net, with a vacuum degree of 0.080-0.098 MPa and a pumping time of 20-25 seconds.

[0027] Preferably, in S2, during the stacking process, the intermediate wet paper web D is transferred to the middle of the two surface wet paper webs B.

[0028] Preferably, in S2, during cold pressing dewatering, absorbent felt pads are used on both the top and bottom of the stacked wet paper webs, the pressing pressure is (8.5~10.5) MPa, and the time is (5~10) min.

[0029] Preferably, in S3, during vacuum drying, the temperature is (105~120)℃, the vacuum degree is (0.7~0.9)MPa, and the time is (10~15)min.

[0030] Preferably, during the hot-press bonding process, the temperature is (180-200)℃, the pressure is (12-15)MPa, and the time is (15-20)min.

[0031] A product obtained according to the preparation process of the layered structure pitch-based carbon fiber skeleton electrothermal base paper.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] First, this application discloses a process for preparing a layered structure pitch-based carbon fiber skeleton electrothermal base paper, including the preparation of the surface paper, the preparation of the intermediate layer, the preparation of the layered structure paper, and the reinforcement of the layered structure paper. Compared with the disclosed preparation technology, this application designs the formula of the heating surface layer and the conductive intermediate layer through layered forming, so that they are different according to the contact resistance, which is more conducive to the development of the mechanical and electrical properties of carbon fiber. It shows significant advantages in electrical and thermal conductivity, high strength and high modulus, and layered heat control.

[0034] Secondly, the hierarchical structure in this application allows each layer to perform different functions. Adding conductive carbon black to the surface paper can improve the electrothermal conversion efficiency and uniformity. Combined with the filling effect of conductive carbon black on the gaps between fibers, the structure is further compacted, making it more resistant to external impacts and pressures and less prone to damage.

[0035] The intermediate layer of pitch-based carbon fiber skeleton is preferably made of fibers with a larger aspect ratio, which makes it easier to reduce contact resistance and form a stable conductive network. While enhancing the strength and toughness of the paper, it also improves the electrical conductivity of the carbon fiber and increases the heat utilization rate of the carbon fiber distributed throughout the carbon fiber paper. The surface layer and intermediate layer work together to improve the overall performance of the carbon fiber composite paper.

[0036] Furthermore, conductive carbon black possesses excellent electrical conductivity, further enhancing the overall conductivity of carbon fiber paper. This allows electrical energy to be converted into heat energy more efficiently during energization, thus improving heating efficiency. Simultaneously, conductive carbon black can fill gaps in the carbon fiber paper, creating uniform conductive pathways to prevent excessive local current, regulating thermal conductivity to balance heat transfer performance and prevent heat accumulation, thereby improving the uniformity of paper heating.

[0037] Furthermore, the pitch-based carbon fiber skeleton plays a crucial supporting role in the hierarchical structure. This skeleton structure is similar to a stable frame, which can restrict the disordered movement of various parts inside the paper. When an electric current passes through and generates heat, the carbon fiber skeleton can maintain the relative position stability of each part, avoiding fluctuations in electrothermal performance caused by local structural changes, thereby reducing electrothermal drift.

[0038] Furthermore, by regulating the interlayer structure of carbon fibers and introducing carbon black heating functional components, this invention achieves high response and high heating efficiency under low voltage with almost no additional components or cost, demonstrating high engineering potential. At the same time, the design concept and structural innovations of this invention can be extended to other types of electrothermal materials, providing valuable reference for the further construction of similar principle electrothermal materials. Attached Figure Description

[0039] Figure 1This is a flowchart of the preparation process of a layered structure pitch-based carbon fiber skeleton electrothermal base paper according to the present invention;

[0040] Figure 2 It is the carbon fiber paper containing 0.3g of carbon black obtained in Example 1;

[0041] Figure 3 This is a magnified SEM image of the cross-section of the carbon fiber paper obtained in Example 1;

[0042] Figure 4 This is a SEM image of the surface of the carbon fiber paper obtained in Example 1;

[0043] Figure 5 This is a graph showing the temperature of the carbon fiber paper in Example 1 as the voltage increases.

[0044] Figure 6 It is the carbon fiber paper containing 0.5g of carbon black obtained in Example 2;

[0045] Figure 7 This is a magnified SEM image of the cross-section of the carbon fiber paper obtained in Example 2;

[0046] Figure 8 This is a SEM image of the surface of the carbon fiber paper obtained in Example 2;

[0047] Figure 9 This is a graph showing the temperature of the carbon fiber paper in Example 2 as the voltage increases.

[0048] Figure 10 This is a graph showing the temperature of the carbon fiber paper in Example 1 as the voltage increases and decreases.

[0049] Figure 11 This is a graph showing the temperature of the carbon fiber paper in Example 2 as the voltage increases and decreases.

[0050] Figure 12 The implementation of XRD performance testing of carbon fiber paper in Case 1 and Case 2 is as follows. Detailed Implementation

[0051] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0052] This invention discloses a layered structure pitch-based carbon fiber skeleton electrothermal base paper and its preparation process, referring to... Figure 1 This includes the following steps:

[0053] S1, Preparation of surface paper web: Weigh a certain amount of aramid pulp, aramid precipitate, conductive carbon black, carbon fiber and PEO dispersion and add them to the disintegration tank in sequence. Obtain mixed system pulp A through disintegration. Then, through pulp dilution, turbulent homogenization and negative pressure dewatering, form surface wet paper web B.

[0054] Among them, the aramid pulp is para-aramid fiber with a freeness of (45-48)°SR, a specific surface area of ​​(9-11) m² / g, and a total dry weight of (0.26-0.27) g; the aramid precipitate is a differentiated product of meta-aramid fiber with a freeness of (42-45)°SR, a moisture content of (70-85)%, and a total dry weight of (3.64-3.65) g; the carbon fiber is pitch-based carbon fiber with a fiber length of (3-4) mm, a fiber diameter of (6-10) micrometers, and a total dry weight of (0.37-0.38) g; the conductive carbon black has a mass of (0.30-0.50) g ​​and an electrical conductivity of (0.20-0.50) S·cm-1; the polyethylene oxide (PEO) dispersion has a concentration of (10-15) g / L and a volume of (10.00-11.00) mL.

[0055] The descaling speed is 25,000~30,000 rpm; the dilution water volume is (2.0~3.0) L; the turbulent homogenization is (8~10) times; the water is vacuumed through an (80~100) mesh forming screen with a vacuum degree of 0.080~0.098 MPa and a vacuum pumping time of (20~25) s.

[0056] Preparation of intermediate layer paper web: A mixed pulp C was obtained by weighing carbon fiber, aramid precipitate, and PEO, followed by dewatering. This pulp was then diluted with water, homogenized under turbulent conditions, and dewatered under negative pressure to form a carbon fiber intermediate layer wet paper web D. The carbon fiber was pitch-based carbon fiber with a fiber length of (7–8) mm, a fiber diameter of (6–10) micrometers, and a total dry weight of (0.87–0.88) g. The aramid precipitate was a differentiated meta-aramid fiber product with a freeness of (45–50)°SR, a water content of (85–92)%, and a total dry weight of (2.18–2.19) g. The polyethylene oxide (PEO) dispersion concentration was (10–15) g / L, and the volume measured was (10.00–11.00) mL. The dewatering rotation was 30,000 revolutions. rpm; dilution water volume is (2.0~3.0)L; turbulent homogenization is performed (8~10) times; vacuum water is pumped through an (80~100) mesh forming screen for (20~25)s.

[0057] S2, prepare layered paper by stacking the intermediate wet paper web D and the surface wet paper web B, followed by cold pressing and dewatering to obtain layered paper web E. Specifically, transfer the intermediate wet paper web D between the two surface wet paper webs B, stack them, and then cold press and dewater to obtain paper web E; when using a cold press for dewatering, absorbent pads should be used on both the top and bottom, the pressing pressure is (8.5~10.5) MPa, and the time is (5~10) min.

[0058] S3, Layered Structure Paper Reinforcement: The paper web E is vacuum dried in the drying section of the paper forming machine and hot-pressed and bonded in a flat vulcanizing machine to obtain the layered structure pitch-based carbon fiber skeleton electrothermal base paper F; wherein, during the vacuum drying treatment, the temperature is (105~120)℃, the vacuum degree is (0.7~0.9)MPa, and the time is (10~15)min; the hot-pressing and bonding temperature of the flat vulcanizing machine is (180~200)℃, the pressure is (12~15)MPa, and the time is (15~20)min.

[0059] This invention utilizes a clever combination of carbon fibers of different lengths, aramid pulp, aramid precipitate, and carbon black to form a "sandwich" layered structure. The carbon black introduced in the surface layer reduces the resistance of the insulating fiber, stabilizes the heating power, prevents heat loss, and improves the uniformity of heating. The long carbon fibers used in the middle layer can provide a current conduction path, thereby improving the overall utilization rate of carbon fibers.

[0060] Example 1

[0061] Step 1: Weigh 0.2636g of aramid pulp with a freeness of 45°SR and a specific surface area of ​​10m² / g, weigh 3.6486g of aramid precipitate with a freeness of 45°SR and a moisture content of 85%, weigh 0.30g of conductive carbon black with a conductivity of 0.20S·cm-1, weigh 0.3763g of carbon fiber with a fiber length of 3mm and a fiber diameter of 6μm, and add them sequentially to the dewatering tank. Obtain the mixed system pulp A through dewatering treatment at 30000 rpm, then add 3.0L of dilution water, perform 10 cycles of turbulent homogenization, and dewater under negative pressure on an 80-mesh forming wire for 25 seconds to form the surface wet paper web B.

[0062] Weigh 0.8782g of carbon fiber with a length of 7mm and a diameter of 6microns, weigh 2.1873g of aramid precipitate with a freeness of 45°SR and a moisture content of 85%, and mix it with 10.00mL of PEO dispersion with a concentration of 10g / L. Obtain mixed pulp C by passing it through a disintegration process at 30000rpm. Then add 3.0L of dilution water, perform 10 cycles of turbulent homogenization, and perform negative pressure dewatering treatment on an 80-mesh forming wire for 25 seconds to form the surface wet paper web D.

[0063] Step 2: Transfer the intermediate wet paper web D to the middle of the two surface wet paper webs B, stack them together, and pad them with absorbent felt on the top and bottom. Use a cold press with a pressing pressure of 9.0 MPa to dehydrate for 5 minutes to obtain paper web E.

[0064] Step 3: The paper web E is vacuum dried for 10 minutes in the drying section of a paper forming machine at a temperature of 105℃ and a vacuum degree of 0.8MPa; after hot pressing and bonding for 15 minutes in a flat vulcanizing machine at a temperature of 200℃ and a pressure of 13MPa, a layered structure pitch-based carbon fiber skeleton electrothermal base paper F is obtained.

[0065] The layered structure pitch-based carbon fiber skeleton electrothermal paper obtained in this embodiment (such as...) Figure 2 , 3 (As shown in Figure 4), the paper basis weight is 40 g / m³. 2 It has a thickness of 0.142 mm, a sheet resistance of 18.16 Ω, a tensile strength of 1.08 kN / m, and a paper weight of 4.37 g. It can be heated to 193℃ at 12V with a heating rate of 2.05℃ / s, exhibiting high electrothermal performance under low voltage. (Reference) Figure 5 The surface temperature of carbon fiber paper containing 0.3g of carbon black increases with increasing voltage. At 4V, the surface temperature can reach 39℃; at 8V, it can reach 99℃; and at 12V, it can reach 193℃.

[0066] Example 2

[0067] Step 1: Weigh 0.2640g of aramid pulp with a freeness of 45°SR and a specific surface area of ​​10m² / g, weigh 3.6457g of aramid precipitate with a freeness of 45°SR and a moisture content of 85%, weigh 0.50g of conductive carbon black with a conductivity of 0.20S·cm⁻¹, weigh 0.3766g of carbon fiber with a fiber length of 3mm and a fiber diameter of 6μm, and add them sequentially to the dewatering tank. Obtain the mixed pulp system A by dewatering at 30000 rpm, then add 3.0L of dilution water, perform 10 cycles of turbulent homogenization, and dewater under negative pressure on an 80-mesh forming wire for 25 seconds to form the surface wet paper web B.

[0068] Weigh 0.8795g of carbon fiber with a length of 7mm and a diameter of 6microns, weigh 2.1863g of aramid precipitate with a freeness of 45°SR and a moisture content of 85%, and mix it with 10.00mL of PEO dispersion with a concentration of 10g / L. Obtain mixed pulp C by passing it through a disintegration process at 30000rpm. Then add 3.0L of dilution water, perform 10 cycles of turbulent homogenization, and perform negative pressure dewatering treatment on an 80-mesh forming wire for 25 seconds to form the surface wet paper web D.

[0069] Step 2: Transfer the intermediate wet paper web D to the middle of the two surface wet paper webs B, stack them together, and pad them with absorbent felt on the top and bottom. Use a cold press with a pressing pressure of 9.0 MPa to dehydrate for 5 minutes to obtain paper web E.

[0070] Step 3: The paper web E is vacuum dried for 10 minutes in the drying section of a paper forming machine at a temperature of 105℃ and a vacuum degree of 0.8MPa; after hot pressing and bonding for 15 minutes in a flat vulcanizing machine at a temperature of 200℃ and a pressure of 13MPa, a layered structure pitch-based carbon fiber skeleton electrothermal base paper F is obtained.

[0071] The layered structure pitch-based carbon fiber skeleton electrothermal paper obtained in this embodiment (such as...) Figure 6 , 7 (As shown in Figure 8), the paper basis weight is 40 g / m³. 2 It has a thickness of 0.175 mm, a sheet resistance of 19.49 Ω, a tensile strength of 1.13 kN / m, and a paper weight of 4.53 g. It can be heated to 250℃ at 12V with a heating rate of 2.27℃ / s, exhibiting high electrothermal performance under low voltage. (Reference) Figure 9 The surface temperature of carbon fiber paper containing 0.5g of carbon black increases with increasing voltage. At 4V, the surface temperature can reach 40℃; at 8V, it can reach 140℃; and at 12V, it can reach 250℃.

[0072] Figure 10 and Figure 11 The temperature curve over time shows three processes: heating up, stable heating up, and power-off / power-off cooling. It can be seen that the heating performance or saturation temperature of carbon fiber paper can be adjusted by controlling the carbon black content and the power supply voltage.

[0073] Figure 12 The XRD patterns of carbon fiber paper containing 0.3g and 0.5g of carbon black are shown. The XRD patterns show relatively sharp peaks, indicating that the microstructure of carbon fibers in the samples is more regular. As can be seen from the figure, the carbon fibers have a broad peak at 2θ=26.25° and 26.18°, which corresponds to the graphite (002) crystal plane, indicating that carbon atoms are connected to each other in a sp² hybridization manner.

[0074] Figure 7 , 8 The images shown are SEM magnifications of the cross-section and surface of the carbon fiber paper obtained in Examples 1 and 2, respectively, showing that the carbon fibers are uniformly wound and connected.

[0075] Example 3

[0076] Step 1: Weigh 0.2600g of aramid pulp with a freeness of 45°SR and a specific surface area of ​​9m² / g, weigh 3.6400g of aramid precipitate with a freeness of 42°SR and a moisture content of 70%, weigh 0.30g of conductive carbon black with a conductivity of 0.20S·cm-1, weigh 0.3700g of carbon fiber with a fiber length of 3mm and a fiber diameter of 6μm, and add them sequentially to the dewatering tank. Obtain the mixed pulp system A by dewatering treatment at 30000 rpm, then add 2.0L of dilution water, perform 8 rounds of turbulent homogenization, and 20 seconds of negative pressure dewatering on an 80-mesh forming wire to form the surface wet paper web B.

[0077] Weigh 0.8700g of carbon fiber with a fiber length of 7mm and a diameter of 6microns, weigh 2.1800g of aramid precipitate with a freeness of 45°SR and a moisture content of 85%, and mix it with 10.00mL of PEO dispersion with a concentration of 10g / L. Obtain mixed pulp C by passing it through a disintegration process at 30000rpm. Then add 2.0L of dilution water, perform 8 cycles of turbulent homogenization, and 20 seconds of negative pressure dewatering treatment on an 80-mesh forming wire to form the surface wet paper web D.

[0078] Step 2: Transfer the intermediate wet paper web D to the middle of the two surface wet paper webs B, stack them together, and pad them with absorbent felt on the top and bottom. Use a cold press with a pressing pressure of 8.5 MPa to dehydrate for 5 minutes to obtain paper web E.

[0079] Step 3: The paper web E is vacuum dried for 10 minutes in the drying section of a paper forming machine at a temperature of 105℃ and a vacuum degree of 0.7MPa; after hot pressing and bonding for 15 minutes in a flat vulcanizing machine at a temperature of 180℃ and a pressure of 12MPa, a layered structure pitch-based carbon fiber skeleton electrothermal base paper F is obtained.

[0080] In this embodiment, the layered pitch-based carbon fiber skeleton electrothermal paper has a basis weight of 40 g / m³. 2 It has a thickness of 0.138mm, a sheet resistance of 20.11Ω, a tensile strength of 1.03kN / m, a paper weight of 4.30g, and can be heated to 187℃ at 12V with a heating rate of 1.98℃ / s, possessing high electrothermal function under low voltage.

[0081] Example 4

[0082] Step 1: Weigh 0.2650g of aramid pulp with a freeness of 46°SR and a specific surface area of ​​10m² / g, weigh 3.6452g of aramid precipitate with a freeness of 43°SR and a moisture content of 80%, weigh 0.40g of conductive carbon black with a conductivity of 0.40S·cm-1, weigh 0.3754g of carbon fiber with a fiber length of 3.5mm and a fiber diameter of 8μm, and add them sequentially to the dewatering tank. Obtain the mixed pulp system A by dewatering treatment at 30000 rpm, then add 2.5L of dilution water, perform 9 rounds of turbulent homogenization, and 22 seconds of negative pressure dewatering on a 90-mesh forming wire to form the surface wet paper web B.

[0083] Weigh 0.8751g of carbon fiber with a length of 7.5mm and a diameter of 8μm, weigh 2.1853g of aramid precipitate with a freeness of 48°SR and a moisture content of 89%, and mix it with 10.50mL of PEO dispersion with a concentration of 13g / L. Obtain mixed pulp C by passing it through a disintegration process at 30000rpm. Then add 2.5L of dilution water, perform 9 cycles of turbulent homogenization, and perform negative pressure dewatering treatment on a 90-mesh forming wire for 23 seconds to form the surface wet paper web D.

[0084] Step 2: Transfer the intermediate wet paper web D to the middle of the two surface wet paper webs B, stack them together, and pad them with absorbent felt on the top and bottom. Use a cold press with a pressing pressure of 9.0 MPa to dehydrate for 8 minutes to obtain paper web E.

[0085] Step 3: The paper web E is vacuum dried for 12 minutes in the drying section of a paper forming machine at a temperature of 110℃ and a vacuum degree of 0.8MPa; after hot pressing and bonding in a flat vulcanizing machine at a temperature of 190℃ and a pressure of 13MPa for 18 minutes, a layered structure asphalt-based carbon fiber skeleton electrothermal base paper F is obtained.

[0086] The layered pitch-based carbon fiber skeleton electrothermal paper obtained in this embodiment has a basis weight of 40 g / m³. 2 It has a thickness of 0.152mm, a sheet resistance of 19.24Ω, a tensile strength of 1.15kN / m, a paper weight of 4.46g, and can be heated to 249℃ at 12V with a heating rate of 2.25℃ / s. It also has high electrothermal function under low voltage.

[0087] Example 5

[0088] Step 1: Weigh 0.2700g of aramid pulp with a freeness of 48°SR and a specific surface area of ​​11m² / g, weigh 3.6500g of aramid precipitate with a freeness of 45°SR and a moisture content of 85%, weigh 0.50g of conductive carbon black with a conductivity of 0.50S·cm-1, weigh 0.3800g of carbon fiber with a fiber length of 4mm and a fiber diameter of 10μm, and add them sequentially to the dewatering tank. Obtain the mixed system pulp A through dewatering treatment at 30000 rpm, then add 3.0L of dilution water, perform 10 cycles of turbulent homogenization, and 25 seconds of negative pressure dewatering on a 100-mesh forming wire to form the surface wet paper web B.

[0089] Weigh 0.8800g of carbon fiber with a fiber length of 8mm and a diameter of 10μm, weigh 2.1900g of aramid precipitate with a freeness of 50°SR and a water content of 92%, and mix it with 11.00mL of PEO dispersion with a concentration of 15g / L. Obtain mixed pulp C by passing it through a disintegration process at 30000rpm. Then add 3.0L of dilution water, perform 10 cycles of turbulent homogenization, and perform negative pressure dewatering treatment on a 100-mesh forming wire for 25 seconds to form the surface wet paper web D.

[0090] Step 2: Transfer the intermediate wet paper web D to the middle of the two surface wet paper webs B, stack them together, and pad them with absorbent felt on the top and bottom. Use a cold press with a pressing pressure of 10.5 MPa to dehydrate for 10 minutes to obtain paper web E.

[0091] Step 3: The paper web E is vacuum dried for 15 minutes in the drying section of a paper forming machine at a temperature of 110℃ and a vacuum degree of 0.9MPa; after hot pressing and bonding for 20 minutes in a flat vulcanizing machine at a temperature of 200℃ and a pressure of 15MPa, a layered structure pitch-based carbon fiber skeleton electrothermal base paper F is obtained.

[0092] The layered structure pitch-based carbon fiber skeleton electrothermal paper obtained in this embodiment has a basis weight of 40 g / m2, a thickness of 0.181 mm, a sheet resistance of 17.43 Ω, a tensile strength of 1.18 kN / m, and a paper weight of 4.61 g. It can be heated to 282°C at 12V and the heating rate is 2.35°C / s, demonstrating high electrothermal function under low voltage.

[0093] Table 1. Technical parameters of the hierarchical pitch-based carbon fiber skeleton electrothermal base paper prepared from the implementation case.

[0094]

[0095] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A process for preparing a layered structure pitch-based carbon fiber skeleton electrothermal base paper, characterized in that, Includes the following steps: S1, Preparation of surface paper web: Weigh aramid pulp, aramid precipitate, conductive carbon black, carbon fiber and PEO dispersion, mix and then dissolve to obtain mixed system pulp A. Then, through pulp dilution, turbulent homogenization and negative pressure dewatering, surface wet paper web B is formed. When preparing the surface paper web, the aramid pulp is para-aramid fiber with a freeness of (45-48)°SR and a specific surface area of ​​(9-11)m². 2 / g, the total dry weight is (0.26~0.27)g; Aramid precipitation is a differentiated product of meta-aramid fiber, with a freeness of (42-45)°SR, a moisture content of (70-85)%, and a total dry weight of (3.64-3.65)g; The carbon fiber is pitch-based carbon fiber with a fiber length of (3–4) mm, a fiber diameter of (6–10) μm, and a total dry weight of (0.37–0.38) g; the conductive carbon black has a mass of (0.30–0.50) g ​​and an electrical conductivity of (0.20–0.50) S·cm. -1 ; Preparation of intermediate layer paper web: Weigh carbon fiber, aramid precipitate and PEO dispersion, mix and dissolve to obtain mixed slurry C, then dilute and add water, turbulent homogenize and dewater under negative pressure to form carbon fiber intermediate layer wet paper web D; When preparing the intermediate layer paper web, the carbon fiber is pitch-based carbon fiber with a fiber length of (7-8) mm, a fiber diameter of (6-10) micrometers, and a total dry weight of (0.87-0.88) g. Aramid precipitation is a differentiated product of meta-aramid fiber, with a freeness of (45-50)°SR, a moisture content of (85-92)%, and a total dry weight of (2.18-2.19) g; S2, the intermediate wet paper web D and the surface wet paper web B are stacked together, and then cold-pressed to dewater to obtain the layered paper web E; during cold-pressing, absorbent felt pads are used on both the top and bottom of the stacked wet paper webs, the pressing pressure is (8.5~10.5) MPa, and the time is (5~10) min. S3, the layered paper web E is subjected to vacuum drying and hot pressing bonding treatment to obtain the layered asphalt-based carbon fiber skeleton electrothermal base paper F; during the hot pressing bonding treatment, the temperature is (180~200)℃, the pressure is (12~15)MPa, and the time is (15~20)min.

2. The preparation process of a layered structure pitch-based carbon fiber skeleton electrothermal base paper according to claim 1, characterized in that, In S1, when preparing the surface paper web, the concentration of the PEO dispersion is (10-15) g / L, and the volume is (10.00-11.00) mL.

3. The process for preparing a layered structure pitch-based carbon fiber skeleton electrothermal base paper according to claim 1, characterized in that, In S1, the unwinding speed during the preparation of the surface paper web is 25,000 to 30,000 rpm; The amount of water added for dilution is (2.0~3.0) L; The turbulent homogenization was repeated (8-10) times. Vacuum pumping is performed using an 80-100 mesh forming net, with a vacuum degree of 0.080-0.098 MPa and a pumping time of 20-25 seconds.

4. The preparation process of the layered structure pitch-based carbon fiber skeleton electrothermal base paper according to claim 1, characterized in that, In S1, when preparing the intermediate layer paper web, the concentration of the PEO dispersion is (10-15) g / L, and the volume is (10.00-11.00) mL.

5. The process for preparing a layered structure pitch-based carbon fiber skeleton electrothermal base paper according to claim 1, characterized in that, In S1, when preparing the intermediate layer paper web, the unwinding speed is 25,000~30,000 rpm; The amount of water added for dilution is (2.0~3.0) L; The turbulent homogenization was repeated (8-10) times. Vacuum pumping is performed using an 80-100 mesh forming net, with a vacuum degree of 0.080-0.098 MPa and a pumping time of 20-25 seconds.

6. The preparation process of a layered structure pitch-based carbon fiber skeleton electrothermal base paper according to claim 1, characterized in that, In S2, during the stacking process, the middle layer wet paper web D is transferred to the middle of the two surface layer wet paper webs B.

7. The preparation process of a layered structure pitch-based carbon fiber skeleton electrothermal base paper according to claim 1, characterized in that, In S3, during vacuum drying, the temperature is (105~120)℃, the vacuum degree is (0.7~0.9)MPa, and the time is (10~15)min.

8. A product obtained by the preparation process of layered structure pitch-based carbon fiber skeleton electrothermal base paper according to any one of claims 1 to 7.

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