Aramid paper as well as preparation method and application thereof

Abstract

The invention provides aramid paper as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) coating two surfaces of an aramid woven fabric with an aramid polymer coating liquid, solidifying, washing with water, and drying to obtain aramid base paper; and (2) carrying out hot pressing on the aramid base paper prepared in the step (1) at 270-350 DEG C to obtain the aramid paper, the solid content of the aramid fiber high polymer coating liquid is 10%-17%. The aramid paper provided by the invention is flat, smooth and glossy, has the same appearance as the aramid paper prepared by the traditional method, but has higher breaking strength and elongation at break, small difference between longitudinal breaking strength and transverse breaking strength, and higher dielectric strength.

Description

Technical Field

[0001] The invention belongs to the technical field of aramid materials, and in particular relates to aramid paper and a preparation method and application thereof. Background Art

[0002] Aramid paper has high temperature resistance, good insulation, excellent mechanical strength and electrical properties, and is successfully used in electrical equipment such as motors, transformers, capacitors, etc. Honeycomb core structural materials made of aramid paper have the characteristics of light weight, impact resistance, high strength, and aging resistance. They are mainly used in aircraft, missiles, satellite broadband wave-transmitting materials or high-rigidity secondary load-bearing structural components (wings, flow cover cabin linings, aircraft doors, floors, cargo holds and partitions), etc., and have very broad market prospects.

[0003] With the continuous development of the application of meta-aramid paper, the requirements for the preparation technology of aramid paper are getting higher and higher. At present, the preparation technology of aramid paper is to use aramid short fibers and aramid pulp as the main raw materials, and make traditional aramid paper through pulping, flow conveying, papermaking, pressing, drying, hot pressing, slitting and other processes. CN1932148A discloses an aramid paper using para-aramid short fibers as raw materials and a preparation method thereof. The aramid paper using para-aramid short fibers as raw materials contains the following components, by weight percentage, para-aramid short fibers 10% to 90%, meta-aramid fibrids 10% to 90%, polyester short fibers 0 to 60%, and mica 0 to 50%. The technical solution uses para-aramid short fibers, meta-aramid fibrids, polyester short fibers and mica as raw materials to make aramid paper through traditional processes.

[0004] CN107022929A discloses a method for manufacturing high-performance para-aramid insulating paper for circuit boards, the method comprising the following steps: (1) shearing of aramid fibers: shearing the para-aramid fibers into short fibers; (2) preparing a pretreatment solution: diluting ammonia water into a solution with a mass fraction of 5% to 50% to obtain a pretreatment solution for standby use; (3) pretreatment process: maintaining the pretreatment solution prepared in step (2) at a temperature of 25 to 100° C. to pretreat the aramid fibers, the pretreatment process comprising soaking and stirring, the soaking time being 10 to 90 minutes, and obtaining pretreated aramid fibers or pulp; (4) introduction of fiber surface active groups: drying the pretreated aramid fibers or pulp obtained in step (3), and then modifying the pretreated aramid fibers or pulp with a coupling agent; (5) papermaking process: the aramid fiber or pulp treated in step (4) is washed to remove excess coupling agent, and a dispersant is added to the aramid fiber or pulp to obtain a dispersant loading amount of 0.5% to 10% of the volume of the fiber suspension. The aramid fiber or pulp is subjected to a debonding process at 3,000 to 100,000 revolutions and is formed into paper using an automatic papermaking machine. (6) paper drying: the aramid paper obtained in step (5) is dried under vacuum conditions for 15 to 60 minutes. (7) high pressure process: the aramid paper obtained in step (6) is subjected to a high pressure light treatment for 15 to 60 minutes to obtain a highly dense fiber structure and a smooth and bright aramid paper surface.

[0005] However, the aramid paper production process in the prior art is complicated and has high production costs. Aramid is a linear polymer compound with a flat chain structure of main chain molecules. Although the aramid chain has extremely high toughness and molecular interlacing, the side groups of aramid are often large and bulky, which leads to weak interactions between aramid molecules. Therefore, when aramid paper is made by traditional processes, it is difficult for aramid fibers to form a relatively tight network structure, resulting in low breaking strength of aramid paper. Moreover, the difference between the transverse breaking strength and the longitudinal breaking strength of traditional aramid paper is too large, and the longitudinal breaking strength is about two to three times the transverse breaking strength; the dielectric strength is low, averaging about 10 kV / mm, and the elongation at break performance of aramid paper still needs to be further improved.

[0006] Therefore, it is necessary to develop an aramid paper with high breaking strength and high breaking elongation. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention aims to provide an aramid paper and a preparation method and application thereof. The preparation method of the aramid paper has a simple process flow, is easy to operate and control, and the aramid paper prepared has high breaking strength and breaking elongation, a small difference between longitudinal breaking strength and transverse breaking strength, and high dielectric strength.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing aramid paper, the preparation method comprising the following steps:

[0010] (1) coating aramid polymer coating liquid on both sides of aramid woven fabric, wherein the solid content of the aramid polymer coating liquid is 10% to 17% (e.g., 11%, 12%, 13%, 14%, 15% or 16%), and coagulating, washing and drying the aramid base paper;

[0011] (2) hot pressing the aramid base paper obtained in step (1) at 270-350° C. (e.g., 280° C., 290° C., 300° C., 310° C., 320° C., 330° C., or 340° C.) to obtain the aramid paper.

[0012] In the present invention, aramid paper is prepared by coating aramid polymer coating liquid on both sides of aramid woven fabric, and then solidifying, washing, drying and hot pressing. The preparation method has a simple process flow and is easy to operate and regulate. The prepared aramid paper is flat, smooth and glossy, and has the same appearance as the aramid paper prepared by the traditional method. It has high breaking strength and breaking elongation, a small difference between the longitudinal breaking strength and the transverse breaking strength, and higher dielectric strength.

[0013] Preferably, the aramid polymer coating liquid is prepared by mixing an aramid polymer stock solution and a solvent.

[0014] Preferably, the mixing is performed under the protection of dry nitrogen.

[0015] Preferably, the solid content of the aramid polymer stock solution is 20% to 25%, for example, 20.5%, 21%, 21.5%, 22%, 22.5%, 23%, 23.5%, 24% or 24.5%.

[0016] Preferably, the intrinsic viscosity of the aramid polymer in the aramid polymer stock solution is 1.3-1.9 dL / g, for example, 1.4 dL / g, 1.5 dL / g, 1.6 dL / g, 1.7 dL / g or 1.8 dL / g.

[0017] Preferably, the aramid polymer stock solution includes a meta-aramid polymer stock solution and / or a para-aramid polymer stock solution.

[0018] Preferably, the solvent is the same as the solvent in the aramid polymer stock solution.

[0019] Preferably, the solvent comprises an amide solvent.

[0020] Preferably, the amide solvent includes any one of N,N-dimethylacetamide (DMAC), N-methylpyrrolidone or N-acetylpyrrolidone, or a combination of at least two thereof.

[0021] Preferably, the water content of the solvent is ≤120 ppm, for example, 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm or 110 ppm.

[0022] Preferably, the temperature of the aramid polymer coating liquid is 10-50°C, for example, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C or 45°C.

[0023] Preferably, the aramid woven fabric is made by weaving aramid filament bundles.

[0024] Preferably, the weaving is performed by weaving on a loom.

[0025] Preferably, the aramid filament bundle comprises a meta-aramid filament bundle and / or a para-aramid filament bundle.

[0026] It should be noted that the type of aramid polymer used in the aramid filament bundle and the type of aramid polymer in the aramid high polymer coating liquid may be the same or different.

[0027] Preferably, the fineness of the aramid filament bundle is in the range of 10 to 114D, for example, 20D, 30D, 40D, 50D, 60D, 70D, 80D, 90D, 100D or 110D.

[0028] In the present invention, the fineness of the aramid filament bundle affects the thickness of the aramid woven fabric.

[0029] Preferably, the fineness of the aramid filament monofilament in the aramid filament bundle is 1D to 3D, for example, 1.5D.

[0030] Preferably, the coating has a thickness of 2 to 12 μm, for example, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm or 11 μm.

[0031] It should be noted that the coating thickness in the present invention refers to the coating thickness of the aramid polymer coating liquid coated on one side of the aramid woven fabric.

[0032] Preferably, the coagulation is performed in a coagulation bath.

[0033] Preferably, the temperature of the coagulation bath is 10-50°C, such as 15°C, 20°C, 25°C, 30°C, 35°C, 40°C or 45°C.

[0034] Preferably, the coagulation bath comprises an amide solvent and water, and the amide solvent in the coagulation bath and the solvent in the aramid polymer coating liquid are of the same substance.

[0035] Preferably, the mass percentage concentration of the amide solvent in the coagulation bath is 30% to 70%, for example, 35%, 40%, 45%, 50%, 55%, 60% or 65%.

[0036] Preferably, the coagulation bath after coagulation is sent to a solvent recovery system for solvent recovery.

[0037] Preferably, part of the solvent of the aramid polymer coating liquid comes from the solvent recovered by sending the coagulation bath into the solvent recovery system.

[0038] Preferably, the water washing includes a first water washing and a second water washing.

[0039] Preferably, the temperature of the first water washing is 20-60°C, for example, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C or 55°C.

[0040] Preferably, the temperature of the second water washing is 60-100°C, for example, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C or 95°C.

[0041] Preferably, the water washing is reverse energy-saving water washing, the first water washing is performed by using the washing water obtained from the second water washing, and the second water washing is performed by using desalted water.

[0042] Preferably, the conductivity of the desalted water is less than 10 μs / cm (e.g., 2 μs / cm, 3 μs / cm, 4 μs / cm, 5 μs / cm, 6 μs / cm, 7 μs / cm, 8 μs / cm or 9 μs / cm, etc.), and the concentration of Fe element is less than or equal to 50 μg / L (5 μg / L, 10 μg / L, 15 μg / L, 20 μg / L, 25 μg / L, 30 μg / L, 35 μg / L, 40 μg / L or 45 μg / L). / L, etc.), hardness ≤2μmol / L (for example, 0.2μmol / L, 0.4μmol / L, 0.6μmol / L, 0.8μmol / L, 1.0μmol / L, 1.2μmol / L, 1.4μmol / L, 1.6μmol / L or 1.8μmol / L, etc.), pH is 7-8 (for example, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8 or 7.9, etc.).

[0043] It should be noted that the hardness of the desalted water in the present invention is measured in terms of the molar concentration of CaCO3. The coagulation bath can be prepared by directly mixing an amide solvent with water, or by adding an amide solvent to the washing water obtained by the first water washing to prepare a coagulation bath of the desired mass percentage concentration.

[0044] Preferably, the drying temperature is 110-160°C, for example, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C or 155°C.

[0045] Preferably, the linear pressure of the hot pressing is 50-200 kg / cm, for example, 70 kg / cm, 90 kg / cm, 110 kg / cm, 130 kg / cm, 150 kg / cm, 170 kg / cm or 190 kg / cm.

[0046] In a second aspect, the present invention provides an aramid paper, wherein the aramid paper is prepared by the preparation method described in the first aspect.

[0047] In a third aspect, the present invention provides a use of the aramid paper as described in the second aspect in a honeycomb core structural material.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The invention prepares aramid paper by coating aramid polymer coating liquid on both sides of aramid woven fabric, solidifying, washing, drying and hot pressing. The preparation method has simple process flow, easy operation and regulation, and the prepared aramid paper is flat, smooth and glossy, and has the same appearance as the aramid paper prepared by the traditional method, high breaking strength and breaking elongation, small difference between longitudinal breaking strength and transverse breaking strength, and higher dielectric strength. The transverse breaking strength is 10 to 100 times that of the aramid paper prepared by the traditional method, the transverse breaking elongation is 3 to 6 times that of the aramid paper prepared by the traditional method, the longitudinal breaking strength is 10 to 40 times that of the aramid paper prepared by the traditional method, the longitudinal breaking elongation is 3 to 6 times that of the aramid paper prepared by the traditional method, and the dielectric strength is 20% to 50% higher than that of the aramid paper prepared by the traditional method. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 The present invention provides a schematic flow chart of the method for preparing aramid paper. DETAILED DESCRIPTION

[0051] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0052] Example 1

[0053] This embodiment provides an aramid paper and a preparation method thereof. The preparation method of the aramid paper is as follows: Figure 1 As shown, the following steps are included:

[0054] Preparation of aramid polymer coating liquid: Under the protection of dry nitrogen, a meta-aramid polymer stock solution (the meta-aramid polymer stock solution consists of DMAC and meta-aramid polymer, with a solid content of 21%, wherein the intrinsic viscosity of the meta-aramid polymer is 1.35 dL / g) and a solvent (DMAC) are mixed at room temperature, stirred evenly, and the temperature is controlled at 20° C. to obtain an aramid polymer coating liquid, wherein the solid content of the aramid polymer coating liquid is 11%.

[0055] Preparation of aramid woven fabric: 75D meta-aramid filament bundles (single filament fineness is 1.5D) are woven through a loom to obtain aramid woven fabric.

[0056] (1) The aramid woven fabric is coated on both sides with the aramid polymer coating liquid by a coating device, and the coating thickness on one side is 9 μm. The fabric is then coagulated and formed by the coagulation bath. The temperature of the coagulation bath is controlled to be 20° C. The fabric is then washed with water to remove the solvent. The washing process is reverse energy-saving washing. The first washing is performed by washing water obtained by the second washing. The second washing is performed by washing with desalted water (with a conductivity of 8 μs / cm, a concentration of Fe element of 45 μg / L, a hardness of 1 μmol / L, and a pH of 7). The temperature of the first washing is 60° C., and the temperature of the second washing is 90° C. The fabric is finally dried. The surface temperature of the drying roller is 150° C. to obtain aramid base paper.

[0057] The coagulation bath comprises desalted water and DMAC, and the mass percentage concentration of DMAC in the coagulation bath is 65%.

[0058] The solidification bath after solidification is sent to the solvent recovery system for solvent recovery.

[0059] (2) hot pressing the aramid base paper obtained in step (1), wherein the surface temperature of the hot pressing roller used in the hot pressing is 330° C. and the line pressure is 180 kg / cm, to obtain the aramid paper.

[0060] Example 2

[0061] This embodiment provides an aramid paper and a preparation method thereof, wherein the preparation method of the aramid paper comprises the following steps:

[0062] Preparation of aramid polymer coating liquid: Under the protection of dry nitrogen, a meta-aramid polymer stock solution (the meta-aramid polymer stock solution consists of DMAC and meta-aramid polymer, with a solid content of 21%, wherein the intrinsic viscosity of the meta-aramid polymer is 1.45 dL / g) and a solvent (DMAC) are mixed at room temperature, stirred evenly, and the temperature is controlled at 25° C. to obtain an aramid polymer coating liquid, wherein the solid content of the aramid polymer coating liquid is 13%.

[0063] Preparation of aramid woven fabric: 57D para-aramid filament bundle (single filament fineness is 1.5D) is woven through a loom to obtain aramid woven fabric.

[0064] (1) The aramid woven fabric is coated on both sides with the aramid polymer coating liquid by a coating device, and the coating thickness on one side is 7 μm. The fabric is then coagulated and formed by the coagulation bath. The temperature of the coagulation bath is controlled to be 25° C. The fabric is then washed with water to remove the solvent. The washing process is reverse energy-saving washing. The first washing is performed by washing water obtained by the second washing. The second washing is performed by washing with desalted water (with a conductivity of 6 μs / cm, a concentration of Fe element of 40 μg / L, a hardness of 2 μmol / L, and a pH of 8). The temperature of the first washing is 50° C., and the temperature of the second washing is 80° C. The fabric is finally dried. The surface temperature of the drying roller is 140° C. to obtain aramid base paper.

[0065] The coagulation bath comprises desalted water and DMAC, and the mass percentage concentration of DMAC in the coagulation bath is 55%.

[0066] The solidification bath after solidification is sent to the solvent recovery system for solvent recovery.

[0067] (2) The aramid base paper obtained in step (1) is subjected to hot pressing, wherein the surface temperature of the hot pressing roller used for hot pressing is 320° C. and the line pressure is 160 kg / cm, to obtain the aramid paper.

[0068] Example 3

[0069] This embodiment provides an aramid paper and a preparation method thereof, wherein the preparation method of the aramid paper comprises the following steps:

[0070] Preparation of aramid polymer coating liquid: Under the protection of dry nitrogen, a meta-aramid polymer stock solution (the meta-aramid polymer stock solution consists of DMAC and meta-aramid polymer, with a solid content of 21%, wherein the intrinsic viscosity of the meta-aramid polymer is 1.6 dL / g) and a solvent (DMAC) are mixed at room temperature, stirred evenly, and the temperature is controlled at 35° C. to obtain an aramid polymer coating liquid, wherein the solid content of the aramid polymer coating liquid is 15%.

[0071] Preparation of aramid woven fabric: 45D meta-aramid filament bundles (single filament fineness is 1.5D) are woven through a loom to obtain aramid woven fabric.

[0072] (1) The aramid woven fabric is coated on both sides with the aramid polymer coating liquid by a coating device, and the coating thickness on one side is 5 μm. The fabric is then coagulated and formed by the coagulation bath. The temperature of the coagulation bath is controlled to be 35° C. The fabric is then washed with water to remove the solvent. The washing process is reverse energy-saving washing. The first washing is performed by washing water obtained by the second washing. The second washing is performed by washing with desalted water (with a conductivity of 8 μs / cm, a concentration of Fe element of 45 μg / L, a hardness of 1 μmol / L, and a pH of 7). The temperature of the first washing is 40° C., and the temperature of the second washing is 70° C. The fabric is finally dried. The surface temperature of the drying roller is 130° C. to obtain aramid base paper.

[0073] The coagulation bath comprises desalted water and DMAC, and the mass percentage concentration of DMAC in the coagulation bath is 45%.

[0074] The solidification bath after solidification is sent to the solvent recovery system for solvent recovery.

[0075] (2) The aramid base paper obtained in step (1) is subjected to hot pressing, wherein the surface temperature of the hot pressing roller used for hot pressing is 300° C. and the line pressure is 110 kg / cm, to obtain the aramid paper.

[0076] Example 4

[0077] This embodiment provides an aramid paper and a preparation method thereof, wherein the preparation method of the aramid paper comprises the following steps:

[0078] Preparation of aramid polymer coating liquid: Under the protection of dry nitrogen, a meta-aramid polymer stock solution (the meta-aramid polymer stock solution consists of DMAC and meta-aramid polymer, with a solid content of 21%, wherein the intrinsic viscosity of the meta-aramid polymer is 1.8 dL / g) and a solvent (DMAC) are mixed at room temperature, stirred evenly, and the temperature is controlled at 45° C. to obtain an aramid polymer coating liquid, wherein the solid content of the aramid polymer coating liquid is 16%.

[0079] Preparation of aramid woven fabric: 27D para-aramid filament bundles (single filament fineness is 1.5D) are woven through a loom to obtain aramid woven fabric.

[0080] (1) The aramid woven fabric is coated with the aramid polymer coating liquid on both sides through a coating device, and the coating thickness on one side is 3 μm. The fabric is then coagulated and formed in the coagulation bath. The temperature of the coagulation bath is controlled to be 45° C. The fabric is then washed with water to remove the solvent. The washing process is a reverse energy-saving washing process. The first washing process is washing with the washing water obtained from the second washing process. The second washing process is washing with desalted water (with a conductivity of 8 μs / cm, a concentration of Fe element of 45 μg / L, a hardness of 1 μmol / L, and a pH of 7). The temperature of the first washing process is 30° C., and the temperature of the second washing process is 65° C. The fabric is finally dried. The surface temperature of the drying roller is 120° C. to obtain aramid base paper.

[0081] The coagulation bath comprises desalted water and DMAC, and the mass percentage concentration of DMAC in the coagulation bath is 35%.

[0082] The solidification bath after solidification is sent to the solvent recovery system for solvent recovery.

[0083] (2) hot pressing the aramid base paper obtained in step (1), wherein the surface temperature of the hot pressing roller used in the hot pressing is 290° C. and the line pressure is 80 kg / cm, to obtain the aramid paper.

[0084] Example 5

[0085] This embodiment provides an aramid paper and a preparation method thereof, which is different from Embodiment 1 only in that the coating thickness on one side in step (1) is adjusted to 12 μm, and other conditions are the same as those in Embodiment 1.

[0086] Example 6

[0087] This embodiment provides an aramid paper and a preparation method thereof, which differs from Embodiment 1 only in that, in the preparation of the aramid woven fabric, the 75D meta-aramid filament bundle (the fineness of the single filament is 1.5D) is replaced by a 75D para-aramid filament bundle (the fineness of the single filament is 1.5D), and other conditions are the same as those in Embodiment 1.

[0088] Comparative Example 1

[0089] This comparative example provides an aramid paper and a preparation method thereof, which differs from Example 1 only in that the amount of solvent added during the preparation of the aramid polymer coating liquid is adjusted so that the solid content of the aramid polymer coating liquid is 5%, and other conditions are the same as those of Example 1.

[0090] Comparative Example 2

[0091] This comparative example provides an aramid paper and a preparation method thereof, which differs from Example 1 only in that the amount of solvent added during the preparation of the aramid polymer coating liquid is adjusted so that the solid content of the aramid polymer coating liquid is 20%, and other conditions are the same as those of Example 1.

[0092] Comparative Example 3

[0093] This comparative example provides an aramid paper and a preparation method thereof, which differs from Example 1 only in that the surface temperature of the hot pressing roller used in the hot pressing in step (2) is adjusted to 210° C., and other conditions are the same as those in Example 1.

[0094] Comparative Example 4

[0095] This comparative example provides an aramid paper and a preparation method thereof, which differs from Example 1 only in that the surface temperature of the hot pressing roller used in the hot pressing in step (2) is adjusted to 370° C., and other conditions are the same as those in Example 1.

[0096] Comparative Example 5

[0097] The comparative example provides an aramid paper and a preparation method thereof. The raw materials for preparing the aramid paper are meta-aramid short fibers and meta-aramid fibrids. The preparation method of the aramid paper comprises the following steps: passing the meta-aramid short fibers and the meta-aramid fibrids through a hydraulic pulper respectively, uniformly mixing them with desalted water, and after pulping and deslagging, mixing the meta-aramid short fibers and the meta-aramid fibrids in a mass ratio of 1:1 to prepare pulp with a concentration of 1%; then forming the pulp through an inclined wire paper machine, and then pressing, drying and hot pressing, the drying temperature is 150°C, the hot pressing temperature is 330°C, and the hot pressing roller line pressure is 180kg / cm, to prepare aramid paper with a thickness of 0.511mm.

[0098] Comparative Example 6

[0099] This comparative example provides an aramid paper and a preparation method thereof, which differs from comparative example 5 only in that the drying temperature is 140°C, the hot pressing temperature is 320°C, the hot pressing roller line pressure is 160kg / cm, and the aramid paper with a thickness of 0.382mm is prepared. Other conditions are the same as those in comparative example 5.

[0100] Comparative Example 7

[0101] This comparative example provides an aramid paper and a preparation method thereof, which differs from comparative example 5 only in that the drying temperature is 130°C, the hot pressing temperature is 300°C, the hot pressing roller line pressure is 110kg / cm, and the prepared thickness is 0.303mm. Other conditions are the same as those of comparative example 5.

[0102] Comparative Example 8

[0103] This comparative example provides an aramid paper and a preparation method thereof, which differs from comparative example 5 only in that the drying temperature is 120°C, the hot pressing temperature is 290°C, the hot pressing roller line pressure is 80kg / cm, and the prepared thickness is 0.185mm. Other conditions are the same as those of comparative example 5.

[0104] The aramid papers provided in the above-mentioned Examples 1 to 6 and Comparative Examples 1 to 8 were tested, and the specific testing method is as follows:

[0105] Breaking strength and elongation at break: tested in accordance with GB / T12914-2018.

[0106] Dielectric strength: Tested in accordance with GB / T 1408.1-2016.

[0107] The test results are shown in Tables 1 and 2 below:

[0108] Table 1

[0109]

[0110]

[0111] In Table 1, “ / ” means that the test was not conducted.

[0112] Table 2

[0113]

[0114] It can be seen from the contents of Table 1 that the aramid paper provided in Examples 1 to 6 is light yellow, smooth and glossy, has a transverse breaking strength of 332 to 1913 kN / m, a transverse breaking elongation of 33.7% to 42.8%, a longitudinal breaking strength of 334 to 1918 kN / m, a longitudinal breaking elongation of 34.1% to 43.2%, and a dielectric strength of 11.7 to 13.6 kV / mm.

[0115] Compared with Example 1, if the solid content of the aramid polymer coating liquid is too low (Comparative Example 1), but after the coagulation bath in step (1) is solidified, the aramid polymer coating liquid cannot be solidified and formed; the reason is that the solid content of the aramid polymer coating liquid is too low, and the solvent in the aramid polymer coating liquid cannot be precipitated in time. If step (2) is continued to be hot-pressed, the appearance of the aramid paper prepared is uneven, with pinholes of different sizes, the aramid woven fabric at the pinholes is exposed, and the aramid polymer cannot fully cover the aramid woven fabric.

[0116] Compared with Example 1, if the solid content of the aramid polymer coating liquid is too high (Comparative Example 2), the aramid polymer coating liquid cannot be evenly coated when the aramid woven fabric is coated on both sides in step (1). The reason is that the solid content of the aramid polymer coating liquid is too high, resulting in too high viscosity of the aramid polymer coating liquid. The excessively high viscosity causes the aramid polymer coating liquid to be unable to be evenly coated. If step (2) is continued with hot pressing, the appearance of the prepared aramid paper is uneven, and the woven fabric has an irregular shape.

[0117] Compared with Example 1, if the surface temperature of the hot pressing roller used in hot pressing is adjusted too low (Comparative Example 3), then after the hot pressing in step (2), the solidified aramid polymer coating layer cannot complete plasticization and crystallization, and the aramid polymer coating layer and the aramid woven fabric cannot be tightly combined; the reason is that the glass transition temperature of the aramid polymer is 270°C, and only when the surface temperature of the hot pressing roller is ≥270°C, the aramid polymer coating layer can complete plasticization and crystallization. The appearance of the prepared aramid paper is smooth but dull, which is different from the appearance of the aramid paper prepared by the traditional method.

[0118] Compared with Example 1, if the surface temperature of the hot pressing roller used in hot pressing is adjusted too high (Comparative Example 4), during the hot pressing in step (2), the solidified aramid polymer coating layer is plasticized and sticks to the hot pressing roller, and the aramid polymer coating layer is peeled off from the aramid woven fabric; the reason is that the surface temperature of the hot pressing roller is too high, causing the aramid polymer coating layer to be over-plasticized and then peeled off from the aramid woven fabric.

[0119] Compared with the aramid paper prepared by the traditional method (Comparative Examples 5 to 8), the aramid paper provided by Examples 1 to 6 at the same thickness has higher transverse breaking strength, transverse breaking elongation, longitudinal breaking strength, longitudinal breaking elongation and dielectric strength, and the difference between the longitudinal breaking strength and the transverse breaking strength is very small.

[0120] In summary, the present invention prepares aramid paper by coating aramid polymer coating liquid on both sides of aramid woven fabric, solidifying, washing, drying and hot pressing. The prepared aramid paper is flat, smooth and glossy, and has the same appearance as the aramid paper prepared by the traditional method. The transverse breaking strength is 10 to 100 times that of the aramid paper prepared by the traditional method, the transverse breaking elongation is 3 to 6 times that of the aramid paper prepared by the traditional method, the longitudinal breaking strength is 10 to 40 times that of the aramid paper prepared by the traditional method, the longitudinal breaking elongation is 3 to 6 times that of the aramid paper prepared by the traditional method, the dielectric strength is 20% to 50% higher than that of the aramid paper prepared by the traditional method, and the difference between the longitudinal breaking strength and the transverse breaking strength is very small.

[0121] The applicant declares that the present invention illustrates the process method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned process steps, that is, it does not mean that the present invention must rely on the above-mentioned process steps to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing aramid paper, characterized in that: The preparation method comprises the following steps: (1) coating aramid polymer coating liquid on both sides of aramid woven fabric, wherein the solid content of the aramid polymer coating liquid is 10% to 17%, and coagulating, washing and drying to obtain aramid base paper; (2) hot-pressing the aramid base paper obtained in step (1) at 270-350° C. to obtain the aramid paper.

2. The preparation method according to claim 1, characterized in that: The aramid polymer coating liquid is prepared by mixing an aramid polymer stock solution and a solvent; Preferably, the mixing is carried out under the protection of dry nitrogen; Preferably, the solid content of the aramid polymer stock solution is 20% to 25%; Preferably, the intrinsic viscosity of the aramid polymer in the aramid polymer stock solution is 1.3 to 1.9 dL / g; Preferably, the aramid polymer stock solution includes a meta-aramid polymer stock solution and / or a para-aramid polymer stock solution.

3. The preparation method according to claim 2, characterized in that: The solvent is the same substance as the solvent in the aramid polymer stock solution; Preferably, the solvent comprises an amide solvent; Preferably, the amide solvent includes any one of N,N-dimethylacetamide, N-methylpyrrolidone or N-acetylpyrrolidone, or a combination of at least two thereof; Preferably, the water content of the solvent is ≤120 ppm.

4. The preparation method according to any one of claims 1 to 3, characterized in that The temperature of the aramid polymer coating liquid is 10-50°C.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The aramid woven fabric is made by weaving aramid filament bundles; Preferably, the weaving is performed by weaving on a loom; Preferably, the aramid filament bundle comprises a meta-aramid filament bundle and / or a para-aramid filament bundle; Preferably, the fineness of the aramid filament bundle is in the range of 10D to 114D; Preferably, the fineness of the aramid filament monofilament in the aramid filament bundle is 1D to 3D.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The coating has a thickness of 2 to 12 μm; Preferably, the coagulation is carried out in a coagulation bath; Preferably, the temperature of the coagulation bath is 10 to 50°C; Preferably, the coagulation bath comprises an amide solvent and water, and the amide solvent in the coagulation bath and the solvent in the aramid polymer coating liquid are the same substance; Preferably, the mass percentage concentration of the amide solvent in the coagulation bath is 30% to 70%.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The water washing includes a first water washing and a second water washing; Preferably, the temperature of the first water washing is 20 to 60°C; Preferably, the temperature of the second water washing is 60-100°C; Preferably, the water washing is reverse energy-saving water washing, the first water washing is performed by using the washing water obtained from the second water washing, and the second water washing is performed by using desalted water; Preferably, the conductivity of the desalted water is less than 10 μs / cm, the concentration of Fe element is ≤50 μg / L, the hardness is ≤2 μmol / L, and the pH is 7-8; Preferably, the drying temperature is 110-160°C.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The linear pressure of the hot pressing is 50-200 kg / cm.

9. Aramid paper, characterized in that: The aramid paper is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the aramid paper according to claim 9 in honeycomb core structural materials.

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