An aramid paper for a resin infiltration-resistant honeycomb core material and a preparation method thereof

Abstract

The present invention relates to the technical field of aramid paper, and particularly relates to an aramid paper for a resin-resistant infiltration honeycomb core and a preparation method thereof. In the preparation process of the aramid paper for the resin-resistant infiltration honeycomb core, high-temperature-resistant meta-aramid short fibers, meta-aramid precipitated fibers and aramid nanofibers are used as main raw materials for composite papermaking. At the same time, a new hot pressing process of pre-drying followed by high temperature and low pressure and then low temperature and high pressure is adopted. The prepared aramid paper has good resin-resistant infiltration property, small impregnation sizing amount, and high tear strength can be maintained at a high level before and after impregnating with resin, which can effectively improve the problems of large brittleness and poor toughness of the honeycomb core prepared from traditional aramid paper, and can be applied to the field of aramid paper honeycombs for aerospace.

Description

Technical Field

[0001] The present invention relates to an aramid paper for a resin-resistant infiltration honeycomb core material and a preparation method thereof, belonging to the technical field of aramid paper. Background Art

[0002] With the continuous progress of industrialization and technology, the demand for high-performance composite materials has gradually increased. Aramid honeycomb core material is a high-performance sandwich composite material, which combines the excellent properties of aramid paper and the unique structure of honeycomb, and has many advantages such as light weight and high strength, flame retardant and high temperature resistance, chemical corrosion resistance, good sound insulation and heat insulation performance, and excellent impact resistance performance. It is widely used in the fields of aerospace, automotive, construction, etc. The processing process of aramid honeycomb core material is relatively complex, and it is generally prepared through processes such as gluing, laminating, pressing and curing, stretching and shaping, dipping and re-curing, etc. Its main raw materials are aramid paper, core strip glue and impregnating resin. The processing process of honeycomb core material has relatively high requirements for the overall performance of aramid paper, especially the tear strength index of aramid paper after impregnating resin.

[0003] At present, most aramid paper products on the domestic market are prone to embrittlement after impregnating resin, and the overall tear strength index is relatively low, resulting in poor tensile pull-out performance and low drum peel strength of aramid honeycomb during application, and it is difficult to meet the high-end application requirements in directions such as aerospace equipment. The reasons are as follows. On the one hand, the interfacial bonding force between fibers in conventional aramid paper is relatively poor, resulting in a relatively high porosity of aramid paper. During the dipping process of honeycomb core material, excessive resin enters into the interior of aramid paper, causing problems such as high brittleness and poor toughness of the honeycomb. On the other hand, during the production process of aramid paper, the traditional hot pressing process at high temperature and high pressure will cause a certain degree of damage to the main body structure of aramid fibers, restricting the effective transfer of stress between fibers, resulting in a significant decrease in the tear strength of aramid paper after hot pressing. Therefore, developing an aramid paper for resin-resistant infiltration honeycomb is an urgent issue to be solved.

[0004] Chinese Patent Application CN114211847A discloses an aramid paper special for aramid paper honeycomb and a preparation method thereof. Although the problem of aramid paper being soaked by resin during the preparation process of honeycomb core material is solved by the method of compounding meta-aramid paper and para-aramid paper, delamination is prone to occur during application, and the introduction of adhesives will also have an adverse impact on the gluing and dipping processes of preparing honeycomb core material. Summary of the Invention

[0005] In view of the deficiencies existing in the prior art, the present invention provides an aramid paper for a resin-resistant infiltration type honeycomb core material and a preparation method thereof. The aramid paper has good resin-resistant infiltration property, a small impregnation sizing amount, and can maintain a high level of tear strength before and after impregnating with resin. It can effectively improve the problems of large brittleness and poor toughness of the honeycomb core material prepared from traditional aramid paper, and can be applied to the field of aramid paper honeycombs for aerospace.

[0006] The technical solution for the present invention to solve the above technical problems is as follows: A preparation method of an aramid paper for a resin-resistant infiltration type honeycomb core material, and the preparation method is as follows:

[0007] S1. Add high-temperature resistant functional powder and a first dispersant into a solvent, mix evenly to obtain a dispersion liquid containing high-temperature resistant functional powder; mix the dispersion liquid containing high-temperature resistant functional powder with a meta-aramid polymerization liquid evenly to obtain a spinning solution;

[0008] The high-temperature resistant functional powder is aluminum diethylphosphinate powder and boron nitride powder;

[0009] S2. The spinning solution is spun by wet spinning, and then through processes of high-temperature coagulation bath, room-temperature coagulation bath, water washing, drying, heat treatment, oxygen plasma surface treatment, crimping and cutting to obtain high-temperature resistant meta-aramid short cut fibers;

[0010] S3. Make the high-temperature resistant meta-aramid short cut fibers into a high-temperature resistant meta-aramid short cut fiber slurry in water;

[0011] Make meta-aramid precipitated fibers into a meta-aramid precipitated fiber slurry;

[0012] Mix the high-temperature resistant meta-aramid short cut fiber slurry and the meta-aramid precipitated fiber slurry evenly to obtain a mixed slurry;

[0013] S4. Flow the mixed slurry to a double-layer composite inclined wire paper machine for papermaking. After the bottom wire wet paper web is formed, evenly spray an aramid nanofiber dispersion liquid on the upper surface of the bottom wire wet paper web, and then composite it with the top wire wet paper web, so that the aramid nanofibers are in the middle of the bottom wire wet paper web and the top wire wet paper web, and obtain an aramid paper base paper after pressing and drying;

[0014] S5. After the aramid base paper is dried and preheated, perform two hot pressing treatments to obtain the aramid paper for the resin-resistant infiltration type honeycomb core material.

[0015] Further, in step S1, the mass ratio of the aluminum diethylphosphinate powder to the boron nitride powder is 1:(2 - 3);

[0016] The first dispersant is any one of polymethacrylic acid and polyvinylpyrrolidone.

[0017] Further, in step S1, the solvent in the meta-aramid polymerization solution is N,N-dimethylformamide; the solvent for preparing the dispersion is N,N-dimethylformamide;

[0018] The solid content of the meta-aramid polymerization solution is 25-28%, and the viscosity at 25°C is 450-650P;

[0019] The mass content of the high-temperature resistant functional powder in the dispersion is 20-35%, and the mass content of the first dispersant in the dispersion is 1.0-2.5%;

[0020] The mass ratio of the dispersion to the meta-aramid polymerization solution is 1:(13-18).

[0021] Further, in step S2, the temperature of the high-temperature coagulation bath is 50-90°C, the high-temperature coagulation bath is N,N-dimethylformamide and water, and the mass concentration of N,N-dimethylformamide in the coagulation bath is 28-32%;

[0022] The temperature of the room-temperature coagulation bath is 20-30°C, the room-temperature coagulation bath is N,N-dimethylformamide and water, and the mass concentration of N,N-dimethylformamide in the room-temperature coagulation bath is 25-30%.

[0023] Further, in step S2, the temperature of the heat treatment is 250-350°C; the equipment for oxygen plasma surface treatment is an inductively coupled plasma generator, the treatment frequency is 1000-1300Hz, and the treatment time is 8-10min; the length of the high-temperature resistant meta-aramid short cut fibers is 5-8mm.

[0024] Further, in step S3, the preparation method of the high-temperature resistant meta-aramid short cut fiber slurry is: putting the high-temperature resistant meta-aramid short cut fibers into deionized water and stirring, adding a second dispersant to disperse uniformly, to obtain a high-temperature resistant meta-aramid short cut fiber slurry with a mass concentration of 0.2%-1.0%, and the mass content of the second dispersant in the high-temperature resistant meta-aramid short cut fiber slurry is 0.1-0.5%; the second dispersant is any one of polyethylene oxide and polyacrylamide;

[0025] The preparation method of the meta-aramid precipitated fiber slurry is: using a high-speed shear emulsifier to emulsify the meta-aramid precipitated fibers, the treatment speed is 13000-15000rpm, the treatment time is 10-15min, and then beating and dispersing to make a meta-aramid precipitated fiber slurry with a mass concentration of 0.5%-1.5%; the size distribution of the meta-aramid precipitated fibers is 40-120 mesh.

[0026] Further, the aramid nanofiber dispersion consists of aramid nanofibers and deionized water, wherein the mass fraction of aramid nanofibers in the aramid nanofiber dispersion is 0.05 - 0.20%;

[0027] The aramid nanofibers are any one of meta-aramid nanofibers and para-aramid nanofibers, and the diameter of the aramid nanofibers is 40 - 100 nm.

[0028] Further, in step S5, a tunnel drying device is used for drying and preheating, and the temperature of the drying and preheating is 200 - 260 °C;

[0029] The two-stage hot pressing includes a first-stage high-temperature and low-pressure hot pressing operation and a second-stage low-temperature and high-pressure hot pressing operation. The temperature of the first-stage high-temperature and low-pressure hot pressing operation is 290 - 340 °C, the pressure is 120 - 180 N / mm, and the vehicle speed is 15 - 30 m / min; the temperature of the second-stage low-temperature and high-pressure hot pressing operation is 230 - 270 °C, the pressure is 350 - 400 N / mm, and the vehicle speed is 15 - 30 m / min.

[0030] Further, in the process of preparing the aramid paper, by weight, 30 - 50 parts of meta-aramid precipitated fibers, 50 - 70 parts of high-temperature-resistant meta-aramid short fibers, and 8 - 15 parts of aramid nanofibers are used.

[0031] The present invention also discloses an aramid paper for a resin-resistant infiltration honeycomb core material, and the aramid paper is prepared by the preparation method described in the present invention.

[0032] The beneficial effects of the present invention are as follows:

[0033] The present invention prepares a high-temperature-resistant meta-aramid short fiber, which improves the high-temperature resistance of aramid fibers, reduces the damage to the strength and structure of aramid fibers during the hot pressing process, and uses the oxygen plasma treatment method to perform surface treatment on the high-temperature-resistant meta-aramid short fiber. Without affecting the strength index of the short fiber, the hydrophilicity and chemical reaction activity of the fiber are effectively improved, and the dispersion effect and the binding ability between the fibers are better. At the same time, a new hot pressing process of pre-drying followed by high-temperature and low-pressure and then low-temperature and high-pressure is used, which effectively improves the phenomenon that the tear strength of the aramid paper drops significantly after hot pressing. Pre-drying can not only avoid the wrinkling of the aramid paper due to sudden shrinkage when it enters the high-temperature hot pressing environment, but also keep the aramid paper fully dry and improve the problem of the decrease in tear strength caused by the swelling of the fibers due to moisture. The high-temperature and low-pressure treatment ensures the effective plasticization of the aramid paper due to high temperature while reducing the adverse effect of pressure on its tear strength performance, and a second-stage hot pressing of low-temperature and high-pressure is set to ensure that the basic indexes such as the thickness and tightness of the aramid paper meet the requirements.

[0034] In addition, in the papermaking process of the present invention, aramid nanofibers are added by means of spraying. Aramid nanofibers are nanofibers composed of aromatic polyamide molecules, with a large specific surface area and high surface energy. The addition of aramid nanofibers can significantly improve the bonding force between fibers and the flexibility of aramid paper, and overall reduce the porosity of aramid paper, improving the problems of excessive impregnation amount and penetration when aramid paper is impregnated with resin.

[0035] In summary, the aramid paper prepared by the present invention has good resin infiltration resistance, a small impregnation sizing amount, and can maintain a high level of tear strength before and after impregnation with resin, effectively improving the problems of high brittleness and poor toughness of the honeycomb core material prepared from traditional aramid paper. Description of the Drawings

[0036] Figure 1 It is a process flow chart for the preparation of the aramid paper described in the present invention. Detailed Embodiments

[0037] The following provides a detailed description of the specific embodiments of the present invention. The present invention can be implemented in many other ways different from those described herein. Those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used are only for describing specific embodiments and do not limit the present invention.

[0039] As Figure 1 shown, a method for preparing aramid paper for a resin infiltration-resistant honeycomb core material, the preparation method is as follows:

[0040] S1. Add a high-temperature resistant functional powder and a first dispersant to a solvent, mix them evenly to obtain a dispersion containing the high-temperature resistant functional powder; mix the dispersion containing the high-temperature resistant functional powder with a meta-aramid polymerization solution evenly to obtain a spinning solution;

[0041] The high-temperature resistant functional powder is aluminum diethylphosphinate powder and boron nitride powder;

[0042] S2. The spinning solution is spun by wet spinning, and then through a high-temperature coagulation bath, a room-temperature coagulation bath, water washing, drying, heat treatment, oxygen plasma surface treatment, crimping and cutting processes to obtain high-temperature resistant meta-aramid short fibers;

[0043] S3. Make the high-temperature resistant meta-aramid short fibers into a high-temperature resistant meta-aramid short fiber slurry in water;

[0044] Prepare the meta-aramid precipitated fiber into a meta-aramid precipitated fiber slurry;

[0045] Mix the high-temperature resistant meta-aramid short fiber slurry and the meta-aramid precipitated fiber slurry evenly to obtain a mixed slurry;

[0046] S4. Feed the mixed slurry to a double-layer composite inclined wire paper machine for papermaking. After the bottom wire wet paper web is formed, evenly spray the aramid nanofiber dispersion liquid on the upper surface of the bottom wire wet paper web, and then composite it with the top wire wet paper web, so that the aramid nanofibers are in the middle of the bottom wire wet paper web and the top wire wet paper web, and obtain the aramid paper base paper after pressing and drying;

[0047] S5. After the aramid base paper is dried and preheated, perform two hot pressing treatments to obtain the aramid paper for the resin-resistant infiltration type honeycomb core material.

[0048] Specifically, in step S1, the mass ratio of the aluminum diethylphosphinate powder to the boron nitride powder is 1:(2 - 3);

[0049] The first dispersant is any one of polymethacrylic acid and polyvinylpyrrolidone.

[0050] Specifically, in step S1, the solvent in the meta-aramid polymerization liquid is N,N-dimethylformamide; the solvent for preparing the dispersion liquid is N,N-dimethylformamide.

[0051] More specifically, the preparation method of the meta-aramid polymerization liquid is: in a system with N,N-dimethylformamide as an organic solvent, carry out solution polymerization with isophthaloyl chloride and m-phenylenediamine to obtain a meta-aromatic polyamide solution containing isophthaloyl m-phenylenediamine as a repeating unit, and use calcium oxide to neutralize the generated hydrochloric acid to obtain the meta-aramid polymerization liquid.

[0052] The solid content of the meta-aramid polymerization liquid is 25 - 28%, and the viscosity at 25°C is 450 - 650P;

[0053] The mass content of the high-temperature resistant functional powder in the dispersion liquid is 20 - 35%, and the mass content of the first dispersant in the dispersion liquid is 1.0 - 2.5%;

[0054] The mass ratio of the dispersion liquid to the meta-aramid polymerization liquid is 1:(13 - 18).

[0055] Specifically, in step S2, the temperature of the high-temperature coagulation bath is 50 - 90°C, the high-temperature coagulation bath is N,N-dimethylformamide and water, and the mass concentration of N,N-dimethylformamide in the room-temperature coagulation bath is 28 - 32%;

[0056] The temperature of the room-temperature coagulation bath is 20 - 30°C. The room-temperature coagulation bath is N,N-dimethylformamide and water. The mass concentration of N,N-dimethylformamide in the high-temperature coagulation bath is 25 - 30%.

[0057] Specifically, in step S2, the temperature of the heat treatment is 250 - 350°C; the equipment for oxygen plasma surface treatment is an inductively coupled plasma generator, the treatment frequency is 1000 - 1300 Hz, and the treatment time is 8 - 10 min; the length of the high-temperature resistant meta-aramid short-cut fibers is 5 - 8 mm.

[0058] Specifically, in step S3, the preparation method of the high-temperature resistant meta-aramid short-cut fiber slurry is as follows: Put the high-temperature resistant meta-aramid short-cut fibers into deionized water and stir, add a second dispersant and disperse evenly to obtain a high-temperature resistant meta-aramid short-cut fiber slurry with a mass concentration of 0.2% - 1.0%. The mass content of the second dispersant in the high-temperature resistant meta-aramid short-cut fiber slurry is 0.1 - 0.5%; the second dispersant is any one of polyethylene oxide and polyacrylamide;

[0059] The preparation method of the meta-aramid precipitated fiber slurry is as follows: Use a high-speed shear emulsifier to emulsify the meta-aramid precipitated fibers, the treatment rotation speed is 13000 - 15000 rpm, the treatment time is 10 - 15 min, and then beat and disperse to make a meta-aramid precipitated fiber slurry with a mass concentration of 0.5% - 1.5%; the size distribution of the meta-aramid precipitated fibers is 40 - 120 mesh.

[0060] Specifically, the component of the aramid nanofiber dispersion liquid is aramid nanofibers and deionized water, and the mass fraction of aramid nanofibers in the aramid nanofiber dispersion liquid is 0.05 - 0.20%;

[0061] The aramid nanofibers are any one of meta-aramid nanofibers and para-aramid nanofibers, and the diameter of the aramid nanofibers is 40 - 100 nm.

[0062] Specifically, in step S5, a tunnel drying device is used for drying and preheating, and the temperature of the drying and preheating is 200 - 260°C;

[0063] The two-stage hot pressing includes the first high-temperature and low-pressure hot pressing operation and the second low-temperature and high-pressure hot pressing operation. The temperature of the first high-temperature and low-pressure hot pressing operation is 290 - 340°C, the pressure is 120 - 180 N / mm, and the vehicle speed is 15 - 30 m / min; the temperature of the second low-temperature and high-pressure hot pressing operation is 230 - 270°C, the pressure is 350 - 400 N / mm, and the vehicle speed is 15 - 30 m / min.

[0064] Specifically, in the process of preparing the aramid paper, by weight, 30-50 parts of meta-aramid precipitated fiber, 50-70 parts of high-temperature resistant meta-aramid short cut fiber, and 8-15 parts of aramid nanofiber are used.

[0065] An aramid paper for a resin-resistant infiltration honeycomb core material, which is prepared by the preparation method described in the present invention.

[0066] Sources of raw materials used in the embodiments of the present invention:

[0067] N,N-dimethylformamide is provided by Wuhan Rongcan Biotechnology Co., Ltd.; calcium oxide is provided by Shenyang KETUO Chemical Co., Ltd.; aluminum diethylphosphinate is provided by Hubei Hongjing Chemical Co., Ltd.; boron nitride powder is provided by Henan Xinyuan Chemical Products Co., Ltd.; meta-aramid precipitated fiber, isophthaloyl chloride and m-phenylenediamine are provided by Tayho Advanced Materials Co., Ltd.; polymethacrylic acid is provided by Hubei Dongcao Chemical Technology Co., Ltd.; polyvinylpyrrolidone is provided by Hefei Tianjian Chemical Co., Ltd.; polyethylene oxide is provided by Suzhou Qihang Biotechnology Co., Ltd.; polyacrylamide is provided by Shandong Tongli Chemical Co., Ltd. However, it does not constitute a limitation to the technical solution of the present invention.

[0068] Example 1

[0069] This example exemplifies an aramid paper for a resin-resistant infiltration honeycomb core material, which is composed of the following raw materials by weight: 40 parts of meta-precipitated fiber; 60 parts of high-temperature resistant meta-aramid short cut fiber; 10 parts of aramid nanofiber.

[0070] A preparation method of an aramid paper for a resin-resistant infiltration honeycomb core material, comprising the following steps:

[0071] (1) In a nitrogen atmosphere, in a system with N,N-dimethylformamide as an organic solvent, solution polymerization is carried out using isophthaloyl chloride and m-phenylenediamine to obtain a meta-aromatic polyamide solution containing isophthaloyl m-phenylenediamine as a repeating unit, and calcium oxide is used to neutralize the generated hydrochloric acid to obtain a meta-aramid polymerization solution; the solid content of the meta-aramid polymerization solution is 25%, and the viscosity (25°C) is 500P;

[0072] (2) Add high-temperature resistant functional powder and a first dispersant to N,N-dimethylformamide solvent and stir evenly to obtain a dispersion liquid containing high-temperature resistant functional powder; the high-temperature resistant functional powder is a combination of aluminum diethylphosphinate powder and boron nitride powder, and the corresponding weight ratio is 1:3. The first dispersant is polymethacrylic acid. The mass content of the high-temperature resistant functional powder in the dispersion liquid is 30%, and the mass content of the first dispersant in the dispersion liquid is 1.5%.

[0073] (3) Mix the meta-aramid polymerization solution in step (1) with the dispersion liquid in step (2) and stir evenly to obtain a spinning solution. The mass ratio of the dispersion liquid to the meta-aramid polymerization solution is 1:15. The spinning solution is spun by wet spinning, and then through a high-temperature coagulation bath, a room-temperature coagulation bath, water washing, drying, heat treatment, oxygen plasma surface treatment, crimping and cutting processes to obtain high-temperature resistant meta-aramid short cut fibers; the temperature of the high-temperature coagulation bath is 80 °C, and the mass concentration of N,N-dimethylformamide in the high-temperature coagulation bath is 27%; the temperature of the room-temperature coagulation bath is 30 °C, and the mass concentration of N,N-dimethylformamide in the room-temperature coagulation bath is 25%. The temperature of the heat treatment is 300 °C, the frequency of the oxygen plasma surface treatment is 1300 Hz, and the treatment time is 10 min; the length of the high-temperature resistant meta-aramid short cut fibers is 7 mm.

[0074] (4) Put the high-temperature resistant meta-aramid short cut fibers into deionized water and stir, add a second dispersant with a mass concentration of 0.1% and disperse evenly by disintegration to obtain a high-temperature resistant meta-aramid short cut fiber slurry with a mass concentration of 0.2%; emulsify the meta-aramid precipitated fibers, and then beat and disperse them to make a meta-aramid precipitated fiber slurry with a mass concentration of 0.5%; mix the high-temperature resistant meta-aramid short cut fiber slurry with a mass concentration of 0.2% and the meta-aramid precipitated fiber slurry with a mass concentration of 0.5%, and stir evenly to obtain a mixed slurry; the second dispersant is polyethylene oxide, the rotation speed of the emulsification treatment is 15000 rpm, and the time is 15 min.

[0075] (5) Feed the mixed slurry in step (4) to a double-layer composite inclined wire paper machine for papermaking. After the bottom wire wet paper web is formed, use a pressure spraying device to evenly spray the aramid nanofiber dispersion liquid on the upper surface of the bottom wire wet paper web, and then composite it with the top wire wet paper web, so that the aramid nanofibers are in the middle of the bottom wire wet paper web and the top wire wet paper web, and obtain the aramid paper base paper after pressing and drying; the aramid nanofibers are meta-aramid nanofibers with a diameter of 50 nm, and the components of the aramid nanofiber dispersion liquid are aramid nanofibers and deionized water, and the mass fraction of the aramid nanofibers is 0.05%.

[0076] (6) Thoroughly dry and preheat the aramid paper base paper obtained in step (5) through a channel-type hot drying device, and then enter a roll-type hot press for two hot pressing treatments. The first hot pressing is high temperature and low pressure, and the second hot pressing is low temperature and high pressure. After the hot pressing is completed, an aramid paper for a resin infiltration-resistant honeycomb core material is obtained. The set temperature of the drying device in the drying channel is 240 °C, the temperature of the first hot pressing at high temperature and low pressure is 320 °C, the pressure is 150 N / mm, the vehicle speed is 20 m / min, the temperature of the second hot pressing at low temperature and high pressure is 240 °C, the pressure is 400 N / mm, and the vehicle speed is 20 m / min.

[0077] Example 2

[0078] This example exemplifies an aramid paper for a resin-resistant infiltration honeycomb core material, which is composed of the following raw materials in parts by weight: 45 parts of meta-precipitated fiber; 55 parts of high-temperature-resistant meta-aramid short fibers; 10 parts of aramid nanofibers.

[0079] A preparation method of an aramid paper for a resin-resistant infiltration honeycomb core material includes the following steps:

[0080] (1) In a nitrogen atmosphere, in a system with N,N-dimethylformamide as an organic solvent, solution polymerization is carried out using isophthaloyl chloride and m-phenylenediamine to obtain a meta-aromatic polyamide solution containing isophthaloyl m-phenylenediamine as a repeating unit, and calcium oxide is used to neutralize the generated hydrochloric acid to obtain a meta-aramid polymerization solution; the solid content of the meta-aramid polymerization solution is 25%, and the viscosity (25 °C) is 500 P;

[0081] (2) Add high-temperature-resistant functional powder and the first dispersant to the N,N-dimethylformamide solvent and stir evenly to obtain a dispersion liquid containing high-temperature-resistant functional powder; the high-temperature-resistant functional powder is a combination of aluminum diethylphosphinate powder and boron nitride powder, and the corresponding weight ratio is 1:3. The first dispersant is polymethacrylic acid. The mass content of the high-temperature-resistant functional powder in the dispersion liquid is 30%, and the mass content of the first dispersant in the dispersion liquid is 1.5%.

[0082] (3) Mix the meta-aramid polymerization solution in step (1) with the dispersion liquid in step (2) and stir evenly to obtain a spinning solution. The mass ratio of the dispersion liquid to the meta-aramid polymerization solution is 1:15. The spinning solution is spun by wet spinning, and then through a high-temperature coagulation bath, a room-temperature coagulation bath, water washing, drying, heat treatment, oxygen plasma surface treatment, crimping and cutting processes to obtain high-temperature-resistant meta-aramid short fibers; the temperature of the high-temperature coagulation bath is 80 °C, and the mass concentration of N,N-dimethylformamide in the high-temperature coagulation bath is 27%; the temperature of the room-temperature coagulation bath is 30 °C, and the mass concentration of N,N-dimethylformamide in the room-temperature coagulation bath is 25%. The temperature of the heat treatment is 310 °C, the frequency of the oxygen plasma surface treatment is 1100 Hz, and the treatment time is 8 min; the length of the high-temperature-resistant meta-aramid short fibers is 7 mm.

[0083] (4) Put the high-temperature resistant meta-aramid short fibers into deionized water and stir. Add a second dispersant with a mass concentration of 0.1% and disperse evenly by beating to obtain a high-temperature resistant meta-aramid short fiber slurry with a mass concentration of 0.2%. Emulsify the meta-aramid precipitated fibers, and then beat and disperse them to make a meta-aramid precipitated fiber slurry with a mass concentration of 0.5%. Mix the high-temperature resistant meta-aramid short fiber slurry with a mass concentration of 0.2% and the meta-aramid precipitated fiber slurry with a mass concentration of 0.5%, and stir evenly to obtain a mixed slurry. The second dispersant is polyethylene oxide. The rotation speed of the emulsification treatment is 15000 rpm and the time is 15 min.

[0084] (5) Feed the mixed slurry in step (4) to a double-layer composite inclined wire paper machine for papermaking. After the bottom web wet paper web is formed, use a pressure spraying device to evenly spray the aramid nanofiber dispersion liquid on the upper surface of the bottom web wet paper web, and then composite it with the top web wet paper web so that the aramid nanofibers are in the middle of the bottom web wet paper web and the top web wet paper web. After pressing and drying, obtain the aramid paper base paper. The aramid nanofibers are meta-aramid nanofibers with a diameter of 50 nm. The composition of the aramid nanofiber dispersion liquid is aramid nanofibers and deionized water, and the mass fraction of the aramid nanofibers is 0.05%.

[0085] (6) Fully dry and preheat the aramid paper base paper obtained in step (5) through a channel-type hot drying device, and then enter a roll-type hot press for two hot pressing treatments. The first hot pressing is at high temperature and low pressure, and the second hot pressing is at low temperature and high pressure. After the hot pressing is completed, a kind of aramid paper for resin-resistant infiltration honeycomb core material is obtained. The set temperature of the drying device in the drying channel is 240 °C. The temperature of the first hot pressing at high temperature and low pressure is 330 °C, the pressure is 140 N / mm, the vehicle speed is 18 m / min. The temperature of the second hot pressing at low temperature and high pressure is 240 °C, the pressure is 380 N / mm, and the vehicle speed is 18 m / min.

[0086] Example 3

[0087] This example exemplifies an aramid paper for resin-resistant infiltration honeycomb core material, which is composed of the following raw materials in parts by weight: 47 parts of meta-aramid precipitated fibers; 55 parts of high-temperature resistant meta-aramid short fibers; 8 parts of aramid nanofibers.

[0088] A preparation method of an aramid paper for resin-resistant infiltration honeycomb core material, comprising the following steps:

[0089] (1)In a nitrogen atmosphere, solution polymerization is carried out with isophthaloyl chloride and m-phenylenediamine in a system with N,N-dimethylformamide as the organic solvent to obtain a meta-aramid solution containing isophthaloyl m-phenylenediamine as the repeating unit. Calcium oxide is used to neutralize the hydrochloric acid generated by the reaction to obtain a meta-aramid polymerization solution; the solid content of the meta-aramid polymerization solution is 25%, and the viscosity (25 °C) is 600 P;

[0090] (2)The high-temperature resistant functional powder and the first dispersant are added to the N,N-dimethylformamide solvent and stirred evenly to obtain a dispersion liquid containing the high-temperature resistant functional powder; the high-temperature resistant functional powder is a combination of aluminum diethylphosphinate powder and boron nitride powder, and the corresponding weight ratio is 1:3. The first dispersant is polymethacrylic acid. The mass content of the high-temperature resistant functional powder in the dispersion liquid is 32%, and the mass content of the first dispersant in the dispersion liquid is 2.0%.

[0091] (3)The meta-aramid polymerization solution in step (1) is mixed with the dispersion liquid in step (2) and stirred evenly to obtain a spinning solution. The mass ratio of the dispersion liquid to the meta-aramid polymerization solution is 1:16. The spinning solution is spun by wet spinning, and then undergoes processes such as a high-temperature coagulation bath, a room-temperature coagulation bath, water washing, drying, heat treatment, oxygen plasma surface treatment, crimping and cutting to obtain high-temperature resistant meta-aramid short cut fibers; the temperature of the high-temperature coagulation bath is 80 °C, and the mass concentration of N,N-dimethylformamide in the high-temperature coagulation bath is 28%; the temperature of the room-temperature coagulation bath is 30 °C, and the mass concentration of N,N-dimethylformamide in the room-temperature coagulation bath is 25%. The temperature of the heat treatment is 300 °C, the frequency of the oxygen plasma surface treatment is 1000 Hz, and the treatment time is 9 min; the length of the high-temperature resistant meta-aramid short cut fibers is 8 mm.

[0092] (4)The high-temperature resistant meta-aramid short cut fibers are put into deionized water and stirred, and a second dispersant with a mass concentration of 0.1% is added to disperse and dissolve evenly to obtain a high-temperature resistant meta-aramid short cut fiber slurry with a mass concentration of 0.2%; the meta-aramid precipitated fibers are emulsified and then beaten and dispersed to make a meta-aramid precipitated fiber slurry with a mass concentration of 0.5%; the high-temperature resistant meta-aramid short cut fiber slurry with a mass concentration of 0.2% and the meta-aramid precipitated fiber slurry with a mass concentration of 0.5% are mixed and stirred evenly to obtain a mixed slurry; the second dispersant is polyethylene oxide, and the rotation speed of the emulsification treatment is 15000 rpm and the time is 15 min.

[0093] (5) Feed the mixed slurry from step (4) to a double-layer composite inclined wire paper machine for papermaking. After the bottom wire wet paper web is formed, use a pressure spraying device to evenly spray the aramid nanofiber dispersion on the upper surface of the bottom wire wet paper web, and then composite it with the top wire wet paper web, so that the aramid nanofibers are in the middle of the bottom wire wet paper web and the top wire wet paper web. After pressing and drying, obtain the aramid paper base paper; the aramid nanofibers are meta-aramid nanofibers with a diameter of 60 nm. The aramid nanofiber dispersion consists of aramid nanofibers and deionized water, and the mass fraction of aramid nanofibers is 0.08%.

[0094] (6) Thoroughly dry and preheat the aramid paper base paper obtained in step (5) through a channel-type hot drying device, and then enter a roll-type hot press for two hot pressing treatments. The first hot pressing is at high temperature and low pressure, and the second hot pressing is at low temperature and high pressure. After the hot pressing is completed, an aramid paper for a resin-resistant infiltration type honeycomb core material is obtained. The set temperature of the drying device in the drying channel is 250 °C. The temperature of the first hot pressing at high temperature and low pressure is 310 °C, the pressure is 160 N / mm, the machine speed is 19 m / min. The temperature of the second hot pressing at low temperature and high pressure is 230 °C, the pressure is 360 N / mm, and the machine speed is 19 m / min.

[0095] Example 4

[0096] This example exemplifies an aramid paper for a resin-resistant infiltration type honeycomb core material, which is composed of the following raw materials in parts by weight: 47 parts of meta-precipitated fiber; 54 parts of high-temperature resistant meta-aramid short fibers; 9 parts of aramid nanofibers.

[0097] A preparation method of an aramid paper for a resin-resistant infiltration type honeycomb core material, comprising the following steps:

[0098] (1) In a nitrogen atmosphere, in a system with N,N-dimethylformamide as an organic solvent, carry out solution polymerization with isophthaloyl chloride and m-phenylenediamine to obtain a meta-aromatic polyamide solution containing isophthaloyl m-phenylenediamine as a repeating unit, and use calcium oxide to neutralize the generated hydrochloric acid to obtain a meta-aramid polymerization solution; the solid content of the meta-aramid polymerization solution is 28%, and the viscosity (25 °C) is 550 P;

[0099] (2) Add the high-temperature resistant functional powder and the first dispersant to the N,N-dimethylformamide solvent and stir evenly to obtain a dispersion liquid containing the high-temperature resistant functional powder; the high-temperature resistant functional powder is a combination of aluminum diethylphosphinate powder and boron nitride powder, and the corresponding weight ratio is 1:3. The first dispersant is polymethacrylic acid. The mass content of the high-temperature resistant functional powder in the dispersion liquid is 35%, and the mass content of the first dispersant in the dispersion liquid is 1.5%.

[0100] (3) Mix the meta-aramid polymerization solution in step (1) with the dispersion in step (2) and stir evenly to obtain a spinning solution. The mass ratio of the dispersion to the meta-aramid polymerization solution is 1:18. The spinning solution is spun by wet spinning, and then through a high-temperature coagulation bath, a room-temperature coagulation bath, water washing, drying, heat treatment, oxygen plasma surface treatment, crimping and cutting processes to obtain heat-resistant meta-aramid short-cut fibers; the temperature of the high-temperature coagulation bath is 90 °C, and the mass concentration of N,N-dimethylformamide in the high-temperature coagulation bath is 28%; the temperature of the room-temperature coagulation bath is 25 °C, and the mass concentration of N,N-dimethylformamide in the room-temperature coagulation bath is 30%. The temperature of the heat treatment is 340 °C, the frequency of the oxygen plasma surface treatment is 1200 Hz, and the treatment time is 8 min; the length of the heat-resistant meta-aramid short-cut fibers is 5 mm.

[0101] (4) Put the heat-resistant meta-aramid short-cut fibers into deionized water and stir, add a second dispersant with a mass concentration of 0.1% for uniform dispersion and dissociation to obtain a heat-resistant meta-aramid short-cut fiber slurry with a mass concentration of 0.2%; emulsify the meta-aramid precipitated fibers, and then beat and disperse them to make a meta-aramid precipitated fiber slurry with a mass concentration of 0.5%; mix the heat-resistant meta-aramid short-cut fiber slurry with a mass concentration of 0.2% and the meta-aramid precipitated fiber slurry with a mass concentration of 0.5%, and stir evenly to obtain a mixed slurry; the second dispersant is polyethylene oxide, the rotation speed of the emulsification treatment is 15000 rpm, and the time is 12 min.

[0102] (5) Feed the mixed slurry in step (4) to a double-layer composite inclined wire paper machine for papermaking. After the bottom wire wet paper web is formed, use a pressure spraying device to evenly spray the aramid nanofiber dispersion on the upper surface of the bottom wire wet paper web, and then compound it with the top wire wet paper web, so that the aramid nanofibers are in the middle of the bottom wire wet paper web and the top wire wet paper web, and obtain the aramid paper base paper after pressing and drying; the aramid nanofibers are meta-aramid nanofibers with a diameter of 50 nm, and the components of the aramid nanofiber dispersion are aramid nanofibers and deionized water, and the mass fraction of the aramid nanofibers is 0.18%.

[0103] (6) Thoroughly dry and preheat the aramid paper base paper obtained in step (5) through a channel-type hot air drying device, and then enter a roll-type hot press for two hot pressing treatments. The first hot pressing is high temperature and low pressure, and the second hot pressing is low temperature and high pressure. After the hot pressing is completed, an aramid paper for a resin-resistant infiltration honeycomb core material is obtained. The set temperature of the drying device in the drying channel is 260 °C, the temperature of the first hot pressing at high temperature and low pressure is 340 °C, the pressure is 180 N / mm, the vehicle speed is 15 m / min, the temperature of the second hot pressing at low temperature and high pressure is 270 °C, the pressure is 400 N / mm, and the vehicle speed is 15 m / min.

[0104] Example 5

[0105] This example exemplifies an aramid paper for a resin-resistant infiltration honeycomb core material, which is composed of the following raw materials in parts by weight: 47 parts of meta-precipitated fiber; 51 parts of high-temperature-resistant meta-aramid short-cut fiber; 12 parts of aramid nanofiber.

[0106] A preparation method of an aramid paper for a resin-resistant infiltration honeycomb core material includes the following steps:

[0107] (1) In a nitrogen atmosphere, in a system with N,N-dimethylformamide as an organic solvent, solution polymerization is carried out with isophthaloyl chloride and m-phenylenediamine to obtain a meta-aromatic polyamide solution containing isophthaloyl m-phenylenediamine as a repeating unit, and calcium oxide is used to neutralize the generated hydrochloric acid to obtain a meta-aramid polymerization solution; the solid content of the meta-aramid polymerization solution is 25%, and the viscosity (25 °C) is 600 P;

[0108] (2) Add high-temperature-resistant functional powder and a first dispersant to the N,N-dimethylformamide solvent and stir evenly to obtain a dispersion liquid containing high-temperature-resistant functional powder; the high-temperature-resistant functional powder is a combination of aluminum diethylphosphinate powder and boron nitride powder, and the corresponding weight ratio is 1:3. The first dispersant is polymethacrylic acid. The mass content of the high-temperature-resistant functional powder in the dispersion liquid is 32%, and the mass content of the first dispersant in the dispersion liquid is 2.0%.

[0109] (3) Mix the meta-aramid polymerization solution in step (1) with the dispersion liquid in step (2) and stir evenly to obtain a spinning solution. The mass ratio of the dispersion liquid to the meta-aramid polymerization solution is 1:16. The spinning solution is spun by wet spinning, and then undergoes high-temperature coagulation bath, room-temperature coagulation bath, water washing, drying, heat treatment, oxygen plasma surface treatment, crimping and cutting processes to obtain high-temperature-resistant meta-aramid short-cut fibers; the temperature of the high-temperature coagulation bath is 85 °C, and the mass concentration of N,N-dimethylformamide in the high-temperature coagulation bath is 30%; the temperature of the room-temperature coagulation bath is 29 °C, and the mass concentration of N,N-dimethylformamide in the room-temperature coagulation bath is 25%. The temperature of the heat treatment is 260 °C, the frequency of the oxygen plasma surface treatment is 1400 Hz, and the treatment time is 10 min; the length of the high-temperature-resistant meta-aramid short-cut fibers is 8 mm.

[0110] (4) Put the high-temperature resistant meta-aramid short-cut fibers into deionized water and stir. Add a second dispersant with a mass concentration of 0.1% for defibrillation and uniform dispersion to obtain a high-temperature resistant meta-aramid short-cut fiber slurry with a mass concentration of 0.2%. Emulsify the meta-aramid precipitated fibers, and then beat and disperse them to make a meta-aramid precipitated fiber slurry with a mass concentration of 0.5%. Mix the high-temperature resistant meta-aramid short-cut fiber slurry with a mass concentration of 0.2% and the meta-aramid precipitated fiber slurry with a mass concentration of 0.5%, and stir evenly to obtain a mixed slurry. The second dispersant is polyethylene oxide. The rotation speed of the emulsification treatment is 15,000 rpm, and the time is 14 min.

[0111] (5) Feed the mixed slurry in step (4) to a double-layer composite inclined wire paper machine for papermaking. After the bottom wire wet paper web is formed, use a pressure spraying device to evenly spray the aramid nanofiber dispersion liquid on the upper surface of the bottom wire wet paper web, and then composite it with the top wire wet paper web so that the aramid nanofibers are in the middle of the bottom wire wet paper web and the top wire wet paper web. After pressing and drying, obtain the aramid paper base paper. The aramid nanofibers are meta-aramid nanofibers with a diameter of 50 nm. The components of the aramid nanofiber dispersion liquid are aramid nanofibers and deionized water, and the mass fraction of the aramid nanofibers is 0.14%.

[0112] (6) Thoroughly dry and preheat the aramid paper base paper obtained in step (5) through a channel-type hot drying device, and then enter a roll-type hot press for two hot pressing treatments. The first hot pressing is at high temperature and low pressure, and the second hot pressing is at low temperature and high pressure. After the hot pressing is completed, an aramid paper for honeycomb core material is obtained. The set temperature of the drying device in the drying channel is 210 °C. The temperature of the first hot pressing at high temperature and low pressure is 310 °C, the pressure is 170 N / mm, the vehicle speed is 25 m / min. The temperature of the second hot pressing at low temperature and high pressure is 240 °C, the pressure is 360 N / mm, and the vehicle speed is 25 m / min.

[0113] Comparative Example 1

[0114] Use the same method as in Example 5 to prepare the aramid paper for honeycomb core material, the difference is that: in this Comparative Example 1, no aramid nanofibers were sprayed during papermaking. The specific experimental process is as follows:

[0115] This Comparative Example exemplifies an aramid paper for honeycomb core material, which is composed of the following raw materials in parts by weight: 50 parts of meta-aramid precipitated fibers; 60 parts of high-temperature resistant meta-aramid short-cut fibers.

[0116] A preparation method of an aramid paper for honeycomb core material, comprising the following steps:

[0117] (1) In a nitrogen atmosphere, in a system with N,N-dimethylformamide as an organic solvent, solution polymerization is carried out using isophthaloyl chloride and m-phenylenediamine to obtain a meta-aramid solution containing isophthaloyl m-phenylenediamine as a repeating unit. Calcium oxide is used to neutralize the hydrochloric acid generated by the reaction to obtain a meta-aramid polymerization solution; the solid content of the meta-aramid polymerization solution is 25%, and the viscosity (25 °C) is 600 P;

[0118] (2) The high-temperature resistant functional powder and the first dispersant are added to the N,N-dimethylformamide solvent and stirred evenly to obtain a dispersion liquid containing the high-temperature resistant functional powder; the high-temperature resistant functional powder is a combination of aluminum diethylphosphinate powder and boron nitride powder, and the corresponding weight ratio is 1:3. The first dispersant is polymethacrylic acid. The mass content of the high-temperature resistant functional powder in the dispersion liquid is 32%, and the mass content of the first dispersant in the dispersion liquid is 2.0%.

[0119] (3) The meta-aramid polymerization solution in step (1) and the dispersion liquid in step (2) are mixed and stirred evenly to obtain a spinning solution. The mass ratio of the dispersion liquid to the meta-aramid polymerization solution is 1:16. The spinning solution is spun by wet spinning, and then undergoes high-temperature coagulation bath, room-temperature coagulation bath, water washing, drying, heat treatment, oxygen plasma surface treatment, crimping and cutting processes to obtain high-temperature resistant meta-aramid short cut fibers; the temperature of the high-temperature coagulation bath is 85 °C, and the mass concentration of N,N-dimethylformamide in the high-temperature coagulation bath is 30%; the temperature of the room-temperature coagulation bath is 29 °C, and the mass concentration of N,N-dimethylformamide in the room-temperature coagulation bath is 25%. The temperature of the heat treatment is 260 °C, the frequency of the oxygen plasma surface treatment is 1400 Hz, and the treatment time is 10 min; the length of the high-temperature resistant meta-aramid short cut fibers is 8 mm.

[0120] (4) The high-temperature resistant meta-aramid short cut fibers are put into deionized water and stirred, and a second dispersant with a mass concentration of 0.1% is added to disperse and mix evenly to obtain a high-temperature resistant meta-aramid short cut fiber slurry with a mass concentration of 0.2%; the meta-aramid precipitated fibers are emulsified and then beaten and dispersed to make a meta-aramid precipitated fiber slurry with a mass concentration of 0.5%; the high-temperature resistant meta-aramid short cut fiber slurry with a mass concentration of 0.2% and the meta-aramid precipitated fiber slurry with a mass concentration of 0.5% are mixed and stirred evenly to obtain a mixed slurry; the second dispersant is polyethylene oxide, and the rotation speed of the emulsification treatment is 15000 rpm and the time is 14 min.

[0121] (5) The mixed slurry in step (2) is sent to a double-layer composite inclined wire paper machine for papermaking. After the bottom web wet paper web is formed, it is combined with the top web wet paper web, and then undergoes pressing and drying to obtain the original aramid paper;

[0122] (6) The aramid paper base paper obtained in step (5) is fully dried and preheated through a tunnel-type hot air drying device, and then enters a roll-type hot press for two hot pressing treatments. The first hot pressing is at high temperature and low pressure, and the second hot pressing is at low temperature and high pressure. After the hot pressing is completed, an aramid paper for a resin-resistant infiltration honeycomb core material is obtained. The set temperature of the tunnel-type drying device is 210 °C. The temperature of the first hot pressing at high temperature and low pressure is 310 °C, the pressure is 170 N / mm, the vehicle speed is 25 m / min. The temperature of the second hot pressing at low temperature and high pressure is 240 °C, the pressure is 360 N / mm, and the vehicle speed is 25 m / min.

[0123] Comparative Example 2

[0124] The aramid paper for a honeycomb core material was prepared by the same method as in Example 5, except that: in this Comparative Example 2, high-temperature-resistant meta-aramid short fibers were not used, but conventional meta-aramid short fibers of the same size were used. The specific experimental process is as follows:

[0125] This Comparative Example exemplifies an aramid paper for a honeycomb core material, which is composed of the following raw materials in parts by weight: 47 parts of meta-precipitated fibers; 51 parts of conventional meta-aramid short fibers; 12 parts of aramid nanofibers.

[0126] A preparation method of an aramid paper for a honeycomb core material, comprising the following steps:

[0127] (1) The conventional meta-aramid short fibers are put into deionized water and stirred, and a second dispersant with a mass concentration of 0.1% is added and dispersed evenly by defibration to obtain a conventional meta-aramid short fiber slurry with a mass concentration of 0.2%; the meta-aramid precipitated fibers are emulsified and then beaten and dispersed to make a meta-aramid precipitated fiber slurry with a mass concentration of 0.5%; the conventional meta-aramid short fiber slurry with a mass concentration of 0.2% and the meta-aramid precipitated fiber slurry with a mass concentration of 0.5% are mixed, and after stirring evenly, a mixed slurry is obtained; the second dispersant is polyacrylamide, and the rotation speed of the emulsification treatment is 15000 rpm and the time is 14 min.

[0128] (2) The mixed slurry in step (1) is sent to a double-layer composite inclined wire paper machine for papermaking. After the bottom wire wet paper web is formed, an aramid nanofiber dispersion liquid is evenly sprayed on the upper surface of the bottom wire wet paper web by using a pressure spraying device, and then it is compounded with the top wire wet paper web, so that the aramid nanofibers are in the middle of the bottom wire wet paper web and the top wire wet paper web, and after pressing and drying, an aramid paper base paper is obtained; the aramid nanofibers are meta-aramid nanofibers with a diameter of 50 nm, and the components of the aramid nanofiber dispersion liquid are aramid nanofibers and deionized water, wherein the mass fraction of the aramid nanofibers is 0.14%.

[0129] (3) The aramid paper base paper obtained in step (2) is fully dried and preheated through a tunnel-type hot air drying equipment, and then enters a roll-type hot press for two hot pressing treatments. The first hot pressing is at high temperature and low pressure, and the second hot pressing is at low temperature and high pressure. After the hot pressing is completed, an aramid paper for honeycomb core material is obtained. The set temperature of the tunnel-type drying device is 210 °C, the temperature of the first hot pressing at high temperature and low pressure is 310 °C, the pressure is 170 N / mm, the vehicle speed is 25 m / min, the temperature of the second hot pressing at low temperature and high pressure is 240 °C, the pressure is 360 N / mm, and the vehicle speed is 25 m / min.

[0130] Comparative Example 3

[0131] The aramid paper for honeycomb core material was prepared by the same method as in Example 5, except that: in step (6) of this Comparative Example 3, two hot pressings were not carried out, and only one hot pressing operation at high temperature and high pressure was carried out, specifically as follows:

[0132] This degree ratio example illustrates an aramid paper for resin-resistant infiltration honeycomb core material, which is composed of the following raw materials in parts by weight: 47 parts of meta-precipitated fiber; 51 parts of high-temperature-resistant meta-aramid short-cut fiber; 12 parts of aramid nanofiber.

[0133] A preparation method of an aramid paper for resin-resistant infiltration honeycomb core material, comprising the following steps:

[0134] (1) In a nitrogen atmosphere, in a system with N,N-dimethylformamide as an organic solvent, solution polymerization is carried out with isophthaloyl chloride and m-phenylenediamine to obtain a meta-aromatic polyamide solution containing isophthaloyl m-phenylenediamine as a repeating unit, and calcium oxide is used to neutralize the hydrochloric acid generated by the reaction to obtain a meta-aramid polymerization solution; the solid content of the meta-aramid polymerization solution is 25%, and the viscosity (25 °C) is 600 P;

[0135] (2) Add the high-temperature-resistant functional powder and the first dispersant to the N,N-dimethylformamide solvent and stir evenly to obtain a dispersion liquid containing the high-temperature-resistant functional powder; the high-temperature-resistant functional powder is a combination of aluminum diethylphosphinate powder and boron nitride powder, and the corresponding weight ratio is 1:3. The first dispersant is polymethacrylic acid. The mass content of the high-temperature-resistant functional powder in the dispersion liquid is 32%, and the mass content of the first dispersant in the dispersion liquid is 2.0%.

[0136] (3) Mix the meta-aramid polymerization solution in step (1) with the dispersion in step (2) and stir evenly to obtain a spinning solution. The mass ratio of the dispersion to the meta-aramid polymerization solution is 1:16. The spinning solution is spun by wet spinning, and then through a high-temperature coagulation bath, a room-temperature coagulation bath, water washing, drying, heat treatment, oxygen plasma surface treatment, crimping and cutting processes to obtain high-temperature resistant meta-aramid short cut fibers; the temperature of the high-temperature coagulation bath is 85 °C, and the mass concentration of N,N-dimethylformamide in the high-temperature coagulation bath is 30%; the temperature of the room-temperature coagulation bath is 29 °C, and the mass concentration of N,N-dimethylformamide in the room-temperature coagulation bath is 25%. The temperature of the heat treatment is 260 °C, the frequency of the oxygen plasma surface treatment is 1400 Hz, and the treatment time is 10 min; the length of the high-temperature resistant meta-aramid short cut fibers is 8 mm.

[0137] (4) Put the high-temperature resistant meta-aramid short cut fibers into deionized water and stir, add a second dispersant with a mass concentration of 0.1% for uniform dispersion and defibration to obtain a high-temperature resistant meta-aramid short cut fiber slurry with a mass concentration of 0.2%; emulsify the meta-aramid precipitated fibers, and then beat and disperse them to make a meta-aramid precipitated fiber slurry with a mass concentration of 0.5%; mix the high-temperature resistant meta-aramid short cut fiber slurry with a mass concentration of 0.2% and the meta-aramid precipitated fiber slurry with a mass concentration of 0.5%, and stir evenly to obtain a mixed slurry; the second dispersant is polyethylene oxide, the rotation speed of the emulsification treatment is 15000 rpm, and the time is 14 min.

[0138] (5) Feed the mixed slurry in step (4) to a double-layer composite inclined wire paper machine for papermaking. After the bottom wire wet paper web is formed, use a pressure spraying device to evenly spray the aramid nanofiber dispersion on the upper surface of the bottom wire wet paper web, and then composite it with the top wire wet paper web so that the aramid nanofibers are in the middle of the bottom wire wet paper web and the top wire wet paper web, and obtain the aramid paper base paper after pressing and drying; the aramid nanofibers are meta-aramid nanofibers with a diameter of 50 nm, and the components of the aramid nanofiber dispersion are aramid nanofibers and deionized water, and the mass fraction of the aramid nanofibers is 0.14%.

[0139] (6) Thoroughly dry and preheat the aramid paper base paper obtained in step (5) through a tunnel-type hot air drying device, and then enter a roll-type hot press for a single hot pressing treatment, that is, a high-temperature and high-pressure hot pressing treatment. After the hot pressing is completed, an aramid paper for honeycomb core material is obtained. The set temperature of the drying device in the drying channel is 210 °C, the temperature of the high-temperature and high-pressure hot pressing treatment is 310 °C, the pressure is 360 N / mm, and the vehicle speed is 25 m / min.

[0140] Comparative Example 4

[0141] The aramid paper for honeycomb core material was prepared by the same method as in Example 5, except that: in step (6) of this Comparative Example 4, two hot presses were not carried out, and only one hot press operation at low temperature and low pressure was carried out, specifically as follows:

[0142] This comparative example exemplifies an aramid paper for a resin-resistant infiltration type honeycomb core material, which is composed of the following raw materials in parts by weight: 47 parts of meta-precipitated fiber; 51 parts of high-temperature-resistant meta-aramid short fibers; 12 parts of aramid nanofibers.

[0143] A method for preparing an aramid paper for a resin-resistant infiltration type honeycomb core material, comprising the following steps:

[0144] (1) In a nitrogen atmosphere, in a system with N,N-dimethylformamide as an organic solvent, solution polymerization was carried out using isophthaloyl chloride and m-phenylenediamine to obtain a meta-aromatic polyamide solution containing isophthaloyl m-phenylenediamine as a repeating unit, and calcium oxide was used to neutralize the hydrochloric acid generated by the reaction to obtain a meta-aramid polymerization solution; the solid content of the meta-aramid polymerization solution was 25%, and the viscosity (25°C) was 600P;

[0145] (2) The high-temperature-resistant functional powder and the first dispersant were added to the N,N-dimethylformamide solvent and stirred evenly to obtain a dispersion liquid containing the high-temperature-resistant functional powder; the high-temperature-resistant functional powder was a combination of aluminum diethylphosphinate powder and boron nitride powder, and the corresponding weight ratio was 1:3. The first dispersant was polymethacrylic acid. The mass content of the high-temperature-resistant functional powder in the dispersion liquid was 32%, and the mass content of the first dispersant in the dispersion liquid was 2.0%.

[0146] (3) The meta-aramid polymerization solution in step (1) was mixed with the dispersion liquid in step (2) and stirred evenly to obtain a spinning solution. The mass ratio of the dispersion liquid to the meta-aramid polymerization solution was 1:16. The spinning solution was spun by wet spinning, and then passed through a high-temperature coagulation bath, a room-temperature coagulation bath, water washing, drying, heat treatment, oxygen plasma surface treatment, crimping and cutting processes to obtain high-temperature-resistant meta-aramid short fibers; the temperature of the high-temperature coagulation bath was 85°C, and the mass concentration of N,N-dimethylformamide in the high-temperature coagulation bath was 30%; the temperature of the room-temperature coagulation bath was 29°C, and the mass concentration of N,N-dimethylformamide in the room-temperature coagulation bath was 25%. The temperature of the heat treatment was 260°C, the frequency of the oxygen plasma surface treatment was 1400Hz, and the treatment time was 10min; the length of the high-temperature-resistant meta-aramid short fibers was 8mm.

[0147] (4) Put the high-temperature resistant meta-aramid short-cut fibers into deionized water and stir. Add a second dispersant with a mass concentration of 0.1% and disperse evenly by defibration to obtain a high-temperature resistant meta-aramid short-cut fiber slurry with a mass concentration of 0.2%. Emulsify the meta-aramid precipitated fibers, and then beat and disperse them to make a meta-aramid precipitated fiber slurry with a mass concentration of 0.5%. Mix the high-temperature resistant meta-aramid short-cut fiber slurry with a mass concentration of 0.2% and the meta-aramid precipitated fiber slurry with a mass concentration of 0.5%, and stir evenly to obtain a mixed slurry. The second dispersant is polyethylene oxide. The rotation speed of the emulsification treatment is 15,000 rpm, and the time is 14 min.

[0148] (5) Feed the mixed slurry in step (4) to a double-layer composite inclined wire paper machine for papermaking. After the bottom wire wet paper web is formed, use a pressure spraying device to evenly spray the aramid nanofiber dispersion liquid on the upper surface of the bottom wire wet paper web, and then composite it with the top wire wet paper web so that the aramid nanofibers are in the middle of the bottom wire wet paper web and the top wire wet paper web. After pressing and drying, obtain the aramid paper base paper. The aramid nanofibers are meta-aramid nanofibers with a diameter of 50 nm. The components of the aramid nanofiber dispersion liquid are aramid nanofibers and deionized water, and the mass fraction of the aramid nanofibers is 0.14%.

[0149] (6) Fully dry and preheat the aramid paper base paper obtained in step (5) through a tunnel-type hot drying equipment, and then enter a roll-type hot press for a single hot pressing treatment, that is, a high and low temperature and low pressure hot pressing treatment. After the hot pressing is completed, an aramid paper for honeycomb core material is obtained. The set temperature of the drying device of the drying tunnel is 210 °C, the temperature of the low temperature and low pressure hot pressing treatment is 240 °C, the pressure is 170 N / mm, and the vehicle speed is 25 m / min.

[0150] Comparative Example 5

[0151] Use the same method as in Example 5 to prepare the aramid paper for honeycomb core material, the difference is that: in this Comparative Example 5, the high-temperature resistant functional powder is only boron nitride powder, specifically as follows:

[0152] This example illustrates an aramid paper for resin infiltration-resistant honeycomb core material, which is composed of the following raw materials in parts by weight: 47 parts of meta-aramid precipitated fibers; 51 parts of high-temperature resistant meta-aramid short-cut fibers; 12 parts of aramid nanofibers.

[0153] A preparation method of an aramid paper for resin infiltration-resistant honeycomb core material, comprising the following steps:

[0154] (1) In a nitrogen atmosphere, in a system with N,N-dimethylformamide as an organic solvent, solution polymerization is carried out using isophthaloyl chloride and m-phenylenediamine to obtain a meta-aramid solution containing isophthaloyl m-phenylenediamine as a repeating unit. Calcium oxide is used to neutralize the hydrochloric acid generated by the reaction to obtain a meta-aramid polymerization solution; the solid content of the meta-aramid polymerization solution is 25%, and the viscosity (25 °C) is 600 P;

[0155] (2) The high-temperature resistant functional powder and the first dispersant are added to the N,N-dimethylformamide solvent and stirred evenly to obtain a dispersion liquid containing the high-temperature resistant functional powder; the high-temperature resistant functional powder is boron nitride powder; the first dispersant is polymethacrylic acid. The mass content of the high-temperature resistant functional powder in the dispersion liquid is 32%, and the mass content of the first dispersant in the dispersion liquid is 2.0%.

[0156] (3) The meta-aramid polymerization solution in step (1) is mixed with the dispersion liquid in step (2) and stirred evenly to obtain a spinning solution. The mass ratio of the dispersion liquid to the meta-aramid polymerization solution is 1:16. The spinning solution is spun by wet spinning, and then undergoes a high-temperature coagulation bath, a room-temperature coagulation bath, water washing, drying, heat treatment, oxygen plasma surface treatment, crimping and cutting processes to obtain high-temperature resistant meta-aramid short cut fibers; the temperature of the high-temperature coagulation bath is 85 °C, and the mass concentration of N,N-dimethylformamide in the high-temperature coagulation bath is 30%; the temperature of the room-temperature coagulation bath is 29 °C, and the mass concentration of N,N-dimethylformamide in the room-temperature coagulation bath is 25%. The temperature of the heat treatment is 260 °C, the frequency of the oxygen plasma surface treatment is 1400 Hz, and the treatment time is 10 min; the length of the high-temperature resistant meta-aramid short cut fibers is 8 mm.

[0157] (4) The high-temperature resistant meta-aramid short cut fibers are put into deionized water and stirred, and a second dispersant with a mass concentration of 0.1% is added to disperse and dissolve evenly to obtain a high-temperature resistant meta-aramid short cut fiber slurry with a mass concentration of 0.2%; the meta-aramid precipitated fibers are emulsified and then beaten and dispersed to make a meta-aramid precipitated fiber slurry with a mass concentration of 0.5%; the high-temperature resistant meta-aramid short cut fiber slurry with a mass concentration of 0.2% and the meta-aramid precipitated fiber slurry with a mass concentration of 0.5% are mixed and stirred evenly to obtain a mixed slurry; the second dispersant is polyethylene oxide, the rotation speed of the emulsification treatment is 15000 rpm, and the time is 14 min.

[0158] (5) Feed the mixed slurry from step (4) to a double-layer composite inclined wire paper machine for papermaking. After the bottom wire wet paper web is formed, evenly spray the aramid nanofiber dispersion liquid on the upper surface of the bottom wire wet paper web using a pressure spraying device, and then composite it with the top wire wet paper web, so that the aramid nanofibers are in the middle of the bottom wire wet paper web and the top wire wet paper web. After pressing and drying, obtain the aramid paper base paper; the aramid nanofibers are meta-aramid nanofibers with a diameter of 50 nm, and the aramid nanofiber dispersion liquid consists of aramid nanofibers and deionized water, wherein the mass fraction of aramid nanofibers is 0.14%.

[0159] (6) Sufficiently dry and preheat the aramid paper base paper obtained in step (5) through a tunnel-type hot drying device, and then enter a roll-type hot press for two hot pressing treatments. The first hot pressing is at high temperature and low pressure, and the second hot pressing is at low temperature and high pressure. After the hot pressing is completed, an aramid paper for honeycomb core material is obtained. The set temperature of the drying device in the drying tunnel is 210 °C, the temperature of the first hot pressing at high temperature and low pressure is 310 °C, the pressure is 170 N / mm, the vehicle speed is 25 m / min, the temperature of the second hot pressing at low temperature and high pressure is 240 °C, the pressure is 360 N / mm, and the vehicle speed is 25 m / min.

[0160] Comparative Example 6

[0161] Prepare the aramid paper for honeycomb core material by the same method as in Example 5, except that: in this Comparative Example 6, the high-temperature resistant functional powder is only aluminum diethylphosphinate powder, specifically as follows:

[0162] This example of the proportion demonstrates an aramid paper for resin-resistant infiltration honeycomb core material, which is composed of the following raw materials in parts by weight: 47 parts of meta-precipitated fiber; 51 parts of high-temperature resistant meta-aramid short fibers; 12 parts of aramid nanofibers.

[0163] A preparation method of an aramid paper for resin-resistant infiltration honeycomb core material, comprising the following steps:

[0164] (1) In a nitrogen atmosphere, in a system with N,N-dimethylformamide as an organic solvent, carry out solution polymerization using isophthaloyl chloride and m-phenylenediamine to obtain a meta-aromatic polyamide solution containing isophthaloyl m-phenylenediamine as a repeating unit, and use calcium oxide to neutralize the generated hydrochloric acid to obtain a meta-aramid polymerization solution; the solid content of the meta-aramid polymerization solution is 25%, and the viscosity (25 °C) is 600 P;

[0165] (2) Add the high-temperature resistant functional powder and the first dispersant into the N,N-dimethylformamide solvent and stir evenly to obtain a dispersion containing the high-temperature resistant functional powder; the high-temperature resistant functional powder is aluminum diethylphosphinate powder; the first dispersant is polymethacrylic acid. The mass content of the high-temperature resistant functional powder in the dispersion is 32%, and the mass content of the first dispersant in the dispersion is 2.0%.

[0166] (3) Mix the meta-aramid polymerization liquid in step (1) with the dispersion in step (2) and stir evenly to obtain a spinning solution. The mass ratio of the dispersion to the meta-aramid polymerization liquid is 1:16. The spinning solution is spun by wet spinning, and then undergoes a high-temperature coagulation bath, a room-temperature coagulation bath, water washing, drying, heat treatment, oxygen plasma surface treatment, crimping and cutting processes to obtain high-temperature resistant meta-aramid short cut fibers; the temperature of the high-temperature coagulation bath is 85°C, and the mass concentration of N,N-dimethylformamide in the high-temperature coagulation bath is 30%; the temperature of the room-temperature coagulation bath is 29°C, and the mass concentration of N,N-dimethylformamide in the room-temperature coagulation bath is 25%. The temperature of the heat treatment is 260°C, the frequency of the oxygen plasma surface treatment is 1400 Hz, and the treatment time is 10 min; the length of the high-temperature resistant meta-aramid short cut fibers is 8 mm.

[0167] (4) Put the high-temperature resistant meta-aramid short cut fibers into deionized water and stir, add a second dispersant with a mass concentration of 0.1% and disperse evenly by defibration to obtain a high-temperature resistant meta-aramid short cut fiber slurry with a mass concentration of 0.2%; emulsify the meta-aramid precipitated fibers, and then beat and disperse them to make a meta-aramid precipitated fiber slurry with a mass concentration of 0.5%; mix the high-temperature resistant meta-aramid short cut fiber slurry with a mass concentration of 0.2% and the meta-aramid precipitated fiber slurry with a mass concentration of 0.5%, and stir evenly to obtain a mixed slurry; the second dispersant is polyethylene oxide, the rotation speed of the emulsification treatment is 15000 rpm, and the time is 14 min.

[0168] (5) Feed the mixed slurry in step (4) to a double-layer composite inclined wire paper machine for papermaking. After the bottom wire wet paper web is formed, use a pressure spraying device to evenly spray the aramid nanofiber dispersion on the upper surface of the bottom wire wet paper web, and then compound it with the top wire wet paper web, so that the aramid nanofibers are in the middle of the bottom wire wet paper web and the top wire wet paper web, and obtain the aramid paper base paper after pressing and drying; the aramid nanofibers are meta-aramid nanofibers with a diameter of 50 nm, and the components of the aramid nanofiber dispersion are aramid nanofibers and deionized water, and the mass fraction of the aramid nanofibers is 0.14%.

[0169] (6) The aramid paper base paper obtained in step (5) is fully dried and preheated through a tunnel-type hot drying device, and then enters a roller-type hot press for two hot pressing treatments. The first hot pressing is at high temperature and low pressure, and the second hot pressing is at low temperature and high pressure. After the hot pressing is completed, an aramid paper for honeycomb core material is obtained. The set temperature of the tunnel-type drying device is 210°C, the temperature of the first hot pressing at high temperature and low pressure is 310°C, the pressure is 170 N / mm, the vehicle speed is 25 m / min, the temperature of the second hot pressing at low temperature and high pressure is 240°C, the pressure is 360 N / mm, and the vehicle speed is 25 m / min.

[0170] Comparative Example 7

[0171] The aramid paper for honeycomb core material was prepared by the same method as in Example 5, except that: in this Comparative Example 7, the meta-aramid precipitated fiber was not emulsified, specifically as follows:

[0172] This example exemplifies an aramid paper for resin-resistant infiltration honeycomb core material, which is composed of the following raw materials in parts by weight: 47 parts of meta-precipitated fiber; 51 parts of high-temperature-resistant meta-aramid short-cut fiber; 12 parts of aramid nanofiber.

[0173] A preparation method of an aramid paper for resin-resistant infiltration honeycomb core material includes the following steps:

[0174] (1) In a nitrogen atmosphere, in a system with N,N-dimethylformamide as an organic solvent, isophthaloyl chloride and m-phenylenediamine are subjected to solution polymerization to obtain a meta-aromatic polyamide solution containing isophthaloyl m-phenylenediamine as a repeating unit, and calcium oxide is used to neutralize the generated hydrochloric acid to obtain a meta-aramid polymerization solution; the solid content of the meta-aramid polymerization solution is 25%, and the viscosity (25°C) is 600 P;

[0175] (2) The high-temperature-resistant functional powder and the first dispersant are added to the N,N-dimethylformamide solvent and stirred evenly to obtain a dispersion liquid containing the high-temperature-resistant functional powder; the high-temperature-resistant functional powder is a combination of aluminum diethylphosphinate powder and boron nitride powder, and the corresponding weight ratio is 1:3. The first dispersant is polymethacrylic acid. The mass content of the high-temperature-resistant functional powder in the dispersion liquid is 32%, and the mass content of the first dispersant in the dispersion liquid is 2.0%.

[0176] (3) Mix the meta-aramid polymerization solution in step (1) with the dispersion in step (2) and stir evenly to obtain a spinning solution. The mass ratio of the dispersion to the meta-aramid polymerization solution is 1:16. The spinning solution is spun by wet spinning, and then through a high-temperature coagulation bath, a room-temperature coagulation bath, water washing, drying, heat treatment, oxygen plasma surface treatment, crimping and cutting processes to obtain high-temperature-resistant meta-aramid short cut fibers; the temperature of the high-temperature coagulation bath is 85 °C, and the mass concentration of N,N-dimethylformamide in the high-temperature coagulation bath is 30%; the temperature of the room-temperature coagulation bath is 29 °C, and the mass concentration of N,N-dimethylformamide in the room-temperature coagulation bath is 25%. The temperature of the heat treatment is 260 °C, the frequency of the oxygen plasma surface treatment is 1400 Hz, and the treatment time is 10 min; the length of the high-temperature-resistant meta-aramid short cut fibers is 8 mm.

[0177] (4) Put the high-temperature-resistant meta-aramid short cut fibers into deionized water and stir, add a second dispersant with a mass concentration of 0.1% and disperse evenly to obtain a high-temperature-resistant meta-aramid short cut fiber slurry with a mass concentration of 0.2%; beat and disperse the meta-aramid precipitated fibers to make a meta-aramid precipitated fiber slurry with a mass concentration of 0.5%; mix the high-temperature-resistant meta-aramid short cut fiber slurry with a mass concentration of 0.2% and the meta-aramid precipitated fiber slurry with a mass concentration of 0.5%, and stir evenly to obtain a mixed slurry; the second dispersant is polyethylene oxide.

[0178] (5) Feed the mixed slurry in step (4) to a double-layer composite inclined wire paper machine for papermaking. After the bottom wire wet paper web is formed, use a pressure spraying device to evenly spray the aramid nanofiber dispersion on the upper surface of the bottom wire wet paper web, and then compound it with the top wire wet paper web so that the aramid nanofibers are in the middle of the bottom wire wet paper web and the top wire wet paper web, and obtain the aramid paper base paper after pressing and drying; the aramid nanofibers are meta-aramid nanofibers with a diameter of 50 nm, and the components of the aramid nanofiber dispersion are aramid nanofibers and deionized water, and the mass fraction of the aramid nanofibers is 0.14%.

[0179] (6) Subject the aramid paper base paper obtained in step (5) to sufficient drying and preheating through a tunnel-type hot air drying device, and then enter a roll-type hot press for two hot pressing treatments. The first hot pressing is high temperature and low pressure, and the second hot pressing is low temperature and high pressure. After the hot pressing is completed, an aramid paper for honeycomb core material is obtained. The set temperature of the drying device in the drying tunnel is 210 °C, the temperature of the first hot pressing at high temperature and low pressure is 310 °C, the pressure is 170 N / mm, the vehicle speed is 25 m / min, the temperature of the second hot pressing at low temperature and high pressure is 240 °C, the pressure is 360 N / mm, and the vehicle speed is 25 m / min.

[0180] Comparative Example 8

[0181] The aramid paper for honeycomb core material was prepared by the same method as in Example 5, except that in this Comparative Example 8, no oxygen plasma surface treatment was carried out during the preparation of the high-temperature resistant meta-aramid short fibers, specifically as follows:

[0182] This example exemplifies an aramid paper for resin-resistant honeycomb core material, which is composed of the following raw materials in parts by weight: 47 parts of meta-precipitated fibers; 51 parts of high-temperature resistant meta-aramid short fibers; 12 parts of aramid nanofibers.

[0183] A method for preparing an aramid paper for resin-resistant honeycomb core material includes the following steps:

[0184] (1) In a nitrogen atmosphere, in a system with N,N-dimethylformamide as an organic solvent, solution polymerization was carried out using isophthaloyl chloride and m-phenylenediamine to obtain a meta-aromatic polyamide solution containing isophthaloyl m-phenylenediamine as a repeating unit, and calcium oxide was used to neutralize the hydrochloric acid generated in the reaction to obtain a meta-aramid polymerization solution; the solid content of the meta-aramid polymerization solution is 25%, and the viscosity (25 °C) is 600 P;

[0185] (2) The high-temperature resistant functional powder and the first dispersant were added to the N,N-dimethylformamide solvent and stirred evenly to obtain a dispersion liquid containing the high-temperature resistant functional powder; the high-temperature resistant functional powder is a combination of aluminum diethylphosphinate powder and boron nitride powder, and the corresponding weight ratio is 1:3. The first dispersant is polymethacrylic acid. The mass content of the high-temperature resistant functional powder in the dispersion liquid is 32%, and the mass content of the first dispersant in the dispersion liquid is 2.0%.

[0186] (3) The meta-aramid polymerization solution in step (1) was mixed with the dispersion liquid in step (2) and stirred evenly to obtain a spinning solution. The mass ratio of the dispersion liquid to the meta-aramid polymerization solution is 1:16. The spinning solution was spun by wet spinning, and then passed through a high-temperature coagulation bath, a room-temperature coagulation bath, water washing, drying, heat treatment, crimping and cutting processes to obtain high-temperature resistant meta-aramid short fibers; the temperature of the high-temperature coagulation bath is 85 °C, and the mass concentration of N,N-dimethylformamide in the high-temperature coagulation bath is 30%; the temperature of the room-temperature coagulation bath is 29 °C, and the mass concentration of N,N-dimethylformamide in the room-temperature coagulation bath is 25%. The temperature of the heat treatment is 260 °C, and the length of the high-temperature resistant meta-aramid short fibers is 8 mm.

[0187] (4) Put the high-temperature resistant meta-aramid short cut fibers into deionized water and stir. Add the second dispersant with a mass concentration of 0.1% and disperse them evenly by defibration to obtain a high-temperature resistant meta-aramid short cut fiber slurry with a mass concentration of 0.2%. Beat and disperse the meta-aramid precipitated fibers to make a meta-aramid precipitated fiber slurry with a mass concentration of 0.5%. Mix the high-temperature resistant meta-aramid short cut fiber slurry with a mass concentration of 0.2% and the meta-aramid precipitated fiber slurry with a mass concentration of 0.5%, and stir evenly to obtain a mixed slurry. The second dispersant is polyethylene oxide.

[0188] (5) Feed the mixed slurry in step (4) to a double-layer composite inclined wire paper machine for papermaking. After the bottom wire wet paper web is formed, use a pressure spraying device to evenly spray the aramid nanofiber dispersion liquid on the upper surface of the bottom wire wet paper web, and then composite it with the top wire wet paper web so that the aramid nanofibers are in the middle of the bottom wire wet paper web and the top wire wet paper web. After pressing and drying, obtain the aramid paper base paper. The aramid nanofibers are meta-aramid nanofibers with a diameter of 50 nm. The components of the aramid nanofiber dispersion liquid are aramid nanofibers and deionized water, and the mass fraction of the aramid nanofibers is 0.14%.

[0189] (6) Subject the aramid paper base paper obtained in step (5) to sufficient drying and preheating through a tunnel-type hot air drying equipment, and then enter a roll-type hot press for two hot pressing treatments. The first hot pressing is at high temperature and low pressure, and the second hot pressing is at low temperature and high pressure. After the hot pressing is completed, an aramid paper for honeycomb core material is obtained. The set temperature of the tunnel-type drying device is 210 °C. The temperature of the first hot pressing at high temperature and low pressure is 310 °C, the pressure is 170 N / mm, the paper speed is 25 m / min. The temperature of the second hot pressing at low temperature and high pressure is 240 °C, the pressure is 360 N / mm, and the paper speed is 25 m / min.

[0190] Conduct relevant performance tests on the aramid paper samples prepared in the above examples and comparative examples before and after impregnating with resin. The impregnating resin is phenolic resin (PR type), provided by Nantong Sumitomo Bakelite Co., Ltd. The specific test results are shown in Table 1 below. The specific test methods involved are:

[0191] Detect the basis weight of the aramid paper samples according to the GB / T 451.2-2002 standard, and calculate the impregnated sizing amount according to (basis weight after impregnation - basis weight before impregnation) / basis weight before impregnation.

[0192] Detect the tearing strength of the aramid paper samples according to the GB / T455-2001 standard.

[0193] Table 1 Performance test data of aramid papers prepared in examples and comparative examples

[0194]

[0195] According to the data in Table 1, it can be seen that Examples 1-5 all showed a low impregnation sizing amount, indicating that the overall compactness of the aramid paper is good, and the tear strength before and after impregnation can be maintained at a high level.

[0196] From the comparison of the data of Comparative Example 1 and Example 5, it can be seen that: if aramid nanofibers are not added during the papermaking process, the impregnation sizing amount of the aramid paper increases significantly, and the tear strength before and after impregnation is also at a low level. This shows that aramid nanofibers can reduce the porosity of the aramid paper and reduce the amount of resin entering the interior of the aramid paper.

[0197] From the comparison of the data of Comparative Example 2 and Example 5, it can be seen that: if high-temperature resistant meta-aramid short cut fibers are not used, but conventional meta-aramid short cut fibers of the same size are used, the impregnation sizing amount of the aramid paper increases slightly, but the tear strength before and after impregnation decreases significantly. This shows that the high-temperature resistant meta-aramid short cut fibers prepared by the present invention can effectively improve the tear strength of the aramid paper before and after impregnating with resin.

[0198] From the comparison of the data of Comparative Example 3 and Example 5, it can be seen that: if only one hot pressing operation under high temperature and high pressure is carried out, the impregnation sizing amount does not change significantly, but the tear strength before and after impregnation decreases significantly. This shows that the hot pressing method under high temperature and high pressure will cause a certain degree of damage to the strength and structure of the aramid paper.

[0199] From the comparison of the data of Comparative Example 4 and Example 5, it can be seen that: if only one hot pressing operation under low temperature and low pressure is carried out, the impregnation sizing amount increases significantly, and the tear strength before and after impregnation decreases significantly. This shows that the hot pressing method under low temperature and low pressure cannot effectively plasticize the aramid paper, and the overall compactness and mechanical strength of the aramid paper are poor.

[0200] From the comparison of the data of Comparative Example 5, Comparative Example 6 and Example 5, it can be seen that: if the high-temperature resistant functional powder is only aluminum diethylphosphinate powder or only boron nitride powder, the tear strength before and after impregnation decreases significantly. This shows that the combination of the two has a synergistic effect, and when used alone, both will reduce the strength and resin infiltration resistance of the aramid paper.

[0201] From the comparison of the data of Comparative Example 7 and Example 5, it can be seen that: if the meta-aramid precipitated fibers are not emulsified, the size of the aramid precipitated fibers is too large, which is not conducive to the combination between aramid fibers, resulting in a slight increase in the impregnation sizing amount of the aramid paper, and the tear strength before and after impregnation decreases significantly.

[0202] From the data comparison between Comparative Example 8 and Example 5, it can be seen that: if the oxygen plasma surface treatment is not carried out during the preparation of the high-temperature resistant meta-aramid short fibers, the hydrophilicity and surface activity of the high-temperature resistant meta-aramid short fibers are poor, which is not conducive to the dispersion of the fibers during the pulping process and the bonding between the aramid fibers, resulting in a significant increase in the sizing amount after the aramid paper is impregnated with the resin and a significant decrease in the tear strength before and after impregnation.

[0203] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, all possible combinations of the technical features in the above-described embodiments are not exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0204] For those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. The protection scope of the present invention shall be subject to the appended claims.

Claims

1. A method for preparing aramid paper for resin-impregnated honeycomb core material, characterized in that: The preparation method is: S1, adding the high temperature resistant functional powder and the first dispersant into a solvent and mixing them evenly to obtain a dispersion containing the high temperature resistant functional powder; and mixing the dispersion containing the high temperature resistant functional powder and the meta-aramid polymer solution evenly to obtain a spinning solution; The high temperature resistant functional powder is aluminum diethylphosphinate powder and boron nitride powder; S2, spinning the spinning solution by wet spinning, and then going through a high-temperature coagulation bath, a room-temperature coagulation bath, washing, drying, heat treatment, oxygen plasma surface treatment, curling and cutting process to obtain high-temperature resistant meta-aramid short fibers; S3, preparing a high temperature resistant meta-aramid chopped fiber slurry by mixing the high temperature resistant meta-aramid chopped fiber in water; preparing meta-aramid fibrid into meta-aramid fibrid slurry; The high temperature resistant meta-aramid chopped fiber slurry and the meta-aramid fibrid slurry are uniformly mixed to obtain a mixed slurry; S4, sending the mixed slurry to a double-layer composite inclined wire paper machine for papermaking, after the bottom wire wet paper web is formed, spraying the aramid nanofiber dispersion on the upper surface of the bottom wire wet paper web, and then compounding it with the surface wire wet paper web, so that the aramid nanofiber is located between the bottom wire wet paper web and the surface wire wet paper web, and obtaining the aramid paper base paper after pressing and drying; S5. After being dried and preheated, the aramid paper base paper is subjected to two hot pressing processes to obtain the aramid paper for the resin impregnation resistant honeycomb core material.

2. The method for preparing the aramid paper for the resin impregnation resistant honeycomb core material according to claim 1, characterized in that: In step S1, the mass ratio of the aluminum diethylphosphinate powder to the boron nitride powder is 1:(2-3); The first dispersant is any one of polymethacrylic acid and polyvinyl pyrrolidone.

3. The method for preparing the aramid paper for the resin impregnation resistant honeycomb core material according to claim 1, characterized in that: In step S1, the solvent in the meta-aramid polymer solution is N,N-dimethylformamide; the solvent for preparing the dispersion is N,N-dimethylformamide; The meta-aramid polymer solution has a solid content of 25-28% and a viscosity of 450-650P at 25°C; The mass content of the high temperature resistant functional powder in the dispersion is 20-35%, and the mass content of the first dispersant in the dispersion is 1.0-2.5%; The mass ratio of the dispersion to the meta-aramid polymer solution is 1:(13-18).

4. The method for preparing the aramid paper for the resin impregnation resistant honeycomb core material according to claim 1, characterized in that: In step S2, the temperature of the high temperature coagulation bath is 50-90°C, the high temperature coagulation bath is N,N-dimethylformamide and water, and the mass concentration of N,N-dimethylformamide in the high temperature coagulation bath is 28-32%; The temperature of the room temperature coagulation bath is 20-30° C. The room temperature coagulation bath is N,N-dimethylformamide and water. The mass concentration of N,N-dimethylformamide in the room temperature coagulation bath is 25-30%.

5. The method for preparing the aramid paper for the resin impregnation resistant honeycomb core material according to claim 1, characterized in that: In step S2, the heat treatment temperature is 250-350°C; the oxygen plasma surface treatment equipment is an inductively coupled plasma generator, the treatment frequency is 1000-1300 Hz, and the treatment time is 8-10 min; the length of the high temperature resistant meta-aramid chopped fibers is 5-8 mm.

6. The method for preparing the aramid paper for the resin impregnation resistant honeycomb core material according to claim 1, characterized in that: In step S3, the preparation method of the high temperature resistant meta-aramid short fiber slurry is as follows: the high temperature resistant meta-aramid short fiber is placed in deionized water for stirring, and a second dispersant is added to disperse the fibers uniformly to obtain a high temperature resistant meta-aramid short fiber slurry with a mass concentration of 0.2%-1.0%, wherein the mass content of the second dispersant in the high temperature resistant meta-aramid short fiber slurry is 0.1-0.5%; the second dispersant is any one of polyethylene oxide and polyacrylamide; The preparation method of the meta-aramid fibrillation slurry is as follows: the meta-aramid fibrillation is emulsified by a high-speed shearing emulsifier, the processing speed is 13000-15000rpm, and the processing time is 10-15min; then the meta-aramid fibrillation slurry with a mass concentration of 0.5%-1.5% is prepared by beating and dispersing; the size distribution of the meta-aramid fibrillation is 40-120 meshes.

7. The method for preparing the aramid paper for the resin impregnation resistant honeycomb core material according to claim 1, characterized in that: The aramid nanofiber dispersion comprises aramid nanofibers and deionized water, wherein the mass fraction of the aramid nanofibers in the aramid nanofiber dispersion is 0.05-0.20%; The aramid nanofiber is any one of meta-aramid nanofiber and para-aramid nanofiber, and the diameter of the aramid nanofiber is 40-100 nm.

8. The method for preparing the aramid paper for the resin impregnation resistant honeycomb core material according to claim 1, characterized in that: In step S5, drying and preheating are performed using a drying tunnel drying device, and the drying and preheating temperature is 200-260°C; The two hot pressing steps include a first high-temperature and low-pressure hot pressing operation and a second low-temperature and high-pressure hot pressing operation. The temperature of the first high-temperature and low-pressure hot pressing operation is 290-340°C, the pressure is 120-180N / mm, and the vehicle speed is 15-30m / min; the temperature of the second low-temperature and high-pressure hot pressing operation is 230-270°C, the pressure is 350-400N / mm, and the vehicle speed is 15~30m / min.

9. The method for preparing the aramid paper for the resin impregnation resistant honeycomb core material according to claim 1, characterized in that: In the process of preparing the aramid paper, the meta-aramid fibrids are 30-50 parts by weight, the high temperature resistant meta-aramid chopped fibers are 50-70 parts by weight, and the aramid nanofibers are 8-15 parts by weight.

10. A resin-impregnated aramid paper for honeycomb core material, characterized in that: The aramid paper is prepared according to the preparation method according to any one of claims 1 to 9.

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