Aramid aerogel insulation board and preparation method thereof

Abstract

The present invention relates to the technical field of thermal insulation materials, and specifically to an aramid aerogel insulation board and a preparation method thereof, belonging to the technical field. The preparation method comprises: performing a polymerization reaction between an aromatic diamine and an aromatic dicarboxylic acid chloride in a polar solvent to obtain an aramid stock solution; diluting the aramid stock solution to a certain viscosity with a polar solvent, adding a gelling agent, and uniformly dispersing and stirring to obtain a core layer microfiber dispersion; diluting the aramid stock solution to a certain viscosity with a polar solvent to obtain a shell layer liquid; forming the core layer from the core layer microfiber dispersion into a core layer by a template freeze molding method, immersing the core layer into the shell layer liquid, and then removing the core layer for coagulation bath molding to obtain a precursor; and washing and freeze-drying the precursor to obtain the insulation board. The aramid aerogel insulation board has good thermal insulation performance, high flame retardancy, and high strength performance, and has a single material component and is easy to use.

Description

Technical Field

[0001] The invention relates to an aramid aerogel insulation board and a preparation method thereof, belonging to the technical field of thermal insulation materials. Background Art

[0002] Insulation board is a functional material board used to reduce heat transfer. It is widely used in construction, industrial equipment, transportation and other fields. It maintains temperature stability by blocking heat conduction, convection and radiation.

[0003] Currently, commonly used insulation board materials include: organic foam materials, inorganic fiber materials, nanoporous materials, multi-layer composite board materials, etc. Typical materials for organic foam insulation boards include polystyrene and polyurethane. For example, the patent application with publication number CN118322619A discloses a process for preparing vacuum insulation boards with foam boards as the core material: foaming into rigid foam boards according to the ingredients of phenolic boards; baking the cut foam boards; setting slots on the foam boards and placing getter; covering the foam boards with barrier bags, vacuuming and sealing the barrier bags to make vacuum insulation boards; wherein the material of the rigid foam boards is phenolic foam, polyurethane foam, melamine-formaldehyde foam, extruded polystyrene foam or polyimide. The insulation boards prepared using this material can achieve thermal insulation and are lightweight and easy to process; however, they are flammable and have poor temperature resistance, so it is necessary to introduce barrier bags made of additional materials to achieve flame retardancy, which makes the entire preparation process complicated and the insulation board composition complex, making it difficult to recycle in an environmentally friendly manner later.

[0004] Common raw materials for inorganic fiber insulation boards include rock wool board, glass wool board, calcium silicate board, etc. For example, the insulation boards disclosed in patent applications with publication numbers CN118991150A, CN117759810A, and CN114001237A all use inorganic fiber materials, which can enable the insulation boards to achieve excellent fire resistance and high temperature resistance. However, this type of material has strong hygroscopicity and often requires a composite moisture-proof layer.

[0005] In addition, the patent applications with publication numbers CN119329139A and CN119217798A both disclose insulation boards containing aerogel materials. Aerogel is a porous solid material composed of a skeleton material and internal micropores and mesopores. The skeleton structure determines the volume of the aerogel, and the ratio of internal micropores and mesopores determines the specific surface area and density of the aerogel. The essence of the thermal insulation performance of the material is to limit heat transfer (heat convection, heat conduction, and heat radiation), that is, to pursue still air, no contact, and infinitely long heat radiation paths. The pore structure inside the aerogel makes it difficult for air to flow inside the material, and the heat radiation path is slowly transmitted in the channel formed by a large number of holes. Therefore, aerogel is a perfect thermal insulation material, but this type of material often has low strength and easy brittle cracking problems, and often needs to be used in conjunction with nanomaterials, which will cause powder loss problems.

[0006] For insulation boards with composite structure design, the advantages of different materials can be combined to finally obtain insulation boards with relatively good performance in all aspects. However, the overall process is complicated and there are many types of materials, which is not conducive to subsequent material recycling.

[0007] Therefore, it is of great value to develop an insulation board with good thermal insulation performance, excellent flame retardant performance, high strength performance and a single material composition. Summary of the Invention

[0008] In view of the deficiencies in the prior art, the present invention provides an aramid aerogel insulation board and a preparation method thereof. The aramid aerogel insulation board has good thermal insulation performance, high flame retardancy and high strength performance, and has a single material composition and is easy to use.

[0009] The present invention solves the above technical problems with the following technical solutions: a method for preparing an aramid aerogel insulation board, the preparation method comprising:

[0010] S1. Preparation of aramid stock solution:

[0011] Aromatic diamine and aromatic dicarboxylic acid chloride undergo polymerization reaction in a polar solvent to obtain aramid stock solution;

[0012] S2. Preparation of core layer microfiber dispersion and shell layer stock solution:

[0013] The aramid stock solution is diluted with a polar solvent to a certain viscosity, a gelling agent is added, and the mixture is dispersed and stirred to obtain the core layer microfiber dispersion;

[0014] Diluting the aramid stock solution with a polar solvent to a certain viscosity to obtain a shell liquid;

[0015] S3. Preparation of precursor:

[0016] The core layer microfiber dispersion is formed into a core layer by a template freeze molding method, the core layer is immersed in the shell layer liquid, and then taken out for coagulation bath molding to obtain a precursor;

[0017] S4. Preparation of insulation board:

[0018] The precursor is washed and freeze-dried to obtain the thermal insulation board.

[0019] Furthermore, the aromatic diamine is one or a combination of two of m-phenylenediamine, p-phenylenediamine, 3,4-diaminodiphenyl ether, 4,4-diaminodiphenyl ether, and 4,6-diamino-m-diphenol;

[0020] The aromatic dicarboxylic acid chloride is any one of isophthaloyl chloride and terephthaloyl chloride;

[0021] The polar solvent is any one of dimethylacetamide, dimethylformamide, N-methylpyrrolidone and dimethyl sulfoxide.

[0022] Furthermore, the specific preparation process in step S1 is:

[0023] The aromatic diamine is dissolved in a polar solvent containing a solubilizing salt, the system is cooled to -10°C-0°C, aromatic dicarboxylic acid chloride is added in two batches, and the polymerization is stirred. When the climbing phenomenon occurs, the stirring is stopped, and the system is heated to 60-80°C for aging. After 20-24 hours, the aramid stock solution is obtained.

[0024] Furthermore, when preparing the core layer microfiber dispersion, the viscosity of the aramid stock solution after being diluted with a polar solvent is 1-1000 cP.

[0025] Furthermore, when preparing the core layer microfiber dispersion, the gelling agent is an aqueous solution of ethanol, and the mass content of ethanol is 70-80%; the aramid stock solution is diluted with a polar solvent to obtain a dilution, and the mass ratio of the dilution to the gelling agent is 1: (20-30).

[0026] Furthermore, when preparing the shell liquid, the aramid stock solution is diluted to 30,000-50,000 cP using a polar solvent.

[0027] Furthermore, in step S3, the core layer is immersed in the shell layer liquid, and taken out after 3-5 minutes for coagulation bath molding. The coagulation bath is a mixed solution of a polar solvent and water, the mass concentration of the polar solvent in the coagulation bath is 3-10%, the coagulation bath temperature is 5-10°C, and the coagulation bath treatment time is 1-2 min.

[0028] Furthermore, in step S4, the cleaning process is a two-step process. The first step is to use an ethanol-water solution to clean and remove the polar solvent; the second step is to use pure water to clean and remove the ethanol.

[0029] Furthermore, in step S4, the temperature of the freeze-drying process is set in a gradient, and the specific process is: freeze-drying at -20~-15℃ for 4-5h; drying at -3~0℃ for 2-3h; drying at 8~10℃ for 4-5h, drying at 12~15℃ for 4-5h, drying at 18~20℃ for 4-5h, and drying at 23~25℃ for 4-5h.

[0030] The invention also discloses an aramid aerogel insulation board, which is prepared according to the preparation method of the invention.

[0031] The beneficial effects of the present invention are:

[0032] The present invention proposes a technical route that integrates polymerization, molding, compounding, gelation, and freeze-drying to prepare a low-density, high-strength composite aramid aerogel insulation board. The preparation method of the present invention uses the same stock solution as the core layer and outer layer of the aerogel insulation board through different processing methods, and assembles the same material by infiltration gel compounding. The core layer structure is composed of microfibers, which serve as a skeleton. Ice crystals create a large number of mesoporous structures inside. This method is rapid in molding, with controllable density and composition. The outer layer is wrapped by a gel layer, and the outer layer forms a microporous structure during the gelation process. The core layer provides mechanical strength, and the outer layer acts as a wrapper to prevent powder from falling. Both the core layer and the outer layer contain a porous structure, which not only ensures that the insulation board has high strength, but also ensures that the insulation board has good insulation performance.

[0033] The core and shell layers are homologous polymers, providing structural continuity. The shell layer is formed as a gel on the core layer's surface from a stock solution. Hydrogen bonds and van der Waals forces create a tight bond between the core and shell layers after formation. Furthermore, the core and shell layers of the insulation board are made of the same aramid material, further facilitating the recycling of waste insulation board materials.

[0034] Compared to solutions that form monolithic gel panels, the present invention's preparation method offers rapid molding and enables rapid, continuous production. Compared to inorganic aerogel panels, aramid aerogel insulation panels exhibit excellent integrity, high strength, and ease of use, while also being flame-retardant compared to common polymer insulation materials. They require no flame-retardant modification, carbonize in the presence of open flames and high temperatures, do not drip, and release no harmful substances.

[0035] Aramid is a high-performance fiber with an aromatic ring structure in the main chain. The molecular chains inside the fiber are highly oriented and crystallized, so it has high strength, high temperature resistance, and chemical corrosion resistance. Preparing aramid material into an aerogel structure can obtain an aramid aerogel insulation board that is highly efficient in heat preservation and flame retardant. Compared with single-component inorganic aerogel materials, aramid aerogel insulation boards have higher strength and do not shed powder. Different molds can be used to flexibly prepare insulation boards of various shapes, which are used in many fields such as building exterior wall insulation, industrial pipeline insulation, and power battery pack insulation. The present invention uses aramid material as the raw material of the insulation board, which combines the flame retardant and corrosion resistance of the material itself with the thermal insulation properties of the aerogel structure. The limiting oxygen index is 28-30%, and the BET test value is 120-180 m 2 / g, and the thermal conductivity is 0.010-0.017 W / m•K.

[0036] The insulation panels described in this invention have the potential for large-scale production. The core and shell layers are synthesized using the same route, yielding two alternative materials through different processing methods. This composite processing approach provides a prerequisite for modifying the insulation panels. For example, silica aerogel, colorants, antimicrobial agents, and other modified nanomaterials can be added to the shell stock solution to produce aerogel insulation panels with varying performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a SEM image of the cross section of the thermal insulation board prepared in Example 1;

[0038] Figure 2 This is a SEM image of the cross section of the thermal insulation board prepared in Example 2;

[0039] Figure 3 This is a nitrogen adsorption and desorption curve of the insulation board prepared in Example 1;

[0040] Figure 4 Actual pictures of the thermal insulation panels prepared in Examples 1 to 3. DETAILED DESCRIPTION

[0041] The present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used are only for describing specific embodiments and are not intended to limit the present invention.

[0043] A method for preparing an aramid aerogel insulation board, the preparation method comprising:

[0044] S1. Preparation of aramid stock solution:

[0045] Aromatic diamine and aromatic dicarboxylic acid chloride undergo polymerization reaction in a polar solvent to obtain aramid stock solution;

[0046] S2. Preparation of core layer microfiber dispersion and shell layer stock solution:

[0047] The aramid stock solution is diluted with a polar solvent to a certain viscosity, a gelling agent is added, and the mixture is dispersed and stirred to obtain the core layer microfiber dispersion;

[0048] Diluting the aramid stock solution with a polar solvent to a certain viscosity to obtain a shell liquid;

[0049] S3. Preparation of precursor:

[0050] The core layer microfiber dispersion is formed into a core layer by a template freeze molding method, the core layer is immersed in the shell layer liquid, and then taken out for coagulation bath molding to obtain a precursor;

[0051] S4. Preparation of insulation board:

[0052] The precursor is washed and freeze-dried to obtain the thermal insulation board.

[0053] Specifically, the aromatic diamine is one or a combination of two of m-phenylenediamine, p-phenylenediamine, 3,4-diaminodiphenyl ether, 4,4-diaminodiphenyl ether, and 4,6-diamino-m-diphenol;

[0054] The aromatic dicarboxylic acid chloride is any one of isophthaloyl chloride and terephthaloyl chloride;

[0055] The polar solvent is any one of dimethylacetamide, dimethylformamide, N-methylpyrrolidone and dimethyl sulfoxide.

[0056] Specifically, the specific preparation process in step S1 is:

[0057] The aromatic diamine is dissolved in a polar solvent containing a solubilizing salt, the system is cooled to -10°C-0°C, aromatic dicarboxylic acid chloride is added in two batches, and the polymerization is stirred. When the climbing phenomenon occurs, the stirring is stopped, and the system is heated to 60-80°C for aging. After 20-24 hours, the aramid stock solution is obtained.

[0058] More specifically, the molar ratio of the aromatic diamine to the aromatic dicarboxylic acid chloride in the embodiment of the present invention is 1:1.

[0059] More specifically, the dissolution-advantageous salt is calcium chloride or lithium chloride.

[0060] More specifically, during the preparation of the aramid stock solution, the content of the aromatic diamine in the polar solvent is 0.25-0.4 mol / L, and the amount of the solubilizing salt used is 2-8 wt% of the mass of the polar solvent.

[0061] More specifically, the viscosity of the aramid stock solution is 500,000-800,000 cP (viscosity measured at 25° C.).

[0062] Specifically, when preparing the core layer microfiber dispersion, the viscosity of the aramid stock solution after dilution with a polar solvent is 1-1000 cP (viscosity measured at 25° C.).

[0063] Specifically, when preparing the core layer microfiber dispersion, the gelling agent is an aqueous solution of ethanol, and the mass content of ethanol is 70-80%; the aramid stock solution is diluted with a polar solvent to obtain a dilution, and the mass ratio of the dilution to the gelling agent is 1:(20-30).

[0064] Specifically, when preparing the shell layer liquid, the aramid stock solution is diluted with a polar solvent to a viscosity of 30,000-50,000 cP (viscosity measured at 25° C.).

[0065] Specifically, in step S3, the core layer is immersed in the shell layer liquid, and taken out after 3-5 minutes for coagulation bath molding. The coagulation bath is a mixed solution of a polar solvent and water, the mass concentration of the polar solvent in the coagulation bath is 3-10%, the coagulation bath temperature is 5-10°C, and the coagulation bath treatment time is 1-2 minutes.

[0066] More specifically, in the embodiment of the present invention, the specific process of template freezing molding in step S3 is: placing the prepared core layer material in a fixed template, and freezing it in a -20°C refrigerator for 10-12 hours to prepare a freeze-dried precursor.

[0067] Specifically, in step S4, the cleaning process is a two-step process. The first step is to use an ethanol-water solution for cleaning at a cleaning temperature of 35-50°C and a processing time of 5-6 hours to remove the polar solvent; the second step is to use pure water for cleaning, which is repeated 5-8 times at a cleaning temperature of 55-65°C and a processing time of 1-3 hours each time to remove the ethanol.

[0068] Specifically, in step S4, the temperature of the freeze-drying process is set in a gradient, and the specific process is: freeze-drying at -20~-15℃ for 4-5h; drying at -3~0℃ for 2-3h; drying at 8~10℃ for 4-5h, drying at 12~15℃ for 4-5h, drying at 18~20℃ for 4-5h, and drying at 23~25℃ for 4-5h.

[0069] More specifically, during the production and preparation process, 1-3% of the shell liquid mass of modified nanomaterials, such as silica aerogel powder, nano-scale colorants, nano-antibacterial agents, anti-ultraviolet agents, etc., can be added to the shell liquid, mixed evenly and used as the modified shell liquid. The corresponding substances can be selected for modification according to the processing characteristics.

[0070] Example 1

[0071] A method for preparing an aramid aerogel insulation board, the preparation method comprising:

[0072] S1. Preparation of aramid stock solution:

[0073] The aromatic diamine is dissolved in a polar solvent containing a solubilizing salt, the system is cooled to -5°C, aromatic dicarboxylic acid chloride is added in two batches, and the polymerization is stirred. When the climbing phenomenon occurs, the stirring is stopped, and the system is heated to 70°C for aging. After 24 hours, the aramid stock solution is obtained.

[0074] The aromatic diamine is m-phenylenediamine, the aromatic dicarboxylic acid chloride is isophthaloyl dichloride, the polar solvent is dimethylacetamide, the solubilizing salt is calcium chloride, the content of the aromatic diamine in the polar solvent is 0.3 mol / L, and the amount of the solubilizing salt is 5 wt% of the mass of the polar solvent.

[0075] S2. Preparation of core layer microfiber dispersion and shell layer stock solution:

[0076] The aramid stock solution was diluted to 850 cP using a polar solvent to obtain a dilution, a gelling agent was added, and the mixture was dispersed and stirred to obtain the core layer microfiber dispersion; the gelling agent was a 70% ethanol aqueous solution, and the mass ratio of the dilution to the gelling agent was 1:30.

[0077] The aramid stock solution is diluted to 45000 cP using a polar solvent to obtain a shell liquid;

[0078] S3. Preparation of precursor:

[0079] The core layer microfiber dispersion is formed into a core layer by using a template freeze molding method, the core layer is immersed in the shell layer liquid for 3 minutes, and then taken out for coagulation bath molding to obtain a precursor;

[0080] The template freezing molding process is as follows: placing the prepared core layer material in a fixed template, and freezing it in a -20°C refrigerator for 10-12 hours to prepare a freeze-dried precursor.

[0081] The coagulation bath is a mixed solution of a polar solvent and water, the mass concentration of the polar solvent in the coagulation bath is 5%, the coagulation bath temperature is 8° C., and the coagulation bath treatment time is 2 min.

[0082] S4. Preparation of insulation board:

[0083] washing and freeze-drying the precursor to obtain the thermal insulation board;

[0084] The cleaning process is a two-step process. The first step is to use an ethanol-water solution (the mass concentration of ethanol is 60%) for cleaning at a temperature of 40°C for 6 hours to remove the polar solvent. The second step is to use pure water for cleaning, which is repeated 7 times at a temperature of 60°C for 1.5 hours each time to remove the ethanol.

[0085] The temperature of the freeze-drying process is set in a gradient, and the specific process is: freeze-drying at -20°C for 5 hours; drying at 0°C for 3 hours; drying at 10°C for 4 hours, drying at 15°C for 4 hours, drying at 20°C for 5 hours, and drying at 25°C for 5 hours.

[0086] Example 2

[0087] A method for preparing an aramid aerogel insulation board, the preparation method comprising:

[0088] S1. Preparation of aramid stock solution:

[0089] The aromatic diamine is dissolved in a polar solvent containing a solubilizing salt, the system is cooled to -10°C, aromatic dicarboxylic acid chloride is added in two batches, and the polymerization is stirred. When the climbing phenomenon occurs, the stirring is stopped, and the system is heated to 80°C for aging. After 20 hours, the aramid stock solution is obtained.

[0090] The aromatic diamine is p-phenylenediamine, the aromatic dicarboxylic acid chloride is terephthaloyl chloride, the polar solvent is dimethylformamide, the solubilizing salt is lithium chloride, the content of the aromatic diamine in the polar solvent is 0.25 mol / L, and the amount of the solubilizing salt is 2 wt% of the mass of the polar solvent.

[0091] S2. Preparation of core layer microfiber dispersion and shell layer stock solution:

[0092] The aramid stock solution is diluted to 150 cP using a polar solvent to obtain a dilution, a gelling agent is added, and the dispersion is uniformly stirred to obtain the core layer microfiber dispersion; the gelling agent is an 80% ethanol aqueous solution, and the mass ratio of the dilution to the gelling agent is 1:20.

[0093] The aramid stock solution is diluted to 30000 cP using a polar solvent to obtain a shell liquid;

[0094] S3. Preparation of precursor:

[0095] The core layer microfiber dispersion is formed into a core layer by using a template freeze molding method, the core layer is immersed in the shell layer liquid for 5 minutes, and then taken out for coagulation bath molding to obtain a precursor;

[0096] The template freezing molding process is as follows: placing the prepared core layer material in a fixed template, and freezing it in a -20°C refrigerator for 10-12 hours to prepare a freeze-dried precursor.

[0097] The coagulation bath is a mixed solution of a polar solvent and water, the mass concentration of the polar solvent in the coagulation bath is 3%, the coagulation bath temperature is 5° C., and the coagulation bath treatment time is 1 min.

[0098] S4. Preparation of insulation board:

[0099] washing and freeze-drying the precursor to obtain the thermal insulation board;

[0100] The cleaning process is a two-step process. The first step is to use an ethanol-water solution (ethanol mass concentration of 60%) for cleaning at a temperature of 50°C for 5 hours to remove the polar solvent. The second step is to use pure water for cleaning, which is repeated 5 times at a temperature of 65°C for 2 hours each time to remove the ethanol.

[0101] The temperature of the freeze-drying process was set in a gradient, and the specific process was: freeze-drying at -15°C for 4 hours; drying at -3°C for 2 hours; drying at 8°C for 5 hours, drying at 12°C for 5 hours, drying at 18°C for 4 hours, and drying at 23°C for 5 hours.

[0102] Example 3

[0103] A method for preparing an aramid aerogel insulation board, the preparation method comprising:

[0104] S1. Preparation of aramid stock solution:

[0105] The aromatic diamine is dissolved in a polar solvent containing a solubilizing salt, the system is cooled to 0°C, aromatic dicarboxylic acid chloride is added in two batches, and the polymerization is stirred. When the climbing phenomenon occurs, the stirring is stopped, and the system is heated to 60°C for aging. After 24 hours, the aramid stock solution is obtained.

[0106] The aromatic diamine is p-phenylenediamine and 3,4-diaminodiphenyl ether (molar ratio is 4:1), the aromatic dicarboxylic acid chloride is terephthaloyl chloride, the polar solvent is N-methylpyrrolidone, the solubilizing salt is lithium chloride, the content of the aromatic diamine in the polar solvent is 0.4 mol / L, and the amount of the solubilizing salt is 8 wt% of the mass of the polar solvent.

[0107] S2. Preparation of core layer microfiber dispersion and shell layer stock solution:

[0108] The aramid stock solution was diluted to 1000 cP using a polar solvent to obtain a dilution, a gelling agent was added, and the mixture was dispersed and stirred to obtain the core layer microfiber dispersion; the gelling agent was a 70% ethanol aqueous solution, and the mass ratio of the dilution to the gelling agent was 1:25.

[0109] The aramid stock solution is diluted to 50,000 cP using a polar solvent to obtain a shell liquid;

[0110] S3. Preparation of precursor:

[0111] The core layer microfiber dispersion is formed into a core layer by using a template freeze molding method, the core layer is immersed in the shell layer liquid for 4 minutes, and then taken out for coagulation bath molding to obtain a precursor;

[0112] The template freezing molding process is as follows: placing the prepared core layer material in a fixed template, and freezing it in a -20°C refrigerator for 10-12 hours to prepare a freeze-dried precursor.

[0113] The coagulation bath is a mixed solution of a polar solvent and water, the mass concentration of the polar solvent in the coagulation bath is 10%, the coagulation bath temperature is 10° C., and the coagulation bath treatment time is 2 min.

[0114] S4. Preparation of insulation board:

[0115] washing and freeze-drying the precursor to obtain the thermal insulation board;

[0116] The cleaning process is a two-step process. The first step is to use an ethanol-water solution (the mass concentration of ethanol is 60%) for cleaning at a temperature of 35°C for 6 hours to remove the polar solvent. The second step is to use pure water for cleaning, which is repeated 8 times at a temperature of 55°C for 3 hours each time to remove the ethanol.

[0117] The temperature of the freeze-drying process is set in a gradient, and the specific process is: freeze-drying at -20°C for 5 hours; drying at 0°C for 3 hours; drying at 10°C for 4 hours, drying at 15°C for 4 hours, drying at 20°C for 4 hours, and drying at 25°C for 5 hours.

[0118] Example 4

[0119] A method for preparing an aramid aerogel insulation board, the preparation method comprising:

[0120] S1. Preparation of aramid stock solution:

[0121] The aromatic diamine is dissolved in a polar solvent containing a solubilizing salt, the system is cooled to -5°C, aromatic dicarboxylic acid chloride is added in two batches, and the polymerization is stirred. When the climbing phenomenon occurs, the stirring is stopped, and the system is heated to 70°C for aging. After 24 hours, the aramid stock solution is obtained.

[0122] The aromatic diamine is m-phenylenediamine and 4,4-diaminodiphenyl ether (molar ratio is 3:1), the aromatic dicarboxylic acid chloride is isophthaloyl dichloride, the polar solvent is dimethyl sulfoxide, the solubilizing salt is lithium chloride, the content of the aromatic diamine in the polar solvent is 0.25 mol / L, and the amount of the solubilizing salt is 5 wt% of the mass of the polar solvent.

[0123] S2. Preparation of core layer microfiber dispersion and shell layer stock solution:

[0124] The aramid stock solution is diluted to 1 cP using a polar solvent to obtain a dilution, a gelling agent is added, and the dispersion is uniformly stirred to obtain the core layer microfiber dispersion; the gelling agent is a 70% ethanol aqueous solution, and the mass ratio of the dilution to the gelling agent is 1:20.

[0125] The aramid stock solution is diluted to 30000 cP using a polar solvent to obtain a shell liquid;

[0126] S3. Preparation of precursor:

[0127] The core layer microfiber dispersion is formed into a core layer by a template freeze molding method, the core layer is immersed in the shell layer liquid for 5 minutes, and then taken out for coagulation bath molding to obtain a precursor;

[0128] The template freezing molding process is as follows: placing the prepared core layer material in a fixed template, and freezing it in a -20°C refrigerator for 10-12 hours to prepare a freeze-dried precursor.

[0129] The coagulation bath is a mixed solution of a polar solvent and water, the mass concentration of the polar solvent in the coagulation bath is 5%, the coagulation bath temperature is 10° C., and the coagulation bath treatment time is 2 min.

[0130] S4. Preparation of insulation board:

[0131] washing and freeze-drying the precursor to obtain the thermal insulation board;

[0132] The cleaning process is a two-step process. The first step is to use an ethanol-water solution (ethanol mass concentration of 60%) for cleaning at a temperature of 40°C for 5 hours to remove the polar solvent. The second step is to use pure water for cleaning, which is repeated 6 times at a temperature of 60°C for 1 hour each time to remove the ethanol.

[0133] The temperature of the freeze-drying process is set in a gradient, and the specific process is: freeze-drying at -20°C for 5 hours; drying at 0°C for 3 hours; drying at 10°C for 4 hours, drying at 15°C for 4 hours, drying at 20°C for 5 hours, and drying at 25°C for 5 hours.

[0134] Comparative Example 1

[0135] The same method as in Example 1 was used to prepare the insulation board, except that the aramid stock solution was not diluted in this comparative example 1, but the core layer and the skin layer structure were directly prepared using the aramid stock solution, that is, the board was formed into one piece.

[0136] Comparative Example 2

[0137] The insulation board was prepared by the same method as in Example 1, except that the amount of the gelling agent was reduced in Comparative Example 2, and the mass ratio of the diluent to the gelling agent in Comparative Example 2 was 1:10.

[0138] Comparative Example 3

[0139] The insulation board was prepared by the same method as in Example 1, except that the amount of the gelling agent was increased in Comparative Example 3, and the mass ratio of the diluent to the gelling agent in Comparative Example 3 was 1:40.

[0140] Comparative Example 4

[0141] The same method as in Example 1 was used to prepare the insulation board, except that in Comparative Example 4, the core layer was not immersed in the shell layer liquid, and the insulation board prepared had only a core layer structure.

[0142] Comparative Example 5

[0143] The insulation board was prepared by the same method as in Example 1, except that in Comparative Example 5, the prepared aramid stock solution was directly used as the shell liquid (ie, it was not diluted, and the viscosity of the aramid stock solution was 500-750 Po).

[0144] Comparative Example 6

[0145] The insulation board was prepared by the same method as in Example 1, except that no temperature gradient was set during the freeze-drying process, and freeze-drying was performed only at low temperature. The specific conditions were:

[0146] The temperature condition of the freeze-drying process is: freeze-drying at -20°C for 72 hours.

[0147] Comparative Example 7

[0148] The insulation board was prepared by the same method as in Example 1, except that only two temperature changes were set during the freeze-drying process. The specific conditions were:

[0149] Freeze-dry at -20°C for 20 h; dry at 20°C for 20 h.

[0150] The insulation boards prepared in the above embodiments and comparative examples were subjected to performance tests. The specific test results are shown in Table 1 below. The testing methods involved are: thermal conductivity and BET test were tested according to GB / T 11048-2008 method, and limiting oxygen index test was tested according to GB5454-85.

[0151] Table 1 Insulation board performance test results

[0152]

[0153] The data in the table above demonstrate that Examples 1-4 are insulation panels produced according to the preparation method of the present invention. These panels exhibit high strength while ensuring excellent thermal insulation and flame retardancy. The present invention prepares an aromatic polyamide stock solution through low-temperature solution polymerization. The resulting stock solution is diluted, a gelling agent is added, and a dispersion device is used to produce an aromatic polyamide microfiber dispersion for later use. A solvent (and, if necessary, functional additives) is added to the polymerized stock solution and diluted to a desired viscosity to produce a shell solution for the insulation panel. The aromatic polyamide microfiber dispersion is then frozen using a template to form a core insulation layer. Ice crystals squeeze the microfibers, forming a skeletal structure. The locations of the ice crystals define the future pore structure. The core layer is immersed in the shell solution, which coats the core layer with a gel. After a period of time, the core layer is removed and immersed in a coagulation bath, where the outer layer gels. After washing to remove the organic solvent, a double-layer aerogel insulation panel precursor is obtained. The precursor is dried to produce the aramid aerogel insulation panel.

[0154] in addition, Figure 1 and Figure 2 The SEM images of the cross sections of the insulation boards of Example 1 and Example 2 are shown in FIG. Figure 1 、 Figure 2 It can be seen that the aerogel core layer consists of a dense fiber structure and aerogel pores, and the skin layer has a rough cross-section structure, indicating that the fiber and aerogel structure of the core layer provide good thermal insulation effect, while the skin structure provides good strength.

[0155] Figure 3 The nitrogen adsorption and desorption curve of the insulation board prepared in Example 1 is as follows: Figure 3 It can be seen that its BET surface area is 140 m 2 / g, has a good aerogel structure, thus ensuring that the material has good thermal insulation effect.

[0156] Figure 4 The thermal insulation board obtained in Example 1 to Example 3 is shown in FIG. Figure 4 It can be seen that the insulation board prepared by the preparation method of the present invention has a smooth surface and has good use effect.

[0157] From the comparison of the data of Comparative Example 1 and Example 1, it can be seen that when the prepared meta-aramid stock solution is directly used to prepare the insulation board material without dilution, the interior of the material is too dense, resulting in a reduction in the internal aerogel pores, which in turn leads to a decrease in the thermal insulation effect.

[0158] From the comparison of the data of Comparative Example 2 and Example 1, it can be seen that if the proportion of the gelling agent is reduced, the core layer structure will be incompletely solidified, and the internal structure will be loose during freeze-drying, resulting in a decrease in the porosity and strength of the aerogel insulation board.

[0159] From the comparison of the data of Comparative Example 3 and Example 1, it can be seen that if the proportion of the gelling agent is increased, the structure of the skin layer and the core layer will be dense, which will lead to a decrease in the thermal insulation effect.

[0160] From the comparison of the data of Comparative Example 4 and Example 1, it can be seen that without the skin structure, the strength performance of the aerogel insulation board will be greatly reduced, and it is impossible to prepare a material with high strength and good performance.

[0161] From the data comparison of Comparative Example 5 and Example 1, it can be seen that if the skin structure is not prepared by dilution, the skin of the insulation board is too dense and uneven, and a uniform product cannot be prepared. In addition, the unevenness of the skin will affect the thermal insulation effect of the insulation board.

[0162] From the comparison of the data of Comparative Example 6 and Example 1, it can be seen that: no gradient temperature change is set, and the material is only freeze-dried under low temperature conditions. The freeze-drying is not thorough, and the aerogel structure cannot be formed inside, resulting in no thermal insulation effect.

[0163] From the comparison of the data of Comparative Example 7 and Example 1, it can be seen that during the freeze-drying process, only two levels of temperature change are provided, and the core layer and the skin layer of the aerogel insulation board cannot be completely frozen, resulting in poor insulation effect.

[0164] The technical features of the above-described embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0165] For those skilled in the art, several variations and improvements may be made without departing from the scope of the present invention, which all fall within the scope of protection of the present invention. The scope of protection of the present invention shall be based on the appended claims.

Claims

1. A method for preparing an aramid aerogel insulation board, characterized in that: The preparation method is: S1. Preparation of aramid stock solution: Aromatic diamine and aromatic dicarboxylic acid chloride undergo polymerization reaction in a polar solvent to obtain aramid stock solution; S2. Preparation of core layer microfiber dispersion and shell layer stock solution: The aramid stock solution is diluted with a polar solvent to a certain viscosity to obtain a diluent, a gelling agent is added, and the mixture is dispersed and stirred to obtain the core layer microfiber dispersion; the mass ratio of the diluent to the gelling agent is 1:(20-30); Diluting the aramid stock solution with a polar solvent to a certain viscosity to obtain a shell liquid; When preparing the core layer microfiber dispersion, the viscosity of the aramid stock solution after dilution with a polar solvent is 1-1000 cP; when preparing the shell layer solution, the aramid stock solution is diluted with a polar solvent to 30,000-50,000 cP; S3. Preparation of precursor: The core layer microfiber dispersion is formed into a core layer by a template freeze molding method, the core layer is immersed in the shell layer liquid, and then taken out for coagulation bath molding to obtain a precursor; S4. Preparation of insulation board: washing and freeze-drying the precursor to obtain the thermal insulation board; The temperature of the freeze-drying process is set in a gradient, and the specific process is: freeze-drying at -20~-15°C for 4-5 hours; drying at -3~0°C for 2-3 hours; drying at 8~10°C for 4-5 hours, drying at 12~15°C for 4-5 hours, drying at 18~20°C for 4-5 hours, and drying at 23~25°C for 4-5 hours.

2. The method for preparing an aramid aerogel insulation board according to claim 1, characterized in that: The aromatic diamine is one or a combination of two of m-phenylenediamine, p-phenylenediamine, 3,4-diaminodiphenyl ether, 4,4-diaminodiphenyl ether, and 4,6-diamino-m-diphenol; The aromatic dicarboxylic acid chloride is any one of isophthaloyl chloride and terephthaloyl chloride; The polar solvent is any one of dimethylacetamide, dimethylformamide, N-methylpyrrolidone and dimethyl sulfoxide.

3. The method for preparing an aramid aerogel insulation board according to claim 1, characterized in that: The specific preparation process in step S1 is: The aromatic diamine is dissolved in a polar solvent containing a solubilizing salt, the system is cooled to -10°C-0°C, aromatic dicarboxylic acid chloride is added in two batches, and the polymerization is stirred. When the climbing phenomenon occurs, the stirring is stopped, and the system is heated to 60-80°C for aging. After 20-24 hours, the aramid stock solution is obtained.

4. The method for preparing an aramid aerogel insulation board according to claim 1, characterized in that: When preparing the core layer microfiber dispersion, the gelling agent is an ethanol aqueous solution, and the mass content of ethanol is 70-80%.

5. The method for preparing an aramid aerogel insulation board according to claim 1, characterized in that: In step S3, the core layer is immersed in the shell layer liquid, and taken out after 3-5 minutes for coagulation bath molding. The coagulation bath is a mixed solution of a polar solvent and water, the mass concentration of the polar solvent in the coagulation bath is 3-10%, the coagulation bath temperature is 5-10°C, and the coagulation bath treatment time is 1-2 minutes.

6. The method for preparing an aramid aerogel insulation board according to claim 1, characterized in that: In step S4, the cleaning process is a two-step process. The first step is to use an ethanol-water solution to clean and remove the polar solvent; the second step is to use pure water to clean and remove the ethanol.

7. An aramid aerogel insulation board, characterized in that: The thermal insulation board is prepared according to the preparation method according to any one of claims 1 to 6.

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