Low-temperature-bending-resistant sulfur-free fireproof coating for aerogel blanket encapsulation and preparation method therefor

Abstract

A low-temperature-bending-resistant sulfur-free fireproof coating for aerogel blanket encapsulation and a preparation method therefor. The coating comprises the following components in parts by weight: 35-50 parts of a sulfur-free resin, 20-45 parts of a pigment paste, 0-20 parts of a flame retardant, 0.1-2 parts of a defoamer, 0.1-2 parts of a substrate wetting agent, 0.5-2 parts of a thickener, 0-10 parts of an antifreeze agent, and 0-10 parts of a plasticizer. In the technical solution, the sulfur content of resin, pigment and additives used in the coating is measured, and the resin for which a test result is that no sulfur content is detected is selected for the design of a sulfur-free coating formula, thus obtaining a coating that does not contain sulfur, passes a dryness test and a low-temperature flexibility test, and is applicable to aerogel blanket encapsulation. Further, by means of adding the specific flame retardant, it is possible to achieve both fire resistance (having a class of 1 to 5) and good thermal insulation performance.

Description

A sulfur-free fire-retardant coating for low-temperature bending resistance in aerogel felt encapsulation and its preparation method. Technical Field

[0001] This invention relates to the field of coating technology, specifically to an encapsulation coating and its preparation method, and more particularly to a sulfur-free fire-retardant coating for low-temperature bending resistant aerogel felt encapsulation and its preparation method. Background Technology

[0002] Aerogel felt is a flexible thermal insulation felt made by in-situ generating silica or metal aerogel composites in a supercritical environment using glass fiber, carbon fiber, ceramic glass fiber cotton, or pre-oxidized fiber felt as the base material. Due to its excellent thermal insulation properties, it is widely used in electric vehicle battery packs. In previous research, our team developed an environmentally friendly flame-retardant coating for aerogel felt encapsulation to address the powder shedding problem and improve the flame retardancy of the encapsulation material. See patent document CN118029170A for details. This coating uses a material with a tensile strength of 10 N / mm². 2 The coating prepared by combining a resin dispersion with an elongation at break of 800% or more and a minimum film-forming temperature of 0°C or more with filler slurry, flame retardant and other additives has the properties of flame retardancy rating of UL94 V0, flexibility of 180° bending without cracking and shear strength of 0.8MPa or more.

[0003] However, according to the Basel Convention, its goal is to reduce the generation of hazardous waste and ensure its environmentally sound treatment in the country of origin or receiving country. Sulfur-containing raw materials are likely to generate sulfur-containing hazardous waste during production and use. Improper handling of this waste can cause air pollution and acid rain, or leaks that pollute soil and water bodies, posing a threat to ecosystems and human health. Therefore, major international automakers have sulfur-free requirements for the raw materials and components they purchase. The environmentally friendly flame-retardant coating for aerogel felt encapsulation previously developed by our team failed to meet the sulfur-free requirement after testing. Tests showed that the sulfur content of this environmentally friendly flame-retardant coating (the coating prepared in the examples) was above 180 ppm. Based on this, this invention attempts to develop a new sulfur-free coating for aerogel felt encapsulation to meet customer needs.

[0004] In addition, customers also require resistance to low-temperature bending and fire resistance. Therefore, this invention further attempts to develop sulfur-free coatings that combine resistance to low-temperature bending and fire resistance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a sulfur-free fire-retardant coating for aerogel felt encapsulation that is resistant to low-temperature bending and its preparation method.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] In a first aspect, the present invention provides a sulfur-free fire-retardant coating for low-temperature bending resistance for aerogel felt encapsulation, comprising the following components in parts by weight:

[0008] As a preferred embodiment, the sulfur-free resin is selected from at least one of aqueous polyurethane dispersion and ethylene-acrylic acid copolymer emulsion.

[0009] As a preferred embodiment, the waterborne polyurethane dispersion includes at least one of Leasys 3502, YC-102, RH-1358, and RH-1335;

[0010] The ethylene-acrylic acid copolymer emulsion includes Twax-7014.

[0011] As a preferred embodiment, the sulfur-free resin is at least one of RH-1358 and RH-1335, or a combination of YC-102 and Twax-7014.

[0012] As a further preferred embodiment, when the sulfur-free resin is a combination of YC-102 and Twax-7014, the weight ratio of YC-102 to Twax-7014 is 1:0.8-1.2, and more preferably, the weight ratio of YC-102 to Twax-7014 is 1:1.

[0013] As a preferred embodiment, the sulfur-free fire-retardant coating for low-temperature bending resistance used in aerogel felt encapsulation comprises the following components in parts by weight:

[0014] The sulfur-free fire-retardant coating prepared under this weight ratio has OK drying properties, does not crack in low-temperature flexibility tests, and has a fire rating of 1-5.

[0015] As a further preferred embodiment, the sulfur-free fire-retardant coating for low-temperature bending resistance used in aerogel felt encapsulation comprises the following components in parts by weight:

[0016] The sulfur-free fire-retardant coating prepared under this weight ratio has OK drying properties, does not crack in low-temperature flexibility tests, and has a fire rating of 3-5.

[0017] As the preferred embodiment, the sulfur-free fire-retardant coating for low-temperature bending resistance used in aerogel felt encapsulation comprises the following components in parts by weight:

[0018] The sulfur-free fire-retardant coating prepared under this weight ratio has OK drying properties, does not crack in low-temperature flexibility test, has a fire rating of 4, and has a small amount of coating adhering to the edge of the cold plate in the heat insulation performance test.

[0019] As a preferred embodiment, the pigment paste comprises the following components in parts by weight:

[0020] As a preferred embodiment, the sulfur-free pigment in the pigment paste is selected from at least one of sulfur-free white pigment, sulfur-free black pigment, sulfur-free red pigment, sulfur-free blue pigment, sulfur-free green pigment, sulfur-free purple pigment, and sulfur-free yellow pigment. The selection of sulfur-free pigment is based on meeting the requirements of the desired color of the coating and ensuring that the sulfur content is NA as determined by testing according to EN 14582-2016 "Waste Characteristics - Halogen and Sulfur Content - Closed System Oxygen Combustion and Determination Method". No particular limitations are imposed in this invention.

[0021] As a further preferred option, the sulfur-free pigment is selected from titanium dioxide (such as rutile titanium dioxide).

[0022] As a preferred embodiment, the defoamer in the pigment paste is selected from at least one of mineral oil defoamers and modified polyether-modified siloxanes.

[0023] As a preferred embodiment, the dispersant in the pigment slurry is selected from polyether-modified siloxane.

[0024] As a further preferred embodiment, the dispersant in the pigment paste is selected from at least one of BYK190, BYK192, and Tego 760.

[0025] As a preferred embodiment, the defoamer in the pigment paste is selected from at least one of Airex 902W, BYK032, BYK028, and BYK011.

[0026] As a preferred embodiment, the method for preparing the pigment paste includes the following steps: adding sulfur-free pigment, defoamer, dispersant and water weighed in parts by weight into a grinding mill, and grinding and dispersing to prepare the pigment paste.

[0027] As a preferred embodiment, the flame retardant in the sulfur-free fireproof coating is selected from ammonium polyphosphate flame retardants.

[0028] As a further preferred embodiment, the ammonium polyphosphate flame retardant includes AP462.

[0029] As a preferred embodiment, the plasticizer in the sulfur-free fire-retardant coating is selected from 2,2,4-trimethyl-1,3-pentanediol diisobutyrate.

[0030] As a preferred embodiment, in the sulfur-free fireproof coating, the defoamer is selected from at least one of mineral oil defoamers and modified polyether-modified siloxanes.

[0031] As a further preferred option, the defoamer is selected from at least one of Airex 902W, BYK032, BYK028, and BYK011.

[0032] As a preferred embodiment, in the sulfur-free fire retardant coating, the substrate wetting agent is selected from at least one of BYK346, BYK347, BYK348, BYK349, and Tego 270.

[0033] As a preferred embodiment, the thickener in the sulfur-free fire-retardant coating is selected from at least one of RHEOLATE 299, ASE60, and RDS.

[0034] As a preferred embodiment, the antifreeze agent in the sulfur-free fire-retardant coating is selected from propylene glycol. The purpose of adding the antifreeze agent is to ensure that the coating prepared using the coating of this application can meet the possible low-temperature requirements during low-temperature storage and transportation. When the storage and transportation temperature range is 5-30℃, no antifreeze agent is needed. Therefore, there are no particular limitations on the addition of the antifreeze agent.

[0035] As a preferred embodiment, the sulfur-free fire-retardant coating also includes a pH adjuster in the form of 0-2 parts by weight.

[0036] As a further preferred option, the pH adjuster is selected from DMEA.

[0037] Secondly, the present invention provides a method for preparing a sulfur-free fire-retardant coating resistant to low-temperature bending for aerogel felt encapsulation, comprising the following steps:

[0038] A. Add the flame retardant to water and disperse it evenly to form a flame retardant dispersion;

[0039] B. Mix sulfur-free resin, plasticizer, defoamer, substrate wetting agent, and thickener, and disperse at high speed to prepare a high-shear water-based base material;

[0040] B. Add the pigment paste and flame retardant dispersion to the high-shear water-based base material prepared in step A, and disperse at high speed to obtain the sulfur-free fireproof coating for low-temperature bending resistance for aerogel encapsulation.

[0041] Thirdly, the present invention provides a method for encapsulating aerogel felt, comprising the following steps: applying the aforementioned low-temperature bending-resistant sulfur-free fire-retardant coating to the surface of the aerogel felt by dip coating, spraying, roller coating or curtain coating, thereby achieving encapsulation of the aerogel felt.

[0042] Fourthly, the present invention provides a heat insulation pad, comprising an aerogel felt and the aforementioned sulfur-free fire-retardant coating resistant to low-temperature bending; the sulfur-free fire-retardant coating resistant to low-temperature bending is applied to the surface of the aerogel felt for encapsulating the aerogel felt.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] 1) This invention determines the sulfur content of the resin used in the coating and selects the resin in which the sulfur content is not detected to design a sulfur-free coating formulation, thereby obtaining a coating that is sulfur-free according to the EN 14582-2016 method and passes the drying and low-temperature flexibility tests, and can be applied to aerogel felt encapsulation.

[0045] 2) This invention further determines the sulfur content of the flame retardants used in the coating and selects ammonium polyphosphate flame retardants with undetectable sulfur content in the test results to design a sulfur-free coating formulation, thereby obtaining a coating that simultaneously possesses fire-retardant properties (level 1-5). Furthermore, by optimizing the formulation of each raw material component, a fire-retardant level of 4-5 can be achieved.

[0046] 3) In order to further meet the requirements of the draft for comments on the "Safety Requirements for Power Batteries for Electric Vehicles" GB 38031 regarding heat diffusion, this invention optimizes the formulation of each raw material component to obtain a coating with better heat insulation performance (in the heat insulation performance test, the test result is OK if the cold plate reaches 300°C for more than 5 minutes; the material surface coating test result is that a small amount of coating is adhered to the edge of the cold plate). Detailed Implementation

[0047] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0048] The terms "preferred," "more preferably," and "more suitable" used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0049] It should be understood that, except in any operational instance or otherwise indicated, all figures representing the amounts of ingredients used, for example, in the specification and claims, should be understood to be modified in all cases by the term "about". Therefore, unless otherwise stated, the numerical parameters set forth in the following specification and appended claims are approximations varying with the desired performance to be obtained according to the invention. It is not at all an attempt to limit the application of the doctrine of equivalents to the scope of the claims; each numerical parameter should be interpreted at least according to the number of significant figures reported and by applying ordinary rounding techniques.

[0050] Although the numerical ranges and parameters illustrating the broad scope of the invention are approximate, the values ​​listed in the specific examples are reported as precisely as possible. However, any numerical value inherently contains some error that is necessarily caused by the standard deviation found in their respective test measurements.

[0051] To meet the sulfur-free requirement, the inventors first tested the sulfur content of the core raw material for coating preparation—the polymer resin. Since none of the commercially available polymer resins currently available provide sulfur content test results, it is impossible to directly determine whether each polymer resin contains sulfur, or the level of sulfur content. Therefore, we conducted sulfur content tests on different types and grades of polymer resins. The test method was based on EN 14582-2016 "Waste Characteristics—Halogen and Sulfur Content—Closed System Oxygen Combustion and Determination Methods". The test results are shown in Table 1 (Note: NA indicates not detected).

[0052] Table 1

[0053] As can be seen from the results in Table 1, only YC-102, RH-1358, RH-1335, and Twax-7014 are sulfur-free, while the other resins contain sulfur, with sulfur content ranging from 86 to 2840 ppm.

[0054] The present invention further tested the sulfur content of the flame retardant, and the test results are shown in Table 2.

[0055] Table 2

[0056] As can be seen from the results in Table 2, only AP462 is sulfur-free, while the other flame retardants all contain sulfur, with sulfur content ranging from 504 to 1762 ppm.

[0057] Based on the above test results, we developed a sulfur-free coating. Furthermore, we adjusted and optimized the coating formulation based on other performance requirements.

[0058] In the following embodiments, the other raw materials used in the preparation of the specific coatings and their sources are as follows:

[0059] The defoamer was a modified polyether-modified siloxane, model Airex 902W, purchased from Tego.

[0060] The substrate wetting agent is BYK-349, purchased from BYK.

[0061] The dispersant was a polyether-modified siloxane, model BYK-190, purchased from BYK Corporation.

[0062] The plasticizer is 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, model TXIB, purchased from Eastman; its sulfur content was tested and found to be NA.

[0063] The thickener was RHEOLATE299, purchased from Haiming Sideqian Company; its sulfur content was tested and found to be NA.

[0064] The titanium dioxide is rutile titanium dioxide, Ti-Pure. TM R-902+, purchased from Chemours, USA; its sulfur content was tested and found to be NA.

[0065] The antifreeze is propylene glycol, purchased from Dow Chemical Company.

[0066] The pH adjuster is DMEA.

[0067] Examples 1-11

[0068] Examples 1-11 provide a sulfur-free fire-retardant coating for low-temperature bending resistance for aerogel felt encapsulation, and the weight parts of each component are shown in Table 3.

[0069] Table 3

[0070] Note: 50% AP462 refers to an aqueous solution of AP462 with a mass content of 50%. The amount added in Table 3 is the weight part of 50% AP462. Examples 5-8 are converted to 15 parts by weight of AP462. 10% DMEA refers to an aqueous dispersion of DMEA with a mass content of 10%. The amount added in Table 3 is the weight part of 10% DMEA. This is converted to 0.1 parts by weight of DMEA.

[0071] In Table 3, the pigment paste used is prepared by mixing the raw materials in Table 4 according to the weight ratio.

[0072] Table 4

[0073] The preparation method of the sulfur-free fire-retardant coating resistant to low-temperature bending described in each embodiment specifically includes the following steps:

[0074] 1) Weigh the resins, Airex 902W, BYK-349, TXIB, and RHEOLATE299 according to the weight parts in Table 3, mix them, and disperse them at high speed to prepare a uniform high-shear waterborne base material.

[0075] 2) Add the titanium dioxide, Airex 902W, BYK-190 and water weighed according to the parts in Table 4 to a grinder, grind and disperse to prepare pigment paste, and determine the fineness to be below 20μm according to GB / T 1724-2019 Determination of Grinding Fineness of Paints, Varnishes and Printing Inks.

[0076] 3) In step 1, add pigment paste and 50% AP462 for high-speed dispersion. According to GB / T 1724-2019 Determination of grinding fineness of paints, varnishes and printing inks, the fineness is determined to be below 20μm. The pH is adjusted to 8.0-8.5 by 10% DMEA (i.e., 10% DMEA aqueous solution). The sulfur-free fireproof coating for low-temperature bending resistance for aerogel encapsulation is obtained.

[0077] Comparative Example 1

[0078] This comparative example provides a sulfur-free fire-retardant coating for low-temperature bending resistance in aerogel felt encapsulation. Its components and weight percentages are basically the same as in Example 1, except that Twax-7014 is not added in this comparative example, while the weight percentage of YC-102 is 45 parts. The weight percentages of each component are shown in Table 1.

[0079] The preparation method of the sulfur-free fire-retardant coating for low-temperature bending resistance used in aerogel felt encapsulation is the same as in Example 1.

[0080] Comparative Example 2

[0081] This comparative example provides a sulfur-free fire-retardant coating for low-temperature bending resistance used in aerogel felt encapsulation. Its components and weight percentages are basically the same as in Example 1, except that YC-102 is not added in this comparative example, while the weight percentage of Twax-7014 is 45 parts. The weight percentages of each component are shown in Table 1.

[0082] The preparation method of the sulfur-free fire-retardant coating for low-temperature bending resistance used in aerogel felt encapsulation is the same as in Example 1.

[0083] Comparative Example 3

[0084] This comparative example provides a sulfur-free fire-retardant coating for low-temperature bending resistance in aerogel felt encapsulation. Its components and weight percentages are basically the same as in Example 5, except that Twax-7014 is not added in this comparative example, while the weight percentage of YC-102 is 40 parts. The weight percentages of each component are shown in Table 1.

[0085] The preparation method of the sulfur-free fire-retardant coating for low-temperature bending resistance used in aerogel felt encapsulation is the same as in Example 5.

[0086] Comparative Example 4

[0087] This comparative example provides a sulfur-free fire-retardant coating for low-temperature bending resistance in aerogel felt encapsulation. Its components and weight percentages are basically the same as in Example 7, except that DA-102 is used instead of RH-1358 in this comparative example. The weight percentages of each component are shown in Table 1.

[0088] The preparation method of the sulfur-free fire-retardant coating for low-temperature bending resistance used in the aerogel felt encapsulation is the same as in Example 7.

[0089] Examples 12-16

[0090] Examples 12-16 provide a sulfur-free fire-retardant coating for low-temperature bending resistance in aerogel felt encapsulation. The components and weight percentages are basically the same as in Example 5, except that: Example 12 adds 5 parts by weight of propylene glycol (in the preparation method of Example 1, propylene glycol is added in step 3 along with the pigment paste and 50% AP462); Examples 13-16 use different weight percentages of Twax-7014 and YC-102. The specific weight percentages of each component are shown in Table 5.

[0091] Table 5

[0092] The preparation method of the sulfur-free fire-retardant coating for low-temperature bending resistance used in aerogel felt encapsulation is the same as in Example 5.

[0093] Examples 17-20

[0094] Examples 17-20 provide a sulfur-free fire-retardant coating for low-temperature bending resistance for aerogel felt encapsulation, and the weight parts of each component are shown in Table 6.

[0095] Table 6

[0096] In Table 6, each pigment paste is prepared by mixing the raw materials in Table 7 according to the weight ratio. The preparation method of the pigment paste is the same as that in Example 1.

[0097] Table 7

[0098] The preparation methods of the low-temperature bending-resistant sulfur-free fireproof coatings described in each embodiment are the same as those in Example 12.

[0099] Performance verification:

[0100] 1) The coatings prepared in the above embodiments and comparative examples were subjected to sulfur content testing, drying performance testing, and low-temperature flexibility testing. Sulfur content testing was conducted according to the method in EN 14582-2016; drying performance testing was conducted according to the method in GB / T 1728-1979 "Determination of Drying Time of Coating Film" (OK indicates passing the finger-touch drying test with no sticking); the flexibility test adopted the standard in GB / T 1731-2020 "Determination of Flexibility of Paint Film and Putty Film". Specifically, after the coatings prepared in the embodiments and comparative examples were formed into films, they were placed at -30℃ for 3 hours, and then the samples were folded in half at -30℃ to observe the cracking of the coating and determine the flexibility. In Examples 15 and 16, and Comparative Example 2, the coatings failed to form films during film formation; therefore, drying performance and flexibility were not tested.

[0101] 2) The coatings prepared in the above embodiments and comparative examples were applied to the surface of the aerogel felt by dip coating, and the aerogel felt was encapsulated. The encapsulated aerogel felt was then subjected to high-temperature testing and fire resistance testing. The fire resistance test equipment used was the S8162X mica board combustion tester manufactured by Shanghai Sixuan Testing Equipment Co., Ltd. The specific method for the fire resistance test was as follows: the aerogel was selected as pre-oxidized fiber-loaded silica aerogel with a thermal conductivity of 0.018~0.022w / (m·k) and a thickness of 3.4mm. After coating both sides of the aerogel felt with the coatings prepared in each embodiment, a coating layer was formed, and then it was cut into 15cm×15cm test specimens. The two sides of the test specimen with the coating were used as the front and back sides, respectively. The front side was subjected to open flame erosion at 900~1000℃. The change in the appearance of the coating on the front side with erosion time was tested, and the temperature change on the back side with erosion time was monitored. Aerogel felt material (i.e., uncoated aerogel felt) was used as a test sample and tested according to this method. The temperature on the back of the test sample reached 186.5℃ in 60 seconds and 272.7℃ in 300 seconds. Based on this, and in conjunction with the requirements for thermal diffusion in the draft of GB 38031 "Safety Requirements for Power Batteries for Electric Vehicles", a fire resistance rating standard for encapsulated aerogel felt was designed. The specific fire resistance classifications are shown in Table 8. In Examples 15 and 16, and Comparative Example 2, the coatings failed to form a film during the film-forming process; therefore, their fire resistance performance was not tested.

[0102] Table 8

[0103] 3) The coatings prepared in the above embodiments and comparative examples were applied to the surface of the aerogel felt by dip coating, and the aerogel felt was encapsulated. The encapsulated aerogel felt was then used as a sample for thermal insulation performance testing. The purpose of thermal insulation performance testing is to further meet the requirements for thermal diffusion in the draft of GB 38031 Safety Requirements for Power Batteries for Electric Vehicles. The test method is as follows: the hot plate of the thermal insulation testing machine is heated to 600°C, the test material (100×100mm) is placed on the cold plate, the cold plate is installed and pressed against the hot plate, and a pressure of 5000N is applied. The test is stopped when the cold plate reaches 300°C, the time is recorded, and it is noted whether the encapsulation coating of the sample is adhered to the cold plate. Among them, the coatings in Examples 15 and 16 and Comparative Example 2 could not form a film during film formation, so their thermal insulation performance was not tested.

[0104] The results of each performance test are shown in Table 9.

[0105] Table 9

[0106] As shown in Table 9, the coatings prepared using Examples 1-12 and 17-20 are sulfur-free, have OK drying properties, and exhibit flexibility at low temperatures, remaining crack-free even after 180° bending. Furthermore, the coatings prepared using Examples 5-12, 17-18, and 20, due to the addition of a certain amount of flame retardant, further enhance fire resistance, achieving fire ratings of 1-5.

[0107] The comparison results between Example 5 and Comparative Example 3, and between Example 1 and Comparative Examples 1 and 2, show that when only YC-102 sulfur-free resin is used, the flexibility test at low temperature results in cracking after bending at 180°; while when only Twax-7014 sulfur-free resin is used, film formation fails. Further comparison results between Example 5 and Examples 13-16 show that when only a combination of YC-102 and Twax-7014 sulfur-free resin is used, an excessively high YC-102 content still results in cracking after bending at 180° at low temperature; and an excessively high Twax-7014 content also results in failure to form a film. Only when the ratio of the two is approximately 1:1 can both low-temperature bending resistance and film formation be achieved.

[0108] Compared with Comparative Example 4, when DA-102 was used instead of RH-135 in Example 7, the sulfur content of the prepared coating did not meet the requirements, the flexibility tested at low temperature was cracked when bent at 180°, and the heat insulation performance was also worse (the coating was completely adhered to the cold plate).

[0109] This invention has many specific applications, and the above description is only a preferred embodiment. It should be noted that the above embodiments are for illustrative purposes only and are not intended to limit the scope of protection of this invention. For those skilled in the art, several improvements can be made without departing from the principle of this invention, and these improvements should also be considered within the scope of protection of this invention.

Claims

1. A sulfur-free fire-retardant coating for low-temperature bending resistance in aerogel felt encapsulation, characterized in that, The components include the following parts by weight:

2. The sulfur-free fire-retardant coating for low-temperature bending resistance used in aerogel felt encapsulation according to claim 1, characterized in that, The sulfur-free resin is selected from at least one of aqueous polyurethane dispersion and ethylene-acrylic acid copolymer emulsion.

3. The sulfur-free fire-retardant coating for low-temperature bending resistance used in aerogel felt encapsulation according to claim 2, characterized in that, The aqueous polyurethane dispersion includes at least one of Leasys 3502, YC-102, RH-1358, and RH-1335; The ethylene-acrylic acid copolymer emulsion includes Twax-7014.

4. The sulfur-free fire-retardant coating for low-temperature bending resistance used in aerogel felt encapsulation according to claim 3, characterized in that, The sulfur-free resin is at least one of RH-1358 and RH-1335, or a combination of YC-102 and Twax-7014.

5. The sulfur-free fire-retardant coating for low-temperature bending resistance used in aerogel felt encapsulation according to claim 1, characterized in that, The pigment paste comprises the following components in parts by weight:

6. The sulfur-free fire-retardant coating for low-temperature bending resistance used in aerogel felt encapsulation according to claim 5, characterized in that, The sulfur-free pigment is selected from at least one of sulfur-free white pigment, sulfur-free black pigment, sulfur-free red pigment, sulfur-free blue pigment, sulfur-free green pigment, sulfur-free purple pigment, and sulfur-free yellow pigment; The defoamer is selected from at least one of mineral oil defoamers and modified polyether-modified siloxanes; The dispersant is selected from polyether-modified siloxanes.

7. The sulfur-free fire-retardant coating for low-temperature bending resistance used in aerogel felt encapsulation according to claim 6, characterized in that, The defoamer is selected from at least one of Airex 902W, BYK032, BYK028, and BYK011; The dispersant is selected from at least one of BYK190, BYK192, and Tego 760.

8. The sulfur-free fire-retardant coating for low-temperature bending resistance used in aerogel felt encapsulation according to claim 5, 6, or 7, characterized in that, The preparation method of the pigment paste includes the following steps: adding sulfur-free pigment, defoamer, dispersant and water weighed in parts by weight into a grinding mill, and grinding and dispersing to prepare pigment paste.

9. The sulfur-free fire-retardant coating for low-temperature bending resistance used in aerogel felt encapsulation according to claim 1, characterized in that, The flame retardant is selected from ammonium polyphosphate flame retardants; The plasticizer is selected from 2,2,4-trimethyl-1,3-pentanediol diisobutyrate; The defoamer is selected from at least one of mineral oil defoamers and modified polyether-modified siloxanes; The substrate wetting agent is selected from at least one of BYK346, BYK347, BYK348, BYK349, and Tego 270; The thickener is selected from at least one of RHEOLATE 299, ASE60, and RDS; The antifreeze is selected from propylene glycol.

10. The environmentally friendly flame-retardant coating for aerogel felt encapsulation according to claim 9, characterized in that, The ammonium polyphosphate flame retardant includes AP462; The defoamer is selected from at least one of Airex 902W, BYK032, BYK028, and BYK011.

11. The sulfur-free fire-retardant coating for low-temperature bending resistance used in aerogel felt encapsulation according to claim 1, characterized in that, The coating also includes a pH adjuster in parts by weight of 0-2 parts; The pH adjuster is selected from DMEA.

12. A method for preparing a sulfur-free fire-retardant coating resistant to low-temperature bending for aerogel felt encapsulation according to any one of claims 1-11, characterized in that, Includes the following steps: A. Add the flame retardant to water and disperse it evenly to form a flame retardant dispersion; B. Mix sulfur-free resin, plasticizer, defoamer, substrate wetting agent, and thickener, and disperse at high speed to prepare a high-shear water-based base material; B. Add the pigment paste and flame retardant dispersion to the high-shear water-based base material prepared in step A, and disperse at high speed to obtain the sulfur-free fireproof coating for low-temperature bending resistance for aerogel encapsulation.

13. A method for encapsulating aerogel felt, characterized in that, The process includes the following steps: applying the low-temperature bending-resistant, sulfur-free fire-retardant coating as described in any one of claims 1-11 to the surface of the aerogel felt by means of dip coating, spraying, roller coating or curtain coating, thereby encapsulating the aerogel felt.

14. A heat insulation pad, characterized in that, It includes aerogel felt and the sulfur-free fire-retardant coating with low-temperature bending resistance as described in any one of claims 1-11; the sulfur-free fire-retardant coating with low-temperature bending resistance is applied to the surface of the aerogel felt for encapsulating the aerogel felt.

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