Preparation method of phenolic aldehyde / silicon dioxide sol and preparation method of phenolic aldehyde / silicon dioxide aerogel composite fiber felt cold insulation material

Abstract

The invention discloses a preparation method of phenolic aldehyde / silicon dioxide sol and a preparation method of a phenolic aldehyde / silicon dioxide aerogel composite fiber felt cold insulation material, relates to the technical field of composite materials, and aims to solve the problem of poor matching property of silicon dioxide sol and phenolic aldehyde sol. The preparation method of the phenolic aldehyde / silicon dioxide sol comprises the following steps: hydrolyzing a silicon source to form silicon dioxide sol under an acidic condition; the method comprises the following steps: catalyzing a phenol source and an aldehyde source to form phenolic sol in the presence of a first basic catalyst; adding the phenolic aldehyde sol into the silicon dioxide sol, and adding a second basic catalyst to obtain phenolic aldehyde / silicon dioxide sol.

Description

Technical Field

[0001] The present application relates to the technical field of composite materials, and in particular to a method for preparing a phenolic / silica sol and a method for preparing a phenolic / silica aerogel composite fiber felt cold insulation material. Background Art

[0002] Liquefied natural gas (LNG) pipelines are an important part of LNG storage and transportation equipment. The quality of pipeline cold insulation not only affects the transportation efficiency of pipeline media, but also directly affects the safe operation of LNG storage and transportation equipment. The selection of LNG pipeline cold insulation materials is the key to ensure the safe, efficient and low-temperature operation of LNG pipelines. Suitable cold insulation materials can reduce the heat transfer from the surrounding environment into the pipeline and prevent condensation on the outer wall of the pipeline.

[0003] At present, the materials commonly used for LNG pipeline cold insulation mainly include rigid polyurethane (PUR) foam plastics, polyisocyanurate (PIR) foam plastics, foam glass (CG), etc. However, these cold insulation materials have high thermal conductivity and are not effective in the extreme environment of LNG pipelines.

[0004] Silica aerogel is a three-dimensional amorphous porous solid material with a special structure of high specific surface area, high porosity and low volume density, and has an extremely low thermal conductivity coefficient, which can reach 0.013W / (m·K) at room temperature, which is lower than that of static air, and has excellent thermal insulation performance. In addition, silica aerogel also has the characteristics of high stability and green environmental protection, and can be used in cold insulation materials.

[0005] In some implementations, an organosilicon precursor and a phenolic compound are dispersed in an acidic aqueous solution, the organosilicon precursor is hydrolyzed to obtain a mixed solution, which is mixed with chitosan, an aldehyde compound and water to form a sol, and then subjected to a hydrothermal reaction to obtain a phenolic / silica composite sol, which is further dried with supercritical carbon dioxide to obtain a composite aerogel. However, the phenolic network is not well cross-linked under acidic conditions, the silica sol and the phenolic sol are poorly compatible, and the mechanical properties of the resulting composite aerogel are poor. Summary of the invention

[0006] The purpose of the present application is to provide a method for preparing a phenolic / silica sol and a method for preparing a phenolic / silica aerogel composite fiber felt cold insulation material, aiming to solve the problem of poor matching between silica sol and phenolic sol.

[0007] In order to achieve the above objectives, this application adopts the following technical solutions:

[0008] In a first aspect, the present application provides a method for preparing a phenolic / silica sol. The method for preparing a phenolic / silica sol comprises:

[0009] Under acidic conditions, the silicon source is hydrolyzed to form a silica sol.

[0010] In the presence of a first alkaline catalyst, a phenol source and an aldehyde source are catalyzed to form a phenol-formaldehyde sol.

[0011] The phenolic sol is added into the silica sol, and a second alkaline catalyst is added to obtain the phenolic / silica sol.

[0012] In the preparation method of phenolic / silica sol provided in the embodiment of the present application, acidic conditions promote the hydrolysis of silicon source to form silica sol; the first alkaline catalyst can accelerate the polycondensation reaction between phenolic source and aldehyde source to form phenolic sol. Phenolic sol and silica sol are mixed, and silica sol can be modified by phenolic sol; wherein, the added second alkaline catalyst can adjust the pH value of phenolic / silica sol, improve the matching between silica sol and phenolic sol, not only can promote the formation of Si-O-Si bonds in silica network and the formation of phenolic network, but also can make phenolic sol and silica sol more compatible, improve the crosslinking degree between silica and phenolic network, construct a uniform organic-inorganic interpenetrating network, strengthen the neck of silica aerogel formed subsequently, improve the skeleton strength of silica aerogel, and then improve the mechanical properties of silica aerogel.

[0013] In some embodiments, the pH of the phenolic / silica sol is in the range of 4-7.

[0014] In some embodiments, the mass ratio of the phenolic sol to the silica sol ranges from 1% to 20%.

[0015] In some embodiments, the pH of the silica sol is in the range of 2-4.

[0016] In some embodiments, the pH of the phenolic sol is in the range of 5-9.

[0017] In some embodiments, the molar ratio of the phenol source to the aldehyde source is 1:1.4-2.0.

[0018] In some embodiments, the sum of the mass of the phenol source and the mass of the aldehyde source accounts for 20% to 50% of the mass of the phenol-formaldehyde sol.

[0019] In a second aspect, the present application provides a method for preparing a phenolic / silicon dioxide aerogel composite fiber felt cold insulation material. The method for preparing the phenolic / silicon dioxide aerogel composite fiber felt cold insulation material comprises:

[0020] The fiber felt is impregnated with the phenolic / silica sol obtained by the preparation method of the phenolic / silica sol in any one of the above embodiments.

[0021] After the gel is aged, a phenolic / silicon dioxide wet gel composite fiber felt cold-insulating material is formed.

[0022] The phenolic / silica wet gel composite fiber felt cold insulation material was aged in an ethanol solution.

[0023] The phenolic / silica wet gel composite fiber felt cold insulation material is immersed in an ethanol solution to perform solvent replacement.

[0024] The phenolic / silicon dioxide wet gel composite fiber felt cold insulation material is subjected to ethanol supercritical drying to obtain the phenolic / silicon dioxide aerogel composite fiber felt cold insulation material.

[0025] It can be understood that the beneficial effects that can be achieved by the method for preparing the phenolic / silica aerogel composite fiber felt cold insulation material provided in the above embodiments of the present application can be referred to the beneficial effects of the phenolic / silica sol mentioned above, which will not be repeated here.

[0026] In addition, the fiber felt has good strength and rigidity. After the fiber felt and phenolic / silica aerogel are composited, the fiber felt serves as an effective support for the phenolic / silica aerogel, which enables the phenolic / silica aerogel to fill the gaps between the fiber felts, thereby increasing the structural strength of the phenolic / silica aerogel and improving the mechanical properties of the phenolic / silica aerogel. The low thermal conductivity of the phenolic / silica aerogel enhances the overall cooling effect, while the fiber felt can further reduce the airflow and heat transfer pathways, thereby improving the cooling performance. Moreover, the combination of the fiber felt and the phenolic / silica aerogel can form a multi-layer insulation structure, which effectively reduces potential thermal bridges, reduces heat conduction, and further improves the cooling effect. In addition, the phenolic / silica aerogel composite fiber felt cooling material also has excellent hydrophobicity under the synergistic effect of the roughness of the surface fiber felt and the hydrophobic phenolic / silica sol.

[0027] In some embodiments, the phenolic / silicon dioxide wet gel composite fiber felt cold insulation material is aged in an ethanol solution, the aging temperature range is 25° C. to 150° C., and the aging time range is 12 h to 48 h. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 A flow chart of a method for preparing a phenolic / silica sol is provided for an embodiment of the present application;

[0030] Figure 2 Provide a flowchart of a preparation method for a phenolic / silica aerogel composite fiber felt cold insulation material for embodiments of the present application;

[0031] Figure 3 Provide a physical cross-sectional view of a phenolic / silica aerogel composite fiber felt cold insulation material provided in Embodiment 1 of the present application;

[0032] Figure 4 Provide a scanning electron microscope image of a phenolic / silica sol in a phenolic / silica aerogel composite fiber felt cold insulation material provided in Embodiment 1 of the present application;

[0033] Figure 5 Provide a scanning electron microscope image of a phenolic / silica aerogel composite fiber felt cold insulation material provided in Embodiment 1 of the present application;

[0034] Figure 6 Provide a hydrophobicity test image of a phenolic / silica aerogel composite fiber felt cold insulation material provided in Embodiment 2 of the present application;

[0035] Figure 7 Provide a scanning electron microscope image of a phenolic / silica aerogel composite fiber felt cold insulation material provided in Embodiment 4 of the present application. Detailed implementation manners

[0036] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0037] The terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise stated, the meaning of "a plurality" is two or more.

[0038] In the embodiments of the present application, words such as "exemplary" or "for example" are used to represent examples, illustrations or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the embodiments of the present application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Exactly, using words such as "exemplary" or "for example" is intended to present relevant concepts in a specific manner.

[0039] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0040] Liquefied natural gas (LNG) pipelines are an important part of LNG storage and transportation equipment. The quality of pipeline cold insulation not only affects the transportation efficiency of pipeline media, but also directly affects the safe operation of LNG storage and transportation equipment. The selection of LNG pipeline cold insulation materials is the key to ensure the safe, efficient and low-temperature operation of LNG pipelines. Suitable cold insulation materials can reduce the heat transfer from the surrounding environment into the pipeline and prevent condensation on the outer wall of the pipeline.

[0041] At present, the materials commonly used for LNG pipeline cold insulation mainly include rigid polyurethane (PUR) foam plastics, polyisocyanurate (PIR) foam plastics, foam glass (CG), etc. However, these cold insulation materials have high thermal conductivity and are not effective in the extreme environment of LNG pipelines.

[0042] Silica aerogel is a three-dimensional amorphous porous solid material with a special structure of high specific surface area, high porosity and low volume density, and has an extremely low thermal conductivity coefficient, which can reach 0.013W / (m·K) at room temperature, which is lower than that of static air, and has excellent thermal insulation performance. In addition, silica aerogel also has the characteristics of high stability and green environmental protection, and can be used in cold insulation materials.

[0043] In some implementations, an organosilicon precursor and a phenolic compound are dispersed in an acidic aqueous solution, the organosilicon precursor is hydrolyzed to obtain a mixed solution, which is mixed with chitosan, an aldehyde compound and water to form a sol, which is then subjected to a hydrothermal reaction to obtain a phenolic / silica composite sol, which is further dried with supercritical carbon dioxide to obtain a composite aerogel. However, the phenolic network is not well cross-linked under acidic conditions, the silica sol and the phenolic sol are poorly compatible, and the resulting aerogel material has poor mechanical properties.

[0044] In addition, in some implementations, phenols, aldehydes, aminosilanes, and siloxanes with one or two hydrocarbon groups are mixed with a solvent and dried at normal pressure to obtain block-shaped hydrophobic phenolic / silica composite aerogels. Although this saves time, the silicon source is not fully hydrolyzed under alkaline conditions, and a condensation reaction occurs rapidly to form a short-chain cross-linked three-dimensional structure. The cross-linking effect is weak, and macropores are easily formed, which increases the thermal conductivity and affects the cold preservation performance.

[0045] Based on this, the embodiments of the present application provide a method for preparing phenolic / silica sol. Figure 1 As shown, the preparation method of the phenolic / silicon dioxide sol includes: S1 to S3.

[0046] S1: Under acidic conditions, the silicon source is hydrolyzed to form a silica sol.

[0047] Exemplarily, the silicon source may be tetraethyl orthosilicate (TEOS).

[0048] For example, tetraethyl orthosilicate (TEOS) is used as a silicon source, deionized water and ethanol are used as solvents, and hydrochloric acid is added for hydrolysis to obtain an acidic silica sol.

[0049] Exemplarily, the concentration of silica in the silica sol is 6 wt % to 10 wt %.

[0050] S2: In the presence of a first alkaline catalyst, a phenol source and an aldehyde source are catalyzed to form a phenol-formaldehyde sol.

[0051] Exemplarily, the first alkaline catalyst may be at least one of aqueous ammonia, γ-aminopropyltriethoxysilane (APTES), hexamethylenetetramine (in an amount of 10 wt % to 20 wt % of the phenolic sol content), and tetramethylammonium hydroxide.

[0052] Exemplarily, the phenol source may be resorcinol.

[0053] Exemplarily, the aldehyde source may be formaldehyde.

[0054] Exemplarily, resorcinol, formaldehyde, a first alkaline catalyst and ethanol are mixed and stirred to obtain a phenolic sol.

[0055] S3: adding phenolic sol to silica sol, and adding a second alkaline catalyst to obtain phenolic / silica sol.

[0056] Exemplarily, the second alkaline catalyst may be at least one of aqueous ammonia, γ-aminopropyltriethoxysilane (APTES), and tetramethylammonium hydroxide.

[0057] For example, the mixing and stirring time of the silica sol and the phenolic sol may be 0.5 h to 3 h.

[0058] Understandably, phenolic resin raw materials are cheap, have the characteristics of not becoming brittle at low temperatures and have good compressive and tensile properties. Its combination with silica sol can improve the brittleness of silica sol and enhance the mechanical properties of silica sol.

[0059] However, pure silica aerogel is brittle due to the fragile Si-O-Si bonding at the neck. That is, the microstructure of silica sol is composed of a three-dimensional network formed by cross-linking silica nanoparticles and a large number of gaps between the networks. The fine skeleton structure of pure silica aerogel and the fragile neck connection between particles make it have poor resistance to external forces, making it brittle and easy to break.

[0060] The acidic conditions in S1 promote the hydrolysis of the silicon source and form a silica sol; the first alkaline catalyst in S2 can accelerate the polycondensation reaction between the phenol source and the aldehyde source to form a phenolic sol. In S3, the phenolic sol and the silica sol are mixed, and the silica sol can be modified by the phenolic sol; the added second alkaline catalyst can adjust the pH value of the phenolic / silica sol, improve the matching between the silica sol and the phenolic sol, not only promote the formation of Si-O-Si bonds in the silica network and the formation of the phenolic network, but also make the phenolic sol and the silica sol more compatible, improve the cross-linking degree between the silica and the phenolic network, and construct a uniform organic-inorganic interpenetrating network, so that the neck of the silica aerogel formed subsequently is strengthened, the skeleton strength of the silica aerogel is improved, and the mechanical properties of the silica aerogel are improved.

[0061] In some embodiments, the pH of the phenolic / silica sol is in the range of 4-7.

[0062] For example, the pH of the phenolic / silica sol may be 4, 5, 6 or 7, etc., which is not limited here.

[0063] It can be understood that the above-mentioned setting can enable the phenolic formaldehyde / silica sol to gel at an appropriate rate to obtain a uniform gel network.

[0064] In some embodiments, the mass ratio of the phenolic sol to the silica sol ranges from 1% to 20%.

[0065] For example, the mass ratio of the phenolic sol to the silica sol may be 1%, 5%, 10%, 15% or 20%, etc., which is not limited herein.

[0066] It can be understood that the above setting controls the amount of phenolic sol added within the above setting range, which can provide a skeleton support effect, ensure that the aerogel system is still mainly composed of a three-dimensional silica skeleton, and retain the high porosity and low thermal conductivity advantages brought by the unique structure of silica aerogel; on the other hand, it prevents the high phenolic content from forming clusters between polymers, blocking pores, increasing solid conduction paths, and affecting the cold preservation effect.

[0067] In some embodiments, the pH of the silica sol is in the range of 2-4.

[0068] For example, the pH of the silica sol can be 2, 2.5, 3, 3.5 or 4, etc., which is not limited here.

[0069] It can be understood that under acidic conditions of pH = 2 to 4, the hydrolysis rate of the silicon source can be made greater than the condensation rate, which promotes the full hydrolysis of the silicon source. Stable and fully hydrolyzed silica aerogel is beneficial to obtaining a uniform aerogel structure.

[0070] In some embodiments, the pH of the phenolic sol ranges from 5-9.

[0071] For example, the pH of the phenolic sol may be 5, 6, 7, 8 or 9, etc., which is not limited here.

[0072] It can be understood that within the range of pH=5 to 9, the polycondensation reaction between the phenol source and the aldehyde source can be effectively promoted, which is beneficial to the formation of a cross-linked structure of the phenol-formaldehyde sol.

[0073] In some embodiments, the molar ratio of the phenol source to the aldehyde source is 1:1.4-2.0.

[0074] For example, the molar ratio of the phenol source to the aldehyde source can be 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2.0, etc., which is not limited here.

[0075] It can be understood that the above arrangement can improve the catalytic reaction of the phenol source and the aldehyde source, make the polymerization process more complete, promote the cross-linking reaction between phenol and aldehyde, and help improve the cross-linking degree of the phenol-formaldehyde sol.

[0076] In some embodiments, the sum of the mass of the phenol source and the mass of the aldehyde source accounts for 20% to 50% of the mass of the phenol-formaldehyde sol.

[0077] For example, the sum of the mass of the phenol source and the mass of the aldehyde source may account for 20%, 30%, 40% or 50% of the mass of the phenol-formaldehyde sol, and the amount is not limited thereto.

[0078] It can be understood that the catalytic reaction of the phenol source and the aldehyde source can be promoted under a suitable viscosity in the mixed system of the phenol source and the aldehyde source, so that the polymerization process is more complete and helps to improve the crosslinking degree of the phenol-formaldehyde sol.

[0079] The embodiment of the present application provides a method for preparing a phenolic / silicon dioxide aerogel composite fiber felt cold insulation material. Figure 2 As shown, the preparation method of the phenolic / silicon dioxide aerogel composite fiber felt cold insulation material includes: R1 to R5.

[0080] R1: Impregnate the fiber mat with phenolic / silica sol.

[0081] It can be understood that the phenolic formaldehyde / silica sol is the phenolic formaldehyde / silica sol obtained by the preparation method of the phenolic formaldehyde / silica sol in any one of the above embodiments.

[0082] Exemplarily, the fiber mat may be a glass fiber mat.

[0083] Exemplarily, vacuum impregnation may be performed at 20°C to 25°C.

[0084] R2: After aging of the gel, a phenolic / silica wet gel composite fiber felt cold insulation material is formed.

[0085] R3: Aging the phenolic / silica wet gel composite fiber felt cold insulation material in an ethanol solution.

[0086] R4: Soak the phenolic / silica wet gel composite fiber felt cold insulation material in an ethanol solution to perform solvent replacement.

[0087] Exemplarily, ethanol may be replaced every 6 to 12 hours, and the operation may be repeated 2 to 4 times.

[0088] R5: The phenolic / silica wet gel composite fiber felt cold insulation material is subjected to supercritical ethanol drying to obtain a phenolic / silica aerogel composite fiber felt cold insulation material.

[0089] Exemplarily, the supercritical conditions of ethanol may be: maintaining the temperature in the range of 250° C. to 270° C. and the pressure in the range of 7 MPa to 10 MPa, maintaining the temperature and pressure for 0.5 h to 1.5 h, and then releasing the pressure.

[0090] Understandably, R1 can ensure that the phenolic / silica sol fully penetrates into the fiber felt; R2 forms a preliminary phenolic / silica wet gel composite fiber felt insulation material after a certain period of aging; R3 aging process is to allow the condensation reaction of the phenolic / silica wet gel in the wet gel composite fiber felt insulation material with a relatively fragile skeleton to continue, strengthen the gel skeleton, promote the interaction between the silica sol and the phenolic sol, and help form a more uniform composite structure. In R4, the medium (such as water) in the pores of the aged phenolic / silica wet gel composite fiber felt insulation material needs to be completely replaced with ethanol to reduce the surface tension of the gas-liquid interface and prepare for subsequent supercritical drying. The supercritical drying of ethanol in R5 can convert ethanol from liquid to gas and then to supercritical fluid state, eliminating the surface tension of the gas-liquid interface. In the supercritical state, ethanol can penetrate and take away the moisture in the phenolic / silica wet gel without destroying its microporous structure, and complete the drying, finally obtaining phenolic / silica aerogel composite fiber felt; and the high temperature environment provided by ethanol supercritical conditions can promote the esterification reaction between Si-OH on the gel surface and ethanol to form Si-OC 2 H 5 , giving the phenolic / silica sol certain hydrophobic properties; supercritical drying can effectively protect the microstructure of the material and avoid excessive shrinkage or damage that may occur during conventional drying.

[0091] In some embodiments, R3 ages the phenolic / silica wet gel composite fiber felt cold insulation material in an ethanol solution, the aging temperature ranges from 25° C. to 150° C., and the aging time ranges from 12 h to 48 h.

[0092] For example, the aging temperature may be 25° C., 50° C., 75° C., 100° C., 125° C., or 150° C., etc., but is not limited thereto.

[0093] Exemplarily, the aging time may be 12 h, 20 h, 28 h, 36 h, 40 h or 48 h, etc., which is not limited here.

[0094] It can be understood that the above settings can optimize the performance of the phenolic / silica aerogel composite fiber felt cold insulation material to achieve a good performance balance, achieve more sufficient cross-linking, and improve the mechanical properties of the phenolic / silica aerogel composite fiber felt cold insulation material.

[0095] The embodiment of the present application provides a cold-insulating material, which comprises: a phenolic / silicon dioxide aerogel composite fiber felt cold-insulating material prepared by the method for preparing a phenolic / silicon dioxide aerogel composite fiber felt cold-insulating material in the above embodiment.

[0096] It can be understood that when the cold insulation material includes a phenolic / silica aerogel composite fiber felt cold insulation material, the fiber felt has good strength and rigidity. After the fiber felt and the phenolic / silica aerogel are composited, the fiber felt serves as an effective support for the phenolic / silica aerogel, allowing the phenolic / silica aerogel to fill the gaps between the fiber felts, thereby increasing the structural strength of the phenolic / silica aerogel and improving the mechanical properties of the phenolic / silica aerogel. While the low thermal conductivity of the phenolic / silica aerogel enhances the overall cold insulation effect, the fiber felt can further reduce the airflow and heat transfer pathways, thereby improving the cold insulation performance. Moreover, the combination of the fiber felt and the phenolic / silica aerogel can form a multi-layer insulation structure, effectively reducing potential thermal bridges, reducing heat conduction, and further improving the cold insulation effect. Furthermore, the phenolic / silica aerogel composite fiber felt cold insulation material also has excellent hydrophobicity under the synergistic effect of the roughness of the surface fiber felt and the hydrophobic phenolic / silica sol.

[0097] In some embodiments, the phenolic / silicon dioxide aerogel composite fiber felt cold insulation material meets at least one of the following conditions:

[0098] The density range of cold insulation materials is 0.20g / cm 3 ~0.25g / cm 3 .

[0099] For example, the density of the cold insulation material can be 0.20 g / cm 3, 0.21g / cm 3 , 0.22g / cm 3 , 0.23g / cm 3 , 0.24g / cm 3 or 0.25g / cm 3 Etc., there is no limitation here.

[0100] The thermal conductivity of the cold-insulating material at 20°C to 25°C ranges from 0.020 W / (m·K) to 0.030 W / (m·K).

[0101] Exemplarily, the thermal conductivity of the cold insulation material at 20°C to 25°C can be 0.020W / (m·K), 0.022W / (m·K), 0.024W / (m·K), 0.026W / (m·K), 0.028W / (m·K) or 0.030W / (m·K), etc., but there is no limitation here.

[0102] The compressive strength of the cold insulation material is in the range of 0.3 MPa to 0.8 MPa under a strain of 8% to 12%.

[0103] For example, the density of the compressive strength of the cold-insulating material under a strain of 8% to 12% may be 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa or 0.8 MPa, etc., which is not limited here.

[0104] The tensile strength of the cold insulation material ranges from 0.5 MPa to 3.0 MPa under a strain of 8% to 12%.

[0105] For example, the tensile strength of the cold-insulating material under a strain of 8% to 12% may be 0.5 MPa, 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa or 3 MPa, etc., which is not limited here.

[0106] It can be understood that the cold-insulating material of the present application is light in weight and has low thermal conductivity and excellent mechanical properties, meeting the requirements of industrial production for light weight, heat insulation and high strength.

[0107] The contents of this application are further described below in conjunction with embodiments.

[0108] Example 1

[0109] Embodiment 1 provides a phenolic / silicon dioxide aerogel composite fiber felt cold insulation material. The phenolic / silicon dioxide aerogel composite fiber felt cold insulation material comprises the following preparation steps:

[0110] Step (1): using tetraethyl orthosilicate as a silicon source for hydrolysis, deionized water and ethanol as solvents, adding hydrochloric acid for hydrolysis for 4 hours to obtain a silica sol; wherein the concentration of silica is 6 wt%.

[0111] Step (2): Mix resorcinol, formaldehyde, APTES and ethanol, and stir at room temperature for 2 hours to obtain a phenolic sol; wherein the molar ratio of resorcinol:formaldehyde:ethanol is 1:1.6:5, and the pH of the phenolic sol is 8.

[0112] Step (3): adding phenolic sol to silica sol, adding tetramethylammonium hydroxide to adjust the pH to 7, to obtain phenolic / silica sol; wherein the mass ratio of phenolic sol to silica sol is 2.5%.

[0113] Step (4): immerse the glass fiber felt in the phenolic / silica sol obtained in step (3), put it into a vacuum drying oven, and perform vacuum impregnation at room temperature. After the gel is aged, a phenolic / silica wet gel composite fiber felt cold insulation material is obtained.

[0114] Step (5): placing the phenolic / silica wet gel composite fiber felt cold insulation material in ethanol and aging it at 60° C. for 24 hours.

[0115] Step (6): Soak the phenolic / silica wet gel composite fiber felt cold insulation material in ethanol to replace the solvent, replace the ethanol every 8 hours, and replace it 3 times.

[0116] Step (7): subjecting the phenolic / silica wet gel composite fiber felt cold insulation material to ethanol supercritical drying, wherein the temperature in the supercritical drying kettle is 250° C. and the pressure is 9 MPa, and the pressure is released after the heat and pressure are maintained for 1 hour to obtain the phenolic / silica aerogel composite fiber felt cold insulation material.

[0117] The macroscopic cross-sectional view of the phenolic / silicon dioxide aerogel composite fiber felt cold insulation material provided in Example 1 is shown in the attached figure. Figure 3 As shown, the appearance is complete, without delamination and obvious defects; the microscopic morphology of the phenolic / silica sol in the phenolic / silica aerogel composite fiber felt cold insulation material is as shown Figure 4 As shown, it is a pearl chain nano-mesoporous network; the combination of the fiber felt and the phenolic / silica sol is shown in Figure 5 The density of the phenolic / silicon dioxide aerogel composite fiber felt cold insulation material provided in Example 1 is 0.22 g / cm 3 The room temperature thermal conductivity is 0.024W / (m·K), the compressive strength is 0.55MPa under 10% strain, and the tensile strength is 2.20MPa, which has excellent hydrophobic properties.

[0118] Example 2

[0119] Example 2 provides a phenolic / silicon dioxide aerogel composite fiber felt cold insulation material. The phenolic / silicon dioxide aerogel composite fiber felt cold insulation material includes the following preparation steps:

[0120] Step (1): using tetraethyl orthosilicate as a silicon source for hydrolysis, deionized water and ethanol as solvents, adding hydrochloric acid for hydrolysis for 2 hours to obtain a silica sol; wherein the concentration of silica is 10 wt%.

[0121] Step (2): mixing resorcinol, formaldehyde, ammonia water and ethanol, and stirring at room temperature for 3 hours to obtain a phenolic sol; wherein the molar ratio of resorcinol:formaldehyde:ethanol is 1:2:7, and the pH of the phenolic sol is 9.

[0122] Step (3): adding phenolic sol to silica sol, and adding ammonia water to adjust the pH to 5 to obtain phenolic / silica sol; wherein the mass ratio of phenolic sol to silica sol is 5%.

[0123] Step (4): immerse the glass fiber felt in the phenolic / silica sol obtained in step (3), put it into a vacuum drying oven, and perform vacuum impregnation at room temperature. After the gel is aged, a phenolic / silica wet gel composite fiber felt cold insulation material is obtained.

[0124] Step (5): placing the phenolic / silica wet gel composite fiber felt cold insulation material in ethanol and aging it at 50° C. for 48 hours.

[0125] Step (6): Soak the phenolic / silica wet gel composite fiber felt cold insulation material in ethanol to replace the solvent, replace the ethanol every 6 hours, and replace it 4 times.

[0126] Step (7): subjecting the phenolic / silica wet gel composite fiber felt cold insulation material to ethanol supercritical drying, wherein the temperature in the supercritical drying kettle is 270° C. and the pressure is 7 MPa. After maintaining the temperature and pressure for 1 hour, the pressure is released to obtain the phenolic / silica aerogel composite fiber felt cold insulation material.

[0127] The density of the phenolic / silicon dioxide aerogel composite fiber felt cold insulation material provided in Example 2 is 0.20 g / cm 3 The room temperature thermal conductivity is 0.022W / (m·K), the compressive strength is 0.45MPa at 10% strain, and the tensile strength is 0.85MPa. It has excellent hydrophobic properties. The hydrophobic properties test is as follows: Figure 6 As shown, it has excellent hydrophobic properties.

[0128] Example 3

[0129] Example 3 provides a phenolic / silicon dioxide aerogel composite fiber felt cold insulation material. The phenolic / silicon dioxide aerogel composite fiber felt cold insulation material includes the following preparation steps:

[0130] Step (1): using tetraethyl orthosilicate as a silicon source for hydrolysis, deionized water and ethanol as solvents, adding hydrochloric acid for hydrolysis to obtain a silica sol; wherein the concentration of the silica is 8 wt%.

[0131] Step (2): Mix resorcinol, formaldehyde, APTES and ethanol, and stir at room temperature for 3 hours to obtain a phenolic sol; wherein the molar ratio of resorcinol:formaldehyde:ethanol is 1:1.4:2, and the pH of the phenolic sol is 8.5.

[0132] Step (3): adding phenolic sol to silica sol, and adding ammonia water to adjust the pH to 5 to obtain phenolic / silica sol; wherein the mass ratio of phenolic sol to silica sol is 10%.

[0133] Step (4): immerse the glass fiber felt in the phenolic / silica sol obtained in step (3), put it into a vacuum drying oven, and perform vacuum impregnation at room temperature. After the gel is aged, a phenolic / silica wet gel composite fiber felt cold insulation material is obtained.

[0134] Step (5): placing the phenolic / silica wet gel composite fiber felt cold insulation material in ethanol and aging it at 120° C. for 24 hours.

[0135] Step (6): soaking the phenolic / silica wet gel composite fiber felt cold insulation material in ethanol to replace the solvent, replacing the ethanol every 12 hours, and replacing twice;

[0136] Step (7): subjecting the phenolic / silica wet gel composite fiber felt cold insulation material to ethanol supercritical drying, wherein the temperature in the supercritical drying kettle is 260° C. and the pressure is 8 MPa. After maintaining the temperature and pressure for 1 hour, the pressure is released to obtain the phenolic / silica aerogel composite fiber felt cold insulation material.

[0137] The phenolic / silica aerogel composite fiber felt cold insulation material provided in Example 3 has a thermal conductivity of 0.026 W / (m·K), a compressive strength of 0.78 MPa at 10% strain, and a tensile strength of 2.75 MPa, and has excellent hydrophobic properties.

[0138] Example 4

[0139] Example 4 provides a phenolic / silicon dioxide aerogel composite fiber felt cold insulation material. The phenolic / silicon dioxide aerogel composite fiber felt cold insulation material comprises the following preparation steps:

[0140] Step (1): using tetraethyl orthosilicate as a silicon source for hydrolysis, deionized water and ethanol as solvents, adding hydrochloric acid for hydrolysis for 5 hours to obtain a silica sol; wherein the concentration of silica is 9wt%.

[0141] Step (2): mixing resorcinol, formaldehyde, hexamethylenetetramine and ethanol and stirring for 1 hour to obtain a phenolic sol; wherein the molar ratio of resorcinol:formaldehyde:ethanol is 1:1.5:10, and the pH of the phenolic sol is 5.

[0142] Step (3): adding phenolic sol to silica sol, and adding ammonia water to adjust the pH to 6 to obtain phenolic / silica sol; wherein the mass ratio of phenolic sol to silica sol is 15%.

[0143] Step (4): immerse the glass fiber felt in the phenolic / silica sol obtained in step (3), put it into a vacuum drying oven, and perform vacuum impregnation at room temperature. After the gel is aged, a phenolic / silica wet gel composite fiber felt cold insulation material is obtained.

[0144] Step (5): placing the phenolic / silica wet gel composite fiber felt cold insulation material in ethanol and aging it at 120° C. for 18 h.

[0145] Step (6): soaking the phenolic / silica wet gel composite fiber felt cold insulation material in ethanol to replace the solvent, replacing the ethanol every 6 hours, and replacing it 4 times;

[0146] Step (7): subjecting the phenolic / silica wet gel composite fiber felt cold insulation material to ethanol supercritical drying, wherein the temperature in the supercritical drying kettle is 250° C. and the pressure is 8.5 MPa. After maintaining the temperature and pressure for 1 hour, the pressure is released to obtain the phenolic / silica aerogel composite fiber felt cold insulation material.

[0147] The microscopic morphology of the phenolic / silicon dioxide aerogel composite fiber felt cold insulation material provided in Example 4 is as follows: Figure 7 As shown, the density of the composite material is 0.25 g / cm 3 The room temperature thermal conductivity is 0.027W / (m·K), the compressive strength is 0.36MPa at 10% strain, and the tensile strength is 1.08MPa, which has excellent hydrophobic properties.

[0148] Example 5

[0149] Example 5 provides a phenolic / silicon dioxide aerogel composite fiber felt cold insulation material. The phenolic / silicon dioxide aerogel composite fiber felt cold insulation material comprises the following preparation steps:

[0150] Step (1): using tetraethyl orthosilicate as a silicon source for hydrolysis, deionized water and ethanol as solvents, adding hydrochloric acid for hydrolysis for 5 hours to obtain a silica sol; wherein the concentration of silica is 7 wt%.

[0151] Step (2): resorcinol, formaldehyde, tetramethylammonium hydroxide and ethanol are mixed and stirred at room temperature for 1 hour to obtain a phenolic sol; wherein the molar ratio of resorcinol:formaldehyde:ethanol is 1:1.7:4, and the pH of the phenolic sol is 6.5.

[0152] Step (3): adding phenolic sol to silica sol, and adding APTES to adjust the pH value to 7 to obtain phenolic / silica sol; wherein the mass ratio of phenolic sol to silica sol is 20%.

[0153] Step (4): immersing the glass fiber felt with the phenolic / silica sol obtained in step (3), placing the glass fiber felt in a vacuum drying oven, and performing vacuum impregnation at room temperature, and obtaining a phenolic / silica wet gel composite fiber felt cold insulation material after aging the gel;

[0154] Step (5): placing the phenolic / silica wet gel composite fiber felt cold insulation material in ethanol and aging it at 150° C. for 24 hours;

[0155] Step (6): soaking the phenolic / silica wet gel composite fiber felt cold insulation material in ethanol to replace the solvent, replacing the ethanol every 8 hours for 3 times;

[0156] Step (7): subjecting the phenolic / silica wet gel composite fiber felt cold insulation material to ethanol supercritical drying, wherein the temperature in the supercritical drying kettle is 270° C. and the pressure is 9 MPa. After maintaining the temperature and pressure for 1 hour, the pressure is released to obtain the phenolic / silica aerogel composite fiber felt cold insulation material.

[0157] The density of the phenolic / silicon dioxide aerogel composite fiber felt cold insulation material provided in Example 5 is 0.22 g / cm 3 The room temperature thermal conductivity is 0.028W / (m·K), the compressive strength is 0.52MPa at 10% strain, and the tensile strength is 1.82MPa, which has excellent hydrophobic properties.

[0158] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing a phenolic / silica sol, characterized in that: include: Under acidic conditions, the silicon source is hydrolyzed to form a silica sol; In the presence of a first alkaline catalyst, a phenol source and an aldehyde source are catalyzed to form a phenol-formaldehyde sol; The phenolic sol is added into the silica sol, and a second alkaline catalyst is added to obtain the phenolic / silica sol.

2. The method for preparing phenolic / silica sol according to claim 1, characterized in that: The pH range of the phenolic formaldehyde / silicon dioxide sol is 4-7.

3. The method for preparing phenolic / silica sol according to claim 1, characterized in that: The mass ratio of the phenolic sol to the silica sol is in the range of 1% to 20%.

4. The method for preparing phenolic / silica sol according to claim 1, characterized in that: The pH range of the silica sol is 2-4.

5. The method for preparing phenolic / silica sol according to claim 1, characterized in that: The pH range of the phenolic sol is 5-9.

6. The method for preparing phenolic / silica sol according to claim 1, characterized in that: The catalytic molar ratio of the phenol source to the aldehyde source is 1:1.4-2.

0.

7. The method for preparing phenolic / silica sol according to claim 1, characterized in that: The sum of the mass of the phenol source and the mass of the aldehyde source accounts for 20% to 50% of the mass of the phenol-formaldehyde sol.

8. A method for preparing a phenolic / silicon dioxide aerogel composite fiber felt cold insulation material, characterized in that: include: The fiber felt is impregnated with the phenolic / silica sol obtained by the method for preparing the phenolic / silica sol according to any one of claims 1 to 7; After the gel is aged, a phenolic / silicon dioxide wet gel composite fiber felt cold-insulating material is formed; Aging the phenolic / silicon dioxide wet gel composite fiber felt cold insulation material in an ethanol solution; The phenolic / silicon dioxide wet gel composite fiber felt cold insulation material is immersed in an ethanol solution to perform solvent replacement; The phenolic / silicon dioxide wet gel composite fiber felt cold insulation material is subjected to ethanol supercritical drying to obtain the phenolic / silicon dioxide aerogel composite fiber felt cold insulation material.

9. The method for preparing the phenolic / silicon dioxide aerogel composite fiber felt cold insulation material according to claim 8, characterized in that: The phenolic / silicon dioxide wet gel composite fiber felt cold insulation material is aged in an ethanol solution, the aging temperature range is 25° C. to 150° C., and the aging time range is 12 h to 48 h.

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