Preparation method of polyurethane modified phenolic aerogel and prepared polyurethane modified phenolic aerogel

Abstract

The invention provides a preparation method of polyurethane modified phenolic aerogel and the prepared polyurethane modified phenolic aerogel. The preparation method comprises the following steps: S1, preparing a polyurethane prepolymer terminated by a phenol ring; s2, mixing the phenol ring-terminated polyurethane prepolymer with phenolic resin to prepare a mixed solution, and adding a curing agent to carry out gel reaction to prepare polyurethane modified phenolic resin gel; s3, a liquid phase in the polyurethane modified phenolic resin gel is removed, and the polyurethane modified phenolic resin aerogel is obtained. According to the preparation method disclosed by the invention, a phenol ring is introduced into a polyurethane prepolymer as an end group to obtain a phenol ring-terminated polyurethane prepolymer, and then the phenol ring-terminated polyurethane prepolymer is mixed with phenolic resin to prepare the aerogel, so that the problem that polyurethane cannot be effectively introduced into a phenolic resin system is solved, and the preparation method has the characteristics of simple process, short period and suitability for industrial production; and the prepared aerogel has good mechanical properties.

Description

Technical Field

[0001] The invention belongs to the technical field of aerogel materials, and particularly relates to a method for preparing polyurethane-modified phenolic aerogel. Background Art

[0002] Aerogel is a low-density, high-specific-surface-area material with a three-dimensional network structure of continuous pores composed of interconnected particles. Aerogel has attracted extensive attention from scientists in various fields due to its unique physical and chemical properties. With the rapid development of aerogel, various high-performance aerogel materials have emerged, and have shown attractive application prospects in the fields of environmental protection, energy storage and conversion, and biomedicine. Phenolic resin is a traditional industrial material with economical and readily available raw materials. Aerogel made of phenolic resin has excellent thermal and chemical stability, thermal insulation and fire resistance, and high residual carbon rate. Therefore, phenolic resin aerogel has good application prospects in thermal insulation materials.

[0003] However, due to the poor toughness of phenolic aerogel, what is obtained is a brittle solid with low mechanical strength. The aerogel is easily broken under the action of external force, which restricts the application of phenolic aerogel. In order to improve the mechanical properties of phenolic aerogel, the common method is to modify it by fiber blending, but this method increases the density of aerogel due to the introduction of fiber, and the process is complicated. How to develop a phenolic aerogel with a simple preparation process and excellent performance to achieve high strength of phenolic aerogel through the regulation of aerogel intrinsic structure, such as aerogel pore structure and aerogel skeleton molecular structure, has important application value.

[0004] Polyurethane is a block copolymer synthesized by the reaction of polyisocyanate and polyol, in which polyol is used as soft segment and polyisocyanate constitutes hard segment. The structural characteristics of soft segment make the material have good impact resistance and elasticity. The soft segment in polyurethane can be used to modify the rigidity brought by the structure of phenolic resin itself, and polyurethane is introduced into the skeleton structure of phenolic aerogel, which is expected to achieve a reinforcing effect. However, since polyurethane is prepared by the reaction of isocyanate and active hydrogen, in the preparation process of phenolic aerogel, low-toxicity and low-cost solvents such as water and alcohol are mostly selected. Such solvents can react with isocyanate by themselves, and stable sol cannot be obtained, so that the polyurethane component cannot be effectively introduced into the skeleton structure of phenolic aerogel, and the modification effect cannot be achieved. Therefore, how to design the molecular structure of polyurethane so that it can form a stable sol with phenolic, and further introduce the polyurethane component into the skeleton of phenolic aerogel through gel curing of sol, play a reinforcing effect, and match the preparation process of aerogel, is extremely important for the preparation of high-strength phenolic aerogel.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] One of the purposes of the present invention is to provide a method for preparing polyurethane-modified phenolic aerogel and the prepared polyurethane-modified phenolic aerogel in view of the problems in the above-mentioned prior art. The present invention introduces phenolic rings as end groups into polyurethane prepolymers to obtain phenolic ring-terminated polyurethane prepolymers, which are then mixed with phenolic resins to prepare aerogels, thereby solving the problem that polyurethane cannot be effectively introduced into phenolic resin systems; by introducing a polyurethane structure into the skeleton structure of phenolic aerogels, the mechanical strength of phenolic aerogels is greatly improved.

[0007] By adopting the preparation method of the polyurethane modified phenolic aerogel of the present invention, polyurethane is smoothly introduced into the phenolic aerogel, and the intrinsic mechanical properties of the phenolic resin are improved. At the same time, the aerogel can be smoothly prepared by the existing aerogel preparation method, and can be fully adapted to the existing aerogel preparation process.

[0008] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a polyurethane modified phenolic aerogel, comprising the following steps:

[0009] S1, preparing a polyurethane prepolymer terminated with a phenol ring;

[0010] S2, mixing a phenol ring-terminated polyurethane prepolymer with a phenolic resin to obtain a mixed solution, and adding a curing agent to perform a gel reaction to obtain a polyurethane-modified phenolic resin gel;

[0011] S3, removing the liquid phase in the polyurethane-modified phenolic resin gel to obtain the polyurethane-modified phenolic aerogel.

[0012] In the above scheme, polyurethane is introduced into the phenolic aerogel system in the form of a polyurethane prepolymer terminated with a phenolic ring. Since the isocyanate group has reacted with the phenolic ring, it will not react further after being introduced into the phenolic aerogel system, thereby solving the problem of poor compatibility between the terminal isocyanate group in the polyurethane and the phenolic aerogel preparation system, and the generation of aerogel will not be affected by the introduction of the polyurethane. Since the polyurethane contains soft segments and hydrogen bonds, the elasticity and toughness of the phenolic resin are improved after being introduced into the phenolic aerogel system.

[0013] Furthermore, step S1 specifically includes:

[0014] Polyurethane is prepared by reacting diol and diisocyanate, and then the polyurethane is terminated by phenolic compounds to obtain a phenol ring terminated polyurethane prepolymer;

[0015] The phenolic compound contains a phenolic hydroxyl group and at least one functional group having a reactive activity with an isocyanate group.

[0016] In the above scheme, the phenolic compound is limited to have a phenolic hydroxyl group and at least one functional group capable of reacting with isocyanate, so that after the phenolic compound is blocked by the functional group having reaction activity with isocyanate and the polyurethane, the phenolic ring at the end still has a hydroxyl group, and then the polyurethane can be connected to the phenolic resin molecule through the reaction of the blocked phenolic ring with the phenolic resin, thereby achieving the improvement of the intrinsic mechanical properties of the phenolic resin.

[0017] Furthermore, the functional groups reactive with isocyanate include hydroxyl, amino, phenolic hydroxyl, mercapto, hydroxymethyl, and aminomethyl. Regarding the differences in the reactivity of different functional groups, technical researchers have found that amino functional groups have high reactivity with isocyanate and can react quickly at room temperature; at the same time, the position of the functional group on the phenol ring can be ortho, meta, and para. Ortho functional group phenols include salicyl alcohol, meta functional group phenols include resorcinol and meta-aminophenol, and para functional group phenols include 4-mercaptophenol. Phenolic molecules with meta functional group structures have higher reactivity at the reaction sites on the benzene ring, which is conducive to further curing reactions.

[0018] Preferably, the phenolic compound is m-aminophenol.

[0019] In the above scheme, the phenolic compound is selected as m-aminophenol, and isocyanate and amino groups are reacted to form

[0020] Furthermore, the diol has a molecular weight in the range of 250-2000.

[0021] The molecular weight range defined in the above scheme is a more suitable molecular weight range found by technicians based on a large number of studies and experiments; when the molecular weight is too low, the soft segment in the polyurethane is too short, and the toughening and reinforcing effect on the aerogel is poor, and the phenolic aerogel modified by polyurethane still presents the inherent brittleness and easy breakage problem of phenolic aerogel; when the molecular weight of the diol is too large, the content of the introduced soft segment is too large, which affects the strength of the network skeleton network of the overall aerogel; at the same time, the appropriate molecular weight is conducive to the refinement of the aerogel pore size, thereby ensuring that the aerogel has a higher strength.

[0022] Furthermore, the diol in step S1 is selected from polyether diol or polyester diol.

[0023] Preferably, the diol is polytetramethylene ether glycol.

[0024] Preferably, the diisocyanate is selected from aliphatic diisocyanate, alicyclic diisocyanate and aromatic diisocyanate.

[0025] Preferably, the diisocyanate is toluene diisocyanate.

[0026] In the above scheme, the inventors found, based on a large amount of research and experiments, that polytetramethylene ether glycol has suitable flexibility and suitable ether bond content; if polydimethylene ether glycol is used, its hydrophilicity will increase the difficulty of removing water during the preparation process, resulting in more side reactions and poor aerogel performance; if aliphatic diol is used, the polyurethane modifier will be insufficiently flexible and have poor mechanical properties.

[0027] Further, in step S2, the phenolic resin is selected from linear phenolic resin;

[0028] Preferably, the softening point of the linear phenolic resin is in the range of 80-130°C;

[0029] Preferably, the softening point of the linear phenolic resin is in the range of 90-110°C.

[0030] In the above scheme, the inventors found, based on a large number of studies and experiments, that if the softening point is less than 80°C, its ablation performance and residual carbon rate will be greatly reduced; at the same time, if the softening point is higher than 120°C, the resin solution needs to be heated and dissolved when it is prepared, which is not conducive to the simplicity of the overall preparation process. Considering the comprehensive performance and processability, the preferred resin softening point temperature is 90-110°C.

[0031] Furthermore, in step S2, the mass ratio of the phenolic ring terminated polyurethane prepolymer to the phenolic resin is (5-50):100.

[0032] In the above scheme, the mixing ratio of polyurethane prepolymer and phenolic resin is a relatively excellent ratio range obtained by the inventors based on a large number of experiments and studies. The polyurethane prepolymer within the above range can significantly improve the mechanical properties, compression modulus and strength of phenolic aerogel. If the amount of polyurethane prepolymer is too much, the crosslinking density of phenolic aerogel will decrease significantly, resulting in a significant decrease in modulus and attenuation of compression strength; if the amount of polyurethane prepolymer is less than 5, the aerogel still exhibits the characteristics of brittleness and powdering, and its lack of toughness is not improved.

[0033] Furthermore, the curing agent is selected from at least one of hexamethylenetetramine, formaldehyde or paraformaldehyde.

[0034] In the above scheme, hexamethylenetetramine is selected by the inventors as an excellent curing agent. Its raw materials are easily available and less toxic than formaldehyde and non-volatile. Its decomposition rate is related to temperature, which is beneficial to control the curing reaction rate.

[0035] Furthermore, in step S2, the gel reaction is carried out in a closed reactor, the reaction temperature is 70-110° C., and the reaction time is 12-48 hours.

[0036] Preferably, the reaction temperature of the gel reaction is 90° C. and the reaction time is 24 h.

[0037] Furthermore, in step S3, the liquid phase in the polyurethane modified phenolic resin gel is removed by high temperature drying, the temperature is 50-90° C., and the normal pressure drying time is 12h-48h;

[0038] Preferably, the drying temperature is 90° C. and the drying time is 12 h.

[0039] Another object of the present invention is to provide a polyurethane modified phenolic resin aerogel prepared by the above preparation method;

[0040] Preferably, the compression modulus of the polyurethane modified phenolic resin aerogel is ≥60 MPa, the compression strength is ≥10 MPa, and the compression strain is ≥50%.

[0041] The beneficial effects of the present invention are:

[0042] 1. The present invention designs and synthesizes a polyurethane prepolymer terminated with a phenolic ring, introduces a polyurethane component into a phenolic resin through the phenolic ring, realizes the intrinsic modification of the phenolic aerogel, and utilizes the soft segment and abundant hydrogen bonds in the polyurethane component to significantly improve the mechanical properties of the phenolic aerogel.

[0043] 2. By limiting the molecular weight of the diol in the polyurethane prepolymer, the length of the polyurethane soft segment can be controlled. The appropriate soft segment length can improve the brittleness of the phenolic aerogel without reducing the strength of the phenolic aerogel network skeleton. At the same time, it can also refine the pore size in the aerogel, which is beneficial to the improvement of the strength of the phenolic aerogel.

[0044] 3. Since the polyurethane prepolymer is capped with a phenolic ring, the polyurethane prepolymer can directly enter the phenolic aerogel preparation system without reacting with the solvent, that is, there is no need to change the preparation process of the phenolic aerogel. The aerogel can be prepared by the existing conventional sol-gel-normal pressure drying process, which is easy to realize industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 The compressive stress-strain curves of the polyurethane-modified phenolic aerogel and the pure phenolic aerogel prepared by the preparation method of the present invention in Example 1 are shown.

[0046] Figure 2 The pore size distribution diagram of the polyurethane modified phenolic aerogel and the pure phenolic aerogel prepared by the preparation method of the present invention in Example 1 is shown.

[0047] Figure 3 The carbon residue rate results of the polyurethane modified phenolic aerogel prepared in Example 1, Example 6 and Comparative Example 2;

[0048] Figure 4This is the compressive stress-strain curve of the uncapped polyurethane modified phenolic aerogel in Comparative Example 3. DETAILED DESCRIPTION

[0049] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Those skilled in the art will appreciate that the following embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0050] It should be noted that:

[0051] The compression tests in the present invention were all carried out on an Instron universal material testing machine (model instron5567), with a compression rate of 1 mm / min, and the samples were cut into cylindrical specimens with a diameter of 17 mm and a height of 17 mm. The aerogel compression test method refers to "Polymer porous elastic materials-Determination of compressive stress-strain characteristics" (GB / T 18942.1-2003).

[0052] The compression modulus is determined based on the slope of the initial linear portion of the stress-strain curve. The compressive stress is taken from the measured value of the sample when it breaks under compression, and the compressive strain is taken from the corresponding value of the compressive stress.

[0053] The pore structure of the aerogel sample was analyzed by mercury porosimetry. The mercury intrusion was measured in the pressure range of 0.1 to 37500 Psia using a mercury intrusion instrument MicroActive AutoPore (model: V9600). The pore size and distribution of the aerogel were calculated based on the Washburn equation.

[0054] The volume of the aerogel was calculated by measuring the mass, diameter and height of the aerogel sample completely dried at normal pressure, and the density was obtained by the ratio of mass to volume (all measurements were carried out at room temperature).

[0055] The drugs and sources used in the following examples are shown in the following table:

[0056] Table 1

[0057] Drug name / marketed product name Drug specifications (purity and other parameters) Manufacturer Polytetrahydrofurandiol 500mL, Mn=1000g / mol Inokai Chemical Reagent Co., Ltd. Polytetrahydrofurandiol 1000g, Mn=2000g / mol BASF Polyoxypropylene glycol 500g, Mn=2000g / mol Inokai Chemical Reagent Co., Ltd. Toluene 2,4-diisocyanate 500g，98％ Anaiji Chemical Reagent Co., Ltd. Methylene diphenyl diisocyanate 500g，97％ Anaiji Chemical Reagent Co., Ltd. Tetrahydrofuran AR500ml Beijing Chemical Plant m-Aminophenol 500g，99％ Inokai Chemical Reagent Co., Ltd. Salicyl alcohol 500g，99％ Inokai Chemical Reagent Co., Ltd. Novolac resin Industrial grade, grade 8020 Shandong Jinan Shengquan Group Co., Ltd. Hexamethylenetetramine Graded pure Sinopharm Chemical Reagent Co., Ltd. Ethanol AR500ml Beijing Chemical Plant

[0058] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0059] Example 1

[0060] (1) Preparation of polyurethane prepolymer

[0061] 10g of polytetrahydrofuran diol (molecular weight of 1000g / mol) and 3.48g of toluene 2,4-diisocyanate (2,4-TDI) were dissolved in 20g of tetrahydrofuran, and reacted at 75°C for 2 hours. Then, 2.1g of m-aminophenol was added and reacted at 50°C for 1 hour. The solvent tetrahydrofuran was removed by distillation under reduced pressure to obtain a phenol ring-terminated polyurethane prepolymer.

[0062] (2) Preparation of polyurethane modified phenolic aerogel

[0063] A phenolic ring-terminated polyurethane prepolymer, a linear phenolic resin (softening point of 105°C), hexamethylenetetramine, and ethanol are stirred and fully dissolved in a mass ratio of 10:90:15:300 to obtain a stable and uniform polyurethane / phenolic sol. The sol is cured at 90°C for 24 hours under closed conditions to obtain a polyurethane-modified phenolic wet gel. The wet gel is then dried at 90°C for 12 hours to obtain a polyurethane-modified phenolic aerogel.

[0064] The polyurethane modified phenolic aerogel has good mechanical properties. Figure 1 The compressive stress-strain curves of the aerogel and pure phenolic aerogel (comparative example) show that, compared with phenolic aerogel, the compressive strength, compression modulus and compression strain of polyurethane-modified phenolic aerogel are greatly improved.

[0065] Figure 2 This is the pore size distribution diagram of the aerogel and pure phenolic aerogel (mercury intrusion test). The pore size of the aerogel is also significantly smaller than that of the pure phenolic aerogel.

[0066] Figure 3 The residual carbon rate of the aerogel prepared in this example is shown in FIG.

[0067] Example 2

[0068] (1) Preparation of polyurethane prepolymer

[0069] 10g of polytetrahydrofuran diol (molecular weight 2000g / mol) and 1.74g of toluene 2,4-diisocyanate (2,4-TDI) were dissolved in 20g of tetrahydrofuran, reacted at 75°C for 2 hours, then 0.92g of m-aminophenol was added, reacted at 50°C for 1 hour, and the solvent tetrahydrofuran was removed by reduced pressure distillation to obtain a phenol ring-terminated polyurethane prepolymer.

[0070] (2) Preparation of polyurethane modified phenolic aerogel

[0071] A phenolic ring-terminated polyurethane prepolymer, a linear phenolic resin (softening point of 120°C), hexamethylenetetramine, and ethanol are stirred and fully dissolved in a mass ratio of 10:90:15:300 to obtain a stable and uniform polyurethane / phenolic sol. The sol is cured at 90°C for 24 hours under closed conditions to obtain a polyurethane-modified phenolic wet gel. After the wet gel is dried at 90°C for 12 hours, a polyurethane-modified phenolic aerogel is obtained.

[0072] Example 3

[0073] (1) Preparation of polyurethane prepolymer

[0074] 10g of polytetrahydrofuran diol (molecular weight of 1000g / mol) and 3.48g of toluene 2,4-diisocyanate (2,4-TDI) were dissolved in 20g of tetrahydrofuran, reacted at 75°C for 2 hours, then 2.1g of m-aminophenol was added, reacted at 50°C for 1 hour, and the solvent tetrahydrofuran was removed by reduced pressure distillation to obtain a phenol ring-terminated polyurethane prepolymer.

[0075] (2) Preparation of polyurethane modified phenolic aerogel

[0076] A phenolic ring-terminated polyurethane prepolymer, a linear phenolic resin (softening point of 105°C), hexamethylenetetramine, and ethanol are stirred and fully dissolved in a mass ratio of 30:70:15:300 to obtain a stable and uniform polyurethane / phenolic sol. The sol is cured at 90°C for 24 hours under closed conditions to obtain a polyurethane-modified phenolic wet gel. After the wet gel is dried at 90°C for 12 hours, a polyurethane-modified phenolic aerogel is obtained.

[0077] Example 4

[0078] (1) Preparation of polyurethane prepolymer

[0079] 10g of polyoxypropylene glycol (molecular weight 2000g / mol) and 2.5g of diphenylmethane diisocyanate (MDI) were dissolved in 20g of tetrahydrofuran, reacted at 75°C for 2 hours, then 0.97g of m-aminophenol was added, reacted at 50°C for 1 hour, and the solvent tetrahydrofuran was removed by reduced pressure distillation to obtain a phenol ring-terminated polyurethane prepolymer.

[0080] (2) Preparation of polyurethane modified phenolic aerogel

[0081] A phenolic ring-terminated polyurethane prepolymer, a linear phenolic resin (softening point of 105°C), hexamethylenetetramine, and ethanol are stirred and fully dissolved in a mass ratio of 30:70:15:300 to obtain a stable and uniform polyurethane / phenolic sol. The sol is cured at 100°C for 24 hours under closed conditions to obtain a polyurethane-modified phenolic wet gel. After the wet gel is dried at 90°C for 12 hours, a polyurethane-modified phenolic aerogel is obtained.

[0082] Example 5

[0083] (1) Preparation of polyurethane prepolymer

[0084] 10g of polytetrahydrofuran diol (molecular weight of 1000g / mol) and 3.48g of toluene 2,4-diisocyanate (2,4-TDI) were dissolved in 20g of tetrahydrofuran, reacted at 75°C for 2 hours, then 2.43g of salicyl alcohol was added, reacted at 50°C for 1 hour, and the solvent tetrahydrofuran was removed by reduced pressure distillation to obtain a phenol ring-terminated polyurethane prepolymer.

[0085] (2) Preparation of polyurethane modified phenolic aerogel

[0086] A phenolic ring-terminated polyurethane prepolymer, a linear phenolic resin (softening point of 105°C), hexamethylenetetramine, and ethanol are stirred and fully dissolved in a mass ratio of 30:70:15:300 to obtain a stable and uniform polyurethane / phenolic sol. The sol is cured at 90°C for 24 hours under closed conditions to obtain a polyurethane-modified phenolic wet gel. After the wet gel is dried at 90°C for 12 hours, a polyurethane-modified phenolic aerogel is obtained.

[0087] Example 6

[0088] The difference between this embodiment and embodiment 1 is that the softening point of the linear phenolic resin used is 90°C, and other conditions are the same. Figure 3 shown.

[0089] Comparative Example 1

[0090] (1) Preparation of pure phenolic aerogel

[0091] Linear phenolic resin (softening point is 105°C), hexamethylenetetramine and ethanol are mixed in a mass ratio of 100:15:300 and dissolved to obtain a stable and uniform phenolic sol. The sol is cured at 90°C for 24 hours under closed conditions to obtain a phenolic wet gel. The wet gel is dried at 90°C for 12 hours to obtain a pure phenolic aerogel.

[0092] Comparative Example 2

[0093] The difference between this comparative example and Example 1 is that the softening point of the linear phenolic resin used is 60°C.

[0094] (1) The preparation of polyurethane prepolymer is the same as in Example 1;

[0095] (2) Preparation of polyurethane modified low softening point phenolic aerogel

[0096] A phenolic ring-terminated polyurethane prepolymer, a linear phenolic resin (softening point of 60°C), hexamethylenetetramine, and ethanol are stirred and fully dissolved in a mass ratio of 10:90:15:300 to obtain a stable and uniform polyurethane / phenolic sol. The sol is cured at 90°C for 24 hours under closed conditions to obtain a polyurethane-modified phenolic wet gel. After the wet gel is dried at 90°C for 12 hours, a polyurethane-modified low-softening-point phenolic aerogel is obtained.

[0097] The results are as follows Figure 3 shown.

[0098] Comparative Example 3

[0099] The difference between this comparative example and Example 1 is that an unterminated polyurethane prepolymer is used.

[0100] (1) Preparation of unterminated polyurethane prepolymer

[0101] 10 g of polytetrahydrofuran diol (molecular weight of 1000 g / mol) and 3.48 g of toluene 2,4-diisocyanate (2,4-TDI) were dissolved in 20 g of tetrahydrofuran, reacted at 75° C. for 2 hours, and the solvent tetrahydrofuran was removed by distillation under reduced pressure to obtain an uncapped polyurethane prepolymer.

[0102] (2) Preparation of uncapped polyurethane modified phenolic aerogel

[0103] Uncapped polyurethane prepolymer, linear phenolic resin (softening point of 105°C), hexamethylenetetramine and tetrahydrofuran are stirred and fully dissolved in a mass ratio of 10:90:15:300 to obtain a stable and uniform polyurethane / phenolic sol. The sol is cured at 90°C for 24 hours under closed conditions to obtain a polyurethane-modified phenolic wet gel. After the wet gel is dried at 90°C for 12 hours, an uncapped modified low-softening-point phenolic aerogel is obtained.

[0104] Figure 4 The compression stress-strain curve of Comparative Example 3 shows that the compression strain of the uncapped polyurethane modified phenolic aerogel is small and the compression stress is low. At the same time, Comparative Example 3 produces a large shrinkage during the preparation process, so its density is significantly higher than that of other embodiments (see Table 2). The uncapped polyurethane modified phenolic aerogel has a very high reaction activity of the uncapped polyurethane during the curing reaction process, and the rate is too fast, which is uncontrollable as a whole, resulting in the inability to form a uniform network with phenolic, resulting in severe shrinkage and low mechanical properties.

[0105] Experimental Example 1

[0106] The properties of the aerogels prepared in Examples 1-5 and Comparative Examples 1-3 were tested, and the results are shown in the following table:

[0107] Table 2

[0108]

[0109]

[0110] Result analysis:

[0111] It can be seen from the above table that, compared with Comparative Example 1, the compression modulus, compression strength and compression strain of the polyurethane modified phenolic aerogels prepared by the method of the present invention in Examples 1-5 are significantly improved compared with the pure phenolic aerogel; and from the comparison between Example 1 and Example 3, it can be seen that the difference between Example 1 and Example 3 is that the ratio of the phenolic ring-terminated polyurethane prepolymer to the linear phenolic resin is different, and the proportion of the linear phenolic resin in Example 1 is higher than that in Example 3, and the corresponding compression strain is larger, and the compression modulus and compression strength are lower, indicating that within the ratio range specified by the present invention, with the increase in the amount of the phenolic ring-terminated polyurethane prepolymer, the brittleness of the aerogel is gradually reduced, showing a better deformation ability.

[0112] From the comparison between Example 3 and Example 4, it can be seen that the soft segment accounts for a larger proportion in the phenol ring-terminated polyurethane prepolymer prepared in Example 3, and the molecular weight of the diol forming the soft segment is higher. The compression strain of Example 4 is improved to a certain extent compared with that of Example 3, indicating that the increase in the soft segment content is conducive to the aerogel showing better deformation ability.

[0113] Furthermore, Examples 1 to 5 exhibited higher compression modulus and compression strength than Comparative Example 1, which fully confirmed that the phenolic ring-terminated polyurethane prepolymer not only improved the deformation ability of the phenolic aerogel, but also led to the refinement of the pore size in the aerogel and improved the overall strength of the aerogel, which can also be seen from Figure 2 It can be clearly seen in.

[0114] In Example 1, Example 6 and Comparative Example 2, only the softening point of the linear phenolic resin used is different, and other conditions are the same. Figure 3 It can be seen from the results that the residual carbon rate is 52.86% (Example 1) when the softening point is 105°C, 52.42% (Example 6) when the softening point is 90°C, and 47.61% (Comparative Example 2) when the softening point is 60°C. The thermal stability of the aerogels of Example 1 and Example 6 is much higher than that of Comparative Example 2. Therefore, Example 1 shows better thermal stability and residual carbon rate under nitrogen than Comparative Example 2, which fully proves the importance of preferably using linear phenolic resin with a softening point of 90-105°C. Figure 3 It can be seen that the low softening point linear phenolic resin (60°C) loses weight faster during pyrolysis and has a lower carbon residue rate.

[0115] The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this patent can make some changes or modifications to equivalent embodiments of equivalent changes by using the technical content suggested above without departing from the scope of the technical solution of the present invention. The implementation scheme in the above embodiment can also be further combined or replaced. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the solution of the present invention.

Claims

1. A method for preparing polyurethane modified phenolic resin aerogel, characterized in that: The steps include: S1, preparing a polyurethane prepolymer terminated with a phenol ring; S2, mixing a phenol ring-terminated polyurethane prepolymer with a phenolic resin to obtain a mixed solution, and adding a curing agent to perform a gel reaction to obtain a polyurethane-modified phenolic resin gel; S3, removing the liquid phase in the polyurethane-modified phenolic resin gel to obtain the polyurethane-modified phenolic resin aerogel.

2. The method for preparing polyurethane modified phenolic resin aerogel according to claim 1, characterized in that: Step S1 specifically includes: Polyurethane is prepared by reacting diol and diisocyanate, and then the polyurethane is terminated by phenolic compounds to obtain a phenol ring terminated polyurethane prepolymer; The phenolic compound contains a phenolic hydroxyl group and at least one functional group having a reactive activity with an isocyanate group; Preferably, the functional group reactive with isocyanate includes hydroxyl, amino, phenolic hydroxyl, mercapto, hydroxymethyl, and aminomethyl; Preferably, the phenolic compound includes salicyl alcohol, resorcinol, m-aminophenol, and 4-mercaptophenol; Preferably, the phenolic compound is m-aminophenol.

3. The method for preparing polyurethane modified phenolic resin aerogel according to claim 2, characterized in that: The diol has a molecular weight ranging from 250 to 2000.

4. The method for preparing polyurethane modified phenolic resin aerogel according to claim 2, characterized in that: The diol in step S1 is selected from polyether diol or polyester diol; the diisocyanate is selected from aliphatic diisocyanate, alicyclic diisocyanate, and aromatic diisocyanate; Preferably, the diol is polytetramethylene ether glycol; Preferably, the diisocyanate is toluene diisocyanate.

5. The method for preparing the polyurethane modified phenolic resin aerogel according to any one of claims 1 to 4, characterized in that: In step S2, the phenolic resin is selected from linear phenolic resin; Preferably, the softening point of the linear phenolic resin is in the range of 80-130°C; Preferably, the softening point of the linear phenolic resin is in the range of 90-110°C.

6. The method for preparing the polyurethane modified phenolic resin aerogel according to any one of claims 1 to 5, characterized in that: In step S2, the mass ratio of the phenolic ring terminated polyurethane prepolymer to the phenolic resin is (5-50):

100.

7. The method for preparing the polyurethane modified phenolic resin aerogel according to any one of claims 1 to 6, characterized in that: The curing agent is selected from at least one of hexamethylenetetramine, formaldehyde or paraformaldehyde.

8. The method for preparing the polyurethane modified phenolic resin aerogel according to any one of claims 1 to 7, characterized in that: In step S2, the gel reaction is carried out in a closed reactor at a reaction temperature of 70-110° C. and a reaction time of 12-48 hours.

9. The method for preparing the polyurethane modified phenolic resin aerogel according to any one of claims 1 to 8, characterized in that: In step S3, the polyurethane modified phenolic resin gel is heated and dried at normal pressure to remove the liquid phase to obtain polyurethane modified phenolic aerogel, wherein the temperature of the normal pressure heating and drying is 50° C.-90° C. and the normal pressure drying time is 12 h-48 h.

10. A polyurethane modified phenolic resin aerogel prepared by the preparation method according to any one of claims 1 to 9; Preferably, the compression modulus of the polyurethane modified phenolic resin aerogel is ≥60 MPa, the compression strength is ≥10 MPa, and the compression strain is ≥50%.

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