A hot-pressed self-adhesive aerogel and thermal insulation material

Abstract

The present invention relates to the field of thermal insulation materials, and discloses a hot-press self-adhesive aerogel and a thermal insulation material. The preparation of the hot-press self-adhesive aerogel includes: (1) applying porous aerogel particles to the top of an inclined groove under heating and allowing them to roll down along the inclined groove paved with hot-melt adhesive powder to obtain an aerogel; (2) loading n-pentane to obtain the hot-press self-adhesive aerogel. In the present invention, the smaller-sized hot-melt adhesive powder is first attached to the surface of the larger-sized porous aerogel particles in a dispersed manner, and the obtained aerogel has hot-press self-adhesive properties and can be bonded by simply hot-pressing. This method can reduce the amount of hot-melt adhesive used without significantly affecting the bonding strength, thereby avoiding the influence of the porosity of the aerogel layer after the hot-melt adhesive melts. By loading n-pentane before using the aerogel in the present invention, the porosity of the porous aerogel particles can be increased during hot-pressing.

Description

Technical Field

[0001] The present invention relates to the field of thermal insulation materials, and particularly to a hot-pressed self-adhesive aerogel and a thermal insulation material. Background Art

[0002] Aerogel is a solid material form with a developed pore structure and high porosity, so its density is very low. There are many types of aerogels, including silicon-based, carbon-based, sulfur-based, metal oxide-based, metal-based, etc. Generally, the common aerogel is silica aerogel.

[0003] Due to the high porosity characteristics of aerogel, it has become a widely used thermal insulation material with very ideal thermal insulation effect. Using the thermal insulation performance of aerogel, highly efficient aerogel thermal insulation composite materials can be made and applied in various fields.

[0004] Currently, the most common aerogel material products on the market are aerogel felts, aerogel coatings, etc. Among them, aerogel felts have been widely used in the field of heat preservation of petrochemical pipelines. In the prior art, an aerogel felt usually consists of a fabric substrate and an aerogel coating attached to the surface of the fabric substrate. The preparation method is usually to immerse the fabric substrate in a silicon source impregnating solution such as tetraethyl orthosilicate, adjust the impregnating solution to be acidic or alkaline, and use the sol-gel method to form a silica aerogel layer on the surface of the fabric substrate. The disadvantage of this process is that a large amount of solvent is required, and the process flow is relatively complex, which is not conducive to cost reduction.

[0005] If the aerogel particles are directly mixed with hot melt adhesive and then coated on the surface of the fabric substrate and hot-pressed and cured to prepare a thermal insulation material, the preparation process can be greatly shortened and the cost can be reduced. However, this method also has the following defects: First, in practice, it is found that a large amount of hot melt adhesive is often required to maintain a certain mechanical strength after the aerogel particles are hot-pressed and bonded together. However, if the content of the hot melt adhesive is too high, it will melt during the hot-pressing process and coat the surface of the aerogel particles in a large area, or penetrate into the internal pores of the aerogel particles, or fill between the aerogel particles, resulting in a significant reduction in the porosity of the thermal insulation material and affecting the thermal insulation effect; Second, under high-temperature hot-pressing conditions, the pore structure of the aerogel particles themselves is prone to collapse. In the subsequent experiments of the applicant, it was found that if the amount of hot melt adhesive is reduced, although the thermal insulation effect of the material can be improved to a certain extent, the disadvantage is that after reducing the amount of hot melt adhesive, the strength of the aerogel thermal insulation material is poor and it is easily damaged or powdered by external force impact. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a preparation method of a hot-pressing self-adhesive aerogel and its application in thermal insulation materials. In the present invention, a hot-melt adhesive powder with a smaller particle size is first attached to the surface of porous aerogel particles with a larger particle size in a dispersed manner to obtain an aerogel. This aerogel has the property of hot-pressing self-adhesion and can be bonded simply by hot-pressing. This method can significantly reduce the amount of hot-melt adhesive used on the premise of ensuring the strength of the obtained thermal insulation material, thereby avoiding the negative impact of the melting of the hot-melt adhesive on the porosity of the thermal insulation material and improving the thermal insulation effect. Before using the aerogel, the present invention loads n-pentane, which can assist in maintaining the porosity of the porous aerogel particles during hot-pressing and further improve the thermal insulation effect.

[0007] The specific technical solution of the present invention is as follows:

[0008] A preparation method of a hot-pressing self-adhesive aerogel, comprising:

[0009] S1: Uniformly spread the hot-melt adhesive powder on a heatable inclined chute to form a hot-melt adhesive powder layer; under the condition that the inclined chute is heated to a temperature 5 - 15 °C higher than the softening point temperature of the hot-melt adhesive, apply porous aerogel particles at the top of the inclined chute and let them roll down along the inclined chute. During the rolling process, the surface of the porous aerogel particles adheres to the hot-melt adhesive powder. After cooling and screening out the unbonded hot-melt adhesive powder, an aerogel is obtained with porous aerogel particles as the core and hot-melt adhesive powder attached in a dispersed manner (in discrete dot form) as the shell.

[0010] In S1, after the inclined chute starts heating, the temperature of the chute surface is 5 - 15 °C higher than the softening point temperature of the hot-melt adhesive. In this specific temperature range, the hot-melt adhesive powder will be heated and softened, having a lower viscosity (at this temperature, the hot-melt adhesive has not melted and does not have high adhesiveness. Only when the temperature is at least 30 °C higher than the softening point, the hot-melt adhesive will completely melt and have high adhesiveness). Therefore, during the rolling process of the porous aerogel particles, a small amount of it can adhere to the surface of the porous aerogel particles, thereby obtaining the aerogel.

[0011] S2: Before use, immerse the aerogel in n-pentane at a temperature lower than the boiling point of n-pentane, let it stand, and filter to obtain an aerogel loaded with n-pentane, that is, a hot-pressing self-adhesive aerogel.

[0012] As described in the background art of the present application, in the prior art, a large amount of hot melt adhesive is often required to maintain a certain mechanical strength after the aerogel particles are bonded together by hot pressing. However, if the content of the hot melt adhesive is too high, it will melt during the hot pressing process and coat the surface of the aerogel particles in a large area, or penetrate into the internal pores of the aerogel particles, or fill between the aerogel particles, resulting in a significant reduction in the porosity of the thermal insulation material and affecting the thermal insulation effect. In addition, under high-temperature hot pressing conditions, the pore structure of the aerogel particles themselves is prone to collapse. If the amount of the hot melt adhesive is reduced, the strength of the aerogel thermal insulation material will be poor, and it is easy to be damaged or powdered under external force impact.

[0013] Therefore, the present invention changes the traditional idea and optimizes the mixing of the hot melt adhesive with the aerogel during hot pressing to pre-bond the hot melt adhesive with the aerogel particles. That is, first, the hot melt adhesive powder with a smaller particle size is uniformly attached to the surface of the porous aerogel particles with a larger particle size in a dispersed manner (i.e., in discrete dots) to obtain an aerogel with the porous aerogel particles as the core and the hot melt adhesive powder as the shell. The present invention pre-attaches the hot melt adhesive to the surface of the aerogel particles in a dispersed manner, and the obtained aerogel has the characteristic of self-adhesion during hot pressing, and can be bonded only by simple hot pressing during use. This method can significantly reduce the amount of the hot melt adhesive without significantly affecting the strength of the aerogel layer, thereby avoiding the negative impact of the molten hot melt adhesive on the porosity of the aerogel thermal insulation material.

[0014] Furthermore, on the above basis, the present invention loads n-pentane with a low boiling point (36 °C) and easy to volatilize and expand on the aerogel before use. The above treatment has the following effects during subsequent hot pressing: ① When hot pressing, n-pentane will volatilize and expand when heated, and the generated gas can increase the resistance of the hot melt adhesive to penetrate into the internal pores of the porous aerogel particles during the outward diffusion process, and at the same time can also increase the voids between the porous aerogel particles; ② At the moment when n-pentane volatilizes and expands when heated, the internal air pressure of the porous aerogel particles is greater than the external air pressure, and this internal and external air pressure difference can resist the hot pressing force to a certain extent, thereby playing a protective role for the porous aerogel particles and avoiding a large amount of collapse of their internal pore structures. The reason why the present invention selects n-pentane is that its boiling point is more appropriate and it is in a liquid state at room temperature (the boiling points of most low-boiling-point and easy-to-volatilize substances are lower than room temperature).

[0015] Furthermore, the particle size of the porous aerogel particles is in the micron level, and its porous structure is in the nanometer level; the particle size ratio of the hot melt adhesive powder to the porous aerogel particles is 1 / 10 - 1 / 5.

[0016] It should be noted that the present invention also finds that the particle size of the porous aerogel particles, the pore size, and the particle size of the hot melt adhesive powder have an important influence on the above technical effects. If the particle size of the porous aerogel particles is too large compared to the hot melt adhesive powder, at the same hot melt adhesive loading, a larger number of smaller-sized hot melt adhesives will adhere to the surface of the porous aerogel particles; thus, when hot pressing, the smaller-sized hot melt adhesive has better fluidity after melting and is more likely to spread on the surface of the porous aerogel particles, thereby forming a continuous coating layer with a thinner thickness and a larger area. At the same time, it is also more likely to penetrate into the pores inside the porous aerogel particles and fill the spaces between different porous aerogel particles. All of the above situations will significantly reduce the porosity of the obtained aerogel layer and ultimately affect the heat insulation performance. On the contrary, if the particle size of the porous aerogel particles is too small compared to the hot melt adhesive powder, the weight and volume of a single hot melt adhesive powder particle will be too large and it will not easily adhere to the surface of the porous aerogel particles (poor bonding force and easy to fall off). Finally, the present invention finds that selecting porous aerogel particles with a micron-sized particle size and controlling the particle size ratio of the two at 1 / 10 - 1 / 5 can effectively avoid the above negative effects. At a more reasonable particle size ratio, the hot melt adhesive powder can smoothly adhere to the surface of the porous aerogel particles in a dispersed manner, and after melting, the larger-sized hot melt adhesive has poor fluidity and is more inclined to form bonding points with a thicker thickness and a smaller occupied area on the surface of the porous aerogel particles. It will not only overwrap the surface of the porous aerogel particles and penetrate into the internal pores in large quantities, but also the adjacent porous aerogel particles are bonded through the above larger-sized bonding points, and the mutual spacing is also larger, which is beneficial to maintaining the voids between the particles.

[0017] Further preferably, in S1, the particle size of the porous aerogel particles is 50 - 100 μm, the porosity is 80 - 99%, and the pore size is 10 - 50 nm; the particle size of the hot melt adhesive powder is 5 - 20 μm.

[0018] After optimization by the present invention, the particle size of the porous aerogel particles is controlled at 50 - 100 μm, and the particle size of the hot melt adhesive powder is controlled at 5 - 20 μm. Under the above absolute particle size and particle size ratio, the comprehensive performance of the obtained aerogel layer is better. In addition, the present invention selects porous aerogel particles with a pore size of 10 - 50 nm, and its advantages are as follows: on the one hand, the smaller pore structure has a greater hindrance to the penetration of the hot melt adhesive, which is beneficial to maintaining the high porosity of the obtained aerogel layer; on the other hand, the pore size of 10 - 50 nm is smaller than the mean free path of air molecules (70 nm), so the pores of this size can lock air molecules, which is not conducive to air convection, and at the same time can form a longer heat conduction path, thereby making the material have a lower thermal conductivity.

[0019] Further, in S1, the hot melt adhesive is an EVA hot melt adhesive with a softening point temperature of 65 - 85 °C.

[0020] The present invention selects an EVA hot melt adhesive with a softening point temperature of 65 - 85°C. This relatively low softening point temperature allows the heating temperature of the inclined groove and the subsequent hot pressing temperature to be set at a lower level, reducing energy consumption. At the same time, it can also avoid the structural damage to the porous aerogel particles caused by high temperatures during the hot pressing process.

[0021] Further, in S1, the porous aerogel particles are silica aerogel particles.

[0022] Further, in S2, the inclined groove is spiral along the rolling direction.

[0023] The inclined groove is designed to be spiral so that the porous aerogel particles can turn as many times as possible during the rolling process, enabling all parts of their surfaces to come into contact with the inclined groove, which is beneficial for obtaining an aerogel with a uniform distribution of hot melt adhesive powder.

[0024] Further, in S1, the proportion of the hot melt adhesive powder in the aerogel is 5 - 10 wt%.

[0025] On the premise of ensuring the bonding strength, in order to further improve the porosity of the porous aerogel particles after hot pressing, the present invention controls the proportion of the hot melt adhesive powder within the above range. If the proportion is too low, it will have a certain negative impact on the bonding strength. If the proportion is too high, it is not conducive to obtaining an aerogel layer with a high porosity.

[0026] Further, in S2, the proportion of n - pentane in the aerogel loaded with n - pentane is 10 - 20 wt%.

[0027] In order to further improve the porosity of the porous aerogel particles after hot pressing, the present invention controls the proportion of n - pentane within the above range. If the proportion is too low, the improvement effect on the porosity of the aerogel layer formed by hot pressing is not obvious enough. If the proportion is too high, a large amount of gas will affect the bonding effect of the hot melt adhesive.

[0028] A preparation method of a heat - insulating material: at a temperature lower than the boiling point of n - pentane, uniformly apply the hot - press self - adhesive aerogel on the surface of the fiber felt, then perform hot pressing and cooling to obtain a heat - insulating material with a fiber felt as the base material and an aerogel layer as the surface layer.

[0029] The aerogel of the present invention has the characteristic of hot - press self - adhesion. Before hot pressing, it only needs to be uniformly applied on the surface of the fiber felt, and after hot pressing, an aerogel layer with high porosity and high heat - insulating performance can be formed.

[0030] Further, the hot - press forming specifically is: first, perform pre - hot pressing at a temperature 30 - 50°C higher than the softening point temperature of the hot melt adhesive (pressure is 10 - 15 MPa, time is 10 - 20 s), and then perform secondary hot pressing at a temperature 25 - 30°C higher than the softening point temperature of the hot melt adhesive (pressure is 1 - 5 MPa, time is 1 - 3 min).

[0031] In order to further obtain an aerogel layer with a higher porosity, the present invention designs the hot pressing process as a two-step hot pressing, that is, first performing a "high temperature, high pressure, short time" pre-hot pressing, and then performing a "low temperature, low pressure, long time" secondary hot pressing. The reason for first performing the "high temperature, high pressure, short time" is as follows: At the initial stage of hot pressing, the n-pentane in the hot-pressing self-adhesive aerogel has not volatilized yet. Since it can hinder the penetration of the hot melt adhesive into the interior of the porous aerogel particles and buffer the hot pressing force during the volatilization process, using a higher temperature and higher pressure will not bring too much negative impact on the porosity of the aerogel layer. At the same time, high temperature and high pressure can also improve the bonding strength of the aerogel layer. In the secondary hot pressing stage, the n-pentane has basically volatilized, and the porous aerogel particles have basically achieved mutual bonding, that is, the skeleton structure of the aerogel layer has basically taken shape. At this time, performing the "low temperature, low pressure, long time" secondary hot pressing can play a stabilizing role on the skeleton structure of the aerogel layer, and at the same time, it can also prevent the excessive fluidity of the hot melt adhesive at high temperature from affecting the porosity.

[0032] Compared with the prior art, the present invention has the following technical effects:

[0033] (1) The present invention optimizes the mixing of the hot melt adhesive with the aerogel during hot pressing to pre-bind it with the aerogel particles, that is, first uniformly attaching the hot melt adhesive powder with a smaller particle size to the surface of the porous aerogel particles with a larger particle size in a dispersed manner to obtain the aerogel. The aerogel has the characteristic of self-adhesion during hot pressing and can be bonded only by simple hot pressing. This method can significantly reduce the amount of the hot melt adhesive used without significantly affecting the strength of the obtained aerogel layer, thereby avoiding the negative impact of the molten hot melt adhesive on the porosity of the aerogel layer and improving the heat insulation effect.

[0034] (2) The present invention loads low-boiling and easily volatile and expandable n-pentane on the aerogel before use. This treatment can assist in maintaining the porosity of the porous aerogel particles during hot pressing and further improve the heat insulation effect.

[0035] (3) The present invention adopts a hot pressing process of first performing a "high temperature, high pressure, short time" pre-hot pressing and then a "low temperature, low pressure, long time" secondary hot pressing, which can further obtain an aerogel layer with a higher porosity. Specific embodiments

[0036] (I) Comparison between the hot-pressing self-adhesive aerogel and the conventional aerogel

[0037] Example 1 (using the hot-pressing self-adhesive aerogel)

[0038] Preparation of hot-pressed self-adhesive aerogel: Uniformly spread the hot-melt adhesive powder (EVA, softening point about 80 °C, average particle size 11 μm) on a helical inclined groove (with side walls on both sides of the inclined groove) to form a hot-melt adhesive powder layer; heat the groove surface of the inclined groove to 90 °C, and uniformly pour out silica porous aerogel particles (average particle size about 101 μm, average porosity 98%, pore size 10 - 50 nm) at the top of the inclined groove and let them roll down along the inclined groove. During the rolling process, the silica porous aerogel particles are attached with hot-melt adhesive powder on the surface. After rolling, collect the silica porous aerogel particles, cool them to room temperature, and sieve out the unbound hot-melt adhesive powder to obtain aerogel (calculate the average loading rate of the hot-melt adhesive powder is about 6 wt%); Immerse the aerogel in n-pentane at 20 °C at a ratio of 100 g / 1 L, let it stand for 30 min, and filter to obtain a hot-pressed self-adhesive aerogel loaded with n-pentane (control the loading rate of n-pentane is about 10 wt%).

[0039] Preparation of thermal insulation material: At 20 °C, immediately and uniformly apply the hot-pressed self-adhesive aerogel on the surface of the fiber felt (thickness 0.5 mm), and perform hot pressing: first pre-heat press at 130 °C (pressure 12 MPa, time 15 s), then perform secondary hot pressing at 105 °C (pressure 3 MPa, time 2 min). After cooling and curing, obtain a thermal insulation material with a fiber felt as the base material and an aerogel layer (thickness 200 μm) on the surface layer.

[0040] Comparative Example 1 (using conventional aerogel)

[0041] Preparation of thermal insulation material: Mix silica porous aerogel particles (average particle size about 101 μm, average porosity 98%, pore size 10 - 50 nm) and hot-melt adhesive powder (EVA, softening point about 80 °C, average particle size 11 μm) evenly at a mass ratio of 94:6, uniformly apply them on the surface of the fiber felt (thickness 0.5 mm), and perform hot pressing: first pre-heat press at 130 °C (pressure 12 MPa, time 15 s), then perform secondary hot pressing at 105 °C (pressure 3 MPa, time 2 min). After cooling and curing, obtain a thermal insulation material with a fiber felt as the base material and an aerogel layer (thickness 200 μm) on the surface layer.

[0042] Performance testing

[0043] Take samples (10 cm × 10 cm) from the aerogel layers in the thermal insulation materials obtained in Example 1 and Comparative Example 1 for various performance tests, and the results are shown in the following table:

[0044] Group number Thermal conductivity Porosity Fracture strength Example 1 0.0017 W / (m·K) 96% 37 MPa Comparative Example 1 0.0027 W / (m·K) 83% 41 MPa

[0045] (II) Comparison of the particle size ratios of different silica porous aerogel particles and hot-melt adhesive powder

[0046] (A) Preparation of hot-press self-adhesive aerogel: Uniformly spread the hot-melt adhesive powder (EVA, softening point about 80 °C, average particle size 5 - 40 μm) on a helical inclined groove (with side walls on both sides of the inclined groove) to form a hot-melt adhesive powder layer; heat the groove surface of the inclined groove to 90 °C, and uniformly pour out silica porous aerogel particles (average particle size about 101 μm, average porosity 98%, pore size 10 - 50 nm) at the top of the inclined groove and let them roll down along the inclined groove. During the rolling process, the silica porous aerogel particles adhere to the hot-melt adhesive powder on the surface. After rolling, collect the silica porous aerogel particles, cool them to room temperature, and sieve out the unbound hot-melt adhesive powder to obtain aerogel; impregnate the aerogel in n-pentane at 20 °C at a ratio of 100 g / 1 L, let it stand for 30 min, and filter to obtain a hot-press self-adhesive aerogel loaded with n-pentane (control the loading rate of n-pentane to be about 10 wt%).

[0047] (B) Preparation of thermal insulation material: At 20 °C, immediately and uniformly apply the hot-press self-adhesive aerogel on the surface of the fiber felt (thickness 0.5 mm), and perform hot pressing: first pre-heat press at 130 °C (pressure 12 MPa, time 15 s), then perform secondary hot pressing at 105 °C (pressure 3 MPa, time 2 min). After cooling and curing, a thermal insulation material with a fiber felt as the base material and an aerogel layer (thickness 200 μm) on the surface is obtained.

[0048] Performance testing

[0049] Samples (10 cm × 10 cm) were taken from the aerogels (without n-pentane loading) obtained in each example and comparative example and the aerogel layers in the thermal insulation materials for various performance tests. The results are shown in the following table:

[0050] Group number Average particle size of hot melt adhesive powder, μm Average loading rate of hot melt adhesive powder, wt% Thermal conductivity Porosity Fracture strength Comparative Example 2 5 7 0.0024W / (m·K) 87% 39 MPa Example 1 11 6 0.0017 W / (m·K) 96% 37 MPa Example 2 19 6 0.0018W / (m·K) 93% 36 MPa Comparative Example 3 30 3 / / / Comparative Example 4 38 1 / / /

[0051] Note: In Comparative Example 3 and Comparative Example 4, due to the too low loading rate of the hot-melt adhesive powder, it could not be completely formed after hot pressing, and a large amount of slag and powder fell off, so there were no test data.

[0052] (C) Comparison of different n-pentane loading rates

[0053] Preparation of hot-pressed self-adhesive aerogel: Uniformly spread the hot-melt adhesive powder (EVA, softening point about 80 °C, average particle size 11 μm) on the helical inclined groove (with side walls on both sides of the inclined groove) to form a hot-melt adhesive powder layer; heat the groove surface of the inclined groove to 90 °C, and uniformly pour out the silica porous aerogel particles (average particle size about 101 μm, average porosity 98%, pore size 10 - 50 nm) at the top of the inclined groove and let them roll down along the inclined groove. During the rolling process, the silica porous aerogel particles adhere to the hot-melt adhesive powder on their surfaces. After rolling, collect the silica porous aerogel particles, cool them to room temperature, and sieve out the unbonded hot-melt adhesive powder to obtain the aerogel; impregnate the aerogel in n-pentane at 20 °C at a ratio of 100 g / 1 L, let it stand for 30 min, and filter to obtain the hot-pressed self-adhesive aerogel loaded with n-pentane (control the loading rate of n-pentane to be about 0 - 25 wt%).

[0054] Preparation of thermal insulation material: At 20 °C, immediately and uniformly apply the hot-pressed self-adhesive aerogel on the surface of the fiber felt (thickness 0.5 mm) and perform hot pressing: first pre-hot press at 130 °C (pressure 12 MPa, time 15 s), then perform secondary hot pressing at 105 °C (pressure 3 MPa, time 2 min). After cooling and curing, obtain the thermal insulation material with the fiber felt as the base material and the aerogel layer (thickness 200 μm) as the surface layer.

[0055] Performance testing

[0056] Sample the aerogel layer in the thermal insulation materials obtained in each example and comparative example (10 cm × 10 cm) and conduct various performance tests. The results are shown in the following table:

[0057] Group number n-Pentane loading rate, wt% Thermal conductivity Porosity Fracture strength Comparative Example 5 0 0.0023 W / (m·K) 89% 40 MPa Comparative Example 6 5 0.0019W / (m·K) 92% 39 MPa Example 1 10 0.0017 W / (m·K) 96% 37 MPa Example 3 15 0.0017 W / (m·K) 97% 36 MPa Example 4 20 0.0016 W / (m·K) 98% 35 MPa Comparative Example 7 25 0.0016 W / (m·K) 98% 32 MPa

[0058] Comparison of different hot-pressing processes

[0059] Example 5 (secondary hot pressing)

[0060] Preparation of hot-pressed self-adhesive aerogel: Uniformly spread the hot-melt adhesive powder (EVA, softening point about 80 °C, average particle size 11 μm) on a helical inclined groove (with side walls on both sides of the inclined groove) to form a hot-melt adhesive powder layer; heat the groove surface of the inclined groove to 90 °C, and uniformly pour out silica porous aerogel particles (average particle size about 101 μm, average porosity 98%, pore size 10 - 50 nm) at the top of the inclined groove and let them roll down along the inclined groove. During the rolling process, the silica porous aerogel particles adhere to the hot-melt adhesive powder on their surfaces. After rolling, collect the silica porous aerogel particles, cool them to room temperature, and sieve out the unbonded hot-melt adhesive powder to obtain aerogel; immerse the aerogel in n-pentane at 20 °C at a ratio of 100 g / 1 L, let it stand for 30 min, and filter to obtain a hot-pressed self-adhesive aerogel loaded with n-pentane (control the loading rate of n-pentane to be about 10 wt%).

[0061] Preparation of thermal insulation material: At 20 °C, immediately and uniformly apply the hot-pressed self-adhesive aerogel on the surface of the fiber felt (thickness 0.5 mm), and perform hot pressing: first pre-hot press at 120 °C (pressure 15 MPa, time 15 s), and then perform secondary hot pressing at 110 °C (pressure 5 MPa, time 2 min). After cooling and curing, obtain a thermal insulation material with a fiber felt as the base material and an aerogel layer (thickness 200 μm) as the surface layer.

[0062] Comparative Example 8 (single hot pressing)

[0063] Preparation of hot-pressed self-adhesive aerogel: The same as in Example 5.

[0064] Preparation of thermal insulation material: At 20 °C, immediately and uniformly apply the hot-pressed self-adhesive aerogel on the surface of the fiber felt (thickness 0.5 mm), and perform hot pressing: hot press at 120 °C and a pressure of 15 Mpa for 60 s. After cooling and curing, obtain a thermal insulation material with a fiber felt as the base material and an aerogel layer (thickness 200 μm) as the surface layer.

[0065] Performance testing

[0066] Take samples (10 cm × 10 cm) from the aerogel layers in the thermal insulation materials obtained in each example and comparative example, and conduct various performance tests. The results are shown in the following table:

[0067] Group number Hot pressing process Thermal conductivity Porosity Fracture strength Example 5 Pre-hot pressing: 120°C, pressure 15MPa, 15s; secondary hot pressing: 110°C, pressure 5MPa, 2min 0.0017 W / (m·K) 95% 39 MPa Comparative Example 8 120°C, pressure 15MPa, 60s 0.0020 W / (m·K) 91% 40MPa

Claims

1. A method for preparing a hot-pressed self-adhesive aerogel, characterized in that: The following steps are involved: S1: evenly spread the hot melt adhesive powder on a heatable inclined groove; under the condition that the inclined groove is heated to a temperature 5-15°C higher than the softening point of the hot melt adhesive, porous aerogel particles are applied to the top of the inclined groove and rolled down along the inclined groove, and the hot melt adhesive powder is attached to the surface of the porous aerogel particles during the rolling process. After cooling and sieving out the unbound hot melt adhesive powder, an aerogel with porous aerogel particles as the core and the hot melt adhesive powder attached in a dispersed manner as the shell is obtained; The particle size of porous aerogel particles is micrometer-level, and its porous structure is nanometer-level; the particle size ratio of hot melt adhesive powder to porous aerogel particles is 1 / 10-1 / 5; S2: Before use, the aerogel is immersed in n-pentane at a temperature lower than the boiling point of n-pentane, allowed to stand, and filtered to obtain an aerogel loaded with n-pentane, namely, a hot-pressed self-adhesive aerogel.

2. The preparation method according to claim 1, characterized in that: In S1, the particle size of the porous aerogel particles is 50-100 μm, the porosity is 80-99%, and the pore size is 10-50 nm; the particle size of the hot melt adhesive powder is 5-20 μm.

3. The method for preparing the hot-pressed self-adhesive aerogel according to claim 1 or 2, characterized in that: In S1, the hot melt adhesive is an EVA hot melt adhesive with a softening point temperature of 65-85°C.

4. The method for preparing the hot-pressed self-adhesive aerogel according to claim 1 or 2, characterized in that: In S1, the porous aerogel particles are silica aerogel particles.

5. The method for preparing the hot-pressed self-adhesive aerogel according to claim 1, characterized in that: In S1, the inclined groove is spiral along the rolling direction.

6. The method for preparing the hot-pressed self-adhesive aerogel according to claim 1 or 2, characterized in that: In S1, the proportion of hot melt adhesive powder in the aerogel is 5-10wt%.

7. The method for preparing the hot-pressed self-adhesive aerogel according to claim 1, characterized in that: In S2, the proportion of n-pentane in the aerogel loaded with n-pentane is 10-20wt%.

8. A method for preparing a thermal insulation material, characterized in that: At a temperature lower than the boiling point of n-pentane, the hot-pressed self-adhesive aerogel obtained by the preparation method as described in any one of claims 1 to 7 is uniformly applied to the surface of the fiber felt, hot-pressed, and cooled to obtain a thermal insulation material with a fiber felt substrate and an aerogel layer on the surface.

9. The method for preparing the thermal insulation material according to claim 8, characterized in that: The hot pressing molding is specifically as follows: firstly preheating and pressing at a temperature 30-50°C higher than the softening point of the hot melt adhesive, with a pressure of 10-15MPa and a time of 10-20s; Then, a secondary hot pressing is performed at a temperature 25-30°C higher than the softening point of the hot melt adhesive, a pressure of 1-5MPa, and a time of 1-3min.