Preparation method of phase change material composite building thermal insulation material based on porous structure

Abstract

The invention relates to the technical field of building materials, and discloses a preparation method of a phase change material composite building thermal insulation material based on a porous structure. 13 to 18 parts of modified diatomite; 9 to 13 parts of nano cellulose aerogel; 7 to 11 parts of food-grade palmitic acid; 8 to 13 parts of microcapsule bio-based PCM; 0.9 to 1.4 parts of modified graphene; 11 to 15 parts of environment-friendly polylactic acid; 7 to 10 parts of montmorillonite; 1-2 parts of nano silicon dioxide; by compounding the expanded perlite, the modified diatomite and the nanocellulose aerogel, a basic framework with high porosity and low heat conductivity is constructed, heat conduction is effectively blocked, by introducing food-grade palmitic acid and microcapsule bio-based PCM, the material is endowed with heat storage and temperature regulation functions, phase change latent heat is improved, and the thermal conductivity of the material is improved. By adding modified graphene and nano silicon dioxide, an efficient heat conduction network and a heat insulation structure are formed, and the heat conductivity coefficient of the composite building heat preservation material is further reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, in particular to a method for preparing a phase change material composite building thermal insulation material based on a porous structure. Background Art

[0002] In the field of building energy conservation, the performance of insulation materials directly impacts building energy consumption and indoor comfort. Traditional building insulation materials, such as rock wool and polystyrene boards, rely primarily on porous structures or air layers to achieve thermal insulation, providing only passive insulation and failing to actively regulate indoor temperature. When ambient temperature fluctuates dramatically, the indoor thermal environment becomes unstable, leading to frequent operation of air conditioning and heating equipment, significantly increasing energy consumption.

[0003] To improve temperature control performance, early attempts involved mechanically mixing phase change materials directly with insulation materials, hoping to leverage the latent heat of phase change to achieve temperature control. However, this approach has significant drawbacks: phase change materials tend to agglomerate during mixing, and liquid phase change materials tend to leak out at high temperatures, severely impacting material durability and causing insulation failure. Furthermore, pure phase change materials are often soft or liquid, lacking mechanical strength. Even when combined with traditional insulation materials, this reduces the compressive strength of the composite material, making it difficult to meet the demands of building structure applications.

[0004] Therefore, from a long-term perspective, phase change materials experience performance degradation due to decreased crystallinity and reduced latent heat during frequent phase change cycles. Some organic phase change materials also release volatile organic compounds (VOCs), threatening indoor air quality and human health. Therefore, there is an urgent need to develop a new preparation method that can address the shortcomings of traditional insulation materials and phase change material composite technologies, thereby achieving efficient, energy-saving, and environmentally friendly building insulation. Summary of the Invention

[0005] (1) Technical problems solved In response to the shortcomings of the existing technology, the present invention provides a method for preparing a phase change material composite building insulation material based on a porous structure, which has the advantages of active temperature control, leakage prevention, high strength, long life and environmental protection. It solves the problems of high passive insulation energy consumption of traditional insulation materials, leakage and agglomeration of phase change materials after composite, poor mechanical properties, long-term performance degradation and environmental pollution.

[0006] (2) Technical solution To achieve the above object, the present invention provides the following technical solution: a method for preparing a phase change material composite building insulation material based on a porous structure, comprising the following steps: Step 1. Prepare raw materials: Weigh the formula ratio of expanded perlite, modified diatomaceous earth, nanocellulose aerogel, food-grade palmitic acid, microcapsule bio-based PCM, modified graphene, environmentally friendly polylactic acid, montmorillonite, nanosilica and aluminum hydroxide as the main materials, and then prepare the formula ratio of pure acrylic emulsion and non-woven glass fiber mat covered with aluminum foil as auxiliary materials for surface treatment and reflective layer composite; Step 2: Raw material pretreatment: pretreating the prepared expanded perlite, modified diatomaceous earth, nanocellulose aerogel, microencapsulated bio-based PCM and food-grade palmitic acid; Step 3: Basic skeleton construction: Mix expanded perlite, modified diatomaceous earth, environmentally friendly polylactic acid and aluminum hydroxide at 35-40°C and 120-180r / min for 5-10 minutes to form a basic skeleton; Step 4: Phase change material compounding: under a pressure of 0.5-1.0 MPa, add molten food-grade palmitic acid to the basic skeleton, stir at a speed of 120-180 r / min for 5-10 minutes, and then add bio-based PCM microcapsule powder after mixing. Mix at 35-40 ° C and 120-180 r / min for 10-15 minutes to fully compound the phase change material and the basic skeleton to obtain a composite phase change material basic skeleton; Step 5: Functionalization enhancement: Adding modified graphene, montmorillonite, and 1 / 5 of nano-silica to the composite phase change material base skeleton under vacuum conditions below -0.08 MPa, and mixing at a speed of 200-300 r / min for 12-18 minutes to obtain a functional mixture; Step 6: Vacuum impregnation strengthening: Add the functional mixture into a vacuum tank and maintain pressure for 25 to 30 minutes under the environmental conditions of vacuum degree -0.095 to -0.05 MPa and temperature 40-45°C, then release the pressure and allow the material to stand at normal pressure for 18 to 24 hours; Step 7: Low-temperature compression molding: inject the vacuum impregnation-strengthened mixture into a compression molding machine, set the pressure to 10-15 MPa, hold the pressure for 8-10 minutes, and press to obtain a preliminarily formed sheet; Step 8: Surface treatment: Use double-sided roller coating process to evenly apply pure acrylic emulsion on the surface of the board; Step 9: Laminating the reflective layer: Under the conditions of temperature 75-80°C, pressure 0.1-0.2 MPa and holding time of 20-25 seconds, before the pure acrylic emulsion is completely cured, first apply the non-woven glass fiber mat to the surface of the board, then coat the remaining 4 / 5 of nano-silica on the surface of the glass fiber mat, and finally cover with aluminum foil and hot press; Step 10, curing: placing the composite board in an environment with a temperature of 23±1°C and a relative humidity of 50±5% for 96 to 100 hours, and after curing, cutting and quality inspection are performed to obtain a composite building insulation material.

[0007] Preferably, the main material formula and proportion in step one are: 20-30 parts of expanded perlite; 13-18 parts of modified diatomaceous earth; 9-13 parts of nanocellulose aerogel; 7-11 parts of food-grade palmitic acid; 8-13 parts of microcapsule bio-based PCM; 0.9-1.4 parts of modified graphene; 11-15 parts of environmentally friendly polylactic acid; 7-10 parts of montmorillonite; 1-2 parts of nanosilica; and 3-6 parts of aluminum hydroxide.

[0008] Preferably, the main material formula and its proportion are: 28 parts of expanded perlite; 15 parts of modified diatomaceous earth; 9 parts of nanocellulose aerogel; 10 parts of food-grade palmitic acid; 9 parts of microcapsule bio-based PCM; 1 part of modified graphene; 14 parts of environmentally friendly polylactic acid; 9 parts of montmorillonite; 1.5 parts of nanosilica; and 4 parts of aluminum hydroxide.

[0009] Preferably, the main material formula and its proportion are: 29 parts of expanded perlite; 16 parts of modified diatomaceous earth; 13 parts of nanocellulose aerogel; 11 parts of food-grade palmitic acid; 11 parts of microcapsule bio-based PCM; 1.3 parts of modified graphene; 12 parts of environmentally friendly polylactic acid; 7 parts of montmorillonite; 2 parts of nanosilica; and 6 parts of aluminum hydroxide.

[0010] Preferably, the auxiliary materials and their proportions in step 1 are: pure acrylic emulsion coating amount 75-80g / m 2 ; The thickness of the non-woven glass fiber felt is 0.8~1.2mm; the thickness of the aluminum foil film is 0.07~0.12mm, and the reflectivity is >97%.

[0011] Preferably, the pretreatment in step 2 comprises: calcining the expanded perlite and the modified diatomaceous earth at 600-800° C. for 2-3 hours, and then grinding them to control the particle size to be between 50-100 μm.

[0012] Preferably, the pretreatment in step 2 includes: vacuum drying the nanocellulose aerogel and the microencapsulated bio-based PCM separately, drying them under a vacuum pressure of -0.09 to -0.05 MPa and a temperature of 55-60°C for 1 to 2 hours, and grinding the dried microencapsulated bio-based PCM to a particle size of <50 microns.

[0013] Preferably, the pretreatment in step 2 comprises: placing food-grade palmitic acid in a water bath at 55-60° C. and heating it to a melting point of 8° C. or above, melting it into a liquid state and keeping it warm for later use.

[0014] Preferably, the pretreatment in step 2 comprises: reacting montmorillonite with hexadecyltrimethylammonium bromide, and the reaction formula is: Na-MMT+CTAB→CTAB-MMT+NaBr In the formula, Na-MMT represents sodium montmorillonite, CTAB represents hexadecyltrimethylammonium bromide, CTAB-MMT represents modified montmorillonite, and NaBr represents a by-product generated by the reaction.

[0015] Preferably, in step nine, the remaining 4 / 5 of the nano-silica is evenly coated between the aluminum foil film and the glass fiber felt with a thickness of 0.1 to 0.5 mm to form a nano-silica transition layer.

[0016] Compared with the prior art, the present invention provides a method for preparing a phase change material composite building insulation material based on a porous structure, which has the following beneficial effects: 1. The present invention constructs a basic skeleton with synergistic high porosity and low thermal conductivity by compounding expanded perlite, modified diatomaceous earth and nanocellulose aerogel porous materials, thereby effectively blocking the heat conduction of composite building insulation materials. At the same time, food-grade palmitic acid and microencapsulated bio-based PCM are introduced into the raw materials and compounded with the basic skeleton to give the material the function of heat storage and temperature regulation, thereby increasing the material's phase change latent heat. By adding modified graphene and nano-silica, an efficient heat conduction network and thermal insulation structure are formed, thereby further reducing the thermal conductivity coefficient, verifying that the synergistic optimization of the porous structure and phase change material of the present invention has a significant effect on improving the thermal insulation performance.

[0017] 2. The present invention improves the reflective thermal insulation performance of the material by adding an aluminum foil reflective layer. The composite design of the nano-silica transition layer and the aluminum foil reflective layer helps to enhance the interfacial bonding strength and durability of the reflective layer of the composite building insulation material, thereby avoiding stratification. Traditional ordinary cellulose aerogel or the lack of nanomaterials will lead to a decrease in compressive strength. Therefore, it is verified that the nanomaterials in the formula of the present invention can enhance the mechanical properties of the composite building insulation material.

[0018] 3. The present invention adopts a vacuum impregnation process and a curing process, which have a synergistic effect and can effectively reduce radiation heat transfer and surface heat loss. Among them, the vacuum impregnation process ensures the full adsorption of the phase change material in the capillary, and combines with the curing process to form a stable structure, so that the material maintains good performance after multiple thermal cycles. Therefore, the vacuum impregnation process and curing process used have a core contribution to the long-term thermal insulation performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A flow chart was prepared for the present invention. DETAILED DESCRIPTION

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] See also Figure 1 The method for preparing a phase change material composite building insulation material based on a porous structure comprises the following steps: Step 1. Prepare raw materials: Weigh the formula ratio of expanded perlite, modified diatomaceous earth, nanocellulose aerogel, food-grade palmitic acid, microcapsule bio-based PCM, modified graphene, environmentally friendly polylactic acid, montmorillonite, nanosilica and aluminum hydroxide as the main materials, and then prepare the formula ratio of pure acrylic emulsion and non-woven glass fiber mat covered with aluminum foil as auxiliary materials for surface treatment and reflective layer composite; Step 2: Raw material pretreatment: pretreating the prepared expanded perlite, modified diatomaceous earth, nanocellulose aerogel, microencapsulated bio-based PCM and food-grade palmitic acid; Step 3: Basic skeleton construction: Mix expanded perlite, modified diatomaceous earth, environmentally friendly polylactic acid and aluminum hydroxide at 35-40°C and 120-180r / min for 5-10 minutes to form a basic skeleton; Step 4: Phase change material compounding: under a pressure of 0.5-1.0 MPa, add molten food-grade palmitic acid to the basic skeleton, stir at a speed of 120-180 r / min for 5-10 minutes, and then add bio-based PCM microcapsule powder after mixing. Mix at 35-40 ° C and 120-180 r / min for 10-15 minutes to fully compound the phase change material and the basic skeleton to obtain a composite phase change material basic skeleton; Step 5: Functionalization enhancement: Adding modified graphene, montmorillonite, and 1 / 5 of nano-silica to the composite phase change material base skeleton under vacuum conditions below -0.08 MPa, and mixing at a speed of 200-300 r / min for 12-18 minutes to obtain a functional mixture; Step 6: Vacuum impregnation strengthening: Add the functional mixture into a vacuum tank and maintain pressure for 25 to 30 minutes at a vacuum degree of -0.095 to -0.05 MPa and a temperature of 40-45°C. Then slowly release the pressure and allow the material to stand at normal pressure for 18 to 24 hours to ensure that the capillaries completely absorb the phase change material (PCM), thereby further improving the thermal insulation performance and stability of the material. Step 7: Low-temperature compression molding: inject the vacuum impregnation-strengthened mixture into a compression molding machine, set the pressure to 10-15 MPa, hold the pressure for 8-10 minutes, and press to obtain a preliminarily formed sheet; Step 8. Surface treatment: Use a double-sided roller coating process to evenly apply pure acrylic emulsion (zero VOCs) to the surface of the board to provide waterproofness and weather resistance, thereby enhancing the surface crack resistance and durability of the material. The pure acrylic emulsion forms a waterproof layer, and the glass fiber mat resists external impact through the grid structure to prevent surface cracking; Step 9, reflective layer composite: Under the conditions of temperature 75-80℃, pressure 0.1-0.2MPa and holding time of 20-25 seconds, before the pure acrylic emulsion is completely cured, first apply non-woven glass fiber mat to the surface of the board, then apply the remaining 4 / 5 of nano-silicon dioxide to the surface of the glass fiber mat as a transition layer, and finally cover with aluminum foil and hot press to make the nano-silicon dioxide transition layer tightly bonded to the aluminum foil and glass fiber mat, so as to ensure that the reflective layer is tightly bonded to the substrate and avoid delamination. Since the reflectivity of the aluminum foil is greater than 97%, it can reduce radiant heat transfer, thereby further reducing heat transfer. The hot pressing process forms a strong interface between the aluminum foil and the glass fiber mat, which helps to enhance the stability and durability of the composite structure. Step 10: Curing: Place the composite board in an environment with a temperature of 23±1°C and a relative humidity of 50±5% for 96 to 100 hours to complete natural curing. After the curing is completed, cut and quality test are performed to finally obtain the composite building insulation material.

[0022] The advantages are: by adopting the vacuum impregnation process and the curing process, the two have a synergistic effect, which can effectively reduce radiation heat transfer and surface heat loss. Among them, the vacuum impregnation process ensures the full adsorption of the phase change material in the capillary, and combines the curing process to form a stable structure, so that the material can still maintain good performance after multiple thermal cycles. Therefore, the vacuum impregnation process and curing process used have a core contribution to the long-term thermal insulation performance.

[0023] Specifically, the main material formula and its proportion in step one are: 20-30 parts of expanded perlite; 13-18 parts of modified diatomaceous earth; 9-13 parts of nanocellulose aerogel; 7-11 parts of food-grade palmitic acid; 8-13 parts of microcapsule bio-based PCM; 0.9-1.4 parts of modified graphene; 11-15 parts of environmentally friendly polylactic acid; 7-10 parts of montmorillonite; 1-2 parts of nanosilica; and 3-6 parts of aluminum hydroxide.

[0024] The advantages are: by compounding expanded perlite, modified diatomaceous earth and nanocellulose aerogel porous materials, a basic skeleton with high porosity and low thermal conductivity is constructed, thereby effectively blocking the heat conduction of composite building insulation materials. At the same time, food-grade palmitic acid and microcapsule bio-based PCM are introduced into the raw materials and compounded with the basic skeleton to give the material the function of heat storage and temperature regulation, thereby increasing the phase change latent heat of the material. By adding modified graphene and nano-silica, an efficient heat conduction network and insulation structure are formed, thereby further reducing the thermal conductivity coefficient, so as to verify that the synergistic optimization of the porous structure and phase change material of the present invention has a significant effect on improving the thermal insulation performance.

[0025] Specifically, the auxiliary materials and their proportions in step 1 are: pure acrylic emulsion (zero VOCs) coating amount 75-80g / m 2 ; The thickness of the non-woven glass fiber felt is 0.8~1.2mm; the thickness of the aluminum foil film is 0.07~0.12mm, and the reflectivity is >97%.

[0026] The raw material role table is as follows: Table 1

[0027] Note: (1) The main material is responsible for providing the core properties of thermal insulation, energy storage, mechanical strength and stability.

[0028] (2) Auxiliary materials are used for surface treatment and reflective layer composite to enhance the waterproofness, weather resistance, crack resistance, durability and thermal insulation properties of the material.

[0029] Specifically, the pretreatment in step 2 includes: calcining the expanded perlite and modified diatomaceous earth at 600-800° C. for 2-3 hours, and then grinding them to control the particle size between 50-100 microns to ensure that they can be evenly dispersed in the subsequent mixing process.

[0030] Specifically, the pretreatment in step 2 includes: vacuum drying the nanocellulose aerogel and the microencapsulated bio-based PCM separately, drying them at a vacuum pressure of -0.09 to -0.05 MPa and a temperature of 55-60°C for 1 to 2 hours to ensure their structural stability, and grinding the dried microencapsulated bio-based PCM to a particle size of <50 microns.

[0031] Specifically, the pretreatment in step 2 includes: placing food-grade palmitic acid in a water bath at 55-60° C. and heating it to a melting point of 8° C. or above, melting it into a liquid state and keeping it warm for later use.

[0032] Specifically, the pretreatment in step 2 includes: reacting montmorillonite with hexadecyltrimethylammonium bromide to modify the montmorillonite, thereby improving its adsorption performance and stability. The process reaction formula is: Na-MMT+CTAB→CTAB-MMT+NaBr In the formula, Na-MMT represents sodium montmorillonite, CTAB represents hexadecyltrimethylammonium bromide, CTAB-MMT represents modified montmorillonite, and NaBr represents a by-product generated by the reaction.

[0033] The advantages are: through the pretreatment of raw materials, the expanded perlite and modified diatomaceous earth are calcined at high temperature and the particle size is controlled to ensure that they can be evenly dispersed in the subsequent mixing process; the nanocellulose aerogel and microencapsulated bio-based PCM are vacuum dried to ensure their structural stability and control the particle size; the food-grade palmitic acid is heated and melted to facilitate subsequent mixing; the montmorillonite is modified to improve its adsorption performance and stability. The above pretreatment steps can finally assist the subsequent preparation process, so that the thermal insulation performance, mechanical properties and stability of the prepared finished product are greatly improved.

[0034] Specifically, in step nine, the remaining 4 / 5 of the nano-silica is evenly coated between the aluminum foil film and the glass fiber felt with a thickness of 0.1 to 0.5 mm to form a nano-silica transition layer to enhance the interface bonding strength and durability of the reflective layer.

[0035] The advantages are: by adding an aluminum foil film reflective layer, the reflective heat insulation performance of the material is improved. Among them, the composite design of the nano-silica transition layer and the aluminum foil film reflective layer helps to enhance the interfacial bonding strength and durability of the reflective layer of the composite building insulation material, thereby avoiding stratification. Traditional ordinary cellulose aerogel or the lack of nanomaterials will lead to a decrease in compressive strength. Therefore, it is verified that the nanomaterials in the formula of the present invention can enhance the mechanical properties of the composite building insulation material.

[0036] Example 1 Raw materials preparation: Main material formula: 28 parts of expanded perlite; 15 parts of modified diatomaceous earth; 9 parts of nanocellulose aerogel; 10 parts of food-grade palmitic acid; 9 parts of microcapsule bio-based PCM; 1 part of modified graphene; 14 parts of environmentally friendly polylactic acid; 9 parts of montmorillonite; 1.5 parts of nanosilica; 4 parts of aluminum hydroxide.

[0037] The auxiliary material ratio is: pure acrylic emulsion (zero VOCs) coating amount 78g / m 2 The thickness of the non-woven glass fiber felt is 1mm; the thickness of the aluminum foil film is 0.10mm, and the reflectivity is 98%.

[0038] Preparation process: Prepare according to the method of the present invention.

[0039] Comparative Example 1 The same process flow as in Example 1 was followed, except that "1 part of modified graphene" and "1.5 parts of nano-silicon dioxide" in the main material formula of Example 1 were removed, and the ratio of auxiliary materials remained unchanged.

[0040] Example 2 Raw materials preparation: Main material formula: 29 parts expanded perlite; 16 parts modified diatomaceous earth; 13 parts nanocellulose aerogel; 11 parts food-grade palmitic acid; 11 parts microcapsule bio-based PCM; 1.3 parts modified graphene; 12 parts environmentally friendly polylactic acid; 7 parts montmorillonite; 2 parts nanosilica; 6 parts aluminum hydroxide.

[0041] The auxiliary material ratio is: pure acrylic emulsion (zero VOCs) coating amount 75g / m 2 The thickness of the non-woven glass fiber felt is 0.8mm; the thickness of the aluminum foil film is 0.07mm, and the reflectivity is 98%.

[0042] Same process as Example 1.

[0043] Comparative Example 2 The formula and preparation process are the same as those in Example 2, except that “13 parts of nanocellulose aerogel” is replaced by “13 parts of ordinary cellulose aerogel”.

[0044] Same process as Example 1.

[0045] Example 3 Raw materials preparation: Main material formula: 25 parts of expanded perlite; 14 parts of modified diatomaceous earth; 12 parts of nanocellulose aerogel; 8 parts of food-grade palmitic acid; 13 parts of microcapsule bio-based PCM; 0.9 parts of modified graphene; 13 parts of environmentally friendly polylactic acid; 8 parts of montmorillonite; 1.2 parts of nanosilica; 5 parts of aluminum hydroxide.

[0046] Auxiliary material ratio: pure acrylic emulsion (zero VOCs) coating amount 76g / m 2 ; Non-woven glass fiber felt thickness 1.1mm; aluminum foil film thickness 0.09mm, reflectivity 99%.

[0047] Same process as Example 1.

[0048] Comparative Example 3 The raw material formula is the same as that of Example 3, but step nine is adjusted as follows: only the non-woven glass fiber felt is applied without adding the aluminum foil reflective layer.

[0049] Example 4 Completely follow the formula and preparation process of the present invention.

[0050] Comparative Example 4 The raw material formula is the same as that of Example 4, and the nano-silicon dioxide transition layer is not formed in step nine.

[0051] The examples and comparative examples were prepared into finished composite building insulation materials, and the finished products were subjected to quality inspection. The inspection data are shown in Table 2 below: Table 2

[0052] From the analysis of Table 2, it can be seen that Examples 1-4 reduce the thermal conductivity of the composite material by adding modified graphene and nano-silica to form a thermal conductive network and thermal insulation structure; while Comparative Example 1 increases its thermal conductivity due to the removal of these two key materials, thereby verifying the key role of modified graphene and nano-silica in reducing heat conduction. The tabular data shows that the phase change latent heat of Comparative Example 1 is reduced, indicating that the complete formulation can improve the phase change energy storage capacity of the material; Comparative Example 2 replaces the nanocellulose aerogel with ordinary cellulose aerogel, resulting in a decrease in compressive strength, thereby verifying the enhancing effect of nanomaterials on mechanical properties; Comparative Example 3 does not add aluminum foil, and the reflectivity decreases significantly, highlighting the core role of the reflective layer in blocking radiative heat transfer in the embodiment; Comparative Example 4 does not form a nano-silica transition layer, so the reflectivity is slightly lower than that of Example 4, indicating that the transition layer of the embodiment helps to improve the bonding of the aluminum foil. In summary, the embodiments maintain good performance after multiple thermal cycles by optimizing the formulation and process, thereby reflecting the role of the coordinated design of process and formulation in improving the long-term stability of the material.

[0053] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a phase change material composite building insulation material based on a porous structure, characterized in that: The following steps are involved: Step 1. Prepare raw materials: Weigh the formula ratio of expanded perlite, modified diatomaceous earth, nanocellulose aerogel, food-grade palmitic acid, microcapsule bio-based PCM, modified graphene, environmentally friendly polylactic acid, montmorillonite, nanosilica and aluminum hydroxide as the main materials, and then prepare the formula ratio of pure acrylic emulsion and non-woven glass fiber mat covered with aluminum foil as auxiliary materials for surface treatment and reflective layer composite; Step 2: Raw material pretreatment: pretreating the prepared expanded perlite, modified diatomaceous earth, nanocellulose aerogel, microencapsulated bio-based PCM and food-grade palmitic acid; Step 3: Basic skeleton construction: Mix expanded perlite, modified diatomaceous earth, environmentally friendly polylactic acid and aluminum hydroxide at 35-40°C and 120-180r / min for 5-10 minutes to form a basic skeleton; Step 4: Phase change material compounding: under a pressure of 0.5-1.0 MPa, add molten food-grade palmitic acid to the basic skeleton, stir at a speed of 120-180 r / min for 5-10 minutes, and then add bio-based PCM microcapsule powder after mixing. Mix at 35-40 ° C and 120-180 r / min for 10-15 minutes to fully compound the phase change material and the basic skeleton to obtain a composite phase change material basic skeleton; Step 5: Functionalization enhancement: Adding modified graphene, montmorillonite, and 1 / 5 of nano-silica to the composite phase change material base skeleton under vacuum conditions below -0.08 MPa, and mixing at a speed of 200-300 r / min for 12-18 minutes to obtain a functional mixture; Step 6: Vacuum impregnation strengthening: Add the functional mixture into a vacuum tank and maintain pressure for 25 to 30 minutes under the environmental conditions of vacuum degree -0.095 to -0.05 MPa and temperature 40-45°C, then release the pressure and allow the material to stand at normal pressure for 18 to 24 hours; Step 7: Low-temperature compression molding: inject the vacuum impregnation-strengthened mixture into a compression molding machine, set the pressure to 10-15 MPa, hold the pressure for 8-10 minutes, and press to obtain a preliminarily formed sheet; Step 8: Surface treatment: Use double-sided roller coating process to evenly apply pure acrylic emulsion on the surface of the board; Step 9: Laminating the reflective layer: Under the conditions of temperature 75-80°C, pressure 0.1-0.2 MPa and holding time of 20-25 seconds, before the pure acrylic emulsion is completely cured, first apply the non-woven glass fiber mat to the surface of the board, then coat the remaining 4 / 5 of nano-silica on the surface of the glass fiber mat, and finally cover with aluminum foil and hot press; Step 10, curing: placing the composite board in an environment with a temperature of 23±1°C and a relative humidity of 50±5% for 96 to 100 hours, and after curing, cutting and quality inspection are performed to obtain a composite building insulation material.

2. The method for preparing a porous phase change material composite building insulation material according to claim 1, characterized in that: The main material formula and proportion in step 1 are: 20-30 parts of expanded perlite; 13-18 parts of modified diatomaceous earth; 9-13 parts of nanocellulose aerogel; 7-11 parts of food-grade palmitic acid; 8-13 parts of microcapsule bio-based PCM; 0.9-1.4 parts of modified graphene; 11-15 parts of environmentally friendly polylactic acid; 7-10 parts of montmorillonite; 1-2 parts of nanosilica; and 3-6 parts of aluminum hydroxide.

3. The method for preparing a porous phase change material composite building insulation material according to claim 2, characterized in that: The main material formula and its proportion are: 28 parts of expanded perlite; 15 parts of modified diatomaceous earth; 9 parts of nanocellulose aerogel; 10 parts of food-grade palmitic acid; 9 parts of microcapsule bio-based PCM; 1 part of modified graphene; 14 parts of environmentally friendly polylactic acid; 9 parts of montmorillonite; 1.5 parts of nano silicon dioxide; 4 parts of aluminum hydroxide.

4. The method for preparing a porous structure-based phase change material composite building insulation material according to claim 2, characterized in that: The main material formula and its proportion are: 29 parts of expanded perlite; 16 parts of modified diatomaceous earth; 13 parts of nanocellulose aerogel; 11 parts of food-grade palmitic acid; 11 parts of microcapsule bio-based PCM; 1.3 parts of modified graphene; 12 parts of environmentally friendly polylactic acid; 7 parts of montmorillonite; 2 parts of nanosilica; and 6 parts of aluminum hydroxide.

5. The method for preparing a porous structure-based phase change material composite building insulation material according to claim 1, characterized in that: The auxiliary materials and their proportions in step 1 are as follows: pure acrylic emulsion coating amount 75-80g / m 2 ; The thickness of the non-woven glass fiber felt is 0.8~1.2mm; the thickness of the aluminum foil film is 0.07~0.12mm, and the reflectivity is >97%.

6. The method for preparing a porous structure-based phase change material composite building insulation material according to claim 1, characterized in that: The pretreatment in step 2 includes: calcining the expanded perlite and the modified diatomaceous earth at 600-800° C. for 2-3 hours, and then grinding them to control the particle size to be between 50-100 microns.

7. The method for preparing a porous structure-based phase change material composite building insulation material according to claim 1, characterized in that: The pretreatment in step 2 includes: vacuum drying the nanocellulose aerogel and the microencapsulated bio-based PCM separately, drying them for 1 to 2 hours under a vacuum pressure of -0.09 to -0.05 MPa and a temperature of 55-60° C., and grinding the dried microencapsulated bio-based PCM to a particle size of <50 μm.

8. The method for preparing a porous structure-based phase change material composite building insulation material according to claim 1, characterized in that: The pretreatment in step 2 includes: placing food-grade palmitic acid in a water bath at 55-60° C. and heating it to a melting point of 8° C. or above, melting it into a liquid state and keeping it warm for later use.

9. The method for preparing a porous structure-based phase change material composite building insulation material according to claim 1, characterized in that: The pretreatment in step 2 includes reacting montmorillonite with hexadecyltrimethylammonium bromide, and the reaction formula is: Na-MMT+CTAB→CTAB-MMT+NaBr In the formula, Na-MMT represents sodium montmorillonite, CTAB represents hexadecyltrimethylammonium bromide, CTAB-MMT represents modified montmorillonite, and NaBr represents a by-product generated by the reaction.

10. The method for preparing a porous structure-based phase change material composite building insulation material according to claim 1, characterized in that: In the step nine, the remaining 4 / 5 of the nano-silicon dioxide is evenly coated between the aluminum foil film and the glass fiber felt with a thickness of 0.1 to 0.5 mm to form a nano-silicon dioxide transition layer.

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