Preparation method of biomass-based building exterior wall material with radiation refrigeration, heat preservation and energy saving performance

Abstract

The invention discloses a preparation method of a biomass-based building exterior wall material with radiation refrigeration, heat preservation and energy conservation performance. The method comprises the following steps: (1) wood delignification; (2) solution replacement is conducted, specifically, the wood board subjected to lignin removal in the step (1) is soaked in deionized water, and a residual solvent is replaced till the wood board is neutral; (3) microwave drying is conducted, specifically, the delignification wood board full of the deionized water in the step (2) is subjected to microwave drying for 2-5 min, and most of water is removed; and (4) hot pressing and drying, wherein the delignification wood board obtained in the step (3) is placed in a 60 DEG C hot press to be pressurized and dried till the weight is constant. The material is a wood fiber porous material, has the advantages of light weight, high mechanical strength, excellent thermal insulation performance and environmental protection of a cellulose material, can perform multiple reflection and scattering on solar radiation, has relatively high infrared emissivity in an atmospheric window wave band (8-13 microns), and can effectively reduce the surface temperature of the material.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation and utilization of building functional materials, and more specifically to a preparation method of a biomass-based building exterior wall material with radiative cooling and heat preservation and energy-saving properties. Background Art

[0002] At present, the energy consumption in the construction field accounts for 45% of the national energy consumption, and the carbon emissions account for 50.6% of the national total. From the perspective of sustainable development, it is very important to develop new energy-saving building materials that are resource-saving and environmentally friendly. Radiative cooling technology is a passive, energy-free, pollution-free, and green refrigeration technology. It radiates its own heat to the cold outer space through the atmospheric window (8-13 μm), and reduces the absorption of solar energy through the high reflectivity in the solar spectral band (0.3-2.5 μm), thereby achieving passive radiative cooling. Research shows that delignifying natural wood and hot pressing can significantly reduce the thermal conductivity of the material and improve its mechanical properties. At the same time, delignified wood boards have high reflectivity in the solar band (0.3-2.5 μm) and high emissivity in the atmospheric window band (8-13 μm). When used as building exterior wall materials, they can effectively prevent the temperature of the target object from rising and save building energy consumption. Compared with traditional building exterior wall insulation materials (such as polystyrene, foam board, extruded polystyrene board, rock wool board, etc.), the biomass insulation material after delignification treatment and hot pressing has higher mechanical strength and higher feasibility in energy conservation and consumption reduction, improving indoor comfort, enhancing building durability, and environmental protection and sustainability, which conforms to the development trend of sustainable buildings. The application of radiative cooling wood in building radiative cooling and heat preservation can effectively reduce building energy consumption and achieve the goals of energy conservation, emission reduction, and carbon neutrality. However, the cost of raw materials and the relatively complex production process have always been important issues restricting the wide promotion of this technology. Summary of the Invention

[0003] The technical problems solved by the present invention are as follows: Traditional building exterior wall insulation materials do not have radiative cooling characteristics and have poor mechanical strength. Natural wood needs to be treated by special processes to achieve radiative cooling and improvement of mechanical strength, but there are no relevant standards and implementation methods for the current treatment processes. There is no relevant mature technology for bio-based building exterior wall insulation materials that combine radiative cooling, heat preservation, and mechanical strength. In view of the above problems, an environmentally friendly biomass-based building exterior wall material with good heat preservation effect and mechanical properties and capable of achieving radiative cooling and its preparation method are provided.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A preparation method of a biomass-based building exterior wall material with radiative cooling and heat preservation and energy-saving properties, comprising the following steps:

[0006] S1. Wood delignification: Cut natural wood to a thickness of about 1 cm, and cut the width and length according to the actual required dimensions. Prepare a 30% hydrogen peroxide solution with a solid-liquid ratio of 1:35 (g / m1), soak the wood in the solution for 24 h, and then cook it at 100 °C for 6 h to remove lignin and hemicellulose in the natural wood.

[0007] S2. Solution replacement: Immerse the delignified board obtained in S1 in deionized water, and change the water treatment every 12 h until the solution is neutral.

[0008] S3. Microwave drying: Subject the delignified board saturated with deionized water obtained in S2 to microwave heating for 2 - 5 min to rapidly evaporate the moisture inside the board, so that the delignified board retains the cellulose porous structure.

[0009] S4. Hot pressing and drying: Place the delignified board obtained in S3 flat in a hot press, wrap it with filter paper, compact it with the hot press, and dry it at 60 °C until the weight is constant to obtain a building thermal insulation and energy-saving board.

[0010] Further, the natural wood is balsa wood.

[0011] Further, in S3, the delignified board is microwave-dried to 2.5 - 3.0 times the weight of the natural wood.

[0012] Further, in S4, the delignified board is hot-pressed in the hot press to 40% of its original thickness.

[0013] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit this invention application.

[0014] In the above technical solution, the preparation method of a biomass-based building exterior wall material with radiative cooling and thermal insulation and energy-saving performance provided by the present invention has the following beneficial effects:

[0015] 1. Compared with traditional building exterior wall thermal insulation materials, the biomass-based building exterior wall material provided by the present invention is an environmentally friendly and renewable lignocellulose porous material with a long service life, which can maintain the long-term stability of the building's thermal insulation performance. Its thermal conductivity is as low as 0.038 W / (m·K), which can effectively prevent heat transfer, and has great advantages in environmental protection and sustainable development.

[0016] 2. After the biomass-based building exterior wall material provided by the present invention undergoes delignification treatment and hot pressing, most of the light-absorbing materials are removed. Based on the low absorption rate of cellulose in the visible light range and the high emissivity in the infrared band, it can effectively reflect sunlight, reduce the heat absorption of the exterior wall, radiate its own heat, and lower the surface temperature of the exterior wall. Tests show that during the noon period, the average temperature drop of the back panel of this material compared to the ambient temperature can reach 4.2°C, which can effectively reduce the heat transferred into the building and has a certain building energy-saving effect.

[0017] 3. The biomass-based building exterior wall material provided by the present invention has sufficient strength. Its tensile strength is 7.2 MPa and its flexural strength is 16.8 MPa, which has exceeded that of conventional polymer insulation foams and reached the mechanical strength required for insulation materials in the construction field. At the same time, the microwave drying treatment method can greatly reduce the preparation time of the material and is suitable for large-scale promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the spectral test chart of Example 1 of the present invention;

[0019] Figure 2 It is the climate parameter chart of the actual temperature drop test of Example 1 of the present invention;

[0020] Figure 3 It is the actual temperature drop test chart of Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] The technical solutions of the present invention will be described in detail below with reference to the accompanying drawings.

[0022] Example 1

[0023] (1) Cut natural balsa wood into thin cuboids of 5 cm × 5 cm × 1 cm with a saw. Prepare 150 ml of H2O2 solution with a mass fraction of 30%. Place 3.5 g of balsa wood weighed in a 500 ml beaker. According to the solid-liquid ratio of 1:35 (g / ml), add 122.5 ml of H2O2 solution with a mass fraction of 30% to the 500 ml beaker and seal it with plastic wrap. After the solvent infiltrates the balsa wood for 24 h, cook it in a constant temperature oil bath at 100°C for 6 h to remove lignin and hemicellulose.

[0024] (2) Take out the cooked wooden blocks from the solution in step (1), rinse the surface residual solvent with deionized water, and then place them in 500 ml of deionized water to fully displace the internal residual solvent. Replace the deionized water every 12 h until the solution is neutral to obtain a pure white delignified wooden board saturated with deionized water.

[0025] (3) Place the pure white delignified wooden board saturated with deionized water obtained in step (2) in a microwave oven and dry it at a power of 300 w for 5 min to quickly remove most of the internal moisture. The weight decreases from 26.3 g to 10.5 g, and the regular cellulose porous structure inside is retained.

[0026] (4) Wrap both the upper and lower surfaces of the delignified wooden board obtained in step (3) with filter paper, place it flat in a hot press and compact it. The thickness is compressed from the original 1 cm to 0.4 cm, and it is hot pressed at a constant temperature of 60 °C until the weight is constant. The constant weight of the delignified wooden board after hot pressing is 1.8 g, and a thermal insulation board is obtained.

[0027] Test Example 1

[0028] For the thermal conductivity test of the material, use a Hot Disk2500S thermal conductivity meter with the transient plane heat source method to measure the thermal conductivity of Example 1 according to GB / T 4857.2-2005. Each sample is tested 3 times repeatedly, and the average value is taken. The measurement time is 20 s and the heating power is 800 mw. The measured thermal conductivity of Example 1 is 0.038 W / (m·K).

[0029] Test Example 2

[0030] For the mechanical property test of the material, use a WDW-E100 microcomputer-controlled electronic universal testing machine to measure the tensile strength and flexural strength of Example 1 with reference to GB / T 1040.1-2018 "Determination of Tensile Properties of Plastics" and GB / T 9341-2008 "Determination of Flexural Properties of Plastics". The tensile rate is 2 mm / min and the flexural rate is 1 mm / min. 5 specimens are tested for each sample, and the average value is taken. The measured tensile strength of Example 1 is 7.2 MPa and the flexural strength is 16.8 MPa.

[0031] Test Example 3

[0032] The spectral test of Example 1 is carried out in two parts. First, use a UV-Vis-NIR spectrophotometer (UH4150) to test the reflectivity of Example 1 in the solar spectrum band (0.3~2.5 μm). Use an infrared spectrometer (IS20) with an integrating sphere accessory to test the emissivity of Example 1 in the atmospheric window band (8~13 μm). The test results are shown in Figure 1 , from Figure 1 it can be seen that Example 1 has a high reflectivity in the solar spectrum band (0.3~2.5 μm), with an average reflectivity of 89.8%, and a high emissivity in the atmospheric window band (8~13 μm), with an average emissivity of 88.9%. Therefore, it can better reflect the heat of sunlight, radiate its own heat, reduce the temperature of the target object, and achieve the energy-saving effect.

[0033] Test Example 4

[0034] The cooling test was carried out on Example 1. The test method was to place Example 1 1 cm below the upper surface of a foam box with an opening of 15 cm × 15 cm × 15 cm. Aluminum foil was pasted on the outside of the foam box to minimize the influence of heat convection and heat conduction on the experimental results. The backplane temperature and ambient temperature of Example 1 were measured using thermocouples respectively. The test time was between 10:00 and 14:00 on October 14, 2023. The test location was Tianjin, China. The climate parameters during the test period are shown in Figure 2 , and from Figure 2 it can be seen that during the noon period (between 10:00 and 14:00), the average wind speed was 1.55 m / s, the relative humidity was 22.25%, and the solar radiation intensity was 382 - 635 w / m 2 . The actual cooling test results of Example 1 are shown in Figure 3 , and from Figure 3 it can be seen that the average temperature of Example 1 was lower than the ambient temperature, and the average cooling amplitude was 4.2 °C, having a good cooling effect. When applied to the exterior wall of a building under hot climate conditions, it can effectively achieve the purpose of building energy conservation.

[0035] The embodiments of the present invention application have been described above. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art in the technical field without departing from the scope and spirit of the described embodiments. The selection of the terms used herein is intended to best explain the principles of the embodiments, the practical application, or the improvement of the technology in the market, or to enable other ordinary skill in the art in the technical field to understand the disclosed embodiments.

Claims

1. A preparation method of a biomass-based building exterior wall material with radiative cooling and heat preservation and energy-saving performance, characterized in that, It includes the following steps: S1. Wood delignification: Cut natural wood to a thickness of about 1 cm, and cut the width and length according to the actual required dimensions. Prepare a 30% hydrogen peroxide solution with a solid-liquid ratio of 1:35 (g / ml), soak the wood with the solution for 24 h, and then cook it at 100 °C for 6 h to remove lignin and hemicellulose in the natural wood; S2. Solution replacement: Immerse the delignified board obtained in S1 in deionized water, and change the water treatment every 12 h until the solution is neutral; S3. Microwave drying: Perform microwave heating treatment on the delignified wood board saturated with deionized water obtained in S2 for 2 - 5 min to quickly evaporate the moisture inside the wood board, so that the delignified wood board retains the cellulose porous structure; S4. Hot pressing and drying: Place the delignified wood board obtained in S3 flat in a hot press, wrap it with filter paper, compact it with the hot press, and dry it at 60 °C until the weight is constant to obtain a building thermal insulation and energy-saving material.

2. The manufacturing method according to claim 1, characterized in that, The natural wood is balsa wood.

3. The manufacturing method according to claim 1, characterized in that, In S3, the delignified wood board is microwave-dried to 2.5 - 3.0 times the weight of the natural wood.

4. The manufacturing method according to claim 1, characterized in that, In S4, the delignified wood board is hot-pressed to 40% of its original thickness in the hot press.

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