Biomass-based heat-insulation flame-retardant foaming material and preparation process thereof

Abstract

The invention relates to a biomass-based thermal insulation flame-retardant foamed sheet and a preparation process thereof, the material is composed of treated plant fiber, a silicon skeleton, polyvinyl alcohol, poly epsilon-caprolactone, pectin and a mildew preventive, and is integrally formed by a hydrolysis-mold pressing foaming process. The material has good obdurability, low heat conductivity, high heat capacity and better flame retardant property, can be degraded under a composting condition, and can be applied to construction of buildings such as field simple panel houses and toilets.

Description

Technical Field

[0001] The invention relates to a biomass-based foaming board and a preparation process thereof, and in particular to a preparation process of a foaming material which has high strength and toughness, heat preservation, thermal insulation and flame retardant effects and can be degraded under composting conditions. Background Art

[0002] Plant fiber is a natural renewable resource that is widely found in agricultural and forestry resources and their processing waste. It is often not fully utilized and is abandoned in nature as garbage or destroyed by incineration, which on the one hand causes serious environmental pollution and on the other hand leads to a large amount of resource waste.

[0003] Plant fibers are used as industrial or civil materials, which require good formability during processing, and the molded materials have good strength and toughness. Tight bonding of fibers can be achieved through molding and other methods, but the notice of compacting the fibers during molding will also lead to an increase in the density of the product, thereby limiting its application, and lightweighting is still a problem that must be solved. The general method for lightweighting plant fiber materials is foaming, that is, during the molding or extrusion process, volatile substances such as water vapor and oils are volatilized to form holes, thereby reducing the density. Although the method is simple, there are still many problems, such as how to ensure the stable bonding of fibers and ensure strength while ensuring the presence of a large number of bubbles; how to deal with the relationship between plant fiber fluidity and uniform foaming during processing. In order to achieve the above goals, many foamable plastic materials with stable performance are used to composite with plant fibers, such as the invention patent 2022112811789, which discloses a microporous plant fiber composite material and its preparation method, which uses thermoplastic plastics and plant fibers for composite foaming to form microfoam pores; the invention patent 2006102004816 discloses a case of composite foaming of plant fibers and EVA. Inorganic substances are also used for composites, such as 202010355961X, a plant fiber foam wall insulation material and its preparation method, which mixes plant fibers and silicate cement for foaming. Because it has a stable high-strength structure, the foaming material has good performance. However, the addition of the above materials will make the foam non-degradable, causing environmental problems. The development of fully degradable plant fiber-based foaming composite materials with good mechanical properties is still a difficult problem in the industry.

[0004] The molding of plant fiber-based foam materials is mainly controlled by the following factors: first, the composition of the composite material, which will determine the basis of the material performance; second, the rheological processability and melt strength of the raw materials, which will determine the foaming size and distribution of the plant fiber-based composite material; third, the combination between the substances, which will determine the uniform energy dissipation of the material; fourth, the processing method and conditions must match the characteristics of the material. Only when all the above factors are coordinated can the performance goals be achieved. In addition to mechanical properties, although pure plant fiber-based foam materials already have pores, their barrier properties and the resulting thermal insulation and heat preservation are still difficult to meet practical requirements. This is because they are often determined by the open-pore pore structure and the heat conductivity of the material itself, which requires the assistance of other materials to achieve.

[0005] To address this problem, this patent has developed a special formula system based on plant fibers. By utilizing the uniformity and surface characteristics of the processed fibers, combined with in-situ hydrolysis technology and multi-biomass skeleton construction, a board material with excellent mechanical properties and barrier and thermal insulation properties has been developed, providing a better option for the development of fully degradable plant fiber products. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of mechanical properties and thermal insulation properties of plant fiber-based foaming materials, and to provide a method for preparing a plant fiber-based foaming material which has good strength and toughness, low thermal conductivity, high thermal capacity and good flame retardant properties and can be degraded under composting conditions.

[0007] The objective of the present invention is achieved through the following technical solutions: A biomass-based thermal insulation and flame-retardant foaming material, comprising treated plant fibers, a silicon skeleton, polyvinyl alcohol, poly-ε-caprolactone, and pectin, wherein the proportions of the components are as follows: Processed plant fibers: 100 Silicon skeleton: 15-25 Polyvinyl alcohol: 5-10 Poly-ε-caprolactone: 5-10 Pectin: 3-6 Antifungal agent: 1-2 Furthermore, the preparation process of the foaming material includes: I: dissolving tetramethoxysilane in water to prepare an aqueous solution with a mass concentration of 5-10%, then adding polyvinyl alcohol, raising the solution temperature to 60-80°C, stirring evenly to obtain premix A, and keeping the temperature for standby use; II: Mix the treated plant fiber and water to prepare a slurry with a moisture content of 60-80%, add poly-ε-caprolactone particles to the slurry, then add weak acid, stir evenly to prepare a composite slurry B, and control the moisture content of the composite slurry B to be between 40-80%, and the pH value to be between 4-5; III: soak the pectin in excess water at 20-40°C for 10-20 minutes to allow the pectin to fully absorb water and swell, then filter out the free water to obtain pectin material C for later use; IV: Before molding and foaming, preheat the composite slurry B to 60-80°C, add 0.2-0.4 volume of premix A, add pectin C and moisture-proof agent, stir well to obtain molding blank D, keep the temperature stable between 60-80°C, and stand to evaporate water to keep the mass fraction of water in the molding blank D between 50-80%; V: Put the molded blank D into the mold of the molding machine, maintain the pressure at 100-120℃ and 2-4MPa for 2-3 minutes, quickly release the pressure within 2-4s, and then continue to pressurize for the second time at 120-140℃ and 4-6MPa, maintain the pressure for 2-3 minutes, and quickly release the pressure within 2-4s to obtain the final product.

[0008] Furthermore, in the preparation process, premix A is added in step IV, and the molding blank D is put into the molding machine mold and pressurized in step V. The interval time between the two steps does not exceed 15 minutes. The above time is to ensure that tetramethoxysilane is hydrolyzed under acidic conditions to generate a silicon skeleton.

[0009] Furthermore, the treated plant fibers are a combination of treated long fibers and treated short fibers; wherein the mass proportion of the treated long fibers in all plant fibers is between 0-60%, and the mass proportion of the treated short fibers in all plant fibers is between 40-100%; the diameter of the treated long fibers is between 10-50 μm, and the length is between 1-10 mm; the diameter of the treated short fibers is between 1-10 μm, and the length is between 100 μm-1 mm.

[0010] Furthermore, the treated long fibers and the treated short fibers are obtained by removing impurities and crushing the plant fibers, sieving them to obtain crude fibers of corresponding mesh sizes, and then treating them with biological enzymes and acids; the mesh size of the untreated original long fibers is between 300-500 meshes, and the mesh size of the untreated original short fibers is between 1000-2000 meshes.

[0011] Furthermore, the treated long fibers and the treated short fibers are both treated in the following manner: after removing impurities from the plant fibers, the plant fibers are crushed to a certain mesh size to obtain crude fibers, the crude fibers are put into a kneader, water is added to prepare a uniform slurry with a mass fraction of 30-50%, a small amount of cellulase is added, the kneader is closed, and the mixture is slowly stirred at 20-40°C for 4-8 hours, and then the material is directly taken out, the water is filtered out, and then immersed in a weak acid aqueous solution at 40-60°C and a pH value between 4-5, and allowed to stand for 2-4 hours, and then the fibers are filtered out and washed to remove the acid to obtain the treated plant fibers, wherein the volume of the weak acid aqueous solution is between 0.6-1.5 times that of the slurry.

[0012] Furthermore, the content of the cellulase is between 0.6% and 1.2% of the fiber, and the enzyme activity is 3000-6000 U / g.

[0013] Furthermore, after the treatment, impurities, pectin, hemicellulose and lignin on the fiber surface are substantially removed, the crystallinity is reduced to below 10%, and a large number of hydroxyl groups exist on the fiber surface.

[0014] Furthermore, if the acid solution is not removed by washing in the final step of treating the plant fibers, the process of adding a weak acid in step II of the processing may also be omitted.

[0015] Furthermore, the raw material of the plant fiber is any one or more of straw fiber, reed fiber, sugarcane fiber, wood fiber and bamboo fiber in any proportion.

[0016] Furthermore, the silicon skeleton is obtained by rapid hydrolysis of tetramethoxysilane in an acid environment, and its mass is calculated according to the chemical dosage formula of adding tetramethoxysilane for hydrolysis.

[0017] Furthermore, the molecular weight of the polyvinyl alcohol is between 20,000 and 50,000, and the alcoholysis degree is between 75% and 100%.

[0018] Furthermore, the molecular weight of the poly-ε-caprolactone is between 12000-30000, and the melting point is between 40-60°C.

[0019] Furthermore, the pectin may be one of apple pectin, orange pectin and guar gum.

[0020] Furthermore, the mildew preventer can be a quaternary ammonium salt or an inorganic nano mildew preventer, and both can be commercially available products.

[0021] Furthermore, the diameter of the pores of the foaming material is between 100-800 μm.

[0022] Furthermore, the foaming material has the following beneficial effects: (1) Plant fibers treated with biological enzymes and weak acids are purer and more uniform, with more hydroxyl groups exposed on the surface, which is beneficial to fluidity during processing and their combination with each other and other substances to increase the strength and toughness of the material; the combination of long fibers and short fibers combines fluidity, strength and connectivity, which is beneficial to the strength and toughness of the material.

[0023] (2) In-situ acid hydrolysis technology is used to form a uniformly distributed silicon skeleton in the foaming material, which increases the toughness and barrier properties. At the same time, it has hydroxyl groups and is easy to combine with plant fibers.

[0024] (3) Highly fluid poly-ε-caprolactone and polyvinyl alcohol are used to flow and evenly distribute in the material at a certain temperature. Polyvinyl alcohol has a large number of hydroxyl groups, which can have a good bond with plant fibers; poly-ε-caprolactone has good toughness, which can provide better elasticity and toughness for the material; (4) The present invention uses water vapor as a foaming agent and adopts a double-pressure release method to fully achieve foaming and ensure that the foaming is uniform and there are no excessively large bubbles.

[0025] (5) Due to the presence of silicon skeleton and evenly distributed polymers such as pectin and polyvinyl alcohol, a carbon layer can be formed during combustion to prevent further combustion.

[0026] Further, the performance of the foaming material is tested in the following manner: (1) The tensile properties of the foamed material, including tensile strength and elongation at break, are tested by cutting the sheet into standard dumbbell specimens; (2) The compression performance of the foam material is determined by cutting the sheet into 5 cm x 5 cm x 2 cm sheets and then performing a compression test in a mechanical testing machine to measure its strength when the compression deformation is 50%.

[0027] (3) The thermal conductivity of the foamed material is tested by a thermal conductivity tester.

[0028] (4) The flame retardancy of the foamed material is measured by an oxygen index meter and a horizontal flammability tester. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the SEM image of Example 1; Figure 2 This is the SEM image of Example 2. DETAILED DESCRIPTION

[0030] The exemplary implementation methods of the present invention will be described in detail below, but these implementation methods are for exemplary purposes only and the present invention is not limited thereto. Example 1

[0031] A biomass-based thermal insulation and flame-retardant foaming material, comprising treated plant fibers, a silicon skeleton, polyvinyl alcohol, poly-ε-caprolactone, and pectin, wherein the proportions of the components are as follows: Processed plant fibers: 100 Silicon skeleton: 20 Polyvinyl alcohol: 6 Poly-ε-caprolactone: 8 Pectin: 4 Antifungal agent: 1.2 The preparation process of the foaming material comprises: I: Tetramethoxysilane was dissolved in water to prepare an aqueous solution with a mass concentration of 6.5%, and polyvinyl alcohol was added. The solution temperature was raised to 75°C, and the mixture was stirred evenly to obtain premix A, and the temperature was maintained; II: Add poly-ε-caprolactone particles to the treated plant fiber slurry with a moisture content of 70%, add a small amount of hydrochloric acid aqueous solution, stir evenly to prepare composite slurry B, the moisture content of composite slurry B is 65%, and the pH value is adjusted to 4.5; III: Soak the pectin in excess water at 35°C for 15 minutes to allow the pectin to fully absorb water and swell, then filter to obtain pure pectin material C for later use; IV: Before molding and foaming, preheat the composite slurry B to 75°C, add 0.3 volume of premix A, add pectin C and moisture-proof agent, stir well to obtain molding blank D, keep the temperature stable at 75°C throughout the process, let it stand and evaporate water to keep the water content of molding blank D at 65%; V: The blank D is put into the mold of the molding machine, and the pressure is maintained at 115°C and 3.5MPa for 2.5 minutes, and the pressure is quickly released within 3 seconds. Then, the pressure is continued to be maintained at 135°C and 5.5MPa for 2.5 minutes, and the pressure is quickly released within 3.5 seconds to obtain the final product.

[0032] The processed plant fibers include processed long fibers and processed short fibers, wherein the mass proportion of the processed long fibers in the total fibers is 45%, and the mass proportion of the processed short fibers in the total fibers is 55%. The diameter of the processed long fibers is between 20-50 μm, and the length is between 1-5 mm. The diameter of the processed short fibers is between 2-8 μm, and the length is between 200 μm-1 mm.

[0033] The treated long fibers and the treated short fibers are both treated in the following manner: after removing impurities from the plant fibers, the plant fibers are crushed to a certain mesh size to obtain crude fibers, the crude fibers are put into a kneader, water is added to prepare a uniform slurry with a mass fraction of 40%, 0.9% of the fiber mass and 3000U / g of cellulase activity are added, the kneader is closed, the material is slowly stirred at 30°C for 6 hours, the material is directly taken out, the water is filtered out, and the material is immersed in a weak acid aqueous solution at 55°C, a pH value of 4.5, and a volume 1.2 times that of the material, and the fiber is filtered out and washed to remove the acid to obtain the treated plant fibers.

[0034] The raw material of the plant fiber is straw fiber, the processed long fiber is crushed to a mesh size between 400-500 meshes; the processed short fiber is crushed to a mesh size between 1200-2000 meshes; The molecular weight of the polyvinyl alcohol is between 20,000 and 40,000, and the alcoholysis degree is 89%.

[0035] The molecular weight of the poly-ε-caprolactone is 24,000 and the melting point is 52°C.

[0036] The pectin may be apple pectin.

[0037] like Figure 1 As shown, the cell diameter of the foaming material is between 100-500 μm.

[0038] The properties of the materials are shown in Table 1.

[0039] Example 2 A biomass-based thermal insulation and flame-retardant foaming material, comprising treated plant fibers, a silicon skeleton, polyvinyl alcohol, poly-ε-caprolactone, and pectin, wherein the proportions of the components are as follows: Processed plant fibers: 100 Silicon skeleton: 25 Polyvinyl alcohol: 7 Poly-ε-caprolactone: 6 Pectin: 5 Antifungal agent: 1.5 The preparation process of the foaming material comprises: I: Tetramethoxysilane was dissolved in water to prepare an aqueous solution with a mass concentration of 8.5%, and polyvinyl alcohol was added. The solution temperature was raised to 70°C, and the mixture was stirred evenly to obtain premix A, and the temperature was maintained; II: Add poly-ε-caprolactone particles to the treated plant fiber slurry with a moisture content of 75%, add a small amount of acetic acid aqueous solution, stir evenly to prepare composite slurry B, the moisture content of composite slurry B is 50%, and the pH value is adjusted to 4.5; III: Soak the pectin in excess water at 40°C for 12 minutes to allow the pectin to fully absorb water and swell, then filter to obtain pure pectin material C for later use; IV: Before molding and foaming, preheat the composite slurry B to 70°C, add 0.25 volume of premix A, add pectin C and moisture-proof agent, stir well to obtain molding blank D, keep the temperature stable at 75°C throughout the process, let it stand and evaporate water to keep the water content of molding blank D at 65%; V: The blank D is put into the mold of the molding machine, and the pressure is maintained at 110°C and 3MPa for 3 minutes, and the pressure is quickly released within 2.5s. Then, the pressure is continued to be maintained at 130°C and 6MPa for 2 minutes, and the pressure is quickly released within 3s to obtain the final product.

[0040] The processed plant fibers include processed long fibers and processed short fibers, wherein the mass proportion of the processed long fibers in the total fibers is 20%, and the mass proportion of the processed short fibers in the total fibers is 80%. The diameter of the processed long fibers is between 10-30 μm, and the length is between 1-8 mm; the diameter of the processed short fibers is between 1-5 μm, and the length is between 200 μm-800 μm.

[0041] The treated long fibers and the treated short fibers are both treated in the following manner: after removing impurities from the plant fibers, the plant fibers are crushed to a certain mesh size to obtain crude fibers, the crude fibers are put into a kneader, water is added to prepare a uniform slurry with a mass fraction of 45%, 0.7% of the fiber mass and 4000U / g of cellulase are added, the kneader is closed, the material is slowly stirred at 35°C for 5 hours, the material is directly taken out, the water is filtered out, and the material is immersed in a weak acid aqueous solution at 60°C, a pH value of 4.8, and a volume 0.8 times that of the material, and the fiber is allowed to stand for 3.5 hours, and then the fiber is filtered out and washed to remove the acid to obtain the treated plant fibers.

[0042] The raw material for preparing the long fiber in the plant fiber is reed fiber, and the raw material for preparing the short fiber is bamboo fiber. The processed long fiber has a mesh number between 300-400 mesh after being crushed; the processed short fiber has a mesh number between 1500-2000 mesh after being crushed; The molecular weight of the polyvinyl alcohol is between 30,000 and 50,000, and the alcoholysis degree is 92%.

[0043] The molecular weight of the poly-ε-caprolactone is 27,000 and the melting point is 55°C.

[0044] The pectin may be orange pectin.

[0045] like Figure 2 As shown, the cell diameter of the foaming material is between 100-700 μm.

[0046] The properties of the materials are shown in Table 1.

[0047] Example 3 A biomass-based thermal insulation and flame-retardant foaming material, comprising treated plant fibers, a silicon skeleton, polyvinyl alcohol, poly-ε-caprolactone, and pectin, wherein the proportions of the components are as follows: Processed plant fibers: 100 Silicon skeleton: 16 Polyvinyl alcohol: 5 Poly-ε-caprolactone: 10 Pectin: 4 Antifungal agent: 1.8 The preparation process of the foaming material comprises: I: Tetramethoxysilane was dissolved in water to prepare an aqueous solution with a mass concentration of 9%, and polyvinyl alcohol was added thereto. The solution temperature was raised to 72°C, and the mixture was stirred evenly to obtain premix A, and the temperature was maintained; II: Add poly-ε-caprolactone particles to the treated plant fiber slurry with a moisture content of 78%, add a small amount of acetic acid aqueous solution, stir evenly to prepare composite slurry B, the moisture content of composite slurry B is 60%, and the pH value is adjusted to 4.2; III: Soak the pectin in excess water at 35°C for 15 minutes to allow the pectin to fully absorb water and swell, then filter to obtain pure pectin material C for later use; IV: Before molding and foaming, preheat the composite slurry B to 75°C, add 0.35 volume of premix A, add pectin C and moisture-proof agent, stir well to obtain molding blank D, keep the temperature stable at 72°C throughout the process, let it stand and evaporate water to keep the water content of molding blank D at 60%; V: The blank D is put into the mold of the molding machine, and the pressure is maintained at 115°C and 3.2MPa for 2.5 minutes, and the pressure is quickly released within 3 seconds. Then, the pressure is continued to be maintained at 135°C and 5.5MPa for 3 minutes, and the pressure is quickly released within 3 seconds to obtain the final product.

[0048] The processed plant fibers include processed long fibers and processed short fibers, wherein the mass proportion of the processed long fibers in the total fibers is 30%, and the mass proportion of the processed short fibers in the total fibers is 70%. The diameter of the processed long fibers is between 20-40 μm, and the length is between 3-10 mm. The diameter of the processed short fibers is between 1-8 μm, and the length is between 400 μm-900 μm.

[0049] The treated long fibers and the treated short fibers are both treated in the following manner: after removing impurities from the plant fibers, the plant fibers are crushed to a certain mesh size to obtain crude fibers, the crude fibers are put into a kneader, water is added to prepare a uniform slurry with a mass fraction of 48%, 1.0% of the fiber mass and an enzyme activity of 5000U / g of cellulase are added, the kneader is closed, the material is slowly stirred at 40°C for 6 hours, the material is directly taken out, the water is filtered out, and the material is immersed in a weak acid aqueous solution at 60°C, a pH value of 4.8, and a volume 0.8 times that of the material, and the fiber is allowed to stand for 3.5 hours, and the fiber is filtered out and washed to remove the acid to obtain the treated plant fibers.

[0050] The raw material for preparing the long fiber in the plant fiber is straw fiber, and the raw material for preparing the short fiber is wood fiber. The processed long fiber has a mesh number between 400-500 mesh after crushing; the processed short fiber has a mesh number between 1200-1800 mesh after crushing; The molecular weight of the polyvinyl alcohol is between 20,000 and 30,000, and the alcoholysis degree is 79%.

[0051] The molecular weight of the poly-ε-caprolactone is 24,000 and the melting point is 51°C.

[0052] The pectin may be orange pectin.

[0053] The diameter of the pores of the foaming material is between 200-800 μm.

[0054] The properties of the materials are shown in Table 1.

[0055] Example 4 A biomass-based thermal insulation and flame-retardant foaming material, comprising treated plant fibers, a silicon skeleton, polyvinyl alcohol, poly-ε-caprolactone, and pectin, wherein the proportions of the components are as follows: Processed plant fibers: 100 Silicon skeleton: 18 Polyvinyl alcohol: 9 Poly-ε-caprolactone: 9 Pectin: 5 Antifungal agent: 1.4 The preparation process of the foaming material comprises: I: Tetramethoxysilane was dissolved in water to prepare an aqueous solution with a mass concentration of 6%, and polyvinyl alcohol was added. The solution temperature was raised to 76°C, and the premix A was obtained after stirring evenly, and the temperature was maintained; II: Add poly-ε-caprolactone particles to the treated plant fiber slurry with a moisture content of 62%, add a small amount of acetic acid aqueous solution, stir evenly to prepare composite slurry B, the moisture content of composite slurry B is 45%, and the pH value is adjusted to 4.0; III: Soak the pectin in excess water at 40°C for 12 minutes to allow the pectin to fully absorb water and swell, then filter to obtain pure pectin material C for later use; IV: Before molding and foaming, preheat the composite slurry B to 78°C, add 0.45 volume of premix A, add pectin C and moisture-proof agent, stir well to obtain molding blank D, keep the temperature stable at 78°C throughout the process, let it stand and evaporate water to keep the water content of molding blank D at 70%; V: The blank D is put into the mold of the molding machine, and the pressure is maintained at 120°C and 3.8MPa for 2 minutes, and the pressure is quickly released within 3s. Then, the pressure is continued to be maintained at 130°C and 6MPa for 3 minutes, and the pressure is quickly released within 2.5s to obtain the final product.

[0056] The processed plant fibers include processed long fibers and processed short fibers, wherein the mass proportion of the processed long fibers in the total fibers is 50%, and the mass proportion of the processed short fibers in the total fibers is 50%; the diameter of the processed long fibers is between 10-30 μm, and the length is between 4-8 mm; the diameter of the processed short fibers is between 2-6 μm, and the length is between 500 μm-1 mm.

[0057] The treated long fibers and the treated short fibers are both treated in the following manner: after removing impurities from the plant fibers, the plant fibers are crushed to a certain mesh size to obtain crude fibers, the crude fibers are put into a kneader, water is added to prepare a uniform slurry with a mass fraction of 42%, 1.2% of the fiber mass and an enzyme activity of 5500U / g of cellulase are added, the kneader is closed, and the material is directly taken out after slowly stirring at 32°C for 7 hours, the water is filtered out, and then immersed in a weak acid aqueous solution at 55°C, a pH value of 4.2, and a volume 1.4 times that of the material, and the fiber is allowed to stand for 3.8 hours, and then the fiber is filtered out and washed to remove the acid to obtain the treated plant fibers.

[0058] The raw material for preparing the long fiber in the plant fiber is reed fiber, and the raw material for preparing the short fiber is sugarcane fiber. The processed long fiber has a mesh number between 300-400 mesh after crushing; the processed short fiber has a mesh number between 1000-1500 mesh after crushing; The molecular weight of the polyvinyl alcohol is between 25000 and 40000, and the alcoholysis degree is 89%.

[0059] The molecular weight of the poly-ε-caprolactone is 28,000 and the melting point is 56°C.

[0060] The pectin may be guar gum.

[0061] The diameter of the pores of the foaming material is between 100-600 μm.

[0062] The properties of the materials are shown in Table 1.

[0063] Table 1. Properties of materials prepared in Examples.

Claims

1. A biomass-based thermal insulation flame retardant foam material, comprising treated plant fiber, a silicon skeleton, polyvinyl alcohol, poly-ε-caprolactone, pectin and a mildew inhibitor, wherein the proportions of the components are as follows: Processed plant fibers: 100 Silicon skeleton: 15-25 Polyvinyl alcohol: 5-10 Poly-ε-caprolactone: 5-10 Pectin: 3-6 Antifungal agent: 1-2 The preparation process includes: I: dissolving tetramethoxysilane in water to prepare an aqueous solution with a mass concentration of 5-10%, then adding polyvinyl alcohol, raising the solution temperature to 60-80°C, stirring evenly to obtain premix A, and keeping the temperature for standby use; II: Mix the treated plant fiber and water to prepare a slurry with a moisture content of 60-80%, add poly-ε-caprolactone particles to the slurry, then add weak acid, stir evenly to prepare a composite slurry B, and control the moisture content of the composite slurry B to be between 40-80%, and the pH value to be between 4-5; III: soak the pectin in excess water at 20-40°C for 10-20 minutes to allow the pectin to fully absorb water and swell, then filter out the free water to obtain pectin material C for later use; IV: Before molding and foaming, preheat the composite slurry B to 60-80°C, add 0.2-0.4 volume of premix A, add pectin C and moisture-proof agent, stir well to obtain molding blank D, keep the temperature stable between 60-80°C, and stand to evaporate water to keep the mass fraction of water in the molding blank D between 50-80%; V: Put the molded blank D into the mold of the molding machine, maintain the pressure at 100-120℃ and 2-4MPa for 2-3 minutes, quickly release the pressure within 2-4s, and then continue to pressurize for the second time at 120-140℃ and 4-6MPa, maintain the pressure for 2-3 minutes, and quickly release the pressure within 2-4s to obtain the final product.

2. The biomass-based thermal insulation and flame-retardant foam material according to claim 1, wherein the processed plant fibers are a combination of processed long fibers and processed short fibers; wherein: The mass proportion of the treated long fibers in all plant fibers is between 0-60%, and the mass proportion of the treated short fibers in all plant fibers is between 40-100%; the diameter of the treated long fibers is between 10-50 μm, and the length is between 1-10 mm; the diameter of the treated short fibers is between 1-10 μm, and the length is between 100 μm-1 mm.

3. The biomass-based thermal insulation and flame-retardant foam material as described in claim 2, wherein the processed long fibers and processed short fibers are obtained by removing impurities and crushing the plant fibers, sieving them to obtain coarse fibers of corresponding mesh size, and then treating them with biological enzymes and acids.

4. The biomass-based thermal insulation and flame-retardant foam material as described in claim 3, wherein the treated long fibers and the treated short fibers are both treated by the following process: after removing impurities from the plant fibers, the plant fibers are crushed to a certain mesh size to obtain crude fibers, the crude fibers are put into a kneader, water is added to prepare a uniform slurry with a mass fraction of 30-50%, a small amount of cellulase is added, the kneader is closed, and the mixture is slowly stirred at 20-40°C for 4-8 hours, and then the material is directly taken out, the water is filtered out, and then immersed in a weak acid aqueous solution at 40-60°C and a pH value between 4-5, and allowed to stand for 2-4 hours, and then the fibers are filtered out and washed to remove the acid to obtain treated plant fibers; the content of the cellulase is between 0.6-1.2% of the plant fibers, the enzyme activity is between 3000-6000U / g, and the volume of the weak acid aqueous solution is between 0.6-1.5 times that of the slurry.

5. The biomass-based thermal insulation and flame-retardant foam material according to claim 1, wherein the raw material of the plant fiber is a combination of any one or more of straw fiber, reed fiber, sugarcane fiber, wood fiber and bamboo fiber in any proportion.

6. The biomass-based thermal insulation and flame-retardant foam material according to claim 1, wherein the molecular weight of the polyvinyl alcohol is between 20,000 and 50,000, and the alcoholysis degree is between 75 and 100%.

7. The biomass-based thermal insulation and flame-retardant foam material according to claim 1, wherein the molecular weight of the poly-ε-caprolactone is between 12000-30000 and the melting point is between 40-60°C.

8. The biomass-based thermal insulation and flame-retardant foaming material according to claim 1, wherein the pectin can be one of apple pectin, orange pectin and guar gum.

9. The biomass-based thermal insulation and flame-retardant foam material as claimed in claim 1, wherein the premix A is added in step IV of the preparation process, and the molding blank D is put into the molding machine mold and pressurized in step V, and the interval time between the two steps does not exceed 15 minutes.

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