Ultrathin thermal insulation material and preparation method thereof

Abstract

The invention belongs to the field of new materials, and relates to an ultrathin thermal insulation material and a preparation method thereof. Aiming at main problems of existing aerogel heat insulation products and actual requirements of related fields on efficient heat insulation products, in combination with functional characteristics of nano-porous silicon, natural plant fibers are taken as carriers, SiO2 aerogel, nano-porous silicon and other functional materials are uniformly mixed with the plant fibers, and the composite material is prepared. And an environment-friendly and degradable new product with heat preservation and heat insulation functions is obtained through a papermaking process. The heat conductivity coefficient of the obtained ultrathin heat preservation and insulation material is smaller than or equal to 0.025 W / (m.K), and a convenient method is provided for large-scale and continuous production of the low-cost ultrathin heat preservation and insulation material. The method is easy and flexible to operate, high in operability and easy to industrially popularize and apply.

Description

Technical Field

[0001] The present invention belongs to the field of new materials and relates to an ultra-thin thermal insulation material and a preparation method thereof. Background Art

[0002] The new composite thermal insulation materials mainly refer to the composite materials containing nano-porous materials, which can be widely used in the fields of electrical components, electronic products, food packaging, new energy batteries, etc. SiO2 aerogel has an extremely low thermal conductivity, so SiO2 aerogel is mostly used as the nano-porous material in the new thermal insulation materials. However, due to the high cost of SiO2 aerogel, its large-scale application in most fields is limited. Using it in combination with other low-cost nano-porous materials is a potential solution. In addition, due to the characteristics of light weight and low thermal conductivity of plant fiber materials, the products made thereof have been widely used in the thermal protection of various devices. Therefore, an insulation and heat preservation material prepared by combining SiO2 aerogel and nano-porous silicon with low thermal conductivity and then compounding with plant fibers has the advantages of low cost and high efficiency, can solve the bottleneck problems of existing aerogel products, and greatly expand the market application range.

[0003] The traditional process for preparing SiO2 aerogel / fiber composites all adopts steps such as fiber impregnation, modification, and supercritical drying. The process is relatively complex, the production cycle is long, and in the sol-gel process, parameters such as pH value, temperature, and modifier have large variability, resulting in differences in the structure and performance of the composite materials and poor repeatability. While directly using SiO2 aerogel powder and nano-porous silicon powder as thermal insulation materials and using the wet papermaking process to form composites with fibers greatly shortens the preparation cycle of the thermal insulation material, is more suitable for batch production, and can significantly reduce the production cost. The ultra-thin thermal insulation materials mainly filled with nano-porous silicon and aerogel all have the remarkable advantages of low thermal conductivity and high cost performance, solve the bottleneck problems of high cost and low processing efficiency of existing aerogel ultra-thin thermal insulation materials, and are a new type of thermal insulation product with great development prospects, which can be widely used in the fields of food and industrial thermal insulation. Summary of the Invention

[0004] The purpose of the present invention is to provide an ultra-thin thermal insulation material and a preparation method thereof. Under certain process conditions, the present invention uses natural plant fibers as a carrier, uniformly mixes SiO2 aerogel, nano-porous silicon and other functional materials with plant fibers, and obtains an environmentally friendly and degradable new product with thermal insulation function through the papermaking process.

[0005] The technical solution of the present invention is as follows: A preparation method of an ultra-thin thermal insulation material, comprising the following steps: (1) Adding a modifier, SiO2 aerogel powder, and nanoporous silicon powder to water in sequence and dispersing them at high speed to obtain a uniform powder slurry; by using the modifier, the superhydrophobic aerogel powder can be modified to a hydrophilic type without affecting the structure and performance, thereby ensuring its uniform distribution in the aqueous system; (2) adding the powder slurry obtained in step (1) to the pre-modulated plant fiber slurry, and mixing and beating the two in a beating machine, so that the powder material and the plant fiber are fully contacted and combined, and a fiber composite slurry is obtained; the mass percentage of SiO2 aerogel to plant fiber in the powder slurry is 3-5%, and the mass percentage of nanoporous silicon to plant fiber is 30-36%; the mixed beating process can ensure a high retention rate of nanoporous silicon and SiO2 aerogel powder in the subsequent papermaking process, and can improve the strength of the paper-based ultra-thin thermal insulation material, while making the plant fiber filaments broom, the functional powder material is combined with the fiber through hydrogen bonding, embedding, etc., to ensure the strength after molding and avoid the problem of powder loss during the use of paper; (3) diluting the fiber composite slurry obtained in step (2) and making paper to obtain an ultra-thin thermal insulation material.

[0006] Preferably, the nanoporous silicon in step (1) has the following properties: specific surface area ≥ 200m 2 / g, pore volume ≥ 0.6cm 3 / g, average pore size 20-30nm, average particle size 15-25μm; SiO2 aerogel performance meets: specific surface area ≥600m 2 / g, pore volume ≥ 0.9cm 3 / g, average pore size 5-30nm, average particle size 10-15μm; high specific surface area powder materials have a more developed pore structure, the heat transfer path is more tortuous, which greatly increases the thermal barrier capacity. Therefore, in order to obtain paper-based ultra-thin thermal insulation materials with low thermal conductivity, it is necessary to increase the specific surface area of nanoporous silicon and aerogel powder materials as much as possible.

[0007] Preferably, the modifier in step (1) is a surfactant or a wetting agent, such as sodium dodecylbenzenesulfonate or an organosilicon wetting agent; the amount of the modifier is 3-10% of the mass of the absolute dry SiO2 aerogel.

[0008] Preferably, during the high-speed dispersion in step (1), the linear speed of the stirring blade is greater than 12 m / s, the dispersed solid content is 10-40%, and the dispersion time is 20-30 min.

[0009] Preferably, the plant fiber in step (2) is coniferous pulp fiber.

[0010] Preferably, the mixing beating treatment time in step (2) is 20-30 min.

[0011] Preferably, sizing agents, retention aids, strengthening agents and other functional aids such as AKD sizing agent, polyacrylamide retention aid and starch strengthening agent can be added before dilution in step (3).

[0012] Preferably, the dilution concentration in step (3) is 0.8-1.2%.

[0013] Preferably, the basis weight of the paper-based material formed by papermaking in step (3) is 100-200 g / m 2 Preferably, the heat conduction coefficient of the ultra-thin thermal insulation material obtained in step (3) ≤0.025 W / (m·K) can meet the use requirements.

[0014] In view of the main problems existing in current aerogel thermal insulation products and the actual needs of the related fields for high-efficiency thermal insulation products, and combining with the functional characteristics of nano-porous silicon, the present invention adopts the wet papermaking process technology to add SiO2 aerogel, nano-porous silicon and other functional materials into the paper to obtain a paper-based ultra-thin thermal insulation material with high-efficiency thermal insulation function.

[0015] Compared with the prior art, the present invention has the following technical effects: The present invention prepares a new type of ultra-thin thermal insulation material through the wet papermaking process of paper. The heat conduction coefficient of the product ≤0.025 W / (m·K), which provides a convenient method for the large-scale and continuous production of low-cost ultra-thin thermal insulation materials, fills the industry gap and has a broad market prospect. The operation of the present invention is simple, flexible, highly operable and easy to be industrialized and popularized. Description of the Drawings

[0016] Figure 1 SEM electron microscope photograph of the combination of powder slurry and plant fiber after the mixing beating treatment in Example 4; Figure 2 SEM electron microscope photograph of the formed ultra-thin thermal insulation material in Example 4, where Figure 2 a is the surface of the material, Figure 2 b is the cross-section of the material. Detailed Embodiments

[0017] The present invention will be further described below in conjunction with specific implementation schemes. The advantages and features of the present invention will become clearer with the description. However, these embodiments are only exemplary and do not constitute any limitation to the scope of the present invention. Those skilled in the art should understand that the details and forms of the technical solutions of the present invention can be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements all fall within the protection scope of the present invention.

[0018] Example 1 Preparation method of an ultra-thin thermal insulation material The properties of the nano-porous silicon used are as follows: specific surface area 220 m 2 / g, pore volume 0.7 cm 3 / g, average pore diameter 25 nm, average particle size 16 μm; the main properties of the SiO2 aerogel are as follows: specific surface area 610 m 2 / g, pore volume 0.95 cm 3 / g, average pore diameter 12 nm, average particle size 14 μm. The preparation process of the ultra-thin thermal insulation material is as follows: (1) Weigh 150 kg of tap water and add it to the hopper of a high-speed mixer. Start stirring, add 500 g of sodium hexametaphosphate and 900 g of wetting agent, then add 10 kg of aerogel powder and 90 kg of nano-porous silicon powder, and disperse the materials at high speed. After uniform dispersion, a powder slurry for papermaking filler is obtained. When dispersing at high speed, the linear velocity of the stirring blade is 15 m / s, the dispersion solid content is 20%, and the dispersion time is 30 min; (2) Add the powder slurry obtained in step (1) to a batching tank and mix it evenly with softwood pulp fibers. The addition amount of the powder slurry (in terms of absolute dry powder) to the fibers is 34%, and use a Valley beater to mix and beat for 30 min; (3) After diluting the pulp slurry to a concentration of 1.0%, carry out paper making on a small-scale test paper machine with a width of 400 mm to obtain the ultra-thin thermal insulation material.

[0019] The ultra-thin thermal insulation material prepared by this method has a smooth and delicate surface, no powder dropping phenomenon, and a thermal conductivity of 0.025 W / (m·K).

[0020] Example 2 Preparation method of an ultra-thin thermal insulation material The properties of the nano-porous silicon used are as follows: specific surface area 220 m 2 / g, pore volume 0.7 cm 3 / g, average pore diameter 25 nm, average particle size 16 μm; the main properties of the SiO2 aerogel are as follows: specific surface area 610 m 2 / g, pore volume 0.95 cm 3 / g, average pore diameter 12 nm, average particle size 14 μm. The preparation process of the ultra-thin thermal insulation material is as follows: (1) Weigh 150 kg of tap water and add it to the hopper of a high-speed mixer. Start stirring, add 500 g of sodium hexametaphosphate and 900 g of wetting agent, then add 10 kg of aerogel powder and 90 kg of nano-porous silicon powder. Disperse the materials at high speed. After uniform dispersion, a powder slurry for papermaking filling is obtained. When dispersing at high speed, the linear velocity of the stirring blade is 15 m / s, the solid content of dispersion is 20%, and the dispersion time is 30 min; (2) Add the powder slurry obtained in step (1) to the batching tank and mix it evenly with softwood pulp fibers. The filling amount of the powder slurry (in terms of absolute dry powder) to the fibers is 36%. Use a Valley beater to mix and beat for 30 min; (3) After diluting the pulp slurry to a concentration of 1.0%, conduct paper making on a small-scale test paper machine with a width of 400 mm to obtain an ultra-thin thermal insulation material.

[0021] The ultra-thin thermal insulation material prepared by this method has a smooth and delicate surface, no powder dropping phenomenon, and a thermal conductivity of 0.022 W / (m·K).

[0022] Example 3 A preparation method of an ultra-thin thermal insulation material The properties of the nano-porous silicon used are as follows: specific surface area 220 m 2 / g, pore volume 0.7 cm 3 / g, average pore diameter 25 nm, average particle size 16 μm; The main properties of SiO2 aerogel are as follows: specific surface area 610 m 2 / g, pore volume 0.95 cm 3 / g, average pore diameter 12 nm, average particle size 14 μm. The preparation process of the ultra-thin thermal insulation material is as follows: (1) Weigh 150 kg of tap water and add it to the hopper of a high-speed mixer. Start stirring, add 500 g of sodium hexametaphosphate and 900 g of wetting agent, then add 10 kg of aerogel powder and 90 kg of nano-porous silicon powder. Disperse the materials at high speed. After uniform dispersion, a powder slurry for papermaking filling is obtained. When dispersing at high speed, the linear velocity of the stirring blade is 15 m / s, the solid content of dispersion is 20%, and the dispersion time is 30 min; (2) Add the slurry obtained in step (1) to the batching tank and mix it evenly with softwood pulp fibers. The filling amount of the powder slurry (in terms of absolute dry powder) to the fibers is 38%. Use a Valley beater to mix and beat for 30 min; (3) After diluting the pulp slurry to a concentration of 1.0%, then conduct paper making on a small-scale test paper machine with a width of 400 mm to obtain an ultra-thin thermal insulation material.

[0023] The ultra-thin thermal insulation material prepared by this method has a smooth and delicate surface, no powder dropping phenomenon, and a thermal conductivity of 0.021 W / (m·K).

[0024] Example 4 Preparation Method of an Ultra-thin Thermal Insulation Material The properties of the nano-porous silicon used are as follows: specific surface area 350 m 2 / g, pore volume 0.8 cm 3 / g, average pore diameter 22 nm, average particle size 15 μm; the main properties of the SiO2 aerogel are as follows: specific surface area 610 m 2 / g, pore volume 0.95 cm 3 / g, average pore diameter 12 nm, average particle size 14 μm. The preparation process of the ultra-thin thermal insulation material is as follows: (1) Weigh 150 kg of tap water and add it to the hopper of a high-speed mixer. Start stirring, add 500 g of sodium hexametaphosphate and 900 g of wetting agent, then add 10 kg of aerogel powder and 90 kg of nano-porous silicon powder, and disperse the materials at high speed. After uniform dispersion, a powder slurry for papermaking filling is obtained. The linear velocity of the stirring blade during high-speed dispersion is 15 m / s, the solid content of dispersion is 20%, and the dispersion time is 30 min; (2) Add the powder slurry obtained in step (1) to a batching tank and mix it evenly with softwood pulp fibers. The filling amount of the powder slurry (in terms of absolute dry powder) for the fibers is 40%. Use a Valley beater to mix and beat for 30 min. The SEM electron micrograph of the combination of the powder slurry and plant fibers is as Figure 1 shown; (3) After diluting the pulp to a concentration of 1.0%, paper is made on a small-scale test paper machine with a width of 400 mm to obtain an ultra-thin thermal insulation material. The SEM electron micrograph is as Figure 2 shown, where Figure 2 a is the surface of the material, Figure 2 b is the cross-section of the material.

[0025] The ultra-thin thermal insulation material prepared by this method has a smooth and delicate surface, no powder dropping phenomenon, and a thermal conductivity of 0.020 W / (m·K).

Claims

1. A preparation method of an ultra-thin thermal insulation material, characterized in that, The preparation method comprises the following steps: (1) Add a modifier, SiO2 aerogel powder, and nano-porous silicon powder into water in sequence, and perform high-speed dispersion to obtain a uniform powder slurry; (2) Add the powder slurry obtained in step (1) into a pre-prepared plant fiber slurry, and the two are subjected to mixed beating treatment by a beater to obtain a fiber composite slurry; the mass percentage content of SiO2 aerogel in the powder slurry with respect to the plant fiber is 3-5%, and the mass percentage content of nano-porous silicon with respect to the plant fiber is 30-36%; (3) Dilute the fiber composite slurry obtained in step (2), and perform paper making to obtain an ultra-thin thermal insulation material.

2. The preparation method according to claim 1, characterized in that, The properties of the nanoporous silicon in step (1) are as follows: specific surface area ≥ 200 m 2 / g, pore volume ≥ 0.6 cm 3 / g, average pore diameter 20 - 30 nm, average particle size 15 - 25 μm; The properties of the SiO2 aerogel are as follows: specific surface area ≥ 600 m 2 / g, pore volume ≥ 0.9 cm 3 / g, average pore diameter 5 - 30 nm, average particle size 10 - 15 μm.

3. The preparation method according to claim 1, characterized in that, In step (1), the modifier is a surfactant or a wetting agent, such as sodium dodecyl benzene sulfonate or silicone wetting agent; the dosage of the modifier is 3-10% of the mass of absolutely dry SiO2 aerogel.

4. The preparation method according to claim 1, wherein In step (1), during high-speed dispersion, the linear velocity of the stirring blade > 12 m / s, the dispersion solid content is 10-40%, and the dispersion time is 20-30 min.

5. The preparation method according to claim 1, characterized in that, In step (2), the plant fiber is softwood pulp fiber.

6. The preparation method according to claim 1, wherein, In step (2), the time for mixed beating treatment is 20-30 min.

7. The preparation method according to claim 1, wherein In step (3), the dilution concentration is 0.8-1.2%; functional aids such as a sizing agent, a retention aid, and a strengthening agent can be added before dilution. The sizing agent is AKD, the retention aid is polyacrylamide, and the strengthening agent is starch.

8. The preparation method according to claim 1, characterized in that, The basis weight of the paper-based material made in the step (3) is 100-200 g / m 2 .

9. The preparation method according to claim 1, wherein The ultra-thin thermal insulation material obtained in step (3) can meet the use requirements as long as its thermal conductivity ≤ 0.025 W / (m·K).

10. An ultra-thin thermal insulation material obtained by the preparation method according to any one of claims 1-9.

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