A method for preparing hydrophobic zinc oxide aerogel

Abstract

This invention discloses a method for preparing hydrophobic zinc oxide aerogel, belonging to the technical field of zinc oxide aerogel materials. The disclosed method utilizes polyethylene glycol (PEG) to aid in the dispersion of zinc salts. Simultaneously, the polymer network structure formed by PEG molecules in aqueous solution binds particles in the solution, restricting ion movement and promoting more uniform dispersion within the network structure. Furthermore, PEG attracts solid substances to its surface, and its hydrophilic groups establish a steric shielding effect, resulting in more stable dispersion and distribution of particles dissolved and dispersed in the polymer solution. Combined with freeze-drying technology, the zinc oxide aerogel is obtained through calcination and then subjected to monomer-initiated polymerization for hydrophobic treatment to obtain the hydrophobic zinc oxide aerogel. The combination of PEG during freeze-drying allows for controllable strength and shape of the aerogel precursor, enabling the preparation of hydrophobic zinc oxide aerogel materials with various geometric shapes.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of zinc oxide aerogel and specifically relates to a preparation method of hydrophobic zinc oxide aerogel. BACKGROUND

[0002] Aerogel has the characteristics of low density and high porosity and is widely used as thermal insulation materials, matt agents, catalysts and the like. Oxide aerogel includes non-metallic and metallic oxide aerogel materials such as aluminum oxide, titanium dioxide and zinc oxide. However, the preparation method thereof is complex and the source is not extensive. Pajonk et al. converted isobutylene into methacrylonitrile by reacting with NO on zinc oxide aerogel. UV irradiation can strengthen the antibacterial ability of the nanometer zinc oxide aerogel. Lu et al. prepared a unidirectional chitosan / zinc oxide aerogel as a water transport support, which can prevent bio-deposition in the early stage of bacterial adhesion and biofilm growth. Mir et al. synthesized vanadium-doped zinc oxide aerogel by sol-gel method, and Chen et al. prepared zinc oxide aerogel with high porosity and large specific surface area by using polyacrylic acid and zinc oxide. Pan Jingjing et al. disclosed the preparation and antibacterial capacity analysis of gelatin / ethyl cellulose aerogel loaded with nanometer zinc oxide. Yang Rongsheng et al. disclosed the preparation and antibacterial performance research of cellulose / ultrafine zinc oxide composite aerogel. CN201710366441.7 discloses a zinc oxide aerogel and a preparation method thereof, and the skeleton constituting the aerogel is natural cellulose. The natural cellulose is nanocellulose prepared by oxidizing paper pulp. In fact, it contains natural cellulose and is not pure zinc oxide aerogel, but fiber composite aerogel or fiber reinforced aerogel. The harsh preparation process, low efficiency and high cost of zinc oxide limit its industrial production and large-scale use. As a person skilled in the art, it is urgent to develop a new preparation method of hydrophobic zinc oxide aerogel. SUMMARY

[0003] The purpose of the application is to provide a preparation method of hydrophobic zinc oxide aerogel in view of the existing problems.

[0004] The application is implemented by the following technical scheme:

[0005] A preparation method of hydrophobic zinc oxide aerogel, comprising the following steps: first step, stirring at 70-80 DEG C in a heating kettle until complete dissolution, preparing a polyethylene glycol aqueous solution with a mass fraction of 12-15%, and cooling for standby; second step, weighing zinc nitrate solid, dissolving in the polyethylene glycol aqueous solution obtained in the previous step, so that the mass ratio of polyethylene glycol to zinc nitrate is 1:3-4, and uniformly mixing and stirring; third step, rapidly freezing the mixed solution by using dry ice, then placing into a refrigerator at-20 DEG C and freezing until complete freezing, then transferring into a vacuum freeze dryer, vacuumizing to less than or equal to 10 Pa, and then freeze-drying at-50 DEG C to remove water, so as to obtain an aerogel precursor; fourth step, placing the aerogel precursor into a crucible, placing into a muffle furnace, setting the heating rate to 4-5 DEG C / min from room temperature to 500-550 DEG C, keeping constant temperature for 3-4 h, and then naturally cooling to obtain the zinc oxide aerogel; fifth step, placing the obtained zinc oxide aerogel into 50-60 parts of water according to a bath ratio of 1:3-4, adjusting the pH to 6-6.5, then adding 0.5-0.7 parts of vinyl tri(2-methoxyethoxy) silane into the water, keeping constant temperature at 80-85 DEG C for 1-2 h, then adding monomer hexadecyl methacrylate or octadecyl methacrylate with a mass concentration of 10%-15%, and aqueous solution of potassium persulfate and aqueous solution of sodium bisulfite, and reacting for 3-3.5 h, then cooling to room temperature, centrifugally washing with distilled water for 3 times, and then air-drying to obtain the hydrophilic zinc oxide aerogel.

[0006] Further, the polyethylene glycol in the first step is polyethylene glycol with a molecular weight of 4000-6000.

[0007] Further, the mass ratio of potassium persulfate to sodium bisulfite in the fifth step is 3-4:1.

[0008] Further, the potassium persulfate accounts for 0.15%-0.2% of the mass of the monomer hexadecyl methacrylate or octadecyl methacrylate in the fifth step.

[0009] Further, the aqueous solution of sodium bisulfite in the fifth step has a mass concentration of 4-6 g / L.

[0010] The present application has the following advantages:

[0011] The application discloses a preparation method of hydrophobic zinc oxide aerogel, which uses polyethylene glycol, and helps to obtain zinc salt with good dispersibility and uniform particle size distribution. The polyethylene glycol molecule has good surface activity, which is very beneficial to the dispersion of zinc oxide in the aqueous solution of water-soluble polymer. Meanwhile, the high-molecular network structure formed by the polyethylene glycol high-molecular molecule in the aqueous solution can limit the movement of particles in the solution, so that the ions tend to be uniformly distributed in the network structure. In addition, the polymer molecule group can attract solid substances to be adsorbed to the surface thereof, and establish the stereoscopic shielding effect of hydrophilic groups, so that the dispersed particles in the polymer solution are more stable in dispersion and distribution. By combining the freeze drying technology and calcination, the zinc oxide aerogel is obtained, and then the initiation polymerization and hydrophobic treatment of monomer hexadecyl methacrylate or octadecyl methacrylate are carried out, so that the hydrophobic zinc oxide aerogel can be obtained. In the freeze drying process, the polyethylene glycol is combined, so that the aerogel precursor has controllable strength and shape, and various geometric shapes of the hydrophobic zinc oxide aerogel material can be prepared. DETAILED DESCRIPTION

[0012] The application is described below with specific examples, but is not limited to the application. Example 1

[0013] Raw materials: Bolyike BLK-FD-1 vacuum freeze dryer, Lekai polyethylene glycol HMPEG4000, Wunai potassium persulfate, Xinyaling Chemical Sodium Bisulfite, Muffle furnace PR-MP1200, GR-SI172 vinyl tri (2-methoxyethoxy) silane, and Jinfeng Chemical octadecyl methacrylate.

[0014] The preparation method of the hydrophobic zinc oxide aerogel comprises the following steps: first, stirring at 70 DEG C in a heating kettle until complete dissolution to prepare a 12% mass fraction polyethylene glycol aqueous solution, and cooling for standby; second, weighing zinc nitrate solid, dissolving in the polyethylene glycol aqueous solution obtained in the first step, so that the mass ratio of polyethylene glycol to zinc nitrate is 1:3, and uniformly mixing and stirring; third, rapidly freezing the mixed solution by using dry ice, and then placing in a refrigerator at minus 20 DEG C to freeze completely, and then transferring to a vacuum freeze dryer to remove water at minus 50 DEG C after vacuumizing to 10 Pa, so as to obtain an aerogel precursor; fourth, placing the aerogel precursor into a crucible, and placing in a muffle furnace to calcine, setting the heating rate to 4 DEG C / min from room temperature to 500 DEG C, keeping constant temperature for 3 h, and obtaining the zinc oxide aerogel after natural cooling; and fifth, placing the obtained zinc oxide aerogel in 50 parts of water according to a bath ratio of 1:3, adjusting the pH to 6, adding 0.5 parts of vinyl tri(2-methoxyethoxy) silane into the water, reacting at 80 DEG C for 1 h, and then adding monomer hexadecyl methacrylate or octadecyl methacrylate with a mass concentration of 10%, the mass ratio of potassium persulfate to sodium bisulfite being 3:1, the mass fraction of potassium persulfate in the monomer hexadecyl methacrylate or octadecyl methacrylate being 0.15%, the mass concentration of the sodium bisulfite aqueous solution being 4 g / L, and the potassium persulfate aqueous solution and the sodium bisulfite aqueous solution reacting for 3 h, and then cooling to room temperature, washing three times by centrifugation with distilled water, and air-drying to obtain the hydrophilic zinc oxide aerogel.

[0015] Product performance: density 35.4 Kg / m³; thermal conductivity 0.012 W / m.K; hydrophobicity 99%; specific surface area 578 m 2 / g; combustion performance level A or above; smoke toxicity ZA1. Example 2

[0016] Raw materials: Boleike BLK-FD-1 vacuum freeze dryer; potassium persulfate from Cologne Chemicals; PEG6000 from Nanhua Reagent, sodium bisulfite from Kaiyang Chemical Industry; muffle furnace PR-MP1200; vinyl tri(2-methoxyethoxy) silane from Chengguang New Materials; hexadecyl methacrylate.

[0017] The preparation method of the hydrophobic zinc oxide aerogel comprises the following steps: first, preparing a 15% polyethylene glycol aqueous solution by stirring at 80 DEG C in a heating kettle until completely dissolved, and cooling for standby; second, dissolving zinc nitrate solid in the polyethylene glycol aqueous solution obtained in the first step, so that the mass ratio of polyethylene glycol to zinc nitrate is 1:4, and uniformly mixing and stirring; third, rapidly freezing the mixed solution with dry ice, and then freezing in a refrigerator at minus 20 DEG C until completely frozen, and then transferring to a vacuum freeze dryer to remove water by vacuum freezing drying at minus 50 DEG C, so as to obtain an aerogel precursor; fourth, transferring the aerogel precursor into a crucible, and calcining in a muffle furnace, setting the heating rate to 5 DEG C / min from room temperature to 550 DEG C, keeping constant temperature for 4 h, and then naturally cooling to obtain a zinc oxide aerogel; and fifth, placing the obtained zinc oxide aerogel in 60 parts of water according to a bath ratio of 1:4, adjusting the pH to 6.5, adding 0.7 parts of vinyl tri(2-methoxyethoxy) silane into the water, reacting at 85 DEG C for 2 h, and then adding monomer hexadecyl methacrylate or octadecyl methacrylate with a mass concentration of 15%, the mass ratio of potassium persulfate to sodium bisulfite being 4:1, the mass fraction of potassium persulfate in the monomer hexadecyl methacrylate or octadecyl methacrylate being 0.2%, the mass concentration of the sodium bisulfite aqueous solution being 6 g / L, and the potassium persulfate aqueous solution and the sodium bisulfite aqueous solution reacting for 3.5 h, and then cooling to room temperature, washing three times by centrifugation with distilled water, and air drying to obtain a hydrophilic zinc oxide aerogel.

[0018] Product performance: density 35.8 Kg / m³; thermal conductivity 0.013 W / m.K; hydrophobicity 98%; specific surface area 553 m 2 / g; combustion performance level A level or above; smoke toxicity ZA1.

[0019] Note: The thermal conductivity is measured according to GB / T 10295-2008; the hydrophobicity is measured according to GB / T 10299-2011; the combustion performance level is measured according to GB / T 5464-2010; the smoke toxicity is measured according to GB / T 20285-2006; and the specific surface area is measured according to GB / T 19587-2004.

Claims

1. A method for preparing a hydrophobic zinc oxide aerogel, characterized in that, The method comprises the following steps: first, preparing a polyethylene glycol solution with a mass fraction of 12-15% by stirring in a heating kettle at 70-80 DEG C until completely dissolved, and cooling for standby; second, dissolving zinc nitrate in the polyethylene glycol solution obtained in the first step, so that the mass ratio of polyethylene glycol to zinc nitrate is 1:3-4, and uniformly mixing and stirring; third, rapidly freezing the mixed solution with dry ice, and then freezing in a refrigerator at-20 DEG C until completely frozen, and then transferring to a vacuum freeze dryer to remove water by freeze-drying at-50 DEG C under a vacuum of less than or equal to 10 Pa, so as to obtain an aerogel precursor; fourth, placing the aerogel precursor in a crucible, and calcining in a muffle furnace, and setting the heating rate to 4-5 DEG C / min from room temperature to 500-550 DEG C, and keeping the temperature constant for 3-4 h, and then naturally cooling to obtain a zinc oxide aerogel; and fifth, placing the obtained zinc oxide aerogel in 50-60 parts of water according to a bath ratio of 1:3-4, adjusting the pH to 6-6.5, adding 0.5-0.7 parts of vinyl tri(2-methoxyethoxy) silane to the water, and reacting at 80-85 DEG C for 1-2 h, and then adding a monomer of 10%-15% (mass fraction) of hexadecyl methacrylate or octadecyl methacrylate, and an aqueous solution of potassium persulfate and an aqueous solution of sodium bisulfite, and reacting for 3-3.5 h, and then cooling to room temperature, and washing with distilled water by centrifugation for 3 times, and then air-drying to obtain a hydrophilic zinc oxide aerogel.

2. The method of claim 1, wherein the hydrophobic zinc oxide aerogel is prepared by the steps of: The polyethylene glycol in the first step has a molecular weight of 4,000-6,000.

3. The method of claim 1, wherein the hydrophobic zinc oxide aerogel is prepared by the steps of: The mass ratio of potassium persulfate to sodium bisulfite in the fifth step is 3-4:

1.

4. The method of claim 1, wherein the hydrophobic zinc oxide aerogel is prepared by the steps of: The mass fraction of potassium persulfate in the monomer of hexadecyl methacrylate or octadecyl methacrylate in the fifth step is 0.15%-0.2%.

5. The method of claim 1, wherein the hydrophobic zinc oxide aerogel is prepared by the steps of: The aqueous solution of sodium bisulfite in the fifth step has a mass concentration of 4-6 g / L.