CN103203206B - Cellulose/titanium dioxide/silica aerogel and preparation method thereof - Google Patents

Abstract

The invention relates to a cellulose/titanium dioxide/silica airgel and a preparation method thereof, comprising preparation of cellulose sol, surface loading of nano-titanium dioxide, surface coating of silicon dioxide, aging, aging, hydrophobization, bonding and molding and drying treatment steps, mainly using nano-cellulose as the core body, first loaded with nano-titanium dioxide, and then covering the silicon dioxide layer, after aging, aging, hydrophobization, bonding molding and drying treatment, etc., to obtain Cellulose/titanium dioxide/silica airgel. The airgel has the properties of flexibility, high strength, antibacterial, anti-ultraviolet, deodorization, heat preservation, heat insulation and sound insulation, and can be widely used in thermal underwear, body armor, heat preservation materials, compression materials, special coatings, aviation materials and other fields.

Description

Cellulose/titanium dioxide/silica airgel and preparation method thereof

technical field

The invention relates to the field of airgel preparation, in particular to the preparation of a cellulose/titanium dioxide/silica airgel with flexibility, high strength, antibacterial, anti-ultraviolet, deodorization, heat preservation, heat insulation and sound insulation properties method.

Background technique

Airgel is a solid with a porous, sponge-like structure, about 95% of which is air, with ultra-low density, ultra-large pores, ultra-large internal surface area, ultra-low thermal conductivity, ultra-low sound velocity, and excellent thermal stability and Mechanical properties, widely used in catalysis, aerospace, advanced materials and other fields.

Silica airgel is a lightweight nanoporous material with a density as low as 3Kg/m ³ and a porosity as high as 99%. Its slender nanoporous network structure effectively suppresses solid, gaseous and radiative heat conduction, making it an efficient and lightweight nanoporous heat-insulating and heat-resistant material. As a light-weight thermal insulation material, it has broad application prospects in the fields of aviation, aerospace, chemical industry, metallurgy and energy-saving buildings. However, pure silica aerogels are transparent to infrared rays with a wave band of 3-8 μm, resulting in a sharp increase in thermal conductivity of pure silica aerogels under high temperature conditions, thus limiting the use of pure silica aerogels in applications under high temperature conditions. In order to improve the heat insulation performance of silica airgel at high temperature, composite or doped titanium dioxide with infrared blocking effect can be used, so that the composite or doped silica airgel can effectively block the radiation heat conduction role in order to be used as a high-efficiency thermal insulation and heat-resistant material at high temperatures. Chinese patent CN1981925B mixes surfactant-modified silica sol and titania sol to prepare titania/silica airgel, but the strength and flexibility of the airgel are poor, and the raw materials are expensive and the cost is high .

Cellulose, the most abundant renewable resource on earth, has good biocompatibility and excellent tensile strength. The production of regenerated cellulose fibers, cellophane, and non-woven fabrics from cellulose through the viscose method has been widely used. The theoretical macroscopic elastic modulus (128GPa) of cellulose is higher than that of aluminum (70GPa) and glass fiber (76GPa), and its theoretical ultimate tensile strength (17.8GPa) is more than seven times that of iron. Chinese patent CN101906233A replaces the organic solvent in the cellulose organic gel with acrylic polymer monomer or their mixed solution, or immerses the cellulose airgel in the acrylic polymer monomer or their mixed solution to polymerize A cellulose gel/acrylic polymer composition was obtained. The composition has excellent mechanical properties and flexibility, but the cellulose is prone to mildew and lacks heat resistance.

At present, nano-cellulose is used as the core, first loaded with nano-titanium dioxide, and then covered with a silica layer, and finally through aging, aging, hydrophobicity, bonding molding and drying to obtain cellulose/titanium dioxide/silica Aerogels have not been reported in the literature. Cellulose enhances the mechanical properties and biocompatibility of the airgel, titanium dioxide improves the antibacterial performance of the airgel, and at the same time endows the aerogel with high heat resistance with silica, and the binder improves the airgel The flexibility can be widely used in thermal underwear, body armor, thermal insulation materials, compression materials, special coatings, aviation materials and other fields.

Contents of the invention

The object of the present invention is to provide a preparation method of cellulose/titanium dioxide/silica airgel with flexibility, high strength, antibacterial, anti-ultraviolet, deodorization, heat preservation, heat insulation and sound insulation properties.

The technical solution to achieve the above purpose is: use nano-cellulose as the core body, first load nano-titanium dioxide, then coat the silicon dioxide layer, and finally undergo aging, aging, hydrophobicity, bonding molding and drying to obtain cellulose / Titanium dioxide / Silica airgel.

The preparation process of a cellulose/titanium dioxide/silica airgel includes preparing cellulose sol, loading nano-titanium dioxide on the surface, coating silicon dioxide on the surface, aging, aging, hydrophobization, bonding molding and drying treatment.

Concrete operation steps of the present invention are as follows:

1. Preparation of cellulose sol: disperse cellulose into water to prepare cellulose sol, wherein the mass ratio of cellulose to water is 0.05-0.25:1;

2. Nano-titanium dioxide loaded on the surface: under continuous stirring, add 0.5-4.0mol/L inorganic titanium salt solution and 0.5-4.0mol/L lye into the cellulose sol in step 1 for mixed reaction, and the reaction temperature is ≤50℃ , pH ≤ 1.00, then heated up to 70-100°C, and reacted at constant temperature for 1-10 hours to obtain cellulose sol supported by nano-titanium dioxide;

3. Surface-coated silica: under continuous stirring, add 0.3-2.0mol/L silicate aqueous solution to the cellulose sol supported by nano-titanium dioxide for reaction. The reaction temperature is maintained at 75-95°C, and the reaction solution is added After finishing, heat preservation and aging for 0.5-2 hours, then adjust the pH to 6.00-7.50 with 0.5-2.0 mol/L alkali or acid aqueous solution, then heat preservation and aging for 0.5-2 hours, and wash with deionized water to obtain cellulose/titanium dioxide/dioxide silicone gel;

4. Aging and aging treatment: Aging the cellulose/titanium dioxide/silica gel for 1-3 days, using absolute ethanol as the aging solution, aging the aged gel for 1-10 days, and changing the absolute ethanol once a day ;

5. Hydrophobic treatment: place cellulose/titanium dioxide/silica gel in a modified solution with a volume ratio of modifier to organic solvent of 0.1 to 8:1 for hydrophobic modification for 1 to 15 hours, and then use absolute ethanol to Clean the surface of the gel;

6. Adhesive molding and drying treatment: place the cellulose/titanium dioxide/silica hydrophobic gel and the adhesive in the forming mold, and the mass ratio of the adhesive to the cellulose/titanium dioxide/silica hydrophobic gel is 0.1 to 5:1, and filled with absolute ethanol, and then freeze-drying or supercritical drying or drying at normal temperature and pressure to obtain cellulose/titanium dioxide/silicon dioxide airgel.

The inorganic titanium salt described in step 2 is one or more of titanium tetrachloride, titanium sulfate and titanyl sulfate.

The alkali described in step 2 and step 3 is one or more of sodium hydroxide, potassium hydroxide, ammonia water, sodium carbonate, potassium carbonate, ammonium carbonate and ammonium bicarbonate.

The amount of the inorganic titanium salt described in step 2 is based on the mass of titanium dioxide produced by the complete reaction, and the mass ratio of titanium dioxide to cellulose is 0.2-1.5:1.

The silicate described in step 3 is one or both of sodium silicate and potassium silicate.

The amount of the silicate described in step 3 is based on the mass of silica produced by the complete reaction, and the mass ratio of silica to cellulose is 0.1-0.6:1.

The acid described in step 3 is one or more of sulfuric acid, hydrochloric acid, nitric acid and acetic acid.

The modifying agent described in step 5 is long-chain organic amine salt, dimethyldiethoxysilane, trimethylchlorosilane, glycerol, hexamethyldisiloxane, hexamethyldisilazane, One or more of methyltrimethoxysilane, stearate, tetraethoxysilane, vinylalkoxysilane, N-enoic acid glycidyl ether, and amphoteric macromolecular copolymer.

The organic solvent described in step 5 is one or more of n-hexane, ethanol, butanol, propanol, benzene, toluene.

The adhesive described in step 6 is cellulose ester, vinyl polymer, polyester polymer, polyether polymer, polyamide polymer, polyacrylate polymer, polyvinyl acetal polymer One or more of compounds, ethylene-vinyl acetate copolymers, silicone polymers, and organic fluorine polymers.

The beneficial effects of the present invention are:

1. The present invention uses cellulose as the core body (template), and the prepared airgel has a fibrous porous structure, which is easy to form a reinforced structure in the use system and has excellent reinforcing properties. In addition, cellulose also has excellent biological properties. Compatibility, and can improve the flexibility of airgel.

2. Nano-titanium dioxide and nano-silicon dioxide are attached to the cellulose of the present invention. Among them, nano-titanium dioxide can bring antibacterial, anti-ultraviolet, deodorizing and other properties to the airgel, and together with nano-silicon dioxide, the airgel is more High heat resistance.

3. In the present invention, an adhesive is added during the forming process, which improves the flexibility of the airgel.

4. The present invention can form various shapes through molds, and can be used in various fields that require heat insulation and warmth, bulletproof and pressure resistance, antibacterial and deodorizing, sound insulation and shockproof.

Description of drawings

Further explanation will be made in conjunction with accompanying drawings.

Fig.1 TEM photo of cellulose/titanium dioxide/silica airgel

detailed description

Below in conjunction with embodiment the present invention is described in further detail.

Example 1:

1. Preparation of cellulose sol: Add 20.0g of cellulose to 400.0g of water, and use KQ2200DB numerical control ultrasonic cleaner to ultrasonically disperse for 1 hour to make cellulose sol;

2. Nano titanium dioxide loaded on the surface: While stirring, add 94.0 mL of 4.0 mol/L TiCl ₄ aqueous solution to the cellulose sol, maintain the reaction temperature at 10°C, and then add 2.0 mol/L potassium hydroxide aqueous solution to adjust the pH of the system The value is 1.00, the temperature is raised to 100°C, and the reaction is carried out at a constant temperature of 100°C for 1 hour to obtain a cellulose sol supported by nano-titanium dioxide;

3. Surface-coated silica: under continuous stirring, 300.0mL of 2.0mol/L sodium silicate aqueous solution and 2.0mol/L hydrochloric acid aqueous solution were simultaneously (cocurrently) dropped into the cellulose sol supported by nano-titanium dioxide for reaction , the reaction temperature is maintained at 75°C. After adding the reaction liquid, heat-preserve and mature for 0.5h, then adjust the pH to 6.00 with 2.0mol/L sodium hydroxide or hydrochloric acid aqueous solution, and then heat-preserve for 2h, suction filter, and wash with deionized water Until the conductivity of the filtrate is 215 μS/cm, the washing is completed to obtain a cellulose/titanium dioxide/silica gel;

4. Aging and aging treatment: Aging the cellulose/titanium dioxide/silica gel for 1 day, using absolute ethanol as the aging solution, aging the aged gel for 1 day, and replacing the absolute ethanol once a day;

5. Hydrophobic treatment: place the cellulose/titanium dioxide/silica gel in a modified solution with a cetyltrimethylammonium bromide:absolute ethanol volume ratio of 8:1 for hydrophobic modification for 1 hour, and then Clean the gel surface with absolute ethanol;

6. Molding and drying treatment: place cellulose/titanium dioxide/silica hydrophobic gel and acrylic resin in the molding mold, and the mass ratio of adhesive to cellulose/titanium dioxide/silica hydrophobic gel is 5:1 , and filled with absolute ethanol, and then freeze-dried to obtain the cellulose/titanium dioxide/silica airgel.

Example 2:

1. Preparation of cellulose sol: Add 20.0g of cellulose into 80.0g of water, and ultrasonically disperse for 1 hour with a KQ2200DB numerical control ultrasonic cleaner to make cellulose sol;

2. Surface-loaded nano-titanium dioxide: While stirring, add 100.0 mL of 0.5 mol/L TiCl ₄ aqueous solution and 120.0 mL of 0.5 mol/L ammonia solution to the cellulose sol, maintain the reaction temperature at 21°C, and finish adding the reaction solution Finally, the pH value of the system is 0.33, the temperature is raised to 70°C, and the reaction is carried out at a constant temperature of 70°C for 10 hours to obtain a cellulose sol supported by nano-titanium dioxide;

3. Surface-coated silicon dioxide: Under constant stirring, 111.1 mL of 0.3 mol/L sodium silicate aqueous solution and 0.5 mol/L sulfuric acid aqueous solution were simultaneously (cocurrently) dropped into the cellulose sol supported by nano-titanium dioxide for reaction , the reaction temperature is maintained at 95°C. After the addition of the reaction solution, heat-preserve and mature for 2 hours, then adjust the pH to 7.50 with 0.5mol/L ammonia water or sulfuric acid aqueous solution, then heat-retain and mature for 0.5 hours, filter with suction, and wash with deionized water until the filtrate The conductivity is 300μS/cm, and after washing, a cellulose/titanium dioxide/silica nanocomposite filter cake is obtained;

4. Aging and aging treatment: Aging the cellulose/titanium dioxide/silica gel for 3 days, using absolute ethanol as the aging solution, aging the aged gel for 10 days, and changing the absolute ethanol once a day;

5. Hydrophobic treatment: place the cellulose/titanium dioxide/silica gel in a modified solution with a volume ratio of hexamethyldisilazane:glycerol of 0.1:1 for hydrophobic modification for 15 hours, and then use anhydrous Ethanol cleaning gel surface;

6. Forming and drying treatment: place the cellulose/titanium dioxide/silica hydrophobic gel and polyvinyl alcohol resin in the forming mold, and the mass ratio of the adhesive to the cellulose/titanium dioxide/silica hydrophobic gel is 0.10 : 1, and filled with absolute ethanol, and then adopt the method of high-temperature ethanol supercritical drying to obtain cellulose/titanium dioxide/silica airgel.

Example 3:

1. Preparation of cellulose sol: add 20.0g of cellulose to 200.0g of water, and use KQ2200DB numerical control ultrasonic cleaner to ultrasonically disperse for 1 hour to make cellulose sol;

2. Surface loaded nano-titanium dioxide: While stirring, add 160.0 mL of 4.0 mol/L sodium hydroxide aqueous solution to the cellulose sol, maintain the reaction temperature at 50 ° C, and then add 100.0 mL of 2.5 mol/L TiCl ₄ aqueous solution, TiCl ₄ After adding the aqueous solution, the pH value of the system is 0.10, the temperature is raised to 85°C, and the reaction is carried out at a constant temperature of 85°C for 3 hours to obtain a cellulose sol supported by nano-titanium dioxide;

3. Surface-coated silicon dioxide: Under continuous stirring, 100.0 mL of 1.0 mol/L sodium silicate aqueous solution and 1.0 mol/L acetic acid aqueous solution were dropped into the slurry at the same time (parallel flow) to react, and the reaction temperature was maintained at 90°C, after the addition of the reaction solution, heat and mature for 1h, then adjust the pH to 6.50 with 1.0mol/L ammonia water or acetic acid aqueous solution, then heat and heat for 1h, filter with suction, and wash with deionized water until the conductivity of the filtrate is 120μS/cm , after washing, cellulose/titanium dioxide/silica gel is obtained;

4. Aging and aging treatment: Aging the cellulose/titanium dioxide/silica gel for 3 days, using absolute ethanol as the aging solution, aging the aged gel for 8 days, and changing the absolute ethanol once a day;

5. Hydrophobic treatment: place the cellulose/titanium dioxide/silica gel in a hydrophobic solution with a volume ratio of trimethylchlorosilane and n-hexane of 0.2:1 for hydrophobic modification for 14 hours, and then wash the gel with absolute ethanol surface;

6. Molding and drying treatment: place cellulose/titanium dioxide/silica hydrophobic gel and silicone resin in a molding mold, and the mass ratio of adhesive to cellulose/titanium dioxide/silica hydrophobic gel is 1: 1. Fill up with absolute ethanol, and then use low-temperature carbon dioxide supercritical drying method to obtain cellulose/titanium dioxide/silica airgel.

Example 4:

1. Preparation of cellulose sol: Add 20.0g of cellulose to 150.0g of water, and use FSH-2 adjustable high-speed homogenizer (Jintan Jerry Electric Co., Ltd.) to disperse for 20 minutes at a speed of 15,000 rpm. Made into cellulose sol;

2. Surface-loaded nano-titanium dioxide: While stirring, add 50.0 mL of 2.0 mol/L titanium sulfate aqueous solution to the cellulose sol, maintain the reaction temperature at 30 ° C, and then add 1.0 mol/L sodium carbonate aqueous solution to adjust the pH value of the system 0.50, the temperature was raised to 100°C, and a constant temperature reaction was carried out at 100°C for 5 hours to obtain nano-titanium dioxide-supported cellulose sol;

3. Surface-coated silica: under continuous stirring, 140.0 mL of 0.5 mol/L potassium silicate aqueous solution and 1.0 mol/L nitric acid aqueous solution were simultaneously (cocurrently) dropped into the slurry for reaction, and the reaction temperature was maintained at 85°C, after adding the reaction liquid, heat and mature for 1.5h, then adjust the pH to 7.30 with 0.5-2.0mol/L potassium carbonate or nitric acid aqueous solution, then heat and heat for 40min, filter with suction, and wash with deionized water until the conductivity of the filtrate It is 208μS/cm, after washing, a cellulose/titanium dioxide/silica gel is obtained;

4. Aging and aging treatment: Aging the cellulose/titanium dioxide/silica gel for 2.5 days, using absolute ethanol as the aging solution, aging the aged gel for 9 days, and replacing the absolute ethanol once a day;

5. Hydrophobic treatment: place the cellulose/titanium dioxide/silica gel in a hydrophobic solution with a volume ratio of dimethyldiethoxysilane:n-hexane of 0.5:1 for hydrophobic modification for 14 hours, and then use absolute ethanol Clean the surface of the gel;

6. Molding and drying treatment: place cellulose/titanium dioxide/silica hydrophobic gel and organic fluorine resin in a molding mold, and the mass ratio of adhesive to cellulose/titanium dioxide/silica hydrophobic gel is 2: 1. Fill up with absolute ethanol, and then dry at normal temperature and pressure to obtain cellulose/titanium dioxide/silica airgel.

Comparative Example 1: Step 1 was omitted in Example 3, that is, titanium dioxide/silica aerogel was directly prepared without preparing cellulose sol, and the others were the same as in Example 3.

Comparative Example 2: Step 2 was omitted in Example 3, that is, the cellulose surface was not loaded with nano-titanium dioxide, and the cellulose/silica airgel was directly prepared. Others were the same as in Example 3.

Comparative Example 3: Step 2 and Step 3 were omitted in Example 3, that is, the cellulose aerogel was directly prepared without nano-titanium dioxide and nano-silicon dioxide loaded on the surface of the cellulose, and the others were the same as in Example 3.

Comparative Example 4: In Comparative Example 3, the step of adding the adhesive in step 6 was omitted, that is, no adhesive was added for molding, and the others were the same as in Example 3.

Comparative Example 5: Step 2, Step 3 and Step 6 were omitted in Comparative Example 3, that is, the cellulose airgel without adding adhesive, and the others were the same as in Example 3.

Table 1 Performance test table of cellulose/titanium dioxide/silica airgel

sample Elastic modulus/GPa Tensile strength/GPa Heat resistance/℃ Example 1 140 twenty two 860 Example 2 123 14 1185 Example 3 138 19 1138 Example 4 135 18 1095 Comparative example 1 42 1.2 1200 Comparative example 2 120 12 850 Comparative example 3 180 10 120 Comparative example 4 96 5 1000 Comparative Example 5 100 15 200

Claims (9)

1. A cellulose/titanium dioxide/silica airgel, characterized in that the preparation method may further comprise the steps: (1) Prepare cellulose sol: disperse cellulose in water to prepare cellulose sol, wherein the mass ratio of cellulose to water is 0.05～0.25:1; (2) Nano-titanium dioxide loaded on the surface: under constant stirring, add 0.5-4.0 mol/L inorganic titanium salt solution and 0.5-4.0 mol/L lye into the cellulose sol in step 1 for mixed reaction, and the reaction temperature is ≤50 ℃, pH ≤ 1.00, then raise the temperature to 70-100 ℃, and react at constant temperature for 1-10 hours to obtain nano-titanium dioxide-supported cellulose sol; (3) Surface-coated silica: under continuous stirring, add 0.3-2.0mol/L silicate aqueous solution to the cellulose sol supported by nano-titanium dioxide for reaction, the reaction temperature is maintained at 75-95°C, and the reaction solution After adding, heat-preserve and mature for 0.5-2 hours, then adjust the pH to 6.00-7.50 with 0.5-2.0 mol/L alkali or acid aqueous solution, then heat-retain and mature for 0.5-2 hours, and wash with deionized water to obtain cellulose/titanium dioxide/dioxide Silica gel; (4) Aging and aging treatment: age the cellulose/titanium dioxide/silica gel for 1-3 days, use absolute ethanol as the aging solution, age the aged gel for 1-10 days, and replace the absolute ethanol every day once; (5) Hydrophobic treatment: place cellulose/titanium dioxide/silica gel in a modified solution with a volume ratio of modifier to organic solvent of 0.1 to 8:1 for hydrophobic modification for 1 to 15 hours, and then use anhydrous Ethanol cleaning gel surface; (6) Adhesive molding and drying treatment: place the cellulose/titanium dioxide/silica hydrophobic gel and the adhesive in the forming mold, the mass ratio of the adhesive to the cellulose/titanium dioxide/silica hydrophobic gel The ratio is 0.1 to 5:1, and absolute ethanol is added, and then the cellulose/titanium dioxide/silica airgel is obtained by freeze-drying or supercritical drying or drying at normal temperature and pressure. 2. A cellulose/titanium dioxide/silica airgel according to claim 1, characterized in that the inorganic titanium salt is one or more of titanium tetrachloride, titanium sulfate and titanyl sulfate. 3. A kind of cellulose/titanium dioxide/silica airgel according to claim 1, characterized in that the alkali is sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, potassium carbonate, ammonium carbonate and ammonium bicarbonate one or more of them. 4. a kind of cellulose/titanium dioxide/silica airgel according to claim 1, is characterized in that the consumption of inorganic titanium salt is by the mass meter of titanium dioxide generated by its complete reaction, and the mass ratio of titanium dioxide and cellulose is 0.2～1.5:1. 5. A cellulose/titanium dioxide/silica airgel according to claim 1, characterized in that the silicate is one or both of sodium silicate and potassium silicate. 6. A kind of cellulose/titanium dioxide/silica airgel according to claim 1, characterized in that the consumption of silicate is based on the mass of silicon dioxide generated by its complete reaction, and silicon dioxide and cellulose The mass ratio is 0.1～0.6:1. 7. A kind of cellulose/titanium dioxide/silica airgel according to claim 1, characterized in that modifier is long-chain organic amine salt, dimethyldiethoxysilane, trimethylchlorosilane , Glycerol, Hexamethyldisiloxane, Hexamethyldisilazane, Methyltrimethoxysilane, Stearate, Tetraethoxysilane, Vinylalkoxysilane, N Acrylic Acid Shrink One or more of glyceryl ethers and amphoteric macromolecular copolymers. 8. A kind of cellulose/titanium dioxide/silica airgel according to claim 1, characterized in that the organic solvent is one or more of n-hexane, ethanol, butanol, propanol, benzene, toluene . 9. A kind of cellulose/titanium dioxide/silica airgel according to claim 1, characterized in that the adhesive is cellulose ester, vinyl polymer, polyester polymer, polyether polymer One or more of polyamide polymers, polyacrylate polymers, polyvinyl acetal polymers, ethylene-vinyl acetate copolymers, silicone polymers, and organic fluorine polymers .