CN111303477A - High-hydrophobicity cellulose acetate aerogel and preparation method thereof - Google Patents
High-hydrophobicity cellulose acetate aerogel and preparation method thereof Download PDFInfo
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Abstract
The invention provides a high-hydrophobicity cellulose acetate aerogel and a preparation method thereof, which comprises the steps of taking cellulose acetate as a raw material, dissolving the cellulose acetate in a solvent, adding a cross-linking agent and a catalyst, and performing supercritical drying to obtain the cellulose acetate aerogel; placing the cellulose acetate aerogel into a closed container, and adding a hydrophobic agent for hydrophobic treatment to obtain the high-hydrophobicity cellulose acetate aerogel; the maximum pore diameter of the highly hydrophobic cellulose acetate aerogel obtained by the method can be controlled within 49nm, the water contact angle is increased from 50 degrees to 136 degrees, and the saturated mass moisture absorption rate is reduced from 24 percent to 4.1 percent, so that the highly hydrophobic cellulose acetate aerogel prepared by the method has excellent hydrophobicity.
Description
Technical Field
The invention relates to the technical field of biomass aerogel materials, in particular to a high-hydrophobicity cellulose acetate aerogel and a preparation method thereof.
Background
Cellulose acetate is a cellulose derivative which is firstly commercially produced, is a chemically modified natural high polymer obtained by esterifying hydroxyl in cellulose molecules with acetic acid, usually adopts cotton fibers or wood fibers as raw materials, has the characteristics of wide sources, simple synthesis process, low cost, transparency, good gloss, high strength and good toughness, has strong light and heat resistance, is not easy to burn, is non-toxic, and belongs to an environment-friendly material.
The cellulose aerogel material is a third-generation aerogel material independent of inorganic aerogel materials and organic polymer aerogel materials, has the advantages of the traditional aerogel materials such as low density, high specific surface area, high porosity and small pore size distribution, and also has the advantages of biodegradability and biocompatibility, high mechanical strength and other excellent properties. Therefore, the cellulose aerogel material has excellent development prospect in the fields of mechanics, thermal, optics, electromagnetism, electrochemistry and the like.
The cellulose acetate can be well dissolved in an organic solvent, and the cellulose acetate aerogel material is prepared by mixing the cellulose acetate with an organic cross-linking agent. Cellulose acetate aerogel material belongs to novel degradable aerogel material, has good heat preservation and insulation performance, can be applied to the building field. As is well known, as energy consumption is getting larger and larger, energy consumption of buildings accounts for 11% to 25% of the total global energy consumption, and heat preservation and insulation materials for buildings are receiving more and more attention. However, the field of thermal insulation requires that the material has a certain hydrophobic property, a certain amount of hydroxyl groups exist in the cellulose acetate, and the hydroxyl groups belong to hydrophilic groups, so that the aerogel material must have a hydrophobic function in addition to meeting the performances of compression, thermal insulation and the like to ensure that the aerogel material can be normally used in a humid environment. The water contact angle of the traditional hydrophobic aerogel material is 70-90 degrees, the saturation mass moisture absorption rate is about 15%, the hydrophobic effect is not ideal enough, and the hydrophobic effect is to be improved urgently.
Disclosure of Invention
The invention aims to provide a high-hydrophobicity cellulose acetate aerogel material, and the invention also aims to provide a preparation method of the high-hydrophobicity cellulose acetate aerogel material. The preparation method not only provides a novel high-hydrophobicity cellulose acetate aerogel material, but also solves the problems of small water contact angle and high saturated mass and moisture absorption rate of the traditional aerogel material.
The high-hydrophobicity cellulose acetate aerogel provided by the invention has the advantages that the water contact angle of the cellulose acetate aerogel is increased to 136 degrees from 50 degrees, and the saturated mass moisture absorption rate is reduced to 4.1 percent from 24 percent.
The invention also provides a preparation method of the highly hydrophobic cellulose acetate aerogel, which comprises the following steps:
step one, preparing cellulose acetate sol: dissolving cellulose acetate in a solvent, adding a cross-linking agent and a catalyst, and stirring to obtain a cellulose acetate sol with the mass volume concentration of 10-110 g/L;
step two, preparing cellulose acetate gel: standing the cellulose acetate sol to obtain cellulose acetate gel;
step three, aging and solvent exchange: aging the cellulose acetate gel to obtain mature cellulose acetate gel, and replacing a solvent in the mature cellulose acetate gel with an organic solvent for 1-5 days;
step four, supercritical drying: carrying out supercritical drying on the mature cellulose acetate gel after solvent replacement to obtain cellulose acetate aerogel;
step five, high hydrophobic treatment: and putting the cellulose acetate aerogel into an oven for heat treatment, and then carrying out hydrophobic treatment on the cellulose acetate aerogel by using a hydrophobic agent to obtain the high-hydrophobicity cellulose acetate aerogel.
Further, the volume percentage concentration of the cross-linking agent in the solution is as follows: 0.05-45%, and the ratio of the volume of the cross-linking agent to the mass of the cellulose acetate is as follows: (0.05 mL-4 mL) 1 g.
Further, the solvent is any one or a group consisting of dimethylformamide, N-methylpyrrolidone, 1, 4-butyrolactone, methylethyl acetone, N-methylmorpholine, acetone, N-dimethylacetamide, glacial acetic acid and cyclohexanone.
Further, the crosslinking agent is any one or any combination of dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, 4 '-diphenylmethane diisocyanate, 2,4' -diphenylmethane diisocyanate, ethyl isocyanate, 2, 4-tolylene diisocyanate, 2-phenylethyl isocyanate and dimethylbiphenyl diisocyanate.
Further, the catalyst is any one or a group consisting of 3, 5-dichloropyridine, 3,4, 5-trichloropyridine, forchlorfenuron, 2-chloro-5-chloromethylpyridine, 2-chloro-5-trichloromethylpyridine, pyridine and 2-methyl-3-hydroxypyridine.
Further, the aging temperature is: and aging for 1-10 days at 25-35 ℃.
Further, the supercritical drying uses carbon dioxide as a drying fluid, and the supercritical temperature is as follows: at 35-45 ℃, the pressure is as follows: 8 to 18MPa, preferably 8 to 15 MPa.
Further, the heat treatment temperature is 60-90 ℃, and the time is 1-5 h.
Further, the hydrophobic agent is one or any one of oleic acid, tetrafluoroethylene, hexamethyldisilazane, methyltriethoxysilane, perfluorodecyltriethoxysilane, trimethylsilanol and dichloromethane, the mass ratio of the hydrophobic agent to the aerogel is 0.1-1.0, the hydrophobic treatment temperature is 70-95 ℃, and the time is 0.5-15 days.
The invention has the beneficial effects that:
1. according to the high-hydrophobicity cellulose acetate aerogel and the preparation method thereof, after the prepared cellulose acetate aerogel is subjected to hydrophobic treatment, the water contact angle is increased to 136 degrees from 50 degrees, the saturated mass moisture absorption rate is reduced to 4.1 percent from 24 percent, and the hydrophilicity of the cellulose acetate aerogel is obviously changed;
2. according to the high-hydrophobicity cellulose acetate aerogel and the preparation method thereof, the maximum pore diameter of the prepared high-hydrophobicity cellulose acetate aerogel can be controlled within 49nm, the specific surface area and the pore volume are reduced, the volume of the surface physically adsorbed liquid water and the mass of the chemically combined water are reduced, and therefore the high-hydrophobicity cellulose acetate aerogel has excellent hydrophobicity;
3. the high-hydrophobicity cellulose acetate aerogel and the preparation method thereof provided by the invention have the advantages that the raw material source of the high-hydrophobicity cellulose acetate aerogel is wide, the preparation method of the high-hydrophobicity cellulose acetate aerogel is environment-friendly, the process is simple, the operability is strong, and the preparation method is suitable for industrial production.
The above and other aspects of the present invention will be apparent from the following description, with particular reference to various examples presented in accordance with the highly hydrophobic cellulose acetate aerogel and the method for preparing the same.
Drawings
FIG. 1 is a flow chart of the preparation of a highly hydrophobic cellulose acetate aerogel provided by the present invention;
FIG. 2 is a photograph showing the hydrophobic effect of the highly hydrophobic cellulose acetate aerogel obtained in example 5 of the present invention;
FIG. 3 is a graph of water contact angle of highly hydrophobic cellulose acetate aerogel obtained in example 5 of the present invention;
FIG. 4 is a graph comparing changes in moisture absorption rate in one week before and after the cellulose acetate aerogel in example 5 of the present invention was subjected to hydrophobic treatment;
FIG. 5 is a pore size distribution diagram of highly hydrophobic cellulose acetate aerogel obtained in example 5 of the present invention.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention.
Referring to fig. 1, the present invention provides a highly hydrophobic cellulose acetate aerogel and a method for preparing the same, comprising the steps of:
1) preparing cellulose acetate gel: dissolving cellulose acetate serving as a raw material in a solvent, adding a cross-linking agent and a catalyst to obtain a cellulose acetate sol with the mass volume concentration of 10-110 g/L, and stirring and standing to obtain cellulose acetate gel;
2) the method comprises the steps of ageing cellulose acetate gel to obtain mature cellulose acetate gel, replacing a solvent in the mature cellulose acetate gel for 1-5 days by using an organic solvent, performing supercritical drying to obtain cellulose acetate aerogel, and performing hydrophobic treatment on the cellulose acetate aerogel by using a hydrophobic agent to obtain the high-hydrophobicity cellulose acetate aerogel.
Preferably, the volume percentage concentration of the cross-linking agent in the solution is as follows: 0.05-45%, and the ratio of the volume of the cross-linking agent to the mass of the cellulose acetate is as follows: (0.05 mL-4 mL) 1 g.
Preferably, the solvent is any one or any combination of dimethylformamide, N-methylpyrrolidone, 1, 4-butyrolactone, methylethyl acetone, N-methylmorpholine, acetone, N-dimethylacetamide, glacial acetic acid and cyclohexanone.
Preferably, the crosslinking agent is any one or any combination of dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, 4 '-diphenylmethane diisocyanate, 2,4' -diphenylmethane diisocyanate, ethyl isocyanate, 2, 4-tolylene diisocyanate, 2-phenylethyl isocyanate and dimethylbiphenyl diisocyanate.
Preferably, the catalyst is any one or any combination of 3, 5-dichloropyridine, 3,4, 5-trichloropyridine, forchlorfenuron, 2-chloro-5-chloromethylpyridine, 2-chloro-5-trichloromethylpyridine, pyridine and 2-methyl-3-hydroxypyridine.
Preferably, the aging temperature is: 25-35 ℃ for 1-10 days.
Preferably, the supercritical drying uses carbon dioxide as a drying fluid, and the supercritical temperature is as follows: at 35-45 ℃, the pressure is as follows: 8-18 MPa, and the preferable pressure is as follows: 8-15 MPa.
Preferably, the heat treatment temperature is 60-90 ℃ and the time is 1-5 h.
Preferably, the hydrophobic agent is any one or any one of oleic acid, tetrafluoroethylene, hexamethyldisilazane, methyltriethoxysilane, perfluorodecyltriethoxysilane, trimethylsilanol and dichloromethane, the mass ratio of the hydrophobic agent to the aerogel is 0.1-1.0, the hydrophobic treatment temperature is 70-95 ℃, and the time is 0.5-15 days.
Specifically, the highly hydrophobic cellulose acetate aerogel and the preparation method thereof provided by the invention comprise the following steps:
1) preparing cellulose acetate gel: taking cellulose acetate as a raw material, dissolving the raw material in a solvent, mixing the cellulose acetate and the solvent at room temperature, and stirring the mixture until a clear solution is obtained. Then adding a cross-linking agent and a catalyst, continuously stirring to obtain cellulose acetate sol, transferring the cellulose acetate sol into a mould, and standing to obtain cellulose acetate gel;
the volume percentage concentration of the cross-linking agent in the solution is as follows: 0.05-45%, and the ratio of the volume of the cross-linking agent to the mass of the cellulose acetate is as follows: (0.05 mL-4 mL) of 1 g; the solvent is any one or a group consisting of dimethylformamide, N-methylpyrrolidone, 1, 4-butyrolactone, methyl ethyl acetone, N-methylmorpholine, acetone, N-dimethylacetamide, glacial acetic acid and cyclohexanone; the cross-linking agent is any one or a group consisting of dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, 4 '-diphenylmethane diisocyanate, 2,4' -diphenylmethane diisocyanate, ethyl isocyanate, 2, 4-tolylene diisocyanate, 2-phenylethyl isocyanate and dimethyl biphenyl diisocyanate; the catalyst is any one or a group consisting of 3, 5-dichloropyridine, 3,4, 5-trichloropyridine, forchlorfenuron, 2-chloro-5-chloromethylpyridine, 2-chloro-5-trichloromethylpyridine, pyridine and 2-methyl-3-hydroxypyridine.
2) And sealing the obtained cellulose acetate gel, and placing the sealed cellulose acetate gel in a constant-temperature water bath kettle for aging treatment for 1-10 days at the aging temperature of 25-35 ℃ to obtain mature cellulose acetate gel.
3) And replacing the obtained mature cellulose acetate aerogel with an organic solvent for 1-5 days, and then performing supercritical drying by using carbon dioxide as a drying fluid to obtain the cellulose acetate aerogel.
The temperature of supercritical drying is: at 35-45 ℃, the pressure is as follows: 8 to 18MPa, preferably 8 to 15 MPa.
4) And putting the cellulose acetate aerogel obtained by supercritical drying into an oven for heat treatment, and then carrying out hydrophobic treatment by using a hydrophobic agent to obtain the high-hydrophobicity cellulose acetate aerogel.
The heat treatment temperature is 60-90 ℃, and the time is 1-5 h.
The hydrophobic agent is one or a group consisting of methyl triethoxysilane, oleic acid, tetrafluoroethylene, hexamethyldisilazane, perfluorodecyl triethoxysilane, trimethylsilanol and dichloromethane, the mass ratio of the hydrophobic agent to the aerogel is 0.1-1.0, the hydrophobic treatment temperature is 70-95 ℃, and the time is 0.5-15 d.
Examples
Materials and equipment used in the following examples are commercially available.
Example 1
0.6g of cellulose acetate was dissolved in 60mL of dimethylformamide and stirred at room temperature for 1h to obtain a clear solution. Subsequently, 3, 5-dichloropyridine was added, and stirring was continued for 10min, and then 0.8mL of dicyclohexylmethane diisocyanate was added, and stirring was continued for 15min to obtain a cellulose acetate sol. And transferring the obtained cellulose acetate sol into a mold, sealing, and standing at room temperature and atmospheric pressure to obtain cellulose acetate gel. Then, aging the cellulose acetate gel in a 25 ℃ constant temperature water bath for 1d to obtain mature cellulose acetate gel. And (3) performing solvent replacement on the mature cellulose acetate aerogel, and then performing supercritical drying at 35 ℃ under the condition of 8MPa to obtain the cellulose acetate aerogel. And then putting the cellulose acetate aerogel into a 60 ℃ oven for heat treatment for 1h, then putting the cellulose acetate aerogel into a closed container, adding 0.06g of methyltriethoxysilane, and carrying out hydrophobic treatment at 70 ℃ for 0.5d to obtain the high-hydrophobicity cellulose acetate aerogel.
The prepared highly hydrophobic cellulose acetate aerogel has a water contact angle of 130 degrees, a saturated mass moisture absorption rate of 5.4 percent and a good hydrophobic effect.
Example 2
0.83g of cellulose acetate was dissolved in 68mL of methyl ethyl acetone and stirred at room temperature for 1h to obtain a clear solution. Subsequently, 3,4, 5-trichloropyridine was added, and stirring was continued for 10min, and then 0.1mL of hexamethylene diisocyanate was added, and stirring was continued for 15min to obtain a cellulose acetate sol. And transferring the obtained cellulose acetate sol into a mold, sealing, and standing at room temperature and atmospheric pressure to obtain cellulose acetate gel. Then, aging the cellulose acetate gel in a 25 ℃ constant temperature water bath for 2d to obtain mature cellulose acetate gel. And (3) performing solvent replacement on the mature cellulose acetate aerogel, and then performing supercritical drying at 35 ℃ under the condition of 10MPa to obtain the cellulose acetate aerogel. And then putting the cellulose acetate aerogel into a 65 ℃ oven for heat treatment for 1.5h, then putting the cellulose acetate aerogel into a closed container, adding 0.09g of tetrafluoroethylene, and carrying out hydrophobic treatment for 1d at 75 ℃ to obtain the high-hydrophobicity cellulose acetate aerogel.
The prepared highly hydrophobic cellulose acetate aerogel has a water contact angle of 133 degrees, a saturated mass moisture absorption rate of 5.0 percent and a good hydrophobic effect.
Example 3
1.8g of cellulose acetate was dissolved in 100mL of acetone and stirred at room temperature for 1h to obtain a clear solution. And adding forchlorfenuron, continuing to stir for 10min, adding 0.5mL of 4,4' -diphenylmethane diisocyanate, and continuing to stir for 15min to obtain the cellulose acetate sol. And transferring the obtained cellulose acetate sol into a mold, sealing, and standing at room temperature and atmospheric pressure to obtain cellulose acetate gel. Then, aging the cellulose acetate gel in a 30 ℃ constant temperature water bath for 4d to obtain mature cellulose acetate gel. And (3) performing solvent replacement on the mature cellulose acetate aerogel, and then performing supercritical drying at 40 ℃ under the condition of 10MPa to obtain the cellulose acetate aerogel. And then placing the cellulose acetate aerogel into a 70 ℃ oven for heat treatment for 1.5h, then placing the cellulose acetate aerogel into a closed container, adding 0.2g of hexamethyldisilazane, and carrying out hydrophobic treatment for 3d at 80 ℃ to obtain the high-hydrophobicity cellulose acetate aerogel.
The water contact angle of the prepared highly hydrophobic cellulose acetate aerogel is 133 degrees, the saturated mass moisture absorption rate is 4.75 percent, and the hydrophobic effect is good.
Example 4
6.2g of cellulose acetate was dissolved in 100mL of N, N-dimethylacetamide and stirred at room temperature for 1h to obtain a clear solution. Subsequently, 2-chloro-5-chloromethylpyridine was added thereto, and the mixture was further stirred for 10 minutes, and then 0.5mL of 2,4' -diphenylmethane diisocyanate was added thereto, and the stirring was further continued for 15 minutes, thereby obtaining a cellulose acetate sol. And transferring the obtained cellulose acetate sol into a mold, sealing, and standing at room temperature and atmospheric pressure to obtain cellulose acetate gel. Then, aging the cellulose acetate gel in a 30 ℃ constant temperature water bath for 5d to obtain mature cellulose acetate gel. And (3) performing solvent replacement on the mature cellulose acetate aerogel, and then performing supercritical drying at 40 ℃ and 12MPa to obtain the cellulose acetate aerogel. And then placing the cellulose acetate aerogel into a 75 ℃ oven for heat treatment for 2.5h, then placing the cellulose acetate aerogel into a closed container, adding 0.8g of mixed solution of hexamethyldisilazane and perfluorodecyl triethoxysilane, and carrying out hydrophobic treatment for 5d at 85 ℃ to obtain the highly hydrophobic cellulose acetate aerogel.
The prepared highly hydrophobic cellulose acetate aerogel has a water contact angle of 135 degrees, a saturated mass moisture absorption rate of 4.75 percent and a good hydrophobic effect.
Example 5
10g of cellulose acetate was dissolved in 150mL of glacial acetic acid and stirred at room temperature for 1h to give a clear solution. Subsequently, 2-chloro-5-trichloromethyl pyridine was added, and stirring was continued for 10min, and then 5mL of 2-phenethyl isocyanate was added, and stirring was continued for 15min to obtain a cellulose acetate sol. And transferring the obtained cellulose acetate sol into a mold, sealing, and standing at room temperature and atmospheric pressure to obtain cellulose acetate gel. Then, aging the cellulose acetate gel in a 30 ℃ constant temperature water bath for 6d to obtain mature cellulose acetate gel. And (3) performing solvent replacement on the mature cellulose acetate aerogel, and then performing supercritical drying at 45 ℃ and 14MPa to obtain the cellulose acetate aerogel. And then putting the cellulose acetate aerogel into an oven at 80 ℃ for heat treatment for 3h, then putting the cellulose acetate aerogel into a closed container, adding 1.3g of trimethylsilanol, and carrying out hydrophobic treatment at 90 ℃ for 7d to obtain the high-hydrophobicity cellulose acetate aerogel.
As shown in fig. 3, the water contact angle of the prepared highly hydrophobic cellulose acetate aerogel is 136 °; as shown in fig. 4, the saturated mass moisture absorption rate of the highly hydrophobic cellulose acetate aerogel obtained after the hydrophobic treatment was 4.1%; from this, it was found that the highly hydrophobic cellulose acetate aerogel has a good hydrophobic effect.
As shown in FIG. 5, the maximum pore diameter of the prepared highly hydrophobic cellulose acetate aerogel can be controlled within 49nm, the specific surface area and the pore volume are both reduced, and the volume of the surface physically adsorbed liquid water and the quality of chemically bound water are reduced, so that the highly hydrophobic cellulose acetate aerogel has excellent hydrophobicity.
Example 6
15g of cellulose acetate was dissolved in 150mL of a mixture of glacial acetic acid and cyclohexanone, and stirred at room temperature for 1h to obtain a clear solution. And then adding 2-methyl-3-hydroxypyridine, continuing to stir for 10min, adding 15mL of 2-phenylethyl isocyanate and dimethyl biphenyl diisocyanate mixed solution, and continuing to stir for 15min to obtain the cellulose acetate sol. And transferring the obtained cellulose acetate sol into a mold, sealing, and standing at room temperature and atmospheric pressure to obtain cellulose acetate gel. Then, aging the cellulose acetate gel in a 35 ℃ constant temperature water bath for 8d to obtain mature cellulose acetate gel. And (3) performing solvent replacement on the mature cellulose acetate aerogel, and then performing supercritical drying at 45 ℃ and 15MPa to obtain the cellulose acetate aerogel. And then putting the cellulose acetate aerogel into an oven at 85 ℃ for heat treatment for 3.5h, then putting the cellulose acetate aerogel into a closed container, adding 10g of mixed solution of trimethyl silanol and dichloromethane, and carrying out hydrophobic treatment at 95 ℃ for 12d to obtain the high-hydrophobicity cellulose acetate aerogel.
The prepared highly hydrophobic cellulose acetate aerogel has a water contact angle of 138 degrees, a saturated mass moisture absorption rate of 3.8 percent and a good hydrophobic effect.
Example 7
18g of cellulose acetate was dissolved in 180mL of a mixture of dimethylformamide and N-methylpyrrolidone, and the mixture was stirred at room temperature for 1 hour to obtain a clear solution. Subsequently, 2-methyl-3-hydroxypyridine was added, and stirring was continued for 10min, and then 30mL of 4,4' -diphenylmethane diisocyanate was added, and stirring was continued for 15min to obtain a cellulose acetate sol. And transferring the obtained cellulose acetate sol into a mold, sealing, and standing at room temperature and atmospheric pressure to obtain cellulose acetate gel. Then, aging the cellulose acetate gel in a 30 ℃ constant temperature water bath for 8.5 days to obtain mature cellulose acetate gel. And (3) performing solvent replacement on the mature cellulose acetate aerogel, and then performing supercritical drying at 40 ℃ and 16MPa to obtain the cellulose acetate aerogel. And then putting the cellulose acetate aerogel into an oven at 85 ℃ for heat treatment for 4.5h, then putting the cellulose acetate aerogel into a closed container, adding 15g of methyltriethoxysilane, and carrying out hydrophobic treatment at 90 ℃ for 14d to obtain the high-hydrophobicity cellulose acetate aerogel.
The prepared highly hydrophobic cellulose acetate aerogel has a water contact angle of 141 degrees, a saturated mass moisture absorption rate of 3.4 percent and a good hydrophobic effect.
Example 8
19.8g of cellulose acetate was dissolved in 180mL of cyclohexanone and stirred at room temperature for 1h to a clear solution. Subsequently, pyridine was added, stirring was continued for 10min, then 79.2mL of dimethylbiphenyl diisocyanate was added, and stirring was continued for 15min to obtain a cellulose acetate sol. And transferring the obtained cellulose acetate sol into a mold, sealing, and standing at room temperature and atmospheric pressure to obtain cellulose acetate gel. Then, aging the cellulose acetate gel in a 35 ℃ constant temperature water bath for 10d to obtain mature cellulose acetate gel. And (3) performing solvent replacement on the mature cellulose acetate aerogel, and then performing supercritical drying at 45 ℃ and 18MPa to obtain the cellulose acetate aerogel. And then putting the cellulose acetate aerogel into a 90 ℃ oven for heat treatment for 5h, then putting the cellulose acetate aerogel into a closed container, adding 19.8g of dichloromethane, and carrying out hydrophobic treatment at 95 ℃ for 15d to obtain the high-hydrophobicity cellulose acetate aerogel.
The water contact angle of the prepared highly hydrophobic cellulose acetate aerogel is 145 degrees, the saturated mass moisture absorption rate is 3.3 percent, and the hydrophobic effect is good.
It will be clear to a person skilled in the art that the scope of the present invention is not limited to the examples discussed in the foregoing, but that several amendments and modifications thereof are possible without deviating from the scope of the present invention as defined in the attached claims. While the invention has been illustrated and described in detail in the drawings and the description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments.
Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the term "comprising" does not exclude other steps or elements, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims shall not be construed as limiting the scope of the invention.
Claims (10)
1. A highly hydrophobic cellulose acetate aerogel characterized by: the water contact angle of the cellulose acetate aerogel is increased from 50 degrees to 136 degrees, and the saturated mass moisture absorption rate is reduced from 24 percent to 4.1 percent.
2. The method for preparing highly hydrophobic cellulose acetate aerogel according to claim 1, wherein: the preparation method comprises the following steps:
step one, preparing cellulose acetate sol: dissolving cellulose acetate in a solvent, adding a cross-linking agent and a catalyst, and stirring to obtain a cellulose acetate sol with the mass volume concentration of 10-110 g/L;
step two, preparing cellulose acetate gel: standing the cellulose acetate sol to obtain cellulose acetate gel;
step three, aging and solvent exchange: aging the cellulose acetate gel to obtain mature cellulose acetate gel, and replacing a solvent in the mature cellulose acetate gel with an organic solvent for 1-5 days;
step four, supercritical drying: carrying out supercritical drying on the mature cellulose acetate gel after solvent replacement to obtain cellulose acetate aerogel;
step five, high hydrophobic treatment: and putting the cellulose acetate aerogel into an oven for heat treatment, and then carrying out hydrophobic treatment on the cellulose acetate aerogel by using a hydrophobic agent to obtain the high-hydrophobicity cellulose acetate aerogel.
3. The method for preparing highly hydrophobic cellulose acetate aerogel according to claim 2, wherein: in the first step, the solvent is any one or a group consisting of dimethylformamide, N-methylpyrrolidone, 1, 4-butyrolactone, methyl ethyl acetone, N-methyl morpholine, acetone, N-dimethylacetamide, glacial acetic acid and cyclohexanone.
4. The method for preparing highly hydrophobic cellulose acetate aerogel according to claim 2, wherein: in the first step, the cross-linking agent is any one or any combination of dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, 4 '-diphenylmethane diisocyanate, 2,4' -diphenylmethane diisocyanate, ethyl isocyanate, 2, 4-tolylene diisocyanate, 2-phenylethyl isocyanate and dimethyl biphenyl diisocyanate.
5. The method for preparing highly hydrophobic cellulose acetate aerogel according to claim 2, wherein: the volume percentage concentration of the cross-linking agent in the cellulose acetate sol in the step one is as follows: 0.05-45%, and the ratio of the volume of the cross-linking agent to the mass of the cellulose acetate is as follows: (0.05 mL-4 mL) 1 g.
6. The method for preparing highly hydrophobic cellulose acetate aerogel according to claim 2, wherein: in the first step, the catalyst is any one or a group consisting of 3, 5-dichloropyridine, 3,4, 5-trichloropyridine, forchlorfenuron, 2-chloro-5-chloromethylpyridine, 2-chloro-5-trichloromethylpyridine, pyridine and 2-methyl-3-hydroxypyridine.
7. The method for preparing highly hydrophobic cellulose acetate aerogel according to claim 2, wherein: the aging temperature in the third step is as follows: and aging for 1-10 days at 25-35 ℃.
8. The method for preparing highly hydrophobic cellulose acetate aerogel according to claim 2, wherein: in the fourth step, supercritical drying is carried out, wherein carbon dioxide is used as a drying fluid, and the supercritical temperature is as follows: at 35-45 ℃, the pressure is as follows: 8 to 18 MPa.
9. The method for preparing highly hydrophobic cellulose acetate aerogel according to claim 2, wherein: and fifthly, the heat treatment temperature is 60-90 ℃, and the time is 1-5 h.
10. The method for preparing highly hydrophobic cellulose acetate aerogel according to claim 2, wherein: and in the fifth step, the hydrophobic agent is any one or any one of oleic acid, tetrafluoroethylene, hexamethyldisilazane, methyltriethoxysilane, perfluorodecyltriethoxysilane, trimethylsilanol and dichloromethane, the mass ratio of the hydrophobic agent to the cellulose acetate aerogel is 0.1-1.0, the hydrophobic treatment temperature is 70-95 ℃, and the time is 0.5-15 days.
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