Preparation method of viscose-based air filtering material
阅读说明：本技术 一种粘胶基空气过滤材料的制备方法 (Preparation method of viscose-based air filtering material ) 是由 杨红军 马思甜 王晗 许愿 汪林锋 刘昌俊 庄燕 徐卫林 于 2019-09-16 设计创作，主要内容包括：本发明涉及一种粘胶基空气过滤材料的制备方法,属于材料工程技术领域。本发明利用了定向冷冻和低温相变相结合的技术,以粘胶溶液为原料,采用仿生方式制备与树木结构相似的粘胶基空气过滤材料。粘胶基空气过滤材料具有比表面积大,阻力小,过滤效果好等优点。本发明所采用的工艺技术简单,结构可控性好等优点,且本发明方法制备的粘胶基空气过滤材料空气过滤效果高,环境污染小。(The invention relates to a preparation method of an adhesive-based air filtering material, belonging to the technical field of material engineering. The invention utilizes the technology of combining directional freezing and low-temperature phase change, takes viscose solution as raw material, and adopts a bionic mode to prepare the viscose-based air filter material with a structure similar to that of trees. The viscose-based air filtering material has the advantages of large specific surface area, small resistance, good filtering effect and the like. The process technology adopted by the invention has the advantages of simple technology, good structure controllability and the like, and the viscose-based air filter material prepared by the method has high air filtering effect and small environmental pollution.)
1. The preparation method of the viscose-based air filter material is characterized by comprising the following steps:
Preparation of a Filter type Membrane
Pouring the viscose solution into a mould, arranging a metal conductor for transferring temperature at the bottom of the mould, wherein the temperature of the metal conductor is-80 to-10 ℃, and transferring the temperature upwards from the bottom of the mould through the viscose solution until the viscose solution in the mould is completely frozen to obtain a filter material type membrane for later use;
Wherein the viscosity of the viscose solution is 15-35 s; the content of alpha-cellulose in the viscose solution is 5-10%; the alkali concentration in the viscose solution is 4-6%;
b preparation of coagulation bath
The mass ratio of water to ethanol is 99: 1-90: 10 as solvent, adding Na2SO4，ZnSO4And H2SO4Preparing a solution as a coagulating bath, and refrigerating the coagulating bath at a low temperature of-30 to-5 ℃ for later use;
Wherein Na is present in the coagulation bath2SO4A concentration of 200 to 500g/l, H2SO4ZnSO with a concentration of 50-300 g/l4The concentration is 80-200 g/l;
c shaping and washing of filter material type film
Placing the filter material type membrane prepared in the step a into the coagulating bath prepared in the step b, standing for 5-7 days for shaping at the temperature of minus 30-minus 5 ℃, placing the shaped filter material type membrane into water, soaking for 3-5 days at room temperature, and replacing the water once a day;
Preparation of d viscose-based air filtering material
And c, freezing the filter material type membrane washed in the step c in an environment at the temperature of-20 to-10 ℃, taking out after 1 to 2 days, placing the filter material type membrane in an environment at the temperature of-60 to-20 ℃ and the vacuum degree of 1 to 20Pa for freeze drying, and taking out after 3 to 4 days to obtain the viscose-based air filter material.
Technical Field
The invention relates to a preparation method of an adhesive-based air filtering material, belonging to the technical field of material engineering.
Background
in recent years, the air pollution caused by the combustion of fossil fuels such as petroleum, the emission of factory exhaust gas and the emission of automobile exhaust gas is becoming more serious, and in addition, the PM2.5 pollution caused by human activities brings great threats to human health. As far as now, biodegradable air filter materials are considered to be the most promising filter materials for development and application, with cellulose-based air filter materials being the most effective. At present, micropores in common cellulose-based porous materials are randomly distributed and are disordered. The common cellulose-based porous material has a series of problems of high air resistance, high energy consumption, low use efficiency and the like.
The viscose fiber belongs to cellulose fiber, and is prepared from natural fiber through alkalization, aging, sulfonation and other processes. In the production, cellulose sulfonate is dissolved in dilute alkali liquor to prepare viscose by wet spinning. The invention prepares the viscose fiber into the oriented film by adopting the technology of combining oriented freezing and low-temperature phase change, and the oriented film is used as an air filtering material and has the characteristics of large specific surface area, no secondary pollution and the like.
chinese patent publication No. CN104140100A, published as 11/12/2014, discloses a method for preparing microporous activated carbon for gas adsorption by vacuum freeze drying. The method has complicated steps, and the filter material can be obtained by the steps of drying, crushing, stirring and the like after freeze drying. The invention can be directly put into use after being frozen, dried and formed without other procedures.
The cellulose has the advantages of high treatment temperature of more than 250 ℃, stable property, almost no corrosion to the cellulose by common solvents, acids and alkalis, small specific gravity, strong dispersibility, large specific surface area and the like, and a large number of free hydroxyl groups exist in molecules and are easy to form hydrogen bonds with water molecules, so the cellulose has strong hygroscopicity, and in addition, the cellulose is nontoxic and pollution-free, is harmless to human bodies and the environment, and belongs to a green and environment-friendly product.
Chinese patent publication No. CN108187407A, published as No. 22/6/2018, discloses a preparation method of an air filtering material, which takes softwood cellulose as a raw material, adopts technical methods such as defibering, grinding, stirring, freezing and the like in the preparation process, and then adds polyethylene terephthalate, ZIF-8 nanocrystals and a cobalt-based MOFs material with gas adsorption property. The method is complicated, and the polyethylene terephthalate and the cobalt-containing base material have certain influence on the environment. Chinese patent publication No. CN106582113A, published as No. 26 4/2017, discloses an air filter paper material containing bacterial cellulose fibers, which is prepared by taking bacterial cellulose fibers, glass fibers, plant fibers and chemical synthetic fibers as raw materials and papermaking by a wet nonwoven fabric process. The air filter material prepared by the method needs higher pressure to ensure that air smoothly passes through the material in the using process, so that the energy consumption is high. The bacterial cellulose prepared by the method has low molecular weight and poor structural strength. In addition, the preparation process is complex and mass production is not easy to realize.
Disclosure of Invention
In view of the above problems, the present invention is to provide a method for preparing an adhesive-based air filter material.
The preparation method of the viscose-based air filter material comprises the following steps:
Preparation of a Filter type Membrane
Pouring the viscose solution into a mould, arranging a metal conductor for transferring temperature at the bottom of the mould, wherein the temperature of the metal conductor is-80 to-10 ℃, and transferring the temperature upwards from the bottom of the mould through the viscose solution until the viscose solution in the mould is completely frozen to obtain the filter material type membrane for later use.
Wherein the viscosity of the viscose solution is 15-35 s; the content of alpha-cellulose in the viscose solution is 5-10%; the alkali concentration in the viscose solution is 4-6%; the mould is a round or rectangular or square column.
b preparation of coagulation bath
The mass ratio of water to ethanol is 99: 1-90: 10 as solvent, adding Na2SO4，ZnSO4And H2SO4The prepared solution is used as a coagulating bath which is refrigerated at the low temperature of minus 30 to minus 5 ℃ for standby.
Wherein the coagulation bathIn Na2SO4A concentration of 200 to 500g/l, H2SO4ZnSO with a concentration of 50-300 g/l4the concentration is 80-200 g/l.
c shaping and washing of filter material type film
And (c) placing the filter material type membrane prepared in the step (a) into the coagulating bath prepared in the step (b), standing for 5-7 days for shaping at the temperature of-30 to-5 ℃, placing the shaped filter material type membrane into water, soaking for 3-5 days at room temperature, and replacing the water once every day.
Preparation of d viscose-based air filtering material
And c, freezing the filter material type membrane washed in the step c in an environment at the temperature of-20 to-10 ℃, taking out after 1 to 2 days, placing the filter material type membrane in an environment at the temperature of-60 to-20 ℃ and the vacuum degree of 1 to 20Pa for freeze drying, and taking out after 3 to 4 days to obtain the viscose-based air filter material.
By adopting the technical scheme, the preparation method of the invention pours the viscose solution into a mould, carries out freeze forming under the action of a metal conductor, and prepares the air filter material by utilizing a freeze drying method. The temperature of the metal conductor is-60 to-10 ℃, the temperature is transferred upwards from the bottom of the die through the viscose solution, and water molecules in the viscose solution form ice crystals under the action of low temperature and grow directionally along the temperature transfer direction. The height of the die is selected to be 3-8cm, mainly considering production efficiency. If the height range is higher than 8cm, the directional freezing time is longer, greatly reducing the production efficiency. If the height range is less than 3cm, the product height is low, the filtering effect is not obvious, and the use is influenced. Therefore, the height of the die is determined to be 3-8cm, so that the die has good production efficiency, and meanwhile, the subsequent products have good filtering effect. The shape of the mould can be round or rectangular or square. The material of the mould can be polytetrafluoroethylene or organic glass.
The method takes the existing viscose solution as a raw material, directly forms a through hole structure with the length of 10mm or more under the orientation effect, and can greatly reduce the resistance of air passing. The wall surface of the through hole structure comprises a large number of micropores, and the oriented holes arranged in parallel are connected, so that the specific surface area of the material is greatly increased. The structure has a very large surface area, can be fully contacted with air, completely adsorbs pollutants in the air, can be directly combusted and treated by using a cellulose filtering material without secondary pollution, and is an efficient and environment-friendly air filtering material. The coagulating bath used in the method can replace the whole number of the solvents after the viscose is shaped, and the obtained shaped film is more stable and efficient.
The coagulating bath used in the method is a mixed solution of water and ethanol, and the mass ratio of the water to the ethanol is 99: 1-90: 10, adding 200-500 g/l of Na2SO4，50～300g/l H2SO4，80～200g/l ZnSO4The coagulating bath is used at a low temperature of-30 to-5 ℃, and if the temperature is higher than 0 ℃, the oriented structure of the viscose fiber type membrane can be damaged, so that the material fails. The coagulating bath is at low temperature and can keep the original directional structure of the formed film. Na in coagulation bath2SO4And H2SO4NaOH in the viscose solution can be neutralized, and the existence of the NaOH can influence the shaping of the shaped membrane structure. The traditional way of preparing cellulose porous membranes is to freeze-dry an aqueous solution of cellulose directly after freezing at low temperature. The water contained in the freeze-drying process can be removed, but inorganic salts and the like used in dissolving cellulose cannot be removed. If the freeze-dried cellulosic material is exposed to water again, the dissolution may be problematic, which is very disadvantageous for subsequent product use. The technology used by the invention is low-temperature phase change technology, namely the original directional structure is preserved in a low-temperature environment, and Na is added2SO4、H2SO4And ZnSO4Under the action of the inorganic acid, the cellulose sulfonate is reduced into cellulose, and redundant inorganic salt is taken away, so that the oriented porous material only containing the cellulose is obtained, and the prepared product has good physical properties and product shape retention.
The sulfuric acid in the coagulating bath used in the method can decompose the cellulose sulfonate solution, neutralize NaOH in the viscose solution and regenerate the viscose.
the freeze drying process is to sublimate frozen water from solid state directly in high vacuum environment by means of ice crystal sublimation principle, and the dried film still has original oriented structure. The traditional method for preparing the cellulose porous membrane is to freeze and dry a cellulose aqueous solution directly at low temperature, so that a sample with a randomly distributed microporous structure can be obtained, and formed pores are in a cellular structure and are not beneficial to other pores to transfer, so that the air resistance is very high. When the traditional preparation of cellulose membrane is used as a filter material, large pressure is required to be generated on two sides of the material so as to enable other materials to pass through the porous material, the consumption of energy is high, and the filtered pollutants are accumulated on the surface of the membrane by the solution, so that the subsequent use is difficult. The invention abandons the former method, and forms a through hole structure with larger major diameter in the cellulose material by using the ice crystal as a template, and the through hole structures are vertically arranged, and the adjacent through holes are connected together through the micropores, thereby ensuring that the micropores can be communicated, greatly reducing the air resistance of the porous material and reducing the energy consumption. In addition, the communicated microporous structure can increase the specific surface area of the cellulose material and improve the filtering effect.
The viscose-based air filter material prepared by the method is simple in method, high in efficiency and easy to realize mass production. The viscose type membrane prepared by the method is convenient to use, high in energy efficiency, capable of being directly combusted after use, free of secondary pollution and environment-friendly.
Detailed Description
The present invention will be described in further detail with reference to specific examples below:
The preparation method of the viscose-based air filter material comprises the following steps:
Preparation of a Filter type Membrane
Pouring the viscose solution into a mould, arranging a metal conductor for transferring temperature at the bottom of the mould, wherein the temperature of the metal conductor is-80 to-10 ℃, and transferring the temperature upwards from the bottom of the mould through the viscose solution until the viscose solution in the mould is completely frozen to obtain the filter material type membrane for later use.
wherein the viscosity of the viscose solution is 15-35 s; the content of alpha-cellulose in the viscose solution is 5-10%; the alkali concentration in the viscose solution is 4-6%.
b preparation of coagulation bath
The mass ratio of water to ethanol is 99: 1-90: 10 as solvent, adding Na2SO4，ZnSO4And H2SO4The prepared solution is used as a coagulating bath which is refrigerated at the low temperature of minus 30 to minus 5 ℃ for standby.
Wherein Na is present in the coagulation bath2SO4A concentration of 200 to 500g/l, H2SO4ZnSO with a concentration of 50-300 g/l4The concentration is 80-200 g/l.
c shaping and washing of filter material type film
and (c) placing the filter material type membrane prepared in the step (a) into the coagulating bath prepared in the step (b), standing for 5-7 days for shaping at the temperature of-30 to-5 ℃, placing the shaped filter material type membrane into water, soaking for 3-5 days at room temperature, and replacing the water once every day.
Preparation of d viscose-based air filtering material
And c, freezing the filter material type membrane washed in the step c in an environment at the temperature of-20 to-10 ℃, taking out after 1 to 2 days, placing the filter material type membrane in an environment at the temperature of-60 to-20 ℃ and the vacuum degree of 1 to 20Pa for freeze drying, and taking out after 3 to 4 days to obtain the viscose-based air filter material.
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