阅读说明：本技术 成型粉末碱溶法制备芳纶纳米纤维的方法 (Method for preparing aramid nano-fiber by molding powder alkali dissolution method ) 是由 张学同 刘增伟 于 2019-09-29 设计创作，主要内容包括：本发明公开了一种成型粉末碱溶法制备芳纶纳米纤维的方法,其包括：在空气气氛或保护性气氛中,使包含芳纶粉末、碱以及溶剂的混合反应体系于室温～80℃条件下反应4～100h,获得芳纶纳米纤维散液。本发明实施例提供的成型粉末碱溶法制备芳纶纳米纤维的方法解决了现有技术中存在的反应时间耗时过长、原材料昂贵、反应浓度低、生产效率低下等问题；基由本发明提供的方法所获得的芳纶纳米纤维强度高、耐高温性能优异、稳定性好,在复合材料、生物、医药、电子、能源等领域具有广阔的应用前景。(The invention discloses a method for preparing aramid nano-fiber by a molded powder alkali dissolution method, which comprises the following steps: and reacting the mixed reaction system containing aramid fiber powder, alkali and a solvent for 4-100 hours at room temperature-80 ℃ in an air atmosphere or a protective atmosphere to obtain the aramid fiber nano-fiber dispersion liquid. The method for preparing the aramid nano-fiber by the molding powder alkali dissolution method provided by the embodiment of the invention solves the problems of overlong reaction time, expensive raw materials, low reaction concentration, low production efficiency and the like in the prior art; the aramid nano-fiber obtained by the method provided by the invention has the advantages of high strength, excellent high-temperature resistance and good stability, and has wide application prospect in the fields of composite materials, biology, medicine, electronics, energy and the like.)

1. A method for preparing aramid nano-fiber by a molding powder alkali dissolution method is characterized by comprising the following steps:

and reacting the mixed reaction system containing aramid fiber powder, alkali and a solvent for 4-100 hours at room temperature-80 ℃ in an air atmosphere or a protective atmosphere to obtain the aramid fiber nano-fiber dispersion liquid.

2. The method for preparing the aramid nano-fiber by the alkali dissolution method of the molding powder according to claim 1, which is characterized in that: the dosage ratio of the aramid fiber powder, the alkali and the solvent is 0.5-20 g: 0.5-10 g: 100 ml.

3. The method for preparing the aramid nanofibers by the alkali dissolution method of the molding powder according to claim 1 or 2, characterized in that: the alkali comprises any one of organic alkali and inorganic alkali; preferably, the inorganic base comprises any one or a combination of more than two of calcium hydroxide, sodium hydroxide and potassium hydroxide; preferably, the organic base comprises an organic base containing metal ions or no metal ions; preferably, the organic base containing metal ions comprises any one or a combination of more than two of sodium tert-butoxide, potassium tert-butoxide, n-butyllithium, potassium hexamethyldisilazide, sodium hexamethyldisilazide and lithium diisopropylamide; the organic base without metal ions comprises any one or the combination of more than two of triethylamine, triethylene diamine, 1, 8-diazabicycloundec-7-ene, 1, 5-diazabicyclo [4.3.0] -5-nonene, 4-dimethylaminopyridine, pyridine, N-methylmorpholine, tetramethylethylenediamine and tetramethylguanidine.

4. The method for preparing the aramid nanofibers by the alkali dissolution method of the molding powder according to claim 1 or 2, characterized in that: the solvent comprises an organic solvent, and the organic solvent comprises any one or a combination of more than two of dimethylformamide, dimethyl sulfoxide, N-methyl pyrrolidone, formic acid, methanol, ethanol and water.

5. The method for preparing the aramid nano-fiber by the alkali dissolution method of the molding powder according to claim 1, which is characterized in that: the aramid powder includes para-aramid and/or meta-aramid.

6. The method for preparing the aramid nanofibers by the alkali dissolution method of the molding powder according to claim 1 or 5, characterized by comprising: the aramid fiber powder is obtained by adopting a mode of in-situ polymerization purification grinding, aramid fiber grinding or aramid chopped grinding.

7. The method for preparing the aramid nano-fiber by the alkali dissolution method of the molding powder according to claim 1, which is characterized in that: the particle size of the aramid fiber powder is 10-600 mu m.

8. The method for preparing the aramid nano-fiber by the alkali dissolution method of the molding powder according to claim 1, which is characterized in that: the purity of the aramid fiber powder is 30-100%.

9. The method for preparing the aramid nano-fiber by the alkali dissolution method of the molding powder according to claim 1, which is characterized in that: the concentration of the aramid nano-fiber dispersion liquid is 0.1-20%.

10. The method for preparing the aramid nano-fiber by the alkali dissolution method of the molding powder according to claim 1, which is characterized in that: the diameter of the aramid nano-fiber is 20 +/-15 nm.

Technical Field

The invention relates to a preparation method of nano-fibers, in particular to a method for preparing aramid nano-fibers by a formed powder alkali dissolution method, and belongs to the technical field of nano-materials.

Background

Aramid fiber (PPTA) is an excellent high-performance chemical fiber with high strength, excellent flame retardant property, good heat resistance and good chemical stability, and is an important material in the fields of national defense, aerospace, petrochemical industry and the like. The aramid fiber has the characteristics of high strength and high temperature resistance due to a rigid chain structure formed by pi-pi conjugation among internal molecular chains of the aramid fiber, intermolecular hydrogen bonds, van der waals acting force and the like, but the aramid fiber also has few surface active groups and is difficult to compound with other materials, so that the application of the aramid fiber in the fields of composite materials, nano materials, biomedical materials and the like is limited. Aramid nanofibers are a polymer nanofiber material that has emerged in this year. First, by a chemical alkali dissolution method (Yang M, Cao K, Sui L, et al.dispersions of aromatic nanofibers: a new nanoscale building block [ J ]. Acs Nano, 2011, 5 (9): 6945-54.) taught by the American group of subjects of Nicholas A.Kotov, aramid fibers were mixed with KOH and dimethyl sulfoxide and continuously stirred at room temperature for 7-10 days to obtain an ANFs/DMSO dispersion. The nanofiber has a unique structure with a large length-diameter ratio, and has excellent mechanical properties and high-temperature resistance of aramid fiber materials; compared with aramid fiber, the aramid nanofiber has wider application prospects in the fields of composite materials, biology, medicines, electronics, energy sources and the like.

However, in the existing aramid fiber preparation method, a KOH/DMSO strong base system is used for destroying the hydrogen bond effect among aramid fiber molecular chains, and meanwhile, an N-H bond on an amide bond is deprotonated to form nitrogen anions, so that a negatively charged molecular chain is formed, and the aramid fiber nanofibers are dispersed under the mutual action of electrostatic repulsion, a rigid chain structure formed by pi-pi conjugation and van der Waals acting force; however, the method is long in time (180-300 h), the raw materials are expensive (aramid fibers), and the concentration of the obtained fiber dispersion liquid is low, so that the method only has laboratory research value, and almost has no industrial production and commercial value.

Disclosure of Invention

The invention mainly aims to provide a method for preparing aramid nano-fibers by a molding powder alkali-dissolution method, so as to overcome the defects in the prior art. The method provided by the invention has the advantages of short time consumption (4-100 h), cheap and easily-obtained raw materials, high concentration (up to 20%) of the obtained aramid nano-fiber dispersion liquid, capability of directly modifying continuous production on the existing aramid preparation production line, and huge industrialization and commercialization potentials.

In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:

the embodiment of the invention provides a method for preparing aramid nano-fiber by a molded powder alkali-dissolution method, which comprises the following steps:

and reacting the mixed reaction system containing aramid fiber powder, alkali and a solvent for 4-100 hours at room temperature-80 ℃ in an air atmosphere or a protective atmosphere to obtain the aramid fiber nano-fiber dispersion liquid.

Furthermore, the dosage ratio of the aramid fiber powder, the alkali and the solvent is 0.5-20 g: 0.5-10 g: 100 ml.

Further, the base includes any one of an organic base and an inorganic base.

Preferably, the inorganic base includes any one or a combination of two or more of calcium hydroxide, sodium hydroxide and potassium hydroxide, but is not limited thereto.

Preferably, the organic base comprises an organic base containing metal ions or no metal ions.

Preferably, the organic base containing metal ions includes any one or a combination of two or more of sodium tert-butoxide, potassium tert-butoxide, n-butyllithium, KHMDS (potassium hexamethyldisilazide), NaHMDS (sodium hexamethyldisilazide), LDA (lithium diisopropylamide), but is not limited thereto; the metal ion-free organic base includes any one or a combination of two or more of triethylamine, triethylenediamine, DBU (1, 8-diazabicycloundecen-7-ene), DBN (1, 5-diazabicyclo [4.3.0] -5-nonene), DMAP (4-dimethylaminopyridine), pyridine, N-methylmorpholine, tetramethylethylenediamine, and TMG (tetramethylguanidine), but is not limited thereto.

Further, the solvent includes an organic solvent including any one or a combination of two or more of DMF (dimethylformamide), DMSO (dimethyl sulfoxide), NMP (N-methylpyrrolidone), formic acid, methanol, ethanol, and water, but is not limited thereto.

Further, the aramid powder comprises para-aramid and/or meta-aramid.

Furthermore, the aramid powder can be obtained by adopting in-situ polymerization purification grinding, aramid fiber grinding or aramid chopped grinding or the like, or can be obtained by adopting waste aramid product grinding.

In some more specific embodiments, the particle size of the aramid powder is 10 to 600 μm.

Furthermore, the purity of the aramid fiber powder is 30-100%, and impurities except strong acid can be contained in the aramid fiber powder.

Further, the concentration of the aramid nano-fiber dispersion liquid is 0.1-20%.

Further, the diameter of the aramid nano-fiber is 20 +/-15 nm.

Compared with the prior art, the invention has the advantages that:

(1) according to the method for preparing the aramid nano-fiber by the molding powder alkali dissolution method, the intermediate aramid powder in the aramid fiber preparation process is used as the raw material, so that the problem that the aramid fiber skin layer is increased due to spinning hot pressing and other processes in the aramid nano-fiber preparation process is solved, the contact area of the aramid fiber and an alkali dissolution system is increased, the deprotonation process is accelerated, the preparation flow of the aramid nano-fiber is greatly simplified, the preparation efficiency of the aramid nano-fiber is obviously improved, and the method has great potential for industrial production;

(2) the method for preparing the aramid nano-fiber by the molding powder alkali dissolution method provided by the embodiment of the invention solves the problems of overlong reaction time, expensive raw materials, low reaction concentration, low production efficiency and the like in the prior art; the aramid nano-fiber obtained by the method provided by the invention has the advantages of high strength, excellent high-temperature resistance and good stability, and has wide application prospect in the fields of composite materials, biology, medicine, electronics, energy and the like.

Drawings

Fig. 1 is a scanning electron microscope photograph of the aramid nanofibers obtained in example 1 of the present invention;

fig. 2 is a TG curve of the aramid nanofibers obtained in example 1 of the present invention;

fig. 3 is an SEM photograph of the aramid nanofibers obtained in example 2 of the present invention;

fig. 4 is an SEM photograph of the aramid nanofibers obtained in example 2 of the present invention.

Detailed Description

In view of the deficiencies in the prior art, the inventors of the present invention have made extensive studies and extensive practices to provide technical solutions of the present invention. The technical solution, its implementation and principles, etc. will be further explained as follows.

According to the method for preparing the aramid nano-fiber by the molding powder alkali dissolution method, an alkali dissolution system (namely an alkaline solution formed by alkali and a solvent) is added before the nano-fiber is tightly stacked to form a sheath-core structure due to the fact that a micron-sized aramid fiber (the diameter of the aramid fiber is micron level and the aramid fiber is composed of the nano-fiber) is prepared by the aramid polymer (ppta) through a spinning process from powder, so that the reaction area is remarkably increased, the interference of a compact sheath layer on the reaction is removed, and the aramid fiber is more easily subjected to deprotonation reaction with the alkali dissolution system; the method fully utilizes an alkali dissolution system, greatly shortens the reaction time (the shortest time is 4 hours), simultaneously greatly improves the concentration of the aramid nano-fiber dispersion system (the maximum concentration can reach 20 percent), and has great industrial and commercial potential.

The aramid fiber is in a skin-core structure with a large number of nano fibers wrapped by skins, and the traditional aramid nanofiber preparation process is to obtain the aramid fiber after dissolving and spinning powder, and then remove the skin structure through alkali dissolution to obtain the aramid nanofiber; because the nano-fibers in the aramid fibers formed by spinning are tightly stacked and the outer skins are thick, the aramid fibers prepared by the traditional process are seriously influenced by the skin layer structure, and the invention bypasses the step of forming the skin layers and directly obtains the nano-fibers.

The technical solution of the present invention is further described in detail by several embodiments and with reference to the accompanying drawings. However, the selected examples are only for explaining the technical solution of the present invention, and do not limit the scope of the present invention.