CN113150336A - Method for preparing high-crystallization high-orientation regenerated cellulose material by high-voltage electrostatic field assisted self-assembly and product - Google Patents
Method for preparing high-crystallization high-orientation regenerated cellulose material by high-voltage electrostatic field assisted self-assembly and product Download PDFInfo
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- CN113150336A CN113150336A CN202110295844.3A CN202110295844A CN113150336A CN 113150336 A CN113150336 A CN 113150336A CN 202110295844 A CN202110295844 A CN 202110295844A CN 113150336 A CN113150336 A CN 113150336A
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Abstract
The invention discloses a method for preparing a high-crystallization high-orientation regenerated cellulose material by high-voltage electrostatic field assisted self-assembly and a product thereof, wherein the method comprises the following steps: (1) dissolving a cellulose raw material in a dissolving solution to obtain a cellulose solution; (2) coating the cellulose solution on a substrate, and drying the substrate in a high-voltage electrostatic field to form a film; (3) and after film formation, post-treatment is carried out to obtain the high-crystallization high-orientation regenerated cellulose material. The invention adopts a method of high-voltage electrostatic field assisted self-assembly, can accurately and controllably prepare the regenerated cellulose material with high crystallization and high orientation, and the regenerated cellulose material has obvious high orderliness on structure.
Description
Technical Field
The invention relates to the technical field of material preparation, in particular to a method for preparing a high-crystallization high-orientation regenerated cellulose material by high-voltage electrostatic field assisted self-assembly and a product.
Background
Natural crystalline polysaccharides, such as cellulose, are a material having excellent properties of biocompatibility, biodegradability and non-toxicity, and have been the focus of research. However, the microstructure of the regenerated cellulose material prepared by the prior art is mostly disordered or short-range ordered, and the crystallinity and the orientation degree are low, so the application of the regenerated cellulose material is greatly limited.
The chinese patent application No. 201510255365.3 discloses a method for preparing a highly oriented polysaccharide cellulose material, which utilizes a directional temperature field freezing technique to control the growth direction of ice crystals, thereby forming a highly oriented cellulose material. However, the preparation process is relatively complex, the cost consumption is high, and the orientation degree cannot be accurately controlled.
The chinese patent application No. 201611062361.4 discloses a method for preparing a highly oriented cellulose film, which mainly uses an oriented stretching method to stretch and fix a cellulose film plasticized by an ionic liquid, and removes the plasticizer in a stretched state, thereby preparing a cellulose film with high strength and high orientation.
Although the prior art orients cellulose films to improve their properties, the search for new methods for regulating the microstructure of regenerated cellulose materials is still of great significance in the field of the preparation of new cellulose materials. Self-assembly is a controllable preparation process, and how to regulate and control the microstructure of the regenerated cellulose material through self-assembly of regenerated cellulose macromolecules needs to be deeply developed.
Disclosure of Invention
In order to prepare the regenerated cellulose material with high crystallization and high orientation, improve the comprehensive performance of the regenerated cellulose material and expand the application range of the regenerated cellulose material, the invention provides a method for preparing the regenerated cellulose material with high crystallization and high orientation by high-voltage electrostatic field assisted self-assembly.
The technical scheme of the invention is as follows:
a method for preparing a high-crystalline high-orientation regenerated cellulose material by high-voltage electrostatic field assisted self-assembly comprises the following steps:
(1) dissolving a cellulose raw material in a dissolving solution to obtain a cellulose solution;
(2) coating the cellulose solution on a substrate, and drying the substrate in a high-voltage electrostatic field to form a film;
(3) and after film formation, post-treatment is carried out to obtain the high-crystallization high-orientation regenerated cellulose material.
The polymerization degree of cellulose molecules of the cellulose raw material is 100-2000; the viscosity average molecular weight of the cellulose raw material is 1.62 multiplied by 104～3.24×105。
Further preferably, the cellulose raw material is at least one of cotton linter pulp, absorbent cotton pulp and wood pulp.
The dissolving solution is at least one of an NMMO aqueous solution, a lithium chloride (LiCl)/N, N-Dimethylformamide (DMAC) system, an alkali/urea system and an alkali/thiourea system.
Preferably, the concentration of the cellulose in the cellulose solution is 1-8 wt%; it is further preferred that the concentration of cellulose is 2-6 wt%.
The polymerization degree and concentration of the cellulose raw material directly influence the solubility of the cellulose raw material in the dissolving solution, and the cellulose raw material cannot be completely dissolved in the dissolving solution due to the excessive polymerization degree or the excessive concentration, so that a uniform and stable regenerated cellulose solution cannot be obtained.
In the step (1), the cellulose is dissolved in the dissolving solution by stirring at a stirring speed of 300-2000 rpm.
In step (2), the cellulose solution may be coated onto the substrate by dipping, knife coating, brush coating, or the like.
The substrate is a flat substrate and can be one of a glass sheet, a polyethylene terephthalate (PET) plate, a polypropylene (PP) plate and a Polytetrafluoroethylene (PTFE) plate.
Preferably, in step (2), the coating thickness of the cellulose solution is 100-.
When the coating thickness is small, the regenerated cellulose content in the solution is small, so that the crystallinity is low. When the concentration of the cellulose solution is further increased, the effective crystallinity of the cellulose solution is increased. However, when the coating thickness is too high, the regenerated cellulose content in the solution is too high, so that the movement of the regenerated cellulose is limited in the high-voltage electrostatic self-assembly process, and the orientation degree of the regenerated cellulose is influenced.
It is further preferred that the coating thickness is 100-.
Preferably, in the step (2), drying the film in a high-voltage electrostatic field for 12 to 48 hours; more preferably, the mixture is placed in a high-voltage electrostatic field to be dried into a film for 12 to 24 hours.
Preferably, the electric field intensity of the high-voltage electrostatic field is 600-2000V-cm-1。
The electric field intensity of the high-voltage electrostatic field is changed by adjusting the voltage of the high-voltage electrostatic field and the distance between the electric fields (the distance between the positive electrode plate and the negative electrode plate). When the voltage is larger and the electric field distance is smaller, the electric field intensity of the obtained high-voltage electrostatic field is stronger. When the electric field intensity is too weak, a highly crystalline, highly oriented regenerated cellulose material cannot be obtained.
Further preferably, the voltage of the high-voltage electrostatic field is 10-24 kV; the electric field distance is 10-25 cm; preferably, the voltage of the high-voltage electrostatic field is 12-20 kV; the electric field distance is 10-20 cm.
In the step (3), the post-treatment comprises the following steps: and (3) placing the film-formed cellulose material into deionized water, cleaning and drying.
The drying is natural drying or vacuum heating drying.
Preferably, the drying is vacuum heating drying; the heating temperature is 40-80 ℃; the relative vacuum degree is 0 to-60 KPa.
The invention also provides a high-crystallization high-orientation regenerated cellulose material prepared by the method.
Compared with the prior art, the invention has the beneficial effects that:
the invention adopts a method of high-voltage electrostatic field assisted self-assembly, can accurately and controllably prepare the regenerated cellulose material with high crystallization and high orientation, and the regenerated cellulose material has obvious high orderliness on structure, thereby greatly widening the practical application range of the regenerated cellulose material.
The preparation process is simple, can realize large-area production, does not use toxic organic reagents, is green and renewable in raw materials, and has great significance in the field of environmental protection.
Drawings
FIGS. 1 (a) and (b) are SEM electron micrographs of the regenerated cellulose material of example 3 and comparative example 1, respectively;
fig. 2 is XRD patterns of the regenerated cellulose materials of example 3 and comparative example 1.
Detailed Description
Example 1
Taking cellulose (viscosity average molecular weight M)η＝9.72×104)4 g, 100 g of mixed aqueous solution of 7 wt% sodium hydroxide and 12 wt% urea (namely 7 wt% sodium hydroxide and 12 wt% urea) is added, stirred in an ice-water bath for 10 minutes, then placed in a refrigerator for freezing for 3 hours, taken out and fully stirred to obtain colorless transparent solution. After a small amount of undissolved cellulose is removed by filtration, a film is scraped on glass, the glass is placed in a high-voltage electrostatic field, the voltage of the electrostatic field is 14kV, the distance between a positive electrode plate and a negative electrode plate is 15cm, and after the film is formed, the glass is cleaned and dried at 40 ℃ in vacuum, so that the regenerated cellulose material with high crystallization and high orientation is obtained.
Example 2
Taking cellulose (viscosity average molecular weight M)η＝9.72×104)4 g, 100 g of 7 wt%/12 wt% aqueous alkali urea solution is added, stirred in an ice-water bath for 10 minutes, then placed in a refrigerator for freezing for 3 hours, taken out and fully stirred to obtain a colorless transparent solution. After a small amount of undissolved cellulose is removed by filtration, a film is scraped on glass, the glass is placed in a high-voltage electrostatic field, the voltage of the electrostatic field is 16kV, the distance between a positive electrode plate and a negative electrode plate is 15cm, and after the film is formed, the glass is cleaned and dried at 40 ℃ in vacuum, so that the regenerated cellulose material with high crystallization and high orientation is obtained.
Example 3
Taking cellulose (viscosity average molecular weight M)η＝9.72×104)4 g, 100 g of 7 wt%/12 wt% aqueous alkali urea solution is added, stirred for 10 minutes in an ice-water bath and then placed in a refrigeratorFreezing for 3 hours, taking out and fully stirring to obtain a colorless transparent solution. After a small amount of undissolved cellulose is removed by filtration, a film is scraped on glass, the glass is placed in a high-voltage electrostatic field, the voltage of the electrostatic field is 18kV, the distance between a positive electrode plate and a negative electrode plate is 15cm, and after the film is formed, the glass is cleaned and dried at 40 ℃ in vacuum, so that the regenerated cellulose material with high crystallization and high orientation is obtained.
Example 4
Taking cellulose (viscosity average molecular weight M)η＝9.72×104)4 g, 100 g of 7 wt%/12 wt% aqueous alkali urea solution is added, stirred in an ice-water bath for 10 minutes, then placed in a refrigerator for freezing for 3 hours, taken out and fully stirred to obtain a colorless transparent solution. After a small amount of undissolved cellulose is removed by filtration, a film is scraped on glass, the glass is placed in a high-voltage electrostatic field, the voltage of the electrostatic field is 20kV, the distance between a positive electrode plate and a negative electrode plate is 15cm, and after the film is formed, the glass is cleaned and dried at 40 ℃ in vacuum, so that the regenerated cellulose material with high crystallization and high orientation is obtained.
Comparative example 1
Taking cellulose (viscosity average molecular weight M)η＝9.72×104)4 g, 100 g of 7 wt%/12 wt% aqueous alkali urea solution is added, stirred in an ice-water bath for 10 minutes, then placed in a refrigerator for freezing for 3 hours, taken out and fully stirred to obtain a colorless transparent solution. After a small amount of undissolved cellulose was removed by filtration, the film was scraped off from the glass, and the film was naturally formed at room temperature in the same manner as in example 3, and then washed and dried at 40 ℃.
The method for calculating the crystallinity and orientation degree of the regenerated cellulose material comprises the following steps:
XRD analysis was performed using X-ray diffractometer model D8 Advance, brueck, germany: cu (Kalpha) ray, voltage 40kV, current 40mA, scanning range 2 theta of 5-50 DEG, and scanning speed of 2 DEG cm-1The crystallinity calculation was performed according to the two-phase structure theory method using the following formula:
Xc＝(Sc/(Sc+Sa)
in the formula: scAnd SaThe areas of diffraction of the crystalline and amorphous regions of regenerated cellulose in the sample, respectively.
Use ofThe orientation degree analysis was carried out on a two-dimensional X-ray diffractometer model D8 Discover from Bruker, Germany: the test voltage was 40kV, the current was 40mA, and the incident X-ray wavelength was 1.5418X 10-10And m is selected. According to the measured two-dimensional diffraction pattern, integrating each crystal face (shown as bright spots on the two-dimensional pattern) to obtain a one-dimensional diffraction peak pattern, performing fitting peak separation processing by a computer, and calculating the orientation degree according to the following formula:
fc＝(180°-H°)/180°
in the formula: f. ofcIs the degree of orientation; h is the peak width at half height.
In FIG. 1, (a) and (b) are SEM images of the regenerated cellulose film of example 3 self-assembled by high-voltage static electricity and comparative example 1 under natural drying, respectively. It can be found from the figure that compared with the regenerated cellulose membrane which is naturally dried, the regenerated cellulose membrane which is self-assembled by high-voltage static electricity has an obvious orientation structure, the direction of the orientation structure is consistent with the direction of a high-voltage static field, and the high-voltage static electricity method is used for self-assembling the regenerated cellulose membrane in the drying process, so that the ordered structure is obtained, and the orientation degree of the ordered structure is greatly improved.
Meanwhile, the XRD patterns of the regenerated cellulose films obtained in example 3 and comparative example 1 are shown in fig. 2, and comparative analysis shows that diffraction peaks of regenerated cellulose appear at 12.4 °, 20.2 ° and 21.9 °, thus confirming the formation of regenerated cellulose.
The calculation of the crystallinity and the orientation degree shows that compared with the comparative example 1, the crystallinity and the orientation degree of the regenerated cellulose membrane obtained by high-voltage electrostatic self-assembly in the example 3 are greatly improved, which shows that the high-voltage electrostatic self-assembly method can effectively improve the crystallinity and the orientation degree of the material.
The above-mentioned embodiments are intended to illustrate the technical solutions and advantages of the present invention, and it should be understood that the above-mentioned embodiments are only specific embodiments of the present invention, and are not intended to limit the present invention, and any modifications, additions, equivalents, etc. made within the scope of the principles of the present invention should be included in the scope of the present invention.
Claims (10)
1. A method for preparing a high-crystallization high-orientation regenerated cellulose material by high-voltage electrostatic field assisted self-assembly is characterized by comprising the following steps:
(1) dissolving a cellulose raw material in a dissolving solution to obtain a cellulose solution;
(2) coating the cellulose solution on a substrate, and drying the substrate in a high-voltage electrostatic field to form a film;
(3) and after film formation, post-treatment is carried out to obtain the high-crystallization high-orientation regenerated cellulose material.
2. The method for preparing the high-crystallization high-orientation regenerated cellulose material by self-assembly assisted by the high-voltage electrostatic field according to claim 1, wherein the polymerization degree of cellulose molecules of the cellulose raw material is 100-2000.
3. The method for preparing the high-crystallization high-orientation regenerated cellulose material by self-assembly assisted by the high-voltage electrostatic field according to claim 2, wherein the cellulose raw material is at least one of cotton linter pulp, absorbent cotton pulp and wood pulp.
4. The method for preparing the high-crystalline high-orientation regenerated cellulose material by self-assembly assisted by the high-voltage electrostatic field according to claim 1, wherein the concentration of the cellulose in the cellulose solution is 1-8 wt%.
5. The method for preparing high-crystalline high-orientation regenerated cellulose material by self-assembly assisted by high-voltage electrostatic field as claimed in claim 1, wherein the coating thickness of the cellulose solution in step (2) is 100-2000 μm.
6. The method for preparing the high-crystalline high-orientation regenerated cellulose material by self-assembly assisted by the high-voltage electrostatic field according to claim 1, characterized in that in the step (2), the film is dried in the high-voltage electrostatic field for 12-48 h.
7. The high voltage electrostatic field of claim 1 or 6 is assisted byThe method for assembling and preparing the high-crystalline high-orientation regenerated cellulose material is characterized in that the electric field intensity is 600-2000V-cm-1。
8. The method for preparing the high-crystalline high-orientation regenerated cellulose material by the self-assembly assisted by the high-voltage electrostatic field according to claim 1, wherein in the step (3), the post-treatment is as follows: and (3) placing the film-formed cellulose material into deionized water, cleaning and drying.
9. The method for preparing the high-crystalline high-orientation regenerated cellulose material by the self-assembly assisted by the high-voltage electrostatic field according to claim 8, wherein the drying is vacuum heating drying; the heating temperature is 40-80 ℃; the relative vacuum degree is 0 to-60 KPa.
10. A highly crystalline, highly oriented regenerated cellulose material prepared by the process of any one of claims 1 to 9.
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Citations (5)
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| JP2001129839A (en) * | 1999-08-25 | 2001-05-15 | Konica Corp | Method for producing cellulose ester film and cellulose ester film |
| JP2008201046A (en) * | 2007-02-21 | 2008-09-04 | Fujifilm Corp | Manufacturing method of cellulose ester film |
| CN101270198A (en) * | 2008-05-15 | 2008-09-24 | 东华大学 | Method for electrostatic blending polyacrylonitrile/glycol cellulose nano-fibrous membrane |
| US20120328885A1 (en) * | 2011-06-21 | 2012-12-27 | Applied Materials, Inc. | Deposition of polymer films by electrospinning |
| CN111607106A (en) * | 2020-05-21 | 2020-09-01 | 浙江理工大学 | Dissolving of cellulose and preparation method of regenerated cellulose |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001129839A (en) * | 1999-08-25 | 2001-05-15 | Konica Corp | Method for producing cellulose ester film and cellulose ester film |
| JP2008201046A (en) * | 2007-02-21 | 2008-09-04 | Fujifilm Corp | Manufacturing method of cellulose ester film |
| CN101270198A (en) * | 2008-05-15 | 2008-09-24 | 东华大学 | Method for electrostatic blending polyacrylonitrile/glycol cellulose nano-fibrous membrane |
| US20120328885A1 (en) * | 2011-06-21 | 2012-12-27 | Applied Materials, Inc. | Deposition of polymer films by electrospinning |
| CN111607106A (en) * | 2020-05-21 | 2020-09-01 | 浙江理工大学 | Dissolving of cellulose and preparation method of regenerated cellulose |
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