CN109228420B - High-strength bacterial cellulose membrane, preparation method thereof, product and preparation method of product - Google Patents
High-strength bacterial cellulose membrane, preparation method thereof, product and preparation method of product Download PDFInfo
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- CN109228420B CN109228420B CN201810905530.9A CN201810905530A CN109228420B CN 109228420 B CN109228420 B CN 109228420B CN 201810905530 A CN201810905530 A CN 201810905530A CN 109228420 B CN109228420 B CN 109228420B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D7/00—Producing flat articles, e.g. films or sheets
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- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
- B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
Abstract
The invention relates to a high-strength bacterial cellulose membrane, a preparation method thereof, a product and a preparation method of the product, wherein the preparation method of the high-strength bacterial cellulose membrane comprises the following steps: soaking the wet bacterial cellulose basement membrane in a solvent and stretching to prepare a high-strength bacterial cellulose membrane; the solvent is NMP, NMMO or ethanolamine, and the concentration of NMMO is 50 wt%. The prepared high-strength bacterial cellulose membrane has a dry thickness of more than or equal to 50 mu m and a tensile strength of more than or equal to 400 MPa. The method for preparing the ultrathin and ultrastrong nanofiber membrane from the high-strength bacterial cellulose membrane comprises the following steps: and stripping the surface part of the dry high-strength bacterial cellulose membrane by adopting a micro-mechanical stripping method, and then stripping the rest part by pulling the stripped part to obtain the product. The thickness of the ultra-thin super-strong nanofiber membrane in a dry state is less than or equal to 10 microns, and the tensile strength is more than or equal to 400 MPa. The preparation method of the invention has simple process and low cost; the prepared product has thin thickness and high tensile strength.
Description
Technical Field
The invention belongs to the field of membranes, and relates to a high-strength bacterial cellulose membrane and a preparation method thereof, an ultrathin and ultrastrong nanofiber membrane prepared from the high-strength bacterial cellulose membrane and a preparation method thereof.
Background
The nano-fiber membrane is also called nano-fiber paper, and is a thin membrane prepared by filtering, casting or dipping nano-cellulose or a nano-fiber compound. Among them, filtration is the simplest method, which is to remove the solvent from the nanocellulose solution system by gravity or vacuum suction force, and then dry it at a certain temperature and pressure to obtain the nanofiber membrane, and patent CN 102787518A obtains a cotton cellulose nanofibril membrane by chemical pretreatment, mechanical separation and suction filtration of cotton to form a membrane. The casting is to cast a prepared nanocellulose solution into a mold, then evaporate the solvent by a certain treatment method, and the patent CN 105107390A pours the casting solution obtained after modifying the nanocellulose into a casting film forming container, and after standing in vacuum and removing bubbles, puts into a baking oven, and after the solvent is completely evaporated, the modified CNFs film is obtained. The impregnation is mainly used for preparing a nanofiber composite membrane, and patent CN 105107390A discloses a preparation method of a cellulose acetate/nano-cellulose blended ultrafiltration membrane, wherein a product membrane is obtained by carrying out membrane scraping, membrane forming and the like on a cellulose acetate/nano-cellulose blended liquid.
Although the nanofiber membrane can be obtained by the method, the filtering, casting and dipping processes are accompanied with the disordering process of the nanocellulose, so that the excellence on the nanometer scale in the nanofiber membrane cannot be reflected, and the mechanical property of the macroscopic nanofiber membrane is poor (the strength is lower than 100 MPa). Therefore, how to better embody the nanometer scale superiority in the nanometer cellulose membrane becomes a great research hotspot at present.
The stretching orientation is the simplest method for orderly arranging the nano fibers, the mechanical strength of the film and the fibers can be greatly improved through simple stretching, and the orientation degree of cellulose molecules in a matrix is improved through stretching, so that the mechanical property of a macroscopic material is improved. The patent CN 104610557A discloses a regenerated cellulose membrane, a functional membrane and a preparation method thereof, wherein cellulose/ionic solution is shaped by a method of die head extrusion, calendaring or tape casting, a cellulose gel membrane is formed by a coagulating bath after shaping, and finally the gel membrane is subjected to biaxial tension, and the tensile strength of the membrane after biaxial tension is 80-210 MPa. Although the orientation degree of cellulose fibers in the film is improved to a certain degree, a large amount of intermolecular and intramolecular hydrogen bonds exist among cellulose molecules, and the orientation among the nano fibers is hindered in the stretching process due to the existence of the acting force, so that the maximum orientation of the nano fibers cannot be realized.
Bacterial cellulose is a novel biological nanomaterial with an ultrafine fibrous network produced by fermentation of microorganisms such as Acetobacter. During the synthesis process, glucose chains generated in bacteria are extruded through micropores on cell envelopes, then the glucose chains are combined to form microfibers, the microfibers are further aggregated to form cellulose bands, namely nanofibers, then the nanofibers generate a net structure, a large number of gaps exist among the fibers, and since a plurality of hydroxyl groups exist on the surfaces of the nanofibers, the hydroxyl groups can form hydrogen bonds pairwise or form hydrogen bonds with water molecules to retain the water molecules in the network, the bacteria cellulose exists in a gel state in a macroscopic state, and the water content in the bacteria cellulose is high. And because the cultured bacteria are aerobic bacteria and can only produce bacterial cellulose under the action of oxygen, the bacterial cellulose is produced at an air-water interface, and the film grows downwards to a certain thickness along with the prolonging of the culture time until all cells trapped in the film become ineffective or die due to oxygen deficiency. The resulting bacterial cellulose gel (film) is actually formed from a large number of thin nearly parallel cellulose layers. Strong hydrogen bonding also exists between these parallel thin cellulose layers. The BC (bacterial cellulose) nano-fiber is researched and found to be the finest natural fiber at present, the cross section of the BC nano-fiber is rectangular, the length and the width of the BC nano-fiber are respectively 6-10 nm and 70-80 nm, and the length of the BC nano-fiber is 1-9 microns. Compared with other cellulose nanofibers, the BC fiber has a larger length-diameter ratio (larger than 100), higher crystallinity (70-89%) and excellent mechanical properties (Young modulus reaches 114GPa), however, due to the characteristic of disordered movement of bacteria, the nanofiber forms a disordered structure through hydrogen bonding, and the disordered structure greatly influences the mechanical properties of the bacterial cellulose nanofiber.
Therefore, the method has practical significance for improving the orientation degree of the nanofiber and further improving the mechanical property of the bacterial cellulose nanofiber by destroying the hydrogen bond effect on the bacterial cellulose nanofiber scale.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, provides a method for improving the orientation degree of nanofibers by breaking the hydrogen bonding effect on the dimension of the bacterial cellulose nanofibers and a high-strength bacterial cellulose membrane prepared by the method, and also provides a method for preparing an ultrathin and ultrastrong nanofiber membrane from the high-strength bacterial cellulose membrane and a prepared ultrathin and ultrastrong nanofiber membrane.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of a high-strength bacterial cellulose membrane comprises the steps of soaking a wet bacterial cellulose base membrane in a solvent and stretching to obtain the high-strength bacterial cellulose membrane; the solvent is NMP, NMMO or ethanolamine, wherein the concentration of NMMO is 50 wt%. The concentration of NMMO is too high, the activity of oxygen anions in the system is too strong, the crystal structure of the bacterial cellulose is damaged, the concentration of NMMO is too low, the activity of oxygen in the system is too weak, and hydrogen bonds among the bacterial cellulose nanofibers are difficult to damage. According to the invention, the solvent containing oxygen atoms is selected, the activity of the oxygen atoms is specific, the hydrogen bonding effect on the bacterial cellulose nanofiber scale can be damaged, and the hydrogen bonding effect between the bacterial cellulose macromolecules is hardly influenced, so that the bacterial cellulose base film is easily oriented in the stretching process to obtain higher orientation degree, and simultaneously keeps higher crystallinity, and the mechanical property of the film is improved along with the increase of the crystallinity and the orientation degree, so that the high-strength bacterial cellulose film is finally prepared.
As a preferred technical scheme:
the preparation method as described above, the stretching is multi-stage stretching, soaking in the solvent is performed before each stage of stretching, the stretching direction of each stage is the same, the stretching ratio and the soaking time increase with the increase of the stretching stage, and the stretching rate decreases with the increase of the stretching stage; the stretching ratio is a ratio of a length of the film at the end of stretching to a length of the film at the start of stretching in a direction parallel to the stretching direction.
Along with the stretching, the distance between the bacterial cellulose nanofibers is gradually reduced, the difficulty of the solvent molecules penetrating into the bacterial cellulose nanofibers is gradually increased, so that the stretching ratio and the soaking time are gradually increased along with the stretching, the stretching speed is gradually reduced, and the hydrogen bonding effect between the fibers is weakened when the solvent molecules penetrate into the bacterial cellulose nanofibers. Only by the arrangement, the good orientation degree of the bacterial cellulose nanofiber in the membrane can be ensured, and the good mechanical property of the bacterial cellulose membrane can be ensured.
The preparation method comprises the following specific steps:
(1) soaking the wet bacterial cellulose base membrane in a solvent for 1-3 hours, and then performing primary stretching, wherein the stretching ratio is 1.2-1.3, and the stretching speed is 1.5-2 mm/min;
(2) continuously soaking in the solvent for 1-3 hours, and then carrying out secondary stretching, wherein the stretching ratio is 1.3-1.4, and the stretching speed is 1-1.5 mm/min;
(3) continuously soaking in the solvent for 1-3 hours, and then carrying out third-stage stretching, wherein the stretching ratio is 1.4-1.5, and the stretching speed is 1-1.2 mm/min;
(4) washing and hot pressing to obtain the high-strength bacterial cellulose membrane.
The reason for setting the soaking time, the stretching ratio and the stretching rate of each stage of stretching is as follows: the soaking time is too short, solvent molecules cannot well permeate into the bacterial cellulose nanofibers, and the soaking time is too long, so that the permeation amount of the solvent molecules cannot be increased, and the time cost is wasted; the wet bacterial cellulose basement membrane can be broken by too large a stretching ratio, and the orientation degree of the bacterial cellulose in the membrane cannot be ensured by too small a stretching ratio; too high a stretching rate may cause shrinkage of the stretched bacterial cellulose film, which is disadvantageous to orientation, and in addition, it is liable to cause breakage of the wet bacterial cellulose-based film, too low a stretching rate, which takes too long.
According to the preparation method, the bacterial cellulose basement membrane is a bacterial cellulose membrane subjected to biosynthesis and fermentation, and is preserved in ultrapure water after being subjected to alkaline cooking treatment; the thickness of the bacterial cellulose base film is 5-10 mm, and the water content is 97-99 wt%; the hot pressing temperature is 40-80 ℃, and the hot pressing time is 8-24 hours. The hot pressing temperature and the hot pressing time are not limited to these, and may be set according to actual conditions. Generally, the hot pressing time is reduced along with the increase of the hot pressing temperature, for example, the hot pressing temperature is too high, the hot pressing time is short, and the precise control is inconvenient; if the hot pressing temperature is too low, the hot pressing time is longer, and the time cost is wasted.
The invention also provides the high-strength bacterial cellulose membrane prepared by the preparation method, wherein the thickness of the dry high-strength bacterial cellulose membrane is more than or equal to 50 mu m, and the tensile strength is more than or equal to 400 MPa. Compared with the prior art, the invention improves the tensile strength of the bacterial cellulose membrane on the premise of ensuring the lower thickness of the bacterial cellulose membrane, because the invention destroys the hydrogen bond action on the bacterial cellulose nanofiber scale and simultaneously reserves the hydrogen bond action among the bacterial cellulose macromolecules, and the prepared high-strength bacterial cellulose membrane has high crystallinity and high orientation degree simultaneously, thereby having excellent mechanical property.
As a preferred technical scheme:
the high-strength bacterial cellulose membrane has the dry-state high-strength bacterial cellulose membrane thickness of 50-80 mu m, the tensile strength of 400-800 MPa and the elongation at break of 4-6%.
The invention also provides an ultrathin superstrong nanofiber membrane prepared from the high-strength bacterial cellulose membrane, wherein the thickness of the dry ultrathin superstrong nanofiber membrane is less than or equal to 10 micrometers, and the tensile strength is more than or equal to 400 MPa.
As a preferred technical scheme:
the thickness of the dry ultrathin superstrong nanofiber membrane is 3-10 mu m, the tensile strength is 400-906 MPa, the breaking strain is 6-12%, and the breaking work is 20-80 MJ/m-3. The rupture strain of the nanofiber membrane with the same thickness in the prior art is only 4-6%, and the rupture work does not exceed 25MJ/m-3. Compared with the prior art, the mechanical property of the ultrathin and ultrastrong nanofiber membrane is greatly improved.
The invention also provides a method for preparing the ultrathin superstrong nanofiber membrane, which is characterized in that a micromechanical stripping method is adopted to strip the surface part of the dry-state high-strength bacterial cellulose membrane, and then the stripped part is pulled to strip the rest part to obtain the ultrathin superstrong nanofiber membrane. In the process of preparing the high-strength bacterial cellulose membrane, under the soaking action of the solvent, solvent molecules are soaked among the nanofibers, and the hydrogen bonding action among the bacterial cellulose nanofiber layers in the membrane is weakened, so that the ultrathin and super-strong nanofiber membrane can be prepared by a simple top-down micro-mechanical stripping method.
As a preferred technical scheme:
the method specifically comprises the following operations: firstly, adhering the end of the dry high-strength bacterial cellulose membrane with an adhesive tape, then peeling the adhesive tape, and finally pulling the adhesive tape to peel off the whole nanofiber membrane. The stripping of the invention is different from the stripping in the general sense, the stripping in the general sense is mostly to strip the rest parts except the surface after the adhesive tape is completely adhered to the surface, but the stripping is completed after the adhesive tape is adhered to the surface part of the dry high-strength bacterial cellulose membrane, because the high-strength bacterial cellulose membrane of the invention is a continuous membrane and the acting force between the parts is stronger, the adhesive tape only needs to be adhered to the surface part, which is essentially different from the stripping method of graphene and other materials in the prior art. Because the hydrogen bond effect between the bacterial cellulose nanofiber layers is also damaged by solvent molecules of the bacterial cellulose soaked by the solvent, the ultrathin bacterial cellulose film can be prepared by a simple top-down micro-mechanical stripping method. The present invention is only illustrative of a conventional preparation method, and the scope of the present invention is not limited thereto, and other conventional methods for preparing ultra-thin super strong nanofiber membranes from bacterial cellulose membranes may be applied to the present invention.
The invention mechanism is as follows:
in order to destroy disordered structures formed by hydrogen bond bonding among the nano fibers in the bacterial cellulose, the invention firstly soaks the bacterial cellulose in a solvent to swell the bacterial cellulose, weakens the strong hydrogen bond action in the bacterial cellulose, and then leads the bacterial cellulose to be oriented by multi-stage stretching with different stretching rates, thereby destroying the hydrogen bond action among the nano fibers to the maximum extent, embodying the excellence of the nano structure and improving the mechanical property of a macroscopic membrane material.
According to the invention, NMP, NMMO or ethanolamine is selected as a solvent to weaken the hydrogen bond effect on the bacterial cellulose nanofiber scale, rather than the hydrogen bond effect based on a cellulose macromolecular chain, because active oxygen atoms exist on NMP, NMMO or ethanolamine molecules, and the activity of the oxygen atoms is higher than that of oxygen atoms on water molecules, when a bacterial cellulose wet film is soaked in the solvent, NMP, NMMO or ethanolamine preferentially forms hydrogen bonds with hydroxyl groups on the surface of the bacterial cellulose nanofiber, and simultaneously, because the volume of solvent molecules is larger than that of water molecules, the distance between the bacterial cellulose nanofiber is enlarged, and the hydrogen bond effect between the nanofibers is weakened. However, the oxygen on NMP, NMMO or ethanolamine is not active enough to break the lattice energy in the bacterial cellulose, so that the hydrogen bonding action on the macromolecules based on the bacterial cellulose cannot be weakened by the solvents, and the high crystallinity of the bacterial cellulose can be still maintained after the bacterial cellulose is soaked in the solvents. Meanwhile, the base film is subjected to multistage stretching at different stretching rates to be oriented, so that the hydrogen bond effect among the nanofibers is damaged to the maximum extent, the mechanical property of the macroscopic film material is improved, and the mechanical property of the macroscopic film material is improved.
Has the advantages that:
(1) the high-strength bacterial cellulose membrane is thin in thickness and high in tensile strength, and has a great market prospect;
(2) the preparation method of the high-strength bacterial cellulose membrane has the advantages of simple process, low cost and great application prospect;
(3) the ultrathin and ultrastrong nanofiber membrane prepared from the high-strength bacterial cellulose membrane is thin in thickness, high in tensile strength, good in mechanical property and good in application prospect;
(4) the preparation method of the ultrathin and ultrastrong nanofiber membrane has the advantages of simple process and low cost.
Drawings
FIG. 1 is a stress-strain curve of the ultra-thin super strong nanofiber membrane prepared in example 1;
FIG. 2 is a stress-strain curve of the ultra-thin super strong nanofiber membrane prepared in example 2;
fig. 3 is a stress-strain curve of the ultra-thin super strong nanofiber membrane prepared in example 3.
Detailed Description
The invention will be further illustrated with reference to specific embodiments. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.
Example 1
A preparation method of a high-strength bacterial cellulose membrane comprises the following specific steps:
(1) cutting a wet bacterial cellulose membrane which is subjected to biosynthesis fermentation and alkaline cooking treatment and then is stored in ultrapure water into a square shape with the width of 30mm and the length of 100mm, wherein the thickness of the bacterial cellulose basement membrane is 6mm, and the water content is 99 wt%;
(2) soaking the wet bacterial cellulose membrane in NMP for 1 hour, and then stretching, wherein the stretching ratio is 1.3, and the stretching speed is 2 mm/min;
(3) after washing, hot pressing is carried out for 24 hours at the temperature of 60 ℃ to prepare the high-strength bacterial cellulose membrane.
The prepared high-strength bacterial cellulose membrane is in a dry state, the thickness of the high-strength bacterial cellulose membrane is 60 mu m, the tensile strength is 586MPa, and the elongation at break is 4.6%.
The method for preparing the ultrathin and ultrastrong nanofiber membrane from the high-strength bacterial cellulose membrane comprises the following specific operations: firstly, adhering the end of the dry high-strength bacterial cellulose membrane with an adhesive tape, then peeling the adhesive tape, and finally pulling the adhesive tape to peel the whole nanofiber membrane to obtain the ultrathin super-strong nanofiber membrane.
The finally prepared ultra-thin super strong nanofiber membrane is in a dry state, the thickness of the membrane is 5 mu m, the tensile strength is 625.7MPa, the breaking strain is 8 percent, and the breaking work is 25.84MJ/m-3The stress-strain curve is shown in figure 1, and as can be seen from figure 1, the prepared ultrathin and super-strong nanofiber membrane has good strength and toughness and reaches the standard of high-strength and high-toughness bacterial cellulose membranes.
Example 2
A preparation method of a high-strength bacterial cellulose membrane comprises the following specific steps:
(1) cutting a wet bacterial cellulose membrane which is subjected to biosynthesis fermentation and alkaline cooking treatment and then is stored in ultrapure water into a square shape with the width of 20mm and the length of 70mm, wherein the thickness of the bacterial cellulose basement membrane is 6mm, and the water content is 99 wt%;
(2) soaking the wet bacterial cellulose membrane in NMP for 1 hour, and then carrying out primary stretching, wherein the stretching ratio is 1.3, and the stretching speed is 2 mm/min;
(3) continuously soaking in NMP for 3 hours, and then performing secondary stretching, wherein the stretching ratio is 1.4, and the stretching speed is 1.5 mm/min;
(4) after washing, hot pressing is carried out for 24 hours at the temperature of 60 ℃ to prepare the high-strength bacterial cellulose membrane.
The prepared high-strength bacterial cellulose membrane is dry, the thickness of the high-strength bacterial cellulose membrane is 65 mu m, the tensile strength of the high-strength bacterial cellulose membrane is 689MPa, and the elongation at break of the high-strength bacterial cellulose membrane is 5%.
The method for preparing the ultrathin and ultrastrong nanofiber membrane from the high-strength bacterial cellulose membrane comprises the following specific operations: firstly, adhering the end of the dry high-strength bacterial cellulose membrane with an adhesive tape, then peeling the adhesive tape, and finally pulling the adhesive tape to peel the whole nanofiber membrane to obtain the ultrathin super-strong nanofiber membrane.
The finally prepared ultra-thin super-strong nanofiber membrane is in a dry state, the thickness of the membrane is 6 mu m, the tensile strength is 732.7MPa, the breaking strain is 10 percent, and the breaking work is 40.03MJ/m-3The stress-strain curve is shown in fig. 2, and as can be seen from fig. 2, the prepared ultrathin and ultrastrong nanofiber membrane has good strength and toughness, and reaches the standard of high-strength and high-toughness bacterial cellulose membranes.
Example 3
A preparation method of a high-strength bacterial cellulose membrane comprises the following specific steps:
(1) cutting a wet bacterial cellulose membrane which is subjected to biosynthesis fermentation and alkaline cooking treatment and then is stored in ultrapure water into a square shape with the width of 20mm and the length of 70mm, wherein the thickness of the bacterial cellulose basement membrane is 6mm, and the water content is 99 wt%;
(2) soaking the wet bacterial cellulose membrane in NMP for 1 hour, and then carrying out primary stretching, wherein the stretching ratio is 1.3, and the stretching speed is 2 mm/min;
(3) continuously soaking in NMP for 3 hours, and then performing secondary stretching, wherein the stretching ratio is 1.4, and the stretching speed is 1.5 mm/min;
(4) continuously soaking in NMP for 1 hour, and performing third-stage stretching at a stretching ratio of 1.5 and a stretching rate of 1 mm/min;
(5) after washing, hot pressing is carried out for 24 hours at the temperature of 60 ℃ to prepare the high-strength bacterial cellulose membrane.
The prepared high-strength bacterial cellulose membrane is dry, the thickness of the high-strength bacterial cellulose membrane is 50 mu m, the tensile strength of the high-strength bacterial cellulose membrane is 800MPa, and the elongation at break of the high-strength bacterial cellulose membrane is 6%.
The method for preparing the ultrathin and ultrastrong nanofiber membrane from the high-strength bacterial cellulose membrane comprises the following specific operations: firstly, adhering the end of the dry high-strength bacterial cellulose membrane with an adhesive tape, then peeling the adhesive tape, and finally pulling the adhesive tape to peel the whole nanofiber membrane to obtain the ultrathin super-strong nanofiber membrane.
The finally prepared ultra-thin super-strong nanofiber membrane is in a dry state, the thickness of the membrane is 4 mu m, the tensile strength is 906MPa, the breaking strain is 12 percent, and the breaking work is 55.51MJ/m-3The stress-strain curve is shown in fig. 3, and it can be seen from fig. 3 that the strength and toughness of the prepared ultrathin and ultrastrong nanofiber membrane are good, and the ultrathin and ultrastrong nanofiber membrane reaches the standard of a high-strength and high-toughness bacterial cellulose membrane. In addition, when the analysis is carried out by combining the examples 1, 2 and 3, the orientation degree of the bacterial cellulose nano fibers in the product film is increased along with the increase of the stretching ratio, and the tensile strength and the breaking work of the final product are increased.
Example 4
A preparation method of a high-strength bacterial cellulose membrane comprises the following specific steps:
(1) cutting a wet bacterial cellulose membrane which is subjected to biosynthesis fermentation, is subjected to alkaline cooking treatment and is stored in ultrapure water into a square shape with the width of 30mm and the length of 100mm, wherein the thickness of the bacterial cellulose basement membrane is 5mm, and the water content is 97 wt%;
(2) soaking a wet bacterial cellulose membrane in NMMO with the concentration of 50 wt% for 1 hour, and then performing first-stage stretching, wherein the stretching ratio is 1.2, and the stretching speed is 1.5 mm/min;
(3) continuously soaking in NMMO for 2 hours, and then performing second-stage stretching, wherein the stretching ratio is 1.3, and the stretching speed is 1.3 mm/min;
(4) continuously soaking in NMMO for 3 hours, and then carrying out third-stage stretching, wherein the stretching ratio is 1.4, and the stretching speed is 1.2 mm/min;
(5) after washing, hot pressing is carried out for 8 hours at 40 ℃ to prepare the high-strength bacterial cellulose membrane.
The prepared high-strength bacterial cellulose membrane is in a dry state, the thickness of the high-strength bacterial cellulose membrane is 100 mu m, the tensile strength is 400MPa, and the elongation at break is 4%.
The method for preparing the ultrathin and ultrastrong nanofiber membrane from the high-strength bacterial cellulose membrane comprises the following specific operations: firstly, adhering the end of the dry high-strength bacterial cellulose membrane with an adhesive tape, then peeling the adhesive tape, and finally pulling the adhesive tape to peel the whole nanofiber membrane to obtain the ultrathin super-strong nanofiber membrane.
The finally prepared ultra-thin super-strong nanofiber membrane is in a dry state, the thickness of the membrane is 10 mu m, the tensile strength is 400MPa, the breaking strain is 6 percent, and the breaking work is 20MJ/m-3。
Example 5
A preparation method of a high-strength bacterial cellulose membrane comprises the following specific steps:
(1) cutting a wet bacterial cellulose membrane which is subjected to biosynthesis fermentation and alkaline cooking treatment and then is stored in ultrapure water into a square shape with the width of 30mm and the length of 100mm, wherein the thickness of the bacterial cellulose basement membrane is 10mm, and the water content is 98 wt%;
(2) soaking the wet bacterial cellulose membrane in ethanolamine for 2 hours, and then carrying out primary stretching, wherein the stretching ratio is 1.25, and the stretching speed is 1.6 mm/min;
(3) continuously soaking in ethanolamine for 2.5 hours, and then performing secondary stretching, wherein the stretching ratio is 1.35, and the stretching speed is 1.4 mm/min;
(4) continuously soaking in ethanolamine for 3 hours, and then carrying out third-stage stretching, wherein the stretching ratio is 1.45, and the stretching speed is 1.1 mm/min;
(5) after washing, hot pressing is carried out for 12 hours at 40 ℃ to prepare the high-strength bacterial cellulose membrane.
The prepared high-strength bacterial cellulose membrane is dry, the thickness of the high-strength bacterial cellulose membrane is 70 mu m, the tensile strength of the high-strength bacterial cellulose membrane is 490MPa, and the elongation at break of the high-strength bacterial cellulose membrane is 4.2%.
The method for preparing the ultrathin and ultrastrong nanofiber membrane from the high-strength bacterial cellulose membrane comprises the following specific operations: firstly, adhering the end of the dry high-strength bacterial cellulose membrane with an adhesive tape, then peeling the adhesive tape, and finally pulling the adhesive tape to peel the whole nanofiber membrane to obtain the ultrathin super-strong nanofiber membrane.
The finally prepared ultra-thin super-strong nanofiber membrane is in a dry state, the thickness of the membrane is 8 mu m, the tensile strength is 504MPa, the breaking strain is 7 percent, and the breaking work is 30MJ/m-3。
Example 6
A preparation method of a high-strength bacterial cellulose membrane comprises the following specific steps:
(1) cutting a wet bacterial cellulose membrane which is subjected to biosynthesis fermentation and alkaline cooking treatment and then is stored in ultrapure water into a square shape with the width of 30mm and the length of 100mm, wherein the thickness of the bacterial cellulose-based membrane is 8mm, and the water content is 99 wt%;
(2) soaking a wet bacterial cellulose membrane in NMMO with the concentration of 50 wt% for 1 hour, and then performing first-stage stretching, wherein the stretching ratio is 1.3, and the stretching speed is 1.6 mm/min;
(3) continuously soaking in NMMO for 2 hours, and then performing second-stage stretching, wherein the stretching ratio is 1.4, and the stretching speed is 1.1 mm/min;
(4) continuously soaking in NMMO for 2.5 hours, and then carrying out third-stage stretching, wherein the stretching ratio is 1.5, and the stretching speed is 1 mm/min;
(5) after washing, hot pressing is carried out for 9 hours at 80 ℃ to prepare the high-strength bacterial cellulose membrane.
The prepared high-strength bacterial cellulose membrane is dry, the thickness of the high-strength bacterial cellulose membrane is 52 mu m, the tensile strength is 780MPa, and the elongation at break is 5.9%.
The method for preparing the ultrathin and ultrastrong nanofiber membrane from the high-strength bacterial cellulose membrane comprises the following specific operations: firstly, adhering the end of the dry high-strength bacterial cellulose membrane with an adhesive tape, then peeling the adhesive tape, and finally pulling the adhesive tape to peel the whole nanofiber membrane to obtain the ultrathin super-strong nanofiber membrane.
The finally prepared ultra-thin super-strong nanofiber membrane is in a dry state, the thickness of the membrane is 4 mu m, the tensile strength is 850MPa, the breaking strain is 9.8 percent, and the breaking work is 65MJ/m-3。
Example 7
A preparation method of a high-strength bacterial cellulose membrane comprises the following specific steps:
(1) cutting a wet bacterial cellulose membrane which is subjected to biosynthesis fermentation, is subjected to alkaline cooking treatment and is stored in ultrapure water into a square shape with the width of 30mm and the length of 100mm, wherein the thickness of the bacterial cellulose basement membrane is 5mm, and the water content is 97 wt%;
(2) soaking the wet bacterial cellulose membrane in ethanolamine for 1 hour, and then carrying out primary stretching, wherein the stretching ratio is 1.2, and the stretching speed is 1.5 mm/min;
(3) continuously soaking in ethanolamine for 1.5 hours, and then performing secondary stretching, wherein the stretching ratio is 1.3, and the stretching speed is 1.2 mm/min;
(4) continuously soaking in ethanolamine for 2 hours, and then carrying out third-stage stretching, wherein the stretching ratio is 1.4, and the stretching speed is 1 mm/min;
(5) after washing, hot pressing is carried out for 22 hours at 50 ℃ to obtain the high-strength bacterial cellulose membrane.
The prepared high-strength bacterial cellulose membrane is in a dry state, the thickness of the high-strength bacterial cellulose membrane is 80 mu m, the tensile strength of the high-strength bacterial cellulose membrane is 420MPa, and the elongation at break of the high-strength bacterial cellulose membrane is 4.3%.
The method for preparing the ultrathin and ultrastrong nanofiber membrane from the high-strength bacterial cellulose membrane comprises the following specific operations: firstly, adhering the end of the dry high-strength bacterial cellulose membrane with an adhesive tape, then peeling the adhesive tape, and finally pulling the adhesive tape to peel the whole nanofiber membrane to obtain the ultrathin super-strong nanofiber membrane.
The finally prepared ultra-thin super-strong nanofiber membrane is in a dry state, the thickness of the membrane is 9 mu m, the tensile strength is 430MPa, the breaking strain is 7 percent, and the breaking work is 28.5MJ/m-3。
Example 8
A preparation method of a high-strength bacterial cellulose membrane comprises the following specific steps:
(1) cutting a wet bacterial cellulose membrane which is subjected to biosynthesis fermentation and alkaline cooking treatment and then is stored in ultrapure water into a square shape with the width of 30mm and the length of 100mm, wherein the thickness of the bacterial cellulose basement membrane is 10mm, and the water content is 97 wt%;
(2) soaking the wet bacterial cellulose membrane in NMP for 1 hour, and then carrying out primary stretching, wherein the stretching ratio is 1.2, and the stretching speed is 2 mm/min;
(3) continuously soaking in NMP for 2 hours, and then performing secondary stretching, wherein the stretching ratio is 1.3, and the stretching speed is 1.2 mm/min;
(4) continuously soaking in NMP for 3 hours, and then carrying out third-stage stretching, wherein the stretching ratio is 1.45, and the stretching speed is 1.1 mm/min;
(5) after washing, hot pressing is carried out for 8 hours at 80 ℃ to obtain the high-strength bacterial cellulose membrane.
The prepared high-strength bacterial cellulose membrane is in a dry state, the thickness of the high-strength bacterial cellulose membrane is 60 mu m, the tensile strength is 650MPa, and the elongation at break is 4.9%.
The method for preparing the ultrathin and ultrastrong nanofiber membrane from the high-strength bacterial cellulose membrane comprises the following specific operations: firstly, adhering the end of the dry high-strength bacterial cellulose membrane with an adhesive tape, then peeling the adhesive tape, and finally pulling the adhesive tape to peel the whole nanofiber membrane to obtain the ultrathin super-strong nanofiber membrane.
The finally prepared ultra-thin super-strong nanofiber membrane is in a dry state, the thickness of the membrane is 4 mu m, the tensile strength is 720MPa, the breaking strain is 9 percent, and the breaking work is 60MJ/m-3。
Claims (8)
1. A preparation method of a high-strength bacterial cellulose membrane is characterized by comprising the following steps: soaking the wet bacterial cellulose basement membrane in a solvent and stretching to prepare a high-strength bacterial cellulose membrane; the solvent is NMMO, and the concentration of the NMMO is 50 wt%;
the stretching is multi-stage stretching, soaking is carried out in a solvent before each stage of stretching, the stretching direction of each stage of stretching is the same, the stretching ratio and the soaking time are increased along with the increase of the stretching stages, and the stretching speed is reduced along with the increase of the stretching stages; the stretching ratio is a ratio of a length of the film at the end of stretching to a length of the film at the start of stretching in a direction parallel to the stretching direction;
the preparation method of the high-strength bacterial cellulose membrane comprises the following specific steps:
(1) soaking the wet bacterial cellulose base membrane in a solvent for 1-3 hours, and then performing primary stretching, wherein the stretching ratio is 1.2-1.3, and the stretching speed is 1.5-2 mm/min;
(2) continuously soaking in the solvent for 1-3 hours, and then carrying out secondary stretching, wherein the stretching ratio is 1.3-1.4, and the stretching speed is 1-1.5 mm/min;
(3) continuously soaking in the solvent for 1-3 hours, and then carrying out third-stage stretching, wherein the stretching ratio is 1.4-1.5, and the stretching speed is 1-1.2 mm/min;
(4) washing and hot pressing to obtain the high-strength bacterial cellulose membrane.
2. The preparation method according to claim 1, wherein the bacterial cellulose-based membrane is a bacterial cellulose membrane subjected to biosynthesis and fermentation, and is preserved in ultrapure water after being subjected to alkaline cooking treatment; the thickness of the bacterial cellulose base film is 5-10 mm, and the water content is 97-99 wt%; the hot pressing temperature is 40-80 ℃, and the hot pressing time is 8-24 hours.
3. A high-strength bacterial cellulose film produced by the production method according to claim 1 or 2, characterized in that: the dry high-strength bacterial cellulose membrane has a thickness of more than or equal to 50 μm and a tensile strength of more than or equal to 400 MPa.
4. The high-strength bacterial cellulose membrane according to claim 3, wherein the dry high-strength bacterial cellulose membrane has a thickness of 50-80 μm, a tensile strength of 400-800 MPa, and an elongation at break of 4-6%.
5. The ultra-thin ultra-strong nanofiber membrane prepared by using the high-strength bacterial cellulose membrane of claim 3, wherein: the thickness of the dry ultra-thin super-strong nanofiber membrane is less than or equal to 10 microns, and the tensile strength is more than or equal to 400 MPa.
6. The ultra-thin super-strong nanofiber membrane as claimed in claim 5, wherein the thickness of the dry ultra-thin super-strong nanofiber membrane is 3-10 μm, the tensile strength is 400-906 MPa, the breaking strain is 6-12%, and the breaking work is 20-80 MJ/m-3。
7. The method for preparing the ultra-thin ultra-strong nanofiber membrane as claimed in claim 5, wherein: the surface part of the dry high-strength bacterial cellulose membrane is stripped by adopting a micro-mechanical stripping method, and then the stripped part is pulled to strip the rest part to prepare the ultrathin super-strong nanofiber membrane.
8. The method according to claim 7, characterized by the specific operations of: firstly, adhering the end of the dry high-strength bacterial cellulose membrane with an adhesive tape, then peeling the adhesive tape, and finally pulling the adhesive tape to peel off the whole nanofiber membrane.
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