CN113736147A - Waterproof and antibacterial chitosan transparent film and preparation method thereof - Google Patents
Waterproof and antibacterial chitosan transparent film and preparation method thereof Download PDFInfo
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- 229920001661 Chitosan Polymers 0.000 title claims abstract description 57
- 230000000844 anti-bacterial effect Effects 0.000 title claims abstract description 36
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 96
- 229920002101 Chitin Polymers 0.000 claims abstract description 70
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims abstract description 48
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 32
- 239000002002 slurry Substances 0.000 claims abstract description 24
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 16
- 238000002791 soaking Methods 0.000 claims abstract description 15
- 241000238557 Decapoda Species 0.000 claims abstract description 10
- 238000003756 stirring Methods 0.000 claims abstract description 7
- 239000000843 powder Substances 0.000 claims abstract description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 62
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims description 26
- 239000000835 fiber Substances 0.000 claims description 24
- 238000000034 method Methods 0.000 claims description 16
- 229910000019 calcium carbonate Inorganic materials 0.000 claims description 13
- 239000000049 pigment Substances 0.000 claims description 13
- 102000004169 proteins and genes Human genes 0.000 claims description 13
- 108090000623 proteins and genes Proteins 0.000 claims description 13
- 238000007731 hot pressing Methods 0.000 claims description 12
- 241000371997 Eriocheir sinensis Species 0.000 claims description 8
- 238000000967 suction filtration Methods 0.000 claims description 8
- 238000003825 pressing Methods 0.000 claims description 7
- 238000001704 evaporation Methods 0.000 claims description 5
- 239000000654 additive Substances 0.000 claims description 4
- MBLBDJOUHNCFQT-LXGUWJNJSA-N aldehydo-N-acetyl-D-glucosamine Chemical compound CC(=O)N[C@@H](C=O)[C@@H](O)[C@H](O)[C@H](O)CO MBLBDJOUHNCFQT-LXGUWJNJSA-N 0.000 claims description 2
- 238000004140 cleaning Methods 0.000 claims description 2
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- 239000000463 material Substances 0.000 abstract description 11
- 239000000126 substance Substances 0.000 abstract description 11
- 239000002994 raw material Substances 0.000 abstract description 3
- 238000000280 densification Methods 0.000 abstract description 2
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- 239000003814 drug Substances 0.000 abstract 1
- 229940079593 drug Drugs 0.000 abstract 1
- 238000004806 packaging method and process Methods 0.000 abstract 1
- 239000010408 film Substances 0.000 description 86
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- 229910021641 deionized water Inorganic materials 0.000 description 9
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- 125000000738 acetamido group Chemical group [H]C([H])([H])C(=O)N([H])[*] 0.000 description 1
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- 210000002390 cell membrane structure Anatomy 0.000 description 1
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
- C08J7/12—Chemical modification
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2305/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2301/00 or C08J2303/00
- C08J2305/08—Chitin; Chondroitin sulfate; Hyaluronic acid; Derivatives thereof
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Abstract
The invention discloses a waterproof and antibacterial chitosan transparent film and a preparation method thereof. The preparation method comprises the following steps: firstly, sequentially soaking shrimp shells, crab shells or chitin powder in dilute hydrochloric acid solution, dilute sodium hydroxide solution and ethanol solution to remove impurities; placing the purified chitin into a dilute acetic acid solution, stirring the chitin into slurry, and dehydrating the slurry to form a film; prepressing and forming the chitin film, and then placing the chitin film in a concentrated sodium hydroxide solution for high-temperature treatment to form a waterproof staggered and cross-linked structure; and finally, placing the film in a press for densification to obtain the high-strength waterproof transparent film. The film prepared by the invention has excellent wet strength, antibacterial property and transparency, is rich in raw material source, low in cost, simple in preparation process, free of any other substances, and has wide application prospect in the fields of flexible electronic substrates, packaging, optical materials, biological medicines and the like.
Description
Technical Field
The invention relates to a waterproof and antibacterial chitosan transparent film and a preparation method thereof, belonging to the field of bio-based nano materials.
Background
With the rapid development of human society and the continuous promotion of industrialization, waste produced by human in a short time is rapidly accumulated, which causes increasingly serious environmental problems and harms the life health of human. Meanwhile, the petroleum-based polymeric materials are limited in development and use due to the increasing exhaustion of non-renewable resources such as petroleum. Under the background that the strategy of sustainable development becomes a global consensus, renewable biomass resources in the nature are reasonably developed and utilized, and environment-friendly new materials capable of replacing plastics are developed, which are increasingly receiving attention of people.
In recent years, natural materials represented by cellulose, chitin and the like have attracted more and more attention because of their advantages of environmental friendliness, reproducibility, biodegradability, mass storage and the like. The natural fiber materials have abundant hydroxyl and amino groups, and a large number of hydrogen bonds are formed between molecules and in molecules, so that the materials have high mechanical strength in a dry environment. However, the hydrogen bonding method has a major problem that the hydrogen bonding between fibers is destroyed by water invasion, and the material is easy to be structurally destroyed and fail to function when being used in a humid or water environment for a long time. This problem has been a major obstacle limiting the range of applications of natural fiber materials and is one of the key problems to be solved.
Various studies have been made on how to enhance the wet strength of natural fiber materials. In the case of paper, the wet strength is generally obtained by adding a thermosetting synthetic resin wet strength agent (such as polyamide polyamine epichlorohydrin PAE) to form a water-insoluble polymer network to limit the swelling of paper fibers, but low-molecular chlorinated organic matters in the paper cause certain harm to the environment and human health. In addition, the water resistance of natural fiber materials is improved by means of coating waterproof coatings, constructing super-hydrophobic surface structures, crosslinking and the like. However, in general, the existing means have difficulty in meeting the application requirements of the materials in the aspects of economy, operability, sustainable development concept and the like. It has been difficult to prepare environment-friendly high-strength water-resistant materials completely composed of natural fibers (such as cellulose and chitosan) without adding other substances.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a high-strength water-resistant antibacterial pure chitosan transparent film which is low in cost, simple in process and free of other components and a preparation method thereof.
The technical scheme adopted by the invention is as follows:
a water-resistant antibacterial chitosan transparent film is formed by recombining fibers extracted from shrimp and crab shells, wherein the fibers are mutually and crisscross entangled to form a compact three-dimensional cross-linked network structure; the film is free of additional additives.
Further, the thickness of the film is 10-500 μm, and the diameter of the chitosan fiber is 10nm-5 μm.
Further, the film has a dry tensile strength of 90-140MPa and a wet tensile strength of 40-60 MPa.
Further, the film has a transparency of 85 to 92%.
The invention also provides a preparation method of the waterproof and antibacterial chitosan transparent film, which comprises the following steps:
(1) putting shrimp shell, crab shell or chitin powder in dilute hydrochloric acid solution, sodium hydroxide solution and ethanol solution in sequence at normal temperature for reaction to remove calcium carbonate, protein and pigment respectively, and then cleaning with water;
(2) soaking the chitin obtained in the step (1) in a dilute acetic acid solution for a certain time, stirring the chitin into uniform slurry, and preparing a film by combining suction filtration with a pre-pressing method or a solution evaporation method;
(3) and (3) treating the chitin film obtained in the step (2) in a sodium hydroxide solution to form a finger-crosslinked network structure, and then placing the finger-crosslinked network structure in a press for hot pressing to obtain the high-strength waterproof antibacterial chitosan transparent film.
Preferably, in the step (1), the shrimp shells are lobster shells, and the crab shells are eriocheir sinensis or swimming crab shells.
Further, in the step (1), the concentration of the dilute hydrochloric acid is 0.1-2mol/L, and the treatment time is 1-24 hours; the concentration of the sodium hydroxide solution is 2-10 wt.%, and the treatment time is 6-48 hours; the concentration of the ethanol solution is 100 percent, and the treatment time is 2 to 48 hours.
Further, in the step (2), the pH value of the dilute acetic acid solution is 3-3.5, and the soaking time is 6-48 hours.
Further, in the step (2), when a pre-pressing method is used, the pre-pressing temperature of a press is 25-100 ℃, the pressure is 1-10MPa, and the pressure maintaining time is 6-48 hours; when the solution evaporation method is used, the temperature is 25-50 ℃ and the time is 24-72 hours.
Further, in the step (3), the concentration of the sodium hydroxide solution is 30-50 wt.%, the treatment temperature is 60-100 ℃, the treatment time is 1-20 hours, the press temperature is 25-100 ℃, the pressure is 1-10MPa, and the dwell time is 6-48 hours.
The invention takes shrimp, crab shell or chitin powder as raw materials to prepare the high-strength waterproof antibacterial chitosan transparent film, and has the advantages that:
(1) the obtained chitosan film has excellent water resistance, optical transparency and antibacterial property, and the wet tensile strength can reach 40-60MPa, which is superior to most polysaccharide-based film materials.
(2) The raw materials have wide sources, are waste shrimp and crab shells, can be regenerated and have low cost.
(3) The preparation process is simple, the instruments and equipment are simple, the production cost is low, and the method is suitable for large-scale industrial production.
(4) The waterproof antibacterial chitosan transparent film disclosed by the invention contains pure chitosan, does not contain other additives, can be completely biodegraded, is green and environment-friendly, and can be used for partially replacing the existing films, packages, substrate materials (such as glass and plastics) and the like.
Drawings
FIG. 1 is a schematic structural diagram of a chitosan transparent film of the present invention.
FIG. 2 is a scanning electron microscope cross-sectional profile of the chitosan film prepared in example 1.
FIG. 3 is an electron micrograph of a chitosan thin film prepared in example 1 and showing a cross-linked structure.
FIG. 4 is a comparative surface electron microscope image of chitosan film (a) and chitin film (b) prepared in example 1 after soaking in water for 24 hours.
Fig. 5 is a stress-strain graph of the chitosan film prepared in example 1 in a wet state.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.
The invention provides a waterproof and antibacterial chitosan transparent film, which is formed by recombining fibers extracted from shrimp and crab shells, wherein the diameter of the fibers is 10nm-5 mu m, and the fibers are mutually and crisscross entangled to form a compact three-dimensional cross-linked network structure, as shown in figure 1. The water-resistant chitosan film prepared by the invention does not contain any other additive, is only tightly combined through the intersectional cross-linking, entanglement and hydrogen bonding between fibers, and the interaction can still be maintained in water. In addition, the chitosan film also has excellent mechanical strength, antibacterial property, high transparency, dyeability and thermal stability. The chitosan waterproof film prepared by the invention can be completely biodegraded, is environment-friendly, has excellent performance and wide use scene, and has good commercial prospect.
The invention also provides a preparation method of the waterproof and antibacterial chitosan transparent film, which comprises the following steps:
(1) putting shrimp, crab shell or chitin powder into a dilute hydrochloric acid solution, a sodium hydroxide solution and an ethanol solution with certain concentration at normal temperature in sequence for reaction so as to remove calcium carbonate, protein and pigment respectively, and then washing with water;
(2) soaking the chitin obtained in the step (1) in a dilute acetic acid solution for a certain time, stirring the chitin into uniform slurry, and preparing a film by combining suction filtration with a pre-pressing method or a solution evaporation method;
(3) and (3) placing the chitin film obtained in the step (2) in a sodium hydroxide solution at a certain temperature and a certain concentration for reaction to form a finger-pointing cross-linked structure, and then placing the chitosan film in a press for hot-pressing densification to obtain the high-strength waterproof antibacterial chitosan transparent film.
In the invention, the soaking treatment of the dilute hydrochloric acid solution, the sodium hydroxide solution and the ethanol solution respectively removes impurities such as calcium carbonate, protein, pigment and the like. The purified chitin is soaked in dilute acetic acid solution, so that amino groups on molecular chains of the chitin can be protonated to carry positive charges, and electrostatic repulsion among molecular chains of the chitin is increased, thereby facilitating the defibration of chitin fibers into nanofibers under the high-speed stirring of a wall breaking machine. After vacuum filtration and film formation, the chitin nano-fibers are subjected to hot pressing and drying for a certain time to fully remove moisture, so that a compact network structure is formed among the chitin nano-fibers, a strong hydrogen bond bonding force is formed among the fibers, and a stable structure of the chitin nano-fibers can be maintained in a subsequent concentrated alkali treatment process. And then, the obtained chitin film is placed in a sodium hydroxide solution with certain temperature and certain concentration for treatment. In this process, the chitin fibers are first swollen so that the alkali can penetrate into the amorphous and crystalline regions inside the fibers. The acetamido on the chitin molecule further reacts with alkali to be converted into amino, the molecular chain of chitin becomes more flexible and stretched in the process, and adjacent molecular chains spontaneously generate mutual interdigitation and entanglement to form a stable cross-linking structure which can still be kept in water. After the alkali liquor is cleaned and removed, the molecular chains are self-assembled again to form fiber bundles, and the interdigitated structure is fixed, so that the fibers have strong interaction, intermolecular hydrogen bonds are well maintained in the compact network structure and are not easily damaged by water molecules, and the material is endowed with high mechanical strength and water resistance. The material structure is further densified in the hot pressing process, so that structural gaps among the fibers are reduced, and the interaction force among the fibers is enhanced. Notably, when the amino group content in the molecular chain is more than 50% after the concentrated alkali treatment, it is considered that the chitin is converted into chitosan. The chitosan molecular chain has abundant amino groups to make the chitosan molecular chain have positive charges, and can destroy the cell membrane structure of bacteria, thereby having good antibacterial property.
Example 1
Putting the Eriocheir sinensis shell into 1mol/L dilute hydrochloric acid solution at normal temperature for 12 hours to remove calcium carbonate, then putting into 4 wt.% sodium hydroxide solution for 24 hours to remove protein, then putting into pure ethanol solution to soak for 12 hours to remove pigment, and then washing with water to remove residual chemical substances. The obtained chitin is put into a dilute acetic acid solution with the pH value of 3 to be soaked for 24 hours, and then the chitin is put into a wall breaking machine to be stirred at high speed for 30 minutes to form uniform slurry. Diluting the chitin slurry to the concentration of 1 wt.% by using deionized water, performing vacuum filtration to form a film, and then placing the film in a hot press to perform hot pressing for 12 hours under the conditions that the temperature is 50 ℃ and the pressure is 5MPa to obtain an initial chitin film. The film was reacted in 50 wt.% sodium hydroxide solution at 90 ℃ for 8 hours, after which the sample was taken out and washed clean in water. And finally, placing the sample in a hot press, and maintaining the pressure for 24 hours under the conditions that the temperature is 50 ℃ and the pressure is 5MPa to finally obtain the waterproof and antibacterial chitosan transparent film. The wet tensile strength of the film after 24 hours immersion in water was 57 MPa.
FIG. 2 is a scanning electron microscope image of a cross section of the chitosan thin film prepared in this example, which shows the structure of the chitosan nanofibers densely arranged. FIG. 3 is an electron microscope image of the chitosan film and the finger-crosslinked structure, from which it can be seen that two chitosan fibers are finger-crosslinked. Fig. 4 is a comparative electron microscope image of the prepared chitosan film and the chitin film after being soaked in water for 24 hours, and it can be seen from the image that the chitosan fibers are still tightly interwoven, and the chitin fibers are moistened and expanded into a loose structure. FIG. 5 is a stress-strain curve diagram of a chitosan film in a wet state after being soaked in water for 24 hours, wherein the wet tensile strength is 57MPa, and the chitosan film shows excellent water resistance.
Example 2
The lobster shell is placed in 1mol/L dilute hydrochloric acid solution at normal temperature for 12 hours to remove calcium carbonate, then placed in 4 wt.% sodium hydroxide solution for 24 hours to remove protein, then placed in pure ethanol solution for soaking for 12 hours to remove pigment, and then washed by water to remove residual chemical substances. The obtained chitin is placed in a dilute acetic acid solution with the pH value of 3 for soaking for 24 hours, and then the chitin is placed in a wall breaking machine for high-speed stirring for 30 minutes to obtain uniform slurry. Diluting the chitin slurry to the concentration of 1 wt.% by using deionized water, performing suction filtration to form a film by using a vacuum filtration method, and then placing the film in a hot press to perform hot pressing for 12 hours under the conditions that the temperature is 50 ℃ and the pressure is 5MPa to obtain an initial chitin film. The film was reacted in 50 wt.% sodium hydroxide solution at 90 ℃ for 8 hours, after which the sample was taken out and washed clean in water. And finally, placing the sample in a hot press, and maintaining the pressure for 24 hours under the conditions that the temperature is 50 ℃ and the pressure is 5MPa to finally obtain the waterproof and antibacterial chitosan transparent film. The wet tensile strength of the film after 24 hours immersion in water was 49 MPa.
Example 3
Putting swimming crab shells into 0.2mol/L dilute hydrochloric acid solution at normal temperature for 24 hours to remove calcium carbonate, then putting the swimming crab shells into 8 wt.% sodium hydroxide solution for 8 hours to remove protein, then putting the swimming crab shells into pure ethanol solution to soak for 24 hours to remove pigment, and then washing the swimming crab shells with water to remove residual chemical substances. Soaking the obtained chitin in dilute acetic acid solution with pH of 3.5 for 24 hr, and stirring in a wall breaking machine at high speed for 5 min to obtain uniform slurry. Diluting the chitin slurry to the concentration of 1 wt.% by using deionized water, performing suction filtration to form a film by using a vacuum filtration method, and then placing the film in a hot press to perform hot pressing for 12 hours under the conditions that the temperature is 50 ℃ and the pressure is 10MPa to obtain an initial chitin film. The film was reacted in 50 wt.% sodium hydroxide solution at 90 ℃ for 8 hours, after which the sample was taken out and washed clean in water. And finally, placing the sample in a hot press, and maintaining the pressure for 24 hours under the conditions that the temperature is 50 ℃ and the pressure is 10MPa to finally obtain the waterproof and antibacterial chitosan transparent film. The wet tensile strength of the film after 24 hours immersion in water was 42 MPa.
Example 4
Putting the Eriocheir sinensis shell into 2mol/L dilute hydrochloric acid solution at normal temperature for 4 hours to remove calcium carbonate, then putting into 4 wt.% sodium hydroxide solution for 24 hours to remove protein, then putting into pure ethanol solution to soak for 2 hours to remove pigment, and then washing with water to remove residual chemical substances. The obtained chitin is placed in a dilute acetic acid solution with the pH value of 3 for soaking for 24 hours, and then the chitin is placed in a wall breaking machine for high-speed stirring for 30 minutes to obtain uniform slurry. Diluting the chitin slurry to the concentration of 1 wt.% by using deionized water, performing suction filtration to form a film by using a vacuum filtration method, and then placing the film in a hot press to perform hot pressing for 6 hours under the conditions that the temperature is 80 ℃ and the pressure is 5MPa to obtain an initial chitin film. The film was reacted in 50 wt.% sodium hydroxide solution at 70 ℃ for 12 hours, after which the sample was taken out and washed clean in water. And finally, placing the sample in a hot press, and maintaining the pressure for 24 hours under the conditions that the temperature is 50 ℃ and the pressure is 5MPa to finally obtain the waterproof and antibacterial chitosan transparent film. The wet tensile strength of the film after 24 hours immersion in water was 46 MPa.
Example 5
Putting the Eriocheir sinensis shell into 1mol/L dilute hydrochloric acid solution at normal temperature for 12 hours to remove calcium carbonate, then putting into 4 wt.% sodium hydroxide solution for 24 hours to remove protein, then putting into pure ethanol solution to soak for 48 hours to remove pigment, and then washing with water to remove residual chemical substances. The obtained chitin is put into a dilute acetic acid solution with the pH value of 3 to be soaked for 24 hours, and then the chitin is put into a wall breaking machine to be stirred at high speed for 30 minutes to form uniform slurry. Diluting the chitin slurry to the concentration of 1 wt.% by using deionized water, and then placing the chitin slurry in a press to press for 48 hours under the conditions that the temperature is 25 ℃ and the pressure is 1MPa to obtain an initial chitin film. The film was reacted in 30 wt.% sodium hydroxide solution at 90 ℃ for 20 hours, after which the sample was taken out and washed clean in water. And finally, placing the sample in a hot press, and maintaining the pressure for 48 hours under the conditions that the temperature is 60 ℃ and the pressure is 1MPa to finally obtain the waterproof and antibacterial chitosan transparent film. The wet tensile strength of the film after 24 hours immersion in water was 46 MPa.
Example 6
Putting the Eriocheir sinensis shell into 1mol/L dilute hydrochloric acid solution at normal temperature for 12 hours to remove calcium carbonate, then putting into 4 wt.% sodium hydroxide solution for 24 hours to remove protein, then putting into pure ethanol solution to soak for 12 hours to remove pigment, and then washing with water to remove residual chemical substances. The obtained chitin is put into a dilute acetic acid solution with the pH value of 3.5 to be soaked for 24 hours, and then the chitin is put into a wall breaking machine to be stirred for 30 minutes at high speed to form uniform slurry. Diluting the chitin slurry to the concentration of 1 wt.% by using deionized water, performing suction filtration to form a film by using a vacuum filtration method, and then placing the film in a hot press to perform hot pressing for 6 hours under the conditions that the temperature is 100 ℃ and the pressure is 5MPa to obtain an initial chitin film. The film was reacted in 50 wt.% sodium hydroxide solution at 90 ℃ for 8 hours, after which the sample was taken out and washed clean in water. And finally, placing the sample in a hot press, and maintaining the pressure for 6 hours under the conditions that the temperature is 100 ℃ and the pressure is 10MPa to finally obtain the waterproof and antibacterial chitosan transparent film. The wet tensile strength of the film after 24 hours immersion in water was 52 MPa.
Example 7
Putting the Eriocheir sinensis shell into 1mol/L dilute hydrochloric acid solution at normal temperature for 12 hours to remove calcium carbonate, then putting into 4 wt.% sodium hydroxide solution for 24 hours to remove protein, then putting into pure ethanol solution to soak for 12 hours to remove pigment, and then washing with water to remove residual chemical substances. The obtained chitin is placed in a dilute acetic acid solution with the pH value of 3 for soaking for 24 hours, and then the chitin is placed in a wall breaking machine for high-speed stirring for 60 minutes to form uniform slurry. The chitin slurry was diluted to a concentration of 1 wt.% with deionized water and the initial chitin film was obtained by solvent evaporation. The film was reacted in 50 wt.% sodium hydroxide solution at 90 ℃ for 8 hours, after which the sample was taken out and washed clean in water. And finally, placing the sample in a hot press, and maintaining the pressure for 12 hours under the conditions that the temperature is 80 ℃ and the pressure is 10MPa to finally obtain the waterproof and antibacterial chitosan transparent film. The wet tensile strength of the film after 24 hours immersion in water was 41 MPa.
Example 8
Commercial chitin powder is placed in 0.5mol/L dilute hydrochloric acid solution at normal temperature for 2 hours to remove calcium carbonate, then placed in 4 wt.% sodium hydroxide solution for 6 hours to remove protein, then placed in pure ethanol solution for 4 hours to remove pigment, and then washed with water to remove residual chemical substances. And (3) soaking the purified chitin in a dilute acetic acid solution with the pH value of 3 for 24 hours, and then placing the chitin in a wall breaking machine and stirring the chitin at a high speed for 30 minutes to obtain uniform slurry. Diluting the chitin slurry to the concentration of 1 wt.% by using deionized water, performing vacuum filtration to form a film, and then placing the film in a hot press to perform hot pressing for 12 hours under the conditions that the temperature is 50 ℃ and the pressure is 5MPa to obtain an initial chitin film. The film was reacted in 50 wt.% sodium hydroxide solution at 90 ℃ for 8 hours, after which the sample was taken out and washed clean in water. And finally, placing the sample in a hot press, and maintaining the pressure for 24 hours under the conditions that the temperature is 50 ℃ and the pressure is 5MPa to finally obtain the waterproof and antibacterial chitosan transparent film. The wet tensile strength of the film after 24 hours immersion in water was 48 MPa.
Comparative example 1
Putting the Eriocheir sinensis shell into 1mol/L dilute hydrochloric acid solution at normal temperature for 12 hours to remove calcium carbonate, then putting into 4 wt.% sodium hydroxide solution for 24 hours to remove protein, then putting into pure ethanol solution to soak for 12 hours to remove pigment, and then washing with water to remove residual chemical substances. The obtained crab shell chitin is placed in a dilute acetic acid solution with the pH value of 3 for soaking for 24 hours, and then the crab shell chitin is placed in a wall breaking machine for stirring at high speed for 30 minutes to form uniform slurry. Diluting the chitin slurry to the concentration of 1 wt.% by using deionized water, performing suction filtration to form a film by using a vacuum filtration method, and then placing the film in a hot press to perform hot pressing for 12 hours under the conditions that the temperature is 50 ℃ and the pressure is 5MPa to obtain the chitin film. The film has a wet tensile strength of only 7MPa after being soaked in water for 24 hours because of no sodium hydroxide treatment, and has very low water resistance.
Claims (10)
1. The waterproof and antibacterial chitosan transparent film is characterized in that the film is formed by recombining fibers extracted from shrimp and crab shells, and the fibers are mutually and crisscross entangled to form a compact three-dimensional cross-linked network structure; the film is free of additional additives.
2. The water-resistant antibacterial chitosan transparent film as claimed in claim 1, wherein the thickness of the film is 10 μm to 500 μm, and the diameter of chitosan fiber is 10nm to 5 μm.
3. The water-resistant antibacterial chitosan transparent film as claimed in claim 1, wherein the dry tensile strength of the film is 90-140MPa, and the wet tensile strength is 40-60 MPa.
4. The water-resistant antibacterial chitosan transparent film as claimed in claim 1, wherein the transparency of the film is 85-92%.
5. A preparation method of a waterproof and antibacterial chitosan transparent film is characterized by comprising the following steps:
(1) putting shrimp shell, crab shell or chitin powder in dilute hydrochloric acid solution, sodium hydroxide solution and ethanol solution in sequence at normal temperature for reaction to remove calcium carbonate, protein and pigment respectively, and then cleaning with water;
(2) soaking the chitin obtained in the step (1) in a dilute acetic acid solution for a certain time, stirring the chitin into uniform slurry, and preparing a film by combining suction filtration with a pre-pressing method or a solution evaporation method;
(3) and (3) treating the chitin film obtained in the step (2) in a sodium hydroxide solution to form a finger-crosslinked network structure, and then placing the finger-crosslinked network structure in a press for hot pressing to obtain the high-strength waterproof antibacterial chitosan transparent film.
6. The preparation method of the water-resistant antibacterial chitosan transparent film as claimed in claim 5, wherein in the step (1), the shrimp shells are of lobsters, and the crab shells are of eriocheir sinensis or swimming crabs.
7. The method for preparing a water-resistant antibacterial chitosan transparent film as claimed in claim 5, wherein in the step (1), the concentration of the dilute hydrochloric acid is 0.1-2mol/L, and the treatment time is 1-24 hours; the concentration of the sodium hydroxide solution is 2-10 wt.%, and the treatment time is 6-48 hours; the concentration of the ethanol solution is 100 percent, and the treatment time is 2 to 48 hours.
8. The method for preparing a water-resistant antibacterial chitosan transparent film as claimed in claim 5, wherein in the step (2), the pH value of the dilute acetic acid solution is 3-3.5, and the soaking time is 6-48 hours.
9. The method for preparing a water-resistant antibacterial chitosan transparent film as claimed in claim 5, wherein in the step (2), when using a pre-pressing method, the pre-pressing temperature of the press is 25-100 ℃, the pressure is 1-10MPa, and the pressure holding time is 6-48 hours; when the solution evaporation method is used, the temperature is 25-50 ℃ and the time is 24-72 hours.
10. The method for preparing a water-resistant antibacterial chitosan transparent film as claimed in claim 5, wherein in step (3), the sodium hydroxide solution concentration is 30-50 wt.%, the treatment temperature is 60-100 ℃, the treatment time is 1-20 hours, the press temperature is 25-100 ℃, the pressure is 1-10MPa, and the dwell time is 6-48 hours.
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