Method for regulating and controlling wet mechanical properties of nanocellulose-based macroscopic fibers
By crosslinking nanocellulose with cations and spinning in acid solution, the problem of poor water absorption in the existing nanocellulose spinning molding method is solved, and the water resistance and wet strength of the fiber are significantly improved.
Patent Information
- Application Number
- CN202510620244.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-14
- Publication Date
- 2025-06-27
AI Technical Summary
In the existing nanocellulose spinning molding method, extremely volatile organic solvents are used as the solidification bath, resulting in extremely poor water absorption of macro fibers, which affects its application and environmental pollution.
The wet mechanical properties of nanocellulose-based macrofibers are regulated by crosslinking nanocellulose-based macrofibers. Specific steps include treatment of plant fiber materials, TEMPO oxidation and high pressure homogenization, weak crosslinking of metal cations, spinning and drying in acid solution to obtain crude fibers, and testing their wet mechanical properties.
The water resistance and wet strength of the macroscopic fiber are significantly improved and enhanced. Through the synergistic action of H+ and metal cations, the water resistance and wet strength of the fiber are further improved.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of regulating the wet mechanical properties of fibers, and particularly to a method for regulating the wet mechanical properties of nanocellulose-based macrofibers Background Art
[0002] With the rapid economic development and urbanization, the industrialization process has accelerated, and the phenomena of energy crisis and white pollution have become increasingly serious. Cellulose, with the characteristics of rich reserves, renewable, degradable, and good biocompatibility (Paper Science and Technology, 2017, 36: 36-39), is expected to become one of the alternatives to petroleum-based materials. Among them, nanocellulose has nanoscale dimensions, extremely high mechanical properties, and a surface that is easy to chemically modify (Transactions of China Pulp and Paper, 2023, 38: 126-133). Nanocellulose materials can be widely applied in energy storage, textiles, optoelectronic devices, etc. (Packaging Engineering, 2024, 45, 40-53). However, for the spinning and forming of nanocellulose, researchers often use organic solvents to dehydrate and form it
[0003] Currently, researchers apply the materials formed by spinning nanocellulose in textiles, sensing, etc. The methods for spinning and forming nanocellulose suspensions include: wet spinning, dry spinning, etc. Among them, wet spinning is the main method for spinning and forming nanocellulose, which mainly spins and forms through an organic coagulation bath and a high-concentration ionic solution. Shinichiro et al. used acetone as the coagulation bath to spin and form a 1 wt% nanocellulose suspension, and obtained fibers with a tensile strength and tensile stress of 23.9 GPa and 321 MPa respectively (Biomacromolecules, 2011, 3, 831–836). Wang et al. used ethanol as the coagulation bath to spin and form a nanocellulose suspension, and obtained fibers with a tensile strength and tensile stress of 15 GPa and 232 MPa respectively (Scientific Reports, 2019, 9, 16691). Yao et al. also used acetone as the coagulation bath to continuously spin a bacterial nanocellulose suspension, and spun at a concentration of 5.4 wt%, obtaining a tensile strength and tensile stress of 12 GPa and 198 MPa (ACS Applied Materials & Interfaces, 2017, 9(24), 20330-20339.)
[0004] For the methods of spinning and forming nanocellulose suspensions disclosed above, most of the selected coagulation baths are highly volatile organic solvents. There is an electrostatic repulsion of anions inside the prepared macrofibers, resulting in extremely poor water absorption, which affects the application of the macrofibers in life. And the environmental pollution is also relatively large Summary of the Invention
[0005] In view of the deficiencies of the prior art, the present invention provides a method for regulating the wet mechanical properties of nanocellulose-based macrofibers, enabling the nanocellulose-based macrofibers to have excellent wet properties.
[0006] To achieve the above objectives, the present invention is realized through the following technical solutions:
[0007] The present invention crosslinks nanocellulose with one or more cations, providing a new method for regulating the wet mechanical properties of nanocellulose-based macrofibers.
[0008] The present invention discloses a method for regulating the wet mechanical properties of nanocellulose-based macrofibers, comprising the following steps:
[0009] (1) Subjecting plant fiber materials to alkali, bleaching, and alkali / urea treatments respectively;
[0010] (2) Subjecting the treated materials to TEMPO oxidation and high-pressure homogenization to obtain a uniformly dispersed nanocellulose suspension, and adding metal cations to the nanocellulose suspension for weak crosslinking;
[0011] (3) The nanocellulose suspension enters acid solutions of different concentrations and is directly pulled up to form fibers by spinning;
[0012] (4) Obtaining coarse fibers through drying and water washing, and testing their wet mechanical properties.
[0013] Preferably, in step (1), the plant fiber material is one or more of bamboo, reed, rice straw, wheat straw, bagasse, and their processing residues.
[0014] Preferably, in step (1), the alkali is NaOH, and a 1-5% NaOH solution is used to react at 80°C for 1-2 hours.
[0015] Preferably, in step (1), the bleaching treatment is: using 1-3% NaClO to react at 60-80°C for 1-4 hours.
[0016] Preferably, in step (1), the alkali / urea treatment process is: using a 5-7wt% NaOH and 1wt% urea solution to keep the temperature constant at 30-50°C for 30 minutes, and treating three times.
[0017] Preferably, in step (2), the TEMPO oxidation process is: reacting the treated materials with 0.015g / g TEMPO, 0.1g / g NaBr, and 4-12mmol / g NaClO for 1-5 hours.
[0018] Preferably, in step (2), the high-pressure homogenization process is as follows: the oxidized material is homogenized 5 times or more at 600-2000 bar, and the concentration of the obtained nano-cellulose suspension is above 1 wt%.
[0019] Preferably, in step (2), the cation is a polyvalent metal cation, and the addition amount of the cation < 0.4 mmol / g.
[0020] Preferably, in step (3), the acid solution is any one of hydrochloric acid, sulfuric acid, phytic acid, phosphoric acid, and nitric acid, the concentration of the acid solution ≥ 0.01 M, and the spinning rate should be 10-50 m / s;
[0021] Preferably, in step (4), for the water washing and drying, first soak in 0.0003 M HCl at 40-60 °C for 10-120 min, then carry out drying, the drying temperature is 30-100 °C, wash once with deionized water, and then dry again; for the wet mechanical property test, first soak in water for more than 1 h, and then use a universal material tensile machine for testing.
[0022] The present invention has the following beneficial effects:
[0023] In the present invention, H + and metal cations are used to regulate the wet properties of nano-cellulose-based macrofibers. The results show that the water resistance and wet strength of the macrofibers are significantly improved and enhanced. Among them, through the synergistic effect of H + and metal cations, the water resistance and wet strength of the macrofibers are further improved. Description of the Drawings
[0024] Figure 1 It is the FTIR diagram of the macrofiber formed by the acid solution;
[0025] Figure 2 It is the scanning electron microscope diagram of the macrofiber surface;
[0026] Figure 3 It is the scanning electron microscope diagram of the macrofiber cross-section;
[0029] Figure 4 It is the infrared and EDS diagrams of the double-crosslinked macrofiber;
[0030] Figure 5 It is the stress-strain curve diagram of the wet mechanical properties of the macrofiber. Detailed Embodiments
[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.
[0032] Unless otherwise specified, the technical means used in the implementation examples are conventional means well known to those skilled in the art.
[0033] The present invention discloses a method for regulating the wet mechanical properties of nano-cellulose-based macro fibers, including the following steps:
[0034] (1) The plant fiber materials are respectively treated with alkali, bleaching, and alkali / urea to remove most of the lignin and hemicellulose; the alkali is NaOH, and a 1-5% NaOH solution is used to react at 80°C for 1-2 h to fully disperse the fibers. The bleaching treatment is as follows: 1-3% NaClO is used to react at 60-80°C for 1-4 h to almost completely remove the lignin. The alkali / urea treatment process is as follows: a 5-7 wt% NaOH and 1 wt% urea solution are used to keep the temperature constant at 30-50°C for 30 min, and the treatment is carried out three times.
[0035] According to the present invention, the raw material is a non-wood raw material. Preferably, the raw material is one or more of bamboo, reed, rice straw, wheat straw, bagasse, and their processing residues; more preferably, it is one or more of moso bamboo, Neosinocalamus affinis, Neosinocalamus breviflorus, Bambusa pervariabilis×Dendrocalamopsis grandis, Phyllostachys viridis, Lingnania chungii, Sinobambusa tootsik, bamboo processing residues, and pulp and paper-making residues, thereby improving the resource utilization rate.
[0036] (2) The treated materials are subjected to TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl radical) oxidation and high-pressure homogenization to obtain a uniformly dispersed nano-cellulose suspension, and metal cations are added to the nano-cellulose suspension for weak crosslinking; the TEMPO oxidation process is as follows: the treated materials are reacted with 0.015 g / g TEMPO, 0.1 g / g NaBr, and 4-12 mmol / g NaClO for 1-5 h. The high-pressure homogenization process is as follows: the oxidized materials are homogenized at 600-2000 bar for more than 5 times, and the concentration of the obtained nano-cellulose suspension is above 1 wt%, and nano-cellulose with a diameter of about 1-5 nm, a length of more than micron level, and a high carboxyl content can be obtained. The cation is a polyvalent metal cation, and the addition amount of the cation < 0.4 mmol / g. The metal includes but is not limited to any one of Fe, Cu, Al, Ca, and Zn. Among them, the high-pressure homogenization method can be any one of high-pressure homogenizer homogenization and ultrasonic machine dispersion.
[0037] (3) The nanofibrillated cellulose suspension is extruded into different concentrations of acid solutions through a micro-injection pump and syringe, and then directly pulled up to form fibers by spinning. The acid solution can be any one of hydrochloric acid, sulfuric acid, phytic acid, phosphoric acid, and nitric acid. The concentration of the acid solution is ≥ 0.01 M. The syringe model can be 18-22G, with a length of 5-15 cm, and the spinning rate should be 10-50 m / s.
[0038] (4) Coarse fibers are obtained by drying and washing, and their wet mechanical properties are tested according to international standards. For the washing and drying process, first soak in 0.0003 M HCl at 40-60 °C for 10-120 min, then dry at a drying temperature of 30-100 °C, wash once with deionized water, and dry again. For the wet mechanical property test, first soak in water for more than 1 h, and then test using a universal material tensile testing machine. Among them, the drying method can be any one of vacuum oven drying, forced air drying, and microwave drying.
[0039] The macroscopic cellulose prepared by the present invention has a size of 50-70 μm, and its tensile stress ranges from 160-470 MPa. The wet macroscopic fiber has a size of 80-130 μm, and its tensile stress is 12-120 MPa.
[0040] The present invention will be further elaborated below in conjunction with specific embodiments.
[0041] Example 1
[0042] A method for regulating the wet mechanical properties of nanofibrillated cellulose-based macroscopic fibers includes the following steps:
[0043] (1) Moso bamboo primary fibers are successively reacted in 5% NaOH at 80 °C for 1 h, and then reacted in 1.5% NaClO at 80 °C for 1 h. Then, they are placed in a 40 °C constant temperature water bath with 6% NaOH and 1 wt% urea and reacted for 30 min, washed to neutrality, and the above alkali / urea steps are repeated three times to remove most of the lignin and hemicellulose, obtaining bamboo fibers with a higher cellulose purity.
[0044] (2) The bamboo fibers after removing most of the lignin and hemicellulose are reacted with 0.015 g / g TEMPO, 0.1 g / g NaBr, and 10 mmol / g NaClO for 4 h, diluted to 1 wt%, and then subjected to high-pressure homogenization 6 times at 1800 bar to obtain a nanofibrillated cellulose suspension that is uniformly dispersed in an aqueous solution.
[0045] (3) The nanofibrillated cellulose suspension is extruded into a 0.01 M hydrochloric acid solution through a micro-injection pump and directly pulled up to form fibers by spinning.
[0046] (4) Immerse in 200 ml of 0.0003 M HCl solution at 50 °C for 10 min, carry out water washing, then place in an oven for drying, wash with deionized water again, and dry again to obtain macrofibers with excellent mechanical properties.
[0047] (5) Immerse the macrofibers in water for more than 1 h, and test their wet-state mechanical properties through a universal tensile testing machine.
[0048] The average diameter of the macrofibers is 65.65 μm, the tensile stress is 263 ± 26 MPa, the diameter of the macrofibers in the wet state is 113.45 μm, and the tensile stress is 25 ± 7 MPa.
[0049] Example 2
[0050] A method for regulating the wet-state mechanical properties of nanocellulose-based macrofibers, comprising the following steps:
[0051] (1) Moso bamboo primary fibers are successively reacted in 5% NaOH at 80 °C for 1 h, reacted in 1.5% NaClO at 80 °C for 1 h; placed in a 40 °C constant temperature water bath and reacted in 6% NaOH and 1 wt% urea for 30 min, washed to neutrality, and the above-mentioned alkali / urea steps are repeated three times to remove most of the lignin and hemicellulose to obtain bamboo fibers with a relatively high cellulose purity.
[0052] (2) The bamboo fibers after removing most of the lignin and hemicellulose are reacted with 0.015 g / g TEMPO, 0.1 g / g NaBr, and 10 mmol / g NaClO for 4 h, diluted to 1 wt%, and subjected to high-pressure homogenization 6 times at 1800 bar to obtain a nanocellulose suspension with uniform dispersion in an aqueous solution.
[0053] (3) The nanocellulose suspension is extruded into a 0.02 M hydrochloric acid solution through a micro-injection pump and directly pulled up to form fibers by spinning.
[0054] (4) Immerse in 200 ml of 0.0003 M HCl solution at 50 °C for 10 min, carry out water washing, then place in an oven for drying, wash with deionized water again, and dry again to obtain macrofibers with excellent mechanical properties.
[0055] (5) Immerse the macrofibers in water for more than 1 h, and test their wet-state mechanical properties through a universal tensile testing machine.
[0056] The average diameter of the macrofibers is 63.56 μm, the tensile stress is 295 ± 29 MPa, the diameter of the macrofibers in the wet state is 107.78 μm, and the tensile stress is 39 ± 5 MPa.
[0057] Example 3
[0058] A method for regulating the wet mechanical properties of nanocellulose-based macrofibers, comprising the following steps:
[0059] (1) The original moso bamboo fibers are reacted successively in 5% NaOH at 80 °C for 1 h, in 1.5% NaClO at 80 °C for 1 h; and in 6% NaOH and 1 wt% urea in a 40 °C constant temperature water bath for 30 min, washed to neutrality, and the above alkali / urea steps are repeated three times to remove most of the lignin and hemicellulose, obtaining bamboo fibers with a higher cellulose purity.
[0060] (2) The bamboo fibers after removing most of the lignin and hemicellulose are reacted with 0.015 g / g TEMPO, 0.1 g / g NaBr, and 10 mmol / g NaClO for 4 h, diluted to 1 wt%, and then subjected to high-pressure homogenization 6 times at 1800 bar to obtain a uniformly dispersed nanocellulose suspension in an aqueous solution;
[0061] (3) The nanocellulose suspension is extruded into a 0.04 M hydrochloric acid solution through a micro-injection pump and directly pulled up to form fibers by spinning.
[0062] (4) Soak in a 200 ml 0.0003 M HCl solution at 50 °C for 10 min, wash with water, then place in an oven for drying, wash again with deionized water, and dry again to obtain macrofibers with excellent mechanical properties.
[0063] (5) Immerse the macrofibers in water for more than 1 h, and test their wet mechanical properties with a universal tensile machine.
[0064] The average diameter of the macrofibers is 68.02 μm, the tensile stress is 239 ± 27 MPa, the diameter of the macrofibers in the wet state is 97.05 μm, and the tensile stress is 54 ± 6 MPa.
[0065] Example 4
[0066] A method for regulating the wet mechanical properties of nanocellulose-based macrofibers, comprising the following steps:
[0067] (1) The original moso bamboo fibers are reacted successively in 5% NaOH at 80 °C for 1 h, in 1.5% NaClO at 80 °C for 1 h; and in 6% NaOH and 1 wt% urea in a 40 °C constant temperature water bath for 30 min, washed to neutrality, and the above alkali / urea steps are repeated three times to remove most of the lignin and hemicellulose, obtaining bamboo fibers with a higher cellulose purity.
[0068] (2) The bamboo fibers after removing most of the lignin and hemicellulose are reacted with 0.015 g / g TEMPO, 0.1 g / g NaBr, and 10 mmol / g NaClO for 4 h, diluted to 1 wt%, and then subjected to high-pressure homogenization 6 times at 1800 bar to obtain a uniformly dispersed nanocellulose suspension in an aqueous solution.
[0069] (3) The nanocellulose suspension is extruded into a 0.01 M sulfuric acid solution through a micro-injection pump and directly pulled up to form fibers by spinning.
[0070] (4) Soak in a 200 ml 0.0003 M HCl solution at 50 °C for 10 min, wash with water, then place in an oven to dry, wash again with deionized water, and dry again to obtain macroscopic fibers with excellent mechanical properties.
[0071] (5) Immerse the macroscopic fibers in water for more than 1 h and test their wet mechanical properties using a universal tensile testing machine.
[0072] The average diameter of the macroscopic fibers is 61.11 μm, the tensile stress is 262 ± 20 MPa, the diameter of the macroscopic fibers in the wet state is 104.07 μm, and the tensile stress is 39 ± 10 MPa.
[0073] Example 5
[0074] A method for regulating the wet mechanical properties of nanocellulose-based macroscopic fibers, comprising the following steps:
[0075] (1) The original moso bamboo fibers are successively reacted in 5% NaOH at 80 °C for 1 h, in 1.5% NaClO at 80 °C for 1 h; placed in a 40 °C constant temperature water bath in 6% NaOH and 1 wt% urea and reacted for 30 min, washed to neutral, and the above alkali / urea steps are repeated three times to remove most of the lignin and hemicellulose to obtain bamboo fibers with a higher cellulose purity.
[0076] (2) The bamboo fibers after removing most of the lignin and hemicellulose are reacted with 0.015 g / g TEMPO, 0.1 g / g NaBr, and 10 mmol / g NaClO for 4 h, diluted to 1 wt%, and then subjected to high-pressure homogenization 6 times at 1800 bar to obtain a uniformly dispersed nanocellulose suspension in an aqueous solution.
[0077] (3) The nanocellulose suspension is extruded into a 0.02 M sulfuric acid solution through a micro-injection pump and directly pulled up to form fibers by spinning.
[0078] (4) Immerse in 200 ml of 0.0003 M HCl solution at 50 °C for 10 min, wash with water, then place in an oven to dry, wash again with deionized water, and dry again to obtain macroscopic fibers with excellent mechanical properties.
[0079] (5) Immerse the macroscopic fibers in water for more than 1 h, and test their wet mechanical properties using a universal tensile testing machine.
[0080] The average diameter of the macroscopic fibers is 63.16 μm, the tensile stress is 249 ± 34 MPa, the diameter of the macroscopic fibers in the wet state is 93.52 μm, and the tensile stress is 58 ± 8 MPa.
[0081] Example 6
[0082] A method for regulating the wet mechanical properties of nanocellulose-based macroscopic fibers, comprising the following steps:
[0083] (1) The raw moso bamboo fibers are successively reacted in 5% NaOH at 80 °C for 1 h, in 1.5% NaClO at 80 °C for 1 h; placed in a 40 °C constant temperature water bath and reacted in 6% NaOH and 1 wt% urea for 30 min, washed to neutrality, and the above alkali / urea steps are repeated three times to remove most of the lignin and hemicellulose to obtain bamboo fibers with a higher cellulose purity.
[0084] (2) React the bamboo fibers after removing most of the lignin and hemicellulose with 0.015 g / g TEMPO, 0.1 g / g NaBr, and 10 mmol / g NaClO for 4 h, dilute to 1 wt%, and perform high-pressure homogenization 6 times at 1800 bar to obtain a nanocellulose suspension with uniform dispersion in an aqueous solution;
[0085] (3) The nanocellulose suspension is extruded into a 0.04 M sulfuric acid solution through a micro-injection pump and directly pulled up to form fibers by spinning.
[0086] (4) Immerse in 200 ml of 0.0003 M HCl solution at 50 °C for 10 min, wash with water, then place in an oven to dry, wash again with deionized water, and dry again to obtain macroscopic fibers with excellent mechanical properties.
[0087] (5) Immerse the macroscopic fibers in water for more than 1 h, and test their wet mechanical properties using a universal tensile testing machine.
[0088] The average diameter of the macroscopic fibers is 63.35 μm, the tensile stress is 191 ± 31 MPa, the diameter of the macroscopic fibers in the wet state is 88.71 μm, and the tensile stress is 68 ± 18 MPa.
[0089] Example 7
[0090] A method for regulating the wet mechanical properties of nanocellulose-based macrofibers, comprising the following steps:
[0091] (1) The raw moso bamboo fibers are reacted successively in 5% NaOH at 80 °C for 1 h, in 1.5% NaClO at 80 °C for 1 h; and in 6% NaOH and 1 wt% urea in a 40 °C constant temperature water bath for 30 min, washed to neutrality, and the above-mentioned alkali / urea steps are repeated three times to remove most of the lignin and hemicellulose, obtaining bamboo fibers with a higher cellulose purity.
[0092] (2) The bamboo fibers after removing most of the lignin and hemicellulose are reacted with 0.015 g / g TEMPO, 0.1 g / g NaBr, and 10 mmol / g NaClO for 4 h, diluted to 1 wt%, and then subjected to high-pressure homogenization 6 times at 1800 bar to obtain a uniformly dispersed nanocellulose suspension in an aqueous solution.
[0093] (3) The nanocellulose suspension is extruded into a 0.01 M phosphoric acid solution through a micro-injection pump and directly pulled up to form fibers by spinning.
[0094] (4) It is soaked in a 200 ml 0.0003 M HCl solution at 50 °C for 10 min, washed with water, then placed in an oven for drying, washed again with deionized water, and dried again to obtain macrofibers with excellent mechanical properties.
[0095] (5) The macrofibers are soaked in water for more than 1 h, and their wet mechanical properties are tested by a universal tensile machine.
[0096] The average diameter of the said macrofibers is 60.32 μm, the tensile stress is 243 ± 26 MPa, the diameter of the macrofibers in the wet state is 109.85 μm, and the tensile stress is 32 ± 10 MPa.
[0097] Example 8
[0098] A method for regulating the wet mechanical properties of nanocellulose-based macrofibers, comprising the following steps:
[0099] (1) The raw moso bamboo fibers are reacted successively in 5% NaOH at 80 °C for 1 h, in 1.5% NaClO at 80 °C for 1 h; and in 6% NaOH and 1 wt% urea in a 40 °C constant temperature water bath for 30 min, washed to neutrality, and the above-mentioned alkali / urea steps are repeated three times to remove most of the lignin and hemicellulose, obtaining bamboo fibers with a higher cellulose purity;
[0100] (2) The bamboo fibers after removing most of the lignin and hemicellulose are reacted with 0.015 g / g TEMPO, 0.1 g / g NaBr, and 10 mmol / g NaClO for 4 h, diluted to 1 wt%, and then subjected to high-pressure homogenization 6 times at 1800 bar to obtain a uniformly dispersed nanocellulose suspension in an aqueous solution.
[0101] (3) The nanocellulose suspension is extruded into a 0.02 M phosphoric acid solution through a micro-injection pump and directly pulled up to form fibers by spinning.
[0102] (4) Immerse in a 200 ml 0.0003 M HCl solution at 50 °C for 10 min, wash with water, then place in an oven to dry, wash again with deionized water, and dry again to obtain macroscopic fibers with excellent mechanical properties.
[0103] (5) Immerse the macroscopic fibers in water for more than 1 h and test their wet mechanical properties using a universal tensile testing machine.
[0104] The average diameter of the macroscopic fibers is 62.84 μm, the tensile stress is 234 ± 23 MPa, the diameter of the macroscopic fibers in the wet state is 100.76 μm, and the tensile stress is 42 ± 6 MPa.
[0105] Example 9
[0106] A method for regulating the wet mechanical properties of nanocellulose-based macroscopic fibers, comprising the following steps:
[0107] (1) The raw bamboo fibers of Phyllostachys edulis are successively reacted in 5% NaOH at 80 °C for 1 h, reacted in 1.5% NaClO at 80 °C for 1 h; placed in a 40 °C constant temperature water bath in 6% NaOH and 1 wt% urea and reacted for 30 min, washed to neutrality, and the above-mentioned alkali / urea steps are repeated three times to remove most of the lignin and hemicellulose to obtain bamboo fibers with a relatively high cellulose purity;
[0108] (2) The bamboo fibers after removing most of the lignin and hemicellulose are reacted with 0.015 g / g TEMPO, 0.1 g / g NaBr, and 10 mmol / g NaClO for 4 h, diluted to 1 wt%, and then subjected to high-pressure homogenization 6 times at 1800 bar to obtain a uniformly dispersed nanocellulose suspension in an aqueous solution.
[0109] (3) The nanocellulose suspension is extruded into a 0.04 M phosphoric acid solution through a micro-injection pump and directly pulled up to form fibers by spinning.
[0110] (4) Immerse in 200 ml of 0.0003 M HCl solution at 50 °C for 10 min, carry out water washing, then put it in an oven for drying, wash with deionized water again, and dry again to obtain macrofibers with excellent mechanical properties.
[0111] (5) Immerse the macrofibers in water for more than 1 h, and test their wet mechanical properties through a universal tensile testing machine.
[0112] The average diameter of the macrofibers is 64.50 μm, the tensile stress is 215 ± 32 MPa, the diameter of the macrofibers in the wet state is 96.48 μm, and the tensile stress is 49 ± 10 MPa.
[0113] Example 10
[0114] A method for regulating the wet mechanical properties of nanocellulose-based macrofibers, comprising the following steps:
[0115] (1) Moso bamboo primary fibers are successively reacted in 5% NaOH at 80 °C for 1 h, reacted in 1.5% NaClO at 80 °C for 1 h; placed in a 40 °C constant temperature water bath and reacted in 6% NaOH and 1 wt% urea for 30 min, washed to neutrality, and the above-mentioned alkali / urea steps are repeated three times to remove most of the lignin and hemicellulose to obtain bamboo fibers with higher cellulose purity;
[0116] (2) React the bamboo fibers after removing most of the lignin and hemicellulose with 0.015 g / g TEMPO, 0.1 g / g NaBr, and 10 mmol / g NaClO for 4 h, dilute to 1 wt%, and carry out high-pressure homogenization 6 times at 1800 bar to obtain a uniformly dispersed nanocellulose suspension in an aqueous solution.
[0117] (3) The nanocellulose suspension is extruded into a 0.01 M phytic acid solution through a micro-injection pump and directly pulled up to form fibers by spinning.
[0118] (4) Immerse in 200 ml of 0.0003 M HCl solution at 50 °C for 10 min, carry out water washing, then put it in an oven for drying, wash with deionized water again, and dry again to obtain macrofibers with excellent mechanical properties.
[0119] (5) Immerse the macrofibers in water for more than 1 h, and test their wet mechanical properties through a universal tensile testing machine.
[0120] The average diameter of the macrofibers is 64.52 μm, the tensile stress is 245 ± 33 MPa, the diameter of the macrofibers in the wet state is 105.15 μm, and the tensile stress is 54 ± 6 MPa.
[0121] Example 11
[0122] A method for regulating the wet mechanical properties of nanocellulose-based macrofibers, comprising the following steps:
[0123] (1) The raw moso bamboo fibers are reacted successively in 5% NaOH at 80 °C for 1 h, in 1.5% NaClO at 80 °C for 1 h; in 6% NaOH and 1 wt% urea in a 40 °C constant temperature water bath for 30 min, washed to neutrality, and the above-mentioned alkali / urea steps are repeated three times to remove most of the lignin and hemicellulose, obtaining bamboo fibers with a higher cellulose purity.
[0124] (2) The bamboo fibers after removing most of the lignin and hemicellulose are reacted with 0.015 g / g TEMPO, 0.1 g / g NaBr and 10 mmol / g NaClO for 4 h, diluted to 1 wt% and then subjected to high-pressure homogenization 6 times at 1800 bar to obtain a uniformly dispersed nanocellulose suspension in an aqueous solution.
[0125] (3) The nanocellulose suspension is extruded into a 0.02 M phytic acid solution through a micro-injection pump and directly pulled up to form fibers by spinning.
[0126] (4) It is soaked in a 200 ml 0.0003 M HCl solution at 50 °C for 10 min, washed with water, then dried in an oven, washed again with deionized water, and dried again to obtain macrofibers with excellent mechanical properties.
[0127] (5) The macrofibers are soaked in water for more than 1 h, and their wet mechanical properties are tested by a universal tensile machine.
[0128] The average diameter of the macrofibers is 63.36 μm, the tensile stress is 233 ± 24 MPa, the diameter of the macrofibers in the wet state is 92.20 μm, and the tensile stress is 67 ± 11 MPa.
[0129] Example 12
[0130] A method for regulating the wet mechanical properties of nanocellulose-based macrofibers, comprising the following steps:
[0131] (1) The raw moso bamboo fibers are reacted successively in 5% NaOH at 80 °C for 1 h, in 1.5% NaClO at 80 °C for 1 h; in 6% NaOH and 1 wt% urea in a 40 °C constant temperature water bath for 30 min, washed to neutrality, and the above-mentioned alkali / urea steps are repeated three times to remove most of the lignin and hemicellulose, obtaining bamboo fibers with a higher cellulose purity.
[0132] (2) The bamboo fibers after removing most of the lignin and hemicellulose are reacted with 0.015 g / g TEMPO, 0.1 g / g NaBr, and 10 mmol / g NaClO for 4 h, diluted to 1 wt%, and then subjected to high-pressure homogenization 6 times at 1800 bar to obtain a uniformly dispersed nanocellulose suspension in an aqueous solution.
[0133] (3) The nanocellulose suspension is extruded into a 0.04 M phytic acid solution through a microinjection pump and directly pulled up to form fibers by spinning.
[0134] (4) It is soaked in a 200 ml 0.0003 M HCl solution at 50 °C for 10 min, washed with water, then placed in an oven for drying, washed again with deionized water, and dried again to obtain macroscopic fibers with excellent mechanical properties.
[0135] (5) The macroscopic fibers are soaked in water for more than 1 h, and their wet mechanical properties are tested by a universal tensile testing machine.
[0136] The average diameter of the macroscopic fibers is 62.80 μm, the tensile stress is 231 ± 35 MPa, the diameter of the macroscopic fibers in the wet state is 89.21 μm, and the tensile stress is 76 ± 10 MPa.
[0137] Example 13
[0138] A method for regulating the wet mechanical properties of nanocellulose-based macroscopic fibers, comprising the following steps:
[0139] (1) The original moso bamboo fibers are successively reacted in 5% NaOH at 80 °C for 1 h, in 1.5% NaClO at 80 °C for 1 h; placed in a 40 °C constant temperature water bath in 6% NaOH and 1 wt% urea for 30 min, washed to neutrality, and the above alkali / urea steps are repeated three times to remove most of the lignin and hemicellulose, obtaining bamboo fibers with a relatively high cellulose purity.
[0140] (2) The bamboo fibers after removing most of the lignin and hemicellulose are reacted with 0.015 g / g TEMPO, 0.1 g / g NaBr, and 10 mmol / g NaClO for 4 h, diluted to 1 wt%, and then subjected to high-pressure homogenization 6 times at 1800 bar to obtain a uniformly dispersed nanocellulose suspension in an aqueous solution, and then 0.1 mmol / g of Al 3+ is added and stirred evenly with a blender.
[0141] (3) The nanocellulose suspension is extruded into a 0.02 M hydrochloric acid solution through a microinjection pump and directly pulled up to form fibers by spinning.
[0142] (4) Immerse it in 200 ml of 0.0003 M HCl solution at 50 °C for 10 min, carry out water washing, then put it in an oven for drying, wash it with deionized water again, and dry it again to obtain macrofibers with excellent mechanical properties.
[0143] (5) Immerse the macrofibers in water for more than 1 h, and test their wet mechanical properties through a universal tensile testing machine.
[0144] The tensile stress of the macrofibers is 432 ± 27 MPa, and the tensile stress of the macrofibers in the wet state is 101.7 ± 10.5 MPa. Compared with the macrofibers using only 0.02 M hydrochloric acid coagulation bath, the wet performance is improved by 62 MPa.
[0145] Example 14
[0146] A method for regulating the wet mechanical properties of nanocellulose-based macrofibers, comprising the following steps:
[0147] (1) Moso bamboo raw fibers are successively reacted in 5% NaOH at 80 °C for 1 h, reacted in 1.5% NaClO at 80 °C for 1 h; placed in a 40 °C constant temperature water bath and reacted in 6% NaOH and 1 wt% urea for 30 min, washed to neutral, and the above-mentioned alkali / urea steps are repeated three times to remove most of the lignin and hemicellulose to obtain bamboo fibers with higher cellulose purity.
[0148] (2) The bamboo fibers after removing most of the lignin and hemicellulose are reacted with 0.015 g / g TEMPO, 0.1 g / g NaBr and 10 mmol / g NaClO for 4 h, diluted to 1 wt% and then subjected to high-pressure homogenization 6 times at 1800 bar to obtain a nanocellulose suspension uniformly dispersed in an aqueous solution, and then 0.1 mmol / g of Ca 2+ is added and stirred evenly with a blender.
[0149] (3) The nanocellulose suspension is extruded into a 0.02 M hydrochloric acid solution through a micro-injection pump and directly pulled up to form fibers by spinning.
[0150] (4) Immerse it in 200 ml of 0.0003 M HCl solution at 50 °C for 10 min, carry out water washing, then put it in an oven for drying, wash it with deionized water again, and dry it again to obtain macrofibers with excellent mechanical properties.
[0151] (5) Immerse the macrofibers in water for more than 1 h, and test their wet mechanical properties through a universal tensile testing machine.
[0152] The macroscopic fiber tensile stress is 373 ± 32 MPa, and the macroscopic fiber tensile stress in the wet state is 74 ± 10 MPa. Compared with the macroscopic fiber using only 0.02 M hydrochloric acid coagulation bath, its wet state performance has increased by 35 MPa.
[0153] Figure 1 FTIR diagrams of different acid coagulation baths for Examples 1 - 12; among them, Figure (a) is the coagulation bath with different concentrations of HCl; Figure (b) is the coagulation bath with different concentrations of H2SO4; Figure (c) is the coagulation bath with different concentrations of H3PO4; Figure (d) is the coagulation bath with different concentrations of PA. The results show that after the fiber passes through the acid coagulation bath, a peak of carboxylic acid at 1728 cm -1 appears, indicating that during the formation process in the acid coagulation bath, dehydration and crosslinking occur simultaneously.
[0154] Figure 2 SEM surface morphology diagrams of different acid coagulation baths for Examples 1 - 12; among them, Figures (a1 - a3) are the coagulation baths with 0.01 - 0.04 M concentrations of HCl; Figures (b1 - b3) are the coagulation baths with 0.01 - 0.04 M concentrations of H2SO4; Figures (c1 - c3) are the coagulation baths with 0.01 - 0.04 M concentrations of H3PO4; Figures (d1 - d3) are the coagulation baths with 0.01 - 0.04 M concentrations of PA. The results show that the surfaces of the macroscopic fibers formed through the acid coagulation bath are relatively smooth and have obvious fiber orientation structures.
[0155] Figure 3 SEM cross-section morphology diagrams of different acid coagulation baths for Examples 1 - 12; Figures (a1 - a3) are the coagulation baths with 0.01 - 0.04 M concentrations of HCl; Figures (b1 - b3) are the coagulation baths with 0.01 - 0.04 M concentrations of H2SO4; Figures (c1 - c3) are the coagulation baths with 0.01 - 0.04 M concentrations of H3PO4; Figures (d1 - d3) are the coagulation baths with 0.01 - 0.04 M concentrations of PA. The results show that the cross-sections of the macroscopic fibers formed in the acid coagulation bath are approximately circular.
[0156] Figure 4 FTIR and EDS diagrams of the macroscopic fiber after weak crosslinking; Figure (a) is the FIRT diagram, Figure (b) is the EDS diagram of the uncrosslinked state, Figure (c) is the EDS diagram of the Al 3+ crosslinked state, Figure (d) is the EDS diagram of the Ca 2+ crosslinked state. The results show that after weak crosslinking, the nanocellulose suspension in the acid coagulation bath still undergoes crosslinking. There is a peak of carboxylic acid at 1728 cm -1 In the EDS energy spectrum, Al and Ca still show crosslinking on the macroscopic fiber, indicating that double crosslinking has occurred on the macroscopic fiber.
[0157] Figure 5It is the stress-strain curve diagram of the wet mechanical properties of the macro fibers in Example 2, Example 13 and Example 14. The results show that: compared with the simple H + crosslinking in Examples 1-12, the water resistance and wet strength of the macro fibers obtained by double crosslinking have been greatly improved.
[0158] The dry macro fiber diameters and mechanical properties under different acid coagulation baths in Examples 1-12 are shown in Table 1, and the wet macro fiber diameters and mechanical properties under different acid coagulation baths are shown in Table 2.
[0159] Table 1 is the table of dry macro fiber diameters and mechanical properties under different acid coagulation baths
[0160]
[0161]
[0162] Table 2 is the wet macro fiber diameters and mechanical properties under different acid coagulation baths
[0163] Coagulation bath Diameter (m) Young's modulus (GPa) Tensile stress (MPa) Tensile rate (%) 0.01 M HCl 113.45 1±0.5 25±7 4.3±1.7 0.02 M HCl 107.78 1.2±0.6 39±5 4.9±1.4 0.04 M HCl 97.50 3.2±1.1 54±6 3.3±1.2 <![CDATA[0.01M H2SO4]]> 104.07 1,4±0.6 39±10 4.3±1.5 <![CDATA[0.02M H2SO4]]> 93.52 2.8±1.5 58±8 4.0±1.6 <![CDATA[0.04M H2SO4]]> 88.71 3.9±1.7 68±18 3.5±1.8 <![CDATA[0.01M H3PO4]]> 109.85 1.7±0.8 32±10 3.2±1.2 <![CDATA[0.02M H3PO4]]> 100.76 2.1±1.1 42±6 3.8±1.5 <![CDATA[0.01M H3PO4]]> 96.48 2±0.8 49±10 4.2±1.4 0.01 M PA 105.15 2.8±1.1 54±6 4.0±1.1 0.02 M PA 92.20 3.1±1.5 67±11 4.4±1.5 0.04 M PA 89.21 3.0±1.5 76±10 4.7±1.2
[0164] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.
Claims
1. A method for regulating the wet mechanical properties of nanocellulose-based macroscopic fibers, characterized in that: The following steps are involved: (1) treating the plant fiber material with alkali, bleaching and alkali / urea respectively; (2) subjecting the treated material to TEMPO oxidation and high-pressure homogenization to obtain a uniformly dispersed nanocellulose suspension, and adding metal cations to the nanocellulose suspension for weak crosslinking; (3) The nanocellulose suspension enters acid solutions of different concentrations and is directly pulled up to form fibers by spinning; (4) The crude fibers were obtained by drying and washing, and their wet mechanical properties were tested.
2. A method for regulating the wet mechanical properties of nanocellulose-based macroscopic fibers according to claim 1, characterized in that: In step (1), the plant fiber material is one or more of bamboo, reed, straw, wheat straw, bagasse and processing residues thereof.
3. A method for regulating the wet mechanical properties of nanocellulose-based macroscopic fibers according to claim 1, characterized in that: In step (1), the base is NaOH, and a 1-5% NaOH solution is used to react at 80° C. for 1-2 hours.
4. A method for regulating the wet mechanical properties of nanocellulose-based macroscopic fibers according to claim 3, characterized in that: In step (1), the bleaching treatment is: using 1-3% NaClO to react at 60-80° C. for 1-4 hours.
5. A method for regulating the wet mechanical properties of nanocellulose-based macroscopic fibers according to claim 4, characterized in that: In step (1), the alkali / urea treatment process is: using 5-7wt% NaOH and 1wt% urea solution at a constant temperature of 30-50°C for 30 minutes, and treating three times.
6. A method for regulating the wet mechanical properties of nanocellulose-based macroscopic fibers according to claim 1, characterized in that: In step (2), the TEMPO oxidation process is: the treated material is reacted with 0.015 g / g TEMPO, 0.1 g / g NaBr and 4-12 mmol / g NaClO for 1-5 h.
7. A method for regulating the wet mechanical properties of nanocellulose-based macroscopic fibers according to claim 6, characterized in that: In step (2), the high-pressure homogenization process is: homogenizing the oxidized material at 600-2000 bar for more than 5 times, and the concentration of the obtained nanocellulose suspension is above 1wt%.
8. A method for regulating the wet mechanical properties of nanocellulose-based macroscopic fibers according to claim 7, characterized in that: In step (2), the cation is a multivalent metal cation, and the added amount of the cation is less than 0.4 mmol / g.
9. A method for regulating the wet mechanical properties of nanocellulose-based macroscopic fibers according to claim 1, characterized in that: In step (3), the acid solution is any one of hydrochloric acid, sulfuric acid, phytic acid, phosphoric acid and nitric acid, the concentration of the acid solution is ≥0.01M, and the spinning rate should be 10-50m / s.
10. A method for regulating the wet mechanical properties of nanocellulose-based macroscopic fibers according to claim 1, characterized in that: In step (4), the washing and drying are firstly soaking in 0.0003M HCl at 40-60°C for 10-120min, then drying at a drying temperature of 30-100°C, then washing once with deionized water, and drying again; The wet mechanical property test is performed by first immersing the sample in water for more than 1 hour and then using a universal material tensile testing machine for testing.