Method for preparing cationic hydroxypropyl nanocellulose

Abstract

The application relates to the technical field of nanocellulose preparation, in particular to a preparation method of cationic hydroxypropyl nanocellulose, which is used to solve the technical problem that cationic nanocellulose is not good in water solubility, a solution is not clear and transparent, and the application in the washing and protecting field is affected in the related technology. The application comprises the following steps: adding a nanocellulose aqueous solution into an alkaline aqueous solution; adding an etherifying agent to carry out a first reaction to obtain cationic nanocellulose; and adding propylene oxide to carry out a second reaction to obtain cationic hydroxypropyl nanocellulose. The cationic hydroxypropyl nanocellulose prepared by the preparation method is good in water solubility, a solution is clear and transparent, and can be widely applied in the washing and protecting field.

Description

Technical Field

[0001] This application relates to the field of nanocellulose preparation technology, specifically to a method for preparing cationic hydroxypropyl nanocellulose. Background Technology

[0002] Cellulose, as one of the most abundant natural polymers, possesses properties such as biodegradability, thermal stability, and chemical stability, making it an ideal alternative to fossil fuels. Compared to cellulose, nanocellulose has advantages such as a higher specific surface area and greater biocompatibility, and it has applications in many fields, including materials science, biomedicine, environmental protection, and papermaking.

[0003] Cationicizing cellulose nanoparticles endows them with cationic properties. Besides possessing the general characteristics of cellulose nanoparticles, such as good mechanical properties, high specific surface area, high aspect ratio, and biodegradability, they also carry a positive charge on their surface, altering the original charge properties of cellulose. This allows for applications in the hair care industry, such as as a shampoo conditioner. However, cationic cellulose nanoparticles have poor water solubility, resulting in solutions that are not clear and transparent, which limits their use in hair care. Summary of the Invention

[0004] This application provides a method for preparing cationic hydroxypropyl cellulose nanoparticles, which solves the technical problems in related technologies such as poor water solubility of cationic cellulose nanoparticles and unclear solutions, which affect their application in the field of washing and care.

[0005] To achieve the above objectives, this application adopts the following technical solution:

[0006] This application provides a method for preparing cationic hydroxypropyl cellulose nanoparticles, comprising the following steps:

[0007] Add the aqueous solution of nanocellulose to the alkaline aqueous solution;

[0008] An etherifying agent was added to carry out the first reaction, yielding cationic cellulose nanoparticles;

[0009] A second reaction was carried out by adding propylene oxide to obtain cationic hydroxypropyl cellulose nanoparticles.

[0010] In some embodiments of this application, the concentration of the nanocellulose aqueous solution is 0.1~12wt%, and the concentration of the alkaline aqueous solution is 8~35wt%.

[0011] In some embodiments of this application, the volume ratio of the nanocellulose aqueous solution to the alkaline aqueous solution is 1:(1~3).

[0012] In some embodiments of this application, the molar ratio of the etherifying agent to the nanocellulose in the aqueous nanocellulose solution is (2~20):1.

[0013] In some embodiments of this application, the molar ratio of propylene oxide to nanocellulose in the aqueous nanocellulose solution is (2~20):1.

[0014] In some embodiments of this application, after adding the nanocellulose aqueous solution to the alkaline aqueous solution, the mixture is stirred and heated for 10 min to 60 min at a pressure of 0.1 MPa-0.2 MPa and a temperature of 60℃-70℃.

[0015] In some embodiments of this application, when the etherifying agent is added to carry out the first reaction, the mixture is stirred and heated for 3-5 hours at a pressure of 0.1 MPa-0.2 MPa and a temperature of 60°C-70°C.

[0016] In some embodiments of this application, when propylene oxide is added to carry out the second reaction, the mixture is stirred and heated for 1-24 hours at a pressure of 0.1-0.2 MPa and a temperature of 65-75°C.

[0017] In some embodiments of this application, after adding propylene oxide to carry out a second reaction, the mixture is cooled to room temperature, the pH is adjusted to 7-9, and then filtered, washed, and dried sequentially.

[0018] In some embodiments of this application, the alkaline aqueous solution includes one or more of sodium hydroxide solution, potassium hydroxide solution, or lithium hydroxide solution;

[0019] And / or, the etherifying agent includes one or more of 2-chloroethyltrimethylammonium chloride, 2,3-epoxypropyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrimethylammonium chloride, and 3-chloro-2-hydroxypropyldimethyllauryl ammonium chloride.

[0020] This application provides a method for preparing cationic hydroxypropyl cellulose nanoparticles, comprising the following steps: adding an aqueous solution of cellulose nanoparticles to an alkaline aqueous solution; adding an etherifying agent to carry out a first reaction to obtain cationic cellulose nanoparticles; and adding propylene oxide to carry out a second reaction to obtain cationic hydroxypropyl cellulose nanoparticles. The cationic hydroxypropyl cellulose nanoparticles prepared by this method exhibit good water solubility and a clear, transparent solution, and can be widely used in the field of personal care products. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A flowchart illustrating the preparation method of cationic hydroxypropyl cellulose nanoparticles provided in the embodiments of this application;

[0023] Figure 2 Another flowchart illustrating the preparation method of cationic hydroxypropyl cellulose nanofibers provided in the embodiments of this application;

[0024] Figure 3 The nuclear magnetic resonance image of the cationic hydroxypropyl cellulose nanoparticles provided in Example 1 of this application;

[0025] Figure 4 The nuclear magnetic resonance image of the cationic hydroxypropyl cellulose nanoparticles provided in Example 2 of this application;

[0026] Figure 5 The nuclear magnetic resonance image of the cationic hydroxypropyl cellulose nanoparticles provided in Example 3 of this application;

[0027] Figure 6 The nuclear magnetic resonance image of the cationic cellulose nanoparticles provided in the comparative examples of this application. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] In related technologies, cellulose can be prepared into nanocellulose by changing its size. Compared with cellulose, nanocellulose has advantages such as higher specific surface area and higher biocompatibility, and has applications in many fields such as materials science, biomedicine, environmental protection, and papermaking. Cationicizing nanocellulose can endow cellulose with cationic properties. In addition to possessing the good mechanical properties, high specific surface area, high aspect ratio, and biodegradability of general nanocellulose, its surface also carries a certain positive charge, changing the original charge properties of cellulose. This allows it to be used in the hair care industry, such as as a shampoo conditioner. However, cationic nanocellulose has poor water solubility, and the solution is not clear and transparent, which affects its use in the hair care industry. It is necessary to add some hydrophilic groups to improve its water solubility, such as introducing hydroxypropyl groups.

[0030] In view of this, this application provides a method for preparing cationic hydroxypropyl cellulose nanoparticles, comprising the following steps: adding an aqueous solution of cellulose nanoparticles to an alkaline aqueous solution; adding an etherifying agent to carry out a first reaction to obtain cationic cellulose nanoparticles; and adding propylene oxide to carry out a second reaction to obtain cationic hydroxypropyl cellulose nanoparticles. The cationic hydroxypropyl cellulose nanoparticles prepared by the method of this application have good water solubility and the solution is clear and transparent, and can be widely used in the field of washing and care.

[0031] The contents of this application will now be described in detail with reference to the accompanying drawings, so that those skilled in the art can have a clearer and more detailed understanding of the contents of this application.

[0032] Please see Figures 1-2 This application provides a method for preparing cationic hydroxypropyl cellulose nanofibers, comprising the following steps:

[0033] Add the aqueous solution of nanocellulose to the alkaline aqueous solution;

[0034] It should be noted that cellulose has a wide range of sources. Besides wood pulp, plants such as hemp, flax, jute, ramie, and cotton are also important sources of cellulose. In addition, cellulose also has non-plant sources, such as bacteria and tunicates. By changing the size of cellulose, it can be prepared into nanocellulose.

[0035] Urea can be added to alkaline aqueous solutions. Urea is an organic compound with good solubility; it improves the solubility of nanocellulose in water and the stability of its crystal phase by forming hydrogen bonds with water and nanocellulose.

[0036] When nanocellulose is added to an alkaline aqueous solution, under alkaline conditions, the active hydroxyl groups on the nanocellulose are oxidized into oxygen anions. These anions act as nucleophiles, attacking the etherifying agents or carbocations in propylene oxide within the system to form new ether bonds, here represented by S. N 2. Substitution reaction.

[0037] An etherifying agent was added to carry out the first reaction, yielding cationic cellulose nanoparticles;

[0038] It should be noted that the first reaction is a cationization reaction. Under alkaline conditions, the hydroxyl groups on the nanocellulose are oxidized to oxygen anions, which act as nucleophiles to attack the carbocations of the etherifying agent (quaternary ammonium salt) in the system. At this time, the halogen (chlorine) is replaced, generating cationic nanocellulose. The first reaction yields cationic nanocellulose.

[0039] A second reaction was carried out by adding propylene oxide to obtain cationic hydroxypropyl cellulose nanoparticles.

[0040] It should be noted that the propylene oxide added in the second reaction is pure propylene oxide. The second reaction is a hydroxypropylation reaction. Specifically, under alkaline conditions, the hydroxyl groups on the nanocellulose are oxidized into oxygen anions, which act as nucleophiles to attack the carbocations of propylene oxide in the system. At the same time, propylene oxide undergoes ring opening to form new hydroxyl groups, resulting in cationic hydroxypropyl nanocellulose. That is, cationic hydroxypropyl nanocellulose can be obtained after the second reaction.

[0041] In some embodiments of this application, the concentration of the nanocellulose aqueous solution is 0.1~12wt%, and the concentration of the alkaline aqueous solution is 8~35wt%.

[0042] It should be noted that an aqueous solution of nanocellulose is used instead of nanocellulose directly because nanocellulose is easier to maintain in aqueous solution and is more convenient for subsequent applications. When the concentration of the nanocellulose aqueous solution is 0.1~12wt%, the particle size remains intact, and the flowability is good, uniform and stable.

[0043] When the concentration of the alkaline aqueous solution is 8~35wt%, this range is a suitable range. Below this value, the alkaline concentration is low, the activation is incomplete, and the subsequent reaction is insufficient. When the alkaline concentration is high, the viscosity of the system is too high, and the etherification reaction is not easy to control.

[0044] In some embodiments of this application, the volume ratio of the nanocellulose aqueous solution to the alkaline aqueous solution is 1:(1~3).

[0045] This setup ensures that the concentration of the mixed solution prepared from the nanocellulose aqueous solution and the alkaline aqueous solution is moderate, neither too thick nor too thin, allowing the reaction to proceed normally.

[0046] In some embodiments of this application, the molar ratio of the etherifying agent to the nanocellulose in the aqueous nanocellulose solution is (2~20):1.

[0047] In some embodiments of this application, the molar ratio of propylene oxide to nanocellulose in the aqueous nanocellulose solution is (2~20):1.

[0048] In some embodiments of this application, after adding the aqueous solution of nanocellulose to an alkaline aqueous solution, the mixture is stirred and heated for 10-60 minutes at a pressure of 0.1-0.2 MPa and a temperature of 60-70°C. It should be noted that stirring and heating can accelerate the reaction rate.

[0049] In some embodiments of this application, when the etherifying agent is added to carry out the first reaction, the mixture is stirred and heated for 3-5 hours at a pressure of 0.1 MPa-0.2 MPa and a temperature of 60°C-70°C. It should be noted that stirring and heating can accelerate the reaction rate.

[0050] In some embodiments of this application, when propylene oxide is added to carry out the second reaction, the mixture is stirred and heated for 1-24 hours at a pressure of 0.1-0.2 MPa and a temperature of 65-75°C. It should be noted that stirring and heating can accelerate the reaction rate.

[0051] In some embodiments of this application, after adding propylene oxide to carry out a second reaction, the mixture is cooled to room temperature, the pH is adjusted to 7-9, and then filtered, washed, and dried sequentially.

[0052] Specifically, during cooling, the small-scale test can be conducted through natural cooling or with the aid of an ice-water bath. The pH value is adjusted using hydrochloric acid, acetic acid, citric acid, and maleic acid to neutralize any residual alkali. The concentration of hydrochloric acid is in the range of 0.5-1.0 mol / L. Filtration can be performed using a funnel, followed by washing with 75% ethanol and then pure water. Ethanol is used to wash away residual propylene oxide and oil-soluble impurities, while water is used to wash away etherifying agents, residual acids, and water-soluble impurities. Washing continues until the intermediate control test is passed, i.e., the residual etherifying agent content is ≤50 ppm, the ash content is ≤3%, and other residues are undetectable.

[0053] It should be noted that the solid obtained after washing is cationic hydroxypropyl cellulose nanoparticles; it can be dried using a vacuum drying oven or a regular oven. Specifically, for small-scale experiments, a vacuum drying oven can be used to isolate water and oxygen; for laboratories with high cleanliness levels, a regular oven can be used for drying at a temperature of 50℃~70℃ for 4-6 hours.

[0054] In some embodiments of this application, the alkaline aqueous solution includes one or more of sodium hydroxide solution, potassium hydroxide solution, or lithium hydroxide solution;

[0055] And / or, the etherifying agent includes one or more of 2-chloroethyltrimethylammonium chloride, 2,3-epoxypropyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrimethylammonium chloride, and 3-chloro-2-hydroxypropyldimethyllauryl ammonium chloride.

[0056] The present invention will be further described below through specific embodiments and comparative examples. Unless otherwise specified, the reagents, materials and instruments used below are all conventional reagents, materials and instruments, all of which are commercially available, and the reagents and materials involved can also be synthesized by conventional synthetic methods.

[0057] Example 1:

[0058] 10 g of sodium hydroxide (NaOH) was weighed and dissolved in 33 mL of water to obtain a sodium hydroxide solution (NaOH solution). 22 g of a 3 wt% aqueous solution of nanocellulose was suspended in the NaOH solution and heated with stirring at 65 °C for 30 min. Then, 6.4 g of 2-chloroethyltrimethylammonium chloride was added to the suspension, and the mixture was stirred at 65 °C for 5 h. Subsequently, 0.6 g of propylene oxide was added to the reaction system, and the mixture was stirred at 70 °C for 10 h. After cooling to room temperature, the pH of the resulting suspension was adjusted to 7–9 using 1 mol / L hydrochloric acid, filtered using a funnel, and then washed successively with 75% ethanol and pure water. The washed solid was placed in a vacuum drying oven and dried at 60 °C for 6 h to obtain cationic hydroxypropyl nanocellulose (referred to as sample 1).

[0059] Prepare an aqueous solution from sample 1:

[0060] Measure 200 mL of distilled water into a beaker, add 0.60 g of powdered sample 1, and stir magnetically to disperse it. Continue stirring magnetically until the viscosity is released. Cover the beaker and place it in a 25°C water bath for 2 hours. Using distilled water as a reference, measure the transmittance of the aqueous solution prepared from sample 1 at a wavelength of 550 nm using a UV spectrophotometer. Perform two parallel measurements, with the difference between the measurements not exceeding 0.5%. Take the arithmetic mean of the results.

[0061] It should be noted that a magnetic stirrer can be used to stir the distilled water and sample 1 in the beaker. Magnetic stirrers are mainly used for stirring or simultaneously heating and stirring low-viscosity liquids or solid-liquid mixtures. The basic principle is based on the repulsion and attraction of like poles in a magnetic field. The magnetic field drives a magnetic stir bar placed in the container to rotate in a circular motion, thereby achieving the purpose of stirring the liquid. Combined with a heating and temperature control system, the sample temperature can be heated and controlled according to specific experimental requirements, maintaining the necessary temperature conditions to ensure the liquid is mixed to the required experimental consistency.

[0062] An ultraviolet spectrophotometer is an analytical instrument based on the principle of ultraviolet-visible spectrophotometry. It uses the absorption of radiation by molecules in the ultraviolet-visible spectral region to perform analysis. It mainly consists of components such as a light source, monochromator, absorption cell, detector, and signal processor.

[0063] When zeroing a UV spectrophotometer, distilled water is typically used as the reference solution. Distilled water absorbs very little UV light, almost negligible, making it an ideal reference solution to eliminate optical errors and electronic noise inherent in the instrument, thereby improving measurement accuracy.

[0064] Parallel determination refers to taking several identical samples and measuring them under the same operating conditions, which can reduce random errors.

[0065] Example 2:

[0066] 10g of sodium hydroxide (NaOH) and 8g of urea were weighed and dissolved in 33mL of water to obtain a sodium hydroxide solution (NaOH solution) containing urea. It should be noted that urea is an organic compound with good solubility; it enhances the solubility of nanocellulose in water and the stability of its crystal phase by forming hydrogen bonds with water and nanocellulose. 22g of 3wt% nanocellulose was suspended in the NaOH solution and heated at 65℃ for 30 min with stirring. Then, 6.4g of 2-chloroethyltrimethylammonium chloride was added to the suspension, and the mixture was stirred at 65℃ for 5 hours. Subsequently, 0.6g of propylene oxide was added to the reaction system, and the mixture was stirred at 70℃ for 10 hours. After cooling to room temperature, the resulting suspension was adjusted to pH 7-9 using 1mol / L hydrochloric acid, filtered using a funnel, and then washed successively with 75% ethanol and pure water. The washed solid was placed in a vacuum drying oven and dried at 60℃ for 6 hours to obtain cationic hydroxypropyl nanocellulose (referred to as sample 2).

[0067] Prepare an aqueous solution from sample 2:

[0068] Measure 200 mL of distilled water into a beaker, add 0.60 g of powdered sample 2, and stir magnetically to disperse it. Continue stirring magnetically until the viscosity is released. Cover the beaker and place it in a 25°C water bath for 2 hours. Using distilled water as a reference, measure the transmittance of the aqueous solution prepared from sample 2 at a wavelength of 550 nm using a UV spectrophotometer. Perform two parallel measurements, with the difference between the measurements not exceeding 0.5%. Take the arithmetic mean of the results.

[0069] Example 3:

[0070] 10g of sodium hydroxide (NaOH) and 9g of urea were weighed and dissolved in 33mL of water to obtain a sodium hydroxide solution (NaOH solution) containing urea. It should be noted that urea is an organic compound with good solubility; it enhances the solubility of nanocellulose in water and the stability of its crystal phase by forming hydrogen bonds with water and nanocellulose. 22g of 3wt% nanocellulose was suspended in the NaOH solution and heated with stirring at 65℃ for 30 min. Then, 6.0g of 2,3-epoxypropyltrimethylammonium chloride was added to the suspension, and the mixture was stirred at 65℃ for 5 hours. Subsequently, 0.6g of propylene oxide was added to the reaction system, and the mixture was stirred at 70℃ for 10 hours. After cooling to room temperature, the resulting suspension was adjusted to pH 7-9 using 1mol / L hydrochloric acid, filtered using a funnel, and then washed successively with 75% ethanol and pure water. The washed solid was placed in a vacuum drying oven and dried at 60℃ for 6 hours to obtain cationic hydroxypropyl nanocellulose (referred to as sample 3).

[0071] Prepare an aqueous solution from sample 3:

[0072] Measure 200 mL of distilled water into a beaker, add 0.60 g of powdered sample 3, and stir magnetically to disperse it. Continue stirring magnetically until the viscosity is released. Cover the beaker and place it in a 25°C water bath for 2 hours. Using distilled water as a reference, measure the transmittance of the aqueous solution prepared from sample 3 at a wavelength of 550 nm using a UV spectrophotometer. Perform two parallel measurements, with the difference between the measurements not exceeding 0.5%. Take the arithmetic mean of the results.

[0073] Comparative Example:

[0074] Using commercially available cationic nanocellulose (denoted as Sample 4), Sample 4 was prepared into an aqueous solution:

[0075] Measure 200 mL of distilled water into a beaker, add 0.60 g of powdered sample 4, and stir magnetically to disperse it. Continue stirring magnetically until the viscosity is released. Cover the beaker and place it in a 25°C water bath for 2 hours. Using distilled water as a reference, measure the transmittance of the aqueous solution prepared from sample 4 at a wavelength of 550 nm using a UV spectrophotometer. Perform two parallel measurements, with the difference between the measurements not exceeding 0.5%. Take the arithmetic mean of the results.

[0076] Please see Figures 3-6 , Figure 3 The nuclear magnetic resonance image of the cationic hydroxypropyl cellulose nanoparticles provided in Example 1 of this application; Figure 4 The nuclear magnetic resonance image of the cationic hydroxypropyl cellulose nanoparticles provided in Example 2 of this application; Figure 5 The nuclear magnetic resonance image of the cationic hydroxypropyl cellulose nanoparticles provided in Example 3 of this application; Figure 6 The nuclear magnetic resonance image of the cationic cellulose nanoparticles provided in the comparative examples of this application.

[0077] In the NMR spectrum, the horizontal axis represents the chemical shift (the chemical shift value of the resonance signal of hydrogen atoms in the sample molecule relative to the reference compound (0 for tetramethylsilane), and the vertical axis represents the absorption peak intensity.

[0078] Figure 3 The characteristic peak of hydroxypropyl at a chemical shift of approximately 1.2 indicates that hydroxypropylation has been completed, and the characteristic peak of methyl quaternary ammonium salt at a chemical shift of approximately 3.3 indicates that cationization has been completed.

[0079] Figure 4 The characteristic peak of hydroxypropyl at a chemical shift of approximately 1.2 indicates that hydroxypropylation has been completed, and the characteristic peak of methyl quaternary ammonium salt at a chemical shift of approximately 3.3 indicates that cationization has been completed.

[0080] Figure 5The characteristic peak of hydroxypropyl at a chemical shift of approximately 1.2 indicates that hydroxypropylation has been completed, and the characteristic peak of methyl quaternary ammonium salt at a chemical shift of approximately 3.3 indicates that cationization has been completed.

[0081] Figure 6 The characteristic peak of methyl quaternary ammonium salt with a chemical shift of approximately 3.3 indicates that cationization has been completed, and no characteristic peak of hydroxypropyl with a chemical shift of approximately 1.2 was observed.

[0082] pass Figures 3-5 It can be seen that the cationization and hydroxypropylation reactions of the nanocellulose in Examples 1-3 have been completed; through Figure 6 It can be seen that the nanocellulose in the comparative example only completed the cationization reaction.

[0083] The transmittance of aqueous solutions prepared from samples 1 to 4 was measured, and the measured transmittance data are shown in Table 1.

[0084] Table 1 Solution transmittance

[0085]

[0086] Table 1 shows the transmittance of the cationic hydroxypropyl nanocellulose aqueous solutions in Examples 1-3 and the comparative examples. As can be seen from the data in Table 1, the transmittance of the cationic hydroxypropyl nanocellulose aqueous solutions in Examples 1-3 is comparable and significantly higher than that in the comparative examples. Therefore, the cationic hydroxypropyl nanocellulose prepared by the method of this application exhibits good water solubility and a clear, transparent solution, making it suitable for wide application in the washing and care industry.

[0087] It should be noted that the terms "one embodiment," "embodiment," "exemplary embodiment," "some embodiments," etc., mentioned in the specification indicate that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Moreover, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments, whether explicitly described or not, is within the knowledge scope of those skilled in the art.

[0088] Generally speaking, terms should be understood at least in part by their use in context. For example, at least in part by context, the term "one or more" as used in the text can be used to describe any feature, structure, or characteristic of the singular meaning, or a combination of features, structures, or characteristics of the plural meaning. Similarly, at least in part by context, terms such as "a" or "the" can also be understood to convey either singular or plural usage.

[0089] It should be readily understood that the terms “on,” “above,” and “on top of” in this application should be interpreted in the broadest possible sense, such that “on” means not only “directly on something” but also “on something” with an intermediate feature or layer therebetween, and that “above” or “on top of” means not only “on something” but also “on something” without an intermediate feature or layer therebetween (i.e., directly on something).

[0090] Furthermore, for ease of explanation, spatially relative terms such as "below," "below," "under," "above," and "above" may be used to describe the relationship of one element or feature relative to other elements or features as shown in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation other than those shown in the figures. The device may have other orientations (rotated 90° or in other orientations), and the spatially relative descriptive terms used herein may be interpreted accordingly.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing cationic hydroxypropyl cellulose nanofibers, characterized in that, Includes the following steps: Add the aqueous solution of nanocellulose to the alkaline aqueous solution; An etherifying agent was added to carry out the first reaction, yielding cationic cellulose nanoparticles; A second reaction was carried out by adding propylene oxide to obtain cationic hydroxypropyl cellulose nanoparticles.

2. The method for preparing cationic hydroxypropyl cellulose nanofibers according to claim 1, characterized in that, The concentration of the nanocellulose aqueous solution is 0.1~12wt%, and the concentration of the alkaline aqueous solution is 8~35wt%.

3. The method for preparing cationic hydroxypropyl cellulose nanofibers according to claim 1, characterized in that, The volume ratio of the nanocellulose aqueous solution to the alkaline aqueous solution is 1:(1~3).

4. The method for preparing cationic hydroxypropyl cellulose nanofibers according to claim 1, characterized in that, The molar ratio of the etherifying agent to the nanocellulose in the aqueous nanocellulose solution is (2~20):

1.

5. The method for preparing cationic hydroxypropyl cellulose nanofibers according to claim 1, characterized in that, The molar ratio of propylene oxide to nanocellulose in the aqueous nanocellulose solution is (2~20):

1.

6. The method for preparing cationic hydroxypropyl cellulose nanofibers according to claim 1, characterized in that, After adding the aqueous solution of nanocellulose to the alkaline aqueous solution, the mixture was stirred and heated for 10-60 minutes at a pressure of 0.1-0.2 MPa and a temperature of 60-70°C.

7. The method for preparing cationic hydroxypropyl cellulose nanofibers according to claim 1, characterized in that, When adding the etherifying agent to carry out the first reaction, stir and heat for 3-5 hours at a pressure of 0.1MPa-0.2MPa and a temperature of 60℃-70℃.

8. The method for preparing cationic hydroxypropyl cellulose nanofibers according to claim 1, characterized in that, When adding propylene oxide to carry out the second reaction, stir and heat for 1-24 hours at a pressure of 0.1-0.2 MPa and a temperature of 65-75°C.

9. The method for preparing cationic hydroxypropyl cellulose nanofibers according to claim 1, characterized in that, After adding propylene oxide for the second reaction, the mixture is cooled to room temperature, the pH is adjusted to 7-9, and then filtered, washed, and dried sequentially.

10. The method for preparing cationic hydroxypropyl cellulose nanofibers according to claim 1, characterized in that, The alkaline aqueous solution includes one or more of sodium hydroxide solution, potassium hydroxide solution, or lithium hydroxide solution; And / or, the etherifying agent includes one or more of 2-chloroethyltrimethylammonium chloride, 2,3-epoxypropyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrimethylammonium chloride, and 3-chloro-2-hydroxypropyldimethyllauryl ammonium chloride.

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