A cellulose nanoribbon and its preparation method and application

Abstract

A cellulose nanoribbon, preparation method, and application thereof, comprising the steps of: S1. mixing a cellulose-containing raw material with a solvent to obtain a cellulose slurry; S2. mixing the cellulose slurry with an acid anhydride; the solvent comprising dimethyl sulfoxide and an inorganic base; and the acid anhydride comprising at least one of butyric anhydride, phthalic anhydride, succinic anhydride, and maleic anhydride. The cellulose nanoribbon preparation method of the present invention effectively eliminates the problems encountered in conventional cellulose nanofiber preparation processes, such as low production efficiency, small specific surface area due to large size, poor mechanical properties due to a small aspect ratio, and uneven size distribution.

Description

Technical Field

[0001] The present invention relates to the field of preparation of composite materials, and in particular to a cellulose nanoribbon and a preparation method and application thereof. Background Art

[0002] Cellulose, found widely in the cell walls of various plants, is one of the most abundant natural polymers. Cellulose is a chain-like polymer composed of D-glucans connected by β-1-4 bonds. Cellulose is widely available, highly productive, widely distributed, and renewable. It also possesses advantages not found in synthetic polymers, such as environmental friendliness, biocompatibility, and biodegradability. Nanocellulose refers to cellulose with nanometer-sized diameters, typically obtained through chemical, physical, biological, or a combination of methods. Common nanocellulose types include cellulose nanofibers, cellulose nanocrystals, and bacterial cellulose. Nanocellulose is widely used in energy, biomedicine, and the preparation of biodegradable materials due to its fine nanostructure and excellent mechanical strength. Cellulose nanoribbons, similar to cellulose nanofibers, are novel bionanomaterials with a high aspect ratio and large surface area. Cellulose nanoribbons combine the excellent properties of cellulose with mechanical properties comparable to those of steel, thus holding great promise for applications in functional textiles, biomedicine, structural materials, and energy.

[0003] Cellulose does not melt at high temperatures and is difficult to dissolve in conventional solvents due to the large number of hydrogen bonds and van der Waals forces between its molecular chains, which limits its processing and application. In addition, under the strong interaction force between cellulose molecular chains, cellulose nanofibers have a highly ordered natural network structure, which makes it difficult to peel off small-sized cellulose nanofibers. The methods for extracting cellulose nanofibers in the prior art are generally mechanical methods, chemical reaction methods, biological enzymatic methods, or a combination of these. Mechanical methods generally include ball milling, high-pressure homogenization, and ultrasonic crushing. Under this method, the cellulose fibers have a larger diameter, usually 100-200nm, and a length of tens of microns. They are still large aggregates, which reduces the efficiency of material use; and the preparation process requires long-term high-power mechanical processing, which consumes a lot of energy. Chemical methods, such as hydrolysis of cellulose with concentrated sulfuric acid, hydrochloric acid, or nitric acid, effectively remove amorphous and partially crystalline regions from the cellulose raw material, yielding highly crystalline cellulose nanocrystals. However, the resulting cellulose nanocrystals typically have a diameter of 20 to 100 nm and a length of 100 to 500 nm. The crystalline nanocrystals are short, rod-like, with a low aspect ratio of only 15 to 20. Enzymatic hydrolysis can only partially treat substances on the cellulose surface and cannot effectively penetrate between cellulose molecular chains, effectively disrupting the hydrogen bonds between them. The resulting cellulose nanofibers are generally larger than 10 nm in diameter.

[0004] Therefore, it is urgent to provide a preparation method of cellulose nanoribbons that can solve the problems of uneven size distribution, poor mechanical properties and small surface area in the preparation of cellulose nanoribbons. Summary of the Invention

[0005] The present invention aims to address at least one of the technical problems existing in the prior art. To this end, the present invention provides a cellulose nanoribbon, a preparation method, and applications thereof, which effectively eliminate the problems encountered in conventional cellulose nanoribbon preparation processes, such as low production efficiency, a small specific surface area resulting from large size, a small aspect ratio that does not provide good mechanical properties, and uneven size distribution.

[0006] The invention also provides a cellulose nanoribbon prepared by the preparation method.

[0007] The present invention also proposes an application of the cellulose nanoribbons prepared by the preparation method in the fields of wet gas power generation, Pickering emulsion, phase change material and optics.

[0008] According to a first embodiment of the present invention, a method for preparing cellulose nanoribbons is provided, comprising the steps of:

[0009] S1, mixing a raw material containing cellulose and a solvent to obtain a cellulose slurry;

[0010] S2, mixing the cellulose pulp and acid anhydride;

[0011] The solvent includes dimethyl sulfoxide and an inorganic base;

[0012] The acid anhydride includes at least one of butyric anhydride, phthalic anhydride, succinic anhydride and maleic anhydride.

[0013] According to the method of the embodiment of the first aspect of the present invention, the reaction principle of the present invention is:

[0014] Sufficient swelling of cellulose is the basis for preparing extremely small cellulose nanoribbons. The present invention uses dimethyl sulfoxide (DMSO) and alkali to form a solvent, which can achieve sufficient swelling of cellulose. Acid anhydride is then added to chemically modify the cellulose to graft polar charged groups, thereby increasing the effective repulsion between cellulose molecular chains, weakening the formation of hydrogen bonds between cellulose molecular chains, and reducing the van der Waals forces between cellulose molecular chains.

[0015] The method according to the embodiment of the first aspect of the present invention has at least the following beneficial effects:

[0016] 1. The solvent of the present invention is a mixed solvent, which can also be defined as a "quasi-solvent", in which dimethyl sulfoxide (DMSO) can effectively penetrate into the crystalline region of the raw material containing cellulose. The coordinated action of DMSO and alkali ions (at least one of lithium ions, sodium ions and potassium ions) is beneficial to breaking the hydrogen bonds between the cellulose molecular chains, stripping the hydrogen of the active hydroxyl groups on the cellulose molecular chains, and also inhibiting the formation of hydrogen bonds on the cellulose molecular chains, effectively expanding the interplanar spacing, that is, the cellulose can be well swollen and dispersed without dissolving the cellulose, maintaining the original crystalline structure of the cellulose. Under the coordinated action of DMSO and alkali ions, the enlarged interplanar spacing forms a channel of sufficient size, which is beneficial for the anhydride molecules to penetrate into the interior of the cellulose for reaction, and can effectively react inside and outside the molecular chain, thereby obtaining a cellulose nanoribbon with a homogeneous reaction. This method is different from the traditional method of layer-by-layer peeling. It reacts layer by layer from the outside to the inside, which is time-consuming and energy-consuming, and can effectively reduce energy consumption and improve production efficiency.

[0017] 2. The acid anhydride in the present invention has a polarity close to that of DMSO and a suitable molecular size (i.e., it matches the size of the channel between the molecular chains and can allow the acid anhydride molecules to enter the pores to react). It can form sufficient polarity after the acid anhydride and cellulose are grafted to provide a certain repulsive force. Except for butyric anhydride (butyric anhydride matches the polarity of the solvent and can be dispersed in DMSO even without electrostatic effect, but the yield is lower than that of charged acid anhydrides), they can provide negative electrostatic force, so that they can repel each other under alkaline conditions and are conducive to peeling, thereby obtaining cellulose nanobelts of suitable size and uniform size distribution.

[0018] According to some embodiments of the present invention, the inorganic base includes at least one of lithium hydroxide, sodium hydroxide and potassium hydroxide.

[0019] According to some embodiments of the present invention, the molar ratio of the cellulose to the acid anhydride is 1:0.5-4.

[0020] According to some embodiments of the present invention, the molar ratio of the cellulose to the acid anhydride is 1:0.9-1.1.

[0021] According to some embodiments of the present invention, the raw material containing cellulose includes at least one of cotton linters, absorbent cotton and wood pulp.

[0022] According to some preferred embodiments of the present invention, the acid anhydride is at least one of octylsuccinic anhydride and phthalic anhydride.

[0023] According to some embodiments of the present invention, the cellulose raw material includes a cellulose raw material solution.

[0024] According to some embodiments of the present invention, the mass concentration of cellulose in the cellulose raw material solution is 0.4-2%.

[0025] According to some preferred embodiments of the present invention, the mass concentration of cellulose in the cellulose raw material solution is 0.9-1.1%.

[0026] The swelling process of cellulose at the above concentration can achieve high production efficiency while ensuring appropriate system viscosity to prevent cellulose gelation due to excessive viscosity.

[0027] According to some embodiments of the present invention, the volume ratio of the dimethyl sulfoxide to the base is 1 ml: 0.5-10 mg.

[0028] According to some preferred embodiments of the present invention, the mass ratio of the volume of the dimethyl sulfoxide to the base is 1 ml: 0.9-1.1 mg.

[0029] The solvent composed of alkali solution and DMSO at the above mass concentration can more effectively destroy the hydrogen bonds between cellulose molecular chains, inhibit the formation of hydrogen bonds of cellulose molecules, increase the distance between the molecular chains of cellulose molecules, and facilitate the penetration of acid anhydride molecules into the interior of cellulose for reaction, thereby obtaining cellulose nanobelts with homogeneous reaction.

[0030] According to some embodiments of the present invention, in step S1, the mixing method includes stirring;

[0031] The stirring speed is 1200-1500 r / min;

[0032] The stirring time is 6 to 48 hours.

[0033] The aforementioned stirring speed provides sufficient shear force, accelerating the rate and degree of swelling of the solvent in the cellulose-containing raw material. After the aforementioned steps, the cellulose-containing raw material is fully swollen, resulting in a high viscosity and an amber-like, transparent appearance with no visible suspended matter or only a small amount of very small matter.

[0034] According to some embodiments of the present invention, in step S1, the mixing temperature is 20°C to 50°C.

[0035] According to some embodiments of the present invention, in step S2, the mixing temperature is 20°C to 50°C.

[0036] The above mixing temperature can prevent the solvent from solidifying.

[0037] According to some embodiments of the present invention, step S2 further comprises dispersing the mixture obtained after the mixing to obtain a cellulose dispersion.

[0038] According to some embodiments of the present invention, in step S2, the mixing includes stirring and mixing.

[0039] According to some embodiments of the present invention, the stirring speed is 1200-1500 r / min, and the stirring time is 5-30 min.

[0040] Under the above conditions, the acid anhydride is guaranteed to fully react and be grafted onto the cellulose molecular chain, ensuring a sufficient degree of reaction between cellulose and the acid anhydride.

[0041] According to some embodiments of the present invention, the dispersing includes a first dispersion and a second dispersion.

[0042] According to some embodiments of the present invention, the first dispersion is a dilution dispersion.

[0043] According to some embodiments of the present invention, the second dispersion is ultrasonic dispersion.

[0044] According to some embodiments of the present invention, the diluent for dilution and dispersion includes DMSO.

[0045] According to some embodiments of the present invention, the mass concentration of cellulose in the mixture obtained by dilution and dispersion is 0.1-0.25%.

[0046] Cellulose gelation was avoided at the above mass concentration.

[0047] According to some embodiments of the present invention, the ultrasonic dispersion is performed in an ultrasonic cell disruptor.

[0048] According to some embodiments of the present invention, the power of the ultrasonic cell disruptor is 50-200W.

[0049] According to some embodiments of the present invention, the ultrasonic cell disruptor has an ultrasonication time of 5 to 20 minutes.

[0050] According to some embodiments of the present invention, the cellulose dispersion is obtained after the ultrasonic dispersion.

[0051] According to some embodiments of the present invention, the preparation method further comprises removing impurities from the obtained mixture after the second dispersion.

[0052] According to some embodiments of the present invention, the impurity removal method includes centrifugal stratification.

[0053] According to some embodiments of the present invention, the centrifugal speed is 8000-10000 r / min, and the centrifugal time is 5-20 min.

[0054] According to some embodiments of the present invention, after the centrifugation and stratification, the supernatant is taken.

[0055] After the above separation, the lower layer is large-sized cellulose that cannot be dispersed in the solvent.

[0056] In some preferred embodiments of the present invention, the number of centrifugal stratification is no less than four times.

[0057] According to some embodiments of the present invention, the method further comprises filtering the supernatant and then drying the filtered filtrate to obtain a cellulose nanoribbon membrane.

[0058] According to some embodiments of the present invention, the drying method comprises one of solvent evaporation, solvent replacement and solvent freeze-drying.

[0059] According to some embodiments of the present invention, the drying further comprises filtering the cellulose nanoribbon membrane.

[0060] The preparation method of the cellulose nanoribbons of the present invention is simple to operate. It can not only effectively prepare cellulose nanoribbons with small size and uniform distribution, but also the solvent can be recycled and reused, energy consumption is low, production costs are reduced, and it is in line with green and environmentally friendly industrial development. It can be directly applied to large-scale industrial production.

[0061] According to an embodiment of the second aspect of the present invention, a cellulose nanoribbon produced by the preparation method is provided.

[0062] According to some embodiments of the present invention, the width of the cellulose nanoribbon is about 8-20 nm; the height of the cellulose nanoribbon is 1-20 nm; the length of the cellulose nanoribbon is 300-3000 nm, and the aspect ratio of the cellulose nanoribbon is 50-300.

[0063] According to an embodiment of the third aspect of the present invention, an application of the cellulose nanoribbons prepared by the preparation method in the fields of wet gas power generation, Pickering emulsion, phase change materials, optics, etc. is proposed.

[0064] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments with reference to the following drawings, in which:

[0066] Figure 1 This is an AFM image of the cellulose nanoribbons obtained in Example 1 of the present invention;

[0067] Figure 2 This is an AFM image of the cellulose nanoribbons obtained in Example 2 of the present invention;

[0068] Figure 3 This is an AFM image of the cellulose nanoribbons obtained in Example 3 of the present invention;

[0069] Figure 4 This is an SEM image of the cellulose nanoribbons obtained in Example 1 of the present invention;

[0070] Figure 5 A Pickering emulsion was prepared for the cellulose nanoribbons obtained in Example 10 of the present invention. DETAILED DESCRIPTION

[0071] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0072] In the description of the present invention, if there is a description of first, second, etc., it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0073] In the description of the present invention, it should be understood that descriptions involving orientation, such as the orientation or positional relationship indicated by up, down, etc., are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0074] In the description of the present invention, it should be noted that, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0075] Example 1

[0076] This embodiment provides a cellulose nanoribbon and a preparation method thereof, specifically:

[0077] A1. Prepare a mixed solvent with stirring at a concentration of 1 mg potassium hydroxide per 1 ml of DMAO.

[0078] A2. Add cotton linters to the mixed solvent in step A1 at a mass concentration of 1%, and stir at 1500 rpm for 48 hours at 25°C to obtain a fully swollen cellulose slurry;

[0079] A3. To the cellulose slurry obtained in A2, phthalic anhydride was added in a molar ratio of 1:1 between cellulose and anhydride for esterification modification. The mixture was stirred for 20 min, then diluted with DMSO to a cellulose concentration of 0.125 wt %. The mixture was then treated with an ultrasonic cell disrupter at a power of 200 W for 20 s to obtain a cellulose nanoribbon dispersion.

[0080] A4. Centrifuge the cellulose nanoribbon dispersion obtained in A3 at a rate of 10,000 r / min for 10 min, separate the layers, remove the lower sediment, repeat the centrifugation four times, remove the lower sediment, and collect the supernatant.

[0081] A5. Filter the supernatant obtained in step A4, collect the filter cake, and evaporate the solvent to obtain cellulose nanoribbons.

[0082] The obtained cellulose nanowires have a width of 8 to 12 nm, a height of 3 to 4 nm, and a length of 0.5 to 1.5 μm.

[0083] Figure 1 This is an AFM image of the cellulose nanoribbons obtained in Example 1 of the present invention;

[0084] Example 2

[0085] This embodiment provides a cellulose nanoribbon and a preparation method thereof, specifically:

[0086] A1. Prepare a mixed solvent with stirring at a concentration of 1 mg sodium hydroxide per 1 ml of DMSO.

[0087] A2. Add cotton linters to the mixed solvent described in step 1 at a mass concentration of 1%, and stir at 1500 rpm for 48 hours at room temperature to obtain a fully swollen cellulose slurry;

[0088] A3. To the cellulose slurry obtained in A2, phthalic anhydride was added in a molar ratio of cellulose to anhydride of 1:1 for esterification modification. The mixture was reacted under stirring for 20 minutes, and then diluted with DMSO to a cellulose concentration of 0.125 wt%. The mixture was then treated with an ultrasonic cell disrupter at a power of 200 W for 20 seconds to obtain a cellulose nanoribbon dispersion.

[0089] A4. Centrifuge the cellulose nanoribbon dispersion obtained in A3 at a rate of 10,000 r / min for 10 min, separate the layers, remove the lower sediment, and repeat the centrifugation of the supernatant to remove the lower sediment; collect the supernatant.

[0090] A5. Filter the supernatant obtained in step A4, collect the filter cake, and evaporate the solution to obtain cellulose nanoribbons. The obtained cellulose nanoribbons have a width of 50-100 nm, a height of 3-10 nm, and a length of 0.8-2 μm.

[0091] Figure 2 This is an AFM image of the cellulose nanoribbons obtained in Example 2 of the present invention.

[0092] Example 3

[0093] This embodiment provides a cellulose nanoribbon and a preparation method thereof, specifically:

[0094] A1. Prepare a mixed solvent with stirring at a concentration of 1 mg lithium hydroxide per 1 ml of DMSO;

[0095] A2. Add cotton linters to the mixed solvent described in step 1 at a mass concentration of 1%, and stir at 1500 rpm for 48 hours at room temperature to obtain a fully swollen cellulose slurry;

[0096] A3. To the cellulose slurry obtained in A2, phthalic anhydride was added in a molar ratio of cellulose to anhydride of 1:1 for esterification modification. The mixture was reacted under stirring for 20 minutes, and then diluted with DMSO to a cellulose concentration of 0.125 wt%. The mixture was then treated with an ultrasonic cell disrupter at a power of 200 W for 20 seconds to obtain a cellulose nanoribbon dispersion.

[0097] A4. Centrifuge the cellulose nanoribbon dispersion obtained in A3 at a rate of 10,000 r / min for 10 min, separate the layers, remove the lower sediment, and repeat the centrifugation of the supernatant to remove the lower sediment; collect the supernatant.

[0098] A5. Filter the supernatant obtained in step A4, collect the filter cake, and evaporate the solvent to obtain cellulose nanoribbons. The obtained cellulose nanoribbons have a width of 10-20 nm, a height of 1-3 nm, and a length of 0.3-1 μm.

[0099] Figure 3 This is an AFM image of the cellulose nanoribbons obtained in Example 3 of the present invention.

[0100] Example 4

[0101] This embodiment provides a cellulose nanoribbon and a preparation method thereof, specifically:

[0102] A1. Prepare a mixed solvent with stirring at a concentration of 1 mg potassium hydroxide per 1 ml of DMSO.

[0103] A2. Adding absorbent cotton to the mixed solvent described in step 1 at a mass concentration of 1%, stirring at 1500 rpm for 48 h at room temperature to obtain a fully swollen cellulose slurry;

[0104] A3. To the cellulose slurry obtained in A2, phthalic anhydride was added in a molar ratio of cellulose to anhydride of 1:1 for esterification modification. The mixture was reacted under stirring for 20 minutes, and then diluted with DMSO to a cellulose concentration of 0.125 wt%. The mixture was then treated with an ultrasonic cell disrupter at a power of 200 W for 20 seconds to obtain a cellulose nanoribbon dispersion.

[0105] A4. Centrifuge the cellulose nanoribbon dispersion obtained in A3 at a rate of 10,000 r / min for 10 min, separate the layers, remove the lower sediment, and repeat the centrifugation of the supernatant to remove the lower sediment; collect the supernatant.

[0106] A5. Filter the supernatant obtained in step A4, collect the filter cake, and evaporate the solvent to obtain cellulose nanoribbons. The obtained cellulose nanoribbons have a width of 30 nm, a height of 4-10 nm, and a length of 0.8-3 μm.

[0107] Figure 4 This is the SEM image of the cellulose nanoribbons obtained in Example 1 of the present invention.

[0108] Example 5

[0109] This embodiment provides a method for preparing a Pickering emulsion, specifically:

[0110] A1. Prepare a mixed solvent with stirring at a concentration of 1 mg sodium hydroxide per 1 ml of DMSO.

[0111] A2. Adding absorbent cotton to the mixed solvent described in step 1 at a mass concentration of 1%, stirring at 1500 rpm for 48 h at room temperature to obtain a fully swollen cellulose slurry;

[0112] A3. To the cellulose slurry obtained in A2, phthalic anhydride was added in a molar ratio of cellulose to anhydride of 1:1 for esterification modification. The mixture was reacted under stirring for 20 minutes, and then diluted with DMSO to a cellulose concentration of 0.125 wt%. The mixture was then treated with an ultrasonic cell disrupter at a power of 200 W for 20 seconds to obtain a cellulose nanoribbon dispersion.

[0113] A4. Centrifuge the cellulose nanoribbon dispersion obtained in A3 at a rate of 10,000 r / min for 10 min, separate the layers, remove the lower sediment, and repeat the centrifugation of the supernatant to remove the lower sediment; collect the supernatant.

[0114] A5. Filter the supernatant obtained in step A4, collect the filter cake, and evaporate the solvent to obtain cellulose nanoribbons. The obtained cellulose nanoribbons have a width of 50-100 nm, a height of 8-20 nm, and a length of 1-3 μm.

[0115] Example 6

[0116] This embodiment provides a cellulose nanoribbon and a preparation method thereof, specifically:

[0117] A1. Prepare a mixed solvent with stirring at a concentration of 1 mg lithium hydroxide per 1 ml of DMSO;

[0118] A2. Adding absorbent cotton to the mixed solvent described in step 1 at a mass concentration of 1%, stirring at 1500 rpm for 48 h at room temperature to obtain a fully swollen cellulose slurry;

[0119] A3. To the cellulose slurry obtained in A2, phthalic anhydride was added in a molar ratio of cellulose to anhydride of 1:1 for esterification modification. The mixture was stirred for 20 minutes, then diluted with DMSO to a cellulose concentration of 0.125 wt%. The mixture was then treated with an ultrasonic cell disrupter at a power of 300 W for 20 seconds to obtain a cellulose nanoribbon dispersion.

[0120] A4. Centrifuge the cellulose nanoribbon dispersion obtained in A3 at a rate of 10,000 r / min for 10 min, separate the layers, remove the lower sediment, and repeat the centrifugation of the supernatant to remove the lower sediment; collect the supernatant.

[0121] A5. Filter the supernatant obtained in step A4, collect the filter cake, and evaporate the solvent to obtain cellulose nanoribbons. The obtained cellulose nanoribbons have a width of 10-30 nm, a height of 2-10 nm, and a length of 1-3 μm.

[0122] Example 7

[0123] This embodiment provides a cellulose nanoribbon and a preparation method thereof, specifically:

[0124] A1. Prepare a mixed solvent with stirring at a concentration of 1 mg potassium hydroxide per 1 ml of DMSO.

[0125] A2. Adding absorbent cotton to the mixed solvent described in step 1 at a mass concentration of 1%, stirring at 1500 rpm for 48 h at room temperature to obtain a fully swollen cellulose slurry;

[0126] A3. To the cellulose slurry obtained in A2, phthalic anhydride was added in a molar ratio of cellulose to anhydride of 1:1 for esterification modification. The mixture was stirred for 20 minutes, then diluted with DMSO to a cellulose concentration of 0.125 wt%. The mixture was then treated with an ultrasonic cell disrupter at a power of 300 W for 20 seconds to obtain a cellulose nanoribbon dispersion.

[0127] A4. Centrifuge the cellulose nanoribbon dispersion obtained in A3 at a rate of 10,000 r / min for 10 min, separate the layers, remove the lower sediment, and repeat the centrifugation of the supernatant to remove the lower sediment; collect the supernatant.

[0128] A5. Filter the supernatant obtained in step A4, collect the filter cake, and evaporate the solvent to obtain cellulose nanoribbons. The obtained cellulose nanoribbons have a width of 8 to 20 nm, a height of 3 to 4 nm, and a length of 1 to 3 μm.

[0129] Example 8

[0130] This embodiment provides a cellulose nanoribbon and a preparation method thereof, specifically:

[0131] A1. Prepare a mixed solvent with stirring at a concentration of 1 mg potassium hydroxide per 1 ml of DMSO.

[0132] A2. Add cotton linters to the mixed solvent described in step 1 at a mass concentration of 1%, and stir at 1500 rpm for 48 hours at room temperature to obtain a fully swollen cellulose slurry;

[0133] A3. To the cellulose slurry obtained in A2, octyl succinic anhydride was added in a molar ratio of cellulose to anhydride of 1:1 for esterification modification. The mixture was stirred for 20 minutes, then diluted with DMSO to a cellulose concentration of 0.125 wt%. The mixture was then treated with an ultrasonic cell disrupter at a power of 300 W for 20 seconds to obtain a cellulose nanoribbon dispersion.

[0134] A4. Centrifuge the cellulose nanoribbon dispersion obtained in A3 at a rate of 10,000 r / min for 10 min, separate the layers, remove the lower sediment, and repeat the centrifugation of the supernatant to remove the lower sediment; collect the supernatant.

[0135] A5. Filter the supernatant obtained in step A4, collect the filter cake, and evaporate the solvent to obtain cellulose nanoribbons. The obtained cellulose nanoribbons have a width of 8 nm, a height of 0.8-4 nm, and a length of 0.8-1.5 μm.

[0136] Example 9

[0137] This embodiment provides a cellulose nanoribbon and a preparation method thereof, specifically:

[0138] A1. Prepare a mixed solvent with stirring at a concentration of 1 mg potassium hydroxide per 1 ml of DMSO.

[0139] A2. Add cotton linters to the mixed solvent described in step 1 at a mass concentration of 1%, and stir at 1500 rpm for 48 hours at room temperature to obtain a fully swollen cellulose slurry;

[0140] A3. To the cellulose slurry obtained in A2, maleic anhydride was added in a molar ratio of cellulose to anhydride of 1:1 for esterification modification. The mixture was stirred for 20 minutes, then diluted with DMSO to a cellulose concentration of 0.125 wt%. The mixture was then treated with an ultrasonic cell disrupter at a power of 300 W for 20 seconds to obtain a cellulose nanoribbon dispersion.

[0141] A4. Centrifuge the cellulose nanoribbon dispersion obtained in A3 at a rate of 10,000 r / min for 10 min, separate the layers, remove the lower sediment, and repeat the centrifugation of the supernatant to remove the lower sediment; collect the supernatant.

[0142] A5. Filter the supernatant obtained in step A4, collect the filter cake, and evaporate the solvent to obtain cellulose nanoribbons. The obtained cellulose nanoribbons have a width of 8 nm, a height of 0.8-4 nm, and a length of 0.8-1.5 μm.

[0143] Example 10

[0144] This embodiment provides a cellulose nanoribbon and a preparation method thereof, specifically:

[0145] A1. Prepare a mixed solvent with stirring at a concentration of 1 mg potassium hydroxide per 1 ml of DMSO.

[0146] A2. Add cotton linters to the mixed solvent described in step 1 at a mass concentration of 1%, and stir at 1500 rpm for 48 hours at room temperature to obtain a fully swollen cellulose slurry;

[0147] A3. To the cellulose slurry obtained in A2, butyric anhydride was added in a molar ratio of cellulose to anhydride of 1:1 for esterification modification. The mixture was stirred for 20 minutes, then diluted with DMSO to a cellulose concentration of 0.125 wt%. The mixture was then treated with an ultrasonic cell disrupter at a power of 300 W for 20 seconds to obtain a cellulose nanoribbon dispersion.

[0148] A4. Centrifuge the cellulose nanoribbon dispersion obtained in A3 at a rate of 10,000 r / min for 10 min, separate the layers, remove the lower sediment, and repeat the centrifugation of the supernatant to remove the lower sediment; collect the supernatant.

[0149] A5. Filter the supernatant obtained in step A4, collect the filter cake, and evaporate the solvent to obtain cellulose nanoribbons. The obtained cellulose nanoribbons have a width of 8 nm, a height of 0.8-4 nm, and a length of 0.8-1.5 μm.

[0150] Example 10

[0151] This embodiment provides a method for preparing a Pickering emulsion, specifically:

[0152] A6. Dialyze the supernatant obtained in step A4 of Example 1 in deionized water using a dialysis bag with a molecular weight cutoff of 8000-14000 for 3-7 days, changing the deionized water daily. After dialysis, collect the dispersion from the dialysis bag, adjust the pH to 10, and stir to redisperse some of the precipitate in the water.

[0153] A7. Add oleic acid to the dispersion obtained in step A6 of Example 1 at a water-oil ratio of 7:3, and homogenize in a high-speed homogenizer (speed: 1000 rpm) or an ultrasonic cell disrupter (power: 100 W) for 1 min to obtain a stable Pickering emulsion.

[0154] Figure 5 This is the Pickering emulsion prepared from the cellulose nanoribbons obtained in this example.

[0155] Comparative Example 1

[0156] This comparative example provides a cellulose nanoribbon and a preparation method thereof. The difference between this comparative example and Example 1 is that the potassium hydroxide in Example 1 is not included, and the other conditions are the same.

[0157] Cellulose nanoribbons cannot be obtained under the above reaction conditions.

[0158] Comparative Example 2

[0159] This comparative example provides a cellulose nanoribbon and a preparation method thereof. The difference between this comparative example and Example 1 is that the added acid anhydride is benzoic anhydride, and other conditions are the same.

[0160] A1. Prepare a mixed solvent with stirring at a concentration of 1 mg potassium hydroxide per 1 ml of DMSO.

[0161] A2. Add cotton linters to the mixed solvent described in step 1 at a mass concentration of 1%, and stir at 1500 rpm for 48 hours at room temperature to obtain a fully swollen cellulose slurry;

[0162] A3. Add benzoic anhydride to the cellulose slurry obtained in A2 for esterification modification. After stirring for 20 minutes, dilute with DMSO to 0.125 wt %. Then, treat with an ultrasonic cell disrupter at a power of 200 W for 20 seconds to obtain a cellulose nanoribbon dispersion.

[0163] A4. Centrifuge the cellulose nanoribbon dispersion obtained in A3 at a rate of 10,000 r / min for 10 min, separate the layers, remove the lower sediment, and repeat the centrifugation of the supernatant to remove the lower sediment; collect the supernatant.

[0164] A5. The supernatant obtained in step A4 is filtered and the solvent is evaporated to obtain a product with a yield of less than 10%.

[0165] Test Example 1

[0166] This test example tests the performance of the cellulose nanoribbons of Examples 1 to 10 and Comparative Examples 1 to 2. The test results are shown in Table 1.

[0167] Yield calculation method: Use a vacuum filtration device to take an appropriate amount of filtrate and filter it using a 200nm pore size filter membrane. After filtration, vacuum dry the product and weigh it. Calculate the total solid content of the product according to the concentration and calculate the yield by adding it to the mass of the raw materials.

[0168] Potential test method: The obtained cellulose nanobelt dispersion was dialyzed to replace the solvent with water, and sodium hydroxide solution was added dropwise to adjust the pH to 10. The solution was then set up and tested in a Malvern potentiometric particle size tester in the UK.

[0169] Testing method for breaking strength and elongation at break: The cellulose nanobelt dispersion is vacuum filtered to obtain a filter cake, which is removed after vacuum drying and cut into long strips. The strips are tested on an Instron universal testing machine in the United States at a tensile rate of 2 mm / min. The obtained data are analyzed to obtain the elongation at break and breaking strength.

[0170] Transmittance test method: The dried cellulose nanoribbon membrane obtained by filtration was placed in a German PerkinElmer Lambda 950 UV-visible spectrophotometer and measured in the transmittance mode in the 200-800 nm band to obtain data.

[0171] Table 1 Cellulose nanoribbon performance test

[0172]

[0173]

[0174] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention's description and drawings, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing cellulose nanoribbons, characterized in that: For the steps: A1. Prepare a mixed solvent with stirring at a concentration of 1 mg potassium hydroxide per 1 ml of DMSO. A2. Add cotton linters to the mixed solvent in step A1 at a mass concentration of 1%, and stir at 1500 rpm for 48 hours at 25°C to obtain a fully swollen cellulose slurry; A3. To the cellulose slurry obtained in A2, phthalic anhydride was added in a molar ratio of 1:1 between cellulose and anhydride for esterification modification. The mixture was stirred for 20 min, then diluted with DMSO to a cellulose concentration of 0.125 wt %. The mixture was then treated with an ultrasonic cell disrupter at a power of 200 W for 20 s to obtain a cellulose nanoribbon dispersion. A4. Centrifuge the cellulose nanoribbon dispersion obtained in A3 at 10,000 rpm for 10 min, separate the layers, and discard the lower sediment. Repeat the centrifugation of the supernatant four times, and discard the lower sediment. Collect the supernatant; A5. Filter the supernatant obtained in step A4, collect the filter cake, and evaporate the solvent to obtain cellulose nanoribbons; The obtained cellulose nanowires have a width of 8 to 12 nm, a height of 3 to 4 nm, and a length of 0.5 to 1.5 μm.

2. Application of the cellulose nanoribbons prepared by the preparation method according to claim 1 in the fields of wet gas power generation, Pickering emulsion, phase change materials and optics.

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