Hydrophobic nanocellulose and methods of making and using the same

Abstract

The application discloses hydrophobic nanocellulose and a preparation method and application thereof. The hydrophobic nanocellulose has a nanoscale diameter, is obtained by surface modification of cellulose by a hydrophobic modifier, and the cellulose is natural cellulose which is pretreated by an alkaline solution on the surface; and the hydrophobic modifier is an isocyanate group modifier. The hydrophobic nanocellulose provided by the application contains lignin, has a small diameter, and the cellulose film prepared from the hydrophobic nanocellulose has adjustable optical properties (high light transmittance and high haze), hydrophobicity, degradability, ultraviolet resistance and good mechanical properties.

Description

Technical Field

[0001] This invention relates to the technical field of cellulose modification. More specifically, it relates to a hydrophobic nanocellulose, its preparation method, and its applications. Background Technology

[0002] Biomass resources, due to their environmental friendliness, biodegradability, and high chemical stability, have become promising materials to replace non-degradable polymers. Therefore, further improving the high-value utilization of natural resources is necessary. Plant fiber is one of the most important biomass resources, and its efficient utilization is of great significance in scientific research and industrial development. Plant fiber is mainly composed of cellulose, lignin, and hemicellulose. Lignin-containing cellulose nanofibers (LCNFs) have attracted widespread attention due to their UV shielding effect and hydrophobicity. However, lignin-containing cellulose often requires delignification before nanostructuring for utilization. The process of separating and extracting LCNFs from natural lignocellulose suffers from high energy consumption and complex procedures.

[0003] Patent CN202010901463.0 first involves enzymatically hydrolyzing lignocellulose in an acidic buffer solution, followed by high-temperature inactivation and washing. The lignocellulose is then dispersed in water and ball-milled, requiring further ultra-high-speed mechanical dispersion to obtain LCNF. The resulting LCNF has a diameter of less than 40 nm and a crystallinity of less than 60%. This preparation process is relatively complex, resulting in larger diameters and a significant decrease in crystallinity.

[0004] Patent 202010918318.3 describes a process where pineapple peel residue is dried, pulverized, treated with hot water for 2-3 hours, followed by alkali treatment for 2-3 hours, and then placed in a sodium chlorite solution for varying degrees of lignin removal. The residue is then nano-sized under high-pressure homogenization. The resulting fibers have a diameter of 20-70 nm. This process involves a relatively long pretreatment time and produces fibers with a large diameter.

[0005] Patent 201880083025.9 first treats lignin-containing cellulose materials with organic solvents, then treats them with derivatives of N-oxygen free radical compounds and hypochlorite compounds, and finally mechanically processes them to obtain LCNF. This patent modifies the carboxyl groups of LCNF, which reduces the hydrophobicity of the fiber itself to a certain extent. Summary of the Invention

[0006] Based on the above problems, the purpose of this invention is to provide a hydrophobic nanocellulose, its preparation method, and its application. The hydrophobic nanocellulose provided by this invention contains lignin, and the hydrophobic nanocellulose has a small diameter. The cellulose membrane prepared from it simultaneously possesses tunable optical properties (high light transmittance and high haze), hydrophobicity, biodegradability, UV resistance, and good mechanical properties.

[0007] On one hand, the present invention provides a hydrophobic nanocellulose, wherein the diameter of the hydrophobic nanocellulose is on the nanometer scale, and the hydrophobic nanocellulose is obtained by surface modification of cellulose with a hydrophobic modifier; and

[0008] The cellulose is natural cellulose whose surface has been pretreated with an alkaline solution;

[0009] The hydrophobic modifier is an isocyanate-based modifier.

[0010] Furthermore, the natural cellulose contains lignin, and the natural cellulose is derived from natural herbaceous plants or natural woody plants.

[0011] Furthermore, the natural cellulose is derived from one or more of wood flour, bamboo flour, straw, or straw pulp.

[0012] Furthermore, the isocyanate-based modifier is selected from one or more of monoisocyanates or diisocyanates.

[0013] Furthermore, the monoisocyanate is selected from one or more of dichlorophenyl isocyanate, octadecyl isocyanate, 2-chloroethyl isocyanate or benzyl isocyanate.

[0014] Furthermore, the diisocyanate is selected from one or more of 4,4-methylene bis-(phenyl isocyanate) or hexamethylene diisocyanate.

[0015] Furthermore, the diameter of the hydrophobic nanocellulose is less than 10 nm.

[0016] Furthermore, the diameter of the hydrophobic nanocellulose is less than 5 nm.

[0017] Furthermore, the diameter of the hydrophobic nanocellulose is less than 3 nm.

[0018] Furthermore, the preprocessing method includes the following steps:

[0019] The alkaline solution is mixed with natural cellulose, heated and stirred, dried, and then the natural cellulose is washed until neutral and dried.

[0020] Furthermore, the concentration of the alkaline solution is 0.3-5 wt%.

[0021] Furthermore, in the alkaline solution, the alkaline substance is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, or sodium bicarbonate.

[0022] Furthermore, the solid-liquid ratio of the natural cellulose to the alkaline solution is 1:9 to 1:99.

[0023] Furthermore, the solid-liquid ratio of the natural cellulose to the alkaline solution is 1:13 to 1:24.

[0024] Furthermore, the surface modification method includes the following steps:

[0025] The cellulose and hydrophobic modifier were mixed in the presence of a non-proton polar organic solvent, and the raw material was nano-modified by mechanochemical method. After modification, excess hydrophobic modifier was removed to obtain the hydrophobic nanocellulose.

[0026] Furthermore, the mass ratio of the cellulose to the aprotic polar organic solvent is 0.5 to 5:100.

[0027] Furthermore, the mass ratio of the cellulose to the hydrophobic modifier is 1:0.75 to 1:3.

[0028] Furthermore, the mass ratio of the cellulose to the hydrophobic modifier is 1:0.75 to 1:2.

[0029] Furthermore, the mass ratio of the cellulose to the hydrophobic modifier is 1:1 to 1:1.5.

[0030] Furthermore, the aprotic polar organic solvent is selected from one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, or N-methylpyrrolidone.

[0031] Furthermore, the mechanochemical method is either ball milling or disc milling.

[0032] Furthermore, the ball mill operates at a speed of 200-500 rpm for 0.5-12 hours.

[0033] Furthermore, the ball mill operates at a speed of 200-300 rpm for 1-6 hours.

[0034] In another aspect, the present invention provides a method for preparing the hydrophobic nanocellulose as described above, the method comprising the following steps:

[0035] The natural cellulose was pretreated with an alkaline solution to obtain the cellulose.

[0036] A hydrophobic modifier is mixed with the cellulose in the presence of an aprotic polar organic solvent, and the raw material is nano-modified using a mechanochemical method.

[0037] After modification, excess hydrophobic modifier is removed to obtain the hydrophobic nanocellulose.

[0038] In another aspect, the present invention provides a nanocellulose membrane, which is obtained by dispersing the hydrophobic nanocellulose as described above in an organic solvent and then filtering or casting it into a membrane.

[0039] The beneficial effects of this invention are as follows:

[0040] The hydrophobic nanocellulose provided by this invention has a small diameter, no two-dimensional network structure, good crystallinity stability, and good hydrophobicity and strength properties. The nanocellulose membrane prepared by this hydrophobic nanocellulose has the characteristics of high strength, high transparency, high haze, good hydrophobicity and strong UV resistance.

[0041] The method for preparing hydrophobic nanocellulose provided by this invention is simple and rapid, and can prepare nanocellulose with small diameter in a very short time. Attached Figure Description

[0042] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0043] Figure 1 The AFM morphology of the hydrophobic lignin-containing nanocellulose prepared in Example 2 is shown.

[0044] Figure 2 A physical image of the fiber membrane prepared in Example 2 is shown.

[0045] Figure 3 The AFM morphology of the hydrophobic lignin-containing nanocellulose prepared in Example 5 is shown.

[0046] Figure 4 The AFM morphology of the hydrophobic lignin-containing nanocellulose prepared in Comparative Example 2 is shown. Detailed Implementation

[0047] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0048] To address existing methods of delignification, which suffer from issues such as long pretreatment times, large cellulose nanoparticle diameters, and challenges in improving the strength, transparency, haze, hydrophobicity, and UV resistance of nanocellulose, this invention provides a hydrophobic nanocellulose with a nanometer-scale diameter. This hydrophobic nanocellulose is obtained by surface modification of cellulose using a hydrophobic modifier.

[0049] The cellulose is natural cellulose whose surface has been pretreated with an alkaline solution;

[0050] The hydrophobic modifier is an isocyanate-based modifier.

[0051] In this embodiment, the natural cellulose contains lignin, meaning that the natural cellulose is not subjected to additional delignification treatment during use. Even after pretreatment, the resulting cellulose still contains lignin.

[0052] The natural cellulose is derived from natural herbaceous plants or natural woody plants. For example, the natural cellulose is derived from one or more of wood flour, bamboo flour, straw, or straw pulp.

[0053] In this embodiment, using an isocyanate-based modifier as a hydrophobic modifier to modify untreated natural cellulose that has undergone alkali pretreatment results in hydrophobic nanocellulose with smaller diameter and higher strength. For example, the isocyanate-based modifier is selected from one or more of monoisocyanates or diisocyanates.

[0054] In some specific examples, the monoisocyanate is selected from one or more of dichlorophenyl isocyanate, octadecyl isocyanate, 2-chloroethyl isocyanate or benzyl isocyanate.

[0055] In some other specific examples, the diisocyanate is selected from one or more of 4,4-methylene bis-(phenyl isocyanate) or hexamethylene diisocyanate.

[0056] The hydrophobic nanocellulose provided in this embodiment has a very small diameter, less than 10 nm, and exemplary less than 5 nm and less than 3 nm.

[0057] In some examples, the preprocessing method includes the following steps:

[0058] The alkaline solution is mixed with natural cellulose, heated and stirred, dried, and then the natural cellulose is washed until neutral and dried.

[0059] In some examples, the concentration of the alkaline solution is 0.3-5 wt%. In this example, the concentration of the alkaline solution is very low, and pretreatment of the surface of natural cellulose with the alkaline solution is more conducive to obtaining small-diameter hydrophobic nanocellulose.

[0060] In some examples, the alkaline substance in the alkaline solution is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, or sodium bicarbonate;

[0061] In some examples, the solid-liquid ratio of the natural cellulose to the alkaline solution is 1:9 to 1:99, more preferably 1:13 to 1:24.

[0062] In some examples, the surface modification method includes the following steps:

[0063] The cellulose and hydrophobic modifier were mixed in the presence of a non-proton polar organic solvent, and the raw material was nano-modified by mechanochemical method. After modification, excess hydrophobic modifier was removed to obtain the hydrophobic nanocellulose.

[0064] Hydrophobic nanocellulose with small diameter was obtained by modifying cellulose with isocyanate-based modifiers using a mechanochemical method.

[0065] In some examples, the mass ratio of the cellulose to the aprotic polar organic solvent is 0.5 to 5:100.

[0066] In some examples, the mass ratio of cellulose to the hydrophobic modifier is 1:0.75 to 1:3, preferably 1:0.75 to 1:2, and more preferably 1:1 to 1:1.5. In this case, the resulting hydrophobic nanocellulose exhibits superior mechanical and optical properties.

[0067] In some examples, the aprotic polar organic solvent is selected from one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, or N-methylpyrrolidone.

[0068] In some examples, the mechanochemical method is either ball milling or disc milling.

[0069] In some examples, the ball milling speed is 200-500 rpm, and the time is 0.5-12 h. In this embodiment, hydrophobic nanocellulose with a very small particle size can be obtained with a very short ball milling time.

[0070] In some examples, the ball mill rotates at 200-300 rpm for 1-6 hours.

[0071] In another aspect, the present invention provides a method for preparing the hydrophobic nanocellulose as described above, comprising the following steps:

[0072] The natural cellulose was pretreated with an alkaline solution to obtain the cellulose.

[0073] A hydrophobic modifier is mixed with the cellulose in the presence of an aprotic polar organic solvent, and the raw material is nano-modified using a mechanochemical method.

[0074] After modification, excess hydrophobic modifier is removed to obtain the hydrophobic nanocellulose.

[0075] In another aspect, the present invention provides a nanocellulose membrane, which is obtained by dispersing the hydrophobic nanocellulose as described above in an organic solvent and then filtering or casting it into a membrane.

[0076] For example, the nanocellulose membrane is formed by casting hydrophobic lignin-containing nanocellulose, after centrifugation and washing to remove excess modifiers, onto a glass substrate, or by filtration through a solvent filter, and drying at 60-100°C for 2-12 hours. The membrane thickness is preferably controlled to be 15-45 μm.

[0077] Exemplary organic solvents include, but are not limited to, dimethyl sulfoxide and N,N-dimethylformamide.

[0078] For example, the ratio of the hydrophobic lignin-containing nanocellulose to the organic solvent is 1g:20-50ml. The lignin-containing nanocellulose membrane prepared by the above method has high transparency, high haze, and good hydrophobicity.

[0079] The technical solution of the present invention will be described below with reference to some specific embodiments:

[0080] Example 1

[0081] This embodiment provides a method for pretreatment of natural cellulose, including the following steps:

[0082] Sodium hydroxide was dissolved in deionized water to obtain a 1 wt% alkaline aqueous solution. 20 g of natural bamboo powder was weighed and added to 380 g of the alkaline aqueous solution. The mixture was heated and stirred at 80°C for 2 hours. The treated cellulose was washed with water until neutral and then dried.

[0083] Example 2

[0084] This embodiment provides a method for preparing hydrophobic lignin-containing nanocellulose and its membrane, including the following steps:

[0085] Weigh 1g of bamboo cellulose raw material treated in Example 1, 1.74g of dichlorophenyl isocyanate, and 20mL of dimethyl sulfoxide into a grinder for one-step mechanochemical modification. Ball mill the mixture at 300rpm for 1h. Centrifuge and wash the product to remove excess dichlorophenyl isocyanate modifier, and prepare hydrophobic lignin-containing nanocellulose.

[0086] The lignin-containing nanocellulose has a diameter concentrated between 1-3 nm, with a maximum of 8 nm. Furthermore, this nanocellulose exhibits a high degree of defibrillation and lacks a two-dimensional network structure. Its AFM morphology is shown below. Figure 1 As shown, even with a very short ball milling time, the resulting nanocellulose has a very small diameter.

[0087] The product, after centrifugation to remove excess modifier, was filtered through a solvent filter to form a membrane. It was then dried at 60-100℃ for 2-12 hours, with the membrane thickness controlled at 20 μm. X-ray diffraction showed the crystallinity of the cellulose membrane to be 65.5. UV spectrophotometry revealed a transmittance of 84%, a haze of 83%, and a UV shielding efficiency of 88.5%. The water contact angle was measured to be 75.1°. Its tensile strength was 85 MPa. The cellulose membrane... Figure 2 As shown. Among them, Figure 2 The image on the left shows the fiber membrane placed directly on a piece of white paper with letters on it, clearly demonstrating the excellent transparency of the fiber membrane. Figure 2 The image on the right shows the fiber membrane being lifted from the white paper with letters (at a distance of more than 1 cm). It can be seen that the letters on the white paper cannot be seen through the fiber membrane at this time, indicating that the fiber membrane has good haze.

[0088] Example 3

[0089] This embodiment provides a method for preparing hydrophobic lignin-containing nanocellulose and its membrane, including the following steps:

[0090] Weigh 1g of bamboo cellulose raw material treated in Example 1, 1.74g of dichlorophenyl isocyanate, and 20mL of dimethyl sulfoxide and add them to a grinder for one-step mechanochemical modification. Ball mill at 300rpm for 4h. Centrifuge and wash the product to remove excess modifier dichlorophenyl isocyanate and prepare hydrophobic lignin-containing nanocellulose.

[0091] The prepared lignin-containing nanocellulose has a diameter concentrated between 1-3 nm, and the nanocellulose has a high degree of defibrillation and no two-dimensional network structure.

[0092] The product, after centrifugation to remove excess modifier, was filtered through a solvent filter to form a membrane, which was then dried at 60-100℃ for 2-12 hours, with the membrane thickness controlled at 20 μm. X-ray diffraction determined the crystallinity of the cellulose membrane to be 64.4. Ultraviolet spectrophotometry showed that the membrane had a transmittance of 84%, a haze of 81%, and an ultraviolet shielding efficiency of 88.9%. The water contact angle was measured to be 84.8°. Its tensile strength was 82 MPa.

[0093] Example 4

[0094] This embodiment provides a method for preparing hydrophobic lignin-containing nanocellulose and its membrane, including the following steps:

[0095] Weigh 1g of bamboo cellulose raw material treated in Example 1, 1.74g of dichlorophenyl isocyanate, and 20mL of dimethyl sulfoxide into a grinder for one-step mechanochemical modification. Ball mill at 300rpm for 12h. Centrifuge and wash the product to remove excess modifier dichlorophenyl isocyanate, and prepare hydrophobic lignin-containing nanocellulose.

[0096] The prepared lignin-containing nanocellulose has a diameter concentrated between 1-2 nm, and the nanocellulose has a high degree of defibrillation and no two-dimensional network structure.

[0097] The product, after centrifugation to remove excess modifier, was filtered through a solvent filter to form a membrane, which was then dried at 60-100℃ for 2-12 hours, with the membrane thickness controlled at 20 μm. X-ray diffraction determined the crystallinity of the cellulose membrane to be 66.6. Ultraviolet spectrophotometry showed that the membrane had a transmittance of 88%, a haze of 80%, and an ultraviolet shielding efficiency of 90.7%. The water contact angle was measured to be 81.6°. Its tensile strength was 72 MPa.

[0098] Example 5

[0099] This embodiment provides a method for preparing hydrophobic lignin-containing nanocellulose and its membrane, including the following steps:

[0100] 1g of treated bamboo cellulose powder, 1g of dichlorophenyl isocyanate, and 20mL of dimethyl sulfoxide were weighed and added to a mill for one-step mechanochemical modification. The mixture was ball-milled at 300rpm for 6 hours. The product was then centrifuged and washed to remove excess modifier, yielding hydrophobic lignin-containing nanocellulose. The lignin-containing nanocellulose exhibited a diameter concentrated between 1-5nm, high degree of defibrillation, and no two-dimensional network structure. Its AFM morphology is as follows: Figure 3 As shown.

[0101] The membrane prepared using the method described in Example 2 had a transmittance of 82%, a haze of 84%, an ultraviolet shielding efficiency of 92.6%, and a water contact angle of 72.0° as measured by a contact angle meter. The crystallinity of the cellulose membrane was determined to be 68.2% by X-ray diffraction. Its tensile strength was 85 MPa.

[0102] Example 6

[0103] This embodiment provides a method for preparing hydrophobic lignin-containing nanocellulose and its membrane, including the following steps:

[0104] 1g of treated bamboo cellulose raw material, 1.25g of dichlorophenyl isocyanate, and 20mL of dimethyl sulfoxide were weighed and added to a grinder for one-step mechanochemical modification. The mixture was ball-milled at 300rpm for 6 hours. The product was then centrifuged and washed to remove excess modifier, yielding hydrophobic lignin-containing nanocellulose. The diameter of this lignin-containing nanocellulose was concentrated between 1-3nm, and the nanocellulose exhibited a high degree of defibrillation and lacked a two-dimensional network structure.

[0105] The membrane prepared using the method described in Example 2 had a transmittance of 85%, a haze of 84%, an ultraviolet shielding efficiency of 90.5%, and a water contact angle of 82.2° as measured by a contact angle meter. The crystallinity of the cellulose membrane was determined to be 66.9% by X-ray diffraction. Its tensile strength was 83 MPa.

[0106] Example 7

[0107] This embodiment provides a method for preparing hydrophobic lignin-containing nanocellulose and its membrane, including the following steps:

[0108] 1g of treated bamboo cellulose powder, 1.5g of dichlorophenyl isocyanate, and 20mL of dimethyl sulfoxide were weighed and added to a grinder for one-step mechanochemical modification. The mixture was ball-milled at 300rpm for 6 hours. The product was then centrifuged and washed to remove excess modifier, yielding hydrophobic lignin-containing nanocellulose. The diameter of this lignin-containing nanocellulose was concentrated between 1-2nm, and it exhibited a high degree of defibrillation and lacked a two-dimensional network structure.

[0109] The membrane prepared using the method described in Example 2 had a transmittance of 86%, a haze of 81%, an ultraviolet shielding efficiency of 90.8%, and a water contact angle of 86.4° as measured by a contact angle meter. The crystallinity of the cellulose membrane was determined to be 68.1% by X-ray diffraction. Its tensile strength was 82 MPa.

[0110] Example 8

[0111] This embodiment provides a method for preparing hydrophobic lignin-containing nanocellulose and its membrane, including the following steps:

[0112] Sodium hydroxide was dissolved in deionized water to obtain a 1 wt% alkaline aqueous solution. 20 g of natural bamboo powder was weighed and added to 250 g of the alkaline aqueous solution. The mixture was heated and stirred at 80 °C for 1 hour. The treated cellulose was washed with water until neutral and then dried.

[0113] 1g of treated bamboo cellulose powder, 1.5g of dichlorophenyl isocyanate, and 20mL of dimethyl sulfoxide were weighed and added to a grinder for one-step mechanochemical modification. The mixture was ball-milled at 300rpm for 6 hours. The product was then centrifuged and washed to remove excess modifier, yielding hydrophobic lignin-containing nanocellulose. The diameter of this lignin-containing nanocellulose was concentrated between 2-6nm, and the nanocellulose exhibited a high degree of defibrillation and lacked a two-dimensional network structure.

[0114] The product, after centrifugation to remove excess modifier, was filtered through a solvent filter to form a membrane, which was then dried at 60-100℃ for 2-12 hours, with a membrane thickness controlled at 20 μm. The membrane's transmittance was 86%, haze was 77%, and water contact angle was 80.5°, as measured by UV spectrophotometry. X-ray diffraction revealed the cellulose membrane to have a crystallinity of 68%. Its tensile strength was 87 MPa.

[0115] Example 9

[0116] This embodiment provides a method for preparing hydrophobic lignin-containing nanocellulose and its membrane, including the following steps:

[0117] Sodium hydroxide was dissolved in deionized water to obtain a 0.5 wt% alkaline aqueous solution. 20 g of natural bamboo powder was weighed and added to 380 g of the alkaline aqueous solution. The mixture was heated and stirred at 80°C for 2 hours. The treated cellulose was washed with water until neutral and then dried.

[0118] 1g of treated bamboo cellulose powder, 1.5g of dichlorophenyl isocyanate, and 20mL of dimethyl sulfoxide were weighed and added to a grinder for one-step mechanochemical modification. The mixture was ball-milled at 300rpm for 6 hours. The product was then centrifuged and washed to remove excess modifier, yielding hydrophobic lignin-containing nanocellulose. The diameter of this lignin-containing nanocellulose was concentrated between 3-10nm, and it exhibited a high degree of defibrillation and lacked a two-dimensional network structure.

[0119] The product, after centrifugation to remove excess modifier, was filtered through a solvent filter to form a membrane, which was then dried at 60-100℃ for 2-12 hours, with the membrane thickness controlled at 20 μm. The membrane's transmittance was 83%, haze was 80%, and water contact angle was 77.9°, as measured by UV spectrophotometry. The crystallinity of the cellulose membrane was determined to be 67% by X-ray diffraction. Its tensile strength was 84 MPa.

[0120] Comparative Example 1

[0121] 1g of cellulose raw material that has not been treated with alkaline solution, 1.74g of dichlorophenyl isocyanate, and 20mL of dimethyl sulfoxide were weighed and added to a mill for one-step mechanochemical modification. The mixture was ball-milled at 300rpm for 12h. After centrifuging and washing to remove excess modifier, it was found that the defibrillation effect was poor, and it was impossible to form small-diameter nanocellulose as described in this invention.

[0122] Comparative Example 2

[0123] Sodium hydroxide was dissolved in deionized water to obtain a 1 wt% alkaline aqueous solution. 20 g of natural bamboo powder was weighed and added to 380 g of the alkaline aqueous solution. The mixture was heated and stirred at 80°C for 2 hours. The treated cellulose was washed with water until neutral and then dried.

[0124] Weigh 1g of the above-treated bamboo cellulose raw material, 0.5g of dichlorophenyl isocyanate, and 20mL of dimethyl sulfoxide, and add them to a grinder for one-step mechanochemical modification. Ball mill at 300rpm for 6 hours. The resulting nanocellulose is in a defibrinated state with a diameter of approximately 50nm. Figure 4 .

[0125] Furthermore, it should be noted that when 1g of treated bamboo cellulose raw material was subjected to mechanochemical modification with 20mL of dimethyl sulfoxide, and ball-milled at 300rpm for 6 hours, the diameter of the nanocellulose was approximately 100nm, but it was not in an undefibrinated state. Therefore, the purpose of this application is to promote the nano-sizing degree and defibrinated state of lignin-containing cellulose, thereby obtaining nanocellulose with a smaller diameter and better defibrinated state.

[0126] Comparative Example 3

[0127] Sodium hydroxide was dissolved in deionized water to obtain a 9 wt% alkaline aqueous solution. 20 g of natural bamboo powder was weighed and added to 380 g of the alkaline aqueous solution. The mixture was heated and stirred at 80°C for 2 hours. The treated cellulose was washed with water until neutral and then dried.

[0128] 1g of treated bamboo cellulose raw material, 1.75g ​​of dichlorophenyl isocyanate, and 20mL of dimethyl sulfoxide were weighed and added to a grinder for one-step mechanochemical modification. The mixture was ball-milled at 300rpm for 6 hours. It was found that if the concentration of the alkaline solution was too high, the resulting cellulose was a network cellulose, unable to form individual fibers.

[0129] Comparative Example 4

[0130] This embodiment provides a method for pretreatment of natural cellulose, including the following steps:

[0131] Sodium hydroxide was dissolved in deionized water to obtain a 1 wt% alkaline aqueous solution. 20 g of natural bamboo powder was weighed and added to 380 g of the alkaline aqueous solution. The mixture was heated and stirred at 80°C for 2 hours. The treated cellulose was washed with water until neutral and then dried.

[0132] 1g of treated bamboo cellulose raw material, 3g of dodecyl succinic anhydride, and 20mL of dimethyl sulfoxide were weighed and added to a grinder for one-step mechanochemical modification. The mixture was ball-milled at 300rpm for 6 hours. The product was then centrifuged and washed to remove excess modifier, yielding hydrophobic lignin-containing nanocellulose. The diameter of this lignin-containing nanocellulose was concentrated around 50nm.

[0133] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. Hydrophobic nanocellulose, characterized in that, The hydrophobic cellulose nanoparticles have a diameter in the nanometer range and are obtained by surface modification of cellulose with a hydrophobic modifier. The diameter of the hydrophobic cellulose nanoparticles is less than 10 nm, and the mass ratio of cellulose to the hydrophobic modifier is 1:0.75 to 1:

3. The cellulose is natural cellulose whose surface has been pretreated with an alkaline solution, wherein the concentration of the alkaline solution is 0.3~5wt%, and the solid-liquid ratio of the natural cellulose to the alkaline solution is 1:13~1:

24. The hydrophobic modifier is an isocyanate-based modifier; The natural cellulose contains lignin, and the natural cellulose is derived from natural herbaceous plants or natural woody plants; The isocyanate-based modifier is selected from monoisocyanates; The monoisocyanate is selected from one or more of dichlorophenyl isocyanate, octadecyl isocyanate, 2-chloroethyl isocyanate or benzyl isocyanate; The surface modification method includes the following steps: The cellulose and hydrophobic modifier were mixed in the presence of a non-proton polar organic solvent, and the raw material was nano-modified by mechanochemical method. After modification, excess hydrophobic modifier was removed to obtain the hydrophobic nanocellulose.

2. The hydrophobic nanocellulose according to claim 1, characterized in that, The natural cellulose is derived from one or more of wood flour, bamboo flour, straw, or straw pulp.

3. The hydrophobic nanocellulose according to claim 1, characterized in that, The diameter of the hydrophobic nanocellulose is less than 5 nm.

4. The hydrophobic nanocellulose according to claim 1, characterized in that, The diameter of the hydrophobic nanocellulose is less than 3 nm.

5. The hydrophobic nanocellulose according to claim 1, characterized in that, The preprocessing method includes the following steps: The alkaline solution is mixed with natural cellulose, heated and stirred, dried, and then the natural cellulose is washed until neutral and dried.

6. The hydrophobic nanocellulose according to claim 5, characterized in that, In the alkaline solution, the alkaline substance is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, or sodium bicarbonate.

7. The hydrophobic nanocellulose according to claim 1, characterized in that, The mass ratio of cellulose to the aprotic polar organic solvent is 0.5~5:

100.

8. The hydrophobic nanocellulose according to claim 1, characterized in that, The mass ratio of cellulose to the hydrophobic modifier is 1:0.75 to 1:

2.

9. The hydrophobic nanocellulose according to claim 1, characterized in that, The mass ratio of cellulose to the hydrophobic modifier is 1:1 to 1:1.

5.

10. The hydrophobic nanocellulose according to claim 1, characterized in that, The aprotic polar organic solvent is selected from one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, or N-methylpyrrolidone.

11. The hydrophobic nanocellulose according to claim 1, characterized in that, The mechanochemical method is either ball milling or disc milling.

12. The hydrophobic nanocellulose according to claim 11, characterized in that, The ball milling speed is 200~500 rpm, and the time is 0.5~12 h.

13. The hydrophobic nanocellulose according to claim 11, characterized in that, The ball mill operates at a speed of 200-300 rpm for 1-6 hours.

14. The method of preparing hydrophobic nanocellulose according to any one of claims 1 to 13, c h a ra cte ri zed i n that, Includes the following steps: The natural cellulose was pretreated with an alkaline solution to obtain the cellulose. A hydrophobic modifier is mixed with the cellulose in the presence of an aprotic polar organic solvent, and the raw material is nano-modified using a mechanochemical method. After modification, excess hydrophobic modifier is removed to obtain the hydrophobic nanocellulose.

15. A nanocellulose film, characterized in that, The nanocellulose membrane is obtained by dispersing the hydrophobic nanocellulose as described in any one of claims 1-13 in an organic solvent and then filtering or casting it into a membrane.

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