WO2018227894A1 - High-concentration and deep dyeing method for nanocellulose - Google Patents

Abstract

Disclosed in the present invention is a high-concentration and deep dyeing method for nanocellulose. Said method comprises the steps of: adding a strong electrolyte salt to an aqueous solution of nanocellulose, performing centrifugation, and then adding ethanol and water to formulate a nanocellulose mixed solution; adding an active dye, an alkali or a strong alkali weak acid salt to the mixed solution, and then heating, condensing and refluxing the solution; and after completion of the reaction, performing centrifugation, and collecting the precipitate, so as to obtain deeply dyed nanocellulose. The concentration of the nanocellulose in the present invention can be increased to 5%-10% from 0.5%-2% of common nanocellulose in a dyeing reaction, thereby increasing the graft rate. The dye-uptake of a dye can be increased to 50%-70% from 20%-40% of common nanocellulose, thereby increasing the utilization rate of the dye. The present invention is beneficial to the treatment of reaction wastewater. Furthermore, the dyed nanocellulose prepared by the present invention has very good stability, does not easily fade, is small in size, and has a high dyeability, being desirable to be applied in fields such as nanocellulose inkjet printing and paper anti-counterfeiting, having high practical value.

Description

High-concentration depth dyeing method of nano cellulose

Technical field

 The invention belongs to the field of nanofiber materials, and particularly relates to a high-concentration dyeing method for nanocellulose.

Background technique

 Since the nanocellulose is jelly-like when the concentration is slightly larger, the concentration of the nanocellulose and the reactive dye in the ordinary aqueous solution is generally 0.5%-2% It is difficult to achieve deep dyeing of nanocellulose and full utilization of dyes. Since both nanocellulose and reactive dyes have strong electronegativity, a large amount of strong electrolyte salts must be added during the reaction to counteract the negative electrical influence. The addition of a large amount of salt also increases the difficulty of wastewater treatment. The method of the invention can increase the concentration of nanocellulose during the reaction to 5%-10% To achieve high-concentration, nano-cellulose-free salt-free dyeing. The amount of grafting of the reactive dye on the nanocellulose and the dye uptake rate are greatly improved. The prepared nanocellulose is promising for use in the field of anti-counterfeiting of paper or inkjet printing of nanocellulose, and has strong practical value.

Summary of the invention

In order to overcome the deficiencies of the prior art, the present invention provides a high-concentration depth dyeing method of nanocellulose. The dyed nanocellulose prepared by the invention has small size and high dyeing degree, and is highly expected to be applied to the fields of inkjet printing of nanocellulose and anti-counterfeiting of paper, and has strong practical value.

 The present invention is achieved by the following technical solutions.

 A high-concentration depth dyeing method for nanocellulose, comprising the following steps:

 ( 1 Adding a strong electrolyte salt to the nanocellulose aqueous solution, and centrifuging to precipitate the nanocellulose; then dispersing the obtained precipitate into ethanol, and adding water to prepare a nanocellulose mixture;

 (2) in step (1) Adding a reactive dye to the obtained nanocellulose mixed solution, adding a base or a strong base weak acid salt, stirring uniformly, heating up, condensing and refluxing reaction, so that the dye is sufficiently dyed onto the nanocellulose;

 (3 After the reaction is completed, the reaction vessel is rapidly cooled with cold water, and the reaction solution is centrifuged in a high-speed refrigerated centrifuge to remove the unreacted dye and the surface of the fiber, and the obtained precipitate is dispersed in an aqueous solution of a strong electrolyte salt, and the centrifugation is repeated. Until the supernatant is colorless, the precipitate obtained is the deeply dyed nanocellulose.

Preferably, the strong electrolyte salt of the step (1) is one or more of NaCl, KCl, Na ₂ SO ₄ and K ₂ SO ₄ ; the strong electrolyte salt is used in an amount of 0.5 wt% of the aqueous nanocellulose solution. -3wt%.

 Preferably, the mass ratio of nanocellulose to water in the nanocellulose mixture in step (1) is 5:95-10:90 The volume ratio of ethanol to water is 50:50-95:5.

 Preferably, the step (2 The reactive dye is one or more of reactive red, active orange, active yellow, active green, reactive blue, reactive violet, reactive brown, reactive ash and reactive black; the amount of reactive dye is nanocellulose 0.2 wt% -30 Wt%.

Preferably, the reaction liquid of the step (2) is added with or without a strong electrolyte salt; the strong electrolyte salt is one or more of NaCl, KCl, Na ₂ SO ₄ and K ₂ SO ₄ ; The amount of the strong electrolyte salt in the reaction liquid is 0-40 g/L.

Preferably, the base or strong base weak acid salt of step (2) is one or more of ammonia water, NaOH, KOH, Na ₂ CO ₃ , K ₂ CO ₃ and pH buffer.

 Preferably, the step (2 The medium-strong electrolyte salt, the reactive dye, the alkali or the strong base weak acid salt may be added before the temperature rise or may be added after the temperature rise, or may be added after the temperature is added before the temperature is added.

 Preferably, in the step (2), the pH of the reaction solution is 9-13, the reaction time is 30-240 min, and the reaction temperature is 60 °C -80 °C.

Preferably, in the step (3), after the reaction is completed, the pH of the reaction solution can be adjusted to neutral by acid, or the pH can be adjusted without acid, and the mixture is centrifuged several times until the pH of the solution is neutral; the pH value is adjusted. The acid used in the case of the sex is one or more of a HCl solution, a H ₂ SO ₄ solution, a HNO ₃ solution, an H ₃ PO ₄ solution, and a CH ₃ COOH solution.

Preferably, the strong electrolyte salt of the step (3) is one or more of NaCl, KCl, Na ₂ SO ₄ and K ₂ SO ₄ ; the concentration of the strong electrolyte salt in the aqueous solution is 0.5 wt% -3 Wt%.

 Preferably, a high-concentration depth dyeing method of nanocellulose comprises the following steps:

0.5 wt% to 3 wt% of a strong electrolyte salt was added to the aqueous nanocellulose solution, and the nanocellulose was precipitated by high speed centrifugation. A mixture of nanocellulose, ethanol and water is prepared in a certain ratio. To the prepared mixture was added 0-40 g/L NaCl, 0.2 wt%-30 wt% reactive dye, 5-40 g/L Na ₂ CO ₃ . After stirring uniformly, the temperature was raised to 80-90 ° C, and it was condensed and refluxed for 30-240 min. After completion of the reaction, the reaction vessel was rapidly cooled with cold water, and the reaction liquid was centrifuged by a high-speed refrigerated centrifuge. The obtained precipitate was sufficiently dispersed in an ethanol water mixture or a 0.5 wt% to 3 wt% strong electrolyte salt solution, and the centrifugation was repeated until the supernatant was colorless, and the precipitate obtained was a deeply dyed nanocellulose.

In the present invention, nanocellulose is reacted with a reactive dye in a mixture of ethanol and water. Since the nanocellulose and the reactive dye are insoluble in ethanol, the nanocellulose and the reactive dye are only grafted in a small amount of water in the mixed solution during the actual reaction.

 Compared with the prior art, the present invention has the following advantages and benefits:

 1 The invention can realize the graft reaction of the high-concentration nano cellulose with the high-concentration dye. The concentration of nanocellulose during the reaction can be increased from 0.5 wt% to 2 wt% in the normal aqueous solution of nanocellulose. Wt%-10 wt% can greatly improve the dyeing depth of nanocellulose. The dye uptake rate can be increased from 20%-40% in the normal aqueous solution of nanocellulose to 50%-70%. It can greatly improve the dye utilization rate and reduce the inefficient hydrolysis of the dye.

 2 The grafting reaction of the invention is carried out at a high concentration, and the grafting reaction between the nanocellulose and the reactive dye can be realized without adding a strong electrolyte salt, thereby reducing the amount of washing water and the salt content of the water after washing, which is beneficial to Treatment of reaction wastewater.

 3

In the present invention, the nanocellulose and the reactive dye are covalently bonded, have very good stability, are not easy to fade, and no toxic substances participate or are formed in the whole dyeing process, and the prepared nanocellulose is promising for paper. In the field of anti-counterfeiting or nano-cellulose printing, it has high practical value.

detailed description

 The specific implementation of the present invention will be further described below with reference to examples, but the embodiments of the present invention are not limited thereto.

The grafting amount and dyeing rate described below are determined according to the following methods: UV-visible full-wavelength scanning is performed on different dyes to determine the maximum absorption peak corresponding wavelength (for example, Reactive Red 120 513nm The maximum absorption peak is at the wavelength; the standard curve of the dye is made at this wavelength; the centrifugation solution is centrifuged several times after the completion of the reaction, and the volume and absorbance are measured; the dye content in the centrate is calculated according to the standard curve, and the dye is on the nanocellulose. The graft amount and the dye uptake rate. The specific calculation formula is as follows:

Graft amount: m _graft = (m _{dye -} Abs * V / a) / m _NFC

Dye _{uptake: G = (m dye -Abs *} V / a) / m dye

m _graft : dye grafting amount

m _dye : dye usage

 Abs : Absorbance of total supernatant obtained after centrifugation after completion of reaction

 a : standard curve slope

 V: total supernatant volume obtained after centrifugation after completion of the reaction

m _NFC : nanocellulose dosage

 G: dye uptake rate.

 Example 1

1 wt% of NaCl was added to 500 ml of a 0.5 wt% aqueous nanocellulose solution, and centrifuged at a high speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in absolute ethanol, and the centrifugation was repeated a plurality of times. Deionized water was added to the prepared nanocellulose ethanol mixture to prepare a nanocellulose mixture (the mass ratio of nanocellulose to water was 5:95, and the volume ratio of absolute ethanol to water was 80:20). 10 wt% of Reactive Red 120 reactive dye, 10 g/L of NaCl, and 10 g/L of Na ₂ CO ₃ were added to the prepared nanocellulose mixture, and the mixture was uniformly stirred. The mixture was heated to reflux and refluxed for 120 min. After completion of the reaction, the reaction vessel was rapidly cooled with cold water, and the reaction liquid was centrifuged by a high-speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in a NaCl solution having a concentration of 1 wt%, and the centrifugation was repeated until the supernatant was colorless, and the precipitate obtained was a deeply dyed nanocellulose.

 The grafting amount of Reactive Red 120 in the dyed nanocellulose prepared in this example was 30.1 mg/g. Nanocellulose, the dye uptake rate was 47.3%, and the dyed nanocellulose did not produce obvious physical changes such as size change and curl.

Example 2

1 wt% of NaCl was added to 500 ml of a 0.5 wt% aqueous nanocellulose solution, and centrifuged at a high speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in absolute ethanol, and the centrifugation was repeated a plurality of times. Deionized water was added to the prepared nanocellulose ethanol mixture to prepare a nanocellulose mixture (the mass ratio of nanocellulose to water was 10:90, and the volume ratio of absolute ethanol to water was 95:5). To the prepared mixture, 10 wt% of Reactive Red 120 reactive dye, 10 g/L of NaCl, and 10 g/L of Na ₂ CO _{3 were added} and stirred well. The mixture was heated to reflux and refluxed for 120 min. After completion of the reaction, the reaction vessel was rapidly cooled with cold water, and the reaction liquid was centrifuged by a high-speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in a 1 wt% NaCl solution, and the centrifugation was repeated until the supernatant was colorless, and the precipitate obtained was a deeply dyed nanocellulose.

 The grafting amount of Reactive Red 120 in the dyed nanocellulose prepared in this example was 65.5 mg/g. Nanocellulose, the dye uptake rate was 56.6%, and the dyed nanocellulose did not produce obvious physical changes such as size change and curl.

 Example 3

1 wt% of NaCl was added to 500 ml of a 0.5 wt% aqueous nanocellulose solution, and centrifuged at a high speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in absolute ethanol, and the centrifugation was repeated a plurality of times. Deionized water was added to the prepared nanocellulose ethanol mixture to prepare a nanocellulose mixture (the mass ratio of nanocellulose to water was 7.5:92.5, and the volume ratio of absolute ethanol to water was 50:50). To the prepared mixture, 10 wt% of Reactive Red 120 reactive dye, 10 g/L of NaCl, and 10 g/L of Na ₂ CO _{3 were added} and stirred well. The mixture was heated to reflux and refluxed for 120 min. After completion of the reaction, the reaction vessel was rapidly cooled with cold water, and the reaction liquid was centrifuged by a high-speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in a 1 wt% NaCl solution, and the centrifugation was repeated until the supernatant was colorless, and the precipitate obtained was a deeply dyed nanocellulose.

 The grafting amount of Reactive Red 120 in the dyed nanocellulose prepared in this example was 50.1 mg/g. Nanocellulose, the dye uptake rate was 51.3%, and the dyed nanocellulose did not produce obvious physical changes such as size change and curl.

 Example 4

1 wt% of NaCl was added to 500 ml of a 0.5 wt% aqueous nanocellulose solution, and centrifuged at a high speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in absolute ethanol, and the centrifugation was repeated a plurality of times. Deionized water was added to the prepared nanocellulose ethanol mixture to prepare a nanocellulose mixture (the mass ratio of nanocellulose to water was 5:95, and the volume ratio of absolute ethanol to water was 80:20). 2 wt% of Reactive Red 120 reactive dye, 10 g/L of Na ₂ CO ₃ was added to the prepared mixture, and the mixture was stirred well. The mixture was heated to reflux and refluxed for 120 min. After completion of the reaction, the reaction vessel was rapidly cooled with cold water, and the reaction liquid was centrifuged by a high-speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in a 50% aqueous solution of ethanol, and the centrifugation was repeated until the supernatant was colorless, and the precipitate obtained was a deeply dyed nanocellulose.

 The grafting amount of Reactive Red 120 in the dyed nanocellulose prepared in this example was 55.3 mg/g. Nanocellulose, the dye uptake rate was 61.8%, and the dyed nanocellulose did not produce obvious physical changes such as size change and curl.

 Example 5

1 wt% of NaCl was added to 500 ml of a 0.5 wt% aqueous nanocellulose solution, and centrifuged at a high speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in absolute ethanol, and the centrifugation was repeated a plurality of times. Deionized water was added to the prepared nanocellulose ethanol mixture to prepare a nanocellulose mixture (the mass ratio of nanocellulose to water was 5:95, and the volume ratio of absolute ethanol to water was 80:20). 0.2 wt% of Reactive Red 120 reactive dye, 10 g/L of NaCl, and 10 g/L of Na ₂ CO ₃ were added to the prepared mixture, and the mixture was stirred well. The mixture was heated to reflux and refluxed for 240 min. After completion of the reaction, the reaction vessel was rapidly cooled with cold water, and the reaction liquid was centrifuged by a high-speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in a 1 wt% NaCl solution, and the centrifugation was repeated until the supernatant was colorless, and the precipitate obtained was a deeply dyed nanocellulose.

 The grafting amount of Reactive Red 120 in the dyed nanocellulose prepared in this example was 6.3 mg/g. Nanocellulose, dye dyeing rate was 70.3%, and the dyed nanocellulose did not produce obvious physical changes such as size change and curl.

 Example 6

1 wt% of NaCl was added to 500 ml of a 0.5 wt% aqueous nanocellulose solution, and centrifuged at a high speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in absolute ethanol, and the centrifugation was repeated a plurality of times. Deionized water was added to the prepared nanocellulose ethanol mixture to prepare a nanocellulose mixture (the mass ratio of nanocellulose to water was 5:95, and the volume ratio of absolute ethanol to water was 80:20). To the prepared mixture, 30 wt% of Reactive Red 120 reactive dye, 10 g/L of NaCl, and 10 g/L of Na ₂ CO _{3 were added} and stirred well. The mixture was heated to reflux and refluxed for 30 min. After completion of the reaction, the reaction vessel was rapidly cooled with cold water, and the reaction liquid was centrifuged by a high-speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in a 1 wt% NaCl solution, and the centrifugation was repeated until the supernatant was colorless, and the precipitate obtained was a deeply dyed nanocellulose.

 The grafting amount of Reactive Red 120 in the dyed nanocellulose prepared in this example was 70.3 mg/g. Nanocellulose, dye dyeing rate was 30.7%, and the dyed nanocellulose did not produce obvious physical changes such as size change and curl.

 Example 7

1 wt% of NaCl was added to 500 ml of a 0.5 wt% aqueous nanocellulose solution, and centrifuged at a high speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in absolute ethanol, and the centrifugation was repeated a plurality of times. Deionized water was added to the prepared nanocellulose ethanol mixture to prepare a nanocellulose mixture (the mass ratio of nanocellulose to water was 5:95, and the volume ratio of absolute ethanol to water was 80:20). To the prepared mixture, 15.1 wt% of Reactive Red 120 reactive dye, 10 g/L of NaCl, and 10 g/L of Na ₂ CO _{3 were added} and stirred well. The mixture was heated to reflux and refluxed for 135 min. After completion of the reaction, the reaction vessel was rapidly cooled with cold water, and the reaction liquid was centrifuged by a high-speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in a 1 wt% NaCl solution, and the centrifugation was repeated until the supernatant was colorless, and the precipitate obtained was a deeply dyed nanocellulose.

 The grafting amount of Reactive Red 120 in the dyed nanocellulose prepared in this example was 66.7 mg/g. Nanocellulose, dye dyeing rate was 58.9%, and the dyed nanocellulose did not produce obvious physical changes such as size change and curl.

 Example 8

1 wt% of NaCl was added to 500 ml of a 0.5 wt% aqueous nanocellulose solution, and centrifuged at a high speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in absolute ethanol, and the centrifugation was repeated a plurality of times. Deionized water was added to the prepared nanocellulose ethanol mixture to prepare a nanocellulose mixture (the mass ratio of nanocellulose to water was 10:90, and the volume ratio of absolute ethanol to water was 95:5). 2 wt% of Reactive Red 120 reactive dye, 10 g/L of NaCl, and 10 g/L of Na ₂ CO ₃ were added to the prepared mixture, and the mixture was stirred well. The mixture was heated to reflux and refluxed for 120 min. After completion of the reaction, the reaction vessel was rapidly cooled with cold water, and the reaction liquid was centrifuged by a high-speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in a 1 wt% NaCl solution, and the centrifugation was repeated until the supernatant was colorless, and the precipitate obtained was a deeply dyed nanocellulose.

 The grafting amount of Reactive Red 120 in the dyed nanocellulose prepared in this example was 61.4 mg/g. Nanocellulose, dye dyeing rate was 71.2%, and the dyed nanocellulose did not produce obvious physical changes such as size change and curl.

 Example 9

1 wt% of NaCl was added to 500 ml of a 0.5 wt% aqueous nanocellulose solution, and centrifuged at a high speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in absolute ethanol, and the centrifugation was repeated a plurality of times. Deionized water was added to the prepared nanocellulose ethanol mixture to prepare a nanocellulose mixture (the mass ratio of nanocellulose to water was 5:95, and the volume ratio of absolute ethanol to water was 80:20). To the prepared mixture, 10 wt% of Reactive Yellow 84 reactive dye, 10 g/L of NaCl, and 10 g/L of Na ₂ CO _{3 were added} and stirred well. The mixture was heated to reflux and refluxed for 120 min. After completion of the reaction, the reaction vessel was rapidly cooled with cold water, and the reaction liquid was centrifuged by a high-speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in a 1 wt% NaCl solution, and the centrifugation was repeated until the supernatant was colorless, and the precipitate obtained was a deeply dyed nanocellulose.

 The grafting amount of Reactive Red 120 in the dyed nanocellulose prepared in this example was 28.4 mg/g. Nanocellulose, dye dyeing rate was 44.0%, and the dyed nanocellulose did not produce obvious physical changes such as size change and curl.

 Example 10

1 wt% of NaCl was added to 500 ml of a 0.5 wt% aqueous nanocellulose solution, and centrifuged at a high speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in absolute ethanol, and the centrifugation was repeated a plurality of times. Deionized water was added to the prepared nanocellulose ethanol mixture to prepare a nanocellulose mixture (the mass ratio of nanocellulose to water was 5:95, and the volume ratio of absolute ethanol to water was 80:20). To the prepared mixture, 10 wt% of M-3RE Yellow reactive dye, 10 g/L of NaCl, and 10 g/L of Na ₂ CO _{3 were added} and stirred well. The mixture was heated to reflux and refluxed for 30 min. After completion of the reaction, the reaction vessel was rapidly cooled with cold water, and the reaction liquid was centrifuged by a high-speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in a 1 wt% NaCl solution, and the centrifugation was repeated until the supernatant was colorless, and the precipitate obtained was a deeply dyed nanocellulose.

 The grafting amount of Reactive Red 120 in the dyed nanocellulose prepared in this example was 25.3 mg/g. Nanocellulose, the dye uptake rate was 41.8%, and the dyed nanocellulose did not produce obvious physical changes such as size change and curl.

 Example 11

1 wt% of NaCl was added to 500 ml of a 0.5 wt% aqueous nanocellulose solution, and centrifuged at a high speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in absolute ethanol, and the centrifugation was repeated a plurality of times. Deionized water was added to the prepared nanocellulose ethanol mixture to prepare a nanocellulose mixture (the mass ratio of nanocellulose to water was 5:95, and the volume ratio of absolute ethanol to water was 80:20). To the prepared mixture, 10 wt% of Reactive Blue 71 reactive dye, 10 g/L of NaCl, and 10 g/L of Na ₂ CO _{3 were added} and stirred well. The mixture was heated to reflux and refluxed for 30 min. After completion of the reaction, the reaction vessel was rapidly cooled with cold water, and the reaction liquid was centrifuged by a high-speed refrigerated centrifuge (9000 rpm). The obtained precipitate was dispersed in a 1 wt% NaCl solution, and the centrifugation was repeated until the supernatant was colorless, and the precipitate obtained was a deeply dyed nanocellulose.

The grafting amount of Reactive Red 120 in the dyed nanocellulose prepared in this example was 32.7 mg/g nanocellulose, and the dye uptake rate was 49.0%. The dyed nanocellulose did not produce significant dimensional change, curl, etc. Physical form changes.

Claims (10)

1. A high-concentration dyeing method for nanocellulose, characterized in that it comprises the following steps:

   ( 1 Adding a strong electrolyte salt to the nanocellulose aqueous solution, and centrifuging to precipitate the nanocellulose; then dispersing the obtained precipitate into ethanol, and adding water to prepare a nanocellulose mixture;

   (2) in step (1) Adding a reactive dye to the obtained nanocellulose mixed solution, adding a base or a strong base weak acid salt, stirring uniformly, heating up, and condensing and refluxing;

   (3 After the reaction is completed, the reaction solution is cooled, centrifuged, and the obtained precipitate is dispersed in an aqueous solution of a strong electrolyte salt, and the centrifugation is repeated until the supernatant is colorless, and the precipitate obtained is a deeply dyed nanocellulose.
2. The high-concentration depth dyeing method of nanocellulose according to claim 1, wherein the strong electrolyte salt in the step (1) is one of NaCl, KCl, Na ₂ SO ₄ and K ₂ SO ₄ . Or several; the strong electrolyte salt is used in an amount of 0.5% by weight to 3% by weight of the aqueous nanocellulose solution.
3. The method for dyeing high-density depth of nanocellulose according to claim 1, wherein the mass ratio of nanocellulose to water in the nanocellulose mixture in the step (1) is 5:95-10: 90, the volume ratio of ethanol to water is 50:50-95:5.
4. The method for dyeing high-density depth of nanocellulose according to claim 1, wherein the reactive dye in the step (2) is active red, active orange, active yellow, active green, reactive blue, active violet, One or more of active brown, reactive ash and reactive black; the amount of the reactive dye is 0.2 of nanocellulose Wt%-30 wt%.
5. The method for dyeing high-density depth of nanocellulose according to claim 1, wherein a strong electrolyte salt or no strong electrolyte salt is added to the reaction liquid of the step (2); the strong electrolyte salt is NaCl, One or more of KCl, Na ₂ SO ₄ and K ₂ SO ₄ ; the strong electrolyte salt is used in the reaction liquid in an amount of 0-40 g/L.
6. The method for dyeing high-density depth of nanocellulose according to claim 1, wherein the alkali or strong base weak acid salt of the step (2) is ammonia water, NaOH, KOH, Na ₂ CO ₃ , K _{2 .} One or several of CO ₃ and pH buffer.
7. The method for dyeing high-density depth of nanocellulose according to claim 1, wherein the strong electrolyte salt, the reactive dye, the alkali or the strong base weak acid salt in the step (2) can be added before the temperature rise or After the temperature is raised, it may be added partially before the temperature rise, and then added after the temperature rise.
8. The method for dyeing high-density depth of nanocellulose according to claim 1, wherein in the step (2), the pH of the reaction solution is 9-13, the reaction time is 30-240 min, and the reaction temperature is 60. °C-80 °C.
9. The method for dyeing high-concentration depth of nanocellulose according to claim 1, wherein in the step (3), after the reaction is completed, the pH of the reaction solution can be adjusted to neutral by acid, or the pH can be adjusted without acid. Value, multiple centrifugation until the pH of the solution is neutral; the acid used to adjust the pH to neutral is HCl solution, H ₂ SO ₄ solution, HNO ₃ solution, H ₃ PO ₄ solution and CH ₃ COOH solution One or more.
10. The high-concentration dyeing method for nanocellulose according to claim 1, wherein the strong electrolyte salt in the step (3) is one or more of NaCl, KCl, Na2SO4 and K2SO4; The concentration of strong electrolyte salt in aqueous solution is 0.5 Wt%-3 wt%.