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Preparation method of nano-cellulose

A nano-cellulose and cellulose technology, applied in the field of nano-materials, can solve the problems of difficult hydrolysis acid solution, complicated post-treatment process, and difficult treatment of reaction acid solution, so as to speed up the oxidation reaction speed, improve the oxidation reaction efficiency, and react The effect of increased accessibility

Active Publication Date: 2014-12-10
INST OF CHEM IND OF FOREST PROD CHINESE ACAD OF FORESTRY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Although the method is simple to operate and the reaction conditions are easy to control, there are problems such as complex post-treatment process, high requirements for production equipment, and difficult handling of reaction acid.
For example, CN101509209A discloses a preparation method of rod-shaped nanocellulose, which uses concentrated sulfuric acid with a concentration of 50%-65% to hydrolyze the cellulose raw material. The hydrolysis acid solution is difficult to handle, and the post-treatment process of the product is complicated and difficult to operate.
[0004] One of the ways to oxidize cellulose is: use N-oxygen compounds as cellulose oxidation catalysts to treat cellulose raw materials in the presence of sodium bromide and sodium hypochlorite, and can introduce carboxyl groups into cellulose macromolecules. During the reaction, the N-oxygen compound, sodium bromide and sodium hypochlorite react together to generate oxidizing nitrosonium ions, thereby oxidizing the C6 primary hydroxyl on the cellulose surface to carboxyl, and a small amount of nanofibers are also produced during the oxidation process. However, due to the high crystallinity of cellulose, it is difficult for the oxidizing agent to enter the interior of the cellulose crystallization region, resulting in too long reaction time
In addition, the processed cellulose raw material has a low concentration, the mass concentration is only about 1%, and the production efficiency is very low
CN101903572A discloses a method for manufacturing cellulose nanofibers. First, the cellulose raw material is oxidized, and then the oxidized cellulose is subjected to 12,000 rpm high-speed defibrillation treatment to obtain a cellulose nanofiber suspension. The method includes defibrilation treatment. High speed, high energy consumption, and high requirements for equipment

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0023] Example 1: Preparation of nanocellulose:

[0024] (1) Pretreatment: After soaking 5 grams of microcrystalline cellulose with 50 grams of sodium hydroxide aqueous solution with a mass concentration of 7% for 10 hours at room temperature, filter out the cellulose and wash with deionized water until the pH of the filtrate The value is 8.

[0025] (2) Oxidation reaction: Disperse the filtered cellulose in 100mL deionized water, add 0.5g sodium bromide and 0.05g 2,2,6,6-tetramethylpiperidine-1-oxide, and stir to After dissolving, add 20g of sodium hypochlorite solution with a mass concentration of 5%, turn on the ultrasonic oscillation, the ultrasonic power is 300w, the frequency is 20kHz, and the pH of the reaction solution is adjusted with 0.5mol / L sodium hydroxide aqueous solution to maintain the pH value of the reaction solution at 10. -11 or so.

[0026] (3) Post-treatment: When the pH value does not change significantly (the reaction lasts for 150 minutes), the reaction sol...

Embodiment 2

[0027] Example 2: Preparation of nano cellulose:

[0028] Disperse 5 grams of microcrystalline cellulose in 30 grams of 9% sodium hydroxide aqueous solution, soak at room temperature for 15 hours, filter out the cellulose and wash with deionized water until the pH of the filtrate is 7. Disperse the filtered cellulose in 200mL deionized water, add 0.75g sodium bromide and 0.1g 2,2,6,6-tetramethylpiperidine-1-oxide respectively, stir to dissolve, add 25g mass The sodium hypochlorite solution with a concentration of 5% is turned on ultrasonic oscillation, the ultrasonic power is 500w, the frequency is 30kHz, and the pH value of the reaction solution is adjusted with 0.5mol / L sodium hydroxide aqueous solution to maintain the pH value of the reaction solution at about 10-11. When there is no significant change in the pH value (reaction lasts 85 minutes), the reaction solution is centrifuged 4 times at 10000 rpm to remove large-size cellulose, and the suspension is freeze-dried to obta...

Embodiment 3

[0029] Example 3: Preparation of nanocellulose:

[0030] Disperse 5 grams of microcrystalline cellulose in 80 grams of 4% potassium hydroxide aqueous solution, soak at room temperature for 20 hours, filter out the cellulose and wash with deionized water until the pH of the filtrate is 6. Disperse the filtered cellulose in 300mL of deionized water, add 0.7g of sodium bromide and 0.03g of 2,2,6,6-tetramethylpiperidine-1-oxide respectively, stir to dissolve, add 15g of mass The sodium hypochlorite solution with a concentration of 5%, turn on the ultrasonic oscillation, the ultrasonic power is 400w, the frequency is 40kHz, and the pH of the reaction solution is adjusted with 0.5mol / L sodium hydroxide aqueous solution to maintain the pH value of the reaction solution at about 10-11. When the reaction reaches the same pH value (reaction lasts 115 minutes), the reaction solution is centrifuged twice at a speed of 15000 rpm to remove large-size cellulose, and the suspension is freeze-dri...

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Abstract

The invention discloses a preparation method of nano-cellulose, comprising the following steps of: firstly, swelling the raw material cellulose by aqueous alkali, soaking for a while, centrifugally separating out cellulose, and washing by deionized water till the filter liquor is neutral; dispersing the separated cellulose in water, adding sodium bromide, 2, 2, 6, 6-tetramethyl piperidine-1-oxide and sodium hypochlorite solution, carrying out an oxidation reaction under sonic oscillation, centrifugally separating after reaction, and carrying out freeze drying treatment on suspension liquid to obtain the nano-cellulose powder. Compared with the prior art, the preparation method is incompact in cellulose structure, can enlarge the unit cell distance, and can improve the reaction accessibility after the raw material cellulose is pretreated, so that the oxidation reaction efficiency can be improved, and the product yield can be obviously improved; the oxidation reaction conditions are mild, and are easy to control, and the product quality can not be influenced due to the fact that only a small quantity of sodium chloride and minute quantity of oxidizing agent are mixed in a reaction system after the reaction; and the sonic oscillation is adopted in the process of reaction, so that the oxidation reaction speed can be accelerated, and the reaction time can be obviously shortened.

Description

Technical field [0001] The invention relates to a method for preparing nano cellulose and belongs to the technical field of nano materials. Background technique [0002] As a natural polymer nanomaterial, nanocellulose has the advantages of low price, easy availability, renewable, biocompatible, simple preparation, chemical or physical modification, etc. It is used in polymer composite reinforcement materials, template materials, biological It is widely used in molecular fixation and optical materials. [0003] The preparation method of nanocellulose is usually concentrated sulfuric acid hydrolysis. The concentrated acid separates nanocellulose with high purity and complete crystallinity by hydrolyzing the crystalline and amorphous regions of cellulose. Although this method is simple to operate and easy to control reaction conditions, it has problems such as complex post-treatment processes, high requirements for production equipment, and difficult handling of reaction acid. For ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C08B15/02
Inventor 王丹商士斌宋湛谦刘鹤宋杰
Owner INST OF CHEM IND OF FOREST PROD CHINESE ACAD OF FORESTRY
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