Carboxylation-modified nanocellulose crystal and preparation method thereof

Abstract

The invention discloses a carboxylation-modified nanocellulose crystal and a preparation method thereof. The preparation method comprises the following steps: adding acetic acid buffer solution to microcrystalline cellulose, preparing microcrystalline cellulose dispersion liquid after uniformly mixing, and adding TEMPO-sodium periodate-sodium hypochlorite-sodium chlorite polybasic oxidizing agent, stirring and reacting for 5-48 h in 25-35 DEG C under a dark condition, performing suction filtration, washing, enabling a product to be prepared as dispersion liquid of which a mass fraction is 0.1-4%, and processing for 1-10 times by using a micro-jet high-pressure homogenizer, obtaining the carboxylation-modified nanocellulose crystal. An oxidation system of the preparation method is capableof selectively oxidizing in allusion to different sites of the cellulose, and improving the oxidation efficiency of the natural cellulose with a high crystallinity degree. Surface carboxyl group content, a water retention value, a carboxyl substitution degree, and the crystallinity degree of the nanocellulose crystal are remarkably improved, and the process is stable, the operation is simple and convenient. A raw material is cheap in price and abundant, and pollution-free. The carboxylation-modified nanocellulose crystal can be popularized and produced in large scale, and has the good application prospect in the fields of papermaking, foods, cosmetics, electronic products, medicine and the like.

Description

technical field [0001] The invention relates to the field of biopolymer materials, in particular to a carboxylated modified nano-cellulose crystal and a preparation method thereof. Background technique [0002] With the severe shortage of resources and people's increasing emphasis on environmental protection, it is of great significance to effectively utilize cheap and abundant green renewable resources, and cellulose, as the most abundant biodegradable polymer material in nature, can be used to Spinning, film making, production of non-woven fabrics and various cellulose derivatives. By manipulating cellulose molecules in the nanoscale range, nanocellulose can be separated by physical, chemical or biological methods. Compared with natural cellulose and microcrystalline cellulose, nanocellulose crystals have many excellent properties, such as larger Specific surface area, high crystallinity, high hydrophilicity, high modulus, high strength, ultra-fine structure and high tran...

AI Technical Summary

Problems solved by technology

[0004] The traditional method of preparing nanocellulose crystals is acid hydrolysis, which requires the use of concentrated acid, and the purification of the product is cumbersome, which limits its industrial production

At present, relevant domestic researches include: Chinese patent CN102675475B discloses a preparation method of hemp fiber carboxylated cellulose nanocrystals, which uses TEMPO oxidation system for oxidation pretreatment, and then prepares cellulose nanocrystals through multi-step mechanical treatment. Complicated; Chinese patent CN105603020A discloses a method for preparing nanocellulose crystals. The method is to prepare nanocellulose crystals through multi-step mechanical treatment in the process of enzyme treatment. The operation is complicated, and nanocellulose lacks charge repulsion on the surface. , the dispersion is not stable enough; Chinese patent CN104448007A discloses a method for preparing nanocellulose, which uses formic acid to hydrolyze cellulose to prepare nanocellulose crystals, and the product purification process is relatively complicated

[0005] The mechanical treatment of nanocellulose fibers includes high-pressure homogenization, grinding, ultrasonic cell crushing, etc., but the high-pressure homogenizer is expensive and easy to block