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Method for preparation of cellulose nanocrystals and nanofibrils

a technology of nanofibrils and nanocrystals, which is applied in the field of preparation of cellulose nanocrystals and nanofibrils, can solve the problems of large amount of acidic waste, high cost, and general harsh conditions of hydrolysis methods

Inactive Publication Date: 2017-04-13
UNIV OF MASSACHUSETTS
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Benefits of technology

The patent describes methods for producing nanocellulose by oxidizing cellulosic materials using various compounds, such as alkali metal bromide, iodide, fluoride, chloride, or a combination thereof, and a nitroxyl radical compound. The resulting oxidized cellulose mixture contains nanocrystals with an average diameter of 1 to 10 nanometers and an average length of 50 to 500 nanometers. The technical effect of this patent text is the improved production of nanocellulose with enhanced efficiency and stability.

Problems solved by technology

The acid hydrolysis methods generally require harsh conditions and involve a substantial amount of concentrated acid.
Strong acid can corrode production equipment and post-processing brings about a large amount of acidic waste, which is not environmentally friendly.
Furthermore, methods utilizing harsh acids are hydrolytic, resulting in decreased yields and decreased fibril length.
Most of the reported nanofibrillated cellulose suffers from irreversible agglomeration, namely, hornification, and therefore it cannot be redispersed in water after drying.

Method used

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  • Method for preparation of cellulose nanocrystals and nanofibrils
  • Method for preparation of cellulose nanocrystals and nanofibrils
  • Method for preparation of cellulose nanocrystals and nanofibrils

Examples

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example 1

[0047]Preparation of Oxidized Cellulose Nanofibrils Without TEMPO

[0048]A solution of mechanically treated cellulose pulp (37.5 grams, 2.67% solid content) was dispersed in water (62.5 milliliters) containing sodium bromide (0.1 grams). A solution of sodium hypochlorite (2.1 grams, active chlorine 10-15%) was added to the suspension. Sodium hydroxide (5.5 grams, 0.5 M in water) was introduced to the mixture to adjust pH to about 12. The reaction mixture was stirred for 20 hours at room temperature, then centrifuged at 4000 rpm for 15 minutes. The supernatant was discarded, and the precipitate was redispersed in water and centrifuged to remove the remaining reagents. The redispersion and centrifugation was repeated three times until the pH of supernatant is close to DI water (about 6). After centrifuging, the precipitate was isolated, dispersed in 80 milliliters of water, and sonicated for 50 minutes to disintegrate the nanocellulose into single nanofibrils. The nanofibril solution wa...

example 2

[0050]Preparation of Oxidized Nanocellulose With TEMPO

[0051]A solution of mechanically treated cellulose pulp (37.5 grams, 2.67% solid content) was dispersed in water (62.5 milliliters) containing sodium bromide (0.1 grams) and 2,2,6,6-tetramethyl-1-piperidine-N-oxy (TEMPO, 0.016 grams). A solution of sodium hypochlorite (2.1 grams, active chlorine 10-15%) was added to the suspension. Sodium hydroxide (5.5 grams, 0.5 M in water) was introduced to the mixture to adjust pH to 12. The reaction mixture was stirred for 20 hours at room temperature, then centrifuged at 4000 rpm for 15 minutes.

[0052]A cellulose nanocrystal colloidal solution was isolated as the transparent supernatant following centrifugation. The colloidal solution was precipitated in acetone and washed with ethanol or methanol three times to remove residual salts and TEMPO. The precipitated cellulose nanocrystals were dried at room temperature under vacuum for 24 hours. The cellulose nanocrystals were observed to have a ...

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Abstract

A method for producing nanocellulose is described herein. The method includes contacting a cellulosic material with an oxidizing agent, and a compound selected from the group consisting of an alkali metal bromide, an alkali metal iodide, an alkali metal fluoride, an alkali metal chloride, or a combination thereof, in an aqueous solution to provide an oxidized cellulose mixture. The nanocellulose prepared according to the method is also described.

Description

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH & DEVELOPMENT[0001]This invention was made with government support under the Materials Research Science and Engineering Center on Polymers (DMR-0820506) awarded by the National Science Foundation, and under CMMI-1025020 awarded by the University of Massachusetts Center for Hierarchical Manufacturing (CHM). The government has certain rights in the invention.BACKGROUND OF THE INVENTION[0002]Derived from cellulose, one of the most abundant natural products on the planet, nanocellulose, including cellulose nanocrystals (NC or nanowhiskers) and cellulose nanofibrils (CNF), has a great number of interesting properties. Besides renewability and biodegradability, nanocellulose has low density, high elastic modulus, low thermal expansion coefficient, and good barrier properties. Potential applications of nanocellulose include but are not limited to packaging coatings, paper fillers, absorbent products, drug delivery, flexible displays, pharmac...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): D21H11/18D21C3/00D21C5/00D21C3/02
CPCD21H11/18D21C5/00D21C3/003D21C3/02C08B15/04C08L1/04D21C3/16D21C3/18D21C9/002D21C9/007
Inventor CARTER, KENNETH RAYMONDLI, YINYONG
Owner UNIV OF MASSACHUSETTS
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