Method for preparing cellulose nanofiber capable of being stably dispersed

Abstract

A method for preparing stably dispersed cellulose nanofibers comprises the following steps: 1) mixing cellulose and an organic solvent, the percentage of the cellulose being 1% to 15% in weight; 2) adding an esterification agent into the resultant mixture of step 1), the molar ratio of the esterification agent to the cellulose being from 1:0.1 to 4; and 3) physically breaking the resultant mixture of step 2) until a suspension liquid with stably dispersed cellulose nanofibers of 2-1000 nm in diameter and 10-100 μm in length is obtained, an esterification reaction of hydroxyl group(s) on the surface of cellulose fibers occurring at the time of the breaking. Also disclosed are dispersed cellulose nanofibers with improved compatibility to the matrix than the untreated cellulose and an improved strength of the composite materials.

Claims

1. A method for preparing stably dispersed cellulose nanofibers, comprising the following steps: 1) mixing a cellulose with an organic solvent, the percentage of the cellulose being 1%-15% in weight; 2) adding an esterification agent into the resultant mixture of step 1), wherein the molar ratio of the esterification agent to the cellulose is 1:0.1 to 4; and 3) physically breaking the resultant mixture of step 2) until a suspension liquid with stably dispersed cellulose nanofibers of 2-1000 nm in diameter and 10-100 μm in length is obtained, wherein an esterification reaction of hydroxyl group(s) on the surface of cellulose fibers occurs during the breaking step, wherein the organic solvent contains no hydroxyl group, wherein the organic solvent is selected from the group consisting of acetone, methanamide, ethanamide, N,N-dimethylformamide, N,N-dimethylacetamide, phenylamine, tetrahydrofuran, diethyl ether, benzene, methylbenzene, dimethylbenzene, chlorobenzene, hexane, dimethyl sulfoxide, dioxane, ethyl acetate, ethanoic acid, ethanenitrile, pyridine, methacrylic acid, and trichloromethane, and wherein the esterification agent is selected from the group consisting of acetyl chloride, butyryl chloride, hexanoyl chloride, and lauroyl chloride.

2. The method of claim 1, further comprising a step of washing the resultant suspension liquid of step 3) by centrifugation to obtain a suspension liquid with cellulose nanofibers dispersed in the organic solvent.

3. The method of claim 1, wherein the cellulose is a natural plant cellulose.

4. The method of claim 3, wherein the natural plant cellulose is natural herbaceous cellulose or natural wood cellulose.

5. The method of claim 3, wherein the natural plant cellulose is one or more regenerated cellulose from natural herbaceous plants or natural woody plants.

6. The method of claim 1, wherein the physical breaking is implemented by a ball mill, a disc mill, a high pressure homogenizer, a sonicator or a mortar grinder.

Description

DESCRIPTION OF THE DRAWINGS

(1) The present invention will be further explained with reference to the drawings.

(2) FIG. 1 shows a flow-birefringent organic suspension of product of example 1 viewed through crossed polarizers.

(3) FIG. 2 shows a TEM image of example 1.

(4) FIG. 3 shows a TEM image of drying and re-dispersion of example 1.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

(5) A method for preparing stably dispersed cellulose nanofibers, comprising following steps: 1) mixing natural wood cellulose with N,N-dimethylformamide, the percentage of the cellulose is 1% in weight; 2) adding acetyl chloride into the resultant mixture of step 1), the molar ratio of acetyl chloride to cellulose is 1:0.1; 3) physically breaking the resultant mixture of step 2) by a disc mill until a suspension liquid with stably dispersed cellulose nanofibers of 2-1000 nm in diameter and 10-100 μm in length is obtained, an esterification reaction of hydroxyl group(s) on the surface of cellulose fibers is occurring at the meantime of the disc milling; 4) washing the resultant suspension liquid of step 3) by centrifugation to obtain a suspension liquid with cellulose nanofibers dispersed in N,N-dimethylformamide.

(6) A flow-birefringent phenomenon is observed in the obtained cellulose nanofibers suspension through crossed polarizers.

(7) In a comparative example to Example 1, the above steps are repeated without any esterification agent added, the resultant cellulose will precipitate quickly because of insufficient dispersion.

Example 2

(8) A method for preparing stably dispersed cellulose nanofibers, comprising following steps: 1) mixing natural wood cellulose with N,N-dimethylacetamide, the percentage of the cellulose is 7% in weight; 2) adding acetic anhydride into the resultant mixture of step 1), the molar ratio of acetic anhydride to cellulose is 1:1; 3) physically breaking the resultant mixture of step 2) by a ball mill until a suspension liquid with stably dispersed cellulose nanofibers of 2-1000 nm in diameter and 10-100 μm in length is obtained, an esterification reaction of hydroxyl group(s) on the surface of cellulose fibers is occurring at the meantime of the ball milling; 4) washing the resultant suspension liquid of step 3) by centrifugation to obtain a suspension liquid with cellulose nanofibers dispersed in N,N-dimethylacetamide.

(9) A flow-birefringent phenomenon is observed in the obtained cellulose nanofibers suspension through crossed polarizers.

(10) In a comparative example to Example 2, the above steps are repeated without any esterification agent added, the resultant cellulose will precipitate quickly because of insufficient dispersion.

Example 3

(11) A method for preparing stably dispersed cellulose nanofibers, comprising the following steps: 1) mixing natural herbaceous cellulose with tetrahydrofuran, the percentage of the cellulose is 10% in weight; 2) adding butyryl chloride into the resultant mixture of step 1), the molar ratio of butyryl chloride to cellulose is 1:2; 3) physically breaking the resultant mixture of step 2) by a high pressure homogenizer until a suspension liquid with stably dispersed cellulose nanofibers of 2-1000 nm in diameter and 10-100 μm in length is obtained, an esterification reaction of hydroxyl group(s) on the surface of cellulose fibers is occurring at the meantime of the physically breaking; 4) washing the resultant suspension liquid of step 3) by centrifugation to obtain a suspension liquid with cellulose nanofibers dispersed in tetrahydrofuran.

(12) A flow-birefringent phenomenon is observed in the obtained cellulose nanofibers suspension through crossed polarizers.

(13) In a comparative example to Example 3, the above steps are repeated without any esterification agent added, the resultant cellulose will precipitate quickly because of insufficient dispersion.

Example 4

(14) A method for preparing stably dispersed cellulose nanofibers, comprising the following steps: 1) mixing natural wood cellulose with trichloromethane, the percentage of the cellulose is 13% in weight; 2) adding succinic anhydride into the resultant mixture of step 1), and the molar ratio of succinic anhydride to cellulose is 1:3; 3) physically breaking the resultant mixture of step 2) by a sonicator until a suspension liquid with stably dispersed cellulose nanofibers of 2-1000 nm in diameter and 10-100 μm in length is obtained, an esterification reaction of hydroxyl group(s) on the surface of cellulose fibers is occurring at the meantime of the physical breaking; 4) washing the resultant suspension liquid of step 3) by centrifugation to obtain a suspension liquid with cellulose nanofibers dispersed in trichloromethane.

(15) A flow-birefringent phenomenon is observed in the obtained cellulose nanofibers suspension through crossed polarizers.

(16) In a comparative example to Example 4, the above steps are repeated without any esterification agent added, the resultant cellulose will precipitate quickly because of insufficient dispersion.

Example 5

(17) A method for preparing stably dispersed cellulose nanofibers, comprising the following steps: 1) mixing natural herbaceous cellulose with methanamide, the percentage of the cellulose is 15% in weight; 2) adding hexanoyl chloride into the resultant mixture of step 1), the molar ratio of hexanoyl chloride to cellulose is 1:4; 3) physically breaking the resultant mixture of step 2) with a mortar grinder until a suspension liquid with stably dispersed cellulose nanofibers of 2-1000 nm in diameter and 10-100 μm in length is obtained, an esterification reaction of hydroxyl group(s) on the surface of cellulose fibers is occurring at the meantime of the physical breaking; 4) washing the resultant suspension liquid of step 3) by centrifugation to obtain a suspension liquid with cellulose nanofibers dispersed in methanamide.

(18) A flow-birefringent phenomenon is observed in the obtained cellulose nanofibers suspension through crossed polarizers.

(19) In a comparative example to Example 5, the above steps are repeated without any esterification agent added, the resultant cellulose will precipitate quickly because of insufficient dispersion.

Example 6

(20) Example 1 is repeated. Differences from Example 1 are that the organic solvent is dimethyl sulfoxide and the esterification agent is lauroyl chloride.

Example 7

(21) Example 2 is repeated. Differences from Example 2 are that the organic solvent is dioxane and the esterification agent is maleic anhydride.

Example 8

(22) Example 3 is repeated. Differences from Example 3 are that the organic solvent is ethyl acetate and the esterification agent is acetyl chloride.

Example 9

(23) Example 4 is repeated. Differences from Example 4 are that the organic solvent is ethanoic acid and the esterification agent is acetyl chloride.

Example 10

(24) Example 5 is repeated. Differences from Example 5 are that the organic solvent is acetone and the esterification agent is acetyl chloride.

Example 11

(25) Example 1 is repeated. Differences from Example 1 are that the organic solvent is ethanenitrile and the esterification agent is butyryl chloride.

Example 12

(26) Example 2 is repeated. Differences from Example 2 are that the organic solvent is pyridine and the esterification agent is lauroyl chloride.

Example 13

(27) Example 3 is repeated. Differences from Example 3 are that the organic solvent is methacrylic acid and the esterification agent is maleic anhydride.

Example 14

(28) Example 1 is repeated. Differences from Example 1 are that the organic solvent is ethanamide and the esterification agent is butyryl chloride.

Example 15

(29) Example 2 is repeated. Differences from Example 2 are that: the organic solvent is diethyl ether and the esterification agent is lauroyl chloride.

Example 16

(30) Example 3 is repeated. Differences from Example 3 are that the organic solvent is benzene and the esterification agent is maleic anhydride.

Example 17

(31) Example 1 is repeated. Differences from Example 1 are that the organic solvent is methylbenzene and the esterification agent is acetic anhydride.

Example 18

(32) Example 2 is repeated. Difference from Example 2 is that the organic solvent is dimethylbenzene.

Example 19

(33) Example 3 is repeated. Difference from Example 3 is that the organic solvent is chlorobenzene.

Example 20

(34) Example 1 is repeated. Difference from Example 1 is that the organic solvent is hexane.

Example 21

(35) Example 2 is repeated. Differences from Example 2 is that the organic solvent is phenylamine.

(36) It is apparently that the above examples of the present invention are only for illustration of the present invention without any limitation to the embodiments of the present invention. Various modifications or variations can be made for a skilled person in the art based on the above description. It is impossible to list all the embodiments here. Any obvious modification or variation derived from the embodiments of the present invention is still within the scope of the present invention.