CN109053906B

CN109053906B - Preparation method of nano cellulose fiber dry powder

Info

Publication number: CN109053906B
Application number: CN201811050809.XA
Authority: CN
Inventors: 邵自强; 周逸; 魏洁; 吕妍妍; 王飞俊; 王文俊; 王建全; 张大伦
Original assignee: Beijing North Century Cellulose Technology Research & Development Co ltd; Beijing Institute of Technology BIT
Current assignee: Beijing North Century Cellulose Technology Research & Development Co ltd; Beijing Institute of Technology BIT
Priority date: 2018-09-10
Filing date: 2018-09-10
Publication date: 2021-02-12
Anticipated expiration: 2038-09-10
Also published as: CN109053906A

Abstract

The present invention relates to a preparation method of nano-cellulose fiber dry powder. The mass fraction of the organic acid in the solution is 20-30%, the reaction solution is heated to 140-160 ° C, the cellulose raw material obtained in step 1) is added, kept warm and stirred; 3) After the cellulose raw material is fully destroyed and dispersed, the reaction system Carry out solid-liquid separation treatment to obtain reaction recovery liquid and solid powder. After the solid powder is washed with alcohol, it is dispersed into alcohol to obtain a solid powder dispersion liquid; 4) The solid powder dispersion liquid obtained in step 3) is subjected to homogenization treatment, Obtain the nanocellulose fiber dispersion; 5) evaporate the alcohol in the nanocellulose fiber dispersion in step 4) to obtain the nanocellulose fiber dry powder.

Description

Preparation method of nano cellulose fiber dry powder

Technical Field

The invention relates to the field of cellulose treatment, in particular to a preparation method of nano cellulose fiber dry powder.

Background

Cellulose is a macromolecular polysaccharide composed of glucose, is a polysaccharide which is widely distributed and contained in the largest quantity in the nature, is widely present in metabolites of plants and partial bacteria, and is a valuable natural renewable resource.

Crystalline regions with orderly arranged and stacked macromolecules and amorphous regions with disordered and stacked macromolecules exist in the microstructure of the cellulose fiber, wherein the physical and chemical properties of the crystalline regions are more stable. Thus, a smaller size of the cellulose material, i.e. nanocellulose material, is obtained by the disruption of the amorphous regions.

The cellulose material under the nanometer scale has special physical and chemical properties different from the cellulose material under larger size, and can be further applied to the fields of food, biomedicine, automobile manufacturing, aerospace, 3D printing, building, military special materials, electronic products, cosmetics, coatings, paints, papermaking, composite materials, polymer reinforcement and the like. Has huge application prospect and economic value, and more applications and mass production exploration aiming at the cellulose nano material are reported.

The method for manufacturing the cellulose nano-material mainly comprises the following steps: chemical methods, physical methods, biological methods, and the like. Specifically, the method comprises biological enzymolysis, ultrasonic method, homogenizing method, grinding method, ball milling method, acidolysis method, TEMPO oxidation method, etc. The common point of the methods is that the water consumption is large in the preparation process, the prepared product is aqueous dispersion of cellulose nano-materials, and the main defects of the product are as follows: the product is easy to be polluted by microorganism, has high requirement on storage temperature, is easy to generate phase change and settle after long-term storage, has high transportation cost, is limited in application conditions in water, has the property of colloid, and has the same defect of easy damage and stability of electrolyte as the colloid.

The existing nano cellulose material dry powder preparation technology or operation procedure is complex, or the dispersing agent uses ionic liquid and the like, so that the price is high, the requirement on reaction conditions is severe, the cost control after mass production is not facilitated, and the environmental hazard is large due to high toxicity of the used solvent. Therefore, how to simply, inexpensively and environmentally prepare nano-cellulose materials is a problem to be solved by those skilled in the art.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides the anhydrous preparation method which has low cost, strong reaction controllability, high yield of the cellulose nano material and dry powder-shaped products.

The technical scheme of the invention is as follows: the preparation method of the nano cellulose fiber dry powder is characterized by comprising the following steps:

1) taking cellulose, crushing and drying to obtain a cellulose raw material for later use;

2) mixing organic acid with alcohol to obtain reaction liquid, wherein the mass fraction of the organic acid in the reaction liquid is 20-30%, heating the reaction liquid to 140-;

3) after the cellulose raw material is fully destroyed and dispersed, carrying out solid-liquid separation treatment on the reaction system to obtain reaction recovery liquid and solid powder, and dispersing the solid powder into alcohol after the solid powder is washed by alcohol to obtain solid powder dispersion liquid;

4) homogenizing the solid powder dispersion liquid obtained in the step 3) to obtain a nano cellulose fiber dispersion liquid;

5) and (4) evaporating the alcohol in the nano cellulose fiber dispersion liquid in the step 4) to obtain the nano cellulose fiber dry powder.

The cellulose in the step 1) is selected from plant pulp rich in cellulose, preferably wood pulp or bamboo pulp, and is crushed to 200 meshes; or, the cellulose raw material in the step 1) is purified cotton, and the viscosity of the purified cotton is not higher than 40mPa & s.

In the step 2), the organic acid is monobasic or polybasic anhydrous micromolecule acid with thermal decomposition temperature not lower than 160 ℃ and good alcohol dissolubility, and the organic acid is citric acid, oxalic acid, malonic acid, succinic acid, maleic acid, benzenesulfonic acid, chloroacetic acid or a mixture of one or more of the acids.

The alcohol in the step 2) is monohydric or polyhydric small molecule alcohol with the boiling point higher than 160 ℃, and the alcohol is ethylene glycol, propylene glycol, butanediol, n-octanol, pentanediol or a mixture of one or more of the alcohols.

In the step 2), the ratio of the mass of the added cellulose raw material to the volume of the reaction solution is 1 g: 80-150 mL.

And 2) keeping condensation and reflux in the heating and heat preservation processes.

And (3) recycling the washing alcohol in the step 3), wherein the washing alcohol and the dispersing alcohol are small molecular alcohols which do not form colloidal dispersion with the cellulose material, can disperse the cellulose material and have a boiling point lower than 100 ℃, preferably, the washing alcohol and the dispersing alcohol are ethanol and are dispersed into the alcohol, and the mass-to-volume ratio of the dispersed solid powder to the alcohol is 1 g: 450 and 1000 mL.

And 3) cooling the reaction system to room temperature in the step 3), and then carrying out solid-liquid separation treatment.

The homogenization treatment in the step 4) is to treat the solid powder dispersion liquid by a high-pressure homogenizer, wherein the treatment pressure of the high-pressure homogenizer is 20000-.

The invention also provides the nano-cellulose dry powder prepared by the preparation method, the diameter of the nano-cellulose dry powder is less than or equal to 100nm, the length of the nano-cellulose dry powder is more than or equal to 200nm, and the redispersion rate in pure water is 15-25%.

Adopt above-mentioned technical scheme to have following beneficial effect:

1. the method for preparing the nano cellulose fiber dry powder has the advantages that the whole preparation process has no water and centrifugal treatment operation, the industrial large-scale production is facilitated, the parameter control of each step of the preparation method is simple and mild, the yield of the nano cellulose fiber dry powder is not lower than 80 percent (depending on the type of raw materials), and the redispersion rate of the obtained dry powder in water is 15-25 percent. The prepared nano cellulose fiber dry powder has stable size distribution and good repeatability, is easier to store and transport than aqueous dispersion prepared by the traditional method, widens the practical application range of the nano cellulose fiber, is not limited to a water phase system any more, and enriches the types of products which can be prepared. Can be used as chelating agent, coupling agent, shape-keeping agent, reinforcing agent, solubilizer, thickening agent, excipient and the like in the fields of biological medicine, paper making, 3D printing, food and life science, and has huge application potential.

2. No matter the nanocellulose fiber aqueous dispersion prepared by the traditional method is subjected to evaporation, freeze drying, supercritical drying, atomization drying and other methods, the agglomeration or film formation of the nanocellulose fibers cannot be avoided, and the characteristics and functions of the nanomaterials are lost. The drying process of the nano cellulose fiber dispersion liquid is simple and rapid, dry powder of the nano cellulose fiber can be obtained only by evaporating the alcohol dispersion liquid, and the coalescence and film formation of the nano cellulose fiber are effectively avoided.

3. The cellulose raw material is treated by the reaction liquid at the temperature of 140-. If the temperature of the reaction liquid is lower than 140 ℃, the alcoholysis reaction can not be normally carried out, the damage degree of the cellulose raw material is insufficient, the size is overlarge, and the pipelines of equipment are blocked during high-pressure homogenization treatment; if the temperature of the reaction solution is higher than 160 ℃, the thermal decomposition of the alcohol or acid will cause the reaction to proceed unsuccessfully, or the alcoholysis reaction will be too severe to reduce the yield of the final product. After being washed and dispersed, the solid powder can pass through a high-pressure homogenizer smoothly when being homogenized, and the nano cellulose fiber with high purity and stable size distribution is obtained.

4. According to the preparation method, the reaction liquid (alcohol and organic acid), the washing liquid (alcohol) and the evaporated alcohol can be recycled by using a conventional means, and the heat capacity of the reaction liquid (alcohol and organic acid) system is obviously reduced compared with that of water, so that the energy consumption during heating is reduced, and the cost for producing the nano cellulose fiber dry powder can be greatly reduced.

The following further description is made with reference to the accompanying drawings and detailed description.

Drawings

FIG. 1 is a scanning electron micrograph of cellulose used in examples 1 to 3 of the present invention;

FIG. 2 is a transmission electron microscope image of the nano cellulose fiber dry powder prepared in example 3 of the present invention;

fig. 3 is a picture of the nano cellulose fiber dry powder prepared in examples 1 to 4 of the present invention.

Detailed Description

Examples 1-8 preparation parameters are shown in Table 1

Table 1 examples 1-8 preparation parameters

Examples 1-8 were prepared according to the following preparation:

1) taking cellulose/cellulose raw materials (wood pulp powder, M30 refined cotton, bamboo pulp, straw pulp, reed pulp and filter paper), wherein a scanning electron microscope image of the wood pulp powder is shown in figure 1, the cellulose is seen to be a large fibrous structure, and as a comparison image, the wood pulp powder, the bamboo pulp, the straw pulp, the reed pulp and the filter paper are crushed, sieved by a 200-mesh sieve and dried to obtain the cellulose raw materials for later use;

2) dissolving organic acid (citric acid, oxalic acid, malonic acid and maleic acid) in alcohol (ethylene glycol, propylene glycol, pentanediol and n-octanol), preparing reaction liquid with the volume corresponding to the volume in table 1, wherein the mass fraction of the organic acid in the reaction liquid is shown in table 1, heating the temperature of the reaction liquid to the parameters in table 1 under the stirring condition, weighing 1g of cellulose raw material, adding the cellulose raw material into the reaction liquid, and keeping the temperature and the stirring state for reaction time which is shown in table 1 until the cellulose raw material is completely dispersed;

3) and after the cellulose raw material is completely dispersed, cooling the reaction system to room temperature, and performing solid-liquid separation treatment through suction filtration to obtain reaction recovery liquid and solid powder, wherein the reaction recovery liquid can be recycled, the reuse times are not more than 6, after the reuse times are more than 6, the reaction recovery liquid needs to be neutralized, distilled and purified and then continuously used, and the distillation temperature is selected according to the boiling point of the used alcohol. Washing the solid powder with ethanol, and dispersing into ethanol until the mass fraction of the solid powder is 0.2% to obtain a solid powder dispersion liquid;

4) treating the solid powder dispersion liquid obtained in the step 3) by a high-pressure homogenizer, wherein the homogenization pressure is 30000 or 40000psi, and the treatment flow rate is 30mL/min, so as to obtain a nanofiber dispersion liquid;

5) and (3) evaporating the ethanol in the nanofiber dispersion liquid in the step 4) to obtain the nanocellulose fiber dry powder, wherein a photograph is shown in figure 3, and a transmission electron microscope image of the nanocellulose fiber dry powder is shown in figure 2, so that the nanocellulose fiber is clearly seen to have the diameter within 100nm and the length of not less than 300 nm.

The redispersion rate of the nano cellulose fiber dry powder obtained by the preparation method in pure water is 15-25%, the cellulose-containing material is used as the raw material, the nano cellulose fiber dry powder can be prepared with high yield, the whole preparation process is anhydrous, the organic acid and alcohol used in the preparation process can be recycled, the dry powder product is easy to store and transport, and simultaneously, a good basis is provided for low-cost mass production and application in the later period of the product.

Claims

1. a preparation method of nano-cellulose fiber dry powder, is characterized in that, has the following steps:

1) Take cellulose, pulverize and dry to obtain cellulose raw materials, which are ready for use;

2) get organic acid and mix with alcohol, obtain reaction solution, described organic acid is any in citric acid, oxalic acid, malonic acid, succinic acid, maleic acid, benzenesulfonic acid, chloroacetic acid or several mixtures, the alcohol is any one or several mixtures of ethylene glycol, propylene glycol, butanediol, n-octanol, and pentanediol, and the mass fraction of the organic acid in the reaction solution is 20-30%, The reaction solution is heated to 140-160°C, the cellulose raw material obtained in step 1) is added, the mass ratio of the cellulose raw material to the volume ratio of the reaction solution is 1 g: 80-150 mL, and the temperature is maintained and stirred;

3) After the cellulose raw material is fully destroyed and dispersed, the reaction system is subjected to solid-liquid separation treatment to obtain a reaction recovery liquid and solid powder, and the solid powder is washed with alcohol and dispersed into alcohol to obtain a solid powder dispersion;

4) Homogenizing the solid powder dispersion obtained in step 3) to obtain a nanocellulose fiber dispersion;

5) Evaporate to dryness step 4) the alcohol in the nanocellulose fiber dispersion to obtain nanocellulose fiber dry powder.

2 . The method for preparing nanocellulose fiber dry powder according to claim 1 , wherein the cellulose in step 1) is selected from cellulose-rich plant pulp. 3 .

3. The preparation method of nanocellulose fiber dry powder according to claim 2, characterized in that: the plant pulp is selected from wood pulp or bamboo pulp, and pulverized to 200 meshes.

4 . The method for preparing nanocellulose fiber dry powder according to claim 1 , wherein the cellulose raw material in step 1) is refined cotton, and the viscosity of the refined cotton is not higher than 40 mPa·s. 5 .

5 . The preparation method of nanocellulose fiber dry powder according to claim 1 , characterized in that: in step 2), during the heating and heat preservation process, condensation and reflux are maintained. 6 .

6. The preparation method of nanocellulose fiber dry powder according to claim 1, characterized in that: in step 3), the alcohol for washing is recycled, and the alcohol for washing and the alcohol for dispersing are not to form a colloidal dispersion with the cellulose material , Can disperse cellulosic materials and the boiling point is lower than 100 ℃ of small molecular alcohols.

7. the preparation method of nanocellulose fiber dry powder according to claim 6, is characterized in that: alcohol for washing, alcohol for dispersing are ethanol, be dispersed in alcohol, and the mass ratio of dispersed solid powder to alcohol volume is 1g: 450 -1000mL.

8 . The preparation method of nanocellulose fiber dry powder according to claim 1 , wherein the reaction system in step 3) is cooled to room temperature and then subjected to solid-liquid separation treatment. 9 .

9. The preparation method of nanocellulose fiber dry powder according to claim 1, wherein the homogenization treatment in step 4) is to process the solid powder dispersion through a high-pressure homogenizer, and the high-pressure homogenizer The processing pressure is 20000-45000psi, and the homogenization processing speed is 30mL/min.

10. A nanocellulose dry powder, characterized in that, prepared by the preparation method according to any one of claims 1-9, the diameter of the nanocellulose dry powder≤100nm, the length≥200nm, the regrind in pure water. The dispersion rate is 15-25%.