WO2019105287A1

WO2019105287A1 - Nanocellulose, preparation method therefor and use thereof

Info

Publication number: WO2019105287A1
Application number: PCT/CN2018/117072
Authority: WO
Inventors: 张金柱; 王鹏辉; 张安; 刘顶
Original assignee: 济南圣泉集团股份有限公司
Priority date: 2017-12-01
Filing date: 2018-11-23
Publication date: 2019-06-06
Also published as: CN109867728A

Abstract

The present invention relates to a method for preparing nanocellulose, wherein the method comprises: (1) adding a cellulose raw material to a molten solution of an anhydride compound, increasing the temperature to the melting point or higher, performing a pretreatment reaction, and filtering same after the reaction is finished to obtain a pretreated cellulose raw material; (2) dispersing the pretreated cellulose raw material in water to obtain a dispersion; and (3) mechanically pulverizing the dispersion to obtain a nanocellulose dispersion. In the present invention, by contacting the cellulose raw material with the molten solution of the anhydride, anhydride molecules enter between elementary unit fibers, and the nanocellulose is obtained by peeling same off under the action of a mechanical force, and no other organic solvent, except the anhydride, is added during the treatment process, the amount of environmental pollution is small, the process method is simple, the energy consumption is low, and the cost is low. In the present invention, the nanocellulose prepared by treating the cellulose raw material with an anhydride is rich in carboxyl groups on the surface thereof, and same also has a good water dispersibility and storage stability.

Description

Nano cellulose and preparation method and use thereof

Technical field

The present disclosure is in the field of nanomaterial preparation, such as a nanocellulose and its preparation and use.

Background technique

Nanocellulose is a cellulose crystal which is at least one dimension at the nanometer scale (1 to 100 nm) and can be dispersed in water to form a stable suspension, and nanocellulose having different properties may be obtained due to different preparation methods. Nanocellulose has the basic structure and properties of natural cellulose, such as sustainable regenerability, biodegradability, etc., and also has some characteristics of nanoparticles, such as large chemical reactivity, high degree of polymerization, high crystallinity, and high Purity and high transparency make it suitable for a wide range of applications. However, there are also shortcomings: the large number of hydroxyl groups on the surface of nanocellulose determines that it is not well dissolved in weak polar solvents and polymer media; 2 nanocellulose has a large specific surface area, high thermodynamic potential, crystal It is easy to agglomerate, etc., so it is necessary to modify the nanocellulose to further broaden its application fields.

CN102443067A discloses a method for carbonylation of modified nanocellulose, which overcomes the problem that nanocellulose is easily agglomerated due to hydrogen bonding, but the modifier thionyl chloride used in the preparation process is a toxic reagent, which is harmful to human body and environment. Effect; CN104877033A discloses a preparation method of carboxymethyl modified nanocellulose, which effectively improves the performance of nanocellulose, but the preparation process requires multiple alkalization treatments, complicated operation, and chlorine used in the etherification reaction. Ethanol is a toxic reagent that can cause certain damage to the human body during use.

In the prior art, nanocellulose is prepared by first pretreating a cellulose raw material with an acid, a base or an organic solvent, then adding a modifier to modify the cellulose, and finally mechanically treating the cellulose to obtain a modified cellulose. Nanocellulose. A large amount of inorganic acid, alkali or organic solvent is used in the pretreatment process to pollute the environment, and the operation steps are complicated and time consuming.

There is a need in the art to develop a method for preparing nanocellulose, which has a small amount of chemical reagent, simple operation, low cost, low environmental pollution, and good dispersibility.

Summary of the invention

The following is a summary of the subject matter described in detail in this disclosure. This Summary is not intended to limit the scope of the claims.

One of the objects of the present disclosure is to provide a method for preparing nanocellulose, which comprises:

(1) adding a cellulose raw material to a melt of an acid anhydride compound, raising the temperature to a melting point or higher, performing a pretreatment reaction, and filtering after completion of the reaction to obtain a pretreated cellulose raw material;

(2) dispersing the pretreated cellulose raw material into water to obtain a dispersion;

(3) The dispersion was mechanically pulverized to obtain a nanocellulose dispersion.

Cellulose is formed by elemental unit fibers being bonded step by step by self hydrogen bonding, lignin or the like, and the element unit fibers are aggregated by several tens of cellulose molecules, and a diameter of about 5 nm is formed, and the length is Fine fiber filaments of micron order and alternately arranged of crystalline and amorphous regions. The present disclosure mixes the cellulose raw material with the molten state of the acid anhydride, the acid anhydride enters between the unit cell fibers, is grafted onto the surface of the unit cell, weakens the bonding between the cell elements, and then cooperates with mechanical force, mechanical The unit cell fibers are peeled off to obtain nanocellulose fibers. The acid anhydride can enter between the unit cell fibers without breaking into the amorphous region like the concentrated acid solution, entering the interior of the cell unit fiber, and not lowering the grafting rate of cellulose to the cellulose as the acidity of the dilute acid solution is too low. , nanocellulose is not available.

Preferably, the nanocellulose has a diameter of 4 to 50 nm (for example, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, etc.) and an aspect ratio of 50 to 300 (for example, 100, 150, 200, 250, etc.).

The diameter of the nanocellulose defined by the present disclosure is the D90 diameter of the nanocellulose, i.e., the particle size of 90% of the nanocellulose is below the D90 diameter.

The aspect ratio defined by the present disclosure is the average of the aspect ratio of the nanocellulose.

Preferably, the concentration of the nanocellulose dispersion is 2 to 7 wt% (e.g., 3 wt%, 4 wt%, 5 wt%, 6 wt%, etc.).

Preferably, the acid anhydride compound is an acid anhydride compound having a melting point of 120 ° C or lower, and preferably includes any one or a combination of at least two of acetic anhydride, dodecenyl succinic anhydride, maleic anhydride or succinic anhydride, and further preferably maleic anhydride.

An acid anhydride compound having a melting point of less than 120 ° C has a lower melting energy consumption and can better retain the structure of cellulose at a melting temperature.

Preferably, the cellulose raw material comprises any one or a combination of at least two of wood pulp, grass pulp, cotton pulp, bamboo pulp, mash pulp, hemp pulp, bagasse pulp, and crop straw pulp.

Preferably, the mass ratio of the cellulose raw material to the acid anhydride compound is 1:3 to 1:10 (for example, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, etc.), It is preferably 1:6 to 1:8.

Preferably, the temperature of the pretreatment reaction is 80 to 100 ° C (for example, 85 ° C, 90 ° C, 95 ° C, etc.), and the time is 1 to 4 h (for example, 2 h, 3 h, etc.).

Preferably, the filtering comprises atmospheric filtration or reduced pressure filtration.

Preferably, in step (1), after filtration, the filter residue is washed.

Preferably, the washing comprises a water wash, a dilute lye wash.

Preferably, the mechanical pulverization of the step (3) includes any one or a combination of at least two of ball milling, disc grinding, sanding, high pressure homogenizer, ultrasonic crusher and mortar pulverization;

Preferably, the condition of the mechanical comminution is homogenization by a high pressure homogenizer.

As a preferred technical solution, the present disclosure performs the step (4) after the step (3) to post-treat the nanocellulose dispersion to obtain a nanocellulose powder.

The purpose of the post-treatment is to remove the solvent of the nanocellulose dispersion to obtain a nanocellulose powder.

Preferably, the post treatment comprises any one or a combination of at least two of washing, grinding, and spray drying.

A second object of the present disclosure is to provide a nanocellulose which is prepared by the preparation method described in one of the objects.

Preferably, the nanocellulose has a diameter of 4 to 50 nm and an aspect ratio of 100 to 300.

In the preparation of the nanocellulose provided by the present disclosure, the cellulose is treated by an acid anhydride such that the surface of the nanocellulose obtained by the peeling is rich in a carboxyl group.

The third object of the present disclosure is to provide a nanocellulose according to the second object, which is characterized in that the nanocellulose is used in the textile field, the pharmaceutical field, the high performance auxiliary field, the adsorption material field, and the food packaging. Fields, composite materials.

Compared with the prior art, the present disclosure has the following beneficial effects:

(1) The present disclosure separates the cellulose raw material from the anhydride melt to cause the acid anhydride molecules to enter between the unit cell fibers, and peels off to obtain nanocellulose under the action of mechanical force, and the process does not add any other organic solvent except the acid anhydride. , low environmental pollution, simple process, low energy consumption and low cost;

(2) The nanocellulose surface prepared by treating the cellulose raw material with an acid anhydride in the present disclosure is rich in a carboxyl group, which has good water dispersibility and storage stability.

Detailed ways

The technical solutions of the present disclosure will be further described below by way of specific embodiments.

It should be understood by those skilled in the art that the present invention is not to be construed as limited.

Example 1

A nanocellulose, the preparation method comprises the following steps:

(1) Weigh 80g of maleic anhydride and heat it to 52 °C to melt, add 10g of wood pulp powder to the maleic anhydride melt, heat to 90 °C and stir the reaction for 4h, carry out pretreatment reaction, complete the reaction, filter, filter residue is pre Treated cellulosic feedstock;

(2) dispersing the pretreated cellulose raw material in water to obtain a dispersion;

(3) High-pressure homogenizer The dispersion was subjected to high-pressure pulverization to obtain a nanocellulose dispersion having a concentration of 5 wt%, a nanocellulose D90 having a diameter of 4 to 10 nm, and an aspect ratio of 300.

Examples 2-7

The difference from Example 1 is that the amount of maleic anhydride added in step (1) is 30 g (Example 2), 50 g (Example 3), 60 g (Example 4), 100 g (Example 5), 20 g (implementation) Examples 6), 12g (Example 7) and the like.

Example 8

A nanocellulose, the preparation method comprises the following steps:

(1) Weigh 70g of acetic anhydride (liquid), add 10g of cotton pulp to the acetic anhydride melt, heat to 80 °C, stir the reaction for 4h, carry out pretreatment reaction, complete the reaction, filter, filter residue as pretreated cellulose raw material ;

(3) High-pressure homogenizer The dispersion was subjected to high-pressure pulverization to obtain a nanocellulose dispersion having a concentration of 5 wt%, a nanocellulose D90 having a diameter of 4 to 10 nm, and an aspect ratio of 260.

Example 9

A nanocellulose, the preparation method comprises the following steps:

(1) Weighing 70 g of dodecenyl succinic anhydride and heating to 43 ° C to melt, adding 10 g of wood pulp to the dodecenyl succinic anhydride melt, heating to 90 ° C, stirring at room temperature for 4 h, pretreatment reaction, the reaction is completed, Filtration, the filter residue is a pretreated cellulose raw material;

(3) High-pressure homogenizer The dispersion was subjected to high-pressure pulverization to obtain a nanocellulose dispersion having a concentration of 5 wt%, a nanocellulose D90 having a diameter of 6 to 12 nm, and an aspect ratio of 200.

Example 10

A nanocellulose, the preparation method comprises the following steps:

(1) Weigh 40g succinic anhydride and heat to 120 ° C to melt, add 10g wood pulp to the succinic anhydride melt, heat to 120 ° C constant temperature stirring reaction for 3h, carry out pretreatment reaction, the reaction is completed, filtered, filter residue as pretreated fiber Prime raw material;

(3) High-pressure homogenizer The dispersion was subjected to high-pressure pulverization to obtain a nanocellulose dispersion having a concentration of 2 wt%, a nanocellulose D90 having a diameter of 10 to 50 nm, and an aspect ratio of 135.

Comparative example 1

A nanocellulose, the preparation method comprises the following steps:

(1) Weigh 80g of maleic acid solution (concentration: 80wt%), add 10g of wood pulp to the maleic acid solution, heat to 90 °C, stir the reaction for 4h, carry out pretreatment reaction, complete the reaction, filter, filter residue is pre Treated cellulosic feedstock;

(3) High-pressure homogenizer The high-pressure pulverization of the dispersion liquid is carried out to obtain a nano-cellulose dispersion liquid having a concentration of 5 wt%, a nano cellulose D90 having a diameter of 4 to 10 nm, a length of less than 500 nm, and a long diameter. The ratio is 30.

Comparative example 2

A nanocellulose, the preparation method comprises the following steps:

(1) Weigh 80g of maleic acid solution (concentration: 20wt%), add 10g of wood pulp to the maleic acid solution, heat to 90 °C, stir the reaction for 4h, carry out pretreatment reaction, complete the reaction, filter, filter residue Treated cellulosic feedstock;

(3) High-pressure homogenizer The dispersion was subjected to high-pressure pulverization to obtain a nanocellulose dispersion having a concentration of 5 wt%, a nanocellulose D90 having a diameter of 180 to 200 nm, and an aspect ratio of 20.

It can be seen from the results of the examples and the comparative examples that the acid anhydride can peel off the nanocellulose (diameter 4 to 50 nm, aspect ratio 100 to 300) just right, and the corresponding concentrated acid causes the nanocellulose structure to be destroyed, and the size cannot be obtained. Longer nanocellulose fibers, while dilute acids do not strip out nanometer-sized nanocellulose.

The Applicant declares that the present disclosure illustrates the process of the present invention by the above-described embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. It is to be understood by those skilled in the art that any modifications of the present disclosure, equivalent substitutions of the materials selected for the present disclosure, and the addition of the auxiliary components, the selection of the specific manners, and the like, are all within the scope of the present invention.

Claims

A preparation method of nano cellulose, the preparation method thereof comprises:

(1) adding a cellulose raw material to a melt of an acid anhydride compound, raising the temperature to a melting point or higher, performing a pretreatment reaction, and filtering after completion of the reaction to obtain a pretreated cellulose raw material;

(2) dispersing the pretreated cellulose raw material into water to obtain a dispersion;

(3) The dispersion was mechanically pulverized to obtain a nanocellulose dispersion.
The production method according to claim 1, wherein the nanocellulose has a diameter of 4 to 50 nm and an aspect ratio of 100 to 300.
The production method according to claim 1 or 2, wherein the nanocellulose dispersion has a concentration of 2 to 7 wt%.
The production method according to any one of claims 1 to 3, wherein the acid anhydride compound is an acid anhydride compound having a melting point of 120 ° C or less, preferably including acetic anhydride, dodecenyl succinic anhydride, maleic anhydride or succinic anhydride. Any one or a combination of at least two, more preferably maleic anhydride;

Preferably, the cellulose raw material comprises any one or a combination of at least two of wood pulp, grass pulp, cotton pulp, bamboo pulp, mash pulp, hemp pulp, bagasse pulp, and crop straw pulp.
The preparation method according to any one of claims 1 to 4, wherein the mass ratio of the cellulose raw material to the acid anhydride compound is from 1:3 to 1:10, preferably from 1:6 to 1:8;

Preferably, the pretreatment reaction has a temperature of 80 to 120 ° C and a time of 1 to 4 hours.
The preparation method according to any one of claims 1 to 5, wherein the filtering comprises atmospheric filtration or reduced pressure filtration;

Preferably, in step (1), after filtering, the filter residue is washed;

Preferably, the washing is a water wash.
The production method according to any one of claims 1 to 6, wherein the mechanical pulverization in the step (3) includes any one of ball milling, disc grinding, sanding, high-pressure homogenizer, ultrasonic crusher, and mortar pulverization. Or a combination of at least 2;

Preferably, the condition of the mechanical comminution is homogenization by a high pressure homogenizer.
The preparation method according to any one of claims 1 to 7, wherein after step (3), step (4) is carried out to post-treat the nanocellulose dispersion to obtain nanocellulose powder;

Preferably, the post treatment comprises any one or a combination of at least two of washing, grinding, and spray drying.
A nanocellulose prepared by the production method according to any one of claims 1 to 8.
The nanocellulose according to claim 9, wherein the nanocellulose has a diameter of 4 to 50 nm and an aspect ratio of 50 to 300.
A use of the nanocellulose according to claim 9 or 10, which is used in the textile field, the pharmaceutical field, the high performance auxiliary field, the adsorption material field, the food packaging field, and the composite material field.