A method for dissolving cellulose

Abstract

A method for dissolving cellulose, belonging to the technical field of cellulose dissolution, can solve the problems of high energy consumption, high cost and low solubility in the existing methods for dissolving cellulose. This method uses an aqueous solution of quaternary ammonium base and an amine substance as raw materials. First, 5 wt% - 80 wt% of the amine substance is mixed evenly with cellulose at room temperature, and then the aqueous solution of quaternary ammonium base is added. Standing or stirring at a certain temperature can obtain a cellulose solution with a cellulose content of 2 wt% - 20 wt%. The raw materials used in this method are inexpensive, have high solubility and fast dissolution rate, and the obtained cellulose solution has good stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of cellulose dissolution, and particularly relates to a method for dissolving cellulose. Background Art

[0002] Cellulose is the most abundant renewable resource in nature, mainly derived from hardwood plants such as wood, bagasse, straw, cotton, bamboo, and flax, as well as deep-sea tunicates. At the same time, it is an environmentally friendly material. Making full use of it can well protect the environment, and cellulose is inexhaustible. Therefore, it is expected to become a substitute for fossil fuels. The functional applications of cellulose are relatively extensive, and it has relatively good application prospects in water treatment, biomedicine, electrochemistry, and catalysis. At present, some existing methods for dissolving cellulose have high energy consumption, high cost, and low solubility. Summary of the Invention

[0003] Aiming at the problems of high energy consumption, high cost, and low solubility of the existing methods for dissolving cellulose, the present invention provides a method for dissolving cellulose, which has low energy consumption, short dissolution time, and high solubility.

[0004] To achieve the above object, the present invention adopts the following technical scheme:

[0005] A method for dissolving cellulose, comprising the following steps:

[0006] Mix cellulose with an amine substance at room temperature, then add an aqueous solution of a quaternary ammonium base, and let it stand or stir at 5 - 90 °C to obtain a cellulose solution. The content of cellulose in the obtained cellulose solution is 3 wt% - 20 wt%.

[0007] Further, the amine substance includes any one of primary amines, secondary amines, and tertiary amines.

[0008] The amine substance includes any one of cyclopropylamine, n-propylamine, ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, 1,4-butanediamine, N-ethylethylenediamine, N,N-dimethylethylenediamine, N,N'-dimethylethylenediamine, N,N,N-trimethylethylenediamine, tetramethylethylenediamine, and diethylenetriamine.

[0009] Further, the aqueous solution of the quaternary ammonium base includes any one of an aqueous solution of tetramethylammonium hydroxide, an aqueous solution of tetraethylammonium hydroxide, an aqueous solution of tetrapropylammonium hydroxide, and an aqueous solution of tetrabutylammonium hydroxide.

[0010] Further, the content of the amine substance is 5 wt% - 80 wt%, and the rest is the aqueous solution of the quaternary ammonium base.

[0011] Further, the dissolution time of the cellulose is 0.5 h - 48 h.

[0012] Furthermore, the degree of polymerization of the cellulose is 15 - 3000.

[0013] The mechanism of the present invention is as follows:

[0014] In the quaternary ammonium hydroxide aqueous solution and amine system, the amine substance and OH - can enter the interior of the cellulose crystal region to disrupt the hydrogen bond network inside the cellulose and form a new hydrogen bond network structure. The hydrophilic end of the cellulose binds to water, and the hydrophobic end binds to the quaternary ammonium hydroxide cation, so that the cellulose can be better dissolved in this system.

[0015] The cellulose solution obtained by the present invention has a high solubility and good stability, and can maintain good stability after standing at room temperature for several days.

[0016] Compared with the prior art, the innovations of the present invention are as follows:

[0017] 1. The dissolution process of cellulose is simple and easy to operate, the raw materials are cheap and easily available, and the dissolution of cellulose with a relatively low degree of polymerization only needs to be carried out at room temperature, with a wide temperature adaptation range, and the energy consumption and cost are lower compared to other dissolution technologies;

[0018] 2. The content of cellulose in the cellulose solution can reach 20 wt%, with a high solubility, and can be stored for a long time at room temperature;

[0019] 3. The system can dissolve cellulose with a wide range of degrees of polymerization and has strong adaptability to cellulose raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is an image (20μm) taken under a Leica polarized light microscope with an objective lens of 20 times of the cellulose solution prepared in Example 1 of the present invention.

[0021] Figure 2 is an image (20μm) taken under a Leica polarized light microscope with an objective lens of 20 times of the cellulose solution prepared in Example 2 of the present invention.

[0022] Figure 3 is an image (20μm) taken under a Leica polarized light microscope with an objective lens of 20 times of the cellulose solution prepared in Example 3 of the present invention.

[0023] Figure 4 is an image of microcrystalline cellulose before and after dissolution in Example 4 of the present invention.

[0024] Figure 5 is an image of imported wood pulp cellulose before and after dissolution in Example 5 of the present invention.

[0025] Figure 6 This is an image (20μm) of the cellulose solution prepared in Example 6 of the present invention taken under a Leica polarized light microscope with an objective lens of 20 times magnification.

[0026] Figure 7 This is an image (20μm) of the cellulose solution prepared in Example 7 of the present invention taken under a Leica polarized light microscope with an objective lens of 20 times magnification. Detailed implementation manners

[0027] To further understand the present invention, the content of the present invention will be further clarified below in conjunction with examples, but the content is not limited to the following examples only.

[0028] Example 1

[0029] Take 10 grams of ethylenediamine solution, add 5.97 grams of microcrystalline cellulose (with a polymerization degree of about 230), stir at room temperature, and then add 30 grams of an aqueous solution of 25 wt% tetraethylammonium hydroxide. After stirring evenly at room temperature, a transparent cellulose solution is obtained. The content of ethylenediamine is about 22 wt%, the content of cellulose is about 13 wt%, and the rest is the aqueous solution of tetraethylammonium hydroxide. When observed under a Leica polarized light microscope, no obvious undissolved cellulose particles are found, as shown in the appendix. Figure 1 As shown.

[0030] Example 2

[0031] Take 16 grams of 1,3-propanediamine solution, add 5.45 grams of microcrystalline cellulose (with a polymerization degree of about 230), stir at room temperature, and then add 24 grams of an aqueous solution of 25 wt% tetraethylammonium hydroxide. After stirring evenly at room temperature, a transparent cellulose solution is obtained. The content of cellulose is about 12 wt%, the content of 1,3-propanediamine is about 35 wt%, and the rest is the aqueous solution of tetraethylammonium hydroxide. The prepared cellulose solution has good stability, as shown in the appendix. Figure 2 As shown.

[0032] Example 3

[0033] Take 20 grams of 1,3-propanediamine solution, add 4.94 grams of microcrystalline cellulose (with a polymerization degree of about 230), stir at room temperature, and then add 20 grams of an aqueous solution of 25 wt% tetrapropylammonium hydroxide. After stirring evenly at room temperature, a transparent cellulose solution is obtained. The content of 1,3-propanediamine is about 44.5 wt%, the content of cellulose is about 11 wt%, and the rest is the aqueous solution of tetrapropylammonium hydroxide. When observed under a Leica polarized light microscope, no obvious undissolved cellulose particles are found, as shown in the appendix. Figure 3 As shown.

[0034] Example 4

[0035] Take 16 g of cyclopropylamine solution, add 3.01 g of microcrystalline cellulose (with a degree of polymerization of about 230), stir at room temperature, then add 24 g of an aqueous solution of 25 wt% tetraethylammonium hydroxide, and stir well at room temperature to obtain a transparent cellulose solution. The content of cyclopropylamine is 37.2 wt%, the content of cellulose is about 7 wt%, and the rest is the aqueous solution of tetraethylammonium hydroxide. The prepared cellulose has good stability, as shown in the appendix Figure 4 as follows.

[0036] Example 5

[0037] Take 12 g of N-ethyl ethylenediamine solution, add 2.11 g of imported wood pulp powder (with a degree of polymerization of about 600), stir at room temperature, then add 28 g of an aqueous solution of 40 wt% tetrabutylammonium hydroxide, and stir well at room temperature to obtain a clear and transparent cellulose solution. The content of cellulose is 5 wt%. The prepared cellulose solution has good stability, as shown in the appendix Figure 5 as follows.

[0038] Example 6

[0039] Take 7.5 g of ethylenediamine solution, add 2.25 g of degummed hemp fiber (with a degree of polymerization of about 2600), soak at room temperature, then add 22.5 g of an aqueous solution of 25 wt% tetraethylammonium hydroxide, and stir well at 80 °C to obtain a viscous cellulose solution. The mass concentration of cellulose is 7 wt%. The prepared cellulose solution has good stability, as shown in the appendix Figure 6 as follows.

[0040] Example 7

[0041] Take 7.5 g of ethylenediamine solution, add 2.60 g of degummed hemp fiber (with a degree of polymerization of about 3000), soak at room temperature, then add 22.5 g of an aqueous solution of 25 wt% tetraethylammonium hydroxide, and stir well at 80 °C to obtain a viscous cellulose solution. The mass concentration of cellulose is about 8 wt%. Observed under a Leica polarized light microscope, no obvious undissolved cellulose particles were found, as shown in the appendix Figure 7 as follows.

Claims

1. A method for dissolving cellulose, characterized in that: It includes the following steps: Mix cellulose with an amine substance at room temperature, then add an aqueous solution of quaternary ammonium base, and let it stand or stir at 5-90 °C to obtain a cellulose solution. The cellulose content in the obtained cellulose solution is 3 wt%-20 wt%.

2. The method for dissolving cellulose according to claim 1, wherein: The amine substance includes any one of primary amines, secondary amines, and tertiary amines.

3. The method for dissolving cellulose according to claim 2, characterized in that: The amine substance includes any one of cyclopropylamine, n-propylamine, ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, 1,4-butanediamine, N-ethylethylenediamine, N,N-dimethylethylenediamine, N,N'-dimethylethylenediamine, N,N,N-trimethylethylenediamine, tetramethylethylenediamine, and diethylenetriamine.

4. A method for dissolving cellulose according to claim 1, characterized in that: The aqueous solution of quaternary ammonium base includes any one of an aqueous solution of tetramethylammonium hydroxide, an aqueous solution of tetraethylammonium hydroxide, an aqueous solution of tetrapropylammonium hydroxide, and an aqueous solution of tetrabutylammonium hydroxide.

5. A method for dissolving cellulose according to claim 1, characterized in that: The content of the amine substance is 5 wt%-80 wt%, and the rest is the aqueous solution of quaternary ammonium base.

6. A method for dissolving cellulose according to claim 1, characterized in that: The dissolution time of the cellulose is 0.5h-48h.

7. A method for dissolving cellulose according to claim 1, characterized in that: The degree of polymerization of the cellulose is 15-3000.

Images