KR20190096097A - Method for manufacturing cellulose nanofiber - Google Patents

Abstract

The present invention relates to a method for manufacturing cellulose nanofibers, comprising the steps of: manufacturing a suspension by adding pulp to an organic solvent including an amine group and an alcohol group and performing primary stirring; and adding lithium amide to the suspension and performing secondary stirring. According to the present invention, cellulose nanofibers which have been miniaturized can be manufactured in a simple process within a short time.

Description

Method for producing cellulose nanofibers {METHOD FOR MANUFACTURING CELLULOSE NANOFIBER}

The present specification relates to a method for producing cellulose nanofibers.

Recently, due to the excellent physical properties of nano-sized materials, interest in making nanocomposites has increased greatly around the world. Most studies use inorganic materials such as carbon nanotubes and organic materials such as nanocellulose as reinforcing materials for making nanocomposites. Nanocellulose is an ultrafine fiber with a diameter of only nanoscale, and its application potential is infinite. Nanocellulose is a lightweight material that is five times stronger than steel, and has properties such as 1/50 linear expansion coefficient and high aspect ratio of glass, so it can be used in pharmaceutical packaging materials, separators for lithium-ion batteries, displays, solar cells, electronic paper and It can be used in various fields such as sensors.

However, due to the disadvantage that the processing and molding is difficult, there is a limit in the applicability, there is a difficulty in commercialization, the situation that requires further research.

Korean Patent Publication No. 10-2008-0075627

The present specification is to provide a method for producing cellulose nanofibers and cellulose nanofibers produced thereby.

One embodiment of the present specification

Preparing a suspension by putting pulp in an organic solvent including an amine group and an alcohol group and first stirring; And

It provides a method for producing cellulose nanofibers comprising the step of adding a second step of the lithium amide to the suspension.

According to the manufacturing method of the cellulose nanofibers of the exemplary embodiment of the present specification, it is possible to manufacture the cellulose nanofibers which have been miniaturized by a simple process within a short time, and there is an advantage that the process cost can be reduced.

FIG. 1 compares SEM (scanning electron microscope) photographs before and after LiNH ₂ addition of cellulose suspension.
Figure 2 is a diagram showing the result of stirring the pulp in monoethanolamine and ammonia water for 5 minutes at room temperature, respectively.

Hereinafter, this specification is demonstrated in detail.

In the present specification, when a member is located 'on' another member, this includes not only when one member is in contact with another member but also when another member exists between the two members.

In the present specification, when a part is used to 'include' a certain component, this means that the component may further include other components, except for the case where there is no description to the contrary.

In one embodiment of the present specification, the method for producing cellulose nanofibers includes a step of preparing a suspension by first putting pulp in an organic solvent including an amine group and an alcohol group.

In one embodiment of the present specification, the pulp is subjected to a deligination process of refining cellulose from wood raw materials, for example, to remove other components such as hemicellulose, lignin, pentosan and the like from cellulose in plants such as wood. it means.

In one embodiment of the present specification, an organic solvent including an amine group (-NH ₂ ) and an alcohol group (-OH) may be used as a solvent for dissolving the pulp.

In one embodiment of the present specification, the organic solvent including the amine group and the alcohol group is at least one selected from monoethanolamine and monopropanol.

Conventionally, dimethylacetamide, dimethylformamide, or ammonia water is used as a solvent for dissolving pulp. However, when an organic solvent containing an amine group (-NH ₂ ) and an alcohol group (-OH) is used at the end, There was a problem that the dispersion of pulp is lower than. Figure 2 shows the result of stirring the pulp in monoethanolamine (MEA) and ammonia water (ammonia water) for 5 minutes at room temperature, in the case of the left sample dissolved in monoethanolamine, the color of the solution is uniform so that the pulp is evenly distributed. It can be seen that the right sample dissolved in ammonia water showed a darker color toward the bottom, indicating that the pulp was not evenly distributed.

In addition, Figure 1 is a SEM photograph of the state before and after the addition of lithium amide to the suspension prepared by stirring the pulp in monoethanolamine. 1, the microfibers were formed before the lithium amide was added, whereas when the lithium amide was added, the cellulose was much finer and thus the nanofibers were formed.

In one embodiment of the present specification, the content of the pulp is 0.1 to 10% by weight, preferably 0.3 to 5% by weight, more preferably 0.6 to 3% by weight based on the total weight of the organic solvent. Weight percent.

When the content of the pulp is included in the above range, it is possible to prevent the problem that the suspension does not flow due to the increased viscosity while ensuring the efficiency of the process, preventing the progress of the process.

In one embodiment of the present specification, the first stirring is performed at room temperature, for example, at a temperature of 20 ° C to 30 ° C. In addition, the first stirring is performed for 1 minute to 10 minutes, preferably 2 minutes to 8 minutes, more preferably 3 minutes to 7 minutes.

This means that by using an organic solvent containing an amine group and an alcohol group, the degree of dispersion of the pulp is increased, so that no additional heating process is required, and the stirring time can also be shortened.

In one embodiment of the present specification, the method for preparing cellulose nanofibers includes adding lithium amide to the suspension and performing secondary agitation.

When lithium amide is added, the cellulose constituting the pulp is refined, thereby increasing the hydroxyl group (-OH) on the surface of the cellulose and increasing the viscosity due to strong hydrogen bonding between the hydroxy groups. That is, the viscosity of the solution containing cellulose is a measure by which the degree of miniaturization of cellulose can be known.

The lithium amide is a lithium salt such as LiCl, LiClO and LiNO ₃ used in the prior art; Sodium salts such as NaBr and NaOH; And the effect of increasing the viscosity of the solution containing cellulose is superior to Urea and the like having an amine functional group, which is effective for the swelling effect of cellulose by the complexation of lithium ions of lithium amide and the acceleration of fibrosis by amide groups This is because the swelling effect of the cellulose acts at the same time.

In one embodiment of the present specification, the second agitation is performed at a temperature of 10 ° C to 40 ° C, preferably at a temperature of room temperature, such as 20 ° C to 30 ° C. In addition, the secondary agitation is performed for 1 minute to 1 hour, preferably 2 minutes to 30 minutes, more preferably 3 minutes to 10 minutes.

Conventionally, cellulose was refined by adding acid or heating to increase the temperature. However, since the method of manufacturing cellulose nanofibers according to the exemplary embodiment of the present invention uses lithium amide, the cellulose can be refined within a short time at room temperature, thereby simplifying the process. There is an advantage that it is possible.

In one embodiment of the present specification, the weight ratio of the pulp and lithium amide is 1: 2 to 1: 5, preferably 1: 1.5 to 1: 4, more preferably 1: 2 to 1: 3.

When the weight ratio of pulp and lithium amide is in the above range, the viscosity of the suspension after the second agitation is completed may be at least 3,000 cps, preferably at least 3,500 cps, more preferably at least 4,000 cps.

The viscosity means a value measured for 1 minute at 10 rpm using a Brookfield viscometer DV2T instrument and Vane spindle # 74 at room temperature.

Hereinafter, the present invention will be described in detail with reference to Examples. However, embodiments according to the present disclosure may be modified in various other forms, and the scope of the present disclosure is not interpreted to be limited to the embodiments described below. The embodiments of the present specification are provided to more fully describe the present specification to those skilled in the art.

<Example>

Example 1.

0.4 g of pulp (Morim Paper Co., Ltd.) was added to 40 g of monoethanolamine and stirred at room temperature for 5 minutes. 0.8 g of lithium amide was added to the stirred solution, and further stirred at room temperature for 5 minutes to prepare a solution containing cellulose nanofibers.

Example 2.

A solution was prepared in the same manner as in Example 1, except that the content of lithium amide in Example 1 was changed to 1.0 g.

Example 3.

A solution was prepared in the same manner as in Example 1, except that the content of lithium amide was changed to 1.2 g in Example 1.

Example 4.

A solution was prepared in the same manner as in Example 1, except that the content of lithium amide was changed to 1.6 g in Example 1.

Example 5.

A solution was prepared in the same manner as in Example 1, except that the content of lithium amide was changed to 2.0 g in Example 1.

Example  6.

A solution was prepared in the same manner as in Example 1, except that the content of lithium amide in Example 1 was changed to 0.2 g.

Example  7.

A solution was prepared in the same manner as in Example 1, except that the content of lithium amide was changed to 0.4 g in Example 1.

Example  8.

A solution was prepared in the same manner as in Example 1, except that the content of lithium amide was changed to 4.0 g in Example 1.

Comparative Example 1.

A solution was prepared in the same manner as in Example 1, except that lithium amide was not added in Example 1.

Comparative example  2.

A solution was prepared in the same manner as in Example 2, except that lithium chloride (LiCl) was used instead of lithium amide in Example 2.

Comparative example  3.

A solution was prepared in the same manner as in Example 2, except that lithium hypochlorite (LiClO) was used instead of lithium amide in Example 2.

Comparative example  4.

A solution was prepared in the same manner as in Example 2, except that lithium nitrate (LiNO ₃ ) was used instead of lithium amide in Example 2.

Comparative example  5.

A solution was prepared in the same manner as in Example 2, except that Urea ((NH ₂ ) ₂ CO) was used instead of lithium amide in Example 2.

Comparative example  6.

A solution was prepared in the same manner as in Example 2, except that sodium bromide (NaBr) was used instead of lithium amide in Example 2.

Experimental Example

For the solutions prepared in Examples 1 to 8 and Comparative Examples 1 to 6, the viscosity measured for 1 minute at 10 rpm using a Brookfield viscometer DV2T instrument and Vane spindle # 74 at room temperature is shown in Table 1 below.

Kind of salt Pulp: weight ratio of salt Viscosity (cp) Example 1 LiNH ₂ 1: 2 3273.1 ± 66.1 Example 2 LiNH ₂ 1: 2.5 4078.5 ± 86.7 Example 3 LiNH ₂ 1: 3 3786.1 ± 118.3 Example 4 LiNH ₂ 1: 4 3806.8 ± 21.4 Example 5 LiNH ₂ 1: 5 3455.1 ± 89.5 Example 6 LiNH ₂ 2: 1 1923 ± 60.2 Example 7 LiNH ₂ 1: 1 2091.0 ± 71.3 Example 8 LiNH ₂ 1:10 2359.5 ± 13.2 Comparative Example 1 - - 500.2 ± 10.5 Comparative Example 2 LiCl 1: 2.5 432.4 ± 17.9 Comparative Example 3 LiClO 1: 2.5 320.7 ± 25.3 Comparative Example 4 LiNO ₃ 1: 2.5 462.0 ± 36.1 Comparative Example 5 Urea 1: 2.5 366.5 ± 27.3 Comparative Example 6 NaBr 1: 2.5 524.3 ± 28.8

Through the results in Table 1, it can be seen that when the lithium amide is added according to one embodiment of the present specification, it shows a higher viscosity than when other salts are added. In particular, it can be seen that when the weight ratio of pulp and salt is in the range of 1: 2 to 1: 5, a high viscosity of 3,000 cps or more can be obtained.

Claims (10)

Preparing a suspension by putting pulp in an organic solvent including an amine group and an alcohol group and first stirring; And
Method of producing a cellulose nanofiber comprising the step of adding a second step of the lithium amide in the suspension. The method according to claim 1,
The organic solvent comprising the amine group and the alcohol group is one or more selected from monoethanolamine and amino propanol. The method of claim 1, wherein the pulp content is 0.1 wt% to 10 wt% based on the total weight of the organic solvent. The method according to claim 1,
The first stirring is a method for producing cellulose nanofibers is performed for 1 to 10 minutes. The method according to claim 1,
The first stirring is a method for producing cellulose nanofibers is carried out at a temperature of 20 ℃ to 30 ℃. The method according to claim 1,
The second agitation is a method for producing cellulose nanofibers is performed for 1 minute to 1 hour. The method of claim 1, wherein the secondary stirring is carried out at a temperature of 10 ° C to 40 ° C. The method according to claim 1,
The weight ratio of the pulp and lithium amide is 1: 2 to 1: 5 manufacturing method of cellulose nanofibers. The method according to claim 1,
After the second stirring, the viscosity of the suspension is 3,000 cps or more manufacturing method of cellulose nanofibers. The method according to claim 1,
Method for producing a cellulose nanofiber further comprising the step of drying after the second stirring.

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