KR102171777B1 - Deep Eutectic Solvents For NanoCellulose and Its Preparing Method - Google Patents

Abstract

The present invention provides a eutectic solvent for producing nanocellulose and a method for producing nanocellulose using the same.
The eutectic solvent for nanocellulose production of the present invention can be prepared by simple mixing and has the advantage of excellent economical efficiency due to its simple treatment. It has the advantage of excellent reaction efficiency because it uses a material with a lower melting point than that of a conventional hydrogen bond donor or hydrogen bond acceptor have. In addition, since the eutectic solvent for nanocellulose production of the present invention consists of an ammonium salt, a halide, and a hydrogen bond donor, it is an environmentally friendly biocompatible compound that is not dangerous even if released. have.

Description

A eutectic solvent for manufacturing nanocellulose and a method for manufacturing nanocellulose using the same {Deep Eutectic Solvents For NanoCellulose and Its Preparing Method}

The present invention relates to a eutectic solvent for producing nanocellulose and a method for producing nanocellulose using the same.

Nano-sized materials are widely used as reinforced composite materials because they have excellent physical, chemical, and mechanical properties. Cellulose, a natural polymer that exists most abundantly on the planet and has excellent biodegradability and biocompatibility, has attracted attention as an alternative resource for fossil resources, and research is being conducted to use it for various purposes. In particular, interest in nanocellulose is greatly increasing. Nanocellulose has the shape of a rod or fiber with a diameter of nanometers and a length of nano or micrometers. Nanocellulose is a bio-based material with a small density, excellent strength, and a large specific surface area. Nanocellulose can be broadly classified into cellulose nanofibrill (CNF) and cellulose nanocrystal (CNC) according to the manufacturing method. CNF is a fiber manufactured by strong mechanical shearing force and frictional force such as high pressure homogenizing, grinding, and refining, and has disadvantages that require energy consumption and time. To overcome this, chemical pretreatment is applied to reduce energy consumption using TEMPO catalytic oxidation and enzymes. However, such a chemical pretreatment has to go through a complicated process such as attaching functional groups such as cationic, anionic and amphiphilic groups to the surface in order to mitigate the strong hydrogen bonds of cellulose. In addition, the chemical pretreatment method causes problems such as wastewater treatment, flotation and aggregation, depending on the solvent used. Therefore, it is believed that using a non-toxic, recyclable, non-reactive, and non-reactive solvent that improves nanofibrilation of cellulose could open a new route for nanocellulose production.

The patent documents and references mentioned in this specification are incorporated herein by reference to the same extent as if each document was individually and clearly specified by reference.

Korean Patent Publication 10-2009-0110322

Eunjung Lee et. al., J. Korean Soc. Int. Agric. 2016 28(2): 268~273.

The present invention is designed to solve the above problems, and provides a method for producing nanocellulose using a eutectic solvent that is simple to process, is safe, is cost-effective, and does not cause problems during purification or disposal.

Accordingly, an object of the present invention is to provide a eutectic solvent for preparing nanocellulose including a salt of choline and a hydrogen bond donor, and a method for producing nanocellulose using the same.

Other objects and technical features of the present invention are presented in more detail by the following detailed description, claims, and drawings.

The eutectic solvent for preparing nanocellulose of the present invention is a salt of choline having the following formula:

[Chemical Formula]

(X is a eutectic solvent for producing nanocellulose containing fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).), and a hydrogen bond donor.

The hydrogen bond donor is glycerol (glycerilne), urea, or lactic acid, and the choline salt and the hydrogen bond donor are mixed at a molar ratio of 1: 2 to 10 (choline salt: hydrogen bond donor). .

The present invention comprises the steps of preparing cellulose; Treating the cellulose with a eutectic solvent for producing nanocellulose; And pulverizing the cellulose treated with the eutectic solvent to produce nanocellulose.

The step of preparing the cellulose is characterized in that lignin is removed from the wood by delignification treatment (aka Wise method) using chlorite salt and acetic acid.

The present invention provides a eutectic solvent for producing nanocellulose and a method for producing nanocellulose using the same.

The eutectic solvent for nanocellulose production of the present invention can be prepared by simple mixing and has the advantage of excellent economical efficiency due to its simple treatment. It has the advantage of excellent reaction efficiency because it uses a material with a lower melting point than that of a conventional hydrogen bond donor or hydrogen bond acceptor have. In addition, since the eutectic solvent for producing nanocellulose of the present invention is composed of an ammonium salt, a halide, and a hydrogen bond donor, it is an environmentally friendly compound that is not dangerous even if released, so there is no concern of cost and environmental pollution associated with purification or disposal.

1 shows an FTIR spectrum of a sample treated with a choline chloride/lactic acid eutectic solvent. Panel A) is the result of treating pine sapwood, and panel B) is the result of treating pine heartwood.
Figure 2 shows the FTIR spectrum of the choline chloride / urea eutectic solvent treatment sample. Panel A) is the result of treating pine sapwood, and panel B) is the result of treating pine heartwood.
3 shows an FTIR spectrum of a sample treated with a choline chloride/glycerol eutectic solvent. Panel A) is the result of treating pine sapwood, and panel B) is the result of treating pine heartwood.
4 shows an FTIR spectrum of a sample treated with the Wise method. Panel A) is the result of treating pine sapwood, and panel B) is the result of treating pine heartwood.
5 shows the results of observation with a transmission electron microscope for nanocellulose prepared by performing Wise method and choline chloride/lactic acid (1:6) eutectic solvent treatment and grinding. Panel A) is the result of treatment with the Wise method for 3 hours, and Panel B) is the result of treatment with the Wise method for 6 hours.
6 shows the results of observation with a transmission electron microscope for nanocellulose prepared by performing Wise method and choline chloride/urea (1:6) eutectic solvent treatment and grinding. Panel A) is the result of treatment with the Wise method for 3 hours, and Panel B) is the result of treatment with the Wise method for 6 hours.
7 shows the results of observation with a transmission electron microscope for nanocellulose prepared by performing the Wise method and the choline chloride/glycerol (1:6) eutectic solvent treatment and grinding. Panel A) is the result of treatment with the Wise method for 3 hours, and Panel B) is the result of treatment with the Wise method for 6 hours.

The present invention in the eutectic solvent for producing nanocellulose (deep eutectic solvent),

A salt of choline having the formula:

[Chemical Formula]

(The X is fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).), and a hydrogen bond donor (hydrogen bond donor) to provide a eutectic solvent for manufacturing nanocellulose containing do.

Nanocellulose is a natural polymer that can be obtained mechanically or chemically from the plant cell wall, and has advantages such as transparency, reproducibility, biodegradability, biostability, thermal stability, and moldability. The dimensions of the nanocellulose are several-hundreds of nm in width, and the length of the nanocellulose is a rod-shaped or fibrous material ranging from several nm to several μm.

The deep eutectic solvent refers to a eutectic mixture in which two types of components are mixed and has a lower melting point than each component, and is mainly present in a liquid state at 100° C. or lower. The eutectic solvent has characteristics similar to ionic liquids in physicochemical properties such as viscosity, density, conductivity and solubility, and by fine-tuning the physicochemical properties by changing the properties of the tetraammonium salt and the hydrogen bond donor, it is possible to create a eutectic solvent tailored to various tasks. have.

The eutectic solvent of the present invention is a eutectic solvent optimized for nanocellulose production, and if used after a delignification process such as sodium chlorite, it has the advantage of being able to produce nanocellulose having a width of only a few nm with only a simple grinding operation.

The eutectic solvent of the present invention uses a salt of choline as an ammonium salt. The salt of choline may be a salt in which choline having the above formula and fluorine (F), chlorine (Cl), bromine (Br), or iodine (I) are combined, preferably chlorine (Cl). .

The eutectic solvent of the present invention may use glycerol (glycerilne), urea (urea), or lactic acid (lactic acid) as a hydrogen bonding donor, preferably glycerol.

The smaller the width of the nanocellulose is, the more excellent the dispersibility is, the more diverse its uses. Therefore, as nanocelluloses having a smaller width are manufactured, the industrial applicability increases.

To this end, in the present invention, a eutectic solvent capable of producing nanocellulose having a small width was developed through Examples, and this was experimentally confirmed.

According to an embodiment of the present invention, the eutectic solvent of the present invention is prepared by mixing the choline salt and the hydrogen bond donor in a molar ratio of 1: 2 to 10 (choline salt: hydrogen bond donor). If the mixed molar ratio of the salt of choline and the hydrogen bond donor is less than 1:2, the number of hydrogen bond donors is too small to relieve strong hydrogen bonds between cellulose. If the hydrogen bonding is not relaxed, the pulverization time of the cellulose takes more time, thereby reducing economic efficiency. In addition, even if the mixing molar ratio of the salt of choline and the hydrogen bond donor exceeds 1:10, the width of the prepared nanocellulose is not smaller. Preferably, the eutectic solvent of the present invention uses glycerol as the salt of choline and the hydrogen bond donor, and the mixed molar ratio of the salt of choline and glycerol is 1:6.

The present invention provides a method for producing nanocellulose using the eutectic solvent for producing nanocellulose.

The method of manufacturing the nanocellulose includes the first step: preparing cellulose; Second step: treating cellulose with a eutectic solvent for producing nanocellulose; Third step: comprising the step of pulverizing the cellulose treated with a eutectic solvent to produce nanocellulose.

The first step: preparing cellulose is a step of improving the cellulose content of wood or biomass. If wood is used, lignin contained in wood should be removed. The lignin surrounds cellulose. Therefore, if lignin is not removed, the chemical treatment is limited due to the influence of this component surrounding cellulose.

First, wood is pulverized to prepare a powder that can be dispersed, and then treated with a salt of chlorite and acetic acid (Wise method) to remove lignin. The Wise method may be performed by adding a certain amount of sodium chlorite to the acetic acid solution and stirring at a temperature of 80°C.

According to an embodiment of the present invention, the removal of lignin using the Wise method is performed by reacting for 2 to 6 hours. It is preferably carried out by reacting for 3 hours or more. If the reaction time is less than 2 hours, the cellulose yield may be lowered due to the lignin that has not been removed, and the pulverization time for producing nanofibers may be further required. In addition, when the reaction time exceeds 6 hours, the cellulose is excessively decomposed and the yield of cellulose is lowered. The reaction time is most preferably 3 hours. In this case, a mixture of choline salt and glycerol in a molar ratio of 1:6 is used as a eutectic solvent for producing cellulose nanofibers. When pulverized after 6 hours treatment with the eutectic solvent, excellent cellulose nanofibers having a width of 2.1±0.8 nm can be prepared. The sample treated by the Wise method can be used in the next step by neutralizing after filtration.

The second step: treating with a eutectic solvent for preparing nanocellulose is a step of swelling by breaking hydrogen bonds between molecular aggregates of the prepared cellulose. When the lignin is removed by the first step, a space is created between the cellulose molecular agglomerates, thereby facilitating the penetration of the eutectic solvent of the present invention and allowing the hydrogen bonds between the cellulose molecular agglomerates to be relaxed by the hydrogen bond donor of the eutectic solvent. Therefore, the cellulose can be nano-ized only by simple grinding.

The cellulose prepared in the first step is treated with a eutectic solvent for producing nanocellulose. The eutectic solvent for producing nanocellulose is a mixture of choline salt and glycerol in a molar ratio of 1:6. The eutectic solvent treatment is carried out by stirring at 400 rpm at 100°C. After the above treatment, it is filtered and stored refrigerated in a wet state.

The third step: pulverizing the cellulose to prepare nanocellulose is a step of mechanically nano-izing the eutectic solvent-treated cellulose. To this end, the raw material is pulverized for 5 minutes at 22,000 rpm with a concentration of 0.5% using a blender.

The present invention will be described in detail through the following examples.

Example

1. Preparation of Cellulose: Wise Method Treatment for Wood Powder

1.1 Analysis of yield and chemical composition of samples treated with Wise method

After making wood flour by crushing sapwood and heartwood of pine, lignin was removed by Wise method treatment using chlorite and acetic acid.

Table 1 below shows the analysis results and yield of chemical composition by reaction time by the Wise method treatment. Ara stands for Arabinose, Gal stands for Galactose, Glu stands for Glucose, Xyl stands for xylose, and Man stands for Mannose. Comparative Example 1 of Table 1 shows the results for untreated samples as a control.

As a result of the experiment, it was found that constituent sugars and lignin (Examples 1, 2, 3, and 4) were reduced by treatment by the wise method than the result presented in Comparative Example 1. The content of acid-insoluble lignin decreased with treatment time, and heartwood showed a somewhat efficient lignin removal rate compared to sapwood.

Glucose showed a tendency to decrease the highest as the treatment time increased, and it was found that Arabinose and Galactose were also degraded more as the treatment time increased.

As the treatment time increased, the yield decreased, and the yield of sapwood was 56.7% and that of the heartwood by 6 hours treatment. However, it was found that the yield change between sapwood and heartwood was not large.

In general, the ratio of cellulose and hemicellulose accounts for about 70 to 80%, but it shows a lower yield, and it is estimated that if the chlorite treatment time is lengthened, carbohydrate components other than lignin are also decomposed.

Reaction time location Ara Gal Glu Xyl Man Per whole Acid insoluble lignin Yield after Wise method treatment Comparative Example 1 - Sapwood 2.0 3.7 46.5 6.3 13.9 72.3 28.7 - Heartwood 2.5 4.9 48.9 8.7 12.4 77.5 27.1 - Example 1 3 hours Sapwood 1.2 2.3 40.8 5.0 9.8 59.1 11.3 76.2% Heartwood 1.4 1.2 37.1 6.9 9.0 55.6 8.0 75.4% Example 2 4 hours Sapwood 1.0 1.7 33.7 4.4 8.1 49.0 6.5 68.6% Heartwood 1.2 1.0 37.0 6.4 7.9 53.5 4.7 71.3% Example 3 5 hours Sapwood 0.8 1.2 33.4 4.2 6.8 46.4 1.7 57.6% Heartwood 0.8 0.6 35.5 5.3 6.1 48.3 0.9 59.1% Example 4 6 hours Sapwood 0.8 1.1 32.9 4.1 6.8 45.8 1.4 56.7% Heartwood 0.6 0.4 35.0 4.4 5.5 45.9 0.1 54.9%

1.2 Relative Crystallinity and Infrared Spectroscopic Analysis of Wise-Processed Samples

Table 2 below shows the relative crystallinity of samples treated with the Wise method. Comparative Example 1 shows the relative crystallinity of the untreated material not treated by the wise method. The longer the reaction time (Examples 1, 2, 3, and 4) by the wise treatment, the higher the relative crystallinity, and the core material was higher than that of the sapwood.

In the FTIR spectrum analysis, the Wise method treatment showed a strong peak at 1,632 ㎝ ^-1 in sapwood and heartwood samples carried out for 5 hours and is confirmed to be 1,506 ㎝ ^-1 peak is reduced the longer the reaction time remove lignin effective This suggests that strong hydrogen bonds of cellulose appear (see Fig. 1).

Reaction time Relative crystallinity Sapwood Heartwood Comparative Example 1 - 46.2% 53.8% Example 1 3 hours 56.8% 57.3% Example 2 4 hours 59.7% 63.5% Example 3 5 hours 63.7% 68.3% Example 4 6 hours 63.7% 74.6%

2. Preparation of Cellulose: Treated with eutectic solvent for wood flour

2.1 Yield analysis by eutectic solvent treatment

After the sapwood and heartwood of pine were crushed to prepare wood powder, a deep eutectic solvent treatment was performed. The eutectic solvent of the present invention uses choline as an ammonium salt, chloride as a halide, and uses lactic acid, urea, and glycerol as a hydrogen bond acceptor.

The eutectic solvent of the present invention is a choline chloride/lactic acid eutectic solvent prepared by mixing choline chloride and lactic acid, choline chloride/urea eutectic solvent prepared by mixing choline chloride and urea, and choline chloride and glycerol ( Glycerine) was used as a eutectic solvent prepared by mixing choline chloride/glycerol. The mixing was prepared by mixing choline chloride and lactic acid, urea, or glycerol as a hydrogen bond acceptor at a molar ratio of 1:2, 1:6, and 1:10, respectively.

Table 3 below shows the yield obtained by the eutectic solvent treatment. The yield includes cellulose, hemicellulose and lignin.

Overall, it was found that the yield decreased as the molar ratio and treatment time of the covalent solvent composition increased. When the choline chloride/lactic acid eutectic solvent was treated, it was confirmed that the variation in yield was large. In addition, in the case of a eutectic solvent in which the mixing ratio (molar ratio) of choline chloride and lactic acid is 1:10, the yield of the core material was 50.6% when treated for 12 hours, and the acid-chlorite treatment group (Wise method treatment-Example 1, 2, 3 and 4) showed lower yields. On the other hand, it was found that the yield reduction was not large for the choline chloride/urea eutectic solvent and the choline chloride and glycerol eutectic solvent.

Eutectic solvent Mixing ratio (molar ratio) Reaction time yield Sapwood Heartwood Example 5 Choline chloride + lactic acid 1:2 2 hours 79.7% 73.6% Example 6 Choline chloride + lactic acid 1:2 4 hours 75.6% 69.7% Example 7 Choline chloride + lactic acid 1:2 6 hours 72.6% 66.8% Example 8 Choline chloride + lactic acid 1:2 12 hours 62.7% 60.0% Example 9 Choline chloride + lactic acid 1:6 2 hours 73.8% 68.5% Example 10 Choline chloride + lactic acid 1:6 4 hours 67.7% 61.8% Example 11 Choline chloride + lactic acid 1:6 6 hours 62.7% 56.8% Example 12 Choline chloride + lactic acid 1:6 12 hours 56.4% 51.8% Example 13 Choline chloride + lactic acid 1:10 2 hours 70.7% 64.9% Example 14 Choline chloride + lactic acid 1:10 4 hours 67.6% 62.3% Example 15 Choline chloride + lactic acid 1:10 6 hours 57.5% 55.7% Example 16 Choline chloride + lactic acid 1:10 12 hours 56.4% 50.6% Example 17 Choline chloride + urea 1:2 2 hours 90.6% 87.9% Example 18 Choline chloride + urea 1:2 4 hours 90.7% 84.6% Example 19 Choline chloride + urea 1:2 6 hours 90.9% 82.7% Example 20 Choline chloride + urea 1:2 12 hours 85.5% 81.2% Example 21 Choline chloride + urea 1:6 2 hours 85.6% 81.1% Example 22 Choline chloride + urea 1:6 4 hours 85.4% 81.7% Example 23 Choline chloride + urea 1:6 6 hours 86.2% 79.3% Example 24 Choline chloride + urea 1:6 12 hours 85.5% 76.2% Example 25 Choline chloride + urea 1:10 2 hours 86.4% 81.4% Example 26 Choline chloride + urea 1:10 4 hours 84.6% 82.1% Example 27 Choline chloride + urea 1:10 6 hours 86.7% 80.1% Example 28 Choline chloride + urea 1:10 12 hours 84.7% 74.6% Example 29 Choline chloride + glycerol 1:2 2 hours 92.4% 87.8% Example 30 Choline chloride + glycerol 1:2 4 hours 90.1% 84.8% Example 31 Choline chloride + glycerol 1:2 6 hours 89.7% 82.7% Example 32 Choline chloride + glycerol 1:2 12 hours 84.5% 80.5% Example 33 Choline chloride + glycerol 1:6 2 hours 83.5% 79.6% Example 34 Choline chloride + glycerol 1:6 4 hours 85.2% 78.1% Example 35 Choline chloride + glycerol 1:6 6 hours 84.4% 74.9% Example 36 Choline chloride + glycerol 1:6 12 hours 84.6% 73.0% Example 37 Choline chloride + glycerol 1:10 2 hours 85.4% 80.1% Example 38 Choline chloride + glycerol 1:10 4 hours 85.9% 80.6% Example 39 Choline chloride + glycerol 1:10 6 hours 84.8% 79.8% Example 40 Choline chloride + glycerol 1:10 12 hours 83.0% 79.0%

2.2 Analysis of chemical composition of eutectic solvent treated sample

2.2.1 Analysis of samples treated with choline chloride/lactic acid eutectic solvent

Table 4 below shows the results of analyzing the contents of sugar and lignin in Examples treated with choline chloride/lactic acid eutectic solvent.

Total sugar showed a tendency to decrease as the molar ratio and treatment time of the co-solvent composition increased. In particular, heartwood showed a higher reduction rate than sapwood. Glucose (Glucose, Glu) showed a tendency to decrease with the increase of the molar ratio of the eutectic solvent and the treatment time, and Arabinose (Ara) and galactose (Galactose, Gal) were overall It was lower than other ingredients The lignin content was not significantly changed according to the molar ratio and treatment time, and there was no significant difference between the lignin content of the untreated sample.

Choline chloride/lactic acid eutectic solvent treatment is believed to mainly decompose hemicellulose, and it is believed that an increase in the molar ratio and treatment time of the covalent solvent composition affects glucose decomposition.

ratio Reaction time location Ara Gal Glu Xyl Man Per whole Acid insoluble lignin Example 5 1:2 2 hours Sapwood 0.2 1.8 44.3 3.7 7.5 57.6 28.9 Heartwood 0.1 0.8 41.4 4.6 6.2 53.2 26.0 Example 6 1:2 4 hours Sapwood 0.2 1.3 45.8 3.2 6.7 57.2 26.8 Heartwood 0.1 0.6 37.7 3.9 5.2 47.6 26.0 Example 7 1:2 6 hours Sapwood 0.1 0.3 48.8 2.5 5.3 57.0 23.5 Heartwood 0.1 0.4 39.3 3.6 5.0 48.4 28.6 Example 8 1:2 12 hours Sapwood 0.1 0.5 36.2 2.2 4.3 43.3 27.6 Heartwood 0.1 0.2 34.8 2.7 3.5 41.3 23.0 Example 9 1:6 2 hours Sapwood 0.1 0.8 43.0 2.8 6.2 53.0 27.5 Heartwood 0.1 0.5 38.3 3.5 5.1 47.4 25.6 Example 10 1:6 4 hours Sapwood 0.1 0.4 43.2 2.5 5.4 51.7 27.1 Heartwood 0.1 0.2 36.0 3.0 4.2 43.4 22.5 Example 11 1:6 6 hours Sapwood 0.1 0.9 38.1 2.4 4.9 46.4 29.1 Heartwood 0.1 0.1 34.7 2.5 3.4 40.8 28.5 Example 12 1:6 12 hours Sapwood 0.0 0.1 39.1 2.0 3.6 44.9 21.6 Heartwood 0.0 0.1 32.6 2.3 3.1 38.2 25.9 Example 13 1:10 2 hours Sapwood 0.1 0.7 39.1 3.1 6.3 49.3 26.5 Heartwood 0.1 0.5 20.9 3.6 4.3 29.4 26.4 Example 14 1:10 4 hours Sapwood 0.1 0.6 36.3 2.7 5.5 45.1 26.6 Heartwood 0.1 0.3 22.8 3.3 4.1 30.6 25.6 Example 15 1:10 6 hours Sapwood 0.1 0.3 33.2 2.2 4.0 39.8 27.9 Heartwood 0.1 0.1 22.4 2.8 3.3 28.7 24.3 Example 16 1:10 12 hours Sapwood 0.1 0.2 34.7 2.1 3.8 40.9 27.9 Heartwood 0.0 0.1 32.6 2.5 3.3 38.6 28.3

2.2.2 Choline chloride/urea eutectic solvent treatment sample analysis

Table 5 below shows the sugar and lignin contents of samples treated with choline chloride (ChCl) / urea (Urea) eutectic solvent under various conditions.

Total sugar showed a tendency to decrease with increasing molar ratio and treatment time. In particular, heartwood showed a higher rate of decline than sapwood. Overall, it was found that the rate of change of cellulose and hemicellulose constituents by treatment with choline chloride/urea eutectic solvent was lower than that of other eutectic solvent conditions. However, the lignin content was similar to that of the untreated sample. In some conditions, the lignin content of the untreated sample was slightly higher.

ratio Reaction time location Ara Gal Glu Xyl Man Per whole Acid insoluble lignin Example 17 1:2 2 hours Sapwood 1.5 2.8 44.2 5.4 12.3 66.2 27.5 Heartwood 1.7 1.6 42.6 7.6 10.4 63.7 27.2 Example 18 1:2 4 hours Sapwood 1.5 2.9 46.2 5.6 12.4 68.7 27.1 Heartwood 1.6 1.5 40.4 7.6 10.1 61.2 26.3 Example 19 1:2 6 hours Sapwood 1.4 2.9 45.0 5.4 11.7 66.4 29.3 Heartwood 1.6 1.5 39.6 7.2 9.7 59.6 31.2 Example 20 1:2 12 hours Sapwood 1.2 2.5 42.0 5.3 10.5 61.5 28.6 Heartwood 1.4 1.2 37.6 7.5 9.7 57.3 24.9 Example 21 1:6 2 hours Sapwood 1.3 2.4 37.4 5.5 11.4 58.0 28.9 Heartwood 1.4 1.3 34.4 7.2 8.8 53.1 28.4 Example 22 1:6 4 hours Sapwood 1.2 2.3 33.6 5.3 9.8 52.3 29.7 Heartwood 1.4 1.4 38.0 7.5 10.1 58.4 29.0 Example 23 1:6 6 hours Sapwood 1.1 2.3 32.4 5.5 9.8 51.2 29.3 Heartwood 1.2 1.2 34.6 6.9 8.5 52.6 28.9 Example 24 1:6 12 hours Sapwood 1.2 2.4 42.4 5.6 10.7 62.2 31.4 Heartwood 1.2 1.2 38.8 6.8 8.9 56.9 30.2 Example 25 1:10 2 hours Sapwood 1.4 2.6 41.7 5.8 11.5 63.0 32.6 Heartwood 1.5 1.4 40.9 7.6 9.9 61.3 31.3 Example 26 1:10 4 hours Sapwood 1.2 2.5 44.9 5.5 11.1 65.4 29.8 Heartwood 1.4 1.3 37.0 7.4 9.9 57.0 28.6 Example 27 1:10 6 hours Sapwood 1.2 2.6 46.3 5.7 11.5 67.4 29.3 Heartwood 1.2 1.2 29.8 6.7 8.2 47.0 29.5 Example 28 1:10 12 hours Sapwood 1.1 2.4 44.7 5.4 10.9 64.6 30.5 Heartwood 1.0 1.0 30.9 6.2 7.5 46.7 29.0

2.2.3 Choline chloride/glycerol eutectic solvent treatment sample analysis

Table 6 below shows the sugar and lignin content of samples treated with a eutectic solvent of choline chloride (ChCl)/glycerol (Glycerine) under various conditions. Ara stands for Arabinose, Gal stands for Galactose, Glu stands for Glucose, Xyl stands for xylose, and Man stands for Mannose.

Overall, it was similar to the result of treatment with choline chloride (ChCl)/urea (Urea) eutectic solvent. However, the content of glucose showed the lowest value compared to other conditions.

ratio Reaction time location Ara Gal Glu Xyl Man Per whole Acid insoluble lignin Example 29 1:2 2 hours Sapwood 1.7 3.3 48.6 6.0 13.6 73.1 25.7 Heartwood 1.8 1.8 41.2 7.5 10.6 62.9 26.1 Example 30 1:2 4 hours Sapwood 1.5 3.0 45.5 5.6 12.4 67.9 24.3 Heartwood 1.7 1.7 39.5 7.4 10.0 60.3 25.6 Example 31 1:2 6 hours Sapwood 1.4 3.0 45.4 5.5 12.4 67.8 29.1 Heartwood 1.6 1.8 38.0 7.0 10.0 58.4 24.2 Example 32 1:2 12 hours Sapwood 1.0 2.7 42.8 5.5 11.1 63.2 27.1 Heartwood 1.4 1.6 40.1 8.2 11.2 62.6 24.4 Example 33 1:6 2 hours Sapwood 1.3 2.6 39.8 5.2 10.4 59.4 27.7 Heartwood 1.5 1.6 41.1 7.4 9.9 61.5 32.3 Example 34 1:6 4 hours Sapwood 1.3 2.6 36.2 5.4 10.6 56.0 26.3 Heartwood 1.5 1.5 35.6 7.2 10.0 55.8 26.8 Example 35 1:6 6 hours Sapwood 1.2 2.7 39.2 5.7 11.3 60.1 28.3 Heartwood 1.3 1.4 36.4 7.1 9.8 56.1 26.6 Example 36 1:6 12 hours Sapwood 1.1 2.7 40.0 5.7 11.3 60.8 28.5 Heartwood 1.0 1.2 24.3 6.4 7.7 40.6 26.7 Example 37 1:10 2 hours Sapwood 1.3 2.5 27.4 5.5 9.8 46.5 29.0 Heartwood 1.5 1.5 26.4 6.8 8.3 44.4 29.1 Example 38 1:10 4 hours Sapwood 1.3 2.5 25.9 5.7 9.8 45.2 28.7 Heartwood 1.3 1.3 23.9 6.7 8.0 41.1 28.6 Example 39 1:10 6 hours Sapwood 1.3 2.7 28.2 6.1 10.5 48.9 28.4 Heartwood 1.3 1.4 24.9 6.8 8.3 42.6 28.0 Example 40 1:10 12 hours Sapwood 1.1 2.5 26.8 5.7 9.9 45.9 28.5 Heartwood 1.2 1.3 23.6 6.5 7.7 40.2 27.8

2.3 Analysis of relative crystallinity for samples treated with eutectic solvent

The method of treating the eutectic solvent of the present invention is a chemical treatment method, and unlike a mechanical treatment method, a cellulose nanocrystal can be made. X-ray diffraction analysis was performed to analyze the degree of relative crystallization of the samples treated with each eutectic solvent. Table 7 below shows the relative crystallinity calculated from the X-ray diffraction intensity curve.

The samples treated with the eutectic solvent were found to have a cellulose I crystal structure in (1-10), (110) and (200) planes under all conditions. The eutectic solvent-treated samples did not significantly change the relative crystallinity according to the treatment conditions, and showed similar trends in sapwood and corewood.

menstruum Mixing ratio (molar ratio) Reaction time Relative crystallinity Sapwood Heartwood Example 5 Choline chloride + lactic acid 1:2 2 hours 57.3% 51.7% Example 6 Choline chloride + lactic acid 1:2 4 hours 58.2% 55.7% Example 7 Choline chloride + lactic acid 1:2 6 hours 57.7% 57.7% Example 8 Choline chloride + lactic acid 1:2 12 hours 59.7% 58.5% Example 9 Choline chloride + lactic acid 1:6 2 hours 57.9% 55.6% Example 10 Choline chloride + lactic acid 1:6 4 hours 57.4% 56.7% Example 11 Choline chloride + lactic acid 1:6 6 hours 58.3% 56.8% Example 12 Choline chloride + lactic acid 1:6 12 hours 60.9% 60.0% Example 13 Choline chloride + lactic acid 1:10 2 hours 56.1% 54.5% Example 14 Choline chloride + lactic acid 1:10 4 hours 56.5% 54.8% Example 15 Choline chloride + lactic acid 1:10 6 hours 57.7% 57.3% Example 16 Choline chloride + lactic acid 1:10 12 hours 57.9% 57.3% Example 17 Choline chloride + urea 1:2 2 hours 50.0% 52.1% Example 18 Choline chloride + urea 1:2 4 hours 52.1% 53.0% Example 19 Choline chloride + urea 1:2 6 hours 51.7% 55.1% Example 20 Choline chloride + urea 1:2 12 hours 53.2% 53.1% Example 21 Choline chloride + urea 1:6 2 hours 51.1% 48.2% Example 22 Choline chloride + urea 1:6 4 hours 50.4% 51.4% Example 23 Choline chloride + urea 1:6 6 hours 50.0% 50.6% Example 24 Choline chloride + urea 1:6 12 hours 51.8% 51.9% Example 25 Choline chloride + urea 1:10 2 hours 53.2% 52.6% Example 26 Choline chloride + urea 1:10 4 hours 50.0% 52.7% Example 27 Choline chloride + urea 1:10 6 hours 52.8% 51.4% Example 28 Choline chloride + urea 1:10 12 hours 50.8% 52.5% Example 29 Choline chloride + glycerol 1:2 2 hours 52.5% 51.6% Example 30 Choline chloride + glycerol 1:2 4 hours 53.0% 52.5% Example 31 Choline chloride + glycerol 1:2 6 hours 53.1% 52.9% Example 32 Choline chloride + glycerol 1:2 12 hours 53.3% 53.1% Example 33 Choline chloride + glycerol 1:6 2 hours 51.4% 52.2% Example 34 Choline chloride + glycerol 1:6 4 hours 50.0% 51.3% Example 35 Choline chloride + glycerol 1:6 6 hours 52.5% 52.6% Example 36 Choline chloride + glycerol 1:6 12 hours 51.0% 51.6% Example 37 Choline chloride + glycerol 1:10 2 hours 51.4% 52.4% Example 38 Choline chloride + glycerol 1:10 4 hours 50.5% 50.0% Example 39 Choline chloride + glycerol 1:10 6 hours 50.6% 51.0% Example 40 Choline chloride + glycerol 1:10 12 hours 50.7% 50.6%

2.4 Infrared spectral analysis of eutectic solvent-treated samples

In order to determine the degree of change of a specific component due to the eutectic solvent treatment of the present invention, an attenuated total reflectance Fourier transform infrared (ATR-FTIR) experiment was performed and analyzed.

2 to 4 show the ATR-FTIR spectra of the example subjected to the eutectic solvent treatment. Spectrum of all samples showed prominent absorbance regions at 2,800 to 3,500 cm ^-1 and 800 to 1,700 cm ^-1 . The broad absorbance region appearing in the range of 3,300 to 3,500 cm ^-1 is a peak due to OH stretching of a hydroxyl group. The peak due to the hydroxyl group is a peak due to the hydroxyl group of cellulose, hemicellulose, and lignin. The absorbance by CH stretching is observed in the range of 2,800 to 2,900 cm ^-1 , and the absorbance is due to the crystal region of cellulose. The absorption peak at 1,632 cm ^-1 is due to the presence of a strong cellulose-water interaction, and the absorption peak at 1,730 cm ^-1 (C=O stretching) is related to the acetyl or uron ester group of hemicellulose. In addition, the absorption band (CC stretching) at 1,506 ㎝ ^-1 is a peak due to aromatic skeletal vibration in lignin, and the 1,430 ㎝ ^-1 absorption peak (CH ₂ bending vibration) is related to the crystallinity of cellulose. The 1,317 cm ^-1 absorption peak (CH ₂ wagging) is a peak due to intermolecular hydrogen bonds, and the absorption peaks at 1,053 cm ^-1 and 1,160 cm ^-1 (COC asymmetric valence vibration) are related to the pyranose ring skeleton. Characteristic, and the peak (CH rocking vibration) located at 895 cm ^-1 is related to the β-glycoside bond vibration.

As a result of ATR-FTI spectrum analysis, the eutectic solvent as a whole showed no noticeable change in absorption peak due to the decrease in specific components.

3. Preparation of cellulose nanofibers

3.1 Cellulose nanofiber manufacturing method

Nanocellulose was prepared based on the results of the Wise method and eutectic solvent treatment for wood flour. The wood flour treated by the Wise method is lignin removed. When the lignin is removed, nanospaces are formed between the cellulose molecular aggregates. The presence of lignin between the celluloses is a major cause of making mechanical pulverization difficult for producing nanocelluloses. Therefore, in the present invention, chemical treatment using a eutectic solvent was performed in order to effectively prepare nanocellulose, to remove lignin between cellulose molecular aggregates and to alleviate hydrogen bonds between cellulose molecules.

The nanocellulose manufacturing method of the present invention comprises the steps of preparing wood flour; Preparing cellulose from which lignin has been removed by performing a Wise method treatment using chlorite and acetic acid on the wood flour; Treating the cellulose with a eutectic solvent for producing nanocellulose; And pulverizing the cellulose treated with the eutectic solvent to produce nanocellulose.

The wood flour was used having a size of 40-80 mesh. The Wise method treatment was carried out using sodium chlorite/acetic acid, 2 g of a degreasing sample was added to 150 ml of distilled water, 0.2 g of sodium chlorite and 0.2 ml of acetic acid were added, followed by stirring at 80°C. At this time, 0.2 g of sodium chlorite and 0.2 ml of acetic acid were added once per hour, followed by 3 hours or 6 hours.

The content of acid-insoluble lignin was measured by the Klason lignin assay. The sugar composition analysis was performed with the filtrate filtered after performing the second hydrolysis in the Klason lignin content measurement. The degree of crystallinity of cellulose was analyzed by X-ray diffraction method.

As the eutectic solvent, a eutectic solvent prepared by mixing choline chloride and a hydrogen bond receptor including lactic acid, urea, and glycerol in a molar ratio of 1:6 was used for a sample treated for 3 hours or 6 hours by the Wise method. It was carried out by stirring at 400 rpm at 100 ℃.

Mechanical decomposition for preparing the nanocellulose was performed for 5 minutes at 22,000 rpm using an experimental high-speed blender.

The experiment was conducted on the basis of the results judged as optimal conditions from the experimental examples, and the pine corewood was judged somewhat more efficiently than the sapwood, so the corewood was analyzed.

3.2 Characteristics of nanocellulose

5 to 7 are transmission electron microscopy of nanocellulose prepared by treating each eutectic solvent for 6 hours after treatment by the Wise method for 3 or 6 hours and grinding for 5 minutes at high speed using a blender. microscope). As a result of observation, cellulose nanofibers having a width of less than 10 nm were confirmed in samples prepared by treating all types of eutectic solvents.

With respect to the observation result of the transmission electron microscope, the width of the cellulose nanofibers was calculated using the image J program. Table 8 below shows the calculation results.

Wise method processing time Eutectic solvent (molar ratio 1:6) Fiber width of cellulose nanofibers Kinds Reaction time Example 41 3hr Choline chloride + lactic acid 6 hours 7.6±2.9 nm Example 42 6hr Choline chloride + lactic acid 6 hours 4.7±1.1 nm Example 43 3hr Choline chloride + urea 6 hours 4.3±0.3 nm Example 44 6hr Choline chloride + urea 6 hours 5.1±0.3 nm Example 45 3hr Choline chloride + glycerol 6 hours 2.1±0.8 nm Example 46 6hr Choline chloride + glycerol 6 hours 5.4±0.8 nm

In the case of Examples 43 and 44 using choline chloride/urea eutectic solvent, it was confirmed that cellulose nanofibers having a similar fiber width could be prepared regardless of the wise method treatment time.

In the case of the example using the choline chloride/glycerol eutectic solvent, it was confirmed that cellulose nanofibers having a small width were produced when the Wise method treatment time was short.

The smallest width was prepared by treating with the Wise method for 3 hours to remove lignin and then treating it with a choline chloride/glycerol (1:6) eutectic solvent, and the width of the cellulose nanofibers was 2.1±0.8 nm.

The specific embodiments described herein are meant to represent preferred embodiments or examples of the present invention, and the scope of the present invention is not limited thereby. It will be apparent to those skilled in the art that variations and other uses of the invention do not depart from the scope of the invention described in the claims of this specification.

Claims (5)

In the eutectic solvent for producing nanocellulose (deep eutectic solvent),
A salt of choline having the formula:
[Chemical Formula]

(The X is chlorine (Cl).) and a hydrogen bond donor, glycerol is mixed in a molar ratio of 1:6, a eutectic solvent for producing nanocellulose.
delete delete Preparing cellulose from which lignin has been removed by treating the powdered wood with a salt of chlorous acid and acetic acid for 3 hours;
Mixing the cellulose with a eutectic solvent for producing nanocellulose, stirring at 100° C. at a speed of 400 rpm, and treating for 6 hours; And
Adjusting the concentration of the cellulose treated with the eutectic solvent for producing nanocellulose to be 0.5% and pulverizing for 5 minutes at 22,000 rpm using a blender to prepare nanocellulose;
As a method for producing nanocellulose comprising a,
The eutectic solvent for preparing nanocellulose is a salt of choline having the following formula:
[Chemical Formula]

(The X is chlorine (Cl).) and glycerol, a hydrogen bond donor, are mixed in a molar ratio of 1:6.
The nanocellulose manufactured by the above manufacturing method has a width of 2.1 ± 0.8 nm.
delete

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