KR101702576B1 - Method of preparing a nanocellulose - Google Patents

Abstract

The method of producing nanocellulose of the present invention comprises the steps of: (a) irradiating cellulose-based materials with radiation; (b) mixing a radiation-irradiated cellulose-based material and an aqueous acid solution to prepare a suspension of nanocellulose; And (c) separating the nanocellulose from the suspension. The manufacturing method is an economical process because it shortens the manufacturing time and improves the yield compared to the conventional manufacturing method.

Description

[0001] METHOD OF PREPARING A NANOCELLULOSE [0002]

The present invention relates to a method for producing a nanocellulose from a cellulose-based material through an extraction method using radiation.

Nano-cellulose is an organic polymer material having excellent tensile strength and is an environmentally friendly regeneration resource since it is obtained from natural materials such as various kinds of wood and plant resources. The manufacturing cost of nanocellulose is recognized as being considerably high, and when considering from the viewpoint of yield and mass production, many research and development are required until the industrialization stage.

Furthermore, research to find optimal conditions for the production of nanocellulose according to the inherent characteristics of various natural materials should be accompanied. For this purpose, the acid hydrolysis treatment of cellulose is an essential step in the extraction of nanocellulose, and it is an object of acid hydrolysis of the amorphous region (amorphous region) of the cellulose structure to isolate the crystalline region having acid resistance as compared with the amorphous region .

At this time, the degree of crystallization, degree of polymerization and mechanical properties of nanocellulose differ depending on the concentration of acid used for acid hydrolysis, temperature and time.

1. Hanieh, K. et al., "Effects of hydrolysis conditions on the morphology, crystallinity, and thermal stability of cellulose nanocrystals extracted from kenaf bast fibers," Cellulose, Vol. 19, pp. 855-866 (2012). 2. Mark, D. et al., "Electron Beam Irradiation of Cellulose," Radiation Physics and Chemistry, Vol. 78, pp. 539-542 (2009).

It is an object of the present invention to provide a method for producing nanocellulose from a cellulose-based material, which comprises irradiating a nanocellulose with a nanocellulose capable of shortening the time required for manufacturing the nanocellulose, And to provide an effective method for producing the same.

The method of manufacturing nanocellulose according to an embodiment of the present invention includes the steps of: (a) irradiating cellulose-based materials with radiation; (b) mixing a radiation-irradiated cellulose-based material and an aqueous acid solution to prepare a suspension of nanocellulose; And (c) separating the nanocellulose from the suspension.

The step (b) comprises the steps of: preparing a mixture comprising the cellulose-based material irradiated with the radiation and an aqueous acid solution; And subjecting the mixture to a hydrolysis reaction by stirring to produce a nanocellulose suspension.

The acid aqueous solution may be any one selected from the group consisting of sulfuric acid, nitric acid, hydrochloric acid, and combinations thereof.

If the concentration of the aqueous acid solution to be mixed in step (b) is 65% or more, the reaction time may be less than 90 minutes.

The concentration of the aqueous acid solution mixed in step (b) may be less than 65%.

The step (b) may be carried out at a temperature of 20 to 100 ° C.

In the step (b), 0.1 to 20 parts by weight of the cellulose-based material may be mixed based on 100 parts by weight of the aqueous acid solution.

(A ') before the step (a'), and the step (a ') may further include a step of treating the cellulosic material so that the content of cellulose contained in the cellulosic material is 90% .

In the step (a), the irradiation dose of the irradiated radiation may be 10 to 300 kGy.

Said step (a) can increase the solubility of the amorphous region of cellulose contained in the cellulose-based material to the acid in the irradiation of radiation.

The radiation may include any one selected from the group consisting of alpha rays, beta rays, gamma rays, electron beams, ion beams, ultraviolet rays, X-rays, plasma, neutron rays, and combinations thereof.

The cellulosic material may include a cellulosic biomass.

The cellulosic biomass may include any one selected from the group consisting of a fiber-based, wood-based, seaweed-based, and combinations thereof.

The cellulosic material may include any one selected from the group consisting of powders, pellets, sheets, and combinations thereof.

The separation in step (c) may be performed by a method including any one selected from the group consisting of filtration, centrifugation, precipitation, recrystallization, and combinations thereof.

The step (c) may include an ultrasonic treatment.

The separated nanocellulose may have a particle size of 100 to 1500 nm.

The yield of the nanocellulose may be 25 to 40%.

The present invention provides a method for producing nanocellulose, and the present invention will be described in more detail below.

A method of manufacturing a nanocellulose according to an embodiment of the present invention includes the steps of: (a) irradiating a cellulose-based material with radiation; (b) mixing a radiation-irradiated cellulose-based material and an aqueous acid solution to prepare a suspension of nanocellulose; And (c) separating the nanocellulose from the suspension.

The step (a) may be a step of irradiating the cellulosic material with radiation using a radiation irradiation apparatus.

The cellulosic material refers to a material containing celluloses including both crystalline and amorphous regions, and may include cellulose-based biomass such as wood, pulp, and the like.

The cellulosic biomass may be a primary or secondary biomass, for example, a fibrous biomass, a woody biomass, a seaweed biomass, or a mixture thereof. If the material contains cellulose, Can be applied as a cellulose-based material.

When the cellulose-based material is irradiated with radiation, the solubility of the amorphous region of the cellulose in the acid in the acid can be increased. That is, the radiation can be selectively irradiated to the amorphous region, and the irradiated radiation physically damages the amorphous region of the cellulose, thereby weakening the glucosidic binding force between the cellulose chains in the amorphous region, Can be increased.

The form of the cellulose-based material is not particularly limited, but may be in the form of, for example, powder, pellet or sheet. When the cellulose-based material is a powder, the radiation irradiated due to the surface-increasing effect can be uniformly irradiated onto the entire cellulose-based material, thereby increasing the yield of finally separated nanocellulose. In the case of pellets, And storage can be facilitated.

As the radiation, for example, an alpha ray, a beta ray, a gamma ray, an electron ray, an ion beam, an ultraviolet ray, an X ray, a plasma, a neutron ray, or a combination thereof may be applied. There is no particular limitation on the kind of the radiation to be irradiated, and it can be applied as long as the bonding force of the amorphous region of the cellulose is weakened by the irradiation of the radiation to increase the solubility to the acid.

The dose of the radiation may be 10 to 300 kGy, preferably 10 to 200 kGy, more preferably 50 to 200 kGy. If the dose of radiation is less than 10 kGy, the above-mentioned effects to be obtained by irradiation can not be obtained. If the irradiation dose exceeds 300 kGy, not only the amorphous region but also the crystalline region of cellulose are physically damaged Which may increase the solubility of the crystal region in the acid, and thus the yield of finally separated nanocellulose may be lowered.

The method of manufacturing the nanocellulose may further include a step of pre-treating the cellulose-based material (a ') before the step (a), wherein the step (a') comprises: To 90% or more, preferably 94 to 98%.

By performing the pretreatment for increasing the purity of the cellulose-based material in the step (a '), it is possible to improve the yield of finally separated nanocellulose, and it is possible to improve the yield of the finally separated nanocellulose, Can be saved.

Wherein the step (b) comprises: preparing a mixture comprising the cellulose-based material irradiated with the radiation and an aqueous acid solution; And subjecting the mixture to a hydrolysis reaction by stirring to produce a nanocellulose suspension.

The cellulose-based material may be mixed in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the aqueous acid solution.

If the amount of the cellulose-based material is less than 0.1 part by weight based on 100 parts by weight of the aqueous acid solution, excessive use of the acid may occur, and an excess amount of acid may cause corrosion of the apparatus or damage to the finally separated nanocellulose , The yield of nanocellulose may be lowered. On the other hand, if it exceeds 20 parts by weight, the acid necessary for the hydrolysis reaction may be insufficient to complete the reaction, thereby lowering the yield of the nanocellulose, deteriorating the physical properties of the finally isolated nanocellulose, For example, the particle size of nanocellulose may be large.

The acid aqueous solution may include any one selected from the group consisting of sulfuric acid, nitric acid, hydrochloric acid, and combinations thereof. Any aqueous acid solution generally used in the art can be used without limitation, Or strong acids.

The acid aqueous solution to be mixed in the step (b) may be one in which acid is diluted in an aqueous solution, and both high concentration and low concentration acid can be applied, so that the concentration of the aqueous acid solution can be more freely determined in the production of nanocellulose.

For example, when the concentration of the acid aqueous solution is 65% or more, the acid hydrolysis reaction time of the step (b) may be less than 90 minutes, preferably 60 minutes or less, more preferably 30 minutes or less, There may be no reduction in yield. However, if the reaction time is not taken into consideration, the concentration of the acid aqueous solution may be less than 65%.

In the case where the concentration of the acid aqueous solution is high at 65% or more, the time required for manufacturing nanocellulose can be significantly shortened due to irradiation of radiation, and the production of nanocellulose, which can be manufactured per unit time, Can be greatly increased.

The hydrolysis reaction may be a reaction in which an acid is added to selectively decompose an amorphous region of cellulose to separate it from a crystal region, and the reaction may be performed at a temperature of 20 to 100 ° C, preferably 25 to 95 ° C. In such a temperature range, vaporization of the mixture during the acid hydrolysis reaction can be prevented, and at least energy necessary for the hydrolysis reaction can be supplied.

The physical properties and yield of the nanocellulose prepared from the cellulose-based material are determined depending on the kind of the acid used in the acid hydrolysis reaction, the concentration, the reaction temperature, the treatment time, etc. Therefore, The method of producing nanocellulose of the present invention which can shorten the time and maintain and improve the yield can contribute to the improvement of the productivity of the nanocellulose having excellent physical properties.

The separation of the step (c) may be a step of separating the nanocellulose, that is, the cellulose composed only of the crystal region, the acid, and other substances, from the suspension in which the hydrolysis reaction has been completed in the step (b) .

As the separation method, for example, filtration, centrifugation, precipitation, recrystallization, or a combination thereof may be applied and may include ultrasonic treatment, and the ultrasonic treatment may be performed using an ultrasonic washing machine.

The finally separated nanocellulose may have a yield of 25 to 40%, preferably 30 to 35%. This is an improved numerical value as compared with that produced by the conventional method, and it is also possible to obtain an effect that the time can be greatly shortened by irradiating the radiation and using a concentrated aqueous acid solution.

The finally separated nanocellulose may have a particle size of 100 to 1500 nm, preferably 100 to 1000 nm. The particle size range is a range of particle sizes that can be obtained when a hydrolysis reaction is carried out for a long period of time by a conventional method or when a considerably high concentration of an acid aqueous solution is used. In the present invention, even if a high concentration aqueous solution of an acid is used, The nanocellulose having the above-mentioned particle size range can be produced, and the yield of the nanocellulose can be improved.

INDUSTRIAL APPLICABILITY By selectively irradiating the amorphous region of the cellulose contained in the cellulosic material with the radiation, the method of the present invention can exhibit an improved yield over a yield that can be obtained by the conventional method of producing a nanocellulose, Since the manufacturing time can be greatly shortened, it can be very effective in terms of time and economy.

FIG. 1 is a graph showing the particle size distribution of nanocellulose by irradiation dose according to an embodiment of the present invention.
2 is a graph showing the particle size distribution of nanocellulose by time according to an embodiment of the present invention.
FIG. 3 is a graph showing the particle size distribution of nanocellulose over time according to the conventional method.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Example  1: Depending on the dose of radiation Of nanocellulose  Produce

As the cellulose-based material, Avicel PH-101 from Aldrich, rice straw, kenaf core and wood were directly extracted, and the content of cellulose contained in the cellulose-based material was 94 to 98%.

1) Investigation of radiation

40 g of the pretreated high-purity cellulose material was irradiated with an electron beam at an irradiation intensity of 25 kGy / scan using a linear electron beam accelerator device (ELV-8-type electron beam accelerator from EBtech) as the irradiation device. The irradiation was carried out such that the irradiation dose was finally 50, 100, 200 and 300 kGy, respectively, and these were designated as Examples 1-1, 1-2, 1-3 and 1-4, respectively.

2) Acid hydrolysis reaction

190 g of an aqueous acid solution having a concentration of 65% in which sulfuric acid and water were mixed at a ratio of 65 to 35 was preheated at 45 占 폚 and mixed with 10 g of the cellulose material of Examples 1-1 to 1-4 irradiated with the electron beam, After the decomposition reaction was allowed to proceed for 30 minutes, the reaction was stopped with cooled distilled water to obtain a nanocellulose suspension.

3) Nano-cellulose  Separation of suspension

The hydrolysis-treated nanocellulose suspension of Examples 1-1 to 1-4 was centrifuged in a centrifuge at 0 ° C for 10 minutes, and then the sulfate was separated using a cellulose acetate dialysis membrane for 48 hours. Then, it was dispersed in an ultrasonic washing machine for 15 minutes and then dried in a freeze dryer for 48 hours to obtain nano-cellulose, and its particle size distribution is shown in Fig. At this time, the yields were 36% for Example 1-1, 33% for Examples 1-2, 21% for Examples 1-3, and 6% for Examples 1-4.

Example  2: Depending on acid hydrolysis reaction time Of nanocellulose  Produce

The irradiation dose of the final irradiation was fixed to 50 kGy and the hydrolysis reaction time was 30, 60, 90 and 120 minutes, respectively. The results are shown in Table 2-1 (the same conditions as in Example 1-1), 2 -2, 2-3, and 2-4, the nanocellulose was prepared in the same manner as in Example 1, and the particle size distribution of the nanocellulose was shown in FIG. At this time, the yields were 36% for Example 2-1, 33% for Example 2-2, 29% for Example 2-3, and 23% for Example 2-4.

Comparative Example  1: without irradiation Of nanocellulose  Produce

Nano-cellulose was produced in the same manner as in Example 2 except that no radiation was irradiated, and the hydrolysis reaction times of 30, 60, 90, and 120 minutes were compared with those of Comparative Examples 1-1, 1-2, 1-3, 1-4. The particle size distribution of the nanocellulose obtained at a yield of about 20 to 25% is shown in Fig.

Analysis

Referring to FIGS. 1 and 3, when the hydrolysis reaction was carried out for 30 minutes, the nanocellulose of Example 1-1, which was irradiated with 50 kGy of radiation, had a particle size distribution of about 70 to 700 nm, In the case of Comparative Example 1-1 in which the hydrolysis reaction was carried out for 30 minutes without irradiation, it was about 1500 to 2700 nm. In Comparative Example 1-3 in which the reaction time was 90 minutes, the particle size distribution was about 470 to 1350 nm , It was confirmed that the particle size distribution was significantly larger than that in Example 1-1.

The particle size distribution of the nanocells of Examples 2-1 to 2-4 shown in FIG. 2 is also similar to the particle size distribution of the nanocells of Examples 1-1 to 1-4 shown in FIG. 1, When the hydrolysis reaction proceeded, the particle size distribution of nanocellulose in Example 2-2 irradiated with 50 kGy of radiation was 60 to 500 nm, but in Comparative Example 1-2 irradiated with no radiation, 840 to 1700 nm, The reaction was carried out for 60 minutes. However, it was confirmed that the difference in particle size distribution of the obtained nanocellulose was remarkable, and at the same time, the nanocellulose having a desired particle size could be obtained in a short time.

It was confirmed from this that, when the nanocellulose was produced through the manufacturing method of the present invention for irradiating the radiation, the manufacturing time could be shortened by about 1/3, and at the same time, It was confirmed that the particle size distribution was narrow in comparison with the case where the particle size distribution was not observed.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of the right.

Claims (18)

(a ') pre-treating the cellulose-based material so that the content of cellulose contained in any one of the cellulose-based materials selected from the group consisting of a fibrous, woody, seaweed, and combinations thereof is 95% or more;
(a) selectively irradiating only the amorphous region of the crystalline region and the amorphous region included in the cellulose-based material;
(b) mixing the aqueous solution of sulfuric acid having a concentration of 65% or more based on the mass of the cellulose-based substance and the solution irradiated with the radiation, and hydrolyzing the cellulose-based material at a temperature of 45 to 50 ° C for 30 minutes or less, Preparing a suspension; And
(c) separating the nanocellulose from the suspension,
The step of irradiating the radiation comprises:
Characterized in that the dose of radiation is 10 to 300 kGy,
Wherein the yield of the nanocellulose is 25 to 40%. delete delete delete delete delete The method according to claim 1,
Wherein 0.1 to 20 parts by weight of the cellulose-based material is mixed with 100 parts by weight of the aqueous solution of sulfuric acid in the step (b). delete delete delete The method according to claim 1,
Wherein the radiation comprises any one selected from the group consisting of alpha rays, beta rays, gamma rays, electron beams, ion beams, ultraviolet rays, X-rays, plasma, neutron rays, and combinations thereof. delete delete The method according to claim 1,
Wherein the cellulose-based material comprises any one selected from the group consisting of powders, pellets, sheets, and combinations thereof. The method according to claim 1,
Wherein the separation in step (c) is performed by a method comprising any one selected from the group consisting of filtration, centrifugation, precipitation, recrystallization, and combinations thereof. The method according to claim 1,
Wherein said step (c) comprises ultrasonic treatment. The method according to claim 1,
Wherein the separated nanocellulose has a particle size of 100 to 1500 nm. delete

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