KR101725079B1 - Method of preparing a nanocellulose - Google Patents

Abstract

The method for producing a nanocellulose according to the present invention comprises the steps of: (a) irradiating cellulose-based materials with radiation; And (b) the cellulose-based material irradiated with the radiation is pulverized. By irradiating the above-mentioned radiation, the manufacturing method can significantly reduce the time required for the pulverization process compared with the conventional manufacturing method, thereby reducing the power consumption, which is economical.

Description

[0001] METHOD OF PREPARING A NANOCELLULOSE [0002]

The present invention relates to a method for producing nanocellulose from a cellulose-based material through irradiation and pulverization processes of 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 .

Such a method using acid hydrolysis has a danger of handling during processing due to the use of a high concentration of sulfuric acid and is highly corrosive and involves limitations of the reactor or the process and causes environmental problems such as post- .

In order to improve this, there is a method of producing nanocellulose using a mechanical method, but it is inefficient in terms of energy consumption, so that it is difficult to put it into practical use.

1. Abe, K. et al., "Obtaining cellulose nanofibers with a uniform width of 15 nm from wood," Biomacromolecules, Vol.8, pp. 3276-3278 (2007). 2. Zimmermann, T. et al., "Properties of nanofibrillated cellulose from different raw materials and its reinforcement potential", Carbohydrate polymers, Vol. 79, pp. 1086-1093 (2010).

It is an object of the present invention to provide a method of manufacturing nanocellulose from a cellulose material through a mechanical grinding process by using radiation to minimize energy consumption and to produce nano- So as to provide an effective manufacturing method.

The method of manufacturing nanocellulose according to an embodiment of the present invention includes the steps of: (a) irradiating cellulose-based materials with radiation; And (b) the cellulose-based material irradiated with the radiation is pulverized.

(A ') immediately before or immediately after the step (a), and the step (a') may further comprise a step of subjecting the cellulosic material to a pretreatment of a cellulosic material having a cellulosic content of 90% . ≪ / RTI >

In the step (a), the size of the produced nanocellulose can be controlled by adjusting the dose of radiation.

In step (a), the dose of radiation may be 10 to 500 kGy.

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 step (b) may be carried out by a mechanical grinding process, and the grinding process may include any one selected from the group consisting of a milling process, a grinding process, a microfluidic process, a homogenizer process, and a combination thereof can do.

The milling of step (b) may be carried out for 10 to 60 minutes.

Separating the nanocellulose from the pulverized cellulose-based material after the step (b), and separating the nanocellulose from the pulverized cellulose-based material by centrifugation, Lt; / RTI >

The cellulosic material may comprise 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, solutions, and combinations thereof.

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

The method of manufacturing nanocellulose according to an embodiment of the present invention includes the steps of: (a) irradiating cellulose-based materials with radiation; And (b) the cellulose-based material irradiated with the radiation is pulverized.

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 physical interaction existing between the amorphous region and the crystalline region coexisting in the cellulose-based material, for example, the binding force, can be weakened. Time can be significantly shortened.

In the production of nanofibers through mechanical pulverization, the role of radiation may be twofold. First, it is possible to minimize the number of repetitive mechanical grinding cycles. Generally, when nanocellulose is obtained through mechanical pulverization, the pulverization process should be repeated 30 to 50 times. In the case of irradiation, nanocellulose can be produced by about 2 repeated pulverization processes.

The second is that the radiation reduces the crystallinity of the cellulose. That is, it is possible to control the particle size of the produced nanocellulose by controlling the irradiation dose of the radiation. The number of ether bonds exposed on the surface of the cellulose and the regular and strongly arranged layers of the inner cellulosic laminate are combined Lt; RTI ID = 0.0 > hydrogen bond. ≪ / RTI >

When the irradiation dose of the radiation is increased, the ether bonds and the hydrogen bonds are weakened or dissociated and the ether bonds are dissociated, whereby the outer surface of the cellulose surface is removed to form the nanofibers, and the hydrogen bonds between the laminations are weakened The network structure between the crystalline region and the amorphous region can be released, and nanocellulose having a small particle size can be produced.

On the other hand, when the dose of radiation is reduced, nanocellulose having a large particle size can be produced by minimizing the influence on the inside of cellulose.

The form of the cellulose-based material is not particularly limited, but may be a powdery or pellet-like solid state, and may be in a liquid state such as a solution or suspension containing a cellulosic-based substance.

When the cellulose-based material is in the form of a powder, for example, the radiation irradiated due to the surface-increasing effect can be uniformly irradiated onto the whole of the cellulose-based material, thereby increasing the yield of finally separated nanocellulose. The supply and storage can be facilitated. In addition, when the cellulose-based material is a solution or suspension in a liquid state, for example, pulverization can be easily performed in the pulverization process, and damage to the produced nanocellulose may be small.

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. The kind of radiation to be irradiated is not particularly limited and may be applied as long as the binding force between the amorphous region and the crystalline region of the cellulose is weakened by the irradiation of the radiation to facilitate the pulverization.

The irradiation dose of the radiation may be 10 to 500 kGy, preferably 50 to 300 kGy, more preferably 50 to 200 kGy. When the dose of radiation is less than 10 kGy, the above-mentioned effects to be obtained by irradiation of radiation can not be obtained. When the dose of radiation exceeds 500 kGy, only the binding force between the amorphous region and the crystalline region of cellulose is weakened However, it may greatly affect the crystal region, which may result in damage such as a part of the crystal region being transformed into an amorphous state, and the yield of finally separated nanocellulose may be lowered.

The method of manufacturing the nanocellulose may further comprise the step of pre-treating the cellulose-based material (a ') before or after 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.

The step (b) may be a step of pulverizing the cellulose-based material irradiated with the radiation using a mechanical grinding process, and the mechanical grinding process may be a milling process, a grinding process, a microfluidic process, A homogenizer process, or a combination thereof may be used. However, the present invention is not limited thereto, and any of the mechanical milling processes conventionally used for producing nano-cellulose may be applied.

For example, when the milling process is milling, it may be ball milling. In this case, the blending ratio of the ball and the sample powder is preferably set to about 1:10 to 1:20, Suitably the size is about 0.1 to 0.2 mm, and the ratio of the larger to the smaller can be about 1: 1 to 1: 2.

The pulverization process may be repeatedly performed, and the time required for the pulverization process may be 10 to 60 minutes. Nano-cellulose can be prepared for at least 10 minutes to perform a pulverizing process that repeats a specific number of times, and if it is carried out for a maximum of 60 minutes, it is possible to obtain better properties than nanocellulose prepared by conventional methods.

Generally, the pulverization process should be performed for a considerably long time of at least 5 hours when producing the nanocellulose using the conventional mechanical method. However, even if the pulverization process is performed for about 20 minutes in the case of the present invention, It is possible to produce nanocellulose having a size equal to or smaller than that of the nanocellulose.

Further, in the case of irradiating with radiation, the size of the nanocellulose can be controlled by adjusting the amount of irradiation, so that the time of the pulverization process can be greatly shortened compared with the conventional case where the size is controlled by simply lengthening the time It is possible to obtain the nano-cellulose having physical properties, and it can be economically advantageous because the time is shortened.

Processes having mechanical action such as a pulverizing process may consume a lot of electrical energy and cause a number of troubles such as noise and dust, and it may be desirable to complete the process in as short a time as possible. That is, if the time required for the pulverization process is shortened according to the irradiation of the radiation as described above, it is possible to solve the accompanying problems that occur together with the reduction of the energy. Concretely, the consumption of electric energy per hour , It can be seen that energy savings of about 30% or more can be obtained when compared with the conventional case.

As described above, when the irradiation of the radiation is preceded by the mechanical grinding process, economical effects such as energy saving and shortening of time can be great. Therefore, in case of applying to the actual industry, A significant energy, cost and time saving effect can be obtained.

(C) separating the nanocellulose composed of only the crystalline region in the pulverized cellulose-based material, and the separating method may be applied to various separation methods, But not limited to, centrifugal separator, membrane dialysis, washing, or a combination thereof.

For example, with the above separation method, when centrifugation is applied, it can be separated using about 10% aqueous acid solution, and when cleaning is applied, a urea / lithium hydroxide aqueous solution or 1 to 3% Hydrochloric acid aqueous solution, or may be separated by applying a high-temperature and / or high-pressure reactor.

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 applying a mechanical grinding process.

The finally separated nanocellulose may have a particle size of 1500 nm or less, preferably 1000 nm or less, more preferably 300 nm or less. 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.

The method of producing nanocellulose according to the present invention reduces the physical interaction between the amorphous region and the crystalline region by irradiating the cellulose-based material with radiation, thereby shortening the time required for the pulverization process more than the conventional manufacturing method And thus energy consumption can also be reduced, which can be very effective in terms of time and economy. Furthermore, the size of the nanocellulose can be controlled by adjusting the irradiation dose of radiation, so that productivity can be predicted as compared with controlling through the grinding time.

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 according to an embodiment of the present invention.
3 is a graph showing the particle size distribution of nanocellulose by the pulverization time without irradiation of radiation.
FIG. 4 is a graph showing the pulverization time at which nanocellulose similar to the particle size distribution of the nanocellulose according to FIG. 2 was produced without irradiation of radiation.
FIG. 5 is a graph illustrating power consumption of a grinding process according to an embodiment of the present invention.

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: Measured according to the irradiation dose adjustment Of nanocellulose  Granularity

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

1) Investigation of radiation

40 g of the powdery cellulose-based 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 of EBtech) as the irradiation device. After the irradiation, a high purity cellulose of 98% or more was obtained through a chemical pretreatment process. At this time, the ultimate irradiation dose was 50, 100, 200 and 300 kGy, respectively.

2) Ball milling  Crushing through

The ball was made of a titanium ball having a diameter of 0.1 mm and a diameter of 0.2 mm. The ratio of the balls was adjusted to about 1: 1, and the ratio of the balls to the powdery cellulose-based material was about 1:20 All the cellulose-based materials irradiated with different amounts of radiation were subjected to ball milling for 40 minutes.

3) Of nanocellulose  detach

The powder mixed with the amorphous region and the crystalline region of the ball milled cellulose was separated through a separation membrane using a 10% hydrochloric acid aqueous solution, the solid state nano-cellulose was separated through a centrifugal separator, and finally, about 30 to 35 %, And the particle size distribution of the nanocellulose was shown in Fig.

Referring to FIG. 1, it was confirmed that nanocrystalline particles having different particle sizes were prepared even though the pulverization process was performed for the same time as the irradiation dose was adjusted to 50 to 300 kGy. When irradiated with 300 kGy, about 274 nm Of the nanocellulose can be produced. It was confirmed that the particle size of the nanocellulose can be controlled by adjusting the dose of radiation.

Example  2: Measured according to the control of mechanical grinding time Of nanocellulose  Granularity

The nanocellulose was prepared in the same manner as in Example 1, except that the final irradiation dose was fixed at 300 kGy and the milling time was 10, 20, 30 and 40 minutes. , And the nanocellulose was obtained in the same yield as in Example 1. The particle size distribution of the nanocellulose was shown in Fig.

Comparative Example : Prepared without irradiation of radiation Of nanocellulose  Granularity

1) According to grinding time fixed Of nanocellulose  Granularity

The nanoclusters were prepared under the same conditions as in Example 2, except that no radiation was irradiated, with the same milling time, and the particle size distribution is shown in Fig.

2) Of nanocellulose  Grinding time due to particle size fixation

The nanocellulose was produced under the same conditions as in Example 2 except that no radiation was irradiated. Unlike the comparative example 1, until the nanocellulose had a particle size distribution similar to that produced in Example 2, To prepare nano-cellulose. The particle size distribution and the pulverizing time are shown in Fig.

2 and 4, it can be seen from FIG. 2 that the particle size of the nanocellulose becomes smaller as the milling time becomes longer. As compared with FIG. 3, The nanocellulose having a size of 300 nm or less can be produced by irradiating the nanocellulose with a radiation dose of more than 2000 nm when the radiation is not irradiated even though it is pulverized for 40 minutes. It was confirmed that the particle size of the produced nanocellulose had a considerable influence.

2 and FIG. 4, when irradiated with radiation, the nanocellulose having a particle size of 300 nm or less could be produced even if it was pulverized for 40 minutes, but when it was not irradiated, it was pulverized for 4 hours , And it was confirmed that nanocellulose having a size similar to that of irradiation was obtained.

Example  3: Measurement of the power consumption of the grinding process according to the dose of irradiation

When the nanocellulose was prepared in the same manner as in Example 1, the cumulative power required for the pulverization process was measured according to the irradiation dose of 50, 100, 200 or 300 kGy, and the cumulative power consumption Is shown in Fig.

Referring to FIG. 5, when the irradiation dose is 200 kGy, the energy consumed in the pulverizing process can be reduced by about 20%, and when irradiated with 300 kGy, the energy can be reduced by about 30% or more there was.

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 (9)

(a) irradiating cellulose-based materials with radiation of 50 to 300 kGy;
(b) pulverizing the irradiated cellulosic material for 10 to 60 minutes; And
(c) washing the pulverized cellulose-based material with an aqueous acid solution so as to separate the nanocellulose composed of the crystalline region from the pulverized cellulose-based material, and then separating the nanocellulose with a centrifugal separator. As a method,
Wherein the nanocellulose separated from the cellulosic material pulverized for 10 to 60 minutes has a particle size of 300 nm or less. 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. The method according to claim 1,
The step (b) is carried out by a mechanical pulverizing process,
Wherein the pulverizing step comprises any one selected from the group consisting of a milling process, a grinding process, a microfluidic process, a homogenizer process, and a combination thereof. delete delete The method according to claim 1,
Wherein the cellulosic material comprises cellulosic biomass. ≪ RTI ID = 0.0 > 21. < / RTI > The method according to claim 1,
Wherein the cellulose-based material comprises any of cellulose selected from the group consisting of a fiber-based, wood-based, seaweed-based, and combinations thereof. The method according to claim 1,
Wherein the cellulose-based material includes any one selected from the group consisting of powders, pellets, solutions, and combinations thereof.

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