KR101912736B1 - Method for producing cellulose nanofibril using electron beam irradiation and carboxymethylation reaction - Google Patents

Abstract

The present invention relates to a method for producing cellulose nanofibers using electron beam irradiation and carboxymethylation. More specifically, the present invention provides the method for producing cellulose nanofibers by carboxymethylation of a pulp irradiated with the electron beam. The above method reduces a mechanical grinding time by significantly reducing the number of grinding passes and time compared to the carboxymethylation of a pulp which is not irradiated with the electron beam. Therefore, it is possible to reduce a cost and time required for manufacturing the cellulose nanofibers, and thus, can be usefully used for producing the cellulose nanofibers.

Description

[0001] The present invention relates to a method for producing cellulose nanofibers using electron beam irradiation and carboxymethylation reaction,

The present invention relates to a method for producing cellulose nanofibers using electron beam irradiation and carboxymethylation.

Cellulose nanofibrils (CNF) are not only excellent in strength properties, but also biodegradable, environmentally friendly natural polymer materials. Cellulose nanofibrils exhibit anionic properties in aqueous systems due to functional groups derived from hemicellulose or introduced through pulping and bleaching processes. The electrochemical properties of such a cellulose nanofibril surface can be controlled through surface modification. When ionic properties are controlled by surface modification, coagulation, dispersion, rheology and dehydration of cellulose nano - fibrils are influenced and it is thought that the characteristics of final product will be changed. As a result of controlling the ionicity of the cellulose nano-fibril surface by using a layer-by-layer (LbL) multilayering method, which is one of the surface modifying methods, the ionic properties of the cellulose nano- Of dehydration was affected. Since the surface of cellulose has many hydroxyl groups (-OH), ionic properties of the surface can be controlled not only by adsorption method by electrostatic attraction but also by chemical treatment. Carboxymethylation has long been used as a means to increase the anionicity of pulp fiber surfaces, which allows introduction of carboxymethyl groups (-CH ₂ COOH) at the hydroxyl positions of the fibers. Through the reaction with chloroacetic acid, the substituted carboxymethyl group is ionized in the aqueous system and is present in the form of CH ₂ COO ^- , thereby giving anionic property to the surface of the cellulose fiber. Depending on the degree of carboxymethyl group substitution, the solubility in water and the viscosity characteristics are different.

On the other hand, electron beams have strong permeability and decomposition ability, and are used in various industries by rapidly changing materials. Sterilization of foods, genetic engineering, etc., which remove toxic substances by irradiating electron beams to medical and abolished condensed milk such as scars, etc. In the case of electron beam accelerators, investment facilities are very expensive, but they have been studied for a long time since they have a short process time, low water penetration between processes, and all reactions are possible at room temperature. The electron beam is a flow of electrons accelerated near the speed of light by using a high voltage in a vacuum state. The electron beam can produce ions and has a high permeability so that the intermolecular bonds within the object are cut off or polymerized. In the state, a radical is formed and a reaction occurs. When such an electron beam is irradiated onto cellulose, it decomposes the chemically bonded cellulose. After the decomposition, the free radical reaction takes place further, and the chain is broken or oxidized to decompose the cellulose.

Meanwhile, Korean Patent No. 1400674 discloses microbial cellulose nanofibers for introducing biomolecules using radiation and a manufacturing method thereof. However, the method for producing cellulose nanofibers using electron beam irradiation and carboxymethylation reaction of the present invention has not yet been disclosed none.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described needs, and it is an object of the present invention to provide a pulp which is irradiated with electron beams and carboxymethylated with pulses irradiated with electron beams, The time and cost required for the production of the cellulose nanofibers can be reduced, thereby completing the present invention.

In order to solve the above-described problems, the present invention provides a method of manufacturing a wood pulp, comprising: 1) irradiating wood pulp with electron beams; 2) Carboxymethylation of the wood pulp irradiated with electron beam in the step 1); And 3) subjecting the carboxymethylated pulp obtained in the step 2) to mechanical pulverization. The present invention also provides a method for producing cellulose nanofibers.

The present invention also provides a cellulose nanofiber produced by the above method.

The present invention provides a method for producing cellulose nanofibers by carboxymethylation of pulp irradiated with electron beams, and this method remarkably reduces the number of grinding passes and time compared to the case of carboxymethylation of a pulp not irradiated with an electron beam, By reducing the time, it is possible to reduce the cost and time required for manufacturing the cellulose nanofiber, and therefore, it can be usefully used for producing the cellulose nanofiber.

FIG. 1 is a Fourier Transform Infrared (FT-IR) analysis result obtained by determining the presence or absence of carboxymethylation of softwood pulp (A) and hardwood pulp (B) according to an embodiment of the present invention. (A), Sw control is a cellulose nanofiber prepared without any treatment of softwood pulp, Sw CMC is cellulose nano fiber produced by carboxymethylation of softwood pulp, EB-Sw CMC is a cellulose nano fiber produced by irradiating electron beam irradiated softwood pulp with carboxy Hw CMC is cellulose nano fiber prepared by carboxymethylation of hardwood pulp, and EB-Hw CMC (cellulose triacetate) is a cellulose nano fiber produced by methylation of a hardwood pulp, and Hw control is cellulose nano fiber prepared without any treatment of hardwood pulp. Is a cellulose nanofiber prepared by carboxymethylation of a hardwood pulp irradiated with an electron beam.
FIG. 2 is a graph showing the relationship between the zeta-potential (A) and the zeta potential difference (zeta-potential) of the cellulose nanofibers prepared according to the embodiment of the present invention with or without electron beam irradiation and carboxymethylation (B).
FIG. 3 is a graph showing the relationship between the zeta-potential (A) and the zeta potential difference (zeta-potential) of the cellulose nanofibers produced according to the embodiment of the present invention, (B).

In order to achieve the object of the present invention,

1) irradiating wood pulp with electron beams;

2) Carboxymethylation of the wood pulp irradiated with electron beam in the step 1); And

3) subjecting the carboxymethylated pulp obtained in the step 2) to mechanical pulverization. The present invention also provides a method for producing cellulose nanofibers.

In the present invention, the cellulose nanofiber may have a fiber width of 100 nm or less and an aspect ratio of 100 or more, but the present invention is not limited thereto.

In the method for producing a cellulose nanofiber of the present invention, the dose of the electron beam in the step 1) may be 20 to 100 kGy, preferably 50 kGy, but is not limited thereto. If the irradiation dose of the electron beam is less than 20 kGy, the reduction of the degree of polymerization of the cellulose fiber is insignificant and it is difficult to expect the promotion of the oxidation reaction by the electron beam and the improvement of the efficiency of the nano-manufacturing process. When the irradiation amount exceeds 100 kGy, The function or merit of the nanofiber can not be secured.

In addition, the raw material of the wood pulp in the above step 1) may be, but is not limited to, a broad-leaved tree or a coniferous tree.

In addition, the mechanical pulverization in the step 3) may be, but not limited to, high pressure homogenization or grinding.

In addition, the carboxymethylation of step 2)

a) dissolving the pulp irradiated with the electron beam using a high-speed dissociator, adding ethanol, and performing solvent substitution by vacuum filtration;

b) immersing the solvent-substituted pulp in step a) in a mixture of chloroacetic acid and isopropyl alcohol, removing the pulp, adding the mixture to a mixed solution of sodium hydroxide, isopropyl alcohol and methanol, and allowing the pulp to react with stirring in a constant temperature water bath;

c) washing the reactant of step b) with water and neutralizing with acetic acid to terminate the reaction;

d) after completion of the reaction in step c), dipping the obtained pulp in a sodium hydrogen carbonate solution to prepare a sodium salt form and washing with water to obtain a carboxymethylated pulp , But is not limited thereto.

In addition, the method for producing the cellulose nanofibers of the present invention

1) irradiating a wood pulp with an electron beam of 20 to 100 kGy;

2) dissolving the pulp irradiated with the electron beam in the step 1) using a high-speed dissolver, adding ethanol of 3500 ~ 4500 parts per 100 parts by weight of the pulp, and performing solvent substitution by vacuum filtration;

3) In step 2), the solvent-substituted pulp is poured into a mixture of chloroacetic acid and isopropyl alcohol and immersed for 20 to 40 minutes. The pulp is taken out and added to a mixed solution of sodium hydroxide, isopropyl alcohol and methanol, Reacting in a constant temperature water bath with stirring for 45 to 75 minutes;

4) neutralizing the reactant in step 3) with acetic acid to terminate the reaction;

5) After completion of the reaction in step 4), the obtained pulp was immersed in a 2 to 6% (w / v) sodium hydrogencarbonate solution to prepare a sodium salt form and washed with water to obtain a carboxymethylated pulp ; And

6) performing mechanical pulverization on the carboxymethylated pulp obtained in the step 5), and preferably,

1) irradiating wood pulp with an electron beam of 50 kGy;

2) dissolving the pulp irradiated with the electron beam in the step 1) using a high-speed dissolver, adding 4000 parts of skin ethanol per 100 parts by weight of pulp, and performing solvent substitution by vacuum filtration;

3) In step 2), the solvent-substituted pulp was added to a mixture of 0.2 to 2.0% of chloroacetic acid and 200 to 300 mL of isopropyl alcohol to immerse in the mixture for 30 minutes, and the pulp was taken out to prepare a 15 to 30% (w / v) Adding pulp to a mixed solution of 1,000 to 1,700 mL of isopropyl alcohol and 250 to 2,500 mL of methanol, and reacting with stirring in a constant temperature water bath at 65 DEG C for 60 minutes;

4) neutralizing the reactant in step 3) with 0.1 M acetic acid to terminate the reaction;

5) After completion of the reaction in step 4), the obtained pulp was immersed in 1,000 mL of a 4% (w / v) sodium hydrogencarbonate solution to prepare a sodium salt form, followed by washing with water to obtain a carboxymethylated pulp ; And

6) performing mechanical pulverization on the carboxymethylated pulp obtained in the step 5), but the present invention is not limited thereto.

The present invention also provides a cellulose nanofiber produced by the above method.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are merely illustrative of the present invention and that the scope of the present invention is not limited thereto.

Materials and methods

1. Disclosure Material

The disclosed pulps used in the present invention were softwood bleached kraft pulp (Sw-BKP) and hardwood bleached kraft pulp (Hw-BKP) sold by Moorim P & P as raw materials.

2. Electron beam irradiation

Electron beam irradiation of softwood bleached kraft pulp (Sw-BKP) and hardwood bleached kraft pulp (Hw-BKP) was performed using an electron beam accelerator (ELV-8-type 2.5 MeV Electron Beam Accelerator, EB Tech. And stored at a low temperature for about 7 days to stabilize the pulp and used in the following examples.

3. Pulp Carboxymethylation  And substituted functional group analysis

Cellulose nanofibers are prepared by carboxymethylation of pulp in two ways. High carboxymethylated cellulose (High CMC) and low carboxymethylated cellulose (Low CMC) according to the degree of substitution of carboxymethyl groups, Can be produced.

In the present invention, carboxymethylation of the pulp was carried out by a method using low substituted cellulose. Specifically, 40 g of the pulp was loosened using a high-speed dissociator, 1,600 mL of ethanol was added thereto, and the solvent was replaced by vacuum filtration. The solvent-substituted pulp was washed with 0.2 to 2.0% chloroacetic acid and 200 to 300 mL of isopropyl alcohol , And the mixture was put into a mixture of 15 to 30% (w / v) sodium hydroxide, 1,000 to 1,700 mL of isopropyl alcohol and 250 to 2,500 mL of methanol, and stirred in a constant temperature water bath at 65 ° C. And reacted for 1 hour. After completion of the reaction, the reaction mixture was washed with distilled water, neutralized with 0.1 M acetic acid, and then washed with distilled water. Thereafter, the obtained pulp was immersed in 1,000 mL of a 4% (w / v) sodium hydrogencarbonate solution to prepare a sodium salt (-COONa) and washed with water to obtain a carboxymethylated pulp.

The degree of substitution of the carboxymethyl group (-CH ₂ COOH) with the cellulose nanofiber by FT-IR (Fourier transform infrared spectroscopy, Jasco, Japan) after preparing carboxymethylated pulp with a basis weight of 80 g / m ² pad Respectively.

4. Carboxymethylated  Manufacture of Cellulose Nanofibers of Pulp

Cellulose nanofibers were prepared by passing pulps (Sw-BKP and Hw-BKP) irradiated with electron beams and carboxymethylated through a nano grinder (Super Masscollover, Masuko Sangyo Co., Ltd., Japan) at 1,500 rpm and a stone interval of 150 탆 (Table 1).

Cellulose nanofibers with or without electron beam irradiation and carboxymethylation Cellulose nanofibers pulp Electron beam irradiation Carboxymethylation Sw control Sw-BKP 0 kGy X Sw CMC 0 kGy 0 EB-Sw CMC 50 kGy 0 Hw control Hw-BKP 0 kGy X Hw CMC 0 kGy 0 EB-Hw CMC 50 kGy 0

Sw control is cellulosic nanofiber prepared without any treatment of softwood pulp, Sw CMC is cellulose nanofiber prepared by carboxymethylation of coniferous pulp, EB-Sw CMC is irradiated softwood pulp with electron beam and carboxymethylation Hw CMC is a cellulose nanofiber prepared by carboxymethylation of hardwood pulp and EB-Hw CMC is a cellulose nano fiber produced by irradiating hardwood pulp with an electron beam And a cellulose nanofiber prepared using a carboxymethylation reaction.

Example  1. Electron beam irradiation and Carboxymethylation  Evaluation of Efficiency of Cellulose Nanofibers Using Reaction

In Example 1, the degree of substitution of carboxyl groups by FT-IR was analyzed for the cellulose nanofibers prepared by electron beam irradiation and carboxymethylation reaction. As a result, as shown in FIG. 1, the peak value of carboxylic acid at FT-IR analysis was 1700 to 1730 cm ^-1 , which was higher than that at a carboxymethylated softwood pulp at 1700 to 1750 cm ^-1 Peak value, and it was confirmed that the peak value was the highest at the same wavelength band in the case of softwood pulp subjected to electron beam irradiation and carboxymethylation. The results of hardwood pulp were the same as those of softwood pulp.

When the cellulose nanofibers were produced by irradiation of electron beams and carboxymethylation of softwood pulp and hardwood pulp, the final grinding time and the number of passes were measured. As a result, when pulp irradiated with electron beams was carboxymethylated (EB-Sw CMC and EB (hereinafter, referred to as EB-Sw CMC and Hw CMC) when the pulps not irradiated with electron beams were carboxymethylated -Hw CMC), it can be confirmed that the number and time of the final grinding pass are remarkably reduced.

The number of times of grinding pass and time measurement of cellulose nano fiber prepared according to the presence of electron beam irradiation and carboxymethylation reaction of softwood pulp sample Electron beam irradiation Carboxymethylation Grinding
Number of passes Grinding time Sw control 0 kGy × 10 5 hours 13 minutes 20 seconds Sw CMC 0 kGy ○ 8  3 hours 36 minutes 40 seconds EB-Sw CMC 50 kGy ○ 6 2 hours 33 minutes 20 seconds

Sw control is cellulosic nanofiber prepared without any treatment of softwood pulp, Sw CMC is cellulose nano fiber prepared by carboxymethylation of softwood pulp, and EB-Sw CMC is produced by carboxymethylation of irradiated softwood pulp Cellulosic nanofiber.

The number of times of grinding pass and time measurement of cellulose nanofibers produced according to the presence of electron beam irradiation and carboxymethylation of hardwood pulp sample Electron beam irradiation Carboxymethylation Grinding
Number of passes Grinding time Hw control 0 kGy × 10 5 hours Hw CMC 0 kGy ○ 8  3 hours 43 minutes 20 seconds EB-Hw CMC 50 kGy ○ 5 2 hours 3 minutes 20 seconds

Hw control is a cellulose nanofiber prepared by treating nothing with hardwood pulp. Hw CMC is a cellulose nanofiber prepared by carboxymethylation of hardwood pulp. EB-Hw CMC is a cellulose nanofiber prepared by carboxymethylation of electron beam irradiated hardwood pulp Cellulosic nanofiber.

Example  2. Electron beam irradiation and Carboxymethylation  Characterization of Cellulose Nanofibers Prepared by Reaction

The cellulosic nanofibers prepared according to the presence or absence of electron beam irradiation and carboxymethylation of softwood pulp and hardwood pulp were subjected to fiber classification with a mesh wire of 400 mesh and then collected using a zeta potential analyzer Zeta potential (mV) was measured using a Zeta Potential Analyzer, Malvern and NANO ZS, UK. As a result, in the experimental groups (Sw CMC and Hw CMC) in which the softwood pulp and the hardwood pulp were carboxymethylated in contrast to the control groups (Sw Control and Hw Control) in which nothing was treated as shown in FIG. 2, the negative charge value of the zeta potential was increased In particular, it was confirmed that the negative charge value of the zeta potential was further increased in the experimental groups (EB-Sw CMC and EB-Hw CMC) in which the softwood pulp and the hardwood pulp irradiated with electron beams of the present invention were carboxymethylated. When the zeta potential difference (Δzeta-potential) with or without electron beam irradiation is calculated, the absolute value of the zeta potential difference of the cellulose nanofiber prepared by carboxymethylation of the pulp irradiated with the electron beam is carboxymethylated Which is higher than that of one cellulosic nanofiber. These results indicate that carboxymethyl group (-CH ₂ COOH) is introduced at the hydroxyl group (-OH) position of the pulp fiber by using the carboxymethylation reaction that regulates the ionicity through surface modification, thereby increasing the anionic property of the fiber surface It is also believed that the pretreatment of electron beam further promotes the anionicity of the cellulose nanofibers.

Claims (7)

1) irradiating a wood pulp with an electron beam of 20 to 100 kGy;
2) dissolving the pulp irradiated with the electron beam in the step 1) using a high-speed dissolver, adding ethanol of 3500 ~ 4500 parts per 100 parts by weight of the pulp, and performing solvent substitution by vacuum filtration;
3) In step 2), the solvent-substituted pulp is poured into a mixture of chloroacetic acid and isopropyl alcohol and immersed for 20 to 40 minutes. The pulp is taken out and added to a mixed solution of sodium hydroxide, isopropyl alcohol and methanol, Reacting in a constant temperature water bath with stirring for 45 to 75 minutes;
4) neutralizing the reactant in step 3) with acetic acid to terminate the reaction;
5) After completion of the reaction in step 4), the obtained pulp was immersed in a 2 to 6% (w / v) sodium hydrogencarbonate solution to prepare a sodium salt form and washed with water to obtain a carboxymethylated pulp ; And
6) Performing mechanical pulverization on the carboxymethylated pulp obtained in step 5). delete The method according to claim 1, wherein the raw material of wood pulp in step 1) is a hardwood or a conifer. The method of claim 1, wherein the mechanical pulverization in step (6) is high pressure homogenization or grinding. delete delete The cellulose nanofibers produced by the method of any one of claims 1, 3, and 4.

Images