KR102167227B1 - Process Of Producing Cellulose Nano―Fiber/Water Dispersed Polyurethane Complex Film Using Complex-Enzyme Treated Cellulose Nano Fiber - Google Patents

Abstract

The present invention uses cellulose-based fibers as a raw material to produce high-purity cellulose nanofibers by complex enzyme treatment, and improves the dispersion effect in the cellulose nanofiber dispersion to provide a cellulose nanofiber/water-dispersible polyurethane composite film having excellent strength and flexibility. Regarding the manufacturing method, by providing a cellulose nanofiber/water-dispersible polyurethane composite film with increased dispersibility using cellulose nanofibers having uniform dispersion characteristics according to the present invention, films and laminations requiring pressure resistance, high elasticity, and high physical properties are required. And it can be applied to coated airbag material and protective equipment, protective clothing material.

Description

TECHNICAL FIELD {Process Of Producing Cellulose Nano-Fiber/Water Dispersed Polyurethane Complex Film Using Complex-Enzyme Treated Cellulose Nano Fiber}

The present invention uses cellulose-based fibers as a raw material to produce high-purity cellulose nanofibers by complex enzyme treatment, and improves the dispersion effect in the cellulose nanofiber dispersion to provide a cellulose nanofiber/water-dispersible polyurethane composite film having excellent strength and flexibility. It relates to a method of manufacturing.

Cellulose is one of the renewable polymer materials that can be obtained from biomass, and is the most abundant natural polymer among organic compounds in nature. Research on high-functional materials using cellulose biomass raw materials derived from plant fibers is also underway. Recently, a new material through nanoization due to its excellent performance and properties such as biodegradability, biocompatibility, high mechanical strength, and thermal stability of cellulose materials. Is being developed.

Nanocellulose is a material made by mechanically or chemically thinning plant fibers obtained from wood, etc. to nano (10 ^-9 )m units, and its weight is only 1/5 of that of steel, but it forms a strong crystal structure by hydrogen bonding and has strength. Since it is more than 5 times higher than carbon fiber, it is in the spotlight as a next-generation new material. It can be extracted not only from wood pulp, but also from weeds and fruit residue, so there is little risk of depletion and it is an eco-friendly eco-friendly polymer material. In addition, it is highly viscous and airtight, maintains transparency even when mixed with various polymer resins such as plastics, and is strong against heat, so it is applied to various fields such as interior and exterior materials for transportation, construction materials, filters, sensors/electronic parts, and durable protective equipment products.

Methods of manufacturing nanocellulose can be largely divided into a chemical method and a mechanical method. A typical chemical method is acid hydrolysis, and it is a method of decomposing into an amorphous region of cellulose under appropriate conditions such as concentration, reaction temperature, and time, and mechanical methods are grinder, homogenizer, and refining. It is a method of decomposing into nano-sized fibers using mechanical power such as. However, mechanical fibrillation alone has a disadvantage in that it consumes a lot of energy, time, and cost during manufacturing.To compensate for this, a treatment that accelerates fibrillation of fibers by hydrolyzing fibers through chemical treatments such as TEMPO oxidation or enzymes before mechanical treatment is required. need.

Cellulose fiber materials are composed of materials other than cellulose, such as cellulose, which is the basic tissue fiber of plants, and polysaccharides such as pectin, lignin, and hemicellulose, which are complex carbohydrates, and the content of impurities other than cellulose varies from 6 to 50%. Included. Mainly, impurities other than cellulose are removed through an alkali treatment process, and the content of impurities greatly affects the fiber structure and properties, and fibers from which impurities are removed improve the strength of the composite material. However, the removal of impurities by alkali treatment affects the cellulose itself, resulting in deterioration in properties such as crystal structure deformation, cellulose damage, and discoloration within the cellulose, resulting in deterioration of the quality of the cellulose cellulose itself, as well as the use of a large amount of chemicals, and high pressure and high temperature hot water treatment Since it is manufactured under conditions, high energy is used, which causes environmental problems. Therefore, for the production of high-quality cellulose materials, an eco-friendly method of removing impurities in plant fibers selectively removes them through a low-energy process that can be treated simply under normal pressure and relatively low temperature without chemicals. It is a required situation.

In general, the enzyme treatment for cellulose is mainly carried out at about room temperature or under mild conditions of 30 to 50°C, and is an eco-friendly process that does not use chemicals. Enzymes for selective removal of pectin, which has sticky properties of galacturonic acid, among impurities other than cellulose fiber, are polygalacturonase that hydrolyzes α-1,4 glycosidic bonds of galacturonic acid, methyl esterified galacturonic acid. Pectinase enzymes such as pectin lyase, which degrade α-1,4 bonds of, are applied.

As an enzyme for removing lignin, a fat-soluble phenolic polymer that creates a dark brown color of plants as an aromatic polymer compound present in about 20 to 30% in plants, the ligninase enzyme of laccase and lignin peroxidase is applied to selectively decompose lignin. Laccase is capable of decomposing lignin by radical oxidation of phenolic hydroxyl groups, and is an enzyme that oxidizes p-diphenol (hydroquinone) by oxygen to make p-quinone. Lignin peroxidase breaks down lignin into small molecules by breaking the benzene ring structure by cleaving the 1,2-diaryl propane in the lignin molecule or the -C-C-bond in the allyl glycerol structure. In addition, hemicellulase enzyme capable of decomposing and removing flexible polysaccharides (xylan, glucan, mannan), which are the main components, may be applied to remove complex carbohydrate hemicellulose, and amylase may be applied to remove starch and sugars.

In the pretreatment to facilitate swelling and fibrillation of the main component of cellulose fibrin in plant fibers, cellulase enzymes that hydrolyze β-1,4 glycosidic bonds of cellulose and other beta glucans and β-1,3 or β of beta glucans It is mainly carried out using the enzyme endoglucanase, which hydrolyzes the -1,4 glycosidic bond. In this case, some of the hemicellulose removal is possible in parallel.

However, if the enzyme pretreatment is carried out under too severe conditions, the amorphous region may be completely decomposed and cellulose may be saccharified, so it is necessary to set detailed appropriate conditions.

On the other hand, anionic water-dispersed polyurethane (Waterborn-PolyUrethane, WPU) has excellent adhesion to various adherends, as Bronsted acid is introduced into the main chain, as well as excellent physical properties such as water resistance and water dispersion stability. It is used for bonding metals, woods, plastics, synthetic and natural rubbers, or coating the surface.

Such anionic water-dispersible polyurethanes contain carboxyl groups in the main chain, so they have excellent compatibility with hydrophilic cellulose nanofibers, so they are easy to disperse when preparing nanofibers/water-dispersible polyurethane composite solutions and have good binding properties with resins. The conditions that can be used as materials are excellent.

However, if impurities such as hemicellulose, pectin, and lignin are not completely removed from the cellulose fiber during the pretreatment process of the cellulose fiber for producing nanocellulose (or cellulose nanofiber), physical and mechanical strength is required during cellulose separation and fibrillation. As it is necessary, the work process load and energy loss are large, and when the cellulose nanofibers are dispersed in a solution, the dispersibility of the cellulose nanofibers in the dispersion is inevitably deteriorated, causing difficulties in producing uniform cellulose nanofibers. In addition, when mixing with resins such as water-dispersible polyurethane, nanofiber cellulose can be aggregated or agglomerated, which can degrade product quality such as dispersibility and strength reduction when applied to material products.Therefore, impurities removal is essential when manufacturing cellulose nanofibers. However, since the removal is not completely performed and mainly uses an alkali treatment method, there are problems of damage and dispersibility of fibers, and strength reduction as well as environmental and energy loads.

Japanese Patent Application Publication No. 2017-517589 (published on June 29, 2017)

Therefore, in the present invention, in the production of nanocellulose, the impurity components of the cellulose-based plant fiber material, such as hemicellulose, pectin, lignin, and sugars, are efficiently removed and hydrolysis pretreatment steps using a complex enzyme before mechanical decomposition. It is a low-load, low-energy, eco-friendly process that produces cellulose nanofibers for economical use in the entire process, while on the other hand, through the production of nanocellulose of uniform quality with good dispersibility, dispersibility is improved when mixed with water-dispersible polyurethane resin Its purpose is to provide a composite film material for coating and laminating that has excellent physical properties such as water pressure and pressure resistance, friction resistance, strength and elasticity enhancement.

Therefore, according to the present invention, after pulverizing the cellulose fiber and mixing it with distilled water, a cellulose fiber suspension manufacturing step of stirring at 10,000 to 20,000 rpm for 30 to 60 minutes;

Pectinase, ligninase, and hemicellulase are added to the cellulose fiber suspension in an amount of 1 to 5% by weight, and the first enzyme treatment is performed at a pH of 5 to 7 and a reaction temperature of 50 to 60°C for 30 to 60 minutes, and 10 to 20 at 100°C. After inactivating for a minute, repeat washing with hot and cold water twice or more to remove residual impurities, and then add cellulase at a concentration of 0.1 to 1% by weight to the cellulose fiber suspension for 20 to 60 minutes at a pH of 6 and a reaction temperature of 50 to 60°C. After performing the second enzyme treatment and inactivating at 100°C for 10 to 20 minutes, the enzyme is adsorbed to the surfactant using an anionic surfactant and washed to prepare a cellulose microfiber suspension. Hydrolysis step;

An ultrasonic dispersion step of performing ultrasonic treatment for 30 minutes to 1 hour at a driving frequency of 20 to 30 kHz by using an ultrasonic dispersing machine to loosen the entanglement of fibers in the cellulose microfiber suspension;

Cellulose nanofiber manufacturing step of passing the cellulose microfiber suspension through a nozzle having a diameter of 80 to 100 μm 5 to 20 times under a pressure condition of 1700 to 2000 bar using a high pressure homogenizer;

After dispersing the cellulose nanofibers in distilled water at 5,000 to 10,000 rpm for 5 to 10 minutes to prepare a cellulose nanofiber dispersion having a concentration of 0.01 to 1% by weight, 0.01 to 1.0% by weight of the cellulose nanofiber dispersion, anionic water dispersion poly 40-60% by weight of urethane, cellulose nanofibers/water-dispersible polyurethane composite solution preparation step of mixing distilled water as the balance;

The cellulose nanofibers/water-dispersible polyurethane composite solution is cast through a solution casting method, followed by drying and curing, and then drying and curing the cellulose nanofibers/water-dispersible polyurethane composite film. A method of manufacturing a cellulose nanofiber/water-dispersible polyurethane composite film using fibers is provided.

In addition, in the manufacturing method of the cellulose nanofiber/water-dispersible polyurethane composite film using the complex enzyme-treated cellulose nanofiber of the present invention, the anionic water-dispersible polyurethane in the manufacturing step of the cellulose nanofiber/water-dispersible polyurethane composite solution has a solid content of 40 It is characterized in that the ~60% by weight, viscosity 100 ~ 300mPa.s, density 1.00 ~ 1.10g / cm3.

In addition, in the first enzyme treatment during the hydrolysis step, one or more of laccase and amylase is additionally added to the cellulose fiber suspension, and endo-glucanase enzyme is additionally added in the second enzyme treatment.

Therefore, the present invention is a complex enzymatic pretreatment process before mechanical decontamination of cellulose-based plant fibers. It is possible to separate and manufacture reliable cellulose nanofibers through selective removal of impurities and hydrolysis treatment steps. Film that requires pressure resistance, high elasticity, and high physical properties by providing a cellulose nanofiber/water-dispersible polyurethane composite film with increased dispersibility by using cellulose nanofibers having uniform dispersion characteristics as a result of manufacturing cellulose nanofibers for economic practical use. And it can be applied to laminating and coating airbag materials and protective equipment, protective clothing materials.

1 is a FI-IR graph of the enzyme-treated linen cellulose fiber of Example 1,
2 is a FI-IR graph of the enzyme-treated linen cellulose fiber of Comparative Example 1,
3 is a photograph of a comparison of dispersibility of samples of Example 1 and Comparative Example 1,
4 is an FE-SEM photograph of Example 1,
5 is a TEM photograph of Example 1,
6 is a photograph of a cellulose nanofiber/water-dispersible polyurethane composite solution prepared in Example 1,
7 is a photograph of a cellulose nanofiber water-dispersed polyurethane composite film prepared according to Example 1,
8 is a photomicrograph of the cellulose nanofiber water-dispersed polyurethane composite film of Example 1,
9 is a photomicrograph of the cellulose nanofiber water-dispersed polyurethane composite film of Comparative Example 1.

Hereinafter, the present invention will be described in more detail.

The present invention is a cellulose-based vegetable natural raw material such as flax, hemp, jute, kenaf, bamboo, ramie, cotton, rice straw, wood flour, etc. in cellulose plant fibers, pectin, lignin, hemicellulose, and other adhesive impurities and polysaccharide impurities Cellulose nanofibers with excellent dispersion in resin and improved manufacturing process for nanofiberization of cellulose through a low-energy, high-efficiency eco-friendly process that separates more high-purity cellulose fibers by selectively removing etc. and at the same time helps swelling and cellulose fibrillation in the amorphous region of cellulose. It relates to a method for preparing a high-physical cellulose nanofiber/water-dispersible polyurethane composite film having excellent strength and flexibility by adding and complexing it to a resin.

The manufacturing method of cellulose nanofibers and water-dispersible polyurethane composite films using the complex enzyme-treated cellulose nanofibers of the present invention is largely a cellulose fiber suspension manufacturing step, hydrolysis step, ultrasonic dispersion step, cellulose nanofiber manufacturing step, cellulose nanofiber It consists of a manufacturing step of a /water-dispersible polyurethane composite solution and a step of manufacturing a cellulose nanofiber/water-dispersion polyurethane composite film.

In the step of manufacturing the cellulose fiber suspension, dry cellulose fiber materials such as flax, hemp, jute, kenaf, bamboo, ramie, cotton, rice straw, and wood powder, which are natural vegetable raw materials, are pulverized into 0.5mm using a continuous grinder. After mixing with distilled water, immersion and agitation. A cellulose-based plant fiber raw material is treated in a 1% solution hydrogen peroxide solution (35% reagent concentration), bleached at 95°C for 60 minutes, and then used as a cellulose fiber material and pulverized. The resulting cellulosic fibers are added to distilled water at a concentration of 1 to 5 wt% and stirred at 10,000 to 20,000 rpm for 30 to 60 minutes using an Ultraturrax homogenizer to beat it.

In the cellulose fiber suspension, impurities such as pectin, lignin, hemicellulose, sugars, etc. are removed from the cellulose fiber suspension, and a hydrolysis step is performed to facilitate swelling and separation of the cellulose fiber.

The hydrolysis step is divided into a first enzyme treatment, which is an impurity removal step, and a second enzyme treatment, which is a hydrolysis step of cellulose fibrils.The first enzyme treatment is performed by adding pectinase, ligninase and hemicellulase to the cellulose fiber suspension from 1 to 5% by weight is added to the first enzyme treatment for 30 to 60 minutes at a pH of 5 to 7 and a reaction temperature of 50 to 60°C to remove pectin, lignin, and hemicellulose, which are impurities other than cellulose in the fiber. After inactivating for ~20 minutes, wash with hot water and cold water twice or more to remove residual impurities.

In the hydrolysis step, the enzyme is mixed with the cellulose fiber suspension and stirred at a specific temperature and pH for a certain period of time to reduce energy consumption and remove impurities such as pectin, lignin, and sugars present in the cellulose. This is the pretreatment step.

In a general mechanical decomposition method, micro-sized cellulose fibers are manufactured through a grinder or refining after preparing a cellulose suspension, and then passed through a high-pressure homogenizer to produce cellulose nanofibers. Pretreatment of hydrolysis through enzymes can be called a low energy process by minimizing the process by reducing the grinder or refining step.

In addition to the cellulose component, cellulose contains components such as pectin, lignin, and hemicellulose, but if these substances are not removed, it is inefficient due to the need for a lot of mechanical force when separating cellulose, and the dispersibility is low, so the cellulose nanofibers of the present invention/water dispersion It causes defects in the manufacture of polyurethane composite films, and when these materials are applied, cellulose nanofibers are aggregated and the dispersibility with the resin is lowered, and thus product quality such as strength may be deteriorated, so removal is necessary. In the hydrolysis step of the present invention to remove such ancillary components, enzymes are added to the cellulose fiber suspension and treated to remove impurities other than cellulose such as pectin, lignin, and hemicellulose, as well as hydrolysis for micro-nanoization of cellulose fibers. It is done.

After the first enzyme treatment, cellulase was added to the cellulose fiber suspension at a concentration of 0.1 to 1% by weight, and the second enzyme treatment was performed at a pH of 6 and a reaction temperature of 50 to 60° C. for 20 to 60 minutes, and at 100° C. After inactivating for 10 to 20 minutes, the enzyme is adsorbed to the surfactant using an anionic surfactant and washed to prepare a cellulose microfiber suspension. The hydrolysis step is completed.

Each enzyme is capable of selective hydrolysis and removal of impurities on the target substrate due to its substrate specificity, so a first enzymatic treatment step for removing impurities other than cellulose and a second enzymatic treatment step for swelling and separation of cellulose are required.

In this way, in the present invention, the second enzyme treatment is performed to swell and inactivate the cellulose fibers to smoothly nanonize the cellulose fibers, and then the enzyme is adsorbed to the surfactant and washed with an anionic surfactant.

The average diameter of the individual fibers of the cellulose fiber suspension before the second enzymatic treatment was 200 to 300 μm, but the average diameter after the second enzymatic treatment was 20 to 30 μm, and the average diameter decreased by enzymatic hydrolysis treatment.

When the second enzyme treatment is reacted for more than 1 hour, the cellulose is completely decomposed and it is difficult to manufacture cellulose nanofibers, so it is important to set an appropriate reaction time.In the present invention, the second enzyme treatment is performed for 20 to 60 minutes. , After the enzyme reaction, the enzyme activity was stopped, and in order to completely remove the residual enzyme, the enzyme was adsorbed to the surfactant by using an eco-friendly anionic surfactant and washed to remove it.

In the first enzyme treatment during the hydrolysis step, laccase can be added to the cellulose fiber suspension to improve complete removal of the lignin component, and amylase can be added to improve the removal of sugar and starch components. In the secondary enzyme treatment, endo-glucanase enzyme can be added to improve the hydrolysis of cellulose fibrin.

After the hydrolysis step, an ultrasonic dispersion step is performed, and ultrasonic treatment is performed for 0.5 to 1 hour at a driving frequency of 20 to 30 kHz by using an ultrasonic disperser in order to loosen the entanglement of fibers in the cellulose microfiber suspension.

Thereafter, the cellulose microfiber suspension is passed through a nozzle having a diameter of 80 to 100 μm 5 to 20 times in a pressure condition of 1700 to 2000 bar using a high-pressure homogenizer, and has a length of 80 to 150 nm. 1-2% cellulose nanofibers are obtained.

Thereafter, the cellulose nanofibers are dispersed in distilled water at 5,000 to 10,000 rpm for 5 to 10 minutes to prepare a cellulose nanofiber dispersion having a concentration of 0.01 to 1 wt%, and then the cellulose nanofiber dispersion is 0.01 to 1.0% by weight, anionic water dispersion. A cellulose nanofiber/water-dispersible polyurethane composite solution preparation step is performed in which 40-60% by weight of polyurethane and distilled water are mixed with the balance.

Thereafter, the cellulose nanofibers/water of the present invention through the manufacturing step of the cellulose nanofibers/water-dispersible polyurethane composite film, which is then dried and cured after casting with the cellulose nanofibers/water-dispersible polyurethane composite solution through a solution casting method. Disperse polyurethane composite film is prepared.

The anionic water-dispersible polyurethane is preferably 40 to 60% by weight of solid content, 100 to 300 mPa.s of viscosity, and 1.05 to 1.10 g/cm 3 of density in terms of compatibility with cellulose nanofibers and dispersion and binding properties when preparing a composite solution.

The cellulose nanofiber/water-dispersible polyurethane composite film thus prepared has excellent elongation, elasticity, and strength, and thus can be efficiently applied to processing of laminating and coating airbag materials, protective gear, and protective clothing.

In the following examples, non-limiting examples of preparing the cellulose nanofibers/water-dispersible polyurethane composite film of the present invention are given.

[Example 1]

1. Cellulose Fiber Suspension Manufacturing Step

Prepare a cellulose fiber material bleached at 95°C for 60 minutes by treating only a 1% solution of a cellulose-based plant fiber (linen fiber top) raw material with a hydrogen peroxide solution (35% reagent concentration), and the cellulose-based plant fiber material in a dry state Was pulverized to 0.5 mm using a continuous grinder, and then 30 g of the pulverized cellulose-based plant fiber material was added to 1500 ml of distilled water at a concentration of 2 wt% to prepare a cellulose fiber suspension. To beat this, the mixture was stirred at 20,000 rpm for 60 minutes using an Ultraturrax homogenizer.

2. Hydrolysis step of cellulose fiber suspension

Pectinase, ligninase, and hemicellulase were added to the cellulose fiber suspension in a total of 3 wt%, followed by the first enzyme treatment for 30 minutes at a pH of 5 to 6 and a reaction temperature of 50° C., inactivated at 100° C. for 10 minutes, and then heated 5 times. After repeated washing and cold water washing to remove residual impurities, cellulase enzyme was added to the cellulose fiber suspension at a concentration of 1 wt%, followed by the second enzyme treatment at pH 6 and reaction temperature of 50°C for 30 minutes, and then at 100°C for 10 minutes. After inactivation, the enzyme was adsorbed onto the surfactant and washed using an anionic surfactant. As a result, it was confirmed that the average diameter of the individual fibers of the cellulose fiber suspension before the enzyme treatment was 200 to 300 μm, but the average diameter after the enzyme treatment was 20 to 30 μm, which was reduced by enzymatic hydrolysis treatment.

3. Ultrasonic dispersion step

Cellulose was dispersed through ultrasonic treatment for 1 hour at a driving frequency of 20 kHz using an ultrasonic disperser (Ultrasonic Processor) in order to release the entanglement of fibers in the cellulose suspension after enzymatic hydrolysis.

4. Manufacturing cellulose nanofibers through mechanical treatment

The cellulose nanofiber suspension was passed through a nozzle having a diameter of 80-100 μm 20 times under a pressure condition of 1700 bar using a high-pressure homogenizer to obtain 150 nm cellulose nanofibers. The obtained samples are shown in Figs. 4 and 5 showing the morphology of cellulose nanofibers manufactured using a Field Emission Scanning Electron Microscope and a Bio Transmission Electron Microscope.

5. Preparation of cellulose nanofiber/water-dispersible polyurethane composite solution

Cellulose nanofibers (1-2%) prepared through enzyme treatment were dispersed for 5 minutes at 10,000 rpm using an Ultraturrax homogenizer to prepare a cellulose nanofiber dispersion having a concentration of 1.0% by weight. A cellulose nanofiber/water-dispersible polyurethane composite solution was prepared by mixing 1.0% by weight of the prepared dispersion, 60% by weight of anionic water-dispersed polyurethane, and distilled water as the balance. Anionic water-dispersible polyurethane was used having a solid content of 40% by weight, a viscosity of 100 mPa·s, and a density of 1.00 g/cm 3 (Fig. 6).

6. Cellulose nanofiber/water-dispersible polyurethane composite film manufacturing

Using the prepared cellulose nanofiber/water-dispersible polyurethane composite solution, cast the solution in a film form on a glass plate through a solution casting method, and then cure it in a dryer (70 ^o C) for 12 hours to achieve a concentration of 1.0 wt%. A cellulose nanofiber/water-dispersible polyurethane composite film was prepared. (Figure 7 city)

[Comparative Example 1]

In the step of removing impurities from the cellulose fiber suspension and enzymatic hydrolysis in Example 1, pectinase, ligninase, and hemicellulase enzymes were added to the cellulose fiber suspension at a concentration of 3 wt%, and the first enzyme was at pH 6 and a reaction temperature of 50° C. for 30 minutes. It does not use the method of performing the complex enzyme treatment process of the second enzyme treatment for 30 minutes at pH 6 and reaction temperature 50℃ by adding the cellulase enzyme to the treatment and 1wt% concentration. It is a physical method without enzyme treatment. Microcellulose fibers having a particle size of 50-100㎛ were prepared only by a physical process by stirring 10 times for 60 minutes at 20,000rpm using an Ultraturrax homogenizer, and the subsequent process was carried out in the same manner as in Example 1. A fiber/water dispersion polyurethane composite film was prepared.

In order to examine whether impurities in the cellulosic plant fiber material are removed by the enzyme treatment in the hydrolysis step of Example 1 and Comparative Example 1, FT-IR measurement graphs for the fibers after treatment are shown in FIGS. 1 and 2, As can be seen in FIG. 1, in Example 1, it was confirmed that impurities such as pectin were removed.

The dispersibility of the sample in the manufacturing step of cellulose nanofibers through the mechanical treatment of Example 1 and Comparative Example 1 is shown in FIG. 3, and it was confirmed that the dispersibility of the sample of Example 1 from which impurities were removed was more stable.

In the case of the cellulose nanofibers of Example 1, non-cellulosic (pectin, lignin, and polysaccharide impurities such as hemicellulose) were efficiently removed, so that the cellulose nanofibers were relatively easy to disperse in the solution, and dispersion stability was also excellent. In the case of the cellulose of Example 1, even after leaving for 8 hours than in the case of Comparative Example 1, the occurrence of precipitation was not large, and it was confirmed that it was better than the dispersibility.

In order to evaluate the mechanical properties of the cellulose nanofibers/water-dispersible polyurethane composite films prepared in Example 1 and Comparative Example 1, using a tensile tester (Zwick), ISO 527-3 (Standard for tensile properties of films and sheets) The tensile strength and tensile strain of the composite film were measured using mutatis mutandis and shown in Table 1. In the case of tensile strength, Example 1 increased by about 10 to 17% compared to Comparative Example 1, and in the case of tensile strain, by about 5 to 9%.

Cellulose nanofiber content
(CNF Contenths wt%) Tensile strength Tesnsile strength
(MPa) Tensile Strain Strain
(%) Example 1 101.7±2.4 ~ 115.2±5.4 2110.2±60.1 ~ 2143.4±25.3 Comparative Example 1 81.8±2.4 ~ 105.6±6.2 1712.4±5.8 ~ 1810.76±80.6

In the case of the cellulose nanofibers prepared through the enzymatic treatment of Example 1, non-cellulosic (adhesive impurities and polysaccharide impurities such as pectin, lignin, etc.) were efficiently removed, so that the cellulose nanofibers were relatively easy to disperse, and dispersion stability was also excellent. .

In addition, in the case of the composite film of Example 1 (Fig. 8), compared to the composite film of Comparative Example 1 (Fig. 9), the dispersibility in the polyurethane resin is excellent, and the physical and chemical interaction at the interface between the resin and the fiber is excellent. Compared to the composite film of Comparative Example 1 (FIG. 9), the tensile strength increased by about 10 to 17%, and the tensile strain increased by about 5 to 9%. This shows the difference in the dispersion mechanism by efficiently removing non-cellulose (impurities such as pectin, lignin, and hemicellulose) and polysaccharide impurities through the hydrolysis step of Example 1.

Claims (3)

After pulverizing the cellulose fibers and mixing them with distilled water, a cellulose fiber suspension manufacturing step of stirring at 10,000 to 20,000 rpm for 30 to 60 minutes;
Pectinase, ligninase, and hemicellulase are added to the cellulose fiber suspension in an amount of 1 to 5% by weight, and the first enzyme treatment is performed at a pH of 5 to 7 and a reaction temperature of 50 to 60°C for 30 to 60 minutes, and 10 to 20 at 100°C. After inactivating for a minute, repeat washing with hot and cold water twice or more to remove residual impurities, and then add cellulase at a concentration of 0.1 to 1% by weight to the cellulose fiber suspension for 20 to 60 minutes at a pH of 6 and a reaction temperature of 50 to 60°C. After performing the second enzyme treatment and inactivating at 100°C for 10 to 20 minutes, the enzyme is adsorbed to the surfactant using an anionic surfactant and washed to prepare a cellulose microfiber suspension. Hydrolysis step;
An ultrasonic dispersion step of performing ultrasonic treatment for 30 minutes to 1 hour at a driving frequency of 20 to 30 kHz by using an ultrasonic dispersing machine to loosen the entanglement of fibers in the cellulose microfiber suspension;
Cellulose nanofiber manufacturing step of passing the cellulose microfiber suspension through a nozzle having a diameter of 80 to 100 μm 5 to 20 times under a pressure condition of 1700 to 2000 bar using a high pressure homogenizer;
After dispersing the cellulose nanofibers in distilled water at 5,000 to 10,000 rpm for 5 to 10 minutes to prepare a cellulose nanofiber dispersion having a concentration of 0.01 to 1% by weight, 0.01 to 1.0% by weight of the cellulose nanofiber dispersion, anionic water dispersion poly 40-60% by weight of urethane, cellulose nanofibers/water-dispersible polyurethane composite solution preparation step of mixing distilled water as the balance;
Cellulose nanofibers/water, characterized in that the cellulose nanofibers/water-dispersible polyurethane composite film is produced by drying and curing after casting with the cellulose nanofibers/water-dispersible polyurethane composite solution through a solution casting method. Method for producing a dispersed polyurethane composite film The method of claim 1,
In the step of preparing the cellulose nanofiber/water-dispersible polyurethane composite solution, the anionic water-dispersible polyurethane has a solid content of 40 to 60% by weight, a viscosity of 100 to 300 mPa.s, and a density of 1.00 to 1.10 g/cm 3. / Manufacturing method of water-dispersible polyurethane composite film. The method of claim 1,
Cellulose nanofibers, characterized in that at least one of laccase and amylase is additionally added to the cellulose fiber suspension in the first enzyme treatment during the hydrolysis step, and endo-glucanase enzyme is additionally added in the second enzyme treatment. / Manufacturing method of water-dispersible polyurethane composite film.

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