KR102432045B1 - Method for manufacturing cellulose-based porous material and cellulose-based porous material manufactured by the same - Google Patents

Abstract

The present invention relates to a method for producing a cellulosic porous material having excellent biodegradability, water absorption rate, and elastic recovery, and to a cellulosic porous material prepared thereby.

Description

Method for producing a cellulosic porous material and a cellulosic porous material prepared thereby

The present invention relates to a method for producing a cellulosic porous material and to a cellulosic porous material prepared thereby.

Super absorbent polymer (SAP) refers to a hydrophilic polymer having a three-dimensionally cross-linked structure, and is a functional material that can absorb a water-soluble liquid thousands of times its own weight. However, since the main raw material of commercially used SAP is petroleum-based polymers, various problems such as depletion of petroleum resources, carbon dioxide emission, and environmental pollution due to incombustibility appear.

Among them, cellulose, a natural biomass resource, is an eco-friendly polymer abundant in nature, and micro fibers (micro fibers, microfibrillated cellulose, cellulose nanofibrils, etc.) and biodegradability, so many studies on the manufacture of porous materials such as aerogel, xerogel, cryogel, etc. are being conducted.

Such a porous material is obtained by replacing the liquid in the structure with air while maintaining the gel structure in a hydrogel state. Since most of the volume is filled with air, this material is light and low in density, so it can be effectively applied to moisture absorption, sound absorption and heat insulation materials. However, cellulosic porous materials generally produced have a problem in that when exposed to moisture due to hydrogen bonds between fibers, the bonds are broken and dissociated in water.

Accordingly, there is a need for a technology capable of easily manufacturing a cellulosic porous material having excellent physical properties such as moisture absorption and elastic recovery while stably maintaining its structure even when exposed to moisture.

An object of the present invention is to provide a method for producing a cellulosic porous material having excellent biodegradability, water absorption rate, and elastic recovery, and a cellulosic porous material prepared thereby.

However, the problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

An exemplary embodiment of the present invention comprises the steps of producing a pulp using a biomass raw material; producing, from the pulp, cellulose fibers comprising at least one of cellulose microfibers and cellulose fibrils; preparing a suspension containing the cellulose fibers and a solvent; preparing a hydrogel by adding a crosslinking agent including a glycidyl compound to the suspension; and removing the solvent contained in the hydrogel to prepare a porous material; provides a method for producing a cellulosic porous material comprising a.

In addition, an exemplary embodiment of the present invention provides a cellulosic porous material prepared by the above manufacturing method.

The method for manufacturing a cellulosic porous material according to an exemplary embodiment of the present invention may stably prepare a porous material having a three-dimensional network structure.

In addition, the method for producing a cellulosic porous material according to an exemplary embodiment of the present invention can produce an environmentally friendly and efficient cellulosic porous material.

In addition, the cellulosic porous material according to an exemplary embodiment of the present invention may have excellent biodegradability, moisture absorption, elasticity and recovery.

However, the effects of the present invention are not limited to the above-described effects, and may be variously expanded without departing from the spirit and scope of the present invention.

1 shows SEM photographs of cellulose-based airgels prepared in Examples 1 to 4 of the present invention.

Throughout this specification, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

Throughout this specification, when a member is said to be located “on” another member, this includes not only a case in which a member is in contact with another member but also a case in which another member is present between the two members.

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

An exemplary embodiment of the present invention comprises the steps of producing a pulp using a biomass raw material; producing, from the pulp, cellulose fibers comprising at least one of cellulose microfibers and cellulose fibrils; preparing a suspension containing the cellulose fibers and a solvent; preparing a hydrogel by adding a crosslinking agent including a glycidyl compound to the suspension; and removing the solvent contained in the hydrogel to prepare a porous material; provides a method for producing a cellulosic porous material comprising a.

The method for manufacturing a cellulosic porous material according to an exemplary embodiment of the present invention may stably prepare a porous material having a three-dimensional network structure. In addition, the method for producing a cellulosic porous material according to an exemplary embodiment of the present invention can produce an environmentally friendly and efficient cellulosic porous material.

According to an exemplary embodiment of the present invention, the biomass raw material may include at least one of a lignocellulosic biomass raw material and a non-woody biomass raw material. Specifically, the lignocellulosic biomass raw material may include at least one of softwood wood chips and hardwood wood chips, but the type of the lignocellulosic biomass raw material is not limited. In addition, the non-wood-based biomass raw material may include at least one of kenaf, hemp, rice, bagasse, bamboo, seaweed, corn stalk, corn core, rice straw, rice husk, wheat straw and sugar cane stalk. However, the type of the non-wood-based biomass raw material is not limited. By using the above-described type of biomass raw material, the cellulosic porous material having high biodegradability and being an eco-friendly material can be manufactured.

According to an exemplary embodiment of the present invention, the manufacturing of the pulp may include reacting the biomass raw material with a mixed solvent of a glycol ether-based solvent and an acid. That is, organic solvent pulp can be prepared from the biomass raw material. Specifically, the pulp may be formed by reacting the biomass raw material with a mixed solvent of a glycol ether-based solvent and an acid. When the biomass raw material is reacted with a mixed solvent of a glycol ether-based solvent and an acid to form pulp, physical properties such as water absorption, water retention, and elastic recovery of the produced porous material can be effectively improved.

According to an exemplary embodiment of the present invention, the mixed solvent may be a mixture of a glycol ether-based solvent and an acid. The glycol ether-based solvent is ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, propylene glycol methyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and at least one of dipropylene glycol methyl ether. However, the type of the glycol ether-based solvent is not limited. In addition, hydrochloric acid, sulfuric acid, nitric acid, etc. may be used as the acid, but the type of the acid is not limited.

According to an exemplary embodiment of the present invention, the mixed solvent may have a volume ratio of the glycol ether-based solvent to the acid of 95:5 to 99:1. Specifically, the volume ratio of the glycol ether-based solvent and the acid included in the mixed solvent may be 96:4 to 98.5:1.5, 96.5:3.5 to 98:2, or 97:3 to 97.5:2.5. When the volume ratio of the glycol ether-based solvent and the acid included in the mixed solvent is within the above range, pulp can be effectively prepared from the biomass raw material.

According to an exemplary embodiment of the present invention, in the forming of the pulp, the mixed solvent may be reacted at a mixing ratio of 1L to 3L with respect to 1 Kg of the biomass raw material. Specifically, the mixing ratio of the mixed solvent to 1 Kg of the biomass raw material may be 1.5L to 2.5L, or 2L. By adjusting the mixing ratio of the biomass raw material and the mixed solvent to the above-mentioned range, it is possible to improve the yield of the produced pulp.

According to an exemplary embodiment of the present invention, the step of forming the pulp may be performed at a temperature of 100 ℃ or more and 150 ℃ or less. Specifically, the temperature of the step of forming the pulp may be 110 ℃ or more and 140 ℃ or less, or 120 ℃ or more and 130 ℃ or less. By controlling the temperature at which the step of forming the pulp is performed in the above-described range, the pulp can be stably formed from the biomass raw material.

In addition, the step of forming the pulp may be performed for a time of 60 minutes or more and 180 minutes or less, 90 minutes or more and 160 minutes or less, or 120 minutes or more and 150 minutes or less. When the time for performing the step of forming the pulp is within the above range, the pulp may be stably formed, and the yield of the pulp may be improved.

According to an exemplary embodiment of the present invention, in the manufacturing of the pulp, kraft pulp, sulfite pulp, and seaweed pulp may be manufactured using the biomass raw material. In addition, the produced pulp may be used after bleaching or without bleaching.

According to an exemplary embodiment of the present invention, it is possible to wash the produced pulp. Specifically, impurities contained in the pulp may be removed using distilled water. Through this, it is possible to effectively prevent the deterioration of the physical properties of the prepared cellulosic porous material.

According to an exemplary embodiment of the present invention, the manufacturing of the cellulose fiber comprises: preparing a pulp slurry by mixing the pulp with a basic solution; and adding the pulp slurry to a mixer and kneading to prepare the cellulose microfiber. That is, by performing the above process, it is possible to manufacture cellulose microfibers from the pulp.

According to an exemplary embodiment of the present invention, the basic solution may include a sodium hydroxide solution, a potassium hydroxide solution, and a lithium hydroxide solution, but the type of the basic solution is not limited thereto.

According to an exemplary embodiment of the present invention, the concentration of the basic solution included in the pulp slurry may be 0.1 N or more and 1 N or less. Specifically, the concentration of the basic solution may be 0.15 N or more and 0.8 N or less, 0.2 N or more and 0.6 N or less, or 0.25 N or more and 0.5 N or less. When the concentration of the basic solution is within the above range, it is possible to effectively form cellulose microfibers from the pulp slurry.

According to an exemplary embodiment of the present invention, the pH of the pulp slurry may be 8 or more and 14 or less. Specifically, the pH of the pulp slurry may be 9 or more and 13 or less, or 10 or more and 12 or less. By adjusting the pH of the pulp slurry to the above-mentioned range, it is possible to effectively form cellulose microfibers from the pulp slurry. In addition, when the pH of the pulp slurry is within the above range, the swelling of the fibers included in the pulp slurry is promoted, so that finer cellulose microfibers can be effectively manufactured through a kneading treatment to be described later.

According to an exemplary embodiment of the present invention, based on 100 parts by weight of the pulp slurry, the content of the pulp may be 3 parts by weight or more and 15 parts by weight or less. Specifically, with respect to 100 parts by weight of the pulp slurry, the content of the pulp is 4.5 parts by weight or more and 12.5 parts by weight or less, 5 parts by weight or more and 10 parts by weight or less, 3 parts by weight or more and 10 parts by weight or less, or 7.5 parts by weight or more 15 It may be less than or equal to parts by weight. For example, the content of the pulp included in the pulp slurry may be 3% by weight or more and 15% by weight or less.

By adjusting the content of the pulp included in the pulp slurry to the above-mentioned range, friction and dispersion between fibers are efficiently performed during the kneading process using a mixer, thereby making it possible to easily manufacture micronized cellulose microfibers. On the other hand, when the content of the pulp included in the pulp slurry is too small, the frictional efficiency between the fibers is lowered, so that it is impossible to easily manufacture the micronized cellulose microfibers. In addition, when the content of the pulp included in the pulp slurry is too large, the pulp slurry has a problem in that kneading is not performed smoothly due to high viscosity.

According to an exemplary embodiment of the present invention, the kneading step may be performed at a rotation speed of 100 rpm or more and 600 rpm or less. Specifically, the rotation speed at which the kneading step is performed may be 150 rpm or more and 550 rpm or less, 200 rpm or more and 500 rpm or less, 250 rpm or more and 450 rpm or less, or 300 rpm or more and 400 rpm or less. By adjusting the rotation speed at which the kneading step is performed within the above-described range, the manufactured cellulose microfiber can be more stably formed. The rotation speed may mean a rotation speed of a mixer used in the kneading step.

According to an exemplary embodiment of the present invention, the kneading step may be performed at a temperature of 20 ℃ or more and 35 ℃ or less. By adjusting the temperature of the step of performing the kneading to the above-mentioned range, it is possible to suppress deformation and damage to the cellulose microfibers produced.

According to an exemplary embodiment of the present invention, in the method for manufacturing the cellulose microfibers, the physical properties of the cellulose microfibers to be manufactured can be controlled by controlling the time for performing the kneading. Specifically, the step of performing the kneading may be performed for a time of 1 hour or more and 3 hours or less. Through this, it is possible to effectively improve the physical properties of the produced cellulose-based porous material, such as moisture absorption, moisture retention, and elastic recovery.

According to an exemplary embodiment of the present invention, the mixer to which the pulp slurry is added is a kneader, and may be a Hobart mixer, a spiral mixer, or a vertical mixer. However, the type of the mixer is not limited, and a known device capable of applying a shearing force to the pulp slurry may be used.

According to an exemplary embodiment of the present invention, the manufacturing of the cellulose fiber may include homogenizing the pulp to prepare the cellulose fibrils. Specifically, it is possible to prepare cellulose fibrils by homogenizing the organic solvent pulp described above. Through this, cellulose nanofibrils (CNF), or microfibrillated cellulose (microfibrillated cellulose, MFC) can be prepared. In order to homogenize the pulp, a high-pressure homogenizer, a high-pressure emulsifier, etc. used in the art may be used. For example, when homogenizing the pulp using a high-pressure homogenizer, the number of times the pulp is passed through the high-pressure homogenizer, the operating pressure of the high-pressure homogenizer, etc. are adjusted to determine the size, shape, etc. of the cellulose fibrils produced. can be controlled

According to an exemplary embodiment of the present invention, the lignin content of the cellulose fiber may be 30% by weight or less. That is, the lignin content of the cellulose microfibers prepared from the pulp may be 30% by weight or less, and the lignin content of the cellulose fibrils prepared from the pulp may be 30% by weight or less.

Specifically, the lignin content of the prepared cellulose fibers (cellulose microfibers or cellulose fibrils) is 0.1 wt% or more and 30 wt% or less, 1 wt% or more and 28 wt% or less, 5 wt% or more and 25 wt% or less, 10 wt% % or more and 22.5 wt% or less, or 15 wt% or more and 20 wt% or less. On the other hand, by bleaching the prepared cellulose fiber to remove lignin, it is possible to form a cellulose fiber having a lignin content of 0 wt%.

When the lignin content of the cellulose fiber is within the above-mentioned range, physical properties such as water absorption rate, water retention amount, elastic recovery force, and tensile strength of the prepared cellulosic porous material can be effectively improved.

According to an exemplary embodiment of the present invention, the size of the cellulose fiber may be 0.1 μm or more and 500 μm or less. That is, the size of the cellulose microfibers prepared from the pulp may be 0.1 μm or more and 500 μm or less, and the size of the cellulose fibrils prepared from the pulp may be 0.1 μm or more and 500 μm or less. Specifically, the size of the cellulose fibers is 1 µm or more and 475 µm or less, 5 µm or more and 450 µm or less, 10 µm or more and 400 µm or less, 20 µm or more and 375 µm or less, 30 µm or more and 350 µm or less, 40 µm or more and 320 µm or less. , 0.1 μm or more and 100 μm or less, 10 μm or more and 100 μm or less, 15 μm or more and 97.5 μm or less, 20 μm or more and 95 μm or less, or 25 μm or more and 92.5 μm or less. When the size of the cellulose fiber is within the above range, the water absorption rate, water retention amount, elastic recovery force, tensile strength and compressive strength of the produced cellulosic porous material can be effectively improved. In addition, the size of the cellulose fibers may mean the average size of the particles.

According to an exemplary embodiment of the present invention, a suspension may be prepared by mixing the cellulose fibers and a solvent. Distilled water, water, acetone, ethanol, methanol, etc. can be used as the solvent.

According to an exemplary embodiment of the present invention, based on 100 parts by weight of the suspension, the content of the cellulose fiber may be 0.5 parts by weight or more and 10 parts by weight or less. Specifically, the content of the cellulose fiber included in the suspension is based on 100 parts by weight of the suspension, 1 part by weight or more and 8.5 parts by weight or less, 1 part by weight or more and 5 parts by weight or less, 1 part by weight or more and 3 parts by weight or less, 2.5 It may be at least 7.5 parts by weight, at least 4.5 parts by weight and up to 6 parts by weight, at least 0.5 parts by weight and not more than 5 parts by weight, or at least 5 parts by weight and not more than 10 parts by weight. By adjusting the content of the cellulose fibers included in the suspension to the above-described range, the hydrogel can be effectively prepared.

According to an exemplary embodiment of the present invention, the molar ratio of the cellulose fiber and the crosslinking agent may be 1:0.1 to 1:10. Specifically, the molar ratio of the cellulose fiber and the crosslinking agent included in the suspension is 1:0.3 to 1:8.5, 1:0.5 to 1:7, 1:1 to 1:5, 1:1 to 1:3, 1 :0.1 to 1:5, 1:0.5 to 1:3.5, or 1:1 to 1:2. When the molar ratio of the cellulose fibers and the crosslinking agent included in the suspension is within the above range, crosslinking between the cellulose fibers can be effectively formed, whereby a porous material having a three-dimensional network structure can be stably formed. Through this, it is possible to effectively improve the physical properties of the produced cellulosic porous material, such as water absorption, water retention, elastic recovery force, tensile strength, compressive strength.

According to an exemplary embodiment of the present invention, the crosslinking agent may include a glycidyl-based compound. Specifically, the glycidyl-based compound may include at least two or more glycidyl groups in the molecular structure. More specifically, the glycidyl compound is glycerol diglycidyl ether, diglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol It may include at least one of diglycidyl ether, and poly (propylene glycol) diglycidyl ether.

By using the glycidyl compound as the crosslinking agent, crosslinking between the cellulose fibers can be effectively formed. In addition, when a glycidyl-based compound is used as a crosslinking agent, the prepared cellulosic porous material does not dissociate in water even when immersed in water, and its shape can be stably maintained. On the other hand, the conventional formaldehyde used as a crosslinking agent has a problem that is harmful to the human body and the environment, but the glycidyl-based compound can solve this problem because it is non-toxic.

According to an exemplary embodiment of the present invention, preparing the hydrogel may include adding a basic catalyst to the suspension. By adding the basic catalyst to the suspension including the cellulose fibers and the crosslinking agent, it is possible to promote a crosslinking reaction between the cellulose fibers. In addition, by using the basic catalyst, the time of the crosslinking reaction can be shortened, and there is an advantage in that the temperature at which the crosslinking reaction is performed can be lowered. The basic catalyst may include at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

According to an exemplary embodiment of the present invention, the molar ratio of the cellulose fiber to the basic catalyst may be 1:0.1 to 1:3. Specifically, the molar ratio of the cellulose fiber to the basic catalyst may be 1:0.3 to 1:2.5, 1:0.5 to 1:2, 1:0.7 to 1:1.8, or 1:1 to 1:1.5. When the content of the basic catalyst included in the suspension is within the above-described range, it is possible to effectively promote a crosslinking reaction between the cellulose fibers, thereby reducing the cellulosic porous material manufacturing process time and improving manufacturing efficiency.

According to an exemplary embodiment of the present invention, the step of preparing the hydrogel may be performed at a temperature of 20 ℃ or more and 100 ℃ or less, for a time of 5 minutes or more and 180 minutes or less. Specifically, the step of preparing the hydrogel is 25 ℃ or more and 85 ℃ or less, 30 ℃ or more and 70 ℃ or less, 35 ℃ or more and 55 ℃ or less, 40 ℃ or more and 100 ℃ or less, 50 ℃ or more and 90 ℃ or less, or 60 ℃ or more. It can be carried out at a temperature of 80 °C or less. In addition, the step of preparing the hydrogel may be performed for a time of 15 minutes or more and 160 minutes or less, 30 minutes or more and 140 minutes or less, 45 minutes or more and 120 minutes or less, or 60 minutes or more and 90 minutes or less. By controlling the temperature and time for preparing the hydrogel in the above-described ranges, the hydrogel can be stably prepared from the suspension.

According to an exemplary embodiment of the present invention, preparing the porous material may include freezing and freeze-drying the hydrogel. In order to freeze the hydrogel, the hydrogel may be ice-templated using a freezer or liquid nitrogen. By freezing the hydrogel, pores can be formed therein, and then, by removing the solvent through freeze-drying, a porous material can be prepared.

According to an exemplary embodiment of the present invention, the freezing of the hydrogel is performed at a temperature of -50 ℃ or more and -5 ℃ or less, and the freeze-drying is -85 ℃ or more and -40 ℃ or less and 1 mTorr or more and 50 mTorr or less can be carried out at a pressure of Specifically, the freezing of the hydrogel is -45 ℃ or more -10 ℃ or less, -40 ℃ or more -15 ℃ or less, -35 ℃ or more -20 ℃ or less, or -30 ℃ or more and -25 ℃ or less to be performed at a temperature. can By controlling the temperature for freezing the hydrogel in the above-mentioned range, it is possible to effectively freeze the solvent contained in the hydrogel, thereby efficiently forming pores in the hydrogel.

In addition, the temperature at which the freeze-drying is performed may be -80 °C or more and -50 °C or less, or -70 °C or more and -60 °C or less. The pressure at which the freeze drying is performed may be 5 mTorr or more and 45 mTorr or less, 10 mTorr or more and 40 mTorr or less, 15 mTorr or more and 35 mTorr or less, or 20 mTorr or more and 30 mTorr or less. By adjusting the temperature and pressure for freeze-drying the frozen hydrogel to the above-mentioned ranges, the solvent frozen in the hydrogel can be effectively removed, and through this, the porous structure of the cellulosic porous material can be stably formed. have.

An exemplary embodiment of the present invention provides a cellulosic porous material prepared by the above manufacturing method.

The cellulosic porous material according to an exemplary embodiment of the present invention may have excellent biodegradability, moisture absorption, elasticity and recovery.

According to an exemplary embodiment of the present invention, the cellulosic porous material may be formed in the form of airgel, xerogel, or cryogel.

According to an exemplary embodiment of the present invention, the density of the cellulosic porous material may be 0.05 g/cm ³ or less. Specifically, the density of the cellulosic porous material is 0.045 g/cm ³ or less, 0.04 g/cm ³ or less, 0.035 g/cm ³ or less, 0.03 g/cm ³ or less, 0.025 g/cm ³ or less, or 0.023 g/cm 3 or less. cm ³ or less. In addition, the density of the cellulosic porous material may be 0.01 g/cm ³ or more, 0.015 g/cm ³ or more, or 0.02 g/cm ³ or more. The cellulosic porous material satisfying the density in the above-mentioned range may have excellent physical properties such as moisture absorption, moisture retention, elastic recovery, tensile strength, and compressive strength.

According to an exemplary embodiment of the present invention, the water absorption rate of the cellulosic porous material may be 2,000% or more and 6,000% or less. Specifically, the water absorption rate of the cellulosic porous material is 2,500% or more and 6,000% or less, 3,000% or more and 6,000% or less, 3,500% or more and 6,000% or less, 4,000% or more and 6,000% or less, 4,500% or more, 6,000% or less, 5,000% or more 6,000% or less, or 5,500% or more and 6,000% or less. The cellulosic porous material satisfying the moisture absorption rate in the above range can be effectively applied to the moisture absorption material.

According to an exemplary embodiment of the present invention, the moisture retention per 1 g of the cellulosic porous material may be 20 g or more. Specifically, the moisture retention per 1 g of the cellulosic porous material is 20 g or more and 60 g or less, 25 g or more 60 g or less, 30 g or more 60 g or less, 35 g or more 60 g or less, 40 g or more 60 g or less, 45 g It may be 60 g or more, 50 g or more and 60 g or less, or 55 g or more and 60 g or less. The cellulosic porous material satisfying the moisture retention amount in the above-described range can be effectively applied to the moisture absorption material.

According to an exemplary embodiment of the present invention, the tensile strength of the cellulosic porous material may be 150 gf/mm ² or more. Specifically, the tensile strength of the cellulosic porous material is 150 gf/mm ² or more, 170 gf/mm ² or more, 200 gf/mm ² or more, 250 gf/mm ² or more, 300 gf/mm ² or more, 350 gf/ mm ² or more, 400 gf/mm ² or more, 450 gf/mm ² or more, 500 gf/mm ² or more, 550 gf/mm ² or more. In addition, the tensile strength of the cellulosic porous material may be 600 gf/mm ² or less, 580 gf/mm ² or less, 550 gf/mm ² or less, or 500 gf/mm ² or less.

According to an exemplary embodiment of the present invention, the compressive strength of the cellulosic porous material may be 500 gf/mm ² or more. Specifically, the compressive strength of the cellulosic porous material is 550 gf/mm ² or more, 600 gf/mm ² or more, 650 gf/mm ² or more, 700 gf/mm ² or more, 750 gf/mm ² or more, 800 gf/ mm ² or more, 850 gf/mm ² or more, 900 gf/mm ² or more, 950 gf/mm ² or more, 1,000 gf/mm ² or more, 1,100 gf/mm ² or more, 1,300 gf/mm ² or more, 1,500 gf/mm It can be ² or more. In addition, the compressive strength of the cellulosic porous material may be 1,800 gf/mm ² or less, 1,600 gf/mm ² or less, 1,500 gf/mm ² or less, and 1,400 gf/mm ² or less.

The cellulosic porous material having tensile strength and compressive strength satisfying the above-mentioned ranges may have excellent mechanical properties such as durability and impact resistance against external impact.

Hereinafter, examples will be given to describe the present invention in detail. However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention is not to be construed as being limited to the embodiments described below. The embodiments of the present specification are provided to more completely explain the present invention to those of ordinary skill in the art.

Example 1

Preparation of Cellulose Microfibers

Softwood wood chips were prepared. The prepared coniferous wood chips had a clasone lignin content of about 28.7%, and the chip size was 35 (±3) mm high X 8 (±3) mm wide X 7 (±2) mm thick.

Thereafter, sulfuric acid (95%) was prepared with ethylene glycol monomethyl ether and acid as a glycol ether-based solvent, and a mixed solvent was prepared by mixing ethylene glycol monomethyl ether and sulfuric acid in a volume ratio of 97:3.

After that, it was put into a high-pressure steam treatment device (autoclave, HST 506-6, Hanbaek ST, Korea) at a mixing ratio of 2L of mixed solvent for 1Kg of wood chips, reacted at 120°C for 120 minutes, filtered with distilled water, and 680 mL of freeness An organic solvent pulp (lignin content 27.4%) having (CSF) was prepared.

A pulp slurry was prepared by mixing the prepared organic solvent pulp and 0.25 N aqueous NaOH solution (500 mL). At this time, the content of the organic solvent pulp was 5 parts by weight (5.0 weight %) based on 100 parts by weight of the pulp slurry, and the pH of the pulp slurry was about 13.

Then, about 499.5 mL of the pulp slurry was added to a Hobart mixer having a maximum capacity (total volume) of 4,500 mL, and kneaded at a rotation speed of 281 rpm for 3 hours to obtain cellulose microfibers.

Thereafter, 2,000 mL of 0.5 N NaOH aqueous solution was added to the obtained cellulose microfiber, followed by filtration and dehydration to elute lignin. The water washing process was repeated to remove residual NaOH components to finally prepare cellulose microfibers.

Preparation of cellulosic porous material

The cellulose microfiber prepared above was mixed with distilled water to prepare a suspension. At this time, based on 100 parts by weight of the suspension, the content of the cellulose microfiber was 1 part by weight.

Thereafter, glycerol diglycidyl ether as a crosslinking agent and sodium hydroxide as a basic catalyst were added to the suspension. In this case, the molar ratio of the cellulose microfiber:crosslinking agent:basic catalyst was 1:1:1.

Thereafter, the suspension was stirred for about 5 minutes using a stirrer, and reacted in a constant temperature water bath at 60° C. for 1 hour to prepare a hydrogel. After freezing the prepared hydrogel in a freezer at -28 ° C. for 6 hours, it was dried in a freeze dryer (temperature: -40 ° C., pressure: 50 mTorr) for 48 hours to prepare a cellulose-based airgel.

Example 2

In Example 1, a cellulose-based airgel was prepared in the same manner as in Example 1, except that the prepared cellulose microfibers were treated with chlorous acid and bleached.

Example 3

The organic solvent pulp prepared in Example 1 was prepared. Then, by passing through a high pressure homogenizer (Ariete NS311OH, GEA Niro Soavi, Italy) at a pressure of about 900 bar three times, microfibrillated cellulose (MFC) was prepared.

Thereafter, a cellulose-based airgel was prepared in the same manner as in Example 1, except that the microfibrillated cellulose prepared above was used instead of the cellulose microfiber in Example 1.

Example 4

After pre-treating hardwood bleached kraft pulp (HwBKP) with endo-glucanase, a cellulose-based degrading enzyme, it was passed through a high pressure homogenizer (Ariete NS311OH, GEA Niro Soavi, Italy) at a pressure of about 900 bar 7 times to pass cellulose nanofibrils (CNF) ) was prepared.

Thereafter, a cellulose-based airgel was prepared in the same manner as in Example 1, except that the cellulose nanofibrils prepared above were used instead of the cellulose microfibers in Example 1.

Example 5

Red algae pulp was produced using agar agar stems as raw materials, followed by fiberization and bleaching using hydrogen peroxide and caustic soda. Thereafter, red algae MFC was prepared by passing the red algae pulp through a high-pressure homogenizer (Microfluidizer, NH500, ILSHIN AUTOCLAVE, Korea) 5 times at a pressure of 800 bar.

Thereafter, a cellulose-based airgel was prepared in the same manner as in Example 1, except that the red algae MFC prepared above was used instead of the cellulose microfiber in Example 1.

Comparative Example 1

The suspension prepared in Example 1 was prepared. Then, epichlorohydrin as a crosslinking agent and sodium hydroxide as a basic catalyst were added to the suspension. In this case, the molar ratio of the cellulose microfiber:crosslinking agent:basic catalyst was 1:1:1.

Thereafter, a cellulose-based airgel was prepared in the same manner as in Example 1.

Comparative Example 2

The suspension prepared in Example 1 was prepared. Then, glutaraldehyde as a crosslinking agent and aluminum sulfate as a catalyst were added to the suspension. At this time, the molar ratio of cellulose microfiber:crosslinking agent:catalyst was 1:1:1.

Thereafter, a cellulose-based airgel was prepared in the same manner as in Example 1.

Experimental example

Porosity analysis of cellulosic airgel

Using a scanning electron microscope (Scanning Electron Microscope, SEM, JSM-7900F, JEOL Ltd., Japan), the cellulose-based airgels prepared in Examples 1 to 4 were photographed, and the photographed photograph is shown in FIG. .

1 shows SEM photographs of cellulose-based airgels prepared in Examples 1 to 4 of the present invention.

Referring to FIG. 1 , it was confirmed that the cellulose-based airgels prepared in Examples 1 to 4 had a three-dimensional network structure including pores.

Determination of residual lignin content

The residual lignin content of the cellulose microfiber prepared in Example 1 was measured as follows.

Specifically, the sample was prepared by freeze-drying the cellulose microfiber prepared in Example 1, and 5 mL of 72% sulfuric acid was added to 0.2 g of the cellulose microfiber sample in a dry state, and stirred every hour for 4 hours. It was left standing at room temperature. Then, after dilution by adding 196 mL of distilled water, the reaction was carried out at a temperature of 120° C. in an autoclave for 2 hours. After the reaction was completed, it was filtered under reduced pressure through a glass filter using distilled water, and the residue of the glass filter was dried in a dryer at 105°C. Thereafter, the residual lignin content was calculated by Equation 1 below.

[Equation 1]

L = W/S X 100

In Equation 1, “L” is the residual lignin content, “S” is the total dry weight of the sample (g), and “W” is the weight of the dried residue (g).

In addition, the residual lignin content was measured for the bleached cellulose microfiber prepared in Example 2, MFC prepared in Example 3, CNF prepared in Example 4, and red algae MFC prepared in Example 5, and are shown in Table 1 below. indicated.

Particle size measurement

The particle size of the cellulose microfiber prepared in Example 1 was measured as follows.

Specifically, the average particle size of the cellulose microfibers prepared in Example 1 was analyzed using a particle size analyzer (Mastersizer 3000, alvern Instruments Ltd., orcestershire, UK).

In addition, the average particle size of the bleached cellulose microfibers prepared in Example 2, MFC prepared in Example 3, CNF prepared in Example 4, and red algae MFC prepared in Example 5 were analyzed, and the results are shown in Table 1 below. indicated.

Density measurement

The mass and volume of the cellulose-based airgel prepared in Example 1 were measured, and the density was calculated as the mass per unit volume, and is shown in Table 2 below.

In addition, the densities of the cellulosic airgels prepared in Examples 2 to 5 and Comparative Examples 1 to 2 are shown in Table 2 below.

Determination of water absorption and water retention

The water absorption and water retention of the cellulose-based airgel prepared in Example 1 were measured as follows.

The cellulosic airgel was completely dried, and the dried cellulosic airgel was immersed in distilled water for 24 hours. Thereafter, the cellulose-based airgel was removed and the water falling for 5 minutes was removed, then the water absorption rate was calculated through Equation 2 below, and the water retention amount was calculated through Equation 3 below.

[Equation 2]

W _t1 = (W - W ₀ )/W ₀ X 100

[Equation 3]

W _t2 = (W - W ₀ )/W ₀

In Equation 2, W _t1 is the water absorption rate, W is the mass of the cellulosic airgel after immersion for 24 hours, and W ₀ is the mass of the initially dried cellulosic airgel. In addition, in Equation 3, W _t2 is the water retention amount, W is the mass of the cellulosic airgel after immersion for 24 hours, and W ₀ is the mass of the initially dried cellulosic airgel.

Thereafter, the moisture absorption and moisture retention of the cellulosic airgels prepared in Examples 2 to 5 and Comparative Examples 1 to 2 are shown in Table 2 below.

Elastic recovery force measurement

The elastic recovery force of the cellulose-based airgel prepared in Example 1 was measured as follows.

First, the thickness before compression of the cellulose-based airgel was measured. Thereafter, the cellulose-based airgel was compressed at a strain rate of 95% under compression conditions of 50kgf and 1mm/min using a universal tensile strength tester, and the compressed cellulose-based airgel was immersed in distilled water for 24 hours, and then the cellulose-based airgel was rescued. After removing the dripping water for 5 minutes, the thickness of the cellulose-based airgel was measured. Then, the rate of change in thickness of the cellulose-based airgel before and after compression was calculated.

Then, the elastic recovery force of the cellulose-based airgel prepared in Examples 2 to 5 and Comparative Examples 1 to 2 is shown in Table 3 below.

Tensile strength measurement

The tensile strength of the cellulose-based airgel prepared in Example 1 was measured as follows.

Specifically, the tensile strength of the cellulose-based airgel was measured using a universal tensile strength tester (Hounsfield H500M, England). At this time, in order to measure the tensile strength, a cellulose-based airgel was prepared as a specimen having a height of 20 mm and a diameter of 10 mm, and the load cell load was set to 50 kgf and the tensile speed was set to 2 mm/min.

In addition, the tensile strengths of the cellulose-based airgels prepared in Examples 2 to 5 and Comparative Examples 1 to 2 were measured, and are shown in Table 4 below.

Compressive strength measurement

The compressive strength of the cellulose-based airgel prepared in Example 1 was measured as follows.

Specifically, the compressive strength of the cellulose-based airgel was measured using a universal tensile strength tester (Hounsfield H500M, England). At this time, in order to measure the compressive strength, a cellulose-based airgel was prepared as a specimen having a height of 10 mm and a diameter of 10 mm, and the final strain was set to 75% and measured at a rate of 1 mm/min.

The compressive strengths of the cellulose-based airgels prepared in Examples 2 to 5 and Comparative Examples 1 to 2 are shown in Table 4 below.

Particle size (㎛) Lignin content (%) Example 1 92.05 17.8 Example 2 90.01 3.5 Example 3 48.62 21.4 Example 4 22.68 0.0 Example 5 25.68 1.2

Density (g/cm ³ ) Moisture absorption rate (%) Water retention (g) Example 1 0.021 5858.5 ± 93.6 58.6 Example 2 0.021 5868.4 ± 184.3 58.7 Example 3 0.029 3392.4 ± 190.4 33.9 Example 4 0.025 4338.2 ± 120.7 43.4 Example 5 0.026 3866.6 ± 78.8 38.7 Comparative Example 1 0.054 3108.9 31.1 Comparative Example 2 0.06 3078.4 30.8

Elastic recovery force (%) 1 compression 2 compressions 3 compressions 4 compressions 5 compressions Example 1 98.7 93.5 91.0 91.3 86.8 Example 2 92.5 87.0 84.5 85.4 81.9 Example 3 83.6 76.8 74.0 72.5 69.2 Example 4 98.8 95.7 93.1 93.0 87.9 Example 5 98.9 97.4 95.4 93.4 91.2 Comparative Example 1 70.55 55.93 47.1 44.32 39 Comparative Example 2 67.71 57.4 45.85 47.85 36.7

Tensile strength (gf/mm ² ) Compressive strength (gf/mm ² ) Example 1 303.31 977.67 Example 2 316.04 1003.74 Example 3 172.72 768.01 Example 4 575.13 1548.33 Example 5 389.24 1100.71 Comparative Example 1 33.3 26.7 Comparative Example 2 30.6 22.3

Referring to Tables 1 to 4, it was confirmed that the cellulosic airgels prepared in Examples 1 to 5 of the present invention were excellent in water absorption rate, water retention amount, elastic recovery force, tensile strength and compressive strength.

On the other hand, it was confirmed that the cellulose-based airgels prepared in Comparative Examples 1 and 2 were inferior in water absorption rate, water retention amount, elastic recovery force, tensile strength and compressive strength compared to Examples 1 to 5.

Therefore, the method for producing a cellulosic porous material according to an exemplary embodiment of the present invention can produce a cellulosic porous material having high biodegradability and excellent water absorption, water retention, elastic recovery, tensile strength and compressive strength. can be known

The above detailed description illustrates and describes the present invention. In addition, the foregoing is merely to indicate and describe preferred embodiments of the present invention, and as described above, the present invention can be used in various other combinations, modifications and environments, the scope of the concept of the invention disclosed herein, and the writing Changes or modifications are possible within the scope equivalent to one disclosure and/or within the skill or knowledge in the art. Accordingly, the detailed description of the present invention is not intended to limit the present invention to the disclosed embodiments. In addition, the appended claims should be construed to include other embodiments as well.

Claims (17)

manufacturing pulp using biomass raw material;
producing, from the pulp, cellulose fibers comprising at least one of cellulose microfibers and cellulose fibrils;
preparing a suspension containing the cellulose fibers and a solvent;
preparing a hydrogel by adding a crosslinking agent including a glycidyl compound to the suspension; and
Including; removing the solvent contained in the hydrogel to prepare a porous material;
The step of preparing the porous material,
A method for producing a cellulosic porous material comprising the step of freezing and freeze-drying the hydrogel.
The method of claim 1,
The biomass raw material is a method for producing a cellulosic porous material comprising at least one of a lignocellulosic biomass raw material and a non-woody biomass raw material.
The method of claim 1,
The step of producing the pulp,
A method for producing a cellulosic porous material comprising the step of reacting the biomass raw material with a solvent mixture of a glycol ether-based solvent and an acid.
4. The method of claim 3,
With respect to 1 Kg of the biomass raw material, the method for producing a cellulosic porous material by reacting the mixed solvent at a mixing ratio of 1L to 3L.
The method of claim 1,
The step of producing the cellulose fiber,
mixing the pulp with a basic solution to prepare a pulp slurry; and
The method for producing a cellulosic porous material comprising a; adding the pulp slurry to a mixer and kneading to prepare the cellulose microfiber.
The method of claim 1,
The step of producing the cellulose fiber,
Method for producing a cellulosic porous material comprising the step of homogenizing the pulp to prepare the cellulose fibrils.
The method of claim 1,
The lignin content of the cellulose fiber is a method for producing a cellulosic porous material that is 30% by weight or less.
The method of claim 1,
Based on 100 parts by weight of the suspension, the content of the cellulose fiber is 0.5 parts by weight or more and 10 parts by weight or less.
The method of claim 1,
The molar ratio of the cellulose fibers and the crosslinking agent is 1:0.1 to 1:10 of the method for producing a cellulosic porous material.
The method of claim 1,
The step of preparing the hydrogel,
adding a basic catalyst to the suspension;
The molar ratio of the cellulose fibers and the basic catalyst is 1:0.1 to 1:3 of the method for producing a cellulosic porous material.
The method of claim 1,
The step of preparing the hydrogel,
A method of producing a cellulosic porous material that is carried out at a temperature of 20 ° C. or more and 100 ° C. or less, for a time of 5 minutes or more and 180 minutes or less.
delete The method of claim 1,
The freezing of the hydrogel is carried out at a temperature of -50 ℃ or more and -5 ℃ or less, and the freeze-drying is performed at a temperature of -85 ℃ or more and -40 ℃ or less and a pressure of 1 mTorr or more and 50 mTorr or less. A method for producing a porous material.
A cellulosic porous material prepared by the method according to claim 1 .
15. The method of claim 14,
The cellulosic porous material has a density of 0.05 g/cm ³ or less of the cellulosic porous material.
15. The method of claim 14,
The cellulosic porous material has a water absorption rate of 2,000% or more and 6,000% or less of the cellulosic porous material.
15. The method of claim 14,
The cellulosic porous material having a water retention amount of 20 g or more per 1 g of the cellulosic porous material.

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