Paramylum-cellulose mixed fiber and manufacturing method thereof

Abstract

To provide a paramylum-cellulose mixed fiber with elevated water resistance, a nonwoven fabric fabricated by using the mixed fiber, and a sanitation mask fabricated by using the nonwoven fabric.SOLUTION: A mass ratio of a paramylum-cellulose mixed fiber is set in a range of paramylum:cellulose=70:30-50:50. A manufacturing method of the paramylum-cellulose mixed fiber includes a dope preparation step of dissolving and mixing cellulose and paramylum in an ionic solution and a spinning step of discharging the dope obtained in the dope preparation step to a coagulation liquid for forming yarns by a dry wet spinning method, wherein a sum total of the cellulose and the paramylum is 10-30 mass% of the ionic solution, and a mass ratio of the cellulose and the paramylum is set in the range of 70:30-50:50.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a paramylon-cellulose blend fiber and a method for producing the same. [Background technology]

[0002] In modern society, the use of sustainable resources that minimize environmental impact is becoming increasingly important, and renewable resources in particular are attracting increasing attention. Regenerated cellulose, one such renewable resource, is extracted or produced from natural cellulose-derived biomass and is used in a variety of industrial sectors. In particular, regenerated cellulose is applied to a wide range of products and processes, including textiles, packaging, building materials, bioplastics, and medical materials, and is recognized for its sustainability and positive environmental impact.

[0003] Meanwhile, the spread of the novel coronavirus (COVID-19) has raised awareness of the importance of wearing masks as an effective means of preventing infection, and demand for masks increased so much that they were difficult to obtain in Japan at one point. Masks can prevent the spread of pathogens such as viruses and bacteria, reducing the risk of infection. Furthermore, because individual behavior is an important means of preventing the spread of infectious diseases, wearing masks is also important for promoting the formation of herd immunity. Nonwoven fabric, one of the materials used to make masks, can be made from regenerated cellulose fibers, so the development of biomass-derived nonwoven fabrics is needed to prevent the spread of infectious diseases while reducing the environmental impact.

[0004] Paramylon is a type of polysaccharide found in the microalgae Euglena (Japanese name: Midorimushi). Paramylon is primarily in the form of β-1,3-glucan, and is a polysaccharide stored within the cells of Euglena. Paramylon is being researched as an ingredient for immune regulation and health promotion, particularly in the food, cosmetics, and pharmaceutical fields. β-1,3-glucan is believed to have immunostimulatory effects, and paramylon, which is a β-1,3-glucan, may also contribute to improving immune function.

[0005] In an example of the application of paramylon in the textile field, it is known that embedding paramylon into regenerated cellulose fibers, which are the base materials for rayon, cupra, lyocell, etc., can improve various physical properties such as elongation, color, water swelling, and dye absorption without reducing strength (Patent Document 1). The amount of paramylon contained in the paramylon-containing cellulose fibers in Patent Document 1 is 0.5 to 10% by weight, and the properties of cellulose fibers containing 10% or more by weight of paramylon have not been evaluated.

[0006] Another example of the application of paramylon in the textile field is Patent Document 2. It has been reported that wet-spun fibers made using 100% paramylon by the viscose method have higher moisture absorption rates, decomposition temperatures, and elongation than wet-spun fibers made using cellulose (Patent Document 2). The objective of Patent Document 2 is to provide wet-spun fibers containing β-1,3-glucan as the only constituent molecule, a method for producing the same, and submicron fibrils and a method for producing the same. Patent Document 2 discloses a blended fiber with a 50:50 mass ratio of cellulose:paramylon, but this is disclosed as a negative control in which the cellulose / paramylon blended fiber does not form submicron fibrils, and does not disclose mechanical properties such as breaking strength and elongation that are important for practical use.

[0007] Curdlan is a bacterial polysaccharide, and like paramylon, is a crystal of unbranched β-1,3-glucan. Because curdlan has strong intermolecular hydrogen bonds, it is insoluble in water or alcohol, but is soluble in alkaline solutions and DMSO. Utilizing this property, it has been reported that recycled curdlan fiber made from curdlan as a raw material was spun using a dry-wet spinning method (Non-Patent Document 1). However, Non-Patent Document 1 does not consider spinning paramylon or paramylon-cellulose blend fibers using a dry-wet spinning method. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent Publication No. 2021-031785 [Patent Document 2] Japanese Patent Publication No. 2023-086237 [Non-patent literature]

[0009] [Non-Patent Document 1] Suzuki, S., Togo, A. and Iwata, T. (2022) 'Dry-jet wet spinning of β-1,3-glucan and α-1,3-glucan', Polymer Journal, 54, pp493-501. Summary of the Invention [Problem to be solved by the invention]

[0010] The inventors of the present invention attempted to produce a nonwoven fabric from paramylon fiber in order to make a sanitary mask containing paramylon, but were unsuccessful. Specifically, they attempted to spin 100% paramylon fiber using a wet-dry spinning method and then use the spun 100% paramylon fiber to produce a nonwoven fabric using a spunlace method that utilizes a water flow, but they were faced with the problem that the physical properties of 100% paramylon fiber deteriorated significantly when immersed in water, making it impossible to form a nonwoven fabric.

[0011] The present disclosure has been made in view of the above-mentioned problems, and an object of the present disclosure is to provide a paramylon-cellulose blend fiber with improved water resistance. [Means for solving the problem]

[0012] The present inventors discovered that by spinning a mixed fiber of paramylon and cellulose using a dry / wet spinning method, it is possible to improve the water resistance to the same level as that of general-purpose fibers, and have thereby completed the present disclosure.

[0013] That is, the present disclosure provides the following (1) to (9). (1) Paramylon-cellulose mixed fiber having a mass ratio of paramylon:cellulose within the range of 30:70 to 50:50. (2) Tensile strength in water at 20°C is 0.80 cN dtex -1 The paramylon-cellulose mixed fiber according to (1) above. (3) A nonwoven fabric containing the paramylon-cellulose mixed fiber described in (1) or (2). (4) A sanitary mask comprising the nonwoven fabric described in (3). (5) A method for producing paramylon-cellulose blended fibers, comprising: a spinning dope preparation step in which paramylon and cellulose are dissolved and mixed in an ionic solution; and a spinning step in which the spinning dope obtained in the spinning dope preparation step is discharged into a coagulation liquid and threads are formed by a dry-wet spinning method, wherein the total weight of the paramylon and the cellulose is 5 to 20 mass% of the weight of the spinning dope, and the mass ratio of the paramylon to the cellulose is within the range of 30:70 to 50:50. (6) The method for producing paramylon-cellulose blended fibers according to (5), wherein the ionic solution contains at least one selected from the group consisting of imidazolium-based ionic solutions, DMSO, [DBNH][OAc], [mTBDH][OAc], and [DBUH][OAc]. (7) The method for producing paramylon-cellulose blended fibers according to (6), wherein the imidazolium-based ionic solution contains at least one selected from the group consisting of BmimCl, EmimDEP, EmimCl, and EmimAc. (8) The method for producing paramylon-cellulose mixed fibers according to (5), wherein the coagulation liquid contains at least one selected from the group consisting of denatured ethanol, ethanol, methanol, isopropanol, and water. (9) A method for producing a nonwoven fabric, comprising a step of producing a nonwoven fabric by a spunlace method using the paramylon-cellulose mixed fiber obtained by the method for producing a nonwoven fabric according to any one of (5) to (8). [Effects of the Invention]

[0014] According to the present disclosure, it is possible to produce paramylon-cellulose blend fibers that exhibit water resistance comparable to that of general-purpose fibers. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram of an example of a spinning apparatus for use in practicing the present disclosure. [Figure 2] FIG. 1 is a schematic diagram showing an example of an apparatus for conducting a tensile test on spun fibers in water. [Figure 3] FIG. 1 shows stress-strain curves of tensile tests in water for the paramylon-cellulose mixed fibers or paramylon fibers produced in Examples 1 and 2 and Comparative Examples 1 and 2. [Figure 4] 1A is a photograph of a nonwoven fabric processed from the paramylon-cellulose mixed fiber produced in Example 2 of the present disclosure, and FIG. 1B is a micrograph of the same. [Figure 5] FIG. 1 shows an example of a test system for evaluating the virus control effect of a nonwoven fabric processed with the paramylon-cellulose mixed fiber produced in Example 2 of the present disclosure. [Figure 6] 1 is a bar graph showing the virus control effects of a nonwoven fabric containing a paramylon-cellulose mixed fiber and a commercially available nonwoven fabric. [Figure 7] FIG. 1 shows an example of a test system for treating a sample fiber with heated steam. [Figure 8] This figure shows an X-ray diffraction pattern of a paramylon-cellulose blend fiber (paramylon:cellulose=50:50) spun with a nozzle diameter of 0.35 mm and then treated with heated steam. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present disclosure relates to a paramylon-cellulose blended fiber and a method for producing the same. Hereinafter, the paramylon-cellulose blended fiber and the method for producing the paramylon-cellulose blended fiber according to the present disclosure will be described in detail. Unless otherwise defined herein, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of this disclosure, the preferred methods and materials are described below.

[0017] (cellulose) In this disclosure, "cellulose" refers to a type of natural polymeric compound in which numerous β-glucose molecules are polymerized in a linear chain via glycosidic bonds. It is the main component of plant cell walls. Cellulose sources include, but are not limited to, wood, cotton, flax, bamboo, honeysuckle, agricultural waste, etc. Wood sources include, but are not limited to, pine, cypress, linden, oak, and cedar. Cotton is the primary source of cotton fiber. Linen fiber extracted from the stems of flax plants contains cellulose. Bamboo is a fast-growing plant and is used as bamboo fiber due to its rich cellulose content. Honeysuckle is used to extract cellulose from its stems and leaves and produce products such as nonwoven fabrics. Agricultural waste sources include, but are not limited to, corn straw, rice straw, and wheat straw. Cellulose can also be extracted and reused from these agricultural by-products. Cellulose can be extracted from these plant materials and processed appropriately to obtain cellulose fibers. Cellulose fibers are widely used as materials for textile and paper products.

[0018] (Euglena) In the present disclosure, "Euglena" includes microorganisms taxonomically classified in the genus Euglena, their variants, and closely related species in the family Euglenaceae. Specific examples of species in the genus Euglena include Euglena chadefaudii, Euglena deses, Euglena gracilis, Euglena granulata, Euglena mutabilis, Euglena proxima, Euglena spirogyra, and Euglena viridis. Euglena species are widely distributed in freshwater bodies such as ponds and marshes, and may be isolated from these bodies for use. Alternatively, any Euglena species that has already been isolated may be used. The genus Euglena encompasses all variants. These variants also include those obtained by genetic methods such as recombination, transduction, and transformation.

[0019] (paramylon) In this disclosure, "paramylon" refers to a polymer (β-1,3-glucan) formed by the polymerization of approximately 700 glucose molecules via β-1,3-bonds, and is a storage polysaccharide contained in Euglena algae, including the genus Euglena. Paramylon particles are flat, spheroidal particles formed by helically entangled β-1,3-glucan chains. In this disclosure, paramylon obtained by removing impurities such as proteins and lipids with high precision from Euglena cells was used to produce paramylon-cellulose composite fibers or paramylon fibers.

[0020] (paramylon fiber) In this disclosure, "paramylon fiber" refers to a material obtained by forming paramylon into a fibrous form using only paramylon as a raw material. The raw material is not particularly limited, but paramylon powder derived from Euglena gracilis can be used.

[0021] (Paramylon-cellulose blend fiber) In this disclosure, "paramylon-cellulose mixed fiber" refers to a fiber obtained by mixing paramylon and cellulose and forming them into a fiber. The mass ratio of paramylon to cellulose is 20:80 to 60:40, preferably 30:70 to 50:50. The mechanical properties of paramylon-cellulose mixed fibers, such as breaking strength and elongation, vary depending on spinning conditions such as the spinning method, nozzle diameter, and take-up speed, even when the mass ratio of paramylon to cellulose is the same. Paramylon-cellulose mixed fibers are preferred if they exhibit mechanical properties comparable to those of commonly used natural and chemical fibers. Specifically, they should have a breaking strength of 1.0 cN dtex or less under standard conditions of a temperature of 20°C and a relative humidity of 65%. -1 More than 1.5 cN dtex, preferably 1.5 cN dtex -1 More preferably, 2.0 cN dtex -1 It can replace natural and chemical fibers. Paramylon-cellulose blended fiber has a breaking strength of 0.8 cN dtex in water. -1 More than 0.9 cN dtex, preferably 0.9 cN dtex -1More preferably, 1.0 cN dtex -1 When the strength ratio of the breaking strength in water to the breaking strength in the standard state of the paramylon-cellulose mixed fiber is 40% or more, preferably 50% or more, and more preferably 60% or more, the mixed fiber can replace natural fibers and chemical fibers and exhibit sufficient water resistance for processing into nonwoven fabrics by the spunlace method.

[0022] (Nonwoven fabric and method of manufacturing nonwoven fabric) In this disclosure, "nonwoven fabric" refers to a type of textile product made by bonding fibers, filaments, powders, etc. without using a weaving or knitting method. Methods for producing nonwoven fabrics include, but are not limited to, spunlace, thermal bonding, and needle punching. The spunlace method involves spraying a jet of water onto deposited fibers, entangling the fibers under pressure and bonding them into a sheet. While this method has the advantage of causing less fiber damage, it has the disadvantage of requiring a certain level of water resistance from the fibers. The thermal bonding method uses heat-melting fibers and applies heat to a sheet that has been carded to remove impurities and align the fibers in a certain direction, thereby fusing and bonding the fibers within the sheet. While this method has the advantage of being low cost, it has the disadvantage of only being applicable to thermoplastic fibers. The needle punching method involves repeatedly piercing the material with a needle that moves up and down at high speed, entangling the fibers, to produce nonwoven fabrics. While it has the advantage of being able to produce nonwoven fabrics from any fiber, it has the disadvantage of not being able to produce thin fabrics such as sanitary masks. In an embodiment of the present disclosure, the spunlace method is suitable for processing the paramylon-cellulose mixed fiber or paramylon fiber into a nonwoven fabric for a sanitary mask.

[0023] (Deodorizing properties of nonwoven fabrics containing paramylon-cellulose blended fibers) In the present disclosure, nonwoven fabrics containing paramylon-cellulose blended fibers have the effect of removing odorous components. Examples of odorous components include, but are not limited to, isovaleric acid gas, nonenal gas, and indole gas. Compared to cellulose fibers, paramylon-cellulose blended fibers have particularly high isovaleric acid gas removal performance. Isovaleric acid gas has an unpleasant, irritating odor similar to cheese, sweat odor, foot odor, and halitosis caused by aging. Nonenal gas smells like body odor, old oil, candles, old books, dried grass, and rotten cheese. Indole gas smells like feces. The deodorizing effect of nonwoven fabrics containing paramylon-cellulose blended fibers is presumably due to the blending of paramylon with cellulose. Therefore, it is believed that paramylon-cellulose blended fibers before being processed into nonwoven fabrics also have a similar deodorizing effect.

[0024] (Uses of paramylon-cellulose blended fibers and nonwoven fabrics containing paramylon-cellulose blended fibers) Paramylon-cellulose mixed fibers and nonwoven fabrics containing the paramylon-cellulose mixed fibers can also be suitably used for clothing, hygiene materials, etc. Examples of clothing include, but are not limited to, T-shirts, dress shirts, polo shirts, underwear, socks, hats, sweatshirts, hoodies, jackets, dresses, etc. Examples of hygiene materials include, but are not limited to, sanitary napkins, diapers, medical gauze, hygiene masks, etc.

[0025] (Hygiene mask) In this disclosure, masks used daily for purposes such as protection against colds and pollen, and for keeping warm and moisturized are referred to as "hygienic masks" or simply "masks." As long as they are made of nonwoven fabric, they also include medical masks used for infection prevention in medical procedures such as surgery, and industrial masks used primarily as dust protection during work in factories, etc. In this disclosure, nonwoven fabrics containing paramylon-cellulose blended fibers have the same virus prevention effect as commercially available nonwoven fabrics, and are therefore suitable for use as hygienic masks.

[0026] (spinning) In this disclosure, "spinning" refers to the process of liquefying raw materials to produce chemical fibers and extruding them through a spinneret (nozzle) to form long, thin fibers. The spinning method is not particularly limited, but examples include melt spinning, dry spinning, wet spinning, and dry-wet spinning. Melt spinning is a method in which raw materials are melted by heat, extruded through a spinneret to form fibers, and then cooled and solidified. It is used for thermoplastic polyester, nylon, polypropylene, etc. Dry spinning is a method in which raw materials are dissolved in a solvent that vaporizes when heated, extruded through a spinneret in a heated atmosphere, and the solvent is evaporated to form fibers. It is used for acetate, acrylic, vinylon, etc. Wet spinning is a method in which raw materials are dissolved in a solvent and extruded through a spinneret in a solution called a coagulation liquid, coagulated by desolventization or phase separation, or subjected to a chemical reaction, and then the solvent is removed to form fibers. It is used for rayon, acrylic, vinylon, etc.

[0027] (dry and wet spinning method) In the present disclosure, the "wet-dry spinning method" refers to a spinning method in which a spinning solution is extruded into air from a spinneret, then immersed in a coagulation bath containing a coagulation solution, and then pulled out of the coagulation bath into the air to obtain a coagulated fiber bundle. The wet-dry spinning method in the embodiments of the present disclosure will be specifically described below.

[0028] (Spinning process) The dry-wet spinning method of the present disclosure will be described with reference to FIG. 1. The spinning dope used is placed in a cylinder 2 and heated to a predetermined temperature by a heater 1. The spinning dope is extruded from the discharge hole of a spinning nozzle 3, and cooling is promoted by a low-temperature chamber 4 in the air gap between the spinning nozzle 3 and the coagulation liquid 6 in the spinning bath 5. Upon contact with the coagulation liquid 6 in the spinning bath 5, the solvent in the spinning dope diffuses, resulting in a spun fiber 8. The spun fiber 8 is wound onto a take-up bobbin 10 of a winder 9 via a guide 7. The temperature of the coagulation liquid is 0 to 40°C, and the take-up speed on the take-up bobbin 10 is 50 to 500 m / min. The wound fiber is washed with the same liquid as the coagulation liquid or water until the solvent is removed. The mechanical properties of the fiber vary depending on the nozzle diameter. A nozzle diameter of 0.20 mm or more is preferable because fibers with sufficient breaking strength, elongation, and fiber diameter can be obtained, and a nozzle diameter of 0.35 mm or more is more preferable because the elongation is improved and the toughness of the fiber is increased. Note that the spinning apparatus in Figure 1 is merely an example, and the present disclosure is not limited thereto.

[0029] (Spinning dope) In the wet-dry spinning method of the present disclosure, an ionic solution is preferably used as the spinning dope. The ionic solution is not particularly limited as long as it dissolves cellulose and paramylon, but examples include imidazolium-based ionic solutions, dimethyl sulfoxide (DMSO), 1,5-diazabicyclo[4.3.0]non-5-en-1-ium acetate ([DBNH][OAc]), 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-enium acetate ([mTBDH][OAc]), and 1,8-diazabicyclo[5.4.0]undec-7-enium acetate ([DBUH][OAc]). Examples of imidazolium ion solutions include, but are not limited to, 1-butyl-3-methylimidazolium chloride (BmimCl), 1-ethyl-3-methylimidazolium diethylphosphate (EmimDEP), 1-ethyl-3-methylimidazolium chloride (EmimCl), and 1-ethyl-3-methylimidazolium acetate (EmimAc). These solvents may be used alone or in combination. The concentration of the paramylon and cellulose mixture or paramylon in the spinning dope is not particularly limited as long as it is within a concentration range that allows spinning. From the viewpoint of productivity, the concentration is preferably 1 to 30% by mass, more preferably 5 to 25% by mass, and even more preferably 5 to 20% by mass. The temperature of the spinning dope is not particularly limited as long as it can be stably maintained in the dope tank without changing over time. Among these, a temperature of 50 to 150°C is preferred from the viewpoint of preventing gelation, and a temperature of 60 to 160°C is more preferred from the viewpoint of the viscosity of the dope.

[0030] (Air gap) In the present disclosure, the term "air gap" refers to the air layer between the discharge hole of the spinning nozzle and the liquid surface of the coagulation liquid in the dry-wet spinning method. The distance between the discharge hole of the spinning nozzle and the liquid surface of the coagulation liquid is referred to as the "air gap distance," and the gas temperature in the air gap is referred to as the "air gap temperature." The air gap distance is not particularly limited, but is preferably 3 to 200 mm. The air gap temperature is not particularly limited, but the difference between the air gap temperature and the temperature of the spinning dope before discharge is preferably 0°C or higher and 150°C or lower, more preferably 20°C or higher and 150°C or lower, and most preferably 50°C or higher and 150°C or lower.

[0031] There are various methods for cooling the gas in the air gap. For example, it is preferable to blow laminar cooling air from one side or to use a cylindrical cooling tube and gently blow cooling air from the outer periphery toward the center where the yarn passes, from the viewpoint of stabilizing spinning.

[0032] (coagulation liquid) In the dry / wet spinning method of the present disclosure, the composition of the coagulation liquid used is not particularly limited, but alcohol or water is used. Using alcohol alone is preferable from the viewpoint of stable coagulation. Examples of alcohol include denatured ethanol (e.g., Alcosol manufactured by Amakasu Chemical Industry Co., Ltd.), ethanol, methanol, isopropanol, etc. From the viewpoint of stable coagulation, ethanol is particularly preferable. Although the coagulation rate is slower than that of alcohol, water can also be used as the coagulation liquid. Using water is preferable from the viewpoint of cost and work environment. A mixture of alcohol and water can also be used. The temperature of the coagulation liquid is preferably 0°C or higher from the viewpoint of energy cost reduction and workability during fiber production, and more preferably 5°C or higher. Furthermore, from the viewpoint of polymer coagulation properties and solvent exchangeability, the temperature of the coagulation liquid is preferably 40°C or lower, and even more preferably 20°C or lower. The temperature of the coagulation liquid affects the coagulation state, which in turn affects the maximum winding speed on the take-up bobbin. From the viewpoint of the state of the coagulation liquid, the temperature is preferably higher than the freezing point temperature of the coagulation liquid being used; for example, the coagulation liquid is preferably 0°C or higher. From this viewpoint, the temperature of the coagulation liquid is preferably 0 to 40°C, and more preferably 5 to 20°C.

[0033] (take-up bobbin) In the present disclosure, the winding speed on the take-up bobbin is preferably 5 to 200 m / min, and more preferably 10 to 100 m / min.

[0034] (Heat steam treatment of paramylon-cellulose blended fiber) When paramylon-cellulose mixed fibers are steam-treated in a heat-resistant container at 120°C for 24 hours, the crystallinity and crystalline orientation of the paramylon-cellulose mixed fibers are improved. Fibers with high crystallinity and crystalline orientation have excellent water resistance, so when paramylon-cellulose mixed fibers are steam-treated, their water resistance is further improved. [Example]

[0035] Hereinafter, the present disclosure will be specifically described based on specific examples, but the present disclosure is not limited to these.

[0036] Test 1: Tensile strength test of paramylon-cellulose blended fiber and paramylon fiber 1-1. Preparation of paramylon and raw cellulose (1) Paramylon The raw material paramylon used was paramylon powder derived from Euglena gracilis (manufactured by Euglena Co., Ltd.).

[0037] (2) Raw cellulose Dissolving pulp (manufactured by Georgia-Pacific Co., Ltd., degree of polymerization approximately 700) was used as the raw cellulose.

[0038] 1-2. Preparation of spinning solution and spinning by dry-wet spinning method Example 1 A mixture of paramylon and cellulose was dissolved in a solvent to a concentration of 12 wt% to prepare a spinning solution. The mixture of paramylon and cellulose contained in the spinning solution is referred to as the "polymer." The solvent used was 1-ethyl-3-methylimidazolium diethyl phosphate (EmimDEP, manufactured by Nippon Nyukazai Co., Ltd.). The mass ratio of paramylon to cellulose contained in the polymer was paramylon:cellulose = 30:70.

[0039] A wet-spinning tester manufactured by AIKI Liotech Co., Ltd. was used as the dry-wet spinning apparatus. The spinning dope prepared by the above method was introduced into the syringe of the dry-wet spinning apparatus. The temperature of the spinning dope was maintained at 100°C, and it was extruded into air at a rate of 0.1 mL / min through a spinneret with a nozzle diameter of 0.25 mm. The dope was then extruded into a coagulation solution (denatured ethanol, Alcosol NP-9 manufactured by Amakasu Chemical Industry Co., Ltd., 15°C). The spinning solution was extruded at a temperature of 20°C, with an air gap of 15 cm between the spinning nozzle and the coagulation solution. The extruded fiber came into contact with the coagulation solution, releasing the ionic solution and forming a fiber. The resulting fiber was wound onto a take-up bobbin (diameter 110 mm) at a winding speed of 35 m / min to obtain a spun fiber.

[0040] <Example 2> A spinning dope was prepared in the same manner as in Example 1, except that the mass ratio of paramylon to cellulose contained in the polymer was changed to paramylon:cellulose = 50:50. A wet-spinning tester manufactured by Kasen Nozzle Manufacturing Co., Ltd. and a coagulation tank manufactured by AIKI Liotech were used as the dry-wet spinning apparatus. Spinning conditions other than the dry-wet spinning apparatus and coagulation tank were the same as in Example 1, and spun fibers were obtained.

[0041] <Comparative Example 1> A spinning dope was prepared in the same manner as in Example 1, except that the mass ratio of paramylon to cellulose contained in the polymer was changed to paramylon:cellulose = 70:30. Spinning conditions using a dry-wet spinning apparatus were the same as in Example 1, and spun fibers were obtained.

[0042] <Comparative Example 2> Paramylon was dissolved in a solvent (1-butyl-3-methylimidazolium chloride, manufactured by Nippon Nyukazai Co., Ltd.) to a concentration of 20 wt% to prepare a spinning solution.

[0043] A wet-spinning tester manufactured by AIKI Liotech Co., Ltd. was used as the dry-wet spinning apparatus. The spinning dope prepared by the method described above was introduced into the dope tank of the spinning apparatus. The temperature of the spinning dope was maintained at 100°C, and the dope was extruded into air at a rate of 0.1 mL / min through a spinneret with a nozzle diameter of 0.25 mm. The dope was then extruded into a coagulation solution (denatured ethanol, Alcosol NP-9 manufactured by Amakasu Chemical Industry Co., Ltd., 15°C). The spinning dope was extruded at a temperature of 20°C, with an air gap of 15 cm between the spinning nozzle and the coagulation solution. Dry-wet spinning was performed. The extruded fiber came into contact with the coagulation solution, releasing the ionic solution and forming a fiber. The resulting fiber was wound onto a take-up bobbin (diameter 110 mm) at a winding speed of 35 m / min to obtain a spun fiber.

[0044] 1-3. Tensile strength test of spun fibers The tensile strength of the spun fibers in the atmosphere in Examples 1 and 2 and Comparative Examples 1 and 2 was measured using a tensile tester (EZ-SX, manufactured by Shimadzu Corporation). The measurement conditions were a room temperature of 20°C and a relative humidity of 65% (hereinafter referred to as "standard conditions" in this specification), a test length of 20 mm, and a pulling speed of 20 mm / min. The stress at which the sample broke was measured, and the tensile strength at break (hereinafter referred to as "breaking strength") was calculated. The fineness was measured using a fineness meter (Denier Computer DC21A, Search Co., Ltd.) after conditioning by leaving the sample standing overnight or longer. The breaking strengths of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 1.

[0045] 1-4. Underwater tensile strength test of spun fibers The tensile strength of the spun fibers in water in Examples 1 and 2 and Comparative Examples 1 and 2 was measured using a tensile testing machine (Tensilon RTC-1250A manufactured by A&D Co., Ltd.). An overview of the tensile strength test in water is shown in Figure 2. The spun fiber 25 is fixed to an upper sample gripper (hereinafter referred to as the "upper chuck") 26 and a lower chuck 27, and the tensile strength of the spun fiber 25 is measured by pulling up the hook 24 that fixes the upper chuck. To measure the tensile strength of the spun fiber 25 in water, an acrylic cylindrical water tank 22 is placed on the fixture 21 so as to cover the upper chuck 26 and the lower chuck 27, and the acrylic cylindrical water tank 22 is filled with distilled water 23 up to above the upper chuck 26 so that the spun fiber 25 is sufficiently immersed in water. The breaking strength was calculated by measuring the stress at which the sample broke after immersion in distilled water at 20°C for 5 minutes at a test length of 20 mm and a tensile speed of 20 mm / min. The results are shown in Table 1. The stress-strain curves of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Figure 3.

[0046] [Table 1]

[0047] 1-5. Results and Discussion According to Table 1, the breaking strength of each fiber under standard conditions was 2.44 cN dtex in Example 1, where the mass ratio of paramylon to cellulose was 30:70. -1 In Example 2, where the mass ratio of paramylon to cellulose was 50:50, the value was 1.69 cN dtex. -1 , and 0.64 cN dtex in Comparative Example 1 where the mass ratio of paramylon:cellulose was 70:30. -1 , and 0.52 cN dtex in Comparative Example 2 where the mass ratio of paramylon:cellulose was 100:0. -1 The fiber density of each mixed fiber was not measured, but the fiber density of cellulose and paramylon alone measured separately was 1.5 g / cm. 3 and 1.4 g / cm 3 Calculations using these values revealed that the breaking strength was 359 MPa for Example 1, 245 MPa for Example 2, 92 MPa for Comparative Example 1, and 73 MPa for Comparative Example 2. Since the breaking strength of the general-purpose fiber was 100 MPa to 800 MPa, it was shown that Examples 1 and 2 were fibers exhibiting strength equivalent to that of the general-purpose fiber.

[0048] According to Table 1 and Figure 3, the breaking strength of each fiber in water was 1.57 cN dtex in Example 1, where the mass ratio of paramylon to cellulose was 30:70. -1 , and 0.92 cN dtex in Example 2 where the mass ratio of paramylon:cellulose was 50:50. -1 , and 0.11 cN dtex in Comparative Example 1 where the mass ratio of paramylon:cellulose was 70:30. -1 In Comparative Example 2, where the mass ratio of paramylon to cellulose was 100:0, the value was 0.01 cN dtex. -1According to Table 1, the strength ratio {(B) / (A)}, which indicates the breaking strength in water (B) relative to the breaking strength under standard conditions (A), was 64.3% for Example 1, 54.4% for Example 2, 5.8% for Comparative Example 1, and 1.9% for Comparative Example 2. The breaking strength in water of 100% paramylon fiber decreased to 1.9% of the breaking strength under standard conditions, which poses a problem in terms of water resistance. However, it was shown that water resistance can be improved by using a mixed fiber of paramylon and cellulose. Example 2, which had a paramylon:cellulose mass ratio of 50:50, had a strength ratio {(B) / (A)} of 54.4%, an improvement of 28.6 times that of Comparative Example 1.

[0049] Test 2: Effect of nozzle diameter on the mechanical properties of paramylon-cellulose blend fibers When spinning paramylon-cellulose blended fibers (paramylon:cellulose mass ratio 50:50), the nozzle diameter was varied and the mechanical properties of the fibers were compared. The nozzle diameters were 0.35 mm (Example 3), 0.31 mm (Example 4), 0.26 mm (Example 5), and 0.20 mm (Example 6), and the spinning conditions other than the nozzle diameter were the same as in "1-2. Preparation of spinning dope and spinning by dry-wet spinning method." Tensile strength tests were the same as in "1-3. Tensile strength tests of spun fibers." The results are shown in Table 2.

[0050] [Table 2]

[0051] According to Table 2, there was little difference in breaking strength and fiber diameter due to differences in nozzle diameter. It was found that the largest nozzle diameter, 0.35 mm, had high elongation and good toughness. Generally, it is thought that as the nozzle diameter increases, the draft ratio increases, making it easier for molecular orientation to progress, and therefore elongation tends to decrease. The characteristic of paramylon-cellulose blend fibers, in which elongation increases with increasing nozzle diameter, is presumably influenced by the orientation of paramylon, which has a low orientation and a helical structure.

[0052] Test 3: Preparation of paramylon-cellulose blended fiber nonwoven fabric and performance evaluation of paramylon-cellulose blended fiber nonwoven fabric masks 3-1. Preparation of paramylon-cellulose blend fiber nonwoven fabric The paramylon-cellulose blended fibers of Example 2 (paramylon:cellulose mass ratio 50:50) were processed into a nonwoven fabric using the spunlace method. The paramylon-cellulose blended fibers were fed into a sample roller carding machine, after which the fibers were finely untangled with gears and arranged into a nonwoven fabric. The fibers were defibrated by carding, forming a uniform web (fiber sheet). Next, the web was exposed to a high-speed water stream using a water jet spray at a water pressure of 20 MPa, and the nonwoven fabric was finished. The basis weight of the nonwoven fabric was 80 g / m 2 After finishing, the nonwoven fabric was collected after 10 hours of natural drying. The nonwoven fabric made from the paramylon-cellulose mixed fiber (hereinafter referred to as "paramylon cellulose nonwoven fabric") is shown in Figure 4.

[0053] 3-2. Evaluation test of the virus filtration performance of paramylon cellulose nonwoven fabric An overview of the virus filtration test is explained using Figure 5. Bacteriophage φX174 (virus) was prepared using Escherichia coli C strain as an amplification host. Nutrient broth (NITE, 802 medium) was used to culture the Escherichia coli, and shaking culture was carried out at 37°C. The prepared phage solution 32 was diluted with HEPES buffer (50 mM, pH 7.4) to a concentration of 4.8 x 10 5After adjusting the concentration to pfu / mL, the solution was added to the nebulizer 31. The test filters were configured as a triple-layer structure with a meltblown nonwoven fabric sandwiched between them, and were placed on an acrylic cylinder 37 in an acrylic container 35 to minimize gaps. Vacuum grease was applied between the acrylic cylinder 37 and the nonwoven fabric filter 36 to prevent leakage. When testing the meltblown nonwoven fabric, the filtration performance of the single-layer filter was measured. 10 mL of PBS solution 41 was added to the midget impinger 39 to capture virus droplets. After setting up the various equipment, virus droplets 33 were sprayed for 30 seconds. Air containing virus droplets 33 was sprayed through tube 34, passed through the nonwoven fabric filter 36 and tube 38, and sent to the midget impinger 39. Simultaneously with the spraying of virus droplets 33, suction was performed with a suction pump 40 at a flow rate of 16 L / min for 2 minutes. After the aspiration was completed, the PBS solution 41 inside the midget impinger 39 was collected, and the number of plaques (amount of collected virus) was measured by qPCR. The test samples used as nonwoven fabric filters were blank (passed through the filter), paramylon cellulose nonwoven fabric (80 g / m 2 ), polypropylene nonwoven fabric, rayon nonwoven fabric, and rayon pulp nonwoven fabric were used.

[0054] The results are shown in Figure 6. When paramylon cellulose nonwoven fabric (paramylon:cellulose mass ratio 50:50) was used as a filter, the virus concentration was reduced by approximately 85% compared to blank. These results demonstrate that paramylon cellulose nonwoven fabric has a virus control effect equivalent to that of polypropylene nonwoven fabric, rayon nonwoven fabric, rayon pulp nonwoven fabric, and meltblown nonwoven fabric.

[0055] Test 4: Deodorizing evaluation test of paramylon cellulose nonwoven fabric Paramylon-cellulose nonwoven fabric (50:50 mass ratio of paramylon to cellulose) and cellulose nonwoven fabric were used as samples. The test method used was the method specified in the certification standards for deodorizing textile products. Specifically, the sample and the target gas were placed in a sampling bag, and the gas concentration after two hours was measured with a detector tube to calculate the reduction rate. The target gases used were isovaleric acid gas, nonenal gas, and indole gas. Isovaleric acid gas has an unpleasant, pungent odor similar to cheese, sweat odor, foot odor, or bad breath due to aging. Nonenal gas smells like body odor, old oil, candles, old books, dry grass, and rotten cheese. Indole gas smells like feces. The results are shown in Table 3.

[0056] [Table 3]

[0057] According to Table 3, the odor component reduction rate for isovaleric acid gas was 87% for the paramylon-cellulose nonwoven fabric and 66% for the cellulose nonwoven fabric, indicating that the paramylon-cellulose nonwoven fabric had a higher odor component reduction rate than the cellulose nonwoven fabric. The odor component reduction rate for nonenal gas was 12% for the paramylon-cellulose nonwoven fabric and 17% for the cellulose nonwoven fabric, indicating that the paramylon-cellulose nonwoven fabric had a slightly lower odor component reduction rate than the cellulose nonwoven fabric. The odor component reduction rate for indole gas was 89% for the paramylon-cellulose nonwoven fabric and 83% for the cellulose nonwoven fabric, indicating that the paramylon-cellulose nonwoven fabric had a slightly higher odor component reduction rate than the cellulose nonwoven fabric. These results indicate that the deodorizing ability of the paramylon-cellulose nonwoven fabric was higher for isovaleric acid gas than the cellulose nonwoven fabric, but was comparable to the cellulose nonwoven fabric for nonenal gas and indole gas.

[0058] Test 5: Effect of heated steam treatment on the mechanical properties and structure of fibers As shown in Figure 7, ten strands of paramylon-cellulose mixed fibers (paramylon:cellulose mass ratio 50:50) were fixed as sample fibers 55 to a fixing table 54, placed in a heat-resistant heating container 51, and treated in an oven at 120°C for 24 hours. To prevent the sample fibers 55 from breaking, silicone rubber 53 was inserted and the sample fibers 55 were fixed with stainless steel clips 52. Distilled water 56 was poured into the bottom of the heat-resistant heating container 51 to the extent that the fibers were not submerged in water. The nozzle diameter when spinning the paramylon-cellulose mixed fibers was 0.35 mm.

[0059] Figure 8 shows the X-ray diffraction pattern of the paramylon-cellulose blended fiber treated with heated steam, measured by X-ray diffraction. The paramylon-cellulose blended fiber treated with heated steam had high crystallinity, with the crystalline orientation of the cellulose component reaching a high value of 87.4%. Fibers with high crystallinity and crystalline orientation have excellent water resistance, suggesting that treating the paramylon-cellulose blended fiber with heated steam improves its water resistance. [Industrial Applicability]

[0060] This disclosure demonstrates that paramylon-cellulose blended fibers exhibit tensile strength equivalent to commonly used natural and chemical fibers under standard conditions, and that while 100% paramylon fibers exhibit extremely low tensile strength in water, using paramylon-cellulose blended fibers improves water resistance. Because paramylon-cellulose blended fibers have improved water resistance compared to 100% paramylon fibers, the spunlace method, which uses a water current, can be used to create nonwoven fabrics. Mask filters using paramylon-cellulose blended fibers exhibited virus prevention effects equivalent to those of other commercially available nonwoven fabrics, demonstrating that paramylon-cellulose blended fiber nonwoven fabric masks have industrial applicability as masks for public safety. [Explanation of symbols]

[0061] 1 heater 2 cylinders 3 Spinning nozzle 4 Low humidity chamber 5 Spinning bath 6 Coagulation liquid 7 Guide 8 Spun Fibers 9 Winder 10 Take-up bobbin 21 Fixtures 22 Acrylic cylindrical aquarium 23 Distilled water 24 Hook 25 Spun Fibers 26 Upper sample grip 27 Lower sample grip 31 Nebulizer 32 Phage solution 33 Viral droplets 34 tubes 35 Acrylic container 36 Nonwoven fabric filter 37 Acrylic Cylinder 38 tubes 39 Midget Impinger 40 Suction pump 41 PBS solution 51 Heat-resistant heating container 52 Stainless steel clip 53 Silicone Rubber 54 Fixed stand 55 Sample Fiber 56 Distilled water

Claims

1. Paramylon-cellulose mixed fiber, in which the mass ratio of paramylon to cellulose is within the range of 30:70 to 50:

50.

2. Tensile strength in water at 20°C is 0.80 cN dtex -1 The paramylon-cellulose mixed fiber according to claim 1,

3. A nonwoven fabric comprising the paramylon-cellulose mixed fiber according to claim 1 or 2.

4. A hygienic mask comprising the nonwoven fabric of claim 3.

5. A method for producing paramylon-cellulose mixed fibers, a spinning solution preparation step of dissolving and mixing paramylon and cellulose in an ionic solution; a spinning step of discharging the spinning dope obtained in the spinning dope preparation step into a coagulation liquid and forming yarns by a dry-wet spinning method, the total weight of the paramylon and the cellulose is 5 to 20% by mass of the weight of the spinning solution, The mass ratio of the paramylon to the cellulose is within the range of 30:70 to 50:

50. Method for producing paramylon-cellulose blended fiber.

6. 6. The method for producing paramylon-cellulose blended fibers according to claim 5, wherein the ionic solution contains at least one selected from the group consisting of an imidazolium-based ionic solution, DMSO, [DBNH][OAc], [mTBDH][OAc], and [DBUH][OAc].

7. The method for producing paramylon-cellulose blended fibers according to claim 6, wherein the imidazolium-based ionic solution contains at least one selected from the group consisting of BmimCl, EmimDEP, EmimCl, and EmimAc.

8. The method for producing paramylon-cellulose mixed fibers according to claim 5, wherein the coagulation liquid contains at least one selected from the group consisting of denatured ethanol, ethanol, methanol, isopropanol, and water.

9. A method for producing a nonwoven fabric, comprising a nonwoven fabric production step of producing a nonwoven fabric by a spunlace method using the paramylon-cellulose mixed fiber obtained by the production method according to any one of claims 5 to 8.

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