JPWO2015053226A1 - High strength and high elastic cellulose filament - Google Patents

Abstract

It is an object to obtain a regenerated cellulose long fiber having high strength and high elasticity. Cellulose long fibers obtained by dissolving a cellulose raw material in an ionic liquid and spinning the cellulose long fibers having an average degree of polymerization of 500 or more and 3000 or less and an average fiber diameter of 30 μm or less provide high strength and high elasticity. Fiber can be provided.

Description

  The present invention relates to a regenerated cellulose long fiber having good spinnability, high strength and high elasticity, and a method for producing the same, in a regenerated cellulose fiber obtained by dissolving a cellulose raw material in an ionic liquid and reprecipitating it in a solvent by spinning.

  In order to increase the strength and rigidity of plastics, fiber composite materials containing high-strength and high-elastic fibers such as glass fibers are used in various fields such as automobile parts, sporting goods, building materials, and general goods.

  Glass fiber reinforced composite materials that have been used as lightweight high strength materials exhibit excellent properties during use. However, when glass fiber is used as the reinforcing fiber, a residue is generated at the time of disposal, which causes a problem that the load on the environment is large.

  Moreover, in order to improve insulation and rigidity also in the printed wiring board, glass fiber is used as a base material. However, when glass fiber is also used here, a residue is generated at the time of disposal, which causes a problem that the load on the environment is large.

  Therefore, it is necessary to use cellulose having excellent properties such as high mechanical properties, dimensional stability, low thermal expansion, electrical insulation, and low specific gravity as the base material for fiber reinforced composite materials and printed wiring boards. It is being considered. Since cellulose is derived from plants and has biodegradability, no residue is produced at the time of disposal, and the environmental load during production and disposal is small (for example, Patent Document 1).

  So far, fiber reinforced composite materials using cellulosic natural fibers such as cotton, hemp, kenaf, bamboo and the like as reinforcing fibers have been studied. However, there are many problems such as variations in strength, and short fibers cannot be used in a wide range of applications. Therefore, the cellulose purity and cellulose crystallinity are high, the quality is stable, and regenerated cellulose fibers that are long fibers are required for fiber-reinforced composite materials and electrical materials.

  As regenerated cellulose fibers, regenerated cellulose fibers such as rayon fiber, cupra fiber, and lyocell fiber are known. However, since any fiber uses a highly toxic solvent or a solvent having a high risk of explosion, etc., there is a risk in the production process, a highly safe method for producing cellulose fibers is required. It was.

  Accordingly, a method has been developed in which an ionic liquid composed of an imidazolium compound is used as a solvent and a cellulose raw material is dissolved in the ionic liquid to produce regenerated cellulose fibers (see, for example, Patent Documents 2 to 4).

  However, at present, as disclosed in these documents, although it has been studied to dissolve cellulose raw materials in ionic liquids, almost no consideration is given to industrially spinning regenerated cellulose long fibers. It has not been.

  For example, Patent Document 2 describes that a nonwoven fabric is produced from cellulose dissolved in an ionic liquid, but there is no description about obtaining cellulose long fibers. Patent Documents 3 and 4 describe that a cellulose raw material is dissolved in an ionic liquid to spin a fiber, but industrially stable spinning is not considered. If regenerated cellulose long fibers can be stably obtained, secondary processing such as cloth, cloth, sheet, membrane material, and cutting into lengths according to applications such as chopped strands will be easy. It can be used in a wide range of applications as electrical materials and fiber reinforced composite materials. For this reason, it has been necessary to industrially spin regenerated cellulose filaments stably using an ionic liquid. The inventors of the present invention have established and already disclosed a technique that can be industrially stably produced from a cellulose raw material dissolved in an ionic liquid (Patent Document 5).

JP2011-236321A JP 2008-248466 A JP 2009-203467 A Japanese Patent Application Laid-Open No. 2012-21048 International Publication No. 2012/108390

Wada, M., Nishiyama, Y., Cellulose Commun. Vol.18, No.2, P87-P90, (2011)

  Although the present inventors have established a technique for dissolving cellulose raw material in an ionic liquid and spinning it with high productivity, the strength and elastic modulus for use as a composite material and electrical material for spun regenerated cellulose long fibers Has not been studied so far.

  An object of the present invention is to obtain a regenerated cellulose long fiber having high productivity and high strength and high elasticity.

  The present invention is a regenerated cellulose long fiber obtained by dissolving a cellulose raw material in an ionic liquid and spinning, wherein the average degree of polymerization is 500 or more and 3000 or less, and the average fiber diameter is 30 μm or less. It is a high strength and high elasticity cellulose continuous fiber.

  In the present invention, the high-strength and high-elasticity cellulose continuous fiber means one having at least a tensile strength of 0.55 GPa or more and a tensile modulus of 35 GPa or more.

  The inventors of the present invention have obtained a regenerated cellulose long fiber obtained by dissolving a cellulose raw material in an ionic liquid and spinning it, and spinning it as a thin fiber having an average fiber diameter of 30 μm or less, whereby a tensile strength of 0.55 GPa or more, It has been clarified that the tensile elastic modulus is high strength and high elasticity cellulose long fiber of 35 GPa or more.

  There has never been a report that there is a correlation between the fiber diameter of the regenerated cellulose fiber and the tensile strength and tensile elastic modulus, which is the first discovery by the present inventors. In addition, it is an advanced technique to obtain fine long fibers using a cellulose solution in which a cellulose raw material is dissolved in an ionic liquid, but the average fiber diameter is 30 μm by controlling the spinning conditions such as nozzle diameter, spinning speed and stretching. The following fibers can be obtained. Furthermore, the present inventors can spin long fibers with high productivity if the average polymerization degree dissolved in the ionic liquid is 500 or more and 3000 or less, and by adjusting the fiber diameter, It has been found that highly elastic cellulose filaments can be spun.

  Furthermore, the high-strength and high-elasticity cellulose continuous fiber of the present invention is characterized in that the intramolecular hydrogen bond degree is 42% or more and 60% or less.

  The degree of intramolecular hydrogen bonding indicates the bonding strength between adjacent glucoses in the cellulose molecule, and it is considered that the higher the value, the denser the structure. When the intramolecular hydrogen bond degree is 42% or more and 60% or less, a high strength and highly elastic cellulose continuous fiber having a tensile strength of 0.55 GPa or more and a tensile modulus of 35 GPa or more can be realized.

In addition, the high-strength and highly elastic cellulose long fiber of the present invention is characterized in that the birefringence is 68Δ × 10 ⁻³ or more and 90Δ × 10 ⁻³ or less.

The birefringence is said to correlate with the molecular orientation in the entire structure consisting of a crystalline structure and an amorphous structure forming the fiber. When the birefringence is 68Δ × 10 ⁻³ or more and 90Δ × 10 ⁻³ or less, a high strength and highly elastic cellulose continuous fiber having a tensile strength of 0.55 GPa or more and a tensile elastic modulus of 35 GPa or more can be realized.

  Moreover, the high-strength and highly elastic cellulose continuous fiber of the present invention is characterized in that the intramolecular hydrogen bond degree is 45% or more and 60% or less.

  When the intramolecular hydrogen bond degree is 45% or more and 60% or less, a high-strength and highly elastic cellulose continuous fiber having a tensile strength of 0.80 GPa or more and a tensile modulus of 45 GPa or more can be obtained. If the fiber has a tensile strength of 0.80 GPa or more and a tensile elastic modulus of 45 GPa or more, it can exhibit characteristics equivalent to or higher than those of glass fibers when used as a reinforcing fiber or a substrate.

Furthermore, the high-strength and highly elastic cellulose continuous fiber of the present invention has a birefringence of 70Δ × 10 ⁻³ or more and 90Δ × 10 ⁻³ or less.

When the birefringence is 70Δ × 10 ⁻³ or more and 90Δ × 10 ⁻³ or less, a high-strength and highly elastic cellulose continuous fiber having a tensile strength of 0.80 GPa or more and a tensile modulus of 45 GPa or more can be obtained. If the fiber has a tensile strength of 0.80 GPa or more and a tensile elastic modulus of 45 GPa or more, it can exhibit characteristics equivalent to or higher than those of glass fibers when used as a reinforcing fiber or a substrate.

  Furthermore, in the method of spinning high-strength and high-elasticity cellulose long fibers of the present invention, the cellulose raw material is dissolved in an ionic liquid so that the average degree of polymerization is 500 or more and 3000 or less, so that the average fiber diameter is 30 μm or less. It is characterized by being spun into

  By dissolving the cellulose raw material in the ionic liquid so that the average degree of polymerization is 500 or more and 3000 or less, fibers having an average fiber diameter of 30 μm or less can be industrially spun, and the tensile elastic modulus is 35 GPa. The high-strength and high-elasticity cellulose long fibers as described above can be obtained.

  In addition, the fiber-reinforced composite material of the present invention is obtained by mixing a high-strength and highly elastic cellulose long fiber and a resin.

  By mixing the high-strength and highly elastic cellulose long fibers of the present invention with a resin, a fiber-reinforced composite material having a strength equal to or higher than that of a composite material in which glass fibers are mixed as reinforcing fibers can be obtained.

  Hereinafter, the present invention will be described with reference to examples. In the present invention, the high-strength and high-elasticity cellulose long fiber refers to those having a tensile strength of 0.55 GPa or more and a tensile modulus of 35 GPa or more. Further, in this specification, the long fiber means a fiber of 5 m or longer. However, in order to perform spinning with high productivity, it is desirable that continuous spinning is possible without cutting 10,000 m or longer.

  In addition, the high-strength and highly elastic cellulose long fiber of the present invention is characterized by having an average degree of polymerization of 500 to 3000 and an average fiber diameter of 30 μm or less. The present inventors have found that there is a correlation between the average fiber diameter and the fiber strength, and when the average fiber diameter is 30 μm or less, the tensile strength is 0.55 GPa or more and the tensile elastic modulus is 35 GPa or more. It revealed that. If the tensile elastic modulus is 35 GPa or more, it has a specific elastic modulus substantially equivalent to that of glass fiber, and thus functions sufficiently as a substitute for glass fiber.

  The average fiber diameter is preferably 22 μm or less because the tensile strength is 0.75 GPa or more and the tensile modulus is 40 GPa or more. The average fiber diameter is 20 μm or less, and the tensile strength is 0.80 GPa. As described above, the tensile modulus is more preferably 45 GPa or more, and the average fiber diameter is preferably 12 μm or less, more preferably 0.95 GPa or more and the tensile modulus is 50 GPa or more. Is preferably 6 μm or less, since the tensile strength is 1.10 GPa or more and the tensile modulus is 55 GPa or more, and the average fiber diameter is 4 μm or less, the tensile strength is 1.50 GPa or more, and the tensile elasticity is The rate is most preferable because it is 60 GPa or more. Here, as a lower limit value of the average fiber diameter of the high-strength and high-elasticity cellulose continuous fiber of the present invention, 1 μm can be mentioned at present from the viewpoint of manufacturing difficulty.

  The high-strength and highly elastic cellulose long fiber of the present invention has an average degree of polymerization of 500 to 3000 and an average fiber diameter of 30 μm or less. If the average degree of polymerization exceeds 3000, it is difficult to dissolve in the ionic liquid, and therefore, the influence of undissolved substances and the viscosity of the cellulose solution become too high, so that it is difficult to stably spin fine fibers. Further, if the average degree of polymerization is 500 or less, fibers having high tensile strength and high tensile modulus cannot be spun.

  Further, the high-strength and highly elastic cellulose continuous fiber of the present invention preferably has an average degree of polymerization of 500 or more and 2000 or less from the viewpoint of spinnability, and an average degree of polymerization of 600 or more and 1800 or less is excellent spinnability. Further, it is more preferable because a fiber having tensile strength and tensile elastic modulus can be obtained. In order to obtain a finer yarn, the smaller the average degree of polymerization, the easier it is to spin. However, in order to obtain a high strength and highly elastic cellulose filament, a certain degree of average degree of polymerization is required. When the average degree of polymerization is within the above range, it is possible to obtain cellulose continuous fibers having good spinnability and high strength and high elasticity.

  When the intramolecular hydrogen bond degree is 42% or more and 60% or less, the high-strength and highly elastic cellulose long fiber of the present invention has a tensile strength of 0.55 GPa or more and a tensile modulus of 35 GPa or more. When the hydrogen bond degree is 44% or more and 60% or less, the tensile strength is preferably 0.70 GPa or more and the tensile modulus is 40 GPa or more, and the intramolecular hydrogen bond degree is 45% or more and 60% or less. More preferably, the tensile strength is 0.80 GPa or more and the tensile modulus is 45 GPa or more.

The high-strength and high-elasticity cellulose long fiber of the present invention has a birefringence of 68Δ × 10 ⁻³ or more and 90Δ × 10 ⁻³ or less, a tensile strength of 0.55 GPa or more, and a tensile modulus of 35 GPa or more, Furthermore, it is preferable that the birefringence is 69Δ × 10 ⁻³ or more and 90Δ × 10 ⁻³ or less because the tensile strength is 0.75 GPa or more and the tensile elastic modulus is 40 GPa or more, and the birefringence is 70Δ × 10. ^{−3 to} 90Δ × 10 ⁻³ is more preferable because the tensile strength is 0.80 GPa or more and the tensile modulus is 45 GPa or more, and the birefringence is 71Δ × 10 ⁻³ or more and 90Δ × 10 ^−3. or less is, a tensile strength above 1.00GPa, tensile more preferably from becoming a more 50GPa modulus, degree birefringence 74Δ × ^{10 -3} or more 90Δ × ^{10 -3} der less It tensile strength above 1.05GPa, particularly preferred since the tensile modulus is equal to or greater than 53GPa, that the degree of birefringence is less than 80Δ × ^{10 -3} or more 90Δ × ^{10 -3,} tensile strength 1. The most preferable is 50 GPa or more and the tensile elastic modulus is 60 GPa or more.

Here, the high-strength and highly elastic cellulose long fiber of the present invention has an average degree of polymerization of 700 to 2000, an average fiber diameter of 6 μm or less, an intramolecular hydrogen bond degree of 49% to 60%, and a birefringence of 74Δ. It is particularly preferable that the tensile strength is 1.10 GPa or more and the tensile elastic modulus is 55 GPa or more, and the average degree of polymerization is 700 to 2000 and the average fiber diameter is × 10 ⁻³ or more and 90Δ × 10 ⁻³ or less. Most preferably, it is 4 μm or less, the intramolecular hydrogen bond degree is 50% or more and 60% or less, and the birefringence is 80Δ × 10 ⁻³ or more and 90Δ × 10 ⁻³ or less.

[Method for producing high-strength and high-elasticity cellulose continuous fiber]
The high-strength and highly elastic cellulose long fiber of the present invention is obtained by dissolving a cellulose raw material in an ionic liquid composed of an imidazolium compound to obtain a cellulose solution. Next, the cellulose solution is extruded into a coagulating liquid in which the imidazolium compound is soluble and insoluble in cellulose, and the cellulose contained in the cellulose solution is coagulated to produce.

  The cellulose raw material may be basically any material, for example, natural cellulose raw materials such as wood pulp, cotton, cotton linter, hemp, bamboo, abaca, regenerated cellulose fibers such as rayon, cupra, lyocell, and the like. The resulting paper or clothing may be reused as a cellulose raw material. From the viewpoint of economy, natural cellulose raw materials are preferable, and among them, dissolving pulp, cotton linter and bamboo are preferable because of high cellulose purity and average cellulose polymerization degree.

  When the cellulose raw material has a high cellulose purity, there are few impurities such as fats and oils, lignin and hemicellulose contained in the cellulose raw material, and the homogeneity of the cellulose solution, spinnability during spinning, and stretchability are not impaired.

  In addition, the average degree of polymerization of cellulose is preferably at least 500 or more and preferably 3000 or less in view of solubility, considering the physical properties of the obtained fiber.

  Examples of the ionic liquid comprising an imidazolium compound include 1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium diethyl phosphate, 1-butyl-3. -Methylimidazolium acetate, 1,3-dimethylimidazolium acetate, 1-ethyl-3-methylimidazolium propionate, 1-allyl-3-methylimidazolium chloride and the like. Preferred examples include 1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium chloride, and 1-ethyl-3-methylimidazolium diethyl phosphate.

  If these ionic liquids are used, cellulose having a relatively large average degree of polymerization having an average degree of polymerization of 800 or more can be easily dissolved.

  What is necessary is just to melt | dissolve a cellulose raw material until it becomes a homogeneous solution by adjusting melt | dissolution time and melt | dissolution temperature according to the average degree of polymerization of a cellulose, and the kind of ionic liquid.

  Any heating means may be used, but general heating means such as heating with an oven, heating with a water or oil bath, heating with a microwave, etc. may be used.

  In heating, it is preferable to perform stirring in order to promote dissolution of the cellulose raw material. Stirring means are also optional, and among the known stirring methods represented by mechanical stirring with a stirrer or stirring blade, stirring by shaking the container, stirring by ultrasonic irradiation, etc., an appropriate means according to the scale etc. Adopt it.

  Furthermore, it is preferable to dissolve in an inert gas atmosphere such as nitrogen in order to suppress the oxidation / decomposition of cellulose during heating and dissolution.

  The cellulose solution obtained by dissolving the cellulose raw material in the ionic liquid may be used as it is in the subsequent step, but if undissolved or insoluble matter remains in the solution, after filtering these It may be used.

  The obtained cellulose solution may be used immediately, but may be used after being stored for a predetermined time as long as various properties such as moldability and physical properties of the molded product can be maintained. In particular, if the product is stored at a temperature below room temperature while paying attention to moisture absorption, it can be stored for a long time.

  The dissolved cellulose is extruded from a nozzle and then spun by being immersed in a coagulation liquid. As the coagulation liquid, water having a temperature in the range of 0 ° C. or higher and 100 ° C. or lower, or a lower alcohol, a polar solvent, a nonpolar solvent, or the like having a temperature in the range of −40 ° C. or higher and 100 ° C. or lower can be used. In view of economy and work environment, it is preferable to use water. The lower alcohol means an alcohol having 1 to 5 carbon atoms.

  Spinned regenerated cellulose long fibers are washed with water, but the remaining amount of the ionic liquid after washing is 10000 ppm or less when converted from the amount of nitrogen detected by elemental analysis of the regenerated cellulose long fibers to the amount of ionic liquid.

  In order to produce regenerated cellulose long fibers having different fiber diameters, a cellulose solution may be extruded from nozzles having different diameters while controlling the extrusion flow rate, and spinning may be performed while controlling the winding speed and stretching conditions. For example, for a cellulose fiber having a fiber diameter of 20 μm, a winding speed is gradually increased until the fiber diameter reaches 20 μm while fixing an extrusion flow rate in a range of 0.01 to 1 mL / min using a nozzle having a diameter of 0.15 mm. It can be obtained by spinning while increasing the draw ratio.

  Moreover, when producing a fiber reinforced composite material, at least one resin selected from the group consisting of a thermoplastic resin and a thermosetting resin and a high-strength and highly elastic cellulose long fiber are mixed. Examples of the thermoplastic resin in the fiber reinforced composite material include polyamide (nylon), polyacetal, polycarbonate, polyvinyl chloride, ABS, polysulfone, polyethylene, polypropylene, polystyrene, (meth) acrylic resin, fluororesin, and melamine resin. Examples of the curable resin include unsaturated polyester resins, epoxy resins, melamine resins, and phenol resins. When the fiber reinforced composite material includes a thermosetting resin, the fiber reinforced composite material includes a prepreg in which the thermosetting resin is semi-cured in addition to the fiber reinforced composite material in which the thermosetting resin is completely cured. Is also included. The fiber reinforced composite material contains additives such as a low shrinkage agent, a flame retardant, a flame retardant aid, a plasticizer, an antioxidant, an ultraviolet absorber, a colorant, a pigment, and a filler as necessary. It may be.

[Measurement of physical properties of regenerated cellulose filaments]
The physical properties of the cellulose fibers obtained by the above method were measured by the following methods and summarized in Table 1.

(Average fiber diameter)
The average fiber diameter was measured with a scanning electron microscope (manufactured by Hitachi, Ltd., SN-3400N). Ten fiber diameters were measured from the regenerated cellulose long fiber slice (fiber length 20 mm), and the average value was defined as the average fiber diameter.

(Tensile strength, tensile modulus, elongation)
Tensile strength, tensile modulus, and elongation were tested using a tensile tester (Orientec, TENSILON RTC-1150A) under the conditions of test piece length: 50 mm, tensile test speed: 5 mm / min, load cell load: 2N. . The test piece was subjected to an absolute drying treatment at 110 ° C. for 1 hour, and was evaluated after cooling to room temperature in a desiccator.

(Birefringence)
The birefringence was measured by a compensator method using an incident light of 546 nm with a polarizing microscope (Olympus, BH-2), and obtained from the following calculation formula. In the present invention, the birefringence is defined as a value measured by this method.
Δn = {nλ + aλ (x−1605)} / d
n: number of fringes found in the fiber cross section, λ: wavelength of incident light (546 nm), d: fiber thickness (nm), aλ: constant determined by light source and compensator (0.97), x: reading value (average polymerization) Every time)
The average degree of polymerization of cellulose was calculated by measuring the average molecular weight by the TAPPI T230 standard method (viscosity method) and dividing the measured average molecular weight by the molecular weight of glucose, which is a constituent unit of cellulose. In the present invention, the average degree of polymerization is defined as a value calculated by this method.

(Crystal orientation)
The crystal orientation was measured according to JIS K0131. Specifically, it measured by the transmission method using ROTA-Flex RTP-300 by Rigaku Corporation which is an X-ray diffraction apparatus. The regenerated cellulose long fiber set on the fiber sample stage was irradiated with X-rays for 30 minutes, detected with an imaging plate detector, and the detected value was determined by analyzing with a reading device (R-AXIS DS3C, manufactured by Rigaku Corporation). In the present invention, the degree of crystal orientation is defined as a value measured by this method.

(Crystallinity)
The crystallinity was measured by a reflection method using a Multi Flex manufactured by Rigaku Corporation which is an X-ray diffractometer. While the regenerated cellulose long fiber was placed on the sample stage, the sample stage was rotated at 120 rpm, X-rays were irradiated, and detection was performed using a scintillation counter at a measurement speed of 1 ° / min in a measurement range of 5 ° to 40 °. Based on the obtained spectrum data, the crystallinity was calculated using a peak separation method (area method) (Non-patent Document 1). In the present invention, crystallinity is defined as a value measured by this method.

(Intramolecular hydrogen bond measurement)
The intramolecular hydrogen bond degree was measured by CPMAS method using AVANCE300 manufactured by Bruker, which is a solid-state NMR measurement apparatus. The detection nucleus was ¹³ C (resonance frequency 75.4 MHz), the MAS condition was 3 kHz, and the contact time was 2 milliseconds. In the present invention, the degree of intramolecular hydrogen bonding is defined as a value measured by this method.

  In Examples 1 to 8 and Comparative Examples 1 and 2, the cellulose raw material was dissolved in an ionic liquid and then spun by extrusion from a nozzle. At that time, fibers having different diameters were obtained by changing the nozzle diameter, winding speed, stretching conditions, and the like, and the physical properties were measured.

  In Comparative Example 1, the average degree of polymerization is 880, which is within the range of the present invention, but the average fiber diameter is as large as 41.0 μm, and in Comparative Example 2, the average degree of polymerization is smaller than the range of the present invention. It is the result of having measured the physical property of the obtained fiber. Comparative Examples 3 to 5 show the results of measuring physical properties of conventional regenerated cellulose long fibers within the fiber diameter range of the present invention. Comparative Example 3 is a cupra, Comparative Example 4 is a rayon, and Comparative Example 5 is a lyocell.

  As shown in Table 1, the regenerated cellulose long fibers obtained by dissolving a cellulose raw material in an ionic liquid and spinning it have higher tensile strength and tensile elastic modulus as the average fiber diameter becomes smaller.

  In particular, as shown in Example 1, a thin regenerated cellulose long fiber having an average fiber diameter of 3.1 μm has a tensile strength of 1.54 GPa, a tensile elastic modulus of 62.5 GPa, and physical properties equivalent to or higher than those of glass fiber produced from E glass. It has.

  In addition, as shown in Comparative Examples 3 to 5, analysis was also performed on existing regenerated cellulose long fibers such as cupra, rayon, and lyocell, but none of the high strength and high elasticity criteria referred to in the present invention was found. .

  Comparative Examples 3 to 5 show evaluations such as the tensile strength and tensile elastic modulus of cupra, rayon, and lyocell having an average fiber diameter of about 10 μm. As for other regenerated cellulose long fibers such as cupra, it is also possible that, as with the long fibers obtained by dissolving the cellulose raw material of the present invention in an ionic liquid and spinning, the strength and elasticity become higher as the fiber diameter becomes smaller. .

  However, the regenerated cellulose long fiber of the present invention having an average fiber diameter of 27.9 μm shown in Example 8 has a high tensile strength and tensile strength even though the fiber diameter is about 3 times that of the cupra of Comparative Example 3. Elastic modulus is obtained. Therefore, even if another regenerated cellulose long fiber having a thin fiber diameter of about 3 μm, such as cupra, is obtained, it is considered that the regenerated cellulose long fiber of the present invention has a higher strength and higher elasticity. Absent.

  Regenerated cellulose filaments such as rayon are high because of differences in crystallinity of cellulose due to various spinning conditions (stretching, drying, etc.), and low polymerization degree due to treatment with strong acid or strong alkali. It is considered that regenerated cellulose long fibers having physical properties are difficult to obtain.

  In the regenerated cellulose long fiber having a low average degree of polymerization dissolved in the ionic liquid of Comparative Example 2, since the regenerated cellulose long fiber having high physical properties cannot be obtained even when a thin fiber is spun, the average degree of polymerization is high and This is one of the important factors for obtaining highly elastic cellulose filaments. Further, since the dissolution method using an ionic liquid is a relatively mild dissolution method, regenerated cellulose long fibers can be obtained without significantly reducing the average degree of polymerization of cellulose.

  In addition, other regenerated cellulose long fibers such as cupra are currently not commercially available with a minimum fiber diameter of about 3 μm in this example, and it is considered difficult to obtain fine fibers with high productivity.

  In addition, the degree of intramolecular hydrogen bonding is an index indicating that hydrogen and oxygen are bonded more closely between cellulose molecular chains. In high-strength and high-elasticity cellulose long fibers dissolved and spun in an ionic liquid, It was also shown that the degree of crystallinity, the degree of crystal orientation, the tensile strength, and the tensile modulus are highly correlated. On the other hand, as shown in Comparative Examples 3 to 5, in the case of cellulose fibers produced by other methods, there is not always a strong correlation between the degree of intramolecular hydrogen bonding, tensile strength, and tensile modulus.

  As described above, the cellulose raw material is dissolved in an ionic liquid, and the regenerated cellulose long fibers are spun to an average degree of polymerization of 500 to 3000 and an average fiber diameter of 30 μm or less. It has become possible to spin high-strength and high-elasticity cellulose long fibers that can replace glass fibers as a base material for reinforcing fibers and printed wiring boards.

  Next, the regenerated cellulose filaments of Example 4 were actually aligned in one direction, impregnated with epoxy resin, drawn into the mold, heated and cured in the mold, and then removed from the mold. A fiber reinforced composite material was prepared and evaluated for physical properties such as flexural modulus, flexural strength, and thermal expansion coefficient (developed product). As a control, cupra and E glass fibers, which are general regenerated cellulose long fibers and have relatively high physical properties, were mixed with a resin at the same fiber content to prepare a composite material. The results are shown in Table 2.

  As shown in Table 2, when a fiber reinforced composite material was used, the flexural modulus and thermal expansion coefficient of the developed product were almost the same as when E glass fiber was used. The regenerated cellulose long fiber of the present invention was obtained for the first time using the regenerated cellulose long fiber, and the same bending elastic modulus as that of the glass fiber, and the substrate of the printed wiring board required to have high elastic modulus and low thermal expansion A wide range of applications are expected as reinforcing fibers for fiber-reinforced composite materials.

  As described above, the high-strength and high-elasticity cellulose long fiber of the present invention exhibits a much higher tensile strength and tensile modulus than conventional cellulose fibers, and the specific modulus obtained by dividing the tensile modulus by specific gravity. Is equal to or better than glass fiber. Further, when mixed with resin as a reinforcing fiber or a base material, a fiber-reinforced composite material having an excellent bending elastic modulus and a thermal expansion coefficient similar to that when E glass is used can be obtained.

Claims (7)

A cellulose long fiber obtained by dissolving a cellulose raw material in an ionic liquid and spinning,
The average degree of polymerization is 500 or more and 3000 or less,
A high-strength and high-elasticity cellulose continuous fiber having an average fiber diameter of 30 μm or less. The high-strength and highly elastic cellulose filament according to claim 1,
A high-strength and highly elastic cellulose long fiber having an intramolecular hydrogen bond degree of 42% or more and 60% or less. The high-strength and high-elasticity cellulose continuous fiber according to claim 1 or 2,
A high-strength and highly elastic cellulose continuous fiber having a birefringence of 68Δ × 10 ⁻³ or more and 90Δ × 10 ⁻³ or less. The high-strength and high-elasticity cellulose continuous fiber according to claim 2 or 3,
A high-strength and highly elastic cellulose continuous fiber having an intramolecular hydrogen bond degree of 45% or more and 60% or less. The high-strength and high-elasticity cellulose continuous fiber according to any one of claims 2 to 4,
A high-strength and highly elastic cellulose continuous fiber having a birefringence of 70Δ × 10 ⁻³ or more and 90Δ × 10 ⁻³ or less. A method of spinning a high-strength and high-elasticity cellulose continuous fiber having a tensile modulus of 35 GPa or more,
Cellulose raw material is dissolved in an ionic liquid so that the average polymerization degree is 3000 or more and
A method for spinning high-strength and high-elasticity cellulose continuous fibers, wherein spinning is performed so that an average fiber diameter is 30 μm or less. A fiber-reinforced composite material obtained by mixing the high-strength and high-elasticity cellulose continuous fiber according to any one of claims 1 to 5 and a resin.