JP5811871B2 - Polyvinyl alcohol composite fiber and method for producing the same - Google Patents

Description

  The present invention relates to a polyvinyl alcohol composite fiber having a Young's modulus of 10 GPa or more and a method for producing the same.

Polyvinyl alcohol (hereinafter also referred to as PVA) fibers have been used for industrial materials because they are relatively high strength and high Young's modulus among conventional polymers. Recently, as a substitute for asbestos fibers, attention has been focused on cement reinforcing fibers that make use of the characteristics of alkali resistance. If PVA fibers with higher strength and high Young's modulus are developed, products that are excellent in terms of safety, durability, lightness and the like can be expected as reinforcing materials for rubber and plastics.
PVA fibers are produced by a wet spinning method, a dry spinning method, and a gel spinning method using water or an organic solvent (Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4). Among these, the gel spinning method is known as a method for producing a high-strength PVA fiber, and is a method in which the concept of gel spinning / ultra-stretching of ultrahigh molecular weight polyethylene is applied to PVA.

  Incidentally, in recent years, graphene oxide has attracted attention as a substance having unique characteristics. Since the graphene oxide particles are dispersed in water and have a planar shape, there is no entanglement between the particles and the dispersion is easy. However, it is not a perfect graphene structure when oxidized, and has many defects, so the Young's modulus is as low as about 208 GPa compared to 1000 GPa, which is said to be SWNT (single-walled carbon nanotube). (Non-Patent Document 1).

Since graphene oxide is dispersed in water, a composite material of graphene oxide and PVA is produced by mixing with PVA dissolved in water (Non-patent Documents 2 and 3). . However, these have low Young's modulus of PVA not added with graphene oxide, about 2 GPa, and the Young's modulus after addition of graphene oxide is about 5 GPa. When used as a fiber, a Young's modulus of about 5 GPa is insufficient, and it is necessary to realize a Young's modulus of preferably 10 GPa or more, more preferably 15 GPa or more. However, it is predicted from the compound law that the effect of adding graphene oxide having a Young's modulus of 208 GPa cannot be expected at a high Young's modulus exceeding 10 GPa. The composite law is a theory that is often used as a method for predicting the physical properties of composite materials. However, when the composite law is considered as a composite material having a Young's modulus of 10 GPa or more, the increase in Young's modulus due to the addition of graphene oxide is large However, it is about 3 to 4 GPa, and the increase in Young's modulus is not sufficient. More specifically, first, if the amount of graphene oxide added is too large, the viscosity when combined becomes too high to perform uniform spinning, so the upper limit of the amount added is about 3% by mass. From an industrial point of view, it is not desirable to add a large amount of graphene oxide, which is more expensive than a PVA polymer, and an appropriate addition amount is about 1% by mass. Therefore, the upper limit of the addition amount was set to 3% by mass, and the Young's modulus of the composite material after the addition of graphene oxide was calculated according to the Young's modulus when no graphene oxide was added, from the following calculation formula according to the composite rule. In addition, when converting the unit from mass% to volume%, calculation was performed using 1.3 g / cm ³ as the specific gravity of PVA and 2.2 g / cm ³ as the specific gravity of graphene oxide.

Formula of composite law (Young's modulus of composite material) = V _GO × (Young's modulus of graphene oxide)
+ V _PVA x (Young's modulus of PVA)
V _GO : Volume ratio of graphene oxide V _PVA : Volume ratio of _PVA

The results of the trial calculation are shown in Table 1. When Table 1 is viewed, the increase in Young's modulus due to the combination with graphene oxide is about 3 to 4 GPa even at the maximum addition of 3% by mass. It increases only about 1 GPa. When the composite material is considered to be 10 GPa or more, the amount of increase in Young's modulus is not large. In order to greatly improve the Young's modulus of PVA having a Young's modulus of 10 GPa or more, it is considered effective to combine with a material having a higher Young's modulus than graphene oxide.

A carbon nanotube (CNT) is known as a material having a high Young's modulus. CNT is said to have a maximum Young's modulus of about 1000 GPa, and attempts have been made to improve the strength and Young's modulus of PVA by combining with PVA. As before, the Young's modulus of the composite material when it was combined with CNTs having a Young's modulus of 1000 GPa was estimated. In the calculation, the specific gravity of CNT was calculated using 2.2 g / cm ³ which is the same as that of graphene oxide. The results of the trial calculation are shown in Table 2. In this case, the increase in Young's modulus due to the composite is expected to be about 17 to 18 GPa when 3% by mass is added, and about 6 GPa even when 1% by mass is added. It is expected that the above PVA can greatly improve the Young's modulus. However, in order to fully develop the performance of CNT, it is necessary to disperse CNT neatly in PVA. However, CNT has many problems of being entangled and difficult to disperse without causing aggregation. (Patent Document 5).

JPB 6-11927 JP 59-100700 JP 7-6085 JP 59-130314 JP2010-2116018

“Mechanical Properties of Monolayer Graphene Oxide”, Ji Won Suk, Richard D. Piner, Jinho An, and Rodney S. Ruoff, ACS Nano, 2010, 4 (11), 6557-6564. "Molecular-level Dispersion of Graphene into Poly (vinyl alcohol), and Effective Reinforcement of Their Nanocomposites", Jiajie Liang, Yi Huang, Long Zhang, Yan Wang, Yanfeng Ma, Tianyin Guo and Yongsheng Chen, Adv Funct Mater, 2009,19 , 2297-2302. “Strong and ductile poly (vinyl alcohol) / graphene oxide composite films with a layered structure”, Yuxi Xu, Wenjing Hong, Hua Bai, Chun Li, Gaoquan Shi, Carbon, 2009, 47, 538-3543.

  An object of the present invention is to provide a high Young's modulus PVA composite fiber having a large increase in Young's modulus due to the composite with graphene oxide and a method for producing the same.

  The present inventors have a composite fiber having a high composite effect with a material other than CNT that is likely to agglomerate in a PVA composite fiber having a high Young's modulus of 10 GPa or more, more preferably 15 GPa or more, which is useful for cement reinforcing fibers and the like. We examined with the aim of providing. As a result, it has been found that the production method for obtaining a PVA fiber having a high Young's modulus when no filler is added tends to increase the Young's modulus increase due to the composite when combined with graphene oxide, thereby completing the present invention. It was.

  In other words, graphene oxide has no entanglement between particles and good dispersibility, so it is effective as a material for a composite material with a PVA polymer. However, since Young's modulus is 208 GPa, it has a high Young's modulus of 10 GPa or more. It was thought that it was not effective as a filler for polyvinyl alcohol composite fibers having the following. Surprisingly, however, graphene oxide is oxidized when a similar production method is used when a technique (spinning method, stretching, etc.) in which the Young's modulus of the PVA fiber without a filler is higher is used. It has been found that the amount of increase in Young's modulus due to the addition of graphene tends to increase, and it has been found that even a high Young's modulus of 10 GPa or more is useful as a filler for polyvinyl alcohol composite fibers. The reason for this is not clear, but it is believed that there is some interaction between graphene oxide and the PVA polymer, and that interaction becomes stronger as the Young's modulus of the PVA polymer increases. In addition, since graphene oxide has a large specific surface area, it is considered that the fact that there are many interfaces between the PVA polymer and graphene oxide also enhances the effect. Thus, the special effect of the graphene oxide was discovered and it succeeded in implement | achieving the fiber with a high composite effect in the high Young's modulus PVA type composite fiber of 10 GPa or more. In addition to improving the Young's modulus, it is expected to improve the gas barrier property and the melting temperature in addition to the graphene oxide having a planar shape (“Transparent and high gas barrier films based on poly (vinyl alcohol) / graphene oxide composites ”, Thin Solid Films (2011), 519 (22), 7766-7771).

The present invention is as follows.
[1] It contains (A) a polyvinyl alcohol polymer and (B) graphene oxide particles, and the mass ratio of components (A) and (B) is 0.01 ≦ 100 × (B) / (A) ≦ 3 A polyvinyl alcohol composite fiber characterized by having a Young's modulus of 10 GPa or more.
[2] The polyvinyl alcohol-based composite fiber according to [1], wherein the polymerization degree of the polyvinyl alcohol-based polymer (A) is 1500 to 6000.
[3] The polyvinyl alcohol composite fiber according to [1] or [2], wherein the (B) graphene oxide particles have an oxygen content in an elemental analysis range of 5 to 50% by mass.
[4] The polyvinyl alcohol composite according to any one of [1] to [3], wherein the graphene oxide particles (B) have a ratio of the number of particles having a thickness of 5 nm or less of 60% or more. fiber.
[5] The polyvinyl alcohol composite fiber according to any one of [1] to [4], wherein the (B) graphene oxide particles have an average particle diameter of 0.5 μm or more.
[6] A polyvinyl alcohol composite fiber according to any one of [1] to [5] is produced by spinning a spinning dope containing (A) a polyvinyl alcohol polymer and (B) graphene oxide particles. A method for producing a polyvinyl alcohol composite fiber.
[7] The polyvinyl alcohol system according to [6], wherein the solvent of the spinning dope is at least one selected from the group consisting of dimethylsulfoxide, dimethylacetamide, dimethylformamide, N-methylpyrrolidone, and water. A method for producing a composite fiber.
[8] The spinning dope is prepared by mixing a graphene oxide dispersion with a polyvinyl alcohol polymer or a polyvinyl alcohol polymer solution. The polyvinyl alcohol composite fiber according to [6] or [7], Production method.
[9] The method for producing a polyvinyl alcohol-based composite fiber according to any one of [6] to [8], further including a step of stretching the fiber, wherein a stretching ratio is 5 times or more.
[10] The method for producing a polyvinyl alcohol-based composite fiber according to [9], wherein the temperature during stretching is 250 ° C. or lower.

According to the present invention, it is possible to provide a polyvinyl alcohol composite fiber having a high Young's modulus with a large increase in Young's modulus due to the composite, without using CNT that is likely to cause aggregation.

The present invention is a polyvinyl alcohol composite fiber characterized by containing a specific amount of (A) a polyvinyl alcohol polymer and (B) graphene oxide particles and having a Young's modulus of 10 GPa or more, and a production method thereof. .

(PVA polymer)
The PVA polymer used in the present invention is not particularly limited as long as it has a vinyl alcohol unit as a main constituent component, and may have other constituent components. The main component here means 1/10 or less, preferably 1/50 or less of the number of units of components other than the vinyl alcohol unit. Examples of monomers that form such a structural component include olefins such as ethylene, propylene, and butylene, fatty acid vinyl esters such as vinyl acetate, acrylic acid and its salts and acrylic esters such as methyl acrylate, methacrylic acid, and the like. And salts thereof, methacrylic acid esters such as methyl methacrylate, acrylamide derivatives such as acrylamide and N-methylacrylamide, methacrylamide, methacrylamide derivatives such as N-methylol methacrylamide, N-vinylpyrrolidone, N-vinylformamide, N -N-vinylamides such as vinylacetamide, allyl ethers having polyalkylene oxide in the side chain, vinyl ethers such as methyl vinyl ether, nitriles such as acrylonitrile, halogens such as vinyl chloride Vinyl chloride, maleic acid and salts thereof, or anhydrides and esters thereof. Such a monomer introduction method may be a copolymerization method or a post-reaction introduction method.

  The degree of polymerization of the PVA polymer is desirably 1000 or more and 6000 or less, and more desirably 1500 or more and 5000 or less. When the degree of polymerization is 1000 or less, it is difficult to achieve a high Young's modulus, and when the degree of polymerization is 6000 or more, the viscosity when combined with graphene oxide becomes too high, and spinning becomes difficult. . The degree of polymerization of the PVA polymer can be evaluated by, for example, JIS K6726.

  Although there is no big restriction | limiting about the saponification degree of a PVA-type polymer, 90 mol% or more is preferable from a heat resistant and water-resistant viewpoint, and it is still more preferable that it is 99 mol% or more of a PVA-type polymer. The degree of saponification of PVA can be evaluated by, for example, JIS K6726.

(Graphene oxide)
Graphene oxide can be obtained by exfoliating graphite oxide in layers. Graphite oxide is produced by oxidizing graphite by a specific method. As a method for oxidizing graphite to obtain graphite oxide, known Brodie method (using nitric acid and potassium chlorate), Staudenmaier method (nitric acid, Sulfuric acid, potassium chlorate are used), Hummers-Offeman method (sulfuric acid, sodium nitrate, potassium permanganate is used), and methods obtained by improving these methods can be used. Of these, oxidation proceeds particularly in the Hummers-Offeman method (WS Hummerset al., J. Am. Chem. Soc., 80, 1339 (1958); US Pat. No. 2,798,878 (1957)). This oxidation method is particularly recommended.

In order to exfoliate graphite oxide in layers and obtain graphene oxide, graphite oxide may be sufficiently purified. For the purification operation, known means such as decantation, filtration, centrifugation, dialysis, and ion exchange may be used. At the time of purification, separation of the multilayer structure occurs spontaneously, but in addition to this, addition of a stirring operation such as shaking or a physical force such as a shearing force is desirable because the separation is further promoted. Although ultrasonic irradiation can also be used, it is desirable to use it when it is desired to reduce the particle size because the basic structure of each layer is destroyed along with the separation of the layers and the particle size becomes small.

Strictly speaking, graphite oxide having a single-layer structure should be defined as graphene oxide. In general, graphite oxide thinned to a single layer level is often referred to as graphene oxide. Graphite oxide having a number of layers of 10 or less (average thickness of about 8.3 nm when converted from the generally known interlayer distance of 0.83 nm of graphite oxide) is also broadly treated as graphene oxide. For these reasons, the graphene oxide in the present invention means graphite oxide having a thickness of 10 nm or less.

The graphene oxide in the present invention is a process that causes a compositional change or a structural change (for example, reduction treatment, chemical modification (using organic functional groups such as carboxylic acid contained in graphene oxide to chemically bond organic substances)). The graphene oxide performed is also included. The treatment for causing the composition change / structure change can be performed before or after combining the graphene oxide and the PVA polymer. As the treatment before compounding the graphene oxide, for example, a heat treatment is performed on the graphene oxide-containing solution, a light irradiation is performed, a heat treatment is performed by adding a reducing agent, and the like. As the treatment performed after being combined with the PVA polymer, heat treatment, treatment exposed to a reducing atmosphere, light irradiation, and the like are possible.

  The graphene oxide can have an oxygen-containing group such as a hydroxyl group or a carboxylic acid group, and the oxygen content by elemental analysis can be, for example, in the range of 5 to 50% by mass. If the oxygen content is less than 5% by mass, a strong interaction with the PVA polymer tends to be difficult to obtain, preferably 10% by mass or more, more preferably 20% by mass or more, and further preferably 30% by mass or more. is there. On the other hand, if it exceeds 50% by mass, the structure as graphene oxide tends to be unable to be maintained. However, it is not intended to be limited to these ranges. The oxygen content can be evaluated by energy dispersive X-ray analysis combined with XPS (X-ray photoelectron spectroscopy), SEM (scanning electron microscope), and TEM (transmission electron microscope).

Graphene oxide is said to be formed with a portion that retains the graphite-derived graphene structure and an amorphous structure portion, and functions different from graphene are expressed by the presence of the amorphous structure portion. The presence of the amorphous structure portion can be confirmed by a Raman spectrum, and the ratio of peak heights H _G / H _D in the Raman spectrum of graphene oxide is preferably in the range of H _G / H _D ≦ 100. It is more desirable that _{G 1} / H _D ≦ 10. Here, _{H G} denotes the height of the peaks derived from the G rays detected near a Raman shift 1650 cm ^-1 (derived unoxidized region), _{H D} is detected near a Raman shift 1350 cm ^-1 It means the height of the peak derived from the D line (derived from the region where the graphene structure is broken by oxidation). The value of H _G / _{H D} tends to strong interaction is difficult to obtain the larger the PVA based polymer than 100.

The thinner the graphene oxide particles are, the more desirable, since the area that becomes the interface between the graphene oxide particles and the PVA polymer increases. Therefore, the thickness of the graphene oxide particles is preferably 60% or more of graphene oxide particles having a thickness of 5 nm or less, and more preferably 60% or more of graphene oxide particles having a thickness of 1.5 nm or less. preferable. The thickness can be evaluated by the following method using an atomic force microscope. Drop the diluted aqueous dispersion of graphene oxide particles onto the substrate (mica), find isolated particles that do not overlap with the atomic force microscope, and measure the height of the substrate and the isolated particles measured by the atomic force microscope. The difference is the thickness of the particles. In the case where wrinkles are formed in the particles, the wrinkled portion does not reflect the thickness. Therefore, the thickness is evaluated based on the difference in height between the wrinkled portion and the substrate. Because of the influence of adsorbed water, it is considered that the number of graphene oxide layers is one when the thickness is 1.5 nm or less. The content ratio of graphene oxide having a certain thickness or less is calculated by measuring the thickness of 30 particles and calculating the ratio of graphene oxide having a certain thickness or less in 30 particles.

The particle diameter of the graphene oxide particles is preferably 0.5 μm or more and 300 μm or less, more preferably 1 μm or more and 200 μm or less, and further preferably 5 μm or more and 100 μm or less. When the particle diameter is smaller than 0.5 μm, there is a problem that the amount of increase in Young's modulus is small. On the other hand, when the particle diameter is larger than 300 μm, it is necessary to use large graphite as a raw material, and there is a problem that the time required for oxidation becomes long. Here, the particle diameter means the maximum diameter (the length when any two points on the outer contour line are selected so that the length between them is maximized), and is calculated by the average value of 30 particles. I decided to. The outline of the particles can be confirmed with an atomic force microscope, SEM (scanning electron microscope) or the like.

(Production method of composite fiber)
As a method for producing the composite fiber of the present invention, a method in which graphene oxide and a PVA polymer are mixed in a solution, and the mixed solution is spun as a spinning stock solution is desirable. As a method of adjusting the mixture,
(1) Method of mixing graphene oxide dispersion and PVA polymer solution (2) Method of adding PVA polymer to graphene oxide dispersion and dissolving PVA polymer (3) Solid graphene oxide in PVA polymer solution The method of (1) and (2) is desirable because it is important that the graphene oxide is uniformly dispersed in the mixed solution. Here, spinning in the present invention means a step of processing a material having fiber forming ability into a fiber shape, and the spinning dope contains 50% by mass or more of a solvent and is processed into a fiber shape by spinning. Means something.

The solvent of the spinning dope is preferably a solvent in which graphene oxide can be dispersed and in which the PVA polymer dissolves. For example, polar solvents such as water, dimethylsulfoxide (hereinafter abbreviated as DMSO), dimethylacetamide, dimethylformamide, and N-methylpyrrolidone And polyhydric alcohols such as glycerin and ethylene glycol. These solvents can be used alone or as a mixture of a plurality of solvents. When a solvent other than water is added to water, a gel state with less intermolecular entanglement is formed, and a fiber having a higher Young's modulus can be produced. As a solvent other than water, DMSO is most preferable in terms of low-temperature solubility, low toxicity, low corrosivity, dispersibility of graphene oxide, and the like. The ratio of the solvent other than water (the total of the water and the solvent other than water is 100% by mass) is preferably 60% by mass or more, and more preferably 70% by mass or more. When the proportion of the solvent other than water is less than 60% by mass, it becomes difficult to form a gel state with little intermolecular entanglement, and it is difficult to sufficiently increase the Young's modulus of the obtained fiber.

In addition to PVA and solvent, various additives such as pigments, coloring agents such as pigments, antifreezing agents, antioxidants, crosslinking agents, UV absorbers, surfactants, reducing agents, pH adjustment A necessary amount of an agent may be added. Furthermore, for solvents having a relatively high freezing temperature, such as DMSO, if a solidifying agent such as methanol is added within a range where PVA does not solidify, the spinning dope is frozen even if the coagulation bath is kept below the freezing temperature of the solvent. May not be preferable. The amount of additives other than graphene oxide is preferably 20% by mass or less, more preferably 10% by mass or less, and still more preferably 5% by mass or less in order not to cause deterioration of the physical properties of the fiber.

The PVA polymer concentration of the spinning dope (the total of the PVA polymer and the solvent is 100% by mass) varies depending on the polymerization degree of the PVA polymer and the type of the solvent, but is usually 2 to 30% by mass, preferably 5 to 20%. Mass%. When the PVA polymer concentration is higher than 30% by mass, the viscosity of the liquid becomes too high and spinning becomes difficult, and when the concentration is lower than 2% by mass, single yarn breakage during spinning tends to occur.

  As a spinning method of the polyvinyl alcohol composite fiber of the present invention, a wet spinning method using water as a solvent for spinning, a dry-wet spinning method or a dry spinning method, a gel spinning method using an organic solvent, or the like can be used. Among these, the gel spinning method is most desirable because it can realize a very high Young's modulus. Wet spinning is a method in which a spinning stock solution is discharged directly from a spinning nozzle into a solidification bath, and dry and wet spinning is a method in which a spinning stock solution is temporarily placed in air or inert gas at an arbitrary distance from the spinning nozzle. It is a method of discharging and then introducing into the solidification bath. Dry spinning is a method of discharging a spinning solution into air or an inert gas. The gel spinning method means a method of spinning with a stock solution of a solvent containing 10% by mass or more of an organic solvent other than water. As a method for discharging the spinning dope, any method can be used as long as the spinning dope can be processed into a yarn shape. Examples thereof include a method using a nozzle and a method of injecting the spinning dope once into a tube.

It is desirable to perform stretching after spinning. The reason is not clear, but when the graphene oxide and PVA polymer composite fiber is stretched, the Young's modulus increase rate increases due to the special action of graphene oxide and PVA polymer. The draw ratio is desirably 5 times or more, more desirably 10 times or more, and further desirably 15 times or more. When the draw ratio is less than 5, the Young's modulus increase rate due to the addition of graphene oxide is small. The stretching temperature is preferably 250 ° C. or lower, and more preferably 210 ° C. or lower. If the temperature at the time of stretching exceeds 250 ° C., there is a problem that the reduction of graphene oxide proceeds at the time of stretching and the interaction between the PVA polymer and graphene oxide is weakened.

As the addition amount of graphene oxide in the polyvinyl alcohol-based composite fiber, the mass ratio of (A) polyvinyl alcohol-based polymer and (B) graphene oxide particles is 0.01 ≦ 100 × (B) / (A) ≦ 3 It is preferable that there is 0.05 ≦ 100 × (B) / (A) ≦ 1. If the value of 100 × (B) / (A) is less than 0.01, a sufficient Young's modulus increase effect cannot be obtained, and if it exceeds 3, there is a problem that the tensile strength tends to decrease.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in more detail, this invention is not limited to a following example at all.

(Synthesis example of graphene oxide)
Natural graphite SNO-3 (manufactured by SEC Carbon, purity 99.97% by mass or more) 10 g, sodium nitrate (purity 99%) 7.5 g, sulfuric acid (purity 96%) 621 g, potassium permanganate (purity 99%) The mixture was placed in a mixed solution consisting of 45 g and allowed to stand at about 20 ° C. for 5 days with gentle stirring. The obtained high-viscosity liquid was added to 1000 cm ³ of a 5% by mass sulfuric acid aqueous solution with stirring for about 1 hour, and further stirred for 2 hours. Hydrogen peroxide (30 mass% aqueous solution) 30g was added to the obtained liquid, and it stirred for 2 hours.
The liquid was sufficiently purified with water to obtain a flat graphene oxide dispersion in water. From the result of vacuum drying a part of the liquid at 40 ° C. and measuring the mass change before and after drying, the solid content concentration of graphene oxide in the liquid was calculated to be 1.3% by mass. Further, in the XPS analysis of graphene oxide vacuum-dried at 40 ° C., oxygen was 42% by mass. Results of the measurement of the Raman spectrum, the ratio H _{G /} H _D of the height H _D of the peak derived from the height H _G and D lines of the peak derived from the G line was 1.29. A portion of the liquid was diluted with water, dried on mica, and the thickness of graphene oxide was evaluated using an atomic force microscope. The thickness confirmed for 30 particles was 1.1 nm. 2 nm, 0.8 nm, 0.9 nm, 1.7 nm, 1.5 nm, 1.1 nm, 1.8 nm, 0.9 nm, 1.0 nm, 1.6 nm, 2.2 nm, 1.1 nm, 1.0 nm, 1.3 nm, 0.9 nm, 0.9 nm, 1.2 nm, 1.9 nm, 1.4 nm, 1.7 nm, 1.8 nm, 1.0 nm, 1.3 nm, 1.1 nm, 0.8 nm, 2. 0 nm, 1.4 nm, 1.8 nm, and 1.3 nm, 20 graphene oxide particles having a thickness of 1.5 nm or less, 67%, and 30 graphene oxide particles having a thickness of 5 nm or less, 30 particles and 100%. It contained 60% or more of the whole. The particle diameter (maximum diameter (the length when any two points on the outer contour line are selected so that the length between them is maximized)) determined by 30 particles is 2.0 μm, 4. 3 μm, 5.4 μm, 2.5 μm, 1.0 μm, 6.8 μm, 10.5 μm, 2.3 μm, 4.4 μm, 1.4 μm, 4.1 μm, 1.6 μm, 1.5 μm, 2.1 μm, 1.2 μm, 1.6 μm, 1.1 μm, 1.0 μm, 1.4 μm, 1.7 μm, 2.9 μm, 4.4 μm, 2.9 μm, 1.9 μm, 1.2 μm, 1.8 μm, 2. The average particle diameter was 6 μm, 6.8 μm, 1.8 μm, and 6.0 μm. A dispersion obtained by adjusting the concentration of the above 1.3 mass% graphene oxide aqueous dispersion to 1.0 mass% is hereinafter referred to as “dispersion A”.

In order to reduce the particle size of the graphene oxide, the dispersion A was subjected to ultrasonic treatment to prepare a graphene oxide aqueous dispersion having a concentration of 1.0% by mass. This dispersion is hereinafter referred to as “Dispersion B”. In XPS analysis of graphene oxide obtained by vacuum drying the dispersion B at 40 ° C., oxygen was 42% by mass. Results of the measurement of the Raman spectrum, the ratio H _{G /} H _D of the height H _D of the peak derived from the height H _G and D lines of the peak derived from the G line was 1.29. A portion of the liquid was diluted with water, dried on mica, and the thickness of graphene oxide was evaluated using an atomic force microscope. The thickness confirmed for 30 particles was 0.9 nm, 0 .8 nm, 1.0 nm, 1.3 nm, 0.9 nm, 0.9 nm, 0.8 nm, 1.1 nm, 1.8 nm, 0.9 nm, 1.0 nm, 0.8 nm, 1.7 nm, 1.1 nm 0.8 nm, 0.8 nm, 1.4 nm, 0.8 nm, 1.3 nm, 1.1 nm, 1.1 nm, 1.0 nm, 1.4 nm, 1.1 nm, 0.9 nm, 1.7 nm, 1 .2 nm, 1.0 nm, 1.0 nm, 1.3 nm, 27% graphene oxide particles with a thickness of 1.5 nm or less, 90%, 30 graphene oxides with a thickness of 5 nm or less, 30 with 100%, Also contained 60% or more of the total. The particle diameter confirmed by 30 particles (the maximum diameter (the length when any two points on the outer contour line are selected so that the length between them is maximized)) is 0.8 μm, 2. 0 μm, 2.3 μm, 1.0 μm, 3.7 μm, 5.4 μm, 1.1 μm, 2.1 μm, 0.8 μm, 0.7 μm, 1.7 μm, 0.6 μm, 0.9 μm, 0.8 μm, 0.7 μm, 0.7 μm, 0.6 μm, 0.8 μm, 2.2 μm, 0.9 μm, 1.2 μm, 4.1 μm, 0.8 μm, 1.0 μm, 1.2 μm, 2.7 μm,. The average particle size was 8 μm, 0.6 μm, 1.7 μm, 1.3 μm, and 1.5 μm.

In order to further reduce the particle diameter of the graphene oxide, the dispersion B was subjected to ultrasonic treatment to prepare a graphene oxide aqueous dispersion having a concentration of 1.0% by mass. This dispersion is hereinafter referred to as “Dispersion C”. In XPS analysis of graphene oxide obtained by vacuum drying dispersion C at 40 ° C., oxygen was 40% by mass. Results of the measurement of the Raman spectrum, the ratio H _{G /} H _D of the height H _D of the peak derived from the height H _G and D lines of the peak derived from the G line was 1.27. A portion of the liquid was diluted with water, dried on mica, and the thickness of graphene oxide was evaluated using an atomic force microscope. The thickness confirmed for 30 particles was 1.0 nm, 0 .9 nm, 0.8 nm, 1.0 nm, 0.9 nm, 0.9 nm, 0.8 nm, 1.1 nm, 1.1 nm, 0.8 nm, 1.5 nm, 0.9 nm, 1.0 nm, 0.8 nm 1.0 nm, 0.8 nm, 1.2 nm, 0.8 nm, 1.1 nm, 0.9 nm, 1.4 nm, 1.2 nm, 1.1 nm, 1.0 nm, 1.1 nm, 1.4 nm, 1 0.0, 1.2, 1.0, 1.1 nm, 30% of graphene oxide particles having a thickness of 1.5 nm or less, 30%, and 30% of graphene oxide particles of 5 nm or less, 100%, Also contained 60% or more of the total. The particle diameter (maximum diameter (the length when any two points on the outer contour line are selected so that the length between them is maximized)) determined by 30 particles is 0.3 μm, 0. 2 μm, 0.5 μm, 0.2 μm, 0.5 μm, 0.5 μm, 0.1 μm, 0.3 μm, 0.2 μm, 0.5 μm, 0.3 μm, 0.2 μm, 0.2 μm, 0.5 μm, 0.3 μm, 1.2 μm, 0.3 μm, 0.2 μm, 2.8 μm, 0.1 μm, 1.5 μm, 0.5 μm, 1.0 μm, 0.6 μm, 0.1 μm, 0.4 μm,. They were 3 μm, 0.6 μm, 0.2 μm, and 0.4 μm, and the average particle size was 0.5 μm.

(Tensile test method)
A fiber having an initial length of 20 mm dried for 48 hours under reduced pressure at 40 ° C., using an autograph AGS-1kND manufactured by Shimadzu Corporation at room temperature under a tensile rate of 20 mm / min, Young's modulus, breaking Strength and elongation at break were measured. The test was performed on 10 fibers, and the average value was calculated.

(Measurement method of fiber diameter)
For fibers having a circular cross-sectional shape, the fibers were observed with an optical microscope, and the width was taken as the diameter. If the cross-sectional shape of the fiber is different from a circular shape, observe the cross-sectional shape of the fiber with an optical microscope, calculate the equivalent circle diameter (the diameter of the circle with the same cross-sectional area) using image analysis software, and calculate the equivalent circle diameter. The diameter of the fiber. The diameter was measured at five locations, and the average value was calculated.

Comparative Example 1
Nippon Synthetic Chemical Industry Co., Ltd. polyvinyl alcohol (Gohsenol NH-18, saponification degree 99% or more, polymerization degree 1,800) powder 5.000g and water 50.000g are mixed and heated to 80 ° C to dissolve the polyvinyl alcohol. A spinning solution was prepared. The spinning solution was spun into methanol from the tip of the needle with the spinning solution at 75 ° C. and the tip of a 0.80 mm inner diameter needle immersed in methanol at −40 ° C. After being immersed in methanol at −40 ° C. for 24 hours, the wound fiber was immersed in methanol at room temperature for 12 hours. The thus produced fiber was dried at room temperature in the air for 24 hours, and further at 40 ° C. under reduced pressure for 48 hours to obtain a PVA polymer fiber. Table 3 shows the results of measurement of the diameter of the obtained fiber and tensile test.

Comparative Example 2
The fiber obtained in Comparative Example 1 was stretched 6 times by heating at 150 ° C. Table 3 shows the results of measurement of the diameter of the obtained fiber and tensile test.

Comparative Example 3
The fiber obtained in Comparative Example 1 was stretched 9 times by heating at 150 ° C. Table 3 shows the results of measurement of the diameter of the obtained fiber and tensile test.

Example 1
Nippon Synthetic Chemical Industry Co., Ltd. polyvinyl alcohol (Gosenol NH-18, saponification degree 99% or more, polymerization degree 1,800) powder 5.000g, dispersion A 0.500g, water 49.505g was mixed and heated to 80 ° C. Polyvinyl alcohol was dissolved to prepare a spinning dope. The spinning stock solution was spun at 75 ° C., and the spinning stock solution was spun from the tip of the needle into methanol with the tip of the 0.80 mm inner diameter needle immersed in methanol at −40 ° C. After being immersed in methanol at −40 ° C. for 24 hours, the wound fiber was immersed in methanol at room temperature for 12 hours. The fiber thus produced was dried at room temperature in the air for 24 hours, and further at 40 ° C. under reduced pressure for 48 hours to obtain a PVA polymer composite fiber. Table 3 shows the results of measurement of the diameter of the obtained fiber and tensile test.

Example 2
The fiber obtained in Example 1 was stretched 6 times by heating at 150 ° C. Table 3 shows the results of measurement of the diameter of the obtained fiber and tensile test.

Example 3
The fiber obtained in Example 1 was stretched 9 times by heating at 150 ° C. Table 3 shows the results of measurement of the diameter of the obtained fiber and tensile test.

Example 4
A PVA polymer composite fiber was obtained in the same manner as in Example 1 except that the addition amounts of polyvinyl alcohol powder, dispersion A and water in Example 1 were changed to 5,000 g, 2.500 g and 47.525 g, respectively. . Table 3 shows the results of measurement of the diameter of the obtained fiber and tensile test.

Example 5
The fiber obtained in Example 4 was stretched 6 times by heating at 150 ° C. Table 3 shows the results of measurement of the diameter of the obtained fiber and tensile test.

Example 6
The fiber obtained in Example 4 was stretched 9 times by heating at 150 ° C. Table 3 shows the results of measurement of the diameter of the obtained fiber and tensile test.

Example 7
A PVA polymer composite fiber was obtained in the same manner as in Example 1 except that the addition amounts of polyvinyl alcohol powder, dispersion A and water in Example 1 were changed to 5,000 g, 5.000 g and 45.050 g, respectively. . Table 3 shows the results of measurement of the diameter of the obtained fiber and tensile test.

Example 8
The fiber obtained in Example 7 was stretched 6 times by heating at 150 ° C. Table 3 shows the results of measurement of the diameter of the obtained fiber and tensile test.

Example 9
The fiber obtained in Example 7 was stretched 9 times by heating at 150 ° C. Table 3 shows the results of measurement of the diameter of the obtained fiber and tensile test.

Comparative Example 4
The fiber obtained in Comparative Example 1 was stretched 6 times by heating at 200 ° C. Table 3 shows the results of measurement of the diameter of the obtained fiber and tensile test.

Comparative Example 5
The fiber obtained in Comparative Example 1 was stretched 9 times by heating at 200 ° C. Table 3 shows the results of measurement of the diameter of the obtained fiber and tensile test.

Example 10
The fiber obtained in Example 1 was stretched 6 times by heating at 200 ° C. Table 3 shows the results of measurement of the diameter of the obtained fiber and tensile test.

Example 11
The fiber obtained in Example 1 was stretched 9 times by heating at 200 ° C. Table 3 shows the results of measurement of the diameter of the obtained fiber and tensile test.

Example 12
The fiber obtained in Example 4 was stretched 6 times by heating at 200 ° C. Table 3 shows the results of measurement of the diameter of the obtained fiber and tensile test.

Example 13
The fiber obtained in Example 4 was stretched 9 times by heating at 200 ° C. Table 3 shows the results of measurement of the diameter of the obtained fiber and tensile test.

Example 14
The fiber obtained in Example 7 was stretched 6 times by heating at 200 ° C. Table 3 shows the results of measurement of the diameter of the obtained fiber and tensile test.

Example 15
The fiber obtained in Example 7 was stretched 9 times by heating at 200 ° C. Table 3 shows the results of measurement of the diameter of the obtained fiber and tensile test.

Comparative Example 6
Kuraray Co., Ltd. polyvinyl alcohol (PVA145H, saponification degree 99% or more, polymerization degree 4,500) powder 5 g, water 100.000 g, dimethyl sulfoxide (DMSO) 40.000 g are mixed and heated to 90 ° C. Dissolved to prepare a spinning dope. After returning to room temperature, the spinning dope was sucked into a glass tube having an inner diameter of 1 mm and subjected to a freezing treatment at −20 ° C. for 24 hours. Subsequently, the spinning stock solution subjected to the freezing treatment was spun by drawing out from the glass tube, and immersed in methanol at room temperature for 24 hours. The thus produced fiber was dried at room temperature in the air for 24 hours, and further at 40 ° C. under reduced pressure for 48 hours to obtain a PVA polymer fiber. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Comparative Example 7
The fiber obtained in Comparative Example 6 was stretched 10 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Comparative Example 8
The fiber obtained in Comparative Example 6 was stretched 20 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Comparative Example 9
The fiber obtained in Comparative Example 6 was stretched 30 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Comparative Example 10
The fiber obtained in Comparative Example 6 was stretched 50 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Comparative Example 11
Kuraray Co., Ltd. polyvinyl alcohol (PVA145H, saponification degree 99% or more, polymerization degree 4,500) powder 5g, dispersion A 0.250g, water 9.753g, dimethyl sulfoxide (DMSO) 40.000g is mixed, 90 ℃ And the polyvinyl alcohol was dissolved to prepare a spinning dope. After returning to room temperature, the spinning solution was sucked into a glass tube having an inner diameter of 1 mm and subjected to a freezing treatment at −20 ° C. for 24 hours. Subsequently, the spinning stock solution subjected to the freezing treatment was spun by drawing out from the glass tube, and immersed in methanol at room temperature for 24 hours. The fiber thus produced was dried at room temperature in the air for 24 hours, and further at 40 ° C. under reduced pressure for 48 hours to obtain a PVA polymer composite fiber. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 16
The fiber obtained in Comparative Example 11 was stretched 10 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 17
The fiber obtained in Comparative Example 11 was stretched 20 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 18
The fiber obtained in Comparative Example 11 was stretched 30 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 19
The fiber obtained in Comparative Example 11 was stretched 50 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Comparative Example 12
The PVA polymer was the same as Comparative Example 11 except that the addition amounts of polyvinyl alcohol powder, dispersion A, water and DMSO in Comparative Example 11 were changed to 5.000 g, 0.500 g, 9.505 g and 40.000 g, respectively. Of composite fiber was obtained. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 20
The fiber obtained in Comparative Example 12 was stretched 10 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 21
The fiber obtained in Comparative Example 12 was stretched 20 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 22
The fiber obtained in Comparative Example 12 was stretched 30 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 23
The fiber obtained in Comparative Example 12 was stretched 50 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Comparative Example 13
A PVA polymer was prepared in the same manner as in Comparative Example 11 except that the addition amounts of polyvinyl alcohol powder, dispersion A, water and DMSO in Comparative Example 11 were changed to 5,000 g, 2.500 g, 7.525 g and 40.000 g, respectively. Of composite fiber was obtained. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 24
The fiber obtained in Comparative Example 13 was stretched 10 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 25
The fiber obtained in Comparative Example 13 was stretched 20 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 26
The fiber obtained in Comparative Example 13 was stretched 30 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 27
The fiber obtained in Comparative Example 13 was stretched 50 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Comparative Example 14
A PVA polymer was prepared in the same manner as in Comparative Example 11 except that the addition amounts of the polyvinyl alcohol powder, dispersion A, water and DMSO in Comparative Example 11 were changed to 5,000 g, 5.000 g, 5.050 g and 40.000 g, respectively. Of composite fiber was obtained. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 28
The fiber obtained in Comparative Example 14 was stretched 10 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 29
The fiber obtained in Comparative Example 14 was stretched 20 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 30
The fiber obtained in Comparative Example 14 was stretched 30 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 31
The fiber obtained in Comparative Example 14 was stretched 50 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Comparative Example 15
A PVA polymer composite fiber was obtained in the same manner as in Comparative Example 14 except that Dispersion B was used instead of Dispersion A. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 32
The fiber obtained in Comparative Example 15 was stretched 10 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 33
The fiber obtained in Comparative Example 15 was stretched 20 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 34
The fiber obtained in Comparative Example 15 was stretched 30 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 35
The fiber obtained in Comparative Example 15 was stretched 50 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Comparative Example 16
A PVA polymer composite fiber was obtained in the same manner as in Comparative Example 14 except that Dispersion C was used instead of Dispersion A. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 36
The fiber obtained in Comparative Example 16 was stretched 10 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 37
The fiber obtained in Comparative Example 16 was stretched 20 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 38
The fiber obtained in Comparative Example 16 was stretched 30 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Example 39
The fiber obtained in Comparative Example 16 was stretched 50 times by heating at 150 ° C. Table 4 shows the results of measuring the diameter of the obtained fiber and conducting a tensile test.

Regarding the results in Table 3, Table 5 shows the amount of increase in Young's modulus due to the addition of graphene oxide when fibers were produced under the same conditions. Table 5 shows that the amount of increase in Young's modulus due to the addition of graphene oxide tends to increase as the Young's modulus without graphene oxide is higher.
Similarly, with respect to the results in Table 4, Table 6 shows the amount of increase in Young's modulus due to the addition of graphene oxide when fibers were produced under the same conditions. Table 6 shows that even in a system in which DMSO is added to the spinning solution, the amount of increase in Young's modulus due to the addition of graphene oxide tends to increase as the Young's modulus without addition of graphene oxide increases.
Furthermore, Table 4 shows that the amount of increase in Young's modulus due to the addition of graphene oxide tends to increase as the particle size increases.

Claims (10)

(A) contains polyvinyl alcohol polymer and (B) graphene oxide particles, the mass ratio of components (A) and (B) is 0.01 ≦ 100 × (B) / (A) ≦ 3, and A polyvinyl alcohol-based composite fiber having a Young's modulus of 10 GPa or more. 2. The polyvinyl alcohol-based composite fiber according to claim 1, wherein the degree of polymerization of the (A) polyvinyl alcohol-based polymer is 1500 to 6000. The polyvinyl alcohol composite fiber according to claim 1 or 2, wherein the (B) graphene oxide particles have an oxygen content of 5 to 50 mass% by elemental analysis. The polyvinyl alcohol composite fiber according to any one of claims 1 to 3, wherein the (B) graphene oxide particles have a ratio of the number of particles having a thickness of 5 nm or less of 60% or more. The polyvinyl alcohol composite fiber according to any one of claims 1 to 4, wherein the (B) graphene oxide particles have an average particle diameter of 0.5 µm or more. A polyvinyl alcohol composite fiber according to any one of claims 1 to 5 is produced by spinning a spinning dope containing (A) a polyvinyl alcohol polymer and (B) graphene oxide particles. Method for manufacturing a composite fiber. The solvent for the spinning dope is at least one selected from the group consisting of dimethylsulfoxide, dimethylacetamide, dimethylformamide, N-methylpyrrolidone, and water. Production method. The method for producing a polyvinyl alcohol composite fiber according to claim 6 or 7, wherein the spinning stock solution is prepared by mixing a graphene oxide dispersion with a polyvinyl alcohol polymer or a polyvinyl alcohol polymer solution. . Furthermore, the process of extending | stretching a fiber is included, The magnification of extending | stretching is 5 times or more, The manufacturing method of the polyvinyl alcohol-type composite fiber in any one of Claims 6-8 characterized by the above-mentioned. The temperature at the time of drawing is 250 degrees C or less, The manufacturing method of the polyvinyl alcohol-type composite fiber of Claim 9 characterized by the above-mentioned.