Carbon fiber rope, infrastructure material using same, and carbon fiber bundle for rope

Abstract

In order to provide a carbon fiber rope having exceptional tensile strength and handleability, the present invention provides a carbon fiber rope in which two or more carbon fiber bundles are twisted together, and in which the fluctuation width of the fiber axis when single fibers of the carbon fiber bundles are observed in the range of a linear distance of 1 mm from the side surface is 1.5-10 μm.

Description

Carbon fiber ropes and infrastructure materials using carbon fiber ropes, and carbon fiber bundles for ropes

[0001] This invention relates to carbon fiber ropes, infrastructure materials using the carbon fiber ropes, and carbon fiber bundles for ropes.

[0002] Because carbon fiber is lightweight yet possesses excellent strength and elastic modulus, it is used in many fields, including aircraft components, spacecraft components, automotive components, shipbuilding components, civil engineering and construction materials, and sporting goods, as a composite material combined with various matrix resins.

[0003] For example, Patent Document 1 discloses a technique for creating a composite material having a core wire formed by twisting carbon fiber bundles, binding them with a restraining material, and then solidifying them with a hardening agent, thereby making it less prone to breakage when subjected to bending stress and bringing its handling closer to that of metal wire. Patent Document 2 also discloses a technique for creating a linear structure in which carbon fiber bundles are twisted, covered with a covering thread, and then the outer circumference is covered with an elastomer, thereby achieving both strength and lightness exceeding that of metal wire. Furthermore, Patent Document 3 discloses a technique for a power transmission line containing a carbon fiber composite material in its center, where, assuming that the carbon fiber composite material is weak against bending stress, the power transmission line cracks and releases a coloring agent to the outside when the power transmission line is bent to a bending radius exceeding a critical bending radius at which damage occurs to a part of the carbon fiber composite material.

[0004] International Publication No. 2014 / 196432, Japanese Patent Publication No. 2023-70242, Japanese Patent Publication No. 2019-153408

[0005] However, in Patent Document 1, flexibility in the bending direction could be increased by twisting the carbon fiber bundle and solidifying it with a hardening agent, but there was a limit to the range in which it could be bent due to its solidification, and problems arose such as increased weight due to resin impregnation and increased costs due to the complicated manufacturing process and low productivity. In addition, in Patent Document 2, it was found that because the carbon fiber bundle was originally untwisted and then twisted afterward, slack occurred in the single fibers inside the carbon fiber bundle, and stress transmission between the single fibers inside the carbon fiber bundle decreased, making it difficult to improve tensile strength without resin impregnation. In Patent Document 3, when the power transmission line was bent to a bending radius above the critical bending radius, it cracked and released a coloring agent to the outside, making it possible to quickly detect internal damage to the outside, but it was not possible to suppress the internal damage itself when it was bent.

[0006] Therefore, the present invention aims to provide a carbon fiber rope with excellent tensile strength and handling properties, an infrastructure material using the carbon fiber rope, and a carbon fiber bundle for ropes.

[0007] As a result of diligent research, the inventors of the present invention have found that the above problem can be solved by keeping the fluctuation range of a specific fiber axis in a carbon fiber bundle within a certain range, and have completed the present invention described below.

[0008] In other words, the present invention provides the following (1) to (13): (1) A carbon fiber rope in which two or more carbon fiber bundles are twisted together, and the fluctuation width of the fiber axis when a single fiber of the carbon fiber bundle is observed from the side at a straight-line distance of 1 mm is 1.5 μm or more and 10 μm or less. (2) The carbon fiber rope according to (1), wherein the twist angle of the surface layer of the carbon fiber bundle is 1.5° or more and 7.5° or less. (3) The carbon fiber rope according to (1) or (2), wherein the weight percentage of carbon fibers in the carbon fiber rope is 90% by weight or more. (4) The carbon fiber rope according to any one of (1) to (3), which includes a carbon fiber bundle having 10,000 or more filaments. (5) The carbon fiber rope according to any one of (1) to (4), which includes carbon fibers having a tensile strength of 4 GPa or more and 10 GPa or less. (6) A carbon fiber rope according to any one of (1) to (5), comprising carbon fibers having a tensile modulus of 200 GPa or more and 600 GPa or less. (7) A carbon fiber rope according to any one of (1) to (6), comprising carbon fibers having a single fiber diameter of 4 μm or more and 8 μm or less. (8) A carbon fiber rope according to any one of (1) to (7), comprising a carbon fiber bundle having an average O / C ratio of the single fiber surface in the carbon fiber bundle of 0.08 or more. (9) A carbon fiber rope according to any one of (1) to (8), wherein the weight percentage of the sizing agent contained in the carbon fiber bundle in the carbon fiber rope is 0.1% by weight or more and 5.0% by weight or less. (10) A carbon fiber rope according to any one of (1) to (9), wherein the drape value of the carbon fiber bundle in the carbon fiber rope is 3 cm or more and 24 cm or less. (11) A carbon fiber rope according to any one of (1) to (10), characterized in that when the carbon fiber rope is cut to a length of 10 cm and divided in the direction of the fiber axis, the carbon fiber bundles and the carbon fiber bundles and components other than the carbon fiber bundles can be physically separated. (12) An infrastructure material using the carbon fiber rope according to any one of (1) to (11). (13) A carbon fiber bundle for ropes, wherein the fluctuation width of the fiber axis when a single fiber of the carbon fiber bundle is observed from the side at a straight-line distance of 1 mm is 1.5 μm or more and 10 μm or less.

[0009] According to the present invention, it is possible to provide a carbon fiber rope with excellent tensile strength and handling properties, an infrastructure material using the carbon fiber rope, and a carbon fiber bundle for ropes.

[0010] This is a schematic diagram illustrating a method for evaluating the fluctuation range of the fiber axis. This is a schematic diagram illustrating a method for evaluating the drape value of a carbon fiber bundle.

[0011] The embodiments for carrying out the present invention will be described below. In this specification, the term "carbon fiber" is used as a general term for carbon fiber bundles and carbon fiber single fibers (hereinafter, carbon fiber single fibers may also be simply referred to as "single fibers"). A carbon fiber bundle refers to a bundle of multiple carbon fiber single fibers. In this specification, the term "carbon fiber rope" is used as a general term for structures in which two or more carbon fiber bundles are twisted together in a single or multi-layer structure. Furthermore, the upper and lower limits of the numerical ranges described below can be combined arbitrarily. In addition, the equipment or software used to measure the above items is not limited to the specific equipment or software described in the examples below, and equipment that can obtain equivalent accuracy may be used.

[0012] <Carbon Fiber Bundles for Rope> The carbon fiber bundles for rope of the present invention are characterized in that the fluctuation width of the fiber axis when a single fiber is observed from the side at a straight-line distance of 1 mm is 1.5 μm or more and 10 μm or less. Setting the fluctuation width of the fiber axis to 1.5 μm or more improves stress transmission between single fibers within the carbon fiber bundle, and improves the tensile strength when used for rope applications, even when there is no resin impregnation, or when there is resin impregnation but the amount of resin is very small. Setting the fluctuation width of the fiber axis to 10 μm or less maintains the straightness of the single fiber within an appropriate range, and improves the tensile strength when used for rope applications. From these viewpoints, the fluctuation width of the fiber axis is preferably 1.8 μm or more, more preferably 2.0 μm or more, preferably 8.0 μm or less, more preferably 6.0 μm or less, and even more preferably 5.0 μm or less.

[0013] Here, the fluctuation width of the fiber axis is defined as follows, as shown in Figure 1: an arbitrary point on the fiber axis of an observed single fiber is designated as point A, and a point on the fiber axis located 1 mm away in a straight line from point A is designated as point B. When point A is the origin in the XY coordinate system, i.e., the point where X = 0 μm and Y = 0 μm, and point B is a point on the X axis, i.e., X = 1,000 μm and Y = 0 μm, the maximum value of the Y coordinate that the fiber axis passes through is Y = 0 μm. ｍａｘ (μm) to minimum value Y ｍｉｎ It is defined as the residual ΔY (μm) obtained by subtracting (μm). The fluctuation width of the fiber axis in this invention is measured by the method described in the examples.

[0014] Furthermore, the degree of fluctuation in the fiber axis can be controlled by imparting bends to the fiber bundles during the flame-retardant treatment process, the pre-carbonization treatment process, and the carbonization treatment process. Known methods for imparting bends include twisting the fiber bundles or braiding the fiber bundles together in a three-strand or four-strand braiding manner. From an industrial standpoint, employing a twist method that can be handled with simple equipment is particularly preferable.

[0015] The carbon fiber bundle for ropes of the present invention can be manufactured from known raw materials, but the use of a polyacrylonitrile-based carbon fiber precursor bundle is preferable from the viewpoint of mechanical property development. The polyacrylonitrile-based carbon fiber precursor bundle can be manufactured by known methods. After flame-retardant treatment of such a polyacrylonitrile-based carbon fiber precursor bundle, the carbon fiber bundle for ropes of the present invention can be obtained by performing a pre-carbonization treatment, a carbonization treatment, and a surface treatment. Note that each of these treatment steps may also be referred to as the flame-retardant treatment step, the pre-carbonization step, the carbonization step, and the surface treatment step.

[0016] In the flame-retardant process, it is preferable to heat-treat the polyacrylonitrile carbon fiber precursor fiber bundles at 200 to 300°C in an oxygen-containing atmosphere. In the pre-carbonization process, which pre-carbonizes the fiber bundles obtained in the flame-retardant process, it is preferable to heat-treat the obtained flame-retardant fiber bundles at a maximum temperature of 500 to 1,000°C in an inert atmosphere. If the maximum temperature of the pre-carbonization process is 500°C or higher, the pre-carbonized fiber bundles can be carbonized in the subsequent carbonization process without breaking due to thermal decomposition. There is no particular upper limit to the maximum temperature of the pre-carbonization process, but it is preferable to keep it below 1,000°C for functional separation from the subsequent carbonization process.

[0017] In the carbonization step of carbonizing the pre-carbonized fiber bundles, it is preferable to heat-treat the obtained pre-carbonized fiber bundles in an inert atmosphere at a maximum temperature of 1,000 to 3,000°C. From the viewpoint of increasing the elastic modulus of the resulting carbon fibers, a higher maximum temperature in the carbonization step is preferable, but from the viewpoint of maintaining the strength of the resulting carbon fibers, it is preferable to keep it below a certain temperature. For the above reasons, it is more preferable that the maximum temperature in the carbonization step be 1,200 to 2,500°C, and even more preferable that be 1,400 to 2,000°C.

[0018] It is preferable to impart twist to the precursor fiber bundle during the flame-retardant treatment process. To add twist to the fiber bundle, the desired number of twists can be added by first winding the precursor fiber bundle onto a bobbin and then rotating the bobbin in a plane perpendicular to the winding direction when unwinding the fiber bundle, or by bringing a rotating roller or belt into contact with the fiber bundle while it is moving without winding it onto a bobbin.

[0019] In the surface treatment step for imparting oxygen functional groups to the carbon fibers obtained in the carbonization step, liquid-phase electrolytic oxidation is preferable from the viewpoint of high productivity and uniform treatment. In the present invention, there are no particular restrictions on the conditions for liquid-phase electrolytic oxidation, and it can be carried out by known methods.

[0020] Examples of electrolytes used in liquid-phase electrolytic oxidation include acidic electrolytes and alkaline electrolytes. Examples of acidic electrolytes include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, boric acid, and carbonic acid; organic acids such as acetic acid, butyric acid, oxalic acid, acrylic acid, and maleic acid; or salts such as ammonium sulfate and ammonium bisulfate. Examples of alkaline electrolytes include aqueous solutions of hydroxides such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, and barium hydroxide; aqueous solutions of carbonates such as sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, barium carbonate, and ammonium carbonate; aqueous solutions of bicarbonates such as sodium bicarbonate, potassium bicarbonate, magnesium bicarbonate, calcium bicarbonate, barium bicarbonate, and ammonium bicarbonate; and aqueous solutions of ammonia, tetraalkylammonium hydroxide, and hydrazine.

[0021] Furthermore, a sizing agent may be applied to the carbon fibers after liquid-phase electrolytic oxidation. The sizing agent can be appropriately selected within the range in which the effects of the present invention are exhibited, and the amount of application may be appropriately adjusted from the viewpoint of handling and higher processability. The sizing agent can be applied by known methods, and can be arbitrarily selected from the dip method, spray coating method, roll coating method, etc. From the viewpoint of uniform adhesion, the dip method is preferable. When applying the sizing agent, it is preferable to use a sizing agent-containing solution obtained by diluting the sizing agent component with a solvent. Examples of solvents include water, methanol, ethanol, isopropanol, acetone, methyl ethyl ketone, dimethylformamide, and dimethylacetamide, but among these, an aqueous solution or an aqueous dispersion emulsified with a surfactant is preferably used because it is easy to handle and advantageous from the viewpoint of safety. Furthermore, after applying the sizing agent-containing solution to the carbon fibers, it is preferable to evaporate the solvent and dry it. Examples of heating methods include heating rollers, heated air, microwave irradiation, infrared irradiation, etc.

[0022] <Carbon Fiber Rope> The carbon fiber rope of the present invention is a carbon fiber rope in which two or more carbon fiber bundles are twisted together, and the fluctuation width of the fiber axis when a single fiber of the carbon fiber bundle is observed from the side within a straight-line distance of 1 mm is 1.5 μm or more and 10 μm or less. By twisting together two or more carbon fiber bundles in which the fluctuation width of the fiber axis when a single fiber of the carbon fiber bundle is observed from the side within a straight-line distance of 1 mm is 1.5 μm or more and 10 μm or less, stress transmission between the carbon fiber bundles can be improved and the tensile strength of the carbon fiber rope can be stabilized. In addition, the handling can be improved by integrating the carbon fiber bundles with each other.

[0023] In this specification, "tensile strength of carbon fibers," as an indicator of carbon fiber quality, is measured in accordance with the resin-impregnated strand test method of JIS R7608 (2007). In this measurement, resin is impregnated into the carbon fiber bundle, allowing for the evaluation of the inherent strength of individual fibers.

[0024] On the other hand, the carbon fiber rope of the present invention is intended to be used without resin impregnation, or with a very small amount of resin impregnation. The preferred weight ratio of carbon fibers in the carbon fiber rope in this case will be described later. To evaluate the practical tensile strength in such applications, it is appropriate to use the "bundle strength of carbon fiber bundles" measured without resin impregnation. The bundle strength of carbon fiber bundles is measured by the method described in the examples. Although there is a difference between the tensile strength of carbon fibers and the bundle strength of carbon fiber bundles depending on whether or not resin impregnation is performed, the present invention achieves high bundle strength by controlling the fluctuation width of the fiber axis.

[0025] The carbon fiber rope of the present invention has a structure in which two or more carbon fiber bundles are twisted together. The number of carbon fiber bundles twisted together can be appropriately selected depending on the application, but from the viewpoint of obtaining a good balance of tensile strength and flexibility, three or more are preferred, and five or more are more preferred. Furthermore, there is no particular upper limit to the number of carbon fiber bundles twisted together, but from the viewpoint of handling and manufacturing efficiency, 1000 or fewer is preferred.

[0026] Methods of twisting include single-twist structures, where multiple carbon fiber bundles are twisted in one direction, and multi-twist structures, where multiple carbon fiber bundles are twisted together and then further twisted. Single-twist structures are easy to manufacture, while multi-twist structures tend to yield high tensile strength.

[0027] In the carbon fiber rope of the present invention, the twist angle of the surface layer of the carbon fiber bundle is preferably 1.5° or more and 7.5° or less. Setting the twist angle to 1.5° or more improves stress transmission between individual fibers within the carbon fiber bundle, making it easier to improve the tensile strength of the carbon fiber rope even when there is no resin impregnation, or when the amount of resin impregnation is very small. Furthermore, setting the twist angle of the surface layer of the carbon fiber bundle to 7.5° or less makes it easier to take advantage of the high tensile strength of the individual fibers within the carbon fiber bundle, making it easier to improve the tensile strength of the carbon fiber rope. From these viewpoints, a twist angle of 1.8° or more is more preferable, 2.0° or more is even more preferable, 6.5° or less is even more preferable, and 5.5° or less is even more preferable. Here, the twist angle of the surface layer of the carbon fiber bundle can be calculated from the number of twists, the number of filaments in the carbon fiber bundle, and the diameter of the individual fibers. The twist angle of the surface layer of the carbon fiber bundle in the present invention is measured by the method described in the examples.

[0028] Regarding the method for setting the twist angle of the surface layer of the carbon fiber bundle to 1.5° or more and 7.5° or less, there are, for example, a method of later imparting twist to the carbon fiber bundle and a method of imparting twist to the precursor fiber bundle during the flame-retardant treatment process. The latter method is more preferable. By imparting twist during the flame-retardant treatment process, it becomes easier to maintain the twisted form without impregnating with resin or covering the carbon fiber bundle with a coating material, thus improving the handlingability of the carbon fiber rope. Furthermore, by imparting twist during the flame-retardant treatment process, slack in the single fibers inside the carbon fiber bundle in the twisted state is suppressed, further improving stress transmission between single fibers within the carbon fiber bundle, and making it easier to improve the tensile strength of the carbon fiber rope even when there is no resin impregnation, or when the amount of resin impregnation is very small.

[0029] In the carbon fiber rope of the present invention, it is preferable that the weight percentage of carbon fibers in the carbon fiber rope is 90% by weight or more. By setting the weight percentage of carbon fibers in the carbon fiber rope to 90% by weight or more, the flexibility of the carbon fiber rope can be easily improved, and the handling can be easily improved. It is more preferable that the weight percentage of carbon fibers be 95% by weight or more, and even more preferable that be 98% by weight or more. Furthermore, there is no particular upper limit to the weight percentage of carbon fibers in the carbon fiber rope, but for example, it is 100% or less or less than 100%.

[0030] The carbon fiber rope of the present invention preferably includes a carbon fiber bundle having 10,000 or more filaments. By having 10,000 or more filaments in the carbon fiber bundle, the twist angle can be efficiently increased even with a small number of twists, which makes it easier to improve stress transfer between individual fibers within the carbon fiber bundle and thus easier to improve the tensile strength of the carbon fiber rope. The number of filaments is more preferably 15,000 or more, and even more preferably 20,000 or more. Furthermore, the upper limit of the above number of filaments is not particularly limited, but for example, it is 100,000 or less, more preferably 50,000 or less.

[0031] The carbon fiber rope of the present invention preferably contains carbon fibers having a tensile strength of 4 GPa or more and 10 GPa or less. Setting the tensile strength of the carbon fibers to 4 GPa or more makes it easier to improve the tensile strength of the carbon fiber rope. Setting the tensile strength of the carbon fibers to 10 GPa or less makes it easier to utilize as a carbon fiber rope. From these viewpoints, a tensile strength of 5 GPa or more is more preferable, 6 GPa or more is even more preferable, 8 GPa or less is even more preferable, and 7 GPa or less is even more preferable.

[0032] Here, when determining the tensile strength of carbon fibers contained in a carbon fiber rope, the carbon fiber rope is cut to the length required for the strand tensile test, and the carbon fiber bundle is extracted before evaluation. If the carbon fiber rope is coated with resin or coating yarn, the resin or coating yarn is removed by methods such as physical separation, dissolution with a solvent, or burning off at high temperature under a nitrogen atmosphere before the carbon fiber bundle is extracted. The tensile strength of the carbon fibers in this invention is measured by the method described in the examples. However, the composition in the resin formulation may be an epoxy resin / boron trifluoride monoethylamine / acetone = 100 / 3 / 4 (parts by weight) containing 97% by weight or more of (3',4'-epoxycyclohexane)methyl-3,4-epoxycyclohexylcarboxylate, with an epoxy equivalent of 130 g / eq and a viscosity of 240 mPa·s at 25°C.

[0033] The carbon fiber rope of the present invention preferably contains carbon fibers having a tensile modulus of 200 GPa or more and 600 GPa or less. Setting the tensile modulus of the carbon fibers to 200 GPa or more makes it possible to obtain a carbon fiber rope with rigidity similar to that of a steel wire rope. Furthermore, setting the tensile modulus of the carbon fibers to 600 GPa or less makes it easier to maintain the tensile strength of the carbon fibers, thus maintaining the tensile strength of the carbon fiber rope. From these viewpoints, a tensile modulus of 250 GPa or more is more preferable, 300 GPa or more is even more preferable, 500 GPa or less is even more preferable, and 400 GPa or less is even more preferable.

[0034] When determining the tensile modulus of carbon fibers contained in a carbon fiber rope, the carbon fiber rope is cut to the length required for the strand tensile test, and the carbon fiber bundles are extracted before evaluation. Furthermore, if the carbon fiber rope is coated with resin or coating threads, the resin or coating threads are removed by methods such as physical separation, dissolution with a solvent, or burning off at high temperatures under a nitrogen atmosphere before the carbon fiber bundles are extracted. The tensile modulus of carbon fibers in this invention is measured by the method described in the examples. However, the composition in the resin formulation may be any composition with respect to the tensile strength of the carbon fibers as described above.

[0035] The carbon fiber rope of the present invention preferably contains carbon fibers with a single filament diameter of 4 μm or more and 8 μm or less. A single filament diameter of 4 μm or more makes it easier to increase the twist angle, thereby improving the tensile strength of the carbon fiber rope. Furthermore, a single filament diameter of 8 μm or less makes it easier to maintain the tensile strength of the carbon fibers. From these viewpoints, a single filament diameter of 4.5 μm or more is more preferable, 5 μm or more is even more preferable, 7.5 μm or less is even more preferable, and 7 μm or less is even more preferable. The single filament diameter of the carbon fibers in the present invention is measured by the method described in the examples.

[0036] The carbon fiber rope of the present invention preferably contains a carbon fiber bundle in which the average O / C of the surface of a single fiber in the carbon fiber bundle is 0.08 or higher. Setting the O / C to 0.08 or higher increases the amount of oxygen functional groups on the substrate surface compared to general carbon fibers, strengthening the interaction between single fibers within the carbon fiber bundle, improving stress transmission, and making it easier to improve the tensile strength when used for rope applications. An O / C of 0.10 or higher is more preferable, and 0.12 or higher is even more preferable. Furthermore, an average O / C of the surface of a single fiber is preferably 0.30 or lower, and even more preferably 0.20 or lower. Excessive application of oxygen functional groups in the surface treatment process may reduce the tensile strength of the carbon fiber, but setting the O / C to 0.30 or lower makes it easier to suppress the reduction in carbon fiber strength. Known methods for increasing the average O / C of the surface of a single fiber include lowering the temperature of the carbonization process, applying a high voltage in the electrolyte, or using sulfuric acid as the electrolyte.

[0037] The average single fiber surface in a carbon fiber bundle refers to the substrate surface of a single fiber in a carbon fiber bundle when no sizing agents or dirt are attached. Here, O / C is an index representing the surface oxygen concentration (atomic ratio) of the carbon fiber, and is measured by X-ray photoelectron spectroscopy (ESCA). In this invention, the O / C of the average single fiber surface in a carbon fiber bundle is measured by the method described in the examples.

[0038] Also, hereinafter, the O / C of the average single fiber surface in the carbon fiber bundle may sometimes be simply referred to as O / C. When measuring the O / C of the average single fiber surface in the carbon fiber bundle, the carbon fiber bundle is washed with acetone to remove the dirt adhering to the surface, and then the measurement is carried out. Also, when a sizing agent is adhered to the carbon fiber bundle, the sizing agent is removed by repeating washing with acetone or a solvent suitable for the corresponding sizing agent, and then the measurement is carried out. Generally, since the surface of carbon fiber has low activity, the O / C is increased by imparting oxygen functional groups in the surface treatment process.

[0039] In the carbon fiber rope of the present invention, the weight ratio of the sizing agent contained in the carbon fiber bundle in the carbon fiber rope is preferably 0.1% by weight or more and 5.0% by weight or less. By setting the weight ratio of the sizing agent to 0.1% by weight or more, it becomes easier to improve the convergence property of the carbon fiber bundle, so it becomes easier to suppress the separation of the single fibers in the carbon fiber bundle even when a strong external force is applied, and it becomes easier to improve the handling property. Also, it becomes easier to reflect the high tensile strength and tensile elastic modulus of the carbon fiber in the physical properties of the carbon fiber rope. The weight ratio of the sizing agent is more preferably 0.5% by weight or more, and further preferably 1.0% by weight or more. On the other hand, by setting the weight ratio of the sizing agent to 5.0% by weight or less, the flexibility of the carbon fiber bundle is more easily improved, so the degree of freedom when bending the carbon fiber rope increases, and it becomes easier to improve the workability. The weight ratio of the sizing agent is more preferably 4.0% by weight or less, and further preferably 3.0% by weight or less. The weight ratio of the sizing agent in the present invention is measured by the method described in the examples.

[0040] In the carbon fiber rope of the present invention, the drape value of the carbon fiber bundle in the carbon fiber rope is preferably 3 cm or more and 24 cm or less. The drape value is a value that represents the stiffness of the carbon fiber bundle, and the larger the drape value, the stiffer the carbon fiber bundle is. Note that if the carbon fiber bundle is extremely stiff, it may not be possible to measure the drape value. Setting the drape value to 3 cm or more makes it easier to improve the convergence of the carbon fiber bundle, making it easier to suppress the unraveling of the single fibers in the carbon fiber bundle even when a strong external force is applied, improving handling, and making it easier to reflect the high tensile strength and tensile modulus of carbon fibers in the physical properties of the carbon fiber rope. A drape value of 5 cm or more is more preferable, and 7 cm or more is even more preferable. On the other hand, setting the drape value to 24 cm or less improves the flexibility of the carbon fiber bundle, increasing the degree of freedom when bending the carbon fiber rope and improving workability. A drape value of 23 cm or less is more preferable, and 22 cm or less is even more preferable. When evaluating the drape value of carbon fiber bundles in a carbon fiber rope, the carbon fiber rope is cut to the length required for drape value evaluation, and the carbon fiber bundles are extracted before evaluation. If the carbon fiber rope is coated with resin or coating threads, the resin or coating threads are physically removed before extracting the carbon fiber bundles. The drape value of the carbon fiber bundles in this invention is measured by the method described in the examples.

[0041] Factors that affect the drape value of a carbon fiber bundle include the type and weight ratio of sizing agents contained in the carbon fiber bundle. However, from the perspective of controlling the drape value of a carbon fiber bundle, it is preferable to control it by the type and weight ratio of sizing agents due to the simplicity of the process and ease of control.

[0042] Regarding the type of sizing agent, in order to control the drape value of the carbon fiber bundle to a lower level, a sizing agent with high flexibility and / or low reactivity can be used. As the sizing agent with high flexibility and / or low reactivity, for example, a sizing agent containing polyethylene glycol and / or a surfactant can be used. Also, in order to control the drape value of the carbon fiber bundle to a higher level, a sizing agent with low flexibility and / or high reactivity can be used. As the sizing agent with low flexibility and / or high reactivity, for example, a sizing agent containing an epoxy resin or a vinyl ester resin can be used.

[0043] Regarding the weight ratio of the sizing agent, reducing the weight ratio of the sizing agent makes it easier to control the drape value of the carbon fiber bundle to a lower level, and increasing the weight ratio of the sizing agent makes it easier to control the drape value of the carbon fiber bundle to a higher level.

[0044] The carbon fiber rope of the present invention is preferably such that when the carbon fiber rope is cut out to a length of 10 cm and split into two in the fiber axis direction, the carbon fiber bundles and the components other than the carbon fiber bundles can be physically separated from each other. When the carbon fiber rope is cut out to a length of 10 cm and split into two in the fiber axis direction, if the carbon fiber bundles and the components other than the carbon fiber bundles can be physically separated from each other, the carbon fiber bundles are not overly constrained, so it is easy to increase the flexibility as a carbon fiber rope and improve the handleability. Here, "being able to physically separate the carbon fiber bundles and the components other than the carbon fiber bundles" means that the components other than the carbon fiber bundles contained in the carbon fiber rope can be separated from the carbon fiber bundles without using chemical separation methods such as burning off or dissolving in a solvent.

[0045] <Infrastructure Material Using Carbon Fiber Rope> The infrastructure material using carbon fiber rope of the present invention is preferably an earthquake-resistant reinforcement material. By including the carbon fiber rope of the present invention, high levels of tensile strength, tensile modulus, and handling can be achieved, thus reducing the amount used as an earthquake-resistant reinforcement material, thereby minimizing the impact on the appearance, and making it easier to reinforce according to the target of reinforcement. Furthermore, because handling is improved, the winding diameter of the earthquake-resistant reinforcement material can be reduced to improve ease of transportation, and it is easier to unwind it more quickly during installation. In the earthquake-resistant reinforcement material of the present invention, only a joining member between the carbon fiber rope of the present invention and the target of reinforcement may be included, or a small amount of material such as a covering material may be included.

[0046] The infrastructure material using the carbon fiber rope of the present invention is preferably an electric wire cable. By including the carbon fiber rope of the present invention, high levels of tensile strength, tensile modulus, and handling can be achieved. Therefore, by using the carbon fiber rope as the core wire, it becomes possible to support more conductive wires than before without changing the thickness of the core wire, making it easier to increase the power transmission capacity. In addition, because handling is improved, the winding diameter of the electric wire cable can be reduced to improve ease of transportation, and unwinding during installation can be done more quickly. The electric wire cable of the present invention may include only the core wire containing the carbon fiber rope of the present invention and conductive wires, or it may include components such as a covering material.

[0047] The infrastructure material using the carbon fiber rope of the present invention is preferably a bridge cable. By including the carbon fiber rope of the present invention, high levels of tensile strength, tensile modulus, and handling can be achieved, making it easier to support large main girders without changing the number of bridge cables. Furthermore, because handling is improved, it is possible to reduce the winding diameter of the bridge cable to improve ease of transportation and to unwind it more quickly during installation. In the bridge cable of the present invention, only the connecting members between the carbon fiber rope of the present invention and the main girders or towers may be included, or small amounts of members such as covering materials may be included.

[0048] The infrastructure material using the carbon fiber rope of the present invention is preferably a mooring rope. By including the carbon fiber rope of the present invention, high levels of tensile strength, tensile modulus, and handling can be achieved, making it easier to secure large floating objects without increasing the thickness or number of mooring ropes. Furthermore, the improved handling makes it easier to transport the mooring rope by reducing its winding diameter, and also makes it easier to unwind it more quickly during installation. The mooring rope of the present invention may contain only the carbon fiber rope of the present invention, or it may contain a small amount of other components such as a covering material.

[0049] The infrastructure material using the carbon fiber rope of the present invention is preferably a tensioning material for civil engineering and construction. By including the carbon fiber rope of the present invention, high levels of tensile strength, tensile modulus, and handling are achieved, which suppresses the strain range required when applying tension with a jack, thus increasing the degree of freedom during construction. Furthermore, because handling is improved, the winding diameter of the tensioning material for civil engineering and construction can be reduced to improve ease of transportation, and unwinding during installation can be performed more quickly. The tensioning material for civil engineering and construction of the present invention may contain only the carbon fiber rope of the present invention, or it may contain a small amount of other components such as a covering material.

[0050] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these examples.

[0051] The measurement and evaluation methods for each physical property are as follows.

[0052] <Average value of the fluctuation range of the fiber axis of a single fiber> A single carbon fiber to be measured is 1 to 5 mm in length and placed on a sheet of copy paper on a horizontal table. If the single fiber sticks to the copy paper due to static electricity, the static electricity should be removed using a general method. The paper surface is observed from the vertical direction using an optical microscope and an image is acquired. The magnification of the optical microscope's objective lens is set to 10x. The image is saved in jpg format with a width of 2,592 pixels and a height of 1,944 pixels. At this time, the imaging range is set so that when an image of a scale of 1,000 μm in actual size is taken, the scale corresponds to 2,320 to 2,340 pixels. The acquired image is loaded into the open-source image processing software "ImageJ," and an arbitrary point on the fiber axis is designated as point A, and a point on the fiber axis 1,000 μm away from point A is designated as point B. Next, "Binear Interpolation" is selected as the interpolation algorithm for rotation, and the image is rotated so that points A and B are horizontal. After binarization, skeletonization is performed to extract the fiber axis as a curve with a width of 1 pixel. At this time, if dust or other debris is attached to the fiber surface, the fiber axis may branch, but side chains other than the fiber axis are ignored. When point A is the origin in the XY coordinate system, i.e., the point where X = 0 μm, Y = 0 μm, and point B is a point on the X axis, i.e., X = 1,000 μm, Y = 0 μm, the residual ΔY (μm) obtained by subtracting the minimum value Ymin from the maximum value Ymax of the Y coordinate through which the fiber axis passes between points A and B is read, and this is taken as the fluctuation width of the measured single fiber. The fluctuation widths measured for 10 different single fibers are averaged and adopted as the average value of the fluctuation width in this invention. In this embodiment, a Leica Microsystems DM2700M upright microscope was used as the optical microscope.

[0053] <Single Fiber Diameter of Carbon Fibers> The single carbon fiber is evaluated by observing it with a scanning electron microscope (SEM). Fifty single fibers are evaluated, and the average diameter of these single fibers is defined as the single fiber diameter. In this example, observation was performed using the SEM "S-4800" manufactured by Hitachi High-Technologies Corporation.

[0054] <Twist Angle of the Surface Layer of Carbon Fiber Bundles> After calculating the overall diameter of the fiber bundle (μm) from the single filament diameter (μm) and number of filaments of the carbon fiber using the following formula, the remaining twist angle (°) of the surface layer of the fiber bundle is calculated using the twist count (turns / m) and the following formula. Overall diameter of fiber bundle (μm) = {(single filament diameter of carbon fiber)} ２ × Number of filaments ０．５ The remaining twist angle (°) on the surface of the fiber bundle = atan(total diameter of the fiber bundle × 10) －６ (xπ x number of strands).

[0055] <Weight percentage of carbon fibers in carbon fiber rope> After measuring the weight of a carbon fiber rope cut to a desired size, the rope is placed in an electric furnace with a nitrogen atmosphere set to a temperature of 450°C to burn off components other than carbon fibers, and the weight of the resulting carbon fibers is measured to determine the weight percentage of carbon fibers.

[0056] <Weight percentage of sizing agent contained in carbon fiber bundles in carbon fiber ropes> For carbon fiber bundles used in carbon fiber ropes, the bundles were cut to an arbitrary length and weighed (W1). Then, they were placed in an electric furnace with a nitrogen atmosphere set to a temperature of 450°C to thermally decompose the sizing agent. The resulting carbon fiber bundles were weighed (W2), and the weight loss due to heating was calculated by subtracting W2 from W1. This weight loss due to heating was converted to a weight percentage in the carbon fiber bundle and defined as the weight percentage (weight%) of the sizing agent contained in the carbon fiber bundle.

[0057] <Tensile Strength and Tensile Modulus of Carbon Fibers> The tensile strength and tensile modulus of carbon fibers are determined in accordance with the resin-impregnated strand test method of JIS R7608 (2007), following the procedure below. However, if the carbon fiber bundle has twists, the twists are removed by applying the same number of reverse twists as the number of twists before evaluation. The resin formulation used is "Celoxide (registered trademark)" 2021P (manufactured by Daicel Corporation) / boron trifluoride monoethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) / acetone = 100 / 3 / 4 (parts by weight), and the curing conditions are atmospheric pressure, temperature 125°C, and time 30 minutes. Ten strands of the carbon fiber bundle were measured, and the average values ​​were taken as the tensile strength and tensile modulus, respectively. The strain range when calculating the tensile modulus was set to 0.1 to 0.6%.

[0058] <O / C of the average single fiber surface in the carbon fiber bundle>In this example, the O / C of the average single fiber surface in the carbon fiber bundle was measured by X-ray photoelectron spectroscopy according to the following procedure. First, the carbon fiber bundle was washed with acetone to remove dirt and sizing agent adhering to the surface. Subsequently, the carbon fiber was cut into 20 mm lengths, evenly spread and arranged on a copper sample support base to a thickness of 10 - 20 μm, and then AlKα １、２ was used as the X-ray source, the inside of the sample chamber was maintained at 1×10 －８ Torr, and X-ray photoelectron spectroscopy measurement was performed with the photoelectron escape angle set at 45°. The measurement locations were randomly selected at 20 points from the spread carbon fibers for measurement. In addition, as the correction value for the peak associated with charging during measurement, the binding energy value of the main peak of C １Ｓ was adjusted to 285 eV. The C １Ｓ peak area was obtained by drawing a straight baseline in the range of binding energy values from 275 to 290 eV. The O １Ｓ peak area was obtained by drawing a straight baseline in the range of binding energy from 525 to 540 eV. Here, O / C can be calculated as an atomic ratio using the sensitivity correction value specific to the apparatus from the ratio of the above O １Ｓ peak area and C １Ｓ peak area. The O / C of the average single fiber surface in the carbon fiber bundle was obtained by calculating the average value of O / C at the above 20 locations. In this example, ESCA-1600 manufactured by ULVAC-PHI, Inc. was used as the X-ray photoelectron spectroscopy apparatus.

[0059] <Bundle strength of the carbon fiber bundle>The bundle strength of the carbon fiber bundle was measured using a Tensilon universal material testing machine RTC-1210A (manufactured by A&D Company, Limited) with a chuck distance of 500 mm, a crosshead speed of 100 mm / min, and a sample number n = 10.

[0060] <Drape Value of Carbon Fiber Bundles in Carbon Fiber Rope> For carbon fiber bundles used in carbon fiber rope, after cutting them to a length of 30 cm, in an atmosphere of 25°C, the carbon fiber bundles 2 are placed on a rectangular horizontal stand 3 with 90° corners, as shown in Figure 2, with 25 cm of the bundle extending beyond the stand, while being supported to prevent bending. The carbon fiber bundles 2 on the horizontal stand 3 are then secured with tape. After that, the support for the carbon fiber bundles 2 extending beyond the horizontal stand 3 is removed and they hang down. After 1 second, the horizontal distance L (cm) from the support point is measured, and the average value of n (5 measurements) is taken as the drape value. A larger drape value indicates that the carbon fiber bundle has a stiffer characteristic.

[0061] <Handling of Carbon Fiber Rope> After obtaining a carbon rope by twisting together seven carbon fiber bundles, or by impregnating and curing resin after twisting together seven carbon fiber bundles, the handling was evaluated according to the following criteria. S: The convergence of the carbon fiber bundles is very high, making it very easy to twist the carbon fibers together to produce a carbon fiber rope. The carbon fiber bundles contained in the carbon fiber rope do not break even when winding the carbon fiber rope onto a 10 cm diameter bobbin or bending it freely like a string game. A: It is easy to twist the carbon fibers together to produce a carbon fiber rope. The carbon fiber bundles contained in the carbon fiber rope do not break even when winding the carbon fiber rope onto a 10 cm diameter bobbin or bending it freely like a string game. B: When producing a carbon fiber rope, the convergence of the carbon fiber bundles is low and it is difficult to twist them together. However, the carbon fiber bundles contained in the carbon fiber rope do not break even when winding the carbon fiber rope onto a 10 cm diameter bobbin or bending it freely like a string game. C: The carbon fiber rope cannot be wound onto a 10 cm diameter bobbin or bent freely like a string game, and the carbon fiber bundles contained in the carbon fiber rope break.

[0062] <Sizing Agents> The sizing agents used in each example are as follows: Sizing agent D-1: Polyethylene glycol (PEG600, HLB: 20, molecular weight: 600, manufactured by Sanyo Chemical Industries, Ltd.) Sizing agent D-2: Bisphenol A epoxy ("jER®" 828, manufactured by Mitsubishi Chemical Corporation) (Example 1) Polyacrylonitrile carbon fiber precursor fiber bundles with a single fiber fineness of 0.8 dtex obtained by a known method were bonded together to obtain 12,000 single fibers, twisted at 21 turns / m, and heat-treated in an oven at 230-280°C in an air atmosphere to convert them into flame-resistant fiber bundles. Next, the obtained flame-resistant fiber bundles were subjected to a twisting treatment and a pre-carbonization treatment was performed in a nitrogen atmosphere at a temperature of 300-800°C to obtain pre-carbonized fiber bundles. Next, the preliminary carbonized fiber bundles were subjected to a carbonization treatment at the maximum carbonization temperature of 1400°C and a draw ratio of 0.96 as shown in Table 1. Then, an electrolytic surface treatment was performed using an aqueous sulfuric acid solution as the electrolyte at an electric charge of 15 C / g, followed by washing with water and drying in heated air to obtain carbon fiber bundles. Furthermore, a carbon fiber rope was fabricated by twisting together seven of the obtained carbon fiber bundles. The evaluation results of the carbon fiber bundles and carbon fiber rope are shown in Tables 1 and 2, confirming that the carbon fiber rope exhibits excellent tensile strength, handling properties, and tensile modulus.

[0063] (Example 2) The procedure was carried out in the same manner as in Example 1, except that the amount of electricity used when performing the electrolytic surface treatment was changed as shown in Table 1. As shown in Tables 1 and 2, it was confirmed that the carbon fiber rope had excellent tensile strength, handling properties, and tensile modulus.

[0064] (Example 3) The procedure was carried out in the same manner as in Example 2, except that the number of twists in the precursor fiber bundle was changed as shown in Table 1. As shown in Tables 1 and 2, it was confirmed that the carbon fiber rope had excellent tensile strength, handling properties, and tensile modulus.

[0065] (Example 4) The procedure was carried out in the same manner as in Example 2, except that the number of single fibers, the number of twists in the precursor fiber bundle, the maximum carbonization temperature, and the stretch ratio were changed as shown in Table 1 when splicing the polyacrylonitrile carbon fiber precursor fiber bundles. As shown in Tables 1 and 2, it was confirmed that the carbon fiber rope had excellent tensile strength, handling properties, and tensile modulus.

[0066] (Example 5) The same procedure as in Example 4 was followed, except that the single fiber fineness of the polyacrylonitrile carbon fiber precursor fiber bundle, the number of twists in the precursor fiber bundle, the maximum carbonization temperature, and the amount of electricity during electrolytic surface treatment were changed as shown in Table 1. As shown in Tables 1 and 2, it was confirmed that the carbon fiber rope had excellent tensile strength, handling properties, and tensile modulus.

[0067] Examples 6 to 14 were carried out in the same manner as in Example 1, except that the number of single fibers when splicing polyacrylonitrile carbon fiber precursor fiber bundles, the fineness of the single fibers of the polyacrylonitrile carbon fiber precursor fiber bundles, the number of twists in the precursor fiber bundles, the maximum carbonization temperature and stretching ratio, the amount of electricity during electrolytic surface treatment, and the type and content ratio of the sizing agent were changed as shown in Table 1. The results, as shown in Tables 1 and 2, confirmed that the carbon fiber rope had particularly excellent handling properties and also excellent tensile strength and tensile modulus.

[0068] (Comparative Example 1) The procedure was carried out in the same manner as in Example 1, except that the number of twists in the precursor fiber bundle and the amount of electricity during electrolytic surface treatment were changed as shown in Table 1. As shown in Tables 1 and 2, it was confirmed that the carbon fiber rope had low tensile strength and was somewhat difficult to handle.

[0069] (Comparative Example 2) Carbon fiber bundles were obtained in the same manner as in Comparative Example 1, except that the single fiber fineness and maximum carbonization temperature of the polyacrylonitrile-based carbon fiber precursor fiber bundles were changed as shown in Table 1. After that, a twist of 20 turns / m was applied and the bundle tensile evaluation was performed. Furthermore, seven strands of the obtained carbon fiber bundles, which had a twist of 20 turns / m, were twisted together, and a carbon fiber rope with shape retention was produced by impregnating and curing it with the resin used in the resin impregnation strand test method. As shown in Tables 1 and 2, it was confirmed that the carbon fiber rope had poor handling properties.

[0070] (Comparative Example 3) Using Toray Industries, Inc.'s "Torayca (registered trademark)" T700SC-12000, a bundle tensile strength evaluation was performed after applying a twist of 60 turns / m. As shown in Tables 1 and 2, although the bundle strength was improved compared to Comparative Example 1, it remained significantly lower in absolute value. Furthermore, a carbon fiber rope was produced by twisting together seven strands while maintaining the 60 turns / m twist. As shown in Tables 1 and 2, it was confirmed that the carbon fiber rope had low tensile strength and was somewhat difficult to handle.

[0071] (Comparative Example 4) Using Toray Industries, Inc.'s "Torayca (registered trademark)" T700SC-24000, a bundle tensile strength evaluation was performed after applying a twist of 30 turns / m. As shown in Tables 1 and 2, although the bundle strength was improved compared to Comparative Example 1, it remained significantly lower in absolute value. Furthermore, a carbon fiber rope was produced by twisting together seven strands while they were still twisted at 30 turns / m. As shown in Tables 1 and 2, it was confirmed that the resulting carbon fiber rope had low tensile strength and was somewhat difficult to handle.

[0072]

[0073]

[0074] 1: Single carbon fiber 2: Carbon fiber bundle 3: Horizontal stand

Claims

1. A carbon fiber rope in which two or more carbon fiber bundles are twisted together, and the fluctuation width of the fiber axis when a single fiber of the carbon fiber bundle is observed from the side within a straight-line distance of 1 mm is 1.5 μm or more and 10 μm or less.

2. The carbon fiber rope according to claim 1, wherein the twist angle of the surface layer of the carbon fiber bundle is 1.5° or more and 7.5° or less.

3. The carbon fiber rope according to claim 1 or claim 2, wherein the weight ratio of carbon fibers in the carbon fiber rope is 90% by weight or more.

4. The carbon fiber rope according to claim 1 or claim 2, comprising a carbon fiber bundle having 10,000 or more filaments.

5. A carbon fiber rope according to claim 1 or claim 2, comprising carbon fibers having a tensile strength of 4 GPa or more and 10 GPa or less.

6. A carbon fiber rope according to claim 1 or claim 2, comprising carbon fibers having a tensile modulus of 200 GPa or more and 600 GPa or less.

7. A carbon fiber rope according to claim 1 or claim 2, comprising carbon fibers having a single filament diameter of 4 μm or more and 8 μm or less.

8. The carbon fiber rope according to claim 1 or claim 2, comprising a carbon fiber bundle in which the average O / C of the surface of a single fiber in the carbon fiber bundle is 0.08 or higher.

9. The carbon fiber rope according to claim 1 or claim 2, wherein the weight percentage of the sizing agent contained in the carbon fiber bundle in the carbon fiber rope is 0.1% by weight or more and 5.0% by weight or less.

10. The carbon fiber rope according to claim 1 or claim 2, wherein the drape value of the carbon fiber bundle in the carbon fiber rope is 3 cm or more and 24 cm or less.

11. The carbon fiber rope according to claim 1 or claim 2, wherein when the carbon fiber rope is cut to a length of 10 cm and divided into two in the direction of the fiber axis, the carbon fiber bundles and the carbon fiber bundles and components other than the carbon fiber bundles can be physically separated.

12. An infrastructure material using the carbon fiber rope according to claim 1 or claim 2.

13. A carbon fiber bundle for ropes in which the fluctuation width of the fiber axis when a single fiber of the carbon fiber bundle is observed from the side within a straight-line distance of 1 mm is 1.5 μm or more and 10 μm or less.

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