Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
  • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
  • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
  • D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
  • D01F9/20—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products
  • D01F9/21—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D01F9/22—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
  • D06M13/00—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with non-macromolecular organic compounds; Such treatment combined with mechanical treatment
  • D06M13/10—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with non-macromolecular organic compounds; Such treatment combined with mechanical treatment with compounds containing oxygen
  • D06M13/11—Compounds containing epoxy groups or precursors thereof
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
  • D06M15/00—Treating fibres, threads, yarns, fabrics, or fibrous goods made from such materials, with macromolecular compounds; Such treatment combined with mechanical treatment
  • D06M15/19—Treating fibres, threads, yarns, fabrics, or fibrous goods made from such materials, with macromolecular compounds; Such treatment combined with mechanical treatment with synthetic macromolecular compounds
  • D06M15/37—Macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • D06M15/55—Epoxy resins
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
  • D06M2101/00—Chemical constitution of the fibres, threads, yarns, fabrics or fibrous goods made from such materials, to be treated
  • D06M2101/40—Fibres of carbon

Definitions

• the present invention relates to carbon fiber bundles containing a sizing agent that are suitable for use in aircraft, automobile and ship components, as well as in sports applications such as golf shafts and fishing rods, and other general industrial applications, and in particular to carbon fiber bundles, carbon fiber reinforced composite materials and pressure vessels that contain a sizing agent that provides excellent strength when made into carbon fiber reinforced composite materials.
• PAN Polyacrylonitrile (hereinafter sometimes abbreviated as "PAN”)-based carbon fibers have higher specific strength and specific modulus than other fibers, and as a reinforcing fiber for composite materials, in addition to the traditional sports and aerospace applications, they are being widely deployed in general industrial applications such as automobiles, civil engineering and construction, pressure vessels, and wind turbine blades, and there is a strong demand for even higher performance.
• PAN Polyacrylonitrile
• Increasing the mechanical properties of carbon fiber contributes to weight reduction in components such as pressure vessels, so it is important to improve mechanical properties such as tensile strength and tensile modulus. In particular, even higher strength is required for pressure vessels for automobiles.
• CFRP tanks in addition to increasing the strand tensile strength of the carbon fiber used, it is important to improve how efficiently the mechanical properties of carbon fiber can be expressed when used as a reinforcing fiber for composite materials.
• Patent documents 1 to 4 propose preventing thread breakage and improving the opening of carbon fiber bundles and resin impregnation when molding the carbon fiber reinforced composite material to improve moldability when made into a carbon fiber reinforced composite material, and improving strength development by eliminating unimpregnated and excess resin areas.
• Patent document 1 proposes a technology that achieves both abrasion resistance, thread breakage resistance, and resin impregnation by applying a sizing agent to the inner layer of the carbon fiber bundle and then blowing gas to remove the sizing agent from the outer layer of the carbon fiber bundle.
• Patent Document 2 proposes a technology that improves moldability when forming a composite material by entangling carbon fiber precursor fiber bundles to make them less susceptible to yarn breakage when opening them to form a composite material.
• Patent Document 3 proposes a technology that improves resin impregnation by narrowing the fiber diameter of each single fiber that makes up the carbon fiber bundle and forming grooves of a specific depth in the fiber axis direction on the surface of the single fiber.
• Patent Document 4 proposes a technology that improves opening during molding by flattening the shape of the carbon fiber bundle to form a homogeneous molded body.
• Patent documents 5 to 7 propose improving the mechanical properties of carbon fiber bundles.
• Patent document 5 proposes that the 0° tensile strength of carbon fiber reinforced composite materials be easily achieved by controlling the crystal structure in the carbon fibers to a preferred state through the sintering conditions in the flame retardant and carbonization processes.
• Patent documents 6 and 7 propose a technology in which the surface layer of a carbon fiber bundle obtained from a precursor fiber bundle whose density has been increased by dry and wet spinning is electrolytically oxidized in an aqueous electrolyte solution containing nitrate ions as an essential component.
• Patent Document 8 also proposes a technique for suppressing the deterioration of mechanical properties from when carbon fiber bundles are processed into a prepreg form until when they are processed into a final molded product, by hydrolyzing excess epoxy groups contained in the sizing agent either before or after the sizing agent is applied to the carbon fiber bundle, or both.
• Patent Document 9 proposes a technology for obtaining carbon fiber bundles that can increase the number of filaments to improve production efficiency, while at the same time, by making heat treatment uniform, improving the fracture toughness of single fibers, and controlling the entanglement of fiber bundles, it is possible to obtain carbon fiber reinforced composite materials with excellent stability of thread shape and high tensile strength when molding the composite material.
• Patent Documents 1 to 4 are merely techniques for improving the moldability of carbon fiber bundles, and when good moldability has already been established, improvements in mechanical properties cannot be expected.
• Patent Document 1 proposes a technique for adhering a sizing agent to the inside of a yarn bundle and a technique for improving uneven adhesion inside and outside the bundle, but none of the patent documents mentions optimizing the adhesiveness at the interface between the carbon fiber and the resin.
• Patent Document 4 shows that flattening a carbon fiber bundle in a resin-impregnated state suppresses the rate of decrease in ring tensile strength relative to the strength of a resin-impregnated strand, but its purpose is to improve performance by obtaining a homogeneous molded body, and there is no mention of optimizing the adhesiveness at the interface between the carbon fiber and the resin, and the level of strength achieved is insufficient.
• Patent Document 5 claims that the 0° tensile strength of the carbon fiber reinforced composite material is high relative to the strength of the resin-impregnated strand of the carbon fiber bundle, but the absolute strength is not sufficient.
• the technologies of Patent Documents 6 and 7 show an improvement in strand strength for both types of resin before and after nitric acid treatment, but require post-treatment of the fine carbon fibers with single fiber fineness, including nitric acid treatment, drying, and inactivation in a nitrogen atmosphere at 700°C for several minutes, which results in problems with quality degradation due to the generation of fuzz, and with the need for post-treatment in terms of productivity and costs.
• Patent Document 8 suppresses the loss of strength that occurs from processing into a prepreg form until processing into a final molded product, but does not improve strength.
• Patent Document 9 succeeds in improving the 0° tensile strength of carbon fiber reinforced composite materials by improving the fracture toughness and moldability of the carbon fiber bundles, but there is no mention of the adhesion at the interface between the carbon fiber and the resin, and it does not achieve the further increase in strength that can be achieved by optimizing not only the carbon fiber but also the adhesion at the interface between the carbon fiber and the resin.
• the evaluation method based on the resin composition and method in JIS R7608 (2007) is excellent in that test specimens can be easily prepared and stable test results can be obtained, but compared to practical resins used in carbon fiber reinforced composite materials, it has fewer functional groups and often has poor adhesion to carbon fiber bundles. For this reason, there may be a discrepancy between the resin-impregnated strand strength specified in JIS R7608 (2007) and the 0° tensile strength of carbon fiber reinforced composite materials using practical resins.
• the present invention aims to find an evaluation method using a resin composition that reflects the strength exhibited when made into a carbon fiber reinforced composite material, and to provide a carbon fiber bundle that can efficiently exhibit tensile strength when made into a carbon fiber reinforced composite material.
• the present invention comprises the following configuration.
• a carbon fiber bundle containing a sizing agent the strand strength evaluated using the following resin formulation A based on JIS R7608 (2007) being 5.9 GPa or more
• the strand strength (strand strength B') evaluated using the following resin formulation B based on JIS R7608 (2007) being 5.7 GPa or more
• a ratio of the strand strength B' to the strand strength A'
• FIG. 1 is a diagram showing a method for preparing a sample used for measuring the drape value.
• FIG. 2 is a diagram showing a method for measuring the drape value.
• FIG. 1 is a schematic diagram of an apparatus for performing a pressure test on a pressure vessel.
• the carbon fiber bundle containing the sizing agent of the present invention has a strand strength evaluated according to the tensile test method for resin-impregnated strands described in JIS R7608 (2007) using the resin formulation A described below, which is a combination of resins described in JIS R7608 (2007) (hereinafter, the strand strength with this resin formulation A may be referred to as "strand strength A'") of 5.9 GPa or more, preferably 6.3 GPa or more and 8.5 GPa or less.
• Celloxide (registered trademark) 2021P is an epoxy resin that contains 97% or more by mass of (3',4'-epoxycyclohexane)methyl-3,4-epoxycyclohexylcarboxylate, has an epoxy equivalent of 130 g/eq, and has a viscosity of 240 mPa ⁇ s at 25°C, and an equivalent product may be used.
• Strand strength A' is an index showing how difficult it is for carbon fibers to break when a load is applied, and is an index showing the strength of the carbon fiber bundle itself containing a sizing agent. If strand strength A' is 5.9 GPa or more, it is easy to increase the strength when made into a carbon fiber reinforced composite material. The higher the strand strength A', the more preferable it is, but if strand strength A' is 6.2 GPa or more, it is easy to make a carbon fiber reinforced composite material that can withstand practical use, and 8.5 GPa is often sufficient.
• the strand strength A' can be controlled by manufacturing according to the carbon fiber manufacturing method described below.
• the carbon fiber bundle containing the sizing agent of the present invention has a strand strength evaluated according to the tensile test of a resin-impregnated strand described in JIS R7608 (2007) using resin formulation B described below (hereinafter, the strand strength using resin formulation B may be referred to as "strand strength B'") of 5.7 GPa or more, preferably 6.0 GPa or more and 7.8 GPa or less, and more preferably 6.5 GPa or more and 7.8 GPa or less.
• Resin formula B is a practical resin for filament winding and has a viscosity suitable for preparing strand test pieces using the impregnation method described in JIS R7608 (2007). Furthermore, compared to the resin composition described in JIS R7608 (2007), resin formula B has more functional groups and has strong adhesion to carbon fibers. Therefore, it was found that strand strength B' in resin formula B can be used as an index that represents the strength of the carbon fiber bundle when it is made into a carbon fiber reinforced composite material.
• the strength B' is 5.7 GPa or more, the strength can be increased when it is actually made into a carbon fiber reinforced composite material. Also, if the strand strength B' is 6.0 GPa or more, it is likely to be a practical carbon fiber reinforced composite material, and if it is 6.5 GPa or more, the amount of carbon fiber used in the carbon fiber reinforced composite material can be effectively reduced, which is expected to reduce the weight of the carbon fiber reinforced composite material, but 7.8 GPa is often sufficient.
• Strand strength B' can be controlled by producing a carbon fiber bundle containing a sizing agent according to the method for producing a carbon fiber bundle containing a sizing agent described below.
• the carbon fiber bundle containing the sizing agent of the present invention has a ratio of strand strength B' to strand strength A' (hereinafter referred to as "strength utilization rate") of 90% or more, preferably 93% or more, and more preferably 95% to 99%.
• the strength utilization rate is an index of strength manifestation when the carbon fiber bundle is made into a carbon fiber reinforced composite material. If the strength utilization rate is 90% or more, it is easy to increase the strength when actually made into a carbon fiber reinforced composite material, and if it is 95% or more, the mechanical properties of the carbon fiber can be efficiently manifested when made into a carbon fiber reinforced composite material. The closer to 100% the strength utilization rate is, the more preferable, but in many cases, 99% is sufficient as a carbon fiber reinforced composite material.
• the carbon fiber bundle containing the sizing agent of the present invention has an interfacial shear strength of 16 MPa or less, preferably 10 MPa to 16 MPa, more preferably 12 MPa to 16 MPa.
• the interfacial shear strength is an index that represents the adhesion between the carbon fiber and the resin contained in the carbon fiber bundle when the carbon fiber reinforced composite material is made.
• adhesion between the carbon fiber and the resin is low, peeling may occur at the interface between the carbon fiber and the resin, leading to the breakage of the entire carbon fiber reinforced composite material. If the adhesion is 10 MPa or more, it is expected that peeling at the interface between the carbon fiber and the resin can be suppressed in practical use when the carbon fiber reinforced composite material is made. If the adhesion between the carbon fiber and the resin is too high, stress concentration is likely to occur at the breakage starting point when the carbon fiber reinforced composite material is made, leading to the breakage of the entire carbon fiber reinforced composite material, so it is preferable to make it 16 MPa or less.
• the single fiber diameter of the carbon fiber bundle containing the sizing agent of the present invention is 5.1 ⁇ m or more and less than 6.0 ⁇ m, preferably 5.1 ⁇ m or more and 5.8 ⁇ m or less, and more preferably 5.2 ⁇ m or more and 5.8 ⁇ m or less.
• the breaking load per single fiber is determined by the strand strength and the single fiber cross-sectional area, so the single fiber diameter affects the breaking load per single fiber.
• the larger the single fiber diameter the less fuzzing due to abrasion during the process tends to occur, which affects the quality.
• the single fiber diameter is 5.2 ⁇ m or more, the quality is likely to be good when producing carbon fiber or when making it into a carbon fiber reinforced composite material. If the single fiber diameter is too large, there is a possibility that the reaction will be uneven within the single yarn during the baking process, so it is preferable that it is less than 6.0 ⁇ m.
• the carbon fiber bundle containing the sizing agent of the present invention is expected to have improved tensile strength when made into a carbon fiber reinforced composite material, since the strand strength A' in resin formulation A, the strand strength B' in resin formulation B, the ratio of strand strength B' to strand strength A', the single fiber diameter, and the interfacial shear strength all satisfy the above ranges.
• the sizing agent contains at least one type of component containing an epoxy group, and when the epoxy value of the sizing agent eluted by immersing the carbon fiber bundle containing a sizing agent in an N,N-dimethylformamide solvent and subjecting it to ultrasonic treatment is X meq./g, and the content ratio of the sizing agent contained in the carbon fiber bundle containing a sizing agent is Y mass %, it is preferable that X and Y satisfy the relationship of the following formula 1, and more preferably satisfy the relationship of the following formula 2. 0.10 meq. /g ⁇ X ⁇ Y ⁇ 0.68meq. /g...Formula 1 0.10 meq. /g ⁇ X ⁇ Y ⁇ 0.40meq. /g...Formula 2.
• the epoxy value is an index that indicates the amount of epoxy groups contained per gram of sizing agent; the higher the epoxy value, the more epoxy groups are contained per gram of sizing agent.
• the content of sizing agent is the total mass of sizing agent eluted by immersing a carbon fiber bundle containing sizing agent in N,N-dimethylformamide and subjecting it to ultrasonic treatment, expressed as a percentage (mass%) with the mass of the carbon fiber bundle containing sizing agent being 100 mass%.
• X ⁇ Y in formulas 1 and 2 is an index showing the amount of epoxy groups contained in the carbon fiber bundle containing the sizing agent, and when X ⁇ Y is large, it is easier to increase the adhesion at the interface between the carbon fiber contained in the carbon fiber bundle containing the sizing agent and the resin that constitutes the carbon fiber reinforced composite material.
• the carbon fiber bundle containing the sizing agent of the present invention preferably has a drape value of 18 cm or less, more preferably 4 cm or more and 16 cm or less, and even more preferably 4 cm or more and 10 cm or less.
• the drape value is an index that represents the hardness of the carbon fiber bundle, and the higher the drape value, the harder the carbon fiber bundle is.
• the fiber bundle is soft and is prone to bending and twisting when it is exposed to a guide such as a comb that is used to align the yarn pulled out from the bobbin during the production of composite materials. If bending or twisting occurs, it becomes difficult to open that part, which is undesirable as it will cause uneven opening. Also, if the drape value is more than 18 cm, the fiber bundle is hard and may be prone to fuzzing when it comes into contact with a guide such as a comb and deforms. A drape value of 4 cm or more and 10 cm or less is preferable as it can suppress both uneven opening and fuzzing when it comes into contact with a guide.
• the carbon fiber bundle containing the sizing agent of the present invention preferably has 24,000 or more filaments, and more preferably 36,000 or more filaments.
• productivity depends on the yarn speed and the number of filaments, so a large number of filaments allows the composite material to be manufactured efficiently.
• a filament number of 24,000 or more is satisfactory from the viewpoint of productivity.
• the number of filaments is preferably 48,000 or less.
• the carbon fiber precursor fiber bundle can be obtained by spinning a spinning solution of polyacrylonitrile copolymer.
• the polyacrylonitrile copolymer is not limited to a homopolymer obtained only from acrylonitrile, but may also contain other monomers in addition to the main component acrylonitrile. Specifically, the polyacrylonitrile copolymer preferably contains 90 to 100% by mass of acrylonitrile and less than 10% by mass of a copolymerizable monomer.
• Examples of monomers that can be used as copolymerizable monomers with acrylonitrile include acrylic acid, methacrylic acid, itaconic acid and their alkali metal salts, ammonium salts and lower alkyl esters, acrylamide and its derivatives, allylsulfonic acid, methallylsulfonic acid and their salts or alkyl esters, etc.
• the polyacrylonitrile copolymer is dissolved in a solvent in which the polyacrylonitrile copolymer is soluble, such as dimethyl sulfoxide, dimethylformamide, dimethylacetamide, nitric acid, an aqueous zinc chloride solution, or an aqueous sodium rhodanide solution, to obtain a spinning solution.
• a solvent in which the polyacrylonitrile copolymer is soluble such as dimethyl sulfoxide, dimethylformamide, dimethylacetamide, nitric acid, an aqueous zinc chloride solution, or an aqueous sodium rhodanide solution.
• the spinning process includes a coagulation process in which the spinning solution is discharged from a spinneret into a coagulation bath and spun, a water washing process in which the coagulated yarn obtained in the coagulation process is washed in a water bath, a water bath drawing process in which the fiber obtained in the water washing process is drawn in a water bath, and a dry heat treatment process in which the fiber obtained in the water bath drawing process is dry heat treated, and may include a steam drawing process in which the fiber obtained in the dry heat treatment process is steam drawn.
• the spinning solution is prepared by dissolving the polyacrylonitrile polymer described above in a solvent in which polyacrylonitrile is soluble, such as dimethyl sulfoxide, dimethylformamide, or dimethylacetamide.
• the coagulation bath preferably contains the solvent used in the spinning solution, such as dimethyl sulfoxide, dimethylformamide, or dimethylacetamide, and a coagulation-promoting component.
• the coagulation-promoting component may be one that does not dissolve the polyacrylonitrile polymer and is compatible with the solvent used in the spinning solution. Specifically, it is preferable to use water as the coagulation-promoting component.
• the water washing process is carried out for the purpose of introducing the fibers obtained in the spinning process into a water washing bath and further removing the organic solvent from the coagulated fiber bundle.
• drawing may be carried out in the water washing process.
• the water bath stretching process can usually be carried out in a single or multiple water baths whose temperatures are controlled to 30 to 98°C.
• the stretching ratio in the water bath stretching process is preferably set to 2 to 6 times.
• the oil application process is a process in which an oil is applied after the bath drawing process in order to prevent adhesion between the fibers. It is preferable to use an oil whose main component is silicone as the oil used in this process. If the oil does not contain silicone, it will not be possible to suppress interfiber adhesion during the flame-proofing process, and strand strength will decrease. It is also preferable to use a silicone oil that contains modified silicone, such as amino-modified silicone, which has high heat resistance. Other silicone oils include silicones modified with epoxy or alkylene oxide.
• a publicly known method can be used for the drying process. From the viewpoint of improving productivity and the degree of crystal orientation, it is preferable to perform stretching in a heating medium after the drying process.
• a heating medium for example, pressurized steam or superheated steam is preferably used in terms of operational stability and cost.
• a dry heat stretching process or a steam stretching process may be added.
• a method for producing a carbon fiber bundle containing the sizing agent of the present invention will be described.
• a carbon fiber precursor fiber bundle produced by the method described above is subjected to a flame retardant process in an oxidizing atmosphere at a temperature of 200 to 300°C, a preliminary carbonization process in an inert atmosphere at a maximum temperature of 500 to 1,200°C, and then a carbonization process in an inert atmosphere at a maximum temperature of 1,200 to 2,000°C to produce a carbon fiber bundle.
• the ratio of the peak intensity at 1,453 cm ⁇ 1 to the peak intensity at 1,370 cm ⁇ 1 in the infrared spectrum of the obtained flame-resistant fiber is in the range of 0.60 to 0.75, and the ratio of the peak intensity at 1,254 cm ⁇ 1 to the peak intensity at 1,370 cm ⁇ 1 in the infrared spectrum is in the range of 0.50 to 0.65.
• the peak at 1,453 cm ⁇ 1 in the infrared spectrum is derived from an alkene and decreases as the flame-resistant process progresses.
• the peaks at 1,370 cm ⁇ 1 and 1,254 cm ⁇ 1 are peaks derived from the flame-resistant structure and increase as the flame-resistant process progresses.
• the ratio of the peak intensity at 1,254 cm ⁇ 1 to the peak intensity at 1,370 cm ⁇ 1 decreases as the flameproofing progresses, and the decrease is particularly large in the initial stage. However, depending on the flameproofing conditions, the peak intensity ratio may not reach 0.65 or less even if the time is increased.
• the conditions should basically be set by focusing mainly on the following: the amount of copolymerization component contained in the polyacrylonitrile-based polymer constituting the precursor fiber is small, the degree of crystal orientation of the precursor fiber is high, the single fiber fineness of the precursor fiber is small, and the flame retardation temperature is increased in the latter half.
• the flame-stabilizing step is preferably carried out in two stages: a first flame-stabilizing step in which the fiber is flame-stabilized for 8 to 40 minutes until the ratio of the peak intensity at 1,453 cm -1 to the peak intensity at 1,370 cm -1 in the infrared spectrum reaches a range of 0.80 to 1.05; and a second flame-stabilizing step in which the fiber obtained in the first flame-stabilizing step is flame-stabilized for 5 to 40 minutes, preferably 5 to 30 minutes, until the ratio of the peak intensity at 1,453 cm -1 to the peak intensity at 1,370 cm -1 in the infrared spectrum reaches a range of 0.60 to 0.75 and the ratio of the peak intensity at 1,254 cm -1 to the peak intensity at 1,370 cm -1 in the infrared spectrum reaches a range of 0.50 to 0.65.
• the flame-proofing temperature in the first flame-proofing step is preferably set to 200 to 250°C, more preferably 230 to 250°C, in order to control it within the above-mentioned infrared spectrum range.
• the second flame-resistant process is preferably performed at a higher flame-resistant temperature than the first flame-resistant process.
• the flame-resistant temperature may be adjusted higher, but the appropriate flame-resistant temperature depends on the characteristics of the precursor fiber.
• the flame-resistant temperature does not need to be constant, and multiple temperature settings may be used.
• flame retardation refers to heat treating the precursor fiber in an oxygen-containing atmosphere at 200 to 310°C.
• the flame-resistant time mentioned here means the time the fiber is retained in the flame-resistant furnace.
• the flame-resistant fiber means the fiber after the flame-resistant process and before the preliminary carbonization process.
• the peak intensity mentioned here means the absorbance at each wavelength after a small amount of the flame-resistant fiber is sampled and the infrared spectrum is measured, and the spectrum obtained is baseline corrected, and no peak division is performed.
• the sample concentration when measuring the infrared spectrum is diluted with KBr to 0.67 mass%. In this way, the infrared spectrum is measured every time the flame-resistant condition settings are changed, and the conditions are examined according to the preferred manufacturing method described below.
• Air is preferably used as the oxidizing atmosphere in the flame-resistant treatment.
• the preliminary carbonization treatment and the carbonization treatment are carried out in an inert atmosphere.
• gases used in the inert atmosphere include nitrogen, argon, and xenon, and from an economical point of view, nitrogen is preferably used.
• the obtained carbon fiber bundles can be electrolytically treated to modify their surface. This is because electrolytic treatment can optimize the adhesion between the carbon fiber matrix and the resulting fiber-reinforced composite material.
• a sizing process is performed to give the carbon fiber bundles bundling properties.
• a sizing agent that has good compatibility with the matrix resin can be selected appropriately depending on the type of resin used, but it is important to control adhesion in order to simultaneously suppress interfacial peeling between the carbon fiber and resin when made into a carbon fiber reinforced composite material and alleviate stress concentration, thereby achieving good mechanical properties.
• the electrolytic treatment conditions such as the type and concentration of the electrolyte, the deposition rate of the sizing agent, and control the amount of functional groups contained in the sizing agent.
• the sizing agent contains epoxy groups, it is preferable to hydrolyze the epoxy groups before applying the sizing agent, and to adjust the amount of epoxy groups by hydrolyzing the epoxy groups by subjecting the carbon fiber bundle after applying the sizing agent to an aging treatment at constant temperature and humidity.
• Carbon fiber bundles containing the sizing agent of the present invention are preferably used as reinforcing fibers for carbon fiber reinforced composite materials.
• Members using such carbon fiber reinforced composite materials can be used in many fields, such as aviation and space, automobiles, railway vehicles, ships, civil engineering and construction, and sporting goods. In particular, they can be used favorably as hollow containers such as pressure vessels, and cylindrical members.
• the method for producing carbon fiber reinforced composite materials using carbon fiber bundles containing the sizing agent of the present invention can utilize known methods, but in particular, when producing hollow containers such as pressure vessels and cylinders, it is preferable to apply a molding method using filament winding or a towpreg in which the fibers are pre-impregnated with resin.
• ⁇ Infrared spectrum intensity ratio> The flame-resistant fiber to be measured was precisely weighed and collected after freeze-pulverization, and then mixed well with 300 mg of KBr, placed in a molding tool, and pressed at 40 MPa for 2 minutes using a press machine to prepare a tablet for measurement.
• the tablet was set in a Fourier transform infrared spectrophotometer, and the spectrum was measured in the range of 1,000 to 2,000 cm ⁇ 1 .
• background correction was performed by subtracting the minimum value in the range of 1,700 to 2,000 cm ⁇ 1 from each intensity so that the minimum value was 0.
• Paragon 1000 manufactured by PerkinElmer was used as the Fourier transform infrared spectrophotometer.
• the peak intensity ratio was calculated using the peak intensity at each wave number obtained in this way.
• Total fineness> A 10 m length sample was taken from the carbon fiber bundle containing the sizing agent to be measured, and the sample was completely dried at 120° C. for 2 hours. The measured mass (unit: grams) was then divided by 10 to obtain the total fineness (unit: g/m), which is the mass per 1 m.
• the carbon fiber bundle was then transferred to a container in a dry nitrogen flow of 20 liters/minute, and cooled for 15 minutes, after which it was weighed (W 2 ) (read to four decimal places), and the content of the sizing agent in the carbon fiber bundle containing the sizing agent was calculated by W 1 -W 2.
• the content of the sizing agent was divided by W 1 to obtain a value converted to mass% (rounded off to the third decimal place) when the entire carbon fiber bundle containing the sizing agent was taken as 100 mass%, and the content ratio Y (mass%) of the sizing agent was calculated.
• the measurement was performed twice, and the average value was taken as the content ratio Y (mass%) of the sizing agent.
• the epoxy value X (meq./g) was determined by immersing 30 g of a carbon fiber bundle containing a sizing agent in 150 ml of N,N-dimethylformamide solvent at 25° C. and performing ultrasonic treatment three times for 30 minutes at a frequency of 40 kHz to analyze a solution containing the sizing agent eluted from the fibers.
• the amount of the sizing agent remaining in the carbon fiber was set to 0.20 mass % or less.
• the epoxy group was opened with hydrochloric acid using the eluted sizing agent solution, and the epoxy value X (meq./g) was determined by acid-base titration.
• a weight 3 was hung from a carbon fiber bundle 2 containing a sizing agent cut to 50 cm in an atmosphere at a temperature of 25 ° C. with a load of 0.0375 [g / tex], and the bundle was left for 30 minutes or more to remove twisting. A portion of the bundle 2 with a length of 30 cm from the center was sampled, and as shown in Fig.
• the carbon fiber bundle 2 containing a sizing agent was placed while being supported so as not to be broken so that the carbon fiber bundle 2 containing a sizing agent protruded 25 cm from a rectangular horizontal stand 4 with a 90 ° angle, and the carbon fiber bundle 2 containing a sizing agent on the horizontal stand 4 was fixed with tape. Thereafter, the support of the carbon fiber bundle 2 containing a sizing agent protruding from the horizontal stand 4 was removed to allow it to hang down, and the horizontal distance L from the fulcrum was measured after 1 second. The measurement was performed five times, and the arithmetic average value was taken as the drape value.
• IFSS Interfacial Shear Strength
• the interfacial shear strength which is an index of the adhesive strength of the carbon fiber and resin interface, was calculated by the following formula. The measurement was performed five times, and the arithmetic average was taken as the test result.
• Interfacial shear strength (MPa) strand strength A' (MPa) x d ( ⁇ m) / (2 x lc) ( ⁇ m).
• a carbon fiber bundle containing a sizing agent with 24,000 filaments was hung on the metal bars, the unwinding tension from the package was set to 1600 g, and the metal bar was passed by pulling at 4 m/min with a driving roll, and the number of fluffs in one minute after passing the second metal bar was counted to determine the process passability.
• the release tension is set to 2,400g, and the counted number of process fluff is divided by ⁇ 1.5 to obtain the process passability.
• the conditions for the measurement other than the unwinding tension are the same as when the number of filaments is 24,000.
• a and B are preferable results in the present invention, and A is more preferable result.
• Burst pressure 107 MPa or more A: Burst pressure 99 MPa or more but less than 107 MPa
• Carbon fiber bundle manufacturing method I A copolymer of acrylonitrile and itaconic acid was dissolved in dimethyl sulfoxide to prepare a spinning solution. The obtained spinning solution was extruded into the air from a spinneret with 6,000 holes, and then introduced into a coagulation bath of an aqueous solution of dimethyl sulfoxide to prepare a fiber bundle by a dry-wet spinning method. The fiber bundle was washed with water at 30 to 98°C and stretched by a conventional method. Subsequently, an amino-modified silicone-based silicone oil was applied to the fiber bundle after the water bath stretching, and the fiber bundle was dried and densified using a heating roller at 160°C. The number of filaments was increased to 12,000, and then the fiber bundle was stretched 3.7 times in pressurized steam to obtain a polyacrylonitrile-based precursor fiber bundle with a single fiber fineness of 0.7 dtex at a total stretch ratio of 13 times.
• the polyacrylonitrile precursor fiber bundles obtained were bundled as necessary to obtain the number of filaments shown in Table 1, and then processed in the following baking process to produce carbon fiber bundles.
• the first flame-resistant process was carried out under conditions of a flame-resistant temperature of 240°C and a flame-resistant time of 36 minutes, and the second flame-resistant process was carried out under conditions of a flame-resistant temperature of 250°C and a flame-resistant time of 37 minutes.
• the carbon fiber precursor fiber bundle was stretched at a draw ratio of 1 in an oven in an air atmosphere to perform a flame-resistant treatment, thereby obtaining a flame-resistant fiber.
• the ratio of the peak intensity at 1,453 cm -1 to the peak intensity at 1,370 cm -1 in the infrared spectrum of the fiber after the first flame-proofing step was 0.87.
• the ratio of the peak intensity at 1,453 cm -1 to the peak intensity at 1,370 cm- 1 in the infrared spectrum of the fiber after the second flame-proofing step was 0.63, and the ratio of the peak intensity at 1,254 cm - 1 to the peak intensity at 1,370 cm-1 was 0.60.
• the obtained flame-retardant fiber was subjected to a pre-carbonization process in a nitrogen atmosphere at a maximum temperature of 900°C with a draw ratio of 0.96 to obtain a pre-carbonized fiber.
• the obtained pre-carbonized fiber was subjected to a carbonization process in a nitrogen atmosphere at a maximum temperature of 1,500°C with a draw ratio of 0.950.
• carbon fiber bundles were subjected to electrolytic surface treatment using an aqueous sulfuric acid solution as the electrolyte, and then washed with water and dried to obtain carbon fiber bundles that did not contain a sizing agent.
• the carbon fiber bundles obtained by carbon fiber bundle manufacturing method I are referred to as carbon fiber I in the table.
• Carbon Fiber Bundle Manufacturing Methods II to IV Carbon fiber bundles not containing a sizing agent were obtained by changing the flame retardancy, pre-carbonization, and carbonization conditions shown in Table 1 based on the carbon fiber bundle manufacturing method I.
• the manufacturing methods for each carbon fiber are designated as manufacturing methods II to IV, and the obtained carbon fiber bundles are conveniently referred to as carbon fibers II to IV in the table, similarly to manufacturing method I.
• Examples 1 to 14, Comparative Examples 1 to 7 The carbon fiber bundles I to IV not containing a sizing agent obtained in Reference Example 1 were impregnated with the sizing agents i to iv obtained in Reference Example 2 after adjusting the concentration of the aqueous sizing agent solution so as to obtain the combination and content ratio of the sizing agent shown in Table 3. Then, a heat treatment was performed at a temperature of 210° C. for 75 seconds to obtain a carbon fiber bundle containing a sizing agent.
• a 7.5 L polyethylene liner was placed in a filament winding molding device, and resin composition B, which had been uniformly mixed in advance at 25°C, was impregnated into the carbon fiber bundles to which the sizing had been applied, so that the amount of resin composition B imparted to the total mass of the carbon fiber bundles and resin composition B was 22 to 28 mass %.
• a hoop layer that is at an angle of +89° to the axial direction of the liner and a hoop layer that is at an angle of -89° to the axial direction of the liner were alternately formed, and then wound to a thickness of 1.4 mm to form the first layer.
• a helical layer was wound around the liner at an angle of ⁇ 20° to the axial direction to a thickness of 2.2 mm to form the second layer.
• the intermediate body in which the carbon fiber bundle containing the sizing agent impregnated with resin composition B was wound around a 7.5 L polyethylene liner as described above, was rotated at a speed of 7 rpm and held in an environment of 20°C for 15 minutes.
• the intermediate body was heated at a temperature of 80°C for 120 minutes and then at a temperature of 110°C for 240 minutes to harden mixture B and obtain a pressure vessel for pressure resistance testing.
• Examples 4 and 5 used carbon fiber bundles manufactured using the same carbon fiber bundle manufacturing method I, and although strand strength A' was equivalent, strand strength B' and the pressure resistance of the pressure vessel were improved. This shows that by optimizing the adhesion at the interface between the carbon fiber and the resin using a sizing agent, the tensile strength of the carbon fiber can be efficiently expressed, and the pressure resistance of the pressure vessel can be increased to a high level.
• Example 8 used carbon fiber bundles manufactured using the same carbon fiber bundle manufacturing method II, and although strand strength A' was equivalent, strand strength B' and the pressure resistance of the pressure vessel were improved. This shows that by optimizing the adhesion at the interface between the carbon fiber and the resin using a sizing agent, the tensile strength of the carbon fiber can be efficiently expressed, and the pressure resistance of the pressure vessel can be increased to a high level.
• Example 11 Compared to Comparative Example 6, Example 11 used carbon fiber bundles produced using the same carbon fiber bundle manufacturing method III, and although strand strength A' was equivalent, strand strength B' and the pressure resistance of the pressure vessel were improved. This shows that by optimizing the adhesion at the interface between the carbon fiber and the resin using a sizing agent, the tensile strength of the carbon fiber can be efficiently expressed, and the pressure resistance of the pressure vessel can be increased to a high level.
• Example 14 used carbon fiber bundles produced using the same carbon fiber bundle manufacturing method IV, and although strand strength A' was equivalent, strand strength B' and the pressure resistance of the pressure vessel were improved. This shows that by optimizing the adhesion at the interface between the carbon fiber and the resin using a sizing agent, the tensile strength of the carbon fiber can be efficiently expressed, and the pressure resistance of the pressure vessel can be increased to a high level.
• Examples 15 to 18 The carbon fiber bundles of Comparative Examples 3, 5, 6, and 7 were left to stand in a constant temperature and humidity environment of 60° C. and 90% relative humidity for 200 hours to perform aging treatment, thereby obtaining carbon fiber bundles of Examples 15 to 18. Thereafter, pressure vessels for pressure resistance tests were obtained in the same manner as in Comparative Examples 3, 5, 6, and 7. The physical properties of the obtained carbon fiber bundles are summarized in Table 4. Compared to before the aging treatment, the strand strength B' was improved, and the pressure resistance of the pressure vessel was also improved. In other words, this shows that by optimizing the adhesion at the interface between the carbon fiber and the resin, the tensile strength of the carbon fiber can be efficiently expressed, and the pressure resistance of the pressure vessel can be increased to a high level.
• Fixing bar 2 Carbon fiber bundle 3: Weight 4: Horizontal stand 5: Compressed air line 6: Booster 7: Water pressure pump 8: Liquid supply hose 9: Fixing mechanism 10: Pressure vessel 11: Safety cover 12: Data logger

Landscapes

• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Reinforced Plastic Materials (AREA)
• Treatments For Attaching Organic Compounds To Fibrous Goods (AREA)
• Mechanical Engineering (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

Family

ID=94395232

Family Applications (1)

Country Status (5)

Citations (16)

• 2024
  • 2024-07-23 WO PCT/JP2024/026274 patent/WO2025028341A1/ja active Pending
  • 2024-07-23 KR KR1020257038801A patent/KR20260042350A/ko active Pending
  • 2024-07-23 CN CN202480045003.9A patent/CN121443796A/zh active Pending
  • 2024-07-23 JP JP2024544945A patent/JPWO2025028341A1/ja active Pending
  • 2024-07-23 EP EP24848996.5A patent/EP4726102A1/en active Pending

Patent Citations (16)

Also Published As

Similar Documents

Legal Events