CN117120676A

CN117120676A - Carbon fiber bundle

Info

Publication number: CN117120676A
Application number: CN202280023345.1A
Authority: CN
Inventors: 中村祐太郎; 太田究
Original assignee: Mitsubishi Chemical Corp
Current assignee: Mitsubishi Chemical Corp
Priority date: 2021-03-26
Filing date: 2022-03-25
Publication date: 2023-11-24
Also published as: US20240018695A1; EP4317552A1; WO2022203046A1; JPWO2022203046A1

Abstract

A carbon fiber bundle having a total fineness of 2g/m or more has a variation rate of the thickness of the fiber bundle in the width direction of the fiber bundle of 30% or less. A method for producing a carbon fiber bundle, wherein a sizing agent is applied to a carbon fiber bundle, and after drying, one surface of the carbon fiber bundle in the width direction and the opposite surface thereof are alternately brought into contact with two or more parallel rods, and the carbon fiber bundle is passed through and wound around a bobbin.

Description

Carbon fiber bundle

Technical Field

The present application relates to a carbon fiber bundle which can obtain a molded article having good handling and uniform distribution of carbon fibers in advanced processing even when the total fineness of the carbon fiber bundle is large.

The present application claims priority based on the japanese patent application No. 2021-052932 of the application of japan at 3 months of 2021, 26, and the contents thereof are incorporated herein.

Background

Carbon fibers have excellent specific strength and specific elastic modulus, and therefore are widely used for sports and leisure products to aerospace applications. In addition to sports applications such as golf shafts and fishing rods, and aircraft applications, development of so-called general industrial applications such as wind turbine components for power generation, automobile components, CNG tanks, seismic reinforcement for buildings, and ship components has been advanced, and carbon fiber bundles having a large mass per unit length (total fineness) are required.

When a carbon fiber bundle having a large total fineness is processed into a prepreg by a roll winding method (dry winding) or molded into various composite materials by a filament winding method (filament winding) or the like, a resin is applied to the carbon fiber bundle by a contact roll method, but in the conventional technique, there are portions having a high fiber content and portions having a low fiber content in a molded article, and the portions having a low fiber content may become starting points for early breakage.

One of the reasons for this is considered to be uneven thickness in the width direction of the carbon fiber bundles having a large total fineness. In the production process of the carbon fiber precursor fiber bundles, in order to prevent entanglement or blocking due to contact between adjacent process fiber bundles in the firing process, the sizing agent applying process, and the like, the carbon fiber bundles having a large total fineness have to be limited in lateral width using a width limiting yarn guide or the like. When passing through the width limiting yarn guide, the fiber bundle is pressed from both sides, and uneven thickness is likely to occur.

In addition, when winding the carbon fiber bundle, the width is reduced by the yarn guide bent into the die, and thus the thickness unevenness is liable to occur.

Patent document 1 discloses a method for producing a carbon fiber bundle, namely: when 60000 carbon fiber bundles were wound, the carbon fiber bundles were twisted by 90 degrees at the traverse position, and then twisted back, and were wound by a yarn guide bent into a female die, whereby carbon fiber bundles having a small yarn width fluctuation, a uniform yarn width, and a wide total fineness were produced.

Patent document 2 discloses a method of reducing variation in yarn width by a yarn guide that stabilizes a yarn passage when winding 36000 carbon fiber bundles.

Patent document 3 discloses a carbon fiber bundle: 24000 fiber bundles are sintered and then impregnated with sizing agent, and the fiber bundles are contacted with a hot roller with the surface temperature of 120-140 ℃ for 15-30 seconds, so that the flatness ratio (the ratio of the width to the thickness of the carbon fiber bundles) of the cross section of the fiber bundles is 40-90, and the drape value (the softness of the carbon fiber bundles) is 50-100 mm.

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2011-11830

Patent document 2: japanese patent application laid-open No. 2012-154000

Patent document 3: japanese patent laid-open publication No. 2011-252264

Disclosure of Invention

Problems to be solved by the application

However, in patent document 1, as shown in comparative example of the present application, the variation rate of the thickness is large.

Patent documents 2 and 3 do not describe the thickness variation rate of the carbon fiber bundles, and do not control the thickness variation rate.

In the sizing agent applying step, the comb guide is dried and wound in a state where the thickness variation rate is large, and therefore the thickness variation rate is large.

The present application solves the conventional problems, and an object of the present application is to provide a carbon fiber bundle that can obtain a molded article having a uniform distribution of carbon fibers and a uniform fiber content, even when the carbon fiber bundle has a large total fineness.

Means for solving the problems

The carbon fiber bundle of the present application has the following features.

[1] A carbon fiber bundle having a total fineness of 2g/m or more, wherein the variation rate of the thickness of the fiber bundle in the width direction of the fiber bundle is 30% or less.

[2] The carbon fiber bundle according to [1], wherein the number of single fibers is 20000 or more.

[3] The carbon fiber bundle according to [1] or [2], wherein the average thickness of the fiber bundle is 0.18 to 0.28mm.

[4] The carbon fiber bundle according to any one of [1] to [3], wherein a variation rate of a width of the fiber bundle in a longitudinal direction of the fiber bundle is 13% or less.

[5] The carbon fiber bundle according to any one of [1] to [4], wherein the width of the fiber bundle is 13 to 18mm.

[6] The carbon fiber bundle according to any one of [1] to [5], wherein the flatness (width/average thickness) of the fiber bundle is 60 to 70.

[7] The carbon fiber bundle according to any one of [1] to [6], wherein the cantilever value is 210 to 250mm and the adhesiveness is 0.18m or less.

[8] The carbon fiber bundle according to any one of [1] to [7], wherein the amount of the sizing agent to be adhered is 0 to 20% by mass.

[9] The carbon fiber bundle according to any one of [1] to [8], wherein the inter-fiber dynamic friction coefficient is 0.2 or less.

[10] The carbon fiber bundle according to any one of [1] to [9], wherein the coefficient of dynamic friction between fiber metals is 0.18 or less.

[11] A method of manufacturing a carbon fiber bundle, comprising: in an averaging member having two or more parallel rods arranged between a sizing agent dryer and a winder (winder) or a retractor, a surface A of a carbon fiber bundle and a surface B on the opposite side of the surface A are brought into contact with the rods 1 or more times, respectively, and the carbon fiber bundle is passed through the averaging member.

[12] The method of producing a carbon fiber bundle according to [11], wherein the distance between adjacent ones of the parallel rods is 15 to 50mm.

[13] The method of producing a carbon fiber bundle according to [11] or [12], wherein the carbon fiber bundle is passed in contact with the parallel rod while being twisted by 90 ° in a plane direction of the carbon fiber bundle in contact with a roller preceding the parallel rod during the passing.

[14] The method for producing a carbon fiber bundle according to any one of [11] to [13], wherein the carbon fiber bundle is passed through the passage so that the maximum width of the carbon fiber bundle in contact with the parallel rod is enlarged by 5 to 20% with respect to the width of the carbon fiber bundle in contact with the roller preceding the parallel rod.

[15] The production method according to [13] or [14], wherein the roll is located upstream of the parallel rods in the traveling direction of the carbon fiber bundles, and the longitudinal direction of the roll is substantially perpendicular to the longitudinal direction of the parallel rods.

[16] The production method according to any one of [13] to [15], wherein a distance from the center of the roll to the center of the parallel bar is preferably 200 to 1500mm, more preferably 500 to 1000mm, at a shortest position.

[17] The method of producing a carbon fiber bundle according to any one of [11] to [16], wherein in the passing, the carbon fiber bundle is flattened, one surface a of the carbon fiber bundle is brought into contact with the parallel rod located upstream in the traveling direction of the carbon fiber bundle, and then the other surface B of the carbon fiber bundle is brought into contact with the parallel rod located downstream in the traveling direction of the carbon fiber bundle, whereby the carbon fiber bundle is passed through the averaging member.

[18] The method for producing a carbon fiber bundle according to any one of [11] to [17], comprising: before the passage, the surface direction of the carbon fiber bundle is changed with the longitudinal direction of the carbon fiber bundle as an axis.

[19] The production method according to [18], wherein when the plane direction is changed, the plane of the carbon fiber bundle is preferably inclined in the range of 30 ° to 150 ° in the width direction with the longitudinal direction of the carbon fiber bundle as an axis; more preferably, the surface of the carbon fiber bundle is inclined in the width direction by an angle of 45 ° to 135 ° with the longitudinal direction of the carbon fiber bundle as an axis; more preferably, the surface of the carbon fiber bundle is inclined in the width direction by 60 ° to 120 ° with the longitudinal direction of the carbon fiber bundle as an axis; particularly preferably, the surface of the carbon fiber bundle is inclined by approximately 90 ° in the width direction with the longitudinal direction of the carbon fiber bundle as an axis.

[20] The production method according to [18] or [19], wherein the change of the plane direction is performed between a roll located upstream of the two or more parallel rods and a parallel rod located furthest upstream of the two or more parallel rods in the traveling direction of the carbon fiber bundle.

[21] The method of producing a carbon fiber bundle according to any one of [11] to [20], wherein the method of producing a carbon fiber bundle according to any one of [1] to [10 ].

The carbon fiber bundle of the present application also has the following features.

[1a] A method of manufacturing a carbon fiber bundle, comprising: contacting one face a of the carbon fiber bundle with a first rod; and bringing the other face B of the carbon fiber bundle into contact with a second rod.

[2a] The production method according to [1a ], comprising: the surface direction of the carbon fiber bundles is changed with the longitudinal direction of the carbon fiber bundles as an axis.

[3a] According to the production method of [2a ], when the plane direction is changed, it is preferable that the plane of the carbon fiber bundle is inclined in the range of 30 ° to 150 ° in the width direction with the longitudinal direction of the carbon fiber bundle as an axis; more preferably, the surface of the carbon fiber bundle is inclined in the width direction by an angle of 45 ° to 135 ° with the longitudinal direction of the carbon fiber bundle as an axis; more preferably, the surface of the carbon fiber bundle is inclined in the width direction by 60 ° to 120 ° with the longitudinal direction of the carbon fiber bundle as an axis; particularly preferably, the surface of the carbon fiber bundle is inclined by approximately 90 ° in the width direction with the longitudinal direction of the carbon fiber bundle as an axis.

[4a] The production method according to [2a ] or [3a ], which comprises the steps of: changing the direction of the surface; contact with the first rod; and contacting the second rod.

[5a] The production method according to any one of [2a ] to [4a ], wherein the surface direction is changed, and the carbon fiber bundles are brought into contact with the first rod and the second rod in this order, whereby the width of the carbon fiber bundles after the steps is widened to a range of 105 to 120% with respect to the width of 100% of the carbon fiber bundles before the steps.

[6a] The method of producing a carbon fiber bundle according to any one of [1] to [10], wherein the method of producing a carbon fiber bundle is any one of [1] to [5a ].

Effects of the application

The carbon fiber bundles of the present application can obtain a molded article having good handling and uniform distribution of carbon fibers in advanced processing, even when the carbon fiber bundles have a large total fineness.

Drawings

Fig. 1 is a diagram showing a method for calculating a change rate of the thickness of a carbon fiber bundle.

Fig. 2 is a diagram showing an example of an apparatus for measuring the inter-fiber kinetic friction coefficient of a carbon fiber bundle.

Fig. 3 is a view showing an example of an averaging member for producing the carbon fiber bundle of the present application.

Fig. 4 is a perspective view showing an example of a state in which the carbon fiber bundle of the present application passes through parallel rods.

Fig. 5 is a plan view showing an example of a state in which the carbon fiber bundle of the present application passes through parallel rods.

Fig. 6 is a view showing an example of the arrangement position of the averaging member of the present application.

Fig. 7 is a view showing an example of the winder of the present application.

Detailed Description

The carbon fiber bundle of the present application has a total fineness of 2g/m or more, and a variation rate of the thickness of the fiber bundle in the width direction of the fiber bundle is 30% or less.

The carbon fiber bundles of the present application have a total fineness of 2.0g/m or more. Since the productivity of the carbon fiber bundles depends on the total fineness of the carbon fiber bundles, the carbon fiber bundles can be efficiently produced by making the mass per unit length of the carbon fiber bundles large. The total fineness is more preferably 2.5g/m or more, and most preferably 3g/m or more.

If expressed in dtex, the total titer of 2.0g/m is recorded as 20000dtex.

The change rate of the thickness of the carbon fiber bundle in the width direction of the fiber bundle (hereinafter, the "change rate of the thickness of the carbon fiber bundle in the width direction of the fiber bundle" may be simply expressed as "change rate of the thickness") of the carbon fiber bundle of the present application can be measured by a method described later.

The carbon fiber bundles of the present application preferably have a variation in thickness of 30% or less. By setting the variation rate of the thickness of the carbon fiber bundles to 30% or less, a molded article in which carbon fibers are uniformly distributed can be produced. The variation in thickness of the carbon fiber bundles is more preferably 20% or less, and still more preferably 15% or less.

The number of the single fibers of the carbon fiber bundle of the present application is preferably 20000 or more.

The larger the number of filaments, the higher the productivity, and thus, it is preferable. Further, the larger the number of single fibers, the larger the thickness variation, so the method for producing a carbon fiber bundle of the present application can be easily applied. From these viewpoints, the number of single fibers is more preferably 30000 or more, and still more preferably 40000 or more.

The carbon fiber bundles of the present application preferably have an average thickness of 0.18 to 0.28mm.

If the average thickness of the fiber bundles is 0.18mm or more, the width of the carbon fiber bundles having a large total fineness does not become excessively large, and the handleability is easily improved, and if the average thickness is 0.28mm or less, the thickness variation is easily reduced.

From these viewpoints, the average thickness of the fiber bundle is more preferably 0.20 to 0.27mm, and still more preferably 0.21 to 0.25mm.

The carbon fiber bundle of the present application preferably has a variation rate of the width of the fiber bundle in the longitudinal direction of the fiber bundle of 13% or less. By setting the variation rate of the width of the fiber bundle to 13% or less, a molded article in which carbon fibers are uniformly distributed can be easily produced. The variation in thickness of the carbon fiber bundles is more preferably 12% or less, and still more preferably 11% or less.

The change rate of the width of the carbon fiber bundle in the longitudinal direction of the fiber bundle according to the present application can be measured by a method described later.

(average value of thickness of carbon fiber bundles, fluctuation ratio of thickness, and method for measuring fluctuation ratio of width and width of carbon fibers)

The measurement was performed at room temperature of 25℃and humidity of 50%. In a state where a tension of 0.40cN/tex is applied to the carbon fiber bundle, the carbon fiber bundle is brought into contact with a freely rotating drum having a diameter of 60mm at a holding angle θ=pi (rad) of 10 m/min, a two-dimensional linear laser displacement meter is provided at a midpoint of the holding angle of the rotating drum, displacement data are obtained for one row at equal intervals of 0.1mm in the width direction of the carbon fiber bundle, and in the obtained one row of displacement data, an average value and a standard deviation of displacement are calculated except for a measurement point in a region where the displacement is 5% or less of the maximum value at both ends of the one row of displacement data, and the fluctuation ratio is calculated from the ratio of both. The average value of the displacement is set as the average value of the thickness. At this time, the width of the range of the average value and the standard deviation of the calculated thickness was recorded as the width of the fiber bundle. The average value of the fluctuation ratios of points measured at 300 points at 2cm intervals in the longitudinal direction of the carbon fiber bundle was defined as the "thickness fluctuation ratio in the width direction of the carbon fiber bundle" of the carbon fiber bundle to be measured. The average value and standard deviation of the widths of 300 fiber bundles obtained at the same time were calculated, the ratio of the two was defined as the "width fluctuation ratio in the longitudinal direction of the carbon fiber bundles" of the carbon fiber bundles to be measured, and the average value of the widths of the fiber bundles was defined as the width of the carbon fibers.

The carbon fiber bundles of the present application preferably have a width of 13 to 18mm.

If the width of the carbon fiber is 13mm or more, the thickness will not become excessively large, the variation rate of the thickness will be easily reduced, and if it is 18mm or less, the fiber bundles will not break, and the handling will be easily facilitated.

From these viewpoints, the width of the carbon fiber bundles is more preferably 13.5 to 16.5mm, and still more preferably 14 to 17mm.

The carbon fiber bundles of the present application preferably have a flatness (width/average thickness) of 60 to 70.

If the flatness of the carbon fiber bundles is 60 or more, the thickness of the carbon fiber bundles does not become excessively large, and if the thickness is 70 or less, the width is not excessively wide, and the operability is easily improved.

From these viewpoints, the flatness is more preferably 61 to 69, and still more preferably 62 to 68.

The carbon fiber bundles of the present application preferably have a cantilever value of 210 to 250mm.

If the cantilever value is 210mm or more, the bundling property of the carbon fiber bundles traveling in the yarn path during advanced processing can be ensured, and fluff can be prevented from being generated in the yarn path from the bobbin holder containing the carbon fiber bundles when the resin is impregnated into the carbon fiber bundles to the resin impregnation step. If the cantilever value is 250mm or less, good fiber opening properties between carbon fiber filaments can be ensured at the time of advanced processing. The cantilever value is more preferably 220mm to 240 mm.

The cantilever value of the carbon fiber bundle can be measured by a method described later.

(method for measuring cantilever value of carbon fiber bundle)

The measurement was performed at room temperature of 25℃and humidity of 50%. The carbon fiber bundles were wound out and cut out of the carbon fiber bundle package by about 1m without applying tension. To eliminate the influence of the winding tendency of the cut carbon fiber bundles, one end of the carbon fiber bundles was fixed, a weight of 13mg/tex was attached to the other end, the carbon fiber bundles were held in a state suspended in the vertical direction for 30 minutes, and after that, the weight was removed, and 30cm was cut out without the end, to obtain carbon fiber bundles for test. The test carbon fiber bundles were placed on the horizontal plane of a measuring table having a horizontal plane and a slope inclined downward from one end (straight line) of the horizontal plane by an inclination angle of 45 degrees in a state of no torsion or turbulence, and the ends (straight line) of the test carbon fiber bundles were aligned with the boundary line between the slope and the horizontal plane. A metal platen was placed on the carbon fiber bundle for test, and the end (straight line) of the platen was aligned with the boundary line. Then, the platen was moved at a speed of 0.5 cm/sec in the horizontal direction toward the inclined surface, and when the end of the carbon fiber bundle for test was brought into contact with the inclined surface, the movement of the platen was stopped, and the shortest distance between the point at which the end of the carbon fiber bundle was brought into contact with the inclined surface and the boundary line was measured. The measurement was performed once for each of the 5 carbon fiber bundles for test, and the simple average of the obtained values was set as the cantilever value of the carbon fiber bundles.

The carbon fiber bundles of the present application preferably have an adhesion of 0.18m or less.

If the adhesion is 0.18m or less, the bundling property of the carbon fiber bundles traveling in the yarn path during advanced processing can be ensured, and fluff can be prevented from being generated in the yarn path from the bobbin holder containing the carbon fiber bundles when impregnating the carbon fiber bundles with the matrix resin to the resin impregnation step. The adhesion is more preferably 0.16m or less.

The adhesiveness of the carbon fiber bundles can be measured by a method described later.

(method for measuring adhesion of carbon fiber bundles)

The measurement was performed at room temperature of 25℃and humidity of 50% in a windless environment. A reel having a diameter of 20-25 cm around which a carbon fiber bundle is wound is held so that the axial direction thereof is horizontal, the carbon fiber bundle is wound out without applying tension, and the carbon fiber bundle is cut at a position 10cm from the axial center of the reel. Next, from the contact start point of the carbon fiber bundle wound by unwinding the carbon fiber bundle and the reel, the reel is vertically raised and held without applying vibration in a direction in which the carbon fiber bundle is obliquely wound on the reel as an upward traveling direction. After holding for 10 minutes, the carbon fiber bundles were cut at a position 10cm from the contact start point with the reel, and the length of the carbon fiber bundles peeled off from the reel was measured. The measurement was performed 3 times, and a simple average of the obtained values was used as a measurement value of the adhesiveness of the carbon fiber bundles.

The carbon fiber bundles of the present application preferably have an adhesion amount of 0 to 20 mass% of the sizing agent.

If the amount of the sizing agent is 20 mass% or less, the fiber bundles are less likely to adhere to each other, and thus the thickness variation is easily reduced.

From this viewpoint, the amount of the sizing agent to be adhered is more preferably 15 mass% or less, still more preferably 10 mass% or less, and most preferably 5 mass% or less.

The lower limit value is preferably 0 mass% from the viewpoint of thickness unevenness, but is more preferably 0.5 mass% or more, and even more preferably 1 mass% or more, from the viewpoint of satisfactory handleability by collecting carbon fiber bundles.

The carbon fiber bundles of the present application preferably have a kinetic coefficient of friction between fibers of 0.2 or less.

If the inter-fiber dynamic friction coefficient is 0.2 or less, the frictional force between filaments is reduced, so that generation of fluff due to friction between carbon fiber filaments can be suppressed, and a phenomenon called "fuzzing" in which fluff surrounds a bobbin and a carbon fiber bundle cannot be wound out can be prevented. More preferably 0.17 or less.

The inter-fiber dynamic friction coefficient can be measured by a method described later.

(method for measuring inter-fiber dynamic Friction coefficient)

Fig. 2 shows an example of the measuring apparatus. The carbon fiber bundle 1 to be measured was wound around and fixed at a lead angle in a thickness range of 0.1 to 0.5mm in a uniform manner on the drive roller 1 having a diameter of 30mm provided with a heating device. In a state where the driving of the drum 1 is stopped, the carbon fiber bundle 2 to be measured is disposed in the yarn path shown in fig. 2 so that the holding angle θ=pi (rad). The surface temperature of the driving roller 1 was set to 30 ℃. A weight 4 (t1=0.53 g/tex) was attached to one end of the carbon fiber bundle 2 disposed in the yarn path, and a spring balance 5 was attached to the opposite end. The driving roller 1 was rotated at a rotation speed of 60rpm, and the center value T2 (g) of the indication value of the spring balance 5 after 1 minute was read. 2 measurements were performed, and the interfiber coefficient of dynamic friction was calculated from the average value of T2 obtained.

Interfiber coefficient of kinetic friction = pi ^-1 ln ((average value of T2)/(T1×total fineness))

The carbon fiber bundles of the present application preferably have a fiber intermetallic dynamic friction coefficient of 0.18 or less.

If the coefficient of dynamic friction between the fiber and the metal is 0.18 or less, the friction between the metal yarn carrier and the carbon fiber filaments decreases, and thus the friction resistance increases. The coefficient of dynamic friction between the fiber and the metal is more preferably 0.16 or less.

The coefficient of dynamic friction between fibers can be measured by a method described later.

(method for measuring dynamic Friction coefficient between fiber metals)

Fig. 2 shows an example of the measuring apparatus. The carbon fiber bundle 2 to be measured was placed in the yarn path shown in fig. 2 so as to have a holding angle θ=pi (rad) with the driving roller 1 having a diameter of 30mm having a heating device stopped. In the method for measuring the inter-fiber metal dynamic friction coefficient, unlike the method for measuring the inter-fiber dynamic friction coefficient, only the carbon fiber bundle 2 to be measured is hung on the driving roller 1 without winding the carbon fiber bundle 1. The driving roller 1 is a metal roller (material: S45C-H, texture processing of mesh 400), and the surface temperature is set to 30 ℃. A weight 4 (t3=0.53 g/tex) was attached to one end of the carbon fiber bundle disposed in the yarn path, and a spring balance 5 was attached to the opposite end. The driving roller 1 was rotated at a rotation speed of 60rpm, and the center value T4 (g) of the indication value of the spring balance after 5 minutes was read. 2 measurements were performed, and the fiber-to-metal dynamic friction coefficient was calculated from the average value of T4 obtained.

Interfiber metal kinetic coefficient of friction = pi ^-1 ln ((average value of T4)/(T3. Times. Total titre))

(method for producing carbon fiber bundle)

The method for producing the carbon fiber bundles of the present application is not particularly limited, and can be produced, for example, by a method having the following steps (a) to (i).

(a) And spinning and solidifying the spinning solution to obtain solidified yarns.

(b) And (3) washing and stretching the solidified yarn to obtain the precursor process yarn.

(c) And a step of adhering an oil agent to the precursor filaments and drying and densifying the filaments to obtain precursor fiber bundles.

(d) And a step of subjecting the precursor fiber bundles to flame-resistant treatment to obtain flame-resistant fiber bundles.

(e) And carbonizing the flame-resistant fiber bundles to obtain carbonized fiber bundles.

(f) And a step of subjecting the carbonized fiber bundle to surface oxidation treatment.

(g) And a step of applying a sizing agent to the surface-oxidized carbonized fiber bundle.

(h) And homogenizing the carbonized fiber bundles after the sizing agent is applied.

(i) And a winding step of winding the carbon fiber bundle around a bobbin.

Fig. 6 and 7 are general process charts showing the transition of the step of applying the sizing agent to the carbon fiber bundles, and the averaging member of the present application is arranged in the broken line portion shown in a of fig. 6.

In the step (a), the spinning dope is spun and coagulated to obtain a coagulated yarn.

The spinning dope used in the step (a) is not particularly limited. From the viewpoint of exhibiting mechanical properties such as strength of carbon fibers, an organic solvent solution of an acrylonitrile copolymer is preferable. The acrylonitrile copolymer is a polymer having 90 mass% or more of a repeating unit derived from acrylonitrile, and preferably a copolymer having 95 mass% or more of a repeating unit derived from acrylonitrile.

Examples of the repeating units derived from acrylonitrile other than acrylonitrile (hereinafter referred to as "copolymerized components") include acrylic acid, methacrylic acid, itaconic acid, acrylic acid derivatives such as methyl acrylate, methacrylic acid derivatives such as methyl methacrylate, acrylamide, methacrylamide, N-methylolacrylamide, acrylamide derivatives such as N, N-dimethylacrylamide, and vinyl monomers such as vinyl acetate. The copolymerization component may be one kind or two or more kinds. As the copolymerization component, a vinyl monomer having one or more carboxyl groups is preferable.

The polymerization method for producing the acrylonitrile copolymer is not particularly limited, and examples thereof include solution polymerization in an organic solvent in which the acrylonitrile copolymer is dissolved, precipitation polymerization in water, and the like.

Examples of the organic solvent used in the spinning dope include polar organic solvents such as dimethylacetamide, dimethylsulfoxide, and dimethylformamide. The spinning dope obtained using these polar organic solvents is free from metal elements, and therefore the metal element content of the obtained carbon fiber bundles can be reduced. The solid content concentration of the spinning dope is preferably 20 mass% or more.

The spinning method may be either wet spinning or dry-wet spinning. For example, in wet spinning, a plurality of filaments are spun from a spinning spinneret provided with a plurality of discharge holes into a temperature-controlled coagulation liquid, and coagulated, and the formed filaments are collected and retrieved as coagulated filaments. As the coagulation liquid, a known coagulation liquid such as a mixed solution of a polar organic solvent and water used in the spinning dope can be used.

In the step (b), the coagulated filaments obtained in the step (a) are washed and drawn to obtain precursor process filaments. The washing method may be any method as long as the solvent can be removed from the coagulated fiber, and a known method can be used. Before washing the coagulated filaments, the fibers are drawn in air in an aqueous solvent solution having a solvent concentration lower than that of the coagulating liquid and a high temperature, whereby a more dense fibril structure can be formed. Further, after washing the coagulated filaments, the fibers are drawn in hot water, whereby the orientation of the acrylonitrile copolymer in the fibers can be further improved.

In the step (c), the precursor filaments obtained in the step (b) are attached with an oil solution, and dried and densified to obtain a precursor fiber bundle. As the oil agent, a known oil agent can be used, and examples thereof include oil agents composed of silicone compounds such as silicone oils.

The method of dry densification is not particularly limited as long as the precursor wire to which the oil agent is attached is dried by a known drying method to densify the wire.

The dried and densified fibers may be stretched to 1.8 to 6 times in a pressurized steam at 130 to 200 ℃ or on a heated roll or a heated plate, as needed, to further increase the orientation of the precursor fiber bundles and densify the precursor fiber bundles.

In the step (d), the precursor fiber bundle obtained in the step (c) is subjected to flame resistant treatment to obtain a flame resistant fiber bundle.

Examples of the flame-resistant treatment include a method of passing the hot blast stove through a hot blast stove set so as to rise in temperature stepwise at 220 to 260 ℃ within 30 to 100 minutes. The fibers may also be stretched during the flame resistant treatment. By performing moderate elongation in the flame resistant treatment,thus, the orientation of the fibril structure in which the fibers are formed can be maintained or improved, and a carbon fiber bundle excellent in mechanical properties can be easily obtained. The density of the single fibers constituting the flame-resistant fiber bundles is preferably set to 1.33 to 1.40g/cm ³ 。

In the step (e), the flame-resistant fiber bundles obtained in the step (d) are carbonized to obtain carbonized fiber bundles. Examples of the carbonization treatment include the following treatments including: a first carbonization treatment of heating the substrate at a maximum temperature of 600 to 800 ℃ in an inert atmosphere such as nitrogen; and a second carbonization treatment of heating the material under an inert atmosphere such as nitrogen at a maximum temperature of 1200 ℃ to 2000 ℃.

The treatment time for the first carbonization treatment is preferably 1 to 3 minutes. In the first carbonization treatment, it is preferable to perform an elongation operation of 1% to 5% in terms of promoting the regular orientation of the carbon structure.

The treatment time in the second carbonization treatment is preferably 1.3 to 5 minutes. The strength and elastic modulus of the carbon fiber bundles can be controlled by the temperature and the treatment time in the second carbonization treatment. In the second carbonization treatment, since the fibers undergo a large shrinkage, the elongation is preferably set to-5% to-2%. After the second carbonization treatment, a third carbonization treatment may be additionally performed as needed.

In the step (f), the carbonized fiber bundle obtained in the step (e) is subjected to a surface oxidation treatment. The surface oxidation treatment may be performed by a known method, and examples thereof include electrolytic oxidation, chemical oxidation, and air oxidation. Among them, electrolytic oxidation is preferable.

In the step (g), a sizing agent is applied to the carbonized fiber bundle obtained in the step (f). The sizing agent may be applied to the carbon fiber bundles by applying a solution obtained by dissolving the sizing agent in an organic solvent or an emulsion obtained by dispersing the sizing agent in water with an emulsifier or the like to the carbon fiber bundles, followed by drying.

Before and after the sizing agent is applied, adjacent carbon fiber bundles are preferably separated in advance by a comb carrier or the like so as not to adhere to each other.

The sizing agent is selected from sizing agents having a coefficient of interfiber dynamic friction of 0.20 or less and a coefficient of interfiber dynamic friction of 0.18 or less, as measured by the method described in the specification. The sizing agent is not particularly limited as long as the inter-fiber dynamic friction coefficient is 0.20 or less and the inter-fiber metal dynamic friction coefficient is 0.18 or less.

The amount of the sizing agent attached to the carbon fiber bundles can be adjusted by adjusting the concentration of the sizing agent in the solution or emulsion, or by adjusting the extrusion amount after the solution or emulsion is applied. The amount of the sizing agent attached to the carbon fiber bundles is preferably 0.4 to 2.0% based on the total mass of the carbon fiber bundles to which the sizing agent is attached. The method of drying after the solution or emulsion is applied is not particularly limited, and may be performed using, for example, hot air, a hot plate, a heated roller, an infrared heater, or the like.

In the step (h), the width of the carbonized fiber bundle is enlarged and the thickness of the fiber bundle is made uniform by using an averaging member for the carbonized fiber bundle until the carbonized fiber bundle obtained in the step (g) is wound.

The averaging member preferably expands the width of the fiber bundle by applying an external force to the fiber bundle, so as to be untwisted for easy movement of the single fibers. As a method for applying an external force to the single fibers, friction between the fibers and the metal member, air flow, vibration, and the like can be used, and friction with the metal member can be realized by a simple device, which is preferable.

In the case of manufacturing a plurality of carbon fiber bundles, it is preferable to expand in a direction to avoid contact with adjacent bundles. The averaging member always gives a physical external force to the single fibers constituting the advancing fiber bundle, and the single fibers change positions within the fiber bundle, thereby obtaining a carbon fiber bundle having a good cantilever value and adhesion.

The averaging member used for producing the carbon fiber bundles of the present application may be any method as long as it always imparts a physical external force to the individual fibers, and the averaging member can prevent adjacent and traveling carbon fiber bundles from contacting each other and can change the positions of the individual fibers constituting the carbon fiber bundles by the physical external force to homogenize the distribution.

The shape of the averaging member for applying an external force to the single fibers by friction between the fibers and the metal member is not particularly limited. As the averaging means, a parallel bar yarn guide, a comb yarn guide, or the like can be used, and it is preferable to use a parallel bar yarn guide that can efficiently apply an external force to the single fibers and can adjust the applied external force. Fig. 3 shows an example of a parallel bar yarn carrier. The parallel bar yarn guide preferably has two bars that are smooth and straight in surface and are held in parallel.

The method for manufacturing the carbon fiber bundle of the present application comprises: in an averaging member having two or more parallel rods arranged between a sizing agent dryer and a traverse guide device or a winding device, the rods are brought into contact with a surface A of a carbon fiber bundle and a surface B on the opposite side of the surface A, respectively, at least once.

Thereby, the fiber bundle expands in the width direction, and the single fibers adhere to each other but are easily unraveled.

The rod may be parallel to the surface in contact with the carbon fiber bundle. The shape of the rod is not particularly limited, and is preferably a curved surface, since fluff is easily generated if the surface in contact with the carbon fiber bundles is angled.

The rod is in contact with the surface a and the surface B once, respectively, whereby the fiber bundle is unwound, and the thickness variation is easily reduced.

If the fiber bundle is unwound, it is preferable that the first rod is in contact with the surface a and the second rod is in contact with the surface B, and the first rod, the surface B, the surface a, and the surface B are alternately in this order.

In the method for producing a carbon fiber bundle of the present application, the distance between adjacent ones of the parallel rods is preferably 15 to 50mm.

If the distance between adjacent ones of the parallel rods is 15mm or more, the carbon fiber bundles are likely to pass therethrough, and if 50mm or less, the effect of widening the width is likely to occur.

From these viewpoints, the distance between adjacent ones of the parallel bars is more preferably 17 to 45mm, and still more preferably 19 to 40mm.

In the method for producing a carbon fiber bundle of the present application, it is preferable that the carbon fiber bundle is passed in contact with the parallel rod while being twisted by 90 ° in the plane direction of the carbon fiber bundle in contact with the roller preceding the parallel rod.

By twisting the carbon fiber bundle by 90 °, an external force is applied to the carbon fiber bundle, and the width of the carbon fiber bundle is easily enlarged. In addition, in the case where a plurality of carbon fiber bundles are arranged in parallel, adjacent carbon fiber bundles are not brought into contact with each other, and thus, the space is preferably not occupied.

In the method for producing a carbon fiber bundle of the present application, it is preferable that the maximum width of the carbon fiber bundle in contact with the parallel rod is enlarged by 5 to 20% with respect to the width of the carbon fiber bundle in contact with the roller immediately preceding the parallel rod.

The rod is preferably fixed, but if the rod has a resistance such that the surface speed of the rod is slower than the speed of the fiber bundle, and an external force is applied by friction between the carbon fiber bundle and the fiber bundle, the rod may be rotated.

In the winding process of step (i), the carbon fiber bundle is wound around the winding core while applying a traverse to obtain a winding shaft of the carbon fiber bundle. The method of winding the carbon fiber bundle may be any method as long as the carbon fiber bundle can be wound on the reel without twisting or the like. The yarn guide 11 having the recessed free roller is provided before traversing, and the fiber bundle is narrowed, but the thickness unevenness does not occur by the averaging member of the present application.

In addition to being wound around a reel, the sheet may be wound around a package or the like.

Examples

Hereinafter, the present application will be specifically described with reference to examples, but the following examples do not limit the scope of the present application.

(method for measuring Friction fluff)

The carbon fiber bundle was wound from the bobbin at a winding-out tension of 0.40cN/tex and a traveling speed of 20m/min, and was rubbed by contacting a fixed metal rod (material: SUS304, chrome plating-mirror surface treatment) having a diameter of 8mm at a holding angle of 15 ° via a roller. The travel of the carbon fiber bundles was stopped after 500m, and the fluff deposited on the stainless steel rod was collected to measure the mass. The measurement was performed 3 times, and the simple average of the obtained values was set as the amount of fuzz friction.

Examples 1 to 10

(production of carbon fiber bundles)

A precursor fiber bundle having a single fiber fineness of 1.33dtex and a single fiber number of 50,000 was subjected to flame resistance treatment for 66 minutes in a heated air at 240 to 260℃with an expansion ratio of-3.9% in a heated air circulation type flame resistance furnace to obtain a flame resistant fiber bundle, and then subjected to pre-carbonization treatment for about 1.5 minutes in a heat treatment furnace at 700℃at a maximum temperature under nitrogen atmosphere, and then subjected to carbonization treatment for about 1.5 minutes with an expansion ratio of-4.5% in a heat treatment furnace at 1350℃at a maximum temperature under nitrogen atmosphere to obtain a carbonized fiber bundle.

Next, the carbon fiber bundles were made to travel in an aqueous solution of 5 mass% of ammonium bicarbonate, and the carbon fiber bundles were set as anodes, were subjected to an electric current passing between the anodes so that 30 coulomb charge was obtained per 1g of the carbon fiber bundles, and were then washed with hot water at 90 ℃ and dried. Then, the mixture was immersed in an aqueous dispersion containing 6.0% of a sizing agent containing bisphenol A type epoxy resin as a main component. Next, the carbon fiber bundles having 1.6wt% sizing agent attached thereto were obtained by passing the carbon fiber bundles through a nip roller and then contacting the carbon fiber bundles with a roller heated to 150 ℃ for 30 seconds, thereby drying the water.

A step of averaging the carbon fiber bundles to which the sizing agent is attached. For the averaging member, a parallel rod in which two cylinders having a diameter of 5mm are arranged in parallel with a center-to-center distance of 30mm was used, and the parallel rod was arranged at right angles to the surface having the width direction of the fiber bundle. The parallel bars were adjusted in the setting angle in such a manner that the clearance between the cylinders was 0mm as seen from the traveling direction of the carbon fiber bundles. The carbon fiber bundle was twisted by 90 ° in the axial direction by the parallel rod, the width direction of the fiber bundle was set to be the vertical direction, the carbon fiber bundle was contacted with the parallel rod and passed through, and then twisted again by 90 ° by the horizontal roller, and the carbon fiber bundle was wound around 10 reels.

Various evaluations of the carbon fiber bundles thus obtained were performed. For measuring the thickness of the carbon fiber bundle, a two-dimensional laser displacement meter (manufactured by ken corporation, sensor head LJ-V7080, controller LJ-V7000) was used to simultaneously obtain thickness data for one row in the width direction of the carbon fiber bundle. The results are shown in table 1.

The thickness variation of the carbon fiber bundles was half or less, and the results were good, as compared with the comparative example in which the conventional process was not performed with parallel bars as an averaging member.

It was found that the cantilever value and the adhesiveness were lower than those of the comparative examples, and the fiber bundles were untwisted.

Since the carbon fiber bundles obtained in these examples have a small variation in the thickness of the bundles in the width direction of the bundles, a certain amount of resin can be applied to a unit amount of carbon fibers by the contact roller system, and thus the fiber content in the molded article becomes uniform.

Comparative examples 1 to 4

A carbon fiber bundle was obtained in the same manner as in example 1, except that the carbon fiber bundle was wound on 4 reels at the winding portion without performing a step of homogenizing the carbon fiber bundle after the sizing step. The results of the various evaluations are shown in table 1. The obtained carbon fiber bundles were poor in that the thickness variation rate of the carbon fiber bundles was more than 35%.

TABLE 1

Industrial applicability

Symbol description

1: driving roller

2: carbon fiber bundle

3: free roller

4: weight

5: spring balance

6: parallel bars (averaging component)

7: carbonized fiber bundle

8: sizing agent bath

9: drying machine

10: winding device

11: free roller

A: the arrangement position of the averaging member is averaged.

Claims

1. A carbon fiber bundle having a total fineness of 2g/m or more, wherein the variation rate of the thickness of the fiber bundle in the width direction of the fiber bundle is 30% or less.

2. The carbon fiber bundle according to claim 1, wherein the number of single fibers is 20000 or more.

3. The carbon fiber bundle according to claim 1 or 2, wherein the average thickness of the fiber bundle is 0.18 to 0.28mm.

4. The carbon fiber bundle according to any one of claims 1 to 3, wherein a variation rate of a width of the fiber bundle in a longitudinal direction of the fiber bundle is 13% or less.

5. The carbon fiber bundle according to any one of claims 1 to 4, wherein the width of the fiber bundle is 13 to 18mm.

6. The carbon fiber bundle according to any one of claims 1 to 5, wherein the flatness, i.e., width/average thickness of the fiber bundle is 60 to 70.

7. The carbon fiber bundle according to any one of claims 1 to 6, having a cantilever value of 210 to 250mm and an adhesion of 0.18m or less.

8. The carbon fiber bundle according to any one of claims 1 to 7, wherein the amount of the sizing agent is 0 to 20 mass%.

9. The carbon fiber bundle according to any one of claims 1 to 8, wherein the inter-fiber kinetic friction coefficient is 0.2 or less.

10. The carbon fiber bundle according to any one of claims 1 to 9, wherein a coefficient of dynamic friction between fiber metals is 0.18 or less.

11. A method of manufacturing a carbon fiber bundle, comprising: in an averaging member having two or more parallel rods arranged between a sizing agent dryer and a winder or a winding device, the rods are brought into contact with a surface A of a carbon fiber bundle and a surface B on the opposite side of the surface A, respectively, at least once, and the carbon fiber bundle is passed through the averaging member.

12. The method for producing a carbon fiber bundle according to claim 11, wherein the distance between adjacent ones of the parallel rods is 15 to 50mm.

13. The method for producing a carbon fiber bundle according to claim 11 or 12, wherein the carbon fiber bundle is contacted with the parallel rod and passed in a state in which the surface direction of the carbon fiber bundle contacted with the previous roller of the parallel rod is twisted by 90 °.

14. The method for producing a carbon fiber bundle according to any one of claims 11 to 13, wherein the carbon fiber bundle in contact with the parallel rod is passed so that a maximum width of the carbon fiber bundle in contact with the parallel rod is enlarged by 5 to 20% with respect to a width of the carbon fiber bundle in contact with a preceding roll of the parallel rod.

15. The manufacturing method according to claim 13 or 14, wherein the roll is located further upstream than the parallel bars in a traveling direction of the carbon fiber bundle, and a longitudinal direction of the roll is substantially perpendicular to a longitudinal direction of the parallel bars.

16. The manufacturing method according to any one of claims 13 to 15, wherein the distance from the center of the roll to the center of the parallel bars is preferably 200 to 1500mm, more preferably 500 to 1000mm, at the shortest position.

17. The manufacturing method of a carbon fiber bundle according to any one of claims 11 to 16, wherein in the passing, the carbon fiber bundle is flattened, and after one face a of the carbon fiber bundle is brought into contact with the parallel rod located upstream in the traveling direction of the carbon fiber bundle, the other face B of the carbon fiber bundle is brought into contact with the parallel rod located downstream in the traveling direction of the carbon fiber bundle, thereby passing the carbon fiber bundle through the averaging member.

18. The method for producing a carbon fiber bundle according to any one of claims 11 to 17, comprising: before the passing, the surface direction of the carbon fiber bundle is changed by taking the length direction of the carbon fiber bundle as an axis.

19. The production method according to claim 18, wherein when the plane direction is changed, the plane of the carbon fiber bundle is preferably inclined in a range of 30 ° to 150 ° in the width direction with the longitudinal direction of the carbon fiber bundle as an axis; more preferably, the surface of the carbon fiber bundle is inclined in the width direction by an angle of 45 ° to 135 ° with the longitudinal direction of the carbon fiber bundle as an axis; more preferably, the surface of the carbon fiber bundle is inclined in the width direction by 60 ° to 120 ° with the longitudinal direction of the carbon fiber bundle as an axis; particularly preferably, the surface of the carbon fiber bundle is inclined by approximately 90 ° in the width direction with the longitudinal direction of the carbon fiber bundle as an axis.

20. The manufacturing method according to claim 18 or 19, wherein the changing of the plane direction is performed between a roll located upstream of the two or more parallel rods and a parallel rod located most upstream of the two or more parallel rods in a traveling direction of the carbon fiber bundle.

21. The production method according to any one of claims 11 to 20, which is the production method of a carbon fiber bundle according to any one of claims 1 to 10.