JP2005264383A - Carbon fiber bundle and method for opening the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carbon fiber bundle uniformly and widely openable without varying yarn width ratio at room temperature and without applying any heat in its opening step, and to provide a method for opening the same. <P>SOLUTION: The carbon fiber bundle substantially having no twist and imparted with a sizing agent is provided. The carbon fiber bundle has the following properties: (1) drape value X2 at 25°C is 5-12 cm, (2) the ratio (X1/X2) of drape value X1 at 80°C to the drape value at 25°C is 0.8-1.1, and (3) F/F coefficient of friction is 0.10-0.28. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a carbon fiber bundle to which a sizing agent is applied, and a carbon fiber bundle that can be opened without applying heat in a fiber opening step, and a method for opening the carbon fiber bundle.

  Carbon fibers are used for a wide range of applications such as aircraft members and sports equipment as reinforcing fibers because they exhibit extremely high specific strength, specific elastic modulus, and excellent heat resistance.

  Usually, carbon fiber is used as carbon fiber reinforced plastic impregnated and molded with resin (hereinafter sometimes abbreviated as CFRP). There are various production methods for CFRP, and one of typical production methods is a production method via an intermediate substrate called a prepreg.

  The prepreg is obtained by making carbon fiber into a woven fabric or a sheet in which a plurality of carbon fibers are arranged in parallel and impregnating with a thermosetting resin. This prepreg is laminated and cured in accordance with the target shape to obtain CFRP. In the present invention, weaving carbon fibers into a woven fabric or impregnating with a resin to form a prepreg is collectively referred to as higher processing. Of the prepregs, what is impregnated with a thermosetting resin in a woven fabric is called a woven fabric prepreg, and what is impregnated with a thermosetting resin into a plurality of sheets arranged in parallel is sometimes called a unidirectional prepreg. In particular, in the present invention, the unidirectional prepreg and the fabric prepreg are simply referred to as a prepreg.

  The required properties of CFRP include a reduction in the weight of the applied member (thinning of the member). However, in the case of a molded product via a prepreg, there is a design limit to reduce the number of laminated layers, so the prepreg itself is made thin. It is necessary to make it. For this purpose, in order to reduce the overlap of fibers in the thickness direction, it is necessary to expand the individual fibers in the carbon fiber bundle as a raw material in the width direction. In the present invention, expanding the fiber bundle in the width direction is expressed as opening.

  When a prepreg is produced using carbon fibers having poor spreadability, the fibers do not spread in the width direction, so that a prepreg having poor quality in which gaps remain between the carbon fiber yarns is obtained. Since the prepreg cuts and laminates the sheet into various shapes depending on what is to be molded, the prepreg having such a gap cannot be maintained in the shape of the sheet.

  In addition, if the carbon fiber bundle with poor spreadability is forcibly opened, the carbon fiber bundle is a brittle material, so the single fiber in the fiber bundle breaks and fluffing occurs. As a result, there was a problem that the process passability deteriorated.

  As for the improvement of the opening property of the carbon fiber bundle, the opening method at the time of producing the prepreg has been conventionally studied, but many improvement studies with the sizing agent of the carbon fiber bundle have been made.

  For example, when manufacturing a prepreg by a hot melt method, it has good scratch resistance, and at the same time the prepreg has surface smoothness, so that it is a liquid, solid epoxy resin, unsaturated polyester resin, stearic acid at room temperature A sizing agent containing an ester as a component has been proposed (for example, see Patent Document 1). However, in this method, the yarn bundle can be opened in a heated state, but cannot be opened at room temperature.

  In addition, in order to satisfy the spreadability and scratch resistance during prepreg production, excellent prepreg resin impregnation, and to satisfy composite material properties, liquid and solid epoxy resins, water-soluble polyurethane resins, stearates A sizing agent containing as a component has been proposed (see, for example, Patent Document 2). This sizing agent does not require special drying heat treatment such as pressing with a heating roller, but may not be opened at room temperature due to a change in the carbon fiber substrate.

Thus, the carbon fiber bundle which can achieve favorable openability at normal temperature was not found, and the further improvement was needed.
JP-A-7-197381 Japanese Patent Laid-Open No. 9-250087

  The object of the present invention is to solve such conventional drawbacks, and the yarn width ratio does not change at room temperature, and it is possible to expand the carbon fiber bundle uniformly and greatly without applying heat in the fiber opening process. An object of the present invention is to provide a carbon fiber bundle and a method for opening the same.

The present invention employs the following means in order to solve the above problems. That is,
[1] A carbon fiber bundle characterized by substantially having no twist, being provided with a sizing agent, and having the following properties (1) to (3).

(1) The drape value X2 at 25 ° C. is 5 cm or more and 12 cm or less,
(2) The ratio (X1 / X2) of the drape value X1 at 80 ° C. and the drape value X2 at 25 ° C. is 0.8 or more and 1.1 or less,
(3) F / F friction coefficient is 0.10 or more and 0.28 or less.

  [2] The carbon fiber bundle according to [1], wherein a thread width ratio on a bobbin of the carbon fiber bundle is 0.3 to 1.0 μm / filament.

  [3] The sizing agent contains at least one selected from glycidyl ether type, glycidyl ester type, and glycidyl amine type aliphatic epoxy resins, and has a viscosity at 25 ° C. of 50 mPa.s. s to 200 mPa.s The carbon fiber bundle according to [1] or [2], which is s or less.

  [4] The carbon fiber bundle according to any one of claims 1 to 3, wherein an adhesion amount of the sizing agent is 0.1 to 3.0% by weight.

  [5] A prepreg obtained by impregnating a resin into the carbon fiber bundle according to any one of [1] to [4].

  [6] A method for opening a carbon fiber bundle in which the yarn tension when the carbon fiber bundle according to any one of [1] to [4] is drawn from a creel is 0.13 g / tex or more and 0.25 g / tex or less. .

  [7] The carbon fiber bundle according to [6], wherein the carbon fiber bundle is drawn from the creel at a pulling angle of 30 ° to 90 ° and transferred to the next step via a ring guide having a diameter of 10 mm to 80 mm. Opening method.

  The present invention provides the carbon fiber bundle with a sizing agent obtained by optimizing the drape value at 25 ° C., the drape value at 80 ° C., and the F / F friction coefficient of the carbon fiber bundle by adopting the above-mentioned means. Thus, it is possible to provide a carbon fiber bundle excellent in openability without heating.

  Hereinafter, the present invention will be described in more detail.

  In the carbon fiber bundle in the present invention, the raw material is not particularly limited, such as polyacrylonitrile, pitch or rayon, and so-called carbonaceous fiber, carbon fiber, Any graphite fiber may be used. The number of filaments in the carbon fiber bundle is preferably in the range of 3,000 to 72,000.

The present invention is a carbon fiber bundle characterized by substantially having no twist, imparting a sizing agent, and having the following characteristics (1) to (3).
(1) The drape value X2 at 25 ° C. is 5 cm or more and 12 cm or less,
(2) The ratio (X1 / X2) of the drape value X1 at 80 ° C. and the drape value X2 at 25 ° C. is 0.8 or more and 1.1 or less,
(3) F / F friction coefficient is 0.10 or more and 0.28 or less.

  In the above description, the carbon fiber bundle having substantially no twist refers to a carbon fiber bundle having no twist at all or having 0.5 turns or less per 1 m.

The drape value is a value representing the hardness of the carbon fiber bundle, and is measured by the following method. Specifically, as shown in FIG. 1 (a), a carbon fiber bundle 1 drawn out from a bobbin without applying tension is cut to a length of 40 cm, one end is fixed with a stopper tape 2, and the other end is fixed with 100 g. The weight 3 is suspended and the twist and the bend are corrected, and then left in the atmosphere at the measurement temperature for 30 minutes. Thereafter, the weight is removed and, as shown in FIG. 1 (b), the carbon fiber bundle 5 is placed so that the carbon fiber bundle 5 protrudes 25 cm from the horizontal portion from the horizontal rectangular base 4 having a corner of 90 °, and the 40 cm carbon fiber bundle does not break. After fixing the carbon fiber part on the table with the stop tape 6 while supporting it like this, remove the support from the part protruding from the table and hang it down, measure the length of the horizontal distance L from the starting point after 2 seconds, and n The average of several times was taken as the drape value. The larger the drape value, the harder the characteristic.
The drape value at 80 ° C. was the same as the method at 25 ° C. except that the ambient temperature was 80 ° C.

  When the drape value is less than 5 cm, the fiber bundle is soft, so that it is bent or twisted by a guide such as a comb for the purpose of aligning the yarn drawn from the bobbin during prepreg manufacture. If bending or twisting occurs, it is difficult to open the portion, and unevenness in opening occurs, which is not preferable. If the drape value is larger than 12 cm, the fiber bundle is hard, so that it is difficult to open the fiber. In extreme cases, a gap is formed between the aligned fiber bundles.

  Further, the ratio (X1 / X2) of the drape value X1 at 80 ° C. and the drape value X2 at 25 ° C. is preferably 0.8 or more and 1.1 or less. If X1 / X2 is less than 0.8, it is not preferable because it becomes too soft at 80 ° C., and a gap is formed in the sheet by changing the yarn width ratio when the prepreg passes through the heating process. If it is larger than 1.1, the yarn becomes hard after resin impregnation, and the handling property is lowered in the prepreg process. More preferably, it is 0.9 or more and 1.0 or less.

  The F / F friction coefficient is measured as follows. That is, as shown in FIG. 2, a winding density of 0.9 to 1.4 g / cm 3 and a wind ratio of 5 to 15 so that the thickness is uniform on the bobbin 8 fixed so as not to rotate. The same carbon fiber bundle as that of the wound product is wound around the surface of the carbon fiber bundle wound in step 3 so that the contact angle is 3π (rad) 540 ° so as not to overlap the circumference. When a weight 9 (T1) is attached to one end of the wound carbon fiber bundle, the opposite end is pulled with a spring 10 at a speed of 1 m / min, and the tension when the wound carbon fiber bundle 11 starts moving is T2. The following equation is used.

“F / F friction coefficient = ln (T2 / T1) / θ”
T2: Tension when carbon fiber starts to move (= indicated value of spring only)
T1: Weight of weight (= 0.19 g / tex)
θ: Total contact angle between the wound material and the wound yarn (= 3π rad)
The number of n is 5, and is obtained by a simple average. The measurement bobbin is used to the measurement atmosphere temperature and humidity conditions at least 2 hours before the measurement (measurement conditions: 23 ± 3 ° C./60±5%).

  When the F / F coefficient of friction exceeds 0.28, the single fiber is broken and fluff is likely to occur, and the quality of the product is deteriorated. If it is less than 0.10, the yarn spreads but the stable yarn width can be maintained. Since it is difficult, it is 0.10 or more and 0.28 or less. Preferably they are 0.15 or more and 0.25 or less.

  The carbon fiber bundle preferably has a yarn width ratio of 0.3 to 1.0 μm / filament. As shown in FIG. 3, the yarn width ratio is a value obtained by measuring a tape-like width (bobbin upper thread width) W of a carbon fiber bundle wound around a bobbin and dividing it by the number of filaments 13. .

When the yarn width ratio is less than 0.3 μm / filament, in order to expand the carbon fiber bundle, a larger tension is required, and thus fluff is likely to occur. When the yarn width ratio is larger than 1.0 μm / filament, uneven tension occurs in the width direction in the carbon fiber bundle when the yarn is pulled out, causing yarn breakage. More preferably, it is 0.5 to 0.6 μm / filament.
In order to achieve the drape value and F / F friction coefficient of the carbon fiber bundle within the target ranges, it is necessary to select a sizing agent.

  The component of the sizing agent desirably contains at least one selected from glycidyl ether type, glycidyl ester type, and glycidyl amine type aliphatic epoxy resins. The glycidyl ether type may include polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and the like.

  As other components of the sizing agent, an ether component and an ester component may be contained in an amount of 1 to 20%. Specifically, the ether component is polyoxyalkylene (POA) tristyrenated phenyl ether, polyoxyalkylene (POA) tribenzylated phenyl ether, polyoxyalkylene (POA) pentabenzylated phenyl ether, polyoxyalkylene (POA) alkyl ether. , Polyoxyethylene (POE) bisphenol A type, propylene oxide / ethylene oxide (PO / EO), and the like. The ester component is pentaerythritolate, polyoxyethylene (POE) hardened castor oil maleyl stearate, polyoxyethylene (POE) lauryl ester, octyl oleate, stearyl laurate, oleyl oleate, bisphenol A type (BPA) adipirlau Rate and the like.

  The viscosity of the sizing agent at 25 ° C. was measured with a Tokimec E-type viscometer (VISCONIC ED type). Moreover, as a sampling method of the sizing agent stock solution, about 500 g of the sizing agent was collected, put into a beaker, and water was completely evaporated using a hot plate at 100 ° C. for 6 hours.

  The viscosity at 25 ° C. is 50 mPa.s. s to 200 mPa.s It is desirable that it is s or less. Viscosity is 50 mPa.s. If it is less than s, the carbon fiber bundle after sizing is easily scattered and fluff is likely to occur. 200 mPa.s. If it exceeds s, the drape value after sizing is 12 cm or more, and the drape value ratio (X1 / X2) is less than 0.8, making it difficult to open and spreading.

  The adhesion amount of the sizing agent is preferably 0.1 to 3.0% by weight. If the amount of adhesion is less than 0.1%, the yarn is easily sprinkled, which causes fluffing. If it is higher than 3.0%, the yarn becomes hard at room temperature, and the unwinding property further deteriorates. More preferably, it is 1.5 to 2.0% by weight.

The carbon fiber is impregnated with a resin and used as a reinforcing material for a molded composite material. The matrix resin can be used as both a thermosetting resin and a thermoplastic resin. Among these, an epoxy resin is preferable from the viewpoint of the strength of the composite material. Specifically, bisphenol A type epoxy resin, bisphenol F type epoxy resin, naphthalene type epoxy resin, fluorene type epoxy resin, glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, phenol novolac type epoxy resin Etc.
As a method for achieving the yarn width ratio of the carbon fiber bundle, for example, a method of pressing against a heated drum drive in the drying step after sizing is given. Specifically, after applying the sizing agent, it can be achieved by contacting the drum at a surface temperature of 100 to 160 ° C. with a surface pressure of 2 to 4 kg and a contact time of 2 to 8 seconds. As other methods, there are a method of opening by blowing hot air and a method of directly vibrating and opening the carbon fiber bundle, but here, a method of contacting with a heated drum drive is desirable.

  As shown in FIG. 4, the tension when pulling out the carbon fiber bundle 14 from the creel is preferably 0.13 g / tex or more and 0.25 g / tex or less, more preferably 0.15 g / tex or more and 0.20 g / tex or less. is there. If it is less than 0.13 g / tex, the friction is low in the step of opening with a metal guide or the like and the spreadability becomes insufficient. If it exceeds 0.25 g / tex, the friction becomes high and fluff is generated.

  The pulling angle θ when pulling out the carbon fiber bundle from the creel is preferably 30 ° or more and 90 ° or less, and is preferably supplied to the next step via the ring guide 16 having a diameter of 10 mm or more and 80 mm or less. More preferably, it is 45 ° or more and 90 ° or less. If the pulling angle is less than 30 °, yarn breakage may occur when pulling out the carbon fiber bundle. When the carbon fiber bundle is pulled out, a gap is formed between the yarn and the yarn. Further, even if the diameter of the ring guide b is less than 10 mm, the folding may occur, and when the carbon fiber bundle is aligned, a gap is formed between the yarns. On the other hand, when the diameter exceeds 80 mm, when the carbon fiber bundles are aligned, the running position is not stable, which causes a gap between the yarns. Note that the thread pulling angle θ for bobbin traverse varies from 30 to 90 ° depending on the location.

Hereinafter, the present invention will be described more specifically with reference to examples. The carbon fiber used in the examples was a PAN-based carbon fiber having 12,000 filaments that has substantially no twist.
In addition, the measuring method in an Example is as follows.

(1) Drape value (cm)
As shown in FIG. 1 (a), a carbon fiber bundle 1 drawn out from a bobbin without applying tension is cut to a length of 40 cm, one end is fixed with a stop tape 2, and a 100 g weight 3 is suspended at the other end. After correcting the twist and the bend, it is left for 30 minutes in the atmosphere of the measurement temperature. Next, the weight is removed and, as shown in FIG. 1 (b), the carbon fiber bundle 5 is placed so that the carbon fiber bundle 5 protrudes 25 cm from the horizontal rectangular base 4 having a corner of 90 ° so that the 40 cm carbon fiber bundle does not break. After fixing the carbon fiber part on the table with the stop tape 6 while supporting, remove the support of the part protruding from the table and let it hang down. After 2 seconds, measure the length of the horizontal distance L from the starting point, n number 3 The average of the times was taken as the drape value. The drape value at 80 ° C. was the same as the method at 25 ° C. except that the ambient temperature was 80 ° C.

(2) Sizing adhesion amount After weighing (W1) about 2 g of carbon fiber bundle, it was left in an electric furnace (capacity 120 cm ³ ) set at a temperature of 450 ° C. for 15 minutes in a nitrogen stream of 50 liters / minute, and a sizing agent Was completely pyrolyzed. And it moved to the container in the dry nitrogen stream of 20 liter / min, and the carbon fiber bundle after cooling for 15 minutes was weighed (W2), and the sizing adhesion amount was calculated | required from following Formula.
Sizing adhesion amount (%) = [W1 (g) −W2 (g)] / [W1 (g)] × 100
(3) Spread width Metal satin guide (cylinder with a diameter of 20 mm, surface roughness Rmax is 3S) (the surface roughness referred to here is arithmetic average roughness measured by JIS B0601) 17-20 in FIG. As shown in the figure, four carbon fiber bundles 22 are alternately arranged via the ring guide 21 so that the contact angle with all the guides becomes 720 ° in total, and the driving roller (speed 4 m / min, pulling tension = 120 g). / St), the carbon fiber bundle was pulled out. The width of the carbon fiber bundle on the final guide 17 was measured with calipers every 5 seconds for a total of 100 points, and the average was taken as the spread width.

(4) F / F friction coefficient As shown in FIG. 2, the winding density is 0.9 to 1.4 g / cm ³ , so that the thickness is uniform on the bobbin 8 fixed so as not to rotate. The same carbon fiber bundle as that of the wound product is wound around the surface of the carbon fiber bundle wound at a wind ratio of 5 to 15 so as not to overlap the circumference so that the contact angle is 3π (rad) 540 °. When a weight 9 (T1) is attached to one end of the wound carbon fiber bundle, the opposite end is pulled with a spring 10 at a speed of 1 m / min, and the tension when the wound carbon fiber bundle 11 starts moving is T2. The following equation is used.

“F / F friction coefficient = ln (T2 / T1) / θ”
T2: Tension when carbon fiber starts to move (= indicated value of spring only)
T1: Weight of weight (= 0.19 g / tex)
θ: Total contact angle between the wound material and the wound yarn (= 3π rad)
The number of n is 5, and is obtained by a simple average. The measurement bobbin is used to the measurement atmosphere temperature and humidity conditions at least 2 hours before the measurement (measurement conditions: 23 ± 3 ° C./60±5%).

(5) Viscosity The viscosity of the sizing agent at 25 ° C. was measured with an E-type viscometer (VISCONIC ED type) manufactured by Tokimec Corporation. Moreover, as a sampling method of the sizing agent stock solution, about 500 g of the sizing agent was collected, put into a beaker, and water was completely evaporated using a hot plate at 100 ° C. for 6 hours.

(6) A unidirectional prepreg sheet is produced by a method of prepreg quality or less, and the presence or absence of a gap between carbon fiber yarns in the prepreg sheet is confirmed.
○: No gap between carbon fiber yarns △: There is a gap between carbon fiber yarns, but there is no gap with a length of 50 mm or more (no problem in handling)
X: Evaluation was made in three stages, ie, there was a gap exceeding 50 mm in length and there was a problem in handling.

<Preparation of prepreg>
Epicoat (registered trademark) 1001 (manufactured by Japan Epoxy Resin Co., Ltd., bisphenol A type epoxy resin, bifunctional, epoxy equivalent 450-500), 40 parts, Epicoat (registered trademark) 828 (registered trademark, manufactured by Japan Epoxy Resin Co., Ltd.) 30 parts of bisphenol A type epoxy resin, bifunctional, epoxy equivalent of 184 to 194), 30 of Epicoat (registered trademark) 154 (registered trademark, manufactured by Japan Epoxy Resin Co., Ltd., phenol novolac type epoxy resin, epoxy equivalent of 176 to 180) Parts, Denka Formal (registered trademark) # 20 (manufactured by Denki Kagaku Kogyo Co., Ltd., polyvinyl formal resin) 3 parts by weight Further, as a curing agent, 4 parts of DICY7 (registered trademark, manufactured by Japan Epoxy Resin Co., Ltd., dicyandiamide) Registered trademark An epoxy resin composition mixed with 4 parts of 3- (3,4-dichlorophenyl) -1,1-dimethylurea) manufactured by Kaya Chemical Industry Co., Ltd. was applied onto release paper using a reverse roll coater, and resin A film was prepared.

Next, the carbon fiber bundles are pulled out under the pulling conditions in the examples and comparative examples in the table (the distance of the center of the ring guide through which each bobbin passes 15 mm), aligned in one direction, and two produced resin films are aligned. The carbon fiber bundles are overlapped so as to be sandwiched from both sides, and the carbon fiber bundle is impregnated with resin while being pressed with a heating nip roll, and a unidirectional prepreg sheet (fiber basis weight: 75 g / m ² , fiber content: 76% by weight) is obtained. Obtained.

(Example 1)
An aqueous sizing agent of 100% polyethylene glycol diglycidyl ether (molecular weight = 510) was added to the carbon fiber bundle by 1.7% by weight. In the present invention, the dip type was used as the method for attaching the sizing agent for the carbon fiber bundle to the carbon fiber bundle. After applying the sizing agent, the carbon fiber bundle was taped for 3 seconds on a drum drive heated to 150 ° C. in order to finish it into a tape shape. After that, the temperature in the drying process for completely dispersing the organic solvent or water in which the sizing agent is dissolved is dried at 200 ° C. to 250 ° C. for 1 minute, and then applied to the bobbin with a tension of 500 g / st without twisting. Winded up.

(Example 2)
An aqueous sizing agent of 100% polyglycerin polyglycidyl ether (molecular weight = 670) was added to the carbon fiber bundle by 1.0% by weight.

(Example 3)
A mixed water sizing agent of 90% component of polyethylene glycol diglycidyl ether (molecular weight = 510) and 10% component of polypropylene glycol diglycidyl ether (molecular weight = 650) was added to the carbon fiber bundle by 1.0% by weight.

(Comparative Example 1)
In the same application method as in the examples, 40% component of bisphenol A type epoxy resin (molecular weight = 370), 40% component of bisphenol A type ethylene oxide maleate ester (molecular weight = 2500) as unsaturated ester resin, and 20% emulsifier An SZ agent as a component was added to the carbon fiber bundle by 1.0% by weight.

(Comparative Example 2)
0.2% by weight of a sizing agent using a bisphenol A-type ethylene oxide adduct (molecular weight = 1020) was applied to the carbon fiber bundle by the same application method as in the examples.

Example 4
The same sizing agent as in Example 1 was applied to a carbon fiber bundle in an amount of 1.5% by weight, and a bobbin thread width ratio of 0.25 μm / filament was used.

(Example 5)
The same sizing agent as in Example 1 was added to the carbon fiber bundle by 1.5% by weight, and the yarn tension when being pulled out from the creel was 0.10 g / tex.

(Example 6)
The same sizing agent as in Example 1 was added to the carbon fiber bundle by 1.5% by weight, and the pulling angle when pulling from the creel was 20 °.

(Example 7)
The same sizing agent as in Example 1 was applied to the carbon fiber bundle by 1.5% by weight, and when it was pulled out from the creel, it was passed through a ring guide having a diameter of 100 mm.

As can be seen from Table 1, Examples 1, 2, and 3 can produce a thin prepreg of good quality having a good spread width (12.5 mm or more) and no gap between carbon fiber yarns. did it.
In Examples 4, 5, 6, and 7, there were gaps between the carbon fiber yarns, but they were all gaps of 50 mm or less, and a prepreg having no problem in handling was obtained.
On the other hand, in Comparative Examples 1 and 2, the spread width of the carbon fiber was small, and there were many gaps with a length exceeding 50 mm, resulting in prepregs with poor handling properties.

It is a conceptual diagram which shows the measuring method of a drape value. It is a conceptual diagram which shows the measuring method of F / F friction coefficient. It is a conceptual diagram which shows the measuring method of a yarn width ratio. It is a conceptual diagram which shows the angle which pulls out a thread | yarn from a creel. It is a conceptual diagram which shows the measuring method of an expansion width.

Explanation of symbols

1: Carbon fiber bundle 2: Stopping tape 3: Weight 4: Horizontal rectangular base 5: Carbon fiber bundle 6: Stopping tape L: Horizontal distance from start point 8: Bobbin fixed so as not to rotate 9: Weight 10: Spring only 11: Carbon fiber bundle W: Tape-like width 13: Number of filaments 14: Carbon fiber bundle θ: Lead angle 16: Ring guide 17: Metal pear (finally fixed) guide 18: Metal pear (fixed) guide 19: Metal Satin (fixed) guide 20: Metal satin (fixed) guide 21: Ring guide 22: Carbon fiber bundle

Claims (7)

A carbon fiber bundle that has substantially no twist, is provided with a sizing agent, and has the following characteristics (1) to (3).
(1) The drape value X2 at 25 ° C. is 5 cm or more and 12 cm or less,
(2) The ratio (X1 / X2) of the drape value X1 at 80 ° C. and the drape value X2 at 25 ° C. is 0.8 or more and 1.1 or less,
(3) F / F friction coefficient is 0.10 or more and 0.28 or less   The carbon fiber bundle according to claim 1, wherein a yarn width ratio on a bobbin of the carbon fiber bundle is 0.3 to 1.0 µm / filament.   The sizing agent includes at least one selected from glycidyl ether type, glycidyl ester type, and glycidyl amine type aliphatic epoxy resins, and has a viscosity at 25 ° C. of 50 mPa.s. s to 200 mPa.s The carbon fiber bundle according to claim 1 or 2, which is s or less.   The carbon fiber bundle according to any one of claims 1 to 3, wherein an adhesion amount of the sizing agent is 0.1 to 3.0% by weight.   A prepreg obtained by impregnating a resin into the carbon fiber bundle according to claim 1.   A method for opening a carbon fiber bundle, wherein the yarn tension when the carbon fiber bundle according to any one of claims 1 to 4 is drawn from a creel is 0.13 g / tex or more and 0.25 g / tex or less.   The method for opening a carbon fiber bundle according to claim 6, wherein the carbon fiber bundle is drawn from the creel at a pulling angle of 30 ° to 90 ° and transferred to the next step via a ring guide having a diameter of 10 mm to 80 mm. .

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