JP5741836B2 - Unidirectional reinforced fabric and method for producing the same, prepreg and carbon fiber composite material using the same - Google Patents

Description

  The present invention relates to a unidirectional reinforcing fabric formed using a carbon fiber bundle, a method for producing a unidirectional reinforcing fabric using a carbon fiber bundle, a prepreg using the unidirectional reinforcing fabric, and a carbon fiber composite material.

  Carbon fiber composites are very useful in earth building applications such as bridge piers and tunnel reinforcements. In particular, a carbon fiber composite material in which a carbon fiber as a warp is combined with a resin and a unidirectionally reinforced fabric in which carbon fibers are constrained by a weft is widely used in earthwork applications, and further improvement in performance is required.

  In general, to improve the performance of carbon fiber composite materials, it is necessary to maintain the linearity of the carbon fibers in the carbon fiber composite material in addition to improving the performance of the carbon fiber itself and optimizing the interface between the carbon fiber and the resin. It is. However, in an earthenware application, since carbon fiber is impregnated manually with a resin to form a prepreg and further cured, it is not in an environment where the linearity of the carbon fiber can be sufficiently maintained. Therefore, the device which maintains the linearity of carbon fiber has been made regardless of the working environment.

  For example, in Patent Document 1, in a woven fabric having a plain weave structure in which a carbon fiber bundle is a warp and a weft, by flattening the carbon fiber bundle, in a cross section perpendicular to the width direction of the fiber bundle that is the warp, A method is described in which the angle representing the disturbance of the linearity of the warp is set to 1 degree or less.

Japanese Patent No. 3279048

  However, Patent Document 1 only defines the linearity of carbon fibers in a cross section perpendicular to the width direction of the carbon fiber bundle of a flat carbon fiber bundle fabric, and when the fabric surface is viewed from above. The linearity of carbon fiber is not specified. In order to spread and impregnate the resin in the carbon fiber bundle fabric manually, there is generally an operation of pressing a brush or a roll against the fabric surface and sliding it. By this operation, the linearity of the carbon fiber when the fabric surface is viewed from above may be lowered, which may lead to a decrease in physical properties.

  The present invention has been made in view of the above circumstances, and is a unidirectional reinforced fabric formed using a carbon fiber bundle, and the fabric loses its shape even in various molding processing environments such as resin impregnation operations. An object of the present invention is to provide a unidirectionally reinforced fabric that is difficult to maintain the linearity of carbon fibers in the woven fabric, a method for producing the same, a prepreg using the unidirectionally reinforced fabric, and a carbon fiber composite material.

The present invention includes the following [1] to [8].
[1] A unidirectional reinforced fabric comprising warp yarns composed of carbon fiber bundles and weft yarns that restrain the warp yarns, satisfying the following conditions (a), (b), and (d), and satisfying the following conditions c-1 and / or h A unidirectional reinforced fabric satisfying 2.
Condition A: The basis weight of the unidirectional reinforcing fabric is 100 g / m ² or more and 500 g / m ² or less.
Condition b: The cantilever value of the unidirectional reinforced fabric measured by the following measuring method (b) is 170 mm or more.
Condition C-1: The degree of orientation of single fibers in the carbon fiber bundle constituting the unidirectional reinforced fabric measured by the following measurement method (C-1) is 91% or more.
Condition C-2: In a cured product of a unidirectionally reinforced fabric and a resin measured by the following measurement method (C-2), the degree of orientation of the single fiber in the carbon fiber bundle constituting the cured product is 91% or more. is there.
Condition d: The roundness of the cross section of the single fiber in the carbon fiber bundle constituting the unidirectional reinforced fabric measured by the following measuring method (d) is 92% or less.

[Measurement method (b)]
(Procedure 1) A test piece having a size of 40 cm in the warp fiber axis direction and 1 inch in the direction perpendicular to the warp fiber axis is cut out from the unidirectional reinforcing fabric.
(Procedure 2) Place the test piece on the horizontal plane of a measuring table having a horizontal plane and a slope with an inclination angle of 45 degrees inclined downward from one end of the horizontal plane. Align with the boundary line A between the slope and the horizontal plane. A pressing plate is placed on the test piece, and the end of the pressing plate is aligned with the boundary line A.
(Procedure 3) Next, the pressing plate is moved in the horizontal direction toward the slope at a speed of 2 cm / second, and the movement of the pressing plate is stopped when the end of the test piece comes into contact with the slope.
(Procedure 4) The moving distance of the pressing plate is the cantilever value of the unidirectional reinforced fabric.

[Measurement method (C-1)]
(Procedure 1) A test piece having a side of 11.2 cm is cut out from the unidirectional reinforcing fabric.
(Procedure 2) An observation image of the test piece is obtained using an optical microscope. The observation direction is a direction perpendicular to the surface of the unidirectional reinforcing fabric, the observation magnification is 50 times, and the observation place is a carbon fiber bundle portion near the weft.
(Procedure 3) A two-dimensional Fourier transform is performed on the observed image to obtain a transformed image.
(Procedure 4) In the converted image, luminance information at a constant radius from the origin is acquired in the circumferential direction, and a one-dimensional profile is obtained with the horizontal axis representing the angle and the vertical axis representing the luminance information. The constant radius is a length corresponding to a period of 20 μm in the observation image.
(Procedure 5) In the one-dimensional profile, two peaks derived from the period of the carbon fiber are at positions different by 180 degrees in angle. If the peak is divided by 0 degrees or 360 degrees in angle, this is not recognized as a peak. An analysis target peak is an arbitrary peak for two peaks and a peak for one peak.
(Procedure 6) The analysis target peak is fitted with a composite curve of a Gaussian function and a Lorentz function, and the half width of the obtained composite curve is obtained. The half width is a difference θ2−θ1 between the angle θ1 on the low angle side and the angle θ2 on the wide angle side, which is half the peak height of the composite curve.
(Procedure 7) The degree of orientation is obtained from the following formula (1-1) using the half width.
Degree of orientation [%] = (180−half width) / 180 × 100 Formula (1-1)

[Measurement method (C-2)]
(Procedure 1) A test piece having a side of 11.2 cm is cut out from the unidirectional reinforcing fabric.
(Procedure 2) Two square release films each having a side of 20 cm and having a release treatment on at least one side are prepared.
(Procedure 3) Place one sheet of the release film with the release treatment surface facing upward, drop 3 g of epoxy resin on the center, and place the test piece obtained in Procedure 1 on this. . Next, 3 g of an epoxy resin is dropped on the center of the test piece, and another release film is placed on the test piece so that the release treatment surface faces down to obtain a laminate. Next, a glass plate having a size of 21 cm × 23 cm × 4 mm and a weight of 0.6 kg was placed on the laminate and allowed to stand for 3 minutes, and then the bottom of the glass plate was a square having a size of 11 cm × 12 cm. The epoxy resin is cured by placing a weight of 10.5 kg and allowing to stand for 5 days. Thereafter, the weight and the glass plate are removed, and the two release films are peeled off to obtain a unidirectional reinforced fabric resin cured product in which the unidirectional reinforced fabric test piece and the epoxy resin cured product are integrated. As the epoxy resin in this procedure, Bond E2500S (product name, main agent / curing agent = 2/1 (mass ratio)) manufactured by Konishi Co., Ltd. is used.
(Procedure 4) An evaluation object region is provided at the center of the obtained unidirectional reinforced fabric resin cured product. The evaluation target region is a square having a side of 4 cm so that the two sides are parallel to the fiber axis direction. Using the optical microscope, the said evaluation object area | region is observed from a perpendicular | vertical direction with respect to the surface of a unidirectional reinforced textile resin cured | curing material, and an observation image is obtained. The observation conditions are an observation magnification of 50 times, a slanted illumination, and a dark field, and the observation place is a carbon fiber bundle portion near the weft.
(Procedure 5) Hereinafter, the degree of orientation is determined in the same manner as in Procedures 3 to 7 in the measurement method (C-1).

[Measurement method (d)]
(Procedure 1) A unidirectional reinforced fabric is impregnated with a resin and cured to obtain a cured product.
(Procedure 2) A polished surface having a cross section perpendicular to the fiber axis of the carbon fiber bundle of the cured product is obtained.
(Procedure 3) The polished surface is observed with a microscope from a direction perpendicular to the polished surface to obtain an observation image of a single fiber cross section.
(Procedure 4) The minimum ferret diameter and the maximum ferret diameter of the cross section of the single fiber are obtained from the observed image.
(Procedure 5) The roundness of the cross section of the single fiber is obtained from the minimum ferret diameter and the maximum ferret diameter using the following equation (1-2).
Roundness [%] = minimum ferret diameter / maximum ferret diameter × 100 Formula (1-2)

[2] The unidirectional reinforcing fabric according to [1], wherein the carbon fiber bundle is a carbon fiber bundle to which the following carbon fiber sizing agent is attached.
An ester of an epoxy compound having a plurality of epoxy groups in the molecule and an unsaturated monobasic acid, the compound having at least one epoxy group in the molecule (A);
A bifunctional urethane acrylate oligomer (B) having a tensile elongation of the cured product of 40% or more;
Containing one or more thermoplastic resins (C) selected from the group consisting of a styrene elastomer resin (C-1), a phenoxy resin (C-2), and a terpene resin (C-3);
The ratio (mass ratio) of the content of the compound (A) and the urethane acrylate oligomer (B) is within the range of urethane acrylate oligomer (B) / compound (A) = 1/3 to 2/1.
The ratio of the total amount of the compound (A) and the urethane acrylate oligomer (B) in all sizing components is 18% by mass or more, and the ratio of the thermoplastic resin (C) in all sizing components is 5%. Carbon fiber sizing agent in a range of ˜40 mass%.

[3] The carbon fiber sizing agent further includes an ester compound (D) of an alkylene oxide adduct of bisphenols and a dicarboxylic acid compound, the acid value of which is 50 or more, and the ester compound The unidirectionally reinforced fabric of [2], wherein the content of (D) is 2.0 mass times or less of the total amount of the compound (A) and the urethane acrylate oligomer (B).

[4] The unidirectional reinforcing fabric according to any one of [1] to [3], wherein a cantilever value of the carbon fiber bundle measured by the following measurement method (e) is 200 mm or more.
[Measurement method (e)]
(Procedure 1) A test carbon fiber bundle having a length of 40 cm is cut out from the carbon fiber bundle.
(Procedure 2) The test carbon fiber bundle is placed on the horizontal plane of a measuring table having a horizontal plane and a slope with an inclination angle of 45 degrees inclined downward from one end of the horizontal plane. The end of the fiber bundle is aligned with the boundary line A between the slope and the horizontal plane. A pressing plate is placed on the test carbon fiber bundle, and the end of the pressing plate is aligned with the boundary line A.
(Procedure 3) Next, the presser plate is moved in the horizontal direction toward the slope at a speed of 2 cm / second, and the movement of the presser plate is stopped when the end of the test carbon fiber bundle comes into contact with the slope.
(Procedure 4) The moving distance of the pressing plate in the procedure 3 is a numerical value x.
(Procedure 5) Next, the test carbon fiber bundle is turned upside down and the positions of both ends are reversed, and the moving distance y is obtained in the same procedure as in Procedures 2 to 4.
(Procedure 6) The average value of the numerical value x and the numerical value y is set as the cantilever value of the carbon fiber bundle.

[5] A prepreg obtained by impregnating the unidirectional reinforced fabric according to any one of [1] to [4] with a resin.
[6] A carbon fiber composite material obtained by curing the prepreg of [5].

[7] A unidirectional reinforcing woven fabric having a weight per unit area of 200 g / m ² consisting of a warp consisting of a carbon fiber bundle and a weft binding the warp is manufactured, and the obtained unidirectional reinforcing woven fabric has the following conditions When the following conditions C-1 and / or C-2 are satisfied, the basis weight is 100 g / m ² or more and 500 g by adjusting the fiber density of the warp yarn in the production conditions where the unidirectional reinforced fabric is obtained. / m ² to produce the following unidirectional reinforcing fabric manufacturing method of the unidirectional reinforcing fabric.
Condition b: The cantilever value of the unidirectionally reinforced fabric measured by the measurement method (b) is 170 mm or more.
Condition C-1: The degree of orientation of the single fibers in the carbon fiber bundle constituting the unidirectional reinforced fabric measured by the measurement method (C-1) is 91% or more.
Condition C-2: In the cured product of the unidirectionally reinforced fabric and the resin measured by the above measurement method (C-2), the degree of orientation of the single fiber in the carbon fiber bundle constituting the cured product is 91% or more. is there.
Condition d: The roundness of the cross section of the single fiber in the carbon fiber bundle constituting the unidirectional reinforced fabric measured by the measurement method (d) is 92% or less.

[8] The method for producing a unidirectional reinforced fabric according to [7], wherein a cantilever value of the carbon fiber bundle measured by the measurement method (e) is 200 mm or more.

The unidirectional reinforced fabric of the present invention is a unidirectional reinforced fabric formed using carbon fiber bundles, and is less likely to lose its shape even in various working environments such as resin impregnation operations. The linearity of the carbon fiber is kept good.
According to the method for producing a unidirectional reinforced fabric of the present invention, a unidirectional reinforced fabric formed using a carbon fiber bundle, and the woven fabric loses its shape even in various working environments such as a resin impregnation operation. A unidirectional reinforced fabric that is less likely to occur and that maintains the linearity of the carbon fibers in the fabric is obtained.
The prepreg of the present invention is excellent in carbon fiber linearity.
The carbon fiber composite material of the present invention is excellent in carbon fiber linearity.

It is a figure for demonstrating the measuring method of the cantilever value of a unidirectional reinforcement fabric. It is a figure for demonstrating the measuring method of the orientation degree of the single fiber in the carbon fiber bundle in the hardened | cured material of a unidirectional reinforcement fabric and resin. It is a figure for demonstrating the measuring method of the orientation degree of the single fiber in the carbon fiber bundle in the hardened | cured material of a unidirectional reinforcement fabric and resin. It is a figure for demonstrating the measuring method of the orientation degree of the single fiber in the carbon fiber bundle in the hardened | cured material of a unidirectional reinforcement fabric and resin. It is a figure for demonstrating the measuring method of the orientation degree of the single fiber in a carbon fiber bundle.

<One-way reinforced fabric>
The unidirectional reinforcing fabric of the present invention is composed of warp yarns composed of carbon fiber bundles and weft yarns for restraining the warp yarns. “One-way reinforcement” means that carbon fiber bundles that are reinforcing fibers are arranged in one direction. The term “weft yarn that restrains the warp yarn” means that the movement of the warp yarn is restricted by the weft yarn so that the carbon fiber bundle that is the warp yarn does not come apart and does not move in the radial direction of the bundle.
The carbon fiber constituting the carbon fiber bundle which is the warp may be obtained from any raw material such as pitch, rayon, polyacrylonitrile, etc., high strength type (low elastic modulus carbon fiber), medium high elasticity carbon Either fiber or ultrahigh elasticity carbon fiber may be used.
The carbon fiber bundle is preferably a carbon fiber bundle to which a sizing agent is attached (hereinafter also referred to as a sizing-treated carbon fiber bundle).

The weft is not particularly limited as long as the carbon fiber bundle that is the warp can be constrained, but it is preferable to use a heat-bonded fiber that can melt a part of the component by heating and can be firmly bonded to the warp.
As the heat-fusible fiber, a fiber that melts at a temperature higher than room temperature (heat-fusing temperature) and exhibits adhesiveness, a fiber in which a substance exhibiting heat-fusible property is adhered to the surface, and a heat-fusible fiber and fusible Examples thereof include twisted yarn with fibers not shown.
Specific examples of heat-bonding fibers include fibers made of a resin that exhibits heat-fusibility, such as polyethylene, polyester, polypropylene, and nylon; fibers obtained by easily fusing these fibers; and fusibility of glass fibers and the like. Examples thereof include fibers in which a resin exhibiting such heat-fusibility is attached to the surface of a non-fiber, such as twisted yarns of glass fibers and heat-fusible fibers.
When the weft is a heat-sealed fiber, the warp yarns made of carbon fiber bundles are aligned in one direction, the heat-bonded fibers are arranged at intervals in the direction perpendicular to this, and the warp yarn is A unidirectional reinforced fabric constrained by the weft is obtained. The method of arranging the weft may be a method of weaving using a loom with the carbon fiber bundle as the warp and the heat fusion fiber as the weft, or simply placing the heat fusion fiber on the surface of the carbon fiber bundle.

[Condition I: Fabric weight]
The basis weight of the unidirectional reinforcing fabric can be adjusted by the fiber density of the warp. Moreover, it changes also with the number of filaments of the carbon fiber bundle which is a warp, and the density of carbon fiber. If the basis weight is small, it is necessary to increase the number of laminated unidirectional reinforcing fabrics when used as a carbon fiber composite material, which increases labor. On the other hand, if the basis weight is large, the thickness of the unidirectionally reinforced fabric increases and the handleability decreases. Therefore, the basis weight is preferably 100 to 500 g / m ² . Further, when the carbon fiber composite material of resin-impregnated unidirectional reinforcing fabric, in that easy good impregnation property can be obtained in the resin is preferably ^{100~500g / m 2, 200~300g / m} 2 is More preferred.

[Condition B: Cantilever value of unidirectional reinforced fabric]
The cantilever value of the unidirectional reinforced fabric in the present invention is a value obtained by the following measurement method, and is an index representing the bending resistance of the unidirectional reinforced fabric. It shows that rigidity is so high that this value is large. In the present invention, the cantilever value of the unidirectional reinforcing fabric is set to 170 mm or more. Preferably it is 175 mm or more.
When the cantilever value of the unidirectionally reinforced fabric is 170 mm or more, the shape of the fabric is not easily lost even in various working environments such as a resin impregnation operation. For example, regardless of the working environment when a unidirectionally reinforced fabric is impregnated with a resin to obtain a carbon fiber composite material, it is possible to obtain a carbon fiber composite material in which the linearity of the carbon fibers is easily maintained and the physical properties are excellent.
The upper limit of the cantilever value is not particularly limited, but the object to be reinforced is not limited to a flat surface, and may have a curved surface or a bent portion. Is more preferable.
The cantilever value of the unidirectionally reinforced fabric is increased by using a sizing carbon fiber bundle as the warp and can be adjusted by changing the composition of the sizing agent. Moreover, it changes also with the fabric weight of a unidirectional reinforcement fabric, and the adhesion amount of a sizing agent.
As the sizing agent, a sizing agent for carbon fiber described later is preferably used.

[Cantilever value of carbon fiber bundle]
Further, when a carbon fiber bundle that is a warp yarn has a cantilever value of a carbon fiber bundle obtained by the following measurement method of 200 mm or more, the cantilever value of the unidirectional reinforcing fabric is likely to be 170 mm or more. The cantilever value of the carbon fiber bundle is preferably 220 mm or more. The upper limit of the cantilever value of the carbon fiber bundle is not particularly limited, but is preferably 700 mm or less and more preferably 500 mm or less from the viewpoint of avoiding troubles in the process of producing the carbon fiber bundle.
The cantilever value of the carbon fiber bundle is increased by attaching a sizing agent to the carbon fiber bundle, and can be adjusted by changing the composition of the sizing agent. As the sizing agent, a sizing agent for carbon fiber described later is preferably used.
When a sizing-treated carbon fiber bundle is used as the warp, the cantilever value of the carbon fiber bundle in the present invention is a measured value for the carbon fiber after the sizing agent is attached.

[Condition C: Degree of orientation of single fiber in carbon fiber bundle]
The unidirectional reinforcing fabric of the present invention satisfies at least one of the following (Condition C-1) or (Condition C-2). Both may be satisfied.
(Condition C-1) The degree of orientation of the single fiber in the carbon fiber bundle constituting the unidirectional reinforced fabric measured by the following measurement method is 91% or more.
It shows that the linearity of the carbon fiber in a unidirectional reinforcement fabric is so high that the orientation degree of this condition is high. When a unidirectional reinforcing fabric having an orientation degree of 91% or more is impregnated with a resin to obtain a carbon fiber composite material, a carbon fiber composite material having high carbon fiber linearity and excellent physical properties can be obtained.

(Condition C-2) About the cured product of the unidirectionally reinforced fabric and the resin, the degree of orientation of the single fiber in the carbon fiber bundle constituting the cured product, measured by the following measurement method, is 91% or more.
The higher the degree of orientation in this condition, the higher the linearity of carbon fibers in a cured product obtained by impregnating a unidirectionally reinforced fabric with a resin and curing it. As shown in the examples described later, the degree of single fiber orientation in the cured product is equal to or lower than the degree of single fiber orientation (condition C-1) in the unidirectional reinforcing fabric before impregnation with the resin. Therefore, when a carbon fiber composite material is produced using a unidirectional reinforced fabric such that the degree of orientation under these conditions is 91% or more, a carbon fiber composite material having high linearity of carbon fibers and excellent physical properties can be obtained.

  The degree of orientation in (Condition C-1) or the degree of orientation in (Condition C-2) can vary depending on the type of carbon fiber bundles that are warp yarns, the type of weft yarns, and the production conditions of the unidirectional reinforcing fabric. Examples of methods for increasing the degree of orientation include, for example, a method of selecting both materials so that the tensile elastic modulus of the weft yarn is lower than the strand elastic modulus of the warp yarn, and a carbon fiber bundle using a carbon fiber sizing agent described later. And the like, and the like.

[Condition D: Roundness of single fiber cross section]
In the present invention, the roundness of the cross section of the single fiber in the carbon fiber bundle constituting the unidirectional reinforcing fabric is a value obtained by the following measuring method.
The closer the roundness is to 100%, that is, the closer the cross section of the single fiber is to a perfect circle, the higher the convergence of the carbon fiber bundle and the lower the resin impregnation property. When the resin impregnation property of the carbon fiber bundle is low, when the prepreg obtained by impregnating the unidirectionally reinforced fabric with the resin is cured to form a carbon fiber composite material, the physical properties of the carbon fiber composite material are likely to deteriorate. Therefore, the roundness is preferably 95% or less, and more preferably 92% or less.
The roundness of the single fiber cross section varies depending on the production conditions of the carbon fiber. For example, when a carbon fiber precursor fiber is obtained by dry and wet spinning, the roundness tends to be high, and when it is obtained by wet spinning, the roundness tends to be low.
Or you may select and use what has the roundness of this single fiber cross section in a preferable range among commercially available carbon fiber bundles.

<Method for producing unidirectional reinforced fabric>
As a method for producing the unidirectional reinforced fabric of the present invention from the warp and the weft, a known method for producing a unidirectional reinforced fabric can be appropriately used. The unidirectional reinforcing fabric of the present invention satisfies the above conditions (i), (b), and (d) and satisfies the above conditions c-1 and / or c-2. In this case, the linearity of the carbon fiber bundle is high, and the woven fabric is not easily deformed even in various molding work environments such as resin impregnation, and the linearity of the carbon fiber bundle is easily maintained.
When the carbon fiber bundle that is the warp yarn has a cantilever value of 200 mm or more, the unidirectional reinforcing fabric that satisfies these conditions can be easily obtained.

Further, as shown in the examples described later, even in the case of a unidirectional reinforcing fabric manufactured using the same carbon fiber bundle, when the fiber density of the warp increases and the basis weight of the unidirectional reinforcing fabric increases, Condition b) The cantilever value of the unidirectionally reinforced fabric increases, and the degree of orientation in the above (Condition C-1) and (Condition C-2) tends to increase slightly. The roundness of the cross section of the single fiber in the above (Condition D) hardly changes.
Therefore, a unidirectional reinforced fabric having a basis weight of 200 g / m ² consisting of a warp consisting of carbon fiber bundles and a weft binding the warp is manufactured, and the obtained unidirectional reinforced fabric is the above (condition b) and (condition d). ) And satisfying the above (Condition C-1) and / or (Condition C-2), the fabric weight is adjusted by adjusting the fiber density of the warp yarns in the production conditions where the unidirectional reinforced fabric is obtained. By producing a unidirectional reinforced fabric of 100 g / m ² or more and 500 g / m ² or less, a unidirectional reinforced fabric is obtained which is less likely to lose its shape even in various molding work environments such as resin impregnation operations.
Also in this method, it is preferable to use a carbon fiber bundle whose carbon fiber bundle has a cantilever value of 200 mm or more.

In particular, a unidirectional reinforcing woven fabric having a basis weight of 200 g / m ² consisting of warp yarns composed of carbon fiber bundles and weft binding the warp yarns was produced. ) And satisfying the above (Condition C-1) and / or (Condition C-2), the fabric weight is adjusted by adjusting the fiber density of the warp yarns in the production conditions where the unidirectional reinforced fabric is obtained. According to the method for producing a unidirectional reinforced fabric that exceeds 200 g / m ² and is 500 g / m ² or less, the above (Condition B) and (Condition D) are satisfied, and the above (Condition C-1) and / or ( A unidirectional reinforced fabric satisfying the condition C-2) is obtained.
Also in this method, it is preferable to use a carbon fiber bundle whose carbon fiber bundle has a cantilever value of 200 mm or more.

<Prepreg and carbon fiber composite material>
The prepreg of the present invention is obtained by impregnating the unidirectional reinforcing fabric of the present invention with a resin, and the carbon fiber composite material of the present invention is obtained by curing the resin impregnated in the prepreg.
As the resin impregnated in the unidirectionally reinforced fabric, a known resin can be appropriately used as a resin impregnated in a fabric made of carbon fiber in the field of carbon fiber composite materials. As a method for impregnating the unidirectional reinforcing fabric of the present invention with a resin and a method for curing the resin, known methods can be appropriately used.

<Measurement method of cantilever value of unidirectional reinforced fabric>
A method for measuring the cantilever value of the unidirectionally reinforced fabric described above (condition b) will be described. In the following, measurement conditions and numerical values may be limited. This is to prevent a difference in measurement value due to a difference in measurer or measurement environment.

  First, a test piece having a size of 20 to 50 cm in the fiber axis direction and 1 inch (1 inch = 25.4 mm) in the direction perpendicular to the fiber axis is cut out from the unidirectional reinforcing fabric. If it is 50 cm, it is sufficient for measurement, and if it is shorter than 20 cm, measurement may not be possible. In order to measure mechanically efficiently, it is preferable to limit to 40 cm.

  Next, as shown in FIG. 1, the test piece 1 is placed on the horizontal surface 2 of the measuring table having the horizontal surface 2 and the inclined surface 4 having an inclination angle of 45 degrees inclined downward from one end of the horizontal surface 2, The edge of the end portion 1 a of the test piece 1 is aligned with the boundary line A between the slope 4 and the horizontal plane 2. On top of that, the pressing plate 3 shown in FIG. 1 is placed so that the edge of the end 3 a is aligned with the boundary line A. If there is a JIS standard (L1096) 45-degree cantilever method measuring device, the cantilever value of the unidirectional reinforced fabric can be easily obtained by diverting it, so the inclination angle of the slope 4 is 45 degrees.

  Next, the pressing plate 3 is moved horizontally toward the slope 4 side. At this time, the test piece 1 is also moved by the holding plate 3 to the inclined surface 4 side, and the end 1a of the test piece 1 bends downward due to its own weight. When the end 1a of the test piece 1 comes into contact with the inclined surface 4, the movement of the pressing plate 3 is stopped. The speed at which the pressing plate 3 is horizontally moved to the inclined surface 4 side is preferably 1 cm / second or more from the viewpoint of shortening the measurement efficiency. Moreover, since the measurement of the cantilever value of the unidirectional reinforced fabric uses a phenomenon in which the unidirectional reinforced fabric bends due to its own weight, the measurement accuracy decreases if the test piece 1 is horizontally moved before it is bent to the limit. Therefore, the horizontal movement speed is preferably 3 cm / second or less. That is, the moving speed is preferably 1 cm / second or more and 3 cm / second or less, and more preferably limited to 2 cm / second in order to reduce the variation in measured values among workers.

  The distance that the pressing plate 3 has moved before the end 1a of the test piece 1 contacts the inclined surface 4 is defined as a cantilever value. The movement distance can be measured by grading the pressing plate 3 or by grading the horizontal surface 2 of the measuring table.

<Measurement method of orientation degree of single fiber in carbon fiber bundle>
Curing in the method for measuring the degree of orientation of single fibers in the carbon fiber bundle constituting the unidirectional reinforcing fabric (Condition C-1) and the cured product of the unidirectional reinforcing fabric and resin (Condition C-2) A method for measuring the degree of orientation of single fibers in the carbon fiber bundle constituting the object will be described.
In the following, the measurement device, measurement conditions, and numerical values may be limited. This is to prevent a difference in measurement value due to a difference in measurer or measurement environment.

In the measurement of the degree of orientation in (Condition C-1), an observation image of the carbon fiber bundle portion constituting the unidirectional reinforcing fabric is obtained using an optical microscope from a direction perpendicular to the surface of the unidirectional reinforcing fabric. Since the carbon fiber bundles are not in the same plane, there are places where the focus is in the field of view and does not match. In this case, this phenomenon can be avoided by placing a glass plate on the unidirectional reinforcing fabric. The observation conditions are an observation magnification of 50 times, falling illumination, and a dark field. In order to obtain an observation image, a CCD camera may be installed in the lens barrel of the optical microscope. Since the physical properties of the unidirectional reinforcing fabric are affected by the disorder of the orientation in the vicinity of the weft that restrains the carbon fiber bundle, the observation place is the carbon fiber bundle portion and near the weft.
The observation image thus obtained is used for the measurement of the degree of orientation described in (Condition C-1).

In the measurement of the degree of orientation of the cured product (Condition C-2), it is necessary to perform an operation of impregnating a unidirectional reinforced fabric with a resin and curing it before the measurement.
First, a square having a size of 10 to 15 cm in the fiber axis direction and 10 to 15 cm in the direction perpendicular to the fiber axis is cut out from the unidirectional reinforced fabric to obtain a unidirectional reinforced fabric test piece. If the test piece is smaller or larger than this range, the subsequent workability is lowered. When the test piece is cut out, if the unidirectional reinforcing fabric is cut directly with scissors, the fibers are exposed as fluff from the cut surface, so that a clean end face cannot be obtained. Therefore, as shown in FIG. 5, an adhesive having a width of 12 mm in a square shape having a length of 10 cm in the fiber axis direction (indicated by symbol X in the figure) and 10 cm in the direction perpendicular to the fiber axis direction X is placed on the unidirectional reinforcing fabric 31. By attaching the tape 32 and cutting the central portion in the width direction of the pressure-sensitive adhesive tape 32, a square unidirectional reinforced fabric test piece 11 having an end face of 11.2 cm on one side can be obtained. In the figure, reference numeral 33 indicates a cut portion. Note that the presence of the adhesive tape 32 does not affect the subsequent operations.

Next, two square release films 12 and 13 each having a side of 15 to 25 mm and having a release treatment on at least one side are prepared. It is essential that the release films 12 and 13 are larger than the unidirectional reinforced fabric test piece 11. When one side of the unidirectional reinforced fabric test piece 11 is 11.2 cm, one side of the release films 12 and 13 is 20 cm. preferable. As the performance of the release films 12 and 13, performance capable of being released from the cured epoxy resin used later is required. For example, a film (SP-PET-01-75BU) manufactured by Panac Co., Ltd. can be used. Next, one release film 12 is placed so that the release treatment surface is on top, 3 g of epoxy resin 14 is dropped on the center portion, and the unidirectional reinforced fabric test piece 11 is placed on top of FIG. Place as shown. Next, as shown in FIG. 3, 3 g of the same kind of epoxy resin 15 is dropped on the center of the unidirectional reinforced fabric test piece 11, and another release film 13 is released thereon. The laminate is obtained by placing it so that the treated surface is at the bottom. As the epoxy resins 14 and 15, the main component of the main agent is an epoxy resin, the main components of the curing agent are a modified aliphatic polyamine and a modified alicyclic polyamine, and these are 2/1 (mass of the main agent / curing agent). Ratio) is a green viscous body (viscosity at 20 ° C. is 22.0 ± 5.0 Pa · s), and the bending strength of the cured product obtained by curing this is 40 N / mm ² or more, A material having a tensile strength of 30 N / mm ² or more and a tensile shear strength of 10 N / mm ² or more is used. For example, Bond E2500S (product name: main agent / curing agent = 2/1 (mass ratio)) manufactured by Konishi Co., Ltd. is preferable. In order to drop 3 g of the epoxy resin 14, the release film 12 may be placed on a balance with the top plate horizontal, and the amount of the dropped resin may be dropped on the balance. The same applies when 3 g of the epoxy resin 15 is dropped.

Next, a glass plate (21 cm × 23 cm × 4 mm, weight 0.6 kg) was placed on the laminate obtained above and allowed to stand for 3 minutes, and then a weight (bottom of 11 cm × 12 cm square, weight 10). 5 kg) is placed on a glass plate and allowed to stand for 5 days to cure the epoxy resins 14 and 15.
The glass plate needs to be larger than the laminate, that is, larger than the release films 12 and 13, and be able to withstand the load of the weight placed thereon. From the above viewpoint, the glass plate preferably has a side of 20 to 25 cm, a thickness of 3 to 5 mm, and a weight of 0.3 to 1 kg. Furthermore, in order to prepare a large amount with a certain shape and weight, it is more preferable that the size is 21 cm × 23 cm × 4 mm and the weight is 0.6 kg. Moreover, the time to let it stand immediately after mounting | wearing a glass plate is the objective to spread the epoxy resins 14 and 15 on the unidirectional reinforced fabric test piece 11, and 1 to 5 minutes are preferable.
In order to reduce the variation in measurement, the time for standing still may be limited to 3 minutes.

  The weight placed on the glass plate is necessary for uniformly spreading the epoxy resins 14 and 15 existing under the glass plate and impregnating the unidirectional reinforced fabric test piece 11. The shape of the weight needs to be flat on the surface in contact with the glass plate and smaller than the glass plate. If the area in contact with the glass plate is too small, the glass plate may break. Accordingly, the side of the bottom surface of the weight is preferably 10 to 15 cm, and is limited to 11 cm × 12 cm in order to reduce measurement variation. The weight of the weight does not break the glass plate, and the load required to impregnate the epoxy resins 14 and 15 is required. In this respect, the weight is preferably 5 to 15 kg, and the variation in measurement is reduced. Limited to 11.5 kg. The curing time is limited to 5 days in order to reduce measurement variation.

  Next, when the weight and the glass plate are removed and the two release films 12 and 13 are peeled off, the unidirectional reinforced fabric test piece 11 is impregnated with the epoxy resins 14 and 15, and the epoxy resins 14 and 15 A cured product obtained by curing is obtained. That is, the unidirectional reinforced fabric resin cured product 21 in which the unidirectional reinforced fabric and the epoxy resin cured product are integrated is obtained. In addition, the operation so far is performed at room temperature of 5-15 degreeC.

Next, as shown in FIG. 4, an evaluation target region 22 is provided at the center of the unidirectional reinforced fabric resin cured product. The evaluation target region 22 is a square having one side of 4 cm so that the two sides are parallel to the fiber axis direction X. An observation image of the evaluation target region 22 is obtained by observing from the direction perpendicular to the surface of the unidirectional reinforced fabric resin cured product 21 using an optical microscope. The observation conditions are an observation magnification of 50 times, falling illumination, and a dark field. In order to obtain an observation image, a CCD camera may be installed in the lens barrel of the optical microscope. Since the physical properties of the unidirectional reinforcing fabric are affected by the disorder of the orientation in the vicinity of the weft that restrains the carbon fiber bundle, the observation place is the carbon fiber bundle portion and near the weft.
The observation image thus obtained is used for the measurement of the degree of orientation described above (Condition C-2).

In the method for measuring the degree of orientation described in (Condition C-1) and the method for measuring the degree of orientation described in (Condition C-2), a method for obtaining the degree of orientation by processing the observation images obtained in each case is common.
First, a two-dimensional Fourier transform is performed on the observed image to obtain a converted image. The two-dimensional Fourier transform can be performed using commercially available image analysis software (for example, product name: Image Pro, manufactured by Media Cybernetics).

  Next, in the converted image, luminance information at a constant radius from the origin is acquired in the circumferential direction, and a one-dimensional profile is obtained with the horizontal axis representing the angle and the vertical axis representing the luminance information. Here, the origin is the center of the image in the converted image. In the observed image, the longer the component, the closer to the origin of the converted image, the luminance, and the shorter the component in the observed image, the farther from the origin of the converted image. With brightness. If the observed image has a shape oriented in one direction, that is, if the carbon fiber is oriented in one direction at the observation location, the converted image can obtain bright band-like luminance information diagonally from the origin. It is done. The constant radius from the origin is the position of the luminance information of the converted image corresponding to the period of the carbon fiber array in the observed image. In the observed image, single fibers of carbon fibers aligned in one direction and bubbles in the resin can be confirmed. In the converted image, the constant radius for obtaining the luminance information in the circumferential direction is preferably larger than the diameter of the carbon fiber and smaller than the bubble in the observed image. If the carbon fiber has a diameter of about 7 μm, the length corresponding to 15 to 25 μm in the observed image is preferably set to a constant radius in the converted image, and in order to grasp the difference between samples, it is limited to 20 μm. More preferably. A one-dimensional profile based on luminance information acquired in the circumferential direction, with the horizontal axis as the angle and the vertical axis as the luminance information, can be created as a macro in image analysis software (for example, product name: Image Pro, manufactured by Media Cybernetics). If you can get.

  In the one-dimensional profile, the two peaks are at different positions by 180 degrees. Of these, peaks whose angles are divided by 0 degrees or 360 degrees are not recognized as peaks. A peak having two peaks is an arbitrary peak, and a peak having one peak is the peak to be analyzed.

Next, the analysis target peak is fitted with a composite curve of a Gaussian function and a Lorentz function, and the half width of the obtained composite curve is obtained. Waveform separation software may be used for fitting and half-value width calculation. The half width is a difference θ2−θ1 between the angle θ1 on the low angle side and the angle θ2 on the wide angle side, which is half the peak height of the composite curve.
Finally, the degree of orientation (unit:%) is obtained from the following formula (1-1) using the half width.
Degree of orientation [%] = (180−half width) / 180 × 100 Formula (1-1)

<Measurement method of roundness of single fiber cross section>
A method for measuring the roundness of the cross section of the single fiber in the carbon fiber bundle constituting the unidirectional reinforcing fabric (condition d) will be described.
In the following, the measurement device, measurement conditions, and numerical values may be limited. This is to prevent a difference in measurement value due to a difference in measurer or measurement environment.
First, a unidirectional reinforcing fabric is impregnated with a resin and cured to obtain a cured product for observation. The resin is not particularly limited as long as the unidirectional reinforced fabric can be hardened to such an extent that its cross section can be polished. For example, an appropriate thermosetting resin can be used. Or what cut out a part of said one-way reinforced textile resin hardened | cured material 21 is good also as a hardened | cured material for observation.

  Next, the surface perpendicular to the fiber axis of the cured product for observation is polished to obtain a polished surface. This polished surface is observed from a direction perpendicular to the polished surface using a microscope to obtain an observation image of a single fiber cross section. If an electron microscope is used as the microscope, the magnification is 5000 times, and observation is performed with a reflected electron image without vapor deposition, the single fiber cross section can be clearly observed.

Next, the minimum ferret diameter and the maximum ferret diameter of the cross section of the single fiber are obtained from the obtained observation image. The minimum ferret diameter is the minimum value of one side when a circumscribed rectangle is drawn from any angle with respect to the single fiber cross section. The maximum ferret diameter is the maximum value of one side when a circumscribed rectangle is drawn from any angle with respect to the single fiber cross section. The minimum ferret diameter and the maximum ferret diameter are obtained by taking the observation image into image processing software, and cutting out the image of only the single fiber cross section by tracing the outline of the single fiber cross section, and then image analysis software (for example, manufactured by Media Cybernetics, It can be obtained by using the maximum (minimum) ferret diameter calculation function of the product name (Image Pro).
The roundness of the cross section of the single fiber is determined from the obtained minimum ferret diameter and maximum ferret diameter using the following formula (1-2).
Roundness [%] = (minimum ferret diameter / maximum ferret diameter) × 100 Formula (1-2)

<Measurement method of cantilever value of carbon fiber bundle>
A method for measuring the cantilever value of the carbon fiber bundle will be described. In the following, measurement conditions and numerical values may be limited. This is to prevent a difference in measurement value due to a difference in measurer or measurement environment.
First, 40 cm is cut out from the carbon fiber bundle in the fiber axis direction to obtain a test carbon fiber bundle. The movement distance x of the pressing plate is set in the same manner as the measurement method of the cantilever value of the unidirectional reinforcing fabric except that the test carbon fiber bundle is used instead of the test piece 1 in the measurement method of the cantilever value of the unidirectional reinforcing fabric. taking measurement. Next, the front and back surfaces of the test carbon fiber bundle are reversed and the movement distance y of the pressing plate is measured in the same procedure. Let the average value of the numerical value x and the numerical value y be a cantilever value of a carbon fiber bundle.

<Carbon fiber sizing agent>
In the present invention, a carbon fiber sizing agent preferable as a sizing agent to be attached to the carbon fiber bundle is an ester of an epoxy compound having a plurality of epoxy groups in the molecule and an unsaturated monobasic acid, and at least in the molecule. Compound (A) having one epoxy group (hereinafter referred to as “component (A)”), and bifunctional urethane acrylate oligomer (B) (hereinafter referred to as “component (B)”) having a tensile elongation of the cured product of 40% or more. And one or more thermoplastic resins (C) selected from the group consisting of a styrene elastomer resin (C-1), a phenoxy resin (C-2), and a terpene resin (C-3) (hereinafter, (C) component)) as an essential component.
Furthermore, it is preferable to include an ester compound (D) (hereinafter referred to as “component (D)”), which is an ester of an alkylene oxide adduct of bisphenols and a dicarboxylic acid compound and has an acid value of 50 or more.

[(A) component]
The component (A) has at least one epoxy group in the molecule. In the present specification and claims, an epoxy group means a group whose ring skeleton has a three-membered ring composed of two carbon atoms and one oxygen atom in its structure.
Examples of the epoxy group include a group represented by the following formula (e1), a group represented by the following formula (e2) (glycidyl group), and other cyclic aliphatic epoxy groups. Examples of other cycloaliphatic epoxy groups include groups having a cyclic structure formed by the three-membered ring and a monocyclic or polycyclic aliphatic ring in the structure. For example, the following formula (e3 ) To (e5).

  In the component (A), the “epoxy compound having a plurality of epoxy groups in the molecule” which forms an ester is not particularly limited. For example, bisphenol epoxy compound, bisphenol alkylene oxide addition epoxy compound, hydrogenation Examples thereof include bisphenol epoxy compounds and hydrogenated bisphenol alkylene oxide addition epoxy compounds.

The bisphenols are not particularly limited, and examples thereof include bisphenol F type, bisphenol A type, and bisphenol S type.
Epoxy resins such as phenol novolak type, cresol novolak type, diphenyl type, dicyclopentadiene type, naphthalene skeleton type other than epoxy compounds of bisphenols can also be used as “epoxy compounds having a plurality of epoxy groups in the molecule”. . The “epoxy compound having a plurality of epoxy groups in the molecule” may have a linear aliphatic skeleton.

In the component (A), the “unsaturated monobasic acid” constituting the ester is not particularly limited as long as it is a compound having one unsaturated group and one carboxyl group.
The unsaturated group is not particularly limited, but is preferably a vinyl group or a propenyl group, more preferably a vinyl group, because it is not bulky and does not lower the rigidity of the main chain of the ester formed.
Particularly preferred as the unsaturated monobasic acid is acrylic acid or methacrylic acid. That is, the component (A) is preferably an ester of the “epoxy compound having a plurality of epoxy groups in the molecule” and acrylic acid or methacrylic acid.

Component (A) is an ester obtained by reacting an “epoxy compound having a plurality of epoxy groups in the molecule” with an unsaturated monobasic acid. In this reaction, the compound having a plurality of epoxy groups Of the epoxy groups, at least one epoxy group remains unreacted, and at least one epoxy group is ring-opened by an unsaturated monobasic acid to form a so-called half ester having an unsaturated group.
The component (A) includes an epoxy group derived from a compound having a plurality of epoxy groups in the molecule and an unsaturated group derived from an unsaturated monobasic acid (for example, CH ₂ ═CH—COO— derived from acrylic acid). And the molecular structure is a coupling between a carbon fiber and a molecule of a resin (hereinafter sometimes referred to as a matrix resin) impregnated in a unidirectionally reinforced fabric when forming a prepreg. Demonstrate the function and greatly improve the interfacial adhesion between the carbon fiber and the matrix resin. In particular, radical polymerization resins such as unsaturated polyester resins, vinyl ester resins, and acrylic resins can be strongly bonded to carbon fibers, and excellent interfacial adhesion can be exhibited.

  The component (A) is an ester of a compound having an epoxy group at both ends of the molecule and an unsaturated monobasic acid, particularly because of the excellent effects described above, and at one end of the main chain of the molecule. A compound having an unsaturated group and having an epoxy group at the other end is preferred. By using the compound as the component (A), the radical polymerization resin and the carbon fiber can be strongly bonded, and excellent interfacial adhesiveness can be expressed.

As the compound having an epoxy group at both ends of the molecule, one or both of a bisphenol diepoxy compound and a bisphenol alkylene oxide addition diepoxy compound are particularly preferred. That is, the component (A) is an ester of one or both of a bisphenol diepoxy compound and a bisphenol alkylene oxide addition diepoxy compound and an unsaturated monobasic acid, and is one end of the main chain of the molecule. A compound having an unsaturated group in the part and an epoxy group in the other end is preferred. For example, one-terminal acrylic acid-modified diglycidyl ether bisphenol A can be used.
(A) A component can be synthesize | combined with a well-known manufacturing method, and can also be obtained from a commercial item.
(A) A component may be used individually by 1 type and may use 2 or more types together.

[Component (B)]
The component (B) has an effect of forming an interface phase excellent in flexibility at the interface between the matrix resin and the carbon fiber. By forming an interface phase excellent in flexibility at the interface between the matrix resin and the carbon fiber, the interfacial adhesion between the matrix resin and the carbon fiber is improved. In addition, when radical polymerization resins such as vinyl ester resins and unsaturated polyester resins are used as the matrix resin, many of those resins have low toughness, and due to high toughness by softening the interface phase, Interfacial adhesion improves dramatically.

  In addition, when the sizing-treated carbon fiber bundle and the matrix resin are combined, the sizing agent component on the surface of the carbon fiber diffuses into the matrix resin, and the sizing agent component is contained in the matrix resin near the interface in a high concentration. A region is formed. This region affects the mechanical properties of the carbon fiber composite material. And since (B) component is an acrylate oligomer, when forming a carbon fiber composite material, it will be integrated in the hardening reaction of a matrix resin, and integration of an interface phase and a matrix resin phase will be aimed at. Therefore, by including this component (B), even when the radical polymerization resin is used as the matrix resin, the mechanical properties of the carbon fiber composite material are at the same level as when the epoxy resin is used as the matrix resin. can do.

(B) A component is a specific urethane acrylate oligomer. In the present invention, the urethane acrylate oligomer is a compound having a urethane bond and an acryloyl group (CH ₂ ═CH—CO—) in the molecule.
The structure of the urethane acrylate oligomer can be broadly classified into an aromatic type having an aromatic group in the structure and an aliphatic type having no aromatic group. The structure of the urethane acrylate oligomer used in the present invention is not particularly limited, and may be aromatic or aliphatic. Since the balance between the tensile elongation percentage and the tensile strength of the cured product is good, an aliphatic system is preferable.

The component (B) needs to have a tensile elongation of the cured product of 40% or more, and is excellent in the effect of increasing the toughness of the interfacial phase. Therefore, it is more preferably 45% or more, and 50% or more. More preferred. The upper limit of the tensile elongation rate (%) is preferably 900% or less, more preferably 700% or less in consideration of a significant reduction in the elastic modulus of the resin near the interface.
The value of the tensile elongation of the cured product of the component (B) in the present invention is a value obtained by the following measuring method. That is, 3 g of a curing agent (manufactured by Merck Japan Co., Ltd., product name: Darocur # 1173) is added to 97 g of urethane acrylate oligomer as component (B), and mixed well to obtain a mixture. The obtained mixture is applied on a glass plate to obtain a film having a thickness of 100 μm. The film is cured by irradiating with ultraviolet rays from a position having a height of 10 cm using an ozone type lamp (80 W / cm). About the obtained hardened | cured film, based on JISK7113, a tensile elongation rate is measured by the tension speed of 300 mm / min.

The component (B) needs to be bifunctional. If it is a tri- or higher functional type, the crosslink density becomes too high and sufficient toughness is not exhibited. On the other hand, in the monofunctional type, the crosslinking reaction with the matrix resin is only on one side, and a sufficient toughening effect cannot be obtained.
As the component (B), in particular, since the effect of improving the toughness of the interfacial phase is very large, it is preferable that the viscosity at 60 ° C. is 10,000 mPa · s or more and the cured product has a tensile strength of 6 MPa or more.
The viscosity value of the component (B) in the present invention is a value obtained with a B-type viscometer.

(B) The large viscosity of a component shows that the molecular weight of the oligomer is large, or the cohesion force between oligomer molecules is large. When the molecular weight is large or the cohesive force between the molecules is large, the component (B) is unevenly distributed in the interfacial phase between the carbon fiber surface and the matrix resin without diffusing into the matrix resin, resulting in the effect of the interfacial phase. Flexibility can be achieved.
(B) As for the viscosity in 60 degreeC of a component, 20000 mPa * s or more is more preferable, and 40000 mPa * s or more is further more preferable. As the upper limit of the viscosity, the one not solid at 60 ° C. is superior from the viewpoint of the preparation of the sizing agent and the temporal stability of the sizing agent.

The glass transition temperature (Tg) of the cured product (B) is preferably −5 ° C. or higher, more preferably 5 ° C. or higher. If the Tg of the cured product is −5 ° C. or more, not only can the appropriate softening be achieved by the interfacial phase, but the value of the stress leading to fracture also increases, so that a stronger interfacial phase can be formed and the above effects are achieved. improves. In other words, the interfacial phase has a function of supporting the reinforcing fibers, and excessive softening impairs the mechanical properties of the composite material. As an upper limit of Tg of hardened | cured material, when the function as a flexible component is considered, 100 degrees C or less is preferable and 80 degrees C or less is more preferable.
The Tg of the cured product of the component (B) in the present invention is heated at a rate of 2 ° C./min using a cured film obtained in the same manner as the above-described tensile elongation rate measurement method as a test piece, The dynamic viscoelasticity and loss tangent of the test piece are measured, and the value is obtained from the peak temperature (tan δMAX) of the loss tangent.

(B) As a component, you may select and use a suitable thing from a commercially available urethane acrylate oligomer. Examples of such urethane acrylate oligomers include product names manufactured by Sartomer: CN-965, CN-981, CN-9178, CN-9788, CN-9893, CN-971, CN-973, CN-9882, manufactured by Kyoeisha Chemical. Product name: UF-8001, Shin-Nakamura Chemical Co., Ltd. product name: UA-122P and the like.
In this invention, (B) component may be used individually by 1 type, and may use 2 or more types together.

[Contents of Component (A) and Component (B)]
The ratio (mass ratio) of the content of the component (A) and the component (B) needs to be in the range of (B) component / (A) component = 1/3 to 2/1.
When the content of the component (B) is less than 1/3 of the content of the component (A), the interfacial phase becomes insufficiently flexible and high toughness. On the other hand, if the ratio exceeds 2/1, the effect of developing good adhesion, which is the function of component (A), is inhibited, and the effect of improving the adhesion of carbon fibers to the matrix resin cannot be sufficiently obtained.
The content ratio of component (A) to component (B) is preferably (B) component / (A) component = 1/2 to 3/2, more preferably 2/3 to 1/1. .

Moreover, it is preferable that the ratio of the total amount of (A) component and (B) component which occupies in all the sizing components is 18 mass% or more. If the amount is less than 18% by mass, the functions of these two components are not sufficiently exhibited.
Here, the “total sizing component” is the total amount of all components imparted to the carbon fiber after the sizing treatment among the components contained in the sizing agent for carbon fiber. For example, after sizing such as water or an organic solvent. The removed component represents an active ingredient not included. That is, the “total sizing component” is the total amount of the above-described component (A), component (B), component (C) and optional component (D), component (E) described below, and other components. As required. The proportion of the total amount of the component (A) and the component (B) is preferably 20% by mass or more, more preferably 25% by mass or more, and further preferably 30% by mass or more in all sizing components.

[Component (C)]
Component (C) is a thermoplastic resin that has the effect of stabilizing the shape of the carbon fiber bundle. By making the shape of the carbon fiber bundle fixed, it becomes easy to optimize the resin pickup in the resin impregnation step in pultrusion molding, filament winding molding, or the like. In addition, the effect of stabilizing the shape of the carbon fiber bundle after impregnating the resin is remarkably improved, and the orientation of the carbon fiber monofilament in the molded product is distorted due to the effect of preventing the deformation of the fabric and misalignment. Is suppressed, and the strength development of the molded product can be remarkably improved.

  As the component (C), a styrene elastomer resin (C-1) is suitable. Many vinyl ester resins and unsaturated polyester resins, which are matrix resins, contain styrene and phthalic acid as copolymerization components, and the styrene elastomer resin (C-1) has excellent compatibility with these resins. is there. Therefore, good compatibility with these matrix resins contributes to the formation of a uniform interface phase in the curing process. On the other hand, since the styrene elastomer resin (C-1) is a thermoplastic resin, it takes time to dissolve in the resin impregnation process. Therefore, during the resin impregnation step, the form of the carbon fiber bundle can be maintained, and the occurrence of rough alignment and meandering of the single fiber can be strongly suppressed.

There is no restriction | limiting in particular as styrene-type elastomer resin (C-1). The abundance ratio of styrene units in the molecular structure is preferably 10 to 70% by mass. This is to ensure compatibility with styrene and phthalic acid. Furthermore, since these resins are of an elastomer type, there is also an effect of softening the interfacial phase, and it can be made excellent in the expression of mechanical performance as a composite material.
Specific examples of the styrene-based elastomer resin (C-1) include Tough Plain, Asaplain, Tuf Tech H or Tuf Tech M manufactured by Asahi Kasei Kogyo Co., Ltd., Epofriend CT310 or AT501 manufactured by Daicel Chemical Industries, and Modiper A4100 manufactured by Nippon Oil & Fats And a graft polymer of ethylene glycidyl methacrylate copolymer and polystyrene, composition ratio: 70/30).
In particular, Tuftec M is a type in which a reactive group such as a carboxylic acid or an amino group is introduced. Similarly, Epofriend or Modiper A4100 is a type in which an epoxy group is introduced. The action is strong and the interface of the matrix resin after curing can be made strong.

  The main epoxy resins used as matrix resins are bisphenol type, phenol novolac, cresol novolac, etc., and these styrenic elastomer resins have excellent compatibility even in combination with epoxy resins. Similarly, during the resin impregnation step, since the form of the carbon fiber bundle can be maintained, the occurrence of rough alignment and meandering of single fibers can be strongly suppressed.

  Moreover, as (C), a phenoxy resin (C-2) or a terpene resin (C-3) is preferable. This is because the vinyl ester resin and epoxy resin, which are mainly used as a matrix resin, have a bisphenol skeleton, a phenol novolak or a cresol novolak skeleton, and thus are superior to the phenoxy resin (C-2) or the terpene resin (C-3). This is because they have compatibility. These resins are solid in the range of room temperature to 50 ° C., can stabilize the shape of the carbon fiber bundle, and can maintain the shape of the carbon fiber bundle during the matrix resin impregnation step.

  Phenoxy resin (C-2) is a polyhydroxy polyether resin synthesized from bisphenols and epichlorohydrin. Y basic phenoxy resin manufactured by Tohto Kasei; P-50, YP-50S, YP-55U and special phenoxy resins; YP-70, FX-316, YPB-43C, YPB-43M, PKHB, PKHC, PKHH, PKHJ manufactured by InChem, or PKCP-67, PKCP-80 partially modified with caprolactone; HP3 manufactured by HYDROSIZE TECHNOLOGIES -02 etc. can be mentioned (all are product names).

The terpene resin (C-3) is a thermoplastic resin obtained by polymerizing a terpene monomer, and includes a polyterpene resin, an aromatic modified terpene resin, a terpene phenol resin, an aromatic modified hydrogenated terpene resin, and the like. be able to.
As the terpene resin (C-3), YS resin PX series of terpene resin manufactured by Yashara Chemical Co., YS resin TO, YS resin TR of aromatic modified terpene resin, YS polyster series and Mighty Ace series of terpene phenol resin, aromatic Examples of the modified hydrogenated terpene resins are chloralon M and chloralon K (all are product names). In particular, an aromatic modified terpene resin, a terpene phenol resin, and an aromatic modified hydrogenated terpene resin having an aromatic structure in the molecule are more preferable from the viewpoint of compatibility with the matrix resin.

  5-40 mass% is preferable and, as for the ratio of the (C) component which occupies in all the sizing components, 10-35 mass% is more preferable. If it is less than 5% by mass, the effect of increasing the cantilever value of the sizing-treated carbon fiber bundle cannot be obtained sufficiently. If the amount exceeds 40% by mass, the carbon fiber bundle becomes too rigid, and trouble occurs in the production stage of the carbon fiber bundle or the unidirectional reinforcing fabric.

[(D) component]
The component (D) is an ester of an alkylene oxide adduct of bisphenols and a dicarboxylic acid compound, and has an acid value of 50 or more. When the acid value is 50 or more, a main component is a compound having a molecular weight of about 1000 and having a carboxyl group at one end of the molecule. Such a component (D) exhibits excellent compatibility with the matrix resin. Therefore, the wettability of the sized carbon fiber to the resin is improved, and the resin impregnation property is further improved.

The “alkylene oxide adduct of bisphenols” forming the component (D) is preferably a bisphenol obtained by adding 2 to 4 moles of ethylene oxide or propylene oxide. When bisphenols are added with 5 mol or more of ethylene oxide or propylene oxide, the molecular chains inherent in bisphenols lose their rigidity, and the affinity with the matrix resin may deteriorate.
More preferably, bisphenols are added with 2 mol of ethylene oxide or propylene oxide.
The alkylene oxide adducts of bisphenols may be used alone or as a mixture of a plurality of compounds.

The “dicarboxylic acid compound” that forms an ester with an alkylene oxide adduct of bisphenols is preferably an aliphatic compound having 4 to 6 carbon atoms. When an aromatic compound is used as the dicarboxylic acid compound, the resulting ester compound has a high melting point and may be poorly soluble in the matrix resin, thereby failing to develop good wettability. On the other hand, when an aliphatic compound having 7 or more carbon atoms is used as the dicarboxylic acid compound, the rigidity of the resulting ester compound is lost, and the affinity with the matrix resin may be reduced.
Examples of the dicarboxylic acid compound include fumaric acid, maleic acid, methyl fumaric acid, methyl maleic acid, ethyl fumaric acid, ethyl maleic acid, glutaconic acid, itaconic acid, malonic acid, succinic acid, methyl succinic acid, glutaric acid, and adipic acid. It is done.
In this invention, (D) component may be used individually by 1 type, and may use 2 or more types together.

In this invention, it is preferable that content of (D) component is 2.0 mass times or less with respect to the total amount of (A) component and (B) component. When it exceeds 2.0 mass times, the interaction between the (A) component and the carbon fiber surface is caused by the interaction between the epoxy group of the (A) component and the acidic group (carboxy group, etc.) of the (D) component. As a result, the coupling function between the carbon fiber and the matrix resin of the component (A) is not sufficiently exhibited, and the adhesiveness may be lowered.
As for content of (D) component, 1.75 mass times or less is more preferable with respect to the sum total of (A) component and (B) component, and 1.55 mass times or less are still more preferable.
The lower limit of the content of the component (D) is not particularly limited, but for the effect of the component (D), 0.2 mass times the total of the components (A) and (B). The above is preferable, and 0.4 mass times or more is more preferable.

[Nonionic surfactant (E) (hereinafter referred to as component (E))]
The sizing agent for carbon fiber may contain (E) component. The nonionic surfactant as the component (E) is not particularly limited, but an aliphatic nonionic surfactant is preferable because the reaction activity reducing action is extremely excellent.
Aliphatic nonionic surfactants include higher alcohol ethylene oxide adducts, fatty acid ethylene oxide adducts, polyhydric alcohol fatty acid esters ethylene oxide adducts, glycerol fatty acid esters, sorbitol and sorbitan fatty acid esters, and pentaerythritol fatty acid esters. Etc. In these ethylene oxide adducts, a type in which propylene oxide units are randomly or block-containing in a part of the polyethylene oxide chain is also preferably used.

As higher alcohol ethylene oxide adducts, fatty acid ethylene oxide adducts, polyhydric alcohol fatty acid ester ethylene oxide adducts, those containing propylene oxide units randomly or in blocks in part of these polyethylene oxide chains are more preferred. . This is because these are excellent in the ability to reduce the reaction activity of ammonium ions on epoxy groups.
As the fatty acid ethylene oxide adduct and polyhydric alcohol fatty acid ester ethylene oxide adduct, monoester type, diester type, triester, tetraester type and the like can be used.

  The sizing agent for carbon fiber can be produced by mixing and stirring each component by a conventional method. In the sizing treatment of the carbon fiber bundle, the carbon fiber sizing agent is usually applied to the carbon fiber bundle as a sizing agent solution dispersed or dissolved in water or an organic solvent.

[Aqueous dispersion of sizing agent]
The carbon fiber sizing agent is easy to apply to the carbon fiber bundle, and it is industrially and safer compared to the case where it is dissolved in an organic solvent. It is preferable to use it as an aqueous dispersion.
When the sizing agent is used as an aqueous dispersion, the sizing agent preferably contains the above-described component (E). The component (E) has a function of stably dispersing the component (A) in water, so that the obtained aqueous dispersion has good liquid stability and good handleability.
In this case, the blending amount of the component (E) is 5 to 30% by mass in the total sizing agent component, so that the emulsion stability of the sizing agent liquid is good and the effect of the sizing agent is not adversely affected. Therefore, it is preferable. A more preferred lower limit is 7% by mass, and a more preferred upper limit is 20% by mass.

The aqueous dispersion of the carbon fiber sizing agent preferably has an active ingredient content of 0.1 to 60% by mass, more preferably 0.2 to 40% by mass. The “active ingredient” has the same meaning as all the sizing ingredients described above.
The method for applying the carbon fiber sizing agent to the carbon fiber bundle can be performed by adhering the sizing agent or a dispersion of the sizing agent to the carbon fiber by a roller dipping method or a roller contact method, followed by drying.
0.1-5 mass% is preferable with respect to the mass of a carbon fiber bundle, and, as for the quantity of the sizing agent provided to a carbon fiber bundle, 0.2-3 mass% is still more preferable. When the application amount is within this range, the carbon fiber can be sufficiently provided with convergence and scratch resistance, and wettability with the matrix resin and interfacial adhesion can be improved. Therefore, the carbon fiber composite material obtained using the sizing-treated carbon fiber bundle can obtain good mechanical properties.
The application amount of the sizing agent for carbon fiber can be adjusted by adjusting the concentration of the sizing agent solution or adjusting the squeezing amount.

When the sizing agent for carbon fiber according to the present invention is applied to the carbon fiber bundle, a sizing-treated carbon fiber bundle in which the cantilever value of the carbon fiber bundle is in a preferable range can be easily obtained, and by using this, the cantilever value of the unidirectional reinforcing fabric can be obtained. Is obtained in a suitable range.
Further, the sizing-treated carbon fiber bundle to which the sizing agent for carbon fiber according to the present invention is applied is less prone to fluff due to mechanical friction and the like, and is excellent in the impregnation property and adhesiveness of the matrix resin. Moreover, since the sizing agent contains the component (B) and the component (C) together with the component (A), the cured prepreg (fiber reinforced composite material) in which the sizing-treated carbon fiber bundle is impregnated with a matrix resin. Mechanical properties exhibit good mechanical properties.
The sizing-treated carbon fiber bundle has excellent processability such as weaving and can be suitably processed into a unidirectional reinforcing fabric. Particularly in weaving, carbon fibers are usually prone to fluff due to rubbing, but sizing-treated carbon fiber bundles can remarkably suppress fuzz.

Hereinafter, the present invention will be described in detail with reference to examples.
Example 1
<Preparation of sizing agent S1>
A sizing agent by transfer emulsification was prepared according to the following procedure using Hibis Disper Mix (made by Tokushu Kika Kogyo Co., Ltd., homomixer specification: model 3D-5 type).
In the formulation shown in S1 of Table 1, (A) component, (B) component, (C) component, (D) component, other additives and emulsifier (E) component or other nonionic surfactant, After kneading and mixing together, the temperature was lowered to 60 ° C. in a kneaded state, and deionized water was dropped little by little to effect phase inversion emulsification to obtain an emulsion having an active ingredient content of about 40% by mass. This is designated as sizing agent S1.
In addition, (A) component and (D) component are the synthetic products obtained by the following procedure in more detail, respectively.

(A) As a component, acrylic acid-modified diglycidyl ether bisphenol A: 378 parts of bisphenol A type epoxy resin (Japan Epoxy Resin JER828) is added with 86 parts of acrylic acid, 1 part of hydroquinone, and 1 part of lithium chloride. A mixture of JER828 / JER828 one-end acrylic modified epoxy resin (half ester) / JER828 both-end acrylic modified epoxy resin (diester), obtained by heating at 100 ° C., at a mixing ratio of 1/2/1. The half ester component effective as the component (A) is 1/2, and the remaining 1/2 is an unreacted product and a diester product. The blending amount of the component (A) shown in Table 1 represents the total amount of the half ester component, the unreacted product, and the diester product. Therefore, the effective component amount as a half ester is ½ of the blending amount of the component (A) shown in Table 1.

(D) As propylene oxide 3 mol addition fumaric acid ester of bisphenol A: PO adduct of bisphenol A added by 3 mol of PO to 1 mol of bisphenol A (“New Paul BP” manufactured by Sanyo Chemical Industries, Ltd.) −3P ”), 800 parts, fumaric acid 278 parts (alcohol / acid = 1 / 1.2 molar ratio) and tetraisopopropoxytitanate 1 part under reduced pressure to −0.1 MPa at 180 ° C. under nitrogen flow in a glass reaction vessel. The reaction was carried out for 10 hours while distilling off the water.

(D) Copolymer of propylene oxide 3 mol addition fumaric anhydride of bisphenol A and ethylene oxide 10 mol addition fumaric anhydride of bisphenol A as component (D) 3 mol of PO is added to 1 mol of bisphenol A 400 parts of the bisphenol A PO adduct (“Newpol BP-3P” manufactured by Sanyo Chemical Industries, Ltd.), 139 parts of fumaric acid (alcohol / acid = 1 / 1.2 molar ratio) and 1 part of tetraisopopropoxy titanate In a glass reaction vessel, the reaction was carried out for 10 hours while distilling off water at 180 ° C. under nitrogen flow. Further, 668 parts of an EO addition product of bisphenol A (“New Pole BPE-100” manufactured by Sanyo Chemical Industries, Ltd.) in which 10 parts by mole of EO is added to 1 part by mole of bisphenol A, and the pressure is reduced to −0.1 MPa at 180 ° C. It was obtained by reacting for 10 hours while distilling off water.

<Manufacture of sizing-treated carbon fiber bundles>
The sizing agent S1 was added to the carbon fiber bundle by the following procedure to produce a sized carbon fiber bundle.
A carbon fiber bundle (Pyrofil TR50S (product name), Mitsubishi Rayon Co., Ltd.) filled with an aqueous dispersion of the sizing agent S1 in an immersion tank having an immersion roller therein and not provided with a sizing agent in the aqueous dispersion. Manufactured, 12,000 filaments, strand strength 5000 MPa, strand elastic modulus 242 GPa). Thereafter, the sizing agent-treated carbon fiber bundle was obtained by drying with hot air. The obtained size-treated carbon fiber bundle was wound up on a bobbin.

<Production of unidirectional reinforced fabric>
Weft was obtained by combining glass fiber (D450 1/2 4.4S) manufactured by Unitika and nylon fiber (Elder 50/10 melting point 110-120 ° C.) manufactured by Toray.
The size-treated carbon fiber bundle obtained above is arranged in one direction at a fiber density of 6.4 / inch as warp, and the weft is woven at a fiber density of 5 / inch using a Tsuda Koma rapier loom. Subsequently, the warp yarn and the weft yarn were bonded and fixed by contacting with a heat roll at 125 ° C. to obtain a unidirectional reinforced fabric having a basis weight of 200 g / m ² . The following evaluation was performed about the obtained unidirectional reinforcement fabric. The results are shown in Table 2.

<Evaluation 1: Cantilever value of unidirectional reinforced fabric>
First, the measurement equipment of 45 degree cantilever method of JIS standard (L1096) shown in FIG. 1 was prepared. The horizontal surface 2 of the table was calibrated in millimeters. The cantilever value was measured according to the above-mentioned “Method for Measuring Cantilever Value of Unidirectional Reinforced Fabric”. The test piece used was a unidirectional reinforced fabric cut out 40 cm in the axial direction of the carbon fiber and 1 inch in the vertical direction to the fiber axis. The moving speed of the pressing plate was 2 cm / second. The results are shown in Table 2.

<Evaluation 2: Orientation degree of single fiber in carbon fiber bundle constituting unidirectional reinforced fabric>
The degree of orientation in (Condition C-1) was measured according to the above-mentioned “Method for measuring degree of orientation of single fibers in carbon fiber bundle”.
As shown in FIG. 5, the unidirectional reinforced fabric test piece is obtained by attaching an adhesive tape 32 having a width of 12 mm on one side of the unidirectional reinforced fabric 31 so that the exposed carbon fiber is a 10 cm square. It was obtained by cutting the central portion 33. In addition, when the cutting operation was performed without fixing the carbon fiber with the adhesive tape 32, the cut surfaces became uneven, which was unsuitable as a unidirectional reinforced fabric test piece.
The observation of the unidirectionally reinforced fabric test piece was performed using a microscope (product name: Nikon ECLIPSE ME600, manufactured by Nikon) equipped with a CCD camera. An image from the CCD camera was projected on the display unit and used as a field of view. The unidirectional reinforced fabric test piece was placed on a microscope stage, and a glass plate (120 mm × 120 mm × 1 mm, mass 60 g) was placed thereon. The orientation of the carbon fiber bundle with respect to the field of view was the left-right direction, and the observation place was the carbon fiber bundle part and the part as close to the weft as possible within the range where the weft did not enter the field of view. Observation images were obtained under the conditions of oblique illumination, no dimming, objective lens 50 times, and dark field. Ten observation images were obtained at random positions.

  Next, this observation image was read by image analysis software (trade name: Image Pro, manufactured by Media Cybernetics), converted into an 8-bit gray scale, and then subjected to two-dimensional Fourier transform to obtain a converted image. Luminance information appeared in the vertical direction in the converted image. Next, the luminance information at a position of 100 pixels from the origin of the converted image (corresponding to a length of 20 μm period in the observation image) is read by creating a macro program in the circumferential direction, the horizontal axis is the angle, and the vertical axis is the luminance information. A one-dimensional profile was obtained.

  Next, the one-dimensional plot was read by the waveform separation software fityk. The waveform had one large peak at a position near 180 degrees in angle, and a large divided peak at a position near 0 degrees or 360 degrees in angle. Near 90 ° and 270 °, there were peaks about half the size of the 180 ° peak, and many finer peaks were confirmed. The peak is around 180 degrees with the analysis target as an angle, the minimum value at both ends of the peak is connected by a straight line and subtracted as the base line to obtain the processing peak, and then the processing peak is fitted with a composite curve of Gaussian function and Lorentz function Then, parameters of Gaussian function and Lorentz function were obtained.

  Based on the obtained parameters, the half-value width of the composite curve was obtained using spreadsheet software (Excel) manufactured by Microsoft Corporation. Finally, the degree of orientation was determined from the above formula (1-1) using the half width. The results obtained by averaging the 10 observation images are shown in Table 2 in the form of mean ± standard deviation (the same applies hereinafter).

<Evaluation 3: Orientation degree of single fiber in carbon fiber bundle constituting cured product in cured product of unidirectional reinforced fabric and resin>
The degree of orientation of (Condition C-2) was measured according to the above-mentioned “Method for measuring degree of orientation of single fibers in carbon fiber bundle”. As the test piece, the same unidirectional reinforced fabric test piece as in Evaluation 2 was used.
A cured product of a unidirectionally reinforced fabric and a resin was obtained in an environment where the room temperature was 8 ° C. to 14 ° C. by the following procedure.
First, a main resin 20 g of Bond E2500S manufactured by Konishi Co., Ltd. and a curing agent 10 g were weighed into a 100 cc disposable cup and kneaded with a chopstick to obtain a cured resin. Next, a glass plate (210 mm × 230 mm × 4 mm, 0.6 kg) was placed on a balance. A release film (a release film (SP-PET-01-75BU) manufactured by Panac Co., Ltd. cut into a 20 cm square) was placed on this so that the release surface was on top, and then the release film 3 g of the cured resin is dropped at the center, and a unidirectional reinforced fabric test piece is placed thereon. Further, 3 g of the cured resin is further dropped to obtain an object on which a release film is placed so that the release surface is further down. It was.
Next, in order to prevent this object from bending, it is placed on a smooth laboratory bench from glass, a glass plate is placed on this object, and a weight (bottom 110 mm × 120 mm, 10.5 kg) is further placed on it for 5 days. did.

Next, after removing the weight and the glass plate, two release films were peeled off, and excess resin other than the one-way reinforced fabric test piece was cut off to obtain a one-way reinforced fabric resin cured test piece.
Next, a microscope (product name: Nikon ECLIPSE ME600, manufactured by Nikon) equipped with a CCD camera was prepared. An image from the CCD camera was projected on the display unit and used as a field of view. The unidirectional reinforced fabric resin cured specimen was placed on a microscope stage. The orientation of the carbon fiber bundle with respect to the field of view was the left-right direction, and the observation place was the carbon fiber bundle part, and the part as close to the weft as possible within the range where the weft did not enter the field of view. Observation images were obtained under the conditions of oblique illumination, no dimming, objective lens 50 times, and dark field. The observation target region was a 4 cm square near the center of the unidirectional reinforced fabric resin cured product as shown in FIG.
The procedure for measuring the degree of orientation from the observed image was the same as in <Evaluation 2>.

<Evaluation 4: Roundness of single fiber cross section>
The circularity of (Condition D) was measured in accordance with the above “Method for measuring roundness of single fiber cross section”.
That is, in the unidirectional reinforced fabric resin cured test piece in <Evaluation 3>, a test piece was cut out from a portion that was not the observation target region so as to be 1 cm in the fiber axis direction and 2 cm in the direction perpendicular to the fiber axis. The test piece was embedded in a resin (Technobit 4000 Kultzer) so that the end surface in the direction perpendicular to the fiber axis was a polished surface, and was polished with a polishing machine.
The polished surface was subjected to an electron microscope (manufactured by Hitachi, product name: S-3400N / E-350), without vacuum deposition, low vacuum mode (30 Pa), reflected electron image (3D), acceleration voltage 15 kV, magnification 5000 times. The observation image was obtained.
The obtained observation image was taken in with Microsoft's paint software, and the single fiber cross section was painted black by tracing the outline of the single fiber cross section. This image is read by image analysis software (Media Cybernetics, product name: Image Pro), and then binarized to obtain an image in which the cross section of the single fiber is black while the background is white. It was. The minimum and maximum ferret diameters were automatically calculated from this image.
From the obtained minimum ferret diameter and maximum ferret diameter, the roundness of the cross section of the single fiber was determined using the above equation (1-2). Table 2 shows the average roundness for 10 cross-sections of single fibers.

<Evaluation 5: Cantilever value of carbon fiber bundle>
First, the measurement equipment of 45 degree cantilever method of JIS standard (L1096) shown in FIG. 1 was prepared. The horizontal surface 2 of the table was calibrated in millimeters. The cantilever value was measured in accordance with the above “Method for Measuring Cantilever Value of Carbon Fiber Bundle”. As the carbon fiber bundle for testing, a carbon fiber bundle used as warp was cut by 40 cm in the axial direction. The moving speed of the pressing plate was 2 cm / second. The results are shown in Table 2.
<Evaluation 6: Evaluation of carbon fiber composite material>
The obtained unidirectional reinforced fabric is actually impregnated with a resin (manufactured by Konishi Co., Ltd., E2500S main agent / curing agent = 2/1) manually to produce a cured product (carbon fiber composite material) and cured. It was visually observed whether the orientation state of the single fibers in the carbon fiber bundles constituting the product was good. In this example, the orientation state of the single fiber example was good. Moreover, the cured product could be produced without any practical problems, and the productivity of the carbon fiber composite material was also good.

(Example 2)
In Example 1, a unidirectional reinforced fabric with a basis weight of 300 g / m ² was obtained in the same manner except that the fiber density of the warp yarn when producing the unidirectional reinforced fabric was changed to 9.5 yarns / inch. And evaluated in the same manner.
In the cured product (carbon fiber composite material) obtained using the unidirectional reinforcing fabric of this example, the orientation state of the single fibers in the carbon fiber bundle was good. Moreover, the cured product could be produced without any practical problems, and the productivity of the carbon fiber composite material was also good.

(Example 3)
<Preparation of sizing agent S2>
Using the same Hibis Disper mix as in Example 1, a sizing agent by transfer emulsification was prepared by the following procedure.
In the formulation shown in S2 of Table 1, (A) component, (B) component, (D) component, other additives and (E) component which is an emulsifier, or other nonionic surfactant are kneaded and mixed together Thereafter, the temperature was lowered to 60 ° C. in a kneaded state, and deionized water was added dropwise little by little to effect phase inversion emulsification. Next, the component (C) was mixed to obtain an emulsion having an active ingredient content of about 40% by mass. This is designated as sizing agent S2. In addition, (C) component is an emulsion and the compounding quantity of Table 1 was described in the active ingredient content in (C) component.
<Manufacture of sizing treated carbon fiber bundles and unidirectional reinforced fabric>
In Example 1, except that the sizing agent S1 was changed to the sizing agent S2, a unidirectional reinforced fabric having a basis weight of 200 g / m ² was obtained and evaluated in the same manner as in Example 1.
In the cured product (carbon fiber composite material) obtained using the unidirectional reinforcing fabric of this example, the orientation state of the single fibers in the carbon fiber bundle was good. Moreover, the cured product could be produced without any practical problems, and the productivity of the carbon fiber composite material was also good.

Example 4
In Example 3, a unidirectional reinforced fabric with a basis weight of 300 g / m ² was obtained in the same manner except that the fiber density of the warp when producing the unidirectional reinforced fabric was changed to 9.5 yarns / inch. And evaluated in the same manner.
In the cured product (carbon fiber composite material) obtained using the unidirectional reinforcing fabric of this example, the orientation state of the single fibers in the carbon fiber bundle was good. Moreover, the cured product could be produced without any practical problems, and the productivity of the carbon fiber composite material was also good.

(Comparative Example 1)
<Preparation of sizing agent S3>
Sizing agent S3 was prepared by the same method as in Example 1 with the formulation shown in S3 of Table 1.
<Manufacture of sizing treated carbon fiber bundles and unidirectional reinforced fabric>
In Example 1, except that the sizing agent S1 was changed to the sizing agent S3, a unidirectional reinforced fabric having a basis weight of 200 g / m ² was obtained and evaluated in the same manner as in Example 1.
When a cured product (carbon fiber composite material) was manufactured by impregnating the unidirectional reinforced fabric with resin in this example outdoors, the cantilever value of the unidirectional reinforced fabric was low, which caused problems with manufacturability. there were. Moreover, the orientation of the single fiber in the carbon fiber bundle which comprises hardened | cured material was bad visually.

(Comparative Example 2)
<Preparation of sizing agent S4>
Sizing agent S4 was prepared in the same manner as in Example 2 with the formulation shown in S4 of Table 1.
<Manufacture of sizing treated carbon fiber bundles and unidirectional reinforced fabric>
In Example 1, except that the sizing agent S1 was changed to the sizing agent S4, a unidirectional reinforced fabric having a basis weight of 200 g / m ² was obtained and evaluated in the same manner as in Example 1.
When a cured product (carbon fiber composite material) was manufactured by impregnating the unidirectional reinforced fabric with resin in this example outdoors, the cantilever value of the unidirectional reinforced fabric was low, which caused problems with manufacturability. there were. Moreover, the orientation of the single fiber in the carbon fiber bundle which comprises hardened | cured material was bad visually.

(Comparative Example 3)
In Example 3, except that the fiber density of the warp yarn of the unidirectional reinforced fabric was changed to 19 / inch, a unidirectional reinforced fabric having a basis weight of 600 g / m ² was obtained and the same as in Example 1. And evaluated.
When an attempt was made to obtain a cured product by actually impregnating the unidirectional reinforced fabric of this example with a resin outdoors, the resin impregnation property was poor. Therefore, the orientation of the single fiber in the carbon fiber composite material is not evaluated.

(Comparative Example 4)
In Example 3, the carbon fiber bundle used as the warp was changed to Pyrofil TR40 (product name), manufactured by Mitsubishi Rayon Co., Ltd. (12,000 filaments, strand strength 4700 MPa, strand elastic modulus 235 GPa). Similarly, a unidirectional reinforced fabric having a basis weight of 200 g / m ² was obtained and evaluated in the same manner as in Example 1.
When an attempt was made to obtain a cured product by actually impregnating the unidirectional reinforced fabric of this example with a resin outdoors, the resin impregnation property was poor. Therefore, the orientation of the single fiber in the carbon fiber composite material is not evaluated.

  From the results of Table 2, the unidirectional reinforced fabrics obtained in Examples 1 to 4 satisfy all of Condition A, Condition B, Condition C-1, Condition C-2, and Condition D in the present invention. Thus, even when the resin impregnation operation was performed manually, the woven fabric was not easily deformed, and the linearity of the carbon fiber was kept good.

Further, in Example 2, a unidirectional reinforced fabric with a basis weight of 200 g / m ² was manufactured, and the obtained unidirectional reinforced fabric satisfies all of Condition B, Condition C-1, Condition C-2, and Condition D. This is an example of producing a unidirectional reinforced fabric with a basis weight of 300 g / m ² by changing only the fiber density of the warp yarn under the production conditions of Example 1. Also in Example 2, a unidirectional reinforcing fabric satisfying all of the conditions (a), (b), (c) -1, (c) -2, and (d) was obtained.
Similarly, in Example 4, a unidirectional reinforced fabric having a basis weight of 200 g / m ² was manufactured, and the unidirectional reinforced fabric obtained had all of Condition B, Condition C-1, Condition C-2, and Condition D. This is an example of producing a unidirectional reinforced fabric with a basis weight of 300 g / m ² by changing only the fiber density of the warp yarn under the production conditions of Example 3 to be satisfied. Also in Example 3, a unidirectional reinforced fabric satisfying all of the conditions (a), (b), (c) -1, (c) -2, and (d) was obtained.

On the other hand, Comparative Examples 1 and 2 in which the sizing agent used in the production of the sizing-treated carbon fiber bundle was the sizing agents S3 and S4 having a low C component content had a low cantilever value for the sizing-treated carbon fiber bundle. B, Condition C-1 and Condition C-2 were not satisfied, and the manufacturability of the carbon fiber composite material and the orientation of the single fiber in the oriented carbon fiber composite material were not good.
In Comparative Example 3, a unidirectional reinforced fabric with a basis weight of 200 g / m ² was manufactured, and the obtained unidirectional reinforced fabric satisfied all of Condition B, Condition C-1, Condition C-2, and Condition D. In the production conditions of Example 3, only the fiber density of the warp is changed, but the basis weight is as large as 600 g / m ² and does not satisfy the condition A. The obtained unidirectional reinforced fabric satisfied Condition B, Condition C-1, Condition C-2, and Condition D, but the resin impregnation property was poor.
In Comparative Example 4, the roundness of the cross section of the single fiber is high and does not satisfy the condition d. The obtained unidirectional reinforced fabric satisfies Condition A, Condition B, Condition C-1 and Condition C-2, but the resin impregnation property was poor.

DESCRIPTION OF SYMBOLS 1 Test piece 1a End part of test piece 2 Horizontal surface 3 Press plate 3a End part of press plate 4 Slope 11 Unidirectional reinforced fabric test piece 12, 13 Release film 14, 15 Epoxy resin 21 Unidirectional reinforced fabric resin cured product 22 Evaluation Target area 31 Unidirectional reinforced fabric 32 Adhesive tape 33 Cut location X Fiber axis direction

Claims (8)

A unidirectionally reinforced fabric composed of warp yarns composed of carbon fiber bundles and weft yarns that restrain the warp yarns, satisfying the following conditions (a), (b), and (d), and satisfying the following conditions c-1 and / or c-2 , One-way reinforced fabric.
Condition A: The basis weight of the unidirectional reinforcing fabric is 100 g / m ² or more and 500 g / m ² or less.
Condition b: The cantilever value of the unidirectional reinforced fabric measured by the following measuring method (b) is 170 mm or more.
Condition C-1: The degree of orientation of single fibers in the carbon fiber bundle constituting the unidirectional reinforced fabric measured by the following measurement method (C-1) is 91% or more.
Condition C-2: In a cured product of a unidirectionally reinforced fabric and a resin measured by the following measurement method (C-2), the degree of orientation of the single fiber in the carbon fiber bundle constituting the cured product is 91% or more. is there.
Condition d: The roundness of the cross section of the single fiber in the carbon fiber bundle constituting the unidirectional reinforced fabric measured by the following measuring method (d) is 92% or less.
[Measurement method (b)]
(Procedure 1) A test piece having a size of 40 cm in the warp fiber axis direction and 1 inch in the direction perpendicular to the warp fiber axis is cut out from the unidirectional reinforcing fabric.
(Procedure 2) Place the test piece on the horizontal plane of a measuring table having a horizontal plane and a slope with an inclination angle of 45 degrees inclined downward from one end of the horizontal plane. Align with the boundary line A between the slope and the horizontal plane. A pressing plate is placed on the test piece, and the end of the pressing plate is aligned with the boundary line A.
(Procedure 3) Next, the pressing plate is moved in the horizontal direction toward the slope at a speed of 2 cm / second, and the movement of the pressing plate is stopped when the end of the test piece comes into contact with the slope.
(Procedure 4) The moving distance of the pressing plate is the cantilever value of the unidirectional reinforced fabric.
[Measurement method (C-1)]
(Procedure 1) A test piece having a side of 11.2 cm is cut out from the unidirectional reinforcing fabric.
(Procedure 2) An observation image of the test piece is obtained using an optical microscope. The observation direction is a direction perpendicular to the surface of the unidirectional reinforcing fabric, the observation magnification is 50 times, and the observation place is a carbon fiber bundle portion near the weft.
(Procedure 3) A two-dimensional Fourier transform is performed on the observed image to obtain a transformed image.
(Procedure 4) In the converted image, luminance information at a constant radius from the origin is acquired in the circumferential direction, and a one-dimensional profile is obtained with the horizontal axis representing the angle and the vertical axis representing the luminance information. The constant radius is a length corresponding to a period of 20 μm in the observation image.
(Procedure 5) In the one-dimensional profile, two peaks derived from the period of the carbon fiber are at positions different by 180 degrees in angle. If the peak is divided by 0 degrees or 360 degrees in angle, this is not recognized as a peak. An analysis target peak is an arbitrary peak for two peaks and a peak for one peak.
(Procedure 6) The analysis target peak is fitted with a composite curve of a Gaussian function and a Lorentz function, and the half width of the obtained composite curve is obtained. The half width is a difference θ2−θ1 between the angle θ1 on the low angle side and the angle θ2 on the wide angle side, which is half the peak height of the composite curve.
(Procedure 7) The degree of orientation is obtained from the following formula (1-1) using the half width.
Degree of orientation [%] = (180−half width) / 180 × 100 Formula (1-1)
[Measurement method (C-2)]
(Procedure 1) A test piece having a side of 11.2 cm is cut out from the unidirectional reinforcing fabric.
(Procedure 2) Two square release films each having a side of 20 cm and having a release treatment on at least one side are prepared.
(Procedure 3) Place one sheet of the release film with the release treatment surface facing upward, drop 3 g of epoxy resin on the center, and place the test piece obtained in Procedure 1 on this. . Next, 3 g of an epoxy resin is dropped on the center of the test piece, and another release film is placed on the test piece so that the release treatment surface faces down to obtain a laminate. Next, a glass plate having a size of 21 cm × 23 cm × 4 mm and a weight of 0.6 kg was placed on the laminate and allowed to stand for 3 minutes, and then the bottom of the glass plate was a square having a size of 11 cm × 12 cm. The epoxy resin is cured by placing a weight of 10.5 kg and allowing to stand for 5 days. Thereafter, the weight and the glass plate are removed, and the two release films are peeled off to obtain a unidirectional reinforced fabric resin cured product in which the unidirectional reinforced fabric test piece and the epoxy resin cured product are integrated. As the epoxy resin in this procedure, Bond E2500S (product name, main agent / curing agent = 2/1 (mass ratio)) manufactured by Konishi Co., Ltd. is used.
(Procedure 4) An evaluation object region is provided at the center of the obtained unidirectional reinforced fabric resin cured product. The evaluation target region is a square having a side of 4 cm so that the two sides are parallel to the fiber axis direction. Using the optical microscope, the said evaluation object area | region is observed from a perpendicular | vertical direction with respect to the surface of a unidirectional reinforced textile resin cured | curing material, and an observation image is obtained. The observation conditions are an observation magnification of 50 times, a slanted illumination, and a dark field, and the observation place is a carbon fiber bundle portion near the weft.
(Procedure 5) Hereinafter, the degree of orientation is determined in the same manner as in Procedures 3 to 7 in the measurement method (C-1).
[Measurement method (d)]
(Procedure 1) A unidirectional reinforced fabric is impregnated with a resin and cured to obtain a cured product.
(Procedure 2) A polished surface having a cross section perpendicular to the fiber axis of the carbon fiber bundle of the cured product is obtained.
(Procedure 3) The polished surface is observed with a microscope from a direction perpendicular to the polished surface to obtain an observation image of a single fiber cross section.
(Procedure 4) The minimum ferret diameter and the maximum ferret diameter of the cross section of the single fiber are obtained from the observed image.
(Procedure 5) The roundness of the cross section of the single fiber is obtained from the minimum ferret diameter and the maximum ferret diameter using the following equation (1-2).
Roundness [%] = minimum ferret diameter / maximum ferret diameter × 100 Formula (1-2) The unidirectional reinforcing fabric according to claim 1, wherein the carbon fiber bundle is a carbon fiber bundle to which the following carbon fiber sizing agent is attached.
An ester of an epoxy compound having a plurality of epoxy groups in the molecule and an unsaturated monobasic acid, the compound having at least one epoxy group in the molecule (A);
A bifunctional urethane acrylate oligomer (B) having a tensile elongation of the cured product of 40% or more;
Containing one or more thermoplastic resins (C) selected from the group consisting of a styrene elastomer resin (C-1), a phenoxy resin (C-2), and a terpene resin (C-3);
The ratio (mass ratio) of the content of the compound (A) and the urethane acrylate oligomer (B) is within the range of urethane acrylate oligomer (B) / compound (A) = 1/3 to 2/1.
The ratio of the total amount of the compound (A) and the urethane acrylate oligomer (B) in all sizing components is 18% by mass or more, and the ratio of the thermoplastic resin (C) in all sizing components is 5%. Carbon fiber sizing agent in a range of ˜40 mass%.   The carbon fiber sizing agent further includes an ester compound (D) of an alkylene oxide adduct of bisphenols and a dicarboxylic acid compound, the acid value of which is 50 or more, and the ester compound (D) The unidirectional reinforcing fabric according to claim 2, wherein the content of is 2.0 mass times or less of the total amount of the compound (A) and the urethane acrylate oligomer (B). The unidirectional reinforcing fabric according to any one of claims 1 to 3, wherein a cantilever value of the carbon fiber bundle measured by the following measuring method (e) is 200 mm or more.
[Measurement method (e)]
(Procedure 1) A test carbon fiber bundle having a length of 40 cm is cut out from the carbon fiber bundle.
(Procedure 2) The test carbon fiber bundle is placed on the horizontal plane of a measuring table having a horizontal plane and a slope with an inclination angle of 45 degrees inclined downward from one end of the horizontal plane. The end of the fiber bundle is aligned with the boundary line A between the slope and the horizontal plane. A pressing plate is placed on the test carbon fiber bundle, and the end of the pressing plate is aligned with the boundary line A.
(Procedure 3) Next, the presser plate is moved in the horizontal direction toward the slope at a speed of 2 cm / second, and the movement of the presser plate is stopped when the end of the test carbon fiber bundle comes into contact with the slope.
(Procedure 4) The moving distance of the pressing plate in the procedure 3 is a numerical value x.
(Procedure 5) Next, the test carbon fiber bundle is turned upside down and the positions of both ends are reversed, and the moving distance y is obtained in the same procedure as in Procedures 2 to 4.
(Procedure 6) The average value of the numerical value x and the numerical value y is set as the cantilever value of the carbon fiber bundle.   A prepreg obtained by impregnating the unidirectional reinforced fabric according to any one of claims 1 to 4 with a resin.   A carbon fiber composite material obtained by curing the prepreg according to claim 5. A fabric having a fabric weight of 200 g / m ^{2 having} a weight per unit consisting of carbon fiber bundles and a weft binding the warp yarn is produced, and the obtained unidirectional reinforcing fabric satisfies the following conditions (b) and (d): when satisfying the following condition c-1 and / or c -2 wherein the unidirectional reinforcing manufacturing conditions the fabric is obtained, by adjusting the fiber density of the warp yarns having a basis weight 100 g / ^{m 2} or more 500 g / ^{m 2} The manufacturing method of the unidirectional reinforcement fabric which manufactures the following unidirectional reinforcement fabric.
Condition b: The cantilever value of the unidirectional reinforced fabric measured by the following measuring method (b) is 170 mm or more.
Condition C-1: The degree of orientation of single fibers in the carbon fiber bundle constituting the unidirectional reinforced fabric measured by the following measurement method (C-1) is 91% or more.
Condition C-2: In a cured product of a unidirectionally reinforced fabric and a resin measured by the following measurement method (C-2), the degree of orientation of the single fiber in the carbon fiber bundle constituting the cured product is 91% or more. is there.
Condition d: The roundness of the cross section of the single fiber in the carbon fiber bundle constituting the unidirectional reinforced fabric measured by the following measuring method (d) is 92% or less.
[Measurement method (b)]
(Procedure 1) A test piece having a size of 40 cm in the warp fiber axis direction and 1 inch in the direction perpendicular to the warp fiber axis is cut out from the unidirectional reinforcing fabric.
(Procedure 2) Place the test piece on the horizontal plane of a measuring table having a horizontal plane and a slope with an inclination angle of 45 degrees inclined downward from one end of the horizontal plane. Align with the boundary line A between the slope and the horizontal plane. A pressing plate is placed on the test piece, and the end of the pressing plate is aligned with the boundary line A.
(Procedure 3) Next, the pressing plate is moved in the horizontal direction toward the slope at a speed of 2 cm / second, and the movement of the pressing plate is stopped when the end of the test piece comes into contact with the slope.
(Procedure 4) The moving distance of the pressing plate is the cantilever value of the unidirectional reinforced fabric.
[Measurement method (C-1)]
(Procedure 1) A test piece having a side of 11.2 cm is cut out from the unidirectional reinforcing fabric.
(Procedure 2) An observation image of the test piece is obtained using an optical microscope. The observation direction is a direction perpendicular to the surface of the unidirectional reinforcing fabric, the observation magnification is 50 times, and the observation place is a carbon fiber bundle portion near the weft.
(Procedure 3) A two-dimensional Fourier transform is performed on the observed image to obtain a transformed image.
(Procedure 4) In the converted image, luminance information at a constant radius from the origin is acquired in the circumferential direction, and a one-dimensional profile is obtained with the horizontal axis representing the angle and the vertical axis representing the luminance information. The constant radius is a length corresponding to a period of 20 μm in the observation image.
(Procedure 5) In the one-dimensional profile, two peaks derived from the period of the carbon fiber are at positions different by 180 degrees in angle. If the peak is divided by 0 degrees or 360 degrees in angle, this is not recognized as a peak. An analysis target peak is an arbitrary peak for two peaks and a peak for one peak.
(Procedure 6) The analysis target peak is fitted with a composite curve of a Gaussian function and a Lorentz function, and the half width of the obtained composite curve is obtained. The half width is a difference θ2−θ1 between the angle θ1 on the low angle side and the angle θ2 on the wide angle side, which is half the peak height of the composite curve.
(Procedure 7) The degree of orientation is obtained from the following formula (1-1) using the half width.
Degree of orientation [%] = (180−half width) / 180 × 100 Formula (1-1)
[Measurement method (C-2)]
(Procedure 1) A test piece having a side of 11.2 cm is cut out from the unidirectional reinforcing fabric.
(Procedure 2) Two square release films each having a side of 20 cm and having a release treatment on at least one side are prepared.
(Procedure 3) Place one sheet of the release film with the release treatment surface facing upward, drop 3 g of epoxy resin on the center, and place the test piece obtained in Procedure 1 on this. . Next, 3 g of an epoxy resin is dropped on the center of the test piece, and another release film is placed on the test piece so that the release treatment surface faces down to obtain a laminate. Next, a glass plate having a size of 21 cm × 23 cm × 4 mm and a weight of 0.6 kg was placed on the laminate and allowed to stand for 3 minutes, and then the bottom of the glass plate was a square having a size of 11 cm × 12 cm. The epoxy resin is cured by placing a weight of 10.5 kg and allowing to stand for 5 days. Thereafter, the weight and the glass plate are removed, and the two release films are peeled off to obtain a unidirectional reinforced fabric resin cured product in which the unidirectional reinforced fabric test piece and the epoxy resin cured product are integrated. As the epoxy resin in this procedure, Bond E2500S (product name, main agent / curing agent = 2/1 (mass ratio)) manufactured by Konishi Co., Ltd. is used.
(Procedure 4) An evaluation object region is provided at the center of the obtained unidirectional reinforced fabric resin cured product. The evaluation target region is a square having a side of 4 cm so that the two sides are parallel to the fiber axis direction. Using the optical microscope, the said evaluation object area | region is observed from a perpendicular | vertical direction with respect to the surface of a unidirectional reinforced textile resin cured | curing material, and an observation image is obtained. The observation conditions are an observation magnification of 50 times, a slanted illumination, and a dark field, and the observation place is a carbon fiber bundle portion near the weft.
(Procedure 5) Hereinafter, the degree of orientation is determined in the same manner as in Procedures 3 to 7 in the measurement method (C-1).
[Measurement method (d)]
(Procedure 1) A unidirectional reinforced fabric is impregnated with a resin and cured to obtain a cured product.
(Procedure 2) A polished surface having a cross section perpendicular to the fiber axis of the carbon fiber bundle of the cured product is obtained.
(Procedure 3) The polished surface is observed with a microscope from a direction perpendicular to the polished surface to obtain an observation image of a single fiber cross section.
(Procedure 4) The minimum ferret diameter and the maximum ferret diameter of the cross section of the single fiber are obtained from the observed image.
(Procedure 5) The roundness of the cross section of the single fiber is obtained from the minimum ferret diameter and the maximum ferret diameter using the following equation (1-2).
Roundness [%] = minimum ferret diameter / maximum ferret diameter × 100 Formula (1-2) The manufacturing method of the unidirectional reinforcement fabric of Claim 7 whose cantilever value of the said carbon fiber bundle measured by the following measuring methods (e) is 200 mm or more.
[Measurement method (e)]
(Procedure 1) A test carbon fiber bundle having a length of 40 cm is cut out from the carbon fiber bundle.
(Procedure 2) The test carbon fiber bundle is placed on the horizontal plane of a measuring table having a horizontal plane and a slope with an inclination angle of 45 degrees inclined downward from one end of the horizontal plane. The end of the fiber bundle is aligned with the boundary line A between the slope and the horizontal plane. A pressing plate is placed on the test carbon fiber bundle, and the end of the pressing plate is aligned with the boundary line A.
(Procedure 3) Next, the presser plate is moved in the horizontal direction toward the slope at a speed of 2 cm / second, and the movement of the presser plate is stopped when the end of the test carbon fiber bundle comes into contact with the slope.
(Procedure 4) The moving distance of the pressing plate in the procedure 3 is a numerical value x.
(Procedure 5) Next, the test carbon fiber bundle is turned upside down and the positions of both ends are reversed, and the moving distance y is obtained in the same procedure as in Procedures 2 to 4.
(Procedure 6) The average value of the numerical value x and the numerical value y is set as the cantilever value of the carbon fiber bundle.

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