JP2003292633A - Carbon fiber strand, and carbon fiber reinforced unsaturated matrix resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carbon fiber strand which excels in the adhesion to an unsaturated matrix resin, excels in the properties of a carbon fiber reinforced composite material, and industrially excels in the moldability of the composite material, and a carbon fiber reinforced unsaturated matrix resin. <P>SOLUTION: The carbon fiber strand for the unsaturated matrix resin contains ≥30 mass% vinyl ester resin and a sizing agent adhering thereto, and has a flatness (width-to-thickness) ratio in running at a tension of 200 gf of 25-70, and the unsaturated matrix resin is reinforced with the above fiber strand. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a carbon fiber for resin reinforcement and an unsaturated matrix resin such as an unsaturated polyester resin or a vinyl ester resin reinforced by the carbon fiber.

[0002]

2. Description of the Related Art Carbon fibers have characteristics of higher strength and elastic modulus and lighter weight than other fibers, and are therefore used in various industries including aerospace industry. Further, it is mainly used as a reinforcing material for a composite material containing a thermoplastic resin or a thermosetting resin related to the present invention as a matrix resin.

As a method for producing a composite material using a thermosetting resin as a matrix resin, in addition to a method of forming by using a prepreg which is an intermediate substrate, pultrusion molding, resin transfer molding (RTM) method, filament・ Winding (FW) method, sheet molding compound (SMC) method, bulk molding compound (BMC) method, hand lay-up method, etc.

As the thermosetting matrix resin, in addition to epoxy resin, unsaturated matrix resin such as unsaturated polyester resin or vinyl ester resin is used.

Unsaturated polyester resins and vinyl ester resins are generally used together with a polymerizable monomer such as styrene, have a lower viscosity and a higher curing speed than epoxy resins, and are used as composite materials produced by RTM or pultrusion molding. Widely used as matrix resin.

However, when carbon fiber having a conventional epoxy resin sizing agent is used as a reinforcing material for a composite material containing an unsaturated polyester resin or a vinyl ester resin as a matrix resin, the physical properties of the resulting composite material are epoxy. It may be lower than the composite material in which the resin is a matrix resin. Specifically, among the various physical properties, the adhesiveness between the carbon fiber and the unsaturated polyester resin or the vinyl ester resin, especially the shear strength is lower than that of the epoxy resin, and it may be difficult to put into practical use as a composite material. is there.

As a technique for improving the adhesiveness between the carbon fiber and the unsaturated matrix resin, a method of attaching a vinyl ester resin to the carbon fiber (Japanese Patent Publication No. 62-18671) or a urethane compound having an unsaturated group is used. A method of attaching to a fiber (JP-A-56-167715, JP-A-63-50573), and a method of attaching an ester compound having a terminal unsaturated group to a carbon fiber (JP-A-6).
3-105178). But,
Since the morphology and surface characteristics of carbon fiber were not taken into consideration, its effect was insufficient.

Also disclosed is a method of adhering a compound having an isocyanate group and a terminal unsaturated group to a carbon fiber whose surface functional group amount is adjusted to improve the adhesiveness to an unsaturated matrix resin (JP-A-11-93078). Has been done.
However, since the carbon fiber morphology after the sizing agent is not considered, impregnation defects and cutting problems occur in the field of pultrusion molding where unsaturated polyester resins and vinyl ester resins are widely used as matrix resins for composite materials. This is the current situation.

[0009]

The present inventor has made various investigations to solve the above-mentioned problems, and found that the form of carbon fibers is a strand (a fiber bundle composed of hundreds to tens of thousands of filaments). By setting the flatness of the carbon fiber strands during running in a predetermined range and containing a vinyl ester resin in a predetermined amount or more as a sizing agent, the obtained carbon fiber strands are suitable for unsaturated matrix resin-based composite materials. As a result, they have come to complete the present invention by knowing that they can be used as a reinforcing material.

Therefore, the object of the present invention is to provide a carbon fiber strand excellent in adhesiveness with an unsaturated matrix resin, a physical property of a carbon fiber reinforced composite material, and an industrially excellent composite material moldability, and the above-mentioned fiber. It is to provide an unsaturated matrix resin reinforced by strands.

[0011]

The present invention for achieving the above object is as described below.

[1] 30 mass% of vinyl ester resin
A carbon fiber strand for reinforcing an unsaturated matrix resin, in which 0.3 to 5.0% by mass of the above-described sizing agent is adhered, and is flat during running after being rollered at a tension of 200 gf at a speed of 5 m / min. Rate (width / thickness)
25-70 carbon fiber strands.

[2] 1000 to 1000 carbon fiber strands
The carbon fiber strand according to [1], which comprises 50,000 carbon fiber filaments.

[3] The carbon fiber strand according to [1], wherein the carbon fiber strand has a texture of 150 to 1500 gf / mm ² .

[4] The carbon fiber strand according to [1], wherein the degree of poor dispersion of the carbon fiber strand in a styrene solvent is 3 to 50 per 10,000 carbon fiber filaments.

[5] The carbon fiber strand according to [1], wherein the vinyl ester resin is a bis type methacrylic vinyl ester resin.

[6] The carbon fiber according to [1], wherein the carbon fiber constituting the carbon fiber strand has a surface oxygen concentration ratio O / C measured by X-ray photoelectron spectroscopy of 0.1 to 0.3. Strand.

[7] A carbon fiber reinforced unsaturated matrix resin reinforced by the carbon fiber strand according to any one of [1] to [6].

[8] The carbon fiber reinforced unsaturated matrix resin according to [7], wherein the unsaturated matrix resin is an unsaturated polyester resin or a vinyl ester resin and is used for pultrusion molding.

The present invention will be described in detail below.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The carbon fiber strand of the present invention has a sizing agent attached thereto, and the sizing agent contains 30% by mass or more of a vinyl ester resin. This vinyl ester resin is a chain polymer compound having a reactive unsaturated group only at the terminal and can be synthesized, for example, with an epoxy resin and an unsaturated monobasic acid.

The vinyl ester resin contained in the sizing agent attached to the carbon fiber strand of the present invention is not particularly limited, but a bis-methacrylic vinyl ester resin is particularly preferable because it has excellent toughness. Examples of the bis-based methacrylic vinyl ester resin include epoxy ester 3002M and epoxy ester 3000M manufactured by Kyoeisha Chemical Co., Ltd.

As will be described later, the carbon fiber strand of the present invention has a running flatness of 25 to 70 after being rollered at a speed of 5 m / min and a tension of 200 gf, and particularly preferably 30 to 60. When the running flatness is less than 25, it is difficult to impregnate the inside of the fiber strands with the matrix resin, and particularly when impregnating the resin during traveling such as pultrusion molding, it is extremely remarkable, which is not preferable. If the running flatness exceeds 70, the amount of resin brought into the die in the next step from the resin bath during drawing will increase, and the drawing tension will increase.
Eventually, problems such as cutting are likely to occur, which is not preferable.

The running flatness is defined by the following equation (1).

[0025]

## EQU00001 ## Running flatness = running carbon fiber strand width (W1) / carbon fiber strand thickness (D) (1) The carbon fiber strand of the present invention is a bundle of carbon fiber filaments. The number is preferably 1,000 to 50,000 per bundle.

The carbon fiber constituting the carbon fiber strand is not particularly limited as a raw material, but polyacrylonitrile (PAN) type carbon fiber, pitch type carbon fiber, rayon type carbon fiber and the like can be exemplified. Of these carbon fibers, P suitable for handling performance and manufacturing process passing performance
AN-based carbon fiber is particularly preferable. Here, the PAN-based carbon fiber is a carbon fiber-based copolymer containing an acrylonitrile structural unit as a main component and containing vinyl monomer units such as itaconic acid, acrylic acid, and acrylic ester within 10 mol%. is there.

The carbon fiber constituting the carbon fiber strand of the present invention has a surface oxygen concentration ratio O / C measured by X-ray photoelectron spectroscopy of 0.1 to 0. It is preferably 3.

If the surface oxygen concentration O / C is less than 0.1, the adhesiveness with the matrix resin will be poor and this will cause deterioration of the physical properties of the composite material. On the other hand, when the surface oxygen concentration O / C exceeds 0.3, the strength of the carbon fiber itself decreases, which is not preferable.

In order to keep the surface oxygen concentration ratio O / C of the carbon fiber within the above range, it is preferable to carry out a surface treatment after the carbonization treatment in the carbon fiber production process.

Examples of such surface treatment include liquid phase treatment and gas phase treatment. In the present invention, the liquid-phase electrolytic surface treatment is preferable from the viewpoint of productivity, treatment uniformity, stability and the like.

As an index for controlling the degree of surface treatment of carbon fiber, the surface oxygen concentration ratio O / C of carbon fiber measured by X-ray photoelectron spectroscopy (XPS) is preferable.

The O / C can be obtained by the following method as an example. By using an X-ray photoelectron spectroscope ESCA JPS-9000MX manufactured by JEOL Ltd., the carbon fiber preliminarily stripped of the sizing agent was put into a measuring chamber depressurized to 10-6 Pa, and the electron beam accelerating voltage 10 k with Mg as a counter electrode
The X-ray generated under the conditions of V and 10 mA is irradiated, the spectrum of photoelectrons generated from carbon atoms and oxygen atoms is measured, and the area ratio is calculated.

The proportion of photoelectrons generated differs depending on each element. This X-ray photoelectron spectrometer ESCA manufactured by JEOL Ltd.
The conversion factor according to the device characteristics of JPS-9000MX is 2.69.

It is preferable that the surface-treated carbon fiber is thoroughly washed to remove the electrolyte, and then the above-mentioned sizing agent is applied thereto.

The sizing agent is applied by a spray method, a liquid immersion method,
Although a known method such as a transfer method can be adopted, the liquid immersion method is particularly preferable because it is excellent in versatility, efficiency, and uniformity of application.

When the carbon fiber strands are dipped in the sizing liquid, opening and squeezing are repeated through the immersion roller or the immersion roller provided in the sizing liquid to impregnate the sizing agent to the core of the strand. It is preferable.

The sizing agent can be applied by a solvent method in which carbon fibers are immersed in a solution in which vinyl ester is dissolved in a solvent such as acetone, but an emulsion in which carbon fibers are immersed in an aqueous emulsion using an emulsifier or the like. The method is preferable from the viewpoint of safety to the human body and prevention of pollution of the natural environment.

Further, auxiliary components such as a dispersant and a surfactant may be added in order to improve the handling property, scratch resistance, fluff resistance and impregnation property of the carbon fiber. Further, other compounds such as polyurethane, polyester, polyamide and epoxy resin may be added in order to further improve the focusing property.
These may be added to the size bath containing the vinyl ester resin, or may be applied in two or more stages. The addition amount of the auxiliary component is preferably 50% by mass or less of the attached amount of the sizing agent.

The amount of the sizing agent deposited is 0.3 to 5.0% by mass.
Is preferable in terms of handleability. When the amount of the sizing agent attached is less than 0.3% by mass, the carbon fiber cannot obtain the adhesiveness with the unsaturated matrix resin satisfying the present invention, and the sizing property is poor, which is not preferable. On the other hand, the amount of sizing agent deposited is 5.
When it exceeds 0% by mass, it impedes the impregnation of the carbon fiber strands with the matrix resin, which is not preferable.

After the sizing treatment, the carbon fiber strands are dried by a usual drying process such as water which is a dispersion medium at the time of sizing or a solvent which is a solvent. For the drying step, a known method such as a method of passing through a drying furnace or a method of contacting with a heated roller can be adopted. The drying temperature is not particularly limited, but in the case of a general-purpose aqueous emulsion, it is usually set to 80 ° C to 200 ° C. Further, in the present invention, after the drying step, a heat treatment step at 200 ° C. or higher can be performed.

The carbon fiber strand of the present invention has a texture of 150 to 1500 g obtained by the measuring method described later.
It is preferably f / mm ² (1.5 to 15 MPa). If the texture is less than 150 gf / mm ² , partial sagging of the carbon fiber strands will occur in the process such as pultrusion molding where the distance between the fulcrums of the fulcrums (guide rollers, etc.) supporting the carbon fiber strands is large. ,
It is not preferable because it easily causes troubles such as winding and cutting. On the other hand, if it exceeds 1500 gf / mm ² , it is not preferable because the spreadability of the carbon fiber strands is reduced and the impregnation property of the matrix resin is reduced.

The carbon fiber strand in the present invention preferably has a degree of poor dispersion in a styrene solvent of 3 to 50 per 10,000 filaments.

When the degree of dispersion failure is less than 3, the carbon fiber strands are unnecessarily opened and impregnated during the resin impregnation in the pultrusion molding or FW molding of an unsaturated matrix resin such as unsaturated polyester or vinyl ester. This is not preferable because the bundle-forming property after that is deteriorated, and troubles such as cutting of a single yarn with a guide roller or a die are likely to occur.

On the other hand, when the degree of dispersion failure exceeds 50,
The unsaturated matrix resin is impregnated unevenly, which causes deterioration of the physical properties of the composite material, which is not preferable.

The strand tensile strength of the carbon fiber strand is preferably 4000 MPa or more, and 4500 MPa.
The above is more preferable.

Hereinafter, the present invention will be described in more detail with reference to examples.

[0047]

EXAMPLES Carbon fiber strands were produced under the conditions of the following examples and comparative examples. Various physical properties of each carbon fiber strand were measured by the following methods.

<Carbon Fiber Strand Width During Running> As shown in FIG. 1, the carbon fiber strand 4 wound from the set bobbin 2 comes in contact with the guide rollers 6, 8, 10 and 12 and then moves on the image sensor 14. Let it pass. Then, it was made to pick up by the nip rollers 16a and 16b at a speed of 5 m / min. At that time, be careful not to twist the carbon fiber strands 4, and the tension of the carbon fiber strands between the guide roller 6 and the nip rollers 16a and 16b is 200 gf (2N).
I adjusted it to be. The reading of the image sensor was started when the tension etc. became stable. Reading was performed at 2-second intervals for 1 minute, and the average of the readings was taken as the running carbon fiber strand width (W1).

The image sensor is manufactured by Keyence Corporation (sensor head VG-035, controller V
G-300) was used.

<Carbon fiber strand width at rest> Five bundles of carbon fiber strands cut to a length of 4 cm were prepared, and the width of each carbon fiber strand was measured by the above image sensor.
The average value was used as a carbon fiber strand at rest (W2).

<Carbon Fiber Strand Thickness> After the measurement of the width of the carbon fiber strand during running, the driving of the apparatus shown in FIG. 1 is stopped, and any carbon fiber strand between the guide roller 6 and the nip rollers 16a and 16b is stopped. 5
The thickness of the portion was measured using a thickness gauge (thickness gauge No. 2050F manufactured by Mitutoyo Corporation), and the average value was used as the carbon fiber strand thickness (D).

<Handling degree> The handing degree was measured using a hydrometer model: HOM-2 manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd. under the following conditions. Measurement sample: 20 cm long carbon fiber strand slit width: 5 mm (S) Measurement method: The sample was placed on the sample stand at right angles to the slit and with the center of the sample on the slit. Then width 1
This sample was pushed into the slits to a depth of 10 mm at a speed of 10 mm / sec using a metal plate having a length of 200 mm and a length of 200 mm, and the maximum load applied to the metal plate at this time was measured. For measurement, read the value indicated by the indicator, and measure 5
The measurement was repeated, and the average value was used as the measurement value (F).

[0053]

[Equation 2] F: Hydrometer measurement value [gf] S: Slit width (= 5 mm) W2: Resting carbon fiber strand width [mm] D: Carbon fiber strand thickness [mm] From the above measurement values, the texture is calculated by the above formula ( Calculated in 2).

<Dispersion Defect in Styrene Solvent> The carbon fiber strand was cut into a length of 3 mm and put into a 100 ml beaker containing 10 ml of a styrene solvent containing 0.5% by mass of a surfactant. This beaker is an ultrasonic cleaner (Honda Electronics Co., Ltd. 3-frequency ultrasonic cleaner model W-133)
The ultrasonic wave of 45 kHz was applied for 10 seconds. afterwards,
It was observed with an optical microscope at a magnification of 20 times, and the number of undispersed parts such as carbon fiber filaments entangled with each other was counted. A value obtained by converting the number value per 10,000 filaments was obtained, and this converted value was defined as the degree of dispersion failure (for example, 1
When measuring a carbon fiber strand composed of 2000 filaments, the number of undispersed parts was divided by 1.2. ).

<Pull-out test> 100 parts of a vinyl ester resin (Lipoxy R-806 manufactured by Showa Polymer Co., Ltd.) and 2 parts of a peroxide curing agent (Percure-O manufactured by NOF CORPORATION) were used as resin matrices (long). Size: 400 mm, width: 120
mm, height: 100 mm). An appropriate number of carbon fiber strands cut into a length of 30 cm are bundled in parallel (hereinafter referred to as a sample bundle), and both ends are commercially available carbon fiber strands (Besphite 1200 manufactured by Toho Tenax Co., Ltd.).
0 filaments, a tensile strength of 3900 MPa, a tensile elastic modulus of 235 GPa) are tied and fixed. Of these, for one end, one bundle of commercially available carbon fiber strands used for fixation (hereinafter referred to as induction yarn) is passed through a drawing guide and a tubular mold (content cross section: 10 mm x 3 mm, length 300 mm) in advance. I let it. The sample bundle was dipped in parallel with the length direction of the resin bath, and after soaking for 30 seconds, the guide yarn was pulled so that the sample bundle fits in the mold. After that, the guide yarn was cut and removed. The number of carbon fiber strands forming the sample bundle was determined by the cross-sectional area of the carbon fiber single fibers and the number of filaments of the carbon fiber strand (adjusted so that the carbon fiber volume content Vf was 60%). From the above pulling test, ○: no particular problem △: fluff lumps were generated at the drawing guide or the mold inlet ×: guide yarn was cut during induction Based on the above pullability index, the pullability was evaluated. .

<Interlaminar Shear Strength (ILSS)> The mold filled with the above sample bundle was placed in an oven at 150 ° C. for 7 minutes to cure the matrix resin. A test piece conforming to JIS K7078 was prepared from the released molded product, and ILSS was measured according to the same regulations.

<Wettability> In the above-mentioned molded product, a portion not used for ILSS measurement was subjected to bending test fracture, and the fracture surface was observed by SEM. ◎: Resin adhered to almost the entire fiber surface ○: Fiber surface Resin adheres to the most part Δ: Resin adheres to a part of the fiber surface ×: Almost no resin adhesion to the fiber surface can be observed. The wettability was evaluated based on the above wettability index.

Examples 1 to 5, Comparative Examples 1 to 2 Unsized carbon fiber strands (produced by Toho Tenax Co., Ltd.) in which the surface oxygen concentration ratio O / C of carbon fibers measured by X-ray photoelectron spectroscopy is 0.2. Bethfight 1200
0 filament, tensile strength 4800 MPa, tensile elastic modulus 240 GPa) bisphenol A methacrylic vinyl ester resin (Kyoeisha Chemical Co., Ltd. epoxy ester 30
100 M) was continuously dipped in a sizing bath containing a water emulsion obtained by emulsifying 100 parts of polyoxyethylene styrenated phenol ether with 40 parts, and then water was removed by drying to obtain a carbon fiber strand. At that time, the carbon fiber strands listed in Table 1 were obtained by adjusting the bath concentration, the drying temperature, and the sizing method. Using these carbon fiber strands, the various evaluation tests listed above were performed. The results are summarized in Table 1.

As the sizing method, method A, method B, method C, method D and method E shown in FIGS. 2, 3, 4, 5 and 6, respectively, were appropriately used.

In each of the sizing methods of FIGS. 2, 3, 4, 5 and 6, carbon fiber strands 22, 32,
42, 52 and 72 are guide rollers 24, 34, 4
4, 54 and 74, sizing baths 26, 36, 4
6, 56 and 76 were continuously dipped. Then, if necessary, the squeezing rollers 28, 30, 38, 58 and 7
8, and heat rollers 60, 62, 64, 66,
It was conveyed to a drying furnace via 80 and 82.

As shown in the results of Table 1, Examples 1 to 6
In all cases, satisfactory results were obtained. However, in Comparative Example 1, the flatness of the carbon fiber strand during traveling was low and the wettability was Δ.
Etc., no satisfactory result was obtained. In Comparative Example 2, the running flatness of the carbon fiber strands, the texture, and the degree of poor dispersion were high, and the drawability was x and the like, and satisfactory results were not obtained.

[0062]

[Table 1] Table 1 ──────────────────────────────────── Example No Comparative Example No ── ──────────── ───── 1 2 3 4 5 1 2 ─────────────────────────── ────────── Sizing agent concentration (g / L) 17 29 32 22 22 20 20 Drying temperature (℃) 120 120 120 100 160 120 200 Sizing method A E A B E C D Sizing agent Adhesion amount (% by mass) 0.7 1.6 2.0 1.0 1.0 1.0 1.0 Width of running carbon fiber strand (mm) 6.7 7.1 6.0 6.3 8.2 5.3 10.5 Width of resting carbon fiber strand (mm) 6.2 5.7 5.5 5.8 7.5 4.9 10.3 Thickness of carbon fiber strand ( mm) 0.16 0.15 0.16 0.20 0.15 0.22 0.14 Running flatness (%) 42 47 38 32 55 24 75 Texture (gf / mm ² ) 536 741 817 388 948 486 2551 Dispersion degree 21 32 41 9 36 46 82 Pullability ○ ○ ○ ○ ○ ○ × Wettability ◎ ◎ ○ ◎ △ ○ ○ ILSS (MPa) 80 83 85 81 86 76 80 ────────────────────────────────── Example 6 An unsized carbon fiber strand having a surface oxygen concentration ratio O / C of carbon fiber measured by X-ray photoelectron spectroscopy of 0.2 (Besphite, 1200 manufactured by Toho Tenax Co., Ltd., 1200
0 filament, tensile strength 3900 MPa, tensile elastic modulus 235 GPa), bisphenol A methacrylic vinyl ester resin (Kyoeisha Chemical Co., Ltd. epoxy ester 3
(002M) 100 parts of polyoxyethylene styrenated phenol ether was continuously immersed in a sizing bath containing a water emulsion having a concentration of 20 g / l. After that, the water content is dried and removed at 120 ° C. (sizing method: B method) to obtain a carbon fiber strand having a size adhesion amount of 0.9%, a running flatness of 32, a texture of 454 gf / mm ² , and a dispersibility of 12. It was A pulling test was conducted using this carbon fiber strand, and the pullability was ◯, ILSS
Was 78 MPa and the wettability was ◯.

Comparative Example 3 An unsized carbon fiber strand having a surface oxygen concentration ratio O / C of 0.2 measured by X-ray photoelectron spectroscopy (Besphite, 1200 manufactured by Toho Tenax Co., Ltd.)
0 filament, tensile strength of 4800 MPa, tensile elastic modulus of 240 GPa), bisphenol A type epoxy resin (Epicote 1001 manufactured by Yuka Shell Epoxy Co., Ltd.) 100
Concentration of 25 parts emulsified with 30 parts of PO / EO polyether
It was continuously immersed in a sizing bath containing g / l of water emulsion. Then, the water content was dried and removed at 120 ° C. (sizing method: method A) to obtain a carbon fiber strand having a size adhesion amount of 1.3%, a running flatness of 30, a texture of 1423 gf / mm ² , and a dispersibility of 34. . When a pulling test was conducted using this carbon fiber strand, the pullability was ◯, the ILSS was 74 MPa, and the wettability was x, and the adhesion to the matrix resin was not satisfactory.

Comparative Example 4 An unsized carbon fiber strand having a surface oxygen concentration ratio O / C of 0.2 measured by X-ray photoelectron spectroscopy (Besphite, 1200 manufactured by Toho Tenax Co., Ltd.)
0 filament, tensile strength 4800 MPa, tensile elastic modulus 240 GPa, urethane modified epoxy resin (DIC
It was continuously immersed in a sizing bath containing a 20 g / l aqueous solution of N320). Then, the water content is dried and removed at 120 ° C. (sizing method: E method), and the size adhesion amount of 0.
6%, flatness during running 61, texture 425 gf / m
A carbon fiber strand having m ² and a dispersibility of 28 was obtained. When a pulling test was performed using this carbon fiber strand, the pullability was Δ, the ILSS was 72 MPa, and the wettability was ×, which were unsatisfactory results.

[0065]

Since the carbon fiber strand of the present invention has excellent adhesiveness with the unsaturated matrix resin, it is possible to obtain a carbon fiber reinforced unsaturated matrix resin composite material having excellent physical properties. Particularly in pultrusion molding, there are advantages that it is excellent in impregnating property and pultrusion property, and troubles during molding are prevented.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an example of a tester for measuring a running flatness of a carbon fiber strand.

FIG. 2 is a schematic explanatory diagram showing a sizing method for carbon fiber strands: Method A.

FIG. 3 is a schematic explanatory view showing a sizing method for carbon fiber strands: method B.

FIG. 4 is a schematic explanatory diagram showing a carbon fiber strand sizing method: method C.

FIG. 5 is a schematic explanatory view showing a sizing method of carbon fiber strands: D method.

FIG. 6 is a schematic explanatory view showing a carbon fiber strand sizing method: E method.

[Explanation of symbols]

2 bobbins 4 carbon fiber strands 6, 8, 10, 12 guide rollers 14 image sensors 16a, 16b nip rollers 22, 32, 42, 52, 72 carbon fiber strands 24, 34, 44, 54, 74 guide rollers 26, 36, 46, 56, 76 Sizing bath 28, 30, 38, 58, 78 Squeezing roller 60, 62, 64, 66, 80, 82 Heat roller

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Isao Nishimura             Toho Tena 234 Uechikari, Nagaizumi-cho, Sunto-gun, Shizuoka Prefecture             X Co., Ltd. (72) Inventor Sadataka Umemoto             Toho Tena 234 Uechikari, Nagaizumi-cho, Sunto-gun, Shizuoka Prefecture             X Co., Ltd. F-term (reference) 4F072 AA04 AA07 AB10 AB14 AB15                       AB17 AB22 AC05 AC14 AD08                       AD23 AD38 AK17

Claims (8)

[Claims] 1. A carbon fiber strand for reinforcing an unsaturated matrix resin, comprising 0.3 to 5.0% by mass of a sizing agent containing 30% by mass or more of a vinyl ester resin, the carbon fiber strand being at a speed of 5 m / min. Flatness (width / thickness) during running after rolling with a roller at a tension of 200 gf is 25
~ 70 carbon fiber strands. 2. The carbon fiber strand is 1000 to 500.
The carbon fiber strand according to claim 1, which is composed of 00 carbon fiber filaments. 3. The texture of carbon fiber strands is 150.
The carbon fiber strand according to claim 1, having a weight of ˜1500 gf / mm ² . 4. The carbon fiber strand according to claim 1, wherein the carbon fiber strand has a poor degree of dispersion in a styrene solvent of 3 to 50 per 10,000 carbon fiber filaments. 5. The carbon fiber strand according to claim 1, wherein the vinyl ester resin is a bis type methacrylic vinyl ester resin. 6. The carbon fiber strand according to claim 1, wherein the carbon fiber forming the carbon fiber strand has a surface oxygen concentration ratio O / C measured by X-ray photoelectron spectroscopy of 0.1 to 0.3. . 7. A carbon fiber reinforced unsaturated matrix resin reinforced by the carbon fiber strand according to claim 1. 8. The carbon fiber reinforced unsaturated matrix resin according to claim 7, wherein the unsaturated matrix resin is an unsaturated polyester resin or a vinyl ester resin and is used for pultrusion molding.