JP2003328271A - Carbon fiber strand, and carbon fiber-reinforced resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carbon fiber strand which has excellent adhesiveness to unsaturated matrix resins and gives carbon fiber-reinforced composite materials having excellent physical properties and industrially excellent moldability, and to provide a carbon fiber-reinforced resin. <P>SOLUTION: This carbon fiber strand to which a sizing agent is adhered in an amount of 0.3 to 5.0 wt.% has a weight loss rate of ≤1.0%, when heated at 200°C for 1 hr in air, and has a calorific value of 20 to 1,200 mJ/g at an exothermic peak and a heat release-initiating temperature of ≤200°C, when the carbon fiber strand is measured with a differential scanning calorimeter. And, the resin reinforced with the 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 a 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 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 polyester resin and vinyl ester resin which are unsaturated matrix resins related to the present invention are 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. Method of adhering to fibers (JP-A-56-167715, JP-A-63-50573, JP-A-11-9307)
8), a method of attaching an ester compound having a terminal unsaturated group to carbon fibers (JP-A-63-105178)
Is disclosed. However, since the control of the reactivity of the attached thermosetting compound is not taken into consideration, the curing rate is unstable in a molding method such as pultrusion molding or RTM in which shaping and curing proceed simultaneously. However, a stable molded product may not be obtained.

[0008]

The inventors of the present invention have made various investigations to develop a carbon fiber suitable for reinforcing a thermosetting resin. A fiber bundle consisting of tens of thousands of filaments), a sizing agent within a predetermined range is attached to this carbon fiber strand, a compound having an exothermic reactivity is used for this sizing agent, and its reactivity (heating value) is controlled. By doing
The inventors have learned that the carbon fiber strands can be a reinforcing material suitable for a thermosetting resin-based composite material, and have completed the present invention.

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

[0010]

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

[1] 0.3 to 5.0% by mass of sizing agent
Carbon fiber strands that have been attached and are in air 2
The mass reduction rate when heated at 00 ° C. for 1 hour is 1.0% or less, and the exothermic peak is 20 to 1 when the carbon fiber strand is measured by a differential scanning calorimeter.
A carbon fiber strand having 200 mJ / g and an exothermic start temperature of 200 ° C. or lower.

[2] The carbon fiber strand according to [1], wherein the sizing agent contains 30 mass% or more of a compound having an addition-polymerizable functional group.

[3] The carbon fiber strand according to [2], wherein the compound having an addition polymerizable functional group is a chain polymer having an addition polymerizable functional group at both ends.

[4] The carbon fiber strand according to [2], wherein the addition-polymerizable functional group is an unsaturated group.

[5] The carbon fiber strand according to [1], wherein the sizing agent contains 30% by mass or more of a vinyl ester resin.

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

[7] The flatness (width / thickness) of the cross section when the carbon fiber strand is cut perpendicularly to the length direction is 20.
The carbon fiber strand according to [1], which is ˜80.

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

[0019]

[9] The carbon fiber strand according to [1], wherein the carbon fiber strand has a texture of 150 to 2500 gf / mm ² .

[10] The carbon fiber strand according to [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.

[11] A carbon fiber reinforced resin in which an unsaturated polyester resin or a vinyl ester resin is reinforced with the carbon fiber strand according to any one of [1] to [10].

[12] The carbon fiber reinforced resin according to [11] for pultrusion.

[13] The carbon fiber reinforced resin according to [11] for resin transfer molding.

The present invention will be described in detail below.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The carbon fiber strand of the present invention has a sizing agent adhered thereto in an amount of 0.3 to 5.0% by mass.

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. on the other hand,
When the amount of the sizing agent attached exceeds 5.0% by mass, it impedes the impregnation of the carbon fiber strands with the matrix resin, which is not preferable.

The carbon fiber strand of the present invention has a mass reduction rate of 1. when heated in air at 200 ° C. for 1 hour.
It is 0% or less. If the mass reduction rate exceeds 1.0%, voids may be generated in the molded composite material, and the decomposed product may cause partial runaway of the curing of the matrix resin, resulting in poor physical properties of the molded composite material, which is not preferable. .

Further, the carbon fiber strand of the present invention has a calorific value of 20 to 1200 when measured with a differential scanning calorimeter.
It exhibits an exothermic peak with mJ / g and an exothermic onset temperature of 200 ° C. or lower.

When the calorific value is less than 20 mJ / g, the effect of the matrix resin and the carbon fiber as a binder is poor, the wettability of the resin to the carbon fiber is poor, and satisfactory physical properties of the composite material cannot be obtained, which is not preferable.

On the other hand, when the calorific value exceeds 1200 mJ / g, in a molding method in which shaping and curing proceed simultaneously such as pultrusion molding and RTM molding, curing is runaway and a stable molded product cannot be obtained. There is a possibility that it is not preferable.

If the heat generation start temperature, which is the rising point from the baseline of the DSC curve, exceeds 200 ° C.,
It is not preferable because the reactivity of the carbon fiber strands does not contribute during molding.

The sizing agent attached to the carbon fiber strand of the present invention preferably contains 30% by mass or more of a compound having an addition polymerizable functional group. The compound having an addition polymerizable functional group is preferably a chain polymer compound having an addition polymerizable functional group at both ends. Further, the addition-polymerizable functional group is preferably an unsaturated group.

More specifically, the size of the sizing agent adhered to the carbon fiber strand of the present invention is not particularly limited as long as it has heat resistance and appropriate reactivity, and examples thereof include epoxy resin, urethane resin and polyester resin. , Vinyl ester resin, polyamide resin, polyether resin, acrylic resin, polyolefin resin, polyimide resin and modified products thereof.

A suitable sizing agent can be appropriately selected according to the matrix resin. Also, these are 2
It is also possible to use a combination of more than one type.

In the present invention, it is particularly preferable to use a compound having an addition-polymerizable functional group as the sizing agent. On the other hand, when a compound having a polycondensable functional group is used as the sizing agent, water, alcohol, etc. are produced during the reaction, which is not preferable.

As the addition-polymerizable functional group, an epoxy group or an unsaturated group is particularly preferable because it easily exhibits addition-polymerization regardless of the self or partner functional group. The addition-polymerizable functional group is
Although it may be present in the side chain or in the middle of the main chain, it is preferable that it is at both ends of the main chain of the chain polymer compound because the reactivity can be easily controlled.

The matrix resin in the present invention is preferably a thermosetting resin such as an epoxy resin, an unsaturated polyester resin or a vinyl ester resin, but a polyamide resin,
Thermoplastic resins such as polyester resins, polyolefin resins, and polycarbonate resins can also be used.

The flatness of the cross section of the carbon fiber strand of the present invention is preferably 20 to 80, and particularly preferably 25 to 70. When the oblateness is less than 20, it is difficult to impregnate the inside of the fiber strand with the matrix resin, which is not preferable. If the oblateness exceeds 80, the amount of resin carried from the resin bath to the die in the next step increases and the drawing tension increases, as in the case of, for example, pultrusion molding, which eventually causes problems such as cutting. It is not preferable because it is easy to cause.

Here, the flatness is defined by the following equation (1).

[0040]

[Formula 1] Running flatness = Carbon fiber strand width (W) / Carbon fiber strand thickness (D) (1) The carbon fiber strand of the present invention is a bundle of carbon fiber filaments, and the number of filaments is 1000 to 50000 pieces per bundle is preferable.

The carbon fiber constituting the carbon fiber strand is not particularly limited as a raw material, but examples thereof include polyacrylonitrile (PAN) carbon fiber, pitch carbon fiber, rayon carbon fiber and the like. 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 production process of the carbon fiber.

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. The carbon fiber from which the sizing agent was previously removed was put into a measuring chamber decompressed to 10 ⁻⁶ Pa by an X-ray photoelectron spectrometer ESCA JPS-9000MX manufactured by JEOL Ltd., and an electron beam accelerating voltage 10 kV with Mg as a counter electrode.
Irradiation with X-rays generated under the condition of 10 mA, carbon atoms,
The spectrum of photoelectrons generated from oxygen atoms is measured, and the area ratio is calculated.

The ratio 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,
A known method such as a transfer method can be adopted. Versatility, efficiency,
The liquid immersion method is particularly preferable because of excellent uniformity of application.

When the carbon fiber strands are dipped in the sizing liquid, the carbon fiber strands are repeatedly opened and squeezed through the immersion roller or the liquid immersion roller provided in the sizing liquid to reach the core of the strands. It is preferable to impregnate the agent.

The sizing agent application treatment can be carried out by a solvent method in which carbon fibers are immersed in a solution in which a compound serving as a sizing agent is dissolved in a solvent such as acetone, but carbon fibers are added to an aqueous emulsion by using an emulsifier or the like. The dipping emulsion 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 handleability, scratch resistance, fluff resistance and impregnation property of the carbon fiber. These may be added in advance to the resin composition serving as the sizing agent, or may be added separately. The amount of auxiliary ingredients added is 7 times the amount of sizing agent attached.
It is preferably 0% by mass or less.

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, known methods such as a method of passing through a drying furnace and a method of contacting with a heated roller can be adopted. The drying temperature is not particularly specified, but in the case of a general-purpose water-based emulsion, it is usually set to 80 to 200 ° C. Further, in the present invention, after the drying step, a heat treatment step at 200 ° C. or higher can be performed.

By the sizing treatment and the like as described above,
Adhesion amount of sizing agent, mass reduction rate of carbon fiber strands when heated in air at 200 ° C. for 1 hour, and heat generation amount and heat generation at exothermic peak when carbon fiber strands were measured by a differential scanning calorimeter The starting temperature can be in the range mentioned above.

The carbon fiber strand of the present invention has a texture of 150 to 2500 g obtained by the measuring method described later.
It is preferably f / mm ² (1.5 to 25 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 easy to induce problems such as winding and cutting, RTM
In molding, there is a problem in that the form of the preform made of carbon fiber strands cannot be maintained during resin transfer, which is not preferable. On the other hand, the texture is 2500 gf
If it exceeds / mm ² , the spreadability of the carbon fiber strands is reduced, and the impregnability of the matrix resin is reduced, which is not preferable.

The carbon fiber strand in the present invention preferably has a degree of poor dispersion in a styrene solvent of 2 to 90 per 10,000 filaments.

When the degree of dispersion failure is less than 2, 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, if the degree of dispersion failure exceeds 90,
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.

In the present invention, the carbon fiber strand of the present invention can be produced by appropriately adjusting the carbon fiber strand, surface oxygen concentration, sizing agent and the like.

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

[0063]

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> Five bundles of carbon fiber strands cut to a length of 4 cm were prepared, and an image sensor (sensor head VG-03) manufactured by Keyence Corporation was prepared.
5, the controller VG-300) was used to measure the width of each carbon fiber strand, and the average value was used as the carbon fiber strand width (W).

<Carbon Fiber Strand Thickness> The thickness of the carbon fiber strand whose width was measured is measured by a thickness gauge (thickness gauge No. 2050 manufactured by Mitutoyo Corporation).
It measured using F), and made the average value carbon fiber strand thickness (D).

<Handling degree> The handing degree was measured using a hydrometer model: HOM-2 manufactured by Daiei Kagaku Seiki Seisakusho KK 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).

[0067]

[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 placed in 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. ).

<Mass Reduction Ratio> After drying 5 g of carbon fiber strands at 110 ° C. for 2 hours, it was cooled to room temperature in a desiccator, and the mass (G1) of carbon fibers was measured. Then
After heating for 1 hour in a hot air circulation dryer at 200 ° C ± 5 ° C, the mixture was cooled to room temperature in a desiccator, and the mass (G2) was measured. The mass reduction rate was calculated by the following formula: mass reduction rate (%) = (G1−G2) × 100 / G1.

<Heat generation amount and heat generation starting temperature> The heat generation amount and heat generation starting temperature were measured using a differential scanning calorimeter (DSC3100, manufactured by Mac Science Co.). The measurement conditions were a sample amount of 20 mg, a nitrogen flow rate of 100 mL / min, and a heating rate of 10 ° C./min (in accordance with JIS K 7122 “Plastic transition heat measurement method” and JIS K 7121 “Plastic transition temperature measurement method”). .

<Pullability> Matrix resin adjusted to 100 parts by mass of a vinyl ester resin (Lipoxy R-806 manufactured by Showa High Polymer Co., Ltd.) and 2 parts by mass of a peroxide curing agent (Percure-O manufactured by NOF CORPORATION) was used as a resin bath. (Length: 400 mm, width:
120 mm, height: 100 mm) was put in an appropriate amount.

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),
Both ends are commercially available carbon fiber strands (Besphite manufactured by Toho Tenax Co., Ltd., 12000 filaments, tensile strength 39
It was tied and fixed at 00 MPa and a tensile elastic modulus of 235 GPa).

Of these, one bundle of commercially available carbon fiber strands used for fixing one end (hereinafter referred to as induction yarn) was previously drawn by a drawing guide and a cylindrical mold (content cross section: 10 mm × 3 m).
m, length 300 mm). Further, the mold through which the induction yarn was passed was kept warm at 130 ° C. using a flexible ribbon heater.

The sample bundle was immersed in a resin bath parallel to the length direction of the resin bath, and after being immersed for 30 seconds, the sample bundle was pulled and placed in a 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%). . The result of the above-mentioned pull-out test is expressed as ◯: no particular problem ×: as if the guide yarn was cut during induction.

<Interlayer 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 K 7078 was prepared from the released molded product, and ILSS was measured according to the same regulations.

<Wettability> Of the above-mentioned molded product, a portion not used for ILSS measurement was broken in the same manner as in the bending test, and the fracture surface was observed by SEM. The result is represented by ◯: The resin adheres to most of the fiber surface. ×: The resin adherence to the fiber surface is hardly observed, and is represented by ◯.

<RTM Formability> RTM shown in FIGS.
It measured using the moldability tester.

Stainless plate 2 (dimensions 450 mm × 300
mm), a carbon fiber woven fabric 4 (plain weave, size 200 mm × 1) prepared by using a carbon fiber strand as a test object.
50 mm, unit weight 200 g / m ² ) was installed. This carbon fiber woven fabric 4 is used as an inner film 6 (size 260 mm × 210 m
m), and the periphery was sealed to form the inner film seal portion 8. Further, when forming the inner film seal portion 8, the inner film outlets 10a and 10b are formed, and the inner film passage 14 in which the inner film outlets 10a and 10b are communicated with the inlet side Teflon (registered trademark) tube 12 is formed. Formed.

Next, the inner film 6 is replaced with the outer film 16
The outer film seal portion 18 was formed by covering the outer periphery with (dimensions of 400 mm × 270 mm) and sealing the periphery. When forming the outer film seal portion 18, the inner film passage 14 is formed.
The outer film passage 22 in which the inlet side Teflon (registered trademark) tube 12 and the outlet side Teflon (registered trademark) tube 20 communicate with each other was formed. Inner film outlet 1
The outer film passage 22 was formed as shown in FIGS. 1 and 2 so as to form a pool for the resin exuded from 0a and 10b.

The stainless plate 2 set as described above was set on a hot plate. In addition, the Teflon (registered trademark) tube 12 on the inlet side has a flexible tube 2 on the inlet side.
It was connected via 4 to the resin tank. On the other hand, Teflon on the outgoing side
The (registered trademark) tube 20 was connected to a vacuum pump via the outlet flexible tube 26 and a trap.

Matrix resin adjusted to 100 parts of vinyl ester resin (Lipoxy R-806 manufactured by Showa High Polymer Co., Ltd.) and 2 parts of peroxide curing agent (Percure-O manufactured by NOF CORPORATION) was added to a resin tank (capacity 2 L) in an appropriate amount. I put it in. After the stainless steel plate was kept warm at 140 ° C. by a hot plate, the vacuum pump was activated and the matrix resin was transferred from the resin tank into the inner film. The evaluation result of the above RTM moldability was expressed as ◯: The matrix resin spreads over almost the entire area of the carbon fiber woven fabric ×: The matrix resin spreads over only a part of the carbon fiber woven fabric.

Examples 1 to 6 and Comparative Example 1 Unsized carbon fiber strands (Vesphite manufactured by Toho Tenax Co., Ltd., 12000 filaments, tensile strength 4)
800 MPa, tensile modulus of 240 GPa) was continuously emulsified in a sizing bath containing a water emulsion obtained by emulsifying 100 parts of bisphenol A methacrylic vinyl ester resin (epoxy ester 3000M manufactured by Kyoeisha Chemical Co., Ltd.) with 40 parts of polyoxyethylene styrenated phenol ether. After being dipped in, the 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 and method C shown in FIGS. 3, 4 and 5 were appropriately used.

In the respective sizing methods of FIGS. 3, 4 and 5, carbon fiber strands 32, 42 and 52 are provided.
Was continuously immersed in sizing baths 36, 46 and 56 via guide rollers 34, 44 and 54. Then, if necessary, the squeezing rollers 38, 40, 48 and 5
8 and the heat rollers 60 and 62, and conveyed to the drying furnace.

As shown in the results of Table 1, Examples 1 to 6
In all cases, satisfactory results were obtained. However, Comparative Example 1 is an exothermic peak when the carbon fiber strands are measured by a differential scanning calorimeter, the calorific value is small, the degree of texture and the degree of poor dispersion are high, and the wettability is x, which is a satisfactory result. Was not obtained.

[0087]

[Table 1]

Comparative Example 2 Unsized carbon fiber strands (Vesphite manufactured by Toho Tenax Co., Ltd., 12000 filaments, tensile strength of 4)
800 MPa and a tensile modulus of 240 GPa) were continuously immersed in a sizing bath containing an acetone solution (concentration 22 g / L) of a glycerin dimethacrylate hexamethylene diisocyanate compound (UA101H manufactured by Kyoeisha Chemical Co., Ltd.). After that, acetone was removed by drying at 100 ° C. (sizing method: method A), the amount of adhered size was 1.0% by mass, the amount of mass reduction was 0.12%, and the calorific value was 1350 mJ / g.
Heat generation start temperature 101 ° C, flatness 37%, texture 445
A carbon fiber strand with g / mm ² and a degree of dispersion failure of 26 was obtained. When a pull-out test was performed using this carbon fiber strand, ILSS was 79 MPa and wettability was ◯,
The drawability x, RTM moldability x and moldability were problems.

Comparative Example 3 Unsized carbon fiber strands (Vesphite manufactured by Toho Tenax Co., Ltd., 12000 filaments, tensile strength 4
800 MPa, tensile elastic modulus 240 GPa), polyoxy of bisphenol A methacrylic vinyl ester resin 30 parts (Kyoeisha Chemical Co., Ltd. epoxy ester 3000M) and aliphatic acrylic vinyl ester 70 parts (Kyoeisha Chemical Epoxy ester 200EA). Concentration of 35g emulsified with 30 parts of ethylene styrenated phenol ether
It was continuously immersed in a sizing bath containing / L of water emulsion. After that, the water content is dried and removed at 100 ° C. (sizing method: method A), the amount of attached size is 2.2% by mass, the amount of mass reduction is 1.4%, the heat generation amount is 1280 mJ / g, the heat generation start temperature is 107 ° C., and the flatness is 34%, texture 615g
A carbon fiber strand having a dispersibility of 17 / mm ² was obtained. When a drawing test was conducted using this carbon fiber strand, the wettability was ◯, but the drawability was × and ILSS was 7
It was inferior to 1 MPa and RTM moldability was inferior to x.

[0090]

EFFECTS OF THE INVENTION The carbon fiber strand of the present invention is excellent in adhesiveness with the unsaturated matrix resin, and thus it is possible to obtain a carbon fiber reinforced resin composite material having excellent physical properties. Particularly, in pultrusion molding and RTM molding, there are advantages that the impregnation property and the moldability are excellent and troubles during molding are prevented.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view (plan view) showing an example of an RTM formability tester.

FIG. 2 is a schematic explanatory view (side sectional view) showing an example of an RTM formability tester.

FIG. 3 Sizing method for carbon fiber strands (method A)
It is a schematic explanatory drawing which shows.

FIG. 4 Sizing method for carbon fiber strands (method B)
It is a schematic explanatory drawing which shows.

FIG. 5: Sizing method for carbon fiber strands (method C)
It is a schematic explanatory drawing which shows.

[Explanation of symbols]

2 stainless steel plate 4 carbon fiber fabric Film in 6 8 Inner film seal part 10a, 10b inner film outlet 12 Inlet Teflon (registered trademark) tube 14 Inside film passage 16 outer film 18 Outer film seal part 20 Outgoing Teflon (registered trademark) tube 22 Outside film passage 24 Entry side flexible tube 26 Outlet flexible tube 32, 42, 52 carbon fiber strands 34, 44, 54 Guide rollers 36, 46, 56 Sizing bath 38, 40, 48, 58 Squeezing roller 60,62 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 AA02 AB10 AC04 AC05 AD04                       AD09 AD38 AD41 AD44 AL01                 4L033 AA09 AB03 AC15 CA12 CA18                       CA45 CA47 CA49

Claims (13)

[Claims] 1. A carbon fiber strand having a sizing agent adhered thereto in an amount of 0.3 to 5.0% by mass, which is 200 ° C. in air.
The mass reduction rate when heated for 1 hour at 1.0% or less, and the exothermic peak when the carbon fiber strand is measured by a differential scanning calorimeter, the exothermic amount is 20 to 1200.
A carbon fiber strand having mJ / g and a heat generation starting temperature of 200 ° C. or lower. 2. The carbon fiber strand according to claim 1, wherein the sizing agent contains 30% by mass or more of a compound having an addition-polymerizable functional group. 3. The carbon fiber strand according to claim 2, wherein the compound having an addition polymerizable functional group is a chain polymer compound having an addition polymerizable functional group at both ends. 4. The carbon fiber strand according to claim 2, wherein the addition-polymerizable functional group is an unsaturated group. 5. The carbon fiber strand according to claim 1, wherein the sizing agent contains 30% by mass or more of a vinyl ester resin. 6. The carbon fiber strand according to claim 5, wherein the vinyl ester resin is a bis type methacrylic vinyl ester resin. 7. The flatness (width / thickness) of the cross section when the carbon fiber strand is cut perpendicularly to the length direction is 20 to 80.
The carbon fiber strand according to claim 1, which is 8. The carbon fiber strand is 1000 to 500.
The carbon fiber strand according to claim 1, which is composed of 00 carbon fiber filaments. 9. The texture of carbon fiber strands is 150.
The carbon fiber strand according to claim 1, which has a value of 2,500 gf / mm ² . 10. 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. 11. A carbon fiber reinforced resin in which an unsaturated polyester resin or a vinyl ester resin is reinforced with the carbon fiber strand according to any one of claims 1 to 10. 12. The carbon fiber reinforced resin according to claim 11, which is for pultrusion molding. 13. The carbon fiber reinforced resin according to claim 11 for resin transfer molding.