JP2002020975A - Carbon fiber bundle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide carbon fiber bundles of high performance that has good processability to prepregs and gives the composite material developing excellent strength properties, when it is combined with a resin. SOLUTION: The objective carbon fiber bundles having organic fine particles on their carbon fiber surfaces are produced by coating the fiber surfaces of the bundles with a surface-treating agent including organic fine particles wherein the surface area ratio of the single fibers constituting the fiber bundles is <=1.02.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a composite material obtained by combining a resin with a resin having excellent applicability to a prepreg.
It can be suitably used for sporting goods and aerospace applications, etc.
Related to high quality carbon fiber bundles.

[0002]

2. Description of the Related Art Carbon fiber is a material excellent in specific strength and specific elastic modulus, and a composite material obtained by combining it with a resin is widely used in sporting goods, aerospace applications, and the like.
In recent years, there has been an increasing number of occasions in which a resin is impregnated, processed into an intermediate base material called a prepreg, and formed into a composite material.

When a carbon fiber is processed into a prepreg, the fiber bundle is manufactured by widening the fiber bundle and impregnating with a resin in a thin sheet shape. Since the strength characteristics of the composite material may be impaired, a method of protecting the fiber bundle from abrasion by coating the fiber with a surface treatment agent has been generalized.

However, the carbon fiber bundle in which a plurality of constituent single fibers are bundled by coating with a surface treatment agent has a reduced widening property of the fiber bundle when impregnated with a resin, and in particular, processing of a thin prepreg is difficult. Sometimes it was difficult.

[0005] Above all, when carbon fibers having a smooth fiber surface are used in order to reduce surface defects, the above-mentioned tendency becomes remarkable, and there is a problem that the strength of the obtained composite material is reduced.

[0006] As described above, with a suitable focusing property,
At present, no satisfactory fiber bundle has been obtained which effectively suppresses fluffing of the carbon fiber bundle and abrasion on the surface, and at the same time, achieves a widening property required for processing into a prepreg.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high-performance carbon fiber which has good processability into a prepreg and, moreover, provides a composite material exhibiting excellent strength characteristics when combined with a resin. Is to provide a bunch.

[0008]

The present invention employs the following structure in order to solve the above-mentioned problems. That is, a carbon fiber bundle coated with a surface treatment agent containing organic fine particles and having the organic fine particles adhered to the surface thereof, wherein the surface area ratio of the single fibers constituting the fiber bundle is 1.02 or less. Fiber bundle. A carbon fiber bundle coated with a surface treating agent containing organic fine particles and having the organic fine particles adhered to the surface thereof, wherein the surface area ratio of the single fibers constituting the fiber bundle is 1.02 or less. It is.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION
A carbon fiber bundle coated with a surface treating agent containing organic fine particles, wherein the organic fine particles are adhered, and the surface area ratio of the single fibers constituting the fiber bundle is a specified value. It was sought to solve all the problems at once.

The carbon fiber bundle according to the present invention is coated with a surface treating agent containing organic fine particles, and an appropriate amount of organic fine particles adhere to the surface of the fiber by the surface treating agent. .

Examples of the organic fine particles include at least one selected from a polymethyl methacrylate (hereinafter abbreviated as PMMA) compound and a polystyrene (hereinafter abbreviated as PSt) compound. Examples of the PMMA compound include polymethyl methacrylate and the like, and examples of the PSt compound include polystyrene latex and the like.

As the organic fine particles, those having a uniform particle size and a small particle size distribution are preferable, and those having a crosslinked structure from the viewpoint of heat resistance can be preferably used.

In the present invention, when the fine particles are a material other than organic materials, for example, inorganic fine particles such as carbon black and metal fine particles, the dispersibility in an aqueous solution is reduced, and the fine particles are uniformly attached to the constituent single fibers. It may be difficult, and, because inorganic fine particles have excessive hardness of the fine particles,
May cause fiber damage.

In the present invention, the surface treatment agent can be appropriately selected according to the resin to be combined when forming the composite material. Specifically, an epoxy resin or the like can be used. Further, the amount of the surface treatment agent to be applied is 10% by weight of the carbon fiber.
0.2 to 5% by weight, preferably 0.2% to 0% by weight
It is preferably in the range of 3% by weight. When the content is less than 0.2% by weight, the bundle properties of the fiber bundle are insufficient, the fibers are fuzzy, and the surface is liable to be scratched. As a result, the strength characteristics of the obtained carbon fiber bundle may be insufficient. If it exceeds 5% by weight, the widening property may be reduced.

In the present invention, the organic fine particles include:
Preferably, it is substantially spherical. A shape other than a true sphere, such as an elliptical shape, may cause abrasion on the fiber surface.

The organic fine particles have a carbon fiber weight of 10%.
0.1 to 1% by weight, preferably 0.1 to 0% by weight
It is preferable that the content is in the range of about 0.6% by weight to the carbon fiber surface. If it is less than 0.1% by weight, the widening property may be reduced, and if it exceeds 1% by weight, it may be difficult to uniformly adhere to the constituent single fibers.

The organic fine particles have an average particle size of 0.1 to 1 μm, preferably 0.2 to 0.5 μm. If it is less than 0.1 μm, the widening property may be reduced, and if it is more than 0.5 μm, penetration of fine particles between single fibers may be hindered.

In the carbon fiber bundle according to the present invention, the surface area ratio of the single fibers constituting the fiber bundle must be 1.02 or less, and preferably 1.01 or less. 1.
If it exceeds 02, the widening property may be reduced.

The carbon fiber bundle according to the present invention has a bundle expansion coefficient ratio calculated by a method described later of 1.5 or more, preferably 1.6 or more. If less than 1.5,
It may be difficult to produce a thin prepreg, and furthermore, the strength characteristics of a composite material produced from the obtained prepreg may be reduced. It should be noted that a bundle spreading coefficient ratio of 3.0 is often sufficient for achieving the effects of the present invention.

Next, an example of the method for producing a carbon fiber bundle according to the present invention will be described.

In the present invention, as the acrylic copolymer as a raw material of the fiber, one comprising 90% by weight, preferably 95% by weight or more of acrylonitrile (hereinafter abbreviated as AN) can be used.

The comonomer to be copolymerized with AN is an organic acid such as acrylic acid or itaconic acid, or a methyl ester, ethyl ester, propyl ester, butyl ester, alkali metal salt, ammonium salt, or allyl sulfone of the organic acid. Organic acids such as acid, methallyl sulfonic acid, styrene sulfonic acid and the like, and metal salts of these organic acids and the like.

The acrylic copolymer can be polymerized by a known method such as emulsion polymerization, bulk polymerization, solution polymerization and the like. The spinning stock solution is prepared by using dimethylacetamide, dimethylsulfoxide, dimethylformamide, nitric acid, aqueous solution of rhoda soda and the like. Can be adjusted. The concentration of the copolymer in the spinning solution is 13 to 25% by weight, preferably 1 to 25% by weight.
The content is preferably 5 to 20% by weight. If the content is less than 13% by weight, irregularities due to fibrils may be apparent on the surface of the fiber obtained by the dry-wet spinning method, and the strength characteristics of the obtained carbon fiber may be reduced.

Next, the spinning solution is once extruded from a die into the air, spun into a coagulation bath comprising a solvent and water, spinned by a wet-wet spinning method, washed with water, stretched in a bath, and dried and densified. The acrylic precursor fiber is obtained by drawing in a heat medium such as pressurized steam according to the above.

Here, after the stretching in the bath and before the drying and densification, it is preferable to apply a silicone oil containing an amino-modified silicone as an essential component in order to effectively suppress the adhesion between the constituent single fibers.

The obtained acrylic precursor fiber was treated with 200
A flame-resistant yarn bundle is obtained by performing flame-resistance while stretching as needed in an air atmosphere at a temperature of from 300C to 300C.

Next, the oxidized yarn bundle is heated at a maximum temperature of 600 ° C.
A pre-carbonized yarn bundle is obtained by carbonizing in a nitrogen atmosphere at 1000 ° C. while stretching as necessary. Next, a carbon fiber bundle is obtained by carbonizing the pre-carbonized yarn bundle while stretching it in a nitrogen atmosphere having a maximum temperature of 1200 ° C. to 1900 ° C. as necessary. The obtained carbon fiber bundle can be further graphitized in a high-temperature nitrogen atmosphere to obtain graphitized fibers.

The carbon fiber or the graphite fiber thus obtained may be subjected to a surface oxidation treatment in order to enhance the adhesiveness with the resin.

Next, after washing with water and drying, a surface treating agent containing organic fine particles is applied, and dried to obtain a carbon fiber bundle as a final product. Here, the organic fine particles are attached to the surface of the constituent single fibers of the carbon fiber bundle via a surface treatment agent.

The concentration of the spherical fine particles in the surface treating agent is 1
The content is preferably in the range of 0 to 50% by weight. If it is less than 10% by weight, the widening property may be reduced, and if it is more than 50% by weight, it may be difficult to uniformly adhere to the constituent single fibers.

Further, when drying after applying the surface treatment agent, the carbon fiber bundle is conveyed in a zigzag manner using a plurality of rollers and dried because the widening property of the obtained fiber bundle is further improved. Is preferred.

[0032]

The present invention will be described more specifically with reference to the following examples. In the examples, each property value was measured by the following method. <Surface ratio of carbon fiber> 5 carbon fibers (samples) to be measured
It is cut to a length of mm and fixed on a base of a silicon wafer using a silver paste.

Next, using an atomic force microscope (AFM),
The measurement conditions are set as follows, and the central portion of the single fiber is observed to obtain a three-dimensional surface shape image.

Scanning mode: Tapping mode Scanning range: OMCL-AC120TS, a probe integrated with a Si cantilever manufactured by Olympus Engineering Co., Ltd. Scanning range: 2.5 μm × 2.5 μm Scanning speed: 0.4 Hz Pixel number: 512 × 512 ・ Measurement environment: room temperature, in the air In this example, Digital Instruments N
An anoScope IIIa Dimension 3000 stage system was used.

For each sample, an image obtained by observing one single thread at a time was processed by software (NanoScope III version 4.22r2) attached to the apparatus, and a primary Flatten filter and Lowpass filter were processed. , 3
Next, filtering is performed using a Plane Fit filter, and the actual surface area is calculated for the entire obtained image. In addition, about a projection area, an observation visual field (2.5 micrometers x 2.5 micrometers)
Area.

For each sample, the above measurement was carried out for five arbitrarily selected single fibers, and the surface area ratio was determined by the following equation. The arithmetic mean value of the three points excluding the maximum value and the minimum value of the surface area ratio was finally calculated. Surface area ratio.

Surface area ratio = actual surface area / projected area <Measurement of bundle spreading coefficient ratio> A carbon fiber bundle to be measured was placed on a cylindrical bar having a diameter of 50 mmφ at a speed of 1 m / min and a contact angle of 90.
° and the fiber bundle is conveyed while being rubbed so as to obtain the spread width of the fiber bundle on the cylindrical bar, measured by a gauge, and the value obtained by dividing the spread width by the fineness (dtex) of the fiber bundle (mm / dtex) is defined as the bundle coefficient. I do. Here, a cylindrical bar having a satin finish surface treatment of hard chrome plating # 200 is used.

In this manner, the bundle coefficient measured assuming that the tension of the fiber bundle on the exit side of the cylindrical bar is 75 mg / dtex is R
_1, similarly when the beam coefficient measured tension as 15 mg / dtex was R _2, obtaining the beam spread coefficient ratio R by the following equation. The larger the value of R, the higher the carbon fiber bundle in which both the convergence property and the widening property are compatible.

R = R ₁ / R ₂ <Measurement of 90 ° Tensile Strength> Carbon fiber bundles to be measured are arranged in one direction, and a resin composition having the following composition is sandwiched between resin films coated on silicone resin coated paper. Then, a resin is impregnated into the carbon fiber bundle with a pressure roll to prepare a prepreg sheet. (Thermosetting resin) ・ Bisphenol A type epoxy resin ("Ehjicoat" Ep828,
(Registered trademark), 40 parts by weight ・ Bisphenol A type epoxy resin ("Ehjicoat" Ep1001,
(Registered trademark), 50 parts by weight ・ Phenol nophorac type epoxy resin (“Epikote” Ep154, registered trademark), 10 parts by weight (thermoplastic resin) ・ Polyvinyl formal resin (“Pinirek” K, registered trademark), 5 parts by weight (addition・ Dicyandiamide (curing agent), 3.5 parts by weight ・ 3,4-dichlorophenyl-1,1-dimethylurea (curing aid), 3 parts by weight The resin is cured at a temperature of 130 ° C. under a pressure of 3.0 MPa for 2 hours to prepare a flat plate having a thickness of about 2 mm.

This flat plate is cut by a cutter, and has a length of 190 mm in a direction perpendicular to the fiber direction and a width of 5 mm in the same direction as the fiber direction.
A rectangular test piece of 0 mm is prepared.

The test piece is subjected to a tensile test using an Instron under the condition of a tensile speed of 1 mm / min, and the tensile strength (MPa) is determined by the following equation.

Tensile strength (MPa) = Load (KN) × 3/4 × (1 /
(Test piece thickness) × (1 / test piece width) × 1000 (Example, Comparative Example) AN copolymer having an intrinsic viscosity [η] of 1.8 consisting of 99.5 mol% of AN and 0.5 mol of itaconic acid. Dimethyl sulfoxide (DMS containing 20% by weight of
The spinning stock solution of O) was adjusted, and ammonia gas was blown until the pH reached 8.0.

Thereafter, the spinning solution, which had been heated to 45 ° C., was spun into a coagulation bath filled with a DMSO aqueous solution from a die having a number of holes of 3000 by a dry-wet spinning method.
000 coagulated yarns were obtained.

Next, the coagulated yarn was washed with hot water, stretched 4-fold in a bath at 90 ° C., and further emulsified with a nonylphenol EO adduct with an amino-modified silicone oil through an oil bath. 2.0% by weight of a silicone oil agent was added at 0.7% by weight to 100% by weight of carbon fiber.

After the oil agent has been applied, the yarn is dried and densified using a heating roller adjusted to 150 ° C., then stretched 4 times in pressurized steam, and dried by a heating roller adjusted to 180 ° C. And single fiber fineness 1.0dtex, total fineness 30
An acrylic precursor fiber of 00 dtex was obtained.

The precursor fiber is first heated at 250 to 280 ° C.
In the air atmosphere, a stabilization treatment was performed to obtain an oxidized fiber.

Next, in a nitrogen atmosphere, the maximum atmosphere temperature is 8
In a pre-carbonizing furnace of 00 ° C., a pre-carbonizing treatment is performed at an atmosphere temperature of 400 to 500 ° C. at a temperature rising rate of 100 ° C./min and a draw ratio of 1.02. Carbon fibers were obtained by carbonizing in a furnace at an atmosphere temperature of 1000 to 1200 ° C. at a temperature increasing rate of 200 ° C./min and a draw ratio of 0.97.

Then, an electric charge of 10 coulombs per 1 g of carbon fiber was given in an aqueous solution of ammonium carbonate, anodized, washed with water and dried to give a surface treatment agent shown in Table 1.

As a result, as shown in Table 1, in each of the examples, the fluffing of the carbon fiber bundle was small, the bunching property and the widening property were good, and the 90 ° tensile strength of the obtained molded product was high. became.

On the other hand, the carbon fiber bundle of Comparative Example 1 was insufficient in convergence, easily fluffed, and insufficient in widening. In Comparative Example 2, the penetration of the fine particles between the single fibers was prevented, and the widening property was insufficient. In Comparative Example 3, the convergence of the carbon fiber bundle was excessive, and the widening property was insufficient.
In each of the comparative examples, the obtained molded product was insufficient in 90 ° tensile strength.

[0051]

[Table 1]

[0052]

According to the present invention, it is possible to produce a high-performance carbon fiber bundle which has good processability into a prepreg, and which can provide a composite material exhibiting excellent strength characteristics in combination with a resin. it can.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4L033 AA09 AB01 AC09 AC15 CA13 CA18 4L037 AT02 AT03 CS03 FA01 FA12 PA55 PA57 PA65 PC10 PC11 PF45 PF47 PF52 PF54 PF59

Claims (6)

[Claims] 1. A carbon fiber bundle coated with a surface treating agent containing organic fine particles and having the organic fine particles adhered to the surface thereof, wherein the surface area ratio of the single fibers constituting the fiber bundle is 1.02.
A carbon fiber bundle that is: 2. The carbon fiber bundle according to claim 1, wherein the organic fine particles are mainly composed of a compound selected from a polymethyl methacrylate compound and a polystyrene compound. 3. The carbon fiber bundle according to claim 1, wherein the coating amount of the surface treatment agent is 0.2 to 5% by weight based on 100% by weight of the carbon fiber. 4. The carbon fiber bundle according to claim 1, wherein said organic fine particles are substantially spherical. 5. The carbon fiber bundle according to claim 1, wherein the amount of the organic fine particles attached is 0.1 to 1% by weight based on 100% by weight of the carbon fibers. 6. The organic fine particles having an average particle size of 0.1 to 1
The carbon fiber bundle according to any one of claims 1 to 5, which is within a range of µm.