JP2003003376A - Carbon fiber bundle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon fiber bundle which has excellent openability even when comprising many filaments, has excellent mechanical characteristics, and can produce a prepreg having a low weight. SOLUTION: This carbon fiber bundle is characterized by comprising 20,000 to 1000,000 filaments and being adhered to a sizing agent which contains at least polyoxyalkylene groups and epoxy groups in the component, has an epoxy equivalent of 0.2 to 5.0×10<-3> equivalents/g and in which the amount of the polyoxyalkylene group-containing compound contained in the sizing agent is >=40 wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called thick carbon fiber having a large number of filaments, yet having excellent workability for a woven fabric or a prepreg and having excellent composite material properties. Regarding

[0002]

2. Description of the Related Art Demand for carbon fiber is increasing year by year, and not only for aircraft and sports, but also for general industrial applications such as automobiles and building materials.

In recent years, carbon fibers having a filament number of 20000 or more, based on acrylic fibers for clothing, so-called large tow type carbon fibers have been put on the market.

The large tow type carbon fiber is characterized in that since the amount of treatment per fiber bundle can be increased in the manufacturing process, the production efficiency is high and the cost can be reduced. Therefore, it is expected to be deployed in general industrial applications requiring low cost.

Conventional large tow carbon fibers have a low production cost compared to so-called small tow carbon fibers having a filament number of up to 12,000, but they have many fluffs and are inferior in quality. Fiber was the mainstream. In order to expand the demand for carbon fiber, it is indispensable to expand to applications such as prepreg and woven fabric that require uniform openability, but in the current large tow type carbon fiber, openability is filament type. However, there is a problem that it is difficult to apply to the use.

As the carbon fiber having excellent openability, for example, a specific compound as disclosed in Japanese Patent No. 2812147 is attached at least 0.1 to 0.5% by weight based on the weight of the carbon fiber bundle, and the carbon thickness is The width of the carbon fiber bundle is 1
A carbon fiber bundle characterized by being 5 to 250 has been proposed. However, the compound to be attached in the patent, that is, the sizing agent does not contain an epoxy group and is excellent in openability, but there is a problem in that the adhesiveness is inferior in the composite characteristics of a composite material using an epoxy resin as a matrix. It was Further, in this publication, the amount of the sizing agent attached to the carbon fiber is small, and the large tow carbon fiber having a large number of filaments of the fiber is likely to have uneven sizing amount. As a result, there is also a problem that sufficient openability cannot be obtained.

[0007]

In view of such background of the prior art, the present invention has excellent openability and excellent mechanical properties even with carbon fibers having a large number of filaments.
An object of the present invention is to provide a carbon fiber bundle capable of producing a prepreg having a low basis weight.

[0008]

The present invention employs the following means in order to solve the above problems. That is, the carbon fiber bundle of the present invention is a carbon fiber having a number of filaments of 20,000 to 100,000, to which a sizing agent containing at least a polyoxyalkylene group and an epoxy group is attached in the component, and the sizing. Epoxy equivalent of agent is 0.2 to 5.0 × 10 ^-3
Equivalent / g, and the ratio of the compound containing a polyoxyalkylene group contained in the sizing is 40% by weight or more.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention has the above-mentioned problems, that is, even in the case of carbon fibers having a large number of filaments, excellent openability,
Furthermore, in addition to having excellent mechanical properties, a carbon fiber bundle capable of producing a prepreg having a low basis weight is earnestly studied, and a sizing agent containing a compound containing a sizing agent and a polyoxyalkylene group containing an epoxy resin,
When a specific amount was added to the carbon fiber bundle, it was clarified that these problems could be solved all at once.

The carbon fiber bundle of the present invention has two filaments.
0000 to 100,000, preferably 30,000 to 75
It is essential that it is a so-called large tow composed of 000 carbon fibers. That is, the number of filaments is 2
If it is less than 0000, even if the conventional technique is adopted, the high-order processability is satisfied, but there is a problem that the production efficiency is lowered, and if the number of filaments exceeds 100,000, the technique of the present invention is used. Even if adopted, since the number of fibers is too large, good openability cannot be obtained, and basic physical properties of carbon fiber such as decrease in strand strength and elastic modulus due to uneven processing in the fiber bundle are deteriorated. There's a problem.

In the present invention, the sizing agent applied to the carbon fiber is constituted so that the component contains at least a polyoxyalkylene group and an epoxy group.

Here, the polyoxyalkylene group is-(R
-O) n- is a general term for functional groups represented by the structure,
Here, R represents an alkylene group, for example, R
If but ethylene, - is intended to mean those (CH ₂ CH ₂ -O) n- that the structure, i.e. a polyoxyethylene group.

That is, one form of the sizing agent contains a compound containing both an epoxy group and a polyoxyalkylene group in the molecule.
Specifically, there is a compound in which an epoxy group is added to the end of polyoxyalkylene, preferably a compound in which polyoxyalkylene is graft-polymerized to the main chain of a polymer constituting an epoxy resin.

Another form of the sizing agent is a mixture of epoxy resin and polyoxyalkylene. The epoxy resin refers to an ordinary epoxy resin, for example, a glycidyl epoxy resin represented by bisphenol type, phenol type, ester type, ether type, or a non-glycidyl type epoxy resin represented by epoxidized butadiene.

The polyoxyalkylene is a polymer obtained by using alkylene oxide such as ethylene oxide or propylene oxide as a monomer, and random or block copolymerization. Among such polyoxyalkylenes, the molecular weight is preferably 300 to 30,000, more preferably 1,000 to 10,000.

The sizing agent has an epoxy equivalent of 0.2 to 5.0 × 10 ^−3.
It is essential that both of the equivalent weight / g and the weight of the compound containing a polyoxyalkylene group are 40% by weight or more.

The epoxy equivalent means the epoxy resin 1
It represents the equivalent amount of the epoxy group contained per g, and is usually quantified by measurement by a hydrochloric acid-dioxane solution or a hydrochloric acid-pyridine method.

When the epoxy equivalent is less than 0.2 × 10 ⁻³ equivalent / g, the epoxy group is too small and the adhesive property of the composite material using the epoxy resin as a matrix is deteriorated. On the other hand, when it exceeds 5 × 10 ⁻³ equivalent / g, the viscosity of the sizing agent becomes high and the spreadability is lowered. Therefore, the preferable range of the epoxy equivalent is 0.4 × 10 ⁻³ equivalent / g to 4 × 10 ⁻³ equivalent / g.

It is essential that the weight fraction of the polyoxyalkylene group-containing compound in the sizing agent is 40% by weight or more, preferably 50 or more. That is,
If the weight fraction of polyoxyalkylene is less than 40%, the frictional resistance of the yarn becomes large, and when the yarn is brought into contact with the metal guide bar, the yarn does not move easily, and satisfactory opening property cannot be obtained.

The amount of the sizing agent attached is preferably 0.5 to 3.0% by weight, more preferably 0.8 to 3.0% by weight.
2.0 wt% is good. When the amount of the sizing agent attached is low, the fiber-opening property is deteriorated, and when it exceeds 3.0% by weight, the fiber bundles are excessively bundled and the fiber-opening property is insufficient.

In the present invention, the coefficient of static friction between the fiber and the metal is preferably 0.10 to 0.25, more preferably 0.40 to 0.60. If the coefficient of static friction is greater than 0.25, the thread will not move easily even if it is squeezed by a guide bar or the like, and it will be difficult to widen the thread. On the other hand, if the coefficient of static friction is less than 0.10, the thread will be easily handled, On the contrary, the thread will not spread easily.

Here, the friction coefficient of the fiber with respect to the metal is a value measured as follows. That is, the carbon fiber bundle is brought into contact with a cylindrical guide bar having a diameter of 20 mm, and the wrap angle is 180
The weight of 500 g is applied to one side and the spring is applied to the other side to measure the load at which the fibers slide on the guide bar when the spring is pulled. The coefficient was used. The evaluation was repeated three times, and the average value was used as the coefficient of static friction.

[0023]

[Formula 1]

The fiber entanglement value of the yarn in the present invention is
Preferably 5 to 30 m ^-1 , more preferably 8 to 20 m ^-1
It should be in the range of. The fiber entanglement value is 5 mm ^-1
If it becomes lower, the entanglement between the single fibers of the fiber is too strong, and the yarns are restrained from each other, so that the fiber is less likely to be widened. When the fiber entanglement value is low, that is, higher than 30 m ^-1 ,
The fiber tends to be loosened, the handleability is poor, and the carbon fiber is likely to be wound around a roller or the like in the process of producing the fiber, and the yield of the carbon fiber tends to be low due to yarn breakage or the like.

The entanglement value of such fibers is measured as follows. That is, a fiber bundle without twist is 200
A weight of 10 g (hook) is hooked on the center of the fiber bundle and the fall distance is A (mm).
F shown by the following formula was made into the hook drop value (CF value).

F = 1000 / A The evaluation was carried out at n = 50, and the maximum value and the minimum value were each 10
Each point was deleted, and the average value of n = 30 was used as the hook drop value.

[0027]

EXAMPLES The present invention will now be described in more detail by way of examples.

Various evaluations in the examples are carried out as follows.
It was (1) Expandable fiber weight 10mm diameter stainless steel rod (chrome plating, surface roughness
1 to 1.5S) 5 lines at 50mm intervals, each in parallel,
The carbon fiber bundles have a contact angle of 120 degrees on the surface of these rods.
Place the bars in a zigzag so that they pass while touching
The device was used. 1.1 dt on the carbon fiber bundle on the entrance side
Applying a tension of 9 mg per ex, at a speed of 1 m / min,
Of the device. Guy with the final (fifth) carbon fiber
Measure the spread width X (mm) of the fiber bundle immediately after passing over
When determined, y (g / m ²) Can be widened
And

Y (g / m ² ) = 1000 / X (mm) ×
Unit weight of carbon fiber (g / m) The spread width of carbon fiber is measured every 0.5 m,
The average value of n = 20 was used as the basis weight for widening. 130 or less was set as a good value for the widening basis weight. (2) Abrasion of fibers Five stainless steel rods (chrome plating, surface roughness 1 to 1.5S) having a diameter of 10 mm are parallel to each other at 50 mm intervals, and the carbon fiber bundles have a contact angle of 120 degrees on the surfaces of these rods. A scraping device was used in which the rods were arranged in a zigzag manner so that they passed in contact. The carbon fiber bundle on the inlet side was given a tension of 0.09 g per 1.1 dtex and passed through this device at a speed of 3 m / min. A fluff detector was used which counts the number of fluffs by irradiating a laser beam perpendicularly to the carbon fiber bundle from the side surface. The number of rubbing fluff was set per 1 m, and the average value of three measurements was taken as the number of rubbing fluff. The number of fluffs was 20 / m or less as a good value. (5) Strand Tensile Strength, Elastic Modulus The following strand tensile strength and elastic modulus are JIS-R-760.
It measured according to the resin impregnation strand test method of 1. Bakelite (registered trademark) ERL4221 / 3 Hooker boron monoethylamine / acetone = 100/3/4 (parts by weight) manufactured by Union Carbide was used as the resin formulation, and the curing conditions were atmospheric pressure, 130 ° C., and 30 minutes. Ten strands were measured and the average value was calculated. (6) Composite ILSS Using Epicoat 828 as matrix resin, AS
It was measured based on TM D-2344. ILSS is 8
A value of 0 MPa or more was regarded as a good value.

Example 1 An acrylic fiber having a single fineness of 1.7 dtex and a filament number of 50,000 was obtained by using a copolymer composed of 99.4% acrylonitrile and 0.6% methacrylic acid. The obtained fiber bundle was heat-treated in air at 200 to 250 ° C. at a draw ratio of 1.05 to obtain flame-resistant fibers. Then, the temperature rising rate in the temperature range of 300 to 900 ° C. in a nitrogen atmosphere is 200 ° C. /
Minutes, 2% stretching was performed, and then firing was performed up to 1400 ° C. to obtain a carbon fiber bundle.

The carbon fiber bundle was surface-treated with an electrolytic solution, and a sizing agent prepared by diluting the resin component with water to 3% was applied to the carbon fibers by an immersion method and dried at 200 ° C. for 5 minutes. A carbon fiber having a sizing adhesion amount of 1.1% was obtained. Epoxy resin (Epicoat 100
1, a mixture of Epicoat 828), 20 parts by weight, a mixture of 75 parts by weight of polyethylene glycol and 5 parts by weight of an emulsifier, and the epoxy equivalent of the sizing agent applied is 0.
It was 7 × 10 ⁻³ equivalent / g, and was%. The strand strength of the carbon fiber thus obtained was 3900 MPa, and the elastic modulus was 232 GPa. The coefficient of static friction of this carbon fiber, the fiber entanglement value by the hook drop method, the number of fluffs,
The widening unit weight and ILSS were measured. The results are shown in Table 1.

Example 2 A carbon fiber bundle obtained by the same method as in Example 1 was surface-treated with an electrolytic solution, and subsequently, 100% polyethylene glycol diglycidyl ether was used as a sizing agent.
A sizing agent diluted with water so that the resin component becomes 3% was prepared and applied to the carbon fiber by the dipping method,
Drying was performed at ° C. The adhered amount was 1.2%.

The epoxy equivalent of the sizing agent is 3.7 ×
It was 10 ⁻³ equivalent / g. The carbon fiber strand thus obtained has a tensile strength of 3970 MPa and an elastic modulus of 2
It was 30 GPa. The static friction coefficient, the fiber entanglement value by the hook drop method, the number of scratched fluffs, the widening basis weight, and the ILSS of this carbon fiber were measured. The results are shown in Table 1.

Comparative Example 1 An acrylic fiber having a single fineness of 1.7 dtex and a filament number of 120,000 was obtained using a copolymer of 99.4% acrylonitrile and 0.6% methacrylic acid. The obtained acrylic fiber was treated in the same manner as in Example 1 to obtain a carbon fiber. This carbon fiber bundle is subjected to surface treatment with an electrolytic solution,
Then, using polyethylene glycol diglycidyl ether as a sizing agent, a sizing agent diluted with water so that the resin component became 3% was prepared, and sizing was applied by a dipping method, followed by drying at 200 ° C. The adhered amount was 1.5%. The strand strength of this carbon fiber was 2600 MPa, and the elastic modulus was 215 GPa.

The static friction coefficient of this carbon fiber, the fiber entanglement value by the hook drop method, the number of scratched fluffs, the widening basis weight, I
LSS was measured. The results are shown in Table 1.

Comparative Example 2 A surface treatment with an electrolytic solution was carried out in the same manner as in Example 1, and an epoxy resin (Epicoat 1001) was used as a sizing agent.
A mixture of 80 parts by weight and 20 parts by weight of an emulsifier was added to the resin component 3
It was diluted with water so as to be 100%, applied to carbon fibers by a dipping method, and dried at 200 ° C. for 5 minutes. Adhesion amount is 1.1
%Met.

The sizing agent applied had an epoxy equivalent of 2.7 × 10 ^-3 equivalent / g and contained no compound having a polyoxyethylene group. The carbon fiber thus obtained had a strand strength of 4000 MPa and an elastic modulus of 230 GPa. The static friction coefficient of this carbon fiber, the fiber entanglement value by the hook drop method, the number of fluffs,
The widening unit weight and ILSS were measured. The results are shown in Table 1.

Comparative Example 3 A surface treatment with an electrolytic solution was carried out in the same manner as in Example 1, polyethylene glycol having a molecular weight of 12000 was dissolved in water as a sizing agent, and the resin component was adjusted to 3% by an immersion method. It was applied to carbon fiber and dried at 200 ° C. The adhered amount was 1.3%. Since the applied sizing agent contained no epoxy resin, the epoxy equivalent was 0 × 10 ⁻³ equivalent / g and the polyoxyethylene group content was 99.9%. The carbon fiber thus obtained had a strand strength of 4000 MPa and an elastic modulus of 230 GPa. The static friction coefficient of this carbon fiber, the fiber entanglement value by the hook drop method, the number of fluffs,
The widening unit weight and ILSS were measured. The results are shown in Table 1.

[0039]

[Table 1]

As is clear from Table 1, the carbon fibers of Examples 1 and 2 are superior to the carbon fibers of Comparative Examples 1 to 3 in the fiber-spreading property, and the machine of the composite molded product is excellent. It can be seen that the characteristics are excellent.

[0041]

EFFECTS OF THE INVENTION According to the method of the present invention, carbon fiber having a large number of filaments has excellent openability.
A prepreg having a low basis weight can be produced, and a composite material having excellent mechanical properties can be provided.

Claims (3)

[Claims] 1. The number of filaments from 20,000 to 10,000
0 carbon fiber, a sizing agent containing at least a polyoxyalkylene group and an epoxy group is attached to the component, and the epoxy equivalent of the sizing agent is 0.2 to 5.0 × 10. ^-3 equivalents / g, and the ratio of the compound containing a polyoxyalkylene group contained in the sizing is 40% by weight or more. 2. The carbon fiber bundle according to claim 1, wherein the sizing agent adheres to the carbon fiber in an amount of 0.5 to 3% by weight. 3. The carbon fiber bundle has a coefficient of static friction with metal of 0.10 to 0.25, and a fiber entanglement value by the hook-drop method as defined in the text of the carbon fiber bundle of 5.
The carbon fiber bundle according to claim 1 or 2, wherein the carbon fiber bundle has a size of -30 m ^-1 .