JP2000170050A - Production of carbon fiber bundle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a carbon fiber bundle having a light strength without using an expensive device. SOLUTION: This method for producing a carbon fiber bundle comprises sequentially dipping a carbon fiber bundle comprising many carbon filaments in two kinds of different resin liquids. Therein, the contact angle of the resin liquid 4 containing the first resin with the carbon fibers is <=5 degree, and the viscosity of the resin liquid 5 containing the second resin at 20 deg.C is 5-100 poises.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

2. Description of the Related Art In recent years, television interference caused by high-rise buildings has become a major social problem. this is,
High-rise buildings use a large amount of steel as a structural member, and the outer wall is made of concrete.Concrete has extremely poor radio wave absorption characteristics, so radio waves reflected by steel materials cause radio interference. Is believed to be.

[0002] As one method of preventing radio interference, a concrete wall is coated with a material having a good radio wave absorption property such as a ferrite tile. However, ferrite tiles have good electromagnetic wave absorption properties, but have a large specific gravity. Therefore, when ferrite tiles are used, there is a problem that the strength of structural members must be increased, and construction costs increase.

Therefore, a radio wave absorber composed of a resistive film layer, a dielectric layer, and a reflective layer is used in such a manner that the resistive film layer is oriented in the direction of arrival of the radio wave and the carbon fiber bundle is parallel to the electric field direction of the radio wave. By installing the antenna on the outer wall as described above, the radio waves are efficiently absorbed. Such a radio wave absorber is called a λ / 4 type radio wave absorber, and 377 Ω is used as a resistive film layer.
By using a material having a sheet resistance of / □ and arranging a dielectric layer having a thickness of d (cm) obtained by the following equation between the resistive film layer and the reflective layer, thereby absorbing radio waves. That is.

D = λ / (4√ε) (where λ is the wavelength (cm) of the radio wave to be absorbed,
[epsilon]: relative dielectric constant of dielectric) Usually, as the resistive film layer, a material obtained by solidifying a number of long carbon fibers with a resin to form a bundle and then forming a lattice shape is used.

[0005]

As a method of installing such a radio wave absorber on an outer wall, first, a grid of carbon fiber bundles serving as a resistive film layer is provided at a predetermined position in a mold for casting the outer wall. After that, concrete forming the outer wall is poured into a mold, and finally, a reflective layer is attached.

In this case, the intervals between the carbon fiber bundles are set so that the sheet resistance becomes a specific value. However, if the rigidity and strength of the carbon fiber bundles are insufficient, the concrete may be cast when casting concrete. , Due to the impact of concrete, the carbon fiber bundle bends,
Since the distance between the carbon fiber bundles deviates from the set value, there is a problem that the sheet resistance changes and radio waves cannot be effectively absorbed.

Conventionally, to produce such a carbon fiber bundle, a draw molding method is used in which an epoxy resin is impregnated while applying a tension of 100 to 1000 g to the carbon fiber bundle, and the epoxy resin is heated and cured in place. However, there is a problem that the equipment is expensive and cannot be easily implemented, and it is difficult to control the resistance value due to thread breakage or the like because excessive tension is applied.

Therefore, it is desired to produce the carbon fiber bundle by a simple drawing method in which the carbon fiber bundle is passed through a resin liquid impregnation tank, the carbon fiber bundle is wound, and then dried. However, in this method, it was difficult to secure the thickness of the resin layer sufficient to secure the rigidity and strength of the carbon fiber bundle. That is, in order to increase the thickness of the resin layer, a high-viscosity resin may be used,
If a high-viscosity resin is to be impregnated into a carbon fiber bundle, the impregnation of the resin into the fiber bundle is poor, and the thickness cannot be ensured. On the other hand, when the viscosity of the resin is reduced by using a solvent in order to improve the impregnation property of the resin into the fiber bundle, the use of the solvent is not preferable in terms of affecting the human body. In addition, when a resin having a low viscosity is used, it is necessary to apply the resin, then dry, and then apply the resin. Further, when a resin whose viscosity is reduced by a solvent is used, the resin layer is liable to open due to volatilization of the solvent in the drying step, and as a result, there is a problem that the rigidity and strength of the carbon fiber bundle are insufficient.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to solve these problems, and as a result, the carbon fiber bundle is first impregnated with a resin having good wettability, so that the carbon fiber bundle is The present inventors have found that a method of impregnating a high-viscosity resin after the resin has been blended with the resin can provide a carbon fiber bundle having a small amount of voids and a thick resin layer in the resin, and have reached the present invention. That is, the gist of the present invention is a method of manufacturing a carbon fiber bundle in which a carbon fiber bundle in which a number of long carbon fibers are bundled is sequentially impregnated with two different types of resin liquids. A contact angle between the resin and the carbon fiber is 5 degrees or less, and the viscosity of the resin liquid containing the second resin at 20 ° C. is 5 to 100 poise.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
One example of the present invention is shown in FIG. The present invention is characterized in that a carbon fiber bundle obtained by bundling a number of long carbon fibers is sequentially impregnated with two different types of resin liquids. Carbon fiber is usually 100
0 to 20,000 carbon fiber single yarns 2 are pulled out from the bobbin 1 and are impregnated with a resin liquid in a state where they are bundled together. The tension applied to the carbon fibers when impregnated with the resin liquid is usually 50 to 500 g, preferably 100 to 300 g.
g. If the tension is less than 50 g, the carbon fibers will sag, making it difficult to produce a uniform carbon fiber bundle. If the tension exceeds 500 g, the carbon fibers may be cut.

The diameter of the carbon fiber used in the present invention is usually 5 to 20 μm. The resistivity of carbon fiber is usually 1 to
It is 50 kΩ / m, preferably 10 to 20 kΩ / m. If the resistivity is less than 1 kΩ / m, a large amount of carbon fiber is required to obtain the sheet resistance of the resistive film layer, which is not economically preferable. 5
If it is larger than 0 kΩ / m, the amount of carbon fibers for obtaining the sheet resistance of the resistive film layer is too small, so that it is difficult to obtain a stable resistive film layer.

A bundle of carbon fibers is first impregnated with a resin liquid 4 containing a first resin. The resin liquid containing the first resin is made of a resin having a contact angle with carbon fibers of 5 degrees or less. If the contact angle is more than 5 degrees, porosity tends to occur between carbon fibers. When voids occur, the strength of the fiber bundle itself decreases. The contact angle can be obtained by dropping one drop (0.2 to 1.0 g) of the resin liquid on thousands to tens of thousands of carbon fibers laid horizontally and arranging the carbon fibers and the resin 30 seconds later. Is measured by a contact angle meter manufactured by Kyowa Interface Science Co., Ltd. As the type of the first resin,
There is no particular limitation as long as the condition of the contact angle is satisfied, but a resin that has good compatibility with the second resin and is capable of curing itself is preferable. Examples of such a resin include an epoxy resin and a phenol resin.

In order to adjust the contact angle of the resin solution containing the first resin, alcohols such as butanol glycidyl ether and glycidyl ether of higher alcohols, phenols such as butylphenyl glycidyl ether and cresyl glycidyl ether, and Monofunctional reactive diluents such as glycidyl acrylate and carboxylic acid, 1,4-butanediol diglycidyl ether,
Dihydric alcohols such as 6-hexanediol glycidyl ether; trihydric alcohols such as trimethylolpropane triglycidyl ether; glycerin triglycidyl ether; polyglycols such as polyethylene glycol diglycidyl ether and polypropylene glycol diglycidyl ether; dimer acid dimer The reaction is performed by blending a reactive diluent such as a polyfunctional reactive diluent such as a dibasic acid based glycidyl ester.

When the first resin is an epoxy resin, a diluent for diluting the first resin preferably has an epoxy group from the viewpoint of compatibility and sharing of a curing agent.
The larger the amount of the reactive diluent, the smaller the contact angle of the resin liquid with the carbon fiber and the better the wettability, but the more difficult it is to cure the resin itself. Is preferred. The upper limit of the amount of the reactive diluent added varies depending on the type, but the same amount as the epoxy is a standard.
The weight ratio of epoxy to reactive diluent is reactive diluent / epoxy = 10-200, preferably 30-100.

The reactive diluent may be used alone or in combination of two or more. The resin liquid containing the first resin includes:
A curing agent for curing the epoxy resin may be blended. Examples of the curing agent include amine compounds such as aliphatic amines, polyaminoamides, aromatic diamines, alicyclic diamines, and imidazoles, acid anhydride compounds, phenol resins, amino resins, mercaptan compounds, diamine diamides, and Lewis acid complexes. And the like.

The impregnation time of the carbon fiber into the resin liquid comprising the first resin is generally 0.1 to 10 seconds, preferably 0.5 to 10 seconds.
3 seconds. If the time is shorter than 0.1 second, the impregnation is not sufficiently performed, and if the time is longer than 10 seconds, there is no problem in the performance of the obtained carbon fiber bundle, but the productivity is undesirably reduced. The temperature of the resin solution is usually 0 ° C to 40 ° C, preferably 5 ° C to 25 ° C. If the temperature is too low, it is difficult to adjust the temperature. If the temperature is too high, the curing of the resin may be too fast, resulting in poor workability.

The amount of impregnation of the first resin into the carbon fiber bundle is not particularly limited, but it is preferable that the amount of the resin is preferably 10% by weight or less based on the weight of the carbon fiber. After the carbon fiber bundle is impregnated with the resin liquid containing the first resin, it may be dried or thermally cured before being impregnated with the resin liquid containing the second resin. The carbon fiber bundle impregnated with the resin liquid 4 containing the first resin is then impregnated with the resin liquid 5 containing the second resin.

As the second resin, a thermosetting resin such as an epoxy resin or a phenol resin is usually used, and an epoxy resin is particularly preferably used from the viewpoint of alkali resistance and water resistance. It is preferably an epoxy resin, and as the epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy resin, cycloaliphatic epoxy resin, glycidyl ester resin, glycidylamine resin Resins and heterocyclic epoxy resins. The resin liquid containing the second resin is obtained by adding a curing agent to the above resin,
Obtained by blending additives such as diluents

In the present invention, the viscosity of the resin liquid containing the second resin at 20 ° C. is adjusted to be less than 5 to 100 poise. If the viscosity of the resin liquid is less than 5 poise, it is difficult to secure the thickness of the resin layer, and if it exceeds 100 poise, the resin adheres more than necessary,
It is not preferable because it causes fiber breakage. In addition, it causes voids in the carbon fiber bundle, and lowers the strength. Here, if any of the resin occurs, the resin adheres to the manufacturing equipment, so that it is necessary to frequently remove the adhered resin. Further, the amount of wasted resin increases, and the yield deteriorates. If the carbon fibers are cut during the production of the carbon fiber bundle, it is difficult to control the conductivity of the obtained carbon fiber bundle to a target range, which is not preferable.

The adjustment of the viscosity of the resin solution can be performed by selecting the type of the curing agent or by blending a reactive diluent. Examples of the curing agent include amine compounds such as aliphatic amines, polyaminoamides, aromatic diamines, alicyclic diamines, and imidazoles, acid anhydride compounds, phenol resins, amino resins, mercaptan compounds, diamine diamides, and Lewis acid complexes. And the like.

The amount of the curing agent is usually calculated from the epoxy equivalent of the epoxy and the reactive diluent. When the amount of the curing agent is c, the weight of the epoxy is a, the weight of the epoxy is Wa, the weight of the diluent is b, and the weight of the epoxy is Wb. For example, when the curing agent is an amine, the hydrogen is equivalent to Wc. Can be.

C = Wc × (a / Wa + b / Wb) / (a + b) Examples of the reactive diluent include alcohols such as butanol glycidyl ether and glycidyl ether of higher alcohol, butylphenyl glycidyl ether, and cresyl glycidyl ether. Monofunctional reactive diluents such as phenolic, glycidyl methacrylate and carboxylic acid, dihydric alcohols such as 1,4 butanediol diglycidyl ether and 1,6 hexanediol glycidyl ether, and trimethylol Trihydric alcohols such as propane triglycidyl ether and glycerin triglycidyl ether; polyglycols such as polyethylene glycol diglycidyl ether and polypropylene glycol diglycidyl ether; and dibasic acids such as dimer acid diglycidyl ester are used. Capacity type reactive diluents and the like.

In order to prevent dripping of the resin liquid, the particle diameter of the resin liquid containing the second resin is usually 0.01 to 1 μm.
An inorganic powder such as silica sol of m may be blended. In the present invention, it is desirable that the first resin and the second resin are the same type of resin. This is because if the resins are of the same type, there is no risk of peeling between the first resin and the second resin.

The impregnation time of the carbon fiber into the resin solution containing the second resin is generally 0.1 to 10 seconds, preferably 0.5 to 3 seconds.
Seconds. If it is shorter than 0.1 second, the impregnation is not performed sufficiently,
If the time is longer than 10 seconds, there is no problem in the performance of the obtained carbon fiber bundle, but the productivity is undesirably reduced. The temperature of the resin solution is usually 0 ° C to 40 ° C, preferably 5 ° C to 25 ° C. If the temperature is too low, it is difficult to adjust the temperature. If the temperature is too high, the curing of the resin may be too fast, resulting in poor workability.

After impregnating with the resin liquid containing the second resin, the carbon fiber bundle 3 is heated by a drier to thermoset the resin, and then wound up by the winder 6. Alternatively, the resin is heat-cured by a drier after being wound on the winder 6 to thermally cure the resin. The curing temperature varies depending on the type of the resin, but is usually 50 to 120 ° C., preferably 60 to 10 ° C.
0 ° C. When the curing agent for the epoxy resin is a room temperature curing type, the curing may be performed without heating, by simply drying the surface of the resin with a dryer.

The carbon fiber bundle thus obtained has a bending load, which is one of the indexes of rigidity, usually 2.0 kg or more.
Preferably it is 2.0 to 50 kg. There is no particular problem when the bending load is large, but the rigidity is insufficient when the load is less than 2.0 kg. Therefore, the carbon fiber bundle is bent by the impact at the time of placing the concrete, so that the interval between the carbon fiber bundles is reduced. Instead, a deviation may occur from the predetermined sheet resistance value, and a sufficient radio wave absorbing ability may not be obtained. In the present invention, the bending load of the carbon fiber bundle is such that one carbon fiber bundle
A 0 mm bisection bending load was performed, and the maximum load was measured.

In the carbon fiber bundle, the thickness of the resin layer on the outside of the carbon fiber is usually 70 μm or more, preferably 90 to 1 μm.
40 μm. There is no problem with the thickness even if the thickness is 140 μm or more, but it is economically undesirable to attach the resin excessively. If the thickness is less than 70 μm, sufficient strength cannot be obtained, and the concrete will be broken during casting. The diameter of the carbon fiber bundle is usually 1.5 to 5.0 mm, preferably 2.0 to 4.0 mm.

When the carbon fiber bundle is used for the resistance film layer of the radio wave absorber, the carbon fiber bundle has a lattice spacing of usually 5 to 1000.
mm, placed in a formwork such as a wall, then cast concrete, and make the distance between the resistive layer and d (cm) approximately equal to the following formula. A radio wave absorbing wall can be formed by bonding a metal plate to the metal plate. d = λ / (4√ε) (where λ is the wavelength of the radio wave to be absorbed (cm),
ε: dielectric constant of dielectric)

[0029]

<Example 1> Using a production line as shown in FIG. 1, an impregnation tank 7 containing a resin A in a resin liquid containing a first resin and a resin liquid containing a resin liquid containing a second resin. The resin L was put in 8, and threading was performed as shown in FIG. 1 so that the carbon fiber bundle in which 12,000 carbon fibers were bundled in the order of the impregnation tanks 7 and 8 was impregnated. The tension applied to the carbon fibers was 200 to 300 g throughout. The carbon fiber bundle is supplied to the impregnation tank 7
After 0.5 second, the impregnating tank 8 was 2.0 seconds, and the carbon fiber bundle exiting the impregnating tank 1 had 5% by weight of resin A attached thereto.

The carbon fiber bundle impregnated with the resin A and the resin B was wound by a winder. The wound carbon fiber bundle was cured for 1 hour in a dryer at 100 ° C. The thickness, porosity, bending load, and diameter of the resin of the obtained carbon fiber bundle were measured. The thickness of the resin of the carbon fiber bundle was measured by observing the cross section of the cured carbon fiber bundle with a scanning electron microscope. The thickness was measured from any 10 locations and determined by the average value. As a result of electron microscopic observation, the void amount of the carbon fiber bundle was evaluated as x when there was a void of 50% or more of the total cross-sectional area.

The bending load of the carbon fiber bundle is calculated using TOYO BALDWIN T
Using ENSILON, bending was carried out at 2 equally divided points with a span of 50 mm, and the maximum load was measured. The dripping property of the resin liquid was evaluated as x when comparing the total amount of resin dropped directly below the winder 6 with the total amount of resin attached to the fibers as fiber bundles, when the former exceeded 10% of the latter. The contact angle of the resin liquid with the carbon fiber was measured 30 seconds after dropping by a contact angle meter manufactured by Kyowa Interface Science Co., Ltd., and the viscosity was measured by a B-type viscometer. The results are summarized in Table 1.

<Example 2> The procedure of Example 1 was repeated, except that the resin B was used instead of the resin A. Table 2 summarizes the results. <Example 3> The procedure of Example 1 was repeated, except that the resin M was used instead of the resin L. Table 2 summarizes the results.

<Comparative Example 1> The procedure of Example 1 was repeated, except that the resin D was used instead of the resin L. Table 2 summarizes the results. <Comparative Example 2> The same operation as in Example 1 was performed except that resin N was used instead of resin L. Table 2 summarizes the results.

<Comparative Example 3> The procedure of Example 1 was repeated, except that the resin C was used instead of the resin A. Table 2 summarizes the results. <Comparative Example 4> The same operation as in Example 1 was performed except that resin A was used instead of resin L. Table 2 summarizes the results. <Comparative example 5> Except not using resin A, it carried out similarly to Example 1. Table 2 summarizes the results.

[0035]

[Table 1] Bisphenol A type epoxy resin 1: "Epicoat 828" manufactured by Yuka Shell Epoxy Co., Ltd. Bisphenol A type epoxy resin 2: "Epotherm Resin 750R" manufactured by Yuka Shell Epoxy Co. * 1: Carboxylic monofunctional reactive diluent: "Kajura E10" Amine-based curing agent manufactured by Yuka Shell Epoxy: "Epomate RD-1" manufactured by Yuka Shell Epoxy

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

According to the present invention, a strong carbon fiber bundle can be easily manufactured.

[Brief description of the drawings]

FIG. 1 shows an example of the present invention.

[Explanation of symbols]

 Reference Signs List 1 bobbin 2 single carbon fiber yarn 3 carbon fiber bundle 4 resin liquid containing first resin 5 resin liquid containing second resin 6 winding machine 7 impregnation tank 8 impregnation tank

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) // D06M 101: 40 F term (reference) 4F100 AD11A AH03H AK01B AK01C AK53 BA03 BA07 BA10A BA10C CA02 DA16 DD31 DG04A EA021 EA022 EJ083 EJ423EJ EJ822 GB41 JA06C JA20B JK01 JK04A YY00B YY00C 4L033 AA09 AC11 AC15 CA49 CA70 4L036 MA04 RA24 UA25

Claims (3)

[Claims] 1. A method for producing a carbon fiber bundle, comprising sequentially impregnating a carbon fiber bundle obtained by bundling a plurality of long carbon fibers with two different types of resin liquids, comprising a resin liquid containing a first resin and a carbon fiber A contact angle of not more than 5 degrees and a viscosity of the resin liquid containing the second resin at 20 ° C. of 5 to 100 poise. 2. The method according to claim 1, wherein the bending load of the carbon fiber bundle is 2.0 kg or more. 3. The method for producing a carbon fiber bundle according to claim 1, wherein the carbon fiber bundle is used for a resistance film layer of a radio wave absorber.