JPH10195718A - Carbon yarn and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a carbon yarn capable of being condensed into a yarn bundle of high denier, securing excellent resin impregnation properties, providing an improved FRP, by making the bundle of a polyacrylonitrile-based yarn fire- resistance in an oxidizing atmosphere and carbonizing in an inert atmosphere at a high temperature. SOLUTION: A yarn obtained by spinning an acrylonitrile-based polymer from a spinneret having >=10mm diameter (a), a fiber width (b) of a yarn on a guide and a distance (c) between the spinneret and the guide in correlation of the equation 0.02>=tanθ=(a-b)/2c>=0.006 to give a yarn, which is condensed to give a handle of a polyacrylonitrile-based yarn having 10-40 (1/m) fiber interlaced value CF value by fook drop method, which is made fire-resistance in an oxidizing atmosphere at 200-300 deg.C. Then, the yarn is carbonized in an inert atmosphere at 500-1,500 deg.C to give the objective carbon yarn having >=25,000 denier and 10-100 (1/m) fiber interlacement value CF value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon fiber bundled into a thick denier fiber bundle and a method for producing the same.

[0002]

2. Description of the Related Art The demand for carbon fiber is increasing year by year, and the demand is expanding from premium applications such as aircraft and sports to general industrial applications related to construction, civil engineering and energy. In general industrial applications, especially when molding large-sized structural materials, the total denier required in, for example, woven fabric and filament winding methods is as large as about 100,000 denier. At present, several yarns of about 10,000 to 20,000 denier are drawn and formed.

[0003] However, when the filament yarns are aligned, the fibers are liable to be broken for each unit of the filament yarns, streak-like yarn cracks are generated, and the amount of impregnated resin tends to be uneven, and defects are apt to be formed during molding. Further, there is a problem that the resin once impregnated oozes out on the roller and a molded article having a target fiber content cannot be obtained.

[0004] In contrast to this situation, if carbon fibers having a large number of filaments and excellent in resin impregnating properties are present, advantages such as a reduction in the number of installations to higher-order processing equipment and a compact creel equipment are obtained. As a result, a great effect can be expected in using carbon fibers.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide carbon fibers which are bundled, particularly, in a thick denier fiber bundle, and which are excellent in resin impregnation in order to satisfy the above-mentioned demands. is there.

[0006]

In order to solve the above-mentioned problems, a carbon fiber according to the present invention is a carbon fiber bundled into a substantially non-twisted fiber bundle having a fineness of 25,000 denier or more. The fiber entanglement CF value in the drop method is in the range of 10 to 100 (1 / m).

Further, in the method for producing carbon fiber according to the present invention, the fiber entanglement value CF of the hook drop method obtained by bundling a fiber obtained by spinning an acrylonitrile polymer from a die with a guide is 10 to 10. A bundle of polyacrylonitrile fibers in the range of 40 (1 / m) is made flame-resistant at 200 to 300 ° C. in an oxidizing atmosphere, and then 500 to 500 ° C. in an inert atmosphere.
It is a method characterized by carbonizing at 1500 ° C. to obtain carbon fibers having a fineness of 25,000 denier or more.

In the above manufacturing method, the diameter a of the base is
It is preferable that the diameter is not less than 100 mm, and the diameter a of the die, the yarn width b of the fiber on the guide, and the distance c between the die and the guide have the following relationship. 0.02 ≧ tan θ = (ab) /2c≧0.006

The above a, b, and c have the relationship shown in FIG. In FIG. 1, 1 is a base, 2 is a take-off guide, 3
Denotes a coagulation bath, and 4 denotes an acrylonitrile-based polymer fiber bundle.

In the above-mentioned production method, it is preferable that a high-speed fluid of 0.2 to ² kgf / cm ² be sprayed from a direction perpendicular to the yarn before winding the polyacrylonitrile-based fiber.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. Any carbon fiber may be used as long as it has a strand strength of 250 to 700 kgf / mm ² and an elastic modulus of 15 to 60 tf / mm ² .

In the present invention, the convergence of the carbon fibers to be bundled in the fiber bundle is defined by the entanglement value by the hook drop method. The entanglement value of the carbon fiber by the hook drop method is measured by the following method. . The carbon fibers are lined up and down to give a weight of 200 g. Insert a key needle with a weight (10 g) into the carbon fiber thread and drop
After the first measurement, the CF value is calculated from the following equation using the average value x (cm) of the values obtained by removing 10 pieces from the largest one and 10 pieces from the smallest one in ascending order. CF = 100 / x (1 / m) Further, as a unit representing the confounding unevenness, a value obtained by dividing the standard deviation of the numerical value used for the above average value by the average value was defined as a CV value.

When the CF value of the carbon fiber measured in this way is smaller than 10, the resin is prevented from entering the gap between the single yarns during the high-order processing, and impregnation failure occurs. 100
If it is larger, the interference between the single yarns becomes large, which is disadvantageous in high-order processing applications requiring spreadability such as filament winding. The CF value for obtaining carbon fibers excellent in high order workability is in the range of 10 to 100 (1 / m). More preferably, it is in the range of 20 to 50 (1 / m). Moreover, since the carbon fibers according to the present invention are bundled in a fiber bundle, the CV value of the CF value is usually 5 to 40%.

As a method for obtaining the carbon fiber, a fiber entanglement value CF by a hook drop method is 10 to 40 (1 / m).
Using a polyacrylonitrile fiber in the range of 200 to 300 in an oxidizing atmosphere in a substantially untwisted state.
Flame resistant at 500C and carbonized at 500-1500C in an inert atmosphere.

Here, the entanglement value of the acrylic fiber is measured by the same method as described above, but for a fiber having a crimp, it is measured after removing the crimp. As a method, the iron is heated to 120 ° C., the tension is applied to the thread by hand, and the thread is pressed from above the thread for about 15 seconds. If the CF value is smaller than 10 (1 / m), as in the case of the carbon fiber, penetration of the resin into the gap between the single yarns during high-order processing is prevented, impregnation failure occurs, and if the CF value is larger than 40 (1 / m), Interference between single yarns increases, which is disadvantageous in high-order processing applications requiring spreadability such as filament winding. The above-mentioned CF value for obtaining a carbon fiber excellent in high order workability is 10 to 4
Any value may be used as long as it is in the range of 0 (1 / m), but more preferably 20 to 35 (1 / m).

In the present invention, the substantially untwisted state means
It means that the number of twists per meter is 1 or less. The oxidizing atmosphere may be any of oxygen, hydrochloric acid, and the like, but air is preferably used as a gas which can be obtained inexpensively and easily.

The inert atmosphere for carbonizing is not limited to nitrogen, argon, neon, etc., but nitrogen which can be obtained at relatively low cost is desirable.

As a method for imparting the entanglement to the acrylic fiber, there are a method of imparting an entanglement at a spun portion of the acrylic fiber and a method of spraying a high-pressure fluid. As shown in FIG. 1, the former is a spinning part, that is, the diameter of the spinneret is 100 mm or more when coagulating, the diameter a of the spinneret to be spun, the yarn width b on a roller for picking up the spun polymer, and the spinneret. The following relationship exists between the distance c to the guide. 0.02 ≧ tan θ = (ab) /2c≧0.006 That is, when tan θ is in the range of the above expression, single yarns cross each other when collected from a large die to a small guide,
The entanglement occurs due to the skewed yarn. tanθ
Is smaller than 0.006, each of the single yarns tries to go straight, and confounding of the single yarns decreases, and conversely, tan θ
Is larger than 0.02, the angle from the base surface, especially from the outer peripheral portion to the focusing guide becomes steep, and the yarn is damaged. tanθ
Is more preferably in the range of 0.008 to 0.018, and still more preferably in the range of 0.010 to 0.015.

The spun yarn is washed with water, drawn in a bath, applied with an oil agent,
After being wound around a bobbin or crimped through a process such as drying, it is stored in a can and subjected to a firing process.

Here, the polyacrylonitrile fiber is obtained by spinning out from a die a polyacrylonitrile polymer copolymerized with 90 parts by weight or more of acrylonitrile as a component.

The number of filaments of the acrylic fiber, that is, the number of holes for spinning the fiber is not limited, but the solidification speed may be uneven at the center and at the end of the spinneret, and stable spinning may not be possible. , 300,000
The following is desirable, and in order to obtain the advantage of multiple yarns,
00 or more is desirable.

Another method of imparting entanglement is to blow a high-pressure fluid in a direction perpendicular to the yarn, for example, onto the yarn immediately before bobbin winding or crimping before subjecting it to a flame-proofing step, and forcibly apply the fiber. This is a method of imparting confounding in a localized manner.

The high-pressure fluid to be sprayed may be a liquid or a gas, but the liquid is preferably a gas because the oil tends to fall off during spraying. For gas, air,
Any material can be used as long as it is easy to handle, such as nitrogen, oxygen, carbon dioxide, etc., but inexpensive air is desirable.

The greater the pressure of the fluid to be blown, the greater the entanglement applied to the yarn. However, in order to obtain an entanglement value of 10 to 40 (1 / m) and to prevent mechanical damage to the yarn, 0.2
A pressure in the range of ２2 kgf / cm ² is desirable.

The shape of the entangled nozzle to be sprayed and the spraying direction are not limited, but it is desirable to spray the yarn from the 360-degree direction (that is, evenly from all directions) in order to impart uniform entanglement to the yarn.

The reticulated carbon fiber thus produced is
Since the voids exist inside the yarn, the resin easily penetrates into the voids when the resin is impregnated. Therefore, voids are less likely to occur during FRP molding, the volume content of the fiber can be increased, and a high-strength FRP can be obtained. The volume content of the fiber referred to here is represented by the following equation. Fiber volume content = [weight of fiber base (g) ÷ fiber density (g
/ cm ³ )] ÷ [FRP volume (cm ³ )]

The carbon fiber is formed as a bundle of thick denier fibers having a fineness of 25,000 denier or more. In the case where carbon fibers of 10,000 to 20,000 denier are aligned, the yarn breaks in each alignment unit at the time of molding to cause unevenness in the impregnation of the resin, but the carbon fiber according to the present invention breaks the yarn. In addition, since the degree of entanglement is constant due to the production method, unevenness in impregnation of the resin is unlikely to occur. In addition, since the single yarn has binding power,
There is also an advantage that the yarn is less likely to be judged, a single yarn is not wound around a roller at the time of high-order processing, and a stable operation can be performed.

[0028]

【Example】

Example 1 A polyacrylonitrile-based dimethyl sulfoxide (DMSO) solution obtained by copolymerizing 95 parts by weight of acrylonitrile, 4 parts by weight of methyl acrylate, and 1 part by weight of itaconic acid was dissolved in a 60% DMSO aqueous solution at 30 ° C. with 8 filaments.
Wet spinning was performed from a 4,000 die. At this time, the die diameter is 130 mm, the thread width on the focusing guide is 10 mm, the distance between the die and the focusing guide is 4,500 mm, and tan θ = 0.0013
And

The bundled fibers were subjected to crimping through stretching, washing with water, applying an oil agent and the like. After removing the crimp from the fiber, the entanglement value was measured by the hook drop method and found to be 15 (1 / m), and the CV value was 20%. This fiber was subjected to a flame-resistant treatment in a hot-air circulation oven at 240 ° C for 80 minutes, and then carbonized at 1,400 ° C.
/ m (57,600 denier) carbon fiber was obtained. The entanglement value of this carbon fiber measured by the hook drop method was 30 (1 / m), and the CV value showing variation was 15%. The tensile strength of this carbon fiber by the epoxy resin strand method is 400 kgf / mm ² , and the tensile modulus is 23 tf / m
It was m ^2.

Using the carbon fiber as the warp and the glass fiber as the weft (ECE225-1 / 2, manufactured by Nitto Boseki Co., Ltd.) as an auxiliary yarn, a unidirectional woven fabric having a basis weight of 300 g / m ² was prepared. . The operability at the time of fabric preparation was good, there was no occurrence of thread breakage due to winding or the like, and the target fabric could be obtained with a yield of 95%. When a cured plate which was impregnated with a vinyl ester resin by a hand lay-up method and cured by an autoclave was prepared, it showed a high fiber volume content of 55%, was completely impregnated with the resin, and had no voids. . The hardened plate obtained in this manner was subjected to JIS-K
When evaluated in accordance with the tensile test method of CFRP (carbon fiber reinforced plastic) of 7073, the tensile breaking strength in the carbon fiber orientation direction was 170 kgf / mm ² , and the elastic modulus was 10,100 kgf / mm ^2.
Met.

Comparative Example 1 The same polyacrylonitrile polymer DMSO as in Example 1
The solution was wet-spun from a base having 84,000 holes. The die diameter at that time is 130mm, and the thread width on the focusing guide is 90m
m, the distance between the base and the focusing guide is 4,500 mm, and tan θ
= 0.004, stretching, washing with water in the same manner as in Example 1,
After the oil agent applying step and the like, crimping was performed and packed in a can.

After the above crimp was removed from this fiber, the entanglement value was measured by the hook drop method to find 5 (1 / m).
And the CV value was 25%. This fiber was subjected to a flameproofing treatment at 240 ° C for 80 minutes in a hot air circulating oven, and then carbonized at 1,400 ° C to give a basis weight of 6.4 g / m (57,600 denier).
Was obtained. The confounding value of this carbon fiber measured by the hook drop method was 8 (1 / m),
The CV value was 35%. The tensile strength of this carbon fiber by the epoxy resin strand method was 400 kgf / mm ² , and the tensile modulus was 23 tf / mm ² .

Except that this carbon fiber was used as a warp,
In the same manner as in Example 1, a basis weight of a plain weave structure of 300 g / m ²
Was made. The operability at the time of fabric production was good, and there was no yarn breakage due to winding or the like, and the target fabric could be obtained at a yield of 95%. However, the vinyl ester resin was impregnated by a hand lay-up method, and the autoclave was used. When a cured board was prepared, when the yarn was spread on a roller, a bar-code-shaped gap was opened, and uneven impregnation of fibers was observed. Although the fiber volume content was 45%, which was not much lower than that of Example 1, voids were found everywhere. The cured plate obtained in this manner was used in Example 1
When evaluated in the same manner as above, the tensile strength at break was 104 kgf / mm ² ,
The elastic modulus was 8,700 kgf / mm ² .

Comparative Example 2 The same polyacrylonitrile polymer DMSO as in Example 1
The solution was wet-spun from a die having 84,000 holes. In this case, the die diameter was 200 mm, the thread width on the focusing guide was 10 mm, and the distance between the die and the focusing guide was 2,500 mm.
When nθ = 0.038, normal spinning could not be performed due to yarn breakage on the die surface.

Comparative Example 3 The same polyacrylonitrile polymer DMSO as in Example 1
The solution was wet-spun from a die having 12,000 holes. In this case, the die diameter is 130 mm, the thread width on the focusing guide is 10 mm, and the distance between the die and the focusing guide is 4,500 mm.
nθ was set to 0.013.

The bundled fibers were subjected to crimping through stretching, rinsing, oiling step and the like. After removing the crimp from the fiber, the entanglement value was measured by the hook drop method. The entanglement value was 20 (1 / m) and the CV value was 14%. This fiber was subjected to a flameproofing treatment at 240 ° C for 80 minutes in a hot-air circulation oven, and then carbonized at 1,400 ° C to give a basis weight of 0.8 g.
/ m (7,200 denier) carbon fiber was obtained. The entanglement value of this carbon fiber measured by the hook drop method was 30 (1 / m), and the CV value was 12%.
Eight lines were aligned to obtain the same basis weight as in Example 1, and the degree of confounding was measured again. The CF value was 10 (1 / m) and the CV
The value increased to 70%. The tensile strength of this carbon fiber by the epoxy resin strand method was 390 kgf / mm ² , and the tensile modulus was 23 tf / mm ² .

A unidirectional woven fabric having a basis weight of 300 g / m ² was prepared in the same manner as in Example 1 except that eight carbon fibers were drawn and used as warp yarns. The operability at the time of fabric production is good, there is no yarn breakage due to winding etc.,
Although the desired woven fabric could be obtained with a yield of 95%, a cured plate was impregnated with a vinyl ester resin by a hand lay-up method and cured by an autoclave. The resin flowed from the formed gap, the fiber volume content was 35%, which was lower than that of Example 1, and voids were observed. When the cured plate thus obtained was evaluated in the same manner as in Example 1, the tensile breaking strength was
90 kgf / mm ^2, an elastic modulus of 7,300kgf / mm ^2.

Example 2 An oil nozzle capable of spraying high-pressure air after applying an oil agent in the spinning process to the yarn under the conditions of Comparative Example 2 was attached in a direction perpendicular to the yarn traveling direction. The hole diameter for blowing high-pressure air was 2 mm, and six holes were arranged in 360-degree directions at 60-degree intervals. When the blowing pressure was 1 kgf / mm ² , the CF value of the obtained acrylic fiber was measured. The CF value was 30 (1 / m), and the CV value was 10%.

The fibers were placed in a hot air circulating oven at 240 ° C. for 80 hours.
After the flame treatment, the carbonization treatment is performed at 1,400 ° C.
A carbon fiber with a basis weight of 6.4 g / m (57,600 denier) was obtained. The entanglement value of this carbon fiber measured by the hook drop method was 40 (1 / m), and the CV value (standard deviation divided by the average value) indicating variation was 15%. The tensile strength of this carbon fiber by the epoxy resin strand method was 370 kgf / mm ² , and the tensile modulus was 23 tf / mm ² .

Except that this carbon fiber was used as the warp,
In the same manner as in Example 1, a basis weight of a plain weave structure of 300 g / m ²
Was made. The operability at the time of fabric preparation was good, there was no occurrence of thread breakage due to winding or the like, and the target fabric could be obtained with a yield of 95%. When a cured plate was impregnated with a vinyl ester resin by the hand lay-up method and cured in an autoclave, the fiber volume content was 60%.
And the resin was completely impregnated and free from voids. The cured plate obtained in this manner was used in Example 1
When evaluated in the same manner as above, the tensile breaking strength was 160 kgf / m
m ² and the elastic modulus were 9,700 kgf / mm ² .

Comparative Example 4 When the blowing pressure was set to 0.1 kgf / mm ^{2 in the same} manner as in Example 2, the CF value of the obtained acrylic fiber was measured. The CF value was 7 (1 / m) and the CV value was 20. %.

The fibers were placed in a hot air circulating oven at 240 ° C. for 80 hours.
After the flame treatment, the carbonization treatment is performed at 1,400 ° C.
A carbon fiber with a basis weight of 6.4 g / m (57,600 denier) was obtained. The entanglement value of this carbon fiber measured by the hook drop method was 9 (1 / m), and the CV value (standard deviation divided by the average value) indicating the variation was 15%. The tensile strength of this carbon fiber by the epoxy resin strand method was 380 kgf / mm ² , and the tensile modulus was 23 tf / mm ² .

Except that this carbon fiber was used as a warp,
In the same manner as in Example 1, a basis weight of a plain weave structure of 300 g / m ²
Was made. The operability during the production of the woven fabric was good, there was no yarn breakage due to winding, etc., and the desired woven fabric could be obtained with a yield of 95%. A molded article was obtained in the same manner as described above. The fiber volume content was 45%, and voids were confirmed in some places. The cured plate had a tensile strength at break of 87 kgf / mm ² and an elastic modulus of 7,200 kgf / mm ² .

Comparative Example 5 When the blowing pressure was set at 2.5 kgf / mm ^{2 in the same} manner as in Example 2, the CF value of the obtained acrylic fiber was measured. The CF value was 50 (1 / m) and the CV value was 20. %.

The fibers were placed in a hot air circulating oven at 240 ° C. for 80 hours.
After the flame treatment, the carbonization treatment is performed at 1,400 ° C.
A carbon fiber having a basis weight of 6.4 g / m (57,600 deniers) was obtained. In particular, yarn breakage in the oxidization process and winding of a single yarn around a roller frequently occurred, and the process passage rate was 60%. The entanglement value of this carbon fiber measured by the hook drop method was 110 (1 / m), and the CV value (standard deviation divided by the average value) indicating the variation was 45%. The tensile strength of this carbon fiber by epoxy resin strand method is 30
The tensile modulus was 5 kgf / mm ² and the tensile modulus was 23 tf / mm ² .

Except that this carbon fiber was used as a warp,
In the same manner as in Example 1, a basis weight of a plain weave structure of 300 g / m ²
Was made. The operability at the time of fabric production was similar to that of the carbon fiber production process, in which thread breakage occurred frequently due to winding and the like, and the process passage rate was 50%. About the thread which passed through the process, the molded object was obtained by the same method as the above. The fiber volume content is 50%, and the tensile strength at break of the cured plate is 65kg.
f / mm ² and elasticity were 6,000 kgf / mm ² .

The results of Examples 1 and 2 and Comparative Examples 1 to 5 are summarized in Table 1.

[0048]

[Table 1]

[0049]

As described above, according to the carbon fiber of the present invention and the method for producing the same, the fineness of the fiber is 25,000 denier or more and the fiber entanglement C in the hook drop method.
Since the F value is in the range of 10 to 100 (1 / m), it is made of thick denier carbon fiber, so that it can be formed into a thick fiber bundle form while ensuring excellent resin impregnation, and work in high-order processing Thus, it is possible to improve the performance and make the equipment compact, and to obtain an FRP with excellent performance.

[Brief description of the drawings]

FIG. 1 is a plan view of an acrylonitrile-based polymer fiber bundle spinning unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cap 2 Pickup guide 3 Coagulation bath 4 Acrylonitrile polymer fiber bundle

Claims (4)

[Claims] 1. A carbon fiber bundled into a substantially twistless fiber bundle having a fineness of 25,000 denier or more, and having a fiber entanglement value CF of 10 to 10 in a hook drop method.
Carbon fiber characterized by being in the range of 0 (1 / m). 2. A fiber entanglement CF value by a hook drop method obtained by bundling a fiber obtained by spinning an acrylonitrile-based polymer from a die with a guide is 10 to 40 (1/1).
m) a bundle of polyacrylonitrile fibers in the range of
A method for producing carbon fibers, comprising: after oxidizing at 200 to 300 ° C in an oxidizing atmosphere, carbonizing at 500 to 1500 ° C in an inert atmosphere to obtain carbon fibers having a fineness of 25,000 denier or more. 3. The method according to claim 1, wherein the diameter a of the mouthpiece is 100 mm or more, and the diameter a of the mouthpiece, the thread width b of the fiber on the guide, and the distance c between the mouthpiece and the guide have the following relationship. The method for producing a carbon fiber according to claim 2, wherein 0.02 ≧ tan θ = (ab) /2c≧0.006 4. A polyacrylonitrile-based fiber,
The method for producing carbon fibers according to claim 2 or 3, wherein a high-speed fluid of 0.2 to ² kgf / cm2 is sprayed from a direction perpendicular to the yarn.