JP2010255168A - Process for producing carbon fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pieced part preventing yarn breakage stemming from heat storage even during a flame-proofing step and further causing no rupture even under high tension on filament yarns in respective steps, and a process for producing a carbon fiber with a pieced part in high productivity. <P>SOLUTION: In producing the carbon fiber with a filament number of 3,000 or more by joining the end of a first precursor fiber bundle and the end of a second precursor fiber bundle to each other via a third fiber bundle, the third fiber bundle has the following characteristics: the thermal conductivity is 3-700 W/(m×K); the filament number is not less than 3,000; the drape value is 2-15 cm; and the flatness index is not less than 20. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention reduces the heat storage of the yarn splicing joint by a simple method, and does not break the yarn splicing joint due to heat storage in the firing process, and the yarn splicing joint that can pass through the process while maintaining a high temperature, and its The present invention relates to a continuous carbon fiber manufacturing method in which fiber bundles are joined using a yarn joining joint.

  In general, in a carbon fiber manufacturing process, a precursor fiber bundle for carbon fiber manufacturing is supplied to the firing process in a form wound up on a bobbin or the like, or in a form folded and laminated in a box. Therefore, in order to continuously fire these precursor fiber bundles and convert them into carbon fibers, the form wound up on the bobbin, or the start end portion of the precursor fiber bundle accommodated in the box, It is necessary to join to the terminal portion of the precursor fiber bundle that is passing through the firing process by some means.

  As a means for joining the end portions of the precursor fiber bundles and continuously supplying the precursor fiber bundles to the carbon fiber manufacturing process to improve operability, the end portions of the carbon fiber precursor fiber bundles There is known a method of joining them by entangling them with a pressurized fluid (see Patent Document 1).

  Although it is possible to join the end portions of the precursor fiber bundle of carbon fiber by this method, the fiber bundle density becomes high in the formed yarn splicing joint, so that the precursor fiber bundle itself in the flameproofing process There is a problem that the oxidation reaction proceeds excessively due to heat generation, and the yarn joining portion is burned out. In order to prevent yarn breakage at the spliced joint due to heat storage, the temperature of the flameproofing furnace process must be lower than the temperature at which the precursor fiber bundle breaks. That is, since it is necessary to reduce the production rate by the amount of the heat treatment temperature in the flameproofing step, it is difficult to improve productivity even if continuous processing is attempted.

  As measures against these, for example, a method of joining a precursor fiber bundle and a non-heat-generating flameproof yarn as a connection medium has been taken (see Patent Document 2). However, even in this method, although there is an effect of reducing the heat storage amount, yarn breakage due to heat storage or the like still tends to occur at the joint where the precursor fiber bundle density becomes high because heat removal is not sufficient. Therefore, when the yarn splicing joint passes through the flameproofing step, the flameproofing temperature must be lowered, and the production rate has to be reduced to compensate for the reduced heat quantity. In addition, the flameproof yarn and the polyacrylonitrile-based precursor fiber bundle are different in the degree of fiber bundle bundling, so that the polyacrylonitrile-based precursor fiber bundle and the flameproof yarn are not easily mixed and are entangled uniformly. It's not enough. Therefore, both fiber bundles are broken by the tension in the process, and the production efficiency cannot be sufficiently improved.

  Other than the tangled joining formed by the pressurized fluid, a method in which the end portions are divided and knitted and joined is also employed (see Patent Document 3). Since the strength varies, there is a problem in that stress concentrates on a connection portion having a low binding strength, and breaks sequentially from a joint portion having a low binding strength.

In addition, an acrylic fiber for producing carbon fiber having a joint portion in which the end of the precursor fiber is made into a flame resistant fiber having a density of 1.30 g / cm ³ or more in advance and the end portions are entangled and integrated is proposed. (See Patent Document 4). In this case, although there is a tendency to improve the yarn breakage due to heat accumulation at the joint, a dedicated facility is required to make the end of the precursor fiber a flame-resistant fiber. I can not say.

JP-A-6-206667 JP-A-10-226918 JP 2007-46177 A JP 2000-144534 A

  Therefore, in view of the above-described problems, the object of the present invention is to reduce the heat storage of the yarn splicing joint by a simple method, and in the firing step, the yarn splicing joint is not broken due to heat storage, and the process is maintained at a high temperature. An object of the present invention is to provide a thread-bonding joint that can pass, and a continuous carbon fiber manufacturing method that joins fiber bundles using the thread-joining joint.

  The present invention aims to achieve the above object, and the method for producing carbon fiber of the present invention comprises an end portion of a first precursor fiber bundle and an end portion of a second precursor fiber bundle. When producing carbon fibers having 3000 or more filaments by connecting via the third fiber bundle, the third fiber bundle has a thermal conductivity of 3 W / (m · K) or more and 700 W / (m · K) or less, a carbon fiber bundle having 3000 or more filaments, a drape value of 2 cm or more and 15 cm or less, and a flatness of 20 or more.

  The fineness of the third fiber bundle is preferably between 0.2 and 3.0 times the fineness of the first and second precursor fiber bundles.

  Furthermore, the connection part of the 1st precursor fiber bundle and the 3rd fiber bundle, and the connection part of the 2nd precursor fiber bundle and the 3rd fiber bundle align and overlap the fiber bundles to be connected. A yarn splicing joint formed by injecting and entanglement with a pressurized fluid in a state where the third fiber bundle is sandwiched between the first and second precursor fiber bundles. It is preferable that the tensile strength in a normal temperature atmosphere is 20 g / tex or more, and each joint portion is composed of a plurality of intertwined portions. Here, the cross-sectional area of the tensile strength is based on the first or second precursor fiber bundle.

  Furthermore, in the method for producing a carbon fiber according to the present invention, when the end portion of the first precursor fiber bundle and the end portion of the second precursor fiber bundle are connected via the third fiber bundle, A plurality of fluid jets in series in the width direction of the fiber bundle at the overlapping portion of the first precursor fiber and the third fiber bundle and the overlapping portion of the third fiber bundle and the second precursor fiber The first fiber bundle is formed by injecting pressurized fluid by at least one pair of entanglement processing means in which a row of holes is opened and the fluid injection hole rows are arranged in two or more rows at intervals in the fiber bundle direction. And the third fiber bundle, and the second fiber bundle and the single fiber of the third fiber bundle are entangled with each other simultaneously or sequentially, and an entangled portion having a plurality of partial entanglements in the width direction of the fiber bundle is provided. It is characterized by forming a spliced yarn joining portion.

  According to the method for producing carbon fiber of the present invention, during the firing process, since it has a high effect of removing heat generated from the yarn, there is no breakage due to heat storage, and further there is a high entanglement, so that there is a tension. Can be prevented from breaking. This allows the joint to pass through to the final winding process without lowering the temperature in the flameproofing furnace in the firing process, so that carbon fibers can be continuously produced while maintaining high production conditions. And production efficiency can be greatly improved.

An overall schematic side view illustrating the yarn splicing joint of the present invention in which the first precursor fiber bundle and the third fiber bundle, and the third fiber bundle and the second precursor fiber bundle are joined one by one. FIG. The whole which illustrates the other yarn splicing joint part of this invention which joined the 1st precursor fiber bundle and the 3rd fiber bundle, the 3rd fiber bundle, and the 2nd precursor fiber bundle each 3 places It is a schematic side view. It is an example of the thread | yarn splicing junction schematic plan view of this invention. (A)-(c) is a schematic side view which shows the measuring method of the drape value used by this invention. It is the schematic which shows an example of the arrangement | sequence of the injection hole of the yarn splicing apparatus used for this invention.

  First, an embodiment of a carbon fiber manufacturing process according to the present invention will be described. As precursor fibers for producing carbon fibers, polyacrylonitrile fiber bundles, pitch fiber bundles, and cellulosic fiber bundles can be suitably used. However, since high strength is easily expressed, polyacrylonitrile fiber A bundle is preferred. Since the speed of the process for producing the precursor fiber bundle and the speed of the firing process are usually significantly different, the precursor fiber bundle is wound up on a bobbin or folded and stacked in a box, and is then stored in the firing process. It is generally used to be supplied. In the present invention, the number of filaments of the precursor fiber bundle is 3000 or more. If the number is less than 3000, the fiber bundle is thin, making it difficult to create an effective entanglement with the third fiber bundle. Not only is it easy to break due to high tension during the process, but also the high separation in the present invention. Even if the thermal effect is not used, the heat is often sufficiently removed by hot air passing through the flameproofing furnace, and the need to apply the technique described in the present invention is low. The higher the number of filaments, the better because it makes use of the high heat removal effect of the present invention in order to make use of the high temperature flameproofing furnace, but if it is too thick, the entangled part with the precursor fiber bundle becomes too thick. Since there is a possibility that problems such as fiber mixing between adjacent yarns may occur during passing through the process, the number is preferably 100,000 or less.

  Hereinafter, the precursor fiber bundle passing through the firing process is referred to as a first fiber bundle, and then the precursor fiber bundle to be passed through the firing process is referred to as a second fiber bundle, and each fiber bundle is wound up on a bobbin. An example in the case of being supplied in the form will be described. In particular, when there is no need to distinguish the first and second precursor fiber bundles, they are simply referred to as precursor fiber bundles.

  The precursor fiber bundle wound up on the bobbin is drawn out from the bobbin and then subjected to a flameproofing treatment in a flameproofing furnace in the firing step. In this flameproofing treatment, the first fiber bundle is usually heat-treated at a temperature of 200 to 300 ° C. in an oxidizing atmosphere to be converted into flameproofing yarn. The obtained flame resistant yarn is subsequently carbonized in a carbonization furnace to obtain carbon fibers. The carbon fiber is subjected to surface treatment such as surface modification treatment or sizing agent application as necessary, and is taken up in a winding process to obtain a carbon fiber product. When the first precursor fiber bundle wound around the bobbin comes near the end portion, the second precursor fiber bundle wound as the next bobbin at the end portion of the first precursor fiber bundle The start ends of the are joined. That is, the end portions of the precursor fiber bundle are joined together, and the joined second precursor fiber bundle is continuously fired to continuously produce carbon fibers.

  The present invention is a yarn breakage due to heat accumulation in the yarn splicing joint during passage of the above-mentioned flameproofing step, and also breakage of the yarn splicing joint during passage of not only the flameproofing step but also a carbonization step that may become higher tension. More specifically, the first precursor fiber bundle and the second precursor fiber bundle are joined via a third fiber bundle made of carbon fiber bundles. Is the method.

  FIG. 1 is a schematic side view illustrating an example of a yarn splicing joint of the present invention in which a first and second precursor fiber bundles are joined by a pair of entanglement processing means via a third fiber bundle. is there.

  FIG. 2 is a schematic side view illustrating a yarn splicing joint when joined at a plurality of positions. In the example of FIG. 2, the first precursor fiber bundle 1 and the third fiber bundle 3, and the third fiber bundle and the second precursor fiber bundle 2 are each entangled at three locations. Show.

  As shown in FIGS. 1 and 2, the third fiber bundle 3 is sandwiched between the first precursor fiber bundle 1 and the second precursor fiber bundle 2. Carbon fiber having a thermal conductivity of 3 W / (m · K) to 700 W / (m · K), a filament number of 3000 or more, a drape value of 2 cm to 15 cm, and a flatness of 20 or more. A bundle can be used to form the yarn splicing joint of the present invention. In this case, for example, the end portion of the first precursor fiber bundle 1 and the third fiber bundle 3 are overlapped, or the third fiber bundle 3 and the start end portion of the second precursor fiber bundle 2 are overlapped. Are installed in the entanglement processing equipment. At this time, carbon fiber is used for the third fiber bundle. Hereinafter, the third fiber bundle may be simply referred to as a carbon fiber bundle without particular notice.

  At the junction between the precursor fiber bundle and the carbon fiber bundle, the first precursor fiber bundle 1 and the third fiber bundle 3, and the third fiber bundle 3 and the second precursor fiber bundle 2 are entangled with each other. The thread splicing joint A is formed at each of the combined portions. Fig. 1 shows one joint each, and the larger the number of joints, the more stable the tensile strength of the whole joint. However, if a plurality of joints are created at the same time, the facility becomes large. This increases the cost in terms of equipment. Although it can be done by processing the equipment for creating one joint part a plurality of times, the number of workability increases, so two places, or three places or four places as shown in FIG. 2 are preferable. In addition, a third medium serving as a connection medium is formed at the joint portion in which the first precursor fiber bundle and the third precursor fiber bundle, and the third fiber bundle and the second precursor fiber bundle are entangled with each other. The end portion 4 of the fiber bundle, the end portion 5 of the first precursor fiber bundle, and the end portion 6 of the second precursor fiber bundle are preferably cut at about 1 cm to 5 cm from the joint end. The precursor fiber bundle may be shrunk by heat treatment in a flameproofing furnace, and it is preferable that the precursor fiber bundle is cut while leaving about 1 cm in order to prevent untangling of the entangled portion. However, leaving more than 5 cm is not preferable because it may cause troubles such as blending of adjacent yarns.

  The third fiber bundle is a carbon fiber bundle having a thermal conductivity of 3 W / (m · K) to 700 W / (m · K) and a filament number of 3000 or more, and a drape value of 2 cm or more. It is important that the thickness is 15 cm or less, and further, the flatness described later is 20 or more.

  The number of filaments of the third fiber bundle can be appropriately selected according to the number of filaments of the precursor fiber bundle to be entangled, but if it is less than 3000, the process is not sufficiently entangled with the precursor fiber bundle. May break due to medium tension. Increasing the number of filaments can efficiently remove the heat of reaction generated from the precursor fiber in the flameproofing furnace, but if it is too thick, the entangled part with the precursor fiber bundle becomes too thick. Since there is a possibility that problems such as fiber mixing between adjacent yarns may occur during passing through the process, the number is preferably 100,000 or less.

  If the third fiber bundle is a carbon fiber bundle having a thermal conductivity of less than 3 W / (m · K), the heat generated in the spliced joint cannot be sufficiently dissipated when flame resistance is achieved, that is, the heat removal effect is low. It will cause breakage due to heat storage. On the other hand, if it exceeds 700 W / (m · K), the elastic modulus of the fiber bundle is so high that the yarn joining portion is not formed well, and the effect of high heat removal is offset. The thermal conductivity is more preferably 7 W / (m · K) or more and 50 W / (m · K) or less.

The thermal conductivity here is calculated from the following formula (1) from the thermal diffusivity, density, and specific heat of the fiber bundle.

λ = αρCp (1)

λ: Thermal conductivity (W / (m · K))
α: Thermal diffusivity (m ² / s) Calculated according to the optical alternating current method shown in the following literature.

T. Yamane, S. Katayama, M. Todoki and I. Hatta: J. Appl. Phys., 80
(1996) 4385.
ρ: Density (kg / m ³ ) Weight W ₁ (kg) of the object to be measured in air, and weight W ₂ in the liquid when the object to be measured is submerged in a liquid of density ρ _L Based on (kg), it was calculated by the following equation (2).

ρ = W ₁ × ρ _L / (W ₁ −W ₂ ) (2)

Cp: specific heat (J / (kg · K)) A value measured by DSC (differential scanning calorimeter) at 25 ° C. with reference to JIS R1672. The DSC is sufficient if it has a function equivalent to that of DSC-7 manufactured by Perkin-Elmer, and sapphire (α-Al 2 O 3) and an aluminum container can be used as standard materials.

In addition, the average value measured by n = 2 for the thermal diffusivity and specific heat of the fiber bundle and n = 6, respectively, is used.

  Further, if the drape value of the third fiber bundle exceeds 15 cm, the yarn bundle becomes too hard, and therefore the yarn bundle is difficult to be broken during fluid entanglement processing such as air, and the first precursor fiber bundle and the second precursor fiber bundle The entanglement with is not evenly applied. For this reason, the preferable range of the drape value is 10 cm or less, and the more preferable range is 8 cm or less. The drape value represents the hardness of the yarn bundle, and it can be said that the smaller the value is, the softer the shape is and the less the shape retention is. The lower limit of this drape value is 2 cm. That is, it is easy to bend and the more soft the yarn bundle, the more likely it is to be entangled, but if it is less than 2 cm, it is too soft and difficult to handle. Further, since the yarn bundle is easily separated, each single yarn effective for heat removal is easily cut at the time of joining with the precursor fiber, and the tensile strength for withstanding the process tension is also reduced. There are various means for controlling the drape value, but typically, it can be suitably controlled by the sizing adhesion amount applied to the third fiber bundle, and if the sizing adhesion amount is increased, the drape value becomes higher, Since it becomes low if it lowers, it can be adjusted to a desired value.

  The drape value here will be described with reference to FIG. 4A to 4C are schematic side views showing a method for measuring the drape value used in the present invention. As shown in FIG. 4 (a), a fiber bundle cut to about 50 cm is hung with a tension of 0.0375 g / tex in an atmosphere of a temperature of 23 ° C. and a humidity of 60%, and left for 30 minutes or more. It is cut into a length of 30 cm, and as shown in FIG. 4B, one end thereof is fixed to the upper surface of the rectangular column 7 so as to be parallel to the floor surface so as not to hang down in a cantilevered state. At this time, the fiber bundle is shown in FIG. 2B so that the fiber bundle is perpendicular to the side surface of the square column 7 and the length from the side surface of the square column 7 to the tip of the fiber bundle is 25 cm. As shown in FIG. Thereafter, as shown in FIG. 4C, only the flat plate 8 is quickly removed, and the closest distance X (cm) formed by the tip of the fiber bundle hanging down due to gravity and the side surface of the square column 7 is measured. At this time, the distance X (cm) one second after the flat plate 8 is removed and the fiber bundle starts to sag is defined as the drape value.

  Further, in order to make the fluid entanglement process more uniform with respect to the overlapping portion of the first precursor fiber and the third fiber bundle and the overlapping portion of the second precursor fiber and the third fiber bundle. It is important that the third carbon fiber bundle has a flatness of 20 or more. When the flatness is less than 20, since the yarn bundle is thin, the method of making a tangling process during fluid entanglement tends to be non-uniform, leading to a decrease in the tensile strength of the yarn splicing joint and a decrease in the yarn breakage temperature. In addition, the upper limit of the flatness is about 200, and if it exceeds 200, the yarn bundle becomes too wide, so that the entanglement between the first precursor fiber bundle and the second precursor fiber bundle is likely to occur, This leads to a decrease in the tensile strength of the joint.

  The flatness referred to here can be obtained by W / T from the width W of the carbon fiber bundle and the thickness T of the carbon fiber bundle shown below. Here, the width W of the carbon fiber bundle is a value measured in a state where the third carbon fiber bundle is allowed to stand, and is a value obtained by directly measuring the width of the carbon fiber bundle with a ruler.

Further, the thickness T (mm) of the connecting fiber bundle is such that the single yarn fineness Y (g / m), the density ρ (kg / m ³ ) of each filament in the multiple filaments forming the connecting fiber bundle, the connecting fiber Based on the number F of filaments forming the bundle and the width W (mm) of the connecting fiber bundle, the value is calculated from the following expressions (3) and (4).

D (mm) = √ (4 × Y × 10 ³ / (π × ρ)) (3)

T (mm) = F × D ² / W (4)

The fineness of the third fiber bundle is preferably between 0.2 and 3.0 times the fineness of the first precursor fiber bundle and the second precursor fiber bundle. If it is less than 0.2 times, an entanglement defect portion that does not entangle with the third fiber bundle tends to occur in the first precursor fiber bundle and the second precursor fiber bundle portion, which is not preferable. On the other hand, if it exceeds 3.0 times, it is not preferable because the confounding defect is likely to occur in the third fiber bundle. The fineness of the third fiber bundle is more preferably 0.3 to 1.2 times, and 0.4 to 0.8 times the fineness of the first precursor fiber bundle and the second precursor fiber bundle. Further preferred. Even when the fineness of both the first and second precursor fiber bundles is the same, it can be continuously produced with good productivity by keeping the above range.

  In this invention, it can be set as carbon fiber by baking the precursor fiber bundle of the carbon fiber which has the yarn splicing junction obtained by the manufacturing method of said precursor fiber bundle.

  Moreover, it is preferable that the tensile strength in the normal temperature atmosphere of the junction part between a precursor fiber bundle and a carbon fiber bundle is 20 g / tex or more. The normal temperature here refers to the working atmosphere for bonding the precursor fiber bundle and the carbon fiber bundle, that is, the outside air temperature, specifically 20 ° C. to 30 ° C., and bonded at all temperatures in this temperature range. The tensile strength of the part is preferably 20 g / tex or more. In the present invention, it is more preferable if the tensile strength of the joint is 20 g / tex or more at all temperatures in the temperature range of about 5 ° C. to 50 ° C. If the temperature is less than 20 g / tex at any temperature in such a temperature range, the joint may not be able to withstand the tension in each process such as flame resistance, which may cause a trouble that breaks. A higher tensile strength at the joint is preferable from the viewpoint of processability. However, in order to increase the entanglement in order to increase the tensile strength, on the contrary, each of the precursor fiber bundle and further the carbon fiber bundles. Since the yarn breaks, it may not be fully raised. It is often sufficient to have about 50 g / tex.

  The tensile strength here is defined as a value obtained by measurement as follows. Maximum when tensile strength between both ends where a precursor fiber bundle and a carbon fiber bundle are joined is measured at a tensile speed of 100 mm / min using a tensile tester having a capability of approximately ORIENTEC (model: RTC-1225A) The value is divided by the fineness (tex) of the fiber bundle on the broken side of the first or second precursor fiber bundle to obtain the tensile strength. When the precursor fiber bundles having the same thickness and the same number of filaments are connected by the third fiber bundle, the first and second precursor fiber bundles have the same value and satisfy the range described in the claims of the present application. There is a need. When precursor fiber bundles having different numbers of filaments of the first and second fiber bundles, that is, different thicknesses are connected by a specific third fiber bundle, the first precursor fiber bundle and the third fiber bundle It is necessary that both the fiber bundle and the joint between the third fiber bundle and the second precursor fiber bundle are within the range defined in the claims.

  The third fiber bundle used in the present invention is a carbon fiber bundle having a thermal conductivity of 3 W / (m · K) or more and 700 W / (m · K) or less, a filament number of 3000 or more, and a drape value. Is 2 cm to 15 cm and the flatness is 20 or more, the excellent effect of the present invention is exhibited. Carbon fibers having a thermal conductivity of 3 W / (m · K) or more and 700 W / (m · K) or less and having a filament number of 3000 or more are carbonized or graphitized depending on the number of single fibers of the precursor fiber and firing conditions. It can be obtained by adjusting the degree of. Next, an example of a preferable production method in which the drape value is 2 cm or more and 15 cm or less and the flatness is 20 or more is shown below. As a precursor fiber, a polyacrylonitrile fiber bundle spun using polyacrylonitrile as a raw material is once wound up on a bobbin or the like, the polyacrylonitrile fiber bundle is drawn out from the bobbin, and subjected to a flame resistance treatment at 230 to 280 ° C. in air. Next, carbonization is performed in a carbonization furnace controlled to a maximum temperature of 1900 ° C. or less to obtain a carbon fiber bundle. If necessary, the obtained carbon fiber bundle can be heated to a maximum temperature of 1900 to 2600 ° C. to obtain a graphitized fiber bundle. The carbon fiber bundle or graphitized fiber bundle thus obtained is applied with a sizing agent under a tension of 1.5 to 6.0 g / tex, preferably 2.0 to 5.5 g / tex. A carbon fiber bundle having a drape value of 2 cm or more and 15 cm or less and a flatness of 20 or more can be obtained by pressing it onto a hot roll controlled to about 150 ° C. to 150 ° C. and drying it while flattening it. Note that the sizing agent to be applied can be used without any particular limitation, and in order to adjust the drape value to the above range, the adhesion amount, the adhesion method, and the drying temperature may be appropriately selected.

  In the present invention, through the use of the carbon fiber bundle having the above-mentioned characteristics as a connection medium, the heat generated in the flame-proofing furnace is efficiently removed, and the excellent effect of greatly improving productivity is achieved. In order to further enhance the excellent effect, it is preferable to use the following method for joining the precursor fiber bundle and the carbon fiber bundle. For connecting the precursor fiber bundles used in the present invention, a plurality of rows of fluid ejection holes are opened in series in the width direction of the fiber bundle, and the rows of the fluid ejection holes are spaced apart in the fiber bundle direction by two or more rows. It is preferable that pressurized fluid is ejected by at least one pair of entanglement processing means arranged in the above to create the joint, and the joint has a plurality of entangled portions in the bundle direction. An example of a preferable arrangement of the injection holes is shown in FIG. FIG. 5 shows the case of two rows as the injection holes. When the row of the fluid ejection holes is singular in series, the entangled portion is unlikely to be plural, and the portion easily loses heat storage. In the case of singular, this is the case where there is only one row of holes shown in FIG. The number of holes is not particularly determined, but can be adjusted according to the fineness of the precursor fiber bundle each time. Further, it is not preferable that the number of the fluid ejection holes is one because the heat dissipating part indicated by X in FIG. 3 is sufficiently difficult to be taken, and the joining part accumulates heat and easily breaks the yarn. However, as the number of holes increases, the amount of pressurized fluid used increases, and a special device may be required, and two lines are often sufficient.

  The form of the connecting portion obtained by injecting the pressurized fluid will be described with reference to FIG.

  FIG. 3 is an example of a schematic plan view of the yarn splicing joint portion of the present invention. In the yarn splicing joint portion A of the present invention, a yarn formed by overlapping both end portions of the precursor fiber bundle and the carbon fiber bundle. In the connecting and entangled portion A, both fiber bundles are opened, and the heat dissipating part B that can release heat to the outside and the heat dissipating part B are present at both ends of the heat dissipating part B. An entangled portion C having a plurality of partial entanglements D in the width direction is provided. That is, by using one set of pressurized fluid ejecting means, a configuration having one heat radiating part B and two entangled parts is obtained. Here, if the precursor fiber bundle and the carbon fiber bundle have a heat dissipation part B, the reaction heat generated from the precursor fiber bundle will come into contact with the carbon fiber bundle and the single yarn, and excellent heat removal by the carbon fiber. Not only can the effect be utilized, but also the hot air that is blown in easily passes for the purpose of removing heat from the precursor fiber bundle in the normal flameproofing process, including the reaction heat generated from the precursor fiber bundle present in the entangled part Therefore, it is considered possible to remove heat efficiently. Here, the number of entangled bundles refers to the total number of bundles per row of the partial entangled D. For example, the number of entangled bundles in FIG. The number of entangled bundles is preferably 2 or more, more preferably 3 or more. Usually, the upper limit of the number of entangled bundles is about 10 bundles from the performance of the air entanglement processing equipment and the total number of filaments in the fiber bundle. When the number of entangled bundles is one, the density of the fiber bundle becomes high, so that the oxidation reaction occurs rapidly due to the heat generation of the precursor fiber bundle itself in the flameproofing process, and the yarn splicing joint tends to burn out, which is not preferable. In other words, the yarn entanglement portion increases the number of entanglement bundles and reduces the number of filaments per bundle, thereby reducing the heat generation of the precursor fiber bundle itself without impairing the tensile strength of the yarn connection portion. Can be further efficiently removed. In this invention, it can be set as carbon fiber by baking the precursor fiber bundle of the carbon fiber which has the yarn splicing junction obtained by the manufacturing method of said precursor fiber bundle.

  Hereinafter, the effects of the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

  In the examples of the present invention, the yarn splicing joint was run using the firing manufacturing process described above as one embodiment of the carbon fiber manufacturing process.

  The conditions of the flameproofing furnace are such that the wind speed in the furnace is 1.0 m / sec in the vertical direction with respect to the traveling direction of the precursor fiber bundle, and the tension applied to the traveling yarn in the process is 1.5 g / tex. It adjusted so that it might become. And the upper limit temperature which can pass the junction part in this flameproofing furnace was measured. In addition, the passing state of the carbonization process is basically a temperature that is lowered by 10 ° C. from the temperature that can pass through the flame-proofing furnace having no joint in consideration of temperature spots in the flame-proofing furnace and errors in the measuring instrument. It was set and subjected to flameproofing treatment, and further the passing situation in the subsequent carbonization process was measured.

  Further, in the examples of the present invention, the precursor fiber bundle is a polyacrylonitrile-based precursor fiber bundle having a single fiber fineness of 1.1 dtex and a polyacrylonitrile-based precursor fiber bundle having 24,000 filaments having substantially no twist. The results are summarized in Table 1 for each comparative example.

Example 1
Carbon fiber bundles, which are third fiber bundles having 48,000 filaments, 24000 filaments, and 12,000 filaments, were superposed on the end portions of the first and second precursor fiber bundles, respectively, to prepare three types of bonded samples. At this time, using the entanglement processing means arranged in two rows, the first or second precursor and the carbon fiber bundle as the third fiber bundle were combined, and a relaxation amount of 9.0% was given. Thereafter, 0.4 MPa of compressed air was injected for 2 seconds. As a result, three connecting portions A having the form shown in FIG. 3 were formed as shown in FIG.

  As a result, as shown in Table 1, the temperature at which each sample can pass through the flameproofing furnace is reduced by 0 to 1 ° C. as compared with the reference example of the continuous raw yarn having no connection part, and the joint part is flameproofing furnace. The temperature drop that can pass through was small. In addition, each connection part from (a) to (c) was moved to each process after the flameproofing furnace, but not only the flameproofing process but also the carbonization process, and finally the heat storage until it was wound up on the bobbin with a winder. No yarn breakage due to tension during the process was observed, and it was possible to connect the yarns without changing the production conditions, which greatly improved production efficiency.

(Examples 2 and 3)
In Example 2, the carbon fiber for tying was changed to that shown in Table 1, and Example 3 was carried out in the same manner as Example 1 except that the number of joints was 1. As a result, the temperature at which the flameproofing furnace can pass was lowered by 3 to 4 ° C. compared to the reference example, and some yarn breakage due to the tension was observed even in the carbonization process, but it was at a level that could sufficiently handle production. .

(Examples 4 and 5)
This was carried out in the same manner as in Example 1 except that the carbon fiber for yarn joining was shown in the table and the fineness ratio was set to 3.09 (Example 4) and 0.15 (Example 5). As a result, the temperature at which the flame-proofing furnace can pass was lowered by 5 ° C. compared to the reference example, and yarn breakage was observed even in the carbonization process, but it was at a level that could support production.

(Example 6)
The same procedure as in Example 1 was carried out except that the entanglement treatment means used was one in which fluid ejection holes were arranged in one row. When the first fiber bundle and the third fiber bundle, and further the respective joint portions (corresponding to the joint portion A in FIG. 3) of the third fiber bundle and the second fiber bundle are visually observed, the respective fiber bundles are observed. Although uniform entanglement between the constituent single yarns was observed, the partial entanglement D shown in FIG. 3 was not observed clearly, but was roughly divided into two at the center. The temperature at which the obtained flame-proofing furnace of the joint portion can pass was reduced by 7 ° C. compared to the reference example, and the carbonization process passage rate was also reduced to a level capable of production.

(Comparative Example 1)
The end portions of the precursor fiber bundle having 24,000 filaments that are the first and second fiber bundles are the same as those in Example 1 without using the carbon fiber bundle for yarn joining that is the third fiber bundle. Joined under yarn splicing conditions. As a result, the form of the joint part, tensile strength, number of joints, and number of partial entanglements were almost the same as in Example 1, but the joint part is a bundle of precursor fibers, so in the flameproofing furnace As a result of the heat removal and heat-damaging of the joints in the flame-proofing furnace, the upper limit temperature at which flame-proofing can be passed is 250 ° C., which is significantly lower than the blank and examples. . The joint passed through the flameproofing furnace without any yarn breakage, but in the carbonization furnace, yarn breakage was seen at the joint, and it was necessary to pass the furnace again, which caused a heavy work load.

(Comparative Example 2)
Measurement was performed by joining under the same yarn joining conditions as in Example 1 except that the drape value of the third fiber bundle for yarn joining was 20 cm. As a result, since the third fiber bundle is too hard to expand, sufficient entanglement with the first or second fiber bundle cannot be obtained, so that the tensile strength of the joint portion is low, and the precursor fiber generates heat. It became impossible to remove heat efficiently. Since the drape value of the third fiber bundle is as high as 20 cm, that is, the fiber bundle is hard, the precursor fiber bundle and the spliced fiber bundle are not uniformly joined, so the tensile strength is also low, and the joined portion is susceptible to heat storage and damage. The upper limit temperature at which flameproofing can be performed was 247 ° C., which was significantly lower. As a result, the temperature that can pass through the flameproofing process is lower than that of Comparative Example 1 that does not use the third fiber bundle as well as Example 1, and is lower than the temperature of hot air blown into the flameproofing furnace. . At the same temperature, yarn breakage occurs even in a flameproofing furnace, so the set temperature has to be lowered. As a result, in order to compensate for the insufficient heat treatment amount, the entire furnace was slowed down, that is, productivity was unavoidable. For the cases where the upper limit temperature that can pass through the flameproofing furnace is lower than 250 ° C., including the subsequent comparative examples, from the upper limit temperature that can pass through the flameproofing furnace in each example in order to pass through the flameproofing furnace. At a temperature reduced by 10 ° C., the temperature reduction and the speed were reduced and the subsequent steps including the carbonization step were passed. However, in this sample where the tensile strength of the joint is low, there are many states in which the yarn breaks in such a form that the entanglement between the precursor fiber bundle and the carbon fiber bundle is unraveled even when passing in the carbonization process, Further, the productivity was low.

(Comparative Example 3)
Except that the drape value of the third fiber bundle for yarn joining was set to 1 cm, bonding was performed under the same yarn joining conditions as in Examples, and measurement was performed under the same conditions. As a result, the yarn splicing fiber bundle is too profitable, the handling property is remarkably deteriorated, and the time required for the splicing work is greatly increased. The shape of the finished yarn splicing part was generally good although many single fiber breaks of the carbon fiber bundle were observed, and the upper limit temperature at which the flame resistance could pass was 252 ° C., and the degree of reduction was small. Although yarn breakage was not observed when heat treatment was performed at the same blowing temperature into the flameproofing furnace as in Example 1, the tensile strength was greatly reduced due to the single yarn breakage, so the yarn was passed through the carbonization process continuously. As a result, strip breakage occurred frequently and the passing rate was low.

(Comparative Example 4)
Except that the flatness of the fiber bundle for yarn joining was set to 14, the joining was performed under the same yarn joining conditions as in Examples, and measurement was performed under the same conditions. As a result, as in Comparative Example 2, it is presumed that the yarn-binding fiber bundle is difficult to spread and the joining between the precursor fiber bundle and the yarn-binding fiber bundle is non-uniform, but the tension applied to the joint in the flameproof atmosphere is high. Although it became non-uniform and the upper limit temperature at which flameproofing could pass was lowered and the blowing temperature and speed of the flameproofing furnace were reduced, the carbonization process passing rate was low due to the low tensile strength.

(Comparative Example 5)
The third fiber bundle was joined under the same conditions as in Example 1 except that continuous fibers (flame-resistant yarn) that passed through the flame-proofing step were used. The thermal conductivity of the flame resistant yarn was 1 W / (m · K). As a result, since the thermal conductivity is too low, the heat dissipation of the joint in the flameproof atmosphere is insufficient, so yarn breakage due to heat storage is likely to occur, and the convergence speed of the precursor fiber speed and the flameproof fiber bundle is reduced. Although it was estimated that the difference was inconsistent, the temperature of the entangled portion was confirmed to be low, the temperature at which the flameproofing could pass was as low as 245 ° C., and the carbonization process passing rate was low.

(Comparative Example 6)
The third fiber bundle was joined under the same yarn splicing conditions as in the examples except that the carbon fiber temperature was increased and the thermal conductivity was 800 W / (m · K), and measurement was performed under the same conditions. . As a result, since the yarn was hard and brittle, the single fluid of the third fiber bundle was frequently cut by the jetted fluid, and it was not possible to create a joint that allowed the process to pass.

    (Comparative Example 7) First and second precursor fiber bundles having a filament number of 1000 filaments and a single fiber fineness of 1.1 dtex and a substantially 3,000 untwisted filament number of 3,000 Except for joining, joining was performed under the same yarn joining conditions as in the Examples, and measurement was performed under the same conditions. As a result, since the fiber bundle for yarn joining is too thin, it hardly joins with the first and second precursor fiber bundles, so the tensile strength is extremely low, and the tensile strength and the upper limit that can be passed in the flameproofing process. Temperature etc. could not be measured.

(Comparative Example 8)
A polyacrylonitrile-based precursor fiber bundle having a number of filaments of 3000 and a single fiber fineness of 1.1 dtex, a polyacrylonitrile-based precursor fiber bundle of 1,000 filaments having substantially no twist; Except for joining the second precursor fiber bundle, joining was performed under the same yarn joining conditions as in Examples, and measurement was performed under the same conditions. As a result, since the precursor fiber bundle is too thin, the yarn-binding fiber bundle is hardly joined to the first and second precursor fiber bundles, so the tensile strength is remarkably low. Was not measurable.

  From the above examples and comparative examples, the method for connecting precursor fiber bundles according to the present invention is extremely effective for industrially producing continuous carbon fibers with high productivity, particularly for the flameproofing treatment. It turns out that it is.

A: Yarn splicing joint B: Heat dissipating part C: Entangling part D: Partial intertwining X: Length in the fiber bundle direction of the heat dissipating part Y: Length in the fiber bundle direction of the partial intertwining 1: First fiber bundle 2: Second fiber bundle 3: Third fiber bundle (connection medium for yarn connection)
4: Third fiber bundle end 5: End of first precursor fiber bundle 6: End of second precursor fiber bundle

Claims (4)

When manufacturing the carbon fiber having the number of filaments of 3000 or more by connecting the end portion of the first precursor fiber bundle and the end portion of the second precursor fiber bundle via the third fiber bundle, The third fiber bundle has a thermal conductivity of 3 W / (m · K) to 700 W / (m · K), a number of filaments of 3000 or more, a drape value of 2 cm to 15 cm, and a flatness. Is a carbon fiber bundle of 20 or more. The fineness of the third fiber bundle is between 0.2 and 3.0 times the fineness of the first and second precursor fiber bundles. A method for producing carbon fiber. The connection part of the 1st precursor fiber bundle and the 3rd fiber bundle, and the connection part of the 2nd precursor fiber bundle and the 3rd fiber bundle are the state where the fiber bundles to be connected are aligned and overlapped Room temperature atmosphere of the yarn splicing joint formed by injecting a pressurized fluid and entanglement with the third fiber bundle sandwiched between the first and second precursor fiber bundles The manufacturing method of the carbon fiber in any one of 1-2 characterized by the tensile strength in being 20 g / tex or more. When the end portion of the first precursor fiber bundle and the end portion of the second precursor fiber bundle are connected via the third fiber bundle, the first precursor fiber and the third fiber bundle are connected. A plurality of fluid ejection holes in series in the width direction of the fiber bundle, and the overlapping part of the third fiber bundle and the second precursor fiber. The first fluid bundle, the third fiber bundle, and the third fluid bundle are ejected by at least one set of entanglement processing means in which the rows are spaced in the fiber bundle direction and arranged in two or more rows. The single fiber of the fiber bundle and the second fiber bundle are entangled with each other to form a yarn splicing joint having a joint having a plurality of partial entanglements in the width direction of the fiber bundle. 4. The method for producing a carbon fiber according to any one of 3 above.

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