JP2012162835A - Method for producing carbon fiber-containing nonwoven fabric - Google Patents

Abstract

A carbon fiber-containing non-woven fabric and a carbon fiber non-woven fabric that are excellent in form retention with almost no falling off or falling off of carbon fibers.
SOLUTION: Fineness of 0.05 to 0 comprising an acrylonitrile-based polymer containing 40 to 95% by mass of carbon short fibers (A) having a fine diameter of 3 to 8 μm and a cut length of 2 to 6 mm and 50% by mass or more of acrylonitrile. .3 dtex, 5 to 60% by mass of ultrafine acrylonitrile fiber (B) having a cut length of ² to 6 mm, and a method for producing a nonwoven fabric having a basis weight of 20 to 200 g / m ² and a fabric thickness of 0.1 to 2.0 mm. The step of forming the papermaking web from the papermaking slurry containing the short carbon fiber (A) and the ultrafine acrylonitrile fiber (B) is repeated, and the multilayered papermaking web is produced. A step of confounding and integrating the multi-layered paper web by water jet punching on the paper web;
[Selection figure] None

Description

  The present invention relates to a carbon fiber-containing nonwoven fabric that can be used for an antistatic material, a gas diffuser of a fuel cell, and the like.

  Since carbon fibers have higher strength and higher elasticity than other fibers and have properties that are hard and difficult to bend, it is difficult to entangle carbon fibers, and it is difficult to obtain a nonwoven fabric that can maintain its shape with carbon fibers alone. For this reason, an attempt has been made to produce a nonwoven fabric containing carbon fibers by dispersing such carbon fibers that are easily bent and having entanglement performance, and performing entanglement treatment. However, it is difficult to obtain a carbon fiber-containing nonwoven fabric that is sufficiently entangled and that can maintain a good sheet form as a nonwoven fabric, and it is necessary to use a binder fiber, a resin, or the like that binds the fibers together.

  For example, Patent Document 1 proposes a method for producing a nonwoven fabric composed of carbon fibers, which comprises forming a nonwoven fabric composed of carbon fiber and binder fiber staples, and then burning the nonwoven fabric to remove the binder fibers. Yes.

  In Patent Document 2, a slurry containing at least polyacrylonitrile-based carbon short fibers is prepared so that the content of the carbon short fibers in the nonwoven fabric is 70% by mass or more, and the slurry is made by a continuous paper making method. There is provided a method for producing a carbon fiber nonwoven fabric, in which a columnar high-pressure water stream is applied to a web obtained in such a manner that the carbon short fibers are entangled. In Patent Document 2, PVA (polyvinyl alcohol) short fibers are mixed as a binder, and a solid binding point is formed by a drying process to maintain the sheet form. Therefore, the strength of the web in a wet state is not necessarily good, and the processability and handling properties in the dehydration process and the drying process after the web formation are relatively low. In addition, when carbon short fibers are entangled with a high-pressure water stream, there are problems such as rough sheet surfaces and fibers falling off from the rough portions.

JP 10-314519 A JP 2002-266217 A

  This invention makes it a subject to provide the manufacturing method of the carbon fiber containing nonwoven fabric which has almost no drop-off | omission of a carbon fiber and omission, and is excellent in form retainability.

This invention provides the manufacturing method of a carbon fiber containing nonwoven fabric including the following processes.
(1) A step of preparing a papermaking slurry containing 40 to 90% by mass of carbon short fibers (A) and 5 to 60% by mass of ultrafine acrylonitrile-based short fibers (B).
(2) A step of forming a papermaking web from the slurry.
(3) The process of repeating the said process and preparing the multilayered papermaking web.
(4) A step of subjecting the multilayered papermaking web to water jet punching to entangle the multilayered papermaking web.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to manufacture the carbon fiber containing nonwoven fabric excellent in the form retainability which does not drop | omit or drop | omit carbon fiber.

It is a figure which shows the confounding pattern which consists of a water jet locus | trajectory formed with a high pressure liquid injection nozzle (1). It is a figure which shows the confounding pattern which consists of a water jet locus | trajectory formed with a high pressure liquid injection nozzle (2). It is a figure which shows the confounding pattern which consists of a water jet locus | trajectory formed by using two high pressure liquid injection nozzles (1). It is a figure which shows the confounding pattern which consists of a water jet locus | trajectory formed by using two high pressure liquid injection nozzles (1) and a high pressure liquid injection nozzle (2). It is a photograph which shows the surface of the carbon fiber containing nonwoven fabric in which the confounding locus | trajectory pattern by a water jet exists.

  The present invention relates to a method for producing a carbon fiber-containing nonwoven fabric containing 40 to 90% by mass of carbon short fibers (A) and 5 to 60% by mass of ultrafine acrylonitrile-based short fibers (B).

  In the present specification, a sheet of raw material fibers including a sheet-forming web in a single stage, a multilayered stage, a wet stage, and a dried stage is referred to as a sheet.

[Short carbon fiber (A)]
The carbon fiber-containing non-woven fabric contains carbon short fibers. Here, the short carbon fiber (A) refers to a carbon fiber having a fiber diameter of 3 to 9 μm and an average fiber length of 2 to 6 mm. The carbon short fibers are contained in the carbon fiber-containing nonwoven fabric in an amount of 40 to 90% by mass.

As the carbon short fiber (A), a carbon fiber such as polyacrylonitrile-based carbon fiber (hereinafter referred to as “PAN-based carbon fiber”), pitch-based carbon fiber, rayon-based carbon fiber or the like may be cut to an appropriate length. Can be mentioned. From the viewpoint of the mechanical strength of the sheet, PAN-based carbon fibers are preferable. Specific examples include carbon short fibers obtained by cutting Mitsubishi Rayon Co., Ltd., trade name: Pyrofil TR50S, Toray Industries, Inc., trade name: Trading Card T-300, and the like into appropriate lengths.
The fiber diameter of the short carbon fiber (A) is preferably 3 to 9 μm from the viewpoint of the production cost and dispersibility of the short carbon fiber, and more preferably 4 to 8 μm from the smoothness of the sheet. .

  Moreover, it is preferable that the average fiber length of a carbon short fiber (A) is about 2-6 mm from the point of a dispersibility.

  When the average fiber length of the short carbon fibers (A) is 2 mm or more, the carbon fibers are less dropped from the formed sheet, and a sheet having excellent shape retention can be formed. When the average fiber length is 6 mm or less, the carbon fiber has good separability and is easily disaggregated, and defects such as fiber entanglement are unlikely to occur.

  Moreover, 40 to 90 mass% of carbon short fibers (A) are contained in the carbon fiber-containing nonwoven fabric. When the content of the short carbon fiber (A) in the carbon fiber-containing nonwoven fabric is 40% by mass or more, it becomes possible to impart carbon fiber conductivity, thermal conductivity, heat resistance, and corrosion resistance to the nonwoven fabric. When the content of the short carbon fiber (A) is 90% by mass or less, the produced carbon fiber-containing non-woven fabric is not too rigid and is easy to handle.

  Here, the short carbon fiber (A) mentioned above is not entangled in fiber enough to maintain the sheet form. In addition, a wet papermaking sheet formed only of short carbon fibers (A) does not have sheet strength and is difficult to peel off from the papermaking net. Even if it is peeled off, the obtained carbon fiber-containing non-woven fabric does not exhibit sheet strength that can pass through post-processing steps such as dehydration, drying, resin impregnation, and molding.

  Therefore, in the present invention, in addition to the short carbon fiber (A), the ultrafine acrylonitrile fiber (B) that has a strong entanglement property between the fibers when formed into a sheet and can impart sheet shape retention performance is dispersed in the papermaking slurry. In addition, by entanglement by water jet punching, the shape retention is excellent even in wet undried sheets, and the formation of a sheet that easily passes through the post-dehydration, drying, molding, and winding processes is also possible. Make it possible.

[Ultrafine acrylonitrile fiber (B)]
The ultrafine acrylonitrile fiber (B) is made of an acrylonitrile polymer containing 50% by mass or more of acrylonitrile. The ultrafine acrylonitrile fiber (B) may be a polymer of acrylonitrile alone, but may be a copolymer of acrylonitrile and another monomer. The monomer copolymerizable with acrylonitrile is not particularly limited as long as it is an unsaturated monomer constituting a normal acrylic fiber. For example, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, acrylic acid 2 -Acrylic esters represented by ethylhexyl, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, etc., methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-methacrylic acid t- Methacrylates such as butyl, n-hexyl methacrylate, cyclohexyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, diethylaminoethyl methacrylate, etc. Acid esters, acrylic acid, methacrylic acid, maleic acid, itaconic acid, acrylamide, N-methylol acrylamide, diacetone acrylamide, styrene, vinyl toluene, vinyl acetate, vinyl chloride, vinylidene chloride, vinylidene bromide, vinyl fluoride, fluorine And vinylidene chloride. Furthermore, p-sulfophenyl methallyl ether, methallyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid and alkali metal salts thereof are copolymerized for the purpose of improving dyeability. You may do it.

  The ultrafine acrylonitrile fiber (B) can be produced using wet spinning. For example, the polymer used as a raw material for the fiber (B) is dissolved in a solvent to form a spinning stock solution, and discharged from a pore nozzle into a coagulation bath containing a non-solvent for the polymer constituting the fiber (B). The fiber (B) can be produced by wet-heat stretching, washing, dry-baking, and dry-heat stretching. As the solvent to be used, an organic solvent such as dimethylamide, dimethylformamide, dimethyl sulfoxide or the like can be used. As the coagulant, for example, water, methanol, ethanol or the like can be used. The coagulation bath can be a solvent / non-solvent mixture.

  The molecular weight of the acrylonitrile-based polymer is not particularly limited, but a weight average molecular weight of 50,000 to 1,000,000 is desirable. When the weight average molecular weight is 50,000 or more, the spinnability tends to be excellent as well as the spinnability. When the weight average molecular weight is 1,000,000 or less, it can be easily prevented that the polymer concentration that gives the optimum viscosity of the spinning dope is lowered, and the productivity can be easily prevented from decreasing.

  The ultrafine acrylonitrile fiber (B) has a fineness of 0.05 to 0.3 dtex. If the fineness is 0.05 dtex or more, those having yarn quality and cut length capable of expressing sheet strength are industrially mass-produced and are easily available. If the fineness is 0.3 dtex or less, the fiber diameter is moderate and easy to bend, so that the fiber entanglement becomes strong, and a sheet having high form retention and good handling properties can be obtained.

  The ultrafine acrylonitrile fiber (B) has a fiber length of 2 to 6 mm. When the fiber length is 2 mm or more, the fibers can be prevented from falling off from the nonwoven fabric when formed into a sheet. When the cut length is 6 mm or less, the carbon fiber has good separability and is easily disaggregated, and defects such as fiber entanglement are unlikely to occur.

  The ultrafine acrylonitrile fiber (B) is preferably an ultrafine acrylonitrile fiber having a uniform fiber diameter and fiber length obtained by direct spinning. The ultrafine acrylonitrile fiber (B) is contained in the carbon fiber-containing nonwoven fabric in an amount of 5 to 60% by mass.

If the content of the ultrafine acrylonitrile fiber (B) in the carbon fiber-containing nonwoven fabric is 5% by mass or more, the entanglement between the fibers of the papermaking sheet is good, and paper strength that can be handled is generated. If it is 60 mass% or less, it becomes possible to provide the nonwoven fabric with the conductivity, thermal conductivity, heat resistance, and corrosion resistance of carbon fibers.
[Easily split acrylonitrile polymer blend fiber (C)]
From the viewpoint of strengthening the entanglement and enhancing the paper strength of the carbon fiber-containing non-woven fabric, the carbon fiber-containing non-woven fabric contains 5% easily splittable acrylonitrile-based polymer blend fiber (C) blended with an acrylonitrile-based polymer and a different polymer. It is preferable to contain 40 mass%. Further, the fiber (C) may be partially broken or split fiber (C ^* ). The fineness of the fiber (C) is preferably 1.0 to 5.0 dtex. The fiber (C) contains 50 to 70% by mass of an acrylonitrile-based polymer and 50 to 30% by mass of the different polymer, and the acrylonitrile-based polymer contains 50% by mass or more of acrylonitrile.

The fiber (C) can be beaten or split by peeling of the phase separation interface due to mechanical external force, and a part of the fiber (C) can be changed into a fiber (C ^* ) form. The fiber (C ^* ) is preferably a fibril fiber having a freeness of 100 to 700 ml according to JIS P8121. The fibril fiber having a freeness of 100 ml or more is easy to handle, and if it is less than 700 ml, it is easy to obtain a state in which a part thereof is beaten or split.

  The fiber (C) can be produced by using a wet spinning method (see, for example, JP-A-2007-182641). The acrylonitrile-based polymer constituting the fiber (C) and the heterogeneous polymer are dissolved in a solvent for dissolving them to form a spinning dope, and the coagulation containing a non-solvent for these polymers constituting the fiber (C) from the pore nozzle. The fiber (C) can be obtained by discharging the spinning solution into a bath and coagulating, taking, wet-heat drawing, washing, dry-baking and dry-heat drawing.

  As the solvent to be used, an organic solvent such as dimethylamide, dimethylformamide, dimethyl sulfoxide or the like can be used. As the coagulant, for example, water, methanol, ethanol or the like can be used. The coagulation bath can be a solvent / non-solvent mixture.

  The molecular weight of the acrylonitrile polymer used for the fiber (C) is preferably 50,000 to 1,000,000. If the mass average molecular weight is 50,000 or more, the spinnability tends to be excellent and the fiber quality is also excellent. When the mass average molecular weight is 1,000,000 or less, it is possible to easily prevent the polymer concentration that gives the optimum viscosity of the spinning dope from being lowered, and to easily prevent the productivity from being lowered.

  Examples of the heterogeneous polymer include polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polyvinyl pyrrolidone, cellulose acetate, and (meth) acrylic resin. Among these, (meth) acrylic resin is a preferable different polymer component. The (meth) acrylic resin is a copolymer having an acidic group such as carboxylic acid or sulfonic acid. For example, (meth) acrylic acid, monobasic such as crotonic acid, fumaric acid, maleic acid, itaconic acid, isophthalic acid Dibasic acids such as these, partial esters thereof and the like may be copolymerized.

  In addition to the above monomers, for example, methyl acrylate, ethyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, ethyl methacrylate, methyl methacrylate, n-butyl methacrylate, methacryl Monomers such as i-butyl acid and t-butyl methacrylate may be copolymerized with (meth) acrylic acid. Further, for other purposes such as suppressing the water solubility of the polymer, an aromatic vinyl compound such as styrene, α-methylstyrene, p-methylstyrene, benzyl methacrylate or the like may be copolymerized.

  The weight average molecular weight of the acrylic resin and / or methacrylic resin used for the fiber (C) is not particularly limited, but is preferably 10,000 to 1,000,000. When the weight average molecular weight is 10,000 or more, the fibers can be easily prevented from falling off during the spinning process, and when the molecular weight is 1,000,000 or less, excellent spinnability can be obtained. The acrylic resin and / or methacrylic resin is desirably poorly soluble in water. When the solubility in water is low, it is possible to easily prevent the fibers from falling into the spinning coagulation tank, to easily prevent fiber fluffing and yarn breakage, and to easily prevent deterioration in process passability.

  The fiber (C) forms a clearer streaky phase separation structure inside the acrylic fiber and easily fibrillates.

[Fibrillated acrylic fiber (D)]
The carbon fiber-containing non-woven fabric can contain 5 to 40% by mass of the fibrillated acrylic fiber (D). The fiber (D) is composed of a fibril-like and film-like material having a width of 0.1 μm to 30 μm and a length of 10 μm to 10 mm made of an acrylonitrile-based polymer containing 50% by mass or more of acrylonitrile.

  The fiber (D) has a fibril-like or film-like ratio of at least 5% having a length of at least 1000 μm.

As the fiber (D), synthetic pulp such as fibrillated polyethylene fiber, acrylic fiber, and aramid fiber is used. A fibrillated polyethylene fiber is preferred from the viewpoints of affinity with carbon fiber, handleability, and cost. Specifically, a polyethylene pulp (made by Mitsui Chemicals) etc. can be illustrated.
The fiber (D) has a structure in which a large number of fibrils having a diameter of several μm or less (for example, 0.1 to 3 μm) are branched from a fibrous trunk having a diameter of about 0.1 to 10 μm.

  When making paper, it is preferable that the fiber (D) is insoluble in the dispersion medium during paper making and does not swell. From the viewpoint of efficiently forming the entangled structure, the surface free energy of the fibers constituting the fiber (D) is preferably larger than the surface free energy of the carbon short fibers (A).

  The fibrillated acrylic fiber (D) is preferably a fibril fiber having a freeness of 100 to 700 ml according to JIS P8121. The fibril fiber having a freeness of 100 ml or more is easy to handle, and if it is 700 ml or less, the fiber form is particularly suitable for forming a sheet.

The fibrillated acrylic fiber (D) can be obtained by the method shown below. That is, a polymer solution prepared by dissolving acrylonitrile-based polymer in the solvent is quantitatively supplied to a nozzle and discharged into a cell through a discharge hole formed as a narrow path. At the same time, the non-solvent pressurized water vapor of the polymer is supplied from the slits provided in the periphery so as to be supplied in substantially the same direction as the polymer solution discharge flow direction. Thereby, the polymer is made to collide with the discharged polymer solution in the cell, and the polymer is solidified and ejected from the cell outlet of the nozzle in a state where the solidified polymer is torn off by the shearing stress applied by the pressurized steam flow. The fiber (D) is formed as an aggregate that exists as a fiber or a film or a mixture thereof by completely solidifying in a coagulation bath to form fibril fibers, washing and extracting the solvent remaining in the fibril fibers, and drying. Obtainable.
The width and length of the fibrous or film-like material constituting the fibril fiber is determined by the discharge hole shape, slit shape, polymer solution concentration, supply amount, water vapor supply amount, supply pressure, supply collision angle, and cell shape. Is done.

[Manufacture of carbon fiber-containing nonwoven fabric]
The method for producing the carbon fiber-containing nonwoven fabric of the present invention is as follows.
A process I for producing a multi-layered paper web by repeating the process I ^* for forming a paper web from a papermaking slurry containing short carbon fibers (A) and ultrafine acrylonitrile fibers (B); and
Step II of confounding and integrating the multilayered paper web by water jet punching on the multilayered paper web
Have

The carbon fiber-containing nonwoven fabric obtained by the above method has a basis weight of 20 to 200 g / m ² and a fabric thickness of 0.1 to 2.0 mm. When the basis weight is 20 g / m ² or more, it becomes easy to pass through the step I (the step of repeating the paper making step I ^{* of} each layer) and the entanglement step (step II) by water jet punching, and it can be peeled off from the paper making net without problems. preferable. When the basis weight is 200 g / m ² or less, dehydration under reduced pressure in the papermaking or water jet punching process is facilitated, and a good uniform sheet can be formed.

In step I, wet papermaking using a papermaking slurry having a fiber concentration of 0.1 to 3.0 g / L is preferably performed. In step I, the paper making speed (paper making slurry transport speed) is preferably 1 to 10 m / min. In step I, and multi-layered paper making web having a basis weight 10~66g / m ^2, to form a sheet (multi-layered papermaking web) having a basis weight 20 to 200 g / m ^2, the paper strength can take off from the paper making net It is preferable.

  The papermaking speed depends on the distribution capacity of the flow box (FB) supplied on the papermaking net for supplying papermaking slurry and the dewatering performance of the suction box (SB). If the fiber concentration is within the above range, the fiber dispersibility, The texture and homogeneity are preferable.

  The papermaking slurry can be dehydrated under reduced pressure by a suction box (SB) provided under the papermaking net after being quantitatively discharged onto the papermaking net through a flow box (FB) that uniformly distributes the papermaking sheet width. In a general papermaking method, it is performed in a region lower than the fiber concentration (0.1 to 3.0 g / L), but even if the papermaking slurry concentration is set high by using a flow box capable of uniform distribution, the papermaking sheet Manufacture is possible, and a compact papermaking unit can be assembled.

  When the fiber concentration in the papermaking slurry used in Step I is 0.1 g / L or more, the multi-layered papermaking web has a high basis weight and can be easily made into a thick sheet, and can be easily peeled off from the papermaking net. It is easy to do. When the fiber concentration in the papermaking slurry is 3.0 g / L or less, uniform dispersion of the fibers in the slurry and formation of a uniform flow of the papermaking slurry can be easily achieved, and a good texture and uniform sheet can be obtained. Is easy.

The papermaking slurry can be dewatered under reduced pressure in a suction box installed under the papermaking net. At that time, by making a papermaking web having a papermaking basis weight of 66 g / m ² or less, it is easy to obtain a sheet that is easily dehydrated and has a good texture. Also, in Step II, when performing dehydration or entanglement treatment of a high-pressure water stream, dehydration is facilitated, suction can be performed easily, and a phenomenon in which fibers are scattered and roughened on the sheet is easily prevented. be able to.

  In Step I, after a plurality of layers of papermaking webs are laminated by the wet papermaking method, the papermaking webs multilayered by water jet punching in Step II can be entangled and integrated. By water jet punching, the entanglement integration of the short carbon fiber (A) and the ultrafine acrylonitrile fiber (B) and the entanglement integration of the laminated papermaking web are performed.

In step I ^* , it is preferable to laminate a papermaking web of 10 to 60 g / m ² from the viewpoint of obtaining a good texture of the carbon fiber-containing nonwoven fabric. It is preferable to form a sheet having a basis weight of 20 to 200 g / m ² by repeating a paper making of 10 to 60 g / m ² (step I ^* ) a plurality of times.

  It is preferable to continuously perform the paper making in Step I and the entanglement by water jet punching in Step II by incorporating them on a single net conveyance device. A non-woven sheet can be formed with a compact device incorporating a papermaking unit and a water jet punching unit.

  In this invention, after forming a papermaking web using the papermaking slurry containing a carbon short fiber (A) and a super extra fine acrylonitrile fiber (B), the fiber entanglement process by water jet punching is performed. By containing ultra-fine fibers (B) with high fiber entanglement performance and entanglement by water jet punching, not only the wet papermaking sheet can be peeled off from the net, but also the sheet form is retained after drying. A sheet can be formed. It is possible to produce a carbon fiber-containing non-woven fabric that not only has a small change in shape but also has almost no loss of short carbon fibers (A).

  In water jet punching, a sinusoidal entanglement pattern (entanglement locus) can be formed on the surface of a sheet (multilayered web) by applying vibration to a high-pressure liquid jet nozzle used for water jet punching. This is effective not only in the entanglement in the sheet length direction but also in the entanglement in the sheet width direction, and can improve sheet form stability.

[First water jet punching]
One form of water jet punching will be described. This form is called first water jet punching.

  In the first water jet punching, a high-pressure liquid jet nozzle (first high-pressure liquid jet nozzle, hereinafter referred to as a high-pressure liquid jet nozzle (1)) having nozzle holes arranged in a row that vibrates in a direction perpendicular to the sheet conveying direction. Is used, and water jet punching is performed so that a sinusoidal confounding locus having a period of 20 to 100 mm and an amplitude of 1 to 3 mm is drawn on the sheet surface.

  Step I (multilayer papermaking) and step II (water jet punching) are preferably performed by a continuous process on a papermaking net installed on a flat net type machine that conveys the papermaking web.

  In water jet punching, the water jet nozzles arranged in a line perpendicular to the sheet conveyance direction are vibrated to draw a sinusoidal water jet trajectory on the surface of the sheet and perform the confounding process. Uniformity can be achieved.

  The trajectory of water jet punching formed on the sheet surface is determined by the relationship between the sheet conveyance speed, the nozzle vibration speed, and the nozzle swing width. As a nozzle frequency, it is practical to control with about 1 to 1000 rpm and a swing width of about 6 mm. When the sheet conveyance speed is set to 1 to 10 m / min, the cycle is 20 to 100 mm and the amplitude is 1 to 3 mm. A sine curve can be formed on the sheet.

  In order to further strengthen the entanglement process, it is possible to repeatedly perform the process using the water jet nozzle. For example, the pitch between rows of nozzles can be set to 30 cm, and two nozzles can be fixed and vibration can be applied by a single nozzle vibration device.

  In the first water jet punching, two high-pressure liquid jet nozzles (1) are used to superimpose sine curve-shaped confounding trajectories having a period of 20 to 100 mm and an amplitude of 1 to 3 mm.

[Second water jet punching]
Another form of water jet punching will be described. This form is called second water jet punching.

  In the second water jet punching, high-pressure liquid jet nozzles (second high-pressure liquid jet nozzles; hereinafter referred to as high-pressure liquid jet nozzles (2)) provided with three rows of nozzle holes that vibrate in a direction perpendicular to the sheet conveying direction. Is used to form a confounding locus by water jet punching on the surface of the sheet, in which three lines are superimposed with a period of 10 to 20 mm, an amplitude of 1 to 3 mm, and a phase difference of 120 °. The high-pressure liquid jet nozzles (2) are nozzles arranged in three rows. When the sheet is conveyed while vibrating the nozzles, a three-phase sine curve is drawn on the sheet surface. If the vibration condition is selected so that the phase difference of the sine curve of the three-phase wave is 120 °, the confounding trajectories overlap each other so that a periodic horizontal pattern is not formed on the sheet surface.

  The nozzle hole diameter of the high pressure liquid jet nozzles (1) and (2) for generating a high pressure water flow is preferably Φ (diameter) 0.05 to 0.3 mm. When the diameter is 0.05 mm or more, the water jet punching force is suitable, and the entanglement process can be performed efficiently. If the diameter is 0.3 mm or less, it is possible to easily prevent the water jet punching water amount from increasing and the striking force to become strong, and to easily prevent the surface from becoming rough due to the thick trajectory remaining on the sheet surface.

  The pitch between the nozzle holes of the high-pressure liquid jet nozzles (1) and (2) is not particularly limited. The narrower the pitch between holes, the higher the density of the entanglement treatment becomes possible. However, when considering the straightness of the high-pressure water flow generated from the water jet nozzle, the balance between the amount of water used and the amount of drainage, the processing accuracy of the nozzle, etc. 3 mm is preferred.

  The pressure of the high-pressure water flow of the high-pressure liquid jet nozzles (1) and (2) is preferably 0.1 to 6 MPa. When the pressure is 0.1 MPa or more, it is easy to improve the entanglement of the fibers. When the pressure is 6 MPa or less, it is possible to easily prevent the shape of the nonwoven fabric from collapsing and breaking.

  It is preferable to perform entanglement integration by water jet punching by combining the entanglement processing by the high pressure liquid injection nozzles (1) and (2). That is, in step II, it is preferable to perform both the first and second water jet punching.

[Manufacture of carbon fiber nonwoven fabric]
After the carbon fiber-containing nonwoven fabric is hot-pressed at a temperature of 100 to 250 ° C., preferably 120 to 200 ° C., it is possible to obtain a carbon fiber nonwoven fabric by carbonizing at 1000 to 3000 ° C. This carbon fiber nonwoven fabric can be used as a porous electrode substrate. The basis weight of the carbon fiber nonwoven fabric is preferably 15 to 150 g / m ² .

  The carbonization treatment is preferably performed in an inert gas in order to increase conductivity. Carbonization treatment is preferably performed in a temperature range of 1000 to 3000 ° C, and a temperature range of 1000 to 2200 ° C is more preferable. The carbon fiber nonwoven fabric obtained by carbonization at a temperature of 1000 ° C. or higher has excellent conductivity for use as a porous electrode substrate for fuel cells.

  A pretreatment by firing in an inert atmosphere of about 300 to 800 ° C. may be performed after the hot pressing and before the carbonization treatment.

  The carbon fiber-containing non-woven fabric can be fused with the entangled portion and the bound portion by heating and pressing (hot pressing) at a temperature of 200 ° C. or lower before the carbonization treatment. Thickness unevenness can be reduced by pressurizing and molding. Any technique can be applied to the heat and pressure molding as long as the technique can uniformly heat and pressurize the carbon fiber-containing nonwoven fabric. For example, there are a method of hot pressing with smooth rigid plates from both the upper and lower surfaces and a method of using a continuous belt press apparatus.

  The molding pressure is not particularly limited, but the viewpoint of obtaining an excellent effect in the above points, the viewpoint of preventing the destruction of the carbon fiber nonwoven fabric during molding, and the densification of the structure when used as a porous electrode base material are prevented. From the viewpoint, for example, pressurization can be performed at a pressure of 20 kPa to 10 MPa. The time for heat and pressure molding can be, for example, 30 seconds to 10 minutes.

  The carbon fiber-containing nonwoven fabric is preferably subjected to an oxidation treatment at a temperature of 200 ° C. or more and less than 300 ° C. after the heat and pressure molding and before the carbonization treatment in terms of fusing the resin portion as a component.

  This oxidation treatment is preferably performed in a temperature range of 200 ° C. or more and less than 300 ° C., and more preferably performed at 240 to 270 ° C. The oxidation treatment is preferably performed in an air atmosphere.

  The present invention will be specifically described with reference to examples and comparative examples. Examples of the present invention, papermaking raw materials, mixed composition, fiber concentration in papermaking slurry, papermaking basis weight, common preparation conditions other than the number of layers, machine setting conditions, and process passability evaluation method Is shown below.

In addition, Table 1 summarizes the outline of Examples and Comparative Examples. In Table 1, each column has the following meaning.
Substrate type: Specification of fiber used,
Sheet composition: Composition (% is mass%) of the produced carbon fiber-containing nonwoven fabric,
CF (A): carbon short fiber (A),
Super extra fine (B): Super extra fine acrylonitrile fiber (B),
Split fiber (C): easy split fiber acrylonitrile-based polymer blend fiber (C) and a part of which is split or beaten (C ^* ),
Fibrid (D): Fibrilized acrylic fiber (D),
Papermaking slurry concentration: concentration of fibers in the papermaking slurry,
Sheet basis weight: basis weight of the produced carbon fiber-containing nonwoven fabric,
Paper basis weight: The basis weight of each layer in multilayer papermaking,
FB: Process passability evaluation result in the flow box of process I,
Paper making: Evaluation result of decontamination under vacuum at step I in process I,
WJ: Evaluation result of confounding process by water jet punching in process II,
Net peeling: Evaluation results related to peeling of the sheet from the net,
Mangle dehydration: Evaluation results regarding removal of sheets from the mangle,
Drying: Evaluation results regarding removal of sheet from dryer,
Fabric weight and fabric thickness of molded sheet: Fabric weight and fabric thickness when carbon fiber-containing nonwoven fabric is hot-pressed,
Fabric weight and fabric thickness of fired sheet: Fabric weight and fabric thickness of the produced carbon fiber nonwoven fabric.

[Disaggregation and beating of papermaking materials (floc)]
-Disaggregation treatment of carbon short fiber (A) Polyacrylonitrile-based carbon fiber (trade name: Pyrofil TR50S, manufactured by Mitsubishi Rayon Co., Ltd.) having a fine diameter of 7 μm was cut to a length of 3 mm. Hereinafter, the fiber raw material may be referred to as a flock or a raw material flock. This raw material floc was dispersed in water so as to have a fiber concentration of 1% by mass, and then disaggregated by a disc refiner (manufactured by Kumagai Riki). The disaggregation process was performed using a disc rotation speed of 5000 rpm, a disc clearance of 0.4 mm, and a B type disc.

-Disaggregation treatment of ultrafine acrylonitrile fiber (B) An ultrafine acrylonitrile fiber having a fineness of 0.13 dtex was cut into a length of 3 mm (product name: MVP D122, manufactured by Mitsubishi Rayon). This raw material floc was dispersed in water so as to have a fiber concentration of 1% by mass, and then disaggregated by the disc refiner. The disaggregation process was performed using a disc rotation speed of 5000 rpm, a disc clearance of 0.4 mm, and a B type disc.

・ Preparation product (C ^* ) of easily split acrylonitrile polymer blend fiber (C) Easy split acrylonitrile polymer blend fiber (C) (Made by Mitsubishi Rayon, trade name: C651, polyacrylonitrile polymer / Diase = 70/30) was cut to a length of 3 mm. The raw material floc was dispersed in water at a fiber concentration of 1% by mass and disaggregated by the disc refiner. The beating process was carried out using a disc rotation speed of 5000 rpm, a disc clearance of 0.05 mm, and a B type disc. The freeness (CSF) of the prepared beating product (C ^* ) was 320 cc.

-Preparation of fibrillated acrylic fiber (D) An acrylonitrile polymer was dissolved in dimethylacetamide by heating at 80 ° C to prepare a polymer solution having a polymer concentration of 23% by mass. The polymer solution was coagulated and sheared with pressurized steam, and ejected into a coagulation bath made of water, and then the coagulum suspended in the coagulation bath was collected by filtration. The polymer solution was kept at 60 ° C. and was discharged into a cell having a diameter of 2 mm and a length of 10 mm from a discharge hole having a diameter of 0.2 mm by a gear pump at 24 ml / min. Pressurized water vapor with a pressure of 0.25 MPa was supplied into the cell through a slit provided around the cell so as to be supplied in a direction of 60 degrees with respect to the direction of the polymer solution discharge flow.
The freeness (CSF) of the prepared fibrillated acrylic fiber (D) was 350 cc. The fiber was dispersed in water at a fiber concentration of 1% by mass and disaggregated by the disc refiner. The disaggregation process was performed using a disc rotation speed of 5000 rpm, a disc clearance of 0.4 mm, and a B type disc. The freeness (CSF) of the prepared beaten product (C ^* ) was 350 cc.

[Paper making slurry]
A disaggregated carbon short fiber (A) and a disaggregated ultrafine fiber (B), and optionally a disaggregated product (C ^* ) of fiber (C) and / or a disaggregated product of fibrillated fiber (D), It put into the slurry adjustment tank and diluted water was added, and it prepared to the predetermined slurry fiber density | concentration and mixed composition. Further, polyacrylamide was added to prepare a papermaking slurry having a viscosity of 22 centipoise (0.022 Pa · s).

[Net drive and sheet conveyance]
Interlacing was performed by papermaking (fiber loading) and water jet punching on a device (called a net transport device) that connected the papermaking net in a belt shape and rotated it continuously. A plurality of units for a papermaking slurry supply device, a water jet nozzle, and a vacuum dewatering device were arranged in the net conveyance device. The sheet conveying speed was 3.5 m / min, and a PE (polyethylene) plain woven paper net (trade name: FOP76, manufactured by Nippon Filcon) was used as the paper net.

[Multilayer paper making process I]
Since the fiber (floc) loading amount is determined by the slurry supply amount, the fiber concentration in the supply slurry, the papermaking net conveyance speed, and the slurry supply unit width, the above parameters were adjusted and set to have a predetermined basis weight. After the slurry for papermaking is uniformly distributed and fed through the flow box (FB) on the papermaking net, it is dehydrated naturally while passing through a stationary part that is dehydrated at normal pressure (natural), and then placed under the net. Was dehydrated. At this time, the prepared slurry was dispensed and poured on the papermaking net through a flow box that was dispensed by a metering pump to make the flow uniform. The width of the flow box used for papermaking was 48 cm, and the paper supply was carried out with a fixed amount of slurry supplied at 30 L / min. Three papermaking slurry feeders were placed on the net transport device, and a plurality of papermaking webs were stacked.

  The process passability of the multilayer paper making process I was evaluated by visual inspection, and the case where the flow of the flow box (FB) was uniform was good, and the case where the flow was poor was x. The suction box (SB) in which paper was successfully dewatered under reduced pressure was marked as ◯, and the paper that had not been dewatered was marked as x.

[Entanglement integration process II]
A water jet punching device (WJ entanglement device) was arranged behind the paper making unit (fiber loading unit) of the net conveying device. The following two types of water jet nozzles were arranged on the apparatus. By using two high-pressure liquid jet nozzles (1) and one high-pressure liquid jet nozzle (2) and using a nozzle vibration device that vibrates each nozzle in a direction perpendicular to the sheet conveyance direction, A nozzle curve with a sine curve was drawn. Details of the dimensions and configuration of the high-pressure liquid injection nozzle used in the examples are shown below.
・ High pressure fluid injection nozzle (1) x 2
Fixing two nozzles arranged in a row and vibrating with one vibration device
Number of nozzle holes: 501hole x 2 (row)
Hole diameter: φ0.10mm
Width between holes: 1mm
1 row arrangement, nozzle pitch (row spacing): 300mm
Nozzle swing width: 3.0 mm (sine curve amplitude 1.5 mm)
Nozzle vibrator rotation speed: 144 rpm (1.91 cycle / sec)
・ High-pressure fluid ejection nozzle (2) x 1 3-row nozzle hole diameter: φ0.15mm
Number of nozzle holes: 1002hole
Width direction hole pitch: 1.5mm
Inter-row pitch 5mm
Nozzle swing width 3.0mm (sine curve amplitude 1.5mm)
Nozzle vibrator rotation speed: 233 rpm (389 cycles / sec)
The process passability of the confounding integrated process II was evaluated with the following definition. The case where the entanglement process was satisfactorily performed on the sheet by water jet punching and the entanglement locus was drawn on the surface of the sheet was indicated as “◯”, and the case where the sheet was broken or a large hole was opened was indicated as “X”.

[Peeling from papermaking net]
The sheet that has passed through the multilayer paper making process I and the entanglement integration process II is a wet paper that has been dehydrated under reduced pressure but is in a wet state. The sheet water adhesion amount (pickup) was 550 to 600% by mass. The definition of the pickup [%] was (sheet wet mass-dry mass) / dry mass.

  When the sheet is peeled from the papermaking net, the sheet cannot be taken out without the wet paper strength that can be handled. The handling ability to peel off from the papermaking net was evaluated as follows. After the sheet is manually peeled off from the papermaking net, it is transferred to the 1 belt conveyor that is transported at the same speed as the net papermaking net at a position 1 m away from the rear end of the papermaking net, and then the floor from the end of the belt conveyor. The sheet was transferred to the floor with a height of 1.5 m to the surface. It was confirmed that the sheet could be continuously collected without tearing the wet paper under tension due to its own weight. The case where the sheet was peeled off from the net and was continuously transferred onto the floor surface by the belt conveyor was evaluated as “Good”, and the sheet was not peeled off and was not transferred onto the floor surface due to tearing or tearing.

[Dehydration]
The sheet peeled off from the papermaking net was squeezed with a mangle. The sheet water adhesion amount (pickup) was adjusted to 250 to 300% by mass.
In the evaluation of the process passability, the sheet was taken out from the mangle and the sheet was not torn, and the sheet was not peeled off and was torn or torn.

[Drying treatment]
Next, it was dried at 130 ° C. for 4 minutes by a pin tenter tester (trade name: PT-2A-400, manufactured by Sakurai Dyeing Machine). The pin chain of the dryer was set at an inlet width of 39 cm and an outlet width of 40 cm, and was processed while being widened by 1 cm. In the evaluation of process passability, the sheet was taken out and it was not torn, and the sheet was torn, and the sheet was torn or torn was rated as x.

[Example 1]
Fiber concentration 1 containing a papermaking substrate of carbon short fiber (A) / ultrafine fiber (B) / beaten product (C ^* ) / fibrillated fiber (D) = 50/30/10/10 (mass%) A papermaking slurry of .68 g / L was prepared. Using this, repeated twice basis weight 30 g / m ² in each layer papermaking process I ^*, to form a papermaking web laminate sheet having a basis weight of 60 g / m ² (double-layered papermaking web).

  The flow and distribution of the flow box in the multilayer paper making process I were uniform, and the dehydration from the suction box arranged under the net was also good. A paper-making web having a uniform surface and no rough surface was formed.

  Next, the obtained multi-layered web was passed through two high-pressure liquid jet nozzles (1) and one high-pressure liquid jet nozzle (2) to perform the entanglement integration step II. The pressure of the high-pressure liquid jet nozzle (1) was set at 1 MPa for the first, 2 MPa for the second, and 3 MPa for the third, and the entanglement integration step II for water jet punching was performed.

  By processing with the high-pressure liquid jet nozzle (1), the sheet is drawn on the sheet with an amplitude of 1.5 mm and a cycle of 31 mm, and the high-pressure liquid jet nozzle (2) shows a sine curve with an amplitude of 1.5 mm and a cycle of 15 mm. The confounding pattern superimposed on is drawn.

  FIG. 1 shows an entanglement pattern composed of a water jet locus formed by using one high-pressure liquid jet nozzle (1). FIG. 2 shows an entanglement pattern composed of a water jet trajectory formed by using one high-pressure liquid jet nozzle (2). FIG. 3 shows an entanglement pattern composed of a water jet trajectory formed by using two high-pressure liquid jet nozzles (1). FIG. 4 shows an entanglement pattern composed of a water jet locus formed by using two high-pressure liquid jet nozzles (1) and one high-pressure liquid jet nozzle (2).

  Even in the entanglement integration step II by water jet punching, the sheet surface and form were good, and the entanglement locus pattern of water jet punching was formed on the sheet surface. Moreover, the sheet which finished the process of the process I and the process II was able to peel continuously from a papermaking net | network.

Next, the sheet obtained after dehydrating the sheet with mangles was dried with a pin tenter tester. When dried, the sheet could be processed without tearing. As a result, a carbon fiber-containing non-woven fabric having a basis weight of 60 g / m ² and a fabric thickness of 0.6 mm and having good sheet form stability without delamination and fiber dropping was obtained. The obtained carbon fiber-containing nonwoven fabric is shown in FIG.

[Example 2]
A papermaking slurry having carbon short fibers (A) / ultrafine fibers (B) = 70/30 (mass%) and a fiber concentration of 1.68 g / L was prepared. Others were carried out in the same manner as in Example 1. As a result, a carbon fiber-containing non-woven fabric having a basis weight of 60 g / m ² and a fabric thickness of 0.6 mm and having good sheet form stability without delamination and fiber dropping was obtained.

Example 3
A papermaking slurry having carbon short fibers (A) / ultrafine fibers (B) = 90/10 (mass%) and a fiber concentration of 1.68 g / L was prepared. Others were carried out in the same manner as in Example 1. As a result, a carbon fiber-containing non-woven fabric having a basis weight of 60 g / m ² and a fabric thickness of 0.9 mm and having good sheet form stability without delamination and fiber dropping was obtained.

[Comparative Example 1]
A papermaking slurry having carbon short fibers (A) / ultrafine fibers (B) = 95/5 (mass%) and a fiber concentration of 1.68 g / L was prepared. Others were carried out in the same manner as in Example 1, but the wet paper strength was not sufficient, and peeling from the papermaking net was not possible, so that a continuous sheet could not be formed.

[Comparative Example 2]
A papermaking slurry having carbon short fibers (A) / ultrafine fibers (B) = 70/30 (mass%) and a fiber concentration of 0.56 g / L was prepared. A papermaking process I ^* having a basis weight of 10 g / m ² was performed only once to form a single papermaking web sheet (not multi-layered). The strength of the wet paper was not sufficient, so that it could not be peeled off from the papermaking net and a continuous sheet could not be formed.

Example 4
A papermaking slurry having carbon short fibers (A) / ultrafine fibers (B) = 70/30 (mass%) and a fiber concentration of 0.84 g / L was prepared. The paper making process I ^* having a basis weight of 15 g / m ² was repeated twice to form a paper making web laminated sheet (double-layer paper making web) having a basis weight of 30 g / m ² . Others were carried out in the same manner as in Example 1. As a result, a carbon fiber-containing non-woven fabric having a basis weight of 30 g / m ² and a fabric thickness of 0.4 mm and having good sheet form stability without delamination and fiber dropping was obtained.

Example 5
A papermaking slurry having short carbon fibers (A) / ultrafine fibers (B) = 70/30 (mass%) and a fiber concentration of 1.12 g / L was prepared. The basis weight 20 g / m ² of the paper making process I ^* repeated three times to form a papermaking web laminate sheet having a basis weight of 60 g / m ² (three-layer papermaking web). Others were carried out in the same manner as in Example 1. As a result, a carbon fiber-containing non-woven fabric having a basis weight of 60 g / m ² and a fabric thickness of 0.7 mm and having good sheet form stability without delamination and fiber dropping was obtained.

Example 6
A papermaking slurry having carbon short fibers (A) / ultrafine fibers (B) = 70/30 (mass%) and a fiber concentration of 2.52 g / L was prepared. The basis weight 45 g / m ² of the paper making process I ^* repeated three times to form a basis weight 135 g / m ² of papermaking web laminate sheet (three-layer papermaking web). Others were carried out in the same manner as in Example 1. As a result, a carbon fiber-containing nonwoven fabric having a basis weight of 135 g / m ² and a fabric thickness of 1.3 mm and having good sheet form stability without delamination and fiber dropping was obtained.

[Comparative Example 3]
A papermaking slurry having short carbon fibers (A) / ultrafine fibers (B) = 70/30 (mass%) and a fiber concentration of 3.92 g / L was prepared. Basis weight of 70 g / m ² and paper making process I ^* repeated three times to form a papermaking web laminate sheet having a basis weight of 210g / m ² (three-layer papermaking web). Others were carried out in the same manner as in Example 1, but the flow from the flow box (FB) in the paper making process I was uneven, the vacuum dehydration by the suction box (SB) was not sufficient, and the surface was rough. The sheet became uneven.

[Comparative Example 4]
A papermaking slurry having carbon short fibers (A) / ultrafine fibers (B) = 70/30 (mass%) and a fiber concentration of 1.68 g / L was prepared. The basis weight 30 g / m ² of the paper making process I ^* was repeated twice to form a papermaking web laminate sheet having a basis weight of 60 g / m ² (two-layer papermaking web). The same process as in Example 2 was performed except that the entanglement process by water jet punching was not performed. Although peeling from the papermaking net was possible, delamination and fiber peeling occurred in the dehydration process and drying process due to the mangle, and a sheet with good shape stability could not be obtained.

Example 7
A paper-making web laminate sheet (double-layer paper-making web) having a basis weight of 60 g / m ² was formed in the same manner as in Comparative Example 4. The entanglement integration process II by water jet punching was performed using two high-pressure liquid jet nozzles (1). The high pressure liquid injection nozzle (2) was not used. Others were carried out in the same manner as in Example 1. As a result, a carbon fiber-containing non-woven fabric having a basis weight of 60 g / m ² and a fabric thickness of 0.6 mm and having good sheet form stability without delamination and fiber dropping was obtained. On the surface of the sheet, there was interference of the confounding locus due to water jet punching, and a periodic weft pattern as shown in FIG. 3 was observed.

Example 8
A paper-making web laminate sheet (double-layer paper-making web) having a basis weight of 60 g / m ² was formed in the same manner as in Comparative Example 4. The entanglement integration process II by water jet punching was performed using only the high-pressure liquid jet nozzle (2). Others were carried out in the same manner as in Example 1. The confounding pattern shown in FIG. 2 was formed on the sheet surface without interference of the confounding locus due to water jet punching. As a result, a carbon fiber-containing non-woven fabric having a basis weight of 60 g / m ² and a fabric thickness of 0.6 mm and having good sheet form stability without delamination and fiber dropping was obtained.

[Comparative Example 5]
A papermaking slurry having carbon short fibers (A) / ultrafine fibers (B) = 70/30 (mass%) and a fiber concentration of 1.68 g / L was prepared. As the ultrafine fiber (B), an ultrafine fiber having a fineness of 1.0 dtex and a cut length of 5 mm was used. Others were carried out in the same manner as in Example 2.
The basis weight 30 g / m ² of the paper making process I ^* was repeated twice to form a papermaking web laminate sheet having a basis weight of 60 g / m ² (two-layer papermaking web). The form stability of the dried sheet was unsatisfactory, and it was a sheet in which fibers were lost or dropped.

Example 9
A papermaking slurry having a short carbon fiber (A) / ultrafine fiber (B) / beaten product (C ^* ) = 50/30/20 (mass%) and a fiber concentration of 1.68 g / L was prepared. Others were carried out in the same manner as in Example 1. As a result, a carbon fiber-containing non-woven fabric having a basis weight of 60 g / m ² and a fabric thickness of 0.6 mm and having good sheet form stability without delamination and fiber dropping was obtained.

Next, batch press was performed by applying a pressure of 10 MPa to the carbon fiber-containing nonwoven fabric at a temperature of 180 ° C. for 3 minutes. Then, it carbonized in 1800 degreeC and 1 minute in inert gas (nitrogen) atmosphere. As a result, a carbon fiber nonwoven fabric having a basis weight of 44 g / m ² and a cloth thickness of 0.2 mm was obtained.

Example 10
A papermaking slurry having short carbon fibers (A) / ultrafine fibers (B) / fibrillated fibers (D) = 50/30/20 (mass%) and a fiber concentration of 1.68 g / L was prepared. Others were carried out in the same manner as in Example 1. As a result, a carbon fiber-containing non-woven fabric having a basis weight of 60 g / m ² and a fabric thickness of 0.6 mm and having good sheet form stability without delamination and fiber dropping was obtained.

The obtained carbon-containing nonwoven fabric was batch-pressed by applying a pressure of 10 MPa at a temperature of 180 ° C. for 3 minutes, and then carbonized in an inert gas (nitrogen) atmosphere at a temperature of 1800 ° C. for 1 minute. As a result, a carbon fiber nonwoven fabric having a basis weight of 45 g / m ² and a cloth thickness of 0.2 mm was obtained.

Example 11
A papermaking slurry having carbon short fibers (A) / ultrafine fibers (B) / beaten processed products (C ^* ) = 70/10/20 (mass%) and a fiber concentration of 1.68 g / L was prepared. Others were carried out in the same manner as in Example 1. As a result, a carbon fiber-containing non-woven fabric having a basis weight of 60 g / m ² and a fabric thickness of 0.6 mm and having good sheet form stability without delamination and fiber dropping was obtained.

The resulting carbon fiber-containing non-woven fabric was batch pressed by applying a pressure of 10 MPa at 180 ° C. for 3 minutes. Then, it carbonized in 1800 degreeC and 1 minute in inert gas (nitrogen) atmosphere. As a result, a carbon fiber nonwoven fabric having a basis weight of 50 g / m ² and a fabric thickness of 0.2 mm was obtained.

Example 12
A papermaking slurry having short carbon fibers (A) / ultrafine fibers (B) / fibrillated fibers (D) = 70/10/20 (mass%) and a fiber concentration of 1.68 g / L was prepared. Others were carried out in the same manner as in Example 1. As a result, a carbon fiber-containing non-woven fabric having a basis weight of 60 g / m ² and a fabric thickness of 0.6 mm and having good sheet form stability without delamination and fiber dropping was obtained.

The obtained carbon-containing nonwoven fabric was batch-pressed by applying a pressure of 10 MPa at a temperature of 180 ° C. for 3 minutes, and then carbonized in an inert gas (nitrogen) atmosphere at a temperature of 1800 ° C. for 1 minute. As a result, a carbon fiber nonwoven fabric having a basis weight of 51 g / m ² and a cloth thickness of 0.2 mm was obtained.

  The carbon fiber-containing non-woven fabric and the carbon fiber non-woven fabric are useful as a non-woven fabric having a porous structure excellent in conductivity, thermal conductivity, heat resistance, corrosion resistance, and gas permeability.

  The carbon fiber-containing non-woven fabric of the present invention can be used as a carbon fiber reinforced resin by impregnating an antistatic material, an electromagnetic shielding material, other filters, and a resin without causing the carbon fiber to fall off. Moreover, the porous carbon fiber nonwoven fabric obtained by carbonizing the carbon fiber-containing nonwoven fabric of the present invention can be used as a material for a gas diffuser of a polymer electrolyte fuel cell.

Claims (6)

The manufacturing method of a carbon fiber containing nonwoven fabric including the following processes.
(1) A step of preparing a papermaking slurry containing 40 to 90% by mass of carbon short fibers (A) and 5 to 60% by mass of ultrafine acrylonitrile-based short fibers (B).
(2) A step of forming a papermaking web from the slurry.
(3) The process of repeating the said process and preparing the multilayered papermaking web.
(4) A step of subjecting the multilayered papermaking web to water jet punching to entangle the multilayered papermaking web.   In the step (1), 50 to 70% by mass of the acrylonitrile-based polymer, and 50 to 30% by mass of the polymer that is incompatible with the acrylonitrile-based polymer and is soluble in the same solvent as the acrylonitrile-based polymer. The manufacturing method of Claim 1 containing the easily split fiber acrylonitrile-type polymer blend fiber (C) containing this. In step (4), water jet punching
A first high-pressure liquid jet nozzle comprising a plurality of nozzle holes arranged in a row,
The nozzle includes a first water jet punching that vibrates in a direction perpendicular to the conveyance direction of the papermaking web and draws a sinusoidal confounding locus with a period of 20 to 100 mm and an amplitude of 1 to 3 mm on the surface of the papermaking web.
The manufacturing method of Claim 1 or 2. In step (4), water jet punching
A water jet that uses two of the first high-pressure liquid jet nozzles and superimposes the confounding trajectories drawn by the two first high-pressure liquid jet nozzles to form horizontal interference fringes at intervals of 10 to 50 mm. Including punching,
The manufacturing method of Claim 3. In step (4), water jet punching
Using a second high-pressure liquid jet nozzle having nozzle holes arranged in three rows that vibrates in a direction perpendicular to the conveying direction of the papermaking web, the cycle is 10 to 20 mm, the amplitude is 1 to 3 mm, and the phase difference is 120 °. The manufacturing method of the carbon fiber containing nonwoven fabric in any one of Claims 1-4 including the 2nd water jet punching which draws the superimposition sine curve-shaped confounding locus | trajectory on the multilayered papermaking web surface. Including a step of hot pressing the carbon fiber-containing nonwoven fabric produced by the method according to any one of claims 1 to 5, and a step of carbonizing the hot-pressed carbon fiber-containing nonwoven fabric at a maximum temperature of 1000 to 3000 ° C.
A method for producing a carbon fiber nonwoven fabric.