JP2006219808A - Papermaking carbon fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a papermaking carbon fiber having excellent dispersibility in case of papermaking. <P>SOLUTION: In this papermaking carbon fiber, a water permeability of a fiber bundle composed of carbon fiber filaments is not less than 1 mg/g, before the bundle is washed by water, and not more than 0.5 mg/g, after washed by the water, and an especially specified coefficient of static friction between fibers of the fiber bundle is 0.01-0.3, after washed by the water. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a carbon fiber having excellent dispersibility during papermaking. That is, it is related with the carbon fiber suitable for the papermaking use which needs to disperse | distribute uniformly in a short time.

  Carbon fiber has high strength, excellent heat resistance and corrosion resistance, and has electrical conductivity and electromagnetic wave shielding properties. Therefore, it is a composite material reinforcing material used in aircrafts, secondary battery electrode materials, or an electronic computer housing. Used as a body electromagnetic shielding material.

  Usually, a prepreg is a sheet-like material in which continuous fiber bundles called strands are arranged in one direction or a plurality of directions and impregnated with a resin. Conventionally, a composite material is manufactured by laminating, molding and curing the prepreg.

  In addition, short fibers called chopped strands are used in injection molding and the like, and it is possible to obtain a complex composite material relatively easily.

  Carbon fiber paper is a material using such short carbon fibers. This carbon fiber paper is used as an electrode material, a sheet heating element, or an electromagnetic wave shielding material. Generally, the requirements for strength are small, rather the carbon fiber is kept so that the current density is kept uniform and no local current is generated. The uniformity of the dispersed state is required.

  In order to obtain carbon fiber paper with high uniformity of carbon fiber dispersion, there are known a method of spraying and depositing raw carbon short fibers such as opened fibers and a method of using a wet paper machine.

  However, since the raw carbon short fibers are usually produced by mechanically cutting a continuous fiber bundle to which a sizing agent has been added, they are often supplied as a lump of fibers that are difficult to open. It is difficult to obtain a spread state and a uniform dispersion state. Also, in the wet method, carbon fibers are more hydrophobic than hydrophilic pulp fibers and the like, and it is difficult to obtain a carbon fiber paper having a uniform texture even when the opened state is obtained.

In order to improve the dispersibility of the short fibers for papermaking, a method of omitting the surface treatment of carbon fibers and the application of a sizing agent (see Patent Document 1) or a method of applying a sizing agent containing a water-soluble compound (see Patent Document 2) ) Has been proposed. However, since only the chemical properties of the carbon fiber surface were changed in all cases, the initial dispersibility in the papermaking process was not sufficient, or it was dispersed by re-aggregation due to entanglement between dispersed fibers in the middle to late stage of the papermaking process. The carbon fiber paper with uniform texture cannot be obtained efficiently. That is, in the former case, since the hydrophilicity is poor, the fiber soaks into the water and dispersibility is insufficient, or in the latter case, the fiber soaks into the water, but the water-soluble matter that remains fixed and remains on the fiber surface. There was a problem that fibers once dispersed by mechanical stirring by the compound entangled and re-aggregated.
Japanese Patent Laid-Open No. 10-162838 JP 2003-293264 A

  In view of the background of such prior art, the present invention provides a carbon fiber having excellent dispersibility during papermaking.

The present invention employs the following means in order to solve such problems. That is, the carbon fiber for papermaking of the present invention has a water permeability of a fiber bundle composed of carbon fiber filaments of 1 mg / g or more before water washing and 0.5 mg / g or less after water washing, and The fiber-fiber static friction coefficient of the fiber bundle after the water washing specified is 0.01 to 0.3.

  According to the present invention, it is possible to provide a carbon fiber that can be uniformly dispersed in a short time during paper making, and that smooth and strong paper making can be obtained.

  The present invention has been intensively studied on the above-mentioned problem, that is, carbon fibers having excellent dispersibility during papermaking, and the carbon fibers satisfying specific parameters, that is, the water permeability is 1 mg / g or more before water washing. It satisfies the two requirements at the same time: 0.5 mg / g or less after water washing, and that the fiber-fiber static friction coefficient of the fiber bundle after water washing is 0.01 to 0.3. As a result, it was clarified that such problems can be solved at once.

  That is, the fiber bundle composed of the carbon fiber filament of the present invention can be obtained by simply separating the fibers physically by mechanically stressing the fibers while the fibers are soaked in water and chemically separating the fibers. In addition, the present invention is characterized in that the dispersibility during papermaking is improved by suppressing reaggregation due to entanglement of fibers in water.

  The water penetration degree in the present invention is as defined below.

That is, 25 g of carbon fiber bundles (3300 to 26400 dtex) are packed into a down proof of 25 cm × 25 cm (40/40: T120 / L120 (inch)), and JIS-L1096-1999 “General Textile Testing Method” In accordance with Method A (method using a stirrer-type washing machine) described in No. 8.23.1, a water-washed carbon fiber bundle sample is obtained. In addition, a sample not washed with water is used as a carbon fiber bundle sample before washing with water.
Using a contact angle meter (preferably a contact angle meter DCAT11 manufactured by Data Physics), 0.1 mm of a carbon fiber bundle sample (3300 to 26400 dtex) cut to 25 mm is immersed in water and left for 10 minutes, and left for 10 minutes. The water per 1 g of sample absorbed by the soaking was determined as water permeability [mg / g].
Water permeability = (W2-W1) / (W1 × 1000)
W1: Sample weight before immersion in water [mg]
W2: Sample weight after immersion in water for 10 minutes [mg]
It is important that the water permeability thus obtained is 1 mg / g or more before water washing and 0.5 mg / g or less after water washing, preferably 1.5 mg / g or more before water washing. It is 0.3 mg / g or less later, particularly preferably 2 mg / g or more before water washing and 0.1 mg / g or less after water washing. That is, if the water permeability is less than 1 mg / g before washing with water, the water penetration into the fiber bundle becomes poor, and the dispersibility during papermaking becomes poor.

  The fiber-fiber static friction coefficient in the present invention is as defined below.

  That is, 25 g of a fiber bundle (3300 to 26400 dtex) made of carbon fiber filaments is packed in a down proof of 25 cm × 25 cm (40/40: T120 / L120 (inch)), and JIS-L1096-1999 “General Wash with water once according to Method A (method using a stirring type washing machine) described in 8.23.1 of “Textile Testing Method”. The fiber bundle after water washing was measured according to the static friction coefficient measuring method described in 8.13 of JIS-L1015-1999 “Testing method for chemical fiber staples”. The measuring method is as follows. Of the fiber bundle 25g after water washing, 20g is wound around a paper tube, the paper tube is leveled and fixed so as not to rotate. Using the remaining 5 g, the following procedure is repeated 20 times to calculate the fiber-fiber static friction coefficient μ. The fiber bundle 0.2 g after water washing is wound around the fixed paper tube so that the fiber bundles are in contact with each other by a half turn (3π rad), a load T2 of 150 g is applied to one end of the sample, and a tension is applied to the other end. Measure. The tension meter is pulled downward, the tension T1 when the load starts to move is measured, and the fiber-fiber static friction coefficient μ is calculated from the following equation. The number of tests is 20 times for 25 g of fiber bundle, and is represented by the average value.

μ = Ln (T1 / T2) / θ
μ: Fiber-to-fiber static friction coefficient [-]
T1: Exit tension [g]
T2: Input side tension (load) [g]
θ: contact angle [rad]
The fiber-to-fiber static coefficient of friction μ is an evaluation scale for the entanglement between fibers in the middle to late stage of the paper making process (the state in which the bundling agent is eluted and disappears from the fiber surface). 3 is important, preferably 0.01 to 0.2. That is, when the static friction coefficient μ exceeds 0.3, even if temporarily dispersed during papermaking, re-aggregation occurs due to the catching of fibers, resulting in poor dispersibility. Conversely, when the static friction coefficient μ is less than 0.01, uniform papermaking can be obtained, but the strength of the papermaking itself is weakened. By making the static friction coefficient μ in the range of 0.01 to 0.3, smooth and strong papermaking can be provided.

  Further, in order to improve the initial dispersibility in the paper making process, it is preferable that the form of the fiber bundle made of carbon fiber filaments is also specific in the present invention, and the flatness and the entanglement degree of the fiber bundle are specified. More preferably.

  The flatness in the present invention is defined as follows.

  That is, a thickness T [mm] and a width W [mm] of a fiber bundle (3300 to 26400 dtex) made of carbon fiber filaments are measured with a caliper or the like, and obtained by the following formula. However, the measurement locations are 10 locations spaced by 1 m in the longitudinal direction, and the flatness of each location is calculated and expressed as an average value.

Flatness = W / T
W: width of the fiber bundle [mm]
T: thickness of the fiber bundle [mm]
Such flatness is preferably 1 to 50, and more preferably 1 to 20. When this flatness exceeds 50, the convergence property of the fiber bundle made of carbon fiber filaments is deteriorated, and the unwinding property from the bobbin around which the fiber bundle is wound is deteriorated.

  The degree of entanglement in the present invention is defined as follows.

  That is, it was measured according to the entanglement degree measuring method of JIS-L1013 “Testing method for chemical fiber filament yarn”. The measuring method is as follows. One end of a fiber bundle sample (3300 to 26400 dtex) made of carbon fiber filaments is attached to an upper grip part of a hanging device having an appropriate performance, and a load (100 g) is suspended at a position 1 m below the grip part, and the sample is vertically Hang on. A hook (wire shape with a diameter of 1 mm) is inserted so that the fiber bundle is divided into two at a point 1 cm below the upper grip portion of the sample. A predetermined load (10 g) is attached to the other end of the hook, and the hook is lowered at a speed of about 2 cm / second. The lowering distance L [mm] of the hook up to the point where the hook stopped due to the yarn entanglement was obtained, and it was obtained by the following equation. The above operation is repeated 50 times (1 time / m × 50), and the average value is expressed.

Degree of confounding = 1000 / L
L: Descent distance of hook [mm]
The degree of entanglement is preferably in the range of 1 to 10, more preferably in the range of 1 to 5. If the degree of entanglement exceeds 10, the fiber bundle becomes too converging, and the water permeation into the fiber bundle becomes worse, so that the dispersibility during paper making becomes worse.

  The fiber bundle made of the carbon fiber filament of the present invention is made up of bundles of hundreds to tens of thousands of known carbon fiber filaments such as polyacrylonitrile (PAN), rayon, and pitch systems, and has particularly high strength. A PAN-based carbon fiber from which a fiber bundle made of carbon fiber filaments can be easily obtained is preferable for obtaining a reinforcing effect. Further, from the viewpoint of unwinding property, scratch resistance, dispersibility, etc. in the subsequent papermaking process, as a final product, the single yarn fineness of the carbon fiber filament is 0.1 to 3.0 dtex. The total number of single yarns is preferably 100 to 100,000, more preferably 1000 to 24,000, and particularly preferably 1,000 to 9000.

Further, the strength and elastic modulus of the carbon fiber filament are not particularly limited, but from the viewpoint of the paper characteristics as the carbon fiber papermaking, the strength of the filament is preferably 100 to 1000 kgf / mm ² , and 200 to 700 kgf / mm ² is more preferred. Moreover, 10-100 t / mm < ² > is preferable and the elastic modulus of this filament has more preferable 15-60 t / mm < ² >. The carbon fiber filament includes carbonized fiber and graphitized fiber.

  When paper is made by cutting the carbon fiber of the present invention, the cut length is not particularly limited, but the effect of the present invention, that is, carbon fiber that can be uniformly dispersed in a short time when paper is made. In addition, 3 to 30 mm is preferable, 3 to 12 mm is more preferable, and 3 to 9 mm is particularly preferable in order to sufficiently bring out the effect of obtaining smooth and strong papermaking.

  Details will be described below by taking the case of a PAN-based carbon fiber as an example. As the spinning method, a wet method, a dry method, a dry-wet method, and the like can be adopted. However, a wet method is preferably employed in which a fiber having an appropriate sizing property can be obtained and the effects of the present invention can be easily obtained. As the spinning dope, a polyacrylonitrile homopolymer or a solution or suspension of a copolymer component can be used. The spinning dope is solidified, washed with water, and stretched, and then an oil agent is applied to obtain a carbon fiber precursor. The precursor is subjected to flameproofing treatment and carbonization treatment to obtain carbonized fibers, or further graphitized as necessary to obtain graphitized fibers. The obtained carbonized fibers and graphitized fibers are subjected to electrolytic surface treatment and sizing agent addition in order to improve papermaking process passability and papermaking quality stability, and become the carbon fiber filament of the present invention.

The specific means for obtaining the carbon fiber of the present invention is not particularly limited,
For example, there are the following means. That is, by changing the physical or chemical structure of the fiber surface of the carbon fiber filament, the fiber-to-fiber static friction coefficient is changed to 0.01 to 0.3 carbon fiber filament, and the water washing durability is not hydrophilic. Water penetrability is 1 mg / g or more before water washing and 0 after water washing by adding a natural sizing agent or specifying a bundle form so as to utilize a capillary phenomenon as a fiber bundle made of carbon fiber filaments. Carbon fiber filaments of 5 mg / g or less can be obtained.

  In order to set the fiber-fiber static friction coefficient of the carbon fiber filament to 0.01 to 0.3, for example, the atomic ratio of surface oxygen atoms to carbon atoms (number of oxygen atoms / carbon by X-ray photoelectron spectroscopy). The number of atoms) is preferably 0.35 or less, more preferably 0.20 or less, and particularly preferably 0.10 or less. The chemical structure of the carbon fiber filament surface can be changed by coating with a strong film of a smoothing agent such as silicone. Further, the physical structure of the carbon fiber filament surface can be changed by coating the surface of the carbon fiber filament with a strong film of a smoothing agent such as silicone.

  As the silicone that forms a strong film on the surface of the carbon fiber filament, a reactive modified silicone is preferably used. As the modified silicone, an amino-modified silicone having a modified amount of 0.1 to 10% by weight is used. An epoxy-modified silicone having a modification amount of 0.1 to 10% by weight is more preferably used. Each of the reactive modified silicones can be used alone or in combination, and the amount of adhesion thereof is preferably 0.01 to 5% by weight and 0.01 to 3% by weight based on the carbon fiber filament. Is more preferable, and 0.01 to 0.1% is more preferable. When the content exceeds 5% by weight, the dispersibility during paper production is deteriorated due to pseudo-adhesion between filament single yarns via a modified silicone. Conversely, if it is less than 0.01%, the smoothing effect by silicone cannot be expected.

  In order to increase the water permeability of the carbon fiber to 1 mg / g or more, for example, the carbon fiber is sized with a sizing agent containing a hydrophilic compound having no water washing durability represented by the general formula (1), or as described later. The bundle form can be specified so that the capillary phenomenon as the carbon fiber bundle can be used.

R1O-POA-R2 (1)
(Here, POA: polyoxyalkylene composed of at least one alkylene oxide having 2 to 4 carbon atoms, R1, R2: aliphatic hydrocarbon group having 1 to 50 carbon atoms, aromatic carbonization having 1 to 50 carbon atoms) Any one selected from a hydrogen group, an alicyclic hydrocarbon group having 1 to 50 carbon atoms, and hydrogen, O: oxygen.)
The basic structure of the compound represented by the general formula (1) is a polyoxyalkylene structure, which improves the convergence and dispersibility of the carbon fiber. In the general formula (1), POA may be a polyoxyalkylene in which an alkylene oxide having 2 to 4 carbon atoms is repeated alone, or a polyoxyalkylene in which at least two kinds of alkylene oxides having 2 to 4 carbon atoms are copolymerized. But it ’s okay. In consideration of convergence and hydrophilicity, polyoxyethylene obtained by repeating ethylene oxide having 2 carbon atoms alone in the range of 4 to 100, preferably 4 to 50 is preferable. In the general formula (1), R1 and R2 are each an aliphatic hydrocarbon group having 1 to 50 carbon atoms, an aromatic hydrocarbon group having 1 to 50 carbon atoms, an alicyclic hydrocarbon group having 1 to 50 carbon atoms, Either is acceptable. In consideration of smoothness and hydrophilicity, the number of carbon atoms is preferably 5 to 30.

  Although the compound of General formula (1) may be individual, you may mix another compound. In the case of mixing in consideration of hydrophilicity, the compound of the general formula (1) is preferably 10 to 100% by weight, more preferably 50 to 100% by weight. The adhesion amount of the sizing agent containing the compound of the general formula (1) is preferably 0.1 to 5.0% by weight, more preferably 0.5 to 3.0% by weight with respect to the carbon fiber. It is good.

In addition, in order to be able to use the effect of the capillary action of the carbon fiber bundle, the surface fibril of the carbon fiber is enlarged by firing with a carbon fiber precursor whose surface fibril is enlarged by wet spinning, or the carbon fiber bundle It is also effective to use a twisted yarn by twisting 1 to 100 turns / m, more preferably 5 to 30 turns / m.
In the present invention, Sr / Sp, which is the ratio of the actual surface area Sr of carbon fiber filaments to the projected area Sp, is used as a scale representing the size of the surface fibrils for the carbon fiber filaments. The ratio Sr / Sp between the actual surface area Sr and the projected area Sp can be measured as follows. That is, first, a carbon fiber bundle is cut into a length of several mm, and single fibers are extracted. Next, a single fiber is fixed on a silicon wafer using a silver paste, and an image of a three-dimensional surface shape is obtained using an atomic force microscope, for example, a Dimension 3000 stage system of a Digitalscopes Nanoscope IIIa atomic force microscope. . The scanning mode is a tapping mode, and for example, an Olympus Optical Co., Ltd. Si cantilever integrated probe OMCL-AC120TS is used. The scanning speed is 0.4 Hz, the number of pixels is 512 × 512, and the measurement atmosphere is 25 ± 2 ° C. air. Next, the obtained image is subjected to data processing using the software Nanoscope III version 4.22r2 attached to the atomic force microscope, filtered using a first order filter, a lowpass filter, and a third order plane fit filter. The actual surface area Sr and the projected area Sp are calculated for the entire obtained image, and the ratio thereof, that is, Sr / Sp is obtained. Note that the projected area is a projected area on a cubic curved surface that approximates the curvature of the curved surface, considering that the single fiber has a curved surface. And the said measurement is performed about five places arbitrarily selected about one single fiber, and let the ratio Sr / Sp be the arithmetic mean value of three places except the maximum value and the minimum value. The number of n in the Sr / Sp measurement is 3, and is determined as a simple average value.
As such Sr / Sp, in order to utilize the effect of the capillary phenomenon of the carbon fiber bundle, it is preferable to set the range of 1 ≦ Sr / Sp <1.1, and 1.03 <Sr / Sp <1.07. More preferably.
Further, for example, the total number of single yarns constituting the carbon fiber bundle is preferably 1000 to 24000, more preferably 1000 to 9000, and the carbon fiber bundle is preferably 1 to 100 turns / m, more preferably 5 to 30 turns / Preferably, the carbon fiber bundle is 1 to 10 kg / bundle, more preferably 4 to 8 kg / bundle at the time of sizing treatment (curing on the carbon fiber surface of the sizing agent). By applying a pressure contact force, the flatness and the entanglement degree of the carbon fiber bundle can be set to the above-described ranges, thereby making it possible to further utilize the effect of the carbon fiber bundle due to the capillary phenomenon or the like.

Hereinafter, the present invention will be described in more detail with reference to examples. In addition, flatness, entanglement degree in this example,
The water permeability and the fiber-fiber static friction coefficient were determined by the following methods, respectively.
(1) Water penetration degree 25 cm × 25 cm (No. 40 / No. 40: T120 / L120 (inch)) down proof is packed with 25 g of carbon fiber bundles (3300 to 26400 dtex), and JIS-L1096-1999 “General Wash with water once in accordance with Method A (method using a stirring type washing machine) described in 8.23.1 of “Textile Testing Method” to obtain a carbon fiber bundle sample after water washing. In addition, a sample not washed with water is used as a carbon fiber bundle sample before washing with water.
Using a contact angle meter DCAT11 manufactured by Data Physics, 0.1 mm of a carbon fiber bundle sample (3300 to 26400 dtex) cut to 25 mm is immersed in water and left for 10 minutes, and the sample is absorbed by immersion for 10 minutes. The water per 1 g of the obtained sample is determined as the water permeability [mg / g].
Water permeability = (W2-W1) / (W1 × 1000)
W1: Sample weight before immersion in water [mg]
W2: Sample weight after immersion in water for 10 minutes [mg]
(2) Coefficient of static friction between fiber and fiber Side fabric 25cm x 25cm (40/40: T120 / L120 (inch)) down proof, stuffed with carbon fiber bundle (3300-26400dtex) 25g, JIS-L1096- Wash with water once according to Method A (method using a stirring type washing machine) described in 8.23.1 of 1999 “General Textile Testing Method”. The carbon fiber bundle after water washing was measured according to the static friction coefficient measurement method described in 8.13 of JIS-L1015-1999 “Testing method for chemical fiber staples”. The measuring method is as follows. Of the 25 g carbon fiber bundle after water washing, 20 g is wound around a paper tube, the paper tube is leveled, and fixed so as not to rotate. Using the remaining 5 g, the following procedure is repeated 20 times to calculate the fiber-fiber static friction coefficient μ. Wrapped carbon fiber bundle 0.2g after water washing so that the fiber bundles are in contact with the fixed paper tube for one and a half turn (3π rad), 150 g of load T2 is applied to one end of the sample, and a tension meter is applied to the other end. Turn on. Pull the tension meter downward, measure the tension T1 when the load starts to move, and calculate the fiber-fiber static friction coefficient μ from the following equation. The number of tests is 20 times for 25 g of fiber bundle, and the average value is shown.

μ = Ln (T1 / T2) / θ
μ: Fiber-to-fiber static friction coefficient [-]
T1: Exit tension [g]
T2: Input side tension (load) [g]
θ: contact angle [rad]
(3) Flatness The thickness T [mm] and the width W [mm] of the carbon fiber bundle (3300 to 26400 dtex) are measured with a calibrated caliper, and obtained by the following equation. The measurement locations are 10 locations with a 1 m interval in the longitudinal direction, and the flatness of each location is calculated and expressed as an average value.

Flatness = W / T
W: Width of fiber bundle [mm]
T: Fiber bundle thickness [mm]
(4) Entanglement degree It measured according to the entanglement degree measuring method of JIS-L1013 "Chemical fiber filament yarn test method". The measuring method is as follows. One end of a carbon fiber bundle sample (3300 to 26400 dtex) is attached to an upper grip portion of a drooping device having appropriate performance, a load (100 g) is suspended at a position 1 m below the grip portion, and the sample is suspended vertically. A hook (wire shape with a diameter of 1 mm) is inserted so as to divide the fiber bundle into two at a point 1 cm below the upper grip part of the sample. A predetermined load (10 g) is attached to the other end of the hook, and the hook is lowered at a speed of about 2 cm / second. The hook lowering distance L [mm] to the point where the hook stops due to the yarn entanglement is obtained, and the following equation is obtained. The above operation is repeated 50 times (1 time / m × 50), and the average value is expressed.

Degree of confounding = 1000 / L
L: Descent distance of hook [mm]
(5) Dispersion After throwing a carbon fiber bundle sample (3300 to 26400 dtex) cut to a length of 6 mm into 100 ml of water stirred at a speed of 500 rpm, the lump of the fiber bundle is dispersed and disappears. Measure the time [seconds] required. The above operation is repeated 10 times (10 samples × 1 time), and the average value is expressed. It is desirable to be within 20 seconds.

Example 1
After polymerizing 99.9 mol% of acrylonitrile, 0.5 mol% of allyl sulfonic acid soda and 0.5 mol% of 2-hydroxyethylacrylonitrile by a solution polymerization method using dimethyl sulfoxide as a solvent, Then, it was drawn into a dimethyl sulfoxide aqueous solution by a wet spinning method at a draw ratio of 13.0 and washed with water to obtain an acrylic yarn that becomes a carbon fiber precursor having a single yarn fineness of 1.1 dtex and a single yarn number of 3000. The raw yarn is twisted so as to have a twist number of 15 T / m and then heated in air at 250 ° C. to obtain an oxidized fiber having a moisture content of 4.0% by weight while being drawn at a draw ratio of 1.05. It was. This oxidized fiber was carbonized in a nitrogen atmosphere at 1400 ° C. to obtain carbonized fiber having the number of oxygen atoms / number of carbon atoms = 0.10 on the fiber surface. Without electrolytic surface treatment of this carbonized fiber, polyoxyethylene oleyl ether was attached by a dip method so that the amount of attachment was 1% by weight, and then dried by applying a pressure of 6 kg / bundle with hot air at 150 ° C. By performing (curing), carbon fibers with Sr / Sp = 1.05 shown in Table 1 were obtained.

Example 2
The carbonized fiber obtained in Example 1 was anodized in an aqueous ammonium bicarbonate solution, and the number of oxygen atoms / number of carbon atoms on the fiber surface was set to 0.23. Next, polyoxyethylene oleyl ether was attached by a dip method so that the attached amount was 1% by weight, and dried (curing) while applying a pressure of 6 kg / bundle with hot air at 150 ° C. The carbon fiber of Sr / Sp = 1.05 shown in FIG.

Example 3
The spinning stock solution used in Example 1 was drawn in a dimethyl sulfoxide aqueous solution by a dry and wet spinning method at a draw ratio of 13.0, washed with water, and a carbon fiber precursor having a single yarn fineness of 1.1 dtex and a single yarn number of 24,000, Acrylic yarn was obtained. The raw yarn was heated in air at 250 ° C., and an oxidized fiber having a moisture content of 4.0% by weight was obtained while drawing at a draw ratio of 1.05. This oxidized fiber was carbonized in a nitrogen atmosphere at 1400 ° C. to obtain a carbonized fiber. This carbonized fiber was anodized in an aqueous solution of ammonium bicarbonate, and the number of oxygen atoms / number of carbon atoms on the fiber surface was set to 0.25. Next, an amino-modified silicone having an amino equivalent of 2000 and a viscosity of 2000 centipoise is emulsified with a nonionic surfactant at a ratio of 8: 2 (weight ratio) so that the adhesion amount becomes 1 wt% by the dip method. It was allowed to adhere and dried (curing) while applying a pressure of 7 kg / bundle with hot air at 150 ° C. Furthermore, polyoxyethylene oleyl ether was attached by a dip method so that the amount of attachment was 1% by weight, and dried (curing) while applying a pressure of 7 kg / bundle with hot air at 150 ° C. The carbon fiber of Sr / Sp = 1.02 shown was obtained.

Example 4
The spinning dope used in Example 1 was drawn in a dimethyl sulfoxide aqueous solution by a wet spinning method at a draw ratio of 13.0 and washed with water to obtain a carbon fiber precursor having a single yarn fineness of 1.1 dtex and a single yarn number of 3000. Acrylic raw yarn was obtained. The raw yarn was heated in air at 250 ° C., and an oxidized fiber having a moisture content of 4.0% by weight was obtained while drawing at a draw ratio of 1.05. This oxidized fiber was carbonized in a nitrogen atmosphere at 1400 ° C. to obtain a carbonized fiber. This carbonized fiber was anodized in an aqueous solution of ammonium bicarbonate, and the number of oxygen atoms / number of carbon atoms on the fiber surface was set to 0.15. Next, an amino-modified silicone having an amino equivalent of 2000 and a viscosity of 2000 centipoise is emulsified with a nonionic surfactant at a ratio of 8: 2 (weight ratio), and the adhesion amount is 0.05% by dip method. And dried (curing) while applying a pressure of 6 kg / bundle with hot air at 150 ° C. Furthermore, polyoxyethylene oleyl ether was attached by a dip method so that the amount of attachment was 1% by weight, and dried (curing) while applying a pressure of 6 kg / bundle with hot air at 150 ° C. The carbon fiber of Sr / Sp = 1.05 shown was obtained.

Example 5
The carbonized fiber obtained in Example 1 was anodized in an aqueous ammonium bicarbonate solution, and the number of oxygen atoms / the number of carbon atoms on the fiber surface was set to 0.25. Next, polyoxyethylene oleyl ether was attached by a dip method so that the attached amount was 5% by weight, and dried (curing) while applying a pressure of 6 kg / bundle with hot air at 150 ° C. The carbon fiber of Sr / Sp = 1.05 shown in FIG.

Example 6
The carbonized fiber obtained in Example 1 was anodized in an aqueous ammonium bicarbonate solution, and the number of oxygen atoms / number of carbon atoms on the fiber surface was set to 0.23. Next, polyoxyethylene oleyl ether is attached by a dip method so that the attached amount is 0.1% by weight, and dried (curing) while applying a pressure of 6 kg / bundle with hot air at 150 ° C. Carbon fibers with Sr / Sp = 1.05 shown in Table 1 were obtained.

Example 7
The spinning dope used in Example 1 was drawn into a dimethyl sulfoxide aqueous solution by a wet spinning method at a draw ratio of 13.0 and washed with water to obtain a carbon fiber precursor having a single yarn fineness of 1.1 dtex and a single yarn number of 6000. Acrylic raw yarn was obtained. The raw yarn is twisted to a twist number of 100 T / m and then heated in air at 250 ° C. to obtain an oxidized fiber having a moisture content of 4.0% by weight while being drawn at a draw ratio of 1.05. It was. This oxidized fiber was carbonized in a nitrogen atmosphere at 1400 ° C. to obtain a carbonized fiber. This carbonized fiber was anodized in an aqueous solution of ammonium bicarbonate, and the number of oxygen atoms / number of carbon atoms on the fiber surface was set to 0.30. Next, polyoxyethylene octyl ether was attached by a dip method so that the amount of attachment was 3% by weight, and dried (curing) while applying a pressure of 6 kg / bundle with hot air at 150 ° C. The carbon fiber of Sr / Sp = 1.05 shown in FIG.

Example 8
The acrylic raw yarn obtained in Example 7 was twisted so as to have a twist number of 3 T / m, heated in air at 250 ° C., and stretched at a draw ratio of 1.05, and a moisture content of 4.0 weight. % Oxidized fiber was obtained. This oxidized fiber was carbonized in a nitrogen atmosphere at 1400 ° C. to obtain a carbonized fiber. This carbonized fiber was anodized in an aqueous solution of ammonium bicarbonate to make the number of oxygen atoms / number of carbon atoms = 0.35 on the fiber surface. Next, polyoxyethylene octyl ether was attached by a dip method so that the amount of attachment was 3% by weight, and dried (curing) while applying a pressure of 6 kg / bundle with hot air at 150 ° C. The carbon fiber of Sr / Sp = 1.05 shown in FIG.

Example 9
The spinning dope used in Example 1 was drawn in a dimethyl sulfoxide aqueous solution by a dry and wet spinning method at a draw ratio of 13.0 and washed with water to obtain a carbon fiber precursor having a single yarn fineness of 1.1 dtex and a single yarn number of 48,000. Acrylic yarn was obtained. The raw yarn was heated in air at 250 ° C., and an oxidized fiber having a moisture content of 4.0% by weight was obtained while drawing at a draw ratio of 1.05. This oxidized fiber was carbonized in a nitrogen atmosphere at 1400 ° C. to obtain a carbonized fiber. This carbonized fiber was anodized in an aqueous solution of ammonium bicarbonate, and the number of oxygen atoms / number of carbon atoms on the fiber surface was set to 0.40. Next, an amino-modified silicone having an amino equivalent of 2000 and a viscosity of 2000 centipoise is emulsified with a nonionic surfactant at a ratio of 8: 2 (weight ratio) so that the adhesion amount becomes 4 wt% by the dip method. It was attached and dried (curing) while applying a pressure of 11 kg / bundle with hot air at 150 ° C. Further, polyoxyethylene lauryl ether was attached by a dip method so that the amount of attachment was 0.5% by weight, and dried (curing) while applying a pressure contact force of 11 kg / bundle with hot air at 150 ° C. The carbon fiber of Sr / Sp = 1.02 shown in 1 was obtained.

Example 10
The spinning dope used in Example 1 was drawn in a dimethyl sulfoxide aqueous solution by a dry and wet spinning method at a draw ratio of 13.0, washed with water, and a carbon fiber precursor having a single yarn fineness of 1.1 dtex and a single yarn number of 12000, Acrylic yarn was obtained. The raw yarn is twisted so as to have a twist number of 200 T / m, and then heated in air at 250 ° C. to obtain an oxidized fiber having a moisture content of 4.0% by weight while drawing at a draw ratio of 1.05. It was. This oxidized fiber was carbonized in a nitrogen atmosphere at 1400 ° C. to obtain a carbonized fiber. The carbonized fiber was anodized in an aqueous solution of ammonium bicarbonate, and the number of oxygen atoms / number of carbon atoms on the fiber surface was set to 0.18. Next, polyoxyethylene lauryl ether was attached by a dip method so that the amount of attachment was 0.5% by weight, and dried (curing) while applying a pressure contact force of 11 kg / bundle with hot air at 150 ° C. Carbon fibers with Sr / Sp = 1.02 shown in Table 1 were obtained.

Example 11
The spinning dope used in Example 1 was drawn in a dimethyl sulfoxide aqueous solution by a dry and wet spinning method at a draw ratio of 13.0, washed with water, and a carbon fiber precursor having a single yarn fineness of 1.1 dtex and a single yarn number of 12000, Acrylic yarn was obtained. The raw yarn was heated in air at 250 ° C., and an oxidized fiber having a moisture content of 4.0% by weight was obtained while drawing at a draw ratio of 1.05. This oxidized fiber was carbonized in a nitrogen atmosphere at 1400 ° C. to obtain a carbonized fiber. This carbonized fiber was anodized in an aqueous solution of ammonium bicarbonate, and the number of oxygen atoms / number of carbon atoms on the fiber surface was set to 0.25. Next, polyoxyethylene lauryl ether is attached by dip method so that the amount of attachment is 0.5% by weight, and dried (curing) while applying a pressure of 0.5 kg / bundle with hot air at 150 ° C. Thus, carbon fibers with Sr / Sp = 1.02 shown in Table 1 were obtained.

Comparative Example 1
The spinning dope used in Example 1 was washed with water in a dimethyl sulfoxide aqueous solution by a dry and wet spinning method and drawn at a draw ratio of 13.0 to obtain a carbon fiber precursor having a single yarn fineness of 1.1 dtex and a single yarn number of 24,000. Acrylic raw yarn was obtained. The raw yarn was heated in air at 250 ° C. to obtain an oxidized fiber having a moisture content of 4.0% while drawing at a draw ratio of 1.05. This oxidized fiber was carbonized in a nitrogen atmosphere at 1400 ° C. to obtain a carbonized fiber. The carbonized fiber was anodized in an aqueous solution of ammonium bicarbonate, and the number of oxygen atoms / number of carbon atoms on the fiber surface was set to 0.18. Next, glycerin is attached by a dip method so that the amount of attachment is 1% by weight, and then dried (curing) while applying a pressure of 7 kg / bundle with hot air at 150 ° C., as shown in Table 1. A carbon fiber with Sr / Sp = 1.02 was obtained.

Comparative Example 2
The spinning dope used in Example 1 was drawn in a dimethyl sulfoxide aqueous solution by a dry and wet spinning method at a draw ratio of 13.0, washed with water, and a carbon fiber precursor having a single yarn fineness of 1.1 dtex and a single yarn number of 12000, Acrylic yarn was obtained. The raw yarn was heated in air at 250 ° C., and an oxidized fiber having a moisture content of 4.0% by weight was obtained while drawing at a draw ratio of 1.05. This oxidized fiber was carbonized in a nitrogen atmosphere at 1400 ° C. to obtain a carbonized fiber. This carbonized fiber was anodized in an aqueous solution of ammonium bicarbonate, and the number of oxygen atoms / number of carbon atoms on the fiber surface was set to 0.30. Next, an amino-modified silicone having an amino equivalent of 2000 and a viscosity of 2000 centipoise is emulsified with a nonionic surfactant at a ratio of 8: 2 (weight ratio) so that the adhesion amount becomes 6 wt% by the dip method. It was attached and dried (curing) while applying a pressure of 11 kg / bundle with hot air at 150 ° C. Furthermore, polyoxyethylene oleyl ether was attached by a dip method so that the amount of attachment was 0.3% by weight, and dried (curing) while applying a pressure of 11 kg / bundle with hot air at 150 ° C. The carbon fiber of Sr / Sp = 1.02 shown in 1 was obtained.

Comparative Example 3
The spinning dope used in Example 1 was drawn in a dimethyl sulfoxide aqueous solution by a wet spinning method at a draw ratio of 13.0 and washed with water to obtain a carbon fiber precursor having a single yarn fineness of 1.1 dtex and a single yarn number of 3000. Acrylic raw yarn was obtained. The raw yarn is twisted so as to have a twist number of 200 T / m and then heated in air at 250 ° C. to obtain an oxidized fiber having a moisture content of 4.0% by weight while being drawn at a draw ratio of 1.05. It was. This oxidized fiber was carbonized in a nitrogen atmosphere at 1400 ° C. to obtain a carbonized fiber. This carbonized fiber was anodized in an aqueous solution of ammonium bicarbonate, and the number of oxygen atoms / number of carbon atoms on the fiber surface was set to 0.40. Next, polyoxyethylene oleyl ether is attached by dip method so that the attached amount becomes 1.0% by weight, and dried (curing) while applying a pressure of 0.5 kg / bundle with hot air at 150 ° C. Thus, carbon fibers with Sr / Sp = 1.05 shown in Table 1 were obtained.

  About each sample of these Examples and Comparative Examples, (1) water penetration degree, (2) fiber-fiber static friction coefficient, (3) flatness, (4) entanglement degree, (5) evaluation of dispersity The results are shown in Table 2.

  The evaluation was made in four steps, with ◎ being excellent, ○ being good, △ being slightly bad, and × being impossible, and the determination results are also shown in Table 2. In the examples of the present invention, ◎ (excellent) and ◯ (good) are acceptable.

  As a result, as can be seen from Tables 1 and 2, all of the carbon fibers of Examples 1 to 11 of the present invention had good dispersibility, whereas they were preferable as raw materials for papermaking. The carbon fibers of Comparative Examples 1 to 3 have poor dispersibility and were not preferable as a papermaking raw material.

Claims (6)

A fiber bundle made of carbon fiber filaments has a water permeability of 1 mg / g or more before water washing, 0.5 mg / g or less after water washing, and the fibers of the fiber bundle after water washing specified in the text- A carbon fiber for papermaking, wherein a coefficient of static friction between fibers is 0.01 to 0.3. The carbon fiber for papermaking according to claim 1, wherein the flatness and the entanglement degree of the fiber bundle are 1 to 50 and 1 to 10, respectively. 3. The carbon fiber filament according to claim 1, wherein the carbon fiber filament has been sized with a sizing agent containing a hydrophilic compound having a water-washing durability and represented by the general formula (1). 4. Carbon fiber for papermaking.
R1O-POA-R2 (1)
(Here, POA: polyoxyalkylene composed of at least one alkylene oxide having 2 to 4 carbon atoms, R1, R2: aliphatic hydrocarbon group having 1 to 50 carbon atoms, aromatic carbonization having 1 to 50 carbon atoms) Any one selected from a hydrogen group, an alicyclic hydrocarbon group having 1 to 50 carbon atoms, and hydrogen, O: oxygen.) The carbon fiber for papermaking according to any one of claims 1 to 3, wherein an atomic ratio of oxygen atoms to carbon atoms on the surface of the carbon fiber filament by X-ray photoelectron spectroscopy is 0.35 or less. The carbon fiber for papermaking according to any one of claims 1 to 4, wherein the fiber bundle made of the carbon fiber filament is a twisted yarn twisted at 1 to 100 T / m. The carbon fiber for papermaking according to any one of claims 1 to 5, wherein the carbon fiber filament is coated with a silicone film.