JP2009030215A - Carbon fiber and molded article using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide carbon fibers which can give heat-releasing materials having heat releasability and surface characteristics in a proper range. <P>SOLUTION: The carbon fibers are produced by spinning an optically anisotropic pitch in a state that an introduction angle α, a L/D ratio, wherein L is the length of extrusion port, and D is the diameter of the extrusion port, and a viscosity at a spinning temperature of the optically anisotropic pitch are controlled, and then infusibilizing, carbonizing and graphitizing the obtained pitch fibers, and having the layer surface direction spreading La of graphite crystal crystallite, electric resistivity, heat conductivity, and end face and front face smoothness in proper ranges, respectively, to a composition using the carbon fibers and to a molded article using the carbon fibers. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a carbon fiber having a high thermal conductivity and excellent surface smoothness suitable for use as a heat conductive material. Furthermore, the present invention relates to a thermally conductive molded body using pitch-based carbon fibers.

  High-performance carbon fibers can be classified into PAN-based carbon fibers made from polyacrylonitrile (PAN) and pitch-based carbon fibers made from a series of pitches. Carbon fibers are widely used in aerospace applications, construction / civil engineering applications, sports / leisure applications, etc., taking advantage of their extremely high strength and elastic modulus compared to ordinary synthetic polymers.

  Carbon fibers are said to have higher thermal conductivity and better heat dissipation than ordinary synthetic polymers. Carbon materials such as carbon fibers are said to achieve high thermal conductivity by phonon movement. Phonons are well transmitted in materials where the crystal lattice is developed. It cannot be said that a commercially available PAN-based carbon fiber has a sufficiently developed crystal lattice, and its thermal conductivity is usually smaller than 200 W / (m · K), and is not necessarily suitable from the viewpoint of thermal management. It's hard to say. On the other hand, it is recognized that pitch-based carbon fibers have high graphitization properties, so that the crystal lattice is well developed, and it is easy to achieve high thermal conductivity compared to PAN-based carbon fibers.

  In recent years, with the increase in the density of heat-generating electronic components and the reduction in size, thickness, and weight of electronic devices such as portable personal computers, there has been an increasing demand for lower heat resistance of heat-dissipating members used in them. Further improvement of characteristics is required. The heat radiating member includes a thermally conductive sheet made of a cured product filled with a thermally conductive filler, a thermally conductive spacer made of a cured product having flexibility and filled with a gel material, and a liquid matrix. Flowable heat conductive paste filled with heat conductive filler, heat conductive paint diluted with solvent to further improve flowability, heat with curable substance filled with heat conductive filler Examples thereof include a conductive adhesive, a phase change type heat radiation member utilizing a phase change of resin, and the like.

In order to improve the thermal conductivity of these heat radiating members, further high thermal conductivity of the thermal conductive material used here is required. Patent Document 1 introduces a pitch-based carbon fiber exhibiting a thermal conductivity exceeding 1100 W / m · K.
Japanese Patent No. 29985455

  However, the technique described in Patent Document 1 enhances the pitch orientation in order to exhibit high thermal conductivity. Therefore, when graphitizing at a temperature of 2500 ° C. or higher, the carbon fiber is easily broken. If the surface smoothness of the carbon fiber is lowered due to cracking or the like, the viscosity when the matrix and the carbon fiber are mixed increases, and there arises a problem that the moldability is lowered. Therefore, from the viewpoint that a heat conductive material having excellent thermal conductivity and excellent moldability is required, a carbon fiber having high thermal conductivity and excellent surface smoothness suitable for use as a heat conductive material. It is an object of the present invention to provide

  In view of providing an excellent heat conductive material for producing a heat dissipation material excellent in thermal conductivity and excellent in moldability, the present inventors provide a pitch-based carbon fiber manufactured under specific manufacturing conditions. The present invention has been found out to satisfy the objective of the present invention.

  That is, an object of the present invention is to provide a carbon fiber having a high thermal conductivity and excellent surface smoothness, and an optically anisotropic pitch having a viscosity of 30 to 250 poise (3 to 25 Pa · S). ) In a temperature condition in the range of 10) to 55 °, and a nozzle having a ratio L / D of the discharge port length L to the discharge port diameter D in the range of 6 to 20 is used. A pitch-based carbon fiber obtained by spinning by a melt-blowing method to obtain pitch fibers, in which the obtained pitch fibers are infusible, and then carbonized and / or graphitized. It can be achieved by pitch-based carbon fibers in a range of ˜200 nm, an electrical resistivity of greater than 1.1 and less than 4.0 μΩm, and a thermal conductivity of 250 to 1100 W / m · K.

  In the present invention, the graphene sheet is closed in the filler end face observation with the transmission electron microscope observed with the transmission electron microscope, the observation surface with the scanning electron microscope is substantially smooth, and the average average fiber diameter is This can be achieved with pitch-based carbon fibers having a fiber diameter dispersion percentage (CV value) of 2 to 20 μm and an average fiber diameter of 5 to 20.

  Furthermore, the present invention comprises a composition comprising a pitch-based carbon fiber and a thermoplastic resin and / or a thermosetting resin, the composition containing 3 to 200 parts by volume of the carbon fiber relative to 100 parts by volume of the resin, and a thermoplastic resin. At least selected from the group consisting of polycarbonates, polyesters, aliphatic polyamides, aromatic polyamides, polyolefins, polyether ketones, polyether sulfones, polyphenylene sulfides, and acrylonitrile / butadiene / styrene copolymer resins The composition, which is a kind of resin, and the thermosetting resin are selected from the group consisting of epoxies, acrylics, urethanes, silicones, phenols, imides, thermosetting modified PPEs, and thermosetting PPEs A composition that is at least one kind of resin, heat transfer in a state of being formed into a flat plate shape A composition having a rate of 2 W / (m · K) or more, the above-mentioned composition is formed by injection molding, press molding, calendar molding, roll molding, extrusion molding, cast molding, and blow molding. It can be achieved by a molded body obtained by molding by at least one method selected from the group consisting of:

  The pitch-based carbon fiber of the present invention controls the electrical resistivity within an appropriate range and enables high performance of the heat dissipation material. The pitch-based carbon fiber of the present invention has excellent moldability due to excellent high thermal conductivity and excellent surface smoothness, and is suitably used for heat dissipation materials such as electronic parts.

Next, embodiments of the present invention will be described sequentially.
The electrical resistivity of the pitch-based carbon fiber of the present invention is in the range of more than 1.1 and less than 4.0 μΩm. When the electrical resistivity is less than 4.0 μΩm, high thermal conductivity is exhibited. Further, when spinning under conditions such that the electrical specific resistance is greater than 1.1 μΩm, the surface smoothness of the carbon fiber is maintained. The electrical resistivity of the pitch-based carbon fiber is fixed at both ends of the pitch-based carbon fiber with a conductive paste such as silver paste, the electrical resistance between the terminals is measured, the distance between the terminals and the fiber diameter of the pitch-based carbon fiber are obtained, It can be obtained by calculating from there.

The thermal conductivity of the pitch-based carbon fiber is in the range of 250 to 1100 W / m · K. The thermal conductivity shown here can be obtained by calculation from the following relational expression (refer to Japanese Patent No. 3648865) of the thermal conductivity and the electrical resistance from the electrical specific resistance, and K = 1272.4 / ER-49.4.
(K is the thermal conductivity of carbon fiber, ER is the electrical resistivity of carbon fiber)
Substantially synonymous with electrical resistivity.

  The pitch-based carbon fiber of the present invention preferably has a structure in which the graphene sheet is closed when the shape of the filler end face is observed with a transmission electron microscope. When the end face of the filler is closed as a graphene sheet, generation of extra functional groups and localization of electrons due to shape do not occur, so the concentration of impurities such as water can be reduced, For example, it is preferable from the viewpoint that hydrolysis resistance is improved when it is combined with a resin that is affected by hydrolysis, such as a condensation polymer. In addition, vertical cracking is likely to occur due to the shrinkage of carbon fibers during graphitization, but this is suppressed when the end face is closed. In particular, in the filler having a fiber length shorter than 1 mm as in the present invention, the structure in which the graphene sheet is closed is particularly preferable because the ratio of the end face to the filler surface area is high.

  Note that the graphene sheet is closed means that the end of the graphene sheet itself constituting the carbon fiber is not exposed at the end of the carbon fiber, the graphite layer is curved in a substantially U shape, and the curved portion is the end of the carbon fiber. It is in the state exposed to the part.

  The pitch-based carbon fiber of the present invention preferably has a substantially smooth observation surface with a scanning electron microscope. Here, the term “smooth” means that surface irregularities are not observed, surface cracks are not confirmed, and carbon fiber cracks are not confirmed in observation with a scanning electron microscope. Here, the term “substantially smooth” means that the number of the defective portions is 10 or less per carbon fiber in the visual field (magnification 1000) in observation with an electron microscope.

  When the surface to be observed with a scanning electron microscope is substantially smooth, when a pitch-based carbon fiber and a matrix are mixed to create a thermally conductive molded body, the interaction between the pitch-based carbon fiber and the matrix is reduced, As a result, the viscosity of the mixture of pitch-based carbon fiber and matrix is reduced, and the moldability is improved. Conversely, if the surface of the pitch-based carbon fiber is not smooth, the interaction between the pitch-based carbon fiber and the matrix increases, and as a result, the viscosity of the mixture of the pitch-based carbon fiber and the matrix increases and the moldability decreases.

  A pitch-based carbon fiber having a graphene sheet closed or a smooth observation surface in filler end face observation with a transmission electron microscope can be obtained by graphitizing after pulverizing the carbon fiber filler, as will be described in detail later. When pulverized after graphite, the end face once closed due to graphitization reopens, or the pitch-based carbon fiber has more irregularities, and irregularities are observed on the observation surface with a scanning electron microscope.

  The average fiber diameter of the pitch-based carbon fiber of the present invention is desirably in the range of 2 to 20 μm. When the thickness is 2 μm or less, the shape of the mat used as a raw material may not be maintained, and productivity is poor. When the fiber diameter exceeds 20 μm, unevenness in the infusibilization process becomes large, and a part where fusion occurs partially occurs. More preferably, it is 5-15 micrometers. The average fiber diameter of the pitch-based carbon fiber is determined by observing with an optical microscope and measuring with a scale as shown in JIS R7607.

  In addition, the CV value calculated | required as a percentage of fiber diameter dispersion | distribution with respect to an average fiber diameter needs to be 5-20. It is impossible in the process that the CV value is less than 5. On the other hand, if the CV value exceeds 20, there is a high possibility that fibers having a diameter of 20 μm or more will cause trouble due to infusibilization, which is not preferable from the viewpoint of productivity.

  In the pitch-based carbon fiber of the present invention, the spread La in the layer surface direction of the graphite crystallite derived from the growth direction of the hexagonal network surface is in the range of 30 to 200 nm. When La is in this range, it means that the degree of graphitization of the pitch-based carbon fiber is appropriate, and an appropriate electrical resistivity and thermal conductivity are exhibited. The reason why the spread of the surface fragrance of the graphite crystallite is important is that heat conduction is mainly carried by phonons, and that phonons are generated by crystals. When La is less than 30 nm, the degree of graphitization is insufficient, and conversely, when La exceeds 200 nm, it means that graphitization has progressed too much. The spread La in the layer surface direction of the graphite crystallite derived from the growth direction of the hexagonal mesh surface can be determined by a known method, and is determined by the diffraction line from the (110) plane of the carbon crystal obtained by the X-ray diffraction method. Can do.

  In order to obtain the above pitch-based carbon fiber, it is necessary to control the shearing force applied to the optically anisotropic pitch and set the spinning conditions so that the aromatic rings are appropriately arranged. Hereinafter, each process is demonstrated about the suitable manufacturing method of the pitch-type carbon fiber of this invention taking a melt blow method as an example.

  Examples of the raw material for the pitch-based carbon fiber of the present invention include condensed polycyclic hydrocarbon compounds such as naphthalene and phenanthrene, and condensed heterocyclic compounds such as petroleum-based pitch and coal-based pitch. Among them, condensed polycyclic hydrocarbon compounds such as naphthalene and phenanthrene are preferable, and optically anisotropic pitch, that is, mesophase pitch is particularly preferable. This is because the mesophase pitch is particularly preferable for improving the thermal conductivity of the carbon fiber because the degree of graphitization is easily improved when the graphitization treatment is performed.

  The softening point of the optically anisotropic pitch serving as the raw material pitch can be determined by the Mettler method, and is preferably 250 ° C. or higher and 350 ° C. or lower. When the softening point is lower than 250 ° C., fusion between fibers and large heat shrinkage occur during infusibilization. On the other hand, when the temperature is higher than 350 ° C., thermal decomposition of the pitch occurs and it becomes difficult to form a yarn.

  The optically anisotropic pitch can be fiberized by melt spinning after being melted and discharged from a nozzle and cooled. Specific examples of the spinning method include a normal spinning method in which a pitch discharged from a die is drawn by a winder, a melt blow method using hot air as an atomizing source, and a centrifugal spinning method in which a pitch is drawn using centrifugal force. Among these, the melt blow method is preferably used for reasons such as control of the radius of curvature and high productivity.

  The optically anisotropic pitch is melt-spun, then infusibilized, fired, pulverized as necessary, and finally graphitized to form pitch-based carbon fibers. The pitch-based carbon fiber of the present invention is preferably characterized in that the graphene sheet is closed in the filler end face observation with a transmission electron microscope. Such pitch-based carbon short fibers are graphitized after milling. It can preferably be obtained by carrying out. Hereinafter, preferred embodiments of the respective steps will be described by taking the melt blow method as an example.

  The temperature at the time of spinning is a temperature at which the viscosity of the optically anisotropic pitch is in the range of 30 to 250 poise (3 to 25 Pa · S). The temperature is more preferably in the range of 50 to 200 poise (5 to 20 Pa · S). As the spinning nozzle, a nozzle having an introduction angle α of 10 to 55 ° and a ratio L / D of the discharge port length L to the discharge port diameter D in the range of 6 to 20 is preferably used. When the spinning conditions are within this range, the shearing force applied to the optically anisotropic pitch can arrange the aromatic rings to some extent. When the spinning condition deviates from this condition, for example, when the shear force is stronger, such as when the viscosity is larger, the introduction angle is smaller, or when the L / D is larger, the alignment is too advanced and graphitization occurs. In addition, the carbon fiber is easily broken, and the surface smoothness of the pitch-based carbon fiber is deteriorated. On the contrary, under conditions where the shearing force is small, such as the viscosity is smaller, the introduction angle is larger, or the L / D is smaller, and the shearing force is small, the aromatic rings are not arranged so much. The degree of graphitization does not improve so much and high thermal conductivity cannot be obtained.

  The pitch fibers drawn out from the nozzle holes are shortened by blowing a gas having a linear velocity of 100 to 10,000 m per minute heated to 100 to 350 ° C. in the vicinity of the thinning point. As the gas to be blown, air, nitrogen, or argon can be used, but air is preferable from the viewpoint of cost performance.

Pitch fibers are collected on a wire mesh belt to form a continuous mat, and further cross-wrapped to form a three-dimensional random mat.
The three-dimensional random mat refers to a mat in which pitch fibers are entangled three-dimensionally in addition to being cross-wrapped. This entanglement is achieved in a cylinder called chimney while reaching the wire mesh belt from the nozzle. Since the linear fibers are entangled three-dimensionally, the characteristics of the fibers that normally exhibit only one-dimensional behavior are reflected in the three-dimensional.

  The three-dimensional random mat made of pitch fibers thus obtained is infusible by a known method. Infusibilization is achieved at 200 to 350 ° C. using air or a gas obtained by adding ozone, nitrogen dioxide, nitrogen, oxygen, iodine, bromine to air. Considering safety and convenience, it is preferable to carry out in the air. The infusibilized pitch fiber is fired at 600-1500 ° C. in vacuum or in an inert gas such as nitrogen, argon, krypton, and then graphitized at 2000-3500 ° C. In many cases, the graphitization is performed in low-cost nitrogen, and graphitization is generally performed by changing the type of the inert gas according to the type of furnace used.

  After infusibilization or firing, the obtained fiber is pulverized. The pulverization can be performed by a known method. Specifically, a cutter, a ball mill, a jet mill, a crusher, or the like can be used. In order to perform milling efficiently, a method of cutting fibers in a direction perpendicular to the fiber axis by rotating a rotor to which blades are attached at high speed is appropriate.

  The above-mentioned milled and sieved fibers are heated to 2300-3500 ° C. and graphitized to obtain the final pitch-based carbon short fibers. Graphitization is carried out in an atmosphere capable of blocking external physical and chemical effects in an Atchison furnace or the like. The graphitization temperature is preferably 2000 to 3500 ° C. in order to increase the thermal conductivity of the carbon fiber. More preferably, it is 2300-3500 degreeC. It is preferable to put it in a graphite crucible at the time of graphitization because the physical and chemical action from the outside can be blocked. The graphite crucible is not limited in size and shape as long as the above-described carbon fiber can be put in a desired amount, but the oxidizing gas in the furnace during graphitization or cooling, or In order to prevent damage to the carbon fiber due to reaction with water vapor, a highly airtight one with a lid can be suitably used.

  In the present invention, the pitch-based carbon fiber may be surface-treated, and then the sizing agent may be added to 0.01 to 10 parts by weight, preferably 0.1 to 2.5 parts by weight with respect to 100 parts by weight of the filler. As the sizing agent, any commonly used sizing agent can be used. Specifically, an epoxy compound, a water-soluble polyamide compound, a saturated polyester, an unsaturated polyester, vinyl acetate, water, alcohol, glycol are used alone or in a mixture thereof. Can do. Such surface treatment is effective in view of increasing the bulk density. However, since the excessive sizing agent is added to the heat resistance, it can be carried out according to the required physical properties.

  A composition in which pitch-based carbon fibers are mixed with a thermoplastic resin and / or a thermosetting resin is also included. At this time, the pitch-based carbon fiber is added in an amount of 3 to 200 parts by volume with respect to 100 parts by volume of the resin. When the addition amount is less than 3 parts by volume, it is difficult to ensure sufficient thermal conductivity. On the other hand, it is often difficult to add more than 200 parts by volume of pitch-based carbon fiber to the resin.

  The resin contains any one or more of a thermoplastic resin and a thermosetting resin, and a thermoplastic resin and a thermosetting resin may be appropriately mixed and used in order to develop desired physical properties in the composite molded body. it can.

  Examples of thermoplastic resins that can be used in the matrix include ethylene-α-olefin copolymers such as polyethylene, polypropylene, and ethylene-propylene copolymers, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, and ethylene-acetic acid. Vinyl copolymer, polyvinyl alcohol, polyacetal, fluororesin (polyvinylidene fluoride, polytetrafluoroethylene, etc.), polyethylene terephthalate, polybutylene terephthalate, polyethylene 2,6 naphthalate, polystyrene, polyacrylonitrile, styrene-acrylonitrile copolymer, ABS Resins, polyphenylene ether (PPE) resins, modified PPE resins, aliphatic polyamides, aromatic polyamides, polyimides, polyamideimides, polymethacrylic acids ( Polymethacrylates such as methyl methacrylate), polyacrylic acids, polycarbonate, polyphenylene sulfide, polysulfone, polyethersulfone, polyethernitrile, polyetherketone, polyetheretherketone, polyketone, liquid crystal polymer, ionomer, etc. It is done.

  Among these, as thermoplastic resins, polycarbonates, polyethylene terephthalates, polybutylene terephthalates, polyethylene 2,6 naphthalates, nylons, polypropylenes, polyethylenes, polyether ketones, polyphenylene sulfides, and acrylonitrile-butadiene-styrene Preferred is at least one resin selected from the group consisting of system copolymer resins.

  In addition, examples of the thermosetting resin include epoxies, acrylics, urethanes, silicones, phenols, imides, thermosetting modified PPEs, thermosetting PPEs, and the like. Even if it uses, you may use in combination of 2 or more types as appropriate.

  The composite material and composite molded body of the present invention are prepared by mixing pitch-based carbon fibers and a resin. When mixing, a kneader, a mixer, a blender, a roll, an extruder, a milling machine, a self-revolving type A mixing device such as a stirrer or a kneading device is preferably used. The composite molded body can be molded by a molding method such as an injection molding method, a press molding method, a calendar molding method, a roll molding method, an extrusion molding method, a casting molding method, or a blow molding method. The molding conditions strongly depend on the method and the matrix. In the case of a thermoplastic resin, the molding is performed in a state where the temperature is higher than the melt viscosity of the resin. In the case where the matrix is a thermosetting resin, a method of applying a curing temperature of the resin in an appropriate mold can be exemplified.

  Further, in the composite material and composite molded body of the present invention, a heat conductive filler other than carbon fibers can be used as necessary. Specifically, metal oxides such as silica, aluminum oxide, magnesium oxide and zinc oxide, metal hydroxides such as aluminum hydroxide and magnesium hydroxide, metal nitrides such as boron nitride and aluminum nitride, silver, gold and copper And metals or alloys such as aluminum, carbon materials such as graphite, expanded graphite, and diamond.

  In the composition of the present invention, glass fiber, potassium titanate whisker, zinc oxide whisker, aluminum borate whisker, aramid fiber, alumina fiber, silicon carbide fiber, ceramic fiber, asbestos fiber, as long as the effects of the present invention are not impaired. Fibrous filler such as stone fiber, metal fiber, wollastonite, zeolite, sericite, kaolin, mica, clay, pyrophyllite, bentonite, asbestos, talc, alumina silicate, etc., calcium carbonate, magnesium carbonate, Non-fibrous fillers such as carbonates such as dolomite, sulfates such as calcium sulfate and barium sulfate, glass beads, glass flakes, ceramic beads, silicon carbide and silica, which may be hollow, Can use two or more of these together It is a function.

  When the composition of the present invention is formed into a flat plate and the thermal conductivity is measured, it shows a thermal conductivity of 2 W / (m · K) or more. The thermal conductivity of 2 W / (m · K) is about one digit higher than that of the resin used as the matrix.

  The composition of the present invention can be used as a heat sink for electronic components by utilizing its high thermal conductivity. In addition, since high thermal conductivity can be obtained by increasing the amount of pitch-based carbon fiber added, even in electronic components, automobiles that require relatively high heat resistance and industrial power modules that require large currents are used. It can be suitably used for a connector or the like. More specifically, it can be used for a heat sink, a semiconductor package component, a heat sink, a heat spreader, a die pad, a printed wiring board, a cooling fan component, a housing, and the like. It can also be used as a part of a heat exchanger. Can be used for heat pipes. Furthermore, it can be suitably used as a radio wave shielding member particularly in the GHz band by utilizing the radio wave shielding properties of pitch-based carbon fibers.

Examples are shown below, but the present invention is not limited thereto.
In addition, each value in a present Example was calculated | required according to the following method.
(1) The viscosity of the optically anisotropic pitch was measured by calculating the shear rate from the discharge amount of the optically anisotropic pitch and the shape of the discharge port and using a Capillograph 1D manufactured by Toyo Seiki Seisakusho under these conditions.
(2) The average fiber diameter of pitch-based carbon fibers was determined from the average value of 60 pitch-based carbon fibers subjected to graphitization using a scale under an optical microscope according to JIS R7607.
(3) The spread La in the layer surface direction of the pitch-based carbon fiber was determined by the Gakushin method by measuring the reflection from the (110) surface appearing in X-ray diffraction.
(4) The electrical resistivity of the pitch-based carbon fiber is fixed using silver paste so that the distance between both ends of the carbon fiber is 1 cm, and 20 electrical resistances at both ends are measured with a tester. Calculated using the radius.
(5) The thermal conductivity of the pitch-based carbon fiber was determined by calculation from the following relational expression (refer to Japanese Patent No. 3648865) of the thermal conductivity and electrical resistance from the electrical specific resistance determined in (4).
K = 1272.4 / ER-49.4
(K is the thermal conductivity of carbon fiber, ER is the electrical resistivity of carbon fiber)
(6) The surface of the pitch-based carbon fiber was observed with 100 carbon fibers with a scanning electron microscope (magnification 1000) to observe cracks and cracks.
(7) The end face of the pitch-based carbon short fiber was observed with a transmission electron microscope at a magnification of 1,000,000 times, magnified on a photograph at a magnification of 4 million times, and a graphene sheet was confirmed.
(8) The thermal conductivity of the flat molded body was measured with QTM-500 manufactured by Kyoto Electronics.

[Example 1]
A pitch made of a condensed polycyclic hydrocarbon compound was used as a main raw material. The optical anisotropy ratio was 100%, and the softening point was 283 ° C. Using a cap with an introduction angle α35 ° C., a discharge port diameter D 0.2 mm, and a discharge port length L 2 mm (L / D = 10), the optical anisotropy pitch temperature at the discharge port is 325 ° C., and 350 ° C. from the slit. Heated air was ejected at a linear velocity of 5500 m / min, and the melt pitch was pulled to produce pitch fibers with an average fiber diameter of 11.0 μm. The viscosity of the optical anisotropic pitch at 325 ° C. was 185 poise (18.5 Pa · S). The spun fibers were collected on a belt to form a mat, and a three-dimensional random mat made of pitch-based short fibers having a basis weight of 320 g / m ^{2 by} cross-wrapping.

This three-dimensional random mat was heated from 170 ° C. to 285 ° C. at an average heating rate of 2 ° C./min to be infusible, and further fired at 800 ° C. This three-dimensional random mat was pulverized at 800 rpm with a cutter (manufactured by Turbo Kogyo) and graphitized at 3000 ° C.
The average thread diameter of the pitch-based carbon fiber after graphitization was 8.8 μm. The spread La in the interlayer direction of the graphite crystallites was 90 nm. The electrical resistivity was 2.2 μΩm, and the thermal conductivity was 500 W / m · K.

  It was confirmed that the graphene sheet was closed on the end face of the pitch-based carbon fiber by observation with a transmission microscope. The surface was substantially smooth with four irregularities as observed with a scanning electron microscope.

  40 parts by weight of the above-described pitch-based carbon fiber and 60 parts by weight of a silicone resin (manufactured by Toray Dow Silicone, SE1740) were kneaded with a self-revolving stirrer (Shinky Awatori Rentaro AR-250) to obtain a composite slurry. This slurry is placed in a square metal frame with a side of 300 mm, pressed with a vacuum press (manufactured by Kitagawa Seiki), and thermoset at 130 ° C., so that a flat carbon fiber / silicone with a thickness of 0.5 mm is obtained. A composite was obtained. It was 5.0 W / (m * K) when the heat conductivity of the produced carbon fiber / silicone composite was measured.

  40 parts by weight of the above pitch-based carbon fiber and 60 parts by weight of a polycarbonate resin (manufactured by Teijin Chemicals, L-1225WP) were kneaded with a biaxial kneader (manufactured by Kurimoto Iron Works) to obtain a master chip. This chip was mixed with an injection molding machine (M-50B manufactured by Meiki Seisakusho Co., Ltd.) to obtain a 2 mm-thick flat plate composite molded body to obtain a carbon fiber / polycarbonate composite. When the thermal conductivity of the produced carbon fiber / polycarbonate composite was measured, it was 2.9 W / (m · K).

  40 parts by weight of the above-described pitch-based carbon fiber and 60 parts by weight of polyphenylene sulfide resin (manufactured by Polyplastics, 0220A9) were kneaded with a biaxial kneader (manufactured by Kurimoto Iron Works) to form a master chip. Using a molding machine (M-50B manufactured by Meiki Seisakusho Co., Ltd.), a 2 mm-thick flat composite molded body was mixed to obtain a carbon fiber / polyphenylene sulfide composite.The heat conduction of the produced carbon fiber / polyphenylene sulfide composite. When the rate was measured, it was 3.3 W / (m · K).

[Example 2]
In Example 1, a pitch-based carbon fiber filler was produced under the same conditions except that the pitch temperature at the discharge port was 335 ° C. The viscosity of the optical anisotropic pitch at 335 ° C. was 90 poise (9 Pa · S).
The average thread diameter of the graphitic carbon fiber after graphitization was 8.0 μm. The spread La in the interlayer direction of the graphite crystallites was 80 nm. The electrical resistivity was 2.8 μΩm, and the thermal conductivity was 440 W / m · K.

It was confirmed that the graphene sheet was closed on the end face of the pitch-based carbon fiber by observation with a transmission microscope. The surface was substantially smooth with four irregularities as observed with a scanning electron microscope.
40 parts by weight of the above-described pitch-based carbon fiber and 60 parts by weight of a silicone resin (manufactured by Toray Dow Silicone, SE1740) were kneaded with a self-revolving stirrer (Shinky Awatori Rentaro AR-250) to obtain a composite slurry. This slurry is placed in a square metal frame with a side of 300 mm, pressed with a vacuum press (manufactured by Kitagawa Seiki), and thermoset at 130 ° C., so that a flat carbon fiber / silicone with a thickness of 0.5 mm is obtained. A composite was obtained. When the thermal conductivity of the produced carbon fiber / silicone composite was measured, it was 4.8 W / (m · K).

[Comparative Example 1]
A pitch-based carbon fiber was produced in the same manner as in Example 1 except that the discharge port length was 1 mm (L / D = 5).
The average thread diameter of the pitch-based carbon fiber after graphitization was 8.3 μm. The spread La in the interlayer direction of the graphite crystallites was 160 nm. The electrical resistivity was 1.0 μΩm, and the thermal conductivity was 1200 W / m · K.

It was confirmed that the graphene sheet was closed on the end face of the pitch-based carbon fiber by observation with a transmission microscope. Moreover, the surface was 19 unevenness | corrugations by observation with the scanning electron microscope, and was not substantially smooth.
40 parts by weight of the above-mentioned pitch-based carbon fiber and 60 parts by weight of a silicone resin (made by Toray Dow Silicone, SE1740) were kneaded with a self-revolving stirrer (Shinky Awatori Rentaro AR-250). I couldn't work on it.

[Comparative Example 2]
In Example 1, pitch-based carbon fibers were produced in the same manner except that the melting temperature of the pitch at the discharge port was changed to 345 ° C. The viscosity of the optical anisotropic pitch at 345 ° C. was 20 poise (2 Pa · S).
The yarn diameter of the pitch-based carbon fiber filler after graphitization was 8.1 μm on average. The spread La in the interlayer direction of the graphite crystallites was 140 nm. The electrical resistivity was 1.0 μΩm, and the thermal conductivity was 1200 W / m · K.

It was confirmed that the graphene sheet was closed on the end face of the pitch-based carbon fiber by observation with a transmission microscope. Further, the surface was 16 uneven as observed by a scanning electron microscope, and was not substantially smooth.
40 parts by weight of the above-mentioned pitch-based carbon fiber and 60 parts by weight of a silicone resin (made by Toray Dow Silicone, SE1740) were kneaded with a self-revolving stirrer (Shinky Awatori Rentaro AR-250). I couldn't work on it.

  The pitch-based carbon fiber of the present invention has excellent thermal conductivity and surface characteristics by controlling the conditions when spinning the pitch fiber, and the composite material using this has high thermal conductivity and moldability. It is possible to have. As a result, it can be used in places where high heat dissipation characteristics are required, and thermal management is ensured.

It is a section explanatory view of a spinning nozzle used for manufacture of pitch system carbon fiber of the present invention.

Claims (8)

  The optically anisotropic pitch has an introduction angle α in the range of 10 to 55 ° under a temperature condition in which the viscosity is in the range of 30 to 250 poise (3 to 25 Pa · S), the discharge port length L and the discharge A pitch fiber is obtained by spinning with a melt blow method using a nozzle having a ratio L / D of the outlet diameter D in the range of 6 to 20, and the obtained pitch fiber is made infusible and then carbonized and / or graphitized. A pitch-based carbon fiber having a spread La in the layer surface direction of graphite crystallites in the range of 30 to 200 nm, an electrical resistivity in the range of greater than 1.1 and less than 4.0 μΩm, and a thermal conductivity of 250. Pitch-based carbon fiber in the range of ˜1100 W / m · K.   The pitch-based carbon fiber according to claim 1, wherein the graphene sheet is closed in the filler end face observation with a transmission electron microscope, and the observation surface with a scanning electron microscope is substantially smooth.   3. The pitch-based carbon according to claim 1, wherein an average fiber diameter is 2 to 20 μm, and a percentage (CV value) of fiber diameter dispersion with respect to the average fiber diameter is in the range of 5 to 20. 4. fiber.   It consists of the pitch-type carbon fiber of any one of Claims 1-3, a thermoplastic resin, and / or a thermosetting resin, The carbon fiber of 3-200 volume parts with respect to 100 volume parts of resin. Containing composition.   Thermoplastic resins are polycarbonates, polyethylene terephthalates, polybutylene terephthalates, polyethylene 2,6 naphthalates, nylons, polypropylenes, polyethylenes, polyether ketones, polyphenylene sulfides, and acrylonitrile-butadiene-styrene copolymers. The composition according to claim 4, which is at least one resin selected from the group consisting of polymerized resins.   The thermosetting resin is at least one resin selected from the group consisting of epoxies, acrylics, urethanes, silicones, phenols, imides, thermosetting modified PPEs, and thermosetting PPEs Item 5. The composition according to Item 4.   The composition in any one of Claims 4-6 whose heat conductivity in the state shape | molded in flat form is 2 W / (m * K) or more.   The composition according to any one of claims 4 to 7 is selected from the group consisting of an injection molding method, a press molding method, a calender molding method, a roll molding method, an extrusion molding method, a casting molding method, and a blow molding method. A molded body obtained by molding by at least one method.

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