JP2008069474A - Carbon fiber aggregate suitable for reinforcing material/heat-dissipating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To develop a carbon fiber-reinforced material having extremely high thermal conductivity as a whole molded material and excellent mechanical property. <P>SOLUTION: The carbon fiber aggregate is produced by blending a pitch-based carbon fiber A having an average diameter of 1-20μm, a fiber length of 1-100μm, and an aspect ratio of 1-100 with a carbon fiber B having an average fiber diameter of 2-40μm and an average fiber length of 0.1-150 mm at a weight ratio of fiber A to fiber B of 1:99 to 99:1. The pitch-based carbon fiber A of the carbon fiber aggregate has a microcrystal size of ≥5 nm in the growing direction of hexagonal carbon layer, and the carbon fiber aggregate has a thickness of 0.05-5 mm and is produced by forming an aggregate containing the pitch-based carbon fiber having a porosity of 50-95 vol.% in the form of a plane. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a carbon fiber aggregate used as a reinforcing material by mixing pitch-based carbon fibers having different fiber lengths, and to a carbon fiber reinforced composite material obtained by impregnating a matrix in the carbon fiber aggregate. . More specifically, in addition to the performance as a reinforcing material, pitch-based carbon fibers excellent in thermal conductivity are mixed and used by changing the fiber length, so that the carbon fiber filling rate is high and the mechanical properties and thermal conductivity are excellent. The present invention relates to a carbon fiber reinforced composite material that can obtain a carbon fiber aggregate and further develop its excellent performance when used in combination with a matrix.

  High-performance carbon fibers are carbon fibers derived from fiber-like chain polymers made from chain polymers such as cellulose, polyvinyl alcohol, polyacrylonitrile (PAN), etc., and petroleum and coal made of cyclic hydrocarbons. Can be classified into pitch-based carbon fibers made from these pitches. The former carbon fiber derived from a chain polymer can be used as a tough fiber only by performing carbonization treatment.

  In particular, PAN-based carbon fiber effectively uses the performance that is significantly higher in strength and elastic modulus than ordinary synthetic polymers, and is used in aerospace equipment, construction and civil engineering materials, sports and leisure equipment, etc. Widely used in In contrast, the latter pitch-based carbon fiber exhibits its characteristics and exhibits the performance of graphite crystals when subjected to graphitization treatment, which is a high-temperature heat treatment.

  In other words, when comparing the former carbonized fiber with the latter graphitized fiber, the latter has a network structure as a microcrystal, although the crystal itself is small and not a single crystal. Therefore, when graphitization (crystallization) proceeds sufficiently, this graphitized fiber has higher electrical conductivity and thermal conductivity than carbonized fiber, and has excellent mechanical properties.

  Therefore, from the role of the carbon fiber composite material simply as a reinforcing material, the graphitized fiber, that is, the heat conductivity as the pitch-based carbon fiber is also used, and the heat storage property and heat dissipation property as the composite material are used. There is an expectation that the way of comprehensive use of carbon fiber composite materials can be opened.

  On the other hand, on the other hand, an efficient use method of energy typified by energy saving has attracted attention, but there is a possibility that carbon fiber can be applied to heating, heat retention, etc. by applying livestock heat. On the other hand, the heat generation of the CPU of the electronic computer and the heat generation due to the Joule heat of the integrated circuit due to the increase in speed are problems. To solve these problems, heat is processed by an efficient transmission path. It is necessary to develop effective heat dissipation means. That is, there is a request to achieve so-called heat management for these issues.

  From this point of view, when reviewing carbon fibers, carbon fibers generally have higher thermal conductivity than ordinary organic synthetic polymers, but further improvements in thermal conductivity are being studied. However, the thermal conductivity of commercially available PAN-based carbon fibers is usually less than 200 W / (m · K), and is not necessarily a suitable material from the viewpoint of heat management. On the other hand, pitch-based carbon fibers potentially have the advantage that high thermal conductivity is easily achieved as compared to PAN-based carbon fibers.

  By the way, in order to effectively use the high thermal conductivity of the carbon fiber, some matrix material that can fill the gaps in the carbon fiber assembly is interposed, and in this state, the carbon fiber has a high filling rate and heat. It is preferable to form a network structure for maintaining conduction. When the network structure is formed three-dimensionally, high heat conduction specific to the carbon fiber is achieved not only in the in-plane direction of the molded body but also in the thickness direction. Is considered to be very effective. However, the conventional carbon fiber composite material that has been woven into a composite with a matrix has improved the in-plane thermal conductivity, but the heat conduction in the thickness direction forms a network of carbon fibers. Therefore, it is difficult to say that heat transfer is insufficient and heat dissipation is good.

  For these reasons, many attempts have been made to drastically improve the thermal conductivity of carbon fibers. For example, Patent Document 1 discloses a thermally conductive molded article having high mechanical strength in which carbon fiber aligned in one direction is impregnated with graphite powder and a thermosetting resin. Moreover, although patent document 2 discloses improving the physical properties of carbon fiber as a subject, improving physical properties such as thermal conductivity, has the clear performance improvement of the thermal properties of the molded body been achieved? There is not enough consideration on whether or not, and the details can only be said to be unknown.

JP-A-5-017593 JP-A-2-242919

  As described above, material development is progressing from the viewpoint of increasing the thermal conductivity of carbon fibers. However, from the viewpoint of heat management, it is necessary to have a high thermal conductivity as a molded body and to have an excellent heat dissipation effect. Accordingly, carbon having an appropriate thermal conductivity, carbon fiber reinforcing material capable of increasing the carbon fiber content in the molded body, and carbon material having extremely high thermal conductivity as a whole molding material and excellent mechanical properties. Fiber reinforced composite materials are strongly desired.

  The present inventors tried to improve the thermal conductivity in both the in-plane direction and the thickness direction of the carbon fiber reinforced composite material, and the paper was made on pitch-based carbon fibers having a specific thermal conductivity and shape. It has been found that when a carbon fiber aggregate is impregnated with a matrix such as a resin, the filling rate of the carbon fibers in the impregnated composite material is increased, and the thermal conductivity in the thickness direction is remarkably improved. The present invention has been achieved.

  That is, in the invention according to claim 1, the average diameter (D1) of the single fiber is in the range of 1 to 20 μm, and the ratio (CV1) of the fiber diameter distribution (S1) to D1 is in the range of 5 to 20%. A pitch-based carbon fiber A (which is simply referred to as a short fiber A) having an average fiber length (L1) of a single fiber of 1 to 100 μm or less and a ratio of the average fiber length to the average diameter (D1), that is, an aspect ratio of 1 to 100 The average fiber diameter (D2) is in the range of 2 to 40 μm, and the ratio (CV2) of the fiber diameter distribution (S2) to D2 is in the range of 5 to 20%. The weight ratio of the short fiber A to the short fiber B of the carbon fiber B (which may be simply referred to as the short fiber B) in which L2) is 0.1 to 150 mm is a ratio of 1:99 to 99: 1. A carbon fiber assembly obtained by mixing the carbon Crystallite size derived from the growth direction of the hexagonal surface of the short fiber A in 維集 polymer is a carbon fiber aggregate is 5nm or more.

  In the invention according to claim 2, the true density of the short fibers A in the carbon fiber aggregate is in the range of 1.5 to 2.5 g / cc, and the thermal conductivity in the fiber axis direction is at least 200 W / (m The carbon fiber aggregate according to claim 1, which is K).

  Furthermore, the invention according to claim 3 specifies that the thermal conductivity in the thickness direction of the carbon fiber aggregate according to claim 1 or 2 is at least 3 W / (m · K). And this carbon fiber aggregate | assembly has the characteristics containing the pitch-type carbon fiber whose thickness is 0.05-5 mm and whose porosity is 50-95 volume%.

  That is, the above-mentioned problem in the present invention is that the short fibers A have an average diameter (D1) of the fibers of 1 to 20 μm, a fiber length (L1) of 100 μm or less, and a growth direction of the hexagonal mesh surface. The content of the short fibers A in the pitch-based carbon fiber aggregate having a microcrystal grain size of 5 nm or more derived from is 1 to 99% by weight, and in addition, the carbon content of the short fibers A is 80% by weight or more. And the thickness of the entire carbon fiber assembly including the carbon fiber B is 0.05 to 5 mm, and the porosity of the carbon fiber assembly is 50 to 95% by volume. The

  Furthermore, in the present invention, the true density of the pitch-based carbon fiber A is in the range of 1.5 to 2.5 g / cc, and the thermal conductivity in the fiber axis direction is 200 W / (m · K) or more. When the pitch-based carbon fiber A according to claim 1 is effectively mixed, the heat conductivity in the thickness direction of the entire assembly including the carbon fiber B reaches 3 W / (m · K) or more. A carbon fiber aggregate containing pitch-based carbon fibers excellent in the above can be obtained.

  Moreover, in this invention, it is often used as a carbon fiber reinforced composite material obtained by impregnating a pitch-based carbon fiber aggregate with a matrix. As an embodiment, when the matrix is a carbon fiber reinforced composite material containing a thermoplastic resin, the pitch-based carbon fiber aggregate is formed so as to occupy 10 to 80% by volume with respect to the matrix resin.

  The carbon fiber reinforced composite material has a thermal conductivity in the thickness direction of at least 1 W / (m · K) in a carbon fiber aggregate molded into a flat plate shape. The carbon fiber mixture which is the base material of the carbon fiber reinforced composite material is a short fiber B composed of short fibers A which are pitch-based carbon fibers and carbon fibers (which may contain a small amount of non-pitch-based carbon fibers such as PAN-based carbon). It is a composite material containing the matrix resin comprised from these. That is, it is preferable that the short fiber B contains a pitch-type carbon fiber in the carbon fiber mixture used as the base material of the carbon fiber reinforced composite material.

  In the carbon fiber reinforced composite material, for example, the matrix is a thermoplastic resin, and examples thereof include polycarbonates, polyethylene terephthalates, polyethylene 2,6 naphthalates, nylons, aromatic polyamides, polypropylenes, polyethylenes, poly Ether ketones, polyphenylene sulfides, and polylactic acids can be specified. Such a carbon fiber reinforced composite material of the present invention exhibits a thermal conductivity of 1 W / (m · K) or more in the thickness direction in a sheet-like material formed into a flat plate shape (planar shape).

  For the matrix, for example, a thermosetting resin or a precursor thereof can be applied, and thermosetting silicone elastomer, unsaturated polyester elastomer, epoxy resin, unsaturated polyester resin, phenol resin, silicone resin, polyurethane resin. And polyimide resin, thermosetting modified polyphenylene ether resin, and thermosetting polyether ether ketone resin.

  Furthermore, in the present invention, the carbon fiber aggregate is made into a sheet by a dry or wet method in the presence of a binder, the carbon content is 80% by weight or more, and the thickness is in the range of 0.05 to 5 mm. And a method for producing a pitch-based carbon fiber assembly including a step of obtaining a fiber assembly having a porosity of 50 to 95% by volume.

  Further, the present invention uses a binder in which at least 1% by weight of the amount used can remain in the carbon fiber aggregate as carbonaceous material, and is fired in a temperature range of 500 to 1000 ° C. in an inert gas atmosphere after papermaking. And a method of producing a carbon fiber aggregate including a step of graphitizing at a temperature of 1000 ° C. to 3500 ° C.

In the step of impregnating the pitch-based carbon fiber aggregate with the matrix resin, the impregnation can be performed under a pressurized condition in a vacuum state.
In addition, specific applications using carbon fiber reinforced composite materials as main materials include heat sinks for electronic components, heat exchangers, counter electrodes for wet solar cells, substrates for shielding electromagnetic waves, and solid abrasives.

  The carbon fiber reinforced composite material according to the present invention has a thermal conductivity distribution in a molded body in the presence of an impregnated matrix by effectively combining and mixing carbon long fibers and pitch-based carbon short fibers. Since it is almost equal not only in the plane of the body but also in the thickness direction of the molded body, it increases the heat conduction efficiency of heat sinks and heat exchangers for electronic parts and is required for the housing Strength can be increased and weight reduction as a molded product can be achieved.

The presence of very fine short fibers A increases the chance of contact between the fibers, which increases the thermal conductivity, and has the advantage that the thermal conductivity is homogeneous without directionality (anisotropy). .
A molding material having no anisotropy in heat conduction and heat transfer has an advantage that molding is easy and no special condition setting or caution is required. As a molded body and a part, there is an advantage that it is homogeneous and rich in compatibility.

Next, embodiments of the present invention will be described in detail.
Invention of Claim 1 is the range whose average diameter (D1) of a single fiber is 1-20 micrometers, the average fiber length (L1) of a single fiber is 1-100 micrometers, ratio of the average fiber length with respect to an average diameter (D1), That is, the pitch-based carbon short fibers A having an aspect ratio of 1 to 100, the fiber average diameter (D2) is in the range of 2 to 40 μm, and the single fiber average fiber length (L2) is 0.1 to 150 mm. A carbon fiber aggregate obtained by mixing a short carbon fiber B so that the weight ratio of the short fiber A to the short fiber B is 1 to 99 to 99 to 1, and the carbon fiber aggregate The crystallite size derived from the growth direction of the hexagonal network surface of the pitch-based carbon fiber short fibers A in the above is 5 nm or more, the carbon fiber aggregate has a thickness of 0.05 to 5 mm, and the porosity is A mixture containing pitch-based carbon fiber that is 50 to 95% by volume A carbon fiber aggregate obtained by molding into a planar shape.

  Examples of raw materials for obtaining two types of carbon fibers having different fiber lengths according to the present invention include condensed polycyclic hydrocarbon compounds such as naphthalene and phenanthrene, condensed heterocyclic compounds such as petroleum pitch and coal pitch, and the like. Can be mentioned. Among them, condensed polycyclic hydrocarbon compounds such as naphthalene and phenanthrene are preferable, and a pitch exhibiting optical anisotropy, that is, mesophase pitch is particularly preferable. One of these may be used alone, or two or more may be used in appropriate combination. However, it is desirable to use a mesophase pitch alone in order to obtain a carbon fiber having high thermal conductivity.

  In addition, if it can obtain for the short fiber B, the carbon fiber derived from a commercially available linear polymer (for example, PAN fiber) can also be utilized. This is a case where such a carbon fiber is used as a matrix to form a network structure and the network structure is used as a heat transfer path.

  The softening point of the raw material pitch can be obtained by the Mettler method. As the raw material pitch, a pitch having a softening point in the range of 250 to 350 ° C. is preferable. When the softening point is lower than 250 ° C., it is not preferable because fusion between fibers or large heat shrinkage occurs during infusibilization. Further, those having a softening point higher than 350 ° C. are liable to cause thermal decomposition of the pitch and are difficult to be formed into a fibrous form, and therefore are not suitable for spinning and yarn production.

The raw material pitch is spun by a melt blow method, and then a three-dimensional random sheet (mat) -like carbon fiber aggregate can be formed by infusibilization treatment and further baking. If necessary, it can be graphitized (crystallized) at a higher temperature.
Each manufacturing / processing process will be described below.

In the present invention, pitch fibers are obtained using a spinning nozzle from a preferable pitch material such as a mesoface pitch having an appropriate softening point as described above.
Although there is no particular restriction on the shape of the spinning nozzle used in this step, the ratio of the round length of the nozzle hole to the hole diameter (so-called L / D) is preferably 20 or less, more preferably more than 15. Smaller ones are used.

  As in the present invention, changing the fiber length of the carbon fiber or similarly changing the fiber diameter can be achieved by changing the ratio of the round length of the nozzle hole to the hole diameter. Further, even when the temperature of the nozzle at the time of spinning is appropriately changed, it is possible to easily obtain long and short fibers having different fiber lengths. Further, it is possible to change the fiber length and fiber diameter of the pitch fiber by changing the spraying speed of the heating gas described later. These spinning conditions, including the shape of the nozzle, the melt viscosity of the pitch, and the thinning conditions, can be determined by trial and error, and the conditions can be set empirically along with the selection of the raw material pitch.

  In general, the spinning temperature is not particularly limited, and may be a temperature at which a stable spinning state can be maintained, that is, a temperature at which the spinning pitch viscosity is 2 to 80 Pa · s, preferably 5 to 30 Pa · s.

  Pitch fibers (that is, carbon fiber precursors) ejected from the nozzle holes are blown with gas at a linear velocity of 100 to 10000 m per minute heated to 100 to 450 ° C. near the thinning point. It is refined and fiberized by. As the gas to be blown, air or an inert gas such as nitrogen, carbon dioxide, or argon can be used, but air is sufficient from the viewpoint of cost performance.

  It goes without saying that combustion gas (carbon dioxide) can be used as the fiberizing (thinning) gas in addition to heated air. This heating gas can be made into pitch fibers having long and short fiber lengths by appropriately selecting the temperature, spraying speed, and the like. In this case, the thinning condition can be set by a trial and error method.

  The pitch fibers thus obtained are collected on a wire mesh belt to become a sheet-like material having a continuous three-dimensional random shape, and it is also possible to randomly laminate the sheet-like material by applying cross-wrapping or the like. is there.

  The three-dimensional random pitch fiber sheet thus obtained can be infusibilized by a known method. That is, the infusibilization process is a process using only air or a gas obtained by adding a small amount of a third component such as ozone, nitrogen dioxide, nitrogen, oxygen, iodine or bromine to the air. This is achieved by setting the infusibilization temperature to 150 to 400 ° C. The infusibilization of pitch fibers is preferably performed in the air in consideration of safety and convenience.

  Subsequent to this infusibilization step, the pitch fiber sheet is fired and graphitized at 500 to 3500 ° C. to be stabilized as graphitized (carbon) fibers. That is, a pitch-based carbon fiber aggregate having a three-dimensional random shape is obtained. This infusible pitch fiber firing step is performed in a vacuum or in an inert gas such as nitrogen, argon or krypton. Usually, it is desirable to carry out under normal pressure nitrogen, and low-cost nitrogen is commonly used.

  As the firing (graphitization) temperature of the pitch fiber, it is preferable to select a high temperature of 2300 to 3500 ° C. to enhance graphitization in order to obtain high thermal conductivity as carbon fiber. More preferably, the temperature is 2500 to 3500 ° C. When graphitizing in a graphite container during the firing treatment, the influence of physical and chemical effects from the outside can be blocked, which is a preferred embodiment. The graphite container is not particularly limited in size and shape as long as it has a capacity capable of storing a predetermined amount of pitch fiber sheet material that has undergone infusibilization. However, in order to prevent damage to the pitch-based carbon fiber aggregate due to reaction with oxidizing gas or carbon vapor in the furnace during the firing process or subsequent cooling, a highly airtight one with a lid is used. It is preferable.

  Here, the pitch-based carbon fiber aggregate obtained in the present invention has a three-dimensional random shape. A short fiber B is used as a skeleton, and short fibers A having a shape close to powder are dispersed in a three-dimensional random shape, the short fibers are in close contact with each other, and the pitch-based carbon fiber aggregate Are not oriented in a specific direction (both short fibers B and short fibers A). Thus, since the pitch-based carbon fiber aggregate has a three-dimensional random shape, the obtained carbon fiber reinforced composite material has the property of being able to conduct heat equivalently in all directions (all directions). Which can be achieved and is a preferred embodiment.

  On the other hand, when a carbon fiber reinforced composite material is manufactured using a carbon fiber bundle (UD material) in which each fiber is oriented in a specific direction, it is easy to conduct heat in a specific direction. Since the problem of low thermal conductivity occurs in the direction, it cannot be said that such a carbon fiber aggregate is preferable from the viewpoint of thermal conductivity. However, since such an anisotropic carbon fiber aggregate has directionality also in mechanical strength, it goes without saying that it is used to make use of this performance.

  The carbon fibers constituting the pitch-based carbon fiber aggregate used in the present invention have a microcrystal size derived from the growth direction of the hexagonal network surface of 5 nm or more. The size of the graphite crystal, that is, the microcrystal size derived from the growth direction of the hexagonal mesh plane can be determined by a known method, for example, by the diffraction line from the (110) plane of the carbon crystal obtained by the X-ray diffraction method. Can be sought. The size of the microcrystals is important because heat conduction is mainly carried by phonons, and the place where phonons are generated is the graphite crystals. The crystallite size of the hexagonal network surface is desirably 20 nm or more, and more desirably 30 nm or more.

  The fiber diameter of the short carbon fibers A constituting the pitch-based carbon fiber aggregate is 1 to 20 μm. When the fiber diameter is 1 μm or less, the shape of the fiber may not be maintained, and productivity is lowered. Conversely, when the fiber diameter is 20 μm or more, cooling unevenness occurs in the spinning and thinning process, and this fiber unevenness causes the fiber itself in the infusibilization process even if the heating conditions are the same. The temperature non-uniformity is greatly amplified, and there is an increased concern that the fusion between the fibers is partially induced. Therefore, the fiber diameter is preferably 3 to 17 μm, and more desirably 5 to 15 μm.

  As a method for producing short carbon fibers, polyacrylonitrile-based carbon fibers obtained by conventionally known production methods cannot be used. However, in addition to the pitch-based carbon fiber itself, the pitch-based carbon fiber is formed into a sheet in the presence or absence of a binder, and the obtained carbon fiber aggregate is pulverized by a known pulverizing means. . This pulverization method is not particularly limited, but a pulverizer such as a Victory mill, a jet mill, a high-speed rotary mill, or a cutting machine is preferably used. In order to perform pulverization efficiently, the rotor with blades is rotated at high speed. Therefore, a method of cutting fibers in a direction perpendicular to the fiber axis is appropriate. The average length of carbon fibers generated by pulverization can be controlled by adjusting the number of rotations of the rotor, the angle of the blade, and the like. Furthermore, the desired fiber length can be fractionated with a sieve.

  The adjustment of the fiber diameter and fiber length of the carbon fiber can be preferably achieved by combining the coarseness of the sieve. Moreover, the carbon fiber of this invention is good also as a final carbon fiber by heating the pitch fiber which finished sieving to 2300-3500 degreeC, and graphitizing.

  A supplementary explanation will be given regarding the shape of the short carbon fiber of the present invention. The length of the short carbon fiber, when the above-described sieving is performed, the diameter and the dispersion ratio of the diameter are almost uniquely determined by the spinning process. And the diameter of a carbon fiber becomes a value smaller by 1-2 micrometers than the fiber diameter of the pitch fiber (original yarn) at the time of spinning. This is because a small amount of fiber is lost due to infusibilization and firing treatment.

  Next, the fiber length of the short carbon fiber B constituting the pitch-based carbon fiber aggregate is 150 mm or less. When both AB fibers have a fiber length of less than 0.01 mm, handling as fibers becomes somewhat difficult. On the other hand, when the fiber length exceeds 150 mm, the entanglement of the fiber is remarkably increased, and the handleability is also lowered. Preferably it is 120 mm or less, More preferably, it is 100 mm or less.

  As described above, pitch-based carbon fiber is desirable as a raw material for the short carbon fiber B used in the present invention. However, the carbon fiber derived from polyacrylonitrile fiber can be made uniform in fiber length and fiber diameter. It can be used for a part of the long fibers constituting the carbon fiber aggregate. For these reasons, pitch-based carbon fibers and polyacrylonitrile fiber-derived carbon fibers may be used together. However, from the viewpoint of maintaining a high thermal conductivity, the blending ratio of pitch-based carbon short fibers should be kept at a high level.

  The mixing ratio of the pitch-based carbon short fibers B and the short fibers A can be in the range of 1:99 to 99: 1 by weight, and more preferably 20:80 to 80:20. If the mixing ratio of AB fibers in the pitch-based carbon fiber aggregate is 5 wt% or less, the thermal conductivity in the thickness direction cannot be sufficiently expressed, and if it is 95 wt% or more, the filling rate of the carbon fiber situation cannot be increased. Therefore, it is not preferable.

  The true density of the pitch-based carbon fiber aggregate depends on the firing / graphitization temperature, but is preferably in the range of 1.5 to 2.5 g / cc. More preferably, it is 1.6-2.5 g / cc. The thermal conductivity in the fiber axis direction of the pitch-based carbon fibers constituting the pitch-based carbon fiber aggregate is 200 W / (m · K) or more, and more preferably 300 W / (m · K) or more. Further, the thermal conductivity in the thickness direction of the aggregate itself is 3 W / (m · K) or more.

Next, in the present invention, a non-woven fabric in which short carbon fibers and long carbon fibers are mixed is impregnated with a thermosetting resin or a thermosetting resin precursor to obtain a carbon fiber reinforced composite material.
The matrix (base material) resin to be impregnated into the pitch-based carbon fiber aggregate is a thermosetting resin precursor or a thermosetting resin, and impregnated in the case of a precursor (including monomer, polymerization catalyst, etc.) Polymerization is performed later.

  Examples of thermosetting resins include thermosetting silicone elastomers, unsaturated polyester elastomers, epoxy resins, unsaturated polyester resins, phenol resins, silicone resins, polyurethane resins, polyimide resins, thermosetting modified polyphenylene ether resins, and heat. It contains at least one thermosetting resin selected from the group of curable polyetheretherketone resins. These may be used alone or in appropriate combination of two or more. For example, a polymer alloy composed of two or more kinds of polymer materials may be used.

  The volume fraction that the pitch-based carbon fiber aggregate occupies with respect to the base resin is usually about 10 to 80% by volume. The proportion of the pitch-based carbon fiber reinforcing material in the carbon fiber reinforced composite material in the present invention is 3 to 60% by volume, preferably 5 to 50% by volume. If the proportion of the pitch-based carbon fiber reinforcing material is 3% or less, the desired thermal conductivity cannot be obtained, and if it is 60% or more, molding becomes difficult.

  The carbon fiber reinforced composite material thus obtained has a thermal conductivity in the thickness direction of 1 W / (m · K) or more in a state of being shaped into a flat plate. The carbon fiber reinforced composite material according to the present invention preferably has a high thermal conductivity as a composite material, but the thermal conductivity calculated from thermal diffusion to the front and back is 1 W / (m · K) or more. More desirably, it is 2 W / (m · K) or more, and further desirably 5 W / (m · K) or more.

  In the present invention, the method for dispersing the short carbon fibers into the pitch-based short carbon fiber aggregate is not particularly limited. A method of dry blending carbon short fibers B into pitch-based carbon short fibers A; after dispersing carbon short fibers B in a liquid dispersion material, the dispersion is immersed in pitch-based carbon short fibers A; The dispersion can be removed by wet blending means such as drying. Conversely, the method of dispersing pitch-based short fibers into a non-woven aggregate composed of carbon short fibers B is exactly the same, and dry blend or wet blend can be applied.

  The method for immersing the matrix resin in the carbon fiber aggregate in the present invention is not particularly limited, but when the matrix resin is liquid at room temperature, it can be carried out by a kneading apparatus such as a mixer. When the matrix resin is solid at room temperature, it can be melted by heating and can be carried out by a kneading apparatus such as a twin screw extruder.

In the present invention, the molding method for obtaining the carbon fiber reinforced composite material is not particularly limited, and examples thereof include an injection molding method, a press molding method, a calendar molding method, an extrusion molding method, a casting molding method, and a blow molding method. The following two methods can be used.
The first method is a method in which, in the above method, carbon fibers are dispersed in a matrix resin, and then the matrix resin in which the carbon fibers are dispersed is introduced into the pitch-based carbon fiber aggregate together with the carbon fibers.

  When the matrix is a thermosetting resin including a curing catalyst or its precursor is a liquid at room temperature, it is introduced into the pitch-based carbon fiber aggregate previously charged in the mold by the RIM method, the RTM method, etc. A carbon fiber reinforced composite material can be obtained by curing the matrix resin.

  When the matrix resin is solid at room temperature, the carbon fiber is dispersed in the matrix resin by the above method, and then the carbon fiber is injected by injection molding to a pitch-based carbon fiber assembly previously charged in the mold. A reinforced composite material can be obtained.

A carbon fiber reinforced composite material can be obtained by processing a matrix resin in which carbon fibers are dispersed into a flat shape or the like in advance and press-molding the matrix resin in a state of being laminated with a pitch-based carbon fiber aggregate.
In addition, at the time of vacuum press molding, it is preferable to mold in a vacuum state for the purpose of suppressing generation of voids (voids).

  As a second method, there is a method in which short carbon fibers are dispersed in a pitch-based carbon fiber aggregate by the above-described method, and then a matrix resin is introduced into the pitch-based carbon fiber aggregate. When the matrix resin is in a liquid state at room temperature, it is introduced into the pitch-based carbon fiber in which the carbon fibers previously charged in the mold are dispersed by the RIM method, the RTM method, etc., and the matrix resin is cured, A carbon fiber reinforced composite material can be obtained.

When the matrix resin is solid at room temperature, a carbon fiber reinforced composite material can be obtained by injection molding a pitch-based carbon fiber assembly in which carbon fibers previously charged in a mold are dispersed.
The carbon fiber reinforced composite material can also be obtained by processing the matrix resin into a flat shape or the like in advance and press-molding it in a state of being laminated with a pitch-based carbon fiber aggregate in which carbon fibers are dispersed.

Also in this case, at the time of vacuum press molding, molding in a vacuum state for the purpose of suppressing generation of voids is the same as in the first method.
The pitch-based carbon fiber aggregate and / or the short carbon fiber may be surface-treated and then a sizing agent may be added thereto.

  As the surface treatment method, the surface may be modified by oxidation treatment such as electrolytic oxidation, or by treatment with a coupling agent or sizing agent. Also, by means such as electroless plating, electrolytic plating, physical vapor deposition such as vacuum deposition, sputtering, ion plating, chemical vapor deposition, painting, dipping, and mechanochemical methods for mechanically fixing fine particles. A metal or ceramic coated on the surface may be used.

  The sizing agent may be 0.1 to 15% by weight, preferably 0.4 to 7.5% by weight of the sizing agent based on pitch-based carbon fiber aggregates and / or short carbon fibers, Specifically, an epoxy compound, a water-soluble polyamide compound, a saturated polyester, an unsaturated polyester, vinyl acetate, water, alcohol, glycol alone or a mixture thereof can be used.

  In addition, as a supplementary explanation, as a method for producing the short carbon fiber A, polyacrylonitrile-based carbon fiber and pitch-based carbon fiber obtained by a conventionally known production method, and the pitch-based carbon fiber described in the present invention are pulverized. It can also be obtained by processing.

  The pulverization method is not particularly limited, but a pulverizer such as a Victory mill, a jet mill, a high-speed rotary mill, or a cutting machine is preferably used. In order to efficiently perform the pulverization, the blade-mounted rotor is rotated at a high speed. Thus, a method of cutting fibers in a direction perpendicular to the fiber axis is appropriate. The average length of carbon fibers generated by pulverization is controlled by adjusting the number of rotations of the rotor, the angle of the blade, and the like.

  Next, the shape of the carbon fiber of the present invention will be described. The length of the carbon long fiber B is determined by the sieving described above, but the fiber diameter is almost uniquely determined by the spinning process. And the diameter of the carbon fiber B becomes a value smaller by 1 to 2 μm than the diameter of the original yarn when it is spun.

The second object of the present invention is to provide a carbon fiber reinforced composite material obtained by impregnating a pitch-based carbon fiber aggregate with a matrix resin.
The matrix resin used in the present invention is not particularly limited, and any of a thermosetting resin and a thermoplastic resin can be used, but a thermoplastic resin can be preferably used from the viewpoint of the degree of freedom in shape and productivity.

  The thermoplastic resin is any one selected from the group consisting of polycarbonates, polyethylene terephthalates, polyamides, aramids, polyethylene 2,6 naphthalates, nylons, polypropylenes, polyethylenes, polyether ketones, and polyphenylene sulfides. Two or more polymer resin compositions are preferably used. More specifically, polyethylene, polypropylene, ethylene-α-olefin copolymers such as ethylene-propylene copolymer, polymethylpentene, polyvinyl chloride, Polyvinylidene chloride, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl alcohol, polyacetal, fluororesin (polyvinylidene fluoride, polytetrafluoroethylene, etc.), polyethylene terephthalate, polybutylene terephthalate Polyethylene naphthalate, polystyrene, polyacrylonitrile, styrene-acrylonitrile copolymer, ABS resin, polyphenylene ether (PPE) resin, modified PPE resin, aliphatic polyamide, aromatic polyamide, polyimide, polyamideimide, polymethacrylic acid (poly And polyacrylic acid esters such as methyl methacrylate), polyacrylic acids, polycarbonate, polyphenylene sulfide, polysulfone, polyether sulfone, polyether nitrile, polyether ketone, polyketone, liquid crystal polymer, and ionomer. And a high molecular resin composition may be used individually by 1 type, may be used in combination of 2 or more types suitably, and may use the polymer alloy which consists of 2 or more types of polymeric materials.

  Examples of thermosetting resins include epoxy resins, phenol resins, silicone resins, polyurethane resins, unsaturated polyester resins, vinyl ester resins, polyimide resins, thermosetting modified polyphenylene ether resins, thermosetting polyphenylene ether resins, and the like. It is done. And these may be used by 1 type, may be used in combination of 2 or more types suitably, and can also use the polymer alloy which consists of 2 or more types of polymeric materials.

  The ratio of the pitch-based carbon fiber aggregate in the carbon fiber reinforced composite material in the present invention is preferably 10 to 80% by volume with respect to the matrix resin. If the volume fraction is lowered, the thermal conductivity of the carbon fiber reinforced composite material is lowered, so that desired physical properties cannot be obtained. Further, if the volume fraction is increased, the thermal conductivity is improved, but the molding becomes difficult.

  In the present invention, a thermally conductive filler other than carbon fiber can be used as necessary. Specifically, metal oxides such as 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, copper and aluminum Examples thereof include metals such as metals and alloys, carbon materials such as graphite, expanded graphite, and diamond.

  In the resin composition used in the present invention, glass fiber, potassium titanate whisker, zinc oxide whisker, aluminum borate whisker, aramid fiber, alumina fiber, silicon carbide fiber, ceramic fiber, as long as the effects of the present invention are not impaired. Fibrous fillers such as asbestos fibers, stone fiber, metal fibers, wollastonite, zeolite, sericite, kaolin, mica, clay, pyrophyllite, bentonite, silicates such as asbestos, talc, alumina silicate, calcium carbonate, Non-fibrous fillers such as carbonates such as magnesium carbonate and dolomite, sulfates such as calcium sulfate and barium sulfate, glass beads, glass flakes, ceramic beads, silicon carbide and silica may be used. Well, more than two of these It is also possible to use.

  The carbon fiber reinforced composite material in the present invention preferably has a high thermal conductivity as the composite material, but the thermal conductivity calculated from the thermal diffusion to the front and back is at least 1 W / (m · K), more preferably. Is 2 W / (m · K) or more, more preferably 3 W / (m · K) or more.

  A further problem of the present invention is that the carbon content obtained by papermaking pitch-based carbon fiber or its precursor in the presence of a binder is 80% by weight or more, the thickness is 0.05 to 5 mm, and the porosity is It is providing the manufacturing method of the pitch-type carbon fiber aggregate | assembly which is 50-95 volume%.

  As the binder used in the present invention, at least one kind selected from fibrous, fibrid (fine film), pulp, and particulate can be used. The binder is easily entangled with the pitch-based carbon fiber or its precursor, and it is necessary to improve papermaking properties. However, the binder itself may be a thermoplastic resin or a thermosetting resin.

  The amount of the binder used is 1 to 20% by weight, preferably 3 to 15% by weight, based on the pitch-based carbon fiber A or its precursor. Deviating from these ranges is not preferable because handling properties after papermaking are poor.

  The paper making method of pitch-based carbon fiber or its precursor is a wet paper making method in which the fiber is dispersed and rescued in a large amount of dispersion, and the fiber dispersed air stream is sprayed after the fiber is dispersed in the air stream. For example, there is a dry method in which a thin layer is formed by, for example, and further laminated. However, in consideration of the dispersibility and productivity of the fiber, the wet papermaking method is preferable.

The paper-like aggregate thus made is then subjected to processing such as calendering or baking as required, and the selection of the binder is preferably matched to these processing methods.
When performing the calendering treatment, a thermoplastic resin such as polyamide, aramid, polyester, polypropylene, or polyethylene is preferable. When performing the calcining treatment, a resin having a relatively high residual carbon ratio such as PVA, aramid, or phenol resin is preferable. Can be used.

  The firing treatment is first performed at a temperature of 500 ° C. to 1000 ° C. in an inert gas atmosphere. In this case, the carbon content of the obtained pitch-based carbon fiber aggregate is 95% by weight or more. Further, if necessary, it is preferable to continue firing at a higher temperature (over 1000 ° C.).

  The molding method for obtaining the carbon fiber reinforced composite material in the present invention is not particularly limited, and examples thereof include an injection molding method, a press molding method, a calendar molding method, an extrusion molding method, a casting molding method, and a blow molding method. The following two methods can be used.

  As a specific method, for example, a matrix resin that has become liquid at room temperature or by heating is introduced into a pitch-based carbon fiber aggregate that has been charged in advance in a mold by the RIM method, the RTM method, etc. By solidifying or curing, a carbon fiber reinforced composite material can be obtained.

As another method, a carbon fiber reinforced composite material can be obtained by preparing a pitch-based carbon fiber aggregate and a matrix resin in a mold and melt-impregnating the matrix resin.
In the latter case, the matrix resin may be formed into a shape such as a sheet that can be easily loaded into the mold, and it is preferable to impregnate the matrix resin under a pressurized condition in a vacuum state from the viewpoint of degassing property and impregnating property.
In addition, the pitch-based carbon fiber aggregate may be surface-treated and then a sizing agent may be attached thereto.

  As the surface treatment method, the surface may be modified by oxidation treatment such as electrolytic oxidation, or by treatment with a coupling agent or sizing agent. Also, by electroless plating method, electrolytic plating method, physical vapor deposition method such as vacuum deposition, sputtering, ion plating, chemical vapor deposition method, painting, immersion, mechanochemical method for mechanically fixing fine particles, etc. A metal or ceramic coated on the surface may be used.

  The sizing agent is 0.1 to 15% by weight, preferably 0.4 to 7.5% by weight, based on the pitch-based carbon fiber aggregate, and any sizing agent that is usually used can be used. Water-soluble polyamide compound, saturated polyester, unsaturated polyester, vinyl acetate, water, alcohol, glycol alone or a mixture thereof can be used.

The use of the molded product made mainly of the carbon fiber reinforced composite material of the present invention is a heat sink for electronic parts and a heat exchanger.
Specifically, as a heat radiating member, a heat transfer member, or a component material for effectively radiating heat generated by a semiconductor element or electronic component to the outside, a heat radiating plate, a semiconductor package component, a heat sink, a heat spreader, A die pad, a printed wiring board, a cooling fan component, a heat pipe, a housing, or the like can be molded and used.
The carbon fiber reinforced composite material of the present invention can also be used as a radio wave absorbing material or a conductive material.

Although the thermal conductivity of the carbon fiber of the present invention can be measured by a known method, the laser flash method is desirable because it aims to improve the thermal conductivity in the thickness direction of the carbon fiber composite material. In the laser flash method, the specific heat capacity Cp (J / gK) and the thermal diffusivity α (cm ² / sec) are measured, and the thermal conductivity λ (W / cmK) is calculated from the separately measured density ρ (g / cc). Unit conversion can be performed by obtaining λ = α · Cp · ρ.

In general, the thermal conductivity of carbon fiber itself is several hundred W / (m · K), but when it is molded, the thermal conductivity is drastically reduced due to defects, air contamination, and unexpected voids. To do. Accordingly, it has been considered difficult for the carbon fiber composite material to have a thermal conductivity substantially exceeding 1 W / (m · K). However, in the present invention, this is solved by using a three-dimensional random mat-like carbon fiber, and 1 W / (m · K) or more can be achieved as a carbon fiber composite material. Desirably, it is 2 W / (m · K) or more, and more desirably 5 W / (m · K) or more.
The carbon fiber reinforced composite material thus obtained can be suitably used for heat management applications.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely using an Example, this invention is not restrict | limited to these.
In addition, each value in a present Example was calculated | required according to the following method.
(1) The diameter of the pitch-based carbon fiber A was obtained by photographing the fired fiber by extracting 10 fields of view under a scanning electron microscope at a magnification of 800 times.
(2) The yarn length of the pitch-based carbon fiber A was measured with a length measuring device by extracting the fired fiber.
(3) The thermal conductivity in the fiber axis direction of the pitch-based carbon fiber A is determined by measuring the resistivity of the yarn after firing, and the thermal conductivity and electrical resistivity disclosed in JP-A-11-117143. It calculated | required from following formula (1) showing a relationship.
[Equation 1]
K = 1272.4 / ER-49.4 (1)
Here, K represents the thermal conductivity W / (m · K) of the carbon fiber, and ER represents the electrical specific resistance μΩm of the carbon fiber.
(4) The thermal conductivity in the thickness direction of the carbon fiber reinforced composite material was measured by a laser flash method.
(5) The crystal size of the three-dimensional random mat-like carbon fiber was determined by the Gakushin method by measuring reflection from the (110) plane appearing in X-ray diffraction.

[Example 1]
Manufacture of short fiber A In order to obtain a carbon fiber aggregate having two types of fiber lengths that are reasonably long and short while suppressing production cost, the pitch fiber is spun under substantially the same conditions using the same pitch raw material. The pitch fiber is collected on the wire mesh belt without changing the conditions such as the spinneret, spinning temperature, discharge rate per hour, heated gas temperature / spout speed from the slit, and spout position, and if necessary, cross-wrapping. After adjusting the basis weight, lightly adhering with a binder, adding a rolling press, infusibilizing, further firing, and then shortening this pitch fiber using a milling device, short fiber A Get.

Preparation of mixed fiber aggregate of short fibers A and short fibers B Next, blended with pitch-based carbon fibers composed of long fibers B previously collected on a wire mesh belt, a flat mixed fiber aggregate is obtained. obtain. When adjusting to this sheet form, a wet papermaking method in which a water-swellable organic polymer such as polyvinyl alcohol (PVA) fiber is partially used instead of a binder is applied, or short fibers A are utilized by utilizing the amount of air. It is possible to apply a dry papermaking method in which the short fibers B are mixed and fused with a thermoplastic resin instead of a binder.
After that, if necessary, a carbon fiber aggregate for a composite material that can be mixed with a matrix is obtained through various steps such as infusibilization, firing treatment, and graphitization treatment.

An example is shown concretely.
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 284 ° C. Using a spinneret having a circular cross-sectional hole with a diameter of 0.2 mm, heated air was ejected from the slit at a linear velocity of 5000 m / min, and the melt pitch was pulled to produce pitch-based short fibers having an average diameter of 13 μm. The spun long fibers were collected on a belt to form a mat, and further formed into a mat-like pitch fiber having a basis weight of 250 g / m ^{2 by} cross wrapping.

  The mat-like pitch fiber was heated in the air from 170 ° C. to 310 ° C. at an average heating rate of 5 ° C./min for infusibilization. The infusible mat-like pitch fibers were fired at 700 ° C., then shortened with a pulverizer, and then fired at 3000 ° C. to obtain pitch-based carbon fibers. The average diameter (D1) of the pitch-based carbon fibers was 11 μm, and the ratio of the fiber diameter dispersion to D1 (CV1) was 12%. The average fiber length (L1) was 80 μm. The crystallite size in the growth direction of the hexagonal network surface was 46 nm. The thermal conductivity in the fiber axis direction was 590 W / (m · K). The true density of the pitch-based carbon short fibers was 2.1 g / cc.

Next, 70 parts by weight of the above-mentioned pitch-based carbon short fibers A, 20 parts by weight of carbon long fibers B (average fiber length 8.5 mm) in a fired state, and PVA fibers (trade name: Vinylon) having an average fiber length of 5 mm as a binder ) 10 parts by weight of the paper was made, and then fired at 1500 ° C. in a nitrogen atmosphere to obtain a pitch-based carbon fiber aggregate.
The pitch-based carbon fiber aggregate had a carbon content of 99% by weight, a thickness of 1.2 mm, and a porosity of 85% by volume.

  Next, a maleic acid-modified polypropylene film manufactured by Sanyo Kasei Co., Ltd. was used as the matrix resin, the pitch-based carbon fiber aggregate was set as a reinforcing material, and the volume ratio of the molded body was set to 30%, and a vacuum made by Kitagawa Seiki Co., Ltd. Using a press machine, press molding was performed so that the inner diameter of the inner mold was 200 mm and the thickness became 1 mm. It was 4.5 W / (m * K) when the heat conductivity of the thickness direction of the shape | molded carbon fiber reinforced composite material was measured.

[Example 2]
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 284 ° C. A spinneret having a circular cross-sectional hole having a diameter of 0.2 mm was used, heated air was ejected from the slit at a linear velocity of 5000 m / min, and the melt pitch was pulled to produce pitch-based short fibers having an average diameter of 13 μm. The spun long fibers were collected on a belt to form a mat, and further formed into a mat-like pitch fiber having a basis weight of 255 g / m ^{2 by} cross wrapping.

  This mat-like pitch fiber was heated from 170 ° C. to 305 ° C. in air at an average temperature rising rate of 5 ° C./min for infusibilization. The infusible mat-like pitch fibers were fired at 700 ° C., then shortened with a pulverizer, and then further fired at 2900 ° C. to obtain pitch-based carbon short fibers A. The pitch-type carbon fiber had an average diameter (D1) of 11 μm, a ratio of diameter dispersion to D1 (CV1) of 11%, and an average fiber length (L1) of 50 μm. The crystallite size in the growth direction of the hexagonal network surface was 42 nm. The thermal conductivity in the fiber axis direction was 510 W / (m · K). The true density of the pitch-based carbon fiber A was 2.1 g / cc.

Next, 70 parts by weight of pitch-based carbon short fibers A, 20 parts by weight of carbon short fibers B (average fiber length 8.5 mm) in a fired state, and 10 parts by weight of polyethylene terephthalate fibers having an average fiber length of 10 mm as a binder Papermaking was performed, and then a calendar process was performed at 280 ° C. to obtain a pitch-based carbon fiber aggregate.
The pitch-based carbon fiber aggregate had a carbon content of 90% by weight, a thickness of 1.2 mm, and a porosity of 70% by volume.

  Next, using a polycarbonate (trade name: Panlite) film as a matrix resin, the pitch-based carbon fiber reinforcement is set to 35% as a volume ratio of the molded body, and in a vacuum press machine manufactured by Kitagawa Seiki Co., Ltd. Press molding was performed so that the inner diameter was 1 mm with a 200 mm mold. It was 4.3 W / (m * K) when the heat conductivity of the thickness direction of the shape | molded carbon fiber reinforced composite material was measured.

[Comparative 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 285 ° C. Using a spinneret with a 0.2 mm diameter circular cross-sectional hole, heated air was ejected from the slit at a linear velocity of 5000 m / min, and the melt pitch was pulled to produce pitch-based long fibers having an average diameter of 10 μm. The spun fibers were collected on a belt to form a mat, and further a pitch fiber mat having a three-dimensional random shape with a basis weight of 250 g / m ^{2 by} cross wrapping.

  The pitch fiber mat was heated from 170 ° C. to 295 ° C. in air at an average heating rate of 7 ° C./min for infusibilization. The infusible three-dimensional random mat was fired at 800 ° C. The pitch-based carbon fiber constituting the pitch-based carbon fiber mat after firing had an average diameter (D1) of 9 μm and a yarn diameter dispersion ratio (CV1) to D1 of 18%. The average fiber length (L1) was 40 μm. The crystallite size in the growth direction of the hexagonal network surface was 3 nm. The thermal conductivity in the fiber axis direction was 35 W / (m · K).

Next, 70 parts by weight of pitch-based carbon fibers and 10 parts by weight of PVA fibers (trade name Vinylon) having an average fiber length of 5 mm as a binder were made to obtain a pitch-based carbon fiber aggregate.
The pitch-based carbon fiber aggregate had a carbon content of 65% by weight, a thickness of 1.5 mm, and a porosity of 80% by volume.

  Next, a maleic acid-modified polypropylene film manufactured by Sanyo Kasei Co., Ltd. was used as the matrix resin, and the pitch-based carbon fiber aggregate was set as a reinforcing material so that the volume ratio of the molded product was 30%. A vacuum press manufactured by Kitagawa Seiki Co., Ltd. Using a machine, press molding was performed so that the inner diameter was 1 mm with a 200 mm mold. When the thermal conductivity in the thickness direction of the molded carbon fiber reinforced composite material was measured, it was less than 1 W / (m · K), which was a small value of thermal conductivity.

[Comparative Example 2]
In Example 1, the maleic acid-modified polypropylene resin alone was used as a molded body without using a pitch-based carbon fiber aggregate, and the thermal conductivity in the thickness direction was measured. The result was less than 1 W / (m · K). It was.

Claims (11)

The average diameter (D1) of the single fibers is in the range of 1 to 20 μm, and the ratio (CV1) of the fiber diameter distribution (S1) to D1 is in the range of 5 to 20%, and the average fiber length (L1) of the single fibers 1 to 100 μm, the ratio of the average fiber length to the average diameter (D1), that is, the pitch-based carbon fiber A having an aspect ratio of 1 to 100,
The fiber average diameter (D2) is in the range of 2 to 40 μm, and the ratio (CV2) of the fiber diameter distribution (S2) to D2 is in the range of 5 to 20%. The average fiber length (L2) of the single fiber is Carbon fiber B that is 0.1 to 150 mm,
A carbon fiber mixture obtained by mixing so that the weight ratio of the short fiber A to the long fiber B is 1 to 99 to 99 to 1,
The carbon fiber aggregate whose microcrystal size derived from the growth direction of the hexagonal mesh surface of the pitch-based carbon fiber short fibers A in the carbon fiber mixture is 5 nm or more.   The true density of the short carbon fiber A is in the range of 1.5 to 2.5 g / cc, and the thermal conductivity in the fiber axis direction of the short fiber A is 200 W / (m · K) or more. The carbon fiber aggregate described in 1.   The thermal conductivity in the thickness direction of the mixture in which the short fibers A and the short fibers B are mixed is 3 W / (m · K) or more, and the carbon fiber mixture has a thickness of 0.05 to 5 mm. The carbon fiber aggregate according to claim 1 or 2, comprising pitch-based carbon fibers having a porosity of 50 to 95% by volume.   The carbon fiber aggregate according to any one of claims 1 to 3, wherein the short fibers B include pitch-based carbon fibers, the carbon fiber-reinforced composite obtained by impregnating the carbon fiber aggregate with a matrix made of a synthetic resin. material.   The carbon fiber reinforced composite material according to claim 4, wherein the matrix is a thermoplastic resin.   The carbon fiber reinforced composite material according to claim 4, wherein the matrix contains a thermosetting resin or a precursor thereof.   The carbon fiber reinforced composite material according to claim 4, wherein the carbon fiber aggregate contains 10 to 80% by volume with respect to the matrix.   The carbon fiber reinforced composite material according to any one of claims 4 to 7, wherein the thermal conductivity in the thickness direction in a state of being formed into a flat plate is 1 W / (m · K) or more.   The pitch-based carbon fiber mixture is captured in the presence of a binder to form a non-woven fiber assembly having a carbon content of 80% by weight or more. A method for producing a carbon fiber aggregate, comprising a step of obtaining a planar aggregate obtained by adjusting the thickness to 0.05 to 5 mm and further adjusting the porosity to 50 to 95% by volume.   At least 1% by weight of the amount used is carbonaceous to form a non-woven aggregate using a binder that can remain in the carbon fiber aggregate after firing, and then fired at a temperature of 500 to 1000 ° C. in an inert gas atmosphere. The manufacturing method of the pitch-type carbon fiber aggregate | assembly of Claim 9 formed by giving baking treatment and / or a graphitization process at predetermined temperature in the range of 1000 to 3500 degreeC.   A method for producing a carbon fiber reinforced composite material, wherein the impregnation treatment of the matrix resin is carried out under vacuum and under pressurized conditions.