JP2007291576A - Thermoconductive filler and compounded molded article by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pitch-based carbon short fiber filler having a high thermoconductivity and a high molding property, and a compounded molding material. <P>SOLUTION: This carbon short fiber filler is characterized by having a closed graphene sheet at the end face of a filler as observed by a transmission type electron microscope, and the small unevenness of the filler surface as observed by the transmission microscope. Also a controlled mean fiber diameter and distribution of the same is prepared and the compounded molded article is also produced by using the same. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a thermally conductive filler. More specifically, the present invention relates to a heat conductive filler using pitch-based carbon short fibers as a raw material.

  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 fiber is widely used for aerospace applications, construction / civil engineering applications, industrial robots, sports / leisure applications, etc., taking advantage of its significantly higher strength and elastic modulus than ordinary synthetic polymers. . In addition, PAN-based carbon fibers are often used mainly in the field of utilizing the strength, and pitch-based carbon fibers are used in the field of utilizing the elastic modulus.

  In recent years, an efficient method of using energy typified by energy saving has attracted attention, while heat generation due to Joule heat in a CPU and an electronic circuit that have been speeded up has been recognized as a serious problem. In order to solve these problems, it is necessary to achieve so-called thermal management in which heat is efficiently processed.

  In order to realize thermal management, inorganic materials having high thermal conductivity such as metal, metal oxide, metal nitride, metal oxynitride, and alloy are often used. Metal die casting can be considered a typical example. However, in order to manufacture a housing for an electric component having a complicated shape, it is desirable from the viewpoint of cost effectiveness to use the above-mentioned material as a composite material mixed with some matrix as a filler. However, the thermal conductivity of the synthetic resin often used for the matrix is about 1/100 or less that of the filler, and a large amount of filler needs to be mixed. However, the addition of a large amount of filler causes deterioration of moldability and impairs practicality. Therefore, there has been a demand for a highly thermally conductive filler that takes into consideration a shape that can efficiently exhibit thermal conductivity.

  In general, carbon fibers are said to have higher thermal conductivity than other synthetic polymers, but further improvements in thermal conductivity are being studied for thermal management applications. However, the thermal conductivity of commercially available PAN-based carbon fibers is usually smaller than 200 W / (m · K). This is because the PAN-based carbon fiber is a so-called non-graphitizable carbon fiber, and it is very difficult to improve the graphitization property that bears heat conduction. On the other hand, pitch-based carbon fibers are called graphitizable carbon fibers, and can be made more graphitic than PAN-based carbon fibers, and are recognized to easily achieve high thermal conductivity. Therefore, there is a possibility that a highly thermally conductive filler in which consideration is given to a shape capable of efficiently expressing thermal conductivity can be obtained.

  However, it is difficult to process a carbon fiber alone into a heat conductive member, and it is necessary to use a very special method. Therefore, like a metallic filler or the like, it is required to form a composite material of some matrix and carbon fiber, to form a molded body, and to improve the thermal conductivity of the molded body.

  And in order for a molded object to achieve sufficient heat conduction, it is necessary for the filler mainly responsible for heat conduction to form a three-dimensional network. For example, in the case of spherical fillers of uniform size, the filler network in the molded body depends on the dispersion state, but if uniform dispersion is assumed, it becomes a percolation behavior. Accordingly, in order to obtain sufficient thermal conductivity and electrical conductivity, it is necessary to add a certain amount of filler. However, in the method of forming a molded body, it is often very difficult to disperse the medium and the filler at a certain concentration or more.

In view of such a background, studies have been made to give fillers three-dimensional crosslinking. For example, Patent Document 1 discloses an attempt to transport a heat flow by forming a metal network. However, it is considered that a very high level of technology is required for dispersion into the matrix. Patent Document 2 discloses that alloying causes the matrix and filler to melt simultaneously, and as a result, high thermal conductivity is achieved while maintaining formability.
However, the addition of a metal material having a specific gravity greater than that of the resin also increases the specific gravity of the resin composition, and must be considered disadvantageous for applications in which weight reduction is discussed on the order of 1 g.

Japanese Patent Laid-Open No. 6-196684 International Publication No. 03/029352 Pamphlet

  As mentioned above, in order to create a resin composition that is lightweight and has high thermal conductivity, a material with high thermal conductivity and low specific gravity is required, and the maximum thermal conductivity is exhibited in the final use state. Such filler control has been strongly desired.

  The inventors of the present invention aim to improve the thermal conductivity and reduce the specific gravity in the final molded body, and the pitch-based carbon short fibers having high thermal conductivity as the thermal conductive material are sized and dispersed. The inventors of the present invention have found that this can be achieved by paying attention to the surface shape and fine structure, appropriately controlling, and further dispersing in a matrix.

That is, the object of the present invention is to
The end face observed with a transmission electron microscope is closed, the pitch-based carbon short fiber filler has a substantially flat observation surface with a scanning electron microscope, and the average fiber diameter (D1) observed with an optical microscope Is a range of 7 μm or more and 12 μm or less, and can be achieved by a pitch-based carbon short fiber filler in which the fiber fraction (S1) 100-percentage of the average fiber diameter (D1) is in the range of 3-20.

  In the present invention, the average fiber length (L1) is in the range of 10 to 700 μm, the ratio of L1 to D1 is 1 to 100, and the true density is in the range of 1.5 to 2.2 g / cc. The thermal conductivity in the fiber axis direction is 300 W / (m · K) or more, the crystallite size derived from the thickness direction of the hexagonal network surface is 10 nm or more, and is derived from the growth direction of the hexagonal network surface. The crystallite size is 8 nm or more, the pitch-based carbon short fiber filler according to any one of claims 1 to 4 and a matrix, wherein the filler having a volume fraction of 3 to 60% by volume with respect to the matrix. The composite molded body to be contained, the matrix is a thermoplastic resin and / or a thermosetting resin, the thermoplastic resin is a polycarbonate, polyethylene terephthalate, polyethylene 2,6 naphthalate, It is at least one resin selected from the group of nylons, polypropylenes, polyethylenes, polyepoxy ether ketones, polyphenylene sulfides, and thermosetting resins are epoxies, acrylics, urethanes, silicones, phenols The composite molding according to any one of claims 5 to 8, which is at least one kind of resin selected from a group of resins, has a thermal conductivity of 2 W / (m · K) or more in a state of being molded into a flat plate shape. A composite molded body produced by a combination of at least one method selected from the group of injection molding, press molding, calendar molding, roll molding, extrusion molding, cast molding, and blow molding A heat sink for an electronic component comprising the composite molded body according to any one of claims 5 to 8 as a main material, Electric wave shielding plate for a composite molding according mainly material or Re, the heat exchanger for a composite molding according mainly material to any of the claims 5-8 are included.

  The pitch-based carbon short fiber filler of the present invention has a specific shape and is controlled in size, so that high thermal conductivity can be imparted to the composite molded body while suppressing an increase in the viscosity of the matrix. Therefore, a composite molding material having good moldability and high thermal conductivity can be obtained. The composite molded body can increase the efficiency of the heat sink for electronic parts and the heat exchanger. Furthermore, since the pitch-based carbon short fibers are excellent in radio wave shielding in a frequency band of several GHz, it is possible to supply a radio wave shielding plate.

Next, embodiments of the present invention will be described sequentially.
Examples of the raw material for pitch-based carbon short fibers used in 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. These may be used singly or in combination of two or more, but it is particularly desirable to use mesophase pitch alone in order to improve the thermal conductivity of the short carbon fiber.

The softening point of the raw material pitch can be determined by the Mettler method, and is preferably 230 ° C. or higher and 340 ° C. or lower. If the softening point is lower than 230 ° C., fusion between fibers or large heat shrinkage occurs during infusibilization. On the other hand, when the temperature is higher than 340 ° C., thermal decomposition of the pitch occurs and it becomes difficult to form a yarn. Further, gas components are generated, bubbles are generated in the yarn, and strength is deteriorated.
The raw material pitch is spun by the melt blow method, and then becomes pitch-based carbon short fibers by infusibilization, firing, milling, sieving, and graphitization. Each step will be described below.

  In the present invention, there is no particular limitation on the shape of the spinning nozzle of the pitch fiber used as the raw material for the pitch-based carbon short fiber, but the nozzle hole length / hole diameter ratio is preferably smaller than 3, more preferably Is about 1.5. The temperature of the nozzle at the time of spinning 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 viscosity of the spinning pitch is 1 to 100 Pa · S, preferably 50 to 60 Pa · S.

  The pitch fibers drawn out from the nozzle holes are shortened by blowing a gas having a linear velocity of 100 to 10000 m per minute heated to 100 to 370 ° 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 are further cross-wrapped to form a web with a constant basis weight.
The web made of pitch fibers thus obtained is infusible by a known method and fired at 700 to 900 ° C. Infusibilization is achieved by applying heat treatment at a temperature of 200 to 300 ° C. for a certain period of time using air or a gas obtained by adding ozone, nitrogen dioxide, nitrogen, oxygen, iodine, or bromine to air. Considering safety and convenience, it is desirable to carry out in air. The infusible pitch fiber is fired in vacuum or in an inert gas such as nitrogen, argon, krypton, etc., but at normal pressure and at low cost.

  The web made of infusibilized and fired pitch fibers is further milled and sieved in order to further shorten the fibers and make them a certain length. For milling, a pulverizer such as a Victory mill, a jet mill, a high-speed rotary mill, or a cutting machine is 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 average fiber length of the fibers produced by milling is controlled by adjusting the rotational speed of the rotor, the angle of the blade, and the like. Furthermore, it divides into 10-60 micrometers by a sieve, More preferably, it is 15-50 micrometers. Alternatively, it is divided into 100 to 700 μm, more preferably 100 to 300 μm. Such adjustment of the average fiber length can be achieved by combining the coarseness of the sieve.

  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 performed in a non-oxidizing atmosphere in an Atchison furnace or the like.

  Next, the shape of the pitch-based carbon short fiber filler of the present invention will be described. The pitch-based carbon short fibers of the present invention have 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, the affinity with expanded graphite can be further increased, which is preferable. 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 short fiber filler of the present invention is required to have a substantially flat observation surface with a scanning electron microscope.
Here, “substantially flat” means that the surface does not have severe unevenness like a fibril structure, and when there is intense unevenness on the surface of the filler, the surface area of the filler is reduced during kneading with the matrix resin. It causes an increase in viscosity accompanying the increase and deteriorates moldability. Therefore, it is desirable that the surface unevenness is as small as possible.
The pitch-based carbon short fiber filler described above can be easily obtained by performing graphitization after milling.

  The average fiber diameter (D1) observed with an optical microscope of the pitch-based short carbon fiber filler of the present invention is required to be 7 to 12 μm, and more preferably 8 to 11 μm. When D1 is larger than 12 μm, it is easy to cause fusion with adjacent yarns in the infusibilization process. When D1 is smaller than 7 μm, the surface area per weight of the pitch-based short carbon fiber filler is increased, and the fiber surface is substantially Even if it is flat, the moldability is deteriorated in the same manner as the fiber having irregularities on the surface, which is not preferable for practical use. The percentage of fiber diameter dispersion (S1), which is the dispersion of fiber diameters observed with an optical microscope, with respect to D1 is preferably in the range of 3-20.

  The average fiber length (L1) of the pitch-based carbon short fiber filler of the present invention is preferably 10 to 700 μm. L1 has an optimum value depending on the purpose, but in the case of providing a reinforcing effect that the filler is secondaryly produced, a range of 300 to 700 μm is preferable. More preferably, it is the range of 300-500 micrometers. On the other hand, when the filler is used for preparing a heat transfer path, that is, for a heat dissipation aid, L1 is preferably in the range of 10 to 300 μm. More preferably, it is the range of 10-100 micrometers. When L1 is shorter than 10μ, it deviates from the fiber shape and deviates from the gist of the present invention. When L1 exceeds 700 μm, the bulk density becomes small and mixing with the matrix component becomes difficult. The ratio of L1 to D1 (L1 / D1) is preferably in the range of 1-100.

  Although L1 / D1 also depends on the average fiber length, when L1 / D1 is smaller than 1, powder falling in the final molded product becomes remarkable. On the other hand, if L1 / D1 exceeds 100, the percentage of fibers that breaks increases, making it difficult to achieve the original performance. More preferably, it is 1.5 to 10 when the average fiber length is 10 to 100 μm, and 30 to 50 when the average fiber length is 300 to 500 μm.

  In the present invention, the true density of the pitch-based carbon short fiber filler strongly depends on the graphitization temperature, but is preferably in the range of 1.5 to 2.2 g / cc. More preferably, it is 1.6-2.0 g / cc. Further, the thermal conductivity in the fiber axis direction of the pitch-based short carbon fibers is 300 W / (m · K) or more, and more preferably 400 W / (m · K) or more.

  The pitch-based carbon short fiber filler preferably has a crystallite size derived from the thickness direction of the hexagonal network surface of 10 nm or more, and further has a crystallite size derived from the growth direction of the hexagonal network surface of 8 nm or more.

  The crystallite size corresponds to graphitization in both the thickness direction of the hexagonal network surface and the growth direction of the hexagonal network surface, and a certain size or more is necessary to exhibit thermophysical properties. The crystallite size derived from the thickness direction of the hexagonal mesh surface and the crystallite size in the growth direction of the hexagonal mesh surface can be obtained by an X-ray diffraction method. The measurement method was the concentration method, and the Gakushin method was used as the analysis method. The crystallite size in the thickness direction of the hexagonal mesh plane is obtained using a diffraction line from the (002) plane, and the crystallite size in the growth direction of the hexagonal mesh plane is obtained using a diffraction line from the (110) plane, respectively. It was.

  In the present invention, the pitch-based carbon short fiber filler may be surface-treated and then a sizing agent may be added to the filler in an amount of 0.01 to 10% by weight, preferably 0.1 to 2.5% by weight. 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, this can be carried out according to the required physical properties.

  In the present invention, a pitch-based carbon short fiber filler and a matrix are mixed to produce a composite molded body. At this time, the pitch-based carbon short fiber filler is added in a volume fraction of 3 to 60% with respect to the matrix. If the addition amount is less than 3% by volume, it is difficult to ensure sufficient thermal conductivity. On the other hand, it is often difficult to add more than 60% by volume of pitch-based carbon short fiber filler to the matrix.

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

  The thermoplastic resin may be selected from at least one selected from the group consisting of polycarbonates, polyethylene terephthalates, polyethylene 2,6 naphthalates, nylons, polypropylenes, polyethylenes, polyepoxy ether ketones, and polyphenylene sulfides. it can.

  More specifically, ethylene-α-olefin copolymers such as polyethylene, polypropylene, ethylene-propylene copolymer, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, ethylene-vinyl acetate copolymer , Polyvinyl alcohol, polyacetal, fluorine resin (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 (polymethacrylate such as polymethylmethacrylate) Ester), polyacrylic acids, polycarbonate, polyphenylene sulfide, polysulfone, polyether sulfone, polyether nitrile, polyether ketone, polyketone, liquid crystal polymer, ionomer and the like. As the matrix, one kind of them may be used alone, or two or more kinds may be used in appropriate combination, or a polymer alloy made of two or more kinds of polymer materials may be used.

  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 molded body of the present invention is prepared by mixing a pitch-based carbon short fiber filler and a matrix. During mixing, a kneader, a mixer, a blender, a roll, an extruder, a milling machine, a self-revolving agitator A mixing device such as a machine 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 manufacturing 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.

  When the composite molded body of the present invention is molded into a flat plate shape 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 polymer material used as the matrix.

  The composite molded body of the present invention can be used as a heat radiating plate 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 short fiber filler added, even in electronic parts, automobiles that require relatively high heat resistance and industrial power that requires large currents It can be suitably used for a connector of a module. 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 heat exchanger component. Can be used for heat pipes. Furthermore, the radio wave shielding property of the pitch-based carbon short fiber filler can be utilized, and can be suitably used particularly as a radio wave shielding member in the GHz band.

Examples are shown below, but the present invention is not limited thereto.
(1) Average fiber diameter and fiber diameter dispersion of pitch-based carbon short fiber filler:
The pitch-based carbon fiber filler that had undergone graphitization was determined by photographing 10 fields of view at 400 times under an optical microscope.
(2) Average fiber length of pitch-based carbon short fiber filler:
The pitch-based short carbon fiber filler that had undergone graphitization was determined by photographing 10 visual fields under an optical microscope. The magnification was appropriately adjusted according to the yarn length.
(3) True density of pitch-based carbon short fiber filler:
It calculated | required using the specific gravity method.
(4) Crystal size:
Obtained by X-ray diffraction, the crystallite size derived from the thickness direction of the hexagonal mesh surface is obtained using diffraction lines from the (002) plane, and the crystallite size derived from the growth direction of the hexagonal mesh surface is the (110) plane. It was determined using the diffraction line from. In addition, the request was made in accordance with the Gakushin Law.
(5) Thermal conductivity of pitch-based carbon short fiber filler:
The resistivity of pitch-based short carbon fibers after graphitization prepared under the same conditions except for the pulverization step is measured, and the relationship between the thermal conductivity and electrical resistivity disclosed in JP-A-11-117143 is expressed. It calculated | required from following formula (1).
[Equation 1]
K = 1272.4 / ER-49.4 (1)
Here, K represents the thermal conductivity W / (m · K) of the pitch-based short carbon fiber after graphitization, and ER represents the electrical specific resistance μΩm of the same pitch-based short carbon fiber.
(6) Thermal conductivity of flat molded body:
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 hole cap having a diameter of 0.2 mmφ, heated air was ejected from the slit at a linear velocity of 5000 m / min, and the melt pitch was pulled to produce pitch short fibers having an average fiber diameter of 15 μm. The spun short fibers were collected on a belt to form a mat, and then a web made of pitch-based short fibers having a basis weight of 320 g / m ^{2 by} cross wrapping.

  The web was infusibilized by increasing the temperature from 175 ° C. to 280 ° C. in air at an average temperature increase rate of 7 ° C./min. The infusible web was fired at 800 ° C. in a nitrogen atmosphere, and then milled, and sieved to a short fiber filler having an average fiber length of 25 μm. Then, it graphitized by heat-processing at 3000 degreeC with the electric furnace made into the non-oxidizing atmosphere, and it was set as the pitch-type carbon short fiber filler. The average fiber diameter was 9.7 μm. The percentage of the fiber diameter dispersion to the average fiber diameter was 14%. The true density was 2.05 g / cc.

The image was observed with a transmission electron microscope at a magnification of 1,000,000 times and magnified on a photograph at 4 million times. It was confirmed that the graphene sheet was closed at the end face of the pitch-based carbon short fiber filler. Further, the surface of the pitch-based carbon short fiber filler, which was observed with a scanning electron microscope at a magnification of 4000 times, was smooth with no large irregularities.
The crystallite size in the thickness direction of the hexagonal network surface determined by the X-ray diffraction method was 15 nm. The crystallite size in the growth direction of the hexagonal network surface was 20 nm.

A single yarn was extracted from a graphitized web prepared by the same process up to firing and not milled, and heat-treated at 3000 ° C. in an electric furnace in a non-oxidizing atmosphere, and the electrical resistivity was measured. It was 2.4 μΩm. The thermal conductivity obtained using the following formula (1) was 480 W / (m · K).
[Equation 2]
K = 1272.4 / ER-49.4 (1)

[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 283 ° C. Using a hole cap with a diameter of 0.2 mmφ, heated air was ejected from the slit at a linear velocity of 6000 m / min, and the melt pitch was pulled to produce pitch short fibers having an average fiber diameter of 11 μm. The spun short fibers were collected on a belt to form a mat, and then a web made of pitch-based short fibers having a basis weight of 280 g / m ^{2 by} cross wrapping.

  The web was infusibilized by increasing the temperature from 175 ° C. to 280 ° C. in air at an average temperature increase rate of 7 ° C./min. The infusible web was fired at 800 ° C. in a nitrogen atmosphere and then milled and sieved to a short fiber filler having an average fiber length of 30 μm. Then, it graphitized by heat-processing at 3000 degreeC with the electric furnace made into the non-oxidizing atmosphere, and it was set as the pitch-type carbon short fiber filler. The average fiber diameter was 8.1 μm. The percentage of the fiber diameter dispersion to the average fiber diameter was 16%. The true density was 2.0 g / cc. The image was observed with a transmission electron microscope at a magnification of 1,000,000 times and magnified on a photograph at 4 million times. The graphene sheet was closed on the end face of the pitch-based carbon short fiber filler. Further, the surface of the pitch-based carbon short fiber filler, which was observed with a scanning electron microscope at a magnification of 4000 times, was smooth with no large irregularities.

The crystallite size in the thickness direction of the hexagonal network surface determined by the X-ray diffraction method was 17 nm. The crystallite size in the growth direction of the hexagonal network surface was 25 nm.
A single yarn was extracted from a graphitized web prepared by the same process up to firing and not milled, and heat-treated at 3000 ° C. in an electric furnace in a non-oxidizing atmosphere, and the electrical resistivity was measured. 2.2 μΩm. The thermal conductivity obtained using the above formula (1) was 530 W / (m · K).

[Example 3]
The opening of the sieving after milling was adjusted with the same web as in Example 1 to obtain a pitch-based carbon short fiber filler having an average fiber length of 350 μm.
The average fiber diameter was 9.9 μm. The percentage of the fiber diameter dispersion to the average fiber diameter was 16%. The true density was 2.05 g / cc. The image was observed with a transmission electron microscope at a magnification of 1,000,000 times and magnified on a photograph at 4 million times. The graphene sheet was closed on the end face of the pitch-based carbon short fiber filler. Further, the surface of the pitch-based carbon short fiber filler, which was observed with a scanning electron microscope at a magnification of 4000 times, was smooth with no large irregularities.

The crystallite size in the thickness direction of the hexagonal network surface determined by the X-ray diffraction method was 14 nm. The crystallite size in the growth direction of the hexagonal network surface was 19 nm.
The thermal conductivity is the same as in Example 1 because the graphitized material is used as it is as the web before milling.

[Example 4]
The opening of the sieving after milling was adjusted with the same web as in Example 2 to obtain a pitch-based carbon short fiber filler having an average fiber length of 400 μm.
The average fiber diameter was 7.9 μm. The percentage of the fiber diameter dispersion to the average fiber diameter was 15%. The true density was 2.0 g / cc. The image was observed with a transmission electron microscope at a magnification of 1,000,000 times and magnified on a photograph at 4 million times. The graphene sheet was closed on the end face of the pitch-based carbon short fiber filler. Further, the surface of the pitch-based carbon short fiber filler, which was observed with a scanning electron microscope at a magnification of 4000 times, was smooth with no large irregularities.

The crystallite size in the thickness direction of the hexagonal network surface determined by the X-ray diffraction method was 16 nm. The crystallite size in the growth direction of the hexagonal network surface was 24 nm.
The thermal conductivity is the same as that of Example 2 because the graphitized material is used as it is as the web before milling.

[Example 5]
The process up to milling was the same as in Example 1, and graphitized at 2300 ° C. in an electric furnace in a non-oxidizing atmosphere to obtain a pitch-based carbon short fiber filler. The average fiber length was 30 μm.
The average fiber diameter was 10.6 μm. The percentage of the fiber diameter dispersion to the average fiber diameter was 13%. The true density was 1.8 g / cc. The image was observed with a transmission electron microscope at a magnification of 1,000,000 times and magnified on a photograph at 4 million times. The graphene sheet was closed on the end face of the pitch-based carbon short fiber filler. Further, the surface of the pitch-based carbon short fiber filler, which was observed with a scanning electron microscope at a magnification of 4000 times, was smooth with no large irregularities.

The crystallite size in the thickness direction of the hexagonal network surface determined by the X-ray diffraction method was 11 nm. The crystallite size in the growth direction of the hexagonal network surface was 10 nm.
A single yarn was extracted from a graphitized web prepared by the same process up to firing and not milled, and heat-treated at 2300 ° C. in an electric furnace in a non-oxidizing atmosphere, and the electrical resistivity was measured. It was 3.4 μΩm. The thermal conductivity obtained using the above formula (1) was 320 W / (m · K).

[Comparative Example 1]
The process up to milling was the same as in Example 1, and sieving was performed on pitch-based carbon short fiber filler having an average fiber length of 28 μm. Then, it graphitized by heat-processing at 1300 degreeC with the electric furnace made into the non-oxidizing atmosphere, and it was set as the pitch type | system | group carbon short fiber filler. The average fiber diameter was 10.8 μm. The percentage of the fiber diameter dispersion to the average fiber diameter was 12%. The true density was 1.4 g / cc.

  The image was observed with a transmission electron microscope at a magnification of 1,000,000 times and magnified on a photograph at 4 million times. On the end face of the pitch-based carbon short fiber filler, a portion where the graphene sheet is closed and a portion where the graphene sheet is open are mixed. Further, the surface of the pitch-based carbon short fiber filler, which was observed with a scanning electron microscope at a magnification of 4000 times, was smooth with no large irregularities.

The crystallite size in the thickness direction of the hexagonal network surface determined by the X-ray diffraction method was 3 nm. The crystallite size in the growth direction of the hexagonal network surface was 2 nm.
A single yarn was extracted from a graphitized web prepared by the same process up to firing and not milled, and heat treated at 1300 ° C. in an electric furnace in a non-oxidizing atmosphere, and the electrical resistivity was measured. 20 μΩm. The thermal conductivity obtained using the above formula (1) was 14 W / (m · K).

[Comparative Example 2]
A pitch-based carbon short fiber filler having an average fiber length of 19 μm is graphitized at 3000 ° C. in an electric furnace having a non-oxidizing atmosphere with the same web as in Example 1 until milling, followed by milling and sieving. Got.

  The average fiber diameter was 9.4 μm. The percentage of the fiber diameter dispersion to the average fiber diameter was 18%. The true density was 1.98 g / cc. The image was observed with a transmission electron microscope at a magnification of 1,000,000 times and magnified on a photograph at 4 million times. The graphene sheet was open on the end face of the pitch-based carbon short fiber filler. Further, the surface of the pitch-based carbon short fiber filler, which was observed with a scanning electron microscope at a magnification of 4000 times, had many irregularities and was fibrillar.

The crystallite size in the thickness direction of the hexagonal network surface determined by the X-ray diffraction method was 15 nm. The crystallite size in the growth direction of the hexagonal network surface was 20 nm.
A single yarn was extracted from the graphitized web and the electrical resistivity was measured and found to be 2.8 μΩm. The thermal conductivity obtained using the above formula (1) was 400 W / (m · K).
The physical properties from Example 1 to Comparative Example 2 are summarized in Table 1.

[Example 6]
As a thermoplastic resin, Teijin Chemicals polycarbonate was selected, and the pitch-based carbon short fiber filler produced in Example 1 was compounded with a Kurimoto biaxial kneader at a volume ratio of 60:40, and master chip and did. This chip was processed into a 2 mm thick flat plate with an injection molding machine manufactured by Meiki Seisakusho to obtain a composite molded body. The thermal conductivity of this composite molded body was measured and found to be 4.0 W / (m · K).

[Example 7]
As a thermoplastic resin, Teijin Chemicals polycarbonate was selected, and the pitch-based carbon short fiber filler produced in Example 1 was compounded with a Kurimoto biaxial kneader at a volume ratio of 70:30. did. This chip was processed into a 2 mm thick flat plate with an injection molding machine manufactured by Meiki Seisakusho to obtain a composite molded body. The thermal conductivity of the composite molded body was measured and found to be 3.3 W / (m · K).

[Example 8]
As a thermoplastic resin, Teijin Chemicals polycarbonate was selected, and the pitch-based carbon short fiber filler produced in Example 1 was compounded with a Kurimoto biaxial kneader at a volume ratio of 80:20 to obtain a master chip. did. This chip was processed into a 2 mm thick flat plate with an injection molding machine manufactured by Meiki Seisakusho to obtain a composite molded body. When the thermal conductivity of this composite molded body was measured, it was 2.0 W / (m · K).

[Example 9]
As a thermoplastic resin, Teijin Chemicals polycarbonate was selected, and the pitch-based carbon short fiber filler produced in Example 4 was compounded at a volume ratio of 70:30 using a Kurimoto biaxial kneader, did. This chip was processed into a 2 mm thick flat plate with an injection molding machine manufactured by Meiki Seisakusho to obtain a composite molded body. The thermal conductivity of this composite molded body was measured and found to be 3.6 W / (m · K).

[Example 10]
As a thermoplastic resin, Teijin Chemicals polycarbonate was selected, and the pitch-based carbon short fiber filler produced in Example 5 was compounded with a Kurimoto biaxial kneader at a volume ratio of 70:30 to obtain a master chip. did. This chip was processed into a 2 mm thick flat plate with an injection molding machine manufactured by Meiki Seisakusho to obtain a composite molded body. When the thermal conductivity of this composite molded body was measured, it was 2.5 W / (m · K).

[Comparative Example 3]
Teijin Chemicals polycarbonate was selected as the thermoplastic resin, and the pitch-based carbon short fiber filler produced in Comparative Example 2 was compounded with a Kurimoto biaxial kneader at a volume ratio of 70:30. A master chip with increased and insufficient kneading was produced. This chip was processed into a 2 mm-thick flat plate by an injection molding machine manufactured by Meiki Seisakusho, but the moldability was poor and a flat plate could not be obtained under the same conditions as in Example 9.

[Example 11]
Polyphenylene sulfide (PPS) was selected as the thermoplastic resin, and the pitch-based carbon short fiber filler produced in Example 1 was compounded at a volume ratio of 70:30 with a Kurimoto biaxial kneader, and master chip It was. This chip was processed into a 2 mm thick flat plate with an injection molding machine manufactured by Meiki Seisakusho to obtain a composite molded body. The thermal conductivity of this composite molded body was measured and found to be 4.1 W / (m · K).

[Example 12]
Polypropylene was selected as the thermoplastic resin, and the pitch-based carbon short fiber filler produced in Example 1 was compounded at a volume ratio of 70:30 with a Kurimoto biaxial kneader to obtain a master chip. This chip was processed into a 2 mm thick flat plate with an injection molding machine manufactured by Meiki Seisakusho to obtain a composite molded body. It was 3.9 W / (m * K) when the heat conductivity of this composite molded object was measured.

[Example 13]
A silicone resin manufactured by Toray Dow Corning Co. was selected as the thermosetting resin, and the pitch-based carbon short fiber filler produced in Example 1 was mixed with a self-revolving kneading machine at a volume ratio of 70:30. Then, it was placed on a 300 mm square metal frame and pressed with a vacuum press to obtain a flat composite molded body having a thickness of 0.5 mm. The thermal conductivity of this composite molded body was measured and found to be 4.1 W / (m · K).

[Comparative Example 4]
A flat plate made of polycarbonate to which no pitch-based carbon short fiber filler was added was prepared.

[Comparative Example 5]
A flat plate made of polyphenylene sulfide to which no pitch-based carbon short fiber filler was added was prepared. The thermal conductivity was 0.2 W / (m · K).

[Comparative Example 6]
A flat plate made of silicone resin without the addition of pitch-based carbon short fiber filler was prepared. The thermal conductivity was 0.4 W / (m · K).

[Example 14]
A weight heated to 70 ° C. was placed on the flat composite molded body produced in Example 7 to obtain a heat conductive sheet. The thermal conductivity was higher than that of Comparative Example 4. It was found that it functions as a heat dissipation member.

[Example 15]
A weight heated to 70 ° C. was placed on the flat composite molded body produced in Example 11 to obtain a heat conductive sheet. The thermal conductivity was higher than that of Comparative Example 5. It was found that it functions as a heat dissipation member.

[Example 16]
A weight heated to 70 ° C. was placed on the flat composite molded body produced in Example 13 to obtain a heat conductive sheet. The thermal conductivity was higher than that of Comparative Example 6. It was found that it functions as a heat dissipation member.

[Example 17]
The radio wave shielding property of the flat plate-like composite molded body produced in Example 7 was higher than that of Comparative Example 4.

Claims (13)

  The end face observed with a transmission electron microscope is closed, the pitch-based carbon short fiber filler has a substantially flat observation surface with a scanning electron microscope, and the average fiber diameter (D1) observed with an optical microscope Is a pitch-based carbon short fiber filler in which the fiber diameter dispersion (S1) with respect to the average fiber diameter (D1) is in the range of 3 to 20 in the range of 7 to 12 μm.   The pitch-based carbon short fiber filler according to claim 1, wherein the average fiber length (L1) is in the range of 10 µm to 700 µm, and the ratio of L1 to D1 is 1 to 100.   The pitch-based carbon short fiber filler according to claim 1 or 2, wherein a true density is in a range of 1.5 to 2.2 g / cc, and a thermal conductivity in a fiber axis direction is 300 W / (m · K) or more. .   4. The pitch-based carbon short according to claim 1, wherein the crystallite size derived from the thickness direction of the hexagonal network surface is 10 nm or more, and the crystallite size derived from the growth direction of the hexagonal network surface is 8 nm or more. Fiber filler.   A composite molded body comprising the pitch-based carbon short fiber filler according to any one of claims 1 to 4 and a matrix, wherein the filler contains 3 to 60% by volume of the filler in a volume fraction with respect to the matrix.   The composite molded body according to claim 5, wherein the matrix is a thermoplastic resin and / or a thermosetting resin.   The thermoplastic resin is at least one resin selected from the group consisting of polycarbonates, polyethylene terephthalates, polyethylene 2,6 naphthalates, nylons, polypropylenes, polyethylenes, polyepoxy ether ketones, and polyphenylene sulfides. Item 7. A composite molded article according to Item 6.   The composite molded body according to claim 6, wherein the thermosetting resin is at least one resin selected from the group consisting of epoxies, acrylics, urethanes, silicones, and phenols.   The composite molded body according to any one of claims 5 to 8, wherein the thermal conductivity in a state of being formed into a flat plate is 2 W / (m · K) or more.   The composite molded body according to any one of claims 5 to 8, at least 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 method for producing a composite molded body produced by a combination of one or more techniques.   The heat sink for electronic components which uses the composite molded object in any one of Claims 5-8 as a main material.   A radio wave shielding plate comprising the composite molded body according to any one of claims 5 to 8 as a main material.   The heat exchanger which uses the composite molded object in any one of Claims 5-8 as a main material.