JP2009108424A - Thermally conductive filler and molded product using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly thermally conductive pitch-based carbon short fiber filler having high moldability, and to provide a composite molding material. <P>SOLUTION: The pitch-based carbon short fiber filler has >10 to ≤40 μm average fiber diameter (L1) observed under an optical microscope, a closed graphene sheet in observation of a filler end face under a transmission type electron microscope, and a substantially flat surface observed under a scanning electron microscope. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a short carbon fiber filler having high productivity and excellent thermal conductivity, a composition comprising the same and a resin, and a molded body obtained by molding the same. More specifically, the present invention relates to a heat conductive filler using a pitch-based carbon short fiber filler having high productivity and cost merit, and a heat countermeasure material using the same.

  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.
Furthermore, in view of price trends in recent years, achieving cost merit has a very important aspect for materials, and cost performance is extremely important.

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. In addition, high cost performance was also 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 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. In addition, the inventors have found that a specific fiber length can be used to increase the productivity and supply a material with high cost performance, thereby reaching the present invention.

That is, the object of the present invention is to
The average fiber length (L1) observed with an optical microscope is 10 μm or more and less than 40 μm, the graphene sheet is closed in the filler end face observation with a transmission electron microscope, and the observation surface with a scanning electron microscope is substantially flat It is to provide a pitch-based carbon short fiber filler.

A further object of the present invention is to provide a composition comprising the pitch-based carbon short fiber filler and a thermoplastic resin and / or a thermosetting resin, and containing 10 to 900 parts by volume of the filler with respect to 100 parts by volume of the resin. It is to provide.
Furthermore, the object of the present invention is to provide a heat radiating material for electronic parts, a radio wave shielding material, or a heat exchanger, the main component of which is the molded body.

  In the pitch-based carbon short fiber filler of the present invention, the graphene sheet is closed in the filler end face observation with the transmission electron microscope, the observation surface with the scanning electron microscope is substantially flat, and the size is further controlled. This makes it possible to impart a high thermal conductivity to the composite molded body while suppressing an increase in viscosity when it is made into a composition with a resin, and a composite molding material with good moldability and high thermal conductivity. It is possible to The molded body obtained from the composition of the pitch-based carbon short fiber filler resin of the present invention 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. Moreover, it is excellent in productivity and can improve cost performance.

Next, embodiments of the present invention will be described sequentially.
The pitch-based carbon short fiber filler of the present invention has an average fiber length (L1) of 10 μm or more and less than 40 μm, more preferably 10 μm or more and 35 μm or less. When the average fiber length is shorter than 10 μm, it is almost in a powder state, and thermal conductivity may be inferior when a composite material and / or composite molded body is obtained. If it is 40 μm or more, locally long fibers begin to exist, the dispersibility in the resin becomes worse, and high fiber filling may be difficult. Further, the short average fiber length indicates that the bulk density and the tap density are large, and there is an advantage that the transportation and graphitization costs can be compressed. Here, the average fiber length is a number average fiber length, and a predetermined number is measured in a plurality of fields of view using a length measuring device under an optical microscope, and can be obtained from the average value.

  The pitch-based carbon short fiber filler of the present invention is characterized in that the graphene sheet has a closed structure 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 the shape do not occur, so the concentration due to adsorption and adhesion of impurities such as water is reduced. Furthermore, for example, it is possible to further increase the affinity with a different kind of filler such as expanded graphite, which is preferable. Moreover, when the graphene sheet is closed, vertical cracking of the pitch-based carbon short fiber filler is suppressed. In particular, in the pitch-based carbon short fiber filler having an average fiber length shorter than 40 μm as in the present invention, the graphene sheet is closed because the ratio of the end face to the pitch-based carbon short fiber filler surface area is high. Is particularly preferred. Such a structure has an effect of suppressing vertical cracking of the pitch-based carbon short fiber filler. Moreover, since the affinity with water is secondarily poor, the wet heat durability performance is improved.

  Note that the graphene sheet is closed when the end of the graphene sheet itself constituting the pitch-based carbon short fiber filler is not exposed at the end of the pitch-based carbon short fiber filler, and the graphite layer is curved in a substantially U shape. The curved portion is exposed at the end of the pitch-based carbon short fiber filler.

In addition, the pitch-based carbon short fiber filler of the present invention is characterized in that the observation surface with a scanning electron microscope is substantially flat.
Here, “substantially flat” means that the surface of the pitch-based carbon short fiber filler does not have severe unevenness like a fibril structure. When defects such as severe irregularities are present on the surface of the pitch-based carbon short fiber filler, an increase in the viscosity accompanying an increase in the surface area is caused at the time of kneading with the matrix resin, and the moldability is deteriorated. Therefore, it is desirable that defects such as surface irregularities be as small as possible. More specifically, it is assumed that there are 10 or less defects such as irregularities in the observation visual field in an image observed at 1000 times with a scanning electron microscope.
The pitch-based carbon short fiber filler of the present invention can be preferably obtained by performing graphitization after milling as will be described later.

  The average fiber diameter (D1) of the pitch-based carbon short fiber filler of the present invention observed with an optical microscope is preferably 2 to 20 μm. More preferably, it is 6-15 micrometers, More preferably, it is 8-11 micrometers. In the case of D1 larger than 20 μm, it is easy to cause fusion with adjacent yarns in the infusibilization process. 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.

  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 1.9 to 2.3 g / cc. More preferably, it is 2.0-2.2 g / cc. The thermal conductivity in the fiber axis direction of the pitch-based carbon short fiber filler is 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 a crystallite size derived from the growth direction of the hexagonal network surface of 20 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 diffraction lines from the (002) plane, and the crystallite size in the growth direction of the hexagonal mesh plane is obtained using diffraction lines from the (110) plane. be able to.

Hereinafter, a preferred method for producing the pitch-based carbon short fiber filler of the present invention will be described.
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 obtained 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. Furthermore, a gas component is generated, bubbles are generated in the yarn, and the strength is deteriorated.

  The raw material pitch is spun by a melt blow method, and then becomes pitch-based carbon short fibers by infusibilization, firing, milling, and graphitization. In some cases, a sieving step may be included after milling. The pitch-based carbon short fiber filler of the present invention is characterized in that the end face observed with a transmission electron microscope is closed. Such pitch-based carbon short fiber filler is subjected to graphitization after milling. By doing so, it can be preferably obtained. Hereinafter, preferred embodiments of each step will be described.

  In the present invention, the shape of the spinning nozzle is not particularly limited, but those having a ratio L / D of the nozzle hole diameter D to the nozzle hole length L of preferably 5 or more and 20 or less, more preferably 8 or more and 15 or less. It is. 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 raw material pitch is 2 to 25 Pa · s, preferably 8 to 17 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 performed under air or an oxidizing gas using a gas obtained by adding ozone, nitrogen dioxide, nitrogen, oxygen, iodine, or bromine to air. The infusibilization temperature is achieved by applying a heat treatment for a certain time at a temperature of 150 to 340 ° C. More preferably, it is 170-320 degreeC, More preferably, it is the range of 190-300 degreeC. In view of safety and convenience, it is desirable to carry out in air. The heating rate is appropriately 1 to 10 ° C./min. Productivity is poor at 1 ° C. or lower, and unevenness occurs at 10 ° C. or higher, causing troubles such as fusion. In addition, there is a close relationship with the basis weight of the web, and when the basis weight is larger than 750 g / m 2, the unevenness of the oxygen adsorption amount due to infusibilization increases, resulting in process troubles such as unevenness of the product and fusion to the belt.

  And the infusible pitch fiber is fired in a non-oxidizing atmosphere using an inert gas such as nitrogen, argon, or krypton in the range of 400 to 1000 ° C., but at normal pressure, And it is carried out in low-cost nitrogen.

  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, hammer type using impact action, pin type, ball type and rod type, high speed rotary type using collision between particles, single axis, double axis and multi-axis rotary blade type using shear / cut action In addition, a roll type, a cone type, a screw type or the like using a compression / tearing action is used.

  The average fiber length of the fibers generated by milling is controlled by adjusting the number of rotations of the rotor, the supply amount, the screen hole diameter, the clearance between the blades, the residence time in the system, and the like. In this invention, it grind | pulverizes by these grinders so that an average fiber length may be 10 micrometers or more and less than 40 micrometers. Furthermore, it is also possible to use a sieve, which is divided into 10 to 35 μm. Such adjustment of the average fiber length can be achieved by combining the coarseness of the sieve.

  The pitch-based short fibers prepared by using the above milling treatment and, in some cases, sieving together, are heated to 2500-3500 ° C. and graphitized to obtain the final pitch-based carbon short fiber filler. Graphitization is performed in a non-oxidizing atmosphere in an Atchison furnace, an electric furnace or the like.

  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, it can be carried out according to the required physical properties.

  In the present invention, a composition obtained by mixing a pitch-based carbon short fiber filler with a thermoplastic resin and / or a thermosetting resin is also included. At this time, 10 to 900 parts by volume of the pitch-based carbon short fiber filler is added to 100 parts by volume of the resin. If the addition amount is less than 10 parts by volume, it is difficult to ensure sufficient thermal conductivity. On the other hand, it is often difficult to add more than 900 parts by volume of pitch-based carbon short fiber filler to the resin.

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

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

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

  Examples of the thermosetting resin include epoxies, acrylics, urethanes, silicones, phenols, imides, thermosetting modified PPEs, thermosetting PPEs, and the like. Or two or more types may be used in appropriate combination.

  The composition of the present invention is prepared by mixing a pitch-based carbon short fiber filler and a resin. When mixing, a kneader, a mixer, a blender, a roll, an extruder, a milling machine, a self-revolving stirrer For example, a mixing device or a kneading device is preferably used. The composite material and / or the composite molded body is molded by a molding method such as an injection molding method, a press molding method, a calender molding method, a roll molding method, an extrusion molding method, a casting molding method, or a blow molding method. Is possible. 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 composition of the present invention is formed into a flat plate and the thermal conductivity is measured, it shows a thermal conductivity of 2 W / (m · K) or more. The thermal conductivity of 2 W / (m · K) is about one digit higher than that of the resin used as the matrix.

  In order to further improve the thermal conductivity, moldability, and mechanical properties of the composition of the present invention, a filler other than the pitch-based carbon short fiber filler may be added as necessary. Specifically, metal oxides such as aluminum oxide, magnesium oxide, silicon oxide, and zinc oxide, metal hydroxides such as aluminum hydroxide and magnesium hydroxide, metal nitrides such as boron nitride and aluminum nitride, oxynitride Examples thereof include metal oxynitrides such as aluminum, metal carbides such as silicon carbide, metals or metal alloys such as gold, silver, copper, and aluminum, and carbon materials such as natural graphite, artificial graphite, expanded graphite, and diamond. Furthermore, for functions that require fibrous fillers such as glass fiber, potassium titanate whisker, zinc oxide whisker, aluminum boride whisker, boron nitride whisker, aramid fiber, alumina fiber, silicon carbide fiber, asbestos fiber, gypsum fiber, metal fiber, etc. You may add suitably according to it. Wollastonite, zeolite, sericite, kaolin, mica, clay, pyrophyllite, bentonite, asbestos, talc, alumina silicate and other silicates, calcium carbonate, magnesium carbonate, dolomite and other carbonates, calcium sulfate, barium sulfate, etc. Non-fibrous fillers such as sulfate, glass beads, glass flakes, and ceramic beads can be added as necessary. These may be hollow, and two or more of these may be used in combination. However, many of the above compounds have a density higher than that of the pitch-based carbon short fiber filler, and when the purpose is to reduce the weight, it is necessary to pay attention to the addition amount and the addition ratio.

  The molded body obtained by molding the composition of the present invention can be used as a heat radiating material 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 part of a heat exchanger. Can be used for heat pipes. Furthermore, the radio wave shielding property of the pitch-based carbon short fiber filler is utilized, and can be suitably used particularly as a radio wave shielding material 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:
According to JIS R7607, 60 pitch-based carbon fiber fillers that had undergone graphitization were measured with an optical microscope using a scale, and the average value was obtained.
(2) Average fiber length of pitch-based carbon short fiber filler:
The average fiber length is the number average fiber length. The pitch-based carbon short fiber filler that has undergone graphitization is measured with an optical microscope with a length measuring instrument (measured by 10 fields and 200 lines each), and obtained from the average value. It was. 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.
(7) Confirmation of a substantially flat surface:
The number of defects such as irregularities was counted in an image obtained by observing the pitch-based carbon short fiber filler with a scanning electron microscope at 1000 times.
(8) Productivity evaluation:
The production cost per unit weight in Comparative Example 1 was evaluated as 100.

[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 288 ° C. A pitch of 10 Pa · s melted at 340 ° C., using a mouthpiece with a diameter of 0.2 mmφ, and heated air is ejected from the slit at a linear velocity of 4500 m / min. Produced a pitch-based short fiber of 11.0 μm. The spun short fibers were collected on a belt to form a mat, and a web made of pitch-based short fibers having a basis weight of 350 g / m ^{2 by} cross wrapping.

  The web was infusibilized by raising the temperature from 170 ° C. to 290 ° C. in air at an average temperature rising rate of 4 ° C./min. The infusibilized web was fired at 800 ° C. in a nitrogen atmosphere, milled, and then graphitized by heat treatment at 3000 ° C. in an electric furnace in a non-oxidizing atmosphere to obtain a pitch-based carbon short fiber filler. The average fiber diameter (D1) was 8.1 μm. The average fiber length (L1) was 38 μm. The true density was 2.15 g / cc.

  The obtained pitch-based carbon short fiber filler was observed with a transmission electron microscope at a magnification of 1,000,000 times and magnified on a photograph to 4,000,000 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 observed with a scanning electron microscope at a magnification of 1000 was smooth and free from defects such as large irregularities.

The crystallite size in the thickness direction of the hexagonal network surface determined by the X-ray diffraction method was 36 nm. The crystallite size in the growth direction of the hexagonal network surface was 80 nm.
A single yarn was extracted from a graphitized web which was produced in the same process until firing and was not milled, and heat treated at 3000 ° C. in an electric furnace in a non-oxidizing atmosphere, and the electrical resistivity was measured. 1.6 μΩm. The thermal conductivity was 750 W / (m · K).
When the production cost of Comparative Example 1 was 100, the production cost was 71.

[Example 2]
Milling and sieving the web produced by the same method as in Example 1 until baking at 800 ° C., and then graphitizing by heat treatment at 3000 ° C. in an electric furnace in a non-oxidizing atmosphere, and pitch-based carbon short fiber filler It was. The average fiber diameter (D1) was 7.9 μm. The average fiber length (L1) was 22 μm. The true density was 2.18 g / cc.

  The obtained pitch-based carbon short fiber filler was observed with a transmission electron microscope at a magnification of 1,000,000 times and magnified on a photograph to 4,000,000 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 observed with a scanning electron microscope at a magnification of 1000 times had two defects such as large irregularities and was smooth.

The crystallite size in the thickness direction of the hexagonal network surface determined by the X-ray diffraction method was 43 nm. The crystallite size in the growth direction of the hexagonal network surface was 95 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. 1.6 μΩm. The thermal conductivity was 750 W / (m · K).
When the production cost of Comparative Example 1 was 100, the production cost was 58.

[Example 3]
The process up to milling was the same as in Example 1, and graphitized at 2700 ° C. in an electric furnace in a non-oxidizing atmosphere to obtain a pitch-based carbon short fiber filler. The average fiber diameter (D1) was 8.2 μm. The average fiber length (L1) was 36 μm. The true density was 1.9 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 observed with a scanning electron microscope at a magnification of 1000 times had three irregularities and was smooth.

The crystallite size in the thickness direction of the hexagonal network surface determined by the X-ray diffraction method was 21 nm. Further, the crystallite size in the growth direction of the hexagonal network surface was 30 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 2700 ° C. in an electric furnace in a non-oxidizing atmosphere, and the electrical resistivity was measured. 2.5 μΩm. The thermal conductivity was 460 W / (m · K).
When the production cost of Comparative Example 1 is 100, the production cost is 73.

[Comparative Example 1]
The web produced by the same method as in Example 1 until baking at 800 ° C. was graphitized by heat treatment at 3000 ° C. in an electric furnace in a non-oxidizing atmosphere to obtain a pitch-based carbon short fiber filler. The average fiber diameter (D1) was 7.9 μm. The average fiber length (L1) was 370 μm. The true density was 2.17 g / cc.

  The obtained pitch-based carbon short fiber filler was observed with a transmission electron microscope at a magnification of 1,000,000 times and magnified on a photograph to 4,000,000 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 observed with a scanning electron microscope at a magnification of 1000 times had one defect such as large irregularities and was smooth.

The crystallite size in the thickness direction of the hexagonal network surface determined by the X-ray diffraction method was 38 nm. The crystallite size in the growth direction of the hexagonal network surface was 81 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. 1.7 μΩm. The thermal conductivity was 700 W / (m · K).
The production cost was 100.

[Comparative Example 2]
Milling and sieving the web produced by the same method as in Example 1 until baking at 800 ° C., and then graphitizing by heat treatment at 3000 ° C. in an electric furnace in a non-oxidizing atmosphere, and pitch-based carbon short fiber filler It was. The average fiber diameter (D1) was 7.8 μm. The average fiber length (L1) was 8 μm. The true density was 2.18 g / cc.

  The obtained pitch-based carbon short fiber filler was observed with a transmission electron microscope at a magnification of 1,000,000 times and magnified on a photograph to 4,000,000 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 observed with a scanning electron microscope at a magnification of 1000 times had one defect such as large irregularities and was smooth.

The crystallite size in the thickness direction of the hexagonal network surface determined by the X-ray diffraction method was 45 nm. The crystallite size in the growth direction of the hexagonal network surface was 89 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. 1.6 μΩm. The thermal conductivity was 750 W / (m · K).
When the production cost of Comparative Example 1 was 100, the production cost was 52.

[Comparative Example 3]
Example 1 A web was produced by the same method and heat-treated at 3000 ° C. in an electric furnace in a non-oxidizing atmosphere, and then milled. The average fiber diameter (D1) was 8.3 μm. The average fiber length (L1) was 35 μm. The true density was 2.2 g / cc.
The obtained pitch-based carbon short fiber filler was observed with a transmission electron microscope at a magnification of 1,000,000 times and magnified on a photograph to 4,000,000 times. It was confirmed that there was a portion where the graphene sheet on the end face of the pitch-based carbon short fiber filler was open. Further, the surface of the pitch-based carbon short fiber filler observed with a scanning electron microscope at a magnification of 1000 times had 18 defects such as large irregularities, and was not smooth.

[Example 4]
A polycarbonate resin (L-1225WP manufactured by Teijin Chemicals Ltd.) was selected as the thermoplastic resin, and the pitch-based carbon short fiber filler prepared in Example 1 was added to the Kurimoto biaxial kneader at a ratio of 100 parts by volume to 70 parts by volume. And compounded into a composite material. This composite material was processed into a flat plate having a thickness of 2 mm by 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 2.9 W / (m · K).
When this composite molded body was subjected to a wet heat durability test at 60 ° C. and 90% RH, the thermal conductivity was 2.9 W / (m · K) even after 1000 hours.

[Example 5]
A polycarbonate resin (L-1225WP manufactured by Teijin Chemicals Ltd.) was selected as the thermoplastic resin, and the pitch-based carbon short fiber filler prepared in Example 2 was added to the Kurimoto biaxial kneader at a ratio of 100 parts by volume to 70 parts by volume. And compounded into a composite material. This composite material was processed into a flat plate having a thickness of 2 mm by 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 2.3 W / (m · K).

[Example 6]
A polycarbonate resin (L-1225WP manufactured by Teijin Chemicals Ltd.) is selected as the thermoplastic resin, and the pitch-based carbon short fiber filler prepared in Example 1 is added to the Kurimoto biaxial kneader at a ratio of 100 parts by volume: 45 parts by volume. And compounded into a composite material. This composite material was processed into a flat plate having a thickness of 2 mm by 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).

[Example 7]
A polycarbonate resin (L-1225WP manufactured by Teijin Chemicals Ltd.) is selected as the thermoplastic resin, and the pitch-based carbon short fiber filler prepared in Example 1 is added to the Kurimoto biaxial kneader at a ratio of 100 parts by volume: 100 parts by volume. And compounded into a composite material. This composite material was processed into a flat plate having a thickness of 2 mm by 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 3.1 W / (m · K).

[Comparative Example 4]
A composite molded body was obtained under the same conditions as in Example 5 except that the pitch-based carbon short fiber filler prepared in Comparative Example 1 was used. It was non-uniform so that there were few places.

[Comparative Example 5]
A composite material was obtained under the same conditions as in Example 5 except that the pitch-based carbon short fiber filler prepared in Comparative Example 2 was used. This composite material was processed into a flat plate having a thickness of 2 mm using an injection molding machine manufactured by Meiki Seisakusho to obtain a composite molded body. This composite molded body had a thermal conductivity of 1.4 W and did not reach the regulations.

[Comparative Example 6]
A composite material was obtained under the same conditions as in Example 5 except that the pitch-based carbon short fiber filler prepared in Comparative Example 3 was used, but the viscosity of the composite material was higher than that in Example 5. This composite material was processed into a flat plate having a thickness of 2 mm using an injection molding machine manufactured by Meiki Seisakusho to obtain a composite molded body. The composite molded body had a thermal conductivity of 2.4 W.
When this composite molded body was subjected to a wet heat durability test at 60 ° C. and 90% RH, after 1000 hours, the deterioration progressed and the composite molded body was broken.

[Example 8]
A polyphenylene sulfide resin (polyplastics 0220A9) was selected as the thermoplastic resin, and the pitch-based carbon short fiber filler produced in Example 1 was added to the Kurimoto biaxial kneader at a ratio of 100 parts by volume: 100 parts by volume. And compounded into 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. The thermal conductivity of the composite molded body was measured and found to be 3.3 W / (m · K).

[Example 9]
A polypropylene resin (PM900A manufactured by Sun Allomer) was selected as the thermoplastic resin, and the pitch-based carbon short fiber filler prepared in Example 1 was compounded with a Kurimoto biaxial kneader at a ratio of 100 parts by volume to 45 parts by volume. To make 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. The thermal conductivity of this composite molded body was measured and found to be 2.3 W / (m · K).

[Example 10]
A silicone resin (SE-1740 manufactured by Toray Dow Silicone) was selected as the thermosetting resin, and the pitch-based carbon short fiber filler produced in Example 1 was used in a ratio of 100 parts by volume to 45 parts by volume using a planetary mixer. Was mixed in a square metal frame with a side of 300 mm, and pressed with a vacuum press to obtain a flat composite molded body with a thickness of 0.5 mm. The thermal conductivity of this composite molded body was measured and found to be 2.6 W / (m · K).

[Example 11]
A silicone resin (SE-1740 manufactured by Toray Dow Silicone) was selected as the thermosetting resin, and the pitch-based carbon short fiber filler produced in Example 2 was used in a ratio of 100 parts by volume to 45 parts by volume using a planetary mixer. Was mixed in a square metal frame with a side of 300 mm, and pressed with a vacuum press to obtain a flat composite molded body with a thickness of 0.5 mm. The thermal conductivity of this composite molded body was measured and found to be 2.2 W / (m · K).

[Comparative Example 7]
A flat plate was produced from a polycarbonate resin (L-1225WP manufactured by Teijin Chemicals) to which no pitch-based carbon short fiber filler was added. The thermal conductivity was 0.2 W / (m · K).

[Comparative Example 8]
A flat plate was prepared from a silicone resin (SE-1740 manufactured by Toray Dow Silicone) to which no pitch-based carbon short fiber filler was added. The thermal conductivity was 0.3 W / (m · K).

[Example 12]
A weight heated to 70 ° C. was placed on the flat composite molded body produced in Example 4 to obtain a heat conductive sheet. The thermal conductivity was higher than that of Comparative Example 7. It was found that it functions as a heat dissipation member.

[Example 13]
A weight heated to 70 ° C. was placed on the flat composite molded body produced in Example 10 to obtain a heat conductive sheet. The thermal conductivity was higher than that of Comparative Example 8. It was found that it functions as a heat dissipation member.

[Example 14]
The radio wave shielding property of the flat plate-shaped composite molded body produced in Example 4 was higher than that of Comparative Example 7.

[Example 15]
The radio wave shielding property of the flat plate-shaped composite molded body produced in Example 10 was higher than that of Comparative Example 8.

[Example 16]
When the flat composite molded body produced in Example 4 was shaped to produce a heat exchanger, it acted as a heat exchanger.

Claims (12)

  The average fiber length (L1) observed with an optical microscope is 10 μm or more and less than 40 μm, the graphene sheet is closed in the filler end face observation with a transmission electron microscope, and the observation surface with a scanning electron microscope is substantially flat A pitch-based carbon short fiber filler.   The pitch-based carbon short fiber filler according to claim 1, wherein an average fiber diameter (D1) observed with an optical microscope is greater than 2 µm and 20 µm or less.   The pitch-based carbon short according to claim 1, wherein the true density is in the range of 1.9 to 2.3 g / cc, and the thermal conductivity in the fiber axis direction is 400 W / (m · K) or more. Fiber filler.   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 20 nm or more. Fiber filler.   It consists of the pitch-type carbon short fiber filler in any one of Claims 1-4, a thermoplastic resin, and / or a thermosetting resin, and contains the said filler of 10-900 volume parts with respect to 100 volume parts of resin. Composition.   Thermoplastic resins are polycarbonates, polyethylene terephthalates, polybutylene terephthalates, polyethylene 2,6 naphthalates, nylons, polypropylenes, polyethylenes, polyether ketones, polyphenylene sulfides, polybutylene terephthalates, and acrylonitrile- The composition according to claim 5, which is at least one resin selected from the group consisting of butadiene-styrene copolymer resins.   The thermosetting resin is at least one resin selected from the group consisting of epoxies, acrylics, urethanes, silicones, phenols, imides, thermosetting modified PPEs, and thermosetting PPEs, The composition according to claim 5.   The composition in any one of Claims 5-7 whose heat conductivity in the state shape | molded in flat form is 2 W / (m * K) or more.   The composition according to any one of claims 5 to 8 is selected from the group consisting of an injection molding method, a press molding method, a calender molding method, a roll molding method, an extrusion molding method, a cast molding method, and a blow molding method. A molded body obtained by molding by at least one method.   A heat dissipating material for electronic parts, the main component of which is the molded body according to claim 9.   A radio wave shielding material comprising the molded article according to claim 9 as a main material.   The heat exchanger which uses the molded object of Claim 9 as a main material.