WO2011013840A1

WO2011013840A1 - Insulated pitch-based graphitized short fibers

Info

Publication number: WO2011013840A1
Application number: PCT/JP2010/062988
Authority: WO
Inventors: 佐野　弘樹; 原　寛
Original assignee: 帝人株式会社
Priority date: 2009-07-28
Filing date: 2010-07-27
Publication date: 2011-02-03
Also published as: JPWO2011013840A1; TW201118121A

Abstract

Disclosed is a thermally conductive material which has insulating properties and excellent thermal conductivity at the same time. Specifically disclosed are insulated pitch-based graphitized short fibers that are characterized by being obtained by coating pitch-based graphitized short fibers with such a resin which does not have a melting point at 250˚C or less and the precursor of which is in a liquid state, or with such a resin which or the precursor of which is soluble in at least one kind of solvent.

Description

Insulated pitch-based graphitized short fiber

In the present invention, the surface of pitch-based graphitized short fibers is coated with a resin that does not have a melting point at 250 ° C. and that the precursor is liquid or that the precursor or itself is soluble in a solvent. It relates to insulated pitch-based graphitized short fibers, and is suitably used for heat dissipation members of electronic devices and electronic components.

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. Similarly, an electroluminescent element that uses electron injection as a light emission principle is also manifesting as a serious problem. On the other hand, when considering the process of forming various elements, an environmentally conscious process is demanded, and as a countermeasure against this, switching to so-called lead-free solder to which lead is not added has been made. Since lead-free solder has a higher melting point than ordinary lead-containing solder, efficient use of process heat is required. And in order to solve the problem originating in the heat which such a product and process includes, it is necessary to achieve the efficient process (thermal management) of heat.
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.
Next, the characteristics of the molded body used for thermal management are considered. In general, carbon fibers exhibit electrical conductivity. Therefore, a composition in which carbon fibers are combined with a matrix exhibits conductivity. However, the CPU and electronic circuit described above are often attached to an insulating substrate. Therefore, it is difficult to use a composition using carbon fiber for an electronic substrate.
Patent Documents 1 and 2 propose a method of coating an insulating layer on a thermally conductive composition. However, since it is not processing with respect to the heat conductive filler, it is difficult to cope with the insulating treatment of a complicated molded body. Patent Document 3 proposes a method of covering a thermally conductive filler with an insulating layer made of silicon oxide, and Patent Document 4 with an insulating layer made of silica or silicon carbide. However, the insulating layer made of an inorganic compound is fragile, and the coating is peeled off during kneading with the resin, so that it is difficult to maintain insulation. Among these, silicon carbide has a high hardness, and there is a concern of damage to the kneader.
JP 2008-208316 A JP 2008-205453 A JP 2007-128986 A JP 2007-107151 A

An object of the present invention is to provide an insulated pitch-based graphitized short fiber having excellent network forming ability in a matrix and having both high thermal conductivity and insulating properties. Another object of the present invention is a thermally conductive composition comprising an insulated pitch-based graphitized short fiber and at least one matrix component selected from the group consisting of a thermoplastic resin, a thermosetting resin, and rubber, and The object is to provide a molded body from that.
Means for Solving the Problems As a result of intensive investigations to obtain a heat conductive material having high thermal conductivity and insulating properties, the present inventors have found that pitch-based graphitized short fibers excellent in thermal conductivity. High thermal conductivity by coating with a resin that has a melting point at 250 ° C. or lower and the precursor is liquid, or the precursor or itself is soluble in at least one solvent. The present inventors have found that it is possible to obtain a heat conductive material having both insulating properties and the present invention.
The present invention is characterized in that the surface is coated with a resin that does not have a melting point at 250 ° C. or less and the precursor is liquid, or the precursor or itself is soluble in at least one solvent. Insulated pitch-based graphitized short fiber.
Effects of the Invention According to the present invention, an insulated pitch-based graphitized short fiber having both high thermal conductivity and insulating properties can be provided, and thereby a thermally conductive composition having insulating properties and a molded body thereof can be obtained. Application to electronic devices, electronic boards, and the like that require higher heat dissipation characteristics becomes possible.

FIG. 1 is a scanning electron microscopic photograph of the insulated pitch-based graphitized short fiber obtained in Example 1.
FIG. 2 is a scanning electron microscope photograph of the insulated pitch-based graphitized short fiber obtained in Example 4.

Hereinafter, embodiments of the present invention will be sequentially described.
[Insulated pitch-based graphitized short fibers]
The insulated pitch-based graphitized short fiber of the present invention is a pitch-based graphitized short fiber having a resin layer that does not have a melting point at 250 ° C. or less and whose precursor is liquid or dissolved in a solvent. Features. Insulated pitch-based graphitized short fibers have a resin layer by coating on the surface. For the purpose of insulating the graphitized short fibers, it is preferable that the surface of the graphitized short fibers is almost completely covered with a resin layer.
The specific resistance of pitch-based graphitized short fibers is 10 ^-4 Conductivity is shown on the order of Ω · cm. Also, when a molded product is mixed with a resin, the molded product exhibits conductivity. For this reason, it is difficult to use it as a heat countermeasure for a portion where conductivity such as a sealant is not desired. In contrast, resin is generally 10 ¹⁴ It is on the order exceeding Ω · cm and shows high insulation. Therefore, it is possible to insulate the pitch-based graphitized short fibers by coating each pitch-based graphitized short fiber with a resin. However, resins are generally larger than pitch-based graphitized short fibers and have poor thermal conductivity. Therefore, when insulating the pitch-based graphitized short fibers with a resin, it is necessary to coat with a small amount of resin. For this reason, a resin precursor or a solution in which a resin is dissolved is required to be liquid. This is because if the coating agent is liquid, the pitch-based graphitized short fibers can be uniformly coated with a resin layer, and the amount of resin can be suppressed.
The specific resistance of the insulated pitch-based graphitized short fiber of the present invention is 1.0 × 10 ⁶ It is preferable that it is Ω · cm or more. Specific resistance is 1.0 × 10 ⁶ If it is less than Ω · cm, it cannot be expected to impart high electrical resistance to the specific resistance of the molded product. The practical upper limit of the specific resistance of the insulating pitch-based graphitized short fiber is 1.0 × 10 ¹⁴ Ω · cm.
The insulated pitch-based graphitized short fiber of the present invention is a pitch-based graphitized short fiber having a uniform insulating layer formed on the surface thereof, that is, the surface observed with a scanning electron microscope is substantially flat. preferable. The term “substantially flat” means that one pitch-based graphitized short fiber has 10 or less irregularities and defects in an observation field of an image observed at 800 to 1000 times with a scanning electron microscope, or 2000 It is assumed that there are 15 or less irregularities and defects per line in the observation field of the image observed at double magnification. Here, the unevenness means that there are severe unevenness on the surface of the insulated pitch-based graphitized short fiber, that is, the coated surface, specifically, a height or depth of 3 μm or more when observed with a scanning electron microscope. Means. A defect means that when observed with a scanning electron microscope, a resin is not applied to a part of the insulated pitch-based graphitized short fiber, and a part of the surface of the pitch-based graphitized short fiber is exposed. It means being observed.
In the insulated pitch-based graphitized short fibers of the present invention, the presence of the coated resin is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the pitch-based graphitized short fibers. If the presence of the coated resin is 1 part by weight or less, the pitch-based graphitized short fibers cannot be sufficiently coated, and insulation cannot be expected. On the other hand, if the amount of the coated resin is 10 parts by weight or more, the amount of the resin that coats the pitch-based graphitized short fibers is too large, and it tends to be difficult to obtain high thermal conductivity when forming a molded product. The amount is preferably 3 to 7 parts by weight, more preferably 3 to 5 parts by weight, based on 100 parts by weight of the pitch-based graphitized short fibers.
[Coating resin]
A characteristic required for a resin that coats pitch-based graphitized short fibers is that the resin does not have a melting point at 250 ° C. or lower. When a thermoplastic resin is used as the matrix, it is often kneaded at a temperature equal to or higher than the melting point of the matrix. When the melting point of the resin to be coated is lower than the melting point of the matrix, the resin to be coated is melted and removed, so that it is difficult to maintain insulation. Therefore, it is required to have no melting point at 250 ° C. or lower, which is higher than the melting point of many thermoplastic resins. “No melting point at 250 ° C. or lower” means that the melting point exceeds 250 ° C. or does not have the melting point itself. More preferably, the melting point is not higher than 300 ° C. The melting point can be measured with a differential scanning calorimeter or the like.
In addition, from the viewpoint that pitch-based graphitized short fibers can be coated and fixed on the surface of pitch-based graphitized short fibers, the resin used for coating is a precursor.

It is required to be. Here, the term “soluble in a solvent” specifically means that 0.1 to 10 parts by weight of a precursor or a resin is dissolved with respect to 100 parts by weight of a solvent under the conditions of 20 ° C. to 10 ° C. lower than the boiling point of the solvent. It means that is possible.
The resin to be coated is not particularly limited as long as it does not have a melting point at 250 ° C. and the precursor is in a liquid state or the precursor or itself is soluble in at least one solvent. Although it can be used, preferably a thermosetting resin, aromatic polyamide, aromatic polyimide, or aliphatic polyimide is used.
Although there is no limitation in particular in a thermosetting resin, Specifically, an epoxy resin, a thermosetting acrylic resin, a urethane resin, and a silicone resin are mentioned. Among them, epoxy resin is particularly excellent in affinity with pitch-based graphitized short fibers, and the adhesive strength between pitch-based graphitized short fibers and resin is high, and pitch-based graphitized short fibers insulated with resin are mixed with a matrix. Even when a molded body is formed, the insulating resin is unlikely to be peeled off from the pitch-based graphitized short fibers, and it tends to be possible to maintain high insulation.
Although there is no limitation in particular in an epoxy resin, the main ingredient and the hardening | curing agent which are resin before hardening can be mixed and a thermosetting reaction can be carried out. Examples of the main agent include aliphatic epoxy resins and aromatic epoxy resins including bisphenol. Further, examples of the curing agent include an amine curing agent and an acid anhydride curing agent. Furthermore, you may use a curing catalyst as needed. Examples of the curing catalyst include an imidazole-based curing catalyst. These main agents, curing agents, and curing catalyst components can be appropriately mixed and used as necessary.
The aromatic polyamide is not particularly limited, and specifically, an aromatic dicarboxylic acid component composed of terephthalic acid and / or isophthalic acid, 1,4-phenylenediamine, 1,3-phenylenediamine, 3,4′-diamino Wholly aromatic polyamides derived from at least one aromatic diamine component selected from the group consisting of diphenyl ether, 4,4′-diaminodiphenyl ether and 1,3-bis (3-aminophenoxy) benzene, and aromatic polyamideimides and The copolymer is exemplified.
The aromatic polyimide is not particularly limited, and specific examples include aromatic tetracarboxylic dianhydride composed of pyromellitic anhydride and aromatic diamine polymer composed of 4,4-diaminodiphenyl ether and the like. The
Although there is no limitation in particular as an aliphatic polyimide, Specifically, a saturated alicyclic tetracarboxylic dianhydride and / or bicyclo (2, 2, 2) oct-7-ene-2, 3, 5, At least selected from the group consisting of 6-tetracarboxylic dianhydride and / or 5- (2,5-dioxo-tetrafurfuryl) -3-methyl-4-cyclohexene-1,2-dicarboxylic anhydride A type of aliphatic tetracarboxylic dianhydride and 1,3-bis (3-aminomethyl) cyclohexane, 4,4'-diamino-dicyclohexyl-methane, bis (2-aminoethoxy) ethane, N, N-bis A polymer of at least one aliphatic diamine selected from the group consisting of (3-aminopropyl) methylamine and ethylenediamine is exemplified.
Aromatic polyamide, aromatic polyimide, and aliphatic polyimide may be used as a copolymer as long as the characteristics are not lost.
[Resin coating method]
The resin coating method is not particularly limited, and examples thereof include 1) a method in which an insulating solution is prepared and used for coating, or 2) a gas treatment method in which no solvent is used.
The insulating solution 1) is a liquid precursor, a liquid precursor mixed with a solvent as necessary, or a precursor or resin dissolved in a solvent.
As a particularly preferable solvent constituting the insulating solution, in the case of an epoxy resin, it is a case where a solvent is further used with respect to a mixed liquid of a main agent and a curing agent which are resins before curing, preferably acetone, toluene , Methyl ethyl ketone, and methyl isobutyl ketone. Similarly, in the case of a silicone resin, a solvent is further used for the mixed liquid of the main agent and the curing agent, which are resins before curing, and preferably toluene and hexane are used. In the case of an aromatic polyamide, N, N-methylpyrrolidone, dimethylacetamide, and dimethylformamide which can dissolve the aromatic polyamide are exemplified. In the case of an aromatic polyimide, N, N-methylpyrrolidone in which the precursor is soluble is exemplified. In the case of aliphatic polyimide, N, N-methylpyrrolidone in which the precursor is soluble can be mentioned.
As a specific method of 1), in the case of a thermosetting resin, aromatic polyimide, or aliphatic polyimide, a precursor and, if necessary, a solvent are further added to obtain an insulating solution, which is then pitch graphitized. There is a technique in which short fibers are mixed, a necessary insulating solution is coated by a technique such as spraying or filtration, and then the resin is cured by heat treatment. In the case of aromatic polyamide, dissolve it in a solvent to obtain an insulating solution, mix it with pitch-based graphitized short fibers, coat the necessary insulating solution by spraying, filtration, etc., and then remove the solvent by drying The method of doing is mentioned.
Specific examples of the gas treatment method 2) include a method of polymerizing and coating a gas, which is a resin raw material compound, on pitch-based graphitized short fibers. In the gas treatment method, it is preferable to subject the pitch-based graphitized short fibers to surface treatment in order to cause the reaction to proceed on the pitch-based graphitized short fibers.
Since the coating resin amount is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the pitch-based graphitized short fibers as described above, in the method 1), the amount of the insulating solution is ensured so that a desired resin amount can be secured after coating. Is preferably selected. Here, when the amount of the insulating solution used for coating in the method 1) is excessive, the solution and the filler are aggregated due to the surface tension of the solution, and it becomes difficult to coat uniformly. As a result, many defects occur in the insulating layer, and it becomes difficult to uniformly coat the entire filler and achieve insulation. Moreover, many organic compounds and inorganic compounds are inferior in thermal conductivity to pitch-based graphitized short fibers. Therefore, when insulating the pitch-based graphitized short fibers with an organic compound or an inorganic compound, it is necessary to form an insulating surface with as little amount as possible in order to suppress a decrease in thermal conductivity. Therefore, it is necessary to coat uniformly with a small amount when forming the insulating surface. A preferable weight ratio of the insulating solution is 1 to 10 parts by weight of a resin or a precursor with respect to 100 parts by weight of pitch-based graphitized short fibers. When a solvent is used, the amount of the solvent is 1000 to 20000 parts by weight with respect to 100 parts by weight of the resin or precursor.
By separating the distance between the fillers and reducing the amount of the insulating solution in contact with the filler surface, the drying time can be shortened and aggregation can be suppressed, and coating with a uniform insulating layer can be achieved. Alternatively, when the insulating layer is coated, agglomeration can be avoided unless a solution is used as in the gas treatment method of 2). In consideration of productivity, a spray-drying method capable of continuous treatment is preferable.
[Spray drying method]
In the spray drying method, a spray composed of an insulating layer forming solution and pitch-based graphitized short fibers are sprayed from a rotating disk or a nozzle to discharge a mist-like spray. By applying hot air to the spray, the solvent dries almost instantaneously, and the coating of the surface of the pitch-based graphitized short fiber can be achieved. Moreover, when using a thermosetting resin for an insulating layer, it can harden | cure with this hot air and can coat an insulating layer with high heat resistance.
The solution used in the spray method is only required to be able to disperse the pitch-based graphitized short fibers and to dissolve or disperse the insulating layer forming material and to be sprayed in the form of a mist. The following organic solvents are preferably used.
The preferable solvent constituting the solution of the spray method is the same as that mentioned in the column of the insulating solution.
A preferred weight ratio of the spray solution is 1 to 10 parts by weight of resin or precursor with respect to 100 parts by weight of pitch-based graphitized short fibers, and 1000 to 20000 parts by weight of solvent with respect to 100 parts by weight of resin or precursor.
[Pitch-based graphitized short fibers]
The pitch-based graphitized short fiber in the present invention is preferably a pitch-type graphitized short fiber having a specific shape from the viewpoints of formability when filled, expression of thermal conductivity, and the like.
The pitch-based graphitized short fibers in the present invention preferably have an average fiber diameter (D1) of 2 to 20 μm observed with an optical microscope. When D1 is less than 2 μm, the number of the short fibers increases when they are combined with the resin, so that the viscosity of the resin / short fiber mixture becomes high and molding may be difficult. On the other hand, if D1 exceeds 20 μm, the number of short fibers decreases when combined with the resin, so that the short fibers do not easily come into contact with each other, and it is difficult to exhibit effective heat conduction when used as a composite material. There is. A preferable range of D1 is 5 to 15 μm, and more preferably 7 to 13 μm.
In the pitch-based graphitized short fibers of the present invention, the percentage (CV value) of the fiber diameter dispersion (S1) to the average fiber diameter (D1) in the pitch-based graphitized short fibers observed with an optical microscope is preferably 3 to 15%. The CV value is an index of fiber diameter variation, and the smaller the value, the higher the process stability and the smaller the product variation. When the CV value is less than 3%, the fiber diameters are extremely uniform, so the amount of small short fibers entering the gaps between the pitch-based graphitized short fibers decreases, and the pitch-based graphitized short fibers are packed more densely. It can be difficult to achieve and, as a result, it can be difficult to obtain high performance composites. On the other hand, when the CV value is larger than 15%, dispersibility is deteriorated when composited with a resin, and it may be difficult to obtain a composite material having uniform performance. The CV value is preferably 5 to 13%. The CV value is adjusted by adjusting the viscosity of the melt mesophase pitch at the time of spinning. Specifically, when spinning by the melt blow method, the melt viscosity at the nozzle hole at the time of spinning is 5.0-25.0 Pa · S. It can be realized by adjusting to.
There are generally two types of pitch-based graphitized short fibers: milled fibers having an average fiber length of less than 1 mm and cut fibers having an average fiber length of 1 mm or more and less than 10 mm. Since the appearance of the milled fiber is powdery, it is excellent in dispersibility, and the appearance of the cut fiber is close to the fiber shape.
The pitch-based graphitized short fibers in the present invention correspond to milled fibers, and the average fiber length (L1) is preferably 20 to 500 μm. 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. When L1 is smaller than 20 μm, it becomes difficult for the short fibers to come into contact with each other, and it becomes difficult to expect effective heat conduction. On the other hand, when it is larger than 500 μm, the viscosity of the matrix / short fiber mixture tends to be high when mixing with the resin, and the moldability tends to be low. More preferably, it is in the range of 20 to 300 μm. There is no particular limitation on the method for obtaining such pitch-based graphitized short fibers, but when milling with a cutter, etc., the rotation speed of the cutter, the rotation speed of the ball mill, the air velocity of the jet mill, the collision of the crusher The average fiber length can be controlled by adjusting the number of times and the residence time in the milling apparatus. Moreover, it can adjust by performing classification operation, such as a sieve, from pitch-type carbon short fiber after milling, and removing pitch-type carbon short fiber of short fiber length or long fiber length.
The pitch-based graphitized short fibers in the present invention are preferably made of graphite crystals, and the crystallite size derived from the growth direction of the hexagonal network surface is preferably 30 nm or more. The crystallite size corresponds to the degree of graphitization in any of the growth directions of the hexagonal network surface, and a certain size or more is necessary to exhibit thermophysical properties. The crystallite size in the growth direction of the hexagonal network surface can be obtained by an X-ray diffraction method. The measurement method is a concentration method, and the Gakushin method is preferably used as an analysis method. The crystallite size in the growth direction of the hexagonal mesh plane can be obtained using diffraction lines from the (110) plane.
In the pitch-based graphitized short fiber in the present invention, it is preferable that the end face of the graphene sheet is closed in the fiber end observation with a transmission electron microscope. When the end face of the graphene sheet is closed, generation of extra functional groups and localization of electrons due to the shape are difficult to occur. For this reason, active points do not occur in the pitch-based graphitized short fibers, and when coating with resin, it becomes possible to suppress poor curing due to a decrease in catalytic active points. Moreover, adsorption | suction of water etc. can also be reduced, for example, also in kneading | mixing with resin accompanying hydrolysis like polyester, the remarkable heat-and-heat durability performance improvement can be brought about. The end face of the graphene sheet is preferably 80% closed in the field of view of a transmission electron microscope magnified 500,000 to 4,000,000 times. If it is 80% or less, generation of extra functional groups and localization of electrons due to the shape may be caused, and the reaction with other materials may be promoted. The closing rate of the graphene sheet end face is preferably 90% or more, and more preferably 95% or more.
The graphene sheet end face structure varies greatly depending on whether pulverization is performed before graphitization or pulverization is performed after graphitization. That is, when a pulverization process is performed after graphitization, the graphene sheet grown by graphitization is cut and broken, and the graphene sheet end face tends to be open. On the other hand, when the pulverization treatment is performed before graphitization, the graphene sheet end face is curved in a U-shape during the graphite growth process, and the curved portion is likely to be exposed at the pitch-based graphitized short fiber end. For this reason, in order to obtain a pitch-based graphitized short fiber having a graphene sheet end face closing rate exceeding 80%, it is preferable to perform graphitization after pulverization.
The pitch-based graphitized short fibers in the present invention preferably have a substantially flat side observation surface with a scanning electron microscope. Here, “substantially flat” means that the pitch-based graphitized short fibers do not have severe unevenness like a fibril structure. When defects such as severe irregularities are present on the surface of pitch-based graphitized short fibers, an increase in viscosity accompanying an increase in 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. There are 15 or less irregularities and defects in one field of view in an image observed at a magnification of 2000 times.
A technique for obtaining such pitch-based graphitized short fibers can be preferably obtained by performing graphitization after milling.
A preferred method for producing pitch-based carbon short fibers used in the present invention will be described below.
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 these, condensed polycyclic hydrocarbon compounds such as naphthalene and phenanthrene are preferable, and mesophase pitch is particularly preferable. The mesophase ratio of the mesophase pitch is at least 90% or more, more preferably 95% or more, and further preferably 99% or more. The mesophase ratio of the mesophase pitch can be confirmed by observing the pitch in the molten state with a polarizing microscope.
Furthermore, the softening point of the raw material pitch is preferably 230 ° C. or higher and 340 ° C. or lower. The infusibilization treatment needs to be performed at a temperature lower than the softening point. For this reason, when the softening point is lower than 230 ° C., it is necessary to perform the infusibilization treatment at a temperature at least lower than the softening point. On the other hand, if the softening point exceeds 340 ° C., a high temperature exceeding 340 ° C. is required for spinning, which causes thermal decomposition of the pitch and causes problems such as generation of bubbles in the yarn due to the generated gas. A more preferable range of the softening point is 250 ° C. or higher and 320 ° C. or lower, and more preferably 260 ° C. or higher and 310 ° C. or lower. The softening point of the raw material pitch can be obtained by the Mettler method. Two or more raw material pitches may be used in appropriate combination. The mesophase ratio of the raw material pitch to be combined is preferably at least 90% or more, and the softening point is preferably 230 ° C. or higher and 340 ° C. or lower.
The mesophase pitch is spun by a melting method and then converted into pitch-based graphitized short fibers by infusibilization, carbonization, pulverization, and graphitization. In some cases, a classification step may be added after the pulverization.
Hereinafter, preferred embodiments of each step will be described.
The spinning method is not particularly limited, but a so-called melt spinning method can be applied. Specific examples include a normal spinning drawing method in which a mesophase pitch discharged from a die is drawn with a winder, a melt blow method using hot air as an atomizing source, and a centrifugal spinning method in which a mesophase pitch is drawn using centrifugal force. Among these, it is desirable to use the melt blow method for reasons such as control of the form of the pitch-based carbon fiber precursor and high productivity. For this reason, the melt blow method will be described below for the method for producing pitch-based graphitized short fibers in the present invention.
The spinning nozzle for forming the pitch-based carbon fiber precursor may have any shape. Normally, a perfect circle is used, but there is no problem even if a nozzle having an irregular shape such as an ellipse is used in a timely manner. The ratio of the nozzle hole length (LN) to the hole diameter (DN) (LN / DN) is preferably in the range of 2-20. When LN / DN exceeds 20, a strong shearing force is imparted to the mesophase pitch passing through the nozzle, and a radial structure appears in the fiber cross section. The expression of the radial structure is not preferable because it may cause a crack in the fiber cross-section during the graphitization process and may cause a decrease in mechanical properties. On the other hand, if LN / DN is less than 2, shearing cannot be imparted to the raw material pitch, resulting in a pitch-based carbon fiber precursor having a low orientation of graphite. For this reason, even when graphitized, the degree of graphitization cannot be sufficiently increased, and it is difficult to improve the thermal conductivity. In order to achieve both mechanical strength and thermal conductivity, it is necessary to apply appropriate shear to the mesophase pitch. For this reason, the ratio (LN / DN) of the nozzle hole length (LN) to the hole diameter (DN) is preferably in the range of 2 to 20, more preferably in the range of 3 to 12.
There are no particular restrictions on the temperature of the nozzle during spinning, the shear rate when the mesophase pitch passes through the nozzle, the amount of air blown from the nozzle, the temperature of the wind, etc., and the conditions under which a stable spinning state can be maintained, that is, the mesophase pitch The melt viscosity at the nozzle hole may be in the range of 1 to 100 Pa · s.
When the melt viscosity of the mesophase pitch passing through the nozzle is less than 1 Pa · s, the melt viscosity is too low to maintain the yarn shape, which is not preferable. On the other hand, when the melt viscosity of the mesophase pitch exceeds 100 Pa · s, a strong shearing force is applied to the mesophase pitch and a radial structure is formed in the fiber cross section, which is not preferable. In order to keep the shearing force applied to the mesophase pitch within an appropriate range and maintain the fiber shape, it is necessary to control the melt viscosity of the mesophase pitch passing through the nozzle. Therefore, the melt viscosity of the mesophase pitch is preferably in the range of 1 to 100 Pa · s, more preferably in the range of 3 to 30 Pa · s, and further preferably in the range of 5 to 25 Pa · s. .
The pitch-based graphitized short fibers used in the present invention preferably have an average fiber diameter (D1) of 2 to 20 μm or less. However, the control of the average fiber diameter of the pitch-based graphitized short fibers can be performed by changing the nozzle hole diameter. It can be adjusted by changing the discharge amount of the raw material pitch from the nozzle or changing the draft ratio. The change of the draft ratio can be achieved by blowing a gas having a linear velocity of 100 to 20000 m / min heated to 100 to 400 ° C. in the vicinity of the thinning point. There is no particular restriction on the gas to be blown, but air is desirable from the viewpoint of cost performance and safety.
The pitch-based carbon fiber precursor is collected on a belt such as a wire mesh to form a pitch-based carbon fiber precursor web. At that time, the weight per unit area can be adjusted according to the belt conveyance speed, but if necessary, it may be laminated by a method such as cross wrapping. The basis weight of the pitch-based carbon fiber precursor web is 150 to 1000 g / m in consideration of productivity and process stability. ² Is preferred.
The pitch-based carbon fiber precursor web thus obtained is infusibilized by a known method to form a pitch-based infusible fiber web. Infusibilization can be performed in air or in an oxidizing atmosphere using a gas in which ozone, nitrogen dioxide, nitrogen, oxygen, iodine, or bromine is added to air, but in consideration of safety and convenience, it is performed in air. It is desirable. Further, both batch processing and continuous processing can be performed, but continuous processing is desirable in consideration of productivity. The infusibilization treatment is achieved by applying a heat treatment for a certain time at a temperature of 150 to 350 ° C. A more preferable temperature range is 160 to 340 ° C. The temperature increase rate is preferably 1 to 10 ° C./min. In the case of continuous treatment, the above temperature increase rate can be achieved by sequentially passing through a plurality of reaction chambers set at arbitrary temperatures. A more preferable range of the heating rate is 3 to 9 ° C./min in consideration of productivity and process stability.
The pitch-based infusible fiber web is carbonized at a temperature of 600 to 2000 ° C. in a vacuum or in a non-oxidizing atmosphere using an inert gas such as nitrogen, argon, or krypton, to become a pitch-based carbon fiber web. . Carbonization treatment is preferably performed at normal pressure and in a nitrogen atmosphere in consideration of cost. Further, both batch processing and continuous processing can be performed, but continuous processing is desirable in consideration of productivity.
The carbonized pitch-based carbon fiber web is subjected to processing such as cutting, crushing and pulverization in order to obtain a desired fiber length. In some cases, classification processing is performed. The treatment method is selected according to the desired fiber length, but a guillotine type, uniaxial, biaxial and multi-axial rotary cutters are preferably used for cutting, and an impact action is used for crushing and crushing. Hammer type, pin type, ball type, bead type and rod type, high speed rotary type using collision between particles, roll type using compression / tearing action, cone type and screw type etc. Preferably used. In order to obtain a desired fiber length, cutting, crushing and pulverization may be configured by a plurality of machines. The treatment atmosphere may be either wet or dry. For the classification treatment, a classification device such as a vibration sieve type, a centrifugal separation type, an inertial force type, and a filtration type is preferably used. The desired fiber length can be obtained not only by selecting a model, but also by controlling the number of revolutions of the rotor / rotating blade, supply amount, clearance between blades, residence time in the system, and the like. Moreover, when using a classification process, desired fiber length can be obtained also by adjusting a sieve mesh hole diameter.
The pitch-based carbon short fibers prepared by using the above-described cutting, crushing / pulverizing treatment, and, in some cases, classification treatment, are heated to 2000-3500 ° C. and graphitized to obtain the final pitch-based graphitized short fibers. Graphitization is performed in an Atchison furnace, an electric furnace, or the like, and is performed in a vacuum or in a non-oxidizing atmosphere using an inert gas such as nitrogen, argon, or krypton.
In the present invention, the pitch-based graphitized short fibers may be subjected to a surface treatment for the purpose of further enhancing the affinity with the insulating resin and ensuring the insulating properties. The surface treatment method is not particularly limited, and specific examples include electrodeposition treatment, plating treatment, ozone treatment, plasma treatment, and acid treatment.
[Thermal conductive composition]
The insulated pitch-based graphitized short fiber of the present invention can be combined with a matrix to form a heat conductive composition. At this time, 3 to 300 parts by weight of the insulating pitch-based carbon short fibers are added to 100 parts by weight of the matrix. When the addition amount is less than 3 parts by weight, it is difficult to ensure sufficient thermal conductivity. On the other hand, it is often difficult to add more than 300 parts by weight of insulating pitch-based carbon short fibers to the matrix. More preferably, it is 20 to 100 parts by weight with respect to 100 parts by weight of the matrix.
The matrix is preferably at least one selected from the group consisting of thermoplastic resins, thermosetting resins, aromatic polyamide resins, and rubber. In order to express desired physical properties in the composite molded body, these matrices can be appropriately mixed and used.
The resin used for the matrix may be the same as or different from the resin used for the insulated pitch-based graphitized short fibers. In the case of the same type, it can be expected that the dispersibility and adhesiveness with the resin are good.
Polyolefins and their copolymers (polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, ethylene as thermoplastic resins that can be used in the matrix -Ethylene-α-olefin copolymers such as propylene copolymers), polymethacrylic acids and copolymers thereof (polymethacrylates such as polymethyl methacrylate), polyacrylic acids and copolymers thereof, polyacetals And copolymers thereof, fluororesins and copolymers thereof (polyvinylidene fluoride, polytetrafluoroethylene, etc.), polyesters and copolymers thereof (polyethylene terephthalate, polybutylene terephthalate, polyethylene) , 6 naphthalate, liquid crystalline polymer, etc.), polystyrenes and copolymers thereof (styrene-acrylonitrile copolymers, ABS resins, etc.), polyacrylonitriles and copolymers thereof, polyphenylene ethers (PPE) and copolymers thereof (Including modified PPE resins), aliphatic polyamides and copolymers thereof, polycarbonates and copolymers thereof, polyphenylene sulfides and copolymers thereof, polysulfones and copolymers thereof, polyether sulfones and Copolymers, polyether nitriles and copolymers thereof, polyether ketones and copolymers thereof, polyether ether ketones and copolymers thereof, polyketones and copolymers thereof, elastomers, liquid crystalline polymers, etc. Is mentioned. One of these may be used alone, or two or more may be used in appropriate combination. More preferably, the thermoplastic resin constituting the matrix component is polycarbonates, polyethylene terephthalates, polybutylene terephthalates, polyethylene-2, 6-naphthalates, nylons, polypropylenes, polyethylenes, polyether ketones, polyphenylene sulfide. And at least one resin selected from the group consisting of acrylonitrile-butadiene-styrene copolymer resins.
Examples of thermosetting resins that can be used for the matrix include epoxy resins, thermosetting acrylic resins, urethane resins, silicone resins, phenol resins, thermosetting modified PPE resins, thermosetting PPE resins, polyimide resins, and the like. Examples thereof include copolymers, aromatic polyamideimide resins, and copolymers thereof. One of these may be used alone, or two or more thereof may be used in appropriate combination.
The aromatic polyamide resin that can be used for the matrix includes an aromatic dicarboxylic acid component composed of terephthalic acid and / or isophthalic acid, 1,4-phenylenediamine, 1,3-phenylenediamine, and 3,4′-diamino. Examples include wholly aromatic polyamides derived from at least one aromatic diamine component selected from the group consisting of diphenyl ether, 4,4′-diaminodiphenyl ether and 1,3-bis (3-aminophenoxy) benzene.
The rubber that can be used for the matrix is not particularly limited, but natural rubber (NR), acrylic rubber, acrylonitrile butadiene rubber (NBR rubber), isoprene rubber (IR), urethane rubber, ethylene propylene rubber (EPM), epichlorohydrin rubber, Examples include chloroprene rubber (CR), silicone rubber and copolymers thereof, styrene butadiene rubber (SBR), butadiene rubber (BR), and butyl rubber.
The composition of the present invention is prepared by mixing insulating pitch-based graphitized short fibers and a matrix, and at the time of mixing, a kneader, various mixers, a blender, a roll, an extruder, a milling machine, a self-revolving type A mixing device such as a stirrer or a kneading device is preferably used. Here, when the matrix resin is a thermosetting resin or rubber, the resin or rubber before curing can be mixed with insulating pitch-based graphitized short fibers, and then molded and cured.
In order to further increase the thermal conductivity of the heat conductive composition of the present invention, fillers other than silicon carbide-coated pitch-based graphitized short fibers 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, and carbon materials such as diamond. You may add these suitably according to a function. Two or more types can be used in combination. However, many of the above compounds have a density higher than that of pitch-based graphitized short fibers, and when aiming at weight reduction, it is necessary to pay attention to the maximum addition ratio and addition ratio. In addition, when a conductive filler is added, maintenance of insulation cannot be achieved, so care must be taken.
Furthermore, glass fibers, potassium titanate whiskers, zinc oxide whiskers, aluminum boride whiskers, boron nitride whiskers, aramid fibers, alumina fibers, silicon carbide fibers, asbestos fibers are used to enhance other properties such as moldability and mechanical properties. A fibrous filler such as gypsum fiber may be appropriately added depending on the required function. Two or more of these may be used in combination. 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 sulfates, 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 pitch-based graphitized short fibers, and when aiming at weight reduction, it is necessary to pay attention to the addition amount and addition ratio.
Moreover, you may add two or more other additives to a composition as needed. Examples of other additives include mold release agents, flame retardants, emulsifiers, softeners, plasticizers, and surfactants.
More specifically, the use of the composition will be described. The composition can be used as a heat radiating member, a heat transfer member, or a constituent material thereof for effectively radiating heat generated by electronic components such as a semiconductor element, a power source, and a light source in an electronic device or the like. .
When the matrix is a thermally conductive composition made of a thermoplastic resin, it is selected from the group consisting of injection molding, press molding, calendar molding, roll molding, extrusion molding, cast molding, and blow molding. It can shape | mold by the at least 1 type of method which can be obtained. And a sheet-like molded object can be shape | molded by extrusion molding methods, such as extrusion by a roll and extrusion by die | dye. The molding conditions depend on the molding method and the matrix, and the molding is performed in a state where the temperature is higher than the melt viscosity of the resin.
If the matrix is a thermally conductive composition made of a thermosetting resin, it can be molded using a resin before curing, injection molding, press molding, calendar molding, roll molding, extrusion molding And it can shape | mold by at least 1 type of method chosen from the group which consists of a casting method, and a molded object can be obtained. The molding conditions depend on the molding method and the matrix, and include a method of imparting the curing temperature of the resin during molding or in an appropriate mold.
In the case of a thermally conductive composition whose matrix is composed of an aromatic polyamide resin, the aromatic polyamide resin can be dissolved in a solvent, pitch-based graphitized short fibers can be mixed therein, and molded using a casting method. Here, the solvent is not particularly limited as long as the aromatic polyamide resin can be dissolved. Specifically, amide solvents such as N, N-dimethylacetamide and N-methylpyrrolidone can be used.
When the matrix is a thermally conductive composition made of rubber, it can be molded by at least one method selected from the group consisting of a press molding method, a calendar molding method, and a roll molding method to obtain a molded body. The molding conditions depend on the molding technique and the matrix, and can include a method of imparting the vulcanization temperature of the rubber.
From the heat conductive composition, molding materials such as compounds, sheets, greases, adhesives, and the like, and heat conductive moldings can be obtained. The present invention thus includes a molded body obtained from the above heat conductive composition.

Examples are shown below, but the present invention is not limited thereto.
In addition, each value in a present Example was calculated | required according to the following method.
(1) The average fiber diameters of the insulating pitch-based graphitized short fibers and the pitch-based graphitized short fibers were measured from the average value by measuring 60 fibers using a scale under an optical microscope in accordance with JIS R7607.
(2) The number average fiber length of the insulating pitch-based graphitized short fibers and the pitch-based graphitized short fibers was measured from 1500 using PITA1 manufactured by Seishin Enterprise, and obtained from the average value.
(3) The crystallite size of the pitch-based graphitized short fibers was determined by the Gakushin method by measuring reflection from the (110) plane appearing in X-ray diffraction.
(4) The end faces of the pitch-based graphitized short fibers were observed with a transmission electron microscope at a magnification of 1,000,000 times and magnified on a photograph at 4 million times to confirm a graphene sheet. In the fiber end observation of pitch-based graphitized short fibers with a transmission electron microscope, five end face images of the graphene sheet at a fiber end of 500 to 2.5 million times were observed, and the total length A (nm) and end face of the end face of the graphene sheet at the end of the fiber The length B (nm) of the portion curved in a U-shape was measured, and the closing rate was determined by the closing rate (%) = B / A × 100.
(5) The surfaces of the insulating pitch-based graphitized short fibers and the pitch-based graphitized short fibers were observed with a scanning electron microscope at a magnification of 2000 to confirm defects and irregularities.
(6) The coating amount of the thermosetting resin cured product of the insulated pitch-based graphitized short fibers is calculated from the weight difference between before and after heating by holding the insulated pitch-based graphitized short fibers at 500 ° C. for 3 hours in the air atmosphere. did.
(7) The specific resistance of the insulated pitch-based graphitized short fiber was determined using MCP-PD51 manufactured by Mitsubishi Chemical Analytech.
(8) The specific resistance of the heat conductive composition was determined using Hiresta UP manufactured by Mitsubishi Chemical Analytech.
(9) The thermal conductivity of the thermally conductive composition was determined using QTM-500 manufactured by Kyoto Electronics Industry.
Reference example 1
A pitch made of a condensed polycyclic hydrocarbon compound was used as a main raw material. The optical anisotropy ratio was 100%, and the softening point was 283 ° C. Using a cap with a hole with a diameter of 0.2 mmφ, heated air was ejected from the slit at a linear velocity of 5500 m / min, and the pitch was melted to produce pitch-based short fibers having an average diameter of 11.2 μm. The spinning temperature at this time was 325 ° C., and the melt viscosity was 17.5 Pa · S (175 poise). The spun fibers were collected on a belt to form a mat, and then a pitch-based carbon fiber precursor web made of a pitch-based carbon fiber precursor having a basis weight of 350 g / m ^{2 by} cross wrapping.
This pitch-based carbon fiber precursor web was heated from 170 ° C. to 300 ° C. at an average heating rate of 5 ° C./min to be infusible, and further fired at 800 ° C. This pitch-based carbon fiber web was pulverized at 900 rpm using a cutter (manufactured by Turbo Kogyo) and graphitized at 3000 ° C.
The average fiber diameter of the pitch-based graphitized short fibers was 8.1 μm, and the ratio of the fiber diameter dispersion to the average fiber diameter (CV value) was 11%. The number average fiber length was 100 μm, and the crystal size derived from the growth direction of the hexagonal network surface was 80 nm.
It was confirmed by observation with a transmission microscope that the graphene sheet was closed on the end face of the pitch-based graphitized short fiber. The closing rate of the graphene sheet was 90.3%. Moreover, the surface was substantially smooth with one unevenness | corrugation by observation with the scanning electron microscope.
The specific resistance of the pitch-based graphitized short fibers was 2.5 × 10 ⁻⁴ Ω · cm.
Example 1
100 parts by weight of epoxy resin main agent (registered trademark “Epicoat 871” manufactured by Japan Epoxy Resin), 30 parts by weight of epoxy resin curing agent (registered trademark “Epicure FL240” manufactured by Japan Epoxy Resin), and pitch-based graphitization prepared in Reference Example 1 20 parts by weight of short fibers were mixed for 3 minutes using a self-revolving mixer (registered trademark “Awatori Nertaro ARV310” manufactured by Sinky Corporation) and then filtered to remove excess uncured resin. This was treated at 150 ° C. for 2 hours to obtain insulated pitch-based graphitized short fibers. FIG. 1 shows a scanning electron microscope observation photograph of the obtained insulated pitch-based graphitized short fiber, and it was confirmed that the epoxy resin was coated on the surface of the graphitized short fiber. Irregularities and defects were not observed.
The coating amount of the epoxy resin was 7.8 parts by weight with respect to 100 parts by weight of the pitch-based graphitized short fibers. The specific resistance of the insulated pitch-based graphitized short fiber was 5.0 × 10 ⁸ Ω · cm.
The average fiber diameter of the insulated pitch-based graphitized short fibers was 9.8 μm, and the ratio of the fiber diameter dispersion to the average fiber diameter (CV value) was 12%. The number average fiber length was 100 μm.
Example 2
90 parts by weight of an epoxy resin main agent (registered trademark “Epicoat 806” manufactured by Japan Epoxy Resin), 110 parts by weight of an epoxy resin curing agent (registered trademark “Epicure YH307” manufactured by Japan Epoxy Resin), a product name of an epoxy resin curing catalyst (trade name manufactured by Japan Epoxy Resin) "IMBI102") 2 parts by weight and ethyl methyl ketone 200 parts by weight dissolved in 30 parts by weight of pitch-based graphitized short fibers prepared in Reference Example 1 and a revolutionary mixer (registered trademark "Shinky Co., Ltd. ARV310 ") was mixed for 3 minutes and then filtered to remove excess uncured resin. This was treated at 150 ° C. for 2 hours to obtain insulated pitch-based graphitized short fibers. As a result of surface observation, it was confirmed that the epoxy resin was applied to the pitch-based graphitized short fibers. Irregularities and defects were not observed. The coating amount of the epoxy resin was 3.1 parts by weight with respect to 100 parts by weight of the pitch-based graphitized short fibers. The specific resistance of the insulating pitch-based graphitized short fiber was 7.0 × 10 ⁵ Ω · cm.
The average fiber diameter of the insulated pitch-based graphitized short fibers was 9.0 μm, and the ratio of the fiber diameter dispersion to the average fiber diameter (CV value) was 11%. The number average fiber length was 100 μm.
Example 3
90 parts by weight of an epoxy resin main agent (registered trademark “Epicoat 806” manufactured by Japan Epoxy Resin), 110 parts by weight of an epoxy resin curing agent (registered trademark “EpiCure YH307” manufactured by Japan Epoxy Resin), a registered trademark of an epoxy resin curing catalyst (registered trademark manufactured by Japan Epoxy Resin) 2 parts by weight of “IMBI102”) are dissolved in 100 parts by weight of ethyl methyl ketone, and 30 parts by weight of the pitch-based graphitized short fibers prepared in Reference Example 1 are mixed with a revolutionary mixer (registered trademark “Shinky Corp. ARV310 ") was mixed for 3 minutes and then filtered to remove excess uncured resin. This was treated at 150 ° C. for 2 hours to obtain insulated pitch-based graphitized short fibers. As a result of surface observation, it was confirmed that the epoxy resin was applied to the pitch-based graphitized short fibers. Irregularities and defects were not observed. The coating amount of the epoxy resin was 4.8 parts by weight with respect to 100 parts by weight of the pitch-based graphitized short fibers. The specific resistance of the insulated pitch-based graphitized short fiber was 3.0 × 10 ⁷ Ω · cm.
The average fiber diameter of the insulated pitch-based graphitized short fibers was 9.3 μm, and the ratio of the fiber diameter dispersion to the average fiber diameter (CV value) was 11%. The number average fiber length was 100 μm.
Example 4
90 parts by weight of an epoxy resin main agent (registered trademark “Epicoat 806” manufactured by Japan Epoxy Resin), 110 parts by weight of an epoxy resin curing agent (registered trademark “EpiCure YH307” manufactured by Japan Epoxy Resin), a registered trademark of an epoxy resin curing catalyst (registered trademark manufactured by Japan Epoxy Resin) “IMBI102”) 2 parts by weight and 25 parts by weight of the pitch-based graphitized short fibers prepared in Reference Example 1 were mixed for 3 minutes using a self-revolving mixer (registered trademark “Awatori Nertaro ARV310” manufactured by Shinky Corporation). Then, filtration was performed to remove excess uncured resin. This was treated at 150 ° C. for 2 hours to obtain insulated pitch-based graphitized short fibers. FIG. 2 shows a scanning electron microscope photograph of the insulated pitch-based graphitized short fiber obtained. The surface of the graphitized short fiber was confirmed to have been coated with epoxy resin, but the coated surface had four irregularities. Observed. No defects were observed.
The coating amount of the epoxy resin was 9.2 parts by weight with respect to 100 parts by weight of the pitch-based graphitized short fibers. The specific resistance of the insulated pitch-based graphitized short fiber was 3.0 × 10 ¹⁰ Ω · cm.
The average fiber diameter of the insulated pitch-based graphitized short fibers was 10.3 μm, and the ratio of the fiber diameter dispersion to the average fiber diameter (CV value) was 11%. The number average fiber length was 100 μm.
Example 5
Two-part curable silicone resin (trade name “SE1740A & B” manufactured by Toray Dow Silicone) 5 parts by weight dissolved in 200 parts by weight of toluene, and 100 parts by weight of the pitch-based graphitized short fiber prepared in Reference Example 1 (Registered trademark “Awatori Nertaro ARV310” manufactured by Shinky Corporation) was mixed for 3 minutes, and then toluene was volatilized. This was treated at 150 ° C. for 2 hours to obtain insulated pitch-based graphitized short fibers. As a result of surface observation, it was confirmed that silicone resin was applied to pitch-based graphitized short fibers. Irregularities and defects were not observed.
The coating amount of the silicone resin was 4.8 parts by weight with respect to 100 parts by weight of pitch-based graphitized short fibers. The specific resistance of the insulated pitch-based graphitized short fiber was 7.0 × 10 ⁷ Ω · cm.
The average fiber diameter of the insulated pitch-based graphitized short fibers was 9.0 μm, and the ratio of the fiber diameter dispersion to the average fiber diameter (CV value) was 11%. The number average fiber length was 100 μm.
Example 6
2 parts by weight of an aromatic polyamide resin (registered trademark “Technola” manufactured by Teijin Techno Products) is dissolved in 200 parts by weight of N-methylpyrrolidone, and 100 parts by weight of pitch-based graphitized short fibers prepared in Reference Example 1 are revolving mixed. A mixed slurry was obtained by mixing for 3 minutes using a machine (registered trademark “Awatori Nertaro ARV310” manufactured by Shinky Corporation). This was dried at 200 ° C. in a rotary evaporator. The obtained surface-treated pitch-based graphitized short fibers were dipped in an aromatic polyamide resin solution having the same concentration and dried repeatedly to obtain insulated pitch-based graphitized short fibers. As a result of surface observation, it was confirmed that the aromatic polyamide resin was applied to the pitch-based graphitized short fibers. Irregularities and defects were not observed.
The coating amount of the aromatic polyamide resin was 5.9 parts by weight with respect to 100 parts by weight of the pitch-based graphitized short fibers. The specific resistance of the insulated pitch-based graphitized short fiber was 2.1 × 10 ⁶ Ω · cm.
The average fiber diameter of the insulated pitch-based graphitized short fibers was 9.0 μm, and the ratio of the fiber diameter dispersion to the average fiber diameter (CV value) was 11%. The number average fiber length was 100 μm.
Example 7
In Example 1, 100 parts by weight of a mixed liquid composed of 100 parts by weight of an epoxy resin main agent (registered trademark “Epicoat 871” manufactured by Japan Epoxy Resin) and 30 parts by weight of an epoxy resin curing agent (registered trademark “Epicure FL240” manufactured by Japan Epoxy Resin) 100 parts by weight of the insulated pitch-based graphitized short fibers thus prepared were mixed for 6 minutes using a self-revolving mixer (registered trademark “Awatori Nertaro ARV310” manufactured by Shinky Corporation) to obtain a mixed slurry. This slurry was pressed with a vacuum press (manufactured by Kitagawa Seiki) to obtain a plate-like composite composition having a thickness of 0.5 mm, and cured at 150 ° C. for 4 hours to prepare a heat conductive composition. The specific resistance of the heat conductive composition was 8.5 × 10 ⁹ Ω · cm. The heat conductivity of the heat conductive composition was 6.2 W / (m · K).
Example 8
90 parts by weight of an epoxy resin main agent (registered trademark “Epicoat 806” manufactured by Japan Epoxy Resin), 110 parts by weight of an epoxy resin curing agent (registered trademark “EpiCure 307” manufactured by Japan Epoxy Resin), and a catalyst for curing an epoxy resin (trade name manufactured by Japan Epoxy Resin) “IMBI102”) 100 parts by weight of a mixed solution composed of 2 parts by weight and 100 parts by weight of the insulated pitch-based graphitized short fiber prepared in Example 2 were used in a revolutionary mixer (registered trademark “Awori Nertaro ARV310 manufactured by Shinky Corporation) )) For 6 minutes to obtain a mixed slurry. This slurry was pressed with a vacuum press (manufactured by Kitagawa Seiki) to obtain a plate-like composite composition having a thickness of 0.5 mm, and cured at 150 ° C. for 4 hours to prepare a heat conductive composition. The specific resistance of the heat conductive composition was 6.5 × 10 ⁷ Ω · cm. The thermal conductivity of the thermally conductive composition was 8.3 W / (m · K).
Example 9
A thermally conductive composition was prepared in the same manner as in Example 7 except that the insulating pitch-based graphitized short fibers used were those prepared in Example 3.
The specific resistance of the heat conductive composition was 3.5 × 10 ⁸ Ω · cm. The heat conductivity of the heat conductive composition was 7.3 W / (m · K).
Example 10
A thermally conductive composition was prepared in the same manner as in Example 7 except that the insulating pitch-based graphitized short fibers used were those prepared in Example 4.
The specific resistance of the heat conductive composition was 7.2 × 10 ¹¹ Ω · cm. The heat conductivity of the heat conductive composition was 4.8 W / (m · K).
Example 11
A thermally conductive composition was prepared in the same manner as in Example 7 except that the insulating pitch-based graphitized short fibers used were those prepared in Example 5.
The specific resistance of the heat conductive composition was 7.5 × 10 ⁸ Ω · cm. The heat conductivity of the heat conductive composition was 7.1 W / (m · K).
Example 12
A thermally conductive composition was prepared in the same manner as in Example 7 except that the insulating pitch-based graphitized short fibers used were those prepared in Example 6. The specific resistance of the heat conductive composition was 1.0 × 10 ⁷ Ω · cm. The heat conductivity of the heat conductive composition was 5.9 W / (m · K).
Example 13
100 parts by weight of pitch-based graphitized short fibers prepared in Reference Example 1, 5 parts by weight of a silicone resin (manufactured by Dow Corning Toray, SE1740), and 300 parts by weight of toluene (manufactured by Wako Pure Chemical Industries, Ltd.) Tori Netaro ARV-310) was mixed for 3 minutes to obtain a composite slurry. This was spray-dried with a spray dryer (B-290, manufactured by Shibata Kagaku) to obtain insulated pitch-based graphitized short fibers. The treatment temperature was 200 ° C.
The coating amount of the insulating layer was 5 parts by weight with respect to 100 parts by weight of the pitch-based graphitized short fibers. The specific resistance of the insulated pitch-based graphitized short fiber was 5.0 × 10 ¹² Ω · cm.
The average fiber diameter of the insulated pitch-based graphitized short fibers was 8.5 μm, and the ratio of the fiber diameter dispersion to the average fiber diameter (CV value) was 12%. The number average fiber length was 100 μm. As a result of surface observation, it was confirmed that silicone resin was applied to pitch-based graphitized short fibers. Irregularities and defects were not observed.
Example 14
100 parts by weight of pitch-based graphitized short fibers prepared in Reference Example 1, 2.25 parts by weight of an epoxy resin main agent (registered trademark “Epicoat 806” manufactured by Japan Epoxy Resin), a curing agent of epoxy resin (registered trademark “Epicure manufactured by Japan Epoxy Resin”) 307 ") 2.75 parts by weight, epoxy resin curing catalyst (Japan Epoxy Resin product name" IMBI102 ") 0.05 parts by weight, ethyl methyl ketone (Wako Pure Chemical Industries) 300 parts by weight Awatori Netaro ARV-310) was mixed for 3 minutes to obtain a composite slurry. This was spray-dried with a spray dryer (B-290, manufactured by Shibata Kagaku) to obtain insulated pitch-based graphitized short fibers. The treatment temperature was 200 ° C.
The coating amount of the insulating layer was 5 parts by weight with respect to 100 parts by weight of the pitch-based graphitized short fibers. The specific resistance of the insulated pitch-based graphitized short fiber was 2.0 × 10 ¹² Ω · cm.
The average fiber diameter of the insulated pitch-based graphitized short fibers was 8.5 μm, and the ratio of the fiber diameter dispersion to the average fiber diameter (CV value) was 13%. The number average fiber length was 100 μm. As a result of surface observation, it was confirmed that the epoxy resin was applied to the pitch-based graphitized short fibers, and there were 1 unevenness and 0 defects.
Example 15
100 parts by weight of pitch-based graphitized short fibers prepared in Reference Example 1, 1.12 parts by weight of an epoxy resin main agent (registered trademark “Epicoat 806” manufactured by Japan Epoxy Resin), a curing agent of epoxy resin (registered trademark “Epicure manufactured by Japan Epoxy Resin”) 307 ") 1.38 parts by weight, epoxy resin curing catalyst (Japan epoxy resin product name" IMBI102 ") 0.02 parts by weight, ethyl methyl ketone (Wako Pure Chemical Industries) 300 parts by weight Awatori Netaro ARV-310) was mixed for 3 minutes to obtain a composite slurry. This was spray-dried with a spray dryer (B-290, manufactured by Shibata Kagaku) to obtain insulated pitch-based graphitized short fibers. The treatment temperature was 200 ° C.
The coating amount of the insulating layer was 2.5 parts by weight with respect to 100 parts by weight of pitch-based graphitized short fibers. The specific resistance of the insulated pitch-based graphitized short fiber was 8.9 × 10 ¹¹ Ω · cm.
The average fiber diameter of the insulated pitch-based graphitized short fibers was 8.2 μm, and the ratio of the fiber diameter dispersion to the average fiber diameter (CV value) was 12%. The number average fiber length was 100 μm. Further, as a result of surface observation, it was confirmed that epoxy resin was applied to pitch-based graphitized short fibers, and there were 0 defects and 1 unevenness.
Example 16
100 parts by weight of pitch-based graphitized short fibers prepared in Reference Example 1, 5 parts by weight of tetraethoxysilane (Wako Pure Chemical), 1 part by weight of 28% aqueous ammonia (manufactured by Wako Pure Chemical), 300 of ethanol (manufactured by Wako Pure Chemical) Part by weight and 75 parts by weight of water were mixed for 3 minutes using a self-revolving mixer (Shinky Awatori Nertaro ARV-310) to obtain a composite slurry. This was spray-dried with a spray dryer (B-290, manufactured by Shibata Kagaku) to obtain insulated pitch-based graphitized short fibers. The processing temperature was 130 ° C.
The coating amount of the insulating layer was 5 parts by weight with respect to 100 parts by weight of the pitch-based graphitized short fibers. The specific resistance of the insulated pitch-based graphitized short fiber was 5.0 × 10 ¹¹ Ω · cm.
The average fiber diameter of the insulated pitch-based graphitized short fibers was 8.6 μm, and the ratio of the fiber diameter dispersion to the average fiber diameter (CV value) was 12%. The number average fiber length was 100 μm. As a result of surface observation, it was confirmed that the silicone gel film was applied to the pitch-based graphitized short fibers, and there were 0 defects and 3 irregularities.
Example 17
45 parts by weight of the insulated pitch-based graphitized short fibers obtained in Example 13 and 100 parts by weight of a silicone resin (manufactured by Dow Corning, Toray, SE 1740) were mixed with a revolving mixer (Shinky Awatori Nerita ARV-310). And mixed for 3 minutes to form a composite slurry. The slurry was pressed with a vacuum press (manufactured by Kitagawa Seiki) to obtain a plate-like composite molded body having a thickness of 0.5 mm, and cured at 130 ° C. for 2 hours to prepare a heat conductive composition. The specific resistance of the heat conductive composition was 3.5 × 10 ¹³ Ω · cm. The heat conductivity of the heat conductive composition was 4.9 W / (m · K).
Example 18
45 parts by weight of the insulated pitch-based graphitized short fibers obtained in Example 14 and 100 parts by weight of a silicone resin (manufactured by Dow Corning Toray, SE1740) were mixed with a revolving mixer (Shinky Awatori Nerita ARV-310). And mixed for 3 minutes to form a composite slurry. The slurry was pressed with a vacuum press (manufactured by Kitagawa Seiki) to obtain a plate-like composite molded body having a thickness of 0.5 mm, and cured at 130 ° C. for 2 hours to prepare a heat conductive composition. The specific resistance of the heat conductive composition was 4.0 × 10 ¹³ Ω · cm. The heat conductivity of the heat conductive composition was 4.7 W / (m · K).
Example 19
45 parts by weight of the insulated pitch-based graphitized short fibers obtained in Example 15 and 100 parts by weight of a silicone resin (manufactured by Toray Dow Corning, SE1740) were mixed with a revolving mixer (Shinky Awatori Nerita ARV-310). And mixed for 3 minutes to form a composite slurry. The slurry was pressed with a vacuum press (manufactured by Kitagawa Seiki) to obtain a plate-like composite molded body having a thickness of 0.5 mm, and cured at 130 ° C. for 2 hours to prepare a heat conductive composition. The specific resistance of the heat conductive composition was 1.0 × 10 ¹³ Ω · cm. The heat conductivity of the heat conductive composition was 4.8 W / (m · K).
Example 20
45 parts by weight of the insulated pitch-based graphitized short fibers obtained in Example 16 and 100 parts by weight of a silicone resin (manufactured by Dow Corning, Toray, SE1740) were mixed with a revolving mixer (Shinky Awatori Nertaro ARV-310). And mixed for 3 minutes to form a composite slurry. The slurry was pressed with a vacuum press (manufactured by Kitagawa Seiki) to obtain a plate-like composite molded body having a thickness of 0.5 mm, and cured at 130 ° C. for 2 hours to prepare a heat conductive composition. The specific resistance of the heat conductive composition was 1.0 × 10 ¹³ Ω · cm. The thermal conductivity of the thermally conductive composition was 5.1 W / (m · K).
Comparative Example 1
A thermally conductive composition was prepared in the same manner as in Example 6 except that the insulating pitch-based graphitized short fibers used were those prepared in Reference Example 1. The specific resistance of the heat conductive composition was 6.0 × 10 ⁻¹ Ω · cm. The heat conductivity of the heat conductive composition was 9.3 W / (m · K).

The insulated pitch-based graphitized short fibers of the present invention are coated with a resin whose pitch-based graphitized short fibers having excellent thermal conductivity do not have a melting point at 250 ° C. or less and whose precursor is liquid or solvent-soluble. By doing so, it is possible to provide insulation while exhibiting high thermal conductivity. As a result, it can be widely used for heat dissipating members of electronic devices and electronic parts that require high heat dissipating characteristics, thereby ensuring thermal management.

Claims

The pitch-based graphitized short fibers are coated with a resin having no melting point at 250 ° C. or less and the precursor is liquid, or the precursor or itself is soluble in at least one solvent. Insulated pitch-based graphitized short fibers.
Per observation line in an image observed with a scanning electron microscope at 800 to 1000 times, with 10 or less irregularities and defects per line, or in an observation field with an image observed at 2000 times The insulated pitch-based graphitized short fiber according to claim 1, wherein there are 15 or less irregularities and defects.
The insulated pitch-based graphitized short fiber according to claim 1, wherein the resin is a thermosetting resin.
The insulated pitch-based graphitized short fiber according to claim 3, wherein the thermosetting resin is at least one resin selected from the group consisting of an epoxy resin, a urethane resin, a thermosetting acrylic resin, and a silicone resin.
The insulated pitch-based graphitized short fiber according to claim 4, wherein the thermosetting resin is an epoxy resin.
The insulated pitch-based graphitized short fiber according to claim 1, wherein the resin is at least one selected from the group consisting of aromatic polyamide, aromatic polyimide, and aliphatic polyimide.
The insulated pitch-based graphitized short fiber according to claim 1, wherein the resin used for coating is 1 to 10 parts by weight with respect to 100 parts by weight of the pitch-based graphitized short fiber.
2. The insulated pitch-based graphitized short fiber according to claim 1, wherein the specific resistance of the pitch-based graphitized short fiber is 1.0 × 10 6 Ω · cm or more.
The pitch-based graphitized short fibers are made from mesophase pitch, the average fiber diameter is 2 to 20 μm, the percentage of fiber diameter dispersion (CV value) with respect to the average fiber diameter is 3 to 15%, and the number average fiber length Is 20 to 500 μm, the crystallite size derived from the growth direction of the hexagonal network surface is 30 nm or more, 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 The insulated pitch-based graphitized short fiber according to claim 1, wherein is substantially flat.
A matrix comprising the insulated pitch-based graphitized short fiber according to claim 1 and at least one matrix component selected from the group consisting of a thermoplastic resin, a thermosetting resin, an aromatic polyamide resin, and rubber. A thermally conductive composition containing 3 to 300 parts by weight of an insulated pitch-based graphitized short fiber with respect to 100 parts by weight of the component.
The thermoplastic resin constituting the matrix component is polycarbonates, polyethylene terephthalates, polybutylene terephthalates, polyethylene-2, 6-naphthalates, nylons, polypropylenes, polyethylenes, polyether ketones, polyphenylene sulfides, and The thermally conductive composition according to claim 10, which is at least one resin selected from the group consisting of acrylonitrile-butadiene-styrene copolymer resins.
The thermosetting resin constituting the matrix component is epoxy resin, thermosetting acrylic resin, urethane resin, silicone resin, phenol resin, thermosetting modified PPE resin, thermosetting PPE resin, polyimide resin and its co-polymer The heat conductive composition according to claim 10, which is at least one resin selected from the group consisting of a coalescence, an aromatic polyamideimide resin and a copolymer thereof.
The rubber constituting the matrix component is natural rubber (NR), acrylic rubber, acrylonitrile butadiene rubber (NBR rubber), isoprene rubber (IR), urethane rubber, ethylene propylene rubber (EPM), epichlorohydrin rubber, chloroprene rubber (CR), The heat conductive composition according to claim 10, which is at least one selected from the group consisting of silicone rubber, styrene butadiene rubber (SBR), butadiene rubber (BR), and butyl rubber.
The heat conductive molded object obtained from the heat conductive composition of Claim 10.