JP2016204570A - Heat conductive resin molded body and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat conductive resin molded body containing a thermoplastic resin as a base component, maintaining a layer structure formed by a flaky graphite and a special structure formed by nanofiber dispersed between the layers by suppressing breakage of the nanofiber generated by shear force in a high heat conduction technology of a resin composite material using both of the flaky graphite and the nanofiber and capable of processing by using an injection molding with high heat conductivity, productivity and high shape freedom.SOLUTION: By injection molding a heat conductive resin composition obtained by melting and mixing (a) a thermoplastic resin of 30 o 95 vol.%, (b) 1 to 69 vol.% of a flaky graphite having an aspect ratio, obtained by dividing a flaky major axis by a minor axis, of 10 to 130 and (c) 0.1 to 10 vol.% of a nano fiber having a diameter of 1 μm or less and an aspect ratio, obtained by dividing a fiber length by a diameter, of 20 or more, where (a)+(b)+(c)=100 vol.% and total volume of (b) and (c) is 5 to 70 vol.%, a heat conductive resin molded body is obtained where one or more flat face structure having surfaces of flaky graphite aligned on a same flat face each other is formed, the flat face structure forms one or more layer structure facing in a same flat face direction, a dispersion layer of (c) the nanofiber is formed in (a) the thermoplastic resin layer contacting to the flat face structure and (c) the nanofiber forms a heat conductive path between layers.SELECTED DRAWING: None

Description

  The present invention relates to a thermally conductive resin molded article that is obtained by injection molding of a thermally conductive resin and is further excellent in thermal conductivity, and a method for producing the same.

As a technique for improving the thermal conductivity of a resin, it has been studied to fill a resin with a relatively large carbon-based filler represented by graphite and a nano-sized carbon-based filler.
For example, in Patent Document 1 (Japanese Patent Laid-Open No. 2015-937), a resin composition in which flake-shaped graphite and nano-sized carbon nanofibers are dispersed in a thermosetting resin or a thermoplastic resin is hot-pressed. A technique for forming a graphite layer structure and dispersing carbon nanofibers between the layers has been proposed. In this method, since an efficient heat conduction path is formed, the heat conductivity is dramatically improved with a small amount of filler filling. However, when a thermosetting resin is used for the base resin, a heat curing process is necessary for practical use, and in addition, a hot press is used for the orientation of graphite, so that high-productivity injection molding is impossible. There are drawbacks. Further, in this technique, even when a thermoplastic resin is used, the resulting resin composition is hot-pressed, which is inferior in productivity, and in this patent document, this resin composition is used to achieve thermal conductivity. There is no specific example of obtaining an excellent injection molded article.

  Further, continuous processing using a roll has been proposed as a technique for improving productivity and continuously obtaining a workpiece. In Patent Document 2 (Japanese Patent Application Laid-Open No. 2015-36383), a resin composition in which flat graphite and nano-sized carbon nanofibers are dispersed in a thermoplastic elastomer is converted into a string-like strand using a twin-screw extrusion kneader. A method of continuously obtaining a sheet having high thermal conductivity by processing into a sheet and subsequently pressing it with a roll is shown. According to this method, graphite is oriented by pressing with a roll, and nanofibers are dispersed between layers, thereby forming a highly efficient heat conduction path, and continuously obtaining a workpiece while achieving high heat conductivity. However, since it is premised on pressing with a roll, the degree of freedom of the shape of the obtained workpiece is extremely limited.

  Furthermore, a technique for improving thermal conductivity by mixing flaky aluminum filler and carbon nanotubes (CNT) with a resin is disclosed in Patent Document 3 (Japanese Patent Laid-Open No. 2012-72363). This technique is effective as a technique for improving the thermal conductivity to some extent by using injection-moldable thermoplastic resin, but since aluminum is used among the metals that are soft, aluminum fillers are in contact with each other. When the amount is filled, aluminum is deformed by a shearing force generated during processing, and a layer structure important for improving thermal conductivity cannot be formed. This can be inferred from the fact that the thermal conductivity anisotropy is not so large in the example of Patent Document 3. Therefore, it is difficult to realize a heat conductive resin molded body made of a combination of flaky aluminum filler and CNT and processed by injection molding to achieve a metal-like high thermal conductivity (10 W / m · K or more). is there.

Furthermore, in patent document 4 (Unexamined-Japanese-Patent No. 2006-225648), in the resin composition using the vapor growth carbon fiber whose average aspect-ratio is 65-500 and average fiber diameter is 50-130 nm, electrical conductivity and heat conduction are mentioned. An aspect ratio that maximizes the ratio has been proposed. According to this technology, when vapor-grown carbon fibers are dispersed in a resin using a processing machine, the aspect ratio of vapor-grown carbon fibers is controlled by controlling the shear force using the screw shape and screw rotation speed as parameters. Can be
However, in the technology described in this patent document, the vapor-grown carbon fiber is only used alone in the base resin, and the aspect ratio decreases due to the shear force between the fillers when combined with a larger filler. Is not mentioned.

  As is clear from the description of the prior art described above, in the conventional processing of the nanofiber-containing resin, the dispersion of nanofibers due to the entanglement of the nanofibers and the uneven distribution of the nanofibers is promoted. Therefore, a strong shearing force and a special processing machine are required, and this causes the nanofibers to be destroyed, and the layer structure formed by graphite and the special structure formed entirely by the nanofibers dispersed between the layers There was a problem that could not be maintained.

Japanese Patent Laid-Open No. 2015-937 Japanese Patent Laying-Open No. 2015-36383 JP 2012-72363 A JP 2006-225648 A

  The present invention suppresses the destruction of nanofibers caused by shearing force and forms scaly graphite in a high thermal conductivity technology of a resin composite material using a combination of flaky graphite and nanofibers with a thermoplastic resin as a base component. A heat conductive resin molded body that maintains the layer structure and the special structure formed by the nanofibers dispersed between the layers, and enables processing using injection molding with high thermal conductivity and high productivity and shape flexibility. The purpose is to get.

  As a result of diligent research to achieve the above object, the present inventors have formed a structure in which nanofibers are dispersed between layers formed by dispersing flat inorganic fillers typified by scaly graphite. The inventors have found a graphite size that maximizes the thermal conductivity without destroying the nanofibers so that the above structure can be maintained even after processing with shearing force applied. Furthermore, in order to relieve the shearing force caused by rubbing between the processing machine and the flaky graphite, the material is subjected to shearing using a fluorine resin such as PTFE (polytetrafluoroethylene) as a raw material, and (d) fluorine. By adding a resin, the destruction of nanofibers is suppressed, and the above structure is maintained even when kneading / injection molding is performed, leading to an invention that exhibits high thermal conductivity.

The present invention relates to the following (1) to (8).
(1) (a) A thermally conductive resin composition comprising (b) flake graphite and (c) nanofibers, both of which are thermally conductive in a base resin comprising a thermoplastic resin, ) Thermoplastic resin 30-95% by volume, (b) Scale-like graphite having a surface direction diameter of 0.1-200 μm, and the aspect ratio of the surface direction diameter divided by thickness is 10-150. 1 to 69% by volume, and (c) 0.1 to 15% by volume of nanofibers having a diameter of 1 μm or less and an aspect ratio of fiber length divided by diameter of 20 or more (provided that (a) + (b) + (C) = 100% by volume, and the total volume of (b) and (c) is 5 to 70% by volume). b) forming one or more planar structures in which the surfaces of the flaky graphite are aligned in the same plane, the planar structures having the same planar direction Forming one or more layered structures facing and contacting the planar structure (a) forming a dispersed layer of (c) nanofibers in the thermoplastic resin layer; (c) the nanofibers providing a heat conduction path between the layers A thermally conductive resin molded body formed.
(2) The thermally conductive resin molding according to (1), wherein (a) the thermoplastic resin is at least one selected from the group consisting of a polyarylene resin, a polyamide resin, a polyolefin resin, and a polyester resin. body.
(3) The thermally conductive resin molded article according to (1) or (2), wherein the aspect ratio of (b) flaky graphite is 10 to 130.
(4) (c) Any of (1) to (3), wherein the nanofiber is composed of carbon nanofiber (CNF) and / or carbon nanotube (CNT), and has a diameter of 10 nm to 1 μm and an aspect ratio of 30 or more. The heat conductive resin molding as described in 2.
(5) The total of 100% by weight of components (a) to (c) is further added with 0.1 to 5% by weight of (d) a fluororesin that is fiberized by shearing force. (4) The heat conductive resin molding in any one.
(6) (d) the fluororesin is at least selected from the group of difluoroethylene resin, tetrafluoroethylene resin, tetrafluoroethylene / hexafluoropropylene copolymer resin, and tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin The heat conductive resin molding as described in (5) which is 1 type.
(7) (1-1) (a) Thermoplastic resin and (b) Pellets (MB1) obtained by melting and mixing flaky graphite, (a) Thermoplastic resin and (c) Nanofiber are melt-mixed. The pellets (MB2) obtained in this way are prepared and these MB1 and MB2 are mixed and injection molded, or (1-2) First (a) a thermoplastic resin and (b) flaky graphite. (C) Apply nanofibers to the resulting pellets and injection mold them, or (1-3) (a) a thermoplastic resin, (b) flaky graphite and ( c) The method for producing a thermally conductive resin molded article according to any one of (1) to (4), wherein the nanofibers are melt-kneaded at the same time and then injection-molded.
(8) (a) thermoplastic resin, (b) flaky graphite, (c) nanofibers, and (d) a fluororesin that is fiberized by shearing force are simultaneously melt-kneaded and then injection molded. (5) The manufacturing method of the heat conductive resin molding as described in (6).

  The thermally conductive resin molded body of the present invention can achieve a high thermal conductivity of the molded body with a small filler filling amount, and further maintains a high thermal conductivity in the processing by injection molding because the decrease in thermal conductivity is large in the prior art. However, by using the present invention, the decrease in thermal conductivity can be minimized and high thermal conductivity can be maintained.

It is a schematic diagram of the phase structure in the heat conductive resin molding of this invention. In the heat conductive resin molding of this invention, it is a graph which shows the relationship between the aspect-ratio of the scale-like graphite to contain, and the heat conductivity of a heat conductive resin molding. In the heat conductive resin molding of the invention, it is a graph which shows the relationship between the aspect-ratio of the nanofiber to contain and the heat conductivity of a heat conductive resin molding.

First, the phase structure formed in the heat conductive resin molding of this invention is shown in FIG.
In FIG. 1, reference numeral 1 is a base component (matrix component) (a) a thermoplastic resin, reference numeral 2 is (b) flaky graphite, and reference numeral 3 is (c) nanofibers. From FIG. 1, (a) in the base component (matrix component) made of a thermoplastic resin, (b) one or more planar structures in which the surfaces of scaly graphite are arranged in the same plane are formed. One or more layer structures facing the same plane direction are formed, (c) nanofibers are in contact with the plane structure, (c) a nanofiber dispersion layer is formed, and (c) nanofibers are disposed between the layers. It can be seen that a heat conduction path is formed, and thereby a highly heat conductive resin molded body is obtained.
Such a phase structure cannot be obtained simply by melt-kneading the components (a) to (c). (A) (b) flaky graphite and (c) nanofibers having a specific structure in a thermoplastic resin (B) scale-like graphite by further injection-molding a thermally conductive resin composition mainly composed of (d) (fluorine-based resin if necessary) into a molded body (pellet or finished product). Are oriented in the injection molding direction, and (c) the nanofibers are in contact with this planar structure to form (c) a dispersed phase of the nanofibers, and (c) the nanofibers have a thermally conductive path between the layers. It is thought to form.

In the present invention, the reason why the destruction of the nanofibers is suppressed is not necessarily clear, but is considered as follows.
In other words, if the plane size of the flake graphite is too large, the number of flake graphite is reduced and the number of layers is also reduced. Not only can be formed, but the agglomerates are easily affected by the shearing force, and the destruction of the nanofibers proceeds. On the other hand, if the size of the scaly graphite in the planar direction is small, many layers of scaly graphite are formed, the distance between the layers is narrowed, the number of nanofibers is insufficient, and a sufficient heat conduction path cannot be formed. A shearing force is generated between the scaly graphites, and the nanofibers are ground and destroyed. Therefore, a structure in which nanofibers are dispersed between layers of the scale-like graphite layer structure can be more completely formed by filling the optimum size of the scale-like graphite. Furthermore, by adding (d) a fluorine-based resin that can be fiberized by a melt shearing force, the shearing force generated from a processing machine (melt kneader, injection molding machine, etc.) and scale-like graphite is changed to (d) a fluorine-based resin. It is presumed that it becomes possible to reduce the shearing force applied to the nanofibers by relaxing the fiberization of the resin.
Hereinafter, (a) thermoplastic resin, (b) flaky graphite, (c) nanofiber, (d) fluorine-based resin and the like used in the present invention will be described.

<(A) Thermoplastic resin>
In the thermally conductive resin molded body of the present invention, (a) the thermoplastic resin used as the base component (matrix component) is not particularly limited, but is typically a polyarylene resin, a polyamide resin, Examples include polyolefin resins and polyester resins. In particular, (c) a polyolefin resin having a particularly high affinity with nanofibers is desirable.

  Of these, specific examples of polyarylene resins include polyphenylene sulfide (PPS), polyether ketone (PEK), polyether ether ketone (PEEK), and polyarylene oxide poly (2,6-dimethyl-1, 4-phenylene) ether (PPE) and the like. Styrenic resins such as polystyrene and high impact polystyrene can be added to the polyarylene oxide. Among these, PPS is more preferable from the viewpoints of heat resistance, chemical resistance, and cost.

  As the polyamide-based resin, specifically, nylon 6, nylon 66, nylon 46, nylon 11, nylon 12, nylon obtained by using at least one of amino acids, lactams and diamines and dicarboxylic acid as main raw materials. 610, nylon 69, nylon 6T, nylon 9T, nylon MXD6, nylon 6/66 copolymer, nylon 6/610, nylon 6 / 6T copolymer, nylon 6/66/610 copolymer, nylon 6/12 copolymer, nylon 6T / 12 copolymer , Nylon 6T / 66 copolymer, nylon 6 / 6I, nylon 66 / 6I / 6 copolymer, nylon 6T / 6I copolymer, nylon 6T / 6I / 66 copolymer, nylon 6/66/610/12 copolymer, nylon 6T / M-5T Such as a polymer, and the like. Among these, nylon 6, nylon 66, nylon 12 and copolymers based on these are preferred from the viewpoint of good balance of chemical resistance, impact resistance and fluidity of the obtained resin molded body. A copolymer mainly composed of nylon 6 is more preferable.

  Furthermore, specific examples of polyolefin-based resins include homopolymers or copolymers mainly composed of repeating units generated from α-olefins such as ethylene and propylene. For example, homopolymers of propylene, homopolymers of ethylene, Furthermore, the block or random copolymer which copolymerized ethylene and other alpha olefins (for example, propylene, butene-1, etc.) is mentioned. These can be used by 1 type (s) or 2 or more types in the range which contributes to the characteristic of a resin material. The polyolefin resin used in the present invention may be either linear or branched. In the case of a polypropylene resin as the polyolefin resin, any polypropylene resin such as isotactic, atactic and syndiotactic can be used. Examples of the polyethylene include linear low density polyethylene (LLDPE), low density polyethylene (LDPE), high density polyethylene (HDPE), ultra low density polyethylene (ULDPE), and ultra high molecular weight polyethylene (UHMW-PE). .

  Specific examples of the polyester resin include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polycyclohexanedimethylene terephthalate, polyhexylene terephthalate, polyethylene naphthalate, polypropylene naphthalate, polybutylene naphthalate, polyethylene isophthalate / terephthalate, Polypropylene isophthalate / terephthalate, polybutylene isophthalate / terephthalate, polyethylene terephthalate / naphthalate, polypropylene terephthalate / naphthalate, polybutylene terephthalate / naphthalate, polybutylene terephthalate / decane dicarboxylate, polyethylene terephthalate / cyclohexanedimethylene terephthalate, poly Tylene terephthalate / polyethylene glycol, polypropylene terephthalate / polyethylene glycol, polybutylene terephthalate / polyethylene glycol, polyethylene terephthalate / polytetramethylene glycol, polypropylene terephthalate / polytetramethylene glycol, polybutylene terephthalate / polytetramethylene glycol, polyethylene terephthalate / isophthalate / Polytetramethylene glycol, polypropylene terephthalate / isophthalate / polytetramethylene glycol, polybutylene terephthalate / isophthalate / polytetramethylene glycol, polyethylene terephthalate / succinate, polypropylene terephthalate / succinate, polybutylene terephthalate Succinate, polyethylene terephthalate / adipate, polypropylene terephthalate / adipate, polybutylene terephthalate / adipate, polyethylene terephthalate / sebacate, polypropylene terephthalate / sebacate, polybutylene terephthalate / sebacate, polyethylene terephthalate / isophthalate / adipate, polypropylene terephthalate / isophthalate / adipate, Polybutylene terephthalate / isophthalate / succinate, polybutylene terephthalate / isophthalate / adipate, polybutylene terephthalate / isophthalate / sebacate, bisphenol A / terephthalic acid, bisphenol A / isophthalic acid, bisphenol A / terephthalic acid / isophthalic acid, etc. Cited The Among these, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN) are more preferable from the viewpoints of heat resistance and weather resistance.

  In the present invention, the blending ratio of the thermoplastic resin (a) is 30 to 95% by volume, preferably 35 to 60% by volume in the components (a) to (c). If it is less than 30% by volume, it is not preferable because the strength of the resulting heat conductive resin molded article is inferior or the fluidity required for injection molding cannot be ensured, while it exceeds 95% by volume. Since the blending ratio of the components (b) to (c) having relatively thermal conductivity is decreased, the thermal conductivity of the obtained molded product is lowered, which is not preferable.

<(B) Flaky graphite>
(B) The flaky graphite is not limited as long as it is a flat plate or flake other than the flaky one, but graphite (graphite) is particularly preferable. As the type of graphite, either α graphite or β graphite may be used. Either natural graphite or artificial graphite may be used. In addition to graphite, graphene and the like can be mentioned. Further, graphite and graphene may be combined.
(B) The scaly graphite has a surface direction diameter (length) of 0.1 μm to 200 μm, and an aspect ratio of 10 to 150 obtained by dividing the surface direction diameter by the thickness. The diameter in the plane direction is preferably 1 μm to 30 μm, and the aspect ratio is preferably 10 to 130, more preferably 30 to 80.
(B) When the aspect ratio of the flake graphite deviates from the upper limit or the lower limit, (c) the nanofibers are damaged, and the thermal conductivity tends to be lowered.

(B) Content of scale-like graphite is 1-69 volume% in (a)-(c) component, Preferably it is 10-50 volume%.
The thermally conductive resin molded article of the present invention includes (a) a base resin composed of a thermoplastic resin, (b) flake graphite, a diameter of 1 μm or less, and an aspect ratio of 20 or more (c) nanofibers (B) forming one or more planar structures in which the surfaces of the scaly graphite are aligned in the same plane, and forming one or more layered structures in which the planar structures face the same planar direction, (C) A nanofiber dispersion layer is formed on the resin layer in contact with the planar structure, and (c) the nanofiber forms a heat conduction path between the layers. Therefore, when the content of (b) flaky graphite is less than 1% by volume in the components (a) to (c), the thermal conductivity of the molded body obtained by lacking the planar structure of (b) flaky graphite is low. On the other hand, if it exceeds 70% by volume, the physical properties of the molded product obtained by lowering the blending amount of the thermoplastic resin (a) which is relatively a base resin are lowered, and (c) the content of nanofibers And the thermal conductivity of the molded body also decreases.

<(C) Nanofiber>
(C) The nanofiber is preferably at least one conductive fibrous filler selected from the group consisting of carbon nanofiber (CNF) and carbon nanotube (CNT). The carbon nanotube (CNT) may be a single wall or a multiwall. Moreover, it is preferable that a carbon nanofiber (CNF) has a diameter of nanometer size and a fiber length of micrometer size.
This (c) nanofiber has a diameter of 1 μm or less, preferably 10 nm to 1 μm. When the diameter exceeds 1 μm, the aspect ratio is lowered, and an efficient heat conduction path cannot be formed. Therefore, the heat conductivity of the obtained molded article is undesirably lowered.
The (c) nanofiber used in the present invention has an aspect ratio of 20 or more, preferably 30 or more, which is obtained by dividing the fiber length by the diameter, and most preferably (c) the aspect ratio inherent to the nanofiber is maximized. To do. When the aspect ratio is less than 20, the heat conduction path is not sufficiently formed, and the effect of the present invention cannot be obtained.

(C) The amount of nanofiber blended in the components (a) to (c) is 0.1 to 15% by volume, preferably 0.1 to 10% by volume, more preferably 0.1 to 5% by volume. is there.
If it is less than 0.1% by volume, the thermal conductivity is not sufficient. On the other hand, if it exceeds 15% by volume, the dispersion of the nanofibers in the resin is deteriorated and the surface area of the nanofibers is increased. This is not preferable because the fluidity required for injection molding cannot be secured.

  Furthermore, when the total of (a) thermoplastic resin, (b) flaky graphite, and (c) nanofiber as a main component is 100% by volume, (b) flaky graphite and (c) nanofiber The total volume of is from 5 to 70% by volume, preferably from 30 to 50% by volume. If it is less than 5% by volume, the thermal conductivity of the thermally conductive molded article of the present invention is inferior. On the other hand, if it exceeds 70% by volume, the blending amount of the thermoplastic resin (a), which is the base resin, is relatively small. The physical properties of the molded product are inferior, and the fluidity required for injection molding cannot be ensured.

<(D) Fluorine resin>
Furthermore, in the present invention, a processing machine (kneading machine or injection molding machine) and (b) scaly form are added by adding (d) a fluororesin that is fiberized by shearing force during melt-kneading or injection molding. The shear force generated from graphite can be relaxed, and (c) nanofiber breakage can be prevented. Examples of the (d) fluorine-based resin that is a filler to be fibrillated include a fluoroolefin resin. The fluoroolefin resin is usually a polymer or copolymer containing a fluoroethylene structure. Specific examples include difluoroethylene resin, tetrafluoroethylene resin, tetrafluoroethylene / hexafluoropropylene copolymer resin, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin, and the like. Especially, tetrafluoroethylene resin etc. are mentioned preferably. Examples of the fluoroethylene resin include a fluoroethylene resin having a fibril forming ability.

Examples of the fluoroethylene resin having fibril forming ability include “Polyflon F201L”, “Polyflon F103”, “Polyflon FA500H” manufactured by Daikin Industries, Ltd., “Teflon 6J”, “Teflon 640J” manufactured by Mitsui DuPont Fluorochemical Co., Ltd. For example, “Teflon K10J”.
Furthermore, a fluoroethylene polymer having a multilayer structure formed by polymerizing vinyl monomers can also be used. Examples of such a fluoroethylene polymer include polystyrene-fluoroethylene copolymer, polystyrene-acrylonitrile-fluoro. An ethylene copolymer, a polymethyl methacrylate-fluoroethylene copolymer, a polybutyl methacrylate-fluoroethylene copolymer, and the like can be mentioned, and specific examples thereof include “methabrene A-3800” manufactured by Mitsubishi Rayon Co., Ltd. In addition, 1 type may contain fluoropolymer and 2 or more types may contain it by arbitrary combinations and a ratio.

  (D) The compounding amount of the fluororesin is 0.1 to 5% by weight, preferably 100% by weight of the total of (a) thermoplastic resin, (b) flaky graphite, and (c) nanofibers, preferably It is 0.5 to 3 weight%, More preferably, it is 0.8 to 2 weight%. (D) When the content of the fluororesin is less than the lower limit of the above range, the effect of relaxing the shearing force is insufficient, while when it exceeds the upper limit of the above range, the fluidity in the mold is lowered. , The appearance defect of the molded body and the mechanical strength are likely to decrease.

<Other additives>
Although the heat conductive resin molding of this invention has (a)-(c) component or (a)-(d) component as a main component, it is a well-known thing used at the time of shaping | molding other normal thermoplastic resins. Additives such as heat stabilizers, lubricants, mold release agents, plasticizers, flame retardants, antioxidants, light stabilizers and the like can be added.
In addition, a third component such as a colorant and a foaming agent can be blended in the thermally conductive resin molded body of the present invention.

<Manufacture of heat conductive resin composition>
The thermally conductive resin composition of the present invention for use in injection molding comprises (a) a heatable heater for melting a thermoplastic resin, (b) melted flake graphite and (c) nanofibers It can be produced using equipment such as a twin-screw extrusion kneader or a pressure kneader equipped with a mechanism capable of applying a strong shearing force to knead into the resin. The order in which the raw materials are added is not particularly limited. For example, PTFE is used as a raw material and is made into a fiber by applying a shearing force. (D) Prepared by adding a fluororesin to the resin composition before melt kneading can do. Also, for example, (a) a thermoplastic resin and (b) scaly graphite are melt-kneaded, and the resulting pellet-shaped masterbatch (MB1), (a) a thermoplastic resin, and (c) nanofibers are melt-kneaded. The obtained pellet-shaped masterbatch (MB2) can be mixed, and the mixture can be put into a hopper provided in a processing machine, melted and kneaded. For example, it can be produced by applying (c) nanofibers to the surface of a pellet obtained by melt-kneading (a) a thermoplastic resin and (b) flaky graphite.
The temperature during melt kneading is usually 160 to 280 ° C., preferably 210 to 260 ° C., and the melt kneading time is usually 30 seconds to 10 minutes, preferably 1 minute to 5 minutes.

<Heat conductive resin molding>
The thermally conductive resin composition of the present invention prepared as described above can be formed into a molded body having high thermal conductivity by processing using injection molding that generates shearing force in a screw or a mold. is there. As injection molding, in addition to a general injection molding method, gas injection molding, injection press molding, or the like can be employed. If an example of the injection molding conditions suitable for the heat conductive resin composition of this invention is given, when cylinder temperature is polyolefin resin, it is more than melting | fusing point Tm or flow start temperature, Preferably it is 180-235 degreeC, More preferably, it is 190- The range of 220 ° C. is appropriate. If the cylinder temperature is too low, operability becomes unstable and overload is likely to occur due to poor filling of the molded product. Conversely, if the cylinder temperature is too high, the resin composition will decompose and the molded product obtained. Problems such as reduction in strength and coloration are likely to occur. Further, since there is a difference in the shearing force applied to the molten resin depending on the conditions at the time of injection molding, the nanofibers are destroyed and the thermal conductivity of the molded body is reduced. Although the details differ depending on the molding machine used for processing, further examples of processing conditions include materials input from a hopper in an inline type injection molding machine in which the plasticizing screw and the injection plunger serve as the same screw. When the screw rotation speed when melting and measuring is over 100 rpm, the thermal conductivity of the molded product tends to decrease greatly. Furthermore, when the back pressure during measurement is 140 kg / cm ² or more, the thermal conductivity of the molded product tends to be greatly reduced. Therefore, if the resin composition of the present invention is used, the influence of the shearing force generated in the screw and mold of the injection molding machine can be minimized, but it is also possible to mold in an appropriate condition range during injection molding. This is important to prevent a decrease in thermal conductivity.
Therefore, when (a) a polyolefin resin is employed as the thermoplastic resin, the cylinder temperature is preferably 180 to 235 ° C., the screw rotation speed is 40 to 95 rpm, and the back pressure when light is 70 to 120 kg / cm. ² .
The heat conductive resin molded product of the present invention thus obtained may be a pellet or a molded product which is a final finished product.

In addition, in order to obtain the heat conductive resin molding of this invention, the manufacturing method of following (1) or (2) is especially preferable. (1) A heat conductive resin molding is comprised from said (a)-(c) component. In this case, as described above, (1-1) (a) a thermoplastic resin and (b) pellets (MB1) obtained by melting and mixing flaky graphite, and (a) a thermoplastic resin (C) Pellets (MB2) obtained by melt-mixing nanofibers, these are mixed and injection-molded, or (1-2) First (a) a thermoplastic resin and (b) flaky graphite Is kneaded and pelletized, and (c) nanofibers are applied to the obtained pellets, followed by injection molding. If it does in this way, since the heat conductive resin molding of this invention will be obtained with (c) nanofiber having a high aspect ratio without being destroyed, it will have high heat conductivity. Alternatively, the components (1-3) (a) to (c) may be melt-kneaded at the same time and pelletized before injection molding, or immediately after melt-kneading, injection molding may be performed. That is, by using (b) scaly graphite having an optimal aspect ratio, (b) shear force generated between scaly graphites can be minimized, and (c) nanofiber breakage can be suppressed relatively. A thermally conductive resin molding having high thermal conductivity is obtained.
(2) When the thermally conductive resin molded body is composed of the components (a) to (d) In this case, (d) a fluororesin that can be fiberized by melt kneading is blended. Before kneading, the component (d) is added to the components (a) to (c), and the components (a) to (d) are melt-kneaded at the same time, pelletized and then injection molded, or Immediately following the melt-kneading, the injection molding may be performed immediately. That is, when (d) a fluorine-based resin is blended, the high shearing force is alleviated by (d) the fluorine-based resin that can be fiberized at the time of melt-kneading. Thus, the heat conductive resin molded product of the present invention with little decrease in heat conductivity is obtained.

  The thermally conductive resin molded article of the present invention is a process in which a molten thermal conductive resin composition is fluidized and molded by injection molding, and (a) a base resin composed of a thermoplastic resin contains carbon as a component. (B) flaky graphite having a flat shape and carbon (c) containing nanofibers having a diameter of 1 μm or less, and (b) a plane of scaly graphite lined up in the same plane. Forming one or more structures, forming one or more layer structures in which the planar structure faces the same planar direction, and (c) forming a nanofiber dispersion layer on the resin layer in contact with the planar structure; c) The nanofibers form a heat conduction path between the layers. As a result, the heat conductive resin molding of the present invention is excellent in heat conductivity.

  Since the heat conductive resin molding of this invention is excellent in heat conductivity, it can be used as a heat sink for electronic components by utilizing the high heat conductivity. In addition, (c) by increasing the amount of nanofibers added, high thermal conductivity can be obtained, so even in electronic parts, automobiles that require relatively high heat resistance and industrial power modules that require large currents It can be suitably used for a connector or the like. More specifically, it can be used for a heat sink, a semiconductor package component, a heat sink, a heat spreader, a die pad, a printed wiring board, a cooling fan component, a housing, and the like. It can also be used as a part of a heat exchanger. Can be used for heat pipes. Furthermore, (c) it can be suitably used as a radio wave shielding member in the GHz band by utilizing the radio wave shielding property of the nanofiber.

Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited to the following examples.
Various measurements in the examples are as follows.

<Measurement of thermal conductivity>
After measuring the thermal diffusivity of the sample using a fully automatic laser flash method thermal constant measurement device (TC-7000 manufactured by ULVAC-RIKO), the density (ρ) and specific heat (Cp) of each sample are used (formula The thermal conductivity (λ) was calculated according to 1). As the thermal conductivity, a value in the flow direction of the resin was measured. Α is the thermal diffusivity.
λ (W / m · K) = ρ (g / m ³ ) × Cp (J / g · K) · α (m ² / s) (Formula 1)

<Measurement of fiber length>
The sample whose thermal conductivity was measured was heated with a gas burner, and the thermoplastic resin was volatilized and decomposed to remove it. The residue was observed with a scanning electron microscope S-3400N (SEM) manufactured by Hitachi High-Technologies Corporation. The length of the fiber was measured from the obtained image. Statistical processing was performed on 300 or more samples, and D50 was set as a representative fiber length. The aspect ratio was calculated by dividing the fiber length thus obtained by the fiber diameter.

<Dimension measurement of graphite>
The sample whose thermal conductivity was measured was heated with a gas burner, the thermoplastic resin was volatilized and decomposed to remove it, the residue was observed with SEM, and the thickness of the graphite and the length in the planar direction (diameter) were obtained from the obtained image. The aspect ratio was calculated by dividing the length in the plane direction by the thickness.

Next, (a) thermoplastic resin, (b) flaky graphite, (c) nanofiber, and (d) fluorine-based resin used in this example are as follows.
(A) Thermoplastic resin (a-1) Polypropylene (PP, PM900A manufactured by Sun Allomer Co., Ltd.)
Pellet drying temperature: 80 ° C for 5 hours Kneading temperature: 230 ° C
Molding temperature: 200 ° C
(a-2) Polyethylene (HDPE, J-240 manufactured by Asahi Kasei Corporation)
Pellet drying temperature: 5 hours at 80 ° C Kneading temperature: 220 ° C
Molding temperature: 200 ° C
(a-3) Polyamide (PA6, Unitika A1015LP)
Pellet drying temperature: 5 hours at 100 ° C Kneading temperature: 290 ° C
Molding temperature: 270 ° C

(B) Graphite (b-1) Flaky graphite (“CB150” manufactured by Nippon Graphite Co., Ltd., average length in the plane direction 40 μm, aspect ratio 40)
(B-2) Scaly graphite (“CB100” manufactured by Nippon Graphite Co., Ltd., average length in the plane direction 80 μm, aspect ratio 80)
(B-3) Scaly graphite (“F2” manufactured by Nippon Graphite Co., Ltd., average length in the plane direction 130 μm, aspect ratio 130)
(B-4) Spheroidized graphite (“GCC-20” manufactured by Nippon Graphite Co., Ltd., average particle size 20 μm, aspect ratio 1)

(C) Carbon fiber (c-1) Nanofiber (“VGCF-H” manufactured by Showa Denko KK, average diameter 150 nm, aspect ratio 100 or more)
(C-2) Carbon fiber (Pitch-based carbon fiber “DIALEAD K223HE” manufactured by Mitsubishi Plastics Co., Ltd., average diameter 6 μm, fiber length 3 mm)

(D) Fluororesin (d-1) Fiberized PTFE (polytetrafluoroethylene that can be fiberized) (K-10J, Mitsui, DuPont, Fluorochemical Co., Ltd.)
(D-2) PTFE powder (PTFE KT600M manufactured by Kitamura)

<Sample preparation>
Each raw material is put into a twin-screw extruder kneader (Ikegai Co., Ltd. PCM30, screw diameter 30 mm, L / D17.5) at the ratio shown in Table 1 and Table 2 and melt kneaded. A pellet-shaped sample was obtained by cutting the shaped strand with a cutter. After the pellets were dried, the pellets were put into an injection molding machine (UH-1000 manufactured by Nissei Plastic Industry Co., Ltd.) to obtain an injection molded body of a dumbbell test piece having a thickness of 4 mm, a width of 10 mm, and a length between marked lines of 90 mm. . A rectangular sample of 10 mm × 1 mm × 1 mm was cut out from this molded body to obtain a measurement sample of 10 mm × 10 mm × 1 mm.
In the preparation of the samples of Examples 4 to 8, a pellet was prepared using (a) thermoplastic resin and (b) flaky graphite, and then (c) nanofibers were applied to the pellet to perform injection molding. Pellets were obtained.

Examples 1-3 and Examples 9-14, Comparative Examples 1-5
Each component having the formulation shown in Tables 1 and 2 was first charged into a twin-screw kneading extruder PCM30, and melt kneaded at a predetermined processing temperature at a screw speed of 120 rpm. The discharged melt was cooled in a water bath and cut with a cutter to obtain pellets. After drying the pellet, the pellet was put into an injection molding machine to obtain a dumbbell test piece having a thickness of 4 mm, a width of 10 mm, and a length between marked lines of 90 mm. A rectangular sample of 10 mm × 1 mm × 1 mm was cut out from this molded body to obtain a measurement sample of 10 mm × 10 mm × 1 mm. About this molded object, the heat conductivity, the nanofiber, and the aspect ratio of the scaly graphite were measured according to the said method. The results are shown in Tables 1-2.

Examples 4-8
(A) Thermoplastic resin and (b) flaky graphite shown in Table 1 were put into a twin-screw kneading extruder PCM30, and melt kneaded at a predetermined processing temperature and a screw rotation speed of 120 rpm. The discharged melt was cooled in a water bath and cut with a cutter to obtain pellets. After drying the pellets, (c-1) nanofibers were applied to the surface of the obtained pellets to obtain pellets for injection molding. Thereafter, the pellets were put into an injection molding machine and injection molded to obtain a dumbbell test piece having a thickness of 4 mm, a width of 10 mm, and a length between marked lines of 90 mm. At that time, in order to adjust the aspect ratio of (c-1) nanofibers, the screw rotation speed during measurement and the back pressure during injection molding were adjusted. A rectangular sample of 10 mm × 1 mm × 1 mm was cut out from this molded body to obtain a measurement sample of 10 mm × 10 mm × 1 mm. About this molded object, the heat conductivity, the aspect-ratio of the fiber and the flake graphite were measured according to the said method. The results are shown in Table 1.
In addition, (c-1) The screw rotation speed at the time of measurement and the back pressure at the time of injection molding in each Example for adjusting the aspect ratio of the nanofiber are as follows.
Example 4; screw rotation speed 95 rpm, back pressure 120 kg / cm ²
Example 5: Screw rotational speed 70rpm, back pressure 120kg / cm ²
Example 6: Screw rotation speed 50 rpm, back pressure 120 kg / cm ²
Example 7: Screw rotation speed 95 rpm, back pressure 75 kg / cm ²
Example 8: Screw rotation speed 50 rpm, back pressure 75 kg / cm ²

  Based on the results of Tables 1 and 2, the relationship between the aspect ratio of graphite and the thermal conductivity of the compact is shown in FIG. As is clear from FIG. 2, Examples 1 to 3 using scaly graphite having a high aspect ratio are higher in heat conductivity than Comparative Example 1 using graphite (c-4) having an aspect ratio of 1. Showed the rate. This is probably because the higher the aspect ratio, the higher the efficiency of forming the heat conduction path. However, as the aspect ratio increases, the number of graphite per unit volume decreases, so the thermal conductivity decreases at a certain aspect ratio. The aspect ratio of the most efficient flaky graphite in the examples of the present invention was around 40. By using scaly graphite having this characteristic, the resin molded body in the present invention can maintain high thermal conductivity.

In Examples 4 to 8, (b-1) scale-like graphite, and a high aspect ratio is maintained by adjusting the raw material charging procedure and injection molding conditions. is there. Comparative Example 2 containing the same scaly graphite, but containing no (c-1) nanofibers, and Example 1 containing nanofibers (c-1) which was damaged during processing and had a relatively low aspect ratio. When Comparative Examples 4 and 5 containing micron-sized carbon fiber (c-2) and Examples 4 to 8 were compared, Examples 4 to 8 showed high thermal conductivity.
That is, in the present invention, as apparent from FIG. 3, the higher the aspect ratio of the nanofiber, the higher the efficiency of forming the heat conduction path, and it is considered that Examples 4 to 8 were able to maintain high heat conductivity. . Further, in terms of shape, the fibrous filler needs to be nano-sized, and an effect cannot be obtained with micron-sized carbon fibers. Further, in Example 1 prepared by a conventional general method in which all raw materials are simultaneously charged into a kneader and melt-mixed with a high shear force, (c-1) the nanofibers are damaged by the shear force, and thus the aspect The ratio could not be higher than 8. That is, it becomes possible to achieve a high aspect ratio of nanofibers by using a nano-sized fibrous filler and efficiently forming a heat conduction path by the processing method shown in the present invention. (C-1) High heat conductivity It became possible to maintain.

  Furthermore, in Example 12 and Example 13, it is a molded product when the base resin is changed from (a-1) polypropylene to (a-2) polyethylene and (a-3) polyamide, (c-1) The aspect ratio of the nanofiber and the thermal conductivity of the molded body maintain high values as in Example 10. That is, the effect of the present invention is obtained by the characteristics and blending ratio of the filler, and is not limited by the type of thermoplastic resin.

  Further, in Examples 9 to 13 in which (d) a fluorine-based resin that can be fiberized by melt-kneading is used, (c) nanofiber breakage hardly occurs during melt-kneading or injection molding. (C) Even if the components (d) are melt-kneaded at the same time, it is understood that (c) the nanofibers can ensure a high aspect ratio, and the resulting resin molded article is excellent in thermal conductivity.

  According to the present invention, by using a general processing method such as biaxial extrusion kneading or injection molding in which nanofibers are damaged by shearing force and the thermal conductivity of the resin molding is reduced, the filler filling amount is small. In addition, it is possible to obtain a thermally conductive resin molded article having a high level of thermal conductivity. Therefore, the thermally conductive resin molded body of the present invention is used in applications requiring flexibility in shape, productivity, high thermal conductivity, and high heat dissipation, for example, various parts for automobiles, various parts for electric / electronic devices, high heat It is useful for applications such as conductive sheets, heat sinks, and electromagnetic wave absorbers.

DESCRIPTION OF SYMBOLS 1 ... (a) Thermoplastic resin 2 ... (b) Scale-like graphite 3 ... (c) Nanofiber

Claims (8)

  (a) A thermally conductive resin composition containing (b) flake graphite and (c) nanofibers, both of which are thermally conductive in a base resin made of a thermoplastic resin, and (a) thermoplastic 30-95% by volume of resin, (b) scale-like graphite having a surface-direction diameter of 0.1-200 μm, and an aspect ratio of the surface-direction diameter divided by the thickness of 10-150 is 10-69 volumes. %, And (c) 0.1 to 15% by volume of nanofibers having a diameter of 1 μm or less and an aspect ratio of fiber length divided by diameter of 20 or more (provided that (a) + (b) + (c) = 100% by volume and the total volume of (b) and (c) is 5 to 70% by volume) obtained by injection molding, and (b) scale-like Form one or more planar structures in which graphite faces are aligned in the same plane, and the planar structures face the same plane. Forming one or more layer structures and contacting the planar structure (a) forming a dispersion layer of (c) nanofibers in the thermoplastic resin layer; (c) forming a heat conduction path between the nanofibers A thermally conductive resin molded product.   The thermally conductive resin molded article according to claim 1, wherein (a) the thermoplastic resin is at least one selected from the group consisting of a polyarylene resin, a polyamide resin, a polyolefin resin, and a polyester resin.   (B) The aspect ratio of scaly graphite is 10-130, The heat conductive resin molding of Claim 1 or 2.   (C) The heat conduction according to any one of claims 1 to 3, wherein the nanofiber comprises carbon nanofiber (CNF) and / or carbon nanotube (CNT), has a diameter of 10 nm to 1 µm and an aspect ratio of 30 or more. Resin molding.   5 to 5% by weight of a fluororesin that is made into a fiber by shearing force during melt mixing is added to 100% by weight of the total of components (a) to (c). The heat conductive resin molding in any one.   (D) The fluororesin is at least one selected from the group consisting of difluoroethylene resin, tetrafluoroethylene resin, tetrafluoroethylene / hexafluoropropylene copolymer resin, and tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin. The heat conductive resin molding of Claim 5 which exists.   (1-1) Obtained by melt-mixing (a) a thermoplastic resin and (b) pellets (MB1) obtained by melt-mixing scaly graphite, (a) a thermoplastic resin and (c) nanofibers Pellet (MB2) is prepared, and these MB1 and MB2 are mixed and injection molded, or (1-2) First, (a) a thermoplastic resin and (b) flaky graphite are melt-kneaded. (C) nanofibers are applied to the resulting pellets and injection molded, or (1-3) (a) thermoplastic resin, (b) flake graphite and (c) nanofibers The method for producing a thermally conductive resin molded article according to any one of claims 1 to 4, wherein the components are melt-kneaded at the same time and then injection-molded. (a) a thermoplastic resin, (b) flaky graphite, (c) nanofibers, and (d) a fluororesin that is fiberized by shearing force at the time of melt mixing, and simultaneously melt-kneaded, and then injection molded. The manufacturing method of the heat conductive resin molding of Claim 5 or 6.