JP6657784B2 - Composite resin composition, molded body, heat conductive material and heat conductive material - Google Patents

Description

  The present invention relates to a composite resin composition having excellent thermal conductivity and a molded article. Further, the present invention relates to a heat conductive material containing the composite resin composition and a heat conductive material containing the molded article.

2. Description of the Related Art With the spread of engineering plastics having high heat resistance, plastic materials are widely used as materials for electric, electronic devices, automobiles, and the like as materials to replace metal materials due to productivity and freedom of shape. In recent years, the demand for higher performance, smaller size and lighter weight of devices has been increasing, and the integration and capacity of semiconductor devices have been progressing, and the amount of heat generated has increased. It has become a challenge. In addition, as an improvement in electric power consumption of electric vehicles, there is a strong demand for improving the thermal conductivity of insulating members used for lithium ion batteries, motors, and inverters.
As a method for maintaining the insulating property of a plastic molding material and imparting thermal conductivity, a technique of adding an inorganic filler is known. In order to make the molding material highly thermally conductive, it is necessary to fill the filler with a high amount.However, if the amount of the filler is extremely small, micro or nano voids are generated in the filler layer, and irregular portions on the filler surface are generated. When a void is generated, an air layer having a low thermal conductivity is interposed. This becomes a hindrance to the heat conduction path and causes the molded product to be lower than the theoretical value.

To solve the above problem, Patent Document 1 discloses a composite resin composition and a molded article having high thermal conductivity using polybenzoxazole fiber, which is a high thermal conductive resin, as a filler. The fiber length of the polybenzoxazole fiber used is 500 μm to 10 mm, and by orienting the fiber in the in-plane direction (parallel direction), the heat conductivity in the in-plane direction is smaller than the heat conductivity in the thickness direction. A molded product 2 to 10 times higher is obtained.
However, as the miniaturization and high integration of devices are progressing, the required thermal conductivity is thermal conductivity in the thickness direction, and the problem in this respect has not been overcome.

JP 2014-109024 A

  An object of the present invention is to provide a resin composition which is lightweight, has high thermal conductivity, has no thermal conductivity anisotropy, and has high insulating properties, and a molded article. Another object of the present invention is to provide a heat conductive material containing the resin composition and a heat conductive member containing the molded article.

  The present inventors have conducted intensive studies and have found that a composite resin composition comprising polybenzazole fibers having an average fiber diameter of 200 nm or less, a thermally conductive filler, and a resin, and molding the composition. It has been found that the above-mentioned problems can be solved by providing a molded body made of the above.

  That is, the present invention is characterized by containing a polybenzazole fiber having an average fiber diameter of 200 nm or less, a thermally conductive filler, and a resin, a composite resin composition, and molding the composite resin composition. To provide a molded article.

  Another object is to provide a heat conductive material containing the composite resin composition and a heat conductive member containing the molded article.

  The composite resin composition of the present invention is lightweight and has excellent insulating properties, and the obtained molded article has excellent thermal conductivity not only in the in-plane direction but also in the thickness direction. Therefore, the obtained composite resin composition is suitable as a heat conductive material, and the heat conductive member containing the molded article is suitably used in various fields such as electronic / electrical equipment and automobile members because of its excellent thermal conductivity. Can be used.

<Polybenzazole fiber>
The present invention relates to a composite resin composition containing polybenzazole fiber (hereinafter abbreviated as PBZ fiber), a thermally conductive filler, and a resin.
The PBZ fiber is a fiber formed from a polybenzazole resin, and is obtained by mixing a polybenzoxazole (PBO) homopolymer, a polybenzothiazole (PBT) homopolymer and a random, sequential or block copolymer of PBO and PBT. Say.

  Since the PBZ fiber is a fibrous resin, it is lightweight and flexible. PBZ fiber is more easily blended with resin than metal fiber or inorganic fiber, so that it can be easily blended with resin. In particular, since voids are unlikely to be formed when blended with the resin, interface resistance between the resin and the fiber is hardly generated, so that the thermal conductivity is not easily reduced. Moreover, since it is a resin fiber, it has excellent insulation properties.

  The structural unit contained in the PBZ polymer is preferably selected from a lyotropic liquid crystal polymer, and the monomer unit is represented by the following structural formulas 1 to 8. The polymer preferably consists essentially of monomer units selected from structural formulas 1-8, more preferably consists essentially of monomer units selected from structural formulas 1-3 below, more preferably Is a polyphenylene benzoxazole having the following structural formula 1.

  Suitable solvents for forming the PBZ polymer dope include cresol and non-oxidizing acids that can dissolve the polymer. Examples of suitable acid solvents include polyphosphoric acid, methanesulfonic acid and concentrated sulfuric acid or mixtures thereof, and more suitable solvents are polyphosphoric acid and methanesulfonic acid. The most suitable solvent is polyphosphoric acid.

  The polymer concentration of the solution is preferably at least about 7% by weight, more preferably at least 10% by weight, and most preferably at least 14% by weight. The maximum concentration is limited by practical handling properties such as, for example, polymer solubility and dope viscosity. Because of these limiting factors, the polymer concentration usually does not exceed 20% by weight.

The PBZ fiber of the present invention has an average fiber diameter of 200 nm or less. If it is 200 nm, when it is compounded with a resin, it can exhibit thermal conductivity not only in the in-plane direction but also in all directions such as the thickness direction.
The average fiber length of the PBZ fiber of the present invention is preferably 50 μm or less, more preferably 30 μm or less. When the thickness is 50 μm or less, even if the obtained molded body has a thin shape such as a film, the thermal conductivity in the thickness direction is easily exhibited, and the strength of the molded body is not easily reduced.

<Nanofiber of polybenzazole fiber>
Nanofibers exhibit various properties due to the super-specific surface area effect, the nanosize effect, and the supramolecular arrangement effect. Therefore, in addition to the development of the manufacturing technology, a wide range of application development research utilizing the characteristics is being advanced.
Nanofibers can be manufactured in several ways, including electrospinning, melt spinning, self-assembly, template synthesis, electroblowing, and forcespinning.
At present, as a method for producing nanofibers on an industrial scale, an electrospinning method using a polymer solution and a high voltage as a source for producing nanofibers is known.

However, since polybenzazole is insoluble and infusible and has low processability, it has been difficult to form nanofibers by electrospinning. By applying electrospinning to a polybenzazole precursor having excellent solubility in order to solve this problem, it becomes possible to prepare nanofibers of a polybenzazole resin.
For example, in the case of a polybenzoxazole resin, a poly (o-hydroxyamide) solution which is a precursor of the polybenzobisoxazole resin is obtained by low-temperature polycondensation of tetrakistrimethylsilylation (o-bisaminophenol) and aromatic dicarboxylic acid chloride. Nanofiber preparation becomes possible.

<Thermal conductive filler>
The heat conductive filler of the present invention may be a filler having high heat conductivity, and more preferably a filler having high insulation.
Specific examples of the heat conductive filler include metal-based filers, inorganic compound fillers, and carbon-based fillers. Specifically, for example, silver, copper, aluminum, iron, metal filler such as stainless steel, alumina, magnesia, beryllia, silica, boron nitride, aluminum nitride, silicon carbide, boron carbide, inorganic filler such as titanium carbide, Examples thereof include carbon-based fillers such as diamond, graphite, graphite, and carbon fiber. At least one kind of heat conductive filler is selected and used, but it is also possible to use one kind or plural kinds of heat conductive fillers having different crystal forms, particle sizes and the like in combination. When heat dissipation is required in applications such as electronic equipment, electrical insulation is often required, and among these fillers, both thermal conductivity and volume resistivity are high, alumina, magnesium oxide, It is preferable to use at least one kind of insulating heat conductive filler selected from zinc oxide, beryllia, boron nitride, aluminum nitride, and diamond. The filling amount of the heat conductive filler for the composite resin composition is limited, and if the filling amount is too large, the physical properties such as moldability will be reduced. It is more preferable to use a heat conductive filler of 10 W / m · K or more.

Among them, alumina, aluminum nitride, boron nitride, and magnesium oxide are preferable from the viewpoint of ensuring thermal conductivity and insulating properties, and alumina is more preferable because it improves the resin filling property in addition to the thermal conductivity and insulating properties.

As these heat conductive fillers, those subjected to a surface treatment can also be used. For example, inorganic fillers and the like that have been surface-modified with silane-based, titanate-based, and aluminate-based coupling agents can be used.

  From the fluidity of the composite resin composition and the thermal conductivity of the molded product thereof, it is often better to use a thermally conductive filler treated with the above-described coupling agent. The adhesion between the resin and the thermally conductive filler is further enhanced, the interfacial thermal resistance between the resin and the thermally conductive filler is reduced, and the thermal conductivity is improved.

Among the coupling agents, it is preferable to use a silane coupling agent. For example, as the silane coupling agent, vinyl trichlorosilane, vinyl triethoxy silane, vinyl trimethoxy silane, γ-methacryloxypropyl trimethoxy silane, β ( 3,4 epoxy synchrohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycylimethoxypropylmethyldiethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N- β (aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane And the like.

Although the average particle size of the above-mentioned heat conductive filler is not particularly limited, a preferable lower limit is 0.2 μm and a preferable upper limit is 80 μm. When the average particle diameter of the above-mentioned heat conductive filler is less than 0.2 μm, the viscosity of the composite resin composition becomes high, and workability and the like may be reduced. When a large amount of the above-mentioned thermally conductive filler having an average particle diameter of more than 80 μm is used in a large amount, the moldability of the composite resin composition becomes insufficient, the warpage of the electronic component increases, or cracks or Peeling may occur. A more preferred lower limit of the average particle diameter of the above-mentioned heat conductive filler is 0.4 μm, and a more preferred upper limit is 50 μm.

The shape of the above-mentioned heat conductive filler is not particularly limited, but it is preferably closer to a true sphere from the fluidity of the composite resin composition. For example, the aspect ratio (the ratio of the major axis length of the particle to the minor axis length of the particle (major axis length / minor axis length)) is not particularly limited, but is preferably as close to 1 as possible, and more preferably 1 to 80, and more preferably 1 to 10.

<Resin>
The resin of the present invention may be a known and commonly used resin, and may be a thermoplastic resin or a thermosetting resin. The PBZ fiber used in the present invention has a very high thermal decomposition temperature. Therefore, even if a thermoplastic resin that becomes high in temperature during molding or a thermosetting resin that requires heating during curing is used, the PBZ fiber after compounding is a fiber. Demonstrate high thermal conductivity to maintain the shape of

  The thermosetting resin is a resin having a property of being substantially insoluble and infusible when cured by heating or a means such as radiation or a catalyst. Specific examples thereof include phenol resin, urea resin, melamine resin, benzoguanamine resin, alkyd resin, unsaturated polyester resin, vinyl ester resin, diallyl terephthalate resin, epoxy resin, silicone resin, urethane resin, furan resin, ketone resin, xylene Resins, thermosetting polyimide resins, and the like. These thermosetting resins can be used alone or in combination of two or more.

  The thermoplastic resin refers to a resin that can be melt-molded by heating. Specific examples thereof include polyethylene resin, polypropylene resin, polystyrene resin, rubber-modified polystyrene resin, acrylonitrile-butadiene-styrene (ABS) resin, acrylonitrile-styrene (AS) resin, polymethyl methacrylate resin, acrylic resin, and polyvinyl chloride resin. Polyvinylidene chloride resin, polyethylene terephthalate resin, ethylene vinyl alcohol resin, cellulose acetate resin, ionomer resin, polyacrylonitrile resin, polyamide resin, polyacetal resin, polybutylene terephthalate resin, polylactic acid resin, polyphenylene ether resin, modified polyphenylene ether resin, polycarbonate Resin, polysulfone resin, polyphenylene sulfide resin, polyetherimide resin, polyethersulfone Fat, polyarylate resins, thermoplastic polyimide resins, polyamideimide resins, polyether ether ketone resin, polyketone resin, liquid crystal polyester resins, fluorine resins, syndiotactic polystyrene resin, cyclic polyolefin resin. These thermoplastic resins can be used alone or in combination of two or more.

<Other compounds>
Other compounds may be added to the composite resin composition of the present invention as long as the effects of the present invention are not impaired.
For example, organic pigments, inorganic pigments, extender pigments, various resins, reactive compounds, catalysts, polymerization initiators, organic fillers, inorganic fillers, organic solvents, clay minerals, waxes, surfactants, stabilizers, flow regulators, dyes , Leveling agents, rheology control agents, ultraviolet absorbers, antioxidants, plasticizers and the like.

<Composite resin composition>
The composite resin composition of the present invention is a resin composition obtained by compounding the PBZ fiber, the heat conductive filler, and the resin.
The PBZ fiber of the present invention has a high thermal conductivity and is considered to function as a thermal conductive path covering between the high thermal conductive particles when used in combination with the high thermal conductive filler. Since the PBZ fiber of the present invention is a nanofiber, voids and voids are less likely to be generated when the PBZ fiber is composited, so that the PBZ fiber has excellent thermal conductivity. In addition, since the PBZ fiber of the present invention is a nanofiber, it hardly generates anisotropy when it is compounded with a resin, and therefore exhibits thermal conductivity not only in the in-plane direction but also in all directions including the thickness direction. I do.

  The method of compounding the PBZ fiber, the heat conductive filler, and the resin is not particularly limited, and a known and commonly used mixing method may be used. Specifically, an extruder, a kneader, a roll, a planetary mixer, a rotation-revolution type kneading device, or the like may be used. After blending a filler and a fiber with a predetermined amount of resin and mixing them sufficiently with a stirrer or the like, kneading with a kneader, a roll, a planetary mixer or the like to obtain a composition in which the heat conductive particles are uniformly dispersed. Can be. In kneading, heating or solvent may be used.

  When the total amount of the resin, the PBZ fiber and the heat conductive filler is 100% by mass, the total content of the PBZ fiber and the heat conductive filler is 50%. It is preferable that it is 95% by mass. When the total content of the PBZ fiber and the thermally conductive filler is 50% by mass or more, the resin composition has sufficient thermal conductivity. When the total content of the PBZ fiber and the thermally conductive filler is 95% by mass or less, the moldability and coatability of the resin composition are good. Moreover, when the resin composition is formed into a laminate, peeling or the like hardly occurs. In order to effectively exhibit the function of the thermally conductive filler and obtain high thermal conductivity, it is preferable that the PBZ fiber and the thermally conductive filler are highly filled, and the total content is 60 to 95% by mass. Is preferred. Considering also the fluidity of the resin composition, it is more preferable to use 60 to 85% by mass.

  In the composite resin composition, the content ratio of the PBZ fiber and the thermally conductive filler is 0.2 to 20 when the total of the PBZ fiber and the thermally conductive filler is 100% by mass. It is preferable that the content is mass%. When the content of the PBZ fiber is 0.2% by mass or more, the effect of improving the thermal conductivity is sufficiently obtained, and when the content is 20% by mass or less, the moldability and coatability of the resin are excellent. It is more preferably from 0.2 to 5% by mass, particularly preferably from 0.5 to 3% by mass, and more preferably from 0.5 to 1% by mass because the balance between thermal conductivity and moldability is excellent.

<Molded body>
The molded article of the present invention is a molded article obtained by molding the above-mentioned composite resin composition. The molding method may be a known and commonly used method, and may be appropriately selected depending on the type or use of the resin.
For example, if a plate-shaped product is to be manufactured, an extrusion molding method is generally used, but it is also possible to use a flat press. In addition, a modified extrusion molding method, a blow molding method, a compression molding method, a vacuum molding method, an injection molding method, or the like can be used. In addition, if a film-shaped product is to be produced, a solution casting method can be used in addition to a melt extrusion method. When a melt molding method is used, blown film molding, cast molding, extrusion lamination molding, calender molding, sheet molding. , Fiber molding, blow molding, injection molding, rotational molding, coating molding and the like. In the case of a resin that cures with an active energy ray, a molded article can be manufactured using various curing methods using an active energy ray.

  A molded article obtained by molding the composite resin composition of the present invention preferably has a higher density ratio. When the density ratio is high, the voids in the molded body are small, so that the thermal conductivity does not easily decrease. The density ratio is preferably 95% or more, more preferably 98% or more, and still more preferably 99% or more.

<Heat conductive material>
Since the composite resin composition of the present invention has excellent heat conductivity, it can be suitably used as a heat conductive material. As the heat conductive material, a heat conductive adhesive or the like can be used.

<Heat conduction member>
The heat conductive member of the present invention contains the molded article of the present invention. Since the heat conductive member of the present invention has excellent heat conductivity not only in the in-plane direction but also in the thickness direction, it can be particularly preferably used for an interlayer heat conductive material such as a heat conductive sheet or a heat conductive film. is there. In addition, since the heat conductivity is low in anisotropy, the effect is high even in a small and thin layer, and the insulating property is excellent, the members for electric, electronic equipment and automobiles, semiconductor device members, lithium ion batteries In particular, it can be suitably used for insulating members used for motors and inverters.

  Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to the examples. In the following examples, parts and% are by weight unless otherwise specified.

<Synthesis example 1>
-Resin synthesis Tetrakis trimethylsilylation (4,6'-diaminoresorcinol) and terephthalic acid dichloride are subjected to low-temperature polycondensation in dimethylacetamide (DMAc) to obtain silylated poly (o-hydroxy) which is a precursor of polybenzobisoxazole resin. Amide) solution was prepared.
Preparation of nanofibers About 1 ml of the silylated poly (o-hydroxyamide) solution obtained in the above resin synthesis is placed in a syringe having an inner diameter of 12 mm, and a voltage is applied to a needle having an inner diameter of 340 μm using a DC high-voltage power supply (Towa Keisoku). Electrospinning was performed. A stainless steel plate (10 cm × 10 cm) covered with aluminum foil was used as the target electrode, and the distance between the needle tip and the target electrode was 20 cm.
The yarn produced by electrospinning is immersed in methanol, and then heat-treated at 300 ° C. for 3 hours in a vacuum to convert the yarn into a polybenzobisoxazole resin, thereby obtaining a polybenzobisoxazole resin. By milling for an hour, nanofibers (F-1) of polybenzobisoxazole having an average fiber length of 50 μm and an average fiber diameter of 100 nm were obtained.
The diameter and the fiber length of the fiber were measured by FE-SEM (SU8010, manufactured by Hitachi High-Technologies Corporation), and the distribution of the diameter and the fiber length was determined from measurements at 10 or more locations.

<Synthesis Example 2>
Polybenzobisoxazole nanofibers (F-2) having an average fiber length of 30 µm and an average fiber diameter of 100 nm were obtained in the same manner as in Synthesis Example 1 except that the pulverization time in the atomizer pulverizer was changed to 2 hours.

<Example 1>
-Preparation of resin composition 45.5 g of diglycidyl ether of bisphenol A (manufactured by DIC: EPICLON 850-S, epoxy equivalent: 188 g / eq.), Polytetramethylene glycol diglycidyl ether 30 (Sakamoto Yakuhin Co., Ltd.) (Epoxy equivalent: 412 g / eq.) And 4.5 g of Dicyandiamide Amicure AH-154 (manufactured by Ajinomoto Fine Techno Co., Ltd.) to prepare a resin mixture (E). This resin mixture (E), the high heat conductive fiber (F-1) obtained in Synthesis Example 1 and the heat conductive filler are blended according to the filling ratio in the table, kneaded with three rolls, and defoamed to obtain a resin composition. (C-1) was obtained.

○ Thermal conductivity of cured resin (thickness direction)
Using the resin composition, a resin cured product test piece (60 × 110 × 0.8 mm) was prepared by hot press molding (temporary curing conditions: 170 ° C. × 20 minutes, main curing conditions: 170 ° C. × 2 hours). For a test piece cut out to a size of 10 × 10 mm from the obtained cured product, the thermal conductivity was measured using a thermal conductivity measuring device (LFA447 nanoflash, manufactured by NETZSCH).
○ Thermal conductivity of cured product (in-plane direction)
Using the resin composition, a resin cured product test piece (110 mm × 70 mm × 1 mm) was prepared by hot press molding, and the thermal conductivity was measured using a hot-wire method thermal conductivity measuring device (QTM-500 manufactured by Kyoto Electronics Industry). It was measured.

O Density ratio of cured resin A test piece cut out to a size of 10 x 10 mm from the cured product was cut out in the same manner as in the method of measuring the thermal conductivity in the thickness direction. The density of the obtained test piece was measured by the Archimedes method, and the value obtained by dividing the measured density value by the theoretical density value calculated from the composition ratio was defined as the density ratio.

-Adhesion (adhesion strength) evaluation The resin composition C-1 was used as a heat conductive adhesive to prepare a laminate. The resin composition 1 was applied to one end (25 mm × 100 mm × 1.6 mm) of one side (25 mm × 100 mm × 1.6 mm) of the aluminum pieces, and another piece of the same type of metal was laminated, and then 170 ° C. × 2 hours And cured at 200 ° C. for 2 hours to produce a laminate 1. Using an adhesive strength measuring device “Strograph APII (Toyo Seiki Seisakusho)”, the tensile strength was measured according to a test method (JIS K6850) for shear adhesive strength. The obtained laminate 1 was pulled in parallel with the bonding surface, and the maximum load at the time of breakage was divided by the bonding (shear) area to determine the bonding strength. As the evaluation of adhesiveness, ○ indicates that the adhesive strength was 5 MPa or more, and Δ indicates that the adhesive strength was 3 MPa or more and less than 5 MPa.

<Example 2> to <Example 8>
Resin compositions (C-2) to (C-8) were obtained and evaluated in the same manner as in Example 1, except that the conditions shown in Tables 1 and 2 were used.

<Comparative Example 1, Comparative Examples 4 to 7> Resin compositions (HC-1) and (HC) were prepared by adding the high heat conductive fiber and adding the same formulation as in Example 1 under the blending conditions shown in Tables 1 and 2. -5 to 7), and evaluated in the same manner as in Example 1.

<Comparative Example 2> to <Comparative Example 3>
A commercially available polyparaphenylene benzoxazole fiber (fiber length: 3 mm, fiber diameter: 12 μm, manufactured by Toyobo Co., Ltd., trade name: Zylon HM) (HF-1) was used as the high heat conductive fiber under the blending conditions shown in Table 1. Resin compositions (HC-2) to (HC-3) were obtained with the same formulation as in Example 1, and evaluated in the same manner as in Example 1.

Abbreviations in the table are as follows.
DAW45 (Spherical aluminum oxide 50% particle size 45 μm) Denki Kagaku Kogyo Co., Ltd.
DAW05 (Spherical aluminum oxide 50% particle size 5 μm) Denki Kagaku Kogyo Co., Ltd.
ASFP20 (Spherical aluminum oxide 50% particle size 0.3 μm) Denki Kagaku Kogyo Co., Ltd.

  The composite resin composition of the present invention is lightweight and has excellent insulating properties, and the obtained molded article has excellent thermal conductivity not only in the in-plane direction but also in the thickness direction. Therefore, the obtained composite resin composition is suitable as a heat conductive material, and the heat conductive member containing the molded article is suitably used in various fields such as electronic / electrical equipment and automobile members because of its excellent thermal conductivity. Can be used.

Claims (7)

Polybenzazole fiber containing a polybenzazole fiber having an average fiber diameter of 200 nm or less, a heat conductive filler, and a resin, and when the total of the resin, the polybenzazole fiber, and the heat conductive filler is 100% by mass, the polybenzazole fiber And a total content of the heat conductive filler is 50 to 95% by mass . , The composite resin composition according to claim 1, wherein the average fiber length of the polybenzazole fiber is 50 µm or less. The composite resin composition according to claim 1, wherein the polybenzazole fiber is a polyphenylene benzoxazole fiber. 4. The resin composition according to claim 1, wherein the content of the polybenzazole fiber is 0.2 to 20% by mass, when the total of the polybenzazole fiber and the thermally conductive filler is 100% by mass. 5. the resin composition according to any one. A molded article obtained by molding the composite resin composition according to any one of claims 1 to 4 . Characterized in that it contains a composite resin composition according to any one of claims 1-4, thermally conductive material. A heat conductive member comprising the molded product according to claim 5 .