JP2013014757A - Thermally conductive resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly thermally conductive resin composition which offers both greater filler packing and favorable molding flowability while securing an extremely favorable filler dispersion state.SOLUTION: The thermally conductive resin composition contains 70-20 pts.vol. of a polyester resin (A) having melt viscosity of 5-2,000 dPa s at 200°C and under 10 kgf load; and 30-80 pts.vol. of a heat-conducting filler (B). When the thermally conductive resin composition is processed into a sheet of 0.5 mm thickness, and a cross section thereof formed by cross section polishing is observed by SEM, void area ratio in the SEM observation surface is 1.5% or less.

Description

  The present invention relates to an ultra-low melt viscosity polyester resin and a thermally conductive resin composition containing a thermally conductive filler. More specifically, the filler can be highly filled while maintaining good molding fluidity. In addition, the present invention relates to a thermally conductive resin composition having a very good filler dispersion state.

In recent years, problems of heat generation such as personal computer and display housings, electronic device materials, and interior and exterior of automobiles have been highlighted, and materials having high thermal conductivity are required. When a thermoplastic resin composition is used for these applications, since plastic has a lower thermal conductivity than an inorganic material such as a metal material, it may be a problem that it is difficult to release generated heat. In order to solve such problems, attempts have been widely made to obtain a highly thermally conductive resin composition by highly filling an inorganic compound having high thermal conductivity into a thermoplastic resin. Examples of the inorganic compound having high thermal conductivity include graphite, carbon fiber, metallic silicon, magnesium, aluminum, aluminum nitride, boron nitride, zinc oxide, magnesia, and alumina, and usually 30% by volume or more, and further 50 volume. It is necessary to mix | blend in resin with the high content of more than%. In this filler high-filling technology, what often becomes a problem is formability and filler dispersion.
If you try to mold a high thermal conductivity thermoplastic resin by the injection molding method that is usually used, the resin flowing into the mold will cool and solidify at high speed because of its high thermal conductivity, and the gate part in the mold will solidify. After that, there is a problem that the resin cannot flow into the mold at all. In order to solve this, special molds such as a combination of hot runners and specially shaped gates are required when injection molding high thermal conductivity thermoplastic resin, making it impossible to mold with general purpose molds. There is an obstacle to the spread.
Further, the filler dispersion state is extremely important in physical properties such as kneading of the heat conductive thermoplastic resin and heat conductivity. For example, if the wettability between the resin and the filler is poor and a void (air layer) is formed at the interface between them, the strand becomes unstable and the filler cannot be highly filled, which hinders high thermal conductivity. Alternatively, when the dispersion state of the filler is not uniform, there arises a problem that the thermal conductivity is significantly deteriorated compared to the theoretical value.

  In order to solve such moldability problems, a method of adding a liquid organic compound at room temperature to improve the injection moldability of a thermoplastic resin highly filled with a filler is exemplified (for example, see Patent Document 1). . However, in such a method, there is a problem that a liquid organic compound bleeds out during injection molding and contaminates the mold.

  On the other hand, in order to solve the problem relating to moldability, an invention was made to improve molding fluidity and improve injection moldability by using a resin capable of greatly delaying the solidification rate during cooling in the mold ( For example, see Patent Document 2). However, although this invention has been improved in terms of molding fluidity at the time of injection molding, it is necessary to set the injection molding temperature high, and the filler filling rate is limited to about 60% by volume, and the filler can be used sufficiently. This is a problem in that high thermal conductivity cannot be achieved without high filling. The reason why such a problem occurs is that the wettability between the resin and the filler is not sufficient, so that it is difficult to achieve a high filler filling due to problems such as breakage of strands during kneading, or 60% by volume. There is a problem that injection molding becomes difficult because the melt viscosity of the resin composition is remarkably increased due to the above high filler filling, and both high filler filling and good injection moldability have not been achieved.

  On the other hand, in order to solve such a problem related to the filler dispersion state, a method of improving the fluidity of the filler by mixing a fluidity modifier in order to disperse uniformly in the resin without forming filler aggregates is exemplified. (For example, see Patent Document 3). Such filler surface modification improves the dispersibility in the resin and improves the thermal conductivity, but it has not been achieved in the problem of high filler filling. Furthermore, the number of filler surface modification steps increases, which not only leads to an increase in cost, but also requires a modification of the modifier according to the type of resin, and the variety of filler types makes it difficult to handle. There are issues such as.

Japanese Patent No. 3948240 JP 2009-91440 A Japanese Patent No. 3714502

  The present invention has been made against the background of such prior art problems. That is, an object of the present invention is to provide a highly thermally conductive resin composition that achieves both high filler filling and good molding fluidity and has a very good filler dispersion state.

As a result of intensive studies, the present inventors have found that the above problems can be solved by the following means, and have reached the present invention.
That is, the heat conductive resin composition of the present invention has a polyester resin (A) of 70 to 20 parts by volume having a melt viscosity of 5 to 2000 dPa · s at 200 ° C. and 10 kgf load, and a heat conductive filler (B) 30 to 30 parts. A heat conductive resin composition containing 80 parts by volume, and after processing the heat conductive resin composition into a sheet having a thickness of 0.5 mm, a cross section produced by cross-section polisher was observed by SEM. It is a heat conductive resin composition characterized by the void area ratio of an observation surface being 1.5% or less.
Here, the void area ratio on the SEM observation surface is a void per square region area that is arbitrarily cut out (selected) from the SEM observation image and has a length of 5 times the average particle diameter of the heat conductive filler as one side. The area is measured and calculated.
Hereinafter, the heat conductive filler may be simply referred to as a filler.

  80 mol% or more of the dicarboxylic acid component constituting the polyester resin (A) is terephthalic acid and / or naphthalenedicarboxylic acid, and 40 mol% or more of the diol component constituting the polyester resin (A) is 1 , 4-butanediol. Furthermore, it is preferable that 2 mol% or more of the diol components constituting (A) is polyalkylene ether glycol.

  According to the present invention, it is possible to obtain a thermally conductive resin composition that has a good filler dispersion state and enables high filler filling while maintaining good molding fluidity. Specifically, according to the present invention, the formation of voids at the interface between the resin and the filler can be effectively suppressed without performing a filler surface treatment.

The present invention is described in detail below.
The polyester resin (A) and the heat conductive filler (B) in the heat conductive resin composition of the present invention are 70 to 20 parts by volume of the polyester resin (A) and 30 to 80 parts by volume of the heat conductive filler (B). Contained. The viewpoint that the impact resistance and molding processability of the resulting resin composition are improved and the kneading with the resin during melt kneading tends to be easier as the content of (A) is larger, and (B) In consideration of the viewpoint that the thermal conductivity tends to be improved as the amount increases, the content is preferably (A) 60 to 20 parts by volume and (B) 40 to 80 parts by volume, More preferably, they are (A) 50-25 volume parts and (B) 50-75 volume parts, More preferably, (A) 40-30 volume parts and (B) 60-70 volume parts.

In the heat conductive resin composition of the present invention, the blending ratio of the polyester resin (A) and the heat conductive filler (B) is expressed in volume parts, but when the resin composition is produced, (A), ( B) Based on each specific gravity, it mix | blends on a mass basis. (A) is based on the specific gravity of the resin alone, and (B) is based on the specific gravity of the filler chemical species alone. In this way, the compounding amount is expressed in volume parts because the thermal conductivity, which is an important characteristic of the resin composition obtained according to the present invention, means that the volume ratio is large, not the mass ratio of the heat conductive filler in the composition. Because it has.
Also when the heat conductive resin composition of this invention contains components other than a polyester resin (A) and a heat conductive filler (B), a compounding quantity is determined similarly.
Since the dispersibility of the heat conductive filler (B) in the polyester resin (A) is very good, the heat conductive resin composition of the present invention has almost no voids (air layer) in the resin composition. Therefore, whether or not the heat conductive filler (B) is filled according to the blending ratio can be confirmed based on the specific gravity of (A) and (B) by measuring the specific gravity of the obtained heat conductive resin composition. I can do it.
The heat conductive resin composition of the present invention preferably occupies 90% by volume or more in total of the polyester resin (A) and the heat conductive filler (B). The total of (A) and (B) in the thermally conductive resin composition is more preferably 95% by volume or more, and still more preferably 97% by volume or more.

The heat conductive resin composition of the present invention has a void area ratio of 1 per region area cut out in an SEM observation image of a cross section prepared by cross section polisher processing after processing into a sheet having a thickness of 0.5 mm. Must be less than 5%. When the void area exceeds 1.5%, there is a high possibility that various physical properties such as thermal conductivity will be adversely affected. The void area ratio is preferably 1.0% or less, more preferably 0.7% or less, further preferably 0.5% or less, and most preferably 0.2% or less.
The region arbitrarily cut out here needs to be a range in which the dispersion state of the resin and the filler can be sufficiently confirmed, and is a square region having a length of 5 or more times the average particle size of the filler as one side. Is preferred. When the length of one side of the square region is less than that, only a limited portion is observed, and it is difficult to confirm the entire dispersed state, and an accurate dispersed state cannot be grasped. The length of one side of the square region is preferably 5 to 10 times the average particle diameter of the filler.
By calculating the area of the void portion with respect to the area of the set arbitrary square region, the void area ratio is calculated by the following equation 1.

(Formula 1)
(Total area of voids in arbitrarily cut square area) / (total area of square area arbitrarily cut) × 100

The cross section needs to be manufactured by cross section polisher processing. Other methods for producing the cross section include, for example, a cleaving method using a feather cutter or the like, but this is not preferable because the gap may be crushed during the cutting operation.
In order to easily distinguish the resin, filler, and voids, it is preferable to use carbon vapor deposition for SEM observation. In particular, it is essential to take an SEM image so that the air gap can be identified.

The analysis software for the cross-sectional image observed by SEM is not particularly limited, but it is necessary to be software that can determine the area of the cutout region and the area of the gap.
Among them, it is preferable to use “ImageJ” which is an open source from the viewpoint that it is widely spread and available to anyone.

The heat conductive resin composition of the present invention has a total heat conductive filler amount of 100% by mass, of which 25 to 70% by mass (Bi) is mixed with the polyester resin (A) and kneaded, It can be obtained by adding the remaining heat conductive filler 75 to 30% by mass (B-ii) to the resin composition and kneading. In the present invention, the heat conductive filler mixed first with the polyester resin (A) is (B-i), and the heat conductive filler mixed later is (B-ii).
When this condition is not satisfied, that is, when the amount of filler mixed with the resin at the first time is less than 25% by mass or more than 70% by mass, the effect of dividing the filler may be reduced, and voids may be easily generated. .
More preferably, 30 to 60% by mass (B-i) is mixed with the resin (A) and kneaded, and then 70 to 40% by mass (B-ii) of the remaining filler is added and kneaded. It is more preferable to mix and knead mass% (B-i) with resin (A) and then add 65 to 50 mass% (B-ii) of residual filler.
By adding and kneading the filler in such a divided manner, the dispersibility of the filler is good, and generation of voids (air layer) in the resin composition can be suppressed. The reason for this is that kneading (B-i) increases the melt viscosity of the resin composition at this stage, and when (B-ii) is added, kneading can be performed with a large shearing force. It is considered that the filler dispersion effect is increased.
The addition of the remaining filler may be performed once or may be performed in a plurality of times. It is preferable to add the remaining filler at a time because the manufacturing process is not complicated.

Various methods can be used as the kneading method. For example, one side feed is used, a dry blend of resin and part of the filler (B-i) is added to the original feed, and the remaining filler (B-ii) is added to the side feed to continuously Can be kneaded. Alternatively, two side feeds are used, resin is fed into the original feed, a part of the filler (B-i) in the side feed close to the original feed, and the remaining filler (B-ii) in the side feed far from the original feed May be added and continuously kneaded. Alternatively, the resin (A) and a part of the filler (B-i) may be kneaded, once taken out as pellets, etc., mixed with the remaining filler (B-ii), and then kneaded again. .
Among these, a method using a side feed is preferable because dispersibility is good and production efficiency is good.

  The kneading machine stand of the resin (A) and the heat conductive filler (B) is not particularly limited. For example, it can be produced by melt kneading in a melt kneader such as a single screw or twin screw extruder. Alternatively, a kneader such as a heating roll or a Banbury mixer may be used.

  The heat conductive filler (B) can contain one kind or two or more kinds of fillers. The term “two or more types of fillers” means that two or more types of fillers differ in material type, shape, average particle size, particle size distribution, surface treatment agent, and the like. In addition, the average particle diameter in this invention shall be measured using particle size distribution measuring apparatuses, such as a laser scattering particle size distribution analyzer.

The average particle diameter of the heat conductive filler (B) used in the present invention is preferably 1 to 100 μm. More preferably, it is 1.5-80 micrometers, and it is further more preferable that it is 2-70 micrometers.
When two or more kinds of fillers are used, the way of dividing them is not particularly limited. For example, when two types of fillers having different average particle diameters are used, a filler having a small average particle diameter can be classified as (B-i), and a filler having a large average particle diameter can be classified as (B-ii). A filler having a large average particle size can be classified as (B-i), and a filler having a small average particle size can be classified as (B-ii). A mixture of two types of fillers that is made uniform may be divided into (B-i) and (B-ii).

  When two or more kinds of fillers are used, one side of the square region of the SEM observation image has a length that is five times or more the average particle size of the filler having a larger particle size. The average particle size of the filler having a larger particle size is preferably 5 to 10 times.

  The polyester resin (A) used in the present invention needs to have a melt viscosity at 200 ° C. of 5 to 2000 dPa · s. When the melt viscosity is higher than 2000 dPa · s, the melt viscosity of the resin composition after high filler filling is remarkably increased, and good molding fluidity cannot be obtained. By using a polyester resin having a melt viscosity of 2000 dPa · s or less, preferably 1000 dPa · s or less, good molding fluidity can be obtained even after high filler filling. Further, the melt viscosity at 200 ° C. is preferably low, but considering the mechanical strength of the heat conductive resin composition, the lower limit is required to be 5 dPa · s or more, preferably 20 dPa · s or more, more preferably 100 dPa. · S or more, more preferably 200 dPa · s or more.

The polyester resin (A) preferably contains 80 mol% or more of terephthalic acid and / or naphthalenedicarboxylic acid as the dicarboxylic acid component, assuming that the total amount of dicarboxylic acid components is 100 mol%. More preferably, it is 90 mol% or more, More preferably, it is 95 mol% or more. If it is less than 80 mol%, the mechanical strength and heat resistance tend to decrease.
Naphthalenedicarboxylic acid is preferred as the dicarboxylic acid component from the viewpoint that both high filler filling and good molding fluidity are achieved.
The methyl ester derivative may be used as the dicarboxylic acid component. Naphthalenedicarboxylic acid is preferably 2,6-naphthalenedicarboxylic acid or a methyl ester derivative thereof, among its isomers, in consideration of reactivity and the three-dimensional structure of the polymer chain.

  The polyester resin (A) preferably contains 40 mol% or more of 1,4-butanediol as a glycol component when the total amount of diol components is 100 mol%. More preferably, it is 50 mol% or more. If it is less than 40 mol%, the crystallinity is too low, and blocking, moldability and heat resistance are problematic. The upper limit is preferably 80 mol% or less, more preferably 70 mol% or less. If it exceeds 80 mol%, the crystallization rate becomes too fast, so that the wettability with the filler deteriorates, the strand breakage or the like tends to occur due to the floating of the filler, and it tends to be difficult to achieve high filler filling.

In order to maintain good molding fluidity even after high filler filling, it is desirable that the melt viscosity of the resin before blending the filler is low, and it is desirable to copolymerize polyalkylene ether glycol for that purpose.
Examples of the polyalkylene ether glycol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, poly (ethylene oxide / propylene oxide) copolymer, poly (ethylene oxide / tetrahydrofuran) copolymer, poly (ethylene oxide / propylene oxide / tetrahydrofuran). ) Copolymer, and the like. When the total amount of diol components of the polyester resin (A) is 100%, the polyalkylene ether glycol is preferably 2 mol% or more, more preferably 5 mol%, More preferably, it is 10 mol%, and most preferably 20 mol% or more. The upper limit is preferably 60% by mole or less, more preferably 50% by mole or less in consideration of handling properties such as heat resistance and blocking.

  Polytetramethylene glycol is desirable as the polyalkylene ether glycol. The number average molecular weight of polytetramethylene glycol is preferably 400 or more, more preferably 500 or more, still more preferably 600 or more, particularly preferably 700 or more, and the upper limit is preferably 4000, more preferably 3500, still more preferably. Is 3000 or less. When the number average molecular weight of polytetramethylene glycol is less than 400, hydrolysis resistance may be lowered. On the other hand, when it exceeds 4000, the compatibility with the polyester portion composed of butylene terephthalate and / or butylene naphthalate units is lowered, and it may be difficult to copolymerize in a block form.

  As a method for producing the polyester resin used in the present invention, a known method can be used. For example, the esterification reaction of the above-mentioned dicarboxylic acid and diol component at 150 to 250 ° C., followed by 230 to 300 ° C. while reducing the pressure. The desired polyester can be obtained by polycondensation with. Alternatively, the target polyester can be obtained by polycondensation at 230 ° C. to 300 ° C. under reduced pressure after a transesterification reaction at 150 ° C. to 250 ° C. using a derivative such as dimethyl ester of dicarboxylic acid and a diol component. Can do.

In producing the polyester resin (A), it is preferable to add an antioxidant for the purpose of suppressing thermal deterioration, oxidative deterioration, etc., and it may be added before, during or after the reaction. For example, known hindered phenol-based, phosphorus-based, and thioether-based antioxidants can be used.
These antioxidants can be used alone or in combination. The addition amount is preferably 0.1% by mass or more and 5% by mass or less with respect to the polyester resin (A). If it is less than 0.1% by mass, the effect of preventing thermal deterioration may be poor. If it exceeds 5 mass%, other physical properties may be adversely affected.

  For the polyester resin (A), known components that can be copolymerized can be used as long as the reactivity and the mechanical properties and chemical properties of the obtained copolymer are not impaired. Examples of the component include a divalent or higher aromatic carboxylic acid having 8 to 22 carbon atoms, a divalent or higher aliphatic carboxylic acid having 4 to 12 carbon atoms, and a divalent or higher alicyclic carboxylic acid having 8 to 15 carbon atoms. Carboxylic acids such as acids and their ester-forming derivatives, aliphatic compounds having 2 to 20 carbon atoms, compounds having two or more hydroxyl groups in the molecule, and aromatic compounds having 6 to 40 carbon atoms, Examples thereof include compounds having two or more hydroxyl groups in the molecule, and ester-forming derivatives thereof.

Specifically, as carboxylic acids, in addition to terephthalic acid and naphthalenedicarboxylic acid, for example, isophthalic acid, bis (p-carboxyphenyl) methaneanthracene dicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 1,2-bis (Phenoxy) ethane-4,4′-dicarboxylic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, maleic acid, trimesic acid, trimellitic acid, pyromellitic acid, 1,3-cyclohexanedicarboxylic acid, 1, Examples thereof include carboxylic acids such as 4-cyclohexanedicarboxylic acid and decahydronaphthalenedicarboxylic acid or derivatives thereof having ester-forming ability. Examples of the hydroxyl group-containing compounds include 1,4-butanediol, ethylene glycol, 1,3 -Propanediol, 1,2-propanediol, , 6-hexanediol, neopentyl glycol, cyclohexanedimethanol, 2,2′-bis (4-hydroxyphenyl) propane, 2,2′-bis (4-hydroxycyclohexyl) propane, hydroquinone, glycerin, pentaerythritol, etc. Examples thereof include a compound or a derivative thereof having an ester forming ability.
The amount of copolymerization is preferably 20% by mass or less, more preferably 15% by mass or less, and still more preferably 10% by mass or less.

  The heat conductive filler (B) blended in the heat conductive resin composition of the present invention is not particularly limited. In consideration of the effect of improving the thermal conductivity of the composition, it is preferable that the thermal conductivity of the single component is 10 W / m · K or more. More preferably 15 W / m · K or more, still more preferably 20 W / m · K or more, particularly preferably 30 W / m · K or more. The upper limit of the thermal conductivity of the heat conductive filler (B) alone is not particularly limited, and it is preferably as high as possible. Generally, it is preferably 3000 W / m · K or less, more preferably 2500 W / m · K or less. Used.

  About the shape of a heat conductive filler (B), the thing of a various shape is applicable. For example, particles, particles, nanoparticles, agglomerated particles, wires, rods, needles, plates, irregular shapes, rugby balls, hexahedrons, composite particles in which large particles and fine particles are combined, Various shapes can be exemplified. Further, these heat conductive fillers (B) may be natural products or synthesized ones. In the case of a natural product, there are no particular limitations on the production area and the like, which can be selected as appropriate.

  Specific examples of the thermally conductive filler (B) exhibiting electrical insulation include metal oxides such as aluminum oxide (alumina), magnesium oxide (magnesia), silicon oxide, beryllium oxide, zinc oxide, copper oxide, and cuprous oxide. Metal nitride such as boron nitride, aluminum nitride, silicon nitride, metal carbide such as silicon carbide, metal carbonate such as magnesium carbonate, diamond, and other insulating carbon materials, aluminum hydroxide, magnesium hydroxide, etc. The metal hydroxide can be exemplified. These can be used alone or in combination. Of these, alumina, magnesia, and zinc oxide are preferable because wettability with the resin is relatively good, and alumina and magnesia are more preferable.

  Specific examples of the heat conductive filler (B) exhibiting electrical conductivity include carbon materials such as graphite and carbon fiber, and metal materials such as metal silicon, aluminum and magnesium. These can be used alone or in combination.

  The resin composition in the present invention has a very good filler dispersion state in the resin without performing surface treatment on the heat conductive filler (B), but it can enhance the adhesion at the interface between the resin and the inorganic compound. For the purpose of facilitating workability, surface treatment may be performed with various surface treatment agents such as a silane treatment agent. It does not specifically limit as a surface treating agent, For example, conventionally well-known things, such as a silane coupling agent and a titanate coupling agent, can be used. Among them, an epoxy group-containing silane coupling agent such as epoxy silane, an amino group-containing silane coupling agent such as aminosilane, polyoxyethylene silane, and the like are preferable because they hardly reduce the physical properties of the resin. The surface treatment method of the inorganic compound is not particularly limited, and a normal treatment method can be used.

  In order to make the thermally conductive resin composition obtained by the present invention higher performance, a thermal stabilizer such as a phenol-based stabilizer, a sulfur-based stabilizer, a phosphorus-based stabilizer, etc., alone or in combination of two or more kinds Is preferably added. Furthermore, as necessary, generally well-known stabilizers, lubricants, mold release agents, plasticizers, flame retardants other than phosphorus, flame retardant aids, ultraviolet absorbers, light stabilizers, pigments, dyes, charging An inhibitor, a conductivity imparting agent, a dispersant, a compatibilizing agent, an antibacterial agent and the like may be added alone or in combination of two or more.

  The method for molding the heat conductive resin composition obtained according to the present invention is not particularly limited. For example, a molding method generally used for thermoplastic resins, for example, injection molding, blow molding, extrusion molding, vacuum molding. , Press molding, calendar molding, etc. can be used. Among these, it is preferable to perform injection molding by an injection molding method because the molding cycle is short, the production efficiency is excellent, and the composition has good fluidity at the time of injection molding.

  The composition thus obtained can be used in various forms such as resin films, resin molded products, resin foams, paints and coating agents, electronic materials, magnetic materials, catalyst materials, structural materials, optical materials, medical materials. It can be widely used for various applications such as materials, automobile materials, and building materials. The high thermal conductive thermoplastic resin composition obtained in the present invention has a complicated shape because a general plastic molding machine such as an injection molding machine or an extrusion molding machine that is widely used at present can be used. Molding into products is easy. In particular, since it has excellent properties such as excellent moldability and high thermal conductivity, it is very useful as a resin for a casing of a mobile phone, a display, a computer or the like having a heat source inside.

  The high thermal conductive resin composition obtained by the present invention can be suitably used for injection molded products such as home appliances, OA equipment parts, AV equipment parts, automotive interior / exterior parts, and the like. In particular, it can be suitably used as an exterior material in home appliances and office automation equipment that generate a lot of heat.

  Furthermore, in an electronic device having a heat source inside but difficult to forcibly cool by a fan or the like, it is preferably used as an exterior material of these devices in order to dissipate heat generated inside to the outside. Among these, as preferred devices, small or portable electronic devices such as portable computers such as notebook computers, PDAs, cellular phones, portable game machines, portable music players, portable TV / video devices, portable video cameras, etc. It is very useful as a resin for housings, housings, and exterior materials. It can also be used very effectively as a resin for battery peripherals in automobiles and trains, a resin for portable batteries of home appliances, a resin for power distribution parts such as a breaker, and a sealing material for motors.

  The high thermal conductive resin composition of the present invention has a very small amount of voids in the resin, good thermal conductivity, and good moldability compared to conventionally known compositions. Or it has a useful characteristic for housing | casing.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples. In addition, each measured value described in the Example is measured by the following method.

  The melt viscosity was measured using a flow tester (CFT-500C type) manufactured by Shimadzu Corporation. A resin sample dried to a moisture content of 0.1% or less is filled in a cylinder at the center of a heating body set to 200 ° C. After 1 minute of filling, a load (10 kgf) is applied to the sample via a plunger, and the bottom of the cylinder The melted sample was extruded from the die (hole diameter: 1.0 mm, thickness: 10 mm), the plunger descending distance and the descending time were recorded, and the melt viscosity was calculated. When the melting point of the resin was more than 200 ° C., the temperature was set to 250 ° C. and measured.

Specific heat was measured using DS Instruments 2920 manufactured by TA Instruments. 10.0 mg of the resin composition was put in an aluminum pan, heated from room temperature to 200 ° C. at a temperature rising temperature of 10 ° C./min, held for 5 minutes after reaching 200 ° C., and then cooled at 10 ° C./min. Similarly, 26.8 mg of sapphire as a reference material was placed in an aluminum pan and measured under the same conditions. Furthermore, the empty aluminum pan which has not put the sample as a blank was measured on the same conditions. The value of Heat Flow at 23 ° C. of each DSC curve was read, and the specific heat capacity was calculated by the following formula 2.
Cp is the specific heat of the sample, C′p is the specific heat of the reference material (sapphire) at 23 ° C., h is the difference between the DSC curve of the empty container and the sample, H is the difference of the DSC curve of the empty container and the reference material (sapphire), m is the sample Mass (g) and m ′ represent mass (g) of the reference material (sapphire).
(Formula 2)
Cp = (h / H) × (m ′ / m) × C′p

Sheet samples used for various measurements were prepared using a heat press machine SA-302-I manufactured by Tester Sangyo Co., Ltd. After 3 g of the kneaded resin composition was melted at 190 ° C. for 2 minutes, a load of 100 kgf / cm ² was applied, and after 1 minute, it was immersed in water and quenched to obtain a sheet sample of approximately 0.5 mm. In the case of a composition using a resin having a melting point of 185 ° C. or higher, it was melted at 200 ° C.

  The specific gravity was measured using an automatic hydrometer DH100 manufactured by Toyo Seiki Co., Ltd. A sheet sample obtained by heat pressing was sampled at 10 mm × 10 mm, and the specific gravity was measured by an underwater substitution method.

  The thermal diffusivity was measured using a thermal diffusivity measuring apparatus ai-phase Mobile 1 manufactured by Eye Phase Co., Ltd. The thermal diffusivity in the thickness direction of the sheet sample obtained by heat pressing was measured.

The thermal conductivity was calculated by the following formula 3 from the specific heat, specific gravity, and thermal diffusivity obtained by the above method.
(Formula 3)
Thermal conductivity (W / m · K) = specific gravity × specific heat (J / g · K) × thermal diffusivity (m ² / sec)

(Production example: Polyester resin (A1))
In a reaction vessel equipped with a stirrer, a thermometer, and a condenser for distillation, 194 parts by mass of dimethyl terephthalate, 100 parts by mass of 1,4-butanediol, and polytetramethylene glycol “PTMG2000” having a number average molecular weight of 2000 (Mitsubishi Chemical) 800 parts by mass and 0.25 part by mass of tetrabutyl titanate were added, and an esterification reaction was performed at 170 to 220 ° C. for 2 hours. After completion of the esterification reaction, the temperature was raised to 255 ° C., while the pressure in the system was slowly reduced to 665 Pa at 255 ° C. over 60 minutes. Further, a polycondensation reaction was performed at 133 Pa or less for 30 minutes to obtain a polyester resin (A1). The composition of this polyester resin (A1) was terephthalic acid // 1,4-butanediol / PTMG2000 = 100 // 60/40 mol%, the melting point was 140 ° C., and the melt viscosity was 350 dPa · s.

(Production examples: polyester resins (A2) to (A3), (C1) to (C2))
The polyester resins (A2) to (A3) and (C1) to (C2) were synthesized by the same method as the polyester resin (A1). Each composition and physical property value are shown below. In addition, polyester resin (C1)-(C2) was used as a raw material of a comparative example.
(A2): 2,6-naphthalenedicarboxylic acid // 1,4-butanediol / PTMG2000 = 100 // 60/40 mol%, melting point 160 ° C., melt viscosity 500 dPa · s.
(A3): 2,6-naphthalenedicarboxylic acid // 1,4-butanediol / PTMG2000 = 100 // 70/30 mol%, melting point 185 ° C., melt viscosity 650 dPa · s.
(C1): 2,6-naphthalenedicarboxylic acid // 1,4-butanediol / PTMG1000 = 100 // 97/3 mol%, melting point 240 ° C., melt viscosity 9000 dPa · s (at 250 ° C.).
(C2): terephthalic acid // 1,4-butanediol = 100 // 100 mol%, melting point 227 ° C., melt viscosity 6500 dPa · s (at 250 ° C.).

  The polyester resins (A1) to (A3) have a melt viscosity at 200 ° C. of 5 to 2000 dPa · s, while the polyester resins (C1) to (C2) have a melt viscosity at 200 ° C. of more than 2000 dPa · s. is there.

The raw materials used in Examples and Comparative Examples are as follows.
Thermally conductive filler (B)
(B1): Alumina powder (V325F manufactured by Nippon Light Metal Co., Ltd., thermal conductivity 20-40 W / m · K alone, average particle size 12 μm, volume resistivity 10 ¹² to 10 ¹⁴ Ω · cm, specific gravity 3.98 )
(B2): Alumina powder (LS-210B manufactured by Nippon Light Metal Co., Ltd., single body thermal conductivity 20-40 W / m · K, average particle diameter 3.2 μm, volume resistivity 10 ¹² to 10 ¹⁴ Ω · cm, Specific gravity 3.98)
(B3): Magnesia powder (RF-10C-C manufactured by Ube Materials Co., Ltd., single unit thermal conductivity 42 to 60 W / m · K, average particle size 6.6 μm, volume resistivity 10 ¹⁷ Ω · cm, Specific gravity 3.58)
(B4): Magnesia powder (RF-50-C manufactured by Ube Materials Co., Ltd., thermal conductivity of 42 to 60 W / m · K alone, average particle size of 56.6 μm, volume resistivity of 10 ¹⁷ Ω · cm, Specific gravity 3.58)
(B5): Magnesia powder (RF-10C-C manufactured by Ube Materials Co., Ltd., single unit thermal conductivity 42 to 60 W / m · K, average particle size 12.0 μm, volume resistivity 10 ¹⁷ Ω · cm, Specific gravity 3.58)

Example 1
35 parts by volume of the polyester resin (A1) polymerized by the above method and 30 parts by volume of the heat conductive filler (B1) were put into a desktop kneader Labo Plast Mill 20C200 manufactured by Toyo Seiki Co., Ltd. And kneading at 20 rpm for 10 minutes. After taking out, what was cut into a chip shape was mixed with 35 parts by volume of the heat conductive filler (B1), and then kneaded again at 20 rpm for 10 minutes.

(Examples 2 to 5)
Kneading was carried out in the same manner as in Example 1 except that the types and blending amounts of the polyester resin (A) and the heat conductive filler (B) were changed as shown in Table 1. The kneading of Example 4 using the polyester resin (A3) having a high melting point was performed at 200 ° C.

(Example 6)
Biaxial extrusion, 35 parts by volume of polyester resin (A1) and 30 parts by volume of heat conductive filler (B1) are dry blended and fed from the original feed, and 35 parts by weight of heat conductive filler (B1) is fed from the side feed. Kneading was performed at 200 ° C. and 250 rpm with a machine TEM37BS (manufactured by Toshiba Machine Co., Ltd.).

(Examples 7 to 8)
Kneading was carried out in the same manner as in Example 6 except that the types and blending amounts of the polyester resin (A) and the heat conductive filler (B) were changed as shown in Table 1.

Example 9
35 parts by volume of the polyester resin (A2) is supplied from the original feed, 25 parts by volume of the heat conductive filler (B3) is supplied from the side feed on the original feed side, and 40 parts by volume of the heat conductive filler (B4) is supplied from the side feed on the die side. Then, kneading was performed in TEM37BS at 200 ° C. and 250 rpm.

(Comparative Example 1)
35 parts by volume of the polyester resin (A1) and 65 parts by volume of the heat conductive filler (B1) were put into a lab plast mill preheated to 180 ° C. and kneaded at 20 rpm for 10 minutes.

(Comparative Examples 2 to 4)
Kneading was carried out in the same manner as in Comparative Example 1 or Example 1 except that the types, blending amounts, and preparation methods of the polyester resin and the heat conductive filler were changed as shown in Table 2. The kneading of Comparative Examples 3 and 4 using polyester resins (C1) and (C2) having relatively high melt viscosities was performed at 250 ° C. and 240 ° C., respectively.

(Comparative Example 5)
50 parts by volume of the polyester resin (A2) and 50 parts by volume of the heat conductive filler (B2) were collectively charged into the original feed, and kneaded at 200 ° C. and 250 rpm with a TEM37BS.

(Comparative Example 6)
Kneading was carried out in the same manner as in Comparative Example 5 except that the type and blending amount of the heat conductive filler were changed as shown in Table 2.

[Evaluation method]
The void area ratio was determined as follows.
(Void area ratio)
A cross section of a sheet sample obtained by heat pressing was prepared by cross section polisher processing, and SEM observation was performed. Using the image analysis software “ImageJ”, which is an open source, the void area ratio per square area arbitrarily cut out on the SEM observation surface was calculated according to (Equation 1) described above. One side of the square region was 5 times the average particle size when the average particle size of the filler was 50 μm or more, and 7 times the average particle size otherwise.

  The respective formulations and results are shown in Tables 1 and 2. In any of the kneadable levels, injection molding was possible, but compared to the resin composition outside the present invention, the resin composition obtained by the present invention effectively suppressed the formation of voids at the filler interface, And it turns out that it shows the outstanding heat conductivity resulting from it.

  From the above, the thermoplastic resin composition obtained by the present invention can be filled with a high filler, has a very good filler dispersion state, and also has a high thermal conductivity, and also has an excellent molding fluidity at the time of injection molding. It is a highly heat conductive thermoplastic resin composition and has a great industrial utility value.

Claims (3)

  A heat conductive resin composition containing 70 to 20 parts by volume of a polyester resin (A) having a melt viscosity of 5 to 2000 dPa · s at 200 ° C. under a load of 10 kgf and 30 to 80 parts by volume of a heat conductive filler (B). Then, after processing the thermally conductive resin composition into a sheet having a thickness of 0.5 mm and observing a cross section produced by cross-section polisher with a SEM, the void area ratio on the SEM observation surface is 1.5% or less. A thermally conductive resin composition characterized by being.   80 mol% or more of the dicarboxylic acid component constituting the polyester resin (A) is terephthalic acid and / or naphthalenedicarboxylic acid, and 40 mol% or more of the diol component constituting the polyester resin (A) is 1 The heat conductive resin composition according to claim 1, which is 1,4-butanediol.   The heat conductive resin composition according to claim 1, wherein 2 mol% or more of the diol component of the polyester resin (A) is a polyalkylene ether glycol.