WO2014119462A1 - Heat-conductive filler, method for producing said filler, resin composition using said filler, molded article produced from said resin composition, and highly heat-conductive material - Google Patents

Abstract

Provided are: a heat-conductive filler which is characterized by comprising particles which are produced by coating magnesium oxide with magnesium carbonate; a method for producing a heat-conductive filler, which is characterized by comprising the steps of injecting a carbon dioxide gas into a slurry that is prepared by dispersing magnesium oxide particles in water and then performing a hydrothermal treatment while dissolving carbon dioxide in water; a resin composition prepared using the heat-conducive filler; and a molded product of the resin composition. The heat-conductive filler, the resin composition, the molded product of the resin composition, and a highly heat-conductive material produced using the molded article have excellent heat conductivity and wet heat resistance.

Description

Thermally conductive filler, method for producing the same, resin composition using the same, molded product thereof, and high thermal conductive material

The present invention relates to a heat conductive filler having both heat conductivity and heat and moisture resistance, a resin composition containing the heat conductive filler, a molded product thereof, and a high heat conductive material using the resin composition.

¡Plastic materials are widely used as materials for electric, electronic equipment, automobiles, etc. as materials to replace metal materials due to the widespread use of engineering plastics with high heat resistance, as well as productivity and flexibility in shape. In recent years, there has been a further demand for higher performance, smaller size, and lighter weight of the equipment, and semiconductor devices have become more highly integrated and larger in capacity. As a result, the amount of heat generated from the members has increased. Improving conductivity is an important issue. In addition, there is a strong demand for improving the thermal conductivity of insulating members used in lithium ion batteries, motors, and inverters as an improvement in the electric cost of electric vehicles.

As a method for maintaining the insulation of the plastic material and imparting thermal conductivity, a technique of adding an inorganic filler is known, and examples thereof include boron nitride, aluminum nitride, alumina, magnesium oxide, and magnesium carbonate. . Boron nitride is a filler with high thermal conductivity, but its practicality is low in terms of cost, and since it has a hexagonal flaky crystal structure, the filler composed of boron nitride is oriented in the resin composition and molded. There is a problem that anisotropy occurs in the thermal conductivity of the body. Aluminum nitride has no anisotropy in thermal conductivity, but has a problem of low cost practicality like boron nitride, and further easily hydrolyzes to generate ammonia. Alumina has a high Mohs hardness of 9, and there is a problem that the screw in the extrusion process, the blade of the cutter in the pelletizing process, and the screw and mold of the injection molding machine are worn.

Magnesium oxide is a filler that has relatively high thermal conductivity, does not cause anisotropy, and has the advantage of low cost, and is promising as a filler that imparts thermal conductivity to thermoplastic resins. However, magnesium oxide is inferior in heat and moisture resistance. That is, when a molded product containing magnesium oxide as a filler is exposed to high temperature and high humidity, hydrolysis occurs from the surface of the magnesium oxide filler, and it expands by changing to magnesium hydroxide, increasing the size of the molded product. The problem occurs.

As a technique for improving the heat and moisture resistance, a technique of applying a dry surface treatment coating of magnesium oxide with an alkylalkoxysilane (for example, see Patent Document 1) and a technique of coating with a magnesium phosphate compound (for example, Patent Document) 2). However, the effect of improving the moist heat resistance is insufficient even in a molded product obtained by blending a filler made of magnesium oxide surface-treated with these other compounds into a thermoplastic resin. For example, temperature 121 ° C./humidity 100% / The result of the pressure cooker test at a pressure of 2 atm does not reach the required level in the above-mentioned application.

Magnesium carbonate, on the other hand, has good thermal conductivity, low anisotropy in thermal conductivity, low Mohs height of 3.5, low cost, and good moisture resistance, making it useful as a thermal conductive filler it is conceivable that.

Magnesium carbonate is generally divided into natural and synthetic products. Natural products are obtained by crushing magnesite ore, but they contain more impurities such as soluble salts, acid insolubles, and calcium salts than synthetic products. However, since the crystallinity is low, there is a problem that the thermal conductivity is inferior. On the other hand, as a synthetic product, magnesium hydroxide is used as a starting material, carbon dioxide gas is supplied to the magnesium hydroxide slurry and carbonized, or soluble magnesium salt and soluble carbonate are mixed in water to carbonate the magnesium salt. And the like. Magnesium carbonate produced is a magnesium neutral carbonate _{(MgCO 3 · 3H 2 O)} , and relatively to stable basic magnesium carbonate _{(mMgCO 3 · Mg (OH)} 2 · nH 2 O) ripening conversion To do. Basic magnesium carbonate has a lower thermal conductivity than magnesium oxide and alumina, and when it is highly filled in engineering plastics, the crystal water contained in the processing zone at a high temperature of 250 ° C or higher is released, and foaming and discharge are not possible. There is concern that processability such as stability may be adversely affected. Thus, anhydrous magnesium carbonate obtained by drying after hydrothermal treatment in an autoclave using basic magnesium carbonate and neutral magnesium carbonate as a starting material is provided as a thermal conductive filler for engineering plastics (for example, patents). However, it has not yet reached a practical level as a thermally conductive filler, and further improvements are required.

JP 2011-068757 A JP 2006-151778 A Japanese Patent Laid-Open No. 2005-272752

In view of the above circumstances, an object of the present invention is to provide a resin composition that can provide a high thermal conductivity material excellent in thermal conductivity and moisture and heat resistance, a molded body, and a thermal conductivity that can be suitably used as a filler in the high thermal conductivity material. It is in providing a conductive filler and its manufacturing method.

As a result of intensive studies in order to solve the above problems, the present inventor has processed particles when magnesium oxide is coated with magnesium carbonate and processed into a resin while maintaining high thermal conductivity. Has been found to be excellent and the resulting molded article is excellent in heat and moisture resistance, and the present invention has been completed.

That is, the present invention provides a thermally conductive filler characterized in that magnesium oxide is particles coated with magnesium carbonate, a resin composition obtained by blending this with a resin, a molded product thereof, and a high thermal conductivity material. It is to provide.

According to the present invention, it is possible to obtain a thermally conductive filler that gives a molded article having both high thermal conductivity and low anisotropy of thermal conductivity, low hardness, and good wet heat resistance. In addition, the resin composition containing the heat conductive filler can be easily molded without impairing fluidity, has both high heat conductivity and heat and humidity resistance, and is exposed to a long period of time under high temperature and high humidity. However, it is possible to obtain a molded body capable of maintaining a good appearance. Therefore, the resin composition of the present invention and the molded product thereof are suitable for highly heat-conductive materials that are desired to be thinner and more complicated, such as electric and electronic parts, automobile parts, water heater parts, fibers, and films. It can use suitably for a use etc.

[Thermal conductive filler]
The thermally conductive filler of the present invention is characterized in that it is a particle formed by coating magnesium oxide with magnesium carbonate.

It is known that magnesium oxide is generally hydrolyzed and gradually converted to magnesium hydroxide Mg (OH) ₂ by contact with water vapor in the atmosphere at normal temperature and normal pressure. Further, this outermost layer Mg (OH) ₂ reacts with carbon dioxide in the atmosphere and changes to magnesium carbonate. These reactions are changes over a very long period under normal temperature and pressure. Magnesium oxide obtained by firing at a low temperature of about 600 ° C. using magnesium hydroxide or magnesium carbonate as a starting material is relatively easy to undergo these reactions, whereas it is heated at a high temperature of 1000 ° C. or higher. Things are more dense, stable and less prone to these reactions. That is, the reactivity differs depending on the firing conditions of magnesium oxide, and when the container is filled with magnesium oxide, even when comparing the place where the outermost particles are in contact with the place where it is in contact with the outside air Reactivity is different. Therefore, it is extremely difficult to adjust the amount of change from magnesium oxide to magnesium hydroxide and further to magnesium carbonate. On the other hand, in the present invention, it is quantitatively modified to magnesium carbonate while maintaining the shape of magnesium oxide in an industrially short time.

That is, in the present invention, by covering the surface of magnesium oxide with magnesium carbonate, it was made for the purpose of improving the storage stability as a heat conductive filler and the moisture and heat resistance of a molded article containing this as a filler. Is.

The heat conductive filler of the present invention is a particle formed by coating magnesium oxide with magnesium carbonate as described above, but the particle diameter is not particularly limited, but it is easy to handle as a filler. From a viewpoint that the molded body is excellent in thermal conductivity and heat-and-moisture resistance, the average particle diameter is preferably 20 to 100 μm, particularly preferably 30 to 90 μm. In addition, the measuring method of the particle diameter in this invention is the value which measured after implementing ultrasonic dispersion | distribution for 5 minutes using water as a solvent using the laser diffraction type particle size distribution measuring apparatus.

In general, the larger the average particle diameter of the filler, the higher the thermal conductivity due to the reduction in the area of the resin / filler interface when mixed with the resin. In addition, the filler having a spherical shape with low thermal conductivity anisotropy, as in the present invention, is used in combination with a fibrous high crystalline filler having a high thermal conductivity. A heat conduction path can be formed by contact with the crystalline filler. At this time, the larger the particle diameter of the spherical filler, the more efficient heat conduction path formation can be expected. From this point of view, when trying to obtain a molded body having a higher thermal conductivity than that exhibited when the spherical thermal conductive filler is highly filled, it is a filler having a large particle diameter. Is required.

From such a viewpoint, it is preferable that the average particle diameter of the filler of the present invention is 20 μm or more. In Patent Document 3, since hydrothermal treatment is performed using basic magnesium carbonate or neutral magnesium carbonate that is soluble in water as a starting material, it is difficult to obtain magnesium carbonate having a relatively large particle size. is there.

In addition, when a molded body is obtained by mixing a filler having an average particle diameter exceeding 100 μm with a resin, the thermal conductivity is good, but depending on the blending ratio, impact resistance, bending strength, etc. The mechanical properties may be insufficient and may not be exhibited, or the appearance of the thin-film molded body may be inferior in appearance as a protrusion. From these viewpoints, it is preferable to select the particle diameter according to the shape and performance of the target molded article.

In addition, when manufacturing the heat conductive filler of this invention by the hydrothermal treatment of magnesium oxide so that it may mention later, the particle size of the heat conductive filler from which the particle size of the magnesium oxide particle used as a raw material is obtained is maintained. Therefore, when selecting a particle diameter as a heat conductive filler according to a use, it is easy if the magnesium oxide particle which has the same particle diameter is used as a raw material.

From the viewpoint of low anisotropy as the heat conductive filler and the homogeneity of physical properties of the obtained molded product, the particle size distribution width of the heat conductive filler of the present invention has a coefficient of variation of 0.5 or less. It is preferable that it is 0.4 or less especially. The coefficient of variation used for the evaluation of the particle size distribution width is the standard deviation obtained by (d84% -d16%) / 2 in the particle size distribution measured using a laser diffraction particle size distribution measuring apparatus and water as a solvent. It is a value obtained by dividing by the average particle diameter.

As a method of making the thermally conductive filler of the present invention within the above range, adjusting the particle size distribution width of the magnesium oxide particles used as a raw material in the hydrothermal treatment described later, or in the drying / pulverization step after the hydrothermal treatment, Examples include a method of incorporating a classification step. The magnesium oxide particles used as the raw material are preferably those having a variation coefficient of the particle size distribution width of 0.5 or less.

In addition, the BET specific surface area of the particles that are the heat conductive filler of the present invention is preferably 10 m ² / g or less, particularly preferably in the range of 0.1 to 5 m ² / g. When the BET specific surface area is in this range, it becomes easy to uniformly disperse when kneading with the resin.

The thermally conductive filler of the present invention is a particle in which magnesium oxide is coated with magnesium carbonate, but the ratio of the coated magnesium carbonate can be set according to the purpose, specifically The content of magnesium carbonate in the particles can be controlled at 1 to 99.9% by mass.

In particular, the magnesium carbonate content is preferably in the range of 5 to 50% by mass from the viewpoint of easily obtaining a molded product having both thermal conductivity and heat-and-moisture resistance in a well-balanced manner.

When the thermally conductive filler of the present invention is produced by hydrothermal treatment of magnesium oxide particles, which will be described later, first, the surface layer of the magnesium oxide particles is hydrolyzed to become magnesium hydroxide. Magnesium hydroxide is decomposed into magnesium ions and hydroxide ions in water, but since carbon dioxide is present in the system, it is neutralized instantaneously and deposited as magnesium carbonate on the surface of the magnesium oxide particles. As a result, the magnesium oxide is coated with magnesium carbonate. The heat conductive filler obtained in this manner includes those that are not perfectly spherical, and may have irregularities on the surface.

The coated magnesium carbonate preferably contains anhydrous magnesium carbonate from the viewpoint of being suitably used as a thermally conductive filler. In the case of producing by hydrothermal treatment described later, initially hydrolyzed magnesium ions and hydroxide ions are converted into tetrahydrate basic magnesium carbonate (4MgCO ₃ .Mg (OH) ₂ .4H ₂ ) by the presence of carbon dioxide. Precipitate as O). This basic magnesium carbonate releases crystal water at around 250 ° C. That is, for example, when a TG analysis is performed under a temperature rising rate condition of 10 ° C./min, a peak at the start of weight loss is recognized from around 250 ° C. Since the temperature at which this crystal water is released is lower than the processing temperature of major engineering plastics (300 ° C or higher), water may be removed during extrusion, which may adversely affect workability such as foaming and surging. Less is desirable because it is possible.

If the hydrothermal treatment is further continued, this basic magnesium carbonate can be changed to anhydrous magnesium carbonate.

As described above, the basic magnesium carbonate is anhydrous magnesium carbonate in the magnesium carbonate covering the particles that are the heat conductive filler of the present invention, particularly from the viewpoint that it is not suitable as a heat conductive filler used in engineering plastics. The content of is preferably 30% by mass or more, and particularly preferably 50% by mass or more.

In the thermally conductive filler of the present invention, as a method for discriminating whether the magnesium carbonate covering the magnesium oxide is basic magnesium carbonate or anhydrous magnesium carbonate, a diffraction angle 2θ by X-ray diffraction analysis is used. The method of reading a peak is mentioned. When the coating is tetrahydrate basic magnesium carbonate, a peak can be read at a position where 2θ is 15 °. On the other hand, when the coating is anhydrous magnesium carbonate, a peak can be read at a position where 2θ is 33 °.

When the coating is tetrahydrate basic magnesium carbonate, crystal water is released from 100 ° C. to 300 ° C. and decomposes into anhydrous magnesium carbonate and magnesium hydroxide (4MgCO ₃ .Mg (OH) ₂ .4H ₂ O → 4 MgCO ₃ + Mg (OH) ₂ + 4H ₂ O). Further, from 350 ° C. to 500 ° C., magnesium hydroxide is decomposed into magnesium oxide and water (Mg (OH) ₂ → MgO + H ₂ O), and anhydrous magnesium carbonate is thermally decomposed into magnesium oxide and carbon dioxide (MgCO ₃ → MgO + CO ₂ ) reaction occurs. When TG analysis is performed under the temperature rising rate condition of 10 ° C./min, peaks of weight loss are recognized at around 250 ° C. and around 450 ° C.

When the coating is basic magnesium carbonate, the amount of magnesium carbonate (wt%) in the particles is determined by the following equation.
(Decreased value of X (° C.) obtained by TG analysis−reduced value of 150 ° C.) × (466/72)

In the above formula, X is a temperature between 300 ° C. and 350 ° C. and after the end point of the weight loss peak starting from around 250 ° C. Further, in the above formula, 466 is a tetrahydrate basic magnesium carbonate 4MgCO ₃ .Mg (OH when the atomic weight of Mg is 24, the atomic weight of C is 12, the atomic weight of H is 1, and the atomic weight of O is 16. ) molecular weight of ₂ · 4H ₂ O, 72 is the molecular weight of the 4H ₂ O.

When the coating is anhydrous magnesium carbonate, the magnesium carbonate content (wt%) of the coated magnesium oxide particles is determined by the following formula.
(800 ° C. weight loss value obtained by TG analysis−Y (° C.) weight loss value) × (84/44)
In the above formula, Y is a temperature between 450 ° C. and 500 ° C. and after the end point of the weight loss peak starting from around 250 ° C.

In the above formula, 84 is the molecular weight of anhydrous magnesium carbonate MgCO ₃ when the atomic weight of Mg is 24, the atomic weight of C is 12, the atomic weight of H is 1, and the atomic weight of O is 16, and 44 is the molecular weight of carbon dioxide. , 58 is the molecular weight of magnesium hydroxide Mg (OH) ₂ , and 18 is the molecular weight of water.

When the coating is a mixture of anhydrous magnesium carbonate and magnesium hydroxide, the amount of magnesium carbonate (wt%) in the particles is determined by the following equation.
(800 ° C. weight loss value obtained by TG analysis−450 ° C. weight loss value) × (84/44)

In the above formula, 84 is the molecular weight of anhydrous magnesium carbonate MgCO ₃ when the atomic weight of Mg is 24, the atomic weight of C is 12, the atomic weight of H is 1, and the atomic weight of O is 16, 44 is the molecular weight of carbon dioxide, 58 Is the molecular weight of magnesium hydroxide Mg (OH) ₂ , and 18 is the molecular weight of water.

Depending on the hydrothermal conditions, basic magnesium carbonate and anhydrous magnesium carbonate may coexist. In this case, the weight loss peaks around 250 ° C. and 450 ° C. are recognized by TGA analysis of basic magnesium carbonate. In addition, the determination can be made by observing a weight loss peak around 550 ° C. due to thermal decomposition of anhydrous magnesium carbonate. The amount of magnesium carbonate (wt%) when basic magnesium carbonate and anhydrous magnesium carbonate are mixed is determined by the following equation.

Amount of basic magnesium carbonate A = (reduced value of X (° C.) obtained by TG analysis−reduced value of 150 ° C.) × (466/72)
Anhydrous magnesium carbonate amount B = (800 ° C. reduction value obtained by TG analysis−Y (° C.) reduction value) × (84/44))
Total amount of magnesium carbonate = (A + B)

[Hydrothermal treatment]
Examples of a method for easily obtaining the heat conductive filler of the present invention include a method of hydrothermally treating magnesium oxide particles.

In the present invention, the hydrothermal treatment means that a slurry obtained by dispersing magnesium oxide particles in water is subjected to a reforming treatment at a temperature of 100 ° C. or higher in the presence of carbon dioxide.

The magnesium oxide particles used as a raw material in the present invention include those obtained by firing magnesium hydroxide or magnesium carbonate, but those obtained by any manufacturing method may be used. Further, the average particle size, the maximum particle size, and the amount of impurities such as alumina and iron oxide are not particularly limited, but by using magnesium oxide having an average particle size of preferably 20 to 100 μm, more preferably 30 to 70 μm, In addition to high thermal conductivity, a resin composition giving high fluidity and a molded article having good mechanical properties can be obtained. That is, the average particle diameter and distribution width of the magnesium oxide particles used as the raw material are maintained during the hydrothermal treatment.

By hydrothermal treatment, the surface layer of the magnesium oxide particles is hydrolyzed into magnesium hydroxide as described above. Magnesium hydroxide becomes magnesium ions and hydroxide ions in the water due to the presence of water, but since carbon dioxide is present in the water, it is neutralized instantaneously and magnesium carbonate is formed on the surface of the magnesium oxide particles. To be deposited. Therefore, the amount of change to magnesium carbonate can be adjusted by the hydrothermal treatment time, the amount of water charged into magnesium oxide, and the amount of carbon dioxide.

The amount of change to magnesium carbonate increases by lengthening the hydrothermal treatment time. Moreover, the rate of change to magnesium carbonate is improved by increasing the amount of water charged to magnesium oxide and increasing the amount of carbon dioxide. Since the thermal conductivity of magnesium carbonate is smaller than that of magnesium oxide, the thermal conductivity tends to decrease somewhat as the proportion of the volume of magnesium carbonate in the particle in the volume of magnesium oxide increases. The molded body obtained by using this as a heat conductive filler has good heat and moisture resistance.

For example, in order to improve the moisture resistance of magnesium oxide, as a method of using 20% or more of magnesium carbonate in terms of mass, it is preferable to set the time for hydrothermal treatment while supplying carbon dioxide to 1 hour or more. The treatment temperature also affects the amount of change to magnesium carbonate. Similarly, in order to change 20% or more, the treatment is preferably performed in the range of 100 to 180 ° C.

In order to set the amount of magnesium carbonate in the particles to 90% by mass or more, for example, as a first step, hydrothermal treatment is performed for 1 hour or more while supplying carbon dioxide at a temperature of 100 ° C. or higher and 180 ° C. or lower. As a step, it is desirable to perform hydrothermal treatment for 1 hour or more while supplying carbon dioxide at a temperature of 100 ° C. or more and 250 ° C. The surface of magnesium oxide is changed by the first step, and mainly tetrahydrate basic magnesium carbonate (4MgCO ₃ .Mg (OH) ₂ .4H ₂ O) is generated. At this time, the amount of change in magnesium carbonate varies depending on the treatment temperature and is preferably 100 ° C. to 180 ° C., more preferably 120 ° C. to 140 ° C. When the temperature is 100 ° C. or lower, the rate of change of magnesium carbonate by hydrothermal treatment is reduced. Moreover, since the amount of carbon dioxide which melt | dissolves in water will reduce when it becomes 180 degreeC or more, the rate of change to magnesium carbonate will reduce. Furthermore, as a second step, hydrothermal treatment is performed at a temperature of 100 ° C. or more and 250 ° C. while supplying carbon dioxide, thereby changing magnesium oxide that has not yet been changed to basic magnesium carbonate and producing 4 already produced. Hydrate basic magnesium carbonate can be changed to anhydrous magnesium carbonate. When basic magnesium carbonate changes to anhydrous magnesium carbonate, magnesium hydroxide is also produced at the same time, but by performing hydrothermal treatment while supplying carbon dioxide, the produced magnesium hydroxide is also tetrahydrate basic. After changing to magnesium carbonate, it further changes to anhydrous magnesium carbonate. As a result, the final magnesium hydroxide amount can be reduced, and the mass ratio of magnesium carbonate can be increased.

It is known that magnesium hydroxide in the coating changes in crystallinity depending on the temperature of hydrothermal treatment, and the decomposition temperature into water and magnesium oxide also changes. For example, magnesium hydroxide contained when hydrothermal treatment is performed at 180 ° C. or lower has low crystallinity and a decomposition start temperature of around 350 ° C. Further, when hydrothermal treatment is performed at 180 ° C. or higher, the crystallinity is high, and the decomposition start temperature is around 380 ° C. From this point of view, when the obtained particles are suitably used as a thermally conductive filler, it is desirable that the temperature condition of the hydrothermal treatment is higher in order to control the properties of magnesium hydroxide contained in the particles, especially the second It is desirable to perform hydrothermal treatment at 180 ° C. or higher as a step. That is, in the manufacturing method of this invention, you may have a two-step process from which temperature differs.

The smaller the amount of water charged into the magnesium oxide particles, the lower the rate of change to magnesium carbonate. This is because when magnesium oxide is hydrolyzed to magnesium hydroxide and decomposed into magnesium ions and hydroxide ions into water and eluted into water, the amount of magnesium eluted differs depending on the amount of water. As the amount of change to magnesium carbonate increases, magnesium oxide is coated with magnesium carbonate, and the area where magnesium oxide is exposed decreases, so that the elution rate of magnesium ions gradually decreases, resulting in the rate of change to magnesium carbonate. Becomes smaller.

Also, the smaller the amount of water with respect to the magnesium oxide particles, the higher the viscosity of the slurry, and the lower the productivity of the filtration and washing process after hydrothermal treatment. In the step of hydrolyzing the magnesium oxide particles with water, by adding water in excess of an equimolar amount, the slurry fluidity during the hydrothermal reaction is improved and the workability is greatly improved. However, when there is too much quantity of water, the yield of a heat conductive filler will become small and productivity will fall. The conditions under which a sufficient amount of modification to magnesium carbonate is obtained and the workability and productivity are good are preferably in the range of 50 to 2000 parts by mass, more preferably 100 to 1500 parts by mass with respect to 100 parts by mass of the magnesium oxide particles. Is more preferable, and 150 to 1000 parts by mass is most preferable.

In the hydrothermal treatment, conventionally known various heat conductive fillers and fillers can be added in accordance with the intended use as long as the effects of the present invention are not impaired. Examples of the heat conductive filler include boron nitride, silicon nitride, boehmite, beryllium oxide, zinc oxide, titanium oxide, crystalline silicon oxide, silicon carbide, graphite, and carbon fiber. Examples of the filler include talc, silicon oxide, diatomaceous earth, dolomite, clay, mica, and calcium carbonate. By hydrothermally treating in combination with such other particles, the resulting heat conductive filler can be obtained as a premixed mixture, reducing the complexity of preparing a subsequent resin composition Is possible.

Further, in the hydrothermal treatment, a coupling agent such as a silane coupling agent and a titanate coupling agent, a water-soluble solution, and the like for the purpose of further improving dispersibility and hydrophobicity, as long as the effects of the present invention are not impaired. Resin and various conventionally known additives can be added. These are desirably water-soluble during hydrothermal treatment, and for example, Shin-Etsu Silicone KBM-903, KBE-903, Ajinomoto Fine Techno Preneact KR ET, and the like are preferably used. These can be added before the start of the first step heating, added after the completion of the first step heating hold, or added after the completion of the second step heating hold.

[Resin composition]
The heat conductive filler of the present invention can be blended with various resins to form a resin composition. The resin to be blended may be either a thermosetting resin or a thermoplastic resin, and the thermosetting resin is a phenol resin, urea resin, melamine resin, benzoguanamine resin, alkyd resin, unsaturated polyester resin, vinyl ester resin, diallyl. Examples include terephthalate resin, epoxy resin, silicone resin, urethane resin, furan resin, ketone resin, xylene resin, and thermosetting polyimide resin. These thermosetting resins can be used alone or in combination of two or more. Thermoplastic resins include polyolefin resins such as polyethylene and polypropylene and modified products thereof, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, (meth) acrylic resins such as polymethyl methacrylate and polyethyl methacrylate, polystyrene, acrylonitrile-butadiene- Styrene resin, acrylonitrile-acrylic rubber-styrene resin, acrylonitrile-ethylene rubber-styrene resin, styrene resin such as (meth) acrylate ester-styrene resin, styrene-butadiene-styrene resin, ionomer resin, polyacrylonitrile, 6-nylon , 6,6-Nylon, 6T-PA, 9T-PA, MXD6-Nylon and other polyamide resins, ethylene-vinyl acetate resin, ethylene-acrylic Luric acid resin, ethylene-ethyl acrylate resin, ethylene-vinyl alcohol resin, chlorine resin such as polyvinyl chloride and polyvinylidene chloride, fluorine resin such as polyvinyl fluoride and polyvinylidene fluoride, polycarbonate resin, modified polyphenylene ether resin, methylpentene Resins, cellulose resins, etc., and thermoplastic elastomers such as olefin elastomers, glycidyl modified olefin elastomers, maleic acid modified olefin elastomers, vinyl chloride elastomers, styrene elastomers, urethane elastomers, polyester elastomers, polyamide elastomers, Polyphenylene sulfide resin, polyether imide resin, polyether ether ketone resin, thermoplastic polyimide resin, etc. . These thermoplastic resins can be used alone or in combination of two or more. Among these, it can be suitably blended with a resin called an engineering plastic used for an electric / electronic member. Engineering plastics include thermoplastic resins such as polybutylene terephthalate, nylon 9T, fluororesin, polycarbonate resin, modified polyphenylene ether resin, polyphenylene sulfide resin, polyetherimide resin, polyetheretherketone resin, and thermoplastic polyimide resin. .

Further, when the main component of the resin composition of the present invention is a thermoplastic resin, a small amount of a thermosetting resin may be added within a range that does not impair the properties of the thermoplastic resin. In such a case, it is possible to add a small amount of thermoplastic resin as long as the properties of the thermosetting resin are not impaired.

The amount of the thermally conductive filler is appropriately selected depending on the type of resin, other components in the resin composition, and the desired degree of thermal conductivity. For example, it is blended with polyphenylsulfone resin. In this case, it is preferably blended in the range of 30 to 500 parts by mass, more preferably in the range of 50 to 450 parts by mass, and in the range of 100 to 400 parts by mass in 100 parts by mass of the polyphenylene resin. Is more preferable. When 100 parts by mass of the polyphenylsulfone resin is 50 parts by mass or less, sufficient thermal conductivity cannot be obtained, and when it is 500 parts by mass or more, the viscosity at the time of melting of the resin composition increases. Easy moldability may be reduced.

[Other heat conductive fillers]
As long as the effect of the present invention is not impaired, the resin composition may contain various conventionally known heat conductive fillers depending on the application. For example, boron nitride, aluminum nitride, magnesium oxide, Silicon nitride, aluminum oxide, boehmite, beryllium oxide, zinc oxide, titanium oxide, crystalline silicon oxide, silicon carbide and composite compounds thereof, metal silicone, graphite, carbon fiber, ceramic fiber, metal fiber, potassium titanate whisker, Examples thereof include metal fibers (such as stainless steel fibers), silicon nitride whiskers, aluminum borate whiskers, boron fibers, tetrapotted zinc oxide whiskers, carbon nanotubes, oil furnace carbon black, channel black, ketjen black, and acetylene black.

[Other fillers]
In addition, the resin composition may contain various conventionally known fillers depending on the application as long as the effects of the present invention are not impaired. For example, talc, silica, diatomaceous earth, dolomite, Gypsum, clay, asbestos, mica, glass fiber, glass beads, glass balloon, calcium carbonate, anhydrous magnesium carbonate, barium sulfate, calcium sulfate, calcium sulfite, calcium phosphate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, iron oxide, Natural fiber such as asbestos, sodium silicate, calcium silicate, bentonite, wollastonite, mullite, cordierite, holsteinite, quartz powder, aluminum powder, zirconia powder, cellulose fiber, hemp etc., polyamide fiber, polyester fiber, acrylic fiber Synthetic fibers, mineral fibers, etc. Kuuru, etc.) and the like.

[Other additives]
Further, the resin composition may contain various conventionally known additives depending on its use, as long as the effects of the present invention are not impaired. For example, hydrolysis inhibitor, colorant, Flame retardant, antioxidant, polyethylene wax, oxidized polyethylene wax, polypropylene wax, oxidized polypropylene wax, metal soap, styrene oligomer, polyamide oligomer, polymerization initiator, polymerization inhibitor, titanium crosslinking agent, zirconia crosslinking Agents, other cross-linking agents, UV absorbers, antistatic agents, lubricants, mold release agents, antifoaming agents, leveling agents, light stabilizers (eg, benzotriazoles, hindered amines, etc.), crystal nucleating agents, chelating agents, ions Examples thereof include an exchange agent, a dispersant, an antioxidant, an inorganic pigment, and an organic pigment.

Further, the resin composition may be subjected to a surface treatment with a silane coupling agent or a titanate coupling agent for the purpose of further improving the hydrophobicity as long as the effect of the present invention is not impaired. Good. Examples of silane coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropyl. Triethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxy Silane, 3-acryloxypropyltrimethoxysilane, N-2- (aminoethyl) -3aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3aminopropyltrimethoxysilane, 3-aminopropyl Pulltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, 3-mercaptopropyltri Examples include methoxysilane, bis (triethoxysilylpropyl) tetrasulfide, and 3-isocyanatopropyltriethoxysilane.

Examples of titanate coupling agents include isopropyl triisostearoyl titanate, isopropyl trioctanoyl titanate, isopropyl tri (dioctyl pyrophosphate) titanate, isopropyl dimethacryl isostearoyl titanate, isopropyl tri (N, N-diaminoethyl). Titanate, isopropyltridodecylbenzenesulfonyl titanate, isopropylisostearoyl diacryl titanate, isopropyl tri (dioctyl phosphate) titanate, isopropyl tricumyl phenyl titanate, tetraisopropyl bis (dioctyl phosphate) titanate, tetraoctyl bis (ditridecyl phosphate) Titanate, tetra (2,2-diallyloxymethyl-1 Butyl) bis (ditridecyl) phosphate titanate, bis (dioctyl pyrophosphate) oxy acetate titanate, bis (dioctyl pyrophosphate) ethylene titanate.

In order to blend the heat conductive filler of the present invention into the resin, a publicly known and commonly used method may be used. It can be carried out by a method using a single screw extruder, a twin screw extruder, a pressure kneader, a kneader, a multi-screw extruder or the like. The method for supplying the coated magnesium oxide particles, resin and other additives to the kneader is not particularly limited. Batch supply by dry blending may be used, or each additive may be supplied individually using an individual supply machine. In addition, after preparing a master batch of coated magnesium oxide particles and a resin in advance, it may be mixed and diluted with the resin with a kneader, or the entire amount may be mixed and kneaded without using the master batch.

[Molded body]
A molded body can be obtained by molding the resin composition of the present invention. The method for molding the molded body is not particularly limited. When the resin composition contains a thermosetting resin, various polymerization initiators, curing agents, curing accelerators, polymerization inhibitors, and the like can be blended in the resin composition. If a plate-shaped product is to be manufactured, an extrusion molding method is generally used, but a flat press is also possible. In addition, a profile extrusion molding method, a blow molding method, a compression molding method, a vacuum molding method, an injection molding method, and the like can be used. If a film-like product is manufactured, the solution casting method can be used in addition to the melt extrusion method. When the melt molding method is used, inflation film molding, cast molding, extrusion lamination molding, calendar molding, sheet molding are used. , Fiber molding, blow molding, injection molding, rotational molding, coating molding, and the like. Moreover, in the case of resin hardened | cured with an active energy ray, a molded object can be manufactured using the various hardening methods using an active energy ray.

When the resin composition contains a thermoplastic resin, not only injection molding (injection compression molding, injection press molding, gas assist injection molding), various extrusions (cold runner method, hot runner method), foam molding (supercritical fluid) Various injection molding methods including injection molding), insert molding, in-mold coating molding, heat insulation mold molding, rapid heating / cooling mold molding, two-color molding, sandwich molding, and ultra-high speed injection molding). It can also be used in the form of articles, various extruded sheets, films, fibers and the like. In addition, an inflation method, a calendar method, a casting method, or the like can be used for forming a sheet or a film. Furthermore, it can be formed as a heat-shrinkable tube by applying a specific stretching operation. It is also possible to form a hollow molded product by rotational molding or blow molding.

The molded body of the present invention may have any shape depending on the application, and may be a three-dimensional solid shape, a sheet, a film, or a fiber shape. Further, a part of the molded body or several places may be melted by heat treatment and adhered to a resin or a metal substrate. A coating film applied to a resin or a metal substrate may be used, and a laminate may be formed. Further, secondary processing such as annealing treatment, etching treatment, corona treatment, plasma treatment, emboss transfer, cutting, and surface polishing may be performed on the sheet / film / fibrous molded article.

[High thermal conductivity materials]
When using the said resin composition as a highly heat-conductive material, it can be used for an adhesive agent, a sealing material, a coating material, ink, etc., for example. Moreover, when making a molded object into a highly heat conductive material, what is necessary is just to process according to the intended use, for example, the shape of an electronic-electric-machine member.

The high thermal conductive material of the present invention is excellent in thermal conductivity and heat-and-moisture resistance, and therefore can be suitably used for various applications. Examples include, but are not limited to, electrical / electronic parts, automobile parts, lighting parts, water heater parts, aircraft parts, building materials, containers / packaging members, daily necessities, sports / leisure goods, etc. .

Hereinafter, examples of the present invention will be described, but it is needless to say that the present invention is not limited to this description.

Example 1
<Manufacture of heat conductive filler 1>
100 g of Ube Magnesium oxide particles RF-98 (average particle diameter 68 μm by laser diffraction) and 150 g of water (water / magnesium oxide particle ratio = 1.5) were charged into a 0.5 L autoclave and stirred at 175 ° C. over 18 minutes. The temperature was raised to At this time, carbon dioxide gas was continuously supplied at a pressure of 1 MPa. After reaching 175 ° C., the carbon dioxide gas was continuously supplied and held for 2 hours with stirring to form a coating layer on the surface of the magnesium oxide particles. After holding for 2 hours, the mixture was cooled to 60 ° C., the supply of carbon dioxide gas was stopped and the pressure was reduced, and the product slurry was taken out from the autoclave. This was filtered, dried at 150 ° C. for 2 hours and pulverized to obtain a white particle-like thermally conductive filler 1.

<Preparation of test piece for thermal conductivity evaluation>
62.7% by mass of the heat conductive filler 1 obtained in the above production example and 37.3% by mass of polyphenylene sulfide resin (melt viscosity of 100 ° C. at 300 ° C.) of 37.3% (volume% of the heat conductive filler is 40%) And then blended by using a mixer equipped with a 60 cc mixer in a lab plast mill manufactured by Toyo Seiki Seisakusho, at a mixer temperature of 300 ° C., a rotor rotation speed of 100 rpm, and a mixing time of 5 minutes. . At this time, as an evaluation of processability, it was confirmed whether there were any defects such as foaming and smoke generation. After kneading for 5 minutes, the kneaded product was taken out and allowed to cool to obtain a solid lump-like resin composition. The molding resin composition was dried in a gear oven at 140 ° C. for 2 hours, and then molded using a small vertical injection molding machine under conditions of a cylinder set temperature of 320 ° C. and a mold temperature of 250 ° C., and had a thickness of 1 mm × diameter of 10 mm. A cylindrical test piece was obtained.

<Creation of test piece for wet heat resistance evaluation>
After hand blending 62.7% by mass of the heat conductive filler 1 obtained in the above production example and 37.3% by mass of polyphenylene sulfide resin (melt viscosity of 100 ° C. at 300 ° C.) of 37.3% by mass, a laboratory manufactured by Toyo Seiki Seisakusho Using a mixer equipped with a 60 cc mixer in a plast mill, the mixture was melt-kneaded under conditions of a mixer temperature of 300 ° C., a rotor rotation speed of 100 rpm, and a mixing time of 5 minutes. After drying the molding resin composition in a gear oven at 140 ° C. for 2 hours, the sample was placed on a mold having a thickness of 1 mm × long side 110 mm × short side 70 mm, and a pressure of 2 MPa was applied with a hot press machine at 300 ° C. for 5 hours. After partial heat retention, a pressure of 30 MPa was applied, and pressing was performed at 300 ° C. for 2 minutes. Thereafter, the sample was taken out after cooling to room temperature, and a flat test piece having a thickness of 1 mm × long side 110 mm × short side 70 mm was obtained.

Example 2
<Manufacture of thermally conductive filler 2>
In Example 1, the heat conductive filler 2 was manufactured and evaluated in the same manner except that the treatment time was changed from 2 hours to 4 hours.

Example 3
<Manufacture of thermal conductive filler 3>
In Example 1, the heat conductive filler 3 was produced in the same manner except that the treatment time was changed from 2 hours to 8 hours, and evaluated.

Example 4
<Manufacture of thermally conductive filler 4>
In Example 2, the heat conductive filler 4 was produced and evaluated in the same manner except that the magnesium oxide particles 100 g and the water 150 g were changed to the magnesium oxide particles 50 g and the water 150 g (water / magnesium oxide particle ratio = 3). Went.

Example 5
<Manufacture of thermal conductive filler 5>
In Example 2, the heat conductive filler 5 was produced and evaluated in the same manner except that the magnesium oxide particles 100 g and the water 150 g were changed to the magnesium oxide particles 15 g and the water 150 g (water / magnesium oxide particle ratio = 10). Went.

Example 6
<Manufacture of thermally conductive filler 6>
100 g of Ube Magnesium Oxide RF-98 (average particle diameter 68 μm by laser diffraction) and 150 g of water were charged into a 0.5 L autoclave, and the temperature was raised to 120 ° C. over 12 minutes with stirring. At this time, carbon dioxide gas was continuously supplied at a pressure of 0.4 MPa. After reaching 120 ° C., the carbon dioxide gas was continuously supplied and held for 5 hours with stirring to form a coating layer on the surface of the magnesium oxide particles. After holding for 5 hours, the mixture was cooled to 60 ° C., the supply of carbon dioxide gas was stopped and the pressure was reduced, and the product slurry was taken out from the autoclave. This was filtered and dried at 150 ° C. for 2 hours to obtain a white powdery intermediate. 100 g of this intermediate and 150 g of water were again charged into a 0.5 L autoclave, and the temperature was raised to 175 ° C. over 18 minutes while stirring. At this time, carbon dioxide gas was continuously supplied at a pressure of 1.0 MPa. After reaching 175 ° C., the mixture was further kept for 8 hours with stirring. After holding for 8 hours, the mixture was cooled to 60 ° C., the supply of carbon dioxide gas was stopped and the pressure was reduced, and the product slurry was taken out from the autoclave. This was filtered, dried at 150 ° C. for 2 hours and pulverized to obtain a white particulate heat conductive filler 6.

Example 7
<Manufacture of thermally conductive filler 7>
In Example 6, the heat conductive filler 7 was produced and evaluated in the same manner except that the composition of the intermediate 100 g and water 150 g was changed to the intermediate 15 g and water 150 g.

Example 8
<Manufacture of thermally conductive filler 8>
In Example 2, heat treatment was carried out in the same manner except that Ube Material magnesium oxide RF-98 (average particle diameter by laser diffraction 68 μm) was sieved and classified so that the average particle diameter was 23 μm. Conductive filler 8 was manufactured and evaluated.

Comparative Example 1
In Example 1, instead of the heat conductive filler 1, untreated magnesium oxide RF-98 was used without passing through the hydrothermal treatment step. When the BET specific surface area of this particle was measured, it was 0.2 m ² / g, and the average particle size was 68 μm. Further, when TG-DTA measurement was performed (temperature increase in Air at 10 ° C./min), the weight loss value from 800 ° C. to 450 ° C. was 0.1%. From this, when the amount of magnesium carbonate is determined using the above-described equation for determining the amount of coated magnesium carbonate, 0.1 × 84/44 = 0.2 mass%. The blending ratio of 65% by mass of magnesium oxide and 35% by mass of polyphenylene sulfide resin having a melt viscosity at 300 ° C. of 100 poise so that the volume fraction of the heat-conductive filler is the same as that of Example 1 and under the same conditions as in Example 1 A test piece for heat conduction evaluation and a test piece for wet heat resistance test were prepared.

Comparative Example 2
In the same manner as in Comparative Example 1, except that commercially available anhydrous magnesium carbonate was used instead of magnesium oxide RF-98, a test piece for heat conduction evaluation and a test piece for wet heat resistance test were prepared. When the BET specific surface area of this anhydrous magnesium carbonate particle was measured, it was 0.5 m < ² > / g and the average particle diameter was 25 micrometers. Further, when TG-DTA measurement was performed (temperature increase in Air at 10 ° C./min), the weight loss value from 800 ° C. to 450 ° C. was 51.9%. From this, when the amount of magnesium carbonate is determined using the above-described equation for determining the amount of coated magnesium carbonate, 51.9 × 84/44 = 99% by mass. In order to make the volume fraction of Example 1 and the heat conductive filler equal, a blend of 60% by weight of anhydrous magnesium carbonate and 40% by weight of polyphenylene sulfide resin having a melt viscosity of 300 ° C. at 100 ° C. was carried out under the same conditions. Test pieces and wet heat resistance test pieces were prepared.

Comparative Example 3
In Comparative Example 1, commercially available basic magnesium carbonate was used instead of magnesium oxide RF-98. When the BET specific surface area of this particle was measured, it was 30 m ² / g, and the average particle size was 23 μm. Further, when TG-DTA measurement (temperature increase in Air at 10 ° C./min) was performed, the weight loss value from 320 ° C. to 150 ° C. was 15.0%. From this, when the amount of magnesium carbonate is determined using the above-described equation for determining the amount of coated magnesium carbonate, it is 15.0 × 466/72 = 97 mass%. Example 1 is the same as Example 1 except that the blending ratio is 52% by mass of basic magnesium carbonate and 48% by mass of polyphenylene sulfide resin having a melt viscosity of 100 poise of 300 ° C. so that the volume fraction of the heat conductive filler is the same as Example 1. Similarly, a test piece for heat conduction evaluation and a test piece for wet heat resistance test were prepared.

Comparative Example 4
In Comparative Example 1, commercially available natural magnesite was ground instead of magnesium oxide RF-98. When the BET specific surface area of this particle was measured, it was 0.2 m ² / g, and the average particle size was 60 μm. Further, when TG-DTA measurement was performed (temperature increase in Air at 10 ° C./min), the weight loss value from 800 to 450 ° C. was 50.3%. From this, when the amount of magnesium carbonate is determined using the above-described equation for determining the amount of coated magnesium carbonate, 50.3 × 84/44 = 96% by mass. In order to make the volume fractions of Example 1 and the heat conductive filler equal, a blend of 60% by mass of basic magnesium carbonate and 40% by mass of polyphenylene sulfide resin having a melt viscosity of 100 poise at 300 ° C. is the same as in Example 1. A test piece for heat conduction evaluation and a test piece for wet heat resistance test were prepared under the conditions.

Comparative Example 5
In Comparative Example 1, magnesium oxide RF98 was 32.1% by mass, commercially available basic magnesium carbonate was 29.9% by mass (magnesium oxide: basic magnesium carbonate = 1: 1 by volume), and the melt viscosity at 300 ° C. 100 poise polyphenylene sulfide resin was 38% by mass, and a test piece for heat conduction evaluation and a test piece for heat and humidity resistance test were prepared under the same conditions as in Example 1.

Comparative Example 6
2 parts by weight of decyltrimethoxysilane was added dropwise to 100 parts by weight of Ube Magnesium Oxide RF-98 and mixed for 2 minutes at 100 rpm with a Henschel mixer. After mixing, 64.1% by mass of RF-98 treated with decyltrimethoxysilane and 35.9% by mass of polyphenylene sulfide resin having a melt viscosity of 100 poise at 300 ° C. were conducted under the same conditions as in Example 1. A test piece for evaluation and a test piece for wet heat resistance test were prepared.

Example 9
23% by mass of the thermally conductive filler 7 obtained in Example 7, 27% by mass of boron nitride (BN) (average major axis 20 μm), which is a plate-like highly thermally conductive filler, 19% by mass of glass fiber (GF), A test piece for heat conduction evaluation and a test piece for moisture and heat resistance test were prepared in the same manner except that the polyphenylene sulfide resin having a melt viscosity of 300 ° C. and 100 poise was changed to 31% by mass.

Comparative Example 7
In Example 9, magnesium oxide RF-98 was used instead of the thermally conductive filler 7. In order to make the volume fraction of Example 9 and the heat conductive filler equal, 26% by mass of magnesium oxide, 25% by mass of boron nitride (BN) (average major axis 20 μm), 18% by mass of glass fiber (GF), 300 ° C. A test piece for heat conduction evaluation and a test piece for moisture and heat resistance test were prepared in the same manner as in Example 9 except that a polyphenylene sulfide resin having a melt viscosity of 100 poise was 31% by mass.

Comparative Example 8
In Example 9, a test piece for heat conduction evaluation and a test piece for wet heat resistance test were prepared in the same manner except that commercially available anhydrous magnesium carbonate was used instead of the heat conductive filler 7. In order that the volume fraction of Example 9 and the heat conductive filler is equivalent, anhydrous magnesium carbonate 23 mass%, boron nitride (BN) (average major axis 20 μm) 27 mass%, glass fiber (GF) 19 mass%, A test piece for heat conduction evaluation and a test piece for wet heat resistance test were prepared under the same conditions as in Example 9 except that a polyphenylene sulfide resin having a melt viscosity of 300 ° C. at 100 ° C. was blended in an amount of 31% by mass.

Comparative Example 9
In Example 9, commercially available basic magnesium carbonate was used in place of the thermally conductive filler 7. Example 9 and 18% by mass of basic magnesium carbonate, 28% by mass of boron nitride (BN) (average major axis 20 μm), 21% by mass of glass fiber (GF), so that the volume fraction of the heat conductive filler is the same as Example 9. A test piece for heat conduction evaluation and a test piece for wet heat resistance test were prepared in the same manner as in Example 9 except that a polyphenylene sulfide resin having a melt viscosity at 300 ° C. of 100 poise was changed to 33% by mass.

Comparative Example 10
In Example 9, instead of the thermally conductive filler 7, commercially available natural magnesite was used. In order to make the volume fractions of Example 9 and the heat conductive filler equal, natural magnesite 23 mass%, boron nitride (BN) (average major axis 20 μm) 27 mass%, glass fiber (GF) 19 mass%, 300 A test piece for heat conduction evaluation and a test piece for wet heat resistance test were prepared in the same manner as in Example 9 except that a polyphenylene sulfide resin having a melt viscosity at 100 ° C. of 100 poise was mixed at 31% by mass.

Evaluation of the obtained heat conductive filler and various test pieces was performed by the following methods.
[Average particle size and distribution width]
Using a laser diffraction particle size distribution analyzer, ultrasonic dispersion was performed for 5 minutes as a pretreatment using water as a solvent, and then the particle size distribution was measured. Further, as an evaluation of the particle size distribution width, a variation coefficient obtained by dividing the standard deviation obtained by (d84% −d16%) / 2 by the average particle diameter was used.

[BET specific surface area]
Using FlowSorb II 2300 manufactured by Shimadzu Corporation, nitrogen was used as an adsorption gas, and pretreatment was performed at 100 ° C. for 30 minutes as a degassing condition.

[TG-DTA analysis]
All values such as weight loss and decomposition temperature by TG analysis are measured using EXSTAR-6300 manufactured by SII NanoTechnology under the air (200 ml / min), sample amount 5 mg, and heating condition at 10 ° C / min. The value when used was used.

[Pressure Cooker Test (PCT)]
The obtained test piece was exposed for 200 hours under the conditions of a set temperature of 121 ° C., a humidity of 100 RH%, and a pressure of 2 atm using an accelerated life geodetic device (Pre-Shear Cooker) manufactured by Espec. The mass of the test piece after the exposure was measured, and the mass increase rate with respect to that before the exposure was determined to obtain the water absorption rate (%). Further, the appearance of the plate surface was observed, and when the crack was not generated, it was evaluated as “◯”, and when the crack was generated and the surface was roughed, it was evaluated as “X”.

〔Thermal conductivity〕
A cylindrical test piece having a thickness of 1 mm and a diameter of 10 mm obtained using a small vertical injection molding machine was subjected to heat conduction at a measurement start temperature of 25 ° C. using a xenon flash thermal conductivity meter (LFA447 manufactured by Bruker AXS). The rate was determined.

[Content of anhydrous magnesium carbonate in magnesium carbonate (%)]
Using the weight loss curve obtained by the TG-DTA analysis, the following equation is used.
Amount of basic magnesium carbonate A = (reduced value of X (° C.) obtained by TG analysis−reduced value of 150 ° C.) × (466/72)
Anhydrous magnesium carbonate amount B = (800 ° C. reduction value obtained by TG analysis−Y (° C.) reduction value) × (84/44))
Anhydrous magnesium carbonate content (%) = (B / (A + B)) × 100
X: Temperature after end point of weight loss peak between 300 ° C. and 350 ° C. starting from around 250 ° C. Y: Temperature after end point of weight loss peak starting at around 250 ° C. between 450 ° C. and 500 ° C.

The above evaluation results are shown in Tables 1 to 4.

The test piece obtained in Example 1 had a relatively high thermal conductivity of 1.4, and the moisture resistance evaluation showed good results in both water absorption and appearance. On the other hand, the test piece obtained in Comparative Example 1 (in the case of using a magnesium oxide-untreated sample) had a rough surface appearance of the plate in the moisture resistance evaluation, and obtained a result that was significantly inferior to Example 1.

Further, Comparative Example 3 (when basic magnesium carbonate is used) is inferior to Example 1 in thermal conductivity and water absorption, and further, foaming occurs during the extrusion process to obtain a resin composition. The problem of remarkably lowering occurred.

Further, Comparative Example 5 (in the case of using a 1: 1 blend of basic magnesium carbonate and magnesium oxide) and Comparative Example 6 (in the case of using magnesium oxide subjected to silane coupling treatment) are plates with a moisture resistance evaluation. Surface roughness of the appearance occurred, and the result was significantly inferior to that of Example 1.

The test piece obtained in Example 7 has a thermal conductivity of 1.3, a synthetic product having an average particle size distribution of 50 μm or less, and a natural product having a particle size distribution of 50 μm or more. The results showed good results in both water absorption and appearance. In Comparative Example 1 (when magnesium oxide is used), the thermal conductivity of magnesium oxide particles is slightly higher than that of anhydrous magnesium carbonate, and thus the thermal conductivity is 1.9 W / mK, which is higher than that of Example 1. Although a value was recognized, a result with poor moisture resistance was obtained. Comparative Example 2 (in the case of using commercially available anhydrous magnesium carbonate) Although the moisture resistance evaluation was equivalent to that in Example 7, a result of inferior thermal conductivity was obtained. Further, Comparative Example 3 (in the case of using basic magnesium carbonate) is inferior to Example 7 in thermal conductivity and moisture resistance, and further, a foaming phenomenon occurs during extrusion to obtain a molding resin composition. There was a problem that the workability was significantly reduced. Comparative Example 4 (when natural magnesite was used) The moisture resistance was the same as in Example 7, but the thermal conductivity was inferior. The particle size distribution width is a high value compared with the coefficient of variation 0.6 and 0.39 of Example 7, and it is estimated that the thermal conductivity is inferior from the aspect of forming the heat conduction path.

Also, as in Example 9, when the thermally conductive filler of the present invention was used, the combined use of boron nitride and glass fiber also showed higher thermal conductivity than others. This has an effect as an efficient heat conduction path between boron nitride in the molded product because the average particle diameter of the heat conductive filler is large, and the Mohs hardness of the filler is 3.5 as in anhydrous magnesium carbonate. For this reason, it is presumed that the diameter reduction due to the destruction of boron nitride can be suppressed and high thermal conductivity can be maintained. Also when the magnesium oxide of the comparative example 10 was used, it became a result whose heat conductivity is lower than Example 9, and it is suggested that magnesium oxide has contributed to destruction of boron nitride.

According to the present invention, it is possible to obtain a heat conductive filler having improved moisture and heat resistance. In addition, the resin composition containing the heat conductive filler can be easily molded without impairing fluidity, has both high heat conductivity and heat and humidity resistance, and is exposed to a long period of time under high temperature and high humidity. However, it is possible to obtain a molded body capable of maintaining a good appearance. Therefore, the resin assembly of the present invention is suitable for highly heat-conductive materials that are desired to be thinner and more complicated, for example, electrical and electronic parts, automobile parts, lighting parts, water heater parts, fibers, and film applications. It can use suitably for.

Claims (16)

1. A thermally conductive filler, wherein the magnesium oxide is a particle formed by coating with magnesium carbonate.
2. 2. The thermal conductivity according to claim 1, wherein the average particle diameter of the particles is in the range of 20 to 100 μm, and the value obtained by [(d84% −d16% / 2) / average particle diameter] is 0.5 or less. Filler.
3. The thermally conductive filler according to claim 1 or 2, wherein the content of magnesium carbonate in the particles is 1.0 to 99.9 mass%.
4. The thermally conductive filler according to any one of claims 1 to 3, wherein the magnesium carbonate contains anhydrous magnesium carbonate.
5. The thermally conductive filler according to claim 4, wherein the content of anhydrous magnesium carbonate in the magnesium carbonate is 30% by mass or more.
6. The manufacturing method of the heat conductive filler characterized by including the process of hydrothermally treating the slurry formed by disperse | distributing magnesium oxide particle | grains in water in presence of a carbon dioxide.
7. The method for producing a thermally conductive filler according to claim 6, wherein the average particle diameter of the magnesium oxide particles is in the range of 20 to 100 µm.
8. The method for producing a thermally conductive filler according to claim 6 or 7, wherein the use ratio of the magnesium oxide particles and water in the slurry is in the range of 50 to 2000 parts by mass of water with respect to 100 parts by mass of the magnesium oxide particles.
9. The method for producing a thermally conductive filler according to any one of claims 6 to 8, wherein the hydrothermal treatment includes a step of holding at a temperature of 100 ° C or higher and 270 ° C or lower in the presence of carbon dioxide.
10. The method for producing a thermally conductive filler according to any one of claims 6 to 9, wherein the hydrothermal treatment has a two-stage process at different temperatures.
11. A thermally conductive filler obtained by the production method according to any one of claims 6 to 10.
12. A resin composition comprising the thermally conductive filler according to any one of claims 1 to 5 or 11, and a resin.
13. The resin composition according to claim 12, wherein the resin is a thermoplastic resin.
14. A highly heat-conductive material comprising the resin composition according to claim 12 or 13.
15. A molded article obtained by molding the resin composition according to claim 12 or 13.
16. A highly heat-conductive material comprising the molded product according to claim 15.