Aluminum nitride powder and method for producing same
阅读说明：本技术 氮化铝系粉末及其制造方法 (Aluminum nitride powder and method for producing same ) 是由 田中贵雅 楠井润 中岛克己 东村和哉 菅野周平 于 2018-05-17 设计创作，主要内容包括：本发明课题在于提供一种氮化铝系粉末,其中,无法完全除去的微粉少,对于高分子材料的填充性优异,而且导热性也优异。本发明的氮化铝系粉末是由氮化铝系粒子形成的粉末,其特征在于,(1)平均粒径D50为15～200μm,(2)粒径为5μm以下的粒子的含量以个数基准计为60％以下,(3)碱土金属元素及稀土元素的含量为0.1重量％以下,(4)氧含量为0.5重量％以下,(5)硅含量为1000重量ppm以下,铁含量为1000重量ppm以下。(The present invention addresses the problem of providing an aluminum nitride-based powder that has a small amount of fine powder that cannot be completely removed, has excellent filling properties for polymer materials, and has excellent thermal conductivity. The aluminum nitride-based powder is a powder composed of aluminum nitride-based particles, and is characterized in that (1) the average particle diameter D50 is 15-200 [ mu ] m, (2) the content of particles having a particle diameter of 5 [ mu ] m or less is 60% or less by number, (3) the content of alkaline earth metal elements and rare earth elements is 0.1 wt% or less, (4) the oxygen content is 0.5 wt% or less, (5) the silicon content is 1000 wt ppm or less, and the iron content is 1000 wt ppm or less.)
1. An aluminum nitride-based powder comprising aluminum nitride-based particles, characterized in that,
(1) the average grain diameter D50 is 15-200 μm,
(2) the content of particles having a particle diameter of 5 μm or less is 60% or less by number,
(3) the contents of alkaline earth metal elements and rare earth elements are 0.1 wt% or less,
(4) an oxygen content of 0.5 wt% or less,
(5) the silicon content is 1000 ppm by weight or less, and the iron content is 1000 ppm by weight or less.
2. The aluminum nitride-based powder according to claim 1, which comprises aggregated particles in which fine particles having a particle diameter of 5 μm or less are fixed to particles having a particle diameter of more than 5 μm.
3. The aluminum nitride-based powder according to claim 1, which comprises aggregated particles in which fine particles having a particle diameter of 1 μm or less are fixed to particles having a particle diameter of more than 5 μm, and the average number of fine particles fixed to one surface of particles having a particle diameter of more than 5 μm is 50 or less.
4. The aluminum nitride-based powder according to claim 1, wherein the carbon content is 0.1 wt% or less.
5. The aluminum nitride-based powder according to claim 1, having a BET specific surface area of 0.08m2/g～0.5m2/g。
6. A method for producing an aluminum nitride-based powder, characterized by comprising a step of heat-treating an aluminum nitride powder raw material in a non-oxidizing atmosphere at 1600 to 2000 ℃, wherein a) the content of an alkaline earth metal element and a rare earth element is 0.1 wt% or less, b) the content of oxygen is 0.5 wt% or less, c) the content of silicon is 1000 wt ppm or less, and the content of iron is 1000 wt ppm or less.
7. The production method according to claim 6, wherein the aluminum nitride powder raw material is a pulverized material.
8. The method according to claim 6, wherein the step of preparing the aluminum nitride powder raw material further comprises, before the step of preparing the aluminum nitride powder raw material, the steps of: an aluminum nitride powder raw material is obtained by pulverizing a reactant obtained by reacting aluminum with nitrogen.
9. A composition comprising the aluminum nitride-based powder according to any one of claims 1 to 5 and a polymer material.
Technical Field
The present invention relates to an aluminum nitride-based powder and a method for producing the same. In particular, the present invention relates to aluminum nitride-based particles having high heat dissipation properties and high thermal conductivity, which are suitable as filler powders for heat dissipation sheets, greases, adhesives, paints, and the like, each of which is based on a polymer material such as a resin, and a method for producing the same.
Background
With the miniaturization, thinning, and high functionality of electronic products such as notebook computers and tablet computers, there is an increasing demand for high integration of IPUs, integrated circuits, and the like used in the computers. When the integration is advanced to such a high level, the amount of heat generated during operation increases, and therefore, it is necessary to efficiently dissipate the heat. In general, a polymer material such as a resin is used as a heat dissipating member in these electronic components, but since the heat conductivity thereof is extremely low, it is necessary to combine the heat dissipating member with a filler having high heat conductivity.
Various materials have been proposed as fillers having high thermal conductivity, and particularly, aluminum nitride has high thermal conductivity close to that of metal, and therefore, the sintered body thereof has been put to practical use as a substrate for semiconductor, and in addition, it can be used in the form of powder as a filler for heat dissipation.
Generally, aluminum nitride used as a filler is an aluminum nitride powder having an average particle diameter of about 1 to 100 μm, and is preferably blended in a resin at a filling rate of 60 vol% or more (particularly 70 vol% or more) in order to obtain a desired thermal conductivity. In addition, in order to further increase the filling ratio, fillers having different particle size distributions may be combined. In this case, generally, an aluminum nitride powder having a large average particle diameter of 10 μm or more is excellent in filling property with a resin, and therefore, it exerts an important function as a filler together with a fine aluminum nitride powder.
Therefore, various production methods have been proposed for such an aluminum nitride powder having a relatively large particle diameter.
For example, there is a method for producing a large-particle-size aluminum nitride powder, which is characterized by pressing and granulating a mixed powder composed of 100 parts by weight in total of 30 to 80 parts by weight of a metallic aluminum powder and 70 to 20 parts by weight of an aluminum nitride powder, firing the resulting mixed granules at 800 to 1200 ℃ in a nitrogen-containing non-oxidizing atmosphere, and then crushing and classifying the granules (patent document 1).
Further, for example, a method for producing spherical aluminum nitride-based particles, which is characterized by comprising the steps of: a firing step (I) in which porous alumina particles are fired at a temperature of 1450-1900 ℃ and nitrided until the aluminum nitride content reaches 50-90 mass%; and a firing step (II) in which the particles obtained in the firing step (I) are fired at a temperature of 1580 to 1900 ℃ in an atmosphere having a reducing gas concentration higher than that in the firing step (I) so as to be nitrided to have an aluminum nitride content of 75 to 99 mass%; the spherical aluminum nitride-based particles have an average particle diameter of 10 to 200 [ mu ] m and a sphericity of 0.80 or more, and are formed of a core containing aluminum oxynitride and a surface layer formed of aluminum nitride formed on the surface of the core and having a thickness of 2 [ mu ] m or more, and the particles have an aluminum nitride content of 75 to 99 mass% and a relative density of 85% or more (patent document 2).
Further, there is provided a method for producing aluminum nitride particles, comprising the steps of: a reduction nitridation step of subjecting the porous alumina particles to reduction nitridation at a temperature of 1400 ℃ to 1700 ℃ to obtain porous aluminum nitride particles; and a sintering step of sintering the porous aluminum nitride particles obtained in the reduction-nitridation step at 1580 ℃ to 1900 ℃ inclusive (patent document 3).
Another method is known as a method for producing sintered aluminum nitride particles, which comprises, for example, extrusion-molding a resin composition containing a thermoplastic resin, an aluminum nitride powder and a sintering aid to form a strand-like green body, then cutting the strand-like green body to obtain a green sheet, and then firing the obtained green sheet (patent document 4).
Further, a method for producing aluminum nitride is known, which is characterized by nitriding aluminum metal powder having an average particle size of 10 to 250 μm by a combustion synthesis reaction in a nitrogen atmosphere of 2 to 30 atmospheres (patent document 5).
Disclosure of Invention
Problems to be solved by the invention
However, in the method of patent document 1 or patent document 5, fine aluminum nitride powder is by-produced in the crushing step for obtaining powder, and the fine aluminum nitride powder is hard to be removed by classification or the like because it is strongly adhered to other particles. Further, the aluminum nitride powder mixed with such fine powder which cannot be completely removed is difficult to be mixed in a large amount into the resin, and improvement of the filling ratio with respect to the resin cannot be expected.
The methods of
In the methods of
In the method as in patent document 4, aluminum nitride particles having a large particle diameter can be produced relatively easily, but a sintering aid such as yttrium oxide itself may cause a reduction in thermal conductivity. Further, if the aluminum nitride used as a raw material contains impurities, this also becomes a cause of hindering the improvement of the thermal conductivity.
Accordingly, a main object of the present invention is to provide an aluminum nitride-based powder which has a small amount of fine powder that cannot be completely removed, has excellent filling properties with a polymer material, and has excellent thermal conductivity.
Means for solving the problems
The present inventors have made extensive studies in view of the problems of the prior art, and as a result, have found that an aluminum nitride-based powder obtained by a specific production method has a specific structure and characteristics, and have completed the present invention.
That is, the present invention relates to the following aluminum nitride-based powder and a method for producing the same.
1. An aluminum nitride-based powder comprising aluminum nitride-based particles, characterized in that,
(1) an average particle diameter D50 of 15 to 200 μm,
(2) the content of particles having a particle diameter of 5 μm or less is 60% or less by number,
(3) the contents of alkaline earth metal elements and rare earth elements are 0.1 wt% or less,
(4) an oxygen content of 0.5 wt% or less,
(5) the silicon content is 1000 ppm by weight or less, and the iron content is 1000 ppm by weight or less.
2. The aluminum nitride-based powder according to claim 1, which contains aggregated particles in which fine particles having a particle diameter of 5 μm or less are fixed to particles having a particle diameter of more than 5 μm.
3. The aluminum nitride-based powder according to claim 1, which contains aggregated particles in which fine particles having a particle diameter of 1 μm or less are fixed to particles having a particle diameter of more than 5 μm, and the average number of fine particles fixed to one surface of particles having a particle diameter of more than 5 μm is 50 or less.
4. The aluminum nitride-based powder according to claim 1, wherein the carbon content is 0.1 wt% or less.
5. The aluminum nitride-based powder according to claim 1, which has a BET specific surface area of 0.08 to 0.5m2/g。
6. A method for producing an aluminum nitride-based powder, characterized by comprising a step of heat-treating an aluminum nitride powder raw material in a non-oxidizing atmosphere at 1600 to 2000 ℃, wherein a) the content of an alkaline earth metal element and a rare earth element is 0.1 wt% or less, b) the content of oxygen is 0.5 wt% or less, c) the content of silicon is 1000 wt ppm or less, and the content of iron is 1000 wt ppm or less.
7. The production method according to claim 6, wherein the aluminum nitride powder raw material is a pulverized material.
8. The production method according to item 6 above, wherein, prior to the step, the step of preparing the aluminum nitride powder raw material further comprises: an aluminum nitride powder raw material is obtained by pulverizing a reactant obtained by reacting aluminum with nitrogen.
9. A composition comprising the aluminum nitride-based powder according to any one of items 1 to 5 and a polymer material.
Effects of the invention
According to the present invention, an aluminum nitride-based powder can be provided which has a small amount of fine powder that cannot be completely removed, has excellent filling properties with a polymer material, and also has excellent thermal conductivity.
According to the aluminum nitride-based powder of the present invention, since the fine particles (particularly, fine particles having a particle diameter of 5 μm or less) that inhibit the filling property into the polymer material are reduced, the fine particles can be blended into the polymer material at a high filling ratio, and as a result, a material that can exhibit high thermal conductivity and heat dissipation properties can be provided. Further, the aluminum nitride-based powder of the present invention can be controlled to a desired particle size without using additives such as a sintering aid and an organic binder, and therefore, the original characteristics of aluminum nitride can be obtained more reliably than when these additives are contained.
Further, according to the production method of the present invention, even when a ground product containing a large amount of fine powder is used as a raw material, the fine powder can be taken up into large particles by a predetermined heat treatment and substantially fixed or integrated, and as a result, the fine powder can be efficiently reduced and a powder comprising particles having a large particle size can be obtained.
The aluminum nitride-based powder of the present invention having such characteristics is suitably used, for example, as a highly thermally conductive filler (filler powder) used for a grease, an adhesive, a paint, or the like, in addition to a highly thermally conductive molded product using a polymer material (synthetic resin or the like) as a base. More specifically, the aluminum nitride-based powder of the present invention or the resin composition containing the same can be used as a case, a chassis, a substrate, a sealing material, a heat conductive plate, a heat sink, and other high thermal conductive materials of a device (e.g., IPU, integrated circuit, power module, display, LED lamp, current transformer, charger, etc.) on which a heat generating component is mounted.
Drawings
FIG. 1 is a graph showing the results of observing the particles of the aluminum nitride powder obtained in example 1 with a scanning electron microscope. Fig. 1(a) shows particles before heat treatment. Fig. 1(b) shows the particles after the heat treatment.
FIG. 2 is a graph showing the number of fine particles fixed to the surface of base particles in the aluminum nitride powder obtained in example 1.
FIG. 3 is a graph showing the number of fine particles fixed to the surface of base particles in the aluminum nitride powder obtained in comparative example 4.
Detailed Description
1. Aluminum nitride-based powder
The aluminum nitride-based powder of the present invention (the powder of the present invention) is a powder comprising aluminum nitride-based particles,
(1) an average particle diameter D50 of 15 to 200 μm,
(2) particles having a particle diameter of 5 μm or less are 60% or less by number,
(3) the contents of alkaline earth metal elements and rare earth elements are 0.1 wt% or less,
(4) an oxygen content of 0.5 wt% or less,
(5) the silicon content is 1000 ppm by weight or less, and the iron content is 1000 ppm by weight or less.
The average particle diameter D50 of the powder of the present invention is 15 to 200 μm, preferably 50 to 150 μm. When the average particle diameter D50 is less than 15 μm, the filling property with the polymer material may be lowered. When the average particle diameter D50 exceeds 200 μm, the polymer material may be separated from the polymer material when mixed with a polymer material such as a resin.
In the powder of the present invention, the content of particles having a particle diameter of 5 μm or less is 60% or less, preferably 55% or less by number. If the content exceeds 60%, the filling property into the polymer material is lowered, and a composition having high thermal conductivity or heat dissipation property cannot be obtained. The lower limit of the content is preferably 0%, and usually about 0.1%.
As described above, fine particles having a particle diameter of 5 μm or less (particularly, 1 μm or less) are an obstacle to filling with a polymer material, and if the amount is large, it is difficult to produce a desired resin composition or the like. Therefore, it is desired to remove fine particles, but fine particles do not exist alone and tend to adhere to larger particles. Therefore, it is difficult to completely separate only the fine particles by classification or the like, and even separation requires a large amount of labor and cost. In contrast, in the powder of the present invention, such fine particles are greatly reduced. This makes it possible to reduce the content of fine particles without a separation treatment by fixing or integrating fine particles to other particles (particularly, particles having a particle diameter of more than 5 μm) as in the case of the powder of the present invention obtained by the production method of the present invention. Therefore, one of the characteristics of the powder of the present invention is that it contains at least aggregated particles in which fine particles having a particle diameter of 5 μm or less are fixed to particles having a particle diameter of more than 5 μm. The aggregated particles can be expressed as substantially one particle in at least the polymer material, and do not adversely affect the filling property into the polymer material. Herein, the term "fixed" means a state in which fine particles are fixed to other particles while adhering to each other, and the form of the fine particles is still recognizable.
However, if the number of fine particles having a particle diameter of 5 μm or less (preferably 1 μm or less) is increased for 1 particle (base particle) exceeding 5 μm, the number of fine particles falling off (separated) from the base particle may increase during kneading with a resin or the like, and therefore, the smaller the number of fine particles fixed to the base particle, the better. In particular, when the aggregated particles are composed of base particles to which fine particles having a particle diameter of 1 μm or less are fixed and the number of fine particles having a particle diameter of 1 μm or less fixed to the base particles is observed with an electron microscope or the like, the average number of fine particles fixed to the base particles (the number of fine particles present per 1 base particle) is preferably 50 or less, more preferably 10 or less, in a visual field when the entire base particles are observed from one direction. The lower limit value is preferably as small as possible, for example, 1. More specifically, 30 substrate particles (particles having a particle diameter exceeding 5 μm) having a size of ± 15% with respect to the average particle diameter D50 are arbitrarily selected, and the number of fine particles having a particle diameter of 1 μm or less present on the surface of each substrate particle (in a visual field when one substrate particle is viewed in one direction as a whole) is counted, and the average number of fine particles present in 30 substrate particles (the number of fine particles present per 1 substrate particle) is preferably 50 or less, and more preferably 1 to 10.
The content of the alkaline earth metal element and the rare earth element in the powder of the present invention is 0.1 wt% or less, preferably 0 to 0.05 wt%. If the content exceeds 0.1 wt%, the characteristics inherent in aluminum nitride (particularly, thermal conductivity) may not be sufficiently obtained. The content is the total content of the alkaline earth metal element and the rare earth element.
The alkaline earth metal element includes, for example, at least 1 of calcium, strontium, barium and radium. Further, as the rare earth element, at least 1 of yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium can be cited. Therefore, the powder of the present invention is also characterized by not containing a sintering aid such as yttria or a component derived therefrom (particularly the above-mentioned element).
The oxygen content of the powder of the present invention is usually 0.5% by weight or less, preferably 0.2% by weight or less. If the oxygen content exceeds 0.5% by weight, the thermal conductivity is lowered. The lower limit of the oxygen content is not limited, and may be usually about 0.01 wt%.
The carbon content of the powder of the present invention is usually 0.1% by weight or less, preferably 0.06% by weight or less. If the carbon content exceeds 0.1 wt%, the thermal conductivity may be lowered. The lower limit of the carbon content is not limited, and may be usually about 0.005% by weight.
The powder of the present invention has a silicon content of 1000 ppm by weight or less and an iron content of 1000 ppm by weight or less. The lower limits of the silicon content and the iron content are not particularly limited, and in order to avoid an increase in cost due to purification, they may be generally about 100 ppm by weight. Therefore, as a raw material of the powder of the present invention, an aluminum nitride powder obtained by a so-called direct nitriding method is suitably used. More specifically, an aluminum nitride powder obtained by pulverizing a reaction product obtained by reacting aluminum with nitrogen gas can be used as a raw material.
The BET specific surface area of the powder of the present invention is preferably 0.05 to 0.50m2A specific preferred range is 0.08 to 0.49m2(ii) in terms of/g. Therefore, for example, it can be set to 0.05 to 0.1m2(ii) in terms of/g. Setting within this range can effectively suppress an increase in viscosity up to kneading into a resin or the like, and as a result, a high filling ratio can be obtained.
In the present invention, the viscosity of the mixture obtained when the powder of the present invention is added to a polymer material can be used as an index indicating the filling property with respect to the polymer material.
First, the following aspects can be mentioned: in the mixture of the polymer material and the powder of the present invention, the amount of the powder of the present invention to be blended is large for achieving a certain viscosity. More specifically, as shown in test example 1(5-1) described later, when the amount of the powder of the present invention added is increased relative to the silicone oil, the content (filling ratio) of the powder of the present invention at a time point at which the viscosity of the mixture is in the range of 45 to 50 pas (25 ℃) is used as an index. In the present invention, the filling ratio is preferably 50% by volume or more, particularly preferably 55% by volume or more, and most preferably 60% by volume or more. In the conventional aluminum nitride powder containing fine particles, since the fine particles are present in a large amount, the aluminum nitride powder is thickened by adding a small amount of the aluminum nitride powder to reach the above-mentioned certain viscosity. In contrast, the powder of the present invention may be blended in an amount of 50 vol% or more until the above-mentioned certain viscosity is reached. That is, this value represents that high filling property can be exhibited for a polymer material.
Second, the filling ratio of the powder of the present invention in the mixture is fixed, and the viscosity of the composition thus obtained is used as an index. In the present invention, as shown in test example 1(5-2) described later, the filling ratios of the powder of the present invention in the mixture with the silicone oil were set to 50% by volume and 60% by volume, and the viscosities were measured respectively. The viscosity of the powder of the present invention at a filling rate of 50 vol% is preferably 25 pas or less, and particularly preferably 8 to 22 pas. Similarly, the viscosity of the powder of the present invention having a filling rate of 60 vol% is preferably 45 pas or less, and particularly preferably 25 to 36 pas. Thus, the powder of the present invention can maintain a low viscosity (i.e., high flowability) even at a constant filling rate.
2. Method for producing aluminum nitride powder
The powder of the present invention can be suitably produced, for example, by a method for producing an aluminum nitride-based powder, which comprises a step (heat treatment step) of heat-treating an aluminum nitride powder raw material in a non-oxidizing atmosphere at 1600 to 2000 ℃ wherein a) the content of an alkaline earth metal element and a rare earth element is 0.1 wt% or less, b) the content of oxygen is 0.5 wt% or less, c) the content of silicon is 0 to 1000 ppm by weight, and the content of iron is 0 to 1000 ppm by weight.
Starting material
In the present invention, an aluminum nitride powder raw material having a) a content of an alkaline earth metal element and a rare earth element of 0.1 wt% or less, b) an oxygen content of 0.5 wt% or less, c) a silicon content of 0 to 1000 ppm by weight and an iron content of 0 to 1000 ppm by weight is used as a starting material.
The powder material itself may be any known or commercially available material. Further, an aluminum nitride powder produced by a known production method can be used. For example, any of aluminum nitride powder obtained by reducing an alumina powder (aluminum nitride powder obtained by a reduction method), aluminum nitride powder obtained by nitriding an aluminum powder (aluminum nitride powder obtained by a direct nitriding method), and the like can be used. Among them, the aluminum nitride powder produced by the direct nitriding method is preferably used from the viewpoint of low cost and easy production of the aluminum nitride powder. In the present invention, the direct nitriding method includes a combustion synthesis method in addition to a method of heating the aluminum metal powder to 1000 ℃ or higher in nitrogen (direct nitriding method in a narrow sense). That is, the aluminum nitride powder obtained by the method including the step of nitriding the aluminum metal powder by the combustion synthesis reaction is also suitable as the raw material of the aluminum nitride powder.
In the present invention, as the aluminum nitride powder raw material, a pulverized product is suitably used. That is, a pulverized product obtained by mechanically pulverizing the synthesized aluminum nitride coarse powder or cake can also be suitably used. In the production method of the present invention, even when fine particles (usually having a particle diameter of 5 μm or less, particularly 1 μm or less) are contained as a pulverized product and a part or the whole of such fine particles are composed of a powder which cannot be removed, the fine particles are fixed or integrated into larger particles by a specific heat treatment, and thus the reduction in filling properties due to the fine particles can be effectively suppressed.
Therefore, the present invention is suitable for using, as a starting material, an aluminum nitride powder obtained by a direct nitriding method as a pulverized product. That is, the present invention also includes a method comprising the steps of: the starting material is prepared by a direct nitridation process prior to the heat treatment process. More specifically, the present invention also includes a method comprising, before the heat treatment step, the steps of: an aluminum nitride powder raw material is obtained by pulverizing a reactant obtained by reacting aluminum with nitrogen.
The average particle diameter D50 of the aluminum nitride powder raw material is not particularly limited, but is usually about 1 to 200 μm, and particularly preferably 15 to 100 μm. The shape of the particles constituting the aluminum nitride powder raw material is not limited, and may be, for example, any of spherical, flat, amorphous, and the like. However, since a pulverized product can be used, a powder formed of angular amorphous particles is also suitable as a starting material. According to the production method of the present invention, as shown in fig. 1, for example, the particles having characteristic corner shapes of the pulverized product (fig. 1(a)) are also changed to relatively smooth shapes with their corners removed (fig. 1 (b)). That is, one of the characteristics of the powder of the present invention is composed of aluminum nitride-based particles having a shape with rounded corners. This can be obtained by a heat treatment step described later.
Heat treatment Process
In the heat treatment step, the aluminum nitride powder raw material is heat-treated at 1600 to 2000 ℃ in a non-oxidizing atmosphere.
The heat treatment temperature is usually about 1600 to 2000 ℃, and 1650 to 1950 ℃ is particularly preferable. By heat treatment at such a temperature, fine particles (particularly fine particles having a particle diameter of 5 μm or less) can be effectively fixed or integrated to larger particles. Meanwhile, particles having rounded corners can be produced by removing corners of particles having an amorphous shape with corners. The heat treatment atmosphere may be a non-oxidizing atmosphere, and may be, for example, a reducing atmosphere, an inert gas atmosphere, or a vacuum atmosphere. The heat treatment time is usually set appropriately within a range of 0.5 to 48 hours, but is not limited thereto.
After the heat treatment step, a treatment such as classification may be performed as necessary, and particularly in the present invention, it is desirable not to perform the pulverization step. Since fine powder is generated in the grinding step, it is desirable that the grinding for adjusting the particle size is performed before the heat treatment step.
3. Compositions containing the powders of the invention
The present invention includes a composition containing the powder of the present invention and a polymer material (the composition of the present invention). That is, a highly thermally conductive composition containing a polymer material and the powder of the present invention as a highly thermally conductive filler is also included in the present invention.
Examples of the polymer material include resins, rubbers, and elastomers. More specifically, examples of the resin component include: silicone resin, phenol resin, urea resin, melamine resin, xylene resin, diallyl phthalate resin, epoxy resin, thermosetting polybutadiene, furan resin, polyurethane resin, alkylbenzene resin, melamine resin, unsaturated polyester resin, saturated alkyd resin (glyphosate resin, unsaturated alcohol-modified phthalic acid resin, isophthalic acid resin, terephthalic acid resin, aliphatic polyester resin, polycarbonate resin), and the like. Examples of the rubber include: fluororubbers, silicone rubbers, urethane rubbers, and the like. Examples of the elastomer include: styrene-based elastomers, polyolefin-based elastomers, polyvinyl chloride-based elastomers, polyurethane-based elastomers, polyamide-based elastomers, and the like. These polymer materials may be liquid or solid at ordinary temperature. The polymer materials themselves may be known or commercially available ones.
Among these, the powder of the present invention is suitably used as a filler (filler) for a silicon-based polymer material such as a silicone resin. The powder of the present invention can be blended with a silicon-based polymer material at a high filling ratio.
In the composition of the present invention, additives other than the powder of the present invention may be blended within a range not to impair the effects of the present invention. Examples thereof include fillers, coloring materials, antioxidants, ultraviolet absorbers, plasticizers, and the like other than the powder of the present invention.
By incorporating the powder of the present invention into these various materials, a resin composition having excellent thermal conductivity and the like can be produced. In this case, the content of the powder of the present invention in the composition of the present invention is not particularly limited, and a composition having a high filling rate of usually 50% by volume or more, particularly 60 to 90% by volume, and further 80 to 95% by volume can be produced. The composition (composite material) can exhibit excellent thermal conductivity and heat dissipation properties by blending the powder of the present invention at a high filling ratio.
Any method may be employed for mixing the powder of the present invention with the polymer material as long as the powder can be uniformly mixed. For example, the components may be mixed by using a known mixer such as a stirrer or a kneader.
The composition of the present invention obtained in this manner can be provided in the form of a molded article by further molding. The molding method is not particularly limited, and known molding methods such as press molding, extrusion molding, and injection molding can be used.
In the molded body of the present invention, the specific aluminum nitride-based powder (filler) is relatively uniformly dispersed, and therefore, high thermal conductivity can be obtained. Therefore, for example, the material can be widely used for various products (electronic devices, automobile parts, medical devices, and the like) as a heat dissipating material or a highly heat conductive material. Particularly, it is suitable for use as a component of a device on which a heat generating component is mounted. In this case, the heat-dissipating material and the high-thermal-conductivity material are used under the same conditions as those of the known heat-dissipating material and the known high-thermal-conductivity material, and a desired effect can be obtained.
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