Method for producing granular boron nitride, and granular boron nitride

Abstract

Provided is a novel method for producing boron nitride. The method for producing a boron nitride composition containing granular boron nitride is characterized in that an iron boride composition containing an iron boride is subjected to a heat treatment at 1900-2300 DEG C in a nitrogen atmosphere.

Description

Technical Field

[0001] The present invention relates to a boron nitride composition, and more particularly to a boron nitride composition comprising granular boron nitride and a method for producing the same. The present invention also relates to a resin composition comprising such granular boron nitride and a resin material, a molded body comprising granular boron nitride and a resin material obtained by molding such a resin composition, and a method for producing the same. Background Art

[0002] Boron nitride (hereinafter also referred to as “BN”) is an insulating ceramic, and various crystal forms are known, such as c-BN having a diamond structure, h-BN having a graphite structure, and t-BN having a turbostratic structure.

[0003] Among them, h-BN has excellent thermal conductivity, solid lubricity, chemical stability, and heat resistance, so it is tried to be mixed as a filler into resin materials with low thermal conductivity to improve thermal conductivity. Such resin materials are used as heat dissipation components for integrated circuits in the electrical and electronic fields.

[0004] However, h-BN has the same stacked structure as graphite, and has large crystal anisotropy. h-BN is granular in macroscopic terms, but is a stack of plate-like crystals in microscopic terms. The plate-like crystal planes corresponding to the a-axis direction of the crystal are connected by strong covalent bonds, so they show a large thermal conductivity of nearly 400 W / mK. On the other hand, they are stacked in the thickness direction corresponding to the c-axis direction with weak van der Waals bonding, so they only show a small thermal conductivity of about 1 to 2 W / mK.

[0005] When such a boron nitride is mixed with a resin material to form a resin composition to produce, for example, a plate-shaped molded body, the plate-shaped boron nitride has a strong tendency to be oriented in the flow direction of the resin composition during molding, that is, in the plate surface direction of the molded body, and the obtained molded body has the following problem: although the thermal conductivity is excellent in the plate surface direction, only low thermal conductivity is shown in the thickness direction. Therefore, it is desired to improve the anisotropy of such granular BN.

[0006] For example, Japanese Patent Application Laid-Open No. 2013-147363 discloses a method for producing boron nitride containing metal oxides, which includes the following steps: mixing boron nitride with an oxide of at least one rare earth metal selected from yttrium, cerium and ytterbium and carbon, and performing a heat treatment in a non-oxidizing gas atmosphere. It is explained that the boron nitride produced by this method can maintain good molding processability as a resin composition even when it is added to a resin material in large quantities to form a resin composition for the purpose of improving thermal conductivity, solid lubricity, chemical stability, heat resistance, etc., and improves the thermal conductivity of the molded body in the thickness direction.

[0007] As a method for manufacturing granular boron nitride, the following manufacturing method is disclosed in International Publication No. WO2020 / 195298: a mixture containing a boron nitride component, an oxide of a rare earth element, and calcium oxide is heat-treated in a non-oxidizing gas atmosphere. In the case of using a resin composition obtained by mixing the granular boron nitride obtained by this method with a resin material for molding, the thermal conductivity of the obtained molded body is improved. In addition, in a preferred embodiment, the anisotropy related to the thermal conductivity of the molded body is suppressed. It is particularly described that even in the case of a large amount of mixed boron nitride, good molding processability can be maintained and the thermal conductivity of the obtained molded body can be improved.

[0008] It is explained that when the boron nitride obtained by these methods is mixed with a resin material and molded, the thermal conductivity in the thickness direction can be improved in particular, but when compared with the original thermal conductivity of the above-mentioned boron nitride, the thermal conductivity achieved has room for further improvement.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 2013-147363

[0012] Patent Document 2: International Publication No. WO2020 / 195298 Summary of the invention

[0013] Problems to be solved by the invention

[0014] Therefore, it is desirable to provide a new method for producing granular boron nitride, preferably spherical boron nitride. Furthermore, it is desirable to mix the granular, preferably spherical boron nitride produced by the production method as a filler into a resin material and mold the same, thereby improving the thermal conductivity of the resulting molded body and, in a preferred embodiment, suppressing its anisotropy.

[0015] Solutions for solving problems

[0016] The present inventors have repeatedly conducted intensive studies on the above technical problems and have newly discovered that a boron nitride composition containing granular boron nitride can be produced by nitriding the boron in the iron boride by heat-treating the iron boride in a nitrogen atmosphere.

[0017] The present invention provides a method for producing a boron nitride composition in a first aspect, characterized in that it is a method for producing a boron nitride composition containing granular boron nitride, wherein the iron boride composition containing iron boride is subjected to heat treatment in a nitrogen atmosphere to perform nitridation (specifically, the boron of the iron boride is nitrided). In a preferred embodiment of the present invention, the granular boron nitride also includes spherical boron nitride.

[0018] The present invention provides a boron nitride composition in the second subject matter, which is obtained by the manufacturing method as described above and includes granular boron nitride. In the boron nitride composition, in addition to the granular boron nitride generated by nitridation, it can also include: other components derived from the iron boride composition as a raw material (for example, iron components by-produced by nitridation of boron of the iron boride (for example, iron oxide, iron borate, iron nitride, iron carbide (when carbon is included in the raw material)), unreacted iron boride, impurities contained in the iron boride composition, etc.), amorphous boron nitride that has not become granular boron nitride, etc. In a preferred embodiment, the granular boron nitride also includes spherical boron nitride.

[0019] The present invention provides a granular boron nitride in the third subject matter, which is contained in the above-mentioned boron nitride composition. In a preferred embodiment, the granular boron nitride also includes spherical boron nitride. The granular boron nitride can be obtained in the following manner: the above-mentioned boron nitride composition is subjected to any appropriate treatment to remove the components contained in the boron nitride composition other than the granular boron nitride (such as the above-mentioned other components), for example, at least a part of such components is removed, preferably substantially all are removed. Such removal can be, for example, a washing treatment of the boron nitride composition using an acid (such as an acid aqueous solution), and in another embodiment, it can be a classification treatment to remove granular boron nitride that is smaller and / or larger than a specified size. In a particularly preferred embodiment, it can be such a washing treatment and a subsequent classification treatment. In one embodiment, such granular boron nitride also includes spherical boron nitride. In this case, for example, only spherical boron nitride having a substantially specified particle size distribution width can be taken out by a classification treatment.

[0020] Therefore, the present invention provides a method for producing granular boron nitride in the fourth aspect, wherein the boron nitride composition of the second aspect is acid-cleaned. In a preferred embodiment, the granular boron nitride also includes spherical boron nitride, and spherical boron nitride having a predetermined particle size distribution width can be obtained by applying a classification process.

[0021] The present invention provides a resin composition in the fifth subject matter, which comprises: the boron nitride composition of the second subject matter or the granular boron nitride, preferably spherical boron nitride, of the third subject matter and a resin material. Furthermore, the present invention provides a molding method of a molded body and a method for manufacturing a molded body in the sixth subject matter, characterized in that such a resin material is used for molding. Furthermore, the present invention provides a molded body in the seventh subject matter, which is manufactured by molding as described above.

[0022] Effects of the Invention

[0023] The present invention provides a new method for synthesizing boron nitride. The synthesis method can be applied to a method for manufacturing a boron nitride composition, and the manufactured boron nitride composition contains granular boron nitride. In a preferred embodiment, the boron nitride composition also contains spherical boron nitride. The boron nitride composition or granular boron nitride of the present invention can be used as a filler that can be formulated in a thermally conductive paste, a thermally conductive adhesive, a resin composition for a thermally conductive molded body, etc., and can impart improved thermal conductivity. In a preferred embodiment, the granular boron nitride is spherical in shape and / or has a large particle size, and more preferably has a more uniform particle size. In a molded body formulated with the granular boron nitride, further improved thermal conductivity can be imparted, and the anisotropy of thermal conductivity can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 In the figure, (a) and (b) show examples of SEM (scanning electron microscope) photographs of particulate boron nitride contained in the boron nitride composition obtained in Example 1.

[0025] Figure 2 An example of a SEM photograph of particulate boron nitride contained in the boron nitride composition obtained in Example 7 is shown.

[0026] Figure 3 An example of a SEM photograph of particulate boron nitride contained in the boron nitride composition obtained in Example 14 is shown.

[0027] Figure 4 An example of a SEM photograph of the iron boride composition obtained in Example 10 is shown.

[0028] Figure 5 An example of a SEM photograph of the iron boride composition obtained in Example 1 is shown.

[0029] Figure 6 An example of a SEM photograph of granular boron nitride (before acid cleaning) contained in the boron nitride composition obtained in Example 1 is shown.

[0030] Figure 7 In the figure, (a) is a SEM photograph of the granular boron nitride obtained in Example 1 (before acid cleaning). Corresponding to the SEM photograph, EDS is used to perform color mapping analysis on the C element (Figure (b)), the N element (Figure (c)), the Fe element (Figure (d)) and the O element (Figure (e)), and the EDS (energy dispersive X-ray spectroscopy) photograph obtained is represented in grayscale.

[0031] Figure 8In the figure, (a) is the SEM photograph of the granular boron nitride (after acid cleaning) obtained in Example 1. Corresponding to the SEM photograph, EDS is used to perform color mapping analysis on the C element (Figure (b)), the N element (Figure (c)), the Fe element (Figure (d)) and the O element (Figure (e)), and the EDS photograph obtained is represented by grayscale.

[0032] Fig. 9 Table 1 shows the treatment conditions of boriding and nitriding in Examples 1 to 27 and the measurement results of the shape, average particle size, particle size uniformity and sphericity index of the granular boron nitride contained in the obtained boron nitride composition.

[0033] Fig.10 Table 2 shows the measurement results of the average particle size, particle size uniformity, and ball index of the granular boron nitride obtained in Example 17 and Comparative Example 5 described in Patent Document 2 as Reference Examples 1 and 2.

[0034] Fig.11 Table 3 shows the results of measuring the thermal conductivity of molded bodies produced using the resin compositions of Examples 28 to 44 obtained by adding / mixing the granular boron nitride (after acid washing) obtained in the examples of the present invention to the epoxy resin material, the composition of the resin composition, and the pressing pressure. It should be noted that the results of measuring the thermal conductivity of molded bodies (Reference Examples 3 to 5) using the granular boron nitride of Reference Example 1 or 2 are also shown. DETAILED DESCRIPTION

[0035] Next, the method for producing a boron nitride composition containing granular boron nitride according to the present invention and the produced boron nitride composition will be mainly described in detail.

[0036] The granular boron nitride contained in the boron nitride composition produced by the method of the present invention is a granular boron nitride having various particle sizes. Depending on the production conditions, the granular boron nitride has a wide distribution ranging from powdery particles (granules) with very small particle sizes to particles with larger particle sizes. These are collectively referred to as "granular boron nitride". As described later, such granular boron nitride has various three-dimensional structures. Granular boron nitride whose particle three-dimensional structure is close to a true sphere (specifically, granular boron nitride having a spherical index of 10 or less described later) is simply referred to as "spherical boron nitride".

[0037] Specifically, in one embodiment, the granular boron nitride has a relatively small particle size, and may be a small particle to the extent that its three-dimensional structure is difficult to discern in the SEM photograph, i.e., a powder. In another embodiment, the particle size is relatively large, for example, it may be spherical as described above. The average particle size of the granular boron nitride is generally 1 μm to 100 μm, and in a preferred embodiment, it is 5 μm to 75 μm, for example, 10 μm to 60 μm, 10 μm to 50 μm, and 20 μm to 40 μm. It should be noted that the granular boron nitride contained in the boron nitride composition manufactured by the method of the present invention may also have an average particle size smaller or larger than such a range.

[0038] The spherical boron nitride contained in the boron nitride composition that can be produced by the method of the present invention has an average particle size within the above range, but in one embodiment, the average particle size is preferably 10 μm or more, more preferably 20 μm or more, further preferably 30 μm or more, for example 40 μm or more.

[0039] The method for producing a boron nitride composition of the present invention is characterized in that the iron boride composition containing iron boride is subjected to a heat treatment in a nitrogen atmosphere to perform nitridation. Here, "iron boride" refers to a compound of boron and iron that can be nitrided (i.e., can generate boron nitride) under heat treatment in a nitrogen atmosphere, preferably FeB and / or Fe2B, particularly preferably Fe2B, but not limited thereto. For example, it can also be Fe3B, Fe 3.5 Iron boride such as B.

[0040] When the iron boride composition contains both FeB and Fe2B, the FeB:Fe2B ratio is 0:10 to 10:0 on a molar basis, preferably 0:10 to 5:5, for example, 0:10 to 3:7 (in the case of "0", it essentially contains only one iron boride). It should be noted that the iron boride composition may contain other components (such as moisture, impurities accompanying the iron boride, raw material components used for synthesis when synthesizing the iron boride, other reaction products, etc.) in addition to the iron boride, as long as it does not substantially adversely affect the purpose of the present invention.

[0041] The heat treatment for nitriding can be carried out by heating the iron boride composition under a nitrogen atmosphere to synthesize boron nitride. The pressure of the atmosphere is not particularly limited, and can be under reduced pressure to under increased pressure, and can usually be carried out under normal pressure. The heating is carried out in a manner that maintains a temperature above 1750°C and below 2300°C, preferably below 2200°C, for example, in a manner that maintains 1800°C to 2100°C. At a heating temperature below 1750°C, the yield of boron nitride may sometimes be insufficient. In addition, at a heating temperature exceeding 2300°C, the iron boride may sometimes liquefy before boron nitride is generated. It should be noted that the heat treatment for nitriding can be carried out intermittently or continuously. In another embodiment, it can be carried out in a semi-intermittent manner to form a nitrogen atmosphere under a nitrogen flow.

[0042] The heating time is usually 2 to 20 hours, preferably 3 to 15 hours, for example, about 5 hours or about 10 hours, depending on the heating temperature. By heating in this way, the iron boride contained in the iron boride composition reacts with the nitrogen contained in the atmosphere to obtain a boron nitride composition. In a preferred embodiment, on the surface of the iron boride that is melted and becomes a droplet by heating, the iron boride reacts with nitrogen to generate boron nitride, and this process is repeated to obtain a boron nitride composition containing the generated granular boron nitride. At a heating time of less than 2 hours, the yield of boron nitride may sometimes be insufficient. In addition, at a heating time of more than 20 hours, impurities may sometimes be mixed from the insulating material of the device for heating the iron boride composition.

[0043] After the heat treatment for the prescribed time is implemented as described above, the boron nitride composition is cooled to obtain the boron nitride composition. The cooling can be implemented by any appropriate method, for example, by cooling to room temperature. The boron nitride composition obtained is included in the form of a powder in appearance (therefore, as observed with the naked eye, macroscopically), and in detail (therefore, as magnified and observed, microscopically) has a granular boron nitride of various three-dimensional structures and sizes. It should be noted that the boron nitride composition obtained, in addition to the granular boron nitride as a nitrided reaction product, can also include a very small or amorphous boron nitride that does not become granular boron nitride, an unreacted and residual component in the component contained in the iron boride composition that has been nitrided based on the heat treatment, an iron component (such as iron oxide, iron borate, iron nitride, iron carbide (the case of including carbon in the iron boride composition) etc.) generated by reaction, a component that does not participate in the reaction, etc.

[0044] Nitriding can be carried out, for example, by heating a heat-resistant container (e.g., a boron nitride crucible) containing iron boride under a nitrogen atmosphere, and maintaining the temperature of the iron boride at a predetermined temperature for a predetermined heating time. In one embodiment, the reaction can be carried out under a nitrogen flow in order to react boron with nitrogen in the iron boride and to remove impurities, byproducts during nitriding (e.g., CO, CO2, O2 gas, etc.) and the like (if they exist) outside the system.

[0045] The granular boron nitride contained in the boron nitride composition obtained by such nitridation based on heat treatment is in the form of so-called "granules" (i.e., granular) and has various three-dimensional structures. As such a three-dimensional structure, specifically, for example, it can be a plate-like, polyhedral, spherical, ellipsoidal, cylindrical, and conical shape and one of their parts, and it can also be various combinations of these examples. It should be noted that the obtained boron nitride composition, in addition to containing such granular boron nitride with a distinguishable three-dimensional structure, can also contain smaller substances, that is, very fine and powdery substances (such as species of granular boron nitride or substances such as its precursor) whose three-dimensional structure is not easy to distinguish, and usually such powdery substances also exist at least to some extent.

[0046] In one embodiment, the granular boron nitride contained in the boron nitride composition manufactured by the method of the present invention is a plurality of individual granular boron nitrides, usually an aggregate of many granular boron nitrides, and the individual granular boron nitrides have any of the above-mentioned various three-dimensional structures. Usually, the individual granular boron nitride has any three-dimensional structure of a polyhedron, an ellipsoid, a sphere, a plate, and various combinations thereof. The three-dimensional structure of the individual granular boron nitride can be observed by an electron microscope (e.g., SEM, with a magnification of 2000 times). Based on the microscope photograph, the type of the three-dimensional structure of the granular boron nitride can be determined by visual inspection. In addition, based on the microscope photograph, it can be determined what kind of three-dimensional structure the particles (particles) exist in what proportion. In this specification, very small granular boron nitride, which is not easy to judge the degree of the three-dimensional structure even by observation at such a magnification, is referred to as powdered boron nitride as described above. The particle size of such powdered particles is less than 1 μm.

[0047] An example of a typical SEM photograph of granular boron nitride contained in the boron nitride composition produced by the method of the present invention is shown in Figure 1 , Figure 2 as well as Figure 3 These photos are from Example 1 ( Figure 1 )、Example 7( Figure 2 ) and Example 14 ( Figure 3 ) obtained, it can be seen that the granular boron nitride has various three-dimensional structures and sizes. Figure 1 In Figure 1 A portion of (a) is enlarged and shown in Figure 1 (b). When observing them in detail, it can be seen that the granular boron nitride is a so-called granular (particle) shape that appears to be composed of a (convex) curved wall and has a spherical three-dimensional structure as a whole. It should be noted that Figure 3 It can be seen that in addition to the spherical boron nitride, other three-dimensional structures, such as plate-like granular boron nitride, are also generated. It should be noted that the boron nitride composition obtained in Example 1 was analyzed by X-ray diffraction, and the results confirmed that hexagonal boron nitride (h-NB) was generated and contained FeB, Fe2B, Fe2O3, Fe3O4 and other trace components.

[0048] As can be understood from the above-mentioned SEM photograph, in a preferred embodiment, the granular boron nitride is a spherical boron nitride having a three-dimensional structure close to a true sphere. As for the degree of closeness to a true sphere, the granular boron nitride that can be visually judged to be close to a sphere (i.e., spherical) in the SEM photograph can be evaluated using, for example, the "spherical index" described below.

[0049] <Ball Indicators>

[0050] 45 parts by mass of granular boron nitride whose spherical index is to be measured is added to an epoxy resin material (55 parts by mass), and the mixture is thermally cured without pressure to obtain a disc-shaped resin composite material. In the (two-dimensional) SEM cross-sectional photograph of the granular boron nitride when the disc-shaped resin composite material is cross-sectionally observed in the plate thickness direction (in-plane perpendicular direction) (magnification: 1000 to 3000 times according to the particle size, usually 2000 times), the longest diameter is selected as the major axis, and the length of the axis passing through the midpoint of the major axis and inclined at 45°, 90° and 135° relative to the major axis respectively (i.e., the axial diameter when the major axis is rotated 45° each time from the position of the major axis with the midpoint as the center, i.e., the length of the diameter) and the length of the axial diameter of the major axis (therefore, the length of the four axial diameters) are calculated. Their ratio (standard deviation / average axial diameter) × 100 is used as the spherical index for use in this specification. The smaller the value of the ball index is, the closer it is to a true sphere. For example, when the ball index is 0, it can be regarded as a true sphere. It should be noted that in this specification, spherical boron nitride refers to boron nitride with a ball index of 10 or less as described above. Fig. 9 The ball index described in Table 1 is obtained by measuring all the granular boron nitride present in the field of view of the cross-sectional photograph.

[0051] The sphericity index of the granular boron nitride contained in the boron nitride composition manufactured by the method of the present invention may also be close to 0 (for example, 0 < sphericity index < 0.7), usually less than 10, for example, less than 7, and may be substantially regarded as a true sphere (for example, a sphericity index of 0.7 to 1.4, etc.). The sphericity index is 0.7 to 10 in a preferred embodiment, and 0.7 to 8 in a more preferred embodiment, for example, 0.7 to 3. The sphericity index in such a range can be considered to have a substantially spherical three-dimensional structure. It should be noted that the sphericity index of the granular boron nitride obtained in Example 17 and Comparative Example 5 described in the above-mentioned Patent Document 2 was calculated, and the results were approximately 12.1 and 14.4, respectively.

[0052] As per Figure 1 to Figure 3 As can be understood from the photograph, the granular boron nitride contained in the boron nitride composition manufactured by the method of the present invention can have various particle sizes, and can also have a larger particle size depending on the manufacturing conditions. Specifically, in one embodiment, the granular boron nitride has a smaller particle size, and can be a small particle to the extent that its three-dimensional structure is not easy to distinguish in the SEM photograph (2000 times magnification), that is, the powdered boron nitride as described above. In addition, in another embodiment, the granular boron nitride is a granular with a larger particle size to the extent that the three-dimensional structure can be easily distinguished, and in a preferred embodiment, it can be spherical as described above. Of course, the granular boron nitride can also have both powdered boron nitride and larger granular boron nitride. The average particle size of the granular boron nitride is generally 2μm to 75μm, for example, 2.5μm to 60μm, and in a preferred embodiment, it is 10μm to 50μm, for example, 20μm to 40μm. The particulate boron nitride contained in the boron nitride composition produced by the method of the present invention may have an average particle size smaller or larger than the above range.

[0053] <Average particle size, Log average particle size, and Log standard deviation>

[0054] The boron nitride composition obtained by nitriding by heat treatment and then cooling according to the method of the present invention is pretreated as follows to prepare granular boron nitride (aggregates of individual granular boron nitrides having various particle sizes) whose average particle size is to be measured.

[0055] The boron nitride composition synthesized by nitriding the iron boride composition was acid-cleaned, filtered and dried, and 0.02 to 0.04 g of the obtained material was randomly taken as a sample, added to 20 ml of soapy water (a material obtained by mixing 1 g of kitchen liquid detergent (kitchen fresh, manufactured by Sankyo Oil) in 500 ml of pure water) as a dispersion medium, and stirred for 5 minutes using an ultrasonic cleaning machine (machine model: ultrasonic cleaning machine US-5 manufactured by NSD Co., Ltd.) to disperse the granular boron nitride contained in the sample. Then, the average particle size was measured while irradiating the sample with ultrasonic waves in a flow cell using a laser diffraction particle size distribution measuring device (SALD-2300 manufactured by Shimadzu Corporation).

[0056] Specifically, the horizontal axis represents the particle size interval that is a logarithmic scale of 0.01 to 1000 μm and is divided into 50 equal parts, and the vertical axis represents the volume-based relative particle amount corresponding to the particle size interval. j , X j+1 ](j=1, 2, ..., 50), then based on the logarithmic scale, the representative particle size in each particle size range can be calculated using the following formula (Formula 1).

[0057]

[0058] Although it is called a representative particle size, it is a logarithm, so it is not a unit of particle size at this point in time. j (j=1, 2, ..., 50) is set to be consistent with the particle size interval [x j , x j+1 ] The relative particle amount (difference %) corresponding to each interval is calculated by the following formula (Formula 2) when the total of all intervals is set to 100%.

[0059]

[0060] This μ is a value on a logarithmic scale and does not have a unit for the particle size. Therefore, in order to restore the unit of the particle size, 10 μ That is, μ raised to the power of 10 is used as the average particle size. In addition, the standard deviation for the average particle size can be obtained as follows. Based on μ representing the average particle size on a logarithmic scale, the standard deviation defined on the logarithmic scale can be calculated as follows (Formula 3), and σ is set to Log standard deviation (or Log particle size standard deviation).

[0061]

[0062] For such Log average particle size and Log standard deviation, refer to the following Internet information.

[0063] https: / / www.an.shimadzu.co.jp / powder / lecture / practice / p01 / lesson19.htm

[0064] https: / / www.an.shimadzu.co.jp / powder / lecture / practice / p01 / lesson20.htm

[0065] It should be noted that the average particle size mentioned in this specification has nothing to do with the agglomeration state of the particles. It is a numerical value obtained by the measurement method. Depending on the nature / condition of the particles, it is sometimes the average particle size of the primary particles, and sometimes the average particle size of the secondary particles. Depending on the situation, it is the average particle size measured in a state where both primary particles and secondary particles exist in a mixed state. In addition, the Log standard deviation calculated as described above is used as an indicator of the degree of dispersion of the particle size distribution (also referred to as "dispersion index" or "particle size uniformity"). That is, the smaller the numerical value of the dispersion index, the smaller the unevenness of the particle size, which means that the particle size distribution is sharper (the particle size is consistent).

[0066] As mentioned above, based on Figure 1 As can be understood from the SEM photograph of the boron nitride composition, in a preferred embodiment, the particle size (or size) of the granular boron nitride contained in the boron nitride composition produced by the method of the present invention is relatively uniform. As for the dispersion index of the granular boron nitride contained in the boron nitride composition obtained by the method of the present invention, the dispersion index of the granular boron nitride contained in the boron nitride composition obtained by nitriding is in the range of 0.3 or less in a preferred embodiment, and in the range of 0.2 or less in a more preferred embodiment, for example, in the range of 0.1 to 0.18.

[0067] In the nitriding based on heat treatment of the present invention, in a preferred embodiment, the iron boride composition contains at least one selected from rare earth oxides and alkaline earth metal oxides as an auxiliary agent in addition to iron boride. Preferred oxides as auxiliary agents are, for example, Y2O3, CeO2, La2O3, CaO and MgO. As a possible consideration, it is speculated that if such an auxiliary agent is used, the oxygen contained therein substantially reduces the melting temperature of the iron boride, as a result, the iron boride is helped to melt quickly to form droplets, as a result, the droplet-shaped iron boride can react quickly with the nitrogen contained in the atmosphere, as a result, the formation of boron nitride can be promoted. It should be noted that this speculation does not impose any limitation on the present invention.

[0068] If such an auxiliary agent is mixed into the iron boride composition and nitriding based on heat treatment is carried out, the generated granular boron nitride can have a larger particle size than when it is not mixed. It also depends on the operating conditions, but if the results of the examples described later are considered, the average particle size of the granular boron nitride obtained when the auxiliary agent is mixed is preferably increased by about 20% to 100%, more preferably by about 50 to 200%, for example, by 30% to 250%, compared with the average particle size of the granular boron nitride obtained by nitriding the iron boride composition without the auxiliary agent. For example, as described later, the average particle size of Example 1 is 17.6μm, but in Example 17 it becomes 34.9μm, an increase of about 100%. In addition, in Example 26 (the heat treatment temperature of the boriding is slightly different), the average particle size becomes 57.3μm, an increase of about 200% or more.

[0069] As for the amount of the mixed auxiliary agent, when it is assumed that the iron contained in the iron boride contained in the iron boride composition exists in the form of iron boride (FeB), and it is assumed that the boron contained in the iron boride is all converted into boron nitride, when it is expressed in the form of the ratio (mass %) of the mass of the mixed auxiliary agent to the mass of the generated boron nitride, it is preferably 0.5 mass % to 36 mass %, more preferably 1.4 mass % to 21 mass %, for example 1.4 mass % to 15 mass %. At a mixed amount less than the lower limit of such a range, the effect of the mixed auxiliary agent may not be sufficient, and the growth of the crystal may not be fully promoted. In addition, at a mixed amount more than the upper limit of such a range, the growth of the crystal is promoted, but the excessively grown particles may be destroyed, and the granular boron nitride in the form of a plate is also generated. It should be noted that auxiliary agents such as rare earth oxides and alkaline earth metal oxides increase the particle size of the granular iron boride before nitriding, and become oxides after forming boron nitride, but they can be removed by cleaning as described above or as described later.

[0070] Considering the results of the examples described later, the particularly preferred additives are Y2O3, CeO2 and CaO, and the amounts of these additives mixed are preferably 0.8% to 20% by mass, 1.2% to 31% by mass and 0.5% to 14% by mass, respectively, and more preferably 1.0% to 11% by mass, 1.5% to 26% by mass and 0.7% to 8% by mass, respectively. By mixing the additives in this way, the average particle size of the granular boron nitride contained in the boron nitride composition manufactured by the method of the present invention can be 20 μm or more, preferably 30 μm or more. Based on the results of the examples described later, the upper limit of the average particle size is usually 100 μm, for example 80 μm.

[0071] In a preferred embodiment of the present invention, an iron boride composition obtained by heating a raw material mixture containing an iron oxide component, a boron oxide component and carbon under an inert gas atmosphere (i.e., boriding the iron of the iron oxide component) is used as an iron boride composition that should be heat treated during nitriding.

[0072] The iron oxide component used in the boriding based on heat treatment contains at least one selected from Fe2O3, Fe3O4 and FeO as the iron oxide. In addition, the boron oxide component used in the boriding of iron oxide (specifically, the boriding of iron of iron oxide) contains at least one selected from B2O3, B4O3 and B4O5 as the boron oxide. The iron contained in the iron oxide component and the boron contained in the boron oxide component are preferably used in an equimolar amount or a nearly equimolar amount on a molar basis. Specifically, the molar ratio of the iron element (Fe) derived from the iron oxide to the boron element (B) derived from the boron oxide is 1:2 to 1.5:1, preferably 1:1.2 to 1.2:1, for example, Fe:B=1:1. In a particularly preferred embodiment, for example, Fe2O3 is used as the iron oxide and B2O3 is used as the boron oxide, but as long as an iron boride composition can be obtained from the iron boride and the boron oxide by boriding based on heat treatment, other compounds and other combinations thereof can also be used for the iron oxide and the boron oxide to implement the boriding based on heat treatment.

[0073] As carbon, carbon black, graphite, and a carbon precursor that can be a carbon source at high temperature can be used. Carbon black is preferred from the viewpoint of ease of acquisition. Carbon black can be carbon black produced by furnace process, channel process, etc., acetylene black, etc. The average particle size (volume-based average particle size) of these carbon blacks is arbitrary, for example, 0.01 to 5 μm, preferably 0.01 to 1 μm.

[0074] In addition, a carbon precursor may be used instead of the above carbon or in addition to the above carbon. For example, synthetic resin condensates such as phenolic resin, melamine resin, epoxy resin, furan phenolic resin, etc.; hydrocarbon compounds such as asphalt and tar; organic compounds such as cellulose, sucrose, polyvinylidene chloride, polyphenylene, etc. may be used as precursors. Among them, substances with less metal impurities such as phenolic resin, cellulose, polyphenylene, etc. are particularly preferred. They may be used alone or in combination of two or more.

[0075] As for the amount of carbon (when a carbon precursor is used, the amount of carbon generated thereby is used), in one embodiment, it is preferably an amount stoichiometrically required to convert all oxygen derived from iron oxides and boron oxides into carbon monoxide (of course, even if a stoichiometric amount of carbon is used, it is not necessarily possible to convert all oxygen into carbon monoxide). In another embodiment, it may be more or less than such an amount. In the case of less, iron oxides and / or boron oxides remain after boriding, but as long as the residues are to a degree that does not adversely affect the subsequent nitriding by heat treatment, there is no problem. In the case of more carbon, carbon remains, but again, as long as the residues are to a degree that does not adversely affect the nitriding, there is no problem.

[0076] Boriding is preferably carried out under an inert gas atmosphere, and in order to remove useless reaction products contained in the gas phase such as carbon monoxide, it can be carried out under an inert gas stream. As an inert gas, for example, argon, nitrogen, etc. can be used, preferably argon. Boriding based on heat treatment can be carried out under any appropriate pressure. Therefore, it can be carried out under reduced pressure or under pressure, but can usually be carried out under normal pressure.

[0077] The heat treatment in the boriding is carried out at a temperature at which iron oxide and boron oxide react to form iron boride (therefore, iron is borided), but in consideration of practicality, it is carried out in a manner that maintains a temperature of 1150° C. or higher and 1600° C. or lower, preferably 1200° C. to 1350° C. When the heating temperature is lower than 1150° C., the yield of iron boride may be small, and when the heating temperature is higher than 1600° C., the particle size of iron boride may be excessively increased.

[0078] The heating time can be generally 0.5 to 3 hours, preferably about 1 to 2 hours, depending on the heating temperature. After the heating treatment for a predetermined time, cooling is performed as required to obtain an iron boride composition containing iron boride. Cooling can be performed by any appropriate method, for example, by cooling to room temperature. When the heating time is shorter than 0.5 hours, the output of iron boride may be small. In addition, when the heating time is longer than 3 hours, the particle size of iron boride may be excessively increased.

[0079] By such boriding, an iron boride composition containing iron boride can be obtained. The composition contains iron boride in powder form (e.g., particle size less than 1 μm) to a certain large particle size (e.g., particle size exceeding 20 μm) as in the above-mentioned granular boron nitride. The iron boride composition can contain, for example, an aggregate of granular iron boride with various particle sizes ranging from 3 μm to 10 μm.

[0080] In the boriding based on heat treatment, the iron oxide, boron oxide and carbon contained in the raw material mixture are not all consumed. Depending on the reaction conditions, at least one of these components, usually all components, may be included in the iron boride composition as other components other than iron boride. Such other components can exist in an amount that does not substantially affect the subsequent nitriding based on heat treatment. In one scheme, it is assumed that FeB is stoichiometrically generated as iron boride by boriding, the amount of iron oxide and boron oxide is selected in such a way that the iron element and the boron element contained in the following oxides become equimolar, and the amount of carbon required for converting the oxygen contained in these oxides into the stoichiometric amount of carbon monoxide is selected, and they are used as a raw material mixture for boriding. At this time, the obtained iron boride composition may also contain the above-mentioned other components. Even if the obtained iron boride composition is used as it is for nitriding, it will not be affected in essence, and a boron nitride composition containing granular boron nitride can be obtained.

[0081] It should be noted that, when the iron boride composition contains carbon, the granular boron nitride generated by nitridation or the boron nitride composition containing the granular boron nitride may contain carbon. Depending on the use of the granular boron nitride or the boron nitride composition containing the granular boron nitride, in the case where the included carbon may become a problem (for example, the case where the conductivity caused by the presence of carbon becomes a problem), it is preferred to heat-treat the raw material mixture containing carbon in a minimum amount in such a manner that the amount of carbon remaining in the iron boride composition is minimized, and perform boridation.

[0082] Borization based on heat treatment is carried out in an inert gas atmosphere. For example, it is an atmosphere containing one or more of nitrogen, helium, argon, etc., and argon atmosphere is particularly preferred. It should be noted that in this specification, the inert gas atmosphere may also be a so-called vacuum state or a reduced pressure state that substantially does not contain gas or almost does not contain gas.

[0083] By boriding in this way, an iron boride composition containing iron boride is generated, which can be used for nitriding. The iron boride contained in the iron boride composition usually contains FeB and Fe2B, and may also contain Fe3B depending on the situation, and may further contain unreacted iron oxide and / or boron oxide and carbon, which can be used as the above-mentioned iron boride composition for nitriding based on heat treatment.

[0084] In a preferred embodiment, B2O3 as a boron oxide and Fe2O3 as an iron oxide are used in a molar ratio of 1:1, a stoichiometric amount of carbon is added thereto as described above, and the mixture is subjected to heat treatment to perform boriding (e.g., 1500°C, 1 hour). The iron boride composition obtained by the boriding based on the heat treatment mainly contains FeB and Fe2B (at a molar ratio of about 95:5) as iron borides, and may further contain unreacted B2O3, Fe2O3 and carbon. In order to facilitate the operation in the subsequent nitriding, the obtained iron boride composition can be temporarily cooled to room temperature, for example. A microscopic photograph of the iron boride composition obtained in Example 10 described later (boriding conditions: 1500°C, 1 hour) is shown in FIG. Figure 4 As can be easily understood, there are granular iron borides of various particle sizes. It should be noted that the iron boride composition obtained in Example 10 was analyzed by X-ray diffraction, and the results confirmed that FeB was generated as the main component, and a small amount, usually a trace amount of Fe2B was generated.

[0085] In one embodiment of the present invention, such an iron boride composition is then subjected to the previously described nitriding based on the heat treatment. The nitriding is carried out by heating the obtained iron boride composition, for example, at 2000°C for 5 hours, and a boron nitride composition containing granular boron nitride can be obtained by the nitriding based on the heat treatment. In another embodiment, when the iron boride composition is obtained by boriding in a nitrogen atmosphere, the obtained iron boride composition is not cooled, but heated to a temperature required for nitriding, and a boron nitride composition can be obtained.

[0086] It should be noted that, preferably, before the nitriding based on the heat treatment, the cooled iron boride composition is subjected to a pulverization treatment, the large substances in the contained granular iron boride are refined, and the granular iron boride is crushed in a condensed state so that the granular iron boride has a sharp particle size distribution. Specifically, for example, an automatic mortar can be used to implement a method in which granular iron boride having a particle size exceeding, for example, 20 μm does not substantially exist. In one embodiment, the average particle size can be 9 μm or less and D90 can be pulverized in a manner of 15 μm or less on a volume basis. It can be considered that if the granular iron boride obtained by such a pulverization treatment has a sharper particle size distribution, the melting / dropletization of the iron boride occurs uniformly in the nitriding of the iron boride composition, and as a result, the nitriding reaction is carried out more uniformly, and as a result, a boron nitride composition containing granular boron nitride with a sharp particle size distribution can be obtained.

[0087] In the method for manufacturing a boron nitride composition of the present invention, if the iron boride composition is heat-treated under a nitrogen atmosphere, the iron boride preferentially melts to form droplets, which are combined with the surrounding droplets by the energy applied by heating to form larger droplets. The iron boride present on the surface of such droplets reacts with the nitrogen in the atmosphere to generate boron nitride on the surface of the droplets (usually at various locations on the surface of the droplets). By repeatedly performing this reaction, the boron nitride is generated / grown along the surface of the droplets, and becomes a curved layered portion along the surface shape of the droplets. The curved layered portion thus grown is generated / grown at various locations on the surface of the droplets, combined with other curved layered portions to form a whole, further grown on its inner and outer sides and / or combined with other curved layered portions, and finally becomes a form surrounded by a wall having a certain degree of thickness, preferably a thicker wall, that is, a granular, preferably spherical boron nitride of the present invention having a shell structure of a boron nitride crystal.

[0088] Therefore, inside the granular boron nitride, various components contained in the iron boride composition, such as unreacted iron boride, iron components (such as iron oxide, iron borate, iron oxide, etc.) as byproducts of the nitriding reaction, may be included as contents in the shell in the state of remaining, and depending on the situation (for example, depending on the source of the iron boride composition used for nitriding), a small amount of iron oxide, boron oxide, carbon, iron carbide, etc. may also be included as contents in the shell. As described later, such contents can be removed by washing the granular boron nitride with a liquid such as an acid that dissolves the contents, dissolving it in the liquid. It is speculated that the spherical shell has gap-shaped portions and / or pore-shaped portions (therefore, becoming porous) formed by the joined curved layered portions, so that such washing can be performed.

[0089] As described above, the granular boron nitride contained in the boron nitride composition of the present invention is formed by boron nitride in the form of the wall of the curved layered portion, and can have a firm shell structure by being hexagonal boron nitride and having at least a certain degree of thickness. The shell structure has a round shape on the particle as a whole, and is therefore granular (particle)-shaped. In a strict sense, it can be a so-called spherical, ellipsoidal or polyhedral shape, and generally speaking, it sometimes has a shape of various combinations thereof. In a preferred embodiment, the above-mentioned ball index of the granular boron nitride that can be obtained by the manufacture method of the boron nitride composition of the present invention is very small. Compared with the known granular boron nitride (such as the granular boron nitride disclosed in patent document 2) with a relatively small aspect ratio, it has a shell structure that is further close to a true sphere.

[0090] An example of a typical SEM photograph of the granular boron nitride of the present invention is shown in Figure 7(a). This photograph is a SEM photograph of a cross section of a test piece (thus, a state of the granular boron nitride cut into discs) formed by mixing the granular boron nitride obtained in Example 1 described later (before acid cleaning) with an epoxy resin and curing it in order to observe the granular boron nitride obtained in Example 1 described later (herein, before acid cleaning). If it is observed in detail, it can be seen that the curved surface parts are joined together to form a granular boron nitride having an essentially spherical three-dimensional structure. It should be noted that an SEM photograph was also taken of the granular boron nitride of the present invention (the granular boron nitride obtained in Example 1 described later) in a state where the contents such as oxides in the shell were removed by acid cleaning described later. The photograph is shown in Figure 8 (a). If the two are compared, it can be seen that there is substantially no difference in the particle size of the spherical BN particles before and after the oxides etc. are removed. As a possible explanation for this, it can be considered that the liquid phase component generated during nitridation based on heat treatment remains in the granular boron nitride with a shell structure, and this component is removed by acid cleaning.

[0091] The spherical boron nitride of the present invention Figure 7 (a) and Figure 8 The EDS image corresponding to the SEM image of (a) is shown in Figure 7 (b) to (e) and Figure 8 (b) to (e). They will target Figure 7 (a) and Figure 8 The results of mapping analysis of the granular boron nitride in the state of the SEM photograph (a) using EDS (energy dispersive X-ray analysis) for the C element (photo (b)), the N element (photo (c)), the Fe element (photo (d)), and the O element (photo (e)) are shown in the form of EDS photographs. These SEM photographs are converted from the original color mapping photographs to grayscale photographs, so the clarity is not necessarily sufficient, but in the EDS photographs, the relatively white parts are the parts where the target elements exist.

[0092] If you refer to Figure 7 (c), the nitrogen element exists in a white ring-shaped part around the black circular part. It can be seen that the boron nitride exists around the circular part, that is, it has a shell structure. It should be noted that if we refer to Figure 7 From (d) and (e), it can be seen that there are iron and oxygen elements inside the white circular part. These are iron components (such as iron oxide, iron borate, iron nitride, and iron carbide) generated during the synthesis of iron oxide and boron nitride contained in the iron boride composition as the raw material for nitridation based on heat treatment, and they are included as contents of the shell structure. It should be noted that if referring to Figure 7 From (b), it can be seen that the outside of the circular part is white and there is carbon in this part. This is derived from the epoxy resin used to make the test piece.

[0093] If you refer to Figure 8 (c), the nitrogen element exists around the circular part, but not inside the circular part. Figure 8 (d) is a photo that is essentially pure black and contains no iron. Figure 8 (e), oxygen element exists inside the circular part. If these are taken into consideration, it can be considered that iron oxides and the like, which are contents of the shell structure of granular boron nitride, are removed by washing, and then oxygen originating from the epoxy resin that enters the shell structure when the test piece is formed exists.

[0094] It should be noted that, as described above, the shell is formed, but the granular boron nitride of the present invention includes a component that is finally solidified on the inner side of the shell by cooling after nitriding based on heat treatment as a content. The content may be a component contained in the iron boride composition as a raw material for nitriding and a component that is not consumed when generating the boron nitride reaction (such as FeB, Fe2B, Fe2O3, B2O3, etc.), and an iron or iron compound (such as Fe2O3, Fe3O4, etc.) produced when forming boron nitride. It should be noted that, when an oxide is added as an auxiliary agent during nitriding, such an oxide may also be included in the content. Such content can be substantially removed by a cleaning treatment such as acid treatment described later. Then, by drying, the shell structure of the granular boron nitride of the present invention can substantially become a hollow state.

[0095] The content in the shell structure can be reduced by acid cleaning, for example. Specifically, an acid aqueous solution can be used to react the content (especially oxide) in the shell structure with an acid, convert it into a water-soluble salt, dissolve it in water and remove it, thereby reducing it. For example, when granular boron nitride is used as a thermally conductive filler, the thermal conductivity of the oxide is generally small, so it is preferred that the oxide contained in the granular boron nitride is reduced to a degree that does not substantially adversely affect the thermal conductivity. In addition, in the content, there are substances with semi-conductive properties such as Fe2B and Fe2O3. When the granular boron nitride containing such content is mixed with a plastic resin to manufacture a molded body, the withstand voltage of the molded body may sometimes be insufficient. Therefore, depending on the use of the granular boron nitride, it is sometimes preferred to remove the content of the shell structure. For example, the amount of the content contained in the granular boron nitride becomes, for example, 0.1 to 80% of the total mass of the composition (including the content), preferably 1 to 70%, more preferably 2 to 60%, for example 10 to 53%.

[0096] Therefore, the present invention also provides a granular boron nitride, which is contained in a boron nitride composition and has a shell structure containing contents inside. The granular boron nitride can be obtained by the following method for manufacturing granular boron nitride, the method for manufacturing granular boron nitride being characterized in that the granular boron nitride is obtained from the boron nitride composition by any appropriate treatment (for example, the removal of powdered boron nitride by a classification treatment such as screening and / or the removal of granules with a particle size within a specified range). In addition, the present invention also provides another granular boron nitride, wherein at least a part of the contents of the shell structure of the granular boron nitride, preferably most of them, and more preferably substantially all of the contents are removed, and at least a part of the inside of the shell structure is preferably substantially all hollow. It should be noted that the removal of the contents of the shell structure can also be implemented by any other appropriate method other than acid cleaning as long as it does not excessively affect the properties of the granular boron nitride as a filler. Cleaning with acid is advantageous in terms of not causing adverse effects on the granular boron nitride and being able to substantially remove the oxide. Such another granular boron nitride can be obtained by a method for producing granular boron nitride, wherein the granular boron nitride or the boron nitride composition described above is subjected to acid washing.

[0097] The present invention provides a resin composition, which comprises: granular boron nitride and a resin material, wherein the granular boron nitride is preferably a granular boron nitride obtained by reducing the amount of the contents of the shell structure by washing as described above, and in particular a granular boron nitride having a shell structure with a substantially hollow interior. The resin composition preferably comprises 10 to 90%, more preferably 15 to 88%, for example 30 to 85%, and in particular 50 to 82% of granular boron nitride based on its overall mass. If these ranges are shown as volume ratios, they are slightly different depending on the apparent density of the granular material, and as an example, correspond to about 5 to 80 volume %, about 10 to 70 volume %, and about 15 to 50 volume %, respectively. If the amount of granular boron nitride is too small, the probability of the granular boron nitride being in contact and existing may be reduced, and the heat conduction may be insufficient. On the contrary, if the amount of granular boron nitride is too much, the resin material as a matrix is ​​excessively reduced, which may sometimes have an adverse effect on the strength and withstand voltage of the molded body. Furthermore, in another embodiment, the resin composition may contain the boron nitride composition containing particulate boron nitride of the present invention in the same proportion instead of the above-mentioned particulate boron nitride.

[0098] <Washing of Boron Nitride Composition (Production of Granular Boron Nitride)>

[0099] The granular boron nitride contained in the boron nitride composition of the present invention obtained by nitriding as described above has a shell structure, and contains contents as described above inside it. When the thermal conductivity of the contents is smaller than that of boron nitride, in a preferred embodiment, the thermal conductivity of the granular boron nitride can be improved by reducing the contents. For example, when the granular boron nitride is used as a conductive filler mixed in a resin material to make a resin composition, the resin material may exist in the shell structure of the particles in addition to existing between particles. In this case, when the thermal conductivity of the contents is smaller than that of the resin material, if the contents in the shell structure are reduced in advance, the resin material occupies the reduced amount, and therefore the overall thermal conductivity of the resin composition is improved.

[0100] In addition, sometimes semi-conductive substances (such as Fe2B, Fe2O3, etc.) may be included in the contents, and it is ideal to remove them. Therefore, the contents in the shell structure can be removed from the granular boron nitride of the boron nitride composition obtained by the method of the present invention as needed. The removal can be implemented by washing the granular boron nitride or the boron nitride composition containing the granular boron nitride with an acid such as an acid aqueous solution under heating as needed. In detail, the contents can be removed in the following manner: the metal elements contained in the contents are converted into water-soluble salts corresponding thereto using an acid aqueous solution, and the salt is dissolved in the water present using the reaction to obtain a saline solution, which is removed. As the acid used, organic acids and inorganic acids can be listed, for example, hydrochloric acid, nitric acid, sulfuric acid, etc. can be used.

[0101] The cleaning with acid can be implemented by dispersing the boron nitride composition in an acid aqueous solution under stirring. Then, the granular boron nitride is filtered out from the dispersion, and the obtained granular boron nitride is further washed with water, thereby removing the residual acid, and then dried to obtain granular boron nitride. The total amount of the contents remaining in the shell structure contained in the obtained granular boron nitride is preferably 0.1 to 30%, preferably 1 to 15%, and more preferably 3 to 10% based on the mass of the obtained granular boron nitride (including the contents). It should be noted that the amount of the contents remaining in the shell structure can be easily adjusted by appropriately selecting the cleaning conditions (such as the concentration of the acid, the amount of the aqueous solution used for cleaning and / or the number of cleaning times, etc.), for example, the lower limit of the above range can also be set to below the detection limit of the analytical method (such as elemental analysis, XRD, etc.) (therefore, "0.0").

[0102] It should be noted that the mesh of the filter material used for filtering out can be determined according to the retained particle size or separation capacity, for example, by removing (i.e., classifying) granular boron nitride (e.g., powdered boron nitride) smaller than the specified particle size, other fine solid components other than boron nitride (if present), etc., to obtain granular boron nitride (aggregate) having a particle size greater than the specified particle size. In addition, if necessary, by combining filtering out using filter materials having different meshes, etc., granular boron nitride (aggregate) having a specified particle size distribution width can be obtained.

[0103] The amount of the content (for example, iron oxide) of the particulate boron nitride can be measured as follows.

[0104] In a Teflon-lined pressure-resistant container, 1 g of the acid-cleaned granular boron nitride was added to 60 g of a 1-equivalent hydrochloric acid aqueous solution, sealed, and heat-treated at 100°C for 11 hours. The obtained slurry was filtered with a membrane filter, and the concentration of the solution obtained by diluting the filtrate 200 times with pure water was analyzed using an ICP (ion inductively coupled plasma) emission analyzer (manufactured by Shimadzu Corporation, ICPS-7510), and the amount of iron oxide (e.g., Fe2O3) contained in the granular boron nitride was calculated based on this. In addition, the filter residue was subjected to XRD analysis to confirm that the peak of iron oxide did not exist.

[0105] It should be noted that the confirmation that the filtered particles are granular boron nitride (h-BN) is confirmed by X-ray diffraction patterns. In addition, the following observation results were obtained by SEM: the boron nitride crystals are granular, and in the preferred embodiment, they are substantially spherical. It should be noted that the granular boron nitride has a shell structure, and a SEM observation sample prepared by etching the material obtained by adding granular boron nitride to epoxy resin and curing it with an argon ion beam was used to investigate. When the granular boron nitride particles are cut into discs by etching, it can be confirmed by SEM observation that the stacked c-faces of boron nitride are connected in a circular shape to form a shell, in which substances other than boron nitride exist.

[0106] <Granular Boron Nitride>

[0107] The boron nitride composition of the present invention can be preferably manufactured by the manufacturing method of the boron nitride composition containing granular boron nitride of the present invention, and contains other components in addition to granular boron nitride. The other components include: unreacted iron boride contained in the iron boride composition to be nitrided but not participating in the nitriding reaction and remaining, components contained in the iron boride composition along with the iron boride, and iron components produced as by-products by nitriding, etc.

[0108] The iron oxide and the boron oxide are subjected to boriding by heat treatment to obtain an iron boride composition, and the iron boride composition is nitrided to obtain a boron nitride composition containing granular boron nitride. In this case, at least one of the iron oxide, the boron oxide and the carbon may become a component included in the iron boride composition along with the iron boride as "other components". Such other components can be reduced or substantially removed by acid washing and / or filtering as described above, and the granular boron nitride of the present invention can be obtained.

[0109] The granular boron nitride of the present invention has a spherical three-dimensional structure in a preferred embodiment, so it can be matched to a resin material for the purpose of improving thermal conductivity anisotropy and increasing thermal conductivity. In addition, the solid lubricity derived from the granular boron nitride is maintained, so even when a resin composition is obtained by matching the granular boron nitride to a resin material, the molding processability as the resin composition can be well maintained, and, when a molded body is made, a heat conduction path in the thickness direction is easily formed in the molded body due to the shell structure. As a result, the thermal conductivity in the thickness direction of the molded body can be improved. In addition, the granular boron nitride of the present invention also has chemical stability, heat resistance, etc. derived from boron nitride.

[0110] When the granular boron nitride of the present invention is obtained as described above, the boron nitride composition before cleaning or the boron nitride composition after cleaning (or during cleaning) can be subjected to classification treatment after nitridation based on heat treatment so that the contained granular boron nitride has a particle size within a specified range. Classification can be implemented by any appropriate method, for example, screening (including filtering) can be used. By such classification, excessively small particles and / or excessively large particles can be removed, and granular boron nitride with consistent particle size can be obtained (strictly speaking, an aggregate of individual granular boron nitride, i.e., a granular substance of boron nitride). In a preferred embodiment, an aggregate of individual granular boron nitride, such as spherical boron nitride, can be obtained, and an aggregate of granular boron nitride, such as an aggregate of spherical boron nitride, each (i.e., one by one) granular body, such as a spherical body, has a particle size within a specified particle size distribution width.

[0111] <Resin composition containing particulate boron nitride>

[0112] The resin composition of the present invention, especially the thermally conductive resin composition, comprises the above-mentioned granular boron nitride of the present invention and a resin material. That is, the granular boron nitride of the present invention is preferably used as a thermally conductive filler in the resin composition as described above. It should be noted that, depending on the circumstances, a boron nitride composition comprising granular boron nitride (e.g., the above-mentioned boron nitride composition before cleaning) may also be used instead of the granular boron nitride.

[0113] <Resin material>

[0114] The resin material that functions as a resin forming a matrix in the resin composition is not particularly limited, and may be, for example, a curable resin, a thermoplastic resin, etc. As the curable resin, any curable resin that can be crosslinked, such as a thermosetting resin, a photocurable resin, an electron beam curable resin, etc., is sufficient, and in terms of heat resistance, water absorption, dimensional stability, etc., a thermosetting resin is preferred, and an epoxy resin is particularly preferred.

[0115] The epoxy resin may be an epoxy resin having only one type of structural unit, or may be a combination of a plurality of epoxy resins having different structural units. In addition, the epoxy resin may be used together with an epoxy resin curing agent and a curing accelerator as necessary.

[0116] Here, in order to obtain coating properties, film-forming properties, and adhesion, while reducing voids in the cured product and obtaining a highly thermally conductive cured product, it is preferred that at least the phenoxy resin described later (hereinafter referred to as "epoxy resin (A)") be contained as the epoxy resin. It is particularly preferred that the mass ratio of the epoxy resin (A) relative to the total amount of the epoxy resin is preferably in the range of 5 to 95 mass%, more preferably in the range of 10 to 90 mass%, and further preferably in the range of 20 to 80 mass%, but it is not limited to these.

[0117] Phenoxy resin generally refers to a resin obtained by reacting an epihalohydrin with a dihydric phenol compound or a resin obtained by reacting a divalent epoxy compound with a dihydric phenol compound. In the present invention, a phenoxy resin particularly a high molecular weight epoxy resin having a mass average molecular weight of more than 10,000 is referred to as epoxy resin (A). It should be noted that the mass average molecular weight refers to the value of polystyrene conversion measured by gel permeation chromatography.

[0118] As the epoxy resin (A), a phenoxy resin having the following skeleton is preferred: at least one selected from the group consisting of a naphthalene skeleton, a fluorene skeleton, a biphenyl skeleton, an anthracene skeleton, a pyrene skeleton, a xanthene skeleton, an adamantane skeleton and a dicyclopentadiene skeleton. Among them, heat resistance is further improved, so a phenoxy resin having a fluorene skeleton and / or a biphenyl skeleton is particularly preferred. These can be used alone or in combination of two or more.

[0119] As epoxy resins other than the epoxy resin (A), epoxy resins having two or more epoxy groups in the molecule (hereinafter sometimes referred to as "epoxy resin (B)") are preferred, and examples thereof include various epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, naphthalene type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, phenol aralkyl type epoxy resin, biphenyl type epoxy resin, triphenylmethane type epoxy resin, dicyclopentadiene type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, and polyfunctional phenol type epoxy resin. These may be used alone or in combination of two or more.

[0120] From the viewpoint of melt viscosity control, the mass average molecular weight of the epoxy resin (B) is preferably 100 to 5000, more preferably 200 to 2000. When the mass average molecular weight is less than 100, heat resistance tends to be poor, and when the mass average molecular weight is more than 5000, the melting point of the epoxy resin tends to be high, and workability tends to be reduced.

[0121] In addition, the epoxy resin of the present invention may contain epoxy resins other than epoxy resin (A) and epoxy resin (B) (hereinafter referred to as "other epoxy resins") within a range that does not impair its purpose. The content of other epoxy resins is usually 50% by mass or less, preferably 30% by mass or less relative to the total of epoxy resin (A) and epoxy resin (B).

[0122] In the resin composition of the present invention, the ratio of the epoxy resin (A) in all epoxy resins including the epoxy resin (A) and the epoxy resin (B) is preferably 5 to 95% by mass, preferably 10 to 90% by mass, and more preferably 20 to 80% by mass, as described above, when the total of all epoxy resins is 100% by mass. It should be noted that "all epoxy resins including the epoxy resin (A) and the epoxy resin (B)" refers to the total of the epoxy resin (A) and the epoxy resin (B) when the epoxy resins contained in the resin composition of the present invention are only the epoxy resin (A) and the epoxy resin (B), and refers to the total of the epoxy resin (A), the epoxy resin (B), and the other epoxy resins when other epoxy resins are also included.

[0123] When the ratio of the epoxy resin (A) is greater than or equal to the above lower limit, the effect of improving thermal conductivity by adding the epoxy resin (A) can be sufficiently obtained, and the desired high thermal conductivity can be obtained. When the ratio of the epoxy resin (A) is less than or equal to the above upper limit, especially when the epoxy resin (B) is 10% by mass or more of the total epoxy resin, the effect of adding the epoxy resin (B) is exerted, and the curability and physical properties of the cured product become sufficient.

[0124] The curing agent for epoxy resin can be appropriately selected according to the type of resin used. For example, anhydride curing agents and amine curing agents can be listed. As anhydride curing agents, for example, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride and benzophenonetetracarboxylic anhydride can be listed. As amine curing agents, for example, aliphatic polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, diaminodiphenyl sulfone, diaminodiphenylmethane, diaminodiphenyl ether, aromatic polyamines such as metaphenylenediamine and dicyandiamide can be listed. They can be used alone or in combination of two or more. These epoxy resin curing agents are usually formulated in an equivalent ratio of 0.3 to 1.5 relative to the epoxy resin.

[0125] The curing accelerator can be appropriately selected according to the type of resin and curing agent used. For example, as the curing accelerator for the acid anhydride curing agent, for example, boron trifluoride monoethylamine, 2-ethyl-4-methylimidazole, 1-isobutyl-2-methylimidazole, and 2-phenyl-4-methylimidazole can be listed. They can be used alone or in combination of two or more. These curing accelerators are usually used in the range of 0.1 to 5 parts by mass relative to 100 parts by mass of epoxy resin.

[0126] In addition, the resin material used in the resin composition of the present invention can be a thermoplastic resin. As a thermoplastic resin, for example, polyolefin resins such as polyethylene resin, polypropylene resin, ethylene-vinyl acetate copolymer resin, polyester resins such as polyethylene terephthalate resin, polybutylene terephthalate resin, and liquid crystal polyester resin, polyvinyl chloride resin, phenoxy resin, acrylic resin, polycarbonate resin, polyphenylene sulfide resin, polyphenylene ether resin, polyamide resin, polyamide-imide resin, polyimide resin, polyetheramide-imide resin, polyetheramide resin, and polyetherimide resin, etc. In addition, copolymers such as their block copolymers and graft copolymers are also included. They can be used alone or in combination of two or more.

[0127] In addition, the resin material may be a rubber component, and examples of the rubber component include natural rubber, polyisoprene rubber, styrene-butadiene copolymer rubber, polybutadiene rubber, ethylene-propylene copolymer rubber, ethylene-propylene-diene copolymer rubber, butadiene-acrylonitrile copolymer rubber, isobutylene-isoprene copolymer rubber, chloroprene rubber, silicone rubber, fluororubber, chlorosulfonated polyethylene, polyurethane rubber, etc. These may be used alone or in combination of two or more.

[0128] <Amount of Particulate Boron Nitride in Resin Composition>

[0129] The amount of the granular boron nitride of the present invention (or the boron nitride composition containing granular boron nitride) contained in the resin composition of the present invention is preferably generally 10 to 90% by mass of the resin composition as described above, more preferably 15 to 88%, and further preferably 30 to 85%. When the amount of granular boron nitride in the resin composition is less than such a range, the viscosity of the resin composition (viscosity when melted) is low, and although the molding processability is good, the effect of improving thermal conductivity may become insufficient. When the amount of granular boron nitride in the resin composition is greater than such a range, there is a tendency that the viscosity of the resin composition when melted becomes high, and molding becomes difficult.

[0130] <Other components in the resin composition>

[0131] As long as the effects of the present invention can be obtained, the resin composition of the present invention may also contain other components. Such components include, for example, functional resins such as liquid crystal epoxy resins that impart functionality to the above-mentioned resins, nitride particles such as aluminum nitride, silicon nitride, and fibrous boron nitride, insulating metal oxides such as aluminum oxide, fibrous aluminum oxide, zinc oxide, magnesium oxide, beryllium oxide, and titanium oxide, insulating carbon components such as diamond and fullerene, resin curing agents, resin curing accelerators, viscosity modifiers, and dispersion stabilizers.

[0132] In addition, from the viewpoint of reducing the viscosity of the resin composition, the resin composition of the present invention may contain a solvent. As the solvent, a known solvent that dissolves the resin is used. As such a solvent, for example, methyl ethyl ketone, acetone, cyclohexanone, toluene, xylene, monochlorobenzene, dichlorobenzene, trichlorobenzene, phenol and hexafluoroisopropanol can be listed. They can be used alone or in combination of two or more. The solvent is used in a range of, for example, 0 to 10,000 parts by mass relative to 100 parts by mass of a resin such as an epoxy resin.

[0133] Furthermore, the resin composition of the present invention may contain inorganic fillers such as aluminum hydroxide and magnesium hydroxide, surface treatment agents such as silane coupling agents for improving the interfacial bonding strength between the inorganic filler and the matrix resin, and reducing agents, unless the effects thereof are impaired.

[0134] In addition, for the purpose of maintaining the moldability in the resin composition, the total amount of the particulate boron nitride of the present invention and the inorganic filler in the resin composition is preferably 90% by mass or less.

[0135] <Manufacturing of resin composition>

[0136] The resin composition of the present invention can be obtained by uniformly mixing the granular boron nitride of the present invention (or the boron nitride composition containing granular boron nitride), the resin material and other components added as needed by stirring and kneading. For the mixing, for example, a common kneading device such as a mixer, a kneader, a single shaft or a double shaft kneading machine can be used, and during the mixing, heating can be performed as needed.

[0137] <Method for producing molded article and molded article>

[0138] The molded body of the present invention is obtained by molding the resin composition of the present invention. The molding method of the molded body, i.e., the manufacturing method, can be based on the properties of the resin composition, using the method commonly used in the molding, such as injection molding, mold molding, etc. No matter which molding method is used, the resin composition is heated as needed to fluidize or plasticize it, and the resin composition is molded into a molded body using a mold, so that a certain force acts on the fluidized resin composition. For example, pressure acts when the resin composition is filled into the mold. It can be considered that this situation is consistent regardless of whether the resin material is a curable resin (such as a phenolic resin, an epoxy resin, a melamine resin, a urea resin, etc.) or a thermoplastic resin (such as polyethylene, polypropylene, polyvinyl chloride, polystyrene, acrylic resin, etc.).

[0139] For example, in the case where the resin composition of the present invention has plasticity or fluidity, the resin composition can be formed by curing it in a desired shape, for example, in a state filled into a mold. As the manufacturing method of such a molded body, injection molding, injection compression molding, extrusion molding and compression molding can be used. In addition, in the case where the resin composition of the present invention is a thermosetting resin composition comprising an epoxy resin, a silicone resin, etc., the molding of the molded body, i.e., curing, can be carried out under the curing conditions corresponding to the respective compositions. Moreover, in the case where the resin composition of the present invention is a composition comprising a thermoplastic resin, the molding of the molded body can be carried out under the conditions of a temperature above the melting temperature of the thermoplastic resin and a prescribed molding speed and pressure. It should be noted that the molded body of the present invention can also be obtained by cutting out a desired shape from a solid block material formed by molding or curing the resin composition of the present invention.

[0140] In the molded body of the present invention obtained as described above, depending on the amount of the resin material and the granular boron nitride (or the boron nitride composition containing the granular boron nitride), the thermal conductivity in the direction parallel to the direction of the force applied during molding is generally 10 to 22 W / (m·K) in one embodiment of the resin composition in which the amount of the resin material is 65 to 85% by mass, 13 to 20 W / (m·K) in another embodiment, and 15 to 18 W / (m·K) in another embodiment. In addition, the thermal conductivity in the direction perpendicular to the direction of the pressure applied during molding is generally 10 to 55 W / (m·K), 15 to 45 W / (m·K) in one embodiment, and 17 to 27 W / (m·K) in another embodiment.

[0141] Therefore, if a resin composition is prepared using the granular boron nitride of the present invention, and a molded body is manufactured by press molding using the resin composition, then generally, the thermal conductivity in the direction parallel to the pressing direction (also referred to as the pressing parallel direction) is preferably 70 to 100%, more preferably 80 to 100%, and particularly 90 to 100% of the thermal conductivity in the direction perpendicular to the pressing direction (also referred to as the pressing perpendicular direction), which can greatly suppress the anisotropy of the molded body related to thermal conductivity, and can substantially eliminate the anisotropy depending on the circumstances. This tendency is the same even when the boron nitride composition of the present invention is mixed with a resin material instead of granular boron nitride to obtain a pressed body. In a particularly preferred embodiment, the resin composition contains 65 to 85% by mass of granular boron nitride (or a boron nitride composition containing granular boron nitride) based on its entire mass, and in the molded body manufactured using the resin composition, the ratio of the thermal conductivity in the direction parallel to the pressing to the thermal conductivity in the direction perpendicular to the pressing is generally at least about 80%, and can be less than 100%.

[0142] Example

[0143] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[0144] [Raw materials used]

[0145] The specifications of the raw materials used in the following examples are as follows.

[0146] <Iron oxide (Fe2O3)>

[0147] Iron oxide powder: manufactured by Kojundo Chemical Research Institute Co., Ltd., trade name: α-iron sesquioxide.

[0148] (Purity: 99% or more, average particle size: 1μm)

[0149] <Boron oxide (B2O3)>

[0150] Boron oxide powder: manufactured by FUJIFILM Wako Pure Chemical Co., Ltd., trade name: Boron trioxide.

[0151] (Purity: 99% or more, average particle size: 75μm)

[0152] <Carbon Component>

[0153] Carbon powder: manufactured by Mitsubishi Chemical Co., Ltd., trade name: Carbon Black #2300.

[0154] (Volatile content: 2% or more, average particle size: 15nm)

[0155] <Auxiliary Agents>

[0156] Fine powder yttrium (Y2O3): manufactured by NIPPON YTTRIUM CO., LTD., trade name: fine powder yttrium oxide.

[0157] (Purity: 99.9% or more, average particle size: 0.91 μm)

[0158] Fine powder cerium oxide (CeO2): manufactured by NIPPON YTTRIUM CO., LTD., trade name: Fine powder cerium oxide.

[0159] (Purity: 99.9 or above, average particle size 0.58μm)

[0160] Calcium carbonate (CaCO3): manufactured by FUJIFILM Wako Pure Chemical Co., Ltd., trade name: calcium carbonate.

[0161] (Purity: 99.5%, average particle size 75 μm) decomposes into CaO at around 800°C, so the addition amount of CaCO3 in Table 1 is calculated in the form of conversion into an equimolar amount of CaO.

[0162] <Epoxy resin material>

[0163] Epoxy resin main agent (bisphenol A type epoxy resin): manufactured by MITSUBISHI CHEMICAL CO., LTD., trade name: jER828.

[0164] Epoxy resin curing agent (methylbutyltetrahydrophthalic anhydride): manufactured by Mitsubishi Chemical Co., Ltd., trade name: YH-306.

[0165] Epoxy curing accelerator (2-ethyl-4-methylimidazole): manufactured by Mitsubishi Chemical Co., Ltd., trade name: EMI24.

[0166] Mixing ratio (mass basis, jER828∶YH-306∶EMI24): 100∶80∶2.

[0167] [Boron Nitride Composition Containing Granular Boron Nitride and Production of Granular Boron Nitride]

[0168] <Example 1>

[0169] (boration by heat treatment)

[0170] 15.969 g (0.1 mol) of Fe2O3 powder as an iron oxide component and 6.962 g (0.1 mol) of boron oxide B2O3 powder as a boron oxide component were ground and mixed in an alumina mortar using an automatic mortar (NIKKA Science Co., Ltd., ANM1000 model) for 30 minutes. The mixed powder was transferred to a wide-mouth polyethylene bottle (capacity 500 ml), and further mixed with 7.206 g (0.6 mol) of carbon powder as a carbon component, and further added with silicon nitride balls (400 g) with a diameter of 10 mm for grinding, and dry ball mill mixing (NIKKA Engineering, Type-NS) was performed for 18 hours. 28 g of the obtained mixed raw material powder (Fe2O3 powder, B2O3 powder and carbon powder) is added to a boron nitride crucible, and heat treated at a prescribed heat treatment temperature of 1300°C for 1 hour in a heating treatment furnace (electric furnace, Fuji Electric Industry, HIGH MULTI 5000) in an argon atmosphere to perform boronization to synthesize iron boride, thereby obtaining 16 g of an iron boride composition containing powdered or granular iron boride.

[0171] In addition, the detailed temperature profile during the heat treatment was implemented as follows.

[0172] Room temperature to 1100°C: increase the temperature at 20°C / min.

[0173] 1100°C to the specified heat treatment temperature (1300°C): increase the temperature at 10°C / min.

[0174] Maintain the specified heat treatment temperature (1300°C) for 1 hour.

[0175] The heat treatment temperature was set to room temperature: the temperature was lowered at 20°C / min.

[0176] The atmosphere in the heating furnace is between room temperature and 300°C and less than 1×10 －1 Pa, then argon gas was introduced into the furnace until the pressure reached the atmospheric pressure, and then the argon gas flow was maintained at 1 ml / min until the heat treatment was completed.

[0177] The obtained (observed with the naked eye) powdered iron boride composition was analyzed by X-ray diffraction (XRD), and the results showed that Fe2B and FeB were contained in the crystalline phase. The mixed raw material powder of the boronization based on the heat treatment contains iron oxide and boron oxide in equimolar amounts, and is combined on the premise that they react to generate FeB, but the generation of Fe2B means that the boron oxide is not consumed and remains. It is speculated that the residual part remains in the form of an amorphous layer. It should be noted that in the obtained iron boride composition, in addition to the above-mentioned iron boride, it may also contain residual reaction raw material components (iron oxide, boron oxide and carbon) and other components accompanying the reaction raw material components.

[0178] The SEM photograph (magnification: 2000 times) of the obtained iron boride composition is shown in Figure 5 .exist Figure 5 In the photo, it can be seen that the brightly glowing spherical particles are iron boride (Fe2B or FeB), and the particle size is relatively uniform. It should be noted that the part other than the particles in the photo (such as the glassy amorphous part) is estimated to be B2O3 containing carbon.

[0179] (Nitriding by heat treatment)

[0180] The iron boride composition obtained by the boronization based on the above-mentioned heat treatment was crushed for 5 minutes using an automatic mortar. The particle size distribution of the iron boride composition was measured, and the result showed that particles with a particle size of 20 μm or more were substantially absent. 16 g of the iron boride composition was added to a boron nitride crucible, and heat-treated for 5 hours at a prescribed heat treatment temperature of 2000° C. in a heat treatment furnace (electric furnace, Fuji Electric Industry, HIGHMULTI 5000) in a nitrogen atmosphere, and nitrided to synthesize boron nitride. Observed with the naked eye, 13 g of a powdered boron nitride composition was obtained.

[0181] In addition, the detailed temperature profile during the heat treatment was implemented as follows.

[0182] Room temperature to 1100°C: increase the temperature at 20°C / min.

[0183] 1100℃ to specified heat treatment temperature (2000℃): increase the temperature by 100℃ / 30 minutes.

[0184] Maintain the specified heat treatment temperature (2000°C) for 5 hours.

[0185] The heat treatment temperature was set to room temperature: the temperature was lowered at 20°C / min.

[0186] The atmosphere in the heating furnace is between room temperature and 300°C and less than 1×10 －1 Pa, then nitrogen gas was introduced into the furnace until the pressure reached atmospheric pressure, and then a nitrogen gas flow of 2 ml / min was maintained until the heat treatment was completed.

[0187] The obtained boron nitride composition was analyzed by X-ray diffraction (XRD), and the results showed that hexagonal boron nitride (h-BN) was generated. The iron boride composition subjected to nitridation also contained components other than iron boride such as FeB and Fe2B (oxides such as Fe2O3 and B2O3, trace amounts of carbon, etc.), but no adverse effects on nitridation due to their presence were confirmed.

[0188] The SEM photograph of the obtained boron nitride composition (thus, before cleaning) is shown in Figure 6 .exist Figure 6 It can be seen that many particles (thus, granular boron nitride) with relatively uniform sizes substantially have a spherical three-dimensional structure. That is, these granular boron nitrides are spherical boron nitrides.

[0189] (Acid cleaning)

[0190] The boron nitride composition obtained as described above is acid-cleaned to remove the iron components (iron nitride, iron carbide, etc.), oxides (Fe2O3, B2O3, Fe3BO6, FeBO3, etc.) and unreacted borides (FeB, Fe2B, etc.). In detail, 13 g of the boron nitride composition is added to 20 ml of a 6-equivalent hydrochloric acid aqueous solution in a Teflon-lined sealed pressure vessel, and the reaction is carried out at 100°C for 11 hours to convert the iron components, oxides, borides, etc. contained therein into water-soluble salts. Then, the mixture is washed / filtered with pure water, the salt is removed / dried, and the granular boron nitride of the present invention is obtained. It should be noted that filter paper (made by ADVANTEC, trade name: 5C, retained particle size: 1 μm) is used for filtration.

[0191] The XRD analysis of the obtained granular boron nitride showed that no oxides or borides that may have remained in the granular boron nitride could be detected. Figure 1 .and Figure 6 SEM photo (before cleaning) Figure 1 In (after cleaning), it is found that many particles (thus, granular boron nitride) of relatively uniform size have a substantially spherical three-dimensional structure. In other words, these granular boron nitrides are spherical boron nitrides.

[0192] <Examples 2 to 12>

[0193] In these embodiments, Fig. 9 As shown in Table 1, at least one of the molar ratio of iron oxide to boron oxide in the boriding, the boriding temperature and time, and the nitriding temperature and time was changed. Otherwise, Example 1 was repeated to obtain an iron boride composition, which was nitrided to obtain a boron nitride composition, which was acid-washed / filtered, and then dried to obtain granular boron nitride.

[0194] <Example 13>

[0195] In the case of nitriding by heat treatment, to the iron boride composition obtained by boriding as described above, Fig. 9Yttrium oxide (Y2O3) is added as an auxiliary agent as shown in Table 1, heat treatment is performed, and nitriding is performed. In addition, Example 1 is repeated to perform nitriding based on heat treatment on the iron boride composition to obtain a boron nitride composition containing granular boron nitride, which is acid-washed / filtered to remove oxides including the auxiliary agent, and then dried to obtain granular boron nitride (spherical boron nitride in this example).

[0196] It should be noted that Fig. 9 The amount of additives added in Table 1 is shown in the form of a ratio (mass %) of the mass of the mixed additives to the mass of the boron nitride generated under the following circumstances: it is assumed that the iron contained in the iron boride used in the boriding based on the heat treatment is completely converted into iron boride (FeB), and it is also assumed that the boron contained in the iron boride is completely converted into boron nitride.

[0197] <Examples 14 to 27>

[0198] In these embodiments, Fig. 9 As shown in Table 1, at least one of the temperature and time of the boriding based on the heat treatment, the temperature and time of the nitriding based on the heat treatment, and the type and amount of the added auxiliary agent is changed. Otherwise, Example 13 is repeated to obtain an iron boride composition, which is nitrided to obtain a boron nitride composition containing granular boron nitride, which is acid-washed / filtered / dried to obtain granular boron nitride.

[0199] It should be noted that when using acid cleaning to remove oxides and the like from the boron nitride composition obtained by nitridation, 6 equivalents of relatively concentrated hydrochloric acid are used, so that the oxides added as an auxiliary agent that is relatively difficult to acid clean can also be removed. However, in the case where the auxiliary agent does not necessarily need to be removed, the acid cleaning conditions can be relaxed. For example, the hydrochloric acid concentration can be reduced, the acid cleaning temperature can be reduced, or the acid cleaning time can be reduced.

[0200] The boron nitride compositions containing granular boron nitride obtained in Examples 1 to 27 (randomly sampled after acid washing / filtration / drying) are shown in Table 1 along with the shapes of the granular boron nitride (BN shapes observed by SEM, magnification: 2000 times), the average particle size, particle size uniformity, and ball index described above, and the boriding conditions and nitriding conditions based on heating. It should be noted that for comparison, the average particle size, particle size uniformity, and ball index measurement results of the granular boron nitride obtained in Example 17 and Comparative Example 5 described in Patent Document 2 are shown as Reference Examples 1 and 2. Fig.10 Table 2.

[0201] Based on these results, the following preferred conditions can be derived when manufacturing a boron nitride composition containing granular boron nitride: As boriding conditions for preparing an iron boride composition from Fe2O3, B2O3 and carbon powder, Fe2O3 and B2O3 are preferably mixed at a molar ratio of 1.5:1 to 1:3, particularly preferably 1.2:1 to 1:1.2, and added in such a manner that all oxygen contained in these oxides can be discharged in the form of CO gas, and in such a manner that the molar ratio of oxygen atoms to carbon atoms contained in the oxides becomes 1:1, to prepare a boriding raw material mixture. Such a raw material mixture is preferably subjected to a heat treatment in an argon atmosphere at 1200 to 1500°C for 1 to 2 hours, particularly preferably at 1250 to 1300°C for 1 to 2 hours, to obtain a iron boride composition. Then, the obtained iron boride composition is preferably crushed into particles of 20 μm or less using an automatic mortar, and then preferably heat-treated at 1800 to 2000° C. for 5 to 10 hours, for example, at 2000° C. for 5 to 10 hours in a nitrogen atmosphere, thereby obtaining a boron nitride composition containing granular boron nitride, which also includes spherical boron nitride. In this case, the average particle size of the obtained spherical boron nitride is preferably 20 to 50 μm, for example, 20 to 40 μm, the ball index is, for example, 10 or less, preferably 7 or less, and the dispersion index (particle size uniformity) is, for example, 0.4 or less, preferably 0.3 or less.

[0202] <Manufacturing of resin composition and molded article>

[0203] like Fig.11 As shown in Table 3, the granular boron nitride of the present invention obtained in the above-mentioned several embodiments (after acid washing, filtering and drying) was added / mixed into the epoxy resin material to obtain the resin compositions of Examples 28 to 44. The mass-based composition of the resin composition is 81.7% (70 volume%) of granular boron nitride and 18.3% (30 volume%) of epoxy resin material, or 74.2% (60 volume%) of granular boron nitride and 25.8% (40 volume%) of epoxy resin material. It should be noted that, with respect to the molded bodies using the granular boron nitride of the above-mentioned Reference Examples 1 and 2, the values ​​of thermal conductivity disclosed in Patent Document 2 are included in Table 3 as Reference Examples 3 and 4. In addition, a molded body using the granular boron nitride of Reference Example 1 was prepared as Reference Example 5, and its thermal conductivity was measured.

[0204] Specifically, when 81.7% (70% by volume) of granular boron nitride and 18.3% (30% by volume) of epoxy resin material were mixed, 1.0 g of the obtained granular boron nitride (after acid washing, filtration and drying), 0.1229 g of bisphenol A type liquid epoxy resin (main agent) (manufactured by MITSUBISHI CHEMICAL Co., Ltd.: jER828), 0.0983 g of methylbutyltetrahydrophthalic anhydride (curing agent) (manufactured by MITSUBISHI CHEMICAL Co., Ltd.: YH306), 0.00246 g of 2-ethyl-4-methylimidazole (curing accelerator) (manufactured by MITSUBISHI CHEMICAL Co., Ltd.: EMI24), and 20 g of acetone (manufactured by Wako Pure Chemical Industries, Ltd.: reagent special grade) were added to a 100 ml eggplant flask, and mixed for 5 minutes using ultrasonic waves.

[0205] When 74.2% (60% by volume) of granular boron nitride and 25.8% (40% by volume) of epoxy resin material were mixed, 1.0 g of the obtained granular boron nitride (after acid washing, filtration and drying), 0.1911 g of bisphenol A type liquid epoxy resin (main agent) (manufactured by MITSUBISHI CHEMICAL Co., Ltd.: jER828), 0.1529 g of methylbutyltetrahydrophthalic anhydride (curing agent) (manufactured by MITSUBISHI CHEMICAL Co., Ltd.: YH306), 0.00382 g of 2-ethyl-4-methylimidazole (curing accelerator) (manufactured by MITSUBISHI CHEMICAL Co., Ltd.: EMI24), and 20 g of acetone (manufactured by Wako Pure Chemical Industries, Ltd.: reagent special grade) were added to a 100 ml eggplant flask, and mixed for 5 minutes using ultrasound.

[0206] Next, the acetone was removed using an evaporator. 0.8 g of a mixture of a resin composition containing granular boron nitride and an epoxy resin material remaining in the eggplant-shaped flask after the removal was added to a mold with a diameter of 15 mm, and the resin composition was thermally cured by hot pressing to obtain two molded bodies (diameter 15 mm, thickness 1.2 mm or 1.5 to 2.4 mm).

[0207] The conditions for hot pressing are as follows.

[0208] Regarding Reference Examples 3 and 4 and Examples 26 and 28 to 31, hot pressing was performed at 125° C. and 70 MPa under uniaxial pressure for 120 minutes.

[0209] · Regarding Examples 27 and 32 to 36, hot pressing was performed at 125° C. and 23 MPa under uniaxial pressure for 120 minutes.

[0210] Regarding Reference Example 5 and Examples 37 to 42, hot pressing was performed at 125° C. and 10 MPa under uniaxial pressure for 120 minutes.

[0211] <Measurement of thermal conductivity of molded article>

[0212] The density, specific heat, and thermal diffusivity of the obtained molded body were measured, and the thermal conductivity of the molded body was calculated based on the following formula.

[0213] Thermal conductivity = density × specific heat × thermal diffusivity

[0214] <Determination of density>

[0215] The density of the epoxy resin material / granular boron nitride molded body was determined by the following (Formula 1) by measuring the density of the epoxy resin material / granular boron nitride molded body by the underwater Archimedes method.

[0216] ρ=(ρ a ×m1) / (m1-m2) Formula (1)

[0217] Where ρ is the density of the molded body (g / cm 3 ), ρ a is the density of water at the test temperature (g / cm 3 ), m1 is the mass (g) of the molded body in air, and m2 is the mass of the molded body in water.

[0218] <Measurement of specific heat>

[0219] Using a differential scanning calorimeter (Netzsch, DSC200F·3Maia), a certain amount of heat was applied to a known reference material (sapphire in this measurement) and a molded body as a sample while their temperatures were measured, and the temperature difference was measured. Thermal analysis was performed to obtain the specific heat. The specific heat of the sample was calculated by the following (Formula 2). It should be noted that the temperature measurement range is set to -50°C to 100°C, and the specific heat of 25°C, which is the same measurement temperature as the thermal diffusivity described below, is used to calculate the thermal conductivity.

[0220] Cp=(m / M)×(h / IH)×Cp standard Formula (2)

[0221] Where Cp is the specific heat of the molded sample (J / g / K), Cp standard is the specific heat of the reference substance (J / g / K), m is the weight of the molded sample (g), M is the weight of the reference substance (g), h is the difference between the DSC curves of the empty container and the molded sample, and H is the difference between the DSC curves of the empty container and the reference substance.

[0222] <Measurement of thermal diffusivity>

[0223] The thermal constant measurement device of the xenon flash method (Netzsch, Xe flash analyzer, LFA447Nanoflash) was used. As for the thermal diffusivity (α), a heat source was irradiated to the surface of the molded sample, and the temperature of the back side was measured. The time t was 1 / 2 of the time (ΔTm) until the maximum temperature reached the back side. 1 / 2 (s) and sample thickness L (m) are obtained by the following formula (3).

[0224] α(m 2 / s)=0.1388×L 2 / t 1 / 2 Formula (3)

[0225] It should be noted that the thermal conductivity of the molded body was measured in the pressure direction (pressing direction) of the pressure applied during hot pressing and in the direction perpendicular thereto. With respect to the pressing direction, the surface of the hot press molded body with a diameter of 15 mm and a thickness of 1.2 mm was polished with #1000 water-resistant abrasive paper to prepare a sample with a thickness of about 1 mm, and the sample was measured as described above. With respect to the direction perpendicular to the pressing direction, 5 to 7 prism-shaped segments with a length of 10 mm, a width of 2.0 mm, and a thickness of 1.5 to 2.4 mm were cut out from the molded body with a diameter of 15 mm and a thickness of 2.4 mm, and the prism-shaped segments were laminated in a state where they were rotated 90° so that their width became the thickness direction, to obtain a quadrilateral thin plate-shaped object with a length of about 10 mm, a width of about 10.5 to 12.0 mm, and a thickness of 2.0 mm. The surface of the plate was further polished with #1000 water-resistant abrasive paper to obtain a sample with a length of about 10 mm, a width of 10 mm, and a thickness of about 1 mm, and the sample was measured as described above.

[0226] <Conditions of Examples and Reference Examples and Results of Thermal Conductivity Measurement>

[0227] The conditions of the above-mentioned examples and reference examples and the results of the measurement of thermal conductivity are shown in Fig.11 Table 3.

[0228] These results show that the molded body using the spherical boron nitride as the granular boron nitride of the present invention has a thermal conductivity substantially the same as or higher than that of the molded body using the granular boron nitride described in Patent Document 2 (Reference Examples 3 to 5).

[0229] It should be noted that the granular boron nitride of Reference Examples 1 and 2 includes granular boron nitride with a relatively wide particle size distribution and a small particle size, so in order to achieve high thermal conductivity, a very large pressing pressure (e.g., 70 MPa) is required during molding. Such a pressing pressure may cause the collapse of the three-dimensional structure of the granular boron nitride depending on the situation.

[0230] In the case of a molded body using the spherical boron nitride of the present invention, even at a pressing pressure of 70 MPa, it is possible to provide substantially the same thermal conductivity as that of Patent Document 2 in the direction parallel to the pressing, and also provide increased thermal conductivity in the direction perpendicular to the pressing. In order to mold at an ideal, lower pressing pressure during molding, it is necessary to increase the amount of resin. From the results of Examples 34 to 38, it can be seen that even if the pressing pressure is reduced to 23 MPa (one of the reasons for which it is speculated that the collapse of the granular boron nitride is suppressed), the thermal conductivity is not significantly reduced compared to the case of 70 MPa (if compared with Reference Examples 3 and 4, the thermal conductivity in the direction parallel to the pressing is substantially the same, and the thermal conductivity in the direction perpendicular to the pressing is increased).

[0231] In addition, as in Examples 39 to 44, even if the pressing pressure is set to less than 10 MPa and the amount of resin is increased to 25.8% by mass (one of the reasons is that the particle size uniformity and the larger particle size are presumed), the difference between the thermal conductivity in the direction parallel to the pressing and the thermal conductivity in the direction perpendicular to the pressing is small, and the value itself does not decrease significantly. It can be seen that the granular boron nitride of the present invention can function as a heat transfer filler that can provide a molded body with a thermal conductivity close to isotropic. In addition, compared with Reference Example 5 under the same conditions, the thermal conductivity increases in both directions.

[0232] Referring to the results in Table 3, in the molded body of the present invention, the thermal conductivity in the direction parallel to the pressing is preferably at least 40%, more preferably at least 50%, and particularly preferably at least 90% of the thermal conductivity in the direction perpendicular to the pressing, depending on the method for producing the boron nitride composition. Therefore, the boron nitride composition containing granular boron nitride, granular boron nitride, or spherical boron nitride of the present invention can improve the isotropy of the molded body obtained by mixing with a resin material and molding.

[0233] Industrial Applicability

[0234] Therefore, the resin composition of the present invention and a molded product produced by molding the composition can be preferably used as a thermally conductive filler in heat sinks, thermally conductive pastes, thermally conductive adhesives, etc. that require thermal conductivity in the electrical and electronic fields.

[0235] It should be noted that the present invention includes the following aspects.

[0236] (Solution 1)

[0237] A method for producing a boron nitride composition, characterized in that it is a method for producing a boron nitride composition containing granular boron nitride, wherein the iron boride composition containing iron boride is heat-treated at 1750°C to 2300°C in a nitrogen atmosphere to nitride the boron.

[0238] (Solution 2)

[0239] The method for producing a boron nitride composition according to the above-mentioned embodiment 1 is characterized in that the iron boride is at least one selected from FeB, Fe2B and Fe3B.

[0240] (Solution 3)

[0241] The method for producing a boron nitride composition according to the above-mentioned scheme 1 or 2 is characterized in that the iron boride composition further contains at least one selected from CaO, CeO2 and Y2O3 as an auxiliary agent.

[0242] (Solution 4)

[0243] The method for producing a boron nitride composition according to any one of the above schemes 1 to 3 is characterized in that the iron boride composition is obtained by heating a raw material mixture containing an iron oxide component, a boron oxide component and a carbon component at 1150°C to 1600°C in an inert gas atmosphere to boride the iron.

[0244] (Scheme 5)

[0245] The method for producing a boron nitride composition according to the above-mentioned scheme 4 is characterized in that the iron oxide component includes at least one selected from Fe2O3, Fe3O4 and FeO.

[0246] (Scheme 6)

[0247] The method for producing a boron nitride composition according to the above-mentioned scheme 4 or 5, wherein the boron oxide component includes at least one selected from B2O3, B4O3 and B4O5.

[0248] (Scheme 7)

[0249] The method for producing a boron nitride composition according to any one of aspects 4 to 6, wherein the iron boride composition obtained by boriding by heat treatment is pulverized and then nitrided by heat treatment.

[0250] (Scheme 8)

[0251] The method for producing a boron nitride composition according to any one of the above aspects 1 to 7 is characterized in that a cleaning treatment with an acid is performed after nitriding by heat treatment.

[0252] (Scheme 9)

[0253] A boron nitride composition, characterized in that it contains granular boron nitride, wherein the granular boron nitride has a shell structure and a sphericity index of 10 or less.

[0254] (Scheme 10)

[0255] The boron nitride composition according to claim 9 is characterized in that the average particle size of the granular boron nitride is 2 to 75 μm, preferably 10 to 50 μm.

[0256] (Scheme 11)

[0257] The boron nitride composition according to claim 9 or 10, wherein the dispersion index of the granular boron nitride is 0.3 or less.

[0258] (Scheme 12)

[0259] The boron nitride composition according to Scheme 9 or 10 is characterized in that the boron nitride composition is manufactured by the method for manufacturing a boron nitride composition as described in Scheme 6.

[0260] (Scheme 13)

[0261] A resin composition, characterized in that it contains granular boron nitride and a resin material as described in Scheme 9 or 10.

[0262] (Scheme 14)

[0263] A molded body, characterized in that it is produced by molding the resin composition according to Scheme 13.

Claims

1. A method for producing a boron nitride composition, characterized in that: A method for producing a boron nitride composition containing granular boron nitride, wherein: The iron boride composition including the iron boride is heat-treated at 1750° C. to 2300° C. in a nitrogen atmosphere to nitride the boron in the iron boride.

2. The method for producing a boron nitride composition according to claim 1, characterized in that: The iron boride is at least one selected from FeB, Fe2B and Fe3B.

3. The method for producing a boron nitride composition according to claim 2, characterized in that: The iron boride composition further comprises at least one selected from CaO, CeO2 and Y2O3 as an auxiliary agent.

4. The method for producing a boron nitride composition according to claim 2 or 3, characterized in that: The iron boride composition is obtained by heating a raw material mixture containing an iron oxide component, a boron oxide component, and a carbon component at 1150° C. to 1600° C. in an inert gas atmosphere to boride iron.

5. The method for producing a boron nitride composition according to claim 4, characterized in that: The iron oxide component includes at least one selected from Fe2O3, Fe3O4 and FeO.

6. The method for producing a boron nitride composition according to claim 5, characterized in that: The boron oxide component includes at least one selected from B2O3, B4O3 and B4O5.

7. The method for producing a boron nitride composition according to claim 6, characterized in that: The iron boride composition obtained by the boriding by heat treatment is pulverized and then nitrided by heat treatment.

8. The method for producing a boron nitride composition according to claim 6, characterized in that: After the nitridation by heat treatment, a cleaning treatment using an acid is performed.

9. A boron nitride composition, characterized in that The present invention comprises granular boron nitride having a shell structure and a sphericity index of 10 or less.

10. The boron nitride composition according to claim 9, characterized in that The average particle size of the granular boron nitride is 2 to 75 μm, preferably 10 to 50 μm.

11. The boron nitride composition according to claim 9 or 10, characterized in that: The dispersion index of the granular boron nitride is 0.3 or less.

12. The boron nitride composition according to claim 9 or 10, characterized in that: The boron nitride composition is produced by the method for producing a boron nitride composition according to claim 6.

13. A resin composition, characterized in that The method comprises the granular boron nitride as claimed in claim 9 or 10 and a resin material.

14. A molded body, characterized in that The method is produced by molding the resin composition according to claim 13.

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