Boron nitride powder, inorganic filler, resin composition, and resin molded article

Abstract

To provide a boron nitride powder capable of providing resin molded articles with excellent heat dissipation and insulation properties. [Solution] A boron nitride powder containing aggregated particles composed of aggregated primary particles of hexagonal boron nitride, wherein the orientation index is 12 or less, and in the Raman spectrum obtained by irradiating the aggregated particles with a laser of wavelength 532 nm, the peak showing the maximum intensity is a Raman shift of 1360 cm⁻¹. -1 ~1370cm -1 It exists in the region, and the peak width at half maximum is 30 cm. -1 The following boron nitride powder is provided.

Description

[Technical Field]

[0001] This disclosure relates to boron nitride powder, inorganic fillers, resin compositions, resin molded articles, etc. [Background technology]

[0002] Boron nitride powder possesses high thermal conductivity and insulating properties, and is widely used in applications such as thermal conductive fillers and insulating fillers. In particular, boron nitride powder is used as a filler in heat dissipation components where thermal conductivity is required (for example, Patent Document 1, etc.). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2000-154265 [Overview of the project] [Problems that the invention aims to solve]

[0004] Resin molded articles containing boron nitride powder (e.g., heat dissipation sheets) are used, for example, as heat-generating components in electronic devices. Such resin molded articles preferably possess excellent heat dissipation properties as well as excellent electrical insulation properties.

[0005] One aspect of this disclosure aims to provide boron nitride powder, inorganic fillers, and resin compositions useful for forming resin molded articles with excellent heat dissipation and insulation properties. Another aspect of this disclosure aims to provide resin molded articles with excellent heat dissipation and insulation properties. [Means for solving the problem]

[0006] Thermal conduction in boron nitride is mainly carried by the propagation of waves of vibrations, i.e., "phonons", that travel through the crystal lattice. One of the factors that reduces the thermal conductivity is "phonon scattering". And defects, impurities, grain boundaries, lattice strain (strain due to stress), disorder in crystal orientation, etc. existing inside the crystal are factors that cause phonon scattering. While general crystallinity evaluation (such as XRD, etc.) remains at a specific perspective (such as crystallite size, etc.), the Raman spectrum reflects the vibration state (phonon) of the crystal lattice. Among such Raman spectra, in particular, "the peak showing the maximum intensity existing in the region of 1360 cm , , , , , ~1370 cm -1 has been found to be useful as an indicator showing the degree of phonon scattering.

[0007] One aspect of the present disclosure includes the following [1] to [9]. [1] A boron nitride powder containing agglomerated particles composed of aggregated primary particles of hexagonal boron nitride, having an orientation index of 12 or less, in the Raman spectrum obtained by irradiating the agglomerated particles with a laser having a wavelength of 532 nm, the peak showing the maximum intensity is at a Raman shift of 1360 cm -1 ~1370 cm -1 exists in the region, and the full width at half maximum of the peak is 30 cm -1 or less, the boron nitride powder. [2] The boron nitride powder according to [1], wherein the 50% passing particle size (D50) in the particle size distribution measured by the laser diffraction scattering method is 1 to 150 μm. [3] The boron nitride powder according to [1] or [2], wherein the crushing strength of the agglomerated particles is 5 MPa or more. [4] The boron nitride powder according to any one of [1] to [3], having a graphitization index of 2.3 or less. [5] The boron nitride powder according to any one of [1] to [4], and an inorganic filler containing at least one selected from the group consisting of aluminum oxide and aluminum nitride powder. [6]A resin composition comprising the boron nitride powder according to any one of [1] to [4] above and a resin. [7]A resin composition comprising the inorganic filler according to [5] above and a resin. [8]A resin molded body comprising the boron nitride powder according to any one of [1] to [4] above and a resin. [9]A resin molded body comprising the inorganic filler according to [5] above and a resin.

[0008] Raman shift 1360 cm -1 ~1370 cm -1 The full width at half maximum of the peak showing the maximum intensity in the region is considered to reflect composite factors that inhibit heat conduction, including not only the regularity of the atomic arrangement and the lattice strain in the in-plane direction, but also the disorder of the crystal orientation and the decrease in crystallinity in the stacking direction (stacking defects, turbostratic structure, disorder in the stacking of polycrystalline flakes, etc.). The boron nitride powders of [1] to [4] above have a full width at half maximum of the above peak showing the maximum intensity of 30 cm -1 or less, so the factors that inhibit heat conduction and the factors that reduce electrical insulation are sufficiently reduced. Also, since the orientation index is 12 or less, the thermal anisotropy is sufficiently reduced. Therefore, the above boron nitride powder is considered useful for forming a resin molded body having excellent heat dissipation and excellent insulation.

[0009] Since the inorganic filler of [5] above contains the above boron nitride powder, it is useful for forming a resin molded body having excellent heat dissipation and excellent insulation.

[0010] Since the resin composition of [6] or [7] above contains the above boron nitride powder or the above inorganic filler, it is useful for forming a resin molded body having excellent heat dissipation and excellent insulation.

[0011] Since the resin molded body of [8] or [9] above contains the above boron nitride powder or the above inorganic filler, it has excellent heat dissipation and excellent insulation.

Advantages of the Invention

[0012] According to the present disclosure, it is possible to provide a boron nitride powder, an inorganic filler, and a resin composition useful for forming a resin molded body having excellent heat dissipation and excellent insulation. Further, according to the present disclosure, it is possible to provide a resin molded body having excellent heat dissipation and excellent insulation.

Mode for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present disclosure will be described. However, the following embodiments are examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents. In this specification, a numerical range indicated by the symbol "~" includes a lower limit value and an upper limit value. That is, the numerical range indicated by "x~y" means x or more and y or less.

[0014] Unless otherwise specified, the materials exemplified in this specification can be used alone or in combination of two or more. The content of each component in the composition means the total amount of the plurality of substances present in the composition when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified.

[0015] The boron nitride powder according to one embodiment of the present disclosure includes agglomerated particles formed by aggregation of hexagonal boron nitride primary particles. In the Raman spectrum obtained by irradiating this agglomerated particle with a laser having a wavelength of 532 nm, the peak showing the maximum intensity (hereinafter also referred to as "peak A") has a Raman shift of 1360 cm -1 ~1370 cm -1 in the region, and the full width at half maximum of peak A is 30 cm -1 or less. In this specification, the range of the Raman shift (horizontal axis) in the Raman spectrum is 900~3000 cm -1 is. Also, the peak intensity of the Raman spectrum shall mean the height of the peak from the baseline.

[0016] Raman spectroscopy measurements of boron nitride powder shall be performed by the following method. Specifically, first, a cross-sectional sample of aggregated particles in the powder is prepared using a cross-sectional sample preparation device. Next, the obtained cross-sectional sample is used as the measurement target, and the Raman spectrum is obtained by measuring it using a Raman spectrometer under the measurement conditions described in the examples (horizontal axis: Raman shift (unit is cm)). -1 The vertical axis (intensity) is obtained. For cross-sectional sample preparation equipment, for example, the "CP-9010" (product name) manufactured by JEOL Ltd. can be used. For Raman spectrometers, for example, the "Raman Microscope XploRA" (product name) manufactured by Horiba, Ltd. can be used.

[0017] The full width at half maximum (FWHM) of peak A is 30 cm. -1 The following applies: The full width at half maximum of peak A is 30 cm. -1 The boron nitride powder described below exhibits high crystal periodicity in both the in-plane and stacking directions, suppressing phonon scattering. Therefore, resin molded bodies containing this boron nitride powder have excellent heat dissipation. The full width at half maximum of peak A is 0 cm. -1 Super, 1cm -1 More than 3cm -1 More than 5cm -1 Above 8cm -1 Above 12cm -1 Above 15cm -1 or more, or 20cm -1 The above is acceptable. The full width at half maximum of peak A is set to 28 cm from the viewpoint of further improving the heat dissipation of the resin molded body. -1 Below, 25cm -1 Below, 23cm -1 Below, 20cm -1 Below, 15cm -1 Below or 11cm -1 The following is acceptable. The full width at half maximum of peak A may be adjusted within the above range, for example, 1 to 30 cm. -1 , 3-28cm -1 or 5-25cm -1This may be the case. The full width at half maximum of peak A can be adjusted by the pressure in the nitriding process, the firing temperature in the firing process, etc., as described later. If there are multiple "peaks showing maximum intensity" in the Raman spectrum, the "peak showing maximum intensity (peak A)" in this specification is defined as the peak with a Raman shift of 1366 cm⁻¹ among those peaks. -1 It refers to the peak that is closest to [the specified value].

[0018] The boron nitride powder described above may include primary particles of hexagonal boron nitride and aggregated particles composed of multiple aggregated primary particles of hexagonal boron nitride. In this specification, aggregated particles refer to secondary particles that exist in an aggregated state of multiple primary particles (single particles), where the c-axis direction of each primary particle is random. The aggregated state of primary particles can be confirmed, for example, by SEM (scanning electron microscope). Aggregated particles may be approximately spherical. In aggregated particles, primary particles may be strongly bound to each other.

[0019] The 50% passing particle size (D50) of boron nitride powder in the particle size distribution measured by laser diffraction scattering may be 1 μm or more, 5 μm or more, 10 μm or more, 15 μm or more, 18 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, 43 μm or more, or 44.5 μm or more, from the viewpoint of ensuring the heat dissipation of the resin molded article. The 50% passing particle size (D50) of boron nitride powder may be 150 μm or less, 130 μm or less, 120 μm or less, 100 μm or less, 80 μm or less, 60 μm or less, 55 μm or less, 50 μm or less, 44.5 μm or less, 42 μm or less, 40 μm or less, or 30 μm or less, from the viewpoint of further improving the insulation properties of the resin molded article and reducing the viscosity of the resin composition. The 50% passable particle size (D50) of the boron nitride powder can be adjusted within the above range, for example, 1 to 150 μm, 5 to 100 μm, 10 to 80 μm, or 20 to 50 μm.

[0020] In this specification, the 50% passable particle size (D50) of boron nitride powder refers to the value measured in accordance with the method described in JIS Z 8825:2013 "Particle size analysis - Laser diffraction and scattering method". A laser diffraction and scattering particle size distribution analyzer is used for the measurement. Examples of laser diffraction and scattering particle size distribution analyzers that can be used include the "LS-13 320" (product name) from Beckman Coulter and the Microtrac "MT-3300EXII" (product name) from Microtrac-Bell. When measuring the 50% passable particle size (D50, volume basis) of boron nitride powder, the measurement should be performed without any homogenization or other treatment of the powder to be measured.

[0021] The orientation index of the boron nitride powder is 12 or less. By having an orientation index of 10 or less, the thermal anisotropy of boron nitride can be further reduced, and the heat dissipation of the resin molded article can be improved. The orientation index of the boron nitride powder may be 2 or more, 4 or more, 6 or more, 7.5 or more, or 8.5 or more. From the viewpoint of further improving the heat dissipation of the resin molded article, the orientation index of the boron nitride powder may be 11 or less, 10 or less, 9.8 or less, 9.5 or less, 9.2 or less, 8.5 or less, or 7.5 or less. The orientation index of the boron nitride powder may be adjusted within the above range, for example, 2 to 12 or 4 to 10.

[0022] In this specification, the orientation index refers to a value measured according to the following method: An X-ray diffraction spectrum of boron nitride powder is obtained by performing an X-ray diffraction measurement on the boron nitride powder, and peak intensities I(002) and I(100) corresponding to the (002) plane and (100) plane are obtained from the said X-ray diffraction spectrum. The orientation index [I(002) / I(100)] of the boron nitride powder is calculated using the obtained peak intensities. As an X-ray diffractometer, for example, "ULTIMA-IV" (product name) manufactured by Rigaku Corporation can be used.

[0023] Since the orientation index is measured on boron nitride powder, if aggregated particles are present in the powder and their proportion is large, the orientation index value tends to decrease and approach a value of around 6 to 7. On the other hand, if the powder consists only of primary particles without aggregated particles, or if the proportion of the above primary particles is large, the orientation index value tends to increase.

[0024] The crushing strength of aggregated particles in boron nitride powder may be 1 MPa or higher, 3 MPa or higher, 5 MPa or higher, 7 MPa or higher, 8 MPa or higher, 9 MPa or higher, 10.5 MPa or higher, 11.5 MPa or higher, or 14 MPa or higher, from the viewpoint of suppressing the collapse of aggregated particles and further improving the heat dissipation of the resin molded body. The crushing strength of aggregated particles in boron nitride powder may be 30 MPa or lower, 25 MPa or lower, 20 MPa or lower, 18 MPa or lower, 16 MPa or lower, 13 MPa or lower, 11.5 MPa or lower, or 10.5 MPa or lower, from the viewpoint of reducing voids in the resin molded body and further improving the insulation properties of the resin molded body. The crushing strength of aggregated particles may be adjusted within the above range, for example, 1 to 30 MPa, 5 to 25 MPa, or 8 to 20 MPa.

[0025] In this specification, crushing strength refers to the value measured in accordance with JIS R 1639-5:2007 "Fine ceramics - Method for measuring grain properties - Part 5: Single grain crushing strength". The crushing strength σ (unit: MPa) of a single granule is given by σ = α × P / (π × d), where α (α = 2.48), a dimensionless number that changes depending on the position within the granule, P (unit: N), and d (unit: μm). 2 The value is calculated using the following formula: ( ). The measurement shall be performed on 20 or more granules (aggregated particles), and the value at the point of cumulative destruction rate of 63.2% shall be calculated. A microcompression tester can be used for the measurement. For example, the "MCT-W500" (product name) manufactured by Shimadzu Corporation can be used as a microcompression tester.

[0026] The graphitization index of the boron nitride powder may be 1.0 or higher, 1.2 or higher, 1.3 or higher, 1.4 or higher, 1.5 or higher, 1.6 or higher, or 1.7 or higher. When the graphitization index of the boron nitride powder is above the lower limit, the collapse of aggregated particles due to excessive growth of primary particles is sufficiently suppressed, and the increase in the orientation index of the boron nitride powder is easily suppressed. The graphitization index of the boron nitride powder may be 4.0 or lower, 3.0 or lower, 2.5 or lower, 2.3 or lower, 2.0 or lower, 1.8 or lower, or 1.7 or lower. When the graphitization index of the boron nitride powder is below the upper limit, the crystallinity of the boron nitride primary particles is high, and a resin molded article with excellent heat dissipation is easily obtained. The graphitization index of the boron nitride powder may be adjusted within the above range, for example, 1.0 to 4.0, 1.2 to 3.0, or 1.5 to 2.5. The graphitization index (sometimes called GI) is an indicator of the crystallinity of boron nitride powder.

[0027] The graphitization index used herein is also known as an index value indicating the degree of crystallinity of graphite (e.g., J. Thomas, et al., J. Am. Chem. Soc. 84, 4619 (1962), etc.). The graphitization index is calculated based on the spectrum measured by powder X-ray diffraction of boron nitride powder. First, in the X-ray diffraction spectrum, the area value (in arbitrary units) enclosed by the integrated intensity (i.e., each diffraction peak) of each diffraction peak corresponding to the (100), (101), and (102) planes of the primary particles of hexagonal boron nitride and its baseline is calculated and designated as S100, S101, and S102, respectively. Using the calculated area value, the value of [(S100 + S101) / S102] is calculated to determine the graphitization index. More specifically, it is determined by the method described in the examples herein.

[0028] One embodiment of a method for producing boron nitride powder comprises a nitriding step of obtaining boron carbonitride powder by calcining boron carbide powder under a nitrogen pressurized atmosphere, a calcination step of calcining the boron carbonitride powder under an atmosphere, and a crystallization step of obtaining boron nitride powder by calcining the boron carbonitride powder that has undergone the calcination step under a nitrogen-containing atmosphere.

[0029] Boron carbide powder may be obtained by calcining a mixture of a boron source and carbon black (e.g., acetylene black) under an argon atmosphere. The boron source may include at least one selected from the group consisting of boric acid and boron oxide.

[0030] The boron source content may be 60% by mass or more, 85% by mass or less, or 60-85% by mass, based on the total mass of the boron source and carbon black. The boric acid content, based on the total mass of boric acid and carbon black, may also be within the above ranges. The carbon black content may be 15% by mass or more, 40% by mass or less, or 15-40% by mass, based on the total mass of the boron source and carbon black.

[0031] The calcination temperature when obtaining boron carbide powder may be 1800°C or higher, 2500°C or lower, or 1800 to 2500°C. The calcination time when obtaining boron carbide powder may be 2 hours or more, 8 hours or less, or 2 to 8 hours.

[0032] The average particle size of the boron carbide powder may be 5 μm or more, 10 μm or more, or 20 μm or more. From the viewpoint of further improving the insulating properties of the resin molded article, the average particle size of the boron carbide powder may be 40 μm or less or 30 μm or less. The average particle size of the boron carbide powder may be adjusted within the above range, for example, 5 to 40 μm. The average particle size of the boron carbide powder is the 50% passing particle size (D50) in the volume-based particle size distribution measured in accordance with the method described in JIS Z 8825:2013 "Particle size analysis - Laser diffraction and scattering method".

[0033] The pressure in the nitriding process may be 5 MPa or higher or 9 MPa or higher. When the pressure in the nitriding process is above the lower limit mentioned above, the phase separation of C and BN progresses in the boron carbonitride powder, which is a multiphase of tC (randomly layered carbon) and t-BN (randomly layered boron nitride), and the crystallinity of t-BN improves, resulting in a crystal structure closer to h-BN. As a result, it is presumed that the full width at half maximum of peak A of the boron nitride powder is reduced, making it easier to obtain boron nitride powder that further improves the heat dissipation performance in resin molded articles. From the viewpoint of suppressing an increase in the manufacturing cost of boron nitride powder, the pressure in the nitriding process may be 40 MPa or lower or 30 MPa or lower. The pressure in the nitriding process may be adjusted within the above range, for example, 5 to 40 MPa or 9 to 30 MPa.

[0034] The firing temperature in the nitriding process may be 1500°C or higher or 1800°C or higher, from the viewpoint of allowing the nitriding of boron carbide to proceed more sufficiently. The firing temperature in the nitriding process may be 2500°C or lower or 2300°C or lower, from the viewpoint of suppressing an increase in the manufacturing cost of boron nitride powder. The firing temperature in the nitriding process may be adjusted within the above range, for example, 1500 to 2500°C or 1800 to 2300°C.

[0035] The firing time in the nitriding process may be 10 hours or more, or 20 hours or more, from the viewpoint of allowing the nitriding of boron carbide to proceed more sufficiently. The firing time in the nitriding process may be 50 hours or less, or 40 hours or less, from the viewpoint of suppressing an increase in the manufacturing cost of boron nitride powder. The firing time in the nitriding process may be adjusted within the above range, for example, 10 to 50 hours or 20 to 40 hours.

[0036] In the firing process, the carbon content in the boron carbonitride powder can be reduced by firing the boron carbonitride powder under atmospheric pressure.

[0037] The firing temperature in the firing process may be 650°C or higher, 700°C or higher, or 750°C or higher. By setting the firing temperature within the above range, the amount of carbon in boron carbonitride can be reduced, and the phase separation of carbon and nitride (BN) can be further promoted. As a result, the full width at half maximum (FWHM) of peak A in the boron nitride powder is reduced, making it easier to obtain boron nitride powder that can further improve the heat dissipation in the resin molded article. The firing temperature in the firing process may be 1000°C or lower, or 950°C or lower. By setting the firing temperature within the above range, excessive crystal growth of primary boron nitride particles can be suppressed. As a result, the orientation index of the boron nitride powder can be reduced, making it possible to obtain boron nitride powder that can further improve the heat dissipation in the resin molded article. The firing temperature in the firing process may be adjusted within the above range, for example, 650-1000°C or 700-950°C.

[0038] The firing time in the firing process may be 2 hours or more or 4 hours or more, from the viewpoint of further reducing the carbon content in the boron carbonitride powder. The firing time in the firing process may be 15 hours or less or 10 hours or less, from the viewpoint of more sufficiently suppressing a decrease in the processing efficiency of the firing process. The firing time in the firing process may be adjusted within the above range, for example, 2 to 15 hours or 4 to 10 hours.

[0039] After the firing process and before the crystallization process, the boron carbonitride powder and the boron source may be mixed. The boron source may contain at least one selected from the group consisting of boric acid and boron oxide. From the viewpoint of further improving the crystallinity of boron nitride, the content of the boron source may be 30% by mass or more, based on the total mass of the boron carbonitride powder and the boron source. From the viewpoint of suppressing the excessive growth of primary boron nitride particles and producing boron nitride powder containing aggregated particles with superior crushing strength, the content of the boron source may be 45% by mass or less, based on the total mass of the boron carbonitride powder and the boron source. The content of the boron source may be adjusted within the above range, for example, 30 to 45% by mass, based on the total mass of the boron carbonitride powder and the boron source.

[0040] The pressure during the crystallization process may be 5 kPa or more, and 20 kPa or less, for example, 5 to 20 kPa.

[0041] The firing temperature in the crystallization process may be 1800°C or higher, from the viewpoint of further reducing the carbon content in the boron carbonitride powder. The firing temperature in the crystallization process may be 2200°C or lower, from the viewpoint of suppressing the yellowing of the boron nitride powder. The firing temperature in the crystallization process may be adjusted within the above range, for example, 1800 to 2200°C.

[0042] The firing time in the crystallization process may be 1 hour or more or 3 hours or more, from the viewpoint of further reducing the carbon content in the boron carbonitride powder. The firing time in the crystallization process may be 10 hours or less or 7 hours or less, from the viewpoint of more sufficiently suppressing a decrease in the processing efficiency of the crystallization process. The firing time in the crystallization process may be adjusted within the above range, for example, 1 to 10 hours or 3 to 7 hours.

[0043] The boron nitride powder obtained in the crystallization process may contain primary particles of hexagonal boron nitride, may contain aggregated particles composed of multiple aggregated primary particles, or may contain both primary particles and aggregated particles.

[0044] The method for producing boron nitride powder may further include a crushing step after the crystallization step. In the crushing step, the boron nitride powder obtained by crushing may be classified.

[0045] The crushing time in the crushing process may be 5 minutes or more, or 8 minutes or more, and may be 15 minutes or less, or 12 minutes or less, for example, 5 to 15 minutes or 8 to 12 minutes.

[0046] An inorganic filler according to one embodiment of the present disclosure is an inorganic filler comprising the boron nitride powder described above and an aluminum compound powder containing at least one selected from the group consisting of aluminum oxide and aluminum nitride.

[0047] The content of boron nitride powder in the inorganic filler may be 20% by mass or more, or 40% by mass or more, based on the total mass of the inorganic filler. The content of boron nitride powder in the inorganic filler may be 90% by mass or less, or 80% by mass or less, based on the total mass of the inorganic filler. The content of boron nitride powder in the inorganic filler may be 20-90% by mass or 40-80% by mass, based on the total mass of the inorganic filler.

[0048] The content of aluminum compound powder in the inorganic filler may be greater than 0% by mass, and may be 10% or more by mass, or 20% or more by mass, based on the total mass of the inorganic filler. The content of aluminum compound powder in the inorganic filler may be 80% or less by mass, or 60% or less by mass. The content of aluminum compound powder in the inorganic filler may be 10 to 80% by mass, or 20 to 60% by mass.

[0049] The inorganic filler may contain other compound powders besides boron nitride powder and the aluminum compound powder mentioned above. Examples of other compound powders include silicon oxide powder, silicon nitride powder, zinc oxide powder, and magnesium oxide powder. The content of other compound powders may be 0.1% by mass or more, 1% by mass or less, 0.1 to 1% by mass, or 0% by mass, based on the total mass of the inorganic filler.

[0050] The inorganic filler according to this embodiment contains the boron nitride powder described above, and is therefore useful for forming resin molded articles that have excellent heat dissipation and insulation properties.

[0051] A resin composition according to one embodiment of the present disclosure comprises the boron nitride powder described above and a resin. The resin composition may further comprise an aluminum compound powder comprising at least one selected from the group consisting of aluminum oxide and aluminum nitride. That is, the resin composition may comprise the inorganic filler described above and a resin.

[0052] The content of boron nitride powder in the resin composition may be 20% by volume or more, 30% by volume or more, or 40% by volume or more, based on the total volume of the resin composition, from the viewpoint of further improving the heat dissipation of the resin molded article. The content of boron nitride powder in the resin composition may be 85% by volume or less, 80% by volume or less, or 70% by volume or less, based on the total volume of the resin composition, from the viewpoint of suppressing a decrease in mechanical strength. The content of boron nitride powder in the resin composition may be adjusted within the above range, for example, 20 to 85% by volume, based on the total volume of the resin composition.

[0053] The resin may contain a curable resin (e.g., a thermosetting resin) or consist solely of a curable resin. Examples of curable resins include epoxy resins, silicone resins, phenolic resins, melamine resins, urea resins, polyimides, polyamideimides, polyetherimides, maleimide-modified resins, and the like.

[0054] The resin composition may contain other components in addition to the boron nitride powder and resin described above. Other components may include, for example, a curing agent. The curing agent may be appropriately selected depending on the type of curable resin. For example, if the resin is an epoxy resin, examples of curing agents include phenol novolac compounds, acid anhydrides, amino compounds, imidazole compounds, etc. The content of the curing agent may be 0.5 parts by mass or more, 1 part by mass or more, or 5 parts by mass or more, or 20 parts by mass or less, or 15 parts by mass or less, per 100 parts by mass of resin.

[0055] The resin composition according to this embodiment contains the above-mentioned boron nitride powder or inorganic filler, and is therefore useful for forming resin molded articles that have excellent heat dissipation and insulation properties.

[0056] One embodiment of the present disclosure is a resin molded article comprising the boron nitride powder described above and a resin. The resin molded article may further contain an aluminum compound powder comprising at least one selected from the group consisting of aluminum oxide and aluminum nitride. That is, the resin molded article may contain the inorganic filler described above and a resin. The resin molded article may be formed from the resin composition described above, or it may be a cured product of the resin composition described above. That is, the resin molded article may contain the inorganic filler described above and a cured product of the resin composition. The curing of the resin composition may be, for example, by heat press molding. The resin molded article may be in the form of a sheet, or it may be a heat dissipation sheet.

[0057] The content of boron nitride powder in a resin molded article may be 20% by volume or more, 30% by volume or more, or 40% by volume or more, based on the total volume of the resin molded article, from the viewpoint of further improving the heat dissipation of the resin molded article. The content of boron nitride powder in a resin molded article may be 85% by volume or less, 80% by volume or less, or 70% by volume or less, based on the total volume of the resin molded article, from the viewpoint of suppressing a decrease in mechanical strength. The content of boron nitride powder in a resin molded article may be adjusted within the above range, for example, 20 to 85% by volume, based on the total volume of the resin molded article.

[0058] When the resin molded product is in the form of a sheet, the thickness of the resin molded product may be 0.1 mm or more, 1 mm or less, or between 0.1 and 1 mm.

[0059] The resin molded article according to this embodiment contains the above-mentioned boron nitride powder or inorganic filler, and therefore has excellent heat dissipation and insulation properties.

[0060] A method for manufacturing a resin molded article (heat dissipation sheet) may include the steps of: molding a mixture containing the above-mentioned boron nitride powder, a curable resin, and a curing agent to obtain a sheet-like molded article; and curing the curable resin by heating while applying pressure in the thickness direction of the molded article to obtain a resin molded article. The details of the boron nitride powder, curable resin, and curing agent may be the same as those in the above-mentioned resin composition. The molding pressure is 150 kgf / cm². 2 The above is sufficient, and 300 kgf / cm² 2 The following may apply: 150-300 kgf / cm² 2 That's fine.

[0061] Although several embodiments have been described above, this disclosure is not limited in any way to the embodiments described above. Furthermore, the descriptions of the embodiments described above are applicable to each other. [Examples]

[0062] The present disclosure will be described in more detail below with reference to examples and comparative examples. However, the present disclosure is not limited to the following examples.

[0063] (Example 1) [Preparation of boron carbide powder] 100 parts by mass of orthoboric acid (manufactured by Nippon Denko Co., Ltd., hereinafter simply referred to as "boric acid") and 35 parts by mass of acetylene black (product name: "HS100", manufactured by Denka Co., Ltd.) were mixed using a Henschel mixer and then packed into a graphite crucible. This graphite crucible was placed in an arc furnace and heated at 2200°C for 5 hours in an argon atmosphere to synthesize a lump of boron carbide (B4C) powder. The synthesized lump of boron carbide powder was pulverized in a ball mill for 1 hour, and then sieved using a sieve to remove coarse particles, thereby producing boron carbide powder (B4C powder) with an average particle size of 25 μm.

[0064] [Preparation of boron carbonitride powder] The prepared boron carbide powder was packed into a boron nitride crucible. The crucible was placed in a resistance heating furnace and heated under the conditions of nitrogen gas atmosphere, pressure of 10 MPa, firing temperature of 2050°C, and firing time of 30 hours to obtain a calcined product containing boron carbonitride (B4CN4) powder (nitriding process). The calcined product obtained as described above was heated under an atmospheric atmosphere at 900°C for 5 hours to obtain a heat-treated product (calcination process).

[0065] [Preparation of boron nitride powder] Based on the total mass of the above heat-treated material and boric acid (boron source), boric acid was added so that the boron source content reached 40% by mass, and the mixture was mixed using a Henschel mixer to obtain a mixture. Next, 1.80 kg of the above mixture was filled into a boron nitride container while appropriately compressing it. Then, the above container was placed in a resistance heating furnace and heated in a nitrogen gas atmosphere at a pressure of 10 kPa from room temperature to 2000°C, and held at 2000°C for 6 hours (crystallization process). This decarburized the above heat-treated material and crystallized the individual boron carbonitride particles in the lump boron carbonitride particles into hexagonal boron nitride primary particles, thereby synthesizing boron nitride powder containing aggregated particles formed by the aggregation of multiple primary particles. The synthesized boron nitride powder was crushed in a mortar for 10 minutes, and then further classified using a nylon sieve with a mesh size of 75 μm. The sieved portion was the boron nitride powder from Example 1.

[0066] (Example 2) Boron nitride powder was prepared in the same manner as in Example 1, except that the pressure in the nitriding process was set to 25 MPa.

[0067] (Example 3) Boron nitride powder was prepared in the same manner as in Example 1, except that the sieving conditions were changed to achieve an average particle size of 13 μm for the boron carbide powder, and the sieve size used when sieving the boron nitride powder was set to 45 μm.

[0068] (Example 4) Boron nitride powder was prepared in the same manner as in Example 1, except that the firing temperature was set to 800°C during the firing process.

[0069] (Comparative Example 1) Boron nitride powder was prepared in the same manner as in Example 1, except that the pressure in the nitriding process was set to 0.80 MPa.

[0070] (Comparative Example 2) Boron nitride powder was prepared in the same manner as in Example 1, except that the firing temperature was set to 600°C during the firing process.

[0071] (Comparative Example 3) Boron nitride powder was prepared in the same manner as in Example 1, except that the firing temperature was set to 1100°C during the firing process.

[0072] (Comparative Example 4) Boron nitride powder was prepared in the same manner as in Example 1, except that the average particle size of the boron carbide powder was set to 100 μm, the pressure in the nitriding process was set to 0.90 MPa, and the sieve size used when sieving the boron nitride powder was set to 250 μm.

[0073] <Evaluation of the properties of boron nitride powder> [Raman spectroscopy measurement] For Examples 1-4 and Comparative Examples 1-4, cross-sectional samples of aggregated particles in boron nitride powder were prepared using a cross-sectional sample preparation device (product name "CP-9010", manufactured by JEOL Ltd.). The obtained cross-sectional samples were measured by Raman spectroscopy using a Raman microscope "XploRA" (product name) manufactured by Horiba, Ltd., under the following measurement conditions, to obtain Raman spectra. The measurement involved mapping measurements at approximately 10 μm squares in the center of the aggregated particles observed in the cross-sectional samples, in 1 μm steps (10 points × 10 points), and the spectra from 100 points were integrated. Subsequently, a process was performed to correct for the fluorescence-derived baseline using a polynomial model, and the Raman spectra were obtained. From each obtained Raman spectrum, the peak showing the maximum intensity (maximum height) (peak A) was identified. In each Raman spectrum, the peak showing the maximum intensity corresponds to a Raman shift of 1360 cm⁻¹. -1 ~1370cm -1 It was present in the region. The full width at half maximum (FMAX) of peak A in each Raman spectrum was calculated. The results are shown in Table 1.

[0074] <Raman spectroscopy measurement conditions> Laser: 532nm (light-reducing filter: 10%) Range: 900~3000cm -1 Objective lens: 100x Grating: 1200g Slit: 100 μm Confocal hole: 100 μm Laser polarization: Circular Exposure time: 1 second Number of exposures: 3

[0075] [Particle size distribution measurement] The particle size distribution of boron nitride powder in each example and comparative example was measured in accordance with the method described in JIS Z 8825:2013 "Particle size analysis - Laser diffraction and scattering method". A laser diffraction scattering particle size distribution analyzer (Microtrac "MT-3300EXII" (product name) manufactured by Microtrac-Bell) was used for the measurement. The D50 value in the obtained volume-based particle size distribution was defined as the 50% passing particle size (D50) of the boron nitride powder. The results are shown in Table 1.

[0076] [Orientation Index] X-ray diffraction spectra were obtained by performing X-ray diffraction measurements on boron nitride powder for each example and comparative example. From these X-ray diffraction spectra, the peak intensities I(002) and I(100) corresponding to the (002) and (100) planes were obtained, and the orientation index [I(002) / I(100)] of the boron nitride powder was calculated. Note that "peak intensity" refers to the peak height. The results are shown in Table 1. The X-ray diffractometer used was "ULTIMA-IV" (product name) manufactured by Rigaku Corporation.

[0077] [Crushing strength] The crushing strength of the aggregated particles contained in the boron nitride powder of each example and comparative example was measured in accordance with JIS R 1639-5:2007 "Fine ceramics - Method for measuring particle properties - Part 5: Single particle crushing strength". A microcompression tester (manufactured by Shimadzu Corporation, product name "MCT-W500") was used for the measurement. The measurement was performed on 20 or more aggregated particles, and the value was calculated at a cumulative fracture rate of 63.2%. The results are shown in Table 1.

[0078] [Graphitization Index] The graphitization index of the boron nitride powder in each example and comparative example was calculated from the results of powder X-ray diffraction measurements. In the obtained X-ray diffraction spectra, the area value (in arbitrary units) enclosed by the integrated intensity of each diffraction peak (i.e., each diffraction peak) corresponding to the (100), (101), and (102) planes of the hexagonal boron nitride primary particles and their baseline was calculated and designated as S100, S101, and S102, respectively. Using the area values ​​thus calculated, the graphitization index was determined based on the following equation (1). The results are shown in Table 1. Graphitization index = (S100 + S101) / S102 ... (1)

[0079] [Preparation of evaluation sheet] A mixture of 100 parts by mass of naphthalene-type epoxy resin (product name: HP4032, manufactured by DIC Corporation) and 10 parts by mass of an imidazole compound (product name: 2E4MZ-CN, manufactured by Shikoku Chemicals Holdings Co., Ltd.) as a curing agent was prepared. The mixture was then mixed so that the boron nitride powder of each example and comparative example reached 65% by volume. A solvent (toluene) was added to achieve a coating viscosity to obtain a resin composition. A rotary-orbital stirring and defoaming machine (manufactured by Thinky Co., Ltd., product name: Awatori Rentaro (registered trademark)) was used for mixing with the resin. The mixing conditions were 2000 rpm for 3 minutes. The obtained resin composition was coated onto a PET film to a thickness of 0.2 mm using a coater. Afterwards, a temperature of 150°C and a load of 200 kgf / cm² were applied. 2 A 0.2 mm thick resin sheet (evaluation sheet) was prepared by heating and pressurizing under the specified conditions.

[0080] [Measurement of thermal conductivity and evaluation of heat dissipation] The thermal conductivity of the evaluation sheet described above was measured. Thermal conductivity H (unit: W / (m·K)) is equal to the thermal diffusivity α H (Unit: m) 2 / sec), density ρ (unit: kg / m 3 ) and specific heat capacity C p From the value (unit: J / (kg·K)), H=α H ×ρ×C p The thermal diffusivity α was calculated based on the following formula. HThe specific heat capacity C was determined by processing an evaluation sheet to 10 mm (length) x 10 mm (width) x 0.2 mm (thickness) and using the laser flash method. The measurement device used was a xenon flash analyzer (product name: LFA774NanoFlash, manufactured by NETZSCH) and the measurement was performed at 20°C. The density ρ was determined at 20°C using the Archimedes method. p The thermal conductivity was determined using a DSC (product name: ThermoPlusEvoDSC8230, manufactured by Rigaku Corporation) in an environment of 20°C. The heat dissipation performance was evaluated based on the obtained thermal conductivity according to the following criteria. The results are shown in Table 1.

[0081] A: The thermal conductivity is 15.0 W / (m·K) or higher. B: The thermal conductivity is 13.0 W / (m·K) or more and less than 15.0 W / (m·K). C: The thermal conductivity is 11.0 W / (m·K) or higher and less than 13.0 W / (m·K). D: The thermal conductivity is 9.0 W / (m·K) or higher and less than 11.0 W / (m·K). E: The thermal conductivity is less than 9.0 W / (m·K).

[0082] [Measurement of dielectric breakdown voltage and evaluation of insulation properties] The dielectric breakdown voltage was measured for the evaluation sheets described above. The dielectric breakdown voltage of the obtained evaluation sheets was measured using a withstand voltage tester (device name: TOS-8650, manufactured by Kikusui Electronics Co., Ltd.) in accordance with the description in JIS C 6481-1996 "Test Method for Copper-Clad Laminates for Printed Wiring Boards". Twenty dielectric breakdown voltages were measured for each of Examples 1-4 and Comparative Examples 1-4, and the arithmetic mean was calculated. The insulation properties were evaluated based on the arithmetic mean of the obtained dielectric breakdown voltages according to the following criteria. The results are shown in Table 1.

[0083] A: The average dielectric breakdown voltage is 70kV / mm or higher. B: The average dielectric breakdown voltage is between 60kV / mm and 70kV / mm. C: The average dielectric breakdown voltage is between 50kV / mm and 60kV / mm. D: The average dielectric breakdown voltage is between 40kV / mm and 50kV / mm. E: The average dielectric breakdown voltage is less than 40kV / mm.

[0084] [Table 1]

Claims

1. A boron nitride powder containing aggregated particles composed of aggregated primary particles of hexagonal boron nitride, The orientation index is 12 or less. In the Raman spectrum obtained by irradiating the aggregated particles with a laser of wavelength 532 nm, the peak showing the maximum intensity corresponds to a Raman shift of 1360 cm⁻¹. －１ ~1370cm －１ It exists in the region, and the full width at half maximum of the peak is 30 cm. －１ The following is boron nitride powder.

2. The boron nitride powder according to claim 1, wherein the 50% passing particle size (D50) in the particle size distribution measured by laser diffraction scattering is 1 to 150 μm.

3. The boron nitride powder according to claim 1, wherein the crushing strength of the aggregated particles is 5 MPa or more.

4. The boron nitride powder according to claim 1, wherein the graphitization index is 2.3 or less.

5. Boron nitride powder according to any one of claims 1 to 4, An inorganic filler comprising an aluminum compound powder containing at least one selected from the group consisting of aluminum oxide and aluminum nitride.

6. A resin composition comprising boron nitride powder according to any one of claims 1 to 4 and a resin.

7. A resin composition comprising the inorganic filler described in claim 5 and a resin.

8. A resin molded article comprising boron nitride powder according to any one of claims 1 to 4 and a resin.

9. A resin molded article comprising the inorganic filler described in claim 5 and a resin.

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