WO2021111909A1 - Boron nitride particles and method for manufacturing same - Google Patents

Abstract

An aspect of the present invention is a method for manufacturing boron nitride particles, comprising a reaction step for introducing a first gas including a boric acid ester and a second gas including ammonia each separately into a cylindrical reactor from one end surface of the reactor and reacting the boric acid ester and the ammonia at a temperature of 750°C or higher in the reactor to obtain a boron nitride particle precursor, and a heating step for heating the boron nitride particle precursor to a temperature of 1000°C or higher to obtain boron nitride particles, wherein, in the reaction step, the first gas is introduced into the reactor so that a side surface of the reactor is positioned on an extension line that is in a first direction in which the first gas is introduced into the reactor, and the second gas is introduced into the reactor so that the side surface of the reactor is positioned on an extension line that is in a second direction in which the second gas is introduced into the reactor.

Description

Boron Nitride Particles and Their Manufacturing Methods

The present invention relates to boron nitride particles and a method for producing the same.

In electronic components such as transistors, thyristors, and CPUs, it is an important issue to efficiently dissipate heat generated during use. Therefore, a heat radiating member having high thermal conductivity is used together with such an electronic component. On the other hand, boron nitride particles have high thermal conductivity and high insulating properties, and are therefore widely used as fillers in heat radiating members.

For example, when boron nitride particles are used as a filler for primary sealing an electronic component, boron nitride particles having a relatively small particle diameter are preferable so that the boron nitride particles can enter even in a narrow gap around the electronic component. Is. For example, Patent Document 1 is characterized by having an average particle size of 0.01 to 1.0 μm, an orientation index of 1 to 15, a boron nitride purity of 98.0% by mass or more, and an average circularity of 0.80 or more. Spherical boron nitride fine particles and a method for producing the same are disclosed.

International Publication No. 2015/122379

According to the study by the present inventors, when the boron nitride particles are used as a filler for primary sealing of electronic parts as described above, the boron nitride particles not only have a small average particle size but also have a small average particle size. It is also important that the variation in particle size is small.

Therefore, one aspect of the present invention is to obtain boron nitride particles having a small variation in particle size.

As examined by the present inventors, in the production method for obtaining boron nitride particles from boric acid ester and ammonia, in order to reduce the variation in the particle size of the obtained boron nitride particles, a gas containing boric acid ester and ammonia are used. It has been found that the method of introducing the contained gas into the reactor is important.

One aspect of the present invention is to introduce a first gas containing borate ester and a second gas containing ammonia into the reactor separately from one end surface of the tubular reactor, and inside the reactor. In the above, a reaction step of reacting borate ester and ammonia at 750 ° C. or higher to obtain a precursor of boron nitride particles, and a heating step of heating the precursor of boron nitride particles at 1000 ° C. or higher to obtain boron nitride particles. In the reaction step, the first gas is introduced so that the side surface of the reactor is located on an extension line in the first direction for introducing the first gas into the reactor. Manufacture in which the second gas is introduced into the reactor so that the side surface of the reactor is located on the extension line of the second direction in which the second gas is introduced into the reactor while being introduced into the reactor. The method.

When the angle formed by the extending direction extending from one end surface to the other end surface of the reactor and the first direction is θ ₁ , tan θ ₁ may be 1.2 or more. When the angle formed by the extending direction extending from one end surface to the other end surface of the reactor and the second direction is θ ₂ , tan θ ₂ may be 1.2 or more.

Another aspect of the present invention is the boron nitride particles having an average particle size of 1 μm or less and a difference between the 10% cumulative particle size and the 100% cumulative particle size of 5 μm or less in a volume-based particle size distribution. Is.

The average circularity of the boron nitride particles may be 0.8 or more.

Another aspect of the present invention is a resin composition containing a resin and the above-mentioned boron nitride particles.

According to one aspect of the present invention, boron nitride particles having a small variation in particle size can be obtained.

It is a perspective view which shows an example of the reactor used in the manufacturing method of the boron nitride particle which concerns on one Embodiment. (A) is a side view of the reactor viewed from the first introduction tube side, and (b) is a side view of the reactor viewed from the second introduction tube side.

One embodiment of the present invention comprises a reaction step of reacting boric acid ester and ammonia at 750 ° C. or higher to obtain a precursor of boron nitride particles, and heating the precursor of boron nitride particles at 1000 ° C. or higher to obtain boron nitride particles. A method for producing boron nitride particles, which comprises a heating step for obtaining the particles.

In the reaction step, the first gas containing boric acid ester and the second gas containing ammonia are separately introduced into the reactor.

FIG. 1 is a perspective view showing an example of a reactor. As shown in FIG. 1, the reactor 1 has, for example, a cylindrical shape in which both ends are open (both ends are open surfaces), and is located between one end surface 1a and the other end surface 1b. It has an internal space S. The length of the reactor 1 may be, for example, 1000 mm or more and 1600 mm or less. The inner diameter of the reactor 1 may be, for example, 30 mm or more, and may be 100 mm or less.

Both ends of the reactor 1 are held by the holding member 2 so that the outside and the internal space S of the reactor 1 can be blocked (so that the internal space S can be a closed system if necessary). ing. The reactor 1 is installed so that the heating portion H is located in a resistance heating furnace (not shown) in order to heat only a part (hereinafter referred to as “heating portion”) H between both end faces 1a and 1b. Has been done. The length of the heating portion H (the length in the longitudinal direction of the reactor 1) may be, for example, 500 mm or more and 900 mm or less. When the heating part H of the reactor 1 is heated, the boric acid ester and ammonia react in the heating part H. The temperature of the heating unit H may be, for example, 750 ° C. or higher, and may be 1500 ° C. or lower.

A first introduction pipe 3 and a second introduction pipe 4 are separately attached to one end surface 1a of the reactor 1 so that gas can be introduced into the internal space S from the outside of the reactor 1. FIG. 2A is a side view of the reactor 1 as viewed from the side of the first introduction pipe 3. FIG. 2B is a side view of the reactor 1 as viewed from the side of the second introduction pipe 4.

As shown in FIGS. 1 and 2A, the first introduction pipe 3 has, for example, a shape in which a cylindrical tip is bent in a predetermined direction. The first introduction pipe 3 extends substantially parallel to the extending direction D extending from one end surface 1a of the reactor 1 to the other end surface 1b (extending direction extending from one end surface 1a toward the other end surface 1b). , It is introduced into the internal space S from the outside of the reactor 1, and at a position in the internal space S where the distance from one end surface 1a is, for example, 10 to 40 mm, the angle formed by the extending direction D of the reactor 1 is It bends and extends in the bending direction d1 where θ _{1 is formed.} The bending direction d1 of the first introduction pipe 3 is defined as a direction perpendicular to the tip surface 3a of the first introduction pipe 3.

As shown in FIGS. 1 and 2B, the second introduction pipe 4 has, for example, a shape in which a cylindrical tip is bent in a predetermined direction. The second introduction tube 4 is introduced into the internal space S from the outside of the reactor 1 so as to extend substantially parallel to the extending direction D of the reactor 1, and is a distance from one end surface 1a in the internal space S. For example, at a position of 10 to 40 mm, the reactor 1 bends and extends in the bending direction d2 where the _{angle formed by the extending direction D of the reactor 1 is θ 2.} The bending direction d1 of the second introduction pipe 4 is defined as a direction perpendicular to the tip surface 4a of the second introduction pipe 4.

At the angle θ ₁ , the side surface (side surface along the extension direction D; the same applies hereinafter) 1c of the reactor 1 is located on the extension line of the bending direction d1 of the first introduction pipe 3 (first introduction pipe 3). The extension line of the bending direction d1 intersects the side surface 1c of the reactor 1). Similarly, at the angle θ ₂ , the side surface (side surface along the extending direction D) 1c of the reactor 1 is located on the extension line of the bending direction d2 of the second introduction pipe 4 (of the second introduction pipe 4). The angle is such that the extension line of the bending direction d2 intersects the side surface 1c of the reactor 1).

In the reaction step, the first gas containing the borate ester is introduced into the internal space S from the outside of the reactor 1 through the first introduction tube 3, and the second gas containing ammonia is contained separately from the first gas. Gas is introduced into the internal space S from the outside of the reactor 1 through the second introduction pipe 4.

The first gas is obtained, for example, by passing an inert gas through a liquid boric acid ester. In this case, the first gas is a gas composed of a boric acid ester and an inert gas. The borate ester may be, for example, an alkyl borate ester, preferably trimethyl borate. Examples of the inert gas include rare gases such as helium, neon and argon, and nitrogen gas. The second gas is, for example, a gas composed of ammonia.

The molar ratio of the amount of ammonia introduced to the amount of boric acid introduced (ammonia / boric acid ester) may be, for example, 1 or more and 10 or less.

The boric acid ester and ammonia introduced into the reactor 1 react in the heated reactor 1 to produce a precursor (white powder) of boron nitride particles. A part of the precursor of the generated boron nitride particles adheres to the inside of the reactor 1, but most of the precursors of the boron nitride particles are on the other end surface 1b side of the reactor 1 due to the inert gas or unreacted ammonia gas. It is sent to a collection container (not shown) attached to and collected. The reaction time for reacting the boric acid ester with ammonia is preferably 30 seconds or less from the viewpoint of easily reducing the particle size of the obtained boron nitride particles. The reaction time is the time during which the borate ester and ammonia stay in the heating portion H of the reactor 1, and is adjusted by the gas flow rate when the first gas and the second gas are introduced and the length of the heating portion H. can do.

In the reaction step described above, since the first introduction pipe 3 is _{bent in the bending direction d1 at the angle θ 1} as described above, the first gas is also in the extending direction D of the reactor 1. It is introduced in the first introduction direction (first direction) d1 where the angle formed is θ _1. Similarly, since the second introduction pipe 4 is _{bent in the bending direction d2 at the angle θ 2} as described above, the angle formed by the second gas with the extending direction D of the reactor 1 is θ. _It is introduced in the second introduction direction (second direction) d2 which becomes 2. That is, the side surface 1c of the reactor 1 is located on the extension line of the first gas introduction direction d1 and on the extension line of the second gas introduction direction d2. The first introduction direction d1 is defined as a direction perpendicular to the tip surface 3a of the first introduction pipe 3, similarly to the bending direction d1 of the first introduction pipe 3. The second introduction direction d2 is defined as a direction perpendicular to the tip surface 4a of the second introduction pipe 4, similarly to the bending direction d2 of the second introduction pipe 4.

In this way, by introducing the first gas in the first introduction direction d1 and introducing the second gas in the second introduction direction d2, it is possible to reduce the variation in the particle size of the obtained boron nitride particles. .. The reason is not clear, but by introducing the first gas and the second gas in the first introduction direction d1 and the second introduction direction d2, respectively, the first gas and the second gas can be changed to each other. , While colliding with the side surface 1c of the reactor 1, it advances in the reactor 1 at an angle with respect to the extending direction D of the reactor 1, so that, for example, the first gas and the second gas are extended in the reactor 1. It is presumed that the reason is that the first gas and the second gas are more likely to be mixed uniformly with each other as compared with the case of introducing in parallel with the direction D.

The angles θ ₁ and θ ₂ are preferably 50 ° or more, more preferably 60 ° or more, still more preferably 65 ° or more, and particularly preferably 65 ° or more, respectively, from the viewpoint of further reducing the variation in the particle size of the obtained boron nitride particles. It is 70 ° or more. The angles θ ₁ and θ ₂ are each less than 90 ° and may be, for example, 80 ° or less. In other words, with respect to the angles θ ₁ and θ ₂ , tan θ ₁ and tan θ ₂ are preferably 1.2 or more, more preferably 1.7, respectively, from the viewpoint of further reducing the variation in the particle size of the obtained boron nitride particles. The above is more preferably 2.1 or more, and particularly preferably 2.7 or more. tan θ ₁ and tan θ ₂ may be, for example, 11.4 or less, respectively.

In the heating step, the precursor of the boron nitride particles obtained in the reaction step is heated at 1000 ° C. or higher to obtain boron nitride particles. The heating steps include, for example, a first heating step of heating a precursor of boron nitride particles at 1000 to 1600 ° C. to obtain a first precursor, and a first heating step of heating the first precursor at 1000 to 1600 ° C. It may include a second heating step of obtaining the precursor of 2 and a third heating step of heating the second precursor at 1800 to 2200 ° C. to obtain boron nitride particles. In this case, after the completion of the first heating step and before the start of the second heating step, the environmental temperature at which the first precursor is placed is once lowered to room temperature (10 to 30 ° C.). In another embodiment, in the heating step, the first heating step may be omitted and the second heating step and the third heating step may be performed.

In the first heating step, the precursor of the boron nitride particles obtained in the reaction step is placed in another reaction tube (for example, an alumina tube) installed in the resistance heating furnace, and nitrogen gas and ammonia gas are separately charged. Introduce into the reaction tube. The gas introduced at this time may be only ammonia gas. The flow rates of nitrogen gas and ammonia gas may be appropriately adjusted so that the reaction time becomes a desired value, respectively. For example, the higher the flow rate of nitrogen gas and ammonia gas, the shorter the reaction time.

Subsequently, the reaction tube is heated to 1000 to 1600 ° C. The heating time may be, for example, 1 hour or more and 10 hours or less. This gives the first precursor.

After the first heating step is completed, the power of the resistance heating furnace is turned off, the introduction of nitrogen gas and ammonia gas is stopped, and the temperature in the reaction tube is lowered to room temperature (10 to 30 ° C.). Allow the precursor to stand. The standing time may be, for example, 0.5 hours or more and 96 hours or less.

In the second heating step, nitrogen gas and ammonia gas are reintroduced into the reaction tube, and the reaction tube is heated again to 1000 to 1600 ° C. Examples of the flow rates of nitrogen gas and ammonia gas, and the heating time may be the same as those described in the first heating step. The conditions of the first heating step and the conditions of the second heating step may be the same as each other or may be different from each other. This gives a second precursor.

In the third heating step, the second precursor obtained in the second heating step is placed in a boron nitride rutsubo and heated to 1800 to 2200 ° C. in an induction heating furnace under a nitrogen atmosphere. The heating time may be, for example, 0.5 hours or more, and may be 10 hours or less. As a result, boron nitride particles are obtained.

According to the manufacturing method described above, for example, in the volume-based particle size distribution, the average particle size is 1 μm or less, and the difference between the 10% cumulative particle size and the 100% cumulative particle size is 10 μm or less. Is obtained. That is, in another embodiment of the present invention, in the volume-based particle size distribution, the average particle size is 1 μm or less, and the difference between the 10% cumulative particle size (D10) and the 100% cumulative particle size (D100). (D100-D10) is a boron nitride particle having a size of 10 μm or less.

The average particle size of the boron nitride particles is preferably 0.9 μm or less, 0.8 μm or less, or 0.9 μm or less from the viewpoint of lowering the dielectric constant of the heat radiating member containing the boron nitride particles (hereinafter, also simply referred to as “heat radiating member”). It may be 0.7 μm or less. The average particle size of the boron nitride particles is preferably 0.01 μm or more, 0.05 μm or more, 0.1 μm or more, 0.2 μm or more from the viewpoint of suppressing an increase in viscosity when the boron nitride particles and the resin are mixed. , 0.3 μm or more, or 0.4 μm or more.

Boron nitride particles D100-D10 are preferably 5 μm or less, 4 μm or less, or 5 μm or less, from the viewpoint that the dielectric constant of the heat radiating member is lowered and the variation in particle size is suppressed, which is suitable for the primary sealing of electronic components. It may be 3 μm or less. The D100-D10 of the boron nitride particles may be, for example, 0.5 μm or more, 0.8 μm or more, or 1 μm or more.

The average particle size and D100-D10 of the boron nitride particles are measured by the following procedure.
Distilled water is used as a dispersion medium for dispersing the boron nitride particles, and sodium hexametaphosphate is used as a dispersant to prepare a 0.125 mass% sodium hexametaphosphate aqueous solution. Boron nitride particles are added to this aqueous solution at a ratio of 0.1 g / 80 mL, and ultrasonic dispersion is performed with an ultrasonic homogenizer (for example, manufactured by Nippon Seiki Seisakusho Co., Ltd., trade name: US-300E) at 80% AMPLITUDE (amplitude). A dispersion of boron nitride particles is prepared by performing this once every 1 minute and 30 seconds. This dispersion is separated while stirring at 60 rpm, and the volume-based particle size distribution is measured by a laser diffraction / scattering method particle size distribution measuring device (for example, manufactured by Beckman Coulter, trade name: LS-13 320). At this time, 1.33 is used as the refractive index of water, and 1.7 is used as the refractive index of the boron nitride particles. From the measurement results, the average particle size is calculated as the particle size (median diameter, d50) of the cumulative value of the cumulative particle size distribution of 50%, and the particle size of the cumulative value of the cumulative particle size distribution is 100%. D100-D10 is calculated as the value obtained by subtracting D10.

Boron nitride particles preferably have a spherical shape or a shape close to a spherical shape from the viewpoint of improving the filling property when manufacturing the heat radiating member and making the characteristics (thermal conductivity, dielectric constant, etc.) of the heat radiating member isotropic. have. From the same viewpoint, the average circularity of the boron nitride particles may be preferably 0.8 or more, 0.82 or more, 0.84 or more, 0.86 or more, or 0.88 or more.

The average circularity of the boron nitride particles is measured by the following procedure.
Image analysis software (for example, manufactured by Mountech, trade name: MacView) for images of boron nitride particles (magnification: 10,000 times, image resolution: 1280 x 1024 pixels) taken with a scanning electron microscope (SEM). The projected area (S) and the peripheral length (L) of the boron nitride particles are calculated by image analysis using. Using the projected area (S) and the perimeter (L), the following equation:
Circularity = 4πS / L ²
Calculate the circularity according to. The average value of the circularity obtained for 100 arbitrarily selected boron nitride particles is defined as the average circularity.

The boron nitride particles described above are suitably used for, for example, a heat radiating member. By using the above-mentioned boron nitride particles, a heat radiating member having a low dielectric constant can be obtained. When the boron nitride particles are used for a heat radiating member, they are used, for example, as a resin composition mixed with a resin. That is, another embodiment of the present invention is a resin composition containing the resin and the above-mentioned boron nitride particles.

The content of the above-mentioned boron nitride particles is preferably 30% by volume or more, based on the total volume of the resin composition, from the viewpoint of improving the thermal conductivity of the resin composition and easily obtaining excellent heat dissipation performance. It is preferably 40% by volume or more, more preferably 50% by volume or more, and preferably 85% by volume or less, more preferably 85% by volume or less, from the viewpoint of suppressing the generation of voids during molding and the decrease in insulating property and mechanical strength. It is 80% by volume or less, more preferably 70% by volume or less.

Examples of the resin include epoxy resin, silicone resin, silicone rubber, acrylic resin, phenol resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyolefin (polyethylene, etc.), polyimide, polyamideimide, polyetherimide, and poly. Butylene terephthalate, polyethylene terephthalate, polyphenylene ether, polyphenylene sulfide, total aromatic polyester, polysulfone, liquid crystal polymer, polyether sulfone, polycarbonate, maleimide-modified resin, ABS (acrylonitrile-butadiene-styrene) resin, AAS (acrylonitrile-acrylic rubber / styrene) ) Resin and AES (acrylonitrile / ethylene / propylene / diene rubber-styrene) resin.

The content of the resin may be 15% by volume or more, 20% by volume or more, or 30% by volume or more, based on the total volume of the resin composition, and is 70% by volume or less, 60% by volume or less, or 50% by volume. It may be:

The resin composition may further contain a curing agent that cures the resin. The curing agent is appropriately selected depending on the type of resin. For example, when the resin is an epoxy resin, examples of the curing agent include phenol novolac compounds, acid anhydrides, amino compounds, and imidazole compounds. The content of the curing agent may be, for example, 0.5 parts by mass or more or 1.0 part by mass or more, and may be 15 parts by mass or less or 10 parts by mass or less with respect to 100 parts by mass of the resin.

The resin composition may further contain boron nitride particles other than the above-mentioned boron nitride particles (for example, known boron nitride particles such as massive boron nitride particles formed by aggregating scaly primary particles).

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited to the following examples.

[Manufacturing Example 1]
Boron nitride particles were prepared by the following procedure.
First, in the reaction step, a cylindrical reactor (quartz tube, reactor length: 1300 mm, reactor inner diameter: 75 mm, located in the resistance heating furnace) installed in the resistance heating furnace as shown in FIG. The length of the portion to be heated: 800 mm) was heated to raise the temperature to 1150 ° C. On the other hand, the first gas obtained by passing nitrogen gas through trimethyl borate was introduced into the reactor from the first introduction tube. On the other hand, ammonia gas was introduced directly into the reactor. As the first introduction tube and the second introduction tube, in the internal space of the reactor, the distance from one end surface of the reactor is 25 mm, and the angle formed by the extending direction of the reactor is θ _{1, respectively.} And the one bent in the bending direction of _{θ 2 was provided.} In other words, the first gas and the second gas are arranged so that the angles formed by the introduction direction and the second introduction direction of the first introduction gas and the extension direction of the reactor are θ ₁ and θ ₂ , respectively. Introduced. Note that θ ₁ and θ ₂ were set so that tan θ ₁ and tan θ ₂ had the values shown in Table 1, respectively.

The molar ratio of the amount of ammonia introduced to the amount of trimethyl borate introduced (ammonia / trimethyl borate) was 4.5. As a result, trimethyl borate was reacted with ammonia to obtain a precursor (white powder) of boron nitride particles. The reaction time was 10 seconds.

Subsequently, in the heating step, the precursor of the boron nitride particles obtained in the reaction step is placed in another reaction tube (alumina tube) installed in the resistance heating furnace, and nitrogen gas and ammonia gas are separately charged at 10 L. It was introduced into the reaction tube at a flow rate of / min and 15 L / min. Then, the reaction tube was heated at 1500 ° C. for 2.5 hours. As a result, a first precursor was obtained (first heating step).

Subsequently, the power of the resistance heating furnace was turned off, the introduction of nitrogen gas and ammonia gas was stopped, and the first precursor was allowed to stand for 2 hours in a state where the temperature in the reaction tube was lowered to 25 ° C.

Subsequently, nitrogen gas and ammonia gas were introduced and the inside of the reaction tube was heated under the same conditions as in the first heating step. As a result, a second precursor was obtained (second heating step).

Subsequently, the second precursor obtained in the second heating step was placed in a boron nitride crucible and heated in an induction heating furnace at 2000 ° C. for 5 hours in a nitrogen atmosphere. As a result, boron nitride particles were obtained.

[Manufacturing Examples 2 and 3]
Same as in Production Example 1 except that the introduction direction of the first gas and the introduction direction of the second gas _{are changed to the angles θ 1} and θ _{2 such that tan θ 1} and tan θ ₂ are the values shown in Table 1, respectively. Boron nitride particles were prepared in this manner.

For each of the obtained boron nitride particles, the average particle size, the difference between the 10% cumulative particle size and the 100% cumulative particle size (D100-D10), and the average circularity were measured by the following methods. The results are shown in Table 1.

(Average particle size and D100-D10)
Distilled water was used as a dispersion medium for dispersing the boron nitride particles, and sodium hexametaphosphate was used as a dispersant to prepare a 0.125 mass% sodium hexametaphosphate aqueous solution. Boron nitride particles are added to this aqueous solution at a ratio of 0.1 g / 80 mL, and ultrasonic dispersion is performed with an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho, trade name: US-300E) at 80% AMPLITUDE (amplitude). A dispersion of boron nitride particles was prepared by performing this once every 1 minute and 30 seconds. This dispersion was separated while stirring at 60 rpm, and the volume-based particle size distribution was measured with a laser diffraction / scattering method particle size distribution measuring device (manufactured by Beckman Coulter, trade name: LS-13 320). At this time, 1.33 was used as the refractive index of water, and 1.7 was used as the refractive index of the boron nitride particles. From the measurement results, the average particle size is calculated as the particle size (median diameter, d50) of the cumulative value of the cumulative particle size distribution of 50%, and the particle size of the cumulative value of the cumulative particle size distribution is 100%. D100-D10 was calculated as the value obtained by subtracting D10.

(Average circularity)
First, for an image of boron nitride particles (magnification: 10,000 times, image resolution: 1280 x 1024 pixels) taken with a scanning electron microscope (SEM), image analysis software (for example, manufactured by Mountech Co., Ltd., trade name: The projected area (S) and peripheral length (L) of the boron nitride particles were calculated by image analysis using a MacView). Next, using the projected area (S) and the perimeter (L), the following equation:
Circularity = 4πS / L ²
The circularity was calculated according to. The average value of the circularity obtained for 100 arbitrarily selected boron nitride particles was calculated as the average circularity.

The dielectric constant of each of the obtained boron nitride particles was measured by the following method. The results are shown in Table 1.
Boron nitride particles are kneaded with polyethylene (manufactured by Japan Polyethylene Corporation, trade name "Novatec HY540") in an amount that makes the amount of boron nitride particles 20% by volume, and sheet molding is performed to obtain a 0.2 mm thick sheet. Got Kneading and sheet forming were carried out using a twin-screw extruder under the condition of a temperature of 180 ° C. Using a measuring device of the cavity resonator method, the sheet obtained under the conditions of a frequency of 36 GHz and a temperature of 25 ° C. was measured, and the dielectric constant of the sheet was determined.

1 ... Reactor, 1a ... One end surface of the reactor, 1b ... The other end surface of the reactor, 1c ... Side surface of the reactor, 2 ... Holding member, 3 ... First introduction tube, 3a ... Tip of the first introduction tube Surface, 4 ... 2nd introduction pipe, 4a ... Tip surface of 2nd introduction pipe, D ... Reactor extension direction, S ... Reactor internal space, d1 ... First gas introduction direction, d2 ... Second gas introduction direction.

Claims (6)

A first gas containing a borate ester and a second gas containing ammonia are separately introduced into the reactor from one end surface of the tubular reactor, and the boric acid is introduced in the reactor. A reaction step of reacting the ester and the ammonia at 750 ° C. or higher to obtain a precursor of boron nitride particles.
A heating step of heating the precursor of the boron nitride particles at 1000 ° C. or higher to obtain boron nitride particles,
A method for producing boron nitride particles comprising
In the reaction step, the first gas is introduced into the reactor so that the side surface of the reactor is located on an extension of the first direction in which the first gas is introduced into the reactor. A manufacturing method in which the second gas is introduced into the reactor so that the side surface of the reactor is located on an extension line in the second direction for introducing the second gas into the reactor. .. The production according to claim ₁ , wherein tan θ 1 is 1.2 or more when the angle formed by the extending direction extending from one end surface to the other end surface of the reactor and the first direction is θ _1. Method. The invention according to claim 1 or 2, wherein tan θ ₂ is 1.2 or more when the angle formed by the extending direction extending from one end surface to the other end surface of the reactor and the second direction is θ _2. Manufacturing method. Boron nitride particles having an average particle size of 1 μm or less and a difference between 10% cumulative particle size and 100% cumulative particle size of 5 μm or less in a volume-based particle size distribution. The boron nitride particles according to claim 4, which have an average circularity of 0.8 or more. A resin composition containing a resin and the boron nitride particles according to claim 4 or 5.

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