JP2019218254A - Hexagonal boron nitride powder and manufacturing method therefor - Google Patents

Abstract

To provide a hexagonal boron nitride powder, which has less release of α ray, of which anisotropy of heat conduction is reduced, and which can add high thermal conductivity and dielectric strength to a resin composition constituted by filling the same into a resin.SOLUTION: There is provided a hexagonal boron nitride powder containing a hexagonal boron nitride aggregate, and having concentration degree ofB in all boron of 90% or more, maximum torque measured and calculated according to JIS-K-6217-4 of 0.20 to 0.50 Nm, DBP absorption amount of 50 to 100 ml/100 g, and tap bulk density of 0.66 to 0.95 g/cm, and there is provided a manufacturing method of the hexagonal boron nitride powder capable of the hexagonal boron nitride powder by using a raw material by blending aB concentrated oxygen-containing boron compound, a carbon source, an oxygen-containing calcium compound, andB concentrated boron carbide at a specific ratio, heating the raw material under nitrogen atmosphere at a temperature of 1800 to 2100°C, and reduction nitriding the same.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a novel hexagonal boron nitride powder and a method for producing the same. Specifically, the present invention provides a hexagonal boron nitride powder capable of imparting a high thermal conductivity and a high dielectric strength with a resin composition obtained by filling a resin and emitting less α-rays than before, and a method for producing the same. Is what you do.

Data held in a semiconductor memory such as an SRAM (Static Random Access Memory) or a DRAM (Dynamic Random Access Memory) may be naturally destroyed, and this phenomenon is called a soft error. In recent years, the problem of soft errors has become more important due to miniaturization of semiconductor elements and lower operating voltages. There are three types of radiation that cause soft errors. Α-rays caused by a small amount of radioactive substances contained in semiconductor package materials, fast neutrons caused by cosmic rays, and thermal neutrons. Among them, the soft error caused by thermal neutrons is caused by α rays generated by a complex nuclear reaction of ¹⁰ B and thermal neutrons contained in a semiconductor. Therefore, in order to suppress soft errors caused by thermal neutrons, thermal neutrons must be absorbed by an element having a large neutron capture cross section before entering the semiconductor, or ¹⁰ B around the semiconductor, particularly ¹⁰ B existing near the drain, must be eliminated. Is valid.

Actually, the presence of ¹⁰ B in the BPSG film used in the planarization process has been pointed out, and the BPSG film has been changed to a CMP process or the like. Also, BF ₃ used as an etching gas is pointed out to have a contamination of ¹⁰ B to the wiring, an etching gas containing no B is used, and the B source is in a flow to be excluded. This trend is expected to continue in the future.

  By the way, hexagonal boron nitride powder is generally a white powder having a hexagonal layered structure similar to graphite, and has high thermal conductivity, high electrical insulation, high lubricity, corrosion resistance, mold release properties, and high temperature stability. It has many properties such as properties, low dielectric constant, and chemical stability. Therefore, a resin composition filled with hexagonal boron nitride powder is suitably used as a heat conductive insulating sheet by molding. In addition, a sealing resin sheet as described in Patent Document 1 has been devised, and it is said that boron nitride powder is suitable as a filler for sealing materials.

  However, since the hexagonal boron nitride powder is generally produced using a naturally-derived boron compound as a raw material, it has been confirmed by the present inventors that it is not suitable as a filler for a sealing material. Was.

The reason is as follows. Naturally occurring boron is composed of two stable isotopes, ¹⁰ B and ¹¹ B, and the abundance ratio is 19.9% for ¹⁰ B and 80.1% for ¹¹ B. Except in the case of performing operations such as concentration, the boron compound using a naturally occurring boron compound as a raw material inherits the stable isotope abundance ratio of natural boron. Contains about 20% of ¹⁰ B which causes α-ray emission as described above. Therefore, when the conventional hexagonal boron nitride powder is used as a filler for a sealing material, since the sealing material directly contacts the semiconductor, ¹⁰ B is present particularly near the drain, and as a result, the soft error is reduced. There was a risk of frequent occurrence.

  Further, the hexagonal boron nitride powder used by filling the heat conductive insulating sheet contains primary particles composed of flaky particles derived from a crystal structure, and the flaky particles have thermal anisotropy. . Normally, in the case of a thermally conductive insulating sheet using the boron nitride powder containing the flaky particles as a single particle as a filler, the flaky particles are oriented in the plane direction of the thermally conductive insulating sheet. Heat is transmitted in the c-axis direction having a low thermal conductivity, and the thermal conductivity in the thickness direction of the thermally conductive insulating sheet is low.

  In order to improve the thermal anisotropy of hexagonal boron nitride particles having such a flaky structure, a hexagonal boron nitride powder containing a hexagonal boron nitride aggregate has been proposed (see Patent Document 2). .

  On the other hand, the step of manufacturing a heat conductive insulating sheet by filling the hexagonal boron nitride powder in a thermosetting resin, after mixing the hexagonal boron nitride powder with an uncured resin and a curing agent in an organic solvent, In general, a method of coating to a predetermined thickness and curing while applying pressure to increase the packing density is adopted.

  In the above step, in order to impart high thermal conductivity to the heat conductive insulating sheet, it is necessary to fill the resin composition with 60% by volume or more of hexagonal boron nitride powder. The hexagonal boron nitride powder is uniformly dispersed in the mixture, and in order to ensure a viscosity that can be applied in a step of applying the same, generally, the hexagonal boron nitride powder, the resin, and the curing agent are previously dispersed in a diluting solvent. Then, a method of mixing them as a varnish-like composition has been adopted.

  However, the conventionally proposed hexagonal boron nitride powder containing a hexagonal boron nitride aggregate has a relatively large number of open pores in the aggregate and a DBP (Dibutyl Phthalate) absorption amount indicating the degree of structure of the aggregate surface. When the amount of absorption increases, the required amount of the diluting solvent used for filling the resin tends to increase. The diluting solvent is volatilized in a later step and does not remain in the heat conductive insulating sheet, but it requires time for drying after coating. Also, after drying the diluting solvent, it becomes a gap between the particles constituting the aggregated particles, and in the defoaming process, it may remain as fine bubbles in the heat conductive insulating sheet, and the heat conductivity and the dielectric strength decrease. Cause.

  If the proportion of single particles in the hexagonal boron nitride powder is large, the DBP absorption may be low, and the viscosity when the hexagonal boron nitride powder is filled in the resin may increase. Moreover, the hexagonal boron nitride powder having a large proportion of the single particles has a low tap bulk density, which not only deteriorates the filling property of the resin, but also results in a heat conductive insulating sheet. The filler deviates from the close-packed state in the sheet. Therefore, when press-molding, an extra load is applied to the hexagonal boron nitride aggregate, which causes the aggregate to break. Further, since the single particles are easily oriented in an in-plane direction having a low thermal conductivity, it is difficult to develop a high thermal conductivity.

JP-A-2006-000784 JP 2011-98882 A

  Accordingly, an object of the present invention is to provide a hexagonal boron nitride powder containing the above-mentioned hexagonal boron nitride aggregate, which is easy to be filled into a resin, requires a small amount of a solvent for varnishing, and emits α-rays when filled into the resin. The present invention provides a hexagonal boron nitride powder that has a small amount, exhibits a high thermal conductivity, has almost no relatively large voids that adversely affect the dielectric strength, and can provide a high dielectric strength to the resin composition. is there.

The present inventors have conducted intensive studies in order to solve the above problems. As a result, ¹¹ B-enriched boron carbide is used in combination with a composition comprising ¹¹ B-enriched oxygen-containing boron compound, a carbon source and an oxygen-containing calcium compound, which is known as a raw material for obtaining boron nitride by a reduction nitriding method, and abundance of ^{11 B} in the total boron in this case ^{11 B} enriched oxygen-containing boron compound and ^{11 B} enriched boron carbide for mixing with the reducing nitriding reaction in a proportion of 90% or more, employing a specific manufacturing process To form aggregated particles having a novel aggregated structure having an extremely dense structure, and the abundance ratio of ¹¹ B in the total boron including the aggregated particles is 90% or more. The inventors have found that powder can achieve all of the above objects, and have completed the present invention.

That is, according to the present invention, a hexagonal boron nitride aggregate is included, and the abundance ratio of ¹⁰ B in the total boron is 90% or more, and is measured and calculated in accordance with JIS-K-6217-4. Hexagonal boron nitride powder having a maximum torque of 0.20 to 0.50 Nm, a DBP absorption of 50 to 100 ml / 100 g, and a tap bulk density of 0.66 to 0.95 g / cm ^3. Is provided.

The hexagonal boron nitride powder of the present invention preferably has a specific surface area of 1.3 to 7.0 m ² / g.

  The hexagonal boron nitride powder of the present invention preferably has a particle size at a cumulative volume frequency of 90% of a particle size distribution in a laser diffraction particle size distribution method of 50 to 150 μm.

  Further, the purity of the hexagonal boron nitride of the present invention is preferably 99.95% or more.

  Furthermore, the present invention provides a filler for a resin comprising the boron nitride powder, a resin composition filled with the filler for the resin, the hexagonal boron nitride powder, and a filler mixture containing any one of aluminum nitride and aluminum oxide. The present invention also provides a filled resin composition and a heat dissipating material for electronic parts comprising the above resin composition.

The hexagonal boron nitride powder of the present invention contains ¹¹ B-enriched oxygen-containing boron compound, a carbon source, an oxygen-containing calcium compound, and ¹¹ B-enriched boron carbide in the B source and the carbon source contained in the ¹¹ B-enriched oxygen-containing boron compound. the proportion of the C source is B / C (atomic ratio) converted at 0.75 to 1.05 ^{to, 11} B enriched oxygen-containing boron compound and the total amount of the carbon source _{(B 2 O} 3, C conversion value) 100 weight 5-20 parts by weight of oxygen-containing calcium compound in terms of CaO with respect to ^{part, 11} B enriched oxygen-containing boron compounds, carbon source, _B 2 _O 3, C oxygenates calcium compound, in terms of CaO mass per 100 parts by 10 to 45 parts by mass of the ¹¹ B enriched boron carbide ^{for, 11} B enriched oxygen-containing boron compound and ^{11 11} enrichment of B in the total boron contained in the B concentration boron carbide 90% Furthermore, weight ratio to form, and the mixture was heated to a temperature of 1,800-2,100 ° C. under a nitrogen atmosphere, by reduction nitriding, it is possible to suitably manufacture. Note that ^{"11 B} enriched" refers to a material with increased to exceed the natural boron abundance of ^{11 B.}

  According to the above method, the hexagonal boron nitride powder containing the aggregate of hexagonal boron nitride of the present invention can be directly produced by the reduction nitriding method.

In general, the natural ^boron, and the ¹⁰ B and ¹¹ B ¹⁰ B is ^19.9% as ^isotopes, are ¹¹ B present in a proportion 80.1%. The hexagonal boron nitride powder produced using the natural boron as a raw material inherits the isotope abundance ratio of the natural boron as a raw material, so that the abundance ratio of ¹⁰ B causing α-ray emission is about 20%. And very many. On the other hand, the hexagonal boron nitride powder of the present invention has, as described above, an ¹¹ B abundance ratio in all boron of 90% or more, and the resin composition obtained by such a feature has lower α-ray emission than the conventional one. Few.
In addition, the hexagonal boron nitride powder of the present invention contains a hexagonal boron nitride aggregate having an extremely dense aggregate structure, and therefore has a low maximum torque and aggregation density which are distinguished from the hexagonal boron nitride powder mainly containing single particles. The low DBP absorption that is distinguished from the hexagonal boron nitride powder containing low aggregated particles, and the hexagonal boron nitride powder mainly containing single particles, or the hexagonal boron nitride powder containing the aggregated particles having low aggregation density Hexagonal boron nitride with simultaneously distinguished high tap bulk density.

  Then, the hexagonal boron nitride powder of the present invention exhibits a lower DBP absorption than a hexagonal boron nitride powder containing a hexagonal boron nitride aggregate in a general aggregated state, thereby obtaining a varnish-like composition. The amount of the solvent can be suppressed to the minimum necessary source, and the amount of minute voids generated in the resin when the solvent is defoamed in a later step can be reduced. Therefore, not only can the obtained resin composition be provided with a high dielectric strength, but also the labor for removing the solvent can be reduced.

  Further, since the maximum torque measured and calculated in accordance with JIS-K-6217-4 is lower than that of the conventional hexagonal boron nitride powder containing the hexagonal boron nitride aggregated particles, the hexagonal crystal is used. It is possible to effectively suppress a rise in viscosity when filling the resin with the boron nitride powder.

Further, the general boron nitride aggregate does not increase the tap bulk density due to voids inside the aggregate and the shape anisotropy of the aggregate, inappropriate particle size distribution, etc. The bulk density is as high as 0.66 to 0.95 g / cm ³ , the filling property to the resin is good, and when the heat conductive insulating sheet is used, the hexagonal boron nitride aggregates are in close contact with each other. It is possible to secure a proper heat path, and to impart high heat conductivity to the obtained heat conductive insulating sheet.

  Further, according to the method for producing a hexagonal boron nitride powder of the present invention, by using an oxygen-containing boron compound, a carbon source, an oxygen-containing calcium compound, and boron carbide, the target low DBP absorption, the maximum torque and A hexagonal boron nitride powder containing a hexagonal boron nitride aggregate having a high tap bulk density can be directly produced by a reduction nitriding method.

  The reason why the hexagonal boron nitride powder containing the hexagonal boron nitride aggregate of the present invention can be obtained by the above-mentioned production method is not clear, but the present inventors presume as follows. That is, a reductive nitridation reaction (1) shown by the following reaction formula (1) using an oxygen-containing boron compound, a carbon source, and nitrogen gas occurs, and then a reaction in which boron carbide is directly nitrided (reaction formula (2)), and a reaction formula It is thought that the re-nitriding reaction (1) and the reactions (3) and (4) occur again in concert using C produced as a reducing agent by the reaction (2). At this time, since the particle size of hexagonal boron nitride generated from boron carbide is correlated with the particle size of the raw material boron carbide, hexagonal boron nitride having a large particle size can be efficiently produced, and boron carbide is nitrided from the surface. When C is released and becomes hexagonal boron nitride while reducing and nitriding boron oxide, it forms a hexagonal boron nitride aggregate while depositing on the surface of large-particle hexagonal boron nitride derived from boron carbide, Aggregate, while being an agglomerate, it is difficult to distinguish the grain boundaries of the primary particles, and because there are few open pores, as in the case of hexagonal boron nitride aggregated particles produced by the prior art, such that the primary particles are easily identified. , Different from hexagonal boron nitride aggregated particles having gaps. As described above, it is presumed that by appropriately adjusting the particle size and blending amount of each raw material, the characteristics of the low DBP absorption amount, the maximum torque, and the high tap bulk density are simultaneously realized. Further, by using the above method, the hexagonal boron nitride powder containing the hexagonal boron nitride aggregate of the present invention can be provided in a single firing step.

B ₂ O ₃ + 3C + N ₂ → 2BN + 3CO
B ₄ C + N ₂ → 4BN + C
3B ₄ C + B ₂ O ₃ + 7N ₂ → 14BN + 3CO
B ₄ C + 2B ₂ O ₃ + 5C + 4N ₂ → 8BN + 6CO
Hexagonal boron nitride powder obtained by the production method of the present invention, by controlling the particle size of the raw material boron carbide, suitable as a boron nitride aggregate for heat conductive insulating sheet, particle size distribution by laser diffraction particle size distribution method The particle size of 90% of the cumulative volume frequency can be adjusted to 50 to 150 μm, and the large-diameter boron nitride aggregates are in close contact with each other in the heat conductive insulating sheet to secure a good heat path. And it is possible to impart high thermal conductivity to the heat conductive insulating sheet.

¹¹ is a diagram showing the relationship between the presence ratio and α-ray emission of ^B.

(Hexagonal boron nitride powder)
Hexagonal boron nitride powder of the present invention includes a hexagonal boron nitride agglomerates, and the presence ratio of ^{11 B} in the total boron is 90% or more, measured according to JIS-K-6217-4, The calculated maximum torque is 0.20 to 0.50 Nm, the DBP absorption is 50 to 100 ml / 100 g, and the tap bulk density is 0.66 to 0.95 g / cm ³ .

  The hexagonal boron nitride was identified as a hexagonal boron nitride powder by confirming that the sample powder had no assigned peak other than hexagonal boron nitride in the X-ray diffraction measurement. Here, for the X-ray diffraction measurement, a fully automatic horizontal multipurpose X-ray diffractometer SmartLab (trade name) manufactured by Rigaku Corporation was used. The measurement conditions were a scan speed of 20 degrees / minute, a step width of 0.02 degrees, and a scan range of 10 to 90 degrees.

In the present invention, the abundance ratio of ¹¹ B in the total boron of the hexagonal boron nitride powder can be confirmed by secondary ion mass spectrometry, as shown in Examples described later. For example, it can be measured using PHI ADEPT-1010 manufactured by ULVAC-PHI, Inc.

The abundance ratio of ^{11 B} in the total boron hexagonal boron nitride powder of the present invention is characterized in that 90% or more. In addition, from the viewpoint of reducing α-ray emission, the abundance ratio of ¹¹ B in all boron is more preferably 95% or more. In other words, the emission of α-rays can be further reduced by increasing the abundance ratio of ¹¹ B in all boron.

  The maximum torque measured and calculated in accordance with the above JIS-K-6217-4 is calculated from the horizontal axis: DBP drop amount (ml) and the vertical axis: torque (Nm) curve. , Calculated from the DBP drop amount at a torque value of 70% of the maximum torque. The above measurement can be performed using, for example, S-500 (trade name) manufactured by Asahi Research Institute.

  Further, in the present invention, the tap bulk density of the hexagonal boron nitride powder can be measured by, for example, a tap denser KYT-5000 (trade name) manufactured by Seishin Enterprise Co., Ltd., as shown in Examples described later.

  In the hexagonal nitride powder of the present invention, the maximum torque is 0.20 to 0.50 Nm, preferably 0.20 to 0.45 Nm. The range of the maximum torque indicates that the hexagonal boron nitride powder contains agglomerated particles, that the ratio of the agglomerated particles is large, and that the powder has a relatively wide particle size distribution. When the maximum torque exceeds 0.50 Nm, the single particle size and the ratio of the single particles become large, and the viscosity when the hexagonal boron nitride powder is filled in the resin tends to increase. Further, it is difficult to produce hexagonal boron nitride powder having a maximum torque of less than 0.20 Nm.

  Incidentally, the maximum torque of the hexagonal boron nitride powder having a single particle size and a single particle as a main component is about 0.6 Nm at the lowest, and generally about 0.6 to 0.75 Nm.

  The hexagonal boron nitride powder of the present invention has a DBP absorption of 50 to 100 ml / 100 g, preferably 50 to 80 ml / 100 g, and more preferably 50 to 75 ml / 100 g. That is, the DBP absorption indicates the amount of open pores in the aggregated particles and the presence or absence of a structure on the particle surface among the characteristics of the hexagonal boron nitride powder. The higher it is. The conventional hexagonal boron nitride powder containing aggregated particles has a DBP absorption of more than 100 ml / 100 g, and requires a very large amount of a diluting solvent when filling the resin. For this reason, volatilization and removal in a later step, fine voids remain in the thermally conductive insulating sheet due to the volatilization and removal, and there is a concern that the thermal conductivity and dielectric strength of the obtained molded article may be reduced. Furthermore, if the DBP absorption exceeds 100 ml / 100 g, the viscosity when filling the resin may increase. On the other hand, the hexagonal boron nitride powder of the present invention, despite containing agglomerated particles, is densely agglomerated, so the DBP absorption amount shows a value of 100 ml / 100 g or less, and is filled in the resin. The above problem can be solved.

  As the DBP absorption is lower, the required amount of the diluting solvent is smaller and the effect is more likely to be exhibited. However, those having a DBP absorption of less than 50 ml / 100 g are difficult to produce.

Furthermore, hexagonal boron nitride powder of the present invention, the tap bulk density 0.66~0.95g / cm ^3, preferably, 0.66~0.90g / cm ^3, more preferably 0.73 to 0 0.88 g / cm ³ . That is, the tap bulk density is an index indicating the amount of open pores, the particle shape, and the breadth of the particle size distribution among the characteristics of the hexagonal boron nitride powder. This indicates a state in which there are many agglomerated particles close to and a particle size distribution close to close packing. The range of the present invention is a value that cannot be achieved with the hexagonal boron nitride powder containing the single particles as a main component, and also has a high value as compared with the conventional hexagonal boron nitride powder containing aggregated particles. is there.

Practically, when the tap bulk density is less than 0.66 g / cm ³ , when the heat conductive insulating sheet is used, since the filler is out of the state of closest packing in the sheet, it is difficult to form the heat conductive insulating sheet in the press molding. An extra load is applied to the polycrystalline boron nitride aggregate, causing the aggregate to be destroyed, making it difficult to exhibit high thermal conductivity. Further, the higher the tap bulk density, the easier the above-mentioned effect is exhibited, but the production of hexagonal boron nitride powder having a tap bulk density exceeding 0.95 g / cm ³ is difficult.

  Further, as described above, the hexagonal boron nitride powder of the present invention requires that the DBP absorption amount, the maximum torque, and the tap bulk density satisfy the above ranges at the same time. Hexagonal boron nitride powder having a maximum torque and a high tap bulk density has never been proposed, and has been proposed for the first time in the present invention.

The specific surface area of the hexagonal boron nitride powder of the present invention is preferably 1.3~7.0m ² / g, more preferably if 1.6~6.0m ² / g, 2.0~5 0.0 m ² / g is more preferred. That is, by setting the specific surface area to 7.0 m ² / g or less, the thermal resistance in the insulating heat dissipation sheet can be particularly suppressed, and the scattering of fine particles can be reduced to improve the handling property. On the other hand, by setting the specific surface area to 1.3 m ² / g or more, it is possible to obtain hexagonal boron nitride powder particularly excellent in the filling property to the resin.

  In the present invention, the specific surface area of the hexagonal boron nitride powder is measured by a BET one-point method as shown in Examples described later, and can be confirmed by, for example, Macsorb HM model-1201 (trade name) manufactured by Mountech Corporation. .

  In addition, since the hexagonal boron nitride powder of the present invention contains hexagonal boron nitride aggregates, the particle diameter (D1) at a cumulative volume frequency of 90% of the particle size distribution in the wet laser diffraction particle size distribution method is 50 to 150 μm. It is preferably 60 to 140 μm, and more preferably 65 to 120 μm. If (D1) is less than 50 μm, it is difficult to exhibit high thermal conductivity, and if it exceeds 150 μm, the particle size is too large with respect to the thickness of the heat-dissipating insulating sheet, which tends to be thinner in recent years, and thus is not preferable. .

  The particle size distribution of the hexagonal boron nitride powder is measured by a wet laser diffraction particle size distribution method, as shown in Examples described later, and can be confirmed by, for example, LA-950V2 (trade name) manufactured by HORIBA.

  In the wet laser diffraction particle size distribution, it is difficult to confirm the shape of the particles, and it is difficult to determine whether hexagonal boron nitride is a flake-like single particle or an aggregate. If necessary, particles having a size of 50 μm or more may be confirmed to be hexagonal boron nitride aggregates by SEM (Scanning Electron Microscope) observation or the like. However, in the production method of the present invention, a scale-like single piece having a size of 50 μm or more is used. It is difficult to imagine that particles are generated with high selectivity, and it can be said that the large particle side in the particle size distribution is an aggregate. In addition, when the scale-like single particles of 50 μm or more are highly selectively contained, the DBP absorption amount may fall within the above range, but the tap bulk density does not fall within the range, which satisfies the scope of the present invention. Therefore, in the present invention, if the maximum torque, the DBP absorption amount and the tap bulk density are within the range of the present invention, it can be said that a hexagonal boron nitride aggregate is included.

  In the present invention, the purity of the hexagonal boron nitride powder is measured by a fluorescent X-ray analysis method, as shown in Examples described later. For example, as a fluorescent X-ray analyzer, ZSX Primus2 (trade name) manufactured by Rigaku Corporation ).

  The purity of the hexagonal boron nitride powder of the present invention is preferably at least 99.95% by mass, more preferably at least 99.97% by mass. Since the hexagonal boron nitride powder of the present invention does not contain an organic or inorganic binder as an essential component, such purity can be relatively easily achieved. By setting the purity of boron nitride to 99.95% by mass or more, it is possible to obtain a boron nitride powder in which hardening of the resin due to impurities, thermal conductivity, decrease in dielectric strength, and the like hardly occur. The hexagonal boron nitride powder purity referred to here is a value obtained by subtracting the content mass ratio of impurity elements other than B and N in the measured elements of the hexagonal boron nitride powder measured by the above-described fluorescent X-ray analysis method from 100. It is.

(Production method of boron nitride powder)
Although the method for producing the hexagonal boron nitride powder of the present invention is not particularly limited, examples of typical production methods include: ¹¹ B-enriched oxygen-containing boron compound, carbon source, oxygen-containing calcium compound, ¹¹ B concentrated boron ^{carbide, 11} B concentration contained in the oxygen-containing boron compound is a ratio of B source and C source contained in the carbon source B / C (atomic ratio) in terms of .75 to ^{1.05, 11} B enriched free 5-20 parts by mass of an oxygen-containing calcium compound in terms of CaO with respect to 100 parts by mass of the total amount of the oxygen-boron compound and the carbon source (B ₂ O ₃ , C conversion value), ¹¹ B-enriched oxygen-containing boron compound, carbon source , _B 2 _O 3 in oxygen-containing calcium compound, C, 10 to 45 parts by mass of the ¹¹ B enriched boron carbide relative terms of CaO by weight per 100 parts by ^weight, Contact ¹¹ B enriched oxygen-containing boron compound Beauty ^{11 B} concentration ¹¹ enrichment of ^B in the total boron contained in the boron carbide 90% weight ratio to form, and the mixture was heated to a temperature of from 1,800 to 2100 ° C. under a nitrogen atmosphere, a reducing After nitriding, a method for producing hexagonal boron nitride powder is characterized in that by-products other than boron nitride present in the reaction product are removed by acid washing.

(material)
The most important feature of the production method of the present invention, as a raw material, ^{11 B} enriched oxygen-containing boron compounds, carbon source, oxygen-containing calcium compound, an ^{11 B} enriched boron carbide, as described below, are mixed at a predetermined ratio The point is to use. The role of each raw material is as follows.

( ¹¹ B concentrated oxygenated boron compound)
Since the chemical properties of the oxygen-containing boron compound do not change even if the mass number of boron is different, the influence on the production process due to the difference in the abundance ratio of ¹¹ B, the thermal conductivity of the obtained hexagonal boron nitride, It has been confirmed that there is no influence on insulation properties, lubricity, corrosion resistance, mold release properties, high temperature stability, low dielectric constant, chemical stability, and the like.

Therefore, in the manufacturing method of the present invention, as the ^{11 B} enriched oxygen-containing boron compound of the raw material, compounds containing boron atoms was concentrated ^{11 B} are used without limitation. As the ¹¹ B enriched oxygen-containing boron compounds, for ^{example, 11} B enriched boric ^{acid, 11} B enriched boric ^{anhydride, 11} B concentrated ^{metaborate, 11} B concentrated ^{perborate, 11} B concentration following boric ^{acid, 11} B concentrated four sodium borate, etc. ^{11 B} enriched sodium perborate can be used. Generally, easily available ^{11 B} enriched boric acid, ^{11 B} enriched boron oxide is preferably used.

In view of emission reduction of α rays of boron nitride powder obtained, the ^{11 B} enriched oxygen-containing boron compound material, enrichment of ^{11 B} is preferably at least 90%, more preferably at least 95%.

Also, the ^{11 B} enriched oxygen-containing boron compound may be used singly or combination. If multiple combined, by taking into account the enrichment of ^{11 B} in the oxygen-containing boron compound to be used, by appropriately adjusting the amount of oxygen-containing boron compound, it is possible to satisfy the above range enrichment. For example, an oxygen-containing boron compound having a high enrichment of ¹¹ B and an oxygen-containing boron compound having a low enrichment of ¹¹ B are mixed so as to be within the above-mentioned range so as to be in the above-described enrichment range, May be adjusted.

As the commercially available ¹¹ B enriched oxygen-containing boron compound, present ratio of 95% or more of the ¹¹ B enriched boric acid (Stella Chemifa Co., Yamanaka Serra dynes Ltd.) is, the abundance ratio of 99% or more ¹¹ B concentration Boric acid (manufactured by Yamanaka Seradyne Co., Ltd.) is available.
Although not an average particle diameter of ¹¹ B enriched oxygen-containing boron compound to be used in particular limited, in view of operability and a reduction reaction control, preferably 30 to 800 m, more preferably 50-700 .mu.m, more preferably 100~500μm . That is, by the average particle diameter of ^{11 B} enriched oxygen-containing boron compound to use greater than 30 [mu] m, it becomes easy to handle. However, there is a possibility that the reduction reaction of the more than 800 [mu] m ^{11 B} enriched oxygen-containing boron compound is less likely to proceed.

(Oxygen-containing calcium compound)
Oxygen-containing calcium compound, by forming a composite oxide with ^{11 B} enriched oxygen-containing boron compound to form a composite oxide having a high melting point, has the role of preventing volatilization of the ^{11 B} enriched oxygen-containing boron compound. It has also been confirmed that it plays a role as a catalyst in the reaction (2) for directly nitriding ¹¹ B-enriched boron carbide.

In the production method of the present invention, as the catalyst and ^{11 B} oxygenates calcium compounds used as volatilization inhibitor concentration oxygenated boron compounds, known are used without particular limitation. As the oxygen-containing calcium compound, for example, calcium carbonate, calcium hydrogen carbonate, calcium hydroxide, calcium oxide, calcium nitrate, calcium sulfate, calcium phosphate, calcium oxalate and the like can be used. It is also possible to use. Among them, it is preferable to use calcium oxide and calcium carbonate.

  The average particle diameter of the oxygen-containing calcium compound is preferably from 0.01 to 200 μm, more preferably from 0.05 to 120 μm, particularly preferably from 0.1 to 80 μm.

(Carbon source)
In the production method of the present invention, a known carbon material that acts as a reducing agent is used without particular limitation as the carbon source. Examples include amorphous carbon such as carbon black, activated carbon and carbon fiber, crystalline carbon such as diamond, graphite and nanocarbon, and pyrolytic carbon obtained by thermally decomposing a monomer or polymer. Among them, highly reactive amorphous carbon is preferable, and carbon black is particularly preferably used in view of industrially controlled quality. In addition, acetylene black, furnace black, thermal black, and the like can be used as the carbon black. Further, the average particle size of the carbon source is preferably 0.01 to 5 μm, more preferably 0.02 to 4 μm, and particularly preferably 0.05 to 3 μm. That is, by setting the average particle size of the carbon source to 5 μm or less, the reactivity of the carbon source becomes high, and by setting the average particle size to 0.01 μm or more, handling becomes easy.
( ¹¹ B concentrated boron carbide)
In the production method of the present invention, since as the ^{11 B} concentration boron carbide used to produce better aggregate efficiency, similarly to the oxygen-containing boron compound, the chemical properties even mass number of boron are different is not changed known ^{11 B} enriched boron carbide is used without particular limitation.

The average particle diameter of the ¹¹ B enriched boron carbide is preferably 30～250Myuemu, more preferably from 50~180μm, 70~150μm is particularly preferred. That is, by setting the average particle diameter of the ^{11 B} enriched boron carbide and 250μm or less, to suppress the formation of coarse aggregates, also by a 30μm or more, moderate for ensuring a high thermal conductivity It is easy to produce an aggregate having a particle size. As the commercially available ^{11 B} enriched boron carbide, enrichment of 95% or more ^{11 B} enriched boron carbide (manufactured by Yamanaka Sera dynes Corporation) are available.

  In the production method of the present invention, the supply form of the mixture containing each of the above-mentioned raw materials to the reaction is not particularly limited, and may be in the form of a powder, or may be performed by forming granules.

  In the production method of the present invention, the method of mixing the raw materials is not particularly limited, and a general mixer such as a vibration mill, a bead mill, a ball mill, a Henschel mixer, a drum mixer, a vibration stirrer, and a V-shaped mixer can be used. .

  The granulation method in the case of performing granulation can also be carried out by a known method such as extrusion granulation, tumbling granulation, and granulation using a compactor. In this case, the size of the granules is preferably about 5 to 10 mm.

(Preparation of raw materials)
In the present invention, reduction nitriding reaction is carried out by the supply of carbon source and nitrogen, in order to obtain the hexagonal boron nitride agglomerates of interest effectively, the composite oxide and ^{11 B} enriched oxygen-containing boron compound Is required to be 0.75 to 1.05, preferably 0.75 to 0.95 in terms of B / C (element ratio). That is, when the molar ratio exceeds 1.05, the ratio of ^{11 B} enriched boron compound volatilizes without being reduced increases not only the yield is lowered by the volatilization component adversely affects the production line . Further, the molar ratio is less than 0.75, less ^{11 B} enriched boron oxide content of unreacted upon reaching the reduction nitriding temperature, it becomes difficult to produce the hexagonal boron nitride agglomerates of interest.

In the present invention, in order to effectively obtain the desired hexagonal boron nitride aggregate, the total amount (B ₂ O ₃ , C conversion value) of the ¹¹ B-enriched oxygen-containing boron compound and the carbon source is 100 parts by mass. On the other hand, it is necessary to mix the oxygen-containing calcium compound at a ratio of 5 to 20 parts by mass in terms of CaO. At this time, when the CaO-equivalent mass part is less than 5 parts by mass, the ratio of the ¹¹ B-enriched boron compound which is volatilized without being reduced is increased, and not only the yield is reduced, but also the above-mentioned volatile components adversely affect the production line. It is not preferable. If the CaO equivalent mass exceeds 20 parts by mass, impurities derived from calcium may not only remain, but also plate-like hexagonal boron nitride single particles may not easily grow, which is not preferable.

Further, in the present invention, in order to effectively obtain the desired hexagonal boron nitride powder, it is necessary to prepare an ¹¹ B-enriched oxygen-containing boron compound, a carbon source, and a B ₂ O ₃ , C, and CaO equivalent mass of ¹¹ B-enriched boron carbide. it is important to mix the ^{11 B} enriched boron carbide in a proportion to be 10 to 45 parts by mass relative to the total 100 parts by mass. That is, when the proportion of the boron carbide is less than 10 parts by mass, the content ratio of the target hexagonal boron nitride aggregate is reduced, and the target DBP absorption amount and tap bulk density cannot be realized, which is not preferable. . If the proportion of the composite oxide exceeds 45 parts by mass, unreacted boron carbide may remain, which is not preferable.

Further, in the present invention, in order to obtain a less hexagonal boron nitride powder with α-ray emission of interest effectively is, ¹¹ B in the total boron contained in the ^{11 B} concentration oxygenated boron compound and ^{11 B} enriched boron carbide It is important to mix them at a ratio such that the degree of concentration of the mixture becomes 90% or more. Therefore, use ¹¹ in consideration of the ^B concentration oxygen-containing boron compound and ^{11 B} concentration enrichment of boron carbide, can satisfy the above range enrichment by adjusting their usage as appropriate. For example, a and enrichment high ^{11 B} enriched oxygen-containing boron compound and enrichment low ^{11 B} enriched boron carbide, enrichment of ^{11 B} in the total boron may be used in combination so that more than 90% . At this time, from the viewpoint of reducing α-ray emission of the obtained boron nitride powder, the enrichment of ¹¹ B in all boron is more preferably 95% or more.

(Reduction nitriding)
In the method for producing boron nitride of the present invention, the supply of the nitrogen source to the reaction system can be formed by known means. For example, the most common method is to flow nitrogen gas through a reaction system of a reactor exemplified later. The nitrogen source to be used is not limited to the above-mentioned nitrogen gas, and is not particularly limited as long as it is a gas capable of nitriding in the reductive nitridation reaction. Specifically, it is also possible to use ammonia gas in addition to the nitrogen gas. Further, a gas in which a non-oxidizing gas such as hydrogen, argon, and helium is mixed with nitrogen gas and ammonia gas can also be used.

  In the above production method, in order to obtain a hexagonal boron nitride powder having high crystallinity, the heating temperature in the reductive nitridation reaction is usually 1800 ° C or higher, preferably 1800 to 2100 ° C, more preferably 1900 to 2000 ° C. It is necessary to adopt. That is, if the temperature is lower than 1800 ° C., it is difficult to obtain a hexagonal boron nitride having a high degree of reductive nitridation reaction and high crystallinity. It is.

  Further, the time of the reductive nitridation reaction is appropriately determined, but is generally about 10 to 30 hours.

  The method for producing hexagonal boron nitride powder of the present invention can be carried out using a known reaction apparatus capable of controlling the reaction atmosphere. For example, there is an atmosphere controlled high-temperature furnace for performing heat treatment by high-frequency induction heating or heater heating. In addition to a batch furnace, a continuous furnace such as a pusher tunnel furnace and a vertical reaction furnace can also be used.

(Acid cleaning)
In the production method of the present invention, the reaction product obtained by the above-described reduction nitridation contains, in addition to hexagonal boron nitride powder, impurities such as a boron oxide-calcium oxide composite oxide and the like, Washing is preferred. The method of such acid washing is not particularly limited, and a known method is adopted without any limitation. For example, by-product-containing boron nitride obtained after the nitriding treatment is crushed and put into a container, and 5 to 10 times the amount of diluted hydrochloric acid (10 to 20% by mass HCl) of the hexagonal boron nitride powder containing the impurity is added. And contacting for 4 to 8 hours.

  As the acid used in the acid washing, nitric acid, sulfuric acid, acetic acid and the like can be used in addition to hydrochloric acid.

  After the above acid cleaning, cleaning is performed using pure water for the purpose of cleaning the remaining acid. As for the washing method, after filtering the acid at the time of the acid washing, the acid-washed boron nitride is dispersed in the same amount of pure water as the acid used, and the filtration is performed again.

(Dry)
As the drying conditions for the water-containing mass after the acid washing and the water washing, drying in the air at 50 to 250 ° C. or under reduced pressure is preferable. The drying time is not particularly specified, but it is preferable to dry until the water content approaches 0%.

(Classification)
If necessary, the dried boron nitride powder may be crushed and then subjected to coarse particle removal by a sieve or the like, or fine powder removal by airflow classification or the like.

(Use of boron nitride powder)
The application of the boron nitride powder of the present invention is not particularly limited, and can be applied to known applications without any particular limitation. Examples of applications that are preferably used include those used as fillers in resins for the purpose of improving electrical insulation, imparting thermal conductivity, etc. while reducing emission of α-rays. In the application of the boron nitride powder, the obtained resin composition emits little α-rays and has high electrical insulation and thermal conductivity.

  The resin composition of the present invention can be used for known applications without limitation, but by mixing with a resin described below to form a heat conductive resin composition or a heat conductive molded body, a polymer heat dissipation sheet or a phase change sheet. Thermal interface materials such as heat dissipation tapes, heat dissipation grease, heat dissipation adhesives, organic heat dissipation sheets such as gap fillers, heat dissipation paints such as heat dissipation paints and heat dissipation coats, and heat dissipation resins such as PWB base resin substrates and CCL base resin substrates It can be preferably used for applications such as an insulating layer of a metal base substrate such as a substrate, an aluminum base substrate, and a copper base substrate, and a sealing material for power devices.

  Above all, the boron nitride powder of the present invention is excellent in thermal conductivity and electric insulation, and thus exhibits the greatest effect when the resin composition is used as a heat dissipation insulating sheet.

  Furthermore, since the boron nitride powder of the present invention has neutron absorption performance, it is most preferable to employ the heat dissipation insulating sheet as a heat dissipation insulating member for electronic components as a measure against soft errors caused by neutrons.

  In addition, when the boron nitride powder of the present invention is used as a resin composition, it is preferable to use it by mixing it with a heat conductive filler such as aluminum nitride and aluminum oxide, which are general high heat conductive insulating fillers. By adopting such an embodiment, the thermal conductivity and the electrical insulation can be optimized according to the application, and the cost-effectiveness can be improved.

  As the resin, polyolefin, vinyl chloride resin, methyl methacrylate resin, nylon, thermoplastic resin such as fluororesin, epoxy resin, phenol resin, urea resin, melamine resin, unsaturated polyester resin, silicon resin, bismaleimide triazine resin And the like, a thermosetting resin, a synthetic rubber, and the like.

  Further, the resin composition, if necessary as a compounding agent of the resin composition known polymerization initiator, curing agent, polymerization inhibitor, polymerization retarder, coupling agent, plasticizer, ultraviolet absorber, pigment, Known additives such as dyes, antibacterial agents, organic fillers, and organic-inorganic composite fillers may be included. Further, other inorganic fillers may be contained as long as the effects of the present invention are not impaired.

  Further, the boron nitride powder of the present invention is a raw material of a boron nitride processed product such as cubic boron nitride or a boron nitride molded product, a nucleating agent for engineering plastics, a phase change material, a solid or liquid thermal interface material, It can also be used for applications such as mold release agents for molten metal and molten glass molds, cosmetics, and composite ceramic raw materials.

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

  In the examples, each measurement is a value measured by the following method.

[Isotope ratio of hexagonal boron nitride powder]
The obtained hexagonal boron nitride powder was analyzed for isotope abundance ratio using PHI ADEPT-1010 manufactured by ULVAC-PHI, Inc. From the ratio of the counts of ¹⁰ B and ¹¹ B in the mass spectrum, the abundance ratio of ¹¹ B in the total boron of the boron nitride powder was confirmed.

[DBP absorption amount (ml / 100 g) and maximum torque (Nm) of hexagonal boron nitride powder based on JIS-K-6217-4]
The obtained hexagonal boron nitride powder was measured in accordance with JIS-K-6217-4, with the horizontal axis representing the amount of DBP dripping (ml) and the vertical axis representing the maximum torque (Nm) calculated from the torque (Nm) curve. And the amount of DBP absorption (ml / 100 g) were determined. The measurement was performed using a measuring device S-500 manufactured by Asahi Research Institute. The measurement conditions were the DBP dropping rate of 4 ml / min, the number of revolutions of the stirring blade at 125 rpm, the sample input amount of 30 g, and the DBP absorption amount using the dropping amount of 70% of the maximum torque. DBP (Dibutyl Phthalate) was performed using a special-grade reagent (supplier code: 021-06936) manufactured by Wako Pure Chemical Industries, Ltd.

[Tap bulk density of hexagonal boron nitride powder (g / cm ³ )]
About the obtained hexagonal boron nitride powder, the tap bulk density was measured using the tap denser KYT-5000 made by Seishin Enterprise Co., Ltd. The sample cell was performed under the conditions of 100 ml, tap speed 120 times / min, tap height 5 cm, and tap number 500 times.

[Specific surface area of hexagonal boron nitride powder (m ² / g)]
The specific surface area of the obtained hexagonal boron nitride powder was measured using Macsorb HM model 1201 manufactured by Mountech.

[Diameter D1 (μm) of 90% of cumulative volume frequency of particle size distribution of hexagonal boron nitride powder]
About the obtained hexagonal boron nitride powder, the particle size (D1) of 90% of the cumulative volume frequency of the particle size distribution was measured using LA-950V2 manufactured by HORIBA. The measurement was performed without dispersing the boron nitride powder in an ethanol solvent and performing an operation such as ultrasonic treatment that might destroy the boron nitride aggregated particles. The particle size at a cumulative volume frequency of 90% in the obtained particle size distribution was defined as (D1).
[Hexagonal boron nitride powder purity (% by mass)]
About the obtained hexagonal boron nitride powder, the purity of the hexagonal boron nitride powder was measured using ZSX Primus2 (trade name) manufactured by Rigaku Corporation. The hexagonal boron nitride powder purity is a value obtained by subtracting the content mass ratio of impurity elements other than B and N in the measured elements of the hexagonal boron nitride powder measured by the above-described X-ray fluorescence analysis method from 100.

Example 1
¹¹ B enrichment 95% of the ¹¹ B enriched boric acid 346.4 g, carbon black 84 g, calcium carbonate 44 g, average ¹¹ enrichment of B of particle size 170μm mixtures containing 95% of the ¹¹ B enriched boron carbide 52 g 526 0.4 g was mixed using a ball mill. The (B / C) element ratio conversion of the mixture is 0.8, and the CaO of the oxygenated calcium compound is 100 parts by mass of the ¹¹ B-enriched oxygenated boron compound and carbon source with respect to 100 parts by mass of the total mass in terms of B ₂ O ₃ and C. The reduced mass content ratio is 8.8 parts by mass. ¹¹ B enriched oxygen-containing boron compounds, carbon source, oxygen-containing calcium _compound, B ₂ O 3, C, content of ¹¹ B enriched boron carbide for CaO reduced mass per 100 parts by mass is 17 parts by weight. 100 g of the mixture was subjected to a nitriding treatment by holding it at 1950 ° C. for 17 hours in a nitrogen gas atmosphere using a graphite Tamman furnace.

  Next, the by-product-containing boron nitride was crushed and charged into a vessel, and hydrochloric acid (7% by mass HCl) in an amount 5 times the amount of the by-product-containing boron nitride was added thereto, followed by stirring at 700 rpm for 24 hours. After the acid washing, the acid was filtered, the boron nitride obtained by filtration was dispersed in the same amount of pure water as the acid used, and the resultant was filtered again. After this operation was repeated five times, vacuum drying was performed at 200 ° C. for 6 hours.

The powder obtained after drying was sieved through a sieve having an opening of 120 μm to obtain a white hexagonal boron nitride powder. Abundance of ^{11 B} in the total boron of the resulting hexagonal boron nitride powder, DBP absorption amount, the aforementioned maximum torque, tapped bulk density, specific surface area, purity, a cumulative volume frequency of 90% particle diameter D1 of the particle size distribution It was measured by the method and shown in Table 2.

Example 2
Implemented except that the content ratio of ¹¹ B-enriched boron carbide was 100 parts by mass in terms of B ₂ O ₃ , C, and CaO of the ¹¹ B-enriched oxygen-containing boron compound, carbon source, and oxygen-containing calcium compound was 19 parts by mass. Same as Example 1. The conditions and measured values are shown in Tables 1 and 2.

Example 3
Example 1 Except that the content ratio of the oxygen-containing calcium compound in terms of CaO to 11.2 parts by mass per 100 parts by mass of the total mass in terms of B ₂ O ₃ and C of the ¹¹ B-concentrated oxygen-containing boron compound and carbon source was set to 11.1 parts by mass. Same as 1. The conditions and measured values are shown in Tables 1 and 2.

Example 4
¹¹ B enriched oxygen-containing boron compounds, carbon source, oxygen-containing calcium _{compound, B 2 O 3, C,} 11 parts by mass of the content of the ¹¹ B enriched boron carbide for CaO reduced mass per 100 parts by weight, the reduction nitridation 1900 The procedure was the same as in Example 1 except that the temperature was changed to ° C. The conditions and measured values are shown in Tables 1 and 2.

Example 5
The (B / C) atomic ratio in terms ^{0.81, 11} B enriched oxygen-containing boron compounds, carbon source, oxygen-containing calcium _{compound, B 2 O 3, C,} 11 B enriched carbide for CaO reduced mass per 100 parts by Example 1 was repeated except that the boron content was 23 parts by mass and the reduction nitriding was 2000 ° C. The conditions and measured values are shown in Tables 1 and 2.

Example 6
(B / C) atomic ratio in terms of ^{0.79, 11} B enriched oxygen-containing boron compounds, carbon _sources, CaO reduced mass content of B _{2 O} 3, C reduced mass total amount the oxygen-containing calcium compound to the 100 parts by weight 10.8 parts by mass of the ¹¹ B-enriched boron-containing boron compound, the carbon source, and the oxygen-containing calcium compound in terms of the content ratio of the ¹¹ B-enriched boron carbide with respect to 100 parts by mass in terms of B ₂ O ₃ , C, and CaO in terms of 100 parts by mass. The same procedures as in Example 1 were carried out except that the parts by mass were used. The conditions and measured values are shown in Tables 1 and 2.

Example 7
¹¹ enrichment 99% ¹¹ B enriched boric acid ^B, except that the enrichment of ¹¹ B was 95% of the ¹¹ B enriched boron carbide and in the same manner as in Example 1. The conditions and measured values are shown in Tables 1 and 2.

Example 8
¹¹ enrichment of 90% of the ¹¹ B enriched boric acid ^B, except that the enrichment of ¹¹ B was 95% of the ¹¹ B enriched boron carbide and in the same manner as in Example 1. The conditions and measured values are shown in Tables 1 and 2.

Comparative Example 1
Example 1 was repeated except that boron carbide was not added. The conditions and measured values are shown in Tables 1 and 2.

Comparative Example 2
Boric acid which is not concentrated to ^{11 B,} is as in Example 1 except for using boron carbide which is not concentrated to ^{11 B.} The conditions and measured values are shown in Tables 1 and 2.

Comparative Example 3
Powder properties of a commercially available hexagonal boron nitride powder containing highly agglomerated hexagonal boron nitride particles: PTX25 (trade name: manufactured by Momentive) were measured, and the results are shown in Table 2.

Comparative Example 4
The powder properties of a commercially available PT110 (trade name: manufactured by Momentive) containing single particles of hexagonal boron nitride in a highly selective manner were measured.

Examples 9 to 16
The boron nitride powder obtained in Examples 1 to 8 was filled in an epoxy resin to prepare a resin composition, and the thermal conductivity was evaluated. As the epoxy resin, a mixture of 100 parts by mass (JER828 manufactured by Mitsubishi Chemical Corporation), 5 parts by mass of a curing agent (imidazole-based curing agent, Curesol 2E4MZ manufactured by Shikoku Chemicals Co., Ltd.) and 210 parts by mass of methyl ethyl ketone as a solvent was prepared. Next, the varnish-like mixture and the hexagonal boron nitride powder were mixed by a rotation / revolution mixer (MAZERUSTAR manufactured by Kurashiki Spinning Co., Ltd.) so that the base resin was 30% by volume and the specific boron nitride powder was 70% by volume. Thus, a resin composition was obtained.

The above resin composition is coated and dried on a PET film to a thickness of about 250 to 300 μm using an automatic coating machine PI-1210 manufactured by Tester Sangyo Co., Ltd., and under reduced pressure, temperature: 200 ° C., pressure: 5 MPa, holding Time: cured for 30 minutes to produce a sheet having a thickness of 200 μm.
The sheet was analyzed with a temperature wave thermal analyzer, and the results of calculating the thermal conductivity are shown in Table 3. The sheet filled with the hexagonal boron nitride powder prepared in Examples 1 to 8 had a thermal conductivity of 14.0 W / m · K or more, indicating a high thermal conductivity. The dielectric strength was measured with a withstand voltage tester (manufactured by Tama Denso Co., Ltd.). As a result, the dielectric strength was as high as 40 kV / mm or more, and the amount of voids in the resin composition that caused a decrease in dielectric strength was small. The thing was suggested.

  Next, after mixing 80% by volume of each base resin and 20% by volume of the specific boron nitride powder in a mortar under the same conditions for each test, a B-type viscometer TBA-10 (East) was used at a measurement temperature of 25 ° C. (Manufactured by Kiki Kogyo).

Example 17
Next, the boron nitride powder produced in Example 1, aluminum nitride having an average particle diameter of 30 μm, and aluminum oxide having an average particle diameter of 1 μm were mixed at a volume ratio of 5: 4: 1, and the sheet and viscosity were evaluated in the same manner as in Example 9. Was done.

Example 18
Next, the boron nitride powder produced in Example 1 and aluminum nitride having an average particle diameter of 30 μm were mixed at a volume ratio of 5: 5, and the sheet and the viscosity were evaluated in the same manner as in Example 9.

Example 19
Next, the boron nitride powder produced in Example 4 and aluminum oxide having an average particle diameter of 20 μm were mixed at a volume ratio of 9.5: 0.5, and the sheet and viscosity were evaluated in the same manner as in Example 9.

Comparative Examples 5 to 8
Comparative Examples 5, 6, and 8 were made in the same manner as in Example 9 except that the boron nitride powder obtained in Comparative Examples 1 and 2 and the commercially available boron nitride powder of Comparative Example 4 were used. In Comparative Example 7 using the commercially available hexagonal boron nitride powder of Comparative Example 3, the amount of solvent required to achieve a high DBP absorption amount and a viscosity that allows application was 320 parts by mass, which was the same as in other Examples and Comparative Examples. More was needed than in the example. Further, when the cross section inside the sheet was observed, many voids were confirmed. Table 3 shows the results of analyzing the sheet with a temperature wave thermal analyzer and calculating the thermal conductivity. Table 3 shows the results of measuring the dielectric strength with a withstand voltage tester (manufactured by Tama Denso Co., Ltd.). None of the sheets filled with the boron nitride powder obtained in Comparative Example 1 and the commercially available hexagonal boron nitride powder of Comparative Examples 3 and 4 can achieve 14.0 W / m · K or more than 40 kV / mm. Was.

  Next, after mixing 80% by volume of each base resin and 20% by volume of the specific boron nitride powder in a mortar under the same conditions for each test, a B-type viscometer TBA-10 (Toki Machine Co., Ltd.) was used at a measurement temperature of 25 ° C. (Manufactured by Kogyo Co., Ltd.). The resin composition containing the boron nitride powder obtained in Comparative Example 1 and the commercially available hexagonal boron nitride powder of Comparative Examples 3 and 4 is a resin composition containing the boron nitride powder produced in Examples 1 to 8 and Comparative Example 2. It was higher in viscosity than the composition.

  Next, using the sheets obtained in Examples 9 to 16 and Comparative Examples 5 to 8 described above, the hexagonal boron nitride of the present invention was evaluated for the α-ray emission reduction performance by the method described below.

The amount of emitted α-rays from the sheet was evaluated using a 2π gas flow proportional counting system, LACS-4000m, manufactured by Sumika Chemical Analysis Service, Ltd. Alpha rays are generated by the complex nuclear reaction of ¹⁰ B and thermal neutrons in boron nitride. However, it takes a very long time to measure with thermal neutrons derived from cosmic rays, so a Cf-252 neutron source was used to shorten the measurement time. used. A Cf-252 neutron source was installed at the center of a 20 cm square cubic high-density polyethylene, and a neutron beam derived from Cf-252 was decelerated by the high-density polyethylene to obtain a thermal neutron source. The thermal neutron source was installed at a fixed distance from LACS-4000 m and irradiated with thermal neutrons.

With respect to the amount of emitted α-rays, the relative value was determined assuming that the value obtained in Comparative Example 6 was 1, and the value obtained by measuring without a sheet (blank measurement) was 0, and the relative values were obtained. Plotted on the graph. According to the graph, it can be seen that the higher the abundance ratio of ¹¹ B, the more the emission of α-rays can be reduced. Sheet abundance ratio of ^{11 B} was made using hexagonal boron nitride powder of greater than abundance ratio of ^{11 B} natural boron, hexagonal abundance ratio of ^{11 B} corresponds to the presence ratio of ^{11 B} natural boron The emission amount of α-rays was smaller than the sheet manufactured using the boron nitride powder.

Claims (9)

Includes a hexagonal boron nitride agglomerates, and the presence ratio of ¹¹ B in the total boron is 90% or more, the maximum torque calculated measured according to JIS-K-6217-4 is 0.20 Hexagonal boron nitride powder characterized by having a 0.50 Nm, a DBP absorption of 50 to 100 ml / 100 g, and a tap bulk density of 0.66 to 0.95 g / cm ³ . A specific surface area of 1.3~7.0m ² / g hexagonal boron nitride powder of claim 1, wherein the.   The hexagonal boron nitride powder according to claim 1 or 2, wherein the particle size at a cumulative volume frequency of 90% of the particle size distribution in the wet laser diffraction particle size distribution method is 50 to 150 µm.   The hexagonal boron nitride powder according to any one of claims 1 to 3, having a boron nitride purity of 99.95% by mass or more.   A resin composition comprising the hexagonal boron nitride powder according to claim 1.   A resin composition obtained by filling a mixed powder containing the hexagonal boron nitride powder according to any one of claims 1 to 4 and an aluminum oxide powder and / or an aluminum nitride powder.   A heat dissipation insulating sheet comprising the resin composition according to claim 5.   A heat-radiating insulating member for an electronic component, comprising the heat-radiating insulating sheet according to claim 7. ^{11 B} enriched oxygen-containing boron compounds, carbon source, oxygen-containing calcium compound and ^{11 B} enriched boron carbide, ^{11 B} enriched oxygenated of B reduced mass and carbon source of boron compound C mass in terms of the ratio B / C (atomic ratio) Is 0.75 to 1.05, and the oxygen-containing calcium compound is 5 to 20 in terms of CaO with respect to 100 parts by mass of the B ₂ O ₃ equivalent mass of the ¹¹ B-enriched oxygenated boron compound and the C equivalent mass of the carbon source. parts by weight, and ¹¹ B enriched oxygen-containing boron compounds, carbon source and oxygen-containing calcium compound, respectively _B 2 _O 3, the ¹¹ B concentration boron carbide 10 with respect to the total amount 100 parts by weight of C and CaO reduced mass 45 parts by mass, at a rate such that the enrichment of ¹¹ B in the total boron contained in the ¹¹ B-enriched oxygenated boron compound and the ¹¹ B-enriched boron carbide is 90% or more. Mixing the mixture, heating the mixture to a temperature of 1700 to 2100 ° C. in a nitrogen atmosphere, and reducing and nitriding the mixture, thereby producing a hexagonal boron nitride powder.

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