JP4105141B2 - Method for producing aluminum nitride powder - Google Patents

Description

  The present invention relates to a method for producing a hydrophobized aluminum nitride powder.

Since the aluminum nitride powder has hydrolyzability, the aluminum nitride powder is subjected to a hydrophobic treatment in advance in order to form a molded body using the aqueous slurry. As a hydrophobic treatment method, generally, for example, a silane coupling agent, a silicate treatment agent, a hydrophobic treatment agent such as an inorganic phosphorus compound and aluminum nitride powder are dry-mixed, or an organic solution containing the hydrophobic treatment agent and This is done by mixing the aluminum nitride powder and then removing the solvent by drying. However, these methods cannot be processed on an industrial scale, or it is difficult to blend the processed powder into the resin at a high filling rate. Therefore, the aluminum nitride powder, the silicate treating agent and the silane coupling agent are not used. It has been proposed to prepare a mixture containing the mixture and heat-treat the resulting mixture (Patent Document 1).
JP 2004-083334 A

  However, according to Patent Document 1, although the water resistance of aluminum nitride powder is improved, as shown in the examples, this treatment method involves stirring and mixing aluminum nitride powder in an organic medium such as ethanol, and the like. Subsequent firing is the basic operation, so it cannot always be said to be a treatment method on an industrial scale.

On the other hand, aluminum nitride powder is produced by nitriding metal aluminum powder to produce an aluminum nitride ingot and grinding it, alumina nitriding method by reducing and nitriding mixed powder of alumina powder and carbon, vaporizing metal aluminum powder It is manufactured by vapor phase nitriding. Among these, in the vapor phase method, metal aluminum powder is entrained in a reaction tube with a nitriding gas such as nitrogen gas to be injected into aluminum vapor, and if necessary, nitrogen gas is separately supplied along the inner wall of the reaction tube. The nitriding reaction is performed to form aluminum nitride powder, which is cooled while being guided to the collection device connected to the lower part of the reaction tube using the exhaust gas from the reaction tube, and is collected by the collection device. (Patent Document 2). According to this vapor phase method, the aluminum nitride powder inevitably forms a floating state by the high-temperature exhaust gas while being guided to the collection device.
JP 2003-34511 A

  The object of the present invention is to produce hydrophobized aluminum nitride powder on an industrial scale. The present invention intends to achieve the intended object by utilizing the fact that aluminum nitride powder forms a floating state with high-temperature exhaust gas.

  That is, according to the present invention, metallic aluminum powder is entrained in a nitriding gas and injected into a nitriding furnace for nitriding, and the resulting powder containing the aluminum nitride powder is connected to the lower part of the nitriding furnace while entraining in the exhaust gas. In the method for producing an aluminum nitride powder, the produced powder is subjected to a hydrophobic treatment between the collecting device and the lower portion of the nitriding furnace when being guided to the collecting device.

In the present invention, the average particle diameter of the metal aluminum powder is 10 to 40 μm, the injection amount of the metal aluminum powder is 1 to ³ kg per 1 Nm ^{3 of} the nitriding gas, the gas flow rate of the nitriding gas is 50 to 100 m / s, and the injection pressure is The inner temperature of the nitriding furnace is preferably 1900 to 2200 ° C. The hydrophobizing treatment is preferably performed at a temperature of 500 to 50 ° C, particularly 200 to 100 ° C.

  ADVANTAGE OF THE INVENTION According to this invention, the aluminum nitride powder excellent in water resistance (hydrolysis resistance) can be manufactured on an industrial scale.

  The metal aluminum powder used in the present invention preferably has an average particle size of 10 to 40 μm. Among them, atomized powder with a low risk of explosion is more preferable. If the average particle diameter is significantly coarser than 40 μm, the evaporation of aluminum is suppressed, and if it is finer than 10 μm, it becomes easy to form coarse droplets. In any case, sufficient concentration of aluminum vapor can be obtained in the nitriding furnace. There is a risk of disappearing.

Since metallic aluminum is a low melting point material, it becomes droplets as soon as it is injected into the nitriding furnace, so that evaporation is delayed and a sufficient concentration of aluminum vapor cannot be obtained. Therefore, in the present invention, in order to alleviate this phenomenon, the injection amount of the metal aluminum powder is 1 to ³ kg per 1 Nm ^{3 of} the nitriding gas, the gas flow rate of the nitriding gas is 50 to 100 m / s, and the injection pressure is 0. It is preferable to set it as 2-0.6 MPa. Here, the gas flow rate of the nitriding gas is obtained by dividing the amount of nitriding gas per unit time (Nm ³ / h) by the cross-sectional area of the injection section (for example, the cross-sectional area of a feed pipe described later) (m ² ). Can be sought.

  When the metal aluminum powder is sprayed under such conditions, there is an advantage that a very homogeneous aluminum nitride powder having a non-uniform strain measured by the Rietveld method of 0.05% or less can be produced. Here, the non-uniform distortion due to the Rietveld method is measured using a diffraction pattern using an X-ray diffractometer, for example, “JDX3500” manufactured by JEOL Ltd. (Refer to page, published by Asakura Shoten in February 2002)).

  Aluminum nitride powder with non-uniform strain of 0.05% or less by the Rietveld method has increased heat conductivity when used as a filler for resins and the like due to its homogeneity, and was used as a raw material for sintering. Sometimes the thermal conductivity of the aluminum nitride sintered body increases.

  In order to inject the metal aluminum powder into the nitriding furnace, the metal aluminum powder is quantitatively supplied to the mixer by a feeder such as a table feeder or a screw feeder, and is then transported to the nozzle while being mixed with the nitriding gas. In the vicinity of the outlet of the gas, it can be performed by joining with another nitriding gas and spraying. The gas flow rate and injection pressure of the nitriding gas injected into the nitriding furnace are adjusted by the speed and pressure of the separately added nitriding gas.

  As the nozzle, for example, an orifice, a two-fluid nozzle, a ring nozzle, or the like is used. An example of a ring nozzle is shown in FIG. 1 includes a supply pipe 14 and a discharge pipe 15 having a tapered connection structure, and the width of the slit 18 can be adjusted by the distance (interval) between the tapered surfaces of each other. The tube 15 is fixed, and the slit width is adjusted by the moving distance of the supply tube 14. The nitriding gas chamber 16 is filled with a nitriding gas having a predetermined pressure, and the flow rate is adjusted by the slit width. The metal aluminum powder is introduced into the supply pipe 14 along with the nitriding gas, merges with another nitriding gas ejected from the slit, is further dispersed, and is ejected from the discharge pipe 15. 17 is a pressure gauge.

  In addition, it is preferable that a metal aluminum powder is injected through the zone of 400-600 degreeC, and this can suppress melting of metal aluminum, and can heat and evaporate rapidly.

  The nitriding gas used in the present invention is a gas containing nitrogen for converting aluminum vapor into aluminum nitride (AlN), and a nitrogen gas alone, a mixed gas of nitrogen gas and a gas such as hydrogen, CO, or ammonia. Can be illustrated.

  In the present invention, the nitriding furnace is preferably maintained at 1900 ° C to 2200 ° C. When the temperature is lower than 1900 ° C., it is difficult to evaporate the metal aluminum powder, and when the temperature is higher than 2200 ° C., there is a possibility that an aluminum nitride powder having a nonuniform strain of 0.05 or less cannot be produced.

  An example of an apparatus for producing aluminum nitride powder used in the present invention is shown in FIG. The nitriding furnace is a high-frequency induction heating method, and includes a reaction tube 6 and a heating element 8 disposed around the reaction tube 6 and a quartz outer wall 10 covered with a heat insulator 9. The material of the reaction tube 6 is preferably isotropic graphite or boron nitride. 4 is a resistance heating source for adjusting the supply temperature of the metal aluminum, 5 is a feed tube, 7 is a high frequency induction heating source, and 13 is a temperature measuring body. At the top of the nitriding furnace, metallic aluminum powder injection means comprising a metallic aluminum powder feeder 1, a mixer 2 and a nozzle 3 is installed, and the lower part is connected to a collecting device 11. The produced powder containing the produced aluminum nitride powder is accompanied by exhaust gas from the lower part of the nitriding furnace and guided to the collecting device 11, which is performed by the blower 12. As the collection device 11, for example, a bag filter, an electric dust collector or the like is used.

  The hydrophobization treatment of the product powder containing the aluminum nitride powder is performed at an arbitrary position from the lower part of the nitriding furnace to the collection device. For example, if the hydrophobizing agent addition device 19 is installed at an arbitrary position between the lower part of the nitriding furnace and the collecting device and the hydrophobizing agent is added, the treated powder is collected from the collecting device. In the period up to this time, the produced powder containing the aluminum nitride powder in a floating state is kept in contact with the hydrophobizing agent and subjected to the hydrophobizing treatment. As an apparatus for adding the hydrophobizing agent, an ordinary spraying apparatus is sufficient.

  Examples of the hydrophobizing agent used in the present invention include a silane coupling agent, a silicate treating agent, an inorganic phosphate compound, and an organic phosphate compound. These are preferably used after being dispersed or dissolved in an organic medium such as methanol, ethanol, isopropyl alcohol, toluene, or methyl ethyl ketone. Among these, a silane coupling agent and a silicate treating agent are particularly preferable. For example, γ-methacryloxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxy Propyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-ureidoaminosilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, vinyltrichlorosilane, vinyltris (β-methoxyethoxy) silane, vinyltriethoxysilane, vinyltrimethoxysilane, teto Silane, methyl trimethoxy silane, di marries dimethoxysilane, tetraethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, and the like.

  As described above, the addition position of the hydrophobizing agent may be an arbitrary place between the lower part of the nitriding furnace and the collection device, but preferably a place where the temperature is 300 to 50 ° C., particularly preferably It is the place which is 150-80 degreeC. The amount of the hydrophobizing agent used is preferably 0.1 to 2 parts by mass per 100 parts by mass of the produced powder containing aluminum nitride powder.

  Hydrophobized aluminum nitride powder was produced using the apparatus shown in FIG. The capacity of the nitriding furnace is 170 kVA and the output is 100 kW. A reaction tube 6 (made of boron nitride: inner diameter 200 mm, total length 3000 mm) is installed in the center of the furnace, a heating element 8 (made of graphite) is arranged around it, and heated by a high-frequency induction heating source 7 to react with the reaction agent. It is kept at a predetermined temperature. The reaction temperature is measured by measuring the temperature measuring body 13 (glassy carbon tube) installed at the center of the heating element with an optical thermometer. The heating element 8 is kept warm by a heat insulating material 9 (porous carbon beads) and is held by a quartz outer wall 10 (inner diameter 450 mm, total length 3000 mm). The resulting powder containing aluminum nitride powder is entrained by the exhaust gas from the furnace bottom and guided to the collection device 11 (bag filter) by the blower 12. A hydrophobizing treatment agent addition device 19 (spray spraying device) is installed at a temperature of about 180 ° C. during the time of reaching the collection device, and the hydrophobization treatment agent dispersed in ethanol is sprayed from the device to the collection device 11. Within the time to reach, it is hydrophobized and collected.

  A predetermined amount of metal aluminum powder is conveyed from a metal aluminum powder feeder (screw feeder) 1 to a mixer 2 where it is mixed with a nitriding gas (nitrogen gas) to a nozzle 3 (ring nozzle shown in FIG. 1). It was introduced, merged with another nitriding gas (nitrogen gas) ejected from the slit 18 and injected into the nitriding furnace. At that time, the width of the slit 18 is adjusted to adjust the gas amount of the nitriding gas and its injection pressure, and the output of the resistance heating source 4 installed at the lower part of the nozzle is adjusted to adjust the temperature of the passing zone of the metal aluminum powder. Adjusted. A feed pipe 5 is provided at the center of the resistance heating source 4, and the metal aluminum powder dispersed by the ring nozzle is injected into the reaction pipe 6 through a predetermined temperature and a predetermined flow rate.

Examples 1-9
A metal aluminum powder having a purity of 99.97% by mass was nitrided under the conditions shown in Table 1 to produce a product powder containing aluminum nitride powder, which was hydrophobized. The diameter of the feed tube used in each example is 8 mm in Examples 1 to 6 and 9, 5 mm in Example 7, and 4.3 mm in the Example. Moreover, the temperature of the passage zone of metal aluminum powder is 400 degreeC in Example 9, and 25 degreeC other than that.

  The addition of the hydrophobizing agent was carried out by preparing a solution in which 350 g of the hydrophobizing agent shown in Table 1 was mixed per 1000 ml of ethanol, and that the passing amount of the resulting powder containing the aluminum nitride powder was known. It carried out by spraying continuously so that it might become a mass part shown by Table 1 per 100 mass parts of powder.

  When the content of the aluminum nitride powder in the resulting powder containing the aluminum nitride powder was determined by X-ray diffraction analysis and elemental analysis, it was almost 100% by mass in any of the examples. Further, the recovery rate from the collection device (bag filter) was 90% by mass or more in terms of metal aluminum, and the remainder was recovered from the furnace bottom.

  The water resistance of the hydrophobized aluminum nitride powder was measured. The water resistance is measured by measuring the mass after holding the weighed sample in a constant temperature and humidity chamber with a temperature of 60 ° C. and a humidity of 90% RH, and calculating the percentage of the increase in mass relative to the sample mass before the test. It was. Separately, nonuniform strain was measured by the Rietveld method for the aluminum nitride powder produced under the same conditions as in the Examples except that the hydrophobic treatment was not performed. The results are shown in Table 1.

Comparative Examples 1-3
A powder containing aluminum nitride powder was produced under the same conditions as in Example 1, 5 or 9 except that the hydrophobic treatment was not performed, and the water resistance was tested.

  From Table 1, according to the Example of this invention, the aluminum nitride powder excellent in water resistance was able to be manufactured on an industrial scale. Moreover, the obtained aluminum nitride powder had a non-uniform strain measured by the Rietveld method of 0.055% or less, and had high homogeneity.

  The aluminum nitride powder produced by the present invention can be used as a filler for a resin or the like, or a raw material for sintering an aluminum nitride sintered body.

Explanatory drawing showing an example of a ring nozzle Explanatory drawing which shows an example of the manufacturing apparatus of aluminum nitride powder

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal aluminum powder feeder 2 Mixer 3 Nozzle 4 Resistance heating source 5 Feed tube 6 Reaction tube 7 High frequency induction heating source 8 Heating element 9 Heat insulator 10 Quartz outer wall 11 Collection device 12 Blower 13 Temperature sensor 14 Supply of nozzle Pipe 15 Nozzle discharge pipe 16 Nitride gas chamber 17 Pressure gauge 18 Slit 19 Hydrophobic treatment agent addition device

Claims (2)

The metal aluminum powder is entrained in a nitriding gas and injected into a nitriding furnace for nitriding, and the resulting powder containing the aluminum nitride powder is introduced into the exhaust gas while being entrained in the exhaust gas. Oite the production of aluminum nitride powder to collect, the metallic aluminum powder having an average particle diameter of 10 to 40 [mu] m, the gas flow rate is accompanied by a rate of nitriding gas 1 Nm ³ per 1~3kg of 50 to 100 m / s, it Is sprayed from a nozzle into a nitriding furnace maintained at 1900-2200 ° C. under a spraying pressure of 0.2-0.6 MPa, and the generated powder is silane coupled between the lower part of the nitriding furnace and the collector. agent or wherein the hydrophobic treatment with silicate treatment agent, nitride irregular distortion measured by the Rietveld method is not more than 0.055% Arumini Manufacturing method of the non-powder. The method for producing an aluminum nitride powder according to claim 1, wherein the hydrophobization treatment is performed at a temperature of 500 to 50 ° C.

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