JPH0544402B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a surface-coated aluminum nitride (AlN) powder and a method for producing the same, and particularly relates to a surface-coated aluminum nitride (AlN) powder and a method for producing the same.
This invention relates to AlN powder with a coating formed on its surface in order to improve the stability of the powder against moisture and oxygen, and a method for producing the same. [Prior Art] AlN powder is thermodynamically extremely unstable in the atmosphere, and in particular, its fine powder easily reacts with oxygen and moisture. For example, if AlN powder is kept in an atmosphere of 30° C. and 80% relative humidity for about 40 days, it will change to aluminum hydroxide (Al(OH) ₃ ) such as Bayerite and Boehmite through the reaction shown below. AlN + 3H ₂ O → Al (OH) ₃ + NH ₃ Therefore, when storing AlN powder, it must be completely sealed in a container after drying, or stored under an N ₂ or NH ₃ gas atmosphere, and controlled. is difficult. Even if decomposition into Al(OH) ₃ etc. can be substantially prevented during storage, it is inevitable that decomposed impurities will be generated in the various steps before firing during the production of the sintered body. That is, when a slurry of AlN powder is prepared using water as a medium, some of the Al formed in AlN
(OH) ₃ is mixed in, so when such a slurry is formed and sintered, Al(OH) ₃ is mixed with α-
It changes to alumina (Al ₂ O ₃ ), and the amount of Al ₂ O ₃ in the obtained sintered body increases. Therefore, the properties of the sintered body such as thermal conductivity are significantly impaired. For this reason, in the past, it was not possible to form an aqueous slurry, and molding was performed using an organic solvent and a molding binder, resulting in high processing costs. Therefore, in order to stabilize AlN powder, it has been proposed to form a coating film on the surface of the powder, and recently, after forming a hydrophobic film on the surface of AlN powder,
After forming a hydrophilic film, specifically, the surface of AlN powder is coated with an inorganic or organic surface treatment agent as the first surface treatment to suppress reactivity with water. As a surface treatment, AlN powder has been proposed in which this primary treated powder is treated in a water-based surfactant to improve its dispersibility in water (Japanese Patent Laid-Open No. 62-207770). ). [Problems to be Solved by the Invention] However, the AlN powder disclosed in JP-A-62-207770 has poor heat resistance as a coating (cannot withstand 200°C). Mechanical strength, chemical resistance, and durability of the film are insufficient. , when milling using a mill or spray dryer, the coating is damaged and the AlN
hydration is likely to occur. The present invention solves the above-mentioned conventional problems, forms a water-resistant protective coating on AlN powder that has excellent heat resistance, high mechanical strength, and extremely excellent durability, and processes the AlN powder in an aqueous system. The object of the present invention is to provide a surface-coated AlN powder that can be molded and produce a high-performance AlN sintered body at low cost, and a method for producing the same. [Means for Solving the Problems] The surface-coated AlN powder according to claim 1 is characterized in that the particle surface is coated with a polyamide resin. The method for producing AlN powder according to claim 2 is the method according to claim 1.
In producing the AlN powder, a polyamide resin film is formed on the surface of the hydrophobically treated AlN powder particles by interfacial polymerization. The method for producing AlN powder according to claim 3 is the method according to claim 2.
In carrying out the method described above, AlN powder that has been hydrophobically treated with a coupling agent is dispersed in a solution of a dibasic acid or its derivative, and then diamines or diamine derivatives are added to this AlN powder dispersion liquid to form AlN. It is characterized by producing a polyamide resin coating by causing a polymerization reaction on the surface of powder particles. The present invention will be explained in detail below with reference to the drawings. FIGS. 1 and 2 are schematic cross-sectional views showing an example of the AlN powder of the present invention. As shown in the figure, the surface-coated AlN powder of the present invention has AlN powder particles 2
A polyamide resin coating 4 is preferably formed on the surface of the coupling agent layer 3 via a hydrophobic treatment agent layer such as the coupling agent layer 3. Depending on the manufacturing conditions, etc., the polyamide resin coating 4 is formed directly on the coupling agent layer 3. Powder 1B (Fig. 2) or AlN powder 1A (Fig. 1) on which polyamide resin coating 4 is formed between it and coupling agent layer 3, including residual monomer and organic solvent 5 during coating formation. and so on. In the present invention, there are no particular restrictions on the diameter of the AlN powder particles or the thickness of the coating formed, but generally the diameter is about 0.1 to 10 μm, particularly about 0.5 to 3 μm.
A coupling agent layer of approximately 10 ¹³ to 10 ¹⁵ particles/cm ² and a thickness of 0.01 to 0.2 μm, particularly 0.02 to 0.2 μm, is applied to the AlN powder particles.
It is preferable to use a polyamide resin coating with a thickness of about 0.1 μm. In the present invention, the polyamide resin coating may be formed without forming a coupling agent layer or the like, that is, without subjecting the AlN powder to hydrophobic treatment with a coupling agent or the like. However, since the surface of AlN powder is hydrophilic, when producing a polyamide resin coating by interfacial polymerization as described below, the wettability of AlN powder to a mixed solvent is poor, and the dispersibility of AlN powder is poor. Therefore, the film formed tends to be non-uniform.
Therefore, it is preferable that the AlN powder of the present invention has a polyamide resin coating formed thereon via a hydrophobic layer such as a coupling agent. Next, a method for producing surface-coated AlN powder according to claim 2 will be explained. In the method of claim 2, the AlN powder is first subjected to hydrophobic treatment. Raw material AlN for hydrophobic treatment
An appropriate amount of the powder is taken, a non-aqueous solvent such as acetone is added thereto, and the powder is kneaded. A hydrophobic treatment agent such as a coupling agent is added thereto, the powder is kneaded, dried, and, if necessary, pulverized. In this case, the amount of solvent used for AlN powder is preferably about 100 to 200 ml per 100 g of AlN, and the amount of coupling agent used for AlN powder is preferably about 1.0 to 2.0 ml per 100 g of AlN powder. . In the present invention, the coupling agent specifically includes KBM1003 (manufactured by Shin-Etsu Chemical Co., Ltd., vinyltrimethoxysilane),
KR44 (manufactured by Ajinomoto Co., Inc., isopropyl tri(N-aminoethyl-aminoethyl) titanate), AL-
M (manufactured by Ajinomoto Co., Inc., acetalkoxyaluminum diisopropylate), etc. can be used. After the AlN powder is hydrophobically treated in this manner, a polyamide resin film is formed on the surface of the AlN powder particles by interfacial polymerization. Specifically, a polyamide resin coating is produced by causing the following reactions to occur on the surface of AlN powder particles. In the present invention, the method for forming the polyamide resin film is not limited to the following methods. Polycondensation reaction between diamines or diamine derivatives and dibasic acids or dibasic acid derivatives Reaction between dinitrile or diamide and formamide Polyaddition reaction between diisocyanates and dibasic acids Self-condensation of amino acids or their derivatives Ring-opening polymerization of lactams Next, of the above-mentioned methods, the method according to claim 3 will be explained. In the method of claim 3, the hydrophobically treated
After dispersing AlN powder in a solution of a dibasic acid or its derivative, diamines or diamine derivatives are added to the AlN powder dispersion and a polymerization reaction is caused on the particle surface of the AlN powder. Specifically, the following method is used. First, a dibasic acid such as 1,8-octane dicarbonyl chloride or a derivative thereof is dissolved in an organic solvent such as a mixed solvent of cyclohexane/chloroform = 3:1 (solution) at approximately 0.2 mol. Separately, diamines such as 1,6-diaminohexane or derivatives thereof are dissolved in water (distilled water) at about 0.04 mol/solution (solution). Add the hydrophobically treated AlN powder to the solution and stir to fully disperse it (dispersion). The amount of AlN powder added is 10 per 10 ml of solution.
It is preferable to set it to about 20 g. Next, an aqueous solution of a surfactant (approximately 2 to 10% by volume) is added to this dispersion to emulsify it. In this case, the amount of the surfactant solution is sufficient to cause emulsification, and an emulsion is prepared by appropriately adjusting the amount added. Generally, the amount of surfactant is
Add the surfactant solution to about 2 to 4 ml per 15 g. Next, the solution is added to the emulsion while stirring to cause a polymerization reaction. In this case, the solution contains a diamine such as 1,6-diaminohexane or its derivative in an amount sufficient to cause a polymerization reaction with a dibasic acid such as 1,8-octanedicarbonyl chloride or its derivative in the emulsion. The amount to be added is adjusted accordingly. After forming a polyamide resin film on the surface of AlN powder particles by interfacial polymerization in this way,
Cyclohexane/chloroform = 3:1 (volume ratio)
The reaction is terminated by adding an organic solvent such as a mixed solvent consisting of: In addition, in the above interfacial polymerization method, as the dibasic acid or its derivative, in addition to 1,8-octadicarbonyl chloride, 1,4-butanedicarboxylic acid,
1,7-heptanedicarboxylic acid, 1,5-pentanedicarboxylic acid, 1,6-hexanedicarboxylic acid and chlorides thereof, etc. can be used. In addition to 1,6-diaminohexane, examples of diamines or diamine derivatives include 1,7-diaminoheptane, 1,8-diaminooctane, 1,9
-Diaminononane, 1,10-diaminodecane, ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine and derivatives thereof, etc. can be used. [Function] Polyamide resin forms a coating that is excellent in water resistance and heat resistance, and also has extremely high mechanical strength. In particular, by the method of claim 2, especially claim 3.
By forming a polyamide resin film on the hydrophobically treated AlN powder surface by interfacial polymerization, the film has good adhesion, and the film thickness is thin and uniform, and the particles are small and can be coated almost on a single particle basis. A high-performance AlN powder is obtained. [Examples] The present invention will be described in more detail with reference to Examples and Comparative Examples below, but the present invention is not limited to the following Examples unless it exceeds the gist thereof. In addition, in the following examples and comparative examples, the reagents used are as follows. Reagents used 1,8-octane dicarbonyl chloride: Sebacoyl chloride (manufactured by Wako Pure Chemical Industries, Ltd.) ClCO (CH ₂ ) ₈ COCl=239.1 1,6-diaminohexane (hexamethylene diamine) (manufactured by Wako Pure Chemical Industries, Ltd.) ) NH ₂ (CH ₂ ) ₆ NH ₂ = 116.21 Chloroform (manufactured by Wako Pure Chemical Industries, Ltd.) CHCl ₃ = 119 Cyclohexane (manufactured by Wako Pure Chemical Industries, Ltd.) C ₆ H ₁₂ = 84.2 Surfactant Emulgen A-60 ( (Manufactured by Kao Corporation) (Polyoxyethylene derivative, HLB = 12.8) Coupling agent KBM1003 (Manufactured by Shin-Etsu Chemical Co., Ltd.) CH ₂ CHSi (OCH ₃ ) ₃ = 148.2 In addition, as the raw material AlN powder, the following The following was used as a sintering aid. TOYALNITE, F (manufactured by Toyo Aluminum Co., Ltd.) High purity aluminum nitride, F (manufactured by Tokuyama Soda Co., Ltd.) Y ₂ O ₃ (manufactured by Shin-Etsu Chemical Co., Ltd.) Example 1, Comparative Example 1 Hydrophobicity of AlN powder Treatment Add 50 ml of acetone to 25 g of AlN powder (manufactured by Tokuyama Soda Co., Ltd., high-purity aluminum nitride, F), mix in a glass mortar, and then 0.25 ml of coupling agent.
(1.0% (volume - solvent/weight - AlN)),
The mixture was kneaded for an additional 5 minutes, dried for 10 minutes, and then ground. Formation of polyamide film 25 g of sebacoyl chloride was dissolved in 500 ml of a mixed solvent of cyclohexane/chloroform = 3:1 (volume ratio) to prepare a 0.2 M solution (solution). Separately, 2.32 g of 1,6-diaminohexane was dissolved in 500 ml of distilled water to prepare a 0.04 M solution (solution). 15 g of AlN powder that had been hydrophobically treated by the above method (Example 1) and AlN powder that had not been hydrophobically treated (Comparative Example 1) were each added to the solution, stirred well, and sufficiently dispersed (dispersion liquid). . Next, this dispersion liquid was added to the liquid obtained by adding 1.0 ml of surfactant to 50 ml of distilled water and stirring vigorously to emulsify it (emulsified liquid). Next, the solution was added to this emulsion while stirring to cause a polymerization reaction, thereby forming a polyamide resin coating on the surface of the AlN powder. Finally, the mixed solvent was added to terminate the reaction. Confirmation of polyamide resin coating Powder particles were taken out from the slurries obtained in Example 1 and Comparative Example 1, and the state of coating formation was examined using an optical microscope. The respective optical micrographs are shown in Figures 3 a to c (Example 1) and Figures 4 a to c.
(Comparative Example 1). From FIGS. 3a to 3c, it can be seen that the material obtained in Example 1 was formed because the raw material AlN powder was hydrophobically treated to improve its compatibility with the solvent (wettability) and enhance its dispersibility. It was confirmed that the coating was thin and uniform in thickness, and the particle size was small, and that the coating was formed on almost every single particle. On the other hand, as shown in Figures 4a to 4c, in the case of the material obtained in Comparative Example 1, the AlN powder used as the raw material is hydrophilic and poorly compatible with solvents, and the dispersibility is low, so the formed film is also non-uniform. It was also confirmed that there were particles with large particle sizes and that a film was formed on the particle aggregate. Various Performance Tests Drying in the air at 80°C for 24 hours A small amount of the slurry obtained in Example 1 was placed in a beaker and dried in an air bath at 80°C for 24 hours.
The formation status of Al(OH) ₃ was investigated by X-ray diffraction (CuKα, the same applies hereinafter). Furthermore, an aqueous solution of untreated AlN powder was also subjected to the same treatment, and the state of AlN(OH) ₃ formation was examined by X-ray diffraction. The results are shown in Figure 5. As is clear from this result, untreated AlN
In this case, Al(OH) ₃ (Bayerite = BY) was generated, whereas the surface coating obtained in Example 1
No Al(OH) ₃ peak was detected in AlN. Rapid heat drying at 200℃ The slurry obtained in Example 1 was directly heated at 200℃.
It was rapidly dried on a hot plate heated to 0.degree. C., and the formation of Al(OH) ₃ was examined by X-ray diffraction. Furthermore, an aqueous solution of untreated AlN powder was subjected to the same treatment, and the state of Al(OH) ₃ formation was examined by X-ray diffraction. The results are shown in Figure 6. As is clear from this result, untreated AlN
So Al(OH) ₃ (Bayerite=BY, Boehmite=
BO) was generated, whereas no Al(OH) ₃ peak was detected in the surface-coated AlN obtained in Example 1. Milling treatment The surface-coated AlN powder obtained in Example 1 was
After drying under rapid heat at ℃, alumina pot (powder: 50g, water: 50g, 5mmφ cobblestone: 150g)
After milling for 24 hours at
A rapid heat drying process was performed at 200°C, and the formation status of Al(OH) ₃ was investigated by X-ray diffraction. In addition, untreated AlN powder was also subjected to the same treatment, and the generation status of Al(OH) ₃ was examined by X-ray diffraction. The results are shown in FIG. As is clear from this result, untreated AlN
Then, all of AlN is Al(OH) ₃ (Bayerite=BY)
On the other hand, no Al(OH) ₃ peak was detected in the surface-coated AlN obtained in Example 1. Firing: When drying at 200℃, the X-ray peak of aluminum hydroxide with low crystallinity cannot be detected. Therefore, it is calcined at 1850℃ (in a nitrogen atmosphere) and the presence or absence of Al(OH) ₃ is examined based on the state of corundum formation. View. That is, after the slurry obtained in Example 1 was subjected to the above-mentioned rapid heat drying treatment at 200°C,
℃ in a N ₂ atmosphere, the state of corundum formation was examined by X-ray diffraction, and compared with that before firing. The results are shown in FIG. The following is clear from FIG. After firing, AlN has improved crystallinity, so the AlN peak becomes larger, and the broad peak below 2θ = 25 (deg.) (estimated to be polyamide) disappears. Amorphous in AlN before firing
If Al(OH) ₃ were present, an α-Al ₂ O ₃ peak should appear in the fired AlN, but neither corundum nor aluminum hydroxide peaks were detected in the fired AlN. . Therefore, the broad peak of 2θ = 25 (deg.) or less of AlN before firing does not include the peak of amorphous Al(OH) ₃ , and Al(OH) ₃ does not exist. is clear. Comparative Example 2 (Japanese Unexamined Patent Publication No. 62-207770) AlN obtained by hydrophobic treatment in Example 1
The powder was treated with sodium oleate according to the method described in JP-A-62-207770. The obtained AlN powder was placed in an alumina pot (powder: 50g, water: 50g, 5mmφ cobblestone: 150g).
After milling for 72 hours, the same rapid drying treatment at 200°C as in Example 1 was performed, and the formation of Al(OH) ₃ was examined by X-ray diffraction. Further, the surface-coated AlN powder obtained in Example 1 was also subjected to the same treatment, and the generation status of Al(OH) ₃ was examined by X-ray diffraction. The results are shown in Figure 9. From FIG. 9, the AlN powder of Comparative Example 2 has low mechanical strength and the modified coating is destroyed by milling, so that all the AlN is Al(OH) ₃ (Bayerite=BY,
Gibbsite = GI). In contrast, the surface coating obtained in Example 1
Al(OH) ₃ is not generated in AlN, and the present invention
AlN has excellent mechanical strength and extremely high durability. Example 2 TOYALNITE, F contains 5 Y ₂ O ₃ as a sintering aid
% by weight was added, mixed in acetone for 72 hours in a ball mill (alumina pot), and then rapidly dried at 200°C. Using the obtained AlN-Y ₂ O ₃ powder as a raw material, hydrophobic treatment and formation of a polyamide film were performed in the same manner as in Example 1. The obtained surface-coated AlN powder was stirred in water for 1 hour to evaluate water resistance, and then rapidly dried at 200°C. Next, the powder was press-molded using a mold with a diameter of 10 mm and fired at 1850° C. for 2 hours in a nitrogen atmosphere. The thermal conductivity of the obtained sintered body was measured using a "laser flash thermal constant measuring device (TC-3000" manufactured by Shinku Riko Co., Ltd.). The results are shown in Table 1. Example 3 As AlN powder , high purity AlN manufactured by Tokuyama Soda Co., Ltd.
A sintered body was obtained in the same manner as in Example 1 except that F was used, and its thermal conductivity was measured. The results are shown in Table 1. Comparative Example 3 TOYALNITE, F with 5 Y ₂ O ₃ as a sintering aid
% by weight was added, mixed in acetone for 72 hours in a ball mill (alumina pot), and then rapidly dried at 200°C. After adding 4% by weight of a molding binder (in butanol) to the obtained AlN-Y ₂ O ₃ powder, molding and firing were performed in the same manner as in Example 1, and the thermal conductivity of the obtained sintered body was was measured. The results are shown in Table 1. Comparative Example 4 As AlN powder, high purity AlN manufactured by Tokuyama Soda Co., Ltd.
A sintered body was obtained in the same manner as Comparative Example 3 except that F was used, and its thermal conductivity was measured. The results are shown in Table 1.

[Table] As is clear from Table 1, the sintered bodies of Examples 2 and 3 are comparative examples in which the raw material powder was treated in water, but the raw material powder was not treated in water. Higher thermal conductivity was obtained compared to the sintered bodies No. 3 and 4. Comparative Example 5 Using the following raw materials, follow the steps below.
Surface modification of AlN powder was carried out. Note that this method is the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 62-207770. [Raw materials] AlN powder High purity aluminum nitride TYF (Tokuyama soda) Average particle size 1.8μm Sintering aid Y ₂ O ₃ (Shin-Etsu Chemical) Coupling agent KBM 1003 (Shin-Etsu Chemical) Sodium oleate C ₁₇ H ₃₃ COONa Binder for molding Shin-Etsu Poval (Shin-Etsu Chemical) [Procedure] In a nylon pot, 190 g of AlN powder, 9.5 g of Y ₂ O ₃ powder, 380 ml of butanol, coupling agent.
Add 1.9ml and mix on a universal mill stand for one day. The slurry is dried using a hot plate in a fume hood. (Set temperature: 200°C) Transfer the treated powder to an alumina pot, add an aqueous solution of sodium oleate (10 wt%) so that the solid content is 10 g per 100 g of the treated powder, and stir for about 20 minutes. Perform the drying process in the same manner as above. Comparative Example 5 whose surface was modified in this way
Infrared absorption spectra of AlN powder, the AlN powder obtained in Example 1, and untreated AlN powder (Tokuyama Soda TYF used in Comparative Example 5),
The dispersion preference for various solvents and the properties of the sintered body were measured. In addition, electron microscope (SEM) photographs of each of the dried powders and their sintered bodies (1850°C x 2 hours, N ₂ atmosphere) were also taken. (a) SEM photographs of each powder are as shown in Figures 10 a to c. Note that the powder of Example 1 was bonded with polyamide to become secondary particles,
Easily becomes primary particles by milling. (b) The measurement results of dispersion preference are shown in Table 2 below.

[Table] (c) The measurement results of the infrared absorption spectrum are as shown in Figure 10 (KBr tablet method). (d) From the SEM photograph of the sintered body (not shown), Example 1 is a dense sintered body almost equivalent to untreated powder, but Comparative Example 5 is recognized to have significant grain growth. Ta. Note that while the untreated powder was molded using a non-aqueous solvent (butanol), Example 1 and Comparative Example 5 were molded using water. in this way,
Example 1 can be densely sintered without causing a water reaction even when water is used. (e) The properties of the sintered body are shown in Table 3 below.

[Table] As shown in Table 3, the sintered body of the powder of Example 1, together with the sintered body of the untreated powder, has a considerably higher thermal conductivity than the sintered body of the powder of Comparative Example 5. are doing. [Effect of the invention] As detailed above, the surface-coated
The surface coating of AlN powder not only has excellent water resistance, but also remarkable heat resistance and mechanical strength. Therefore, since the AlN powder particles can be sufficiently protected, the AlN powder can be processed and molded in an aqueous system, and also exhibits high durability against heat treatment, milling treatment, etc. Therefore, according to the surface-coated AlN powder of the present invention, the protective film is not destroyed in treatment steps such as aqueous treatment, heat treatment, and milling treatment, so that the AlN powder is treated with AlN during these treatment steps.
It is said that it is possible to obtain an AlN sintered body that is prevented from changing to (OH) ₃ , does not generate Al ₂ O ₃ , has high thermal conductivity, and has excellent various properties. Therefore, the surface-coated surface of the present invention
AlN powder can be efficiently produced by the method of claim 2, particularly by the method of claim 3,
High-performance polyamide resin coating with high adhesion
It is possible to form it on the surface of AlN powder particles.

[Brief explanation of the drawing]

Figures 1 and 2 show the surface coated surface of the present invention.
FIG. 2 is a schematic cross-sectional view showing an example of AlN powder.
FIGS. 3a to 3c and 4a to 4c are optical micrographs showing the particle structure of the AlN powder obtained in Example 1 and Comparative Example 1, respectively. Figure 5, Figure 6, Figure 7
8 and 8 are X-ray diffraction diagrams showing the measurement results in Example 1, respectively. Figure 9 shows comparative example 2.
FIG. 3 is an X-ray diffraction diagram comparing the characteristics of AlN powder and the AlN powder of Example 1. FIG. 10 is an electron micrograph showing the particle structure of AlN powder in a dry state. FIG. 11 is an infrared absorption spectrum of AlN powder. 1A, 1B...Surface coated AlN powder, 2
...AlN powder particles, 3...coupling agent layer,
4...Polyamide resin coating.

Claims (1)

[Claims] 1. Particle surface coated with polyamide resin
AlN powder. 2. The method according to claim 1, wherein a polyamide resin film is formed on the surface of the hydrophobically treated AlN powder particles by an interfacial polymerization method.
Method for producing AlN powder. 3 AlN hydrophobically treated with coupling agent
After the powder is dispersed in a solution of a dibasic acid or its derivative, a diamine or a diamine derivative is added to the AlN powder dispersion, and a polyamide resin coating is generated by polymerizing on the surface of the AlN powder particles. The second claim characterized in that
The method for producing AlN powder described in section.