JPH0571526B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for coating the surface of aluminum nitride (hereinafter referred to as "direct nitrided AlN") powder produced by a direct nitriding method, and in particular, the present invention relates to a method for coating the surface of aluminum nitride (hereinafter referred to as "direct nitrided AlN") powder. This invention relates to a method for directly coating the surface of nitrided AlN powder, which enables the easy and efficient formation of a high-performance polyamide resin film with high adhesion and adhesion to improve the stability of the powder. [Prior Art and 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, which resulted in a drawback of 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). ). However, the AlN powder disclosed in JP-A No. 62-207770 has a coating with poor heat resistance (cannot withstand temperatures of 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. There were other drawbacks. By solving the above conventional problems, we have formed a water-resistant protective coating on AlN powder that has excellent heat resistance, high mechanical strength, and outstanding durability, making it possible to process and mold AlN powder in aqueous systems. Also, high-performance AlN
As a surface-coated AlN powder and its manufacturing method that can produce a sintered body at low cost,
The applicant has developed AlN powder whose particle surface is coated with polyamide resin, and in producing such AlN powder, a dibasic acid or its We discovered a method for producing a polyamide resin coating through a polycondensation reaction between derivatives and diamines or diamine derivatives, and filed a patent application earlier (Japanese Patent Application No. 1983-
No. 221871. Hereinafter referred to as "prior application". ). [Problems to be Solved by the Invention] According to the method of the earlier application, it is possible to easily and efficiently produce AlN powder on which a high-performance polyamide resin coating is formed. The surface-coated AlN powder manufactured by is a polyamide resin coating formed on the surface of AlN powder particles via a hydrophobic treatment agent layer such as a coupling agent layer, and the surface coating may vary depending on manufacturing conditions, etc. However, rather than AlN powder having a polyamide resin coating formed directly on the coupling agent layer, there is a possibility that residual monomers and organic solvents may be present between the coupling agent layer formed on the surface of the AlN powder particles during coating formation. The resulting AlN powder contains a liquid phase and has a polyamide resin coating formed thereon. That is, the method of the prior application is a so-called liquid-liquid polymerization in which, for example, a dibasic acid or its derivative and a diamine or a diamine derivative are reacted in a liquid phase on the surface of the AlN powder. Residual monomers and liquid phases of organic solvents are likely to be included in the coating. Therefore, the surface coating obtained by the method of the earlier application
AlN powder has the following problems. The press pressure during molding causes the coating to break and the internal liquid phase leaks out. For this reason, press shrinkage and firing shrinkage are large.
Formability and sinterability are impaired, and product defects are likely to occur. In addition, the mold is contaminated by the leached liquid phase, requiring cleaning of the mold, which reduces productivity. Since the formed film itself is relatively thick and contains a liquid phase, the ratio of organic matter in the film and liquid phase to the surface-coated AlN powder is extremely high, for example, about 20%. . For this reason, the amount of chemicals used is large and the cost of raw materials increases, and the inherent properties of the AlN powder may be impaired due to the thick coating and liquid phase coating layer. The present invention solves the problems of the above-mentioned prior application, and in particular does not include a liquid phase directly on the surface of the nitrided AlN powder.
Easily and efficiently deposit relatively thin polyamide coatings.
Direct nitriding allows formation with high productivity
The purpose of this paper is to provide a method for surface coating AlN powder. [Means for solving the problem] The method for surface coating direct nitrided AlN powder of the present invention includes:
When coating the surface of AlN powder produced by direct nitriding with a polyamide resin film, AlN
After oxidizing the powder, the oxidized AlN
A polyamide resin is produced by coating the surface of powder particles with a dibasic acid or its derivative, dispersing the coated AlN powder in a solution of diamine or diamine derivative, and causing a polymerization reaction on the particle surface of the AlN powder. It is characterized by producing a film. The present invention will be explained in detail below. In the method of the present invention, first, direct nitriding is performed.
Oxidation treatment of AlN powder. The oxidation treatment can be easily performed by directly heating the nitrided AlN powder in an oxygen-containing gas atmosphere such as air. The heating conditions for oxidation treatment vary depending on the subsequent coating treatment conditions, etc., but generally 150 to 250
Preferably, the heating time is 10 to 60 minutes at ℃. Next, the surface of the oxidized AlN powder particles is coated with a dibasic acid or its derivative. in particular,
AlN powder and a solution of a dibasic acid or a derivative thereof to which a coupling agent has been added are added and mixed, and the resulting mixed slurry is evaporated and removed by a method such as rapid heat drying. In the present invention, specific coupling agents include KBM1003 (manufactured by Shin-Etsu Chemical Co., Ltd., vinyltrimethoxysilane) and KR44 (manufactured by Ajinomoto Co., Ltd., isopropyl tri(N-aminoethyl-aminoethyl) titanate). , AL-M (manufactured by Ajinomoto Co., Ltd., acetalkoxyaluminum diisopropylate), etc. can be used. Note that when a titanate-based or aluminum-based coupling agent is used, the thermal conductivity of the AlN sintered body becomes higher than when a silane-based coupling agent is used. In addition, as dibasic acids or derivatives thereof, 1,
8-octanedicarboxylic acid, 1,4-butanedicarboxylic acid, 1,7-heptanedicarboxylic acid, 1,5-pentanedicarboxylic acid, 1,6-hexanedicarboxylic acid and chlorides thereof, etc. can be used. Solvents for dissolving such dibasic acids or derivatives thereof include cyclohexane, ethyl alcohol, acetone, hexane, methyl alcohol,
Examples include one or more organic solvents such as chloroform. The amount of coupling agent used is preferably about 1.0 to 4.0 ml per 100 g of AlN powder. In addition, the concentration of the dibasic acid or its derivative solution and the proportion of AlN powder added and mixed with the solution vary depending on the amount of coating of the surface-coated AlN powder to be manufactured, but in the normal case, 0.1 ~40~ for 100ml of solution of ~0.3mol/dibasic acid or its derivative
Preferably, 60 g of AlN powder is mixed. In addition, in the present invention, coating treatment with a dibasic acid or its derivative can also be performed without using a coupling agent. However, since the surface of AlN powder is hydrophilic, it has poor wettability with solutions of dibasic acids or its derivatives during coating treatment, and the dispersibility of AlN powder is poor, resulting in non-uniform coatings. It's easy to become a thing. Therefore, it is preferable to use a coupling agent in the present invention. The AlN powder coated in this way is
Next, a polyamide resin coating is produced by dispersing the AlN powder in a solution of diamine or diamine derivative and causing a polymerization reaction on the surface of the AlN powder particles. Specifically, the coated AlN powder is dispersed in water to which a surfactant has been added to form a slurry, and a solution of diamine or diamine derivative is added to this slurry and mixed and stirred. Examples of surfactants include nonionic surfactants with high HLB values, such as polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene derivatives, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene fatty acid ester, etc. can be used. In addition, as diamine or diamine derivative,
1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine and derivatives thereof etc. can be used. Water is an example of a solvent for dissolving such diamines or diamine derivatives. The amount of surfactant used is preferably about 5 to 10 ml per 100 g of AlN powder. In addition, the concentration of the diamine or diamine derivative solution and the proportion of AlN powder added and mixed with the solution should be set to a level sufficient to cause a polymerization reaction with the dibasic acid or its derivative attached to the surface of the AlN powder particles. It is sufficient that the amount of diamine or diamine derivative is added, and it varies depending on the amount of coating of the surface-coated AlN powder to be produced, but in normal cases, about 0.02 to 0.05 mol/of diamine or diamine derivative is added. Preferably, 50 to 100 g of coated AlN powder is mixed per 100 ml of solution. In this way, by dispersing AlN powder coated with a coupling agent and a dibasic acid or its derivative in a solution of diamine or diamine derivative, the dibasic acid or its derivative and diamine or The diamine derivative undergoes a polycondensation reaction to produce a polyamide resin coating. After the reaction is completed, the solvent such as water is evaporated by drying the slurry under rapid heat to obtain a surface-coated AlN powder on which a polyamide resin film is formed. The surface-coated AlN powder obtained in this way is
This is an AlN powder in which a polyamide resin coating is formed with good adhesion on the surface of AlN powder particles having a coupling agent attached to at least a portion of the surface thereof, with almost no liquid phase included. In addition, when producing AlN powder to be used as a molding or firing material, the method of the present invention can be applied to AlN powder mixed with a predetermined amount of a sintering aid such as Y ₂ O ₃ powder in advance. Needless to say, it can be done. [Function] Unlike the liquid-liquid polymerization of the previous application, the method of the present invention allows the dibasic acid or its derivative on the surface of the AlN powder particles to react with the diamine or diamine derivative in the solution, so to speak. - By forming a polyamide resin film by liquid polymerization, it is possible to obtain a surface-coated AlN powder that does not contain liquid phases such as unreacted monomers and solvents within the film. For this reason, the amount of organic matter in the coating is significantly reduced to approximately 5% compared to the surface-coated AlN powder, and a coating with excellent water resistance, heat resistance, and extremely high mechanical strength can be created without impairing the original properties of AlN powder. It is possible to form a film with good adhesion, a thin and uniform thickness, and to cover almost every single particle. In addition, the amount of coating formed on the surface of AlN powder particles depends on the amount of attached dibasic acid or its derivative, and
It can be easily adjusted by adjusting the amount of diamine or diamine derivative used. By the way, commonly available AlN powder includes:
AlN powder produced by the reductive nitriding method, that is, AlN powder produced by reducing Al ₂ O ₃ with carbon in an N ₂ atmosphere to produce AlN, and AlN powder produced by directly nitriding Al with nitrogen. There is also direct nitriding AlN powder. Among these, AlN powder produced by the reductive nitriding method is
By directly coating this with a dibasic acid or its derivative and dispersing it in a solution of diamine or diamine derivative, a polyamide resin coating can be formed on the particle surface of AlN powder. In other words, AlN powder produced by the reductive nitriding method has OH groups remaining on the particle surface due to the manufacturing process.
A polyamide resin coating can be formed with good adhesion by using a group or the like. On the other hand, in direct nitriding AlN powder, since Al is directly nitrided, there are no OH groups or O atoms on the particle surface, and the surface polarity is extremely high. Therefore, even if directly nitrided AlN powder is directly coated with a dibasic acid or its derivative and dispersed in a solution of diamine or diamine derivative, a polyamide resin film is formed on the particle surface of AlN powder with good adhesion and uniformity. However, problems such as film peeling occur. In contrast, according to the method of the present invention, prior to the formation of the polyamide resin film, the film is directly nitrided in advance.
Direct nitriding by oxidizing AlN powder
O and/or OH groups are introduced to the particle surface of AlN powder, which improves the adhesion of the polyamide resin coating.
It is possible to form the film with good uniformity. [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. Reagent used: 1,8-octanedicarbonyl 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.) 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 the sintering aid. Direct nitriding AlN powder: "TOYALNITE, F" (Toyo Aluminum
(manufactured by Shin-Etsu Chemical Co., Ltd.) Y ₂ O ₃ (manufactured by Shin-Etsu Chemical Co., Ltd.) Example 1 15 g of direct nitrided AlN powder was spread on a hot plate and oxidized by heating at 200° C. for 15 minutes. Separately, add 25 g of sebacoyl chloride to cyclohexane.
Solution A (0.2 mol/) was prepared by dissolving it in 500 ml. Further, 2.32 g of hexamethylene diamine was dissolved in 500 ml of distilled water to prepare solution B (0.04 mol/). 14.25g of oxidized AlN powder and sintering aid
At the same time, 0.75 g of Y ₂ O ₃ powder was mixed in a ball mill, and at the same time, solution A was added to fix sebacoyl chloride.
23 ml (4.6 x 10 ^-3 mol of sebacoyl chloride), 10 ml of cyclohexane and 150 μ of a coupling agent were added and mixed for 24 hours. The resulting slurry was rapidly dried on a hot plate at 120°C to volatilize the cyclohexane and coated with sebacoyl chloride.
AlN powder was obtained. Next, the obtained AlN powder was dispersed in 100 ml of distilled water to which 1 ml of a surfactant was added to obtain slurry C. Next, in order to polymerize sebacoyl chloride and hexamethine diamine on the surface of the AlN powder, 10 to 20 ml of solution B was added to slurry C and stirred for several minutes. Due to the reaction, a polyamide resin film was formed on the surface of the AlN powder particles, so the resulting surface-coated AlN
In order to separate the powder from water, the reaction solution was rapidly dried on a hot plate at 200°C. The physical properties and characteristics of the obtained surface-coated AlN powder were investigated by the following method, and the results are shown in Table 1. Measurement of organic content Using 1 g of surface-coated AlN powder, 600
Firing was carried out at ℃ for 1 hour, and the organic content was measured from the weight loss on calcination. Formability, physical properties of fired body The surface-coated AlN powder was press-molded at 1000 Kgf/cm ² using molds of 12 mmφ and 30 mmφ, and fired at 1880° C. for 1 hour in a nitrogen atmosphere to obtain a fired body.
The quality of the moldability at this time was evaluated in four stages: ◎, ◯, △, and ×, and various physical properties of the obtained fired body were measured. Thermal conductivity The fired body obtained above was measured using the Laser Flash Thermal Constant Measuring Device (TC-
7000). Electrical Properties The fired body obtained above was measured at 1 MHz using a "4192A Impedance Analyzer" manufactured by YHP (Yokogawa Heuretsu Card). Comparative example 1 Direct nitriding AlN powder 14.25g, sintering aid Y ₂ O ₃ powder
0.75 g and 0.60 g of binder (“G7211” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) were mixed for 24 hours using 30 ml of cyclohexane as a solvent. This was spread on a hot plate and subjected to rapid heat drying treatment at 200°C to obtain a mixed powder. The physical properties and characteristics of the obtained powder were investigated in the same manner as in Example 1, and the results are shown in Table 1. Comparative Example 2 Example 1 except that oxidation treatment was not performed
The physical properties and characteristics of the powder obtained in the same manner as above were similarly investigated, and the results are shown in Table 1. Comparative Example 3 (Method of the prior application) 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 mol/solution. Separately,
2.32 g of hexamethylene diamine was dissolved in 500 ml of distilled water to prepare a 0.04 mol/solution. 14.25 g of directly nitrided AlN powder and 0.75 g of sintering aid Y ₂ O ₃ powder were mixed for 24 hours in 30 ml of acetone with the addition of about 150 μ of a coupling agent for hydrophobic treatment. After mixing, the obtained slurry was rapidly dried at 120° C. using a hot plate, and the obtained dry powder was dispersed in 10 to 20 ml of solution. Next, the dispersion was emulsified in 30 ml of distilled water containing 1 ml of surfactant, and 10 to 20 ml of the solution was added to the emulsion to cause polymerization. Thereafter, a mixed solvent (cyclohexane:chloroform = 3:1 volume ratio) was added to stop the reaction, and drying was performed on a hot plate at about 200°C to obtain a surface-specific AlN powder. The physical properties and characteristics of the obtained powder were investigated in the same manner as in Example 1, and the results are shown in Table 1.

[Table] The following is clear from Table 1. In the powder obtained in Comparative Example 1, the density of the molded body is low, and therefore the strength of the fired body is low. The powder obtained in Comparative Example 2 had poor sinterability;
The porosity and water absorption rate are extremely high. Also, the thermal conductivity is extremely low. This is because the polyamide resin coating on the surface of the AlN powder particles partially peeled off due to the lack of oxidation treatment, and the lack of a good surface coating caused the coating to break and generate boehmite. The powder obtained in Comparative Example 3 has a high organic content because it contains a liquid phase consisting of unreacted monomers and solvent. Therefore, the amount of chemicals used is large, and there is also the problem of reduced productivity due to outflow of the liquid phase during molding. In contrast, the surface-coated AlN powder obtained by the method of the present invention has good moldability and
Molded bodies and fired bodies with low porosity and high strength can be obtained with high productivity. Moreover, since there is no problem of inclusion of liquid phase components, the amount of chemicals used is about 1/4 compared to the method of Comparative Example 3, and the cost of raw materials is also reduced. Examples 2 to 4 Example 1 except that the oxidation treatment time of the direct nitrided AlN powder was set to the time shown in Table 2, the amount of solution A used was changed, and the amount of sebacoil chloride added was set to the amount shown in Table 2. Obtain surface-coated AlN powder in the same manner as
The physical properties and characteristics were similarly investigated. The results are shown in Table 2.

[Table] [Effects of the Invention] As detailed above, according to the method of directly coating the surface of nitrided AlN powder of the present invention, it has excellent water resistance, heat resistance, and mechanical strength, and the AlN powder particles can be coated sufficiently. Easy, low-cost, and efficient direct nitriding of high-performance polyamide resin coating layers that can be protected.
It can be formed on the surface of AlN powder particles. According to the surface-coated AlN powder produced according to the present invention, the protective film is not destroyed in treatment steps such as water-based treatment, heat treatment, and milling treatment.
It is said that it is possible to obtain AlN powder that is prevented from changing to (OH) ₃ , does not generate Al ₂ O ₃ , has high thermal conductivity, and has excellent various properties. Moreover, since the liquid phase of unreacted monomers and solvents is not contained inside the polyamide resin coating, there is no problem of press shrinkage or baking shrinkage due to leaching of the liquid phase during molding and firing, and productivity is improved. Significantly improved.

Claims (1)

[Claims] 1. When coating the surface of AlN powder produced by direct nitriding with a polyamide resin film,
After oxidizing the AlN powder, the oxidized
Coating the surface of AlN powder particles with a dibasic acid or a derivative thereof, dispersing the coated AlN powder in a solution of diamine or diamine derivative,
A method for directly coating the surface of nitrided AlN powder, which is characterized by generating a polyamide resin film by causing a polymerization reaction on the particle surface of AlN powder.