Preparation method of superfine spherical alumina powder and spherical alumina product thereof

Abstract

The invention provides a preparation method of superfine spherical aluminum oxide powder and a spherical aluminum oxide product thereof, and the preparation method comprises the following steps: taking superfine aluminum oxide powder, and adding the superfine aluminum oxide powder into a pre-heated dispersion machine bin; uniformly spraying a modifier on the superfine aluminum oxide powder, and stirring and dispersing to obtain an intermediate material; and melting and spheroidizing the intermediate material to obtain the superfine spherical aluminum oxide powder. According to the preparation method, the modifier is added and is stirred and dispersed under the preheating condition, so that the effect of effectively improving the dispersity of the superfine aluminum oxide powder is achieved, agglomeration is reduced, and a spherical aluminum oxide product which is small in particle size, narrow in particle size distribution and high in spheroidization rate is obtained in the melting spheroidization stage.

Description

Technical Field

[0001] The invention belongs to the technical field of alumina material preparation, and in particular relates to a method for preparing ultrafine spherical alumina powder and a spherical alumina product thereof. Background Art

[0002] With the rapid development of modern chip technology, electricity and 5G communication network technology, as well as the integration and miniaturization of electronic products, the functions required by electronic products are increasing, and the assembly density and integration of their components are getting higher and higher, making the power higher and higher. The higher the power, the more heat is generated per unit area, which will affect the service life and reliability of electronic components. Therefore, higher requirements are put forward for insulating thermal conductive materials, and spherical thermal conductive and insulating materials are developed. The spherical shape can reduce viscosity and increase filling rate, and the addition of spherical materials can improve the heat dissipation and low dielectric properties of the materials.

[0003] Thermal conductive fillers are usually prepared by compounding a variety of spherical material products with different particle sizes, among which ultrafine spherical alumina products are one of the ideal raw materials for thermal conductive fillers. When preparing spherical alumina products, the smaller the particle size of the raw alumina powder, the easier it is to agglomerate, and the worse the fluffiness and fluidity; in the melting spheroidization stage, even with the action of external dispersion gas, it is difficult to achieve complete dispersion, which easily causes the spherical alumina powder to stick and agglomerate, resulting in poor spheroidization, a sharp increase in particle size, and a widening of the particle size range, which in turn affects the application performance of the product. Summary of the invention

[0004] In view of the defects of the above-mentioned prior art, the purpose of the present invention is to provide a method for preparing ultrafine spherical alumina powder and a spherical alumina product thereof. The preparation method effectively improves the dispersion of ultrafine alumina powder and reduces agglomeration by adding a modifier and stirring and dispersing under preheating conditions, thereby ensuring that a spherical alumina product with small particle size, narrow particle size distribution range and high spheroidization rate is obtained in the melt spheroidization stage.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A method for preparing ultrafine spherical alumina powder comprises the following steps:

[0007] S1, take ultrafine alumina powder and add it into the preheated disperser silo;

[0008] S2, uniformly spraying a modifier onto the ultrafine alumina powder, stirring and dispersing the powder, and obtaining an intermediate material;

[0009] S3, melting and spheroidizing the intermediate material to obtain ultrafine spherical alumina powder.

[0010] In one embodiment of the present application, one or more of the following are also included:

[0011] The ultrafine alumina powder is α-alumina or γ-alumina;

[0012] The particle size D50 of the ultrafine alumina powder is 0.5-10 μm;

[0013] The Si content of the ultrafine alumina powder is less than 500 ppm;

[0014] The preheating temperature is 50-90°C.

[0015] In one embodiment of the present application, the ultrafine alumina powder is α-alumina;

[0016] The preheating temperature is 60-80°C.

[0017] In one embodiment of the present application, one or more of the following are also included:

[0018] The modifier is silicone oil, silane or siloxane organic solvent;

[0019] The viscosity of the modifier is 10-200 mpa.s;

[0020] The amount of the modifier added is 0.03-0.2% of the mass of the ultrafine alumina powder.

[0021] In one embodiment of the present application, the modifier is a hydrogen- or hydroxyl-terminated silicone oil, silane or siloxane organic solvent;

[0022] The viscosity of the modifier is 15-60 mpa.s.

[0023] In one embodiment of the present application, in step S2, the stirring frequency is 15-30 Hz, and the stirring time is 15-60 min.

[0024] In one embodiment of the present application, in step S2, the stirring frequency is 18-25 Hz, and the stirring time is 20-40 min.

[0025] In one embodiment of the present application, the dispersion degree of the intermediate material is ≥100.

[0026] A spherical alumina product obtained by any of the above methods for preparing ultrafine spherical alumina powder.

[0027] In one embodiment of the present application, the spherical alumina product is a powder product with a particle size D50 of 0.5-12 μm and a spheroidization rate of ≥95%.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The method for preparing ultrafine spherical alumina powder of the present invention can effectively improve the dispersion of ultrafine alumina powder raw materials by adding a modifier and stirring and dispersing under preheating conditions, reduce agglomeration, and further ensure that spherical alumina products with small particle size, narrow particle size distribution range and high spheroidization rate are obtained by melt spheroidization. The preparation method has simple process and is easy to operate and control.

[0030] The modifier in the preparation method of the present application should be a hydrogen- or hydroxyl-terminated silicone oil, silane or siloxane organic solvent, which can ensure the acquisition of an intermediate material with high dispersion and a spherical alumina product with high spheroidization. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 This is the SEM image of the ultrafine spherical alumina powder product prepared in Example 1.

[0033] Figure 2 This is the SEM image of the ultrafine spherical alumina powder product prepared in Example 4.

[0034] Figure 3 This is the SEM image of the ultrafine spherical alumina powder product prepared in Comparative Example 3.

[0035] Figure 4 This is the particle size distribution diagram of the ultrafine spherical alumina powder products prepared in Example 1, Example 3, Example 5 and Comparative Example 3. DETAILED DESCRIPTION

[0036] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0037] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0038] The embodiment of the present invention provides a method for preparing ultrafine spherical alumina powder and a spherical alumina product thereof, the preparation method comprising the following steps:

[0039] S1, take the ultrafine alumina powder raw material and add it into the preheated disperser silo.

[0040] The ultrafine alumina powder may be α-alumina or γ-alumina.

[0041] Preferably, the ultrafine alumina powder is α-alumina, with a particle size D50 of 0.5-10 μm, and preferably the Si content of the ultrafine alumina powder is less than 500 ppm. Since the modifier used subsequently contains silicon, the content of silicon in the raw material is controlled within this range in combination with the addition ratio of the modifier, which can effectively ensure that the Si impurities in the final spherical alumina product do not exceed the standard.

[0042] The preheating temperature of the silo is controlled at 50-90° C., and more preferably, the preheating temperature is controlled at 60-80° C. The silo can be preheated and heated and kept warm by electric heating, water boiling heating, or oil bath heating.

[0043] S2, spraying a certain amount of modifier evenly onto the ultrafine alumina powder in the disperser silo, maintaining the temperature, and stirring at the same time to fully disperse and mix the powder to obtain an intermediate material treated with the modifier.

[0044] The modifier is preferably silicone oil, silane or siloxane organic solvent, and the viscosity of the modifier is selected in the range of 10-200 mPa.s. The amount of the modifier added (by weight) is controlled in the range of 0.03-0.2% of the mass of the ultrafine alumina powder raw material.

[0045] It is further preferred that the modifier is a hydrogen or hydroxyl terminated silicone oil, silane or siloxane organic solvent, and the viscosity of the modifier is selected to be in the range of 15 to 60 mpa.s. The viscosity of the modifier will affect the dispersion of the intermediate material. Selecting a viscous agent with a viscosity in the range of 15 to 60 mpa.s can ensure that the intermediate material with a good dispersion effect is obtained.

[0046] By adopting high-speed stirring, controlling the stirring frequency within the range of 15-30 Hz, and controlling the continuous stirring time after adding the modifier to be more than 15 minutes, preferably within the range of 15-60 minutes, the modifier can fully modify the ultrafine alumina powder to obtain an intermediate material with high dispersion. The dispersion of the intermediate material is above 100. The dispersion is calculated by the formula "dispersion = fluffiness / fluidity*1000", in which the fluffiness is characterized by the bulk density test value, and the fluidity is characterized by the cosine function value of the repose angle.

[0047] Further preferably, the stirring frequency is controlled within the range of 18 to 25 Hz, and the stirring time after adding the modifier is continued within the range of 20 to 40 minutes, so that an intermediate material with sufficient modification and high dispersion can be obtained.

[0048] S3, melt spheroidizing the intermediate material to obtain an ultrafine spherical alumina powder product. The melt spheroidizing is flame melt spheroidizing in a conventional spheroidizing furnace.

[0049] See also Figure 1 and Figure 2 As shown in the figure, the ultrafine spherical alumina powder product is a spherical alumina product, which is in powder form, small in particle size, high in sphericity, and its particle size D50 is in the range of 0.5~12μm, and the spheroidization rate is ≥95%. It has excellent thermal conductivity and insulation when used as a filling material for electronic components, and can effectively improve the filling rate, heat dissipation, and reduce dielectric properties.

[0050] The following is a more specific example.

[0051] Example 1

[0052] Ultrafine alumina powder with a particle size D50 of 0.5 μm and a Si content of less than 500 ppm is used as raw material and added into a disperser silo preheated to 70°C.

[0053] 0.2% (calculated by weight of ultrafine alumina powder) of modifier A was evenly sprayed on the ultrafine alumina powder in the disperser silo, the temperature was maintained at about 70°C, and then the stirring was continued for 35 minutes at a stirring frequency of 20 Hz to obtain the intermediate material treated with the modifier, and the dispersion of the intermediate product was tested by sampling. The test results are shown in Table 1. The modifier A is a hydrogen-terminated silicone oil with a viscosity of 15-20 mPa.s.

[0054] The obtained intermediate product is subjected to a melt spheroidization treatment to obtain an ultrafine spherical alumina powder product.

[0055] Example 2

[0056] It is basically the same as Example 1, except that the modifier used is modifier B, which is hydroxyl-terminated siloxane.

[0057] Example 3

[0058] Compared with Example 1, the differences are that the particle size D50 of the ultrafine alumina powder raw material is 4.6 μm; the spraying addition ratio of the modifier A is 0.03% (calculated by the weight of the ultrafine alumina powder); and the stirring duration is 20 minutes.

[0059] Example 4

[0060] Compared with Example 2, the differences are that the particle size D50 of the ultrafine alumina powder raw material is 4.6 μm; the spraying addition ratio of the modifier B is 0.03% (calculated by the weight of the ultrafine alumina powder); and the stirring duration is 20 minutes.

[0061] Example 5

[0062] Compared with Example 1, the differences are that the particle size D50 of the ultrafine alumina powder raw material is 9.8 μm; the spraying addition ratio of the modifier A is 0.03% (calculated by the weight of the ultrafine alumina powder); and the stirring duration is 20 minutes.

[0063] Comparative Example 1

[0064] It is basically the same as Example 1, except that the modifier used is modifier C, which is amino-terminated silane.

[0065] Comparative Example 2

[0066] Compared with Example 1 and Example 2, no modifier was added by spraying, and the raw materials and other operations were the same as those in Example 1.

[0067] Comparative Example 3

[0068] Compared with Example 3 and Example 4, no modifier was added by spraying, and the raw materials and other operations were the same as those of Example 3 and Example 4.

[0069] Comparative Example 4

[0070] Compared with Example 5, no modifier was added by spraying, and the raw materials and other operations were the same as those in Example 5.

[0071] Comparative Example 5

[0072] Compared with Example 5, the only difference is that the preheating and insulation temperatures during the modification treatment are different. This comparative example 5 performs high-speed stirring treatment at room temperature (about 25°C).

[0073] Comparative Example 6

[0074] Compared with Example 5, the only difference is the stirring frequency. In this comparative example 6, the stirring and dispersion treatment is carried out at a low stirring frequency of 10 Hz.

[0075] Result detection and analysis

[0076] The intermediate materials of Examples 1-5 and Comparative Examples 1-6 were collected, and the bulkiness and fluidity of the intermediate materials were measured. The dispersion of the intermediate materials of each Example and Comparative Example was calculated according to the formula "dispersion = bulkiness / fluidity*1000". The obtained dispersion results are shown in Table 1.

[0077] The ultrafine spherical alumina powder products obtained in Examples 1-5 and Comparative Examples 1-6 were collected, and the particle size D50 and spheroidization rate were measured. The measurement results are shown in Table 1.

[0078] Table 1 shows the processing conditions of the embodiments and comparative examples as well as the test data of intermediate materials and products.

[0079] <![CDATA[Raw material particle size D50 (μm) ① > Heating temperature (℃) <![CDATA[Modifier ② > Modifier viscosity (mpa.s) Modifier addition ratio (%) Stirring time (min) Stirring frequency (Hz) Dispersion of intermediate materials <![CDATA[Product particle size D50 (μm) ③ > <![CDATA[Spheroidization rate of the product (%) ④ > Example 1 0.5 70 A 15-20 0.2 35 20 168.2 0.502 96 Example 2 0.5 70 B 15-20 0.2 35 20 142.6 0.56 95 Example 3 4.6 70 A 15-20 0.03 20 20 157.5 5.442 96 Example 4 4.6 70 B 15-20 0.03 20 20 130.0 5.48 95 Example 5 9.8 70 A 15-20 0.03 20 20 102 11.27 96 Comparative Example 1 0.5 70 C 15-20 0.2 35 20 89.6 0.61 93 Comparative Example 2 0.5 70 - - - 35 20 53.1 0.8 90 Comparative Example 3 4.6 70 - - - 20 20 72.2 5.55 91 Comparative Example 4 9.8 70 - - - 20 20 65.4 13.3 90 Comparative Example 5 9.8 25 A 15-20 0.03 20 20 87.3 12.5 92 Comparative Example 6 9.8 70 A 15-20 0.03 20 10 95.1 12.9 93

[0080] Note: ① is the particle size D50 of the ultrafine alumina powder raw material;

[0081] ② Modifier A is hydrogen-terminated silicone oil; Modifier B is hydroxyl-terminated siloxane; Modifier C is amino-terminated siloxane;

[0082] ③ is the particle size D50 of the ultrafine spherical alumina powder product (i.e. spherical alumina product);

[0083] ④ is the spheroidization rate of the ultrafine spherical alumina powder product (also known as spherical alumina product).

[0084] At the same time, the microscopic morphology of the ultrafine spherical alumina powder products of Example 1, Example 4 and Comparative Example 3 was observed using a scanning electron microscope. The scanning electron microscope images of the ultrafine spherical alumina powder products of Example 1, Example 4 and Comparative Example 3 are as follows: Figure 1-3 shown.

[0085] The spherical aluminum oxide powder products obtained in Example 1, Example 3, Example 5 and Comparative Example 3 were tested by a laser particle size analyzer. The test results are as follows: Figure 4 As shown. Figure 4 It can be seen that the particle size distribution diagrams of the spherical alumina powder products of Example 1, Example 3, Example 5 and Comparative Example 3 all have only one maximum peak, wherein the particle size distribution peaks of Example 1, Example 3 and Example 5 are narrower and higher than those of Comparative Example 3, and it can be clearly seen that the particle size distribution range of Example 3 is significantly smaller than that of Comparative Example 3, especially when compared with Comparative Example 3. This indicates that the preparation method of the present application can obtain an ultrafine spherical alumina powder product with a narrower particle size distribution range.

[0086] From Table 1 and Figure 1-3 It can be seen that the intermediate materials obtained in Examples 1-5 have good dispersion, all above 100, and even above 160 (the dispersion of the intermediate materials in Example 1 is 168.2); the obtained ultrafine spherical alumina powder products (i.e., spherical alumina products) have a spheroidization rate of more than 95%, and a particle size D50 in the range of 0.5-12 μm. This indicates that the preparation method and control and adjustment of the present application can ensure the acquisition of spherical alumina products with small particle size and high spheroidization rate (≥95%).

[0087] Comparative Example 1 is compared with Example 1 and Example 2, indicating that the specific type of modifier has a greater impact on the dispersion of the intermediate material when other conditions remain unchanged. The improvement of the dispersion of the intermediate material (89.6) using amino-terminated siloxane (C) as a modifier is significantly lower than that using hydrogen-terminated silicone oil (A) and hydroxy-terminated siloxane (B) as modifiers. Using hydrogen-terminated silicone oil (A) and hydroxy-terminated siloxane (B) as modifiers can obtain intermediate materials with excellent dispersion (168.2 and 142.6), and then obtain spherical alumina products with high spheroidization rates (96% and 95%), and the particle size D50 of the spherical alumina product obtained is less increased than the particle size D50 of the raw material ultrafine spheroidization rate powder.

[0088] Comparing Comparative Example 2 with Example 1, Example 2, and Comparative Example 1, comparing Comparative Example 3 with Example 3 and Example 4, and comparing Comparative Example 4 with Example 5, it can be seen that the dispersion of the intermediate materials obtained by only stirring without adding a modifier is low, which makes the particle size D50 of the spherical alumina product increase more than the particle size of the raw material (0.5μm increases to 0.8μm, 4.6μm increases to 5.55μm, 9.8μm increases to 13.3μm), and the spheroidization rate of the spherical alumina product is low (90%, 91%, 90%), which is not conducive to obtaining spherical alumina products with small particle size and high spheroidization rate suitable for thermal conductive fillers.

[0089] Comparing Comparative Example 5 with Example 5, it can be seen that when adding a modifier and performing high-speed stirring treatment, treatment under heating conditions (70°C) is more conducive to improving the dispersion degree (87.3, 102) of the intermediate material and the spheroidization rate (92%, 96%) of the spherical alumina product than treatment under normal temperature conditions.

[0090] Comparing Comparative Example 6 with Example 5, it can be seen that when the modifier is added under heating conditions for stirring, the stirring frequency has a significant effect on the dispersion of the intermediate material and the particle size and spheroidization rate of the spherical alumina product. The use of a low stirring frequency (10 Hz) for stirring is not conducive to improving the dispersion of the intermediate material, and is not conducive to obtaining spherical alumina products with small particle size and high spheroidization rate.

[0091] In summary, the method for preparing ultrafine spherical alumina powder of the present invention can effectively improve the dispersion of ultrafine alumina powder raw materials and reduce agglomeration by adding a specific modifier and subjecting the raw materials to high-speed stirring and dispersion treatment under heating conditions, so that the spherical alumina products with small particle size, narrow particle size distribution range and high spheroidization rate are obtained by melt spheroidization, which are suitable for thermal conductive fillers of high-power electronic components. The preparation method has simple process, and is easy to operate and control.

Claims

1. A method for preparing ultrafine spherical alumina powder, characterized in that: The following steps are involved: S1, take ultrafine alumina powder and add it into the preheated disperser silo; S2, uniformly spraying a modifier onto the ultrafine alumina powder, stirring and dispersing the powder, and obtaining an intermediate material; S3, melting and spheroidizing the intermediate material to obtain ultrafine spherical alumina powder.

2. The method for preparing ultrafine spherical alumina powder according to claim 1, characterized in that: Also include one or more of the following: The ultrafine alumina powder is α-alumina or γ-alumina; The particle size D50 of the ultrafine alumina powder is 0.5-10 μm; The Si content of the ultrafine alumina powder is less than 500 ppm; The preheating temperature is 50-90°C.

3. The method for preparing ultrafine spherical alumina powder according to claim 2, characterized in that: The ultrafine alumina powder is α-alumina; The preheating temperature is 60-80°C.

4. The method for preparing ultrafine spherical alumina powder according to claim 1, characterized in that: Also include one or more of the following: The modifier is silicone oil, silane or siloxane organic solvent; The viscosity of the modifier is 10-200 mpa.s; The amount of the modifier added is 0.03-0.2% of the mass of the ultrafine alumina powder.

5. The method for preparing ultrafine spherical alumina powder according to claim 4, characterized in that: The modifier is a hydrogen- or hydroxyl-terminated silicone oil, silane or siloxane organic solvent; The viscosity of the modifier is 15-60 mpa.s.

6. The method for preparing ultrafine spherical alumina powder according to claim 1, characterized in that: In step S2, the stirring frequency is 15-30 Hz, and the stirring time is 15-60 min.

7. The method for preparing ultrafine spherical alumina powder according to claim 6, characterized in that: In step S2, the stirring frequency is 18-25 Hz, and the stirring time is 20-40 min.

8. The method for preparing ultrafine spherical alumina powder according to claim 1, characterized in that: The dispersion degree of the intermediate material is ≥100.

9. A spherical alumina product obtained by the method for preparing ultrafine spherical alumina powder according to any one of claims 1 to 8.

10. The spherical alumina product according to claim 9, characterized in that: The spherical alumina product is a powder product with a particle size D50 of 0.5-12 μm and a spheroidization rate of ≥95%.

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