Method for preparing aluminum hydroxide micropowder

Abstract

The invention relates to a method for preparing aluminum hydroxide micro powder. The method comprises the technological processes of raw material slurry preparation, clinker sintering, clinker dissolution, red mud washing and separation, crude liquid desilicication, sodium aluminate solution refined filtration, seed crystal decomposition, aluminum hydroxide separation and impurity removal. The crude liquid desilicication process comprises pre-desilicication, autoclaving desilicication and normal-pressure desilicication; the aluminum hydroxide separation and impurity removal process comprises three-stage impurity removal and permanent magnet impurity removal. The invention provides a method for preparing aluminum hydroxide micro powder, which comprises the following steps of: obtaining a sodium aluminate solution with an extinction value of less than 0.45 by adopting a technological process of pre-desilicication, autoclaving desilicication and normal-pressure desilicication; by means of the technological process of three-stage impurity removal and permanent magnet impurity removal, magnetic substances and different color points in the product are deeply removed, the magnetic substances in the aluminum hydroxide micro powder are smaller than or equal to 0.22 mg / 300 g, the different color points in the aluminum hydroxide micro powder are smaller than or equal to 7 / 300 g, and the strict requirements of the aluminum hydroxide micro powder in the high-end electronic field are met.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum hydroxide preparation, and in particular to a method for preparing aluminum hydroxide micropowder. Background Art

[0002] Aluminum hydroxide is widely used in the copper clad laminate industry due to its excellent synergistic flame retardant effect. During the production process of copper clad laminates, impurities such as magnetic impurities and discoloration spots in the aluminum hydroxide raw materials will be brought into the copper clad laminates, affecting the appearance, finish and electrical insulation performance of the copper clad laminates. In the context of the pursuit of high-speed and high-frequency integrated circuit applications, international standards require that the magnetic impurity content of aluminum hydroxide used in copper clad laminates be ≤0.25mg / 300g, and the number of discoloration spots shall not exceed 10 / 300g to ensure product quality.

[0003] At present, the domestic high-end aluminum hydroxide powder used in the production of copper clad laminates is highly dependent on imports. This is because the magnetic impurities of aluminum hydroxide produced domestically are generally higher than 0.5mg / 300g, and the number of discoloration points is as high as 50-60 / 300g, which is significantly different from the international standard. Therefore, the development and design of a method for preparing aluminum hydroxide powder is of great significance to break the dependence on imports of high-end aluminum hydroxide powder and meet the increasingly stringent market demand. Summary of the invention

[0004] In view of the problem of high content of magnetic impurities and discoloration spots in aluminum hydroxide micropowder in the above-mentioned prior art, the present invention provides a method for preparing aluminum hydroxide micropowder, which can deeply remove magnetic substances and discoloration spots in aluminum hydroxide. The magnetic substances in the obtained product are ≤0.22 mg / 300 g, and the discoloration spots are ≤7 / 300 g, which meets the strict requirements of aluminum hydroxide micropowder in the field of copper clad laminates.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A method for preparing aluminum hydroxide powder includes a process flow of raw material slurry preparation, clinker sintering, clinker dissolution, red mud washing and separation, crude liquid desiliconization, sodium aluminate solution fine filtration, seed decomposition, aluminum hydroxide separation and impurity removal; the crude liquid desiliconization process includes pre-desiliconization, autoclave desiliconization and atmospheric pressure desiliconization; the aluminum hydroxide separation and impurity removal process includes three-stage impurity removal and permanent magnet impurity removal.

[0007] Furthermore, the molecular ratio of calcium oxide to silicon oxide in the raw slurry is 1.8-1.9:1, and the molecular ratio of aluminum oxide and iron oxide to sodium oxide is 1:0.95-1.00.

[0008] Furthermore, the crude liquid desiliconization process steps are as follows:

[0009] (1) Pre-desiliconization: sodium silicon slag is added to the crude liquid obtained from the red mud washing and separation process as a desiliconization seed, and the reaction is carried out at 80-85°C for 2-2.5 hours for pre-desiliconization;

[0010] (2) Desiliconization by pressure cooking: the pre-desiliconized slurry is sent to the desiliconizer for desiliconization. The desiliconization temperature is 130-140°C and the desiliconization time is 2.5-3h.

[0011] (3) Desiliconization at atmospheric pressure: Add lime milk to the slurry after pressure boiling and desiliconization, and carry out desiliconization at atmospheric pressure at 90-95°C.

[0012] Furthermore, the extinction value of the sodium aluminate solution obtained in the sodium aluminate solution fine filtration step is less than 0.45.

[0013] Furthermore, during the seed crystal decomposition process, the seed ratio is 1.1%-1.3%, the decomposition temperature is 70-75° C., and the decomposition time is 24-26 hours.

[0014] Furthermore, the three-stage impurity removal steps are as follows:

[0015] (1) Primary impurity removal: The slurry after seed crystal decomposition first passes through a primary electromagnet to remove magnetic substances, then passes through a 200-mesh wet screen to remove large particles of impurities, and is separated by a filter press to obtain a filter cake;

[0016] (2) Secondary impurity removal: The filter cake obtained by the primary impurity removal is mixed with hot water to obtain a slurry, which is first passed through a secondary electromagnet to remove magnetic substances, then passed through a 400-mesh wet sieve to remove impurities, and then separated by a filter press to obtain a filter cake;

[0017] (3) Three-stage impurity removal: The filter cake obtained by the two-stage impurity removal is mixed with hot water to obtain a slurry. The slurry is first passed through a three-stage electromagnet to remove magnetic substances, and then passed through a 500-mesh wet screen to remove impurities. After separation by a filter press, a filter cake is obtained. The filter cake is dried and depolymerized by a depolymerizer to obtain aluminum hydroxide powder.

[0018] Furthermore, the permanent magnet impurity removal step is as follows: suspending the permanent magnet on the surface of aluminum hydroxide micropowder to remove magnetic substances.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The invention provides a method for preparing aluminum hydroxide micropowder. By adopting the process of pre-desiliconization, autoclave desiliconization and atmospheric pressure desiliconization, a sodium aluminate solution with an extinction value of less than 0.45 is obtained. By adopting the process of three-stage impurity removal and permanent magnet impurity removal, magnetic substances and heterochromatic spots in the product are deeply removed, so that the magnetic substances in the aluminum hydroxide micropowder are ≤0.22 mg / 300 g, and the heterochromatic spots are ≤7 / 300 g, which meets the strict requirements of the aluminum hydroxide micropowder in the field of high-end electronics. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The embodiments of the present invention are further described below with reference to the accompanying drawings, in which:

[0022] Figure 1 Shown is a process flow chart for the production of aluminum hydroxide micropowder. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] A method for preparing aluminum hydroxide micropowder includes a process flow of raw material slurry preparation, clinker sintering, clinker dissolution, red mud washing and separation, crude liquid desiliconization, sodium aluminate solution fine filtration, seed decomposition, aluminum hydroxide separation and impurity removal; the crude liquid desiliconization process includes pre-desiliconization, autoclave desiliconization and atmospheric pressure desiliconization; the aluminum hydroxide separation and impurity removal process includes three-stage impurity removal and permanent magnet impurity removal.

[0025] Furthermore, the molecular ratio of calcium oxide to silicon oxide in the raw slurry is 1.8-1.9:1, and the molecular ratio of aluminum oxide and iron oxide to sodium oxide is 1:0.95-1.00.

[0026] Further, the steps of the crude liquid desiliconization process are as follows:

[0027] (1) Pre-desiliconization: sodium silicon slag is added to the crude liquid obtained from the red mud washing and separation process as a desiliconization seed, and the reaction is carried out at 80-85°C for 2-2.5 hours for pre-desiliconization;

[0028] (2) Desiliconization by pressure cooking: the pre-desiliconized slurry is sent to the desiliconizer for desiliconization. The desiliconization temperature is 130-140°C and the desiliconization time is 2.5-3h.

[0029] (3) Desiliconization at atmospheric pressure: Add lime milk to the slurry after pressure boiling and desiliconization, and carry out desiliconization at atmospheric pressure at 90-95°C.

[0030] Furthermore, the extinction value of the sodium aluminate solution obtained in the sodium aluminate solution fine filtration step is less than 0.45.

[0031] Furthermore, during the crystal seed decomposition process, the seed ratio is 1.1%-1.3%, the decomposition temperature is 70-75° C., and the decomposition time is 24-26 hours.

[0032] Further, the three-stage impurity removal steps are as follows:

[0033] (1) Primary impurity removal: The slurry after seed crystal decomposition first passes through a primary electromagnet to remove magnetic substances, then passes through a 200-mesh wet screen to remove large particles of impurities, and is separated by a filter press to obtain a filter cake;

[0034] (2) Secondary impurity removal: The filter cake obtained by the primary impurity removal is mixed with hot water to obtain a slurry, which is first passed through a secondary electromagnet to remove magnetic substances, then passed through a 400-mesh wet sieve to remove impurities, and then separated by a filter press to obtain a filter cake;

[0035] (3) Three-stage impurity removal: The filter cake obtained by the two-stage impurity removal is mixed with hot water to obtain a slurry. The slurry is first passed through a three-stage electromagnet to remove magnetic substances, and then passed through a 500-mesh wet screen to remove impurities. After separation by a filter press, a filter cake is obtained. The filter cake is dried and depolymerized by a depolymerizer to obtain aluminum hydroxide powder.

[0036] Furthermore, the permanent magnet impurity removal step is as follows: suspend the permanent magnet on the surface of aluminum hydroxide powder to remove magnetic substances.

[0037] Example 1

[0038] The steps of the crude liquid desiliconization process are as follows: add sodium silicate slag to the crude liquid obtained in the red mud washing and separation process, react at 80°C for 2.5 hours for pre-desiliconization, send the pre-desiliconized slurry into a desiliconizer and react at 130°C for 3 hours for pressure boiling desiliconization; add lime milk to the pressure boiling desiliconized slurry and perform normal pressure desiliconization at 90°C; and obtain a sodium aluminate solution with an extinction value of <0.45 after fine filtration.

[0039] Example 2

[0040] The steps of the crude liquid desiliconization process are as follows: add sodium silicate slag to the crude liquid obtained in the red mud washing and separation process, react at 85°C for 2 hours for pre-desiliconization, send the pre-desiliconized slurry into a desiliconizer and react at 140°C for 2.5 hours for pressure boiling desiliconization; add lime milk to the pressure boiling desiliconized slurry, and desiliconize at normal pressure at 95°C; and obtain a sodium aluminate solution with an extinction value of <0.45 after fine filtration.

[0041] The invention provides a method for preparing aluminum hydroxide micropowder. By adopting the process of pre-desiliconization, autoclave desiliconization and atmospheric pressure desiliconization, a sodium aluminate solution with an extinction value of less than 0.45 is obtained. By adopting the process of three-stage impurity removal and permanent magnet impurity removal, magnetic substances and heterochromatic spots in the product are deeply removed, so that the magnetic substances in the aluminum hydroxide micropowder are ≤0.22 mg / 300 g, and the heterochromatic spots are ≤7 / 300 g, which meets the strict requirements of the aluminum hydroxide micropowder in the field of high-end electronics.

[0042] Some exemplary embodiments of the present invention are described above. It can be understood that the above embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention. The features in these embodiments can be recombined in a suitable manner, and the scheme obtained thereby is still within the protection scope required by the present invention. Based on the above embodiments, all other embodiments obtained by those skilled in the art without making creative work, that is, all modifications, equivalent substitutions and improvements made within the spirit and principles of this application, fall within the protection scope required by the present invention.

Claims

1. A method for preparing aluminum hydroxide micropowder, characterized in that: The invention comprises the process flow of raw material slurry preparation, clinker sintering, clinker dissolution, red mud washing and separation, crude liquor desiliconization, sodium aluminate solution fine filtration, seed crystal decomposition, aluminum hydroxide separation and impurity removal; the crude liquor desiliconization process comprises pre-desiliconization, pressure cooking desiliconization and atmospheric pressure desiliconization; the aluminum hydroxide separation and impurity removal process comprises three-stage impurity removal and permanent magnet impurity removal.

2. A method for preparing aluminum hydroxide micropowder according to claim 1, characterized in that: The molecular ratio of calcium oxide to silicon oxide in the raw slurry is 1.8-1.9:1, and the molecular ratio of aluminum oxide and iron oxide to sodium oxide is 1:0.95-1.

00.

3. A method for preparing aluminum hydroxide micropowder according to claim 1, characterized in that, The steps of the crude liquid desiliconization process are as follows: (1) Pre-desiliconization: sodium silicon slag is added to the crude liquid obtained from the red mud washing and separation process as a desiliconization seed, and the reaction is carried out at 80-85°C for 2-2.5 hours for pre-desiliconization; (2) Desiliconization by pressure cooking: the pre-desiliconized slurry is sent to the desiliconizer for desiliconization. The desiliconization temperature is 130-140°C and the desiliconization time is 2.5-3h. (3) Desiliconization at atmospheric pressure: Add lime milk to the slurry after pressure boiling and desiliconization, and carry out desiliconization at atmospheric pressure at 90-95°C.

4. A method for preparing aluminum hydroxide micropowder according to claim 3, characterized in that, The extinction value of the sodium aluminate solution obtained in the sodium aluminate solution fine filtration step is less than 0.

45.

5. A method for preparing aluminum hydroxide micropowder according to claim 4, characterized in that, During the crystal seed decomposition process, the seed ratio is 1.1%-1.3%, the decomposition temperature is 70-75° C., and the decomposition time is 24-26 hours.

6. A method for preparing aluminum hydroxide micropowder according to claim 5, characterized in that: The three-stage impurity removal steps are as follows: (1) Primary impurity removal: The slurry after seed crystal decomposition first passes through a primary electromagnet to remove magnetic substances, then passes through a 200-mesh wet screen to remove large particles of impurities, and is separated by a filter press to obtain a filter cake; (2) Secondary impurity removal: The filter cake obtained by the primary impurity removal is mixed with hot water to obtain a slurry, which is first passed through a secondary electromagnet to remove magnetic substances, then passed through a 400-mesh wet sieve to remove impurities, and then separated by a filter press to obtain a filter cake; (3) Three-stage impurity removal: The filter cake obtained by the two-stage impurity removal is mixed with hot water to obtain a slurry. The slurry is first passed through a three-stage electromagnet to remove magnetic substances, and then passed through a 500-mesh wet screen to remove impurities. After separation by a filter press, a filter cake is obtained. The filter cake is dried and depolymerized by a depolymerizer to obtain aluminum hydroxide powder.

7. A method for preparing aluminum hydroxide micropowder according to claim 6, characterized in that: The permanent magnet impurity removal step is as follows: suspending the permanent magnet on the surface of aluminum hydroxide micropowder to remove magnetic substances.

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