Aluminum oxide powder and its synthesis

Abstract

An aluminum oxide powder and a method for producing the aluminum oxide powder, wherein the aluminum oxide powder is composed of aggregates of primary particles and has an aggregate size distribution with a median aggregate particle size (D50) of 220 nm to 500 nm, preferably 230 to 400 nm, more preferably 250 nm to 300 nm, as determined by dynamic light scattering measurement, and a BET of 10 m 2 / g~100m 2 / g.

Description

[Technical Field]

[0001] The present invention relates generally to aluminum oxide powder and methods for making aluminum oxide. [Background technology]

[0002] Prior art It is known to produce aluminum oxide powder by a pyrolysis process, which involves flame hydrolysis in which an aluminum halide, typically aluminum chloride, is hydrolyzed at high temperature to form aluminum oxide and hydrochloric acid.

[0003] Many possible uses for aluminum oxide powder are known, including applications in the paper industry, particularly in inkjet paper, as an abrasive in dispersions for chemical mechanical polishing in the electronics industry, and as an additive in lithium ion batteries.

[0004] Generally, existing aluminum oxide powders with large primary particles are formed by high flame temperatures achieved by using a large excess of hydrogen in the reaction mixture. See, for example, U.S. Pat. No. 8,197,791 (B2), Japanese Patent No. 6,147,614 (B2), and German Patent Application Publication (A1) No. 10,360,087. These patent documents describe the synthesis of aluminum oxide using a pyrolysis process in which hydrogen is used in an amount at least 1.6 times greater than the stoichiometrically required amount. Japanese Patent No. 6,147,614 (B2) uses an excess of hydrogen of at least 5 times greater. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] US Patent No. 8197791 (B2) [Patent Document 2] Japanese Patent No. 6147614 (B2) Specification [Patent Document 3] DE Patent Application Publication No. (A1) 10360087 Summary of the Invention [Problem to be solved by the invention]

[0006] However, high excess hydrogen results in small aggregate size and low factory utilization (capacity). [Means for solving the problem]

[0007] An object of the present invention is to provide an aluminum oxide powder having a large aggregate size distribution. By "large" is meant an aggregate size distribution having a median particle size (D50) of 220 nm to 500 nm, preferably 230 nm to 400 nm, and more preferably 250 nm to 300 nm, as determined by dynamic light scattering.

[0008] Another object of the present invention is to provide an improved pyrolysis process for making aluminum oxide powder that improves plant utilization and efficiency and reduces the overall carbon dioxide (CO2) footprint of the produced aluminum oxide.

[0009] It has been unexpectedly discovered that using a lower hydrogen (H) excess relative to the stoichiometrically required amount during pyrolytic synthesis results in aluminum oxide powder with a larger aggregate size distribution. Specifically, by lowering the hydrogen excess in the reaction mixture during pyrolytic synthesis, the aluminum oxide produced has a significantly larger aggregate size distribution than aluminum oxide produced with a higher hydrogen excess in the reaction mixture. This is quite unique to pyrolytic aluminum oxide because it is independent of the BET specific surface area of ​​the aluminum oxide. Typically, in existing pyrolytically produced aluminum oxide powders, the aggregate size distribution shifts to smaller values ​​as the BET specific surface area increases, and conversely, the aggregate size distribution shifts to larger values ​​as the BET specific surface area decreases.

[0010] Additionally, the lower the hydrogen excess in the synthesis process, the higher the factory efficiency and the lower the carbon dioxide (CO2) footprint of the final product.

[0011] Additionally, it has been found that the aluminum oxide obtained by the improved pyrolysis process exhibits significantly improved properties in coating formulations requiring low moisture and high breathability.

[0012] According to one embodiment, there is provided an aluminum oxide powder consisting of aggregates of primary particles, characterized by an aggregate size distribution with a median aggregate size (D50) determined by dynamic light scattering measurement of 220 nm to 500 nm, preferably 230 nm to 400 nm, and more preferably 250 nm to 300 nm.

[0013] Aluminum oxide powder has a BET of 10m 2 / g~100m 2 / g, preferably 10m 2 / g~55m 2 / g.

[0014] The aluminum oxide powder may contain chlorine in an amount of 10 ppm to 3000 ppm.

[0015] The aluminium oxide powder is preferably of pyrolytic origin, which means that it is a pyrolytic aluminium oxide powder.

[0016] The aluminum oxide powder may be obtained by a pyrolysis process in which hydrogen is supplied to the reaction mixture in excess of the amount stoichiometrically required for complete reaction at a gamma ratio of less than 1.6.

[0017] According to one embodiment, there is provided a process for producing aluminum oxide powder, comprising the steps of: supplying vaporized aluminum chloride, hydrogen, and air to a mixing chamber; transferring a mixture of aluminum chloride, hydrogen and air into a reaction chamber; igniting the mixture to produce solid aluminum oxide; isolating the aluminum oxide powder; Equipped with A process is provided in which hydrogen is used in a gamma ratio of less than 1.6, preferably between 1.0 and 1.3, more preferably between 1.0 and 1.1.

[0018] In one embodiment, hydrogen is used at a gamma ratio of 1.05, and the solid aluminum powder produced has a D50 of 250 nm to 300 nm and a BET of 10 m 2 / g~55m 2 / g.

[0019] In this process, aluminum chloride may first be vaporized, the vaporized gas may be transported to a mixing chamber by a carrier gas, hydrogen and air may be supplied to the mixing chamber separately from the aluminum chloride, and the air may be optionally enriched with oxygen and / or optionally preheated. The reaction chamber may be a burner that generates a flame within the reaction chamber. The aluminum oxide powder is separated from the gaseous material and then treated with steam and optionally air.

[0020] The process may have a discharge velocity of the reaction mixture from the mixing chamber to the reaction chamber of at least 10 m / s and a lambda ratio of 1-5.

[0021] The process may further employ a secondary gas consisting of air and / or nitrogen introduced into the reaction chamber, preferably using a primary air / secondary gas ratio of 10 to 0.5.

[0022] The invention further relates to the use of the pyrolytically produced aluminum oxide powder by the above process as an ink absorbing material in inkjet media, or in a dispersion composition for lithium ion battery separator coatings, or as an additive in lithium ion battery anode or cathode active materials.

[0023] These and other features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description and drawings. [Brief explanation of the drawings]

[0024] [Figure 1] 1 shows the aggregate size distribution of aluminum oxide powder obtained by a pyrolysis process according to one embodiment of the present invention and the aggregate size distribution of conventional aluminum oxide powder. [Figure 2] FIG. 1 is a simplified schematic diagram of a pyrolysis process for making aluminum oxide according to one embodiment of the present invention. [Figure 3] FIG. 1 is a simplified schematic diagram of a lithium-ion battery having a separator coated on both sides with an aluminum oxide coating, according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] The aluminum oxide powder of the present invention is a pyrolytically prepared aluminum oxide, also known as fumed aluminum oxide powder or fumed alumina powder. "Pyrogenic" here should be understood to mean a powder obtained by flame hydrolysis or flame oxidation. The powder thus prepared consists of agglomerates of sintered primary particles, sometimes referred to as secondary particles, initially formed during the reaction. Subsequently, multiple agglomerates may form agglomerates. Due to the reaction conditions, pyrolytically prepared powders have very low surface porosity and a pore size of 10 OH / nm. 2 Only the hydroxyl groups on the surface up to 1000 nm are shown.

[0026] In one embodiment, the aluminum oxide powder is BET specific surface area is 10 to 100 m 2 / g, preferably 10 to 55 m 2 / g, D50 is 220 nm to 500 nm, preferably 230 nm to 400 nm, and more preferably 250 nm to 300 nm.

[0027] The aluminum oxide powder may have a chlorine content in an amount greater than 10 ppm and less than 3000 ppm.

[0028] The aluminum oxide powder may further exhibit a unimodal distribution of aggregate particle diameters, meaning that analysis of the aggregate size (or diameter) distribution yields only one single peak signal. The single peak of the unimodal distribution of aggregate diameters may be between 220 nm and 500 nm, preferably between 230 nm and 400 nm, and more preferably between 250 nm and 300 nm.

[0029] Referring now to Figure 2, a pyrolysis process for the synthesis of aluminum oxide powder is provided. The process includes evaporating aluminum chloride (AlCl) in an evaporator 7 and supplying the aluminum chloride vapor "a" to a mixing chamber 1. The vaporized gas may be transported to the mixing chamber via an inert gas. Separately from the aluminum chloride vapor, combustion gases including hydrogen "b" and primary air "c" are introduced into the mixing chamber 1. The air "c" may optionally be enriched with oxygen. The air "c" may optionally be preheated before being supplied to the mixing chamber 1.

[0030] The produced aluminum oxide particles are in the form of agglomerated primary particles, which have no pores and have hydroxyl groups on their surfaces. Hydrochloric acid is formed as a by-product in the conversion of aluminum chloride, and most of it is removed from the aluminum oxide particles by steam treatment. Therefore, only a small amount of chlorine remains on the aluminum oxide particles.

[0031] The hydrogen b is preferably used in slight excess compared to the theoretical amount required for the complete hydrolysis of aluminum chloride according to the following equation:

[0032] 2H2+O2→2H2O 2AlCl3 + 3H2O → Al2O3 + 6HCl The ratio of hydrogen supplied to hydrogen stoichiometrically required is called the "gamma" ratio.

[0033] The ratio of oxygen supplied to oxygen stoichiometrically required is called the "lambda" ratio.

[0034] The "gamma" and "lambda" ratios themselves are generally known to those skilled in the art, as described, for example, in US Pat. No. 8,197,791 (B2).

[0035] The oxygen excess, or lambda ratio, required for this reaction for complete hydrolysis of aluminum chloride is greater than 1 to 5.

[0036] The reaction mixture "d" is fed into a burner (inside the reaction chamber 2) in a central tube and ignited. The exit velocity of the reaction mixture from the burner can range from 10 m / s to 100 m / s. The flame burns in a water-cooled reaction chamber 2. The reaction gases and solids from the reaction chamber are cooled in a cooling coil 3 before entering a gas-solid separation unit 4, e.g., a cyclone and / or a filter.

[0037] The resulting aluminum oxide powder is then separated from the gas in a downstream gas-solid separation unit 4 (e.g., a cyclone) and deposited at the bottom of the gas-solid separation unit 4, where it is collected via a bottom outlet. The powder from 4 is transferred to a deoxidation unit 5 to remove the acid from the powder. The aluminum oxide powder is treated with countercurrent air and steam inside the unit 5 at a high temperature, e.g., about 700 °C. The temperature is not limited to 700 °C and can generally range from 400 °C to 900 °C. The purpose of treating the aluminum oxide powder with air and steam at high temperature is to remove chlorine (e.g., HCl, chlorine gas) and adjust the powder's pH value to a value between 2 and 7. Depending on the specific intended use of the aluminum powder, the powder pH can be adjusted to a specific value within the range of 2 to 7. The powder is collected in a silo 6 and can be further processed as needed, e.g., packaged. The discharge velocity of the reaction mixture from the mixing chamber to the reaction chamber can be at least 10 m / s.

[0038] The gamma ratio may be from 0.9 to less than 1.6, preferably from 1.0 to 1.3, and more preferably from 1.0 to 1.1. A particularly preferred gamma ratio provides a slight excess of hydrogen and may be in the range of from greater than 1.0 to 1.1.

[0039] AlCl3 / m in the range of 0.2kg-0.6kg 3 may be used.

[0040] In a specific embodiment of the process according to the invention, a secondary gas consisting of air and / or nitrogen can be introduced into the reaction chamber. The ratio of primary air to secondary gas preferably has a value between 10 and 0.5. The introduction of the secondary gas can help to avoid caking in the reaction chamber.

[0041] The aluminum oxide powders according to the present invention combine an optimized relationship between aggregate size and BET and can be used in many applications, including, for example, as fillers in cosmetic compositions, as insulating materials in electronic devices, as catalytically active materials in various reactions, as ink absorbing materials in inkjet media, as ceramic coatings, or in lithium ion battery anode or cathode active material compositions.

[0042] Aluminum oxide powder is particularly advantageous in forming dispersions used to coat polyolefin separators in lithium-ion batteries. Figure 3 shows a lithium-ion battery, generally designated 300, including a separator made from a membrane 316 and coated with a coating layer 318. The coating layer 318 is formed on both sides of the membrane 316 by applying an aqueous dispersion of aluminum oxide of the present invention. The lithium-ion battery 300 can be used in electronic and electrical devices 400, including, for example, mobile phones, computers (laptops, desktops, computer pads), electronic watches, key fabs, appliances, power tools, vacuum cleaners, electric lawn mowers, and electric vehicles. The lithium-ion battery 300 further includes a cathode active material 312 on a cathode plate 310 and an anode active material 322 on an anode plate 320. An electrolyte 324 is disposed around the separator and between the anode active material 322 and the cathode active material 312.

[0043] The method for preparing a dispersion containing aluminum oxide includes the steps of: placing the agglomerated aluminum oxide powder, one amino alcohol having 1 to 6 carbon atoms, and at least one carboxylic acid from the group comprising dicarboxylic acids and / or hydroxytricarboxylic acids having 2 to 7 carbon atoms in water; A smaller amount of energy than is required to form the dispersion (e.g., 1000 kJ / m 3 preparing a pre-dispersion by introducing less than then producing a dispersion by introducing the pre-dispersion into a high energy mill and grinding the pre-dispersion using the high energy mill at a pressure of at least 500 bar; Includes:

[0044] For example, the pre-dispersion may have a viscosity of 1000 kJ / m 3( In one embodiment, the pre-dispersion can be formed by introducing less than 200 kJ / m 2 of energy into the aqueous slurry. 3The following energy can be introduced into the aqueous slurry:

[0045] In one embodiment, the pre-dispersion may be split into at least two partial streams, which may be placed into a high energy mill under a pressure of at least 500 bar, discharged through a nozzle, and allowed to impinge on each other in a gas or liquid filled reaction chamber.

[0046] The agglomerated aluminum oxide has a BET specific surface area of ​​10 to 100 m 2 / g, more preferably 10 to 55 m 2 / g.

[0047] Amino alcohols have a specific surface area of ​​2.5 to 8.0 μmol / m of aluminum oxide. 2 The carboxylic acid may be present in the dispersion in an amount of 1.0 to 4.0 μmol / m2 of the specific surface area of ​​aluminum oxide. 2 may be present in an amount of

[0048] The introduction of energy into the water slurry to produce the pre-dispersion can be carried out by using mechanical means. Suitable mechanical means for producing dispersions, such as the pre-dispersions described herein, are generally known in the art and may include, by way of illustrative but non-limiting examples, stirring, agitating, shaking, and / or grinding. In particular, shear conditions can be applied to introduce energy into the water slurry. Suitable devices for preparing the pre-dispersion can be, for example, rotor / stator machines or toothed disks.

[0049] In a preferred embodiment, the pressure during the high-energy milling process may be at least 2000 bar. It should also be noted that it may be advantageous to subject the dispersion to the high-energy milling process several times.

[0050] The present invention provides an aqueous dispersion obtained by the above process. The dispersion may contain Al2O3 particles in an amount of at least 20 wt% solids based on the total weight of the dispersion, preferably 40-60 wt%, more preferably 50-60 wt%, of Al2O3 particles in the total weight of the dispersion, and has a low viscosity of less than 100 mPas, preferably 100-10 mPas, more preferably 60-15 mPas. As used herein, the term solids refers to the weight percentage of aluminum oxide particles in the dispersion.

[0051] The dispersion of aluminum oxide may preferably have a unimodal particle size distribution with a single peak between 220 nm and 500 nm.

[0052] For applying ceramic coatings for lithium-ion battery separators, the dispersion preferably has a basic pH and may be free of hygroscopic components such as sodium dihydrogen phosphate or phosphonic acids used in some conventional metal oxide dispersions. Aluminum oxide dispersions with a more basic pH have been found to provide improved compatibility with binder systems used in coating slurry formulations. [Example]

[0053] analysis The aggregate size distribution is determined by DLS (Dynamic Light Scattering).

[0054] The BET specific surface area of ​​the particles is determined in accordance with DIN 66131.

[0055] Gamma ratio = H2 supplied / H2 stoichiometrically required Lambda ratio = O2 supplied / O2 stoichiometrically required Example 1 Invention: Aluminum chloride (AlCl3) is vaporized and the vaporized gas is transferred to a mixing chamber, into which a combustion gas containing hydrogen and primary air is introduced separately from the raw material. The combustion gas has a 1.02-fold excess of hydrogen compared to the theoretical amount required for the complete hydrolysis of AlCl3 according to the following formula:

[0056] 2H2+O2→2H2O 2AlCl3 + 3H2O → Al2O3 + 6HCl The oxygen excess for this reaction to obtain complete hydrolysis of AlCl3 is 1.04. Therefore, the values ​​of the gamma and lambda ratios were 1.02 and 1.04, respectively.

[0057] The reaction mixture was placed in a central tube and fed to a burner where it was ignited. The exit velocity of the reaction mixture from the burner was 33.7 m / s. The flame was burned in a water-cooled reaction chamber. The powder formed was deposited in a downstream cyclone and filter and then treated with countercurrent air and steam at approximately 700°C.

[0058] The resulting powder has a BET specific surface area of ​​45m 2 The aggregate size distribution obtained by dynamic light scattering is shown in Figure 1, and the D50 value was 260 nm.

[0059] Example 2 Comparison Comparative Example 1 was carried out according to the procedure described in Example 1, except that the combustion gases had 2.21 more hydrogen than the theoretical amount required for complete hydrolysis of aluminum chloride according to the following equation: 2H2+O2→2H2O 2AlCl3 + 3H2O → Al2O3 + 6HCl The oxygen excess for this reaction to obtain complete hydrolysis of AlCl3 was 0.95. The gamma and lambda ratio values ​​for Example 2 were 2.21 and 0.95, respectively.

[0060] The reaction mixture was placed in a central tube and fed to a burner where it was ignited. The exit velocity of the reaction mixture from the burner was 37.6 m / s. The flame was burned in a water-cooled reaction chamber. The powder formed was deposited in a downstream cyclone and filter and then treated with countercurrent air and steam at 700 °C.

[0061] The resulting powder has a BET specific surface area of ​​48m 2 / g.

[0062] The aggregate size distribution obtained by dynamic light scattering is shown in Figure 1, with a D50 value of 206 nm.

[0063] Measurement of aggregate size distribution: The aggregate size distribution is determined by DLS measurements using a SYMPATEC NANOPHOX instrument. For analysis, a 20 g dispersion of 1 wt% aluminum oxide in water is prepared by sonication using an ultrasonicator (Hielscher UP400St, amplitude 50%) for 5 min. For accurate measurements using NANOPHOX, a single scattering ratio in the range of 20-80% is set by diluting 100-500 mg of this as-prepared dispersion with distilled water to a total volume of 2.5 g.

[0064] Further examples were carried out in the same manner as in Example 1, and the important parameters of the reaction conditions and the physicochemical values ​​of the produced aluminum oxide powders are included in Table 1. Examples 1 and 3 are examples according to the invention. Examples 2 and 4 are comparative examples.

[0065] [Table 1]

[0066] In Table 1, *v B is the exit velocity from the burner. Also, the gamma and lambda values ​​are based on a core gas of primary air, hydrogen, and inert gases. The concentration of Al2O3 ("c") in the total gas volume is based on the core gas (i.e., AlCl3 (as gas phase) and PH2; primary air), which is all gases passing through the core tube. All other gases (MH2 and secondary air) are not considered in the concentration of the Al2O3 core concentration. The Al2O3 concentration (all) refers to the concentration of Al2O3 based on the entire gas stream, including MH2 and secondary air. Note that MH2 and secondary air do not contribute to product variation; only the core gas contributes to product variation.

[0067] While the present invention has been described with reference to only certain examples, it should be understood that the invention is not limited to only the particular examples described. After reading this disclosure, one skilled in the art will be able to envision several variations of the described examples and other examples that fall within the scope of the invention as defined in the following claims. For example, an element described as used alone or in combination with other features in one example may also be used with a different combination of features in another example without departing from the scope of the disclosed and claimed invention.

Claims

1. An aluminum oxide powder consisting of aggregates of primary particles, having an aggregate size distribution with a median aggregate particle size (D50) of 220 nm to 500 nm, preferably 230 to 400 nm, more preferably 250 nm to 300 nm, as determined by dynamic light scattering measurements, and a BET ２ / g to 100m ２ / g.

2. BET is 10m ２ / g~55m ２ 10. The aluminum oxide powder of claim 1, further characterized by having a % SiO2 / g.

3. D50 is 250 nm to 300 nm and BET is 10 m ２ / g~55m ２ 3. The aluminum oxide powder according to claim 1, wherein the aluminum oxide powder has a molecular weight of 1.001 or 1.001g.

4. 4. The aluminum oxide powder according to claim 1, further characterized in that it contains chlorine in an amount greater than 10 ppm and less than 3000 ppm.

5. The aluminum oxide powder according to any one of claims 1 to 4, further characterized as being a pyrolytic aluminum oxide powder.

6. 6. The aluminum oxide powder of claim 5, further characterized in that it is obtained by a pyrolysis process in which hydrogen is supplied to the reaction mixture in excess of the amount stoichiometrically required for complete reaction at a gamma ratio of less than 1.

6.

7. 2. A process for producing the aluminum oxide powder of claim 1, comprising: supplying vaporized aluminum chloride, hydrogen, and air to a mixing chamber; transferring the mixture of aluminum chloride, hydrogen and air into a reaction chamber; igniting the mixture to produce solid aluminum oxide; separating the aluminum oxide powder; Equipped with The process is characterized in that the hydrogen is used in a gamma ratio of less than 1.6, preferably between 0.9 and 1.3, more preferably between 1.0 and 1.

1.

8. The hydrogen was used at a gamma ratio of 1.05, and the produced solid aluminum powder had a D50 of 250 nm to 300 nm and a BET of 10 m ２ / g~55m ２ 8. The process according to claim 7, characterized in that:

9. The aluminum chloride is first vaporized, and the vaporized gas is transported to the mixing chamber by a carrier gas; the hydrogen and air are supplied to the mixing chamber separately from the aluminum chloride; the air is optionally enriched with oxygen and / or optionally preheated, the reaction chamber is a burner, and the flame burns within the reaction chamber; the aluminum oxide powder is separated from the gaseous substance; It is then treated with steam and optionally air.

9. The process according to claim 7 or 8, characterized in that

10. 10. The process according to any one of claims 7 to 9, characterized in that the discharge velocity of the reaction mixture from the mixing chamber to the reaction chamber is at least 10 m / s and the lambda ratio is between 1 and 5.

11. 11. The process according to any one of claims 7 to 10, characterized in that a secondary gas consisting of air and / or nitrogen is introduced into the reaction chamber, preferably in a ratio of primary air / secondary gas between 10 and 0.

5.

12. 12. Use of the aluminium oxide powder produced by flame hydrolysis according to any one of claims 7 to 11 as an ink absorbing material in ink jet media, or in a dispersion composition for lithium ion battery separator coatings, or as an additive in lithium ion battery anode or cathode active materials.

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