Method for preparing ceramic microbeads based on environment-friendly non-aqueous gel system

Abstract

The invention discloses a method for preparing ceramic microbeads based on an environment-friendly non-aqueous gel system, which comprises the following steps: carrying out ball milling on ceramic powder, a dispersing agent and an organic solvent to obtain first slurry; adding an EBECRYL acrylic acid cross-linking agent into the first slurry, continuing ball milling, and defoaming to obtain second slurry; polyethylene glycol and water are mixed to obtain a polyethylene glycol aqueous solution, oil is poured into the polyethylene glycol aqueous solution to obtain a curing medium with the upper layer being an oil layer and the lower layer being a polyethylene glycol aqueous solution layer, the oil is insoluble in polyethylene glycol, and the density is smaller than that of polyethylene glycol and water; and under ultraviolet irradiation, dropping the second slurry into a curing medium to form a spherical green body, taking out the spherical green body after the size of the spherical green body is not changed any more, drying and sintering to obtain the ceramic microbead. The method disclosed by the invention is energy-saving and environment-friendly, and the prepared ceramic microbeads also have the advantages of concentrated size distribution, high relative density, good sphericity and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic microbead preparation, and in particular relates to a method for preparing ceramic microbeads based on an environmentally friendly non-aqueous gel system. Background Art

[0002] Oxide and non-oxide ceramic grinding media balls have gained wide favor in the industry due to their many outstanding advantages such as high strength, high hardness, excellent wear resistance and corrosion resistance. In order to adapt to the rapid development of the ultrafine grinding industry, more and more researchers have focused on how to prepare monodisperse sub-millimeter-level ceramic grinding media balls with excellent performance and strong adaptability, or even with a particle size of less than 300 μm. At present, the main preparation processes for ceramic balls include plastic extrusion molding, external gel molding, rolling molding, isostatic pressing, etc. However, although these technologies are relatively mature and can produce ceramic media balls for grinding, these ceramic media balls all have certain defects and cannot simultaneously have the characteristics of high relative volume density, high strength and hardness, and excellent stability.

[0003] Gel casting is a wet molding method, which has attracted wide attention due to its advantages of simple operation, low cost, uniform microstructure of gel, few defects, and net size molding. Yang Jinlong and others from Tsinghua University mixed organic monomers, crosslinking agents and water, added different ceramic powders, then defoamed the slurry, and then added an initiator during stirring. The obtained slurry was dripped into an oily medium, and the interfacial tension difference of different media was used to make the slurry into balls, and the spherical slurry was quickly solidified into a gel by adding a catalyst to the oily medium, and finally a high-density, wear-resistant ceramic ball was obtained. However, in this method, the monomer is neurotoxic and carcinogenic, and long-term use is harmful to the human body and the environment. At the same time, there are many parameters that need to be controlled, the process is complicated, and it is difficult to achieve stable preparation. Therefore, how to stably prepare an environmentally friendly, spherical, and high-relative-density ceramic ball is of great significance. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing ceramic microbeads based on an environmentally friendly non-aqueous gel system, which is simple to operate, energy-saving and environmentally friendly, and has concentrated size, high sphericity and high relative density.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: A method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system comprises the following steps: (1) mixing ceramic powder, dispersant and ethyl acetate, and ball milling to obtain a first slurry; (2) adding an acrylic crosslinking agent to the first slurry, wherein the acrylic crosslinking agent is EBECRYL acrylic crosslinking agent, and continuing ball milling to remove bubbles to obtain a second slurry; (3) Mixing polyethylene glycol and water to obtain a polyethylene glycol aqueous solution, pouring oil into the mixture, and obtaining a solidification medium in which the upper layer is an oil layer and the lower layer is a polyethylene glycol aqueous solution layer, wherein the oil is insoluble in the polyethylene glycol and has a density lower than that of the polyethylene glycol and water; (4) under ultraviolet light, dripping the second slurry into the curing medium to form a spherical body, and taking out the spherical body after the size of the spherical body no longer changes to obtain a spherical wet body; (5) Drying and sintering the spherical wet blank to obtain ceramic microbeads.

[0006] In the above-mentioned method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system, preferably, in step (1), the ceramic powder is 60% to 85%, the ethyl acetate is 10% to 35%, and the dispersant is 0.1% to 5% by mass; In the above-mentioned method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system, preferably, in step (2), the amount of the EBECRYL acrylic crosslinking agent added is 5% to 15% of the mass of the ceramic powder.

[0007] In the above-mentioned method for preparing ceramic microbeads based on an environmentally friendly non-aqueous gel system, preferably, in step (3), the mass percentage of polyethylene glycol in the polyethylene glycol aqueous solution is 90% to 98%; the oil is vegetable oil, the thickness of the oil layer is 1 cm to 3 cm, and the thickness of the polyethylene glycol aqueous solution layer is 15 cm to 30 cm.

[0008] In the above-mentioned method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system, preferably, in step (1), the ceramic powder is any one of aluminum oxide, zirconium oxide, silicon carbide, silicon nitride, titanium carbide and titanium nitride; and the dispersant is any one or more of the BYK series dispersants.

[0009] In the above-mentioned method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system, preferably, the ceramic powder is zirconia-toughened alumina ceramic.

[0010] In the above-mentioned method for preparing ceramic microbeads based on an environmentally friendly non-aqueous gel system, preferably, in step (1), the ceramic powder also includes a sintering aid, and the sintering aid is one or more of silicon oxide, calcium oxide, magnesium oxide, lanthanum oxide, yttrium oxide, ytterbium oxide and boron carbide; the ball milling medium is one of aluminum oxide balls, zirconium oxide balls and silicon nitride balls; the material ball mass ratio is 1:1-3; the ball milling time is 12h-48h, and the ball milling speed is 200rad / min-400rad / min.

[0011] In the above-mentioned method for preparing ceramic microbeads based on an environmentally friendly non-aqueous gel system, preferably, in step (2), the EBECRYL acrylic crosslinker is EBECRYL-4765 acrylic crosslinker; the time for continuing ball milling is 5 min to 20 min; the degassing is vacuum degassing, the degassing time is 15 min to 30 min, and the vacuum degree of degassing is 100 Pa to 1000 Pa.

[0012] In the above-mentioned method for preparing ceramic microbeads based on an environmentally friendly non-aqueous gel system, preferably, in step (3), the vegetable oil is one or more of castor oil, peanut oil and palm oil, and the polyethylene glycol is any one or more of polyethylene glycol 200 to 600; the volume ratio of the oil to the polyethylene glycol aqueous solution is 1:10 to 30.

[0013] In the above-mentioned method for preparing ceramic microbeads based on an environmentally friendly non-aqueous gel system, preferably, in step (4), the outlet size of the second slurry when dripping into the curing medium is 0.2 mm to 0.5 mm; and the dripping rate of the second slurry when dripping into the curing medium is 5 drops / second to 20 drops / second.

[0014] In the above-mentioned method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system, preferably, in step (5), the drying system is first dried at 60°C for 6h to 24h, then dried at 90°C for 6h to 24h, and then dried at 120°C for 6h to 24h; the sintering method is pressureless sintering or gas pressure sintering, the sintering temperature is 1500°C to 2300°C, the insulation time is 2h to 5h, the sintering atmosphere is one of air atmosphere, nitrogen atmosphere and argon atmosphere, the heating rate between 0°C and 600°C is 0.2°C / min to 1°C / min, and the heating rate from 600°C to the sintering temperature is 1°C / min to 5°C / min.

[0015] Compared with the prior art, the advantages of the present invention are: (1) The method for preparing ceramic microspheres based on environmentally friendly non-aqueous gel casting of the present invention uses EBECRYL acrylic crosslinker as a curing agent, which has the characteristics of light / wet dual curing, and promotes the green body to be formed by synergistic action with ultraviolet irradiation and oil-polyethylene glycol aqueous solution, wherein the coordination of ultraviolet light with oil and polyethylene glycol aqueous solution is crucial and indispensable. This curing method is not only energy-saving and environmentally friendly, but also can play a complementary and reinforcing role, so that the ceramic microsphere green body can maintain good sphericity, and the prepared ceramic microspheres have concentrated size distribution, high relative density, good sphericity, simple process operation, and easy batch preparation. Compared with the traditional acrylamide gel casting system, the acrylic crosslinker used in the environmentally friendly non-aqueous gel casting of the present invention has the advantages of low toxicity and environmental protection, and does not pollute the human body and the environment.

[0016] (2) The method for preparing ceramic microbeads based on environmentally friendly non-aqueous gel injection molding of the present invention uses ethyl acetate as a solvent, which has good wettability on ceramic powders and can prepare ceramic slurries with high solid content. At the same time, ethyl acetate has a small surface tension, and the capillary force caused during the drying process is small, which can effectively avoid the drying cracking of spherical green bodies. Combined with the molding and liquid phase drying process of the oil-polyethylene glycol aqueous solution, it is easy to achieve safe and efficient molding and drying of spherical ceramic green bodies. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a process flow chart of the method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system according to Example 1 of the present invention.

[0018] Figure 2 This is a schematic diagram of the principle of the method for preparing ceramic microbeads based on an environmentally friendly non-aqueous gel system according to Example 1 of the present invention. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with specific preferred embodiments, but the protection scope of the present invention is not limited thereby. The materials and instruments used in the following embodiments are all commercially available, among which alumina powder is purchased from Alteo Company, product model PL172LSB; zirconium oxide powder is purchased from Oriental Zirconium Industry, product model OZ-3Y; dispersant is purchased from BYK Additives (Shanghai) Co., Ltd., product model BYK-170; EBECRYL acrylic crosslinker is purchased from Allnex Company, product model EBECRYL-4765.

[0020] Example 1 A method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system of the present invention, such as Figure 1 As shown, the following steps are included: (1) Weigh 2000 g of alumina powder, 20 g of dispersant, 450 g of ethyl acetate and 4000 g of alumina balls, place them in a ball mill, and mill them at a speed of 200 r / min for 24 h to obtain a first slurry; (2) Add 150 g of EBECRYL acrylic crosslinker to the first slurry, continue ball milling for 10 min, then pour into a vacuum degassing device and degas for 20 min at a vacuum degree of 1000 Pa to obtain a second slurry; (3) Mix polyethylene glycol and water to obtain a polyethylene glycol aqueous solution, pour oil into it, and obtain a solidification medium in which the upper layer is an oil layer and the lower layer is a polyethylene glycol aqueous solution layer. The oil is insoluble in polyethylene glycol and has a density lower than that of polyethylene glycol and water. The oil is a vegetable oil, specifically castor oil. The polyethylene glycol is polyethylene glycol 400, and the mass percentage of polyethylene glycol in the polyethylene glycol aqueous solution is 95%; the thickness of the oil layer is 2 cm, the thickness of the polyethylene glycol aqueous solution layer is 25 cm, and the volume ratio of the oil to the polyethylene glycol aqueous solution is 1:12.5; (4) If Figure 2 As shown, the second slurry is transferred to a storage tank, and then extracted by a delivery pump, and pumped into a dropper through a peristaltic pump. A vibrating dripper is provided at the output end of the dropper. The second slurry forms droplets at the discharge port of the vibrating dripper. The discharge port size is 0.2 mm. Under ultraviolet light, the second slurry is dripped into the curing medium at a speed of 6 drops / second to form a spherical blank. After the size of the spherical blank no longer changes, it is taken out to obtain a solidified spherical wet blank. (5) The spherical wet blank is transferred to an oven for drying at a drying rate of 60°C*8h+90°C*8h+120°C*8h. The dried blank is sintered in a high-temperature sintering furnace to obtain alumina ceramic microbeads. The sintering method is pressureless sintering, the sintering atmosphere is air atmosphere, the sintering temperature is 1600°C, the holding time is 3h, the heating rate between 0°C and 600°C is 0.4°C / min, and the heating rate from 600°C to the sintering temperature is 2°C / min.

[0021] Example 2 A method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system of the present invention, such as Figure 1 As shown, the following steps are included: (1) Weigh 2000 g of alumina powder, 20 g of dispersant, 400 g of ethyl acetate and 4000 g of alumina balls and place them in a ball mill, and mill them at a speed of 200 r / min for 24 h to obtain a first slurry; (2) Add 200 g of EBECRYL acrylic crosslinker to the first slurry, continue ball milling for 10 min, then pour into a vacuum degassing device and degas for 20 min at a vacuum degree of 1000 Pa to obtain a second slurry; (3) Mix polyethylene glycol and water to obtain a polyethylene glycol aqueous solution, pour oil into it, and obtain a solidification medium in which the upper layer is an oil layer and the lower layer is a polyethylene glycol aqueous solution layer. The oil is insoluble in polyethylene glycol and has a density lower than that of polyethylene glycol and water. The oil is vegetable oil, specifically palm oil; the polyethylene glycol is polyethylene glycol 400, and the mass percentage of polyethylene glycol in the polyethylene glycol aqueous solution is 95%; the thickness of the oil layer is 2 cm, and the thickness of the polyethylene glycol aqueous solution layer is 20 cm; the volume ratio of the oil to the polyethylene glycol aqueous solution is 1:10; (4) If Figure 2As shown, the second slurry is transferred to a storage tank, and then extracted by a delivery pump, and pumped into a dropper through a peristaltic pump. A vibrating dripper is provided at the output end of the dropper. The second slurry forms droplets at the discharge port of the vibrating dripper. The discharge port size is 0.2 mm. Under ultraviolet light, the second slurry is dripped into the curing medium at a speed of 6 drops / second to form a spherical blank. After the size of the spherical blank no longer changes, it is taken out to obtain a solidified spherical wet blank. (5) The spherical wet blank is transferred to an oven for drying, and the drying system is 60℃*8h+90℃*8h+120℃*8h; the dried blank is sintered in a high-temperature sintering furnace to obtain alumina ceramic microbeads. The sintering method is pressureless sintering, the sintering atmosphere is air atmosphere, the sintering temperature is 1600℃, the holding time is 3h, the heating rate between 0℃ and 600℃ is 0.4℃ / min, and the heating rate from 600℃ to the sintering temperature is 2℃ / min.

[0022] Example 3 A method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system of the present invention, such as Figure 1 As shown, the following steps are included: (1) Weighing 3000 g of zirconium oxide powder, 30 g of dispersant, 600 g of ethyl acetate and 6000 g of zirconium oxide balls, placing them in a ball mill, and ball milling them at a speed of 250 r / min for 36 h to obtain a first slurry; (2) Add 300 g of EBECRYL acrylic crosslinker to the first slurry, continue ball milling for 10 min, then pour into a vacuum degassing device and degas for 20 min at a vacuum degree of 1000 Pa to obtain a second slurry; (3) Mix polyethylene glycol and water to obtain a polyethylene glycol aqueous solution, pour oil into it, and obtain a solidification medium in which the upper layer is an oil layer and the lower layer is a polyethylene glycol aqueous solution layer. The oil is insoluble in polyethylene glycol and has a density lower than that of polyethylene glycol and water. The oil is a vegetable oil, specifically castor oil; the polyethylene glycol is polyethylene glycol 400, and the mass percentage of polyethylene glycol in the polyethylene glycol aqueous solution is 95%; the thickness of the oil layer is 2 cm, and the thickness of the polyethylene glycol aqueous solution layer is 20 cm; the volume ratio of the oil to the polyethylene glycol aqueous solution is 1:10; (4) If Figure 2 As shown, the second slurry is transferred to a storage tank, and then extracted by a delivery pump, and pumped into a dripping tube through a peristaltic pump. A vibrating dripper is provided at the output end of the dripping tube. The second slurry forms droplets at the discharge port of the vibrating dripper, and the discharge port size is 0.2 mm. Under ultraviolet light, the second slurry is dripped into the curing medium at a speed of 6 drops / second to form a spherical blank. After the size of the spherical blank no longer changes, it is taken out to obtain a solidified spherical wet blank; (5) The spherical wet blank is transferred to an oven for drying at a drying rate of 60°C*8h+90°C*8h+120°C*8h. The dried blank is sintered in a high-temperature sintering furnace to obtain alumina ceramic microbeads. The sintering method is pressureless sintering, the sintering atmosphere is air atmosphere, the sintering temperature is 1550°C, the holding time is 3h, the heating rate between 0°C and 600°C is 0.4°C / min, and the heating rate from 600°C to the sintering temperature is 2°C / min.

[0023] Comparative Example 1 A method for preparing ceramic microbeads is basically the same as that of Example 1, except that in step (3), the solidifying medium is only castor oil.

[0024] Comparative Example 2 A method for preparing ceramic microbeads is basically the same as that of Example 1, except that in step (3), the solidification medium is only a polyethylene glycol aqueous solution.

[0025] Comparative Example 3 A method for preparing ceramic microbeads is substantially the same as that of Example 1, except that in step (4), no ultraviolet light irradiation is used.

[0026] Table 1 Performance test table of Examples 1 to 3 and Comparative Examples 1 to 3

[0027] As can be seen from Table 1, the relative density of the ceramic microbeads provided by Examples 1 to 3 and Comparative Examples 1 to 3 is greater than 99%, indicating that the method for preparing ceramic microbeads based on environmentally friendly non-aqueous gel injection molding provided by the present invention can prepare dense ceramic microbeads with high mechanical strength. In addition, it can be seen that the ceramic microbeads provided by Examples 1 to 3 are more concentrated in size and have a higher sphericity, all greater than 0.95. In contrast, the sphericity of the ceramic microbeads provided by Comparative Examples 1 to 3 is a maximum of 0.92, and the size distribution of the microbeads is wider. The alumina ceramics provided by Examples 1 to 2 have a higher sphericity and a more concentrated size distribution than the alumina ceramics provided by Comparative Examples 1 to 3, respectively. Therefore, the method for preparing ceramic microbeads based on environmentally friendly non-aqueous gel injection molding provided by the present invention can achieve the preparation of high-performance ceramic microbeads.

[0028] Although the present invention is disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any technician familiar with the art can use the above disclosed methods and technical contents to make many possible changes and modifications to the technical solutions of the present invention without departing from the spirit and technical solutions of the present invention, or modify them into equivalent embodiments of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solutions of the present invention still fall within the scope of protection of the technical solutions of the present invention.

Claims

1. A method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system, characterized in that: The following steps are involved: (1) mixing ceramic powder, dispersant and ethyl acetate, and ball milling to obtain a first slurry; (2) adding an acrylic crosslinking agent to the first slurry, wherein the acrylic crosslinking agent is EBECRYL acrylic crosslinking agent, and continuing ball milling to remove bubbles to obtain a second slurry; (3) Mixing polyethylene glycol and water to obtain a polyethylene glycol aqueous solution, pouring oil into the mixture, and obtaining a solidification medium in which the upper layer is an oil layer and the lower layer is a polyethylene glycol aqueous solution layer, wherein the oil is insoluble in the polyethylene glycol and has a density lower than that of the polyethylene glycol and water; (4) under ultraviolet light, dripping the second slurry into the curing medium to form a spherical body, and taking out the spherical body after the size of the spherical body no longer changes to obtain a spherical wet body; (5) Drying and sintering the spherical wet blank to obtain ceramic microbeads.

2. The method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system according to claim 1, characterized in that: In step (1), by mass fraction, the ceramic powder is 60% to 85%, the ethyl acetate is 10% to 35%, and the dispersant is 0.1% to 5%.

3. The method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system according to claim 2, characterized in that: In step (2), the amount of the EBECRYL acrylic crosslinking agent added is 5% to 15% of the mass of the ceramic powder.

4. The method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system according to claim 3, characterized in that: In step (3), the mass percentage of polyethylene glycol in the polyethylene glycol aqueous solution is 90% to 98%; the oil is vegetable oil, the thickness of the oil layer is 1 cm to 3 cm, and the thickness of the polyethylene glycol aqueous solution layer is 15 cm to 30 cm.

5. The method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system according to any one of claims 1 to 4, characterized in that: In step (1), the ceramic powder is any one of aluminum oxide, zirconium oxide, silicon carbide, silicon nitride, titanium carbide and titanium nitride; and the dispersant is any one or more of the BYK series dispersants.

6. The method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system according to any one of claims 1 to 4, characterized in that: In step (1), the ceramic powder also includes a sintering aid, which is one or more of silicon oxide, calcium oxide, magnesium oxide, lanthanum oxide, yttrium oxide, ytterbium oxide and boron carbide; the ball milling medium is one of aluminum oxide balls, zirconium oxide balls and silicon nitride balls; the material ball mass ratio is 1:1-3; the ball milling time is 12h-48h, and the ball milling speed is 200rad / min-400rad / min.

7. The method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system according to any one of claims 1 to 4, characterized in that: In step (2), the EBECRYL acrylic crosslinking agent is EBECRYL-4765 acrylic crosslinking agent; the time for continuing ball milling is 5 min to 20 min; the degassing is vacuum degassing, the degassing time is 15 min to 30 min, and the vacuum degree of degassing is 100 Pa to 1000 Pa.

8. The method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system according to claim 4, characterized in that: In step (3), the vegetable oil is one or more of castor oil, peanut oil and palm oil, and the polyethylene glycol is any one or more of polyethylene glycol 200-600; the volume ratio of the oil to the polyethylene glycol aqueous solution is 1:10-30.

9. The method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system according to any one of claims 1 to 4 or 8, characterized in that: In step (4), the size of the outlet when the second slurry is dripped into the solidifying medium is 0.2 mm to 0.5 mm; the dripping rate when the second slurry is dripped into the solidifying medium is 5 drops / second to 20 drops / second.

10. The method for preparing ceramic microspheres based on an environmentally friendly non-aqueous gel system according to any one of claims 1 to 4 or 8, characterized in that: In step (5), the drying system is first drying at 60°C for 6h to 24h, then drying at 90°C for 6h to 24h, and then drying at 120°C for 6h to 24h; the sintering method is pressureless sintering or gas pressure sintering, the sintering temperature is 1500°C to 2300°C, the insulation time is 2h to 5h, the sintering atmosphere is one of air atmosphere, nitrogen atmosphere and argon atmosphere, the heating rate between 0°C and 600°C is 0.2°C / min to 1°C / min, and the heating rate from 600°C to the sintering temperature is 1°C / min to 5°C / min.

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