CN117069485A - Production process of high-purity spheroidal alumina for display glass - Google Patents

Abstract

The application provides a production process of high-purity spheroidal alumina for display glass, which belongs to the technical field of alumina and comprises the following steps: preparing raw materials; putting the mixed alumina powder into a ball mill for ball milling to obtain more uniform particle size distribution; the alumina powder after ball milling is aggregated into uniform particle groups through a wet granulation or dry granulation process; screening and selecting the granulated particle clusters to control the particle size distribution of the obtained spherical alumina; the sieved particle clusters pass through drying equipment to remove water in the particle clusters, so that the particle clusters have certain fluidity; shaping the dried particle mass by pressing or injection molding equipment according to the requirement to obtain spherical alumina with a required shape; placing the formed spherical alumina into a sintering furnace, and performing high-temperature sintering treatment to enable the particles to be combined into hard alumina particles at high temperature; cooling; screening; and (5) packaging.

Description

Production process of high-purity spheroidal alumina for display glass

Technical Field

The application relates to the technical field of alumina, in particular to a production process of high-purity spheroidal alumina for display glass.

Background

Alumina, also known as aluminum stone, aluminum oxide, sapphire, is a common inorganic compound, consisting of two elements, aluminum and oxygen. It has high melting point and hardness, and is a colorless or white crystal. It is chemically stable, insoluble in water and most organic solvents.

Alumina has a variety of uses. Alumina is commonly used in the manufacture of high voltage capacitors, insulating materials and refractory materials due to its good insulating properties and high temperature resistance. It can be used to produce ceramic products, abrasive materials, catalysts and coatings. Alumina is also commonly used as a precious stone material, where higher purity alumina crystals can be used to make artificial sapphire.

In addition, the alumina nanoparticles also have special properties such as high specific surface area and strong adsorption performance, and thus are widely used in the fields of catalysts, sensors, energy storage materials, and the like.

The existing alumina production is uneven in grinding, so that the specific surface area and the reactivity of the alumina product after the production cannot be improved easily, and therefore, the production process of the high-purity spherical alumina for glass is provided.

Disclosure of Invention

In view of the above, the present application provides a process for producing high purity spheroidal alumina for display glass.

In order to solve the technical problems, the application provides a production process of high-purity spheroidal alumina for display glass, which comprises the following steps:

the first step: raw material preparation: selecting alumina powder suitable for producing high-purity spheroidal alumina as a raw material, and mixing according to a certain proportion;

and a second step of: ball milling: putting the mixed alumina powder into a ball mill for ball milling to obtain more uniform particle size distribution;

and a third step of: granulating: the alumina powder after ball milling is aggregated into uniform particle groups through a wet granulation or dry granulation process;

fourth step: particle size control: screening and selecting the granulated particle clusters to control the particle size distribution of the obtained spherical alumina;

fifth step: and (3) drying: the sieved particle clusters pass through drying equipment to remove water in the particle clusters, so that the particle clusters have certain fluidity;

sixth step: and (3) forming: shaping the dried particle mass by pressing or injection molding equipment according to the requirement to obtain spherical alumina with a required shape;

seventh step: sintering: placing the formed spherical alumina into a sintering furnace, and performing high-temperature sintering treatment to enable the particles to be combined into hard alumina particles at high temperature;

eighth step: and (3) cooling: after sintering, cooling the sintered alumina particles in the furnace to room temperature;

ninth step: and (3) screening: sieving the cooled alumina particles to realize standardized treatment of granularity;

tenth step: and (3) packaging: packaging the sieved high-purity spherical alumina for storage and use.

Preferably, the mixing in the first step requires addition of auxiliary agents, wherein the auxiliary agents comprise a binding agent, an anti-binding agent and a thickening agent.

Preferably, the ball milling time in the second step is 15min, and the rotating speed is 3000 RPM.

Preferably, the wet granulation in the third step adopts the following steps:

mixing the ball-milled alumina powder with a certain proportion of solvent and binder, and spraying into small liquid drops through a sprayer;

then the liquid drops are contacted with hot air to enable the solvent to evaporate rapidly, so as to form bulk particles with larger particle size.

Preferably, the dry granulation in the third step adopts the following steps:

in the compression granulation method, a certain amount of a binder or an additive is added to the alumina powder after ball milling, and then the powder is compressed by a granulation machine to be aggregated into granules.

Preferably, the specific content of the fourth step is:

the particle groups with different particle diameters can be obtained through multi-stage screening, and the purpose of screening is to classify the particle groups according to the size so as to control the particle size distribution.

The separation is performed by using a centrifugal separator, a gravity separator and a gas flow separator device, and the selection is performed according to the density, shape, size and other characteristics of the particles.

Preferably, the specific content of the fifth step is as follows: the method is carried out by adopting hot air drying, vacuum drying, spray drying and other modes, the drying time is 6-8H, and the drying temperature is 120-200 ℃.

Preferably, the forming in the sixth step includes two modes:

and (5) press forming: and (3) placing the dried particle clusters into a die of a pressing machine or a forming machine, and pressing under a certain pressure.

Injection molding: the dried pellet is placed in a bin of an injection molding machine, and the pellet material is injected into a mold by high-pressure injection, wherein the mold gives the pellet a desired shape to form a molded article.

Preferably, in the seventh step, the sintering initiation temperature is 150 degrees celsius, the sintering time is 45 minutes, and the sintering temperature is increased by 5 degrees celsius every five minutes.

Preferably, the eighth cooling treatment uses a natural cooling method, namely, alumina particles in the sintering furnace are placed in a ventilation environment, and the temperature of the particles is gradually reduced by a natural heat dissipation mode.

Preferably, the specific steps of the ninth step include the following:

preparing a screening device: preparing a screen or sieve with proper pore size and mounting the screen or sieve on a sieve frame;

adding particles to be screened: pouring the cooled alumina particles into a sieve frame or sieving equipment;

and (3) screening: shaking or vibrating the screen frame to move the particles over the screen, the larger particles being unable to pass through the openings and deposit over the screen, and the smaller particles being able to pass through the openings and through the bottom of the screen;

separating particles: the sieved particles with different particle sizes are separated, so that fine particles with the lower parts passing through the sieve holes can be collected, and meanwhile, larger particles with the upper parts not passing through the sieve holes are subjected to subsequent treatment;

repeated screening: if alumina particles of different particle sizes are desired, multiple passes may be made with screens of different pore sizes to achieve further particle size standardization.

In summary, compared with the prior art, the application has at least the following beneficial technical effects:

1. the particle size of the alumina powder can be thinned to a certain degree through the grinding effect, so that the specific surface area and the reactivity of the product are improved.

2. In the ball milling process, the particles are continuously collided, ground and mixed, so that the particles are distributed more uniformly, and the non-uniformity among the particles is reduced.

3. The rotation and friction effects of the ball mill enable the alumina powder, the grinding medium and the liquid to be mixed more fully, so that the added auxiliary agent is uniformly dispersed in the powder, and the uniformity and stability of the auxiliary agent are improved.

Drawings

FIG. 1 is a schematic flow chart showing the production process of high purity spheroidal alumina for glass according to the application.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to fig. 1 of the embodiments of the present application. It will be apparent that the described embodiments are some, but not all, embodiments of the application. All other embodiments, which are obtained by a person skilled in the art based on the described embodiments of the application, fall within the scope of protection of the application.

As shown in fig. 1: the embodiment provides a production process of high-purity spheroidal alumina for display glass, which comprises the following steps:

the first step: raw material preparation: alumina powder suitable for producing high-purity spheroidal alumina is selected as a raw material and mixed according to a certain proportion.

Alumina powder suitable for producing high-purity spheroidal alumina is selected as a raw material. The alumina powder should have a high purity, a relatively uniform particle distribution and appropriate physicochemical properties to ensure purity and uniformity of the final product.

Next, alumina powder was mixed in a certain ratio. The determination of the mixing proportion requires comprehensive consideration of factors such as product requirements, production equipment, process conditions and the like. In general, additives such as binders, anti-binders, thickeners, etc. may be added in a certain proportion according to the need to improve the formability and the property stability of the product.

In the selection of the alumina powder and the determination of the mixing ratio, strict quality control and test are required according to the actual situation. The quality of raw materials and the accuracy of proportioning are critical to the quality of the final product, so that the operation is required to be strictly carried out according to the specified standard and flow in the production process so as to ensure that the high-purity spherical alumina product for glass with high quality is produced.

And a second step of: ball milling: the mixed alumina powder is put into a ball mill for ball milling so as to obtain more uniform particle size distribution.

The ball mill is a device for grinding in a liquid medium, and consists of a roller, a grinding medium and a transmission device. During ball milling, the mixed alumina powder, milling media and a proportion of liquid (typically water) are placed in a ball mill, and the machine is then rotated to grind the powder particles into smaller particles by friction and impact forces.

By ball milling, the following several effects can be obtained:

particle refinement: the particle size of the alumina powder can be thinned to a certain degree through the grinding effect, so that the specific surface area and the reactivity of the product are improved.

Particle homogenization: in the ball milling process, the particles are continuously collided, ground and mixed, so that the particles are distributed more uniformly, and the non-uniformity among the particles is reduced.

The mixing effect is enhanced: the rotation and friction effects of the ball mill enable the alumina powder, the grinding medium and the liquid to be mixed more fully, so that the added auxiliary agent is uniformly dispersed in the powder, and the uniformity and stability of the auxiliary agent are improved.

It should be noted that during the ball milling process, the appropriate ball milling time and type and proportion of milling media should be determined according to specific process conditions and product requirements. Too long ball milling time may lead to ultra-fine powder and excessive abrasion of particles, affecting the performance of the product. Therefore, in actual production, proper adjustment is carried out according to experience and experimental results to obtain the best ball milling effect

And a third step of: granulating: the alumina powder after ball milling is aggregated into uniform particle groups through a wet granulation or dry granulation process.

The granulation is a process of gathering the ball-milled alumina powder into relatively uniform particle groups through a wet granulation or dry granulation process.

Wet granulation: wet granulation is typically performed by spray drying or slurry granulation. In the spray drying method, the ball-milled alumina powder is mixed with a solvent and a binder in a certain proportion, sprayed into small liquid drops by a sprayer, and then the liquid drops are contacted with hot air, so that the solvent is quickly evaporated, and the agglomerate-shaped particles with larger particle size are formed. The slurry granulating method is to mix the ball-milled alumina powder with a certain proportion of solvent and binder to form slurry, and then make the slurry form particles by the action of extrusion, shearing and the like.

Dry granulating: dry granulation generally employs compression granulation. In the compression granulation method, a certain amount of a binder or an additive is added to the alumina powder after ball milling, and then the powder is compressed by a granulation machine such as a tablet press or a granulator to be agglomerated into granules.

The purpose of pelletization is to gather the ball-milled alumina powder into relatively uniform particle groups so as to improve the fluidity, the packing property and the processing property of the product. In the granulating process, proper granulating process and process parameters, such as solvent selection, binder addition amount, operating parameters of granulating machinery and the like, are determined according to specific process conditions and product requirements so as to obtain ideal granulating effect.

Fourth step: particle size control: and screening and selecting the granulated particle clusters to control the particle size distribution of the obtained spherical alumina.

Particle size control is a process of sieving and selecting particles of the granulated particle mass to control the particle size distribution of the obtained spherical alumina.

And (3) screening: the screening is to separate the granulated granule by screens with different apertures to separate out the granules meeting the requirements, and the granules not meeting the requirements are screened out. Through multistage screening, particle groups with different particle diameters can be obtained. The purpose of the screening is to sort the clusters by size to control the particle size distribution.

Selecting particles: the granule selection is to select the granules meeting the requirements according to a certain standard aiming at the screened granule group. The selection of particles is usually performed by using a centrifugal separator, a gravity separator, a gas separator, or the like, and may be selected according to the density, shape, size, or the like of the particles. The purpose of the particle selection is to further screen out the target particles to achieve more precise particle size control.

In the process of particle size control, it is also necessary to analyze the particle size of the obtained particles, and a laser particle sizer, an electron microscope, etc. are commonly used. By means of particle size analysis, specific data of the particle size distribution can be determined to adjust the parameters of granulation and selection, and to optimize the particle size distribution of the product.

Particle size control is an important link in the granulation process, and the control of particle size distribution is directly related to the quality and performance of the product. Through reasonable screening and grain selecting operation, the required grain distribution can be obtained, and the requirements of different application fields are met.

Fifth step: and (3) drying: and (3) passing the sieved particle groups through a drying device to remove water in the particle groups so that the particle groups have certain fluidity.

The drying is to treat the particle clusters after sieving and selecting particles by a drying device to remove the moisture in the particle clusters, so that the particles have certain fluidity.

The purpose of the drying is to remove moisture from the particles, as moisture may have an effect on the flowability of the particles and dust generation. The moisture content of the granules can be reduced to a desired level by the drying process for subsequent packaging, storage, and transportation.

The drying equipment is usually performed by adopting modes of hot air drying, vacuum drying, spray drying and the like. The hot air drying is to heat air and pass the air through the particle mass, and evaporate moisture in the particles in the drying process. Vacuum drying is drying under low pressure environment, and the water in the particles is evaporated by utilizing the boiling point reduction of water. Spray drying is the spraying of a mass of particles into hot air, the moisture evaporating rapidly upon contact with the hot gas.

The control of the drying parameters comprises drying temperature, drying time, drying air flow rate and the like, and is adjusted according to the characteristics of the particles and the product requirements. The control of the drying time and temperature is determined according to parameters such as the water content and the size of the particles, so that the problems of cracks or deformation of the particles caused by excessive drying are avoided while the drying effect is ensured.

The drying operation has important influence on granularity control and product quality, and the proper drying process can enable the particle clusters to reach the required drying degree and have certain fluidity, so that the method is beneficial to the follow-up procedures.

Sixth step: and (3) forming: and (3) molding the dried particle clusters through pressing or injection molding equipment according to the requirements to obtain spherical alumina with a required shape.

The forming means that the dried particle mass is formed by pressing or injection molding equipment to obtain the spherical alumina product with the required shape.

The molding process is generally divided into two modes, compression molding and injection molding.

The press forming is to put the dried particle into a press or a die of a forming machine to be pressed under a certain pressure. In the pressing process, the particle clusters are subjected to the action of pressure, so that the internal particles are communicated and combined with each other to form a certain strength and shape. The pressure and time of compaction are generally adjusted according to the characteristics of the granules and the product requirements to ensure the compaction and consistency of the formation.

In injection molding, the dried pellet is placed in a bin of an injection molding machine, and a particulate material is injected into a mold by high-pressure injection, and the mold is provided with a desired shape of the pellet to form a molded product. In the injection molding process, the pellet mass fills the mold cavity sufficiently under the force of the high pressure jet and is then formed into a solid molded article by a curing or drying process.

Whether compression molded or injection molded, the molded spherical alumina product requires curing, baking or sintering to obtain its final physical and chemical properties. The parameters of the forming process, such as pressure, temperature, forming speed, etc., can affect the compactness, particle size distribution, shape, etc., of the final product, so that reasonable adjustment and control are required according to the specific product requirements.

The forming is a very important step in the spherical alumina industry, which can form the particle clusters into the desired shape, meet the needs of customers, and provide a good basis for subsequent processing and applications.

Seventh step: sintering: and (3) placing the formed spherical alumina into a sintering furnace, and performing high-temperature sintering treatment to enable the particles to be combined into hard alumina particles at high temperature.

Sintering means that the formed spherical alumina product is placed in a sintering furnace, and the particles are combined into hard alumina particles at high temperature through high-temperature treatment.

Sintering is one of important process links of spherical alumina, and the structure and performance of the product can be improved through high-temperature treatment. During sintering, the spherical alumina particles are bonded to each other by interaction forces between the particles at high temperatures. These interactions include inter-particle diffusion, surface extrusion, and formation of molten mineral phases.

The sintering temperature is typically controlled within the sintering temperature range of the spherical alumina material, depending on the nature of the material and the product requirements. Too high sintering temperature can cause excessive melting of particles, and strength and structural stability of the product are reduced; too low sintering temperature cannot achieve the effect of particle bonding. Therefore, the control of the sintering temperature is very important, and needs to be adjusted according to the characteristics of the material and the product requirements.

The sintering process may also be enhanced by adding fluxing agents or sintering aids. The fluxing agent can reduce sintering temperature and promote the combination between particles; the sintering aid can change the activity of the material surface and improve the bonding capability and stability between particles. The addition of fluxing agents or sintering aids can improve the sintering effect and the product quality to some extent.

After sintering treatment, the spherical alumina particles become harder and more stable, and have higher compactibility and high temperature resistance. The sintered spherical alumina product can be processed and applied subsequently, such as ceramic material, abrasive, filler and the like, and can be widely applied to various fields of electronics, chemical industry, metallurgy and the like.

Eighth step: and (3) cooling: after sintering, the sintered alumina particles in the furnace are cooled to room temperature.

Cooling means that after the sintering process is finished, the alumina particles in the sintering furnace are subjected to cooling treatment, so that the temperature of the alumina particles is gradually reduced to room temperature.

During sintering, the bonding force between the particles is enhanced due to the high temperature treatment, forming hard alumina particles. However, the high temperature state of the sintered particles may cause an accumulation of internal stress between the particles, and thus it is necessary to cool it to room temperature to reduce the internal stress of the particles and improve the structural stability of the product.

The cooling treatment generally uses a natural cooling method, namely, alumina particles in a sintering furnace are placed in a ventilation environment, and the temperature of the particles is gradually reduced by a natural heat dissipation mode. This process requires a certain amount of time, and the cooling time is usually determined by parameters such as particle size, sintering temperature and sintering time.

During cooling, care is taken to avoid abrupt temperature changes so as not to cause thermal stress cracking of the particles. At the same time, care is taken to prevent collisions and crushing between particles to avoid breakage or deformation of the particles.

After cooling, the sintered alumina particles will gradually cool to room temperature. The particles at this time have high hardness and structural stability and can be processed and applied in the next step. The cooled alumina particles can be used for preparing ceramic materials, abrasive materials, fillers and the like, and can also be used as raw materials in other industrial fields.

Ninth step: and (3) screening: and sieving the cooled alumina particles to realize the standardized treatment of granularity.

During sieving, screens or sieves of different pore sizes are typically used for operation. The pore size of the screen is selected according to the requirement, and screening operations of different stages such as coarse screening, medium screening, fine screening and the like can be performed according to the actual requirement.

The screening steps are generally as follows:

preparing a screening device: a screen or sieve of appropriate pore size is prepared and mounted on a screen frame.

Adding particles to be screened: pouring the cooled alumina particles into a sieve frame or sieving equipment.

And (3) screening: the screen frame is shaken or vibrated to move the particles over the screen. Larger particles cannot pass through the mesh and settle above the screen, while smaller particles pass through the mesh and pass through the bottom of the screen.

Separating particles: the sieved particles with different particle sizes are separated, so that fine particles with the lower part passing through the sieve holes can be collected, and meanwhile, larger particles with the upper part not passing through the sieve holes are subjected to subsequent treatment.

Repeated screening: if alumina particles of different particle sizes are desired, multiple passes may be made with screens of different pore sizes to achieve further particle size standardization.

After sieving, alumina particles of different sizes can be selected and collected as desired. Thus, the particle size distribution of the particles can be ensured to meet the preset requirements, and the requirements of different application fields can be met.

Tenth step: and (3) packaging: packaging the sieved high-purity spherical alumina for storage and use.

While the foregoing is directed to the preferred embodiments of the present application, it will be appreciated by those skilled in the art that various modifications and adaptations can be made without departing from the principles of the present application, and such modifications and adaptations are intended to be comprehended within the scope of the present application.

Claims (10)

1. The production process of the high-purity spheroidal alumina for the display glass is characterized by comprising the following steps of:

the first step: raw material preparation: selecting alumina powder suitable for producing high-purity spheroidal alumina as a raw material, and mixing according to a certain proportion;

and a second step of: ball milling: putting the mixed alumina powder into a ball mill for ball milling to obtain more uniform particle size distribution;

and a third step of: granulating: the alumina powder after ball milling is aggregated into uniform particle groups through a wet granulation or dry granulation process;

fourth step: particle size control: screening and selecting the granulated particle clusters to control the particle size distribution of the obtained spherical alumina;

fifth step: and (3) drying: the sieved particle clusters pass through drying equipment to remove water in the particle clusters, so that the particle clusters have certain fluidity;

sixth step: and (3) forming: shaping the dried particle mass by pressing or injection molding equipment according to the requirement to obtain spherical alumina with a required shape;

seventh step: sintering: placing the formed spherical alumina into a sintering furnace, and performing high-temperature sintering treatment to enable the particles to be combined into hard alumina particles at high temperature;

eighth step: and (3) cooling: after sintering, cooling the sintered alumina particles in the furnace to room temperature;

ninth step: and (3) screening: sieving the cooled alumina particles to realize standardized treatment of granularity;

tenth step: and (3) packaging: packaging the sieved high-purity spherical alumina for storage and use.

2. The process for producing high purity spheroidal alumina for display glass according to claim 1, wherein: the mixing in the first step requires addition of an auxiliary agent, wherein the auxiliary agent comprises a binding agent, an anti-binding agent and a thickening agent.

3. The process for producing high purity spheroidal alumina for display glass according to claim 1, wherein: the ball milling time in the second step is 15min, and the rotating speed is 3000 RPM.

4. The process for producing high purity spheroidal alumina for display glass according to claim 1, wherein: the wet granulation in the third step adopts the following steps:

mixing the ball-milled alumina powder with a certain proportion of solvent and binder, and spraying into small liquid drops through a sprayer;

then the liquid drops are contacted with hot air, so that the solvent is quickly evaporated, and massive particles with larger particle size are formed;

the dry granulation adopts the following steps:

in the compression granulation method, a certain amount of a binder or an additive is added to the alumina powder after ball milling, and then the powder is compressed by a granulation machine to be aggregated into granules.

5. The process for producing high purity spheroidal alumina for display glass according to claim 1, wherein: the specific content of the fourth step is as follows:

the particle groups with different particle diameters can be obtained through multi-stage screening, and the purpose of screening is to classify the particle groups according to the size so as to control the particle size distribution.

The separation is performed by using a centrifugal separator, a gravity separator and a gas flow separator device, and the selection is performed according to the density, shape, size and other characteristics of the particles.

6. The process for producing high purity spheroidal alumina for display glass according to claim 1, wherein: the fifth step comprises the following specific contents: the method is carried out by adopting hot air drying, vacuum drying, spray drying and other modes, the drying time is 6-8H, and the drying temperature is 120-200 ℃.

7. The process for producing high purity spheroidal alumina for display glass according to claim 1, wherein: the forming in the sixth step includes the following two modes:

and (5) press forming: and (3) placing the dried particle clusters into a die of a pressing machine or a forming machine, and pressing under a certain pressure.

Injection molding: the dried pellet is placed in a bin of an injection molding machine, and the pellet material is injected into a mold by high-pressure injection, wherein the mold gives the pellet a desired shape to form a molded article.

8. The process for producing high purity spheroidal alumina for display glass according to claim 1, wherein: in the seventh step, the initial sintering temperature is 150 ℃, the sintering time is 45min, and the sintering temperature is increased by 5 ℃ every five minutes.

9. The process for producing high purity spheroidal alumina for display glass according to claim 1, wherein: and eighth step, cooling treatment adopts a natural cooling method, namely, alumina particles in a sintering furnace are placed in a ventilation environment, and the temperature of the particles is gradually reduced through a natural heat dissipation mode.

10. The process for producing high purity spheroidal alumina for display glass according to claim 1, wherein the ninth step comprises the following steps:

preparing a screening device: preparing a screen or sieve with proper pore size and mounting the screen or sieve on a sieve frame;

adding particles to be screened: pouring the cooled alumina particles into a sieve frame or sieving equipment;

and (3) screening: shaking or vibrating the screen frame to move the particles over the screen, the larger particles being unable to pass through the openings and deposit over the screen, and the smaller particles being able to pass through the openings and through the bottom of the screen;

separating particles: the sieved particles with different particle sizes are separated, so that fine particles with the lower parts passing through the sieve holes can be collected, and meanwhile, larger particles with the upper parts not passing through the sieve holes are subjected to subsequent treatment;

repeated screening: if alumina particles of different particle sizes are desired, multiple passes may be made with screens of different pore sizes to achieve further particle size standardization.