阅读说明：本技术 一种粉体造粒压片方法 (Powder granulation and tabletting method ) 是由 毛召召 李志涛 周游 陈刚 熊良明 杜立华 于 2021-07-12 设计创作，主要内容包括：本发明提出了一种粉体造粒压片方法,先将加入另外粘结剂粉体进行湿法球磨,混合均匀后整体烘干过粗筛得到粉体,结块的粉体进行破碎后再过筛造粒得到压片粉体,接着将压片粉体使用自动压片机压片,最后升温排水排胶后进行烧结,烧结后的压片实际重量与需求重量偏差1％以下,实际尺寸与平均尺寸偏差1％以下。本发明工艺简单,通过球磨湿混避免了粘结剂单独加入造成的分布不均的问题；混合有粘结剂的粉体烘干后通过破碎机破碎成细粉后再造粒,增强了粉体流动性,过筛控制粒径,形成合适的粒径分布,自动压片避免人为干扰,效率高,片材一致性好；烧结后形成了高强度、高精度片材。(The invention provides a powder granulation and tabletting method, which comprises the steps of firstly adding additional binder powder for wet ball milling, uniformly mixing, then drying the whole body and screening the powder by a coarse screen to obtain powder, crushing the agglomerated powder, then sieving and granulating to obtain tabletting powder, then tabletting the tabletting powder by an automatic tabletting machine, finally heating, draining water, discharging glue and then sintering, wherein the deviation of the actual weight and the required weight of the sintered tabletting is less than 1%, and the deviation of the actual size and the average size is less than 1%. The invention has simple process, and avoids the problem of uneven distribution caused by adding the binder independently through ball milling and wet mixing; the powder mixed with the binder is dried and crushed into fine powder by a crusher to form granules, so that the flowability of the powder is enhanced, the particle size is sieved and controlled to form proper particle size distribution, automatic tabletting is realized, the artificial interference is avoided, the efficiency is high, and the consistency of sheets is good; after sintering, a high-strength and high-precision sheet is formed.)

1. A powder granulation and tabletting method is characterized by comprising the following steps:

step one, mixing materials: weighing the powder according to the proportion, and adding the powder into a ball mill with prepared grinding balls for ball-milling wet mixing;

step two, granulation: after the wet mixing of the ball mill is finished, the whole body is dried and sieved by a sieve with 10 to 20 meshes so as to separate the powder from the grinding balls, the powder is crushed by a crusher so that the granularity of the powder is less than 100 meshes, and the powder is sieved and granulated again to obtain tabletting powder;

step three, tabletting: filling the tabletting powder into a die, and tabletting by using an automatic tabletting machine to obtain a primary sheet;

step four, sintering: and transferring the primary sheet to a crucible, heating to remove moisture, heating to remove glue, finally heating to a sintering temperature, carrying out heat preservation sintering, and obtaining the required sheet after sintering.

2. The powder granulation and tabletting method according to claim 1, wherein: in the first step, the weight ratio of the wet-mixed powder, the liquid grinding medium, the binder and the grinding balls is 1:0.3-1.2:0.05-0.2:2-5, the rotation speed of the ball mill is 150-.

3. The powder granulation and tabletting method according to claim 2, wherein: in the ball milling wet mixing, the adopted grinding balls are made of agate, alumina or zirconia.

4. The powder granulation and tabletting method according to claim 2, wherein: in the ball milling wet mixing, the adopted liquid grinding medium is ethanol or pure water.

5. The powder granulation and tabletting method according to claim 2, wherein: in the ball milling wet mixing, the adopted binder is PVA, PVB, paraffin, acrylic acid or terpineol.

6. A powder granulation and tableting method as claimed in claims 1 to 5, wherein: in the second step, the drying temperature is 40-80 ℃, and the mesh number of the powder passing through the screen is 60-120 meshes in the secondary screening process.

7. The powder granulation and tabletting method according to claim 1, wherein: in the third step, the depth of the die is adjusted according to the weight of the required sheet, the automatic tablet press is a single-punch automatic tablet press, and the pressure in the tabletting process is 10-60 kN.

8. The powder granulation and tabletting method according to claim 1, wherein: in the fourth step, the temperature of the moisture removal process is 100-; the temperature in the glue discharging process is any temperature between the boiling point of the binder and 100 ℃, and the heat preservation time is 2-6 h; the sintering temperature in the sintering process is lower than the solid-phase reaction temperature of the powder melting temperature, and the heat preservation time is 4-10 h; before reaching the glue discharging temperature, the heating rate is less than or equal to 5 ℃/h.

Technical Field

The invention belongs to the technical field of material preparation, and relates to a powder granulation method.

Background

The powder tabletting technology is widely applied to the production of ceramics and glass, and is an important general technology. The high-weight and high-dimensional precision ceramic has wide application, and comprises a 5G ceramic filter, a ceramic capacitor, a high-precision ceramic structural part and other various functional ceramics. In the glass preparation process, powder processing and tabletting technologies are also used, and high-weight-precision glass blocks are produced by controlling the tabletting weight.

Currently, in order to obtain better fluidity, fine particle size powders are often processed into spherical aggregates of increased particle size using a binder. The invention patent with publication number CN111995392A provides a low-cost ceramic filter powder for a 5G base station and a preparation method thereof, and PVA is used as a binder for granulation in the technical scheme. The invention patent with the publication number of CN102503391B provides a preparation method of a bismuth ferrite-based composite material with high ferromagnetic property and ferroelectric property, and the technical scheme is that a PVA binder is added into powder, and the powder is sieved by a 60-mesh and 120-mesh sieve to prepare the composite material. The invention patent with publication number CN110194664A provides a garnet-structured low-dielectric-constant microwave dielectric ceramic material and a preparation method thereof, and in the technical scheme, PVA is added as a binder, and the ceramic material is prepared by a method of sieving mixed powder by a sieve of 100 meshes and a sieve of 140 meshes.

The binder mainly has the function of granulation to enhance the powder fluidity, and the pressed sheet is more complete and not easy to delaminate and damage due to the viscosity of the binder. However, in many technical schemes, the binder is directly added into the powder, so that the binder is not uniformly dispersed, agglomeration is easy to form, and the effect is not ideal. Therefore, a better granulation process is developed, and a higher-quality sheet is pressed, so that the method plays an important role in preparing ceramics and glass.

Disclosure of Invention

In order to solve the problems in the background art, the invention provides a powder granulation and tabletting method.

The method comprises the following steps:

step one, mixing materials: weighing the powder according to the proportion, and adding the powder into a ball mill with prepared grinding balls for ball-milling wet mixing;

step two, granulation: after the wet mixing of the ball mill is finished, the whole body is dried and sieved by a sieve with 10 to 20 meshes so as to separate the powder from the grinding balls, the powder is crushed by a crusher so that the granularity of the powder is less than 100 meshes, and the powder is sieved and granulated again to obtain tabletting powder;

step three, tabletting: filling the tabletting powder into a die, and tabletting by using an automatic tabletting machine to obtain a primary sheet;

step four, sintering: and transferring the primary sheet to a crucible, heating to remove moisture, heating to remove glue, finally heating to a sintering temperature, carrying out heat preservation sintering, and obtaining the required sheet after sintering.

In the first step, the weight ratio of the wet-mixed powder, the liquid grinding medium, the binder and the grinding balls is 1:0.3-1.2:0.05-0.2:2-5, the rotation speed of the ball mill is 150-.

In the ball milling wet mixing, the adopted grinding balls are made of agate, alumina or zirconia; the adopted liquid grinding medium is ethanol or pure water; the adopted binder is PVA, PVB, paraffin, acrylic acid or terpineol.

In the second step, the drying temperature is 40-80 ℃, and the mesh number range of the powder passing through the screen is 60-120 meshes in the process of secondary screening and granulation.

In the third step, the depth of the die is adjusted according to the weight of the required sheet, the automatic tablet press is a single-punch automatic tablet press, and the pressure in the tabletting process is 10-60 kN.

In the fourth step, the temperature of the moisture removal process is 100-; the temperature in the glue discharging process is any temperature between the boiling point of the binder and 100 ℃, and the heat preservation time is 2-6 h; the sintering temperature in the sintering process is lower than the solid-phase reaction temperature of the powder melting temperature, and the heat preservation time is 4-10 h; before reaching the glue discharging temperature, the heating rate is less than or equal to 5 ℃/h.

Further, in the first step, the material of the grinding ball is preferably zirconia.

Furthermore, in the third step, when the automatic tablet press is used for tabletting, the end surfaces of the upper die core and the lower die core of the die are horizontal, the pressure applied during tabletting is consistent every time, and the consistency of the pressure applied during tabletting by using the single-punch automatic tablet press is better.

Further, in the fourth step, the crucible used is an alumina crucible or a quartz crucible.

Compared with the prior art, the invention has simple process, the powder and the binder are mixed more uniformly by ball milling and wet mixing, and the problem of uneven distribution caused by adding the binder independently is avoided. The powder mixed with the binder is dried and crushed into fine powder by a crusher to form granules, so that the flowability of the powder is enhanced, the particle size is sieved and controlled to form proper particle size distribution, automatic tabletting is realized, the artificial interference is avoided, the efficiency is high, and the consistency of sheets is good; and finally, heating to remove moisture and remove the binder, sintering to enable the powder to perform solid-phase reaction, wherein the deviation of the actual weight and the required weight of the sintered sheet is less than or equal to 1 percent, and the deviation of the actual size and the average size is less than or equal to 1 percent, so that the high-strength and high-precision sheet is formed.

The invention can press sheets with high weight precision and size precision in batch, can be used for preparing ceramic and glass materials with excellent consistency, and has simple process method and high practicability.

Drawings

FIG. 1 is a photomicrograph at 100X magnification showing the powder granulated and sieved in example 1.

FIG. 2 is a photomicrograph at 100X magnification showing the powder granulated and sieved in example 2.

Detailed Description

The embodiments of the present invention will be described in detail with reference to the accompanying drawings, but the embodiments are not limited to the invention, and the advantages of the invention will be understood more clearly by the description. All modifications which can be derived or suggested by a person skilled in the art from the disclosure of the present invention are to be considered within the scope of the invention. Other parts of the embodiments which are not described in detail are all the prior art.

The operation steps of a powder granulation and tabletting method are described in detail below.

(1) Mixing materials: the powder is weighed according to the proportion, added into a grinding tank of a ball mill with prepared grinding balls, and then added with a liquid grinding medium for ball milling and wet mixing, so that the powder and the binder are fully mixed.

The material of the grinding tank is corundum, zirconia, agate, nylon, polyurethane or polytetrafluoroethylene, preferably polytetrafluoroethylene. The grinding balls are made of agate, alumina and zirconia, and preferably zirconia. The liquid grinding medium is absolute ethyl alcohol or pure water.

The binder used in the powder is PVA, PVB, paraffin, acrylic acid or terpineol, and can be selected to be compatible with the liquid grinding medium according to the use type of the liquid grinding medium.

The weight ratio of the powder, the liquid grinding medium, the adhesive and the grinding ball is 1:0.3-1.2:0.05-0.2: 2-5.

The liquid grinding medium should not be too much, and the mixture is allowed to stand for a period of time, preferably until the supernatant is not more than 4 mm.

The rotating speed of the ball mill is 150-250r/min, and the time is 8-24 h.

(2) And (3) granulation: after the wet mixing of the ball milling is finished, opening the ball milling tank, integrally drying the ball milling tank at the temperature of 40-80 ℃, and sieving the ball milling tank with a 10-20-mesh sieve to separate the grinding balls from the powder.

The agglomerated powder is crushed by a crusher to ensure that the particle size of the powder is smaller than 100 meshes, and after ball milling and mixing, the powder has smaller particle size and is easier to agglomerate, and is difficult to pass through a sieve pore below 100 meshes, and the sieving only needs to ensure that the particle size of the powder is small enough.

Further, the method of pulverizing the agglomerated powder includes manual grinding and automatic grinding.

Then granulating by using a screen, vibrating the screen, pouring powder, and balling the powder under the action of a binder, wherein the mesh range of the screen through which the granulated powder can pass is 60-120 meshes. And (3) crushing the powder which is not sieved by a 60-mesh sieve, and granulating the powder which is sieved by a 120-mesh sieve again to ensure that the granularity of the powder reaches the standard.

The screen cloth that the granulation was used is non-metallic material, preferred nylon material.

(3) Tabletting: and (3) tabletting by using an automatic tablet press, adjusting the end surfaces of the upper die core and the lower die core of the die to be horizontal before tabletting, and adjusting the depth of the die to obtain a sheet with required weight after the diameter of the die is fixed, so that the weight of materials filled into the die every time can be ensured to be the same after the die is fixed, and the pressure applied by the automatic tablet press is consistent every time of tabletting, wherein the pressure range is 10-60 kN.

The automatic tablet press preferably uses a single-punch automatic tablet press, which has a better consistency of the pressure applied during tablet pressing. And (4) carrying out size inversion according to the sintering shrinkage ratio, and determining the required diameter and depth of the die.

(4) And (3) sintering: transferring the pressed sheet into an alumina or quartz crucible, firstly heating to 100-plus-200 ℃ to remove moisture, keeping the temperature for 0.5-2h, then heating to the binder removal temperature, wherein the temperature in the binder removal process is any temperature between the boiling point of the binder and 100 ℃, keeping the temperature for 2-6h, finally heating to the sintering temperature, the sintering temperature is lower than the solid phase reaction temperature of the powder melting temperature, and the temperature can be kept for 4-10h according to the state of the sintered sheet.

Before reaching the glue discharging temperature, the temperature rising rate is not higher than 5 ℃/min.

After sintering, the deviation of the actual weight of the sheet from the required weight is less than 1%, and the deviation of the actual size from the average size is less than 1%.

The method for granulating and tableting the powder will be described in detail below with reference to specific examples.

Example 1

Barium zirconate titanate ceramic (BZT ceramic) of the formula BaZr_xTi_1-xO₃And x is 0.1. The preparation process of the BZT ceramic tablet is as follows:

(1) mixing materials: the raw material is BaCO₃、ZrO₂、TiO₂All of purity is99.99 percent, weighing the required raw materials according to the stoichiometric ratio, pouring the raw materials into a ball milling tank of a ball mill, adding pure water and 5 weight percent of PVA solution of a binder into zirconium oxide serving as a grinding ball material, and carrying out ball milling at the ball milling rotating speed of 200r/min for 10 hours. The weight ratio of the raw materials, pure water, PVA and zirconia grinding balls is 1:0.8:0.08: 4.

(2) And (3) granulation: after ball milling and wet mixing are finished, the whole body is dried at the temperature of 60 ℃, and is sieved by a 10-mesh sieve, so that grinding balls and powder are quickly separated; crushing the agglomerated powder by using a crusher, and enabling the particle size of the powder to be smaller than 100 meshes; granulating with a screen mesh, wherein the mesh number of the powder passing through the screen mesh is 60-120 meshes, and the screen mesh is made of nylon. And (3) crushing the powder which is not sieved by a 60-mesh sieve, and granulating the powder which is sieved by a 120-mesh sieve again to ensure that the granularity of the powder reaches the standard.

(3) Tabletting: and (3) tabletting by using a single-punch automatic tablet press, wherein the diameter of the die is 10mm, the depth of the die is adjusted and then fixed, the materials with the same content are filled every time, the pressure is applied for 40kN, the discharging period is set for 5s, and the ceramic blank preliminary tabletting with the same specification is continuously pressed.

(4) And (3) sintering: primarily tabletting the ceramic blank and transferring the ceramic blank into a quartz crucible, firstly heating to 200 ℃ at the heating rate of 5 ℃/min to remove moisture, and keeping the temperature for 1 h; then heating to the glue discharging temperature of 550 ℃ at the heating rate of 5 ℃/min, and keeping the temperature for 3h, wherein the boiling point of the PVA as a binder is 550 ℃; and finally, heating and sintering, wherein the sintering temperature needs to be lower than the solid-phase reaction temperature of the powder melting temperature, the temperature can be set to 1450 ℃ for the BZT ceramic, and the temperature is kept for 10 hours. After sintering, the deviation of the actual weight of the sheet from the required weight is less than 1%, and the deviation of the actual size from the average size is less than 1%.

And (4) performing size inversion according to the sintering shrinkage ratio to obtain the ceramic with the required size.

The following table is a table of weight and diameter data for preparing 240mg by weight BZT ceramic tablets.

TABLE 1 weight and diameter data sheet of BZT ceramic preform

Example 2

The chemical formula of the microwave dielectric ceramic with the garnet structure is Y₃MgAl₃SiO₁₂. The preparation process of the ceramic tablet is as follows:

(1) mixing materials: the raw material is Y₂O₃、MgO、Al₂O₃And SiO₂The purity of the product is 99.99 percent, the required raw materials are weighed according to the stoichiometric ratio and poured into a ball milling tank, the material of the grinding ball is agate, absolute ethyl alcohol and terpineol serving as a binder are added for ball milling, the ball milling speed is 220r/min, and the time is 16 hours. The weight ratio of the raw materials, the absolute ethyl alcohol, the terpineol and the agate grinding balls is 1:0.6:0.1: 4.

(2) And (3) granulation: after ball milling wet mixing is finished, the whole body is dried at the temperature of 80 ℃, and is sieved by a 10-mesh sieve, so that grinding balls and powder are quickly separated; crushing the agglomerated powder by using a crusher to ensure that the granularity of the powder is less than 100 meshes; granulating with a screen mesh, wherein the mesh number of the powder passing through the screen mesh is 60-120 meshes, and the screen mesh is made of nylon. And (3) crushing the powder which is not sieved by a 60-mesh sieve, and granulating the powder which is sieved by a 120-mesh sieve again to ensure that the granularity of the powder reaches the standard.

(3) Tabletting: and (3) tabletting by using a single-punch automatic tablet press, wherein the diameter of the die is 5mm, the depth of the die is adjusted and then the die is fixed, the materials with the same content are filled every time, the pressure is applied for 50kN, the discharging period is set for 5s, and the ceramic blank preliminary tabletting with the same specification is continuously pressed.

(4) And (3) sintering: the ceramic blank is preliminarily pressed into an alumina crucible, the temperature is raised to 300 ℃ at the heating rate of 3 ℃/min, the heat preservation time is 3 hours, the ablation temperature of the terpineol as a binder is 250 ℃, and in addition, the ethanol has good volatility, so the ceramic blank can be completely volatilized in the drying process of granulation and the heating and heat preservation processes; then heating and sintering, wherein the sintering temperature needs a solid-phase reaction temperature lower than the melting temperature of the powder, and for Y₃MgAl₃SiO₁₂The ceramic can be set at 1500 DEG CKeeping the temperature for 8h, then cooling to 800 ℃ at the cooling rate of 3 ℃/min, and then cooling along with the furnace. After sintering, the deviation of the actual weight of the sheet from the required weight is less than 1%, and the deviation of the actual size from the average size is less than 1%.

And (4) performing size inversion according to the sintering shrinkage ratio to obtain the ceramic with the required size.

The following table shows the preparation of 80mg by weight of Y₃MgAl₃SiO₁₂Table of weight and diameter.

TABLE 2Y₃MgAl₃SiO₁₂Ceramic weight and diameter data sheet

The preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings and specific examples, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.