A skin-free ceramic slurry and a method for preparing the same

Abstract

The application discloses a ceramic slurry without skin and a preparation method thereof, and relates to the technical field of ceramic slurries.In the process of preparing the ceramic slurry, a skin is formed on the surface of the slurry, which is usually distributed in the vertical direction of the stirred slurry.If the stirring is continued, the skin will fall into the interior of the slurry, resulting in defects such as protrusions and lines in the subsequent process.The polyethylene glycol diacrylate molecular chain is adsorbed on the surface of the alumina particles to form a steric hindrance layer; the electrostatic repulsion and steric hindrance effect make the particles dispersed; the surface of the particles is fully wetted by water; and the overall fluidity of the slurry is improved.The montmorillonite and the carboxymethyl cellulose are grafted to form a polymer with a large number of pores, a large pore size and a uniform distribution; the structure can provide more space for the slurry to absorb water and swell, and tightly bind water molecules under the action of hydrogen bonds, so that the water retention capacity of the ceramic slurry is improved, and the generation of the skin on the surface of the slurry is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic slurry, in particular to a ceramic slurry without skin and a preparation method thereof. BACKGROUND

[0002] When the ceramic slurry is defoamed, if a large amount of bubbles generated in the stirring process cannot be discharged, a large amount of bubbles will be left in the slurry, and these residual bubbles will have an impact on the subsequent process, for example, can cause defects such as pits, cracks, pinholes, etc. If the environment is not suitable, the surface of the slurry will form a skin, and this skin is usually distributed in the vertical direction of the stirred slurry. If the stirring continues, the skin will fall into the inside of the slurry, resulting in subsequent defects such as protrusions, lines, etc.

[0003] Therefore, in order to improve the problem of slurry skin, the present application provides a ceramic slurry without skin and a preparation method thereof. SUMMARY

[0004] The present application aims to provide a ceramic slurry without skin and a preparation method thereof to solve the problems in the prior art.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0006] A ceramic slurry without skin and a preparation method thereof, comprising the following steps:

[0007] Step one: add the alumina ceramic slurry to the diaphragm pump, discharge compressed air, the pressure is 0.1-0.5 MPa; filter; heat the defoaming tank body in 32-℃ water circulation for 25-30 min, and discharge the alumina ceramic slurry to the defoaming tank body at a flow rate of 6-15 L / min;

[0008] Step two: keep the defoaming tank constant temperature at 29-45℃, and carry out the first defoaming; adjust the vacuum degree of the defoaming tank body, and carry out the second defoaming; adjust the defoaming speed and the vacuum degree of the defoaming tank body, and carry out the third defoaming, to obtain a ceramic slurry without skin.

[0009] More preferably, in step one, the filtration uses two filters connected in series for filtration, one filter is 200 mesh, and the other filter is 500 mesh.

[0010] More preferably, in step one, the discharge parameters are: the discharge pressure is 0.1-0.55 MPa, the discharge viscosity is 1000-5000 cp, and the discharge solid content is 50-75%.

[0011] More optimized, in step two, the first defoaming, defoaming speed is 30~90r / min, defoaming tank vacuum degree is -50kpa~(-70kpa), water circulation temperature is 30~45℃, time is 20~60min;The second defoaming, defoaming tank vacuum degree is -85kpa~(-97kpa), water circulation temperature is 30~45℃, time is 22~24h, so that the slurry casting viscosity 6000~12000cp, casting solid content 58~66%;The third defoaming, defoaming speed is 5~32r / min, defoaming tank vacuum degree is -70kpa~(-85KPa), water circulation temperature is 30~40℃, time is 2~12h.

[0012] More optimized, in step one, the preparation method of alumina ceramic slurry is as follows:

[0013] Step A: 20g carboxylated alumina is added to 100mL ethanol, ultrasonic dispersion, grinding, drying, to obtain ceramic powder, 10g of ceramic powder is added to 7g of glycerol, mixed uniformly, ultrasonic dispersion for 4~6h, then 0.5g of glycerol and 0.3g of carrageenan are mixed and stirred, and the colloidal pre-solution is carried out, the stirring time is 10~12h, the heating temperature is 80~100℃, and the stirring rate is 500r / min, to obtain a colloid;

[0014] Step B: 10g of the colloid, 3g of polyethylene glycol diacrylate and 2g of potassium persulfate are added to 30mL of mixed solution, stirred uniformly and heated at 200~220℃ for 3~5h to obtain substance A;

[0015] Step C: half of substance A is added to polyethylene glycol, ball milling, with a rotation speed of 500rpm, forward rotation for 10~12min, reverse rotation for 9~11min, and intermittent ball milling for 3~5min, for 6~8h, the remaining substance A is added, with a rotation speed of 500rpm, forward rotation for 10~12min, reverse rotation for 9~11min, and intermittent ball milling for 3~5min, for 12~14h, the rotation speed is adjusted to 5~20r / min, and ball milling is carried out for 1~3h to obtain an alumina ceramic slurry.

[0016] More optimized, the preparation method of the mixed solution is as follows: 3g of carboxymethyl cellulose is dissolved in 100mL of deionized water, magnetic stirring for 30~40min to form a carboxymethyl cellulose solution;1g of montmorillonite is added to 30mL of deionized water to prepare a montmorillonite suspension;30mL of the montmorillonite suspension is added to 50mL of the carboxymethyl cellulose solution, and the mixture is reacted at 80~100℃ for 2~4h, and acetic acid is added dropwise until the pH is 7 to obtain a mixed solution.

[0017] More optimized, the preparation method of carboxylated alumina is as follows: 2.5g of silane coupling agent KH550 is added into 1.3g of succinic anhydride and 30mL of dimethylformamide, and stirring is carried out for 5-7h to obtain a modified liquid; 8g of alumina powder is added into 110mL of dimethylformamide, and ultrasonic dispersion is carried out for 2-4h; 5mL of the modified liquid and 6mL of deionized water are added, and stirring is carried out for 10-12h; then, suction filtration, washing and drying at 100-120 DEG C are carried out to obtain the carboxylated alumina.

[0018] More optimized, the preparation method of carboxymethyl cellulose is as follows: 25g of wood cellulose is added into 100mL of sodium hydroxide solution, and ultrasonic dispersion is carried out for 12-14h; then, filtration is carried out; 100mL of anhydrous ethanol is added, and stirring is carried out uniformly; 12g of chloroacetic acid is added, and reaction is carried out at 70-90 DEG C for 6-8h; then, suction filtration is carried out; 50mL of deionized water is added, and acetic acid is added dropwise until pH=7; then, drying and grinding are carried out to obtain the carboxymethyl cellulose.

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

[0020] 1. The ball mill defoaming device is designed to reduce frictional heat generation at low speed, inhibit evaporation of volatile components, and reduce the generation of skin; the slow flow speed of the material at low speed provides more time for the gas to escape through the gaps between the ceramic slurry, and the slow movement inhibits the retention of air bubbles.

[0021] 2. The filter screen combination is designed to combine 200-mesh and 500-mesh screens to filter out the skin and slurry particles of the ceramic slurry during the ball milling process, and to crush the large air bubbles of the ceramic slurry; the tank is heated to avoid temperature difference contact skin, increase the discharge flow rate control, avoid the filter screen from being stretched and damaged, and improve the filtering effect.

[0022] 3. The defoaming process is designed to solve the skin problem on the surface of the slurry; compressed air is used to avoid direct blowing of air onto the surface of the ceramic slurry, and to improve the skin caused by temperature change and airflow disturbance.

[0023] 4. The present application improves the solid content difference of the ceramic slurry in the tank, and the solid content of the ceramic slurry is 1%.

[0024] 5. The alumina particle slip surface has more electric charge, and the particle repulsion is larger; the polyethylene glycol diacrylate molecular chain is adsorbed on the surface of the alumina particle to form a steric hindrance layer, which hinders the particle aggregation; the electrostatic repulsion and steric hindrance make the particles dispersed, the particle surface is fully wetted by water, the overall flowability of the slurry is improved, and the overall viscosity is reduced.

[0025] 6. Carboxymethyl cellulose molecules contain strongly hydrophilic carboxyl and hydroxyl groups, resulting in a high water vapor permeability coefficient. Montmorillonite is a layered silicate composed of two layers of silicon-oxygen tetrahedra sandwiching a layer of aluminum-oxygen octahedra, which has excellent water vapor barrier properties. Grafting montmorillonite and carboxymethyl cellulose creates a polymer with numerous pores, large pore sizes, and uniform distribution. This structure provides more space for the slurry to absorb water and expand, and the hydrogen bonds firmly bind water molecules, thereby improving the water retention capacity of the ceramic slurry.

[0026] 7. Carboxylating alumina powder through surface modification can improve the dispersibility of alumina powder in solvents. Polyethylene glycol is a hydrophilic polymer. Combining the hydroxyl groups on the surface of polyethylene glycol with carboxylated alumina can further improve the water retention performance of the prepared ceramic slurry. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] The sources and types of substances involved in this invention are not particularly limited, and exemplary examples include:

[0029] The following products were supplied by Shanghai Hongshun Biotechnology Co., Ltd.: KH550 silane coupling agent (Catalog No. S821032); Beijing Naphthalene Biochemical Technology Co., Ltd. (Catalog No. S817605-10kg); Pande (Shanghai) International Trade Co., Ltd. (Catalog No. 68-12-2); Yangzhou Zhongtianli Co., Ltd. (Catalog No. ZTL-GCAO-035); Shanghai Zhenzhun Biotechnology Co., Ltd. (Catalog No. IR-40011); Shanghai Beinuo Biotechnology Co., Ltd. (Catalog No. 285234-500G); and Greenlink (Jining) Chemical Technology Co., Ltd. (Catalog No. P109708-25ml).

[0030] Example 1: A skinless ceramic slurry and its preparation method:

[0031] Step 1: (1) 2.5 g of silane coupling agent KH550 was added to 1.3 g of succinic anhydride and 150 mL of dimethylformamide, and mixed and stirred for 5 h to obtain a modified liquid; 8 g of alumina powder was added to 110 mL of dimethylformamide, and ultrasonic dispersion was performed for 2 h, 5 mL of the modified liquid and 6 mL of deionized water were added, and stirring was performed for 10 h, and then filtration, washing, and drying at 100°C were performed to obtain carboxylated alumina;

[0032] (2) 5 g of the carboxylated alumina was added to 50 mL of ethanol, ultrasonic dispersion was performed, grinding was performed, and drying was performed to obtain ceramic powder, 5 g of the ceramic powder was added to 3 g of glycerol, and mixing was performed, ultrasonic dispersion was performed for 4 h, 0.5 g of glycerol and 0.3 g of carrageenan were added, and mixing and stirring were performed to perform colloidal pre-dissolution, the stirring time was 10 h, the heating temperature was 80°C, and the stirring rate was 500 r / min to obtain a colloid;

[0033] Step 2: (1) 25 g of lignocellulose was added to 100 mL of a sodium hydroxide solution, ultrasonic dispersion was performed for 12 h, filtration was performed, 100 mL of anhydrous ethanol was added, stirring was performed, 12 g of chloroacetic acid was added, and reaction was performed at 70°C for 6 h, filtration was performed, 50 mL of deionized water was added, acetic acid was added dropwise until the pH was 7, and drying and grinding were performed to obtain carboxymethyl cellulose;

[0034] (2) 3 g of the carboxymethyl cellulose was dissolved in 100 mL of deionized water, and magnetic stirring was performed for 30 min to form a carboxymethyl cellulose solution; 1 g of montmorillonite was added to 30 mL of deionized water to prepare a montmorillonite suspension; 30 mL of the montmorillonite suspension was added to 50 mL of the carboxymethyl cellulose solution, and reaction was performed at 80°C for 2 h, and acetic acid was added dropwise until the pH was 7 to obtain a mixed solution;

[0035] (3) 5 g of the colloid, 3 g of polyethylene glycol diacrylate, and 2 g of potassium persulfate were added to 30 mL of the mixed solution, and stirring was performed, and then heating was performed at 200°C for 3 h to obtain substance A;

[0036] Step 3: 5 g of the substance A was added to 7 g of polyethylene glycol as a dispersant, and then was placed into a ball mill, and was subjected to ball milling at a rotation speed of 500 rpm for 10 min in the forward direction, 9 min in the reverse direction, and 3 min of intermittent, and the ball milling was performed for 6 h, 5 g of the substance A was added again, and was subjected to ball milling at a rotation speed of 500 rpm for 10 min in the forward direction, 9 min in the reverse direction, and 3 min of intermittent, and the ball milling was performed for 12 h, and then the rotation speed of the ball mill was adjusted to 5 r / min, and preliminary defoaming treatment was performed for 1 h to obtain an alumina ceramic slurry;

[0037] Step 4: (1) After the alumina ceramic slurry is taken out from the ball mill tank, it is added into a diaphragm pump, and the discharge air pressure is 0.1 MPa; then the alumina ceramic slurry is filtered by using two filters in series, one filter is 200 mesh, and the other filter is 500 mesh; the debubbling tank is preheated by water circulation at 32℃ for 25 min, the alumina slurry is discharged to the 30% volume of the debubbling tank at a flow rate of 6 L / min, the discharge pressure is 0.1 MPa, the discharge viscosity is 1000 cp, the discharge solid content is 50%, the initial slurry temperature in the upper tank is 35℃, and the initial slurry temperature in the lower tank is 30.3℃;

[0038] (2) The debubbling rotation speed is 30 r / min, the debubbling tank vacuum degree is -50 kpa, the water circulation temperature is 30℃, the time is 20 min, the debubbling tank temperature is kept at 39.2℃, and the first debubbling is carried out; the debubbling tank vacuum degree is adjusted to -85 kpa, the water circulation temperature is 30℃, the time is 22 h, and the second debubbling is carried out, so that the slurry casting viscosity is 6000 cp, the casting solid content is 58%; the debubbling rotation speed is adjusted to 5 r / min, the debubbling tank vacuum degree is -70 kPa, the water circulation temperature is 30℃, the time is 2 h, and the third debubbling is carried out, so that the internal viscosity and solid content of the slurry are 1%, and the green body thickness difference is 15 um, thereby preparing a ceramic slurry without skin.

[0039] Example 2: A ceramic slurry without skin and a preparation method thereof:

[0040] Step 1: (1) 2.5 g of silane coupling agent KH550 is added into 1.3 g of succinic anhydride and 150 mL of dimethylformamide, and mixed and stirred for 7 h to obtain a modified liquid; 8 g of alumina powder is added into 110 mL of dimethylformamide, ultrasonically dispersed for 4 h, 5 mL of the modified liquid and 6 mL of deionized water are added, stirred for 12 h, filtered, washed, and dried at 120℃ to obtain carboxylated alumina;

[0041] (2) 5 g of carboxylated alumina is added into 50 mL of ethanol, ultrasonically dispersed, ground, and dried to obtain ceramic powder; 5 g of the ceramic powder is added into 3 g of glycerol, mixed uniformly, ultrasonically dispersed for 6 h, 0.5 g of glycerol and 0.3 g of carrageenan are added and mixed and stirred to carry out colloidal pre-dissolution, the stirring time is 12 h, the heating temperature is 100℃, and the stirring rate is 500 r / min, thereby obtaining a colloid;

[0042] Step 2: (1) 25 g of lignocellulose was added to 100 mL of sodium hydroxide solution, ultrasonic dispersion for 14 h, filtration, 100 mL of anhydrous ethanol was added, stirred uniformly, 12 g of chloroacetic acid was added, reacted at 90℃ for 8 h, suction filtration, added to 50 mL of deionized water, dropwise added acetic acid to pH = 7, dried, ground, to obtain carboxymethyl cellulose;

[0043] (2) 3 g of carboxymethyl cellulose was dissolved in 100 mL of deionized water, magnetic stirring for 40 min to form a carboxymethyl cellulose solution; 1 g of montmorillonite was added to 30 mL of deionized water to prepare a montmorillonite suspension; 30 mL of montmorillonite suspension was added to 50 mL of carboxymethyl cellulose solution, reacted at 100℃ for 4 h, dropwise added acetic acid to pH = 7 to obtain a mixed solution;

[0044] (3) 5 g of glue, 3 g of polyethylene glycol diacrylate and 2 g of potassium persulfate were added to 30 mL of the mixed solution, stirred uniformly and heated at 220℃ for 5 h to obtain substance A;

[0045] Step 3: 5 g of substance A was added to 7 g of polyethylene glycol as a dispersant, then put into a ball mill, rotated at 500 rpm for 12 min, reversed for 11 min, and intermittently ball milled for 5 min for 8 h, then added 5 g of substance A, rotated at 500 rpm for 12 min, reversed for 11 min, and intermittently ball milled for 5 min for 14 h, then the ball milling speed was adjusted to 20 r / min, and the preliminary defoaming treatment was carried out for 3 h to obtain an alumina ceramic slurry;

[0046] Step 4: (1) After the alumina ceramic slurry was taken out from the ball mill tank, it was added to a diaphragm pump, the discharge air pressure was 0.5 MPa; then the alumina ceramic slurry was filtered with two filters in series, one filter was 200 mesh and the other filter was 500 mesh; the defoaming tank body was preheated at 39℃ for 20 min, the alumina slurry was discharged to 70% of the volume of the defoaming tank body at a flow rate of 9 L / min, the discharge pressure was 0.3 MPa, the discharge viscosity was 5000 cp, the discharge solid content was 70%, the initial slurry temperature in the tank body was 37℃, and the initial slurry temperature in the tank body was 31.3℃;

[0047] (2) The defoaming rotation speed is 80 r / min, the defoaming tank body vacuum degree is -70 kPa, the water circulation temperature is 45°C, the time is 60 min, the defoaming tank temperature is kept at 39.2°C, and the first defoaming is carried out; the defoaming rotation speed is adjusted to 90 r / min, the defoaming tank body vacuum degree is -95 kPa, the water circulation temperature is 45°C, the time is 24 h, and the second defoaming is carried out, so that the slurry casting viscosity is 12000 cp and the casting solid content is 66%; the defoaming rotation speed is adjusted to 30 r / min, the defoaming tank body vacuum degree is -80 kPa, the water circulation temperature is 40°C, the time is 12 h, and the defoaming is carried out, so that the internal viscosity and solid content of the slurry are 1%, and the green body thickness difference is 15 um, thereby preparing a ceramic slurry without skin.

[0048] Example 3: A ceramic slurry without skin and a preparation method thereof

[0049] Step 1: (1) 2.5 g of silane coupling agent KH550 is added to 1.3 g of succinic anhydride and 150 mL of dimethylformamide, mixed and stirred for 6 h to obtain a modified liquid; 8 g of alumina powder is added to 110 mL of dimethylformamide, ultrasonically dispersed for 3 h, 5 mL of the modified liquid and 6 mL of deionized water are added, and then filtered, washed and dried at 110°C to obtain carboxylated alumina;

[0050] (2) 5 g of carboxylated alumina is added to 50 mL of ethanol, ultrasonically dispersed, ground and dried to obtain ceramic powder; 5 g of the ceramic powder is added to 3 g of glycerol, mixed uniformly, ultrasonically dispersed for 5 h, and then 0.5 g of glycerol and 0.3 g of carrageenan are added and mixed and stirred for colloid pre-dissolution, the stirring time is 11 h, the heating temperature is 90°C, and the stirring rate is 500 r / min, to obtain a colloid;

[0051] Step 2: (1) 25 g of lignocellulose is added to 100 mL of sodium hydroxide solution, ultrasonically dispersed for 13 h, filtered, 100 mL of anhydrous ethanol is added, stirred uniformly, 12 g of chloroacetic acid is added, and reacted at 80°C for 7 h, filtered, added to 50 mL of deionized water, and then acetic acid is added dropwise until pH=7, dried and ground to obtain carboxymethyl cellulose;

[0052] (2) 3 g of carboxymethyl cellulose is dissolved in 100 mL of deionized water, and magnetically stirred for 35 min to form a carboxymethyl cellulose solution; 1 g of montmorillonite is added to 30 mL of deionized water to prepare a montmorillonite suspension; 30 mL of the montmorillonite suspension is added to 50 mL of the carboxymethyl cellulose solution, and reacted at 90°C for 3 h, and then acetic acid is added dropwise until pH=7 to obtain a mixed solution;

[0053] (3) Add 5g of colloid, 3g of polyethylene glycol diacrylate and 2g of potassium persulfate to 30mL of mixed solution, stir evenly and heat at 210℃ for 4h to obtain substance A;

[0054] Step 3: Take 5g of substance A and add 7g of polyethylene glycol as a dispersant. Then put it into a ball mill and ball mill for 7 hours at a speed of 500rpm, rotating forward for 11 minutes, rotating backward for 10 minutes, and intermittently for 4 minutes. Then add another 5g of substance A and ball mill for 13 hours at a speed of 500rpm, rotating forward for 11 minutes, rotating backward for 10 minutes, and intermittently for 4 minutes. Then adjust the ball mill speed to 12r / min and ball mill for 2 hours to perform preliminary defoaming treatment and obtain alumina ceramic slurry.

[0055] Step 4: (1) After taking the alumina ceramic slurry out of the ball mill jar, add it to the diaphragm pump. The discharge compressed air pressure is 0.3 MPa. Then filter the alumina ceramic slurry using two filters connected in series. The first filter is 200 mesh and the second filter is 500 mesh. Heat the degassing tank in water circulation at 35°C for 30 minutes in advance. Discharge the alumina slurry to 50% of the volume of the degassing tank at a flow rate of 7 L / min. The discharge pressure is 0.15 MPa, the discharge viscosity is 3000 cp, the discharge solid content is 70%, the initial slurry temperature on the tank is 34.5°C, and the initial slurry temperature at the bottom of the tank is 30.2°C.

[0056] (2) The degassing speed was 55 r / min, the vacuum degree of the degassing tank was -60 kPa, the water circulation temperature was 37℃, the time was 40 min, and the temperature of the degassing tank was kept constant at 39.5℃ for the first degassing. The degassing speed was adjusted to 60 r / min, the vacuum degree of the degassing tank was -90 kPa, the water circulation temperature was 35℃, and the time was 23 h for the second degassing, so that the slurry viscosity was 8000 cp and the solid content of the cast slurry was 52%. The degassing speed was 15 r / min, the vacuum degree of the degassing tank was -75 kPa, the water circulation temperature was 35℃, and the time was 7 h for the third degassing, so that the internal viscosity solid content of the slurry was 1% and the green thickness difference was 15 μm, thus preparing a skinless ceramic slurry.

[0057] Comparative Example 1: The filter was changed to 500 mesh, and the rest was the same as in Example 1. The specific operation was as follows:

[0058] Step 4: (1) After the alumina ceramic slurry was taken out from the ball mill tank, it was added into the diaphragm pump, and the discharge compressed air pressure was 0.1 MPa; then the alumina ceramic slurry was filtered, and the filter was 500 mesh; the defoaming tank was heated in advance at 43℃ for 32 min, and the alumina slurry was discharged to the 30% volume of the defoaming tank at a flow rate of 15 L / min, the discharge pressure was 0.55 MPa, the discharge viscosity was 1000 cp, the discharge solid content was 60%, the initial slurry temperature above the tank was 35.1℃, and the initial slurry temperature below the tank was 30.6℃;

[0059] (2) The defoaming rotation speed was 30 r / min, the defoaming tank vacuum degree was -50 kpa, the water circulation temperature was 30℃, the time was 20 min, the defoaming tank temperature was kept at 29.5℃, and the first defoaming was carried out; the defoaming tank vacuum degree was adjusted to -77 kpa, the rotation speed was 50 r / min, the water circulation temperature was 29℃, the time was 22 h, the second defoaming was carried out, the slurry casting viscosity was 6000 cp, and the casting solid content was 58%; the defoaming rotation speed was adjusted to 32 r / min, the defoaming tank vacuum degree was -85 kpa, the water circulation temperature was 37℃, the time was 2 h, the third defoaming was carried out, the internal viscosity and solid content of the slurry were 1%, and the green body thickness difference was 15 um, so that a skin-free ceramic slurry was prepared.

[0060] Comparative Example 2: The filter was changed to 200 mesh, and the rest was according to Example 1, and the specific operation was as follows:

[0061] Step 4: (1) After the alumina ceramic slurry was taken out from the ball mill tank, it was added into the diaphragm pump, and the discharge compressed air pressure was 0.1 MPa; then the alumina ceramic slurry was filtered, and the filter was 200 mesh; the defoaming tank was heated in advance at 25℃ for 18 min, and the alumina slurry was discharged to the 30% volume of the defoaming tank at a flow rate of 8 L / min, the discharge pressure was 0.05 MPa, the discharge viscosity was 1000 cp, the discharge solid content was 75%, the initial slurry temperature above the tank was 36.3℃, and the initial slurry temperature below the tank was 31.8℃;

[0062] (2) The defoaming rotation speed is 30 r / min, the defoaming tank body vacuum degree is -50 kPa, the water circulation temperature is 30°C, the time is 20 min, the defoaming tank temperature is kept at 47°C, and the first defoaming is carried out; the defoaming tank body vacuum degree is adjusted to -97 kPa, the rotation speed is 100 r / min, the water circulation temperature is 37°C, the time is 22 h, and the second defoaming is carried out, so that the slurry casting viscosity is 6000 cp, and the casting solid content is 58%; the defoaming rotation speed is adjusted to 10 r / min, the defoaming tank body vacuum degree is -68 kPa, the water circulation temperature is 29°C, the time is 2 h, and the third defoaming is carried out, so that the internal viscosity and solid content of the slurry are 1%, and the green body thickness difference is 15 um, and a ceramic slurry without skin is prepared.

[0063] Comparative Example 3: No carboxymethyl cellulose and montmorillonite are added, and the rest refers to Example 1, and the specific operation is as follows:

[0064] Step 2: 3 g of polyethylene glycol diacrylate and 2 g of potassium persulfate are added to 5 g of the colloid, stirred uniformly, and heated at 200°C for 3 h to obtain substance A.

[0065] Comparative Example 4: No polyethylene glycol diacrylate is added, and the rest refers to Example 1, and the specific operation is as follows:

[0066] Step 2: (1) 25 g of lignocellulose is added to 100 mL of sodium hydroxide solution, ultrasonically dispersed for 12 h, filtered, 100 mL of anhydrous ethanol is added, stirred uniformly, 12 g of chloroacetic acid is added, reacted at 70°C for 6 h, suction filtered, added to 50 mL of deionized water, and acetic acid is added dropwise until pH=7, dried and ground to obtain carboxymethyl cellulose;

[0067] (2) 3 g of carboxymethyl cellulose is dissolved in 100 mL of deionized water, and magnetically stirred for 30 min to form a carboxymethyl cellulose solution; 1 g of montmorillonite is added to 30 mL of deionized water to prepare a montmorillonite suspension; 30 mL of the montmorillonite suspension is added to 50 mL of the carboxymethyl cellulose solution, and reacted at 80°C for 2 h, and acetic acid is added dropwise until pH=7 to obtain a mixed solution;

[0068] (3) 5 g of the colloid and 2 g of potassium persulfate are added to 30 mL of the mixed solution, stirred uniformly, and heated at 200°C for 3 h to obtain substance A.

[0069] Comparative Example 5: The alumina powder is not carboxylated, and the rest refers to Example 1, and the specific operation is as follows:

[0070] Step 1: 5g of alumina was added to 50mL of ethanol, ultrasonic dispersion, grinding, drying to obtain ceramic powder, 5g of ceramic powder was added to 3g of glycerol, mixed uniformly, ultrasonic dispersion for 4h, then 0.5g of glycerol and 0.3g of carrageenan were added and mixed and stirred for colloidal pre-sol, the stirring time was 10h, the heating temperature was 80℃, and the stirring rate was 500r / min to obtain the colloidal.

[0071] Experiment 1: 200mL of ceramic slurry prepared in Examples 1-3 and Comparative Examples 1-2 was taken respectively, in Examples 1-3, the ceramic slurry was filtered by two filters in series, the first filter was 200 mesh, and the second filter was 500 mesh; in Comparative Example 1, the ceramic slurry was filtered by a 500 mesh filter; in Comparative Example 2, the ceramic slurry was filtered by a 200 mesh filter; and the state of the ceramic slurry was observed after standing for 5h, and the experimental data was as follows:

[0072]

[0073] Conclusion: From the above experimental data, it can be seen that in Examples 1-3, the ceramic slurry prepared by filtering with two filters in series, the first filter being 200 mesh and the second filter being 500 mesh, has a stable state without skinning; in Comparative Example 1, the ceramic slurry has skinning by filtering with a 500 mesh filter; in Comparative Example 2, the ceramic slurry has skinning on the surface by filtering with a 200 mesh filter; therefore, the filtering method should use two filters in series, the first filter being 200 mesh and the second filter being 500 mesh; the designed filter screen combination is 200 mesh and 500 mesh screen combination, which filters out the skinning and slurry particles of the ceramic slurry during ball milling and breaks the large bubbles of the ceramic slurry; the tank heating avoids temperature difference contact skinning, increases the discharge flow rate control, avoids the filter screen from being stretched and damaged, and improves the filtering effect.

[0074] Experiment 2: 200mL of ceramic slurry prepared in Examples 1-3 and Comparative Examples 1-2 was taken respectively, the vacuum degree of the defoaming tank of Example 1 was-70MPa, the vacuum degree of the defoaming tank of Example 2 was-80MPa, the vacuum degree of the defoaming tank of Example 3 was-75MPa, the vacuum degree of the defoaming tank of Comparative Example 1 was-85MPa, and the vacuum degree of the defoaming tank of Comparative Example 2 was-68MPa, and the surface state of the slurry prepared in Examples 1-3 and Comparative Examples 1-2 after defoaming was observed after standing for 5h, and the data was as follows:

[0075]

[0076] Conclusion: From the above experimental data, it can be seen that the slurries prepared in Examples 1-3 have no bubbles and no skin on the surface; the vacuum degree of the degassing tank in Comparative Example 1 is -85 MPa, and bubbles are generated on the surface of the slurry; the vacuum degree of the degassing tank in Comparative Example 2 is -68 MPa, and skin appears on the surface of the slurry; the ball mill degassing is designed, which reduces the friction heat by low speed, inhibits the evaporation of volatile components, and reduces the generation of skin; the material flow speed is slow at low speed, and the gas has more time to escape through the gap between the ceramic slurry, and slow movement inhibits the retention of bubbles.

[0077] Experiment 3: Take 200 mL of ceramic slurry prepared in Examples 1-3 and Comparative Examples 1-2, respectively, and degas the degassing tank at 39.2°C in Examples 1-3 and at 29.5°C in Comparative Example 1, and at 47°C in Comparative Example 2, and observe the surface state of the slurry prepared in Examples 1-3 and Comparative Examples 1-2 after 5h, and the specific data are as follows:

[0078]

[0079] Conclusion: From the above experimental data, it can be seen that after constant temperature degassing at 39.2°C, the surface of the slurry in Examples 1-3 is flat, no skin, and bubbles float out; after constant temperature degassing at 29.5°C, the surface of the slurry in Comparative Example 1 is wrinkled and has skin, and bubbles float out; after constant temperature degassing at 47°C, the surface of the slurry in Comparative Example 2 is wrinkled and has skin, and bubbles float out; therefore, the change of temperature will cause the slurry to have skin.

[0080] Experiment 4: Take 200 mL of ceramic slurry, and observe the state of the slurry under different negative pressures in Examples 1-3 and Comparative Examples 1-2, and the specific data are as follows:

[0081]

[0082] Conclusion: From the above experimental data, it can be seen that after the second degassing of the ceramic slurry prepared in Examples 1-3, the boiling solvent in the slurry is removed; in Comparative Example 1, the vacuum degree in the degassing tank is -77 kpa, and the slurry does not boil and the solvent is not removed; in Comparative Example 2, the vacuum degree in the degassing tank is -97 kpa, and the slurry boils and splashes; the bubbles are lifted to the negative pressure environment on the surface layer of the slurry, and the bubbles and solvent in the slurry are guided to the surface of the liquid to release, so the boiling solvent in the slurry is removed, but the negative pressure is too high, and the slurry boils and splashes; the negative pressure is too low, and the slurry does not boil and the solvent is not removed.

[0083] Experiment 3: 200 mL of ceramic slurry prepared in Example 1, Comparative Example 3, Comparative Example 4 and Comparative Example 5 were taken respectively, and left to stand for 5 h, and the surface state of the slurry was observed, and the results were as follows:

[0084]

[0085] Conclusion: The surface of the slurry prepared in Example 1 was smooth and no skin and bubbles were generated. The surface of the slurry prepared in Comparative Example 3 had skin and bubbles because no montmorillonite was added. The surface of the slurry prepared in Comparative Example 4 had skin because no polyethylene glycol diacrylate was added. The surface of the slurry prepared in Comparative Example 5 had skin because the carboxymethyl cellulose was not grafted with montmorillonite. The reason is that the polymer has more pores, larger pore size and uniform distribution, which can provide more space for the slurry to absorb water and swell, and the water molecules are tightly bound under the action of hydrogen bond, thereby improving the water retention capacity of the ceramic slurry, reducing water evaporation, and the surface of the slurry has no skin. The molecular chain of polyethylene glycol diacrylate is adsorbed on the surface of the alumina particles to form a steric hindrance layer. The electrostatic repulsion and steric hindrance effect make the particles dispersed, the particle surface is fully wetted by water, the overall fluidity of the slurry is improved, and the generation of skin is reduced. Polyethylene glycol is a hydrophilic polymer, which can further improve the water retention performance of the prepared ceramic slurry and reduce the generation of skin.

[0086] It is apparent for those skilled in the art that the present application is not limited to the details of the above-described exemplary embodiments, but can be implemented in other concrete forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, the scope of the present application being defined by the appended claims rather than the above description, and all changes coming within the meaning and range of equivalents of the claims are intended to be embraced therein.

Claims

1. A method for preparing a skinless ceramic slurry, characterized in that: Includes the following steps: Step 1: Add the alumina ceramic slurry to the diaphragm pump, discharge it, and pressurize it with compressed air at a pressure of 0.1-0.5 MPa; filter it, heat the degassing tank, and discharge the alumina ceramic slurry into the degassing tank; Step 2: Maintain a constant temperature in the degassing tank and perform the first degassing; adjust the vacuum level of the degassing tank and perform the second degassing; adjust the degassing speed and the vacuum level of the degassing tank and perform the third degassing to obtain a ceramic slurry without skin formation. The preparation method of the alumina ceramic slurry includes the following steps: Step A: Add carboxylated alumina to ethanol, ultrasonically disperse, grind, and dry to obtain ceramic powder. Add glycerol to the ceramic powder, ultrasonically disperse for 4-6 hours, add glycerol and carrageenan, mix, heat and stir for 10-12 hours to obtain colloid. Step B: Add carboxymethyl cellulose to deionized water and stir magnetically to prepare a carboxymethyl cellulose solution; add montmorillonite to deionized water to prepare a montmorillonite suspension; add the montmorillonite suspension to the carboxymethyl cellulose solution and react for 2-4 hours; add acetic acid dropwise until pH=7 to obtain a mixed solution. Add the colloid, polyethylene glycol diacrylate and potassium persulfate to the mixed solution, stir well, and heat to obtain substance A; Step C: Take half of substance A and add it to polyethylene glycol. Ball mill the mixture at 500 rpm for 10-12 minutes forward, 9-11 minutes reverse, and 3-5 minutes intermittently for 6-8 hours. Add the remaining substance A and ball mill the mixture at 500 rpm for 10-12 minutes forward, 9-11 minutes reverse, and 3-5 minutes intermittently for 12-14 hours. Adjust the speed to 5-20 rpm and ball mill for 1-3 hours to obtain alumina ceramic slurry.

2. The method for preparing a skinless ceramic slurry according to claim 1, characterized in that: In step one, filtration is performed using two filters connected in series: the first filter is 200 mesh and the second filter is 500 mesh.

3. The method for preparing a skinless ceramic slurry according to claim 1, characterized in that: In step one, the discharge parameters are: discharge pressure of 0.1 to 0.55 MPa, discharge viscosity of 1000 to 5000 cp, and discharge solid content of 50 to 75%.

4. The method for preparing a skinless ceramic slurry according to claim 1, characterized in that: In step two, during the first degassing, the degassing speed is 30–90 r / min, the vacuum degree of the degassing tank is -70 kPa to -50 kPa, and the time is 20–60 min; during the second degassing, the vacuum degree of the degassing tank is -97 kPa to -85 kPa, and the time is 22–24 h, resulting in a slurry viscosity of 6000–12000 cp and a cast solids content of 58–66%; during the third degassing, the degassing speed is 5–32 r / min, the vacuum degree of the degassing tank is -85 kPa to -70 kPa, and the time is 2–12 h.

5. The method for preparing a skinless ceramic slurry according to claim 1, characterized in that: The method for preparing the carboxylated alumina is as follows: Silane coupling agent KH550 is added to succinic anhydride and dimethylformamide, and the mixture is stirred for 5-7 hours to obtain a modified solution; alumina powder is added to dimethylformamide, and the mixture is ultrasonically dispersed for 2-4 hours; the modified solution and deionized water are added, and the mixture is stirred for 10-12 hours; the mixture is then filtered, washed, and dried to obtain carboxylated alumina.

6. The method for preparing a skinless ceramic slurry according to claim 1, characterized in that: The method for preparing carboxymethyl cellulose is as follows: lignocellulose is added to sodium hydroxide solution, ultrasonically dispersed for 12-14 hours, filtered, anhydrous ethanol is added, stirred evenly, chloroacetic acid is added, filtered, deionized water is added, acetic acid is added dropwise until pH=7, dried, and ground to obtain carboxymethyl cellulose.

7. A skinless ceramic slurry prepared by the method for preparing a skinless ceramic slurry according to any one of claims 1 to 6.

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