Anti-burning sticking coating for ceramics as well as preparation method and application of anti-burning sticking coating

Abstract

The invention discloses an anti-burning sticking coating for ceramics as well as a preparation method and application thereof. The anti-burning sticking coating for ceramics is prepared from the following raw materials in parts by weight: 30 to 40 parts of aluminum oxide, 2 to 8 parts of kaolin, 40 to 60 parts of quartz sand, 0.5 to 3 parts of zirconium silicate, 2 to 5 parts of black pigment, 0 to 2 parts of ferrozirconium red, 0 to 6 parts of praseodymium yellow and 4 to 7 parts of sodium carboxymethyl cellulose. Aluminum oxide, quartz sand and zirconium silicate serve as main raw materials of the anti-sticking material for ceramics, due to the high-temperature characteristic, no liquid phase is generated at the high temperature, the isolation and anti-sticking effects are effectively achieved, quartz sand is introduced to assist pigment coloring, internal gaps of natural quartz sand are large, pigment easily enters the interior, and color generation is more uniform.

Description

Technical Field

[0001] This invention relates to the field of ceramic production technology, and in particular to an anti-sticking coating for ceramics, its preparation method, and its application. Background Technology

[0002] In the production of sanitary ceramics, the high-temperature firing of ceramics causes deformation. The assembled components, fired together, play a certain role in fixing the ceramic structure. If fired separately, this deformation can lead to poor assembly. However, firing different parts of the product together can also easily cause defects such as adhesion and chipping, resulting in appearance or functional defects. For example, when a ceramic water tank lid is fired on top of a ceramic water tank, the high-temperature liquid phase softening or incomplete glaze treatment can cause the component to stick to the main body, resulting in chipping and product scrap. To improve these defects, alumina is usually applied to the junction. Alumina is a low-temperature raw material with the following characteristics: it easily settles, is difficult to color, and can drift onto the product with airflow, forming defects. Because alumina is difficult to color, there is a significant color difference between the alumina and the ceramic body after firing, causing poor appearance and other defects. Summary of the Invention

[0003] The present invention aims to at least partially solve one of the aforementioned technical problems in the related art. To this end, the present invention proposes an anti-sticking coating for ceramics, its preparation method, and its application.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows:

[0005] This invention proposes a ceramic anti-sticking coating, comprising the following raw materials in parts by weight: 30-40 parts alumina, 2-8 parts kaolin, 40-60 parts quartz sand, 0.5-3 parts zirconium silicate, 2-5 parts black pigment, 0-2 parts zirconium iron red, 0-6 parts praseodymium yellow, and 4-7 parts sodium carboxymethyl cellulose.

[0006] In some embodiments of the present invention, the alumina has a mesh size of 90-150 mesh. Alumina of this size has strong high-temperature stability and does not produce a liquid phase at high temperatures of 1200℃-1300℃. Alumina with an excessively large mesh size is prone to burning and sticking.

[0007] In some embodiments of the present invention, the quartz sand has a mesh size of 5-20 mesh.

[0008] In some embodiments of the present invention, the black pigment is cobalt black. Cobalt black pigment can withstand temperatures above 1200°C, has strong tinting strength and chemical stability, its melanin is stable and does not easily fade, making it suitable for high-temperature environments.

[0009] In some embodiments of the present invention, the particle size distribution of the ceramic anti-stick coating is: D10=1.4μm-1.8μm, D50=14μm-16μm, D90=52μm-60μm.

[0010] In some embodiments of the present invention, the specific gravity of the ceramic anti-stick coating is 1.2-1.25, and the viscosity of the 4-cup coating is 50±5s.

[0011] The present invention also proposes a method for preparing the aforementioned anti-sticking coating for ceramics, comprising the following steps:

[0012] (1) The alumina, kaolin, zirconium silicate, black pigment, zirconium iron red and praseodymium yellow are ball-milled once. After the first ball milling is completed, the quartz sand is added for a second ball milling to obtain the ball milling material.

[0013] (2) The ball milling material, sodium carboxymethyl cellulose and water are mixed to obtain the ceramic anti-burning coating.

[0014] In some embodiments of the present invention, the particle size requirements of the ball milling material are: 40%-48% of the particles are smaller than 10 μm, and 13%-19% are retained on a 325-mesh sieve.

[0015] In some embodiments of the present invention, the time for one ball milling session is 50 min to 70 min.

[0016] In some embodiments of the present invention, the secondary ball milling time is 100 min to 120 min.

[0017] The present invention also proposes the application of the anti-stick coating for ceramics in ceramic firing, wherein the anti-stick coating is applied to the joint between the assembly and the main body, and the assembly and the main body are placed in the kiln for firing in the assembled state.

[0018] According to a preferred embodiment of the present invention, at least the following beneficial effects are achieved:

[0019] 1. The alumina, quartz sand, and zirconium silicate of this invention serve as the main raw materials for anti-sticking materials used in ceramics. Due to their high-temperature characteristics, they do not produce a liquid phase at temperatures of 1200℃-1300℃, effectively isolating and preventing sticking. After sintering, alumina forms dense α-Al2O3 with low porosity, making it difficult for colorants to penetrate into the particles; they can only adhere to the surface, resulting in uneven coloring. Therefore, quartz sand is introduced to assist in coloring the colorants. Natural quartz sand (i.e., raw quartz) contains many impurities such as iron, mica, and feldspar. The large internal gaps in quartz sand allow colorants to easily penetrate. During firing, the colorant, impurities, and quartz form a eutectic, resulting in more uniform coloring. Zirconium silicate is an effective carrier for colorants, improving their adhesion. At high temperatures, it protects the colorants, reduces their volatilization, ensures uniform coloring, and reduces the amount of colorant needed.

[0020] 2. The black pigment of this invention mainly serves to reduce whiteness. Since the sanitary ceramic body is bluish-black, it is necessary to add black pigment to reduce the whiteness of the anti-stick coating. Appropriate amounts of zirconium iron red and praseodymium yellow can also be added according to the color tone of the ceramic body for adjustment. By adjusting the pigment ratio, the anti-stick coating area can be made to maintain the same color tone as the ceramic product, making the product more aesthetically pleasing.

[0021] 3. Kaolin and sodium carboxymethyl cellulose primarily act as suspending agents, preventing the sedimentation of quartz, alumina, and pigment particles. Long-chain sodium carboxymethyl cellulose molecules enhance coating adhesion, ensuring the coating adheres tightly to the surface of the substrate, preventing powdering and peeling after drying. This effectively prevents powdering caused by friction during drying and handling, thus avoiding defects in the appearance or function of ceramic products. The coating system of this invention is a slurry with 40%-48% particles <10μm. The high proportion of coarse particles means kaolin cannot provide sufficient suspension, leading to sedimentation. To overcome this sedimentation problem, the coating particle size can be further reduced. However, while smaller overall particle size improves sedimentation, at specific coating thicknesses, smaller particle sizes increase the risk of coating cracking and burn-sticking. Therefore, sodium carboxymethyl cellulose is introduced to enhance suspension and assist kaolin in stabilizing the coating system, resulting in a smoother, easier-to-spread, and easier-to-apply coating. If too little sodium carboxymethyl cellulose is used, the paint will easily settle, be difficult to apply, difficult to spread, and prone to powdering and peeling after drying. If too much is used, the paint will be too viscous and easy to apply unevenly.

[0022] 4. The raw materials used in this invention have significant initial particle size variations. A secondary ball milling process is required to process alumina, quartz sand, and other raw materials to a suitable particle size distribution. This prevents excessively fine particles from sticking together during burning, and excessively coarse particles from causing sedimentation that affects usability, resulting in defects and an unattractive finish after burning. If a single ball milling method is used, not only is it difficult to grind alumina finely, but it also easily leads to excessively fine quartz sand, causing it to stick together during burning.

[0023] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Detailed Implementation

[0024] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0025] Example 1

[0026] This embodiment prepares an anti-sticking coating for ceramics, and the specific process is as follows:

[0027] (1) By weight, 36 parts of 100-mesh alumina, 5 parts of kaolin, 1 part of zirconium silicate, 3 parts of black pigment, 1 part of zirconium iron red, and 4 parts of praseodymium yellow were added to a ball mill. Water was added and the mixture was ball-milled for 60 minutes. After the first ball milling was completed, 50 parts of 10-mesh quartz sand were added and the mixture was ball-milled for 110 minutes to obtain the ball milled material. The residue on the 325-mesh sieve was 16%, and the proportion of particles smaller than 10 μm was 41.6%.

[0028] (2) Mix the ball milling material, 5.3 parts of sodium carboxymethyl cellulose, bactericide and water, stir, sieve and age to obtain a ceramic anti-stick coating with a specific gravity of 1.21 and a viscosity of 50s in a 4-cup. The particle size distribution measured by a laser particle size analyzer is: D10=1.626μm, D50=15.69μm and D90=57.94μm.

[0029] Example 2

[0030] This embodiment prepares an anti-sticking coating for ceramics, and the specific process is as follows:

[0031] (1) By weight, 30 parts of 100-mesh alumina, 5 parts of kaolin, 1 part of zirconium silicate, 3 parts of black pigment, 1 part of zirconium iron red, and 4 parts of praseodymium yellow were added to a ball mill. Water was added and the ball milling was carried out for 60 minutes. After the first ball milling was completed, 56 parts of 10-mesh quartz sand were added and the ball milling was carried out for 110 minutes to obtain the ball milling material. The residue on the 325-mesh sieve was 17%, and the proportion of particles smaller than 10 μm was 43%.

[0032] (2) Mix the ball milling material, 5.3 parts of sodium carboxymethyl cellulose, bactericide and water, stir, sieve and age to obtain a ceramic anti-stick coating.

[0033] Comparative Example 1

[0034] This comparative example prepared an anti-sticking coating for ceramics. The difference from Example 1 is that the secondary ball milling time was reduced to 60 minutes. The specific process is as follows:

[0035] (1) By weight, 36 parts of 100-mesh alumina, 5 parts of kaolin, 1 part of zirconium silicate, 3 parts of black pigment, 1 part of zirconium iron red, and 4 parts of praseodymium yellow were added to a ball mill. Water was added and the mixture was ball-milled for 60 minutes. After the first ball milling was completed, 50 parts of 10-mesh quartz sand were added and the mixture was ball-milled for 60 minutes to obtain the ball milling material. The residue on the 325-mesh sieve was 21%, and the proportion of particles smaller than 10 μm was 38.2%.

[0036] (2) Mix the ball milling material, 5.3 parts of sodium carboxymethyl cellulose, bactericide and water, stir, sieve and age to obtain a ceramic anti-stick coating.

[0037] Comparative Example 2

[0038] This comparative example prepared an anti-sticking coating for ceramics. The difference from Example 1 is that the secondary ball milling time was increased to 240 min. The specific process is as follows:

[0039] (1) By weight, 36 parts of 100-mesh alumina, 5 parts of kaolin, 1 part of zirconium silicate, 3 parts of black pigment, 1 part of zirconium iron red, and 4 parts of praseodymium yellow were added to a ball mill. Water was added and the mixture was ball-milled for 60 minutes. After the first ball milling was completed, 50 parts of 10-mesh quartz sand were added and the mixture was ball-milled for 240 minutes to obtain the ball milling material. The residue on the 325-mesh sieve was 8%, and the proportion of particles smaller than 10 μm was 54.5%.

[0040] (2) Mix the ball milling material, 5.3 parts of sodium carboxymethyl cellulose, bactericide and water, stir, sieve and age to obtain a ceramic anti-stick coating.

[0041] Comparative Example 3

[0042] This comparative example prepared a ceramic anti-sticking coating. The difference from Example 1 is that it uses 325-mesh high-purity quartz powder. The specific process is as follows:

[0043] (1) By weight, 36 parts of 100-mesh alumina, 5 parts of kaolin, 1 part of zirconium silicate, 3 parts of black pigment, 1 part of zirconium iron red, and 4 parts of praseodymium yellow were added to a ball mill. Water was added and the mixture was ball-milled for 60 minutes. After the first ball milling was completed, 50 parts of 325-mesh high-purity quartz powder were added and the mixture was ball-milled for 110 minutes to obtain the ball milling material. The residue on the 325-mesh sieve was 12%, and the proportion of particles smaller than 10 μm was 49%.

[0044] (2) Mix the ball milling material, 5.3 parts of sodium carboxymethyl cellulose, bactericide and water, stir, sieve and age to obtain a ceramic anti-stick coating.

[0045] Comparative Example 4

[0046] This comparative example prepared a ceramic anti-sticking coating. The difference from Example 1 is that the amount of alumina is increased and the amount of quartz sand is reduced. The specific process is as follows:

[0047] (1) By weight, 56 parts of 100-mesh alumina, 5 parts of kaolin, 1 part of zirconium silicate, 3 parts of black pigment, 1 part of zirconium iron red, and 4 parts of praseodymium yellow were added to a ball mill. Water was added and the ball milling was carried out for 60 minutes. After the first ball milling was completed, 30 parts of 10-mesh quartz sand were added and the ball milling was carried out for 110 minutes to obtain the ball milling material. The residue on the 325-mesh sieve was 16%, and the proportion of particles smaller than 10 μm was 45%.

[0048] (2) Mix the ball milling material, 5.3 parts of sodium carboxymethyl cellulose, bactericide and water, stir, sieve and age to obtain a ceramic anti-stick coating.

[0049] Comparative Example 5

[0050] This comparative example prepared a ceramic anti-sticking coating. The difference from Example 1 is that the amount of kaolin is increased and the amount of sodium carboxymethyl cellulose is decreased. The specific process is as follows:

[0051] (1) By weight, 36 parts of 100-mesh alumina, 10 parts of kaolin, 1 part of zirconium silicate, 3 parts of black pigment, 1 part of zirconium iron red, and 4 parts of praseodymium yellow were added to a ball mill. Water was added and the ball milling was carried out for 60 minutes. After the first ball milling was completed, 50 parts of 10-mesh quartz sand were added and the ball milling was carried out for 110 minutes to obtain the ball milling material. The residue on the 325-mesh sieve was 17.2%, and the proportion of particles smaller than 10 μm was 42%.

[0052] (2) Mix the ball milling material, 3.5 parts of sodium carboxymethyl cellulose, bactericide and water, stir, sieve and age to obtain a ceramic anti-stick coating.

[0053] Comparative Example 6

[0054] This comparative example prepared a ceramic anti-sticking coating. The difference from Example 1 is that the amount of kaolin is increased and the amount of sodium carboxymethyl cellulose is decreased. The specific process is as follows:

[0055] (1) By weight, 36 parts of 100-mesh alumina, 20 parts of kaolin, 1 part of zirconium silicate, 3 parts of black pigment, 1 part of zirconium iron red, and 4 parts of praseodymium yellow were added to a ball mill. Water was added and the mixture was ball-milled for 60 minutes. After the first ball milling was completed, 50 parts of 10-mesh quartz sand were added and the mixture was ball-milled for 110 minutes to obtain the ball milling material. The residue on the 325-mesh sieve was 14%, and the proportion of particles smaller than 10 μm was 45%.

[0056] (2) Mix the ball milling material, 2.5 parts of sodium carboxymethyl cellulose, bactericide and water, stir, sieve and age to obtain a ceramic anti-stick coating.

[0057] Comparative Example 7

[0058] This comparative example prepared a ceramic anti-sticking coating, which differs from Example 1 in that zirconium silicate is not added. The specific process is as follows:

[0059] (1) By weight, 36 parts of 100-mesh alumina, 5 parts of kaolin, 3 parts of black pigment, 1 part of zirconium iron red, and 4 parts of praseodymium yellow were added to a ball mill. Water was added and the ball milling was carried out for 60 minutes. After the first ball milling was completed, 51 parts of 10-mesh quartz sand were added and the ball milling was carried out for 110 minutes to obtain the ball milling material. The residue on the 325-mesh sieve was 16.2%, and the proportion of particles smaller than 10 μm was 41%.

[0060] (2) Mix the ball milling material, 5.3 parts of sodium carboxymethyl cellulose, bactericide and water, stir, sieve and age to obtain a ceramic anti-stick coating.

[0061] Comparative Example 8

[0062] This comparative example prepared a ceramic anti-sticking coating. The difference from Example 1 is that kaolin is not added, and the amount of sodium carboxymethyl cellulose is increased. The specific process is as follows:

[0063] (1) By weight, 36 parts of 100-mesh alumina, 1 part of zirconium silicate, 3 parts of black pigment, 1 part of zirconium iron red, and 4 parts of praseodymium yellow were added to a ball mill. Water was added and the mixture was ball-milled for 60 minutes. After the first ball milling was completed, 50 parts of 10-mesh quartz sand were added and the mixture was ball-milled for 110 minutes to obtain the ball milling material. The residue on the 325-mesh sieve was 16.1%, and the proportion of particles smaller than 10 μm was 41.6%.

[0064] (2) Mix the ball milling material, 8 parts of sodium carboxymethyl cellulose, bactericide and water, stir, sieve and age to obtain a ceramic anti-stick coating.

[0065] Test case

[0066] This experiment tested the performance of the anti-sticking coatings for ceramics prepared in the examples and comparative examples. The test method involved applying the anti-sticking coating to the joint between the assembly and the main body. The assembly and main body were then placed in a kiln for firing in their assembled state. After firing, the powdering and sticking at the joint were observed, and the color of the applied area was measured using a colorimeter. The test results are shown in Table 1.

[0067] Table 1

[0068]

[0069] Lab values: The Lab color model uses the Lab coordinate system, where a larger L value indicates a lighter color, and a smaller value indicates a darker color; a positive a value represents red, and a negative a value represents green; a positive b value represents yellow, and a negative b value represents blue.

[0070] In Comparative Example 1, due to the reduced ball milling time, the coating particles were larger and contained more coarse particles, resulting in obvious powdering and sticking.

[0071] In Comparative Example 2, due to the increased ball milling time, the coating particle size was smaller, with fewer coarse particles and more fine particles. No powdering occurred, but burning and sticking occurred.

[0072] Comparative Example 3 introduced 325-mesh high-purity quartz powder, with a purity exceeding 95%. This quartz underwent impurity removal (removal of iron, mica, and feldspar) and calcination processes, losing the original coloring properties of quartz sand. Pigments struggled to penetrate the quartz interior, resulting in a change in the paint's color after firing. The pigment's color became lighter, the L value increased, and the ab value decreased, leading to a significant color difference between the paint and the ceramic substrate. Furthermore, the small particle size of the quartz powder caused the overall particle size of the paint to be too small, resulting in sticking during firing.

[0073] Comparative Example 4 increased the amount of 100-mesh alumina and reduced the amount of quartz sand. There was no powdering or sticking phenomenon, but the color of the pigment became lighter, resulting in a large color difference between the coating and the ceramic body.

[0074] Comparative Examples 5 and 6 increased the amount of kaolin. The addition of kaolin reduced the fluidity of the slurry. In order to ensure the coating effect, the sodium carboxymethyl cellulose content needed to be reduced, which led to a decrease in the adhesion of the coating and the occurrence of powdering.

[0075] In Comparative Example 7, the removal of zirconium silicate from the formulation resulted in a weakening of the colorant's coloring ability, causing a deviation between the color of the coating and the ceramic body.

[0076] In Comparative Example 8, increasing the amount of sodium carboxymethyl cellulose to ensure the brushability of the coating and reducing the amount of kaolin could not solve the problem of coating spread, resulting in uneven coating and partial burning and sticking at the bonding area.

[0077] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A ceramic anti-seizure coating characterized by, The ceramic anti-sticking coating comprises the following raw materials by weight: 30-40 parts of alumina, 2-8 parts of kaolin, 40-60 parts of quartz sand, 0.5-3 parts of zirconium silicate, 2-5 parts of black pigment, 0-2 parts of zirconium iron red, 0-6 parts of praseodymium yellow, and 4-7 parts of sodium carboxymethyl cellulose.

2. The anti-seizure coating for ceramics according to claim 1, characterized by The alumina has a mesh size of 90-150.

3. The anti-seizure coating for ceramics according to claim 1, characterized by, The quartz sand has a mesh size of 5-20.

4. The anti-seizure coating for ceramics according to claim 1, characterized by, The particle size distribution of the ceramic anti-sticking coating is as follows: D10=1.4-1.8 μm, D50=14-16 μm, and D90=52-60 μm.

5. The anti-seizure coating for ceramics according to claim 1, characterized by, The specific gravity of the ceramic anti-sticking coating is 1.2-1.25, and the 4-cup viscosity is 50±5 s.

6. The method of producing a ceramic anti-sticking coating according to any one of claims 1 to 5, wherein The method comprises the following steps: (1) ball milling the alumina, kaolin, zirconium silicate, black pigment, zirconium iron red, and praseodymium yellow once, and then adding the quartz sand to ball mill again to obtain a ball mill material; (2) mixing the ball mill material, sodium carboxymethyl cellulose, and water to obtain the ceramic anti-sticking coating.

7. The production method according to claim 6, wherein The particle size of the ball mill material is required to be as follows: 40-48% of particles less than 10 μm, and 13-19% of particles passing through a 325 mesh sieve.

8. The preparation method according to claim 6, characterized in that, The first ball milling time is 50-70 min.

9. The preparation method according to claim 6, characterized in that, The second ball milling time is 100-120 min.

10. Use of the anti-seizure coating for ceramics according to any one of claims 1 to 5 in the ceramic firing, characterized in that, The anti-sticking coating is applied to the joint between the assembly and the main body, and the assembly and the main body are put into a kiln for firing in a combined state.

Images