Magnesian reinforced porcelain black glaze coloring agent as well as preparation method and application thereof

Abstract

The invention discloses a magnesium reinforced porcelain black underglaze coloring agent as well as a preparation method and application thereof, and belongs to the technical field of underglaze coloring agents. The magnesium porcelain reinforced porcelain black underglaze coloring agent comprises the following solid components in percentage by weight: 12-15% of potassium feldspar, 9-15% of albite, 9-12% of calcite, 11-15% of quartz, 16-20% of kaolin, 1-1.2% of methyl cellulose and 31-34% of cobalt black pigment. Wherein the weight content of K2O in the potassium feldspar is greater than or equal to 10%; the weight content of Al2O3 in the kaolin is greater than or equal to 37%; and the weight content of Co3O4 in the cobalt black pigment is 15-25%. The prepared black underglaze coloring agent can be well suitable for a magnesium reinforced porcelain body and a cover glaze of a low-temperature fritted glaze, an obtained black underglaze product is full and pure in color development, the blue bleaching phenomenon does not occur after decoration firing, and meanwhile the glaze surface is free of orange color and pinholes.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of underglaze colorant, and particularly relates to a magnesium reinforced porcelain black underglaze colorant and a preparation method and application thereof. BACKGROUND

[0002] Magnesium reinforced porcelain is a high-end daily-use porcelain. According to the national standard, the content of magnesium oxide in the porcelain is required to be greater than or equal to 22%.

[0003] The magnesium reinforced porcelain is mainly made of talc and feldspar, and is fired at 1280±5 DEG C to form porcelain. The magnesium reinforced porcelain belongs to high-temperature fired porcelain, has a dense structure, a water absorption rate of less than or equal to 0.25%, and a strength higher than that of general white porcelain. Since the magnesium reinforced porcelain is put into production, it has been used as decoration production in the form of white body or white body with decals. With the improvement of people's living standards and aesthetic level, and the requirement for green and healthy daily-use ceramic products, the demand for high-grade underglaze color series of magnesium reinforced porcelain is very large, but no domestic manufacturer can produce the same.

[0004] At present, in ceramic decoration, black color materials are mainly realized through the compounding of transition metal oxides (such as cobalt, iron, chromium, manganese, etc.) or spinel structure. There are the following several common types:

[0005] (1) Cobalt-iron-chromium-based spinel black, chemical formula is CoFeCrO4. The colorant has good high-temperature stability and can resist 1200-1300 DEG C, and is commonly used in underglaze color or high-temperature glaze. The colorant is obtained by compounding Co 2+ (blue), Fe 3+ (red-brown), and Cr 3+ (green) to absorb light spectrum and present pure black color. However, the colorant is easily oxidized and discolored (such as Co 2+ → Co 3+ , color is blue-gray) in overglaze color baking (830-860 DEG C).

[0006] (2) Iron-chromium-manganese black, chemical formula is FeCrMnO4. The colorant is a cobalt-free black formula and has low cost. The colorant is obtained by mixing valence states of Fe 3+ , Cr 3+ , and Mn 3+ to absorb visible light and present color. However, the colorant is easily affected by atmosphere at high temperature, and the presented black color is a little reddish brown black color. The colorant is easily reacted with flux to generate brown color (Fe2O3) or green color (Cr2O3) in overglaze color baking.

[0007] (3) Nickel-iron-chromium black, chemical formula is Ni(Fe,Cr)2O4. The colorant uses nickel to replace cobalt, has good stability, and presents cold black color. However, the nickel in the colorant may be harmful to human body.

[0008] (4) Copper-chromium black, chemical formula CuCr204(copper chromite black), this colorant has low cost, but is sensitive to firing atmosphere and unstable in color (Cu 2+ → Cu + , red color).

[0009] At present, black underglaze color produced on the market is realized on ordinary feldspar porcelain, which is mainly composed of feldspar, quartz and kaolin. These raw materials are relatively stable in color development for black colorants. The cobalt-iron-chromium spinel black described above belongs to spinel type colorant, which has very compact structure and small solubility in glaze, thus can resist high temperature and has bright color. The composition of this colorant is CoFe204, CoCr204, which can absorb visible light through Co 2+ , Fe 3+ , Cr 3+ plasma, and present pure black color. This colorant is stable at high temperature, and cobalt black can exist stably in underglaze color (oxidation firing, 1100-1130℃).

[0010] However, the main component of magnesia reinforced porcelain body is talc, and the content of magnesium oxide is ≥22%. Magnesium oxide has strong alkalinity, which has great influence on the color development of black colorants.

[0011] Magnesia reinforced porcelain has high porcelain forming temperature, and the firing temperature is 1280±5℃. The body is easy to deform, and needs to be fired in a simulated mold kiln. Therefore, the production process adopted is high-temperature body firing and low-temperature glazing, and the glazing temperature is 1100-1130℃. Therefore, the transparent glaze for magnesia reinforced porcelain is a low-temperature glaze. In order to adapt to the low-temperature glazing temperature and the magnesia reinforced porcelain body, boracic acid with large surface tension at high temperature melting and strong fluxing alkali compounds such as zinc and lithium are added in the glaze formula. Due to the high magnesium content of magnesia reinforced porcelain, the addition of glaze with boracic acid as the main flux can make the glaze surface of the body flat, smooth and without dull phenomenon at the edge. The low initial melting point of this glaze will have a certain melting on the surface during the overglaze firing (830-860℃), and the boron in the glaze is easy to react with cobalt in the black colorant, resulting in the phenomenon of color change.

[0012] At the same time, the overglaze firing (830-860℃) is easy to cause color change due to different overglaze firing processes.

[0013] (1) Change of valence state of cobalt ion

[0014] Oxidation reaction: overglaze firing is mostly in oxidizing atmosphere, Co 2+ may be oxidized to Co 3+ (such as Co2O3), resulting in color deviation to blue-gray.

[0015] (2) Insufficient temperature or short time of overglaze firing, spinel structure is not completely formed, and the color is not pure.

[0016] (3) Influence of transparent glaze with boric anhydride as main flux on magnesia reinforced porcelain.

[0017] Therefore, it is necessary to provide a black underglaze colorant which is suitable for both magnesia reinforced porcelain body and transparent glaze with boric anhydride as main flux and for black underglaze decoration process. SUMMARY

[0018] In order to overcome the deficiencies of the prior art, the present application provides a black underglaze colorant for magnesia reinforced porcelain, a preparation method and application thereof. The black underglaze colorant for magnesia reinforced porcelain has the advantages of pure color, bright color and high saturation, and the color is not blue after decoration, and the glaze surface is free of orange color and pinholes, which fills the gap in the production of black underglaze color for magnesia reinforced porcelain at home and abroad and meets the demand of people for high-grade black underglaze color series products.

[0019] The technical scheme adopted by the present application to solve the technical problems is:

[0020] The present application provides a black underglaze colorant for magnesia reinforced porcelain, and the solid components thereof include, in terms of percentage by weight, 12-15% of potassium feldspar, 9-15% of sodium feldspar, 9-12% of calcite, 11-15% of quartz, 16-20% of kaolin, 1-1.2% of methyl cellulose and 31-34% of cobalt black pigment.

[0021] The weight content of K2O in the potassium feldspar is ≥10%;

[0022] The weight content of Al2O3 in the kaolin is ≥37%;

[0023] The weight content of Co3O4 in the cobalt black pigment is 15-25%.

[0024] Preferably, the chemical composition of the potassium feldspar is SiO2: 60-70%, Al2O3: 15-20%, CaO: 0.2-0.5%, K2O: 10-12%, Na2O: 2-3%, and the balance is other components.

[0025] Preferably, the chemical composition of the kaolin is SiO2: 40-43%, Al2O3: 37-39%, CaO: 2.5-3.5%, K2O: 0.1-0.2%, and the balance is other components.

[0026] Preferably, the chemical composition of the cobalt black pigment is 15-25% Co3O4, 30-45% Fe2O3, 25-40% Cr2O3 and 5-10% Al2O3.

[0027] Preferably, the magnesium porcelain reinforced porcelain black underglaze colorant further comprises water, with a specific gravity of 1.34-1.36 g / ml.

[0028] The application provides a preparation method of the magnesium porcelain reinforced porcelain black underglaze colorant.

[0029] The potassium feldspar, sodium feldspar, calcite, quartz, kaolin, cobalt black pigment and methyl cellulose are ball milled with water, sieved, slurried, and a magnesium porcelain reinforced porcelain black underglaze colorant is obtained.

[0030] Preferably, the weight ratio of the ball milling material to water is 100:150-170.

[0031] Preferably, the ball milling time is 12-15 h, and the ball milling residue on a 325 mesh sieve is less than 0.05%.

[0032] Preferably, the sieving is performed on a 150-180 mesh sieve.

[0033] Preferably, the slurry has a specific gravity of 1.34-1.36 g / ml and a flow rate of 38-48 s / 100 ml.

[0034] The application provides a magnesium porcelain reinforced porcelain black underglaze color, comprising a magnesium reinforced porcelain body, a black underglaze color layer and a protective glaze layer; the black underglaze color layer is prepared from the magnesium porcelain reinforced porcelain black underglaze colorant or the magnesium porcelain reinforced porcelain black underglaze colorant prepared by the preparation method.

[0035] Preferably, the weight content of MgO in the magnesium reinforced porcelain body is more than 22%; the porcelain is high in whiteness, good in transparency and high in strength, and is liked by consumers.

[0036] Further preferably, the components of the magnesium reinforced porcelain body are SiO2: 61-63%, Al2O3: 4-5%, CaO: 2-3%, MgO: 22-24%, K2O: 0.5-1%, Na2O: 0.2-0.5%, and the balance is other components.

[0037] Preferably, the protective glaze layer is prepared from a low-temperature fused glaze with boric anhydride as the main flux.

[0038] Further preferably, the components of the low-temperature fused glaze are SiO2: 53-55%, Al2O3: 10-12%, CaO: 8-9%, MgO: 0.5-1%, K2O: 3-4%, Na2O: 2-3%, ZnO: 1.5-2%, Li2O: 1.5-2%, B2O3: 10-12%, and the balance is other components.

[0039] The application provides a preparation method of the magnesium reinforced porcelain black underglaze color.

[0040] (1) high temperature sintering of the magnesia reinforced porcelain body, polishing, cleaning, drying, cooling;

[0041] (2) after the cooling of step (1) of the magnesia reinforced porcelain body, drawing glue film, heating, magnesia reinforced porcelain black underglaze colorant spray color, dry, wipe color, baking color, to get magnesia reinforced porcelain black color body;

[0042] (3) glazing of the magnesia reinforced porcelain black color body, dry, glaze firing, to get magnesia reinforced porcelain black underglaze color finished product.

[0043] Preferably, the temperature of step (1) is 1280±5℃, the time is 12-15h, and the atmosphere is oxidation atmosphere (O2 concentration is 3%-5%); the water absorption rate of the body after high temperature sintering is ≤0.25%;

[0044] Preferably, the temperature of step (1) is 60-70℃, and the drying time is 2-3h;

[0045] Preferably, the temperature of step (2) is 100-120℃;

[0046] Preferably, step (2) rotates the magnesia reinforced porcelain body while spraying color;

[0047] Preferably, the thickness of step (2) is 0.2-0.4mm;

[0048] Preferably, step (2) is naturally dried at room temperature in air;

[0049] Preferably, step (2) is to tear off the glue film and wipe off the excess colorant;

[0050] Preferably, the temperature of step (2) is 1120-1140℃, the time is 8-10h, and the atmosphere is oxidation atmosphere, O2 concentration is 3%-5%;

[0051] Preferably, step (3) rotates the magnesia reinforced porcelain black color body while spraying glaze;

[0052] Preferably, the thickness of step (3) is 0.15-0.3mm;

[0053] Preferably, step (3) is naturally dried at room temperature in air;

[0054] Preferably, the temperature of step (3) is 1100-1130℃, the time is 10-12h, and the atmosphere is oxidation atmosphere, O2 concentration is 3%-5%.

[0055] The present invention provides a magnesium reinforced porcelain overglaze color, which is obtained by applying overglaze and baking the above-mentioned magnesium reinforced porcelain black underglaze color or the magnesium reinforced porcelain black underglaze color prepared by the above-mentioned preparation method.

[0056] Preferably, the baking temperature is 830-860°C, the baking time is 4-6 hours, and the baking atmosphere is a weak oxidizing atmosphere or a neutral atmosphere, wherein the O2 concentration of the weak oxidizing atmosphere is >1% and ≤3%, and the CO is 0; the O2 concentration of the neutral atmosphere is 0.5%-1%, and the CO is 0.

[0057] The present invention adjusts the formula of the black underglaze colorant: because the cobalt raw material has good color development and strong molecular activity, it can diffuse into the glaze layer and easily react chemically with other substances. In addition, if the colorant and the flux are not matched, the calcium, magnesium, etc. in the raw material will react with the cobalt to form light-colored compounds (such as CoAl2O4, blue). The adjustment plan is to increase the high-temperature viscosity of the flux so that the cobalt ions are wrapped and isolated by the flux, forming a stable crystalline phase with the flux. Excessive elements such as calcium and magnesium are not added to the flux to avoid reaction with cobalt. In addition, the black underglaze colorant must also be compatible with the expansion coefficient and chemical properties of the glaze.

[0058] The black underglaze colorant prepared by the present invention is well suited for use as a top glaze for magnesium-reinforced porcelain bodies and low-temperature frit glazes with boron trioxide as the primary flux. The resulting black underglaze colored products not only have a rich, pure color, but also exhibit no bluish bleaching after baking, achieving a pass rate of 95%. The potassium feldspar, sodium feldspar, kaolin, and calcite in the black underglaze colorant effectively help the black colorant melt during baking, completely forming a stable crystalline phase with the cobalt ions in the black colorant, ensuring that no free cobalt ions are precipitated during subsequent baking. Therefore, even though the top glaze melts to a certain extent during baking, no excess cobalt ions react with it, resulting in a blue color. Furthermore, the temperature and atmosphere are controlled during the baking process, resulting in a pass rate exceeding 95%.

[0059] Furthermore, the introduction of potassium feldspar with high potassium content is to better reduce the melting temperature of the flux during low-temperature baking, better melt the black colorant, and make the colorant better adsorbed on the blank.

[0060] Furthermore, the introduction of albite also plays a fluxing role, and can also increase the expansion coefficient of the colorant, so that the colorant and the blank are better combined.

[0061] Furthermore, the introduction of quartz can form a stable crystal phase with potassium and sodium.

[0062] Furthermore, the introduction of calcite can react quickly with the quartz in the flux, thereby reducing the melting temperature of the flux and better promoting black color.

[0063] Further, the introduction of kaolin can effectively promote the adsorption of black colorant on the body, increase the high-temperature viscosity of flux, and facilitate better wrapping of cobalt in the black colorant, thereby inhibiting the activity of cobalt.

[0064] The colorant is cobalt black colorant because the colorant belongs to cobalt-iron-chromium-based spinel type colorant, the structure of which is very compact, and the solubility in glaze is very small, so it can resist high temperature and has bright color.

[0065] Further, methyl cellulose is introduced because the colorant in the underglaze colorant is abundant and has low specific gravity, which leads to easy precipitation of the colorant. The addition of methyl cellulose can play a suspending role, and also can improve the viscosity and dry strength of the colorant, which is beneficial to production operation. However, too much methyl cellulose cannot be added, otherwise it will cause the colorant to be very thick, resulting in uneven color spraying defects.

[0066] The present application optimizes the colorant formula and controls the firing process: high-stability spinel structure colorant (such as CoFeCrO4) is used to reduce the risk of oxidation. In addition, aluminum oxide (Al2O3) is added to stabilize the valence state of cobalt ions when the colorant is made. The firing temperature is controlled between 830-860℃ to ensure that the spinel structure is fully formed. A weak oxidation or neutral atmosphere is used during firing to avoid strong oxidation leading to Co 2+ oxidation to Co 3+ (such as Co2O3), which causes the color to deviate to blue-gray.

[0067] The beneficial effects of the present application are:

[0068] The black underglaze colorant prepared by the present application can be well applied to magnesium reinforced porcelain body and low-temperature frit glaze surface glaze. The black underglaze color product obtained not only has full and pure color, but also does not appear blue drift after firing, and the glaze surface is free of orange color and pinholes. DETAILED DESCRIPTION

[0069] The present application will be further described below in conjunction with examples.

[0070] The concept, specific scheme and technical effects of the present application will be described below in conjunction with examples to fully understand the purpose, features and effects of the present application. Obviously, the described examples are only a part of the examples of the present application, but not all examples. Based on the examples of the present application, other examples obtained by those skilled in the art without creative labor are within the scope of protection of the present application. Each technical feature in the present application can be combined with each other without conflict.

[0071] The application provides a kind of magnesium porcelain reinforced porcelain black underglaze colorant, according to percentage by weight, its solid component material includes: potassium feldspar 12-15%, sodium feldspar 9-15%, calcite 9-12%, quartz 11-15%, kaolin 16-20%, methyl cellulose 1-1.2%, cobalt black material 31-34%;

[0072] Among them, the weight content of K2O in potassium feldspar is ≥10%;

[0073] The weight content of Al2O3 in kaolin is ≥37%;

[0074] The weight content of Co3O4 in cobalt black material is 15-25%.

[0075] Preferably, the chemical composition of the potassium feldspar is SiO2: 60-70%, Al2O3: 15-20%, CaO: 0.2-0.5%, K2O: 10-12%, Na2O: 2-3%, and the balance is other components; the content of K2O cannot be too low.

[0076] Further preferably, the chemical composition of the potassium feldspar is SiO2: 67%, Al2O3: 17%, CaO: 0.22%, K2O: 11.2%, Na2O: 2.7%, and the balance is other components.

[0077] Preferably, the chemical composition of the kaolin is SiO2: 40-43%, Al2O3: 37-39%, CaO: 2.5-3.5%, K2O: 0.1-0.2%, and the balance is other components; wherein the content of Al2O3 needs to be ≥37%.

[0078] Preferably, the chemical composition of the cobalt black material is 15-25% Co3O4, 30-45% Fe2O3, 25-40% Cr2O3, and 5-10% Al2O3. Co3O4 is introduced because Co3O4 has a spinel structure.

[0079] Further preferably, the cobalt black material is obtained by adding oxides of cobalt, iron, and chromium to alumina to form a stable spinel structure. First, the oxides are weighed according to the formula, dry mixed uniformly, and then calcined (solid phase reaction) at a temperature of 1200-1400°C for 4-6h, mainly in an oxidizing atmosphere (O2 concentration in the kiln is 3%-5%) to form a spinel phase (such as CoFeCrO4). Then the calcined block is crushed, wet ground to micron level (D50<1μm) to ensure the dispersion of the pigment, then acid washed to remove unreacted impurities, and then dried (100-120°C).

[0080] Preferably, the magnesium porcelain reinforced porcelain black underglaze colorant further includes water with a specific gravity of 1.34-1.36g / ml.

[0081] The present application provides a preparation method of black underglaze colorant, comprising the following steps:

[0082] Potassium feldspar, sodium feldspar, calcite, quartz, kaolin, cobalt black pigment, and methyl cellulose are weighed according to the ratio, put into a ball mill, water is added, the ratio of material to water is 100:150-170, the ball milling time is 12-15h, after ball milling to 325 mesh screen residue <0.05%, the mill is discharged, and then 150-180 mesh screen is passed, and finally the specific gravity is adjusted to 1.34-1.36g / ml, and the flow rate is 38-48s / 100ml.

[0083] Specifically, the weights of the raw materials in the preparation step of the underglaze colorant are as follows: potassium feldspar 12-15%, sodium feldspar 9-15%, calcite 9-12%, quartz 11-15%, kaolin 16-20%, methyl cellulose 1-1.2%, and cobalt black pigment 31-34%.

[0084] The present application provides a use method of the above-mentioned underglaze colorant, comprising the following steps:

[0085] Preparation of the device: the chemical composition of the magnesia reinforced porcelain body of the present application is as follows: SiO2: 61-63%, Al2O3: 4-5%, CaO: 2-3%, MgO: 22-24%, K2O: 0.5-1%, Na2O: 0.2-0.5%, and the balance is other components. The raw materials of these components are weighed according to the ratio, put into a ball mill, and a certain amount of water is added, the ratio of material to water is 100:30-35, the ball milling time is 15-18h, after ball milling, 250-280 mesh screen is passed and iron is removed, the ball milling fineness is 325 mesh screen residue <0.05%, and the obtained slurry is pressed into a mud cake by a filter press, and then the mud cake is aged, and then the mud cake is converted into slurry or mud strip according to the production needs. The slurry or mud strip is put into a gypsum mold, and the slurry or mud strip is formed by injection or rolling, and then the green body is further finished to obtain a finished body.

[0086] High-temperature vitrification: the finished body is placed on a simulated mold, and then is put into a high-temperature kiln for high-temperature vitrification, the high-temperature vitrification temperature is 1280±5℃, the firing time is 12-15h, and the firing atmosphere is an oxidizing atmosphere (the O2 concentration in the kiln is 3%-5%), and the water absorption of the finished body is ≤0.25%.

[0087] Polishing and cleaning: the surface of the finished body is polished and cleaned, and then is placed in an oven for drying, the drying temperature is 60-70℃, the drying time is 2-3h, and a dry device is formed for standby use.

[0088] Cooling of the device: the dry device in the oven is taken out and naturally cooled in room temperature air.

[0089] Heating device: the cooling device is passed through a drawing adhesive film to isolate the color area not needed, and then is placed into a mesh kiln to heat the blank, and the temperature of the mesh kiln is controlled between 100-120℃.

[0090] Spraying color: black colorant is added into an air compressor gun, and then the heated blank is placed on a rotating disc to spray color on the blank, and the rotating disc is rotated to make the colorant on the surface of the blank even, and the thickness of the colorant is between 0.2-0.4mm.

[0091] Air drying: the blank sprayed with color is placed in a fixed area to be naturally air dried.

[0092] Color wiping: the blank air dried is taken off the adhesive film, and the excess colorant is wiped off to avoid the white part of the blank being stained.

[0093] Color baking: the blank sprayed with color is placed into a kiln to be baked, the baking temperature is 1120-1140℃, the baking time is 8-10h, and the atmosphere of the kiln is oxidizing atmosphere (O2 concentration in the kiln is 3%-5%).

[0094] Glazing: the glaze used in the application is a low-temperature frit glaze using boron trioxide as the main flux. The chemical composition of the glaze is: SiO2: 53-55%, Al2O3: 10-12%, CaO: 8-9%, MgO: 0.5-1%, K2O: 3-4%, Na2O: 2-3%, ZnO: 1.5-2%, Li2O: 1.5-2%, B2O3: 10-12%, and the rest is other components. The raw materials are weighed and mixed according to the ratio, and then are placed into a frit kiln to be calcined and fused at a high temperature of 1300-1350℃, the obtained glass melt is condensed into frit by water quenching method, the frit is mixed with water, and then is placed into a ball mill, the ratio of the material to water is 100:35-40, the ball milling time is 25-28h, the residue on a 325 mesh sieve is less than 0.05%, and after being discharged from the ball mill, the material is sieved through a 250-280 mesh sieve and iron is removed, so that the magnesia strengthened porcelain low-temperature frit glaze is obtained.

[0095] The glaze is added into an air compressor gun to spray the baked blank placed on a rotating disc, and the rotating disc is rotated to ensure that the glaze is evenly adsorbed on the blank, and the thickness of the glaze layer is between 0.15-0.3mm.

[0096] Air drying: the blank sprayed with color is placed in a fixed area to be naturally air dried.

[0097] Glaze baking: the blank completely air dried is placed into a glaze baking kiln to be baked, the baking temperature is 1100-1130℃, the baking time is 10-12h, and the atmosphere of the kiln is oxidizing atmosphere (O2 concentration in the kiln is 3%-5%).

[0098] Black underglaze color finished product: after the device is fired, the qualified black underglaze color finished product is obtained after inspection.

[0099] Baking decoration: the qualified black underglaze color finished product of magnesia reinforced porcelain is placed into a baking decoration kiln after being decorated with glaze, the baking decoration temperature is 830-860℃, the baking decoration time is 4-6h, and the baking decoration atmosphere is weak oxidizing atmosphere (O2 concentration in the kiln is >1% and ≤3%, CO is close to 0) or neutral atmosphere (O2 concentration in the kiln is 0.5%-1%, CO is approximately 0).

[0100] In the following examples and comparative examples, the chemical composition of sodium feldspar is SiO2: 70.4%, Al2O3: 18.5%, CaO: 0.12%, K2O: 0.89%, Na2O: 8.93%, and the balance is other components. The chemical composition of calcite is SiO2: 3.5%, Al2O3: 0.18%, CaO: 52.58%, K2O: 0.05%, Na2O: 0.00%, loss on ignition: 41.92%, and the balance is other components. The chemical composition of quartz is SiO2: 98.3%, Al2O3: 0.8%, CaO: 0.07%, K2O: 0.12%, Na2O: 0.00%, and the balance is other components.

[0101] Examples A1-A5:

[0102] Preparation of black underglaze colorant, the specific addition of raw materials is shown in Table 1.

[0103] Among them, the chemical composition of potassium feldspar is SiO2: 67%, Al2O3: 17%, CaO: 0.22%, K2O: 11.2%, Na2O: 2.7%, and the balance is other components. The chemical composition of kaolin is SiO2: 42.7%, Al2O3: 37.2%, CaO: 3.27%, K2O: 0.14%, and the balance is other components. The chemical composition of cobalt black pigment is 20% Co3O4, 35% Fe2O3, 40% Cr2O3, and 5% Al2O3.

[0104] The raw materials are weighed according to the proportion, put into the ball mill, add water, the weight ratio of material to water is 100:160, the ball milling time is 15h, after ball milling to 325 mesh screen residue <0.05%, out of the mill, pass through 150 mesh screen, finally adjust the specific gravity to 1.35g / ml, the flow rate is 48s / 100ml.

[0105] An application method using the prepared black underglaze colorant, comprising the following steps:

[0106] Preparation of the device: the chemical composition of the magnesia reinforced porcelain body of the present application is: SiO2: 61.8%, Al2O3: 4.9%, CaO: 2.6%, MgO: 24%, K2O: 0.82%, Na2O: 0.3%, and the balance is other components. The raw materials of these components are weighed according to the ratio, added with a certain amount of water in a ball mill, the ratio of material to water is 100:30, the ball milling time is 15h, after ball milling, it is sieved through a 250 mesh sieve and de-ironed, the ball milling fineness is less than 0.05% of the residue on a 325 mesh sieve, the obtained slurry is pressed into a mud cake by a filter press, and after aging, the mud cake is converted into slurry or mud strip according to the production needs (slurry in this embodiment). The slurry is then put into a gypsum mold, and the slurry is injected to form a green body, and after further finishing, a fine body is obtained.

[0107] High temperature vitrification: the fine body is placed on a simulated mold, and then put into a high temperature kiln for high temperature vitrification, the temperature is 1280±5℃, the firing time is 15h, and the firing atmosphere is an oxidizing atmosphere (O2 concentration in the kiln is 3%-5%), and the water absorption of the porcelain body is required to be less than or equal to 0.25%.

[0108] Polishing and cleaning: the surface of the porcelain body is polished and cleaned, and then placed in an oven for drying, the drying temperature is 60-70℃, the drying time is 3h, and a dry device is formed for standby.

[0109] Cooling device: the dry device taken out from the oven is placed in a special area and naturally cooled in room temperature air.

[0110] Heating device: the cooled device is coated with a glue film to isolate the areas that do not need color, and then placed in a mesh kiln to heat the body, the mesh kiln temperature is controlled between 100-120℃, and the heating time is 20 minutes.

[0111] Color spraying: black underglaze colorant is added to an air compressor gun, and the heated body (without cooling) is placed on a turntable, and the body is hot sprayed with color, since the body has been completely vitrified and has no water absorption, cold spraying will cause color flow and thin color absorption. The turntable is rotated while spraying to make the colorant evenly adhere to the surface of the body, and the thickness of the colorant is between 0.2-0.4mm.

[0112] Air drying: the body with sprayed color is placed in a fixed area and naturally air dried at room temperature.

[0113] Color wiping: the air dried body is wiped to remove the excess colorant to avoid color contamination on the white exposed part of the body.

[0114] Color baking: the treated body with sprayed color is placed in a kiln for color baking, the color baking temperature is 1140℃, the color baking time is 10h, and the kiln atmosphere is an oxidizing atmosphere (O2 concentration in the kiln is 3%-5%).

[0115] Glazing: The glaze used in the present application is a low temperature frit glaze. The chemical composition of the glaze is: SiO2: 54.6%, Al2O3: 11.8%, CaO: 8.5%, MgO: 0.7%, K2O: 3.4%, Na2O: 2.4%, ZnO: 1.9%, Li2O: 1.9%, B2O3: 11.8%, and the balance is other components. The raw materials are weighed according to the ratio and mixed uniformly, then put into a frit furnace and calcined at a high temperature of 1350°C, the obtained glass melt is condensed into frit by water quenching method, then the frit is mixed with water and put into a ball mill, the ratio of material to water is 100:35, the ball milling time is 25h, and the sieve residue of 325 mesh is less than 0.05%, then the material is sieved through a 250 mesh sieve and iron is removed, and a magnesia strengthened porcelain low temperature frit glaze is obtained.

[0116] The glaze is added to a spray gun with compressed air, and the color baking is sprayed on the turntable, and the turntable is rotated during the spraying process to ensure that the color baking is evenly adsorbed with glaze, and the glaze layer is between 0.15-0.3mm thick.

[0117] Air drying: The glazed device is placed in a fixed area and naturally air dried at room temperature.

[0118] Glaze firing: The completely dried glazed device is placed in a glaze firing kiln for glaze firing, the glaze firing temperature is 1120°C, the glaze firing time is 12h, and the glaze firing atmosphere is an oxidizing atmosphere (O2 concentration in the kiln is 3%-5%).

[0119] Black underglaze color finished product: After the glaze firing, the device is inspected to obtain qualified ceramic finished products.

[0120] Color baking: The black underglaze color qualified finished product of magnesia strengthened porcelain is placed in a color baking kiln after glazing and color baking, the color baking temperature is 860°C, the color baking time is 6h, and the color baking atmosphere is a weak oxidizing atmosphere (O2 concentration in the kiln is >1% and ≤3%, CO is close to 0) or a neutral atmosphere (O2 concentration in the kiln is 0.5%-1%, CO is approximately 0), (this embodiment is a weak oxidizing atmosphere).

[0121] Table 1: Ratio of black underglaze colorant

[0122]

[0123]

[0124] Table 2: Glaze firing and color baking glaze surface results of examples A1-A5

[0125] Item Example A1 Example A2 Example A3 Example A4 Example A5 Orange color of overfired glaze None None None None None Pinholes in overfired glaze None None None None None Color of overfired glaze Good Good Good Good Good Did overfired glaze bloom? None None None None None

[0126] From the above table, it can be seen that the potassium feldspar, sodium feldspar, calcite, quartz, kaolin, methyl cellulose, cobalt black colorant in examples Al-A5, although the amount added is different, but are in the range of potassium feldspar 12-15%, sodium feldspar 9-15%, calcite 9-12%, quartz 11-15%, kaolin 16-20%, methyl cellulose 1-1.2%, cobalt black colorant 31-34%, the glaze obtained is good, and the firing flower is not blue, which shows that the formula range is reasonable.

[0127] Examples Bl-B7

[0128] The preparation of black underglaze colorant, the specific added raw materials are shown in Table 3.

[0129] Among them, the chemical composition of potassium feldspar is SiO2: 67%, Al2O3: 17%, CaO: 0.22%, K2O: 11.2%, Na2O: 2.7%, and the balance is other components. The chemical composition of kaolin is SiO2: 42.7%, Al2O3: 37.2%, CaO: 3.27%, K2O: 0.14%, and the balance is other components. The chemical composition of cobalt black colorant is 20% Co3O4, 35% Fe2O3, 40% Cr2O3, 5% Al2O3.

[0130] The raw materials are weighed according to the ratio, put into the ball mill, add water, the ratio of material to water is 100:160, ball mill for 15h, after ball milling to 325 mesh screen residue less than 0.05%, out of the mill, pass through 150 mesh screen, finally adjust the specific gravity to 1.35g / ml, flow rate 48s / 100ml.

[0131] An application method using the above prepared black underglaze colorant, comprising the following steps:

[0132] The same as examples Al-A5.

[0133] Table 3: Ratio of black underglaze colorant

[0134]

[0135] Table 4: Glaze firing and firing glaze results of examples Bl-B7

[0136]

[0137] From the above table, it can be seen that in example Bl, the amount of potassium feldspar added is not in the formula range, the amount is reduced, and the rest of the components are in the normal range. From the glaze effect, pinholes appear, mainly due to the lack of potassium feldspar, which changes the reaction degree with other components, resulting in poor glaze.

[0138] In Example B2, the addition amount of sodium feldspar is not in the formula range, and the rest of the ingredients are in the normal range. The same will also cause the chemical reaction of this formula to be different, and it will not achieve the effect of common melting, resulting in pinholes on the glaze surface.

[0139] In Example B3, the addition of calcite is not in the formula range, and the rest of the ingredients are in the formula range. Due to the addition of calcite, it can have a strong fluxing effect. If the addition amount is small, it will cause the flux temperature to be too high, resulting in pinhole defects on the glaze surface.

[0140] In Example B4, the addition of quartz is not in the formula range, and the rest of the ingredients are in the formula range. If the addition of quartz is reduced, it will cause the high-temperature viscosity of the flux to decrease, resulting in a low flux temperature, which can easily cause orange glaze and pinhole defects on the glaze surface.

[0141] In Example B5, the addition amount of kaolin is not in the formula range, and the rest of the ingredients are in the formula range. The reduction of kaolin will cause the corresponding reduction of aluminum oxide in the formula. The black pigment cannot form a stable crystal structure with the flux, and free cobalt ions will appear, resulting in a blue shift in the firing pattern.

[0142] In Example B6, although the amount of fluxing agent is in the formula range, the addition of cobalt black pigment is less than the normal range. Therefore, the black color of the glaze is a little gray, not pure enough.

[0143] In Example B7, the amount of fluxing agent is also in the formula range, but the addition of cobalt black pigment is more than the normal range. Although the black color of the glaze is purer, a small part of the black pigment does not form a stable crystal structure with the flux, causing free cobalt ions to precipitate. Therefore, when firing, a blue shift defect will occur.

[0144] Examples C1-C5

[0145] The preparation of the black glaze under-color agent is shown in Table 5.

[0146] Among them, the chemical composition of potassium feldspar is SiO2: 67%, Al2O3: 17%, CaO: 0.22%, K2O: 11.2%, Na2O: 2.7%, and the balance is other components. The chemical composition of kaolin is SiO2: 42.7%, Al2O3: 37.2%, CaO: 3.27%, K2O: 0.14%, and the balance is other components. The chemical composition of cobalt black pigment is 20% Co3O4, 35% Fe2O3, 40% Cr2O3, and 5% Al2O3.

[0147] Weigh the raw materials according to the ratio, put them into the ball mill, add water, the ratio of material to water is 100:160, and the ball milling time is 15 hours. After ball milling until the residue on the 325 mesh sieve is less than 0.05%, remove from the mill, pass through a 150 mesh sieve, and finally adjust the specific gravity to 1.35g / ml, with a flow rate of 48s / 100ml.

[0148] A method for applying the black underglaze colorant prepared above comprises the following steps:

[0149] Same as Examples A1-A5.

[0150] Table 5: Proportions of black underglaze colorants

[0151]

[0152] Table 6: Glaze firing and firing results of Examples C1-C5

[0153]

[0154]

[0155] As shown in the table above, in Example C1, the entire amount of albite was replaced by potassium feldspar. Although both feldspars can reduce the refractoriness of the flux and lower its melting temperature, potassium feldspar has a higher melting point and a lower expansion coefficient than albite. The complete introduction of potassium feldspar results in a higher flux temperature in the black underglaze colorant, preventing it from properly melting the black pigment, resulting in pinholes in the glaze surface. Furthermore, the colorant's expansion coefficient is also lower, affecting the stability of the black underglaze colorant's bond with the body.

[0156] In Example C2, potassium feldspar is completely replaced with albite. Because albite has a lower melting point than potassium feldspar, the melting point of the black colorant is also low, making it prone to overheating during baking, resulting in an orange tint and pinholes on the glaze surface. A reasonable ratio of potassium feldspar to albite in the glaze formula lowers the eutectic temperature. Therefore, incorporating both into the glaze formula produces better results than using either alone.

[0157] In Example C3, adding all the calcite to the potassium feldspar results in a highly refractory flux, making it ineffective at melting the black pigment. This is primarily because calcite reacts with quartz, acting as a strong flux. Therefore, omitting calcite from the flux results in orange glaze defects and pinholes.

[0158] In Example C4, all the quartz is added to kaolin. Since kaolin has a high alumina content, adding too much kaolin will greatly increase the refractoriness of the flux, resulting in the black colorant not being able to melt well during baking, resulting in no color development and a milky white color.

[0159] In Example C5, the amount of kaolin is added to quartz entirely, although the refractoriness of the colorant is reduced, but there is no excessive aluminum oxide to generate stable crystal phase with cobalt in black colorant, so that black underglaze color is prone to appear drift phenomenon when firing.

[0160] Example D

[0161] The preparation of black underglaze colorant, the specific raw materials added are potassium feldspar 14%, sodium feldspar 15%, calcite 9%, quartz 12%, kaolin 17%, methyl cellulose 1%, cobalt black colorant 32%.

[0162] Among them, the chemical composition of potassium feldspar is SiO2: 67%, Al2O3: 17%, CaO: 0.22%, K2O: 11.2%, Na2O: 2.7%, and the balance is other components. The chemical composition of kaolin is SiO2: 42.7%, Al2O3: 37.2%, CaO: 3.27%, K2O: 0.14%, and the balance is other components. The chemical composition of cobalt black colorant is 20% Co3O4, 35% Fe2O3, 40% Cr2O3, 5% Al2O3.

[0163] Comparative Example D1

[0164] The preparation of black underglaze colorant, the specific raw materials added are ordinary potassium feldspar 14%, sodium feldspar 15%, calcite 9%, quartz 12%, kaolin 17%, methyl cellulose 1%, cobalt black colorant 32%.

[0165] Among them, the chemical composition of ordinary potassium feldspar is SiO2: 74%, Al2O3: 14%, CaO: 0.56%, K2O: 8.64%, Na2O: 2.6%, and the balance is other components. The chemical composition of kaolin is SiO2: 42.7%, Al2O3: 37.2%, CaO: 3.27%, K2O: 0.14%, and the balance is other components. The chemical composition of cobalt black colorant is 20% Co3O4, 35% Fe2O3, 40% Cr2O3, 5% Al2O3.

[0166] Comparative Example D2

[0167] The preparation of black underglaze colorant, the specific raw materials added are potassium feldspar 14%, sodium feldspar 15%, calcite 9%, fused quartz 12%, kaolin 17%, methyl cellulose 1%, cobalt black colorant 32%.

[0168] The chemical composition of potassium feldspar is 67% SiO2, 17% Al2O3, 0.22% CaO, 11.2% K2O, and 2.7% Na2O, with the balance being other components. Kaolin is 42.7% SiO2, 37.2% Al2O3, 3.27% CaO, and 0.14% K2O, with the balance being other components. Cobalt black is 20% Co3O4, 35% Fe2O3, 40% Cr2O3, and 5% Al2O3.

[0169] Comparative Example D3

[0170] The preparation of black underglaze colorant, the specific added raw materials are 14% potassium feldspar, 15% sodium feldspar, 9% calcite, 12% quartz, 17% low-aluminum kaolin, 1% methyl cellulose, and 32% cobalt black material.

[0171] Among them, the chemical composition of potassium feldspar is SiO2: 67%, Al2O 3： The chemical composition of kaolin is SiO2: 50.61%, Al2O3: 34.4%, CaO: 0.18%, K2O: 0.88%, MgO: 0.17%, Na2O: 1.95%, with the balance being other components. The chemical composition of cobalt black is 20% Co3O4, 35% Fe2O3, 40% Cr2O3, and 5% Al2O3.

[0172] Comparative Example D4

[0173] The preparation of black underglaze colorant, the specific added raw materials are 14% potassium feldspar, 15% sodium feldspar, 9% calcite, 12% quartz, 17% kaolin, 1% methyl cellulose, and 32% cobalt-free black material.

[0174] The chemical composition of potassium feldspar is SiO2: 67%, Al2O3: 17%, CaO: 0.22%, K2O: 11.2%, Na2O: 2.7%, with the balance being other components. The chemical composition of kaolin is SiO2: 42.7%, Al2O3: 37.2%, CaO: 3.27%, K2O: 0.14%, with the balance being other components. Cobalt-free black pigment is a common commercially available pigment (number: TY-044), with a chemical composition of Fe2O3 50%, Cr2O3 30%, and MnO2 20%.

[0175] The specific preparation method of the black underglaze colorant in the above-mentioned Example D and Comparative Examples D1-D4 is as follows:

[0176] The raw materials are weighed according to the ratio, put into a ball mill, add water, the ratio of material to water is 100:160, ball mill for 15h, after ball milling to 325 mesh sieve residue less than 0.05%, discharge, pass through 150 mesh sieve, finally adjust the specific gravity to 1.35g / ml, flow rate 48s / 100ml.

[0177] An application method using the black underglaze colorant prepared above, comprising the following steps:

[0178] The same as examples A1-A5.

[0179] The glaze firing and baking glaze surface effects of examples D and comparative examples D1-D4 are compared, as shown in table 7:

[0180] Table 7: Comparison of glaze firing and baking glaze surface of examples D and comparative examples D1-D4

[0181] Item Example D Comparative Example D1 Comparative Example D2 Comparative Example D3 Comparative Example D4 Orange color of overfired glaze None Yes Yes None Yes Pinholes in overfired glaze None Yes Yes None Yes Color of overfired glaze Good Bad Bad Good Reddish black color Did overfired glaze bloom? None None None Yes None

[0182] From the above table, it can be seen from the comparison of comparative example D1 and example D that ordinary potassium feldspar is used in comparative example D1, the rest of the raw materials are unchanged, the potassium oxide content in ordinary potassium feldspar is only 8.6%, and the silicon dioxide is increased, so the fluxing effect of ordinary potassium feldspar is relatively poor, and the same amount of addition will increase the refractoriness of the fluxing agent, which cannot melt the black pigment inside well, and pinholes and orange glaze phenomenon are easy to appear after glazing.

[0183] From the comparison of comparative example D2 and example D, it can be seen that fused quartz is used in comparative example D2, because fused quartz is amorphous and has no crystal transformation, the thermal expansion coefficient is lower than that of ordinary quartz, which is easy to cause poor combination of the colorant with the body during baking, and there is a risk of partial peeling. At the same time, pinholes and orange glaze phenomenon also appear after glazing.

[0184] From the comparison of comparative example D3 and example D, it can be seen that the kaolin used in comparative example D3 is kaolin with low aluminum content, and the rest of the raw materials are unchanged. The low aluminum content makes the cobalt in the cobalt black pigment not completely form stable crystal phase, which will cause free cobalt to precipitate, resulting in defects of baking glaze.

[0185] From the comparison of comparative example D4 and example D, it can be seen that the pigment used in comparative example D4 is a cobalt-free black pigment, and the rest of the raw materials are unchanged. Although there is no defect in the glaze, the color is not pure black, but red, which is not pure black.

[0186] Example E1

[0187] The preparation of black underglaze colorant, the specific addition of raw materials is potassium feldspar 14%, sodium feldspar 15%, calcite 9%, quartz 12%, kaolin 17%, methyl cellulose 1%, cobalt black pigment 32%

[0188] The chemical composition of the potassium feldspar is SiO2: 67%, Al2O3: 17%, CaO: 0.22%, K2O: 11.2%, Na2O: 2.7%, and the balance is other components. The chemical composition of the kaolin is SiO2: 42.7%, Al2O3: 37.2%, CaO: 3.27%, K2O: 0.14%, and the balance is other components. The chemical composition of the cobalt black pigment is 25% Co3O4, 35% Fe2O3, 35% Cr2O3, and 5% Al2O3.

[0189] Example E2

[0190] The black underglaze colorant is prepared by adding the following raw materials: potassium feldspar 14%, sodium feldspar 15%, calcite 9%, quartz 12%, kaolin 17%, methyl cellulose 1%, and cobalt black pigment 32%.

[0191] The chemical composition of the potassium feldspar is SiO2: 67%, Al2O3: 17%, CaO: 0.22%, K2O: 11.2%, Na2O: 2.7%, and the balance is other components. The chemical composition of the kaolin is SiO2: 42.7%, Al2O3: 37.2%, CaO: 3.27%, K2O: 0.14%, and the balance is other components. The chemical composition of the cobalt black pigment is 25% Co3O4, 35% Fe2O3, 35% Cr2O3, and 5% Al2O3.

[0192] Example E3

[0193] The black underglaze colorant is prepared by adding the following raw materials: potassium feldspar 14%, sodium feldspar 15%, calcite 9%, quartz 12%, kaolin 17%, methyl cellulose 1%, and cobalt black pigment 32%.

[0194] The chemical composition of the potassium feldspar is SiO2: 67%, Al2O3: 17%, CaO: 0.22%, K2O: 11.2%, Na2O: 2.7%, and the balance is other components. The chemical composition of the kaolin is SiO2: 42.7%, Al2O3: 37.2%, CaO: 3.27%, K2O: 0.14%, and the balance is other components. The chemical composition of the cobalt black pigment is 25% Co3O4, 35% Fe2O3, 35% Cr2O3, and 5% Al2O3.

[0195] Example E4

[0196] The black underglaze colorant is prepared by adding the following raw materials: potassium feldspar 14%, sodium feldspar 15%, calcite 9%, quartz 12%, kaolin 17%, methyl cellulose 1%, and cobalt black pigment 32%.

[0197] The chemical composition of the potassium feldspar is SiO2: 67%, Al2O3: 17%, CaO: 0.22%, K2O: 11.2%, Na2O: 2.7%, and the rest is other components. The chemical composition of the kaolin is SiO2: 42.7%, Al2O3: 37.2%, CaO: 3.27%, K2O: 0.14%, and the rest is other components. The chemical composition of the cobalt black pigment is 26% Co3O4, 34% Fe2O3, 35% Cr2O3, and 5% Al2O3.

[0198] In the present application, the preparation of the cobalt black pigment is as follows: first, the cobalt, iron, chromium oxides and aluminum oxide are weighed according to the formula, and then they are mixed uniformly by dry method and calcined (solid phase reaction). The calcination temperature is 1350°C, and the calcination time is 6h. The calcination atmosphere is mainly oxygen (the O2 concentration in the kiln is 3%-5%), and the spinel phase (such as CoFeCrO4) is formed. Then, the calcined block is crushed, wet ground to micron level (D50<1μm) to ensure the dispersion of the pigment, and then it is pickled to remove unreacted impurities, and finally it is dried (100-120°C).

[0199] The specific preparation method of the black underglaze colorant in the above examples E1-E4 is as follows:

[0200] The raw materials are weighed according to the proportion, put into a ball mill, and water is added. The ratio of material to water is 100:160, and the ball milling time is 15h. After ball milling to less than 0.05% on a 325 mesh sieve, the material is discharged, sieved through a 150 mesh sieve, and finally the specific gravity is adjusted to 1.35g / ml, and the flow rate is 48s / 100ml.

[0201] An application method of using the above prepared black underglaze colorant, comprising the following steps:

[0202] The same as examples A1-A5.

[0203] The glazing and baking glaze surface effects of examples E1-E4 are compared, as shown in Table 8:

[0204] Table 8: Comparison of glazing and baking glaze surface of examples E1-E4

[0205] Item Example E1 Example E2 Example E3 Example E4 Orange color of overfired glaze None None None None Pinholes in overfired glaze None None None None Color of overfired glaze Good Good Redish, grayish greenish color Good Did overfired glaze bloom? None None None Yes

[0206] As can be seen from the above table, in examples E1-E4, only the proportion of each component in the cobalt black pigment is changed, and the rest of the fluxing agent remains unchanged. After glazing, the glaze surface is very good.

[0207] In examples E1 and E2, the amount of cobalt added in the cobalt black pigment is within the normal range (15-25% Co3O4), so the color development is good and the pure black is shown, and the baking glaze is not bleached.

[0208] In example E3, the cobalt addition is less than the normal range (15-25% Co3O4) by one point, although the glaze is not bleached, the color is slightly reddish, which looks impure black. Because of the lack of cobalt, the content of iron and chromium will increase accordingly. Iron and chromium will produce iron red and chromium green under the magnesia reinforced porcelain enamel, so the color tone will look reddish and grayish green.

[0209] In example E4, the cobalt black material has a little more cobalt oxide than the normal range, but the glaze has been bleached. Because the increase of cobalt ions, the spinel structure is unstable, and when the glaze is fired, the excess cobalt ions will react with part of the molten glaze, causing the glaze to be bleached.

[0210] Therefore, the selection of cobalt black material is very important in the magnesia reinforced porcelain black glaze, which is related to the purity of the glaze color and whether the glaze is compatible with the glaze to cause bleaching defects.

[0211] The above is a specific description of the preferred embodiment of the present application, but the present application is not limited to the described embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present application. These equivalent modifications or substitutions are all included in the scope defined by the claims of the present application.

Claims

1. A black underglaze colorant for magnesium-reinforced porcelain, characterized in that: The solid components thereof include, by weight percentage, 12-15% potassium feldspar, 9-15% sodium feldspar, 9-12% calcite, 11-15% quartz, 16-20% kaolin, 1-1.2% methyl cellulose, and 31-34% cobalt black material; Wherein, the weight content of K2O in potassium feldspar is ≥10%; The weight content of Al2O3 in kaolin is ≥37%; The weight content of Co3O4 in the cobalt black material is 15-25%.

2. The black underglaze colorant for magnesium-reinforced porcelain according to claim 1, characterized in that: The chemical composition of the potassium feldspar is SiO2: 60-70%, Al2O3: 15-20%, CaO: 0.2-0.5%, K2O: 10-12%, Na2O: 2-3%, and the balance is other components; The chemical composition of the kaolin is SiO2: 40-43%, Al2O3: 37-39%, CaO: 2.5-3.5%, K2O: 0.1-0.2%, and the balance is other components; The chemical composition of the cobalt black material is 15-25% Co3O4, 30-45% Fe2O3, 25-40% Cr2O3, and 5-10% Al2O3; The black underglaze colorant for magnesium-reinforced porcelain also includes water, with a specific gravity of 1.34-1.36 g / ml.

3. The method for preparing the black underglaze colorant for magnesium-reinforced porcelain according to any one of claims 1 to 2, characterized in that: The steps include: Potassium feldspar, sodium feldspar, calcite, quartz, kaolin, cobalt black material and methyl cellulose are ball-milled with water, sieved and slurried to obtain a black underglaze colorant for magnesium porcelain reinforcement.

4. The method for preparing the black underglaze colorant for magnesium-reinforced porcelain according to claim 3, characterized in that: The weight ratio of material to water in the water-added ball mill is 100:150-170; The ball milling time is 12-15 hours, and the ball milling is performed until the residue on a 325-mesh sieve is less than 0.05%; The sieving is through a 150-180 mesh sieve; The slurry is adjusted to a specific gravity of 1.34-1.36 g / ml and a flow rate of 38-48 s / 100 ml.

5. A black underglaze color of magnesium-reinforced porcelain, characterized in that: It comprises a magnesia-reinforced porcelain body, a black underglaze color layer and a protective glaze layer; the black underglaze color layer is prepared from the magnesia-reinforced porcelain black underglaze colorant described in any one of claims 1-2 or the magnesia-reinforced porcelain black underglaze colorant prepared by the preparation method described in any one of claims 3-4.

6. The black underglaze color of magnesia-reinforced porcelain according to claim 5, characterized in that: The weight content of MgO in the magnesium-reinforced porcelain body is above 22%; The composition of the magnesia-reinforced porcelain body is SiO2: 61-63%, Al2O3: 4-5%, CaO: 2-3%, MgO: 22-24%, K2O: 0.5-1%, Na2O: 0.2-0.5%, and the balance is other ingredients; The protective glaze layer is prepared from a low-temperature frit glaze with boron trioxide as the main flux; The components of the low-temperature frit glaze are SiO2: 53-55%, Al2O3: 10-12%, CaO: 8-9%, MgO: 0.5-1%, K2O: 3-4%, Na2O: 2-3%, ZnO: 1.5-2%, Li2O: 1.5-2%, B2O3: 10-12%, and the balance is other ingredients.

7. The method for preparing black underglaze color of magnesia-reinforced porcelain according to any one of claims 5 to 6, characterized in that: The steps include: (1) bisque firing the magnesia-reinforced porcelain body at high temperature, polishing and cleaning, drying, and cooling; (2) painting a film on the cooled magnesium-reinforced porcelain body obtained in step (1), heating it, spraying a black underglaze colorant on the magnesium-reinforced porcelain body, drying it in the shade, rubbing it, and baking it to obtain a magnesium-reinforced porcelain black color body; (3) glazing the black color body of the magnesium-reinforced porcelain, drying it in the shade, and glaze firing it to obtain the finished product of the magnesium-reinforced porcelain black underglaze color.

8. The method for preparing black underglaze color of magnesia-reinforced porcelain according to claim 7, characterized in that: The high-temperature biscuit firing in step (1) is performed at a temperature of 1280±5°C for 12-15 hours in an oxidizing atmosphere; the water absorption rate of the embryo after high-temperature biscuit firing is ≤0.25%; The drying temperature in step (1) is 60-70° C. and the drying time is 2-3 h; The heating temperature in step (2) is 100-120° C. Step (2) rotating the magnesium-reinforced porcelain body while spraying the color; The thickness of the spray paint in step (2) is 0.2-0.4 mm; The drying in the shade in step (2) is natural drying in the shade under room temperature air; The step (2) of wiping the color is to tear off the film and wipe off the excess colorant; The baking temperature in step (2) is 1120-1140° C., the baking time is 8-10 hours, and the baking atmosphere is an oxidizing atmosphere with an O2 concentration of 3% to 5%; During the glazing process of step (3), the magnesia-reinforced porcelain black color blank is rotated while spraying the glaze; The thickness of the glazing in step (3) is 0.15-0.3 mm; The drying in the shade in step (3) is natural drying in the shade under room temperature air; The glaze firing temperature in step (3) is 1100-1130° C., the glaze firing time is 10-12 hours, and the glaze firing atmosphere is an oxidizing atmosphere with an O2 concentration of 3% to 5%.

9. A magnesium-reinforced porcelain glaze, characterized in that: The obtained product is obtained by applying overglaze decals and baking the black underglaze colored magnesia porcelain reinforced porcelain described in any one of claims 5-6 or the magnesia porcelain reinforced porcelain black underglaze colored prepared by the preparation method described in any one of claims 7-8.

10. The magnesium-reinforced porcelain overglaze color according to claim 9, characterized in that: The baking temperature is 830-860° C., the baking time is 4-6 hours, and the baking atmosphere is a weak oxidizing atmosphere or a neutral atmosphere, wherein the O2 concentration of the weak oxidizing atmosphere is >1% and ≤3%, and the CO is 0; the O2 concentration of the neutral atmosphere is 0.5%-1%, and the CO is 0.

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