A kind of glass is washed with low melting flux, preparation method and the preparation method of opalescent glass overglaze protective film

Abstract

The application discloses a kind of low melting point flux for glass, by weight percentage, including the following components: SiO2 30~40%, Bi2O3 3~10%, R2O 15~25%, ZnO 10~15%, ZrO2 6~12%, B2O3 3~10%, TiO2 3~10%, Al2O3 2~6%, F 1~4%, rare earth oxide 1~3%; wherein, R2O is the basic oxide selected from Na2O, K2O and Li2O;Rare earth oxide is Y2O3 and / or La2O3;F is introduced by one or more of sodium fluosilicate, sodium fluoride, aluminum fluoride or calcium fluoride. The fast firing temperature of the low melting point flux can be as low as 590~600℃, and can be better applied to the surface of overglaze color opaque glass tableware, forming a protective film with high transparency, good color development, strong adhesion, good alkali resistance, maintaining the original color of pigment color, while significantly improving the resistance of overglaze color opaque glass tableware to dishwasher, greatly reducing the lead and cadmium leaching amount of overglaze color pigment.

Description

Technical Field

[0001] This invention relates to the field of glass technology, and in particular to a washable low-melting-point flux for glass, its preparation method, and a method for preparing a protective film for opaque glass enamel. Background Technology

[0002] Opaque glass tableware is a type of high-end everyday glassware with adjustable opacity, made by melting and shaping fluoride-based emulsifiers with raw materials such as quartz sand, alumina, and borax at high temperatures. To increase added value, manufacturers print various pigments on the surface of the product, which are then sintered at high temperatures to form exquisite patterns. To improve the chemical stability of the overglaze patterns and prevent the leaching of heavy metals such as lead and cadmium from the pigments, a layer of low-melting-point flux is printed on the patterns. This flux forms a transparent glass film during the sintering process, providing isolation and protection for the patterns.

[0003] In recent years, due to changes in lifestyle, dishwashers have gradually become an important and widely used component of modern kitchen appliances. However, it has been observed that the overglaze patterns on tableware fade and peel after repeated machine washes, severely affecting the product's appearance and lifespan. Related research indicates that the damage to overglaze patterns caused by the dishwasher washing environment primarily stems from the erosion of the flux's Si-O-Si framework structure by hydroxide ions dissolved in the alkaline detergent. Furthermore, chelating agents such as pyrophosphate, tripolyphosphate, and EDTA added to the detergent react with the CaO on the glass surface. 2+ Mg 2+ The combination of plasma and the constant rinsing with water at around 70°C in the dishwasher both exacerbate the alkaline corrosion.

[0004] Chinese patent CN104445945A discloses an aluminum enamel composite material, which comprises a first frit: silicon dioxide: 40-50%; aluminum dioxide: 3-6%; sodium oxide: 5-10%; potassium oxide: 5-10%; lithium oxide: 5-10%; and a second frit: silicon dioxide: 30-40%; titanium oxide: 15-25%; and vanadium oxide: 5-15%. The coefficient of thermal expansion of the first frit is 430-440 × 10⁻⁶. -7 m / K; the coefficient of thermal expansion of the second melt is 550~580*10 -7 m / K. The substrate involved is aluminum alloy, the coating grilling temperature is 550-570℃, and the grilling time is 3-5 minutes. This composite material can solve the problem of poor alkali resistance and cleaning effect of aluminum enamel cookware surface coatings, ensuring that it can withstand more than 200 dishwasher washes.

[0005] CN106517790A discloses a magnesia ceramic glaze formula, which contains 40-60% frit, 10-20% feldspar, 4-10% calcite, 5-10% kaolin, and 15-25% quartz. The frit composition includes 25-35% quartz powder, 30-40% potassium feldspar, 5-10% zinc oxide, 20-30% calcium carbonate, 3-8% talc, 0-1% zirconium oxide or hafnium oxide, 0-1% strontium carbonate, and 0.1-1% spodumene. This glaze is applied to a magnesia ceramic body and fired together at 1280+10℃, resulting in a smooth glaze surface with good dishwasher resistance and acid and alkali resistance.

[0006] CN105731797A discloses a high-alkali-resistant lead-free ceramic glaze flux for dishwashers, comprising 24-40% silicon oxide, 36-44% boron oxide, 16-24% aluminum oxide, 2-6% lithium oxide, 2-7% potassium sodium oxide, 2-8% calcium oxide, 1-5% niobium oxide, and 1-5% tantalum oxide. The firing temperature of this glaze flux is 900-950℃, with a holding time of 30 minutes.

[0007] Opacity glass tableware has a lower softening point (600-610℃) than ordinary glass, and a coefficient of thermal expansion of 80-90×10⁻⁶. -7 The process involves applying a frit of molten metal (m / K) and simultaneously physical tempering (rapid cooling after heating) to the product. The peak sintering temperature is 590–600℃, and the time to reach the peak temperature from room temperature is 20–25 minutes. To prevent deformation, the holding time at the peak temperature should not exceed 2 minutes. This requires the frit in the overglaze glass to possess the properties of low-temperature rapid firing and quick wetting of the opaque glass surface. Over 90% of my country's opaque glass tableware is exported. As high-end markets in Europe and America place increasingly stringent requirements on the dishwasher resistance of tableware, the problem of poor dishwasher resistance is becoming increasingly prominent in the export of this type of overglaze product. The frit involved in the aforementioned patent is mainly used on ceramic and alloy substrates, and its firing temperature and coefficient of expansion are not entirely suitable for opaque glass tableware. Solving this problem undoubtedly has good application prospects and social benefits. Summary of the Invention

[0008] The main objective of this invention is to provide a washable, low-melting-point flux that is highly transparent, has good color rendering, good alkali resistance, is suitable for use in dishwashers, and can be applied to opaque glass tableware.

[0009] To achieve the above objectives, on the one hand, the present invention proposes a washable low-melting-point flux for glass, comprising the following components by weight percentage: SiO2 30-40%, Bi2O3 3-10%, R2O 15-25%, ZnO 10-15%, ZrO2 6-12%, B2O3 3-10%, TiO2 3-10%, Al2O3 2-6%, F 1-4%, and rare earth oxides 1-3%.

[0010] Among them, R2O is a basic oxide, including one or more of Na2O, K2O and Li2O;

[0011] The rare earth oxide is Y2O3 and / or La2O3;

[0012] The F is introduced through one or more of sodium fluorosilicate, sodium fluoride, aluminum fluoride, or calcium fluoride.

[0013] The glass washing-resistant low-melting-point flux of the present invention does not contain alkaline earth metal oxides such as CaO, MgO, SrO, and BaO, so as to improve the alkali resistance of the flux and thus improve the tolerance of opaque glass tableware after sintering the flux to chelating agents in detergents.

[0014] This invention employs a multi-component compound of Bi2O3, F, B2O3, and rare earth oxides. By adjusting the dosage, it can completely replace PbO in lead-containing glass slurry, lower the melting temperature, ensure matching with the expansion coefficient of opaque glass, and meet the requirements for low-temperature rapid firing on opaque glass substrates. The firing temperature can be as low as 590-600℃. Even at a lower firing temperature, it can quickly form an inorganic glass film with high transparency, good color development, and good alkali resistance. This film adheres to the surface of opaque glass tableware printed with pigments, completely covering the overglaze pigments and avoiding damage to the overglaze pattern caused by the dishwasher washing environment.

[0015] This invention introduces fluorine, which enables the flux to have good wetting ability on the opaque glass substrate, reduces surface tension, and allows the glass slurry to spread and adhere quickly to the opaque glass substrate, enhancing the integrity of the film surface. Under the process conditions of low temperature and fast firing, the overall smoothness and gloss of the glass film layer after firing are improved.

[0016] Preferably, the F is introduced by one or more of sodium fluorosilicate and sodium fluoride.

[0017] Preferably, in the glass-use washable low-melting-point flux, the weight ratio of the content of element F to the total content of SiO2 and Al2O3 is 0.03 to 0.1:1; more preferably, the weight ratio of the content of element F to the total content of SiO2 and Al2O3 is 0.05 to 0.08:1. By controlling the ratio of F to the total amount of SiO2 + Al2O3, the strength of the melt network structure is improved, resulting in a glass film with high washability.

[0018] Preferably, in the glass-use washable low-melting-point flux, the weight ratio of Al2O3 to rare earth oxides is 1 to 3:1. By adjusting the ratio of Al2O3 to rare earth oxides, the glass structure is strengthened, greatly improving the strength and alkali resistance of the glass film.

[0019] Preferably, the Bi2O3 content is 3-6% by weight.

[0020] Furthermore, the present invention provides a method for preparing the above-mentioned washable low-melting-point flux for glass, comprising the following steps:

[0021] a) One-time melting: According to the preparation ratio, other raw materials except rare earth oxides are mixed evenly, melted at high temperature into glass liquid, then quenched and ground into glass particles to obtain a one-time fused block;

[0022] b) Secondary melting: According to the preparation ratio, the rare earth oxides are mixed evenly with the primary melt obtained in step a, and then melted at high temperature into glass liquid, followed by cold quenching and grinding into secondary melt.

[0023] c) Heat treatment: The secondary fused block obtained in step b is placed at 300-350℃ for 5-10 hours and then ground into glass powder with D50≤1μm and D97≤3μm to obtain the glass washable low melting point flux.

[0024] The melting parameters in step a are: melting temperature of 1200-1300℃ and holding time of 3-4 hours.

[0025] The melting parameters in step b are: melting temperature of 900-1000℃ and holding time of 30-60min.

[0026] The quenching process in steps a and b specifically involves: after removing the molten high-temperature glass from the high-temperature furnace, rapidly pouring it into room-temperature cold water within 5 seconds. To ensure rapid and thorough quenching of the glass, the weight ratio of cold water to molten glass should be no less than 100:1.

[0027] This invention employs a two-stage melting process, with rare earth oxides added during the second melting stage. This creates locally rich alumina-rare earth oxide regions within the glass network structure. After heat treatment, fine grains are dispersed within the melt, improving the chemical stability of the flux and extending the lifespan of the glaze pattern in the dishwasher.

[0028] On the other hand, the present invention provides a method for preparing a protective film for opaque glass enamel, comprising the following steps:

[0029] 1) The glass is mixed evenly with a washable, low-melting-point flux and an ink oil, and then ground and dispersed to obtain a glass slurry;

[0030] 2) Apply the glass paste described in step 1 to the surface of the opaque glass product with pigment printed on its surface to form a glass paste layer;

[0031] 3) The opaque glass product coated with glass paste layer in step 2 is fired to obtain the opaque glass glaze protective film.

[0032] In step 2, the thickness of the glass slurry layer is ≥10μm. Because overglaze patterns typically have an uneven surface, controlling the glass slurry layer thickness to be no less than 10μm ensures that the slurry layer completely covers the overglaze pattern on the opaque glass surface, forming a highly smooth protective film for better protection. Preferably, the glass slurry layer thickness is 10–20μm to avoid difficulties in removing organic matter from the ink and carbonization during firing due to an excessively thick film.

[0033] The maximum firing temperature in step 3 is 590-600°C, the time to heat from room temperature to the maximum firing temperature is 20-25 minutes, and the holding time does not exceed 2 minutes.

[0034] The washable, low-melting-point flux for glass described in this invention can meet the requirements for low-temperature, rapid firing on opaque glass substrates, with a firing temperature as low as 590-600℃. Its coefficient of expansion matches that of the opaque glass substrate, and it can quickly form a glass protective film with high transparency, good color rendering, strong adhesion, and good alkali resistance. This allows the pigments to maintain a good color rendering effect on the glass substrate. At the same time, the glass protective film can effectively cover the internal pigments, greatly reducing the leaching of lead and cadmium from the overglaze pigments, and ensuring that the overglaze pattern on the opaque glass maintains its original color effect even after multiple washes in a dishwasher, thus improving its service life. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 The image shows the surface of opaque glass tableware after 250 dishwasher washes following sintering of the wash-resistant low-melting-point flux for glass prepared in Example 2.

[0037] Figure 2 SEM image of the surface of opaque glass tableware after 250 dishwasher washes following sintering of the wash-resistant low-melting-point flux for glass prepared in Comparative Example 4.

[0038] Figure 3 The images show the XRD patterns of the secondary melt in Example 1 before and after heat treatment in step c.

[0039] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the 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. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0041] Description of some of the methods used in this invention to characterize experimental results:

[0042] 1. Accelerated static detergent test and expansion coefficient test

[0043] In the secondary melting process, molten glass is poured into a preheated graphite mold and then placed in a high-temperature furnace at 300–350°C for 5–10 hours for heat treatment (the temperature and time parameters for heat treatment are adjusted according to the preparation process parameters in the specific embodiment). The glass block is then cooled in the furnace to obtain a glass block. After the glass block is cut and polished, glass test strips are obtained for static detergent testing and coefficient of thermal expansion testing.

[0044] Accelerated static detergent testing was performed according to GB / T 32680-2016 and European standard EN12875. The detergent was prepared using 15% sodium hydroxide, 16% trisodium EDTA, and 69% distilled water, and diluted with distilled water to a 2.0% w / w aqueous solution. Glass strips were immersed in the detergent solution at 75±1℃ for 16 hours, then the surface deposits were rinsed off and the strips were dried. The weight loss of the strips after detergent erosion was measured.

[0045] 2. L*a*b*, thermal shock resistance and gloss test

[0046] A glass slurry was prepared by mixing a washable, low-melting-point solvent with ink, and then coated onto the surface of opaque glass tableware printed with pigments (lead-cadmium glass pigments were selected to test the leaching of heavy metals, and the L*a*b* values ​​after sintering were 39, 63, and 25, respectively). After tempering at 590-600℃, opaque glass tableware with a protective film on the surface was obtained. The L*a*b* values, thermal shock resistance under a temperature difference of 100℃, and gloss were tested. The effects of sintering with a washable, low-melting-point solvent on the surface condition, pigment coloring, and thermal shock resistance of the tableware were compared.

[0047] 3. Dishwasher test

[0048] Overglaze opaque glassware with a protective film on the surface, having completed the L*a*b* test, was placed in a household dishwasher and run on normal mode. The dishwasher was tested 250 times with 2.5g–3.0g of dishwasher detergent (Cascade brand) per (6.0±0.5) liters of water. Changes in surface appearance, such as fading, iridescent patterns, and gloss, were observed and recorded as graded. The dishwasher resistance rating is shown in Table 1.

[0049] Table 1 Evaluation of Dishwasher Resistance Rating

[0050] grade state Level 1 No obvious signs of erosion Level 2 At a 45° angle, obvious iridescence or erosion marks are visible, but not at angles less than 30°. Level 3 When viewed at an angle of less than 30°, there are obvious iridescent or erosion marks, but the reflected image is not blurred. Level 4 When viewed at an angle of less than 30°, there are obvious iridescent or erosion marks, and the reflected image is blurred. Level 5 The surface is dull or rough, and powdery. Level 6 The decorative finish has faded noticeably, and pinholes are visible. Level 7 The decorative finish has completely disappeared.

[0051] 4. Heavy metal leaching test

[0052] Referring to GB / T 21170-2007, the test method for lead and cadmium leaching from glass containers was used. The glass was immersed in a 4% acetic acid solution at 22±2℃ for 24 hours. Lead and cadmium leached from the surface of the tableware after 250 dishwasher washes were extracted to evaluate the effectiveness of the wash-resistant, low-melting-point flux protective film for glass in isolating heavy metals from pigments. For flat products with a depth ≤25mm, the upper limit for lead leaching is 0.8 mg / dm³. 2 The maximum allowable leaching limit for cadmium is 0.07 mg / dm³. 2 .

[0053] In the specific embodiments of the present invention, the raw material components SiO2, Bi2O3, Na2O, ZnO, ZrO2, B2O3, TiO2, Al2O3, Y2O3, and La2O3 are analytical grade oxide raw materials, and F is introduced by analytical grade NaF, or sodium fluorosilicate, aluminum fluoride, or calcium fluoride.

[0054] Example 1

[0055] The glass-resistant, washable, low-melting-point flux of this embodiment is composed of the following components by weight percentage: 40% SiO2, 10% Bi2O3, 15% Na2O, 10% ZnO, 6% ZrO2, 4% B2O3, 3% TiO2, 6% Al2O3, 4% F, and 2% Y2O3, wherein the weight ratio of Al2O3 to Y2O3 is 3:1.

[0056] The preparation method of the washable low-melting-point flux for glass in this embodiment includes the following steps:

[0057] a) Mix all components except rare earth oxides evenly in a V-type mixer, place them in a corundum crucible and melt them in a high-temperature furnace at 1200℃ for 4 hours. Then, quench the high-temperature glass melt with water to form glass particles and grind them into primary frits with D97 not greater than 15μm.

[0058] b) Mix the primary frit from step a with Y2O3 evenly, place it in a corundum crucible and melt it at 1000℃ for 30 minutes. Then, quench the high-temperature glass melt into glass particles, i.e., the secondary frit.

[0059] c) Place the secondary fused block from step b at 300°C for 10 hours for heat treatment, and then grind it using an air jet mill until it is a low melting point flux with D50 not exceeding 1μm and D97 not exceeding 3μm. This is the washable low melting point flux for glass.

[0060] Simultaneously, the molten glass obtained in step b is poured into a preheated graphite mold, placed at 300°C for 10 hours for heat treatment, and then cooled in the furnace to obtain a glass block. After cutting and polishing, it is cut into glass test strips of the corresponding size for expansion coefficient and static detergent resistance testing.

[0061] Example 2

[0062] The glass-resistant, washable, low-melting-point flux of this embodiment is composed of the following components by weight percentage: 32.6% SiO2, 6% Bi2O3, 18.5% Na2O, 13.4% ZnO, 9% ZrO2, 6% B2O3, 5.7% TiO2, 4% Al2O3, 2.8% F, 1.7% Y2O3, and 0.3% La2O3, wherein the weight ratio of Al2O3 / (Y2O3+La2O3) is 2:1.

[0063] The preparation method of the washable low-melting-point flux for glass in this embodiment includes the following steps:

[0064] a) Mix all components except rare earth oxides evenly in a V-type mixer, place them in a corundum crucible and melt them in a high-temperature furnace at 1200℃ for 4 hours. Then, quench the high-temperature glass melt with water to form glass particles and grind them into primary frits with D97 not greater than 15μm.

[0065] b) Mix the primary frit from step a with Y2O3 and La2O3 evenly, place it in a corundum crucible and melt it at 950°C for 45 minutes. Then, quench the high-temperature glass melt into glass particles, i.e., the secondary frit.

[0066] c) Place the secondary fused block from step b at 325°C for 7 hours for heat treatment, and then grind it using an air jet mill until it is a low melting point flux with D50 not exceeding 1μm and D97 not exceeding 3μm. This is the washable low melting point flux for glass.

[0067] Simultaneously, the molten glass obtained in step b is poured into a preheated graphite mold, placed at 325°C for 7 hours for heat treatment, and then cooled in the furnace to obtain a glass block. After cutting and polishing, it is cut into glass test strips of the corresponding size for expansion coefficient and static detergent resistance testing.

[0068] Example 3

[0069] The glass-resistant, washable, low-melting-point flux of this embodiment is composed of the following components by weight percentage: 30% SiO2, 3% Bi2O3, 15% Na2O, 15% ZnO, 12% ZrO2, 10% B2O3, 10% TiO2, 2% Al2O3, 1% F, and 2% La2O3, wherein the weight ratio of Al2O3 to La2O3 is 1:1.

[0070] The preparation method of the washable low-melting-point flux for glass in this embodiment includes the following steps:

[0071] a) Mix all components except rare earth oxides evenly in a V-type mixer, place them in a corundum crucible and melt them in a high-temperature furnace at 1200℃ for 4 hours. Then, quench the high-temperature glass melt with water to form glass particles and grind them into primary frits with D97 not greater than 15μm.

[0072] b) Mix the primary frit from step a with La2O3 evenly, place it in a corundum crucible and melt it at 900°C for 60 minutes. Then, quench the high-temperature glass melt into glass particles, i.e., the secondary frit.

[0073] c) Place the secondary fused block from step b at 350°C for 5 hours for heat treatment, and then grind it using an air jet mill until it is a low melting point flux with D50 not exceeding 1μm and D97 not exceeding 3μm. This is the washable low melting point flux for glass.

[0074] Simultaneously, the molten glass obtained in step b is poured into a preheated graphite mold, placed at 350°C for 5 hours for heat treatment, and then cooled in the furnace to obtain glass blocks. After cutting and polishing, the blocks are cut into glass strips of appropriate size for expansion coefficient and static detergent resistance testing.

[0075] Comparative Example 1

[0076] The preparation parameters of the glass-resistant, washable, low-melting-point flux in this comparative example are the same as those in Example 2, except that alkaline earth metal oxides are added to the raw material components. The remaining components are adjusted proportionally. By weight percentage, the required raw material composition is: SiO2 31.0%, Bi2O3 5.7%, Na2O 17.6%, ZnO 12.7%, ZrO2 8.6%, B2O3 5.7%, TiO2 5.4%, Al2O3 3.8%, F 2.7%, Y2O3 1.6%, La2O3 0.3%, MgO 2.5%, and CaO 2.5%.

[0077] Comparative Example 2

[0078] The preparation parameters of the glass-resistant, washable, low-melting-point flux in this comparative example are the same as those in Example 2, except that the amount of rare earth oxides added is adjusted to 3.5%, and the remaining components are adjusted proportionally. By weight percentage, the required raw material composition is: SiO2 32.1%, Bi2O3 5.9%, Na2O 18.2%, ZnO 13.2%, ZrO2 8.9%, B2O3 5.9%, TiO2 5.6%, Al2O3 3.9%, F 2.8%, Y2O3 2.5%, and La2O3 1%.

[0079] Comparative Example 3

[0080] The preparation parameters of the glass-resistant, washable, low-melting-point flux in this comparative example are the same as those in Example 2, except that, by weight percentage, the required raw material composition is: SiO2 33.4%, Bi2O3 6%, Na2O 18.5%, ZnO 13.4%, ZrO2 9%, B2O3 6%, TiO2 5.7%, Al2O3 4%, F 2.8%, Y2O3 1%, and La2O3 0.2%; wherein, the weight ratio of Al2O3 / (Y2O3+La2O3) is 3.3:1.

[0081] Comparative Example 4

[0082] The preparation parameters of the glass-resistant, washable, low-melting-point flux in this comparative example are the same as those in Example 2, except that rare earth oxides are not added. By weight percentage, the required raw material composition is SiO2 33.3%, Bi2O3 6.1%, Na2O 18.9%, ZnO 13.7%, ZrO2 9.2%, B2O3 6.1%, TiO2 5.8%, Al2O3 4.1%, and F 2.8%.

[0083] Blank group

[0084] In comparison, opaque glass tableware with only a printed pigment layer and no glass paste was also tested. The L*a*b* value, gloss, thermal shock resistance under a temperature difference of 100℃, surface changes and lead and cadmium leaching after 250 cycles in a dishwasher were also tested.

[0085] The glass washable low-melting-point flux prepared in Examples 1-2 and Comparative Examples 1-4 was mixed evenly with commercially available organic carrier ink oil and dispersed by a three-roll mill to obtain a glass slurry. The glass slurry was coated onto the surface of opaque glass tableware with pigment printed on it and then tempered by baking. The peak temperature of the tempering baking was 600°C, the time from room temperature to the peak temperature was 20 minutes, and the holding time at the peak temperature was 2 minutes, resulting in opaque glass tableware with a protective film layer on the surface.

[0086] The glass-resistant, washable, low-melting-point flux prepared in Example 3 was mixed evenly with commercially available organic carrier ink oil and then dispersed by a three-roll mill to obtain a glass slurry. The glass slurry was coated onto the surface of opaque glass tableware with pigment printed on it, and then tempered by baking. The peak temperature of the tempering baking was 590°C, the time from room temperature to the peak temperature was 25 minutes, and the holding time at the peak temperature was 2 minutes, resulting in opaque glass tableware with a protective film layer on the surface.

[0087] The performance parameters of the washable low-melting-point fluxes for glass prepared in Examples 1-3 and Comparative Examples 1-4 were examined, as well as the changes in various properties of opaque glass tableware after sintering the flux. The performance parameters are shown in Table 2.

[0088] Table 2 Performance parameters of Examples 1-3, Comparative Examples 1-4, and the blank group.

[0089]

[0090] As shown in Table 2, by comparing the performance parameters of Examples 1-3 and the blank group, the gloss of the glaze area was significantly improved after sintering with the low-melting-point flux described in this invention, without affecting the color development of the pigments or the thermal shock resistance of the product. After 250 washes in a dishwasher, the glaze area on the product surface still maintained Grade 1, a significant improvement compared to the blank group. The leaching of heavy metals remained within the standard allowable range, indicating that the washable low-melting-point flux for glass described in this invention provides excellent protection for the glaze pattern. Figure 1 As can be seen, the surface of the opaque glassware remains smooth and even after 250 dishwasher washes.

[0091] Magnesium oxide and calcium oxide were added to the flux in Comparative Example 1, and the Ca in it... 2+ Mg 2+ It easily reacts with chelating agents such as EDTA in detergents, has poor chemical stability, and exacerbates the alkaline corrosion, resulting in poor washability of sintered opaque glass tableware.

[0092] The samples in Comparative Examples 2-4 showed increased weight loss and decreased dishwasher resistance after detergent immersion, indicating that the amount of yttrium oxide and lanthanum oxide added, as well as the ratio of alumina and rare earth oxides, affects product performance. In Comparative Example 2, the amount of yttrium oxide and lanthanum oxide added was 3.5%, and the flux underwent vitrification during the baking and tempering process, affecting the color development of the pigment layer and the chemical stability of the product. In Comparative Example 3, the weight ratio of Al2O3 / (Y2O3+La2O3) was 3.3:1, and the dishwasher resistance decreased to level 2, indicating that the ratio of alumina to rare earth oxides affects the structural strength of the glass system. When the weight ratio of Al2O3 / (Y2O3+La2O3) is 1-3:1, the sintered protective film layer has better structural strength and alkali resistance. In Comparative Example 4, no yttrium oxide and lanthanum oxide were added, and the weight loss increased to 279.6 mg / dm³ after detergent immersion. 2 The dishwasher's durability rating has been reduced to level 4. Figure 2 It is evident that the surface of the opaque glass tableware showed severe signs of corrosion after 250 dishwasher washes.

[0093] Comparative Examples 5 and 6

[0094] The preparation parameters of the washable low-melting-point flux for glass in Comparative Examples 5 and 6 were the same as those in Example 2, except that the amount of bismuth oxide added in the raw material components was different, while the other components were adjusted proportionally.

[0095] The raw material composition of Comparative Example 5 was 31.2% SiO2, 10% Bi2O3, 17.7% Na2O, 12.8% ZnO, 8.6% ZrO2, 5.7% B2O3, 5.5% TiO2, 3.8% Al2O3, 2.7% F, 1.6% Y2O3, and 0.3% La2O3.

[0096] The raw material composition of Comparative Example 6 was 29.8% SiO2, 14% Bi2O3, 16.9% Na2O, 12.3% ZnO, 8.2% ZrO2, 5.5% B2O3, 5.2% TiO2, 3.7% Al2O3, 2.6% F, 1.6% Y2O3, and 0.3% La2O3.

[0097] The glass prepared in Comparative Examples 5 and 6 was mixed evenly with a washable low-melting-point flux and a commercially available organic carrier ink, and then dispersed by a three-roll mill to obtain a glass slurry. The glass slurry was coated onto the surface of opaque glass tableware with pigments printed on it, and then tempered by baking. The peak temperature of the tempering baking was 600℃, the time from room temperature to the peak temperature was 20 minutes, and the holding time at the peak temperature was 2 minutes, resulting in opaque glass tableware with a protective film layer on the surface.

[0098] The performance parameters of the washable low-melting-point fluxes for glass prepared in Example 2 and Comparative Examples 5 and 6 were examined, as well as the changes in various properties of opaque glass tableware after sintering the flux. The performance parameters are shown in Table 3.

[0099] Table 3 Performance parameters of Example 2 and Comparative Examples 5 and 6

[0100]

[0101] As shown in Table 3, increasing the amount of bismuth oxide does not significantly affect chemical resistance or dishwasher tolerance. However, the low-melting-point flux reacts chemically with the cadmium component in the overglaze pigments during sintering, leading to a significant change in the color of the pigment. Therefore, when the amount of bismuth oxide added is 3%–10%, the resulting washable low-melting-point flux for glass exhibits high transparency, good color development, and maintains the original color of the pigments.

[0102] Comparative Examples 7-9

[0103] The preparation parameters of the glass washable low melting point fluxes of Comparative Examples 7-9 are the same as those of Example 2, except that the amount of F added in the raw material components is 0%, 4%, and 6%, respectively, and the other components are adjusted proportionally.

[0104] The raw material composition of Comparative Example 7 was 33.5% SiO2, 6.2% Bi2O3, 19% Na2O, 13.8% ZnO, 9.3% ZrO2, 6.2% B2O3, 5.9% TiO2, 4.1% Al2O3, 1.7% Y2O3, and 0.3% La2O3.

[0105] The raw material composition of Comparative Example 8 is as follows: SiO2 32.2%, Bi2O3 5.9%, Na2O 18.3%, ZnO 13.2%, ZrO2 8.9%, B2O3 5.9%, TiO2 5.6%, Al2O3 4%, F 4%, Y2O3 1.7%, and La2O3 0.3%.

[0106] The raw material composition of Comparative Example 9 was 31.5% SiO2, 5.8% Bi2O3, 17.9% Na2O, 13% ZnO, 8.7% ZrO2, 5.8% B2O3, 5.5% TiO2, 3.9% Al2O3, 6% F, 1.6% Y2O3, and 0.3% La2O3.

[0107] The glass prepared in Comparative Examples 7-9 was mixed evenly with a washable low-melting-point flux and a commercially available organic carrier ink oil, and then dispersed by a three-roll mill to obtain a glass slurry. The glass slurry was coated onto the surface of opaque glass tableware with pigments printed on it, and then tempered by baking. The peak temperature of the tempering baking was 600℃, the time from room temperature to the peak temperature was 20 minutes, and the holding time at the peak temperature was 2 minutes, resulting in opaque glass tableware with a protective film layer on the surface.

[0108] The performance parameters of the washable low-melting-point fluxes for glass prepared in Example 2 and Comparative Examples 7-9 were examined, as well as the changes in various properties of opaque glass tableware after sintering the flux. The performance parameters are shown in Table 4.

[0109] Table 4 Performance parameters of Examples 2 and Comparative Examples 7-9

[0110]

[0111] As shown in Table 4, when no fluorine (F) was introduced into the flux, the glass slurry coating in Comparative Example 7 could not effectively wet the product surface. The surface of the fired overglaze protective film was rough, unable to properly coat the overglaze pigments, resulting in poor gloss and inability to maintain good color rendering. Furthermore, its strength was poor, leading to reduced durability of the sintered opaque glass tableware dishwasher. In Comparative Example 8, the fluorine addition was 4%. Introducing an appropriate amount of fluorine allowed the flux to have good wetting ability on the opaque glass substrate, reducing surface tension. The resulting glass slurry could spread and adhere quickly to the opaque glass substrate, improving film integrity and meeting the requirements of low-temperature rapid firing. The fired glass film layer had higher smoothness and gloss. In Comparative Example 9, the fluorine addition was 6%. Because fluorine... - The strength of the interionic bonds in the glass network decreases with increasing fluorine (F) content, leading to a reduction in the washability of the sintered opaque glass tableware. Therefore, when the F content is 1%–4%, the protective film layer after flux sintering exhibits high smoothness and gloss while maintaining appropriate network strength.

[0112] Comparative Examples 10-15

[0113] The preparation parameters of the glass washable low melting point fluxes of Comparative Examples 10-15 were the same as those of Example 2, except that the weight ratio of F / (SiO2+Al2O3) in the raw material components was 0.01:1, 0.03:1, 0.05:1, 0.08:1, 0.1:1, and 0.17:1, respectively, and the other components were adjusted proportionally.

[0114] The raw material composition of Comparative Example 10 is 35.6% SiO2, 5.9% Bi2O3, 18.1% Na2O, 13.2% ZnO, 8.9% ZrO2, 5.9% B2O3, 5.6% TiO2, 4.4% Al2O3, 0.4% F, 1.7% Y2O3, and 0.3% La2O3; wherein the weight ratio of F / (SiO2+Al2O3) is 0.01:1.

[0115] The raw material composition of Comparative Example 11 is 35.6% SiO2, 5.8% Bi2O3, 18% Na2O, 13.1% ZnO, 8.7% ZrO2, 5.8% B2O3, 5.5% TiO2, 4.4% Al2O3, 1.2% F, 1.6% Y2O3, and 0.3% La2O3; wherein the weight ratio of F / (SiO2+Al2O3) is 0.03:1.

[0116] The raw material composition of Comparative Example 12 is 35.6% SiO2, 5.7% Bi2O3, 17.8% Na2O, 12.8% ZnO, 8.6% ZrO2, 5.7% B2O3, 5.5% TiO2, 4.4% Al2O3, 2% F, 1.6% Y2O3, and 0.3% La2O3; wherein the weight ratio of F / (SiO2+Al2O3) is 0.05:1.

[0117] The raw material composition of Comparative Example 13 is 35.6% SiO2, 5.6% Bi2O3, 17.4% Na2O, 12.6% ZnO, 8.4% ZrO2, 5.6% B2O3, 5.3% TiO2, 4.4% Al2O3, 3.2% F, 1.6% Y2O3, and 0.3% La2O3; wherein the weight ratio of F / (SiO2+Al2O3) is 0.08:1.

[0118] The raw material composition of Comparative Example 14 is 35.6% SiO2, 5.5% Bi2O3, 17.1% Na2O, 12.4% ZnO, 8.3% ZrO2, 5.5% B2O3, 5.3% TiO2, 4.4% Al2O3, 4% F, 1.6% Y2O3, and 0.3% La2O3; wherein the weight ratio of F / (SiO2+Al2O3) is 0.1:1.

[0119] The raw material composition of Comparative Example 15 was 35.6% SiO2, 5.3% Bi2O3, 16.1% Na2O, 11.8% ZnO, 7.9% ZrO2, 5.3% B2O3, 5.0% TiO2, 4.4% Al2O3, 6.8% F, 1.5% Y2O3, and 0.3% La2O3; wherein the weight ratio of F / (SiO2+Al2O3) was 0.17:1.

[0120] The glass prepared in Comparative Examples 10-15 was mixed evenly with a washable low-melting-point flux and a commercially available organic carrier ink oil, and then dispersed by a three-roll mill to obtain a glass slurry. The glass slurry was coated onto the surface of opaque glass tableware with pigments printed on it, and then tempered by baking. The peak temperature of the tempering baking was 600℃, the time from room temperature to the peak temperature was 20 minutes, and the holding time at the peak temperature was 2 minutes, resulting in opaque glass tableware with a protective film layer on the surface.

[0121] The performance parameters of the washable low-melting-point fluxes for glass prepared in Example 2 and Comparative Examples 10-15 were examined, as well as the changes in various properties of opaque glass tableware after sintering the flux. The performance parameters are shown in Table 5.

[0122] Table 5 Performance parameters of Examples 2 and Comparative Examples 10-15

[0123]

[0124] As shown in Table 5, the addition ratio of F to (SiO2+Al2O3) affects product performance. In Comparative Example 10, when the weight ratio of F / (SiO2+Al2O3) is 0.01:1, the proportion of F as the network exterior is relatively small compared to SiO2 and Al2O3 in the network forming body and network modifier, which cannot effectively play the role of fluxing and reducing surface tension. Therefore, the gloss of the glass protective film decreases, and the protective effect on pigments is also affected. In Comparative Example 15, the weight ratio of F / (SiO2+Al2O3) is 0.17, because F... - With O 2- With similar radii, F - It has stronger non-metallic properties and can easily replace O in the glass network structure. 2- This results in an asymmetrical melt network structure, reduced network integrity, and significantly decreased strength of the molten glass network, leading to poor washability of the sintered opaque glass tableware. Therefore, when the weight ratio of F / (SiO2+Al2O3) is 0.03–0.1, the protective film after solvent sintering exhibits high adhesion, stable chemical properties, and good dishwasher resistance. In particular, the overall performance is optimal when the weight ratio of F / (SiO2+Al2O3) is 0.05–0.08.

[0125] Comparative Example 16

[0126] The glass-resistant, washable, low-melting-point flux of this comparative example uses the same components as in Example 1, the only difference being that the flux of this comparative example is prepared in a single melting process, and the preparation method includes the following steps:

[0127] a) Mix all components evenly in a V-type mixer, place them in a corundum crucible and melt them in a high-temperature furnace at 1200°C for 4 hours. Then, quench the high-temperature glass melt in water to form glass particles and grind them into a molten block with a D97 of no more than 15μm.

[0128] b) Place the fused block from step a at 300°C for 10 hours for heat treatment, and then grind it using an air jet mill until it is a low melting point flux with D50 not exceeding 1 μm and D97 not exceeding 3 μm, thus obtaining a washable low melting point flux for glass.

[0129] Simultaneously, the molten glass obtained in step a is poured into a preheated graphite mold, heat-treated at 300°C for 10 hours, and then cooled in the furnace to obtain a glass block. After cutting and polishing, the block is cut into glass test strips of the appropriate size for expansion coefficient and static detergent resistance testing.

[0130] Comparative Example 17

[0131] The glass-resistant, washable, low-melting-point flux of this comparative example uses the same components as in Example 1, the only difference being that the flux of this comparative example did not undergo a heat treatment step at 300-350°C. The preparation method includes the following steps:

[0132] a) Mix all components except rare earth oxides evenly in a V-type mixer, place them in a corundum crucible and melt them in a high-temperature furnace at 1200℃ for 4 hours. Then, quench the high-temperature glass melt with water to form glass particles and grind them into primary frits with D97 not greater than 15μm.

[0133] b) Mix the primary molten material from step a with Y2O3 until homogeneous, place it in a corundum crucible and melt it at 1000℃ for 30 minutes. Then, quench the high-temperature glass melt into glass particles and grind them into powder with D97 not greater than 15μm. Then, use an air jet mill to grind it into a low-melting-point flux with D50 not greater than 1μm and D97 not greater than 3μm, thus obtaining a washable low-melting-point flux for glass.

[0134] Simultaneously, the molten glass obtained in step b is poured into a preheated graphite mold, then placed in an electric furnace to maintain its temperature and eliminate internal stress. After cooling in the furnace, a glass block is obtained. After cutting and polishing, it is cut into glass test strips of the corresponding size for use in tests of expansion coefficient and static detergent resistance.

[0135] Comparative Example 18

[0136] The glass-resistant, washable, low-melting-point flux used in this comparative example employs the same components as in Example 1, the only difference being that the secondary melting process involves excessively high temperatures and prolonged times. The preparation method includes the following steps:

[0137] a) Mix all components except rare earth oxides evenly in a V-type mixer, place them in a corundum crucible and melt them in a high-temperature furnace at 1200℃ for 4 hours. Then, quench the high-temperature glass melt with water to form glass particles and grind them into primary frits with D97 not greater than 15μm.

[0138] b) Mix the primary frit from step a with Y2O3 evenly, place it in a corundum crucible and melt it at 1100℃ for 120 minutes. Then, quench the high-temperature glass melt into glass particles, i.e., the secondary frit.

[0139] c) Place the secondary fused block from step b at 350°C for 10 hours for heat treatment, and then grind it using an air jet mill until it is a low melting point flux with D50 not exceeding 1 μm and D97 not exceeding 3 μm, thus obtaining a washable low melting point flux for glass.

[0140] Simultaneously, the molten glass obtained in step b is poured into a preheated graphite mold, placed at 300°C for 10 hours for heat treatment, and then cooled in the furnace to obtain a glass block. After cutting and polishing, it is cut into glass test strips of the corresponding size for expansion coefficient and static detergent resistance testing.

[0141] The glass prepared in Comparative Examples 16-18 was mixed evenly with a washable low-melting-point flux and a commercially available organic carrier ink, and then dispersed by a three-roll mill to obtain a glass slurry. The glass slurry was coated onto the surface of opaque glass tableware with pigments printed on it, and then tempered by baking. The peak temperature of the tempering baking was 600℃, the time from room temperature to the peak temperature was 20 minutes, and the holding time at the peak temperature was 2 minutes, resulting in opaque glass tableware with a protective film layer on the surface.

[0142] The performance parameters of the washable low-melting-point fluxes for glass prepared in Example 1 and Comparative Examples 16-18 were examined, as well as the changes in various properties of opaque glass tableware after sintering the flux. The performance parameters are shown in Table 6.

[0143] Table 6 Performance parameters of Example 1 and Comparative Examples 16-18

[0144]

[0145] As shown in Table 6, in Comparative Example 16, yttrium oxide was melted together with all components in a single process to obtain a low-melting-point flux. This process was not conducive to the formation of a locally rich alumina-rare earth oxide state, resulting in poor strength of the protective film after sintering and significantly reduced dishwasher tolerance. In Comparative Example 17, no subsequent heat treatment step at 300–350°C was performed, leading to poor chemical stability of the flux and reduced dishwasher tolerance. See [link to table]. Figure 3 In Example 1, after the secondary melt undergoes heat treatment in step c, the melt is microcrystallized, forming fine grains dispersed within the transparent melt, thereby improving the chemical stability of the flux. In Comparative Example 18, the secondary melting temperature is too high and the melting time is too long, resulting in excessive dissolution of rare earth oxides in the glass melt. This is not conducive to the formation of a locally rich alumina-rare earth oxide state, affecting the subsequent microcrystallization process of heat treatment, thus reducing the overall performance of the flux and failing to achieve good dishwasher tolerance.

[0146] In summary, the washable, low-melting-point flux for glass described in this invention is applicable to opaque glass substrates, meeting the requirements for low-temperature rapid firing. The firing temperature is as low as 590-600℃, and the coefficient of expansion matches that of the opaque glass substrate. It can quickly form a glass protective film with high transparency, good color rendering, strong adhesion, and good alkali resistance, maintaining the original color of the pigments. At the same time, it improves the service life of the opaque glass overglaze pattern in dishwashers and greatly reduces the leaching of lead and cadmium from the overglaze pigments.

[0147] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A washable, low-melting-point flux for glass, characterized in that, By weight percentage, it includes the following components: SiO2 30-40%, Bi2O3 3-10%, R2O 15-25%, ZnO 10-15%, ZrO 26-12%, B2O3 3-10%, TiO2 3-10%, Al2O3 2-6%, F 1-4%, and rare earth oxides 1-3%; Among them, R2O is a basic oxide, including one or more of Na2O, K2O and Li2O; The rare earth oxide is Y2O3 and / or La2O3; The F is introduced through one or more of sodium fluorosilicate, sodium fluoride, aluminum fluoride or calcium fluoride; In the glass-use washable low-melting-point flux, the weight ratio of Al2O3 to rare earth oxides is 1 to 3:

1.

2. The washable, low-melting-point flux for glass as described in claim 1, characterized in that, In the glass-use washable low-melting-point flux, the weight ratio of the content of the element F to the total content of SiO2 and Al2O3 is 0.03 to 0.1:

1.

3. The washable, low-melting-point flux for glass as described in claim 1, characterized in that, Bi2O3 accounts for 3-6% by weight.

4. A method for preparing a washable, low-melting-point flux for glass as described in any one of claims 1 to 3, characterized in that, Includes the following steps: a) One-time melting: According to the preparation ratio, other raw materials except rare earth oxides are mixed evenly, melted at high temperature into glass liquid, then quenched and ground into glass particles to obtain a one-time fused block; b) Secondary melting: According to the preparation ratio, the rare earth oxides are mixed evenly with the primary melt obtained in step a, and then melted at high temperature into glass liquid, followed by cold quenching and grinding into secondary melt. c) Heat treatment: The secondary fused block obtained in step b is placed at 300-350℃ for 5-10 hours and then ground into glass powder with D50≤1μm and D97≤3μm, which is the washable low melting point flux for glass.

5. The preparation method according to claim 4, characterized in that, The high-temperature melting parameters in step a are: melting temperature of 1200-1300℃ and holding time of 3-4 hours.

6. The preparation method according to claim 4, characterized in that, The high-temperature melting parameters in step b are: melting temperature of 900-1000℃ and holding time of 30-60min.

7. A method for preparing a protective film for opaque glass enamel, characterized in that, Includes the following steps: 1) The glass-resistant, washable, low-melting-point flux according to any one of claims 1-3 is mixed evenly with ink, and then ground and dispersed to obtain a glass slurry; 2) Apply the glass paste described in step 1 to the surface of the opaque glass product with pigment printed on its surface to form a glass paste layer; 3) The opaque glass product coated with glass paste layer in step 2 is fired to obtain the opaque glass glaze protective film.

8. The preparation method according to claim 7, characterized in that, The thickness of the glass slurry layer in step 2 is ≥10μm.

9. The preparation method according to claim 7, characterized in that, The maximum firing temperature in step 3 is 590-600°C, the time to heat from room temperature to the maximum firing temperature is 20-25 minutes, and the holding time does not exceed 2 minutes.

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