An opal glass and a method for its production

Abstract

The present application relates to the technical field of glass manufacturing, and particularly relates to a milky white glass and a preparation method thereof. The milky white glass provided by the present application contains uniformly distributed LiAlSi3O8 crystals in the phase thereof, and the preparation raw material comprises, in terms of mass percentage of oxides, SiO2 58-67%, Al2O3 17-23%, Li2O 2-5%, SnO2 2-4%, ZnO 0-2%, ZrO2 1-2%, B2O3 2.5-5%, P2O5 0.5-6%, R2O 0-2% and MO 0-4.4%, wherein MO is at least one of BaO, CaO and MgO, and R2O is at least one of K2O and Na2O. The present application introduces a composite nucleating agent composed of SnO2 and ZrO2 into the raw material, and matches P2O5 nucleation inducer to induce the precipitation of LiAlSi3O8 crystals in the glass matrix raw material, so that the obtained milky white glass has a lower thermal expansion coefficient and excellent thermal shock resistance, and can also present a better milky white appearance.

Description

Technical Field

[0001] This invention relates to the field of glass manufacturing technology, and in particular to a milky white glass and its preparation method. Background Technology

[0002] Milky white glass is a composite material composed of crystalline and glassy phases. It can be used as tableware and has the characteristics of high whiteness, crystal clarity and beauty, and good stain resistance compared to traditional ceramic tableware.

[0003] Currently, the production of milky white glass tableware mainly uses fluoride as an opacifier. Fluoride crystals are precipitated to give the glass a milky white appearance. However, because fluoride ions weaken the integrity of the glass network structure, increase the product's coefficient of thermal expansion, and reduce the product's resistance to thermal shock, it is prone to cracking due to excessive thermal shock in some application environments with large temperature differences, such as ovens and hot oil cooking.

[0004] Patent CN104193174A discloses a method for producing high-whiteness glass-ceramic products, comprising 55.0–65.0% quartz sand, 8.1–11.0% aluminum hydroxide, 6.0–11.0% soda ash, 1.0–3.0% barium carbonate, 0.5–3.5% calcium carbonate, 0–1.5% magnesium carbonate, 0–2.5% potassium nitrate, 3.0–10.0% borax pentahydrate, 3.0–9.0% zinc oxide, and 2.5–4.5% sodium fluorosilicate. The milky-white product prepared by this method achieves a whiteness of 85 and a gloss of 90, but its thermal shock resistance is low, only up to 135℃, which is unsuitable for applications such as ovens.

[0005] Patent CN202010846387.8 discloses a microcrystalline glass vessel and its preparation method. The basic components and molar ratios of the glass are: SiO2: 58-70 mol%; Al2O3: 18-20 mol%; Li2O: 7-11 mol%; ZnO: 2-4 mol%; MgO: 2-4 mol%; TiO2: 0.2-1.0 mol%; ZrO2: 0.2-0.8 mol%; P2O5: 0.4-1.0 mol%; Sb2O3: 0.2 mol%. The microcrystalline glass prepared by this method has a low coefficient of thermal expansion, with a CTE (20-700℃) of 0.34 × 10⁻⁶. -6 / ℃~0.67*10 -6 It has a temperature resistance of 700℃, but its visible light transmittance at 550nm is only 51-85%, making it completely transparent and unable to present a milky white appearance.

[0006] Currently, low-expansion-coefficient microcrystalline glass is mainly produced by adding TiO2 or TiO2-containing composite nucleating agents to precipitate a quartz solid solution with a low expansion coefficient. 4+Strong light absorption in the ultraviolet region causes the glass to appear pale yellow to yellowish-brown. Meanwhile, the presence of Fe impurities or other transition metal oxides in the raw materials exacerbates the coloring effect. Therefore, the core problem this invention aims to solve is how to prepare a milky white glass that balances high whiteness, low coefficient of thermal expansion, and excellent thermal shock resistance. Summary of the Invention

[0007] The present invention addresses the technical problems mentioned in the background art by providing a milky white glass that combines high milky white effect and low coefficient of thermal expansion, while also possessing excellent thermal shock resistance, wherein the phase contains uniformly distributed LiAlSi3O8 crystals.

[0008] The raw material components for preparing the above-mentioned milky white glass, by mass percentage, include: Li2O: 2-5%; Al2O3: 17-23%; SiO2: 58-67%; SnO2: 2-4%; ZrO2: 1-2%; P2O5: 0.5-6%; MO: 0-4.4%; ZnO: 0-2%; B2O3: 2.5-5%; R2O: 0-2%; wherein, MO is at least one of BaO, CaO, and MgO; and R2O is at least one of K2O and Na2O.

[0009] The milky white glass provided by this invention introduces a composite nucleating agent composed of SnO2 and ZrO2 into the raw materials. Under the crystallization and nucleation process, it induces the precipitation of LiAlSi3O8 crystals with a high content and uniform distribution of crystalline phase in the glass matrix raw materials. The LiAlSi3O8 crystals themselves have a low coefficient of thermal expansion, which makes the milky white glass have a low coefficient of thermal expansion and high whiteness.

[0010] Compared with traditional glass obtained by adding TiO2 or a composite nucleating agent containing TiO2, the above method adds a composite nucleating agent composed of SnO2 and ZrO2, combined with P2O5 nucleating inducer, which avoids the influence of TiO2 coloring effect on the whiteness of the product. The resulting glass has higher whiteness, presents a better milky white appearance, and has excellent thermal shock resistance.

[0011] Preferably, the mass ratio of SnO2 to ZrO2 in the above-mentioned raw material formulation is 2:1 to 3:1. When the ratio of SnO2 to ZrO2 in the raw material formulation is 2:1 to 3:1, more LiAlSi3O8 crystals can precipitate in the glass matrix, thereby ensuring that the obtained glass has high whiteness and a low coefficient of thermal expansion.

[0012] Preferably, in the above-mentioned raw material formulation, the mass percentage of BaO is 0.5-2.5%, the mass percentage of CaO is 0.1-1%, and the mass percentage of MgO is 0.1-0.9%. When the above-mentioned chemical composition ratio is used in the milky glass of this scheme, it can promote the melting and forming of glass, reduce the thermal expansion coefficient of hot glass, and improve its thermal shock resistance.

[0013] In addition, the present invention also provides a method for preparing opaline glass, comprising the following steps:

[0014] S1. Weighing and mixing: Weigh the raw materials according to the following parameters based on the mass percentage of oxides: SiO2 58-67%, Al2O3 17-23%, Li2O 2-5%, SnO2 2-4%, ZnO 0-2%, ZrO2 1-2%, B2O3 2.5-5%, P2O5 0.5-6%, R2O 0-2%, and MO 0-4.4%, and mix them evenly. MO is at least one of BaO, CaO, and MgO, and R2O is at least one of K2O and Na2O.

[0015] S2. Melting: Heating the raw materials to melt them into molten glass;

[0016] S3. Shaping: Shaping the molten glass to obtain the desired shape of the milky white glass semi-finished product;

[0017] S4. Annealing: Anneal the semi-finished milky glass to obtain a milky glass blank;

[0018] S5. Nucleation and Crystallization: The annealed milky white glass blank is first heated to undergo nucleation and crystallization treatment, and then cooled to room temperature to obtain milky white glass products.

[0019] Preferably, in the above preparation method, the melting temperature in step S2 is 1500-1550℃. The melting temperature is determined according to the chemical composition of the raw materials. Under the formulation system provided in this patent, a melting temperature of 1500-1550℃ is preferable.

[0020] Preferably, in the above preparation method, the annealing temperature in step S4 is 580-610℃, and the annealing time is ≥1 hour. The purpose of annealing is to eliminate stress in the product and improve its strength.

[0021] Preferably, in the above preparation method, the heating rate of the milky white glass blank in step S5 is 2-6 °C / min. More preferably, the heating rate is 3 °C / min.

[0022] Preferably, in the above preparation method, the nucleation temperature of step S5 is 700–720°C, and the holding time is ≥2 hours; the crystallization temperature is 770–810°C, and the holding time is ≥5 hours. The heating between nucleation and crystallization is also at a heating rate of 2–6°C / min, more preferably 3°C / min.

[0023] In the raw material components, SiO2 serves as the glass network-forming oxide, and Al2O3 serves as the network-modifying oxide. Both provide the basic strength of the glass network structure. The sum of the mass percentages of SiO2 and Al2O3 generally does not exceed 90%. Exceeding 90% will lead to excessively high glass melting temperatures, increased melting and refining difficulties, and processing difficulties. R2O is at least one of sodium oxide and potassium oxide, and its mass percentage generally does not exceed 2%. As an external oxide of the network, it provides free oxygen ions and lowers the glass melting temperature. ZnO, as a glass network modifier, is mainly used to improve the fluxing effect and reduce the glass expansion coefficient. It also helps to improve the glass toughness and can be added in appropriate amounts to the formulation components. Li2O introduces lithium to form LiAlSi3O8 crystals and helps reduce the viscosity of the glass melt. The mass percentage of Li2O is preferably 2-5%; too low a percentage makes it difficult to form a sufficient amount of LiAlSi3O8 crystals. SnO2 and ZrO2 are composite nucleating agents, replacing commonly used TiO2-containing nucleating agents. P2O5 can regulate the melting temperature and also acts as a nucleation inducing, inducing the two-phase separation required for nucleation, promoting crystal nucleation and growth, and lowering the nucleation and crystallization temperatures. The addition ratio of P2O5 is 0.5-6%; too high a ratio will exacerbate glass phase separation and reduce the strength and chemical stability of the glass. B2O3 mainly regulates the melting temperature of the glass raw material, primarily acting as a flux. BaO, CaO, and MgO act as fluxing agents and regulate the properties of the molten glass, benefiting forming and processing, and to some extent reducing the coefficient of thermal expansion of the glass. A combination of these three is preferred. With the above component system, LiAlSi3O8 crystals with a high content and uniform distribution of crystalline phase and a low coefficient of thermal expansion can be precipitated in the glass matrix. This glass has a good opalescent effect, a low coefficient of thermal expansion, and excellent thermal shock resistance.

[0024] This method employs nucleation and crystallization to facilitate the precipitation of LiAlSi3O8 crystals in the opalescent glass preform. The nucleation process involves heating from 580–610℃ to 700–720℃ and holding for 2–4 hours. The temperature is then raised to 770–810℃ and held for 5–7 hours before cooling to room temperature. This process yields opalescent glass that combines high opalescent whiteness with a low coefficient of thermal expansion and excellent thermal shock resistance. Unlike traditional glass nucleation and crystallization temperatures (750–1000℃), this method allows for lower nucleation and crystallization temperatures while still achieving a low coefficient of thermal expansion, resulting in a product that combines excellent thermal shock resistance and high whiteness.

[0025] In addition, the present invention also provides a milky white glass tableware, which is made of the aforementioned milky white glass.

[0026] Compared with the prior art, the milky white glass provided by the present invention has excellent whiteness (L*a*b* value whiteness greater than 50) and excellent thermal shock resistance (>550℃). Tableware made from it can be directly used in heating scenarios such as microwave ovens. Attached Figure Description

[0027] 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.

[0028] Figure 1 This is a cross-sectional SEM image of the opaline glass prepared in Example 2 of this scheme;

[0029] Figure 2 The XRD pattern of the opalescent glass prepared in Example 2 of this scheme is shown.

[0030] Figure 3 The curve of the coefficient of thermal expansion of the opaline glass prepared in Example 2 of this scheme.

[0031] 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

[0032] 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If 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 this invention.

[0034] Examples 1-8

[0035] Refer to Table 1 below, which is the raw material formula table for Examples 1-8, in percentage by mass.

[0036] Table 1

[0037] 1 58 23 2.5 4 1.4 1.2 1.9 0.5 0.4 4 2.6 0.5 0 2 62 20 3.3 3.2 1.4 1.2 1.3 0.5 0.4 3.5 2.2 1 0 3 65.2 17 3.3 3.2 0.8 0.5 1.1 0.5 0.4 3.5 3.5 1 0 4 62 20 3.3 2.5 1.4 1.2 2 0.5 0.4 3.5 2.2 1 0 5 62 20 3.3 4 1.4 1.2 1 0.5 0.4 3.5 2.2 0.5 0 6 67 20 2 2 2 1.2 1 0.5 0.4 2.5 0.5 0.5 0.4 7 58 17 5 4 1.4 1.2 2 0.5 0.4 2.5 6 1 1 8 62 20 3.3 3.2 1.4 1.2 1 0.5 0.4 3.5 2.2 1 0.3

[0038] According to the above formulation system, Examples 1-8 were prepared through the following process flow.

[0039] S1. Weighing: Weigh the raw materials according to the formula system in Table 1 above.

[0040] S2. The above raw materials are continuously fed from the top of the electric furnace. After the top electrode is energized, the glass melt is heated by its conductivity. The temperature of the melting zone is 1500℃~1550℃.

[0041] S3. The molten glass sinks to the bottom of the electric furnace, and then flows through the flow channel, riser and material channel to the forming end. The glass is then dripped into the molded glass semi-finished product using a press or centrifugal equipment.

[0042] S4. The above-mentioned semi-finished milky white glass product is immediately taken out by the robot arm and put into the annealing furnace through the conveyor belt. It is kept at 600°C for 2 hours to obtain the milky white glass blank.

[0043] S5. The above-mentioned milky white glass blank is reheated at a rate of 3℃ / min for nucleation and crystallization. The nucleation temperature is 700℃ and the holding time is 3h, the crystallization temperature is 770℃ and the holding time is 6h, and then it is cooled to room temperature to obtain milky white glass.

[0044] The opaline glass prepared in Examples 1-8 was tested to determine its performance, and the test data are shown in Table 2 below.

[0045] Table 2

[0046] Example 1 83 <![CDATA[1.53*10 -6 / K]]> >750℃ Example 2 86 <![CDATA[1.39*10 -6 / K]]> >750℃ Example 3 81 <![CDATA[1.62*10 -6 / K]]> >750℃ Example 4 61 <![CDATA[2.77*10 -6 / K]]> >550℃ Example 5 53 <![CDATA[3.30*10 -6 / K]]> >550℃ Example 6 55 <![CDATA[3.99*10 -6 / K]]> >550℃ Example 7 80 <![CDATA[1.66*10 -6 / K]]> >750℃ Example 8 82 <![CDATA[2.01*10 -6 / K]]> >750℃

[0047] Appendix Figure 1 SEM image of the cross-section of the opalescent glass prepared in Example 2; attached. Figure 2 The XRD pattern of the opalescent glass prepared in Example 2 shows that the opalescent glass contains a large amount of LiAlSi3O8 crystals; (See attached image) Figure 3The thermal expansion coefficient curve of the opaline glass prepared in Example 2.

[0048] Examples 9-10

[0049] Referring to Examples 2 and 4, the mass ratio of SnO2 and ZrO2 was changed to prepare Examples 9 and 10. The specific formulation is shown in Table 3 below.

[0050] Table 3

[0051]

[0052] The remaining process parameters are the same as in Example 2, and the test data of the prepared opaline glass are shown in Table 4 below.

[0053] Table 4

[0054] Example 2 86 <![CDATA[1.39*10 -6 / K]]> >750℃ Example 4 61 <![CDATA[2.77*10 -6 / K]]> >550℃ Example 9 73 <![CDATA[2.85*10 -6 / K]]> >550℃ Example 10 58 <![CDATA[3.53*10 -6 / K]]> >550℃

[0055] Based on the above comparisons and similar analysis and testing, under this formulation system and process conditions, the mass ratio of tin oxide to zirconium oxide is preferably 2:1 to 3:1, resulting in milky white glass with high whiteness and low coefficient of thermal expansion.

[0056] Comparative Example 1

[0057] The comparative ratio uses the following formulation system: SiO2: 62%, Al2O3: 20%, Li2O: 4.2%, ZnO: 1.4%, BaO: 1.2%, ZrO2: 2%, MgO: 0.5%, CaO: 0.4%, B2O3: 3.5%, P2O5: 3.8%, Na2O: 1%.

[0058] The preparation process is the same as in Examples 1-8. The glass obtained is basically transparent, and the test results are as follows.

[0059] Whiteness (L*a*b*value whiteness): Transparent and colorless;

[0060] Coefficient of thermal expansion (average linear expansion coefficient at 30–800℃): 4.51 * 10 -6 / K;

[0061] Thermal shock resistance: >350℃.

[0062] Comparative Example 2

[0063] The comparative ratio uses the following formulation system: SiO2: 62%, Al2O3: 20%, Li2O: 4.2%, ZnO: 1.4%, BaO: 1.2%, SnO2: 2%, MgO: 0.5%, CaO: 0.4%, B2O3: 3.5%, P2O5: 3.8%, Na2O: 1%.

[0064] The preparation process is the same as in Examples 1-8. The glass obtained is basically transparent, and the test results are as follows.

[0065] Whiteness (L*a*b*value whiteness): 21;

[0066] Coefficient of thermal expansion (average linear expansion coefficient at 30–800℃): 5.85 * 10 -6 / K;

[0067] Thermal shock resistance: >300℃.

[0068] Examples 11-15

[0069] Referring to Example 2, the amounts of barium oxide, magnesium oxide, and calcium oxide were changed. The raw material formula is shown in Table 5 below.

[0070] Table 5

[0071] 2 62 20 3.3 3.2 1.4 1.2 1.3 0.5 0.4 3.5 2.2 1 11 62 20 3.3 2.5 1.4 2.1 1.3 —— —— 3.5 2.2 1 12 62 20 3.3 3.5 1.4 1.1 1.3 —— 1 3.5 2.2 1 13 62 20 3.3 2 1.4 1.2 1.3 0.9 —— 3.5 2.2 1 14 62 20 3.3 2 1.4 0.2 1.3 0.9 1 3.5 2.2 1 15 62 20 3.3 2 1.4 0.5 1.3 0.7 0.9 3.5 2.2 1

[0072] The remaining process parameters are the same as in Example 2, and the test data of the prepared opaline glass are shown in Table 6 below.

[0073] Table 6

[0074] Example 2 86 <![CDATA[1.39*10 -6 / K]]> >750℃ Example 11 85 <![CDATA[3.61*10 -6 / K]]> >550℃ Example 12 83 <![CDATA[3.92*10 -6 / K]]> >550℃ Example 13 85 <![CDATA[2.47*10 -6 / K]]> >650℃ Example 14 86 <![CDATA[1.65*10 -6 / K]]> >750℃ Example 15 85 <![CDATA[1.55*10 -6 / K]]> >750℃

[0075] By comparing experiments similar to those in Examples 11-15, it can be seen that the composite system of BaO, CaO and MgO in MO is more beneficial to the coefficient of thermal expansion and thermal shock resistance of the product. Further optimization shows that the mass percentage of BaO is 0.5-2.5%, the mass percentage of CaO is 0.1-1%, and the mass percentage of MgO is 0.1-0.9%, which is even better.

[0076] In the preparation method, the melting temperature in step S2 is preferably 1500-1550℃. The annealing temperature in step S4 is preferably 580-610℃, and the annealing time is preferably ≥1 hour. The heating rate of the milky white glass preform in step S5 is preferably 2-6℃ / min; too slow a rate will affect efficiency, while too fast a rate will affect LiAlSi3O8 crystal growth. The nucleation temperature in step S5 is 700-720℃, and the holding time is ≥2 hours; the crystallization temperature is 770-810℃, and the holding time is ≥5 hours. The heating rate between nucleation and crystallization is also preferably 2-6℃ / min; too slow a rate will affect efficiency, while too fast a rate will affect LiAlSi3O8 crystal growth.

[0077] 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 type of milky white glass, characterized in that, Its phase contains uniformly distributed LiAlSi3O8 crystals; The raw materials used in its preparation, by mass percentage of oxides, include: SiO2 58-67%, Al2O3 17-23%, Li2O 2-5%, SnO2 2-4%, ZnO 0-2%, ZrO2 1-2%, B2O3 2.5-5%, P2O5 0.5-6%, R2O 0-2%, and MO 0-4.4%. The MO is at least one of BaO, CaO and MgO; The R2O is at least one of K2O and Na2O.

2. The milky white glass as described in claim 1, characterized in that, The mass ratio of SnO2 to ZrO2 is 2:1 to 3:

1.

3. The milky white glass as described in claim 1, characterized in that, The mass percentage of BaO is 0.5-2.5%, the mass percentage of CaO is 0.1-1%, and the mass percentage of MgO is 0.1-0.9%.

4. A method for preparing opalescent glass, characterized in that, The steps include the following: S1. Weighing and mixing: Weigh the raw materials according to the following parameters based on the mass percentage of oxides: SiO2 58~67%, Al2O3 17~23%, Li2O 2~5%, SnO2 2~4%, ZnO 0~2%, ZrO2 1~2%, B2O3 2.5~5%, P2O5 0.5~6%, R2O 0~2%, and MO 0~4.4%, and mix them evenly. The MO is at least one of BaO, CaO, and MgO, and the R2O is at least one of K2O and Na2O. S2. Melting: The raw materials are heated and melted into molten glass; S3. Shaping: The molten glass is shaped to obtain a semi-finished milky white glass product with the desired shape; S4. Annealing: Anneal the semi-finished milky glass to obtain a milky glass blank; S5. Nucleation and crystallization: The milky white glass blank is first heated to perform nucleation and crystallization treatment, and then cooled to room temperature to obtain milky white glass products.

5. The method for preparing opaline glass according to claim 4, characterized in that, In step S2, the melting temperature is 1500-1550℃.

6. The method for preparing opaline glass according to claim 4, characterized in that, In step S4, the annealing temperature is 580-610℃, and the annealing time is ≥1h.

7. The method for preparing opaline glass according to claim 4, characterized in that, In step S5, the heating rate of the milky white glass blank is 2-6℃ / min.

8. The method for preparing opaline glass according to claim 4, characterized in that, In step S5, The nucleation temperature is 700~720℃, and the holding time is ≥2h; The crystallization temperature is 770~810℃, and the holding time is ≥5h.

9. Tableware made of the milky white glass according to any one of claims 1-3.

Images