阅读说明：本技术 一种提高玻璃化学钢化中硝酸盐活性和长效性的方法 (Method for improving activity and long-acting property of nitrate in chemical toughening of glass ) 是由 韩伟军 于 2021-07-30 设计创作，主要内容包括：本发明涉及一种提高玻璃化学钢化中硝酸盐活性和长效性的方法,包括：在化学钢化时,采用硝酸钠、硝酸钙与硝酸钾组成混合熔盐组分,充分混合,熔盐熔化温度可降至350℃-410℃,将预热的玻璃浸渍在熔盐中,恒温沉浸5-8h,即得化学钢化的玻璃制品。本发明明显降低离子交换的温度,提高硝酸盐的活性和寿命,降低生产成本,不影响玻璃增强的强度、透光性和平整度,具有良好的应用前景。(The invention relates to a method for improving the activity and the long-acting property of nitrate in glass chemical toughening, which comprises the following steps: during chemical tempering, sodium nitrate, calcium nitrate and potassium nitrate are adopted to form mixed molten salt components, the molten salt components are fully mixed, the melting temperature of the molten salt can be reduced to 350-410 ℃, preheated glass is immersed in the molten salt for 5-8 hours at constant temperature, and the chemically tempered glass product is obtained. The invention obviously reduces the temperature of ion exchange, improves the activity and the service life of nitrate, reduces the production cost, does not influence the enhanced strength, light transmittance and flatness of glass, and has good application prospect.)

1. A method for improving the activity and the long-acting property of nitrate in the chemical toughening of glass comprises the following steps:

during chemical toughening, sodium nitrate, calcium nitrate and potassium nitrate are adopted as molten salt components and are fully mixed, and the temperature of the heated molten salt is reduced to 350-410 ℃; dipping the preheated glass in molten salt, and immersing at constant temperature to obtain a chemically toughened and reinforced glass product; wherein the addition amount of the sodium nitrate is 10 to 25 weight percent of the potassium nitrate, and the addition amount of the calcium nitrate is 1.0 to 4.0 weight percent of the potassium nitrate.

2. The method of claim 1, wherein: the constant-temperature immersion time is 5-8 h.

Technical Field

The invention belongs to the field of chemical toughening of glass, and particularly relates to a method for improving the activity and the long-acting property of nitrate in chemical toughening of glass.

Background

For Na₂O-CaO-SiO₄The glass is strengthened by chemical toughening, and the main key molten salt raw material is potassium nitrate. Usually, potassium nitrate is heated and melted at 430-500 ℃, potassium ions of the potassium nitrate can exchange with sodium ions in the glass under the action of concentration gradient, and potassium large ions squeeze the positions of sodium small ions, so that compressive stress is generated on the surface of the glass, the performance of the surface of the glass is improved, and the impact resistance and the wear resistance of the glass are improved.

Carrying out chemical toughening process operation, soaking the glass in high-temperature molten salt of potassium nitrate, and generating an ion exchange layer on the surface of the glass after a period of time; the improvement of a certain fused salt temperature is beneficial to the ion exchange, and the usability and the activity of the potassium nitrate begin to be reduced along with the long-term operation of the reaction tank at high temperature.

1. The easier the potassium nitrate is converted into potassium nitrite at high temperature

2KNO₃Heating 2KNO₂+O₂×) and the production environment of oxygen enrichment brings hidden troubles to safety.

2. The potassium nitrite can perform ion exchange in a molten state and also can improve the toughening strength of the glass, but the flatness and the light transmittance of the glass surface are greatly reduced after chemical toughening.

Using KNO₃And KNO₂Chemical tempering result comparison table reagent (3mm glass)

The experimental results also show that the KNO is processed₂The treated glass has rough surface, obvious devitrification and poor optical coefficient; at the same time, KNO was found₂Has strong water absorption, and trace KNO is adhered to the surface of the cleaned toughened glass₂The glass absorbs moisture in the air to cause deliquescence, corrosion and mildew on the surface of the glass. At the same time, due to KNO₂Has strong water absorption and is easy to increase OH in molten salt^-The concentration, as known from research, of OH^-The large increase in the amount of the molten salt causes the molten salt to lose activity in a short period of time, thereby reducing the tempering effect. Therefore, KNO is controlled in the molten salt bath₂Is generated.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for improving the activity and the long-acting property of nitrate in the chemical toughening of glass, which obviously reduces the temperature of ion exchange, does not influence the enhanced strength, light transmittance and flatness of the glass and has good application prospect.

The invention provides a method for improving the activity and the long-acting property of nitrate in glass chemical toughening, which comprises the following steps:

during chemical toughening, sodium nitrate, calcium nitrate and potassium nitrate are adopted as molten salt components and are fully mixed, and the temperature of the heated molten salt is greatly reduced to 350-410 ℃, so that the requirements of an ion exchange process are met; dipping the preheated glass in the multi-component molten salt, and immersing at constant temperature to obtain a chemically tempered glass product; wherein the addition amount of the sodium nitrate is 10 to 25 weight percent of the potassium nitrate, and the addition amount of the calcium nitrate is 1.0 to 4.0 weight percent of the potassium nitrate.

The constant-temperature immersion time is 5-8 h.

The calcium nitrate is added in a certain increment, and the temperature of the molten salt is reduced.

KNO of the invention₃-NaNO₃-Ca(NO₃)₂The multi-component mixed molten salt can reduce the ion exchange reaction temperature of the chemical tempering molten salt by 70-80 ℃ to reach the temperature close to KNO₃、NaNO₃Conversion to KNO by heating₂、NaNO₂The critical point of (a); (the chemical reaction theory is that sodium nitrate starts to decompose at temperatures above 375 ℃ to produce sodium nitrite and oxygen; and nitric acid starts to decompose at temperatures above 380 ℃ to potassium nitrite and oxygen). Along with the reduction of the working temperature of chemical toughening, the speed of converting nitrate into nitrite is rapidly reduced, and the purpose of inhibiting the decomposition of potassium nitrate is achieved.

1. Feasibility of adding sodium nitrate

As can be seen from the following table, the addition of sodium nitrate to the single-component potassium nitrate is beneficial to improving the toughening strength of the glass.

Molten salt component KNO₃；KNO₃+NaNO₃Glass strength change after chemical tempering (3mm)

2. Molten salt melting temperature measurement control

A stainless steel flat-head long sleeve nickel-chromium-nickel-silicon XMT22 digital thermocouple is used, 4 seconds are set as the uniform deep travel time of the thermocouple from the molten salt liquefaction surface to the reaction tank (the tank depth is 3 meters) at a distance of 10 centimeters from the bottom, and the chemical tempering process temperature of freely sinking into molten salt is completed within 4 seconds; and if the time is more than 4 seconds, continuously heating again and searching for the melting temperature of the molten salt.

3. Relation between sodium nitrate addition and molten salt melting temperature

From the above table, it can also be seen that the two-component KNO₃+NaNO₃Adding about 10 wt% of sodium nitrate into molten salt to improve glass resistanceThe folding strength is higher than that of single component potassium nitrate; the breaking strength of the glass is reduced with the increase of the content of the sodium nitrate.

As can be seen from FIG. 1, the single-component nitrate salt has a high melting temperature and KNO₃The initial melting is 337 ℃; low eutectic melting degree of bi-component nitrate, KNO₃Adding 15 wt% of NaNO₃The initial melting degree of the main body of potassium nitrate can be below 300 ℃.

As can be seen from FIG. 2, in KNO₂+NaNO₂The dual component nitrate also had the result of reduced eutectic solubility, but the formation of potassium nitrite was seen, driving up the melting temperature of the molten salt, and figure 2 shows that potassium mono-nitrite has a higher melting degree than potassium nitrate alone by 50 ℃.

4. Relation between calcium nitrate addition and molten salt melting temperature

As can be seen from FIG. 3, the introduction of calcium nitrate as the ion exchange raw material also promotes the reduction of the eutectic temperature of the multi-component nitrate; the calcium ions can also replace sodium ions in the glass to form calcium silicate with silicon, so that the effect of squeezing is achieved, and the compressive stress on the surface of the glass is improved.

Advantageous effects

The invention obviously reduces the temperature of ion exchange, improves the activity and the service life of nitrate, reduces the production cost, does not influence the enhanced strength, light transmittance and flatness of glass, and has good application prospect. For example, the following steps are carried out: 1.5 tons of reagent-grade single potassium nitrate raw materials in the reaction tank are used for 65 days, and multicomponent reagent-grade nitrate raw materials are used, so that the use time can reach 170 days, and the energy consumption is reduced by 25 percent.

Drawings

FIG. 1 shows KNO₃And NaNO₃A molten phase diagram of (2).

FIG. 2 shows KNO₂And NaNO₂A molten phase diagram of (2).

FIG. 3 shows KNO₃、NaNO₃And Ca (NO)₃)₂A molten phase diagram of (2).

FIG. 4 is a graph showing the concentration distribution of each component in the surface layer of the glass sheet.

FIG. 5 is a graph showing the concentration distribution of the components in each layer of the chemically strengthened glass.

Detailed Description

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.

Example 1

In a stainless steel reaction tank, a chemical pure reagent molten salt component KNO₃10 kg+NaNO₃ 0.9kg+Ca(NO₃)₂0.3kg, mixing, heating to 410 deg.C, preheating glass, soaking in high temperature molten salt at constant temperature for 4.5 hr; the flexural strength is 184.3MPa by adopting a CMT5204 electronic multifunctional tester.

Example 2

In a stainless steel reaction tank, a chemical pure reagent molten salt component KNO₃10 kg+NaNO₃1.7kg+Ca(NO₃)₂0.4kg, mixing, heating molten salt, keeping the liquid surface temperature of the molten salt at 349 ℃ (actually measured), and immersing the preheated glass in the molten salt liquid for 7hr at constant temperature; the bending strength of the product is 181.9MPa when measured by a CMT5204 electronic multifunctional tester.

Example 3

In a stainless steel reaction tank, a chemical pure reagent KNO is used for molten salt components₃10 kg+NaNO₃ 1.4kg+Ca(NO₃)₂0.4kg, 376 deg.C (actually measured) in the middle of the molten salt, soaking the glass at constant temperature for 6 hr; the bending strength is 182.1MPa when measured by a CMT5204 electronic multifunctional tester.

Comparative example 3

In a stainless steel reaction tank, a chemical pure reagent KNO is used for molten salt components₃10 kg+NaNO₃ 1.4kg+Ca(NO₃)₂0.4kg, molten salt middle temperature 375 deg.C (measured), soaking glass at constant temperature for 6 hr; the bending strength of the test piece is 188MPa when the test piece is measured by a CMT5204 electronic multifunctional testing machine.

EPMA scanning spectra of three elements of Si, K and Na in a surface layer (0-40 μm) of a sample of chemically tempered glass (3mm) and a glass original sheet in the embodiment 3 are obtained. The abscissa is the depth from the glass surface and the ordinate is the scan intensity in counts per second.

As can be seen from fig. 4, the chemical composition of the original glass sheet is substantially uniform from the surface to the inside. After ion exchange, K⁺The scan intensity of (A) gradually decreases with increasing depth, Na⁺Has a minimum value on the surface, and the intensity gradually increases with the depth (as shown in FIG. 5), K⁺、Na⁺The scanning intensity change curves of the two are similar, the directions are opposite, and the positions are corresponding; ca⁺No scan was taken, indicating little ion exchange.

K⁺、Na⁺The scanning intensity of both was about the same as that of the original glass composition (the scanning intensity was about 140), and the ion exchange interface depth was about 35 μm. From the above, the multi-component nitrate salt is comparable to the compressive stress generated by a single-component nitrate salt during chemically-toughened ion-exchange enhancement. But the reaction temperature of the multi-component nitrate is reduced, and the service life of the potassium nitrate is prolonged, so that the method has remarkable advantages.