JP6811936B2 - Manufacturing method of aluminosilicate glass - Google Patents

Description

The present invention relates to a method for producing aluminosilicate glass using specific aluminum oxide as a raw material contained in a glass batch.

In general, for glass, various kinds of raw materials are mixed to prepare a mixed raw material for glass production (hereinafter referred to as glass batch), which is melted in a glass melting furnace, and then overflow down draw method, float method, and Dunner method. It is continuously produced through a molding process such as.

After being supplied into the glass melting furnace, the glass batch is heated mainly from above by combustion of a burner and melted. In addition, it may be heated by energizing it by an electrode provided at the bottom of the melting furnace.

Further, in the glass batch, each raw material is mixed in a predetermined ratio according to the target composition, but as a method of transporting each raw material into the factory, the hygienic environment in the factory and prevention of foreign matter from entering the raw material are prevented. From this point of view, transportation by compressed air from a powder carrier or transportation by a screw feeder is often adopted.

International Publication No. 2014/103897 JP-A-2015-67523

In glass manufacturing, it is important to accurately mix the raw materials so that the glass batch has the target composition, and for that purpose, the time and amount specified in each process such as transportation, weighing, and mixing of the raw materials are accurate. Need to be managed. And the compounding accuracy is becoming more and more sophisticated in order to improve the productivity and the glass quality.

For example, in the case of aluminosilicate glass, among the raw materials used, raw materials such as silica sand and aluminum oxide have a particularly large proportion of glass batches. Therefore, these raw materials have a large influence on the glass production and the quality of the obtained glass, and particularly strict control is required.

An object of the present invention is a method for producing aluminosilicate glass obtained by melting and molding a glass batch, which enables improvement in productivity and glass quality by improving the mixing accuracy of raw materials. Is to provide.

In the method for producing aluminosilicate glass, the present inventor has noticed that among the raw materials constituting the glass batch, aluminum oxide is particularly prone to over-weighing and insufficient transportation and transportation defects. Over-weighing and poor transportation can fluctuate the composition of glass batches and affect productivity and glass quality.

The method for producing aluminosilicate glass of the present invention is a method for producing aluminosilicate glass obtained by melting and molding a glass batch containing at least aluminum oxide, wherein the BET specific surface area value of aluminum oxide is 1.0 to 13 m ² /. It is characterized in that it is in the range of g. As the BET specific surface area value of the present invention, the value obtained by the gas adsorption method (BET method) using nitrogen gas is used.

By doing so, the compounding process can be accurately controlled, and a glass batch having an appropriate composition can be smoothly introduced into the melting furnace. As a result, high melt stability and productivity can be achieved, which in turn can improve the quality of the glass.

The present inventor investigated diligently and focused on the fact that aluminum oxide exists in a special shape in which its primary particles aggregate to form secondary particles. And, as a cause of over-weighing and insufficient transportation, firstly, the ratio of fine particles may increase due to the crushing of secondary particles during transportation by compressed air or screw feeder, and the powder characteristics of aluminum oxide may change. Secondly, it was found that fluctuations in the degree of compression of aluminum oxide can cause over-weighing and poor transportation.

Here, Patent Document 1 introduces the effect of improving the solubility of aluminosilicate glass, which is obtained by limiting the ratio of the specific surface area values of the silicon source and the aluminum compound raw material. Further, alumina (aluminum oxide) and aluminum hydroxide are mentioned as raw materials for aluminum compounds, and the required specific surface area value is a value converted from a particle size measurement value (assuming that the measurement particles are spheres). However, this method is insufficient as a means for measuring the specific surface area value of aluminum oxide particles when the aluminum oxide particles have a morphological feature that the secondary particles are formed by a collection of primary particles.

Further, Patent Document 2, undissolved or aluminum oxide by limiting the scope and 38μm sieve passing amount of D ₅₀ of aluminum oxide used in the glass batch, to suppress the furnace debris, the stability of the glass composition The effect of improvement is introduced. However, aluminum oxide in a glass batch is usually a secondary particle, and the influence of the secondary particle size on the meltability is almost negligible. Furthermore, particles that cause furnace scattering (destabilization hence the glass composition) is mainly below 10μm fines, D ₅₀ range and a secondary particle size, the only limit the sieve pass component in the transport process The pulverization of the secondary particles of the above cannot be completely prevented, and a sufficient effect cannot be obtained.

As described above, the aluminum oxide particles exist in a special state in which the primary particles are aggregated to form the secondary particles. Therefore, the particle size of aluminum oxide is measured from several tens of μm to one hundred and several tens of μm, but strictly speaking, this is a measurement of the secondary particle size and does not reflect the primary particle size. .. When trying to measure the primary particle size, there are methods such as completely crushing the secondary particles to make them into primary particles, or measuring the primary particles in the secondary particles by image analysis. Is also difficult to measure accurately.

Therefore, the present inventor has a close relationship between the primary particle size of aluminum oxide and the BET specific surface area value, that is, when the same weight of aluminum oxide is measured, the larger the BET specific surface area value, the larger the primary particle size. It was found that the smaller the BET specific surface area value, the larger the primary particle size. Therefore, based on this finding, the present invention regulates the BET specific surface area value of aluminum oxide as an index of the primary particle size.

Further, the present inventor has found that the ease of crushing the secondary particles of aluminum oxide when worn due to friction or the like depends largely on the size of the voids between the primary particles.

That is, in the aluminum oxide manufacturing process, the primary particles gradually grow larger in the form of fusion of the primary particles as the firing progresses, while the secondary particle diameter does not change much during the firing process. Therefore, in each of the secondary particles, it is considered that the number of primary particles decreases as the primary particles grow, and as a result, the gap between the primary particles widens.

Therefore, the degree of ease of crushing the aluminum oxide particles during transportation is related to the BET specific surface area value of the aluminum oxide particles. Specifically, the smaller the BET specific surface area value, the more the aluminum oxide particles are dissolved. It is easily crushed, and the secondary particles of aluminum oxide tend to be excessively crushed into primary particles in the powder handling process. This leads to an increase in dust generation, and is likely to cause excess or deficiency of weighing and unstable powder behavior during transportation, which may adversely affect the productivity of glass.

Further, the larger the BET specific surface area value, the more difficult it is for the aluminum oxide particles to be crushed. However, if the BET specific surface area value is too large, the hygroscopicity of the aluminum oxide itself increases, and the unit weight depends on the temperature and humidity when handling the raw material. There is a risk that the winning rate of Al ₂ O ₃ will fluctuate.

Method for producing aluminosilicate glass of the present invention preferably has an average particle diameter D ₅₀ of aluminum oxide is 30 to 150 [mu] m.

By doing so, aluminum oxide produced through the buyer process can be used. Since the buyer process is a general-purpose manufacturing method for industrially manufacturing aluminum oxide from mineral raw materials such as kaolin and bauxite, the raw material cost can be reduced.

The buyer step is a method of crystallizing aluminum hydroxide from a sodium aluminate solution and firing the obtained aluminum hydroxide at 1000 ° C. or higher to produce aluminum oxide.

Aluminum oxide produced by the buyer process is called α-Al ₂ O ₃ and has a trigonal corundum type crystal structure. Its particle size ranges from several tens of μm to one hundred and several tens of μm. Strictly speaking, it is a secondary particle formed by aggregating primary particles of several μm and has such a structure. It is characterized by a significantly larger specific surface area value than non-existent particles (for example, silica sand particles).

In the buyer process, the primary particle size of aluminum oxide differs depending on the temperature history when firing aluminum hydroxide, which is an intermediate raw material thereof, and has the property of increasing as the firing temperature is higher and the firing time is longer. Therefore, as an example of the method for obtaining aluminum oxide having a BET specific surface area value according to the present invention, it is preferable to bake in a temperature range not exceeding 1500 ° C. in the buyer step.

In the method for producing aluminosilicate glass of the present invention, the degree of compression of aluminum oxide is preferably less than 20%. Here, the degree of compression is calculated by the following formula from the difference between the sparsely packed bulk density and the densely packed bulk density.
Degree of compression (%) = (Densely packed bulk density (g / ml) -Sparsely packed bulk density (g / ml)) ÷ Densely packed bulk density (g / ml) x 100
The sparsely packed bulk density and the tightly packed bulk density were calculated by filling a powder sample in a container having a constant volume using a "powder tester PT-S type" manufactured by Hosokawa Micron and measuring the weight thereof.

By doing so, the fluidity is good, jets are less likely to occur, the powder characteristics of aluminum oxide can be stabilized, and excess / deficiency of weighing and transportation defects are less likely to occur. Therefore, a glass batch having an appropriate composition can be smoothly introduced into the melting furnace, high melting stability and productivity can be achieved, and the quality of the glass can be improved.

The method for producing aluminosilicate glass of the present invention is, in terms of mass% based on oxide, SiO ₂ 50 to 80%, Al ₂ O _{3 to} 25%, B ₂ O _{30 to} 20%, MgO 0 to 15%, It is preferable to prepare a glass batch so as to obtain an aluminosilicate glass containing CaO 1 to 15%, SrO 0 to 15%, and BaO 0 to 15%.

In the method for producing an aluminosilicate glass of the present invention, it is preferable to use the obtained aluminosilicate glass as a substrate glass for a liquid crystal display.

In the method for producing aluminosilicate glass of the present invention, it is possible to form a high-quality glass plate even when it is formed into a plate shape. Therefore, it is suitable for the substrate glass of a liquid crystal display.

It is a graph which shows the relationship between the BET specific surface area and the measurement error of aluminum oxide which concerns on this invention. It is a graph which shows the relationship between the BET specific surface area and the degree of compression of aluminum oxide which concerns on this invention. BET specific surface area of aluminum oxide according to the present invention and Ig. It is a graph which shows the relationship of Loss.

Hereinafter, the present invention will be described in detail.

The method for producing aluminosilicate glass of the present invention includes a step of preparing a glass batch containing aluminum oxide.

The present invention is characterized in that aluminum oxide having a BET specific surface area value of 1.0 to 13 m ² / g is used. The preferred BET specific surface area value of aluminum oxide is 1.0 to 11 m ² / g, 1.5 to 10 m ² / g, and particularly 2.0 to 9.0 m ² / g.

By doing so, the particle size of aluminum oxide can be set within an appropriate range, so that over-weighing and unstable powder behavior during transportation are unlikely to occur, and the composition of the glass batch and the Al ₂ O ₃ yield rate fluctuate. It's hard to do. As a result, high melt stability and productivity can be achieved, which in turn can improve the quality of the glass.

Further, it preferred average particle size _{D 50} of aluminum oxide is 30 to 150 [mu] m, 35～140Myuemu, in particular 40～130Myuemu. By doing so, general-purpose aluminum oxide can be used, so that the raw material cost can be reduced.

Also, the preferred degree of compression of aluminum oxide is less than 20%, less than 19%, especially less than 18%. By doing so, the fluidity is good and jets are less likely to occur, so that excess or deficiency of weighing and poor transportation are less likely to occur. As a result, high melt stability and productivity can be achieved, which in turn can improve the quality of the glass.

The glass composition range suitable for the glass batch according to the present invention and suitable raw materials will be described in detail later.

The method for producing aluminosilicate glass of the present invention includes a step of melting the glass batch to obtain molten glass. The melting temperature of the glass batch is preferably, for example, 1400 ° C to 1700 ° C. The melting temperature can be changed depending on the composition of the glass batch, the particle size of the raw material, and the clarification conditions.

The method for producing aluminosilicate glass of the present invention includes a step of molding the molten glass. As a molding method, various methods such as spinning, a dunner method, a blow molding method, and a press molding method can be adopted according to the target product. Among them, in particular, the present invention preferably molds into a plate shape, and as the plate shape molding method, a float method, an overflow down draw method, a slot down draw method, or the like can be used.

The glass composition range suitable for the glass batch according to the present invention is as follows.

The glass batch according to the present invention has the target composition of SiO ₂ 50 to 80%, Al ₂ O _{3 to} 25%, B ₂ O _{30 to} 20%, MgO 0 to 15% in terms of mass% based on oxides. , CaO 1 to 15%, SrO 0 to 15%, and BaO 0 to 15% are preferably contained. The reason for limiting each component to the above range will be described below. In the following description, unless otherwise specified, "%" means "mass%".

SiO ₂ is a glass network former, the content of which is 50 to 80%. If the content of SiO ₂ is too small, the strain point is lowered, and for example, in the heat treatment step when manufacturing a display device, the glass substrate is liable to crack, and thermal deformation and thermal shrinkage are liable to occur. In addition, the coefficient of thermal expansion becomes too large, making it difficult to obtain consistency with the coefficient of thermal expansion of peripheral materials, and the thermal shock resistance tends to decrease. Furthermore, acid resistance also deteriorates. On the other hand, if the content of SiO ₂ is too large, the high-temperature viscosity becomes high, which makes melting and molding difficult. In addition, the coefficient of thermal expansion becomes too small, and it becomes difficult to obtain consistency with the coefficient of thermal expansion of peripheral materials. A suitable range for the SiO ₂ content is 52-70%.

Al ₂ O ₃ is a component that improves the weather resistance and mechanical strength of glass, and its content is 5 to 25%. If the content of Al ₂ O ₃ is too large, the strain point is lowered, and for example, the glass substrate is liable to crack, thermal deformation, and thermal shrinkage are likely to occur in the heat treatment step when manufacturing a display. On the other hand, if the content of Al ₂ O ₃ is too small, the buffered fluorine resistance is lowered, or the liquidus temperature rises, which makes it difficult to mold the glass substrate. A suitable range for the Al ₂ O ₃ content is 7 to 22%.

B ₂ O ₃ is a component that lowers the viscosity and enhances the meltability, but if it is contained in excess, the strain point becomes low, and for example, the glass substrate may crack during the heat treatment process when manufacturing a display. Thermal deformation and thermal shrinkage are likely to occur. The preferred range for B ₂ O ₃ content is 0-15%.

MgO is a component that lowers the high-temperature viscosity and improves the meltability without lowering the strain point, and the content is 0 to 15%. If the content of MgO is too high, devitrification of cristobalite and enstatite tends to occur. Further, the buffered fluorine acidity is lowered, the glass substrate is eroded in the photoetching step, the reaction product adheres to the surface of the glass substrate, and the glass substrate tends to become cloudy. The preferred range of MgO content is 0-10%.

CaO is a component that improves the meltability by lowering only the high-temperature viscosity without lowering the strain point, and the content is 1 to 15%. If the CaO content is too high, the buffered fusiacid resistance will decrease, and the density and coefficient of thermal expansion will increase. If the CaO content is too small, the high-temperature viscosity increases and the meltability tends to deteriorate. A suitable range of CaO content is 3-12%.

SrO is a component that improves chemical resistance and devitrification resistance, and its content is 0 to 15% by mass. If the SrO content is too high, the density and coefficient of thermal expansion will increase. The preferred range for SrO content is 0-12%.

BaO is a component that improves chemical resistance and devitrification resistance, and its content is 0 to 15% by mass. If the BaO content is too high, the density and coefficient of thermal expansion will increase. The preferred range of BaO content is 0-12%.

In addition to the above, various components can be contained. For example, ZrO ₂ , P ₂ O ₅ , SnO ₂ , ZnO ₂ , Sb ₂ O ₃ , SO ₃ , Cl ₂ , Ni and the like may be contained.

The raw materials that can be used in the present invention are illustrated below. The glass batch may be composed of only these raw materials, but of course, raw materials other than those illustrated may be used, or a glass cullet may be used in combination.

Silica sand (SiO ₂ ) or the like can be used as the silicon source.

As the aluminum source, at least aluminum oxide is contained, and aluminum hydroxide can also be used. BET specific surface area of the aluminum oxide is in the range of 1.0~13m ² / g, preferably in the range of 1.0~11m ² / g, more preferably of 2.0~9.0m ² / g The range.

As boron source, boric acid _{(B 2 O 3 · 3H 2} O), boric anhydride _(B 2 _{O 3)} or the like can be used.

As the source of MgO and CaO, calcium carbonate, dolomite (MgO, CaO, 2CO ₂ ) and the like can be used.

These carbonates, nitrates, hydroxides and the like can be used as SrO and BaO sources.

First, in a silo for aluminum oxide (volume 500 tons) in a glass batch blending facility, 300 tons of aluminum oxide was charged by transportation by compressed air from a powder and granule carrier. Then, 0.5 tons of aluminum oxide were transported from the silo by a screw feeder and then weighed. The measurement error was calculated by the following formula.
Weighing error (%) = (Aluminum oxide weighing value A (t) -Theoretical weighing value of aluminum oxide 0.5 (t)) / Theoretical weighing value of aluminum oxide 0.5 (t) x 100

When the total amount of 300 tons was measured by the method described above, the measured value range of the BET specific surface area value of aluminum oxide was 0.5 to 16.1 m ² / g.

FIG. 1 shows the relationship between the BET specific surface area value of aluminum oxide and the measurement error for each lot. As can be seen from FIG. 1, when the BET specific surface area value was 1.0 m ² / g or more, the measurement error was within 5%. In particular, when it is 2.0 m ² / g or more, the measurement error becomes smaller. The glass batch using aluminum oxide having a measurement error of more than 5% had a particularly large variation in composition, and had poor melt stability and productivity. In addition, the composition of the produced glass fluctuated, and the glass quality was not good.

Next, when the degree of compression of aluminum oxide was measured for any 15 lots, the degree of compression was 7.1 to 24.9%. The relationship between the BET specific surface area value of aluminum oxide and the degree of compression is shown in FIG. As can be seen from FIG. 2, the BET specific surface area value of aluminum oxide and the degree of compression are correlated, and the smaller the BET specific surface area value, the larger the degree of compression. In particular, aluminum oxide having a BET specific surface area value of less than 1.0 m ² / g has a compression degree of more than 20%, has poor fluidity, and is considered to easily generate a jet, which affects measurement errors and transportation. There is a high possibility that it is.

In addition, FIG. 3 shows the BET specific surface area value and Ig. Of aluminum oxide when stored in a high humidity environment (temperature 28 ° C., humidity 90% or more, 24 hours). The relationship with Loss (Ignition weight loss) is shown. As can be seen from this, aluminum oxide having a large BET specific surface area value has high hygroscopicity, and Ig. Loss (Ignition loss) is large. That is, aluminum oxide having an excessively large BET specific surface area value tends to change the Al ₂ O ₃ gain rate per unit weight depending on the storage condition, so even if the measurement accuracy is improved, the composition change at the time of preparation may not be avoided. is there. From FIG. 3, when the BET specific surface area value is 13 m ² / g or less, Ig. If Loss (Ignition loss) is 1% or less, especially if it is 9.0 m ² / g or less, Ig. There is almost no Loss (Ignition loss). However, when it exceeds 13 m ² / g, Ig. Since Loss (Ignition loss) exceeds 1%, the change in Al ₂ O ₃ yield cannot be ignored in consideration of the target value for blending the raw materials.

As is clear from the above, when the BET specific surface area value of aluminum oxide is 1.0 m ² / g or more, the measurement error is within 5% and the degree of compression can be reduced to 20% or less. The fluidity can be improved and the jet flow can be suppressed. Further, when the BET specific surface area value is 13 m ² / g or less, it is possible to avoid fluctuations in the Al ₂ O ₃ gain rate due to the storage environment and the glass batch composition due to scattering. As a result, over- or under-weighing and unstable powder behavior during transportation are less likely to occur, and the accuracy of raw material preparation can be improved.
From a series of results, the BET specific surface area value of aluminum oxide that could be measured accurately and without excess or deficiency was 2.0 to 9.0 m ² / g.

Next, the glass batches were sequentially put into a glass melting furnace, melted and homogenized at a melting temperature of 1500 to 1600 ° C., and molded into a substrate glass for a display. Since the glass batch using aluminum oxide according to the present invention has a small variation in composition and can be introduced into the melting furnace without delay, high melting stability and productivity can be achieved even with glass that is sparingly soluble at high temperature. The quality of the obtained glass was also high.

The method for producing an aluminosilicate glass of the present invention is suitable for a method for producing a display substrate, but improving the mixing accuracy of raw materials is a widely required issue in glass production, and production of flat glass other than the display substrate and other glass. It is also suitable for the method. Specifically, not only display substrate glass and cover glass for FPDs, smartphones, tablet terminals, etc., but also flat glass as a structural material, and other methods for manufacturing tube glass, glass for light bulbs, and fibrous glass. Can be used.

Claims (5)

In a method for producing aluminosilicate glass obtained by melting and molding a glass batch containing at least aluminum oxide, the aluminum oxide has a BET specific surface area value in the range of 1.0 to 13 m ² / g. A method for manufacturing silicate glass. The method for producing aluminosilicate glass according to claim 1, wherein the average particle size D _{50 of the} aluminum oxide is 30 to 150 μm. The method for producing aluminosilicate glass according to claim 1 or 2, wherein the degree of compression of aluminum oxide is less than 20%. % By mass on the oxide _{basis, SiO 2 50~80%, Al 2} O 3 5~25%, B 2 O 3 0~20%, 0~15% MgO, CaO 1~15%, SrO 0~15% The method for producing an aluminosilicate glass according to any one of claims 1 to 3, wherein a glass batch is prepared so that an aluminosilicate glass containing 0 to 15% of BaO can be obtained. The method for producing an aluminosilicate glass according to any one of claims 1 to 4, wherein the obtained aluminosilicate glass is used as a substrate glass for a liquid crystal display.