JP2011173748A - Method for producing las-based crystalline glass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for obtaining LAS (Li<SB>2</SB>O-Al<SB>2</SB>O<SB>3</SB>-SiO<SB>2</SB>)-based crystalline glass excellent in bubble quality by improving the clarifying ability of halogen in glass melting. <P>SOLUTION: The method for producing the LAS-based crystallin glass is provided by which the LAS-based crystalline glass which has composition containing, by mass, 55-75% SiO<SB>2</SB>, 17-27% Al<SB>2</SB>O<SB>3</SB>, 3-6% Li<SB>2</SB>O, 0-2% MgO, 0-2% ZnO, 2-5.5% TiO<SB>2</SB>, 0-3% ZrO<SB>2</SB>, 0.03-1% rare earth oxide and 0.01-0.2% halogen and substantially not containing As<SB>2</SB>O<SB>3</SB>and Sb<SB>2</SB>O<SB>3</SB>is obtained by melting a raw material batch, wherein the raw material batch contains 0.03-1% rare earth oxide and 0.05-1% halogen. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a method for producing a LAS (Li ₂ O—Al ₂ O ₃ —SiO ₂ ) -based crystalline glass having excellent foam quality.

  Conventionally, LAS-based crystallized glass such as transparent crystallized glass having a β-quartz solid solution as a main crystal and opaque crystallized glass having a β-spodumene solid solution as a main crystal is known as a low expansion crystallized glass. Since these LAS-based crystallized glasses are excellent in heat resistance and thermal shock resistance, they are widely used for cooking appliance top plates, stove windows, fire prevention windows, and the like.

  The LAS-based crystallized glass is manufactured by first preparing raw material LAS-based crystallized glass by mixing, melting and molding the raw material, and subjecting the LAS-based crystallized glass to crystallization treatment. The Here, the glass excellent in foam quality can be obtained by performing a clarification process with respect to molten glass at the time of glass melting or after glass melting. However, the LAS crystalline glass has a problem that it is difficult to clarify because the viscosity of the glass melt is high.

Conventionally, As ₂ O ₃ and Sb ₂ O ₃ have been used as fining agents in order to promote glass fining (see, for example, Patent Documents 1 and 2). However, As ₂ O ₃ and Sb ₂ O ₃ are substances with a large environmental load, and in recent years, the amount of use has been reduced as much as possible, or has not been used.

Therefore, halogens such as Cl, SnO ₂ , SO _{3 and the} like are used alone or in combination as a clarifying agent replacing As ₂ O ₃ or Sb ₂ O ₃ (see, for example, Patent Document 3). In particular, halogen is effective as a refining agent because it has a high refining effect and hardly causes unwanted coloring.

JP-A-6-329439 JP 2001-48582 A JP 11-228180 A

  When halogen is used as a fining agent, a halogen-based gas is released from the glass when the glass is melted to produce a fining effect. However, halogen has been problematic in that it tends to remain in glass and does not sufficiently exert its potential fining ability.

  Accordingly, an object of the present invention is to provide a method for obtaining a LAS-based crystalline glass excellent in foam quality by enhancing the clarification ability of halogen during glass melting.

  As a result of intensive studies on the above problems, the inventors of the present invention have improved the halogen refining effect by using halogen as a refining agent and adding specific components in the LAS crystalline glass production method. Therefore, the present invention is proposed.

That is, in the present invention, by melting a raw material batch, the composition is in mass%, SiO ₂ 55 to 75%, Al ₂ O ₃ 17 to 27%, Li ₂ O 3 to 6%, MgO 0 to 2%, _{0~2% ZnO, TiO 2 2~5.5%} , ZrO 2 0~3%, rare earth oxide from 0.03 to 1%, and containing 0.01 to 0.2% halogen, substantially as ₂ A method for producing an LAS-based crystalline glass containing no O ₃ or Sb ₂ O ₃ , wherein 0.03 to 1% of rare earth oxide and 0.05 to 1% of halogen are contained in a raw material batch The present invention relates to a method for producing an LAS-based crystalline glass.

  The present inventors have found that when halogen clarification is performed during melting of LAS-based crystalline glass, the amount of halogen remaining in the glass can be reduced by adding a rare earth oxide. That is, the rare earth oxide promotes the diffusion of halogen in the glass into the remaining bubbles, and the fining effect is enhanced by increasing the diameter of the bubbles to make it easier to float. Therefore, even if the addition amount of the clarifier and the halogen to be used is reduced, a clarification effect equivalent to or higher than the conventional one can be expected.

  Further, when a metal thin film such as aluminum is formed on the glass surface, if halogen remains in the glass, there is a problem that the metal thin film tends to corrode over time. According to the production method of the present invention, the halogen remaining in the glass can be reduced, so that such an effect that corrosion of the metal thin film hardly occurs can be obtained.

  In the present invention, “LAS-based crystalline glass” refers to glass that precipitates as a main crystal LAS-based crystals such as β-quartz solid solution and β-spodumene solid solution by crystallization treatment.

Secondly, the LAS crystalline glass production method of the present invention is characterized in that the rare earth oxide is Nd ₂ O ₃ or Er ₂ O ₃ .

  Thirdly, the present invention relates to a LAS-based crystalline glass produced by any one of the above production methods.

Fourth, the present invention is, in mass% as a _{composition, SiO 2 55~75%, Al 2} O 3 17~27%, Li 2 O 3~6%, 0~2% MgO, 0~2% ZnO, TiO _{2 2 to} 5.5%, ZrO ₂ 0 to 3%, rare earth oxide 0.03 to 1%, halogen 0.01 to 0.2%, substantially As ₂ O ₃ and Sb ₂ O _The present invention relates to a LAS crystalline glass characterized by not containing ₃ .

  Fifth, the present invention relates to a LAS-based crystallized glass obtained by crystallizing the LAS-based crystallized glass described above.

  Sixth, the LAS-based crystallized glass of the present invention is characterized by being precipitated as a main crystal of β-quartz solid solution or β-spodumene solid solution.

In the present invention, the composition is in mass%, SiO ₂ 55 to 75%, Al ₂ O ₃ 17 to 27%, Li ₂ O 3 to 6%, MgO 0 to 2%, ZnO 0 to 2%, TiO ₂ 2 to 2%. 5.5%, ZrO ₂ 0 to 3%, rare earth oxide 0.03 to 1%, halogen 0.01 to 0.2%, and substantially free of As ₂ O ₃ and Sb ₂ O ₃ The present invention relates to a method for producing LAS-based crystalline glass. The reason why the composition of the LAS-based crystalline glass is limited in this way in the present invention will be described below. Unless otherwise specified, “%” in the following description means “% by mass”.

SiO ₂ forms a glass skeleton and is a component constituting an LAS crystal. The SiO ₂ content is preferably 55 to 75%, 58 to 70%, particularly preferably 60 to 68%. When the content of SiO ₂ is less than 55%, the thermal expansion coefficient tends to increase, and it becomes difficult to obtain crystallized glass excellent in thermal shock resistance. In addition, chemical durability tends to decrease. On the other hand, when the content of SiO ₂ exceeds 75%, the meltability of the glass deteriorates, the viscosity of the glass melt increases, and it tends to be difficult to clarify or form the glass.

Al ₂ O ₃ forms a glass skeleton and is a component constituting an LAS crystal. The content of Al ₂ O ₃ is preferably 17 to 27%, 19 to 25%, and particularly preferably 20 to 23%. When the content of Al ₂ O ₃ is less than 17%, the thermal expansion coefficient tends to increase, and it becomes difficult to obtain crystallized glass excellent in thermal shock resistance. In addition, chemical durability tends to decrease. On the other hand, when the content of Al ₂ O ₃ exceeds 27%, the meltability of the glass deteriorates, the viscosity of the glass melt increases, and it tends to be difficult to clarify or form the glass. Further, the mullite crystals tend to precipitate and the glass tends to devitrify, and the glass is easily damaged.

Li ₂ O is a component that constitutes an LAS-based crystal, and has a great influence on crystallinity, and is a component that lowers the viscosity of glass and improves glass meltability and formability. The Li ₂ O content is preferably 3 to 6%, 3.3 to 5.5%, particularly preferably 3.5 to 5%. When the content of Li ₂ O is less than 3%, mullite crystals precipitate and the glass tends to devitrify. Further, when the glass is crystallized, LAS-based crystals are difficult to precipitate, and it becomes difficult to obtain crystallized glass excellent in thermal shock resistance. Furthermore, there is a tendency that the meltability of the glass deteriorates or the viscosity of the glass melt increases, making it difficult to clarify or molding the glass. On the other hand, when the content of Li ₂ O exceeds 6%, the crystallinity becomes too strong, and the glass tends to be devitrified, and the glass is easily broken.

  MgO is a component that dissolves in the LAS crystal. The content of MgO is preferably 0 to 2%, 0 to 1.5%, particularly preferably 0.1 to 1.2%. If the content of MgO exceeds 2%, the crystallinity becomes too strong and tends to devitrify, and the glass tends to break.

  ZnO, like MgO, is a component that dissolves in the LAS crystal. The content of ZnO is preferably 0 to 2%, 0 to 1.5%, particularly preferably 0.1 to 1.2%. If the ZnO content is more than 2%, the crystallinity becomes too strong, and thus the glass tends to devitrify when molded while being slowly cooled. As a result, the glass tends to be broken, so that it becomes difficult to form by, for example, the float process.

TiO ₂ is a nucleation component for precipitating crystals in the crystallization process. The content of TiO ₂ is preferably 2 to 5.5%, 2 to 5.2%, particularly 2 to 5%. When the content of TiO ₂ is more than 5.5%, the glass tends to devitrify and easily break. On the other hand, when the content of TiO ₂ is less than 2%, crystal nuclei are not sufficiently formed, and coarse crystals may be precipitated and damaged.

ZrO ₂ is a nucleation component for precipitating crystals in the crystallization step, like TiO ₂ . The content of ZrO ₂ is preferably 0 to 3%, 0.1 to 2.5%, particularly preferably 0.5 to 2.3%. When the content of ZrO ₂ is more than 3%, the glass tends to be devitrified when it is melted, making it difficult to mold the glass.

  The production method of the present invention is characterized in that the raw material batch contains 0.03 to 1% rare earth oxide and 0.05 to 1% halogen.

As the rare earth oxide, lanthanoid oxides such as Nd ₂ O ₃ , Er ₂ O ₃ , Gd ₂ O ₃ , and CeO ₂ can be used. In particular, Nd ₂ O ₃ and Er ₂ O ₃ have a particularly high effect of promoting the halogen refining ability, and it becomes easy to obtain a LAS-based crystalline glass excellent in foam quality. The rare earth oxide content in the raw material batch is preferably 0.03 to 1%, particularly preferably 0.05 to 0.8%. When the rare earth oxide content is less than 0.03%, it is difficult to obtain the effect of reducing the residual halogen content in the glass, and as a result, it is difficult to obtain a sufficient refining effect. On the other hand, even if the content of the rare earth oxide exceeds 1%, the effect of reducing the residual halogen content in the glass is not likely to increase, but rather the color of the glass becomes too dark and tends to be unsuitable for use depending on the application. is there.

  The rare earth oxide content in the LAS crystalline glass obtained by the production method of the present invention is the same as described above.

  As the halogen, Cl, Br, I, and F are used alone or in combination. Among them, it is preferable to use Cl because of its high fining ability and easy handling. Examples of the halogen raw material include alkali halides (for example, NaCl, KCl, LiCl, etc.). The halogen content in the raw material batch is preferably 0.05 to 1%, particularly preferably 0.1 to 0.8%. If the halogen content in the raw material batch is less than 0.05%, the clarification effect tends to be insufficient. On the other hand, even if the halogen content is more than 1%, the fining effect is not increased, and the residual halogen content in the glass is increased, so that the above-described problem of corrosion of the metal thin film tends to occur.

  The halogen content in the LAS crystalline glass obtained by the production method of the present invention is preferably 0.2% or less, particularly preferably 0.15% or less. When the halogen content in the LAS crystalline glass is more than 0.2%, the above-described problem of corrosion of the metal thin film tends to occur. On the other hand, the lower limit is not particularly limited, but is practically 0.01% or more.

  In the present invention, the halogen content refers to the content as a halogen atom.

As ₂ O ₃ and Sb ₂ O ₃ are also clarifier components, but they have a large environmental burden, so it is important that they are not substantially contained in the present invention. In the present invention, “substantially does not contain” means a level that is not actively used as a raw material and is mixed as an impurity, and specifically means that the content is 0.1% or less. .

The SnO ₂ and SO ₃ which is other fining component may be added. However, since SnO ₂ has an effect of increasing the coloring of Fe or the like contained in the glass raw material as an impurity, it is desirable to keep it at 0.2% or less. SO ₃ is a component that promotes clarification by diffusing into bubbles in the glass, like halogen. However, SO ₃ also has the action of generating bubbles by causing reboil, so the remaining amount in the glass can be kept at 200 ppm or less. desirable.

  In addition to the above, various components can be added as long as the required properties are not impaired.

For example, 0.1% or more of B ₂ O ₃ may be added to suppress the growth of coarse crystals when crystallizing glass. However, if the content of B ₂ O ₃ is too large, the heat resistance of the glass tends to be impaired, so the upper limit is preferably made 2% or less.

P ₂ O ₅ is a component that promotes phase separation of the glass and assists the formation of crystal nuclei, and can be added to the glass in an amount of 0.1% or more. When the content of P ₂ O ₅ is too large, phase separation is likely to occur in the melting step, and it becomes difficult to obtain a glass having a desired composition and tends to be opaque. Therefore, the upper limit is desirably 3% or less.

Further, in order to reduce the viscosity of the glass and improve the meltability and formability, it is possible to add Na ₂ O, K ₂ O, CaO, SrO and BaO in a total amount of 0.1 to 5%. . In addition, since CaO, SrO, and BaO are components which devitrify the glass when the glass is melted, it is preferable that the total amount of these components is 2% or less.

Further, a coloring agent such as NiO, CoO, Cr ₂ O ₃ , Fe ₂ O ₃ , V ₂ O ₅ can be added up to 2% in total.

  A raw material batch in which the above components are prepared is melted at a temperature of 1550 to 1850 ° C., and then molded and annealed to obtain LAS crystalline glass. Various molding methods such as a float method, a press method, and a roll-out method can be applied depending on the target shape.

  Crystallized glass is produced from the crystalline glass thus produced as follows.

  The formed LAS-based crystalline glass is heat-treated at 600 to 800 ° C. for 1 to 5 hours to form crystal nuclei, and further heat-treated at 800 to 1100 ° C. for 0.5 to 3 hours. By precipitating, LAS-based crystallized glass can be obtained. In order to obtain transparent crystallized glass, after forming crystal nuclei, heat treatment is performed at 800 to 950 ° C. for 0.5 to 3 hours to precipitate β-quartz solid solution. In the case of obtaining the β-spodumene solid solution, crystal nuclei are formed and then heat-treated at 1000 to 1100 ° C. for 0.5 to 3 hours.

Moreover, since the crystallized glass of the present invention is formed by precipitating a LAS crystal as a main crystal, it has a low coefficient of thermal expansion of about −10 to 30 × 10 ⁻⁷ / ° C. (measurement range: 30 to 750 ° C.) and is heat resistant And has high mechanical strength.

The LAS-based crystallized glass and the LAS-based crystallized glass of the present invention are in mass% as a composition, SiO ₂ 55-75%, Al ₂ O ₃ 17-27%, Li ₂ O 3-6%, MgO 0-2. %, ZnO 0 to 2%, TiO _{2 2 to} 5.5%, ZrO ₂ 0 to 3%, rare earth oxide 0.03 to 1%, halogen 0.01 to 0.2%, It is characterized by not containing As ₂ O ₃ and Sb ₂ O ₃ . The reason for limiting the composition in this way is as described above. In addition to these components, the above components can be appropriately contained.

  The crystallized glass of the present invention may be subjected to post-processing such as cutting, polishing, bending, or painting on the surface.

  EXAMPLES The present invention will be described in detail below using examples, but the present invention is not limited to these examples.

First, a raw material powder was prepared so as to have a composition shown in Table 1, and Nd ₂ O ₃ or Er ₂ O ₃ and Cl were added at a ratio shown in Tables 2 to 4 to obtain a raw material batch. As the Cl raw material, NaCl was used in batches A and C, and LiCl was used in batch B.

  Each raw material batch was put into a crucible and melted at 1600 ° C. for 20 hours and further at 1700 ° C. for 4 hours. The glass melt was poured onto a carbon plate, leveled to a thickness of about 5 mm with a roller, and annealed with an electric furnace to obtain a glass sample. The annealing was performed by lowering the temperature from 700 ° C. to room temperature at a rate of 100 ° C./hour. About the obtained glass sample, Cl residual amount and clarity were evaluated. The results are shown in Tables 2-4. In addition, in the obtained glass sample, it had content of Tables 1-4 about components other than Cl.

  The residual amount of Cl was measured by processing each glass sample into a 3 mm plate shape, mirror-polishing both surfaces, performing total elemental analysis by fluorescent X-ray analysis (XRF), and correcting for ZAF.

  The clarity is “A” when the number of bubbles per 100 g (bubble diameter is 0.1 mm or more) of the glass sample is “A”, 1-2 is “B”, 3-5 is “ “C”, 6 or more were evaluated as “D”.

Claims (6)

By melting the raw batch, by mass% as a _{composition, SiO 2 55~75%, Al 2} O 3 17~27%, Li 2 O 3~6%, 0~2% MgO, 0~2% ZnO, TiO _{2 2 to} 5.5%, ZrO ₂ 0 to 3%, rare earth oxide 0.03 to 1%, halogen 0.01 to 0.2%, substantially As ₂ O ₃ and Sb ₂ O ₃ a method for manufacturing a LAS-based crystallizable glass containing no, LAS, characterized in that the rare earth oxide from 0.03 to 1% and a halogen-containing 0.05 to 1 percent in the raw batch A method for producing a crystalline glass. The method for producing an LAS-based crystalline glass according to claim 1, wherein the rare earth oxide is Nd ₂ O ₃ or Er ₂ O ₃ .   A LAS-based crystalline glass produced by the production method according to claim 1 or 2. In mass% as a _{composition, SiO 2 55~75%, Al 2} O 3 17~27%, Li 2 O 3~6%, 0~2% MgO, 0~2% ZnO, TiO 2 2~5.5% ZrO ₂ 0 to 3%, rare earth oxide 0.03 to 1%, halogen 0.01 to 0.2%, and substantially free of As ₂ O ₃ and Sb ₂ O ₃ LAS-based crystalline glass.   A LAS-based crystallized glass obtained by crystallizing the LAS-based crystallized glass according to claim 3 or 4.   The LAS-based crystallized glass according to claim 5, wherein β-quartz solid solution or β-spodumene solid solution is precipitated as a main crystal.