Frit and method for producing same, glaze composition for glass lining, glass lining layer and method for forming same, and glass lined product

Abstract

The present invention provides a frit which is suitable for the production of a glass lining layer that is extremely suppressed in the dissolution amount of a sodium component. This frit is mainly composed of SiO2, and has an Na concentration of 300 ppm by mass or less as determined by ICP emission spectrometry.

Description

Frit and manufacturing method thereof, glaze composition for glass lining, glass lining layer and method for forming same, and glass lining product

[0001] The present invention relates to a frit useful for forming a glass lining layer and a method for producing the same, a glaze composition for glass lining, a glass lining layer and a method for forming the same, and a glass-lined product.

[0002] Glass-lined products are used in fields that require high corrosion resistance and high product purity, such as the chemical, pharmaceutical, food, and electronics industries. Glass-lined products are made from a metal substrate such as a low-carbon steel plate or a stainless steel plate, and are produced by fusing a glass lining composition containing a frit with a predetermined composition, mainly composed of SiO2, to the surface of the substrate to form a glass lining layer that is corrosion-resistant, inert, and heat-resistant.

[0003] NaO has traditionally been added to frits constituting glass lining compositions to match the thermal expansion coefficient with that of the metal substrate, lower the temperature during glass melting, and ensure the solubility of multiple components. NaO modifies the glass network structure of the glass lining layer, disrupts the SiO network structure, and (i) increases the linear thermal expansion coefficient and (ii) increases solubility. This makes NaO a valuable component for obtaining high-performance glass lining layers (see Patent Document 4: Japanese Patent No. 3907978, Patent Document 5: Japanese Patent No. 5860713). However, sodium components are easily eluted from glass lining layers containing NaO, and these sodium components are contaminated in chemical solutions during the chemical solution manufacturing process. Therefore, glass lining products containing NaO cannot be used to manufacture chemical solutions used in the manufacturing processes of semiconductors and TFT-type panels.

[0004] Therefore, it has been proposed to obtain a glass lining layer with a small amount of elution of sodium components by using a glass lining glaze composition that does not contain Na2O (Patent Document 1: Japanese Patent No. 5148982, Patent Document 2: Japanese Patent No. 5191384, Patent Document 3: Japanese Patent No. 5164550).

[0005] Patent No. 5148982 Patent No. 5191384 Patent No. 5164550 Patent No. 3907978 Patent No. 5860713

[0006] Thus, glass lining glaze compositions that do not contain Na2O have been proposed, and were thought to be sufficient, but with the recent trend toward higher performance in the semiconductor and liquid crystal fields, further reductions in the amount of sodium elution are required. Specifically, the amount of Na eluted from the glass lining layer into pure water is expected to be 100% when the surface area of ​​the glass lining layer is about 4000 mm2. 2 When the amount of water per 100 mL is taken as 100 mL, it is desirable that the concentration be 10 ppb by mass or less. This was not possible with conventional analytical techniques, but it has become possible to identify this because the detection limit of Na has been lowered by the latest analytical techniques. However, it has been found that even if a conventional glass lining glaze composition that does not contain Na2O is used, it is not possible to meet such high requirements.

[0007] In view of the above circumstances, an object of the present invention, in one embodiment, is to provide a frit suitable for producing a glass lining layer from which the amount of elution of sodium components is extremely low. In another embodiment, an object of the present invention is to provide a method for producing such a frit. In yet another embodiment, an object of the present invention is to provide a glaze composition for glass linings containing such a frit. In yet another embodiment, an object of the present invention is to provide a glass lining layer from which the amount of elution of sodium components is extremely low. In yet another embodiment, an object of the present invention is to provide a method for forming such a glass lining layer. In yet another embodiment, an object of the present invention is to provide a glass-lined product comprising such a glass lining layer.

[0008] The inventors of the present invention have conducted extensive research to solve the above problems and have found that simply not incorporating Na2O into the frit is not enough, and that sodium components contained as impurities in the raw materials, as well as sodium components introduced as impurities during the manufacturing process of the frit, have a significant effect on the amount of sodium eluted from the glass-lining layer. They then identified the cause of the small amount of sodium components introduced during each step of the frit manufacturing process and eliminated the causes of the sodium components as much as possible, thereby succeeding in forming a glass-lining layer with an extremely small amount of sodium components eluted, and have created the present invention, which is exemplified below.

[0009] [Aspect 1] A frit containing SiO2 as a main component, having a Na concentration of 300 ppm by mass or less as measured by ICP atomic emission spectrometry. [Aspect 2] The frit according to Aspect 1, containing 40 to 75% by mass of SiO2, 0 to 10% by mass of ZrO2, 8 to 22% by mass of R2O (wherein R represents one or more elements selected from the group consisting of Li, K, and Cs), and 1 to 7% by mass of R2O (wherein R represents one or more elements selected from the group consisting of Mg, Ca, Sr, and Ba). [Aspect 3] The frit according to Aspect 1 or 2, having a Na concentration of 200 ppm by mass or less. [Aspect 4] The frit according to Aspect 1 or 2, having a Na concentration of 100 ppm by mass or less. [Embodiment 5] The frit according to any one of embodiments 1 to 4, wherein the median diameter is 1.5 to 20 μm when the cumulative particle size distribution on a volume basis is measured by a laser diffraction method. [Aspect 6] Step 1: preparing a raw material blend containing SiO2 as a main component, the raw material blend having a Na concentration of 150 mass ppm or less as measured by ICP optical emission spectrometry; Step 2: melting the raw material blend placed in a crucible in a melting furnace and then rapidly cooling it to obtain a coarsely pulverized product, the operating conditions of which include selecting materials for forming the crucible and the inner wall, ceiling, and hearth of the melting furnace so that the Na concentration in the coarsely pulverized product as measured by ICP optical emission spectrometry is 200 mass ppm or less; and Step 3: pulverizing the coarsely pulverized product to obtain a finely pulverized product, the operating conditions of which include selecting materials that come into contact with the coarsely pulverized product during pulverization so that the Na concentration in the finely pulverized product as measured by ICP optical emission spectrometry is 250 mass ppm or less. and step 4, a step of obtaining a frit by classifying the finely pulverized material, wherein the implementation conditions include selecting a material to come into contact with the finely pulverized material during classification so that the concentration of Na contained in the frit as measured by ICP atomic emission spectrometry is 300 mass ppm or less.Aspect 7: The method of aspect 6, wherein the raw material blend prepared in step 1 contains 40 to 75% by weight of SiO, 0 to 10% by weight of ZrO, 8 to 22% by weight of R2O (wherein R represents one or more elements selected from the group consisting of Li, K, and Cs), and 1 to 7% by weight of R'O (wherein R' represents one or more elements selected from the group consisting of Mg, Ca, Sr, and Ba). Aspect 8: The method of aspect 6 or 7, wherein the conditions for step 2 include selecting a material for forming the crucible so that the Na concentration in the coarsely pulverized product is 180 ppm by mass or less; the conditions for step 3 include selecting a material that comes into contact with the coarsely pulverized product during pulverization so that the Na concentration in the finely pulverized product is 190 ppm by mass or less; and the conditions for step 4 include selecting a material that comes into contact with the finely pulverized product during classification so that the Na concentration in the frit is 200 ppm by mass or less. [Aspect 9] The manufacturing method according to any one of Aspects 6 to 8, wherein the raw material blend prepared in Step 1 has a Na concentration of 50 ppm by mass or less, wherein Step 2 is performed under conditions including selecting a material for forming the crucible such that the Na concentration in the coarsely pulverized product is 80 ppm by mass or less, wherein Step 3 is performed under conditions including selecting a material that will come into contact with the coarsely pulverized product during pulverization such that the Na concentration in the finely pulverized product is 90 ppm by mass or less, and wherein Step 4 is performed under conditions including selecting a material that will come into contact with the finely pulverized product during classification such that the Na concentration in the frit is 100 ppm by mass or less. [Aspect 10] The manufacturing method according to any one of Aspects 6 to 9, wherein the frit obtained in Step 4 has a median diameter of 1.5 to 20 μm when a cumulative particle size distribution on a volume basis is measured by laser diffraction. [Aspect 11] A glass lining glaze composition comprising the frit according to any one of Aspects 1 to 5 and a dispersion medium. [Aspect 12] A method for forming a glass lining layer, comprising applying the glass lining glaze composition according to Aspect 11 to a surface of a base material, and firing the resulting glaze to form a glass lining layer.[Aspect 13] The method for forming a glass lining layer according to Aspect 12, which includes washing the surface of the fired glass lining layer with water. [Aspect 14] A glass lining layer containing SiO2 as a main component, and having a Na concentration of 300 ppm by mass or less as measured by ICP atomic emission spectrometry. [Aspect 15] The glass lining layer according to Aspect 14, containing 40 to 75 mass% of SiO2, 0 to 10 mass% of ZrO2, 8 to 22 mass% of R2O (wherein R represents one or more elements selected from the group consisting of Li, K, and Cs), and 1 to 7 mass% of R'O (wherein R' represents one or more elements selected from the group consisting of Mg, Ca, Sr, and Ba). [Aspect 16] The glass lining layer according to Aspect 14 or 15, having a Na concentration of 200 ppm by mass or less. [Aspect 17] The glass lining layer according to Aspect 14 or 15, wherein the concentration of Na is 100 ppm by mass or less. [Aspect 18] A glass-lined product comprising the glass lining layer according to any one of Aspects 14 to 17.

[0010] Use of a frit according to one embodiment of the present invention is extremely useful in producing a glass-lining layer with an extremely low amount of elution of sodium components. For example, the amount of Na elution from the glass-lining layer obtained by using this frit can be reduced to 10 mass ppb or less, preferably 6 mass ppb or less, and more preferably 4 mass ppb or less. Therefore, in one embodiment, the present invention can provide an excellent glass-lining product that meets the increasing performance needs of the semiconductor and liquid crystal fields.

[0011] <1. Frit> A frit according to one embodiment of the present invention is composed primarily of SiO2 and has a Na concentration of 300 mass ppm or less as measured by ICP atomic emission spectrometry (ICP-AES). The lower the Na concentration in the frit, the more desirable it is. Specifically, the Na concentration is preferably 200 mass ppm or less, more preferably 150 mass ppm or less, even more preferably 100 mass ppm or less, and even more preferably 60 mass ppm or less. By using a frit with such a reduced Na concentration, it is possible to minimize the amount of Na eluted from the resulting glass-lining layer. To reduce the Na concentration in the frit to such a level, it is necessary not only to avoid blending Na2O into the raw materials, but also to minimize the sodium component contained as an impurity in the raw materials and the sodium component introduced as an impurity during the frit manufacturing process.

[0012] Although the lower limit of the Na concentration in the frit measured by ICP atomic emission spectrometry is not particularly set, taking into account the production cost, it may be, for example, 10 ppm by mass or more, 20 ppm by mass or more, or 30 ppm by mass or more. Therefore, the Na concentration in the frit is in the range of 10 to 300 ppm by mass in one embodiment, in the range of 20 to 200 ppm by mass in another embodiment, and in the range of 30 to 100 ppm by mass in yet another embodiment.

[0013] Specifically, the concentration of elements such as Na in a frit can be measured by ICP atomic emission spectrometry (ICP-AES) under the following measurement conditions. Apparatus name: Hitachi High-Tech Science Corporation, Model PS3520UVDDII Measurement procedure: An appropriate amount of sample is weighed out onto a platinum dish, and hydrofluoric acid, nitric acid, and perchloric acid are added to decompose and evaporate to dryness. After cooling, hydrochloric acid is added and heated to dissolve the contents of the platinum dish. The solution is then measured to a constant volume and measured using the above apparatus. Measurements can also be performed using an apparatus with equivalent performance to the above apparatus.

[0014] The frit containing SiO2 as the main component means that the mass concentration of SiO2 in the frit is the highest. The SiO2 concentration in the frit is preferably 40 to 75 mass%, more preferably 45 to 70 mass%. When the SiO2 concentration in the frit is 40 mass% or more, the acid resistance and water resistance are improved. When the SiO2 concentration in the frit is 75 mass% or less, the viscosity does not become too high and the linear thermal expansion coefficient does not become too small.

[0015] In a preferred embodiment, the frit contains 40 to 75 wt % SiO, 0 to 10 wt % ZrO, 8 to 22 wt % RO (wherein R represents one or more elements selected from the group consisting of Li, K, and Cs), and 1 to 7 wt % R'O (wherein R' represents one or more elements selected from the group consisting of Mg, Ca, Sr, and Ba).

[0016] By setting the ZrO2 content in the frit to 10% by mass or less, crystallization becomes difficult and excessive viscosity can be prevented. Furthermore, by setting the ZrO2 content in the frit to 0% by mass or more, water resistance and alkali resistance are improved. The ZrO2 content in the frit is preferably within the range of 2 to 8% by mass.

[0017] When the RO content in the frit is 22% by mass or less, the water resistance is less likely to decrease. When the RO content in the frit is 8% by mass or more, the viscosity can be prevented from becoming too high. The RO content in the frit is preferably in the range of 10 to 20% by mass.

[0018] When the R'O content in the frit is 7% by mass or less, acid resistance is improved. When the R'O content in the frit is 1% by mass or more, water resistance is improved. The R'O content in the frit is preferably in the range of 2 to 5% by mass.

[0019] The frit may also contain one or more elements selected from the group consisting of TiO, AlO, LaO, BO, and ZnO. These elements prevent phase separation and crystallization during firing of the glass lining, are firmly fixed within the glass network structure, and fill and tighten the network, improving water resistance and suppressing the generation of bubbles.

[0020] The content of TiO in the frit is 0 to 16 mass%, preferably 0 to 10 mass%, the content of AlO is 0 to 6 mass%, preferably 0 to 4 mass%, the content of LaO is 0 to 4 mass%, preferably 0 to 2 mass%, the content of BO is 0 to 18 mass%, preferably 0 to 14 mass%, and the content of ZnO is 0 to 6 mass%, preferably 0 to 4 mass%. When two or more of these components are used in combination, their total content is 1 to 10 mass%, preferably 1 to 8 mass%. If the individual or total content of these components exceeds the upper limit, the melting point of the frit increases and solubility tends to deteriorate. If the content is below the lower limit, the effect of adding these components is less likely to be achieved.

[0021] Furthermore, the frit may contain one or more coloring components selected from the group consisting of CoO, NiO, SbO, CrO, FeO, MnO, SnO, and CeO in an amount of up to 3 mass% FeO relative to 100 mass% frit. CoO, a blue component, is preferred as the coloring component from the standpoint of visibility. This has the advantage of making it easier to see the surface condition, such as the corrosion state of the glass lining layer. If the amount of coloring component exceeds 3 mass% FeO, acid resistance decreases and foaming is more likely to occur during firing. The entire text of Japanese Patent No. 5,156,277 is incorporated herein by reference.

[0022] To facilitate melting of the frit, up to 10% by weight of the SiO, AlO, and CaO components may be used in the form of fluorides, such as KSiF, KAlF, and CaF.

[0023] In one embodiment, the median diameter of the frit can be 1.5 to 20 μm. By setting the upper limit of the median diameter of the frit to 20 μm or less, it becomes possible to apply a glaze with a very thin thickness, significantly reducing the thickness of the resulting glass lining layer. Furthermore, since the gaps between frit particles are reduced, the diameter of the bubbles contained in the glass lining layer can be reduced. The median diameter of the frit is preferably 15 μm or less, and more preferably 10 μm or less. Furthermore, by setting the lower limit of the median diameter of the frit to 1.5 μm or more, there is obtained the advantage that particle aggregation is less likely to occur, thereby improving the uniformity of the film thickness when the film is thinned. The median diameter of the frit is preferably 3 μm or more, and more preferably 5 μm or more. Therefore, the median diameter of the frit is preferably 3 to 15 μm, and more preferably 5 to 10 μm, for example.

[0024] In this specification, the median diameter of the frit refers to the median diameter (D50) when the cumulative particle size distribution on a volume basis is measured by a laser diffraction method. In the examples, the measurement was performed using a laser diffraction particle size distribution analyzer (model: LMS-30) manufactured by Seishin Enterprise Co., Ltd.

[0025] <2. Frit Manufacturing Method> Frit having the particle size described above can be obtained, for example, by quenching and coarsely pulverizing a glass melt having a predetermined composition, followed by dry pulverization in a ball mill, and then appropriately performing classification and pulverization. As described above, sodium components are inevitably mixed into the raw materials and manufacturing process of the frit. Therefore, in order to manufacture frit with an extremely small concentration of Na, it is important to prevent the mixing of sodium components as much as possible in the raw materials used and in each manufacturing process.

[0026] A method for producing frit according to one embodiment of the present invention includes: Step 1 of preparing a raw material blend containing SiO2 as a main component and having a Na concentration of 150 ppm by mass or less as measured by ICP optical emission spectrometry; Step 2 of melting the raw material blend placed in a crucible in a melting furnace and rapidly cooling it to obtain a coarsely pulverized product, the operating conditions of which include selecting materials for forming the crucible and the inner wall, ceiling, and hearth of the melting furnace so that the Na concentration in the coarsely pulverized product is 200 ppm by mass or less as measured by ICP optical emission spectrometry; and Step 3 of pulverizing the coarsely pulverized product to obtain a finely pulverized product, the operating conditions of which include selecting a material that comes into contact with the coarsely pulverized product during pulverization so that the Na concentration in the finely pulverized product is 250 ppm by mass or less as measured by ICP optical emission spectrometry. and step 4, a step of obtaining frit by classifying the finely pulverized material, wherein the conditions for carrying out the classification include selecting a material that comes into contact with the finely pulverized material during classification so that the concentration of Na contained in the frit as measured by ICP atomic emission spectrometry is 300 mass ppm or less. Each step will be described in detail below.

[0027] (Step 1) In step 1, a raw material blend is prepared. The raw material blend contains SiO as a main component, and has a Na concentration of 150 mass ppm or less as measured by ICP optical emission spectrometry. The raw material blend preferably has a Na concentration of 100 mass ppm or less as measured by ICP optical emission spectrometry, more preferably 50 mass ppm or less, and even more preferably 20 mass ppm or less.

[0028] Although the lower limit of the Na concentration in the raw material blend measured by ICP atomic emission spectrometry is not particularly set, taking into account the production cost, it may be, for example, 1 ppm by mass or more, 5 ppm by mass or more, or 10 ppm by mass or more. Therefore, the Na concentration in the raw material blend is in the range of 1 to 150 ppm by mass in one embodiment, in the range of 5 to 100 ppm by mass in another embodiment, and in the range of 10 to 50 ppm by mass in yet another embodiment.

[0029] Specifically, the concentration of elements such as Na in a raw material blend can be measured by ICP atomic emission spectrometry (ICP-AES) under the following measurement conditions. Apparatus name: Hitachi High-Tech Science Corporation, Model PS3520UVDDII Measurement procedure: An appropriate amount of sample is weighed out onto a platinum dish, and hydrofluoric acid, nitric acid, and perchloric acid are added to decompose and evaporate to dryness. After cooling, hydrochloric acid is added and heated to dissolve the contents of the platinum dish. The solution is then measured to a constant volume using the above apparatus. Measurements can also be made using an apparatus with equivalent performance to the above apparatus.

[0030] The raw material blend is usually provided as a mixture of raw material powders of the aforementioned components constituting the frit (SiO, ZrO, RO, RO, etc.). The raw material blend may be prepared by blending raw material powders of the respective components so that the frit has a desired composition. Thus, in one embodiment, the raw material blend contains 40 to 75 mass% SiO, 0 to 10 mass% ZrO, 8 to 22 mass% RO (where R represents one or more elements selected from the group consisting of Li, K, and Cs), and 1 to 7 mass% R'O (where R' represents one or more elements selected from the group consisting of Mg, Ca, Sr, and Ba). When the desired frit contains other components such as TiO, AlO, etc., the respective components may be blended in accordance with the respective component concentrations in the frit. Commercially available powders of each component can be used, but it is desirable to use high-purity products so that the concentration of Na as an impurity in the entire raw material blend satisfies the concentration conditions described above.

[0031] Furthermore, when mixing the raw material powders of each component, it is preferable to use a mixer (such as a Loedige mixer, a V-type mixer, or a ball mill) that contains only a small amount of Na or no Na at all, thereby minimizing the incorporation of Na as an impurity into the raw material blend. For example, it is preferable to use corrosion-resistant metals such as stainless steel, or high-purity ceramics such as high-purity alumina or high-purity zirconia, or to provide a lining such as a fluororesin for the members used in the mixer that come into contact with the raw material powders of each component.

[0032] (Step 2) In step 2, a coarsely pulverized material is obtained. The coarsely pulverized material can be obtained by melting the raw material blend placed in a crucible in a melting furnace and then rapidly cooling it. The temperature during melting is desirably equal to or higher than the melting point of the raw material blend, and the raw material blend can be heated to typically 1050 to 1450°C, more typically 1150 to 1350°C. Methods for rapid cooling after melting include water cooling and air cooling. When rapidly cooling, it is preferable to use water cooling with pure water or ultrapure water, or air cooling with clean air that has been passed through a high-performance air filter such as a HEPA filter, to minimize the inclusion of Na as an impurity.

[0033] In step 2, it is desirable to set the conditions so that the Na concentration of the coarsely pulverized material measured by ICP atomic emission spectrometry is 200 mass ppm or less, preferably 180 mass ppm or less, more preferably 140 mass ppm or less, even more preferably 120 mass ppm or less, even more preferably 80 mass ppm or less, and even more preferably 40 mass ppm or less. In particular, in step 2, sodium components are likely to be mixed in from the crucible used, so care must be taken in selecting the material constituting the crucible. Specifically, when a typical clay crucible or quartz crucible is used, sodium components are likely to be mixed in as impurities in the coarsely pulverized material. For this reason, it is desirable to use a crucible that contains only a small amount of Na or no Na at all, so that Na is not mixed in as much as possible as an impurity during melting. Specifically, it is preferable to use high-purity ceramics such as high-purity alumina and high-purity zirconia, as well as noble metal crucibles such as platinum crucibles and platinum alloy crucibles as the material of the crucible.

[0034] Furthermore, it is desirable that the melting furnace into which the crucible is placed contains only a small amount of Na or no Na at all, so that Na is not mixed in as an impurity as much as possible during melting. Specifically, it is preferable to use high-purity ceramics such as high-purity alumina and high-purity zirconia as refractories for the inner walls, ceiling, hearth, etc. of the melting furnace.

[0035] Although the lower limit of the Na concentration in the coarsely pulverized product measured by ICP atomic emission spectrometry is not particularly set, taking into account the production cost, it may be, for example, 5 ppm by mass or more, 10 ppm by mass or more, or 20 ppm by mass or more. Therefore, the Na concentration in the coarsely pulverized product is in the range of 5 to 200 ppm by mass in one embodiment, in the range of 10 to 180 ppm by mass in another embodiment, and in the range of 20 to 140 ppm by mass in yet another embodiment.

[0036] Specifically, the concentration of elements such as Na in coarsely ground material can be measured by ICP atomic emission spectrometry (ICP-AES) under the following measurement conditions. Apparatus name: Hitachi High-Tech Science Corporation, Model PS3520UVDDII Measurement procedure: An appropriate amount of sample is weighed out onto a platinum dish, and hydrofluoric acid, nitric acid, and perchloric acid are added to decompose and evaporate to dryness. After cooling, hydrochloric acid is added and heated to dissolve the contents of the platinum dish. The solution is then measured to a constant volume and measured using the above apparatus. Measurements can also be made using an apparatus with equivalent performance to the above apparatus.

[0037] (Step 3) In step 3, the coarsely pulverized product is pulverized to obtain a finely pulverized product. Examples of pulverization methods include methods using pulverization equipment such as a ball mill or a bead mill. The median diameter of the finely pulverized product can be, for example, 10 to 50 μm, and preferably 20 to 40 μm. The median diameter of the finely pulverized product refers to the median diameter (D50) when the cumulative particle size distribution on a volume basis is measured by laser diffraction. In the examples, the measurement was carried out using a laser diffraction particle size distribution analyzer (model: LMS-30) manufactured by Seishin Enterprise Co., Ltd.

[0038] In step 3, it is desirable to determine the conditions for carrying out the process so that the Na concentration of the finely pulverized product measured by ICP atomic emission spectrometry is 250 mass ppm or less, preferably 190 mass ppm or less, more preferably 150 mass ppm or less, even more preferably 130 mass ppm or less, even more preferably 90 mass ppm or less, and even more preferably 50 mass ppm or less. In particular, in step 3, it is desirable to use milling equipment that contains only trace amounts of Na or no Na at all, thereby minimizing the incorporation of Na as an impurity during milling. Specifically, it is preferable to use high-purity ceramics such as high-purity alumina and high-purity zirconia for components that come into contact with the coarsely pulverized product during milling, such as the milling medium and the container for containing the milling medium.

[0039] Although the lower limit of the Na concentration in the finely pulverized product measured by ICP atomic emission spectrometry is not particularly set, taking into account the production cost, it may be, for example, 5 ppm by mass or more, 10 ppm by mass or more, or 20 ppm by mass or more. Therefore, the Na concentration in the coarsely pulverized product is in the range of 5 to 250 ppm by mass in one embodiment, in the range of 10 to 190 ppm by mass in another embodiment, and in the range of 20 to 150 ppm by mass in yet another embodiment.

[0040] Specifically, the concentration of elements such as Na in finely pulverized material can be measured by ICP atomic emission spectrometry (ICP-AES) under the following measurement conditions. Apparatus name: Hitachi High-Tech Science Corporation, Model PS3520UVDDII Measurement procedure: An appropriate amount of sample is weighed out onto a platinum dish, and hydrofluoric acid, nitric acid, and perchloric acid are added to decompose and evaporate to dryness. After cooling, hydrochloric acid is added and heated to dissolve the contents of the platinum dish. The solution is then measured to a constant volume and measured using the above apparatus. Measurements can also be made using an apparatus with equivalent performance to the above apparatus.

[0041] (Step 4) In step 4, the finely pulverized product is classified to obtain frit having a desired particle size. The preferred particle size (median diameter) of the frit is as described above. Examples of classification methods include a method using a classifier such as a vibrating sieve.

[0042] In step 4, it is desirable to determine the conditions for carrying out the process so that the Na concentration of the frit measured by ICP atomic emission spectrometry is 300 mass ppm or less, preferably 200 mass ppm or less, more preferably 150 mass ppm or less, even more preferably 100 mass ppm or less, and even more preferably 60 mass ppm or less. In particular, in step 4, it is desirable to use a classifier that contains only a small amount of Na or no Na at all, thereby minimizing the incorporation of Na as an impurity during classification. Specifically, it is preferable to use a metal with high corrosion resistance and wear resistance, such as stainless steel, for the members that come into contact with the finely pulverized material during classification.

[0043] Although the lower limit of the Na concentration in the frit measured by ICP atomic emission spectrometry is not particularly set, taking into account the production cost, it may be, for example, 10 ppm by mass or more, 20 ppm by mass or more, or 30 ppm by mass or more. Therefore, the Na concentration in the frit is in the range of 10 to 300 ppm by mass in one embodiment, in the range of 20 to 200 ppm by mass in another embodiment, and in the range of 30 to 100 ppm by mass in yet another embodiment.

[0044] The method for measuring the concentration of Na in the frit by ICP emission spectrometry is as described above.

[0045] <3. Glaze Composition for Glass Lining> A glaze composition for glass lining according to one embodiment of the present invention contains the above-mentioned frit and a dispersion medium. The dispersion medium used is not limited to, but includes water and water-soluble dispersion mediums such as alcohol, with water being preferred because it is odorless and improves the working environment. It is desirable that the dispersion medium contain only a small amount of Na or no Na at all. One method for reducing the Na concentration in the dispersion medium is to carry out an ion exchange treatment.

[0046] Suitable water to be used includes water with a resistivity of 0.5 MΩ cm or more at 25°C, such as pure water (e.g., resistivity at 25°C: 0.5 to 1.0 MΩ cm) and ultrapure water (e.g., resistivity at 25°C: 17.5 to 18.0 MΩ cm). Examples of alcohol include ethanol. It is preferable to use alcohol with a purity of 99.5% by volume or higher. The dispersion medium may be used alone or in combination of two or more. The dispersion medium may be added in an amount of, but not limited to, 1 to 40 parts by mass, preferably 5 to 30 parts by mass, per 100 parts by mass of frit. The alcohol concentration in the glass lining glaze composition is preferably 1% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0% by mass.

[0047] In a preferred embodiment, the glass lining glaze composition can further contain metal fibers. By containing metal fibers in the glass lining glaze composition, the electrical resistance of the glass lining layer is reduced, making it possible to suppress static electricity charging of the glass lining product and also to improve thermal conductivity.

[0048] The metal fibers are not limited to, but preferably include one or more types selected from the group consisting of stainless steel metal fibers, noble metal metal fibers, and alloy fibers of platinum and platinum group metals. Examples of noble metal metal fibers include Ag fibers (volume resistivity: 1.6×10 -8 Ωm), Au fiber (volume resistivity: 2.4 × 10 -8 Ωm), Pt fiber (volume resistivity: 10.6 × 10 -8 As the alloy fiber of platinum and a platinum group metal, for example, an alloy of Pt and one or more elements selected from the group consisting of Pd, Ir, Rh, Os, and Ru can be used.

[0049] The amount of metal fibers added to the frit is preferably 0.01 to 5 parts by mass per 100 parts by mass of the frit. When the amount of metal fibers added is 0.01 part by mass or more per 100 parts by mass of the frit, the conductivity can be significantly improved. The lower limit of the amount of metal fibers added is more preferably 0.05 parts by mass or more per 100 parts by mass of the frit, and even more preferably 0.1 parts by mass or more. Furthermore, when the amount of metal fibers added is 5 parts by mass or less per 100 parts by mass of the frit, the spray applicability is improved. The upper limit of the amount of metal fibers added is more preferably 2 parts by mass or less per 100 parts by mass of the frit, and even more preferably 1 part by mass or less.

[0050] The diameter of the metal fiber is preferably 0.1 to 2 μm, more preferably 0.2 to 2 μm, and even more preferably 0.3 to 1 μm. When the diameter of the metal fiber is 0.1 μm or more, the metal fiber can be processed at low cost. Furthermore, when the diameter of the metal fiber is 2 μm or less, spray application properties are improved. In this specification, the diameter of the metal fiber refers to the diameter of a circle equal to the area of ​​the cross section perpendicular to the extension direction of the metal fiber.

[0051] The length of the metal fibers is preferably 50 to 1000 μm, more preferably 100 to 800 μm. When the length of the metal fibers is 50 μm or more, the effect of adding the metal fibers is more likely to be significantly exhibited. Furthermore, when the length is 1000 μm or less, spray application properties are improved.

[0052] The average aspect ratio of the length / diameter of the metal fibers is preferably at least 50. When the average aspect ratio of the length / diameter of the metal fibers is at least 50, the electrical resistance of the glass lining layer can be reduced without blending a large amount of metal fibers.

[0053] The glass lining glaze composition may contain a thickener. Adding a thickener is particularly preferable when the glass lining glaze composition contains metal fibers. Adding a thickener can prevent the metal fibers from settling and becoming unevenly distributed downward in the glass lining glaze composition. This can improve the electrical conductivity and thermal conductivity of the glass lining layer. The thickener is preferably added in an amount of 32 to 65 parts by mass, more preferably 38 to 60 parts by mass, and even more preferably 45 to 55 parts by mass, calculated as solids content per 100 parts by mass of frit. By adding 32 parts by mass or more of the thickener per 100 parts by mass of frit, the effect of preventing the metal fibers from settling can be enhanced. Furthermore, by adding 65 parts by mass or less of the thickener per 100 parts by mass of frit, the effect of improving spray application can be obtained.

[0054] The thickener may be, but is not limited to, a cellulose derivative. Examples of the cellulose derivative include CMC (carboxymethyl cellulose), HEC (hydroxyethyl cellulose), HPMC (hydroxypropyl methyl cellulose), HPC (hydroxypropyl cellulose), and MC (methyl cellulose). Among these, CMC (carboxymethyl cellulose) is preferred because it suppresses the generation of bubbles during baking. The thickener may be used alone or in combination of two or more.

[0055] The glass lining glaze composition may contain a dispersant. Adding a dispersant is particularly preferable when the glass lining glaze composition contains metal fibers. Adding a dispersant can improve the uniform dispersion of the metal fibers, thereby improving electrical conductivity and thermal conductivity. Furthermore, a glaze composition suitable for spray application can be obtained without using alcohol as a dispersion medium. The dispersant is preferably added in an amount of 0.01 to 0.2 parts by mass, more preferably 0.02 to 0.1 parts by mass, and even more preferably 0.03 to 0.08 parts by mass, per 100 parts by mass of frit. By adding 0.01 parts by mass or more of dispersant per 100 parts by mass of frit, the dispersibility of the metal fibers can be improved. Furthermore, by adding 0.2 parts by mass or less of dispersant per 100 parts by mass of frit, an odor suppression effect can be obtained.

[0056] The dispersant is not limited, but polymeric dispersants such as polycarboxylic acid dispersants, naphthalenesulfonic acid-formalin condensation dispersants, polyethylene glycol, polyether dispersants, and polyalkylene polyamine dispersants can be preferably used to suppress the generation of bubbles during baking. As the polycarboxylic acid dispersant, for example, polycarboxylic acid ammonium salt can be preferably used. The dispersants may be used alone or in combination of two or more.

[0057] In addition, additives commonly used in glass linings (e.g., clay, barium chloride, sodium nitrite, etc.) can be added to the glass lining glaze composition. Clay can be added in an amount of, but not limited to, 3 to 8 parts by mass, preferably 5 to 7 parts by mass, per 100 parts by mass of frit. Barium chloride can be added in an amount of, but not limited to, 0.05 to 0.3 parts by mass, preferably 0.1 to 0.2 parts by mass, per 100 parts by mass of frit. Sodium nitrite can be added in an amount of, but not limited to, 0.1 to 0.6 parts by mass, preferably 0.2 to 0.5 parts by mass, per 100 parts by mass of frit.

[0058] It is desirable that metal fibers, thickeners, dispersants, and other additives contain only trace amounts of Na or no Na at all, so it is preferable to select additives of a grade that contains as little or no Na as possible and keep the amount added as low as possible.

[0059] The glass lining glaze composition can be produced by appropriately blending one or more of the above-mentioned additives in addition to the frit and dispersion medium. The components constituting the glass lining glaze composition can be blended by placing the components in a mixer in a predetermined ratio and stirring them in the mixer. In this case, it is preferable to use a mixer (such as a vertical mixer or a ball mill) that contains only trace amounts of Na or is completely free of Na, thereby minimizing the inclusion of Na as an impurity in the glass lining glaze composition. For example, it is preferable to use corrosion-resistant metals such as stainless steel, or high-purity ceramics such as high-purity alumina or high-purity zirconia, for the components used in the mixer that come into contact with the components, or to provide a lining such as a fluororesin.

[0060] The glass lining glaze composition according to one embodiment of the present invention has a Na concentration of 300 ppm by mass or less as measured by ICP atomic emission spectrometry (inductively coupled plasma atomic emission spectrometry). The lower the Na concentration in the glass lining glaze composition, the more desirable it is. Specifically, it is preferably 200 ppm by mass or less, more preferably 150 ppm by mass or less, even more preferably 100 ppm by mass or less, and even more preferably 80 ppm by mass or less. By using a glass lining glaze composition with such a reduced Na concentration, it is possible to minimize the amount of Na eluted from the resulting glass lining layer.

[0061] Specifically, the concentration of elements such as Na in a glass lining glaze composition can be measured by ICP atomic emission spectrometry (ICP-AES) under the following measurement conditions. Apparatus name: Hitachi High-Tech Science Corporation, Model PS3520UVDDII. Measurement procedure: A sample is collected in a high-purity ceramic evaporating dish and dried in a dryer maintained at a constant temperature and cleanliness to form an aggregate. An appropriate amount is then weighed into a platinum dish, and hydrofluoric acid, nitric acid, and perchloric acid are added to decompose and evaporate to dryness. After cooling, hydrochloric acid is added and the mixture is heated to dissolve the contents of the platinum dish. The resulting solution is then measured using the above-mentioned apparatus. Measurements can also be performed using an apparatus with equivalent performance to the above-mentioned apparatus. Note that the concentration measured here is the concentration when the solids content is 100% by mass, and the solvent is not taken into account.

[0062] 4. Glass Lining Layer A glass lining layer according to one embodiment of the present invention can be formed by applying the above-described glass lining glaze composition to the surface of a substrate and firing the glaze. The glass lining layer according to one embodiment of the present invention may be formed on the surface of a substrate on which no other glass lining layer is formed, or on the surface of a substrate on which another glass lining layer is formed, i.e., on the surface of another glass lining layer (such as a ground coat layer or an intermediate layer). NaO may be added to the ground coat layer and / or the intermediate layer. The glass lining layer according to a preferred embodiment of the present invention constitutes the outermost cover coat layer of the glass lining layer. Metal substrates are typically used as substrates. Examples of metal substrates include, but are not limited to, iron alloys such as low-carbon steel and stainless steel. The shape of the metal substrate is also not particularly limited, and examples include wall-shaped, plate-shaped, blade-shaped, and rod-shaped.

[0063] The conditions for the glazing operation, firing, etc. for forming the glass lining layer are not particularly limited, and conventional, well-known operations for glass lining can be used. However, the glazing operation is preferably performed by spraying, as this makes it easier to control the thickness. Furthermore, it is desirable that the equipment used for the glazing operation, such as tanks, hoses, and spray guns, contain only trace amounts of Na or no Na at all, so that Na is not mixed in as an impurity as much as possible during glazing. Specifically, it is preferable that the components of the equipment used for the glazing operation that come into contact with the glass lining glaze composition be made of corrosion-resistant metals such as stainless steel and aluminum, fluororesins, nylon resins, etc.

[0064] The firing furnace is preferably one that contains only a small amount of Na or no Na at all, thereby minimizing the incorporation of Na as an impurity during firing. Specifically, it is preferable to use high-purity ceramics such as high-purity alumina and high-purity zirconia for the refractories used for the inner walls, ceiling, hearth, etc. of the firing furnace. The firing temperature is preferably 700 to 900°C to prevent deformation of the substrate.

[0065] The glass lining layer according to one embodiment of the present invention is mainly composed of SiO2, and has a Na concentration of 300 mass ppm or less as measured by ICP atomic emission spectrometry. The lower the Na concentration in the glass lining layer, the more desirable it is. Specifically, the Na concentration is preferably 200 mass ppm or less, more preferably 150 mass ppm or less, even more preferably 100 mass ppm or less, and even more preferably 80 mass ppm or less.

[0066] By reducing the concentration of Na contained in the glass-lining layer in this way, it is possible to minimize the amount of Na elution from the glass-lining layer. Furthermore, when manufacturing the glass-lining layer, if high-purity raw materials are used and carefully selected parts are used in the manufacturing equipment to prevent the inclusion of sodium components, then as a result, the glass-lining layer according to one embodiment of the present invention can minimize not only the elution of Na but also the elution of other impurity metal components.

[0067] The amount of Na elution from the glass lining layer can be further reduced by washing the outer surface of the glass lining layer with water (e.g., resistivity at 25°C: 0.1 to 18.0 MΩ cm), preferably pure water (e.g., resistivity at 25°C: 0.5 to 1.0 MΩ cm), and more preferably ultrapure water (e.g., resistivity at 25°C: 17.5 to 18.0 MΩ cm). From the viewpoint of enhancing the washing effect, the lower limit of the temperature of the water used for washing is preferably 10°C or higher, more preferably 40°C or higher, even more preferably 60°C or higher, and even more preferably 80°C or higher. There is no particular upper limit on the temperature of the water used for washing, but since higher water temperatures and resistivity lead to more rapid corrosion of the glass lining layer surface, it is preferably less than 100°C, and more preferably 90°C or lower.

[0068] Although the lower limit of the Na concentration in the glass-lining layer measured by ICP atomic emission spectrometry is not particularly set, taking into account the production cost, it may be, for example, 20 ppm by mass or more, 30 ppm by mass or more, or 40 ppm by mass or more. Therefore, the Na concentration in the glass-lining layer is in the range of 20 to 300 ppm by mass in one embodiment, in the range of 30 to 200 ppm by mass in another embodiment, and in the range of 40 to 100 ppm by mass in yet another embodiment.

[0069] Specifically, the concentration of elements such as Na in the glass lining layer can be measured using ICP atomic emission spectrometry (ICP-AES) under the following measurement conditions. Instrument name: Hitachi High-Tech Science Corporation, Model PS3520UVDDII. Measurement procedure: The glass lining layer is mechanically broken to prevent the inclusion of impurities such as Na, and the fragments are collected and used as the sample for analysis. An appropriate amount of the sample is weighed out and placed on a platinum dish, and hydrofluoric acid, nitric acid, and perchloric acid are added to decompose and evaporate to dryness. After cooling, hydrochloric acid is added and the mixture is heated to dissolve the contents of the platinum dish. The solution is then adjusted to a constant volume and measured using the above instrument. Measurements can also be performed using an instrument with equivalent performance to the above instrument.

[0070] The glass-lining layer containing SiO2 as the main component means that the mass concentration of SiO2 in the glass-lining layer is the highest. The SiO2 concentration in the glass-lining layer is preferably 40 to 75 mass%, and more preferably 45 to 70 mass%. When the SiO2 concentration in the glass-lining layer is 40 mass% or more, acid resistance and water resistance are improved. When the SiO2 concentration in the glass-lining layer is 75 mass% or less, the viscosity does not become too high and the linear thermal expansion coefficient does not become too small.

[0071] In a preferred embodiment, the glass lining layer contains 40 to 75 mass% of SiO, 0 to 10 mass% of ZrO, 8 to 22 mass% of R O (wherein R represents one or more elements selected from the group consisting of Li, K, and Cs), and 1 to 7 mass% of R' O (wherein R' represents one or more elements selected from the group consisting of Mg, Ca, Sr, and Ba).

[0072] By keeping the ZrO2 content in the glass lining layer at 10% by mass or less, crystallization becomes difficult and excessive viscosity can be prevented. Furthermore, by keeping the ZrO2 content in the glass lining layer at 0% by mass or more, water resistance and alkali resistance are improved. The preferred ZrO2 content in the glass lining layer is in the range of 2 to 8% by mass.

[0073] By keeping the R2O content in the glass lining layer at 22 mass% or less, the water resistance is less likely to decrease. Furthermore, by keeping the R2O content in the glass lining layer at 8 mass% or more, the viscosity can be prevented from becoming too high. The preferred R2O content in the glass lining layer is in the range of 10 to 20 mass%.

[0074] When the R'O content in the glass lining layer is 7% by mass or less, acid resistance is improved. When the R'O content in the glass lining layer is 1% by mass or more, water resistance is improved. The preferred R'O content in the glass lining layer is in the range of 2 to 5% by mass.

[0075] Other than that, the composition of the glass lining layer is basically the same as the composition of the frit, so a detailed explanation will be omitted.

[0076] The thickness of the glass lining layer formed by applying a glass lining glaze composition to the surface of a substrate and firing it can be adjusted as needed. For example, the thickness of the glass lining layer can be 0.6 to 2.4 mm, typically 0.8 to 2.0 mm. The glass lining layer can be composed of one layer or multiple layers. When the glass lining layer is a cover coat layer, the thickness is preferably 0.1 to 1.3 mm. A cover coat layer thickness of 1.3 mm or less can enhance thermal conductivity. The cover coat layer thickness is more preferably 1.0 mm or less, and even more preferably 0.8 mm or less. Furthermore, a cover coat layer thickness of 0.1 mm or more has the advantage of effectively suppressing Na elution. The cover coat layer thickness is more preferably 0.2 mm or more, and even more preferably 0.3 mm or more.

[0077] 5. Glass-Lined Product According to one embodiment of the present invention, there is provided a glass-lined product comprising the above-described glass-lining layer. In one embodiment, the glass-lined product comprises a substrate and one or more of the above-described glass-lining layers formed on the surface of the substrate. Examples of glass-lined products include, but are not limited to, reactors, stirring blades, tanks (e.g., stirred tanks), heat exchangers, dryers, evaporators, filters, sampling baffles, etc.

[0078] Examples of the present invention will be described below together with comparative examples. These examples are provided for a better understanding of the present invention and its advantages, and are not intended to limit the present invention.

[0079] <1. Example 1> (1-1. Raw Material Blend) A raw material blend was prepared by mixing raw material powders of each component in a mixer in a predetermined ratio to obtain a frit having the composition shown in Table 1. The raw material powders used for each component were commercially available products, but all were high purity (99% by mass or higher). Furthermore, a Lödige mixer manufactured by Lödige GmbH, Germany, was used as the mixer, which uses stainless steel for parts that come into contact with the raw material powders of each component, in order to minimize the inclusion of Na as an impurity in the raw material blend.

[0080]

[0081] The Na concentration in the resulting raw material blend was measured by ICP atomic emission spectrometry under the measurement conditions described above. The results are shown in Table 2.

[0082] (1-2. Coarsely pulverized product) The above raw material blend placed in a quartz crucible was melted by heating at 1260°C for 4 hours in a melting furnace, and then the melt was rapidly cooled by water cooling with tap water (resistivity at 25°C: 0.005 MΩ cm) to obtain a coarsely pulverized product.

[0083] The Na concentration in the resulting coarsely pulverized product was measured by ICP emission spectrometry under the above-mentioned measurement conditions. The results are shown in Table 2.

[0084] (1-3. Finely pulverized product) The coarsely pulverized product obtained above was dry-pulverized in a ball mill to produce a finely pulverized product with a median diameter of 20 to 40 μm. Alumina balls with a purity of 92% by mass were used as the pulverization medium. Furthermore, alumina with a purity of 92% by mass was used for components that come into contact with the coarsely pulverized product during pulverization, such as the container containing the pulverization medium.

[0085] The Na concentration in the resulting finely pulverized product was measured by ICP emission spectrometry under the above-mentioned measurement conditions. The results are shown in Table 2.

[0086] (1-4. Frit) The finely pulverized material obtained above was classified using a vibrating sieve to produce frit with a median diameter of 20 μm. Stainless steel was used for the members that came into contact with the finely pulverized material during classification to minimize the inclusion of Na as an impurity.

[0087] The Na concentration in the resulting frit was measured by ICP atomic emission spectrometry under the above-mentioned measurement conditions. The results are shown in Table 2.

[0088] (1-5. Glass-lining Glaze Composition) 100 parts by mass of the frit prepared above were charged into a mixer (vertical mixer) so that a 1% by mass aqueous solution of CMC was mixed to a solids content of 45 parts by mass, and the mixture was stirred for 5 minutes. Subsequently, 15 parts by mass of 99.5% by volume ethanol and 30 parts by mass of tap water (resistivity at 25°C: 0.005 MΩ-cm) (dispersion medium) were charged into the mixer and stirred for an additional 20 minutes to obtain a glass-lining glaze composition in a slurry form. The CMC aqueous solution was prepared by blending CMC and tap water in a predetermined ratio using a vertical mixer. All components of the mixer that come into contact with the frit, dispersion medium, and additives were stainless steel. However, because these components were used for mass production of glaze compositions containing sodium components such as Na2O, sodium was present that could not be completely removed by washing.

[0089] The Na concentration in the obtained glass lining glaze composition was measured by ICP emission spectrometry under the measurement conditions described above. The results are shown in Table 2.

[0090] (1-6. Glass Lining Layer) A round bar made of low carbon steel having a diameter of 13 mm and a length of 80 mm was prepared. The surface of the round bar was spray-coated with a glaze composition for glass lining for a ground coat layer, which was prepared by adding, to 100 mass% of frit, a frit having a composition of SiO2+ZrO2: 57.5 mass%, Na2O+K2O+Li2O: 19 mass%, CaO+BaO+MgO: 3.5 mass%, BO3+Al2O3+TiO2+ZnO: 17 mass%, and CoO+NiO+MnO2+CeO2: 3 mass%, silica stone, 20 mass% of an aqueous CMC solution (concentration: 1 mass%), 5 mass% of an aqueous sodium nitrite solution (concentration: 0.3 mass%), 20 mass% of ethanol, and 30 mass% of tap water, in an external proportion of 50 mass% relative to 100 mass% of the frit, and then fired at 860°C for 15 minutes, thereby obtaining a ground coat layer having a thickness of 0.3 to 0.4 mm. Next, a frit having a composition of 71% by weight of SiO2 + ZrO2, 17% by weight of Na2O + KO2 + Li2O, 5% by weight of CaO + BaO + MgO, 6% by weight of BO3 + Al2O3 + TiO2 + ZnO, and 1% by weight of CoO + CeO2 was spray-coated onto the ground coat layer with a glass lining glaze composition for an intermediate layer. The glaze composition was prepared by adding 20% ​​by weight of a CMC aqueous solution (concentration: 1% by weight), 20% by weight of ethanol, and 30% by weight of tap water to 100% by weight of the frit, and then fired at 800°C for 15 minutes three times to obtain an intermediate layer having a thickness of 0.7 to 0.8 mm. Next, the glass lining glaze composition obtained above was applied and fired at 800°C for 15 minutes one to three times to obtain a cover coat layer having a thickness of approximately 0.1 to 0.4 mm. Among the equipment used for the glazing operation, the glazing booth for the cover coat layer was a dedicated booth that had been cleaned and washed, and corrosion-resistant metals (stainless steel or aluminum), fluororesin, and nylon resin were used for the members that came into contact with the glass lining glaze composition. Also, to minimize the inclusion of Na as an impurity during firing, high-purity ceramics were used for the refractories used in the inner walls, ceiling, hearth, etc. of the firing furnace.

[0091] The Na concentration in the cover coat layer of the resulting glass lining layer was measured by ICP emission spectrometry under the measurement conditions described above. The results are shown in Table 2.

[0092] 2. Example 2 (2-1. Raw Material Blend) A raw material blend was prepared by mixing powders of each component in a mixer in a predetermined ratio to obtain a frit having the composition shown in Table 1. However, although the raw material powders of each component used in this raw material blend were commercially available products, they were not particularly pure (98% by mass or less), and therefore the Na concentration was slightly higher than in Example 1. The Na concentration in this raw material blend was the same as that of the raw material blend used in the examples of Japanese Patent No. 5,191,384.

[0093] The Na concentration in the resulting raw material blend was measured by ICP atomic emission spectrometry under the measurement conditions described above. The results are shown in Table 2.

[0094] (2-2. Coarsely pulverized product) The raw material blend obtained above was placed in a platinum crucible and melted by heating in a melting furnace at 1260°C for 4 hours, and then the melt was rapidly cooled by water quenching with pure water (resistivity at 25°C: 1.0 MΩ cm) to obtain a coarsely pulverized product. High-purity ceramics were used for the refractories used in the inner walls, ceiling, hearth, etc. of the melting furnace to minimize the inclusion of Na as an impurity.

[0095] The Na concentration in the resulting coarsely pulverized product was measured by ICP emission spectrometry under the above-mentioned measurement conditions. The results are shown in Table 2.

[0096] (2-3. Finely pulverized product) The coarsely pulverized product obtained above was dry-pulverized in a ball mill to produce a finely pulverized product with a median diameter of 20 to 40 μm. High-purity alumina balls with a purity of 99.5% by mass were used as the grinding medium to minimize the inclusion of Na as an impurity during grinding. Furthermore, high-purity alumina with a purity of 99.5% by mass was used for components that come into contact with the coarsely pulverized product during grinding, such as the container for storing the grinding medium.

[0097] The Na concentration in the resulting finely pulverized product was measured by ICP emission spectrometry under the above-mentioned measurement conditions. The results are shown in Table 2.

[0098] (2-4. Frit) The finely pulverized product obtained above was classified in the same manner as in Example 1 to prepare a frit.

[0099] The Na concentration in the resulting frit was measured by ICP atomic emission spectrometry under the above-mentioned measurement conditions. The results are shown in Table 2.

[0100] (2-5. Glass-lining glaze composition) Instead of tap water, pure water (resistivity at 25°C: 1.0 MΩ cm) was used as the water used to prepare the CMC aqueous solution and as the dispersion medium to be fed into the mixer. As the mixer, a vertical mixer was used in which all parts that come into contact with each component were made of stainless steel, but a dedicated machine was prepared for use with glaze compositions to which no Na component was added, in order to minimize the inclusion of Na as an impurity in the glass-lining glaze composition. Otherwise, a glass-lining glaze composition was obtained in the same manner as in Example 1 using the frit obtained above.

[0101] The Na concentration in the obtained glass lining glaze composition was measured by ICP emission spectrometry under the measurement conditions described above. The results are shown in Table 2.

[0102] (2-6. Glass Lining Layer) The glass lining glaze composition obtained above was used to obtain a glass lining layer by glazing and firing under the same conditions as in Example 1. In order to minimize the inclusion of Na as an impurity during glazing, a dedicated booth that had been cleaned and washed was used as the glazing booth for the cover coat layer among the equipment used for the glazing operation, and corrosion-resistant metals (stainless steel or aluminum), fluororesin, and nylon resin were used for the members that come into contact with the glass lining glaze composition. Furthermore, in order to minimize the inclusion of Na as an impurity during firing, high-purity ceramics were used for the refractories used in the inner walls, ceiling, hearth, etc. of the firing furnace.

[0103] The Na concentration in the cover coat layer of the resulting glass lining layer was measured by ICP emission spectrometry under the measurement conditions described above. The results are shown in Table 2.

[0104] 3. Example 3 (3-1. Raw Material Blend) The same raw material blend as in Example 1 was prepared.

[0105] The Na concentration in the resulting raw material blend was measured by ICP atomic emission spectrometry under the measurement conditions described above. The results are shown in Table 2.

[0106] (3-2. Coarsely pulverized product) The raw material blend obtained above was melted and rapidly cooled in the same manner as in Example 2 to obtain a coarsely pulverized product.

[0107] The Na concentration in the resulting coarsely pulverized product was measured by ICP emission spectrometry under the above-mentioned measurement conditions. The results are shown in Table 2.

[0108] (3-3. Finely pulverized product) The coarsely pulverized product obtained above was dry-pulverized in the same manner as in Example 2 to obtain a finely pulverized product.

[0109] The Na concentration in the resulting finely pulverized product was measured by ICP emission spectrometry under the above-mentioned measurement conditions. The results are shown in Table 2.

[0110] (3-4. Frit) The finely pulverized product obtained above was classified in the same manner as in Example 2 to prepare frit.

[0111] The Na concentration in the resulting frit was measured by ICP atomic emission spectrometry under the above-mentioned measurement conditions. The results are shown in Table 2.

[0112] (3-5. Glaze Composition for Glass Lining) The frit obtained above was stirred in the same manner as in Example 2 to obtain a slurry-like glaze composition for glass lining.

[0113] The Na concentration in the obtained glass lining glaze composition was measured by ICP emission spectrometry under the measurement conditions described above. The results are shown in Table 2.

[0114] (3-6. Glass Lining Layer) A glass lining layer was obtained under the same conditions as in Example 2 using the glass lining glaze composition obtained above.

[0115] The Na concentration in the cover coat layer of the resulting glass lining layer was measured by ICP emission spectrometry under the measurement conditions described above. The results are shown in Table 2.

[0116] 4. Comparative Example 1 (4-1. Raw Material Blend) A raw material blend was prepared by mixing powders of each component in a mixer in a predetermined ratio to obtain a frit having the composition shown in Table 1. However, although the raw material powders of each component used in this raw material blend were commercially available products, they were not highly pure (95% by mass or less), and therefore the Na concentration was higher than in Example 1.

[0117] The Na concentration in the resulting raw material blend was measured by ICP atomic emission spectrometry under the measurement conditions described above. The results are shown in Table 2.

[0118] (4-2. Coarsely pulverized product) The raw material blend obtained above was melted and rapidly cooled in the same manner as in Example 1 to obtain a coarsely pulverized product.

[0119] The Na concentration in the resulting coarsely pulverized product was measured by ICP emission spectrometry under the above-mentioned measurement conditions. The results are shown in Table 2.

[0120] (4-3. Finely pulverized product) The coarsely pulverized product obtained above was dry-pulverized in the same manner as in Example 1 to obtain a finely pulverized product.

[0121] The Na concentration in the resulting finely pulverized product was measured by ICP emission spectrometry under the above-mentioned measurement conditions. The results are shown in Table 2.

[0122] (4-4. Frit) The finely pulverized product obtained above was classified in the same manner as in Example 1 to prepare a frit.

[0123] The Na concentration in the resulting frit was measured by ICP atomic emission spectrometry under the above-mentioned measurement conditions. The results are shown in Table 2.

[0124] (4-5. Glaze Composition for Glass Lining) A glaze composition for glass lining was obtained in the same manner as in Example 1 using the frit obtained above.

[0125] The Na concentration in the obtained glass lining glaze composition was measured by ICP emission spectrometry under the measurement conditions described above. The results are shown in Table 2.

[0126] (4-6. Glass Lining Layer) A glass lining layer was obtained under the same conditions as in Example 1 using the glass lining glaze composition obtained above.

[0127] The Na concentration in the cover coat layer of the resulting glass lining layer was measured by ICP emission spectrometry under the measurement conditions described above. The results are shown in Table 2.

[0128] 5. Comparative Example 2 (5-1. Raw Material Blend) A raw material blend was prepared by mixing powders of each component in a mixer in a predetermined ratio to obtain a frit having the composition shown in Table 1. However, although the raw material powders of each component used in this raw material blend were commercially available products, they were not particularly pure (98% by mass or less), and therefore the Na concentration was slightly higher than in Example 1. The Na concentration in this raw material blend was the same as that of the raw material blend used in the examples of Japanese Patent No. 5,191,384.

[0129] The Na concentration in the resulting raw material blend was measured by ICP atomic emission spectrometry under the measurement conditions described above. The results are shown in Table 2.

[0130] (5-2. Coarsely pulverized product) The raw material blend obtained above was melted and rapidly cooled in the same manner as in Example 1 to obtain a coarsely pulverized product.

[0131] The Na concentration in the resulting coarsely pulverized product was measured by ICP emission spectrometry under the above-mentioned measurement conditions. The results are shown in Table 2.

[0132] (5-3. Finely pulverized product) The coarsely pulverized product obtained above was dry-pulverized in the same manner as in Example 1 to obtain a finely pulverized product.

[0133] The Na concentration in the resulting finely pulverized product was measured by ICP emission spectrometry under the above-mentioned measurement conditions. The results are shown in Table 2.

[0134] (5-4. Frit) The finely pulverized product obtained above was classified in the same manner as in Example 1 to prepare a frit.

[0135] The Na concentration in the resulting frit was measured by ICP atomic emission spectrometry under the above-mentioned measurement conditions. The results are shown in Table 2.

[0136] (5-5. Glaze Composition for Glass Lining) A glaze composition for glass lining was obtained in the same manner as in Example 1 using the frit obtained above.

[0137] The Na concentration in the obtained glass lining glaze composition was measured by ICP emission spectrometry under the measurement conditions described above. The results are shown in Table 2.

[0138] (5-6. Glass Lining Layer) A glass lining layer was obtained under the same conditions as in Example 1 using the glass lining glaze composition obtained above.

[0139] The Na concentration in the cover coat layer of the resulting glass lining layer was measured by ICP emission spectrometry under the measurement conditions described above. The results are shown in Table 2.

[0140]

[0141] 6. Sodium Elution Test A sodium elution test was conducted by immersing each of the glass-lined round bars (without water washing) prepared in the Examples and Comparative Examples in 100 mL of 50°C pure water (resistivity at 25°C: 0.5 MΩ cm) contained in a PTFE container for 100 hours. After the test, the concentrations of Na, Li, Ba, Al, Ni, K, Ca, and Fe in the pure water were measured by inductively coupled plasma mass spectrometry (ICP mass spectrometry) using an Agilent Technologies Inc. (Model: Agilent 7900) to evaluate the amount of sodium elution. The results are shown in Table 3. The results in Table 3 indicate that in Examples 1 to 3, the amount of sodium elution could be reduced to 10 ppb by mass or less.

[0142]

[0143] 7. Relationship between Water Washing and Amount of Eluted Na (0 Number of Washes) The glass-lined round bars of Examples 2 and 3 were fabricated again. Without initial washing, a Na elution test was conducted on each glass-lined round bar. Ultrapure water was used instead of pure water for the Na elution test. This is because the amount of elution increases when ultrapure water is used, making the relationship between the number of water washes and the amount of eluted Na more apparent. Specifically, the Na elution test was conducted by immersing the bar in 100 mL of 50°C ultrapure water (resistivity at 25°C: 18.0 MΩ cm) placed in a PTFE container for 100 hours. After the test, the concentrations of Na, Li, Ba, Al, Ni, K, Ca, and Fe in the ultrapure water were measured by inductively coupled plasma mass spectrometry (ICP-MS) using an Agilent Technologies (Model: Agilent 7900) to evaluate the amount of eluted Na. The results are shown in Table 4.

[0144] (Three Cleanings) The glass-lined round bars of Examples 2 and 3 were again prepared. Each glass-lined round bar was then cleaned (first time) by immersing it in 170 mL of ultrapure water (resistivity at 25°C: 18.0 MΩ cm) at room temperature (25°C) for one hour. After the first cleaning, the ultrapure water used for cleaning was replaced with fresh ultrapure water, and a second cleaning was performed under the same conditions. After the second cleaning, the ultrapure water used for cleaning was replaced with fresh ultrapure water, and a third cleaning was performed under the same conditions. The glass-lined round bar was then removed and subjected to a sodium elution test using the same ultrapure water as above. The results are shown in Table 4.

[0145] (6th Washing) After washing 6 times using the same procedure as in 3rd washing, the glass-lined round bar was removed and subjected to the same sodium elution test using ultrapure water as above. The results are shown in Table 4.

[0146] (9th Washing Count) After washing 9 times using the same procedure as in washing 3, the glass-lined round bar was removed and subjected to the same sodium elution test using ultrapure water as above. The results are shown in Table 4.

[0147]

[0148] 8. Relationship between Quality of Cleaning Water and Amount of Eluted Na The glass-lined rods according to Example 2 were re-prepared in the number required for the following cleaning test. Each glass-lined rod was cleaned using different cleaning water and the number of cleanings as shown in Table 5. Each cleaning was performed by immersing the rod in 170 mL of cleaning water for one hour. The cleaning water was replaced with fresh cleaning water after each cleaning. After cleaning, the glass-lined rod was removed and subjected to a sodium elution test using ultrapure water as described in 7. Relationship between Water Washing and Amount of Eluted Na. The results are shown in Table 5. The cleaning waters shown in Table 5 are as follows: (Cleaning Water) Ultrapure water at 50°C (resistivity at 25°C: 18.0 MΩ cm) 1% hydrochloric acid at 80°C (to verify cleaning performance in acidic solutions) Pure water at 25°C (resistivity at 25°C: 1.0 MΩ cm)

[0149]

Claims

1. A frit containing SiO2 as its main component and having a Na concentration of 300 mass ppm or less as measured by ICP atomic emission spectrometry.

2. The frit according to claim 1, containing 40 to 75 mass% SiO2, 0 to 10 mass% ZrO2, 8 to 22 mass% R2O (wherein R represents one or more elements selected from the group consisting of Li, K, and Cs), and 1 to 7 mass% R'O (wherein R' represents one or more elements selected from the group consisting of Mg, Ca, Sr, and Ba).

3. The frit according to claim 1, wherein the Na concentration is 200 ppm by mass or less.

4. The frit according to claim 1, wherein the Na concentration is 100 ppm by mass or less.

5. The frit according to claim 1, wherein the median diameter is 1.5 to 20 μm when the cumulative particle size distribution on a volume basis is measured by laser diffraction.

6. Step 1: preparing a raw material blend containing SiO2 as a main component, the raw material blend having a Na concentration of 150 mass ppm or less as measured by ICP optical emission spectrometry; Step 2: melting the raw material blend placed in a crucible in a melting furnace and then rapidly cooling it to obtain a coarsely pulverized product, the conditions of which include selecting materials for constituting the crucible and the inner wall, ceiling, and hearth of the melting furnace so that the Na concentration in the coarsely pulverized product as measured by ICP optical emission spectrometry is 200 mass ppm or less; and Step 3: pulverizing the coarsely pulverized product to obtain a finely pulverized product, the conditions of which include selecting materials that come into contact with the coarsely pulverized product during pulverization so that the Na concentration in the finely pulverized product as measured by ICP optical emission spectrometry is 250 mass ppm or less. and step 4, a step of obtaining a frit by classifying the finely pulverized material, wherein the implementation conditions include selecting a material to come into contact with the finely pulverized material during classification so that the concentration of Na contained in the frit as measured by ICP atomic emission spectrometry is 300 mass ppm or less.

7. The manufacturing method according to claim 6, wherein the raw material blend prepared in step 1 contains 40 to 75 mass % SiO2, 0 to 10 mass % ZrO2, 8 to 22 mass % R2O (wherein R represents one or more elements selected from the group consisting of Li, K, and Cs), and 1 to 7 mass % R'O (wherein R' represents one or more elements selected from the group consisting of Mg, Ca, Sr, and Ba).

8. The manufacturing method according to claim 6, wherein the conditions for step 2 include selecting a material for constituting the crucible so that the concentration of Na contained in the coarsely pulverized product is 180 ppm by mass or less; the conditions for step 3 include selecting a material that comes into contact with the coarsely pulverized product during pulverization so that the concentration of Na contained in the finely pulverized product is 190 ppm by mass or less; and the conditions for step 4 include selecting a material that comes into contact with the finely pulverized product during classification so that the concentration of Na contained in the frit is 200 ppm by mass or less.

9. The manufacturing method according to claim 6, wherein the raw material blend prepared in step 1 has a Na concentration of 50 ppm by mass or less; step 2 has defined operating conditions including selecting a material constituting the crucible such that the Na concentration contained in the coarsely pulverized product is 80 ppm by mass or less; step 3 has defined operating conditions including selecting a material that comes into contact with the coarsely pulverized product during pulverization such that the Na concentration contained in the finely pulverized product is 90 ppm by mass or less; and step 4 has defined operating conditions including selecting a material that comes into contact with the finely pulverized product during classification such that the Na concentration contained in the frit is 100 ppm by mass or less.

10. A manufacturing method according to any one of claims 6 to 9, wherein the frit obtained in step 4 has a median diameter of 1.5 to 20 µm when the cumulative particle size distribution on a volume basis is measured by a laser diffraction method.

11. A glass lining glaze composition comprising the frit according to any one of claims 1 to 5 and a dispersion medium.

12. A method for forming a glass lining layer, comprising applying the glass lining glaze composition according to claim 11 to the surface of a substrate, and firing the glaze to form a glass lining layer.

13. The method for forming a glass lining layer according to claim 12, further comprising washing the surface of the fired glass lining layer with water.

14. A glass lining layer whose main component is SiO2 and whose Na concentration measured by ICP emission spectrometry is 300 mass ppm or less.

15. The glass lining layer according to claim 14, containing 40 to 75 mass% of SiO2, 0 to 10 mass% of ZrO2, 8 to 22 mass% of R2O (wherein R represents one or more elements selected from the group consisting of Li, K, and Cs), and 1 to 7 mass% of R'O (wherein R' represents one or more elements selected from the group consisting of Mg, Ca, Sr, and Ba).

16. The glass lining layer according to claim 14, wherein the concentration of Na is 200 ppm by mass or less.

17. The glass lining layer according to claim 14, wherein the concentration of Na is 100 ppm by mass or less.

18. A glass-lined product comprising the glass-lining layer according to any one of claims 14 to 17.