Carbon neutral product, flint-effect glass, and method for producing glass

Abstract

[Problem] The purpose of the present invention is to provide: a carbon neutral product which is formed using a recycled raw material recycled from materials other than glass, which minimizes the discharged amount of by-products such as carbon dioxide derived from primary raw materials, and which contains glass as a primary product; and a method for producing glass. [Solution] Provided is a carbon neutral product that is formed using a silicon-based raw material, a calcium-based raw material and a sodium-based raw material as primary raw materials, with at least one of the silicon-based raw material, calcium-based raw material and sodium-based raw material that serve as primary raw materials being recycled from materials other than glass. The carbon neutral product is characterized by containing: a primary product comprising glass formed by using a material containing a recycled material containing carbon derived from a material as at least a part of the primary product; and a by-product comprising a gas containing a carbon oxide which is derived from the primary raw materials and is not substantially newly produced.

Description

Carbon-neutral product, flint-like glass, and method for producing glass

[0001] The present invention relates to carbon-neutral products, flint-like glasses, and methods for making glasses.

[0002] Conventionally, glass bottles have been reused in the form of reuse or recycling, as disclosed in the following Non-Patent Document 1 and Non-Patent Document 2. Specifically, as disclosed in Non-Patent Document 1, glass bottles can be reused in a form called reuse, in which collected used bottles are washed and reused. Also, as disclosed in Non-Patent Document 2, glass bottles can be reused in a form called recycling, in which cullet obtained by crushing used bottles into small pieces is used to make new glass products such as bottles.

[0003] Glass Bottle 3R Promotion Council website (https: / / www.glass-3r.jp / learn / reuse.html)Glass Bottle 3R Promotion Council website (https: / / www.glass-3r.jp / learn / recycle.html)

[0004] As described above, in the case of crushing glass bottles into cullet and recycling it as a resource for forming glass products, used glass can be utilized to create new glass containers. However, in consideration of the effective utilization of limited resources, it is preferable to be able to utilize not only used glass but also materials other than glass as materials for manufacturing glass.

[0005] Furthermore, from the perspective of environmental issues such as global warming, which have become a concern in recent years, it is desirable to reduce emissions of gases consisting of carbon oxides, such as carbon dioxide and carbon monoxide, that are emitted during glass production. However, most of the glasses provided in the prior art are produced using main raw materials that include silica sand as a silicon-based material, soda ash as a sodium-based material, and limestone as a calcium-based material. Therefore, the glasses according to the prior art have the problem that gases consisting of carbon oxides, such as carbon dioxide, derived from the main raw materials are emitted as by-products during the production process.

[0006] Therefore, the present invention aims to provide a carbon-neutral product, flint-like glass, and a method for manufacturing glass, which is formed using recycled materials recycled from materials other than glass and contains glass as the main product while minimizing emissions of by-products such as carbon dioxide derived from the main raw materials.

[0007] (1) The carbon-neutral product of the present invention is formed using as main raw materials a silicon-based material containing a silicon component, a calcium-based material containing a calcium component, and a sodium-based material containing a sodium component, and at least one of the silicon-based material, calcium-based material, and sodium-based material constituting the main raw materials is recycled using a material other than glass, and is characterized in that it comprises a main product consisting of glass formed by using a material that contains, as at least a part, a recycled material containing carbon derived from the material, and a by-product consisting of a gas containing carbon oxides that is generated from the main raw materials and is not substantially newly generated.

[0008] By providing the carbon-neutral product of the present invention as described above in (1), it is possible to provide glass that uses, as at least a part of the main raw material, a recycled material recycled using a material other than glass. Furthermore, in the carbon-neutral product of the present invention, the gas generated as a by-product derived from the main raw material contains carbon oxides, but is not substantially newly generated. This allows the carbon-neutral product of the present invention to minimize the generation of gases containing carbon oxides, such as carbon dioxide and carbon monoxide, that are substantially newly generated during the production of the main product, glass.

[0009] (2) The carbon-neutral product of the present invention may be characterized in that the silicon-based material is partly or entirely made of recycled material regenerated from plant-derived material.

[0010] By making the carbon-neutral product of the present invention as described above in (2), it is possible to obtain the main product, glass, using recycled materials recycled from plant-derived materials. Furthermore, because the carbon-neutral product of the present invention uses plants as the raw material for the recycled materials, the carbon oxides such as carbon dioxide reduced by the plants are offset by the carbon oxides such as carbon dioxide generated when obtaining the main product, glass, and from the perspective of carbon neutrality and carbon offset, it is possible to substantially suppress the generation of gases containing newly generated carbon oxides.

[0011] (3) The carbon-neutral product of the present invention may be characterized in that a silicate containing a calcium component is used as part or all of the calcium-based material.

[0012] By making the carbon-neutral product of the present invention as described above in (3), the generation of gases consisting of carbon oxides such as carbon dioxide can be suppressed to the extent that silicate is used as a calcium component, compared to when limestone is used as a calcium-based material as in the prior art.

[0013] (4) The carbon-neutral product of the present invention may be characterized in that a silicate containing a sodium component is used as part or all of the sodium-based material.

[0014] By making the carbon-neutral product of the present invention as described above in (4), the generation of gases consisting of carbon oxides such as carbon dioxide can be suppressed to the extent that silicate is used as a material containing sodium components, compared to when soda ash is used as a sodium-based material as in the prior art.

[0015] (5) The flint-like glass of the present invention is glass having flint properties, and is formed using glass raw materials including a silicon-based material containing a silicon component, a calcium-based material containing a calcium component, a sodium-based material containing a sodium component, and an iron-based material containing an iron component, wherein the silicon-based material is recycled using a material other than glass and is formed by using a material that contains, at least in part, a recycled material containing carbon derived from the material, and the calcium-based material and the sodium-based material are formed by using a material that contains, at least in part, a silicate containing a calcium component and a silicate containing a sodium component, respectively, and the iron-based material is contained in the glass raw materials in an amount ranging from 0.026 mass% to 0.35 mass%.

[0016] By providing the flint-toned glass of the present invention as described above in (5), it is possible to provide flint-toned glass having flint attributes while using recycled materials recycled from materials other than glass as at least a part of the main raw materials. Furthermore, in the flint-toned glass of the present invention, gases generated as by-products derived from the main raw materials during the manufacturing process contain carbon oxides, but these gases are not essentially newly generated. This allows the flint-toned glass of the present invention to minimize the generation of gases containing carbon oxides, such as carbon dioxide and carbon monoxide, that are essentially newly generated during the manufacturing process.

[0017] (6) The method for producing glass of the present invention includes a frit preparation step of preparing frits containing, as main raw materials, a silicon-based material containing a silicon component, a calcium-based material containing a calcium component, and a sodium-based material containing a sodium component, and a glass-forming step of obtaining glass by using the frits to create a carbon-neutral product having glass as a main product, wherein the frit preparation step is a step of preparing, as the main raw material, at least one of the silicon-based material, the calcium-based material, and the sodium-based material that is recycled using a material other than glass and that contains, as at least a part of, a recycled material containing carbon derived from the material, and the glass-forming step is a step of obtaining the glass by using the main raw material to create, as the carbon-neutral product, a main product consisting of the glass and a by-product consisting of a gas containing carbon oxides that is derived from the main raw material and is not substantially newly generated.

[0018] By employing the method for producing glass according to the present invention as described above in (5), it is possible to produce glass using, as at least a part of the main raw material, a recycled material recycled using a material other than glass. Furthermore, in the method for producing glass according to the present invention, gases produced as by-products derived from the main raw materials contain carbon oxides, but are not substantially newly produced. As a result, the method for producing glass according to the present invention can minimize the generation of gases containing carbon oxides such as carbon dioxide and carbon monoxide that are substantially newly produced in conjunction with the production of the main product, glass.

[0019] (7) The method for producing glass of the present invention may be characterized in that the silicon-based material is partly or entirely made of a recycled material recycled from a plant-derived material.

[0020] By employing the method for producing glass of the present invention as described above in (7), it is possible to obtain glass as a main product using recycled materials recycled from plant-derived materials. Furthermore, because the method for producing glass of the present invention uses plants as raw materials for the recycled materials, the carbon dioxide and other carbon oxides reduced by the plants are offset by the carbon dioxide and other carbon oxides generated during the production of glass as a main product, and from the perspectives of carbon neutrality and carbon offset, it is possible to substantially suppress the generation of gases containing newly generated carbon oxides.

[0021] (8) The method for producing glass of the present invention may be characterized in that a silicate containing a calcium component is used as part or all of the calcium-based material.

[0022] By using the method for producing glass of the present invention as described above in (8), compared to the prior art where limestone is used as a calcium-based material, the generation of gases consisting of carbon oxides such as carbon dioxide can be suppressed to the extent that silicate is used as a material containing a calcium component.

[0023] (9) The method for producing glass of the present invention may be characterized in that a silicate containing a sodium component is used as part or all of the sodium-based material.

[0024] By using the method for producing glass of the present invention as described above in (9), generation of gases consisting of carbon oxides such as carbon dioxide can be suppressed to the extent that silicate is used as a material containing a sodium component, compared to the prior art in which soda ash is used as a sodium-based material.

[0025] (10) In the glass manufacturing method of the present invention, preferably, in the glass frit preparation step, the glass frits prepared include an iron-based material containing an iron component in a range of 0.026 mass% to 0.35 mass% inclusive, a silicon-based material that is recycled using a material other than glass as part or all of the silicon-based material, a silicate containing a calcium component as part or all of the calcium-based material, and a silicate containing a sodium component as part or all of the sodium-based material.

[0026] By adopting the method for producing glass of the present invention as described above in (10), for example, when glass is produced using silica sand as the silicon-based material and carbonates as the calcium-based material and sodium-based material, it is possible to produce flint-like glass having the attributes of flint while still containing the iron component in an amount sufficient to produce amber glass.

[0027] According to the present invention, it is possible to provide a carbon-neutral product, a flint-like glass, and a method for producing glass that solve the above-mentioned problems.

[0028] 1 is a photograph showing the results of an investigation into the color exhibited in the early stages of melting for RK1 according to an example of the present invention and CH1 according to a comparative example. FIG. 2 is a photograph showing the results of an investigation into the color exhibited in the early stages of melting for RK2 according to an example of the present invention and CH2 according to a comparative example. FIG. 3 is a photograph showing the results of an investigation into the color exhibited in the early stages of melting for RK3 according to an example of the present invention and CH3 according to a comparative example. FIG. 4 is a photograph showing the results of an investigation into the color exhibited in the early stages of melting for RK4 according to an example of the present invention and CH5 according to a comparative example. FIG. 5 is a photograph showing the appearance of glasses according to RK1-A, RK1-B, RK1-C, RK1-D, CH1-A, CH1-B, CH1-C, and CH1-D according to examples of the present invention. (a) and (b) are photographs showing the appearance of conventionally known amber glasses 1 and 2, respectively; (c) and (d) are photographs showing the appearance of samples according to CH1-2 and RK4-2, respectively; and (e) and (f) are photographs showing the state of the glass samples according to CH1-2 and RK4-2 attached to a crucible after melting. This is a graph showing the results of examining the transmission spectra of samples according to conventionally known amber glasses 1 and 2, CH1-2, and RK4-2. This is a graph showing the results of measuring the transmission spectra to evaluate amber absorption for glasses according to RK1 to RK4 according to examples of the present invention. This is a graph showing the results of measuring the transmission spectra to evaluate amber absorption for glasses according to CH1 to CH4 according to comparative examples. This is a graph showing the results of deriving the absorption intensity of amber color for RK1 to RK4 according to examples of the present invention. This is a graph showing the results of deriving the absorption intensity of amber color for CH1 to CH4 according to comparative examples. 1 is a graph plotting the results of amber absorption intensities derived for glasses according to RK1 to RK4 and CH1 to CH4 based on the formula described in [Equation 1]. (a) to (c) are photographs of the appearance of samples according to CH1-3 to CH1-5, (d) to (e) are photographs of the appearance of samples according to RK4-3 to RK4-5, (g) is a photograph showing the appearance of a conventionally known amber glass, and (h) and (i) are photographs showing the state of glass samples according to RK4-3 and RK4-2, respectively, adhered to a crucible after melting.

[0029] Hereinafter, a carbon-neutral product and a method for producing glass according to one embodiment of the present invention will be described.

[0030] <<Regarding Carbon-Neutral Products>> Carbon-neutral products are composed of multiple products including a main product and by-products. The carbon-neutral product of this embodiment includes glass as the main product. The carbon-neutral product of this embodiment also includes by-products such as gases containing carbon oxides, such as carbon dioxide and carbon monoxide, that are generated during the production of the glass, which is the main product.

[0031] The glass, which is the main product, is formed using glass raw materials including a plurality of main raw materials. In this embodiment, a plurality of materials including a silicon-based material, a calcium-based material, and a sodium-based material are used as the main raw materials, and the glass, which is the main product, is formed by using these main raw materials.

[0032] Silicon-based materials are materials containing silicon components. Silicon-based materials used as the main raw material include silicon dioxide (SiO ) recycled from materials other than glass as part or in whole. ２ Specifically, examples of silicon-based materials that can be used include recycled materials derived from grains such as rice husks, corn husks, and peanut husks (grain-derived recycled materials), recycled materials derived from plants such as plankton, seaweed, and diatoms (plant-derived recycled materials), recycled materials derived from animals such as birds like chickens, mammals like cows and pigs, fish, and shellfish (animal-derived recycled materials), and recycled materials derived from steel slag (calumite), zeolite, and construction materials (calcium silicate) (industrially-derived recycled materials), which are recycled materials recycled from materials other than glass that contain silicon components.

[0033] Calcium-based materials are materials containing calcium components. The calcium-based materials used as the main raw material contain, in part or in whole, CaCO ３ (Calcium carbonate: limestone) and Ca(HCO ３ ) ２Although carbonates such as calcium bicarbonate (calcium bicarbonate) can be used, it is preferable to use silicates containing calcium as a part or all of the calcium component. ３ (Monoclinic calc-silicate: wallomnite), Ca ２ SiO ４ (β-calcium dioxide: Rahnite), Ca ３ SiO ５ (calcium silicate trioxide: alite), 3CaO.SiO ２ (calcium silicate trioxide: alite), Ca ３ SiO ５ (calcium silicate trioxide: alite), CaO.SiO ２ (calcium silicate monoxide: berite), Ca ２ SiO ４ (β-calcium dioxide: Rahnite), 3CaO.2SiO ２ (calcium dioxide: cellulite), Ca ３ Si ２ O ７ (disilicate trioxide: rankinite), CaO.SiO ２ Calcium silicate such as calcium silicate (berite) can be suitably used.

[0034] In addition, calcium-based materials include calcium-based materials derived from living organisms such as shells, dicotyledonous plants such as those of the Solanaceae family, shells (turban shells, scallops), fragments of luminous shells using the outer surface of shells, residues from processing the inner and outer surfaces of shells), buttons (decorative items) made from shells, crustacean shells, and food waste (chicken egg shells, animal and fish bones), CO ２ (CO such as CCS, CCUS, BEC, BECCS, DAC, DACCS) ２ Recycled materials (CaCO ３ Recycled materials recycled from materials other than glass containing calcium components, such as calcium-based materials of industrial origin (e.g., glass-based materials), can be suitably used.

[0035] A sodium-based material is a material that contains sodium. ２ CO ３(sodium carbonate: soda ash) and NaHCO ３ Although carbonates such as sodium bicarbonate can be used, it is preferable to use silicates containing sodium as a part or all of the sodium component. ２ SiO ３ (sodium metasilicate) and Na ４ SiO ４ , Na ２ Si ２ O ５ , Na ２ Si ４ O ９ Sodium silicates (sodium silicate) such as the above can be suitably used.

[0036] In addition, sodium-based materials include waste materials (Na ２ SO ４ , NaHSO ４ , NaHSO ３ , Na ２ SO ３ , Na ２ S ２ O ４ , Na ２ S ２ O ３ ), CO ２ (CO such as CCS, CCUS, BEC, BECCS, DAC, DACCS) ２ Recycled materials (Na) regenerated from waste generated by recovery technology ２ CO ３ , NaHCO ３ ) and the like, recycled materials recycled from materials other than glass containing sodium components can be suitably used.

[0037] As described above, recycled materials can be used as part or all of the silicon-based, calcium-based, and sodium-based materials that constitute the main raw materials. Recycled materials are not obtained from glass, as in the case of cullet, but are recycled using materials other than glass. It is preferable to use recycled materials that contain carbon derived from the raw materials. This allows the carbon contained in the recycled materials to be used as part or all of the carbon used in glass production.

[0038] <Glass Manufacturing Method> Next, a method for manufacturing glass according to the present embodiment will be described. The method for manufacturing glass according to the present embodiment is roughly divided into two steps: a glass raw material preparation step and a glass forming step. Each step will be described in more detail below.

[0039] [Glass frit preparation step] The glass frit preparation step is a step of preparing a glass frit containing, as main raw materials, a silicon-based material containing a silicon component, a calcium-based material containing a calcium component, and a sodium-based material containing a sodium component. In the glass frit preparation step, at least one of the silicon-based material, the calcium-based material, and the sodium-based material is prepared as a main raw material by recycling using a material other than glass and including, as at least a part of, a recycled material containing carbon derived from the material.

[0040] Here, the above-mentioned recycled materials can be prepared by any appropriate method, but when preparing recycled materials derived from grains (grain-derived recycled materials), such as recycled materials derived from rice husks, they can be prepared by the grain-derived recycled material manufacturing method exemplified below.

[0041] The grain-derived recycled material production method is a production method that includes, as part or all of its production process, a step of obtaining grain-derived recycled material containing the silicon component contained in the grain-based raw material as a grain-derived silicon component (grain-derived recycled material acquisition step) by heat-treating the grain-based raw material. The grain-derived recycled material production method can simplify the grain-derived recycled material acquisition step by performing the heat treatment of the grain-based raw material in a single stage. Furthermore, the grain-derived recycled material production method can reduce the content of carbon components generated by the heat treatment of the grain-based raw material by performing the heat treatment of the grain-based raw material in multiple stages.

[0042] The grain-derived recycled material obtaining process may be, for example, a process in which heat treatment is performed in two stages: a primary heating process and a secondary heating process. Furthermore, the grain-derived recycled material obtaining process may include heat-treating a grain-derived raw material consisting of grains or grain-derived substances by direct or indirect heating in the primary heating process to form a primary heated product, and then indirectly heating the primary heated product in the secondary heating process. Direct heating of the grain-derived raw material may be performed, for example, by igniting and burning the grain-derived raw material in a combustion furnace. Furthermore, indirect heating of the grain-derived raw material may be performed, for example, by using a heat treatment device such as a rotary kiln, with the conditions set so that the furnace temperature reaches a predetermined temperature. This allows organic matter contained in the grain-based raw material to be thermally decomposed in the primary heating process to obtain a primary heated product containing silicon oxide. Even if organic matter remains in the primary heated product without being thermally decomposed, further heat treatment in the secondary heating process allows the organic matter to be thermally decomposed and obtained as silicon oxide. Furthermore, by setting the temperature for the heat treatment in the secondary heating step to a temperature equal to or higher than the combustion temperature of the carbon components contained in the primary heated material, the carbon components contained in the primary heated material can be removed, thereby reducing the content of the carbon components, increasing the purity of the silicon oxide, and suppressing the variation in the content of the carbon components that occurs between lots.

[0043] The glass frit prepared in the glass frit preparation step can be composed of only the above-mentioned main raw material, or can be composed of the main raw material plus auxiliary raw materials.２ O ３ (alumina), Fe ２ O ３ (iron (III) oxide), TiO ２ (titanium oxide), MgO (magnesium oxide), K ２ O (potassium oxide), MnO (manganese (II) oxide), BaO (barium oxide), CrO ２ (chromium (IV) oxide), Se (metallic selenium), Pt (platinum chloride, platinum), Au (gold chloride, gold), Ag (silver chloride, silver nitrate, silver), H ３ BO ３ (boric acid), K ２ CO ３ (potassium oxide), ZnO (zinc oxide), As(OH) ３ (arsenous acid), Sb ２ O ３ (antimony oxide), CaF ２ (Calcium fluoride), Na ２ SO ４ (sodium sulfate), NaNO ３ (sodium nitrate), C (carbon black), etc. can be used.

[0044] In the glass frit preparation step, glass frits can be prepared in the same manner as in a glass manufacturing step that uses silica sand, limestone, etc. as main raw materials. Specifically, in the glass frit preparation step, the standard blending ratio is set to 69% to 75% by weight of silicon-based material, 10% to 17% by weight of calcium-based material, and 5% to 15% by weight of sodium-based material, and the blending ratio of each component is varied depending on the properties of the glass to be manufactured (e.g., viscosity, thermal expansion coefficient, glass transition temperature, melting point, specific gravity, transmittance, color tone, etc.), to thereby blend the glass frits.

[0045] [Glass-forming step] The glass-forming step is a step of obtaining glass by producing a carbon-neutral product having glass as a main product using glass frits including the main raw materials prepared in the above-mentioned glass frit preparation step. In the glass-forming step, the carbon-neutral product is produced by producing a main product made of glass and a by-product made of a gas containing carbon oxides that is derived from the main raw materials and is not substantially newly produced.

[0046] In the glass-forming process, glass frits containing the main raw materials prepared as described above are introduced into a melting furnace and melted. The melting furnace used in the glass-forming process can be, for example, a large-scale glass melting furnace such as a Siemens-type continuous furnace, or a small-scale tank furnace such as an optical furnace or a hand-blowing furnace. Melting the glass frits in the melting furnace produces a carbon-neutral product. That is, glass can be obtained as the main product by removing the melt obtained by melting the glass frits in the melting furnace from the melting furnace. The glass obtained as the main product can be formed into a shape such as a glass bottle or a glass plate, and then slowly cooled to produce a glass product. Melting the glass frits in the melting furnace can also produce by-products, such as gases containing carbon oxides such as carbon dioxide and carbon monoxide, which are generated during the production of the main product, glass.

[0047] <<Regarding Flint-Tone Glass and a Method for Producing Flint-Tone Glass>> The flint-tone glass of this embodiment is flint-tone glass (glass having flint attributes) with a low amber color concentration. The flint-tone glass can be obtained as glass that constitutes the main product in the carbon-neutral product described above. The flint-tone glass can be produced by using glass raw materials that contain, as main raw materials, a silicon-based material containing a silicon component, a calcium-based material containing a calcium component, and a sodium-based material containing a sodium component, as well as an iron-based material containing an iron component.

[0048] The glass frit for flint-style glass (hereinafter also referred to as "flint-style glass frit") is a silicon-based material recycled using a material other than glass, and contains at least a portion of a recycled material containing carbon derived from the material. The recycled material used for the flint-style glass frit can be the same as the examples of the glass frit for the carbon-neutral product described above. The calcium-based material and the sodium-based material used for the flint-style glass frit are silicates containing a calcium component and silicates containing a sodium component, respectively. These silicates can also be the same as the examples of the glass frit for the carbon-neutral product.

[0049] The flint-like glass raw material contains, as the main raw material, a plurality of materials including a silicon-based material, a calcium-based material, and a sodium-based material, as well as an iron-based material containing an iron component, similar to the glass raw material for the carbon-neutral product described above. ２ O ３ (iron(III) oxide / hematite), Fe ３ O ４ It is preferable that the flint-style glass raw material contains one or more of iron-based materials such as iron (II, III) oxide / magnetite, FeO (iron (II) oxide), etc. Although it is possible to separately prepare and mix these substances as the iron-based material, it is also possible to utilize iron contained as an impurity in rice husks, silica sand, limestone, or glass cullet as a supply source for part or all of the iron-based material. It is also preferable that the iron-based material used in the flint-style glass raw material is contained in the flint-style glass raw material in a range of 0.026 mass% or more and 0.35 mass% or less.

[0050] The method for producing flint-like glass may be the same as the method for producing glass as the main product of the carbon-neutral product described above. That is, in the method for producing flint-like glass, the above-mentioned flint-like glass raw material is prepared in a glass raw material preparation step, and glass is formed using this in a glass forming step.

[0051] Next, an example of a carbon-neutral product and a method for manufacturing glass according to one embodiment of the present invention will be described. In this example, four samples consisting of RK1 to RK4 were prepared as examples of the main product of the carbon-neutral product, as shown in Table 1 below. RK1 to RK4 were formed by selecting the silicon-based material, calcium-based material, and sodium-based material as the main raw materials, respectively, as shown in Table 1, and then obtaining glass as the main product of the carbon-neutral product using the glass manufacturing method according to the above embodiment.

[0052] Specifically, all of the samples RK1 to RK4 use rice husk-derived recycled material (grain-derived recycled material) as the silicon-based material that constitutes the main raw material. Therefore, RK1 to RK4 use silicon dioxide (SiO ２ ) and carbon (C) derived from rice husks. RK1 contains CaCO3 as the main calcium-based material. ３ (Calcium carbonate: limestone), sodium component is Na ２ CO ３ RK2 is made using calcium carbonate (sodium carbonate: soda ash). RK2 uses CaCO3 as the main calcium-based material. ３ (Calcium carbonate: limestone), sodium component is Na ２ SiO ３ RK3 is made using calcium-based material, CaSiO (sodium metasilicate). ３ (Monoclinic calc-silica: wallomnite), sodium component is Na ２ CO ３ RK4 is made using calcium carbonate (sodium carbonate: soda ash). The main raw material of RK4 is calcium-based material, CaSiO ３ (Monoclinic calc-silica: wallomnite), sodium component is Na ２ SiO ３ The glass compositions of RK1 to RK4 are shown in Table 1.

[0053] In this example, four samples, CH1 to CH4, were prepared as comparative examples. The glasses for CH1 to CH4 were formed by selecting the silicon-based material, calcium-based material, and sodium-based material as the main raw materials as shown in Table 1, and by the same manufacturing method as for RK1 to RK4.

[0054] Specifically, all of the samples CH1 to CH4 were made from Chemerton silica sand (SiO ２ Therefore, CH1 to CH4 are formed using silicon-based materials that do not contain carbon (C) as the main raw material. CH1 uses CaCO3 as the main raw material. ３ (Calcium carbonate: limestone), sodium component is Na ２ CO ３ CH2 is made using calcium carbonate (sodium carbonate: soda ash). The main raw material is calcium-based material, CaCO ３ (Calcium carbonate: limestone), sodium component is Na ２ SiO ３ CH3 is made using calcium-based material CaSiO (sodium metasilicate). ３ (Monoclinic calc-silica: wallomnite), sodium component is Na ２ CO ３ CH4 is made using calcium carbonate (sodium carbonate: soda ash). The main raw material is calcium-based material, CaSiO ３ (Monoclinic calc-silica: wallomnite), sodium component is Na ２ SiO ３ The glass compositions of CH1 to CH4 are shown in Table 1.

[0055]

[0056] In the samples RK1 to RK4 and CH1 to CH4 described above, the recycled material derived from rice husks and the silica sand produced in Chemerton were glass raw materials containing SiO ２In each of the above samples, Na was added as a source of ２ SiO ３ (sodium metasilicate) and Na ２ CO ３ (sodium carbonate: soda ash) are glass raw materials containing Na ２ In each of the above samples, CaCO ３ (Calcium carbonate: limestone) and CaSiO ３ (Monoclinic calc-silica: wallomnite) was added to the glass raw materials as a CaO source. ２ SO ４ (Miuranium salt) was added to the glass raw material as a sulfur source. ２ SO ４ The blending amount (content) of SiO ２ The blending amount of 1 ton (1t-SiO ２ ) to Na ２ SO ４ The blending ratio ([Na ２ SO ４ ] / [SiO ２ ]) is 15 kg / t-SiO ２ In this example, carbon was added as a reducing agent, and experiments were carried out by changing the addition rate of the raw material as an index of the degree of reduction. In addition, in the samples according to CH1 to CH4 described above, the amount of Fe was set within a range that is assumed to make the glass obtained by the above manufacturing method colorless and transparent (flint). ２ O ３ In the samples RK1 to RK4 described above, as in the samples CH1 to CH4, the same amount of Fe as that used in the production of conventionally known flint glass (same order of magnitude) was added. ２ O ３ was added.

[0057] The above-mentioned samples RK1 to RK4 and CH1 to CH4 are all made of raw material blends designed for flint glass. In particular, the Fe content in the glass raw materials of the samples RK1 to RK4 and CH1 to CH4 is ２ O ３The content of Fe in the glass raw material when producing amber glass ２ O ３ The content of Na, which functions as an oxidizing agent, is set to a value sufficiently smaller (small at an order of magnitude) than the content of Na (approximately 0.22 mass % in the example described later). ２ SO ４ The blending amount (content) of (Miuranium salt / sodium sulfate) is as described above. ２ The blending amount of 1 ton (1t-SiO ２ ) to Na ２ SO ４ The blending ratio ([Na ２ SO ４ ] / [SiO ２ ]) is 15 kg / t-SiO ２ In addition, among the glass raw materials, the blending amount (content) of carbon (C) which functions as a reducing agent is set to be the same as that of C and Na unless otherwise specified in the following description. ２ SO ４ The C content is [C] / ([C]+[Na ２ SO ４ ]) was set to 6.25 mass%.

[0058] The colors exhibited by the above-mentioned samples RK1 to RK4 and CH1 to CH4 in the early stages of melting were examined. The results are shown in Figures 1 to 4. Figures 1 to 4 show the colors of the samples RK1 to RK4 and CH1 to CH4 at 10, 20, and 30 minutes after the start of melting.

[0059] Figure 1 compares RK1 and CH1. Both RK1 and CH1 contain CaCO3 as a calcium-based material. ３ (Calcium carbonate: limestone), sodium-based material Na ２ CO ３ They share the commonality of using sodium carbonate (soda ash), but RK1 uses recycled rice husk-derived silicon material (grain-derived recycled material), while CH1 uses silica sand (SiO ２When comparing the colors of these samples at the initial stage of melting, it was found that CH1, which uses recycled material derived from rice husks, is almost colorless and transparent (flint), while RK1 exhibits a stronger brown (amber) hue than CH1.

[0060] Figure 2 compares RK2 and CH2. Both RK2 and CH2 contain CaCO3 as a calcium-based material. ３ (Calcium carbonate: limestone) is used, and Na is used as the sodium component. ２ SiO ３ RK2 and CH2 have in common that they use sodium metasilicate (SiO ). On the other hand, RK2 uses recycled rice husk-derived silicon-based material (grain-derived recycled material), while CH2 uses silica sand (SiO ) from Chemerton. ２ RK2 and CH2 were different in that they used the same dye. RK2 and CH2 had a stronger brown (amber) hue than the above-mentioned RK1 and CH1, respectively.

[0061] Figure 3 compares RK3 and CH3. Both RK3 and CH3 contain CaSiO as a calcium-based material. ３ (Monoclinic limestone: wallomnite) is used, and Na is used as the sodium component. ２ CO ３ RK3 and CH3 have in common that they use sodium carbonate (soda ash). On the other hand, RK3 uses recycled rice husk-derived silicon material (grain-derived recycled material), while CH3 uses silica sand (SiO ２ RK3 had a slightly stronger brown (amber) hue than RK1. On the other hand, CH3 was almost colorless and transparent (flint) like CH1.

[0062] Figure 4 compares RK4 and CH4. Both RK4 and CH4 contain CaSiO as a calcium-based material. ３ (Monoclinic limestone: wallomnite) is used, and Na is used as the sodium component. ２ SiO３ RK4 and CH4 have in common the fact that they use silicate (sodium metasilicate). That is, RK4 and CH4 use both calcium-based and sodium-based materials. RK3 uses recycled material derived from rice husks (grain-derived recycled material) as the silicon-based material, while CH3 uses silica sand (SiO ２ RK4 and CH4 were both nearly colorless and transparent (flint) like CH1.

[0063] As described above, the test was conducted to examine the color exhibited by the samples RK1 to RK4 and CH1 to CH4 at the initial stage of melting. ２ It was found that by using rice husk-derived recycled material (grain-derived recycled material) as the source, a strong brown (amber) color was expressed. ２ When silicate is used as either the O or CaO source and carbonate is used as the other, a brown (amber) color is developed. ２ It has been found that when silicic acid is used as both the O source and the CaO source, it is difficult to develop a brownish-brown (amber) color, and the glass tends to become colorless and transparent (flint).

[0064] Here, Fe contained in the glass raw material ２ O ３ Iron oxide (Iron oxide) has the property of giving glass a green or brown tint. Therefore, when producing amber glass, Fe, as well as C (Carbon), is used. ２ O ３ As for iron oxide (iron oxide), its blending amount (content) in glass raw materials is sometimes adjusted as it functions as an amber coloring factor. On the other hand, as mentioned above, the inventors have made extensive studies and found that SiO ２ The source is made from recycled rice husks (grain-derived recycled materials), and Na ２ Under the condition that silicic acid is used as both the O source and the CaO source, SiO ２ Silica sand is used as the source, and Na ２The Fe content of the amber glass is determined by using carbonates as both the O and CaO sources. ２ O ３ The amount of Fe (iron oxide) blended (0.20 to 0.35 mass%) is the same as ２ O ３ It has been found that even when the glass contains more than 0.026 mass % and less than 0.35 mass %, it is difficult to achieve a brown (amber) color, and that a flint-like glass (glass having flint properties) can be obtained even with a blending amount (content) in the range of 0.026 mass % or more and 0.35 mass % or less.

[0065] Based on this finding, in this example, as shown in Table 2 below, among RK1 to RK4 and CH1 to CH4, CH1 and RK4 from which flint glasses were obtained were used as the references, and compared to CH1 and RK4, the C (carbon) content was about the same (same order) but the Fe content was ２ O ３ Samples with an order of magnitude higher blending amount (content) of iron oxide were prepared as CH1-2 and RK4-2 in the same manner as CH1 and RK4, and the color of the glass of these samples was examined. ２ O ３ The blending amount (content) of (iron oxide) was 0.0257 mass% and 0.0141 mass%, respectively, while the Fe ２ O ３ The amount (content) of iron oxide was set to 0.22 mass%, which is within the above-mentioned range of 0.026 mass% to 0.35 mass% (0.20 mass% to 0.35 mass%). Furthermore, conventionally known amber glasses 1 and 2 were prepared as comparative examples.

[0066]

[0067] As shown in FIG. 6, the sample according to CH1-2 exhibited a deep brown (amber) color, similar to the conventionally known amber glasses 1 and 2 prepared as comparative examples. Considering that the sample according to CH1 is a flint glass, the 0.22 mass% Fe ２ O ３It can be seen that the incorporation of SiO (iron oxide) has the effect of increasing the intensity of the amber color. ２ Silica sand is used as the source, and Na ２ The Fe content of the amber glass is determined by using carbonates as both the O and CaO sources. ２ O ３ It can be seen that the range of 0.026 mass% to 0.35 mass% (0.20 mass% to 0.35 mass%) is appropriate as the blending amount (content) of (iron oxide).

[0068] In contrast, the sample according to RK4-2 (see FIG. 6(d)) had a lighter amber color than the sample according to CH1-2 (see FIG. 6(c)), and was flint-like (having flint attributes). ２ While using recycled materials derived from rice husks (grain-derived recycled materials) as a source of sodium ２ When silicic acid was used as both the O source and the CaO source, 0.22 mass% Fe was added, as in CH1-2. ２ O ３ It has been found that even when SiO 2 (iron oxide) is blended, the amber color density of the glass is prevented from increasing, and flint-like glass (glass having the attributes of flint) can be produced. Furthermore, the transmission spectra of samples according to the conventionally known amber glasses 1 and 2, CH1-2, and RK4-2 were examined, and the graph shown in FIG. 7 was obtained. From these results, it was found that the transmittance of the sample according to RK4-2 in the vicinity of 410 nm, which is the absorption wavelength of amber, is higher than that of the samples according to amber glasses 1 and 2 and CH1-2. This shows that the sample according to RK4-2 is flint-like glass (glass having the attributes of flint). From these results, it can be seen that SiO 2 ２ The source is made from recycled rice husks (grain-derived recycled materials), and Na ２ Under the condition that silicic acid is used as both the O source and the CaO source, Fe ２ O ３It has been demonstrated that by setting the blending amount (content) of (iron oxide) to 0.20 to 0.35 mass%, it is possible to obtain flint-like glass that is less likely to develop a brown (amber) color and has the attributes (characteristics) of flint.

[0069] In addition, in consideration of the findings obtained based on the test results for CH1, CH1-2, RK4, and RK4-2 described above, Fe was found to be lower than that of RK1 and CH4. ２ O ３ The samples CH1-3 to CH1-5 and RK4-3 to RK4-5 were prepared by changing the C (carbon) content compared to RK1 and CH4, and the amount of iron oxide (iron oxide) compounded (content) was an order of magnitude larger. ２ O ３ The content of iron oxide is unified within the range of 0.026 mass% or more and 0.35 mass% or less (0.20 mass% or more and 0.35 mass% or less) as described above. Specifically, CH1-3 to CH1-5 and RK4-3 to RK4-5 all contain Fe ２ O ３ The samples were prepared with a uniform blending amount (content) of 0.275 mass% of iron oxide (iron oxide). CH1-3 to CH1-5 were prepared with blending amounts (contents) of 0.195 mass%, 0.234 mass%, and 0.312 mass%, respectively, of carbon (C). RK4-3 to RK1-5 were prepared with blending amounts (contents) of 0.312 mass%, 0.525 mass%, and 0.700 mass%, respectively, of carbon (C). Photographs of the appearances of these samples are shown in FIG. 13.

[0070] As can be seen from FIG. ２ Using silica sand as a source, ２ Compared with CH1-3 to CH1-5, which used carbonates as the O source and CaO source, ２ While using recycled materials derived from rice husks (grain-derived recycled materials) as a source of sodium ２ It was found that RK4-3 to RK4-5, which used silicic acid as both the O source and the CaO source, gave light-colored flint-like glasses. ２Using silica sand as a source, ２ Sample CH1-5, which used carbonates as the O source and CaO source, produced amber-colored glass, while RK4-3, which contained the same amount of C (carbon) as CH1-5, produced a colorless, highly transparent flint-colored glass. ２ Using silica sand as a source, ２ It has been discovered that the use of carbonates as the O source and CaO source reduces the coloring effects of iron-based components and carbon-based components, which are coloring factors in glass production, and functions extremely effectively in producing amber-colored glass.

[0071] There are various reasons why the above results are obtained. For example, SiO ２ While using recycled materials derived from rice husks (grain-derived recycled materials) as a source of sodium ２ It is highly likely that this is due to the fact that the use of silicic acid as both the O source and the CaO source changes the composition of the glass frits during the melting process, causing the glass frits to exhibit different behavior in terms of the change in redox degree compared to conventional glasses such as CH1.

[0072] Here, when cullet obtained by collecting and crushing used glass is used to manufacture new glass, as in conventional glass recycling, there is a concern that the presence of impurities in the collected glass may adversely affect the quality of the glass manufactured using the cullet. For example, iron contained in cullet and carbon derived from paper labels, plastic labels, etc., are coloring factors in glass manufacturing and may be impurities that adversely affect the manufacturing of glass having flint characteristics. Therefore, in the conventional technology of recycling glass resources using cullet, there is a limit to the amount of cullet that can be used when manufacturing flint-like glass, which makes it difficult to increase the recycling rate. However, as mentioned above, SiO ２ While using recycled materials derived from rice husks (grain-derived recycled materials) as a source of sodium ２ By using silicic acid as both a source of O and a source of CaO, SiO２ Using silica sand as a source, ２ When carbonates are used as the O source and CaO source, flint-like glass can be produced even when many iron-based materials and carbon that would otherwise result in amber glass are blended. ２ While using recycled materials derived from rice husks (grain-derived recycled materials) as a source of sodium ２ By using silicic acid as both the O source and the CaO source, flint-like glass can be produced even if the usage rate of cullet in the glass raw materials is increased, which can contribute to an improvement in the recycling rate of glass.

[0073] Also, like RK4 and RK4-2, SiO ２ While using recycled materials derived from rice husks (grain-derived recycled materials) as a source of sodium ２ By using silicic acid as both an O source and a CaO source, C (carbon) and Fe ２ O ３ Since the function of iron oxide as an amber coloring factor can be suppressed, it is a flint-like glass (flint attribute glass) while retaining the properties of C and Fe. ２ O ３ For example, glasses such as RK4 and RK4-2 are flint-like glasses (flint attribute glasses), but compared to conventionally known flint glasses, they have the advantages of Fe, such as ultraviolet absorption function, infrared absorption function, corrosion resistance, and chemical stability. ２ O ３ Furthermore, since C (carbon) in the glass raw materials exerts a desulfurization effect that is exerted during the manufacturing process, glasses such as RK4 and RK4-2, while being flint-like glasses (glasses with flint attributes), have a low sulfur content and are expected to have higher transparency and mechanical properties than conventional flint glasses.

[0074] Here, in order to investigate the influence on the color of glass by varying the blending amount (content) of carbon (C) which functions as a reducing agent in the glass raw materials, RK1 and CH1 were used as the reference samples among the samples related to RK1 to RK4 and CH1 to CH4 described above, and raw materials other than carbon contained in the glass raw materials were the same as those of RK1 and CH1, while the SiO ２ The C content ([C] / [SiO ２ ] mass%) were changed to prepare samples designated RK1-A to RK1-D and CH1-A to CH1-D. The results are shown in FIG.

[0075] The samples RK1-A to RK1-D (RK1-based samples) shown in FIG. 5 are made of glass raw materials that are the same as those of RK1 except for carbon, but the raw materials SiO ２ The C content ([C] / [SiO ２ ] mass%) was set to 0.015, 0.050, 0.075, and 0.100 mass%, respectively. In addition, the samples CH1-A to CH1-D (CH1-based samples) were made with the same raw materials as CH1 except for carbon contained in the glass raw materials, but the raw material SiO ２ The C content ([C] / [SiO ２ ] mass%) were set to 0.13, 0.17, 0.205, and 0.23 mass%, respectively. For the glasses of the RK1-series sample and the CH1-series sample, the batches were melted at 1,450°C for 1 to 2 hours, cast, and then slowly cooled at 570°C for 1 hour. The cast glasses were then ground and polished to a size of approximately 22 mm x approximately 22 mm x approximately 10 mm.

[0076] As can be seen from the results shown in Figure 5, it was found that in both the CH1-based sample and the RK1-based sample, the amber color tends to become stronger as the carbon content increases. Furthermore, when comparing the CH1-based sample and the RK1-based sample, which have similar carbon contents, RK1-D and CH1-A, it was confirmed that RK1-D tends to have a stronger amber color than CH1-A. Therefore, Na２ Under conditions where carbonates are used as both the O and CaO sources, SiO ２ When using rice husk-derived recycled material (grain-derived recycled material) as the source, SiO ２ It was found that the amber color tends to be stronger than when silica sand is used as the source. On the other hand, considering that the sample related to RK4 described above is a flint-like glass, it is possible to obtain a glass with a high SiO ２ Even when using recycled materials derived from rice husks (grain-derived recycled materials) as the source, Na ２ It can be seen that the use of silicate as both the O source and the CaO source suppresses the amber color-intensifying properties of the recycled material derived from rice husks. ２ When using recycled materials derived from rice husks (grain-derived recycled materials) as a source, if you want to obtain flint-like glass, Na ２ Silicates are preferably used as both the O source and the CaO source, and Na is preferred when amber-colored glass is desired. ２ It has been found that it is effective to use carbonate as both the O source and the CaO source.

[0077] 8 and 9 show transmission spectra measured for the glasses CH1 to CH4 and RK1 to RK4 shown in FIG. 5, respectively, in order to evaluate amber absorption (absorption characteristics specific to amber-colored glass). As shown in FIG. 8, when comparing the absorbance curves of the glasses CH1 to CH4, it was found that the transmittance at the amber absorption wavelength of around 410 [nm] decreases as the amount of carbon added increases. Similarly, as shown in FIG. 9, when comparing the absorbance curves of the glasses RH1 to RH4, it was found that the transmittance at the amber absorption wavelength of around 410 [nm] decreases as the amount of carbon added increases. This indicates that the use of silica sand (SiO ２ ) and samples using rice husk-derived recycled materials (grain-derived recycled materials) such as RK1 to RK4. ２It was confirmed that the amber color becomes stronger as the amount of C (carbon) in the glass raw materials increases, regardless of whether silicate is used as the O source or CaO source.

[0078] Furthermore, for the glasses RK1 to RK4 and CH1 to CH4 shown in FIG. 5, the absorption intensity of amber color was derived based on the formula shown in the following [Equation 1]. The results for the glasses RK1 to RK4 are shown in FIG. 10, and the results for the glasses CH1 to CH4 are shown in FIG. 11. Furthermore, using wavelength λ1, which is the wavelength of 400 to 430 nm at which transmittance is minimum, and wavelength λ2, which is the wavelength of 470 to 700 nm at which transmittance is maximum, ΔA' = 2.303 ΔA / d = 2.303 (A1 - A2) / d (d: sample thickness) calculated from the absorbances A1 and A2 at these wavelengths was used as an index of amber absorption intensity. This ΔA' coincides with the absorption coefficient of amber in an ideal situation where scattering and reflection are the same at λ1 and λ2, and there is only amber absorption at λ1 and no absorption at λ2. SiO ２ FIG. 12 shows a graph plotting the ΔA′ of the glass produced from the batch using rice husk-derived recycled material (rice husk ash / grain-derived recycled material) as the source and the ΔA′ of the glass produced from the batch using silica sand against the amount of carbon added.

[0079]

[0080] As can be seen from a comparison of Figures 10 and 11, the rate of increase in the amber absorption intensity in RK1 to RK4 (the amount of increase in the amber absorption intensity relative to an increase in the carbon content) was found to be slower than the rate of increase in the amber absorption intensity in CH1 to CH4. Based on this result, it is clear that the SiO derived from rice husks as in RK1 to RK4 ２ It was discovered that by using a material containing carbon derived from recycled materials, such as silicon oxide, as the main raw material, it is possible to suppress the sharp fluctuation in the intensity of the amber color with increasing amounts of carbon, compared to when the main raw material is made of a material that does not contain carbon derived from recycled materials, such as CH1 to CH4. ２Even when a material such as silicon dioxide, whose carbon content is expected to vary depending on the lot or the raw material of the recycled material, is used as the main raw material, it is possible to suppress large fluctuations in the intensity of the amber color in the produced glass.

[0081] In both cases of CH1 to CH4 shown in Figure 10 and RK1 to RK4 shown in Figure 11, it was found that the rate of increase in the absorption intensity of amber color was the most gradual when both the calcium component and the sodium component constituting the main raw material were silicates. Furthermore, in both cases of CH1 to CH4 shown in Figure 10 and RK1 to RK4 shown in Figure 11, it was found that the rate of increase in the absorption intensity of amber color was more gradual when the calcium component was silicate and the sodium component was carbonate than when the calcium component was carbonate and the sodium component was silicate. Therefore, it was discovered that the rate of increase in the absorption intensity of amber color can be made gradual by preferentially using silicate for the calcium component constituting the main raw material over the sodium component.

[0082] The present invention is suitably applicable to the production of carbon-neutral products using recycled materials recycled from materials other than glass, as well as glass, which is the main product of the carbon-neutral products, and flint-style glass.

Claims

1. A carbon-neutral product formed from main raw materials: a silicon-based material containing a silicon component, a calcium-based material containing a calcium component, and a sodium-based material containing a sodium component, wherein at least one of the silicon-based material, the calcium-based material, and the sodium-based material constituting the main raw materials is recycled using a material other than glass, and the main raw materials contain at least a part of a recycled material containing carbon derived from the material, and a by-product consisting of a gas containing carbon oxides that is generated from the main raw materials and is not substantially newly generated.

2. The carbon-neutral product according to claim 1, characterized in that the silicon-based material is, in whole or in part, made from recycled materials derived from plants.

3. A carbon-neutral product according to claim 1 or 2, characterized in that a silicate containing a calcium component is used as part or all of the calcium-based material.

4. A carbon-neutral product according to claim 1 or 2, characterized in that a silicate containing a sodium component is used as part or all of the sodium-based material.

5. A flint-like glass having flint attributes, characterized in that it is formed using glass raw materials containing: a silicon-based material containing a silicon component; a calcium-based material containing a calcium component; a sodium-based material containing a sodium component; and an iron-based material containing an iron component, wherein the silicon-based material is recycled using a material other than glass and is formed by using a material that contains at least a recycled material containing carbon derived from the material, wherein the calcium-based material and the sodium-based material are formed by using a material that contains at least a silicate containing a calcium component and a silicate containing a sodium component, respectively, and the iron-based material is contained in the glass raw materials in an amount of 0.026 mass% or more and 0.35 mass% or less.

6. A method for producing glass, comprising: a glass frit preparation step of preparing glass frits containing a silicon-based material containing a silicon component, a calcium-based material containing a calcium component, and a sodium-based material containing a sodium component as main raw materials; and a glass forming step of obtaining glass by using the glass frits to create a carbon-neutral product having glass as a main product, wherein the glass frit preparation step is a step of preparing, as the main raw material, at least one of the silicon-based material, the calcium-based material, and the sodium-based material, which is recycled using a material other than glass and contains at least a recycled material containing carbon derived from the material, and the glass forming step is a step of obtaining the glass by using the main raw material to create, as the carbon-neutral product, a main product consisting of the glass and a by-product consisting of a gas containing carbon oxides that is derived from the main raw material and is not substantially newly generated.

7. A method for producing glass according to claim 6, characterized in that the silicon-based material is partly or entirely made of recycled material derived from plants.

8. A method for producing glass according to claim 6 or 7, characterized in that a silicate containing a calcium component is used as part or all of the calcium-based material.

9. A method for producing glass according to claim 6 or 7, characterized in that a silicate containing a sodium component is used as part or all of the sodium-based material.

10. The method for producing glass according to claim 6 or 7, characterized in that in the glass frit preparation step, the glass frit is prepared which includes an iron-based material containing an iron component in the range of 0.026 mass% or more and 0.35 mass% or less, a silicon-based material which is partly or entirely regenerated using a material other than glass, a calcium-based material which is partly or entirely a silicate containing a calcium component, and a sodium-based material which is partly or entirely a silicate containing a sodium component.

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