Granules, method for their production, and method for producing glass product
To provide a method for producing granules as glass raw material without using a binder that contains an alkali metal or boron. In the method, granules are produced by mixing a glass raw material composition and water. A method for producing granules to be used for the production of alkali-free glass, which comprises mixing a glass raw material composition and water, wherein the glass raw material composition essentially comprises an aluminum source containing calcium aluminate represented by CaO.2Al 2 O 3 , a calcium source containing one or both of calcium oxide and calcium hydroxide, and a silicon source.
1. A method for producing granules to be used for the production of alkali-free glass, the method comprising:
mixing a glass raw material composition and water, wherein the glass raw material composition comprises:
calcium oxide and/or calcium hydroxide,
CaO.2Al 2 O 3 , and
a silicon source.
2. The method for producing granules according to claim 1 , wherein the glass raw material composition further comprises CaO.Al 2 O 3 .
3. The method for producing granules according to claim 1 , wherein the glass raw material composition comprises, as a refining agent or a color tone adjuster, a sulfate component and/or a nitrate component.
4. The method for producing granules according to claim 1 , wherein the glass raw material composition comprises the CaO.2Al 2 O 3 in alumina cement, the alumina cement having an Al 2 O 3 content of at least 65 mass %.
5. The method for producing granules according to claim 4 , wherein the alumina cement comprises a calcium aluminate, the calcium aluminate comprising the CaO.2Al 2 O 3 and CaO.Al 2 O 3 in a total amount of from 80 to 100 mass % based on a total amount of the calcium aluminate in the alumina cement, and wherein the CaO.2Al 2 O 3 is present in the alumina cement in an amount of from 2 to 100 mass % based on the total amount of CaO.2Al 2 O 3 and CaO.Al 2 O 3 in the alumina cement.
6. The method for producing granules according to claim 4 , further comprising granulating the glass raw material composition by adding the calcium oxide and/or calcium hydroxide and the silicon source to a hydrate of the alumina cement, and mixing.
7. The method for producing granules according to claim 4 , wherein the alumina cement having an Al 2 O 3 content of at least 65 mass % consists essentially of the CaO.2Al 2 O 3 and CaO.Al 2 O 3 .
8. The method for producing granules according to claim 4 , wherein the alumina cement has an Al 2 O 3 content of at least 90 mass % and further comprises CaO.6Al 2 O 3 .
9. The method for producing granules according to claim 4 , wherein the alumina cement is present in the glass raw material composition in an amount of from 1 to 20 mass %.
10. The method for producing granules according to claim 1 , further comprising, while mixing the glass material composition and water, hardening the composition such that granules are obtained at a temperature of at most 800° C.
11. The method for producing granules according to claim 1 , wherein a total amount of calcium oxide and calcium hydroxide in the glass raw material composition is from 0.1 to 10 mass %.
12. The method for producing granules according to claim 1 , wherein the glass raw material composition comprises boron oxide and/or boric acid in a total amount of from 0 mass % to at most 3 mass %.
13. The method for producing granules according to claim 1 , wherein the alkali-free glass comprises from 40 to 85 mass % of SiO 2 , from 5 to 30 mass % of Al 2 O 3 , from 0 to 18 mass % of MgO and from 2 to 40 mass % of CaO.
14. A method for producing a glass product, comprising:
obtaining granules by the method as defined in claim 1 ,
heating the granules to obtain a glass melt, and
forming and annealing the glass melt to obtain the glass product.
15. The method for producing granules according to claim 1 , wherein the glass raw material composition does not contain boron oxide or boric acid.