EXPANDED-GLASS GRANULAR MATERIAL AND METHOD FOR PRODUCING SAME

Abstract

In a method for producing an expanded-glass granular material, starting materials containing glass powder, water glass, at least one blowing agent, and metakaolin, are mixed in order to form a homogeneous slurry. The slurry is granulated to form raw granular-material particles, which are foamed at a baking temperature between 780° C. and 950° C. in order to form expanded-glass granular-material particles. The expanded-glass granular material has a long-term water absorption of less than 25 volume percent when the expanded-glass granular material is exposed to water for a time period of 21 days.

Claims

1. A method for producing expanded glass granules, which comprises the following steps of: mixing a homogeneous slip from starting materials containing finely ground glass, waterglass, metakaolin, and at least one expandant; granulating the homogeneous slip to form crude granular particles; and foaming the crude granular particles to form expanded glass granular particles at a firing temperature of between 780° C. and 950° C.

2. The method according to claim 1, wherein the starting materials mixed to form the homogeneous slip, based on a total mass of solids contained in the starting materials, contain a metakaolin solids fraction of between 0.5 mass % and 7 mass %.

3. The method according to claim 1, wherein the starting materials mixed to form the homogeneous slip, based on a total mass of solids contained in the starting materials, contain: finely ground glass solids fractions of between 83 mass % and 90 mass %; waterglass solids fractions of between 7.5 mass % and 11 mass %; and expandant solids fractions of between 0.8 mass % and 2.5 mass %.

4. The method according to claim 1, wherein the starting materials mixed to form the homogeneous slip contains potassium waterglass.

5. The method according to claim 4, wherein the starting materials mixed to form the homogeneous slip contain the potassium waterglass and sodium waterglass.

6. The method according to claim 5, wherein the starting materials mixed to form the homogeneous slip, based on a total mass of a solids contained in the starting materials, contain: potassium waterglass solids fractions of between 7 mass % and 9 mass %; and sodium waterglass solids fractions of between 1 mass % and 2.5 mass %.

7. The method according to claim 1, wherein the starting materials mixed to form the homogeneous slip contain sodium nitrate as an expandant.

8. The method according to claim 7, wherein the starting materials mixed to form the homogeneous slip contains sodium nitrate and glucose as expandants.

9. The method according to claim 8, wherein the starting materials mixed to form the homogeneous slip, based on a total mass of solids contained in the starting materials, contains: sodium nitrate solids fractions of between 0.75 mass % and 2.5 mass %; and glucose solids fractions of between 0.05 mass % and 0.5 mass %.

10. The method according to claim 1, wherein the starting materials mixed to form the homogeneous slip contain aluminum hydroxide.

11. The method according to claim 10, wherein the starting materials mixed to form the homogeneous slip, based on the total mass of the solids contained in the starting materials, contain an aluminum hydroxide solids fraction of between 0.25 mass % and 3 mass %.

12. The method according to claim 1, wherein the starting materials mixed to form the homogeneous slip, based on a total mass of solids contained in the starting materials, contain a metakaolin solids fraction of between 1.0 mass % and 5 mass %.

13. The method according to claim 1, wherein the starting materials mixed to form the homogeneous slip, based on a total mass of solids contained in the starting materials, contain: finely ground glass solids fractions of between 85.3 mass % and 88.9 mass %; waterglass solids fractions of between 8.1 mass % and 10.5 mass %; and expandant solids fractions of between 1.0 mass % and 2.3 mass %.

14. The method according to claim 5, wherein the starting materials mixed to form the homogeneous slip, based on a total mass of a solids contained in the starting materials, contain: potassium waterglass solids fractions of between 6.8 mass % and 8.4 mass %; and sodium waterglass solids fractions of between 1.3 mass % and 2.1 mass %.

15. The method according to claim 8, wherein the starting materials mixed to form the homogeneous slip, based on a total mass of solids contained in the starting materials, contains: sodium nitrate solids fractions of between 1.0 mass % and 2.2 mass %; and glucose solids fractions of between 0.06 mass % and 0.16 mass %.

16. Expanded glass granules, comprising: a homogeneous slip containing finely ground glass, waterglass, metakaolin, and at least one expandant, the homogeneous slip being granulated to form crude granular particles, the crude granular particles being foamed to form expanded glass granular particles at a firing temperature of between 780° C. and 950° C.; and the expanded glass granules having a long-term water absorption of less than 25 volume percent when exposed to water for a period of 21 days.

17. The expanded glass granules according to claim 16, wherein the expanded glass granules have an apparent particle density of less than 900 kg/m.sup.3.

18. The expanded glass granules according to claim 16, wherein the expanded glass granules having the long-term water absorption of less than 15 volume percent when exposed to the water for a period of 21 days.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0030] Described below are four working examples of the expanded glass granules of the invention and also of the respectively associated production method, these examples being identified below as B1 to B4.

[0031] For the individual examples B1 to B4, starting materials with the following composition were first provided:

TABLE-US-00001 TABLE 1 Solids fractions of the starting materials for examples B1 to B4 GM AHO NS GL KWG NWG MK B1 88.03 — 2.05 0.16 6.21 2.02 1.54 B2 88.93 — 1.34 0.06 6.27 1.83 1.57 B3 83.75 1.92 1.68 0.10 6.98 0.48 5.10 B4 85.32 — 2.00 0.06 8.18 — 4.44

[0032] The abbreviations in Table 1 have the following meanings: [0033] a)—GM finely ground glass, [0034] b)—AHO aluminum hydroxide (Al(OH).sub.3), [0035] c)—NS sodium nitrate, [0036] d)—GL glucose, [0037] e)—KWG potassium waterglass [0038] f)—NWG sodium waterglass, and [0039] g)—MK metakaolin.

[0040] The values contained in Table 1 relate in each case to the solids fraction of the respective starting material, reported in mass %, relative to the total solids mass of the starting materials, calculated with subtraction of the water fraction.

[0041] The finely ground glass was produced in each case in a step preceding the method, from recycled glass (specifically, a mixture of container glass and flat glass), by grinding in a ball mill to a particle size of d.sub.97<40 μm.

[0042] The starting materials listed in Table 1 were stirred in each case in a mixer for 30 minutes to form a homogeneous slip. The (potassium and/or sodium) waterglass here was added in aqueous solution in each case. Water was added to set target moisture content for the slip that is listed in Table 2.

[0043] The resulting slip was subsequently granulated on a granulating plate. The resultant green particle granules were each dried at a drying temperature of 200° C. for 10 minutes and sieved as and when required. The dried green particle granules were introduced into a rotary tube furnace, with addition of kaolin as separating agent. In the rotary tube furnace, the green particle granules were foamed in each case for around 5 to 10 minutes at a firing temperature which can be seen from Table 2.

TABLE-US-00002 TABLE 2 Target moisture content of slip, grade of expanded glass granules, and firing temperature for examples B1 to B4. Target moisture Firing content Grade temperature B1 17.3 0.5-1.0 825 B2 16.85 0.5-1.0 810 B3 15.89 0.5-1.0 818 B4 40 0.25-0.5  910

[0044] Table 2 contains the target moisture content, in this case in mass % of the water present in liquid form in the slip, based on the total mass of the slip. The grade reported in Table 2 indicates the particle diameter in millimeters of the expanded glass granules (obtained after the foaming operation). The firing temperature is reported in ° C.

[0045] The expanded glass granules resulting from the foaming operation were subsequently cooled and then sieved, to give expanded glass granules having a grade as reported in Table 2.

[0046] The sieved, expanded glass granules were analyzed for strength, bulk density, apparent particle density, water absorption, and chemical composition. The properties resulting from this analysis for examples B1 to B4 are apparent from Tables 3 to 5:

TABLE-US-00003 TABLE 3 Strength, bulk density, and apparent particle density of the expanded glass granules for examples B1 to B4 Apparent particle Strength Bulk density density B1 1.76 311.2 592 B2 3.42 322.2 604 B3 2.50 377 686 B4 3.43 450 816

[0047] Table 3 reports

[0048] the strength according to DIN EN 130055-1 (mean particle strength) in N/mm.sup.2,

[0049] the bulk density in kg/m.sup.3, and

[0050] the apparent particle density in accordance with DIN EN 1097-6, DIN EN 1097-7 (apparent density) in kg/m.sup.3.

[0051] The bulk density reported in Table 3 is determined by filling a 1000 ml measuring cylinder—in full-to-the-brim form—with the sample under analysis in one operation, using a powder hopper, thus forming a cone of bulk material above the end of the measuring cylinder. The cone of bulk material is smoothed off using a ruler guided over the opening of the measuring cylinder. The weight of the filled measuring cylinder minus its empty weight gives the bulk density of the sample under analysis.

TABLE-US-00004 TABLE 4 Long-term water absorption of the expanded glass granules for examples B1 to B4 Long-term water absorption after 7 days after 14 days after 21 days B1 3.1 5.2 7.0 B2 4.5 7.1 10.0 B3 5.2 8.0 10.1 B4 5.3 6.7 7.8

TABLE-US-00005 TABLE 5 Chemical composition of the expanded glass granules for examples B1 to B4 SiO.sub.2 Al.sub.2O.sub.3 Na.sub.2O K.sub.2O MgO CaO Fe.sub.2O.sub.3 Balance B1 69.7 2.1 12.7 2.5 1.8 9.0 0.2 2.0 B2 70.6 2.4 12.0 2.4 1.8 9.1 0.4 1.3 B3 68.9 3.4 12.2 2.2 3.4 7.5 0.2 2.1 B4 69.6 2.8 11.9 3.0 2.4 8.3 0.2 1.8

[0052] In Table 5,

[0053] SiO.sub.2 stands for silicon dioxide,

[0054] Al.sub.2O.sub.3 stands for aluminum oxide,

[0055] Na.sub.2O stands for sodium oxide,

[0056] K.sub.2O stands for potassium oxide,

[0057] MgO stands for magnesium oxide (magnesia),

[0058] CaO stands for calcium oxide,

[0059] Fe.sub.2O.sub.3 stands for iron(III) oxide, and

[0060] Balance stands for fractions of other oxides.

[0061] The numerical figures in Table 5 report the mass fractions of the respective compound or group of compounds in mass %, based on the total (dry) mass of the expanded glass granules.

[0062] The invention is particularly clear from the working examples described above, but is nevertheless not confined to these examples. Instead, numerous further embodiments of the invention can be derived from the claims and from the foregoing description.