Inorganic Foam Based On Geopolymers

Abstract

The present invention relates to a process for preparing a particle-stabilized inorganic foam based on geopolymers, to a particle-stabilized inorganic foam based on geopolymers, to a cellular material obtainable by hardening and optionally drying the particle-stabilized inorganic foam based on geopolymers, and to a composition for preparing an inorganic foam formulation for providing a particle-stabilized inorganic foam based on geopolymers.

Claims

1. A process for preparing an inorganic foam comprising the steps of (1) mixing (i) at least one group of inorganic particles; (ii) at least one amphiphilic compound; (iii) at least one inorganic binder mixture comprising (iiia) at least one inorganic binder selected from the group consisting of blast furnace slag, microsilica, metakaolin, aluminosilicates, and mixtures thereof, (iiib) at least one alkaline activator selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkali metal aluminates, alkali metal silicates, and mixtures thereof; (iv) water; and optionally (v) at least one additive; and (2) foaming the resulting foam formulation by chemical, physical or mechanical foaming, wherein the at least one amphiphilic compound comprises amphiphilic compounds with at least one polar head group and at least one apolar tail group, wherein the at least one head group is selected from the group consisting of phosphates, phosphonates, sulfates, sulfonates, alcohols, amines, amides, pyrrolidines, gallates, and carboxylic acids; and wherein the at least one tail group is selected from an aliphatic or an aromatic or a cyclic group with 2 to 8 carbon atoms, wherein the carbon atoms are optionally substituted with one or more, same or different substituents selected from C.sub.1-C.sub.8-alkyl, secondary OH, and secondary NH.sub.2.

2. The process according to claim 1, wherein the at least one group of inorganic particles is selected from the group consisting of oxides, hydroxides, carbides, nitrides, phosphates, carbonates, silicates, sulfates, and mixtures thereof.

3. The process according to claim 1, wherein the at least one group of inorganic particles is selected from the group consisting of silica particles, alumina particles, zirconia particles, CaCO.sub.3 particles, and mixtures thereof.

4. The process according to claim 1, wherein the at least one group of inorganic particles has a median particle size D.sub.50 in the range of from 30 nm to 300 m.

5. The process according to claim 1, wherein the at least one amphiphilic compound comprises amphiphilic compounds with at least one head group selected from the group consisting of carboxylic acids, gallates and amines, and at least one tail group selected from aliphatic groups with 2 to 8 carbon atoms.

6. The process according to claim 1, wherein the at least one inorganic binder is metakaolin.

7. The process according to claim 1, wherein the at least one alkaline activator is waterglass.

8. The process according to claim 1, wherein the at least one additive is selected from the group consisting of fillers, accelerators, retarders, rheology modifiers, superplasticizers, fibers, surfactants, catalysts, further hydrophobization agents, and mixtures thereof.

9. The process according to claim 1, wherein the amount of amphiphilic compound to inorganic particle surface is from 0.5 to 160 mol/m.sup.2; and/or wherein the inorganic particles are provided in an amount of from 1 to 25 wt.-% with regard to the amount of the at least one inorganic binder mixture; and/or wherein the weight ratio of water to the at least one inorganic binder mixture is from 0.1 to 2.0.

10. The process according to claim 1, wherein step (1) comprises the steps of (1a) dispersing the at least one group of inorganic particles, the at least one amphiphilic compound and optionally the at least one additive in water to obtain an aqueous dispersion; and (1b) mixing the aqueous dispersion with the at least one inorganic binder mixture.

11. An inorganic foam obtained by the process according to claim 1.

12. An inorganic foam comprising (i) at least one group of inorganic particles; (ii) at least one amphiphilic compound; (iii) at least one inorganic binder mixture comprising (iiia) at least one inorganic binder selected from the group consisting of blast furnace slag, microsilica, metakaolin, aluminosilicates, and mixtures thereof, and (iiib) at least one alkaline activator selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkali metal aluminates, alkali metal silicates, and mixtures thereof; (iv) water; and optionally (v) at least one additive.

13. A cellular material obtained by hardening and optionally drying an inorganic foam according to claim 12.

14. A composition for preparing an inorganic foam formulation comprising as components (i) at least one group of inorganic particles; (ii) at least one amphiphilic compound; (iii) at least one inorganic binder mixture comprising (iiia) at least one inorganic binder selected from the group consisting of blast furnace slag, microsilica, metakaolin, aluminosilicates, and mixtures thereof, and (iiib) at least one alkaline activator selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkali metal aluminates, alkali metal silicates, and mixtures thereof; wherein the components (i), (ii), and (iii) are present separately; or the components (i) and (ii) are present as a mixture and the component (iii) is present separately; or the components (i), (ii) and (iii) are present as a mixture.

15. (canceled)

16. A cellular material obtained by hardening and optionally drying an inorganic foam according to claim 11.

Description

EXAMPLES

Comparative Example 1

[0158] A geopolymer foam was prepared from the following composition of raw materials in weight percent:

[0159] 20.5% Metakaolin (Argical 1200S, Imerys)

[0160] 20.5% Fly ash (Microsit M10, BauMineral)

[0161] 7.8% Calcium aluminate cement (Ciment Fondu, Kerneos)

[0162] 1.2% Surfactant (Alkyl Polyglucoside, Glucopon 225 DK, BASF)

[0163] 0.2% PAN Fibers (6 mm, 6.7 dtex)

[0164] 19.5% Water

[0165] 27.4% Waterglass (Kaliwasserglass K58, BASF)

[0166] 2.9% NaOH

[0167] The liquid raw materials were first mixed with NaOH. The solid raw materials were added to the liquid components and stirred until a homogeneous slurry is created. The foam was then generated with a kitchen mixer. The so obtained foam was poured to a mold. The setting reaction took place and the foam started to solidify. The geopolymer foam was stored in humid atmosphere for 3 days to allow proper setting. Thereafter. It was demolded and dried at 70 C. until constant mass.

[0168] The resulting geopolymer foam part exhibited a dimension of 300 mm300 mm40 mm. Its dry density was 144 kg/m.sup.3 and its thermal conductivity 42.1 mW/m.Math.K. The compressive strength was 49 kPa, the flexural strength was 28 kPa. The sample featured an air flow resistivity of 4.2 kPa s/m.sup.2. The foam exhibited mainly open pores.

Working Example 1

[0169] A mixture comprising 79.8 wt.-% calcium carbonate (Socal 31), 15.1 wt.-% butyl gallate and 5.1 wt.-% manganese (IV) oxide was premixed as Foam Formation Powder.

[0170] A geopolymer foam was prepared from the following composition of raw materials in weight percent:

[0171] 19.2% Metakaolin (Argical 1200S, Imerys)

[0172] 19.2% Fly ash (Microsit M10, BauMineral)

[0173] 7.3% Calcium aluminate cement (Ciment Fondu, Kerneos)

[0174] 2.3% Foam Formation Powder

[0175] 0.2% PAN Fibers (6 mm, 6.7 dtex)

[0176] 23.4% Water

[0177] 26.3% Waterglass (Kaliwasserglass K58, BASF)

[0178] 2.8% Hydrogen Peroxide (50 wt.-% solution)

[0179] The foam formation powder was first dispersed in water. Then, the suspension was added to the waterglass. The mix of metakaolin and fly ash was added and the suspension was stirred for 10 min. Subsequently, the calcium aluminate cement was admixed. After 15 min of stirring, the foaming of the suspension was initiated by adding the hydrogen peroxide. The so obtained slurry was poured to a mold where the foam expansion evolves until the decomposition of the hydrogen peroxide was completed. The prepared wet foam was stable until after about 30 min the setting reaction took place and the foam started to solidify. The geopolymer foam was stored in humid atmosphere for 3 days to allow proper setting. Thereafter, it was demolded and dried at 70 C. until constant mass.

[0180] The resulting geopolymer foam part exhibited a dimension of 200 mm200 mm50 mm. Its dry density was 127 kg/m.sup.3 and its thermal conductivity 39.6 mW/mK. The compressive strength was 117 kPa, the flexural strength was 82 kPa. The sample featured an air flow resistivity of 233 kPa s/m.sup.2. The foam exhibited mainly dosed pores.