RU2786460C2 - Inorganic foam based on calcium sulfoaluminate - Google Patents

Abstract

FIELD: building materials.

SUBSTANCE: group of inventions relates to the field of building materials, namely to a method for the production of inorganic foam based on calcium sulfoaluminate, to porous material based on calcium sulfoaluminate, obtained as a result of curing of inorganic foam, to a composition for manufacture of a composition of inorganic foam based on calcium sulfoaluminate, and to their use. The method for the production of inorganic foam includes mixing of at least one group of inorganic particles – CaCO₃; at least one amphiphilic compound with at least one polar head group selected from gallates and carboxylic acids, and with at least one non-polar tail group selected from an aliphatic group containing from 2 to 8 carbon atoms; at least one mixture of inorganic binders, containing at least one mixture of calcium sulfoaluminate and water; foaming of the resulting composition of foam by means of chemical, physical, or mechanical foaming.

EFFECT: obtainment of inorganic foam with closed pores with improved properties, which show heat-conductivity satisfying requirements in combination with a high compressive strength limit, with low density in a dry state.

14 cl, 4 dwg, 4 ex

Description

The present invention relates to a process for producing a calcium sulfoaluminate particle-stabilized inorganic foam, a calcium sulfoaluminate particle-stabilized inorganic foam, a porous material obtainable by curing and optionally drying a calcium sulfoaluminate particle-stabilized inorganic foam, and a composition for manufacturing an inorganic foam composition to obtain a particle-stabilized inorganic foam based on calcium sulfoaluminate.

Inorganic foams can be used as an insulating material, such as a heat insulating material, a sound insulating material or a sound absorbing material, and as a low density building material. Unlike foams based on organic polymers, this material is environmentally friendly, high strength, and non-flammable. The latter can also find applications in the field of fire protection. Typically, foams can be stabilized by the use of surfactants or particulates. Inorganic foams stabilized with surfactants typically have an open cell foam structure. However, closed cell foams are of particular interest because they have improved thermal insulation properties that are accompanied by improved mechanical stability.

It has been found that stable inorganic foams with a closed cell foam structure can be obtained by using inorganic particles as foam stabilizers. Typically, the presence of amphiphilic molecules is required to cause the surface activity of the applied particles. WO 2007/068127 A1 discloses the stabilization of wet foams by the use of colloidal particles, for example in combination with propyl gallate. Juillerat et al. (FK Juillerat, U.T. Gonzenbach, P. Elser, AR Studart, LJ Gauckler, J. Am. Ceram. Soc. 2011, 94, 77-83) disclose the stabilization of ceramic foam materials using colloidal Al ₂ particles O ₃ , which are partially hydrophobized by the adsorption of propyl gallate molecules. US 9540287 B2 discloses the use of propyl gallate molecules in combination with binder particles to stabilize foamed binder suspensions. According to DE 102014103258 A1, a gypsum-based inorganic foam can be stabilized with inorganic particles in combination with amphiphilic molecules such as heptylamine.

As non-combustible insulating materials, inorganic foams based on activated aluminosilicates (geopolymers) are of particular interest. Particle-stabilized closed-cell geopolymer foams have been found to have advantageous properties, in particular in terms of dry density, compressive strength, and airflow resistance, over surfactant-stabilized closed-cell geopolymer foams. At the same time, comparable thermal conductivity can be obtained. However, particle-stabilized closed cell geopolymer foams require a high pH of approximately 14 to cure, which causes safety and application problems. In addition, the cost of raw materials for geopolymer foams is quite high.

Accordingly, it has been an object of the present invention to provide closed cell inorganic foams with comparable or improved properties compared to geopolymer foams, while at the same time ensuring that their manufacturing process does not require such a high pH value. Moreover, it was an object of the present invention to provide said inorganic foam with a lower raw material cost. In particular, the object has been to provide inorganic foams that exhibit satisfactory thermal conductivity combined with high compressive strength, low dry density, and to provide a safe method for making such inorganic foams. In addition, the goal was also to increase the resistance of inorganic foams to airflow compared to geopolymer foams.

Surprisingly, it was found that the above objects can be achieved using the present invention, which is described below.

In particular, it has been found that by combining (I) at least one group of inorganic particles, (II) at least one amphiphilic compound, and (III) at least one mixture of inorganic binders containing at least one mixture of sulfoaluminate calcium and optionally at least one additional inorganic binder selected from the group consisting of hydraulic binders, latent hydraulic binders, pozzolanic binders, and mixtures thereof, inorganic foams can be formed without intermediate formation of a high inorganic foam formulation. pH value. In contrast, the pH value of the inorganic foam formulation can be maintained below 12, which is advantageous with respect to safety and regulatory and legal restrictions, as well as the compatibility of additives (eg, plasticizers) with the inorganic foam formulation. As a result of this, stable inorganic foams with a fine-grained and homogeneous structure with closed pores are obtained. In addition, the inorganic foams according to the invention exhibit satisfactory thermal conductivity combined with high compressive strength, low dry density, and very high airflow resistance.

In one embodiment, the present invention relates to a process for producing an inorganic foam, comprising the steps

(1) mixing

(I) at least one group of inorganic particles;

(II) at least one amphiphilic compound;

(III) at least one mixture of inorganic binders, which contains

(IIIa) at least one mixture of calcium sulfoaluminate, and optionally

(IIIb) at least one additional inorganic binder selected from the group consisting of hydraulic binders, latent hydraulic binders, pozzolanic binders, and mixtures thereof;

(iv) water; and optional

(V) at least one additive; and

(2) foaming the resulting foam composition through chemical, physical or mechanical foaming.

CN 105645887A discloses a high performance building fire retardant fibrous material which is prepared, by weight, from 7-13 parts antimony oxide fire retardant synergy, 4-8 parts kaolin, 0.7-1.6 parts antiseptic, 10-14 parts fly ash , 4-7 parts of wheat straw pulp, 10-20 parts of Chinese nettle fibers, 3-5 parts of straw charcoal, 8-13 parts of secondary alcohol ethoxylate, 0.5-1.2 parts of cetyltrimethylammonium bromide, 2-4 parts oxidation inhibitor, 0.8-1.4 parts of plasticizer, 4-7 parts of epoxypropyl methacrylate, 0.3-0.6 parts of propyl gallate, 2-4 parts of calcium oxide, 0.5-1.4 parts of paraffin, 18-26 parts foamed sulfoaluminate cement, 3-5 parts lithium hardener, 4-6 parts composite stabilizer, and 7-13 parts calcium carbonate. In contrast, foamed sulfoaluminate cement is not used in the present invention. The entire foam composition according to the present invention is foamed at the end by chemical, physical or mechanical foaming.

US 2014/0272376 A1 discloses a suspension used to form a product, the suspension contains: (a) water; b) binder particles; (c) air bubbles with walls formed by water; and (d) surface modifying agents useful for modifying the surface of at least some of the binder particles such that the modified particles sufficiently stabilize air bubbles to form air voids in the product. In this case, the binder particles are particles that contain stucco, calcium sulfate dihydrate, Portland cement, fly ash, or combinations thereof. In contrast, in the present invention, binder mixtures as defined in US 2014/0272376 A1 are not used.

In another embodiment, the present invention relates to inorganic foam, which can be obtained through the method in accordance with the present invention.

In yet another embodiment, the present invention relates to an inorganic foam containing

(I) at least one group of inorganic particles;

(II) at least one amphiphilic compound;

(III) at least one mixture of inorganic binders, which contains

(IIIa) at least one mixture of calcium sulfoaluminate, and optionally

(IIIb) at least one additional inorganic binder selected from the group consisting of hydraulic binders, latent hydraulic binders, pozzolanic binders, and mixtures thereof.

(IV) water; and optional

(V) at least one additive.

In yet another embodiment, the present invention relates to a porous material that can be obtained by curing and optionally drying inorganic foam, as defined in this application.

In yet another embodiment, the present invention relates to a composition for the manufacture of an inorganic foam composition containing as components

(I) at least one group of inorganic particles;

(II) at least one amphiphilic compound;

(III) at least one mixture of inorganic binders, which contains

(IIIa) at least one mixture of calcium sulfoaluminate, and optionally

(IIIb) at least one additional inorganic binder selected from the group consisting of hydraulic binders, latent hydraulic binders, pozzolanic binders, and mixtures thereof;

where

components (I), (II), and (III) are present separately; or components (I) and (II) are present as a mixture and component (III) is present separately; or

components (I), (II) and (III) are present as a mixture.

The present invention is further illustrated with Figures 1, 2, 3 and 4. Figure 1 is presented for comparison purposes, and shows an image of a surfactant-stabilized geopolymer foam with an open cell structure. Figure 2 is also presented for comparison purposes, and shows an image of a particle-stabilized geopolymer foam, preferably with a closed cell structure. Figure 3 shows an image of a particle-stabilized inorganic foam in accordance with the present invention, where the mixture of inorganic binders contains only a mixture of calcium sulfoaluminate, and does not contain additional inorganic binders. Figure 4 shows an image of a particle-stabilized inorganic foam according to the present invention, where the mixture of inorganic binders contains a mixture of calcium sulfoaluminate and a mixture of metakaolin and fly ash as additional inorganic binders. On all Figures, the scale bar on the lower left side is 2 mm.

In connection with embodiments of the present invention, the following definitions are relevant.

The term "approximately" in relation to the measurand refers to the normal deviations of the specified measurand. Such deviations depend on the accuracy of the measuring instrument, or they depend on the statistical deviations expected by a person skilled in the art. It is to be understood that the term "about" means a deviation of ±15%, preferably ±10%, more preferably ±5%.

The term "wt.%" refers to the ratio of the weight of the respective component in relation to the sum of the weight of all components in percent, except for water, unless otherwise indicated. The term vol. % refers to the ratio of the volume of the respective component in relation to the sum of the volume of all components in percent.

The meaning of the term "comprising" is to be construed to include all of the features specifically mentioned, as well as optional, additional, non-specified features, while the term "consisting of" includes only those features that are specified. In addition, it is assumed that in each case the sum of all percentages of the specified and not specified constituent components of the composition in accordance with the invention is always 100%.

In the context of the method for producing an inorganic foam, the inorganic foam itself, the porous material that can be obtained by curing and optionally drying the inorganic foam, and the composition for making the inorganic foam composition in accordance with the present invention, the following definitions are relevant.

In general, there is a difference between the terms "inorganic foam composition" and "inorganic foam". An inorganic foam formulation can be made from a suitable inorganic foam formulation as defined in this application by adding water and optionally at least one additive. The inorganic foam formulation can then be used to produce an inorganic foam through mechanical, physical, or chemical foaming. Freshly prepared inorganic foam must be distinguished from cured inorganic foam, that is, a porous material that can be obtained from freshly prepared inorganic foam by curing, and optionally drying. Unless otherwise indicated, the term "inorganic foam", as used in this application, refers to freshly prepared inorganic foam, and the term "porous material" refers to cured and optionally dried inorganic foam.

Inorganic foams are three-phase systems where one phase is gaseous, one phase is liquid, and one phase is solid. Thus, it is to be understood that the inorganic foam contains a gas. The gaseous phase is present in the form of small gas bubbles separated by cell walls derived from the liquid and solid phases. The cell walls meet each other at edges that meet each other at nodes, thereby forming a scaffold structure. The content of the gaseous phase in the inorganic foam may vary from 20 to 99%, preferably from 50 to 98% by volume. The liquid phase is preferably an aqueous phase, so that the inorganic foam usually also contains water. However, water may be partially removed during drying. The solid phase of the inorganic foam contains an inorganic binder. Inorganic foams can be open-cell foams or closed-cell foams. In closed cell foams, the gas is completely surrounded by the cell walls. Generally, at the same density, closed cell foams are higher strength than open cell foams. Accordingly, closed cell foams are preferred due to their improved mechanical stability.

Porous materials can be obtained from inorganic foams by curing and optionally drying the inorganic foam.

Water, as indicated in this application, may refer to pure, deionized H ₂ O, or water containing up to 0.1 wt. % impurities and/or salts, such as ordinary tap water.

The gas phase that is present in the foam may be introduced by mechanical, physical or chemical foaming. Non-limiting examples of gases include air, nitrogen, noble gas, carbon dioxide, hydrocarbons, hydrogen, oxygen, and mixtures thereof.

The gas phase which is present in the foam can be introduced by means of mechanical foaming in the presence of an appropriate gas. Mechanical foaming can, for example, be carried out by using a mixing device, or by means of an oscillatory process, or by means of a rotor-stator process.

The gas phase can also be introduced into the foam through physical or chemical foaming, where the physical or chemical foaming process is suitable for gas release. Preferably, blowing agents are used which vaporize, decompose or react with water and/or acid to produce a gas. Non-limiting examples of blowing agents are peroxides such as hydrogen peroxide, dibenzyl peroxide, peroxobenzoic acid, peroxoacetic acid, alkali metal peroxides, perchloric acid, peroxomonosulfuric acid, dicumyl peroxide, or cumyl hydroperoxide; isocyanates, carbonates and bicarbonates such as CaCO ₃ , Na ₂ CO ₃ , and NaHCO ₃ , which are preferably used in combination with an acid, eg an inorganic acid; metal powders such as aluminum powder; azides such as methyl azide; hydrazides such as p-toluenesulfonyl hydrazide; hydrazine.

Chemical foaming can be achieved through the use of a catalyst. Suitable catalysts preferably contain Mn ²⁺ , Mn ⁴⁺ , Mn ⁷⁺ or Fe ^{3+ cations} . Alternatively, the enzyme catalase can be used as a catalyst. Non-limiting examples of suitable catalysts include MnO ₂ and KMnO ₄ . Such catalysts are preferably used in combination with peroxide based blowing agents.

Additional details regarding the components that are used in the method for producing an inorganic foam, an inorganic foam, a porous material that can be obtained by curing and optionally drying an inorganic foam, as well as a composition for making an inorganic foam composition in accordance with the present invention, are presented below.

The term "inorganic particles" as used in this application preferably refers to inorganic particles selected from the group consisting of:

- Oxides, which include pure and mixed metal oxides (in particular alumina, silicon dioxide, spinels, gadolinium cerium oxide, zirconium oxide, magnesium oxide, tin oxide, titanium oxide and cerium oxide);

- Hydroxides (in particular aluminum hydroxide, calcium hydroxide, magnesium hydroxide, in particular aluminum hydroxide);

- Carbides (in particular, silicon carbide, boron carbide);

- Nitrides (in particular, silicon nitride, boron nitride);

- Phosphates (in particular calcium phosphates such as tricalcium phosphate, hydroxyapatite);

- Carbonates (in particular nickel carbonate, calcium carbonate (ground limestone or precipitated calcium carbonate), magnesium carbonate);

- Silicates (in particular silica, fine silica dust, fly ash, quartz, crushed glass, slag, calcium silicates, mullite, cordierite, clay minerals such as kaolin or bentonite, zirconium silicate, zeolites, diatomaceous earth, in particular, fine silica dust, clay minerals, zirconium silicate; in particular clay minerals);

- Sulphates (particularly calcium sulfate).

It is to be understood that the inorganic particles (I) exemplified above are not identical to the inorganic binders IIIa and/or IIIb.

Preferably, the inorganic particles are derived from carbonates and/or oxides. Preferred oxides include pure and mixed metal oxides selected from the group consisting of aluminas (which include Al-Mg spinels), silicas, zirconias, and zinc oxides, in particular alumina, silica, and zirconias. The preferred carbonate is calcium carbonate.

The term "group of inorganic particles", as used in this application, should be understood as a number of inorganic particles of the same type. It should also be understood that according to the invention, at least one, ie one or more groups of inorganic particles can be used, which means that different mixtures of the above inorganic particles can also be used.

Thus, in a preferred embodiment of the invention, 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.

In a more preferred embodiment, at least one group of inorganic particles is selected from the group consisting of silica particles, alumina particles, zirconia particles, and CaCO ₃ particles and mixtures thereof.

The particle size of at least one group of inorganic particles may vary within a wide range. For powders (primary particles), suitable median particle sizes D50 range from 30 nm to 300 µm, preferably from 100 nm to 250 µm, more preferably from 100 nm to 150 µm, even more preferably from 100 nm to 100 µm. In a further embodiment, suitable particle sizes range from 100 nm to 10 µm, preferably from 100 nm to 2 µm. It was found that the particle size distribution is not of great importance. Good foams can be obtained with both a narrow and a wide range of particle size distributions.

In a preferred embodiment of the invention, at least one group of inorganic particles has a median particle size D ₅₀ as determined by dynamic light scattering, ranging from 30 nm to 300 μm.

The term "particle size (D _x )" refers to the diameter of the distribution of particles, where x % of the particles have a smaller diameter. Thus, the particle size D ₅₀ is the median particle size. The particle size D _x , for example, can be determined by laser diffraction or dynamic light scattering (DLS) techniques. In accordance with the present invention, dynamic light scattering (DLS) is preferably used in accordance with the international standard ISO 22412:2008. Dynamic Light Scattering (DLS), sometimes referred to as Quasi Elastic Light Scattering (QELS), is a non-penetrating, well-known technique for measuring the size and size distribution of molecules and particles, typically in the submicron region. The present invention investigated particles that were dispersed in a liquid, preferably water or ethanol. The Brownian motion of particles or molecules in a suspension causes laser radiation to scatter with different intensities. Analysis of these intensity fluctuations gives the speed of Brownian motion and hence the size of the particles using the Stokes-Einstein relation. The distribution may be a volumetric distribution (D _v ), a surface distribution (D _s ), or a quantitative distribution (D _n ). In the context of this application, the value of D _x refers to the quantitative distribution, where x(number)% of the particles have a smaller diameter.

The term "amphiphilic compound" is known in the art and refers to organic compounds having a non-polar moiety (also referred to as a tail or R group) and a polar moiety (also referred to as a head group). Accordingly, suitable amphiphilic molecules contain a tail connected to the head group, usually through covalent bonds. Such amphiphilic molecules usually contain one tail group and one head group, but may also contain more than one head group.

The tail group may be aliphatic (linear or branched) or cyclic (alicyclic or aromatic), and may have substituents. Such substituents are, for example, -C _n H _2n+1 where n≤8, a secondary -OH group, a secondary -NH ₂ group, etc. Preferred tail groups are optionally substituted linear carbon chains of 2 to 8 carbon atoms, more preferably linear carbon chains of 2 to 8, 4 to 8, or 5 to 8 carbon atoms. In the present description, "secondary-OH group" and "secondary-NH ₂ group" will mean that the resulting substituted tail group is a secondary alcohol or secondary amine.

The head groups that are connected to the tail group are preferably ionic groups, ionic groups and/or polar groups. Examples of possible head groups and corresponding salts are shown in Table 1 below (where the tail group is designated as R).

Preferred head groups are selected from the groups of carboxylic acids, gallates, amines and sulfonates. Particularly preferred head groups are selected from carboxylic acid groups (ie -C(O)OH groups), gallates and amino groups, where X is preferably H or methyl. The preferred carboxylic acid is enanthic acid (heptanoic acid). The preferred gallate is butyl gallate. The preferred amine is heptylamine. The carboxylic acid groups are most preferred.

Preferably, the amphiphilic molecules reduce the surface tension of the air-water interface to values less than or equal to 65 mN/m for concentrations less than or equal to 0.5 mol/l.

Preferably, the amphiphilic molecules have a critical micelle concentration (CMC) above 10 µmol/l and/or they have a solubility above 1 µmol/l.

It is to be understood that at least one, ie one or more of the constituent amphiphilic compounds can be used according to the invention, which means that various mixtures of the amphiphilic compounds defined above can also be used.

Thus, in a preferred embodiment of the invention, at least one amphiphilic compound is an amphiphilic compound with at least one polar head group and at least one non-polar tail group,

where 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 where at least one tail group is selected from an aliphatic or aromatic or cyclic group containing from 2 to 8 carbon atoms, where the carbon atoms are optionally substituted with one or more, the same or different substituents selected from C ₁ -C ₈ -alkyl , a secondary -OH group, and a secondary -NH ₂ group.

In a more preferred embodiment of the invention, at least one amphiphilic compound is an amphiphilic compound 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 containing from 2 to 8 carbon atoms.

It should be understood that by combining the inorganic particles as defined in this application with the amphiphilic compounds as defined in this application, hydrophobized inorganic particles are formed. The term "hydrophobized inorganic particles" refers to inorganic particles, where the surface of the particle is modified with amphiphilic molecules, as a result of which the hydrophilic properties of the inorganic particles are reduced. Surface modification in this context means that amphiphilic compounds are adsorbed on the particle surface.

In a preferred embodiment, the amount of amphiphilic compound on the surface of the inorganic particle is from 0.5 to 160 µmol/m ² , preferably from 10 to 140 µmol/m ² , more preferably from 20 to 120 µmol/m ² , and in particular from 40 to 100 µmol/m ² . In another preferred embodiment, the inorganic particles are present in an amount ranging from 0.1 to 25 wt. %, relative to the amount of at least one mixture of inorganic binders, which is preferably 0.25-15 wt. %, more preferably 0.5-15 wt. % and in particular 1-15 wt. %.

Hydrophobized inorganic particles are suitable for stabilizing inorganic foams based on a mixture of inorganic binders as defined in this application. In a preferred embodiment, the ratio of the mass of water to the mass of the mixture of inorganic binders in the foam composition is from 0.1 to 2.0, preferably from 0.2 to 1.5, more preferably from 0.3 to 1.2, and in in particular, from 0.3 to 1.

Inorganic binders are inorganic compounds that harden in an aqueous medium (hydraulic) or in the presence of air (non-hydraulic). For example, Portland cement is a hydraulic inorganic binder, while gypsum is a non-hydraulic binder. Latent hydraulic binder refers to a binder that only becomes hydraulic when exposed to an alkaline activator.

In the context of the present invention, a mixture of inorganic binders (III) is used, which contains at least one mixture of calcium sulfoaluminate (IIIa), and optionally at least one additional inorganic binder (IIIb), selected from the group consisting of hydraulic binders, binders with latent hydraulic properties, pozzolanic binders, and mixtures thereof.

At least one mixture of inorganic binders in accordance with the present invention contains at least one mixture of calcium sulfoaluminate (IIIa). The term "calcium sulfoaluminate mixture" refers to a mixture which, upon contact with water, can form a calcium sulfoaluminate phase such as ettringite ((CaO) ₃ (Al ₂ O ₃ )(CaSO ₄ ) ₃ ×30-32H ₂ O) .

Such a mixture of calcium sulfoaluminate may contain, for example:

a) yelimite (4CaO×3Al ₂ O ₃ ×SO ₃ ) and optionally belite (2CaO×SiO ₂ ), and

b) anhydrite (CaSO ₄ ) and/or calcium sulfate hemihydrate (CaSO ₄ × 0.5H ₂ O) and/or gypsum (CaSO ₄ × 2 H ₂ O),

in a weight ratio a):b), which is from 90:10 to 60:40, preferably 80:20-65:35.

The calcium sulfoaluminate mixture has a typical calculated oxide composition which is approximately as follows:

5-35 wt. % _SO3

30-60 wt. % CaO

0-30 wt. % _SiO2

5-35 wt. % Al ₂ O ₃ ,

preferably

10-30 wt. % _SO3

30-50 wt. % CaO

0-20 wt. % _SiO2

15-35 wt. % Al ₂ O ₃ ,

and more preferably

17-27 wt. % _SO3

37-47 wt. % CaO

5-15 wt. % _SiO2

20-30 wt. % Al ₂ O ₃ .

The at least one inorganic binder mixture according to the present invention may optionally further comprise at least one additional inorganic binder (IIIb) selected from the group consisting of hydraulic binders, latent hydraulic binders, pozzolanic binders, and their mixtures.

The terms "latent hydraulic binder" and "pozzolanic binder" refer to inorganic binder systems referred to inter alia as "geopolymers". Geopolymers are described by way of example in US 4 349 386, WO 85/03699 and US 4 472 199.

Geopolymers are binders that are generally based on SiO ₂ and/or Al ₂ O ₃ , such as poly(sialate), poly(siloxo), poly(sialate-siloxo), or poly(sialate-disiloxo), which harden in an alkaline aqueous medium. Sialat is a contraction of silicon-oxo-aluminum. Geopolymers are similar to zeolite, however, their microstructure is amorphous rather than crystalline. Said binders may also contain compounds based on Fe ₂ O ₃ , TiO ₂ , CaO, MgO, NaO, or K ₂ O. Pure geopolymers generally have a low calcium content. WO 2011/064005 A1 describes an inorganic binder system which contains 12 to 25% by weight of CaO and which makes it possible to produce chemical building products that are resistant to chemical attack. Additional non-limiting examples of geopolymers include silica dust, metakaolin, aluminosilicates, fly ash, activated clay, pozzolans, or mixtures thereof. Pozzolans are silica-containing or silica-containing and alumina-containing compounds.

For the purposes of the present invention, a "latent hydraulic binder" is preferably a binder in which the molar ratio (CaO+MgO):SiO ₂ is from 0.8 to 2.5, and in particular from 1.0 to 2.0. Generally, the latent hydraulic binders mentioned above can be selected from industrial and/or synthetic slags, in particular blast furnace slag, electrothermal smelting phosphorus slag, steelmaking slag and mixtures thereof, and "pozzolanic binders" are generally can be selected from amorphous silica, preferably precipitated silica, pyrogenic silica and silica dust, ground glass, metakaolin, aluminosilicates, fly ash, preferably lignite fly ash and coal fly ash, natural pozzolans such as tuff, trass and volcanic ash, natural and synthetic zeolites and mixtures thereof.

As used in this application, the term "slag" refers to a by-product of the smelting process, or synthetic slag. The main application of the smelting process is to convert an ore, scrap or mixture of materials containing different metals into a form from which the desired metals can be removed as a metal layer and unwanted metal oxides, e.g. silicates, alumina, etc. remain in the form of sludge.

Blast furnace slag (BFS) is formed as a by-product during the smelting of iron ore in a blast furnace. Other materials are granulated blast furnace slag (GBFS) and ground granulated blast furnace slag (GGBFS), which are granulated blast furnace slag that has been finely ground. Ground granulated blast-furnace slag varies in terms of fineness and grain size distribution, which depend on the origin and processing method, and the fineness of grinding in this case affects the reactivity. The Blaine fineness is used as a parameter for the fineness of the grind, and is typically on the order of 200 to 1000 m ² kg ^-1 , preferably 300 to 500 m ² kg ^-1 . Finer grinding results in higher reactivity. However, for the purposes of the present invention, the expression "blast furnace slag" is intended to include materials resulting from all levels of processing, grinding, and quality characteristics mentioned (ie, BFS, GBFS and GGBFS). Typically, blast-furnace slag contains 30 to 45 wt % CaO, about 4-17 wt % MgO, about 30-45 wt % SiO ₂ and about 5-15 wt % Al ₂ O ₃ , typically about 40% by weight CaO, about 10% by weight MgO, about 35% by weight SiO ₂ and about 12% by weight Al ₂ O ₃ .

The amorphous silica is preferably X-ray amorphous silica, i.e., silica for which the X-ray diffraction method on a powder sample did not reveal a crystalline state. The content of SiO ₂ in the amorphous silica according to the invention is preferably at least 80% by weight, preferably at least 90% by weight. Precipitated silica is produced on an industrial scale by precipitation methods using water glass as a raw material. Precipitated silica resulting from certain manufacturing processes is also referred to as silica gel.

Silica dust is a fine powder, predominantly containing amorphous SiO ₂ powder, and is a by-product of silicon or ferrosilicon production. The particles have a diameter of about 100 nm and a specific surface area of about 15 to about 30 m ² g ^-1 .

Pyrogenic silica is produced by reacting chlorosilanes, eg silicon tetrachloride, in a hydrogen/oxygen flame. Pyrogenic silica is an amorphous SiO ₂ powder with a particle diameter of 5 to 50 nm and a specific surface area of 50 to 600 m ² g ^-1 .

Metakaolin is obtained when kaolin is dehydrated. While at a temperature of 100 to 200°C, kaolin releases physically bound water, at a temperature of 500 to 800°C, dehydroxylation occurs, with the destruction of the lattice structure and the formation of metakaolin (Al ₂ Si ₂ O ₇ ). Accordingly, pure metakaolin contains about 54% by weight SiO ₂ and about 46% by weight Al ₂ O ₃ .

Aluminosilicates are minerals containing aluminum, silicon, and oxygen, which can be expressed by indicating the content of SiO ₂ and Al ₂ O ₃ . They are the main component of kaolin and other clay minerals. Andalusite, kyanite, and sillimanite are naturally occurring aluminosilicate minerals having the composition Al ₂ SiO ₅ .

Fly ash, among other things, is formed during the combustion of coal in power plants, and contains fine particles of various compositions. The main components of fly ash are silicon oxide, alumina, and calcium oxide. Fly ash class C (lignite fly ash) in accordance with WO 08/012438 contains approximately 10 wt. % CaO, while class F fly ash (coal fly ash) contains less than 8% by weight, preferably less than 4% by weight, and typically about 2% by weight of CaO.

Burnt shale, in particular burnt oil shale, is produced at temperatures of approximately 800° C. by firing natural shale and then grinding it.

An overview of suitable raw materials for geopolymers can be found as an example in Caijun Shi, Pavel V. Krivenko, Delia Roy, Alkali Activated Cements and Concretes, Taylor & Francis, London & New York, 2006, pp. 6-63.

In a preferred embodiment, the at least one additional inorganic binder is selected from the group consisting of blast furnace slag, silica dust, metakaolin, aluminosilicates, fly ash, and mixtures thereof. In a particularly preferred embodiment, the at least one additional inorganic binder is selected from the group consisting of metakaolin, fly ash, and mixtures thereof.

While it is preferable that the composition, composition of inorganic foam, inorganic foam, and porous material in accordance with the present invention does not contain additional alkaline activator. If, however, an alkali activator is added as an additive, it is preferable to choose an alkali activator from alkali metal hydroxides of the formula MOH and alkali metal silicates of the formula m SiO ₂ × n M ₂ O, where M is an alkali metal, preferably Li, Na or K or a mixture thereof, and the m:n molar ratio is ≦4.0, preferably ≦3.0, where ≦2.0 is further preferred, and in particular ≦1.70.

The alkali metal silicate is preferably water glass, particularly preferably aqueous water glass, and in particular sodium water glass or potassium water glass. However, it is also possible to use lithium water glass or ammonium water glass or a mixture of the water glasses mentioned. The m:n ratio indicated above (which is also referred to as "index") should preferably not be exceeded, since otherwise the reaction of the components may not be complete. It is also possible to use much smaller indices, for example, about 0.2. Higher index liquid glasses should be adjusted before use to indices in the range according to the invention using a suitable aqueous alkali metal hydroxide.

The term "water glass" refers to alkali metal silicates which are soluble in water. Water glass can be obtained by reacting alkali metal carbonates with quartz sand (silicon dioxide). However, they can also be prepared from a mixture of reactive silicas with the corresponding aqueous alkali metal hydroxides. Non-limiting examples of water glass include Na ₂ SiO ₃ , K ₂ SiO ₃ , and Li ₂ SiO ₃ . In addition to the anhydrous form, there are also various water glass hydrates. Typical minimum impurities are impurities based on the elements Al, Ca, Cr, Cu, Fe, Mg, and Ti. The ratio of alkali metal to silicate may vary. This ratio is defined as the molar ratio of m SiO ₂ to n M ₂ O, as above. Typical values for the m:n ratio are less than 4, less than 3, less than 2, or about 1.7.

Potassium liquid glasses in the predominant range of indices are mainly sold in the form of aqueous solutions, since they are very hygroscopic; soda water glasses in the predominant range of indices are also available on the market in the form of solids.

The solids content of water glass aqueous solutions is generally 20% by weight to 60% by weight, preferably 40 to 60% by weight.

If an alkaline activator is used, the preferred amount of the alkaline activator is from 1 to 55 wt. %, and in particular from 5 to 25 wt. %.

In a preferred embodiment, at least one mixture of inorganic binders (III) contains at least one cement (Cm) selected from CEM I, CEM II, CEM III, CEM IV, CEM V cements, in accordance with the DIN standard EN 197-1 (11/2011), or calcium aluminate cement, preferably CEM I cement. At least one cement may either be present in component (IIIa), (IIIb) or added separately.

Cement is an inorganic, finely ground hydraulic binder. Different types of cement are classified in accordance with DIN EN 197-1 (11/2011) into categories CEM I-V. These different grades of cement differ from each other in their resistance to various aggressive substances, and therefore these grades of cement have different applications.

CEM I cement, which is also called Portland cement, contains approximately 70 wt. % CaO and MgO, approximately 20 wt. % SiO ₂ , approximately 10 wt. % Al ₂ O ₃ and Fe ₂ O ₃ . This cement is obtained by grinding and roasting limestone, chalk and clay. CEM II cement is a Portland cement with low (about 6 to about 20% by weight) or moderate (about 20 to about 35% by weight) additives. This cement may further include blast-furnace slag, fumed silica (not more than 10% by weight), natural pozzolans, natural fired pozzolans, fly ash, fired shale, or mixtures thereof. CEM III cement, which is also called slag cement, consists of Portland cement, which contains 36-85 wt. % slag. CEM IV cement, which is also called pozzolanic cement, contains, along with Portland cement, 11-65% mixtures of pozzolans, fine silica dust and fly ash. CEM V cement, which is also called composite cement, along with Portland cement, contains 18-50 wt. % slag, or mixtures of natural pozzolans, fired pozzolans, and fly ash. Additionally, different types of cement grades may contain 5 wt. % additional inorganic, finely ground substances.

In addition, various additives may be used in accordance with the present invention. In a preferred embodiment, at least one additive is selected from the group consisting of pH adjusters, fillers, accelerators, retarders, rheology modifiers, superplasticizers, surfactants, fibers, water glass, additional hydrophobising agents, catalysts, and their mixtures.

Rheology modifiers control viscosity and thus flowability and provide a good balance between consistency, longevity and spreadability. These modifiers may be synthetic polymers (eg acrylics), cellulose, silica, starches or clays.

Superplasticizers are polymers that act as dispersants to prevent particle segregation and improve the rheological properties and thus the processability of the suspensions. Superplasticizers generally fall into four categories: lignosulfonates, melamine sulfonates, naphthalene sulfonates, and comb polymers (eg, polycarboxylate esters, polyaromatic esters, cationic copolymers, and mixtures thereof).

The curing time of inorganic foam can be extended/shortened by the addition of certain compounds called retarders/accelerators. Retarders can be classified into groups of lignosulfonates, cellulose derivatives, hydroxyl carboxylic acids, organophosphorus compounds, synthetic retarders, and inorganic compounds. Non-limiting examples of retarders include hydroxyethylcellulose, carboxymethylhydroxyethylcellulose, citric acid, tartaric acid, gluconic acid, glucoheptonate, maleic anhydride, 2-acrylamide-2-methylpropanesulfonic acid (AMPS) copolymers, borax, boric acid, and ZnO. Non-limiting examples of accelerators include CaCl ₂ , KCl, Na ₂ SiO ₃ , NaOH, Ca(OH) ₂ , and CaO×Al ₂ O ₃ , lithium silicate, potassium silicate, and aluminum salts such as aluminum sulfate.

Fibers (or stabilizing fibers) may be added during the foaming process to further improve foam stability. Such fiber can be made from various materials such as rocks (eg basalt), glass, carbon black, organic polymers (eg polyethylene, polypropylene, polyacrylonitrile, polyamides, and polyvinyl alcohols), cellulose, lignocellulose, metals (eg iron or steel), and mixtures thereof. Organic fibers are preferred. The number of fibers can be up to 3 wt. %, preferably from 0.1 to 2 wt. %, more preferably 0.1-1.5 wt. %, and in particular 0.2-1 wt. %, based on at least one mixture of inorganic binders. The fibers preferably have a length of up to 200 mm or up to 120 mm, preferably up to 100 mm, more preferably up to 50 mm, most preferably up to 25 mm, and in particular up to 20 mm, and a diameter up to 100 µm.

The term "filler" generally refers to materials that can be added to increase volume without affecting the properties of the foam. Said fillers may be selected from the group consisting of quartz sand or powdered quartz, calcium carbonate, finely divided rocks, low density fillers (e.g. vermiculite, perlite, diatomaceous earth, mica, ground talc, magnesium oxide, foam glass, hollow spheres, sand foam, clay, polymer particles), pigments (eg titanium dioxide), high density fillers (eg barium sulfate), metal salts (eg zinc salts, calcium salts, etc.), and mixtures thereof. Suitable grain sizes in this case are in particular up to 500 μm. It is particularly preferred that the average grain size is up to 300 µm, preferably up to 150 µm.

Surfactants that may be used in addition to the amphiphilic compounds defined in this application include nonionic surfactants, anionic surfactants, cationic surfactants, zwitterionic surfactants, and proteins or synthetic polymers. . However, surfactants are not preferred as they tend to result in open cell foams.

Nonionic surfactants include fatty alcohols, cetyl alcohol, stearyl alcohol, and cetostearyl alcohol (comprising primarily cetyl and stearyl alcohols), as well as oleyl alcohol. Additional examples include polyethylene glycol alkyl ethers (Brij) CH ₃ -(CH ₂ ) _10-16 -(0-C ₂ H ₄ ) _1-25 -OH, such as octaethylene glycol monododecyl ether or pentaethylene glycol monododecyl ether; polypropylene glycol alkyl ethers CH ₃ -(CH ₂ ) _10-16 -(OC ₃ H ₆ ) _1-25 OH; glucoside alkyl esters CH ₃ -(CH ₂ ) _10-16 -(O-Glucoside) _1-3 -OH such as decyl glucoside, lauryl glucoside, octyl glucoside; polyethylene glycol octylphenyl ethers C ₈ H ₁₇ (C ₆ H ₄ )(OC ₂ H ₄ ) _1-25 -OH such as Triton X-100; polyethylene glycol alkylphenyl ethers C ₉ H ₁₉ -(C ₆ H ₄ )-(OC ₂ H ₄ ) _1-25 -OH such as nonoxynol-9; glycerol alkyl esters such as glyceryl laurate; polyoxyethylene glycol sorbitan alkyl esters such as polysorbate; sorbitan alkyl esters such as spans; cocamide MEA, cocamide DEA; dodecyldimethylamine oxide; block copolymers of polyethylene glycol and polypropylene glycol such as poloxamers; polyethoxylated tallow amine (POEA). Preferred nonionic surfactants also include alkyl polyglucosides. Alkyl polyglucosides generally have the formula H-(C ₆ H ₁₀ O ₅ ) _m -OR ¹ where (C ₆ H ₁₀ O ₅ ) is a glucose residue and R ¹ is a C ₆ -C ₂₂ alkyl group, preferably a C ₈ -C ₁₆ alkyl group, and in particular a C ₈ -C ₁₂ alkyl group, and m=1 to 5.

Anionic surfactants contain anionic functional groups at their head such as sulfate, sulfonate, phosphate, and carboxylates. Known alkyl sulfates include ammonium lauryl sulfate, sodium lauryl sulfate (sodium dodecyl sulfate, SLS, or SDS), and related alkyl ether sulfate-sodium laureth sulfate (sodium lauryl ether sulfate or SLES), as well as sodium myreth sulfate. Other anionic surfactants include docusate (dioctyl sodium sulfosuccinate), perfluorooctane sulfonate (PFOS), perfluorobutane sulfonate, alkyl aryl ether phosphates, alkyl ether phosphates. Preferred carboxylates include alkyl carboxylates such as sodium stearate. More suitable species include sodium lauryl sarcosinate and carboxylate-based fluorinated surfactants such as perfluorononanoate, perfluorooctanoate (PFOA or PFO).

Cationic surfactants include, depending on pH, primary, secondary, or tertiary amines: Primary and secondary amines become positively charged at pH<10. An example is octenidine dihydrochloride. In addition, cationic surfactants include permanently charged quaternary ammonium salts such as cetrimonium bromide (CTAB), cetylpyridinium chloride (CPC), benzalkonium chloride (BAC), benzethonium chloride (BZT), dimethyldioctadecylammonium chloride, dioctadecyldimethylammonium bromide (DODAB).

Zwitterionic (amphoteric) surfactants have both cationic and anionic sites attached to the same molecule. The cationic portion is based on primary, secondary, or tertiary amine cations, or on quaternary ammonium cations. The anionic moiety can be more variable and include sulfonates, as in the sultaines CHAPS (3-[(3-cholamidopropyl)dimethylammonium]-1-propanesulfonate) and cocamidopropyl hydroxysultaine. Betaines such as cocamidopropyl betaine contain an ammonium carboxylate. The most common biological zwitterionic surfactants contain a phosphate anion with an amine or ammonium, such as the phospholipids phosphatidylserine, phosphatidylethanolamine, phosphatidylcholine, and sphingomyelins. Non-limiting examples of proteins are bovine serum albumin, egg ovalbumin, milk treasury or beta-lacto globulin.

The proportion of surfactant may vary within a wide range. The surfactant may be present in an amount of up to 2.5 wt. %, preferably up to 1.5 wt. %.

Liquid glass can act as an alkaline activator as explained above. The term "water glass" has also been defined above.

Catalysts which can be used as additives are catalysts which, for the purpose of foaming, can be used in combination with a blowing agent. Suitable catalysts are mentioned above and below in the context of blowing agents.

Additional details regarding the amounts of components used in accordance with the present invention are defined below.

As mentioned above, the amounts of the components according to the present invention are preferably as follows. In particular,

the amount of amphiphilic compound on the surface of the inorganic particle is from 0.5 to 160 µmol/m; and/or

inorganic particles are presented in an amount ranging from 0.1 to 25 wt. %, relative to the amount of at least one mixture of inorganic binders; and/or

the ratio of the mass of water to a dry mixture of inorganic binders is from 0.1 to 2.0.

In one exemplary embodiment, the amount of amphiphilic compound on the surface of the inorganic particle is 10 to 140 µmol/m ² , preferably 20 to 120 µmol/m ² ; and/or

inorganic particles are presented in an amount ranging from 0.25 to 15 wt. %, relative to the amount of at least one mixture of inorganic binders; and/or

the ratio of the mass of water to the mass of the mixture of inorganic binders is from 0.2 to 1.5.

As explained above, it is to be understood that at least one group, ie one or more groups of inorganic particles, and at least one constituent, ie one or more constituent amphiphilic compounds, may be used. The above amounts refer to the total amount of amphiphilic compounds and inorganic particles, respectively, used in the process according to the invention or present in the composition, inorganic foam or porous material according to the invention. In addition, the above amount in relation to a mixture of inorganic binders refers to the total amount of inorganic binders used in the process according to the invention or present in the composition, inorganic foam or porous material according to the invention.

If at least one mixture of inorganic binders contains

(IIIa) at least one mixture of calcium sulfoaluminate, and

(IIIb) at least one additional inorganic binder selected from the group consisting of hydraulic binders, latent hydraulic binders, pozzolanic binders, and mixtures thereof,

then components (IIIb) and (IIIa) may be present in a relative mass ratio of 0.1 to 3.4, preferably 0.1 to 2.0, more preferably 0.3 to 1.5.

Suitable amounts of additives may vary within a wide range, and also depend on the type of additive. Usually, at least one additive is presented in a weight ratio ranging from 0.0003 to 30 wt. %, or ranging from 0.03-25 wt. %, based on the amount of at least one inorganic binder. However, fillers can be used in higher amounts. In particular, the filler may be present in the same amounts as the inorganic binder. Preferably, the weight ratio of filler to at least one mixture of inorganic binders may be from 2:1 to 1:100, preferably from 1:1 to 1:10.

Additional details regarding the method in accordance with the invention are presented below.

In a preferred embodiment of the method according to the invention, step (1) comprises working steps

(1a) dispersing in water at least one group of inorganic particles, at least one amphiphilic compound, and optionally at least one additive, to obtain an aqueous dispersion; and

(1b) mixing the aqueous dispersion with at least one mixture of inorganic binders.

It should be understood that preferably during operation (1a) at least one group of inorganic particles, at least one amphiphilic compound and optionally at least one additive are first combined with each other, and the resulting mixture is then dispersed in water.

In a preferred embodiment, the inorganic foam composition obtained in step (1) of the process according to the invention has a pH value below 12, which is an important advantage of the present invention in terms of safety, application and compatibility with commonly used additives.

In a preferred embodiment of the method according to the invention, step (2) comprises foaming the resulting foam composition by means of chemical foaming. In another preferred embodiment of the process according to the invention, step (2) comprises foaming the resulting foam composition by means of physical foaming. In yet another preferred embodiment of the process according to the invention, step (2) comprises foaming the resulting foam composition by means of mechanical foaming.

In a preferred embodiment, step (2) of the process for producing an inorganic foam comprises foaming the obtained foam composition using a blowing agent, preferably by mixing the foam composition obtained in step (1) with carbonates or bicarbonates such as CaCO ₃ , Na ₂ CO ₃ , and NaHCO ₃ , aluminum powder, p-toluenesulfonyl hydrazide, hydrogen peroxide, dibenzyl peroxide, perchloric acid, peroxomonosulfuric acid, dicumyl peroxide, cumyl hydroperoxide, or mixtures thereof, more preferably with hydrogen peroxide. In a more preferred embodiment, the foaming of the foam composition in step (2) is carried out using a blowing agent, preferably by mixing the foam composition obtained in step (1) with aluminum powder or carbonate in the presence of an acid, or with an aqueous solution of hydrogen peroxide, optionally in the presence of a catalyst.

In a more preferred embodiment, step (2) of the method for producing an inorganic foam comprises foaming the resulting foam composition using a blowing agent, preferably a blowing agent as defined above, where the blowing agent is added in an amount of 0.1 to 10 wt. %, based on the total amount of the foam composition.

It is possible to accelerate the foaming process, in particular foaming using peroxide as blowing agent, by adding a suitable catalyst. For this reason, in a preferred embodiment, step (2) of the method for producing an inorganic foam comprises foaming the resulting foam composition using a chemical blowing agent in the presence of a catalyst, where the catalyst preferably contains Mn ²⁺ , Mn ⁴⁺ , Mn ⁷⁺ or Fe ³ cations. ⁺ , or where the catalyst is the enzyme catalase. More preferably, the catalyst is selected from the group consisting of MnSO ₄ , MnO ₂ , KMnO ₄ , and mixtures thereof. The catalyst can be used in an amount ranging from 0.01 to 5 wt. %, preferably from 0.01 to 2 wt. %, more preferably from 0.05 to 1.0 wt. % and in particular from 0.1 to 0.6 wt. %, based on the total amount of the foam composition.

In a preferred embodiment, the chemical blowing agent is hydrogen peroxide, presented as an aqueous solution of hydrogen peroxide, which contains from 10 to 60 wt. %, preferably from 20 to 60 wt. % and in particular from 40 to 60 wt. % hydrogen peroxide, where an aqueous solution of hydrogen peroxide is added in an amount ranging from 0.1 to 6 wt. %, preferably from 0.5 to 5.0 wt. %, and in particular, from 1 to 4 wt. %, based on the total weight of the foam composition, based on approximately 50 wt. % hydrogen peroxide solution.

In another preferred embodiment, mechanical foaming is carried out, preferably by using a mixing device, or by means of an oscillatory process, or by means of a rotor-stator process.

After the foaming step (2), an inorganic foam according to the invention is obtained.

In a preferred embodiment, the freshly made inorganic foam after step 2) is allowed to solidify in a sealed container. In a more preferred embodiment, after step 2), the freshly prepared inorganic foam is allowed to solidify in a sealed container for at least 12 hours.

Curing can be carried out at a temperature ranging from 0°C to 100°C, preferably from 20°C to 80°C.

As a result of curing and optionally drying the above inorganic foam, a porous material is obtained. The porous material according to the invention may be in the form of a heat-insulating element, a sound-absorbing element or a flame-retardant element, where the element may, for example, be a sheet or a board in each case.

The inorganic foams and porous materials according to the invention generally have a closed cell structure and the following advantageous features.

The dry density is typically less than 300 kg/m, typically less than 200 kg/m ³ , preferably less than 150 kg/m ³ and more preferably less than 100 kg/m ³ . In particular, the dry density can even be further reduced to less than 100 kg/m ³ , preferably to less than 90 kg/m ³ , if at least one inorganic binder mixture contains not only at least one calcium sulfoaluminate mixture, but also contains at least one additional inorganic binder selected from the group consisting of hydraulic binders, binders with latent hydraulic properties, pozzolanic binders, and mixtures thereof. The advantage is that the dry density is less than the dry density of surfactant-stabilized geopolymer foams and porous materials based on them.

The thermal conductivity (DIN EN 12667) is preferably less than 50 mW/mK, more preferably less than 45 mW/mK, and in particular less than 40 mW/mK. In general, the thermal conductivity is even better than the thermal conductivity of surfactant-stabilized geopolymer foams and porous materials based on them.

The compressive strength (DIN EN 826) is preferably at least 30 kPa. In general, the compressive strength is comparable to the compressive strength of surfactant-stabilized geopolymer foams and porous materials based on them. In fact, due to the lower dry density, the ratio of compressive strength to dry density is improved.

The air flow resistance (DIN EN 29 053) is preferably at least 1000 kPa s/m 2 , more preferably at least 1500 kPa s/m ² , most preferably at least 1800 kPa s/m ² . In particular, the airflow resistance can even further increase to at least 2000 kPa s/m ² if at least one inorganic binder mixture contains not only at least one calcium sulfoaluminate mixture, but also at least one additional inorganic binder a substance selected from the group consisting of hydraulic binders, latent hydraulic binders, pozzolanic binders, and mixtures thereof. The advantage is that the airflow resistance is significantly higher than the airflow resistance of surfactant-stabilized geopolymer foams and porous materials based on them, which typically have an airflow resistance of less than 200 kPa s/m ² or even less than 50 kPa s/ m ² .

Further, the present invention is illustrated using the following examples.

EXAMPLES

Comparative Example 1

Geopolymer foam was obtained from the following composition of raw materials, presented in percent by weight:

20.5% metakaolin (Argical™ M 1200S, Imerys)

20.5% fly ash (Microsit® M10, BauMineral)

7.8% calcium aluminate cement (Ciment Fondu, Kerneos)

1.2% surfactant (alkylpolyglucoside, Glucopon 225 DK, BASF)

0.2% PAN fibers (6 mm, 6.7 dtex)

19.5% water

27.4% liquid glass ("Kaliwasserglass K58", BASF)

2.9% NaOH

The liquid feed was first mixed with NaOH. Solid raw materials were added to the liquid components and mixed until a homogeneous suspension was formed. The foam was then created using a kitchen mixer. The foam thus obtained was poured into a mould. A curing reaction took place and the foam began to harden. The geopolymer foam was stored in a humid atmosphere for 3 days to ensure proper curing. After that, it was taken out of the mold, and dried at a temperature of 70°C until a constant weight was obtained.

The resulting geopolymer foam prototype exhibited dimensions of 300 mm x 300 mm x 40 mm. Its dry density was 144 kg/m and its thermal conductivity was 42.1 mW/mK. The compressive strength was 48 kPa, the flexural strength was 28 kPa. The sample showed an airflow resistance (DIN EN 29 053 standard) of 4.2 kPa s/m. The foam predominantly showed open cells as shown in Figure 1.

Comparative Example 2

Pre-composed a mixture containing 79.8 wt. % calcium carbonate (Socal 31), 15.1 wt. % butyl gallate and 5.1 wt. % manganese (IV) oxide as "foaming powder".

Geopolymer foam was obtained from the following composition of raw materials, presented in percent by weight:

19.07% metakaolin (Argical™ M 1200S, Imerys)

19.07% fly ash (Microsit® M10, BauMineral)

7.25% calcium aluminate cement (Ciment Fondu, Kerneos)

2.28% foaming powder

0.20% PAN fibers (6 mm, 6.7 dtex)

23.23% water

26.12% liquid glass ("Kaliwasserglass K58", BASF)

2.78% hydrogen peroxide (50% solution)

First, the foaming powder was dispersed in water. Then, the suspension was added to liquid glass. A mixture of metakaolin and fly ash was added and the slurry was stirred for 10 minutes. Thereafter, calcium aluminate cement was added. After 15 minutes of stirring, foaming of the suspension was caused by adding hydrogen peroxide. The slurry thus obtained was poured into a mold, where the formation of foam occurred until the decomposition of hydrogen peroxide was completed. The resulting wet foam was stable until, after about 30 minutes, a curing reaction occurred and the foam began to harden. The geopolymer foam was stored in a humid atmosphere for 3 days to ensure proper curing. After that, it was taken out of the mold, and dried at a temperature of 70°C until a constant weight was obtained.

The resulting geopolymer foam prototype exhibited dimensions of 200 mm x 200 mm x 50 mm. Its dry density was 127 kg/m and its thermal conductivity was 39.6 mW/mK. The sample showed an airflow resistance of 233 kPa s/m. The foam showed predominantly closed pores. The image of the foam is presented in Figure 2.

Example according to the invention 1

Previously received a mixture containing 88.5 wt. % calcium carbonate (Schafer Precarb 100), 5.8 wt. % enanthic acid and 5.7 wt. % manganese (IV) oxide as "foaming powder".

Calcium sulfoaluminate foam was prepared from the following raw material composition, expressed as a percentage by weight:

39.4% calcium sulfoaluminate (Alipre®, Italcementi,)

12.2% calcium sulfate dihydrate

6.5% foaming powder

0.3% PAN fibers (6 mm, 6.7 dtex)

38.7% water

2.9% hydrogen peroxide (50% solution)

First, the powder was dispersed in water to form a foam. Then, a mixture of calcium sulfoaluminate and calcium sulfate dihydrate was added. After 15 minutes of stirring, foaming of the suspension was caused by adding hydrogen peroxide. The suspension thus obtained was poured into a mold where foam was formed until the decomposition of hydrogen peroxide was completed. The resulting wet foam was stable until, after about 15 minutes, a curing reaction occurred and the foam began to harden. The calcium sulfoaluminate foam was stored in a humid atmosphere overnight to ensure proper curing. After that, it was taken out of the mold and dried at a temperature of 70°C until a constant weight was obtained.

The resulting calcium sulfoaluminate foam prototype exhibited dimensions of 240 mm x 480 mm x 100 mm. Its dry density was 111 kg/m ³ and its thermal conductivity was 42.1 mW/mK. The compressive strength was 48 kPa. The sample showed resistance to air flow, which was 1990 kPa s/m ² . The foam showed closed cells as shown in Figure 3.

Example according to the invention 2

Previously received a mixture containing 83.7 wt. % calcium carbonate (Schafer Precarb 100), 5.5 wt. % enanthic acid and 10.8 wt. % manganese (IV) oxide as "foaming powder".

Calcium sulfoaluminate foam was prepared from the following raw material composition, expressed as a percentage by weight:

18.7% calcium sulfoaluminate (Alipre, Italcementi,)

5.8% calcium sulfate dihydrate

12.2% metakaolin (Argical™ M 1200S, Imerys)

12.2% fly ash (Microsit® M10, BauMineral)

3.7% foam powder

0.2% PAN fibers (6 mm, 6.7 dtex)

44.0% water

3.2% hydrogen peroxide (50% solution)

First, the powder was dispersed in water to form a foam. Then, a mixture of calcium sulfoaluminate, calcium sulfate dihydrate, metakaolin and fly ash was added. After 15 minutes of stirring, foaming of the suspension was caused by adding hydrogen peroxide. The slurry thus obtained was poured into a mold, where the formation of foam occurred until the decomposition of hydrogen peroxide was completed. The resulting wet foam was stable until, after about 15 minutes, a curing reaction occurred and the foam began to harden. The calcium sulfoaluminate foam was stored in a humid atmosphere for 3 days to ensure proper curing. After that, it was taken out of the mold, and dried at a temperature of 70°C until a constant weight was obtained.

The resulting calcium sulfoaluminate foam prototype exhibited dimensions that were 240 mm x 480 mm x 100 mm. Its dry density was 83 kg/m and its thermal conductivity was 36.4 mW/mK. The compressive strength was 43 kPa, the flexural strength was 28 kPa. The sample showed an airflow resistance of 2220 kPa s/m. The foam showed closed cells as shown in Figure 4.

Claims (43)

1. A method for producing an inorganic foam containing the steps (1) mixing (I) at least one group of inorganic particles; (II) at least one amphiphilic compound; (III) at least one mixture of inorganic binders, which contains (IIIa) at least one mixture of calcium sulfoaluminate and (iv) water; and (2) foaming the resulting foam composition by chemical, physical or mechanical foaming; moreover, at least one group of inorganic particles is selected from particles of CaCO ₃ and moreover, at least one amphiphilic compound is an amphiphilic compound with at least one polar head group and at least one non-polar tail group, where at least one head group is selected from gallates and carboxylic acids and where at least one tail group is selected from an aliphatic group containing from 2 to 8 carbon atoms. 2. The method according to p. 1, where at least one group of inorganic particles has a median particle size D ₅₀ in the range from 30 nm to 300 microns. 3. The method according to p. 1 or 2, where at least one mixture of calcium sulfoaluminate has a calculated oxide composition, which is 5-35 wt.% SO ₃ , 30-60 wt.% CaO, 0-30 wt.% SiO ₂ and 5-35 wt.% Al ₂ O ₃ . 4. The method according to any one of paragraphs. 1-3, where at least one calcium sulfoaluminate mixture contains a) yelimite - 4CaO×3Al ₂ O ₃ ×SO ₃ and optionally belite - 2CaO×SiO ₂ and b) anhydrite - CaSO ₄ , calcium sulfate hemihydrate - CaSO ₄ × 0.5 H ₂ O and/or gypsum - CaSO ₄ ×2 H ₂ O in the ratio of mass a):b), ranging from 90:10 to 60:40. 5. The method according to any one of paragraphs 1-4, wherein at least one additional inorganic binder (IIIb) is present in at least one mixture of inorganic binders (III), and the additional binder is a mixture of metakaolin and fly ash. 6. The method according to any one of paragraphs. 1-5, where at least one mixture of inorganic binders (III) additionally contains (IIIc) at least one cement selected from CEM I, CEM II, CEM III, CEM IV, CEM V cements, or cement based on calcium aluminate, preferably CEM I cement. 7. The method according to any one of paragraphs. 1-6, in which at least one additive is present, which is selected from the group consisting of pH adjusting substances, fillers, accelerators, retarders, rheology modifiers, superplasticizers, surfactants, fibers, water glass, additional hydrophobizing agents , catalysts and their mixtures. 8. The method according to any one of paragraphs. 1-7, where the amount of amphiphilic compounds on the surface of the inorganic particles is from 0.5 to 160 μmol/m ² ; and/or where the inorganic particles are present in an amount ranging from 0.1 to 25 wt.%, relative to the amount of at least one mixture of inorganic binders; and/or where the ratio of the mass of water to the mass of the mixture of inorganic binders is from 0.1 to 2.0. 9. The method according to any one of paragraphs. 1-8, where stage (1) contains work steps (1a) dispersing in water at least one group of inorganic particles, at least one amphiphilic compound, and optionally at least one additive to obtain an aqueous dispersion, and (1b) mixing the aqueous dispersion with at least one mixture of inorganic binders. 10. Inorganic foam obtained by the method according to any one of paragraphs. 1-9. 11. Inorganic foam containing (I) at least one group of inorganic particles; (II) at least one amphiphilic compound; (III) at least one mixture of inorganic binders, which contains (IIIa) at least one mixture of calcium sulfoaluminate and (IV) water; and optionally (V) at least one additive, moreover, at least one group of inorganic particles is selected from particles of CaCO ₃ and moreover, at least one amphiphilic compound is an amphiphilic compound with at least one polar head group and at least one non-polar tail group, where at least one head group is selected from gallates and carboxylic acids and where at least one tail group is selected from an aliphatic group containing from 2 to 8 carbon atoms. 12. Porous material, which can be obtained by curing and optionally drying the inorganic foam according to claim 10 or 11. 13. Composition for the manufacture of an inorganic foam composition, containing as components (I) at least one group of inorganic particles; (II) at least one amphiphilic compound; (III) at least one mixture of inorganic binders, which contains (IIIa) at least one mixture of calcium sulfoaluminate, and where components (I), (II) and (III) are present separately; or components (I) and (II) are present as a mixture and component (III) present separately; or components (I), (II) and (III) are present as a mixture, moreover, at least one group of inorganic particles is selected from particles of CaCO ₃ and moreover, at least one amphiphilic compound is an amphiphilic compound with at least one polar head group and at least one non-polar tail group, where at least one head group is selected from gallates and carboxylic acids and where at least one tail group is selected from an aliphatic group containing from 2 to 8 carbon atoms. 14. The use of an inorganic foam according to claim 10 or 11, a porous material according to claim 12 and / or a composition according to claim 13 as a heat-insulating material, sound-proofing material or sound-absorbing material for fire protection and / or as a building material with a dry density less than 300 kg/m ³ , or less than 200 kg/m ³ , or less than 150 kg/m ³ , or less than 100 kg/m ³ , preferably less than 90 kg/m ³ .

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