Rheology modifier for geopolymer foam formulations

Description

The present invention relates to the use of a cationic copolymer as a rheology modifier in a geopolymer foam formu lation, a geopolymer foam formu lation com prising a cationic copoly mer, a process for preparing a geopolymer foam, a geopolymer foam comprising a cationic copolymer and com position for preparing a geopolymer foam formu lation.

Geopolymer foams can be used as insu lation material, e.g., as a thermal insu lator, acoustic insu lator or acoustic absorber as wel l as construction material with a low density. I n con trast to foams based on organic polymers, this material is eco-friendly, robust, and non flam mable. The latter may also open u p applications in the field of fire protection. Foams in general can be stabilized by use of su rfactants or particles.

General ly the process of producing geopolymer foams is basical ly in two steps, a first step in which the fresh foam is mixed and mechanical energy is employed to the fresh foam and a second step in which the fresh ly prepared foam is al lowed to harden. I n the second step the fresh foam is typical ly left alone without mixing u ntil the hardening of the foams begins. It is im portant that in the fi rst step the foami ng process can be done smooth ly (good workability and foamability) and in the second step the foams should stay stable, which means that the foam shou ld not (partial ly) col lapse or become inhomogeneous u ntil the binder system starts to harden. It is for example particularly disadvantageous if the fresh geopolymer foam is stil l relatively flowable when the geopolymer foam is applied on vertical surfaces, as wel l as when open cavities are fi l led with the geopolymer foam, because the foams may just sim ply flow away and wil l not stay at the intended application place (besides problems of foam col lapsing and possibly becoming in homogeneous) . As a su mmary, du ring the first step a relatively low viscosity of the aqueous suspension system is required in order to guarantee a good foama bility and workability, whereas in the second step the viscosity shou ld become relatively high in order to guarantee the stability of the foams. What is required i n the end, is a thixotropic behavior of the geopolymer foams.

Fu rthermore it is often a problem that a cracking of the hardened sam ples occu rs, which may be induced by sh rin kage of the hardened sam ples. It is needed to avoid or reduce the cracking of the hardened samples in order to avoid a negative influence on the mechanical and insu lation properties.

It is an object of the invention to provide foaming systems with thixotropic properties in order to achieve the before mentioned effects, particu larly in order to al low for a good workability of the geopolymer foams du ri ng the foaming process (du ring mixing) and a good stability of the foams du ring the quiet period after mixing u nti l hardening sets on. Furthermore it is an object of the invention to avoid as far as possible the crack formation of the hardened geo polymer foams. WO 2015/062860 relates to a geopolymer foam formulation, wherein said formulation can additional ly com prise inter alia additives for foam stabilization. It is discloses that for foam stabilization it is possible to use additives from the group consisting of fu med silica, pro teins, rheology-modifying agents, e.g. starches (inter alia xanthan gu m, diutan gum), modi fied starches, poly(meth)acrylates and -(meth)acrylamides bearing su l pho and/or quater- nized ammoniu m grou ps and mixtures thereof. Poly(meth)acrylates and -acrylamides bear ing su l pho grou ps and/or bearing quaternized am moniu m grou ps are described in WO 2008/151878 Al, WO 2007/017286 Al, WO 2005/090424 A1 and WO 02/10229 Al. (Copol ymers of this type are also termed superabsorbing polymers (SAPs) or salt-insensitive su perabsorbing polymers (SISAs) . Materials involved are general ly rheology-modifying agents, and thickeners and, respectively, water-retention agents.

W02015043805 relates to cationic copolymers, a process for the production of these cati onic copolymers and the use of these cationic copolymers as dispersants for geopolymer binder systems.

It has su rprisingly been fou nd that the above objects can be achieved by the present inven tion, which is described hereinafter. I n particular, it has been found that by using at least one cationic copolymer (i) according the present invention as a rheology modifier in a geo polymer foam formu lation geopolymer foams with a good workability du ring the foaming process (mixing) can be obtained. The viscosity of the system at this stage is relatively low. After the foaming process (mixing) the fresh ly prepared foams are stable, they do not col lapse, stay homogeneous and do not flow away in an u ncontrol led man ner, which is due to a relatively high viscosity of the fresh ly prepared foam after the mixing process.

The rheology modifiers of this invention in the form of the cationic copolymer (i) al low the reduction of water in the foaming system. The rheology modifiers of this invention in the form of the cationic copolymer (i) also al low the introduction of thixotropic properties in the foaming system. The rheology modifiers act also as a thixotropic agent. Preferably the term rheology modifier means water reducer and/or thixotropic agent.

I n one embodiment, the present invention is directed to the use of at least one cationic co polymer (i) as a rheology modifier in a geopolymer foam formu lation, wherein the cationic copolymer (i) comprises at least one structu ral u nit (I) com prising at least one cationic group, and optional ly at least one macromonomeric structu ral u nit (I I) com prising at least one polyoxy- al kylene group.

Fu rthermore, in the case of a mandatory incorporation of at least one structu ral u nit (I I) com prising at least one polyoxyal kylene group in the at least one cationic copolymer (i), a more cost-efficient cationic copolymer (i) can be obtained, resu lting in cost-efficient geo- polymer foams with good workability and good stability, the advantageous rheology modify ing effect is maintained. In other words, it has been found that the cationic copolymer (i) according to the present invention, which comprises polyoxyalkylene groups, exhibits the desired rheology modifying effect, while having less cationic groups (lower mol fraction of the cationic monomers) and thus, being more cost-efficient.

In another embodiment, the present invention is directed to a geopolymer foam formulation comprising at least one cationic copolymer (i) according to the present invention, and

(ii) at least one inorganic binder mixture comprising

(iia) at least one inorganic binder selected from the group consisting of latent hy draulic binders, pozzolanic binders and mixtures thereof, and

(iib) 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; and

(iii) water.

In yet another embodiment, the present invention is directed to a process for preparing a geopolymer foam comprising

(1) preparing a geopolymer foam formulation according to the present invention by mixing the at least one cationic copolymer (i) with

(ii) the at least one inorganic binder mixture comprising

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

(iib) 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;

(iii) water; and

(iv) optionally at least one additive; and

(2) foaming of the resulting geopolymer foam formulation by chemical, physical and/or mechanical foaming.

In yet another embodiment, the present invention is directed to a geopolymer foam obtaina ble by the process according to the present invention.

In yet another embodiment, the present invention is directed to a geopolymer foam com prising at least one cationic copolymer (i) according to the present invention;

(ii) at least one inorganic binder mixture comprising

(iia) at least one inorganic binder selected from the group consisting of latent hy draulic binders, pozzolanic binders and mixtures thereof, and

(iib) 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; and

(iii) water. In yet another embodiment, the present invention is directed to a composition for preparing a geopolymer foam formulation comprising as components at least one cationic copolymer

(i) according to the present invention; and

(ii) at least one inorganic binder mixture comprising

(iia) at least one inorganic binder selected from the group consisting of latent hy draulic binders, pozzolanic binders and mixtures thereof, and

(iib) 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 are present separately; or

the components are present in a mixture.

The present invention is also directed to the use of at least one cationic copolymer (i) as a crack reducing agent in a geopolymer foam formulation, wherein the cationic copolymer (i) comprises at least one cationic structural unit (I) comprising at least one cationic group, and optionally at least one macromonomeric structural unit (II) comprising at least one polyoxy- alkylene group.

Preferably the monomeric component (A) forming the structural unit (I) of the cationic copol ymer (i) is selected from the group consisting of ethy lenica I ly unsaturated monomers, which comprise the at least one cationic group, and wherein a monomeric component (B) forming the structural unit (II) of the cationic copolymer (i) is selected from the group consisting of ethylen ica I ly unsaturated monomers, which comprise the at least one polyoxyalkylene group. Preferably the at least one cationic group is a quaternary ammonium group, an iminium group or an N-alkylated heteroaryl group.

Preferably the cationic copolymer (i) for use as a crack reducing agent comprises a) 3 to 97 mol-% of a cationic structural unit of formula (I)

wherein

R ¹ in each occurrence is the same or different and represents hydrogen and/or me thyl,

R ² in each occurrence is the same or different and is selected from the group con sisting of wherein

R ³ , R ⁴ , and R ⁵ in each occu rrence are the same or different and each independently represent hyd rogen, an aliphatic hydrocarbon moiety having 1 to 20 carbon atoms, a cycloaliphatic hyd rocarbon moiety having 5 to 8 carbon atoms, aryl having 6 to 14 car bon atoms and/or a polyethylene glycol (PEG) moiety,

I in each occu rrence is the same or different and represents an integer from 0 to 2, m in each occu rrence is the same or different and represents 0 or 1,

n in each occurrence is the same or different and represents an integer from 0 to 10,

Y in each occu rrence is the same or different and represents an absent grou p, oxygen, N H , and/or N R ³ ,

V in each occu rrence is the same or different and represents -(CH ₂ ) _X -,

x in each occurrence is the same or different and represents an integer from 1 to 6, and

X in each occu rrence is the same or different and represents a halogen atom, a C _j -C^ al kyl su lfate, a C ₁ -C ₄ -a I ky I su lfonate, a C ₆ -C ₁₄ - (a I ky I) a ry I su lfonate and/or a monova lent equivalent of a polyvalent anion, which is selected from a su lfate, a disulfate, a diphosphate, a triphosphate, and/or a polyphosphate; and optional ly

b) 97 to 3 mol-% of a macromonomeric structu ral u nit of formu la (I I)

(ID

wherein

R ⁶ in each occu rrence is the same or different and represents a polyoxyal kylene group of the fol lowing formula

wherein

o in each occu rrence is the same or different and represents an integer from 1 to 300, and

R ¹ , R ³ , I, m, Y, V, and x have the meanings given above.

Preferably the cationic copolymer (i) for use as a crack reducing agent com prises a) 3 to 97 mol-% of a cationic structu ral u nit of formula (I)

wherein

R ¹ in each occurrence is the same or different and represents hyd rogen and/or me thyl,

R ² in each occu rrence is the same or different and is selected from the grou p con sisting of

wherein

R ³ , R ⁴ , and R ⁵ in each occu rrence are the same or different and each independently repre sent hydrogen, an aliphatic hyd rocarbon moiety having 1 to 20 carbon atoms, a cycloali phatic hydrocarbon moiety having 5 to 8 carbon atoms, aryl having 6 to 14 carbon atoms and/or a polyethylene glycol (PEG) moiety,

I in each occu rrence is the same or different and represents an integer from 0 to 2, m in each occu rrence is the same or different and represents 0 or 1,

n in each occu rrence is the same or different and represents an integer from 0 to 10,

Y in each occu rrence is the same or different and represents an absent group, oxygen, N H, and/or N R ³ ,

V in each occu rrence is the same or different and represents -(CH ₂ ) _X -, wherein

x in each occurrence is the same or different and represents an integer from 0 to 6, and

X in each occu rrence is the same or different and represents a halogen atom, a C ₁ -C ₄ -al kyl su lfate, a C ₁ -C ₄ -al kyl sulfonate, a C ₆ -C ₁₄ - (a I ky I) a ry I su lfonate and/or a monovalent equiva lent of a polyvalent anion, which is selected from a sulfate, a disulfate, a diphosphate, a tri phosphate, and/or a polyphosphate; and optional ly

b) 97 to 3 mol-% of a macromonomeric structu ral u nit of formu la (I I)

(ID

wherein

R ⁶ in each occu rrence is pyrrolidone and/or caprolactam, and I, m, Y and V are 0 or absent grou ps.

Preferably the at least one cationic copolymer (i) for use as a crack reducing agent com prises 10 to 90 mol.-% of the cationic structu ral unit (I) and 90 to 10 mol.-% of the macro monomeric structu ral u nit (I I) , preferably 25 to 75 mol.-% of the cationic structural unit (I) and 75 to 25 mol.-% of the macromonomeric structu ral u nit (I I) , more preferably 40 to 60 mol.-% of the cationic structu ral unit (I) and 60 to 40 mol.-% of the macromonomeric struc tu ral u nit (I I) .

I n the context of the present invention, the fol lowing definitions are relevant.

The term "wt.-%" or“% by weight” (also called mass fraction) denotes the percentage of the respective com ponent in relation to the sum of al l com ponents by weight, u nless otherwise stated. The term "vol.-%" or“% by volu me” refers to the percentage of each component in proportion to the sum of al l com ponents by volume, u nless otherwise specified. Further more, the su m of al l percentages of the specified and unspecified com ponents of a com po sition is always 100%.

The term "com prising" means that in addition to the specific featu res mentioned fu rther, not specifical ly mentioned features may be present. Likewise, the term "containing" is to be un derstood. The term "consisting of" means that only the specific features mentioned are in cluded.

The term "forming" in the context of polymers means the formation by radical co-polymeri- zation.

I n general, it is distinguished between the terms“geopolymer foam formulation” and“geo polymer foam”. The geopolymer foam formulation may be obtained from a suitable com po sition for preparing a geopolymer foam formulation as defined herein by adding water and optional ly at least one additive. The geopolymer foam formulation may then be used to pre pare a geopolymer foam by mechanical, physical or chemical foaming. The fresh ly prepared geopolymer foam is to be distinguished from the hardened geopolymer foam, i.e. the cel lu lar material, which is obtainable from the freshly prepared geopolymer foam by hardening and optional ly drying. U n less otherwise indicated, the term“geopolymer foam” as used herein refers to the fresh ly prepared geopolymer foam, and the term“cel lu lar material” refers to the hardened and optional ly d ried geopolymer foam.

For the pu rpose of the present invention, the terms“cationic polymer” and“cationic copoly mer” are used interchangeable. Geopolymer foams are th ree-phase systems, wherein one phase is gaseous, one phase is liquid, and one phase is solid. Thus, it is to be u nderstood that the geopolymer foam com prises a gas. The gaseous phase is present as fine gas bu bbles separated by cel l wal ls ob tained from the liquid and solid phases. The cel l wal ls meet each other at edges, which meet each other at nodes, thereby forming a framework. The content of the gaseous phase in the geopolymer foam may vary in a range of from 20 to 99 %, preferably from 50 to 98 % by volu me. The liquid phase is preferably an aqueous phase, so that the geopolymer foam typical ly also com prises water. However, the water may be partly removed u pon drying. The solid phase of a geopolymer foam com prises an inorganic binder. Geopolymer foams can be open-cel l foams or closed-cel l foams. I n closed-cel l foams, the gas is completely sur rou nded by the cel l wal l. Typical ly, at the same density, closed-cel l foams are more robust than open-cel l foams. Accordingly, closed cel l foams are preferred due to their improved mechanical stability.

Cel lu lar materials can be obtained from geopolymer foams by hardening and optional ly d ry ing a geopolymer foam.

The term "water" as used herein may refer to pure, deionized water or water with u p to 0.1% by weight impurities and / or salts, such as normal tap water.

The gas phase present in the foam can be introduced by mechanical, physical or chemical foaming. Non-limiting examples of gases comprise air, nitrogen, noble gas, carbon dioxide, hyd rocarbons, hydrogen, oxygen, and mixtures thereof.

The gas phase present in the foam can be introduced by mechanical foaming in the pres ence of the respective gas. Mechanical foaming may be performed by using a mixer, or by an oscil lating process, or by a stator-rotor process.

The gas phase can also be introduced into the foam by physical or chemical foaming, wherein the physical or chemical foaming process is suitable to liberate a gas. Preferably, blowing agents are used, which evaporate, decom pose or react with water and/or an acid, so as to liberate the gas. Non-limiting exam ples of blowing agents are peroxides, such as hyd rogen peroxide, dibenzyl peroxide, peroxobenzoic acid, peroxoacetic acid, al kali metal peroxides, perchloric acid, peroxomonosu lfu ric acid, dicu myl peroxide or cu myl hyd roperox ide; isocyanates, carbonates and bicarbonates, such as CaC0 ₃ , Na ₂ C0 ₃ , and NaHC0 ₃ , which are preferably used in combination with an acid, e.g., a mineral acid; metal powders, such as aluminum powder; azides, such as methyl azide; hyd razides, such as p-toluenesulfonyl- hyd razide; hydrazine.

Chemical foaming can be facilitated by the use of a catalyst. Suitable catalysts preferably comprise M n ²⁺ , M n ⁴⁺ , M n ⁷⁺ or Fe ³⁺ cations. Alternatively, the enzyme catalase may be used as catalyst. Non-limiting examples of suitable catalysts are M n0 ₂ and KM n0 ₄ . Such cata lysts are preferably used in combination with peroxide blowing agents. The preferred embodiments of the invention will be explained below. The preferred embodi ments are preferred alone and in combination with each other.

As already stated above, the present invention is directed to the use of at least one cationic copolymer (i) as a rheology modifier in a geopolymer foam formulation, wherein the cationic copolymer (i) comprises at least one structural unit (I) comprising at least one cationic group, and optionally at least one macromonomeric structural unit (II) comprising at least one polyoxy- alkylene group.

In a preferred embodiment, the monomeric component (A) forming the structural unit (I) of the cationic copolymer (i) is selected from the group consisting of ethylenically unsaturated monomers, which comprise the at least one cationic group, and

the monomeric component (B) forming the structural unit (II) of the cationic copolymer (i) is selected from the group consisting of ethylenically unsaturated monomers, which comprise the at least one polyoxyalkylene group.

Preferably, the at least one cationic group is a quaternary ammonium group, an iminium group or an N-alkylated heteroaryl group.

The cationic monomer (A) is preferably selected from quaternized N-vinylimidaz- ole (1), quaternized N-allylimidazole (2), quaternized 4-vinylpyridine (3), quaternized 1- [2-(acryloyl-oxy)ethyl]-lH-imidazole (4), l-[2-(methacryloyloxy)ethyl]-lH-imidazole (5), and mixtures thereof. A graphical representation of these preferred cationic monomers (in non-quaternized form) is given hereinbelow:

The cationic monomer (B) further comprises at least one macromonomeric structural unit (II) comprising at least one polyoxyalkylene group (I I a) . Preferred polyoxyalkylene groups include polyoxyethylene groups, polyoxypropylene groups, and combinations thereof. In par ticular, the oxyalkylene units of the polyoxyalkylene group is preferably selected from eth ylene oxide groups and/or propylene oxide groups, which may be arranged randomly, alter nating^, graduatedly and/or blockwise within the polyoxyalkylene group.

In yet another preferred embodiment, the at least one polyoxyalkylene group (I I a) is a poly oxyethylene or a polyoxypropylene group, and/or wherein each polyoxyalkylene group (I I a) comprises from 1 to 300, preferably from 5 to 300, more preferably from 10 to 200, and in particular from 20 to 100 oxyalkylene units.

In another embodiment the cationic copolymer (i) comprises a) 3 to 97 mol-% of a cationic structural unit of formula (I)

wherein

R ¹ in each occurrence is the same or different and represents hydrogen and/or me thyl,

R ² in each occurrence is the same or different and is selected from the group con- sisting of

wherein R ³ , R ⁴ , and R ⁵ in each occu rrence are the same or different and each independently represent hyd rogen, an aliphatic hydrocarbon moiety having 1 to 20 carbon atoms, a cycloaliphatic hydrocarbon moiety having 5 to 8 carbon atoms, aryl having 6 to 14 car bon atoms and/or a polyethylene glycol (PEG) moiety,

I in each occu rrence is the same or different and represents an integer from 0 to 2, m in each occurrence is the same or different and represents 0 or 1,

n in each occu rrence is the same or different and represents an integer from 0 to 10,

Y in each occu rrence is the same or different and represents an absent grou p, oxygen, N H , and/or N R ³ ,

V in each occurrence is the same or different and represents -(CH ₂ ) _X -, wherein

x in each occurrence is the same or different and represents an integer from 1 to 6, and

X in each occu rrence is the same or different and represents a halogen atom, a C _j -C^ al kyl su lfate, a C ₁ -C ₄ -al kyl su lfonate, a C ₆ -C ₁₄ - (a I ky I) a ry I su lfonate and/or a monova lent equivalent of a polyvalent anion, which is selected from a sulfate, a disulfate, a diphosphate, a triphosphate, and/or a polyphosphate; and optional ly

b) 97 to 3 mol-% of a macromonomeric structural unit of formu la (I I)

wherein

R ⁶ in each occu rrence is the same or different and represents a polyoxyal kylene group of the fol lowing formula (I la)

(I la)

wherein

o in each occu rrence is the same or different and represents an integer from 1 to 300, and

R ¹ , R ³ , I, m, Y, V, and x have the meanings given above.

I n another embodiment the cationic copolymer (i) com prises a) 3 to 97 mol-% of a cationic structu ral u nit of formula (I)

wherein

R ¹ in each occurrence is the same or different and represents hyd rogen and/or me thyl,

R ² in each occu rrence is the same or different and is selected from the group con sisting of

wherein

R ³ , R ⁴ , and R ⁵ in each occurrence are the same or different and each independently repre sent hydrogen, an aliphatic hydrocarbon moiety having 1 to 20 carbon atoms, a cycloali phatic hydrocarbon moiety having 5 to 8 carbon atoms, aryl having 6 to 14 carbon atoms and/or a polyethylene glycol (PEG) moiety,

I in each occurrence is the same or different and represents an integer from 0 to 2, m in each occu rrence is the same or different and represents 0 or 1,

n in each occurrence is the same or different and represents an integer from 0 to 10, Y in each occu rrence is the same or different and represents an absent grou p, oxygen, N H, and/or N R ³ ,

V in each occu rrence is the same or different and represents -(CH ₂ ) _X -,

x in each occurrence is the same or different and represents an integer from 0 to 6, preferably 0, provided that Y represents an absent group when x is 0,

and X in each occurrence is the same or different and represents a halogen atom, a C _j -C alkyl sulfate, a C ₁ -C ₄ -alkyl sulfonate, a C ₆ -C ₁₄ - (a I ky I) a ry I sulfonate and/or a monovalent equivalent of a polyvalent anion, which is selected from a sulfate, a disulfate, a diphos phate, a triphosphate, and/or a polyphosphate; and optionally

b) 97 to 3 mol-% of a macromonomeric structural unit of formula (II)

wherein

R ⁶ in each occurrence is pyrrolidone and/or caprolactam, i.e. I, m, Y and V are 0 or absent groups.

In the context of the present invention, the term“pyrrolidone” encompasses 2-pyrrolidone and 3-pyrrolidone.

Preferably, the pyrrolidone and/or caprolactam are attached via the respective nitrogen at oms.

Exemplary structures of a macromonomeric structural unit of formula (II), wherein R ⁶ is pyr rolidone and/or caprolactam are as follows:

Exemplary structures of a cationic structural unit of formula (I) are as follows: For the purpose of the present invention, a "cationic copolymer" is a copolymer having cati onic groups (as side chains) attached to a polymeric "backbone" or main chain. I n order to exhibit a sufficient electrostatic repulsion, the cationic copolymers of the invention also possess non-adsorbing polyoxyalkylene side chains, i.e. the polyoxyal kylene grou ps of for mula (I I a) . Thus, the cationic copolymers of the present invention form com b structu res and may thus be referred to as comb polymers. Preferably, the structural u nits of formu las (I) and (I I) may be arranged randomly, alternatingly, graduatedly and/or blockwise within the polymeric main chain.

I n the cationic copolymer of the invention, the backbone of the monomeric com ponents cor responding to the structu ral u nits of formulas (I) and (I I) are preferably selected from vinyl ethers, vinyloxy C^-al kyl ethers, in particular vinyloxy butyl ethers, al lyl ethers, methal lyl ethers, 3-butenyl ethers, isoprenyl ethers, acrylic esters, methacrylic esters, acrylamides, methacrylamides, and mixtures thereof. I n other words, preferred backbones of the mono mers corresponding to the structu ral u nits of formulas (I) and (I I) include, but are not lim ited to, the fol lowing partial structures:

Acrylic esters, methacrylic esters, acrylamides, methacrylamides, and the like may be par tial ly su bstituted by the corresponding u nsatu rated dicarboxylic acid derivatives such as maleic acid derivatives, provided that these do not possess free acid fu nctionalities, and vi nyl ethers and the like may be partial ly su bstituted by the corresponding diene derivatives, as long as these derivatives are radicalical ly co-polymerizable.

I n the cationic copolymer of the invention, "o" is preferably from 5 to 300, more preferably 10 to 200, and in particu lar 20 to 100.

I n the cationic copolymer of the invention, the oxyal kylene u nits of the polyoxyal kylene group of formula (I la) are preferably selected from ethylene oxide grou ps and/or propylene oxide grou ps, which may be arranged randomly, alternatingly, graduatedly and/or blockwise within the polyoxyal kylene grou p. Moreover, the polyoxyal kylene grou p of formula (I la) is preferably a mixture with different values for "o" within the specified definition.

The cationic copolymer of the invention preferably com prises 10 to 90 mol-% of the cationic structural u nit and 90 to 10 mol-% of the macromonomeric structu ral unit, more preferably 25 to 75 mol-% of the cationic structural unit and 75 to 25 mol-% of the macromonomeric structu ral u nit and in particular 40 to 60 mol-% of the cationic structural unit and 60 to 40 mol-% of the macromonomeric structural unit. The cationic copolymer has preferably a molecu lar weight in the range of from 1000 to 500000, more preferably 2000 to 150000 and particu larly 4000 to 100000 g/mol.

The present invention is fu rther directed to a geopolymer foam formu lation comprising at least one cationic copolymer (i) according to the present invention, and

(ii) at least one inorganic binder mixtu re com prising

(iia) at least one inorganic binder selected from the grou p consisting of latent hy d rau lic binders, pozzolanic binders and mixtu res thereof, and

(iib) at least one al kaline activator selected from the grou p consisting of al kali metal hyd roxides, al kali metal carbonates, al kali metal alu minates, al kali metal silicates, and mixtu res thereof; and

(iii) water.

Fu rthermore, the present invention is directed to a geopolymer foam comprising at least one cationic copolymer (i) according to the present invention;

(ii) at least one inorganic binder mixtu re com prising

(iia) at least one inorganic binder selected from the grou p consisting of latent hy d rau lic binders, pozzolanic binders and mixtu res thereof, and

(iib) at least one al kaline activator selected from the grou p consisting of al kali metal hyd roxides, al kali metal carbonates, al kali metal alu minates, al kali metal silicates, and mixtu res thereof; and

(iii) water.

For the pu rposes of the present invention, the expression“geopolymer foam formulation” is intended to mean that this formulation comprises al l of the components required in order to provide a geopolymer foam, i.e. an inorganic binder, an al kaline activator, water, optional ly su rfactant(s) and a gas phase. Further optional components such as additives may by com prised. These com ponents can take the form of premix, or else can be in separate form as what is known as a“kit of parts”. The water and the al kaline activator can be provided sep arately from the other com ponents, or the al kaline activator can be in d ry form together with the other components, so that it is on ly then necessary to add water and to carry out foam ing. It is, of cou rse, also possible that the geopolymer foam formu lation is in ready-foamed form.

The geopolymer foam or geopolymer foam formu lation according to the present invention com prises at least one inorganic binder.

It is wel l known that inorganic binder systems can be based on reactive water-insolu ble com pou nds based on Si0 ₂ in conju nction with Al ₂ 0 ₃ which harden in an aqueous al kaline environ ment. Binder systems of this type are termed inter alia“geopolymers”, and are de scribed by way of example in U.S. Pat. No. 4,349,386, WO 85/03699 and U.S. Pat. No.

4,472,199. Materials that can be used as reactive oxide or reactive oxide mixture here are inter alia microsilica, metakaolin, aluminosilicates, flyash, activated clay, pozzolans or a mix tu re thereof. The al kaline environment used to activate the binders includes aqueous solu tions of al kali metal carbonates, al kali metal fluorides, al kali metal hydroxides, al kali metal aluminates and/or al kali metal silicates, e.g. solu ble waterglass. Geopolymers can be less costly and more robust than Portland cement and can have a more advantageous C0 ₂ emis sion balance. I n relation to the term“foam” reference is made to the introduction to the de scription.

For the pu rposes of the present invention, a "latent hyd rau lic binder" is preferably a binder in which the molar ratio (CaO + MgO) : Si0 ₂ is from 0.8 to 2.5 and particularly from 1.0 to 2.0. I n general terms, the above-mentioned latent hyd rau lic binders can be selected from industrial and/or synthetic slag, in particu lar from blast furnace slag, electrothermal phos phorous slag, steel slag and mixtu res thereof, and the "pozzolanic binders" can general ly be selected from amorphous silica, preferably precipitated silica, fu med silica and microsilica, ground glass, metakaolin, alu minosilicates, fly ash, preferably brown-coal fly ash and hard- coal fly ash, natu ral pozzolans such as tuff, trass and volcanic ash, natu ral and synthetic ze olites and mixtu res thereof.

As used herein, the term“slag” refers to the by-product of a smelting process, or synthetic slag. The main use of a smelting process is to convert an ore, scrap or a material mixtu re containing different metals into a form from which the desired metals can be skim med as a metal layer and the u ndesired metal oxides, e.g. silicates, alumina, etc., remain as the slag.

Blast fu rnace slag (BFS) is formed as a by-product du ring the smelting of iron ore in the blast-furnace. Other materials are granu lated blast fu rnace slag (GBFS) and grou nd granu lated blast furnace slag (GGBFS) , which is granulated blast furnace slag that has been finely pu lverized. Grou nd granu lated blast fu rnace slag varies in terms of grinding fineness and grain size distribution, which depend on origin and treatment method, and grinding fine ness influences reactivity here. The Blaine value is used as parameter for grinding fineness, and typical ly has an order of magnitude of from 200 to 1000 m ² kg ¹ , preferably from 300 to 500 m ² kg ^-1 . Finer mil ling gives higher reactivity. For the pu rposes of the present invention, the expression "blast fu rnace slag" is however intended to comprise materials resu lting from al l of the levels of treatment, mil ling, and quality mentioned (i.e. BFS, GBFS and GG BFS). Blast fu rnace slag general ly com prises from 30 to 45 % by weight of CaO, about 4 to 17 % by weight of MgO, about 30 to 45% by weight of Si0 ₂ and about 5 to 15 % by weight of Al ₂ 0 ₃ , typical ly about 40% by weight of CaO, about 10 % by weight of MgO, about 35 % by weight of Si0 ₂ and about 12% by weight of Al ₂ 0 ₃ .

Amorphous silica is preferably an X-ray-amorphous silica, i.e. a silica for which the powder diffraction method reveals no crystal linity. The content of Si0 ₂ in the amorphous silica of the invention is advantageously at least 80% by weight, preferably at least 90% by weight. Precipitated silica is obtained on an industrial scale by way of precipitating processes start ing from water glass. Precipitated silica from some production processes is also cal led silica gel.

Microsilica is a fine powder, main ly comprising amorphous Si0 ₂ powder and is a by-product of silicon or ferrosilicon production. The particles have a diameter of about 100 n m and a specific surface area of from about 15 to about 30 rrPg ¹ . Fu med silica is produced via reaction of chlorosilanes, for example silicon tetrachloride, in a hyd rogen/oxygen flame. Fu med silica is an amorphous Si0 ₂ powder of particle diameter from 5 to 50 n m with specific surface area of from 50 to 600 m ² g T

Metakaolin is produced when kaolin is dehydrated. Whereas at from 100 to 200° C kaolin releases physical ly bou nd water, at from 500 to 800 ° C a dehyd roxylation takes place, with col lapse of the lattice structu re and formation of metakaolin (AI ₂ Si ₂ 0 ₇ ) . Accordingly, pu re metakaolin com prises about 54 % by weight of Si0 ₂ and about 46 % by weight of Al ₂ 0 ₃ .

Aluminosilicates are minerals com prising alu minum, silicon, and oxygen, which may be ex pressed by referring to the Si0 ₂ and Al ₂ 0 ₃ content. They are a major component of kaolin and other clay minerals. Andalusite, kyanite, and sil limanite are natu ral ly occurring alu mino silicate minerals that have the composition AI ₂ Si0 ₅ .

Fly ash is produced inter alia du ring the com bustion of coal in power stations, and com prises fine particles of varying composition. The main ingredients of fly ash are silicon oxide, aluminu m oxide, and calciu m oxide. Class C fly ash (brown-coal fly ash) com prises accord ing to WO 08/012438 about 10 wt.-% CaO, whereas class F fly ash (hard-coal fly ash) com prises less than 8 % by weight, preferably less than 4 % by weight, and typical ly about 3% by weight of CaO.

Bu rnt shale, especial ly bu rnt oil shale is obtained at temperatures of about 800 ° C by burning of natu ral shale and subsequent mil ling.

Electrothermal phosphorous slag is a waste product of electrothermal phosphorous produc tion. It is less reactive than blast fu rnace slag and com prises about 45 to 50% by weight of CaO, about 0.5 to 3% by weight of MgO, about 38 to 43% by weight of Si02, about 2 to 5% by weight of Al ₂ 0 ₃ and about 0.2 to 3% by weight of Fe ₂ 0 ₃ , and also fluoride and phosphate. Steel slag is a waste product of various steel production processes with greatly varying com position.

An overview of suitable raw materials for geopolymers is found by way of example in Caiju n Shi, Pavel V. Kriven ko, Del la Roy, Al kali-Activated Cements and Concretes, Taylor & Francis, London & New York, 2006, pp. 6-63.

Fu rther suitable geopolymer foams, geopolymer foam formulations and processes for the production thereof are described in WO 2015/062860.

The term“particle size (D _x )” refers to the diameter of a particle distribution, wherein x % of the particles have a smal ler diameter. The D ₅₀ particle size is thus the median particle size. The D _x particle size can e.g. be measu red by laser diffraction or dynamic light scattering (DLS) methods. According to the present invention dynamic light scattering (DLS) according to ISO 22412:2008 is preferably used. Dynamic light scattering (DLS), sometimes referred to as Quasi-Elastic Light Scattering (QELS) , is a non-invasive, wel l-established technique for measuring the size and size distribution of molecules and particles typically in the submi cron region. In the present invention the particles were characterized, which have been dis persed in a liquid, preferably water or ethanol. The Brownian motion of particles or mole cules in suspension causes laser light to be scattered at different intensities. Analysis of these intensity fluctuations yields the velocity of the Brownian motion and hence the parti cle size using the Stokes-Einstein relationship. The distribution can be a volume distribution (D _v ), a surface distribution (D _s ), or a number distribution (D _n ). In context of this application, the D _x value refers to a number distribution, wherein x(number) % of the particles have a smaller diameter.

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

The alkaline activator mentioned above is required to establish an alkaline environment for activating the inorganic binder, i.e. the geopolymer binder, so that the latent hydraulic binder will become hydraulic. The alkaline activator can be selected from the group consist ing of alkali metal hydroxides, alkali metal carbonates, alkali metal aluminates, alkali metal silicates and mixtures thereof.

It is preferable to select an alkaline activator from alkali metal hydroxides of the formula MOH and alkali metal silicates of the formula m Si0 ₂ x n M ₂ 0, where M is the alkali metal, preferably Li, Na or K or a mixture thereof, and the molar ratio m:n is < 4.0, preferably < 3.0, with further preference < 2.0, in particular < 1.70.

The alkali metal silicate is preferably water glass, particularly preferably an aqueous water glass and in particular a 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 stated above (also termed "modulus") should preferably not be exceeded, since otherwise reaction of the components is likely to be incomplete. It is also possible to use very much smaller moduli, for example about 0.2. Water glasses with higher moduli should be adjusted before use to moduli in the range of the invention by us ing a suitable aqueous alkali metal hydroxide.

In a preferred embodiment, the at least one alkaline activator is water glass.

The term“water glass” refers to alkali metal silicates, which are water soluble. Water glass can be obtained by the reaction of alkali metal carbonates with quartz sand (silicon diox ide). However, they can also be produced from mixtures of reactive silicas with the appro priate aqueous alkali metal hydroxides. Non-limiting examples of water glass comprise Na ₂ Si0 ₃ , K ₂ Si0 ₃ , and Li ₂ Si0 ₃ . In addition to the anhydrous form, various hydrates of water glass exist as well. Typical trace impurities are based on the elements Al, Ca, Cr, Cu, Fe,

Mg, and Ti. The ratio of alkali metal to silicate can vary. This ratio is defined in terms of the molar ratio of m Si0 ₂ to n M ₂ 0 as mentioned above. Typical values for the ratio m : n are values smal ler than 4, smal ler than 3, smal ler than 2, or in the vicinity of 1.7.

Potassium water glasses in the advantageous modu lus range are mainly marketed as aque ous solutions because they are very hygroscopic; sodium water glasses in the advantageous modulus range are also obtainable commercial ly as solids. The solids contents of the aque ous water glass solutions are general ly from 20% by weight to 60% by weight, preferably from 40 to 60% by weight.

The preferred quantity of the al kaline activator is from 1 to 55 wt.-% and in particular from 10 to 50 wt.-%.

I n a preferred em bodiment, the at least one inorganic binder mixtu re (ii) fu rther com prises at least one additional inorganic binder, preferably cement and/or calciu m su lfate. I n a par ticularly preferred embodiment, the at least one inorganic binder mixtu re comprises at least one additional inorganic binder selected from portland cement, calciu m aluminate cement, calciu msulfoalu minate cement, calciumsu lfate and mixtures thereof. The amou nt of the ad ditional inorganic binder, if present, has to be less than 30 wt.-%, preferably less than 25 wt.-%, more preferably less than 10 wt.-%, based on the inorganic binder (iia) .

Cement is an inorganic, finely mil led hydraulic binder. The different types of cement are classified according to DI N EN 197-1 (11/2011) into the categories CEM l-V. These differ ent cements vary from each other in their stability towards various corrosives and these ce ments therefore have different applications.

CEM I cement, also cal led Portland cement, contains about 70 wt.-% CaO and MgO, about 20 wt.-% Si0 ₂ , about 10 wt.-% Al ₂ 0 ₃ and Fe ₂ 0 ₃ . This cement is obtained by mil ling and bak ing limestone, chal k and clay. CEM I I cement is Portland cement with a low (about 6 to about 20 wt.-%) or moderate (about 20 to about 35 wt.-%) amou nt of additional com po nents. This cement may further contain blast-furnace slag, fu med silica (10 wt.-% at most), natu ral pozzolans, natu ral calcined pozzolans, fly ash, burnt shale, or mixtures thereof. CEM I I I cement, also cal led blast-furnace cement, is com prised of Portland cement hat contains 36 to 85 wt.-% of slag. CEM IV cement, also cal led pozzolanic cement, contains next to Port land cement 11 to 65 % of mixtures of pozzolans, silica fu me and fly ash. CEM V cement, also cal led com posite cement, contains next to Portland cement 18 to 50 wt.-% of slag, or mixtures of natu ral pozzolans, calcined pozzolans, and fly ash. Additional ly, the different types of cements may contain 5 wt.-% of additional inorganic, finely mil led mineral com pounds.

The term“calciu m alu minate cements” refers to cements that predominantly comprise CaO x Al ₂ 0 ₃ . They can, e.g., be obtained by melting calcium oxide (CaO) or limestone (CaC0 ₃ ) and bauxite or aluminate together. Calciu m alu minate cement com prises about 20 to 40% by weight of CaO, u p to about 5% by weight of Si0 ₂ , about 35 to 80% by weight of Al ₂ 0 ₃ and u p to about 20% by weight of Fe ₂ 0 ₃ . Calcium alu minate cements are defined according to DI N EN 14647 (01/2006) . The term“calcium sulfoaluminate cement” refers to a cement which contains ye'elimite as well as calcium sulfate. Calcium sulfate may be provided as calcium sulfate dihydrate (CaS0 ₄ x 2H ₂ 0), calcium sulfate hemihydrate (CaS0 ₄ x ½ H ₂ 0) and anhydrite (CaS0 ₄ ). Natu ral occurring gypsum is CaS0 ₄ x 2H ₂ 0. However, burnt gypsum can be in a variety of hydra tion states according to the generic formula CaS0 ₄ x nH ₂ 0, with 0 < n < 2.

Furthermore, various additives may be used according to the present invention. In a pre ferred embodiment, the at least one additive is selected from the group consisting of pH modifiers, fillers, accelerators, retarders, further rheology modifiers, superplasticizers, fi bers, pigments and anionic, further cationic and/or non-ionic surfactants, catalysts, and mixtures thereof.

The geopolymer foam formulation or the geopolymer foam optionally further comprises at least one additive. Preferable additives are selected from the group consisting of fillers, ac celerators, retarders, rheology modifiers, superplasticizers, fibers, and surfactants.

In that regard, pickering foams are equivalent and have the same effect. Pickering foams are characterized by a cellular structure of close-celled polymer foams.

The geopolymer foam formulation or the geopolymer foam optionally further comprises at least one additive, which is a surfactant. Preferably, the surfactant is a non-ionic surfactant and more preferably an al kyl polyglycoside surfactant.

The geopolymer foam formulation or the geopolymer foam optionally further comprises at least one additive, which is a further rheology modifier. The further rheology modifier is preferably a polymer dispersion, more preferably a polymer dispersion comprising at least one copolymer comprising structural units formed from vinyl acetate and structural units formed from at least one further ethylenically unsaturated monomer. The further rheology modifier does preferably not contain cationic structures.

Rheology modifiers adjust the viscosity and thus the flow behavior and ensure a good bal ance between consistency, durability and application properties. These modifiers can be based on synthetic polymers (e.g. acrylic polymers), cellulose, silica, starches or clays.

Superplasticizers are polymers that function as dispersant to avoid particle segregation and improve the rheology and thus workability of suspensions. Superplasticizers generally can be divided into four categories: lignosulfonates, melamine sulfonates, naphthalene sul fonates, and comb polymers (e.g. polycarboxylate ethers, polyaromatic ethers and mixtures thereof).

The setting time of the geopolymer foam can be prolonged / shortened by the addition of certain compounds called retarders / accelerators. Retarders can be divided into the groups of lignosulfonates, cellulose derivatives, hydroxyl carboxylic acids, organophosphates, syn- thetic retarders, and inorganic compounds. Non-limiting examples of retarders are hydroxy- ethyl cellulose, carboxymethyl hydroxyethyl cellulose, citric acid, tartaric acid, gluconic acid, glucoheptonate, maleic anhydride, 2-Acrylamido-2-methylpropanesulfonic acid (AMPS) co polymers, borax, boric acid, and ZnO. Non-limiting examples of accelerators are CaCI ₂ , KCI, Na ₂ Si0 ₃ , NaOH, Ca(OH) ₂ , and CaO x Al ₂ 0 ₃ , lithium silicate, potassium silicate, and aluminum salts, such as aluminum sulfate.

Fibers (or stabilizing fibers) can be added during the foaming process to further increase the stability of the foam. Such fiber can be made of a variety of materials, such as rock (e.g. basalt), glass, carbon, organic polymers (e.g. polyethylene, polypropylene, polyacrylonitrile, polyamides, and polyvinyl alcohols), cellulose, lignocellulose, metals (e.g. iron or steel), and mixtures thereof. Organic fibers are preferred. The amount of the fibers can be up to 3 wt.- %, preferably from 0.1 to 2 wt.-%, more preferably 0.1 to 1.5 wt.-%, even more preferably 0.1 to 1 wt.-% and in particular 0.2 to 0.7 wt.-%, based on the at least one inorganic binder mix ture. 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 of up to 100 pm.

The term“filler” refers primarily to materials that can be added to increase the volume with out impairing the properties of the foam. The fillers mentioned can be selected from the group consisting of quartz sand or powdered quartz, calcium carbonate, rock flour, low-den sity fillers (for example vermiculite, perlite, diatomaceous earth, mica, talc powder, magne sium oxide, foamed glass, hollow spheres, foam sand, clay, polymer particles), pigments (e.g. titanium dioxide), high density fillers (e.g. barium sulphate), metal salts (e.g. zinc salts, calcium salts, etc.), and mixtures thereof. Grain sizes suitable here are in particular up to 500 pm. It is particularly preferable that the average grain size is up to 300 m m, preferably up to 150 m m.

Surfactants, which may be used in addition to the amphiphilic compound as defined herein, include non-ionic surfactants, anionic surfactants, cationic surfactants, zwitterionic surfac tants and proteins or synthetic polymers mixtures thereof.

Non-ionic surfactants include fatty alcohols, cetyl alcohol, stearyl alcohol, and cetostearyl alcohol (comprising predominantly cetyl and stearyl alcohols), and oleyl alcohol. Further ex amples include polyethylene glycol alkyl ethers (Brij) CH ₃ -(CH ₂ ) _10-16 -(O-C ₂ H ₄ ) _1-25 -OH such as octaethylene glycol monododecyl ether or pentaethylene glycol monododecyl ether; poly propylene glycol alkyl ethers CH ₃ -(CH ₂ ) _10-16 -(O-C ₃ H ₆ ) _1-25 -OH; glucoside alkyl ethers CH ₃ - (CH ₂ ) _10-16 -(O-Glucoside) _1-3 -OH such as decyl glucoside, lauryl glucoside, octyl glucoside; polyethylene glycol octylphenyl ethers ΰ ₈ H ₁₇ -(ΰ ₆ H ₄ )-(0-ΰ ₂ H ₄ ) _1-25 -0H such as Triton X- 100; polyethylene glycol al kyl phenyl ethers C _g H _19- (C ₆ H ₄ )-(0-C ₂ H ₄ ) _1-25- 0H 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 non-ionic sur factants also include alkyl polyglucosides. Alkyl polyglucosides generally have the formula H-(C ₆ H ₁₀ O ₅ ) _m -O-R\ where (C ₆ H ₁₀ O ₅ ) is a glucose unit and R ¹ is a C ₆ -C ₂₂ -alkyl group, prefera bly a C ₈ -C ₁₆ -a I kyl group and in particular a C ₈ -C ₁₂ -a I ky I group, and m = from 1 to 5.

Anionic surfactants contain anionic functional groups at their head, such as sulfate, sul fonate, phosphate, and carboxylates. Prominent alkyl sulfates include ammonium lauryl sul fate, sodium lauryl sulfate (sodium dodecyl sulfate, SLS, or SDS), and the related alkyl- ether sulfates sodium laureth sulfate (sodium lauryl ether sulfate or SLES), and sodium my- reth sulfate. Others include docusate (dioctyl sodium sulfosuccinate), perfluorooctanesul- fonate (PFOS), perfluorobutanesulfonate, alkyl-aryl ether phosphates, alkyl ether phos phates. Preferred carboxylates include the alkyl carboxylates, such as sodium stearate.

More specialized species include sodium lauryl sarcosinate and carboxylate-based fluoro- surfactants such as perfluorononanoate, perfluorooctanoate (PFOA or PFO).

Cationic surfactants include, dependent on the pH, primary, secondary, or tertiary amines: Primary and secondary amines become positively charged at pH < 10. An example is octe- nidine dihydrochloride. Furthermore, cationic surfactants include permanently charged qua ternary ammonium salts, such as cetrimonium bromide (CTAB), cetylpyridinium chloride (CPC), benzalkonium chloride (BAC), benzethonium chloride (BZT), dimethyldioctade- cylammonium chloride, dioctadecyldimethylammonium bromide (DODAB).

Zwitterionic (amphoteric) surfactants have both cationic and anionic centers attached to the same molecule. The cationic part is based on primary, secondary, or tertiary amines or quaternary ammonium cations. The anionic part can be more variable and include sul fonates, as in the sultaines CHAPS (3-[(3-Cholamidopropyl)dimethylammonio]-l-propane- sulfonate) and cocamidopropyl hydroxysultaine. Betaines such as cocamidopropyl betaine have a carboxylate with the ammonium. The most common biological zwitterionic surfac tants have 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 caseins or beta-lactoglobulin.

The proportion of the surfactant can vary over a broad range. The surfactant may be pre sent in an amount of up to 2.5 wt.-%, preferably up to 1.5 wt.-% based on the total weight of the geopolymer foam formulation. The total weight of the geopolymer foam formulation is preferably the sum of the binder(s), activator, water, optionally surfactant and optionally further formulation components like for example fillers, fibers, superplasticizers, further rhe ology modifiers, catalysts and so on.

Catalysts that may be used as additives are catalysts that may be used in combination with a chemical foaming agent. Suitable catalysts are mentioned above and below in the context of blowing agents.

Further details regarding the amounts of the components as used according to the present invention are defined hereinafter. The cationic copolymer is comprised in the geopolymer foam formu lation in the range from 0.01% to 20.0%, preferably from 0.1% to 10.0%, more preferably from 0.2% to 5.0% and most preferably from 0.3 to 2 %, by weight, based on the total weight of the geopolymer foam for mulation. The total weight of the geopolymer foam formu lation is preferably the su m of the binder(s) , activator, water, optional ly su rfactant and optional ly fu rther formu lation com po nents like for exam ple fil lers, fibers, su perplasticizers, fu rther rheology modifiers, catalysts and so on.

Suitable amou nts of the additives may vary over a broad range and also depend on the type of additive. Typical ly, the at least one additive is provided in weight percent amount of from 0.0003 to 30 wt.-%, or of from 0.03 to 25 wt.-%, based on the total weight of the geopolymer foam formu lation. However, fil lers may also be used in higher amounts. I n particular, the fil ler may be present in similar amou nts as the inorganic binder. Preferably, the weight ratio of fil ler to at least one inorganic binder mixtu re may be from 2:1 to 1:100, preferably from 1:1 to 1:10.

Fu rthermore, the present invention is directed to a process for preparing a geopolymer foam comprising

(1) preparing a geopolymer foam formu lation according to the present invention by mixing the at least one cationic copolymer (i) with

(ii) the at least one inorganic binder mixtu re com prising

(iia) at least one inorganic binder selected from the grou p consisting of latent hyd rau lic binders, pozzolanic binders and mixtu res thereof, and

(iib) at least one al kaline activator selected from the grou p consisting of al kali metal hyd roxides, al kali metal carbonates, al kali metal alu minates, al kali metal silicates, and mixtu res thereof;

(iii) water; and

(iv) optional ly at least one additive, preferably a surfactant, more preferably a non ionic surfactant and most preferably an al kyl polyglucoside; and

(2) foaming of the resu lting geopolymer foam formu lation by chemical, physical and/or mechanical foaming.

The present invention is fu rther directed to a geopolymer foam obtained by the above men tioned process for preparing a geopolymer foam.

The present invention is fu rther directed to a cel lu lar material which is obtained by harden ing and optional ly d rying the geopolymer foam obtained by the above mentioned process for preparing a geopolymer foam.

The present invention is fu rther directed to a com position for preparing a geopolymer foam formulation comprising as com ponents at least one cationic copolymer (i) according to the present invention; and

(ii) at least one inorganic binder mixtu re comprising

(iia) at least one inorganic binder selected from the grou p consisting of latent hy d rau lic binders, pozzolanic binders and mixtu res thereof, and (iib) 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 are present separately; or

the components are present in a mixture.

The composition for preparing a geopolymer foam formulation optionally further comprises at least one additive. Preferable additives are selected from the group consisting of fillers, accelerators, retarders, rheology modifiers, superplasticizers, fibers, and surfactants.

The composition for preparing a geopolymer foam formulation optionally further comprises at least one additive, which is a surfactant. Preferably, the surfactant is a non-ionic surfac tant and more preferably an al kyl polyglycoside surfactant.

The composition for preparing a geopolymer foam formulation optionally further comprises at least one additive, which is a further rheology modifier. The further rheology modifier is preferably a polymer dispersion, more preferably a polymer dispersion comprising at least one copolymer comprising structural units formed from vinyl acetate and structural units formed from at least one further ethylenically unsaturated monomer.

The present invention is further illustrated by the following examples

Cationic Polymer Examples

P-1:

A cationic comb polymer composed of MPEG475-MA : l-Vinyl-3-methylimidazolium methyl sulfate in a molar ratio of 1:6, Mw =4.0 kDa, Mn = 1.7 kDa:

MPEG475-MA = methyl poly ethylene glycol (MPEG) ester of methacrylic acid having an Mn of 475 g/ mol

P-2:

A cationic copolymer having no side-chains and being composed of l-Vinyl-3-methylimidaz- olium chloride : N-vinylpyrrolidone in a mass ratio of 95:5, molar weight 40 kDa.

P-3:

A cationic copolymer having no side-chains and being composed of l-Vinyl-3-methylimidaz- olium chloride : N-vinylpyrrolidone in a mass ratio of 50:50, molar weight 80 kDa.

Application Examples

Two sets of experiments with different binder systems were done, each set of experiments is related to the base formulations according to the tables 1 and 2. The following tables contain the com ponents of each formulation (accelerator, (water), surfactant and inorganic binder(s) like for example metakaolin or fly ash) .

Table 1 (metakaolin / fly ash based formulation) :

Component Mass [g]

Water Glass 58 KWGL (BASF) 27.01

NaOH 1.534

Water 13.81 (in exam ples la-4 and lb only 12.43 g)

Su rfactant Al kyl polygl ucoside: Gluco on 0.46

225DK (BASF)

Metakaolin: Argical 1200 S 15.34

Fly ash: Flugasche Steament L10 14.43

Table 2 (metakaolin based formulation) :

Component Mass [g]

K45 potassiu m water glass 216

NaOH 12.4

Water 111.6

Su rfactant Al kyl polygl ucosi 8

225DK (BASF)

Metakaolin: Metamax (BAS 124

Dispersion: Vinnapas 5044 24.5

General Procedu res

Preparation of u nfoamed su pensions

I n a first step, by mixing of the com ponents of each of the before standing tables (without the su rfactant, but with or without the cationic polymers of examples P-1- to P-3) , respective u nfoamed suspensions were obtained. The density of the obtained u nfoamed suspensions is su m marized in each case in table 3.

Preparation of the fresh mineral foams

I n the second step, the su rfactant Glucopon 225DK was added to the u nfoamed suspen sions obtained in the first step and the mixtu re was mixed for fu rther 30 seconds. The sus pensions were pum ped by way of a hose into a ful ly automatic foaming machine for contin- uous foaming of liquids and low-viscosity pastes, operating in accordance with the stator- rotor principle (Magromix+ from Heitec Auerbach G mbH) . The process parameters were as fol lows: mixing head rotation rate 300 rpm, system air pressure approx. 2 bar, material th rough put 120 liters/hour. The air content of the obtained foamed suspensions was determined here by way of the volu me change in comparison with the u nfoamed suspension by a method based on DI N EN 1015-6. The densities of the foamed samples in the wet state are su mmarized in table 3.

A num ber of examples were prepared with the same base formu lations as mentioned in table 1 and 2 with the same two-step procedu re (1 ^st step preparation of u nfoamed suspension and 2 ^nd step preparation of the foam) as explained in the before standing text, with or without the cationic polymers. Details are given in table 3.

Hardening of the mineral foams

For cu ring sam ples were stored at room tem perature and 50 % hu midity for a period of one day.

Test Methods:

As an introduction, in the fol lowing chapter the testing methods and their tech nical meaning are briefly explained. The evaluation was done during or after the before mentioned three steps of producing the u nfoamed suspension, the fresh mineral foams and the hardening of the mineral foams, in most of the cases by relatively simple visual test methods.

As a general remark, it is on the one side desired to obtain a good workability and foamability of the suspensions during the foaming process. Du ring the foaming process mechanical en ergy is introduced into the system by the mixing process. On the one side a relatively low viscosity of the suspension is desirable in order to al low a smooth and effective foaming pro cess. On the other side after the foaming process is finished (after mixing is finished) , it is desired that the foamed samples stay stable and do not col lapse until the setting (hardening) of the inorganic binder system takes place.

The relatively low viscosity of the system during the mixing, fol lowed by a relatively high vis cosity when the foamed samples are no more mixed, is a typical thixotropic behavior. The thixotropic effect is high ly desirable, because it al lows on the one side a smooth and readily workable foami ng process and on the other side the thixotropic effect hel ps considerably to keep the fresh foamed sam ple enough stable (no col lapsing of the fresh foams) u ntil the hardening of the inorganic binder system takes place. I n the fol lowing text each test method is explained in detail.

Workability Test (foamability test by observation du ring mixing process)

I n this test the workability of the foams is evaluated during the mixing of the u nfoamed sus pensions with the su rfactant in order to obtai n the foamed suspensions. Basical ly, the time for obtaining the desi red density of the fresh foamed suspensions is measu red. I n al l of the examples the test conditions were chosen in a way that the time for obtaining the desired target density of the fresh foamed suspensions is in a reasonable range (about 5 minutes). It is supposed that the viscosity of the suspensions is im portant for the workability, it should not be too high in order to ensu re a smooth foaming process.

Stability Test (ST) (beaker method)

A stability test for the fresh foam samples was established as fol lows: a 250 m l_ beaker is fil led with foam and tilt at an angle of 90° . The optimu m resu lt is observed if no liquid foam flows out of the beaker before setting, a slow and partial flowing out is a considerable im provement in comparison to a rather fast flowing. The stability test, especially in com bination with the before mentioned workability test, is a test for thixotropy. It is desirable that the slu rry viscosity during mixing is rather low, but shortly after stopping mixing the foams should be not flowable or only be little flowable in order to guarantee stability for the foams u ntil hardening sets on.

Dripping Test (DT) (spatu la method)

The d ripping test is a similar test as the stability test (beaker method) . It is also a method to evaluate the thixotropy of the foams. The dripping test is done by introducing a spatu la into the fresh ly prepared foam and taking it out of the foam. I n the ideal case the foam is so viscous that the foam adheres to the spatu la and does not drip off from the spatula.

Visual Observation Test (VOT) for cracking (shrinkage)

The obtai ned sam ples were evaluated for cracks by visual observation after hardening. The cu ring conditions were storing of the sam ples at room tem peratu re and 50 % hu midity for a period of one day. It is believed that main ly shrin kage is the reason for the crack formation.

Test Resu lts

An overview of al l the experiments and the results is given in the fol lowing table 3. As men tioned before, the workability (foamability) of al l exam ples was chosen to be in a reasonably wel l workable range.

I n some cases the insu lation properties of the hardened foams were determined by measur ing the lam bda value (mW/m*K) , this is a further indicator for homogeneity of hardened foams on macro- and microstructu re level.

The experiments and resu lts of table 3 show that in com parison to the exam ples with no addition of cationic polymers a considerable improvement of the stability of the foams (re su lts of the stability test and the dripping test) cou ld be achieved. The workability of the samples during mixing (foaming) was in a satisfactory range and a good thixotropic effect cou ld be observed after stopping mixing. The samples proved to have a good foam stability. It was also possible to reduce the amou nt of water (exam ple la-4 and lb) by 10 weight % without negative influence on the thixotropic effect and the workability. At the same time the cracking was in an acceptable range. Also in the visual observation test (cracking) much better resu lts cou ld be obtained for the sam ples according to the invention, compared to the com parative exam ples. The nu mber of cracks was considerably reduced as the table shows.

ble 3: overview of the experiments and the test results

The dosage indications in wt.- % refer to the weight of the cationic polymer (dry polymer) on the weight of the com ponents in tables 1 or 2 (water glass, NaOH, water, su rfactant and respective inorganic binder(s)).

) The nu mber 1 means an excellent resu lt with few or no foam flowing out, 2 means a good resu lt with a mediu m amount of foam flowing out and 3 means an u nsatisfactory resu lt with major amou nt of foam flowing relatively quickly out of the test beaker.

) Similar as in the stability test, the number 1 means an excel lent result with al l of the foam sticking to the spatu la or nearly al l of it, 2 means a medium result with some of the foam d ripping from the spatula and 3 is an u nsatisfactory resu lt with major amount of foam d ripping down from the spatula.

) The nu mber 1 means a good results with no cracks being observable or on ly very few and minor cracks, nu mber 2 means stil l a good result with a stil l acceptable cracking and 3 is an u nsatisfactory result with heavy cracking.

) The amount of water was reduced by 10 wt %, which means that in the case of the Exam ple la-4 and Example lb instead of 13,81 g only 12,43 g of water were used.