Method for forming a quickly hardening, inorganic foam

Abstract

A process is provided for forming a rapid-hardening inorganic foam, based on the reaction of the following two components: (a) a solid component in the form of a reactive powder having at the same time structure-building and pore-forming properties, and (b) a liquid component in the form of an alkali metal silicate (water glass). The reactive powder contains the essential constituents: 45-65% by weight aluminum oxide, 10-20% by weight aluminum nitride, and 5-15% by weight metallic aluminum. The alkali metal silicate has a molar ratio of silicon oxide to metal oxide of 1.0 to 2.2. The two components are mixed in a weight ratio of powder to liquid component of 0.5 to 2 to give a paste from which a foamed body having a bulk density of less than 0.7 g/cm 3 is then formed in an exothermal reaction within less than 10 minutes.

1 - 22 . (canceled) 
     
     
         23 . A process of forming a rapid-hardening inorganic foam based on reaction of two components (a) and (b) as follows:
 a) a solid component in a form of a reactive powder having structure-building and pore-forming properties, and   b) a liquid component in a form of an alkali metal silicate, wherein the reactive powder comprises as essential constituents:   45-65% by weight aluminum oxide,   10-20% by weight aluminum nitride,   5-15% by weight metallic aluminum, and   has a particle size of at least 90% by weight smaller than 1 mm,   the process comprising mixing the two components in a weight ratio of the powder to the liquid component of 0.5 to 2 to yield a paste, and forming a foamed body having a bulk density of less than 0.7 g/cm 3  in an exothermal reaction within less than 10 minutes.   
     
     
         24 . The process in accordance with  claim 23 , wherein the two components are mixed for a maximum of five minutes, optionally a maximum of one minute. 
     
     
         25 . The process in accordance with  claim 23 , wherein the two components are mixed without supply of heat from the outside, optionally at room temperature, to yield the paste. 
     
     
         26 . The process in accordance with  claim 23 , wherein the alkali metal silicate is in a form of a solution having a molar ratio of silicon oxide to metal oxide of 1.0 to 2.2. 
     
     
         27 . The process in accordance with  claim 23 , wherein the reactive powder has a weight ratio of aluminum nitride to metallic aluminum of greater than 1. 
     
     
         28 . The process in accordance with  claim 23 , wherein the reactive powder has a particle size of at least 90% by weight smaller than 300 μm. 
     
     
         29 . The process in accordance with  claim 23 , wherein the reactive powder is mixed with a liquid potassium water glass, having a molar ratio (SiO 2 :K 2 O) of 1.16 to 1.26. 
     
     
         30 . The process in accordance with  claim 23 , wherein the reactive powder and the alkali metal silicate are used in combination with at least one additional mineral raw materials selected from metakaolin, fly ash, slag, pozzolan, cement, lime, gypsum, sand, glass fibers, and mineral fibers. 
     
     
         31 . The process in accordance with  claim 30 , wherein, if necessary, further alkali metal silicate or water is added in a quantity necessary for adjusting a pasty consistency of the mixture. 
     
     
         32 . The process in accordance with  claim 23 , wherein a BET surface area of the reactive powder is smaller than 10 m 2 /g, optionally smaller than 7.5 m 2 /g or smaller than 5 m 2 /g. 
     
     
         33 . The process in accordance with  claim 23 , wherein the reactive powder is a powder which has been recovered from aluminum dross, optionally a powder recovered from aluminum dross by mechanical size reduction and classification. 
     
     
         34 . A reactive powder for forming a rapid-hardening mineral foam by reaction with an alkali metal silicate, wherein the reactive powder comprises as essential constituents:
 45-65% by weight aluminum oxide,   10-20% by weight aluminum nitride, and   5-15% by weight metallic aluminum, and   has a particle size of at least 90% smaller than 1 mm.   
     
     
         35 . The reactive powder in accordance with  claim 34 , wherein the reactive powder has a weight ratio of aluminum nitride to metallic aluminum of greater than 1. 
     
     
         36 . The reactive powder in accordance with  claim 34 , wherein the reactive powder has a particle size at least 90% by weight smaller than 300 μm. 
     
     
         37 . The reactive powder in accordance with  claim 34 , wherein the reactive powder has a BET surface area smaller than 10 m 2 /g, optionally smaller than 7.5 m 2 /g or smaller than 5 m 2 /g. 
     
     
         38 . The reactive powder in accordance with  claim 34 , wherein the reactive powder has been recovered from aluminum dross, optionally by mechanical size reduction and classification. 
     
     
         39 . A method for forming an inorganic foam, particularly a lightweight construction material, by reaction of a solid component in a form of a reactive powder having structure-building and pore-forming properties, wherein the reactive powder has been recovered from aluminum dross and contains as essential constituents:
 45-65% by weight aluminum oxide,   10-20% by weight aluminum nitride, and   5-15% by weight metallic aluminum.   
     
     
         40 . The method according to  claim 39 , wherein at least 90% by weight of the reactive powder has a particle size of less than 1 mm, optionally less than 300 μm. 
     
     
         41 . The method according to  claim 39 , wherein the reactive powder is reacted with a liquid component in the form of an alkali metal silicate to form the inorganic foam. 
     
     
         42 . The method according to  claim 39 , wherein the reactive powder has a weight ratio of aluminum nitride to metallic aluminum of greater than 1. 
     
     
         43 . The method according to  claim 39 , wherein the reactive powder has a BET surface area smaller than 10 m 2 /g, optionally smaller than 7.5 m 2 /g or smaller than 5 m 2 /g. 
     
     
         44 . An inorganic foam or lightweight construction material formed by the process according to  claim 23 , wherein the foam or construction material is at least one of a thermally insulating and a fire-resistant lightweight construction material. 
     
     
         45 . The inorganic foam or lightweight construction material according to  claim 44 , wherein the foam or construction material is present in a form of a finished part, optionally in a form of an insulating board.