COMPOSITION FOR THE FORMATION OF A GEOPOLYMER WITH THERMAL RESISTANCE AT HIGH TEMPERATURES

Abstract

------ COMPOSITION FOR THE FORMATION OF A GEOPOLYMER WITH THERMAL RESISTANCE AT HIGH TEMPERATURES The present invention relates to a composition for the formation of a geopolymer, comprising: an aluminosilicate powder; and an aqueous alkaline solution of at least one alkali metal silicate, characterized in that the alkali metal of said silicate or silicates is potassium, and that the composition comprises, expressed as oxides, the constituents SiO2, K2O, Al2O3 and CaO, and where appropriate the constituents BaO and MgO, in a molar ratio: (SiO2 + Al2O3) / (CaO + BaO + MgO + K2O + Al2O3) of between 1.31 and 3.31, SiO2 from (A); K2O from (B); Al2O3 and CaO from (A); andBaO and MgO, if present, from (A).

Description

Title of the invention: COMPOSITION FOR THE FORMATION OF A GEOPOLYMER WITH THERMAL RESISTANCE AT HIGH TEMPERATURES

[0001] The present invention relates to a composition for forming a geopolymer which enables the formation of a geopolymer having thermal resistance at high temperatures.

[0002] By "geopolymers" is meant aluminosilicate compounds prepared at room temperature. Geopolymer materials are amorphous aluminosilicate gels resulting from the alkaline activation of an aluminosilicate source at low temperature (< below 100°C). The general formula of these materials is M+n{(SiO2)z, Al2O3]n, wH20) with n, the degree of polymerization, z the Si / Al molar ratio and M+ a monovalent cation. The polycondensation and geopolymerization reactions are responsible for the formation of a three-dimensional network of SiO4 and A1O4 tetrahedra leading to the consolidation of the material.

[0003] Geopolymers are generally prepared from a reactive aluminosilicate source ideally consisting of treated kaolins or activated clays, then activated in alkaline aqueous media (soda or potash and alkali silicate). Solid matrices are then obtained by polycondensation reactions of alkali silicates.

[0004] Geopolymers have properties which give them good behavior in the face of thermal stresses, to the point of sometimes being used as fire protection materials.

[0005] The main areas of application for geopolymers are: • the development of new mineral binders with lower energy requirements than cement binders; • the inerting of industrial waste, for example to formulate containment matrices for reactive metallic radioactive waste; • the recovery of industrial co-products or by-products; • the development of thermal protection barriers.

[0006] Patent application FR 3092108 relates to compositions for the formation of a geopolymer making it possible to obtain a geopolymer having satisfactory resistance at 1000°C. However, there is a need for geopolymers which have thermal resistance at temperatures above 1000°C, such as thermal resistance at temperatures of at least 1300°C.

[0007] The need for geopolymers and the extent of their applications are such that it is appropriate to propose new ones. In particular, polymers having good stability properties of mechanical properties at temperatures of at least 1300°C are sought.

[0008] For this purpose, the present invention relates to a composition for the formation of a geopolymer, comprising: A. an aluminosilicate powder; and B. an aqueous alkaline solution of at least one alkali metal silicate,

[0009] characterized in that the alkali metal of said silicate or silicates is potassium, and that the composition comprises, expressed as oxides, the constituents SiO2, K2O, A12O3 and CaO, and where appropriate the constituents BaO and MgO, in a molar ratio:

[0010] (SiO2 + A12O3) / (CaO + BaO + MgO + K2O + A12O3)

[0011] between 1.31 and 3.31, • SiO2 from (A); • K2O from (B); • A12O3 and CaO from (A); and • BaO and MgO, if present, from (A).

[0012] The composition according to the invention may comprise, expressed as molar percentages of oxides: 1. 35 to 75% SiO2; 2. 2 to 10% K2O; 3. 10 to 45% Al2O3; 4. 0.5 to 14% CaO; 5. 0 to 14% BaO; and 6. 0 to 10% MgO,

[0013] the above molar percentages being given for 100% of (1)+(2)+(3)+(4)+(5)+(6).

[0014] In particular, the composition may comprise, expressed as molar percentages of oxides: 1. 39 to 73% SiO2; 2. 4 to 7% K2O; 3. 15 to 42% Al2O3; 4. 0.5 to 5% CaO; 5. 0 to 14% BaO; and 6. 0 to 10% MgO,

[0015] the above molar percentages being given for 100% of (1)+(2)+(3)+(4)+(5)+(6).

[0016] The aluminosilicate powder may consist of a mixture of at least one metakaolin with at least one of: - the sand; CaCo3; - blansil; - mullite; - fireclay; - boehmite; - hydrotalcite; - BaCO3; and A1(OH)3.

[0017] Component (B) may be an aqueous solution of potassium silicate, the potassium having been able to be introduced at least partly in the form of pellets into the alkaline aqueous solution.

[0018] The following Examples illustrate the present invention without, however, limiting its scope.

[0019] In Table 1 below, the constituents used in Examples 1 to 32 of the invention and their respective quantities used according to the general procedure also mentioned below are mentioned.

[0020] Table 2 shows the molar percentages of Si, Al, Ca, Ba, Mg and K calculated as oxides for each of these examples with the corresponding values ​​of (SiO2 + A12O3) / (CaO + BaO + MgO + K2O + A12O3).

[0021] The constituents of the compositions are defined as follows:

[0022] SI: aqueous solution of potassium silicate having a molar ratio Si / K = 1.75, marketed by the Woellner Company (Germany) under the name “Geosil 52434”;

[0023] S3: aqueous solution of potassium silicate having a molar ratio Si / K = 0.67, marketed by the Woellner Company (Germany) under the name “Geosil 14515”;

[0024] K: 86% pure potassium hydroxide pellets, marketed by the company Sigma-Aldrich (United States of America);

[0025] M5: pink metakaolin, marketed by the company ARGECAO (France) under the name “Argicem”, obtained by the flash process and having a Si / Al molar ratio of 1.50;

[0026] Sablon: pink colored sand, produced from the manufacture of metakaolin, having a particle size d50 = 190 pm and composed of 95.6% SiO2;

[0027] Blansil: white sand, marketed by the company SIBELCO (France), having a particle size d50 = 210 pm and composed of 99% SiO2;

[0028] Mullite: an aluminum silicate (3A12O3,2SiO2), marketed by the company Nabaltec (Germany) under the name “Symulox M72”;

[0029] Chamotte 1: a clay calcined in a rotary kiln, marketed by the company Imerys (France) under the name “Clayrac 45P”, with a resistance up to 1780°C and composed of 45% A12O3 and 50.9% SiO2;

[0030] Chamotte 2: a clay calcined in a rotary kiln, marketed by the company Imerys (France) under the name “Clayrac 43”, with a resistance up to 1450°C and composed of 43% A12O3 and 52.9% SiO2;

[0031] Boehmite: a product with a high alumina content and chemical formula y-ALOOH, boehmite is marketed by the company SASOL (Germany) under the name “Dispal 23N4-80” and composed of 85% A12O3;

[0032] Hydrotalcite: magnesium and aluminum hydrocarbonate (CH16A12Mg6O19.4H2o) marketed by the company Sigma-Aldrich (United States of America), composed of 42% MgO and 9.33% A12O3;

[0033] Calcium carbonate: lime carbonate or chalk is a product marketed by the company Ceradel (France);

[0034] Barium carbonate: white powder with the chemical formula BaCO3, marketed by the company CERADEL (France), under the name “Barite”;

[0035] Aluminum hydroxide: powder with chemical formula A1(OH)3, marketed by the company CERADEL (France), under the name “hydrated alumina (SH_150)”. General operating procedure

[0036] Preparation of S1S3: into 17.99g of a mixture of two potassium silicate solutions were introduced 31.6% by weight of a solution having a Si / M ratio of 1.7 and %H2O = 79.28 and 68.4% by weight of another solution having a Si / M ratio of 0.7 and %H2O = 59.4%. The solution mixture is then stirred using a magnetic stirrer for 5 minutes in order to fix the Si / M ratio (with M = K) at 0.8.

[0037] Preparation of S1K: in 15.6g of a potassium solution (having a Si / M ratio of 1.7 and %H2O = 79.28), 3.16g of KOH pellet were dissolved using a magnetic stirrer for 5 minutes in order to fix the Si / M ratio (with M = K) at 0.5.

[0038] In 5.68 g of SI, 12.31 g of S3 or 15.6 g of SI and 3.16 g of K, all the constituents of the aluminosilicate powder are added.

[0039] The resulting mixture is then cast into a predefined shape and stored in an endogenous system for 3 days, before carrying out the temperature resistance test. Temperature resistance test

[0040] The temperature resistance of geopolymers is tested in a cell furnace at a ramp rate of 5°C / min up to 1300°C, followed by a 30 min isotherm. Cooling is carried out naturally.

[0041] [Tables 1] 3 5.68 12, 31 - 22 - - - - - - - - 14.89 11.77 - 2 5.68 12, 31 - 22 - - - - - - - - 9.58 7.56 - 3 5.68 12, 31 - 22 - 5 - 10 5 - - - - - - 4 5.68 12, 31 - 22 - - - - - - - - 5.58 4.41 - 5 5.68 12, 31 - 22 - - - - - - - - 5.58 4.41 5.7 4 6 5.68 12, 31 - 22 - - - - - - - - 2,48 1,96 - 7 5.68 12, 31 - 22 12 3 1 - - - 5,6 - - - 8 5.68 12, 31 - 22 - - - - - - - - 1,17 0,93 4,7 6 9 5.68 12, 31 - 22 - - - - - - - - 1,17 0,93 - 10 5.68 12, 31 - 22 - 5 12 10 5 - - - - - - 11 5.68 12, 31 - 22 12 3 1 5.5 9 - - 2,8 - - - 12 5.68 12, 31 - 22 12 3 1 5,59 0,56 0,56 - 2,4 - - 13 5,68 12, 31 - 22 12 3 1 5,59 0,56 - - 2,8 - - 14 5,68 12, 31 - 22 12 3 1 5,59 - - 0,56 - - - 15 5,68 12, 31 - 22 12 3 1 5,59 2,8 - 0,56 - - - 16 5,68 12, 31 - 22 12 3 1 5,5 9 2,8 0,56 0,56 - - - 17 15,6 - 3,1 6 22 12 3 1 5,5 9 - - - - - - 18 5,68 12, 31 - 22 12 3 1 5,5 9 2,8 0,56 0,56 - - - 19 5,68 12, 31 - 22 12 3 1 5,5 9 - - - - - - 20 5,68 12, 31 - 22 12 3 1 5,5 9 2,8 - - - - - 21 5,68 12, 31 - 22 12 3 1 5,5 9 2,8 - - - - - 22 5,68 12, 31 - 22 12 3 1 5,5 9 5,6 - - - - - 23 15,6 - 3,1 6 22 12 3 1 - - - - - - - 24 15, 6+1 h2o - 3,1 6 22 12 3 1 - - - - - - - 25 5,68 12, 31 - 22 12 3 1 - 5,59 - - - - - 26 10, 54 6,29 1,5 5 22 12 3 1 - - - - - - - 27 15,6 - 3,1 6 22 12 3 1 - 5,59 - - - - - 28 5,68 12, 31 - 22 12 3 1 - - - - - - - 29 15,6 - 3,1 6 22 12 3 1 - 11,2 - - - - - 30 5,68 12, 31 - 22 12 3 1 - 5,59 - - - - - 31 5,68 12, 31 - 22 12 3 1 - 11,2 - - - - - 32 8,74 9,36 - 22 12 3 1 - - - - - - - [Tableaux2]

[0042] Exe mple SiO2 (%) k2o (%) A12O3 (%) CaO (%) BaO (%) MgO (%) (SiO2 + A12O3) / (CaO + BaO + MgO + K2O + A12O3) 1 39,23 5,82 40,64 0,84 13,47 0,00 1,31 2 45,87 6,80 36,23 0,98 10,12 0,00 1,52 3 52,30 5,58 28,97 13,15 0,00 0,00 1,70 4 52,51 7,79 31,81 1,13 6,76 0,00 1,78 5 52,51 7,79 31,81 1,13 6,76 0,00 1,78 6 59,19 8,78 27,37 1,27 3,39 0,00 2,12 7 65,97 5,03 12,58 7,40 0,00 9,02 2,31 8 62,55 9,27 25,14 1,34 1,70 0,00 2,34 9 62,55 9,27 25,14 1,34 1,70 0,00 2,34 10 64,38 4,16 21,64 9,82 0,00 0,00 2,41 11 66,68 4,81 17,12 7,08 0,00 4,31 2,51 12 67,90 4,84 18,31 7,14 1,81 0,00 2,69 13 68,17 4,86 17,69 7,16 2,12 0,00 2,70 14 69,07 4,98 17,73 7,33 0,00 0,89 2,81 15 68,84 4,72 18,66 6,94 0,00 0,84 2,81 16 68,94 4,71 18,57 6,94 0,00 0,84 2,82 17 69,45 5,35 17,83 7,37 0,00 0,00 2,86 18 69,42 4,76 18,82 7,00 0,00 0,00 2,89 19 69,69 5,02 17,89 7,40 0,00 0,00 2,89 20 69,47 4,76 18,76 7,01 0,00 0,00 2,89 21 69,47 4,76 18,76 7,01 0,00 0,00 2,89 22 69,38 4,52 19,45 6,65 0,00 0,00 2,90 23 72,87 5,93 13,02 8.18 0.00 0.00 3.17 24 72.87 5.93 13.02 8.18 0.00 0.00 3.17 25 72.33 4.96 15.40 7.31 0.00 0.00 3.17 26 73.02 5.75 13.04 8.19 0.00 0.00 3.19 27 72.71 5.27 14.76 7.26 0.00 0.00 3.20 , 28 73.15 5.57 13.07 8.21 0.00 0.00 3.21 29 72.57 4.74 16.16 6.53 0.00 0.00 3.24 30 72.95 4.95 14.81 7.29 0.00 0.00 3.25 31 72.79 4.45 16.21 6.55 0.00 0.00 3.27 32 73.75 4.79 13.18 8.28 0.00 0.00 3.31

[0043] Each of the geopolymers obtained in Examples 1 to 32 has a thermal resistance at 1300°C.

[0044] A temperature resistance test was conducted in the same manner as described above, except that the maximum temperature was increased to 1400°C. The geopolymers of Examples 1 and 2, and 4 to 6, and 8 to 9 exhibited resistance at this temperature.

[0045] The geopolymers of Examples 1 and 2 also exhibited thermal resistance in a temperature resistance test at a maximum temperature of 1500°C. Comparative example

[0046] In 15.6g of a potassium solution (having a Si / M ratio of 1.7), 3.16g of KOH pellet were dissolved using a magnetic stirrer for 5 minutes in order to fix the Si / M ratio (with M = K) at 0.5.

[0047] Then, 22g of metakaolin M5, 12g of sablon, 1g of blansil and 3g of calcium carbonate were added which forms a base mixture. In this mixture, 10% by weight of wollastonite of the base mixture was added, the whole is poured into a predefined form and stored in an endogenous system for 3 days, before carrying out the temperature resistance test at 1300°C as for examples 1 to 32 above.

[0048] The molar ratio (SiO2 + A12O3) / (CaO + BaO + MgO + K2O + A12O3) was 3.48.

[0049] This test was unsuccessful, the part presented a split appearance with the formation of glass on the surface.

Claims

Claims

1. - Composition for forming a geopolymer, comprising: A. an aluminosilicate powder; and B. an alkaline aqueous solution of at least one alkali metal silicate, • characterized in that the alkali metal of said silicate or silicates is potassium, and that the composition comprises, expressed as molar percentages of oxides: • 39.23% of SiO2; 5.82% of K2O; 40.64% of Al2O3; 0.84% ​​of CaO; and 13.47% of BaO; or • 45.87% of SiO2; 6.80% of K2O; 36.23% of Al2O3; 0.98% of CaO; and 10.12% of BaO.

2. - Composition according to claim 1, characterized in that the aluminosilicate powder consists of a mixture of at least one metakaolin with at least one of: - sand; CaCo3; - mullite; - chamotte; - boehmite; - hydrotalcite; and A1(OH)3.

3. - Composition according to one of claims 1 and 2, characterized in that (B) is an aqueous solution of potassium silicate, the potassium having been introduced at least partly in the form of pellets into the alkaline aqueous solution.