Silicate precursor for sol-gel processes, method for production thereof and use thereof

Abstract

The present invention relates to alkali metal hydrosilicates and to a method for the production thereof by mixing particulate silica raw materials comprising at least 70% amorphous SiO2 and dry particulate alkali hydroxide with further addition of water, and to the use thereof.

Description

Silicate precursor for sol-gel processes, method for production thereof and use thereof

[0001] The present invention relates to alkali metal hydrosilicates and to a method for the production thereof by mixing particulate silica raw materials comprising at least 70% amorphous SiCh and dry particulate alkali hydroxide with further addition of water.

[0002] The present alkali metal hydrosilicates represent intermediates, more specifically precursors, for producing hydrosilicate gels and / or respective solid silicates via a sol-gel process, the properties of said silicate materials, depending on the composition of the precursors and the conditions of the sol-gel process, possessing valuable properties, such as gluing capability, capability for phase transition heat absorption, capability for water deposition and capability for silicification of cellulose, and, thus, being suitable as materials for fire protection, materials for prevention of thermal runaway and starting materials for producing cellulose based composites. The expression "hydrosilicates" as used herein also encompasses hydroaluminosilicates.

[0003] As mentioned above, the alkali metal hydrosilicates are precursors for sol-gel processes in the meaning as described in Compendium of Polymer Terminology and Nomenclature IUPAC Recommendations 2008, ed. by Richard G. Jones et al., RSC Publishing, 2009, ISBN: 978-0-85404-491- 7, pp.211 - 236, Chapter 11 - Definitions of terms relating to the structure and processing of sols, gels, networks and inorganic -organic hybrid materials.

[0004] The WO 2021 / 248173 A2 describes a method for producing a colloidal aqueous dispersion of an alkali metal hydrosilicate in the nature of a fire protecting system, comprising feeding a comminuted raw silicone dioxide material and a granulated alkali metal hydroxide into a reactor, adding water into the reactor and mixing the components with spontaneous heating. The obtained colloidal aqueous dispersion of an alkali metal hydrosilicate is curable under environmental conditions to give a hard alkali metal hydrosilicate gel and must be stored in a hermetic packaging, preferably vacuum-packed.

[0005] There is still a need to provide an alkali metal hydrosilicate with improved properties, such as fire protection properties due to a high water content, and handling characteristics, in particular, no curing or hardening after storage under Standard Ambient Temperature and Pressure (SATP, 25°C, 100000 kPa / 1 bar) for at least 28 days.

[0006] The object is achieved by the alkali metal hydrosilicates and the method for the production thereof according to the present invention.

[0007] The method according to the present invention comprises the steps of: a) providing a particulate silica raw material comprising at least 70% amorphous Si O2 and a dry particulate alkali hydroxide, and optionally adjusting the humidity content of the silica raw material to at least about 70% by weight and not more than about 84.5% by weight;b) mixing the particulate silica raw material and the dry particulate alkali hydroxide in a ratio of 1 part by weight of alkali hydroxide and 5.25 to 10.5 parts by weight of silica raw material under specific energy input of about 200 kJ / kg to 750 kJ / kg, preferably in an agitator or mixer, respectively, at a rotation speed from 1000 to about 4000 rpm. c) adding water in order to reach a ratio of 1 part by weight of the dry solids to 2.5 to 4.8 parts by total weight of water, preferably under the mixing conditions of step b), to obtain a viscous product, and optionally adjusting the amount of water based on the humidity content of the employed silica raw material.

[0008] Suitable silica raw materials for obtaining the present alkali metal hydrosilicates are natural or artificial materials comprising not less than 70 % by weight of amorphous SiCh (cf. for example, WO 2009 / 105051 Al and WO 00 / 46277 A2). Natural materials are usually selected from sedimentary rocks, such as diatomites, kieselguhrs, tripolis, planner, spongiolites, radiolarites, opals and the like (e.g. Ivanenko V.N., Building materials and products from siliceous rocks, Kiev, publishing house "BUDIVELNIK, 1978, p.5). Artificial materials are, for example, by-products of amorphous silica, including fused silica, silica fume, microsilica and other technogenic types of amorphous silica. One or more silica raw materials can be employed. For handling purposes, the starting materials are employed in crushed and / or milled form, i.e. particulate form. Preferably, the average particle size is equal or less 0.5 mm, more preferable between 50 pm and 150 pm. Preferably, the silica raw material is comminuted to a particle size resulting in a specific surface area of the material in the range of 0.05 to 0.5 m2 / g. Further comminution is not required for the manufacturing process but is encompassed by the present invention. Hereinunder the starting silica materials in particulate form are also indicated as "siliceous sand".

[0009] Preferably, the silica raw material is selected from diatomites and by-products of amorphous silica.

[0010] More preferable silica raw materials are a diatomite (type 1) of the following composition:

[0011] or a diatomite (type 2) of the following composition:

[0012] or amorphous silica by-product (microsilica) of ferroalloys production of the following composition:

[0013] The humidity content (content of moisture) of the employed silica raw materials is preferably at least about 70% by weight and not more than about 81.5% by weight, more preferably from about 71 % by weight to about 80% by weight, even more preferably from about 71.5 % by weight to about 79.5 % by weight, specifically from about 71.9 to about 78.0 % by weight. Preferably, the humidity content of the employed silica raw materials is determined prior to feeding and is adjusted accordingly by drying or adding of water. Since water is added into the reaction mixture, the final water content of the reaction mixture usually is different compared to the humidity content of the employed silica raw materials. The amount of water added to the reaction mixture can be adjusted based on the humidity content of the employed silica raw materials.

[0014] Dry particulate alkali hydroxides in the meaning of the present invention are sodium hydroxide (caustic soda, NaOH) and potassium hydroxide (caustic potash, KOH) or a combination thereof, which are commercially available, usually in form of granules or flakes. Preferably, the employedparticulate alkali hydroxide is air-dry. Thus, a specific storage under controlled atmosphere or a drying or wetting of the alkali hydroxide prior to feeding into the reaction mixture is not necessary. Although not necessary, such a preliminary processing or treatment of the alkali hydroxide is still possible according to the present invention.

[0015] According to the present method the weight ratio of dry particulate alkali hydroxides to particulate dry silica raw material is 1 part by weight of the alkali hydroxide to 5.25 to 10.5 parts by weight of the silica raw material, preferably 1 part by weight of the alkali hydroxide to 5.5 to 10.0 parts by weight of the silica raw material, more preferably 1 part by weight of the alkali hydroxide to 5.56 to 10.0 parts by weight of the silica raw material.

[0016] According to the present method the weight ratio of employed dry solids (dry particulate alkali hydroxides and particulate silica raw material calculated in dry state without moisture) to water is 1 part by weight of the solids to 2.55 to 4.3 parts by weight of water, preferably 1 part by weight of the solids to 2.59 to 4.0 parts by weight of water, more preferably 1 part by weight of the solids to 2.63 to 3.3 parts by weight of the silica raw material.

[0017] Preferably, the water is added with a temperature of about 75 °C to about 95 °C, preferably about 75 °C to about 85 °C.

[0018] It has been surprisingly found that contrary to the standard low-speed mixing approach (rotation speed of about 100 - 150 rpm and with relatively low specific energy input in about 10 - 20 kJ / kg) as usually applied in this technical field, according to the present invention a mixing approach is favourable, wherein the energy input is at least about 1 - 1.5 orders of magnitude higher compared to the common low-speed mixing approach. It is believed that a mechanical activation in the reaction mixture occurs due to said mixing approach. Thus, according to the present invention the mixing is performed a specific energy input of about 200 kJ / kg to 750 kJ / kg, preferably in an agitator or mixer, respectively, at rotation speed from 1000 to 4000 rpm, preferably 2000 rpm. Preferably, the mixing in step b) and step c) are performed under the same conditions. The mixing is usually performed for a time period of 25 min to 45 min, preferably 30 min to 40 min in step b) and of 35 min to 75 min, preferably 40 min to 60 min in step c). The specific energy input during mixing is calculated based on the known amounts of raw materials for producing of the samples of alkali metal hydrosilicate (silicate precursor) in accordance to present invention and the dependencies between the power applied to the mixing elements of a mixer and rotation speed of the mentioned elements, which are specified in the technical guidelines of the mixers which were used for production of samples according to present invention.

[0019] Alkalization of the silica raw material by the alkali hydroxide is accompanied by self-heating due to exothermic dilution / reaction to a temperature of about 85-95°C. Preferably, the temperature of the reaction mixture is maintained between about 75 °C and about 95 °C by heating or cooling.

[0020] According to a preferred embodiment of the method according to the invention the viscosity of the product obtained in step c) is determined, e.g. by taking samples and measuring with a Brookfield viscosimeter.

[0021] The obtained product can be removed from the process into suitable containers for storage and further use. Preferably, the product is removed after a cooling step, which preferably, is performed by maintaining the product without external heating.

[0022] The method of the present invention can be performed in a heat-insulated process vessel equipped with a mixer, batchers for particulate silica raw material, particulate alkali hydroxide and heated water and a product outlet.

[0023] The alkali metal hydrosilicate according to the present invention does not harden (retains a non-solid like state) after storage under Standard Ambient Temperature and Pressure (SATP, 25 °C, 100000 kPa / 1 bar) for at least 28 days. This is determined by loading a sample of the material into a mould (150 mm cube, prepared according to EN 12390-1:2000) and storing for 28 days under SATP. After unloading from the mould, the sample is placed on a flat surface (a table). The non-hardening of the alkali metal hydrosilicate is proven by the fact that the sample of the material according to the invention loses the cubic form after opening the mould which was stored under SATP as it is described above. After opening the mould, the sample usually has a cubic form, however the sample should lose the cubic form within a certain period, typically after about 12 to about 24 hours of storage on the flat surface under SATP. A sample, which keeps the cubic form for a period exceeding 24 hours under SATP is defined to be hardened.

[0024] The alkali metal hydrosilicate according to the present invention, after thermal treatment (dewatering) at a temperature of 250°C ± 5°C for 30 min ± 1 min, shows a chemical elemental composition in % by weight: Silicon - 27-40; Aluminium -0.9-3.5; Iron - 0.2-3.5; Calcium - 0.2-2.0; Magnesium -0.05 - 0.5; Alkali metal (sodium, potassium or combination thereof) -8.0 - 19.0; Oxygen - 43-54; Other elements - not more than 3.0% based on XRF data. The thermal treatment can be performed in a laboratory oven, for example Binder GmbH (Germany), and the elemental composition can be determined by XRF spectrometer, for example Benchtop XRF Spectrometer SPECTROCUBE C (Ametek / SPECTRO, Germany).

[0025] It has been found that the properties of the inventive material are sensitive to the content of Al, Ca, Mg and Fe. A higher content of Al, Ca, Mg and Fe compared to the above chemical elemental composition resulted, in particular, in a significant decrease of the adhesive properties.

[0026] The alkali metal hydrosilicate according to the present invention shows a loss of weight of about 45 % by weight to about 65 % by weight after thermal treatment (dewatering) at a temperature of 250°C ± 5°C for 30 min ± 1 min (thermal treatment can be performed in a laboratory oven, for exampleBinder GmbH (Germany), determination can be performed by a moisture analyser, for example a moisture analyser Sartorius MA 36, which is modified in order to use higher operation temperature during measurements. Said weight loss essentially corresponds to the water content in the material.

[0027] The alkali metal hydrosilicate according to the present invention has a viscosity at a temperature 25 ± 0.5°C of about 100 - about 70000 Pa*sec, preferably about 150 - about 1600 Pa*s, more preferably about 200 - about 1500 Pa*s (measured by a Brookfield viscosimeter, for example IKA ROTA VISC hi-vi II).

[0028] The alkali metal hydrosilicate according to the present invention has a pH value from about 10.2 to about 13, preferably from about 10.6 to about 12. The pH value can be measured with a pH meter, for example model testo 206-ph3.

[0029] It has been surprisingly found that the alkali metal hydrosilicate according to the present invention comprises a so-called "acidic component", which can be extracted from the inventive precursor material, in particular under elevated temperature, preferably below 90°C, more preferably at about 70°C, and reduced pressure, preferably below 0.5 bar, more preferably at about 0. 1 bar.

[0030] Without being bound by theory, it is believed that because of the relatively low concentration of alkali metal (in particular sodium) in the alkali metal hydrosilicate according to the present invention in combination with a high amount of water and a high energetic mixing (compared to common low-speed mixing approach) the occurrence of hydrolysis processes is stimulated. Thus, at a first stage hydrolysis is realized, for example, via reaction:

[0031] At a second stage of hydrolysis, is probably:

[0032] The general properties of the "acidic component" are quite similar to the properties of a mixture of silicic acids. Taking into account the hydrophobic properties the "acidic component" it will affect the process of hardening the material.

[0033] The presence of a high amount of a hydrophobic acidic component in the material might affect the gluing ability. Consequently, it is desirable that the amount of "acidic component" in the alkali metal hydrosilicate according to the present invention does not exceed 10% by weight.

[0034] The present invention also relates to alkali metal hydrosilicates obtainable or obtained by the method according to the present invention.

[0035] The alkali metal hydrosilicates according to the present invention can be transformed by a solgel process into hydrosilicate gels or solid silicates, which depending on the composition of the alkali metal hydrosilicates and the conditions of the sol-gel process, possess valuable properties, such as gluing capability, capability for phase transition heat absorption, capability for water deposition and capability for silicification of cellulose, and, thus, being suitable as materials for fire protection, materials for prevention of thermal runaway and starting materials for producing cellulose based composites. The hydrosilicate gels are obtained by thermal treatment of the alkali metal hydrosilicates, preferably, at a temperature of about 60 to about 80 °C during the time of no less than 6 hours. After such a treatment the hydrosilicate gels usually contain as about 50% of water (moisture), which can be evaporated at elevated temperature of about 120°C to about 250°C to obtain a so-called "rigid" gel. Solid silicates, which can be porous solid silicates or dense solid silicates are obtained after finalization of the sol-gel process, which usually takes please under more rigid conditions of elevated temperature, preferably above about 260°C, more preferably between about 260°C and about 350°C, even more preferably between about 300°C and about 350°C, and, optionally increased pressure, preferably above about 1.2 bar, more preferably between about 1.2 bar to about 12 bar, even more preferably between about 1.5 bar and about 12 bar. There are other methods to transform the inventive precursor into solid silicates, e.g. low pressure, radiation, etc.).

[0036] Thus, a further object of the present invention is the use of the alkali metal hydrosilicates according to the invention for the manufacture of the materials for fire protection, for prevention of thermal runaway and for producing cellulose based composites.

[0037] The invention will be illustrated further with reference to the examples that follow, without restricting the scope to the specific embodiments described. The invention includes all combinations of described and especially of preferred features that do not exclude each other.

[0038] Example 1

[0039] An alkali metal hydrosilicate according to the present invention was produced by using sodium hydroxide as the alkali metal hydroxide. As the silica raw material containing not less than 70% per weight of amorphous SiCE a diatomite (type 1) with the composition presented in Table 1 was employed. The raw material was preliminary crushed using a jaw crusher, and then ground into a "siliceous sand". The average particle size of "sand grains" is not more than 0.5 mm, measured by vibratory sieve shaker AS 300 (Retsch, Germany).

[0040] Table 1. Chemical composition of diatomite type 1 (determined by Benchtop XRF Spectrometer SPECTROCUBE C (Ametek / SPECTRO, Germany)

[0041] The process is carried out in a heat-insulated process vessel equipped with a mixer, batchers for silica raw material, air-dry granulated sodium hydroxide and heated water and metering devices for the components -TRIMIX TXR 250 (RAYNERI, France) - which has maximum volume - 250 litres, equipped by blade type homogenizer and has total power of electromotors - 34.2 kW.

[0042] The humidity content of the silica raw material, measured prior to feeding, is 76 ± 0.5 % by weight.

[0043] The silica raw material was provided in an amount of 50 ± 1 kg.

[0044] Air-dry granulated caustic alkali (sodium hydroxide) was added in an amount of 9 ± 0.1 kg into the process vessel under mixing of the materials at a rotation speed of 2000 ± 50 rpm (mixing system TRIMIX TXR 250) and specific energy input during mixing of 500 ± 50 kl / kg for minimum 35 minutes. After adding of granulated caustic alkali 10 ± 0.5 kg of hot water with the temperature of 80 ± 5 °C were added under mixing of the reaction mixture and the mixing process was carrying out for minimum 45 minutes.

[0045] The silica raw material is comminuted to a particle size he mixing of the reacting mixture is accompanied by self-heating due to exothermal effects of the alkalization reaction of the granulated dry alkali aquation and the amorphous Si O2. Temperature of the reacting mixture is kept in the range of 15- 95°C.

[0046] Process was carried out until a homogenous viscous material is obtained. The viscosity of the material measured by Brookfield viscosimeter IKA ROTAVISC hi-vi II was in the range 100 - 1700 Pa*s depending on the temperature of the material, which is from about 90°C (i.e., average temperature of the reaction mixture) to 25 °C (i.e. SATP conditions). Before the finish of the process the material was kept for minimum 5 minutes without external heating to reduce the temperature thereof.

[0047] Finally, the obtained material was discharged into suitable containers for storage and further use.

[0048] A sample of the material produced was dewatered by drying in a laboratory oven of Binder GmbH (Germany) at 250 ± 5 °C for 30 ± 1 min has the following elemental composition determined by Benchtop XRF Spectrometer SPECTROCUBE C (Ametek / SPECTRO, Germany) in % by weight: Silicon - 35.69; Aluminium - 2.88; Iron - 1.97; Calcium - 1.34; Magnesium - 0.34; Sodium - 9.5; Others - 0.03; Oxygen - 48.25.

[0049] During evaporation of moisture at the temperature 250 ± 1°C from the sample of the material produced the amount of evaporated moisture was measured by moisture analyser Sartorius MA 36 (which is modified in order to use higher operation temperature during measurements) and determined in an amount of 45.92% by weight.

[0050] The pH value of the sample of material produced measured by pH meter model testo 206-pH3 is 11.2.

[0051] In order to determine the gluing ability of a material obtained by subjecting the produced precursor material to a sol -gel process a measuring element of the device PROCEQ DYNA Z16 was glued by means of the precursor to a clean surface of an cathodic dip coating (CDC) (electrophoretic epoxy film layer with a thickness 38 ± 3 pm (measured by device QNIX 1500 (Automation Dr. NIX, Germany) on an 7075 Al alloy sheet with a thickness 1.3 ± 0.01 mm and with a specific volume resistivity of the epoxy layer of 15 ± 0.5 MQ*m (measured by Ohm and Current Meter Mili-T03 (H.-P. FISCHER ELEKTRONIK GmbH & Co, Germany)) and stored in a laboratory oven of Binder GmbH (Germany) at a temperature 70 ± 5 °C for not less than 6 hours in order to transform the precursor material into a rigid form based the occurring sol-gel process thereby obtaining a rigid hydrosilicate gel. The surface tension (adhesion) strength measured by PROCEQ DYNA Z16 is 4.63 MPa.

[0052] In order to confirm that the material produced retains a non-solid like state under SATP, a sample of the material was loaded into a mould (150 mm cube, prepared according to EN 12390-1:2000) and stored for 28 days under conditions of Standard Ambient Temperature and Pressure (SATP, 25°C, 100000 kPa / 1 bar). After unloading from the mould, the sample was placed on the flat surface of a table. During the next 12 hours the sample lost the cubic form.

[0053] Example 2

[0054] In order to produce the other sample of alkali metal hydrosilicate as precursor for sol-gel processes based on sodium hydroxide according to the present invention at the first step selected porous siliceous raw containing no less than 70% per weight of amorphous Si O2 - diatomite type 2 - with a composition presented in Table 2 and mentioned raw material should be crushed using, for example, a jaw crusher, and then grind into a siliceous "sand".

[0055] Table 2. Chemical composition of diatomite type 2 as raw material for production of material(alkali metal hydrosilicate as silicate precursor) (determined by Benchtop XRF Spectrometer SPECTROCUBE C (Ametek / SPECTRO, Germany)

[0056] It is desirable that average size of "sand grains" is no more than 0.5 mm, measured by vibratory sieve shaker AS 300 (Retsch, Germany).

[0057] Siliceous sand should be loaded into heat-insulated process vessel equipped with a mixer, batchers of siliceous "sand" and heated water and a hatchway for charging of the air-dry granulated caustic alkali - sodium hydroxide in order to produce of silicate precursor according to present invention. Moreover, said process vessel can be equipped with a controllable heater (e.g., with a water jacket) as it is in the reactor of mixing system TRIMIX TXR 250 (RAYNERI, France) - which has maximum volume - 250 litres, equipped with a blade type homogenizer and has total power of electromotors - 34.2 kW.

[0058] The humidity content of the silica raw material, measured prior to feeding, is 74 ± 0.5 % by weight.

[0059] The silica raw material was provided in an amount of 100 ± 1 kg

[0060] At the second step the air-dry granulated caustic alkali (sodium hydroxide) is added in an amount 10 ± 0.1 kg into the process vessel together with mixing of the materials with the speed 2000 ± 20 rpm in the reactor of mixing system TRIMIX TXR 250 and specific energy input during mixing of 300 ± 30 kJ / kg for minimum 35 minutes. After adding of granulated caustic alkali 25 ± 0.5 kg of hot water with the temperature of 80 ± 5 °C were added under mixing of the reaction mixture and the mixing process was carrying out for minimum 45 minutes.

[0061] The mixing of the reacting mixture is accompanied by self-heating due to exothermal effects of the alkalization reaction of the granulated dry alkali aquation and the amorphous Si O2. Temperature of the reacting mixture is kept in the range of 75-95°C.

[0062] Process was carried out until a homogenous viscous material is obtained. The viscosity of the material measured by Brookfield viscosimeter IKA ROTAVISC hi-vi II was in the range 500 - 5800 Pa*s depending on the temperature of the material, which is from about 90°C (i.e., average temperature of reaction mixture) to 25°C (i.e., SATP conditions). Before the finish of the process the material was kept for minimum 5 minutes without external heating to reduce the temperature thereof.

[0063] Finally, the obtained material was discharged into suitable containers for storage and further use.

[0064] A sample of the material produced was de watered by drying in a laboratory oven of Binder GmbH (Germany) at 250 ± 5 °C for 30 ± 1 min has the following elemental composition determined by Benchtop XRF Spectrometer SPECTROCUBE C (Ametek / SPECTRO, Germany) in % by weight: Silicon - 35.39; Aluminium - 3.14; Iron - 2.14; Calcium - 1.98; Magnesium - 0.48; Sodium - 8.65; Others - 0.03; Oxygen - 46.62.

[0065] During evaporation of moisture at the temperature 250 ± 1°C from the sample of the material produced the amount of evaporated moisture was measured by moisture analyser Sartorius MA 36 (which is modified in order to use higher operation temperature during measurements) and determined in an amount of 46.28% by weight.

[0066] The pH value of the sample of material produced measured by pH meter model testo 206-pH3 is 11.

[0067] In order to determine the gluing ability of a material obtained by subjecting the produced precursor material to a sol -gel process a measuring element of the device PROCEQ DYNA Z16 was glued by means of the precursor to a clean surface of an cathodic dip coating (CDC) (electrophoretic epoxy film layer with the thickness 38 ± 3 pm (measured by device QNIX 1500 (Automation Dr. NIX, Germany) on an 7075 Al alloy sheet with a thickness 1.3 ± 0.01 mm and with a specific volume resistance of the epoxy layer of 15 ± 0.5 MQ*m (measured by Ohm and Current Meter Mili-T03 (H.-P. FISCHER ELEKTRONIK GmbH & Co, Germany)) and stored in a laboratory oven of Binder GmbH (Germany) at a temperature 70 ± 5 °C for not less than 6 hours in order to transform the precursor material into a rigid form based the occurring sol-gel process thereby obtaining a rigid hydrosilicate gel. The surface tension (adhesion) strength measured by PROCEQ DYNA Z16 is 4.61 MPa

[0068] In order to confirm that the material produced retains a non-solid like state under SATP, a sample of the material was loaded into a mould (150 mm cube, prepared according to EN 12390-1:2000) and stored for 28 days under conditions of Standard Ambient Temperature and Pressure (SATP, 25°C, 100000 kPa / 1 bar). After unloading from the mould, the sample was placed on the flat surface of a table. During the next 18 hours the sample lost the cubic form.

[0069] Example 3 (comparative)

[0070] In order to produce the sample of silicate material with a higher aluminium (Al) content compared to silicate precursor according to present invention at the first step selected porous siliceous raw containing no less than 70% per weight of amorphous Si O2 - metallurgical slag type 1 - with composition presented in Table 3 and mentioned raw material should be crushed using, for example, a jaw crusher, and then grind into a siliceous "sand".

[0071] Table 3. Chemical composition of metallurgical slag as raw material for production of silicate material (determined by Benchtop XRF Spectrometer SPECTROCUBE C (Ametek / SPECTRO, Germany)

[0072] It is desirable that average size of "sand grains" is no more than 0.5 mm, measured by vibratory sieve shaker AS 300 (Retsch, Germany).

[0073] Siliceous sand should be loaded into heat-insulated process vessel equipped with a mixer, batchers of siliceous "sand" and heated water and a hatchway for charging of the air-dry granulated caustic alkali - sodium hydroxide in order to produce of silicate precursor according to present invention. Moreover, said process vessel can be equipped with a controllable heater (e.g., with a water jacket) as it is in the reactor of mixing system TRIMIX TXR 250 (RAYNERI, France) - which has maximum volume - 250 litres, equipped with a blade type homogenizer and has total power of electromotors - 34.2 kW.

[0074] The humidity content of the silica raw material, measured prior to feeding, is 75 ± 0.5 % by weight.

[0075] The silica raw material was provided in an amount of 100 ± 1 kg.

[0076] At the second step the air-dry granulated caustic alkali (sodium hydroxide) is added in an amount 10 ± 0. 1 kg into the process vessel together with mixing of the materials with the speed 2000 ± 20 rpm in the reactor of mixing system TRIMIX TXR 250 and specific energy input during mixing of 300 ± 30 kJ / kg for minimum 35 minutes. After adding of granulated caustic alkali 25 ± 0.5 kg of hot water withthe temperature of 80 ± 5 °C were added under mixing of the reaction mixture and the mixing process was carrying out for minimum 45 minutes.

[0077] The mixing of the reacting mixture is accompanied by self-heating due to exothermal effects of the alkalization reaction of the granulated dry alkali aquation and the amorphous Si O2. Temperature of the reacting mixture is kept in the range of 75-95°C.

[0078] Process was carried out until a homogenous viscous material is obtained. The viscosity of the material measured by Brookfield viscosimeter IKA ROTAVISC hi-vi II was in the range 1000 - 80000 Pa*s depending on the temperature of the material, which is from about 90°C (i.e. average temperature of reaction mixture) to 25 °C (i.e. SATP conditions). Before the finish of the process the material was kept for minimum 5 minutes without external heating to reduce the temperature thereof.

[0079] Finally, the obtained material was discharged into suitable containers for storage and further use.

[0080] A sample of the material produced was dewatered by drying in a laboratory oven of Binder GmbH (Germany) at 250 ± 5 °C for 30 ± 1 min has the following elemental composition determined by Benchtop XRF Spectrometer SPECTROCUBE C (Ametek / SPECTRO, Germany) in % by weight: Silicon - 30.52; Aluminium - 9.98; Iron - 1.77; Calcium - 1.88; Magnesium - 0.79; Sodium - 6.02; Potassium - 0.62; Oxygen - 48.42.

[0081] In order to determine the gluing ability of a material obtained by subjecting the produced precursor material to a sol -gel process a measuring element of the device PROCEQ DYNA Z16 was glued by means of the precursor to a clean surface of an cathodic dip coating (CDC) (electrophoretic epoxy film layer with a thickness 38 ± 3 pm (measured by device QNIX 1500 (Automation Dr. NIX, Germany) on an 7075 Al alloy sheet with a thickness 1.3 ± 0.01 mm and with a specific volume resistance of the epoxy layer of 15 ± 0.5 MQ*m (measured by Ohm and Current Meter Mili-T03 (H.-P. FISCHER ELEKTRONIK GmbH & Co, Germany)) and stored in a laboratory oven of Binder GmbH (Germany) at a temperature 70 ± 5 °C for not less than 6 hours in order to transform the precursor material into a rigid form based the occurring sol-gel process thereby obtaining a rigid hydrosilicate gel. The surface tension (adhesion) strength measured by PROCEQ DYNA Z16 is 0.24 MPa.

[0082] Thus, the values of concentration of aluminium according to the present invention looks as optimal.

[0083] Example 4 (comparative)

[0084] In order to produce the sample of silicate material with a higher calcium (Ca) content compared to silicate precursor according to present invention at the first step selected porous siliceous raw containing around 70% per weight of amorphous Si O2 - metallurgical slag type 2 - with compositionpresented in Table 4 should be crushed using, for example, a jaw crusher, and then grind into a siliceous "sand".

[0085] Table 4. Chemical composition of a metallurgical slag as raw material for production of silicate material (determined by Benchtop XRF Spectrometer SPECTROCUBE C (Ametek / SPECTRO, Germany)

[0086] It is desirable that average size of "sand grains" is no more than 0.5 mm, measured by vibratory sieve shaker AS 300 (Retsch, Germany).

[0087] Siliceous sand should be loaded into heat-insulated process vessel equipped with a mixer, batchers of siliceous "sand" and heated water and a hatchway for charging of the air-dry granulated caustic alkali - sodium hydroxide in order to produce of silicate precursor according to present invention. Moreover, said process vessel can be equipped with a controllable heater (e.g., with a water jacket) as it is in the reactor of mixing system TRIMIX TXR 250 (RAYNERI, France) - which has maximum volume - 250 litres, equipped with a blade type homogenizer and has total power of electromotors - 34.2 kW.

[0088] The humidity content of the silica raw material, measured prior to feeding, is 75 ± 0.5 % by weight.

[0089] The silica raw material was provided in an amount of 100 ± 1 kg.

[0090] At the second step the air-dry granulated caustic alkali (sodium hydroxide) is added in an amount 10 ± 0. 1 kg into the process vessel together with mixing of the materials with the speed 2000 ± 20 rpm in the reactor of mixing system TRIMIX TXR 250 and specific energy input during mixing of 300 ± 30 kJ / kg for minimum 35 minutes. After adding of granulated caustic alkali 25 ± 0.5 kg of hot water with the temperature of 80 ± 5 °C were added under mixing of the reaction mixture and the mixing process was carrying out for minimum 45 minutes.

[0091] The mixing of the reacting mixture is accompanied by self-heating due to exothermal effects of the alkalization reaction of the granulated dry alkali aquation and the amorphous Si O2. Temperature of the reacting mixture is kept in the range of 75-95°C.

[0092] Process was carried out until a homogenous viscous material is obtained. The viscosity of the material measured by Brookfield viscosimeter IKA ROTAVISC hi-vi II was in the range 700 - 40000 Pa*s depending on the temperature of the material, which is from about 90°C (i.e., average temperature of reaction mixture) to 25°C (i.e., SATP conditions). Before the finish of the process the material was kept for minimum 5 minutes without external heating to reduce the temperature thereof.

[0093] Finally, the obtained material was discharged into suitable containers for storage and further use.

[0094] A sample of the material produced was de watered by drying in a laboratory oven of Binder GmbH (Germany) at 250 ± 5 °C for 30 ± 1 min has the following elemental composition determined by Benchtop XRF Spectrometer SPECTROCUBE C (Ametek / SPECTRO, Germany) in % by weight: Silicon - 32.15; Aluminium - 0.43; Iron - 2.19; Calcium - 10.23; Magnesium - 0.91; Sodium - 6.7; Potassium - 1.51; Others - 0.27; Oxygen - 45.61.

[0095] In order to determine the gluing ability of a material obtained by subjecting the produced precursor material to a sol -gel process a measuring element of the device PROCEQ DYNA Z16 was glued by means of the precursor to a clean surface of an cathodic dip coating (CDC) (electrophoretic epoxy film layer with a thickness 38 ± 3 pm (measured by device QNIX 1500 (Automation Dr. NIX, Germany) on an 7075 Al alloy sheet with a thickness 1.3 ± 0.01 mm and with a specific volume resistance of the epoxy layer of 15 ± 0.5 MQ*m (measured by Ohm and Current Meter Mili-T03 (H.-P. FISCHER ELEKTRONIK GmbH & Co, Germany)) and stored in a laboratory oven of Binder GmbH (Germany) at a temperature 70 ± 5 °C for not less than 6 hours in order to transform the precursor material into a rigid form based the occurring sol-gel process thereby obtaining a rigid hydrosilicate gel. The surface tension (adhesion) strength measured by PROCEQ DYNA Z16 is 0. 12 MPa.

[0096] Thus, the values of concentration of calcium according to the present invention looks as optimal.

[0097] Example 5 (comparative)

[0098] In order to produce the sample of silicate material with the higher Iron (Fe) content compared to silicate precursor according to present invention At the first step selected porous siliceous raw containing no less than 70% per weight of amorphous Si O2 - diatomite type 1 - with composition presented in Table 1 should be crushed using, for example, a jaw crusher in amount 90 kg and mixed with 10 kg of crushed and milled copper metallurgical slag with composition presented in the Table 5, and then grind the mixture into a siliceous "sand".

[0099] Table 5. Chemical composition of a metallurgical copper slag as raw material for production of silicate material (determined by Benchtop XRF Spectrometer SPECTROCUBE C (Ametek / SPECTRO, Germany)[000100] It is desirable that average size of "sand grains" is no more than 0.5 mm, measured by vibratory sieve shaker AS 300 (Retsch, Germany).[000101] Siliceous sand should be loaded into heat-insulated process vessel equipped with a mixer, batchers of siliceous "sand" and heated water and a hatchway for charging of the air-dry granulated caustic alkali - sodium hydroxide in order to produce of silicate precursor according to present invention. Moreover, said process vessel can be equipped with a controllable heater (e.g., with a water jacket) as it is in the reactor of mixing system TRIMIX TXR 250 (RAYNERI, France) - which has maximum volume - 250 litres, equipped with a blade type homogenizer and has total power of electromotors - 34.2 kW.[000102] The humidity content of the silica raw material, measured prior to feeding, is 75 ± 0.5 % by weight.[000103] The silica raw material was provided in an amount of 100 ± 1 kg.[000104] At the second step the air-dry granulated caustic alkali (sodium hydroxide) is added in an amount 10 ± 0. 1 kg into the process vessel together with mixing of the materials with the speed 2000 ± 20 rpm in the reactor of mixing system TRIMIX TXR 250 and specific energy input during mixing of 300 ± 30 kJ / kg for minimum 35 minutes. After adding of granulated caustic alkali 25 ± 0.5 kg of hot water with the temperature of 80 ± 5 °C were added under mixing of the reaction mixture and the mixing process was carrying out for minimum 45 minutes.[000105] The mixing of the reacting mixture is accompanied by self-heating due to exothermal effects of the alkalization reaction of the granulated dry alkali aquation and the amorphous Si O2. Temperature of the reacting mixture is kept in the range of 75-95°C.[000106] Process was carried out until a homogenous viscous material is obtained. The viscosity of the material measured by Brookfield viscosimeter IKA ROTAVISC hi-vi II was in the range 800 - 52000 Pa*s depending on the temperature of the material, which is from about 90°C (i.e., average temperature of reaction mixture) to 25°C (i.e., SATP conditions). Before the finish of the process the material was kept for minimum 5 minutes without external heating to reduce the temperature thereof.[000107] Finally, the obtained material was discharged into suitable containers for storage and further use.[000108] A sample of the material produced was dewatered by drying in a laboratory oven of Binder GmbH (Germany) at 250 ± 5 °C for 30 ± 1 min has the following elemental composition determined by Benchtop XRF Spectrometer SPECTROCUBE C (Ametek / SPECTRO, Germany) in % by weight: Silicon - 35.23; Aluminium - 2.94; Iron - 5.9; Calcium - 1.54; Magnesium - 0.37; Sodium - 5.63; Others - 0.08; Oxygen - 48.31.[000109] In order to determine the gluing ability of a material obtained by subjecting the produced precursor material to a sol -gel process a measuring element of the device PROCEQ DYNA Z16 was glued by means of the precursor to a clean surface of an cathodic dip coating (CDC) (electrophoretic epoxy film layer with the thickness 38 ± 3 pm (measured by device QNIX 1500 (Automation Dr. NIX, Germany) on an 7075 Al alloy sheet with a thickness 1.3 ± 0.01 mm and with a specific volume resistance of epoxy layer of 15 ± 0.5 MQ*m (measured by Ohm and Current Meter Mili-T03 (H.-P. FISCHER ELEKTRONIK GmbH & Co, Germany)) and stored in a laboratory oven of Binder GmbH (Germany) at a temperature 70 ± 5 °C for not less than 6 hours in order to transform the precursor material into a rigid form based the occurring sol-gel process thereby obtaining a rigid hydrosilicate gel. The surface tension (adhesion) strength measured by PROCEQ DYNA Z16 is 0.1 MPa.[000110] Example 6[000111] An alkali metal hydrosilicate according to the present invention was produced by using potassium hydroxide as the alkali metal hydroxide. As the silica raw material containing not less than 70% per weight of amorphous SiO2 a diatomite (type 1) with the composition presented in Table 1 was employed. The raw material was preliminary crushed using a jaw crusher, and then ground into a "siliceous sand".[000112] The average particle size of "sand grains" is not more than 0.5 mm, measured by vibratory sieve shaker AS 300 (Retsch, Germany).[000113] Siliceous sand should be loaded into heat-insulated process vessel equipped with a mixer, batchers of siliceous "sand" and heated water and a hatchway for charging of the air-dry granulated caustic alkali - potassium hydroxide in order to produce of silicate precursor according to present invention. Moreover, said process vessel can be equipped with a controllable heater (e.g., with a waterjacket) as it is in the reactor of mixing system TRIMIX TXR 250 (RAYNERI, France) - which has maximum volume - 250 litres, equipped with a blade type homogenizer and has total power of electromotors - 34.2 kW.[000114] The humidity content of the silica raw material, measured prior to feeding, is 76 ± 0.5 % by weight.[000115] The silica raw material was provided in an amount of 50 ± 1 kg.[000116] At the second step the air-dry granulated caustic alkali (potassium hydroxide) is added in an amount 9.4 ± 0.1 kg into the process vessel together with mixing of the materials with the speed 2000 ± 20 rpm in the reactor of mixing system TRIMIX TXR 250 and specific energy input during mixing of 500 ± 50 kl / kg for minimum 35 minutes. After adding of granulated caustic alkali 14 ± 0.5 kg of hot water with the temperature of 80 ± 5 °C were added under mixing of the reaction mixture and the mixing process was carrying out for minimum 45 minutes.[000117] The mixing of the reacting mixture is accompanied by self-heating due to exothermal effects of the alkalization reaction of the granulated dry alkali aquation and the amorphous Si O2. Temperature of the reacting mixture is kept in the range of 75-95°C.[000118] Process was carried out until a homogenous viscous material is obtained. The viscosity of the material measured by Brookfield viscosimeter IKA ROTAVISC hi-vi II was in the range 800 - 52000 Pa*s depending on the temperature of the material, which is from about 90°C (i.e., average temperature of reaction mixture) to 25°C (i.e. SATP conditions). Before the finish of the process the material was kept for minimum 5 minutes without external heating to reduce the temperature thereof.[000119] Finally, the obtained material was discharged into suitable containers for storage and further use.[000120] A sample of the material produced was de watered by drying in a laboratory oven of Binder GmbH (Germany) at 250 ± 5 °C for 30 ± 1 min has the following elemental composition determined by Benchtop XRF Spectrometer SPECTROCUBE C (Ametek / SPECTRO, Germany) in % by weight: Silicon - 34.93; Aluminium - 2.83; Iron - 1.92; Calcium - 1.31; Magnesium - 0.36; Potassium - 12.22; Others - 0.02; Oxygen - 46.41.[000121] During evaporation of moisture at the temperature 250 ± 1°C from the sample of the material produced the amount of evaporated moisture was measured by moisture analyser Sartorius MA 36 (which is modified in order to use higher operation temperature during measurements) and determined in an amount of 45.82% by weight.[000122] The pH value of the sample of material produced measured by pH meter model testo 206-pH3 is 11.[000123] In order to determine the gluing ability of a material obtained by subjecting the produced precursor material to a sol -gel process a measuring element of the device PROCEQ DYNA Z16 was glued by means of the precursor to a clean surface of an cathodic dip coating (CDC) (electrophoretic epoxy fdm layer with the thickness 38 ± 3 pm (measured by device QNIX 1500 (Automation Dr. NIX, Germany) on an 7075 Al alloy sheet with a thickness 1.3 ± 0.01 mm and with a specific volume resistance of the epoxy layer of 15 ± 0.5 MQ*m (measured by Ohm and Current Meter Mili-T03 (H.-P. FISCHER ELEKTRONIK GmbH & Co, Germany)) and stored in a laboratory oven of Binder GmbH (Germany) at a temperature 70 ± 5 °C for not less than 6 hours in order to transform the precursor material into a rigid form based the occurring sol-gel process thereby obtaining a rigid hydrosilicate gel. The surface tension (adhesion) strength measured by PROCEQ DYNA Z16 is 4.58 MPa.[000124] In order to confirm that the material produced retains a non-solid like state under SATP (NTP), a sample of the material was loaded into a mould (150 mm cube, prepared according to EN 12390-1:2000) and stored for 28 days under conditions of Standard Ambient Temperature and Pressure (SATP, 25°C, 100000 kPa / 1 bar). After unloading from the mould, the sample was placed on the flat surface of a table. During the next 15 hours the sample lost the cubic form.[000125] Example 7[000126] An alkali metal hydrosilicate according to the present invention was produced by using potassium hydroxide as the alkali metal hydroxide. As the silica raw material containing not less than 70% per weight of amorphous Si O2 a diatomite (type 1) with the composition presented in Table 1 was employed. The raw material was preliminary crushed using a jaw crusher, and then ground into a "siliceous sand".[000127] The average particle size of "sand grains" is not more than 0.5 mm, measured by vibratory sieve shaker AS 300 (Retsch, Germany).[000128] Siliceous sand should be loaded into heat-insulated process vessel equipped with a mixer, batchers of siliceous "sand" and heated water and a hatchway for charging of the air-dry granulated caustic alkali - potassium hydroxide in order to produce of silicate precursor according to present invention. Moreover, said process vessel can be equipped with a controllable heater (e.g., with a water jacket) as it is in the reactor of mixing system TRIMIX TXR 250 (RAYNERI, France) - which has maximum volume - 250 litres, equipped with a blade type homogenizer and has total power of electromotors - 34.2 kW.[000129] The humidity content of the silica raw material, measured prior to feeding, is 75 ± 0.5 % by weight.[000130] The silica raw material was provided in an amount of 100 ± 1 kg.[000131] At the second step the air-dry granulated caustic alkali (potassium hydroxide) is added in an amount 19 ± 0. 1 kg into the process vessel together with mixing of the materials with the speed 2000 ± 20 rpm in the reactor of mixing system TRIMIX TXR 250 and specific energy input during mixing of 300 ± 30 kl / kg for minimum 35 minutes. After adding of granulated caustic alkali 25 ± 0.5 kg of hot water with the temperature of 80 ± 5 °C were added under mixing of the reaction mixture and the mixing process was carrying out for minimum 45 minutes.[000132] The mixing of the reacting mixture is accompanied by self-heating due to exothermal effects of the alkalization reaction of the granulated dry alkali aquation and the amorphous Si O2. Temperature of the reacting mixture is kept in the range of 75-95°C.[000133] Process was carried out until a homogenous viscous material is obtained. The viscosity of the material measured by Brookfield viscosimeter IKA ROTAVISC hi-vi II was in the range 800 - 52000 Pa*s depending on the temperature of the material, which is from about 90°C (i.e., average temperature of reaction mixture) to 25°C (i.e., SATP conditions). Before the finish of the process the material was kept for minimum 5 minutes without external heating to reduce the temperature thereof.[000134] Finally, the obtained material was discharged into suitable containers for storage and further use.[000135] A sample of the material produced was de watered by drying in a laboratory oven of Binder GmbH (Germany) at 250 ± 5 °C for 30 ± 1 min has the following elemental composition determined by Benchtop XRF Spectrometer SPECTROCUBE C (Ametek / SPECTRO, Germany) in % by weight Silicon - 32.78; Aluminium - 2.92; Iron - 1.08; Calcium - 1.89; Magnesium - 0.44; Sodium - 2.91: Potassium - 11.76; Others - 0.03; Oxygen - 46.19.[000136] During evaporation of moisture at the temperature 250 ± 1°C from the sample of the material produced the amount of evaporated moisture was measured by moisture analyser Sartorius MA 36 (which is modified in order to use higher operation temperature during measurements) and determined in an amount of 43.41 % by weight.[000137] The pH value of the sample of material produced measured by pH meter model testo 206-pH3 is 10.9.[000138] In order to determine the gluing ability of a material obtained by subjecting the produced precursor material to a sol -gel process a measuring element of the device PROCEQ DYNA Z16 was glued by means of the precursor to a clean surface of an cathodic dip coating (CDC) (electrophoretic epoxy film layer with a thickness 38 ± 3 pm (measured by device QNIX 1500 (Automation Dr. NIX, Germany) on an 7075 Al alloy sheet with a thickness 1.3 ± 0.01 mm and with a specific volume resistance of the epoxy layer of 15 ± 0.5 MQ*m (measured by Ohm and Current Meter Mili-T03 (H.-P. FISCHER ELEKTRONIK GmbH & Co, Germany)) and stored in a laboratory oven of Binder GmbH(Germany) at a temperature 70 ± 5 °C for not less than 6 hours in order to transform the precursor material into a rigid form based the occurring sol-gel process thereby obtaining a rigid hydrosilicate gel. The surface tension (adhesion) strength measured by PROCEQ DYNA Z16 is 4. 12 MPa.[000139] In order to confirm that the material produced retains a non-solid like state under SATP, a sample of the material was loaded into a mould (150 mm cube, prepared according to EN 12390-1:2000) and stored for 28 days under conditions of Standard Ambient Temperature and Pressure (SATP, 25°C, 100000 kPa / 1 bar). After unloading from the mould, the sample was placed on the flat surface of a table. During the next 15 hours the sample lost the cubic form.[000140] Example 8 (comparative)[000141] In order to produce a reference sample of a silicate gel material in accordance to the closest prior art - Patent application WO2021248173 - based on sodium hydroxide, a silica raw material containing not less than 70% per weight of amorphous SiO2 a diatomite (type 1) with the composition presented in Table 1 was employed. The raw material was preliminary crushed using a jaw crusher, and then ground into a "siliceous sand".[000142] The average particle size of "sand grains" is not more than 0.5 mm, measured by vibratory sieve shaker AS 300 (Retsch, Germany).[000143] Siliceous sand should be loaded into heat-insulated process vessel equipped with a mixer, batchers of siliceous "sand" and heated water and a hatchway for charging of the air-dry granulated caustic alkali - sodium hydroxide in order to produce a silicate precursor as described in the present invention. Moreover, said process vessel can be equipped with a controllable heater (e.g., with a water jacket) as it is in the reactor of mixing system TRIMIX TXR 250 (RAYNERI, France) - which has maximum volume - 250 litres, equipped by turbine type impeller and has independent electromotor with the power - 2.0 kW.[000144] The humidity content of the silica raw material, measured prior to feeding, is 41 ± 0.5 % by weight.[000145] The silica raw material was provided in an amount of 50 ± 1 kg.[000146] At the second step the air-dry granulated caustic alkali (sodium hydroxide) is added in an amount 25 ± 0. 1 kg into the process vessel together with mixing of the materials with the speed 150 ± 5 rpm in the reactor of mixing system TRIMIX TXR 250 and specific energy input during mixing of 20 ± 2 kJ / kg for minimum 25 minutes. After adding of granulated caustic alkali 10 ± 0.5 kg of hot water with the temperature of 80 ± 5 °C were added under mixing of the reaction mixture and the mixing process was carrying out for minimum 35 minutes.[000147] The mixing of the reacting mixture is accompanied by self-heating due to exothermal effects of the alkalization reaction of the granulated dry alkali aquation and the amorphous Si O2. Temperature of the reacting mixture is kept in the range of 75-95°C.[000148] Process was carried out until a homogenous viscous material is obtained. The viscosity of the material measured by Brookfield viscosimeter IKA ROTAVISC hi-vi II should be higher 1500 Pa*s and can reach the value over 180000 Pa*s depending on the temperature of the material, which is from about 90°C (i.e., average temperature of reaction mixture) to 25°C (i.e. SATP conditions). Before the finish of the process the material was kept for minimum 5 minutes without external heating to reduce the temperature thereof.[000149] Finally, the obtained material was discharged into suitable containers for storage and further use.[000150] A sample of the material produced was de watered by drying in a laboratory oven of Binder GmbH (Germany) at 250 ± 5 °C for 30 ± 1 min has the following elemental composition determined by Benchtop XRF Spectrometer SPECTROCUBE C (Ametek / SPECTRO, Germany) in % by weight Silicon - 27.2; Aluminium - 3.07; Iron - 1.65; Calcium - 1.57; Magnesium - 0.37; Sodium - 23.65: Others - 0.02; Oxygen - 42.47.[000151] During evaporation of moisture at the temperature 250 ± 1°C from the sample of the material produced the amount of evaporated moisture was measured by moisture analyser Sartorius MA 36 (which is modified in order to use higher operation temperature during measurements) and determined in an amount of 30.7 % by weight.[000152] The pH value of the sample of material produced measured by pH meter model testo 206-pH3 is 9.8.[000153] In order to determine the gluing ability of a material obtained by subjecting the produced precursor material to a sol -gel process a measuring element of the device PROCEQ DYNA Z16 was glued by means of the precursor to a clean surface of an cathodic dip coating (CDC) (electrophoretic epoxy film layer with a thickness 38 ± 3 pm (measured by device QNIX 1500 (Automation Dr. NIX, Germany) on an 7075 Al alloy sheet with a thickness 1.3 ± 0.01 mm and with a specific volume resistance of the epoxy layer of 15 ± 0.5 MQ*m (measured by Ohm and Current Meter Mili-T03 (H.-P. FISCHER ELEKTRONIK GmbH & Co, Germany)) and stored in a laboratory oven of Binder GmbH (Germany) at a temperature 70 ± 5 °C for not less than 6 hours in order to transform the precursor material into a rigid form based the occurring sol-gel process thereby obtaining a rigid hydrosilicate gel. The surface tension (adhesion) strength measured by PROCEQ DYNA Z16 is 0.01 MPa.[000154] In order to investigate whether the material produced retains a non-solid like state under SATP, a sample of the material was loaded into a mould (150 mm cube, prepared according to EN 12390-1:2000) and stored for 28 days under conditions of Standard Ambient Temperature and Pressure (SATP, 25 °C, 100000 kPa / 1 bar). After unloading from the mould, the sample was placed on the flat surface of a table. During the next 24 hours the sample did not lose the cubic form[000155] Example 9[000156] In order to determine an optimal range of the main parameters of the material according to present invention additional experiments with diatomite raw materials were made. The samples of alkali metal hydrosilicate according to the present invention were produced as it was described above in the Example 1 and Example 2. However, different rates of humidity of the silica raw material (diatomite) were used in each sample as it is indicated in Table 9. 1 and 9.2 respectively. Also, in the Table 9. 1 and Table 9.2 results of different tests of the performance characteristics are shown, which were carried out as described above in Example 1.[000157] Table 9.1. Composition and performance characteristics.[000158] Table 9.2. Composition and performance characteristics.[000159] The data as presented in the Table 9. 1 and Table 9.2 confirm that the claimed ranges of the parameters of present invention are optimal.[000160] Example 10[000161] In order to determine the possible ranges of dilution of the inventive precursor material an alkali metal hydrosilicate obtained in accordance with Example 1 was used. The material was mixed with an additional amount of water as it is presented in Table 10. The mixing of the precursor material with additional water was carried out in a mixer HOBART N50. The pH value of the diluted material was measured as described in Example 1. Moreover, the surface tension strength of a respective coating on a CDC surface obtained by subjecting the diluted precursor material to a sol-gel process by gluing a measuring element of the device PROCEQ DYNA Z16 by means of the precursor (alkali metal hydrosilicate) on the CDC surface and storing in a laboratory oven of Binder GmbH (Germany) at atemperature 70 ± 5 °C for not less than 6 hours was measured for different samples as described in the Example 1. Results of above-mentioned measurements are presented in the Table 10.[000162] Table 10. Composition and performance characteristics of different samples of diluted precursor material (alkali metal hydrosilicate)[000163] The data is presented in the Table 10 shows that a suitable surface tension strength is maintained to a pH of about 8.[000164] Example 11[000165] In order to determine the optimal range of speed of mixing during the production of the silicate precursor material (alkali metal hydrosilicate) the initial material made in accordance to Example 1 was employed. The samples of the mentioned material were produced by using of High Speed Lab Stirrer (Mixer Direct, USA) which has maximum power of about 150 W and maximum rotation speed of 6000 rpm. The composition of components are presented in the Table 9.2. The viscosity and surface tensile strength for each sample were measured as described in Example 1. The results are presented in the Table 11.[000166] Table 11. Composition and performance characteristics of different samples of material (alkali metal hydrosilicate)[000167] The data as presented in the Table 11 show that rotation speed upon mixing affects the surface tension strength of a coating obtained in result of a sol-gel process of the precursor material.[000168] Example 12[000169] In order to determine the optimal range of the so-called acidic component 10 kg lots from each sample of precursor material (alkali metal hydrosilicate) made as described in Example 9 were investigated. Initial properties of said samples are presented in Table 9.1.[000170] Each sample was heated to a temperature of 70 ± 5 °C in a laboratory oven of Binder GmbH (Germany), subsequently vacuumized to 0. 1 bar in a vacuum chamber within about 15 min. Afterwords the samples were maintained in the chamber for 6-8 hours under vacuum without pumping and without additional heating.[000171] After such processing a layer of relatively transparent liquid on the surface of the samples 12.1, 12.3, 12.4 and 12.5 was observed. It was possible to isolate the liquid into separate vessels for the samples 12.1, 12.4 and 12.5. The pH values of the liquids were measured by pH meter model testo 206- pH3. For the samples 12.2 and 12.3 the pH values were measured on the surfaces by means of pH- indicator paper.[000172] The results of the above-mentioned processing are presented in the Table 12.[000173] Table 12 Composition and performance characteristics of different samples of material.[000174] The data as presented in the Table 12 confirms that atoo high amount of "acidic component' affects the surface tension strength of a coating obtained in result of a sol-gel process of the precursor material.Example 13[000175] In order to produce another sample of alkali metal hydrosilicate as a silicate precursor for solgel processes based on sodium hydroxide according to present invention at the first step selected porous siliceous raw containing no less than 70% per weight of amorphous Si O2 being an amorphous silica byproduct (microsilica) of ferroalloys production - with composition as presented in Table 13 was employed and the mentioned raw material should be crushed using, for example, a jaw crusher, and then grind into a siliceous "sand".[000176] Table 13. Chemical composition of an amorphous silica by-product (microsilica) of ferroalloys production as raw material for production of a material of the present invention (alkali metal hydrosilicate as silicate precursor) (determined by Benchtop XRF Spectrometer SPECTROCUBE C (Ametek / SPECTRO, Germany)[000177] It is desirable that average size of "sand grains" is no more than 0.5 mm, measured by vibratory sieve shaker AS 300 (Retsch, Germany).[000178] Siliceous sand should be loaded into heat-insulated process vessel equipped with a mixer, batchers of siliceous "sand" and heated water and a hatchway for charging of the air-dry granulated caustic alkali - sodium hydroxide in order to produce a silicate precursor according to present invention. Moreover, said process vessel can be equipped with a controllable heater (e.g., with a water jacket) as it is in the reactor of mixing system TRIMIX TXR 250 (RAYNERI, France) - which has maximum volume - 250 litres, equipped with a blade type homogenizer and has total power of electromotors - 34.2 kW.[000179] The humidity content of the silica raw material, measured prior to feeding, is 75 ± 0.5 % by weight.[000180] The silica raw material was provided in an amount of 100 ± 1 kg[000181] At the second step the air-dry granulated caustic alkali (sodium hydroxide) is added in an amount 19 ± 0. 1 kg into the process vessel together with mixing of the materials with the speed 2000 ± 20 rpm in the reactor of mixing system TRIMIX TXR 250 and specific energy input during mixing of 300 ± 30 kJ / kg for minimum 35 minutes. After adding of granulated caustic alkali 25 ± 0.5 kg of hot water with the temperature of 80 ± 5 °C were added under mixing of the reaction mixture and the mixing process was carrying out for minimum 45 minutes.[000182] The mixing of the reacting mixture is accompanied by self-heating due to exothermal effects of the alkalization reaction of the granulated dry alkali aquation and the amorphous Si O2. Temperature of the reacting mixture is kept in the range of 75-95°C.[000183] Process was carried out until a homogenous viscous material is obtained. The viscosity of the material measured by Brookfield viscosimeter IKA ROTAVISC hi-vi II was in the range 450 - 4600 Pa*s depending on the temperature of the material, which is from about 90°C (i.e average temperature ofreacting mixture) to 25°C (i.e., SATP conditions). Before the finish of the process the material was kept for minimum 5 minutes without external heating to reduce the temperature thereof[000184] Finally, the obtained material was discharged into suitable containers for storage and further use.[000185] A sample of the material produced was dewatered by drying in a laboratory oven of Binder GmbH (Germany) at 250 ± 5 °C for 30 ± 1 min has the following elemental composition determined by Benchtop XRF Spectrometer SPECTROCUBE C (Ametek / SPECTRO, Germany) in % by weight: Silicon - 37.19; Aluminium - 0.54; Iron - 1,08; Calcium - 0.76; Magnesium - 0.47; Sodium - 10.71; Others - 0.28; Oxygen - 48.13.[000186] During evaporation of moisture at the temperature 250 ± 1°C from the sample of the material produced the amount of evaporated moisture was measured by moisture analyser Sartorius MA 36 (which is modified in order to use higher operation temperature during measurements) and determined in an amount of 45.74% by weight[000187] The pH value of the sample of material produced measured by pH meter model testo 206-pH3 is 10.9.[000188] In order to determine the gluing ability of a material obtained by subjecting the produced precursor material to a sol -gel process a measuring element of the device PROCEQ DYNA Z16 was glued by means of the precursor to a clean surface of an cathodic dip coating (CDC) (electrophoretic epoxy film layer with a thickness 38 ± 3 pm (measured by device QNIX 1500 (Automation Dr. NIX, Germany) on an 7075 Al alloy sheet with a thickness 1.3 ± 0.01 mm and with a specific volume resistance of the epoxy layer of 15 ± 0.5 MQ*m (measured by Ohm and Current Meter Mili-T03 (H.-P. FISCHER ELEKTRONIK GmbH & Co, Germany)) and stored in a laboratory oven of Binder GmbH (Germany) at a temperature 70 ± 5 °C for not less than 6 hours in order to transform the precursor material into a rigid form based the occurring sol-gel process thereby obtaining a rigid hydrosilicate gel. The surface tension (adhesion) strength measured by PROCEQ DYNA Z16 is 4.06 MPa.[000189] In order to confirm that the material produced retains a non-solid like state under SATP, a sample of the material was loaded into a mould (150 mm cube, prepared according to EN 12390-1:2000) and stored for 28 days under conditions of Standard Ambient Temperature and Pressure (SATP, 25°C, 100000 kPa / 1 bar). After unloading from the mould, the sample was placed on the flat surface of a table. During the next 19 hours the sample lost the cubic form.Example 14[000190] In order to estimate efficiency of an application of the inventive alkali metal hydrosilicate (silicate precursor) for fire protection two dry spruce branches with needles with a weight 10 ± 0. 1 g wereselected. One branch was coated with the material made in accordance to Example 10 - sample number 10.3 by dipping and storing in a laboratory oven of Binder GmbH (Germany) at a temperature 65 ± 5 °C for not less than 6 hours in order to transform the precursor material into a rigid form based the occurring sol-gel process thereby obtaining a rigid hydrosilicate gel on the surface of the sample. Both samples were treated by POWER MAPP high-performance soldering device (Rothenberger Industrial, Germany) with a working temperature of 1250 C.[000191] The untreated sample was burned within 30 seconds with intensive fire. The treated sample failed to set fire even after 60 seconds of treatment by the torch. Fire did not propagate on the surface of the treated branch.[000192] Thus, the high efficiency of application of the material according to present invention for fire protection is confirmed.Example 15[000193] In order to estimate efficiency of an application of the inventive alkali metal hydrosilicate (silicate precursor) for prevention of thermal runaway process two modules of rechargeable batteries were made. The first module was made from three lines of consecutively located 18650 Li-ion rechargeable batteries (Panasonic). All batteries were completely charged and connected consecutively. Also, the module was tightly inserted into a plastic box made from LDPE with the wall thickness of 2 mm.[000194] The second module was made in the same way, however more than 90% of free space inside the box in-between the batteries was filled by the alkali metal hydrosilicate (silicate precursor) obtained in accordance to Example 1. The module which was filled by material in accordance to present invention was stored under SATP during 10 days.[000195] Later as minimum one battery in each module was crashed by sharp metal stick via lateral side in order to initiate mechanically the thermal runaway process. The untreated module burned out within 5 minutes. In the treated module during the first 5 seconds there spark ejection was observed and later all thermal processes inside the module, which were indicated by evaporation of steam, were finished within the next 5 minutes.[000196] Thus, the high efficiency of application of material according to present invention for prevention of thermal runaway process was confirmed[000197] If not otherwise specified any amount in % or parts is by weight and in the case of doubt referring to the total weight of the composition / mixture concerned. A characterization as "approximately", "about" and similar expression in relation to a numerical value means that up to 10 % higher and lower values are included, preferably up to 5 % higher and lower values, and in any case at least up to 1 % higher and lower values, the exact value being the most preferred value or limit.[000198] The term "substantially free" means that a particular material is not purposefully added to a composition, and is only present in trace amounts or as an impurity. As used herein, unless indicated otherwise, the term "free from" means that a composition does not comprise a particular material, i.e. the composition comprises 0 weight percent of such material.

Claims

Claims1. An alkali metal hydrosilicate, which, after thermal treatment at a temperature of 250 ± 5 °C for 30 min ± 1 min, has the chemical elemental composition in % by weight:Silicon 27-40;Aluminium 0.9-3.5;Iron 0.2-3.5;Calcium 0.2-2.0;Magnesium 0.05-0.5;Alkali metal (sodium, potassium or combination thereof) 8.0-19.0;Oxygen 43-54;Other elements - no more 3.0% based on XRF data.

2. The alkali metal hydrosilicate according to claim 1, characterized in that it shows a loss of weight after the thermal treatment at the temperature of 250°C ± 5°C for 30 min ± 1 min of from about 45% by weight to about 65 % by weight determined by moisture analyser.

3. The alkali metal hydrosilicate according to claim 1 or 2, characterized in that it possesses a viscosity at a temperature 25 ± 0.5°C of about 100 - about 70000 Pa*s, preferably about 150 - about 1600 Pa*s, more preferably about 200 - about 1500 Pa*s (measured by a Brookfield viscometer).

4. The alkali metal hydrosilicate according to any one of claims 1 to 3, characterized in that it has a pH value from about 10.2 to about 13, preferably from about 10.6 to about 12.

5. The alkali metal hydrosilicate according to any one of claims 1 to 4, characterized in that it comprises not more than 10% by weight of a liquid acidic component, extracted by heating to a temperature of 70 ± 5 °C, vacuumizing to 0.1 bar within about 15 min and maintaining under vacuum for about 6-8 hours.

6. The alkali metal hydrosilicate according to any one of claims 1 to 5, characterized in that it does not harden after storage under Standard Ambient Temperature and Pressure (SATP, 25°C, 100000 kPa / 1 bar) for at least 28 days.

7. A method for producing an alkali metal hydrosilicate as defined in any one of claims 1 to 5, comprises the steps of: a) providing a particulate silica raw material comprising at least 70% amorphous Si O2 and a dry particulate alkali hydroxide, and optionally adjusting the humidity content of the silica raw material to at least about 70% by weight and not more than about 81.5% by weight;b) mixing the particulate silica raw material and the dry particulate alkali hydroxide in a ratio of 1 part by weight of dry alkali hydroxide and 5.25 to 10.5 parts by weight of dry silica raw material under specific energy input of about 200 kJ / kg to 750 kJ / kg, preferably in an agitator at a rotation speed from 1000 to about 4000 rpm; c) adding water in a ratio of 1 part by weight of the dry solids to 2.55 to 4.3 parts by weight of water, preferably under the mixing conditions of step b), to obtain a viscous product, and optionally adjusting the amount of water based on the humidity content of the employed silica raw material.

8. The method of claim 8, wherein the silica raw material is selected from sedimentary rocks, such as diatomites, kieselguhrs, tripolis, planner, spongiolites, radiolarites, opals, and technogenic byproducts of amorphous silica.

9. The method of claim 7 or 8, wherein the silica raw material is selected from a diatomite (type 1) of the following composition:a diatomite (type 2) of the following composition:or amorphous silica by-product (microsilica) of ferroalloys production of the following composition:

10. The method according to any one of claims 7 to 9, wherein the dry particulate alkali hydroxide is selected from sodium hydroxide, potassium hydroxide or a combination thereof.

11. The method according to any one of claims 7 to 10, wherein in step c) the water is added with a temperature of about 75°C to about 95°C, preferably about 75°C to about 85°C.

12. The method according to any one of claims 7 to 11, further comprising the step of reducing the viscosity of the obtained product by dilution with water, until a pH of at least 8 is reached for the diluted material.

13. An alkali metal hydrosilicate obtainable or obtained by the method according to any one of claims 7 to 12.

14. Use of the alkali metal hydrosilicate according to any one of claims 1 to 6 and 13 for the manufacture of hydrosilicate gels and silicate solids for fire protection, for prevention of thermal runaway and for producing cellulose based composites.

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