SILICA-BASED HYDROPHOBIC GRANULAR MATERIAL WITH AN INCREASED POLARITY

Abstract

Silica-based hydrophobic granular material with an increased polarity Silica-based granular material, comprising silica and at least one IR-opacifier, hydrophobized with a surface treatment agent comprising a silicon atom, wherein the granular material has: a) a cumulative pore volume of pores>4 nm of more than 2.5 cm.sup.3/g, as determined by the mercury intrusion method according to DIN ISO 15901-1; b) a tamped density of 140 g/L to 290 g/L; c) a number of silanol groups relative to BET surface area d.sub.SiOH of at least 0.5 SiOH/nm.sup.2, as determined by reaction with lithium aluminium hydride. d) a number of silicon atoms in the surface treatment agent relative to BET surface area d.sub.[Si] of at least 1.0 [Si atoms]/nm.sup.2.

Claims

1-15. (canceled)

16. A silica-based granular material, comprising silica and at least one IR-opacifier selected from the group consisting of: silicon carbide, titanium dioxide, zirconium dioxide, ilmenites, iron titanates, iron oxides, zirconium silicates, manganese oxides, graphites, carbon blacks and mixtures thereof; and hydrophobized with a surface treatment agent comprising a silicon atom, wherein the silica-based granular material comprises: a) a cumulative pore volume of pores>4 nm of more than 2.5 cm.sup.3/g, as determined by a mercury intrusion method according to DIN ISO 15901-1; b) a tamped density of 140 g/L to 290 g/L; c) a number of silanol groups relative to BET surface area d.sub.SiOH of at least 0.5 SiOH/nm.sup.2, as determined by reaction with lithium aluminium hydride; and d) a number of silicon atoms in the surface treatment agent relative to BET surface area d.sub.[Si] of at least 1.0 [Si atoms]/nm.sup.2.

17. The silica-based granular material of claim 16, comprising 30% to 95% by weight of silica selected from the group consisting of: fumed silica, precipitated silica, silica aerogel, silica xerogel, and mixtures thereof.

18. The silica-based granular material of claim 16, comprising 1% to 70% by weight of at least one IR-opacifier selected from the group consisting of: silicon carbide, titanium dioxide, zirconium dioxide, ilmenites, iron titanates, iron oxides, zirconium silicates, manganese oxides, graphites, carbon blacks and mixtures thereof.

19. The silica-based granular material of claim 16, wherein the surface treatment agent comprising a silicon atom is selected from the group consisting of: organosilanes, silazanes, acyclic polysiloxanes, cyclic polysiloxanes, and mixtures thereof.

20. The silica-based granular material of claim 16, wherein numerical median particle size d.sub.50 of the granular material is from 10 μm to 5000 μm.

21. The silica-based granular material of claim 16, wherein at least 5% by weight of the granular material has a particle size of less than 200 μm.

22. The silica-based granular material of claim 16, wherein carbon content of the granular material is from 0.5% to 10% by weight.

23. The silica-based granular material of claim 16, wherein pore volume for pores smaller than 4 μm of the granular material is 2 cm.sup.3/g-5 cm.sup.3/g, as determined by a mercury intrusion method according to DIN ISO 15901-1.

24. The silica-based granular material of claim 16, comprising a percent ratio of pore volume for pores<4 μm to cumulative pore volume of pores>4 nm of more than 35%, wherein both pore volumes are determined by a mercury intrusion method according to DIN ISO 15901-1.

25. The silica-based granular material of claim 16, wherein skeletal density of the granular material is at least 0.6 g/mL, as determined by a mercury intrusion method according to DIN ISO 15901-1 at 417 Mpa.

26. The silica-based granular material of claim 16, wherein the ratio d.sub.[Si]/d.sub.SiOH is 1 to 10.

27. The silica-based granular material of claim 17, comprising 1% to 70% by weight of at least one IR-opacifier selected from the group consisting of: silicon carbide, titanium dioxide, zirconium dioxide, ilmenites, iron titanates, iron oxides, zirconium silicates, manganese oxides, graphites, carbon blacks and mixtures thereof.

28. The silica-based granular material of claim 27, wherein the surface treatment agent comprising a silicon atom is selected from the group consisting of: organosilanes, silazanes, acyclic polysiloxanes, cyclic polysiloxanes, and mixtures thereof.

29. The silica-based granular material of claim 28, wherein numerical median particle size d.sub.50 of the silica-based granular material is from 10 μm to 5000 μm.

30. The silica-based granular material of claim 28, wherein carbon content of the silica-based granular material is from 0.5% to 10% by weight.

31. The silica-based granular material of claim 28, wherein pore volume for pores smaller than 4 μm of the granular material is 2 cm.sup.3/g-5 cm.sup.3/g, as determined by a mercury intrusion method according to DIN ISO 15901-1.

32. The silica-based granular material of claim 28, wherein the ratio d.sub.[Si]/d.sub.SiOH is 1 to 10.

33. A process for producing the silica-based granular material of claim 16, comprising the following steps: a) dry densifying the powder comprising hydrophilic silica and at least one IR-opacifier selected from the group consisting of: silicon carbide, titanium dioxide, zirconium dioxide, ilmenites, iron titanates, iron oxides, zirconium silicates, manganese oxides, graphites, carbon blacks and mixtures thereof to give a hydrophilic granular material with a tamped density of at least 80 g/L; b) subjecting the hydrophilic granular material produced of step a) to thermal treatment at a temperature of 300° C. to 1400° C.; c) hydrophobizing the hydrophilic granular material subjected to thermal treatment in step b) in the presence of a surface treatment agent comprising a silicon atom and water, wherein the molar ratio of water to the silicon atoms in the surface treatment agent comprising a silicon atom is from 0.1 to 100.

34. A thermal insulating composition comprising the silica-based granular material of claim 16.

35. The thermal insulating composition of claim 34, further comprising a binder selected from the group consisting of: (meth)acrylates, alkyd resins, epoxy resins, gum Arabic, casein, vegetable oils, polyurethanes, silicone resins, hybrid systems containing silicone based and other organic ingredients, wax, cellulose glue, and mixtures thereof.

Description

EXAMPLES

[0168] Analytical Methods. Determination/Calculation of Parameters.

[0169] The cumulative pore volume for pores larger than 4 nm (Hg-pore volume>4 nm) [in cm.sup.3/g] was determined by the mercury intrusion method according to DIN ISO 15901-1 using AutoPore V 9600 device (Micomeritics). Only the pore volume of pores into which mercury can penetrate, i.e. the pores with a pore diameter of >4 nm, at the maximal pressure applied (417 MPa) was detected.

[0170] The cumulative pore volume of pores<4 μm (Hg-pore volume<4 μm, in cm.sup.3/g) was determined by the same mercury intrusion method according to DIN ISO 15901-1 and corresponds to the cumulative pore volume of all pores<4 μm determinable by this method.

[0171] The skeletal density [in g/cm.sup.3] was determined from the results of the analysis of the sample by mercury intrusion method according to DIN ISO 15901-1 after the volume of all pores larger than 4 nm (at the maximal intrusion pressure of 417 MPa) has been excluded from the volume presumed occupied by the material.

[0172] Loss on drying (LOD, in wt. %) was determined according to ASTM D280-01 (method A).

[0173] Specific BET surface area [m.sup.2/g] was determined according to DIN 9277:2014 by nitrogen adsorption in accordance with the Brunauer-Emmett-Teller method.

[0174] Tamped density [g/L] was determined according to DIN ISO 787-11:1995.

[0175] Methanol wettability [vol % of methanol in methanol/water mixture] was determined according to the method described in detail, in WO2011/076518 A1, pages 5-6.

[0176] Carbon content [wt. %] was determined according to EN ISO3262-20:2000 (Chapter 8) by elemental analysis using Carbon Determination System C632 (manufacturer: LECO).

[0177] The analysed sample was weighed into a ceramic crucible, provided with combustion additives and heated in an induction furnace under an oxygen flow. The carbon present is oxidized to CO.sub.2. The amount of CO.sub.2 gas is quantified by infrared detectors (IR). SiC is not burned and therefore does not affect the value of the carbon content.

[0178] The number of silanol groups relative to BET surface area d.sub.SiOH [in SiOH/nm.sup.2] was determined by reaction of the pre-dried samples of granules with lithium aluminium hydride solution as described in detail on page 8, line 17 thru page 9, line 12 of EP 0725037 A1.

[0179] The number of silicon atoms in the surface treatment agent relative to BET surface area of the granular material of the present invention d.sub.[Si] [in Si atoms/nm.sup.2] was calculated from the carbon content related to the presence of the surface treatment (=carbon content determined by elemental analysis for all tested samples), and considering the chemical structure of the surface treatment, e.g. the number of carbon atoms per silicon atom of the surface treatment agent (N.sub.C/Si):

d.sub.[Si] [Si atoms/nm.sup.2]=(C*[wt. %]×N.sub.A)/(Mr.sub.C [g/mol]×N.sub.C/Si×BET [m.sup.2/g]×10.sup.20)  (3),

[0180] wherein Mr.sub.C=12,011 g/mol is an atomic weight of carbon,

[0181] N.sub.A is Avogadro number (˜6.022*10.sup.23).

[0182] N.sub.C/Si is the ratio of carbon to silicon atoms in the surface treatment agent (N.sub.C/Si=3 for hexamethyldisilazane).

[0183] The d.sub.[Si]/d.sub.SiOH ratio was calculated by dividing the number of silicon atoms in the surface treatment agent relative to BET surface area (d.sub.[Si]) by the number of silanol groups relative to BET surface area (d.sub.SiOH).

[0184] Thermal conductivity [in mW/(m*K)] was measured according to EN 12667:2001 by the method with the guarded hot plate and the heat flow meter instrument. The mean measurement temperature was 10° C. and the contact pressure 1000 Pa; the measurement was conducted under air atmosphere at standard pressure.

[0185] Preparation of Silica-Based Materials

Comparative Example 1 (Silica Powder Hydrophobized with HMDS)

[0186] A silica powder AEROSIL® R812 hydrophobized with HMDS (BET=172 m.sup.2/g, manufacturer: EVONIK Resource Efficiency GmbH) was used as a reference material. Physicochemical properties of this silica powder can be found in Table 2.

Comparative Example 2 (Silica/SiC Granules Hydrophobized with HMDS)

[0187] Mixing

[0188] 1000F silicon carbide (Carsimet, manufacturer: Keyvest), 20% by weight, and AEROSIL© R812 hydrophobic silica (hydrophobized with HMDS, BET=172 m.sup.2/g, manufacturer: EVONIK Resource Efficiency GmbH), 80% by weight, were mixed by means of a Minox PSM 300 HN/1 MK ploughshare mixer.

[0189] Densification

[0190] The mixture of AEROSIL© R812 with silicon carbide produced as described above was densified with a Grenzebach densifying roll (Vacupress VP 160/220). The tamped density of the granular material obtained was adjusted via the contact pressure, the roll speed and the reduced pressure applied to 166 g/L. The vacuum applied was less than 300 mbar, absolute. The roll speed was 5 rpm, and the pressure was 2000 N.

[0191] Sieving/Fractionation

[0192] In order to obtain desired fractions, the granular material was first fed to an oscillating sieve mill with mesh size 3150 μm (manufacturer: FREWITT), in order to establish an upper particle limit and hence remove the particles larger than this upper limit. This was followed by fractionation of the particle fractions, obtaining the particle size of from 200 to 1190 μm. This was done using a vibrating sieve from Sweco, model LS18S. Physicochemical properties of the thus prepared silica-based granular material can be found in Table 2.

Comparative Example 3 (without Thermal Treatment)

[0193] Mixing

[0194] 1000F silicon carbide (Carsimet, manufacturer: Keyvest), 20% by weight, and AEROSIL© 300 hydrophilic silica (BET=300 m.sup.2/g, manufacturer: EVONIK Resource Efficiency GmbH), 80% by weight, were mixed by means of a Minox PSM 300 HN/1 MK ploughshare mixer.

[0195] Densification

[0196] The mixture of AEROSIL© 300 with silicon carbide produced above was densified with a Grenzebach densifying roll (Vacupress VP 160/220). The tamped density of the granular material obtained was adjusted via the contact pressure, the roll speed and the reduced pressure applied to 120±5 g/L. The vacuum applied was less than 300 mbar, absolute. The roll speed was 5 rpm, and the pressure was 2000 N.

[0197] Sieving/Fractionation

[0198] In order to obtain desired fractions, the granular material was fed to an oscillating sieve mill with mesh size 1000 μm (manufacturer: FREWITT), in order to establish an upper particle limit and hence remove the particles larger than this upper limit.

[0199] Hydrophobization

[0200] Hydrophilic granules after densification step (100 g) were put in a grounded metal bucket and mixed by a propeller mixer at 200 rpm, and water (8 g) was sprayed at continuous stirring at 25° C. onto their surface, followed by spraying of 12 g of hexamethyldisilazane (HMDS). The mixing was continued for 5 minutes. After this time, the bucket was sealed with a lid containing several holes of 0.5-1 mm diameter for pressure compensation, and stored for 6 hours at 145° C. in an oven. After this time, the granular material was put into a drying pan and dried in the nitrogen atmosphere in an oven at 120° C. for 3 h to evaporate the volatiles.

[0201] Physicochemical properties of the thus prepared silica-based granular material can be found in Table 2.

Comparative Example 4 (with Thermal Treatment, without Hydrophobization)

[0202] Mixing

[0203] 1000F silicon carbide (Carsimet, manufacturer: Keyvest), 20% by weight, and AEROSIL© 300 hydrophilic silica (BET=300 m.sup.2/g, manufacturer: EVONIK Resource Efficiency GmbH), 80% by weight, were mixed by means of a Minox PSM 300 HN/1 MK ploughshare mixer.

[0204] Densification

[0205] The mixture of AEROSIL© 300 with silicon carbide produced above was densified with a Grenzebach densifying roll (Vacupress VP 160/220). The tamped density of the granular material obtained was adjusted via the contact pressure, the roll speed and the reduced pressure applied to 120+/−5 g/L. The vacuum applied was less than 300 mbar, absolute. The roll speed was 5 rpm, and the pressure was 2000 N.

[0206] Sintering/Hardening

[0207] The subsequent thermal hardening was effected in an XR 310 chamber kiln from Schröder Industrieöfen GmbH. For this purpose, multiple layers with a bed of height up to 5 cm were subjected to a temperature programme. The temperature ramp was 300 K/h up to the target temperature of 1025° C.; the hold time was 3 hours; then the sample was cooled (without active cooling) until removal. The tamped density of the obtained sintered granulate was 180+/−10 g/L.

[0208] Sieving/Fractionation

[0209] In order to obtain desired fractions, the thermally hardened granular material was fed to an oscillating sieve mill with mesh size 1000 μm (manufacturer: FREWITT), in order to establish an upper particle limit and hence remove the particles larger than this upper limit.

[0210] Physicochemical properties of the thus prepared silica-based granular material can be found in Table 2.

Comparative Example 5 (with Thermal Treatment, Hydrophobization without Water)

[0211] Mixing

[0212] 1000F silicon carbide (Carsimet, manufacturer: Keyvest), 20% by weight, and AEROSIL© 300 hydrophilic silica (BET=300 m.sup.2/g, manufacturer: EVONIK Resource Efficiency GmbH), 80% by weight, were mixed by means of a Minox PSM 300 HN/1 MK ploughshare mixer.

[0213] Densification

[0214] The mixture of AEROSIL© 300 with silicon carbide produced above was densified with a Grenzebach densifying roll (Vacupress VP 160/220). The tamped density of the granular material obtained was adjusted via the contact pressure, the roll speed and the reduced pressure applied to 120+/−5 g/L. The vacuum applied was less than 300 mbar, absolute. The roll speed was 5 rpm, and the pressure was 2000 N.

[0215] Sieving/Fractionation

[0216] In order to obtain desired fractions, the thermally hardened granular material was first fed to an oscillating sieve mill with mesh size 1000 μm (manufacturer: FREWITT), in order to establish an upper particle limit and hence remove the particles larger than this upper limit.

[0217] Sintering/Hardening

[0218] The subsequent thermal hardening was effected in an XR 310 chamber kiln from Schröder Industrieöfen GmbH. For this purpose, multiple layers with a bed of height up to 5 cm were subjected to a temperature programme. The temperature ramp was 300 K/h up to the target temperature of 1025° C.; the hold time was 3 hours; then the sample was cooled (without active cooling) until removal. The tamped density of the obtained sintered granulate was 180+/−10 g/L.

[0219] Hydrophobization

[0220] Hydrophilic granules after densification step (500 g) were put in a grounded metal bucket and mixed by a propeller mixer at 300-500 rpm and hexamethyldisilazane (HMDS) (60 g) was sprayed at continuous stirring at 25° C. onto their surface. The mixing was continued for 10 minutes. After this time, the bucket was sealed with a lid containing several holes of 0.5-1 mm diameter for pressure compensation, and stored for 6 hours at 145° C. in an oven.

[0221] After this time, the granular material was put into a drying pan and dried in the nitrogen atmosphere at 145° C. in an oven for 3 h to evaporate the volatiles.

[0222] Fractionation of the particle fractions, if necessary, was done using a vibrating sieve from Sweco, model LS18S.

[0223] Physicochemical properties of the thus prepared silica-based granular material can be found in Table 2.

Comparative Example 6 (with Thermal Treatment, Hydrophobization in Vapour Form)

[0224] Preparation of hydrophobized silica granules containing IR-opacifier has been conducted similar to PCT/EP2018/051142:

[0225] Mixing

[0226] 1000F silicon carbide (Carsimet, manufacturer: Keyvest), 20% by weight, and AEROSIL© 300 hydrophilic silica (BET=300 m.sup.2/g, manufacturer: EVONIK Resource Efficiency GmbH), 80% by weight, were mixed by means of a Minox PSM 300 HN/1 MK ploughshare mixer.

[0227] Densification

[0228] The mixture of AEROSIL© 300 with silicon carbide produced above was densified with a Grenzebach densifying roll (Vacupress VP 160/220). The tamped density of the granular material obtained was adjusted via the contact pressure, the roll speed and the reduced pressure applied to 121 g/L. The vacuum applied was less than 300 mbar, absolute. The roll speed was 5 rpm, and the pressure was 2000 N.

[0229] Sintering/Hardening

[0230] The subsequent thermal hardening was effected in an XR 310 chamber kiln from Schröder Industrieöfen GmbH. For this purpose, multiple layers with a bed of height up to 5 cm were subjected to a temperature programme. The temperature ramp was 300 K/h up to the target temperature of 950° C.; the hold time was 3 hours; then the samples were cooled (without active cooling) until removal. The tamped density of the obtained sintered granulate was 180 g/L.

[0231] Hydrophobization

[0232] The final hydrophobization of the thermally hardened granules was effected at elevated temperatures over the gas phase. For this purpose, hexamethyldisilazane (HMDS, 8.6 wt % relative to the weight of the hydrophilic plate) as hydrophobizing agent was evaporated and conducted through by the reduced pressure process in accordance with the process from Example 1 of WO 2013/013714 A1. The specimens were heated to more than 100° C. in a desiccator and then evacuated. Subsequently, gaseous HMDS was admitted into the desiccator until the pressure had risen to 300 mbar. After the sample had been purged with air, it was removed from the desiccator.

[0233] Sieving/Fractionation

[0234] In order to obtain desired fractions, the thermally hardened granular material was first fed to an oscillating sieve mill with mesh size 1000 μm (manufacturer: FREWITT), in order to establish an upper particle limit and hence remove the particles larger than this upper limit.

[0235] Physicochemical properties of the thus prepared silica-based granular material can be found in Table 2.

Example 1

[0236] Granular material according to the invention was prepared similarly to comparative example 5, but for the hydrophobization part, which was conducted as follows: Hydrophilic granules after sintering step (500 g) were put in a grounded metal bucket and mixed by a propeller mixer at 300-500 rpm, and water (40 g) was sprayed at continuous stirring at 25° C. onto their surface followed by spraying of hexamethyldisilazane (HMDS) (60 g). The mixing was continued for 10 minutes. After this time, the bucket was sealed with a lid containing several holes of 0.5-1 mm diameter for pressure compensation, and stored for 6 hours at 145° C. in an oven. After this time, the granular material was put into a drying pan and dried in the nitrogen atmosphere at 145° C. in an oven for 3 h to evaporate the volatiles.

[0237] Physicochemical properties of the thus prepared silica-based granular material can be found in Table 2.

Example 2

[0238] Granular material according to the invention was prepared similarly to comparative example 5, but for the hydrophobization part, which was conducted as follows: Hydrophilic granules after sintering step (500 g) were put in a grounded metal bucket and mixed by a propeller mixer at 300-500 rpm, and water (40 g) was sprayed at continuous stirring at 25° C. onto their surface followed by spraying of hexamethyldisilazane (HMDS) (37.5 g). The mixing was continued for 10 minutes. After this time, the bucket was sealed with a lid containing several holes of 0.5-1 mm diameter for pressure compensation, and stored for 6 hours at 145° C. in an oven. After this time, the granular material was put into a drying pan and dried in the nitrogen atmosphere at 145° C. in an oven for 3 h to evaporate the volatiles.

[0239] Physicochemical properties of the thus prepared silica-based granular material can be found in Table 2.

Example 3

[0240] Granular material according to the invention was prepared similarly to comparative example 5, but for the hydrophobization part, which was conducted as follows: Hydrophilic granules after sintering step (500 g) were put in a grounded metal bucket and mixed by a propeller mixer at 300-500 rpm, and water (20 g) was sprayed at continuous stirring at 25° C. onto their surface followed by spraying of hexamethyldisilazane (HMDS) (40.0 g). The mixing was continued for 10 minutes. After this time, the bucket was sealed with a lid containing several holes of 0.5-1 mm diameter for pressure compensation, and stored for 6 hours at 145° C. in an oven. After this time, the granular material was put into a drying pan and dried in the nitrogen atmosphere at 145° C. in an oven for 3 h to evaporate the volatiles.

[0241] Physicochemical properties of the thus prepared silica-based granular material can be found in Table 2.

Example 4

[0242] Granular material according to the invention was prepared similarly to comparative example 5, but for the hydrophobization part, which was conducted as follows: Hydrophilic granules after sintering step (500 g) were put in a grounded metal bucket and mixed by a propeller mixer at 300-500 rpm, and water (40 g) was sprayed at continuous stirring at 25° C. onto their surface followed by spraying of the mixture containing 60 g of hexamethyldisilazane (HMDS) and 10 g of 3-(trimethoxysilyl)propyl methacrylate (MEMO). The mixing was continued for 10 minutes. After this time, the bucket was sealed with a lid containing several holes of 0.5-1 mm diameter for pressure compensation, and stored for 6 hours at 145° C. in an oven. After this time, the granular material was put into a drying pan and dried in the nitrogen atmosphere at 145° C. in an oven for 3 h to evaporate the volatiles.

[0243] Fractionation of the particle fractions, if necessary (see Table 3), was done using a vibrating sieve from Sweco, model LS18S.

[0244] Physicochemical properties of the thus prepared silica-based granular material can be found in Table 2.

Example 5

[0245] Granular material according to the invention was prepared similarly to comparative example 5, but for the hydrophobization part, which was conducted as follows: Hydrophilic granules after sintering step (500 g) were put in a grounded metal bucket and mixed by a propeller mixer at 300-500 rpm, and water (40 g) was sprayed at continuous stirring at 25° C. onto their surface followed by spraying of the mixture containing 60 g of hexamethyldisilazane (HMDS) and 10 g of 3-(glycidoxypropyl)trimethoxysilane (GLYMO). The mixing was continued for 10 minutes. After this time, the bucket was sealed with a lid containing several holes of 0.5-1 mm diameter for pressure compensation, and stored for 6 hours at 145° C. in an oven. After this time, the granular material was put into a drying pan and dried in the nitrogen atmosphere at 145° C. in an oven for 3 h to evaporate the volatiles.

[0246] Fractionation of the particle fractions, if necessary (see Table 3), was done using a vibrating sieve from Sweco, model LS18S.

[0247] Physicochemical properties of the thus prepared silica-based granular material can be found in Table 2.

[0248] All the granular materials prepared in examples 1-5 showed high porosity, mechanical stability, relatively high values of the skeletal density, relatively high hydrophobicity (high d.sub.[Si], methanol wettability values) and relatively high polarity (d.sub.[SiOH] value) (Tables 1-2).

[0249] These physicochemical properties make such granules well suitable for various applications related to thermal or acoustic insulation. Particularly, for preparing thermal insulation coatings, prepared on the basis of water-based binder systems.

[0250] The granular material from comparative example 2 was prepared by densification of the hydrophobized silica powder Aerosil R812 (comparative example 1) with SiC. The value of porosity (Hg pore>4 nm) was significantly reduced (5.22 cm.sup.3/g vs. 13.13 cm.sup.3/g for granules vs. the powder, respectively) due to the reducing of the interparticle space in the granules compared to the powder. The tamped density and the skeletal density increased due to the densification, whereas the hydrophobicity and the polarity remain unchanged (Tables 1-2).

[0251] The granules in comparative example 3 were prepared similarly to those in example 1 with the only difference that no thermal treatment step has been applied. Tamped density, skeletal density and the overall mechanical stability of this sample were significantly lower than those values for the granules prepared in example 1 (Tables 1-2).

[0252] The granules from comparative examples 5 and 6 prepared without using water during the hydrophobization step, showed significantly lower d.sub.SiOH values than the examples according to the invention, rendering these materials less suitable for incorporation in polar systems, such as water-based thermal insulating coatings.

[0253] Preparation of Liquid Thermal Insulation Compositions: General Procedure

[0254] The mixing vessel was charged with the required amount of acrylic binder dispersion (styrene acrylic dispersion Acronal S790, manufacturer: BASF, 50 wt. % of total formulation). Under slow agitation with an impellor blade, water (17 wt. % of total formulation) is added, followed by a stepwise addition of the granular material (32 wt. % of total formulation). The mixer speed is increased to maintain a vortex. Ceramic fibres (Lapinus Rockwool) of an average fibre length of 900 μm (approximately 1 wt % of total formulation) were added. All granules were completely dispersed within the dispersion/water medium. Modifiers such as plasticiser, rheology control, coalescent, etc. can be added throughout the mixing steps for optimization.

TABLE-US-00001 TABLE 1 Process parameters for preparing silica-based materials. Silanol Water/Si Tamped density d.sub.[OH] BET Si atoms atoms in density (after before surface treatment in surface Water, surface after thermal surface Thermal agent, treatment [wt % treatment densifying, treatment) treatment, treatment, (wt % related agent/BET related to water/BET agent Example [g/L] [SiOH/nm.sup.2] [m.sup.2/g] [° C.] to granules)* [μmol/m.sup.2] granules] [μmol/m.sup.2] [mol/mol] Comparative 60 0.46 300 No HMDS (18)  7.4 0 0 0 example 1 Comparative 166 0.46 300 No HMDS (18)  7.4 0 0 0 example 2 Comparative 121 1.29 232 No HMDS (12)  10.1 8 30.0 2.99 example 3 Comparative 174 (1.18) 148 1025 No 0 0 0 — example 4 Comparative 174 (1.18) 148 1025 HMDS (12)  10.1 0 0 0 example 5 Comparative 174 (1.18) 148 950 HMDS (8.6), in 7.2 0 0 0 example 6 vapour form Example 1 174 (1.18) 148 1025 HMDS (12)  10.1 8 30.0 2.99 Example 2 174 (1.18) 148 1025 HMDS (7.5) 6.3 8 30.0 4.78 Example 3 174 (1.18) 148 1025 HMDS (8)   6.7 4 15.0 2.24 Example 4 174 (1.18) 148 1025 HMDS (12)/ 10.6 8 30.0 2.84 MEMO (2) Example 5 174 (1.18) 148 1025 HMDS (12)/ 10.6 8 30.0 2.83 GLYMO (2) *HMDS = hexamethyldisilazane; MEMO = 3-(trimethoxysilyl)propylmethacrylate; GLYMO = (3-glycidoxypropyl)trimethoxysilane

TABLE-US-00002 TABLE 2 Physicochemical properties of the silica-based materials Hg-pore Hg-pore skeletal volume volume density at tamped methanol d.sub.SiOH, C- Material >4 nm, <4 μm, 417 MPa, LOD, BET, density, wettability, [SIOH/ content, d.sub.[Si], d.sub.[Si]/ (Example) [cm.sup.3/g] [cm.sup.3/g] [g/cm.sup.3] [%] [m.sup.2/g] [g/L] [%] nm.sup.2] [%] [Si/nm.sup.2] d.sub.SiOH Comparative 13.13 4.03 0.513 <0.5 260 60 55 0.46 2.5 1.61 3.5 example 1 Comparative 5.22 2.36 0.797 <0.4 172 166 50-55 0.46 2.0 1.94 4.2 example 2 Comparative 7.09 3.16 0.889 0.3 181 135 50-55 1.29 2.3 2.12 1.6 example 3 Comparative 3.30 <0.1 148 174 0 1.18 0 0 0 example 4 Comparative 5.21 3.04 0.996 0.1 140 182 45-50 0.37 1.1 1.31 3.5 example 5 Comparative 5.31 3.10 1.648 <0.1 152 191 40-45 0.16 0.9 0.99 6.2 example 6 Example 1 5.21 2.88 1.496 0.1 117 188 55-65 0.96 1.9 2.72 2.8 Example 2 4.62 2.61 1.965 0.1 120 211 60-65 1.23 2.1 2.93 2.4 Example 3 4.55 2.58 1.987 0.1 118 192 55-60 0.91 1.6 2.27 2.5 Example 4 5.33 2.92 2.000 0.6 112 172 50-60 1.40 2.9 3.71 2.7 Example 5 5.41 3.08 1.120 0.5 110 190 50 1.40 3.0 3.91 2.8

[0255] Similar to the general procedure with styrene acrylic dispersion Acronal S790, the granular material of the invention could successfully be incorporated in the following binder types leading to the corresponding thermal insulating compositions with high (up to 25-30 wt % of total formulation) loading of the granular material:

[0256] Vinnapas 224 HD (Wacker, styrene acrylic dispersion copolymerized with vinyl silane);

[0257] CE330 Epoxy Binder (two-component, 100% solids epoxy resin, manufacturer:

[0258] Cornerstone Construction Material, LLC);

[0259] 100% solids polyurethane binders;

[0260] Stucco water-based formulations with sand being substituted by the granular material.

[0261] Preparation of Solid (Dried) Thermal Insulating Compositions

[0262] The samples of thermal insulation compositions were applied onto polycarbonate substrates of 20 cm×20 cm×1 cm size, compacted with a spatula to form a wet film of approximately 3-5 cm thickness and were allowed to dry on the air upon the laboratory bench for 24-36 hours at 20° C. and at a humidity of approximately 50% R.H. All thus prepared thermal insulating compositions contained 84.5% by volume of the granular materials in dry film. This volume ratio was calculated as follows: from the amount of granulate M.sub.G100 in grams in 100 g of dried thermal insulation composition and the known tamped density of the granulate d.sub.G (in g/L), the volume of granulate V.sub.G100 in 100 g of this composition was calculated:

V.sub.G100=M.sub.G100/d.sub.G

[0263] From the measured volume V.sub.C100 of 100 g of the dried thermal insulation composition, the volume ratio of granulate in the dried thermal insulation composition was calculated as follows:

r.sub.G(% by volume)=V.sub.G100*100%/V.sub.C100.

[0264] After drying, thermal conductivity measurement of all samples was conducted.

[0265] The results of preparation of liquid and dried thermal insulating compositions are summarized in Table 3.

[0266] Relatively high dynamic viscosity of composition with granular material from the comparative example 5 did not allow applying this composition via spraying. Conversely, thermal insulation composites with granules from examples 1, 3, 4 and 5 could be applied by spray techniques as well as by brushing. Dried films of between 1 and 2.5 mm thickness could be produced in all these cases.

TABLE-US-00003 TABLE 3 Effect of granules on viscosity, ease of application via spraying and thermal conductivity of TIC Dynamic Thermal Particle viscosity Application conductivity size, μm of liquid via of dried Sample (wt % ratio) TIC, cP spraying TIC, mW/mK Comparative <1200 350000 No Not measured example 5 (100%) Example 1 <1000 2032 Yes 46.7 (100%) Example 3 <1000 2368 Yes 49.5 (100%) Example 4 <1200 2475 Yes 65.4 (100%) Example 4 <1200 4167 Yes 61.0 (75%), <200 (25%) Example 5 <1200 2500 Yes 51.8 (100%)