EP3571173A1

EP3571173A1 - Granular thermal insulation material and method for producing the same

Info

Publication number: EP3571173A1
Application number: EP18700427.0A
Authority: EP
Inventors: Matthias Geisler; Ann-Kathrin Herr; Christian MOERS; Gabriele Gärtner
Original assignee: Evonik Degussa GmbH
Current assignee: Evonik Operations GmbH
Priority date: 2017-01-18
Filing date: 2018-01-18
Publication date: 2019-11-27
Also published as: US11565974B2; US20200031720A1; RU2759942C2; MX2019008516A; JP2020506867A; WO2018134275A1; RU2019125106A; JP7050810B2; CN110446692A; RU2019125106A3

Abstract

The invention relates to a granular thermal insulation material, comprising hydrophobed silicon dioxide, at least one IR opacifier, having a tamped density of up to 250 g/L and a compressive stress according to DIN EN 826:2013 at 50% compression of 150 to 300 or greater than 300 kPa. The invention further relates to a method for producing the same and to the use of the same for thermal insulation.

Description

Granular thermal insulation material and method for its production

The present invention relates to a granular material having improved mechanical stability, and to processes for its production and use

Material for thermal insulation.

Effective thermal insulation of homes, industrial plants, pipelines and the like is an important economic problem. Most organic based insulation materials such as polyurethane foams are combustible and can only be used at limited temperatures. The hitherto less widely used thermal insulation materials based on inorganic oxides, for example highly porous silicon dioxide, do not have these disadvantages. at

In contrast, the use of such materials for thermal insulation plays an important role in the optimization of mechanical properties, such as particle size and mechanical stability.

The basis of such silica-based insulating materials are usually the so-called aerogels, as well as precipitated or pyrogenic produced

Silica used. Further information on these silica types can be found in Ullmann's Encyclopedia of Industrial Chemistry, chapter "Silica" published online on 15.04.2008, DOI: 10.1002 / 14356007.a23_583.pub3.

WO 2006/097668 A1 discloses a granular thermal insulation material comprising hydrophobic fumed silica and a clouding agent which is prepared by mixing a hydrophobic silica with clouding agent and the subsequent densification into granules having a size of 0.25 to 2.5 mm. Such products are characterized by a relatively high tamped density of 250 to 450 g / L.

EP2910724A1 discloses a frame filled with heat-insulating material, comprising a mixture of hydrophobized pyrogenically prepared silica having an average diameter of 1 to 100 μm and a clouding agent

Particle sizes from 0.1 to 25 μηη, with a bulk density of 100-200 g / L. This insulating material is thereby mixed by mixing the ingredients and

subsequent compaction produced.

EP 0725037 A1 describes granules having an average grain diameter of 10 to 120 μm based on hydrophobic pyrogenically produced silicon dioxide for use as a catalyst support. Such granules have a tamped density of 260 to 570 g / L and are obtained by spray-drying a silica-containing aqueous Dispersion, tempering at temperatures of 150 to 1 100 ° C and subsequent hydrophobing made with organosilicon compounds.

European Application 16181905.7 discloses the preparation of a heat-insulating material comprising hydrophobic silicas and opacifiers by treating a precipitated powdered silica with a silane, mixing with a hydrophilic pyrogenic silica and subsequent thermal treatment at 40-200 ° C. The resulting powdered mixture can be heated before thermal

Treatment can be optionally compressed to a granulate with a tamped density of 100-400 g / L.

DE 2903487 A1 discloses a process for producing powdery hydrophobic silicon dioxides by the treatment of hydrophilic silicas with

Organosilicon compounds in the presence of ammonia.

US 006099749 A discloses a process for producing finely divided compacted compositions comprising hydrophilic silicas which have been treated with ammonia before compacting.

Although the known silica-based powdery and granular thermal insulation materials ensure sufficient thermal insulation, they have a relatively high density and / or are not optimized with regard to mechanical stability.

The object of the present invention was to provide a hydrophobic thermal insulation material in a simple and practical form, which has very good mechanical stability and Abriebeigenschaften with low densities and thus low cost.

This object was achieved by providing a granulate containing hydrophobized silicon dioxide and at least one IR opacifier, a tamped density of up to 250 g / L and a compressive stress according to DIN EN 826: 2013 at 50% compression of 150 to 300 kPa or greater than 300 kPa has, wherein the compressive stress measurement on a bed with square area, having edge length 200 mm and 20 mm dump height, solved. The term "granules" in the present invention is understood to mean a granular, readily pourable, free-flowing solid.

Tamping densities of various powdery or coarse-grained granular materials can be determined according to DIN ISO 787-1 1: 1995 "General test methods for pigments and fillers - Part 1 1: Determination of tamping volume and tamped density. The filling density of a bed after shaking and pounding is measured. The granules according to the invention have a tamped density of up to 250 g / L, preferably from 50 to 250 g / L, preferably from 100 to 240 g / L, particularly preferably from 130 to 230 g / L.

Mechanical strength of the granules of the invention can be measured by measuring the compressive stress in the packing of such materials. Such a compressive stress measurement is based on DIN EN 826: 2013 "Thermal insulation products for construction - Determination of the

Normally, this standard specifies the compressive stress of plates at 10% compression, which is less optimal for bulk materials due to an inherently too large roughness on the bed surface than for the plates, this roughness would be the measurement inaccuracy of too small upsets, For this reason, in the present application the compressive stress measurement was carried out at 50% compression according to DIN EN 826: 2013, wherein the compressive stress measurement takes place on a bed with a square surface with edge length 200 mm and bed height 20 mm. The lateral boundary was realized with a soft foam which keeps the sample in position during the preparation.

A compressive force at 50% compression, which can be converted into a compressive stress over the surface of the sample, is measured:

O50 F ₅ = o / A, where O5O compression stress in Pa at compression ε = 50%; F ₅ o - a measured compressive force in N; A is a cross-sectional area of the specimen in m ² (in the present case A = 0.04 m ² ).

Compression ε is defined here as the ratio of the reduction in thickness of the test specimen (in the present case, bed consisting of the granules according to the invention) to its initial thickness, measured in the loading direction.

In a preferred embodiment of the invention, the granules according to the invention have a compressive stress according to DIN EN 826: 2013 at 50% compression of 150 to 300 kPa, preferably 170 to 300 kPa, more preferably 200 to 300 kPa, most preferably 250 to 300 kPa, wherein the compressive stress measurement on a bed with square area, having edge length 200 mm and

Pouring height 20 mm.

In another preferred embodiment of the invention, the

granules according to the invention a compressive stress according to DIN EN 826: 2013 at 50% Compression of greater than 300 kPa, preferably from 300 to 5000 kPa, preferably from 400 to 2500 kPa, more preferably from 500 to 2000 kPa, most preferably from 600 to 1500 kPa, wherein the compressive stress measurement on a bed with square area, comprising Edge length 200 mm and height 20 mm.

A numerical mean particle size of the granules according to the invention can be determined according to IS013320: 2009 by laser diffraction particle size analysis. In this case, from the resulting measured particle size distribution, the average value d.sub.so, which represents which particle size does not exceed 50% of all particles, is defined as a numerical average particle size. The granulate according to the invention may have a d.sub.50 value of greater than 10 .mu.m, is preferably from 20 to 4000 .mu.m, preferably from 50 to 3500 .mu.m, more preferably from 100 to 3000 .mu.m, very particularly preferably from 150 to 2500 .mu.m.

The granules of the present invention preferably contains only the particles having a size of at most 6000 μm, preferably from 50 to 5000 μm, particularly preferably from 200 to 4000 μm determined by dynamic image analysis according to ISO 13322-2: 2006. Most preferably, the granules of the invention are free of particles which are smaller than 200 μηι.

The granules according to the invention may have a BET surface area of greater than 20 m ² / g, preferably from 30 to 500 m ² / g, more preferably from 50 to 400 m ² / g, most preferably from 70 to 350 m ² / g. The specific surface area, also called BET surface area, is determined according to DIN 9277: 2014 by nitrogen adsorption using the Brunauer-Emmett-Teller method.

The granules according to the invention contain hydrophobized silica. For the purposes of the present invention, the term "hydrophobic" refers to the particles having a low affinity for polar media such as water, whereas the hydrophilic particles have a high affinity for polar media such as water.The hydrophobicity of the hydrophobic materials, also called hydrophobicity, The degree of hydrophobicity of a hydrophobic silica can be determined, inter alia, by its methanol wettability, as described in more detail, for example, in WO201 1/076518 A1, pages 5-6, in pure water , a hydrophobic silica separates completely from the water and floats on the water

Surface without wetting with the solvent. In pure methanol, on the other hand, a hydrophobic silica is distributed in the entire solvent volume, there is a complete wetting. In the measurement of methanol wettability becomes maximum content of methanol in a methanol-water test mixture determined in which no wetting of the silica takes place, so 100% of the silica used separates after contact with the test mixture of the test mixture, does not remain wetted. This content of methanol in the methanol-water mixture in wt .-% is called methanol wettability. The higher one

Methanol wettability, the more hydrophobic is the silica. The lower the

Methanol wettability, the lower the hydrophobicity and the higher the

Hydrophilicity of the material.

The granules according to the invention have a methanol wettability of greater than 5, preferably from 10 to 80, preferably from 15 to 70, more preferably from 20 to 65, most preferably from 25 to 60 wt .-% methanol content in a methanol-water mixture ,

The granules according to the invention contain at least one IR opacifier. Such an IR opacifier reduces the infrared transmission of a thermal barrier material and thus minimizes the heat transfer by radiation.

Preferably, the IR opacifier is selected from the group consisting of silicon carbide, titania, zirconia, ilmenite, iron titanates, iron oxides, zirconium silicates, manganese oxides, graphites, carbon blacks, and mixtures thereof. The particle size of the opacifier is usually between 0.1 to 25 μηη.

The granules of the present invention may contain from 30 to 95, preferably from 40 to 90, particularly preferably from 50 to 85,% by weight of the silicon dioxide and from 5 to 50, preferably from 10 to 40, particularly preferably from 15 to 30, parts by weight. Contain% of opacifier.

The granules of the present invention are excellent

Thermal insulation properties and can be used for thermal insulation.

The thermal conductivity of the granules according to the invention can be measured according to the method with the disk device and the heat flow meter device according to EN 12667: 2001. The mean measuring temperature is 10 ° C and the

Contact pressure 250 Pa, the measurement is carried out under air atmosphere at atmospheric pressure.

The thermal conductivity of the granulate according to the invention as a bed, measured according to EN 12667: 2001 at an average measurement temperature of 10 ° C, a contact pressure of 250 Pa under air atmosphere and atmospheric pressure, is preferably less than 50 mW / (m ^* K), preferably from 10 to 45, more preferably from 15 to 40, most preferably from 20 to 35 mW / (m ^* K). The granules according to the invention contain silicon dioxide. This silica may include one or more commonly known types of silicas such as the so-called aerogels, xerogels, perlites, precipitated silicas, fumed silicas. The granules according to the invention preferably contain one or more pyrogenic silicas.

Pyrogenic silicas are produced by means of flame hydrolysis or flame oxidation. In this case, hydrolyzable or oxidizable starting materials are generally oxidized or hydrolyzed in a hydrogen-oxygen flame. When

Starting materials for pyrogenic processes can be used organic and inorganic substances. Particularly suitable is silicon tetrachloride. The hydrophilic silica thus obtained is amorphous. Fumed silicas are usually present in aggregated form. By "aggregated" is meant that so-called

Primary particles, which initially arise in the genesis, combine firmly in the further course of the reaction to form a three-dimensional network. The primary particles are largely free of pores and have free on their surface

Hydroxyl groups on.

The granules according to the invention are characterized by a particularly high stability at a low tamped density. This can be shown, for example, by means of the particle size decrease of a suspension of the investigated granules under defined ultrasound application in isopropanol, as is explained in greater detail in the description of the exemplary embodiments. This test shows that the granules according to the invention have a

comparable or better stability but with low tamping density, as the materials of the prior art with comparable particle size fractions.

Thus, with the granules according to the invention in many applications often unwanted material abrasion and breakage is eliminated or reduced, the otherwise

For example, would lead to dust or other adverse effects.

The granules according to the invention can be used for thermal insulation.

Preferably, the granules of the invention may be used in heat-insulating mixtures and / or formulations.

The corresponding heat-insulating mixtures and / or formulations may contain at least one solvent and / or binder and / or one filler.

The solvent may be selected from the group consisting of water, alcohols, aliphatic and aromatic hydrocarbons, ethers, esters, aldehydes, ketones and mixtures thereof. For example, as the solvent, water, methanol, ethanol, propanol, butanol, pentane, hexane, benzene, toluene, xylene, diethyl ether, methyl tert-butyl ether, ethyl acetate, acetone can be used. The binder may contain organic or inorganic substances. The binder preferably contains reactive organic substances. Organic binders may, for example, be selected from the group consisting of (meth) acrylates, alkyd resins, epoxy resins, gum arabic, casein, vegetable oils, polyurethanes, silicone resins, wax, cellulosic glue. Such reactive organic substances may, for example, by polymerization, crosslinking reaction or another chemical reaction type for curing the heat-insulating formulation used and / or the heat-insulating mixture.

In addition to the organic binder or, alternatively, the heat-insulating formulation and / or the heat-insulating mixture may be inorganic curable

Contain substances. Inorganic, also referred to as mineral binders have essentially the same as the organic binder task to combine aggregates together. Furthermore, inorganic binders are used in

divided into non-hydraulic binders and hydraulic binders. Non-hydraulic binders are water-soluble binders such as white limestone, dolomitic lime, gypsum and anhydrite, which harden only in the air. Hydraulic binders are binders that harden in the air and under water and are insoluble in water after curing. These include hydraulic limestones, cements, plaster and masonry binders.

A further subject of the present invention is a process (A) for producing a granulate containing hydrophobized silicon dioxide and at least one

IR opacifier, comprising the following steps:

a) mixing a hydrophilic silica with at least one

IR opacifiers;

b) compression of the mixture obtained in step a) into a granulate;

c) thermal treatment of the granules produced in step b) at a temperature of 200 to 1200 ° C;

d) hydrophobing of the thermally treated granules from step c) with a hydrophobing agent.

Another subject matter of the invention is a further process (B) for producing a granulate containing hydrophobized silica and at least one IR opacifier, comprising the following steps:

a) mixing a hydrophilic silica with at least one IR

Opacifiers;

b) compression of the mixture obtained in step a) into a granulate;

c) treatment of the granules produced in step b) with ammonia; d) hydrophobing of the ammonia-treated granules from step c) with a hydrophobing agent.

The granules according to the invention described above can, for example, by

Method (A) or (B) are produced.

Steps a) and b) of the processes (A) and (B) according to the invention can be carried out as individual, separate stages or alternatively combined in one process step.

Mixing of the hydrophilic silica with at least one IR opacifier according to step b) of process (A) or of process (B) can be carried out with all suitable mixing apparatuses known to those skilled in the art.

Compaction of the mixture obtained in step a) to give granules according to step b) of process (A) or of process (B) can be carried out by venting or compaction.

Thermal treatment of the granules prepared in step b) in process (A) can at temperatures from 200 to 1500 ° C, preferably from 400 to 1400, preferably from 500 to 1200, more preferably from 600 to 1 100, most preferably from 800 to 1 100 ° C are performed.

In step c) of the process (B) according to the invention, the treatment of the granules produced in step b) with ammonia, preferably with gaseous ammonia takes place. The period of time in which step c) of the process (B) according to the invention is carried out depends inter alia on the composition of the heat-insulating molded body and its thickness. In general, the time period is 10 minutes to 100 hours, preferably 0.5 to 20 hours. Preferred temperatures are in the range from 0 to 200 ° C., more preferably from 20 to 100 ° C.

For the treatment with ammonia in step c) of process (B) according to the invention, ammonia can be introduced into the chamber provided for this purpose with the granules to be treated. The only requirement placed on the chamber is that it can maintain the pressures and temperatures required in the process according to the invention. The pressure difference Δρ = p2-p1, with p1 = pressure in the chamber before introduction of the gaseous ammonia, p2 = pressure in the chamber at which the introduction of the gaseous ammonia is stopped, is preferably more than 20 mbar, preferably from 50 mbar to 5 bar, more preferably from 100 mbar to 500 mbar, most preferably from 200 mbar to 400 mbar. In addition to ammonia, in step c) of process (B), steam may be added to the previously prepared granules, preferably at a relative vapor pressure of 50 to 95%.

The hydrophobizing agent used in step d) of process (A) or (B) may contain a silicon-containing compound, which is preferably selected from the group consisting of halosilanes, alkoxysilanes, silazanes or siloxanes.

Such a silicon-containing compound is particularly preferably a liquid compound having at least one alkyl group and a boiling point of less than 200 ° C. It is preferably selected from the group consisting of CH ₃ SiCl ₃ , (CH ₃ ) ₂ SiCl ₂ , (CH ₃ ) ₃ SiCl, C ₂ H ₅ SiCl ₃ , (C ₂ H ₅ ) ₂ SiCl ₂ , (C ₂ H ₅ ) ₃ SiCl, C ₃ H ₈ SiCl ₃ , CH ₃ Si (OCH ₃ ) ₃ , (CH ₃ ) ₂ Si (OCH ₃ ) ₂ , (CH ₃ ) ₃ SiOCH ₃ , C ₂ H ₅ Si (OCH ₃ ) ₃ , (C ₂ H ₅ ) ₂ Si (OCH ₃ ) ₂ , (C ₂ H ₅ ) ₃ SiOCH ₃ , C ₈ Hi ₅ Si (OC ₂ H ₅ ) ₃ , C ₈ Hi ₅ Si (OCH ₃ ) ₃ , (H ₃ C) ₃ SiNHSi (CH ₃₎ _3, and selected mixtures thereof. Particularly preferred are (H ₃ C) ₃ SiNHSi (CH ₃ ) ₃ and (CH ₃ ) ₂ SiCl ₂ .

In the process (A) or (B) according to the invention, after step b) and / or c) and / or d), separation of fractions of the granules of different size from one another can take place such that only one or more fractions having certain particle sizes are separated and further be used.

Examples

Comparative Examples 1 -3

Mix

. Silicon carbide Silcar G14 (ESK-SiC GmbH), 20% by weight and hydrophobized with dimethyldichlorosilane silica AEROSIL ^® R974 (BET = 200 m ² / g, manufactured by EVONIK Resource Efficiency GmbH)., 80% by weight were using a ploughshare mixer PSM 300 HN / 1 MK of the company Minox mixed.

condense

The mixture of AEROSIL ^® R974 with silicon carbide prepared above was compacted with roller compactor Grenzebach (Vacupress VP 160/220). The

Tamping density of the product was adjusted by the contact pressure, the roller speed and the applied negative pressure.

compacting

By means of the roll compactor Pharmapaktor L200 / 50P from Bepex, the previously compacted mixture was then compacted again into manageable granules. Here, the speed, the contact pressure and the vacuum were set accordingly. Seven / fractionation

In order to obtain desired fractions, the compacted granules were first fed to an oscillating sieve mill with a mesh size of 3150 μm (manufacturer

FREWITT) to set a grain upper limit to separate particles larger than this upper limit. Subsequently, the desired fractionation of the particle fractions, for example, from 200 to 1 190 μηη or from 1 190 to 3150 μηη. For this purpose, a vibrating sieve from Sweco, Model LS18S, was used.

The sieved granules thus obtained were no longer treated and had the tamped densities and other parameters given in Table 1.

Comparative Example 4

A commercial hydrophobized airgel granule manufactured by Cabot, product name Enova IC3120, particle size 0.1 to 1.2 mm was analyzed untreated under the same conditions as the other materials, see Table 1.

Examples 1-2

Mix

Silicon carbide 1000F (Carsimet), manufactured by Keyvest, 20% by weight and hydrophilic silica AEROSIL ^® 300 (BET = 300 m ² / g, manufactured by EVONIK Resource Efficiency GmbH).., 80 wt% were using a ploughshare mixer PSM 300 HN / 1 MK of the company Minox mixed.

condense

The mixture of AEROSIL ^® 300 silicon carbide was previously prepared with a compressor roll Grenzebach (Vacupress VP 160/220) compacted. The

Tamped density of the resulting granules was adjusted by the contact pressure, the roller speed and the applied negative pressure. The applied vacuum was less than 300 mbar, absolute. The rolling speed was 5 rpm and the pressing pressure was 2000 N.

Sinter / curing

The subsequent thermal curing took place in a chamber furnace XR 310 from Schröder Industrieöfen GmbH. For this purpose, several layers were treated with a bed of up to 5 cm in height with a temperature program. The temperature ramp was 300 K / h up to the target temperature of 950 ° C, the holding time was 3 hours, then the cooling (without active cooling) of the samples was carried out until removal.

hydrophobilize The final hydrophobing of the thermally cured granules was carried out at elevated temperatures via the gas phase. For this purpose, hexamethyldisilazane (HMDS) was evaporated as the hydrophobizing agent and carried out in a vacuum process on the basis of the method of Example 1 of WO 2013/013714 A1. The samples were heated to over 100 ° C in a desiccator and then evacuated. Subsequently, gaseous HMDS was introduced into the desiccator until the pressure increased to 300 mbar. After rinsing the sample with air, it was removed from the desiccator.

Seven / fractionation

In order to obtain desired fractions, the thermally cured granules were first fed to an oscillating sieve mill with a mesh size of 3150 μm

(Manufacturer FREWITT) to set a grain upper limit and so to separate the particles greater than this upper limit. Subsequently, the desired fractionation of the particle fractions, for example, from 200 to 1 190 μηη or from 1 190 to 3150 μηη. For this purpose, a vibrating sieve from Sweco, Model LS18S, was used.

The values summarized in Table 1 for tamped densities, compressive stress at 50% compression and thermal conductivity were measured as explained in detail in the description above. ultrasound measurements

The ultrasound measurements were carried out with the Retsch Horiba LA-950 Laser Particle Size Analyzer from Horiba. Measuring method: Mie scattering theory, measuring range: 0.5 to 5000 [Ji m. A similar method is described in WO 2014001088 A1. The samples were pretreated prior to measurement by manually sieving particles larger than 2500 μηη so as not to clog the analyzer's gap. In each case 1 g (depends on the

Laser attenuation) used. A duplicate determination of each sample was performed and then an average was calculated. The measurements showed good repeatability. The ultrasound power of the built-in ultrasound standard finger can not be regulated in performance; only the duration can be set. The measurement was carried out at intervals at room temperature. The döo value is evaluated at the beginning of the measurement series and after each time interval. The values "US (20s), dso-quotient" summarized in Table 1 represent the ratios of the döo values after 20 seconds of the ultrasonic treatment (dso 2o _s ) to the corresponding döo values at the beginning of the measurement series (dso beginning):

US (20S), d ₅ 0-QUOtient = d ₅ 0 20 s / d ₅ 0 Start Accordingly, the higher this dso quotient, the more mechanically stable the granules tested.

Figure 1 shows the decrease in the dso quotient (dimensionless plotted on the y-axis) during the sonication time (in seconds plotted on the x-axis). The individual measurement series are identified as follows:

Comparative Example 1 - Triangle (A);

Comparative Example 2 - star (x);

Comparative Example 3 - X (x);

Comparative Example 4 - circle (·);

Example 1 - Square (■)

Example 2 - Rhombus (♦)

The results summarized in Table 1 for granules with

Comparable particle size fractions show that the granules of Examples 1 and 2 according to the invention have a better mechanical stability than the products of Comparative Examples 1 and 4 with less than 260 g / l tamped density.

On the other hand, the granules according to the invention show a comparable or even better mechanical stability than the materials from Comparative Examples 2 and 3 with tamping densities higher than 350 g / l. Accordingly, the

granules according to the invention a unique and economically useful combination of the parameters.

Table 1

^* All materials tested were screened before measuring the dso value to separate particles larger than 2500 pm, see the description of the ultrasonic measurement experiment.

Claims

claims

1 . Granules containing hydrophobized silica and at least one

IR opacifiers,

marked by

a tamped density of up to 250 g / L and

a compressive stress according to DIN EN 826: 2013 at 50% compression of 150 to 300 kPa or greater than 300 kPa, wherein the compressive stress measurement on a bed with a square surface, having edge length 200 mm and

Pouring height 20 mm.

2. Granules according to claim 1,

characterized in that

the IR opacifier selected from the group consisting of silicon carbide, titanium dioxide, zirconium dioxide, ilmenite, iron titanates, iron oxides, zirconium silicates,

Manganese oxides, graphites, carbon blacks and mixtures thereof is selected.

3. Granules according to one of claims 1 or 2,

characterized by a BET surface area of 50 to 400 m ² / g. 4. Granules according to one of claims 1 to 3,

characterized by a tamped density of 100 to 240 g / L.

Granules according to one of claims 1 to 4,

characterized by a compressive stress according to DIN EN 826: 2013 at 50%

Compression of 300 to 2000 kPa, wherein the compressive stress measurement on a bed with square area, having edge length 200 mm and

Pouring height 20 mm.

Granules according to one of claims 1 to 5,

characterized by a thermal conductivity of less than 50 mW / (m ^* K) according to EN 12667: 2001 measured in the bed, with an average measurement temperature of 10 ° C, a contact pressure of 250 Pa under air atmosphere and at atmospheric pressure.

7. Granules according to one of claims 1 to 6,

characterized in that

the silica is pyrogenic.

8. Granules according to one of claims 1 to 7,

characterized by a methanol wettability of 10 to 60 wt .-% methanol content in a methanol-water mixture.

Process for the preparation of granules containing hydrophobicized

Silica and at least one IR opacifier, comprising the following steps:

a) mixing a hydrophilic silica with at least one

IR opacifiers;

b) compression of the mixture obtained in step a) into a granulate;

c) thermal treatment of the granules produced in step b) at temperatures of 200 to 1200 ° C;

10. A process for producing a granulate containing hydrophobicized

Silica and at least one IR opacifier, comprising the following steps:

a) mixing a hydrophilic silica with at least one

IR opacifiers;

b) compression of the mixture obtained in step a) into a granulate;

c) treatment of the granules produced in step b) with ammonia;

d) hydrophobing of the ammonia-treated granules from step c) with a hydrophobing agent.

1 1. Method according to claim 9,

characterized in that

Step c) is carried out at a temperature of 800-1000 ° C.

12. The method according to any one of claims 9 to 1 1,

characterized in that

after step b) and / or c) and / or d) a separation of different sized fractions of the granules takes place from each other.

13. The method according to any one of claims 9 to 12,

characterized in that the hydrophobizing agent used in step d) is selected from the group consisting of halosilanes, alkoxysilanes, silazanes or siloxanes.

14. Granules according to one of claims 1 to 8, prepared by a process according to any one of claims 9 to 13.

15. Use of the granules according to one of claims 1 to 8 in

heat-insulating mixtures and / or formulations.