Granular mixed oxide material and thermal insulating composition on its basis

Abstract

Hydrophobized granular material comprising from 30 to 95% by weight of a pyrogenic mixed oxide based on silica and at least one oxide of metal M selected from of Al, Ti and Fe with the content of metal M oxide in the mixed oxide being from 01 to 10% by weight, and from 5 to 70% by weight of at least one IR-opacifier selected from the group consisting of silicon carbide, zirconium dioxide, ilmenites, iron titanates, zirconium silicates, manganese oxides, graphites, carbon blacks and mixtures thereof.

Claims

1. A hydrophobized granular material comprising from 30 to 95% by weight of a mixed oxide based on silica and at least one oxide of metal M selected from the group consisting of: Al; Ti; and Fe; wherein the mixed oxide comprises from 0.1 to 10% by weight of the metal M oxide, and from 5 to 70% by weight of at least one IR-opacifier selected from the group consisting of: silicon carbide; zirconium dioxide; ilmenites; iron titanates; zirconium silicates; manganese oxides; graphites; carbon blacks; and mixtures thereof.

2. The hydrophobized granular material of claim 1, wherein the mixed oxide is a pyrogenic silica-alumina mixed oxide.

3. The hydrophobized granular material of claim 1, wherein the granular material has a methanol wettability of 10% to 80% methanol by volume in a methanol/water mixture.

4. The hydrophobized granular material of claim 1, wherein the granular material has a numerical median particle size d.sub.50 of greater than 10 ?m.

5. The hydrophobized granular material of claim 1, wherein the granular material is essentially free of particles smaller than 200 ?m.

6. The hydrophobized granular material of claim 1, wherein the hydrophobized granular material has a BET surface area of 50 to 400 m.sup.2/g.

7. The hydrophobized granular material of claim 1, wherein the granular material has a tamped density of 50 to 300 g/L.

8. The hydrophobized granular material of claim 1, wherein the granular material has a hydroxyl group density of no greater than 0.3 mmol OH/g.

9. The hydrophobized granular material of claim 2, wherein the granular material has a methanol wettability of 10% to 80% methanol by volume in a methanol/water mixture.

10. The hydrophobized granular material of claim 9, wherein the granular material has a numerical median particle size d.sub.50 of greater than 10 ?m.

11. The hydrophobized granular material of claim 4, wherein the granular material is essentially free of particles smaller than 200 ?m.

12. The hydrophobized granular material of claim 11, wherein the hydrophobized granular material has a BET surface area of 50 to 400 m.sup.2/g.

13. The hydrophobized granular material of claim 11, wherein the granular material has a tamped density of 50 to 300 g/L.

14. The hydrophobized granular material of claim 13, wherein the granular material has a hydroxyl group density of no greater than 0.3 mmol OH/g.

15. A process for producing a hydrophobized granular material of claim 1, comprising the following steps: a) mixing a hydrophilic silica based mixed oxide with at least one IR opacifier; b) densifying the mixture obtained in step a) to give a hydrophilic granular material; c) either subjecting the hydrophilic granular material produced in step b) to thermal treatment at a temperature of 200 to 1200? C. or treating the hydrophilic granular material produced in step b) with ammonia; d) hydrophobizing the hydrophilic granular material subjected to thermal treatment in step c) with a hydrophobizing agent.

16. The process of claim 15, wherein, in step c), the hydrophilic granular material produced in step b) is subjected to thermal treatment at a temperature of 200 to 1200? C.

17. The process of claim 15, wherein, in step c), the hydrophilic granular material produced in step b) is treated with ammonia.

18. A thermal insulating composition comprising the hydrophobized granular material of claim 1.

19. The thermal insulating composition of claim 18, comprising at least one organic binder selected from the group consisting of: (meth)acrylates; alkyd resins; epoxy resins; gum Arabic; casein; vegetable oils; polyurethanes; silicone resins; wax; cellulose glue; and mixtures thereof.

20. The thermal insulating composition of claim 18, comprising at least one inorganic binder selected from the group consisting of: calcium lime; Dolomitic lime; gypsum; anhydrite; hydraulic limes; cements; masonry cements; and mixtures thereof.

Description

EXAMPLES

(1) Preparation of Silica Granular Material A (Comparative Example)

(2) Preparation of hydrophobized silica granular material containing IR-opacifier has been conducted according to PCT/EP2018/051142:

(3) Mixing

(4) 1000F silicon carbide (Carsimet), manufacturer: Keyvest, 20% by weight, and AEROSIL? 200 hydrophilic silica (BET=200 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.

(5) Densification

(6) The mixture of AEROSIL? 200 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. The vacuum applied was less than 300 mbar, absolute.

(7) The roll speed was 5 rpm, and the pressure was 2000 N.

(8) Sintering/Hardening

(9) The subsequent thermal hardening was effected in an XR 310 chamber kiln from Schr?der Industrie?fen 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.

(10) Hydrophobization

(11) The final hydrophobization of the thermally hardened granular material was effected at elevated temperatures over the gas phase. For this purpose, hexamethyldisilazane (HMDS) 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.

(12) Sieving/Fractionation

(13) In order to obtain desired fractions, the thermally hardened granular material was first fed to an oscillating sieve mill with mesh size 3150 ?m (manufacturer: FREWITT), in order to establish an upper particle limit and hence remove the particles larger than this upper limit. This was followed by the desired fractionation of the particle fractions, for example from 200 to 1190 ?m or from 1190 to 3150 ?m. This was done using a vibrating sieve from Sweco, model LS18S. The average particle size of the sieve fraction of granular material A of from 200 to 1190 ?m was d.sub.50=580 ?m.

(14) Preparation of Silica-Alumina Granular Material B According to the Invention

(15) Silica-alumina granular material B was prepared analog to silica granular material A with the difference, that the raw material AEROSIL? 200 was replaced by AEROSIL? MOX 170 (pyrogenic silica-alumina mixed oxide containing ca. 1 wt. % aluminium oxide with BET=170 m.sup.2/g, manufacturer: EVONIK Resource Efficiency GmbH) and the sintering temperature in sintering/hardening step was reduced to 850? C. The average particle size of the sieve fraction of granular material B of from 200 to 1190 ?m was d.sub.50=440 ?m.

(16) Used Binders

(17) Binder A: Acronal Eco 6270 (manufacturer: BASF); an acrylic-functionalized binder system.

(18) Binder B: Coatosil DRI (manufacturer: Momentive); a siloxane-functionalized binder system.

(19) Viscosity Measurement

(20) A rotational viscometer Brookfield DV2T Extra was used to conduct measurements of the dynamic viscosity of the formulations (mixture of binder and granular material). Spindles and rotational velocity were chosen according to the given viscosity range in the manual.

(21) General Experiment Description for Measuring Viscosity of Compositions with Granular Material after Various Storage Times

(22) Preparation of the Formulations:

(23) Binder (276 g) was filled into a cylindrical glass vessel with 9.5 cm diameter and stirred with a propeller stirrer at 600 rpm. Granular material (24 g, sieve fraction 200-1190 ?m) were gradually added to the stirred binder, and the stirring was continued until a homogeneous mixture has been achieved, i.e. all the granular material was incorporated into the mixture with a binder.

(24) Measurements:

(25) The dynamic viscosity of all samples was measured immediately after their preparation.

(26) The samples were closed with an impermeable lid and additionally sealed with a Parafilm M foil. The thus closed samples were stored at two different temperatures (25? C. and 40? C.) without stirring, opened after defined time of storage for a measurement of the dynamic viscosity, as previously described, and closed again for further storage. For three weeks, all samples were measured twice a week to observe their thickening behaviour.

EXAMPLES

Comparative Example 1

(27) Granular material A (sieve fraction 200-1190 ?m) was tested with binder A at 25? C. according to the general experiment description.

Example 1

(28) Granular material B (sieve fraction 200-1190 ?m) was tested with binder A at 25? C. according to the general experiment description.

Comparative Example 2

(29) Granular material A (sieve fraction 200-1190 ?m) was tested with binder A at 40? C. according to the general experiment description.

Example 2

(30) Granular material B (sieve fraction 200-1190 ?m) was tested with binder A at 40? C. according to the general experiment description.

Comparative Example 3

(31) Granular material A (sieve fraction 200-1190 ?m) was tested with binder B at 25? C. according to the general experiment description.

Example 3

(32) Granular material B (sieve fraction 200-1190 ?m) was tested with binder B at 25? C. according to the general experiment description.

Comparative Example 4

(33) Granular material A (sieve fraction 200-1190 ?m) was tested with binder B at 40? C. according to the general experiment description.

Example 4

(34) Granular material B (sieve fraction 200-1190 ?m) was tested with binder B at 40? C. according to the general experiment description.

Comparative Example 5

(35) Granular material A (sieve fraction 200-1190 ?m) was crushed with a knife mill GRINDOMIX GM 300 (Retsch) for 1 minute at 2000 rpm to obtain a fine powder with an average particle size of d.sub.50=208 ?m. This powder was tested with Binder A at 25? C. according to the general experiment description

Example 5

(36) Granular material B (sieve fraction 200-1190 ?m) was crushed with a knife mill GRINDOMIX GM 300 (Retsch) for 1 minute at 2000 rpm to obtain a fine powder with an average particle size of d.sub.50=158 ?m. This powder was tested with Binder A at 25? C. according to the general experiment description

(37) The results of the viscosity measurement after various storage time are summarized in Table 1. These results show clearly, that the compositions with granular material based on a mixed oxide according to the invention (examples 1-5) provide significantly lower viscosities when compared with the similar materials based on pure silica (comparative examples 1-5).

(38) TABLE-US-00001 TABLE 1 Storage temp- Storage time [days] erature 0 4 7 12 15 19 22 example [? C.] Viscosity [Poise] Comparative 25 26.0 539 696 667 2864 3136 3872 example 1 Example 1 25 10.3 606 314 223 432 571 536 Comparative 40 26.4 2000 2928 3576 3480 4584 3584 example 2 Example 2 40 10.7 790 1552 2010 2312 2496 2568 Comparative 25 17.9 39.4 32.4 25.4 28.4 27.6 28.0 example 3 Example 3 25 4.5 4.9 3.5 4.5 3.6 3.6 3.7 Comparative 40 10.7 19.9 15.2 22.6 15.2 14.8 15.1 example 4 Example 4 40 3.2 3.6 2.9 3.1 3.3 3.2 3.4 Comparative 25 43.2 805 3456 3784 3672 example 5 Example 5 25 33.4 162 214 558 589 680 750