Method for producing a hydrophobic heat-insulating molded body

Abstract

Process for the production of a hydrophobic thermal-insulation moulding, where a hydrophilic thermal-insulation moulding is brought into contact with a hydrophobizing agent in vapour form with formation of a thermal-insulation moulding coated with hydrophobizing agent, and this is then subjected to a press process and during the press process and/or after the press process is reacted with the hydrophobizing agent with formation of the hydrophobic thermal-insulation moulding, where a) the density of the hydrophobic thermal-insulation moulding after the press process and after the reaction with the hydrophobizing agent is from 100 to 250 kg/m.sup.3, and b) the density of the hydrophilic thermal-insulation moulding on contact with the hydrophobizing agent is from 50% to less than 100% of the density of the hydrophobic thermal-insulation moulding.

Claims

1. A process for producing a hydrophobic thermal-insulation molding, comprising: contacting a hydrophilic thermal-insulation molding with a hydrophobizing agent in the form of vapor, thereby forming a thermal-insulation molding coated with the hydrophobizing agent; pressing the thermal-insulation molding coated with the hydrophobizing agent; and during and/or after the pressing, heating the thermal-insulation molding coated with the hydrophobizing agent, thereby forming the hydrophobic thermal-insulation moulding molding, wherein the hydrophilic thermal-insulation molding comprises a thermal-insulation mixture comprising a fine-particle silica, IR opacifier and fiber material, the contacting, the pressing, and the heating take place between two gas-permeable moving belts of a press, a density of the hydrophobic thermal-insulation molding the heating is from 100 to 250 kg/m.sup.3, and a density of the hydrophilic thermal-insulation molding contacted with the hydrophobizing agent is from 50% to less than 100% of the density of the hydrophobic thermal-insulation molding.

2. The process according to claim 1, wherein in the contacting, a contact temperature T.sub.contact is from 30 C. to 150 C.

3. The process according to claim 1, wherein in the heating, a reaction temperature T.sub.reaction is from 50 C. to 500 C.

4. The process according to claim 1, wherein a contact time during the contacting and a heating time during the heating are in each case from 1 minute to 1 hour.

5. The process according to claim 1, wherein the contacting and the heating take place in a chamber, and wherein the hydrophobizing agent is introduced into the chamber until a pressure difference p is 20 mbar, wherein p=p.sub.2p.sub.1, and p.sub.1=pressure in the chamber before the introduction of the hydrophobizing agent, and p.sub.2=pressure in the chamber at which the introduction of the hydrophobizing agent is stopped.

6. The process according to claim 1, wherein the fine-particle silica is a fumed silica.

7. The process according to claim 1, wherein a proportion of the fine-particle silica, based on the thermal-insulation mixture, is from 70 to 95% by weight.

8. The process according to claim 1, wherein a proportion of the IR opacifier, based on the thermal-insulation mixture, is from 2 to 20% by weight.

9. The process according to claim 1, wherein a proportion of the fiber material, based on the thermal-insulation mixture, is from 3 to 10% by weight.

10. The process according to claim 1, wherein the hydrophobizing agent is at least one organosilicon compound selected from the group consisting of R.sub.nSiX.sub.4-n and R.sub.3SiYSiR.sub.3, wherein n=from 1 to 3; RCH.sub.3 or C.sub.2H.sub.5; XCl, Br, OCH.sub.3, OC.sub.2H.sub.5, or OC.sub.3H.sub.8; and YNH or O.

11. The process according to claim 1, wherein a proportion of the hydrophobizing agent, based on the hydrophilic thermal-insulation molding, is from 0.5 to 10% by weight.

12. The process according to claim 1, which is carried out continuously.

13. The process according to claim 2, wherein in the heating, a reaction temperature T.sub.reaction is from 50 C. to 500 C.

14. The process according to claim 2, wherein a contact time during the contacting and a heating time during the heating are in each case from 1 minute to 1 hour.

15. The process according to claim 3, wherein a contact time during the contacting and a heating time during the heating are in each case from 1 minute to 1 hour.

16. The process according to claim 2, wherein the contacting and the heating takes place in a chamber, and wherein the hydrophobizing agent is introduced into the chamber until a pressure difference p is 20 mbar, wherein p=p.sub.2p.sub.1, and p.sub.1=pressure in the chamber before the introduction of the hydrophobizing agent, p.sub.2=pressure in the chamber at which the introduction of the hydrophobizing agent is stopped.

17. The process according to claim 3, wherein the contacting and the heating takes place in a chamber, and wherein the hydrophobizing agent is introduced into the chamber until a pressure difference p is 20 mbar, wherein p=p.sub.2p.sub.1, and p.sub.1=pressure in the chamber before the introduction of the hydrophobizing agent, p.sub.2=pressure in the chamber at which the introduction of the hydrophobizing agent is stopped.

18. The process according to claim 13, wherein the contacting and the heating takes place in a chamber, and wherein the hydrophobizing agent is introduced into the chamber until a pressure difference p is 20 mbar, wherein p=p.sub.2p.sub.1, and p.sub.1=pressure in the chamber before the introduction of the hydrophobizing agent, p.sub.2=pressure in the chamber at which the introduction of the hydrophobizing agent is stopped.

19. The process according to claim 2, wherein the fine-particle silica is a fumed silica.

20. The process according to claim 3, wherein the fine-particle silica is a fumed silica.

Description

EXAMPLES

(1) The thermal-insulation mixture used is composed of 77.7% by weight of AEROSIL300, Evonik Industries, 19.4% by weight of 900 F silicon carbide from Keyvest and 2.9% by weight of BELCOTEX 225 SC6 glass fibres from Belchem. The thermal-insulation mixture is subjected to a press process to give sheets measuring 1409020 mm in a press composed of female press mould, sinter plate and coat. The desired final density of the thermal-insulation sheets is 165 kg/m.sup.3.

Example 1 (Comparative Example)

(2) The final density of the sheet produced from the thermal-insulation mixture by means of the press is 165 kg/m.sup.3. Press and sheet are then heated to 165 C. During this procedure, 20 g of hexamethyldisilazane (HMDS) are vaporized. The female press mould is evacuated to a subatmospheric pressure of 6 mbar, and the vaporized HMDS is sucked through the sheet. After 10 min a sheet can be removed after depressurization. Determination of water-methanol wettability of various samples of this sheet reveals adequately good hydrophobization.

Example 2

(3) The density of the sheet produced from the thermal-insulation mixture by means of the press is 130 kg/m.sup.3, corresponding to 80% of the final density. The temperature of press and sheet is about 20 C. 20 g of HMDS are vaporized. The female press mould is evacuated to a subatmospheric pressure of 6 mbar, and the vaporized HMDS is sucked through the sheet. After 10 min the material is compacted to the final density of 165 kg/m.sup.3, and then the sheet is heated to 165 C. After 10 min a hydrophobic sheet can be removed. Determination of water-methanol wettability of various samples of this sheet reveals uniform hydrophobization of the entire product. Water-methanol wettability is about 30% by volume of methanol.

Example 3

(4) The density of the sheet produced from the thermal-insulation mixture by means of the press is 100 kg/m.sup.3, corresponding to 60% of the final density. The temperature of press and sheet is about 80 C. 20 g of HMDS are vaporized. The female press mould is evacuated to a subatmospheric pressure of 6 mbar, and the vaporized HMDS is sucked through the sheet. After 10 min the material is compacted to the final density of 165 kg/m.sup.3, and then the sheet is heated to 165 C. Determination of water-methanol wettability of various samples of this sheet reveals uniform hydrophobization of the entire product.

(5) Water-methanol wettability is about 30% by volume of methanol.