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 the production of a hydrophobic thermal-insulation moulding, comprising: contacting a hydrophilic thermal-insulation moulding comprising a thermal-insulation mixture comprising a fine-particle silica, IR opacifier and fibre material with a hydrophobizing agent in vapour form thereby forming a thermal-insulation moulding coated with said hydrophobizing agent, then subjected subjecting said thermal-insulation moulding coated with said hydrophobizing agent to a press process, and reacting said thermal-insulation moulding coated with said hydrophobizing agent during the press process and/or after the press process with the hydrophobizing agent thereby forming of the hydrophobic thermal-insulation moulding, wherein 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.

2. The process according to claim 1, wherein the contact temperature T.sub.contact is from −30° C. to 150° C. during said contacting.

3. The process according to claim 1, wherein the reaction temperature T.sub.reaction is from 50° C. to 500° C. during said reacting.

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

5. The process according to claim 1, wherein the contacting and the reacting of the hydrophobizing agent with the hydrophilic thermal-insulation moulding takes place in a chamber, and wherein the hydrophobizing agent is introduced into the chamber until the pressure difference Δp is ≧20 mbar, wherein Δp=p.sub.2−p.sub.1, and p.sub.1=pressure in the chamber before introduction of the hydrophobizing agent, 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 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 fibre 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.n—Si—X.sub.4-n, R.sub.3Si—Y—SiR.sub.3, wherein n=from 1 to 3; R=—CH.sub.3, —C.sub.2H.sub.5; X=—Cl, —Br; —OCH.sub.3, —OC.sub.3, —OC.sub.3H.sub.8, and Y=NH, O.

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

12. The process according to claim 1, which is carried out continuously and the contacting, the press process and the hydrophobizing reaction take place between two gas-permeable, moving belts of a press.

Description

EXAMPLES

[0045] The thermal-insulation mixture used is composed of 77.7% by weight of AEROSIL®300, Evonik Industries, 19.4% by weight of 900F silicon carbide from Keyvest and 2.9% by weight of BELCOTEX 225 SC6 glass fibres from Be!chem. The thermal-insulation mixture is subjected to a press process to give sheets measuring 140×90×20 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

[0046] 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

[0047] 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

[0048] 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.

[0049] Water-methanol wettability is about 30% by volume of methanol.