CORE-HYDROPHOBIC THERMAL INSULATION SHEET HAVING HARDENED SURFACE

Abstract

Silicon dioxide-containing thermal-insulation sheet hydrophobized throughout with hardened surface, wherein the compressive stress at fracture measured on the sheet surface is higher than the compressive stress at fracture measured on the sectional surface in the middle cross section of the sheet parallel to the sheet surface, at, in each case, the same penetration depths of the measurement probe in the test specimen.

Claims

1-17. (canceled)

18. A silicon dioxide-containing thermal-insulation sheet hydrophobized throughout, wherein the compressive stress at fracture measured on the sheet surface is higher than the compressive stress at fracture measured on the sectional surface in the middle cross section of the sheet parallel to the sheet surface, at, in each case, the same penetration depths of the measurement probe in the test specimen.

19. The silicon dioxide-containing thermal-insulation sheet of claim 18, wherein the sheet comprises at least 50% by weight silicon dioxide and at least 5% by weight IR opacifier.

20. The silicon dioxide-containing thermal-insulation sheet of claim 18, wherein the IR opacifier is 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.

21. The silicon dioxide-containing thermal-insulation sheet of claim 18, wherein the sheet comprises from 0.1 to 10% by weight of carbon.

22. The silicon dioxide-containing thermal-insulation sheet of claim 18, wherein the compressive stress at fracture measured on the sheet surface is higher by at least 20% than the compressive stress at fracture measured on the sectional surface in the middle cross section of the sheet parallel to the sheet surface, at, in each case, the same penetration depths of the measurement probe in the test specimen.

23. The silicon dioxide-containing thermal-insulation sheet of claim 18, wherein the sheet has a thickness from 5 to 500 mm.

24. The silicon dioxide-containing thermal-insulation sheet of claim 18, wherein the sheet is surrounded by a coating which has a higher material density than the core of the sheet.

25. The silicon dioxide-containing thermal-insulation sheet of claim 18, wherein the roughness of the sheet surface measured in accordance with DIN EN ISO 4287 has a groove depth R.sub.v from 100 to 500 m and an average interval of the grooves R.sub.sm from 100 to 5000 m.

26. The silicon dioxide-containing thermal-insulation sheet of claim 18, wherein both the sheet surface and the sectional surface in the middle cross section of the sheet parallel to the sheet surface have a methanol wettability of at least 5% by weight of methanol.

27. The silicon dioxide-containing thermal-insulation sheet of claim 19, wherein the IR opacifier is 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 silicon dioxide-containing thermal-insulation sheet of claim 27, wherein the sheet comprises from 0.1 to 10% by weight of carbon and the sheet has a thickness from 5 to 500 mm.

29. The silicon dioxide-containing thermal-insulation sheet of claim 28, wherein the roughness of the sheet surface measured in accordance with DIN EN ISO 4287 has a groove depth R.sub.v from 100 to 500 m and an average interval of the grooves R.sub.sm from 100 to 5000 m and wherein the sheet is surrounded by a coating which has a higher material density than the core of the sheet.

30. A process for producing a silicon dioxide-containing thermal-insulation sheet hydrophobized throughout, comprising: a) treating a hydrophilic silicon dioxide-containing sheet with a silicon-containing surface-modification agent; b) drying and/or thermally treating the sheet treated with surface-modification agent to form a coated sheet; and c) hydrophobizing the coated sheet with a hydrophobization agent.

31. The process of claim 30, wherein the silicon-containing surface-modification agent is selected from the group consisting of: silica sol; siloxane oligomers; silicates; and water glass.

32. The process of claim 30, wherein a solution containing at least one surface-modification agent and at least one solvent selected from the group consisting of: water; alcohols, ethers and esters is used in step a).

33. The process of claim 30, wherein sufficient surface-modification agent is used in step a) such that the layer generated in step b) has an average thickness from 100 to 2000 m.

34. The process of claim 30, wherein at least one organosilane selected from the group consisting of: R.sub.nSiX.sub.4-n; R.sub.3SiYSiR.sub.3; R.sub.nSi.sub.nO.sub.n; (CH.sub.3).sub.3Si(OSi(CH.sub.3).sub.2).sub.nOH; HOSi(CH.sub.3).sub.2(OSi(CH.sub.3).sub.2).sub.nOH; where n=1-8; RH, CH.sub.3, C.sub.2H.sub.5; XCl, Br; OCH.sub.3, OC.sub.2H.sub.5, OC.sub.3H, YNH, O, is used as hydrophobization agent in step c).

35. The process of claim 30, wherein steps a) and b) are carried out two or more times in succession in an alternating manner before step c) is carried out.

36. The process of claim 30, wherein step a) and/or b) is additionally carried out at least once after step c).

37. The thermal-insulation sheet of claim 18, wherein said sheet is treated with a water-based paint, an aqueous coating agent, adhesive and/or an aqueous cement-, render- or mortar-containing formulation.

Description

EXAMPLES

Analysis of the Outer Surface and Core Properties

[0048] The outer sheet surface (FIG. 2, 1) was directly analysed without further preparation, as described below. By contrast, the chemical and mechanical properties of the sheet core were determined on a middle cross-sectional surface of the sheet (FIG. 2, 2). For this purpose, the sheets to be analysed were cut in the middle parallel to the outer surface (FIG. 2), and so the resulting sheet has a halved thickness and a new outer surface (FIG. 2, 2) which imparts properties of the core of the original sheet.

Determination of the Compressive Stress at Fracture and (A/I), %

[0049] The horizontally placed sheet to be analysed with square area having an edge length of at least 100 mm and a thickness of at least 10 mm was, by means of a press centred above the sample and having a punch (FIG. 3: side view; FIG. 4: view from the bottom), pressed from top to bottom. The punch has 9 identical round measurement probes having, in each case, a 3 mm diameter. This punch is used to press into the sample surface at a feed rate of 4 mm/min; at the same time, the resulting compressive force (in N) and the penetration depth (in mm) of the test probes in the surface to be analysed are determined. The measured compressive force at a determined penetration depth of the measurement probe in the surface to be analysed can be converted to compressive stress via the area of the measurement probe:

.sub.n=F.sub.n/A,

where is a compressive stress in Pa at determined penetration depth n (in mm), F.sub.n is a measured compressive force in N; A is a cross-sectional area of the measurement probe in m.sup.2 (in the present case A=9*7.07 mm.sup.2=63.6*10.sup.6 m.sup.2). On the basis of this measurement, it is possible to create a compressive stress-penetration depth curve which is characteristic of the surface in question. If the thus obtained compressive stress-penetration depth curve (standard force [N]deformation [%]) for the outer sheet surface of the sheet according to the invention is viewed, it is possible to easily identify a kink (abrupt change in the slope) (FIG. 5, a), which corresponds to the fracture of the hard surface under the measurement probe. By contrast, if the core of the sheet is analysed in the same way at its middle sectional surface, no kink is viewed in the compressive stress-penetration depth curve profile (FIG. 5, b). If these two curves are then compared with each other, it is possible to relate the compressive stress at fracture on the outer surface of the sheet to the corresponding compressive stress at fracture measured on the inner surface at the same penetration depth. This gives rise to a ratio which imparts a relative hardness of the outer surface to hardness of the core. This ratio multiplied by 100 gives a corresponding ratio of the outer surface hardness to inner surface hardness as a percentage. If 100 is subtracted from this ratio as percentages, what is obtained is a difference between the outer surface hardness and inner surface hardness as a percentage, which difference is listed in Table 1:

(A/I),%=(100*A/I)100

Measurement of the Roughness, R.sub.v, R.sub.sm

[0050] The roughness of the surface was determined in accordance with DIN EN ISO 4287; this involved evaluating the indices groove depth R.sub.v and groove interval R.sub.sm. The instrument used and its setting for this purpose is described below:

TABLE-US-00001 Parameter Value Measurement instrument Alicona InfiniteFocus Measurement principle Focus variation Objective (magnification) 5x Vertical resolution 2 m Lateral resolution 5 m Coaxial illumination (light source: 1.0) 1.25 ms Contrast 2.3 Light amplification 1.0 Ring light on (100%) Data post-processing Elimination of outliers (0.1) Measurement distance ln 40 mm Cut-off wavelength c 8 mm

Determination of the Surface Hydrophobicity, OB.SUB.MEOH., %

[0051] The horizontally placed surface to be analysed was treated with a drop of the water or methanol/water mixture at at least 5 different points. A drop was positioned by means of a suitable pipette. The drops deposited on the surface were visually assessed after a standing time of 1 hour. In the course of this, the drops as a whole could remain on the surface with a contact angle of about 90 to 180 or wet it, i.e. spread on the surface and form a contact angle of less than 90 with the surface, or be entirely absorbed into the material of the sheet. The corresponding behaviour of the majority of drops on the surface was evaluated as the first qualitative result. A test series with the drops with different methanol/water mixtures yielded quantitative information about the extent of the surface hydrophobicity. The maximum content of methanol in % by weight in a methanol/water test mixture at which there is still no wetting of the surface is called methanol wettability of the surface OB.sub.MEOH, %.

Thermal Conductivity

[0052] The thermal conductivity of the sheets was determined at room temperature using a guarded hot plate in accordance with EN 12667:2001.

Coating of the Produced Sheets

[0053] The sheets were applied with a water-based silicate paint (Bauhaus, Swingcolor silicate paint, silicate indoor paint, matt/white) using a brush by painting onto the sheet surface; the paint coat was then dried at room temperature. The adhesion of the paint on the surface was qualitatively assessed both during the application and also after the drying. All the sheets exhibiting a good adhesion of the silicate paint (Examples 1-6) were also able to be coated with cement mortar with great success. In this connection, the latter was directly painted onto the hardened sheet after mixing with water to yield a pasty form using a toothed spatula.

Comparative Example 1

[0054] A desiccator heated to 100 C. is initially charged with a microporous thermal-insulation material panel having dimensions of 25025020 mm, an apparent density of 170 kg/m.sup.3, and a composition of 80.0% by weight of fumed silica having a BET surface area of 200 m.sup.2/g, 16.0% by weight of silicon carbide and 4.0% by weight of glass fibres (diameter=9 m; length=6 mm). The pressure in the desiccator is reduced to 15 mbar with the aid of a water jet pump. Sufficient vaporous hexamethyldisilazane is then slowly introduced into the desiccator to raise the pressure to 300 mbar. After a standing time of 1 hour under a silane atmosphere, the hydrophobized sheet is cooled and vented.

[0055] The sheet thus produced was hydrophobic throughout, had the same hardness for the outer surface and the core and a relatively low roughness for the surface (Table 1). Said sheet exhibited a very poor adhesion of the paint coat both during the application of the silicate paint and after the drying thereof.

Comparative Example 2

[0056] A hydrophobized sheet produced as described in Comparative Example 1 was sprayed with water (300 g/m.sup.2) at 25 C. using an airless spray gun, and then dried at about 25 C. in a fume cupboard.

[0057] The sheet thus produced was hydrophobic throughout, had approximately the same hardness for the outer surface and the core and a roughness for the surface that was somewhat higher than in Comparative Example 1 (Table 1). Said sheet exhibited a very poor adhesion of the paint coat both during the application of the silicate paint and after the drying thereof.

Comparative Example 3

[0058] A microporous thermal-insulation material panel having dimensions of 25025020 mm, an apparent density of 170 kg/m.sup.3, and a composition of 80.0% by weight of fumed silica having a BET surface area of 200 m.sup.2/g, 16.0% by weight of silicon carbide and 4.0% by weight of glass fibres (diameter=9 m; length=6 mm) was coated five times in succession with 100 g/m.sup.2 silica sol IDISIL 1530 (30% by weight of SiO.sub.2 in water, particle size 15 nm, Evonik Resource Efficiency GmbH) and dried in each case. Thereafter, the sheet was hydrophobized with gaseous hexamethyldisilazane in the desiccator as described in Comparative Example 1.

[0059] The sheet thus produced was not hydrophobic throughout. The outer surface was hydrophobic, whereas the core of the sheet was not. The outer surface was harder by 80% than the core of the sheet (Table 1). The roughness of the surface was not determined, but the sheet appeared visually very smooth. Said sheet exhibited a poor adhesion of the paint coat both during the application of the silicate paint and after the drying thereof.

Example 1

[0060] A microporous thermal-insulation material panel having dimensions of 25025050 mm, an apparent density of 170 kg/m.sup.3, and a composition of 80.0% by weight of fumed silica having a BET surface area of 200 m.sup.2/g, 16.0% by weight of silicon carbide and 4.0% by weight of glass fibres (diameter=9 m; length=6 mm) was sprayed with 300 g/m.sup.2 Hydrosil 2627 (water-based amino-functional oligomeric siloxane, Evonik Resource Efficiency GmbH) at 25 C. using an airless spray gun, and then dried at about 25 C. in a fume cupboard. Thereafter, the sheet was hydrophobized with gaseous hexamethyldisilazane in the desiccator as described in Comparative Example 1.

[0061] The sheet thus produced was hydrophobic throughout. The outer surface was harder by 75% than the core of the sheet (Table 1). Said sheet exhibited a good adhesion of the paint coat both during the application of the silicate paint and after the drying thereof.

Example 2

[0062] The sheet was produced as in Example 1, the only difference being that Hydrosil 1153 (water-based amino-functional oligomeric siloxane, Evonik Resource Efficiency GmbH) was used for the coating of the hydrophilic sheet.

[0063] The sheet thus produced was hydrophobic throughout. The outer surface was harder by 40% than the core of the sheet (Table 1). Said sheet exhibited a good adhesion of the paint coat both during the application of the silicate paint and after the drying thereof.

Example 3

[0064] The sheet was produced as in Example 1, the only difference being that silica sol IDISIL 1530 (30% by weight of SiO.sub.2 in water, particle size 15 nm, Evonik Resource Efficiency GmbH) was used for the coating of the hydrophilic sheet.

[0065] The sheet thus produced was hydrophobic throughout. The outer surface was harder by 30% than the core of the sheet (Table 1). Said sheet exhibited a good adhesion of the paint coat both during the application of the silicate paint and after the drying thereof.

Example 4

[0066] The sheet was produced as in Example 1, the only difference being that Protectosil WS 808 (water-based propyl siliconate/silicate, Evonik Resource Efficiency GmbH) was used for the coating of the hydrophilic sheet, and afterwards a glass web having a density per unit area of 30 g/m2 and a web thickness of 0.3 mm was applied to the coated surface and the coating was then dried.

[0067] The sheet thus produced was hydrophobic throughout. The outer surface was harder by 120% than the core of the sheet (Table 1). Said sheet exhibited a good adhesion of the paint coat both during the application of the silicate paint and after the drying thereof.

Example 6

[0068] A hexamethylsilazane-hydrophobized sheet produced as in Comparative Example 1 was sprayed with 300 g/m.sup.2 Dynasilan AR (ethanol-based silica esterhybrid binder with additionally incorporated colloidal SiO.sub.2 particles, Evonik Resource Efficiency GmbH) at 25 C. using an airless spray gun, and then dried at about 25 C. in a fume cupboard.

[0069] The sheet thus produced was hydrophobic throughout. The outer surface was harder by 50% than the core of the sheet (Table 1). Said sheet exhibited a good adhesion of the paint coat during the application of the silicate paint.

[0070] All the sheets according to the invention (Examples 1-6) had a thermal conductivity of less than 20 mW/(m*K).

TABLE-US-00002 TABLE 1 Groove depth R.sub.v Groove interval in accordance with in accordance with Adhesion of Inner surface DIN EN ISO 4287 DIN EN ISO 4287 R.sub.sm the aqueous Outer surface hydrophobicity/ Outer/inner (range/number (range/number silicate paint hydrophobicity/ wetting hardness, of measurements), of measurements), during OB.sub.MEOH, % with water (A/I), % m m application Comparative yes/60 yes 0 70-200/14 400-2000/14 poor Example 1 Comparative yes/60 yes 0 350-520/2 500-710/2 poor Example 2 Comparative yes/n.d. no 80 n.d. n.d. poor Example 3 Example 1 yes/45 yes 75 290-320/2 415-460/2 good Example 2 yes/30 yes 40 260-370/2 550-775/2 good Example 3 yes/60-65 yes 30 114-280/3 1800-2400/3 good Example 4 yes/60 yes 55 160-200/2 750-1050/2 good Example 5 yes/60-65 yes 120 n.d. n.d. good Example 6 yes/55 yes 50 240-310/2 370-470/2 good n.d. = not determinable