DEVICE OPERATING AT HIGH TEMPERATURE COMPRISING AN INSULATING PRODUCT, INSULATING PRODUCT SUITABLE FOR SUCH A DEVICE, AND PROCESSES FOR USING AND OBTAINING SUCH AN INSULATING PRODUCT

Abstract

The invention relates to a device, which operates at high temperature, in particular up to 550 C., and in particular between 50 and 350 C., such as an oven or a part of an oven, this device being equipped with at least one insulating product formed from at least one insulating material ,based>on aerogel(s), advantageously in the form of at least one layer, in particular of at least one fibrous layer. based on aerogel(s), said product comprising less than 0.55% by weight of hydrophobizing agent(s).

The invention also relates to the insulating product suitable for this device and to the use of this product for a high-temperature application.

Claims

1. A device, which operates at high temperature up to 550 C., such as an oven or a part of an oven, the device comprising: at least one insulating product formed from at least one insulating material based on aerogel(s), advantageously in the form of at least one layer, in particular of at least one fibrous layer, based on aerogel(s), said product comprising less than 0.55% by weight of hydrophobizing agent(s).

2. The device as claimed in claim 1, wherein said product comprises less than 0.5% advantageously less than 0.4%, or even less than 0.25%, in particular less than 0.1% or even less than 0.05% by weight of hydrophobizing agent(s), and preferably is devoid of hydrophobizing agent(s).

3. The device as claimed in claim 1, wherein the content of organic components in the insulating product is less than 5.5% by weight of said product, in particular less than 3%, preferably less than 1.65%, said product advantageously being solely mineral.

4. The device as claimed in claim 1, wherein the insulating material comprises from 25% to 95% by weight of aerogel(s).

5. The device as claimed in claim 1, wherein the insulating material is formed from at least one fibrous insulating layer containing aerogels, said layer comprising from 25% to 95% by weight of aerogel(s) and from to 75% by weight of fibers, said fibrous layer having in particular density of between 8 and 90 kg/m3, its thickness being in particular between 5 and 35 mm, said fibrous layer preferentially being a mat based on E- or C-glass fibers.

6. The device as claimed in claim 1, wherein the insulating product has a formaldehyde emission of less than or equal to 10 mg/kg, in particular less than or equal to 8 mg/kg, preferably less than 5 mg/kg, or even less than 3 mg/kg.

7. An insulating product, suitable for the thermal insulation of high-temperature devices, in particular of devices as claimed in claim 1, said product being formed from at least one insulating material based on aerogel(s), advantageously in the form of at least one layer, in particular of at least one fibrous layer, based on aerogel(s), said product comprising less than 0.55% by weight of hydrophobizing agent(s), advantageously less than 0.5%, in particular less than 0.4%, or even less than 0.25%, in particular less than 0.1%, even less than 0.05% by weight of hydrophobizing agent(s), and preferably being devoid of hydrophobizing agent(s).

8. The insulating product as claimed in claim 7, wherein the thermal conductivity of said product less than 50 mW/m.K at 200 C., advantageously less than 50 mW/m.K at 300 C., and particularly advantageously less than or equal to 60 mW/m.K at 400 C.

9. The use of an insulating product as claimed in claim 7, for the insulation at high temperature, in particular of a device subjected to temperatures of up to 550 C., and in particular between 50 and 350 C.

10. A process for obtaining insulating product as claimed in claim 7, said process comprising at least one step of extracting, in particular of calcinating, the hydrophobizing agent(s), of an insulating material formed from aerogel(s) or of a product incorporating said material, in particular such that the content of hydrophobizing agents in the insulating product or material formed from aerogel becomes less than 0.55% by weight, or even such that the product or material is devoid of hydrophobizing agents, said material or said product comprising particular from 25% to 95% by weight of aerogel(s).

11. The process as claimed in claim 10, wherein the extraction step is carried out by subjecting said product or material to a heat treatment temperature of at least 320 C., preferably of at least 350 C. and advantageously less than 550 C., in particular less than 450 C., for at least 10 hours, and preferably for at least 12 h.

12. The device according to claim 1, wherein the device operates at a temperature between 50 C. and 350 C.

Description

[0037] The present invention and the advantages thereof will be understood more clearly on reading the examples which follow, which are given only by way of illustration and which cannot in any way be considered to be limiting.

[0038] In the example according to the invention, a product was formed from an insulating pad in the form of a mat impregnated with silica aerogels analogous to the products of Pyrogel XT-E type sold by the company Aspen Aerogel Inc., this pad having a density of 0.20 g/cm.sup.3. The product formed according to the invention is solely formed from impregnated mat and has a thickness of 20 mm. It is then heat treated at 350 C. for 12 h. Monitoring of the volatile species at the end of the treatment showed that the final product has a final composition containing less than 0.2% of hydrophobizing agent.

[0039] The thermal conductivity measurement was carried out according to the principle of the guarded hot plate according to standard ISO 8302 at a temperature of 200 C. and at atmospheric pressure.

[0040] The amount of formol emitted was measured on a Hermann Moritz tube oven according to standard NF EN 120.

The results obtained were the following: [0041] thermal conductivity A at 200 C.: 30 mW/m.K [0042] thermal conductivity A at 300 C.: 39 mW/m.K [0043] formol emission per kg of product: 10 mg/kg

[0044] The thermal conductivity of this product was compared to that obtained with a usual product for insulating ovens, formed from a mineral wool (reference example), this product being for example the product sold under the reference TNF80120 by the company Saint-Gobain Isover France, the thermal conductivity obtained for this usual product at 200 C. being about from 55 to 70 mW/m.K and that obtained for this usual product at 300 C. being about 75 mW/m.K.

[0045] An oven, of reference De Dietrich CZ5702359 sold by the company Brandt, was also equipped with an insulating interior belt using, firstly, to form this belt, the standard product according to the reference example, and then replacing it with the product according to the invention according to the example, and the consumption of the ovens was measured according to standard EN 60350. The measurements of the heating at the core of the element to be heated were carried out on a brick sold under the reference Hipor by the company Skamol, the brick having been predried, then immersed in a water bath placed in a refrigerator for at least 8 hours until a brick temperature (measured in the brick by two thermocouples) of 5 C. was obtained, the brick saturated with water and drained for approximately 1 min then being placed at the center of the oven.

[0046] The energy consumption of the oven was measured for two cooking positions, the ambient temperature of the oven environment being approximately 23 C., a conventional position according to standard EN 60350 with heating of about 140 (corresponds to a temperature at the center of the oven of 163 C. (140 C. heating relative to 23 C. of ambient temperature)), 180 and 220, and a forced ventilation position according to standard EN 60350 with heating of 135 C. 155 and 175, the test ending when the last of the two thermocouples present in the brick indicates a heating of 55 (absolute temperature of 60 C., the initial temperature of the brick being 5 C.). The arithmetic mean of the energy consumptions for each heating temperature was then calculated, in accordance with standard EN 60350.

[0047] In the case of the oven having an insulating belt formed from the standard product according to the reference example, the oven consumption was 760 Wh, and in the case of the oven having an insulating belt formed from the product according to the invention according to example 1, the oven consumption was 630 Wh.

[0048] The results obtained show that the use of the products according to the invention for insulating domestic ovens or for other uses at high temperature makes it possible to obtain, for the ovens that these products equip, improved energy performance levels, the absence of hydrophobizing agent or the calcination of the hydrophobizing agent by heat treatment not resulting, in addition, in a degradation of the thermal performance levels of the insulator, said insulator having insulating performance levels that are particularly satisfactory even at high temperature, the emission of formol or VOC being in addition particularly limited despite the temperatures during use (10 mg/kg of formol being an acceptable limit for being able to be used in cooking ovens).

[0049] By comparison regarding the latter point, a product was formed from a mat impregnated with aerogels of Pyrogel XT-E type analogous to that of the example according, to the invention, but which had not undergone heat treatment. The analysis of its organic matter content was typical of a composition containing more than 1% by weight of hydrophobizing agent. For this product, a thermal conductivity A 28 mW/m.K at 200 C. and a formol emission per kg of product of greater than 500 mg/kg, which is much too high for use in a domestic cooking oven, were obtained. In the same way, with a less drastic heat treatment of the product (at 200 C. for 12 h), the analysis of the product was typical of a composition still containing more than 1% by weight of hydrophobizing agent and, for this product, a thermal conductivity A 30 mW/m.K at 200 C. and a formol emission per kg of product of 150 mg/kg, also too high for use in a domestic cooking oven, were obtained. Conversely, a product resulting from a heat treatment at 500 C. for 12 h revealed an analysis typical of a composition containing less than 0.1% of hydrophobizing agent (example in accordance with the invention) and, for this product, a thermal conductivity =34 mW/m.K at 200 C. and a particularly satisfactory, formol emission per kg of product of 2 mg/kg were obtained.

[0050] The insulating product used according to the invention is in particular suitable for insulating walls or components of domestic electrical ovens, but can also be used to advantage for the thermal insulation of any other surface, in particular for high-temperature applications (or for insulating products subjected to high temperature).