WO2003002828A1

WO2003002828A1 - Vacuum insulation panel

Info

Publication number: WO2003002828A1
Application number: PCT/CH2002/000336
Authority: WO
Inventors: Gerhard Staufert
Original assignee: Sager Ag
Priority date: 2001-06-29
Filing date: 2002-06-21
Publication date: 2003-01-09

Abstract

The inventive vacuum insulation panel (VIP) has a structure corresponding to the double chamber principle known in vacuum engineering, wherein an inner low-pressure vacuum chamber is surrounded by an outer vacuum chamber in which a rough vacuum prevails. The double-chamber VIP has a core (1) which is, for example, 1-5 cms thick and evacuated to10-3 mbars for example, said core being made of a pressure-resistant large-pored material, surrounded by an inner gastight film (2). Said inner structure is surrounded by a second thin layer of core material (3) evacuated to approximately 1 mbar, also surrounded by an outer gastight film (4). If the pressure inside the outer chamber is allowed to increase to approximately 100 mbars in the course of 50 years, a low-cost plastic-based film can be used, having only a very thin metal layer (i.e. 0.1 µm), whereby an insignificantly small amount of heat conduction can be ensured along the outer covering. .

Description

Thermal insulation panel

The invention relates to a vacuum insulation panel (VIP) with a large-pore core evacuated to pressures of less than 1 mbar and a long-term sealed vacuum envelope.

Vacuum panels with a film-like shell require a pressure-resistant core. The core material must have a low thermal conductivity and be easy to evacuate, i.e. it must be open-pored and have the smallest possible proportion of closed or almost closed pores, have low outgassing behavior, have the smallest possible average diameter of the pores so that thermal conductivities in the range around 5 mW / m ° K are achieved with the lowest possible negative pressure.

The desirability of the lowest possible negative pressures - i.e. preferably not falling below the so-called rough vacuum range (1 mbar - 1000 mbar) - is not important because of the somewhat lower expenditure for generating these negative pressures, but it simplifies the maintenance of the negative pressure above the very high one required on the building "Lifetime" of the vacuum of approx. 50 years. If the vacuum in the rough vacuum range is required, multi-layer plastic foils can be used, which contain very thin, vapor-deposited layers of aluminum with a total thickness of approx. 0.3 μm. This low metal content in the case ensures a small amount of heat conduction along the case materials, what before especially important for panels with small lateral dimensions (> approx. 50 cm).

The only currently known core materials that meet all of the above requirements are the so-called nanoporous materials, which are offered, for example, by the companies Wacker, Degussa and Cabot. These companies also offer covered and evacuated panels on the market that have the desired low thermal conductivity.

However, they have the disadvantage of a high price, so that their use as a general insulation material in the construction of the economy is questioned.

The "next worse" known core material is a pressure-resistant, non-outgassing glass wool, which fulfills the first three requirements as well as the nanoporous materials and costs considerably less than these. Because of the significantly larger internal spaces (hereinafter referred to as pores) However, glass wool - and other insulation materials with large open pores such as XPS - must be evacuated to the so-called fine vacuum range (10 ^"3 mbar - 1 mbar) so that the desired thermal conductivity values in the range of 5 mW / m ° K can be achieved. Long-term compliance with these negative pressures would not be a problem if the casing was to have a significantly higher metal content (metal thickness> a few μm). Without special design measures, however, this is forbidden because of the high heat conduction in the shell, which can drastically increase the effective heat conduction of the entire panel. For example, it is known from the publication of the Swiss Federal Office of Energy "High-performance thermal insulation" from December 2000 that VIP with a nanoporous core, which is covered with a plastic coating containing an approx. 7 μm thick aluminum foil are surrounded, have an effective total thermal conductivity of greater than 20 mW / m ° K below an edge length of approx. 50 cm.

The present patent is therefore based on the object of providing a vacuum insulation panel (VIP) with a large-pore core, the sheathing of which is constructed in such a way that, firstly, a sufficient high “service life” of the necessary fine vacuum of an average of 50 years and above is ensured and that secondly, such low heat conduction along the shell is realized that the effective total thermal conductivity of a panel with edge length down to 20 cm remains below 10 mW / m ° K.

According to the invention, this object is achieved by the features specified in the patent claims. Advantageous embodiments of the invention result from the features of the dependent claims.

The VIP according to the invention has a structure which corresponds to the double chamber principle known in vacuum technology, in which an inner low-pressure vacuum chamber is surrounded by an outer vacuum chamber in which a rough vacuum prevails. The VIP according to the double chamber principle has a (for example 1 to 5 cm thick) evacuated core, for example 10 ^"3 mbar, made of pressure-resistant, large-pored material, which is surrounded by an inner gas-tight film. This inner structure is surrounded by a second, approx. 1 mbar evacuated, thin layer of core material, which in turn is covered with an outer gas-tight film, if the pressure inside the outer chamber increases to approx. 100 mbar in the course of approx. 50 years, an inexpensive one can be used for the outer film Plastic-based film with only a very thin layer (in the order of 0.1 μm) of metal can be used, which ensures negligible heat conduction along the outer shell. Since the pressure difference between the outer and the inner vacuum chamber is only about 10 mbar on average with the above assumptions and since the amount of gas diffusing through a given shell is inversely proportional to the pressure difference, the inner shell may diffuse by a factor of 100 with regard to gas diffusion To be "worse" than in the case of a single-chamber vacuum. This makes it possible to use very inexpensive plastic films for the inner shell, which either have little or no metal at all.

Since the outer vacuum chamber, depending on the structure, can provide a thin but very effective heat insulation and thus a high heat conduction along the inner shell can be neglected overall, it is also conceivable to use an inner shell that is constructed, for example, as a commercially available plastic composite film which includes, for example, a 25 μm thick aluminum layer. With such a construction, the maintenance of the pressure prevailing in the inner chamber of less than 10 ^"1 mbar can be guaranteed over periods of the order of 100 years.

Since different enveloping films are particularly effective against different gases, a further improvement can be realized with the double chamber principle. It is in fact possible to use a material combination for the outer film, for example, which is a just enough diffusion barrier for the gases O ₂ , N ₂ , CO ₂ etc., but is absolutely impermeable to water vapor. The inner shell can then be optimized with regard to O ₂ , N ₂ , CO ₂ etc. and no longer has to take water vapor into account.

An exemplary embodiment according to the invention and further advantages of the invention are explained below with reference to the drawings. Show it : Fig.l a section through a VIP according to the double chamber principle

Fig.2 a possible price / performance scenario in a few years

A first, as inexpensive as possible construction of the VIP according to the double chamber principle with a sufficiently long service life includes, as shown in Fig. 1, an inner core made of pressure-resistant glass wool (1) which does not outgas under vacuum at temperatures up to 100 ° C, which is the actual insulation volume of the VIP. Of course, the inner core can also consist of another suitable material, such as extruded polystyrene (XPS), in which case, however, an appropriate getter must be available due to outgassing. In order to achieve the desired low thermal conductivity of the evacuated core in the range of 5 ± 3 mW / m ° K, this core is evacuated to approximately 10 ^" mbar and welded into an inner gas-tight composite film (2). The thickness of the inner core (1) is aligned depends on the application according to the heat transfer to be observed, which is usually given in W / m ² K. With a thermal conductivity of approx. 4 mW / m ° K and a heat transfer of approx. 0.2 W / m ² K, there is, for example, a thickness of inner core (1) of about 2 to 3 cm.

The inner film (2) is, for example, a 100 μm thick PE film onto which, for example, an approximately 0.1 μm thick aluminum layer is evaporated or sputtered. The PE film acts as a weldable carrier layer, while the aluminum layer forms an effective diffusion barrier for O ₂ , N ₂ , CO ₂ etc. at the average pressure of approx. 10 mbar acting within the outer core material (3).

The inner shell (2) is surrounded by a glass wool fleece, for example 5 mm thick, which forms the outer core (3). The outer core (3) is reduced to approx. 1 mbar evacuated and, of course together with the inner chamber (1) + (2) which it envelops, sealed in an outer gas-tight envelope (4). Over the course of approx. 50 years, the pressure inside the outer chamber (3) + (4) may increase to approx. 100 mbar. The outer core (3) should be compressed without losing the desired effect under the initial pressure acting on it from approx. 999 mbar to a few 0.01 mm. When using a glass fleece, its thickness in the compressed state will be at least a few 0.1 mm.

The outer casing (4) is a film composite with, for example, a PE layer that acts as a weldable layer and is approximately 50 μm thick, and a layer that acts as a diffusion barrier against O ₂ , N ₂ , CO ₂ , etc., for example 0.1 μm vapor-deposited aluminum layer and a PET layer acting as a diffusion barrier against water vapor.

A second design of the VIP, designed for maximum reliability, based on the double chamber principle, again includes, as shown in Fig. 1, an inner core made of pressure-resistant glass wool (1) which does not outgas under vacuum at temperatures up to 100 ° C (1), which the actual insulation volume of the VIP ensures. In order to achieve the desired low thermal conductivity of the evacuated core in the range of 5 ± 3 mW / m ° K, this core is evacuated to approx. 10 ^"3 mbar and welded into an inner gastight envelope (2).

The inner shell (2) is constructed as a composite film, which consists, for example, of an approximately 100 μm thick PE film acting as a carrier layer and as a weldable layer and a laminated approximately 10 - 50 μm thick aluminum film. It is known that aluminum foils with a thickness of approx. 25 μm can be manufactured absolutely free of pinhole without great effort and thus a diffusion barrier for O ₂ , N ₂ , CO ₂ etc. with which pressures in the fine vacuum range (10 ^"3 - 1 mbar) can theoretically be maintained over centuries.

In this case, the outer core (3) consists of a layer of nanoporous material a few mm thick, which is evacuated, for example, to 1 mbar and welded into an outer envelope film (4). Nanoporous materials that have been evacuated to a pressure of less than approx. 100 mbar have a thermal conductivity in the order of 5 mW / m ° K. For this reason, the outer chamber (3) + (4) not only forms a rough vacuum, which drastically increases the service life of the fine vacuum prevailing in the inner chamber (l) + (2), but also represents a very effective thermal insulation layer, which increases the thermal conductivity the inner shell (2) compensated.

The outer shell (4) consists of a commercially available multi-layer plastic film that contains very thin, vapor-deposited layers of aluminum with a total thickness of approx. 0.3 μm and thus the pressure in the outer chamber (3) + (4) of less than Maintains 100 mbar over long periods.

Fig. 2 illustrates a possible price / performance scenario of some VIP variants in a few years.

It becomes clear that - according to the first design variant described above - a VIP with a large-pore core material constructed according to the double chamber principle as inexpensively as possible with a sufficient lifespan with some probability both for a heat transfer of 0.2 W / m K and for one of 0.1 W / m ² K should be significantly cheaper than a single-sleeve VIP with a nanoporous core. A - according to the second variant described above - a VIP with a large-pore core based on the double chamber principle, optimized with regard to vacuum life, will probably be slightly more expensive than a VIP with a nanoporous core for a heat transfer of 0.2 W / m ² K, but for one Heat transfer of 0.1 W / m ² K have a significant price advantage.

It is obvious that similar structures with similarly good properties can be constructed using other large-pore core materials and other cladding materials.

Of course, a nanoporous material could also be used as the material for the inner core (1), but this makes no sense due to the price and the “high” permissible pressure (> maximum 100 mbar) necessary for the effectiveness of these materials.

Claims

1.Vacuum insulation panel with a large-pore inner core evacuated to pressures less than 1 mbar, the inner core consisting of a structure consisting of an inner gas-tight shell, an outer core evacuated to pressures less than 100 mbar and an outer gas-tight shell is encased according to the double comb principle.

2. Vacuum insulation panel according to claim 1, characterized in that the inner core consists of a pressure-resistant glass wool which does not outgas to temperatures of at least 70 ° C.

3. Vacuum insulation panel according to claim 1 or 2, characterized in that the outer core consists of a glass wool fleece.

4. Vacuum insulation panel according to claim 1 or 2, characterized in that the outer core consists of nanoporous material of 1 to 10 mm in thickness.

5. Vacuum insulation panel according to one of claims 1 to 4, characterized in that the inner shell consists of a 50 to 500 μm thick plastic layer acting as a weldable carrier film and a 0.05 to 1 μm thick metallic layer.

6. Vacuum insulation panel according to one of claims 1 to 4, characterized in that the inner shell made of a weldable carrier film acting 50 to 500 microns thick plastic layer and a 1 to 50 microns thick metallic layer.