WO2004001150A1 - Core material for vacuum insulated panels and vacuum insulated panel - Google Patents

Abstract

The invention relates to an open-pored core material for vacuum insulated panels for heat insulation, comprising a material component which is at least partially decomposable and/or dimensionally unstable in contact with the air or humidity. A first type of core material is a fiber composite glued with a water-soluble binding agent for example. A second type of material is produced by foaming a material, wherein a substance,e.g.water, escapes in the form of a gas.

Description

 CORE MATERIAL FOR VACUUM ISOLATION PANELS AND VACUUM ISOLATION PANELS

The invention relates to core materials for vacuum insulation panels, a method for producing such core materials, and vacuum insulation panels.

Buildings are generally insulated by installing insulation panels made of a heat-insulating material in an outer wall. The thermal insulation property of such materials is usually given by the fact that air is enclosed in cavities. A significantly improved insulation effect is achieved when vacuum is used for insulation.

A vacuum insulation panel has a gas-tight shell and enclosed, evacuated open-pore core material. Certain requirements are placed on core materials. For example, they must be pressure-resistant despite the existing cavities in order to maintain their shape even when evacuated. The compressive strength should at least correspond to the air pressure of 0.1 N / mm ² acting on the core material in the evacuated state. In addition, the materials used for the core material must not or only outgass very little in the course of years, as otherwise the vacuum and thus the thermal insulation effect of the panel will be lost. Known core materials are made of glass wool, which is glued with plastic to give the wool the necessary stability. Other known core materials are the so-called nanoporous materials, which are offered, for example, by the Wacker or Cabot companies.

Known vacuum insulation panels have various disadvantages. Glass wool coated with plastic is hardly recyclable and there is a disposal problem. In addition, the material has to be cured at relatively high temperatures, which results in high energy consumption during manufacture. Other materials are very expensive to manufacture. Materials with very small pores, which place less stringent requirements on the outgassing strength and thus also allow the use of cheaper starting materials, can only be evacuated in complex processes.

It is therefore an object of the invention to provide core materials and vacuum insulation panels which avoid disadvantages of known core materials. It is a particular object of the invention to provide inexpensive open-pore core materials and an inexpensive method for their production.

The task is solved by the open-pore core material, the vacuum insulation panels and the processes as defined in the independent patent claims.

The invention makes use of the first finding that in a vacuum insulation panel the material components used for the core material do not have to be resistant to the atmosphere, ie to air and moisture, since these materials are protected from external influences by a gas-impermeable cover. So materials or material components can be used which, at least partially, chemically decompose or dissolve in contact with water or air, or from which other intrinsic material properties would be irreversibly changed.

The invention also uses - not necessarily depending on this - the idea that a fiber composite with a binder that is soluble in a solvent, preferably in water, after curing once again represents an outstandingly recyclable insulation material.

The invention also relates to a mixture of coarsely open-pored material components with nanoporous materials, the nanoporous material at least partially filling up a pore structure of a coarsely open-pored material component. This combines the advantages of nanoporous materials and of coarse-pored materials.

The idea of using materials and material components for open-pore core material or for the production of open-pore core material that are at least partially decomposable and / or dimensionally unstable in contact with air or moisture opens up previously unknown possibilities with regard to the choice of material. Depending on the materials used, core materials according to the invention can be produced very inexpensively and very efficiently and simply. Biodegradable materials can be used. If water-soluble material components are used (again and again after hardening), this also enables simple separation and possible reuse of individual material components.

A core material according to the invention for vacuum insulation panels preferably has a low one even under a normal atmosphere Thermal coefficient on, for. B. less than 40mW / mK. It is also open-pore, ie it has a pore or cavity system that is designed so that it can be evacuated by pumping. In addition, it is dimensionally stable in the absence of air or moisture, for example in a vacuum or under a protective atmosphere, and is pressure-resistant up to 0.1 N / mm ² . In addition, the material essentially does not outgas. The increase in pressure that occurs over the years due to outgassing may not be so great, for example, that within an average lifespan of the VIP - e.g. 50 years for building VIP, 10 years for VIPs for vehicles - the mean free path of the residual gas in the pores exceeds the average pore size. For example. the pressure should not be significantly ^lower for structures with an average pore diameter of 1 mm 2 * 10 ^_1 mbar, for pores of 0.1 mm 10 ^"2 mbar, for a pore size of 1 μm 100 mbar etc. Corresponding formulas and tables can be found in specialist books on vacuum technology.

A core material according to the invention thus essentially consists of non-outgassing, open-pore, heat-insulating materials which decompose at least partially in contact with air or moisture and / or are dimensionally unstable. The core materials can be naturally open-pored, such as foams and open-pored, optionally moldable, materials. However, it can also be used, for example, fibrous or granular materials for producing an open-pore core material by stabilizing and holding together these fibrous or granular material components with a binder material which is also essentially non-outgassing, e.g. B. be glued. Such binder materials are, for example, in a liquid or a solvent, e.g. B. water, detachable material components, which after removal of the solvent, for. B. by evaporation, harden. Any solvent residues present in the core material can be removed, for example, in addition to heat treatment, by gassing or spraying with a suitable liquid which removes the solvent or moisture. A binder material should harden in such a way that no gaseous solvent or liquid emerges from the core material in the evacuated state. Examples of binder materials are sugar, salts, suitable adhesives, borax dissolved in hot water, etc.

The core materials according to the invention or the vacuum insulation panels produced therefrom can be further improved in their properties — preferably heat-insulating properties — with additional measures. Such measures are, for example, the use of opacifiers which are able to reflect and / or absorb infrared light. Opacifiers can be added to the core material.

The invention is explained in more detail below with the aid of a few examples.

Core material type 1: fibrous or granular material fixed by binding material

1. Example: Glass fibers are processed into a fleece-like fiber composite, such as glass wool. In the course of the manufacture of the fiber composite or subsequently, the fiber composite is coated with the sugar dissolved in water, e.g. B. by spraying, soaking or immersing. The sugar serves as a binding material and takes on the property of gluing the fibers and stabilizing the fiber composite in a desired shape without destroying the open pore system in the fiber composite. The sugar-coated glass wool is then tempered, for example at temperatures around 100 ° C., as a result of which the water escapes as a solvent. The resulting core material is dimensionally stable. It was also surprisingly found that it practically does not outgas at temperatures below 100 ° C. Furthermore, sugar is extremely inexpensive to obtain, and manufacturing at a maximum of 100 ° C is much less energy consuming than producing known core materials. If necessary, the resulting material can also be post-treated by means of impregnation, for example with an agent that can bind moisture and remove it from the fiber composite.

In this example, the glass fibers can be replaced by mineral (rockwool) or non-outgassing textile or wood fibers; instead of sugar, another, for example water-soluble material, such as a concentrated salt solution or another, for example organic, is preferably used as the binder material material soluble in a solvent.

2. Example: Instead of fibrous material, essentially non-outgassing, open-pore, granulated materials are used. These granulated substances are arranged or spread out in a desired shape and can then be processed with a binder material to form an open-pore, plate-like core material. Practically any material that is present in the form of granules and does not give off too much gas can be considered as a granulated material. The materials mentioned in Example 1 are again used as binder material, for example.

3. Example: Glass wool is again used as the fiber composite. During or after the production of the glass wool, it is sprayed with borax dissolved in hot water at 80 ° C-90 ° C. The product is then cured at 200 ° to 350 ° C, whereby the borax expands and a firm connection to the "Crossing points" of the glass fibers creates. The material created here also does not outgas.

This embodiment has the advantage that it can also be used outside of vacuum insulation panels and even in a water and air-containing atmosphere. As an additional bonus, the material also keeps insects and other pests away. It cannot be attacked by cold water, the borax only becomes unstable when it comes into contact with water at temperatures of approx. 80 ° C or more.

Core material type 2a: Foamed materials

This second type of core material according to the invention is formed from an inherently stable, open-pore foam. This inherently dimensionally stable foam also has the property that, as soon as it comes into contact with water or air, it at least partially decomposes or becomes dimensionally unstable.

An example of an open-pore foam is a foam made from dry borax powder (Na ₂ B ₄ O ₇ * 10H ₂ O), the borax powder being warmed up to a defined expansion temperature and kept at this temperature for a few minutes. When the powder is heated, the crystal water contained in it escapes, forms pores and escapes through them, so it acts as an "inherent" blowing agent Minimum expansion temperature of approx. 200 ° C creates very small pores and the expansion process takes approx. 10 min; the resulting increase in volume is approx. A factor of 15. At temperatures of approx. 300 to 350 ° C, significantly larger pores and the expansion process occur is completed within about a minute; the resulting increase in volume is approximately a factor of 25 to 30.

If the expansion process of the borax described, if necessary after adding a fibrous “reinforcing material”, is carried out in a closed container, a pressure-resistant plate is formed which is more or less easily breakable depending on the amount of the “reinforcing material”.

If the expansion process is carried out in an open container, more or less large, loosely poured, open-pore borax bodies result. If these are subsequently coated with a binder, for example by spraying or dipping, a core material of type 1, example 2, can be produced. The binder can be, for example, sugar dissolved in water.

Sheets made from foamed borax powder are extremely pressure-resistant, non-flammable, very light, do not outgas and have excellent thermal insulation properties. In experiments, it was surprisingly found that a 1 cm thick plate produced according to the above method could be heated with an open gas flame from the underside of the plate for several minutes without the temperature on the top of the plate rising to over 50 ° C.

There are other examples of the second type of nuclear material. A generally desirable property of starting materials, if they are to be suitable for this type, is that a substance escapes in gaseous form when the material is exposed to certain conditions, for example a heat treatment. The desired open-pore structures are created by the escape of the fabric; the pore size etc. can be regulated by adjusting the process parameters. If this substance is water, in many cases a good one will automatically result Recyclability, since the initial state can be restored if the core material comes into contact with water. The substance can be bound in various forms in the starting material (such as the water of crystallization in borax) or be dissolved or can only arise during a chemical reaction.

To produce a vacuum insulation panel according to the invention, the core material according to the invention is evacuated and enclosed in a gas-tight envelope.

In addition to the examples mentioned, a person skilled in the art is free to use other suitable materials and material components for or for the production of core materials according to the invention. A specialist is also free to take other customary measures to improve the core materials according to the invention or the vacuum insulation panels.

Core material type 2b: Foamed materials with nanoporous material components

This invention also relates quite generally to another type of material, regardless of the features described above. This is based on an idea on the basis of which the advantages of large-pore open-pore material can be combined with those of nanoporous material. According to this embodiment of the invention, in a first step, a foamable material, which does not significantly outgas in a vacuum, is mixed as the first material component with a material that can be formed into nanoporous material (for example, also foamable or already nanoporous) as the second material component. As a foamable material, for example, as described above, borax, that is dry borax powder, is also suitable, but also other materials from the core material. Type 2a. One of the various examples of known nanoporous materials, for example silica or fumed silicas, can be used as the second material component.

The resulting open-pore material is a composite of a structure that is roughly open-pore in itself, the pore structure either being partially filled with nanoporous material or forming an “open matrix” in which the nanoporous material is embedded. “Nanoporous” here means an open-pore structure an average pore diameter of 0.1 μm or smaller. This combines the ideal insulation properties - which, as explained above, can also exist for VIPs with a pressure of up to 100 mbar - depending on the nanoporous materials with the advantageous properties of the coarse-pored materials. In particular, if the very good thermal insulation properties are retained, the volume fraction of the expensive nanoporous materials can be drastically reduced. Overall, there are advantages in terms of - insulation properties

- Resistance (the insulating effect of the nanoporous materials continues even when the vacuum is not perfect)

- Mechanical stability

- Manufacturing process - cost

In addition, if the coarse-pore structures are not completely filled by the nanoporous material, the evacuation of the material will be an order of magnitude easier compared to the nanoporous material according to the prior art. The coarse-pore structures then serve as channels for the evacuation. Example: A mixture of borax powder and silica with a borax mass content of approx. 10-50% is produced. The resulting mixture is then heated to approx. 200 ° C to 350 ° C, causing it to foam and the desired core material to be produced. The borax portion and the temperature serve as parameters with which the pore sizes of the coarse-pored and the nanoporous structures can be controlled.

In addition, combinations with a fiber composite with a binder (as a coarse-pored material) are also conceivable.

In general, other combinations of types 1, 2a and 2b are also conceivable.

Claims

PATENT CLAIMS 1. Open-pore core material for a vacuum insulation panel for thermal insulation, characterized by at least one material component which is at least partially decomposable and / or dimensionally unstable in contact with air or moisture. 2. Open-pore core material, characterized in that the at least one material component is water-soluble. 3. Open-pore core material according to claim 1 or 2, characterized in that it is designed as a fleece-like fiber composite or contains open-pore, granulated material and contains a binder material stabilizing the fiber composite or the granulated material. 4. Open-pore core material according to claim 3, characterized in that the fleece-like fiber composite contains glass fibers and the binder material contains sugar. 5. Open-pore core material according to claim 1 or 2, characterized in that it is formed with the exclusion of air and water as an inherently stable, open-pore foam. 6. Open-pore core material according to claim 5, characterized in that the open-pore foam from a starting material, for example. Borax powder is foamed, the starting material being designed such that a substance escapes in gaseous form when foaming. 7. A method for producing an open-pore core material for vacuum insulation panels according to one of claims 1 to 4, characterized in that fibrous materials to a non-woven Fiber composite are processed, the fiber composite is covered in the course of its manufacture or later with a stabilizing binder material, so that the resulting core material is open-pore and evacuable, the fleece-like fiber composite and / or the binder material being selected such that they are in contact with air or At least partially decompose moisture and / or become dimensionally unstable. 8. Open-pore core material for a vacuum insulation panel for thermal insulation, in particular according to one of claims 1-6, characterized in that it is a mixture of at least a first material component with an open-pore structure with a pore size between 0.1 microns and 10 mm and is present from a second material component with a nanoporous open-pore structure, so that the open-pore structure of the first material component is at least partially filled up by material of the second material component. 9. Open-pore core material for a vacuum insulation panel for thermal insulation, in particular according to one of claims 1-6, characterized in that it is composed of at least two material components, of which a material component in the mixed or unmixed state by a physical and / or chemical Treatment is foamable to an open-pore structure, preferably to an open-pore structure with an average pore size of between 0.1 μm and 10 mm, and of which the or at least one other material component is a nanoporous material component. 10. Open-pore core material according to claim 8 or 9, characterized in that a material component is borax. 11. Process for the production of open-pore core material, wherein a foaming material component and a nanoporous Material component in a liquid or viscous phase and are mixed and the resulting mixture is exposed to such physical and / or chemical conditions that it foams. 12. Vacuum insulation panel comprising a gas-tight envelope and an evacuated open-pore core material according to one of claims 1 to 6, or 8 to 10.