Heat insulating bodies

Stock material or miscellaneous articles – Sheet including cover or casing – Filled with gas other than air; or under vacuum

Patent

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Details

428 71, 428 76, 524062, B32B 106

Patent

active

060634715

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The production of heat-insulating bodies (vacuum panels) from a porous material and a gas-tight film covering it all over, with the "hollow space" formed by the porous material being evacuated, is known. The porous material may consist either of a porous bulk material or else of a rigid foam. The film usually consists of combinations of several layers, with various objects, such as that of providing a diffusion barrier to different gases and giving mechanical strength, being fulfilled by the different layers.
Most marketable vacuum panels have a core of porous bulk material, usually based on silicates.
In EP-B 188 806 rigid polyurethane-based (PU) foams are described as filling material for vacuum panels. The problem with this process is that of achieving the required open-cell structure by precise selection of formulation and by maintaining particular processing variables, since PU rigid foams are predominantly closed-celled. Another problem with the use of PU rigid foams as supporting material for vacuum panels is the evolution of volatile constituents such as amines, blowing agents and possibly also monomers.
An advantage of rigid PU foams as compared with porous bulk materials, on the other hand, is their exact dimensioning as the finished vacuum panel, as well as their exact dimensional accuracy.
Surprisingly, it has now been found that an excellent supporting material for vacuum panels can be economically produced by mixing with binders the plastics foam powder or plastics foam flakes, which arise, for example, during the recycling of waste foams, preferably from refrigerator insulation, and processing the mixture with the use of pressure and optionally temperature to form moulded products having a bulk density of from 50 to 350 kg/m.sup.3, preferably of from 100 to 250 kg/m.sup.3. Here moulded products, for example slabs, having a fine pore structure and high strength and dimensional accuracy are obtained.


SUMMARY OF THE INVENTION

The invention therefore provides a heat-insulating body, comprising: kg/m.sup.3, preferably of from 100 to 250 kg/m.sup.3, which has been obtained by comminution of rigid plastics foam to powder or flakes, and binding of the powder or of the flakes using a binder, with simultaneous or subsequent pressing with shaping and and then hermetically sealed.


DETAILED DESCRIPTION OF THE INVENTION

According to the invention it is preferred that rigid polyurethane foam, from the process of recycling old refrigerators, preferably of from 0.1 to 2 mm, diisocyanate or polyisocyanate, (preferably mixtures of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates), freed from volatile constituents by tempering at temperatures of from 50 to 250 .degree.C., preferably of from 100 to 150.degree. C., optionally at low pressure, prior to further processing, polyethylene/aluminium film or polyethylene/polyvinyl alcohol film. A covering layer may optionally also be a gas-tight, rigid plate.
All known films, for example, combination films, which are also used in the production of commercially available vacuum panels are suitable for the vacuum panel produced according to the invention. Examples which may be named are a combination of polyethylene film with polyvinyl alcohol film or of polyethylene film with aluminium film.
All rigid plastics foams, preferably polyurethane foams, are suitable as foams to be used according to the invention. Although the films used for vacuum panels already possess a high gas density, they are nevertheless not gas/vapour barriers. In particular penetrating water vapour can impair the vacuum and therewith the heat-insulating properties of the vacuum panel. To avoid this, according to the invention vapour-absorbing substances, for example, those based on silicate or aluminium, can be used in quantities of from 5 to 50 wt. %, preferably of from 10 to 25 wt. %. It has been found, however, that a PU sandwich panel according to the invention also already possesses a very strong capacity to absorb water.
Suitable binder

REFERENCES:
patent: 4482597 (1984-11-01), Smith
patent: 4529638 (1985-07-01), Yamamoto et al.
patent: 4668555 (1987-05-01), Uekado et al.
patent: 4726974 (1988-02-01), Nowobilski et al.
patent: 5268209 (1993-12-01), Hunt
patent: 5273801 (1993-12-01), Barry et al.
patent: 5364577 (1994-11-01), Cur et al.

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