HEAT-INSULATING BODY

CORPS THERMO-ISOLANT

English Abstract

The invention concerns a heat-insulating body comprising: a) a porous pressed
shaped part having an apparent density of 50 to 350 kg/m3, preferably 100 to
250 kg/m3, which is obtained by comminuting foamed plastics to form powder or
flakes, binding the powder or flakes with a binder and simultaneously or
subsequently shaping the part by pressing; and b) a foil enveloping the
pressed shaped part. The foil enveloping the pressed shaped part is evacuated
and then hermetically sealed.

French Abstract

L'invention concerne un corps thermo-isolant comprenant a) une pièce moulée par compression, poreuse, présentant une masse volumique apparente comprise entre 50 et 350 kg/m?3¿, de préférence entre 100 et 250 kg/m?3¿, obtenue par broyage sous forme de poudre ou de flocons de mousse de matière plastique, puis par liaison de la poudre ou des flocons avec un liant, et par façonnage simultané ou ultérieur de la pièce par compression; et b) une feuille enveloppant la pièce moulée par compression. L'air est évacué de la feuille enveloppant la pièce moulée par compression, puis la feuille est scellée hermétiquement.

Claims

- 6 -
Claims
1. Heat-insulating body, comprising:
a) a porous pressed moulded part having a bulk
density of from 50 to 300 kg/m3, preferably of
from 100 to 250 kg/m3, 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
b) a film covering the pressed moulded part,
with the film which covers the pressed moulded part
having been evacuated and then hermetically sealed.
2. Heat-insulating body according to claim 1,
characterised in that the plastics foam to be
comminuted is a polyurethane foam.
3. Heat-insulating body according to claim 1 and 2,
characterised in that the plastics foam to be
comminuted is a recycling material, preferably a rigid
polyurethane foam, which originates from the process
of recycling old refrigerators.
4. Heat-insulating body according to claims 1 to 3,
characterised in that the foam powder or the foam
flakes have a particle size of from 0.01 to 5 mm.
5. Heat-insulating body according to claims 1 to 4,
characterised in that the binder used for the pressed
moulded part is a diisocyanate or polyisocyanate.

- 7 -
6. Heat-insulating body according to claims 1 to 5,
characterised in that the pressed moulded part has
been freed from volatile constituents by tempering at
temperatures of from 50 to 250°C, preferably of from
120 to 200°C, optionally at low pressure.
7. Heat-insulating body according to claims 1 to 6,
characterised in that the covering film used is a
multilayer film, preferably a polyethylene/aluminium
film or polyethylene/polyvinyl alcohol film.

Description

' CA 02203418 1997-04-22
LeA 30738-PC
Heat-insulatinq bodies
The production of heat-insulating bodies (vacuum panels)
from a porous material ard a cs-tight film covering it all
over, with the "hollow space" formed by the porous material
being evacuated, is known. The porous r,aterial 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
~aterial, 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 ~oams 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
.. . . . . . .

CA 02203418 1997-04-22
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~m3,
preferably of from 100 to 250 kg/m3. Here moulded products,
~or example slabs, having a fine pore structure and high
strength and dimensional accuracy are obtained.
The invention therefore provides a heat-insulating body,
comprising:
a) a porous pressed moulded part having a bulk density of
from 50 to 300 kg/m3, preferably of from 100 to
250 kg/m3, which has been obtained by comminution of
rigid plastics foam to powder or flakes, and binding
of the powder or of the ~lakes using a binder, with
simultaneous or subsequent pressing with shaping and
b) a film covering the pressed moulded part,
with the ~ilm which covers the pressed moulded part having
been evacuated and then hermetically sealed.
According to the invention it is preferred that
25 - the plastics foam to be comminuted is a rigid
polyurethane foam,
- the plastics ~oam to be comminuted is a recycling
material, preferably a rigid polyurethane foam, from
the process of recycling old refrigerators,
- the foam powder or the foam flakes have a particle
size of from 0.01 to 5 mm, preferably of from
0.1 to 2 ~,
3~
,

' CA 02203418 1997-04-22
- the binder used for the production of the pressed
moulded part is a diisocyanate or polyisocyanate,
(preferably mixtures o~ diphenylmethane diisocyanates
and polyphenylpolymethylene polyisocyanates),
- the ~oam powder or the ~oam flakes or the pressed
moulded part has been freed from volatile constituents
by tempering at temperatures of ~rom S0 to 250C,
preferably of from 100 to 150C, optionally at low
pressure, prior to further processing,
- the covering film used is a multilayer film,
preerably a polyethylene/aluminium ~ilm 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 ~or the vacuum panel produced
according ~o the invention. Examples which may be named are
a combination o~ polyethylene film with polyvinyl alcohol
~ilm or o~ polyethylene ~ilm with aluminium ~ilm.
All rigid plastics foams, preferably polyurethane ~oams,
are suitable as ~oams 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 v~cuum and therewith the heat-
insulating properties o~ the vacuum panel. To avoid this,according to the inven~ion vapour-absorbing substances, ~or
example, those based on silicate or aluminium, can be used
in quantities o~ from 5 to 50 wt.~, pre~erably o~ ~rom

CA 02203418 1997-04-22
-- 4
10 to 25 wt.~. It has been ~ound, however, that a PU
sandwich panel according to the invention also already
Flossesses a very strong capacity to absorb water.
Suitable binders are, ~or example, the diisocyanates and/or
polyisocyanates re~erred to in DE-AS 1 911 645.
The comminution of the rigid foam can be carried out, for
example, by milling, grinding or by picking to pieces.
~ptionally larger pieces o~ ~oam can also be crushed or
pounded.
Another advantage of the vacuum panels according to the
.
invention is that the pressed moulded part can be
prefabricated or that optionally vacuum moulded parts can
also be produced in addition to vacuum panels.
The foam slabs can, ~or example, be cut when upright prior
to the covering with film and evacuation, or appropriate
indentations can be milled out for the assembly of
switches, wiring or ducts
The fineness of the porosity can according to the invention
be adjusted on the one hand by ~he intensity of the milling
process and on the other hand by the fineness of the cell
structure of the foam to be milled.
The pressing with shaping is carried out in a manner known
per se at increased pressure (for example, 1.5 - 20 bar)
and optionally at elevated temperature (~or example,
50 - 250C). In one variant oî the process according to the
invention, after the evacuation the substrate can again be
wholly or partly ~illed with a gas possessing a low thermal
conductivity (for example, ~enon).

- . CA 0220341X 1997-04-22
-- 5
Example
580 g of~ a PU rigid foam powder îrom a refrigerator
recycling plant is evenly mixed with 20 g of water and 58 g
o~ a polyisocyanate mixture comprising diphenylmethane
diisocyanates and polyphenylpolymethylene polyisocyanates
(Desmodur VP PU 1520 A20; Bayer AG) by means of a Lodige
ploughshare mixer having 2 nozzles. From this mixture a
s~aped body of 400 x 400 mm in size is formed in a holding
lo block, evenly compacted and subsequently pressed to 20 mm
in a laboratory press at a pressure of 5 bar and at a
temperature of 120C for 8 minutes, using a timekeeping
programme.
A poxous 20 mm slab having a bulk density of 200 kg/m3 is
thus obtained. The slab is heated to 120C for
approximately 2 hours, in order to free it from all
volatile constituents.
The slab is covered with a film consisting of the layers
polyethylene/polyvinyl alcohol/polyethylene
and evacuated to 0.001 bar. Under vacuum the edges of the
film become sealed. The vacuum panel thus obtained has a
thermal conductivity ~ of 9 m W/Km, measured by the heat-
flow method.