Note: Descriptions are shown in the official language in which they were submitted.
PF 55489
CA 02562128 2006-09-18
THERMAL INSULATION COMPOSITE WITH IMPROVED THERMAL STABILITY AND
IMPROVED FIRE RESISTANCE
Description
The invention relates to a thermal insulation composite, comprising two metal
sheets
with a thermally insulating core material, wherein a fire-protection layer has
been intro-
duced between the thermally insulating core material and at least one of the
metal
sheets, to a process for its production, and to its use for the production of
storage build-
ings or of cold-store buildings.
Sandwich panels composed of a thermally insulating core material and of
bilaterally
adhesive-bonded sheets of steel or of aluminum are used as structural elements
or
cladding in construction applications. Their heat resistance in the event of a
fire is often
inadequate. For example, in the event of a fire thermoplastic foams can melt
merely as
a result of exposure to heat, and impair the mechanical stability of the
sandwich pan-
els.
WO 02/064672 therefore proposes the use, as core material, of a polymer foam
with a
continuous phase composed of a phenolic resin and of dispersed polystyrene
foam
beads.
GB-A 2362586 discloses a process for improving the flame retardancy of
polystyrene
foam slabs, in which the prefoamed polystyrene foam beads are coated with a
liquid
phenolic resin which comprises a flame retardant based on phosphorus or
chlorine
compounds, and are then fused to give slabs. However, these flame-retardant
polysty-
rene foam slabs can be lost via melting on exposure to relatively high
temperatures for
a prolonged period.
DE-A 196 39 842 discloses fire-protected composite systems composed of
polystyrene
foam slabs whose surface has been provided with profiles or with grids or
nets, this
having been saturated with an intumescent composition. The profiles, grids, or
nets are
preferably introduced into the joints between the foam sheets.
EP-A 0 942 107 describes a foam impregnated to give flame retardancy and in es-
sence consisting of PU foam, which is laminated to two self-adhesive films,
between
which an intumescent material has been enclosed, and its use as fire-
protection stop-
per.
It was therefore an object of the present invention to eliminate the
disadvantages men-
tioned and to invent a thermal insulation composite with improved heat
resistance and
improved fire performance, and a process for its production.
PF 55489 CA 02562128 2006-09-18
2
The thermal insulation composite described at the outset has accordingly been
in-
vented. The metal sheets of the thermal insulation composite are generally
composed
of steel or of aluminum with a thickness of from 1 to 10 mm
The thermally insulating core material may be composed of molded polystyrene
foam,
of extruded polystyrene foam sheets (XPS), of polyurethane foams or of PIR
foams, or
of mineral wool. Preference is given to a thermally insulating core material
composed
of molded polystyrene foam sheets, obtainable via sintering of prefoamed
polystyrene
foam beads composed of expandable polystyrene (EPS), because this core
material
has low density together with processability and longlasting insulation
performance.
Preference is given to molded polystyrene foam sheets whose density is in the
range
from 10 to 50 g/I and whose thickness is in the range from 50 to 250 mm.
The fire-protection layer applied to the molding may take the form of
laminate, sheet,
film, dispersion, or solution. The thickness of the fire-protection layer
depends on the
material used and is generally in the range from 0.1 to 50 mm, preferably in
the range
from 1 to 10 mm. An example of a suitable material is a foam film composed of
a heat-
resistant melamine resin foam (e.g. Basotect~) or a fire-protection laminate
composed
of gelled alkali metal silicate solution (e.g. Palusol~). The thermally
insulating core ma-
terial is preferably coated with an intumescent composition. The coating may
be ap-
plied by spraying, immersion, roller-application, or spreading, to one or more
surfaces
of the thermally insulating core material. The coating material itself is
flame-retardant.
The result is that the heat-sensitive core material situated thereunder is
protected from
high temperatures and from flashover, and retains its structural integrity.
Intumescent compositions are materials which foam on exposure to relatively
high
temperatures, generally abovel 80 -100°C, and during this process form
an insulating
and heat-resistant foam which protects the thermally insulating core material
situated
thereunder from exposure to fire and to heat.
The intumescent composition present in the thermal insulation composite is
preferably
an alkali metal silicate, in particular a hydrous sodium silicate, expandable
graphite, or
expandable mica.
The inventive thermal insulation composite may be produced via bonding of two
metal
sheets and of a thermally insulating core material, where a fire-protection
layer is intro-
duced between the thermally insulating core material and at least one metal
sheet,
preferably between the thermally insulating core material and both metal
sheets.
Commercially available machines for producing thermal insulation composites
may be
used for this purpose.
PF 55489 CA 02562128 2006-09-18
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In one preferred process, an intumescent composition is used to coat at least
one sur-
face of the thermally insulating core material, and the material is then
adhesive-bonded
to the metal sheets. It is also possible to mix the intumescent composition
with the ad-
hesive and to apply the materials together to the thermally insulating core
material or to
the metal sheet, or to use an intumescent composition which has sufficient
adhesion to
the metal sheet.
The adhesives used may comprise single- or two-component adhesives based on po-
lyurethane resins or on epoxy resins. However, it is also possible to use
adhesives
based on dispersions, e.g. acrylate dispersions (Acronal~).
In one embodiment, the adhesive forms all or part of the fire-protection
layer. To this
end, additives, such as expandable graphite, hydrous sodium silicates, zinc
borates,
melamine compounds, metal hydroxides, or metal salt hydrates, or a mixtures of
these,
are admixed with the adhesive. The proportion of the additives is generally in
the range
from 2 to 98% by weight, preferably from 40 to 90% by weight, based on the
adhesive.
To improve processability, e.g. during the spreading or spraying process, or
to acceler-
ate drying, or to improve adhesion, other conventional fillers may be admixed
with the
adhesive.
In one preferred embodiment, the fire-protection layer is formed from an
intumescent
composition based on a sodium silicate. To this end, use is made of a
commercially
available waterglass solution with a water content of about 65% by weight, and
this is
mixed with waterglass powder with a water content of about 18% by weight. The
gelling
times for the mixture can be adjusted as desired by way of the amount of
waterglass
powder. If appropriate, amounts of from 0 to 50% by weight of inorganic
fillers, such as
metal hydroxides or metal sulfate hydrates, or else up to 10% by weight of
organic fill-
ers, may be added to the mixture. The liquid mixture may be directly applied
or sprayed
onto the sheets of the panel core material. The coating layer thicknesses here
may be
from 0.05 to 5 mm.
The gelling takes place at room temperature, but can be accelerated by
exposure to
higher temperatures up to 80°C. The sheets of the core material are
thus coated on all
sides, or only on the broad sides subsequently used for adhesion to a metal
sheet.
It is also possible to coat the thermally insulating core material with the
waterglass mix-
ture and to press it with the metal sheets on both sides prior to complete
gelling.
The exposed edges and corners of the core material not covered by the metal
sheets
may also likewise be provided with the coating composition, or critical
points, such as
ends or joints, may be protected from exposure to heat or from flashover via
introduc-
tion of insulating wedges composed of mineral wool into the panel structure.
The foam-
PF 55489 CA 02562128 2006-09-18
4
ing of the coating can also seal apertures produced and thus inhibit flashover
into the
core material.
The inventive thermal insulation composite is preferably suitable in the
construction
industry, for facade cladding, or as what are known as "structural insulation
panels" for
the production of storage buildings or of cold-store buildings.
Examples:
Inventive example 1:
A molded polystyrene foam sheet composed of EPS (600x1000x100 mm) with a foam
density of 18 g/I was provided on both sides with a layer, thickness 2 mm, of
a water-
glass mixture, composed of waterglass solution (water content 65% by weight)
mixed
with waterglass powder (water content 18% by weight). After gelling and
hardening of
the layer, the resultant sheet was coated on both sides with a layer,
thickness 50 Nm,
of a PU adhesive, and steel sheets, thickness 1 mm, were applied by adhesive
bond-
ing. In order to assess heat resistance and flame retardancy, the resultant
panel was
secured horizontally after the adhesive had hardened, and exposed for 30
minutes to a
gas flame (flame temperature >500°C) from below. Only a small
proportion of the EPS
foam core material melted during the entire 30-minute period of the test, and
the mate-
rial did not ignite. The foaming protective layer composed of waterglass
substantially
inhibited damage to the core material, and the structural integrity of the
panel was re-
tained.
Comparative experiment
A molded polystyrene foam sheet composed of EPS (600x1000x100 mm) with a foam
density of 18 g/I was provided on both sides with a layer, thickness 50 Nm, of
a PU ad-
hesive, and steel sheets, thickness 1 mm, were applied by adhesive bonding. In
order
to assess heat resistance and flame retardancy, the resultant panel was
secured hori-
zontally after the adhesive had hardened, and exposed for 30 minutes to a gas
flame
(flame temperature >500°C) from below. After as little as 5 minutes,
the EPS foam core
material melted and ignited, and the structural integrity of the panel was
lost.
