Note: Descriptions are shown in the official language in which they were submitted.
1
HEAT TRANSFER MATERIAL WITH GOOD SOUND ABSORPTION PROPERTIES
Description
Technical area
The invention relates to a heat transfer material which has good sound
absorption properties,
as well as its use.
Prior art
Particularly in modern buildings, it is often desirable, even in temperate
climate zones, to air-
condition the rooms of the building by dissipating heat from or feeding heat
to the building. In such case,
heat dissipation is particularly important for rooms heavily frequented by
people and/or equipped with
numerous electronic devices because they exhibit a significant heat
dissipation in the three-digit watt
range. The same applies, for example, to production halls, where machines and
systems emit
considerable amounts of heat that have to be dissipated from the building.
In principle, there are different options for heat dissipation, wherein large-
area air-conditioning
elements based on the principle of heat dissipation have proven to be
particularly suitable. For the air-
conditioning of rooms, in particular for room cooling, heat transfer devices
or air-conditioning elements,
which are known from the prior art, are used. In principle, such air-
conditioning elements are also
suitable for space heating when the heat transfer direction is reversed.
Ceiling or wall elements, having a frame with a base plate which can be
fastened to the ceiling
or the wall, and having a heating or cooling register arranged in the frame,
are already known from the
prior art. For example, from DE 20 2007 010 215 U1, a wall or ceiling cladding
with a heating or cooling
register in the form of pipes, which are attached to heat-conducting profiles,
is known. On the rear side,
the heat-conducting profiles bear against a cladding surface formed by
cladding panels. The cladding
panels are attached to support rails with a U-shaped cross-section. The
support rails and the cladding
panels attached thereto thus form a frame which is attachable to a ceiling or
a wall and which has a
base formed by the cladding panels. The heat-conducting profiles are arranged
in the interior of said
frame and bear against the cladding panels. The heat-conducting profiles and
the pipes attached thereto
form the heating or cooling register. In order to produce a good heat-
conducting contact between the
pipes and the cladding surface, hold-down devices are arranged transversely to
the elongated heat-
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conducting profiles, which, under spring tension, hold at least two adjacent
heat-conducting profiles to
bear against the cladding panel.
On their rear side, the heat-conducting profiles have an approximately
semicircular step, in
.. which the pipes are arranged. Depending on the intended use as heating or
cooling line, a heating or
cooling medium, e.g., hot or cold water, flows through the pipes. The heat-
conducting profiles are usually
made of metal, such as aluminum. The cladding panels, for example, can be
drywall panels or perforated
metal cassettes made of steel or aluminum.
In order to allow for a more efficient heat transfer between the heating or
cooling register and
the space to be heated or cooled, DE 10 2009 055 440 Al proposes a ceiling or
wall element for
attachment to a ceiling or a wall, wherein the ceiling or wall element
comprises a frame, which has a
base, is attachable to the ceiling (or the wall), and in which a heating or
cooling register is arranged, and
wherein, between the base of the frame and the heating or cooling register, a
non-woven material and
.. a graphite sheet are arranged. The perforated graphite sheet is supposed to
ensure good thermal
contact between the heating or cooling register and the base plate of the
ceiling or wall element, and
the non-woven material is supposed to improve the sound absorption of the
ceiling or wall element. A
carbon fiber non-woven material is described as the preferred non-woven
material because of its high
heat conductivity. The non-woven material and the perforated graphite sheet
arranged thereon are
preferably a composite which can be produced by calendering.
The heat transfer material described is disadvantageous because the heat
transfer in the
vertical direction must be accomplished via the carbon fiber non-woven
material, since the graphite
sheet only allows for a planar heat conduction. For health reasons, carbon
fiber non-woven materials
.. are undesirable in building applications and unattractive in terms of
price. In addition, the use of a film
is disadvantageous because it must be perforated in order to be sound-
permeable and acoustically
effective. As a result, films tear quickly and are brittle.
EP 2 468 974 A2 also addresses the problem of achieving an improvement of the
heat transfer
in heating or cooling elements. For this purpose, this document proposes a
structure for a heating or
cooling element, in particular for an air-handling ceiling, comprising a
perforated, heat-conducting carrier
plate with lines of a heating or cooling register running on its rear side,
said lines being in heat-conductive
contact with the carrier plate, wherein the rear side of the carrier plate and
the heating or cooling lines
are covered by a covering path which has a textile or grid-shaped structure
and consists of a heat-
conducting material or is coated with a heat-conducting material.
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A non-woven material made of or coated with graphite, for example, can be used
as a covering
path. This non-woven material has no special acoustic properties. In order to
improve the acoustics, it
is therefore proposed that an acoustic non-woven material is additionally
laminated onto the rear side
of the covering path.
EP 2 191 058B1 describes a layer for use in a metal ceiling, having a basis
weight of maximally
45g/m2, comprising a fiber mixture which is present in an amount of maximally
30g/m2, and a flame
retardant which is present in an amount of maximally 10g/m2. The layer has
good acoustic properties
because it has a high and defined porosity. Due to its high porosity, however,
the layer is suitable only
to a limited extent for applications, in which heat conduction has priority.
Description of the invention
The invention addresses the problem of providing a material which, with a
simple structure,
combines very good heat-conducting properties with very good acoustic
properties and, as a result, can
be used for heat transfer and sound absorption, for example, in the above-
mentioned heat transfer
devices.
This problem is solved by a heat transfer material with a flow resistance from
60Pa*s/m to
400Pa*s/m, preferably from 100Pa*s/m to 300Pa*s/m, more preferably from
120Pa*s/m to 250Pa*s/m,
which has a textile fabric and a graphite-containing heat-conducting coating,
wherein, based on the
overall weight of the heat transfer material, the graphite is present in an
amount from 5% w/w to 50%
w/w.
Surprisingly, it has been discovered that with the heat transfer material
according to the
invention, very good heat-conducting properties can be combined with very good
acoustic properties.
The heat transfer material can even have a very simple and thin structure.
In a preferred embodiment, the amount of graphite with respect to the heat-
conducting coating
is more than 50% w/w, for example, from 50 to 100% w/w, preferably from 60 to
100% w/w, more
preferably from 70 to 100% w/w, more preferably from 80 to 100% w/w. This is
advantageous because
as a result, the heat-conducting properties of the textile fabric can be
significantly improved. Accordingly,
a good thermal conductivity can thus be realized even with low application
quantities. Low application
quantities are again advantageous because as a result, the porosity and the
air permeability of the textile
fabric are less affected.
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In contrast, heat-conducting coatings of textile fabrics known from the prior
art usually contain
a smaller quantity of graphite because the graphite layer usually contains a
binder of more than 50%
w/w.
When compared to films, the use of a heat-conducting coating is advantageous
because it can
at least partially penetrate the textile material. Penetration into the
material is once again advantageous
because the heat transfer in the direction of the surface normal is improved.
In a preferred embodiment,
the heat-conducting coating has thus penetrated the textile fabric at least to
some extent.
When compared to perforated metal sheets, the heat-conducting coating is
advantageous
because, due to the faster and more uniform distribution of heat in the
textile fabric, an improved
bondability can be achieved.
In a preferred embodiment of the invention, the adjustment of the high portion
of graphite in the
heat-conducting coating is achieved in that the textile fabric comprises
fibers made of a hydrophilic fiber
material. Without committing to a mechanism, it is assumed that the
hydrophilic fiber material has a high
affinity and, related thereto, a particularly good adhesion to the graphite.
This makes it possible to keep
the amount of binder in the heat-conducting coating and/or between the heat-
conducting coating and
the textile fabric very low.
Nevertheless, the heat-conducting coating can contain binders. Exemplary
binders are
polymeric binders from the group of acrylates, vinyl acrylates, vinyl
acetates, ethylene vinyl acetates
(EVA), acrylonitrile butadienes (NBR), styrene butadienes (SBR), acrylonitrile
butadiene styrenes
(ABS), vinyl chlorides, ethylene vinyl chlorides, polyvinyl alcohols,
polyurethanes, starch derivatives,
cellulose derivatives, and their mixtures, and/or copolymers. In a preferred
embodiment of the invention,
the amount of polymeric binder, and in particular of the aforementioned
polymeric binders, in the heat-
conducting coating and/or between the heat-conducting coating and the textile
fabric is less than 50%
w/w, for example, from 1 to 50% w/w, preferably less than 40% w/w, for
example, from 1 to 40% w/w,
more preferably less than 30% w/w, for example, from 1 to 30% w/w, and in
particular less than 20%
w/w, for example, from 1 to 20% w/w. The use of only a small amount or a
complete omission of a
polymeric binder is advantageous because it improves the fire behavior of the
material in case of fire,
and it improves the acoustic properties.
In a preferred embodiment of the invention, the amount of graphite, relative
to the overall weight
of the heat transfer material, lies between 10% w/w and 50% w/w, preferably
between 10% w/w and
35% w/w, more preferably between 10% w/w and 20% w/w.
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In a further preferred embodiment of the invention, the heat-conducting
coating is present in the
form of a pattern on the textile fabric. In other words, some areas of the
surface of the textile fabric are
coated with the heat-conducting coating and other areas are not coated. In
this case, the heat-
conducting coating can also have penetrated the fabric at least to some
extent. The design with a pattern
is advantageous because the coated areas of the heat transfer material are
provided with a high thermal
conductivity, while the uncoated areas are particularly acoustically active,
since their porosity is not
reduced by the application of the heat-conducting coating. The pattern can be
a geometric or irregular
pattern. The degree of surface coating of the heat-conducting coating with
respect to the surface of the
heat transfer material is advantageously 1 to 95%, preferably 10 to 60%,
particularly preferably 30 to
50%. In a preferred embodiment, the pattern has at least partially continuous
lines, preferably with a line
width > 0.5mm, preferably from 2.0 to 10.0 mm, particularly preferably from
4.0 to 7.0mm. Due to the
continuity, a good thermal conductivity in the surface of the heat transfer
material can be achieved.
In a further preferred embodiment, the pattern has at least partially discrete
points, rods and/or
non-continuous surfaces, preferably with a size of < 100mm2, particularly
preferably from 1.0 to 50mm2,
and particularly from 2.0 to 10mm2. Practical tests have shown that this leads
to a rapid heat transfer
through the thickness of the material, i.e., perpendicularly to the plane of
the textile fabric.
The heat transfer material according to the invention is further characterized
by excellent
acoustic properties. The heat transfer material has a flow resistance from
60Pa*s/m to 400Pa*s/m,
preferably from 100Pa*s/m to 300Pa*s/m, more preferably from 120Pa*s/m to
250Pa*s/m. In this case,
the flow resistance is measured according to DIN EN 29053-A: 1993-05. By
reducing or completely
omitting the amount of polymeric binder, the negative influence of the heat-
conducting coating on the
acoustic properties of the material is reduced. A complete closure of the
surface can thus be prevented,
and so a sufficient porosity for acoustic effectiveness is retained. The flow
resistance can be adjusted
in a manner known to a person skilled in the art, for example, by a suitable
selection of the fiber materials
in coordination with the selected parameters during the production and coating
of the textile fabric. It
has been shown that a particularly good sound absorption is made possible with
the flow resistances
selected according to the invention. Thus, the sound absorption coefficient
oi(0) of the heat transfer
material according to the invention, measured in the impedance tube at 1600
Hz, is preferably more
than 0.55, for example, from 0.55 to 1.0, more preferably more than 0.60, for
example, from 0.6 to 1.0,
and particularly more than 0.65, for example, from 0.65 to 1Ø The sound
absorption coefficient is
determined according to DIN EN ISO 10534-1: 2001-10 with the parameters
provided in Example 2.
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According to the invention, the textile fabric preferably contains fibers
selected from the group
consisting of glass fibers, polyolefins, polyesters, in particular
polyethylene terephthalate, polybutylene
terephthalate; polyamide, in particular polyamide 6.6 (Nylon ), polyamide 6.0
(PerIone), aramid, wool,
cotton, silk, hemp, bamboo, kenaf, sisal, cellulose, soya, flax, glass,
basalt, carbon, viscose, and their
mixtures. According to the invention, the fiber material particularly
preferably contains glass fibers,
cellulose and/or their mixtures, in particular glass fibers and cellulose.
The textile fabric can also contain conductive fibers, e.g., metal fibers,
ceramic fibers, carbon
fibers, etc., to further improve the thermal conductivity.
According to the invention, cellulose fibers are particularly preferred.
Cellulose fibers refer to
fibers which contain cellulose, viscose and/or fibrillar or fibrillated
cellulosic components, so-called fiber
pulp or pulp. Particularly preferably, the fibers consist essentially of the
above-mentioned components,
i.e., their portion is greater than 80% w/w.
In a preferred embodiment of the invention, the textile fabric contains
cellulose fibers in an
amount of at least 30% w/w, for example, from 30 to 100% w/w, and/or from 30
to 95% w/w, preferably
from 50 to 100% w/w, and/or from 50 to 90% w/w, more preferably from 60 to 95%
w/w, and particularly
from 65 to 85% w/w, in each case based on the overall quantity of fiber
material in the textile fabric.
In a further preferred embodiment of the invention, the textile fabric
contains glass fibers,
preferably in a quantity from 5 to 80% w/w, more preferably from 5 to 70% w/w,
even more preferably
from 10 to 60% w/w, particularly from 20 to 40% w/w, in each case based on the
overall quantity of fiber
material in the textile fabric. With the addition of glass fibers, the textile
fabric can be provided with a
particularly high structural stability and low thermal shrinkage.
The textile fabric very particularly preferably contains cellulose fibers,
preferably in an amount
from 30 to 95% w/w, more preferably from 50 to 90% w/w, particularly from 65
to 85% w/w, and glass
fibers, preferably in an amount from 5 to 70% w/w, more preferably from 10 to
50% w/w, particularly
from 15 to 35% w/w, in each case based on the overall quantity of fiber
material in the textile fabric.
The textile fabric could be designed as non-woven material, non-woven fabric,
or paper.
According to the invention, a non-woven fabric according to DIN EN ISO 9092 is
preferably used.
For producing the non-woven fabric, a non-woven material is laid dry using a
carding process,
a wet non-woven material process, or a spunbond process in a manner known to a
person skilled in the
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art. The non-woven material is preferably laid using a wet non-woven material
process or a carding
process. As a result, a particularly high uniformity can be achieved, which is
crucial for the acoustic
properties. Accordingly, the non-woven fabric is preferably a wet non-woven
fabric or a carded non-
woven fabric. The laying of non-woven material is particularly preferably
carried out using a wet non-
woven material process, in particular with an inclined screen, since non-woven
fabrics with particularly
high uniformity can be obtained in this manner.
The fiber mixture in the wet non-woven material process could also contain
fibrillar or fibrillated
cellulosic components, so-called fiber pulp or pulp. These components allow
for a very effective
balancing of the acoustic effectiveness of the textile fabric. In a preferred
embodiment, the non-woven
fabric is therefore a wet non-woven fabric containing fiber pulp, particularly
cellulose pulp, and/or pulp,
preferably in an amount of at least 30% w/w, for example, from 30 to 100% w/w
and/or from 30 to 95%
w/w, preferably from 50 to 100% w/w, and/or from 50 to 90% w/w, more
preferably from 60 to 95% w/w,
and particularly from 65 to 85% w/w, in each case based on the overall
quantity of fiber material in the
wet non-woven fabric.
Against this background, it is conceivable that the wet non-woven fabric
contains two or more
different fiber pulp and/or pulp types, which differ with regard to their
fineness. As a result, a particularly
accurate adjustment of the porosity and, associated therewith, a textile
fabric with a particularly effective
acoustic flow resistance is obtainable. It is also conceivable that the wet
non-woven fabric contains finely
ground synthetic pulps, e.g., made of viscose, polyolefin and/or aramid
fibers.
The non-woven material can be solidified mechanically, chemically and/or
thermally into the
non-woven fabric in a known manner. The chemical bond is particularly
preferably achieved by means
of a polymeric binder. Preferred fiber binders are polyacrylates, polyvinyl
acrylates, polystyrene
acrylates, polyvinyl acetates, polyethylene vinyl acetates (EVA),
acrylonitrile butadiene rubber (NBR),
styrene butadiene rubber (SBR), acrylonitrile butadiene styrene rubber (ABS),
polyvinyl chlorides,
polyvinyl ethylene vinyl chlorides, polyvinyl alcohols, polyurethanes, starch
derivatives, cellulose
derivatives, and their copolymers and/or mixtures. Accordingly, the non-woven
fabric is preferably a
chemically bonded non-woven fabric. By means of the fiber binder, a textile
fabric with high strength and
a good aging resistance can be obtained. The fiber binder can be applied by
impregnation, spraying, or
by other customary application methods.
The fiber binder can additionally contain conventional additives, such as a
flame retardant, e.g.,
metal hydroxides, such as aluminum hydroxide, diammonium hydrogen phosphate,
or other nitrogen
and/or phosphorus-based flame retardants, such as ammonium polyphosphates or
nitrogen-containing
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phosphoric acid salts. For fiber bonding, this can also be introduced in the
impregnation mixture via the
fiber binder.
The amount of fiber binder including the additives in the heat transfer
material lies preferably
between 10 and 70% w/w, more preferably between 20 and 50% w/w, and
particularly between 30 and
40% w/w, based on the overall weight of the heat transfer material.
The textile fabric can additionally contain corrosion inhibitors: Condensation
moisture in the
cooling ceiling application can particularly lead to damage to the metal
elements, such as aluminum
profiles, etc. The addition of a corrosion inhibitor can counteract such
damage.
In addition, the textile fabric can be made to be antimicrobial by means of a
biocidal additive.
During use, condensation moisture can lead to bacterial and fungal growth in
the textile fabric, which
can be prevented with said additive.
The basis weight of the heat transfer material lies preferably between 20 and
100g/m2, more
preferably between 40 and 70g/m2, and particularly between 45 and 60g/m2, each
measured according
to ISO 9073-1. For a good fire behavior and good acoustic properties, a
material with low basis weights,
i.e., with low material usage, is recommended.
The thickness of the heat transfer material lies preferably between 0.1 and
0.5mm, more
preferably between 0.15 and 0.4mm, and particularly between 0.2 and 0.3mm,
each measured
according to ISO 9073-2. A thin material, which simultaneously has good
acoustic properties, is
advantageous because it facilitates the processing, i.e., the lamination of
the material in perforated metal
ceilings.
The air permeability of the heat transfer material lies preferably between 100
and 3000L/m2/s,
more preferably between 200 and 1000L/m2/s, and particularly between 300 and
700L/m2/s, in each
case measured according to DIN EN ISO 9237 at 100Pa air pressure. These air
permeabilities result in
particularly good acoustic properties.
The tensile strength in at least one direction, preferably in the machine
direction, of the heat
transfer material is preferably from 20 to 300N/5cm, more preferably from 30
to 150N/5cm, and
especially from 50 to 100N/5cm, each measured according to ISO 9073 to 3.
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In a preferred embodiment of the invention, the textile fabric is metallized.
The metallization can
take place, for example, by a vacuum deposition process or electrochemical
deposition (electroplating).
Aluminum, copper, copper alloys, stainless steel, gold and/or silver have
proven to be particularly
suitable metals. Particularly preferred is the use of stainless steel because
it provides the textile fabric
with a particularly high aging resistance. In addition, a corrosion inhibitor
can be applied.
According to the invention, the heat transfer material comprises a graphite-
containing heat-
conducting coating. According to the invention, "graphite," in addition to
graphite in the narrower sense,
also refers to graphite-analogous compounds, particularly expanded graphite,
graphene, and hexagonal
boron nitride. In a preferred embodiment, the graphite is selected from
graphite in the form of a material
having multiple crystal planes and graphene, i.e., a material having only a
single crystal plane. The
graphite is preferably present in particle form. The average size of the
graphite particles can preferably
be 0.5 to 10 micrometers, particularly preferably 1 to 3 micrometers.
Practical tests have shown that this
results in a good compromise regarding workability and thermal conductivity.
Large graphite particles
are advantageous for good heat conduction, but they are more difficult to
process and preferably remain
on the surface of the textile fabric. This results in a low penetration depth
of the graphite in the heat
transfer material, which leads to a reduced conductivity perpendicularly to
the surface plane.
In one embodiment of the invention, the application weight of the heat-
conducting coating is 1
to 50g/m2, preferably 2 to 30g/m2, particularly preferably 5 to 15g/m2.
Practical tests have shown that
even with a low application weight of graphite, a distinct improvement of the
thermal conductivity can be
observed. At the same time, good acoustic properties can be achieved because
the porosity of the
material is retained.
The heat-conducting coating is applied preferably by providing the textile
fabric with an aqueous
graphite dispersion and the subsequent drying of said dispersion.
A binder, for example a polymeric binder, can be added to the graphite
dispersion in order to
improve the bonding with the textile fabric, e.g., polyacrylates, polyvinyl
acrylates, polyvinyl acetates,
polyethylene vinyl acetates (EVA), acrylonitrile butadienes (NBR), styrene
butadienes (SBR),
acrylonitrile butadiene styrenes (ABS), vinyl chlorides, ethylene vinyl
chlorides, polyvinyl alcohols,
polyurethanes, starch derivatives, cellulose derivatives, and their mixtures
and/or copolymers.
The graphite dispersion can be mixed with further additives, e.g., defoamers,
wetting agents,
surfactants which facilitate processing, bases and/or acids for adjusting the
pH value, flame retardants,
corrosion inhibitors and/or biocides. A wetting agent is used which is
preferably selected from the group
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consisting of: Glycerol, propylene glycol, sorbitol, trihydroxystearin,
phospholipids, ethylene oxide/fatty
alcohol ethers, ethoxylates of propylene oxide with propylene glycol, esters
of sorbitol and/or glycerol,
alkyl sulfonates, alkyl sulfosuccinates, and docusates, and their mixtures.
Practical experiments have shown that an amount of the wetting agent, relative
to the overall
quantity of graphite dispersion, in the range from 0.1 to 5% w/w, preferably
from Ito 4% w/w, particularly
from 1.5 to 3.5% w/w, results in a particularly uniform and homogeneous
wetting and a particularly good
penetration into the material.
All common application methods for fabrics can be used, for example,
impregnation, e.g., by
means of foulard; printing, e.g., flat or screen printing, rotary stencil
printing; kiss-coating, doctor blade,
etc.; spraying; the application can be one-sided or two-sided. Particularly
preferred is the coating, for
example, printing, particularly by means of screen printing or rotary stencil
printing. For example, the
heat-conducting coating can be applied to the textile fabric as a pattern
print. As a result, the heat
transfer material has a high thermal conductivity locally in the printed area,
while the unprinted areas
are acoustically particularly active, since their porosity is not impaired by
the application of the heat-
conducting coating. The degree of surface coating of the heat transfer
material by the heat-conducting
coating in the form of a pattern ranges preferably from 1 to 100%, preferably
from 10 to 60%, particularly
preferably from 30 to 50%. In a preferred embodiment, the printing is carried
out at least partially in the
form of continuous lines, preferably with a line width > 0.5mm, preferably
from 2.0 to 10.0mm, particularly
preferably from 4.0 to 7.0mm. This causes a rapid distribution of heat in the
plane of the textile fabric.
In a further preferred embodiment, the printing can take place at least
partially in the form of
discrete points, rods and/or non-continuous surfaces, preferably with a size
of < 100mm2, particularly
preferably from 1.0 to 50mm2, and in particular from 2.0 to 10mm2. Practical
tests have shown that this
results in a rapid heat transfer through the thickness of the material, i.e.,
perpendicularly to the plane of
the textile fabric.
The drying can be carried out with all common types of drying, e.g., contact
drying with a roller
dryer, circulating-air or through-air drying with a belt dryer; IR or
microwave drying, etc. In order to obtain
the porosity of the material and thus the good acoustic properties, through-
air drying is preferred. The
material can additionally be post-treated with compression rollers in order to
further improve the contact
of the graphite particles with each other and thus the thermal conductivity of
the material.
In a preferred embodiment of the invention, the heat transfer material has an
additional,
preferably discontinuous adhesive mass coating. Preferably, the adhesive mass
coating consists of a
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hot-melt adhesive. The discontinuity of the adhesive mass coating is
advantageous because it does not
significantly affect the acoustic effectiveness of the heat transfer material.
The adhesive mass coating
can be applied, for example, by sprinkling a hot-melt adhesive powder on the
heat transfer material and
a subsequent thermal fixation on the heat transfer material. Advantageously,
the hot-melt adhesive has
a melting point < 125 C.
The basis weight of the adhesive mass coating is preferably 5 to 50g/m2, more
preferably 10 to
40g/m2, particularly preferably 12 to 25g/m2.
The adhesive mass coating preferably consists essentially of a thermoplastic
polymer, e.g., a
substantially amorphous polyester or copolyester, a polyamide or copolyamide,
a polyurethane, a
polyolefin, polyethylene vinyl acetate, and/or mixtures, copolymers or
terpolymers thereof. In this case,
"essentially" refers to a portion of at least 70% w/w, preferably more than
80% w/w, based on the overall
mass of the adhesive mass coating.
The adhesive mass coating can additionally be provided with thermally
conductive additives,
e.g., by compounding the thermoplastic polymer with thermally conductive
fillers (e.g., carbon black,
graphite, metal powders, metal oxides, boron nitride, ceramic compounds, etc.)
in order to further
increase the thermal conductivity of the heat transfer material according to
the invention.
If the adhesive mass coating is applied to the textile fabric in the form of a
powder, the powder
can be processed as a mixture with other thermally conductive powders (e.g.,
metal powders, fine metal
spheres, metal oxide powders, ceramic powders, etc.) in order to further
increase the thermal
conductivity of the heat transfer material. The adhesive mass coating can also
contain a reactive ceramic
adhesive, having, for example, reactive silane groups.
The heat transfer material according to the invention is outstandingly
suitable for heat transfer
and simultaneous sound absorption in ceiling and/or wall elements,
particularly comprising a frame,
which can be fastened to the ceiling and/or wall, with a base, in which a
heating and/or cooling element
is arranged. In such case, the heat transfer material according to the
invention is preferably arranged
between the base of the frame and the heating or cooling element.
The ceiling and/or wall elements could be used in suspended, perforated and/or
slotted metal
ceiling and/or wall systems (also in wood or drywall ceilings, among others).
The use of the heat transfer
material according to the invention in the construction of raised floors is
also conceivable.
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In the following, the invention will be explained in more detail using several
examples.
Example 1: Production of a heat transfer material according to the invention
For producing a heat transfer material according to the invention, a textile
fabric in the form of
a wet non-woven fabric is initially produced. The overall basis weight of the
wet non-woven fabric is
48g/m2. In this case, the textile fabric has a fiber mixture of 70% w/w pulp
and 30% w/w glass fibers.
The fiber mixture contributes with a total of 25g/m2 to the basis weight of
the textile fabric. Furthermore,
the textile fabric has a fiber binder made of polyacrylate binder and flame
retardant with a basis weight
contribution of 23g/m2.
For producing the heat-conducting coating, a commercially available graphite
dispersion with
an average particle diameter of 2.5 micrometers and a solids content of 18%
w/w is used. The
application is carried out by means of rotary stencil printing and subsequent
drying in the through-air
oven. A rectangular diamond pattern is selected as the stencil. The average
width of the printed lines
on the wet non-woven fabric is 5.0mm, the heat-conducting coating coats 52% of
the surface. The
portion of graphite in the heat-conduction coating, measured according to
Example 4, is 80% w/w, which
corresponds to a portion of 14% w/w, based on the overall weight of the heat
transfer material.
The resulting heat transfer material has an overall weight of 57g/m2, a
thickness of 0.23mm, a
tensile strength in machine direction of 65N/5cm, an air permeability of
550L/m2/s at 100Pa, and a flow
resistance of 190Pa*s/m.
Example 2: Determination of the sound absorption coefficient of the heat
transfer material
For tests in the impedance tube, the heat transfer material is provided with
an adhesive mass
coating. The adhesive mass consists of epsilon-polycaprolactone, which is
powdered as a ground
powder with an average particle size of 150 micrometers onto the heat transfer
material and sintered in
the oven. In this case, the application quantity is 15g/m2.
The heat transfer material provided with the adhesive mass coating is
subsequently ironed onto
perforated, painted sheet steel, having a thickness of 0.5mm, a perforation
surface portion of 15%, and
a perforation diameter of 2.3mm. The sound absorption coefficient is
determined on the composite
material and a(0) is specified at a frequency of 1600Hz.
A sound absorption coefficient of a(0) = 0.7 at 1600Hz is determined.
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Example 3: Determination of the thermal conductivity of the heat transfer
material
The thermal conductivity of the heat transfer material, when compared to the
textile fabric
without a heat-conducting coating, is examined. The measurements are carried
out by means of the
plate method according to DIN 52612 on 6-fold stacked test specimens and
according to the hot-disk
method as a single layer according to ISO 22007-2.2:2008, Part 2.
Textile
Heat transfer material
Method thermal conductivity Unit fabric
Plate method W/(K*m) 0.06 0.08
Hot disk W/(K*m) 0.06 0.09
Example 4: Qualitative and quantitative determination of the graphite
A qualitative identification of the graphite is carried out by means of X-ray
angle distribution
(XRD) in accordance with DIN EN 13925-2 2003-07. For this purpose, X-ray
diffractograms of the heat
transfer material are recorded with CoKa radiation at 40kV and 35mA in the
angular range of 5 to 60
(2 theta). An conclusive identification is possible via the sharp reflexes at
30.78 (3.37A); 49.69 (2.13A);
52.19 (2.04A); 64.37 (1.68A); 93.21 (1.23A). The amount of graphite in the
heat transfer material or
the heat-conducting coating can be quantitatively determined by means of
thermogravimetric analysis
(TGA) according to DIN EN ISO 11358 2014-10. The sample is initially heated in
an inert nitrogen
atmosphere to 1000 C and cooled again to 300 C. The sample is subsequently
reheated under oxygen
to 1000 C. This last stage of combustion results in the combustion of the
graphite and (if present) the
carbon black. During this process, carbon black combusts in a temperature
range from 380 C to 700 C
and graphite at temperatures > 700 C. If the combustion of the carbon black is
not completely separated
from that of the graphite, the derivation of the thermogravimetric curve,
which then shows a reversal
point at 700 C, is used to determine the temperature ranges to be evaluated.
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