Note: Descriptions are shown in the official language in which they were submitted.
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FILE, ~J THIS ~ ID~D
l~ff TRANSLATION
Composite Aerogel Material that Contains Fibres
The present invention relates to a composite material that contains 5 to 97%-vol of aerogel
5 particles, at least one binder, and at least one fibre material, the diameter of the aerogel
particles being 2 0.5 mm, a process for m~mlf~cturing this, and the use thereof.
Because of their very low density, great porosity, and small pore diameters, aerogels, in
particular those with a porosity of over 60% and densities of less than 0.4 g/cm3, display an
lo extremely low thermal conductivity and for this reason are used as thermal insulation
materials, as described in EP-A-O 171 722, for example.
However, their high level of porosity leads to a low mechanical stability, both of the gel from
which the aerogel is dried, and of the dried aerogel itself.
In the broadest sense, i.e., when regarded as "gels with air as the dispersant," aerogels are
m~nllf~ctured by drying a suitable gel. When used in this sense, the term "aerogel" includes
aerogels in the narrower sense, such as xerogels and cryogels. A gel is design~ted as an
aerogel in the narrower sense if the liquid is removed from the gel at temperatures above the
20 critical temperature and starting from pressures that are above the critical pressure. In contrast
to this, if the liquid is removed from the gel sub-critically, for example with the formation of a
liquid-vapour boundary phase, then the resulting gel is, in many instances, referred to as
xerogel. It should be noted that the gels according to the present invention are aerogels in the
sense that they are gels with air as the dispersant.
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~he process that shapes the aerogel is concluded during the sol-gel transition. Once the solid
gel structure has been formed, the external shape can only be changed by size reduction, for
example, by pulverizing. The material is too brittle for any other form of stress.
5 For many applications, however, it is necessary to use the aerogel in certain shapes. In
principle, the production of moulded parts is possible even as the gel is being formed.
However, the replacement of solvents that is governed by diffusion (with respect to aerogels,
see, for example, US-A-4 610,863 and EP-A 0 396 0761; with respect to aerogel composite
materials, see, for example, WO 93/06044), and the drying--which is similarly governed by
0 diffusion--lead to production times that are economically unacceptable. For this reason, it is
appropriate to carry out a shaping stage after the production of the aerogel, which is to say,
after it has been dried, and to do this without any essential change of the internal structure of
the aerogel taking place with respect to the particular application.
5 For many applications, however, it in addition to good thermal insulation, an in~ ting
material is also required to provide good insulation against airborne sound. Typically, good
acoustic insulation is found in porous materials, the porosity of which lies on a macroscopic
scale (greater than 0.1 ~lm) for then the velocity waves of the sound are attenuated by friction
of the air on the walls of the pores. For this reason, monolithic materials without any
20 macroscopic porosity display only a very low level of acoustic damping. If a material is only
porous on a microscopic scale, as is the case with monolithic aerogels, the air cannot flow
through the pores; rather, the sound waves are transmitted on to the structure of the material
and this then conducts them with out any marked attenuation.
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DE-A 33 46 180 describes rigid panels from moulded bodies based on silicic acid aerogel
obtained by flame pyrolysis combined with rehlrorcement by long mineral fibres. However,
this silicic acid aerogel that is extracted from flame pyrolysis is not an aerogel in the above
sense since it is not m~mlf~ctured by drying a gel, and for this reason it has a completely
5 di~erenl pore structure. Mechanically, it is much more stable and for this reason can be
pressed without out destruction of the microstructure, although it has a greater thermal
conductivity than typical aerogels in the above sense. The surface of a moulded body such as
this is extremely delicate and for this reason must be hardened, as by the use of a binder, or by
being covered with a film.
EP-A-O 340 707 describes an in~ ting material with a density from 0.1 to 0.4 g/cm3 that
consists of at least 50%-vol silica aerogel particles with a diameter between 0.5 and 5 mm,
that are connected by means of at least one organic and/or inorganic binder. If the aerogel
particles are connected by the binder only on the contact surfaces, the in~ul~ting material that
results is not very stable in the mechanical sense since, under mechanical stress, the part ofthe
aerogel particle that is covered with the binder tears off, so that the particle is no longer
connected and the insulating material becomes cracked. For this reason, as nearly as possible
all the gaps between the aerogel particles should be filled with the binder. In the case of very
small proportions of binder, the resulting material is as stable as pure aerogels although cracks
20 can occur very easily if all the grains of the granulate are not sufficiently enclosed by the
binder.
In the case of a high volumetric percentage of binder that is favourable for achieving a low
degree of thermal conductivity, only very small proportions of the binder will remain in the
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spaces between the particles and, especially in the case of porous binders such as foams with
lower thermal conductivity, this will result in low mechanical stability. In addition, because of
reduced macroscopic porosity (between the particles), filling all the intervening spaces with
binder causes markedly reduced acoustic damping within the material.
EP-A-489 319 describes a composite foam with a low level of thermal conductivity, which
contains 20 to 80%-vol of silica aerogel particles, 20 to 80%-vol of a styrene polymer foam
with a density of 0.01 to 0.15 glcm3 that encloses the aerogel particles and connects them to
each other, and, if necessary, effective quantities of the usual additives. The composite foam
o that is produced in this way is resistant to compression but is not very rigid at high
concentrations of aerogel particles.
German patent applications DE-A 44 30 669 and DE-A-44 30 642 describe panels or mats of
a fibre-reinforced aerogel. Is it is true that, because of the very high proportion of aerogel,
these panels or mats display a very low level of thermal conductivity, but they require
relatively protracted production times because of the above-described diffusion problems.
The as-yet unpublished German patent application P 44 45 771.5 describes a non-woven fibre
textile-aerogel composite material that has at least one layer of non-woven fibre textile and
20 aerogel particles, and is characterised in that the non-woven fibre textile contains at least one
binary fibre material, the fibres of which are connected to each other and to the aerogel
particles by the low melting-point covering material. This composite material has a relatively
low level of thermal conductivity and a high level of macroscopic porosity and, because of
this, good acoustic damping, although the temperature range in which the material can be
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used, and its fire rating, are restricted by the use of binary fibres. In addition, the
corresponding composite materials, in particular complex moulded bodies, are not simple to
m~nl If ~ct~lre.
s For this reason, one of the tasks of the present invention was to produce a composite material
that is based on aerogel granulate, that has a lower level of thermal conductivity, and is both
mechanically stable and easy to m~nllf~chlre.
A further task of the present intention was to produce a composite material that is based on
o aerogel granulate, and that additionally displays good acoustic damping characteristics.
This task is solved by a composite material that contains 5 to 97%-vol aerogel particles, at
least one binder, and at least one fibre material, the diameter of the aerogel particles being
2 0.5mm.
The fibres or aerogels are either connected to each other and with each other by the binder, or
the binder serves as a matrix material in which the fibres and the aerogel particles are
embedded. Connection of the fibres and the aerogel particles to each other and with each other
by the binder and, optionally, including them in a binder matrix, results in a mechanically stable
20 material of very low thermal conductivity.
In contrast to a material that consists solely of aerogel particles that are connected by their
surfaces or embedded in a matrix of adhesive, most surprisingly, even small proportions of
fibres by volume can result in signifiGant mechanical strengthening, given an equal proportion
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of binder by volume, since they assume large part of the load. If a greater volume of fibres is
used with only a small amount of binder, it is possible to obtain a porous material in which the
fibres that are connected by the binder form a mechanically stable structure within which the
aerogel particles are embedded. The air pores that then result lead to a higher level of porosity,
s and thus to improved acoustic damping.
Natural fibres such as cellulose, cotton, or flax fibres, as well as synthetic fibres, can be used
as the fibre material; with respect to synthetic fibres, it is possible to use inorganic fibres such
as glass fibres, mineral fibres, silicon carbide fibres or carbon fibres; and to use polyester
o fibres, polyamide fibres, or polyaramid fibres as organic fibres. The fibres can be new, or
waste material such as shredded glass-fibre waste or waste rags.
The fibres can be straight or crimped, and be in the form of individual fibres, wadding, or a
non-woven or woven fibre material Non-woven fibre material and/or textiles can be contained
in the binder in the form of a cohesive whole and/or in the form of a number of smaller pieces.
The fibres can be round, trilobal, pentalobal, octalobal, in the form of strips, or be shaped like
fir trees, dumb bells, or otherwise. Hollow fibres can also be used.
20 The diameter of the fibres that are used in the composite material should preferably be smaller
than the mean diameter of the aerogel particles, so that a high proportion of aerogel is bound
into the composite material. The selection of very fine fibres makes the composite material
slightly flexible.
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It is preferred that fibres with diameters that are between 0.1 llm and 1 mm are used.
Typically, in the case of fixed proportions of fibres by volume, the use of smaller diameters
results in composite materials that are more resistant to breakage.
There are no restrictions on the lengths of the fibres. Preferably, however, the lengths of the
fibres should be greater than the mean diameter of the aerogel particles, i.e., at least 0. 5 mm.
In addition, mixtures of the above types can be used.
lo The stability and the thermal conductivity of the composite material increase as the proportion
of fibres increases. The volumetric percentage of the fibres should preferably by between 0.1
and 40%-vol, and in particular in the range between 0.1 and 1 5%-vol, depending on the
application.
In order to enhance the way in which they bind into the matrix, the fibres can be coated with
sizing or coupling agents, as is typically done in the case of glass fibres.
Suitable aerogels for the composition according to the present invention are those based on
metallic oxides, which are suitable for the sol-gel technique (C.J. Brinker, G.W. Scherer, Sol-
Gel Science. 1990, Chaps. 2 and 3), for example, Si or Al compounds or such as those based
on organic substances that are suitable for the sol-gel technique, such as melamine-
formaldehyde condensates (US-A-5 086 085) or resorcinformaldehyde condensates (US-A-4
873 218). They can also be based on mixtures ofthe above-cited materials. It is preferred
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that aerogels cont~ining Si compounds, especially SiO2 aerogels, and in particular SiO2
aerogels, be used.
The aerogel can contain IR opacifiers, such as soot, titanium dioxide, iron oxide, or zirconium
dioxide, as well as mixtures of these, in order to reduce the radiation contribution to thermal
conductivity.
Furthermore, the thermal conductivity of the aerogels decreases as porosity increases and
density decreases; this applies down to densities in the vicinity of 0.1 g/cm3. For this reason,
o aerogels with porosities of greater than 60% and densities between 0.1 and 0.4 g/cm3 are
especially prerelled. It is preferred that the thermal conductivity of the aerogel granulate be
less than 40 mW/mK, and in particular less than 25 mW/mK.
In a preferred embodiment, hydrophobic aerogel particles are used; these can be obtained by
incorporating hydrophobic surface groups on the pore surfaces of the aerogels during or after
production of the aerogels.
In the present application1 the term "aerogel particles" is used to designate particles that are
either monolithic, i.e., are composed of one piece, or, essentially, aerogel particles with a
diameter that is smaller than the diameter of the particles that are joined by a suitable binder
and/or compressed to form a larger particle. The size of the grains will depend on the use to
which the material is put. In order to achieve a higher level of stability, the granulate should
not be too coarse, and it is preferred that the diameter of the grains be smaller than 1 cm and,
in particular, smaller than 5 mm.
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On the other hand, the diameter of the aerogel particles should be greater than 0. 5 mm in
order to avoid the difficulties associated with h~n~lling a very fine powder of low density. In
addition, as a rule, during processing, the liquid binder penetrates into the upper layers of the
aerogel that, in this area, loses its great effectiveness as insulation. For this reason, the
s proportion of macroscopic particle surface to particle volume should be as small as possible,
which would not be the case were the particles too small.
In order to achieve low thermal conductivity, on the one hand and, on the other, to achieve
adequate mechanical stability of the composite material, the volumetric percentage of aerogel
0 should preferably by between 20 and 97%-vol, and especially between 40 and 95%-vol, with
greater volumetric percentages leading to lower thermal conductivity and strength. In order to
achieve a high level of porosity of the overall material, and enhanced acoustic absorption, air
pores should be incorporated in the material, to which end the volumetric percentage of
aerogel should preferably be less than 85%-vol.
lS
Granulate with a favourable bimodal grain size distribution can be used to achieve a high
volumetric percentage of aerogel. Other distributions could also be used, depending on the
application, e.g., in the area of acoustic damping.
The fibres or aerogel particles are connected to each other and the fibres and aerogel particles
are connected to each other by at least one binder. The binder can either serve only to join the
fibres and aerogel particles to each other and with each other, or can serve as matrix material.
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In principle, all known binders are suitable for m~nllf~cturing the composite materials
according to the present invention. Inorganic binders such as water glass adhesive, or organic
binders or mixtures thereof can be used. The binder can also contain additional inorganic
and/or organic components.
Suitable organic binders are, for example, thermoplastics such as polyolefins or polyolefin
waxes, styrene polymers, polyamides, ethylenevinylacetate copolymers or blends thereof, or
duroplasts such as phenol, resorcin, urea, or melamine resins. Adhesives such as fusion
adhesives, dispersion adhesives (in aqueous form, e.g., styrene butadiene, and styrene acryl
o ester copolymers), solvent adhesives or plastisols can also be used, also suitable are reaction
adhesives, e.g., in the form of unary systems such as heat-hardened epoxy resins,
formaldehyde condensates, polyimides, polybenzimidazoles, cyanacrylates, polyvinylbutyrals,
polyvinyl alcohols, anaerobic adhesives, polyurethane adhesives, and moisture hardened
silicones, or in the form of binary systems such as methacrylates, cold-hardened epoxy resins,
5 binary silicones and cold-hardened polyurethanes.
It is preferred that polyvinylbutyrals and/or polyvinyl alcohols be used
It is prerell ed that the binder be so selected that if it is in liquid form during specific phases of
20 the processing, within this time frame it cannot penetrate into the very porous aerogel, or can
do so to only an in~i~nificant extent. Penetration of the binder into the interior of the aerogel
particles can be controlled by the selection of the binder and by regulating processing
conditions such as pressure, temperature, and mixing time.
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lf the binder forms a matrix in which the aerogels and fibres are embedded, then, because of
their low thermal conductivity, porous materials with densities of less than 0.75 g/cm3, such as
foams, preferably polymer foams (e.g., polystyrene or polyurethane foams) are used.
5 In order to achieve the good distribution of the binder in the interstices when large proportions
of aerogel are used, and in order to achieve good adhesion, in the event that a solid form of
binder is used, the grains of the binder should preferably be smaller than those of the aerogel
granulate. Processing at greater pressure may also be required.
o If the binder has to be processed at elevated temperatures, as in the case of fusion adhesives or
reaction adhesives such as, for example, mel~mineformaldehyde resins, then the binder must be
so selected that its fusion temperature does not exceed the fusion temperature of the fibres.
In general, the binder is used at a rate of 1 to 50%-vol of the composite material, preferably at
a rate of 1 to 30%-vol. The selection of the binder will be governed by the mechanical and
thermal demands placed on the composite material, as well as requirements with respect to
fire protection.
The binder can also contain effective quantities of other additives such as, for example,
20 colouring agents, pigments, extenders, fire retardant agents, synergists for fire protection
agents, anti-static agents, stabilizers, softeners, and infra-red opacifiers.
In addition, the composite material can also contain additives that are used to manufacture it
or which are formed when it is m~nllfactured; such substances can include slip agents for
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compression, such as zinc stearate, or the reaction products formed from acid or acid- cleaving
hardening accelerators, when resins are used.
The fire rating of the composite material is determined by the fire ratings of the aerogel, the
fibres, and the binder, and--optionally--by that of the other substances contained in it. In order
to arrive at the most favourable fire rating for the composite material, non-fl~mm~ble fibres
such as glass or mineral fibres, or fibres that are difficult to ignite, such as TREVIRA CS~, or
melamine resin fibres, aerogels based on inorganic substanes, preferably based on SiO~, are -
used; also used are binders that are difficult to ignite, such as inorganic binders of urea and
o melamineformaldehyde resins, silicon resin adhesives, polyimide and polybenzimidazol resins.
If the material is used in the form of flat structures such as panels or mats, these can be
covered on at least one side with at least one covering layer in order to improve its surface
properties, and to make it more robust, form it as a vapour barrier, or protect it against
soiling. These covering layers can also enhance the mechanical stability of moulded parts made
from the composite material lf covering layers are used on both sides. these can either be
identical or different
All materials l;nown to the practitioner si~ilied in the art are suitabie for use as covering layers.
~o They can be non-porous and thereby act as a vapour barrier, e.g., plastic fiims, preferably
metal films, or metallized plastic films that reflect thermal radiation. It is also possible to use
porous covering layers such as porous films, papers, textiles, or non-woven fabrics that permit
air to penetrate into the material and thereby enhance its acoustic damping properties.
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The covering layers can themselves consist of a plurality of layers. The covering layers can be
secured with the binder that joins the fibres and the aerogel particles to each other and with
each other, although another, different adhesive can also be used.
s The surface of the composite material can be also be sealed and consolidated by incorporating
at least one suitable material into a surface layer.
Suitable materials are thermoplastic polymers such as polyethylene and polypropylene, or
resins such as melamineformaldehyde resins.
1()
It is preferred that the composite materials according to the present invention have a thermal
conductivity that is between 10 and 100 mW/mK, especially in the range from 10 to 50
mW/mK, and in particular in the range from 15 to 40 mW/mK.
5 A further task of the present invention was to provide for a process to m~nllf~ctllre the
composite materials according to the present invention.
If the binder is initially in the form of a powder that fuses at an elevated temperature and, if
necessary, at an elevated pressure and then reacts, as in the case of reaction adhesives, then
2() the composite material can be obtained as follows: aerogel particles, fibre material, and the
binder are mixed using conventional mixers. The mixture is then subjected to a shaping
process. The mixture will be hardened in the mould by heating, if necessary under pressure,
depending on the type of binder, e.g., in the case of reaction adhesives, or in the case of fusion
adhesives by being heated to a point above the melting point of the binder. A material that is
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porous on a macro scale can be obtained, in particular, according to the following procedure:
in the event that the fibres are not already in the form of wadding (e.g., small tufts of cut fibres
or small pieces of a film) it will be processed to forrn small tufts by methods familiar to the
practitioner skilled in the art. Even in this step it is, if necessary, possible to incorporate the
5 aerogel granulate between the fibres. Subsequently, these tufts together with the binder and,
optionally, the aerogel particles, are mixed, for example in a mixer, until such time as the
binder and, optionally, the aerogel particles are distributed as evenly as possible between the
fibres. The compound is then placed in a mould and, if necessary under pressure, heated to a
temperature that, in the case of fusion adhesives, is above the fusion temperature of the
10 adhesive and, in the case of reaction adhesives, is above the temperature that is required for
the reaction. Once the binder has fused or has reacted, the material is cooled. It is preferred
that polyvinylbutyrals are used here. The density of the composite material can be increased by
using a higher pressure.
5 In one prerelled embodiment, the mixture is compressed. When this is done, the practitioner
skilled in the art can select the press and the pressing die that are best suited for the particular
application. If necessary, the practitioner can add known slip agents such as zinc stearate to
the pressing process when melamineformaldehyde resins are used. The use of vacuum presses
is particularly advantageous because of the large amount of air in the moulding compound that
20 contains aerogels. In a preferred embodiment, the moulding compound that contains the
aerogel is compressed to form panels. In order to avoid the compound baking onto the
pressure ram, the mixture that contains the aerogel and which is to be compressed can be
separated from the pressure ram by release paper. The mechanical strength of the panels that
contain the aerogel can be enhanced by lAminAtin~ mesh fabrics, non-woven fabrics, or papers
14
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onto the surface of the panel. These mesh textiles, non-woven fabrics, or papers can be applied
to the panels that contain aerogel subsequently, in which case the mesh fabrics, non-woven
textiles, or papers are previously impregn~ted with suitable binder or adhesive, and then
bonded to the surface of the panel in a heated press when under pressure. In addition, in one
s prerel l ed embodiment, this can be done in one step by laying up the mesh textiles, non-woven
textiles, and paper, optionally previously impregn~ted with a suitable binder or adhesive, in the
press mould and applying them to the moulding compound that contains the aerogel and which
is to be pressed, and then subjecting them to pressure and elevated temperatures to form a
composite panel that contains aerogels.
Depending on the binder that is used, in any moulds, the pressing generally takes place at
pressures from 1 to 1000 bar and at temperatures from 0 to 300~C.
In the case of phenol, resorcin, urea, and melamineformaldehyde resins, pressing preferably
takes place at pressures from 5 to 50 bar, especially at 10 to 20 bar, and at temperatures
preferablyfrom 100to200~C, especiallyfrom 130to 190 ~C, andinparticularbetween 150
and 175~C.
If the binders is initially in liquid form, the composite material can be obtained in the following
way: the aerogel particles and the fibre material are mixed using conventional mixers. The
20 mixture so obtained is then coated with the binder, for example, by spraying, placed in a
mould, and then hardened in this mould. Depending on the type of binder that is used, the
mixture is hardened under pressure by heating and/or by evaporating offthe solvent or
dispersant that is used. It is preferred that the aerogel particles be swirled with the fibres in a
flow of gas. A mould is then filled with the mixture, with the binder being sprayed on during
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the filling process. A material that is porous on a macro scale can be obtained in the following
way: in the event that the fibres are not already in bulked form (e.g., small tufts of cut fibre or
small pieces of a non-woven fabric), they are processed into small tufts using methods that are
familiar to the practitioner skilled in the art. Even in this step the aerogel granulate can, if
5 necessary, be incorporated between the fibres. Otherwise, these tufts are mixed with the
aerogel granulate in a mixer until the aerogel particles have been distributed as evenly as
possible between the fibres. In this step, or subsequently, the binder is sprayed, divided as
finely as possible, onto the mixture and the mixture is then placed in a mould and heated--if
necessary under pressure--to the temperature that is required for bonding. Subsequently, the
0 composite material is dried using a conventional process.
If a foam is used as binder, the composite material can be produced as follows, depending on
the type of foam that is used.
If the foam is m~nllf~ctured in a mould by the expansion of expandable granulate grains, as in
the case of expanded polystyrene, all the components can be thoroughly mixed and then
typically heated, advantageously by means of hot air or steam. Because of the expansion of the
particles, the pressure in the mould increases, which means that the interstices are filled with
foam and the aerogel particles are fixed in the composite. After cooling, the moulded part of
20 composite material is removed from the mould and dried, should this be necessary.
If the foam is m~m1f~ctl Ired by extrusion or expansion of a non-viscous mixture, with
subsequent solidification, the fibres can be mixed into the liquid. The aerogel particles are
mixed into the res~lltin~ liquid, which then foams.
16
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If the material is to be provided with a covering layer, this can then be laid up in a mould, prior
to or after the filling process, so that coating and shaping can take place in one step, with the
binder used for the composite material also being used as binder for the coating. However, it is
also possible to provide the composite material with a covering layer in a subsequent step.
The shape of the moulded part that consists of the composite material according to the present
invention is in no way restricted; in particular, the composite material can be formed into
panels.
o Because of the high percentage of aerogel and their low thermal conductivity, the composite
materials are particularly well suited as thermal insulation.
Formed into panels, the composite material can be used as sound absorbing material, either
directly in or in the form of resonance absorbers for acoustic insulation. In addition to the
5 damping of the aerogel material, depending on the porosity that results from macroscopic
pores, additional damping is provided as a result of air friction on these macroscopic pores in
the composite material. The macroscopic porosity can be reg~ ted by ch~nging the proportion
of fibres and their diameter, the grain size and proportion of aerogel particles, and the type of
binder. The frequency function of acoustic damping and its degree can be changed by selection
20 of the covering layer, the thickness of the panel, and its macroscopic porosity, which is done in
a manner known to the practitioner skilled in the art.
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Because of its macroscopic porosity and, in particular, its great porosity, and the specific
surface of the aerogel, the composite materials according to the present invention are also
suitable as adsorption materials for liquid, vapours, and gasses.
5 The present invention will be described in greater detail below on the basis of exemplary
embodiments without, however, being restricted to these:
Example 1
Moulded part of aerogel, polyvinylbutyral, and fibres
lo 90%-vol hydrophobic aerogel granulate, 8%-vol Mowital~) (Polymer F) polyvinylbutyral
powder and 2%-vol Trevira~ high-strength fibres are thoroughly mixed.
The hydrophobic aerogel granulate has an average grain size in the range from 1 to 2 mm, a
density of 120 kg/m3, a BET surface of 620 m2/g and a thermal conductivity of 11 mW/mK.
The bottom ofthe press mould, with a base area of 30 cm x 30 cm, is covered with release
paper. The moulding material that contains the aerogel is applied evenly to this, and the whole
is then covered with release paper, after which it is pressed to a thickness of 18 mm at 220~C
for a period of 30 minutes.
2()
The moulded part obtained in this way has a density of 269 kg/m3 and a thermal conductivity
of 20 mW/mK.
18
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Example 2
Moulded part of aerogel, polyvinylbutyral, and recycling fibres
80%-vol hydrophobic aerogel granulate as described in Example 1, 10%-vol Mowital~
(Polymer F) polyvinylbutyral powder and 1 0%-vol of coarsely shredded polyester fibre
s remnants as the recycling fibres are thoroughly mixed.
The bottom of the press mould, with a base area of 30 cm x 30 cm, is covered with release
paper. The moulding material that contains the aerogel is applied evenly to this, and the whole
is then covered with release paper, after which it is pressed to a thickness of 18 mm at 220~C
lo for a period of 30 minutes.
The moulded part obtained in this way has a density of 282 kg/m3 and a thermal conductivity
of 25 mW/mK.
Example 3
Moulded part of aerogel, polyvinylbutyral, and recycling fibres
50%-vol hydrophobic aerogel granulate as described in Example 1, 10%-vol Mowital~
(Polymer F) polyvinylbutyral powder and 40%-vol of coarsely shredded polyester fibre
20 rçmn~nt.c as the recycling fibres are thoroughly mixed.
The bottom ofthe press mould, with a base area of 30 cm x 30 cm, is covered with release
paper. The moulding material that contains the aerogel is applied evenly to this, and the whole
is then covered with release paper, after which it is pressed to a thickness of 18 mm at 220~C
2s for a period of 30 minutes.
19
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The moulded part obtained in this way has a density of 420 kg/m3 and a thermal conductivity
of 55 mW/mK.
Example 4
5 Moulded part of aerogel, polyethylene wax, and fibres
60 %-wt of hydrophobic aerogel granulate as described in Example 1, and 38%-wt Ceridust
130 polyethylene wax powder, and 2%-vol Trevira~) high strength fibres are thoroughly
mixed.
lo The bottom of the press mould, with a base area of 12 cm x 12 cm, is covered with release
paper The moulding material, which contains the aerogel, is applied evenly to this, and the
whole is then covered with release paper. A pressure of 70 bar is applied at 170~C for 30
minutes.
5 The moulded part obtained in this way has a thermal conductivity of 25 mW/mK
Example S
Moulded part of aerogel, polyethylene wax, and fibres
50 %-wt of hydrophobic aerogel granulate as described in Example 1, and 48%-wt Hoechst-
20 Wachs PE 520 polyethylene wax powder, and 2%-vol Trevira~ high strength fibres are
thoroughly mixed.
The bottom of the press mould, with a base area of 12 cm x 12 cm, is covered with release
paper The moulding material, which contains the aerogel, is applied evenly to this, and the
CA 02231428 1998-03-09
whole is then covered with release paper. A pressure of 70 bar is applied at 180~C for 30
minutes.
The moulded part obtained in this way has a thermal conductivity of 28 mW/mK
Example 6
Moulded part of aerogel, polyvinylalcohol, and fibres
90 %-wt of the hydrophobic aerogel granulate as described in Example 1, 8 %-wt of a
0 polyvinylalcohol solution, and 2%-vol Trevira(g) high strength fibres are thoroughly mixed.
The polyvinylalcohol solution consists of 10 %-wt Type 40-88 Mowiol~), 45 %-wt water, and
45 %-wt ethanol.
The bottom of the press mould, with a base area of 12 cm x 12 cm, is covered with release
paper. The moulding material that contains the aerogel is applied evenly to this, and the whole
is then covered with release paper, after which it is pressed at a pressure of 70 bar for a
period of 2 minlltes, and then dried
The moulded part obtained in this way has a thermal conductivity of 24 mW/mK.
The thermal conductivity of the aerogel granulates was measured by a hot-wire method
(see, for example, O. Nielsson, G. Ruschenpohler, J. GroJ3, J. Fricke, High Temperatures -
High Pressures, Vol. 21, pp. 267 - 274 (1989)). The thermal conductivity of the moulded
parts was established in accordance with DrN 52612.
