U.S. patent application number 13/623532 was filed with the patent office on 2013-03-21 for composite materials comprising a polymer matrix and granules embedded therein.
This patent application is currently assigned to Evonik Goldschmidt GmbH. The applicant listed for this patent is Evonik Goldschmidt GmbH. Invention is credited to Christian Eilbracht, Martin Glos, Georg Markowz, Carsten Schiller, Thorsten Schultz.
Application Number | 20130068990 13/623532 |
Document ID | / |
Family ID | 46940235 |
Filed Date | 2013-03-21 |
United States Patent
Application |
20130068990 |
Kind Code |
A1 |
Eilbracht; Christian ; et
al. |
March 21, 2013 |
COMPOSITE MATERIALS COMPRISING A POLYMER MATRIX AND GRANULES
EMBEDDED THEREIN
Abstract
The present invention provides composite materials comprising a
polymer matrix comprising one or more polymers and, embedded into
the polymer matrix, granules which preferably after embedding have
at least one cavity which is closed off relative to the ambient
environment and in which there is an underpressure relative to the
standard pressure of 1 bar (100 kPa), a method for producing such
composite materials, and use as insulating material.
Inventors: |
Eilbracht; Christian;
(Herne, DE) ; Schiller; Carsten; (Muelheim an der
Ruhr, DE) ; Glos; Martin; (Borken, DE) ;
Markowz; Georg; (Alzenau, DE) ; Schultz;
Thorsten; (Hassenroth, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Evonik Goldschmidt GmbH; |
Essen |
|
DE |
|
|
Assignee: |
Evonik Goldschmidt GmbH
Essen
DE
|
Family ID: |
46940235 |
Appl. No.: |
13/623532 |
Filed: |
September 20, 2012 |
Current U.S.
Class: |
252/62 |
Current CPC
Class: |
C08K 7/26 20130101; B29C
44/12 20130101; E04B 2001/742 20130101; F16L 59/065 20130101; C08J
2205/05 20130101; Y02B 80/10 20130101; E04B 1/803 20130101; C08K
7/22 20130101; Y02B 80/12 20130101; C08J 2375/04 20130101; C08J
9/0066 20130101; Y02A 30/242 20180101; C08K 9/10 20130101 |
Class at
Publication: |
252/62 |
International
Class: |
E04B 1/78 20060101
E04B001/78 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 20, 2011 |
DE |
DE102011083011.1 |
Claims
1. A composite material comprising a polymer matrix comprising one
or more polymers and, embedded into the polymer matrix, granules
which have at least one cavity which is closed off relative to an
ambient environment and in which there is an underpressure relative
to a standard pressure of 1 bar (100 kPa).
2. The composite material according to claim 1, wherein the
underpressure is less than 500 mbar.
3. The composite material according to claim 1, wherein the at
least one cavity is closed off relative to the ambient environment
by a bather composed of a glasslike compound or of a plastic-metal
composite.
4. The composite material according to claim 1, wherein the polymer
matrix is a closed-cell polymer foam matrix.
5. The composite material according to claim 4, wherein the polymer
foam matrix is a rigid polyurethane or polyisocyanurate foam.
6. The composite material according to claim 1, wherein the
granules comprise a material having a BET surface area of greater
than 5 m.sup.2/g,.
7. The composite material according to claim 1, wherein the
granules consist substantially of compacted powders of fumed silica
or precipitated silica.
8. A method for producing a composite material comprising mixing a
material for producing a polymer matrix with granules having at
least one cavity which is closed off relative to an ambient
environment and in which there is an underpressure relative to a
standard pressure of 1 bar (100 kPa), and embedding the granules
within the polymer matrix.
9. The method according to claim 8, wherein said embedding the
granules comprises subjecting open-pored porous granules to an
underpressure and furnishing the open-pored porous granules with an
air- or gas-impermeable barrier layer.
10. A method for producing a composite material comprising
subjecting unencapsulated, open-porously porous granules to an
underpressure; and embedding said granules into a polymer matrix,
wherein the embedding comprises enveloping the granules with said
polymer matrix, while maintaining said underpressure in cavities of
the granules.
11. The method according to claim 10, wherein the polymer matrix is
a polymer or a mixture of polymers or are the reactants for
generating the polymer or polymers.
12. The method according to claim 10, wherein the polymer matrix is
a polymer or a mixture of polymers or are the reactants for
generating the polymer or polymers.
13. The method according to claim 8, further comprising
foaming.
14. The method according to claim 10, further comprising
foaming.
15. An insulating material comprising a composite material
according to claim 1.
16. The insulating material according to claim 15, wherein said
insulating material is used for insulating buildings, including
windows, doors and roller-shutter boxes, for insulating space, air,
open-water and/or land vehicles, for insulating pipelines, or for
insulating parts of cooling or heating units or assemblies,
refrigeration equipment, hot-water/coolant reservoirs,
swimming-pool covers and swimming-pool insulation systems.
17. An article comprising a composite material according to claim
1.
Description
FIELD OF THE INVENTION
[0001] The present invention is directed to composite materials
comprising a polymer matrix comprising one or more polymers and,
embedded into the polymer matrix, granules or shapes which
preferably after embedding have at least one cavity which is closed
off relative to the ambient environment and in which there is an
underpressure relative to the standard pressure of 1 bar (100 kPa).
The present intention also relates to a method for producing such
composite materials, and to use of such composite materials as an
insulating material.
BACKGROUND OF THE INVENTION
[0002] In the field of thermal insulation, vacuum insulation panels
(VIPs) manufactured by enveloping a porous core material--for
example, compacted fumed silica (Aerosil), fibre mats or open-cell
foams--with a gas-tight sheet material and then carrying out
evacuation are known. These panels permit excellent thermal
insulation (thermal conductivities<3.5* 10.sup.-3
W*m.sup.-1*K.sup.-1, determined in accordance with DIN 52 612, at
10.degree. C., are realisable), but the insulating effect suffers
markedly if the gas-tight sheet is damaged. These panels,
consequently, have to be produced with particular desired
dimensions and installed in a protected fashion
(http://www.va-q-tec.com/). Moreover, the gas-tight sheets
generally have a finite barrier sealing quality, and so there is
also a more or less rapid age-related deterioration in the
insulating effect.
[0003] Conversely, rigid polyurethane foams have very good
processing qualities. Insulating boards made of rigid polyurethane
can be cut to any size, or the foam can be produced directly in the
cavity that is to be filled. The latter process is commonplace in
the case of refrigeration equipment (fridges). The insulating
properties, however, are well below those of vacuum insulation,
since minimal thermal conductivities of around 20*10.sup.-3
W*m.sup.-1*K.sup.-1 are attained
(http://www.waermedaemmstoffe.com/).
[0004] The topic nexus of energy efficiency and climate protection
that is presently under the spotlight has led to increased
interest, not least among the manufacturers of refrigeration
equipment, in innovative solutions for significant efficiency
boosting--in particular by improved thermal insulation using VIPs.
Solutions currently under discussion envisage the use of VIPs in
combination with rigid PU foam; i.e., the panels are inserted into
the cavity between inner liner and outer sheet-steel skin and then
surround-foamed with polyurethane (PU). In this way, the
established production process for refrigerators can be essentially
retained
(http://www.appliancedesign.com/Articles/Article_Rotation/BNP_GUID.sub.---
9-5-2006_A.sub.--10000000000000893355).
[0005] In the context of the thermal insulation of buildings, the
use of VIPs is substantially more problematic, since VIPs cannot be
cut to size and when the gas-tight outer skin is damaged they loose
their effect, yet the insulating boards are required in different
sizes and shapes. In the buildings sector, moreover, the lifetime
requirements are generally much higher.
SUMMARY OF THE INVENTION
[0006] The present invention provides an insulating material which
combines the superlative thermal insulation of vacuum insulation
panels with the establishedly multi-faceted processing
possibilities of polyurethane foams.
[0007] Surprisingly it has been found that a polymer matrix into
which evacuated granules or (generally) shapes have been embedded
can be used as an insulating material which has both of the above
mentioned properties.
[0008] The present invention accordingly provides composite
materials comprising a polymer matrix comprising one or more
polymers and, embedded into the polymer matrix, granules and/or
shapes which have at least one cavity which is closed off relative
to the ambient environment and in which there is an underpressure
relative to the standard pressure of 1 bar (100 kPa).
[0009] The present invention also provides a method for producing a
composite material, in which a material for producing a polymer
matrix is mixed with granules and/or shapes having at least one
cavity which is closed off relative to the ambient environment and
in which there is an underpressure relative to the standard
pressure of 1 bar (100 kPa), and from this mixture a polymer matrix
is generated in which the granules are embedded.
[0010] The present invention further provides the use of the
inventive composite material as an insulating material, and also
articles which comprise the inventive composite material.
[0011] The composite materials of the invention have the advantage
that they can be manufactured in virtually any imaginable shape and
size. Moreover, the composite materials of the invention can be cut
to any desired sizes and shapes without any critical loss in their
good specific insulating properties. Consequently, the composite
materials of the invention can be employed in a substantially more
multi-faceted way than the vacuum insulation panels known from the
prior art, but at the same time provide better insulation than pure
PU foam insulation materials.
[0012] The composite materials of the invention also have the
advantage, that they have a thermal conductivity (determined in
accordance with DIN 52 612, at 10.degree. C.) of less than
18*10.sup.-3 W*m.sup.-'*K.sup.-1.
DETAILED DESCRIPTION
[0013] The composite materials of the invention, the method for
their production, and the uses thereof are described by way of
example below, without any intention that the invention should be
confined to these exemplary embodiments. Where, below, ranges,
general formulae or classes of compound are indicated, the
intention is that they should encompass not only the corresponding
ranges or groups of compounds that are explicitly stated, but also
all sub-ranges and sub-groups of compounds which are obtainable by
extraction of individual values (ranges) or compounds. Where
documents are cited in the context of the present description, the
intention is that their content, especially with regard to the
substantive subject-matter referred to, should in its entirety form
part of the disclosure content of the present invention. If average
values are indicated below, the average in question, unless
otherwise specified, is the numerical average. If figures in per
cent are indicated below, then the percentage in question, unless
otherwise specified, is % by mass.
[0014] The composite materials of the invention are distinguished
by the fact that they comprise a polymer matrix comprising one or
more polymers and, embedded into the polymer matrix, are granules
or shapes having at least one cavity which is closed off relative
to the ambient environment and in which there is an underpressure
relative to the standard pressure of 1 bar (100 kPa). The
underpressure is less than 500 mbar, preferably from 0.001 to 200
mbar, and more preferably from 0.1 to 100 mbar. The mass fraction
of the granules in the composite material is preferably 20% to 99%
by mass, and more preferably 50% to 90% by mass. The granules or
shapes may consist substantially of one or more organic materials
and/or of one or more inorganic materials. The expression
"substantially" here is intended to denote a %-by-mass fraction of
at least 70%, preferably at least 90%, based on the total mass of
the granule. The granules preferably consist substantially of
inorganic materials, more particularly of oxygen-containing
compounds or salts of metals or semi-metals. Preferred
oxygen-containing compounds are aluminium oxides or
aluminosilicates or silicon dioxides or silicas, more particularly
fumed or precipitated silicas. Especially preferred granules
consist substantially of compacted powders of fumed silica and/or,
preferably, of precipitated silica. Included in addition may be
various opacifiers such as, for example, SiC, carbon black,
graphite, iron oxides or TiO.sub.2, alone or in combination, with
fractions of preferably 1% to 30% by mass, more preferably 5% to
10% by mass (based on the granule or powder mass). The presence of
opacifier may possibly achieve a reduction in radiative thermal
conduction. Furthermore, for the purpose of mechanical
stabilization, the granules or shapes may comprise fibres, such as
glass, ceramic or polymer fibres, for example, and also auxiliaries
from the granulation process, examples include binders.
[0015] The granules preferably have an average grain size d.sub.50
of 50 .mu.m to 100 mm, preferably from 100 .mu.m to 50 mm and more
preferably from 0.5 mm to 20 mm (determined in accordance with DIN
66165-2). In some embodiments of the present invention and in order
to obtain a maximum filling level and/or for improving processing,
it may be useful to use specific distributions of the grain-size
distribution, such as bimodal or trimodal distributions, for
example. Alternatively to granules, having a granule-grain shape
and size distribution dependent on the granulating process, shapes
with defined geometry, examples include spheres or cuboids, can be
used. In this case, corresponding ranges as for the average grain
size of the granules apply in respect of the preferred dimensions
in the three directions of space.
[0016] In accordance with the present invention, the individual
grains of the granule or shapes each must have at least one cavity.
From a morphological view point, the cavity in question may
comprise a single cavity surrounded by solid material, as in the
case of a hollow sphere, for example, or may comprise a plurality
of isolated closed pores, or else may comprise a network of open
pores and/or channels. The granule grains or shapes preferably
consist substantially of compacted powders, and so an open pore
system is maintained between the individual primary particles. In
some embodiments, powders which are very finely divided or even
nanostructured, producing correspondingly finely structured pore
systems, can be used. Preferred powders or materials used have a
BET surface area of greater than 5 m.sup.2/g, more preferably of 50
m.sup.2/g to 1000 m.sup.2/g (in accordance with ISO 9277).
[0017] The granules present in the polymer matrix preferably have a
porosity .PHI., i.e., a ratio of the volume of the closed-off
cavity to the total volume of the granule grain, of 50% to 99.9%,
more preferably of 75% to 99%. The total volume of the granule or
of a granule grain or shape with closed-off cavity can be
ascertained by determining the displaced volume of a suitable
liquid, e.g., water or ethanol. The volume of the closed-off
cavities can be determined by subtracting the volume of the granule
solids from the total volume. The volume of the solids can be
calculated easily from the ascertained mass if the density of the
solids material is known, or else the granules whose total volume
has been determined are ground to an average grain size d.sub.50 of
20 .mu.m, using a mill or mortar, and the volume or density of the
resultant powder is ascertained.
[0018] The cavity or cavities present in the granule grains or
shapes may be closed off relative to the ambient environment by a
gas-impermeable barrier composed of an appropriate material. In the
case of granule grains or shapes with a closed porosity, it is
generally the material of the granule grain itself that takes on
this barrier function. In the case of granules or shapes with an
open porosity, each individual grain, advantageously, is
encapsulated by being enveloped with a suitable material, which may
differ from the base material of the granule or shape. The material
may be selected, for example, from plastics, metals, glasses or a
combination of these substances. In some embodiments of the present
invention and in order to maintain the underpressure in the cavity
or pore system for as long as possible, it may be advantageous if
the barrier is constructed of metal or of a glasslike compound,
preferably glass, or a plastic-metal composite. With particular
preference the cavities are closed off relative to the ambient
environment by a barrier made of glass, more particularly silicate
glass, or by a plastic-metal composite, preferably metallized
plastics sheeting.
[0019] The gas atmosphere enclosed within the cavities/pores has an
underpressure relative to the standard pressure of 1 bar (100 kPa).
The underpressure is preferably less than 500 mbar, preferably from
0.001 to 200 mbar, more preferably from 0.1 to 100 mbar. The gas
pressure can be determined by the following technique: a measured
amount of granule grains having the total volume V.sub.granule is
destroyed in a defined, gas-tight space having the empty volume
V.sub.test chamber. On the basis of the change in the gas pressure
in this space, from P.sub.0 before destruction of the granule
grains to P.sub.i after destruction of the granule grains, it is
possible to determine the pressure prevailing in the pores of the
granules beforehand, P.sub.pore, in accordance with the following
equation:
P.sub.pore=[P.sub.1(V.sub.test
chamber-V.sub.granule(1-.PHI.))-P.sub.0(V.sub.test
chamber-V.sub.granule)]/[V.sub.granule.PHI.]
[0020] An alternative would be to destroy the particles under water
(or in another liquid which wets the particles very effectively)
and to collect the gas volume released.
[0021] The composition of the gas atmosphere is arbitrary. In one
embodiment of the present invention, it is preferred to use a gas
atmosphere with a composition different from that of air. The gas
composition is preferably set specifically and is selected so as to
achieve a low thermal conductivity. There are preferably two
different parameters to be observed here: firstly the gas-phase
thermal conductivity of the gas composition, and secondly the free
path length of the gas molecules. Preferred gases with a low
gas-phase thermal conductivity are the typical propellant gases
such as, for example, CO.sub.2, hydrocarbons having 3 to 5 carbon
atoms, preferably cyclo-, iso- and n-pentane, hydrofluorocarbons
(saturated and unsaturated), preferably HFC 245fa, HFC 134a and HFC
365mfc, hydrofluorochlorocarbons (saturated and unsaturated),
preferably HCFC 141b, oxygen-containing compounds such as methyl
formate and dimethoxymethane, or hydrochlorocarbons, preferably
1,2-dichloroethane. In the case of finely structured pore systems
and low gas pressures, however, the gas-phase thermal conductivity
may drop below the value anticipated for the gas composition. This
effect is called the Knudsen effect. The effect occurs when the
free path length of the gas molecules is greater than the diameter
of the pores in which the gas is located. Collisions of the gas
molecules with the pore walls then become more probable than
collisions of the gas molecules with one another. This may proceed
to an extent such that collisions of the gas molecules with one
another are suppressed entirely. Without collisions, there is no
transfer of thermal energy, and gas-phase thermal conduction is
switched off. In contrast to the thermal conductivity, the free
path length goes up as the molar mass of the gas molecules drops.
In some embodiments of the present invention, it may therefore be
advantageous to use a gas with a low molar mass, such as hydrogen,
helium, methane, ammonia, water or neon, for example, as insulating
gas in the pores of the granule grains or shapes, if the Knudsen
effect outweighs the thermal conductivity--which is actually
high--of these gases.
[0022] The polymer matrix into which the granule grains or the
shapes are embedded may be unfoamed or foamed. The polymer matrix
is preferably a polymer foam matrix. A polymer foam matrix has the
advantage that the insulating performance can be further increased
relative to that of unfoamed polymers, and that, depending on the
polymer material and additives employed, the foamed polymer matrix
may be more flexible than an unfoamed polymer matrix of the same
polymer material. Where the polymer matrix is a polymer foam
matrix, this polymer foam may be of open-cell or closed-cell
configuration. The polymer foam matrix is preferably a closed-cell
polymer foam matrix.
[0023] The polymer matrix may comprise all known polymers,
individually or in blends. The polymer matrix preferably comprises
foamable polymers. Particularly preferred polymers which may be
present in the polymer matrix are selected, for example, from
polystyrene (PS), polyurethane (PU) and polymethyl methacrylate
(PMMA). Particularly preferred polymer matrices are those which
comprise rigid PUR or PIR foams. For producing a polymer foam
matrix it is possible to use commonplace manufacturing methods,
such as RIM (reaction injection molding) processes or extrusion
processes, for example.
[0024] As already stated for the granule, the polymer matrix as
well may comprise an opacifier. An opacifier may be selected, for
example, from carbon black, TiO.sub.2, graphite or SiC, and the
nature and proportion of the opacifier in the polymer matrix may
differ from those in the granule. The fraction of opacifier, based
on the total mass of the polymer matrix, is preferably 0.5% to 30%
by mass, more preferably 1% to 10% by mass.
[0025] The gas phase present in the pores of a foamed polymer
matrix may differ in composition and pressure from the gas phase in
the cavities and/or pores of the granule grains or shapes. The cell
gas in the polymer matrix is determined substantially by the
blowing agents used. Both physical and chemical blowing agents can
be used in the present invention. Preferred blowing agents are
those whose gas-phase thermal conductivity is lower than that of
the air. Suitable physical blowing agents for the purposes of this
invention are gases, for example liquefied CO.sub.2, and volatile
liquids, including, for example, hydrocarbons having 3 to 5 carbon
atoms, preferably cyclo-, iso- and n-pentane, hydrofluorocarbons
(saturated and unsaturated), preferably HFC 245fa, HFC 134a and HFC
365mfc, hydrofluorochlorocarbons (saturated and unsaturated),
preferably HCFC 141b, oxygen-containing compounds such as methyl
formate and dimethoxy methane, or hydrochlorocarbons, preferably
1,2-dichloroethane.
[0026] The composite materials of the invention can be produced in
various ways. Preferred composite materials of the invention are
those which are obtainable by the method of the invention, which is
described below.
[0027] The method of the invention for producing a composite
material of the invention is distinguished by the fact that a
material for producing a polymer matrix is mixed with granules or
shapes having at least one cavity which is closed off relative to
the ambient environment and in which there is an underpressure
relative to the standard pressure of 1 bar (100 kPa), and from this
mixture a polymer matrix is generated in which the granules or
shapes are embedded.
[0028] The granules or shapes that are used are produced preferably
from precursors which are in powder form and have the
above-described composition and properties. For this purpose it is
possible to use all commonplace granulating and tableting
procedures, such as fluidized-bed granulation, compacting and
optionally crushing, or low-pressure extrusion, where appropriate
with use of liquids for dispersing and/or of additional binders,
for example. Granules and shapes obtainable in these ways
frequently have an open porosity. In order to generate the
underpressure that is essential to the invention within the pore
system, the granules/shapes are preferably exposed to an external
underpressure and/or to an elevated temperature and under these
conditions are furnished with a gas-impermeable barrier layer. In
the case of encapsulation at or below room temperature, the
pressure (underpressure) at which the furnishing with the barrier
layer takes place is preferably less than 500 mbar, more preferably
from 0.001 to 200 mbar. Where elevated temperatures are employed
while the barrier layer is applied, the pressure need not be
lowered to such an extent, since the internal pressure reduces
further on cooling of the encapsulated granules.
[0029] The barrier layer can be produced using the materials
specified above for the barrier layer. The cavities are preferably
closed off relative to the ambient environment by a barrier of
glass. Production takes place preferably by superficial melting of
the granule material or of additional additives in the marginal
region of the granules. Alternatively a melt of the barrier
material may be applied to the surface of the open-pored porous
granules, and this melt is subsequently caused to solidify.
Application may be accomplished, for example, by applying the melt
to the granules by spraying or knife coating, or by immersing the
granules into the melt. Solidification of the melt may be
accomplished by simple cooling to room temperature.
[0030] Another method for encapsulating the granule grains is that
of chemically reactive sealing, by means, for example, of silanes,
or using curing polymers. For this purpose, the granule grains may
be immersed into a liquid preparation of the capsule material, or
the preparation may be poured over or applied by spraying to the
granules, or the granules may be otherwise wetted superficially
with said preparation. Alternatively to a chemically reactive
encapsulation material it is also possible to use a melt of a
thermoplastic polymer.
[0031] A third possible method is that of enveloping the granule
grains with a gas-tight sheet. For this purpose it is preferred to
use multi-ply polymeric sheets which comprise a thin metal layer as
a diffusion barrier. In order to close the sheet capsules, the
sheets may be adhesively bonded or welded. In some embodiments of
the present disclosure, it may be advantageous to employ
combinations of the aforementioned encapsulation methods in
two-stage or multi-stage steps.
[0032] Encapsulation of the granules, however, is not absolutely
necessary. The underpressure that is essential to the invention in
the cavities of the granule grains may also be ensured by
implementing the entire operation of the embedding of the granules
into a polymer matrix under reduced pressure--subject to the
proviso that the external polymer matrix itself forms a
sufficiently gas-tight barrier, allowing the underpressure to be
maintained in the granules when the composite material, after being
produced, is exposed to the standard external air pressure. Another
variant of this embodiment is to generate the underpressure in the
cavities in the granule grains by means of chemical reactions or
getter substances. Embedding may then take place at standard
pressure, but the internal pressure within the cavities of the
granule grains goes down after they have been embedded, as a result
of chemical reactions or absorption of the gas molecules. For
example, the granules may be admixed with calcium oxide, the gas
phase within the cavities replaced by carbon dioxide, and the
granules embedded immediately into the polymer matrix. In
subsequent days, the gas pressure in the cavities goes down
automatically as a result of reaction of the calcium oxide with the
carbon dioxide to form calcium carbonate.
[0033] As material for producing the polymer matrix it is possible
to use a polymer or a mixture of polymers, or the reactants for
generating the polymer or polymers. The amount of granules/shapes
and polymers to be used, and/or of their starting materials, is
preferably selected such that the resultant composite material has
the mass fraction of granules/shapes that was indicated above as
being preferred.
[0034] In some embodiments of the present invention, it may be
advantageous if the method of the invention includes at least one
method step in which the material for producing the polymer matrix,
or a part thereof, is at least partly in the liquid aggregate state
and this liquid phase is mixed with the granules. In order to
facilitate the mixing operation of polymer with granule or shapes,
it may be advantageous, in some embodiments, if the polymer is
converted into a liquid or fluid state by being dissolved in a
suitable solvent or by melting. After the mixing operation, the
polymer matrix is solidified by cooling to below the melting
temperature and/or by removal of the solvent. Alternatively, the
mixing operation with the granules may also take place at the stage
of the starting compounds for generating the polymer matrix, i.e.,
with the monomers or prepolymeric compounds. In that case the
polymer matrix comes about directly in the composite material as a
result of a polymerization reaction or crosslinking reaction. This
variant is preferred when the polymer matrix belongs to the group
of the thermosets. In a further embodiment of the method of the
invention, the granules or shapes are mixed with a likewise
granulated polymer. Joining to form the composite material in that
case takes place typically by heating, with the polymer melting or
at least softening, and adhesively bonding the granules.
[0035] In some embodiments, it may be advantageous if the method of
the invention includes a method step of foaming. Foaming may take
place mechanically/physically or chemically. In the case of
mechanical/physical foaming, air or gas, or a gas mixture, is
introduced in gaseous form into a viscous polymer composition, and
this viscous polymer composition is subsequently cured, causing the
introduced air or gas/gas mixture to be enclosed in bubbles in the
polymer composition. Polymer foams can also be generated physically
by admixing a polymer composition with one or more blowing agents
which, on heating, change their aggregate state from liquid or
solid to gaseous and thus likewise lead to foam formation. Suitable
and known blowing agents are, for example, hydrocarbons which are
liquid at room temperature, such as, for example, pentanes. Where
the composition of the invention includes additional blowing
agents, these may be physical or chemical blowing agents. Suitable
physical blowing agents for the purposes of this invention are
gases, examples are liquefied CO.sub.2, and volatile liquids,
examples are hydrocarbons having 3 to 5 carbon atoms, preferably
cyclo-, iso- and n-pentane, hydrofluorocarbons, preferably HFC
245fa, HFC 134a and HFC 365mfc, hydrofluorochlorocarbons,
preferably HCFC 141b, oxygen-containing compounds such as methyl
formate and dimethoxy methane, or hydrochlorocarbons, preferably
1,2-dichloroethane. Chemical generation of foam is possible, for
example, through compounds being formed during the polymerization
that are gaseous at the polymerization temperatures. One typical
chemical blowing agent is, for example, water, which is formed in
polymerization reactions that are based on a condensation reaction.
Besides water, other chemical blowing agents may also be used. In
the case of the production of polyurethane foams, for example,
those which react with the isocyanates used and in so doing give
off gas, such as water or formic acid.
[0036] Using the example of a composite material with a foamed
polyurethane matrix, various versions of the method of the
invention will be discussed in more detail. Foamed polyurethane is
generally a highly crosslinked thermoset which is neither soluble
in common solvents such as water, ethanol or acetone, nor is
meltable (without decomposition). Mixing with the granules
therefore takes place preferably at the stage of monomeric and/or
prepolymeric compounds. A polyurethane system for the production of
insulating foams generally features two components (A) and (B),
with one component composed of compounds having reactive hydrogen
atoms, known as the polyol component (A), and the second component
(B) having one or more isocyanates. Customary auxiliaries and
adjuvants may be formulated into the polyol component (A) or
metered in separately. The granules or shapes are mixed preferably
with the polyol component, with the isocyanate component or--with
particular preference--with a fresh reaction mixture of these
components. The two first-mentioned cases are suitable only for low
levels of filling and small grain diameters on the part of the
granules, since the granules and shapes must be pre-dispersed in
component (A) or (B), and this dispersion must then be intimately
mixed with the second component. The preferred case of
incorporation of the granules/shapes into a fresh reaction mixture
of (A) component and (B) component allows the trouble-free
processing of large grain diameters. The incorporation of
granules/shapes in the reaction mixture may take place prior to
transfer to the mold, or else granules/shapes are introduced as
packing or filling in a hollow mold and are infiltrated, or the
grains surround-foamed, with the liquid, foaming reaction mixture.
For the production of insulating boards, a continuous method
analogous to the production of polyurethane insulating boards, by
the double transport belt method, is also conceivable. In that case
the granules/shapes can be scattered onto the lower top layer
either before or after the application of the polyurethane reaction
mixture, with the individual grains being surround-foamed. In this
case the composite material is cured by the polyaddition reaction
involving crosslinking to form the polyurethane.
[0037] The typical composition of a polyurethane system is
described in more detail below:
[0038] As polyol components (A) it is possible to use the compounds
customary for the formulation of insulating foams, examples are
polyether polyols and polyester polyols. Polyether polyols can be
obtained by reacting polyhydric alcohols or amines with alkylene
oxides. Polyester polyols are based preferably on esters of
polybasic carboxylic acids (usually phthalic acid or terephthalic
acid) with polyhydric alcohols (usually glycols).
[0039] As (poly)isocyanate component (B) it is possible to use the
compounds customary for the formulation of insulating foams,
examples are 4,4'-diphenylmethane diisocyanate (MDI), toluene
diisocyanate (TDI), hexamethylene diisocyanate (HMDI) and
isophorone diisocyanate (IPDI). Particularly suitable is the
mixture of MDI and its analogues with higher degrees of
condensation, having an average functionality of 2 to 4, this
mixture being known as "polymeric MDT" ("crude MDI").
[0040] A suitable ratio of isocyanate and polyol, expressed as the
index of the formulation, is situated in the 50-500 range,
preferably 100-350. The index describes the ratio of isocyanate
actually used to isocyanate calculated (for a stoichiometric
reaction with polyol). An index of 100 stands for a molar ratio of
the reactive groups of 1:1.
[0041] As auxiliaries and additives it is possible to use the
compounds customary for the formulation of insulating foams,
including catalysts, cell stabilizers, blowing agents, flame
retardants, fillers, dyes and light stabilizers.
[0042] Suitable catalysts for the purposes of this invention are,
for example, substances which catalyze the gel reaction
(isocyanate-polyol), the blowing reaction (isocyanate-water) or the
dimerization or trimerization of the isocyanate. Typical examples
are the amines triethylamine, dimethylcyclohexylamine,
tetramethylethylenediamine, tetramethylhexanediamine,
pentamethyldiethylenetriamine, pentamethyldipropylenetriamine,
triethylenediamine, dimethylpiperazine, 1,2-dimethylimidazole,
N-ethylmorpholine,
tris(dimethylaminopropyl)hexahydro-1,3,5-triazine,
dimethylamino-ethanol, dimethylaminoethoxyethanol and
bis(dimethylaminoethyl) ether, tin compounds such as dibutyltin
dilaurate and potassium salts such as potassium acetate and
potassium 2-ethylhexanoate. Suitable amounts for use are guided by
the type of catalyst and are situated typically in the range from
0.05 to 5 parts by weight, or 0.1 to 10 parts by weight for
potassium salts, based on 100 parts by weight of polyol.
[0043] Suitable cell stabilizers are, for example, surface-active
substances such as, for example, organic surfactants or,
preferably, silicone surfactants (polyetherpolydimethylsiloxane
copolymers). Typical amounts of polyethersiloxane cell stabilizers
for use are 0.5 to 5 parts by weight per 100 parts by weight of
polyol, preferably 1 to 3 parts by weight per 100 parts by weight
of polyol.
[0044] The foamable formulation may be admixed with water as a
chemical blowing agent, since it reacts with isocyanates and gives
off carbon dioxide gas in the process. Suitable amounts of water
for the purposes of this invention are dependent on whether, in
addition to the water, physical blowing agents are used as well, or
not. In the case of purely water-blown foaming, the levels for the
water content are preferably 1 to 20 parts by weight per 100 parts
by weight of polyol; where other blowing agents are used in
addition, or where foaming takes place under reduced pressure, the
amount for use reduces preferably to from 0.1 to 5 parts by weight
of water per 100 parts by weight of polyol. Suitable physical
blowing agents have already been specified.
[0045] Insulating foams for the heat insulation of buildings are
subject to fire control requirements and must preferably be made
flame retardant. In principle all customary flame retardants are
suitable. Used with preference as flame retardants are preferably
liquid organic phosphorus compounds, such as halogen-free organic
phosphates, e.g., triethyl phosphate (TEP), halogenated phosphates,
e.g., tris(1-chloro-2-propyl)phosphate (TCPP) and
tris(2-chloroethyl)phosphate (TCEP), or organic phosphonates, e.g.,
dimethyl methanephosphonate (DMMP), dimethyl propanephosphonate
(DMPP) or solids such as ammonium polyphosphate (APP) or red
phosphorus. Additionally suitable as flame retardants are
halogenated compounds, examples are halogenated polyols, and also
solids such as expandable graphite and melamine.
[0046] A typical polyurethane or polyisocyanurate insulating foam
formulation in the sense of this invention would result in a
density of 5 to 50 kg/m.sup.3 and have the following
composition:
TABLE-US-00001 Component Weight fraction Polyol 100 (Amine)
catalyst 0.05 to 5 Potassium trimerization catalyst 0 to 10
Polyethersiloxane 0.5 to 5 Water 0.1 to 20 Blowing agent 0 to 40
Flame retardant 0 to 50 Isocyanate index: 50-500
[0047] The formulations of the invention can be processed to rigid
foams by any of the methods familiar to the skilled person, as for
example in a manual mixing procedure or, preferably, using
high-pressure foaming machinery.
[0048] As an alternative to the surround-foaming of encapsulated
granules, it is also possible to use uncapsulated granules, in
which case the entire surround-foaming operation takes place with a
closed-cell rigid foam under reduced pressure. For this purpose the
granules are placed in a hollow mold with a gas-tight closure,
there being connected to this mold a vacuum pump and the mixing
head of a high-pressure foaming machine. When the hollow mold has
been evacuated to the desired pressure, the foaming machine is used
to inject the liquid polyurethane reaction mixture into the mold.
The reaction mixture runs into the cavities between the granule
grains and begins to foam, and the expanded foam envelopes the
granule grains. After the polyurethane foam has cured, the result
is a composite material in which there is an underpressure not only
in the cavities in the granules but also in the foam cells. The
mechanical strength of the foam ought therefore to be sufficiently
high to withstand the pressure difference (between internal
pressure and the external air pressure) without signs of shrinking.
For this purpose, generally speaking, the required foam density
will be higher than is usual for polyurethane insulating foams. The
pressure for the surround-foaming of the granules is preferably
less than 200 mbar, more preferably less than 100 mbar--the
pressure difference relative to the standard pressure, therefore,
is at least 0.8 bar and more preferably 0.9 bar or more.
[0049] Additionally necessary is the adaptation of blowing agent
type and amount to the underpressure foaming. As well as this batch
mold foaming, continuous production methods of insulating boards in
a double belt process, or of freely risen slab stock foams are
imaginable, with the entire production line encased with an
underpressure chamber. The construction of such a line may be
guided by the "VPF process" that is customary in the production of
flexible foams under reduced pressure.
[0050] As a further example, the production of a composite material
with a foamed polystyrene matrix will be discussed in more detail.
In this case, the preferred starting material for the polymer
matrix comprises granules, preferably encapsulated granules, of
polystyrene with incorporated blowing agent. These expandable
polystyrene granules are mixed with the granules or shapes to be
embedded. As a result of subsequent heating of the granule mixture,
preferably in a hollow mold having the desired geometry, the
polystyrene expands to form a foam and at the same time bonds
adhesively to itself and to the embedded granules, to form a
coherent molding.
[0051] The amount of granules to be used and of polymer and/or
starting materials thereof to be used is preferably selected such
that the resulting composite material has the mass of granules
indicated above and/or has the mass ratio indicated above.
[0052] The composite material of the invention may be used in
particular as insulating material. This insulating material is
preferably used for the insulating of buildings, of space, air,
open-water and/or land vehicles or of parts of cooling or heating
systems and assemblies. The composite materials of the invention
can be used as insulating material in refrigeration equipment and
hot-water reservoirs, and have the advantage in these cases that
they can be produced directly in the cavity to be filled. The same
applies to the filling of profiles for construction purposes,
examples are window frames or door frames, roller shutter elements,
sectional gates, etc. Furthermore, the composite materials of the
invention can be used for insulating pipelines (e.g., local and
district heating lines).
[0053] A distinctive feature of corresponding articles of the
invention is that they comprise a composite material of the
invention.
[0054] In the examples given below, the present invention is
described on an exemplary basis, without any intention that the
invention--the scope of which is evident from the overall
description and the claims--should be restricted to the embodiments
specified in the examples.
EXAMPLES
Example 1
Production of Granules
[0055] 80% by weight of AEROSIL200 (fumed silica from Evonik
Industries AG, BET surface area 200 m.sup.2/g), 15% by weight of
AROSPERSE 15 (thermal carbon black from Orion Engineered Carbons)
and 5% by weight of glass fibres (glass fibre slithers,
approximately 12 mm fibre length) were intimately mixed. This
mixture was transferred in 0.6 g portions into a cylindrical
compression mold with a diameter of 2 cm and compressed by means of
a hydraulic press to form tablets each with a height of 1 cm. The
density of the tablets was approximately 200 kg/m.sup.3.
Example 2
Encapsulation of Evacuated Granules
[0056] The tablets produced in Example 1 were enveloped with a
metallized sheet (multi-layer laminate from TOYO with PET outer
layer, aluminium barrier layer and PE internal layer) by being
placed between two plies of this sheet, followed by the two plies
being welded thermally to one another in an annular fashion around
the tablets. Within the annular weld seam, a small gap remained
open, to which an oil-sealed rotary slide vacuum pump was attached
via a tube. With the aid of the vacuum pump, the tablet was
evacuated for 10 minutes and then under vacuum the opening in the
film was welded, thus closing off the tablet in a gas-tight
fashion. The protruding margin of the film was cut off up to the
weld seam.
Example 3
Production of a Composite Material From Encapsulated Granules and
Foamed Polyurethane Matrix
[0057] The polymer matrix used was a rigid polyurethane foam
formulation in accordance with Table 1.
TABLE-US-00002 TABLE 1 PUR formulation Component Weight fraction
Daltolac R 471* 100 parts N,N-Dimethylcyclohexylamine 1.5 parts
Water 2.6 parts Cyclopentane 13.1 parts TEGOSTAB .RTM. B 8462** 1.5
parts Desmodur 44V20L*** 198.5 Parts *Polyether polyol from
Huntsman **Foam stabilizer from Evonik Industries AG ***Polymeric
MDI from Bayer, 200 mPa * s, 31.5% by weight NCO, functionality
2.7
[0058] The polyurethane foaming operations were conducted in a
manual mixing procedure. Polyol, amine catalyst, water, foam
stabilizer and blowing agent were weighed out into a beaker and
mixed with a plate stirrer (6 cm diameter) at 1000 rpm for 30
seconds. Re-weighing was used to determine the amount of blowing
agent evaporated during the mixing operation, and this amount was
added again. Then the MDI was added and the reaction mixture was
stirred at 3000 rpm with the stirrer described for 5 seconds, then
immediately transferred to an aluminium mould thermostated at
45.degree. C. and measuring 50 cm.times.25 cm.times.5 cm, lined
with polyethylene film. The amount of foam formulation used here
was 15% above the amount necessary to at least fill the mold. After
10 minutes, the foam board was demolded. Using a band saw, a slice
measuring 50 cm.times.25 cm.times.0.5 cm was sawn from this board.
This slice was placed on the base of the aluminium mold, which was
again lined with polyethylene film, and the tablets, produced as
described above and encapsulated under vacuum, were laid out on top
of the slice in three layers, each disposed tightly against one
another. In the same way as for the first foaming operation,
polyurethane reaction mixture was again prepared by stirring, then
poured over the tablets with the mold lid opened, and the lid was
immediately closed. After a further 10 minutes' curing time, the
completed composite material was demolded.
[0059] The resultant board of the composite material was cut with a
band saw to a size of 20 cm.times.20 cm.times.5 cm, and the thermal
conductivity of this specimen was measured using a Hesto HLC-A90
thermal conductivity meter. The measurement value was
15.8*10.sup.-3 W*m.sup.-1*K.sup.-1. This value is well below that
of rigid polyurethane foam. For comparison, a rigid polyurethane
foam board produced with the same formula but without embedded
granules was measured. Its thermal conductivity was
22.5*10.sup.-3W*m.sup.-1*K.sup.-1.
Example 4
Production of a Composite Material by Enveloping Unencapsulated
Granules With Rigid Polyurethane Foam at Underpressure
[0060] The polymer matrix used was a rigid polyurethane foam
formulation in accordance with Table 2.
TABLE-US-00003 TABLE 2 PUR formulation 2 Component Weight fraction
Daltolac R 471* 100 parts N,N-Dimethylaminoethoxyethanol 0.5 parts
Triethylenediamine, 33% in 0.5 parts dipropylene glycol Water 0.5
parts TEGOSTAB .RTM. B 8462** 2.0 parts Desmodur 44V20L*** 189.2
parts *Polyether polyol from Huntsman **Foam stabilizer from Evonik
***Polymeric MDI from Bayer, 200 mPa * s, 31.5% by weight NCO,
functionality 2.7
[0061] The polyurethane foaming procedures were carried out using a
KraussMaffei RIM-Star MiniDos high-pressure foaming machine with
MK12/18ULP-2KVV-G-80-I mixing head. Polyol, catalysts, water and
foam stabilizer were weighed out, mixed thoroughly and transferred
as a mixture into the working container of the machine. The raw
materials--polyol mixture and isocyanate--were heated at 35.degree.
C., the pressures were 130 bar for the polyol and 140 bar for the
isocyanate, and the total discharge rate was 200 g/s. An aluminium
mold thermostated at 45.degree. C. and measuring 50 cm.times.25
cm.times.5 cm, also fitted with a gas-tightly closing lid with a
central pouring hole and a side connection for a vacuum pump
(protected from foam penetration by a screen), was lined with
polyethylene film and sealed, the mixing head was placed into the
pouring hole in a gas-tight fashion, and the hollow mold was
evacuated to 200 mbar using a membrane vacuum pump with vacuum
controller. Polyurethane reaction mixture was injected into the
mold by means of the foaming system, the amount of this reaction
mixture being 15% above the amount necessary to at least fill the
mold. After 10 minutes, the foam board was demolded. A band saw was
used to saw two slices measuring 50 cm.times.25 cm.times.0.5 cm
from this board. One slice was placed on the base of the aluminium
mold, which was lined with polyethylene film again, and the
unencapsulated tablets produced as described above were laid out on
top of the slice in three layers, each arranged closely against one
another. The second slice was attached to the mold lid using
double-sided adhesive tape, and the pouring hole was cut out. The
mold was sealed, evacuated for 10 minutes each in 3 cycles and
ventilated with carbon dioxide. After that it was evacuated to 200
mbar again and after 10 minutes, in the same way as for the first
foaming operation, polyurethane reaction mixture was injected.
After a further 10 minutes' curing time, the completed composite
material was demolded.
[0062] The resultant board of the composite material was cut with a
band saw to a size of 20 cm.times.20 cm.times.5 cm, and the thermal
conductivity of this specimen was measured using a Hesto HLC-A90
thermal conductivity meter. The measurement value was
17.9*10.sup.-3W*m.sup.-1*K.sup.-1.
[0063] While the present disclosure has been particularly shown and
described with respect to preferred embodiments thereof, it will be
understood by those skilled in the art that the foregoing and other
changes in forms and details may be made without departing from the
spirit and scope of the present disclosure. It is therefore
intended that the present disclosure not be limited to the exact
forms and details described and illustrated, but fall within the
scope of the appended claims.
* * * * *
References