Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
PF 70475 CA 02801521 2012-12-04
1
Method for producing porous polyurea-based materials
Description
The present invention relates to a process for producing porous materials,
which
comprises reaction of at least one polyfunctional isocyanate with an amine
component
comprising at least one polyfunctional substituted aromatic amine and also
water in the
presence of a solvent.
The invention further relates to the porous materials which can be obtained in
this way
and the use of the porous materials as insulation material and in vacuum
insulation
panels.
Porous materials, for example polymer foams, having pores in the size range of
a few
microns or significantly below and a high porosity of at least 70% are
particularly good
thermal insulators on the basis of theoretical considerations.
Such porous materials having a small average pore diameter can be, for
example, in
the form of organic xerogels. In the literature, the term xerogel is not used
entirely
uniformly. In general, a xerogel is considered to be a porous material which
has been
produced by a sol-gel process, with the liquid phase having been removed from
the gel
by drying below the critical temperature and below the critical pressure of
the liquid
phase ("subcritical conditions"). In contrast, the term aerogels generally
refers to gels
obtained when the removal of the liquid phase from the gel has been carried
out under
supercritical conditions.
In the sol-gel process, a sol based on a reactive organic gel precursor is
first produced
and the so[ is then gelled by means of a crosslinking reaction to form a gel.
To obtain a
porous material, for example a xerogel, from the gel, the liquid has to be
removed. This
step will hereinafter be referred to as drying in the interests of simplicity.
WO-95/02009 discloses isocyanate-based xerogels which are particularly
suitable for
applications in the field of vacuum insulation. The publication also discloses
a sol-gel-
based process for producing the xerogels, in which known, inter alia aromatic,
polyisocyanates and an unreactive solvent are used. As further compounds
having
active hydrogen atoms, use is made of aliphatic or aromatic polyamines or
polyols. The
examples disclosed in the publication comprise ones in which a polyisocyanate
is
reacted with diaminodiethyltoluene. The xerogels disclosed generally have
average
pore sizes in the region of 50 pm. In one example, mention is made of an
average pore
diameter of 10 pm.
WO-2008/138978 discloses xerogels which comprise from 30 to 90% by weight of
at
least one polyfunctional isocyanate and from 10 to 70% by weight of at least
one
PF 70475 CA 02801521 2012-12-04
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polyfunctional aromatic amine and have a volume average pore diameter of not
more
than 5 microns.
The unpublished EP-A 09178783.8 describes porous materials based on
polyfunctional
isocyanates and polyfunctional aromatic amines, where the amine component
comprises polyfunctional substituted aromatic amines. The porous materials
described
are produced by reacting isocyanates with the desired amount of amine in a
solvent
which is inert toward the isocyanates. The formation of urea linkages occurs
exclusively by reaction of the isocyanate groups with the amino groups used.
However, the materials properties, in particular the mechanical stability
and/or the
compressive strength and also the thermal conductivity, of the known porous
materials
based on polyurea are not satisfactory for all applications. In addition, the
formulations
on which the materials are based display shrinkage, with reduction of the
porosity and
an increase in the density, on drying. Furthermore, the gelling time, i.e. the
time
required for gelling of the starting compounds, is often too long.
A particular problem associated with the formulations based on isocyanates and
amines which are known from the prior art are mixing defects. Mixing defects
occur as
a result of the high reaction rate between isocyanates and amino groups, since
the
gelling reaction has already proceeded a long way before complete mixing.
Mixing
defects lead to porous materials having heterogeneous and unsatisfactory
materials
properties. A concept for reducing the phenomenon of mixing defects is thus
generally
desirable.
It was therefore an object of the invention to avoid the abovementioned
disadvantages.
In particular, a porous material which does not have the abovementioned
disadvantages, or has them to a reduced extent, should be provided. The porous
materials should, compared to the prior art, have improved thermal
conductivity in
vacuo. In addition, the porous materials should have a low thermal
conductivity even at
pressures above the vacuum range, in particular in a pressure range from about
1 mbar to about 100 mbar. This is desirable since an increase in pressure
occurs over
time in vacuum panels. Furthermore, the porous material should at the same
time have
a high porosity, a low density and a sufficiently high mechanical stability.
Finally, mixing defects and thus the heterogeneities in the structure and the
materials
properties of the porous materials formed in the reaction of the isocyanates
with the
amines should be avoided.
We have accordingly found the process of the invention and the porous
materials
which can be obtained in this way.
PF 70475 CA 02801521 2012-12-04
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The process of the invention for producing a porous material comprises
reacting the
following components (a1), (a2) and (a3):
(al) at least one polyfunctional isocyanate,
(a2) at least one polyfunctional substituted aromatic amine (a2-s) having the
general
formula I
Q2 Q3 Q3 Q2
Q R
R2
Q4 Q5 Q5 Q4
where R1 and R2 can be identical or different and are each selected
independently from
among hydrogen and linear or branched alkyl groups having from 1 to 6 carbon
atoms
and all substituents Q1 to Q5 and Q1' to Q5' are identical or different and
are each
selected independently from among hydrogen, a primary amino group and a linear
or
branched alkyl group having from 1 to 12 carbon atoms, where the alkyl group
can
bear further functional groups, with the proviso that
- the compound having the general formula I comprises at least two
primary amino groups, where at least one of Q1, Q3 and Q5 is a primary
amino group and at least one of Q'', Q3' and Q5' is a primary amino
group, and
- Q2, Q4, Q2' and Q4' are selected so that the compound having the
general formula I has at least one linear or branched alkyl group, which
can bear further functional groups, having from 1 to 12 carbon atoms in
the a position relative to at least one primary amino group bound to the
aromatic ring, and
optionally at least one further polyfunctional aromatic amine (a2-u) which
differs from
the amines (a2-s) having the general formula I and
(a3) water
in the presence of a solvent (C) and optionally in the presence of at least
one catalyst
(a4) to form the porous materials of the invention.
PF 70475 CA 02801521 2012-12-04
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Preferred embodiments may be found in the claims and the description.
Combinations
of preferred embodiments do not go outside the scope of the present invention.
Preferred embodiments of the components used are described below.
The polyfunctional isocyanates (al) will hereinafter be referred to
collectively as
component (a1). Analogously, the polyfunctional amines (a2) will hereinafter
be
referred to collectively as component (a2). It will be obvious to a person
skilled in the
art that the monomer components mentioned are present in reacted form in the
porous
material.
For the purposes of the present invention, the functionality of a compound is
the
number of reactive groups per molecule. In the case of the monomer component
(al),
the functionality is the number of isocyanate groups per molecule. In the case
of the
amino groups of the monomer component (a2), the functionality is the number of
reactive amino groups per molecule. A polyfunctional compound has a
functionality of
at least 2.
If mixtures of compounds having different functionalities are used as
component (al) or
(a2), the functionality of the components is in each case given by the number
average
of the functionality of the individual compounds. A polyfunctional compound
comprises
at least two of the abovementioned functional groups per molecule.
Component (al)
In the process of the invention, at least one polyfunctional isocyanate is
reacted as
component (al).
In the process of the invention, the amount of component (al) used is
preferably from
40 to 99.8% by weight, in particular from 55 to 99.3% by weight, particularly
preferably
from 68 to 97.5% by weight, in each case based on the total weight of the
components
(al), (a2) and (a3), which is 100% by weight.
Possible polyfunctional isocyanates are aromatic, aliphatic, cycloaliphatic
and/or
araliphatic isocyanates. Such polyfunctional isocyanates are known per se or
can be
prepared by methods known per se. The polyfunctional isocyanates can also be
used,
in particular, as mixtures, so that the component (a1) in this case comprises
various
polyfunctional isocyanates. Polyfunctional isocyanates which are possible as
monomer
building blocks (al) have two (hereinafter referred to as diisocyanates) or
more than
two isocyanate groups per molecule of the monomer component.
Particularly suitable polyfunctional isocyanates are diphenylmethane 2,2'-,
2,4'- and/or
4,4'-diisocyanate (MDI), naphthylene 1,5-diisocyanate (NDI), tolylene 2,4-
and/or 2,6-
PF 70475 CA 02801521 2012-12-04
diisocyanate (TDI), 3,3'-dimethylbiphenyl diisocyanate, 1,2-diphenylethane
diisocyanate and/or p-phenylene diisocyanate (PPDI), trimethylene,
tetramethylene,
pentamethylene, hexamethylene, heptamethylene and/or octamethylene
diisocyanate,
2-methylpentamethylene 1,5-diisocyanate, 2-ethylbutylene 1,4-diisocyanate,
5 pentamethylene 1,5-diisocyanate, butylene 1,4-diisocyanate, 1-isocyanato-
3,3,5-
trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 1,4-
and/or
1,3-bis(isocyanatomethyl)cyclohexane (HXDI), cyclohexane 1,4-diisocyanate, 1-
methylcyclohexane 2,4- and/or 2,6-diisocyanate and dicyclohexylmethane 4,4'-,
2,4'-
and/or 2,2'-diisocyanate.
As polyfunctional isocyanates (a1), preference is given to aromatic
isocyanates.
Particularly preferred polyfunctional isocyanates of the component (a1) are
the
following embodiments:
i) polyfunctional isocyanates based on tolylene diisocyanate (TDI), in
particular 2,4-
TDI or 2,6-TDI or mixtures of 2,4- and 2,6-TDI;
ii) polyfunctional isocyanates based on diphenylmethane diisocyanate (MDI), in
particular 2,2'-MDI or 2,4'-MDI or 4,4'-MDI or oligomeric MDI, also referred
to as
polyphenylpolymethylene isocyanate, or mixtures of two or three of the
abovementioned diphenylmethane diisocyanates or crude MDI which is obtained
in the production of MDI or mixtures of at least one oligomer of MDI and at
least
one of the abovementioned low molecular weight MDI derivatives;
iii) mixtures of at least one aromatic isocyanate according to embodiment i)
and at
least one aromatic isocyanate according to embodiment ii).
Oligomeric diphenylmethane diisocyanate is particularly preferred as
polyfunctional
isocyanate. Oligomeric diphenylmethane diisocyanate (hereinafter referred to
as
oligomeric MDI) is an oligomeric condensation product or a mixture of a
plurality of
oligomeric condensation products and thus a derivative/derivatives of
diphenylmethane
diisocyanate (MDI). The polyfunctional isocyanates can preferably also be made
up of
mixtures of monomeric aromatic diisocyanates and oligomeric MDI.
Oligomeric MDI comprises one or more condensation products of MDI which have a
plurality of rings and a functionality of more than 2, in particular 3 or 4 or
5. Oligomeric
MDI is known and is frequently referred to as polyphenylpolymethylene
isocyanate or
as polymeric MDI. Oligomeric MDI is usually made up of a mixture of MDI-based
isocyanates having various functionalities. Oligomeric MDI is usually used in
admixture
with monomeric MDI.
The (average) functionality of an isocyanate comprising oligomeric MDI can
vary in the
range from about 2.2 to about 5, in particular from 2.4 to 3.5, in particular
from 2.5 to 3.
PF 70475 CA 02801521 2012-12-04
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Such a mixture of MDI-based polyfunctional isocyanates having various
functionalities
is, in particular, crude MDI which is obtained in the production of MDI.
Polyfunctional isocyanates or mixtures of a plurality of polyfunctional
isocyanates
based on MDI are known and are marketed, for example, by BASF Polyurethanes
GmbH under the name Lupranat .
The functionality of the component (al) is preferably at least two, in
particular at least
2.2 and particularly preferably at least 2.5. The functionality of the
component (a1) is
preferably from 2.2 to 4 and particularly preferably from 2.5 to 3.
The content of isocyanate groups in the component (al) is preferably from 5 to
10 mmol/g, in particular from 6 to 9 mmol/g, particularly preferably from 7 to
8.5 mmol/g. A person skilled in the art will know that the content of
isocyanate groups
in mmol/g and the equivalent weight in g/equivalent have a reciprocal
relationship. The
content of isocyanate groups in mmol/g can be derived from the content in % by
weight
in accordance with ASTM D-5155-96 A.
In a preferred embodiment, the component (al) comprises at least one
polyfunctional
isocyanate selected from among diphenylmethane 4,4'-diisocyanate,
diphenylmethane
2,4'-diisocyanate, diphenylmethane 2,2'-diisocyanate and oligomeric
diphenylmethane
diisocyanate. In this preferred embodiment, the component (al) particularly
preferably
comprises oligomeric diphenylmethane diisocyanate and has a functionality of
at least
2.5.
The viscosity of the component (al) used can vary within a wide range. The
component (a1) preferably has a viscosity of from 100 to 3000 mPa.s,
particularly
preferably from 200 to 2500 mPa.s.
Component (a2)
According to the invention, at least one polyfunctional substituted aromatic
amine
(a2-s) having the general formula I
Q2 Q3 Q3 Q2
1
Q1 / R Q1'
R2
4 5 5' 4
Q Q Q Q (I),
PF 70475 CA 02801521 2012-12-04
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where RI and R2 can be identical or different and are each selected
independently from
among hydrogen and linear or branched alkyl groups having from 1 to 6 carbon
atoms
and all substituents Q' to Q5 and Q1' to Q5' are identical or different and
are each
selected independently from among hydrogen, a primary amino group and a linear
or
branched alkyl group having from 1 to 12 carbon atoms, where the alkyl group
can
bear further functional groups, with the proviso that
- the compound having the general formula I comprises at least two
primary amino groups, where at least one of Q1, Q3 and Q5 is a primary
amino group and at least one of Q'', Q3' and Q5' is a primary amino
group, and
- Q2, Q4, Q2' and Q4' are selected so that the compound having the
general formula I has at least one linear or branched alkyl group, which
can optionally bear further functional groups, having from 1 to 12
carbon atoms in the a position relative to at least one primary amino
group bound to the aromatic ring, and
optionally at least one further polyfunctional aromatic amine (a2-u) which
differs from
the amines (a2-s) having the general formula I is/are reacted as component
(a2).
Component (a2) thus comprises polyfunctional aromatic amines, with the
polyfunctional
aromatic amines (a2-s) having the general formula I being a constituent.
For the purposes of the present invention, polyfunctional amines are amines
which
have at least two amino groups which are reactive toward isocyanates per
molecule.
Here, primary and secondary amino groups are reactive toward isocyanates, with
the
reactivity of primary amino groups generally being significantly higher than
that of
secondary amino groups.
The amount of component (a2) used is preferably from 0.1 to 30% by weight, in
particular from 0.5 to 20% by weight, particularly preferably from 2 to 12% by
weight, in
each case based on the total weight of the components (a1), (a2) and (a3),
which is
100% by weight.
According to the invention, R1 and R2 in the general formula I are identical
or different
and are each selected independently from among hydrogen, a primary amino group
and a linear or branched alkyl group having from 1 to 6 carbon atoms. R1 and
R2 are
preferably selected from among hydrogen and methyl. Particular preference is
given to
R1=R2=H.
PF 70475 CA 02801521 2012-12-04
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Q2, Q4, Q2' and Q4' are preferably selected so that the substituted aromatic
amine
(a2-s) comprises at least two primary amino groups which each have one or two
linear
or branched alkyl groups having from 1 to 12 carbon atoms, which may bear
further
functional groups, in the a position. If one or more of Q2, Q4, Q2' and Q4'
are selected
so that they correspond to linear or branched alkyl groups which have from 1
to 12
carbon atoms and bear further functional groups, preference is given to amino
groups
and/or hydroxy groups and/or halogen atoms as such functional groups.
The alkyl groups as substituents Q in the general formula I are preferably
selected from
among methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl and tert-butyl.
The amines (a2-s) are preferably selected from the group consisting of
3,3',5,5'-
tetraalkyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetraalkyl-2,2'-
diaminodiphenyl-
methane and 3,3',5,5'-tetraalkyl-2,4'-diaminodiphenylmethane, where the alkyl
groups
in the 3,3',5 and 5' positions can be identical or different and are each
selected
independently from among linear or branched alkyl groups which have from 1 to
12
carbon atoms and can bear further functional groups. The abovementioned alkyl
groups are preferably methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl or
t-butyl (in
each case unsubstituted).
In one embodiment, one, more than one or all hydrogen atoms of one or more
alkyl
groups of the substituents Q can have been replaced by halogen atoms, in
particular
chlorine. As an alternative, one, more than one or all hydrogen atoms of one
or more
alkyl groups of the substituents Q can have been replaced by NH2 or OH.
However, the
alkyl groups in the general formula I are preferably made up of carbon and
hydrogen.
In a particularly preferred embodiment, component (a2) comprises 3,3',5,5'-
tetraalkyl-
4,4'-diaminodiphenylmethane, where the alkyl groups can be identical or
different and
are each selected independently from among linear or branched alkyl groups
which
have from 1 to 12 carbon atoms and can optionally bear functional groups. The
abovementioned alkyl groups are preferably selected from among unsubstituted
alkyl
groups, in particular methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl
and tert-butyl,
particularly preferably methyl and ethyl. Very particular preference is given
to 3,3',5,5'-
tetraethyl-4,4'-diaminodiphenylmethane and/or 3,3',5,5'-tetramethyl-4,4'-
diaminodiphenylmethane.
The abovementioned polyfunctional amines of the type (a2-s) are known per se
to
those skilled in the art or can be prepared by known methods. One of the known
methods is the reaction of aniline or derivatives of aniline with formaldehyde
in the
presence of an acid catalyst, in particular the reaction of 2,4- or 2,6-
dialkylaniline.
PF 70475 CA 02801521 2012-12-04
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The component (a2) can optionally also comprise further polyfunctional
aromatic
amines (a2-u) which differ from the amines of the structure (a2-s). The
aromatic
amines (a2-u) preferably have exclusively aromatically bound amino groups, but
can
also have both (cyclo)aliphatically and aromatically bound reactive amino
groups.
Suitable polyfunctional aromatic amines (a2-u) are, in particular, isomers and
derivatives of diaminodiphenylmethane. Isomers and derivatives of
diaminodiphenylmethane which are preferred as constituents of component (a2)
are, in
particular, 4,4'-diaminodiphenylmethane, 2,4'-diaminodiphenylmethane, 2,2'-
diaminodiphenylmethane and oligomeric diaminodiphenylmethane.
Further suitable polyfunctional aromatic amines (a2-u) are, in particular,
isomers and
derivatives of toluenediamine. Isomers and derivatives of toluenediamine which
are
preferred as constituents of component (a2) are, in particular, toluene-2,4-
diamine
and/or toluene-2,6-diamine and diethyltoluenediamines, in particular 3,5-
diethyltoluene-
2,4-diamine and/or 3,5-diethyltoluene-2,6-diamine.
In a first, particularly preferred embodiment, component (a2) consists
exclusively of
polyfunctional aromatic amines of the type (a2-s). In a second preferred
embodiment,
component (a2) comprises polyfunctional aromatic amines of the types (a2-s)
and
(a2-u). In the latter, second preferred embodiment, the component (a2)
preferably
comprises at least one polyfunctional aromatic amine (a2-u), of which at least
one is
selected from among isomers and derivatives of diaminodiphenylmethane (MDA).
In the second preferred embodiment, component (a2) correspondingly
particularly
preferably comprises at least one polyfunctional aromatic amine (a2-u)
selected from
among 4,4'-diaminodiphenylmethane, 2,4'-diaminodiphenylmethane, 2,2'-
diaminodiphenylmethane and oligomeric diaminodiphenylmethane.
Oligomeric diaminodiphenylmethane comprises one or more methylene-bridged
condensation products of aniline and formaldehyde having a plurality of rings.
Oligomeric MDA comprises at least one oligomer, but in general a plurality of
oligomers, of MDA having a functionality of more than 2, in particular 3 or 4
or 5.
Oligomeric MDA is known or can be prepared by methods known per se. Oligomeric
MDA is usually used in the form of mixtures with monomeric MDA.
The (average) functionality of a polyfunctional amine (a2-u) comprising
oligomeric MDA
can vary in the range from about 2.3 to about 5, in particular from 2.3 to 3.5
and in
particular from 2.3 to 3. One such mixture of MDA-based polyfunctional amines
having
differing functionalities is, in particular, crude MDA which is formed, in
particular, as
intermediate in the condensation of aniline with formaldehyde, usually
catalyzed by
hydrochloric acid, in the production of crude MDI.
PF 70475 CA 02801521 2012-12-04
In the abovementioned preferred second embodiment, particular preference is
given to
the component (a2) comprising oligomeric diaminodiphenylmethane as compound
(a2-u) and having an overall functionality of at least 2.1.
5
The proportion of amines of type (a2-s) having the general formula I based on
the total
weight of all polyfunctional amines of the component (a2), which thus add up
to a total
of 100% by weight, is preferably from 10 to 100% by weight, in particular from
30 to
100% by weight, very particularly preferably from 50 to 100% by weight, in
particular
10 from 80 to 100% by weight.
The proportion of polyfunctional aromatic amines (a2-u) which differ from the
amines of
type (a2-s) based on the total weight of all polyfunctional amines of the
component (a2)
is preferably from 0 to 90% by weight, in particular from 0 to 70% by weight,
particularly
preferably from 0 to 50% by weight, in particular from 0 to 20% by weight.
Component (a3) is water. The preferred amount of water used is from 0.1 to 30%
by
weight, in particular from 0.2 to 25% by weight, particularly preferably from
0.5 to 20%
by weight, in each case based on the total weight of the components (al), (a2)
and
(a3), which is 100% by weight.
The preferred amount of water within the ranges presented depends on whether a
catalyst (a4) is or is not used.
In a first embodiment, the reaction of the components (al), (a2) and (a3) is
carried out
in the absence of a catalyst (a4). In this first embodiment, it has been found
to be
advantageous to use from 5 to 30% by weight, in particular from 6 to 25% by
weight,
particularly preferably from 8 to 20% by weight, of water as component (a3),
in each
case based on the total weight of the components (a1), (a2) and (a3), which is
100%
by weight.
In this first embodiment, the abovementioned components (al), (a2) and (a3)
are
preferably used in the following ratio, in each case based on the total weight
of the
components (a 1), (a2) and (a3), which is 100% by weight: from 40 to 94.9% by
weight,
in particular from 55 to 93.5% by weight, particularly preferably from 68 to
90% by
weight, of the component (a1), from 0.1 to 30% by weight, in particular from
0.5 to 20%
by weight, particularly preferably from 2 to 12% by weight, of the component
(a2) and
from 5 to 30% by weight, in particular from 6 to 25% by weight, particularly
preferably
from 8 to 20% by weight, of the component (a3).
A calculated content of amino groups can be derived from the water content and
the
content of reactive isocyanate groups of the component (a1) by assuming
complete
PF 70475 CA 02801521 2012-12-04
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reaction of the water with the isocyanate groups of the component (al) to form
a
corresponding number of amino groups and adding this content to the content
resulting
from component (a2) (total namine). The resulting use ratio of the calculated
remaining
NCO groups nNCO to the amino groups calculated to have been formed and used
will
hereinafter be referred to as calculated use ratio nNCO/namine and is an
equivalence ratio,
i.e. a molar ratio of the respective functional groups.
In the abovementioned first embodiment, the calculated use ratio (equivalence
ratio)
nNcO/namine can vary over a wide range and in particular be from 0.6 to 5.
nNCO/namine is
preferably from 1 to 1.6, in particular from 1.1 to 1.4.
Water reacts with the isocyanate groups to form amino groups and liberate CO2.
Polyfunctional amines are therefore partially produced as intermediate (in
situ). In the
further course of the reaction, they are reacted with isocyanate groups to
form urea
linkages. The production of amines as intermediate leads to porous materials
having
particularly high mechanical stability and low thermal conductivity. However,
the CO2
formed must not disrupt gelling to such an extent that the structure of the
resulting
porous material is influenced in an undesirable way. This gives the
abovementioned
preferred upper limit for the water content based on the total weight of the
components
(al) to (a3), which is preferably not more than 30% by weight, particularly
preferably
not more than 25% by weight, in particular not more than 20% by weight. A
water
content in this range also leads to the advantage that any residual water
after gelling is
complete does not have to be removed in a complicated fashion by drying.
In a second, preferred embodiment, the reaction of the components (al), (a2)
and (a3)
is carried out in the presence of a catalyst (a4). In this second embodiment,
it has been
found to be advantageous to use from 0.1 to 15% by weight, in particular from
0.2 to
15% by weight, particularly preferably from 0.5 to 12% by weight, of water as
component (a3), in each case based on the total weight of the components (al),
(a2)
and (a3), which is 100% by weight. In the abovementioned ranges, particularly
advantageous mechanical properties of the resulting porous materials are
obtained,
which is due to a particularly advantageous network structure. A larger amount
of water
has an adverse effect on the network structure and is disadvantageous in terms
of the
final properties of the porous material.
In the preferred second embodiment, the abovementioned components (a1), (a2)
and
(a3) are preferably used in the following ratio, in each case based on the
total weight of
the components (a1), (a2) and (a3), which is 100% by weight: from 55 to 99.8%
by
weight, in particular from 65 to 99.3% by weight, particularly preferably from
76 to
97.5% by weight, of the component (al), from 0.1 to 30% by weight, in
particular from
0.5 to 20% by weight, particularly preferably from 2 to 12% by weight, of the
PF 70475 CA 02801521 2012-12-04
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component (a2) and from 0.1 to 15% by weight, in particular from 0.2 to 15% by
weight,
particularly preferably from 0.5 to 12% by weight, of the component (a3).
In the abovementioned second embodiment, the calculated use ratio (equivalence
ratio) n"co/namine is preferably from 1.01 to 5. The equivalence ratio
mentioned is
particularly preferably from 1.1 to 3, in particular from 1.1 to 2. An excess
of n"co over
namine leads, in this embodiment, to lower shrinkage of the porous material,
in particular
xerogel, in the removal of the solvent and as a result of synergistic
interaction with the
catalyst (a4) to an improved network structure and to improved final
properties of the
resulting porous material.
The components (al) and (a2) will hereinafter be referred to collectively as
organic gel
precursor (A). It will be obvious to a person skilled in the art that the
partial reaction of
the component (al) with the component (a3) leads to the actual gel precursor
(A) which
is subsequently converted into a gel.
Catalyst (a4)
The process of the invention is preferably carried out in the presence of at
least one
catalyst as component (a4).
Possible catalysts are in principle all catalysts known to those skilled in
the art which
accelerate the trimerization of isocyanates (known as trimerization catalysts)
and/or the
reaction of isocyanates with amino groups (known as gelling catalysts) and/or
the
reaction of isocyanates with water (known as blowing catalysts).
The corresponding catalysts are known per se and have different relative
activities in
respect of the abovementioned three reactions. Depending on the relative
activity, they
can thus be assigned to one or more of the abovementioned types. Furthermore,
it will
be known to a person skilled in the art that reactions other than those
mentioned above
can also occur.
Corresponding catalysts can be characterized, inter alia, according to their
gelling to
blowing ratio, as is known, for example, from Polyurethane, 31d edition, G.
Oertel,
Hanser Verlag, Munich, 1993.
Preferred catalysts (a4) have a balanced gelling to blowing ratio, so that the
reaction of
the component (al) with water is not too strongly accelerated, leading to an
adverse
effect on the network structure, and at the same time results in a short
gelling time so
that the demolding time is advantageously short. Preferred catalysts at the
same time
have a significant activity in respect of trimerization. This favorably
influences the
PF 70475 CA 02801521 2012-12-04
13
homogeneity of the network structure, resulting in particularly advantageous
mechanical properties.
The catalysts can be able to be incorporated as a monomer building block
(incorporatable catalyst) or not be able to be incorporated.
The component (a4) is advantageously used in the smallest effective amount.
Preference is given to employing amounts of from 0.01 to 5 parts by weight, in
particular from 0.1 to 3 parts by weight, particularly preferably from 0.2 to
2.5 parts by
weight, of the component (a4) based on a total of 100 parts by weight of the
components (al), (a2) and (a3).
Catalysts preferred as component (a4) are selected from the group consisting
of
primary, secondary and tertiary amines, triazine derivatives, organic metal
compounds,
metal chelates, quaternary ammonium salts, ammonium hydroxides and also alkali
metal and alkaline earth metal hydroxides, alkoxides and carboxylates.
Suitable catalysts are in particular strong bases, for example quaternary
ammonium
hydroxides such as tetraalkylammonium hydroxides having from 1 to 4 carbon
atoms in
the alkyl radical and benzyltrimethylammonium hydroxide, alkali metal
hydroxides such
as potassium or sodium hydroxide and alkali metal alkoxides such as sodium
methoxide, potassium and sodium ethoxide and potassium isopropoxide.
Further suitable catalysts are, in particular, alkali metal salts of
carboxylic acids, e.g.
potassium formate, sodium acetate, potassium acetate, potassium 2-
ethylhexanoate,
potassium adipate and sodium benzoate, alkali metal salts of long-chain fatty
acids
having from 8 to 20 carbon atoms, in particular from 10 to 20 carbon atoms,
and
optionally lateral OH groups.
Further suitable catalysts are, in particular, N-hydroxyalkyl quaternary
ammonium
carboxylates, e.g. trimethylhydroxypropylammonium formate.
Organic metal compounds as, in particular, gelling catalysts are known per se
to those
skilled in the art and are likewise suitable as catalysts (a4). Organic tin
compounds
such as tin 2-ethylhexanoate and dibutyltin dilaurate are preferred as
constituents of
component (a4).
Tertiary amines are known per se to those skilled in the art as gelling
catalysts and as
trimerization catalysts. Tertiary amines are particularly preferred as
catalysts (a4).
Preferred tertiary amines are, in particular, N,N-dimethylbenzylamine, N,N'-
dimethylpiperazine, N,N-dimethylcyclohexylamine, N,N',N"-
tris(dialkylaminoalkyl)-s-
hexahydrotriazines, such as N,N',N"-tris(dimethylaminopropyl)-s-
hexahydrotriazine,
PF 70475 CA 02801521 2012-12-04
14
tris(dimethylaminomethyl)phenol, bis(2-dimethylaminoethyl) ether, N,N,N,N,N-
pentamethyldiethylenetriamine, methylimidazole, dimethylbenzylamine, 1,6-
diazabicyclo[5.4.0]undec-7-ene, triethylamine, triethylenediamine (IUPAC: 1,4-
diazabicyclo[2.2.2]octane), dimethylaminoethanolamine,
dimethylaminopropylamine,
N,N-dimethylaminoethoxyethanol, N,N,N-trimethylaminoethylethanolamine,
triethanolamine, diethanolamine, triisopropanolamine and diisopropanolamine.
Catalysts which are particularly preferred as component (a4) are selected from
the
group consisting of N,N-dimethylcyclohexylamine, bis(2-dimethylaminoethyl)
ether,
N,N,N,N,N-pentamethyldiethylenetriamine, methylimidazole, dimethylbenzylamine,
1,6-
diazabicyclo[5.4.0]undec-7-ene, trisdimethylaminopropylhexahydrotriazine,
triethylamine, tris(dimethylaminomethyl)phenol, triethylenediamine
(diazabicyclo[2.2.2]octane), dimethylaminoethanolamine,
dimethylaminopropylamine,
N,N-dimethylaminoethoxyethanol, N,N,N-trimethylaminoethylethanolamine,
triethanolamine, diethanolamine, triisopropanolamine, diisopropanolamine,
metal
acetylacetonates, ammonium ethylhexanoates and metal ethylhexanoates.
The use of the catalysts (a4) which are preferred for the purposes of the
present
invention leads to porous materials having improved mechanical properties, in
particular improved compressive strength. In addition, the gelling time is
reduced by
use of the catalysts (a4), i.e. the gelling reaction is accelerated, without
other properties
being adversely affected.
Solvent (C)
According to the present invention, the reaction takes place in the presence
of a
solvent (C).
For the purposes of the present invention, the term solvent (C) comprises
liquid
diluents, i.e. both solvents in the narrower sense and also dispersion media.
The
mixture can, in particular, be a true solution, a colloidal solution or a
dispersion, e.g. an
emulsion or suspension. The mixture is preferably a true solution. The solvent
(C) is a
compound which is liquid under the conditions of step (a), preferably an
organic
solvent.
The solvent (C) can in principle be an organic compound or a mixture of a
plurality of
compounds, with the solvent (C) being liquid under the temperature and
pressure
conditions under which the mixture is provided in step (a) (dissolution
conditions for
short). The composition of the solvent (C) is selected so that it is able to
dissolve or
disperse, preferably dissolve, the organic gel precursor. Preferred solvents
(C) are
those which are a solvent for the organic gel precursor (A), i.e. ones which
dissolve the
organic gel precursor (A) completely under the reaction conditions.
PF 70475 CA 02801521 2012-12-04
The reaction product of the reaction in the presence of the solvent (C) is
initially a gel,
i.e. a viscoelastic chemical network which is swollen by the solvent (C). A
solvent (C)
which is a good swelling agent for the network formed in step (b) generally
leads to a
5 network having fine pores and a small average pore diameter, while a solvent
(C)
which is a poor swelling agent for the gel resulting from step (b) generally
leads to a
coarse-pored network having a large average pore diameter.
The choice of the solvent (C) thus influences the desired pore size
distribution and the
10 desired porosity. The choice of the solvent (C) is also generally made in
such a way
that precipitation or flocculation due to formation of a precipitated reaction
product does
not occur to a significant extent during or after step (b) of the process of
the invention.
When a suitable solvent (C) is chosen, the proportion of precipitated reaction
product is
15 usually less than 1% by weight, based on the total weight of the mixture.
The amount of
precipitated product formed in a particular solvent (C) can be determined
gravimetrically by filtering the reaction mixture through a suitable filter
before the gelling
point.
Possible solvents (C) are the solvents known from the prior art for isocyanate-
based
polymers. Preferred solvents are those which are a solvent for the components
(al),
(a2) and (a3), i.e. solvents which dissolve the constituents of the components
(al), (a2)
and (a3) virtually completely under the reaction conditions. The solvent (C)
is
preferably inert, i.e. unreactive, toward component (al).
Possible solvents (C) are, for example, ketones, aldehydes, alkyl alkanoates,
amides
such as formamide and N-methylpyrollidone, sulfoxides such as dimethyl
sulfoxide,
aliphatic and cycloaliphatic halogenated hydrocarbons, halogenated aromatic
compounds and fluorine-containing ethers. Mixtures of two or more of the
abovementioned compounds are likewise possible.
Further possibilities as solvent (C) are acetals, in particular
diethoxymethane,
dimethoxymethane and 1,3-dioxolane.
Dialkyl ethers and cyclic ethers are likewise suitable as solvents (C).
Preferred dialkyl
ethers are, in particular, those having from 2 to 6 carbon atoms, in
particular methyl
ethyl ether, diethyl ether, methyl propyl ether, methyl isopropyl ether,
propyl ethyl ether,
ethyl isopropyl ether, dipropyl ether, propyl isopropyl ether, diisopropyl
ether, methyl
butyl ether, methyl isobutyl ether, methyl t-butyl ether, ethyl n-butyl ether,
ethyl isobutyl
ether and ethyl t-butyl ether. Preferred cyclic ethers are, in particular,
tetrahydrofuran,
dioxane and tetrahydropyran.
PF 70475 CA 02801521 2012-12-04
16
Further preferred solvents (C) are alkyl alkanoates, in particular methyl
formate, methyl
acetate, ethyl formate, butyl acetate and ethyl acetate. Preferred halogenated
solvents
are described in WO 00/24799, page 4, line 12 to page 5, line 4.
Aldehydes and/or ketones are particularly preferred as solvents (C). Aldehydes
or
ketones suitable as solvents (C) are, in particular, those corresponding to
the general
formula R2-(CO)-R', where RI and R2 are each hydrogen or an alkyl group having
1, 2,
3 or 4 carbon atoms. Suitable aldehydes or ketones are, in particular,
acetaldehyde,
propionaldehyde, n-butyraldehyde, isobutyraldehyde, 2-ethylbutyraldehyde,
valeraldehyde, isopentaldehyde, 2-methylpentaldehyde, 2-ethylhexaldehyde,
acrolein,
methacrolein, crotonaldehyde, furfural, acrolein dimer, methacrolein dimer,
1,2,3,6-
tetrahydrobenzaldehyde, 6-methyl-3-cyclohexenaldehyde, cyanoacetaldehyde,
ethyl
glyoxylate, benzaldehyde, acetone, methyl isobutyl ketone, diethyl ketone,
methyl ethyl
ketone, methyl isobutyl ketone, methyl n-butyl ketone, ethyl isopropyl ketone,
2-
acetylfuran, 2-methoxy-4-methylpentan-2-one, cyclohexanone and acetophenone.
The
abovementioned aldehydes and ketones can also be used in the form of mixtures.
Ketones and aldehydes having alkyl groups having up to 3 carbon atoms per
substituent are preferred as solvents (C). Particular preference is given to
acetone.
In many cases, particularly suitable solvents (C) are obtained by using two or
more
completely miscible compounds selected from the abovementioned solvents in the
form of a mixture.
To obtain a sufficiently stable gel which does not shrink too much during
drying in step
(c) in step (b), the proportion of the components (a1), (a2) and (a3) based on
the total
weight of the components (a1) to (a3) and the solvent (C), which is 100% by
weight,
must generally be not less than 5% by weight. The proportion of the components
(a1),
(a2) and (a3) based on the total weight of the components (a1) to (a3) and the
solvent
(C), which is 100% by weight, is preferably at least 6% by weight,
particularly
preferably at least 8% by weight, in particular at least 10% by weight.
On the other hand, the concentration of the components (al) to (a3) in the
mixture
provided must not be too high since otherwise no porous material having
favorable
properties is obtained. In general, the proportion of the components (al),
(a2) and (a3)
based on the total weight of the components (a1) to (a3) and the solvent (C),
which is
100% by weight, is not more than 40% by weight. The proportion of the
components
(al), (a2) and (a3) based on the total weight of the components (al) to (a3)
and the
solvent (C), which is 100% by weight, is preferably not more than 35% by
weight,
particularly preferably not more than 25% by weight, in particular not more
than 20% by
weight.
PF 70475 CA 02801521 2012-12-04
17
The total proportion by weight of the components (a1), (a2) and (a3) based on
the total
weight of the components (a1), (a2) and (a3) and the solvent (S), which is
100% by
weight, is preferably from 8 to 25% by weight, in particular from 10 to 20% by
weight,
particularly preferably from 12 to 18% by weight. Adherence to the amount of
the
starting materials in the range mentioned leads to porous materials having a
particularly advantageous pore structure, low thermal conductivity and low
shrinking
during drying.
Before the reaction, it is necessary to mix the components used, in particular
to mix
them homogeneously. The rate of mixing should be high relative to the rate of
the
reaction in order to avoid mixing defects. Appropriate mixing methods are
known per se
to those skilled in the art.
Preferred process for producing the porous materials
In a preferred embodiment, the process of the invention comprises at least the
following steps:
(a) provision of the components (al), (a2) and (a3) and the solvent (C) as
described
above,
(b) reaction of the components (al), (a2) and (a3) in the presence of the
solvent (C)
to form a gel and
(c) drying of the gel obtained in the preceding step.
Preferred embodiments of steps (a) to (c) will be described in detail below.
Step (a)
According to the invention, the components (al), (a2) and (a3) and the solvent
(C) are
provided in step (a).
The components (al) and (a2) are preferably provided separately from one
another,
each in a suitable partial amount of the solvent (C). The separate provision
makes it
possible for the gelling reaction to be optimally monitored or controlled
before and
during mixing.
Component (a3) is particularly preferably provided as a mixture with component
(a2),
i.e. separately from component (al). This avoids the reaction of water with
component
(al) to form networks without the presence of component (a2). The prior mixing
of
water with component (al) otherwise leads to less favorable properties in
respect of
the homogeneity of the pore structure and the thermal conductivity of the
resulting
materials.
PF 70475 CA 02801521 2012-12-04
18
The mixture or mixtures provided in step (a) can also comprise customary
auxiliaries
known to those skilled in the art as further constituents. Mention may be made
by way
of example of surface-active substances, flame retardants, nucleating agents,
oxidation
stabilizers, lubricants and mold release agents, dyes and pigments,
stabilizers, e.g.
against hydrolysis, light, heat or discoloration, inorganic and/or organic
fillers,
reinforcing materials and biocides.
Further information regarding the abovementioned auxiliaries and additives may
be
found in the specialist literature, e.g. in Plastics Additive Handbook, 5th
edition,
H. Zweifel, ed. Hanser Publishers, Munich, 2001.
Step (b)
According to the invention, the reaction of the components (al) and (a2) takes
place in
the presence of the solvent (C) to form a gel in step (b). Thus, in step (b)
of the process
of the invention, the component (al) is partly reacted with water to form at
least one
polyfunctional amine and the polyfunctional amines are reacted with the
polyfunctional
isocyanates in a gelling reaction to form a gel.
To carry out the reaction, a homogeneous mixture of the components provided in
step
(a) firstly has to be produced.
The provision of the components provided in step (a) can be carried out in a
conventional way. A stirrer or another mixing device is preferably used here
in order to
achieve good and rapid mixing. The time required for producing the homogeneous
mixture should be short in relation to the time during which the gelling
reaction leads to
at least partial formation of a gel, in order to avoid mixing defects. The
other mixing
conditions are generally not critical; for example, mixing can be carried out
at from 0 to
100 C and from 0.1 to 10 bar (absolute), in particular at, for example, room
temperature and atmospheric pressure. After a homogeneous mixture has been
produced, the mixing apparatus is preferably switched off.
The gelling reaction is a polyaddition reaction, in particular a polyaddition
of isocyanate
groups and amino groups.
For the purposes of the present invention, a gel is a crosslinked system based
on a
polymer which is present in contact with a liquid (known as Solvogel or
Lyogel, or with
water as liquid: aquagel or hydrogel). Here, the polymer phase forms a
continuous
three-dimensional network.
PF 70475 CA 02801521 2012-12-04
19
In step (b) of the process of the invention, the gel is usually formed by
allowing to rest,
e.g. by simply allowing the container, reaction vessel or reactor in which the
mixture is
present (hereinafter referred to as gelling apparatus) to stand. The mixture
is preferably
no longer stirred or mixed during gelling (gel formation) because this could
hinder
formation of the gel. It has been found to be advantageous to cover the
mixture during
gelling or to close the gelling apparatus.
Gelling is known per se to a person skilled in the art and is described, for
example, in
WO-2009/027310 on page 21, line 19 to page 23, line 13, the contents of which
are
hereby fully incorporated by reference.
Step (c)
According to the invention, the gel obtained in the previous step is dried in
step (c).
Drying under supercritical conditions is in principle possible, preferably
after
replacement of the solvent by 002 or other solvents suitable for the purposes
of
supercritical drying. Such drying is known per se to a person skilled in the
art.
Supercritical conditions characterize a temperature and a pressure at which
the fluid
phase to be removed is present in the supercritical state. In this way,
shrinkage of the
gel body on removal of the solvent can be reduced.
However, in view of the simple process conditions, preference is given to
drying the
gels obtained by conversion of the liquid comprised in the gel into the
gaseous state at
a temperature and a pressure below the critical temperature and the critical
pressure of
the liquid comprised in the gel.
The drying of the gel obtained is preferably carried out by converting the
solvent (C)
into the gaseous state at a temperature and a pressure below the critical
temperature
and the critical pressure of the solvent (C). Accordingly, drying is
preferably carried out
by removing the solvent (C) which was present in the reaction without prior
replacement by a further solvent.
Such methods are likewise known to those skilled in the art and are described
in
WO-2009/027310 on page 26, line 22 to page 28, line 36, the contents of which
are
hereby fully incorporated by reference.
Properties of the porous materials and use
The present invention further provides the porous materials which can be
obtained by
the process of the invention.
PF 70475 CA 02801521 2012-12-04
Xerogels are preferred as porous materials for the purposes of the present
invention,
i.e. the porous material which can be obtained according to the invention is
preferably a
xerogel.
5 For the purposes of the present invention, a xerogel is a porous material
which has a
porosity of at least 70% by volume and a volume average pore diameter of not
more
than 50 microns and has been produced by a sol-gel process, with the liquid
phase
having been removed from the gel by drying below the critical temperature and
below
the critical pressure of the liquid phase ("subcritical conditions").
The average pore diameter is determined by scanning electron microscopy and
subsequent image analysis using a statistically significant number of pores.
Corresponding methods are known to those skilled in the art.
The volume average pore diameter of the porous material is preferably not more
than
5 microns. The volume average pore diameter of the porous material is
particularly
preferably not more than 4 microns, very particularly preferably not more than
3 microns and in particular not more than 2.5 microns.
Although a very small pore size combined with a high porosity is desirable
from the
point of view of a low thermal conductivity, from the point of view of
production and to
obtain a sufficiently mechanically stable porous material, there is a
practical lower limit
to the volume average pore diameter. In general, the volume average pore
diameter is
at least 200 nm, preferably at least 400 nm. In many cases, the volume average
pore
diameter is at least 500 nm, in particular at least 1 micron.
The porous material which can be obtained according to the invention
preferably has a
porosity of at least 70% by volume, in particular from 70 to 99% by volume,
particularly
preferably at least 80% by volume, very particularly preferably at least 85%
by volume,
in particular from 85 to 95% by volume. The porosity in % by volume means that
the
specified proportion of the total volume of the porous material comprises
pores.
Although a very high porosity is usually desirable from the point of view of a
minimal
thermal conductivity, an upper limit is imposed on the porosity by the
mechanical
properties and the processability of the porous material.
The components (a1), sometimes firstly reacted with water, and (a2) are
present in
reactive (polymer) form in the porous material which can be obtained according
to the
invention. Owing to the composition according to the invention, the monomer
building
blocks (al) and (a2) are predominantly bound via urea linkages and/or via
isocyanurate
linkages in the porous material, with the isocyanurate groups being formed by
trimerization of isocyanate groups of the monomer building blocks (al). If the
porous
PF 70475 CA 02801521 2012-12-04
21
material comprises further components, further possible linkages are, for
example,
urethane groups formed by reaction of isocyanate groups with alcohols or
phenols.
The components (a1), sometimes firstly reacted with water, and (a2) are
preferably
linked to an extent of at least 50 mol% by urea groups -NH-CO-NH- and/or via
isocyanurate linkages in the porous material. The components (a1) and (a2) are
preferably linked to an extent of from 50 to 100 mol% by urea groups and/or
via
isocyanurate linkages in the porous material, in particular from 60 to 100
mol%, very
particularly preferably from 70 to 100 mol%, in particular from 80 to 100
mol%, for
example from 90 to 100 mol%.
The balance to 100 mol% are present as further linkages, with such further
linkages
being known per se to a person skilled in the art from the field of isocyanate
polymers.
Examples which may be mentioned are ester, urea, biuret, allophanate,
carbodiimide,
isocyanurate, uretdione and/or urethane groups.
The determination of the mol% of the linkages of the monomer building blocks
in the
porous material is carried out by means of NMR spectroscopy (nuclear magnetic
resonance) in the solid or in the swollen state. Suitable methods of
determination are
known to those skilled in the art.
The density of the porous material which can be obtained according to the
invention is
usually from 20 to 600 g/l, preferably from 50 to 500 g/I and particularly
preferably from
70 to 200 g/l.
The process of the invention gives a coherent porous material and not only a
polymer
powder or particles. Here, the three-dimensional shape of the resulting porous
material
is determined by the shape of the gel which is in turn determined by the shape
of the
gelling apparatus. Thus, for example, a cylindrical gelling vessel usually
gives an
approximately cylindrical gel which can then be dried to give a porous
material having a
cylindrical shape.
The porous materials which can be obtained according to the invention have a
low
thermal conductivity, a high porosity and a low density combined with high
mechanical
stability. In addition, the porous materials have a small average pore size.
The
combination of the abovementioned properties allows the materials to be used
as
insulation material in the field of thermal insulation, in particular for
applications in the
vacuum sector where a very low thickness of vacuum panels is preferred, for
example
in refrigeration appliances or in buildings. Thus, the use in vacuum
insulation panels, in
particular as core material for vacuum insulation panels, is preferred. In
addition, use of
the porous materials of the invention as insulation material is preferred.
PF 70475 CA 02801521 2012-12-04
22
Furthermore, uses at pressures of from 1 to 100 mbar and in particular from 10
to
100 mbar are possible because of the low thermal conductivity of the porous
materials
which can be obtained according to the invention. The property profile of the
porous
materials which can be obtained according to the invention opens up, in
particular,
uses in which a long life of the vacuum panels is desired and in which the
thermal
conductivity remains low after many years even in the even of a pressure
increase of
about 2 mbar per year, for example at a pressure of 100 mbar. The porous
materials
which can be obtained according to the invention have advantageous thermal
properties and also advantageous materials properties such as simple
processability
and high mechanical stability, for example low brittleness.
Examples
The thermal conductivity a, was determined in accordance with DIN EN 12667
using a
plate instrument from Hesto (Lambda Control A50).
The following compounds were used:
Component al:
Oligomeric MDI (Lupranat M200) having an NCO content of 30.9 g per 100 g in
accordance with ASTM D-5155-96 A, a functionality in the region of three and a
viscosity of 2100 mPa.s at 25 C in accordance with DIN 53018 (hereinafter
"compound
M200").
Oligomeric MDI (Lupranat M50) having an NCO content of 31.5 g per 100 g in
accordance with ASTM D-5155-96 A, a functionality in the range from 2.8 to 2.9
and a
viscosity of 550 mPa.s at 25 C in accordance with DIN 53018 (hereinafter
"compound
M50").
Component a2:
3,3',5,5'-Tetraethyl-4,4'-diaminodiphenylmethane (hereinafter "MDEA");
3,3',5,5'-
tetramethyl-4,4'-diaminodiphenylmethane (hereinafter "MDMA").
Component a2 (for comparative examples):
Ethacure 100 from Albemarle, a mixture of aromatic diamines, comprising in
particular 3,5-diethyltoluene-2,4-diamine and 3,5-diethyltoluene-2,6-diamine;
Unilink 4200 from UOP, an aromatic diamine having the structure 4,4'-bis(sec-
butylamino)diphenylmethane;
PF 70475 CA 02801521 2012-12-04
23
3,3',5,5'-tetramethyl-4,4'-diaminodicyclohexylmethane; 4,4'-
diaminodiphenylmethane.
Catalysts (a4):
Triethanolamine; triethylenediamine (IUPAC: 1,4-diazabicyclo[2.2.2]octane);
N,N-
dimethylcyclohexylamine.
Example 1
56 g of the compound M50 were dissolved while stirring at 20 C in 210 g of
acetone in
a glass beaker. 4 g of the compound MDEA and 8 g of water were dissolved in
210 g of
acetone in a second glass beaker. The two solutions from step (a) were mixed
with
stirring. This gave a clear, low-viscosity mixture. The mixture was allowed to
stand at
room temperature for 24 hours to effect curing. The gel was subsequently taken
from
the glass beaker and the liquid (acetone) was removed by drying at 20 C for 7
days.
Scanning electron microscopy with subsequent image analysis indicated a
bimodal
pore size distribution having pore diameters in the region of 15 pm and 800
nm. The
thermal conductivity was 2.9 mW/m*K at a pressure of 2.2 * 10-4 mbar.
Example 2
60 g of the compound M200 were dissolved while stirring at 20 C in 210 g of
acetone in
a glass beaker. 8 g of the compound MDEA and 8 g of water were dissolved in
210 g of
acetone in a second glass beaker. The two solutions from step (a) were mixed
with
stirring. This gave a clear, low-viscosity mixture. The mixture was allowed to
stand at
room temperature for 24 hours to effect curing. The gel was subsequently taken
from
the glass beaker and the liquid (acetone) was removed by drying at 20 C for 7
days.
Electron micrographs indicated an average pore diameter of about 1 pm.
The thermal conductivity was 5.5 mW/m*K at a pressure of 2.3 * 10-4 mbar.
Example 3
70 g of the compound M50 were dissolved while stirring at 20 C in 210 g of
acetone in
a glass beaker. 4 g of the compound MDEA, 2 g of triethanolamine and 8 g of
water
were dissolved in 210 g of acetone in a second glass beaker. The two solutions
from
step (a) were mixed with stirring. This gave a clear, low-viscosity mixture.
The mixture
was allowed to stand at room temperature for 24 hours to effect curing. The
gel was
subsequently taken from the glass beaker and the liquid (acetone) was removed
by
drying at 20 C for 7 days.
PF 70475 CA 02801521 2012-12-04
24
Electron micrographs indicated a bimodal pore size distribution having pores
in the
region of 15 pm and 800 nm.
The thermal conductivity was 7.1 mW/m*K at a pressure of 2.3 * 10-a mbar. The
use of
the catalyst led to a reduced gelling time and to improved compressive
strength
compared to a procedure without catalyst.
Example 4
56 g of the compound M50 were dissolved while stirring at 20 C in 210 g of
acetone in
a glass beaker. 4 g of the compound MDEA, 0.5 g of triethylenediamine and 8 g
of
water were dissolved in 210 g of acetone in a second glass beaker. The two
solutions
from step (a) were mixed with stirring. This gave a clear, low-viscosity
mixture. The
mixture was allowed to stand at room temperature for 24 hours to effect
curing. The gel
was subsequently taken from the glass beaker and the liquid (acetone) was
removed
by drying at 20 C for 7 days.
Electron micrographs indicated an average pore diameter of about 1.5 pm.
The thermal conductivity was 4.3 mW/m*K at a pressure of 2.2 * 10-4 mbar. The
use of
the catalyst led to a reduced gelling time and to improved compressive
strength
compared to a procedure without catalyst.
Example 5
70 g of the compound M50 were dissolved while stirring at 20 C in 210 g of
acetone in
a glass beaker. 4 g of the compound MDEA, 2 g of N,N-dimethylcyclohexylamine
and
8 g of water were dissolved in 210 g of acetone in a second glass beaker. The
two
solutions from step (a) were mixed with stirring. This gave a clear, low-
viscosity
mixture. The mixture was allowed to stand at room temperature for 24 hours to
effect
curing. The gel was subsequently taken from the glass beaker and the liquid
(acetone)
was removed by drying at 20 C for 7 days.
Electron micrographs indicated an average pore diameter of about 800 nm.
The thermal conductivity was 7.2 mW/m*K at a pressure of 2.7 * 10-4 mbar. The
use of
the catalyst led to a reduced gelling time and to improved compressive
strength
compared to a procedure without catalyst.
Comparative example 6
3 g of the compound M200 were dissolved while stirring at 20 C in 10.5 g of
acetone in
a glass beaker. 0.1 g of the compound Ethacure 100 and 0.5 g of water were
dissolved in 11 g of acetone in a second glass beaker. The two solutions from
step (a)
PF 70475 CA 02801521 2012-12-04
were mixed with stirring. This gave a clear, low-viscosity mixture. The
mixture was
allowed to stand at room temperature for 24 hours to effect curing. The gel
was
subsequently taken from the glass beaker and the liquid (acetone) was removed
by
drying at 20 C for 7 days.
5
No stable gel could be produced since only a precipitate was formed.
Comparative example 7
10 3 g of the compound M200 were dissolved while stirring at 20 C in 10.5 g of
acetone in
a glass beaker. 0.1 g of the compound Unilink 4200 and 0.5 g of water were
dissolved in 11 g of acetone in a second glass beaker. The two solutions from
step (a)
were mixed with stirring. This gave a clear, low-viscosity mixture. The
mixture was
allowed to stand at room temperature for 24 hours to effect curing. The gel
was
15 subsequently taken from the glass beaker and the liquid (acetone) was
removed by
drying at 20 C for 7 days.
No stable gel could be produced since only a precipitate was formed.
20 Comparative example 8
3 g of the compound M200 were dissolved while stirring at 20 C in 10.5 g of
acetone in
a glass beaker. 0.1 g of the compound 3,3',5,5'-tetramethyl-4,4'-
diaminodicyclohexyl-
methane and 0.5 g of water were dissolved in 11 g of acetone in a second glass
25 beaker. The two solutions from step (a) were mixed with stirring. This gave
a clear, low-
viscosity mixture. The mixture was allowed to stand at room temperature for 24
hours
to effect curing. The gel was subsequently taken from the glass beaker and the
liquid
(acetone) was removed by drying at 20 C for 7 days.
No stable gel could be produced since only a precipitate was formed.
Comparative example 9
3 g of the compound M200 were dissolved while stirring at 20 C in 10.5 g of
acetone in
a glass beaker. 0.1 g of the compound 4,4'-diaminodiphenylmethane and 0.5 g of
water
were dissolved in 11 g of acetone in a second glass beaker. The two solutions
from
step (a) were mixed with stirring. This gave a clear, low-viscosity mixture.
The mixture
was allowed to stand at room temperature for 24 hours to effect curing. The
gel was
subsequently taken from the glass beaker and the liquid (acetone) was removed
by
drying at 20 C for 7 days.
No stable gel could be produced since only a precipitate was formed.
