Note: Descriptions are shown in the official language in which they were submitted.
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1
Core foams of polyurethane for production of wings and blades for wind power
systems in
particular
Description
The present invention relates to a reinforced polyurethane foam having a
density of
above 50 to 300 g/L, a density-independent compressive strength of above
7.5*10-4 MPa
(L/g)1-6, a density-independent compressive modulus of elasticity of above
1.7*10-2 MPa
(L/g)1.7, a density-independent tensile strength of above 6.4*10-4 MPa
(L/g)1.6, a density-
independent tensile modulus of elasticity of above 2.4*10-2 MPa (L/g)1.7, a
density-
independent flexural strength of above 1.25'10-3 MPa (L/g)1-6, and a density-
independent
flexural modulus of elasticity of above 1.75*10-2 MPa (L/g)1.7, obtainable by
mixing (a)
polyisocyanates with (b) compounds having isocyanate-reactive groups, (c)
blowing
agent comprising water, and optionally (d) catalyst and (e) further additives,
to form a
reaction mixture and curing the reaction mixture, wherein the reaction mixture
to be cured
comprises from 1% to 40% by weight of hollow microspheres and/or is applied to
a
porous reinforcing agent (f) capable of forming two-dimensional or three-
dimensional
networks in the polyurethane foam, the compounds having isocyanate-reactive
groups (b)
comprise polyetherols (b1), polyesterols (b2), chain extenders (b3) and
optionally
crosslinkers (b4) and aromatic polyether diols (b5), and said component (b)
comprises a
fraction of polyesterols (b2), chain extenders (b3) and aromatic polyether
diol (b5) that is
equal to at least 50% by weight, based on the total weight of said component
(b). The
present invention further relates to a process for producing such reinforced
polyurethane
foams and to their use as reinforcing foams for load-bearing, stiff areal
elements, in the
interior of wings or blades, and also as insulation material for liquefied
natural gas tanks.
Reinforced rigid foams based on polyurethanes are known and are described in
WO 2010/066635 or WO 2008/083996 for example. These foams are used for example
as insulation material for liquefied natural gas (LNG) tanks and more
particularly on LNG
carriers. Such insulation materials have to meet high mechanical requirements,
since
they perform a load-bearing function in relation to the LNG tank as well as an
insulating
function. High compressive strengths, a high compressive modulus of elasticity
and also
a high shear strength are required here in particular. Although existing foams
already
offer very good properties, an improvement in these properties, more
particularly the
elasticity, is desirable. Vibrations as encountered during transportation in
LNG carriers on
rough seas for example can be more effectively absorbed as a result.
Rigid foams having very good mechanical properties have further applications.
For
instance, these foams are used in wings of sporting aircraft, such as gliders
for example,
or in rotor blades of wind power systems for example. The material currently
most
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commonly used for reinforcement in blades and wings is balsa wood, foam based
on
crosslinked polyvinyl chloride and foam based on polyethylene terephthalate.
The disadvantage with these materials used for reinforcement in blades and
wings is that
balsa wood is a natural resource and hence is costly and not widely available;
that
manufacturing processes for foam based on crosslinked polyvinyl chloride are
very
inconvenient and have an adverse environmental impact due to the high halogen
content;
and that the mechanical properties of foam based on polyethylene terephthalate
are in
need of improvement.
Furthermore, wind power generation in particular appears to trend to ever
larger turbine
systems with longer blades. This feature typically involves applying a load-
bearing glass
fiber/reactive resin layer to the reinforcing foam. The reactive resins used
are mainly
epoxy resins or polyester resins. These resins evolve heat of reaction, or
have to be
heated.
The ever larger blades increase the mechanical demands on these load-bearing
glass
fiber/reactive resin systems used as an outside layer. To meet these
mechanical
demands, the usual thing done is to increase the thickness of the outside
layer. As a
result, the temperature involved in curing rises.
There are also efforts, motivated by the rising production figures in
particular, to shorten
the manufacturing process and hence the curing times of the blades and, more
particularly, of the outside layers. This can be done by raising the curing
temperature for
example. However, reinforcing foams based on crosslinked polyvinyl chloride in
particular
suffer a permanent loss of mechanical stability on heating to elevated
temperatures, such
as temperatures above 75 C for example.
It is further an essential requirement of wind power rotor blades in
particular that they
respond to high loads elastically in that they are able to flex to a certain
degree. The
same holds for wings. At the same time, the reinforcing foams shall be able to
withstand
the shearing forces arising as a result of the flexing/bending.
An essential criterion for a reinforcing foam in blades or wings is low
weight. Blade tips
can reach circumferential speeds on the order of 100 m/s, which produces large
radial
forces. To minimize these, it is desirable for the reinforcing foam to have a
very low
weight.
It is an object of the present invention to provide a foam having very good
mechanical
properties, such as high compressive strength and modulus, and also tensile
and flexural
CA 02818999 2013-05-24
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strength and moduli, and also a high shear resistance coupled with high
elasticity and low
density. The foam shall further have a high flexural modulus of elasticity and
a high
thermal stability and the manufacture of the foam shall be simple and the
recycling and/or
disposal shall be possible in an environmentally friendly manner.
We have found that this object is achieved by a reinforced polyurethane foam
having a
density of above 50 to 300 g/L, a density-independent compressive strength of
above
7.5*10-4 MPa (L/g)1.6, a density-independent compressive modulus of elasticity
of above
1.7*10-2 MPa (L/g)1.7, a tensile strength of above 6.4*10-4 MPa (Ug)16, a
tensile modulus
of elasticity of above 2.4*10-2 MPa (L/g)1 7, preferably 3.0*10-2*10-2 MPa
(L/g)1.7, a flexural
strength of above 1.25*10-3 MPa (Ug)16, preferably 1.50*10-3 MPa (L/g)1-6 and
a flexural
modulus of elasticity of above 1.75*10-2 MPa (L/g)17, obtainable by mixing (a)
polyisocyanates with (b) compounds having isocyanate-reactive groups, (c)
blowing
agent comprising water, and optionally (d) catalyst and (e) further additives
to form a
reaction mixture and curing the reaction mixture, wherein the reaction mixture
to be cured
comprises from 1% to 40% by weight of hollow microspheres and/or is applied to
a
porous reinforcing agent (f) capable of forming two-dimensional or three-
dimensional
networks in the polyurethane foam, the compounds having isocyanate-reactive
groups (b)
comprise polyetherols (b1), polyesterols (b2), chain extenders (b3) and
optionally
crosslinkers (b4) and aromatic polyether diols (b5), and said component (b)
comprises a
fraction of polyesterols (b2), chain extenders (b3) and aromatic polyether
diols (b5) that is
equal to at least 50% by weight, based on the total weight of said component
(b).
Compressive and tensile values herein are measured both perpendicularly and
parallel to
the direction of foaming and are always reported/specified as space averages
computed
as per (x*y*z)1/3. Flexural values and shear strength are always measured and
reported/specified perpendicularly to the direction of foaming.
A reinforced polyurethane foam herein is a reinforced polyurethane foam
wherein the
hollow microspheres and/or the reinforcing agent (f) is or are present in the
form of plies
or in the form of plies and hollow microspheres. Alternatively, there may be a
three-
dimensional reinforcing agent which forms a network, optionally in combination
with
hollow microspheres. Preferably, the reinforcing agent is in the form of at
least two plies
which form a homogeneous distribution in the foam and are preferably
perpendicular to
the direction of foaming. "Homogeneous distribution" in this connection is to
be
understood as meaning that the maximum separation between two adjacent plies,
or
between the upper ply and the top side of the foam, or between the lower ply
and the
bottom side of the foam will not differ from the minimum separation between
two plies, or
between the upper ply and the top side of the foam, or between the lower ply
and the
bottom side of the foam, respectively, by more than a factor of 4, preferably
by more than
a factor of 2 and more particularly by more than a factor of 1.5.
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The reinforcing agents (f) can consist for example of known glass fibers,
aramid fibers,
carbon fibers or polymeric fibers, such as glass fiber mats for example. The
reinforcing
materials may also consist of a combination of these materials of
construction. For
instance, a three-dimensional reinforcing agent can consist of two glass fiber
mats which
are joined together by polyamide fibers.
The ply-shaped reinforcing agent is used in amounts of at least 3.5 to 35 kg
per rn3 of
foam, depending on foam density and desired reinforcing effect. This implies,
for
example, one ply of a reinforcing agent having a density of 450 g/m2 in the
case of a foam
body having an area of 1 m2, a height of 3 cm and a foam density of 100 g/L. A
ply-
shaped reinforcing agent may also have a three-dimensional extent.
Combinations of
hollow microspheres, ply-shaped reinforcing agent and/or three-dimensional
reinforcing
agent are also possible.
The proportion of reinforcing agent (f) and/or hollow microspheres is
preferably in the
range from 1 to 40 percent by weight and more particularly 2-20 percent by
weight, based
on the total weight of the rigid polyurethane foam including reinforcing agent
(f) and/or
hollow microspheres.
The reinforced rigid foam used in the polyurethane composite system of the
present
invention has a DIN 53421/DIN EN ISO 604 density-independent compressive
strength of
above 7.5*10-4 MPa (Lig)16, a density-independent compressive modulus of
elasticity of
above 1.7*10-2 MPa (L/g)1.7, a DIN 53292/DIN EN ISO 527-1 density-independent
tensile
strength of above 6.4*10-4 MPa (Ug)1-6, a density-independent tensile modulus
of
elasticity of above 2.4*10-2 MPa (L/g)1.7, preferably 3.0*10-2 MPa (L/g)17, a
DIN 53423
density-independent flexural strength of above 1.25*10-3 MPa (L/g)1-6,
preferably 1.50*10-3
MPa (L/g)16 and a density-independent flexural modulus of elasticity of above
1.75*10-2
MPa (L/g)1.7. The reinforced polyurethane rigid foam of the present invention
preferably
further has a density-independent shear strength of above 3.8*10-4 MPa (L/g)1-
6 and more
preferably 5.5*10-4 MPa (L/g)16. Density-independent compressive strength was
computed as per compressive strength * (density)-1.6 and the density-
independent
compressive E-modulus was computed as per compressive E-modulus * (density)-1-
7. For
a reinforced rigid foam used in the polyurethane composite system of the
present
invention this means, for a foam density of 100 g/L, a compressive strength of
at least
1.19 MPa and preferably at least 1.2 MPa and a compressive E-modulus of at
least 42.7
MPa and preferably at least 44 MPa, a tensile strength of at least 1.0 MPa and
a tensile
E-modulus of at least 60.3 MPa and preferably at least 75 MPa, a flexural
strength of at
least 1.98 MPa and preferably at least 2.38 MPa and a flexural E-modulus of at
least 44
MPa. The density of the reinforced polyurethane rigid foam used according to
the present
CA 02818999 2013-05-24
invention is above 50 g/L to 300 g/L, preferably in the range from 80 g/L to
250 g/L and
more preferably in the range from 100 g/L to 220 g/L.
The reinforced rigid foams of the present invention preferably further have a
softening
5 temperature of more than 100 C, more preferably more than 120 C and even
more
preferably more than 140 C. The softening temperature is the temperature at
which the
polyurethane rigid foam of the present invention exhibits its maximum loss
modulus G" in
dynamic mechanical analysis (DMA) as per DIN EN ISO 6721-2. A high softening
temperature makes it possible to produce the composite elements of the present
invention at a higher temperature without structural changes in the foam which
lead to
dramatically compromised mechanical properties.
As isocyanates (a), it is possible to use all customary aliphatic,
cycloaliphatic and
preferably aromatic di- and/or polyisocyanates which have a viscosity of less
than 600
mPas, preferably less than 500 mPas and more preferably less than 350 mPas,
when
measured at 25 C. Particular preference for use as isocyanates is given to
toluene
diisocyanate (TDI), diphenylmethane diisocyanate (MDI) and mixtures of
diphenylmethane diisocyanate and polymeric diphenylmethane diisocyanate
(PMDI).
Mixtures of diphenylmethane diisocyanate and PMDI are used in particular.
These
particularly preferred isocyanates may be wholly or partly modified with
uretdione,
carbamate, isocyanurate, carbodiimide, allophanate and preferably urethane
groups.
Useful isocyanates (a) further include prepolymers and also mixtures of the
above-
described isocyanates and prepolymers. These prepolymers are obtained from the
above-described isocyanates and also the hereinbelow described polyethers,
polyesters
or both, and have an NCO content in the range from 14% to 32% by weight and
preferably in the range from 22% to 30% by weight.
As compounds having isocyanate-reactive groups (b) there can be used any
compound
that has at least two isocyanate-reactive groups, such as OH, SH, NH and
carbon-acid
groups. This component (b) herein includes polyetherols (b1), polyesterols
(b2), chain
extenders (b3) and optionally crosslinkers (b4) and/or aromatic polyether
diols (b5),
although this is to be understood as meaning that crosslinkers (b4) and
aromatic
polyether diols (b5) can be included independently of each other.
The polyetherols (b1) are obtained via known methods, for example by an
anionic
polymerization of alkylene oxides in the presence of catalysts which is
initiated with at
least one starter molecule comprising from 2 to 8, and preferably from 2 to 6
reactive
hydrogen atoms in bound form. Useful catalysts include alkali metal
hydroxides, such as
sodium hydroxide or potassium hydroxide, or alkali metal alkoxides, such as
sodium
CA 02818999 2013-05-24
6
methoxide, sodium ethoxide, potassium ethoxide or potassium isopropoxide, or ¨
in the
case of a cationic polymerization ¨ Lewis acids, such as antimony
pentachloride, boron
trifluoride etherate or fuller's earth. Useful catalysts further include
double metal cyanide
compounds, so-called DMC catalysts, and also amine-based catalysts.
The alkylene oxides used preferably comprise one or more compounds having from
2 to
4 carbon atoms in the alkylene radical, such as tetrahydrofuran, 1,3-propylene
oxide, 1,2-
butylene oxide, or 2,3-butylene oxide, each alone or in the form of mixtures,
and
preferably ethylene oxide and/or 1,2-propylene oxide.
Useful starter molecules include ethylene glycol, diethylene glycol, propylene
glycol,
dipropylene glycol, glycerol, trimethylolpropane, pentaerythritol, sugar
derivatives, such
as sucrose, hexitol derivatives, such as sorbitol, methylamine, ethylamine,
isopropylamine, butylamine, benzylamine, aniline, toluidine, toluenediamine,
naphthylamine, ethylenediamine, diethylenetriamine, 4,4'-methylenedianiline,
1,3-
propanediamine, 1,6-hexanediamine, ethanolamine, diethanolamine,
triethanolamine and
also other di- or polyhydric alcohols or mono- or polyfunctional amines.
Preferably, the polyetherols (b1) comprise at least one polyetherol (b1a)
having an
average functionality of 3.5 or greater, preferably in the range from 3.6 to 8
and more
particularly in the range from 3.8 to 6, and a viscosity at 25 C of 15 000
mPas or less,
preferably 10 000 mPas or less. The molecular weight is preferably in a range
of 300-900
g/mol, more preferably 400-800 g/mol and more particularly 450-750 g/mol. The
proportion of the overall weight of component (b) which is contributed by the
polyetherols
(b1a) is preferably in the range from 20% to 50% by weight and more preferably
in the
range from 25% to 40% by weight. The polyetherol (b1) may also comprise from
0% to
20% by weight and preferably from 1% to 10% by weight of polyetherol (b1 b)
having a
molecular weight of above 300 to 3000 g/mol, preferably in the range from 400
to 2500
g/mol and more particularly in the range from 400 to 1000 g/mol. The
polyetherols (b1 b)
preferably have an average functionality in the range from 1.8 to 3.0 and more
preferably
in the range from 1.95 to 2.2 and preferably have secondary OH groups.
Useful polyester alcohols (b2) are usually obtained by condensation of
polyfunctional
alcohols having from 2 to 12 carbon atoms, such as ethylene glycol, diethylene
glycol,
butanediol, trimethylolpropane, glycerol or pentaerythritol, with
polyfunctional carboxylic
acids having from 2 to 12 carbon atoms, examples being succinic acid, glutaric
acid,
adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic
acid, maleic acid,
fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, the isomers
of
naphthalenedicarboxylic acids or the anhydrides of the acids mentioned.
Preference is
given to using aromatic diacids, such as phthalic acid, isophthalic acid
and/or terephthalic
CA 02818999 2013-05-24
7
acid and also their anhydrides as acid component and ethylene glycol,
diethylene glycol,
1,4-butanediol and/or glycerol as alcohol component.
In a further embodiment, the polyester alcohols (b2) can be obtained by
replacing the
diacids or anhydrides thereof by corresponding monomeric esters, such as
dimethyl
terephthalate for example, or polymeric esters, such as polyethylene
terephthalate (PET)
for example.
Useful starting materials for preparing these polyesters further include
hydrophobic
substances. The hydrophobic substances comprise water-insoluble substances
comprising an apolar organic radical and also having at least one reactive
group selected
from the group consisting of hydroxyl, carboxylic acid, carboxylic ester or
mixtures
thereof. The equivalent weight of the hydrophobic materials is preferably
between 130
and 1000 g/mol. Fatty acids can be used for example, such as stearic acid,
oleic acid,
palmitic acid, lauric acid or linoleic acid, and also fats and oils, for
example castor oil,
maize oil, sunflower oil, soyabean oil, coconut oil, olive oil or tall oil.
When polyesters
comprise hydrophobic substances, the proportion of the overall monomer content
of the
polyester alcohol that is accounted for by the hydrophobic substances is
preferably in the
range from 1 to 30 mol% and more preferably in the range from 4 to 15 mol%.
These
polyesters comprising hydrophobic substances are hereinafter referred to as
hydrophobic
polyesters. The proportion of hydrophobic polyesters, based on the total
weight of the
polyesterols (b2), is preferably in the range from 0% to 80% by weight and
more
preferably in the range from 5% to 60% by weight.
Useful polyesterols (b2) preferably have an average functionality in the range
from 1.5 to
5, more preferably in the range from 1.8 to 3.5 and even more preferably in
the range
from 1.9 to 2.2 and viscosities at 25 C of preferably below 3000 mPas and more
preferably below 2500 mPas. The molecular weight is preferably in the range
from 290 to
1000 g/mol, more preferably in the range from 320 to 800 g/mol and even more
preferably in the range from 340 to 650 g/mol.
In a preferred embodiment, the component (b) comprises at least 50% by weight,
based
on the total weight of component (b), of polyesterols (b2). It is very
particularly preferable
for the polyesters (b2) to comprise hydrophobic polyesters in this case.
The compound having isocyanate-reactive groups (b) further comprises chain-
extending
agents (b3) and/or crosslinking agents (b4). The chain-extending and/or
crosslinking
agents used are more particularly di- or trifunctional amines and alcohols,
more
particularly diols, triols or both, each with molecular weights less than 300
g/mol,
preferably in the range from 60 to 300 g/mol and more preferably in the range
from 60 to
CA 02818999 2013-05-24
8
250 g/mol. It is the difunctional compounds which are known as chain extenders
(b3) and
the tri- or higher-functional compounds which are known as crosslinkers (b4).
Possible
examples include aliphatic, cycloaliphatic and/or aromatic diols having from 2
to 14 and
preferably from 2 to 10 carbon atoms, such as ethylene glycol, 1,2-
propanediol, 1,3-
propanediol, 1,2-pentanediol, 1,3-pentanediol, 1,10-decanediol,
1,2-dihydroxycyclohexane, 1,3-dihydroxycyclohexane, 1,4-dihydroxycyclohexane,
diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene
glycol, 1,4-
butanediol, 1,6-hexanediol and bis(2-hydroxyethyl)hydroquinone, triols and
higher
polyols, such as 1,2,4-trihydroxycyclohexane, 1,3,5-trihydroxycyclohexane,
glycerol and
trimethylolpropane, N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine, and
low
molecular weight hydroxyl-containing polyalkylene oxides based on ethylene
oxide and/or
1,2-propylene oxide and the aforementioned diols and/or triols as starter
molecules.
The proportion of the total weight of component (b) that is accounted for by
the
crosslinkers (b4) is preferably in the range from 0% to 40% by weight, and
more
preferably in the range from 1% to 30% by weight. The production of foams for
the
insulation of liquefied natural gas tanks in particular preferably utilizes
from 0.5% to 8%
by weight and more particularly from 1% to 5% by weight of crosslinker, and
this
crosslinker is preferably glycerol.
The chain extender (b3) has on average at least 30%, preferably at least 40%,
more
preferably at least 50% and even more preferably at least 60% of secondary OH
groups.
The chain extender (b3) may comprise individual compounds or mixtures. The
chain
extender (b3) preferably comprises monopropylene glycol, dipropylene glycol,
tripropylene glycol and/or 2,3-butanediol alone or optionally mixed with each
or one
another or with further chain extenders. In a particularly preferred
embodiment,
dipropylene glycol is used together with a second chain extender, for example
2,3-
butanediol, monopropylene glycol or diethylene glycol, as chain extender (b3).
Crosslinking agent (b4) preferably comprises 1,2,4-trihydroxycyclohexane,
1,3,5-
trihydroxycyclohexane, glycerol, N,N,N',N'-tetrakis(2-
hydroxypropyl)ethylenediamine
and/or trimethylolpropane. Preference for use as crosslinking agent is given
to glycerol or
N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine, more particularly
glycerol.
The aromatic polyether diol (b5) is an alkoxylation product of an aromatic
diol, preferably
bisphenol A, and ethylene oxide and/or propylene oxide. The aromatic polyether
diol (b5)
thus has a preferred functionality of 2 and a number average molecular weight
of above
300 g/mol and preferably of above 300 to 600 g/mol.
CA 02818999 2013-05-24
9
The component (b) may include from 5% to 50% by weight of chain extender (b3)
for
example. The amount of chain extender (b3) included in component (b) is
preferably in
the range from 8% to 50%, and more preferably in the range from 10% to 30% by
weight.
It is essential to the present invention for component (b) to comprise a
proportion of
polyesterols (b2), chain extenders (b3) and aromatic polyetherols (b5) which
is equal to at
least 50% by weight, preferably in the range from 50% to 80% by weight, more
preferably
in the range from 55% to 75% by weight and even more preferably in the range
from 60%
to 70% by weight, based on the total weight of component (b). Components (bl)
to (b5)
can each comprise individual compounds or mixtures, in which case each of the
compounds used comes within the definition of (b1) to (b5).
Preferably, component (b) includes at least 50% by weight, more preferably at
least from
55% to 85% and even more preferably from 60% to 75% by weight of compounds
having
two or three isocyanate-reactive groups. These compounds having two or three
isocyanate-reactive groups preferably have a molecular weight of below 2500
g/mol,
more preferably below 1000 g/mol, and more particularly below 800 g/mol. The
number
average molecular weight of these compounds is preferably not more than 500
g/mol,
more preferably in the range from 150 to 450 g/mol and more particularly in
the range
from 250 to 450 g/mol.
The proportion contributed by the polyetherols (b1), (b2), (b3) and optionally
(b4) and (b5)
to the compound having isocyanate-reactive groups (b) is preferably at least
80% by
weight, more preferably at least 90% by weight and more particularly 100% by
weight,
based on the total weight of compound having isocyanate-reactive groups (b).
The molar overall functionality of component (b) is preferably less than 3.0,
more
preferably between 2.0 and 2.9 and even more preferably between 2.4 and 2.8.
The
average OH number of component (b) is preferably greater than 300 mg KOH/g,
more
preferably between 350 and 1000 mg KOH/g and even more preferably between 400
and
600 mg KOH/g.
When isocyanate prepolymers are used as isocyanates (a), the level of
compounds
having isocyanate-reactive groups (b) is reckoned inclusive of the compounds
having
isocyanate-reactive groups (b) that were used in preparing the isocyanate
prepolymers.
Blowing agent (c) comprises blowing agent comprising water. Water can be used
as sole
blowing agent or in combination with further blowing agents. The water content
of blowing
agent (c) is preferably greater than 40% by weight, more preferably greater
than 60% by
weight and even more preferably greater than 80% by weight, based on the total
weight
CA 02818999 2013-05-24
of blowing agent (c). More particularly, water is used as sole blowing agent.
When, in
addition to water, further blowing agents are used, chlorofluorocarbons,
hydrofluorocarbons, hydrocarbons, acids and liquid/dissolved carbon dioxide
may be
used for example. Preferably, blowing agents (c) comprise less than 50% by
weight,
5 preferably less than 20% by weight, more preferably less than 10% by
weight and even
more preferably 0% by weight, based on the total weight of blowing agent (c),
of
chlorofluorocarbons, hydrofluorocarbons and/or hydrocarbons. A further
embodiment may
comprise using a mixture of water and formic acid and/or carbon dioxide as
blowing agent
(c). To simplify dispersion of the blowing agent in the polyol component, the
blowing
10 agent (c) may be admixed with polar compounds, such as dipropylene
glycol.
The blowing agents (c) are used in such an amount that the density of the
rigid
polyurethane foam formed by reaction of components (a) to (e) is inclusive of
reinforcing
agent (f) and/or hollow microspheres, in the range of above 50 g/L to 300 g/L,
preferably
in the range from 80 g/L to 250 g/L and more preferably in the range from 100
g/L to 220
g/L. When the rigid polyurethane foams of the present invention are reinforced
using
hollow glass spheres only, the blowing agents (c) are used in such an amount
that the
density of the rigid polyurethane foam formed by reaction of components (a) to
(e) is
inclusive of hollow microspheres in the range above 30 g/L to 250 g/L,
preferably in the
range from 60 g/L to below 160 g/L and more preferably in the range from 80
g/L to less
than 110 g/L.
Catalyst (d) may be any compound that speeds the isocyanate-water reaction or
the
isocyanate-polyol reaction. Such compounds are known and described for example
in
"Kunststoffhandbuch, volume 7, Polyurethane", Carl Hanser Verlag, 3rd edition
1993,
chapter 3.4.1. These comprise amine-based catalysts and catalysts based on
organometallic compounds.
Useful catalysts based on organometallic compounds include for example
organotin
compounds, such as tin(II) salts of organic carboxylic acids, such as tin(II)
acetate, tin(II)
octoate, tin(II) ethylhexanoate and tin(II) laurate and the dialkyltin(IV)
salts of organic
carboxylic acids, such as dibutyltin diacetate, dibutyltin dilaurate,
dibutyltin maleate and
dioctyltin diacetate, and also bismuth carboxylates such as bismuth(III)
neodecanoate,
bismuth 2-ethylhexanoate and bismuth octanoate or alkali metal salts of
carboxylic acids,
such as potassium acetate or potassium formate.
Catalyst (d) is preferably a mixture comprising at least one tertiary amine.
These tertiary
amines usually comprise compounds which can also bear isocyanate-reactive
groups,
such as OH, NH or NH2 groups. Some of the most frequently used catalysts are
bis(2-
dimethylaminoethyl) ether, N,N,N,N,N-pentamethyldiethylenetriamine, N,N,N-
CA 02818999 2013-05-24
11
triethylaminoethoxyethanol, dimethylcyclohexylamine, dimethylbenzylamine,
triethylamine, triethylenediamine, pentamethyldipropylenetriamine,
dimethylethanolamine,
N-methylimidazole, N-ethylimidazole, tetramethylhexamethylenediamine,
tris(dimethylaminopropyl)hexahydrotriazine, dimethylaminopropylamine, N-
ethylmorpholine, diazabicycloundecene and diazabicyclononene. When low
migration of
catalysts out of the foams of the present invention and/or low emission of VOC
compounds is desired, incorporable catalysts can also be used. And it is also
possible to
dispense with catalysts entirely.
The hollow microspheres are preferably selected from the group consisting of
hollow
thermoplastic microspheres, hollow glass microspheres and hollow microspheres
made
of glass ceramic. Examples of hollow microspheres made of glass and glass
ceramic are
the commercially available hollow microspheres Z-Lite W-1000 from ZeeIan
Industries
and Scotchlite from 3M and also CEL 300 and 650 from PQ Corporation,
respectively.
The use of hollow thermoplastic microspheres is preferred. The hollow
thermoplastic
microspheres used herein are known to a person skilled in the art and are
commercially
available under the product name of Expancel (Akzo Nobel) at Schonox GmbH
(Essen
Germany). In the case of the hollow microspheres concerned here, their shell
consists of
a copolymer based on acrylonitrile and their void space is filled with a
blowing gas. In
general, the unexpanded hollow microspheres have a diameter in the range from
6 to 45
ptm and a density in the range from 1000 to 1300 g/L. The blowing gases
typically
comprise volatile hydrocarbons such as, for example, butane, pentane, hexane,
heptane,
isobutene, isopentane, neopentane, cyclopropane, cyclobutane and cyclopropane.
If
necessary, these hollow spheres can also be manufactured and produced with any
other
low-boiling solvents. When the hollow microspheres are heated, the gas raises
the
internal pressure, the layer of polymer softens and the expansion process
starts. After
complete expansion, the hollow microsphere will have increased its diameter by
three to
four times the original diameter and its volume by more than forty times its
original
volume. The density after expansion is 30 g/L. The expansion temperatures are
generally
in the range between 80-190 C. After cooling, the thermoplastic material
solidifies again,
preserving the expanded volume.
The porous reinforcing agent (f), capable of forming ply-shaped, i.e., two-
dimensional, or
three-dimensional networks in the polyurethane foam can be any material that
will imbue
the rigid polyurethane foam with even higher mechanical stability and is
present in the
rigid polyurethane foam of the present invention in the form of two-
dimensional or three-
dimensional networks. An example of a reinforcing agent forming a two-
dimensional
network is a fiber mat, for example a glass fiber mat, while an example of a
three-
dimensional reinforcing agent is a plurality of mutually crosslinked fiber
mats or rovings
CA 02818999 2013-05-24
12
which are preferably likewise mutually crosslinked. For a reinforcing agent to
qualify as
porous within the context of the present invention the reaction mixture for
producing the
rigid polyurethane foam has to be capable of penetrating into and through the
reinforcing
agent while wetting it completely. The materials forming the three-dimensional
reinforcing
agent, for example, rovings or ribbons/tapes/ligaments, are preferably joined
to one
another, for example by interlooping or interlinking. To form three-
dimensional reinforcing
agents, two or more two-dimensional reinforcing agents, such as fiber mats,
are also to
be linked together. Furthermore, twisted or braided strands of fiber, such as
fiber plaits,
can be used as three-dimensional reinforcing agents.
Such porous reinforcing agents (f) capable of forming ply-shaped or three-
dimensional
networks in the polyurethane foam are for example wovens or knits based on
fibers.
Examples of porous, two-dimensional reinforcing agents which are preferably
used are
fiber mats, for example glass fiber, aramid fiber or carbon fiber mats or mats
of fibers
composed of plastic or ribbons/tapes/ligaments composed of these materials,
preferably
glass fiber mats, for example Unifilo U801 or U809 from Owens Corning
Vetrotex. Glass
fiber roving mats can also be used. The proportion of reinforcing agent (f) is
preferably in
the range from 1 to 40, and more preferably in the range from 2 to 20 percent
by weight,
based on the total weight of components (a) to (f).
Possible further additives (e) include flame retardants, plasticizers, foam
stabilizers,
further fillers and other addition agents, such as antioxidants. Preferably,
at least flame
retardants or plasticizers are used.
Flame retardants used can be the flame retardants generally known from the
prior art.
Suitable flame retardants include for example brominated ethers (Ixol B 251),
brominated
alcohols, such as dibromoneopentyl alcohol, tribromoneopentyl alcohol and PHT-
4-diol,
and also chlorinated phosphates, e.g., tris(2-chloroethyl) phosphate, tris(2-
chloroisopropyl) phosphate (TCPP), tris(1,3-dichloroisopropyl) phosphate,
tris(2,3-
dibromopropyl) phosphate and tetrakis(2-chloroethyl)ethylene diphosphate, or
mixtures
thereof.
In addition to the aforementioned halogen-substituted phosphates, inorganic
flame
retardants, such as red phosphorus, preparations comprising red phosphorus,
expandable graphite, aluminum oxide hydrate, antimony trioxide, arsenic oxide,
ammonium polyphosphate and calcium sulfate or cyanuric acid derivatives, such
as
melamine, or mixtures of at least two flame retardants, such as ammonium
polyphosphates and melamine, and also optionally starch, can also be used for
rendering
the polyurethane rigid foams produced according to the present invention flame
resistant.
CA 02818999 2013-05-24
13
Diethyl ethanephosphonate (DEEP), triethyl phosphate (TEP), dimethyl
propylphosphonate (DMPP), diphenyl cresyl phosphate (DPC) and others can be
used as
further liquid halogen-free flame retardants.
Flame retardants herein are preferably used in an amount ranging from 0% to
25% based
on the total weight of components (b) to (e).
Useful plasticizers include for example esters of polybasic, preferably
dibasic, carboxylic
acids with monohydric alcohols. The acid component of such esters is derivable
for
example from succinic acid, isophthalic acid, terephthalic acid, trimellitic
acid, citric acid,
phthalic anhydride, tetra- and/or hexahydrophthalic anhydride,
endomethylenetetrahydrophthalic anhydride, glutaric anhydride, maleic
anhydride,
fumaric acid and/or dimeric and/or trimeric fatty acids such as oleic acid,
optionally in
admixture with monomeric fatty acids. The alcohol component of such esters is
derivable
for example from branched and/or unbranched aliphatic alcohols having from 1
to 20
carbon atoms, such as methanol, ethanol, propanol, isopropanol, n-butanol, sec-
butanol,
tert-butanol, the various isomers of pentyl alcohol, of hexyl alcohol, of
octyl alcohol (e.g.,
2-ethylhexanol), of nonyl alcohol, of decyl alcohol, of lauryl alcohol, of
myristyl alcohol, of
cetyl alcohol, of stearyl alcohol and/or from naturally occurring fatty and
waxy alcohols or
fatty and waxy alcohols obtainable by hydrogenation of naturally occurring
carboxylic
acids. As alcohol component, it is also possible to use cycloaliphatic and/or
aromatic
hydroxy compounds, for example cyclohexanol and its homologs, phenol, cresol,
thymol,
carvacrol, benzyl alcohol and/or phenylethanol. Useful plasticizers further
include esters
of monobasic carboxylic acids with dihydric alcohols, such as texanol ester
alcohols, for
example 2,2,4-trimethy1-1,3-pentanediol diisobutyrate (TXIB) or 2,2,4-
trimethy1-1,3-
pentanediol dibenzoate; diesters formed from oligoalkylene glycols and alkyl
carboxylic
acids, for example triethylene glycol dihexanoate or tetraethylene glycol
diheptanoate and
analogous compounds.
Useful plasticizers further include esters of the abovementioned alcohols with
phosphoric
acid. Optionally, phosphoric esters of halogenated alcohols, such as
trichloroethyl
phosphate for example, may also be used. In the latter case, a flame-retardant
effect is
obtainable as well as the plasticizer effect. It will be appreciated that it
is also possible to
use mixed esters of the abovementioned alcohols and carboxylic acids.
The plasticizers may also be so-called polymeric plasticizers, for example
polyesters of
adipic, sebacic and/or phthalic acid(s).
CA 02818999 2013-05-24
14
It is further possible to use alkyl sulfonic esters of phenol, e.g., phenyl
paraffinsulfonate,
and aromatic sulfonamides, e.g., ethyltoluenesulfonamide, as plasticizers.
Similarly,
polyethers, for example triethylene glycol dimethyl ether are useful as
plasticizers.
The amount of plasticizer used is preferably in the range from 0.1% to 15% and
more
preferably in the range from 0.5% to 10% by weight, based on the total weight
of
components b) to e). Having plasticizer is a way to further improve the
mechanical
properties of the rigid polyurethane foam at low temperatures in particular.
Foam stabilizers promote the formation of a regular cellular structure during
foam
formation. Examples include silicone-containing foam stabilizers, such as
siloxane-
oxyalkylene copolymers and other organopolysiloxanes. Also alkoxylation
products of
fatty alcohols, oxo process alcohols, fatty amines, alkylphenols,
dialkylphenols,
alkylcresols, alkylresorcinol, naphthol, alkylnaphthol, naphthylamine,
aniline, alkylaniline,
toluidine, bisphenol A, alkylated bisphenol A, polyvinyl alcohol, and also
alkoxylation
products of condensation products formed from formaldehyde and alkylphenols,
formaldehyde and dialkylphenols, formaldehyde and alkylcresols, formaldehyde
and
alkylresorcinol, formaldehyde and aniline, formaldehyde and toluidine,
formaldehyde and
naphthol, formaldehyde and alkylnaphthol and also formaldehyde and bisphenol
A, or
mixtures of two or more of these foam stabilizers.
The amount of foam stabilizer used is preferably in the range from 0.5% to 4%
and more
preferably in the range from 1% to 3% by weight, based on the total weight of
components (b) to (e).
Further fillers, in particular reinforcing fillers, are customary organic and
inorganic fillers
known per se. Specific examples are inorganic fillers such as silicatic
minerals, for
example sheet silicates such as antigorite, serpentine, hornblendes,
amphiboles,
chrysotile, talc; metal oxides, such as kaolin, aluminas, titanias and iron
oxides, metal
salts such as chalk, barite and inorganic pigments, such as cadmium sulfide,
zinc sulfide
and also glass and others. Preference is given to using kaolin (china clay),
aluminum
silicate and coprecipitates formed from barium sulfate and aluminum silicate,
and also
natural and synthetic fibrous minerals such as wollastonite, metal fibers and
in particular
glass fibers of differing length, which may optionally be sized. Organic
fillers include for
example carbon, melamine, rosin, cyclopentadienyl resins and graft polymers
and also
cellulose fibers, polyamide fibers, polyacrylonitrile fibers, polyurethane
fibers, polyester
fibers based on aromatic and/or aliphatic dicarboxylic esters, and more
particularly
carbon fibers.
CA 02818999 2013-05-24
The organic and inorganic fillers can be used singly or as mixtures, and are
advantageously incorporated in the reaction mixture in amounts ranging from 0%
to 30%
by weight and preferably from 1% to 15% by weight based on the weight of
components
(a) to (e). For the purposes of the present invention, the aforementioned
reinforcing
5 agents (f) and/or hollow microspheres are not regarded as fillers and are
not included
under component (e) in reckoning the proportions.
The present invention further provides a process for producing a reinforced
polyurethane
foam comprising mixing (a) polyisocyanates with (b) compounds having
isocyanate-
10 reactive groups, (c) blowing agent comprising water, (d) a catalyst
mixture and optionally
hollow microspheres and (e) further additives, to form a reaction mixture,
applying the
reaction mixture to at least one reinforcing agent (f) and curing the reaction
mixture,
wherein the compounds having isocyanate-reactive groups (b) comprise
polyetherols
(b1), polyesterols (b2), chain extenders (b3) and optionally crosslinkers (b4)
and aromatic
15 polyether diols (b5), and said component (b) comprises a fraction of
polyesterols (b2) and
chain extenders (b3) that is equal to at least 50% by weight, based on the
total weight of
said component (b). The process of the present invention utilizes the
feedstocks
described above. The polyurethane reaction mixture preferably penetrates into
the
reinforcing agent and wets it uniformly. The foaming polyurethane reaction
mixture then
leads to a homogeneous distribution of the reinforcing agent in the foam
wherein the plies
of a ply-shaped reinforcing agent are oriented perpendicularly to the
direction of foaming
for example.
The rigid polyurethane foam of the present invention is preferably produced in
a
continuous manner on a belt. For this purpose, it is preferable to mix
components (b) to
(d) and optionally hollow glass microspheres and (e) together to form a polyol
component.
These are then preferably mixed with the isocyanate component (a) in a low
pressure
mixing device, a high pressure mixing device at reduced pressure of below 100
bar or a
high pressure machine. Alternatively, components (a) to (d) and optionally
hollow
microspheres and (e) can each be introduced individually into the mixing
device. The
reaction mixture thus obtained is then placed on the reinforcing agent (f),
preferably the
glass fiber mats, which are preferably continuously unrolled onto the belt
from multiple
(for example 4-10, preferably 5, 6 or 7) drums and form a corresponding number
of plies
on the belt. The foam obtained is then preferably cured on the belt to such an
extent that
it can be cut into pieces without damage. This can take place at elevated
temperatures,
for example during passage through an oven. The pieces of foam obtained are
then
preferably further stored in order that full mechanical strength may be
acquired.
Another way to produce the rigid polyurethane foam of the present invention is
to batch
foam the reaction mixtures in a mold. The reinforcing agent of the present
invention can
CA 02818999 2013-05-24
16
in this case be introduced into the mold before or at the same time as the
reaction
mixture.
The rigid polyurethane foam obtained is then cut into the shape required for
further
processing.
Isocyanates (a) and compounds having isocyanate-reactive groups (b), blowing
agent
comprising water (c) and optionally catalysts (d) and further additives (e)
are preferably
reacted in such amounts that the isocyanate index is in the range from 100 to
400,
preferably in the range from 100 to 200 and more preferably in the range from
100 to 150.
The isocyanate index for the purposes of the present invention is the
stoichiometric ratio
of isocyanate groups to isocyanate-reactive groups, multiplied by 100. An
isocyanate-
reactive group is any isocyanate-reactive group present in the reaction
mixture, including
chemical blowing agents, but not the isocyanate group itself.
It is particularly advantageous that the reaction mixtures of the present
invention are
quick to penetrate into the reinforcing agents (f), which is beneficial to
achieving a uniform
distribution of the reinforcing agents (f) in the rigid polyurethane foam
obtained. Another
advantage is the long cream time of the reaction mixtures of the present
invention
coupled with a short reaction time.
The reinforced polyurethane foam of the present invention exhibits excellent
mechanical
properties, such as high compressive strength and modulus, and also tensile
and flexural
strength and moduli, and also a high shear strength coupled with high
elasticity and low
density. The reinforced polyurethane foam of the present invention further has
a high
flexural modulus of elasticity and a high thermal stability and is obtainable
in a simple and
environmentally friendly manner. Environmentally friendly disposal of
polyurethane foams
is also possible. For instance, a polyurethane foam can be disassembled, by
glycolysis
for example, back into its starting compounds, which can be reused as raw
materials.
The foam of the present invention is preferably used as a foam in a structural
sandwich
component, the outside layers of which preferably consist of fiber-reinforced
resin. The
resin used can be for example a known epoxy, polyester or polyurethane resin,
which is
laminated onto the polyurethane foam in a conventional manner. Alternatively,
the
polyurethane foam of the present invention can also be adhered to such an
outside layer
or be produced thereon. The fiber-reinforced resin can be used as a mold or
part of a
mold. In addition to fiber-reinforced resins, the outside layers can also
consist of
thermoplastic materials, woodbase materials or metal. The outside layer may
enclose
part of the foam or the entire foam. When the foam is enclosed by an outside
layer, the
CA 02818999 2013-05-24
17
foam of the present invention can fill part of or the entire interior of the
structural sandwich
component. When only part of the structural sandwich component is filled by
the foam of
the present invention, this foam preferably forms a reinforcing ply in the
structural
sandwich component in which the remaining space in the interior of the
structural
__ sandwich component preferably constitutes unfilled gas space.
The reinforced polyurethane foam of the present invention can accordingly be
used as a
reinforcing foam in blades, for example rotor blades, and wings of aircraft,
more
particularly as a core foam. A core foam is a reinforcing ply in a blade or
wing, which
__ either fills out the entire core or, in the case of hollow blades, forms an
interior, reinforcing
ply which is positioned underneath the surface material, which consists of
glass fiber
resins for example. A structural sandwich component according to the present
invention
is preferably used as a blade or wing. A further possible use for structural
sandwich
component is as a boat's hull or as a load-bearing stiff areal element.
The reinforced polyurethane foam of the present invention can further be used
as an
insulation material for liquefied natural gas tanks, particularly onboard
ships.
The examples which follow illustrate the invention.
Production of reinforced polyurethane rigid foams (variant 1):
Table 1:
1 2 V1 V2 V3
polyether 1 40 40 40
polyether 2 25 25 25
polyether 3 28 28
polyether 4 20 20
polyester 1 37 17 25 25 25
chain extender 1 12 12 10 10 10
aromatic diol 20
water 2 2 1.0 1.0 1.0
catalyst 1 0.08 0.08 0.08
stabilizer 1 1 1 1.5 1.5 1.5
isocyanate 1 126 126 126
isocyanate 2 142 152
plies of glass fiber mats 0 0 0 7
hollow glass spheres 17 8.2 8.0
foam density in g/L 100 100 100 112 100
compressive strength in MPa 1.42 1.39 0.91 1.15 0.84
CA 02818999 2013-05-24
18
compressive E-modulus in MPa 52.1 43.6 24.8 43.1 23.4
tensile strength in MPa 1.11 1.16 n.d. n.d. n.d.
tensile E-modulus in MPa 63.4 62.4 n.d. n.d. n.d.
3-point flexural strength in MPa 2.03 2.11 1.62 1.91 n.d.
3-point flexural E-modulus in 55.1 51.2 n.d. n.d. n.d.
MPa
shear strength in MPa 0.62 0.69 0.83 0.79 0.41
The following materials were used:
Polyether 1: sucrose/glycerol-based polypropylene oxide, Fn = 4.5, number
average
molecular weight = 515 g/mol, viscosity = 8000 mPa*s at 25 C
Polyether 2: polypropylene glycol, Fn = 2, number average molecular weight =
1100
g/mol, viscosity = 150 MPa*s at 25 C
Polyether 3: ethylenediamine-based polypropylene oxide, Fn = 3.9, number
average
molecular weight = 470 g/mol, viscosity = 4975 MPa*s at 25 C
Polyether 4: ethylenediamine-based polypropylene oxide, Fn = 4.0, number
average
molecular weight = 300 g/mol
Polyether 4: sorbitol-based polypropylene oxide, OH number = 490 mgKOH/g
(Lupranol
3422 from BASF SE)
Polyester 1: phthalic anhydride/diethylene glycol-based, Fn = 2, number
average
molecular weight = 360 g/mol
Polyester 2: aromatic polyester polyol, OH number = 240 mgKOH/g (Lupraphen
8007
from BASF SE)
Chain extender 1: propylene glycol-based, Fn = 2, molecular weight = 134 g/mol
Aromatic diol: bisphenol-A-initiated polyether polyol based on propylene
oxide, Fn = 2,
number average molecular weight 400 g/mol
Chain extender 2: propylene glycol-based, Fn = 2, MW = 190 g/mol
Chain extender 3: diethylene glycol
Catalyst 1: tertiary aliphatic amine
Stabilizer 1: silicone-containing stabilizer for polyurethane foams
lsocyanate 1: mixtures of diphenylmethane diisocyanate and polymeric
diphenylmethane
diisocyanate, viscosity 200 mPa*s at 25 C
Isocyanate 2: a prepolymer formed from 95.2 parts of mixtures of
diphenylmethane
diisocyanate and polymeric diphenylmethane diisocyanate and 4.8 parts of a
polyesterol
formed from 1 part of adipic acid, 6 parts of oleic acid and 2 parts of
pentaerythritol,
viscosity 250 mPa*s at 25 C.
Glass fiber mats: continuous strand mats of glass fibers, Unifilo U809-450
from
OwensCorningVetrotex
CA 02818999 2013-05-24
19
Hollow glass spheres: iM30K hollow glass sphere from 3M, having a density of
600 g/L
and an average diameter of 15 p.m
Production of reinforced polyurethane rigid foams (variant 2):
Table 2:
V4 V5 3 V1 V2 V6 V7 V8
polyether 1 31 31 31 40 40 39
polyether 2 25 25 24
polyether 4 20
20
polyester 1 56 28 28 25 25 24
polyester 2 40
40
chain extender 1 10 10 10 10 10 10
chain extender 2 28 28
chain extender 3 40
40
glycerol 3 3 3 3
water 1.4 1.45 1.45 1.0 1.0
1.05 1.6
1,1,1,3,3-pentafluoropropane 0 0 0 0 0 0 0
10
catalyst 1 0.11 0.07 0.07 0.08 0.08
0.08 0.12 0.13
stabilizer 1 2.0 2.0 2.0 1.5 1.5 1.5
2 2
isocyanate 1 166 183 183 126 126 140
209 187
plies of glass fiber mats/weight 0 0 7 / 0 7 / 0 0
0
fraction of mats based on all 12 12
components (a) to (e)
foam density in g/L 100 100 112 100 112 100
100 100
compressive E-modulus in MPa 27.7 26.6 48.2
24.8 43.1 22.4 26.4 25.4
MPa
The two tables report the quantities of the materials used in parts by weight.
To produce
the rigid foams as per inventive examples Ito 3 and comparative (V) examples 1
to 8,
the polyols used as per table 1 or table 2 were stirred together with
catalysts, stabilizer
and blowing agents, then mixed with the isocyanate and the reaction mixture
poured into
CA 02818999 2013-05-24
a box having a base area of 225 mm x 225 mm and foamed up therein. The amount
of
water was chosen such that the unreinforced foam had a free foam density of
100 g/L.
The foam densities reported in the tables are based on the overall density of
the foam
cube inclusive of reinforcing agent, if used. To produce the reinforced rigid
foams as per
5 inventive example 3 and comparative example 2, the reaction mixture was
introduced into
the same box, but it now contained multiple plies of glass fiber mats. The
reaction mixture
penetrated into the mats and as the foam rose in the box the mats swelled up
and
became homogeneously distributed throughout the entire foam height. To produce
the
reinforced rigid foams as per inventive examples 1 and 2 and comparative
example 3, the
10 hollow glass spheres were stirred up together with the polyols,
catalysts, stabilizer and
blowing agents used and then proceeded with as in comparative examples 4 to 8
and
comparative example 1. To determine the mechanical properties, cube-shaped
test
specimens were sawn out of the interior of the foams. When the test specimens
had a
density other than 100 g/L, the values obtained in the mechanical tests were
converted to
15 a density of 100 g/L.
As can be seen from table 1 and table 2, formulations according to the present
invention
lead to rigid polyurethane foams having particularly high mechanical
properties compared
with hitherto known pressure- and shear-resistant rigid foams. Even without
the use of
20 reinforcing agents, these rigid polyurethane foams display such
polyurethane foams
already display good mechanical properties, as is evident from comparative
example 5.
This is particularly clear from the comparison with comparative examples V1
and V2, in
which a foam as per example 1 of WO 2010/066635 was reproduced once with and
once
without reinforcing agents. Comparative example V6 shows a modified WO
2010/066635
recipe, further comprising the crosslinking agent glycerol. The mechanical
properties of
this non-reinforced foam are inferior compared with a non-reinforced form as
per
comparative example 5. The processing and application of the polyurethane
reaction
mixture and the visual impression of the foam is very good according to the
inventive
examples as with the comparative examples V1 and V2. Comparative examples V7
and
V8 show a foam as per example 1 of EP 2236537, once with a physical blowing
agent
and once with the blowing agent water. The mechanical properties of a non-
reinforced
foam are distinctly inferior compared with a non-reinforced foam from
comparative
example 5, especially tensile strength, tensile E-modulus and shear strength.
Moreover,
the attempt to produce a reinforced polyurethane foam similarly to inventive
example 3
and comparative example V2 failed, since the polyurethane reaction mixture of
comparative tests V7 and V8 did not wet the glass fiber mats sufficiently, and
so these did
not become uniformly distributed in the rising foam.
CA 02818999 2013-05-24
21
Table 3 shows that a reinforced polyurethane rigid foam as per inventive
example 1 has a
distinctly improved heat resistance compared with PVC foams and compared with
foams
as per comparative example 1.
Table 3:
Foam Crosslinked PVC Comparative 1 Inventive 1
foam
softening 82 C 123 C 144 C
temperature [ C]
