Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR PRODUCING COMPOSITE PROFILES
Description
The invention relates to a process for producing composite profiles comprising
metal shells,
struts comprising a thermoplastic material and a core comprising rigid
polyurethane foam, as
are used, for example, for window frames and doorframes.
Rigid polyurethane foams have been known for a long time and are widely
described in the
literature. They are used, for example, for thermal insulation in
refrigeration appliances, for the
production of composite elements, also referred to as sandwich elements, and
also in building
and construction.
One application of rigid polyurethane foams is the production of composite
profiles which are
used, in praticular, for window frames or doorframes. Here, a hollow profile
is produced from
two metal shells, for example comprising aluminum, and two plastic struts, for
example
comprising polyamide, and the liquid starting components of the rigid
polyurethane foam are
introduced into this where they then cure to form the foam. After curing of
the foam, a surface
coating is applied to the composite elements. For the surface coating, it is
customary to use
powder coatings or baking enamels. This surface coating is carried out at high
temperature,
usually in the region of 200 C, which can lead to deformation of the composite
elements
because of gas expansion in the rigid polyurethane foam and the different
thermal expansion of
aluminum and rigid polyurethane foam.
Concepts for avoiding this deformation are known from the prior art.
Thus, EP-A 1925417 describes a process for producing composite profiles which
are completely
filled with foam and can be surface-coated at high temperatures without
deformation of the
composite elements occurring. However, mineral fillers have to be added here
in order to
counter deformation of the composite elements. In addition, the blowing agents
used in the prior
art have a global warming potential.
However, fillers are disadvantageous for many applications. During cutting or
sawing of hollow
chamber profiles completely filled with foam they sometimes lead to a great
deal of dust. They
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cause brittleness and reductions in the flexibility, particularly in the
temperature range below
0 C.
A process for producing such composite elements is described in DE-A 10035649.
The problem
of deformation of the profiles is solved by the hollow space between the metal
shells and
polyamide struts being only partly filled with polyurethane foam. However, the
incomplete filling
of the profiles with the polyurethane foam can lead either to a deterioration
in the thermal
insulation properties of the profiles or to deformation of the composite
elements which have
been completely filled with foam, in particular as a result of surface
coating.
It was an object of the present invention to avoid the abovementioned
disadvantages. In
particular, a process for producing composite elements of the type mentioned
at the outset
which leads to profiles which do not display deformation on application of a
surface coating at
high temperatures and have good mechanical properties even at temperatures
below 0 C and
can be cut without dust formation should be discovered.
The object is achieved according to the invention by a process for producing
composite profiles
comprising at least two metal shells which are joined by struts comprising a
thermoplastic
material and a core comprising rigid polyurethane foam, which comprises
introduction of the
starting components of the rigid polyurethane foam into a hollow space formed
by the metal
shells, with the rigid polyurethane foam being formed, and subsequent
application of a surface
coating to the outer surface of the composite profile by means of a powder
coating or baking
enamel, where the rigid polyurethane foam is obtained by reaction of the
following components:
G) at least one polyisocyanate,
H) at least one polyfunctional compound which is reactive toward isocyanates,
I) one or more blowing agents comprising at least formic acid,
J)optionally one or more flame retardants,
K) optionally one or more catalysts and
L)optionally further auxiliaries or additives,
wherein the starting components of the rigid polyurethane foam do not comprise
any inorganic
fillers.
For the purposes of the invention, polyurethane foams are foams in accordance
with DIN 7726.
The rigid polyurethane foams used according to the invention have a
compressive stress at
10% deformation of greater than or equal to 80 kPa, preferably greater than or
equal to
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150 kPa, particularly preferably greater than or equal to 180 kPa.
Furthermore, the rigid
polyurethane foam in accordance with DIN ISO 4590 has a proportion of closed
cells of greater
than 85%, preferably greater than 90%.
The metal shells used for producing the composite profiles usually consist of
steel or aluminum.
They are usually produced by mechanical shaping. The size of the metal shell
depends on the
desired size of the window frames and doorframes. The polymer struts inserted,
usually made
of polyamide or ASA, form a hollow space between the metal shells, into which
the
polyurethane foam is introduced and which is subsequently closed.
After shaping, the polyurethane foam is introduced into the composite profile.
This is effected by
mixing the polyisocyanates A) with the components B) to F) and then
introducing the mixture
into the composite profile where the components cure to form the rigid
polyurethane foam.
Introduction is usually carried out, as described above, by means of
conventional metering
devices, usually by means of mixing heads. The amount of foam should be such
that the
composite profile is completely filled but the pressure does not build up to
such an extent that
the composite profile is destroyed or deformed.
After curing of the rigid polyurethane foam, a surface coating is applied to
the composite profile
according to the invention. According to the invention, baking enamels or
powder coatings are
used for surface coating. These types of surface coating have a high scratch
resistance.
Baking enamels are surface coatings which are cured at elevated temperature,
preferably from
100 to 250 C.
Baking enamels are usually surface coatings based on acrylic, epoxy, phenolic,
melamine, urea,
silicone, polyurethane resins which are cured either alone or in combinations
with one another
or with a usually blocked hardener, for example blocked polyisocyanates, at
elevated
temperature, preferably in the range from 100 to 250 C. Curing occurs by means
of crosslinking
reactions brought about by activation of the double bonds present in the
molecules of these
compounds or by reaction of various functional groups with one another. Only
in exceptional
cases are dryers also added. In practice, baking enamels on the workpieces are
cured in baking
ovens or drying ovens of various dimensions under specific baking conditions.
Infrared radiators
or apparatuses operating on the basis of electromagnetic induction are
sometimes used for
generation of heat.
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Liquid starting materials for baking enamels (hereinafter referred to as
baking enamels in the
interests of simplicity) can be either solvent-based or water-borne surface
coating compositions,
pigmented, transparent or clear coating compositions. Preferred binders in
baking enamels are
alkyd, polyester, acrylic or epoxy resins in combination with melamine resins,
amines or
polyisocyanates as crosslinkers.
The baking enamels are adjusted to the processing consistency by means of
organic solvents
or by means of water to which small amounts of 2-propanol, butanol or other
alcohols have
been added.
For the purposes of the present invention, powder coatings are pulverulent,
solvent-free coating
materials which give a coating after melting and optionally baking. The
temperature range for
processing is, as a function of the system present, from 80 C to 250 C. They
are predominantly
applied in powder form to metallic substrates. Powder coatings are usually
thermoset systems.
The film-forming phase of the powder coatings is composed of binders, reaction
partners for
these binders, also referred to as hardeners, fillers, pigments and additives.
The binders and
hardeners used essentially determine the general properties of the powder
coating and thus
also its preferred field of use.
Powder coatings are usually based on epoxy resins, epoxy resin/polyester
mixtures, polyesters,
polyester/isocyanate mixtures and acrylates. The powder coatings produced
therefrom are
called epoxy resin powder coatings, epoxy resin/polyester powder coatings,
polyester powder
coatings, polyurethane powder coatings or acrylate powder coatings.
The composite profiles obtained according to the invention can advantageously
be used for
window frames or doorframes.
As regards the production of the rigid polyurethane foam and the starting
compounds used for
this purpose, the following details may be provided.
Component A)
For the purposes of the present invention, a polyisocyanate is an organic
compound which
contains at least two reactive isocyanate groups per molecule, i.e. the
functionality is at least 2.
If the polyisocyanates used or a mixture of a plurality of polyisocyanates do
not have a uniform
functionality, the weight average functionality of the component A) used is at
least 2.
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Possible polyisocyanates A) are the aliphatic, cycloaliphatic, araliphatic and
preferably aromatic
polyfunctional isocyanates known per se. Such polyfunctional isocyanates are
known per se or
can be produced according to methods known per se. The polyfunctional
isocyanates can, in
particular, also be used as mixtures, in which case the component A) comprises
various
polyfunctional isocyanates. Polyfunctional isocyanates which come into
question as
polyisocyanate have two (hereinafter referred to as diisocyanates) or more
than two isocyanate
groups per molecule.
Specific examples are, in particular: alkylene diisocyanates having from 4 to
12 carbon atoms in
the alkylene radical, e.g. dodecane 1,12-diisocyanate, 2-ethyltetramethylene
1,4-diisocyanate,
2-methylpentamethylene 1,5-diisocyanate, tetramethylene 1,4-diisocyanate and
preferably
hexamethylene 1,6-diisocyanate; cycloaliphatic diisocyanates such as
cyclohexane 1,3- and
1,4-diisocyanate and any mixtures of these isomers, 1-isocyanato-3,3,5-
trimethy1-5-
isocyanatomethylcyclohexane (IPDI), hexahydrotolylene 2,4- and 2,6-
diisocyanate and the
corresponding isomer mixtures, dicyclohexylmethane 4,4'-, 2,2'- and 2,4'-
diisocyanate and the
corresponding isomer mixtures, and preferably aromatic polyisocyanates such as
tolylene 2,4-
and 2,6-diisocyanate and the corresponding isomer mixtures, diphenylmethane
4,4'-, 2,4'- and
2,2'-diisocyanate and the corresponding isomer mixtures, mixtures of
diphenylmethane 4,4'-
and 2,2'-diisocyanates, polyphenylpolymethylene polyisocyanates, mixtures of
diphenylmethane
4,4'-, 2,4'- and 2,2'-diisocyanates and polyphenylpolymethylene
polyisocyanates (crude MDI)
and mixtures of crude MDI and tolylene diisocyanates.
Particularly suitable polyisocyanates are diphenylmethane 2,2'-, 2,4'- and/or
4,4'-diisocyanate
(MDI), 1,5-naphthylene diisocyanate (NDI), tolylene 2,4- and/or 2,6-
diisocyanate (TDI), 3,3'-
dimethyldiphenyl diisocyanate, 1,2-diphenylethane diisocyanate and/or p-
phenylene
diisocyanate (PPD1), trimethylene, tetramethylene, pentamethylene,
hexamethylene,
heptamethylene and/or octamethylene diisocyanate, 2-methylpentamethylene 1,5-
diisocyanate,
2-ethylbutylene 1,4-diisocyanate, pentamethylene 1,5-diisocyanate, butylene
1,4-diisocyanate,
1-isocyanato-3,3,5-trimethy1-5-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.
Use is frequently also made of modified polyisocyanates, i.e. products which
are obtained by
chemical reaction of organic polyisocyanates and have at least two reactive
isocyanate groups
per molecule. Particular mention may be made of polyisocyanates comprising
ester, urea,
biuret, allophanate, carbodiimide, isocyanurate, uretdione, carbamate and/or
urethane groups.
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As polyisocyanates of the component A), particular preference is given to 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 preparation 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).
As polyisocyanate, very particular preference is given to polymeric
diphenylmethane
diisocyanate. Polymeric diphenylmethane diisocyanate (hereinafter referred to
as polymeric
MDI) is a mixture of two-ring MDI and oligomeric condensation products and
thus derivatives of
diphenylmethane diisocyanate (MDI). The polyisocyanates can also preferably be
made up of
mixtures of monomeric aromatic diisocyanates and polymeric MDI.
Polymeric MDI comprises, in addition to two-ring MDI, one or more multiring
condensation
products of MDI having a functionality of more than 2, in particular 3, 4 or
5. Polymeric MDI is
known and is frequently referred to as polyphenylpolymethylene isocyanate or
as oligomeric
MDI. Polymeric MDI is usually made up of a mixture of MDI-based isocyanates
having various
functionalities. Polymeric MDI is usually used in admixture with monomeric
MDI.
The (weight average) functionality of a polyisocyanate comprising polymeric
MDI can vary in the
range from about 2.2 to about 5, in particular from 2.3 to 4, in particular
from 2.4 to 3.5. One
such mixture of MDI-based polyfunctional isocyanates having differing
functionalities is, in
particular, crude MDI which is obtained as intermediate in the preparation 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
LupranatO.
=
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The functionality of the component A) is preferably at least two, in
particular at least 2.2 and
particularly preferably at least 2.4. The functionality of the component A) is
preferably from 2.2
to 4 and particularly preferably from 2.4 to 3.
The content of isocyanate groups in the component A) 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 are inversely proportional. 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 particularly preferred embodiment, the component A) 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 2.4.
The viscosity of the component A) used can vary within a wide range. The
component A)
preferably has a viscosity of from 100 to 3000 mPa*s, particularly preferably
from 200 to
2500 mPa*s.
Component B
According to the invention, component B) comprises at least one polyfunctional
compound
which is reactive toward isocyanates. Polyfunctional compounds which are
reactive toward
isocyanates are those which have at least two hydrogen atoms which are
reactive toward
isocyanates, in particular at least two functional groups which are reactive
toward isocyanates.
The compounds which are used in the component B) preferably have a
functionality of from 2 to
8, in particular from 2 to 6. If a plurality of different compounds are used
in component B), the
weight average functionality of the component B) is preferably from 2.2 to 5,
particularly
preferably from 2.4 to 4, very particularly preferably from 2.6 to 3.8. For
the purposes of the
present invention, the weight average functionality is the value which results
when the
functionality of each compound B) is weighted according to the proportion by
weight of this
compound in the component B).
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Polyether polyols are preferred as compounds B). The term polyether polyol is
used
synonymously with the term polyetherol and denotes alkoxylated compounds
having at least
two reactive hydroxyl groups.
Preferred polyether polyols B) have a functionality of from 2 to 8 and have
hydroxyl numbers of
from 100 mg KOH/g to 1200 mg KOH/g, preferably from 150 to 800 mg KOH/g, in
particular
from 200 mg KOH/g to 550 mg KOH/g. All hydroxyl numbers in the context of the
present
invention are determined in accordance with DIN 53240.
In general, the proportion of component B) based on the sum of the components
B) to F) is from
40 to 98% by weight, preferably from 50 to 97% by weight, particularly
preferably from 60 to
95% by weight.
The polyetherols preferred for component B) can be prepared by known methods,
for example
by anionic polymerization of one or more alkylene oxides having from 2 to 4
carbon atoms using
alkali metal hydroxides such as sodium or potassium hydroxide, alkali metal
alkoxides such as
sodium methoxide, sodium or potassium ethoxide or potassium isopropoxide, or
amine
alkoxylation catalysts such as dimethylethanolamine (DMEOA), imidazole and/or
imidazole
derivatives with addition of at least one starter molecule comprising from 2
to 8, preferably from
2 to 6, reactive hydrogen atoms in bound form or by cationic polymerization
using Lewis acids,
such as antimony pentachloride, boron fluoride etherate or bleaching earth.
Suitable alkylene oxides are, for example, tetrahydrofuran, 1,3-propylene
oxide, 1,2- or 2,3-
butylene oxide, styrene oxide and preferably ethylene oxide and 1,2-propylene
oxide. The
alkylene oxides can be used individually, alternately in succession or as
mixtures. Particularly
preferred alkylene oxides are 1,2-propylene oxide and ethylene oxide.
Component B) preferably comprises at least one polyether polyol having a
hydroxyl number of
from 200 to 400 mg KOH/g, in particular from 230 to 350 mg KOH/g, and a
functionality of from
2 to 3. The abovementioned ranges ensure good flow behavior of the reactive
polyurethane
mixture.
In addition, component B) preferably comprises at least one polyether polyol
having a hydroxyl
number of from 300 to 600 mg KOH/g, in particular from 350 to 550 mg KOH/g,
and a
functionality of from 4 to 8, in particular from 4 to 6. The abovementioned
ranges lead to good
chemical crosslinking of the reactive polyurethane mixture.
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Possible starter molecules are, for example: water, organic dicarboxylic acids
such as succinic
acid, adipic acid, phthalic acid and terephthalic acid, aliphatic and
aromatic, optionally N-
monoalkyl-, N,N- and N,N'-dialkyl-substituted diamines having from 1 to 4
carbon atoms in the
alkyl radical, e.g. optionally monoalkyl- and dialkyl-substituted
ethylenediamine,
diethylenetriamine, triethylenetetramine, 1,3-propylenediamine, 1,3- or 1,4-
butylenediamine,
1,2-, 1,3-, 1,4-, 1,5- and 1,6-hexamethylenediamine, phenylenediamines, 2,3-,
2,4- and 2,6-
toluenediamine and 4,4'-, 2,4'- and 2,2'-diaminodiphenylmethane. Particular
preference is given
to the diprimary amines mentioned, for example ethylenediamine.
Further possible starter molecules are: alkanolamines such as ethanolamine, N-
methylethanolamine and N-ethylethanolamine, dialkanolamines such as
diethanolamine, N-
methyldiethanolamine and N-ethyldiethanolamine and trialkanolamines such as
triethanolamine,
and ammonia.
Preference is given to using dihydric or polyhydric alcohols such as
ethanediol, 1,2- and 1,3-
propanediol, diethylene glycol (DEG), dipropylene glycol, 1,4-butanediol, 1,6-
hexanediol,
glycerol, trimethylolpropane, pentaerythritol, sorbitol and sucrose.
In addition, polyester alcohols having hydroxyl numbers of from 100 to 1200 mg
KOH/g are
possible as compounds in component B).
Preferred polyester alcohols are prepared by condensation of polyfunctional
alcohols, preferably
diols, having from 2 to 12 carbon atoms, preferably from 2 to 6 carbon atoms,
with
polyfunctional carboxylic acids having from 2 to 12 carbon atoms, for example
succinic acid,
glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid,
decanedicarboxylic acid,
maleic acid, fumaric acid and preferably phthalic acid, isophthalic acid,
terephthalic acid and the
isomeric naphthalenedicarboxylic acids.
Preferred compounds of the component B) also include the chain extenders and
crosslinkers
which are optionally used concomitantly. The addition of bifunctional chain
extenders,
trifunctional and higher-functional crosslinkers or optionally mixtures
thereof can prove to be
advantageous for modifying the mechanical properties. As chain extenders
and/or crosslinkers,
preference is given to using alkanolamines and in particular diols and/or
triols having molecular
weights of less than 400, preferably from 60 to 300.
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If desired, chain extenders, crosslinkers or mixtures thereof are
advantageously used in an
amount of from 1 to 20% by weight, preferably from 2 to 5% by weight, based on
the weight of
the component B).
Further information on the preferred polyether alcohols and polyester alcohols
and their
preparation may be found, for example, in Kunststoffhandbuch, volume 7
"Polyurethane", edited
by Gunter Oertel, Carl-Hanser-Verlag, Munich, 3rd edition, 1993.
Component C
According to the invention, the starting components used in the process
comprise one or more
blowing agents. According to the invention, the component C) comprises at
least formic acid. In
a preferred embodiment, not only formic acid but also at least one further
blowing agent, in
particular water, are used in component C).
As blowing agent C), particular preference is given to an aqueous solution of
formic acid. Formic
acid dissolved in water in a concentration of from 50 to 99% by weight, in
particular from 60 to
95% by weight, particularly preferably from 70 to 90% by weight, is
particularly preferably used
as blowing agent C).
(Aqueous) formic acid reacts with isocyanate groups to form carbon dioxide and
carbon
monoxide. Since formic acid and water liberate the blowing gas by means of a
chemical
reaction with the isocyanate groups, they are referred to as chemical blowing
agents.
In addition, it is possible to use physical blowing agents such as low-boiling
hydrocarbons.
Suitable physical blowing agents are, in particular, liquids which are inert
toward the
polyisocyanates A) and have boiling points below 100 C, preferably below 50 C,
at atmospheric
pressure and therefore vaporize under the action of the exothermic
polyaddition reaction.
Examples of such liquids which are preferably concomitantly used are alkanes,
such as
heptane, hexane, n-pentane and isopentane, preferably industrial mixtures of n-
pentanes and
isopentanes, n-butane and isobutane and propane, cycloalkanes such as
cyclopentane and/or
cyclohexane, ethers such as furan, dimethyl ether and diethyl ether, ketones
such as acetone
and methyl ethyl ketone, alkyl carboxylates such as methyl formate, dimethyl
oxalate and ethyl
acetate and halogenated hydrocarbons such as methylene chloride,
dichloromonofluoromethane, difluoromethane, trifluoromethane, difluoroethane,
tetrafluoroethane, chlorodifluoroethanes, 1,1-dichloro-2,2,2-trifluoroethane,
2,2-dichloro-2-
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fluoroethane and heptafluoropropane. Mixtures of these low-boiling liquids
with one another
and/or with other substituted or unsubstituted hydrocarbons can also be
concomitantly used.
Further suitable blowing agents are organic carboxylic acids such as acetic
acid, oxalic acid,
ricinoleic acid and carboxyl-comprising compounds. The additional blowing
agents are
preferably selected from the group consisting of alkanes and cycloalkanes
having at least 4
carbon atoms, dialkyl ethers, esters, ketones, acetals, fluoroalkanes having
from 1 to 8 carbon
atoms and tetraalkylsilanes having from 1 to 3 carbon atoms in the alkyl
chain, in particular
tetramethylsilane. Further suitable blowing agents are fluoroalkanes which are
degraded in the
troposphere and therefore do not damage the ozone layer, e.g.
trifluoromethane,
difluoromethane, 1,1,1,3,3-pentafluorobutane, 1,1,1,3,3-pentafluoropropane,
1,1,1,2-
tetrafluoroethane, difluoroethane and heptafluoropropane and also
hydrofluoroolefins (H F0).
Preference is given to not using any halogenated hydrocarbons as blowing
agents. Pentanes or
mixtures of pentane isomers are preferably used as additional constituents of
the component
C).
The blowing agents are either dissolved completely or partly in the polyol
component (i.e.
B+C+D+E+F) or are introduced via a static mixer immediately before foaming of
the polyol
component. Formic acid/water mixtures or formic acid are preferably completely
or partly
dissolved in the polyol component. The physical blowing agent (for example
pentane) and
optionally part of the chemical blowing agent are optionally metered in "on-
line".
The amount of component C) used is from 1 to 45% by weight, preferably from 1
to 30% by
weight, particularly preferably from 2 to 15% by weight, in each case based on
the weight of the
components B) to F).
If exclusively formic acid or a formic acid/water mixture serves as blowing
agent, the proportion
of component C) in the weight of components B) to F) is preferably from 0.5 to
10% by weight,
in particular from 1 to 8% by weight, particularly preferably from 2 to 6% by
weight.
The addition of the formic acid and optionally water can be carried out in
combination with the
use of the other blowing agents described. In an embodiment, formic acid or a
formic acid/water
mixture is used in combination with pentane, in particular cyclopentane and/or
n-pentane.
Component D
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The reaction to form the rigid polyurethane foam is preferably carried out in
the presence of one
or more flame retardants.
As flame retardants D), it is generally possible to use the flame retardants
known from the prior
art. Suitable flame retardants are, for example, brominated esters, brominated
ethers (Ixol) or
brominated alcohols such as dibromoneopentyl alcohol, tribromoneopentyl
alcohol and PHT-4-
diol and also chlorinated phosphates such as tris(2-chloroethyl) phosphate,
tris(2-chloropropyl)
phosphate (TCPP), tris(1,3-dichloropropyl) phosphate, tricresyl phosphate,
tris(2,3-
dibromopropyl)phosphate, tetrakis(2-chloroethyl) ethylenediphosphate, dimethyl
methanephosphonate, diethyl diethanolaminomethylphosphonate and also
commercial halogen-
comprising flame retardant polyols. As further phosphates or phosphonates, it
is possible to use
diethyl ethanephosphonate (DEEP), triethyl phosphate (TEP), dimethyl
propylphosphonate
(DMPP), diphenyl cresyl phosphate (DPC) as liquid flame retardants.
Apart from the abovementioned flame retardants, it is also possible to use
inorganic or organic
flame retardants such as red phosphorus, preparations comprising red
phosphorus, aluminum
oxide hydrate, antimony trioxide, arsenic oxide, ammonium polyphosphate and
calcium sulfate,
expandable graphite or cyanuric acid derivatives such as melamine or mixtures
of at least two
flame retardants, e.g. ammonium polyphosphates and melamine and optionally
maize starch or
ammonium polyphosphate, melamine, expandable graphite and optionally aromatic
polyesters
for making the rigid polyurethane foams flame-resistant.
Preferred flame retardants do not have any groups which are reactive toward
isocyanate
groups. The flame retardants are preferably liquid at room temperature.
Particular preference is
given to TCPP, DEEP, TEP, DMPP and DPC.
For the purposes of the present invention, the flame retardants are preferably
used in an
amount of from 0 to 65% by weight, preferably from 5 to 60% by weight,
particularly preferably
from 5 to 50% by weight, in particular from 6 to 15% by weight, based on the
total weight of the
components B) to F).
Component E
The reaction to form the rigid polyurethane foam is preferably carried out in
the presence of one
or more catalysts.
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Catalysts E) used for producing the rigid polyurethane foams are, in
particular, compounds
which strongly accelerate the reaction of the compounds comprising reactive
hydrogen atoms,
in particular hydroxyl groups, in the components B) to F) with the
polyisocyanates A).
Use is advantageously made of basic polyurethane catalysts, for example
tertiary amines such
as triethylamine, tributylamine, dimethylbenzylamine, dicyclohexylmethylamine,
dimethylcyclohexylamine, bis(N,N-dimethylaminoethyl) ether,
bis(dimethylaminopropyl)urea, N-
methylmorpholine or N-ethylmorpholine, N-cyclohexylmorpholine, N,N,N',N'-
tetramethyl-
ethylenediamine, N,N,N,N-tetramethylbutanediamine, N,N,N,N-tetramethylhexane-
1,6-diamine,
pentamethyldiethylenetriamine, bis(2-dimethylaminoethyl) ether,
dimethylpiperazine, N-
dimethylaminoethylpiperidine, 1,2-dimethylimidazole, 1-
azabicyclo[2.2.0]octane, 1,4-
diazabicyclo[2.2.2]octane (Dabco) and alkanolamine compounds such as
triethanolamine,
triisopropanolamine, N-methyldiethanolamine and N-ethyldiethanolamine,
dimethylamino-
ethanol, 2-(N,N-dimethylaminoethoxy)ethanol, N,N',N"-
tris(dialkylaminoalkyl)hexahydrotriazines,
e.g. N,N',N"-tris(dimethylaminopropyI)-s-hexahydrotriazine, and
triethylenediamine. However,
metal salts such as iron(II) chloride, zinc chloride, lead octoate and
preferably tin salts such as
tin dioctoate, tin diethylhexanoate and dibutyltin dilaurate and in particular
mixtures of tertiary
amines and organic tin salts are also suitable.
Further possible catalysts are: amidines such as 2,3-dimethy1-3,4,5,6-
tetrahydropyrimidine,
tetraalkylammonium hydroxides such as tetramethylammonium hydroxide, alkali
metal
hydroxides such as sodium hydroxide and alkali metal alkoxides such as sodium
methoxide and
potassium isopropoxide, alkali metal carboxylates and also alkali metal salts
of long-chain fatty
acids having from 10 to 20 carbon atoms and optionally lateral OH groups.
Preference is given
to using from 0.001 to 10 parts by weight of catalyst or catalyst combination,
based on (i.e.
calculated for) 100 parts by weight of the component B). It is also possible
to allow the reaction
to proceed without catalysis. In this case, the catalytic activity of amine-
initiated polyols is
exploited.
If a large excess of polyisocyanate is used for foaming, further possible
catalysts for the
trimerization reaction of the excess NCO groups with one another are:
catalysts which form
isocyanurate groups, for example ammonium salts or alkali metal salts,
especially ammonium or
alkali metal carboxylates, either alone or in combination with tertiary
amines. Isocyanurate
formation leads to particularly flame-resistant PIR foams.
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Further information on the abovementioned and further starting materials may
be found in the
specialist literature, for example Kunststoffhandbuch, volume VII,
Polyurethane, Carl Hanser
Verlag, Munich, Vienna, 1st, 2nd and 3rd edition 1966, 1983 and 1993.
Component F
The reaction can additionally be carried out using further auxiliaries or
additives.
Mention may be made by way of example of surface-active substances, foam
stabilizers, cell
regulators, fillers, dyes, pigments, hydrolysis inhibitors, fungistatic and
bacteriostatic
substances.
Possible surface-active substances are, for example, compounds which serve to
aid the
homogenization of the starting materials and are optionally also suitable for
regulating the cell
structure of the polymers. Mention may be made by way of example of
emulsifiers such as the
sodium salts of castor oil sulfates or of fatty acids and also salts of fatty
acids with amines, e.g.
diethylamine oleate, diethanolamine stearate, diethanolamine ricinoleate,
salts of sulfonic acids,
e.g. alkali metal or ammonium salts of dodecylbenzenesulfonic or
dinaphthylmethanedisulfonic
acid and ricinoleic acid; foam stabilizers such as siloxane-oxyalkylene
copolymers and other
organopolysiloxanes, ethoxylated alkylphenols, ethoxylated fatty alcohols,
paraffin oils, castor
oil esters or ricinoleic esters, Turkey red oil and peanut oil, and cell
regulators such as paraffins,
fatty alcohols and dimethylpolysiloxanes. The above-described oligomeric
acrylates having
polyoxyalkylene and fluoroalkane radicals as side groups are also suitable for
improving the
emulsifying action, the cell structure and/or stabilizing the foam. The
surface-active substances
are usually employed in amounts of from 0.01 to 10 parts by weight, based on
(i.e. calculated
for) 100 parts by weight of the component B).
For the purposes of the present invention, fillers, in particular reinforcing
fillers, are the
customary organic fillers, reinforcing materials, weighting agents, agents for
improving the
abrasion behavior in paints, coating compositions, etc. Possible organic
fillers are, for example:
carbon, melamine, rosin, cyclopentadienyl resins and graft polymers and also
cellulose fibers
and polyamide, polyacrylonitrile, polyurethane, polyester fibers based on
aromatic and/or
aliphatic dicarboxylic esters and in particular carbon fibers.
The organic fillers can be used individually or as mixtures and are
advantageously added to the
reaction mixture in amounts of from 0.5 to 50% by weight, preferably from 1 to
40% by weight,
based on the weight of the components A) to F), although the content of mats,
nonwovens and
CA 02880780 2015-02-03
woven fabrics composed of natural and synthetic fibers can reach values of up
to 80% by
weight, based on the weight of the components A) to F).
Further information on the abovementioned other customary auxiliaries and
additives may be
found in the specialist literature, for example the Monograph by J.H. Saunders
and K.C. Frisch
"High Polymers" volume XVI, Polyurethanes, Parts 1 and 2, lnterscience
Publishers 1962 and
1964, or Kunststoff-Handbuch, volume 7: "Polyurethane", Carl-Hanser-Verlag,
Munich, 3rd
edition, 1993.
To produce the rigid polyurethane foams, the polyisocyanates A) and the polyol
component B)
to F) are preferably reacted in such amounts that the isocyanate index is in
the range from 90 to
700, preferably from 100 to 500.
The rigid polyurethane foams used according to the invention are usually
produced by the two-
component process. In this process, the components B) to F) are mixed to form
the polyol
component and this is reacted with the polyisocyanates A).
The starting components are usually mixed at a temperature of from 15 to 35 C,
preferably from
to 30 C. The reaction mixture can be introduced into the composite profiles by
means of
high- or low-pressure metering machines.
The rigid polyurethane foams used for the process of the invention
surprisingly display no
bloating of the rigid polyurethane foam on application of a surface coating.
In addition, the
profiles can be readily processed and display good use properties even at
subzero
temperatures.
The invention is illustrated by the following examples.
The following polyols were used:
Polyol B-1: polyether polyol having a hydroxyl number of 490 mg KOH/g and
based on
propylene oxide and sorbitol as starter
Polyol B-2: polyether polyol having a hydroxyl number of 248 mg KOH/g and
based on
propylene oxide and propylene glycol as starter
Component C-1: formic acid 85%
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Component C-2: water
Compound D-1: tris(2-chloroisopropyl) phosphate
Compound E-1: N,N-dimethylcyclohexylamine
Compound F-1: silicone-based stabilizer, Niax Silicone L- 6900
The components shown in table 1 were mixed to form a polyol component.
Table 1:
Example 1 Example 2
Component Amount used [% by weight]
B-1 37.1 36.5
B-2 36.5 38.5
C-1 4.5 -
C-2 3.7
D-1 19.0 19.0
F-1 1.7 1.7
E-1 1.2 0.6
A mixture of diphenylmethane 2,4'- and 4,4'-diisocyanate with higher-
functional oligomers and
isomers (crude MDI) having an NCO content of 31.5% (IsoPMDI 92410 from BASF)
was used
as isocyanate component. The foaming experiments on the laboratory scale were
carried out at
an isocyanate index of 115.
In production experiments, polyol and isocyanate components were reacted in a
low-pressure
plant at an isocyanate index of 115 and used to fill aluminum-polyamide
composite profiles
having a height of 70 mm and a width of 250 mm with foam. These profiles were
then
subsequently subjected to powder coating.
Furthermore, aluminum-polyamide composite profiles having a height of 3 cm and
a width of
6 cm were manufactured using the rigid polyurethane foams described and
subjected to powder
coating at 200 C.
In the case of example 1, the profile displayed no deformation even after
surface coating.
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In contrast, when aluminum-polyamide composite profiles were filled with
various filler-free foam
formulations using water as blowing agent, both on the laboratory scale and on
the production
scale, deformation of the completely foam-filled composite elements was
observed, especially
as a result of surface coating (example 2).
Furthermore, formulations comprising formic acid as blowing agent and
comprising increasing
amounts of calcium carbonate (calcium carbonate content of 0-50% by weight)
were tested in
laboratory and production experiments. Here, the incorporation of finely
divided fillers into the
reaction mixture placed severe demands on the wear resistance of the metering
pumps. The
corresponding formulations were tested with increasing low-temperature
flexibility. Furthermore,
the undesirable increase in dust after cutting or sawing of completely foam-
filled hollow chamber
profiles was in many cases observed in the manufacturing process. In addition,
the increase in
density of the finished filler-comprising polyurethane foam is disadvantageous
in many cases.
