Note: Descriptions are shown in the official language in which they were submitted.
Production of rigid polyurethane foams
5 The present invention relates to a process for producing rigid
polyurethane foams by reacting
a) organic and/or modified organic diisocyanates and/or
polyisocyanates with
b) specific polyester polyols and/or polyether ester polyols
which can be prepared by polycondensation of dicarboxylic
acids with polyfunctional alcohols using polyalkylene
terephthalates and, if desired, subsequent reaction with
lower alkylene oxides, plus, if desired, further relatively
high molecular weight compounds containing at least two
reactive hydrogen atoms and, if desired,
c) low molecular weight chain extenders and/or crosslinkers in
the presence of
d) blowing agents
25 e) catalysts and, if desired,
f) further auxiliaries and/or additives.
The production of rigid polyurethane foams by reacting organic
30 and/or modi~ied organic diisocyanates and/or polyisocyanates with
relatively high molecular weight compounds containing at least
two reactive hydrogen atoms, in particular with polyether polyols
from alkylene oxide polymerization or polyester polyols from the
polycondensation of alcohols with dicarboxylic acids, with
35 concomitant use of polyurethane catalysts, chain extenders and/or
crosslinkers, blowing agents and further auxiliaries and
additives is known and has been described in numerous patent and
literature publications.
Mention may be made by way of example of the Kunststoffhandbuch,
Volume VII, Polyurethane, Carl-Hanser-Verlag, Munich, 1st edition
1966, edited by Dr. R. Vieweg and Dr. A. Hochtlen, and 2nd
edition 1983 and 3rd edition 1993, edited by Dr. G. Oertel.
45 Appropriate selection of the formative components and their
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ratios enables rigid polyurethane foams having very good
mechanical properties to be produced.
When using polyester polyols, it is customary to use
5 polycondensates of aromatic and/or aliphatic dicarboxylic acids
and alkanediols and/or alkanetriols or ether diols. However, it
is also possible to process polyester wastes and here i~
particular polyethylene terephthalate (PET) or polybutylene
terephthalate (P~T) wastes. A whole series of processes for this
10 purpose are known and have been described. The basis of some
processes is the conversion of the polyester into a diester of
terephthalic acid, e.g. into dimethyl terephthalate. In
DE-A-1003~14 and US-A-5 051 528, such transesterifications are
carried out using methanol and transesterification catalysts. All
15 these processes have many disadvantages as a result of
complicated technological steps, e.g. use of methanol vapor, and
also secondary reactions which proceed in a more uncontrolled
manner.
Further processes, e.g. as described in DE-C-4227299, add
transesterification catalysts and dialkyl esters for the purpose
of depolymerization. Catalysts used are manganese acetate or zinc
compounds. The processes actually differ only in the catalyst
used: in DE-A-4220473 PBT is prepared by treating PET wastes with
a titanium or tin catalyst and 1,4-butanediol. Polym. Mater. Sci.
Eng. (1990) 63, pp. 1029 - 1033, 5S, lB, 6T, l9Q describes the
use of zinc acetate for the glycolysis of PET wastes. As a result
of the catalyst addition together with alcohol right at the
30 beginning of the glycolysis, dissociation and polycondensation
reactions proceed simultaneously in an uncontrolled manner, the
degradation of PET is interrupted and insoluble constituents
(turbidity) result. These insoluble constituents hinder further
processing to give the polyurethane. In EP-A-134661, these
35 disadvantages are avoided by means of a catalyst-free PET
glycolysis using ethylene glycol and subsequent alkoxylation
using sodium acetate as catalyst. The start of the glycolysis
proceeds uniformly, but the reaction remains very incomplete. The
process enables only certain types of PET to be worked up and the
40 addition of the basic catalyst reinforces a series of undesired
hydrolysis reactions and thus greatly broadens the molecular
weight distribution.
~S-A-2030997 describes the production of rigid polyurethane foam
45 from polyols derived from recycled polyalkylene terephthalate.
The glycolysis of the polyalkylene terephthalates is, as is
generally known, carried out in a single-stage reaction with
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~ alkylene glycols or glycol ethers with the ~pecif ~ c addition of bifi(2-hydroxyethoxyethyl) glutarate. ~hi9 too lead~ to
inh~m~geneitie~ and the precipitatiou of oligomeric dissociation
and reaction product~ t ~iately after th~ tran~e~teri~ication
5 of the polyalkylene terephthalates ~ B concluded and in ~articular
aft~r ~torage of th~ products ~or 2 - ~ dayR ThuR, u~e of qUCh
~olyol ~roducts results, -~imilarly to the ca3e o~ polyols
prepared as described in E~A 0710686, in polyurethane formation
even before the actual polyurethane reaction. Stable-precipitates
10 of the polyol r~rnn~nts of the ~olyurethane formed and rigid
polyurethane fo~s pro~lr~ therefrom have considerable
~hysico~h~;cal deficicncies. In addltlon, the proces6
de~cribed in EP-A-0710686 i~ also extremely ~n~conomlcal to carry
out since, inter alla, large amountR o~ DEG have to be fed iD and
15 have to be distilled off in a distillation at <140~C which i6
di~Eicult to control industrially.
It is an object ~f the ~resent invention to provide a ~roce~ for
prs~c~n~ riqid ~olyurethane foam6 by reactinq in ~articular
20 aromatic dii30cyanates and/or polyi~ocyanate6 with 3peci~ic
~olyol~ which have been pre~ared u~ing all industrially available
typeb of PET/P~, in the presence of customary auxiliari~s and
additives, which process avoid3 undesired hydrolysis reactions
and molecular weight shifts which i~;r the quality.
~5
ne have found that this object i~ achieved by prn~llci nq the rigid
polyurethane ~oams using speci~ic polye~ter polyols and/or
polye her e~ter ~olyols which can be prepared by ~olyc~nA~n~ation
30 of dicarboxylic acids with polyfunctional alcohol~ usin~
~olyalkylena tereph~halates and, lf de~ired, subsequent reaction
with lower alkyle~e 9Yi ~q, wherein the polyester polyola and~or
polyether ester polyol~ are ~repared in a stagewise
~olycon~çn~ation in whic~, ln the fir6t stage, polyalkylene
35 terephthalate is intr~d~ in addltion to the starting
compon~ts into the cQn~n~tion as it ~ ~es and/or while it
i~ underway and, in at least one ~urther stage, catalyt~cally
active substAnc~ are added.
40 The ~re~ent invention accordin~ly ~rovide6 a ~ocess for
~roducing rigid polyurcthane fo~ by reacting
a) organic and/or modified organic diisocYanates and/or
polyi~ocyanat~s with
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.
b) specific polyester polyols and/or polyether ester polyols
which can be prepared by polycondensation of dicarboxylic
acids with polyfunctional alcohols using polyalkylene
terephthalates and, if desired, subsequent reaction with
lower alkylene oxides, plus, if desired, further relatively
high molecular weight compounds containing at least two
reactive hydrogen atoms and, if desired,
c) low molecular weight chain extenders and/or crosslinkers in
the presence of
d) blowing agents,
15 e) catalysts and, if desired,
f) further auxiliaries and/or additives,
wherein the polyester polyols and/or polyether ester polyols are
20 prepared in a stagewise polycondensation where, in the first
stage, polyalkylene terephthalate is introduced in addition to
the starting components into the condensation as it commences
and/or while it is underway and, in at least one further stage,
catalytically active substances are added.
The present invention also provides for the use of these rigid
polyurethane foams as insulation material for the refrigeration
and long-distance energy sectors, as sandwich material in
30 building and construction and as support and forming material in
the furniture sector.
It was surprising and in no way foreseeable that this targeted
multistage polycondensation/transesterification, the accurately
35 matched addition of the polyalkylene terephthalate products and
the subsequent further addition of catalysts and, if desired,
further carboxylic acids and/or alcohols results in--a homogeneous
polyol mixture which re~in.s homogeneous, even for weeks, on its
own and in a mixture as the polyol component of a polyurethane
40 system.
Furthermore, it was also surprising that this process enables all
available polyalkylene terephthalate products to be processed
without losses to give homogeneous polyols. The rigid
45 polyurethane foams produced from these polyol mixtures are of
high quality, processing is without problems, curing and
flowability are optimal and the physicomechanical properties meet
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.
the high demands of the refrigerator, building and long-distance
energy industries.
An economical process has thus been found for producing rigid
5 polyurethane foams which are very suitable as insulation material
for the refrigeration and long-distance energy sectors, as
sandwich material in building and construction and as support and
forming material in the furniture sector.
The speclf1c polyester polyols and/or polyether ester polyols to
be used according to the present invention are preferably
prepared by polycondensation of dicarboxylic acids with
polyfunctional alcohols using polyalkylene terephthalates and, if
15 desired, subsequent reaction with lower alkylene oxides.
According to the present invention, the polyester polyols and/or
polyether ester polyols are prepared in a stagewise
polycondensation. In the first stage of the polycondensation,
20 polyalkylene terephthalate is introduced in addition to the
starting components, viz. the dicarboxylic acids and
polyfunctional alcohols, into the condensation as it commences
and/or while it is underway. The precondensation product is, in
at least one further stage, admixed with catalytically active
25 substances, if desired in combination with further amounts of
dicarboxylic acids and/or polyfunctional alcohols. The product
can be modified to form polyether ester polyols by subsequent
reaction with lower alkylene oxides.
30 The polyalkylene terephthalate is preferably added at a
temperature of the starting components or the condensation
mixture of from 150 to 25~C, in particular from 180 to 240~C, at
atmospheric pressure or under a slightly reduced pressure of from
1 to 200 mbar, in particular from 10 to 100 mbar.
The polyalkylene terephthalates can be used individually or in
admixture with one another. Preference is given to using PET
and/or P~T.
In particular, use is made of polyalkylene terephthalate wastes
such as PBT and PET granules from the recycling of PBT or PET
articles, films, fibers and sheets or else paste-like or liquid
PBT and PET wastes from production.
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.
In the preparation of the polyester polyols and/or polyether
ester polyols to be used according to the present invention, acid
components employed are the dicarboxylic acids customarily used
for this purpose, preferably adipic acid, glutaric acid, succinic
5 acid and/or phthalic acid and/or their anhydrides, in particular
phthalic anhydride.
The dicarboxylic acids are reacted with polyfunctional alcohols,
preferably alkanediols and/or alkanetriols having from 2 to 10
10 carbon atoms and/or ether diols having from 4 to 20 carbon atoms.
In particular, use is made of monoglycols and/or monotriols such
as 1,3- and 1,4-butanediol, hexanediols, neopentyl glycol,
ethylene and/or propylene glycol, glycerol and/or
trimethylolpropane and, as ether diols, preferably diethylene,
lS triethylene and/or polyethylene glycols and/or dipropylene,
tripropylene and/or polypropylene glycols having a mean molecular
weight of up to 1000. Preference is given to using ethylene
and/or propylene glycol as diols and glycerol and/or
trimethylolpropane as triols.
As catalytically active substances in the condensation reaction,
preference is given to using titanium and/or tin compounds and/or
Lewis acids in amounts of up to 1000 ppm, for example tetrabutyl
25 orthotitanate, tin(II) octoate, tin(II) chloride or iron(II)
chloride .
The polyols prepared according to the present invention can be
subjected to an extractive or preferably a distillative
30 treatment. The after-distillation is preferably carried out using
a short residence time at from 100 to 280~C, particularly
preferably at from 250 to 270~C, under a reduced pressure similar
to that in the after-condensation and/or with feeding in of inert
gases. The inert gas used here is particularly preferably
35 nitrogen
The extractive treatment is carried out using an extractant in a
wide temperature range, preferably at from 20 to 250~C.
Extractants used are preferably inert solvents, in particular
40 aliphatic or cycloaliphatic hydrocarbons such as hexane, heptane,
cyclohexane and methylcyclohexane or mixtures thereof.
The removal of the low molecular weight components can be carried
out batchwise in commercial apparatus for liquid-liquid
45 extraction, e.g. in a rotation perforator, or continuously in
countercurrent in a tube. ~e~Aining solvent residues from the
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extraction can easily be removed by subsequent treatment under
reduced pressure, preferably at elevated temperature.
The polyester polyols and/or polyether ester polyols thus
5 prepared are, if desired in admixture with further relatively
high molecular weight compounds containing at least two reactive
hydrogen atoms, as described below, reacted with the other
components to give the rigid polyurethane foams of the present
invention.
These foams have a uniformly high level of mechanical properties
as well as a high hardness and a low thermal conductivity and are
particularly suitable for use in the insulation sector and for
15 producing sandwich elements.
The process of the present invention has the advantage that the
gentle polycondensation in the 1st stage results in a homogeneous
polycondensation/transesterification reaction which leads, by
20 means of the modification in the 2nd stage, to homogeneous
polyols which can be processed into rigid polyurethane foams
having excellent properties. The otherwise usual secondary
reactions, product dissociations and considerable molecular
weight shifts, in particular broadening of the molecular weight
25 distributions which lead to considerable amounts of precipitate
and losses in quality, are completely or largely avoided.
It is surprising that the object of the invention is able to be
achieved by use of the specifically prepared polyester polyols
30 and/or polyether ester polyols of the present invention. Rather,
it would have been expected that the stagewise
polycondensation/transesterification would have resulted,
similarly to the previous processes of the prior art, in turbid,
inhomogeneous polyols whose turbidity occurs immediately or after
35 standing for a short or long time or in a mixture of the polyol
component of the polyurethane.
To produce the rigid polyurethane foams by the process of the
present invention, use is made, apart from the above-described
40 specific polyester polyols and/or polyether ester polyols, of the
formative components known per se about which the following
details may be given.
45 a) Suitable organic and/or modified organic polyisocyanates (a)
are the aliphatic, cycloaliphatic, araliphatic and preferably
aromatic polyfunctional isocyanates known per se.
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Specific examples are: alkylene diisocyanates having from 4
to 12 carbon atoms in the alkylene radical, for example
dodecane l,12-diioscyanate, 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 also any mixtures
of these isomers,
l-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane
(IPDI), hexahydrotolylene 2,4- and 2,6-diisocyanate and also
the corresponding isomer mixtures, dicyclohexylmethane 4,4'-,
2,2~- and 2,4'-diisocyanate and also the corresponding isomer
mixtures, and preferably aromatic diisocyanates and
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 2,4'-, 2,4'- and
2,2'-diisocyanates and polyphenylpolymethylene
polyisocyanates (raw MDI) and mixtures of raw MDI and
tolylene diisocyanates. The organic diisocyanates and
polyisocyanates can be used individually or in the form of
their mixtures.
Use is frequently also made of modified polyfunctional
isocyanates, i.e. products which are obtained by chemical
reaction of organic diisocyanates and/or polyisocyanates.
Examples which may be mentioned are diisocyanates and/or
polyisocyanates containing ester, urea, biuret, allophanate,
carbodiimide, isocyanurate, uretdione and/or urethane groups.
Specific examples are: organic, preferably aromatic
polyisocyanates containing urethane groups and having NCO
contents of from 33.6 to 15 % by weight, preferably from 31
to 21 ~ by weight, based on the total weight, for example
diphenylmethane 4,4~-diisocyanate modified with low molecular
weight diols, triols, dialkylene glycols, trialkylene glycols
or polyoxyalkylene glycols having molecular weights of up to
6000, in particular having molecular weights of up to 1500,
modified diphenylmethane 4,4'- and 2,4'-diisocyanate
mixtures, modified raw MDI or tolylene 2,4- or
2,6-diisocyanate, with examples of dialkylene or
polyoxyalkylene glycols, which can be used individually or as
mixtures, being: diethylene and dipropylene glycols,
polyoxyethylene, polyoxypropylene and
polyoxypropylene-polyoxyethene glycols, triols and/or
tetrols. Also suitable are prepolymers cont~i ni ng NCO groups,
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having NCO contents of from 25 to 3.5 % by weight, preferably
from 21 to 14 % by weight, based on the total weight, and
prepared from the polyester polyols and/or preferably
polyether polyols described below and diphenylmethane
4,4'-diisocyanate, mixtures of diphenylmethane 2,4'- and
4,4'-diisocyanate, tolylene 2,4- and/or 2,6-diisocyanates or
raw MDI. Other polyisocyanates which have been found to be
useful are liquid polyisocyanates containing carbodiimide
groups and/or isocyanurate rings and having NCO contents of
from 33.6 to 15 % by weight, preferably from 31 to 21 % by
weight, based on the total weight, e.g. those based on
diphenylmethane 4,4~-, 2,4'- and/or 2,2~-diisocyanate and/or
tolylene 2,4- and/or 2,6-diisocyanate.
If desired, the modified polyisocyanates can be mixed with
one another or with unmodified organic polyisocyanates such
as diphenylmethane 2,4'- and/or 4,4'-diisocyanate, raw MDI,
tolylene 2,4- and/or 2,6-diisocyanate.
Organic polyisocyanates which have been found to be
particularly useful and are therefore preferably employed
are: mixtures of tolylene diisocyanates and raw MDI or
mixtures of modified organic polyisocyanates containing
urethane groups and having an NCO content of from 33.6 to
15 % by weight, in particular those based on tolylene
diisocyanates, diphenylmethane 4,4~-diisocyanate,
diphenylmethane diisocyanate isomer mixtures or raw MDI and
in particular raw MDI having a diphenylmethane diisocyanate
isomer content of from 30 to 80 ~ by weight, preferably from
30 to 60 % by weight, in particular from 30 to 55 % by
weight.
b) The specific polyester polyols and/or polyether ester polyols
used are those prepared according to the present invention,
as described above. In addition to these, it is possible to
use further relatively high molecular weight compounds
containing at least two reactive hydrogen atoms in an amount
of from 10 to 90 96 by weight, preferably from 20 to 60 % by
weight, based on the weight of the component (b).
The further relatively high molecular weight compounds
cont~in;ng at least two reactive hydrogen atoms which are
used are advantageously those having a functionality of from
2 to 8, preferably from 2 to 6, and a molecular weight of
from 300 to 8000, preferably from 300 to 3000. The compounds
used depend on the des1red properties of the rigid
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polyurethane foam to be produced. Examples of further
relatively high molecular weight compounds which have found
to be useful are polyetherpolyamines and/or preferably
polyols selected from the group consisting of polyether
polyols, polyester polyols, polythioether polyols,
polyesteramides, hydroxyl-containing polyacetals and
hydroxyl-containing aliphatic polycarbonates or mixtures of
at least two of the polyols mentioned. Preference is given to
using polyester polyols and/or polyether polyols. The
hydroxyl number of the polyhydroxyl compounds is here
generally from 150 to 850 mg KOHtg and preferably from 200 to
600 mg KOH/g.
Suitable further polyester polyols can be prepared, for
1~ example, from organic dicarboxylic acids having from 2 to 12
carbon atoms, preferably aliphatic dicarboxylic acids having
from 4 to 6 carbon atoms, and polyhydric alcohols, preferably
diols, having from 2 to 12 carbon atoms, preferably from 2 to
6 carbon atoms. Examples of suitable dicarboxylic acids are:
succinic acid, glutaric acid, adipic acid, suberic acid,
azelaic acid, sebacic acid, decanedicarboxylic acid, maleic
acid, fumaric acid, phthalic acid, isophthalic acid and
terephthalic acid. The dicarboxylic acids can here be used
either individually or in admixture with one another. In
place of the free dicarboxylic acids, it is also possible to
use the corresponding dicarboxylic acid derivatives such as
dicarboxylic esters of the alcohols having from 1 to 4 carbon
atoms or dicarboxylic anhydrides. Preference is given to
using dicarboxylic acid mixtures of succinic, glutaric and
adipic acids in weight ratios of, for example, 20 - 35 : 35 -
50 : 20 - 32, and in particular adipic acid. Examples of
dihydric and polyhydric alcohols, in particular diols, are:
ethanediol, diethylene glycol, 1,2- or 1,3-propanediol,
dipropylene glycol, 1,4-butanediol, 1,5-pentanediol,
1,6-hexanediol, 1,10-decanediol, glycerol and
trimethylolpropane. Preference is given to using ethanediol,
diethylene glycol, 1,4-butanediol, 1,5-pentanediol,
1,6-hexanediol or mixtures of at least two of the diols
mentioned, in particular mixtures of 1,4-butanediol,
1,5-pentanediol and 1,6-hexanediol. It is also possible to
use polyester polyols derived from lactones, e.g. E -capro-
lactone, or hydroxycarboxylic acids, e.g. ~-hydroxycaproic
acid.
To prepare the polyester polyols, the organic, e.g. aromatic
and preferably aliphatic, polycarboxylic acids and/or
derivatives and polyhydric alcohols can be polycondensed in
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the absence of catalysts or preferably in the presence of
esterification catalysts, advantageously in an atmosphere of
inert gas such as nitrogen, carbon monoxide, helium, argon,
etc., in the melt at from 150 to 250~C, preferably from 180
to 220~C, at atmospheric pressure or under reduced pressure
to the desired acid number which is advantageously less than
10, preferably less than 2. According to a preferred
embodiment, the etherification mixture is polycondensed at
the abovementioned temperatures to an acid number of from 80
to 30, preferably from 40 to 30, under atmospheric pressure
and subse~uently under a pressure of less than 500 mbar,
preferably from 50 to 150 mbar. Suitable esterification
catalysts are, for example, iron, cadmium, cobalt, lead,
zinc, antimony, magnesium, titanium and tin catalysts in the
form of metals, metal oxides or metal salts. However, the
polycondensation can also be carried out in the liquid phase
in the presence of diluents and/or entrainers such as
benzene, toluene, xylene or chlorobenzene for azeotropically
distilling off the water of condensation.
To prepare the polyester polyols, the organic polycarboxylic
acids and/or derivatives and polyhydric alcohols are
advantageously polycondensed in a molar ratio of 1:1 - 1.8,
preferably 1:1.05 - 1.2.
The polyester polyols obtained preferably have a
functionality of from 2 to 4, in particular from 2 to 3, and
a molecular weight of from 480 to 3000, preferably from 600
to 2000 and in particular from 600 to 1500.
It is also possible to make concomitant use of polyether
polyols which are prepared by known methods, for example from
one or more alkylene oxides having from 2 to 4 carbon atoms
3S in the alkylene radical by anionic polymerization using
alkali metal hydroxides such as sodium or potassium hydroxide
or alkali metal alkoxides such as sodium methoxide, sodium or
potassium ethoxide or potassium isopropoxide as catalysts
with addition of at least one initiator molecule containing
from 2 to 8, preferably from 2 to 6, reactive hydrogen atoms
in bonded form, or by cationic polymerization using Lewis
acids such as antimony pentachloride, boron fluoride
etherate, etc. or bleaching earth as catalysts.
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.
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12
The alkylene oxides can be used individually, alternately in
succession or as mixtures. Suitable initiator molecules are,
for example: water, organic dicarboxylic acids such as
succinic acid, adipic acid, phthalic acid and terephthalic
acid, aliphatic and aromatic, unalkylated, N-monoalkylated,
N,N- and N,N'-dialkylated diamines having from 1 to 4 carbon
atoms in the alkyl radical, for example unalkylated,
monoalkylated and dialkylated 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-tolylenediamine and
4,4'-, 2,4~- and 2,2'-diamino-diphenylmethane.
Other suitable initiator 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 polyhydric, in particular
dihydric and/or trihydric alcohols such as ethanediol,
1,2- and 1,3-propanediol, diethylene glycol, dipropylene
glycol, 1,4-butanediol, 1,6-hexanediol, glycerol,
trimethylolpropane, pentaerythritol, sorbitol and sucrose.
The polyether polyols, preferably polyoxypropylene and
polyoxypropylene-polyoxyethylenepolyols, have a functionality
of preferably from 2 to 6 and in particular from 2 to 4 and
molecular weights of from 300 to 3000, preferably from 300 to
2000 and in particular from 400 to 2000, and suitable
polyoxytetramethylene glycols have a molecular weight up to
about 3500.
Further suitable polyether polyols are polymer-modified
polyether polyols, preferably graft polyether polyols, in
particular those based on styrene and/or acrylonitrile which
are prepared by in situ polymerization of acrylonitrile,
styrene or preferably mixtures of styrene and acrylonitrile,
e.g. in a weight ratio of from 90 : 10 to 10 : g0, preferably
from 70 : 30 to 30 : 70, advantageously in the abovementioned
polyether polyols using a method similar to that given in the
German Patents 11 11 394, 12 22 669 (US 3 304 273, 3 383 351,
3 523 093), 11 52 536 (GB 10 40 452) and 11 52 537
(GB 987 618), and also polyether polyol dispersions which
contain as dispersed phase, usually in an amount of from 1 to
50 % by weight, preferably from 2 to 25 % by weight: e.g.
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polyureas, polyhydrazides, polyurethanes containing bonded
tertiary amino groups and/or melamine and which are
described, for example, in EP-B-011 752 (US 4 304 708),
US-A-4 374 209 and DE-A-32 31 497.
Like the polyester polyols, the polyether polyols can be used
individually or in the form of mixtures. Furthermore, they
can be mixed with the graft polyether polyols or polyester
polyols or the hydroxyl-containing polyesteramides,
polyacetals, polycarbonates and/or polyetherpolyamines.
Suitable hydroxyl-containing polyacetals are, for example,
the compounds which can be prepared from glycols such as
diethylene glycol, triethylene glycol,
4,4'-dihydroxyethoxy-diphenyldimethylmethane, or hexanediol
and formaldehyde. Suitable polyacetals can also be prepared
by polymerization of cyclic acetals.
Suitable hydroxyl-containing polycarbonates are those of the
type known per se which can be prepared, for example, by
reacting diols such as 1,3-propanediol, 1,4-butanediol and/or
1,6-hexanediol, diethylene glycol, triethylene glycol or
tetraethylene glycol with diaryl carbonates, e.g. diphenyl
carbonate, or phosgene.
The polyester amides include, for example, the predo in~ntly
linear condensates obtained from polybasic, saturated and/or
unsaturated carboxylic acids or their anhydrides and
polyfunctional saturated and/or unsaturated aminoalcohols or
mixtures of polyfunctional alcohols and aminoalcohols and/or
polyamines.
Suitable polyetherpolyamines can be prepared from the
abovementioned polyether polyols by known methods. Examples
which may be mentioned are the cyanoalkylation of
polyoxyalkylene polyols and subsequent hydrogenation of the
nitrile formed (US 3 267 050) or the partial or complete
amination of polyoxyalkylene polyols with amines or ammonia
in the presence of hydrogen and catalysts (DE 12 15 373).
c) The rigid polyurethane foams can be produced with or without
concomitant use of chain extenders and/or crosslinkers (c).
However, the addition of chain extenders, crosslinkers or, if
desired, mixtures thereof can prove to be advantageous for
modifying the mechanical properties, e.g. the hardness. Chain
extenders and/or crosslinkers used are diois and/or triols
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having molecular weights of less than 400, preferably from 60
to 300.~Examples of suitable chain extenders/crosslinkers are
aliphatic, cycloaliphatic and/or araliphatic diols hav~ng -
from 2 to 14, preferably from 4 to 10, carbon atoms, e.g.
ethylene glycol, 1,3-propanediol, l,10-decanediol, o-, m- or
p-dihydroxycyclohexane, diethylene glycol, dipropylene glycol
and preferably 1,4-butanediol, 1,6-hexanediol and
bis(2-hydroxyethyl)hydroquinone, triols such as 1,2,4- and
1,3,5-trihydroxycyclohexane, glycerol and trimethylolpropane
and low molecular weight hydroxyl-containing polyalkylene
oxides based on ethylene and/or 1,2-propylene oxide and the
abovementioned diols and/or triols as initiator molecules.
If chain extenders, crosslinkers or mixtures thereof are
employed for producing the rigid polyurethane foams, they are
advantageously used in an amount of from 0 to 20 % by weight,
preferably from 2 to 8 % by weight, based on the weight of
the component tb).
d) Blowing agents which are used for producing the rigid
polyurethane foams include preferably water which reacts with
isocyanate groups to form carbon dioxide, and/or physically
acting blowing agents. Suitable physically acting blowing
agents are liquids which are inert toward the organic,
unmodified or modified polyisocyanates and have boiling
points below 100~C, preferably below 50~C, in particular from
-50~C to 30~C, at atmospheric pressure so that they vaporize
under the action of the exothermic polyaddition reaction.
Examples of such preferred liquids are alkanes such as
heptane, hexane, n- and iso-pentane, preferably industrial
mixtures of n- and iso-pentanes, n- and iso-butane 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,
chlorodifluoroethane, l,l-dichloro-2,2,2-trifluoroethane,
2,2-dichloro-2-fluoroethane and heptafluoropropane. Mixtures
of these low-boiling liquids with one another and/or with
other substituted or unsubstituted hydrocarbons can also be
used. Also suitable are organic carboxylic acids such as
formic acid, acetic acid, oxalic acid, ricinoleic acid and
compounds containinq carboxyl groups.
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Preference is given to using water, chlorodifluoromethane,
chlorodifluoroethanes, dichlorofluoroethanes, pentane
mixtures, cyclohexane and mixtures of at least two of these
blowing agents, e.g. mixtures of water and cyclohexane,
mixtures of chlorodifluoromethane and
1-chloro-2,2-difluoroethane and, if desired, water.
These blowing agents are usually added to the component (b).
However, they can be added to the isocyanate component (a) or
as a combination both to the component (b) and the isocyanate
component (a) or premixtures of these components with the
other formative components.
The amount of blowing agent or blowing agent mixture used is
from l to 25 ~ by weight, preferably from 5 to 15 % by
weight, in each case based on the polyol component (b).
If water is used as blowing agent it is preferably added to
the formative component (b) in an amount of from 0.5 to 5 ~
by weight, based on the formative component (b). The addition
of water can be carried out in combination with the addition
of the other blowing agents described.
25 e) Catalysts (e) used for producing the rigid polyurethane foams
are, in particular, compounds which strongly accelerate the
reaction of the compounds containing reactive hydrogen atoms,
in particular hydroxyl groups, of the component (b) and, if
used, (c) with the organic, unmodified or modified
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'-tetramethylethylenediamine,
N,N,N',N'-tetramethylbutanediamine,
N,N,N',N'-tetramethylhexane-1,6-diamine,
pentamethyldiethylenetriamine, dimethylpiperazine,
N-dimethylaminoethylpiperidine, 1,2-dimethylimidazole,
l-azabicyclo[2.2.01octane, 1,4-diazabicyclo[2.2.21octane
(Dabco) and alkanolamine compounds such as triethanolamine,
triisopropanolamine, N-methyldiethanolamine and
N-ethyldiethanolamine, dimethylaminoethanol,
2-(N,N-dimethylaminoethoxy)ethanol,
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triisopropanolami~e, N-methyldiethanolamine and
N-ethyldiethanolamine, dimethYlaminoethan
2-(N,N-dimethylaminoethoxy)ethanol,
N,N',N"-tris(dialkylaminoalkyl)hexahyd~otriazines, e.g. ~,N',
Nn-tris(dimethylaminopropyl)-~-hexahydrotriazine, and
triethylenediamine. However, metal salts such as iron(II)
chloride, zinc chloride, lead octoate and preferably tin
6alts such a~ tin dioctoate, tin diethylhe~AnoAte and
dibutyltin dilaurate and also, in particular, mixtures of
~ertiary ~mines and organic tin salts are also useful.
Other ~uitable catalysts are; amidinefi such as
2~3-dimethyl-3~4~5~6-tetrahydropyrimidine~ tetraalkyl~onium
hydroxid~s, such as tetramethyl~o~ium hydroxide, alkali
metal hydroxides, such as sodium hydrQxide and alkali metal
alkoxides such as sodium methoxide and potassium
isopropoxide, and also alkali metal ~alts of long-chain fatty
acids having from 10 to 20 carbon atom6 and po~sibly lateral
OH groups. PrefcrcncQ is given to u~ing from O.001 to 5 ~ by
~~ weight, in particular from 0.05 to 2 ~ ~y weight, of cataly-~t
or catalyst combination, based on the weight of the component
(~) .
f) If desired, further auxiliarie~ and/or additive~ (f) can al~o
be incorporated into the reaction mixture for producing the
rigid ~olyurethane foams. Example3 which may b~ mentioned are
surface-active substances, foam stabilizers, cell regulators,
fillers, dyes, pigments, flame retardants, hydrolysis
inhibitors, fungistatic and bacteriostatic substance6.
Suitable surface-active sub3tance~ are, for example,
compounds which 6erve to aid the homogenization o~ the
s~arting materials and may also be ~uitable ~o~ regulating
the cell ~tructure of the pla~tic~. ~xamples which may be
mentioned are e~uleifiers such a3 the 60dium salts of ca~tor
oil sulfates or of fatty acids and also amine salts o~ fatty
acids, e.g. diethylamine ole~te, diethanolamin~ stear~te,
diethanolamine ricinoleate, salt~ of sulfonic acids, e.g.
4~ alkali metal or A ~ni um salts of dodecylbenzene- or
dinaphthylmeth~ne~i6ulfonic acid and ricinoleic acid; foam
stabilizer~ such as siloxane-oxyalkylenc copolymGr~ and oth~r
organopolysilox~~, ethoxylated alkylphenols, ethoxylat~d
fa~ty alcohols, paraffin oil6, castor oil or rlcinoleic
ester~, Turkey red oil and ~eanut oil, and cell regulator~
such as ~araffing, fatty alcohol6 and dimethylpolysiloxa~es.
Also suitable for improving the emul6ifyi~g action, thQ cell
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usually employed in amounts of from 0.01 to 5 % by weight,
based on lO0 % by weight of the component (b).
Fillers, in particular reinforcing fillers, are the customary
organic and inorganic fillers, reinforcers, weighting agents,
agents for improving the abrasion performance in paints,
coating compositions, etc. known per se. Specific examples
are: inorganic fillers such as siliceous minerals, for
example sheet silicates such as antigorite, serpentine,
hornblends, amphiboles, chrysotile and talc, metal oxides
such as kaolin, aluminum oxides, titanium oxides and iron
oxides, metal salts such as chalk, barite and inorganic
pigments such as cadmium sulfide and zinc sulfide, and also
glass, inter alia. Preference is given to using kaolin ~china
clay), aluminum silicate and coprecipitates of barium sulfate
and aluminum silicate and also natural and synthetic fibrous
minerals such as wollastonite, metal and in particular glass
fibers of various lengths which may also be sized. Suitable
organic fillers are, for example: carbon, melamine, rosin,
cyclopentadienyl resins and graft polymers and also cellulose
fibers, polyamide, polyacrylonitrile, polyurethane and
polyester fibers based on aromatic and/or aliphatic
dicarboxylic esters and, in particular, carbon fibers.
The inorganic and organic fillers can be used individually or
as mixtures and are preferably incorporated into the reaction
mixture in amounts of from 0.5 to 50 % by weight, preferably
from l to 40 % by weight, based on the weight of the
components (a) to (c), although the content of mats,
nonwovens and woven fabrics of natural and synthetic fibers
can be up to 80 % by weight.
Suitable flame retardants are, for example, tricresyl
phosphate, tris(2-chloroethyl) phosphate,
tris(2-chloropropyl) phosphate, tris(1,3-dichloropropyl)
phosphate, tris(2,3-dibromopropyl) phosphate, --
tetrakis(2-chloroethyl)ethylene diphosphate, dimethyl
methanephosphonate, diethyl diethanolaminomethylphosphonate
and also commercial halogen-containing flame-retardant
polyols.
Apart from the halogen-substituted phosphates mentioned
above, it is also possible to use inorganic or organic flame
retardants such as red phosphorus, hydrated aluminum oxide,
antimony trioxide, arsenic oxide, ammonium polyphosphate and
calcium sulfate, expanded graphite or cyanuric acid
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derivatives, e.g. melamine, or mixtures of at least two flame
retardants such as ammonium polyphosphates and melamine and
also, if desired, maize starch or ammonium polyphosphate,
melamine and expanded graphite and/or aromatic or aliphatic
polyesters for making the polyisocyanate polyaddition
products flame resistant. In general, it has been found to be
advantageous to use from 5 to 50 % by weight, preferably from
5 to 25 % by weight, of the specified flame retardants, based
on the component (b).
Further details regarding the abovementioned other customary
auxiliaries and additives may be found in the specialist
literature, for example in the monograph by J.H. Saunders and
K.C. Frisch "High Polymers" Volume XVI, Polyurethanes, Parts
l and 2, Interscience Publishers 1962 and 1964, or the
Kunststoff-Handbuch, Polyurethane, Volume VII, Hanser-Verlag,
Munich, Vienna, 1st and 2nd editions, 1966 and 1983.
20 To produce the rigid polyurethane foams of the present invention,
the organic and/or modified organic polyisocyanates (a),
relatively high molecular weight compounds containing at least
two reactive hydrogen atoms (b) and, if desired, chain extenders
and/or crosslinkers (c) are reacted in amounts such that the
25 equivalence ratio of NCO groups of the polyisocyanates (a) to the
sum of the reactive hydrogen atoms of the components (b) and, if
used, (c) i8 0.85 - 1.25:1, preferably 0.95 - 1.15:1 and in
particular l - 1.05:1. If the rigid polyurethane foams contain at
least some bonded isocyanurate groups, a ratio of NCO groups of
30 the polyisocyanates (a) to the sum of the reactive hydrogen atoms
of the component (b) and, if used, (c) of 1.5 - 60:1, preferably
1.5 - 8:1, is usually employed.
The rigid polyurethane foams are advantageously produced by the
35 one-shot method, for example by means of the high-pressure or
low-pressure technique in open or closed molds, for example metal
molds. Also customary is the continuous application-of the
reaction mixture to suitable belts for producing panels.
40 It has been found to be particularly advantageous to produce the
polyurethane foams by the two-component method and to combine the
formative components (b), (d), (e) and, if used, (c) and (f) to
form the component (A) and to use the organic and/or modified
organic polyisocyanates (a) or mixtures of said polyisocyanates
45 and, if desired, blowing agents (d) as component (B).
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The starting components are mixed at from 15 to 90~C, preferably
from 20 to 60~C and in particular from 20 to 35~C, and introduced
into the open mold or, if desired under increased pressure, into
the closed mold or, in the case of a continuous workstation,
5 applied to a belt which accommodates the reaction mixture. Mixing
can, as already indicated, be carried out mechanically by means
of a stirrer or a stirring screw. The mold temperature is
advantageously from 20 to 110~C, preferably from 30 to 60~C and in
particular from 45 to 50~C.
The rigid polyurethane foams produced by the process of the
present ir,vention have a density of from 0.02 to 0.30 g/cm3,
preferably from 0.025 to 0.24 g/cm3 and in particular from 0.03 to
0.1 g/cm3-. They are particularly suitable as insulation material
15 in the building and refrigeration appliance sectors, e.g. as
intermediate layer for sandwich elements or for filling housings
of refrigerators and freezer chests with foam, and in the
long-distance energy sector, but also as support and forming
material in the furniture sector.
The invention is illustrated by the examples below.
Example 1 (Comparative)
720 g of diethylene glycol together with 225 g of adipic acid
were placed in a 2 1 reaction flask fitted with stirrer,
thermometer and distillation facility and were melted completely
at 130~C. 555 g of PET granules were added thereto a little at a
30 time and 10 ppm of titanium tetrabutoxide were introduced as
catalyst. The reaction mixture was polycondensed at 220~C while
removing the water of reaction formed to an acid number customary
for polyesterols of less than 1 mg KOH/g. The resulting turbid,
green reaction product had the following properties:
Hydroxyl number = 347 mg XOH/g in accordance with DIN 53240
Acid number = 0.65 mg KOH/g in accordance with DIN 53402
Viscosity at 25~C = 120 mPa-s in accordanee with DIN 53015
Example 2 (Comparative)
In a 1.5 1 reaction flask fitted with stirrer, thermometer and
distillation attachment, 360 g of diethylene glycol and 113 g of
45 adipic acid were completely liquefied at 135~C and subsequently
admixed with 278 g of recycled PET added a little at a time while
stirring. To carry out the polycondensation, the reaction
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temperature was increased to 220~C and water of reaction formed
was removed under atmospheric pressure. After an acid number of
less than 5 mg KOH/g had been reached, the remaining water of
reaction was removed under reduced pressure to an acid number
S customary for polyesterols of less than 1 mg KOH/g. The reaction
product thus prepared had the following properties:
Hydroxyl number = 351 mg KOH/g
Acid number = 0.47 mg KOH/g
Viscosity at 25~C = 1041 mPa-s
The turbid reaction product had a dark green color.
15 Example 3 (according to the present invention)
In a 2 1 reaction flask fitted with stirrer, thermometer and
distillation attachment, 40 g of a solution of PET waste were, in
20 a first stage, transesterified with diethylene glycol to a
hydroxyl number of 623 mg KOH/g and admixed with 184 g of
phthalic anhydride. At a reaction temperature of 230~C, water of
reaction formed was distilled off under reduced pressure. After a
reaction time of 5 hours, the reaction product was cooled to
25 140~C, admixed with 168 g of adipic acid and 10 ppm of titanium
tetrabutoxide and, in a further step, polycondensed at 210~C under
reduced pressure. This gave a clear, slightly yellow
low-viscosity reaction product having the following properties:
Hydroxyl number = 299 mg KOH/g
Acid number = 1.04 mg KOH~g
Viscosity at 25~C = 2755 mPa-s
35 Example 4 (according to the present invention)
In a 25 1 stirred reactor for preparing polyesterols, 2.2 kg of
adipic acid were, in a first reaction step, melted in 6.8 kg of
diethylene glycol at 130~C and admixed while stirring with
40 13.54 kg of PBT. At a reaction temperature of 220~C, the mixture
was polycondensed to an acid number of less than 8 mg KOH/g. The
reaction product was subsequently admixed with 10 ppm of tin(II)
isooctoate and, in a second step, dewatered by application of a
vacuum. The resulting pale yellow product was clear and had the
45 following properties:
Hydroxyl number = 253 mg KOH/g
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Acid number = 0.74 mg KOH/g
Water content = 0.06 %
Viscosity at 75~C = 467 mPa-s
Example S (according to the present invention)
In a 25 l reactor for preparing polyesterols, 12.8 kg of
diethylene glycol and 4.0 kg of phthalic anhydride were, in a
lO first reaction step, liquefied at 130~C. After addition of 9.9 kg
of recycled PET while stirring, the reaction temperature was
increased to 210~C and the water of reaction formed was removed
under atmospheric pressure and remaining water of reaction was
removed under reduced pressure. 15.0 kg of the resulting
15 polycondensate having a hydroxyl number of 380 mg KOH/g, an acid
number of 0.77 mg KOH/g and a viscosity at 75~C of 1787 mPa-s
were, in a subsequent reaction step, admixed with 0.3 % of
aqueous KOH as catalyst and alkoxylated with 4.5 kg of ethylene
oxide under pressure in an autoclave, then neutralized with
20 phosphoric acid and freed of the salts formed by filtration. The
slightly turbid reaction product had the following properties:
Hydroxyl number = 301 mg KOH/g
Acid number = 0.42 mg KOH/g
Viscosity at 25~C = 1014 mPa~s
Example 6 (Comparative)
30 The polyol component comprising
50 parts by mass (pbm) of a polyesterol based on adipic acid,
diethylene glycol and PET (from Example l),
OH number 347 mg KOH/g,
31 pbm of a polyetherol based on sucrose, glycerol and propylene
oxide, ~~
OH-number 400 mg KOH/g,
1 pbm of silicone stabilizer B 8409 (Goldschmidt),
l pbm of dimethylcyclohexylamine,
2 pbm of water and
15 pbm of R 141 b,
45 was intensively mixed with 110 pbm of raw MDI, NCO content 31.5 %
by mass (index 110).
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The resulting foam free-foamed in a foaming cup had a density of
31.0 kg/m3.
The resulting foams were examined for curing by means of the
5 indentation test and for flowability by means of the hose test.
Indentation test
10 Using a standardized indenter having a diameter of 20 mm, the
penetration force into the foam is measured at certain intervals
of time after production. In this test, the indenter penetrates
10 mm into the foam.
15 Hose test
Immediately after mixing the components, 100 g of reacting
mixture are poured into a continuous hose made of plastic film
and having a diameter of 4.5 cm. The hose is then clamped off and
20 the length of foam obtained is taken as a measure of the
flowability.
The results obtained are shown in Table 1.
Example 7 (Comparative)
A polyol component as described in Example 6 but comprising
30 50 pbm of a polyesterol based on adipic acid, diethylene glycol
and PET (from Example 2),
OH number 351 mg KOH/g,
35 was intensively mixed with 100.5 pbm of raw MDI (index 110).
The resulting foam had a density of 31.5 kg/m3.
Example 8 (according to the present invention)
A polyol component as described ln Example 6 but comprising
50 pbm of a polyesterol based on adipic acid, phthalic
anhydride, diethylene glycol and PET (from Example 3),
OH number 299 mg KOH/g,
was intensively mixed with 105 pbm of raw MDI (index 110).
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.
23
The resulting foam had a density of 29 kg/m3.
,,
Example 9 (according to the present invention)
A polyol component as described in Example 6 but comprising
50 pbm of a polyesterol based on adipic acid, diethylene glycol
and P~T (from Example 4),
OH number 253 mg KOH/g,
was intensively mixed with 98 pbm of raw MDI (index 110).
The resulting foam had a density of 29.5 kg/m3.
Example 10 (according to the present invention)
A polyol component as described in Example 6 but comprising
20 50 pbm of a polyether esterol based on phthalic anhydride,
diethylene glycol, PET and ethylene oxide (from Example
5),
OH number 301 mg KOH/g,
25 was intensively mixed with 105 pbm of raw MDI (index 110).
The resulting foam had a density of 30 kg/m3.
Table 1: Results of the indentation and hose tests
Ex. 6 7 8 9 10
Penetration force
(N)
35 after 3 min 8 12 25 21 20
after 5 min 12 21 55 50 48
Foam length (cm) 130 134 150 148 145
40 The polyols prepared according to the present invention were
homogeneous immediately after preparation and after storage for
4 weeks. Processing of the polyols both immediately after their
preparation and also after storage for 4 weeks to give
homogeneous polyurethane systems for various applications, i.e.
45 with different system constituents, was possible in all cases.
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The rigid polyurethane foams based on the polyols of the present
invention had significantly better curing and better flow
behavior than those based on the comparative polyols.
~0
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