Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ sAsF Aktienges~llscha~t 960801 O.Z. 0050/47418
Production of tough polyurethane integral foams having improved
tear propagation resistance, elongation at break and tensile
strength
The present invention relates to a process for producing tough
polyurethane integral foams having improved tear propagation
resistance, elongation at break and tensile strength by reacting
10 a) organic and/or modified organic polyisocyanates with
b) at least one relatively high molecular weight compound
containing at least two reactive hydrogen atoms and, if
desired,
c) low molecular weight chain extenders and/or crosslinkers
in the presence of
20 d) catalysts,
e) if desired, blowing agents
f) and also, if desired, further auxiliaries and/or additives.
The present invention further relates to the tough polyurethane
integral foams produced by this process and also to their use as
beer barrel cladding.
30 The production of tough polyurethane integral foams by reacting
organic polyisocyanates and/or modified organic polyisocyanates
with relatively high-functionality compounds containing at least
two reactive hydrogen atoms and, if desired, low molecular weight
chain extenders and/or crosslinkers in the presence of catalysts,
35 blowing agents, auxiliaries and/or additives is known and has
been described many times. A summary overview of the production
of polyurethane integral foams is given, for example, in the
Kunststoff-Handbuch, Volume VII, "Polyurethane~, 1st Edition 1966,
edited by Dr. R. Vieweg and Dr. A. Hochtlen, and 3rd Edition 1993,
40 edited by Becker/Braun (Carl Hanser Verlag, Munich).
It is likewise known that polyurethane foams can be produced
using polyols which in turn have been obtained from polyurethane
waste by reaction with compounds containing at least 2 OH groups,
45 known as glycolysis. Thus, for example, DE-A-25 16 863 describes
the preparation of a polyol mixture ~rom polyurethane waste and
aliphatic diols, which mixture is suitable for the production of
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rigid polyurethane foams. According to DE-A-40 24 601, glycolysis
of polyurethane-urea waste gives a polyol-containing dispersion
which can be used for producing rigid or semirigid polyurethanes
or polyurethane-ureas. According to US 4,014,809 (DE-A-25 57 172),
5 polyol-containing liquid mixtures synthesized fr~m rigid
polyurethane foams are reused as rigid foam components.
Polyol-containing liquids prepared as described in DE-A-37 02 495
from polyurethane waste are described as being suitable for
semirigid and rigid polyurethanes, in particular polyurethane
10 foams.
The recycled polyols prepared by the known processes always
contain the amines which are also formed in the glycolysis and
are hazardous to health and furthermore have an adverse effect on
15 the polyurethane systems formulated from the recycled polyols.
They strongly accelerate the polyurethane formation reaction,
form rigid urea groups and reduce the controllability of the
polyurethane formation reaction by means of other catalysts.
Furthermore, the content of free amines in polyol components of
20 polyurethane systems immediately leads, on contact with
isocyanates, to highly thixotropic masses, as described in
DD-A-156 480.
A variety of processes has become known for the purpose of
25 deamination. The recycled polyol deaminated as described in
DE-A-40 24 601 by addition of monomeric acrylic acid has an acid
number of significantly above 1 mg KOH/g, which can lead to
difficulties in the polyurethane systems containing the recycled
polyol. Furthermore, the distinct acrylic acid odor is a problem.
30 According to DE-A-44 16 322, low molecular weight ureas and/or
carbamic esters can also be used for the deamina~ion.
EP-A-0 592 952 describes the use of glycidyl ethers for preparing
recycled polyols which are low in amines.
35 The recycled polyols obtained in this way are used for producing
semirigid and rigid polyurethane foams. The documents do not
suggest an improvement in the quality of the polyurethane foams
resulting from the use of these recycled polyols. Only
DE-A-44 11 864 indicates that the use of recycled polyol prepared
40 by glycolysis of flexible foam waste using glycidyl ethers
enables rigid polyurethane foams having an increased proportion
of open cells and reduced shrinkage to be produced.
High demands are placed on the mechanical properties of tough
45 polyurethane integral foams. Apart from the formation of
particular cell structures, the foams are required to achieve a
demanding level of mechanical properties. Particularly important
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here are very high tear propagation resistance, elongation at
break and tensile strength, particularly when, as is the case,
for example, for beer barrel cl~;n~, strong external forces act
on the polyurethan-e material.
t is an object of the present invention to develop a simple and
inexpensive process for producing tough polyurethane integral
foams having improved tear propagation resistance, elongation at
break and tensile strength.
We have found that this object is achieved by producing the tough
polyurethane integral foams using a recycled polyol which is
obtained by glycolysis of tough polyurethane integral foams using
glycidyl ethers.
The present invention accordingly provides a process for
producing tough polyurethane integral foams having improved tear
propagation resistance, elongation at break and tensile strength
by reacting
a) organic and/or modified organic polyisocyanates with
b) at least one relatively high molecular weight compound
containing at least two reactive hydrogen atoms and, i~
desired,
c) low molecular weight chain extenders and/or crosslinkers
in the presence of
d) catalysts, "
e) if desired, blowing agents
35 f) and also, if desired, further auxiliaries and/or additives,
wherein the component b) used comprises at least one recycled
polyol which is obtained by glycolysis of tough polyurethane
integral foams using glycidyl ethers.
The present invention further provides the tough polyurethane
integral foams produced by this process and also provides for
their use as beer barrel cladding.
45 It is surprising and was in no way foreseeable that the use of
recycled polyols prepared from tough polyurethane integral foams
by glycolysis again gives high-quality tough polyurethane
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integral foams which have improved tear propagation resistance,
elongation at break and tensile strength. Rather, it would have
been expected that the mechanical properties of the foam would be
worsened by use of-recycled polyols.
J
An economical process for producing tough polyurethane integral
foams which are very suitable for beer barrel cladding has thus
been found.
10 According to the present invention, relatively high molecular
weight compounds containing at least two reactive hydrogen atoms
which are used are completely or partially recycled polyols
either alone or in admixture with one another. For achieving the
desired mechanical properties, recycled polyols are
15 advantageously used in a proportion of at least 30 % by weight,
based on the total amount of the component b). For economic
reasons, the amount of recycled polyol used can be substantially
above 30 % by weight or the component b) can consist entirely of
recycled polyol. Naturally, less than 30 ~ by weight of recycled
20 polyols can also be used.
The recycled polyols are obtained by glycolysis of tough
polyurethane integral foams, in particular their waste, using
short-chain, hydroxyl-containing compounds such as ethylene
25 glycol, diethylene glycol, triethylene glycol, oligoethylene
glycols, propylene glycol, dipropylene glycol, tripropylene
glycol, oligopropylene glycols, butanediols, neopentyl glycol,
glycerol, ethanolamine, diethanolamine and triethanolamine, in
the presence or absence of catalysts such as alkali metal salts
30 of short-chain fatty acids, titanates, stannates and antimonates
at elevated temperatures. "
Tough polyurethane integral foams used are, in particular,
polyurethane waste as is obtained, for example, particularly in
35 the production of beer barrel cladding; these can contain, inter
alia, fillers or reinforcers which do not interfere in the
process.
The recycled polyols used according to the present invention are
40 preferably low in amines. They are obtainable, in particular, by
carrying out the glycolysis of the polyurethane integral foams
while metering in monofunctional and/or difunctional glycidyl
ethers during the entire course of the reaction, as is described
in EP-A-0 592 952.
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. 5
In the preparation of the recycled polyols, it is possible to use
commercial glycidyl ethers which have one or two epoxide groups
in the molecule.
5 Glycidyl ethers which have been found to be part}cularly useful
are the monofunctional glycidyl ethers of the formula (I)
R - O - CH2- CH - ,H2 (I),
where R = phenyl, cyclohexyl, methylcyclohexyl, benzyl, i-propyl,
i-butyl or methyl and/or ethyl-branched hydrocarbon chains having
from 5 to 10 carbon atoms in the straight chain and/or a group of
the formula
CH3 - (CH2) fH C CH2 CH ~ _
A CH2Cl
where A is an alkyl radical having from 1 to 8 carbon atoms, n is
from 3 to 12 and m is from 1 to 6.
Preference is given to using 2-ethylhexyl glycidyl ether or a
2 5 mixture of
from 50 to 85 % by weight of 2-ethylhexyl glycidyl ether,
from 10 to 35 % by weight of one or more compounds having the
structure
~
CH3 (CH2)n CH O - CH2 CH O - CH2 CH - CH2
A CH2Cl
35 and
from 5 to 20 % by weight of one or more compounds having the
structure
CH3 - (CH2)n fH ~ CH2- ICH ~ O CH2 - CH - CH2
A CH2Cl
where A iS an alkyl radical having from 1 to 8 carbon atoms, n is
45 from 3 to 12 and m is from 2 to 6. This glycidyl ether mixture
can be prepared in a known manner from 2-ethylhexanol and
epichlorohydrin as is obtained in the synthesis of 2-ethylhexyl
.
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glycidyl ether and be used as an industrial raw product merely
freed of inorganic constituents, ie. without employing a
distillation step.
5 Other glycidyl ethers which have been found to be useful are the
difunctional glycidyl ethers of the formula
CH2 CH - CH2 - O - R'- ~ CH2 CH - CH2
0
where R' = diphenylmethylene, 2,2-diphenylpropylene (bisphenol A~,
unbranched hydrocarbon chains having from 4 to 10 carbon atoms or
methyl and/or ethyl-branched hydrocarbon ~h~;n~ having from 4 to
15 8 carbon atoms in the straight chain.
Glycidyl ethers used can be monofunctional glycidyl ethers of the
formula (I~, either alone or in admixture with one another,
difunctional glycidyl ethers of the formula (II), either alone or
20 in admixture with one another, or mixtures of two or more
monofunctional and difunctional glycidyl ethers.
The reaction temperature is usually from 180~C to 250~C,
preferably from 200~C to 235~C.
Depending on the crosslinking density of the polyurethanes and/or
polyurea-polyurethanes used, the reaction time is generally from
2 to 6 hours, preferably from 3 to 5 hours.
30 The glycidyl ethers are advantageously added over the entire
reaction time, preferably uniformly, to the mixture comprising
polyurethane integral foams and OH-containing compounds; the
amount of glycidyl ethers added is usually from 5 % by weight to
20 % by weight, based on the total mixture.
To produce the tough polyurethane integral foams by the process
of the present invention, use is made of, besides the
above-described recycled polyols, the formative components known
per se about which the following may be said:
a) Suitable organic and/or modified organic polyisocyanates (a)
are the aliphatic, cycloaliphatic, araliphatic and preferably
aromatic polyfunctional isocyanates known per se.
Specific examples are: alkylene diisocyanates having from 4
to 12 carbon atoms in the alkylene radical, eg. dodecan
1,12-diisocyanate, 2-ethyltetramethylene 1,4-diisocyanate,
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2-methylpentamethylene 1,5-diisocyanate, tetramethylene
1,4-diisocyanate and preferably hexamethylene
1,6-diisocyanate; cycloaliphatic diisocyanates such as
cyclohexane lr3- and 1,4-diisocyanate and also any mixtures
of these isomers, 1-isocyanato-3,3,5-trimethyl-
5-isocyanatomethylcyclohexane (isophorone diisocyanate),
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
2,4'-diisocyanates, polyphenylpolymethylene polyisocyanates,
mixtures of diphenylmethane 4j4'-, 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, ie. 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 o~ suitable modified isocyanates are:
organic, preferably aromatic polyisocyanates containing
urethane groups, having NCO contents of from 33 ~ 6 to 15 % by
weight, preferably from 31 to 21 % by weight, based on the
total weight, and prepared, for example, by reaction with low
molecular weight diols, triols, dialkylene glycols,
trialkylene glycols or polyoxyalkylene glycols having
molecular weights of up to 6000, in particular up to 1500,
modified diphenylmethane 4,4'-diisocyanate, modified
diphenylmethane 4,4'- and 2,4'-diisocyanate mixtures, or
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 glycol,
dipropylene glycol, polyoxyethylene, polyoxypropylene and
polyoxypropylene-polyoxyethylene glycols, triols and/or
tetrols. Also suitable are prepolymers containing NCO groups,
having NCO contents of from 30 to 15 ~ by weight, preferably
from 28 to 20 % by weight, based on the total weight, and
prepared from the polyester and/or preferably polyether
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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 modified 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, for example
those based on diphenylmethane 4,4'-, 2,4'- and/or
2,2'-diisocyanate and/or tolylene 2,4- and/or
2,6-diisocyanate.
The modified polyisocyanates can, if desired, 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
the following aromatic polyisocyanates: raw MDI, 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 55 % by weight.
30 b) As relatively high molecular weight compoundc containing at
least two reactive hydrogen atoms, use is made, according to
the present invention, of the above-described recycled
polyols. In addition thereto, further relatively high
molecular weight compounds containing at least two reactive
hydrogen atoms (b) can be concomitantly used. Compounds
suitable for this purpose are advantageously those having a
functionality of from 2 to 8, preferably from 2 to 6, and a
molecular weight of from 1000 to 8000, preferably from 1200
to 6000. Compounds which have been found to be useful are,
for example, 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
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polyhydroxyl compounds is generally from 25 to 850 and
preferably from 300 to 750.
.
Suitable polyester polyols can be prepared, for example, from
organic dicarboxylic acids having from 2 to ~2 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 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 alcohols having from 1 to 4 carbon
atoms or dicarboxylic anhydrides. Preference is given to
using dicarboxylic acids mixtures of succinic, glutaric and
adipic acid 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, l,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 a~so possible to
use polyester polyols derived from lactones, eg.
~-caprolactone, or hydroxycarboxylic acids, eg.
~-hydroxycaproic acid.
To prepare the polyester polyols, the organic, eg. aromatic
and preferably aliphatic, polycarboxylic acids and~or
derivatives and polyhydric alcohols can be polycondensed in
the absence of catalysts or preferably in the presence of
esterification catalysts, advantageously in an atmosphere of
inert gas such as nitrogen, carbon dioxide, helium, argon
etc, in the melt at from 150 to 250~C, preferably from 180 to
220~C, under atmospheric pressure or reduced pressure to the
desired acid number which is advantageously less than 10,
preferably less than 2. According to a preferred embodiment,
the esterification 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
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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,
~inc, 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 li~uid phase
in the presence of diluents andJor entrainers such as
benzene, toluene, xylene or chlorobenzene to azeotropically
distill 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 12Q0
to 3000 and in particular from 1800 to 2500.
However, polyols which are particularly preferably used are
polyether polyols which are prepared by known methods, for
example from one or more alkylene oxides having from 2 to
4 carbon atoms in the alkylene radical by anionic
polymerization using alkyl 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 formO 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.
The alkylene oxides can be used individually, alternately in
succession or as mixtures. Examples of suitable initiator
molecules are: 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 or dialkylated ethylenediamine,
diethylenetriamine, triethylenetetramine,
1,3-propylenediamine, 1,3- or 1,4-butylenediamine, 1,2-,
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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'-diaminodiphenylmethane.
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,
aerythritol, sorbitol and sucrose.
The polyether polyols, preferably polyoxypropylene and
polyoxypropylene-polyoxyethylene-polyols, have a
functionality of preferably ~rom 2 to 6 and in particular
from 2 to 4 and molecular weights of from 1000 to 8000,
preferably from 1200 to 6000 and in particular from 1800 to
4000, and suitable polyoxytetramethylene glycols have a
molecular weight up to about 3500.
Further suitable polyether polyols are polymer-modified
polyether polyols, pre~erably gra~t 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,
eg. in a weight ratio o~ ~rom 90 : 10 to 10 : 90, preferably
from 70 : 30 to 30 : 70, advantageously in the abovementioned
polyether polyols using methods similar to those described in
; the German Patents 11 11 394, 12 22 669 (US 3 304 273,
3 383 351, 3 523 093), 11 52 536 (Gs 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: eg.
polyureas, polyhydrazides, polyurethanes containing bonded
tert-amino groups and/or melamine and are described, for
example, in EP-B-011 752 (US 4 304 708), US 4 374 209 and
DE-A-32 31 497.
Like the polyether polyols, the polyether polyols can be used
individually or in the ~orm o~ mixtures. They can also be
mixed with the graft polyether polyols or polyester polyols
as well as with the hydroxyl-containing polyesteramides,
polyacetals, polycarbonates and/or polyetherpolyamines.
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Suitable hydroxyl-containing polyacetals are, for example,
the compounds which can be prepared from glycols such as
diethylene glycol, triethylene glycol,
4,4'-dihydroxyethoxydiphenyldimethylmethane or hexanediol and
formaldehyde. Suitable polyacetals can alsa be prepared by
polymerization 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, eg. diphenyl
carbonate, or phosgene.
The polyesteramides include, for example, the predom;n~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 using amines or ammonia
in the presence of hydrogen and catalysts (DE 12 15 373).
30 c) The elastic polyurethane integral foams can be produced with
or without use of chain extenders and/or crosslinkers (c).
However, the use of chain extenders, crosslinkers or, if
desired, mixtures thereof can prove to be advantageous for
modifying the mechanical properties, eg. the hardness. Chain
extenders and/or crosslinkers used are diols and/or triols
having molecular weights of less than 400, preferably from 60
to 300. Suitable chain extenders/crosslinkers are, for
example, aliphatic, cycloaliphatic or araliphatic diols
having from 2 to 14, preferably from 4 to 10, carbon atoms,
for example ethylene glycol, 1,3-propanediol,
l,10-decanediol, o-, m-, 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- or 1,3,5-trihydroxycyclohexane, glycerol and
trimethylolpropane and low molecular weight
hydroxyl-containing polyalkylene oxides based on ethylene
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13
oxide 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 polyurethane integ'ral 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 polyol compound (b).
10 d) Catalysts (d) used for producing the tough polyurethane
integral 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, tc) with the organic, modified or
unmodified polyisocyanates (a). Suitable catalysts are
organic metal compounds, pre~erably organic tin compounds
such as tin(II) salts of organic carboxylic acids, eg.
tin(II) acetate, tin(II) octoate, tin(II) ethylhexoate and
tin(II) laurate, and the dialkyltin(IV) salts of organic
carboxylic acids, eg. dibutyltin diacetate, dibutyltin
dilaurate, dibutyltin maleate and dioctyltin diacetate. The
organic metal compounds are used alone or preferably in
combination with strongly basic amines. Examples are amidines
such as 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, tertiary
amines such as triethylamine, tributylamine,
dimethylbenzylamine, N-methylmorpholine, M-ethylmorpholine,
N-cyclohexylmorpholine, N,N,N',N'-tetramethylethylenediamine,
N,N,N',N'-tetramethylbutanediamine, N,N,N',N'-tetramethyl-
hexane-1,6-diamine, pentamethyldiethylenetriamine,
bis(dimethylaminoethyl) ether, bis(dimethyla~inopropyl)urea,
dimethylpiperazine, 1,2-dimethylimidazole,
l-azabicyclo[3.3.0]octane and preferably
1,4-diazabicyclo[2.2.2]octane, and alkanolamine compounds
such as triethanolamine, triisopropanolamine,
N-methyldiethanolamine and N-ethyldiethanolamine and
dimethylethanolamine.
Eurther suitable catalysts are:
tris(dialkylaminoalkyl)-s-hexahydrotriazines, in particular
tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine,
tetraalkylammonium hydroxides such as tetramethylammonium
hydroxide, alkali metal hydroxides such as sodium hydroxide
and alkali metal alkoxides such as sodium methoxide and
potassium isopropoxide, and also alkali metal salts of
long-chain fatty acids having from 10 to 20 carbon atoms and
possibly lateral OH groups. Preference is given to using from
0.001 to 5 ~ by weight, in particular from 0.05 to 2 ~ by
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weight, of catalyst or catalyst combination, based on the
weight of the component (b).
e) Blowing agents (e) which may, if desired, be used for
producing the polyurethane integral foams include preferably
water which reacts with isocyanate groups to form carbon
dioxide. The amounts of water which are advantageously used
are from 0.1 to 8 parts by weight, preferably from 1.5 to
5.0 parts by weight and in particular from 0.5 to 2.0 parts
by weight, based on 100 parts by weight of the
polyoxyalkylene polyols.
In admixture with water, it is also possible to use
physically acting blowing agents. Suitable physically acting
blowing agents are liquids which are inert toward the
organic, modified or unmodified polyisocyanates (c) 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, chlorodifluoroethanes, "
1,1-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
carboxyl-containing compounds.
Preference is given to using water, chlorodifluoromethane,
chlorodifluoroethanes, dichlorofluoroethanes, pentane
mixtures, cyclohexane and mixtures of at least two of these,
eg. mixtures of water and cyclohexane, mixtures of
chlorodifluoromethane and l-chloro-2,2-difluoroethane and, if
desired, water.
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f) If desired, auxiliaries and/or additives (f) customary in
polyurethane chemistry can also be incorporated into the
reaction mixture for producing the tough polyurethane
integral foams. Examples which may be mentioned are foam
stabilizers, fillers, dyes, pigments, flame ~etardants,
hydrolysis inhibitors, fungistatic and bacteriostatic
substances.
Eor the purposes of the present invention, fillers, in
particular reinforcing fillers, are the customary organic and
inorganic fillers, reinforcers, weighting agents, agents for
improving the abrasion behavior 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, 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, zinc sulfide and also glass, etc. 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 be coated with a size. 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.
Suitable flame retardants are, for example, tricresyl
phosphate, tris(2-chloroethyl) phosphate,
tris(2-chloropropyl) phosphate, tris(l,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 abovementioned halogen-substituted phosphates,
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
derivatives such as melamine, or mixtures of at least two
flame retardants such as ammonium polyphosphates and melamine
and also, if desired, maize starch or ammonium polyphosphate,
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melamine and expanded graphite and/or aromatic or aliphatic
polyesters for making the polyisocyanate polyaddition
products flame resistance. In general, it has been found to
be advantageous to use from 5 to 50 parts by,weight,
preferably from 5 to 25 parts by weight, of the flame
retardants mentioned per 100 parts by weight of the component
(b).
Further details regarding 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, Interscience Publishers 1962 and 1964, or the
Kunststoff-Handbuch, Polyurethane, Volume VII, Hanser-Verlag,
Munich, Vienna, 1st, 2nd and 3rd Editions, 1966, 1983 and
1993.
To produce the tough polyurethane integral foams, the organic
polyisocyanates (a), relatively high molecular weight compounds
20 containing at least two reactive hydrogen atoms (b) and, if
desired, chain extenders and/or crosslinkers (c) are reacted in
such amounts that the equivalence ratio of NCO groups of the
polyisocyanates (a) to the sum of the reactive hydrogen atoms of
the component (b) and, if used, (c) is preferably 0.9-1.15:1.
The tough polyurethane integral foams are advantageously produced
by the one-shot process or prepolymer process by means of the
high-pressure or low-pressure technique in open or closed molds,
for example metal molds, or are free-foamed (in-situ foam). It
30 has been found to be particularly advantageous to employ the
two-component process and to combine the formative components
(b), (d) and, if desired, (c), (e) and (f) as the component (A)
and to use the organic and/or modified organic polyisocyanates
(a) or mixtures of said polyisocyanates and, if desired, blowing
35 agents (d).
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, in the
case of the production of molded foams, introduced into the open
40 or closed mold. 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 tough polyurethane integral foams produced by the process of
45 the present invention have a density of from 600 to 1,100 kg/m3,
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preferably from 700 to 800 kg/m3 . They have a cellular core and a
compacted surface zone.
The tough polyurethane integral foams of the present invention
5 have
a tear propagation resistance of at least 22 N/mm, preferably from
22 to 26 N/mm, determined in accordance with DIN 53507,
10 an elongation at break of at least 27 %, preferably from 27 to
50 %, determined in accordance with DIN 53504, and
a tensile strength of at least 6.8 N/mm2, preferably from 6.8 to
8.0 N/mm2, determined in accordance with DIN 53504.
The tough polyurethane integral foams produced by the process of
the present invention are suitable for all customary applications
for tough polyurethane integral foams. They are used in
particular for beer barrel cladding.
The invention is illustrated by the following examples.
Example 1 (Comparative Example):
25 A Component
Mixture of:
63.51 parts by weight of a glycerol-initiated
polyoxypropylene-polyoxyethylene polyol ha~,ving an OHN
of 35 mg KOH/g,
9.6 parts by weight of a propylene glycol-initiated
polyoxypropylene-polyoxyethylene polyol having an OHN of
29 mg KOH/g,
35 17.95 parts by weight of an ethylenediamine-initiated
polyoxypropylene polyol having an OHN of 740 mg KOH/g,
0.98 part by weight of a 33 % strength by weight solution of
Dabco in dipropylene glycol,
4.86 parts by weight of tris(2-chloroisopropyl) phosphate
(TCPP),
0.5 part by weight of water and
2.60 parts by weight of color paste
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B Component:
Prepolymer containing urethane groups, having an NCO content of
28 ~ and prepared by reacting diphenylmethane diisocyanate/
5 polyisocyanate with a propylene glycol-initiated polyoxypropylene
polyol having an OHN of 250 mg KOH/g.
100 parts by weight of the A component were reacted with 53 parts
by weight of the B component, giving a tough integral foam having
10 the following properties:
Density of molding [kg/m3]: 710
Hardness [Shore D]: 40
Tensile strength tN/mm2]: 6.6
15 Elongation at break [%]: 26.9
Tear propagation resistance [N/mm]: 21.1
Example 2 (Preparation of the recycled polyol)
20 2000 g of tough integral foam waste (beer barrel cladding) were
introduced at 205~C into a mixture of 1000 g of diethylene glycol
(DEG) and 0.1 % by weight of tin(II) octoate (based on DEG and
polyurethane waste) in such a way that the contents of the flask
remained stirrable. This temperature was maintained for 2.5 hours
25 while stirring. During the reaction time, 12 % by weight of
2-ethylhexyl glycidyl ether (based on amount of DEG and
polyurethane waste) was uniformly metered in.
The mixture was subsequently cooled to 150~C, 3 % by weight of
30 2-ethylhexyl glycidyl ether was metered in and the mixture was
reacted at this temperature for 0.5 hour. This gave a homogeneous
black liquid having the following properties:
OHN 370 mg KOH/g
35 AN < 0.1 mg KOH/g
Viscosity 5280 mPa.s
MDA content < 0.1 %
Example 3
A Component
Mixture of:
45 30 parts by weight of recycled polyol prepared as described in
Example 2 from integral foam waste (beer barrel cladding)
and having an OHN of 370 mg KOH/g,
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52.40 parts by weight of a glycerol-initiated
polyoxypropylene-polyoxyethylene polyol having an OHN of
35 mg KOH!g,
10.20 parts by weight of a propylene glycol-initiated
polyoxypropylene-polyoxyethylene polyol having an OHN of
29 mg KOH/g,
6.0 parts by weight of an ethylenediamine-initiated
polyoxypropylene polyol having an OHN of 740 mg KOH/g,
0.90 part by weight of a 33 % strength by weight solution of
Dabco in dipropylene glycol and
0.5 part by weight of water.
B Component: AS in Example 1
15 100 parts by weight of the A component were reacted with
57.3 parts by weight of the B component, giving a tough integral
foam having the following properties:
Density of molding tkg/m3]: 730
20 Hardness [Shore D]: 39
Tensile strength tN/mm2]: 7.9
Elongation at break t~]: 32.4
Tear propagation resistance [N/mm]: 25.1
25 Example 4
A Component
Mixture of:
~
39 parts by weight of recycled polyol prepared as described in
Example 2 from integral foam waste (beer barrel cladding)
and having an OHN of 370 mg KOH/g,
48.9 parts by weight of a glycerol-initiated
polyoxypropylene-polyoxyethylene polyol having an OHN of
35 mg KOH/g,
10.7 parts by weight of a propylene glycol-initiated
polyoxypropylene-polyoxyethylene polyol having an OHN of
29 mg KOH/g,
0.9 part by weight of a 33 ~ strength by weight solution of
Dabco in dipropylene glycol and
0.5 part by weight of water.
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B Component: As described in Example 1
100 parts by weight o~ the A component were reacted with 54 parts
by weight o~ the B component, giving a tough integral ~oam having
5 the ~ollowing properties:
Density of molding tkg/m3]: 700
Hardness tShore D]: 41
Tensile strength [N/mm2]: 7.0
10 Elongation at break t%]: 49.6
Tear propagation resistance tN/mm]: 23.8
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