Note: Descriptions are shown in the official language in which they were submitted.
BASF Aktiengesellschaft Y~ffl~ u.~. u~
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Stabilized polyurethanes
The present invention relates to stabilized polyurethanes,
5 preferably thermoplastic polyurethanes, comprising specific
stabilizers as a stabilizer combination or as a stabilizer
concentrate, and also a process for preparing polyurethanes using
these stabiiizers.
lO Cellular or compact polyurethanes, in particular polyurethane
casting elastomers and thermoplastic polyurethanes (TPU), have
long been known from numerous patent and literature publications.
Their industrial importance is based on the combination of
valuable mechanical properties with the advantages of low-cost
15 processing methods. The use of different chemical formative
components in different ratios makes it possible to prepare
thermoplastically processable or crosslinked, compact or cellular
polyurethanes having a wide variety of mechanical and processing
properties. An overview of polyurethanes and their properties and
20 applications is given, for example, in Kunststoff-Handbuch,
Volume 7, Polyurethane, 1st Edition, 1966, edited by Dr. R.
Vieweg and Dr. A. HOchtlen, and 2nd Edition, 1983, and also 3rd
Edition, 1993, edited by Dr. G. Oertel, (Carl Hanser Verlag,
Munich, Vienna).
Polyurethane casting elastomers can be obtained by introducing,
eg. by casting or injecting, a reaction mixture into an open or
closed mold and curing this mixture.
30 TPUs can be prepared continuously or batchwise by various
methods. The best known, viz. the belt process and the extruder
process, are also utilized industrially.
According to GB-A-l 057 018, a prepolymer is prepared from an
35 essentially linear polyhydroxyl compound and excess organic
diisocyanate and this prepolymer is fed by means of a metering
pump to a mixing head and is there mixed with a certain amount of
a low molecular weight diol. The reaction mixture obtained is
brought onto a conveyor belt and conveyed until it solidifies
40 through an oven heated to from 70 to 130 C. The reaction product
is then comminuted, heated at 120~C for from 6 to 40 hours and can
then, for example, be processed into shaped bodies using
injection-molding machines.
45 In the extruder process, which is described, for example, in
DE-A-20 59 570 (US-A-3 642 964), the formative components are
introduced directly into the extruder and the reaction is carried
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out in the extr~der under particular process conditions. The
polyurethane elastomer formed is converted into the thermoplastic
state, extruded as a continuous extrudate, cooled until it
solidifies in an inert gas atmosphere and comminuted. A
5 disadvantage of this process is that the TPVs obtained are not
suitable for producing films or fine profiles and hoses. TPUs of
the same composition prepared by the extruder process are
transparent, while those from the belt process have an opaque
appearance. Opaque TPUs can be processed to give films which
lO display no blocking, while transparent TPUs are unsuitable for
this purpose.
The polyurethanes can be prepared using the formative components
known per se, for example diisocyanates and polyisocyanates,
15 relatively high molecular weight polyhydroxyl compounds, low
molecular weight chain extenders and crosslinkers and also
further auxiliaries and additives.
Unstabilized polyurethane is sensitive to heat and UV radiation;
20 it tends to undergo oxidation reactions. The main points of
attack are, for both types of polyurethane, the isocyanate
components which often contain aromatic systems and also, in the
case of polyether polyurethanes, the ether bonds which can be
oxidized by atmospheric oxygen to form peroxides; in the case of
Z5 the polyester polyurethanes, it is the ester bonds which are
essentially attacked by H+ ions.
To avoid these disadvantages, stabilizers are incorporated into
the polyurethane elastomers or the formative components used for
30 their preparation. Hydrolysis inhibitors which have been found to
be useful are, for example, carbodiimides (W. Goyert and H.
Hespe, TPU-Eigenschaften und Anwendungen; Kunststoffe 68 (1978),
pages 819 ff). Suitable stabilizers which have been described for
preventing thermal oxidation are antioxidants such as
35 4,4'-thio-bis(3-methyl-6-tert-butylphenol), phenothiazines and
2,2'-thio-bis(4-methyl-6-isobornylphenol). UV stabilizers used
are, for example, substituted resorcinols, salicylates,
benzotriazoles and benzophenones. Also used are stabilizer
combinations comprising a UV stabilizer and an antioxidant, eg.
40 2-(2'-hydroxy-3',5'-di-tert-amyl)benzotriazole and tetrakis-
[methylene 3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]-
methane. (Advances in Urethane Science and Technology, Volume 4,
pages 68 ff, and Volume 6, pages 103 ff; ~Technomic Publishing
Co.). According to DD-A-238 992, the epoxidized synthetic
45 products such as epoxidized triglycerides, alkylepoxy stearates,
phthalates, tetrahydrophthalates or epoxidized natural products
such as epoxidized soybean oil, rape oil and the like are used as
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hydrolysis stabilizers for PU elastomers based on polyester
polyols. According to EP-A-262 527 (US-A-4775558), cellular or
compact polyurethanes which are joined to or combined with other
materials such as PVC, ABS, copolymers and homopolymers of vinyl
5 chloride, styrene, butadiene, isoprene, chloroprene, ethylene,
propene or acrylonitrile, polyvinyl acetate or polyvinyl butyral
can be stabilized against thermolysis and contact discoloration
by the addition of epoxides, preferably higher-functional
epoxides having an epoxide equivalent weight of from 57 to
lO 10,000. The addition of epoxides in the preparation of PU
elastomers, the application of polyurethanes to epoxide materials
or mixing polyurethanes with epoxy resins enable plastics having
improved mechanical properties to be obtained. Although the
addition of stabilizers was able to improve considerably the
15 mechanical properties of the polyurethane elastomers prepared,
these often still do not meet the high mechanical demands made of
them, in particular for specific areas of application.
EP-A-0 564 931 describes a stabilizer combination comprising
20 triglycidyl isocyanurate and a benzotriazole as concentrate with
a TPU. It is a disadvantage for many applications that the
triglycidyl isocyanurate leads to undesired crosslinking
reactions during processing of the TPU.
25 It is an object of the present invention to develop a
polyurethane which has not only good mechanical properties but
also displays good stability, particularly in respect of UV and
thermal degradation, with the stabilizers causing no or
insignificant crosslinking.
We have found that this object is achieved by using diglycidyl
terephthalate and/or triglycidyl trimellitate in combination with
UV filters for stabilizing the polyurethane.
35 The present invention accordingly provides a stabilized
polyurethane comprising as stabilizer diglycidyl terephthalate
and/or triglycidyl trimellitate in combination with UV filters.
The invention further provides a stabilizer concentrate
40 consisting of, based on the total weight,
A) from 20 to 95% by weight of at least one polyurethane,
B) from 3 to 60% by weight of diglycidyl terephthalate and/or
triglycidyl trimellitate and
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C) from 3 to 60% by weight of at least one UV filter of the
benzotriazole type,
and also a process for preparing stabilized polyurethanes by
5 reacting organic and/or modified organic polyisocyanates with
relatively high molecular weight compounds containing at least
two reactive hydrogen atoms and, if desired, low molecular weight
chain extehders and/or crosslinkers and also blowing agents in
the presence of catalysts, stabilizers and, if desired, further
lO auxiliaries and/or additives, wherein said stabilizer
combinations or concentrates are used as stabilizers.
It has surprisingly been found that polyurethanes, in particular
TPUs, to which diglycidyl terephthalate and/or triglycidyl
15 trimellitate in combination with UV filters, preferably of the
benzotriazole type, have been added display very good resistance
to heat aging and UV radiation. A synergistic effect of the
actions of the stabilizer substances whereby, in particular, the
stabilization against UV radiation is further improved is
20 observed. The system of the present invention displays reduced
crosslinking in high-concentration applications.
As UV filters, preference is given to using those of the
benzotriazole type. Particular preference is given to
25 2-~2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole and/or
1,6-hexanediyl bis[3-(3-{benzotriazol-N-yl}-4-hydroxy-5-
tert-butylphenyl)propanoate]. However, it is also possible to use
other UV absorbers such as phenol, 2-(2H-benzotriazol-2-yl)-
4-methyl-6-dodecylphenol, 2,2'-methylene-bis(6-{2H-benzotriazol-
30 2-yl}-4-{1,1,3,3-tetramethylbutyl}phenol) and 2-(2H-benzo-
triazol-2-yl)-4,6-bis(l,1-dimethylethyl)phenol.
A stabilizer which is particularly advantageous and is therefore
preferably used is a combination of diglycidyl terephthalate,
35 triglycidyl trimellitate and 2-(2-hydroxy-3,5-di-tert-amyl-
phenylj-2H-benzotriazole.
The stabilizer combination is, based on the polyurethane,
preferably present in a total amount of from 0.01 to 3% by
40 weight, particularly preferably from 0.1 to 1.5% by weight. In a
particularly advantageous embodiment, the individual constituents
diglycidyl terephthalate, triglycidyl trimellitate and UV filter
are used in a ratio of from 1:1:2 to 1:1:1.
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During processing of the polyurethanes, a crosslinking reaction
does not occur even in the case of an epoxide content
significantly more than 1% by weight as stabilizer.
5 The stabilized polyurethanes of the present invention are
prepared in a customary manner by reacting organic and/or
modified organic polyisocyanates (a) with relatively high
molecular weight compounds containing at least two reactive
hydrogen atoms (b) and, if desired, low molecular weight chain
lO extenders and/or crosslinkers (c) in the presence of stabilizers
(d) and catalysts (e) and also, if desired, further auxiliaries
and/or additives (f), with use being made as stabilizers (d) of
diglycidyl terephthalate and/or triglycidyl trimellitate in
combination with UV filters as described above.
In the preparation of the polyurethanes, the stabilizer
components can be added in a customary manner either
individually, simultaneously or in succession or as a complete or
partial combination.
However, it is particularly advantageous first to make a
stabilizer concentrate consisting of, based on the total weight,
A) from 20 to 95% by weight of at least one polyurethane,
B) from 3 to 60% by weight of diglycidyl terephthalate and/or
triglycidyl trimellitate and
C) from 3 to 60% by weight of at least one of the
above-described UV filters.
The stabilizer concentrate is easy to prepare, can readily be
metered in and is simple to handle.
35 The stabilized polyurethanes of the present invention are also,
in this case, prepared by reacting organic and/or modified
organic polyisocyanates (a) with relatively high molecular weight
compounds containing at least two reactive hydrogen atoms (b)
and, if desired, low molecular weight chain extenders and/or
40 crosslinkers (c) in the presence of stabilizers (d) and catalysts
(e) and also, if desired, further auxiliaries and/or additives
(f), but using as stabilizer (d) a stabilizer concentrate
consisting of, based on the total weight,
~5 A) from 20 to 95% by weight of at least one polyurethane,
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B) from 3 to 60% by weight of diglycidyl terephthalate and/or
triglycidyl trimellitate and
C) from 3 to 60% by weight of at least one UV filter.
In principle, all polyurethanes are suitable for the
stabilization according to the present invention. Particularly
advantageous results have been obtained with TPUs, particularly
when using the stabilizer concentrate.
In order that the polyurethane elastomer matrix does not impair
the stabilizing effect of the stabilizer concentrates, they are
advantageously prepared using TPUs (A) having a hardness in the
range from Shore A 78 to Shore A 98, preferably from Shore A 80
15 to A 88, which are obtained by reacting
an organic diisocyanate, preferably diphenylmethane
4,4'-diisocyanate with
20 a polyhydroxyl compound having a molecular weight of from 800 to
3000, preferably from 1000 to 2500, selected from the group
consisting of polyoxybutylene glycols, poly-1,4-butanediol
adipates, poly-1,6-hexanediol adipates and poly-1,4-butanediol-
1,6-hexanediol adipates and
an alkanediol having from 2 to 6 carbon atoms, preferably from 4
to 6 carbon atoms, in particular 1,4-butanediol, as chain
extender.
30 TPUs (A) prepared by the belt process have been found to be
particularly useful for preparing the stabilizer concentrates of
the present invention.
Withi~ the percentage range given above for the stabilizers (B)
35 and (C), they are advantageously used in a weight ratio of from
0.5:1 to 1:0.5 and preferably of 1:1.
A W stabilizer concentrate which has been found to have
excellent handling properties from a production point of view
40 consists of, based on the total weight,
A) from 50 to 80% by weight of at least one TPU,
B) from 10 to 25% by weight of diglycidyl terephthalate and/or
triglycidyl trimellitate and
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BASF Aktiengesellscha~t
C) from 10 to 25% by weight of 2-~2-hydroxy-3,5-di-tert-
amylphenyl)-2H-benzotriazole.
Particular preference is given to using a stabilizer concentrate
5 consisting of 75% by weight of (A), 12.5% by weight of (B) and
12.5% by weight of (C).
With the exception of the stabilizer components according to the
present invention, both the stabilized polyurethanes and the
10 polyurethane A) required for the stabilizer concentrate are
prepared using the starting components customary in polyurethane
chemistry:
a) Suitable organic and/or modified organic polyisocyanates are,
in particular, aliphatic, cycloaliphatic or preferably
aromatic diisocyanates. Specific examples are: aliphatic
diisocyanates such as hexamethylene 1,6-diisocyanate,
2-methylpentamethylene 1,5-diisocyanate, 2-ethylbutylene
1,4-diisocyanate or mixtures of at least two of the aliphatic
diisocyanates mentioned; cycloaliphatic diisocyanates such as
isophorone diisocyanate, cyclohexane 1,4-diisocyanate,
l-methylcyclohexane 2,4- or 2,6-diisocyanate and also the
corresponding isomer mixtures, dicyclohexylmethane 4,4'-,
2,4'- and 2,2'-diisocyanate and also the corresponding isomer
mixtures; and preferably aromatic diisocyanates such as
tolylene 2,4-diisocyanate, mixtures of tolylene 2,4- and
2,6-diisocyanate, diphenylmethane 4,4~-, 2,4~- and
2,2'-diisocyanate, mixtures of diphenylmethane 2,4'- and
4,4~-diisocyanate, urethane-modified liquid diphenylmethane
4,4'- and/or 2,4'-diisocyanates, 4,4'-diisocyanato(1,2-
diphenylethane), mixtures of 4,4'-, 2,4'- and
2,2'-diisocyanato(1~2-diphenylethane)~ advantageously those
having a 4,4'-diisocyanato(1,2-diphenylethane) content of at
lea'st 95% by weight, and naphthylene 1,5-diisocyanate.
Preference is given to using diphenylmethane diisocyanate
isomer mixtures having a diphenylmethane 4,4'-diisocyanate
content of greater than 96% by weight and in particular
essentially pure diphenylmethane 4,4'-diisocyanate.
The organic diisocyanates can, if desired, be replaced by
subordinate amounts, eg. amounts of up to 3 mol%, preferably
up to 1 mol%, based on the organic diisocyanate, of a
trifunctional or higher-functional polyisocyanate, but its
amount has to be limited to an amount such that
thermoplastically processable polyurethanes are still
obtained. A relatively large amount of such isocyanates
having a functionality of more than 2 is advantageously
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compensated by the concomitant use of compounds containing
reactive hydrogen atoms which have a functionality of less
than 2, so that excessive chemical crosslinking of the
polyurethane is avoided. Examples of isocyanates having a
functionality of more than 2 are mixtures of diphenylmethane
diisocyanates and polyphenylpolymethylene polyisocyanates,
known as raw MDI, and also liquid diphenylmethane 4,4'-
and/or 2,4~-diisocyanates modified with isocyanurate, urea,
biuret, allophanate, urethane and/or carbodiimide groups.
Examples of suitable monofunctional compounds containing a
reactive hydrogen atom, which can also be used as molecular
weight regulators, are: monoamines such as butylamine,
dibutylamine, octylamine, stearylamine, N-methylstearylamine,
pyrrolidone, piperidine and cyclohexylamine, and monoalcohols
such as butanol, amyl alcohol, l-ethylhexanol, octanol,
dodecanol, cyclohexanol and ethylene glycol monoethyl ether.
However, particular preference is given to using: (i)
polyisocyanates containing carbodiimide and/or urethane
groups derived from diphenylmethane 4,4'-diisocyanate or a
mixture of diphenylmethane 4,4'- and 2,4'-diisocyanates and
having an NC0 content of from 33.6 to 8% by weight, (ii) NC0-
containing prepolymers having an NC0 content of from 8 to 25%
by weight, based on the prepolymer weight, prepared by
reacting polyoxyalkylene polyols having a functionality of
from 2 to 4 and a molecular weight of from 600 to 6000 with
diphenylmethane 4,4r-diisocyanate or a mixture of
diphenylmethane 4,4'- and 2,4'-diisocyanates and mixtures of
(i) and (ii).
b) As relatively high molecular weight compounds containing at
least two reactive hydrogen atoms, it is possible to use, for
example, those having a functionality of from 2 to 4 and
moiecular weights of from 500 to 8000. Compounds which have
been found to be useful are particularly polyether diols and
in particular polyester diols. Use is made of, for example,
polybutadiene diols with which good results are obtained,
particularly in the preparation of crosslinkable TPUs. Also
suitable are other hydroxyl-containing polymers having ether
or ester groups in the polymer chain, for example polyacetals
such as polyoxymethylene and in particular water-insoluble
formals, eg. polybutanediol formal and polyhexanediol formal,
and polycarbonates, in particular those prepared from
diphenyl carbonate and 1,6-hexanediol by transesterification.
The polyl,ydroxyl compounds should be at least predominantly
linear and have to be essentially difunctional in the context
of the isocyanate reaction. The polyhydroxyl compounds
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mentioned can be used as individual compounds or in the form
of mixtures.
Suitable polyether diols can be 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 polymer-
ization 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 and with addition of at least one
initiator molecule containing 2 or 3, preferably 2, 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.
Examples of suitable alkylene oxides are tetrahydrofuran,
1,3-propylene oxide, 1,2- or 2,3-butylene oxide and
particularly 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 and/or glutaric
acid, alkanolamines such as ethanolamine, N-alkylalkanol-
amines, N-alkyldialkanolamines such as N-methyldiethanolamine
and N-ethyldiethanolamine and preferably dihydric alcohols
which may contain bonded ether bridges, eg. ethanediol, 1,2-
and 1,3-propanediol, 1,4-butanediol, diethylene glycol,
1,5-pentanediol, 1,6-hexanediol, dipropylene glycol,
2-methylpentane-1,5-diol and 2-ethylbutane-1,4-diol. The
initiator molecules can be used individually or as mixtures.
Preference is given to using polyetherols derived from
1,2-propylene oxide and ethylene oxide in which more than
50%', preferably from 60 to 80%, of the OH groups are primary
hydroxyl groups and in which at least part of the ethylene
oxide is present as a terminal block. Such polyetherols can
be obtained by, for example, polymerizing first the
1,2-propylene oxide and subsequently thereto the ethylene
oxide onto the initiator molecule or first copolymerizing all
the 1,2-propylene oxide together with part of the ethylene
oxide and subsequently polymerizing on the remainder of the
ethylene oxide or, stepwise, first polymerizing part of the
ethylene oxide, then all the 1,2-propylene oxide and then the
remainder of the ethylene oxide onto the initiator molecule.
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Other particularly suitable polyetherols are the hydroxyl-
containing polymerization products of tetrahydrofuran.
The essentially linear polyetherols usually have molecular
weights of from 500 to 8000, preferably from 600 to 6000 and
in particular from 800 to 3500, with the polyoxytetra-
methylene glycols preferably having molecular weights of from
500 to 2800. They can be used either individually or in the
form of mixtures with one another.
Suitable polyester diols can be prepared, for example, from
dicarboxylic acids having from 2 to 12, preferably from 4 to
6, carbon atoms and diols. Examples of suitable dicarboxylic
acids are: aliphatic dicarboxylic acids such as succinic
acid, glutaric acid, adipic acid, suberic acid, azelaic acid
and sebacic acid, and aromatic dicarboxylic acids such as
phthalic acid, isophthalic acid and terephthalic acid. The
dicarboxylic acids can be used individually or as mixtures,
eg. in the form of a succinic, glutaric and adipic acid
mixture. For preparing the polyesterols, it may be
advantageous to replace the dicarboxylic acids with the
corresponding dicarboxylic acid derivatives such as
monoesters or diesters of dicarboxylic acid having from 1 to
4 carbon atoms in the alcohol radical, dicarboxylic
anhydrides or dicarboxylic acid dichlorides. Examples of
diols are glycols having from 2 to 10, preferably from 2 to
6, carbon atoms, for example ethylene glycol, diethylene
glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,
1,10-decanediol, 2,2-dimethylpropane-1,3-diol, 1,3-propane-
diol and dipropylene glycol. Depending on the desired
properties, the diols can be used alone or in admixture with
one another.
Also suitable are esters of carbonic acid with the diols
mentioned, in particular those having from 4 to 6 carbon
atoms, eg. 1,4-butanediol and/or 1,6-hexanediol; condensation
products of ~-hydroxycarboxylic acids, for example ~-hydroxy-
caproic acid, and preferably polymerization products of
lactones, for example unsubstituted or substituted ~-capro-
lactone.
Polyester diols which are preferably used are ethanediol
polyadipates, 1,4-butanediol polyadipates, ethanediol-1,4-
butanediol polyadipates, 1,6-hexanediol-neopentyl glycol
polyadipates, 1,6-hexanediol-1,4-butanediol polyadipates and
polycaprolactones.
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The polyester diols generally have molecular weights of from
500 to 6000, preferably from 800 to 3500.
c) Suitable chain extenders having molecular weights of
generally from 60 to 400, preferably from 60 to 300, are
preferably aliphatic diols having from 2 to 12 carbon atoms,
preferably having 2j 4 or 6 carbon atoms, eg. ethanediol,
1,6-hexanediol, diethylene glycol, dipropylene glycol and in
particular 1,4-butanediol. However, other suitable chain
extenders are diesters of terephthalic acid with glycols
having from 2 to 4 carbon atoms, eg. bis(ethylene glycol)
terephthalate or bis(1,4-butanediol) terephthalate and
hydroxyalkylene ethers of hydroquinone, eg. 1,4-dit~-hydroxy-
ethyl)hydroquinone and also polytetramethylene glycols having
molecular weights of from 162 to 378.
Depending on the desired properties of the polyurethanes of
the present invention, the amounts of the formative
components (b) and (c) which are used can be varied within a
relatively wide range of molar ratios. In the case of the
TPUs preferably prepared, this enables the hardness and melt
flow index to be adjusted, with the hardness and the melt
viscosity rising with an increasing content of chain
extenders (c), while the melt flow index falls.
To prepare relatively soft TPUs, eg. those having a Shore A
hardness of less than 95, preferably from 95 to 75 Shore A,
use can be made, for example, of the essentially difunctional
polyhydroxyl compounds (b) and diols (c) in molar ratios of
advantageously from 1:1 to 1:5, preferably from 1:1.5 to
1:4.5, so that the resulting mixtures of (b) and (c) have a
hydroxyl equivalent weight of greater than 200, in particular
~from 230 to 450, while to prepare relatively hard TPUs, eg.
those having a Shore A hardness of greater than 98,
preferably from 55 to 75 Shore D, the molar ratios of (b):(c)
are in the range from 1:5.5 to 1:15, preferably from 1:6 to
1:12, so that the resulting mixtures of (b) and (c) have a
hydroxyl equivalent weight of from 110 to 200, preferably
from 120 to 180.
d) As stabilizers against UV and thermal degradation, use is
made in particular of the above-described stabilizers,
stabilizer combinations or stabilizer concentrates of the
present invention.
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12
However, other stabilizers customary in polyurethane
chemistry can also be additionally used as further auxil-
iaries and additives (f).
5 e) Suitable catalysts for preparing the polyurethanes of the
present invention, which, in particular, accelerate the
reaction between the NCO groups of the diisocyanates (a) and
the hydroxyl groups of the formative components (b) and (c),
are the customary catalysts known from the prior art, for
example tertiary amines such as triethylamine, dimethyl-
cyclohexylamine, N--methylmorpholine, N,N'-dimethylpiperazine,
diazabicyclol2.2.2]octane and the like, and also, in
particular, organic metal compounds such as titanate esters,
iron compounds, tin compounds, eg. tin diacetate, tin
dioctoate, tin dilaurate or the dialkyltin salts of aliphatic
carboxylic acids, eg. dibutyltin diacetate, dibutyltin
dilaurate or the like. The catalysts are usually used in
amounts of from 0.001 to 0.1 part by weight per 100 parts by
weight of the mixture of polyhydroxyl compound (b) and chain
extender (c).
f) In addition, further auxiliaries and/or additives can also be
added to the formative components in the preparation of the
polyurethanes of the present invention. Examples which may be
mentioned are blowing agents, lubricants, inhibitors, stabil-
izers against hydrolysis or discoloration, dyes, pigments,
inorganic and/or organic fillers and reinforcers.
These auxiliaries and/or additives can be introduced into the
formative components or into the reaction mixture for
preparing the polyurethanes. According to another process
variant, these auxiliaries and/or additives (f) can be mixed
with the polyurethane and, particularly in the case of TPU,
subsequently melted or they are incorporated directly into
the melt.
The auxiliaries and/or additives which can be used may be
found in the specialist literature, for example the monograph
by J.H. Saunders and K.C. Frisch "High Polymers~, Volume XVI,
Polyurethane, Parts 1 and 2 (Interscience Publishers 1962 and
1964), the Kunststoff-Handbuch, Volume 7, Polyurethane 1st,
2nd and 3rd Editions (Carl Hanser Verlag, 1966, 1983 and
1993) or DE-A-29 01 774.
45 To prepare the polyurethanes of the present invention, the
formative components (a), (b) and, if desired, (c) are reacted in
the presence of the stabilizers of the present invention (d) and
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13
of catalysts (e) and, if desired, auxiliaries and/or additives
(f) in amounts such that the equivalence ratio of NCO groups of
the diisocyanates (a) to the sum of the hydroxyl groups of the
components (b) and (c) is 0.95-1.20:1, preferably 0.98-1.08:1 and
5 in particular about 1.0-1.05:1.
To prepare the stabilizer concentrates of the present invention,
in particular those based on TPUs, the stabilizers (B) and (C)
are incorporated successively or preferably simultaneously into
10 the fully reacted, at least flowable, preferably molten TPU (A)
at from 170 to 220 C, preferably from 180 to 200 C. Suitable
processing apparatuses for this purpose are, for example, roll
mills, kneaders and preferably extruders, in particular twin-
screw extruders. The resulting UV stabilizer concentrates can
15 then be subjected to intermediate storage or be granulated
directly, with the granules advantageously having an average
particle diameter of less than 6 mm, preferably from 2 to 4 mm.
The stabilizer concentrates of the present invention are
20 preferably used for stabilizing TPUs known per se prepared by the
extruder or belt process from customary starting materials
against UV and thermal degradation.
For this purpose, from 0.5 to 12 parts by weight, preferably from
25 1 to 10 parts by weight and in particular from 2 to 5 parts by
weight, of the UV stabilizer concentrate are intensively mixed
with 100 parts by weight of TPU, preferably in the form of
granules, at from 10 to 220 C and the stabilizer concentrate/TPU
mixture is then thermoplastically processed at from 170 to 220 C,
30 preferably from 180 to 210 C, for example by blowing to produce
films or by injection-molding to produce moldings. According to
another process variant, the UV stabilizer concentrates can also
be introduced directly, eg. by means of an extruder, into the TPU
melt, homogeneously mixed and extruded to produce a molding.
The following examples illustrate the invention:
Examples Cl to C4 and El to E4
40 1000 parts by weight of polytetrahydrofuran having a mean mole-
cular weight of 1000 were reacted with 600 parts by weight of
4,4'-MDI and 121 parts by weight of 1,4-butanediol to give a TPU
and in the process admixed with the components shown in Table 1.
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Table 1
Example Diglycidyl Triglycidyl Anti- Benzo-
5 No. terephthalate trimellitate oxidant* triazole*
Comparison - - - -
C1
Comparison - - 1%
C2
lO Comparison - - 1% 1%
C3
Comparison 0.5% 0.5% 1%
C4
Example E1 0.125% 0.125% 1% 0.25%
15 EXample E2 0.25% 0.25% 1% 0.5%
Example E3 0.625% 0.625% 1% 0.75%
Example E4 0.5% 0.5% 1% 1%
Benzotriazole* = 2-(2-hydroxy-3,5-di-tert-amylphenyl)-2H-
benzotriazole
Antioxidant* = pentaerythrityl tetrakis[3-(3,5-di-tert-butyl-4-
hydroxyphenyl)propionate]
2 C1 amd E3 were carried out by manual casting. Here, the
stabilizers were added directly and intensively mixed in. The
reaction product was processed to give test specimens. The other
examples were carried out using the belt process. The antioxidant
was, if used, mixed in during the preparation of the TPU. The
stabilizers of the present invention were added here in the form
30 of a concentrate.
Preparation of the stabilizer concentrate of the present
invention:
75 parts by weight of a TPU obtained using the belt process by
reaction of polytetrahydrofuran, 4,4~-MDI and 1,4-butanediol in
the amounts indicated above were melted in an extruder and
intensively mixed at 200 C with
6.25 parts by weight of diglycidyl terephthalate,
6.25 parts by weight of triglycidyl trimellitate and
12.5 parts by weight of the benzotriazole defined above.
4 The homogeneous mixture was extruded and granulated.
CA 022l3l6~ l997-09-02
The stabilizer concentrate was added to the above-described TPU
mix in the following amounts and homogeneously mixed in:
El 2 parts by weight
5 E2 4 parts by weight
E4 8 parts by weight
The reaction product was processed into test specimens.
10 Products giving the results shown in Tables 2 to 4 were obtained.
Table 2
Intrinsic color of the products
Example No. YI L* A* B*
Comparison C1 3.6 96.6 -0.4 1.6
Comparison C2 3.0 46.1 -0.4 1.8
20 Comparison C3 4-9 96.2 -1.1 3.3
Comparison C4 3.6 96.1 -0.5 2.2
Example El 4.8 95.8 -0.6 3.0
Example E2 7.7 95.0 -1.1 4.8
25 EXample E3 10.6 94.6 -1.3 6.7
Example E4 11.9 94.4 -1.4 7.5
YI Yellowness Index
L*A*B*Color values from the CIELAB system
Table 3
Properties after storage for 500 hours at 130 C in a convection
oven;
Example No. TS/MPa EB/% DE* YI
Comparison Cl 10 380 99.8 204.1
Comparison C2 18 830 78.3 107.9
Comparison C3 17 710 81.2 108.5
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Example No. TS/MPa EB/% DE* YI
Comparison C4 29 730 60.1 89.1
Example El 21 770 79.4 111.1
5 Example E2 20 780 72.2 105.8
Example E3 23 810 67.3 102.5
Example E4 25 730 68.6 106.1
TS tensile strength DIN 53 504
EB elongatio~ at break DIN 53 504
DE* Delta E* from the LAB* color system (color change compared
with unilluminated specimen)
YI Yellowness Index
Small DE* and YI values show low discoloration or yellowing.
Table 4
Properties after UV illumination in accordance with DIN 75202
(100 C black-body temperature)
Example No. DE* 300 h YI 300 h DE* 500 h YI 500 h
Comparison Cl 35.1 58.050.1 78.2
Comparison C2 29.6 47.242.4 64.2
Comparison C3 19.8 37.028.7 42.1
Comparison C4 21.8 35.927.6 44.4
Example El 16.0 28.722.4 38.2
Example E2 12.0 25.516.4 32.0
30 Example E3 8.1 22.411.7 27.6
Example E4 7.9 23.311.0 26.9
In Cl to C4, Cl (without any stabilizers) showed very poor
35 mechanical properties after hot storage. The material was
unusable. The mechanical properties improved when antioxidant was
used, but strong discoloration occurred after the UV test.
In El to E4, good mechanical properties were achieved by optimal
40 combination of the stabilizers. Only a slight discoloration
occurred after UV illumination owing to synergistic effects when
epoxide/benzotriazole were used, significantly better than in the
case of C3 (only benzotriazole in combination with antioxidant).
In the manual casting process (E3), despite good properties of
45 the end products, disadvantages were found in the metering of the
solids (dust) and the not-so-flexible handling of the products.
CA 0221316~ 1997-09-02
17
Examples C5 and E5
1000 parts by weight of polytetrahydrofuran having a mean
molecular weight of 1000 were reacted with 1100 parts by weight
5 of 4,4'-MDI and 306 parts by weight of 1,4-butanediol by the
manual casting method to give a TPU; in ES, the components
indicated in Table 5 were mixed in during the process. The
reaction product was processed into test specimens.
10 The optical and mechanical properties found are shown in Tables 6
to 8.
Examples C6 and E6
15 1000 parts by weight of polytetrahydrofuran having a mean
molecular weight of 1000 were reacted with 1200 parts by weight
of 4,4'-MDI and 342 parts by weight of 1,4-butanediol as well as
the amount of antioxidant indicated in Table 5 using the belt
process to give a TPU. In E6, 4% by weight, based on the total
20 mix, of a stabilizer concentrate prepared by a method similar to
that for the above-described (for Examples El, E2 and E4)
stabilizer concentrate but using the TPU employed for C6/E6 was
added and homogeneously mixed in during the process. The reaction
product was processed into test specimens.
The optical and mechanical properties found are shown in Tables 6
to 8.
Examples C7 and E7
1000 parts by weight of a butanediol-hexaneidol adipate having a
mean molecular weight of 2000 were reacted with 425 parts by
weight of 4,4'-MDI, 10 parts by weight of a carbodiimide as
hydrolysis inhibitor and 106 parts by weight of 1,4-butanediol as
35 well as the amount of antioxidant indicated in Table 5 using the
belt process to give a TPU. In E7, 4% by weight, based on the
total mix, of a stabilizer concentrate prepared using a method
similar to that for the above-described (for Examples El, E2 and
E4) stabilizer concentrate but using the TPU employed for C7/E7
40 was added and homogeneously mixed in during the process. The
reaction product was processed into test specimens.
The optical and mechanical properties found are shown in Tables 6
to 8.
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Examples C8 and E8
1000 parts by weight of an ethylene glycol-butanediol adipate
having a mean molecular weight of 2000 were reacted with
5 440 parts by weight of 4,4'-MDI, 10 parts by weight of a
carbodiimide as hydrolysis inhibitor and 110 parts by weight of
1,4-butanediol by the manual casting method to give a TPU and in
the process admixed with the components indicated in Table 5. The
reaction product was processed into test specimens.
The optical and mechanical properties found are shown in Tables 6
to 8.
Table 5
Example No. Diglycidyl Triglycidyl Anti- Benzo-
terephthalate trimellitate oxidant* triazole*
Comparison
C5
Example E5 0.25 0.25 - 0.5 %
Comparison - - 0.5 %
C6
Example E6 0.25 0.25 0.5 %0.5 %
25 Comparison _ _ 0.5 %
C7
Example E7 0.25 0.25 0.5 %0.5 %
Comparison - - 0.5 %
C8
30 Example E8 0.25 0.25 0.25 %0.5 %
Benzotriazole* = 2-(2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzo-
triazole
AntioXidant* = pentaerythrityl tetrakis[3-(3,5-di-tert-butyl-4-
hydroxyp'henyl)propionate]
Table 6
Intrinsic color of the products
Example No. YI L* A* B*
Comparison C5 2.2 96.7 -0.5 1.4
Example E5 6.5 95.9 -1.1 4.3
Comparison C6 3.5 95.9 -0.2 2.0
Example E6 11.3 90.8 -0.4 6.4
Comparison C7 2.6 95.9 -0.1 1.4
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Example No. YI L* A* B*
Example E79.0 89.20.1 4.7
Comparison C8 1.6 96.6 -0.1 0.9
5 Example E89.1 90.0-0.1 5.0
YI Yellowness Index
L*A*B*Color values from the CIELAB system
Table 7
Properties after storage for 500 hours at 130 C in a convection
oven
15 Example No. TS/MPa EB/% DE* YI
Comparison C5 25 330 107.$ 147.7
Example E525 360 104.2 146.1
Comparison C6 29 330 106.2 148.3
Example E634 490 49.7 84.3
Comparison C7 38 770 34.1 53.9
Example E743 790 30.1 47.0
Comparison C8 41 820 37.2 56.2
Example E844 790 22.3 44.4
25 TS tensile strength DIN 53 504
EB elongation at break DIN 53 504
DE* Delta E* from the LAB* color system (color change compared
with unilluminated specimen)
YI Yellowness Index
Small DE* and YI values show low discoloration or yellowing.
i
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- 20
Table 8
Properties after UV illumination in accordance with DIN 75202
(100~C black-body temperature)
Example No. DE* 300 h YI 300 h
Comparison C5 27.6 43.5
Example E5 15.1 29.2
lO Comparison C6 28.9 46.9
Example E6 5.7 21.4
Comparison C7 46.8 66.8
Example E7 9.0 23.1
15 Comparison C8 44.0 65.6
Example E8 17.8 36.6
The additives additionally introduced according to the present
20 invention effect a significant improvement in the UV resistance.
CA 022l3l65 l997-09-02
