Note: Descriptions are shown in the official language in which they were submitted.
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Lea 22,892
A PROCESS FOR THE PRODUCTION OF
THEP~IOPLASTIC POLYURETHANE ELASTOMERS
BACKGROUND OF THE INVENTION
This invention relates to a process for the
production of rigid, elastic, homogeneously Diablo,
substantially non-yellowing, hydrolysis-resistant polyp
urethane elastomers which show low-temperature phlox
ability and outstanding impact strength at low tempera-
lures, tensile strength and a high modulus without any
nickers segregation of the hard segments an which have
a relatively low density of from 1.10 to 1.17 Mg/m3 and
a high Shore-D hardness of from 55 to 80.
The synthesis of polyurethane elastomers from
polytetramethylene ether dills, diisocyanates and chain
extenders is known in principle. However, attempts to
produce highly rigid polyurethane elastomers from polyp
tetramethylene ether dills (e.g., polytetrahydrofuran
dills) of relatively high molecular weight (molecular
weight of the polyether approx. 1200 to 1500), hove
generally produced elastomers having a high degree of
segregation between hard and soft segments when the
molar ratio of diisocyanates (diphenylmethane dozes
Nate "MID") to polyether dills was greater than about
8:1. Such segregation is evidenced by a distinct
nickers effect or, in the case of dyed or pigmented
materials, by serious streaking in the molding. The
strength values particularly tear propagation resist-
ante, are greatly reduced by such segregation. Cons-
quaintly, molded articles with reduced wall thickness
(for example sky boot fastenings have much zoo low
resistance to detachment for many practical applique-
lions.
German Offenle~ungsschrlft 2,854,409 discloses
polyester urethane elastomers chain-extended with
1,4-butane dill in its Examples. However, when the
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Jut
rigidity of products such as these is increased to
around 40 Ma, their impact strength at low temperatures
is extremely moderate (approx. 20 to 40% in impact/
tensile tests). When polyeth~r urethane elastomers are
chain-extended with Boone dill as the sole chain
extender in the manner disclosed in the Examples of
German Offenlegungsschrift 2,854,409, the elastomers
obtained show a pronounced nickers structure and cannot
be used in applications such as ski boots. The products
obtained by this process also are highly yellow.
German Offenlegungsschrift 2,854,407 discloses
thermoplastic blends of thermoplastic polyurethane
based on polyethers or polyesters and a graft product of
I to 95 wit % of an elastomers component serving as the
graft base and 5 to 35 wit % of one or more grafted on
monomers. The blends obtained with these polyethers
show poor impact strength at low temperatures and also
exhibit the segregation phenomena tithe nickers effect).
The strengths of these products are reduced as a result
of such segregation.
The nickers effect is also encountered in
products made by the process described in European
Patent Application 12,343. In this disclosed process,
relatively high molecular weight polypropylene oxide and
polyethylene oxide ether polyols are used as the rota-
lively high molecular weight polyhydroxyl compounds.
The yellowing of these products is very high their
impact strength at low temperatures is inadequate and
their strengths/moduli need i~pro~ement. In this
disclosed process, certain copol~ners or graft polymers
are used together with stabilizers to preappoint degrade-
lion of the products during extrusion.
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According to U.S. Patent 4,179,479, ABS-graft
copolymers together with from 0.5 to 10 it % of process-
in aids in the form of an acrylate polymer having a
molecular weight of from 500,000 to 1,500,000 thomopoly-
mews of methylmethacrylate and butylmethacrylate,copolymers of methylmethacrylate and ethylacrylate and
terpolymers of methylmethacrylate, n-butylacrylate and
styrenes), optionally in admixture with finlike anti-
oxidants and UV-absorbers, may be used in addition to
thermoplastic polyurethane. The acrylate polymer
processing aids make it possible to improve processing
by extrusion. This process also gives nickers products
with relatively poor strength values, even at low
temperatures. The ABS-types used had high styrenes
contents.
European Patent Application 4,939 describes a
dill chain extending mixture (for example of 1,4-butane
dill and 1,6-hexane dill) in which one component is
present in a quantity of from I to 99 wit % and the
other component in a quantity of from 1 to 10 wit % which
is useful in the production ox extruded and calendered
PU-elastomers. There is no suggestion in European
Patent Application 4,939 to use graft rubber. Where a
rigid polyurethane is used in this disclosed process,
the products still show a distinct nickers effect and
also yellow very seriously. Polyurethane thermoplasts
made from the hexamethylene diisocyanate disclosed
therein show excessively reduced strength values after
exposure to ultraviolet light.
SIAM JO TUG I~VEK!ION
It is an object of the present invention to
provide a process for the production of thermoplastic
polyurethane elastomers which are flexible at lo
temperatures, have high mechanical strength, a density
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of from 1.10 to 1.17 Mg/m3 and a Shore-D hardness of
from 55 to 80.
It is also an object of the present invention
to provide a process for the production of homogeneously
Diablo, substantially non-yellowing thermoplastic
polyurethane elastomers in which segregation of the hard
segments is substantially completely eliminated.
It is another object of the invention to
provide a process for the production of thermoplastic
polyurethane elastomers having outstanding impact
strength at low temperatures and high strength and tear
propagation resistance values.
It is a further object of the present invention
to provide a process for the production of thermoplastic
polyurethane elastomers which may be readily extruded or
injection molded to form automobile components and ski
boot components.
These and other objects which will be readily
apparent to those skilled in the art are accomplished by
reacting in quantities which meet specific ratio
requirements 4,4-diisocyanatodiphenylme~hane or mixtures
thereof containing 2,4'-diisocyanatodipheT~ylmethane with
certain polytetramethylene ether dills having molecular
weights of from 800 to 3Q00 in thy presence of a certain
mixture of dill chain extenders, a graft rubber polymer
and optionally, an antioxidant and/or US absorber/light
stabilizer.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a process for
the production of thermoplastic polyurethane elastomers
by reacting a diisocyanate, a relatively high molecular
weight polyol and dill chain-extending agents in
substantially equivalent ratios of NCO-groups to the
OH-groups of the polyol and dill components in the
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presence of a thermoplastic polymer and, optionally,
antioxidant and/or W-absorbers/light stabilizers.
More specifically, rigid-elastic, homogeneous thermos
plastic polyurethane elastomers showing flexibility at
low temperature and high mechanical strength without
any nickers effect through segregation of the hard
segments and having a low density of from 1,10 to 1.17
Mum and a Shore-D hardness of from 55 to 80 are
produced from the components more fully described below.
The diisocyanate employed in the process of the
present invention is 4,4'-diisocyanatodiphenylmethane or
an isomer mixture with up to 5 mole percent of
2,4-diisocyanatodiphenylmethane, preferably from 0.5 to
5 mole percent and, more preferably, from 0.5 to 3.5
15 mole percent. This diisocyanate may be modified with
small quantities of the chain extender mixture.
The relatively high molecular weight polyol is a
polytetramethylene ether dill having a molecular weight
of from 800 to 3000 and preferably from lG00 to 1500,
optionally in admixture with other relatively high
molecular weight polyhydroxyl compounds having a
molecular weight in the range from 800 Jo 3000. Polyp
tetrahydrofuran dill is an example of such a doll.
The mixture of chain extenders employed in the
I process of the present invention is made up of a prince-
pal chain extender and one or more co-chain extender
dills in a molar ratio of from 97:3 Jo 7~:28 and prefer-
ably from 94:6 to 87:13. The principal chain extender
may be either 1,4-butane dill or ennui dill and the
30 co-chain extender Jay be one or Gore other dill.
Preferred co-chain extenders are 1,6-hexane dill,
1,4-butane dill, diethylene glycol, dip and tripropylene
glycol and hydroquinone di-~-hydroxyethyl ether.
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The thermoplastic polymer used in the present
invention is a butadiene-based graft rubber, preferably
a graft rubber containing from 30 to 50 wit % of but-
dine as the raft base and a thermoplastic resin combo-
next of styrenes and acrylonitrile as the graft monomer This thermoplastic polymer is generally used in quanta-
ties of from 5 to 25 wit % and preferably in quantities
of from 6 to 15 wit Jo based on total diisocyanate, high
molecular weight polyol and chain extender mixture.
Finlike antioxidant and/or W -absorbers/light
stabilizers in quantities of from Owe to 3 wit % based
on total diisocyanate, high molecular weight pull and
chain extender mixture) may optionally be used.
Other relatively high molecular weight polyp
hydroxyl compounds, for example other polyethers or
polyesters or polycarbonates may by added to and mixed
with the polytetramethylene ether dill in a quantity of
up to 60 wit % and preferably in a quantity of less than
4Q wit %. Relatively high molecular weight polyols such
as these are described, for example, in Genuine Offend
legungsschrift 2,854,409. However, these other polyols
may have an adverse effect upon impact strength at low
temperatures so combination of such polyols with the
tetramethylene ether dill is not preferred. Other
relatively high molecular weight polyols which have
proven to be particularly advantageous when used in
combination with a ~e~ramethylene ether dill are
1,4-butane dill adipate and 1,4 butane Dylan dill
mixed adipate. The molecular weight of polyether
diol/polyester dill mixtures such as these is preferably
in the range from 1~00 to 2500.
The molar ratio of diocesan to te~ramethyl-
one ether dill and any other high molecular weight polyp
hydroxyl compound should amount to between Al and oily,
preferably 6:1 and 50:l.
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and more preferably to between 6,5:1 and 15:1. Ratios of from
I to 13:1 are particularly preferred. Such molar
ratios result in elastomers having a Shore-D hardness of
from 55 to 80 and preferably from 63 to I
Chain extending mixtures containing 1,4-butane
dill or 1,6-hexane dill as the principal component and
one or more (for example 2, 3 or 4) other dills having a
molecular weight in the range from 62 to 399 as co-chain
extenders (e.g. 1,6-hexane dill, 1,4-butane dill,
diethylene glycol, dipropylene glycol, tripropylene
glycol and hydroquinone Dow hydroxyethyl ether) may be
used as the chain-extending mixture It is preferred to
use a mixture of from 97 to 72 mole percent of
1,4-butane dill and from 3 to 28 mole percent of
1,6-hexane dill. A molar ratio of 94-87:6-13 is
particularly preferred. If 1,6-hexane dill is used as
the principal component and 1,4-butane dill as the
co-chain extender, the products obtained are less
elastic and do not have the same physical properties
obtained ho 1,4-butane dill is the principal chain
extender. At least 5 moles of chain extending mixtures
are used for each mole of polytetramethylene ether dill
to insure production of a rigid product. The co-chain
extender may also be introduced through the dozes-
natodiphenylmethane (MID). Thus, mixtures of dip or
tripropylene gawkily and MID which are liquid at room
temperature may be used in accordance with the invent
lion.
The graft rubbers used in the present invention
are preferably butadiene-based graft rubbers containing
from 30 to 50 wit % of butadiene in the elastomers
component and styrenes acrylonitrile and, optionally,
methacrylates as the graft monomer component. Mixtures
of the monomers styrenes and acrylonitrile in a ratio by
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weight of from 90:10 to 50:50 are preferably used as the
graft monomer component.
Where antioxidant and/or UV-absorbers/light
stabilizers are used in the present invention, they are
used in quantities of from 0.1 to 3 wit %, based on the
total quantity of all the components. It is preferred
to use mixtures of stabilizers.
Suitable antioxidant are known to those in
the art and are described in European Patent Applique-
lo lion 12,343. Preferred antioxidant are those base don starkly hindered phenols such as 2,6-di-t-butyl-
4-methylphenol and pentaerythritol-tetrakis-3-~3,5-di-
t-butyl-4-hydroxyphenyl)-propiona~e (Irganox 1010,
a product of Ciba-Geigy).
The W -absorbers used may be state-of-the-ar~
products, such as 2-(~'-hydroxyphenyl)-benztriazole
derivatives (e.g. those sold under the trademark
Tinuvin~ 326, 327, 328 or Tinuvin P (products of Cuba-
Geigy), hydroxybenzophenone derivatives and others.
Other examples of appropriate hydroxyphenyl benztriazole
derivatives are given in German Auslegeschrif~ 1J794,144
at columns 5-7. Particularly preferred UV-absorbers are
the cyanoacrylate derivatives described in German
Patentschrift 1,793,797, for example the compound
corresponding to the formula
SHEA
Cluck COOK
which is sold by Bayer A under the designation
W -absorber 340.
Examples of suitable fight stabilizers are the
bis-ester of sebacic acid with 4-hydroxy-2,2~6,6-tetra-
~10-~644
I ho
go
methylpiperidine (Tinuvin 770), but especially pent-
methyl derivatives represented by the formula
SHEA
O SHEA 3
C-O ON -SHEA
twill / Ho
--HAYAKAWA C - alkyd - (Cluck)
t-butyl \ I SHEA
C-O ~7~N-CH3
SHEA 3
The product sold under the trademark Tinuvin~l44 is one
such stabilizer. Oligomeric or polymeric, N-substituted
derivatives such as those corresponding to the formula
O O R I
R' - C (SHEA) x C O OH SHEA - OWE
SHEA Ho m
on which
x represents a number from 2 to lo
lo R represents hydrogen or a methyl group and
R' represents an alkyd or a cycloalkyl group
may also be used as light stabilizers. In the above-
given formula, when n represents 2, R represents
hydrogen and R' r presents a methyl group, the formula
lo represents the composition sold under the designation
Tinuvin~622.
Preferred light stabilizers are those based on
2,2,6,6-tetraalkyl piperidines. Light stabilizers based
on l,2,2,6,6-pentaalkyl pip~ridines are particularly
20 preferred.
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Where the light stabilizers used contain a
group of a finlike antioxidant (a starkly hindered
phenol group, such as 2,6-di~t-butylphenol) in addition
Jo a tetraalkyl or (preferably) pentaalkyl (for example
pentamethyl) group in the same molecule, as is the case
with the material designated Tenon, there is no
need for finlike antioxidant Jo be used.
The polyurethane reaction may ox course be
carried out in the presence of the usual catalysts,
release agents, antistatic agents, flame proofing agents,
fillers, glass fibers and pigments employed in this art.
Such materials are described in greater detail in, for
example, German Offenlegungsschriften 2,854,409 and
2,~20,501 and in Herman Patentschrift 3,329 9 775.
Suitable catalysts are, for example, tertiary
amine, organometallic compounds, particularly organic
tin, lead and titanium compounds such as tin
acetate, Tony) ethyl hexoate, dibutyl tin dilaurate
or lead acetate.
Suitable release agents include waxes, oils and
long-chain compounds containing carboxyl~ ester, aside,
urethane or urea groups such as those described in
German Offenlegungsschrift 2,~04,470,
The quantities of diocesan polytetra-
ethylene ether deluge other polyhydroxyl compounds and
chain extender dills used in the process o. the present
invention are generally selected in such a way that the
NCO:OH ratio of diisocyanate to OH-compounds amounts to
between 0.9 and 1.2 and, preferably, to between 1.01 and
1.08.
The polyurethane according to the invention
may be produced by forming a polyurethane in known
manner and by subsequently mixing ~co-extruding) the
polyurethane thus-formed with the graft rubber in
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another stage. It is preferred however to use a one-
shot procedure (described, for example, in German Offend
legungsschrift 2,814,409) in which the graft rubber is
initially introduced into a seli-cleaning twin-screw
kneader and the remaining polyurethane components added
thereto. Before it is introduced into the reactor, the
polyol may even have been reacted with the diisocyanate
to form an NCO-containing prepolymer. The elastomeric
materials may be further processed in the processing
10 machines normally used for thermoplasts, preferably
injection-molding machines.
A major advantage of the polyurethane elect-
mews of the present invention lies in the fact that they
do not show any troublesome separation of the hard
segments, ire no opalescent nickers effect. This
enables satisfactory dyeing or pigmenting of relatively
large injection moldings without any troublesome color
streaks. By contrast, when the graft rubber and chain
extender mixture are not used in the production of the
elastomers hard, thermoplastic polyurethane based on
polytetramethylene ether dills (molecular weight of the
polyether approximately 1500) showing impact resistance
a low temperatures and Shore-D hardness values ox from
63 to 72 show this troublesome nickers effect.
The new polyurethane elastomers of the present
invention show excellent impact strength at low
temperatures. In contrast to thermoplastic polyester
urethanes, they withstand the shattering test according
to DIN 53 443 (weight of 50 kg dropped from a height of
1 meter) at a temperature of -~0C. Very good breaking
elongation values are obtained in the impact/tensile
strength test. Elastomers according to the invention
based on polyte~ramethylene ether diol/polyester dill
show a breaking elongation of from 40 to 100~ whereas
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pure polytetramethylene ether dill products show a
breaking elongation of from 100 to more than 200%. The
antioxidant-UV absorber/light stabilizer combination
also has a favorable effect upon the breaking elongation
values particularly where the product is to be extruded
because thermal damage during extrusion is minimized.
The stiffening factor of the polyurethane
elastomers according to the invention measured at +20C
as against -20C amounts to approximately 1:1.7 to 1:2.5
(determined from the flexural stress at a given deflect
lion in accordance with DIN 53 445). Thermoplastic
polyester urethanes which do not correspond to the
invention show a distinctly higher stiffening factor of,
in general, from 1:2.5 to 1:3 or higher.
The new materials, particularly those based on
polytetramethylene other dill, have a density of from
1.10 to 1.17 Mg/m3. This has considerable advantages in
the case of ski boot shells. Compared with thermos
plastic polyester urethanes (density approximately 1.24
Mg/m3), density is reduced by around 10%.
The elasticity of the polyurethane elastomers
according to the invention is distinctly increased.
Whereas thermoplastic polyester urethanes show a
resilience of at most 40%, the thermoplastic polyether
polyurethane copolymers according to the invention show
increased resilience values of approximately 50~.
The polyurethane elastomers according to the
invention show high tear propagation resistance. This
is extremely important in the case of automobile or ski
boot components. I the mixture of chain extenders
according to the invention is replaced by a single chain
extender, however, tear propagation resistance is
distinctly reduced, even in cases where the graft rubber
is used.
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The invention is illustrated by the following
Examples in which quantities are expressed in parts by
weight, unless otherwise indicated.
EXAMPLES
Production of the thermoplastic PU-elastomers
according to the invention using a twin-screw kneader
A Werner & Pfleiderer ASK 53 V twin-screw
kneader (Werner & Pfleiderer, Stuttgart) with self-
cleaning screws and an approximately 20~ quota of knead-
in elements was used in each of these Examples. The processing section was made up of 12 separately hatable
housings and corresponded in length to approximately 20
times the screw diameter.
The function and mode of operation of the screw
kneader and of the kneading and conveying elements of
the screws etc. are described in detail in Werner
Pfleiderer Brochures and in Gunman Auslegeschrift
2,302,564.
The residence times of the reaction melt in the
Kneader were generally between 0.3 and 30 minutes and
preferably between 0.5 and 4 minutes. The temperature
of the screw housing was between about 60C and 300C
(approximately 80 to 280C in the feed zone; approxi-
mutely 100 to 300C in the middle of the extrude and
approximately 120 to 250C in the discharge zone). The
melt issuing from the Pxtruder was quenched and size-
reduced by known methods.
EXAMPLE 1
_
A thermoplastic polyurethane elastomers was
produced from the following starting materials in the
quantities (parts by weight) indicated:
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15.27 wit % of polytetramethylene ether dill,
molecular weight 1000
15.27 wit % of polytetram~thylene ether dill,
molecular weight 2000
a) 0.12 wit JO of 2,6-di-t-butyl-4-methylphenol
0.21 wit % of pentaerythritol-tetrakis-3-
(3,5 di-t-butyl-4-hydroxyphenyl)-
preappoint (Irganox-1010, a product
of Ciba-Geigy~
0.15 wit % of cyanoacrylic acid ester (US-
absorber 340, a product of Bayer AGO
b) f 12.22 wit % of 1,4-butane dill
1.37 wit % of 1,6-hexane dill
c) 45.21 wit of 4,4'-diisocyanatodiphenylme~hane
containing 2.5 wit of isomer
d) 0.15 wit of stearylamide and
e) 10.00 wit % of graft rubber (containing 50 wit % of
butadiene, 36 wit % of styrenes and 14
wit % acrylonitrile).
The NCO:OH-ratio was 1.06:1.
By means of a gear pump, component a) was
pumped from the storage vessel kept at 120C into
housing 2 of a twin-screw extrude. The dill mixture b)
was also introduced into housing 2 at room temperature
by means of a small piston pump. Component I was
pumped into housing 3 at a temperature of 60C by means
of a gear pump. Components d) and e) were introduced
into housing 1 in powder form by means of metering
screws.
The various housings of the kneader were
adjusted to the following temperatures:
Housing 1 2 3 7 9 11 12 he'd
Temperature 100 210 21~ 200 180 16Q 100 190 C
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Aster storage for 3 days, injection molding in
conventional injection molding machines and tempering of
the test specimens for 15 h at 110C, the thermoplastic
polyurethane elastomers obtained showed the mechanical
properties set out in Table 1. The solidification
behavior of the iniection~molded test specimens was
favorable and their green strength high. Coloring did
not produce any of the otherwise troublesome separation
streaks of the hard segment. The low-temperature impact
strength values were very good for a thermoplast as
rigid as this (impactltensile strength test: 158%
breaking elongation).
Table 1
Test DIN Standard Value Unit
Muddles 53 5Q4 31.6 Ma
Muddles 53 504 51.2 Ma
Tensile strength 53 504 53.3 Ma
Breaking elongation 53 504 310 %
Shore hardness A/D 53 505 aye (A/D)
Elasticity 53 512 51 %
Abrasion 53 516 19 mm3
Tear propagation resistance 53 515 170 Kim
Flexural stress at a given
deflection 23C 53 452 34.9 Ma
Flexural stress at a given
deflection -20C 53 452 69.7 Ma
Impact/tensile strength
test -10C 158 %
Density 53 ~79 1.11 Mg/m3
30 Shrinkage 0.5 %
At 1.11 Mg/m3, density was low, tear propaga-
lion resistance high. The stiffening factor, determined
from the flexural stress at a given deflection at ~23C
as against the value at -20C was 1:2.
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EXAMPLE 2
Relatively high molecular weight polyols made
up of a mixture of polytetramethylene ether dill and
1,4-butane diol/adipic acid polyester dill were used to
produce an elastomers The reaction components were as
follows:
14.53 wit % of polytetramethylene ether dill (OH
number 56.2)
14.53 wit % of 1,4-butane diolladipic acid
polyester dill (OH number 51.9)
a) 0.12 wit % of 2,6-di-t-butyl-4-methylphenol
0.20 wit % of Irganox-1010 products of
0.15 wit % of Tinuvin-622 J Ciba-Geigy
0.15 wit of 2,2'-6,6'-tetraisopropyl diphenyl
carbodiimide
13.08 wit % of Boone dill
1.45 wit % of 1,6-hexane dill
c) 45.64 wit % of 4l4'-diisocyanatodiphenylme~hane
d) 0.15 wit % of Carnauba wax
20 e) 10.00 wit % of the graft rubber used in Example 1.
The NCO:OH-ratio was 1.06:1.
Production and further processing were carried
out in the same way as in Example 1, The mechanical
properties are shown in Table 2.
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Table 2
Test DIN standard Value Unit
Muddles% 53 504 31.4 Ma
Modulus/300% 53 504 54.4 Ma
Tensile strength 53 504 54.9 Ma
Breaking elongation 53 504 301 %
Shore hardness A/D 53 505 98/69
Elasticity 53 512 49 %
lo Tear propagation resistance 53 515 197 Kim
Flexural stress at a given
deflection 23~C 53 452 38.7 Ma
Flexural stress at a given
deflection -20C 53 452 80.3 Ma
15 Impact/tensile strength
test -10C 52 %
Density 53 479 1.13 Mg/m3
This thermoplast was injection-molded to form
satisfactory moldings without any n~creous effect.
Tensile strength and tear propagation resistance were
both high. The low-temperature properties were good,
although not as good as in the preferred polyol range
according to the invention as indicated in Example l
(pure polytetramethylether dill).
EXAMPLES 3 to 11
Thermoplastic polyurethane according to the
invention were produced in the same manner as described
in Examples 1 and 2 using formulations 3 to if shown in
30 Table 3. Examples 3 to 10 represent variations of the
chain extenders and OX the type and quantity of graft
rubber, the ratio of the two chain extellders to one
another being varied in Examples 8 and 9.
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In Example 11, par of the polytetramethylene
ether dill was replaced by a polyester cliol ox rota-
lively high molecular weight.
The polyurethane elastomers described in
Examples 3 to 11 were thermoplastic ally processed in
standard commercially available injection molding
machines. They showed little, if any, separation of the
hard segment and, accordingly, were pigmented without
any problems. They showed high flexibility and high
impact strength at low temperatures for a thermoplastic
polyurethane. In addition, they were distinguished by
good initial elasticity during processing. Their
mechanical properties are shown in Table 4.
Examples 3 and 4 according to the invention are
characterized by a content of 5 wit % of graft rubber.
This reduced separation in the polyurethane, although
not as much as in Examples 1, 5 to 7 according to the
invention which are characterized by the preferred graft
rubber content of 10 wit %.
Slight separation of the hard segment was
evident, even where the content of co-chain extender was
low. This occurred, for example, in formulation 8
according to the invention which contained 4 mule
percent of 1 t 6-hexane dill (and 96 mole percent of
1,4-butane dill) and which was therefore outside the
preferred co-chain extender range of 6 to 13 mole
percent. If more than 13 mole percent of co-chain
extender were used (Example 9), the initial elasticity
of the moldings suffered slightly and the injection
cycle on the injection molding machine became longer.
The same effect also occurred with a relatively high
content of graft rubber (Example 10, I wit % of graft
rubber).
Example 11 according to the invention core-
spends to a "soft" variant of Example 2.
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EXAMPLES 12 to 16 (Comparison Examples)
Comparison Examples 12 to 16 are set out in
Table 5. The mechanical properties associated with
these Comparison Examples are shown in Table 6.
The test specimens produced from the thermos
plastic polyurethane of Example 12 without thy co-chain
extender showed clear signs of separation. In addition,
the mechanical properties, such as breaking elongation,
resilience, tear propagation resistance and low
lo temperature behavior, were poorer than in the comparable
Example 1 according to the invention.
Without the stabilizers according Jo the invent
lion, the test specimens associated with Example 13
showed poor low temperature flexibility compared with
Example 10 according to the invention due to the thermal
degradation of the polyol.
Comparison Example 14 contained only one chain
extender (1,6-hexane dill). The thermoplastic process-
in cycle was extremely long, resilience minimal and
shrinkage very high.
Without the graft rubber according to the
invention, the test specimens associated with Comparison
Examples 15 and 16 showed serious separation of the hard
segment. They could not be pigmented without streaking
and showed serious shrinkage of up to 3.2% coupled with
poor low-tempera~ure properties.
Moe
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Although the invention has been described in
detail in the foregoing for the purpose of illustration,
it is to be understood that such detail is solely for
that purpose and that variations can be made therein by
those skilled in the art without departing from the
spirit and scope of the invention except as it may be
limited by the claims.
Moe
