POLYURETHANNE DE CATEGORIE MOULABLE

MOLDING GRADE POLYURETHANE

Abrégé anglais

ABSTRACT OF DISCLOSURE
A relatively inexpensive injection molding-grade thermo-
plastic polyurethane elastomer is based on a modified polyether
diol--a modified polypropylene glycol (PPG) ether. This elastomer
has improved toughness, abrasion resistance and general good
mechanical properties. Its temperature insensitivity and low
temperature flexibility are exceptional. It is flexible to impact
at -50°F and stiff enough at 250°F to allow painting without dis-
tortion. Of special interest is the fact that this polymer is
injection moldable and possesses properties adequate for exterior
automobile trim components and the like.
The polyether polyol is a poly (oxyalkylene) diol
reacted with a 50/50 styrene/acrylonitrile monomer mixture in the
presence of a free radical catalyst. While a one shot method of
preparation can be used, the capped polyol is preferably reacted
with an aromatic diisocyanate to form a prepolymer in a known
manner. The prepolymer is thereafter reacted with a C2 to C6
alkane diol, pan cast, cured and aged, followed by grinding to
give the molding composition.
It is preferred to blend the polyol with a minor amount
of a poly alkane ether diol prior to forming the prepolymer as
this enhances the moldability and properties of the thermoplastic
polyurethane.

Revendications

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An injection molding-grade thermoplastic polyurethane having
good low temperature properties made by reacting the following:

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wherein:
said grafted polyol is a 2000 to 5000 molecular weight copolymer
of:
(a) 70 to 90 weight percent of a 1000 to 4000 molecular weight
poly (oxy C1-C4 alkene)diol, reacted by a free radical polymerization with
(b) 10 to 30 weight percent of a monomer mixture of 1 part by
weight of a vinylaromatic and 0.1 to 9 parts of an olefinic C2-C6-nitrile,
and said polyalkylane ether diol has a molecular weight in the range of
500 to 2500.

2. The polyurethane according to claim 1 wherein:
said polyalkane ether diol is a 650 to 1500 molecular weight
polytetramethylene ether glycol,
said aromatic polyisocyanate is MDI, and
said C2-C6 alkane diol is 1, 4 butanediol.

3. The polyurethane according to claim 1 wherein said polyol
polyalkane ether diol and aromatic polyisocyanate are first reacted to
form a prepolymer having a free NCO in the range of 8 to 12, followed by
addition of said C2-C6 alkane diol.


4. The polyurethane of claim 3 wherein the mixture is cast as a
slab at a temperature above 210°F, cured for a few days and ground to size
for injection molding.

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5. An automobile exterior trim component made from the polyurethane
of claim 1.

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Description

1~3~
Thermoplastic polyurethanes llave been prepared from polyether
and polyester polyols. The polyester polymers are relatively e~pensive
and have good to excellent physical properties overall but such polymers
have generally poor humidity resistance and low tempe~ature properties.
Injection moldable polyether-based polymers have been based on the PTMEG
polyols which are expensive. Conventional PPG ether based poly~ers are
not amendable to injection molding and have physical properties unacceptable
for use in demanding application such as automobile exterior trim parts.
It has been found that a polyether diol-based urethane elastomer
of injection molding quality and with good to excellent overall physical
properties can be prepared from a polyether diol which has been reacted with
a 50/50 styrene/acrylonitrile monomer misture by a free radical polymeri-
zation. See U.S. Patent Nos. 3,304,273; 3,383,351 and 3,418,354; and
Belgian Patent No. 788,115. ~
According to the present invention, there is provided an in- ~ -
jection molding-grade thermoplastic polyurethane having good low temperature ~ -
properties made by reacting the following:

Parts by weight
Grafted polyol 100
poly alkane ether diol 2 to 70
Aromatic polyisocyanate 40 to 100
- C2-C6 alkane diol 10 to 40 ~
wherein said grafted polyol is a 2000 to 5000 molecular weight copolymer --
of 70 to 90 weight percent of a 1000 to 4000 molecular weight poly
~oxy Cl-C4 alkene)diol, reacted by a free radical polymerization with
10 to 30 weight percent of a monomer mixture of 1 part by weight of a
vinylaromatic and 0.1 to 9 parts of an olefinic C2-C6 nitrile, and said
polyalkylane ether diol has a molecular weight in the range of 500 to
2500.
This modified polyether polyol is preferably reacted in the usual
manner with an aromatic di socyanate to prepare a prepolymer having a free
NCO content in the range of 7 to 15%.
The modified polyether polyol is admixed with a minor amount of

a poly alkane ether diol.
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The prepolylner is thareafter reacted with a short chain alkane
diol and cast in slab form or extruded ancL pelletized. After curing and
aging for a few days the resulting elastomer is ground to prepare the
molding composition. Materials such as colorants and stabilizers may
be blended into the ground elastomer to give a complete molding composition.
The molding composition can be molded in any conventional
manner such as injection molding to 400 to 500F in a plunger-type machine.
The molded product is generally a tough and abrasion resistant and,
somewhat surprisingly, has superior




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humidity and aging resistance, and exceptional low temperature
flexibility.
For example, an elastomer o~ this invention having a
flex modulus (ASTMD-790) of 15000 psi will consistently pass a
-20F painted Dart Impact (FBMS-2-23) and cold flex tes-t (FBTM- ~ -
58-5).
The following table gives the ingredients and the pre- -
ferred proportions that can be used to prepare the present
polyurethane:
Modified polyol, PBW* (with ether diol, i~ used) 100
Aromatic diisocyanate, to FNC0 of: 4 to 15
C2-C6 alkane diol, PBW 5 to 30
*parts by weight
The modified polyol is a 2000 to 5000 molecular weight `~
reaction product of:
a) 70 to 90 weight percent of a 1000 to ~000~ pre~erably
2400 to 3200, molecular weight poly (oxy Cl-C4 alkene) diol,
reacted by a ~ree radical polymerization with
b) 10 to 30 weight percent of a monomer mixture of 1
part by weight of a vinylaromatic and, 0.1 to 9, pre~erably 0~3 s
to 3 parts~ of an olefinic C2-G6 nitrile. ~;
The poly (oxy Cl-C4 alkene) diol is preferably the
reaction product of propylene glycol with first propylene oxide
and then ethylene oxide the ratio of the two oxides being 3-5 parts
o~ the propylene to one o~ the ethylene.
The polyalkane ether diol has a molecular weight in the
ranga of 500 to 2500, preferably 650 to 1500. While quantities
as low as 2 parts by weight will have an observable and desirable
effect on the final polymer and quantities as high as 70 parts by
weight will produce a useful thermop~astLc polymer, for demanding
automotive appIications the physical properties given by 5-50
parts by weight of the poly alkene ether diol are preferred.

-513/518
The aromatic polyisocyanate is any of the co~nercially
used ones and is preferably selected from the group consisting of
4, 4' -diphenylmethane diisocyanate (~I); tolylene diisocyanate
(TDI); 1, 5 naphthalene diisocyanate; dianisidine diisocyanate
(DADI); 3, 3' -demethyl 4~ 4' -bipheneyl diisocyanate (XDI).
The straight-chain C2 C6 alkane diol is preferably end-
terminated with the hydroxy groups.
The prepolymer process is quite straightforward but if
the following procedure is not ~ollowed with reasonable care a
thermoset and sometimes microcellular elastomer may result. The
index of the mixture, the reaction temperatures, and water con-
tents of the ingredients should be closely controlled, as is
known.
The polyol is degassed and heated, for example, to 235F
and the aromatic diisocyanate is added with the mixture being al-
lowed to exotherm, for example, to 250F. It is then degassed and
the free NC0 content obtained. Preferably the free NC0 is in the
range o~ 8 to 12. In the example it was 8.35. The prepolymer can
be stored in readiness for the next step.
The short chain diol such as 1, )~ -butanediol (BD0), is
separately prepared, and dried if necessary, and mixed with the
wax release agent, if a wax is to be used. The diol mixture and
the prepolymer are preferably brought together in a casting ma-
chine in a continuous manner at about 230F. A~ter thorough
mixing o~ the two ingredients, the mixture is cast out in a casting
pan, which is preferably maintained at a temperature above 210F.
The cast layer can for example be 1" thick and a~ter being allowed
to set 4 or 5 minutes, can be cut into 3'1 x 3u chunks~ removed and
placed in containers. A~ter aging ~or a week or so the elastomer
can be ground to the size desired for molding and mixed with
whatever additional materîals may be desired. Alternatively, the
mixture of diol and prepolymer can be extruded and pelletized to



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r-513/51
give a moldable compositlon.
It has also been ~ound that by the addition of catalyst
to the mlxture~ the reactiorls can be speeded up so that poly-
urethane can be directly cast into a~ mold to product a molded
product. The catalyst used can be o-f` the dibutyl-tin~dilaurate,
mercaptide or other known tyoe and the casting temperature can be
substantially lower~ say 105F, with the mold being at 1~0 180F.
The following gives an example o~ the invention:
EXAMPLE
Equivalent PBW
Modified polyol 1.0 100
~DI 5 35.68 ~ -
BD0 L~.02 12.&9
Wax, phr. 0.2
Specific Gravity 1.15 -
Hardness, Shore D (5 secs) 25
Tensile Strength (orig.) 1169 -
after 70 hrs. 212F (+2.6%)1199
- after 7 da/175F/100%RH (~1.5%)1187
Elongation (orig.) 253
- after 70 hrs./212F (-28.8~)180%
after 7 da/175F~100~ORH (-26.1~)187
Tear Stréngth (Die C) 210
Stiffness
@72F 0.5 in lbs. (orig.) 58~9
@-20F 3.0 in lbs. 9855
after 70 hrs/212F 0.5 in/lbs. (~14.3%)6650
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160F 0.25 in lbs. 4839
Tensile set @200% elongation 61.0~o
30 Dart impact-flex @-20F (Fisher Body Test)
as received (no fracture) Penetrate no shatter
after 70 hrs/212F (no fracture) Pass
Stretch test @250F (4~ max.) No change


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r-513/518
The in-teresting point made by the above table is that
while the -20F stiffness value of 9855 psi is outstanding there
is not an unacceptable loss in physical properties at the higher
temperat~res. For example, the 1~0F stiffness value is 4839 psi.
DRAWING
The drawing attached to and forming a part o~ -this
invention is a schematic illustration of the process of this
invention. The elastomer can be prepared by the one shot or
prepolymer procedure, the latter being illustrated.
The drawing also illustrates the use of a poly alkane
ether diol, PTMEG (polytetramethylene ether glycol)~ a pre~erred
embodiment o~ the invention. In this embodiment, the follcwing
proportions are used:
Parts by Weight
~odi~ied polyol 100
Poly alkane ether diol 5-50
Aromatic diisocyanate 40 to 100
C2-C6 alkane diol 10 to 40


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The thermoplastic urethane o~ the prePerred embodiment
have -the following properties:
Test Method `
Specific Gravity 1 14t-0.02 ASTMD-792
Tensile Strength, psi 2500 ~mi.nimum) AST~-412
Elongation, ~ 400 (minimurn) ASTMD-412
Tear Strength~ pi 400 (minimum) ASTMD-624 -~
Hardness3 Shore D~ 5 secO 41+ 3 ASTMD-2240
Modulus of Elasticity, psi . -
(Flexual Modulus) 11,000 (minimum) AS~MD-790
Tensile, set, % (at 200~ ;
Elongation) 70 (maximum) ASTM~-412
1/2" Mandrel Bend, -20F, .
Painted TM-58-5 ;
Durethane 100* Pass
Durethane 200* Pass
*Trademarks o~ PPG Industries, One Gatewa~ Center~ Pittsburgh,
Pennsylvania 15222. :
Aged Properties .- -. :
Heat Aging: 70 hrs/212F, -.
; % change ..
Tensile strength -15(maximum) ASTMD-412
,; : ,.
Elongation -20(maximum) ASTMD-412 .
Dart I~pact Pass FBMS 2-23 .~
Humidity aging: 7 days/ :
175F/100% R H , `
% change
Tensile strength -15 (maximum) ASTMD-412 ~:
Elongati.on -15 (maximum ASTMD-~12
The prepolymer process is quite straightforward but if
the ~ollowing procedure is not ~ollowed with reasonable care a

thermoset and sometimes microcellular elastomer may result. The

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~ -513/51~
index of the mixture, the re~ction temperatures, and water contents
of the in$redients should be closely con-trolled, as i9 known.
With reference to the drawing, the two polyols, the
modified polyol via line ll and the poly alkene ether diol via
line 13, are brought together in a reactor lO degassed and heated,
for example, to 235F.
The aromatic diisocyanate is then added to the reactor
via line 12 and the mixture is allowed to exotherm, for example,
to 250F. It is then degassed and the free NC0 content obtained.
Preferably the free NC0 is in the range of 4 to 15, more preferably
8 to 12. In the following examples, A & B, it was 11.27 and 9.55
respectively. The prepolymer can then be stored in readiness ~or
the next step.
The short chain diol such as 1,4 -butanediol (BD0)~ is
separately prepared, and dried if necessary, and mixed with the
wax release agent, if wax is to be used. The diol mixture and the
prepolymer~ by lines 15 and 14, respectively, are brou~ht together
in a casting machine 20 in a continuous manner at about 230F.
After thorough mixing of the two ingredients, the mixture is cast
out via iine 16 into a casting pan, 30 which is preferably main~
tained at a temperature above 210F. The cast layer can for ex- ~ -
ample be l" thick and, after being allowed to set 4 to 5 minutes,
can be cut into 3" x 3" chunks, removed and placed in containers~ `
as indicated by line 17 and block 40. A~ter having been aged at
40 ~or a weeX or so the elas~omer can be ground to the size de
sired for molding and mixed with whatever additional materials may
be desired. Alternatively, the mixture from line 16 can be ex-
truded and pelletized to give a moldable composition.
It has also been found that by the addition of catalyst
to the mixture in the casting machine 20, the reactions can be
speeded up so that polyurethane can be directly cast into a mold
to producb a molded product. The catalysts used can be of the



~--513/51~ ~4~ ~ 7
dibutyl-tin-dilaurate, mercaptide or other known type and the
casting temperature can be substantially lower~ say 105F, with
the mold being at 160-180F.
The ~ollowing table gives e:xamples of the invention
prepared according to the illustrated process.




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EX~IP1ES
A B
E PBW E PBW
Modified polyol 0.5 100 0;75 100
PT~EG 0.5 28.24 0.25 9.42
~I 6.o 85.64 6.o 57.o8
BD0 5.02 26.20 5.02 17.4
Wax ~3 o.63 0.3 -55
Specific Gravity 1.15 1.14
Hardness, Shore D (5 secs) 45 40
Tensile Strength (orig.) 2995 2624
after 70 hrs/212F (-5.0%)2846 (-10.5~)2348
after 7 da/175F/lOO~RH (-11.1%) (-13~3~)2276 -
Elongation ~orig.) 537% 503%
after 70 hrs/212aF (_13.8%)463% (-14.5~)430%
a~ter 7 da/175F/lOO~RH(-8.2~)493% (-4.6%)480% `~
Tear Strength (Die C) 507 416
Stiffness
@72F 0.5 in lbs. (orig.)Exceeded scale limit 9855
@-20F 3.0 in lbs. 35041 20787 ;
after 70 hrs./212F 0.5 in/lbs Exceeded scale limit (~2.0%)10060
@160F 0.25 in lbs.Exceeded scale limit 5595
Tensile set @200% elongation 62.5% 53.1~o
Dart impact-flex @-20F ~FB)
as received (no fracture) pass pass
after 70 hrs/212F (no fracture) pass pass
Stretch test ~250F (4~0 max.) No change 1.6
In the table:
E=number of equivalents
PBW=parts by weight
FB= a Fisher Body speci~ication



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The modified polyol w~s Union Carbide Company's NIAX
D-432, a polymer of about 4000 molecular weigh~ made by reacting
80 weight percent o a 2800 molecular ueight poly (oxyalkylene)
diol with 20 ~eight percent of a 50/50 (by weigh~) styren0/
acrylonitrile monomer mixture in the presence of a free radical
catalyst (a~obisisobutronitrile), as described in Union Carbide's
Belgian Patent N~. 788,115. The poly ~oxyalkylene) diol is made
by first reacting propylene glyeol with propylene oxide and then
subsequently with ethylene oxide so that the chains tarminate in
ethylene oxide units. The proportions are such that there are
a~out 4.88 propylene oxide units for each ethylene oxide unit.
When the poly (oxyalkylene) diol is reacted with the styrene/
.
acrylonitrile monomer mixture, it appears that some of the two
monomers copolymeri~e and add to the diol and some simply - ~-
copolymerize ~ithout attaching to the diol but belng intimately ~ -
intermixed therewith.
The poly alkylene ether diol was a polytetramethylene
ether glycolJ ~PTMEG)~ Polymeg 1000, sold by the Quaker Oats
Company~ Chemical Division, Merchandise Mart Plaza, Chicago, ;
Illinois 60545. It has a molecular weight of 1000. E. I. duPont
de Nemours Polyglycol 1000 can also be used.
The "MDI" was 4, 4' diph0nylmethane diisocyanate.
The "BDO" was 1, 4-butanediol.
The wax was an ethelyne-bis-steaTamide, Advawax 280F,
sold by Cincinnati Milacron Chemical Inc., Reading, Ohio 45215.
Examples of automobile parts that have been made using -~
this thermpolastic urethane and tested with satisfactory results
are: General Motors 1974: tl) Riviera Center Sight Shield, Part
No. 9694424-439 and ~2) Oldsmobile l'B" Corner Sight Shield, Part
No. 9694662-693.

* Trade Mark

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