Thermoplastic polyurethane prepared from a poly-1,2-propylene ether glycol, a low molecular weight glycol and 2,4-tolylene diisocyanate

A thermoplastic, linear and segmented poly-1,2-propylene ether urethane having a Tg of below about -30.degree. C. for the poly-1,2-propylene ether segments is made by reacting poly-1,2-propylene glycol having a high molecular weight; ethylene glycol, 2,3-butane diol or neopentyl glycol or mixture thereof; and 2,4-tolylene diisocyanate containing from about 55 to 100% by weight of the 2,4-isomer with the balance being the 2,6-isomer.

This invention relates to thermoplastic, linear and segmented polypropylene 
ether urethanes. 
BACKGROUND 
During the last two decades, thermoplastic polyurethanes have gained 
increasing attention. The materials combine the excellent properties of 
urethanes with the processing convenience of thermoplastic materials. 
Thermoplastic polyurethanes are generally of the (AB).sub.n type, where 
flexible polyester or polyether segments (A) alternate with high melting 
polyurethane blocks (B). 
Polyesterglycols (e.g., poly-1,4-butyleneadipate or polycaprolactone) or 
polytetramethylene ether glycols are commonly used as the flexible 
segments, while low molecular weight glycols (e.g., 1,4-butanediol or 
ethylene glycol) are most often chosen for the in situ formation of the 
rigid blocks of the alternating copolymer. A great variety of 
diisocyanates can be utilized in the preparation of these polymers, 
however, for reasons of commercial availability and polymer performance, 
4,4'-diphenyl methane diisocyanate (MDI) has been widely preferred. 
Polyesterurethanes have the disadvantage of inherent hydrolytic 
sensitivity, while polytetrahydrofuran type materials are of relatively 
high cost. 
Linear urethane polymers of the above type based on low cost polypropylene 
ether glycols have not been prepared with satisfactory properties due to 
the fact that about the maximum molecular weight of commercially available 
polypropylene glycols made with alkali catalysts is about 3,000 for 
average functionality approaching 2. Even at this 3,000 M.W. limit for the 
polypropylene ether glycol the loss in end group functionality (--OH 
groups) becomes too large, causing low weights in the resulting linear 
polyurethane. 
Accordingly, it is an object of the present invention to overcome the 
difficulties alluded to hereinabove and provide a method for making a 
thermoplastic linear polyurethane from polypropylene ether glycol having 
improved properties. These and other objects and advantages of the present 
invention will become more apparent to those skilled in the art from the 
following detailed description and working examples. 
SUMMARY OF THE INVENTION 
According to the present invention it has been discovered that 
thermoplastic, linear and segmented polyurethanes can be made by reacting 
poly-1,2-propylene ether glycol having an average molecular weight of from 
3,300 to 14,000; ethylene glycol, 2,3-butanediol and/or neopentyl glycol; 
and 2,4-tolylene diisocyanate or a mixture containing at least about 55% 
by weight of 2,4-tolylene diisocyanate and the balance 2,6-tolylene 
diisocyanate in an equivalent ratio of the diisocyanate to the glycols of 
from about 0.98:1 to 1.08:1, the weight ratio of the urethane segments 
(tolylene diisocyanate plus ethylene glycol, 2,3-butanediol and/or 
neopentyl glycol) to poly-1,2-propylene ether segments being from about 
0.4:1.0 to 1.5:1.0. The resulting polyurethanes exhibit a modulus at 100% 
elongation of at least about 400 p.s.i. and show for their polypropylene 
ether segments glass transition temperatures of below about -30.degree. C. 
The poly-1,2-propylene ether glycol is made by reacting propylene oxide 
with an aliphatic low molecular weight glycol, e.g., diol, telogen in the 
presence of a catalyst of the double metal cyanide complex class. 
DISCUSSION OF DETAILS AND PREFERRED EMBODIMENTS 
The poly-1,2-propylene ether glycol used in the practice of the present 
invention is made by the polymerization (or telomerization) of propylene 
oxide in the presence of a telogen, a low molecular weight aliphatic 
glycol, using as a polymerization or telomerization catalyst a double 
metal cyanide complex compound according to the teaching of U.S. Pat. No. 
3,829,505. Examples of low molecular weight glycols to use as telogens are 
aliphatic glycols like glycol; 1,2-propylene glycol; 1,3-propylene glycol; 
1,4-butane diol; 2,3-butanediol; diethylene glycol; dipropylene glycol; 
1,5-pentanediol; neopentyl glycol; 1,6-hexane diol and the like and 
mixtures of the same. The polymerization may be conducted in bulk or 
solvent. Solvent may be required when the propylene oxide and telogen are 
not miscible or soluble in order to facilitate polymerization. 
Polymerization is conducted to obtain an average molecular weight of from 
3,300 to 14,000. A feature of the use of the double metal cyanide complex 
catalyst is the ability to get high molecular weights with propylene oxide 
in contrast to the limiting value of 3,000 when alkali catalysts are used. 
Furthermore, with the double metal cyanide complex catalyst higher 
functionality is obtained or maintained as compared to alkali catalysts. 
In other words, alkali catalysts show a limit in molecular weight with a 
substantial loss in functionality at the upper limiting molecular weights. 
On the other hand, using the double metal cyanide complex catalyst one is 
able to obtain functionality of about 2 at even very high molecular 
weights. 
Catalysts of the double-metal cyanide complex class are well known. Methods 
for making these catalysts are disclosed by U.S. Pat. Nos. 3,427,256; 
3,427,334 and 3,427,335. Methods for making polyalkylene ether glycols 
with these double metal cyanide catalysts having a high molecular weight, 
having a high hydroxyl functionality and having low unsaturation are shown 
by U.S. Pat. Nos. 3,829,505 and 3,941,849 (a division). 
Ethylene glycol, 2,3-butanediol and/or neopentyl glycol used in the 
practice of the present invention are well known compounds. 
Likewise, 2,4-tolylene diisocyanate is well known as well as mixtures of 
80% by weight of 2,4-tolylene diisocyanate and 20% by weight of 
2,6-tolylene diisocyanate (known as 80/20 2,4-/2,6-TDI). Also known is 
another mixture of 65/35 2,4-/2,6- tolylene diisocyanate. The diisocyanate 
is used in the practice of the invention in a range of from about 55 to 
100% by weight of 2,4-tolylene diisocyanate with the balance being 
2,6-tolylene diisocyanate. 
The polyurethane may be made by the prepolymer process or the one-shot 
process in bulk or in the presence of a solvent. Catalysts such as tin 
catalysts may be used as well as antioxidants or other antidegradants. The 
urethane polymer may be prepared under nitrogen or under conditions to 
exclude water for best results. For more information on making 
polyurethanes see "Polyurethanes Chemistry and Technology," Part II, 
Technology, Saunders and Frisch, Interscience Publishers, a division of 
John Wiley & Sons, New York, 1964. 
The thermoplastic polyether urethanes made by the process of the present 
invention are soluble and can be cast from solution or can be processed on 
plastic processing equipment. Alternatively, these polyurethanes can be 
formed in a mold by a casting or injection molding process directly from 
their liquid precursors. They are useful for the production of decorative 
and protective coatings, shoe soles and heels, sight shields for 
automobiles, energy absorbing bumpers and other automotive items. They may 
be mixed with the usual compounding ingredients like fillers and pigments 
and so forth. 
The following examples will serve to illustrate the present invention with 
more particularity to those skilled in the art. Parts are parts by weight 
unless otherwise indicated.

EXAMPLE I 
A thermoplastic polyether urethane was prepared by reacting together in 500 
g. of dimethyl formamide, at 50.degree. C., 59 g. of poly-1,2-propylene 
ether glycol (A) having an average molecular weight of 5210, 31.2 g. of 
80/20% by weight 2,4-/2,6-tolylene diisocyanate and 9.92 g. of ethanediol 
in the presence of 3 g. of stannous octoate as a catalyst and 1 g. of 
"Ionol" (antioxidant, Shell Chem. Co., 2,6-di-tertiary butyl-4-methyl 
phenol) until a film cast on a NaCl crystal showed no absorption at 4.4 
microns for free-NCO. The resulting polymer was precipitated in water and 
washed free of dimethyl formamide in a Waring blender. The resulting 
polyurethane had an inherent viscosity of 0.7 dl/g. in dimethyl formamide. 
A pressed sheet had 744 p.s.i. modulus (100% elongation), 1667 p.s.i. 
tensile strength, 310% elongation, Graves tear strength of 219 pounds per 
linear inch and a dynamic modulus transition temperature or, Tg*, of 
-48.degree. C. for the polypropylene ether segments of the urethane 
polymer. The weight ratio of urethane segments (NCO+low M.W. diol) to 
polyether segments (high M.W. diol) was 0.70:1. 
EXAMPLE II 
The procedure of Example I was repeated except that 1,4-dioxane was used as 
a solvent. The ingredients of the polyurethane were prepared from 59.2 g. 
of poly-1,2-propylene ether glycol (A) having an av. M.W. of 3360, 10.1 g. 
of ethane diol and 33 g. of 80/20% by weight 2,4l -/2,6-tolylene 
diisocyanate. The resulting polyether urethane had an inherent viscosity 
(in dimethyl formamide) of 0.4 dl/g., a 100% modulus of 830, a tensile 
strength of 3090 p.s.i., an elongation of 770%, a Graves tear strength of 
426 pounds per linear inch and a glass transition temperature (Tg*) of 
-33.degree. C. for the polypropylene ether segments of the polyurethane. 
In the resulting polyurethane the weight ratio of urethane segments 
(NCO+low M.W. diol) to polyether segments (high M.W. diol) was 0.73:1. 
EXAMPLE III 
The procedure of Example I was repeated except that 1,4-dioxane was used as 
a solvent. The ingredients of the polyurethane were prepared from 59 g. of 
poly-1,2-propylene ether glycol (A) having an av. M.W. of 2450, 9.2 g. of 
ethane diol and 33 g. of 80/20% by weight 2,4-/2,6-tolylene diisocyanate. 
The resulting polyether urethane had an inherent viscosity (in dimethyl 
formamide) of 0.35 dl/g., a 100% modulus of 460, a tensile strength of 
2180 p.s.i., an elongation of 800%, a Graves tear strength of 305 pounds 
per linear inch and a glass transition temperature (Tg*) of -6.degree. C. 
for the polypropylene ether segments of the polyurethane. In the resulting 
polyurethane, the weight ratio of urethane segments (NCO+low M.W. diol) to 
polyether segment was 0.71:1. 
EXAMPLE IV 
The method of this example was the same as that of Example II using 50. g. 
of poly-1,2-propylene ether glycol (A) of av. M.W. 5210, 13.9 g. 
2,3-butanediol and 30.7 g. 80/20% by weight 2,4-/2,6-tolylene diisocyanate 
in the presence of 5 g. of stannous octoate and 1.0 g. of "Ionol." The 
resulting polymer had an inherent viscosity in dimethyl formamide of 0.4 
dl/g and a dynamic modulus transition temperature or Tg* of -43.degree. C. 
for the polypropylene ether segments of the polyurethane. In the resulting 
polyurethane the weight ratio of urethane segments (NCO+low M.W. diol) to 
polyether segments was 0.89:1. The polyurethane had a 100% modulus of 749 
p.s.i. 
A polyurethane was prepared in the same way from the same 5210 M.W. 
polypropylene ether glycol (50 g.), 2,3-butanediol (10.8 g.) and MDI (34 
g.). The resulting polyurethane had a 100% modulus of 764 p.s.i., an 
inherent viscosity of 0.55 dl/g. but a Tg* of +33.degree. C. The weight 
ratio of urethane segments to polypropylene ether segments was 0.9:1. 
EXAMPLE V 
A polyurethane polymer was prepared according to the method of Example II 
from 50 g. of poly-1,2-propylene ether glycol (A) having an av. M.W. of 
5210, 15 g. of neopentyl glycol and 29 g. of 80/20% by weight 
2,4-/2,6-tolylene diisocyanate in the presence of 5 g. of stannous 
octoate. The resulting polymer exhibited a glass transition temperature, 
Tg*, of -53.degree. C. for the polypropylene ether segments of the 
polyurethane, 100% modulus of 432 p.s.i. and tensile strength of 569 
p.s.i. The weight ratio of urethane segments to polypropylene ether 
segments was 0.88:1. 
The polyurethane was prepared in the same way from the same 5210 M.W. 
polypropylene ether glycol (50 g.), 13.9 g. of neopentyl glycol and 35.2 
g. of MDI. The resulting polymer had a 100% modulus of 642 p.s.i., an 
inherent viscosity of 0.6 dl/g. but a Tg* of 15.degree. C. The weight 
ratio of urethane segments to polypropylene ether segments was 0.98:1. 
EXAMPLE VI 
Poly-1,2-propylene ether glycol (B) of M.W. 1000 ("Niax" PPG 1025, Union 
Carbide) was dried on a Flash Evaporator at 85.degree. C./2 mm Hg. for one 
hour. The vacuum was released with nitrogen and 80/20% by weight 2,4-/2,6- 
TDI (33.8 g.) and 1,4-dioxane (100 g.) were added to the hot polyol. 
Rotation of the reaction flask was continued in the temperature bath 
(85.degree. C.) under atmospheric pressure for two hours. Ninety-five 
percent of this prepolymer was then added to a solution of 7.5 g. ethylene 
glycol and 5 g. of stannous octoate catalyst in 500 ml dimethyl formamide 
in a stirred glass reactor under N.sub.2. After one hour at 70.degree. C., 
the remainder of the prepolymer was added in small increments over 24 
hours until the solution assumed a viscous oily appearance. The polymer 
obtained after evaporation of the solvent had a glass transition 
temperature, Tg*, of +32.degree. C. for the polypropylene ether segments 
of the polyurethane. The modulus at 100% elongation was 330 p.s.i. The 
weight ratio of the urethane segments to the polyether segments was 
0.71:1. 
The following Table I briefly summarizes the above Examples I to VI: 
TABLE I 
______________________________________ 
Av. M.W. of 
Ex- 100% Low Polypropylene 
Wt. Ratio 
am- Modulus, Tg*, M.W. Ether Urethane/ 
ple p.s.i. .degree.C. 
Glycol Glycol Polyether# 
______________________________________ 
I 744 -48 Ethylene 
5,210 0.70:1 
II 830 -33 " 3,360 0.73:1 
III 460 -6 " 2,450 0.71:1 
IV 749 -43 2,3-butane 
5,210 0.89:1 
764 +33 2,3-butane 
5,210 0.9:1## 
V 432 -53 Neopentyl 
5,210 0.88:1 
642 +15 Neopentyl 
5,210 0.98:1## 
VI 330 +32 Ethylene 
1,000 0.71:1 
______________________________________ 
EXAMPLE VII 
Poly-1,2-propylene ether glycol (A) and an antioxidant were dried in a 
flask on a Flash Evaporator at 100.degree. C. and at 2 mm. Hg. for one 
hour. The vacuum was released with nitrogen, and the glycol was allowed to 
cool to about 60.degree. C. before adding tolylene diisocyanate and a 
small amount of dibutyl tin dilaurate catalyst with mixing. Rotation of 
the flask was continued in a temperature bath (100.degree. C.) under 
reduced pressure for two hours, and then the flask contents were allowed 
to cool under nitrogen. The resulting prepolymer and dry ethylene glycol 
were homogenized by stirring for approximately one minute before 
additional dibutyl tin dilaurate catalyst was added. After stirring, the 
mixture was evacuated to break any bubbles and poured into a gravity, 
tensile sheet mold at about 100.degree. C. The mold consisted of "Teflon" 
(fluorocarbon resin, duPont) coated 3/8" steel side plates with 1/8" 
spacers of "Teflon" to give a mold cavity of 8".times.8".times.1/8". After 
curing overnight at 110.degree. C., the sample was removed from the mold 
and postcured for about six hours at the same temperature. Several 
polypropylene ether urethanes were prepared in this fashion. The 
ingredients of the polypropylene ether urethanes, and the results obtained 
for the polyurethanes are shown in Table II below: 
TABLE II 
__________________________________________________________________________ 
Poly- 
Average ure- 
Poly-1,2- 
molecular thane 
80/20 
Ethyl- 
propylene 
weight of 
Wt. ratio Inh. 
100% Elon- Shore 
2,4-/2,6- 
ene ether gly- 
polypropy- 
urethane Visc., 
Modu- 
Tensile 
ga- Tear, 
A 
TD.sub.I 
glycol, 
col (A), 
lene ether 
to poly- 
Tg*, 
DMF, 
lus, 
strength, 
tion, 
Graves, 
Hard- 
Run 
grams 
grams 
grams glycol (A) 
ether # 
.degree.C. 
dl/g. 
p.s.i. 
p.s.i. 
% p/l.i. 
ness 
__________________________________________________________________________ 
A 26.8 8.05 
103.2 4,600 0.335:1 
-60 0.64 
200 1070 1010 
278 56 
B 37.5 12.1 
91.6 4,600 0.54:1 -61 0.74 
400 2550 920 353 65 
C 50.7 16.6 
98.4 4,600 0.70:1 -60.5 
0.41 
600 2740 800 338 73 
D 68.6 23.5 
60.8 4,600 1.50:1 -60 0.41 
1120 
1610 160 153 82 
E 33.7 10.8 
65.7 11,800 0.70:1 -54 0.73 
1173 
2720 290 333 62 
__________________________________________________________________________ 
Notes for the above examples: 
(A) Poly1,2-propylene ether glycol prepared according to the teachings o 
U.S. Pat. No. 3,829,505 from propylene oxide and a glycol using a 
doublemetal cyanide complex class catalyst. 
(B) Commercial polypropylene ether glycol. 
* The glass transition temperatures of the poly1,2-propylene ether 
segments of the polyurethanes were obtained from the maximum of the 
damping temperature curve determined on a vibrating beam dynamic testing 
apparatus. 
# - Weight ratio of urethane segments (TDI or MDI + low M.W. glycol) to 
poly1,2-propylene ether segments. 
## - MDI used instead of TDI.