Thermally stable polyurethane elastomer useful in molding flexible automobile exterior body parts

Flexible automobile exterior body parts are molded from a polyurethane elastomer prepared from a reaction mixture comprising: PA1 A. a poly(oxypropylene)-poly(oxyethylene) glycol of molecular weight of from about 1500 to about 4000 containing 15 to 50% by weight oxyethylene groups; PA1 B. a "graft" polyol of molecular weight from about 2500 to about 4500, prepared by the in situ polymerization of one or more ethylenically unsaturated monomers in a poly(oxypropylene) and/or poly(oxypropylene)-poly(oxyethylene) glycol containing less than 15% by weight oxyethylene groups; PA1 C. methylenebis(4-phenylisocyanate); PA1 D. 1,4-butanediol. The invention also relates to this polyurethane elastomer.

Flexible exterior body parts for automobiles, including parts associated 
with energy-absorbing bumper system such as sight shields, fender 
extensions and full fascia front and rear ends, require a material with a 
particular set of properties. The material must be capable of flexing 
under impact and then returning to its original shape. Therefore, it must 
be elastomeric in nature. It must have strength as typified by high 
tensile strength and high tear strength. 
In addition, there are two more stringent requirements. It must be capable 
of withstanding dynamic impact at -20.degree. F. and it must be resistant 
to distortion at 250.degree. F. The latter requirement is imposed by 
typical conditions under which painted pieces are dried. 
One class of materials which has been used for this purpose is polyurethane 
elastomers. Polyurethane elastomers are "block" type polymers resulting 
from the reaction of a polymeric diol of molecular weight of from about 
500 to 5000 with a diisocyanate and a low molecular weight difunctional 
compound commonly referred to as the "chain extender". The chain extender 
has a molecular weight below 500 and generally below 300. 
The polymeric diol is recognized as the "soft" segment of the elastomer, 
conferring elasticity and softness to the polymer. Typically, this 
component has a molecular weight of about 1000 to 2000 and may be a 
poly(alkylene ether) glycol such as poly(tetramethylene ether) glycol or 
poly(oxypropylene) glycol, a polyester diol, a polycaprolactone diol or 
polybutadiene diol. 
Another class of polymeric diols recently described for use in polyurethane 
elastomers are "graft" polyols prepared by the in situ polymerization of 
ethylenically unsaturated monomers in a polyol. These products are 
described in U.S. Pat. No. 3,383,351 to Stamberger, May 14, 1968. Among 
the suitable polyols described are poly(oxypropylene) glycols and mixed 
poly(oxyethylene)-poly(oxypropylene) glycols (column 8, lines 28-30). 
Other representative patents describing the preparation of grafted polymer 
polyols and the polyurethanes made from these polyols are as follows: 
U.S. Pat. No. 3,304,273, Feb. 14, 1967, Stamberger, is directed to the 
preparation of cellular polyurethanes by reacting a liquid polymer polyol 
with an organic polyisocyanate. 
U.S. Pat. No. 3,823,201, July 9, 1974, Pizzini et al., describes the 
preparation of highly stable graft copolymer dispersions and the 
preparation of flexible polyurethane foams from these grafted polyols. 
U.S. Pat. No. 3,523,093, Aug. 4, 1970, Stamberger, discloses a method for 
the preparation of polyurethanes. A mixture comprising a liquid polyol and 
a preformed normally solid, film-forming polymeric material is reacted 
with an organic polyisocyanate to form polyurethane foams. 
U.S. Pat. No. 3,652,639, Mar. 28, 1972, Pizzini et al., discloses liquid 
graft copolymers prepared by the in situ polymerization of acrylonitrile 
in an unsaturated polyol and the polyurethane foam produced has improved 
load-bearing properties, as shown at Column 5, lines 30 through 40. 
One big drawback of the thermoplastic polyurethanes based on 
styrene-acrylonitrile grafted poly(oxypropylene) glycols containing from 0 
to about 15% by weight oxyethylene groups is their thermal instability at 
the elevated processing temperatures used for fabricating urethanes made 
from such polyols of molecular weight 2000 or greater. 
While polyurethane elastomers as a class have excellent tear strength and 
tensile strength and can be designed to achieve the required modulus and 
elongation, not all polyurethane elastomers can meet the two requirements 
of low temperature impact resistance and resistance to heat distortion. In 
fact, a polyurethane elastomer based on poly(oxypropylene) glycol as the 
polymeric diol and 1,4-butanediol as the chain extender has not yet been 
used for flexible automobile body parts because of previous deficiencies 
of such an elastomer in these two areas. It is generally recognized (N.E. 
Rustad and R. G. Krawiec, Rubber Age, November 1973, pp. 45-49) that 
elastomers based on poly(oxypropylene) glycols have poorer low temperature 
properties than those based on poly(tetramethylene ether) glycol, another 
polyol used in polyurethane elastomers but higher in cost. One known way 
to improve the low temperture properties is to increase the molecular 
weight of the polyol while keeping the mole ratios of ingredients 
constant. Unfortunately, while the low temperature properties are indeed 
improved, the hardness and rigidity are normally lowered markedly. See 
Table II, page 47 of the Rustad et al. article. 
In U.S. Pat. No. 3,915,937, O'Shea, Oct. 28, 1975, there is described a 
poly(oxypropylene) glycol based elastomer suitable for automobile flexible 
exterior body parts. Such a material can be prepared from a polyol of 
approximately 1750 to 2500 molecular weight, 
methylenebis(4-phenylisocyanate) and 1,4-butanediol, the molar ratio of 
butanediol to polyol being about 3.0:1 to 9.0:1. That patent is based on 
the fact that it was most unexpected to be able to make hard elastomers 
with the necessary high and low temperature properties from 
poly(oxypropylene) glycol. 
While the specific formulation for a poly(oxypropylene) glycol based 
elastomer necessary to achieve the proper combination of properties had 
not been described previously, there had appeared a paper describing a 
similar concept applied to flexible automobile body parts using elastomers 
based on polycaprolactone diol as the polyol. This paper, by F. E. 
Critchfield, J. V. Koleski and C. G. Seefried, Jr., was presented at the 
Automobile Engineering Meeting of the Society of Automobile Engineers in 
Detroit, Michigan during the week of May 14-18, 1973. Summarizing their 
data on the polycaprolactone diol based elastomers, the authors stated 
"for automotive elastomer applications, the thermoplastic polyurethanes 
based on an approximately 2000 M.sub.n diol are more desirable since they 
show less modulus-temperature dependence in the use region." They also 
concluded: "Apparently at similar hard segment concentrations, the 
molecular weight of the urethane polymer soft segment has a greater effect 
on the temperature dependence of physical properties than the hard segment 
sequences." They attributed the unique properties of these materials to be 
the result of incompatibility on a microscopic scale between the hard and 
soft segments. In turn, "Incompatibility quite probably is due to the 
molecular weight of the soft segment being high enough to be immiscible in 
a thermodynamic sense with the hard segment." 
Completely independent of the paper last mentioned above, it was found, in 
accordance with the above-cited O'Shea patent, that polyurethane 
elastomers suitable for the preparation of flexible automobile exterior 
body parts may be obtained from the reaction of a mixture comprising: 
i. a polymeric diol selected from the group consisting of 
poly(oxypropylene) glycol and ethylene oxide "tipped" poly(oxypropylene) 
glycol containing up to 10% by weight ethylene oxide and of molecular 
weight from about 1750 to about 2500 (preferably about 2000); 
ii. methylenebis (4-phenylisocyanate); 
iii. 1,4-butanediol. 
In the O'Shea patent the effect of the polyol molecular weight on the 
required properties was demonstrated. It was shown that polymer based on 
1000 molecular weight polyol failed in the low temperature impact and heat 
distortion tests while the polymer based on 2000 molecular weight polyol 
passed both tests. The acceptable range of polyol molecular weight was 
shown to be 1750 to 2500. An elastomer prepared from a 1500 molecular 
weight polyol was not acceptable with respect to low temperature impact 
while a polymer based on 3000 molecular weight polyol had lowered 
physical properties. The latter result was believed to be due to 
separation of soft and hard phases early enough in the polymerization to 
immobilize reactive end groups and thereby inhibit chain extension. 
Although the polymers described in the O'Shea patent are useful and can be 
handled with reasonable care, they do suffer from one deficiency, that of 
poor thermal stability at processing temperatures. In normal use this 
deficiency may not present a serious problem and may even go unnoticed. 
However, since occasions may and often do arise in which material may be 
left in the barrel of an extruder or in an injection molding machine for 
extended periods at elevated temperatures, it would be advantageous for a 
material to have superior thermal stability. In this way it would be 
possible to leave the material in the machines at temperature during short 
shutdowns and then resume operations with no cleanout and waste necessary. 
In addition, it would insure that inferior parts would not be produced 
because of thermally induced decomposition of the elastomer during the 
process. This is especially of concern when it is desired to use 
"regrind". 
In a copending application, Ser. No. 612,420 of O'Shea, filed Sept. 11, 
1975 (now U.S. Pat. No. 3,983,094, issued Sept. 28, 1976), it was 
demonstrated that elastomers based on poly(oxypropylene)-poly(oxyethylene) 
glycols of oxyethylene group content 15% or more possess significantly 
better thermal stability than those based on polyols containing 10% or 
less oxyethylene group content. Particularly preferred were polyols 
containing 30% or more oxyethylene group content. It was found that this 
improvement in thermal stability could be achieved with no sacrifice in 
the properties essential to automobile flexible body part use. In fact, 
slightly better strength properties appeared to result from the use of 
polyols with higher ethylene oxide content. 
We have now found, in accordance with the present invention, that this 
improvement extends to polymers based on blends of (a) 
poly(oxypropylene)-poly(oxyethylene) glycols of oxyethylene group content 
15% or more in admixture with (b) "graft" polyols prepared by the in situ 
polymerization of one or more ethylenically unsaturated monomers in a 
poly(oxypropylene) and/or poly(oxypropylene)-poly(oxyethylene) glycol 
containing less than 15% by weight oxyethylene groups. Preferred (a) 
glycols are those of molecular weight 1500 to about 4000 and containing 15 
to 50% oxyethylene groups by weight. Particularly preferred (a) glycols 
are poly(oxypropylene)poly(oxyethylene) glycols containing 25 to 50% 
oxyethylene group content. 
Such mixed polyol based polymers provide additional surprising advantages 
in that the resultant elastomers possess improved processability and 
moldability, largely as a consequence of the fact that they have 
unexpectedly higher modulus and are harder at elevated temperatures than 
previously proposed compositions. These unexpected improvements can be 
important in allowing the molding of parts more economically through the 
use of shorter cycles. 
Our invention, therefore, may be described in the following manner: 
Polyurethane elastomers suitable for the preparation of flexible automobile 
exterior body parts may be obtained from the reaction of a mixture 
comprising: 
a. a poly(oxypropylene)-poly(oxyethylene) glycol of molecular weight from 
about 1500 to about 4000 and containing 15% to 50% oxyethylene group 
content by weight; 
b. a "graft" polyol of molecular weight from about 2500 to about 4500 
prepared by the in situ polymerization of one or more ethylenically 
unsaturated monomers in a poly(oxypropylene) and/or 
poly(oxypropylene)-poly(oxyethylene) glycol containing less than 15% by 
weight oxyethylene groups; 
c. methylenebis(4-phenylisocyanate); 
d. 1,4-butanediol. 
In order to study thermal stability the following test was devised. Polymer 
samples were molded into 3 inches .times. 4 inches .times. 0.07 inch 
plaques in a single cavity mold using a 1/2 oz. Newbury injection molding 
machine at barrel and nozzzle temperatures of from 400.degree.-430.degree. 
F. After several pieces were molded, material was allowed to stand in the 
barrel of the machine for twenty minutes at temperature. Then another 
molding was made. Tensile strength was measured on samples molded with and 
without this thermal treatment using standard ASTM procedures. When 
subjected to this test at about 400.degree. F. typical elastomers of the 
invention retain at least twice as much of their original tensile strength 
as similar elastomers in which (a) is omitted or (a) is a 
poly(oxypropylene)-poly(oxyethylene) glycol containing 10% or less of 
oxyethylene group content. 
The elastomers of the invention meet the requirements for flexible exterior 
body parts for automobiles. They have a hardness of about 40 to 55 Shore 
D, preferably 45 to 50 Shore D. They have an elongation greater than 300%, 
an ultimate tensile strength of about 3000 psi or greater and a Die C tear 
strength of 500 pli or greater. 
Painted parts made from these elastomers remain intact under a 5 MPH impact 
at -20.degree. F. To simulate the dynamic conditions involved in a 5 MPH 
impact at -20.degree. F., a drop impact test system was developed. The 
unit consists basically of a vertical guide tube, a drop weight of 
appropriate design and associated instrumentation. 
Polymers to be evaluated were molded into 2 inches .times. 6 inches .times. 
0.08 inch specimens which were conditioned in an evironmental chamber to 
-20.degree. F. and then fitted into two slots 3 inches apart so that the 
sample formed an inverted "U" with a total flexed height of 2 inches. The 
sample was impacted at its center line with a force of 50 ft. lbs., the 
weight traveling at greater than 5 MPH at impact. Drop height above the 
top of the sample was 38 inches. The drop weight is an 18 inch long 
cylinder weighing 16 lbs. It is 2.5 inches in diameter for 16.5 inches of 
its length and then tapers to a blunt end, which is the striking surface. 
Polymers with inadequate low temperature impact resistance invariably 
fractured in this test. This test correlates well with the automobile 
manufacturer's testing where full size parts are made and mounted on a car 
or a portion of a car. After cooling to -20.degree. F., the full size part 
is hit with a pendulum weight which is traveling at 5 MPH. 
Parts made from the present elastomers also withstand paint oven 
temperatures of 250.degree. F. without objectionable shrinkage or 
distortion. To evaluate materials for heat distortion characteristics, a 
sag resistance test (Heat Test O'S) was developed. The apparatus consists 
of a jig to hold a 2 inch .times. 6 inch .times. 0.08 inch injection 
molded sample in a horizontal plane. The sample is mounted with 4 inches 
suspended beyond the edge of the clamp. The jig with the sample is then 
placed in an oven pre-heated at 250.degree. F. for 1/2 hour. The amount of 
sag is the difference in height from the end of the sample to a horizontal 
plane before and after exposure to heat. Experience with a material that 
was acceptable to automobile manufacturers has shown that polyurethane 
elastomers with a sag less than 2.0 inches by this test will perform 
satisfactorily in paint bake oven used to cure painted large automotive 
parts. The present elastomers meet this test. 
The poly(oxypropylene)-poly(oxyethylene) glycol (a) used in the invention 
may be either a "tipped" polyol in which a poly(oxypropylene) glycol is 
reacted further with ethylene oxide giving rise to oxyethylene group 
blocks on each end of the polyol or a more random 
poly(oxypropylene)-poly(oxyethylene) glycol in which the propylene oxide 
and ethylene oxide reactants are introduced together or in alternating 
portions. The preparation of both types of polyol is described in 
"Polyurethanes: Chemistry and Technology", Part I. Chemistry, by J. H.. 
Saunders and K. C. Frisch, Interscience, New York, 1962, pp. 36-37. The 
technique of tipping is further described in "Advances in Urethane Science 
and Technology" by K. S. Frisch and S. L. Reegan, Technomic Publishing 
Company, Westport, Conn. 1973, pp. 188-193. The oxyethylene group content, 
regardless of position in the polyol, is a major factor in improved 
thermal stability. 
The oxyethylene group content of the polyol (a) may range from 15% to 50%, 
preferably 25-50%, with the higher levels being preferred for the higher 
molecular weight polyols. For a 2000 molecular weight polyol the preferred 
oxyethylene group content is 25-45%. The 
poly(oxypropylene)-poly(oxyethylene) glycol (a) employed has, as 
indicated, a molecular weight of from about 1500 to about 4000. 
The ethylenically unsaturated monomeric materials useful for grafting onto 
poly(oxypropylene) and/or poly(oxypropylene)-poly(oxyethylene) glycol to 
prepare polyol (b) are well known in the art and include the hydrocarbon 
monomers such as butadiene, isoprene, 1,4-pentadiene, 1,6-hexadiene, 
1,7-octadiene, styrene, alphamethylstyrene, isopropylstyrene, 
butylstyrene, phenylstyrene, cyclohexylstyrene, benzylstyrene, and the 
like; substituted styrenes such as chlorostyrene, 2,5-dichlorostyrene, 
bromostyrene, flurostyrene, trifluoromethylstyrene, iodostyrene, 
cyanostyrene, nitrostyrene, N,N-dimethylaminostyrene, acetoxystyrene, 
methy 4-vinylbenzoate, phenoxystyrene, p-vinyl diphenyl sulfide, 
p-vinylphenyl phenyl oxide, and the like, the acrylic and substituted 
acrylic monomers such as acrylic acid, methacrylic acid, methylacrylate, 
methyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, 
isopropyl methacrylate, octyl methacrylate, methacrylonitrile, methyl 
alpha chloroacrylate, ethyl alpha-ethoxyacrylate, methyl alpha 
acetaminoacrylate, butyl acrylate, 2-ethylhexy acrylate, phenyl 
ethylencially phenyl methacrylate, 
alpha-chloroacryllonitrile,N,N,-dimethylacrylamide, 
N,N-dibenzylacrylamide, N-butylacrylamide, methacrylyl formamide, and the 
like; the vinyl esters, vinyl ethers, vinyl ketones, etc. such as vinyl 
acetate, vinyl chloroacetate, vinyl butyrate, isopropenyl acetate, vinyl 
formate, vinyl acrylate, vinyl methacrylate, vinyl methoxy acetate, vinyl 
benzoate, vinyl iodide, vinyl toluene, vinyl naphthalene, vinyl bromide, 
vinyl fluoride, vinylidene bromide, 1-chloro-1-fluoroethylene, vinylidene 
fluoride, vinyl methyl ether, vinyl ethyl ether, vinyl propyl ethers, 
vinyl butyl ethers, vinyl 2-ethylhexyl ether, vinyl phenyl ether, vinyl 
2-methoxyethyl ether, methoxybutadiene, vinyl 2-butoxyethyl ether, 
3,4-dihydro-1,3-pyran, 2-butoxy-2-vinyloxy diethyl ether, vinyl 
2-ethylmercaptoethyl ether, vinyl methyl ketone, vinyl ethyl ketone, vinyl 
phenyl ketone, vinyl ethyl sulfide, vinyl ethyl sulfone, N-methyl-N-vinyl 
acetamide, N-vinyl-pyrrolidone, vinyl imidazole, divinyl sulfide, divinyl 
sulfoxide, divinyl suflone, methyl vinyl sulfonate, N-vinyl pyrrole, and 
the like; dimethyl fumarate, dimethyl maleate, maleic acid, crotonic acid, 
fumaric acid, itaconic acid, monomethyl itaconate, 1-butylaminoethyl 
methacrylate, dimethylaminoethyl methacrylate, glycidyl acrylate, 
dichlorobutadine, vinyl pyridine, and the like. Preferred materials are 
the vinyl aryl monomers (especially styrene and alpha-methyl styrene), the 
acrylic nitriles (especially acrylonitrile and methacrylonitrile), and the 
alkyl alkenoate esters (especially methyl and ethyl acrylate and 
methacrylate), Reaction conditions and free radical catalysts which may be 
used in the grafting reaction are described in the above-cited Stamberger 
patent on column 4, lines 15-50. The amounts of polymerized monomer in the 
graft polyol (b) may range from 5 to 50% by weight as described in the 
above patent on column 10, lines 2-3. The preferable concentration is 
about 10% to 30%. The molecular weight of the poly(oxypropylene) and/or 
poly(oxypropylene)-poly(oxyethylene) glycol on which the monomer is 
grafted to make polyol (b) will vary from 2000 to 4000 with a preferred 
molecular weight of about 2500 to about 3000. The glycol employed in 
making the graft (b) is selected from (i) poly(oxypropylene) glycol, (ii) 
poly(oxypropylene)-poly(oxyethylene) glycol containing up to 15% 
oxyethylene groups, introduced either randomly or by "tipping" as 
described above, or (iii) a mixture of (i) and (ii) in any desired 
proportions (e.g., 90:10, 50:50, 10:90 etc.) 
The ratio of (a) poly(oxypropylene)-poly(oxyethylene) glycol to (b) 
ethylenic monomer grafted polyol employed in the invention will range from 
about 10/90 to 90/10 by weight, with a preferred ratio of from about 80/20 
to 40/60. 
The molar ratio of chain extender (d) to polyol [(a) plus (b)] which may be 
used depends on the average molecular weight of the polyol mixture and is 
usually from 6 to 1 to 12 to 1. It ranges from 6 to 1 for a 2500 average 
molecular weight polyol mixture to 12 to 1 for a 4000 molecular weight 
polyol mixture. For example, the molar ratio of chain extender (d) to 
polyol for a 2800 average molecular weight polyol mixture ranges from 5 to 
1 to about 9 to 1 with 6.0 to 8.0 being preferred. The NCO/OH ratio used 
to prepare the flexible thermoplastics may range from 0.95 to 1.10 with 
1.00 to 1.05 being preferred. 
A catalyst may or may not be used as desired. Some examples of useful 
catalysts are N-methyl-morpholine, N-ethyl-morpholine, triethyl amine, 
triethylene diamine (Dabco), N,N'-bis(2-hydroxylpropyl)-2-methyl 
piperazine, dimethyl ethanol amine, tertiary amino alcohols, tertiary 
ester amines, stannous octoate, dibutyl tin dilaurate and the like. 
Polyurethane thermoplastics of this invention can be prepared utilizing 
either prepolymer or one-shot (masterbatch) technique. The prepolymer is 
formed by reacting an organic polyhydroxyl compound which is a mixture of 
(a) a poly(oxypropylene) poly-(oxyethylene) glycol and (b) an ethylenic 
monomer graft on poly(oxypropylene) and/or 
poly(oxypropylene)-poly(oxyethylene) glycol with an organic 
poly-isocyanate, e.g., methylenebis(phenylisocyanate) to form an 
isocyanate terminated prepolymer. The prepolymer is then treated with an 
equivalent amount of a low molecular weight polyol chain extender which is 
1,4-butanediol and heated at elevated temperatures to effect a "cure". The 
one-shot or masterbatch system is effected by mixing polyhydroxyl 
compounds, chain extender and polyisocyanate together simultaneously at 
moderate temperatures and followed by curing at elevated temperatures. 
Flexible polyurethane thermoplastics based on 
poly(oxypropylene)-poly(oxyethylene) glycol alone possess good physical 
properties as well as good thermal stability. However, this type of 
urethane is somewhat defensive in areas of processability and moldability. 
In particular, these polyurethanes possess a relatively low modulus (see 
Example 1, Table 1) and thus are difficult to release when they are 
injection molded into large complex articles. 
Polyurethanes made from styrene-acrylonitrile grafted poly(oxypropylene) 
glycol on the other hand are found to have poor thermal stability (see 
Example 1, Table II). Unfortunately, physical properties of these 
polyurethanes are inferior after a normal thermal treatment at 400.degree. 
F. for 20 minutes, and almost completely deteriorated at 430.degree. for 
20 minutes. 
Unexpectedly, the flexible polyurethane thermoplastics of this invention 
made from blends of (a) poly(oxypropylene)-poly(oxyethylene) glycol and 
(b) ethylenic monomer grafted poly(oxypropylene) and/or 
poly(oxypropylene)-poly(oxyethylene) glycol exhibit a surprisingly unique 
combination of properties which neither (a) 
poly(oxypropylene)-poly(oxyethylene) glycol nor grafted polyol based 
polyurethane possess. Flexible polyurethane thermoplastics of this 
invention possess a unique combination of properties such as high tensile 
strength, high tear resistance, high elongation, good high temperature 
stability and low temperature flexibility, high resiliency, excellent 
processability, good moldability and paintability and the raw materials 
are low in cost. Flexible polyurethane thermoplastics of this invention 
may be smoothly processed and may easily be molded into large complex 
articles.

EXAMPLE I 
Seven polyurethane thermoplastic elastomers, one from a 2000 molecular 
weight polyol containing 45% by weight ethylene oxide, one from a 3500 
molecular weight grafted polyol containing about 10% by weight each of 
styrene and acrylonitrile and five from the mixture of above two polyols 
were prepared in the following manner. 
Elastomer A 
Two hundred thirty-six parts of a 2000 molecular weight poly(oxypropylene) 
glycol tipped with 45% by weight of ethylene oxide ("Poly G-X 427" 
[trademark] from Olin Corp.) was dried at 212.degree. F. under vacuum 
(.about. 3 mm Hg) for one hour). The polyol then was cooled to 120.degree. 
F. under a blanket of dry nitrogen and 192 parts of 4,4'-methylene 
bis(phenylisocyanate) was added. The mixture was heated at 176.degree. F. 
for 1 hour under nitrogen atmosphere to form isocyanate-terminated 
prepolymer having an amine equivalent of 332. 
To 400 parts of the prepolymer at 230.degree. F. was added 54 parts of 
1,4-butanediol at 140.degree. F. The sample was well mixed for 30 seconds 
to 1.0 minute and poured onto a 12 .times. 12 .times. .times. 0.5 open 
mold and cured at 325.degree. F. for 20 minutes. 
The ratio equivalents of polyol/chain extender/diisocyanate in the final 
polymer was 1/5.5/6.5. 
Elastomer B 
Using the identical procedure as described for Elastomer A, 210 parts of a 
3500 molecular weight poly(oxypropylene)-poly(oxyethylene) glycol 
containing about 12% by weight oxyethylene group grafted with about 10% by 
weight each of styrene and acrylonitrile ("Niax 24=" [trademark] obtained 
from Union Carbide Corporation) was allowed to react with 106 parts of 
4,4'-methylenebis(phenyl isocyanate). Similarly, 300 parts of the 
prepolymer was cured with 30.5 parts of 1,4-butanediol. 
The ratio of equivalents of polyol/chain extender/diisocyanate in the final 
polymer was 1/6/7. 
Elastomer C 
Again, the procedure used for Elastomer A was used for preparing Elastomer 
C, 280 parts of a 2000 molecular weight poly(oxypropylene) glycol 
containing 45% by weight of ethylene oxide and 210 parts of a 3500 
molecular weight poly(oxypropylene)-poly(oxyethylene) glycol containing 
about 12% by weight oxyethylene group grafted with about 10% by weight 
each of styrene and acrylonitrile (Niax 24-32) were mixed together and 
dried. The polyol mixture then was allowed to react with 400 parts of 
4,4'-methylenebis(phenyl isocyanate) under nitrogen atmosphere to form an 
isocyanate-terminated prepolymer. To 900 parts of the prepolymer at 
230.degree. F. was added 123 parts of 1,4-butanediol. The polymer was 
cured at 325.degree. F. for 20 minutes. The ratio of equivalents of 
polyol/chain extender/diisocyanate in the final polymer was 1/7/8. 
The resultant polymers (A, B and C) were then diced, dried for 2 hours at 
230.degree. F. and injection molded into either 2 .times. 0.125 .times. 
0.125 inch tensile bars in a four cavity mold or 3 .times. 4 .times. 0.08 
inch plaques using a 1/2 oz. Newbury injection molding machine at barrel 
and nozzle temperature of 400.degree. F. to 430.degree. F. In performing 
the thermal stability test, the polymer sample was allowed to stand in the 
barrel of the machine for 20 minutes at temperature. Physical properties 
were measured on samples molded with and without this thermal treatment. 
Properties of Elastomers A, B and C are summarized in Table I and the 
thermal stability of Elastomers A, B and C are presented in Table II in 
terms of stress-strain properties. 
Table I 
______________________________________ 
Physical Properties of Example I Elastomers 
______________________________________ 
A B C 
______________________________________ 
Hardness (Shore D) 
45 45 45 
100% Modulus 1200 1570 1880 
300% Modulus 2100 2800 2900 
% Elongation 450 420 440 
Tensile 3800 3900 4100 
Die C Tear 750 3900 4100 
-20.degree. F. Impact 
Pass -- Pass 
Heat Sag Test Pass -- Pass 
______________________________________ 
Table II 
______________________________________ 
Physical Properties of Example I Elastomers 
After Heat Treatment 
______________________________________ 
Elastomer A 
Elastomer B 
Elastomer C 
______________________________________ 
Tensile 3620 1084 3800 
100% Modulus 
1150 931 2032 
300% Modulus 
2050 -- 3016 
Elongation % 
400 167 420 
______________________________________ 
In Table II, Elastomer A was heat treated at 400.degree. F. for 20 minutes. 
This polymer had very low viscosity at 430.degree. F. Elastomer B was heat 
treated at 400.degree. F. for 20 minutes. This polymer was found to be 
completely degraded at 430.degree. F. for 20 minutes. No sample could be 
molded. Elastomer C was heat treated at 430.degree. F. for 20 minutes. 
In Table II, the advantages of Elastomer C over Elastomers A and B are well 
demonstrated. For example, Elastomer C showed a much higher modulus 
(stress/strain properties) than that of Elastomer A with other properties 
being equivalent or better. In Table II, the thermal instability of 
Elastomer B was established whereas Elastomer C was thermally stable even 
at a relatively higher temperature. It is also noted that Elastomer A 
stuck a little bit (too soft) when injection molded while Elastomer C 
molded without difficulty. 
Four more polymers were prepared based on the polyol mixtures of ethylene 
oxide (45%) tipped poly(oxypropylene) glycol (EO-PPG) and 
styrene-acrylonitrile grafted polyol (Graft PPG) as described above in the 
preparation of Elastomer C with various mixtures. Physical properties of 
these polymers are summarized in Table III. 
Table III 
______________________________________ 
Elastomers Prepared at Various Ratios 
______________________________________ 
D E F G 
______________________________________ 
EO-PPG/Graft PPG 
80/20 70/30 50/50 33/67 
Hardness (Shore D) 
44 47 45 46 
100% Modulus 1410 1772 1910 1600 
300% Modulus 2700 2730 2840 2560 
Elongation % 440 450 430 450 
Tensile 4160 4010 3900 3700 
Die C Tear 850 995 721 814 
______________________________________ 
EXAMPLE II 
In this example, a polyol mixture of 130 parts of a 1510 molecular weight 
poly(oxypropylene) glycol containing 15% ethylene oxide and 130 parts of 
the styrene-acrylonitrile grafted polyol (as described in Example I) was 
allowed to react with 216 parts of 4,4'-methylenebis-(phenyl isocyanate) 
to form an isocyanate-terminated prepolymer. 470 parts of the prepolymer 
then was cured with 65 parts of 1,4-butanediol. The ratio of equivalents 
of polyol/chain extender/diisocyanate in the final polymer was 1/6/7. 
Physical properties of the elastomer were as follows: 
Hardness (Shore D): 48 
100% modulus:2528 
300% Modulus: 3315 
Elongation %: 400 
Tensile: 3890 
Die C Tear: 837 
EXAMPLE III 
In a similar manner, as that described in Example I (Elastomer C), a 
mixture of 130 parts of 1800 molecular weight poly(oxypropylene) glycol 
tipped with 30% by weight of ethylene oxide and 130 parts of a 3500 
molecular weight polyol grafted with 10% by weight each of styrene and 
acrylonitrile (Niax 24-32) was allowed to react with 222 parts of 
4,4'-methylenebis(phenyl isocyanate). To 475 parts of the prepolymer was 
added 67.3 parts of 1,4-butanediol. The polymer was cured at 325.degree. 
F. for 20 minutes. The ratio of equivalents of polyol/chain 
extender/diisocyanate in the final polymer was 1/7/8. Physical properties 
of the polymer were as follows: 
Hardness (Shore D); 44 
100% modulus: 2328 
300% Modulus: 3337 
% Elongation: 370 
Tensile: 3805 
Die C Tear: 862 
EXAMPLE IV 
A mixture of 130 parts of a 3020 molecular weight poly(oxypropylene) glycol 
containing 30% ethylene oxide and 130 parts of a 3500 molecular weight 
polyol grafted with 10% by weight each of styrene and acrylonitrile (Niax 
2432) was allowed to react with 200 parts of 4,4'-methylenebis (phenyl 
isocyanate). The prepolymer (450 parts) was then cured with 60.3 parts of 
1,4-butanediol to form a polyurethane thermoplastic elastomer. The ratio 
of equivalents of polyol/chain extender/diisocyanate in the final polymer 
was 1/9/10. Physical properties of the elastomer were as follows: 
Hardness (Shore D); 43 
100% modulus: 1790 
300% Modulus: 2660 
Elongation %: 430 
Tensile 3100 
Die C Tear: 698 
EXAMPLE V 
A mixture of 130 parts of a 4000 molecular weight poly(oxypropylene) glycol 
containing 45% ethylene oxide and 130 parts of a 3500 molecular weight 
polyol grafted with 10% by weight each styrene and acrylonitrile (Niax 
24-32) was reacted with 177 parts of 4,4'-methylenebis (phenyl 
isocyanate). Four hundred thirty parts of the prepolymer was then reacted 
with 54 parts of 1,4-butanediol to form an elastomer with a ratio of 
equivalents of polyol/chain extender/diisocyanate being 1/9/10. Physical 
properties of the polymer were as follows: 
Hardness (Shore D): 40 
100% modulus: 1530 
300% Modulus: 2400 
Elongation %: 430 
Tensile: 3100 
Die C Tear: 698 
EXAMPLE VI 
This example demonstrates the use of a different ratio of 
styrene-acrylonitrile graft on poly(oxypropylene)-poly (oxyethylene) 
glycol for the preparation of polyurethanes of this invention. Thus, a 
mixture of 150 parts of a 2000 molecular weight poly(oxypropylene) glycol 
containing 45% ethylene oxide and 150 parts of a 3480 molecular weight 
poly(oxypropylene)-poly(oxyethylene) glycol, containing 12% oxyethylene 
groups, grafted with 5% of styrene monomer and 15% of acrylonitrile 
monomer were allowed to react with 207 parts of 4,4'-methylenebis(phenyl 
isocyanate) to form an isocyanate-terminated prepolymer. Five hundred 
parts of the prepolymer was then cured with 60 parts of 1,4-butanediol to 
give a polymer with a ratio of equivalents of polyol/chain 
extender/diisocyanate being 1/6/7. Physical properties of the polymer were 
as follows: 
Hardness (Shore D): 40 
100% modulus: 1424 
300% Modulus: 2340 
Elongation %: 460 
Tensile: 3406 
Die C Tear: 750 
EXAMPLE VII 
This example illustrates the preparation of polyurethanes of this invention 
using a one-shot or masterbatch technique. 
A mixture of 350 parts of a 2000 molecular weight poly(oxypropylene) glycol 
containing 45% ethylene oxide and 150 parts of a 3500 molecular weight 
polyol grafted with 10% by weight each of styrene and acrylonitrile 
(described in Example I) was dried at 212.degree. F. under vacuum (.about. 
3 mm Hg) for one hour. To this polyol mixture was added 136 parts of 
1,4-butanediol. The temperature of the mixture being maintained at 
230.degree. F., 431 parts of 4,4'-methylenebis(phenyl isocyanate) at 
140.degree. F. was then added. The mixture was allowed to mix well for 30 
seconds and poured onto an open mold (12 .times. 12 .times. 0.5 inch) and 
cured at 325.degree. F. for 20 minutes. The ratio of equivalents of 
polyol/chain extender/diisocyanate in the final polymer was 1/7/8. The 
polymer ws processed and injection molded. Physical properties of the 
polymer are summarized below: 
Hardness (Shore D): 45 
100% modulus: 1850 
300% Modulus: 2600 
Elongation %: 455 
Tensile: 3400 
Die C Tear 850 
The automotive flexible body parts, which are a desired end-product of this 
invention, are fabricated by injection molding using the already prepared 
polyurethane thermoplastic elastomer as the molding material. The polymer 
is made into small dice or pellets suitable for feeding into injection 
molding machines. Using the same preformed material, an automotive part 
may also be made by extrusion techniques including profile extrusion and 
sheet extrusion followed by vacuum forming. Moreover, the automotive part 
may also be prepared by "Reaction Injection Molding (RIM)" techniques, in 
which the reactants are rapidly injected into a mold wherein they cure to 
form the shaped thermoplastic elastomeric article directly. In this "RIM" 
method, the polyol, chain extender and diisocyanate may be reacted in one 
step (one-shot method) or the polyol and diisocyanate may be prereacted to 
form a prepolymer and then injected along with the chain extender to form 
the molded articles (prepolymer method).