Polyureaurethanes having improved low temperature properties based on high molecular weight polyether intermediates

Improved low temperature properties of polyureaurethane are obtained, such as low glass transition temperatures and reduced bending moduli at -400.degree. C., by the use of relatively high moleuclar weight polyether polyol intermediates. The polyureaurethane is made by reacting the polyether polyol intermediate with a diisocyanate and subsequent cure with a metal halide salt complex of methylenedianiline.

FIELD OF THE INVENTION 
The present invention relates to polyureaurethanes made from polyethers and 
cured with a metal salt complex of methyhlenedianiline (MDA) which have 
reduced glass transition temperatures (Tg) and reduced low temperature 
bending moduli with essential retention of other desirable properties. 
BACKGROUND ART 
Heretofore, it has been common knowledge that polyureaurethanes made from 
polypropylene oxide have poor low temperature properties when compared to 
similar polyureaurethanes made from polytetramethylene ether glycol. 
U.S. Pat. No. 3,755,261 to VanGulic relates to the use of metal halide salt 
complexes of methylenedianiline in the cure of urethane polymers. 
U.S. Pat. No. 4,330,454 to Kimball relates to a urethane composition having 
a prolonged storable flowable shelf life at room temperature. A prepolymer 
is made by reacting polyproylene ether glycol with an organic 
polyisocyanate. The prepolymer is mixed with a metal halide complex of 
methylenedianiline curative to form a composition with extended shelf 
life, which can be subsequently cured by appropriate heating. 
U.S. Pat. No. 4,463,155 to Kibler relates to a polyureaurethane derived 
from the cure of a polyether diisocyanate utilizing a metal halide salt 
complex of methylenedianiline and a polyether diol, such as 
polytetramethylene ether glycol. 
U.S. Pat. No. 4,517,331 to Parker relates to a storable polypropylene ether 
polyurethane precurser composition made from a prepolymer of a 
polypropylene ether glycol and an organic polyisocyanate which is cured 
with metal halide salt complex of methylenedianiline in association with a 
crown or pseudocrown ether catalyst. 
The above patents do not teach improved low temperature properties of the 
resultant polyureaurethanes as a consequence of utilizing relatively high 
molecular weight polyether intermediates. 
SUMMARY OF THE INVENTION 
It is therefore an aspect of the present invention to provide a 
polyureaurethane having improved low temperature properties. Low 
temperature properties dictate the lowest ambient temperature at which an 
elastomer is useful without embrittlement or failure in flexure. The 
present invention allows the formulation of polyureaurethane elastomers 
with improved temperature use capability by varying the molecular weight 
of the polyether polyol intermediate. Generally, in the compositions of 
the present invention, the higher the temperature at which the urethane 
polymer can be utilized. While generally retaining favorable properties, 
the polyureaurethanes of the present invention have reduced bending 
modulus, and low glass transition temperatures such as below -20.degree. 
C., desirably -30.degree. C., and preferably below -40.degree. C. These 
and other aspects of the present invention will become apparent from the 
following detailed specification. 
DETAILED DESCRIPTION OF THE INVENTION 
The high molecular weight polyether intermediates of the present invention 
are generally polyethers, that is poly(oxyalkylene) polyols and hence are 
made from various cyclic oxirane monomers containing two or more carbon 
atoms with polyhydric alcohol initiators having from 2 to about 6 carbon 
atoms or water. The preparation of such compounds are well known to the 
art as well as to the literature and, hence, will not be discussed in 
detail. The end result is a hydroxyl terminated poly(oxyalkylene) polyol. 
The poly(oxyalkylene) groups are generally derived from an oxirane or 
alkyl (1 to 4 carbon atoms) substituted oxiranes and contain a total of 
from 2 to about 6 carbon atoms therein. Examples of suitable oxiranes 
include ethylene oxide, propylene oxide, butylene oxide, and the like. 
When reacted, the hydroxyl terminated poly(oxyalkylene) polyols, 
hereinafter referred to as polyether intermediates, have an oxirane or an 
alkyl substituted oxyethylene repeating unit therein with the alkyl group 
having from 1 to 4 carbon atoms. A polyether diol and the polyether triol 
are desired and can be utilized as blends, as for example from about 1 
percent by weight to about 99 percent by weight of the diol bzsed upon a 
total weight of the polyether diol and the polyether triol. In the present 
invention, a hydroxyl terminated poly(oxypropylene) diol or triol, or 
combinations thereof, are preferred. The present invention thus generally 
relates to polyether chains which contain alkyl substituents thereon. It 
is to be understood that other than a polyoxyethylene polyol, the 
polyether intermediates of the present invention contain alkyl 
substituents thereon. Hence, polyether intermediates such as 
polyoxytetramethylene polyol which do not contain any alkyl substituents 
thereon are not utilized and are not within the scope of the present 
invention. 
The various polyether intermediates of the present invention with the 
exception of poly(oxyethylene) diol or triol can contain ethylene oxide 
repeating units therein. That is, inasmuch as poly(oxyethylene) diol or 
triol contains ethylene oxide repeating units, there is no need to add 
ethylene oxide repeating units thereto. One suitable method of adding 
ethylene oxide to the polyether intermediates is to end cap the same. That 
is, block copolymers are formed with at least one ethylene oxide block on 
many or a predominate number of the polyether intermediate chain ends. A 
substantial number of the various intermediates have an average of at 
least 1 to about 20 ethylene oxide units on the chain end and preferably 
from about 4 to about 10 units. That is, of the larger number of 
individual intermediate molecules prepared, the ethylene oxide end caps, 
on the average, will have at least 1 to a maximum of approximately 20 
repeating ethylene oxide units therein. 
Another type of ethylene oxide containing polyether intermediate is 
essentially a random copolymer made by adding the monomers forming the 
polyether intermediate such as propylene oxide and the ethylene oxide 
together and causing a reaction to proceed. A third type of ethylene oxide 
containing polyether intermediate is made by alternating the feed of 
polyether intermediate monomers and ethylene oxide and reacting the same 
until a desired copolymer is produced. In effect, a multiple mini block 
copolymer is produced. 
Regardless of whether an essentially random copolymer, a multiple mini 
block copolymer, or a block copolymer is utilized, the amount of ethylene 
oxide contained therein is from about 2 percent to about 60 percent by 
weight, desirably from about 8 percent to about 25 percent by weight, and 
preferably from about 12 percent to about 20 percent by weight. Such 
compounds are known to the art as well as to the literature. For example, 
preparation of such compounds generally proceed via anionic polymerization 
and, hence, utilize a basic catalyst such as potassium hydroxide, and the 
like. Examples of specific ethylene oxide containing polyethers include 
the various Voranols such as Voranol 4702, Voranol 4701, Voranol 4815, 
Voranol 5148, Voranol 5287 and Voranol 3137, all produced by The Dow 
Chemical Company. Voranol is a trademark of the Dow Chemical Company. 
Ethylene oxide containing polyether intermediates are utilized where 
increased reactivity with metal halide salt complexes of 
methylenedianiline is desired was when the diisocyanate is 
4,4'-diphenylmethane diisocyanate. 
The polyether intermediates which do not contain any ethylene oxide end 
blocks, etc. are also made in a conventional manner as known to the art. 
Whether or not the high molecular weight polyether intermediate contains 
ethylene oxide groups therein or thereon, the number average molecular 
weight of the polyether diol intermediate is from about 200 to about 
9,000, desirably from about 500 to about 8,000, more desirably from about 
1,000 to about 8,000 and oftentimes in excess of 4,000. The number average 
molecular weight of the polyether triol intermediate is generally from 
about 2,000 to about 10,000, desirably from about 3,000 to about 10,000, 
and more desirably from about 4,000 to about 7,500 and oftentimes in 
excess of 7,000. 
The high molecular weight polyether intermediates of the present invention 
are reacted with a conventional polyisocyanate to form the prepolymer. 
Suitable polyisocyanates include those having the formula 
R--(N.dbd.C.dbd.O).sub.n where n is from about 2 to about 4, preferably 
about 2, where R is an aliphatic or desirably an alkyl containing from 
about 2 to about 20 carbon atoms, preferably from 2 to about 10 carbon 
atoms, or a cycloaliphatic containing from about 5 to about 20 carbon 
atoms and desirably a cycloalkyl containing from 5 to about 12 carbon 
atoms, or an aromatic or an alkyl substituted aromatic containing from 6 
to about 10 carbon atoms, and preferably from 6 to about 14 carbon atoms. 
Desirably R is an aromatic or an alkyl substituted aromatic. Examples of 
suitable polyisocyanates include the various 4,4'-diphenyl diisocyanates, 
para-phenylene diisocyanate, the various toluene diisocyanates (TDI), the 
various bitolylene diisocyanates, the various naphthylene diisocyanates 
such as 1,5-naphthylene diisocyanate and 2,6-naphthylene diisocyanate; and 
MDI, that is 4,4'-diphenylmethane diisocyanate. MDI and TDI are preferred. 
Inasmuch as prepolymers are desired containing essentially N.dbd.C.dbd.O 
end groups thereon, an excess of the polyisocyanate is utilized. 
Desirably, an amount of polyisocyanate is utilized such that from about 2 
to about 10 weight percent and desirably from about 3 to about 8 weight 
percent of free isocyanate is present based upon the weight of the 
prepolymer. The reaction conditions between the polyisocyanate and the 
polyether intermediate are generally known to those skilled in the art and 
to the literature. An exemplary temperature range is from about ambient to 
about 100.degree. C., desirably from about 40.degree. C. to about 
90.degree. C., and preferably from about 60.degree. C. to about 80.degree. 
C. At low temperatures, the reaction becomes slow. High temperatures are 
generally avoided since undesirable side reactions are initiated. The 
reaction moreover can be generally carried out at atmospheric pressure or 
under slight pressure, usually in the presence of a dry inert gas such as 
nitrogen. 
The prepolymers of the present invention are cured with a metal halide salt 
complex of MDA, that is 4,4'-methylenedianiline. Various salts can be 
utilized with MDA such as sodium chloride, sodium bromide, sodium iodide, 
sodium nitrite, lithium chloride, lithium bromide, lithium iodide, lithium 
nitrite, and sodium cyanide with sodium chloride being preferred. A 
description of MDA and the various salt complexes thereof which can be 
utilized in the present invention are set forth in U.S. Pat. No. 3,755,261 
to Van Gulick which is hereby fully incorporated by reference. Cure of the 
prepolymer generally takes place at a temperature of from about 
100.degree. C. to about 150.degree. C., and preferably from about 
130.degree. C. to about 140.degree. C. under anhydrous conditions. The 
equivalent ratio of the MDA curing agent to the polyisocyanate is 
conventional as from about 0.80 to about 1.15, desirably from about 0.90 
to about 1.1, and preferably from about 0.95 to about 1.05. 
The cured polyureaurethanes of the present invention have good low 
temperature properties. For example, the glass transition temperature of 
the polyurethane were unexpected. Another unexpected property is the 
improvement in the bending modulia at -40.degree. C. That is, the bending 
moduli of compositions of the present invention are generally reduced as 
the molecular weight of the polyether intermediate is increased. 
Generally, the bending moduli at -40.degree. C. is 40,000 psi or less, 
desirably 30,000 psi or less, and preferably 20,000 psi or less. 
Accordingly, polyureaurethanes having a particular tailor-made low 
temperature end use point can be readily formulated. 
The invention will be better understood by reference to the following 
examples.

EXAMPLE 1 
Preparation of EO Block Triol/MDI Prepolymer 
Into a 5,000 ml three-necked, round bottom flask, equipped with stirrer, 
pressure equilibrating dropping funnel, thermometer, nitrogen bubbler and 
heating mantile, was weighted 1070.8 g of molten 4,4'-diphenylmethane 
diisocyanate (MDI) (Isonate 125M, product of The Dow Chemical Co.) and 
maintained at a temperature of 70.degree. C. While maintaining a blanket 
of dry nitrogen in the reaction vessel, 3,200 g of 5,000MW ethylene oxide 
end blocked polypropylene oxide triol (Voranol 4702), a product of The Dow 
Chemical Company (34.3 hydroxyl number) was added dropwise to the stirred 
MDI, at a rate so as not to exceed 75.degree. C. The reaction mixture was 
stirred and maintained at 70.degree. C. for two hours after all of the 
polyol had been added. The prepolymer was then held under about 1.0 mm Hg 
pressure, with stirring, for two additional hours. The resultant 
prepolymer had a free isocyanate content of 5.93 percent. 
Cure of EO Block Triol/MDI/Caytur-21 
Into a dry 500 ml, three-necked, round bottom flask, equipped with stirrer, 
thermometer, heating mantle, nitrogen bubbler and vacuum, was weighted 
147.7 g of the above EO block triol/MDI prepolymer (5.93 percent NCO). To 
the homogeneously mixed and stirred prepolymer, under a dry nitrogen 
blanket, was added from a tared syringe 44.7 g of a 50/50 dispersion of 
methylenedianiline-sodium chloride complex (3MDA-NaC1) in dioctylphthalate 
carrier (Caytur-21, product of E.I. duPont de Nemours) and 7.1 g 
additional of dioctylphthalate. A vacuum of about 1.0 mm Hg was gradually 
applied and the mixture temperature was raised to 40.degree. C., over a 
period of 20 minutes. Vacuum was broken with nitrogen and the mixture was 
cast into a mold, preheated at 135.degree. C., and then cured in a 
hydraulic laboratory press at 135.degree. C. for 60 minutes. 
The result polyureaurethane had the following properties: 
TABLE I 
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Room Temperature Crescent Tear 
Shore "A" 93 R.T., pli 382 
RT Tensile, psi 
2,192 100.degree. C., pli 
311 
% Elong., 264 Bending Modulus @ 
-40.degree. C., 
5% Modulus, psi 
520 30,683 psi 
100.degree. C. 
Tensile, psi 
1,708 
Elong., % 199 
5% Modulus, psi 
445 
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Utilizing an analogous recipe and procedure as set forth above, similar 
elastomers based on Voranol 2012, a 1,200 mw polypropylene oxide diol, had 
bending moduli in excess of 40,000 psi at -40.degree. C. Thus, the high 
molecular weight polyether intermediate of the present invention resulted 
in reducing the bending modulus in half. Further, blends of 5,000 mw triol 
and 1,200 mw diol MDI prepolymers when cured with Caytur-21, as described 
above, gave elastomers with the Tg's and -40.degree. C. bending moduli 
properties set forth in Table II. 
TABLE II 
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EFFECT OF COMPOSITION ON -40.degree. C. BENDING 
MODULUS BLENDS OF PPO-MDO PREPOLYMERS 
CURED WITH CAYTUR-21 
Triol Prepolymer - (5,000 MW, EO-capped, PPO-triol)MDI, 
6.55% NCO 
Diol Prepolymer - (1,200 MW, PPO-diol)MDI, 6.88% NCO 
Curative - Caytur-21 
Stoichiometry - NH.sub.2 /NCO = 1.0 
Weight % Weight % Tg, -40.degree. C. 
Triol Prepolymer 
Diol Prepolymer 
.degree.C. 
YBM, psi 
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100 0 -67.1 30,683 
75 25 -- 27,193 
50 50 -- 40,911 
25 75 -- 61,366 
0 100 -35.0 93,214 
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EXAMPLE 2 
In a manner similar to Example 1, the following polyureaurethanes were made 
and tested with regard to the Tg of the soft segment. 
TABLE III 
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Soft Segment Glass Transition Temperature 
Polyol Used in Prepolymer 
Tg of Soft Segment 
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VORANOL* 2l20 (2000 MW) -35.degree. C. 
VORANOL* 4701 (4800 MW) -45.degree. C. 
VORANOL* 4815 (6000 MW) -55.degree. C. 
VORANOL* 5148 (7200 MW) -60.degree. C. 
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*Manufactured by The Dow Chemical Company. 
By the term "soft segment," it is meant the polyether intermediate portion 
of the polyureaurethane of the present invention. As apparent from Table 
I, the Tg of the soft segment was reduced as the molecular weight of the 
intermediate increased. 
While in accordance with the Patent Statutes, a best mode and preferred 
embodiment have been set forth, the scope of the invention is not limited 
thereto, but rather by the scope of the attached claims.