Polyurethane elastomers exhibiting improved demold, green strength, and water absorption, and haze-free polyols suitable for their preparation

Polyurethane elastomers exhibiting improved green strength while maintaining short demold times are prepared from ultra-low unsaturation polyoxypropylene polyols containing up to 20 weight percent internal random oxyethylene moieties. The elastomers adsorb less than 10 weight percent water at 0.degree. C. The internal polyoxyethylene moiety-containing polyoxypropylene polyols may be used to prepare ultra-low unsaturation polyoxyethylene capped polyols which are haze-free and which may be used to prepare haze-free 4,4'-MDI prepolymers. Multidisperse blends of monodisperse internal oxyethylene moiety-containing polyoxypropylene polyols of ultra-low unsaturation provide yet further improvements in elastomer processing.

TECHNICAL FIELD 
The present invention pertains to polyurethane elastomers and to haze-free, 
ultra-low unsaturation polyoxypropylene/polyoxyethylene polyols suitable 
for their preparation. More particularly, the subject invention pertains 
to polyurethane elastomers having improved demold and green strength while 
exhibiting low water absorption, and further, to polyoxypropylene polyols 
having random internal oxyethylene moieties suitable for preparing these 
elastomers. Surprisingly, polyoxyethylene-capped polyoxypropylene polyols 
containing random oxyethylene moieties do not develop haze upon storage, 
nor do 4,4'-methylenediphenylene diisocyanate based, isocyanate terminated 
prepolymers prepared from them. 
BACKGROUND ART 
Processing characteristics are critical in assessing the commercial 
viability of polyurethane elastomers. Examples of these processing 
characteristics are the pot life, gel time, demold time, and green 
strength, among others. A commercially useful pot life is necessary to 
enable sufficient working time to mix and degas, where necessary, the 
reactive polyurethane forming components. Gel time is critical in enabling 
complete filling of molds before gelation occurs, particularly when large, 
complex molds are utilized, while demold time is important in maximizing 
part production. Too long a demold time necessitates larger numbers of 
relatively expensive molds for a given part output. Demold time is 
especially critical for glycol extended elastomers which tend to be slow 
curing. These requirements are often competing. For example, a decrease in 
catalyst level will generally result in longer pot life and increased gel 
time, but will often render demold time unsatisfactory, and vice versa. 
Green strength is also important. Green strength is a partially subjective 
measure of the durability of a polyurethane part immediately following 
demold. The characteristics of the polyurethane forming reaction is such 
that full strength of the polyurethane part does not develop for a 
considerable time after casting. The partially cured, or "green" part must 
nevertheless be demolded within a reasonable time. Polyurethane parts 
typically display two types of "poor" green strength. One type is such 
that the part is gelled and rigid, but is brittle and easily torn. Those 
normally skilled in the art of polyurethane elastomers refer to this type 
of poor green strength as "cheesy" in reference to its "cheese-like" 
consistency. The other type of "poor" green strength is when the part is 
soft and pliable, and permanently distorts during the demolding process. 
By contrast, parts which upon demold display durability and which can be 
twisted or bent without permanent damage are said to possess "excellent" 
green strength. While demold time limits production, poor green strength 
increases scrap rate. 
Various methods of increasing green strength and decreasing demold time 
have been examined. Increasing catalyst level, for example, may often 
desirably influence these properties. However, as previously stated, 
increased catalyst levels also decrease both pot life and gel time. 
Moreover, when microcellular elastomers are to be produced, some catalysts 
increase the isocyanate/water reaction to a greater degree than the 
isocyanate/polyol reaction, and thus can affect processability. 
It is well known in the art that polyurea and polyurethane/urea elastomers 
are much easier to process than all urethane elastomers. Polyurea and 
polyurethane/urea elastomers are prepared using amine-terminated polyols 
and/or diamine chain extenders. The most common urethane/urea elastomer 
system uses a toluene diisocyanate prepolymer reacted with the diamine 
extender, methylene-bis-(2-chloroaniline), better known as MOCA or MBOCA. 
This system is known to give a long pot life (10 to 20 minutes) with 
commercially acceptable demold times of less than 60 minutes with 
excellent green strength. In addition to this, there is minimal 
sensitivity to changes in processing conditions with this system. However, 
some of the physical properties of the elastomers containing urea linkages 
are inferior compared to all urethane elastomers (i.e. softness, tear 
strength, resilience and hydrolysis resistance). 
Water absorption is critical in many polyurethane elastomer applications. 
For example, polyurethane elastomeric seals which are exposed to aqueous 
environments may experience seriously diminished physical properties due 
to plasticization by water or by disruption of the hydrogen bonding 
between elastomer polymer polar groups. Elastomers used in expansion 
strips for roadways may swell and extrude from the pavement, necessitating 
frequent replacement. Shoe soles, particularly those of the cellular and 
microcellular types common in athletic shoes, may absorb considerable 
amounts of water, particularly at lower temperatures. For these reasons, 
where exposure to water is contemplated, elastomers based on 
homopolyoxypropylene polyols or polytetramethylene ether glycols (PTMEG) 
have been used. In such applications, water absorption is only c.a. 2 
weight percent at 0.degree. C. and less at higher temperatures. 
However, the PTMEG utilized in PTMEG-based elastomers is a much higher cost 
raw material, and elastomers based on homopolyoxypropylene polyols 
generally have long demold times and less than optimal green strength. 
Addition of greater amounts of catalyst, for example tin octoate, can 
lower demold time and increase green strength, but at the expense of 
shorter pot life and gel times, as discussed previously. 
In U.S. Pat. No. 5,106,874, the use of polyoxypropylene polyols having 
unsaturations in the range of 0.02 meq/g polyol to 0.04 meq/g polyol are 
said to lower demold time. However, as shown in our copending U.S. patent 
application, filed on even date herewith, even at unsaturations as low as 
0.010 meq/g, the demold time of glycol extended elastomers is still quite 
long, with improvement only possible through the use of polyoxypropylene 
polyols having exceptionally low unsaturation in the range of 0.007 meq/g. 
Such ultra-low unsaturation polyols are preferably prepared through the 
use of a substantially amorphous double metal cyanide.t-butyl alcohol 
(DMC-TBA) catalyst. Greater than two fold improvement in demold time is 
possible with such polyols, however green strength is still not optimal. 
Polyoxypropylene polyols having a 10-40 weight percent oxyethylene cap are 
known to lower demold time in polyurethane elastomers, at times 
sacrificing pot life and gel time. The improvement in reactivity is due to 
the primary hydroxyl termination of such polyols. However, elastomers 
prepared from such polyols are notoriously water-sensitive, sometimes 
adsorbing 200 weight percent of water at low temperatures. In U.S. Pat. 
No. 5,106,874, the use of polyoxyethylene capped polyoxypropylene polyols 
having low unsaturation, i.e. 0.02 to 0.04 meq/g, is said to reduce the 
amount of oxyethylene cap necessary to provide the requisite primary 
hydroxyl content and thus lower water sensitivity. However, no measurement 
of water absorption was made. Moreover, the systems exemplified are all 
rigid, diamine extended polyurethane/urea elastomers and not polyurethane 
elastomers. Similar disclosure with respect to polyols having lower 
unsaturation but a high degree of oxyethylene cap may be found in U.S. 
Pat. No. 5,185,420. 
Polyoxypropylene polyols, whether homopolymers or copolymers with other 
alkylene oxides, are generally prepared by base catalyzed oxyalkylation of 
propylene oxide onto a suitably hydric initiator molecule. During the 
polymerization, the competing rearrangement of propylene oxide into 
allylalcohol, as discussed in Block and Graft Polymerization, Vol. 2 
Ceresa, Ed. John Wiley & Sons, pp. 17-21, introduces monofunctional 
species at an increasingly higher rate as oxypropylation proceeds. The 
unsaturation, measured in accordance with ASTM D2849-69, is generally 
conceded as corresponding to the amount of monofunctional species present, 
i.e., polyoxypropylene monols. At equivalent weights of 2000, the mol 
percent of monol may reach as high as 45 to 50 mol percent or more, this 
creating a practical upper limit to polyoxypropylene polyol molecular 
weight. 
The use of lower temperatures and lower levels of catalyst has been found 
to reduce the level of unsaturation, but only marginally, and at the 
expense of greatly increased process time. Use of special catalysts, for 
example alkaline earth hydroxides and combinations of metal naphthenates 
and tertiary amines has been used to lower unsaturation. However, these 
alternative catalysts give only marginal improvements in unsaturation 
content to the range of 0.02 to 0.04 meq/g from the normal levels of 0.06 
to 1.0 meq/g characteristic of base catalysis. 
Significant improvement in monol content of polyoxypropylene polyols has 
been achieved using double metal cyanide.glyme complex catalysts, for 
example the non-stoichiometric zinc hexacyanocobaltate-glyme catalysts 
disclosed in U.S. Pat. No. 5,158,922. Through use of such catalysts, 
polyoxypropylene polyols of much higher molecular weight than previously 
thought possible have been prepared, for example 10,000 Da 
polyoxypropylene triols with unsaturations of 0.017 meq/g. J. W. Reish et 
al., "Polyurethane Sealants and Cast Elastomers With Superior Physical 
Properties", 33RD ANNUAL POLYURETHANE MARKETING CONFERENCE, Sep. 30-Oct. 
3, 1990, pp. 368-374. 
Numerous patents have addressed the use of higher molecular weight polyols 
to prepare polyurethanes. In such cases, the improvements are said to 
result either solely from the ability to provide higher molecular weight 
polyols of useful functionality, or additionally, the low monol content, 
the monol thought to react as "chain-stoppers" during polyurethane 
addition polymerization. Illustrative examples of such patents are U.S. 
Pat. No. 5,124,425 (room temperature cure sealants from high molecular 
weight polyols having less than 0.07 meq/g unsaturation); U.S. Pat. No. 
5,100,997 (diamine extended polyurethane/urea elastomers from high 
molecular weight polyols having less than 0.06 meq/g unsaturation); U.S. 
Pat. No. 5,116,931 (thermoset elastomers from double metal cyanide 
catalyzed polyols having less than 0.04 meq/g unsaturation); and U.S. Pat. 
No. 4,239,879 (elastomers based on high equivalent weight polyols). 
However, none of these patents address processing characteristics, which 
are of paramount importance in the cast elastomer industry. 
C. P. Smith et al., in "Thermoplastic Polyurethane Elastomers Made From 
High Molecular Weight Poly-L.TM. Polyols", POLYURETHANES WORLD CONGRESS 
1991, Sep. 24-26, 1991, pp. 313-318, discloses thermoplastic elastomers 
(TPU) prepared from polyoxyethylene capped polyoxypropylene diols with 
unsaturation in the range of 0.014-0.018 meq/g. The polyols used were 
prepared using double metal cyanide-glyme catalysts, and the elastomers 
showed increased physical properties as compared to elastomers prepared 
from a conventionally catalyzed diol of 0.08 meq/g unsaturation. 
Processability is not discussed. 
It has been discovered that low unsaturation polyols sometimes produce 
polyurethanes with anomalous properties. For example, the substitution of 
a DMC.glyme catalyzed 10,000 Da molecular weight triol for a 6000 Da 
molecular weight conventionally catalyzed triol produced an elastomer of 
higher Shore A hardness where one would expect a softer elastomer, whereas 
substitution of a similarly DMC-glyme catalyzed 6000 Da molecular weight 
triol for a conventional 6000 Da molecular weight triol showed no increase 
in hardness. Moreover, butanediol extended elastomers prepared from 
DMC.glyme catalyzed polyols exhibited demold times of 150 minutes or more, 
which is commercially unacceptable in cast elastomer applications. 
In U.S. Pat. No. 5,470,813 herein incorporated by reference, is disclosed 
novel double metal cyanide t-butanol (DMC.TBA) complex catalysts prepared 
by intimate mixing of catalyst reactants. These catalysts lack the 
crystallinity of DMC.glyme catalysts observed in X-ray diffraction 
studies, and moreover exhibit threefold to tenfold higher activity in 
propylene oxide polymerization. It is especially surprising that the 
unsaturation is lowered to an unprecedented, ultra-low value through use 
of these catalysts, with measured unsaturations of from 0.003 meq/g to 
0.007 meq/g routinely achieved. 
While the measurable unsaturation implies an exceptionally low but finite 
monol content, it is especially surprising that analysis of the product 
polyols by gel permeation chromatography showed no detectable low 
molecular weight fraction. The polyols are essentially monodisperse. The 
virtually complete absence of any low molecular weight monol species 
renders polyols having ultra-low unsaturation different in kind from even 
those prepared from DMC.glyme catalysts. 
Preparation of polyoxyethylene capped polyoxypropylene polyols using double 
metal cyanide catalysts has thus far proven unsuccessful. If 
polymerization onto a double metal cyanide catalyzed polyoxypropylene 
polyol is attempted without changing the double metal cyanide catalyst to 
a conventional base catalyst, a complex mixture of highly capped 
polyoxypropylene polyols and uncapped polyoxypropylene polyols is 
obtained. While not wishing to be bound to any particular theory, it is 
believed that oxyethylation occurs at a substantially higher rate than 
catalyst/substrate transfer in such cases. 
However, even polyoxyethylene capped polyoxypropylene polyols obtained from 
conventional, base catalyzed oxyalkylation of double metal cyanide 
catalyzed polyoxypropylene polyols unfortunately generate a haze upon 
storage, which is generally thought to be undesirable. Moreover, 
isocyanate terminated prepolymers prepared from such polyols and excess 
4,4'-methylenediphenylene diisocyanate (4,4'-MDI) also develop a haze, 
thought to be crystalline 4,4'-MDI. While the effect of polyol haze on 
polymers prepared from such polyols may be difficult to quantify, MDI 
crystals in MDI prepolymers may sediment, and thus artificially create a 
prepolymer with an NCO content which varies with time, temperature, and 
agitation of the storage tank. 
OBJECTS OF THE INVENTION 
It is an object of the present invention to provide polyurethane elastomers 
having improved demold and green strength. 
It is a further object of the present invention to provide polyurethane 
elastomers with low water absorption while maintaining commercially 
feasible processing parameters. 
It is still a further object of the present invention to provide haze-free, 
polyoxyethylene capped, ultra-low unsaturation polyoxypropylene polyols. 
It is yet a further object of the invention to provide preciptate-free 
prepolymers of 4,4'-MDI and ultra-low unsaturation 
polyoxypropylene/polyoxyethylene polyols. 
SUMMARY OF THE INVENTION 
It has now been surprisingly discovered that polyurethane elastomers having 
short demold time and improved green strength can be prepared using 
ultra-low unsaturation polyoxypropylene polyols having from 1 to about 20 
weight percent internal oxyethylene moieties. The elastomers thus prepared 
exhibit surprisingly low water absorption. It has also been surprisingly 
discovered that yet further improvement in green strength and demold is 
possible through the use of polyol blends having multimodal molecular 
weight distribution coupled with ultra-low unsaturation, and that these 
same polyols may be used to prepare both haze-free polyoxyethylene capped 
polyols and precipitate-free 4,4'-MDI prepolymers based on them.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The polyurethane elastomers of the subject invention are prepared by the 
reaction of a di- or polyisocyanate, preferably a diisocyanate, with a 
polyoxyalkylene polyether polyol mixture by either the prepolymer, 
one-shot, or other techniques, using diols as chain extenders. While the 
process of preparing polyurethane elastomers and the raw materials which 
have been used in the past are well known to those skilled in the art, 
reference may be had to the following material for purposes of basic 
reference. 
By the term "polyurethane" is meant a polymer whose structure contains 
predominately urethane 
##STR1## 
linkages between repeating units. Such linkages are formed by the addition 
reaction between an organic isocyanate group R----NCO! and an organic 
hydroxyl group HO--!--R. In order to form a polymer, the organic 
isocyanate and hydroxyl group-containing compounds must be at least 
difunctional. However, as modernly understood, the term "polyurethane" is 
not limited to those polymers containing only urethane linkages, but 
includes polymers containing minor amounts of allophanate, biuret, 
carbodiimide, oxazolinyl, isocyanurate, uretidinedione, and urea linkages 
in addition to urethane. The reactions of isocyanates which lead to these 
types of linkages are summarized in the POLYURETHANE HANDBOOK, Gunter 
Oertel, Ed., Hanser Publishers, Munich, .RTM.1985, in Chapter 2, p. 7-41; 
and in POLYURETHANES: CHEMISTRY AND TECHNOLOGY, J. H. Saunders and K. C. 
Frisch, Interscience Publishers, New York, 1963, Chapter III, pp. 63-118. 
The urethane forming reaction is generally catalyzed. Catalysts useful are 
well known to those skilled in the art, and many examples may be found for 
example, in the POLYURETHANE HANDBOOK, Chapter 3, .sctn.3.4.1 on pages 
90-95; and in POLYURETHANE: CHEMISTRY AND TECHNOLOGY, in Chapter IV, pp. 
129-217. Most commonly utilized catalysts are tertiary amines and 
organotin compounds, particularly dibutyltin diacetate and dibutyltin 
dilautrate. Combinations of catalysts are often useful also. 
In the preparation of polyurethanes, the isocyanate is reacted with the 
active hydrogen-containing compound(s) in an isocyanate to active hydrogen 
ratio of from 0.5 to 1 to 10 to 1. The "index" of the composition is 
defined as the --NCO/active hydrogen ratio multiplied by 100. While the 
extremely large range described previously may be utilized, most 
polyurethane processes have indices of from 70 to about 120 or 130, more 
preferably from 95 to about 110 and most preferably from about 100 to 105. 
In the case of polyurethanes which also contain significant quantities of 
isocyanurate groups, indices of greater than 200 and preferably greater 
than 300 may be used in conjunction with a trimerization catalyst in 
addition to the usual polyurethane catalysts. In calculating the quantity 
of active hydrogens present, in general all active hydrogen containing 
compounds other than non-dissolving solids are taken into account. Thus, 
the total is inclusive of polyols, chain extenders, functional 
plasticizers, etc. 
Hydroxyl group-containing compounds (polyols) useful in the preparation of 
polyurethanes are described in the POLYURETHANE HANDBOOK in Chapter 3, 
.sctn.3.1, pages 42-61; and in POLYURETHANES: CHEMISTRY AND TECHNOLOGY in 
Chapter II, .sctn..sctn. III and IV, pages 32-47. Many hydroxyl-group 
containing compounds may be used, including simple aliphatic glycols, 
dihydroxy aromatics, particularly the bisphenols, and hydroxyl-terminated 
polyethers, polyesters, and polyacetals, among others. Extensive lists of 
suitable polyols may be found in the above references and in many patents, 
for example in columns 2 and 3 of U.S. Pat. No. 3,652,639; columns 2-6 of 
U.S. Pat. No. 4,421,872; and columns 4-6 of U.S. Pat. No. 4,310,632; these 
three patents being hereby incorporated by reference. 
Preferably used are hydroxyl-terminated polyoxyalkylene and polyester 
polyols. The former are generally prepared by well known methods, for 
example by the base catalyzed addition of an alkylene oxide, preferably 
ethylene oxide (oxirane), propylene oxide (methyloxirane) or butylene 
oxide (ethyloxirane) onto an initiator molecule containing on the average 
two or more active hydrogens. Examples of preferred initiator molecules 
are dihydric initiators such as ethylene glycol, 1,6-hexanediol, 
hydroquinone, resorcinol, the bisphenols, aniline and other aromatic 
monoamines, aliphatic monoamines, and monoesters of glycerine; trihydric 
initiators such as glycerine, trimethylolpropane, trimethylolethane, 
N-alkylphenylenediamines, mono-, di-, and trialkanolamines; tetrahydric 
initiators such as ethylene diamine, propylenediamine, 2,4'-, 2,2'-, and 
4,4'-methylenedianiline, toluenediamine, and pentaerythritol; pentahydric 
initiators such as diethylenetriamine and .alpha.-methylglucoside; and 
hexahydric and octahydric initiators such as sorbitol and sucrose. 
Addition of alkylene oxide to the initiator molecules may take place 
simultaneously or sequentially when more than one alkylene oxide is used, 
resulting in block, random, and block-random polyoxyalkylene polyethers. 
The number of hydroxyl groups will generally be equal to the number of 
active hydrogens in the initiator molecule. Processes for preparing such 
polyethers are described both in the POLYURETHANE HANDBOOK and 
POLYURETHANES: CHEMISTRY AND TECHNOLOGY as well as in many patents, for 
example U.S. Pat. Nos. 1,922,451; 2,674,619; 1,922,459; 3,190,927; and 
3,346,557. Preferable are polyether polyols having exceptionally low 
levels of unsaturation, prepared using double metal cyanide complex 
catalysts as described infra. 
Polyester polyols also represent preferred polyurethane-forming reactants. 
Such polyesters are well known in the art and are prepared simply by 
polymerizing polycarboxylic acids or their derivatives, for example their 
acid chlorides or anhydrides, with a polyol. Numerous polycarboxylic acids 
are suitable, for example malonic acid, citric acid, succinic acid, 
glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, 
maleic acid, fumaric acid, terephthalic acid, and phthalic acid. Numerous 
polyols are suitable, for example the various aliphatic glycols, 
trimethylolpropane and trimethylolethane, .alpha.-methylglucoside, and 
sorbitol. Also suitable are low molecular weight polyoxyalkylene glycols 
such as polyoxyethylene glycol, polyoxypropylene glycol, and block and 
heteric polyoxyethylene-polyoxypropylene glycols. These lists of 
dicarboxylic acids and polyols are illustrative only, and not limiting. An 
excess of polyol should be used to ensure hydroxyl termination, although 
carboxy groups are also reactive with isocyanates. Methods of preparation 
of such polyester polyols are given in the POLYURETHANE HANDBOOK and in 
POLYURETHANES: CHEMISTRY AND TECHNOLOGY. 
Also suitable as the polyol are vinyl polymer modified polyols. Such 
polymer polyols are well known to the art, and are prepared by the in situ 
polymerization of one or more vinyl monomers, preferably acrylonitrile 
and/or styrene, in the presence of a polyether or polyester polyol, 
particularly polyols containing a minor amount of natural or induced 
unsaturation. Methods of preparing such polymer polyols may be found in 
columns 1-5 and in the Examples of U.S. Pat. No. 3,652,639; in columns 1-6 
and the Examples of U.S. Pat. No. 3,823,201; particularly in columns 2-8 
and the Examples of U.S. Pat. No. 4,690,956; and in U.S. Pat. Nos. 
4,524,157; 3,304,273; 3,383,351; 3,523,093; 3,953,393; 3,655,553; and 
4,119,586, all of which patents are herein incorporated by reference. 
Non-vinyl polymer modified polyols are also preferred, for example those 
prepared by the reaction of a polyisocyanate with an alkanolamine in the 
presence of a polyol as taught by U.S. Pat. Nos. 4,293,470; 4,296,213; and 
4,374,209; dispersions of polyisocyanurates containing pendant urea groups 
as taught by U.S. Pat. No. 4,386,167; and polyisocyanurate dispersions 
also containing biuret linkages as taught by U.S. Pat. No. 4,359,541. 
Other polymer modified polyols may be prepared by the in situ size 
reduction of polymers until the particle size is less than 20 .mu.m, 
preferably less than 10 .mu.m. 
Many isocyanates are useful in the preparation of urethanes. Examples of 
such isocyanates may be found in columns 8 and 9 of U.S. Pat. No. 
4,690,956, herein incorporated by reference, and in the POLYURETHANE 
HANDBOOK, Chapter 3, .sctn.3.2, pages 62-73 and POLYURETHANES: CHEMISTRY 
AND TECHNOLOGY, Chapter II, .sctn.II, pages 17-31. Modified isocyanates 
such as those containing urethane, biuret, urea, allophanate, uretonimine, 
carbodiimide or isocyanurate linkages are also useful. 
Chain extenders may also be useful in the preparation of polyurethanes. 
Chain extenders are generally considered to be low molecular weight 
polyfunctional compounds or oligomers reactive with the isocyanate group. 
Aliphatic glycol chain extenders commonly used include ethylene glycol, 
propylene glycol, 1,4-butanediol, and 1,6-hexanediol, and the like. 
Other additives and auxiliaries are commonly used in polyurethanes. These 
additives include plasticizers, flow control agents, fillers, 
antioxidants, flame retardants, pigments, dyes, mold release agents, and 
the like. Many such additives and auxiliary materials are discussed in the 
POLYURETHANE HANDBOOK in Chapter 3, .sctn.3.4, pages 90-109 and in 
POLYURETHANES: CHEMISTRY AND TECHNOLOGY, Part II, Technology. 
Polyurethane microcellular elastomers contain an amount of blowing agent 
which is inversely proportional to the desired foam density. Blowing 
agents may be physical (inert) or reactive (chemical) blowing agents. 
Physical blowing agents are well known to those in the art and include a 
variety of saturated and unsaturated hydrocarbons having relatively low 
molecular weights and boiling points. Examples are butane, isobutane, 
pentane, isopentane, hexane, and heptane. Generally the boiling point is 
chosen such that the heat of the polyurethane-forming reaction will 
promote volatilization. 
Until recently, the most commonly used physical blowing agents, however, 
were the halocarbons, particularly the chlorofluorocarbons. Examples are 
methyl chloride, methylene chloride, trichlorofluoromethane, 
dichlorodifluoromethane, chlorotrifluoromethane, chlorodifluoromethane, 
the chlorinated and fluorinated ethanes, and the like. Brominated 
hydrocarbons may also be useful. Blowing agents are listed in the 
POLYURETHANE HANDBOOK on page 101. Current research is directed to 
lowering or eliminating the use of chlorofluorocarbons, and following the 
Montreal Protocol, great strides have been made to reduce or eliminate 
completely, the use of chlorofluorocarbon (CFC) blowing agents which 
exhibit high ozone depletion potential (ODP) and global warming potential 
(GWP). As a result, many new halogenated blowing agents have been offered 
commercially. A preferred group are, for example, the highly fluorinated 
alkanes and cycloalkanes (HFCS) and perfluorinated alkanes and 
cycloalkanes (PFCs). 
Chemical blowing agents are generally low molecular weight species which 
react with isocyanates to generate carbon dioxide. Water is the only 
practical chemical blowing agent, producing carbon dioxide in a one-to-one 
mole ratio based on water added to the foam formulation. Unfortunately, 
completely water-blown systems have not proven successful in some 
applications such as rigid insulation, and thus it is still common to use 
water in conjunction with a physical blowing agent in some cases. 
Polyurethane high resilience microcellular elastomers are typical 
all-water blown foams. 
Blowing agents which are solids or liquids which decompose to produce 
gaseous byproducts at elevated temperatures can in theory be useful, but 
have not achieved commercial success. Air, nitrogen, argon, and carbon 
dioxide under pressure can also be used in theory, but have not proven 
commercially viable. Research in such areas continues, particularly in 
view of the trend away from chlorofluorocarbons. 
Polyurethane microcellular elastomers generally require a surfactant to 
promote uniform cell sizes and prevent foam collapse. Such surfactants are 
well known to those skilled in the art, and are generally polysiloxanes or 
polyoxyalkylene polysiloxanes. Such surfactants are described, for 
example, in the POLYURETHANE HANDBOOK on pages 98-101. Commercial 
surfactants for these purposes are available from a number of sources, for 
example from Wacker Chemie, the Union Carbide Corporation, and the 
Dow-Corning Corporation. 
Processes for the preparation of polyurethane microcellular elastomers and 
the equipment used therefore are well known to those in the art, and are 
described, for example, in the POLYURETHANE HANDBOOK in Chapter 4, pages 
117-160 and in POLYURETHANES: CHEMISTRY AND TECHNOLOGY, Part II, 
Technology, in Chapter VIII, .sctn..sctn. III and IV on pages 7-116 and 
Chapter VIII, .sctn..sctn. III and IV on pages 201-238. 
Having now described polyurethane raw materials generally, the 
polyoxypropylene polyols of the subject invention containing random, 
internal oxyethylene moieties have unsaturations of less than 0.015 meq/g, 
preferably less than 0.010 meq/g, and most preferably from 0.001 to 0.007 
meq/g. The polyols are preferably prepared utilizing double metal cyanide 
complex catalysts. Traditional base catalysis using alkali metal or 
alkaline earth metal hydroxides or alkoxides will not produce polyols with 
these low levels of unsaturation. Suitable double metal cyanide.glyme 
catalysts are disclosed in U.S. Pat. No. 5,158,922, which is herein 
incorporated by reference. 
Preferably, however, DMC.TBA catalysts such as those disclosed in U.S. Pat. 
No. 5,470,813 are used. Examples of suitable catalysts are presented 
hereinafter. Use of the preferred catalysts shows a distinct improvement 
over the DMC.glyme and other catalysts. Not only is the unsaturation 
reduced to incredibly low values, but moreover, despite having a 
measurable unsaturation, gel permeation chromatographic analysis shows no 
detectable lower molecular weight components. The ultra-low unsaturation 
polyols are truly monodisperse and different in kind from even DMC.glyme 
catalyzed polyols which contain from 5-10 mol percent lower molecular 
weight components, assumedly monol. 
The polymerization generally proceeds from a "starter" molecule, most often 
a polyoxypropylene polyol of relatively low molecular weight, i.e., 
200-700 Da. These starter polyols may be prepared by traditional base 
catalyzed propylene oxide polymerization, as at these relatively low 
molecular weights the unsaturation produced is relatively low, and will be 
diluted as polymerization proceeds. Starter polyols in the lower range of 
molecular weight are preferred. 
Following addition of the double metal cyanide catalyst to the starter 
polyol, propylene oxide is added to a pressure of about 4 psig (0.27 bar). 
A rapid drop in pressure indicates that the so-called "induction period" 
characteristic of double metal cyanide catalysts is over and additional 
alkylene oxide may now be safely added at higher pressure, for example 
about 40 psig (2.72 bar). The added alkylene oxide may be initially 
entirely propylene oxide, or may be the desired weight ratio of propylene 
oxide and ethylene oxide. It is important that the ethylene oxide be added 
together with propylene oxide as under these conditions ethylene oxide 
will randomly copolymerize to the same extent as with conventional base 
catalysis. The resulting polyoxypropylene/polyoxyethylene polyol will have 
a random oxyethylene distribution in that part of the polymer formed 
during copolymerization. The amount of ethylene oxide randomly 
copolymerized will be from about 1 to about 20 weight percent based on the 
weight of the polyol. If the ethylene oxide content is greater than about 
20 weight percent, then the elastomers will exhibit considerable water 
absorption. Preferably, from 1 to about 15%, more preferably 5 to about 
12% internal oxyethylene moieties are contained in the subject 
polyoxypropylene polyols. 
If desired, the polyoxypropylene polyols containing random internal 
oxyethylene moieties of the subject invention can be capped with ethylene 
oxide to provide significant amounts of primary hydroxyl groups. When 
polyoxypropylene homopolymers prepared from double metal cyanide catalysts 
are capped with ethylene oxide, the resultant capped polyols rapidly 
develop a haze upon storage, for example within a 3 to 14 day period. It 
has been surprisingly discovered that oxyethylene capped polyoxypropylene 
copolymers containing internal oxyethylene moieties are haze-free even 
after long periods of storage. The amount of internal oxyethylene content 
must be an amount effective to produce the haze-free characteristic. It 
has been found that this amount depends upon the weight percent of 
oxyethylene cap in the finished polyols, with 2.5 weight percent of 
internal oxyethylene moieties sufficient for a 14% oxyethylene capped 
polyol, whereas a larger amount, c.a. 6-8% or more is required for a 
polyol with an 18% oxyethylene cap. The amount of internal oxyethylene 
moieties which is effective in producing a haze-free polyol may readily be 
determined by preparing a series of random, internal 
polyoxypropylene/polyoxyethylene copolymers with varying internal 
oxyethylene content, and capping with the desired amount of ethylene 
oxide. The product is then stored at room temperature for a period of 
about 20 days. The minimum effective amount of internal oxyethylene 
moieties will be that of the polyol with lower internal oxyethylene 
content which remains clear. 
In preparing polyurethane elastomers, it has been unexpectedly discovered 
that the use of polyoxypropylene polyols containing about 20 weight 
percent internal oxyethylene moieties improves green strength as compared 
to polyoxypropylene homopolymers of the same molecular weight. Hardness 
and resilience build also, in general, increase more rapidly. These 
effects are surprising in that the internal oxyethylene moieties do not 
provide significantly greater amounts of primary hydroxyl group 
termination which would be expected of oxyethylene capped polyols. The 
latter would be expected to react faster. 
Further improvement in demold and green strength may be achieved by 
utilizing a multimodal mixture of polyols of different average molecular 
weight. The polyols prepared by double metal cyanide catalysis, 
particularly DMC.TBA, have narrow molecular weight distributions. The 
polydispersity of a polymer or polymer blend may be defined by the ratio 
of Mw/Mn where Mw is the weight average molecular weight and Mn is the 
number average molecular weight. The weight average molecular weight is 
defined as Mw=.SIGMA..sub.i .omega..sub.i M.sub.i where M.sub.i is the ith 
molecular weight and .omega..sub.i is the weight fraction in the total of 
the ith molecular weight component. The number average molecular weight is 
defined as .SIGMA..sub.i n.sub.i M.sub.i where M.sub.i is defined as above 
and n.sub.i is the number fraction of the total of the ith molecular 
weight component. For a theoretically perfect monodisperse polymer where 
all polymeric species have a single molecular weight, M.sub.w =M.sub.n and 
the polydispersity M.sub.w /M.sub.n =1. In practice, true monodispersity 
is never achieved, and in the subject application, polymers described as 
monodisperse have polydispersities less than 2, and often 1.20 or less. 
The molecular weights reported herein are number average molecular 
weights. 
The term "multidisperse" as used herein indicates a bi- or trimodal, etc. 
distribution of molecular weights, with each individual distribution being 
essentially monodisperse. Such multidisperse blends are advantageously 
prepared by mixing two or more essentially monodisperse polyols, or by 
introduction of a second portion of the same or different initiator 
molecule into the polymerization in the presence of a catalyst suitable 
for preparing an ultra-low unsaturation polyol, but at a later time. 
Ultra-low unsaturation polyols may be described as truly monodisperse, as 
they contain but a monomodal molecular weight distribution which is 
relatively narrow. The polydispersity, Mw/Mn is often below 1.10, for 
example. By blending two or more polyoxypropylene polyols of different 
molecular weights, each containing from 1 to about 20 weight percent 
internal oxyethylene moieties and being substantially monodisperse as 
characterized by an unsaturation of less than 0.010 meq/g polyol, or by 
blending one of such polyoxypropylene polyols containing 1-20% internal 
oxyethylene moieties with a polyoxypropylene homopolymer polyol having an 
unsaturation of less than 0.010 meq/g, polyurethane elastomers may be 
prepared from such blends which exhibit improved demold time and green 
strength. The polydispersity of the polyol blends is preferably 1.4 or 
greater. Polydispersities greater than 2.0 are also suitable. 
The polydispersities of a blend of two polyols can be calculated using the 
following equations: 
EQU Mw.sub.blend =Mw.sub.1 .alpha..sub.1 +Mw.sub.2 .alpha..sub.2, 
EQU Mn.sub.blend =Mn.sub.1 Mn.sub.2 /(Mn.sub.1 .alpha..sub.2 +Mn.sub.2 
.alpha..sub.1), 
EQU Polydispersity.sub.blend =Mw.sub.blend /Mn.sub.blend, 
where Mw.sub.1 and Mw.sub.2 are weight average molecular weights, Mn.sub.1 
and Mw.sub.2 are number average molecular weights, and .alpha..sub.1 and 
.alpha..sub.2 are weight fractions of polyols 1 and 2, respectively. 
The isocyanates useful in the preparation of the subject elastomers may, in 
general, be any organic di- or polyisocyanate, whether aliphatic or 
aromatic. However, preferred isocyanates are the commercially available 
isocyanates toluene diisocyanate (TDI) and methylenediphenylene 
diisocyanate (MDI). Toluene diisocyanate is generally used as an 80:20 
mixture of 2,4- and 2,6-TDI, although other mixtures such as the 
commercially available 65:35 mixture as well as the pure isomers are 
useful as well. Methylenediphenylene diisocyanate may also be used as a 
mixture of 2,4'-, 2,2'-, and 4,4'-MDI isomers. A wide variety of isomeric 
mixtures are commercially available. However, most preferable is 4,4'-MDI 
or this isomer containing only most minor amounts of the 2,4'- and 
2,2'-isomers, as the latter may often affect physical properties in a 
manner not desirable for a particular product. 
Modified isocyanates based on TDI and MDI are also useful, and many are 
commercially available. To increase the storage stability of MDI, for 
example, small quantities, generally less than one mole of an aliphatic 
glycol or modest molecular weight polyoxyalkylene glycol or triol may be 
reacted with 2 moles of diisocyanate to form a urethane modified 
isocyanate. 
Also suitable are the well known carbodiimide, allophanate, uretonimine, 
biuret, and urea modified isocyanates based on MDI or TDI. Mixtures of 
diisocyanates and modified diisocyanates may be used as well. Also 
suitable are aliphatic and cycloaliphatic isocyanates such as 1,6-hexane 
diisocyanate, isophorone diisocyanate, 2,4- and 2,6-methylcyclohexyl 
diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate and its isomers, 
1,4-bis(2-(2-isocyanato)propyl)benzene, and mixtures of these and other 
isocyanates. 
In general, the isocyanate index of the overall formulation is adjusted to 
between 70 and 130, preferably 90 and 110, and most preferably about 100. 
Indexes of from 100 to 105 are particularly suitable. Lower indexes 
generally result in softer products of lower tensile strength and other 
physical properties, while higher indexes generally result in harder 
elastomers which require oven cure or cure for long periods at ambient 
temperatures to develop their final physical properties. Use of isocyanate 
indexes appreciably above 130, for example 200-300 generally require 
addition of a trimerization catalyst and result in a crosslinked, less 
extensible elastomer having considerable polyisocyanurate linkages. 
The chain extenders useful in the subject invention elastomers are 
preferably the aliphatic glycols and polyoxyalkylene glycols with 
molecular weights up to about 500 Da, preferably less than 300 Da. 
Aromatic dihydroxy compounds such as hydroquinone, hydroquinone 
bis(2-hydroxyethyl)ether (HQEE), the bisphenols, and 
4,4'-dihydroxybiphenyl may be used as well. The chain extender may be a 
sole chain extender or mixture. Preferred are ethylene glycol, diethylene 
glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 
butylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentylglycol, 
1,4-dihydroxycyclohexane, 1,4-cyclohexanedimethanol, and the like. Most 
preferred are ethylene glycol and in particular 1,4-butanediol and 
1,6-hexanediol. 
Amine chain extenders may also be used, but preferably in most minor 
amount. The resulting elastomers should be characterized as polyurethane 
elastomers rather than polyurethane/urea elastomers which have acquired a 
distinct status in the art. Examples are ethylene diamine and 
1,6-hexanediamine, and diethylenetriamine among the aliphatic amine chain 
extenders. Suitable and preferred aromatic diamine chain extenders are the 
various toluenediamine isomers and their mixtures, the various 
methylenediphenylene diamines and their mixtures, and preferably the 
slower reacting aromatic diamines such as 4,4'-methylene 
bis(2-chloroaniline) (MOCA) and the sterically hindered alkyl substituted 
toluenediamines and methylenediphenylene diamines. 
In the subject invention elastomers, it is the polyether polyol component 
which is critical. Polyoxyalkylene polyether blends containing 
polyoxypropylene polyols having from 1 to less than 20 weight percent 
internal oxyethylene moieties which exhibit exceptionally low unsaturation 
must be used. The measured unsaturation (ASTM test method D-2849-69) is 
most preferably less than 0.010 meq/g for the polyol blend. Furthermore, 
the individual polyols, regardless of the overall blend unsaturation, must 
have individual unsaturations of less than 0.015 meq/g. Preferred are 
polyol blends where the overall unsaturation is less than 0.007 meq/g and 
no individual polyol has an unsaturation greater than 0.010 meq/g. Most 
preferred is the use of individual polyols in the blend where each polyol 
has a measured unsaturation of less than about 0.007 meq/g. 
Thus, the major portion of the polyol blend, in order to have an overall 
unsaturation of less than 0.010 meq/g, must be an essentially monodisperse 
polyoxypropylene polyol containing from 1 to less than 20 weight percent 
internal oxyethylene moieties which may be prepared by polymerizing a 
mixture of propylene oxide and ethylene oxide onto an initiator molecule 
of suitable functionality in the presence of a catalyst capable of 
producing this ultra-low level of unsaturation, for example a 
substantially amorphous double metal cyanide.TBA catalyst such as those 
prepared as disclosed in U.S. Pat. No. 5,470,813, which is herein 
incorporated by reference. An example of catalyst preparation is given in 
Example 1 herein, and an example of polyol preparation in Example 2. It is 
notable that ultra-low unsaturation polyols are generally monodisperse, 
i.e. there is no detectable low molecular weight component. 
The polyoxypropylene polyols containing internal oxyethylene moieties may 
also contain other oxyalkylene moieties derived from C.sub.3-4 alkylene 
oxides such as oxetane, 1,2-butylene oxide, and 2,3-butylene oxide, as 
well as minor amounts of higher alkylene oxides. However, it is preferred 
that the predominate C.sub.3-4 alkylene oxide be propylene oxide, and most 
preferred that it be all propylene oxide. By the term "polyoxypropylene" 
as used herein is meant a polymer whose non-oxyethylene moieties are 
predominantly propylene oxide-derived. 
The random, internal oxyethylene moieties are introduced by 
copolymerization of ethylene oxide and propylene oxide (optionally in 
conjunction with any other alkylene oxides) in the presence of a catalyst 
suitable for preparation of ultra-low unsaturation polyoxyalkylene 
polyols, preferably a double metal cyanide catalyst, and most preferably a 
DMC.TBA catalyst as disclosed in copending U.S. Pat. No. 5,470,813. The 
amount of internal oxyethylene moieties should be between 1 weight percent 
and less than 20 weight percent, preferably between 3 weight percent and 
15 weight percent, more preferably between 5 weight percent and 12 weight 
percent, and most preferably between 5 weight percent and 10 weight 
percent. 
The use of the catalysts disclosed in the aforementioned U.S. Pat. No. 
5,470,813 is particularly preferred, as unprecedentedly low unsaturation, 
on the order of 0.003 to 0.005 meq/g is possible. Moreover, despite the 
measurable unsaturation, gel permeation chromatography of polyols prepared 
with such catalysts surprisingly show no detectable lower molecular weight 
species, i.e., the polyols are essentially monodisperse, having a 
polydispersity of less than 1.20, and usually c.a. 1.06. 
The haze-free polyoxyethylene capped polyoxypropylene polyols containing 
less than 20 weight percent random internal oxyethylene moieties cannot, 
in general, be prepared by terminating propylene oxide addition and 
continuing ethylene oxide addition, as under these circumstances, ethylene 
oxide polymerization, for reasons not clearly understood, is not uniform. 
The polyols resulting from attempts at such polymerizations tend to be 
mixtures containing substantial quantities of uncapped polyoxypropylene 
polyols containing internal oxyethylene moieties and substantial 
quantities of highly oxyethylene capped polyols. Thus, the polyoxyethylene 
capped polyols must be prepared by polymerizing the ethylene oxide-derived 
cap in the presence of other catalysts, for example traditional alkali 
metal hydroxide or alkoxide catalysts. For example, from about 0.1 to 
about 2.0 weight percent sodium or potassium methoxide, preferably 0.1 to 
0.5 weight percent, may be added to the reaction mixture following 
preparation of the backbone polymer. The DMC catalyst need not be removed 
prior to addition of the basic catalyst. The mixture is then stripped 
under vacuum to remove water and/or methanol or other alkanol following 
which ethylene oxide may then be added under conventional conditions. 
Other methods of polyol preparation are also suitable, providing the 
ultra-low unsaturation and other required properties are obtained. 
The multidisperse polyol blends useful in the subject invention are 
advantageously prepared by blending two or more ultra-low unsaturation 
polyols individually having low polydispersity but different molecular 
weights, to form a multidisperse polyol blend with a polydispersity 
greater than 1.4. Gel permeation chromatography of such blends 
demonstrates a bi- or trimodal, etc. molecular weight distribution, with 
each of the original polyols representing a relatively narrow peak. The 
polyol blends may comprise two or more polyoxypropylene polyols containing 
internal oxyethylene moieties; an essentially homopolymeric 
polyoxypropylene polyol and one or more polyoxypropylene polyols 
containing internal oxyethylene moieties; an essentially homopolymeric 
polyoxypropylene polyol and one or more haze-free polyoxyethylene capped 
polyoxypropylene polyols containing internal oxyethylene moieties; or 
other suitable combinations. 
Preferably, the elastomers are prepared by the prepolymer process, however, 
the one shot process is useful as well. In the prepolymer process, the 
polyoxyalkylene polyol mixture is reacted with excess di- or 
polyisocyanate to form an isocyanate-terminated prepolymer containing from 
about 1% to about 25% by weight NCO groups, preferably from about 3% to 
about 12% NCO, more preferably about 4 to about 10% NCO, and most 
preferably about 6% NCO. Prepolymer preparation may be catalyzed, 
preferably by tin catalysts such as dibutyltin diacetate and dibutyltin 
dilaurate, in amounts of from 0.001 to about 5%, more preferably 0.001 to 
about 1% by weight. The manufacture of prepolymers is within the level of 
skill in the art. If desired, the prepolymer polyol component may be 
augmented with hydroxyl-functional polyols other than polyoxyalkylene 
polyols, for example polyester polyols, polycaprolactone polyols, 
polytetramethylene ether glycols, and the like. 
Following prepolymer formation, the prepolymer is then mixed with a 
proportion of one or more chain extenders such that the isocyanate index 
is in the desired range. The prepolymer and chain extender are thoroughly 
mixed, degassed if necessary, and introduced into the proper mold or, if 
thermoplastic polyurethanes are desired, reaction extruded and granulated 
or deposited on a moving belt and subsequently granulated. 
Preferred chain extenders are the aliphatic and cycloaliphatic glycols and 
oligomeric polyoxyalkylene diols. Examples of suitable aliphatic glycol 
chain extenders are ethylene glycol, diethylene glycol, 1,2- and 
1,3-propane-diol, 2-methyl-1,3-propanediol, 1,2- and 1,4-butane diol, 
neopentyl glycol, 1,6-hexanediol, 1,4-cyclohexanediol, 
1,4-cyclohexanedimethanol, hydroquinone bis(2-hydroxyethyl) ether, and 
polyoxyalkylene diols such as polyoxyethylene diols, polyoxypropylene 
diols, heteric and block polyoxyethylene/polyoxypropylene diols, 
polytetramethylene ether glycols, and the like, with molecular weights up 
to about 300 Da. Preferred are ethylene glycol, diethylene glycol, 
1,6-hexanediol and 1,4-butanediol, the latter particularly preferred. 
The subject elastomers are highly suitable for microcellular elastomers, 
for example those suitable for use in shoe midsoles. The formulations of 
such elastomers contain a minor amount of reactive or volatile blowing 
agent, preferably the former. For example, a typical formulation will 
contain from about 0.1 to about 1.0 weight percent, preferably from about 
0.2 to about 0.4 weight percent water, and have a density of less than 0.8 
g/cm.sup.3, preferably from 0.15 to 0.5 g/cm.sup.3, and most preferably 
from about 0.2 to about 0.4 g/cm.sup.3. Isocyanate terminated prepolymers 
are generally utilized in such formulations, and have higher NCO content, 
in general, than the prepolymers used to form non-cellular elastomers. 
Isocyanate group contents of from 8 to 25 weight percent, more preferably 
10 to 22 weight percent, and most preferably 13-15 weight percent are 
suitable. The formulations are generally crosslinked and diol extended, 
the crosslinking being provided by employing, in addition to the glycol 
chain extender, a tri- or higher functional, low unsaturation polyol in 
the B-side, optionally also with a low molecular weight cross-linker such 
as diethanolamine (DEOA). Alternatively, the isocyanate-terminated 
prepolymer may be prepared from a tri- or higher functional low 
unsaturation polyol or a mixture of di- and higher functional low 
unsaturation polyols. Polyols utilized in significant amount in the 
formulation, whether incorporated into prepolymer or in the B-side, should 
have unsaturations of 0.015 meq/g or less, preferably 0.010 meq/g or less 
and the total average unsaturation of all polyol components should also be 
below 0.010 meq/g. 
Having generally described this invention, a further understanding can be 
obtained by reference to certain specific examples which are provided 
herein for purposes of illustration only and are not intended to be 
limiting unless otherwise specified. 
EXAMPLE 1 
Catalyst Preparation 
Preparation of Zinc Hexacyanocobaltate Catalysts by Homogenization With 
Tert-butyl Alcohol as the Complexing Agent 
A double metal cyanide.TBA catalyst is prepared by the method disclosed in 
copending U.S. Pat. No. 5,470,813. 
Potassium hexacyanocobaltate (8.0 g) is added to deionized water (150 mL) 
in a beaker, and the mixture is blended with a homogenizer until the 
solids dissolve. In a second beaker, zinc chloride (20 g) is dissolved in 
deionized water (30 mL). The aqueous zinc chloride solution is combined 
with the solution of the cobalt salt using a homogenizer to intimately mix 
the solutions. Immediately after combining the solutions, a mixture of 
tert-butyl alcohol (100 mL) and deionized water (100 mL) is added slowly 
to the suspension of zinc hexacyanocobaltate, and the mixture is 
homogenized for 10 minutes. The solids are isolated by centrifugation, and 
are then homogenized for 10 minutes with 250 mL of a 70/30 (v:v) mixture 
of tert-butyl alcohol and deionized water. The solids are again isolated 
by centrifugation, and are finally homogenized for 10 minutes with 250 mL 
of tert-butyl alcohol. The catalyst is isolated by centrifugation, and is 
dried in a vacuum oven at 50.degree. C. and 30 in. (Hg) to constant 
weight. 
EXAMPLE 2 
Preparation of Polyoxypropylene Triol With Random Internal Ethylene Oxide 
To a high pressure stainless steel autoclave was charged 7.6 pounds (3.45 
Kg) LHT-240, a glycerine-initiated polyoxypropylated triol of nominal 700 
Da molecular weight and sufficient catalyst as prepared in Example 1 to 
provide 100 ppm catalyst in the polyol product. The mixture is stirred and 
heated to 105.degree. C. under vacuum to remove traces of water from the 
triol starter, and an initial charge of a mixture of propylene oxide and 
ethylene oxide (90:10) is added and the reactor pressure monitored 
carefully. An accelerated pressure drop indicates that the catalyst has 
become activated. Additional propylene oxide/ethylene oxide is added over 
a period of approximately 6.5 hours until a total of approximately 57.5 
lbs. (26.1 Kg) has been added. The reactor is then stripped with nitrogen 
at 117.degree. C. under vacuum and the product discharged through a 
cartridge filter to remove residual catalyst. The resulting polyol is a 
c.a. 6000 Da triol containing 10 weight percent internal oxyethylene 
moieties, and having an unsaturation of c.a. 0.004 meq/g. 
Comparative Example 3 
Preparation of 6000 Da Triol with 14% Polyoxvethylene Cap, No Internal 
Oxyethylene Moieties 
To the stainless steel autoclave of Example 2 was added 7.6 lbs. (3.45 Kg) 
LHT-240 and sufficient catalyst of Example 1 to provide 100 ppm catalyst 
in the polyol product. The reactor was stirred at 105.degree. C. under 
vacuum as before, an initial charge of propylene oxide added and the 
pressure noted. After the catalyst had become activated, a total of 48.3 
lbs. (21.9 Kg) propylene oxide was added over a period of 5.5 hours. To 
the polyoxypropylene homopolymer triol thus obtained was added 332 g of 25 
weight percent sodium methoxide in methanol and 2.8 lbs. hexane. Hexane, 
methanol, and any water present were removed by stripping at 4 psia (0.27 
bar) and 117.degree. C. for 1 hour and then for an additional 3 hours at 
full vacuum. Following stripping, 9.1 lbs. (4.1 Kg) ethylene oxide was 
added at 117.degree. C. over a period of 1.5 hours. The residual catalysts 
were then removed by treatment with magnesol and filtration. The resulting 
product was a c.a. 6000 Da polyoxypropylene triol having a 14 weight 
percent polyoxyethylene cap, no internal oxyethylene moieties, and an 
unsaturation of c.a. 0.006 meq/g. The polyol product developed a haze 
after storage at room temperature for a short period. 
EXAMPLE 4 
The procedure of Example 3 was followed, except that initial oxyalkylation 
was with 48.3 lbs. (21.9 Kg) of a propylene oxide/ethylene oxide mixture 
(93:7) over 6.5 hours at 105.degree. C. Following preparation of the 
polyoxypropylene triol backbone containing random oxyethylene moieties, 
332 g of 25 weight percent sodium methoxide in methanol was added and the 
autoclave stripped as in Example 3. Then, 9.1 lbs. (4.1 Kg) ethylene oxide 
was added at 117.degree. C. over 1.5 hours. The catalysts were removed 
using magnesol treatment and filtration as before. The product was a 
polyoxypropylene triol containing 5% random internal oxyethylene moieties 
with a 14 weight percent polyoxyethylene cap, and an unsaturation of c.a. 
0.003 meq/g. The product was haze-free even after greater than 60 days of 
storage. 
EXAMPLES 5-8 
In a manner similar to that presented in Examples 3 and 4, a series of 
polyoxypropylene, polyoxyethylene capped diols and triols with and without 
internal oxyethylene moieties were prepared. The polyols were stored for 
extended periods at room temperature and examined periodically to defect 
formation of haze. The results are tabulated in Table 1. Examples 5, 3 and 
8 are comparative examples. 
TABLE 1 
__________________________________________________________________________ 
Mol. Wt. EO Cap 
Random EO Days Since.sup.1 
Example 
D.a. Functionality 
wt. % 
wt. % Appearance 
Manufacture 
__________________________________________________________________________ 
5 4000 diol 14 0 hazy -- 
3 6000 triol 14 0 hazy -- 
6 6000 triol 14 2.5 clear 23 
4 6000 triol 14 5 clear 60+ 
7 6000 triol 6 8 clear 60+ 
8 6000 triol 18 5 hazy -- 
__________________________________________________________________________ 
.sup.1 Examples 5, 3 and 8 turned hazy from 3-14 days after manufacture. 
Table 1 shows that as little as 2.5% internal oxyethylene moieties are 
sufficient to render a 14% polyoxyethylene capped polyoxypropylene polyol 
haze-free, while a similar polyol without internal oxyethylene turned 
rapidly hazy. Table 1 further shows that higher degrees of polyoxyethylene 
capping will require additional random, internal oxyethylene moieties to 
render the polyols haze-free. Example 8, with 18% polyoxyethylene cap, was 
not rendered haze-free by 5 weight percent internal oxyethylene moieties. 
A higher amount of internal oxyethylene will be required to produce a 
haze-free polyol in this case. 
EXAMPLES 9-14 
A series of 4000 Da molecular weight polyoxypropylene diols containing 0, 
5, 10, 20, 30 and 40 weight percent internal random ethylene oxide 
moieties were prepared as in Example 2. The diols were reacted with 
4,4'-methylenediphenylene diisocyanate to prepare isocyanate-terminated 
prepolymers containing 6 weight percent NCO, and extended with 
1,4-butanediol to prepare polyurethane elastomers. Dibutyltin dilaurate 
was used as the polyurethane catalyst; the amount of catalyst was adjusted 
to give similar pot life in order that demold times and green strength 
could be subject to proper comparison. Blends of polyoxypropylene 
homopolymer diols having exceptionally low unsaturation and found to 
beneficially affect demold time and green strength as disclosed in our 
copending application filed on even date herewith are also included for 
purposes of comparison. The results are presented in Table 2. The examples 
presented in the first column and the last two columns of Table 2 are 
comparative examples. 
TABLE 2 
__________________________________________________________________________ 
4000 Da 
4000 Da 
4000 Da 
8000 Da 2000 
8000 Da 1000 Da 
POLYOL TYPE 0% int. EO 
5% int. EO 
10% int. EO 
Da 0% int. EO 
0% int. EO 
__________________________________________________________________________ 
Dispersity Monodisperse 
Monodisperse 
Monodisperse 
Multidisperse 
Multidisperse 
Polyol Unsaturation, meq/g 
0.005 0.005 0.0038 0.005 0.005 
PROCESSING CHARACTERISTICS 
Pot Life, sec. 124 119 129 131 116 
Demold Time, min. 
22 25 25 29 25 
Green Strength at Demold 
poor average 
good good good 
PHYSICAL PROPERTIES 
Hardness, Shore A 
71 68 70 71 68 
Resilience, % 68 67 68 66 64 
Elongation, % 903 842 948 890 867 
Tensile Strength, psi 
2960 3233 3553 2764 2625 
100% Modulus, psi 
472 444 448 486 466 
300% Modulus, psi 
896 892 847 873 880 
Die C Tear Strength, psi 
362 360 351 366 349 
__________________________________________________________________________ 
As can be seen from the table, the demold times for the polyoxypropylene 
diols containing 5 weight percent and 10 weight percent internal random 
oxyethylene moieties are similar and in some cases superior to elastomers 
prepared from a monodisperse polyoxypropylene homopolymer diol and 
multidisperse polyoxypropylene homopolymer blends. However, the green 
strength at demold is improved over the monodisperse, low unsaturation 
polyoxypropylene homopolymer, and the tensile strengths of the random 
oxyethylene-containing elastomers are considerably higher than those 
prepared from monodisperse or multidisperse polyoxypropylene homopolymer 
diols. Moreover, the green strength after 60 minutes for the elastomers 
prepared from polyoxypropylene polyols containing 5 and 10 weight percent 
internal oxyethylene moieties was excellent, while that of the elastomer 
prepared from the 4000 Da monodisperse homopolyoxypropylene polyol was 
average. 
The polyoxypropylene polyols of the subject invention, having up to about 
20 weight percent internal oxyethylene moieties and ultra-low 
unsaturation, have been demonstrated to process well in terms of 
exhibiting commercially useful demold times and good green strength, as 
well as providing elastomers with superior physical properties. However, 
as disclosed previously, many elastomers are required to retain their 
physical properties in wet environments. We have found that polyurethane 
elastomers prepared from low unsaturation polyoxypropylene polyols having 
up to about 20 weight percent random oxyethylene moieties surprisingly 
show minimal room temperature water absorption, and elastomers prepared 
from polyols containing less than 20 weight percent random internal 
oxyethylene content, preferably 5-15 weight percent, exhibit water 
absorption of less than 10 weight percent, and generally less than 5 
weight percent, even at 0.degree. C., whereas elastomers prepared with 20 
weight percent or more internal oxyethylene moieties as well as 
oxyethylene capped polyoxypropylene polyols show absorptions of greater 
than 100 weight percent under these conditions. The water absorption at 
0.degree. C., 230.degree. C., and 50.degree. C. of elastomers prepared 
from polyols containing varying amounts of random internal oxyethylene 
moieties is presented in FIG. 1. 
As can be seen from FIG. 1, for elastomers where problems expected with 
respect to water absorption is limited to higher temperatures, i.e. room 
temperature or higher, up to 20 weight percent internal oxyethylene 
moieties are suitable in the polyols used to prepare the elastomers. 
However, when minimal low temperature water absorption is required, for 
example low absorption at 0.degree. C., the amount of internal oxyethylene 
moieties is preferably less than 15 weight percent, more preferably in the 
range of 5 weight percent to 10 weight percent. Under these conditions, 
0.degree. C. water absorption is less than 5% by weight, nearly the same 
as is obtainable with polyoxypropylene homopolymer polyols and PTMEG 
polyols but without the processing problems of the former or the higher 
cost of the latter. 
The actual weight percent water absorption of the elastomers is presented 
in Table 3, along with a comparative elastomer prepared from a 4000 Da, 20 
weight percent polyoxyethylene capped polyoxypropylene diol (Example A), 
having an unsaturation of 0.009 meq/g. 
TABLE 3 
______________________________________ 
Weight Percent Water Absorption As A 
Function of Temperature (6% MDI Prepolymers/BDO Cured) 
Water Immersion 
Percent Temperature 
Example Oxyethylene 
50.degree. C. 
23.degree. C. 
0.degree. C. 
______________________________________ 
9 0 2.1 2.1 2.2 
10 5 2.0 2.1 2.5 
11 10 2.3 2.5 4.7 
12 20 2.3 3.9 110.4 
13 30 3.5 23.1 129.5 
14 40 10.4 116.0 189.0 
C 20% capped 
5.1 14.2 76.4 
______________________________________ 
The development of hardness and resilience build with respect to time are 
considerably enhanced with the subject polyols containing internal 
oxyethylene moieties as compared to polyoxypropylene homopolymer polyols. 
FIG. 2 shows the resilience build of elastomers prepared from a 4000 Da 
molecular weight polyoxypropylene homopolymer diol (no internal EO) (Plot 
A), and a 4000 Da monodisperse polyoxypropylene diol containing 10 weight 
percent random oxyethylene moieties (Plot B). To measure resilience build, 
a series of identical elastomers were prepared from the aforementioned 
polyols and oven cured at 100.degree. C. Elastomers were removed at 
various intervals and resilience measured. As can be seen, even though the 
polyoxypropylene diol containing 10 weight percent internal oxyethylene 
moieties was monodisperse, the resilience build is considerably greater 
than that achieved from a monodisperse, ultra-low unsaturation 
polyoxypropylene diol. Moreover, the physical properties of the elastomers 
prepared from the diol containing internal oxyethylene moieties are far 
superior to those of either of the other two examples. The hardness build 
of the same elastomers is presented in FIG. 3. 
While the best mode for carrying out the invention has been described in 
detail, those familiar with the art to which this invention relates will 
recognize various alternative designs and embodiments for practicing the 
invention as defined by the following claims.